WO2016035787A1 - 水性顔料分散体、インクジェット記録用インク及び印字物 - Google Patents
水性顔料分散体、インクジェット記録用インク及び印字物 Download PDFInfo
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- WO2016035787A1 WO2016035787A1 PCT/JP2015/074836 JP2015074836W WO2016035787A1 WO 2016035787 A1 WO2016035787 A1 WO 2016035787A1 JP 2015074836 W JP2015074836 W JP 2015074836W WO 2016035787 A1 WO2016035787 A1 WO 2016035787A1
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- 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
- C09D11/38—Inkjet printing inks characterised by non-macromolecular additives other than solvents, pigments or dyes
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- 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
- C09D11/02—Printing inks
- C09D11/10—Printing inks based on artificial resins
- C09D11/106—Printing inks based on artificial resins containing macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
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- 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
- C09D11/02—Printing inks
- C09D11/10—Printing inks based on artificial resins
- C09D11/106—Printing inks based on artificial resins containing macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- C09D11/107—Printing inks based on artificial resins containing macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from unsaturated acids or derivatives thereof
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- 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
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- 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
- C09D11/324—Inkjet printing inks characterised by colouring agents containing carbon black
- C09D11/326—Inkjet printing inks characterised by colouring agents containing carbon black characterised by the pigment dispersant
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- 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
- C09D11/328—Inkjet printing inks characterised by colouring agents characterised by dyes
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- 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
- C09D17/00—Pigment pastes, e.g. for mixing in paints
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- 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
- C09D17/00—Pigment pastes, e.g. for mixing in paints
- C09D17/001—Pigment pastes, e.g. for mixing in paints in aqueous medium
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- 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
- C09D17/00—Pigment pastes, e.g. for mixing in paints
- C09D17/002—Pigment pastes, e.g. for mixing in paints in organic medium
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- 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
- C09D17/00—Pigment pastes, e.g. for mixing in paints
- C09D17/003—Pigment pastes, e.g. for mixing in paints containing an organic pigment
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- 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
- C09D17/00—Pigment pastes, e.g. for mixing in paints
- C09D17/004—Pigment pastes, e.g. for mixing in paints containing an inorganic pigment
- C09D17/005—Carbon black
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/34—Silicon-containing compounds
- C08K3/36—Silica
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
- C08K5/0041—Optical brightening agents, organic pigments
Definitions
- the present invention relates to an aqueous pigment dispersion, an ink jet recording ink using the dispersion, and a printed matter.
- Water-based paints and inks are deployed in a wide range of fields because of their safety and low environmental impact.
- water-based ink that can be applied to an ink jet recording system is expected to be used as an alternative to an electrophotographic system in homes, offices, and industrial applications because it can be used in a closed space.
- the optical density also referred to as OD value, image density, and coloring density
- the medium is particularly a plain paper. In this case, there is a problem that the ink easily penetrates into the paper and it is difficult to obtain a high optical density.
- the aqueous ink is generally prepared by diluting an aqueous pigment composition having a high pigment concentration called an aqueous pigment dispersion or pigment paste with water or an aqueous medium.
- an aqueous pigment dispersion or pigment paste with water or an aqueous medium. The investigation on the optical density is conducted not only for inks having a low pigment density but also for pigment dispersions themselves having a high pigment density.
- Patent Document 1 discloses carbon black having a specific primary particle size, specific surface area, and DBP oil absorption as a black pigment dispersion for an aqueous pigment ink for inkjet recording that gives a high color density (OD value) in plain paper.
- An aqueous black pigment dispersion containing a resin having a specific composition / acid value is disclosed.
- the type and characteristics of the pigment are not particularly limited, and a method for realizing a high coloring density in a general aqueous pigment dispersion is not described.
- fumed silica (sometimes referred to as fumed silica) is known as one of inorganic particle additives. Fumed silica is generally used as a thickener for UV flexographic printing inks using a plate (see, for example, Patent Document 2) or as a pigment for a receiving layer of an ink jet recording medium (see, for example, Patent Document 3).
- As an example of blending with an ink for ink jet recording an example is known in which hydrophobic fumed silica is used as an example of hydrophobic silica fine particles for the purpose of improving the bronzing phenomenon of ink blended with a chromatic pigment ( For example, see Patent Document 4 Examples 1 and 2).
- hydrophilic fumed silica into an aqueous pigment dispersion for the purpose of obtaining a high optical density.
- An object of the present invention is to provide an aqueous pigment dispersion that exhibits high optical density while maintaining high dispersion stability, and an ink for ink jet recording using the same.
- an aqueous pigment dispersion containing a pigment, hydrophilic fumed silica, and an aqueous medium expresses a high optical density.
- Patent Document 4 describes an example in which hydrophobic fumed silica is added to an ink for ink jet recording for the purpose of improving the bronzing phenomenon of an ink containing a chromatic pigment.
- fumed silica not only fumed silica but also hydrophobic silica cannot be finely dispersed in an aqueous medium in the composition, and does not affect the optical density or rather adversely affect this (Table 1 of Japanese Patent Application Laid-Open No. 2005-32077). It is clear from the sex assessment).
- it has been found that blending an appropriate amount of hydrophilic fumed silica that can be finely dispersed in an aqueous medium is effective for developing a high optical density which is a problem.
- the present invention provides an aqueous pigment dispersion containing a pigment, hydrophilic fumed silica, and an aqueous medium.
- the present invention also provides an ink for inkjet recording using the aqueous pigment dispersion.
- the present invention also provides a printed matter using the aqueous pigment dispersion described above.
- an aqueous pigment dispersion that exhibits high optical density and high storage stability can be obtained.
- the pigment used in the present invention is at least one pigment selected from known and commonly used organic pigments or inorganic pigments.
- the present invention can also apply treated pigments such as so-called self-dispersing pigments.
- treated pigments such as so-called self-dispersing pigments.
- yellow ink, cyan ink, magenta ink, black ink, and the like are used.
- These pigments used are not particularly limited, and those usually used as pigments for water-based inks can be used. Specifically, it can be dispersed in water or a water-soluble organic solvent, and a known inorganic pigment or organic pigment can be used.
- organic pigments examples include carbon black produced by a known method such as iron oxide, a contact method, a furnace method, and a thermal method.
- Organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazines).
- Pigments thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (for example, basic dye chelates, acidic dye chelates, etc.), nitro pigments, nitroso pigments, aniline black, and the like.
- dye chelates for example, basic dye chelates, acidic dye chelates, etc.
- nitro pigments nitroso pigments, aniline black, and the like.
- pigments used for black ink for example, # 2600 series, # 2300 series, # 1000 series, # 900 series, MA series manufactured by Mitsubishi Chemical Corporation, COLOR-BLACK series manufactured by Orion Engineered Carbons, SPESIAL -BLACK series, PRINTEX series, HIBLACK series, NEROX series, NIPex series, Asahi Carbon's SUNBLACK series, # 70 series, # 80 series, Tokai Carbon's Talker Black # 7000 series, # 8000 series, etc. It is done. Among them, acidic carbon black is preferable because of its high OD value and easy dispersion.
- pigments used in yellow ink include C.I. I. Pigment Yellow 1, 2, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 120, 128, 129, 138, 150, 151, 154, 155, 174, 180, 185 and the like.
- pigments used in magenta ink include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 146, 168, 176, 184, 185, 202, 209, 254, etc. Can be mentioned.
- pigments used for cyan ink include C.I. I. Pigment blue 1, 2, 3, 15, 15: 3, 15: 4, 16, 22, 60, 63, 66, and the like.
- the pigment content is preferably 0.5 to 30% by mass, and more preferably 1.0 to 12% by mass with respect to the total amount of aqueous ink.
- the content is most preferably 3% by mass to 12% by mass. If the content is less than 3% by mass, the print density on plain paper may not be ensured. If the content exceeds 12% by mass, the water-based ink is ejected from the inkjet head due to an increase in ink viscosity. Stability may be deteriorated.
