WO2021172008A1 - Ink-jet ink and method for forming image - Google Patents

Ink-jet ink and method for forming image Download PDF

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Publication number
WO2021172008A1
WO2021172008A1 PCT/JP2021/004862 JP2021004862W WO2021172008A1 WO 2021172008 A1 WO2021172008 A1 WO 2021172008A1 JP 2021004862 W JP2021004862 W JP 2021004862W WO 2021172008 A1 WO2021172008 A1 WO 2021172008A1
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WO
WIPO (PCT)
Prior art keywords
ink
inkjet ink
temperature
inkjet
mass
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Application number
PCT/JP2021/004862
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French (fr)
Japanese (ja)
Inventor
小俣　猛憲
晃央 前田
Original Assignee
コニカミノルタ株式会社
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Priority to JP2022503243A priority Critical patent/JPWO2021172008A1/ja
Publication of WO2021172008A1 publication Critical patent/WO2021172008A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/17—Ink jet characterised by ink handling
    • B41J2/18—Ink recirculation systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/30—Inkjet printing inks
    • C09D11/32—Inkjet printing inks characterised by colouring agents
    • C09D11/322—Pigment inks

Definitions

  • the present invention relates to an inkjet ink and an image forming method. More specifically, the present invention relates to an inkjet ink capable of maintaining good ejection properties and forming a high-quality image, and an image forming method by an inkjet method capable of forming a high-quality image with good workability. Regarding.
  • inkjet ink droplets of inkjet ink (hereinafter, also simply referred to as “ink”) are ejected from the inkjet head (hereinafter, also simply referred to as “head”) toward the base material and land on the base material. After that, the solvent is dried to form a coating film (image).
  • a coating film image
  • a non-absorbent base material made of PET (polyethylene terephthalate) or the like
  • an additive is added to the ink to give it thixotropy, and the ink circulates in the head to increase the share and reduce the viscosity. It is disclosed that the viscosity becomes high, the ink is hard to be absorbed by the absorbent base material, and the image is formed at a high density without heating the platen.
  • Patent Document 1 a water-based inkjet in which a water-soluble polymer compound is added to impart thixotropy to an ink so that the ink viscosity at low share becomes 1.5 times or more the viscosity at high share.
  • the ink is listed.
  • Patent Document 1 when this ink is circulated and discharged by a head, it has a high share and a low viscosity, but when it lands, it has a low share and a high viscosity, and the concentration is lowered by the absorbing base material. It is stated to prevent.
  • Patent Document 1 does not describe an attempt to control the thickening of the ink by combining the thixotropic property of the ink itself and the drying conditions. It is assumed that it is not possible to achieve both good ejection performance and high-quality image formation only by the method of controlling the thixotropic property of the ink itself as in Patent Document 1.
  • Patent Document 2 describes a water-based inkjet ink to which a water-soluble temperature-responsive polymer is added.
  • Patent Document 2 describes the effect of suppressing the penetration of ink into a paper substrate to increase the density.
  • the temperature-responsive polymer is added in an amount of about 5% by mass in the entire ink, and is added twice or more with respect to the coloring material. Then, it is described that the color material is fixed by shrinking the resin and covering the color material when heat is applied.
  • the thixotropic property is not controlled so as to change the viscosity of the ink in the head and at the time of landing. Therefore, it is assumed that the ink described in Patent Document 2 cannot achieve both good ejection performance and high-quality image formation.
  • the present invention has been made in view of the above problems and situations, and the problem to be solved is to provide an inkjet ink that enables both maintenance of good ejection properties and high-quality image formation at the same time.
  • Another object of the present invention is to provide an image forming method capable of forming a high-quality image with good workability in image forming by an inkjet method.
  • the present inventor uses the viscosity at the time of high share at the time of circulation in the head of the inkjet ink and the viscosity at the time of low share at the time of landing as indexes.
  • the composition of the inkjet ink using the temperature-responsive polymer was examined.
  • the viscosity at the time of circulation in the head is low and slightly.
  • the present invention has been made by finding that an ink having a sufficiently high viscosity at the time of landing can be obtained by adjusting the temperature.
  • the ink is an inkjet ink capable of maintaining good ejection properties and forming a high-quality image at the same time. That is, the above problem according to the present invention is solved by the following means.
  • An inkjet ink containing an aqueous solvent, a pigment, a fixing resin, and a temperature-responsive polymer, wherein the temperature-responsive polymer has a lower limit critical eutectic temperature with respect to water, and the pigment is contained in the total amount of the inkjet ink.
  • the amount is in the range of 2 to 10% by mass
  • the content of the fixing resin is in the range of 1 to 10% by mass
  • the content of the temperature-responsive polymer is 0.01 to 1% by mass.
  • Ink ink that is within range.
  • the viscosity of the inkjet ink at a shear rate of 1000 (1 / s) at 25 ° C. is 15 mPa ⁇ s or less, and the shear rate at any temperature in the range of the lower limit critical eutectic temperature ⁇ 10 ° C.
  • the fixing resin contains at least one selected from the group consisting of a polyacrylic resin, a polyurethane resin, and a polyester resin.
  • Item 8 The inkjet ink according to Item 8, wherein the thixotropy-imparting agent contains cellulose nanofibers or smectite clay minerals.
  • An image forming method comprising a landing step of ejecting droplets of inkjet ink from an inkjet head provided with an ink circulation mechanism and landing them on a substrate, wherein the inkjet ink has a viscosity of 15 mPa ⁇ s or less in the inkjet head.
  • the droplets are circulated so as to be, and when they land on the base material or immediately after landing, the mass reduction rate from the inkjet ink is within 20%, and the viscosity is 100 mPa ⁇ s or more.
  • the inkjet head communicates with a pressure chamber into which the inkjet ink is injected via an injection path, a pressure generating means for causing a pressure fluctuation in the pressure chamber, and the pressure chamber, and the pressure fluctuation in the pressure chamber causes the inkjet head to communicate with the pressure chamber.
  • a nozzle that serves as a flow path for the inkjet ink discharged from the pressure chamber to the outside, and two or more circulation paths that communicate with the pressure chamber to discharge the inkjet ink inside the nozzle and return it to the injection path.
  • the inkjet ink of the present invention contains an aqueous solvent, a pigment, a fixing resin, and a temperature-responsive polymer, and the temperature-responsive polymer has a lower limit critical eutectic temperature with respect to water.
  • the content is in the range of 2 to 10% by mass
  • the content of the fixing resin is in the range of 1 to 10% by mass
  • the content of the temperature-responsive polymer is in the range of 0.01 to 1% by mass. It is characterized by being.
  • the lower limit critical eutectic temperature of a temperature-responsive polymer refers to the lower limit critical eutectic temperature with respect to water.
  • the viscosity at the time of high share can be lowered, for example, the viscosity (25 ° C.) of the ink at a shear rate of 1000 (1 / s) can be set to 15 mPa ⁇ s or less.
  • the viscosity is a viscosity at which ink can be smoothly circulated at the head and ejected from the head.
  • the viscosity at the time of landing is increased, for example, the shear rate 1 (1 / s) at any temperature in the range of the lower limit critical eutectic temperature ⁇ 10 ° C. of the temperature-responsive polymer.
  • the viscosity at the time can be 45 mPa ⁇ s or more.
  • the maximum viscosity of the temperature-responsive polymer at a shear rate of 1 (1 / s) within the range of the lower limit critical eutectic temperature of ⁇ 10 ° C. can be 45 mPa ⁇ s or more.
  • the ink of the present invention has a high viscosity required for good pinning within a range of the lower limit critical eutectic temperature ⁇ 10 ° C. of the temperature responsive polymer with water.
  • a large amount of water-based solvent can remain in the ink from the time of ejection to the time of impact, so that the sticking of the solid ink content around the head is suppressed, ejection defects are less likely to occur, and maintenance is easy.
  • the temperature-responsive polymer and the fixing resin in combination, water resistance can be imparted to the ink coating film obtained by image formation. This is considered to be the effect obtained by the temperature-responsive polymer and the fixing resin being entangled in the process of image formation. Further, the entanglement improves the substrate fixability of the ink coating film obtained by image formation.
  • the image forming method of the present invention is an image forming method comprising a landing step of ejecting droplets of inkjet ink from an inkjet head provided with an ink circulation mechanism and landing the ink jet ink on a substrate. It is circulated so that the viscosity is 15 mPa ⁇ s or less.
  • the viscosity is a viscosity at which ink can be smoothly circulated at the head and ejected from the head.
  • the mass reduction rate of the ink droplets when they land on the substrate or immediately after landing from the ink circulating in the head is within 20% and the viscosity.
  • the landing process is performed so that the value is 100 mPa ⁇ s or more.
  • FIG. 1 Schematic configuration of a main part showing an inkjet image forming apparatus including an example of an inkjet head that can be used in the image forming method of the present invention.
  • Top view of the nozzle plate of the inkjet head shown in FIG. The graph used when obtaining the crossover strain (%) of the ink of Example 1.
  • the inkjet ink of the present invention is an inkjet ink containing an aqueous solvent, a pigment, a fixing resin, and a temperature-responsive polymer, and the temperature-responsive polymer has a lower limit critical eutectic temperature with respect to water, and the total amount of the inkjet ink
  • the content of the pigment is in the range of 2 to 10% by mass
  • the content of the fixing resin is in the range of 1 to 10% by mass
  • the content of the temperature-responsive polymer is 0.01 to 1. It is characterized in that it is within the range of mass%.
  • the viscosity at a shear rate of 1000 (1 / s) at 25 ° C. is 15 mPa ⁇ s or less from the viewpoint of maintaining good ejection properties and forming a high-quality image.
  • the viscosity at a shear rate of 1 (1 / s) at any temperature in the range of the lower limit critical eutectic temperature of ⁇ 10 ° C. is 45 mPa ⁇ s or more.
  • the aqueous solvent is removed from the inkjet ink so as to have a mass of 80% of the initial mass from the viewpoint of maintaining good ejection properties and forming a high-quality image.
  • this state is also referred to as “ink drying rate 20%”
  • the viscosity at a shear rate of 1 (1 / s) at any temperature within the range of the lower limit critical co-melting temperature ⁇ 10 ° C. is 100 mPa.
  • -It is preferable that the value is s or more.
  • the lower limit critical eutectic temperature of the temperature-responsive polymer with respect to water is within the range of 30 to 60 ° C. from the viewpoint of maintaining good ejection properties and forming a high-quality image. It is preferable to have. Moreover, it is preferable that the temperature-responsive polymer contains a water-soluble cellulose resin.
  • the content of the aqueous solvent is in the range of 50 to 90% by mass with respect to the total amount of the inkjet ink from the viewpoint of maintaining good ejection properties and forming a high-quality image. It is preferable to have.
  • the fixing resin contains at least one selected from the group consisting of a polyacrylic resin, a polyurethane resin, and a polyester resin from the viewpoint of exhibiting the effect of the present invention.
  • the inkjet ink further contains a thixotropic agent from the viewpoint of maintaining good ejection properties and forming a high-quality image.
  • the thixotropy-imparting agent contains cellulose nanofibers or smectite clay minerals.
  • the content of the thixotropy-imparting agent is preferably in the range of 0.01 to 1% by mass with respect to the total amount of the inkjet ink.
  • the image forming method of the present invention is an image forming method having a landing step of ejecting droplets of inkjet ink from an inkjet head provided with an ink circulation mechanism and landing them on a substrate, wherein the inkjet ink is the inkjet head.
  • the droplets are circulated in the ink jet so as to have a viscosity of 15 mPa ⁇ s or less, and when the droplets land on the base material or immediately after landing, the mass reduction rate from the inkjet ink is within 20%.
  • the landing step is performed so that the viscosity becomes 100 mPa ⁇ s or more.
  • the viscosity of the droplet when landing on the substrate or immediately after landing is 150 mPa ⁇ s or more. ..
  • An embodiment of the image forming method of the present invention includes that the landing step heats the droplets on the substrate in the range of 30 to 60 ° C. from the viewpoint of further exhibiting the effects of the present invention. Is preferable. Further, it is preferable that the droplet is within 100 msec after landing on the base material immediately after the landing.
  • the base material is a non-absorbent base material because the effect of the present invention is more remarkable.
  • the inkjet head has a pressure chamber in which the inkjet ink is injected via an injection path and a pressure fluctuation in the pressure chamber.
  • a nozzle that communicates with the pressure chamber and serves as a flow path for the inkjet ink discharged from the pressure chamber to the outside due to pressure fluctuations in the pressure chamber, and communicates with the pressure chamber. It is preferable to provide two or more circulation paths for discharging the inkjet ink inside the nozzle and returning the inkjet ink to the injection path.
  • the inkjet ink of the present invention As an embodiment of the image forming method of the present invention, it is preferable to use the inkjet ink of the present invention as the inkjet ink from the viewpoint of further exhibiting the effects of the present invention.
  • the ink of the present invention is an inkjet ink containing an aqueous solvent, a pigment, a fixing resin, and a temperature-responsive polymer, and the temperature-responsive polymer has a lower limit critical eutectic temperature with respect to water with respect to the total amount of the inkjet ink.
  • the content of the pigment is in the range of 2 to 10% by mass
  • the content of the fixing resin is in the range of 1 to 10% by mass
  • the content of the temperature-responsive polymer is 0.01 to 1% by mass. It is characterized in that it is within the range of%.
  • the aqueous solvent means water or a solvent containing water and an aqueous solvent.
  • the aqueous solvent is a solvent that is compatible with water at room temperature.
  • the ink of the present invention can contain any component other than the aqueous solvent, the pigment, the fixing resin, and the temperature-responsive polymer, which does not impair the effect of the present invention.
  • the optional component include a thixotropic agent, a pigment dispersant, a surfactant and the like.
  • the temperature-responsive polymer contained in the ink of the present invention is a polymer having a low critical solution temperature (hereinafter, also referred to as “LCST”) with respect to water.
  • LCST critical solution temperature
  • the temperature-responsive polymer has the property of being soluble in water below LCST and insoluble in water above LCST, for example, gelling.
  • the aqueous solution of the temperature-responsive polymer has the property of undergoing a phase change with the LCST as a critical point. The property is reversible.
  • the ink of the present invention can adjust the viscosity of the ink in the head and at the time of landing on the base material within an appropriate range, thereby maintaining good ejection properties. It is possible to achieve both high-quality image formation.
  • the LCST of the temperature-responsive polymer in water can be measured, for example, by measuring the phase transition temperature of the aqueous temperature-responsive polymer solution using a differential scanning calorimeter (DSC). Alternatively, it can be carried out by measuring the change in the light transmittance of the aqueous solution while gradually raising (lowering) the temperature of the aqueous solution of the temperature-responsive polymer.
  • DSC differential scanning calorimeter
  • the temperature-responsive polymer preferably has an LCST in the range of 30 to 60 ° C, more preferably in the range of 40 to 50 ° C.
  • the LCST of the temperature-responsive polymer is 30 ° C. or higher, the ink does not normally increase its viscosity extremely in the temperature range circulating in the head. Further, if the LCST of the temperature-responsive polymer is 60 ° C. or lower, it is possible to increase the viscosity of the ink droplets to a desired level without removing the aqueous solvent without raising the temperature to a high temperature at the time of landing. Become.
  • the aqueous solvent contained in the ink may consist of water as described later, but optionally contains an aqueous solvent in addition to water.
  • the LCST of the temperature-responsive polymer for the aqueous solvent may differ from the LCST of the temperature-responsive polymer for water. The difference between the two is preferably within about 10 ° C. That is, the LCST of the temperature-responsive polymer with respect to the aqueous solvent is preferably within the range of LCST ⁇ 10 ° C. with respect to water of the temperature-responsive polymer.
  • the temperature-responsive polymer examples include water-soluble cellulose resins, poly (N-substituted (meth) acrylamide), poly (N-vinyl acylamide), poly ((meth) acrylic acid alkyl ester), and other temperature-responsive polymers. Examples include polymers. Among these, a water-soluble cellulose resin is preferable as the temperature-responsive polymer used in the ink of the present invention.
  • (meth) acrylamide is a general term of acrylamide and methacrylamide.
  • (meth) acrylic acid is a general term for acrylic acid and methacrylic acid.
  • the water-soluble cellulose resin is a resin to which water solubility is imparted by substituting a part of hydrogen atoms of OH groups possessed by cellulose to eliminate hydrogen bonds.
  • substituent that replaces the hydrogen atom of the OH group include an alkyl group, a hydroxyalkyl group, and a carboxy group.
  • substituent a methyl group, a hydroxypropyl group and a hydroxyethyl group are preferable.
  • one type may be used alone, or two or more types may be used in combination.
  • water-soluble cellulose resin examples include methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose and the like.
  • an alkyl group which may have an ether bond (-O-) between carbon atoms is preferable.
  • the alkyl group may be cyclic, straight chain or branched chain, and may be a combination thereof.
  • the nitrogen atom has one or two substituents, and when there are two substituents, these may be bonded to form a ring.
  • the number of carbon atoms in the alkyl group is preferably 1 to 10.
  • poly (N-substituted (meth) acrylamide) examples include poly (N-ethylacrylamide), poly (Nn-propyl (meth) acrylamide), poly (N-isopropyl (meth) acrylamide), and poly.
  • N-cyclopropyl (meth) acrylamide), poly (N, N-diethyl (meth) acrylamide) and the like can be mentioned.
  • poly (N-substituted (meth) acrylamide) does not have to be composed of a single monomer. That is, poly (N-substituted (meth) acrylamide) may be a copolymer of N-substituted (meth) acrylamide having different substituents. Further, the copolymerization of N-substituted (meth) acrylamide with at least one selected from the following polymers, for example, monomers constituting poly (N-vinylacylamide) and poly ((meth) acrylic acid alkyl ester). It may be coalesced.
  • poly (N-vinylacylamide) examples include poly (N-vinylacetamide), poly (N-vinylpropionic acid amide), poly (N-vinylbutyric acid amide), poly (N-vinylisobutyric acid amide) and the like. ..
  • poly ((meth) acrylic acid alkyl ester) examples include poly (n-butyl methacrylate), poly (dodecyl methacrylate), poly (n-hexyl methacrylate), poly (methyl methacrylate), and poly (n-octyl methacrylate). Can be mentioned.
  • temperature-responsive polymers include poly (N, N-acrylic pyrrolidone), poly (N-acrylic piperidine), and copolymers thereof, alternating copolymers of polyvinyl isobutyl vinyl ether and maleic anhydride, and poly (2-).
  • Methyl-5-vinylpyridine poly (vinyl alcohol), poly (N-vinylpyrrolidone), poly (N-vinylsuccinic acid), poly (vinyl sulfonic acid), poly (oxyethylene), poly (tetrahydrofuran), amylopectin, Examples thereof include amylose, poly (vinyl acetate), poly (propylene glycol), polyvinyl methyl ether (PVME), polyvinyl methyl oxazolidinone and the like.
  • thermoresponsive polymer one of these may be used alone, or two or more thereof may be used in combination.
  • the weight average molecular weight of the temperature-responsive polymer is not particularly limited, but is preferably 10,000 or more and 100,000 or less, and more preferably 20,000 or more and 80,000 or less.
  • the weight average molecular weight of the temperature-responsive polymer is 10,000 or more, the polymer is easily entangled with the fixing resin to impart water resistance to the ink coating film (image). Further, when the weight average molecular weight is 100,000 or less, there is little possibility that the viscosity of the ink becomes too high and the ejection property deteriorates.
  • the weight average molecular weight of the temperature-responsive polymer is a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography (GPC).
  • the temperature responsive polymer As the temperature responsive polymer, a commercially available product may be used. Commercially available products include, for example, water-soluble cellulose resins under the trade names manufactured by Shin-Etsu Chemical Co., Ltd., Metrose SM-04 (methyl cellulose resin, LCST; 55 ° C.), Metrose 60SH-03 (hydroxypropyl methylcellulose resin, LCST). ; 75 ° C.) and the like.
  • poly (N-substituted (meth) acrylamide) examples include poly (as N-isopropylacrylamide, Sigma-Aldrich, for example, poly (N-isopropylacrylamide (LCST; 35 ° C., weight average molecular weight; 30,000)) and the like. Can be mentioned.
  • the content of the temperature-responsive polymer in the ink of the present invention is in the range of 0.01 to 1% by mass with respect to the total amount of the ink.
  • the effect of the present invention can be obtained by blending the temperature-responsive polymer.
  • the content of the temperature responsive polymer is preferably in the range of 0.05 to 0.8% by mass.
  • the ink of the present invention contains a fixing resin.
  • a fixing resin By containing a fixing resin in addition to the temperature-responsive polymer, the ink of the present invention can appropriately adjust the viscosity of the ink when it lands on the head and the base material, and can be used as an ink coating film obtained by image formation. Water resistance can be imparted.
  • the fixing resin further functions as a binder for a pigment which is a colorant, improves the adhesiveness of the coating film to a base material, particularly a non-absorbent base material, and scratch resistance of the coating film obtained by using an ink. It has a function to improve the sex.
  • the fixing resin is preferably a water-insoluble resin.
  • the water-insoluble resin as the fixing resin is preferably used in the form of fine particles dispersed in an aqueous solvent.
  • the fine particles of the water-insoluble resin have a form in which the originally water-insoluble resin is dispersed as microscopic fine particles in an aqueous solvent.
  • the fine particles may be in the form of, for example, forcibly emulsifying a water-insoluble resin using an emulsifier or the like and dispersing them as fine particles in an aqueous solvent.
  • a hydrophilic functional group is introduced into the molecule of the water-insoluble resin to form stable fine particles by itself in an aqueous solvent without using an emulsifier or a dispersion stabilizer, that is, self-emulsified. It may be a thing.
  • the aqueous solvent in which the fine particles of the water-insoluble resin are dispersed the same aqueous solvent as described above can be used, and usually water or a water / alcohol mixed solvent is used.
  • the fine particles of the water-insoluble resin dispersed in the aqueous solvent are also referred to as an aqueous dispersion.
  • the term "water-insoluble resin” means that when the resin is dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C., the amount of the resin dissolved is 10 g or less, preferably 5 g or less. More preferably, it refers to a resin having a weight of 1 g or less. However, when the resin has a salt-forming group, the dissolved amount is the dissolved amount when the salt-forming group of the resin is 100% neutralized with acetic acid or sodium hydroxide, depending on the type.
  • water-insoluble resins such as polyester resin, polyurethane resin and polyacrylic resin are preferable.
  • the fixing resin one of these may be used alone, or two or more thereof may be used in combination.
  • the fixing resin is contained in the range of 1 to 10% by mass with respect to the total mass (100% by mass) of the ink.
  • the content of the fixing resin is preferably in the range of 2 to 8% by mass, more preferably in the range of 3 to 6% by mass.
  • the ratio (percentage) of the content of the temperature-responsive polymer to the total content of the temperature-responsive polymer and the fixing resin is in the range of 0.1 to 20% by mass. It is preferable that the relationship is as follows. The ratio is more preferably 0.5 to 10% by mass. When the ratio of the content of the temperature-responsive polymer to the total content of the temperature-responsive polymer and the fixing resin is within the above range, it is easy to achieve both the water resistance of the coating film (image) obtained from the ink and the good pinning characteristics.
  • the polyester resin used as the fixing resin can be obtained by using a polyhydric alcohol component and a polyvalent carboxylic acid component such as a polyvalent carboxylic acid, a polyvalent carboxylic acid anhydride, or a polyvalent carboxylic acid ester.
  • the polyhydric alcohol component includes a dihydric alcohol (diol), specifically, an alkylene glycol (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1) in the range of 2 to 36 carbon atoms. , 4-butylene glycol, 1,6-hexanediol, etc.), alkylene ether glycol in the range of 4 to 36 carbon atoms (diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polybutylene glycol, etc.), An alicyclic diol having 6 to 36 carbon atoms (1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.) and an alkylene oxide having 2 to 4 carbon atoms of the alicyclic diol (ethylene oxide (hereinafter referred to as ethylene oxide)).
  • dihydric alcohol diol
  • alkylene glycol ethylene glycol, 1,2-propylene glycol, 1,3
  • EO abbreviated as EO
  • PO propylene oxide
  • BO butylene oxide
  • the polyvalent carboxylic acid component includes a divalent carboxylic acid (dicarboxylic acid), specifically, an alkandicarboxylic acid (succinic acid, apidic acid, sebacic acid, etc.) in the range of 4 to 36 carbon atoms, and an alkenyl succinic acid.
  • divalent carboxylic acid divalent carboxylic acid
  • alkandicarboxylic acid succinic acid, apidic acid, sebacic acid, etc.
  • the number average molecular weight of the polyester resin is preferably in the range of 1000 to 50,000, and more preferably in the range of 2000 to 20000.
  • polyester resin a commercially available product
  • a commercially available product for example, a dispersion liquid in which the polyester resin is dispersed in an aqueous solvent as an aqueous dispersion may be used.
  • examples of commercially available products of the dispersion liquid include the following. In the example, the number average molecular weight of the polyester resin contained in the product (dispersion liquid) is shown in parentheses. These may be used alone or in combination of two or more.
  • polyurethane resin As the polyurethane resin used as the fixing resin, one having a hydrophilic group can be used.
  • the hydrophilic group include a carboxyl group (-COOH) and salts thereof, sulfonic acid group (-SO 3 H) and a salt.
  • the salt include alkali metal salts such as sodium salt and potassium salt, amine salts and the like.
  • a carboxy group or a salt thereof is preferable.
  • the above-mentioned polyurethane resin is forcibly emulsified under a strong mechanical shearing force by using an aqueous dispersion in which a self-emulsifying polyurethane having a water-soluble functional group in its molecule is dispersed in an aqueous solvent or a surfactant in combination.
  • the type polyurethane is preferably an aqueous dispersion dispersed in an aqueous solvent.
  • the polyurethane resin in the aqueous dispersion can be obtained by reacting a polyol with an organic polyisocyanate and a hydrophilic group-containing compound.
  • polyester polyols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2- and 1,3-propylene glycol, neopentyl glycol, 1,3- and 1,4-butanediol, 3-methylpentanediol, Low molecular weight polyols such as hexamethylene glycol, 1,8-octanediol, 2-methyl-1,3-propanediol, bisphenol A, hydrogenated bisphenol A, trimethylolpropane, cyclohexanedimethanol; succinic acid, glutaric acid, adipine Includes condensates with polyvalent carboxylic acids such as acids, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, tetrahydrofuran acid, endomethine tetrahydrofuran acid, and hexahydrophthalic acid.
  • polyvalent carboxylic acids such as acids, sebacic acid,
  • polyether polyols examples include polyethylene glycol, polypropylene glycol, polyethylene polytetramethylene glycol, polypropylene polytetremethylene glycol, polytetramethylene glycol and the like.
  • polycarbonate polyols include compounds obtained by reacting carbonic acid derivatives such as diphenyl carbonate, dimethyl carbonate or phosgene with diols.
  • diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2- and 1,3-propylene glycol, neopentyl glycol, 1,3- and 1,4-butanediol, 3-methylpentanediol, etc.
  • Hexamethylene glycol, 1,8-octanediol, 2-methyl-1,3-propanediol, bisphenol A, hydrogenated bisphenol A, trimethylolpropane, cyclohexanedimethanol and the like are included.
  • organic polyisocyanates that can be used to prepare aqueous dispersions of polyurethane resins include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polypeptide MDI, xylylene diisocyanate (XDI), and tetramethylxylylene diisocyanate.
  • Aromatic isocyanates such as (TMXDI); aliphatic isocyanates such as hexamethylene diisocyanate (HMDI); alicyclic isocyanates such as isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI, H12MDI). Is Only one type of these may be used alone, or two or more types may be used in combination.
  • hydrophilic group-containing compounds that can be used to prepare aqueous dispersions of polyurethane resins include 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylolbutyric acid, 2, 2-Carboxylic acid-containing compounds such as valeric acid and glycine, and derivatives thereof such as sodium salts, potassium salts and amine salts; sulfonic acid-containing compounds such as taurine (ie, aminoethyl sulfonic acid) and ethoxypolyethylene glycol sulfonic acid. And derivatives such as sodium salt, potassium salt, amine salt and the like.
  • Polyurethane resin can be obtained by a known method.
  • a polyurethane resin can be obtained by mixing the above-mentioned polyol, organic polyisocyanate, and a hydrophilic group-containing compound and reacting them at 30 to 130 ° C. for 30 minutes to 50 hours.
  • the polyurethane resin becomes a polyurethane resin having a hydrophilic group by being elongated with a chain extender and polymerized.
  • the chain extender is preferably a water and / or amine compound. By using water or an amine compound as the chain extender, the isocyanate-terminated prepolymer can be efficiently extended by reacting with free isocyanate in a short time.
  • amine compounds as chain extenders include aliphatic polyamines such as ethylenediamine and triethylenediamine; aromatic polyamines such as m-xylylenediamine and toluylenediamine; and polyhydradino compounds such as hydrazine and dihydrazide adipic acid.
  • the amine compound may contain, together with the polyamine, a monovalent amine such as dibutylamine, methyl ethyl ketooxime, or the like as a reaction terminator to the extent that it does not significantly inhibit polymerization.
  • a solvent that is inactive with isocyanate and can dissolve the urethane prepolymer may be used.
  • these solvents include dioxane, methyl ethyl ketone, dimethylformamide, tetrahydrofuran, N-methyl-2-pyrrolidone, toluene, propylene glycol monomethyl ether acetate and the like. It is preferable that these hydrophilic organic solvents used in the reaction step are finally removed.
  • an amine catalyst for example, triethylamine, N-ethylmorpholin, triethyldiamine, etc.
  • a tin catalyst for example, dibutyltin dilaurate, dioctyltin dilaurate, tin octylate
  • catalysts such as titanium-based catalysts (eg, tetrabutyl titanate, etc.) may be added.
  • the number average molecular weight of the polyurethane resin is preferably as large as possible by introducing a branched structure or an internal crosslinked structure, and the number average molecular weight is preferably 50,000 to 10,000,000.
  • the number average molecular weight is a value measured by gel permeation chromatography (GPC).
  • the number average molecular weight (Mn) is, for example, "RID-6A” manufactured by Shimadzu Corporation (column: “TSK-GEL” manufactured by Tosoh Corporation, solvent: tetrahydrofuran (THF), column temperature: 40 ° C.). It can be obtained from the calibration curve prepared with a polystyrene standard sample.
  • polyurethane resin a commercially available product may be used.
  • a dispersion liquid in which the polyurethane resin is dispersed in an aqueous solvent as an aqueous dispersion may be used.
  • Examples of commercially available polyurethane resin dispersions include WBR-016U (manufactured by Taisei Fine Chemicals Co., Ltd.), Superflex 620, Superflex 650, Superflex 500M, and Superflex E-2000 (all manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.).
  • the polyacrylic resin used as the fixing resin includes a (co) polymer of the (meth) acrylic acid ester component, or a polymerizable component other than the (meth) acrylic acid ester component such as the (meth) acrylic acid ester component and the styrene component. Copolymer of.
  • (meth) acrylic acid ester components include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and -2-hydroxyethyl (meth) acrylate.
  • styrene components include styrene, 4-methylstyrene, 4-hydroxystyrene, 4-acetoxystyrene, 4-acetylstyrene, styrenesulfonic acid and the like. Only one of these components may be used alone, or two or more of these components may be used in combination.
  • the number average molecular weight (Mn) of the polyacrylic resin is preferably 1000 to 50,000, and more preferably 2000 to 20000.
  • Mn number average molecular weight of the polyacrylic resin
  • the cohesive force of the coating film becomes strong and the adhesion is improved, and when it is 50,000 or less, the solubility in an organic solvent is good and the emulsified dispersion is obtained. This is because the miniaturization of the particle size of is promoted.
  • the polyacrylic resin a commercially available product may be used.
  • a dispersion liquid in which the polyacrylic resin is dispersed in an aqueous solvent as an aqueous dispersion may be used.
  • Examples of commercially available polyacrylic resin dispersions include Delpet 60N, 80N (manufactured by Asahi Kasei Corporation, “Delpet” is a registered trademark of the same company), Dianar BR52, BR80, BR83, BR85, BR88 (Mitsubishi). Chemical Co., Ltd., "Dianar” is a registered trademark of the company), KT75 (Denka Co., Ltd.), or Viniblanc 2680, 2682, 2864, 2685 (Nissin Chemical Industry Co., Ltd., "Viniblanc” is a registered trademark of the company) ), Movinyl 6800D (manufactured by Japan Coating Resin Co., Ltd.) and the like are included.
  • the fixing resin preferably contains an acid structure. If it contains an acid structure, it can be dispersed in an aqueous solvent without the addition of a surfactant, that is, it can be self-emulsified, and the water resistance of the coating film is improved. Such a self-emulsifying resin can be dispersed and stabilized in an aqueous solvent only by the ionicity of the molecule.
  • acids structure carboxy group (-COOH), a contained such an acid group such as a sulfonic acid group (-SO 3 H) is.
  • the acid structure may be present in the side chain or at the end of the resin.
  • the acid structure is neutralized.
  • the neutralizing agent for neutralizing the acid structure organic amines
  • organic amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, N-methyldiethanolamine and triethanolamine are preferably used.
  • azo pigments such as azo lake, insoluble azo pigment, condensed azo pigment, chelate azo pigment, phthalocyanine pigment, perylene and perylene pigment, anthraquinone pigment, quinacridone pigment, dioxandine pigment, thioindigo pigment, isoindolinone pigment, quinophthaloni pigment and the like.
  • cyclic pigments dye lakes such as basic dye type lakes and acidic dye type lakes
  • organic pigments such as nitro pigments, nitroso pigments, aniline blacks and daylight fluorescent pigments
  • inorganic pigments such as carbon black.
  • Specific organic pigments that can be preferably used include the following pigments.
  • pigments for magenta or red examples include C.I. I. Pigment Red 2, C.I. I. Pigment Red 3, C.I. I. Pigment Red 5, C.I. I. Pigment Red 6, C.I. I. Pigment Red 7, C.I. I. Pigment Red 15, C.I. I. Pigment Red 16, C.I. I. Pigment Red 48: 1, C.I. I. Pigment Red 53: 1, C.I. I. Pigment Red 57: 1, C.I. I. Pigment Red 122, C.I. I. Pigment Red 123, C.I. I. Pigment Red 139, C.I. I. Pigment Red 144, C.I. I. Pigment Red 149, C.I. I.
  • Pigment Red 166 C.I. I. Pigment Red 177, C.I. I. Pigment Red 178, C.I. I. Pigment Red 202, C.I. I. Pigment Red 222, C.I. I. Pigment Violet 19 and the like.
  • pigments for orange or yellow examples include C.I. I. Pigment Orange 31, C.I. I. Pigment Orange 43, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 15, C.I. I. Pigment Yellow 15: 3, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 74, C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 128, C.I. I. Pigment Yellow 94, C.I. I. Pigment Yellow 138, C.I. I. Pigment Yellow 155 and the like. Especially in the balance between color tone and light resistance, C.I. I. Pigment Yellow 155 is preferred.
  • pigments for green or cyan examples include C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 2, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 16, C.I. I. Pigment Blue 60, C.I. I. Pigment Green 7 and the like.
  • pigment for black for example, C.I. I. Pigment Black 1, C.I. I. Pigment Black 6, C.I. I. Pigment Black 7 and the like.
  • the content of the pigment in the ink of the present invention is in the range of 2 to 10% by mass.
  • the content of the pigment is within the above range, it functions as an inkjet ink, and high-quality image formation is possible while maintaining good ejection properties.
  • the pigment content is preferably in the range of 3-7% by mass.
  • the ink of the present invention optionally contains a pigment dispersant to disperse the pigment.
  • the pigment dispersant is not particularly limited, but a polymer dispersant having an anionic group is preferable, and those having a number average molecular weight in the range of 5000 to 200,000 can be preferably used.
  • pigment dispersant for example, two kinds selected from styrene, styrene derivative, vinylnaphthalene derivative, acrylic acid, acrylic acid derivative, maleic acid, maleic acid derivative, itaconic acid, itaconic acid derivative, fumaric acid, and fumaric acid derivative.
  • examples thereof include block copolymers having a structure derived from the above monomers, random copolymers and salts thereof, polyoxyalkylenes, polyoxyalkylene alkyl ethers and the like.
  • the pigment dispersant preferably has an acryloyl group and an acidic group.
  • the acidic group is preferably added after being neutralized with a neutralizing base.
  • the neutralizing base is not particularly limited, but is preferably an organic base such as ammonia, monoethanolamine, diethanolamine, triethanolamine, and morpholine.
  • the amount of the pigment dispersant added is preferably in the range of 10 to 100% by mass, more preferably in the range of 10 to 40% by mass with respect to the pigment.
  • the pigment has the form of a so-called capsule pigment in which the pigment is coated with the above pigment dispersant.
  • a method of coating the pigment with a pigment dispersant various known methods can be used. For example, a phase inversion emulsification method, an acid analysis method, or a method of dispersing a pigment with a polymerizable surfactant is used therein.
  • a method of supplying a monomer and coating it while polymerizing can be preferably exemplified.
  • the pigment dispersant is dissolved in an organic solvent such as methyl ethyl ketone, the acidic groups in the resin are partially or completely neutralized with a base, and then the pigment and ion-exchanged water are added and dispersed. After that, a method of removing the organic solvent and adding water as needed can be mentioned.
  • the average particle size of the pigment in the dispersed state in the ink is preferably 50 nm or more and less than 200 nm.
  • the particle size of the pigment can be measured by a commercially available particle size measuring device using a dynamic light scattering method, an electrophoresis method, etc., but the measurement by the dynamic light scattering method is simple and the particle size region can be measured. It can be measured accurately.
  • the pigment can be dispersed and used by a disperser together with a pigment dispersant and other additives necessary for various desired purposes.
  • the disperser a conventionally known ball mill, sand mill, line mill, high-pressure homogenizer, or the like can be used. Above all, it is preferable to disperse the pigment with a sand mill because the particle size distribution becomes sharp.
  • the material of the beads used for the sand mill dispersion is not particularly limited, but is preferably zirconia or zircon from the viewpoint of preventing the formation of bead fragments and the contamination of ionic components. Further, the bead diameter is preferably in the range of 0.3 to 3 mm.
  • the ink of the present invention contains an aqueous solvent.
  • the aqueous solvent contains water as an essential solvent, and preferably contains an arbitrarily known aqueous solvent for viscosity adjustment and the like.
  • the aqueous solvent contains an aqueous solvent, it is preferable to adjust the type and amount of the aqueous solvent to be combined with water so that the temperature-responsive polymer has a lower limit critical eutectic temperature with respect to the aqueous solvent.
  • the water contained in the ink according to the present invention is not particularly limited, and may be ion-exchanged water, distilled water, or pure water.
  • an aqueous solvent that does not significantly change the LCST of the temperature-responsive polymer with respect to the water-based solvent from the LCST of the temperature-responsive polymer with respect to water when used in combination with water is preferable.
  • the difference between the LCST of the temperature-responsive polymer with respect to the aqueous solvent and the LCST of the temperature-responsive polymer with respect to water is approximately 10 ° C. or less.
  • aqueous solvent examples include alcohols, polyhydric alcohols, amines, amides, glycol ethers, 1,2-alkanediols having 4 or more carbon atoms, and the like.
  • alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, t-butanol, 3-methoxy-1-butanol, 3-methoxy.
  • examples thereof include -3-methylbutanol, 1-octanol, 2-octanol, n-nonyl alcohol, tridecyl alcohol, n-undecyl alcohol, stearyl alcohol, oleyl alcohol and benzyl alcohol.
  • polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and the number of polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and propylene oxide groups having 5 or more ethylene oxide groups.
  • examples thereof include polypropylene glycol having 4 or more, butylene glycol, hexanediol, pentandiol, glycerin, hexanetriol, thiodiglycol and the like.