- the particle size of the pigment is preferably 1 ⁇ m or less, more preferably a pigment composed of particles of 10 nm to 150 nm, and still more preferably a pigment composed of particles of 50 nm to 120 nm.
- hydrophilic fumed silica used in the present invention is not particularly limited, and known ones can be used. Fumed silica can be obtained by hydrolyzing highly purified silicon tetrachloride at high temperature in an oxyhydrogen flame, and is divided into hydrophilic fumed silica and hydrophobic fumed silica depending on the presence or absence of surface treatment. In the invention, hydrophilic fumed silica is used.
- hydrophilic silica examples include Aerosil W7520, 130, 200, 300, R816 (trade name, Nippon Aerosil Co., Ltd., manufactured by Degussa), Cabosil MS-5, MS-7 (trade name, manufactured by Cabot), Rheorosil QS-102,103 (trade name, manufactured by Tokuyama Co., Ltd.), Nipsil LP (trade name, manufactured by Nippon Silica Kogyo Co., Ltd.) and the like.
- the fumed silica needs to be finely dispersed in the composition. If it is not finely dispersed, light is scattered under visible light, which may adversely affect the optical density. From this point, the fumed silica used in the aqueous pigment dispersion of the present invention needs to be hydrophilic fumed silica. In the case of hydrophobic fumed silica, it cannot be finely dispersed in an aqueous medium, which adversely affects the optical density. In general, it is desirable to finely disperse so that the particle diameter is about 1 ⁇ 4 or less of the wavelength of light. Therefore, the average primary particle diameter of fumed silica is preferably 50 nm or less, preferably 30 nm or less. More preferably.
- an average primary particle diameter is 5 nm or more, and it is more preferable that it is 7 nm or more. If the average primary particle diameter is smaller than 5 nm, the cohesive force between the silica particles becomes too strong as the surface area increases, and it may be difficult to finely disperse.
- the specific surface area of fumed silica is preferably 50 to 500 m 2 / g by the BET method. The specific surface area is more preferably 100 m 2 / g or more, and more preferably 300 m 2 / g or less.
- the average dispersed particle size of the fumed silica is preferably 250 nm or less, more preferably 50 to 250 nm, more preferably 100 to 200 nm, which is about 1 ⁇ 4 of the wavelength of light, and most preferably 150 to 180 nm.
- the particle size distribution of fumed silica is wide, the effect of improving optical density is high. However, if it is too wide, a portion having a large particle size will adversely affect the discharge properties, and therefore the standard deviation (SD) of the distribution is preferably 50 to 100 nm, more preferably 70 to 85 nm.
- the amount of fumed silica added is not particularly limited, but if it is too small, the effect of improving the OD value is not remarkable. If too much is added, other properties will deteriorate (thickening, scratch resistance of printed surface, drop in ejection properties, etc.), and the OD improvement rate with respect to the amount added will decrease.
- the aqueous pigment dispersion of the present invention is on the surface of the substrate, (i) The viscosity increase rate of the aqueous pigment dispersion during drying is increased, and the pigment in the dispersion is less likely to penetrate into the printing material. As a result, the pigment tends to remain on the surface of the printed material, and the optical density of the printed material increases. (Ii) Due to the presence of silica, the coating film after drying tends to have a gap between the pigments and has a three-dimensional structure. This apparently increases the surface area of the pigment, increases the number of reflections of light, and increases the optical density.
- fumed silica Since fumed silica is characterized by being indefinite, interaction between the pigment and silica is likely to occur during drying, resulting in "viscosity of the dispersion” and “between the pigments in the dry coating. “Gap” is easily formed, and the optical density increases. Etc. are estimated. Such a physical phenomenon is unlikely to occur in colloidal silica that is close to a true sphere and has a narrow particle size distribution, and conversely tends to occur in fumed silica that has a low sphericity and a relatively wide particle size distribution. This is presumed that fumed silica improves the optical density (OD) of printed matter.
- OD optical density
- the aqueous solvent used in the present invention is a water-soluble solvent and / or water. These may be used alone or as a mixed solvent composed of water and a water-soluble solvent.
- the water-soluble solvent include ketones such as acetone, methyl ethyl ketone, methyl butyl ketone, and methyl isobutyl ketone; methanol, ethanol, 2-propanol, 2-methyl-1-propanol, 1-butanol, 2-methoxyethanol, Alcohols such as tetrahydrofuran; ethers such as 1,4-dioxane and 1,2-dimethoxyethane; amides such as dimethylformamide and N-methylpyrrolidone, and particularly ketones having 3 to 6 carbon atoms And a compound selected from the group consisting of alcohols having 1 to 5 carbon atoms.
- a water-soluble organic solvent that can be dissolved in water can also be used.
- glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, polyethylene glycol, and polypropylene glycol; diols such as butanediol, pentanediol, hexanediol, and diols similar to these; propylene laurate Glycol esters such as glycol; glycol ethers such as diethylene glycol monoethyl, diethylene glycol monobutyl, diethylene glycol monohexyl ether, propylene glycol ether, dipropylene glycol ether, and cellosolve containing triethylene glycol ether; methanol, ethanol, isopropyl alcohol , 1-propanol, 2-p Alcohols such as panol, 1-butanol, 2-butanol, butyl alcohol, pentyl alcohol, and alcohol
- water-soluble organic solvents such as lactams; glycerin and derivatives thereof, polyoxyethylene benzyl alcohol ether, and the like can be mentioned.
- These water-soluble organic solvents can be used alone or in combination.
- polyhydric alcohols such as glycols and diols having high boiling point and low volatility and high surface tension are preferable, and glycols such as diethylene glycol and triethylene glycol are particularly preferable.
- the method for producing the aqueous pigment dispersion of the present invention can be obtained by a known method without any particular limitation. For example, (1) A method of adding the hydrophilic fumed silica after adding a pigment and an aqueous medium, if necessary, adding a pigment dispersant and other additives, and preparing by medialess dispersion, (2) A method of preparing a high-concentration aqueous dispersion (pigment paste) of a pigment in advance and adding the hydrophilic fumed silica and, if necessary, other additives when diluting it with an aqueous medium , Etc.
- a pigment dispersant may be used as necessary.
- a known pigment dispersant may be used and dispersed in water, or a surfactant may be used.
- the pigment dispersant is preferably an aqueous resin, and preferable examples include polyvinyl alcohols, polyvinylpyrrolidones, acrylic resins such as acrylic acid-acrylic acid ester copolymers, styrene-acrylic acid copolymers, styrene-methacrylic acid.
- examples thereof include an acrylic copolymer having a group, a styrene-maleic acid copolymer, a styrene-maleic anhydride copolymer, a vinylnaphthalene-acrylic acid copolymer, and a salt of the aqueous resin.
- an acrylic copolymer having an anionic group is preferable.
- acrylic copolymer having an anionic group examples include an acrylic copolymer having an anionic group containing a carboxyl group, a sulfonic acid group or a phosphoric acid group. Specific examples include a copolymer of a monomer having an anionic group such as (meth) acrylic acid and another ethylenically unsaturated monomer copolymerizable therewith.
- (meth) acrylic acid means a generic term for acrylic acid and methacrylic acid. In the case of various esters of (meth) acrylic acid, it is interpreted in the same manner as described above.
- the hydrophobicity of the copolymer is further increased in the same acid value comparison, and the adsorption of the copolymer onto the pigment surface can be made stronger.
- styrene ⁇ -methyl styrene, ⁇ -methyl styrene, 2,4-dimethyl styrene, ⁇ -ethyl styrene, ⁇ -butyl styrene, alkyl styrene such as ⁇ -hexyl styrene, 4-chlorostyrene, 3-chlorostyrene, Halogenated styrene such as 3-bromostyrene, styrene monomers such as 3-nitrostyrene, 4-methoxystyrene, vinyltoluene, benzyl (meth) acrylate, phenyl (meth) acrylate, phenylethyl (meth) acrylate, phenylpropylene Lu (meth) acrylate, phenoxyethyl (meth) acrylate, etc.
- a (meth) acrylic acid ester monomer having a benzene ring It is preferable to use a (meth) acrylic acid ester monomer having a benzene ring.
- a styrene monomer such as styrene, ⁇ -methylstyrene, tert-butylstyrene.
- the copolymer in the present invention may be a copolymer containing a polymerization unit of (meth) acrylic acid and a polymerization unit of other copolymerizable ethylenically unsaturated monomer as essential polymerization units, Or a ternary copolymer of three or more with another copolymerizable ethylenically unsaturated monomer.
- Examples of the ethylenically unsaturated monomer include methyl acrylate, methyl methacrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, tert-butyl acrylate, 2-ethylbutyl acrylate, 1,3-dimethyl Acrylic esters such as butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, ethyl methacrylate, n-butyl methacrylate, 2-methylbutyl methacrylate, pentyl methacrylate, heptyl methacrylate, and nonyl methacrylate Acrylic esters; 3-ethoxypropyl acrylate, 3-ethoxybutyl acrylate, dimethylaminoethyl acrylate, -Acrylic acid ester derivatives and methacrylic acid
- the copolymer used in the present invention is a linear copolymer composed only of polymerized units of monoethylenically unsaturated monomers, various ethylenically unsaturated monomers having various crosslinking properties are used. It may be a copolymer containing a partially cross-linked partly crosslinked part.
- Examples of the ethylenically unsaturated monomer having such crosslinkability include glycidyl (meth) acrylate, divinylbenzene, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di ( Examples include poly (meth) acrylates of polyhydric alcohols such as (meth) acrylates, poly (oxyethyleneoxypropylene) glycol di (meth) acrylates, and tri (meth) acrylates of alkylene oxide adducts of glycerol.
- the reaction rate and the like of each monomer used is considered to be substantially the same, and the charging ratio of each monomer is regarded as the content ratio in terms of mass of the polymerization unit of each monomer.
- the copolymer in the present invention can be synthesized by various conventionally known reaction methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. In this case, a known and usual polymerization initiator, chain transfer agent (polymerization degree adjusting agent), surfactant and antifoaming agent can be used in combination.
- Particularly preferable acrylic copolymers having an anionic group for use in the present invention include, for example, styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid ester- ( A styrene monomer such as a (meth) acrylic acid copolymer, a (meth) acrylic acid ester- (meth) acrylic acid copolymer, and a styrene-acrylic acid copolymer containing (meth) acrylic acid as a raw material monomer Can be mentioned.
- the “styrene-acrylic acid copolymer” is defined as “a copolymer containing a styrene monomer and (meth) acrylic acid as a raw material monomer” as described above.
- General-purpose monomers other than styrene monomers and (meth) acrylic acid may be copolymerized
- the ratio of the styrene monomer used as the raw material for the styrene-acrylic acid copolymer is more preferably 50 to 90% by mass, and particularly preferably 70 to 90% by mass.
- the ratio of the styrene monomer used is 50% by mass or more, the affinity of the styrene-acrylic acid copolymer to the pigment is good, and the dispersion stability of the aqueous pigment dispersion tends to be improved.
- the plain paper recording characteristics of the aqueous inkjet recording ink obtained from the aqueous pigment dispersion are improved, the image recording density tends to increase, and the water resistance tends to improve.
- the amount of the styrene monomer is in the above range of 90% by mass or less, the dispersibility of the pigment coated with the styrene-acrylic acid copolymer in the aqueous medium can be maintained well, and the aqueous pigment dispersion The dispersibility and dispersion stability of the pigment can be improved. Furthermore, the printing stability when used as an ink composition for inkjet recording is improved.
- the styrene-acrylic acid copolymer is obtained by copolymerization of at least one of a styrene monomer, an acrylic acid monomer, and a methacrylic acid monomer, but it is preferable to use acrylic acid and methacrylic acid in combination.
- the reason is that the copolymerization at the time of resin synthesis is improved, the uniformity of the resin is improved, and as a result, the storage stability is improved, and a more finely divided pigment dispersion tends to be obtained. It is.
- the total during the copolymerization of the styrene monomer, the acrylic acid monomer, and the methacrylic acid monomer is preferably 95% by mass or more based on the total monomer components.
- a method for producing the styrene-acrylic acid copolymer a usual polymerization method can be adopted, and a method of performing a polymerization reaction in the presence of a polymerization catalyst such as solution polymerization, suspension polymerization, bulk polymerization, etc. can be mentioned. It is done.
- a polymerization catalyst such as solution polymerization, suspension polymerization, bulk polymerization, etc.
- the polymerization catalyst include 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile), Examples thereof include benzoyl peroxide, dibutyl peroxide, and butyl peroxybenzoate.
- the amount used is preferably 0.1 to 10.0% by mass of the vinyl monomer component.
- the styrene-acrylic acid copolymer may be a random copolymer or a graft copolymer.
- a graft copolymer a copolymer of polystyrene or a nonionic monomer copolymerizable with styrene and styrene is used as a trunk or branch, and a copolymer of acrylic acid, methacrylic acid and other monomers including styrene is branched.
- the graft copolymer used as a trunk can be shown as the example.
- the styrene-acrylic acid copolymer may be a mixture of the graft copolymer and the random copolymer.
- the weight average molecular weight of the acrylic copolymer having an anionic group is preferably in the range of 5,000 to 20,000.
- the weight average molecular weight is preferably in the range of 5000 to 20000, and more preferably in the range of 5000 to 18000. In particular, it is particularly preferably in the range of 5500 to 15000.
- the weight average molecular weight is a value measured by a GPC (gel permeation chromatography) method, and is a value converted to a molecular weight of polystyrene used as a standard substance.
- the styrene-acrylic acid copolymer used in the present invention has a carboxyl group derived from an acrylic acid monomer and a methacrylic acid monomer, and its acid value is preferably 50 to 220 (mgKOH / g), More preferably, it is -200 (mgKOH / g). When the acid value is 220 (mg KOH / g) or less, pigment aggregation tends to be less likely to occur.
- the acid value here is a value measured in accordance with Japanese Industrial Standard “K 0070: 1992. Test method for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponified product of chemical products”. , The amount (mg) of potassium hydroxide required to completely neutralize 1 g of resin.
- the amount (mg) of potassium hydroxide required to completely neutralize 1 g of resin.
- the acid value is too low, pigment dispersion and storage stability are lowered, and when an aqueous ink for inkjet recording described later is prepared, printing stability is deteriorated, which is not preferable.
- If the acid value is too high, the water resistance of the colored recording image is lowered, which is also not preferable.
- (meth) acrylic acid may be included and copolymerized so as to be within the range of the acid value.
- the weight ratio (Resin / Pigment) of the styrene-acrylic acid copolymer to the pigment is preferably 0.05 to 0.50, more preferably 0.10 to 0.40. If this ratio is small, the dispersibility and storage stability of the pigment are likely to deteriorate, and if it is too large, the dischargeability as an inkjet ink tends to deteriorate.
- the basic compound is used for the purpose of neutralizing the anionic group of the acrylic copolymer having the anionic group.
- Known compounds can be used as the basic compound, for example, alkali metal hydroxides such as potassium and sodium; carbonates of alkali metals such as potassium and sodium; carbonates such as alkaline earth metals such as calcium and barium; Inorganic basic compounds such as ammonium hydroxide, amino alcohols such as triethanolamine, N, N-dimethanolamine, N-aminoethylethanolamine, dimethylethanolamine, NN-butyldiethanolamine, morpholine, N And organic basic compounds such as morpholines such as methylmorpholine and N-ethylmorpholine, and piperazine such as N- (2-hydroxyethyl) piperazine and piperazine hexahydrate.