  • amines include ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, and the like. Examples thereof include pentamethyldiethylenetriamine and tetramethylpropylenediamine.
  • amides include formamide, N, N-dimethylformamide, N, N-dimethylacetamide and the like.
  • glycol ethers examples include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, and tripropylene glycol monomethyl ether.
  • examples include ether.
  • 1,2-alkanediols having 4 or more carbon atoms examples include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol and the like. ..
  • a particularly preferably used aqueous solvent is a polyhydric alcohol, which can suitably suppress bleeding during high-speed printing.
  • ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol are preferable.
  • the ink can be contained in one type or a combination of two or more types selected from these aqueous solvents.
  • the water content in the ink of the present invention is preferably in the range of 20 to 80% by mass, and more preferably in the range of 40 to 70% by mass with respect to the total mass of the ink.
  • the content of the aqueous solvent in the ink is preferably in the range of 10 to 60% by mass with respect to the total mass of the ink.
  • the content ratio of water and the aqueous solvent in the ink is preferably adjusted so that the LCST of the temperature-responsive polymer with respect to the aqueous solvent is within the range of LCST of ⁇ 10 ° C. with respect to water of the temperature-responsive polymer.
  • the ink of the present invention contains substantially only an aqueous solvent as a solvent, that is, does not contain a non-aqueous solvent.
  • the content of the aqueous solvent in the ink is preferably in the range of 50 to 95% by mass, preferably in the range of 50 to 90% by mass, as the total content of water and the aqueous solvent. Is more preferable.
  • the ink of the present invention can optionally contain a thixotropic agent.
  • the thixotropic agent imparts thixotropy to the ink, which is low viscosity at the time of high share and high viscosity at the time of low share, thereby maintaining good ejection property and high quality image in the ink of the present invention. It is used for the purpose of enhancing the effect of achieving both formation.
  • the thixotropic agent can be used without particular limitation as long as it is a material that can impart thixotropic property to the ink.
  • the thixotropy-imparting agent preferably has a particle shape (however, the particle shape includes a fiber shape), and more preferably has an aspect ratio of 20 or more.
  • the shape is preferably elliptical, scaly, plate-shaped, needle-shaped, fiber or the like.
  • the aspect ratio indicating the ratio of the major axis to the minor axis of the thixotropic agent is preferably 20 or more. When the aspect ratio is 20 or more, the thixotropic property is easily imparted by the ink.
  • the major axis of the thixotropic agent is preferably 2 ⁇ m or less. If the major axis of the thixotropic agent exceeds 2 ⁇ m, the inkjet ejection property may be affected.
  • the measurement cross section of the aspect ratio of the thixo-imparting agent is a cross section parallel to the length direction of the particles and cut in the thickness direction.
  • the aspect ratio is a value obtained from the average particle major axis and the average particle minor axis of each of the 50 particles obtained from the cross section.
  • the minor axis is the thickness of the particle
  • the major axis is the length of the long side of the aspect ratio measurement cross section of the particle, or the long side when the particle is viewed in a plan view. Length or maximum diameter.
  • the major axis is the length of the particle
  • the minor axis is the major axis of the cross section orthogonal to the length direction of the particle, or the maximum width when the particle is viewed in a plan view.
  • Examples of the material of the thixotropy-imparting agent include polysaccharides and inorganic particles.
  • specific examples of the polysaccharide include cellulose, chitin, chitosan, xanthan gum, welan gum, succinoglycan, guar gum, locust bean gum and derivatives thereof, glycomannan, agar, carrageenan and the like.
  • polysaccharide a natural polysaccharide having a weight average molecular weight of about several million is preferable. Specifically, xanthan gum, guar gum, carrageenan and the like are preferable.
  • a tixo-imparting agent as a tixo-imparting agent, conventional methods such as oxidation treatment using a catalyst, mechanical treatment using a grinder, etc., for an aggregate of polysaccharides such as shells of crustaceans such as trees, crabs, and shrimp.
  • Nanofibers which are polysaccharides obtained by finely breaking the fibers by a known method, are preferably used.
  • the polysaccharide in the polysaccharide nanofiber is preferably at least one of cellulose, chitin and chitosan, with cellulose being more preferred.
  • nanofibers have a width of about 1 to 100 nm and an aspect ratio of 100 or more.
  • the length and width of the nanofibers can be measured, for example, using an electron microscope.
  • the width of the nanofiber may be measured, for example, the width in a plan view, or the diameter of a cross section orthogonal to the length direction of the nanofiber may be measured as the width.
  • the average of the maximum widths of each nanofiber is defined as the "width" of the nanofibers.
  • the "length" of nanofibers is the average length of 50 nanofibers.
  • the aspect ratio of the nanofiber is obtained as a value obtained by dividing the length by the width.
  • the width of the nanofibers is preferably 1 to 50 nm, more preferably 1 to 5 nm.
  • the length of the nanofibers is preferably 0.5 to 2 ⁇ m, more preferably 1 to 5 ⁇ m, but is not limited thereto.
  • the aspect ratio of the nanofibers is more preferably in the range of 100 to 400, and even more preferably in the range of 100 to 300.
  • polysaccharides such as cellulose, chitin, and chitosan exist in a state where structural units called microfibrils are bound to each other. These microfibrils have a width of 3 to 4 nm and a length of several ⁇ m (for example, 2 to 5 ⁇ m), but it is difficult to make one by one.
  • microfibrils have a width of 3 to 4 nm and a length of several ⁇ m (for example, 2 to 5 ⁇ m), but it is difficult to make one by one.
  • nanofibers having a width of about 20 to 50 nm.
  • such nanofibers may be used as the polysaccharide nanofibers, but it is more preferable to use TEMPO-oxidized nanofibers which are more finely dissolved by TEMPO oxidation, for example, in microfibril units.
  • TEMPO oxidation is an oxidation reaction catalyzed by 2,2,6,6-tetramethyl-1-piperidine-oxy radical (TEMPO). Oxidation of the polysaccharide aggregate in the presence of TEMPO gives very fine nanofibers equivalent to microfibrils, eg, 3-4 nm wide and several ⁇ m long (eg 2-5 ⁇ m). ..
  • Cellulose nanofibers used as thixotropy-imparting agents are nanofibers of cellulose.
  • Examples of the nano-ferverized cellulose form include powdered cellulose, microcrystalline cellulose and the like.
  • Cellulose nanofibers include Leocrysta (registered trademark) manufactured by Daiichi Kogyo Seiyaku Co., Ltd., TEMPO oxidized cellulose nanofiber manufactured by Nippon Paper Industries, Serempia TC-01A, Serempia TC-02X (“Serenpia” is a registered trademark), and Sugino Machine Limited.
  • IMa-10002, BMa-12002, WMa-12002, AMa-12002, FMa-12002, ELEX- ⁇ , ELEX-S manufactured by Daio Paper Industries, Auro Visco manufactured by Oji Paper Co., Ltd. and the like can be preferably used. ..
  • the inorganic particles particles of various natural or synthetic clay minerals are preferable.
  • the clay mineral smectite clay mineral is preferable.
  • Smectite clay minerals are classified as layered silicate minerals or bentonite stone group minerals.
  • Smectite clay minerals are classified into montmorillonite subgroup and saponite subgroup according to their laminated structure.
  • the montmorillonite subgroup includes montmorillonite, nontronite or byderite.
  • the saponite subgroup includes hectorite, saponite or saponite.
  • the smectite clay mineral may be a natural product or a synthetic product.
  • the smectite clay mineral is a layered substance in which plate-like bodies are laminated, and when used as a thixotropy-imparting agent, it is usually used as delaminated plate-like particles.
  • the smectite clay mineral is a synthetic product, it has a smaller aspect ratio and a lower impurity content than the natural product.
  • the plate-like particles of smectite clay mineral are preferably in the range of 0.2 to 3.0 nm in thickness and preferably in the range of 10 to 150 nm in length.
  • the plate-like particles have a thickness in the range of 0.2 to 2.0 nm, and more preferably a length in the range of 10 to 125 nm.
  • the aspect ratio is a value obtained by dividing the length of the plate-like particles by the thickness, and is preferably 20 or more. The aspect ratio is more preferably in the range of 20 to 200.
  • the length and thickness of the plate-shaped particles can be measured using, for example, an electron microscope.
  • the thickness of the plate-shaped particles is, for example, an average value of 50 pieces of the thickness of the plate-shaped particles measured in a predetermined cross section.
  • the "length" of the plate-shaped particles is an average value of 50 lengths measured as the maximum diameter when the plate-shaped particles are viewed in a plan view.
  • the aspect ratio of the plate-shaped particles is obtained as a value obtained by dividing the length by the thickness.
  • smectite clay mineral for example, laponite (manufactured by Big Chemie), which is a synthetic layered silicate, can be used.
  • Laponite is a synthetic low-charge clay whose structure and chemical composition are close to those of Hectorite, a natural smectite clay mineral.
  • the main particles of raponite are in the form of discs with a maximum diameter of 30 nm and a thickness of 1 nm.
  • a commercially available product may be used as the smectite clay mineral.
  • Examples of commercially available products include Laponite RD (manufactured by Big Chemie), Kunipia F, which is a refined bentonite manufactured by Kunimie Industries, Ltd., and Kunipia G.
  • alumina nanofibers manufactured by Kawaken Fine Chemical Co., Ltd. (minor axis: 4 nm and major axis: 1400 nm), which are nanofibers, may be used.
  • the content of the thiox property-imparting agent in the ink of the present invention shall be in the range of 0.01 to 1% by mass with respect to the total amount of the ink from the viewpoint of imparting texo property to the ink and further enhancing the effect of the present invention. Is preferable, and more preferably in the range of 0.08 to 0.5% by mass.
  • the thixotropy-imparting agent is preferably made of two or more kinds of materials. Further, one of the two or more materials is preferably a smectite clay mineral.
  • Preferred combinations of thixotropy-imparting agents include a combination of cellulose nanofibers and smectite clay minerals, and a combination of xanthan gum and smectite clay minerals. In particular, a combination of cellulose nanofibers and smectite clay minerals is preferable.
  • Cellulose nanofibers and smectite clay minerals even when used alone, impart elastic properties to the ink by forming a specific gel structure, for example, with an ink drying rate of 20%. It is thought that it can be done. As a result, the ink containing cellulose nanofibers or smectite clay mineral can easily achieve the properties (1-4) and (1-5) described later. Further, it is preferable to use a combination of cellulose nanofibers and smectite clay minerals because the above elastic properties are further enhanced.
  • the ratio of smectite clay mineral to other thixotropy can be selected according to the ink viscosity and thixotropy, but the ratio of smectite clay mineral: other thixotropy is 10: 1 to 1: 1 by mass ratio. It can be adjusted in the range of 10. By combining them, the thixotropy of the ink is greatly improved and the image quality is improved as compared with adding each of them alone. The reason for the improvement in thixotropy is presumed, but it is considered that smectite clay minerals have an electric charge, and smectite clay minerals and other thixotropy-imparting agents electrically associate to form a structure.
  • the ink can optionally contain a surfactant. As a result, it is possible to improve the ejection stability of the ink and control the spread (dot diameter) of the droplets that have landed on the base material.
  • the surfactant can be used without particular limitation as long as the effect of the present invention is not impaired.
  • the ionicity of the surfactant is preferably anionic, nonionic or betaine type.
  • a fluorine-based or silicone-based surfactant having a high ability to reduce static surface tension or an anionic surfactant such as dioctyl sulfosuccinate having a high ability to reduce dynamic surface tension, relatively low.
  • Nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, acetylene glycols, pluronic (registered trademark) type surfactants, and sorbitan derivatives having a molecular weight are preferably used. It is also preferable to use a fluorine-based or silicone-based surfactant in combination with a surfactant having a high ability to reduce dynamic surface tension.
  • ink is mixed with a base material made of various hydrophobic resins such as vinyl chloride sheet and a base material with slow absorption such as printing paper. Can be further suppressed, and a high-quality printed image can be obtained.
  • the silicone-based surfactant is preferably a polyether-modified polysiloxane compound, and examples thereof include KF-351A and KF-642 manufactured by Shin-Etsu Chemical Co., Ltd. and BYK345, BYK347 and BYK348 manufactured by Big Chemie.
  • the above-mentioned fluorine-based surfactant means one in which a part or all of the hydrogen bonded to the carbon of the hydrophobic group of the ordinary surfactant is replaced with fluorine. Of these, those having a perfluoroalkyl group in the molecule are preferable.
  • fluorine-based surfactants some of them are under the trade name of Megafac F from Dainippon Ink and Chemicals Co., Ltd. and the trade name of Surflon from Asahi Glass Co., Ltd. -Manufacturing Company under the trade name of Flurad FC, Imperial Chemical Industry under the trade name of Monflor, and EI Dupont Nemeras & Company under the trade name of Zonyls. It is commercially available under the trade name of Licowet VPF from Parkberke Hext.
  • the content of the surfactant in the ink is not particularly limited, but is preferably in the range of 0.1 to 5.0% by mass.
  • the ink of the present invention includes emission stability, print head and ink cartridge compatibility, storage stability, image storage property, and the like, as necessary, as long as the effects of the present invention are not impaired.
  • Various known additives such as viscosity modifiers, specific resistance modifiers, film-forming agents, UV absorbers, antioxidants, anti-fading agents, anti-corrosion agents, and anti-corrosion agents, depending on the purpose of improving various performances. Etc. can be appropriately selected and used.
  • liquid paraffin dioctylphthalate, tricresyl phosphate, oil droplet fine particles such as silicone oil
  • JP-A-57-74193 JP-A-57-87988, JP-A-62-261476 and the like.
  • UV absorbers JP-A-57-74192, JP-A-57-87989, JP-A-60-72785, JP-A-61-146591, JP-A-1-95091, JP-A-3-13376, etc.
  • the ink is prepared by mixing each of the above components so as to have the above content.
  • the pigment is mixed with other components as a dispersion liquid dispersed in a part of the aqueous solvent by the pigment dispersant.
  • the fixing resin is contained, it is preferable that the fixing resin is mixed with other components as a dispersion liquid dispersed in a part of an aqueous solvent by using a surfactant added as needed.
  • the inkjet ink of the present invention preferably satisfies the following conditions (1-1) and (1-2) with respect to viscosity characteristics. Further, in addition to these, it is more preferable to satisfy the condition (1-3).
  • the viscosity at a shear rate of 1000 (1 / s) at 25 ° C. is 15 mPa ⁇ s or less.
  • (1-2) Temperature response The viscosity of the polymer at a shear rate of 1 (1 / s) at any temperature within the range of the lower limit critical eutectic temperature of ⁇ 10 ° C. with water is 45 mPa ⁇ s or more. That is, the maximum viscosity of the temperature-responsive polymer at a shear rate of 1 (1 / s) within the range of the lower limit critical eutectic temperature of ⁇ 10 ° C. is 45 mPa ⁇ s or more.
  • the viscosity in (1-1) to (1-3) above can be measured with a rotary viscometer.
  • the rotary viscometer include MCR-102 manufactured by Anton Pearl Co., Ltd.
  • the viscosity indicates the viscosity measured at 25 ° C.
  • the ink drying rate of 20% represents a state in which the aqueous solvent is removed from the inkjet ink so that the mass is 80% of the initial mass.
  • the ink drying rate can be calculated by the following formula (A) from the mass before and after drying when the ink is dried under the temperature condition of 60 ° C.
  • Ink drying rate [%] (W BEFORE- W AFTER ) / W BEFORE x 100
  • W BEFORE represents the mass (initial mass) of the ink before drying.
  • W AFTER represents the mass of the ink after drying. Specifically, about 100 mL of ink is dropped on a glass substrate, weighed to determine the mass of the ink before drying, and then heated to 60 ° C. on a hot plate capable of measuring the mass. Do it with.
  • the ink of the present invention has a viscosity of 10 mPa ⁇ s or less at a shear rate of 1000 (1 / s).
  • the lower limit of the viscosity at a shear rate of 1000 (1 / s) is not particularly limited, but is preferably about 5 mPa ⁇ s from the viewpoint of inkjet ejection property.
  • the ink of the present invention has a viscosity at a shear rate of 1 (1 / s) at any temperature in the range of the lower limit critical eutectic temperature ⁇ 10 ° C. of the temperature-responsive polymer with water. It is more preferably 70 mPa ⁇ s or more, and more preferably 100 mPa ⁇ s or more.
  • the upper limit of the viscosity in this case is not particularly limited, but it is preferably about 1000 mPa ⁇ s from the viewpoint of ease of head maintenance.
  • the ink of the present invention has a shear rate of 1 (1) at any temperature in the range of the lower limit critical eutectic temperature ⁇ 10 ° C. of the temperature-responsive polymer at an ink drying rate of 20% with water.
  • the viscosity at / s) is preferably 100 mPa ⁇ s or more, and more preferably 150 mPa ⁇ s or more.
  • the upper limit of the viscosity in this case is not particularly limited, but it is preferably about 1000 mPa ⁇ s from the viewpoint of ease of head maintenance.
  • the viscosity of the temperature-responsive polymer at a shear rate of 1 (1 / s) at any temperature in the range of the lower limit critical coexistence temperature ⁇ 10 ° C. with respect to water is at least 45 mPa ⁇ s.
  • the viscosity of the ink increases as the ink drying rate increases.
  • the temperature-responsive polymer can be at any temperature within the lower limit critical eutectic temperature of ⁇ 10 ° C. with water.
  • a viscosity of 100 mPa ⁇ s can be achieved at a shear rate of 1 (1 / s).
  • the inkjet ink of the present invention further preferably satisfies at least one of the following conditions (1-4) and (1-5), and more preferably both.
  • the loss tangent (tan ⁇ ) in (1-4) and the storage elastic modulus and loss elastic modulus in (1-5) can be measured by a rheometer (viscoelasticity measuring device).
  • a rheometer viscoelasticity measuring device
  • the loss tangent may be simply referred to as “tan ⁇ ”.
  • the tan ⁇ , the storage modulus and the loss modulus are determined by using a rheometer, specifically, using MCR-102 manufactured by Anton Pearl Co., Ltd., in an oscillation mode, with respect to water of the temperature-responsive polymer. It can be measured at any temperature in the range of the lower limit critical eutectic temperature ⁇ 10 ° C. under the measurement conditions of an angular frequency ⁇ 10 rad / s and a swing angle ⁇ 1 to 1000%.
  • the swing angle ⁇ of the cone plate of the rheometer is changed to distort the measurement sample.
  • the measurement sample is distorted following the swing angle ⁇ , the swing angle ⁇ of the cone plate and the distortion of the measurement sample have the same value.
  • tan ⁇ when the strain is 1% is used as an index. If the tan ⁇ is less than 1 when the strain is 1% under the measurement conditions, the ink has more elastic properties, and when compared with similar viscosities, the pinning property is improved and the image quality is further improved. .. In (1-4), the tan ⁇ at 1% strain is more preferably 0.8 or less, and further preferably 0.6 or less.
  • the crossover strain of the storage elastic modulus and the loss elastic modulus when the strain is changed is used as an index.
  • the crossover strain is a graph in which the vertical axis is the storage elastic modulus (Pa) and the horizontal axis is the strain (%) in logarithms, the vertical axis is the loss modulus (Pa), and the horizontal axis is the horizontal axis.
  • the value (%) of the strain at the intersection of the graphs in which the strain (%) is logarithmically shown is shown.
  • the crossover strain is more preferably 30% or more, and even more preferably 40% or more.
  • the loss tangent (tan ⁇ ) at a strain of 1% when the same measurement is performed for the ink of the present invention that is, the ink drying rate of 0%, not the state of the ink drying rate of 20%.
  • the crossover strain is 20% or more when the same measurement is performed for the ink of the present invention, that is, the ink drying rate is 0%, not the state where the ink drying rate is 20%. It is preferably 30% or more, more preferably 40% or more.
  • the tan ⁇ and the crossover strain are almost the same between the state where the ink drying rate is 0% and the state where the ink drying rate is 20%. That is, even when the ink drying rate is 0%, the ink has an elastic behavior within the range of the lower limit critical eutectic temperature ⁇ 10 ° C. with respect to water of the temperature-responsive polymer, and it is easy to pinn and a high-quality image can be formed.
  • the image forming method of the present invention has the following features in an image forming method having a landing step of ejecting droplets of inkjet ink from an inkjet head provided with an ink circulation mechanism and landing them on a substrate.
  • the inkjet ink contains an aqueous solvent, a pigment and a thixotropic agent, and is circulated in the inkjet head so that the viscosity is 15 mPa ⁇ s or less.
  • (2-2) Perform the landing step so that the mass reduction rate from the inkjet ink is within 20% and the viscosity of the droplets when they land on the substrate or immediately after landing is 100 mPa ⁇ s or more. conduct.
  • the image forming method of the present invention usually includes a drying step of removing the aqueous solvent from the ink droplets on the substrate after the landing step. By going through the drying step, a desired image is formed on the base material. Further, the image forming method of the present invention may include a step of forming a primer layer on the surface of the base material (hereinafter, also referred to as a "primer layer forming step") before forming a coating film with the ink. good. In this case, the ink droplets are landed on the primer layer in the landing step.
  • the primer layer can be formed by applying a primer ink containing a resin and a solvent onto a substrate and drying the primer layer. Alternatively, it may be formed by applying a primer ink containing an active energy polymerization type compound and a polymerization initiator and irradiating the coating film with active energy.
  • the method of applying the primer ink is not particularly limited, and any method such as a roll coating method, a spin coating method, a spray coating method, a dipping method, a screen printing method, an inkjet method, a gravure printing method, and an offset printing method may be used. .. Among these, when the surface roughness of the base material is finely controlled, the screen printing method or the inkjet method is preferable, and the inkjet method is particularly preferable.
  • the method of curing or drying the coating film after applying the primer ink is appropriately selected according to the type of the primer ink, and can be, for example, a method of heating or irradiating with active energy.
  • the ink in the head is 15 mPa ⁇ s or less, the ink can be smoothly circulated in the head and discharged from the head.
  • the viscosity of the ink in the head is preferably circulated so as to be 10 mPa ⁇ s or less.
  • the mass reduction rate from the inkjet ink (hereinafter, also simply referred to as “mass reduction rate”) can be defined in the same manner as the ink drying rate described above. If the mass reduction rate and the viscosity of the ink droplets when landing on the substrate or immediately after landing are within the above ranges, good pinning is possible and the obtained image can be of high quality. Further, the sticking of solid ink around the head is suppressed, ejection defects are less likely to occur, and maintenance is easy.
  • the term "immediately after landing” means, for example, within 100 msec after the ink droplets land on the base material. If the mass reduction rate of the ink droplets within 100 msec after landing on the substrate is within 20% and the viscosity is 100 mPa ⁇ s or more, the above effect is sufficiently exhibited.
  • the time when the base material is landed or immediately after the landing is also referred to as "the time when the base material is landed”.
  • the viscosity of the ink droplet at the time of landing on the substrate is preferably 150 mPa ⁇ s or more, more preferably 200 mPa ⁇ s or more, and even more preferably 300 mPa ⁇ s or more.
  • the transport speed of the base material is high (100 m / min), it is within 30 msec, and when it is 50 m / min, etc., it is within 100 msec.
  • an ink or an apparatus is appropriately selected in order to satisfy the above conditions (2-1) and (2-2).
  • the conditions (2-1) and (2-2) can be achieved without particularly changing the apparatus. That is, in the image forming method of the present invention, it is preferable to use the ink of the present invention.
  • the condition (2-2) can be achieved within the range of LCST ⁇ 10 ° C. of the temperature-responsive polymer.
  • the ink droplets are heated on the substrate within the range of LCST ⁇ 10 ° C. of the temperature-responsive polymer in the landing step. Is preferable.
  • the image forming method of the present invention in order to satisfy the condition (2-2), it is preferable to heat the ink droplets on the substrate in the range of 30 to 60 ° C. in the landing step. That is, in the image forming method of the present invention, in order to ensure that the state of the ink droplets at the time of landing on the base material has a mass reduction rate of 20% or less and a viscosity of 100 mPa ⁇ s or more, if necessary. It may have a step of heating the ink droplets at 30-60 ° C. The temperature is sufficiently low, and there is almost no concern that ink will stick around the head and cause ejection failure.
  • Heating may be performed using a non-contact heating type device such as a constant temperature furnace or a hot air blower, or may be performed using a contact heating type device such as a hot plate or a heat roller. ..
  • the heating temperature is (a) an atmospheric temperature such as a furnace temperature or a hot air temperature, and (b) a hot plate, a hot roller, etc.
  • a contact heating type device such as the above is used, it can be obtained by measuring either the temperature of the contact heating part or (c) the surface temperature of the ink droplets, and the measurement location. (C) It is more preferable to measure the surface temperature of the ink droplets.
  • drying process components other than solid components such as an aqueous solvent (hereinafter, also referred to as “volatile components”) are removed from the ink droplets after the landing step, and a primer is used on the substrate or when a primer layer is provided.
  • a primer is used on the substrate or when a primer layer is provided.
  • the mass reduction rate of the ink droplets after the landing step is within 20%. Since the inkjet ink contains, for example, about 50 to 95% by mass of an aqueous solvent, the remaining volatile components including the aqueous solvent are removed by a drying step.
  • the drying step it is preferable to perform drying under conditions where the fixing resin is not completely fused when the ink contains a fixing resin while removing volatile components.
  • the drying temperature is preferably in the range of, for example, 60 to 110 ° C.
  • the drying time is preferably in the range of, for example, 5 to 60 seconds.
  • the drying in the drying step can be performed by, for example, the same method as the heating in the landing step.
  • the base material that can be used in the present invention is not particularly limited, but is preferably a non-absorbent base material. By using a non-absorbent base material, the effect of the image forming method of the present invention is more remarkable.
  • the non-absorbable means non-absorbable to water.
  • non-water-absorbent base material a known plastic film can be used.
  • plastic films such as polyethylene terephthalate, polyethylene films, polypropylene films, polyamide films such as nylon, polystyrene films, polyvinyl chloride films, polycarbonate films, polyacrylonitrile films, and biodegradable films such as polylactic acid films.
  • polyester films such as polyethylene terephthalate, polyethylene films, polypropylene films, polyamide films such as nylon, polystyrene films, polyvinyl chloride films, polycarbonate films, polyacrylonitrile films, and biodegradable films such as polylactic acid films.
  • a film coated with polyvinylidene chloride on one side or both sides of the film, or a film on which a metal oxide is vapor-deposited can also be preferably used.
  • the non-water-absorbent film can be preferably used as an unstretched film or a stretched film.
  • a base material made of an inorganic compound such as a metal or glass can be mentioned.
  • the packaging material for retort pouch foods can also be suitably used as a packaging material for retort foods in which a thermosetting resin is provided as a coating layer on a metal base material.
  • the packaging material for retort pouch foods blocks air, moisture, and light and seals the food inside. Therefore, for example, polypropylene on the food side and polyester on the outside block air, moisture, and light, and inside. It is composed of a film in which a thermoplastic resin layer and an aluminum foil layer for sealing foods are laminated (laminated).
  • the thickness of the base material is preferably in the range of 10 to 120 ⁇ m, more preferably 12 to 60 ⁇ m.
  • the image forming method of the present invention is applied to image forming using an inkjet head provided with an ink circulation mechanism.
  • the inkjet head is not particularly limited as long as it has an ink circulation mechanism, and may be either an on-demand type or a continuous type inkjet head.
  • on-demand inkjet heads include electro-mechanical conversion methods including single cavity type, double cavity type, bender type, piston type, shared mode type and shared wall type, and thermal inkjet type and bubble jet ( "Bubble jet” includes an electric-heat conversion method including a registered trademark of Canon Inc.).
  • the inkjet head uses a piezoelectric element as the electric-mechanical conversion element used in the electric-mechanical conversion method (also referred to as “piezo-type inkjet head").
  • the inkjet head may be either a scan type or a line type inkjet head, but a line type is preferable.
  • a line-type inkjet head is an inkjet head that has a length greater than or equal to the width of the printing range.
  • the line-type inkjet head one head may be used that is equal to or larger than the width of the print range, or a plurality of heads may be combined so as to be equal to or larger than the width of the print range.
  • a plurality of heads may be arranged side by side so that the nozzles of each head are arranged in a staggered manner to increase the resolution of these heads as a whole.
  • the inkjet head used in the image forming method of the present invention communicates with a pressure chamber in which inkjet ink is injected via an injection path, a pressure generating means for causing pressure fluctuation in the pressure chamber, and the pressure chamber.
  • a nozzle that serves as a flow path for the inkjet ink discharged from the pressure chamber to the outside due to a pressure fluctuation in the chamber communicates with the pressure chamber, and the inkjet ink inside the nozzle is discharged and returned to the injection path. It is preferable to provide two or more circulation paths.
  • Such an inkjet head will be described below with reference to the drawings.
  • FIG. 1 is a schematic configuration diagram of a main part showing an inkjet image forming apparatus 100 including an example of an inkjet head that can be used in the image forming method of the present invention, and shows the inkjet head 1 in a partial cross section.
  • the inkjet head and the like shown in FIG. 1 are examples, and the inkjet head and the like to which the image forming method of the present invention can be applied are not limited thereto.
  • the inkjet image forming apparatus 100 ejects ink droplets from the inkjet head 1 and lands them on a base material 109 conveyed in a certain direction (sub-scanning direction) by the conveying means 108, and dries the droplets. Form an image.
  • the inkjet head 1 is fixedly arranged, and in the process of transporting the base material 109, ink droplets are ejected from the nozzle 22 toward the base material 109 and landed on the base material. Form an image.
  • the inkjet head 1 is mounted on the carriage mechanism 107, and in the process of being reciprocated in the main scanning direction by the carriage mechanism 107, ink is ink from the nozzle 22 toward the base material 109. Droplets are ejected and landed on a substrate to form an image.
  • the transport means 108 and the carriage mechanism 107 are driven and controlled by the control unit 104.
  • the inkjet image forming apparatus 100 has a non-contact heating type or contact heating type heater that adjusts the temperature of ink droplets at the time of landing.
  • the heater can also be used when performing the drying step.
  • the inkjet image forming apparatus 100 is used for inks of various colors such as yellow (Y), magenta (M), cyan (C), and black (K).
  • a plurality of inkjet heads 1 are mounted.
  • the ink tank 101 for storing ink and the common ink chamber 41 of the inkjet head 1 are communicated with each other by an ink transfer tube 102 as a transfer path and an ink return tube 103 as a recovery path.
  • a transfer pump 105a which is driven and controlled by the control unit 104 of the inkjet image forming apparatus 100, is provided in the middle of the ink transfer tube 102. By driving the transfer pump 105a, the ink in the ink tank 101 is transferred to the inkjet head 1 via the ink transfer tube 102.
  • a transfer side sub tank 111a is provided in the middle of the ink transfer tube 102.
  • the transfer-side sub-tank 111a is configured as a buffer space in which ink transferred to the inkjet head 1 is temporarily stored.
  • the pressure of the ink in the ink transfer tube 102 can be controlled by the transfer pressure control pump 110a constituting the pressure control means via the transfer side sub tank 111a.
  • the transfer pressure control pump 110a is controlled by the control unit 104a in the inkjet head 1.
  • a return pump 105b which is driven and controlled by the control unit 104, is provided in the middle of the ink return pipe 103. By driving the return pump 105b, the ink in the inkjet head 1 is returned to the ink tank 101 via the ink return tube 103.
  • a return side sub tank 111b is provided in the middle of the ink return pipe 103.
  • the return-side sub-tank 111b is configured as a buffer space in which the ink returned from the inkjet head 1 is temporarily stored.
  • the pressure of the ink in the ink return pipe 103 can be controlled by the return pressure control pump 110b constituting the pressure control means via the return side sub tank 111b.
  • the return pressure control pump 110b is controlled by the control unit 104a in the inkjet head 1.
  • the pressure control means is not limited to the one composed of the transfer pressure control pump 110a and the return pressure control pump 110b, and may be composed of any of these.
  • the return pressure control pump 110b serves as the first pressure control means
  • the transfer pressure control pump 110a serves as the second pressure control means.
  • the ink tank 101 is not particularly limited, but it is preferable that the ink tank 101 is divided into an ink transfer chamber 101b and an ink return chamber 101c by a partition plate 101a that does not reach the bottom surface of the tank.
  • one end of the ink transfer tube 102 is arranged in the ink transfer chamber 101b, and one end of the ink return tube 103 is arranged in the ink return chamber 101c.
  • the partition plate 101a is provided to sufficiently degas the ink so that the bubbles contained in the ink returned to the ink return chamber 101c do not flow into the ink transfer tube 102 again. Since the bubbles themselves have high buoyancy, it is possible to prevent the bubbles from passing under the partition plate 101a and flowing into the ink transfer chamber 101b.
  • Such an embodiment is a preferred embodiment when the ink is used in a circulating manner.
  • the inkjet head 1 includes an ink manifold 4 constituting a common ink chamber 41, a wiring board 3 bonded to the ink manifold 4, a head chip 2 bonded to a lower surface portion of the wiring board 3, and a lower surface of the head chip 2. It is configured to have a nozzle plate 21 adhered to the portion.
  • the ink manifold 4 is formed of a synthetic resin material or the like in a horizontally long box shape having an opening 4a on the lower surface. In the ink manifold 4, the opening 4a is closed by a wiring board 3 adhered to a lower surface portion.
  • the internal space of the ink manifold 4 serves as a common ink chamber 41 in which the ink transferred from the ink tank 101 is stored.
  • the wiring board 3 is, for example, a glass substrate.
  • the wiring board 3 is formed with a wiring pattern (not shown) connected to a power supply circuit (not shown) via an FPC board.
  • an ink supply pipe 5a serving as a flow path for supplying ink into the common ink chamber 41 is continuously provided.
  • the ink supply pipe 5a communicates with the common ink chamber 41 on the side (upper side) far from the wiring board 3.
  • a connecting portion 7a is provided on the upper end side of the ink supply tube 5a.
  • the connection portion 7a is detachably connected to the connection portion 106a on the inkjet image forming apparatus 100 side.
  • the connection portion 106a on the inkjet image forming apparatus 100 side communicates with the ink transfer tube 102.
  • an ink recovery tube 5b that serves as a flow path for collecting ink from the common ink chamber 41 is continuously provided.
  • the ink recovery tube 5b communicates with the common ink chamber 41 on the side (upper side) far from the wiring board 3.
  • a connecting portion 7b is provided on the upper end side of the ink recovery tube 5b.
  • the connecting portion 7b is detachably connected to the connecting portion 106b on the inkjet image forming apparatus 100 side.
  • the connection portion 106b on the inkjet image forming apparatus 100 side communicates with the ink return tube 103.
  • the inkjet head 1 can collect the ink from the common ink chamber 41 and return the ink to the ink tank 101.
  • the flow path from the ink supply tube 5a to the buffer space 6 in the middle of the ink recovery tube 5b is the main flow path F1.
  • FIG. 2 is an enlarged cross-sectional view of the head chip 2 of the inkjet head 1.
  • FIG. 3 is a plan view of the nozzle plate 21 of the inkjet head 1.
  • a plurality of ink channels (pressure chambers) 23 and a plurality of dummy channels (pseudo pressure chambers) 25 are formed on the head chip 2.
  • Each ink channel 23 and each dummy channel 25 are through holes formed from the upper surface portion to the lower surface portion of the head chip 2.
  • the upper end of each ink channel 23 communicates with the common ink chamber 41 via an injection hole 31a provided in the wiring board 3.
  • Each ink channel 23 is filled with ink flowing in from the injection hole 31a by the potential energy of the ink in the ink tank 101 and the pressure controlled by the transfer pressure control pump 110a due to the transfer pump 105a.
  • each ink channel 23 communicates outward (downward) via the nozzle 22.
  • the inside of the nozzle 22 is inside the ink channel 23.
  • the inside of the nozzle 22 is inside the communication passage.
  • the upper end of each dummy channel 25 is closed by the wiring board 3, and the lower end is closed by the nozzle plate 21 to form a closed air chamber.
  • Each ink channel 23 and each dummy channel 25 are arranged in one direction (in the direction of arrow X in FIG. 2) to form a channel sequence.
  • Both wall portions (partition wall between the ink channel 23 and the dummy channel 25) of each ink channel 23 are composed of a pair of piezoelectric elements (driving walls) 24 and 24 that serve as pressure generating means.
  • the piezoelectric elements 24, 24 are sheared and deformed by applying a voltage from a power supply circuit (not shown) through the wiring patterns of the FPC substrate and the wiring substrate 3.
  • the piezoelectric elements 24, 24 forming both walls of the ink channel 23 are sheared and deformed, so that the pressure of the ink channel 23 fluctuates (decompression due to expansion or pressure increase due to contraction). Due to the pressure fluctuation (depressurization or pressure increase) of the ink channel 23, pressure is applied to the ink inside the nozzle 22, that is, in the ink channel 23, and this ink is ejected through the nozzle 22.
  • each ink channel 23 Two piezoelectric elements 24 and 24 are provided for each ink channel 23, forming both wall portions of each ink channel 23. There is a gap between the piezoelectric element 24 forming the wall portion of one ink channel 23 and the piezoelectric element 24 forming the wall portion of the adjacent ink channel 23, and this gap is the dummy channel 25. Therefore, each ink channel 23 can be driven (decompressed or increased in pressure) independently.
  • An introduction path 425 is formed in the head tip 2.
  • the introduction path 425 is provided so as to be located outside the channel row on one end side of the channel row formed by each ink channel 23 and each dummy channel 25.
  • the introduction path 425 is a through hole formed from the upper surface portion to the lower surface portion of the head chip 2, and the cross-sectional opening area is larger than the cross-sectional opening area of one ink channel 23.
  • the introduction path 425 communicates with the common ink chamber 41 through an introduction hole 31c whose upper end is provided in the wiring board 3, and the transfer pressure is controlled due to the potential energy of the ink in the ink tank 101 and the transfer pump 105a. Ink flows in through the introduction hole 31c by the pressure controlled by the pump 110a.
  • a plurality of nozzles 22 corresponding to each ink channel 23 are bored in the flat plate-shaped nozzle plate 21 adhered to the lower surface of the head chip 2.
  • the nozzle 22 is a through hole that allows the ink channel 23 to communicate with the outside.
  • the ink in each ink channel 23 is subjected to ejection pressure by the action of the piezoelectric element 24, and is ejected toward the external (lower) base material through the nozzle 22. That is, the nozzle 22 serves as a flow path for ink discharged from the inside of each ink channel 23 to the outside (downward).
  • the lower surface of the nozzle plate 21 is the ink ejection surface 1S.
  • the inkjet head 1 is provided with a nozzle circulation mechanism that discharges the ink injected into the ink channel 23 from the vicinity of the nozzle 22 and returns it to the injection path to the ink channel 23.
  • Two individual ink circulation paths 26a and 26a are communicated with each ink channel 23, respectively.
  • the individual ink circulation paths 26a and 26a communicate with the ink channel 23 at both ends in the longitudinal direction of the cross section of the ink channel 23. Since air bubbles often remain in the vicinity of both ends of the ink channel 23, it is preferable to provide the individual ink circulation paths 26a and 26a at both ends of the ink channel 23 in the longitudinal direction of the cross section.
  • the individual ink circulation paths 26a and 26a may communicate with the ink channel 23 at any position of the ink channel 23.
  • the number of individual ink circulation paths 26a for one ink channel 23 may be increased or decreased, but it is preferably two or more.
  • Thixotropy occurs in inks to which a temperature-responsive polymer or fixing resin is added, but if there are two or more circulation paths as described above, ink retention is unlikely to occur even if such inks are used, and nozzles It has the effect of easily removing nearby bubbles.
  • the individual ink circulation paths 26a and 26a are formed by closing a flow path forming groove 28 formed on the upper surface of the nozzle plate 21 with a start end in the vicinity of the nozzle 22 by the lower surface of the head tip 2. Has been done.