- alkali metal hydroxides represented by potassium hydroxide, sodium hydroxide, and lithium hydroxide contribute to lowering the viscosity of the aqueous black pigment dispersion, and are preferable from the viewpoint of ejection stability of ink jet recording inks.
- potassium hydroxide is preferred.
- the neutralization rate of the anionic group using these is not particularly limited, but is generally carried out in a range of 80 to 120% by mass.
- the neutralization rate is a numerical value indicating the amount of the basic compound blended relative to the amount necessary for neutralization of all carboxyl groups in the anionic group-containing organic polymer compound. Yes, it is calculated by the following formula.
- the acrylic copolymer having an anionic group may be added to the dispersion at a neutralization rate exceeding 80 to 120% by mass.
- the viscosity is higher than the above range and the handling is inconvenient even if the pigment is within the above range, it may be diluted appropriately with an aqueous medium to obtain an aqueous pigment dispersion having a desired viscosity range. Is possible.
- (1) Medialess dispersion of aqueous pigment dispersion specifically includes ultrasonic dispersion, high-speed disk impeller, colloid mill, roll mill, high-pressure homogenizer, nanomizer, and optimizer.
- An ultrasonic dispersion method is preferable in consideration of productivity and contamination (foreign matter contamination or contamination) due to media wear. The present invention will be described in detail below using an example using an ultrasonic dispersion method.
- the viscosity range at this time is preferably 0.1 to 100 mPa ⁇ s, more preferably 0.5 to 50 mPa ⁇ s, still more preferably 0.5 to 30 mPa ⁇ s, from the viewpoint of ensuring fluidity. 1.0 to 20 mPa ⁇ s is most preferable.
- the pigment concentration at this time is preferably 1 to 30% by mass, more preferably 1 to 25% by mass, still more preferably 3 to 20% by mass, and most preferably 5 to 20% by mass.
- the conditions of ultrasonic irradiation are not particularly limited, but it is preferably performed at an output of 100 to 3000 W and a frequency of 15 to 40 kHz, and more preferably at an output of 150 to 2000 W and a frequency of 15 to 30 kHz.
- the dispersion process by cavitation can be effectively performed, the number of coarse particles in the aqueous pigment dispersion is reduced, and the saturation of the colored coating obtained from the aqueous pigment dispersion itself ( (Texture) has been improved, smooth discharge can be obtained when ink-jet printing of aqueous ink using the aqueous pigment dispersion (good discharge stability), and there is no deterioration in product quality due to sedimentation of pigment particles.
- the erosion (corrosion) of the oscillation rod is remarkably reduced, and the equipment maintenance cost is reduced.
- the ultrasonic irradiation time may be sufficient to ensure that the pigment particles are practically uniformly dispersed in the aqueous pigment dispersion.
- an electric energy of 5 to 100 W / g is applied to the mass of the pigment contained in the dispersion.
- the ultrasonic treatment can be performed for a longer time or can be stopped in a short time.
- the sonication time can be selected within a range that does not hinder the performance such as the dispersed particle size, viscosity, and image definition, and it can be devised so as not to cause a decrease in temporal productivity. preferable.
- dispersion apparatus that can be used in this dispersion step, apparatuses by various known methods can be used and are not particularly limited.
- media dispersion such as sand mill, bead mill, pebble mill, ball mill, pearl mill, basket mill, attritor, dyno mill, bore mill, visco mill, motor mill, SC mill, dry mill, paint conditioner, high speed disk impeller, colloid mill, high pressure homogenizer, nanomizer , Medialess dispersers such as Optimizer.
- media dispersion such as sand mill, bead mill, pebble mill, ball mill, pearl mill, basket mill, attritor, dyno mill, bore mill, visco mill, motor mill, SC mill, dry mill, paint conditioner, high speed disk impeller, colloid mill, high pressure homogenizer, nanomizer , Medialess dispersers such as Optimizer.
- unnecessary physical damage may be caused to the pigment surface as described above.
- the temperature of the aqueous pigment dispersion to be subjected to ultrasonic irradiation is not particularly limited, but it is possible to irradiate ultrasonic waves while controlling the aqueous pigment dispersion so that it becomes a freezing point to 70 ° C. preferable. If the temperature is below the freezing point, ultrasonic dispersion becomes impossible, and if it is above 70 ° C., moisture evaporates, resulting in uncertain conditions such as an increase in pigment concentration.
- a publicly known one, ice cooling, air cooling, water cooling, etc. can be used generally.
- a method of flowing a refrigerant in a jacket (jacket) of a container holding the aqueous pigment dispersion a method of immersing a container containing the aqueous pigment dispersion in the refrigerant, a method of blowing a gas wind,
- a method of cooling with evaporative heat using a coolant such as water and wind can be exemplified. For example, a method of using cooling water that has been cooled to a temperature of more than 0 ° C.
- cooling water can be circulated by the circulation device and at the same time the cooling can be performed by the cooling device.
- cooling water exceeding 0 ° C. does not provide a sufficient cooling effect, it is possible to obtain a cooling water having a temperature lower than that, so that the aqueous pigment dispersion becomes lower in the above temperature range. It becomes possible to carry out ultrasonic irradiation while being held at the same position.
- air cooling it is preferable to use cold air that has been cooled in advance, instead of simply blowing air at ambient temperature.
- the devices used for the ultrasonic irradiation be performed in as few units as possible from the viewpoint of cost.
- a minimum of a plurality of devices can be connected in series or in parallel for processing.
- the end point of ultrasonic irradiation is determined by measuring the particle size of the pigment particles and the composite particles with a particle gauge or a commercially available particle size measuring device, as well as the viscosity, contact angle, and reflection of the coating film prepared by various methods. It may be determined by measuring physical properties such as luminous intensity and color. Alternatively, the determination may be made by direct observation using a microscope or the like.
- the method for preparing the pigment paste in advance is not particularly limited, and a known dispersion method can be used.
- Examples of the method for preparing the pigment paste include the following (i) to (iii).
- the pigment and the pigment dispersant are kneaded using a kneader such as two rolls or a mixer, and the obtained kneaded product is added to an aqueous medium containing water, and the pigment is then mixed using a stirring / dispersing device.
- a method of preparing a paste A method of preparing a paste.
- the kneader is not particularly limited, and examples thereof include a Henschel mixer, a pressure kneader, a Banbury mixer, and a planetary mixer.
- the stirring / dispersing device is not particularly limited, and examples thereof include an ultrasonic homogenizer, a high-pressure homogenizer, a paint shaker, a ball mill, a roll mill, a sand mill, a sand grinder, a dyno mill, a disperse mat, an SC mill, and a nanomizer.
- an ultrasonic homogenizer a high-pressure homogenizer
- a paint shaker a paint shaker
- a ball mill a roll mill
- a sand mill a sand grinder
- a dyno mill a disperse mat
- SC mill and a nanomizer.
- One of these may be used alone, or two or more devices may be used in combination.
- the amount of pigment in the pigment paste is preferably 5 to 60% by mass, more preferably 10 to 50% by mass.
- the amount of the pigment is less than 5% by mass, the aqueous pigment dispersion prepared from the pigment paste and the aqueous ink are not sufficiently colored, and a sufficient image density tends not to be obtained.
- the amount is more than 60% by mass, the dispersion stability of the pigment tends to decrease in the pigment paste.
- the remaining coarse particles cause various image characteristics to deteriorate, it is preferable to appropriately remove the coarse particles by centrifugation or filtration before and after ink preparation.
- an impurity removal step by ion exchange treatment or ultrafiltration treatment may be performed, followed by post-treatment.
- Ion exchange treatment can remove ionic substances such as cations and anions (divalent metal ions, etc.), and by ultra-treatment, impurities dissolved substances (residual substances during pigment synthesis, excess components in dispersion composition) , Resin not adsorbed to the organic pigment, mixed foreign matter, etc.) can be removed.
- a known ion exchange resin is used in the ion exchange treatment.
- the ultratreatment uses a known ultrafiltration membrane and may be either a normal type or a double capacity up type.
- the pigment paste can be appropriately diluted with water when the viscosity is high.
- the addition method of the fumed silica is not particularly limited, and an appropriate amount may be added to the obtained aqueous pigment dispersion and stirred.
- an appropriate amount may be added to the obtained aqueous pigment dispersion and stirred.
- alkali metal hydroxides such as potassium and sodium
- carbonates of alkali metals such as potassium and sodium
- alkaline earth such as calcium and barium
- Carbonates such as alkali metals
- inorganic basic compounds such as ammonium hydroxide, triethanolamine, N, N-dimethanolamine, N-aminoethylethanolamine, dimethylethanolamine, NN-butyldiethanolamine, etc.
- the dispersion device for the fumed silica dispersion is not particularly limited, but from the viewpoint of not impairing the surface properties and shape of the fumed silica, a non-contact type disperser such as an ultrasonic disperser, a high-speed disk impeller, a colloid mill, a roll mill, High pressure homogenizers, nanomizers, optimizers, etc. can be mentioned.
- the ultrasonic dispersion method is preferred in consideration of productivity and contamination (foreign matter contamination or contamination) due to media wear.
- the pigment concentration is not particularly limited, but it is usually used in the range of 1 to 60% by mass with respect to the total amount of the aqueous pigment dispersion, and the range of 5 to 40% by mass is usually used. The range of 10 to 20% by mass is more preferable.
- Water-based ink for inkjet recording Diluting the water-based pigment dispersion to a desired concentration, various fields such as paint fields for automobiles and building materials, printing ink fields such as offset inks, gravure inks, flexo inks, silk screen inks, and ink jet recording ink fields Can be used for various purposes.
- a water-soluble solvent and / or water an anionic group-containing organic polymer compound for the purpose of a binder, and the like are added, and the desired physical properties are added as necessary. It is prepared by adding a wetting agent (drying inhibitor), a penetrating agent, or other additives. After the ink adjustment, a centrifugal separation or filtration process may be added.
- the physical properties of the ink are not particularly limited, but in consideration of the discharge properties as an inkjet ink, the viscosity is preferably 1 to 10 (mPa ⁇ s), and the surface tension is preferably 20 to 50 (mN / m).
- the pigment concentration is preferably 1 to 10% by mass.
- the wetting agent is added for the purpose of preventing the ink from drying.
- the content of the wetting agent in the ink for the purpose of preventing drying is preferably 3 to 50% by mass.
- the wetting agent used in the present invention is not particularly limited, but a wetting agent that is miscible with water and can prevent clogging of the head of an inkjet printer is preferable.
- glycerin ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol having a molecular weight of 2000 or less
- propylene glycol dipropylene glycol, tripropylene glycol, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol, 1,4-butane
- examples include diol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, mesoerythritol, pentaerythritol, and the like.
- the inclusion of propylene glycol and 1,3-butyl glycol has safety and excellent effects in ink drying properties and ejection performance.
- the penetrant is added for the purpose of improving the permeability to a recording medium and adjusting the dot diameter on the recording medium.
- the penetrant include lower alcohols such as ethanol and isopropyl alcohol, ethylene oxide adducts of alkyl alcohols such as ethylene glycol hexyl ether and diethylene glycol butyl ether, and propylene oxide adducts of alkyl alcohols such as propylene glycol propyl ether.
- the surfactant is added to adjust ink properties such as surface tension.
- the surfactant that can be added for this purpose is not particularly limited, and examples include various anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Of these, anionic surfactants and nonionic surfactants are preferred.
- anionic surfactant examples include alkylbenzene sulfonate, alkylphenyl sulfonate, alkylnaphthalene sulfonate, higher fatty acid salt, sulfate of higher fatty acid ester, sulfonate of higher fatty acid ester, higher alcohol ether. Sulfate salts and sulfonates of the above, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, etc.
- dodecylbenzene sulfonate isopropyl naphthalene sulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenyl sulfonate, dibutylphenylphenol disulfate.
- phosphate salt can be mentioned.
- Nonionic surfactants include, for example, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester , Polyoxyethylene glycerin fatty acid ester, polyglycerin fatty acid ester, sucrose fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene fatty acid amide, fatty acid alkylolamide, alkyl alkanolamide, acetylene glycol, oxyethylene adduct of acetylene glycol, Polyethylene glycol polypropylene glycol block copolymer, etc.
- polyoxyethylene nonyl phenyl ether polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, Fatty acid alkylolamide, acetylene glycol, oxyethylene adduct of acetylene glycol, and polyethylene glycol polypropylene glycol block copolymer are preferred.
- surfactants include silicone surfactants such as polysiloxane oxyethylene adducts; fluorine surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and oxyethylene perfluoroalkyl ethers.
- Biosurfactants such as spicrispolic acid, rhamnolipid, lysolecithin and the like can also be used.
- surfactants can be used alone or in combination of two or more.
- the addition amount is preferably in the range of 0.001 to 2% by mass, more preferably 0.001 to 1.5% by mass, based on the total mass of the ink. More preferably, the content is in the range of 01 to 1% by mass.
- the addition amount of the surfactant is less than 0.001% by mass, the effect of adding the surfactant tends to be not obtained, and when it exceeds 2% by mass, problems such as blurring of the image are likely to occur. .
- preservatives can be added as necessary.
- viscosity modifiers pH adjusters, chelating agents, plasticizers, antioxidants, ultraviolet absorbers and the like can be added as necessary.
- the water-based ink prepared from the water-based pigment dispersion of the present invention is particularly suitable for printing on plain paper because it exhibits a high optical density even on plain paper.
- the water-absorbing recording medium include plain paper, (fine) coated paper, fabric, inkjet exclusive paper, inkjet glossy paper, cardboard, wood, and the like.
- g is “mass g” and “%” is “mass%”.
- aqueous pigment dispersion manufacturing method using a resin A which is an acrylic resin having an anionic group as a pigment dispersant, or a resin solution A obtained by dissolving the resin A in methyl ethyl ketone Two methods were used: (1) an ultrasonic dispersion method and (2) a kneading method. Moreover, the obtained aqueous pigment dispersion was evaluated by the improvement rate of optical density and the saturation.
- styrene / methacrylic acid / acrylic acid 77/13/10 (mass ratio), a mass average molecular weight of 8800, an acid value of 150 mgKOH / g, a glass transition point of 107 ° C., resin A50 g, and methyl ethyl ketone ( (Hereinafter abbreviated as MEK) 50 g, ion-exchanged water 87.4 g, and 34 mass% potassium hydroxide (KOH) aqueous solution 22 g were added and stirred well to obtain a resin solution. With respect to this resin solution, MEK was removed under reduced pressure conditions of a water bath temperature of 45 ° C. and 40 hPa, and a resin solid content of 20% by mass was designated as a resin solution A.
- MEK methyl ethyl ketone
- Silica liquids B to E were prepared by mixing a mixture of 15 g of silica powder, 84.7 g of ion-exchanged water and 0.3 g of a basic compound (34% by mass potassium hydroxide aqueous solution) in advance with the same ultrasonic disperser “Hielscher”. “UP200St, maximum output: 200 W, frequency: 26 KHz” is adjusted to a 15 mass% silica solution that is ultrasonically dispersed for 3 minutes. Further, since the silica liquid A and the silica liquids F to I are originally dispersion liquids, ion exchange water is appropriately added to adjust the silica liquid concentration to 15% by mass.