  • Two introduction grooves 425a and 425a are communicated with the introduction path 425.
  • the introduction grooves 425a and 425a communicate with the introduction path 425 at both sides of the introduction path 425.
  • the introduction grooves 425a and 425a may communicate with the introduction path 425 at any position on the introduction path 425. Further, the number of introduction grooves 425a and 425a for one introduction path 425 may be increased or decreased.
  • the introduction grooves 425a and 425a are formed on the upper surface of the nozzle plate 21 with a start end in the vicinity of the introduction path 425, and are closed by the lower surface of the head tip 2 to form a flow path.
  • a common ink circulation path 421 is formed on the lower surface of the head chip 2.
  • the common ink circulation path 421 is formed by abutting a groove formed on the lower surface portion of the head chip 2 and a groove 422 formed on the upper surface portion of the nozzle plate 21.
  • the common ink circulation path 421 is composed of a plurality of flow paths formed in the direction of the channel row (X direction).
  • the individual ink circulation paths 26a and 26a communicating with the ink channels 23 are joined by communicating with the common ink circulation path 421. Due to the pressure difference between each ink channel 23 and the common ink circulation path 421, ink flows from each ink channel 23 to the common ink circulation path 421. Further, the introduction grooves 425a and 425a communicate with the common ink circulation path 421. Due to the pressure difference between the introduction path 425 and the common ink circulation path 421, ink flows from the introduction path 425 to the common ink circulation path 421. Then, these flows merge to generate ink flow in the common ink circulation path 421.
  • the other end side of the common ink circulation path 421 communicates with the lower end of the discharge channel 424 formed in the head chip 2.
  • the discharge channel 424 is provided so as to be located outside the channel row on the other end side of the channel row formed by each ink channel 23 and each dummy channel 25. Since the ink flow rate in the discharge channel 424 is larger than the ink flow rate in the introduction path 425 by the amount of ink merging through each ink channel 23, the ink flow rate crosses the discharge channel 424 in order not to increase the flow path resistance. Increase the surface opening area.
  • the ink discharged from the individual ink circulation path 26a communicating with the ink channel 23, which is the pressure chamber, to the common ink circulation path 421 reaches the buffer space 6 via the discharge channel 424, the ink discharge chamber 412, and the ink discharge pipe 5c. Further, it is returned to the ink tank 101 by the above route. Then, it is introduced into the injection path to the ink channel 23 again.
  • an ink discharge chamber 412 is provided in the ink manifold 4 located above the discharge channel 424.
  • the ink discharge chamber 412 is provided adjacent to the common ink chamber 41 in the ink manifold 4.
  • the ink discharge chamber 412 is separated from the common ink chamber 41 by a partition wall 45.
  • the partition wall 45 can be integrally formed with the ink manifold 4.
  • An ink discharge pipe 5c forming a flow path for discharging ink from the inside of the ink discharge chamber 412 is connected to the ink discharge chamber 412 via a circulation path connecting portion 5d.
  • the circulation path connecting portion 5d is located above the discharge channel 424 and is located outside the channel row on the other end side of the channel row formed by each ink channel 23 and each dummy channel 25. ..
  • the upper end side of the ink discharge tube 5c joins the ink recovery tube 5b.
  • the ink recovery pipe 5b and the ink discharge pipe 5c are joined by being connected to the buffer space portion 6.
  • the introduction path 425 and the individual ink circulation paths 26a and 26a reach the buffer space 6 via the common ink circulation path 421, the discharge channel 424, the discharge hole 31b, the ink discharge chamber 412, and the ink discharge pipe 5c.
  • the flow path becomes the circulation path 423.
  • the circulation path 423 is a flow path that communicates with the introduction path 425 and the ink channel 23, discharges the ink in the introduction path 425 and the ink channel 23, and joins the ink recovery tube 5b in the buffer space 6.
  • the circulation path 423 discharges ink from the individual ink circulation paths 26a and 26a in the vicinity of the nozzle 22 and returns this ink to the injection path to the ink channel 23, it is necessary to limit the route in the middle. No. Then, through the introduction hole 31c and each injection hole 31a, up to the circulation path 423 becomes the sub-flow path F2.
  • the pigment dispersion liquid obtained above and each of the above components were mixed so as to have the composition shown in Table I or Table II, and the obtained mixed liquid was filtered through a 1 ⁇ m filter to obtain an inkjet ink.
  • the content (mass%) of each component indicates the content of the solid content contained in the component when a dispersion liquid or a solution is used as the component.
  • the content of the polyester resin itself excluding the amount of water as a dispersion medium is 5.0% by mass.
  • blanks in the composition column of Table I or Table II indicate that the component is not contained.
  • LCST + 5 ° C means LCST + 5 ° C with respect to water of the temperature-responsive polymer contained in each ink.
  • the measurement temperature was set to 60 ° C. instead of LCST + 5 ° C.
  • (A2) if the viscosity at a shear rate of 1 (1 / s) at LCST + 5 ° C. is 45 mPa ⁇ s or more, the above condition (1-2) is satisfied.
  • (A3) if the viscosity at a shear rate of 1 (1 / s) at an ink drying rate of 20% is 100 mPa ⁇ s or more, the above condition (1-3) is satisfied.
  • FIG. 4 shows the loss tangent (tan ⁇ ), storage elastic modulus G ′ (logarithm), loss elastic modulus G ′′ (logarithm) and strain (logarithm) measured under the above conditions with an ink drying rate of 20% for the ink of Example 1. ) Is shown. From the graph, the loss tangent (tan ⁇ ) at 1% strain of (A5) and the crossover strain of (A6) can be obtained.
  • the base material fixability of the ink coating film was evaluated by the following method.
  • the ink coating film was obtained by applying ink on a substrate with a wire bar # 7 and drying at 100 ° C. for 3 minutes. Cut the obtained ink coating film (100 mm x 100 mm, thickness 10 ⁇ m) with a cutter so that 25 squares of 5 vertical ⁇ 5 horizontal are formed, and attach Nichiban's cellophane tape (registered trademark).
  • the peeled state was evaluated according to the following evaluation criteria.
  • the ink ejection property from the head is good and a high quality printed image can be obtained.
  • the inkjet ink of the present invention it is possible to maintain good ejection performance and to form a high-quality image in the image formation by the inkjet method. Further, according to the image formation of the present invention, it is possible to form a high-quality image with good workability in the image formation by the inkjet method.

Abstract

This ink-jet ink (hereinafter, referred to as "ink") comprises an aqueous solvent, a pigment, a fixing resin, and a temperature-responsive polymer, and is characterized by having, with respect to the whole ink, a content of the pigment in the range of 2-10 mass%, a content of the fixing resin in the range of 2-10 mass%, and a content of the temperature-responsive polymer in the range of 0.01-1 mass%. This method for forming an image includes an ink delivery step in which droplets of an ink are ejected from an ink-jet head equipped with an ink circulation mechanism and are delivered to a base, and is characterized in that the ink is circulated so that the ink within the ink-jet head has a viscosity of 15 mPa·s or lower and the ink delivery step is conducted so that the droplets at the time of delivery to the base or immediately after the delivery have a loss in mass from the ink of 20% or less and have a viscosity of 100 mPa·s or higher.

Description

インクジェットインク及び画像形成方法Inkjet ink and image formation method
　本発明は、インクジェットインク及び画像形成方法に関する。より詳しくは、本発明は、良好な吐出性の維持と高品質な画像形成の両立を可能としたインクジェットインク及び、作業性よく高品質な画像を形成することが可能なインクジェット法による画像形成方法に関する。 The present invention relates to an inkjet ink and an image forming method. More specifically, the present invention relates to an inkjet ink capable of maintaining good ejection properties and forming a high-quality image, and an image forming method by an inkjet method capable of forming a high-quality image with good workability. Regarding.
　インクジェット法による画像形成においては、インクジェットヘッド（以下、単に「ヘッド」ともいう。）から基材に向かってインクジェットインク（以下、単に「インク」ともいう。）の液滴を吐出させ基材に着弾後、溶媒を乾燥させて塗膜（画像）を形成する。このようなインクジェット法によって、ＰＥＴ（ポリエチレンテレフタレート）等からなる非吸収性基材に画像を形成すると、インクが基材に着弾した後、乾燥する前に、隣接するインク液滴が引っ張られてスジ状の不具合を生じる、あるいは、異なる隣接インク液滴の場合は混色してにじみが生じる等の問題があった。 In image formation by the inkjet method, droplets of inkjet ink (hereinafter, also simply referred to as “ink”) are ejected from the inkjet head (hereinafter, also simply referred to as “head”) toward the base material and land on the base material. After that, the solvent is dried to form a coating film (image). When an image is formed on a non-absorbent base material made of PET (polyethylene terephthalate) or the like by such an inkjet method, adjacent ink droplets are pulled and streaks are drawn after the ink has landed on the base material and before it dries. There is a problem that a problem occurs, or in the case of different adjacent ink droplets, color mixing occurs and bleeding occurs.
　このような問題を解決するために、画像形成装置に加熱プラテンを導入し、インクが基材に着弾後に溶媒を瞬時に乾燥させて増粘させることが考えられる。しかしながら、上記にじみを発生させないようにするにはプラテンを高温にする必要があり、ヘッドのメニスカス表面の乾燥が進んでヘッド周りにインクが固着してしまい吐出不良を起こす問題があった。 In order to solve such a problem, it is conceivable to introduce a heated platen into the image forming apparatus and instantly dry the solvent to thicken it after the ink has landed on the base material. However, in order to prevent the above-mentioned bleeding, it is necessary to heat the platen to a high temperature, and there is a problem that the surface of the meniscus of the head becomes dry and the ink sticks around the head, causing ejection failure.
　また、インクに添加剤を添加してチキソ性を持たせ、ヘッド内ではインクが循環することでシェアがかかり低粘度になっているが、インクを吐出して基材に着弾した低シェアの状態では粘度が高くなり、吸収性基材でインクが吸収されにくくなり、プラテン加熱をすることなく高濃度で画像が形成されることが開示されている。 In addition, an additive is added to the ink to give it thixotropy, and the ink circulates in the head to increase the share and reduce the viscosity. It is disclosed that the viscosity becomes high, the ink is hard to be absorbed by the absorbent base material, and the image is formed at a high density without heating the platen.
　例えば、特許文献１には、水溶性高分子化合物を添加してインクにチキソ性を付与することで、高シェア時のインク粘度に対する低シェア時のインク粘度が１．５倍以上となる水性インクジェットインクが記載されている。特許文献１には、このインクをヘッドで循環して吐出する際には高シェアで低粘度であるが、着弾時には低シェアとなることで高粘度となって、吸収基材により濃度が下がることを防止することが記載されている。しかしながら、特許文献１には、インク自体のチキソ性と乾燥条件を組み合わせてインクの増粘を制御しようとする記載はない。特許文献１のようなインク自体のチキソ性を制御する方法のみでは、良好な吐出性と高品質な画像形成の両立は達成しえないと想定される。 For example, in Patent Document 1, a water-based inkjet in which a water-soluble polymer compound is added to impart thixotropy to an ink so that the ink viscosity at low share becomes 1.5 times or more the viscosity at high share. The ink is listed. According to Patent Document 1, when this ink is circulated and discharged by a head, it has a high share and a low viscosity, but when it lands, it has a low share and a high viscosity, and the concentration is lowered by the absorbing base material. It is stated to prevent. However, Patent Document 1 does not describe an attempt to control the thickening of the ink by combining the thixotropic property of the ink itself and the drying conditions. It is assumed that it is not possible to achieve both good ejection performance and high-quality image formation only by the method of controlling the thixotropic property of the ink itself as in Patent Document 1.
　また、特許文献２には、水溶性の温度応答ポリマーを添加した水系インクジェットインクが記載されている。特許文献２には、紙基材に対してインクの浸透を抑制して濃度が高くなる効果が記載されている。特許文献２では、温度応答ポリマーをインク全体で５質量％程度添加し、色材に対して２倍以上添加している。そして、熱をかけたときに樹脂が収縮して色材を覆うことで色材が固定されることが記載されている。しかしながら、特許文献２においては、ヘッド内と着弾時においてインクの粘度を変化させるようにチキソ性を制御することは行っていない。よって、特許文献２に記載されているインクでは良好な吐出性と高品質な画像形成の両立は達成しえないと想定される。 Further, Patent Document 2 describes a water-based inkjet ink to which a water-soluble temperature-responsive polymer is added. Patent Document 2 describes the effect of suppressing the penetration of ink into a paper substrate to increase the density. In Patent Document 2, the temperature-responsive polymer is added in an amount of about 5% by mass in the entire ink, and is added twice or more with respect to the coloring material. Then, it is described that the color material is fixed by shrinking the resin and covering the color material when heat is applied. However, in Patent Document 2, the thixotropic property is not controlled so as to change the viscosity of the ink in the head and at the time of landing. Therefore, it is assumed that the ink described in Patent Document 2 cannot achieve both good ejection performance and high-quality image formation.
特開２０１１－２２５８５９号公報Japanese Unexamined Patent Publication No. 2011-225859 特開平１１－２３６５２３号公報Japanese Unexamined Patent Publication No. 11-236523
　本発明は、上記問題・状況に鑑みてなされたものであり、その解決課題は、良好な吐出性の維持と高品質な画像形成の両立を可能とするインクジェットインクを提供することである。また、インクジェット法による画像形成において、作業性よく高品質な画像を形成することが可能な画像形成方法を提供することである。 The present invention has been made in view of the above problems and situations, and the problem to be solved is to provide an inkjet ink that enables both maintenance of good ejection properties and high-quality image formation at the same time. Another object of the present invention is to provide an image forming method capable of forming a high-quality image with good workability in image forming by an inkjet method.
　本発明者は、上記課題を解決すべく、上記問題の原因等について検討する過程において、インクジェットインクのヘッドでの循環時における高シェア時の粘度と、着弾時における低シェア時の粘度を指標として、温度応答ポリマーを用いたインクジェットインクの組成を検討した。その結果、水系溶媒と顔料を含有するインクジェットインクに、温度応答ポリマーと定着樹脂を組み合わせて用いて、それぞれ所定の含有量の範囲で含有させることにより、ヘッドでの循環時における粘度が低く、僅かな温度調整により着弾時における粘度が十分に高いインクが得られることを見出し本発明に至った。該インクは上記特性を有することで、良好な吐出性の維持と高品質な画像形成の両立が可能なインクジェットインクである。すなわち、本発明に係る上記課題は、以下の手段により解決される。 In the process of examining the cause of the above problem in order to solve the above problems, the present inventor uses the viscosity at the time of high share at the time of circulation in the head of the inkjet ink and the viscosity at the time of low share at the time of landing as indexes. , The composition of the inkjet ink using the temperature-responsive polymer was examined. As a result, by using an inkjet ink containing an aqueous solvent and a pigment in combination with a temperature-responsive polymer and a fixing resin and each containing them within a predetermined content range, the viscosity at the time of circulation in the head is low and slightly. The present invention has been made by finding that an ink having a sufficiently high viscosity at the time of landing can be obtained by adjusting the temperature. By having the above characteristics, the ink is an inkjet ink capable of maintaining good ejection properties and forming a high-quality image at the same time. That is, the above problem according to the present invention is solved by the following means.
　１．水系溶媒、顔料、定着樹脂、及び温度応答ポリマーを含有するインクジェットインクであって、前記温度応答ポリマーが、水に対して下限臨界共溶温度を有し、前記インクジェットインク全量に対する、前記顔料の含有量が、２～１０質量％の範囲内であり、前記定着樹脂の含有量が、１～１０質量％の範囲内であり、前記温度応答ポリマーの含有量が、０．０１～１質量％の範囲内であるインクジェットインク。 1. An inkjet ink containing an aqueous solvent, a pigment, a fixing resin, and a temperature-responsive polymer, wherein the temperature-responsive polymer has a lower limit critical eutectic temperature with respect to water, and the pigment is contained in the total amount of the inkjet ink. The amount is in the range of 2 to 10% by mass, the content of the fixing resin is in the range of 1 to 10% by mass, and the content of the temperature-responsive polymer is 0.01 to 1% by mass. Ink ink that is within range.
　２．前記インクジェットインクが、２５℃でのせん断速度１０００（１／ｓ）時の粘度が、１５ｍＰａ・ｓ以下であり、かつ前記下限臨界共溶温度±１０℃の範囲のいずれかの温度でのせん断速度１（１／ｓ）時の粘度が、４５ｍＰａ・ｓ以上である第１項に記載のインクジェットインク。 2. The viscosity of the inkjet ink at a shear rate of 1000 (1 / s) at 25 ° C. is 15 mPa · s or less, and the shear rate at any temperature in the range of the lower limit critical eutectic temperature ± 10 ° C. The inkjet ink according to item 1, wherein the viscosity at 1 (1 / s) is 45 mPa · s or more.
　３．前記インクジェットインクが、初期質量の８０％の質量となるように前記インクジェットインクから前記水系溶媒を除去した状態で、前記下限臨界共溶温度±１０℃の範囲のいずれかの温度でのせん断速度１（１／ｓ）時の粘度が１００ｍＰａ・ｓ以上となる第１項又は第２項に記載のインクジェットインク。 3. Shear velocity 1 at any temperature within the lower limit critical eutectic temperature ± 10 ° C. in a state where the aqueous solvent is removed from the inkjet ink so that the inkjet ink has a mass of 80% of the initial mass. The inkjet ink according to item 1 or 2, wherein the viscosity at (1 / s) is 100 mPa · s or more.
　４．前記温度応答ポリマーの水に対する下限臨界共溶温度が、３０～６０℃の範囲内にある第１項から第３項までのいずれか一項に記載のインクジェットインク。 4. The inkjet ink according to any one of items 1 to 3, wherein the lower limit critical eutectic temperature of the temperature-responsive polymer with respect to water is in the range of 30 to 60 ° C.
　５．前記温度応答ポリマーが、水溶性セルロース樹脂を含む第１項から第４項までのいずれか一項に記載のインクジェットインク。 5. The inkjet ink according to any one of items 1 to 4, wherein the temperature-responsive polymer contains a water-soluble cellulose resin.
　６．前記インクジェットインク全量に対する、前記水系溶媒の含有量が５０～９０質量％の範囲内である第１項から第５項までのいずれか一項に記載のインクジェットインク。 6. The inkjet ink according to any one of items 1 to 5, wherein the content of the aqueous solvent is in the range of 50 to 90% by mass with respect to the total amount of the inkjet ink.
　７．前記定着樹脂が、ポリアクリル樹脂、ポリウレタン樹脂、及びポリエステル樹脂からなる群から選ばれる少なくとも一種を含む第１項から第６項までのいずれか一項に記載のインクジェットインク。 7. The inkjet ink according to any one of items 1 to 6, wherein the fixing resin contains at least one selected from the group consisting of a polyacrylic resin, a polyurethane resin, and a polyester resin.
　８．前記インクジェットインクが、さらにチキソ性付与剤を含有する第１項から第７項までのいずれか一項に記載のインクジェットインク。 8. The inkjet ink according to any one of items 1 to 7, wherein the inkjet ink further contains a thixotropy-imparting agent.
　９．前記チキソ性付与剤が、セルロースナノファイバー又はスメクタイト粘土鉱物を含む第８項に記載のインクジェットインク。 9. Item 8. The inkjet ink according to Item 8, wherein the thixotropy-imparting agent contains cellulose nanofibers or smectite clay minerals.
　１０．前記チキソ性付与剤の含有量が、前記インクジェットインク全量に対して０．０１～１質量％の範囲内である第８項又は第９項に記載のインクジェットインク。 10. The inkjet ink according to item 8 or 9, wherein the content of the thixotropy-imparting agent is in the range of 0.01 to 1% by mass with respect to the total amount of the inkjet ink.
　１１．インク循環機構を備えるインクジェットヘッドからインクジェットインクの液滴を吐出して基材上に着弾させる着弾工程を有する画像形成方法であって、前記インクジェットインクが、前記インクジェットヘッド内で粘度が１５ｍＰａ・ｓ以下になるように循環され、かつ前記基材に着弾した時、又は着弾直後の前記液滴が、前記インクジェットインクからの質量減少率が２０％以内となるように、かつ粘度が１００ｍＰａ・ｓ以上となるように前記着弾工程を行う画像形成方法。 11. An image forming method comprising a landing step of ejecting droplets of inkjet ink from an inkjet head provided with an ink circulation mechanism and landing them on a substrate, wherein the inkjet ink has a viscosity of 15 mPa · s or less in the inkjet head. The droplets are circulated so as to be, and when they land on the base material or immediately after landing, the mass reduction rate from the inkjet ink is within 20%, and the viscosity is 100 mPa · s or more. An image forming method in which the landing step is performed so as to be.
　１２．前記基材に着弾した時、又は着弾直後の前記液滴の粘度が、１５０ｍＰａ・ｓ以上である第１１項に記載の画像形成方法。 12. The image forming method according to Item 11, wherein the droplet has a viscosity of 150 mPa · s or more when it lands on the substrate or immediately after it lands.
　１３．前記着弾工程が、前記液滴を前記基材上で３０～６０℃の範囲内で加熱することを含む第１１項又は第１２項に記載の画像形成方法。 13. The image forming method according to item 11 or 12, wherein the landing step comprises heating the droplet on the substrate in the range of 30 to 60 ° C.
　１４．前記着弾直後が、前記液滴が前記基材に着弾後１００ｍｓｅｃ以内である第１１項から第１３項までのいずれか一項に記載の画像形成方法。 14. The image forming method according to any one of items 11 to 13, wherein immediately after the landing, the droplet is within 100 msec after landing on the base material.
　１５．前記基材が、非吸収性の基材である第１１項から第１４項までのいずれか一項に記載の画像形成方法。 15. The image forming method according to any one of items 11 to 14, wherein the base material is a non-absorbent base material.
　１６．前記インクジェットヘッドが、注入経路を介して前記インクジェットインクが注入される圧力室と、前記圧力室に圧力変動を生じさせる圧力発生手段と、前記圧力室に連通し、該圧力室の圧力変動により該圧力室内から外部に吐出される前記インクジェットインクの流路となるノズルと、前記圧力室に連通し、前記ノズルよりも内方の前記インクジェットインクを排出させて前記注入経路に戻す２以上の循環路とを備える第１１項から第１５項までのいずれか一項に記載の画像形成方法。 16. The inkjet head communicates with a pressure chamber into which the inkjet ink is injected via an injection path, a pressure generating means for causing a pressure fluctuation in the pressure chamber, and the pressure chamber, and the pressure fluctuation in the pressure chamber causes the inkjet head to communicate with the pressure chamber. A nozzle that serves as a flow path for the inkjet ink discharged from the pressure chamber to the outside, and two or more circulation paths that communicate with the pressure chamber to discharge the inkjet ink inside the nozzle and return it to the injection path. The image forming method according to any one of items 11 to 15, further comprising.
　１７．前記インクジェットインクが、第１項から第１０項までのいずれか一項に記載のインクジェットインクである第１１項から第１６項までのいずれか一項に記載の画像形成方法。 17. The image forming method according to any one of items 11 to 16, wherein the inkjet ink is the inkjet ink according to any one of items 1 to 10.
　本発明の上記手段により、良好な吐出性の維持と高品質な画像形成の両立が可能なインクジェットインクを提供することができる。また、インクジェット法による画像形成において、作業性よく高品質な画像を形成することが可能な画像形成方法を提供することができる。本発明の効果の発現機構ないし作用機構については、明確にはなっていないが、以下のように推察している。 By the above means of the present invention, it is possible to provide an inkjet ink capable of maintaining good ejection properties and forming a high-quality image at the same time. Further, in the image formation by the inkjet method, it is possible to provide an image forming method capable of forming a high-quality image with good workability. Although the mechanism of expression or mechanism of action of the effects of the present invention has not been clarified, it is inferred as follows.
　本発明のインクジェットインクは、水系溶媒、顔料、定着樹脂、及び温度応答ポリマーを含有し、前記温度応答ポリマーは水に対して下限臨界共溶温度を有し、前記インクジェットインク全量に対する、前記顔料の含有量が２～１０質量％の範囲内であり、前記定着樹脂の含有量が１～１０質量％の範囲内であり、前記温度応答ポリマーの含有量が０．０１～１質量％の範囲内であることを特徴とする。本明細書において、特に断りのない限り温度応答ポリマーの下限臨界共溶温度は、水に対する下限臨界共溶温度をいう。 The inkjet ink of the present invention contains an aqueous solvent, a pigment, a fixing resin, and a temperature-responsive polymer, and the temperature-responsive polymer has a lower limit critical eutectic temperature with respect to water. The content is in the range of 2 to 10% by mass, the content of the fixing resin is in the range of 1 to 10% by mass, and the content of the temperature-responsive polymer is in the range of 0.01 to 1% by mass. It is characterized by being. In the present specification, unless otherwise specified, the lower limit critical eutectic temperature of a temperature-responsive polymer refers to the lower limit critical eutectic temperature with respect to water.
　インクの組成を上記範囲内とすることで、高シェア時の粘度を低く、例えば、せん断速度１０００（１／ｓ）時のインクの粘度（２５℃）を１５ｍＰａ・ｓ以下とすることができる。該粘度は、インクのヘッドでの循環及びヘッドからの吐出がスムーズに行える粘度である。 By setting the composition of the ink within the above range, the viscosity at the time of high share can be lowered, for example, the viscosity (25 ° C.) of the ink at a shear rate of 1000 (1 / s) can be set to 15 mPa · s or less. The viscosity is a viscosity at which ink can be smoothly circulated at the head and ejected from the head.
　インクの組成を上記範囲内とすることで、着弾時の粘度を高く、例えば、温度応答ポリマーの下限臨界共溶温度±１０℃の範囲のいずれかの温度でのせん断速度１（１／ｓ）時の粘度を４５ｍＰａ・ｓ以上とすることができる。言い換えれば、温度応答ポリマーの下限臨界共溶温度±１０℃の範囲内でのせん断速度１（１／ｓ）時の最大粘度を４５ｍＰａ・ｓ以上とすることができる。該温度における粘度が上記規定を満たせば、着弾時において、僅かな温度調整のみで、インクから水系溶媒を除去することなく、良好なピニングが可能であり得られる画像が高品質となりうる。すなわち、本発明のインクは、温度応答ポリマーの水に対する下限臨界共溶温度±１０℃の範囲内で、良好なピニングを行うために必要とされる高い粘度を有する。これにより、吐出時から着弾時にかけて、インクに水系溶媒を多く残存させることができるため、ヘッド周りへのインク固形分の固着が抑制され吐出不良も生じにくく、メンテナンスも容易である。 By setting the composition of the ink within the above range, the viscosity at the time of landing is increased, for example, the shear rate 1 (1 / s) at any temperature in the range of the lower limit critical eutectic temperature ± 10 ° C. of the temperature-responsive polymer. The viscosity at the time can be 45 mPa · s or more. In other words, the maximum viscosity of the temperature-responsive polymer at a shear rate of 1 (1 / s) within the range of the lower limit critical eutectic temperature of ± 10 ° C. can be 45 mPa · s or more. If the viscosity at the temperature satisfies the above-mentioned regulation, good pinning is possible without removing the aqueous solvent from the ink with only a slight temperature adjustment at the time of landing, and the obtained image can be of high quality. That is, the ink of the present invention has a high viscosity required for good pinning within a range of the lower limit critical eutectic temperature ± 10 ° C. of the temperature responsive polymer with water. As a result, a large amount of water-based solvent can remain in the ink from the time of ejection to the time of impact, so that the sticking of the solid ink content around the head is suppressed, ejection defects are less likely to occur, and maintenance is easy.
　また、温度応答ポリマーと定着樹脂と併用することで、画像形成により得られるインクの塗膜に耐水性を付与できる。これは、画像形成の過程で、温度応答ポリマーと定着樹脂とが絡み合うことで得られる効果と考えられる。さらに、該絡み合いにより画像形成により得られるインクの塗膜の基材定着性が向上する。 Further, by using the temperature-responsive polymer and the fixing resin in combination, water resistance can be imparted to the ink coating film obtained by image formation. This is considered to be the effect obtained by the temperature-responsive polymer and the fixing resin being entangled in the process of image formation. Further, the entanglement improves the substrate fixability of the ink coating film obtained by image formation.
　本発明の画像形成方法は、インク循環機構を備えるインクジェットヘッドからインクジェットインクの液滴を吐出して基材上に着弾させる着弾工程を有する画像形成方法において、前記インクジェットインクが、前記インクジェットヘッド内で粘度が１５ｍＰａ・ｓ以下になるように循環される。該粘度は、インクのヘッドでの循環及びヘッドからの吐出がスムーズに行える粘度である。 The image forming method of the present invention is an image forming method comprising a landing step of ejecting droplets of inkjet ink from an inkjet head provided with an ink circulation mechanism and landing the ink jet ink on a substrate. It is circulated so that the viscosity is 15 mPa · s or less. The viscosity is a viscosity at which ink can be smoothly circulated at the head and ejected from the head.
　本発明の画像形成方法においては、基材に着弾した時、又は着弾直後のインクの液滴について、ヘッド内を循環しているインクからの質量減少率が２０％以内となるように、かつ粘度が１００ｍＰａ・ｓ以上になるように着弾工程を行う。基材に着弾した時、又は着弾直後のインクの液滴において、上記質量減少率及び粘度が上記範囲であれば、良好なピニングが可能であり得られる画像が高品質となりうる。さらに、ヘッド周りへのインク固形分の固着が抑制され吐出不良も生じにくく、メンテナンスも容易である。 In the image forming method of the present invention, the mass reduction rate of the ink droplets when they land on the substrate or immediately after landing from the ink circulating in the head is within 20% and the viscosity. The landing process is performed so that the value is 100 mPa · s or more. When the ink droplets land on the substrate or immediately after landing, if the mass reduction rate and the viscosity are within the above ranges, good pinning is possible and the obtained image can be of high quality. Further, the sticking of solid ink around the head is suppressed, ejection defects are less likely to occur, and maintenance is easy.
本発明の画像形成方法に使用可能なインクジェットヘッドの一例を備えるインクジェット画像形成装置を示す要部概略構成図Schematic configuration of a main part showing an inkjet image forming apparatus including an example of an inkjet head that can be used in the image forming method of the present invention. 図１に示されるインクジェットヘッドのヘッドチップの拡大断面図An enlarged cross-sectional view of the head chip of the inkjet head shown in FIG. 図１に示されるインクジェットヘッドのノズルプレートの平面図Top view of the nozzle plate of the inkjet head shown in FIG. 実施例１のインクのクロスオーバー歪（％）を求める際に用いたグラフThe graph used when obtaining the crossover strain (%) of the ink of Example 1.
　本発明のインクジェットインクは、水系溶媒、顔料、定着樹脂、及び温度応答ポリマーを含有するインクジェットインクであって、前記温度応答ポリマーは水に対して下限臨界共溶温度を有し、前記インクジェットインク全量に対する、前記顔料の含有量が２～１０質量％の範囲内であり、前記定着樹脂の含有量が１～１０質量％の範囲内であり、前記温度応答ポリマーの含有量が０．０１～１質量％の範囲内であることを特徴とする。この特徴は、本発明のインクジェットインクの下記各実施形態に共通する技術的特徴である。 The inkjet ink of the present invention is an inkjet ink containing an aqueous solvent, a pigment, a fixing resin, and a temperature-responsive polymer, and the temperature-responsive polymer has a lower limit critical eutectic temperature with respect to water, and the total amount of the inkjet ink The content of the pigment is in the range of 2 to 10% by mass, the content of the fixing resin is in the range of 1 to 10% by mass, and the content of the temperature-responsive polymer is 0.01 to 1. It is characterized in that it is within the range of mass%. This feature is a technical feature common to each of the following embodiments of the inkjet ink of the present invention.
　本発明のインクの実施態様としては、良好な吐出性の維持と高品質な画像形成の両立の観点から、２５℃でのせん断速度１０００（１／ｓ）時の粘度が１５ｍＰａ・ｓ以下であり、かつ前記下限臨界共溶温度±１０℃の範囲のいずれかの温度でのせん断速度１（１／ｓ）時の粘度が４５ｍＰａ・ｓ以上であることが好ましい。 In an embodiment of the ink of the present invention, the viscosity at a shear rate of 1000 (1 / s) at 25 ° C. is 15 mPa · s or less from the viewpoint of maintaining good ejection properties and forming a high-quality image. Moreover, it is preferable that the viscosity at a shear rate of 1 (1 / s) at any temperature in the range of the lower limit critical eutectic temperature of ± 10 ° C. is 45 mPa · s or more.
　本発明のインクの実施態様としては、良好な吐出性の維持と高品質な画像形成の両立の観点から、初期質量の８０％の質量となるように前記インクジェットインクから前記水系溶媒を除去した状態（以下、該状態を「インク乾燥率２０％」ともいう。）で、前記下限臨界共溶温度±１０℃の範囲のいずれかの温度でのせん断速度１（１／ｓ）時の粘度が１００ｍＰａ・ｓ以上となることが好ましい。 In an embodiment of the ink of the present invention, the aqueous solvent is removed from the inkjet ink so as to have a mass of 80% of the initial mass from the viewpoint of maintaining good ejection properties and forming a high-quality image. (Hereinafter, this state is also referred to as “ink drying rate 20%”), and the viscosity at a shear rate of 1 (1 / s) at any temperature within the range of the lower limit critical co-melting temperature ± 10 ° C. is 100 mPa. -It is preferable that the value is s or more.
　これにより、インク乾燥率２０％においても、にじみ耐性に必要な粘度になるため、吐出時から着弾時にかけて、インクに水系溶媒を多く残存させることができる。そのため、ヘッド周りへのインク固形分の固着が抑制され吐出不良も生じにくく、メンテナンスも容易である。 As a result, even when the ink drying rate is 20%, the viscosity required for bleeding resistance is obtained, so that a large amount of aqueous solvent can remain in the ink from the time of ejection to the time of landing. Therefore, sticking of solid ink around the head is suppressed, ejection failure is unlikely to occur, and maintenance is easy.
　本発明のインクの実施態様としては、良好な吐出性の維持と高品質な画像形成の両立の観点から、前記温度応答ポリマーの水に対する下限臨界共溶温度が、３０～６０℃の範囲内にあることが好ましい。また、前記温度応答ポリマーが、水溶性セルロース樹脂を含むことが好ましい。 In an embodiment of the ink of the present invention, the lower limit critical eutectic temperature of the temperature-responsive polymer with respect to water is within the range of 30 to 60 ° C. from the viewpoint of maintaining good ejection properties and forming a high-quality image. It is preferable to have. Moreover, it is preferable that the temperature-responsive polymer contains a water-soluble cellulose resin.
　本発明のインクの実施態様としては、良好な吐出性の維持と高品質な画像形成を両立する観点から、前記インクジェットインク全量に対する、前記水系溶媒の含有量が５０～９０質量％の範囲内であることが好ましい。 In an embodiment of the ink of the present invention, the content of the aqueous solvent is in the range of 50 to 90% by mass with respect to the total amount of the inkjet ink from the viewpoint of maintaining good ejection properties and forming a high-quality image. It is preferable to have.
　本発明のインクの実施態様としては、本発明の効果発現の観点から、前記定着樹脂が、ポリアクリル樹脂、ポリウレタン樹脂、及びポリエステル樹脂からなる群から選ばれる少なくとも一種を含むことが好ましい。 As an embodiment of the ink of the present invention, it is preferable that the fixing resin contains at least one selected from the group consisting of a polyacrylic resin, a polyurethane resin, and a polyester resin from the viewpoint of exhibiting the effect of the present invention.
　本発明のインクの実施態様としては、良好な吐出性の維持と高品質な画像形成の両立の観点から、前記インクジェットインクが、さらにチキソ性付与剤を含むことが好ましい。また、同様の観点から、前記チキソ性付与剤が、セルロースナノファイバー又はスメクタイト粘土鉱物を含むことが好ましい。本発明のインクの実施態様としては、同様の観点から、前記チキソ性付与剤の含有量が、前記インクジェットインク全量に対して０．０１～１質量％の範囲内であることが好ましい。 As an embodiment of the ink of the present invention, it is preferable that the inkjet ink further contains a thixotropic agent from the viewpoint of maintaining good ejection properties and forming a high-quality image. From the same viewpoint, it is preferable that the thixotropy-imparting agent contains cellulose nanofibers or smectite clay minerals. In an embodiment of the ink of the present invention, from the same viewpoint, the content of the thixotropy-imparting agent is preferably in the range of 0.01 to 1% by mass with respect to the total amount of the inkjet ink.
　本発明の画像形成方法は、インク循環機構を備えるインクジェットヘッドからインクジェットインクの液滴を吐出して基材上に着弾させる着弾工程を有する画像形成方法であって、前記インクジェットインクが、前記インクジェットヘッド内で粘度が１５ｍＰａ・ｓ以下になるように循環され、かつ前記基材に着弾した時、又は着弾直後の前記液滴が、前記インクジェットインクからの質量減少率が２０％以内となるように、かつ粘度が１００ｍＰａ・ｓ以上となるように前記着弾工程を行うことを特徴とする。この特徴は、本発明の画像形成方法の下記各実施形態に共通する技術的特徴である。 The image forming method of the present invention is an image forming method having a landing step of ejecting droplets of inkjet ink from an inkjet head provided with an ink circulation mechanism and landing them on a substrate, wherein the inkjet ink is the inkjet head. The droplets are circulated in the ink jet so as to have a viscosity of 15 mPa · s or less, and when the droplets land on the base material or immediately after landing, the mass reduction rate from the inkjet ink is within 20%. Moreover, the landing step is performed so that the viscosity becomes 100 mPa · s or more. This feature is a technical feature common to each of the following embodiments of the image forming method of the present invention.
　本発明の画像形成方法の実施態様としては、本発明の効果をより発現させる観点から、前記基材に着弾した時、又は着弾直後の前記液滴の粘度が１５０ｍＰａ・ｓ以上であることが好ましい。 As an embodiment of the image forming method of the present invention, from the viewpoint of further exhibiting the effect of the present invention, it is preferable that the viscosity of the droplet when landing on the substrate or immediately after landing is 150 mPa · s or more. ..
　本発明の画像形成方法の実施態様としては、本発明の効果をより発現させる観点から、前記着弾工程が前記液滴を前記基材上で３０～６０℃の範囲内で加熱することを含むことが好ましい。また、前記着弾直後が、前記液滴が前記基材に着弾後１００ｍｓｅｃ以内であることが好ましい。 An embodiment of the image forming method of the present invention includes that the landing step heats the droplets on the substrate in the range of 30 to 60 ° C. from the viewpoint of further exhibiting the effects of the present invention. Is preferable. Further, it is preferable that the droplet is within 100 msec after landing on the base material immediately after the landing.
　本発明の画像形成方法の実施態様としては、前記基材が非吸収性基材であると本発明の効果がより顕著であり好ましい。 As an embodiment of the image forming method of the present invention, it is preferable that the base material is a non-absorbent base material because the effect of the present invention is more remarkable.
　本発明の画像形成方法の実施態様としては、本発明の効果をより発現させる観点から、前記インクジェットヘッドが、注入経路を介して前記インクジェットインクが注入される圧力室と、前記圧力室に圧力変動を生じさせる圧力発生手段と、前記圧力室に連通し、該圧力室の圧力変動により該圧力室内から外部に吐出される前記インクジェットインクの流路となるノズルと、前記圧力室に連通し、前記ノズルよりも内方の前記インクジェットインクを排出させて前記注入経路に戻す２以上の循環路と、を備えることが好ましい。 In an embodiment of the image forming method of the present invention, from the viewpoint of further exhibiting the effect of the present invention, the inkjet head has a pressure chamber in which the inkjet ink is injected via an injection path and a pressure fluctuation in the pressure chamber. A nozzle that communicates with the pressure chamber and serves as a flow path for the inkjet ink discharged from the pressure chamber to the outside due to pressure fluctuations in the pressure chamber, and communicates with the pressure chamber. It is preferable to provide two or more circulation paths for discharging the inkjet ink inside the nozzle and returning the inkjet ink to the injection path.