- the average dispersion particle size and particle size distribution standard deviation of each silica liquid were measured using a dynamic light scattering nanotrack particle size analyzer UPA-150EX (manufactured by Nikkiso Co., Ltd.) with a silica concentration of 1.5% (solvent: Water, temperature 25 ° C.).
- Optical density (OD) value measurement method The obtained aqueous pigment dispersion was applied to each of plain paper (PPC paper High-White) and color lock paper (HPMP: HPMP) with a wire bar # 3. After natural drying for 24 hours, the OD of the coated material was measured. The measurement results are shown in the formulation table described below. For measurement, “Gretag Macbeth Spectro Scan Transmission” (X-Rite) was used, and the average value of a total of 9 points of 3 vertical points ⁇ 3 horizontal points was adopted as the OD of the coated material.
- the OD improvement rate was calculated by the following formula, and G was defined as N when the optical density was improved by 3% or more, and N was defined when the optical density was not improved by 3% or more. (Note that the fumed silica-free aqueous pigment dispersion is also a comparative example, so the names of comparative examples used in the respective recipes are explained)
- Comparative Examples 1 to 4 in Table 5 which are the same silica but to which 4% by mass of colloidal silica is added are not effective in improving OD.
- the standard deviation of silica F to H used in Comparative Examples 1 to 4 is 20 to 40 nm from Table 1, and does not fall within the preferred standard deviation (SD) range of 70 to 85 nm.
- the standard deviation (SD) of silica I is 79, which falls within the preferred range of 70 to 85 nm, but the optical density is not improved as in Comparative Example 4 in Table 5. This also shows that it is difficult to obtain an optical density improvement effect with colloidal silica.
- Examples 6 to 11 in Tables 3 and 4 are examples in which the addition amount of fumed silica B was changed (1% by mass to 11% by mass), but the OD increased as the addition amount of fumed silica B increased.
- the improvement rate is high.
- Example 8 and 11 it is an example with which 4 mass% of carbon pigments and 11 mass% of fumed silica were mix
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Abstract
Description
しかしながら水性インクは、トナーよりもはるかに顔料濃度が低い液体の状態で印字を行うため、印字した場合の光学濃度(OD値、画像濃度、着色濃度ともいう)が薄く、特にメディアが普通紙の場合インクが紙に浸透し易く、高い光学濃度が得にくいという問題があった。
しかし、特に顔料の種類や特性を限定せず、一般的な水性顔料分散体においても高い着色濃度を実現する方法については述べられていない。
インクジェット記録用インクに配合する例としては、有彩色顔料を配合したインクのブロンズ現象を改善する目的で、疎水性シリカ微粒子の例として疎水性のヒュームドシリカを使用する例が知られている(例えば特許文献4実施例1,2参照)。
しかしながら、親水性ヒュームドシリカを、高い光学濃度を得る目的で水性顔料分散体に配合することは、これまで知られていなかった。
本発明では、水媒体に微細に分散しうる親水性ヒュームドシリカを適量配合することが、課題である高い光学濃度を発現させるために有効であることを見出したものである。
本発明で使用する顔料は、公知慣用の有機顔料あるいは無機顔料の中から選ばれる少なくとも一種の顔料である。また、本発明は未処理顔料の他、いわゆる自己分散性顔料等の処理顔料も適用することができる。普通紙を被記録材とする印刷の場合、イエローインク、シアンインク、マゼンタインク、ブラックインク等が使用される。これらの使用される顔料は特に限定はなく、通常水性インク用の顔料として使用されているものが使用できる。具体的には、水や水溶性有機溶剤に分散可能であり、公知の無機顔料や有機顔料が使用できる。無機顔料としては例えば、酸化鉄、コンタクト法、ファーネス法、サーマル法等の公知の方法によって製造されたカーボンブラック等がある。また、有機顔料としては、アゾ顔料(アゾレーキ、不溶性アゾ顔料、縮合アゾ顔料、キレートアゾ顔料などを含む)、多環式顔料(例えば、フタロシアニン顔料、ペリレン顔料、ペリノン顔料、アントラキノン顔料、キナクリドン顔料、ジオキサジン顔料、チオインジゴ顔料、イソインドリノン顔料、キノフラロン顔料など)、染料キレート(例えば、塩基性染料型キレート、酸性染料型キレートなど)、ニトロ顔料、ニトロソ顔料、アニリンブラックなどを使用することができる。
中でも、高OD値が得られることや、分散が容易であることから、酸性のカーボンブラックが好ましく、例えば三菱化学社製のMAシリーズ、#900シリーズ、#2300シリーズ、オリオンエンジニアドカーボンズ社製のNEROX600、NIPex160IQ、旭カーボン社製のSUNBLACK-Xシリーズ、などのPH=4.5以下のカーボンが好ましい。酸性のカーボンブラックは親水性が良好なため、一般に表面張力を下げ浸透を促進する作用を持つ分散剤の使用を少なくすることが出来、高OD値を発現することが可能となる。
本発明で用いられる親水性ヒュームドシリカは特に限定されることなく公知のものが使用できる。ヒュームドシリカは、高度に精製した四塩化珪素を酸水素炎中で高温加水分解させて得ることができ、表面処理の有無によって親水性ヒュームドシリカと疎水性ヒュームドシリカに分けられるが、本発明では親水性ヒュームドシリカを使用する。
親水性シリカとしては、例えば、Aerosil W7520、130,200,300、R816(商品名、日本アエロジル(株),Degussa社製)、Cabosil MS-5,MS-7(商品名、Cabot社製)、Rheorosil QS-102,103(商品名、(株)トクヤマ製)、Nipsil LP(商品名、日本シリカ工業(株)製)等が挙げられる。