　本発明の画像形成方法の実施態様としては、本発明の効果をより発現させる観点から、前記インクジェットインクとして、上記本発明のインクジェットインクを用いることが好ましい。 As an embodiment of the image forming method of the present invention, it is preferable to use the inkjet ink of the present invention as the inkjet ink from the viewpoint of further exhibiting the effects of the present invention.
　以下、本発明とその構成要素、及び本発明を実施するための形態・態様について詳細な説明をする。なお、本願において、「～」は、その前後に記載される数値を下限値及び上限値として含む意味で使用する。 Hereinafter, the present invention, its constituent elements, and modes and modes for carrying out the present invention will be described in detail. In the present application, "-" is used to mean that the numerical values described before and after the value are included as the lower limit value and the upper limit value.
[インクジェットインクの概要]
＜インクジェットインクの組成＞
　本発明のインクは、水系溶媒、顔料、定着樹脂、及び温度応答ポリマーを含有するインクジェットインクであって、前記温度応答ポリマーは水に対して下限臨界共溶温度を有し、前記インクジェットインク全量に対する、前記顔料の含有量が２～１０質量％の範囲内であり、前記定着樹脂の含有量が１～１０質量％の範囲内であり、前記温度応答ポリマーの含有量が０．０１～１質量％の範囲内であることを特徴とする。 [Overview of inkjet ink]
<Composition of inkjet ink>
The ink of the present invention is an inkjet ink containing an aqueous solvent, a pigment, a fixing resin, and a temperature-responsive polymer, and the temperature-responsive polymer has a lower limit critical eutectic temperature with respect to water with respect to the total amount of the inkjet ink. , The content of the pigment is in the range of 2 to 10% by mass, the content of the fixing resin is in the range of 1 to 10% by mass, and the content of the temperature-responsive polymer is 0.01 to 1% by mass. It is characterized in that it is within the range of%.
　本明細書において、水系溶媒とは、水、又は、水と水性溶媒を含有する溶媒をいう。水性溶媒は、室温において水と相溶性を有する溶媒である。 In the present specification, the aqueous solvent means water or a solvent containing water and an aqueous solvent. The aqueous solvent is a solvent that is compatible with water at room temperature.
　本発明のインクは、水系溶媒、顔料、定着樹脂、及び温度応答ポリマー以外に、本発明の効果を損なわない任意の成分を含有できる。任意成分としては、例えば、チキソ性付与剤、顔料分散剤、界面活性剤等が挙げられる。本発明のインクにおける各成分について以下に説明する。 The ink of the present invention can contain any component other than the aqueous solvent, the pigment, the fixing resin, and the temperature-responsive polymer, which does not impair the effect of the present invention. Examples of the optional component include a thixotropic agent, a pigment dispersant, a surfactant and the like. Each component in the ink of the present invention will be described below.
（温度応答ポリマー）
　本発明のインクが含有する温度応答ポリマーは、水に対して下限臨界共溶温度（Low Critical Solution Temperature；以下、「ＬＣＳＴ」ともいう。）を有するポリマーであ
る。温度応答ポリマーは、水に対するＬＣＳＴを有することで、ＬＣＳＴ未満では水に溶解し、ＬＣＳＴ以上では、例えば、ゲル化する等水に溶解しない性質を有する。言い換えれば、温度応答ポリマーの水溶液はＬＣＳＴを臨界点として相変化する性質を有する。なお、該性質は可逆的である。温度応答ポリマーが該性質を有することで、本発明のインクは、ヘッド内及び基材への着弾時のインクの粘度をそれぞれ適切な範囲に調整することが可能となり、良好な吐出性の維持と高品質な画像形成の両立が可能となる。 (Temperature responsive polymer)
The temperature-responsive polymer contained in the ink of the present invention is a polymer having a low critical solution temperature (hereinafter, also referred to as “LCST”) with respect to water. By having LCST for water, the temperature-responsive polymer has the property of being soluble in water below LCST and insoluble in water above LCST, for example, gelling. In other words, the aqueous solution of the temperature-responsive polymer has the property of undergoing a phase change with the LCST as a critical point. The property is reversible. Since the temperature-responsive polymer has this property, the ink of the present invention can adjust the viscosity of the ink in the head and at the time of landing on the base material within an appropriate range, thereby maintaining good ejection properties. It is possible to achieve both high-quality image formation.
　温度応答ポリマーの水に対するＬＣＳＴの測定は、例えば、示差走査熱量計（ＤＳＣ）を用いて温度応答ポリマー水溶液の相転移温度を測定することで行うことができる。あるいは、温度応答ポリマー水溶液を緩やかに昇温（降温）させながら該水溶液の光の透過率変化を測定することで行うことができる。 The LCST of the temperature-responsive polymer in water can be measured, for example, by measuring the phase transition temperature of the aqueous temperature-responsive polymer solution using a differential scanning calorimeter (DSC). Alternatively, it can be carried out by measuring the change in the light transmittance of the aqueous solution while gradually raising (lowering) the temperature of the aqueous solution of the temperature-responsive polymer.
　温度応答ポリマーはＬＣＳＴが、３０～６０℃の範囲内にあることが好ましく、４０～５０℃の範囲内がより好ましい。温度応答ポリマーのＬＣＳＴが３０℃以上であれば、インクが、通常、ヘッド内を循環する温度域において、粘度を極端に上昇させることがない。また、温度応答ポリマーのＬＣＳＴが６０℃以下であれば、着弾時に高温にまで昇温せずに、水系溶媒を除去することなく、インク液滴の粘度を所望のレベルまで上昇させることが可能となる。 The temperature-responsive polymer preferably has an LCST in the range of 30 to 60 ° C, more preferably in the range of 40 to 50 ° C. When the LCST of the temperature-responsive polymer is 30 ° C. or higher, the ink does not normally increase its viscosity extremely in the temperature range circulating in the head. Further, if the LCST of the temperature-responsive polymer is 60 ° C. or lower, it is possible to increase the viscosity of the ink droplets to a desired level without removing the aqueous solvent without raising the temperature to a high temperature at the time of landing. Become.
　なお、インクが含有する水系溶媒は、後述のとおり、水からなる場合もあるが、水以外に任意に水性溶媒を含有する。水系溶媒が水と水性溶媒を含有する場合、温度応答ポリマーの水系溶媒に対するＬＣＳＴは、温度応答ポリマーの水に対するＬＣＳＴと、異なる場合がある。両者の差は概ね１０℃以内であることが好ましい。すなわち、温度応答ポリマーの水系溶媒に対するＬＣＳＴは、温度応答ポリマーの水に対するＬＣＳＴ±１０℃の範囲内であることが好ましい。 The aqueous solvent contained in the ink may consist of water as described later, but optionally contains an aqueous solvent in addition to water. When the aqueous solvent contains water and an aqueous solvent, the LCST of the temperature-responsive polymer for the aqueous solvent may differ from the LCST of the temperature-responsive polymer for water. The difference between the two is preferably within about 10 ° C. That is, the LCST of the temperature-responsive polymer with respect to the aqueous solvent is preferably within the range of LCST ± 10 ° C. with respect to water of the temperature-responsive polymer.
　温度応答ポリマーとして、具体的には、水溶性セルロース樹脂、ポリ（Ｎ－置換（メタ）アクリルアミド）、ポリ（Ｎ－ビニルアシルアミド）、ポリ（（メタ）アクリル酸アルキルエステル）、その他の温度応答ポリマーが挙げられる。これらの中でも、本発明のインクに用いる温度応答ポリマーとしては、水溶性セルロース樹脂が好ましい。なお、本明細書において、（メタ）アクリルアミドは、アクリルアミド及びメタクリルアミドの総称である。同様に（メタ）アクリル酸はアクリル酸及びメタクリル酸の総称である。 Specific examples of the temperature-responsive polymer include water-soluble cellulose resins, poly (N-substituted (meth) acrylamide), poly (N-vinyl acylamide), poly ((meth) acrylic acid alkyl ester), and other temperature-responsive polymers. Examples include polymers. Among these, a water-soluble cellulose resin is preferable as the temperature-responsive polymer used in the ink of the present invention. In addition, in this specification, (meth) acrylamide is a general term of acrylamide and methacrylamide. Similarly, (meth) acrylic acid is a general term for acrylic acid and methacrylic acid.
　水溶性セルロース樹脂は、セルロースが多数有するＯＨ基の水素原子の一部を置換して水素結合を消失させることで、水溶性が付与された樹脂である。ＯＨ基の水素原子を置換する置換基としては、アルキル基、ヒドロキシアルキル基、カルボキシ基等が挙げられる。置換基としては、メチル基、ヒドロキシプロピル基、ヒドロキシエチル基が好ましい。置換基は、１種が単独で用いられてもよく、２種以上が併用されてもよい。 The water-soluble cellulose resin is a resin to which water solubility is imparted by substituting a part of hydrogen atoms of OH groups possessed by cellulose to eliminate hydrogen bonds. Examples of the substituent that replaces the hydrogen atom of the OH group include an alkyl group, a hydroxyalkyl group, and a carboxy group. As the substituent, a methyl group, a hydroxypropyl group and a hydroxyethyl group are preferable. As the substituent, one type may be used alone, or two or more types may be used in combination.
　水溶性セルロース樹脂として、具体的には、メチルセルロース、ヒドロキシエチルセルロース、ヒドロキシプロピルセルロース、ヒドロキシエチルメチルセルロース、ヒドロキシプロピルメチルセルロース、カルボキシメチルセルロース等が挙げられる。 Specific examples of the water-soluble cellulose resin include methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose and the like.
　ポリ（Ｎ－置換（メタ）アクリルアミド）における置換基としては、炭素原子間にエーテル結合（－Ｏ－）を有してもよいアルキル基が好ましい。アルキル基は環状、直鎖又は分岐鎖であってよく、これらの組み合わせであってもよい。窒素原子が有する置換基は１個又は２個であり、置換基が２個の場合は、これらが結合して環を形成していてもよい。アルキル基における炭素数は１～１０が好ましい。 As the substituent in poly (N-substituted (meth) acrylamide), an alkyl group which may have an ether bond (-O-) between carbon atoms is preferable. The alkyl group may be cyclic, straight chain or branched chain, and may be a combination thereof. The nitrogen atom has one or two substituents, and when there are two substituents, these may be bonded to form a ring. The number of carbon atoms in the alkyl group is preferably 1 to 10.
　ポリ（Ｎ－置換（メタ）アクリルアミド）として、具体的には、ポリ（Ｎ－エチルアクリルアミド）、ポリ（Ｎ－ｎ－プロピル（メタ）アクリルアミド）、ポリ（Ｎ－イソプロピル（メタ）アクリルアミド）、ポリ（Ｎ－シクロプロピル（メタ）アクリルアミド）、ポリ（Ｎ，Ｎ－ジエチル（メタ）アクリルアミド）等が挙げられる。 Specific examples of poly (N-substituted (meth) acrylamide) include poly (N-ethylacrylamide), poly (Nn-propyl (meth) acrylamide), poly (N-isopropyl (meth) acrylamide), and poly. (N-cyclopropyl (meth) acrylamide), poly (N, N-diethyl (meth) acrylamide) and the like can be mentioned.
　なお、ポリ（Ｎ－置換（メタ）アクリルアミド）は、単一モノマーから構成されなくともよい。すなわち、ポリ（Ｎ－置換（メタ）アクリルアミド）は、置換基が異なるＮ－置換（メタ）アクリルアミドの共重合体であってもよい。さらに、Ｎ－置換（メタ）アクリルアミドと、以下のポリマー、例えば、ポリ（Ｎ－ビニルアシルアミド）、ポリ（（メタ）アクリル酸アルキルエステル）を構成するモノマーから選ばれる少なくとも１種との共重合体であってもよい。 Note that poly (N-substituted (meth) acrylamide) does not have to be composed of a single monomer. That is, poly (N-substituted (meth) acrylamide) may be a copolymer of N-substituted (meth) acrylamide having different substituents. Further, the copolymerization of N-substituted (meth) acrylamide with at least one selected from the following polymers, for example, monomers constituting poly (N-vinylacylamide) and poly ((meth) acrylic acid alkyl ester). It may be coalesced.
　ポリ（Ｎ－ビニルアシルアミド）としては、ポリ（Ｎ－ビニルアセトアミド）、ポリ（Ｎ－ビニルプロピオン酸アミド）、ポリ（Ｎ－ビニル酪酸アミド）、ポリ（Ｎ－ビニルイソ酪酸アミド）等が挙げられる。 Examples of poly (N-vinylacylamide) include poly (N-vinylacetamide), poly (N-vinylpropionic acid amide), poly (N-vinylbutyric acid amide), poly (N-vinylisobutyric acid amide) and the like. ..
　ポリ（（メタ）アクリル酸アルキルエステル）としては、ポリ（ｎ－ブチルメタクリレート）、ポリ（ドデシルメタクリレート）、ポリ（ｎ－ヘキシルメタクリレート）、ポリ（メチルメタクリレート）、ポリ（ｎ－オクチルメタクリレート）等が挙げられる。 Examples of poly ((meth) acrylic acid alkyl ester) include poly (n-butyl methacrylate), poly (dodecyl methacrylate), poly (n-hexyl methacrylate), poly (methyl methacrylate), and poly (n-octyl methacrylate). Can be mentioned.
　その他の温度応答ポリマーとしては、ポリ（Ｎ，Ｎ－アクリルピロリドン）、ポリ（Ｎ－アクリルピペリジン）、及びこれらの共重合体、ポリイソブチルビニルエーテルと無水マレイン酸の交互共重合物、ポリ（２－メチル－５－ビニルピリジン）、ポリ（ビニルアルコール）、ポリ（Ｎ－ビニルピロリドン）、ポリ（Ｎ－ビニルコハク酸）、ポリ（ビニルスルホン酸）、ポリ（オキシエチレン）、ポリ（テトラヒドロフラン）、アミロペクチン、アミロース、ポリ（酢酸ビニル）、ポリ（プロピレングリコール）、ポリビニルメチルエーテル（ＰＶＭＥ）、ポリビニルメチルオキサゾリジノン等が挙げられる。 Other temperature-responsive polymers include poly (N, N-acrylic pyrrolidone), poly (N-acrylic piperidine), and copolymers thereof, alternating copolymers of polyvinyl isobutyl vinyl ether and maleic anhydride, and poly (2-). Methyl-5-vinylpyridine), poly (vinyl alcohol), poly (N-vinylpyrrolidone), poly (N-vinylsuccinic acid), poly (vinyl sulfonic acid), poly (oxyethylene), poly (tetrahydrofuran), amylopectin, Examples thereof include amylose, poly (vinyl acetate), poly (propylene glycol), polyvinyl methyl ether (PVME), polyvinyl methyl oxazolidinone and the like.
　本発明において温度応答ポリマーとして、これらの１種を単独で用いてもよく、２種以上を組み合わせて用いてもよい。 In the present invention, as the temperature responsive polymer, one of these may be used alone, or two or more thereof may be used in combination.
　温度応答性ポリマーの重量平均分子量は特に限定はないが、例えば、１０,０００以上１００,０００以下であることが好ましく、２０，０００以上８０，０００以下であることがより好ましい。温度応答ポリマーの重量平均分子量が１０，０００以上であれば、当該ポリマーは定着樹脂と相互に絡み合いインクの塗膜（画像）に耐水性を付与しやすくなる。また、重量平均分子量が１００，０００以下であれば、インクの粘度が高くなり過ぎて射出性が悪化する恐れが少ない。 The weight average molecular weight of the temperature-responsive polymer is not particularly limited, but is preferably 10,000 or more and 100,000 or less, and more preferably 20,000 or more and 80,000 or less. When the weight average molecular weight of the temperature-responsive polymer is 10,000 or more, the polymer is easily entangled with the fixing resin to impart water resistance to the ink coating film (image). Further, when the weight average molecular weight is 100,000 or less, there is little possibility that the viscosity of the ink becomes too high and the ejection property deteriorates.
　なお、温度応答ポリマーの重量平均分子量は、ゲル浸透クロマトグラフィー(ＧＰＣ)により測定される、ポリスチレン換算重量平均分子量である。 The weight average molecular weight of the temperature-responsive polymer is a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography (GPC).
　上記温度応答ポリマーとしては、市販品を使用してもよい。市販品としては、例えば、水溶性セルロース樹脂として、いずれも信越化学工業社製の商品名で、メトローズＳＭ－０４（メチルセルロース樹脂、ＬＣＳＴ；５５℃）、メトローズ６０ＳＨ－０３（ヒドロキシプロピルメチルセルロース樹脂、ＬＣＳＴ；７５℃）等が挙げられる。 As the temperature responsive polymer, a commercially available product may be used. Commercially available products include, for example, water-soluble cellulose resins under the trade names manufactured by Shin-Etsu Chemical Co., Ltd., Metrose SM-04 (methyl cellulose resin, LCST; 55 ° C.), Metrose 60SH-03 (hydroxypropyl methylcellulose resin, LCST). ; 75 ° C.) and the like.
　ポリ（Ｎ－置換（メタ）アクリルアミド）の市販品としては、ポリ（Ｎ－イソプロピルアクリルアミドとして、シグマアルドリッチ社の、例えば、ポリ（Ｎ－イソプロピルアクリルアミド（ＬＣＳＴ；３５℃、重量平均分子量；３００００）等が挙げられる。 Commercially available products of poly (N-substituted (meth) acrylamide) include poly (as N-isopropylacrylamide, Sigma-Aldrich, for example, poly (N-isopropylacrylamide (LCST; 35 ° C., weight average molecular weight; 30,000)) and the like. Can be mentioned.
　本発明のインクにおける温度応答ポリマーの含有量は、インク全量に対して０．０１～１質量％の範囲内である。温度応答ポリマーの含有量が上記範囲内であれば、温度応答ポリマーを配合することによる上記本発明の効果が得られる。温度応答ポリマーの含有量は、好ましくは、０．０５～０．８質量％の範囲内である。 The content of the temperature-responsive polymer in the ink of the present invention is in the range of 0.01 to 1% by mass with respect to the total amount of the ink. When the content of the temperature-responsive polymer is within the above range, the effect of the present invention can be obtained by blending the temperature-responsive polymer. The content of the temperature responsive polymer is preferably in the range of 0.05 to 0.8% by mass.
（定着樹脂）
　本発明のインクは定着樹脂を含有する。本発明のインクは温度応答ポリマーに加えて定着樹脂を含有することで、ヘッド内及び基材への着弾時のインクの粘度の調整が適切に行えるとともに、画像形成により得られるインクの塗膜に耐水性を付与できる。定着樹脂は、さらに、着色剤である顔料のバインダーとして機能し、基材、特には非吸収性基材への塗膜の接着性を向上させ、かつインクを用いて得られる塗膜の耐擦性を向上させる機能を有する。定着樹脂は、水不溶性樹脂であることが好ましい。定着樹脂としての水不溶性樹脂は、水系溶媒中に分散した微粒子の状態で用いられることが好ましい。 (Fixing resin)
The ink of the present invention contains a fixing resin. By containing a fixing resin in addition to the temperature-responsive polymer, the ink of the present invention can appropriately adjust the viscosity of the ink when it lands on the head and the base material, and can be used as an ink coating film obtained by image formation. Water resistance can be imparted. The fixing resin further functions as a binder for a pigment which is a colorant, improves the adhesiveness of the coating film to a base material, particularly a non-absorbent base material, and scratch resistance of the coating film obtained by using an ink. It has a function to improve the sex. The fixing resin is preferably a water-insoluble resin. The water-insoluble resin as the fixing resin is preferably used in the form of fine particles dispersed in an aqueous solvent.
　水不溶性樹脂の微粒子は、本来水不溶性の樹脂がミクロな微粒子として水系溶媒中に分散する形態を有するものである。該微粒子は、例えば、乳化剤等を用いて水不溶性樹脂を強制乳化させ微粒子として水系溶媒中に分散させた形態であってもよい。あるいは、水不溶性樹脂の分子内に親水性の官能基を導入して、乳化剤や分散安定剤を使用することなく、水系溶媒中で、それ自身で安定な微粒子を形成したもの、すなわち自己乳化したもの、であってもよい。水不溶性樹脂の微粒子が分散される水系溶媒は、上記同様の水系溶媒が使用でき、通常、水又は水／アルコール混合溶媒が用いられる。以下、水系溶媒中に分散した水不溶性樹脂の微粒子を水分散体ともいう。 The fine particles of the water-insoluble resin have a form in which the originally water-insoluble resin is dispersed as microscopic fine particles in an aqueous solvent. The fine particles may be in the form of, for example, forcibly emulsifying a water-insoluble resin using an emulsifier or the like and dispersing them as fine particles in an aqueous solvent. Alternatively, a hydrophilic functional group is introduced into the molecule of the water-insoluble resin to form stable fine particles by itself in an aqueous solvent without using an emulsifier or a dispersion stabilizer, that is, self-emulsified. It may be a thing. As the aqueous solvent in which the fine particles of the water-insoluble resin are dispersed, the same aqueous solvent as described above can be used, and usually water or a water / alcohol mixed solvent is used. Hereinafter, the fine particles of the water-insoluble resin dispersed in the aqueous solvent are also referred to as an aqueous dispersion.
　なお、本発明において、「水不溶性樹脂」とは、樹脂を１０５℃で２時間乾燥させた後、２５℃の水１００ｇに溶解させたときに、その溶解量が１０ｇ以下、好ましくは５ｇ以下、更に好ましくは１ｇ以下である樹脂をいう。ただし、樹脂が塩生成基を有する場合、溶解量は、その種類に応じて、樹脂の塩生成基を酢酸又は水酸化ナトリウムで１００％中和したときの溶解量である。 In the present invention, the term "water-insoluble resin" means that when the resin is dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C., the amount of the resin dissolved is 10 g or less, preferably 5 g or less. More preferably, it refers to a resin having a weight of 1 g or less. However, when the resin has a salt-forming group, the dissolved amount is the dissolved amount when the salt-forming group of the resin is 100% neutralized with acetic acid or sodium hydroxide, depending on the type.
　本発明に係る定着樹脂としては、水不溶性樹脂であるポリエステル樹脂、ポリウレタン樹脂及びポリアクリル樹脂等が好ましい。本発明において定着樹脂として、これらの１種を単独で用いてもよく、２種以上を組み合わせて用いてもよい。 As the fixing resin according to the present invention, water-insoluble resins such as polyester resin, polyurethane resin and polyacrylic resin are preferable. In the present invention, as the fixing resin, one of these may be used alone, or two or more thereof may be used in combination.
　定着樹脂は、インクの全質量（１００質量％）に対して、１～１０質量％の範囲内で含有される。定着樹脂の含有量が上記範囲内であれば、定着樹脂を配合することによる上記本発明の効果が得られる。定着樹脂の含有量は、好ましくは、２～８質量％の範囲内であり、より好ましくは、３～６質量％の範囲内である。 The fixing resin is contained in the range of 1 to 10% by mass with respect to the total mass (100% by mass) of the ink. When the content of the fixing resin is within the above range, the effect of the present invention can be obtained by blending the fixing resin. The content of the fixing resin is preferably in the range of 2 to 8% by mass, more preferably in the range of 3 to 6% by mass.
　なお、インクにおける温度応答ポリマーと定着樹脂の含有量については、温度応答ポリマーと定着樹脂の合計含有量に対する温度応答ポリマーの含有量の割合（百分率）が０．１～２０質量％の範囲内となる関係であることが好ましい。該割合は、０．５～１０質量％であることがより好ましい。温度応答ポリマーと定着樹脂の合計含有量に対する温度応答ポリマーの含有量の割合が上記範囲内であることで、インクから得られる塗膜（画像）の耐水性と良好なピニング特性を両立しやすい。 Regarding the content of the temperature-responsive polymer and the fixing resin in the ink, the ratio (percentage) of the content of the temperature-responsive polymer to the total content of the temperature-responsive polymer and the fixing resin is in the range of 0.1 to 20% by mass. It is preferable that the relationship is as follows. The ratio is more preferably 0.5 to 10% by mass. When the ratio of the content of the temperature-responsive polymer to the total content of the temperature-responsive polymer and the fixing resin is within the above range, it is easy to achieve both the water resistance of the coating film (image) obtained from the ink and the good pinning characteristics.
〔ポリエステル樹脂〕
　定着樹脂として用いるポリエステル樹脂は、多価アルコール成分と多価カルボン酸、多価カルボン酸無水物、多価カルボン酸エステル等の多価カルボン酸成分とを用いて得ることができる。 [Polyester resin]
The polyester resin used as the fixing resin can be obtained by using a polyhydric alcohol component and a polyvalent carboxylic acid component such as a polyvalent carboxylic acid, a polyvalent carboxylic acid anhydride, or a polyvalent carboxylic acid ester.
　上記多価アルコール成分としては、２価のアルコール（ジオール）、具体的には炭素数２～３６の範囲内のアルキレングリコール（エチレングリコール、１，２－プロピレングリコール、１，３－プロピレングリコール、１，４－ブチレングリコール、１，６－ヘキサンジオール等）、炭素数４～３６の範囲内のアルキレンエーテルグリコール（ジエチレングリコール、トリエチレングリコール、ジプロピレングリコール、ポリエチレングリコール、ポリプロピレングリコール、ポリブチレングリコール等）、炭素数６～３６の範囲内の脂環式ジオール（１，４－シクロヘキサンジメタノール、水素添加ビスフェノールＡ等）、前記脂環式ジオールの炭素数２～４の範囲内のアルキレンオキシド（エチレンオキシド（以下、ＥＯと略記する。）、プロピレンオキシド（以下、ＰＯと略記する。）、ブチレンオキシド（以下、ＢＯと略記する。））付加物（付加モル数１～３０の範囲）又はビスフェノール類（ビスフェノールＡ、ビスフェノールＦ、ビスフェノールＳ等）の炭素数２～４の範囲内のアルキレンオキシド（ＥＯ、ＰＯ、ＢＯ等）付加物（付加モル数２～３０の範囲）等が挙げられる。これらは、１種単独で使用してもよいし、２種以上を併用してもよい。 The polyhydric alcohol component includes a dihydric alcohol (diol), specifically, an alkylene glycol (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1) in the range of 2 to 36 carbon atoms. , 4-butylene glycol, 1,6-hexanediol, etc.), alkylene ether glycol in the range of 4 to 36 carbon atoms (diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polybutylene glycol, etc.), An alicyclic diol having 6 to 36 carbon atoms (1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.) and an alkylene oxide having 2 to 4 carbon atoms of the alicyclic diol (ethylene oxide (hereinafter referred to as ethylene oxide)). , EO (abbreviated as EO), propylene oxide (hereinafter abbreviated as PO), butylene oxide (hereinafter abbreviated as BO)) adduct (with the number of added moles in the range of 1 to 30) or bisphenols (bisphenol A). , Bisphenol F, Bisphenol S, etc.) alkylene oxides (EO, PO, BO, etc.) in the range of 2 to 4 carbon atoms (range of 2 to 30 moles added) and the like. These may be used alone or in combination of two or more.
　上記多価カルボン酸成分としては、２価のカルボン酸（ジカルボン酸）、具体的には炭素数４～３６の範囲内のアルカンジカルボン酸（コハク酸、アピジン酸、セバシン酸等）、アルケニルコハク酸（ドデセニルコハク酸等）、炭素数４～３６の範囲内の脂環式ジカルボン酸（ダイマー酸（２量化リノール酸）等）、炭素数４～３６の範囲内のアルケンジカルボン酸（マレイン酸、フマル酸、シトラコン酸、メサコン酸等）、又は炭素数８～３６の範囲内の芳香族ジカルボン酸（フタル酸、イソフタル酸、テレフタル酸又はこれらの誘導体、ナフタレンジカルボン酸等）等が挙げられる。これらは、１種単独で使用してもよいし、２種以上を併用してもよい。 The polyvalent carboxylic acid component includes a divalent carboxylic acid (dicarboxylic acid), specifically, an alkandicarboxylic acid (succinic acid, apidic acid, sebacic acid, etc.) in the range of 4 to 36 carbon atoms, and an alkenyl succinic acid. (Dodecenyl succinic acid, etc.), alicyclic dicarboxylic acid in the range of 4 to 36 carbon atoms (dimeric acid (dimerized linoleic acid), etc.), arcendicarboxylic acid in the range of 4 to 36 carbon atoms (maleic acid, fumaric acid, etc.) , Citraconic acid, mesaconic acid, etc.), or aromatic dicarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid or derivatives thereof, naphthalenedicarboxylic acid, etc.) in the range of 8 to 36 carbon atoms can be mentioned. These may be used alone or in combination of two or more.
　上記ポリエステル樹脂の数平均分子量としては、１０００～５００００の範囲内が好ましく、２０００～２００００の範囲内がより好ましい。 The number average molecular weight of the polyester resin is preferably in the range of 1000 to 50,000, and more preferably in the range of 2000 to 20000.
　上記ポリエステル樹脂としては、市販品を使用してもよい。市販品としては、例えば、上記ポリエステル樹脂が水分散体として水系溶媒に分散する分散液を用いてもよい。該分散液の市販品としては、以下のものが例示できる。例示において、括弧内には当該商品（分散液）が含有するポリエステル樹脂の数平均分子量を示す。これらは、１種単独で使用してもよいし、２種以上を併用してもよい。 As the polyester resin, a commercially available product may be used. As a commercially available product, for example, a dispersion liquid in which the polyester resin is dispersed in an aqueous solvent as an aqueous dispersion may be used. Examples of commercially available products of the dispersion liquid include the following. In the example, the number average molecular weight of the polyester resin contained in the product (dispersion liquid) is shown in parentheses. These may be used alone or in combination of two or more.
　以下、いずれも商品名で、エリーテルＫＡ－５０３４（ユニチカ社製、数平均分子量：８５００）、エリーテルＫＡ－５０７１Ｓ（ユニチカ社製、数平均分子量：８５００）、エリーテルＫＡ－１４４９（ユニチカ社製、数平均分子量：７０００）、エリーテルＫＡ－０１３４（ユニチカ社製、数平均分子量：８５００）、エリーテルＫＡ－３５５６（ユニチカ社製、数平均分子量：８０００）、エリーテルＫＡ－６１３７（ユニチカ社製、数平均分子量：５０００）、エリーテルＫＺＡ－６０３４（ユニチカ社製、数平均分子量：６５００）、エリーテルＫＴ－８８０３（ユニチカ社製、数平均分子量：１５０００）、エリーテルＫＴ－８７０１（ユニチカ社製、数平均分子量：１３０００）、エリーテルＫＴ－９２０４（ユニチカ社製、数平均分子量：１７０００）、エリーテルＫＴ－８９０４（ユニチカ社製、数平均分子量：１７０００）、エリーテルＫＴ－０５０７（ユニチカ社製、数平均分子量：１７０００）、エリーテルＫＴ－９５１１（ユニチカ社製、数平均分子量：１７０００）、バイロナールＭＤ－２０００（東洋紡社製、数平均分子量：１８０００）等が挙げられる。 The following are all trade names, such as Elitel KA-5034 (manufactured by Unitica, number average molecular weight: 8500), Elitel KA-5071S (manufactured by Unitica, number average molecular weight: 8500), Elitel KA-1449 (manufactured by Unitica, number). Average molecular weight: 7000), Elitel KA-0134 (manufactured by Unitica, number average molecular weight: 8500), Elitel KA-3556 (manufactured by Unitica, number average molecular weight: 8000), Elitel KA-6137 (manufactured by Unitica, number average molecular weight) : 5000), Elitel KZA-6034 (manufactured by Unitica, number average molecular weight: 6500), Elitel KT-8803 (manufactured by Unitica, number average molecular weight: 15,000), Elitel KT-8701 (manufactured by Unitica, number average molecular weight: 13000) ), Elitel KT-9204 (manufactured by Unitica, number average molecular weight: 17,000), Elitel KT-8904 (manufactured by Unitica, number average molecular weight: 17,000), Elitel KT-0507 (manufactured by Unitica, number average molecular weight: 17,000), Examples thereof include Elitel KT-9511 (manufactured by Unitica, number average molecular weight: 17,000) and Byronal MD-2000 (manufactured by Toyo Boseki, number average molecular weight: 18,000).
〔ポリウレタン樹脂〕
　定着樹脂として用いるポリウレタン樹脂としては、親水基を有するものを用いることができる。上記親水基の例には、カルボキシ基（－ＣＯＯＨ）及びその塩、スルホン酸基（－ＳＯ３Ｈ）及びその塩等が含まれる。上記塩としては、ナトリウム塩、カリウム塩などのアルカリ金属塩、及びアミン塩等が含まれる。上記親水基の中では、カルボキシ基又はその塩であることが好ましい。 [Polyurethane resin]
As the polyurethane resin used as the fixing resin, one having a hydrophilic group can be used. Examples of the hydrophilic group include a carboxyl group (-COOH) and salts thereof, sulfonic acid group (-SO 3 H) and a salt. Examples of the salt include alkali metal salts such as sodium salt and potassium salt, amine salts and the like. Among the above hydrophilic groups, a carboxy group or a salt thereof is preferable.
　上記ポリウレタン樹脂は、その分子内に水溶性官能基を有する自己乳化型ポリウレタンが水系溶媒に分散させた水分散体、又は界面活性剤を併用して強力な機械剪断力の下で乳化した強制乳化型ポリウレタンが水系溶媒に分散させた水分散体であることが好ましい。上記水分散体におけるポリウレタン樹脂は、ポリオールと有機ポリイソシアネート及び親水基含有化合物との反応により得ることができる。 The above-mentioned polyurethane resin is forcibly emulsified under a strong mechanical shearing force by using an aqueous dispersion in which a self-emulsifying polyurethane having a water-soluble functional group in its molecule is dispersed in an aqueous solvent or a surfactant in combination. The type polyurethane is preferably an aqueous dispersion dispersed in an aqueous solvent. The polyurethane resin in the aqueous dispersion can be obtained by reacting a polyol with an organic polyisocyanate and a hydrophilic group-containing compound.
　上記ポリウレタン樹脂の水分散体の調製に使用し得るポリオールの例には、ポリエステルポリオール、ポリエーテルポリオール、ポリカーボネートポリオール、及びポリオレフィン系ポリオールなどが含まれる。 Examples of polyols that can be used to prepare an aqueous dispersion of the polyurethane resin include polyester polyols, polyether polyols, polycarbonate polyols, and polyolefin-based polyols.
　ポリエステルポリオールの例には、エチレングリコール、ジエチレングリコール、トリエチレングリコール、１，２－及び１，３－プロピレングリコール、ネオペンチルグリコール、１，３－及び１，４－ブタンジオール、３－メチルペンタンジオール、ヘキサメチレングリコール、１，８－オクタンジオール、２－メチル－１，３－プロパンジオール、ビスフェノールＡ、水添ビスフェノールＡ、トリメチロールプロパン、シクロヘキサンジメタノール等の低分子ポリオール；コハク酸、グルタル酸、アジピン酸、セバシン酸、フタル酸、イソフタル酸、テレフタル酸、トリメリット酸、テトラヒドロフラン酸、エンドメチンテトラヒドロフラン酸、及びヘキサヒドロフタル酸などの多価カルボン酸との縮合物が含まれる。 Examples of polyester polyols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2- and 1,3-propylene glycol, neopentyl glycol, 1,3- and 1,4-butanediol, 3-methylpentanediol, Low molecular weight polyols such as hexamethylene glycol, 1,8-octanediol, 2-methyl-1,3-propanediol, bisphenol A, hydrogenated bisphenol A, trimethylolpropane, cyclohexanedimethanol; succinic acid, glutaric acid, adipine Includes condensates with polyvalent carboxylic acids such as acids, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, tetrahydrofuran acid, endomethine tetrahydrofuran acid, and hexahydrophthalic acid.
　ポリエーテルポリオールの例には、ポリエチレングリコール、ポリプロピレングリコール、ポリエチレンポリテトラメチレングリコール、ポリプロピレンポリテトレメチレングリコール、及びポリテトラメチレングリコールなどが含まれる。 Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene polytetramethylene glycol, polypropylene polytetremethylene glycol, polytetramethylene glycol and the like.
　ポリカーボネートポリオールの例には、ジフェニルカーボネート、ジメチルカーボネート又はホスゲン等の炭酸誘導体と、ジオールとの反応により得られる化合物が含まれる。上記ジオールの例には、エチレングリコール、ジエチレングリコール、トリエチレングリコール、１，２－及び１，３－プロピレングリコール、ネオペンチルグリコール、１，３－及び１，４－ブタンジオール、３－メチルペンタンジオール、ヘキサメチレングリコール、１，８－オクタンジオール、２－メチル－１，３－プロパンジオール、ビスフェノールＡ、水添ビスフェノールＡ、トリメチロールプロパン、及びシクロヘキサンジメタノールなどが含まれる。 Examples of polycarbonate polyols include compounds obtained by reacting carbonic acid derivatives such as diphenyl carbonate, dimethyl carbonate or phosgene with diols. Examples of the above diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2- and 1,3-propylene glycol, neopentyl glycol, 1,3- and 1,4-butanediol, 3-methylpentanediol, etc. Hexamethylene glycol, 1,8-octanediol, 2-methyl-1,3-propanediol, bisphenol A, hydrogenated bisphenol A, trimethylolpropane, cyclohexanedimethanol and the like are included.
　また、ポリウレタン樹脂の水分散体の調製に使用し得る有機ポリイソシアネートの例には、トリレンジイソシアネート（ＴＤＩ）、ジフェニルメタンジイソシアネート（ＭＤＩ）、ポリメリックＭＤＩ、キシリレンジイソシアネート（ＸＤＩ）、テトラメチルキシリレンジイソシアネート（ＴＭＸＤＩ）などの芳香族イソシアネート；ヘキサメチレンジイソシアネート（ＨＭＤＩ）などの脂肪族イソシアネート；イソホロンジイソシアネート（ＩＰＤＩ）、４，４’－ジシクロヘキシルメタンジイソシアネート（水素添加ＭＤＩ、Ｈ１２ＭＤＩ）などの脂環族イソシアネートが含まれる。これらは、１種類のみを単独で使用してもよく、２種類以上を併用してもよい。 Examples of organic polyisocyanates that can be used to prepare aqueous dispersions of polyurethane resins include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polypeptide MDI, xylylene diisocyanate (XDI), and tetramethylxylylene diisocyanate. Aromatic isocyanates such as (TMXDI); aliphatic isocyanates such as hexamethylene diisocyanate (HMDI); alicyclic isocyanates such as isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI, H12MDI). Is Only one type of these may be used alone, or two or more types may be used in combination.
　また、ポリウレタン樹脂の水分散体の調製に使用し得る親水基含有化合物の例には、２，２－ジメチロールプロピオン酸、２，２－ジメチロールブタン酸、２，２－ジメチロール酪酸、２，２－ジメチロール吉草酸、グリシンなどのカルボン酸含有化合物、及びそのナトリウム塩、カリウム塩、アミン塩などの誘導体；タウリン（すなわち、アミノエチルスルホン酸）、エトキシポリエチレングリコールスルホン酸などのスルホン酸含有化合物、及びそのナトリウム塩、カリウム塩、アミン塩等の誘導体が含まれる。 Examples of hydrophilic group-containing compounds that can be used to prepare aqueous dispersions of polyurethane resins include 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylolbutyric acid, 2, 2-Carboxylic acid-containing compounds such as valeric acid and glycine, and derivatives thereof such as sodium salts, potassium salts and amine salts; sulfonic acid-containing compounds such as taurine (ie, aminoethyl sulfonic acid) and ethoxypolyethylene glycol sulfonic acid. And derivatives such as sodium salt, potassium salt, amine salt and the like.
　ポリウレタン樹脂は、公知の方法により得ることができる。例えば、上述したポリオールと有機ポリイソシアネートと、親水基含有化合物とを混合し、３０～１３０℃で３０分～５０時間反応させることにより、ポリウレタン樹脂を得ることができる。 Polyurethane resin can be obtained by a known method. For example, a polyurethane resin can be obtained by mixing the above-mentioned polyol, organic polyisocyanate, and a hydrophilic group-containing compound and reacting them at 30 to 130 ° C. for 30 minutes to 50 hours.
　上記ポリウレタン樹脂は、鎖伸長剤により伸長してポリマー化することで、親水基を有するポリウレタン樹脂となる。鎖伸長剤としては、水及び／又はアミン化合物であることが好ましい。鎖伸長剤として水やアミン化合物を用いることにより、遊離イソシアネートと短時間で反応して、イソシアネート末端プレポリマーを効率よく伸長させることができる。 The polyurethane resin becomes a polyurethane resin having a hydrophilic group by being elongated with a chain extender and polymerized. The chain extender is preferably a water and / or amine compound. By using water or an amine compound as the chain extender, the isocyanate-terminated prepolymer can be efficiently extended by reacting with free isocyanate in a short time.
　鎖伸長剤としてのアミン化合物の例には、エチレンジアミン、トリエチレンジアミンなどの脂肪族ポリアミン；メタキシレンジアミン、トルイレンジアミンなどの芳香族ポリアミン；ヒドラジン、アジピン酸ジヒドラジド等のポリヒドラジノ化合物等が含まれる。上記アミン化合物には、上記ポリアミンとともに、ポリマー化を大きく阻害しない程度で、ジブチルアミンなどの１価のアミンやメチルエチルケトオキシム等を反応停止剤として含んでいてもよい。 Examples of amine compounds as chain extenders include aliphatic polyamines such as ethylenediamine and triethylenediamine; aromatic polyamines such as m-xylylenediamine and toluylenediamine; and polyhydradino compounds such as hydrazine and dihydrazide adipic acid. The amine compound may contain, together with the polyamine, a monovalent amine such as dibutylamine, methyl ethyl ketooxime, or the like as a reaction terminator to the extent that it does not significantly inhibit polymerization.
　なお、ポリウレタン樹脂の合成においては、イソシアネートと不活性であり、ウレタンプレポリマーを溶解しうる溶媒を用いてもよい。これらの溶媒の例には、ジオキサン、メチルエチルケトン、ジメチルホルムアミド、テトラヒドロフラン、Ｎ－メチル－２－ピロリドン、トルエン、及びプロピレングリコールモノメチルエーテルアセテート等が含まれる。反応段階で使用されるこれらの親水性有機溶媒は、最終的に除去されるのが好ましい。 In the synthesis of the polyurethane resin, a solvent that is inactive with isocyanate and can dissolve the urethane prepolymer may be used. Examples of these solvents include dioxane, methyl ethyl ketone, dimethylformamide, tetrahydrofuran, N-methyl-2-pyrrolidone, toluene, propylene glycol monomethyl ether acetate and the like. It is preferable that these hydrophilic organic solvents used in the reaction step are finally removed.
　また、ポリウレタン樹脂の合成においては、反応を促進させるために、アミン触媒（例えば、トリエチルアミン、Ｎ－エチルモルフォリン、トリエチルジアミン等）、スズ系触媒（例えば、ジブチルスズジラウレート、ジオクチルスズジラウレート、オクチル酸スズ等）、及びチタン系触媒（例えば、テトラブチルチタネート等）などの触媒を添加してもよい。 Further, in the synthesis of polyurethane resin, in order to promote the reaction, an amine catalyst (for example, triethylamine, N-ethylmorpholin, triethyldiamine, etc.) and a tin catalyst (for example, dibutyltin dilaurate, dioctyltin dilaurate, tin octylate) are used. Etc.), and catalysts such as titanium-based catalysts (eg, tetrabutyl titanate, etc.) may be added.
　ポリウレタン樹脂の数平均分子量は、分岐構造や内部架橋構造を導入して可能な限り大きくすることが好ましく、数平均分子量５００００～１０００００００であることが好ましい。分子量を上記範囲内にすることにより、ポリウレタン樹脂が溶剤に溶けにくくなるので、耐候性、耐水性に優れた塗膜が得られるからである。なお、本明細書において、数平均分子量（Ｍｎ）は、ゲル浸透クロマトグラフィー（ＧＰＣ）で測定される値である。数平均分子量（Ｍｎ）は、例えば、株式会社島津製作所製「ＲＩＤ－６Ａ」（カラム：東ソー株式会社製「ＴＳＫ－ＧＥＬ」、溶媒：テトラヒドロフラン（ＴＨＦ）、カラム温度：４０℃）を用いて、ポリスチレン標準試料で作成した検量線から求めることができる。 The number average molecular weight of the polyurethane resin is preferably as large as possible by introducing a branched structure or an internal crosslinked structure, and the number average molecular weight is preferably 50,000 to 10,000,000. By setting the molecular weight within the above range, the polyurethane resin is less likely to dissolve in the solvent, so that a coating film having excellent weather resistance and water resistance can be obtained. In the present specification, the number average molecular weight (Mn) is a value measured by gel permeation chromatography (GPC). The number average molecular weight (Mn) is, for example, "RID-6A" manufactured by Shimadzu Corporation (column: "TSK-GEL" manufactured by Tosoh Corporation, solvent: tetrahydrofuran (THF), column temperature: 40 ° C.). It can be obtained from the calibration curve prepared with a polystyrene standard sample.
　また、上記ポリウレタン樹脂は市販品を用いてもよい。市販品としては、例えば、上記ポリウレタン樹脂が水分散体として水系溶媒に分散する分散液を用いてもよい。 Further, as the polyurethane resin, a commercially available product may be used. As a commercially available product, for example, a dispersion liquid in which the polyurethane resin is dispersed in an aqueous solvent as an aqueous dispersion may be used.
　上記ポリウレタン樹脂の分散液の市販品の例には、ＷＢＲ－０１６Ｕ（大成ファインケミカル株式会社製）、スーパーフレックス６２０、スーパーフレックス６５０、スーパーフレックス５００Ｍ、スーパーフレックスＥ－２０００（いずれも第一工業製薬株式会社製、「スーパーフレックス」は同社の登録商標）、パーマリンＵＣ－２０（三洋化成工業株式会社製、「パーマリン」は同社の登録商標）、パラサーフＵＰ－２２（大原パラヂウム化学株式会社製）、エバファノールＨＡ－５６０（日華化学社製）などが含まれる。 Examples of commercially available polyurethane resin dispersions include WBR-016U (manufactured by Taisei Fine Chemicals Co., Ltd.), Superflex 620, Superflex 650, Superflex 500M, and Superflex E-2000 (all manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.). Company-made, "Superflex" is a registered trademark of the company), Permarin UC-20 (manufactured by Sanyo Kasei Kogyo Co., Ltd., "Permarin" is a registered trademark of the company), Parasurf UP-22 (manufactured by Ohara Palladium Chemical Co., Ltd.), Evafanol HA-560 (manufactured by Nikka Kagaku Co., Ltd.) and the like are included.
〔ポリアクリル樹脂〕
　定着樹脂として用いるポリアクリル樹脂としては、（メタ）アクリル酸エステル成分の（共）重合体、又は（メタ）アクリル酸エステル成分とスチレン成分等の（メタ）アクリル酸エステル成分以外の重合性成分との共重合体が挙げられる。 [Polyacrylic resin]
The polyacrylic resin used as the fixing resin includes a (co) polymer of the (meth) acrylic acid ester component, or a polymerizable component other than the (meth) acrylic acid ester component such as the (meth) acrylic acid ester component and the styrene component. Copolymer of.
　（メタ）アクリル酸エステル成分の例には、（メタ）アクリル酸メチル、（メタ）アクリル酸エチル、（メタ）アクリル酸プロピル、（メタ）アクリル酸ブチル、（メタ）アクリル酸－２－ヒドロキシエチル、（メタ）アクリル酸－２－ヒドロキシプロピル、（メタ）アクリル酸－４－ヒドロキブチル、（メタ）アクリル酸シクロヘキシル、（メタ）アクリル酸テトラヒドロフルフリル、（メタ）アクリル酸イソボルニル、（メタ）アクリル酸ベンジル、（メタ）アクリル酸－２－ヒドロキシブチル、（メタ）アクリル酸ベンジル、（メタ）アクリル酸グリシジル、（メタ）アクリル酸、ジ（メタ）アクリル酸（ジ）エチレングリコール、ジ（メタ）アクリル酸－１，４－ブタンジオ－ル、ジ（メタ）アクリル酸－１，６－ヘキサンジオ－ル、トリ（メタ）アクリル酸トリメチロ－ルプロパン、ジ（メタ）アクリル酸グリセリン、（メタ）アクリル酸－２－エチルヘキシル、（メタ）アクリル酸ラウリル、（メタ）アクリル酸ステアリル、及びアクリルアミド等が含まれる。 Examples of (meth) acrylic acid ester components include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and -2-hydroxyethyl (meth) acrylate. , (Meta) -2-hydroxypropyl acrylate, (meth) -4-hydrokibutyl acrylate, cyclohexyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, (meth) acrylic Benzyl acid, -2-hydroxybutyl (meth) acrylic acid, benzyl (meth) acrylic acid, glycidyl (meth) acrylic acid, (meth) acrylic acid, di (meth) acrylic acid (di) ethylene glycol, di (meth) Acrylic acid-1,4-butanjiol, di (meth) acrylic acid-1,6-hexanediol, tri (meth) acrylic acid trimethylal propane, di (meth) glycerate acrylate, (meth) acrylic acid- 2-Ethylhexyl, lauryl (meth) acrylate, stearyl (meth) acrylate, acrylamide and the like are included.
　スチレン成分の例には、スチレン、４－メチルスチレン、４－ヒドロキシスチレン、４－アセトキシスチレン、４－アセチルスチレン及びスチレンスルホン酸などが含まれる。これらの成分は、１種類のみを単独で使用してもよく、２種類以上を併用してもよい。 Examples of styrene components include styrene, 4-methylstyrene, 4-hydroxystyrene, 4-acetoxystyrene, 4-acetylstyrene, styrenesulfonic acid and the like. Only one of these components may be used alone, or two or more of these components may be used in combination.
　上記ポリアクリル樹脂の数平均分子量（Ｍｎ）は、１０００～５００００であることが好ましく、２０００～２００００であることがより好ましい。上記ポリアクリル樹脂の数平均分子量（Ｍｎ）が１０００以上であると、塗膜の凝集力が強くなり、密着性が向上し、５００００以下であると、有機溶媒に対する溶解性が良く、乳化分散体の粒子径の微小化が促進されるからである。 The number average molecular weight (Mn) of the polyacrylic resin is preferably 1000 to 50,000, and more preferably 2000 to 20000. When the number average molecular weight (Mn) of the polyacrylic resin is 1000 or more, the cohesive force of the coating film becomes strong and the adhesion is improved, and when it is 50,000 or less, the solubility in an organic solvent is good and the emulsified dispersion is obtained. This is because the miniaturization of the particle size of is promoted.
　また、上記ポリアクリル樹脂としては、市販品を用いてもよい。市販品としては、例えば、上記ポリアクリル樹脂が水分散体として水系溶媒に分散する分散液を用いてもよい。 Further, as the polyacrylic resin, a commercially available product may be used. As a commercially available product, for example, a dispersion liquid in which the polyacrylic resin is dispersed in an aqueous solvent as an aqueous dispersion may be used.
　上記ポリアクリル樹脂の分散液の市販品の例には、デルペット６０Ｎ、８０Ｎ（旭化成株式会社製、「デルペット」は同社の登録商標）、ダイヤナールＢＲ５２、ＢＲ８０、ＢＲ８３、ＢＲ８５、ＢＲ８８（三菱ケミカル株式会社製、「ダイヤナール」は同社の登録商標）、ＫＴ７５（デンカ株式会社製）、又はビニブラン２６８０、２６８２、２６８４、２６８５（日信化学工業株式会社製、「ビニブラン」は同社の登録商標）、モビニール６８００Ｄ（ジャパンコーティングレジン社製）等が含まれる。 Examples of commercially available polyacrylic resin dispersions include Delpet 60N, 80N (manufactured by Asahi Kasei Corporation, "Delpet" is a registered trademark of the same company), Dianar BR52, BR80, BR83, BR85, BR88 (Mitsubishi). Chemical Co., Ltd., "Dianar" is a registered trademark of the company), KT75 (Denka Co., Ltd.), or Viniblanc 2680, 2682, 2864, 2685 (Nissin Chemical Industry Co., Ltd., "Viniblanc" is a registered trademark of the company) ), Movinyl 6800D (manufactured by Japan Coating Resin Co., Ltd.) and the like are included.
　これらの中でも、定着樹脂は、酸構造を含有することが好ましい。酸構造を含有すれば、界面活性剤の添加がなくても、水系溶媒中での分散が可能となり、すなわち、自己乳化が可能となり、塗膜の耐水性が向上する。このような自己乳化型の樹脂は、分子のイオン性のみで水系溶媒中に分散安定化しうる。酸構造の例には、カルボキシ基（－ＣＯＯＨ）、スルホン酸基（－ＳＯ３Ｈ）等の酸基等が含まれる。酸構造は、樹脂において側鎖に存在していてもよく、末端に存在していてもよい。 Among these, the fixing resin preferably contains an acid structure. If it contains an acid structure, it can be dispersed in an aqueous solvent without the addition of a surfactant, that is, it can be self-emulsified, and the water resistance of the coating film is improved. Such a self-emulsifying resin can be dispersed and stabilized in an aqueous solvent only by the ionicity of the molecule. Examples of acids structure, carboxy group (-COOH), a contained such an acid group such as a sulfonic acid group (-SO 3 H) is. The acid structure may be present in the side chain or at the end of the resin.
　上記酸構造の一部又は全部は、中和されていることが好ましい。酸構造を中和することにより、樹脂の水分散性を向上させることができる。酸構造を中和する中和剤の例には、有機アミン類が好ましく、トリメチルアミン、トリエチルアミン、トリプロピルアミン、トリブチルアミン、Ｎ－メチルジエタノールアミン、トリエタノールアミン等の有機アミンを用いることが好ましい。 It is preferable that part or all of the acid structure is neutralized. By neutralizing the acid structure, the water dispersibility of the resin can be improved. Organic amines are preferable as examples of the neutralizing agent for neutralizing the acid structure, and organic amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, N-methyldiethanolamine and triethanolamine are preferably used.
（顔料）
　本発明に係るインクに含有される顔料としては、従来公知の有機及び無機顔料が使用できる。例えばアゾレーキ、不溶性アゾ顔料、縮合アゾ顔料、キレートアゾ顔料等のアゾ顔料や、フタロシアニン顔料、ペリレン及びペリレン顔料、アントラキノン顔料、キナクリドン顔料、ジオキサンジン顔料、チオインジゴ顔料、イソインドリノン顔料、キノフタロニ顔料等の多環式顔料や、塩基性染料型レーキ、酸性染料型レーキ等の染料レーキや、ニトロ顔料、ニトロソ顔料、アニリンブラック、昼光蛍光顔料等の有機顔料、カーボンブラック等の無機顔料が挙げられる。 (Pigment)
As the pigment contained in the ink according to the present invention, conventionally known organic and inorganic pigments can be used. For example, azo pigments such as azo lake, insoluble azo pigment, condensed azo pigment, chelate azo pigment, phthalocyanine pigment, perylene and perylene pigment, anthraquinone pigment, quinacridone pigment, dioxandine pigment, thioindigo pigment, isoindolinone pigment, quinophthaloni pigment and the like. Examples thereof include cyclic pigments, dye lakes such as basic dye type lakes and acidic dye type lakes, organic pigments such as nitro pigments, nitroso pigments, aniline blacks and daylight fluorescent pigments, and inorganic pigments such as carbon black.
　好ましく用いることのできる具体的な有機顔料としては、以下の顔料が挙げられる。 Specific organic pigments that can be preferably used include the following pigments.
　マゼンタ又はレッド用の顔料としては、例えば、Ｃ．Ｉ．ピグメントレッド２、Ｃ．Ｉ．ピグメントレッド３、Ｃ．Ｉ．ピグメントレッド５、Ｃ．Ｉ．ピグメントレッド６、Ｃ．Ｉ．ピグメントレッド７、Ｃ．Ｉ．ピグメントレッド１５、Ｃ．Ｉ．ピグメントレッド１６、Ｃ．Ｉ．ピグメントレッド４８：１、Ｃ．Ｉ．ピグメントレッド５３：１、Ｃ．Ｉ．ピグメントレッド５７：１、Ｃ．Ｉ．ピグメントレッド１２２、Ｃ．Ｉ．ピグメントレッド１２３、Ｃ．Ｉ．ピグメントレッド１３９、Ｃ．Ｉ．ピグメントレッド１４４、Ｃ．Ｉ．ピグメントレッド１４９、Ｃ．Ｉ．ピグメントレッド１６６、Ｃ．Ｉ．ピグメントレッド１７７、Ｃ．Ｉ．ピグメントレッド１７８、Ｃ．Ｉ．ピグメントレッド２０２、Ｃ．Ｉ．ピグメントレッド２２２、Ｃ．Ｉ．ピグメントバイオレット１９等が挙げられる。 Examples of pigments for magenta or red include C.I. I. Pigment Red 2, C.I. I. Pigment Red 3, C.I. I. Pigment Red 5, C.I. I. Pigment Red 6, C.I. I. Pigment Red 7, C.I. I. Pigment Red 15, C.I. I. Pigment Red 16, C.I. I. Pigment Red 48: 1, C.I. I. Pigment Red 53: 1, C.I. I. Pigment Red 57: 1, C.I. I. Pigment Red 122, C.I. I. Pigment Red 123, C.I. I. Pigment Red 139, C.I. I. Pigment Red 144, C.I. I. Pigment Red 149, C.I. I. Pigment Red 166, C.I. I. Pigment Red 177, C.I. I. Pigment Red 178, C.I. I. Pigment Red 202, C.I. I. Pigment Red 222, C.I. I. Pigment Violet 19 and the like.
　オレンジ又はイエロー用の顔料としては、例えば、Ｃ．Ｉ．ピグメントオレンジ３１、Ｃ．Ｉ．ピグメントオレンジ４３、Ｃ．Ｉ．ピグメントイエロー１２、Ｃ．Ｉ．ピグメントイエロー１３、Ｃ．Ｉ．ピグメントイエロー１４、Ｃ．Ｉ．ピグメントイエロー１５、Ｃ．Ｉ．ピグメントイエロー１５：３、Ｃ．Ｉ．ピグメントイエロー１７、Ｃ．Ｉ．ピグメントイエロー７４、Ｃ．Ｉ．ピグメントイエロー９３、Ｃ．Ｉ．ピグメントイエロー１２８、Ｃ．Ｉ．ピグメントイエロー９４、Ｃ．Ｉ．ピグメントイエロー１３８、Ｃ．Ｉ．ピグメントイエロー１５５等が挙げられる。特に色調と耐光性のバランスにおいて、Ｃ．Ｉ．ピグメントイエロー１５５が好ましい。 Examples of pigments for orange or yellow include C.I. I. Pigment Orange 31, C.I. I. Pigment Orange 43, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 15, C.I. I. Pigment Yellow 15: 3, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 74, C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 128, C.I. I. Pigment Yellow 94, C.I. I. Pigment Yellow 138, C.I. I. Pigment Yellow 155 and the like. Especially in the balance between color tone and light resistance, C.I. I. Pigment Yellow 155 is preferred.
　グリーン又はシアン用の顔料としては、例えば、Ｃ．Ｉ．ピグメントブルー１５、Ｃ．Ｉ．ピグメントブルー１５：２、Ｃ．Ｉ．ピグメントブルー１５：３、Ｃ．Ｉ．ピグメントブルー１６、Ｃ．Ｉ．ピグメントブルー６０、Ｃ．Ｉ．ピグメントグリーン７等が挙げられる。 Examples of pigments for green or cyan include C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 2, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 16, C.I. I. Pigment Blue 60, C.I. I. Pigment Green 7 and the like.
　また、ブラック用の顔料としては、例えば、Ｃ．Ｉ．ピグメントブラック１、Ｃ．Ｉ．ピグメントブラック６、Ｃ．Ｉ．ピグメントブラック７等が挙げられる。 Further, as a pigment for black, for example, C.I. I. Pigment Black 1, C.I. I. Pigment Black 6, C.I. I. Pigment Black 7 and the like.
　本発明のインクにおける顔料の含有量は２～１０質量％の範囲内である。顔料の含有量が上記範囲内であれば、インクジェットインクとしての機能を果たし、良好な吐出性を維持しながら高品質な画像形成が可能となる。顔料の含有量は、好ましくは、３～７質量％の範囲内である。 The content of the pigment in the ink of the present invention is in the range of 2 to 10% by mass. When the content of the pigment is within the above range, it functions as an inkjet ink, and high-quality image formation is possible while maintaining good ejection properties. The pigment content is preferably in the range of 3-7% by mass.
（顔料分散剤）
　本発明のインクは、顔料を分散させるために任意に顔料分散剤を含有する。顔料分散剤としては、格別限定されないがアニオン性基を有する高分子分散剤が好ましく、数平均分子量が５０００～２０００００の範囲内のものを好適に用いることができる。 (Pigment dispersant)
The ink of the present invention optionally contains a pigment dispersant to disperse the pigment. The pigment dispersant is not particularly limited, but a polymer dispersant having an anionic group is preferable, and those having a number average molecular weight in the range of 5000 to 200,000 can be preferably used.
　顔料分散剤としては、例えば、スチレン、スチレン誘導体、ビニルナフタレン誘導体、アクリル酸、アクリル酸誘導体、マレイン酸、マレイン酸誘導体、イタコン酸、イタコン酸誘導体、フマル酸、フマル酸誘導体から選ばれた２種以上の単量体に由来する構造を有するブロック共重合体、ランダム共重合体及びこれらの塩、ポリオキシアルキレン、ポリオキシアルキレンアルキルエーテル等を挙げることができる。 As the pigment dispersant, for example, two kinds selected from styrene, styrene derivative, vinylnaphthalene derivative, acrylic acid, acrylic acid derivative, maleic acid, maleic acid derivative, itaconic acid, itaconic acid derivative, fumaric acid, and fumaric acid derivative. Examples thereof include block copolymers having a structure derived from the above monomers, random copolymers and salts thereof, polyoxyalkylenes, polyoxyalkylene alkyl ethers and the like.
　顔料分散剤は、アクリロイル基及び酸性基を有することが好ましい。酸性基は中和塩基で中和して添加することが好ましい。ここで中和塩基は特に限定されないが、アンモニア、モノエタノールアミン、ジエタノールアミン、トリエタノールアミン、モルホリン等の有機塩基であることが好ましい。 The pigment dispersant preferably has an acryloyl group and an acidic group. The acidic group is preferably added after being neutralized with a neutralizing base. Here, the neutralizing base is not particularly limited, but is preferably an organic base such as ammonia, monoethanolamine, diethanolamine, triethanolamine, and morpholine.
　また、顔料分散剤の添加量は、顔料に対して、１０～１００質量％の範囲内であることが好ましく、１０～４０質量％の範囲内がより好ましい。 The amount of the pigment dispersant added is preferably in the range of 10 to 100% by mass, more preferably in the range of 10 to 40% by mass with respect to the pigment.
　顔料は、顔料を上記顔料分散剤で被覆した、いわゆるカプセル顔料の形態を有することが特に好ましい。顔料を顔料分散剤で被覆する方法としては、公知の種々の方法を用いることができるが、例えば、転相乳化法、酸析法、又は、顔料を重合性界面活性剤により分散し、そこへモノマーを供給し、重合しながら被覆する方法などを好ましく例示できる。 It is particularly preferable that the pigment has the form of a so-called capsule pigment in which the pigment is coated with the above pigment dispersant. As a method of coating the pigment with a pigment dispersant, various known methods can be used. For example, a phase inversion emulsification method, an acid analysis method, or a method of dispersing a pigment with a polymerizable surfactant is used therein. A method of supplying a monomer and coating it while polymerizing can be preferably exemplified.
　特に好ましい方法として、顔料分散剤を、メチルエチルケトンなどの有機溶剤に溶解し、さらに塩基にて樹脂中の酸性基を部分的、若しくは完全に中和後、顔料及びイオン交換水を添加し、分散したのち、有機溶剤を除去し、必要に応じて加水して調製する方法を挙げることができる。 As a particularly preferable method, the pigment dispersant is dissolved in an organic solvent such as methyl ethyl ketone, the acidic groups in the resin are partially or completely neutralized with a base, and then the pigment and ion-exchanged water are added and dispersed. After that, a method of removing the organic solvent and adding water as needed can be mentioned.
　インク中における顔料の分散状態の平均粒子径は、５０ｎｍ以上、２００ｎｍ未満であることが好ましい。これにより、顔料の分散安定性を向上でき、インクの保存安定性を向上できる。顔料の粒子径測定は、動的光散乱法、電気泳動法等を用いた市販の粒径測定機器により求めることができるが、動的光散乱法による測定が簡便で、且つ該粒子径領域を精度よく測定できる。 The average particle size of the pigment in the dispersed state in the ink is preferably 50 nm or more and less than 200 nm. As a result, the dispersion stability of the pigment can be improved, and the storage stability of the ink can be improved. The particle size of the pigment can be measured by a commercially available particle size measuring device using a dynamic light scattering method, an electrophoresis method, etc., but the measurement by the dynamic light scattering method is simple and the particle size region can be measured. It can be measured accurately.
　顔料は、顔料分散剤及びその他所望する諸目的に応じて必要な添加物とともに、分散機により分散して用いることができる。 The pigment can be dispersed and used by a disperser together with a pigment dispersant and other additives necessary for various desired purposes.
　分散機としては、従来公知のボールミル、サンドミル、ラインミル、高圧ホモジナイザー等を使用できる。中でもサンドミルによって顔料を分散させると、粒度分布がシャープとなるため好ましい。また、サンドミル分散に使用するビーズの材質は、格別限定されないが、ビーズ破片の生成やイオン成分のコンタミネーションを防止する観点から、ジルコニア又はジルコンであることが好ましい。さらに、このビーズ径は、０．３～３ｍｍの範囲内であることが好ましい。 As the disperser, a conventionally known ball mill, sand mill, line mill, high-pressure homogenizer, or the like can be used. Above all, it is preferable to disperse the pigment with a sand mill because the particle size distribution becomes sharp. The material of the beads used for the sand mill dispersion is not particularly limited, but is preferably zirconia or zircon from the viewpoint of preventing the formation of bead fragments and the contamination of ionic components. Further, the bead diameter is preferably in the range of 0.3 to 3 mm.
（水系溶媒）
　本発明のインクは、水系溶媒を含有する。水系溶媒は、水を必須の溶媒として含有し、粘度調整などのために、好ましくは、任意に公知の水性溶媒を含む。水系溶媒が水性溶媒を含む場合、温度応答ポリマーが該水系溶媒に対して下限臨界共溶温度を有するように、水と組み合わせる水性溶媒の種類及び量を調整することが好ましい。 (Aqueous solvent)
The ink of the present invention contains an aqueous solvent. The aqueous solvent contains water as an essential solvent, and preferably contains an arbitrarily known aqueous solvent for viscosity adjustment and the like. When the aqueous solvent contains an aqueous solvent, it is preferable to adjust the type and amount of the aqueous solvent to be combined with water so that the temperature-responsive polymer has a lower limit critical eutectic temperature with respect to the aqueous solvent.
　本発明に係るインクに含まれる水については、特に限定されるものではなく、イオン交換水、蒸留水、又は純水であり得る。 The water contained in the ink according to the present invention is not particularly limited, and may be ion-exchanged water, distilled water, or pure water.
　インクに含有される水性溶媒としては、水と組み合わせて用いた際に、温度応答ポリマーの水系溶媒に対するＬＣＳＴを、温度応答ポリマーの水に対するＬＣＳＴから大きく変化させない水性溶媒が好ましい。上記のとおり、温度応答ポリマーの水系溶媒に対するＬＣＳＴと、温度応答ポリマーの水に対するＬＣＳＴとの差は概ね１０℃以内であることが好ましい。 As the aqueous solvent contained in the ink, an aqueous solvent that does not significantly change the LCST of the temperature-responsive polymer with respect to the water-based solvent from the LCST of the temperature-responsive polymer with respect to water when used in combination with water is preferable. As described above, it is preferable that the difference between the LCST of the temperature-responsive polymer with respect to the aqueous solvent and the LCST of the temperature-responsive polymer with respect to water is approximately 10 ° C. or less.
　水性溶媒としては、例えば、アルコール類、多価アルコール類、アミン類、アミド類、グリコールエーテル類、炭素数が４以上である１，２－アルカンジオール類等が挙げられる。 Examples of the aqueous solvent include alcohols, polyhydric alcohols, amines, amides, glycol ethers, 1,2-alkanediols having 4 or more carbon atoms, and the like.
　アルコール類としては、例えば、メタノール、エタノール、１－プロパノール、２－プロパノール、１－ブタノール、２－ブタノール、２－メチル－１－プロパノール、ｔ－ブタノール、３－メトキシ－１－ブタノール、３－メトキシ－３－メチルブタノール、１－オクタノール、２－オクタノール、ｎ－ノニルアルコール、トリデシルアルコール、ｎ－ウンデシルアルコール、ステアリルアルコール、オレイルアルコール、ベンジルアルコール等が挙げられる。 Examples of alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, t-butanol, 3-methoxy-1-butanol, 3-methoxy. Examples thereof include -3-methylbutanol, 1-octanol, 2-octanol, n-nonyl alcohol, tridecyl alcohol, n-undecyl alcohol, stearyl alcohol, oleyl alcohol and benzyl alcohol.
　多価アルコール類としては、例えば、エチレングリコール、ジエチレングリコール、トリエチレングリコール、テトラエチレングリコール、エチレンオキサイド基の数が５以上のポリエチレングリコール、プロピレングリコール、ジプロピレングリコール、トリプロピレングリコール、プロピレンオキサイド基の数が４以上のポリプロピレングリコール、ブチレングリコール、ヘキサンジオール、ペンタンジオール、グリセリン、ヘキサントリオール、チオジグリコール等が挙げられる。 Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and the number of polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and propylene oxide groups having 5 or more ethylene oxide groups. Examples thereof include polypropylene glycol having 4 or more, butylene glycol, hexanediol, pentandiol, glycerin, hexanetriol, thiodiglycol and the like.
　アミン類としては、例えば、エタノールアミン、ジエタノールアミン、トリエタノールアミン、Ｎ－メチルジエタノールアミン、Ｎ－エチルジエタノールアミン、モルホリン、Ｎ－エチルモルホリン、エチレンジアミン、ジエチレンジアミン、トリエチレンテトラミン、テトラエチレンペンタミン、ポリエチレンイミン、ペンタメチルジエチレントリアミン、テトラメチルプロピレンジアミン等が挙げられる。 Examples of amines include ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, and the like. Examples thereof include pentamethyldiethylenetriamine and tetramethylpropylenediamine.
　アミド類としては、例えば、ホルムアミド、Ｎ，Ｎ－ジメチルホルムアミド、Ｎ，Ｎ－ジメチルアセトアミド等が挙げられる。 Examples of amides include formamide, N, N-dimethylformamide, N, N-dimethylacetamide and the like.
　グリコールエーテル類としては、例えば、エチレングリコールモノエチルエーテル、エチレングリコールモノブチルエーテル、ジエチレングリコールモノエチルエーテル、ジエチレングリコールモノブチルエーテル、トリエチレングリコールモノブチルエーテル、プロピレングリコールモノプロピルエーテル、ジプロピレングリコールモノメチルエーテル、トリプロピレングリコールモノメチルエーテル等が挙げられる。 Examples of glycol ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, and tripropylene glycol monomethyl ether. Examples include ether.
　炭素数が４以上である１，２－アルカンジオール類としては、例えば、１，２－ブタンジオール、１，２－ペンタンジオール、１，２－ヘキサンジオール、１，２－ヘプタンジオール等が挙げられる。 Examples of 1,2-alkanediols having 4 or more carbon atoms include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol and the like. ..
　特に好ましく用いられる水性溶媒は多価アルコール類であり、高速プリント時の滲みを好適に抑制することができる。具体的には、エチレングリコール、ジエチレングリコール、トリエチレングリコール、テトラエチレングリコール、プロピレングリコール、ジプロピレングリコール、トリプロピレングリコールが好ましい。 A particularly preferably used aqueous solvent is a polyhydric alcohol, which can suitably suppress bleeding during high-speed printing. Specifically, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol are preferable.
　インクは、これら水性溶媒から選ばれる１種又は２種以上を組み合わせて含有することができる。 The ink can be contained in one type or a combination of two or more types selected from these aqueous solvents.
　本発明のインクにおける水の含有量は、インクの全質量に対して２０～８０質量％の範囲内の量であることが好ましく、４０～７０質量％の範囲内であることがより好ましい。また、インク中の水性溶媒の含有量は、インクの全質量に対して１０～６０質量％の範囲内の量であることが好ましい。インクにおける水と水性溶媒との含有割合は、温度応答ポリマーの水系溶媒に対するＬＣＳＴが、温度応答ポリマーの水に対するＬＣＳＴ±１０℃の範囲内となるように調整することが好ましい。 The water content in the ink of the present invention is preferably in the range of 20 to 80% by mass, and more preferably in the range of 40 to 70% by mass with respect to the total mass of the ink. The content of the aqueous solvent in the ink is preferably in the range of 10 to 60% by mass with respect to the total mass of the ink. The content ratio of water and the aqueous solvent in the ink is preferably adjusted so that the LCST of the temperature-responsive polymer with respect to the aqueous solvent is within the range of LCST of ± 10 ° C. with respect to water of the temperature-responsive polymer.
　本発明のインクにおいては、溶媒として実質的に水系溶媒のみが含有されること、すなわち、非水性溶媒を含有しないことが好ましい。インク中の水系溶媒の含有量は、水と水性溶媒の合計の含有量として、５０～９５質量％の範囲内の量であることが好ましく、５０～９０質量％の範囲内の量であることがより好ましい。 It is preferable that the ink of the present invention contains substantially only an aqueous solvent as a solvent, that is, does not contain a non-aqueous solvent. The content of the aqueous solvent in the ink is preferably in the range of 50 to 95% by mass, preferably in the range of 50 to 90% by mass, as the total content of water and the aqueous solvent. Is more preferable.
（チキソ性付与剤）
　本発明のインクは任意にチキソ性付与剤を含有することができる。チキソ性付与剤は、インクに、高シェア時は低粘度であり低シェア時は高粘度であるというチキソ性を付与することで、本発明のインクにおける良好な吐出性の維持と高品質な画像形成の両立という効果をより高める目的で用いられる。 (Thixotropic agent)
The ink of the present invention can optionally contain a thixotropic agent. The thixotropic agent imparts thixotropy to the ink, which is low viscosity at the time of high share and high viscosity at the time of low share, thereby maintaining good ejection property and high quality image in the ink of the present invention. It is used for the purpose of enhancing the effect of achieving both formation.
　チキソ性付与剤は、インクにチキソ性を付与できる材料であれば特に制限なく使用できる。チキソ性付与剤は、粒子形状（ただし、粒子形状は繊維形状を含む）であることが好ましく、アスペクト比が２０以上であることがより好ましい。 The thixotropic agent can be used without particular limitation as long as it is a material that can impart thixotropic property to the ink. The thixotropy-imparting agent preferably has a particle shape (however, the particle shape includes a fiber shape), and more preferably has an aspect ratio of 20 or more.
　チキソ性付与剤が粒子形状である場合の形状としては、楕円状、鱗片状、板状、針状、繊維等が好ましい。チキソ性付与剤の短径に対する長径の比を示すアスペクト比は、２０以上であることが好ましい。アスペクト比が２０以上であると、インクによりチキソ性を付与しやすい。なお、チキソ性付与剤の長径は２μｍ以下が好ましい。チキソ性付与剤の長径が２μｍを超えるとインクジェット吐出性に影響を及ぼす場合がある。 When the thixotropic agent has a particle shape, the shape is preferably elliptical, scaly, plate-shaped, needle-shaped, fiber or the like. The aspect ratio indicating the ratio of the major axis to the minor axis of the thixotropic agent is preferably 20 or more. When the aspect ratio is 20 or more, the thixotropic property is easily imparted by the ink. The major axis of the thixotropic agent is preferably 2 μm or less. If the major axis of the thixotropic agent exceeds 2 μm, the inkjet ejection property may be affected.
　なお、本明細書において、チキソ性付与剤のアスペクト比の測定断面は、粒子の長さ方向に平行する断面であって厚さ方向に切った断面である。アスペクト比は、該断面から得られる各５０個の平均粒子長径と平均粒子短径から求めた値である。ここで、粒子形状が、鱗片状、板状の場合、短径は粒子の厚さであり、長径は粒子のアスペクト比測定断面の長辺の長さ、もしくは粒子を平面視した場合の長辺の長さ又は最大径ある。粒子形状が、針状、繊維状の場合、長径は粒子の長さであり、短径は粒子の長さ方向に直交する断面の長径、又は粒子を平面視した場合の最大幅である。 In the present specification, the measurement cross section of the aspect ratio of the thixo-imparting agent is a cross section parallel to the length direction of the particles and cut in the thickness direction. The aspect ratio is a value obtained from the average particle major axis and the average particle minor axis of each of the 50 particles obtained from the cross section. Here, when the particle shape is scaly or plate-shaped, the minor axis is the thickness of the particle, and the major axis is the length of the long side of the aspect ratio measurement cross section of the particle, or the long side when the particle is viewed in a plan view. Length or maximum diameter. When the particle shape is needle-like or fibrous, the major axis is the length of the particle, and the minor axis is the major axis of the cross section orthogonal to the length direction of the particle, or the maximum width when the particle is viewed in a plan view.
　チキソ性付与剤の材質としては、多糖類、無機粒子等が挙げられる。多糖類として、具体的には、セルロース、キチン、キトサン、キサンタンガム、ウェランガム、サクシノグリカン、グアーガム、ローカストビーンガム及びその誘導体、グリコマンナン、寒天、カラギーナン等が挙げられる。 Examples of the material of the thixotropy-imparting agent include polysaccharides and inorganic particles. Specific examples of the polysaccharide include cellulose, chitin, chitosan, xanthan gum, welan gum, succinoglycan, guar gum, locust bean gum and derivatives thereof, glycomannan, agar, carrageenan and the like.
　多糖類としては、重量平均分子量が数百万程度の天然多糖類が好ましい。具体的には、キサンタンガム、グアーガム、及びカラギーナン等が好ましい。 As the polysaccharide, a natural polysaccharide having a weight average molecular weight of about several million is preferable. Specifically, xanthan gum, guar gum, carrageenan and the like are preferable.
　また、本発明のインクにおいてはチキソ性付与剤として、樹木、蟹、海老等の甲殻類の殻等の、多糖類の集合体を、触媒を用いる酸化処理、グラインダー等を用いる機械処理等の従来公知の方法で繊維を極めて細かく解して微細化した多糖類のナノファイバーが好ましく用いられる。多糖類のナノファイバーにおける多糖類としては、セルロース、キチン及びキトサンのうち少なくとも一つであることが好ましく、セルロースがより好ましい。 Further, in the ink of the present invention, as a tixo-imparting agent, conventional methods such as oxidation treatment using a catalyst, mechanical treatment using a grinder, etc., for an aggregate of polysaccharides such as shells of crustaceans such as trees, crabs, and shrimp. Nanofibers, which are polysaccharides obtained by finely breaking the fibers by a known method, are preferably used. The polysaccharide in the polysaccharide nanofiber is preferably at least one of cellulose, chitin and chitosan, with cellulose being more preferred.