一般的には、光の波長の1/4程度以下の粒径になるように微細に分散させることが望ましく、そのためヒュームドシリカの平均一次粒子径は50nm以下であることが好ましく、30nm以下であることがより好ましい。また平均一次粒子径は、5nm以上であることが好ましく、7nm以上であることがより好ましい。平均一次粒子径が、5nmより小さいと、表面積の増大にともなってシリカ粒子どうしの凝集力が強くなり過ぎて、微細に分散することが困難になる場合がある。ヒュームドシリカの比表面積はBET法で50~500m2/gであることが好ましい。比表面積はより好適には100m2/g以上であり、またより好適には300m2/g以下である。
(i)乾燥途中の水性顔料分散体の粘度増加率が大きくなり、分散体中の顔料が被印字物中に浸透しにくくなる。その結果顔料が被印字物表面に残存しやすくなり、印字物の光学濃度が上がる。
(ii)シリカが存在することで乾燥後の塗膜は顔料と顔料の間に隙間が出来やすく、立体的な構造になる。すると見かけ上顔料の表面積が大きくなり光の反射回数が増え、光学濃度が高くなる。
(iii)ヒュームドシリカは不定形であることが特徴であるので、乾燥途中に顔料とシリカのインタラクションが発生しやすくなり、「分散体の増粘」や「乾燥塗膜内での顔料間の隙間」が出来やすく、光学濃度が高くなる。
等を推定している。
このような物理的現象は、真球に近く粒度分布が狭いコロイダルシリカでは発生しにくく、逆に真球度が低く粒度分布が比較的広いヒュームドシリカで発生しやすい。これがヒュームドシリカが印字物の光学濃度(OD)を向上させる理由と推定している。
本発明で使用する水性溶媒は、水溶性溶媒及び/または水等である。これらは水単独で使用してもよいし、水と水溶性溶媒からなる混合溶媒でもよい。水溶性溶媒としては、例えば、アセトン、メチルエチルケトン、メチルブチルケトン、メチルイソブチルケトン、等のケトン類;メタノール、エタノール、2-プロパノール、2-メチル-1-プロパノール、1-ブタノール、2-メトキシエタノール、等のアルコール類;テトラヒドロフラン、1,4-ジオキサン、1,2-ジメトキシエタン、等のエーテル類;ジメチルホルムアミド、N-メチルピロリドン、等のアミド類が挙げられ、とりわけ炭素数が3~6のケトン及び炭素数が1~5のアルコールからなる群から選ばれる化合物を用いるのが好ましい。
また、その他、水性に溶解しうる水溶性有機溶剤も使用することができる。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、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などのグリコール類;ブタンジオール、ペンタンジオール、ヘキサンジオール、およびこれらと同族のジオールなどのジオール類;ラウリン酸プロピレングリコールなどのグリコールエステル;ジエチレングリコールモノエチル、ジエチレングリコールモノブチル、ジエチレングリコールモノヘキシルの各エーテル、プロピレングリコールエーテル、ジプロピレングリコールエーテル、およびトリエチレングリコールエーテルを含むセロソルブなどのグリコールエーテル類;メタノール、エタノール、イソプロピルアルコール、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、ブチルアルコール、ペンチルアルコール、およびこれらと同族のアルコールなどのアルコール類;あるいは、スルホラン;γ-ブチロラクトンなどのラクトン類;N-(2-ヒドロキシエチル)ピロリドンなどのラクタム類;グリセリンおよびその誘導体、ポリオキシエチレンベンジルアルコールエーテルなど、水溶性有機溶剤として知られる他の各種の溶剤などを挙げることができる。これらの水溶性有機溶剤は1種または2種以上混合して用いることができる。
中でも、高沸点、低揮発性で、高表面張力のグリコール類やジオール類等多価アルコール類が好ましく、特にジエチレングリコール、トリエチレングリコール等のグリコール類が好ましい。
本発明の水性顔料分散体の製造方法は、特に限定なく公知の方法で得ることができる。例えば、(1)顔料と水性媒体と、必要に応じて顔料分散剤やその他の添加剤を添加して、メディアレス分散により調製した後、前記親水性ヒュームドシリカを添加する方法、
(2)予め顔料の高濃度水性分散液(顔料ペースト)を作成し、それを水性媒体で希釈する際に前記親水性ヒュームドシリカ、必要に応じてその他の添加剤を添加して調製する方法、等があげられる。
本発明においては、必要に応じて顔料分散剤を使用してもよく好ましい。顔料分散剤としては、公知の顔料分散剤を使用して水に分散してもよいし、界面活性剤を使用してもよい。
前記顔料分散剤としては水性樹脂がよく、好ましい例としては、ポリビニルアルコール類、ポリビニルピロリドン類、アクリル酸-アクリル酸エステル共重合体などのアクリル系樹脂、スチレン-アクリル酸共重合体、スチレン-メタクリル酸共重合体、スチレン-メタクリル酸-アクリル酸エステル共重合体、スチレン-α-メチルスチレン-アクリル酸共重合体、スチレン-α-メチルスチレン-アクリル酸-アクリル酸エステル共重合体などのアニオン性基を有するアクリル系共重合体、スチレン-マレイン酸共重合体、スチレン-無水マレイン酸共重合体、ビニルナフタレン-アクリル酸共重合体、及び該水性樹脂の塩が挙げられる。
中でも、アニオン性基を有するアクリル系共重合体が好ましい。
本発明におけるアニオン性基を有するアクリル系共重合体は、例えば、カルボキシル基、スルホン酸基または燐酸基を含有するアニオン性基を有するアクリル系共重合体が挙げられる。具体的には、(メタ)アクリル酸等のアニオン性基を有する単量体とそれと共重合可能なその他のエチレン性不飽和単量体との共重合体が挙げられる。尚、本発明において(メタ)アクリル酸とは、アクリル酸とメタクリル酸との総称を意味するものとする。(メタ)アクリル酸の各種エステルの場合も前記と同様に解釈される。
前記スチレン-アクリル酸系共重合体においてスチレン系モノマーとアクリル酸モノマーとメタクリル酸モノマーの共重合時の総和は、全モノマー成分に対して95質量%以上であることが好ましい。
酸価が低すぎる場合には顔料分散や保存安定性が低下し、また後記するインクジェット記録用水性インクを調製した場合に、印字安定性が悪くなるので好ましくない。酸価が高すぎる場合には、着色記録画像の耐水性が低下するのでやはり好ましくない。共重合体を該酸価の範囲内とするには、(メタ)アクリル酸を、前記酸価の範囲内となる様に含めて共重合すれば良い。
本発明において塩基性化合物は、前記アニオン性基を有するアクリル系共重合体のアニオン性基を中和する目的で使用する。塩基性化合物としては公知のものを使用でき、例えばカリウム、ナトリウムなどのアルカリ金属の水酸化物;カリウム、ナトリウムなどのアルカリ金属の炭酸塩;カルシウム、バリウムなどのアルカリ土類金属などの炭酸塩;水酸化アンモニウム等の無機系塩基性化合物や、トリエタノールアミン、N,N-ジメタノールアミン、N-アミノエチルエタノールアミン、ジメチルエタノールアミン、N-N-ブチルジエタノールアミンなどのアミノアルコール類、モルホリン、N-メチルモルホリン、N-エチルモルホリンなどのモルホリン類、N-(2-ヒドロキシエチル)ピペラジン、ピペラジンヘキサハイドレートなどのピペラジン等の有機系塩基性化合物が挙げられる。中でも、水酸化カリウム、水酸化ナトリウム、水酸化リチウムに代表されるアルカリ金属水酸化物は、水性黒色顔料分散体の低粘度化に寄与し、インクジェット記録用インクの吐出安定性の面から好ましく、特に水酸化カリウムが好ましい。
この場合は前記アニオン性基を有するアクリル系共重合体を中和率80~120質量%を越えて分散体に添加しても良い。
次に、前述の(1)顔料と水性媒体と、必要に応じて顔料分散剤やその他の添加剤を添加して、メディアレス分散により調製した後、前記親水性ヒュームドシリカを添加する方法、
(2)予め顔料の高濃度水性分散液(顔料ペースト)を作成し、それを水性媒体で希釈する際に前記親水性ヒュームドシリカ、必要に応じてその他の添加剤を添加して調製する方法、について述べる。
本発明において、(1)メディアレス分散とは、具体的には、超音波分散法、高速ディスクインペラー、コロイドミル、ロールミル、高圧ホモジナイザー、ナノマイザー、アルティマイザー等による分散法等があげられるが、生産性やメディアの摩耗によるコンタミ(異物の混入や汚染)などを顧慮すると超音波分散法が好ましい。本発明においては、以下超音波分散法を用いた例を用いて詳細に述べる。