　なお、本明細書において、ナノファイバーは、幅が１～１００ｎｍ程度であって、アスペクト比が１００以上のものをいう。ナノファイバーの長さ及び幅は、例えば、電子顕微鏡を用いて測定することができる。ナノファイバーの幅は、例えば、平面視における幅を測定してもよく、ナノファイバーの長さ方向に直交する断面の直径を幅として測定してもよい。いずれの場合も、５０個のナノファイバーにおいて、各ナノファイバーにおける最大幅の平均をナノファイバーの「幅」とする。ナノファイバーの「長さ」は、５０個のナノファイバーの平均長さである。ナノファイバーのアスペクト比は、該長さを該幅で除した値として求められる。 In this specification, nanofibers have a width of about 1 to 100 nm and an aspect ratio of 100 or more. The length and width of the nanofibers can be measured, for example, using an electron microscope. The width of the nanofiber may be measured, for example, the width in a plan view, or the diameter of a cross section orthogonal to the length direction of the nanofiber may be measured as the width. In each case, for 50 nanofibers, the average of the maximum widths of each nanofiber is defined as the "width" of the nanofibers. The "length" of nanofibers is the average length of 50 nanofibers. The aspect ratio of the nanofiber is obtained as a value obtained by dividing the length by the width.
　本発明に係るインクにおいて、チキソ性付与剤として、多糖類のナノファイバーを用いる場合、ナノファイバーのうちでもより小さいサイズのものが好ましい。ナノファイバーの幅は、好ましくは１～５０ｎｍであり、より好ましくは１～５ｎｍである。また、ナノファイバーの長さは、好ましくは０．５～２μｍであり、より好ましくは１～５μｍであるが、これに限定されない。ナノファイバーのアスペクト比は、１００～４００の範囲内にあるのがより好ましく、１００～３００の範囲内がさらに好ましい。 When a polysaccharide nanofiber is used as the thixotropy-imparting agent in the ink according to the present invention, a smaller size of the nanofibers is preferable. The width of the nanofibers is preferably 1 to 50 nm, more preferably 1 to 5 nm. The length of the nanofibers is preferably 0.5 to 2 μm, more preferably 1 to 5 μm, but is not limited thereto. The aspect ratio of the nanofibers is more preferably in the range of 100 to 400, and even more preferably in the range of 100 to 300.
　多糖類の集合体では、セルロース、キチン、キトサン等の多糖類は、ミクロフィブリルと呼ばれる構造単位が互いに結束した状態で存在している。このミクロフィブリルは、幅が３～４ｎｍ、長さが数μｍ（例えば、２～５μｍ）であるが、１本１本ほどくことは困難である。多糖類の集合体を機械的に破砕する場合、多くの従来法では、幅が２０～５０ｎｍ程度のナノファイバーとなる。本発明においては多糖類のナノファイバーとして、このようなナノファイバーを用いてもよいが、ＴＥＭＰＯ酸化によりより細かく例えばミクロフィブリル単位に解かれたＴＥＭＰＯ酸化ナノファイバーを用いることがより好ましい。 In the aggregate of polysaccharides, polysaccharides such as cellulose, chitin, and chitosan exist in a state where structural units called microfibrils are bound to each other. These microfibrils have a width of 3 to 4 nm and a length of several μm (for example, 2 to 5 μm), but it is difficult to make one by one. When the aggregate of polysaccharides is mechanically crushed, many conventional methods result in nanofibers having a width of about 20 to 50 nm. In the present invention, such nanofibers may be used as the polysaccharide nanofibers, but it is more preferable to use TEMPO-oxidized nanofibers which are more finely dissolved by TEMPO oxidation, for example, in microfibril units.
　ＴＥＭＰＯ酸化とは、２，２，６，６－テトラメチル－１－ピペリジン－オキシラジカル（ＴＥＭＰＯ）を触媒とする酸化反応である。多糖類の集合体をＴＥＭＰＯの存在下で酸化することで、ミクロフィブリルに相当する、例えば、幅が３～４ｎｍ、長さが数μｍ（例えば、２～５μｍ）の極めて細かいナノファイバーが得られる。 TEMPO oxidation is an oxidation reaction catalyzed by 2,2,6,6-tetramethyl-1-piperidine-oxy radical (TEMPO). Oxidation of the polysaccharide aggregate in the presence of TEMPO gives very fine nanofibers equivalent to microfibrils, eg, 3-4 nm wide and several μm long (eg 2-5 μm). ..
　チキソ性付与剤として用いられるセルロースナノファイバーは、セルロースをナノファイバー化したものである。ナノファーバー化されたセルロースの形態としては、例えば、粉末セルロース、微結晶セルロース等が挙げられる。 Cellulose nanofibers used as thixotropy-imparting agents are nanofibers of cellulose. Examples of the nano-ferverized cellulose form include powdered cellulose, microcrystalline cellulose and the like.
　セルロースナノファイバーとしては、第一工業製薬社製のレオクリスタ（登録商標）、日本製紙社製のＴＥＭＰＯ酸化セルロースナノファイバー、セレンピアＴＣ－０１Ａ、セレンピアＴＣ－０２Ｘ（「セレンピア」は登録商標）、スギノマシン社製ＩＭａ－１０００２、ＢＭａ－１０００２、ＷＭａ－１０００２、ＡＭａ－１０００２、ＦＭａ－１０００２、大王製紙社製のＥＬＥＸ－☆、ＥＬＥＸ－Ｓ、王子製紙社製アウロ・ヴィスコ等を好適に利用可能である。 Cellulose nanofibers include Leocrysta (registered trademark) manufactured by Daiichi Kogyo Seiyaku Co., Ltd., TEMPO oxidized cellulose nanofiber manufactured by Nippon Paper Industries, Serempia TC-01A, Serempia TC-02X (“Serenpia” is a registered trademark), and Sugino Machine Limited. IMa-10002, BMa-12002, WMa-12002, AMa-12002, FMa-12002, ELEX- ☆, ELEX-S manufactured by Daio Paper Industries, Auro Visco manufactured by Oji Paper Co., Ltd. and the like can be preferably used. ..
　無機粒子としては、天然又は合成の各種粘土鉱物の粒子が好ましい。粘土鉱物としては、スメクタイト粘土鉱物が好ましい。スメクタイト粘土鉱物は、層状ケイ酸塩鉱物又はベントナイト石群鉱物のフィロシリケート類に分類される。スメクタイト粘土鉱物は、積層構造により、モンモリロナイト亜群及びサポナイト亜群に分類される。モンモリロナイト亜群は、モンモリロナイト、ノントロナイト又はバイデライトを含む。サポナイト亜群は、ヘクトライト、サポナイト又はソーコナイトを含む。 As the inorganic particles, particles of various natural or synthetic clay minerals are preferable. As the clay mineral, smectite clay mineral is preferable. Smectite clay minerals are classified as layered silicate minerals or bentonite stone group minerals. Smectite clay minerals are classified into montmorillonite subgroup and saponite subgroup according to their laminated structure. The montmorillonite subgroup includes montmorillonite, nontronite or byderite. The saponite subgroup includes hectorite, saponite or saponite.
　スメクタイト粘土鉱物は天然物であっても合成物であってもよい。スメクタイト粘土鉱物は板状体が積層された層状物質であって、チキソ性付与剤として用いる場合、通常、層間剥離された板状の粒子として用いられる。スメクタイト粘土鉱物が合成物の場合、天然物と比べて小さいアスペクト比を有するとともに、不純物含有量が少ない。 The smectite clay mineral may be a natural product or a synthetic product. The smectite clay mineral is a layered substance in which plate-like bodies are laminated, and when used as a thixotropy-imparting agent, it is usually used as delaminated plate-like particles. When the smectite clay mineral is a synthetic product, it has a smaller aspect ratio and a lower impurity content than the natural product.
　スメクタイト粘土鉱物の板状粒子は、厚さが０．２～３．０ｎｍの範囲内にあり、長さが１０～１５０ｎｍの範囲内にあるのが好ましい。板状粒子は、厚さが０．２～２．０ｎｍの範囲内にあり、長さが１０～１２５ｎｍの範囲内にあるのがより好ましい。アスペクト比は、板状粒子の長さを厚さで除した値であり、２０以上であることが好ましい。アスペクト比は、２０～２００の範囲内にあるのがより好ましい。 The plate-like particles of smectite clay mineral are preferably in the range of 0.2 to 3.0 nm in thickness and preferably in the range of 10 to 150 nm in length. The plate-like particles have a thickness in the range of 0.2 to 2.0 nm, and more preferably a length in the range of 10 to 125 nm. The aspect ratio is a value obtained by dividing the length of the plate-like particles by the thickness, and is preferably 20 or more. The aspect ratio is more preferably in the range of 20 to 200.
　板状粒子の長さ及び厚さは、例えば、電子顕微鏡を用いて測定することができる。板状粒子の厚さは、例えば、所定の断面で測定される板状粒子の厚さの５０個の平均値である。板状粒子の「長さ」は、板状粒子を平面視したときに最大径として測定される長さの５０個の平均値である。板状粒子のアスペクト比は、該長さを該厚さで除した値として求められる。 The length and thickness of the plate-shaped particles can be measured using, for example, an electron microscope. The thickness of the plate-shaped particles is, for example, an average value of 50 pieces of the thickness of the plate-shaped particles measured in a predetermined cross section. The "length" of the plate-shaped particles is an average value of 50 lengths measured as the maximum diameter when the plate-shaped particles are viewed in a plan view. The aspect ratio of the plate-shaped particles is obtained as a value obtained by dividing the length by the thickness.
　スメクタイト粘土鉱物として、例えば、合成層状ケイ酸塩であるラポナイト（ビッグケミー社製）が使用できる。ラポナイトは、構造及び化学組成が天然スメクタイト粘土鉱物であるヘクトライトに近い合成低電荷粘土である。ラポナイトの主な粒子は、最大径が３０ｎｍ及び厚さが１ｎｍの円盤状の形態である。 As the smectite clay mineral, for example, laponite (manufactured by Big Chemie), which is a synthetic layered silicate, can be used. Laponite is a synthetic low-charge clay whose structure and chemical composition are close to those of Hectorite, a natural smectite clay mineral. The main particles of raponite are in the form of discs with a maximum diameter of 30 nm and a thickness of 1 nm.
　スメクタイト粘土鉱物として、市販品を用いてもよい。市販品としては、例えば、ラポナイトＲＤ（ビッグケミー社製）、クニミエ工業（株）製の精製ベントナイトであるクニピアＦ、クニピアＧ等が挙げられる。 A commercially available product may be used as the smectite clay mineral. Examples of commercially available products include Laponite RD (manufactured by Big Chemie), Kunipia F, which is a refined bentonite manufactured by Kunimie Industries, Ltd., and Kunipia G.
　また、無機粒子として、ナノファイバーである、川研ファインケミカル製のアルミナナノファイバー（短径が４ｎｍで長径が１４００ｎｍ）を用いてもよい。 Further, as the inorganic particles, alumina nanofibers manufactured by Kawaken Fine Chemical Co., Ltd. (minor axis: 4 nm and major axis: 1400 nm), which are nanofibers, may be used.
　本発明のインクにおけるチキソ性付与剤の含有量は、インクにチキソ性を付与して本発明の効果をより高める観点から、インク全量に対して０．０１～１質量％の範囲内であることが好ましく、０．０８～０．５質量％の範囲内であることがより好ましい。 The content of the thiox property-imparting agent in the ink of the present invention shall be in the range of 0.01 to 1% by mass with respect to the total amount of the ink from the viewpoint of imparting texo property to the ink and further enhancing the effect of the present invention. Is preferable, and more preferably in the range of 0.08 to 0.5% by mass.
　本発明のインクにおいて、チキソ性付与剤は１種を単独で用いてもよく、２種以上を併用してもよい。なお、本発明のインクにおいて、チキソ性付与剤は２種以上の材料からなることが好ましい。さらに、該２種以上の材料のうちの１種はスメクタイト粘土鉱物であることが好ましい。チキソ性付与剤の好ましい組み合わせとして、セルロースナノファイバーとスメクタイト粘土鉱物の組み合わせ、キサンタンガムとスメクタイト粘土鉱物の組み合わせが挙げられる。特に、セルロースナノファイバーとスメクタイト粘土鉱物の組み合わせが好ましい。 In the ink of the present invention, one type of thixotropic agent may be used alone, or two or more types may be used in combination. In the ink of the present invention, the thixotropy-imparting agent is preferably made of two or more kinds of materials. Further, one of the two or more materials is preferably a smectite clay mineral. Preferred combinations of thixotropy-imparting agents include a combination of cellulose nanofibers and smectite clay minerals, and a combination of xanthan gum and smectite clay minerals. In particular, a combination of cellulose nanofibers and smectite clay minerals is preferable.
　セルロースナノファイバーとスメクタイト粘土鉱物は、それぞれ単独で用いた場合であっても、例えば、インク乾燥率２０％で、特異的なゲル構造体を形成することで、インクに弾性的な性質を付与することができると考えられる。これにより、セルロースナノファイバー又はスメクタイト粘土鉱物を含有するインクは、後述する（１－４）及び（１－５）の特性が容易に達成できる。また、セルロースナノファイバー及びスメクタイト粘土鉱物を組み合わせて用いることで、上記の弾性的な性質がより高められ、好ましい。 Cellulose nanofibers and smectite clay minerals, even when used alone, impart elastic properties to the ink by forming a specific gel structure, for example, with an ink drying rate of 20%. It is thought that it can be done. As a result, the ink containing cellulose nanofibers or smectite clay mineral can easily achieve the properties (1-4) and (1-5) described later. Further, it is preferable to use a combination of cellulose nanofibers and smectite clay minerals because the above elastic properties are further enhanced.
　スメクタイト粘土鉱物とその他のチキソ性付与剤の比はインク粘度やチキソ性に応じて選択できるが、比率としてはスメクタイト粘土鉱物：その他のチキソ性付与剤が、質量比で、１０：１～１：１０の範囲で調整できる。組み合わせることによりそれぞれを単体で添加するよりもインクのチキソ性が大きく向上して画質が良くなる。チキソ性が向上する理由は推定だが、スメクタイト粘土鉱物は電荷を持っており、スメクタイト粘土鉱物とその他のチキソ性付与剤が電気的に会合して構造体を形成していることが考えられる。 The ratio of smectite clay mineral to other thixotropy can be selected according to the ink viscosity and thixotropy, but the ratio of smectite clay mineral: other thixotropy is 10: 1 to 1: 1 by mass ratio. It can be adjusted in the range of 10. By combining them, the thixotropy of the ink is greatly improved and the image quality is improved as compared with adding each of them alone. The reason for the improvement in thixotropy is presumed, but it is considered that smectite clay minerals have an electric charge, and smectite clay minerals and other thixotropy-imparting agents electrically associate to form a structure.
（界面活性剤）
　インクは任意に界面活性剤を含有することができる。これにより、インクの出射安定性の向上や、基材に着弾した液滴の広がり（ドット径）を制御することができる。 (Surfactant)
The ink can optionally contain a surfactant. As a result, it is possible to improve the ejection stability of the ink and control the spread (dot diameter) of the droplets that have landed on the base material.
　界面活性剤は、本発明の効果を損なうことのない範囲であれば、特に制限なく用いることができる。ただし、インクの他の構成成分にアニオン性の化合物を含有するときは、界面活性剤のイオン性はアニオン、ノニオン又はベタイン型が好ましい。 The surfactant can be used without particular limitation as long as the effect of the present invention is not impaired. However, when an anionic compound is contained in other constituents of the ink, the ionicity of the surfactant is preferably anionic, nonionic or betaine type.
　本発明において、好ましくは静的な表面張力の低下能が高いフッ素系又はシリコーン系界面活性剤や、動的な表面張力の低減能が高いジオクチルスルホサクシネートなどのアニオン界面活性剤、比較的低分子量のポリオキシエチレンアルキルエーテル、ポリオキシエチレンアルキルフェニルエーテル、アセチレングリコール類、プルロニック（登録商標）型界面活性剤、ソルビタン誘導体などのノニオン界面活性剤が好ましく用いられる。フッ素系又はシリコーン系界面活性剤と、動的な表面張力の低減能が高い界面活性剤を併用して用いることも好ましい。 In the present invention, preferably, a fluorine-based or silicone-based surfactant having a high ability to reduce static surface tension, or an anionic surfactant such as dioctyl sulfosuccinate having a high ability to reduce dynamic surface tension, relatively low. Nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, acetylene glycols, pluronic (registered trademark) type surfactants, and sorbitan derivatives having a molecular weight are preferably used. It is also preferable to use a fluorine-based or silicone-based surfactant in combination with a surfactant having a high ability to reduce dynamic surface tension.
　界面活性剤として、シリコーン系又はフッ素系の界面活性剤を添加することで、塩ビシートをはじめ種々の疎水性樹脂からなる基材や、印刷本紙などの吸収が遅い基材に対して、インク混じりをいっそう抑えることができ、高画質な印字画像を得られる。 By adding a silicone-based or fluorine-based surfactant as a surfactant, ink is mixed with a base material made of various hydrophobic resins such as vinyl chloride sheet and a base material with slow absorption such as printing paper. Can be further suppressed, and a high-quality printed image can be obtained.
　上記シリコーン系の界面活性剤としては、好ましくはポリエーテル変性ポリシロキサン化合物があり、例えば、信越化学工業製のＫＦ－３５１Ａ、ＫＦ－６４２やビッグケミー製のＢＹＫ３４５、ＢＹＫ３４７、ＢＹＫ３４８などが挙げられる。 The silicone-based surfactant is preferably a polyether-modified polysiloxane compound, and examples thereof include KF-351A and KF-642 manufactured by Shin-Etsu Chemical Co., Ltd. and BYK345, BYK347 and BYK348 manufactured by Big Chemie.
　上記フッ素系の界面活性剤は通常の界面活性剤の疎水性基の炭素に結合した水素の代わりに、その一部または全部をフッ素で置換したものを意味する。この内、分子内にパーフルオロアルキル基を有するものが好ましい。 The above-mentioned fluorine-based surfactant means one in which a part or all of the hydrogen bonded to the carbon of the hydrophobic group of the ordinary surfactant is replaced with fluorine. Of these, those having a perfluoroalkyl group in the molecule are preferable.
　上記フッ素系の界面活性剤の内、ある種のものは大日本インキ化学工業社からメガファック（Ｍｅｇａｆａｃ）Ｆなる商品名で、旭硝子社からサーフロン（Ｓｕｒｆｌｏｎ）なる商品名で、ミネソタ・マイニング・アンド・マニファクチュアリング・カンパニー社からフルオラッド（Ｆｌｕｏｒａｄ）ＦＣなる商品名で、インペリアル・ケミカル・インダストリー社からモンフロール（Ｍｏｎｆｌｏｒ）なる商品名で、イー・アイ・デュポン・ネメラス・アンド・カンパニー社からゾニルス（Ｚｏｎｙｌｓ）なる商品名で、またファルベベルケ・ヘキスト社からリコベット（Ｌｉｃｏｗｅｔ）ＶＰＦなる商品名で、それぞれ市販されている。 Among the above-mentioned fluorine-based surfactants, some of them are under the trade name of Megafac F from Dainippon Ink and Chemicals Co., Ltd. and the trade name of Surflon from Asahi Glass Co., Ltd. -Manufacturing Company under the trade name of Flurad FC, Imperial Chemical Industry under the trade name of Monflor, and EI Dupont Nemeras & Company under the trade name of Zonyls. It is commercially available under the trade name of Licowet VPF from Farbeberke Hext.
　インクにおける界面活性剤の含有量は、特に限定されないが、０．１～５．０質量％の範囲内であることが好ましい。 The content of the surfactant in the ink is not particularly limited, but is preferably in the range of 0.1 to 5.0% by mass.
（その他の添加剤）
　本発明のインクには、上記説明した以外に、本発明の効果を損なうことのない範囲で必要に応じて、出射安定性、プリントヘッドやインクカートリッジ適合性、保存安定性、画像保存性、その他の諸性能向上の目的に応じて、公知の各種添加剤、例えば、粘度調整剤、比抵抗調整剤、皮膜形成剤、紫外線吸収剤、酸化防止剤、退色防止剤、防ばい剤、防錆剤等を適宜選択して用いることができる。 (Other additives)
In addition to the above description, the ink of the present invention includes emission stability, print head and ink cartridge compatibility, storage stability, image storage property, and the like, as necessary, as long as the effects of the present invention are not impaired. Various known additives such as viscosity modifiers, specific resistance modifiers, film-forming agents, UV absorbers, antioxidants, anti-fading agents, anti-corrosion agents, and anti-corrosion agents, depending on the purpose of improving various performances. Etc. can be appropriately selected and used.
　具体的には、流動パラフィン、ジオクチルフタレート、トリクレジルホスフェート、シリコーンオイル等の油滴微粒子、特開昭５７－７４１９３号公報、同５７－８７９８８号公報、同６２－２６１４７６号公報等に記載の紫外線吸収剤、特開昭５７－７４１９２号公報、同５７－８７９８９号公報、同６０－７２７８５号公報、同６１－１４６５９１号公報、特開平１－９５０９１号公報、同３－１３３７６号公報等に記載の退色防止剤、特開昭５９－４２９９３号公報、同５９－５２６８９号公報、同６２－２８００６９号公報、同６１－２４２８７１号公報、特開平４－２１９２６６号公報等に記載の蛍光増白剤等を挙げることができる。 Specifically, it is described in liquid paraffin, dioctylphthalate, tricresyl phosphate, oil droplet fine particles such as silicone oil, JP-A-57-74193, JP-A-57-87988, JP-A-62-261476 and the like. UV absorbers, JP-A-57-74192, JP-A-57-87989, JP-A-60-72785, JP-A-61-146591, JP-A-1-95091, JP-A-3-13376, etc. The fluorescent whitening agent described in JP-A-59-4-2793, JP-A-59-52689, JP-A-62-28069, JP-A-61-242871, JP-A-4-219266, etc. Agents and the like can be mentioned.
　インクの調製は、上記各成分を上記含有量となるようにして混合することで行う。好ましくは、顔料は顔料分散剤により水系溶媒の一部に分散された分散液として、他の成分と混合することが好ましい。定着樹脂を含有する場合、定着樹脂は、必要に応じて添加される界面活性剤を用いて、水系溶媒の一部に分散された分散液として、他の成分と混合することが好ましい。 The ink is prepared by mixing each of the above components so as to have the above content. Preferably, the pigment is mixed with other components as a dispersion liquid dispersed in a part of the aqueous solvent by the pigment dispersant. When the fixing resin is contained, it is preferable that the fixing resin is mixed with other components as a dispersion liquid dispersed in a part of an aqueous solvent by using a surfactant added as needed.
＜インクジェットインクの物性＞
　本発明のインクジェットインクは、粘度特性について、以下の（１－１）及び（１－２）の条件を満足することが好ましい。さらに、これらに加えて（１－３）条件を満足することがより好ましい。 <Physical characteristics of inkjet ink>
The inkjet ink of the present invention preferably satisfies the following conditions (1-1) and (1-2) with respect to viscosity characteristics. Further, in addition to these, it is more preferable to satisfy the condition (1-3).
（１－１）２５℃でのせん断速度１０００（１／ｓ）時の粘度が１５ｍＰａ・ｓ以下である。
（１－２）温度応答ポリマーの水に対する下限臨界共溶温度±１０℃の範囲のいずれかの温度でのせん断速度１（１／ｓ）時の粘度が４５ｍＰａ・ｓ以上である。すなわち、温度応答ポリマーの下限臨界共溶温度±１０℃の範囲内でのせん断速度１（１／ｓ）時の最大粘度が４５ｍＰａ・ｓ以上である。
（１－３）インク乾燥率２０％で、温度応答ポリマーの水に対する下限臨界共溶温度±１０℃の範囲のいずれかの温度でのせん断速度１（１／ｓ）時の粘度が１００ｍＰａ・ｓ以上である。すなわち、インク乾燥率２０％で、温度応答ポリマーの下限臨界共溶温度±１０℃の範囲内でのせん断速度１（１／ｓ）時の最大粘度が１００ｍＰａ・ｓ以上である。 (1-1) The viscosity at a shear rate of 1000 (1 / s) at 25 ° C. is 15 mPa · s or less.
(1-2) Temperature response The viscosity of the polymer at a shear rate of 1 (1 / s) at any temperature within the range of the lower limit critical eutectic temperature of ± 10 ° C. with water is 45 mPa · s or more. That is, the maximum viscosity of the temperature-responsive polymer at a shear rate of 1 (1 / s) within the range of the lower limit critical eutectic temperature of ± 10 ° C. is 45 mPa · s or more.
(1-3) With an ink drying rate of 20%, the viscosity of the temperature-responsive polymer at a shear rate of 1 (1 / s) at any temperature within the lower limit critical eutectic temperature of ± 10 ° C. is 100 mPa · s. That is all. That is, the maximum viscosity of the temperature-responsive polymer at an ink drying rate of 20% and a shear rate of 1 (1 / s) within the range of the lower limit critical eutectic temperature of ± 10 ° C. is 100 mPa · s or more.
　上記（１－１）～（１－３）において粘度の測定は、回転式粘度計により測定できる。回転式粘度計としては、例えば、アントンパール社製、ＭＣＲ－１０２が挙げられる。本明細書において、特に断らない限り、粘度は２５℃で測定された粘度を示す。 The viscosity in (1-1) to (1-3) above can be measured with a rotary viscometer. Examples of the rotary viscometer include MCR-102 manufactured by Anton Pearl Co., Ltd. In the present specification, unless otherwise specified, the viscosity indicates the viscosity measured at 25 ° C.
　インク乾燥率２０％とは、初期質量の８０％の質量となるようにインクジェットインクから水系溶媒を除去した状態を表す。インク乾燥率は、インクを温度条件６０℃で乾燥した際の乾燥前後の質量から下記式（Ａ）により算出できる。 The ink drying rate of 20% represents a state in which the aqueous solvent is removed from the inkjet ink so that the mass is 80% of the initial mass. The ink drying rate can be calculated by the following formula (A) from the mass before and after drying when the ink is dried under the temperature condition of 60 ° C.
　式（Ａ）　インク乾燥率［％］＝（ＷBEFORE－ＷAFTER）／ＷBEFORE×１００
　ただし、式（Ａ）において、ＷBEFOREはインクの乾燥前の質量（初期質量）を表す。ＷAFTERはインクの乾燥後の質量を表す。インクの乾燥は、具体的には、約１００ｍＬのインクをガラス基板上に滴下し、秤量してインクの乾燥前質量を求めた後、質量測定が可能なホットプレート上で６０℃に加熱することで行う。 Formula (A) Ink drying rate [%] = (W BEFORE- W AFTER ) / W BEFORE x 100
However, in the formula (A), W BEFORE represents the mass (initial mass) of the ink before drying. W AFTER represents the mass of the ink after drying. Specifically, about 100 mL of ink is dropped on a glass substrate, weighed to determine the mass of the ink before drying, and then heated to 60 ° C. on a hot plate capable of measuring the mass. Do it with.
　インク乾燥率２０％での粘度を得るには、初期質量（乾燥前質量）の８０％の質量となった時点で上記乾燥を中止し、得られた乾燥後のインクを用いて粘度を測定すればよい。 To obtain the viscosity at an ink drying rate of 20%, stop the drying when the mass reaches 80% of the initial mass (mass before drying), and measure the viscosity using the obtained dried ink. Just do it.
　上記（１－１）に係り、本発明のインクは、せん断速度１０００（１／ｓ）時の粘度が１０ｍＰａ・ｓ以下であることがより好ましい。なお、せん断速度１０００（１／ｓ）時の粘度の下限は特に制限されないが、インクジェット吐出性の観点から５ｍＰａ・ｓ程度であることが好ましい。 Regarding (1-1) above, it is more preferable that the ink of the present invention has a viscosity of 10 mPa · s or less at a shear rate of 1000 (1 / s). The lower limit of the viscosity at a shear rate of 1000 (1 / s) is not particularly limited, but is preferably about 5 mPa · s from the viewpoint of inkjet ejection property.
　上記（１－２）に係り、本発明のインクは、温度応答ポリマーの水に対する下限臨界共溶温度±１０℃の範囲のいずれかの温度でのせん断速度１（１／ｓ）時の粘度が７０ｍＰａ・ｓ以上であることがより好ましく、１００ｍＰａ・ｓ以上であることがより好ましい。なお、この場合の粘度の上限は特に制限されないが、ヘッドメンテナンスのし易さの観点から１０００ｍＰａ・ｓ程度であることが好ましい。 Regarding (1-2) above, the ink of the present invention has a viscosity at a shear rate of 1 (1 / s) at any temperature in the range of the lower limit critical eutectic temperature ± 10 ° C. of the temperature-responsive polymer with water. It is more preferably 70 mPa · s or more, and more preferably 100 mPa · s or more. The upper limit of the viscosity in this case is not particularly limited, but it is preferably about 1000 mPa · s from the viewpoint of ease of head maintenance.
　上記（１－３）に係り、本発明のインクは、インク乾燥率２０％での温度応答ポリマーの水に対する下限臨界共溶温度±１０℃の範囲のいずれかの温度でのせん断速度１（１／ｓ）時の粘度が１００ｍＰａ・ｓ以上であることが好ましく、１５０ｍＰａ・ｓ以上であることがより好ましい。なお、この場合の粘度の上限は特に制限されないが、ヘッドメンテナンスのし易さの観点から１０００ｍＰａ・ｓ程度であることが好ましい。 In relation to (1-3) above, the ink of the present invention has a shear rate of 1 (1) at any temperature in the range of the lower limit critical eutectic temperature ± 10 ° C. of the temperature-responsive polymer at an ink drying rate of 20% with water. The viscosity at / s) is preferably 100 mPa · s or more, and more preferably 150 mPa · s or more. The upper limit of the viscosity in this case is not particularly limited, but it is preferably about 1000 mPa · s from the viewpoint of ease of head maintenance.
　ここで、本発明のインクにおいて、温度応答ポリマーの水に対する下限臨界共溶温度±１０℃の範囲のいずれかの温度でのせん断速度１（１／ｓ）時の粘度が少なくとも４５ｍＰａ・ｓであれば、基材へのインクの着弾時に、僅かな温度調整のみで、インクから水系溶媒を除去することなく、混色等の発生を抑制しやすい。 Here, in the ink of the present invention, the viscosity of the temperature-responsive polymer at a shear rate of 1 (1 / s) at any temperature in the range of the lower limit critical coexistence temperature ± 10 ° C. with respect to water is at least 45 mPa · s. For example, when the ink lands on the base material, it is easy to suppress the occurrence of color mixing and the like without removing the aqueous solvent from the ink by adjusting the temperature only slightly.
　インクの粘度は、インク乾燥率が高くなるほど増加する。上記（１－３）を満足するインクにおいては、インク乾燥率を高くても２０％とすることで、温度応答ポリマーの水に対する下限臨界共溶温度±１０℃の範囲のいずれかの温度でのせん断速度１（１／ｓ）時の粘度が１００ｍＰａ・ｓを達成できる。これにより、基材へのインクの着弾時において、僅かな温度調整のみで、インクから水系溶媒を過度に除去することなく、混色等の発生を抑制できる。 The viscosity of the ink increases as the ink drying rate increases. For inks that satisfy the above (1-3), by setting the ink drying rate to 20% at the highest, the temperature-responsive polymer can be at any temperature within the lower limit critical eutectic temperature of ± 10 ° C. with water. A viscosity of 100 mPa · s can be achieved at a shear rate of 1 (1 / s). As a result, when the ink lands on the base material, it is possible to suppress the occurrence of color mixing and the like without excessively removing the aqueous solvent from the ink with only a slight temperature adjustment.
　本発明のインクジェットインクは、さらに、以下の（１－４）及び（１－５）の条件の少なくとも１つを満たすことが好ましく、両方を満たすことがより好ましい。 The inkjet ink of the present invention further preferably satisfies at least one of the following conditions (1-4) and (1-5), and more preferably both.
（１－４）インク乾燥率２０％において、温度応答ポリマーの水に対する下限臨界共溶温度±１０℃の範囲のいずれかの温度で、角周波数ω１０ｒａｄ／ｓ、振り角γ１～１０００％の条件で歪を変化させたときの、歪１％時の損失正接（ｔａｎδ）が１未満である。（１－５）インク乾燥率２０％において、温度応答ポリマーの水に対する下限臨界共溶温度±１０℃の範囲のいずれかの温度で、角周波数ω１０ｒａｄ／ｓ、振り角γ１～１０００％の条件で歪を変化させたときの貯蔵弾性率と損失弾性率のクロスオーバー歪が２０％以上である。 (1-4) At an ink drying rate of 20%, at any temperature in the range of the lower limit critical eutectic temperature ± 10 ° C. of the temperature-responsive polymer with respect to water, under the conditions of an angular frequency of ω10 rad / s and a swing angle of γ1 to 1000%. The loss tangent (tan δ) at 1% strain when the strain is changed is less than 1. (1-5) At an ink drying rate of 20%, at any temperature in the range of the lower limit critical eutectic temperature ± 10 ° C. of the temperature-responsive polymer with respect to water, under the conditions of an angular frequency of ω10 rad / s and a swing angle of γ1 to 1000%. The crossover strain of the storage elastic modulus and the loss elastic modulus when the strain is changed is 20% or more.
　（１－４）における、損失正接（ｔａｎδ）、及び（１－５）における、貯蔵弾性率と損失弾性率は、レオメータ（粘弾性測定装置）により測定できる。レオメータとしては、例えば、アントンパール社製、ＭＣＲ－１０２が挙げられる。本明細書において、損失正接を単に「ｔａｎδ」と表す場合もある。 The loss tangent (tan δ) in (1-4) and the storage elastic modulus and loss elastic modulus in (1-5) can be measured by a rheometer (viscoelasticity measuring device). Examples of the rheometer include MCR-102 manufactured by Anton Pearl Co., Ltd. In the present specification, the loss tangent may be simply referred to as “tan δ”.
　本明細書において、ｔａｎδ、貯蔵弾性率及び損失弾性率は、レオメータを用いて、具体的には、アントンパール社製、ＭＣＲ－１０２を用いて、オシレーションモードにて、温度応答ポリマーの水に対する下限臨界共溶温度±１０℃の範囲のいずれかの温度で、角周波数ω１０ｒａｄ／ｓ、振り角γ１～１０００％の測定条件で測定できる。なお、測定時には、レオメータのコーンプレートの振り角γを変化させて測定サンプルを歪ませている。ここで、測定サンプルは振り角γに追従して歪んでいるので、コーンプレートの振り角γと測定サンプルの歪は同じ値になる。 In the present specification, the tan δ, the storage modulus and the loss modulus are determined by using a rheometer, specifically, using MCR-102 manufactured by Anton Pearl Co., Ltd., in an oscillation mode, with respect to water of the temperature-responsive polymer. It can be measured at any temperature in the range of the lower limit critical eutectic temperature ± 10 ° C. under the measurement conditions of an angular frequency ω10 rad / s and a swing angle γ1 to 1000%. At the time of measurement, the swing angle γ of the cone plate of the rheometer is changed to distort the measurement sample. Here, since the measurement sample is distorted following the swing angle γ, the swing angle γ of the cone plate and the distortion of the measurement sample have the same value.
　（１－４）では、上記測定において、歪が１％のときのｔａｎδを指標としている。当該測定条件において歪が１％のときのｔａｎδが１未満であるとインクがより弾性的な性質を有することになり、同じような粘度で比較するとよりピニング性がよくなり、画質がより向上する。（１－４）において、歪１％時のｔａｎδは、０．８以下であることがより好ましく、０．６以下であることがさらに好ましい。 In (1-4), in the above measurement, tan δ when the strain is 1% is used as an index. If the tan δ is less than 1 when the strain is 1% under the measurement conditions, the ink has more elastic properties, and when compared with similar viscosities, the pinning property is improved and the image quality is further improved. .. In (1-4), the tan δ at 1% strain is more preferably 0.8 or less, and further preferably 0.6 or less.
　（１－５）では、上記測定において、歪を変化させたときの貯蔵弾性率と損失弾性率のクロスオーバー歪を指標としている。クロスオーバー歪とは、具体的には、縦軸に貯蔵弾性率（Ｐａ）、横軸に歪（％）をそれぞれ対数でとったグラフと、縦軸に損失弾性率（Ｐａ）、横軸に歪（％）をそれぞれ対数でとったグラフの交点における歪の値（％）を示す。当該測定条件においてクロスオーバー歪（％）が２０％以上であれば、よりインクが弾性的な性質を有することになり、上記と同じようにより画質が向上する。クロスオーバー歪は３０％以上であることがより好ましく、４０％以上であることがさらに好ましい。 In (1-5), in the above measurement, the crossover strain of the storage elastic modulus and the loss elastic modulus when the strain is changed is used as an index. Specifically, the crossover strain is a graph in which the vertical axis is the storage elastic modulus (Pa) and the horizontal axis is the strain (%) in logarithms, the vertical axis is the loss modulus (Pa), and the horizontal axis is the horizontal axis. The value (%) of the strain at the intersection of the graphs in which the strain (%) is logarithmically shown is shown. When the crossover distortion (%) is 20% or more under the measurement conditions, the ink has more elastic properties, and the image quality is further improved in the same manner as described above. The crossover strain is more preferably 30% or more, and even more preferably 40% or more.
　なお、（１－４）において、インク乾燥率２０％の状態ではなく、インク乾燥率０％、すなわち本発明のインクについて、同様の測定を行った場合の、歪１％時の損失正接（ｔａｎδ）は１未満であることが好ましく、０．８以下であることがより好ましく、０．６以下であることがさらに好ましい。 In (1-4), the loss tangent (tan δ) at a strain of 1% when the same measurement is performed for the ink of the present invention, that is, the ink drying rate of 0%, not the state of the ink drying rate of 20%. ) Is preferably less than 1, more preferably 0.8 or less, and even more preferably 0.6 or less.
　また、（１－５）において、インク乾燥率２０％の状態ではなく、インク乾燥率０％、すなわち本発明のインクについて、同様の測定を行った場合の、クロスオーバー歪は２０％以上であることが好ましく、３０％以上であることがより好ましく、４０％以上であることがさらに好ましい。 Further, in (1-5), the crossover strain is 20% or more when the same measurement is performed for the ink of the present invention, that is, the ink drying rate is 0%, not the state where the ink drying rate is 20%. It is preferably 30% or more, more preferably 40% or more.
　本発明のインクは、上記ｔａｎδ及びクロスオーバー歪が、インク乾燥率０％の状態と、インク乾燥率２０％の状態で殆ど変わらない。つまり、インク乾燥率０％の状態でも、温度応答ポリマーの水に対する下限臨界共溶温度±１０℃の範囲内において、インクが弾性的な挙動を持ち、ピニングし易く高画質な画像を形成できる。 In the ink of the present invention, the tan δ and the crossover strain are almost the same between the state where the ink drying rate is 0% and the state where the ink drying rate is 20%. That is, even when the ink drying rate is 0%, the ink has an elastic behavior within the range of the lower limit critical eutectic temperature ± 10 ° C. with respect to water of the temperature-responsive polymer, and it is easy to pinn and a high-quality image can be formed.
[画像形成方法の概要]
　本発明の画像形成方法は、インク循環機構を備えるインクジェットヘッドからインクジェットインクの液滴を吐出して基材上に着弾させる着弾工程を有する画像形成方法において、以下の特徴を有する。
（２－１）インクジェットインクは、水系溶媒、顔料及びチキソ性付与剤を含み、インクジェットヘッド内で粘度が１５ｍＰａ・ｓ以下になるように循環される。
（２－２）基材に着弾した時、又は着弾直後の液滴が、インクジェットインクからの質量減少率が２０％以内となるように、かつ粘度が１００ｍＰａ・ｓ以上になるように着弾工程を行う。 [Outline of image formation method]
The image forming method of the present invention has the following features in an image forming method having a landing step of ejecting droplets of inkjet ink from an inkjet head provided with an ink circulation mechanism and landing them on a substrate.
(2-1) The inkjet ink contains an aqueous solvent, a pigment and a thixotropic agent, and is circulated in the inkjet head so that the viscosity is 15 mPa · s or less.
(2-2) Perform the landing step so that the mass reduction rate from the inkjet ink is within 20% and the viscosity of the droplets when they land on the substrate or immediately after landing is 100 mPa · s or more. conduct.
　本発明の画像形成方法は、通常、着弾工程の後に、さらに、基材上のインク液滴から水系溶媒を除去する乾燥工程を有する。乾燥工程を経ることで、基材上に目的の画像が形成される。また、本発明の画像形成方法においては、上記インクにより塗膜を形成する前に基材の表面にプライマー層を形成する工程（以下、「プライマー層形成工程」ともいう。）を有してもよい。この場合、上記着弾工程においてインクの液滴は、プライマー層上に着弾される。 The image forming method of the present invention usually includes a drying step of removing the aqueous solvent from the ink droplets on the substrate after the landing step. By going through the drying step, a desired image is formed on the base material. Further, the image forming method of the present invention may include a step of forming a primer layer on the surface of the base material (hereinafter, also referred to as a "primer layer forming step") before forming a coating film with the ink. good. In this case, the ink droplets are landed on the primer layer in the landing step.
（プライマー層形成工程）
　プライマー層は、樹脂と、溶媒とを含むプライマーインクを基材上に塗布し、乾燥させることにより形成することができる。また、活性エネルギー重合型化合物と、重合開始剤とを含むプライマーインクを塗布し、塗膜に活性エネルギーを照射させることにより形成してもよい。 (Primer layer forming step)
The primer layer can be formed by applying a primer ink containing a resin and a solvent onto a substrate and drying the primer layer. Alternatively, it may be formed by applying a primer ink containing an active energy polymerization type compound and a polymerization initiator and irradiating the coating film with active energy.
　プライマーインクの塗布方法は特に制限されず、ロールコート法、スピンコート法、スプレー塗布法、浸漬法、スクリーン印刷法、インクジェット法、グラビア印刷法、オフセット印刷法等、いずれの方法であってもよい。これらの中でも、基材の表面粗さを細かく制御したりする場合には、スクリーン印刷法又はインクジェット法であることが好ましく、特にインクジェット法であることが好ましい。 The method of applying the primer ink is not particularly limited, and any method such as a roll coating method, a spin coating method, a spray coating method, a dipping method, a screen printing method, an inkjet method, a gravure printing method, and an offset printing method may be used. .. Among these, when the surface roughness of the base material is finely controlled, the screen printing method or the inkjet method is preferable, and the inkjet method is particularly preferable.
　また、プライマーインクの塗布後、塗膜を硬化もしくは乾燥させる方法は、プライマーインクの種類に応じて適宜選択され、例えば、加熱したり、活性エネルギーを照射する方法とすることができる。 Further, the method of curing or drying the coating film after applying the primer ink is appropriately selected according to the type of the primer ink, and can be, for example, a method of heating or irradiating with active energy.
（着弾工程）
　着弾工程において、上記（２－１）に係り、ヘッド内でのインクの粘度が１５ｍＰａ・ｓ以下であれば、インクのヘッドでの循環及びヘッドからの吐出がスムーズに行える。ヘッド内でのインクの粘度は、１０ｍＰａ・ｓ以下になるように循環されることが好ましい。 (Landing process)
In the landing step, according to (2-1) above, if the viscosity of the ink in the head is 15 mPa · s or less, the ink can be smoothly circulated in the head and discharged from the head. The viscosity of the ink in the head is preferably circulated so as to be 10 mPa · s or less.
　上記（２－２）に係り、インクジェットインクからの質量減少率（以下、単に「質量減少率」ともいう。）は、上記で説明したインク乾燥率と同様に定義できる。基材に着弾した時、又は着弾直後のインクの液滴において、質量減少率及び粘度が上記範囲であれば、良好なピニングが可能であり得られる画像が高品質となりうる。さらに、ヘッド周りへのインク固形分の固着が抑制され吐出不良も生じにくく、メンテナンスも容易である。 Regarding (2-2) above, the mass reduction rate from the inkjet ink (hereinafter, also simply referred to as “mass reduction rate”) can be defined in the same manner as the ink drying rate described above. If the mass reduction rate and the viscosity of the ink droplets when landing on the substrate or immediately after landing are within the above ranges, good pinning is possible and the obtained image can be of high quality. Further, the sticking of solid ink around the head is suppressed, ejection defects are less likely to occur, and maintenance is easy.
　ここで、上記着弾直後とは、例えば、インクの液滴が基材に着弾後１００ｍｓｅｃ以内をいう。基材に着弾してから１００ｍｓｅｃ以内のインクの液滴における、質量減少率が２０％以内であって、かつ粘度が１００ｍＰａ・ｓ以上であれば、上記効果は十分に発現される。ここで、基材に着弾した時、又は着弾直後を、以下、「基材着弾時」ともいう。基材着弾時のインク液滴の粘度は、１５０ｍＰａ・ｓ以上が好ましく、２００ｍＰａ・ｓ以上がより好ましく、３００ｍＰａ・ｓ以上がさらに好ましい。なお、着弾直後は、基材の搬送速度が高速な場合（１００ｍ／分）等のときは３０ｍｓｅｃ以内、５０ｍ／分等のときは１００ｍｓｅｃ以内が目安である。 Here, the term "immediately after landing" means, for example, within 100 msec after the ink droplets land on the base material. If the mass reduction rate of the ink droplets within 100 msec after landing on the substrate is within 20% and the viscosity is 100 mPa · s or more, the above effect is sufficiently exhibited. Here, the time when the base material is landed or immediately after the landing is also referred to as "the time when the base material is landed". The viscosity of the ink droplet at the time of landing on the substrate is preferably 150 mPa · s or more, more preferably 200 mPa · s or more, and even more preferably 300 mPa · s or more. Immediately after landing, when the transport speed of the base material is high (100 m / min), it is within 30 msec, and when it is 50 m / min, etc., it is within 100 msec.
　本発明の画像形成方法においては、上記（２－１）及び（２－２）の条件を満たすためにインク又は装置を適宜選択する。本発明の画像形成方法においては、インクを上記で説明した本発明のインクとすることで、装置を特に変更することなく（２－１）及び（２－２）の条件を達成できる。すなわち、本発明の画像形成方法においては、上記本発明のインクを用いることが好ましい。なお、本発明のインクを用いた場合、例えば、温度応答ポリマーのＬＣＳＴ±１０℃の範囲内で（２－２）の条件が達成され得る。すなわち、本発明のインクを用いた場合、（２－２）の条件を満たすために、着弾工程において、インク液滴を基材上で温度応答ポリマーのＬＣＳＴ±１０℃の範囲内で加熱することが好ましい。 In the image forming method of the present invention, an ink or an apparatus is appropriately selected in order to satisfy the above conditions (2-1) and (2-2). In the image forming method of the present invention, by using the ink of the present invention described above as the ink, the conditions (2-1) and (2-2) can be achieved without particularly changing the apparatus. That is, in the image forming method of the present invention, it is preferable to use the ink of the present invention. When the ink of the present invention is used, for example, the condition (2-2) can be achieved within the range of LCST ± 10 ° C. of the temperature-responsive polymer. That is, when the ink of the present invention is used, in order to satisfy the condition (2-2), the ink droplets are heated on the substrate within the range of LCST ± 10 ° C. of the temperature-responsive polymer in the landing step. Is preferable.
　本発明の画像形成方法においては、（２－２）の条件を満たすために、着弾工程において、インク液滴を基材上で３０～６０℃の範囲内で加熱することが好ましい。すなわち、本発明の画像形成方法においては、基材着弾時のインク液滴の状態が、質量減少率が２０％以内でかつ粘度が１００ｍＰａ・ｓ以上となるようにするために、必要に応じてインク液滴を３０～６０℃で加熱する工程を有してもよい。該温度は十分低い温度であり、ヘッド周りにインクが固着して吐出不良を起こす懸念は殆どない。 In the image forming method of the present invention, in order to satisfy the condition (2-2), it is preferable to heat the ink droplets on the substrate in the range of 30 to 60 ° C. in the landing step. That is, in the image forming method of the present invention, in order to ensure that the state of the ink droplets at the time of landing on the base material has a mass reduction rate of 20% or less and a viscosity of 100 mPa · s or more, if necessary. It may have a step of heating the ink droplets at 30-60 ° C. The temperature is sufficiently low, and there is almost no concern that ink will stick around the head and cause ejection failure.
　加熱は、例えば、恒温炉や熱風送風機などのような非接触加熱型の装置を用いて行ってもよいし、ホットプレートや熱ローラーなどのような接触加熱型の装置を用いて行ってもよい。 Heating may be performed using a non-contact heating type device such as a constant temperature furnace or a hot air blower, or may be performed using a contact heating type device such as a hot plate or a heat roller. ..
　加熱温度は、（ａ）恒温炉や熱風送風機などのような非接触加熱型の装置を用いる場合には、炉内温度又は熱風温度などのような雰囲気温度、（ｂ）ホットプレートや熱ローラーなどのような接触加熱型の装置を用いる場合には、接触加熱部の温度、又は、（ｃ）インク液滴の表面温度から選ばれるいずれか１つを測定することで得ることができ、測定場所としては（ｃ）インク液滴の表面温度を測定することがより好ましい。 When a non-contact heating type device such as a constant temperature furnace or a hot air blower is used, the heating temperature is (a) an atmospheric temperature such as a furnace temperature or a hot air temperature, and (b) a hot plate, a hot roller, etc. When a contact heating type device such as the above is used, it can be obtained by measuring either the temperature of the contact heating part or (c) the surface temperature of the ink droplets, and the measurement location. (C) It is more preferable to measure the surface temperature of the ink droplets.
（乾燥工程）
　乾燥工程は、着弾工程後のインク液滴から水系溶媒等の固形成分以外の成分（以下、「揮発成分」ともいう。）を除去して、基材上に、又はプライマー層を有する場合はプライマー層上に、目的の画像を構成する塗膜を形成する工程である。なお、上記のとおり、着弾工程後のインクの液滴は、質量減少率が２０％以内の状態である。インクジェットインクは、例えば、水系溶媒を５０～９５質量％程度含有することから、乾燥工程により水系溶媒を含む残りの揮発成分を除去する。 (Drying process)
In the drying step, components other than solid components such as an aqueous solvent (hereinafter, also referred to as “volatile components”) are removed from the ink droplets after the landing step, and a primer is used on the substrate or when a primer layer is provided. This is a step of forming a coating film forming a target image on the layer. As described above, the mass reduction rate of the ink droplets after the landing step is within 20%. Since the inkjet ink contains, for example, about 50 to 95% by mass of an aqueous solvent, the remaining volatile components including the aqueous solvent are removed by a drying step.
　乾燥工程は、揮発成分を除去しつつ、インクが定着樹脂を含む場合は、該定着樹脂が完全には融着しないような条件で乾燥を行うことが好ましい。乾燥温度は、例えば、６０～１１０℃の範囲内が好ましい。乾燥時間は、例えば、５～６０秒の範囲内が好ましい。なお、乾燥工程における乾燥は、例えば、着弾工程における加熱と同様の方法で行うことができる In the drying step, it is preferable to perform drying under conditions where the fixing resin is not completely fused when the ink contains a fixing resin while removing volatile components. The drying temperature is preferably in the range of, for example, 60 to 110 ° C. The drying time is preferably in the range of, for example, 5 to 60 seconds. The drying in the drying step can be performed by, for example, the same method as the heating in the landing step.
（基材）
　本発明に用いることができる基材は、特に限定されるものではないが、非吸収性基材であることが好ましい。非吸収性基材を用いることで、本発明の画像形成方法の効果がより顕著である。本発明では、非吸収性とは、水に対する非吸収性を表す。 (Base material)
The base material that can be used in the present invention is not particularly limited, but is preferably a non-absorbent base material. By using a non-absorbent base material, the effect of the image forming method of the present invention is more remarkable. In the present invention, the non-absorbable means non-absorbable to water.
　非吸水性基材の例としては、公知のプラスチックのフィルムが使用できる。具体例としては、ポリエチレンテレフタレート等のポリエステルフィルム、ポリエチレンフィルム、ポリプロピレンフィルム、ナイロン等のポリアミド系フィルム、ポリスチレンフィルム、ポリ塩化ビニルフィルム、ポリカーボネートフィルム、ポリアクリロニトリルフィルム、ポリ乳酸フィルム等の生分解性フィルム等が挙げられる。また、ガスバリアー性、防湿性、保香性などを付与するために、フィルムの片面又は両面にポリ塩化ビニリデンをコートしたものや、金属酸化物を蒸着したフィルムも好ましく用いることができる。非吸水性フィルムは、未延伸フィルムでも延伸フィルムでも好ましく用いることができる。 As an example of the non-water-absorbent base material, a known plastic film can be used. Specific examples include polyester films such as polyethylene terephthalate, polyethylene films, polypropylene films, polyamide films such as nylon, polystyrene films, polyvinyl chloride films, polycarbonate films, polyacrylonitrile films, and biodegradable films such as polylactic acid films. Can be mentioned. Further, in order to impart gas barrier property, moisture resistance, fragrance retention and the like, a film coated with polyvinylidene chloride on one side or both sides of the film, or a film on which a metal oxide is vapor-deposited can also be preferably used. The non-water-absorbent film can be preferably used as an unstretched film or a stretched film.
　これらの他に、非吸水性基材として、金属類やガラス等の無機化合物からなる基材が挙げられる。 In addition to these, as a non-water-absorbent base material, a base material made of an inorganic compound such as a metal or glass can be mentioned.
　また、金属基材上に、熱硬化性樹脂を塗工層として設けた、レトルト食品用の包材などにも好適に用いることができる。前記レトルト食品用の包材は、空気や水分、光を遮断し、内部の食品を密閉するため、例えば、食品側にはポリプロピレン、外側にはポリエステル等の空気や水分、光を遮断し、内部の食品を密閉するといった熱可塑性樹脂層やアルミ箔層を積層加工（ラミネート加工）したフィルムで構成されている。 It can also be suitably used as a packaging material for retort foods in which a thermosetting resin is provided as a coating layer on a metal base material. The packaging material for retort pouch foods blocks air, moisture, and light and seals the food inside. Therefore, for example, polypropylene on the food side and polyester on the outside block air, moisture, and light, and inside. It is composed of a film in which a thermoplastic resin layer and an aluminum foil layer for sealing foods are laminated (laminated).
　本発明においては、基材の厚さは、好ましくは１０～１２０μｍ、より好ましくは１２～６０μｍの範囲内である。 In the present invention, the thickness of the base material is preferably in the range of 10 to 120 μm, more preferably 12 to 60 μm.
（インクジェットヘッド）
　本発明の画像形成方法は、インク循環機構を備えるインクジェットヘッドを用いた画像形成に適用される。 (Inkjet head)
The image forming method of the present invention is applied to image forming using an inkjet head provided with an ink circulation mechanism.
　インクジェットヘッドは、インク循環機構を備えるものであれば特に制限されず、オンデマンド方式及びコンティニュアス方式のいずれのインクジェットヘッドでもよい。オンデマンド方式のインクジェットヘッドの例には、シングルキャビティー型、ダブルキャビティー型、ベンダー型、ピストン型、シェアーモード型及びシェアードウォール型を含む電気－機械変換方式、ならびにサーマルインクジェット型及びバブルジェット（「バブルジェット」はキヤノン株式会社の登録商標）型を含む電気－熱変換方式等が含まれる。 The inkjet head is not particularly limited as long as it has an ink circulation mechanism, and may be either an on-demand type or a continuous type inkjet head. Examples of on-demand inkjet heads include electro-mechanical conversion methods including single cavity type, double cavity type, bender type, piston type, shared mode type and shared wall type, and thermal inkjet type and bubble jet ( "Bubble jet" includes an electric-heat conversion method including a registered trademark of Canon Inc.).
　上記インクジェットヘッドの中では、電気－機械変換方式に用いられる電気－機械変換素子として圧電素子を用いたインクジェットヘッド（「ピエゾ型インクジェットヘッド」ともいう。）であることが好ましい。 Among the above inkjet heads, it is preferable that the inkjet head uses a piezoelectric element as the electric-mechanical conversion element used in the electric-mechanical conversion method (also referred to as "piezo-type inkjet head").
　また、インクジェットヘッドは、スキャン式及びライン式のいずれのインクジェットヘッドでもよいが、ライン式であることが好ましい。 The inkjet head may be either a scan type or a line type inkjet head, but a line type is preferable.
　ライン式のインクジェットヘッドとは、印字範囲の幅以上の長さを持つインクジェットヘッドのことをいう。ライン式のインクジェットヘッドとしては、一つのヘッドで印字範囲の幅以上であるものを用いてもよいし、複数のヘッドを組み合わせて印字範囲の幅以上となるように構成してもよい。 A line-type inkjet head is an inkjet head that has a length greater than or equal to the width of the printing range. As the line-type inkjet head, one head may be used that is equal to or larger than the width of the print range, or a plurality of heads may be combined so as to be equal to or larger than the width of the print range.
　また、複数のヘッドを、互いのノズルが千鳥配列となるように並設して、これらヘッド全体としての解像度を高くしてもよい。 Further, a plurality of heads may be arranged side by side so that the nozzles of each head are arranged in a staggered manner to increase the resolution of these heads as a whole.
　本発明の画像形成方法に用いるインクジェットヘッドは、注入経路を介してインクジェットインクが注入される圧力室と、該圧力室に圧力変動を生じさせる圧力発生手段と、該圧力室に連通し、該圧力室の圧力変動により該圧力室内から外部に吐出される上記インクジェットインクの流路となるノズルと、上記圧力室に連通し、上記ノズルよりも内方のインクジェットインクを排出させて上記注入経路に戻す２以上の循環路とを備えることが好ましい。このような、インクジェットヘッドについて図面を用いて以下に説明する。 The inkjet head used in the image forming method of the present invention communicates with a pressure chamber in which inkjet ink is injected via an injection path, a pressure generating means for causing pressure fluctuation in the pressure chamber, and the pressure chamber. A nozzle that serves as a flow path for the inkjet ink discharged from the pressure chamber to the outside due to a pressure fluctuation in the chamber communicates with the pressure chamber, and the inkjet ink inside the nozzle is discharged and returned to the injection path. It is preferable to provide two or more circulation paths. Such an inkjet head will be described below with reference to the drawings.
　図１は、本発明の画像形成方法に使用可能なインクジェットヘッドの一例を備えるインクジェット画像形成装置１００を示す要部概略構成図であり、インクジェットヘッド１を一部断面で示している。なお、図１に示されるインクジェットヘッド等は例示であって、本発明の画像形成方法が適用可能なインクジェットヘッド等はこれに限定されない。 FIG. 1 is a schematic configuration diagram of a main part showing an inkjet image forming apparatus 100 including an example of an inkjet head that can be used in the image forming method of the present invention, and shows the inkjet head 1 in a partial cross section. The inkjet head and the like shown in FIG. 1 are examples, and the inkjet head and the like to which the image forming method of the present invention can be applied are not limited thereto.
　インクジェット画像形成装置１００は、搬送手段１０８によって一定方向（副走査方向）に搬送される基材１０９上に、インクジェットヘッド１からインクの液滴を吐出して着弾させ、該液滴を乾燥して画像を形成する。ワンパス方式のインクジェット画像形成装置においては、インクジェットヘッド１は固定配置され、基材１０９が搬送される過程で、ノズル２２から基材１０９に向けてインク液滴を吐出、基材上に着弾させ、画像を形成する。また、スキャン方式のインクジェット画像形成装置においては、インクジェットヘッド１は、キャリッジ機構１０７に搭載され、該キャリッジ機構１０７により主走査方向に往復移動される過程で、ノズル２２から基材１０９に向けてインク液滴を吐出、基材上に着弾させ、画像を形成する。搬送手段１０８及びキャリッジ機構１０７は、制御部１０４によって駆動制御される。 The inkjet image forming apparatus 100 ejects ink droplets from the inkjet head 1 and lands them on a base material 109 conveyed in a certain direction (sub-scanning direction) by the conveying means 108, and dries the droplets. Form an image. In the one-pass type inkjet image forming apparatus, the inkjet head 1 is fixedly arranged, and in the process of transporting the base material 109, ink droplets are ejected from the nozzle 22 toward the base material 109 and landed on the base material. Form an image. Further, in the scanning type inkjet image forming apparatus, the inkjet head 1 is mounted on the carriage mechanism 107, and in the process of being reciprocated in the main scanning direction by the carriage mechanism 107, ink is ink from the nozzle 22 toward the base material 109. Droplets are ejected and landed on a substrate to form an image. The transport means 108 and the carriage mechanism 107 are driven and controlled by the control unit 104.
　なお、図１には図示されないが、インクジェット画像形成装置１００は、着弾時のインク液滴の温度を調整する、非接触加熱型又は接触加熱型の加熱器を有する。該加熱器は、乾燥工程を行う際にも用いることができる。 Although not shown in FIG. 1, the inkjet image forming apparatus 100 has a non-contact heating type or contact heating type heater that adjusts the temperature of ink droplets at the time of landing. The heater can also be used when performing the drying step.
　図１では、１つのインクジェットヘッド１のみを示しているが、一般にインクジェット画像形成装置１００には、例えばイエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）、ブラック（Ｋ）等の各色インク用の複数のインクジェットヘッド１が搭載される。インクジェット画像形成装置１００においては、インクを貯蔵するインクタンク１０１とインクジェットヘッド１の共通インク室４１とが、移送路となるインク移送管１０２及び回収路となるインク返送管１０３によって連通されている。 Although only one inkjet head 1 is shown in FIG. 1, in general, the inkjet image forming apparatus 100 is used for inks of various colors such as yellow (Y), magenta (M), cyan (C), and black (K). A plurality of inkjet heads 1 are mounted. In the inkjet image forming apparatus 100, the ink tank 101 for storing ink and the common ink chamber 41 of the inkjet head 1 are communicated with each other by an ink transfer tube 102 as a transfer path and an ink return tube 103 as a recovery path.
　インク移送管１０２の途中には、インクジェット画像形成装置１００の制御部１０４によって駆動制御される移送ポンプ１０５ａが設けられている。この移送ポンプ１０５ａが駆動することにより、インクタンク１０１内のインクが、インク移送管１０２を介してインクジェットヘッド１に移送される。 A transfer pump 105a, which is driven and controlled by the control unit 104 of the inkjet image forming apparatus 100, is provided in the middle of the ink transfer tube 102. By driving the transfer pump 105a, the ink in the ink tank 101 is transferred to the inkjet head 1 via the ink transfer tube 102.
　さらに、インク移送管１０２の途中には、移送側サブタンク１１１ａが設けられている。移送側サブタンク１１１ａは、インクジェットヘッド１に移送されるインクが一旦貯留されるバッファ空間として構成されている。移送側サブタンク１１１ａを介して、圧力制御手段を構成する移送圧力制御ポンプ１１０ａにより、インク移送管１０２内のインクの圧力を制御することができる。移送圧力制御ポンプ１１０ａは、インクジェットヘッド１内の制御部１０４ａによって制御される。 Further, a transfer side sub tank 111a is provided in the middle of the ink transfer tube 102. The transfer-side sub-tank 111a is configured as a buffer space in which ink transferred to the inkjet head 1 is temporarily stored. The pressure of the ink in the ink transfer tube 102 can be controlled by the transfer pressure control pump 110a constituting the pressure control means via the transfer side sub tank 111a. The transfer pressure control pump 110a is controlled by the control unit 104a in the inkjet head 1.
　インク返送管１０３の途中には、制御部１０４によって駆動制御される返送ポンプ１０５ｂが設けられている。返送ポンプ１０５ｂが駆動することにより、インクジェットヘッド１内のインクが、インク返送管１０３を介してインクタンク１０１に返送される。 A return pump 105b, which is driven and controlled by the control unit 104, is provided in the middle of the ink return pipe 103. By driving the return pump 105b, the ink in the inkjet head 1 is returned to the ink tank 101 via the ink return tube 103.
　さらに、インク返送管１０３の途中には、返送側サブタンク１１１ｂが設けられている。返送側サブタンク１１１ｂは、インクジェットヘッド１から返送されてきたインクが一旦貯留されるバッファ空間として構成されている。返送側サブタンク１１１ｂを介して、圧力制御手段を構成する返送圧力制御ポンプ１１０ｂにより、インク返送管１０３内のインクの圧力を制御することができる。返送圧力制御ポンプ１１０ｂは、インクジェットヘッド１内の制御部１０４ａによって制御される。 Further, a return side sub tank 111b is provided in the middle of the ink return pipe 103. The return-side sub-tank 111b is configured as a buffer space in which the ink returned from the inkjet head 1 is temporarily stored. The pressure of the ink in the ink return pipe 103 can be controlled by the return pressure control pump 110b constituting the pressure control means via the return side sub tank 111b. The return pressure control pump 110b is controlled by the control unit 104a in the inkjet head 1.
　なお、圧力制御手段は、移送圧力制御ポンプ１１０ａ及び返送圧力制御ポンプ１１０ｂから構成されるものに限定されず、これらの何れかによって構成されるものであってもよい。この場合には、返送圧力制御ポンプ１１０ｂが第１の圧力制御手段となり、移送圧力制御ポンプ１１０ａが第２の圧力制御手段となる。 The pressure control means is not limited to the one composed of the transfer pressure control pump 110a and the return pressure control pump 110b, and may be composed of any of these. In this case, the return pressure control pump 110b serves as the first pressure control means, and the transfer pressure control pump 110a serves as the second pressure control means.
　インクタンク１０１は、格別限定されないが、タンクの底面に到達しない仕切り板１０１ａによって、インク移送室１０１ｂとインク返送室１０１ｃとに仕切ることが好ましい。この場合、インク移送室１０１ｂ内にインク移送管１０２の一端部を配置し、また、インク返送室１０１ｃ内にインク返送管１０３の一端部を配置する。仕切り板１０１ａは、インク返送室１０１ｃに返送されてきたインクに含まれる気泡が再度インク移送管１０２に流入しないように、インクを十分に脱気するために設けられる。気泡自体は浮力が高いので、気泡が仕切り板１０１ａの下側を通過してインク移送室１０１ｂに流入することが抑制される。このような態様は、インクを循環使用する場合に好ましい態様である。 The ink tank 101 is not particularly limited, but it is preferable that the ink tank 101 is divided into an ink transfer chamber 101b and an ink return chamber 101c by a partition plate 101a that does not reach the bottom surface of the tank. In this case, one end of the ink transfer tube 102 is arranged in the ink transfer chamber 101b, and one end of the ink return tube 103 is arranged in the ink return chamber 101c. The partition plate 101a is provided to sufficiently degas the ink so that the bubbles contained in the ink returned to the ink return chamber 101c do not flow into the ink transfer tube 102 again. Since the bubbles themselves have high buoyancy, it is possible to prevent the bubbles from passing under the partition plate 101a and flowing into the ink transfer chamber 101b. Such an embodiment is a preferred embodiment when the ink is used in a circulating manner.
　インクジェットヘッド１は、共通インク室４１を構成するインクマニホールド４と、このインクマニホールド４に接着された配線基板３と、配線基板３の下面部に接着されたヘッドチップ２と、ヘッドチップ２の下面部に接着されたノズルプレート２１とを有して構成されている。 The inkjet head 1 includes an ink manifold 4 constituting a common ink chamber 41, a wiring board 3 bonded to the ink manifold 4, a head chip 2 bonded to a lower surface portion of the wiring board 3, and a lower surface of the head chip 2. It is configured to have a nozzle plate 21 adhered to the portion.
　インクマニホールド４は、合成樹脂材料等によって、下面部に開口部４ａを有する横長の箱型に形成されている。このインクマニホールド４は、開口部４ａを、下面部に接着された配線基板３によって塞がれている。インクマニホールド４の内部空間は、インクタンク１０１から移送されたインクが貯留される共通インク室４１となる。配線基板３は、例えばガラス基板である。この配線基板３には、図示しない電源回路にＦＰＣ基板を介して接続される図示しない配線パターンが形成されている。 The ink manifold 4 is formed of a synthetic resin material or the like in a horizontally long box shape having an opening 4a on the lower surface. In the ink manifold 4, the opening 4a is closed by a wiring board 3 adhered to a lower surface portion. The internal space of the ink manifold 4 serves as a common ink chamber 41 in which the ink transferred from the ink tank 101 is stored. The wiring board 3 is, for example, a glass substrate. The wiring board 3 is formed with a wiring pattern (not shown) connected to a power supply circuit (not shown) via an FPC board.
　共通インク室４１には、共通インク室４１内にインクを供給する流路となるインク供給管５ａが連設されている。インク供給管５ａは、配線基板３から遠い側（上側）において、共通インク室４１に連通されている。インク供給管５ａの上端側には、接続部７ａが設けられている。接続部７ａは、インクジェット画像形成装置１００側の接続部１０６ａに着脱可能に接続される。インクジェット画像形成装置１００側の接続部１０６ａは、インク移送管１０２に連通している。これにより、インクジェットヘッド１は、インクタンク１０１からのインクの移送及び共通インク室４１へのインクの供給が可能となる。 In the common ink chamber 41, an ink supply pipe 5a serving as a flow path for supplying ink into the common ink chamber 41 is continuously provided. The ink supply pipe 5a communicates with the common ink chamber 41 on the side (upper side) far from the wiring board 3. A connecting portion 7a is provided on the upper end side of the ink supply tube 5a. The connection portion 7a is detachably connected to the connection portion 106a on the inkjet image forming apparatus 100 side. The connection portion 106a on the inkjet image forming apparatus 100 side communicates with the ink transfer tube 102. As a result, the inkjet head 1 can transfer ink from the ink tank 101 and supply ink to the common ink chamber 41.
　また、共通インク室４１には、共通インク室４１内からインクを回収する流路となるインク回収管５ｂが連設されている。インク回収管５ｂは、配線基板３から遠い側（上側）において、共通インク室４１に連通されている。インク回収管５ｂの上端側には、接続部７ｂが設けられている。接続部７ｂは、インクジェット画像形成装置１００側の接続部１０６ｂに着脱可能に接続される。インクジェット画像形成装置１００側の接続部１０６ｂは、インク返送管１０３に連通している。これにより、インクジェットヘッド１は、共通インク室４１からのインクの回収及びインクタンク１０１へのインクの返送が可能となる。 Further, in the common ink chamber 41, an ink recovery tube 5b that serves as a flow path for collecting ink from the common ink chamber 41 is continuously provided. The ink recovery tube 5b communicates with the common ink chamber 41 on the side (upper side) far from the wiring board 3. A connecting portion 7b is provided on the upper end side of the ink recovery tube 5b. The connecting portion 7b is detachably connected to the connecting portion 106b on the inkjet image forming apparatus 100 side. The connection portion 106b on the inkjet image forming apparatus 100 side communicates with the ink return tube 103. As a result, the inkjet head 1 can collect the ink from the common ink chamber 41 and return the ink to the ink tank 101.
　インクジェットヘッド１において、インク供給管５ａから、インク回収管５ｂの途中のバッファ空間部６に至る流路が、主流路Ｆ１となる。 In the inkjet head 1, the flow path from the ink supply tube 5a to the buffer space 6 in the middle of the ink recovery tube 5b is the main flow path F1.
　図２は、インクジェットヘッド１のヘッドチップ２の拡大断面図である。図３はインクジェットヘッド１のノズルプレート２１の平面図である。 FIG. 2 is an enlarged cross-sectional view of the head chip 2 of the inkjet head 1. FIG. 3 is a plan view of the nozzle plate 21 of the inkjet head 1.
　ヘッドチップ２には、複数のインクチャネル（圧力室）２３及び複数のダミーチャネル（擬似圧力室）２５が形成されている。各インクチャネル２３及び各ダミーチャネル２５は、ヘッドチップ２の上面部から下面部に亘って穿設された透孔である。各インクチャネル２３は、上方端が配線基板３に開設された注入孔３１ａを介して共通インク室４１に連通している。各インクチャネル２３には、インクタンク１０１内のインクの位置エネルギー及び移送ポンプ１０５ａに起因し移送圧力制御ポンプ１１０ａにより制御された圧力により、注入孔３１ａからインクが流入されて充填される。 A plurality of ink channels (pressure chambers) 23 and a plurality of dummy channels (pseudo pressure chambers) 25 are formed on the head chip 2. Each ink channel 23 and each dummy channel 25 are through holes formed from the upper surface portion to the lower surface portion of the head chip 2. The upper end of each ink channel 23 communicates with the common ink chamber 41 via an injection hole 31a provided in the wiring board 3. Each ink channel 23 is filled with ink flowing in from the injection hole 31a by the potential energy of the ink in the ink tank 101 and the pressure controlled by the transfer pressure control pump 110a due to the transfer pump 105a.
　各インクチャネル２３の下方端は、ノズル２２を介して外方（下方）に連通している。このインクジェットヘッド１においては、ノズル２２よりも内方は、インクチャネル２３内となる。インクチャネル２３とノズル２２との間に連通路が存在する場合には、ノズル２２よりも内方は、連通路内となる。各ダミーチャネル２５は、上方端を配線基板３により閉蓋され、下方端をノズルプレート２１により閉蓋されて、密閉された空気室となっている。各インクチャネル２３及び各ダミーチャネル２５は、一方向（図２中、矢印Ｘ方向）に配列されてチャネル列を構成している。 The lower end of each ink channel 23 communicates outward (downward) via the nozzle 22. In the inkjet head 1, the inside of the nozzle 22 is inside the ink channel 23. When there is a communication passage between the ink channel 23 and the nozzle 22, the inside of the nozzle 22 is inside the communication passage. The upper end of each dummy channel 25 is closed by the wiring board 3, and the lower end is closed by the nozzle plate 21 to form a closed air chamber. Each ink channel 23 and each dummy channel 25 are arranged in one direction (in the direction of arrow X in FIG. 2) to form a channel sequence.
　各インクチャネル２３の両壁部（インクチャネル２３とダミーチャネル２５との間の隔壁）は、圧力発生手段となる一対の圧電素子（駆動壁）２４，２４により構成されている。圧電素子２４，２４は、図示しない電源回路からＦＰＣ基板及び配線基板３の配線パターンを介して電圧を印加されることによって、せん断変形する。インクチャネル２３の両壁部をなす圧電素子２４、２４がせん断変形することにより、インクチャネル２３の圧力変動（膨張による減圧又は収縮による増圧）が生じる。インクチャネル２３の圧力変動（減圧又は増圧）により、ノズル２２よりも内方、すなわち、インクチャネル２３内のインクに圧力が付与され、このインクがノズル２２を介して吐出される。 Both wall portions (partition wall between the ink channel 23 and the dummy channel 25) of each ink channel 23 are composed of a pair of piezoelectric elements (driving walls) 24 and 24 that serve as pressure generating means. The piezoelectric elements 24, 24 are sheared and deformed by applying a voltage from a power supply circuit (not shown) through the wiring patterns of the FPC substrate and the wiring substrate 3. The piezoelectric elements 24, 24 forming both walls of the ink channel 23 are sheared and deformed, so that the pressure of the ink channel 23 fluctuates (decompression due to expansion or pressure increase due to contraction). Due to the pressure fluctuation (depressurization or pressure increase) of the ink channel 23, pressure is applied to the ink inside the nozzle 22, that is, in the ink channel 23, and this ink is ejected through the nozzle 22.
　圧電素子２４及び２４は、一つのインクチャネル２３あたり２枚（一対）が設けられており、各インクチャネル２３それぞれの両壁部をなしている。一のインクチャネル２３の壁部を構成する圧電素子２４と、隣接するインクチャネル２３の壁部を構成する圧電素子２４との間には空隙があり、この空隙がダミーチャネル２５である。したがって、各インクチャネル２３は、独立して駆動（減圧又は増圧）することができる。 Two piezoelectric elements 24 and 24 are provided for each ink channel 23, forming both wall portions of each ink channel 23. There is a gap between the piezoelectric element 24 forming the wall portion of one ink channel 23 and the piezoelectric element 24 forming the wall portion of the adjacent ink channel 23, and this gap is the dummy channel 25. Therefore, each ink channel 23 can be driven (decompressed or increased in pressure) independently.
　ヘッドチップ２には、導入路４２５を形成している。導入路４２５は、各インクチャネル２３及び各ダミーチャネル２５が構成するチャネル列の一端側の該チャネル列の外側に位置して設けられる。導入路４２５は、ヘッドチップ２の上面部から下面部に亘って穿設された透孔であり、横断面開口面積が、１つのインクチャネル２３の横断面開口面積よりも大きくなっている。導入路４２５は、上方端が配線基板３に開設された導入孔３１ｃを介して共通インク室４１に連通しており、インクタンク１０１内のインクの位置エネルギー及び移送ポンプ１０５ａに起因し移送圧力制御ポンプ１１０ａにより制御された圧力により、導入孔３１ｃからインクが流入される。 An introduction path 425 is formed in the head tip 2. The introduction path 425 is provided so as to be located outside the channel row on one end side of the channel row formed by each ink channel 23 and each dummy channel 25. The introduction path 425 is a through hole formed from the upper surface portion to the lower surface portion of the head chip 2, and the cross-sectional opening area is larger than the cross-sectional opening area of one ink channel 23. The introduction path 425 communicates with the common ink chamber 41 through an introduction hole 31c whose upper end is provided in the wiring board 3, and the transfer pressure is controlled due to the potential energy of the ink in the ink tank 101 and the transfer pump 105a. Ink flows in through the introduction hole 31c by the pressure controlled by the pump 110a.
　ヘッドチップ２の下面部に接着された平板状のノズルプレート２１には、各インクチャネル２３に対応された複数のノズル２２が穿設されている。ノズル２２は、インクチャネル２３を外部に連通させる透孔である。各インクチャネル２３内のインクは、圧電素子２４の作用によって吐出圧力を付与され、ノズル２２を通って外部（下方）の基材に向けて吐出される。すなわち、ノズル２２は、各インクチャネル２３内から外部（下方）に吐出されるインクの流路となる。ノズルプレート２１の下面部がインク吐出面１Ｓとなる。 A plurality of nozzles 22 corresponding to each ink channel 23 are bored in the flat plate-shaped nozzle plate 21 adhered to the lower surface of the head chip 2. The nozzle 22 is a through hole that allows the ink channel 23 to communicate with the outside. The ink in each ink channel 23 is subjected to ejection pressure by the action of the piezoelectric element 24, and is ejected toward the external (lower) base material through the nozzle 22. That is, the nozzle 22 serves as a flow path for ink discharged from the inside of each ink channel 23 to the outside (downward). The lower surface of the nozzle plate 21 is the ink ejection surface 1S.
　インクジェットヘッド１は、インクチャネル２３に注入されたインクをノズル２２の近傍から排出させてインクチャネル２３への注入経路に戻すノズル循環機構を備えている。各インクチャネル２３には、それぞれ２本の個別インク循環路２６ａ、２６ａが連通されている。 The inkjet head 1 is provided with a nozzle circulation mechanism that discharges the ink injected into the ink channel 23 from the vicinity of the nozzle 22 and returns it to the injection path to the ink channel 23. Two individual ink circulation paths 26a and 26a are communicated with each ink channel 23, respectively.
　個別インク循環路２６ａ及び２６ａは、インクチャネル２３の横断面長手方向の両端部においてインクチャネル２３に連通している。インクチャネル２３の両端部近傍は、気泡が残留することが多い箇所であるため、個別インク循環路２６ａ及び２６ａをインクチャネル２３の横断面長手方向の両端部に設けることは好ましい。なお、個別インク循環路２６ａ、２６ａは、インクチャネル２３の何れの箇所においてインクチャネル２３に連通するようにしてもよい。また、１個のインクチャネル２３に対する個別インク循環路２６ａの本数は、増減してもよいが、２個以上が好ましい。温度応答ポリマーや定着樹脂を添加したインクではチキソ性が生じるが、上記のように循環路が２個以上であると、そのようなインクを使用してもインクの滞留が生じがたく、またノズル近傍の泡の除去もしやすい効果がある。 The individual ink circulation paths 26a and 26a communicate with the ink channel 23 at both ends in the longitudinal direction of the cross section of the ink channel 23. Since air bubbles often remain in the vicinity of both ends of the ink channel 23, it is preferable to provide the individual ink circulation paths 26a and 26a at both ends of the ink channel 23 in the longitudinal direction of the cross section. The individual ink circulation paths 26a and 26a may communicate with the ink channel 23 at any position of the ink channel 23. The number of individual ink circulation paths 26a for one ink channel 23 may be increased or decreased, but it is preferably two or more. Thixotropy occurs in inks to which a temperature-responsive polymer or fixing resin is added, but if there are two or more circulation paths as described above, ink retention is unlikely to occur even if such inks are used, and nozzles It has the effect of easily removing nearby bubbles.
　個別インク循環路２６ａ及び２６ａは、ノズルプレート２１の上面部にノズル２２近傍に始端部を有して形成された流路形成溝２８が、ヘッドチップ２の下面部によって閉蓋されることにより構成されている。 The individual ink circulation paths 26a and 26a are formed by closing a flow path forming groove 28 formed on the upper surface of the nozzle plate 21 with a start end in the vicinity of the nozzle 22 by the lower surface of the head tip 2. Has been done.
　導入路４２５には、２本の導入溝４２５ａ及び４２５ａが連通される。導入溝４２５ａ、４２５ａは、導入路４２５の両側部において導入路４２５に連通している。なお、導入溝４２５ａ、４２５ａは、導入路４２５の何れの箇所において導入路４２５に連通するようにしてもよい。また、１個の導入路４２５に対する導入溝４２５ａ、４２５ａの本数は、増減してもよい。 Two introduction grooves 425a and 425a are communicated with the introduction path 425. The introduction grooves 425a and 425a communicate with the introduction path 425 at both sides of the introduction path 425. The introduction grooves 425a and 425a may communicate with the introduction path 425 at any position on the introduction path 425. Further, the number of introduction grooves 425a and 425a for one introduction path 425 may be increased or decreased.
　導入溝４２５ａ及び４２５ａは、ノズルプレート２１の上面部に導入路４２５近傍に始端部を有して形成され、ヘッドチップ２の下面部により閉蓋されて流路を構成している。 The introduction grooves 425a and 425a are formed on the upper surface of the nozzle plate 21 with a start end in the vicinity of the introduction path 425, and are closed by the lower surface of the head tip 2 to form a flow path.
　ヘッドチップ２の下面部には、共通インク循環路４２１が形成されている。共通インク循環路４２１は、ヘッドチップ２の下面部に形成された溝とノズルプレート２１の上面部に形成された溝４２２とが突き合わされることにより構成されている。 A common ink circulation path 421 is formed on the lower surface of the head chip 2. The common ink circulation path 421 is formed by abutting a groove formed on the lower surface portion of the head chip 2 and a groove 422 formed on the upper surface portion of the nozzle plate 21.
　共通インク循環路４２１は、チャネル列の方向（Ｘ方向）に形成された複数本の流路から構成されている。各インクチャネル２３に連通した各個別インク循環路２６ａ、２６ａは、共通インク循環路４２１に連通することにより合流している。各インクチャネル２３内と共通インク循環路４２１内との間の圧力差により、各インクチャネル２３から共通インク循環路４２１へのインクの流動が生じる。また、導入溝４２５ａ、４２５ａは、共通インク循環路４２１に連通している。導入路４２５内と共通インク循環路４２１内との間の圧力差により、導入路４２５から共通インク循環路４２１へのインクの流動が生じる。そして、これら流動が合流して共通インク循環路４２１内のインク流動が生じる。 The common ink circulation path 421 is composed of a plurality of flow paths formed in the direction of the channel row (X direction). The individual ink circulation paths 26a and 26a communicating with the ink channels 23 are joined by communicating with the common ink circulation path 421. Due to the pressure difference between each ink channel 23 and the common ink circulation path 421, ink flows from each ink channel 23 to the common ink circulation path 421. Further, the introduction grooves 425a and 425a communicate with the common ink circulation path 421. Due to the pressure difference between the introduction path 425 and the common ink circulation path 421, ink flows from the introduction path 425 to the common ink circulation path 421. Then, these flows merge to generate ink flow in the common ink circulation path 421.
　共通インク循環路４２１の他端側は、ヘッドチップ２に形成された排出チャネル４２４の下方端に連通されている。排出チャネル４２４は、各インクチャネル２３及び各ダミーチャネル２５が構成するチャネル列の他端側の該チャネル列の外側に位置して設けられている。排出チャネル４２４内のインク流量は、導入路４２５内のインク流量よりも、各インクチャネル２３を経たインクが合流している分だけ多くなるので、流路抵抗を増大させないために排出チャネル４２４の横断面開口面積を大きくする。 The other end side of the common ink circulation path 421 communicates with the lower end of the discharge channel 424 formed in the head chip 2. The discharge channel 424 is provided so as to be located outside the channel row on the other end side of the channel row formed by each ink channel 23 and each dummy channel 25. Since the ink flow rate in the discharge channel 424 is larger than the ink flow rate in the introduction path 425 by the amount of ink merging through each ink channel 23, the ink flow rate crosses the discharge channel 424 in order not to increase the flow path resistance. Increase the surface opening area.
　圧力室であるインクチャネル２３に連通する個別インク循環路２６ａから共通インク循環路４２１に排出されたインクは、排出チャネル４２４、インク排出室４１２及びインク排出管５ｃを経て、バッファ空間部６に至り、さらに、上記経路によりインクタンク１０１に返送される。そして、再びインクチャネル２３への注入経路へと導入される。 The ink discharged from the individual ink circulation path 26a communicating with the ink channel 23, which is the pressure chamber, to the common ink circulation path 421 reaches the buffer space 6 via the discharge channel 424, the ink discharge chamber 412, and the ink discharge pipe 5c. Further, it is returned to the ink tank 101 by the above route. Then, it is introduced into the injection path to the ink channel 23 again.
　図１に示すように、インクマニホールド４内には、排出チャネル４２４の上方に位置して、インク排出室４１２が設けられている。インク排出室４１２は、インクマニホールド４内において、共通インク室４１に隣接して設けられている。インク排出室４１２は、共通インク室４１に対しては、隔壁４５によって分離されている。隔壁４５は、インクマニホールド４に一体的に形成することができる。 As shown in FIG. 1, an ink discharge chamber 412 is provided in the ink manifold 4 located above the discharge channel 424. The ink discharge chamber 412 is provided adjacent to the common ink chamber 41 in the ink manifold 4. The ink discharge chamber 412 is separated from the common ink chamber 41 by a partition wall 45. The partition wall 45 can be integrally formed with the ink manifold 4.
　このようにして、注入孔３１ａからインクチャネル２３に流入されたインクの一部（ノズル２２から吐出されないインク）は、個別インク循環路２６ａ、２６ａから共通インク循環路４２１を経て、排出チャネル４２４に至り、配線基板３に形成された排出孔３１ｂを通って、インク排出室４１２に至る。また、導入孔３１ｃから導入路４２５に流入されたインクは、導入溝４２５ａ、４２５ａ及び共通インク循環路４２１を経て排出チャネル４２４に至り、排出孔３１ｂを通ってインク排出室４１２に至る。 In this way, a part of the ink (ink not ejected from the nozzle 22) flowing into the ink channel 23 from the injection hole 31a passes through the common ink circulation paths 421 from the individual ink circulation paths 26a and 26a to the discharge channel 424. It reaches the ink discharge chamber 412 through the discharge hole 31b formed in the wiring board 3. Further, the ink flowing into the introduction path 425 from the introduction hole 31c reaches the discharge channel 424 via the introduction groove 425a, 425a and the common ink circulation path 421, and reaches the ink discharge chamber 412 through the discharge hole 31b.
　インク排出室４１２には、循環路連結部５ｄを介して、インク排出室４１２内からインクを排出する流路をなすインク排出管５ｃが接続されている。循環路連結部５ｄは、排出チャネル４２４の上方側に位置して、各インクチャネル２３及び各ダミーチャネル２５が構成するチャネル列の他端側の該チャネル列の外側に位置して設けられている。インク排出管５ｃの上端側は、インク回収管５ｂに合流している。インク回収管５ｂとインク排出管５ｃとは、バッファ空間部６に接続されることによって合流している。 An ink discharge pipe 5c forming a flow path for discharging ink from the inside of the ink discharge chamber 412 is connected to the ink discharge chamber 412 via a circulation path connecting portion 5d. The circulation path connecting portion 5d is located above the discharge channel 424 and is located outside the channel row on the other end side of the channel row formed by each ink channel 23 and each dummy channel 25. .. The upper end side of the ink discharge tube 5c joins the ink recovery tube 5b. The ink recovery pipe 5b and the ink discharge pipe 5c are joined by being connected to the buffer space portion 6.
　インクジェットヘッド１において、導入路４２５及び個別インク循環路２６ａ、２６ａから、共通インク循環路４２１、排出チャネル４２４、排出孔３１ｂ、インク排出室４１２及びインク排出管５ｃを経て、バッファ空間部６に至る流路が、循環路４２３となる。循環路４２３は、導入路４２５及びインクチャネル２３に連通し、これら導入路４２５及びインクチャネル２３内のインクを排出させ、バッファ空間部６においてインク回収管５ｂに合流させる流路である。ただし、循環路４２３は、ノズル２２近傍の個別インク循環路２６ａ、２６ａからインクを排出し、このインクをインクチャネル２３への注入経路に戻すものであれば、途中の経路は何ら限定する必要はない。そして、導入孔３１ｃ及び各注入孔３１ａを経て、循環路４２３までが、副流路Ｆ２となる。 In the inkjet head 1, the introduction path 425 and the individual ink circulation paths 26a and 26a reach the buffer space 6 via the common ink circulation path 421, the discharge channel 424, the discharge hole 31b, the ink discharge chamber 412, and the ink discharge pipe 5c. The flow path becomes the circulation path 423. The circulation path 423 is a flow path that communicates with the introduction path 425 and the ink channel 23, discharges the ink in the introduction path 425 and the ink channel 23, and joins the ink recovery tube 5b in the buffer space 6. However, if the circulation path 423 discharges ink from the individual ink circulation paths 26a and 26a in the vicinity of the nozzle 22 and returns this ink to the injection path to the ink channel 23, it is necessary to limit the route in the middle. No. Then, through the introduction hole 31c and each injection hole 31a, up to the circulation path 423 becomes the sub-flow path F2.
　以下、実施例を挙げて本発明を具体的に説明するが、本発明はこれらに限定されるものではない。なお、実施例において「部」あるいは「％」の表示を用いるが、特に断りがない限り「質量部」あるいは「質量％」を表す。 Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, the indication of "parts" or "%" is used, but unless otherwise specified, it indicates "parts by mass" or "% by mass".
［実施例１～１３、比較例１～５］
　以下の材料を用いて、表Ｉ又は表IIに示す組成の各実施例及び比較例のインクジェットインクを調製した。 [Examples 1 to 13, Comparative Examples 1 to 5]
Inkjet inks of Examples and Comparative Examples having the compositions shown in Table I or Table II were prepared using the following materials.
（温度応答ポリマー）
・メトローズＳＭ－０４（商品名、信越化学工業社製、メチルセルロース樹脂、水に対するＬＣＳＴ；５５℃）
・メトローズ６０ＳＨ－０３（商品名、信越化学工業社製、ヒドロキシプロピルメチルセルロース樹脂、水に対するＬＣＳＴ；７５℃）
・ポリ（Ｎ－イソプロピルアクリルアミド）（シグマアルドリッチ社製、水に対するＬＣＳＴ；３５℃、重量平均分子量；３００００） (Temperature responsive polymer)
・ Metrose SM-04 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd., methylcellulose resin, LCST for water; 55 ° C)
・ Metrose 60SH-03 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd., hydroxypropylmethylcellulose resin, LCST for water; 75 ° C.)
Poly (N-isopropylacrylamide) (manufactured by Sigma-Aldrich, LCST with respect to water; 35 ° C., weight average molecular weight; 30,000)
　マゼンタ顔料；ＪＭ２１２０（商品名、ＤＩＣ社製、化合物名：ＰＲ２０２／ＰＶ１９）
　顔料分散剤；ジョンクリル８１９（商品名；ＢＡＳＦ社製、水酸化ナトリウム中和されたカルボキシ基を有するアクリル系分散剤、酸価７５ｍｇＫＯＨ／ｇ、固形分２０質量％）
　水；イオン交換水 Magenta pigment; JM2120 (trade name, manufactured by DIC Corporation, compound name: PR202 / PV19)
Pigment dispersant; John Krill 819 (trade name: BASF, acrylic dispersant having a sodium hydroxide neutralized carboxy group, acid value 75 mgKOH / g, solid content 20% by mass)
Water; ion-exchanged water
（水性溶媒）
・エチレングリコール
・プロピレングリコール
・グリセリン (Aqueous solvent)
・ Ethylene glycol ・ Propylene glycol ・ Glycerin
（定着樹脂）
・バイロナールＭＤ－２０００（商品名；東洋紡社製、数平均分子量が１８０００のポリエステル樹脂の水分散液；固形分４０質量％）
・モビニール６８００Ｄ（商品名；ジャパンコーティングレジン社製、ポリアクリル樹脂の水分散液；固形分４５質量％）
・エバファノールＨＡ－５６０（商品名；日華化学社製、ポリウレタン樹脂の水分散液；固形分３５質量％） (Fixing resin)
-Byronal MD-2000 (trade name; manufactured by Toyobo Co., Ltd., aqueous dispersion of polyester resin having a number average molecular weight of 18,000; solid content 40% by mass)
-Movinyl 6800D (trade name; manufactured by Japan Coating Resin Co., Ltd., aqueous dispersion of polyacrylic resin; solid content 45% by mass)
-Evafanol HA-560 (trade name; Nicca Chemical Co., Ltd., aqueous dispersion of polyurethane resin; solid content 35% by mass)
（界面活性剤）
・ＫＦ－３５１Ａ（商品名、信越化学工業製、ポリエーテル変性ポリシロキサン化合物）・オルフィンＥ１０１０（商品名、日信化学工業社製、アセチレングリコール類）
（チキソ性付与剤）
・セレンピアＴＣ－０１Ａ（商品名、日本製紙社製、セルロースナノファイバー、平均幅３～４ｎｍ、平均長さ０．８μｍ、アスペクト比２００） (Surfactant)
-KF-351A (trade name, manufactured by Shin-Etsu Chemical Co., Ltd., polyether-modified polysiloxane compound) -Orphin E1010 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd., acetylene glycols)
(Thixotropic agent)
-Serenpia TC-01A (trade name, manufactured by Nippon Paper Industries, Ltd., cellulose nanofiber, average width 3-4 nm, average length 0.8 μm, aspect ratio 200)
（顔料分散液の調製）
　マゼンタ顔料（ＪＭ２１２０）を４質量部、顔料分散剤（ジョンクリル８１９）を固形分として１．６質量部、エチレングリコールとイオン交換水の質量比１００：６８からなる水系溶媒を３０．５質量部、加えた混合液をプレミックスした後、０．５ｍｍのジルコニアビーズを体積率で５０％充填したサンドグラインダーを用いて分散し、顔料の含有量が１８質量％の顔料分散液を調製した。この顔料分散液に含まれる顔料粒子の平均粒径は１１０ｎｍであった。なお、平均粒径の測定はマルバルーン社製「ゼータサイザ１０００ＨＳ」により行った。 (Preparation of pigment dispersion)
4 parts by mass of magenta pigment (JM2120), 1.6 parts by mass of pigment dispersant (John Krill 819) as solid content, and 30.5 parts by mass of an aqueous solvent consisting of ethylene glycol and ion-exchanged water in a mass ratio of 100: 68. After premixing the added mixed solution, the mixture was dispersed using a sand grinder filled with 0.5 mm zirconia beads at a volume ratio of 50% to prepare a pigment dispersion having a pigment content of 18% by mass. The average particle size of the pigment particles contained in this pigment dispersion was 110 nm. The average particle size was measured by "Zetasizer 1000HS" manufactured by Maru Balloon.
（インクジェットインクの調製）
　上記で得られた顔料分散液及び上記各成分を表Ｉ又は表IIに示す組成となるように混合して得られた混合液を１μｍのフィルターにより濾過してインクジェットインクを得た。なお、表Ｉ又は表IIにおいて各成分の含有量（質量％）は、当該成分として分散液又は溶液を用いた場合は当該成分が含有する固形分の含有量を示す。例えば、実施例１における、バイロナールＭＤ－２０００については、分散媒である水の量を除いたポリエステル樹脂自体の含有量が５．０質量％である。また、表Ｉ又は表IIの組成欄における空欄は、その成分を含有しないことを示す。 (Preparation of inkjet ink)
The pigment dispersion liquid obtained above and each of the above components were mixed so as to have the composition shown in Table I or Table II, and the obtained mixed liquid was filtered through a 1 μm filter to obtain an inkjet ink. In addition, in Table I or Table II, the content (mass%) of each component indicates the content of the solid content contained in the component when a dispersion liquid or a solution is used as the component. For example, in the case of Byronal MD-2000 in Example 1, the content of the polyester resin itself excluding the amount of water as a dispersion medium is 5.0% by mass. In addition, blanks in the composition column of Table I or Table II indicate that the component is not contained.
（インクの物性の評価）
　上記で得られたインクについて、以下の（Ａ１）～（Ａ８）の物性を評価した。結果を表Ｉ又は表IIに示す。（Ａ１）、（Ａ２）、（Ａ５）及び（Ａ６）は上記で得られたインクをそのまま、すなわちインク乾燥率０％の状態で評価した。 (Evaluation of physical characteristics of ink)
The following physical properties (A1) to (A8) were evaluated for the inks obtained above. The results are shown in Table I or Table II. In (A1), (A2), (A5) and (A6), the inks obtained above were evaluated as they were, that is, in a state where the ink drying rate was 0%.
（Ａ１）せん断速度１０００（１／ｓ）時の粘度（２５℃）
（Ａ２）せん断速度１（１／ｓ）時の粘度（ＬＣＳＴ＋５℃）
（Ａ３）インク乾燥率２０％における、せん断速度１（１／ｓ）時の粘度（ＬＣＳＴ＋５℃）
（Ａ４）インク乾燥率５０％における、せん断速度１（１／ｓ）時の粘度（ＬＣＳＴ＋５℃）
（Ａ５）歪１％時の損失正接（ｔａｎδ）（ＬＣＳＴ＋５℃）
（Ａ６）貯蔵弾性率と損失弾性率のクロスオーバー歪（ＬＣＳＴ＋５℃）
（Ａ７）インク乾燥率２０％における、歪１％時の損失正接（ｔａｎδ）（ＬＣＳＴ＋５℃）
（Ａ８）インク乾燥率２０％における、貯蔵弾性率と損失弾性率のクロスオーバー歪（ＬＣＳＴ＋５℃） (A1) Viscosity (25 ° C.) at a shear rate of 1000 (1 / s)
(A2) Viscosity at shear rate 1 (1 / s) (LCST + 5 ° C)
(A3) Viscosity (LCST + 5 ° C.) at a shear rate of 1 (1 / s) at an ink drying rate of 20%.
(A4) Viscosity at a shear rate of 1 (1 / s) at an ink drying rate of 50% (LCST + 5 ° C.)
(A5) Loss tangent (tan δ) at 1% strain (LCST + 5 ° C)
(A6) Crossover strain of storage elastic modulus and loss elastic modulus (LCST + 5 ° C)
(A7) Loss tangent (tan δ) at 1% strain at an ink drying rate of 20% (LCST + 5 ° C.)
(A8) Crossover strain (LCST + 5 ° C.) of storage elastic modulus and loss elastic modulus at an ink drying rate of 20%
　上記において、ＬＣＳＴ＋５℃は、各インクが含有する温度応答ポリマーの水に対するＬＣＳＴ＋５℃を意味する。ただし、比較例６については、温度応答ポリマーを含有していないため、ＬＣＳＴ＋５℃に代わる測定温度を６０℃とした。（Ａ２）において、ＬＣＳＴ＋５℃におけるせん断速度１（１／ｓ）時の粘度が、４５ｍＰａ・ｓ以上であれば、上記（１－２）の条件を満足する。（Ａ３）において、インク乾燥率２０％における、せん断速度１（１／ｓ）時の粘度が、１００ｍＰａ・ｓ以上であれば、上記（１－３）の条件を満足する。 In the above, LCST + 5 ° C means LCST + 5 ° C with respect to water of the temperature-responsive polymer contained in each ink. However, in Comparative Example 6, since the temperature-responsive polymer was not contained, the measurement temperature was set to 60 ° C. instead of LCST + 5 ° C. In (A2), if the viscosity at a shear rate of 1 (1 / s) at LCST + 5 ° C. is 45 mPa · s or more, the above condition (1-2) is satisfied. In (A3), if the viscosity at a shear rate of 1 (1 / s) at an ink drying rate of 20% is 100 mPa · s or more, the above condition (1-3) is satisfied.
　なお、上記（Ａ１）～（Ａ８）については、アントンパール社製、ＭＣＲ－１０２を用いて測定した。（Ａ４）については比較例５のみ測定した。（Ａ５）～（Ａ８）については、ＭＣＲ１０２のオシレーションモードにて、角周波数ωが１０ｒａｄ／ｓ及び振り角γが１～１０００％の範囲の測定条件で歪を変化させて測定した。時間設定は、測定点が３００点、測定間隔が２Ｓ、せん断速度１（１／ｓ）、温度は１０℃からＬＣＳＴ＋５℃まで線形変化させた。 The above (A1) to (A8) were measured using MCR-102 manufactured by Anton Pearl Co., Ltd. Regarding (A4), only Comparative Example 5 was measured. (A5) to (A8) were measured by changing the strain in the oscillation mode of MCR102 under the measurement conditions in which the angular frequency ω was 10 rad / s and the swing angle γ was in the range of 1 to 1000%. The time was set at 300 measurement points, the measurement interval was 2S, the shear rate was 1 (1 / s), and the temperature was linearly changed from 10 ° C. to LCST + 5 ° C.
　図４に、実施例１のインクについて、インク乾燥率２０％として上記条件で測定した、損失正接（ｔａｎδ）、貯蔵弾性率Ｇ′（対数）及び損失弾性率Ｇ″（対数）と歪（対数）の関係を表すグラフを示す。当該グラフから（Ａ５）の歪１％時の損失正接（ｔａｎδ）及び（Ａ６）のクロスオーバー歪が求められる。 FIG. 4 shows the loss tangent (tan δ), storage elastic modulus G ′ (logarithm), loss elastic modulus G ″ (logarithm) and strain (logarithm) measured under the above conditions with an ink drying rate of 20% for the ink of Example 1. ) Is shown. From the graph, the loss tangent (tan δ) at 1% strain of (A5) and the crossover strain of (A6) can be obtained.
（インクのプリント特性の評価）
　上記で得られたインクについて、インクジェット画像形成装置（インクジェットプリンター（トライテック社製）を用い、ヘッドはコニカミノルタ製ＫＭ１０２４ｉＭＨＥ（２以上の循環路によりヘッド内でインクを循環する機構を有する）を用い、解像度を７２０×７２０ｄｐｉとして、以下の（Ｂ１）、（Ｂ２）及び（Ｂ４）のプリント特性を評価した。なお、（Ｂ３）については以下の方法でインク塗膜を形成し評価した。結果を表Ｉ又は表IIに示す。 (Evaluation of ink print characteristics)
For the ink obtained above, an inkjet image forming apparatus (inkjet printer (manufactured by Tritech) is used, and a head is KM1024iMHE manufactured by Konica Minolta (having a mechanism for circulating ink in the head by two or more circulation paths)). The print characteristics of the following (B1), (B2) and (B4) were evaluated with a resolution of 720 × 720 dpi. Regarding (B3), an ink coating film was formed and evaluated by the following method. Shown in Table I or Table II.
（Ｂ１）射出性
　ＰＥＴ基材上にベタ状および直線状の画像を印刷し、ベタ部のスジの状態と直線の形成状態を以下の評価基準により評価した。 (B1) Ejectability Solid and linear images were printed on a PET substrate, and the state of streaks in the solid portion and the state of formation of straight lines were evaluated according to the following evaluation criteria.
（評価基準）
◎；ベタ部にスジなく、直線もきれいに印刷できている。
〇；ベタ部にスジはなく、直線に一部がたつきがある。
×；ベタ部に白抜けのスジがあり、直線に抜けがある。 (Evaluation criteria)
◎; There are no streaks on the solid part, and straight lines can be printed neatly.
〇; There are no streaks on the solid part, and there is some rattling on the straight line.
×: There are white streaks on the solid part, and there are omissions on the straight line.
（Ｂ２）画質（ピニング性）
　ＰＥＴ基材上に、ベタ部に４ｐｔ、６ｐｔ、及び８ｐｔの大きさの白抜け文字がある画像を印刷し、文字の品質を以下の評価基準により評価した。 (B2) Image quality (pinning property)
Images with white characters having a size of 4 pt, 6 pt, and 8 pt were printed on a PET base material in solid portions, and the quality of the characters was evaluated according to the following evaluation criteria.
（評価基準）
◎；すべての白抜け文字が鮮明に印刷できている。
〇；６ｐｔ以上の文字が鮮明に印刷できている。
×；６ｐｔ以上の文字ににじみがある。 (Evaluation criteria)
◎; All white characters are clearly printed.
〇; Characters of 6 pt or more can be printed clearly.
X; Characters of 6 pt or more have bleeding.
（Ｂ３）基材定着性
　基材として、ＰＥＴ基材を用いて、以下の方法でインク塗膜の基材定着性を評価した。インク塗膜は、インクをワイヤーバー＃７により基材上に塗布し、１００℃、３分間乾燥して得た。得られたインク塗膜（１００ｍｍ×１００ｍｍ、厚さ１０μｍ）に、縦５個×横５個の２５個のマス目ができるようにカッターで切り傷を入れ、ニチバンのセロテープ（登録商標）を貼り付け剥離して密着状態を以下の評価基準により評価した。 (B3) Base Material Fixability Using a PET base material as the base material, the base material fixability of the ink coating film was evaluated by the following method. The ink coating film was obtained by applying ink on a substrate with a wire bar # 7 and drying at 100 ° C. for 3 minutes. Cut the obtained ink coating film (100 mm x 100 mm, thickness 10 μm) with a cutter so that 25 squares of 5 vertical × 5 horizontal are formed, and attach Nichiban's cellophane tape (registered trademark). The peeled state was evaluated according to the following evaluation criteria.
（評価基準）
◎；剥がれなしである。
〇；剥がれが５マス以内である。
×；剥がれが６マス以上である。 (Evaluation criteria)
◎; No peeling.
〇; Peeling is within 5 squares.
X; Peeling is 6 squares or more.
（Ｂ４）塗膜耐水性
　ＰＥＴ基材上にベタ状の画像を印刷した。得られた印刷画像（インク塗膜）上に、水をスポイトで垂らし、綿棒で印刷画像の表面を１０回擦って印刷画像の状態を以下の評価基準により評価した (B4) Water-resistant coating film A solid image was printed on a PET substrate. Water was dropped on the obtained printed image (ink coating film) with a dropper, and the surface of the printed image was rubbed 10 times with a cotton swab to evaluate the state of the printed image according to the following evaluation criteria.
（評価基準）
◎；印刷画像に変化なし。
〇；印刷画像がほとんど変化しない。濃度がやや薄くなる。
×；印刷画像が変化あり、画像がくずれている。 (Evaluation criteria)
◎; No change in printed image.
〇; The printed image hardly changes. The concentration becomes slightly thinner.
X: The printed image is changed and the image is distorted.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表Ｉ及び表IIからわかるように、実施例のインクを用いたインクジェットプリントでは、ヘッドからのインクの吐出性は良好であり、かつ高品質な印刷画像が得られる。 As can be seen from Tables I and II, in the inkjet printing using the inks of the examples, the ink ejection property from the head is good and a high quality printed image can be obtained.
　本発明のインクジェットインクによれば、インクジェット法による画像形成において、良好な吐出性の維持と高品質な画像形成の両立が可能である。また、本発明の画像形成によれば、インクジェット法による画像形成において、作業性よく高品質な画像を形成することが可能である。 According to the inkjet ink of the present invention, it is possible to maintain good ejection performance and to form a high-quality image in the image formation by the inkjet method. Further, according to the image formation of the present invention, it is possible to form a high-quality image with good workability in the image formation by the inkjet method.
　１：インクジェットヘッド（エンドシュータ型）
　　１１：インクジェットヘッド（ＭＥＭＳ型）
　２：ヘッドチップ
　　２１：ノズルプレート
　　２２：ノズル
　　２３：インクチャネル
　　２４：圧電素子
　　２５：ダミーチャネル
　　２６ａ：個別インク循環路
　　２８：流路形成溝
　３：配線基板
　　３１ａ：注入孔
　　３１ｂ：排出孔
　　３１ｃ：導入孔
　４：インクマニホールド
　　４１：共通インク室
　　４１２：インク排出室
　　４２１：共通インク循環路
　　４２２：溝
　　４２３：循環路
　　４２４：排出チャネル
　　４２５：導入路
　　４２５ａ：導入溝
　　４５：隔壁
　５ａ：インク供給管
　５ｂ：インク回収管
　５ｃ：インク排出管
　５ｄ：循環路連結部
　６：バッファ空間部
　７ａ：接続部
　７ｂ：接続部
　Ｆ１：主流路
　Ｆ２：副流路
　１００：インクジェット記録装置
　１０１：インクタンク
　１０２：インク移送管
　１０３：インク返送管
　１０４：制御部
　１０４ａ：制御部
　１０５ａ：移送ポンプ
　１０５ｂ：返送ポンプ
　１０７：キャリッジ機構
　１０８：搬送手段
　１０９：基材
　１１０ａ：移送圧力制御ポンプ
　１１０ｂ：返送圧力制御ポンプ
　１１１ａ：移送側サブタンク
　１１１ｂ：返送側サブタンク 1: Inkjet head (end shooter type)
11: Inkjet head (MEMS type)
2: Head chip 21: Nozzle plate 22: Nozzle 23: Ink channel 24: piezoelectric element 25: Dummy channel 26a: Individual ink circulation path 28: Flow path forming groove 3: Wiring board 31a: Injection hole 31b: Discharge hole 31c: Introduction Hole 4: Ink manifold 41: Common ink chamber 412: Ink discharge chamber 421: Common ink circulation path 422: Groove 423: Circulation path 424: Discharge channel 425: Introduction path 425a: Introduction groove 45: Partition wall 5a: Ink supply pipe 5b: Ink recovery tube 5c: Ink discharge tube 5d: Circulation path connection part 6: Buffer space part 7a: Connection part 7b: Connection part F1: Main flow path F2: Sub-flow path 100: Ink ink recording device 101: Ink tank 102: Ink transfer tube 103: Ink return pipe 104: Control unit 104a: Control unit 105a: Transfer pump 105b: Return pump 107: Carriage mechanism 108: Transfer means 109: Base material 110a: Transfer pressure control pump 110b: Return pressure control pump 111a: Transfer side sub tank 111b: Return side sub tank

Claims (17)

  1. 　水系溶媒、顔料、定着樹脂、及び温度応答ポリマーを含有するインクジェットインクであって、
    　前記温度応答ポリマーが、水に対して下限臨界共溶温度を有し、
    　前記インクジェットインク全量に対する、前記顔料の含有量が、２～１０質量％の範囲内であり、前記定着樹脂の含有量が、１～１０質量％の範囲内であり、前記温度応答ポリマーの含有量が、０．０１～１質量％の範囲内であるインクジェットインク。     An inkjet ink containing an aqueous solvent, a pigment, a fixing resin, and a temperature-responsive polymer.
    The temperature-responsive polymer has a lower critical eutectic temperature with respect to water.
    The content of the pigment is in the range of 2 to 10% by mass, the content of the fixing resin is in the range of 1 to 10% by mass, and the content of the temperature-responsive polymer is in the range of 1 to 10% by mass with respect to the total amount of the inkjet ink. However, the inkjet ink is in the range of 0.01 to 1% by mass.
  2. 　前記インクジェットインクが、２５℃でのせん断速度１０００（１／ｓ）時の粘度が、１５ｍＰａ・ｓ以下であり、かつ前記下限臨界共溶温度±１０℃の範囲のいずれかの温度でのせん断速度１（１／ｓ）時の粘度が、４５ｍＰａ・ｓ以上である請求項１に記載のインクジェットインク。 The viscosity of the inkjet ink at a shear rate of 1000 (1 / s) at 25 ° C. is 15 mPa · s or less, and the shear rate at any temperature in the range of the lower limit critical eutectic temperature ± 10 ° C. The inkjet ink according to claim 1, wherein the viscosity at 1 (1 / s) is 45 mPa · s or more.
  3. 　前記インクジェットインクが、初期質量の８０％の質量となるように前記インクジェットインクから前記水系溶媒を除去した状態で、前記下限臨界共溶温度±１０℃の範囲のいずれかの温度でのせん断速度１（１／ｓ）時の粘度が１００ｍＰａ・ｓ以上となる請求項１又は請求項２に記載のインクジェットインク。 Shear velocity 1 at any temperature within the lower limit critical eutectic temperature ± 10 ° C. in a state where the aqueous solvent is removed from the inkjet ink so that the inkjet ink has a mass of 80% of the initial mass. The inkjet ink according to claim 1 or 2, wherein the viscosity at (1 / s) is 100 mPa · s or more.
  4. 　前記温度応答ポリマーの水に対する下限臨界共溶温度が、３０～６０℃の範囲内にある請求項１から請求項３までのいずれか一項に記載のインクジェットインク。 The inkjet ink according to any one of claims 1 to 3, wherein the lower limit critical eutectic temperature of the temperature-responsive polymer with respect to water is in the range of 30 to 60 ° C.
  5. 　前記温度応答ポリマーが、水溶性セルロース樹脂を含む請求項１から請求項４までのいずれか一項に記載のインクジェットインク。 The inkjet ink according to any one of claims 1 to 4, wherein the temperature-responsive polymer contains a water-soluble cellulose resin.
  6. 　前記インクジェットインク全量に対する、前記水系溶媒の含有量が５０～９０質量％の範囲内である請求項１から請求項５までのいずれか一項に記載のインクジェットインク。 The inkjet ink according to any one of claims 1 to 5, wherein the content of the aqueous solvent is in the range of 50 to 90% by mass with respect to the total amount of the inkjet ink.
  7. 　前記定着樹脂が、ポリアクリル樹脂、ポリウレタン樹脂、及びポリエステル樹脂からなる群から選ばれる少なくとも一種を含む請求項１から請求項６までのいずれか一項に記載のインクジェットインク。 The inkjet ink according to any one of claims 1 to 6, wherein the fixing resin contains at least one selected from the group consisting of a polyacrylic resin, a polyurethane resin, and a polyester resin.
  8. 　前記インクジェットインクが、さらにチキソ性付与剤を含有する請求項１から請求項７までのいずれか一項に記載のインクジェットインク。 The inkjet ink according to any one of claims 1 to 7, wherein the inkjet ink further contains a thixotropic agent.
  9. 　前記チキソ性付与剤が、セルロースナノファイバー又はスメクタイト粘土鉱物を含む請求項８に記載のインクジェットインク。 The inkjet ink according to claim 8, wherein the thixotropy-imparting agent contains cellulose nanofibers or smectite clay minerals.
  10. 　前記チキソ性付与剤の含有量が、前記インクジェットインク全量に対して０．０１～１質量％の範囲内である請求項８又は請求項９に記載のインクジェットインク。 The inkjet ink according to claim 8 or 9, wherein the content of the thixotropy-imparting agent is in the range of 0.01 to 1% by mass with respect to the total amount of the inkjet ink.
  11. 　インク循環機構を備えるインクジェットヘッドからインクジェットインクの液滴を吐出して基材上に着弾させる着弾工程を有する画像形成方法であって、
    　前記インクジェットインクが、前記インクジェットヘッド内で粘度が１５ｍＰａ・ｓ以下になるように循環され、かつ
    　前記基材に着弾した時、又は着弾直後の前記液滴が、前記インクジェットインクからの質量減少率が２０％以内となるように、かつ粘度が１００ｍＰａ・ｓ以上となるように前記着弾工程を行う画像形成方法。     An image forming method including a landing process in which droplets of inkjet ink are ejected from an inkjet head provided with an ink circulation mechanism and landed on a substrate.
    The inkjet ink is circulated in the inkjet head so as to have a viscosity of 15 mPa · s or less, and when the droplets land on the substrate or immediately after landing, the mass reduction rate from the inkjet ink is high. An image forming method in which the landing step is performed so that the content is within 20% and the viscosity is 100 mPa · s or more.
  12. 　前記基材に着弾した時、又は着弾直後の前記液滴の粘度が、１５０ｍＰａ・ｓ以上である請求項１１に記載の画像形成方法。 The image forming method according to claim 11, wherein the droplet has a viscosity of 150 mPa · s or more when it lands on the substrate or immediately after it lands.
  13. 　前記着弾工程が、前記液滴を前記基材上で３０～６０℃の範囲内で加熱することを含む請求項１１又は請求項１２に記載の画像形成方法。 The image forming method according to claim 11 or 12, wherein the landing step includes heating the droplet on the substrate in the range of 30 to 60 ° C.
  14. 　前記着弾直後が、前記液滴が前記基材に着弾後１００ｍｓｅｃ以内である請求項１１から請求項１３までのいずれか一項に記載の画像形成方法。 The image forming method according to any one of claims 11 to 13, wherein the droplet is within 100 msec after landing on the base material immediately after the landing.
  15. 　前記基材が、非吸収性の基材である請求項１１から請求項１４までのいずれか一項に記載の画像形成方法。 The image forming method according to any one of claims 11 to 14, wherein the base material is a non-absorbent base material.
  16. 　前記インクジェットヘッドが、
    　注入経路を介して前記インクジェットインクが注入される圧力室と、
    　前記圧力室に圧力変動を生じさせる圧力発生手段と、
    　前記圧力室に連通し、該圧力室の圧力変動により該圧力室内から外部に吐出される前記インクジェットインクの流路となるノズルと、
    　前記圧力室に連通し、前記ノズルよりも内方の前記インクジェットインクを排出させて前記注入経路に戻す２以上の循環路と
    　を備える請求項１１から請求項１５までのいずれか一項に記載の画像形成方法。     The inkjet head
    A pressure chamber in which the inkjet ink is injected via the injection path, and
    A pressure generating means that causes pressure fluctuation in the pressure chamber, and
    A nozzle that communicates with the pressure chamber and serves as a flow path for the inkjet ink that is discharged from the pressure chamber to the outside due to pressure fluctuations in the pressure chamber.
    The invention according to any one of claims 11 to 15, further comprising two or more circulation paths that communicate with the pressure chamber, discharge the inkjet ink inside the nozzle, and return the inkjet ink to the injection path. Image formation method.
  17. 　前記インクジェットインクが、請求項１から請求項１０までのいずれか一項に記載のインクジェットインクである請求項１１から請求項１６までのいずれか一項に記載の画像形成方法。 The image forming method according to any one of claims 11 to 16, wherein the inkjet ink is the inkjet ink according to any one of claims 1 to 10.
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