また、この時の粘度範囲は流動性を確保する観点から、0.1~100mPa・sが好ましく、0.5~50mPa・sがさらには好ましく、0.5~30mPa・sがさらにより好ましく、1.0~20mPa・sが最も好ましい。また、この時の顔料濃度は、1~30質量%が好ましく、1~25質量%がさらには好ましく、3~20質量%がさらにより好ましく、5~20質量%が最も好ましい。
この分散工程において用いることのできる分散装置として、既に公知の種々の方式による装置が使用でき、特に限定されるものではない。例えばサンドミル、ビーズミル、ペブルミル、ボールミル、パールミル、バスケットミル、アトライター、ダイノーミル、ボアミル、ビスコミル、モーターミル、SCミル、ドライスミル、ペイントコンディショナー等のメディア分散や、高速ディスクインペラー、コロイドミル、高圧ホモジナイザー、ナノマイザー、アルティマイザー等のメディアレス分散機が上げられる。ただし前記したように顔料表面に不必要な物理的損傷を与える場合もあることに留意すべきである。
例えば、冷媒として、予め0℃を越えて20℃以下、好ましくは0℃を越えて10℃以下に冷却された冷却水を使用する方法は、比較的に経済的であり、しかも冷却効率も優れているため望ましい方法の一つである。この際、冷却水を循環装置で循環すると同時に、冷却装置で冷却も行うことが出来る。この際、冷却水中に、エチレングリコール、ジエチレングリコールなどの凍結温度を下げるものを加えたり、塩化ナトリウムなどを加えて凝固点降下を起こさせるのも大変望ましい。その結果、0℃を越える冷却水では十分な冷却効果が得られない時でも、それ以下の温度の冷却水とすることが出来、より水性顔料分散体を前記温度範囲内でもより低温となる様に保持して超音波照射することが可能になる。風冷する場合も、単に雰囲気温度の風を吹き付けるのではなく、予め冷やした冷風を用いることが好ましい。
予め顔料ペーストを作成する方法は、特に限定はなく、公知の分散方法を使用することができる。
(i)顔料分散剤及び水を含有する水性媒体に、顔料を添加した後、攪拌・分散装置を用いて顔料を該水性媒体中に分散させることにより、顔料ペーストを調製する方法。
(ii)顔料、及び顔料分散剤を2本ロール、ミキサー等の混練機を用いて混練し、得られた混練物を、水を含む水性媒体中に添加し、攪拌・分散装置を用いて顔料ペーストを調製する方法。
(iii)メチルエチルケトン、テトラヒドロフラン等のような水との相溶性を有する有機溶剤中に顔料分散剤を溶解して得られた溶液に顔料を添加した後、攪拌・分散装置を用いて顔料を有機溶液中に分散させ、次いで水性媒体を用いて転相乳化させた後、前記有機溶剤を留去し顔料ペーストを調製する方法。
また、攪拌・分散装置としても特に限定されることなく、例えば、超音波ホモジナイザー、高圧ホモジナイザー、ペイントシェーカー、ボールミル、ロールミル、サンドミル、サンドグラインダー、ダイノーミル、ディスパーマット、SCミル、ナノマイザー等を挙げられる。これらのうちの1つを単独で用いてもよく、2種類以上装置を組み合わせて用いてもよい。
例えば、既に水に分散されているヒュームドシリカの場合は、前記得られた水性顔料分散体に適量加えて撹拌すれば良い。また粉体のヒュームドシリカの場合は、事前に水やアルカリ(前記した、カリウム、ナトリウムなどのアルカリ金属の水酸化物;カリウム、ナトリウムなどのアルカリ金属の炭酸塩;カルシウム、バリウムなどのアルカリ土類金属などの炭酸塩;水酸化アンモニウム等の無機系塩基性化合物や、トリエタノールアミン、N,N-ジメタノールアミン、N-アミノエチルエタノールアミン、ジメチルエタノールアミン、N-N-ブチルジエタノールアミンなどのアミノアルコール類、モルホリン、N-メチルモルホリン、N-エチルモルホリンなどのモルホリン類、N-(2-ヒドロキシエチル)ピペラジン、ピペラジンヘキサハイドレートなどのピペラジン等の有機系塩基性化合物、など)と混合分散したヒュームドシリカ分散液を、前記得られた水性顔料分散体に適量加えて撹拌すれば良い。ヒュームドシリカ分散液の分散装置は特に制限はないが、ヒュームドシリカの表面性状や形状を損なわない観点から非接触型分散機、例えば、超音波分散機、高速ディスクインペラー、コロイドミル、ロールミル、高圧ホモジナイザー、ナノマイザー、アルティマイザー等があげられるが、生産性やメディアの摩耗によるコンタミ(異物の混入や汚染)などを顧慮すると超音波分散法が好ましい。
前記水性顔料分散体を所望の濃度に希釈して、自動車や建材用の塗料分野や、オフセットインキ、グラビアインキ、フレキソインキ、シルクスクリーンインキ等の印刷インキ分野、あるいはインキジェット記録用インク分野等様々な用途に使用することができる。
本発明の水性顔料分散体をインクジェット記録用インクに適用する場合は、更に水溶性溶媒及び/または水、バインダー目的のアニオン性基含有有機高分子化合物等を加え、所望の物性に必要に応じて湿潤剤(乾燥抑止剤)、浸透剤、あるいはその他の添加剤を添加して調製する。
インクの調整後に、遠心分離あるいは濾過処理工程を加えてもよい。
前記湿潤剤は、インクの乾燥防止を目的として添加する。乾燥防止を目的とする湿潤剤のインク中の含有量は3~50質量%であることが好ましい。
本発明で使用する湿潤剤としては特に限定はないが、水との混和性がありインクジェットプリンターのヘッドの目詰まり防止効果が得られるものが好ましい。例えば、グリセリン、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、分子量2000以下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、1,3-プロピレングリコール、イソプロピレングリコール、イソブチレングリコール、1,4-ブタンジオール、1,3-ブタンジオール、1,5-ペンタンジオール、1,6-ヘキサンジオール、メソエリスリトール、ペンタエリスリトール、等が挙げられる。中でも、プロピレングリコール、1,3-ブチルグリコールを含むことが安全性を有し、かつインク乾燥性、吐出性能に優れた効果が見られる。
前記浸透剤は、被記録媒体への浸透性改良や記録媒体上でのドット径調整を目的として添加する。
浸透剤としては、例えばエタノール、イソプロピルアルコール等の低級アルコール、エチレングリコールヘキシルエーテルやジエチレングリコールブチルエーテル等のアルキルアルコールのエチレンオキシド付加物やプロピレングリコールプロピルエーテル等のアルキルアルコールのプロピレンオキシド付加物等が挙げられる。
前記界面活性剤は、表面張力等のインク特性を調整するために添加する。このために添加することのできる界面活性剤は特に限定されるものではなく、各種のアニオン性界面活性剤、ノニオン性界面活性剤、カチオン性界面活性剤、両性界面活性剤などが挙げられ、これらの中では、アニオン性界面活性剤、ノニオン性界面活性剤が好ましい。
本発明の水性顔料分散体から作製した水性インク、特にインクジェット記録用インクは、特に普通紙に対しても高い光学濃度を発現させることから、特に普通紙への印字に適しているが、その他の吸収性の記録部材に使用してももちろん構わない。
吸水性の記録媒体の例には、普通紙、(微)塗工紙、布帛、インクジェット専用紙、インクジェット光沢紙、ダンボール、木材、などが含まれる。
なお、特に断りがない限り「g」は「質量g」、「%」は「質量%」である。
また、本実施例においては、顔料分散剤としてアニオン性基を有するアクリル樹脂である樹脂A、あるいは該樹脂Aをメチルエチルケトンに溶解した樹脂溶液Aを使用し、水性顔料分散体の製造方法としては、(1)超音波分散法、(2)混練法の2方法を使用した。
また、得られた水性顔料分散体は、光学濃度の向上率、及び彩度で評価した。
モノマー組成比において、スチレン/メタアクリル酸/アクリル酸=77/13/10(質量比)であり、質量平均分子量8800、酸価150mgKOH/g、ガラス転移点107℃である樹脂Aを使用した。
モノマー組成比において、スチレン/メタアクリル酸/アクリル酸=77/13/10(質量比)であり、質量平均分子量8800、酸価150mgKOH/g、ガラス転移点107℃である樹脂A50gと、メチルエチルケトン(以下、MEKと略記する)50gと、イオン交換水87.4gと、34質量%の水酸化カリウム(KOH)水溶液22gとを加え、良く撹拌し、樹脂溶液を得た。この樹脂溶液について、ウォーターバス温度45℃、40hPaの減圧条件でMEKを除去し、樹脂固形分20質量%としたものを樹脂溶液Aとした。
顔料、樹脂溶液A、及びイオン交換水とを、金属製ビーカーに配合表に記載の量仕込み、手動で十分に攪拌し混合物を得た。その後、超音波分散機「hielscher社製UP200St 最大出力:200W、周波数:26KHz」により10分間超音波分散した。なお、この時与えたエネルギーとしては単位カーボンブラック当りに換算すると2.2W/gである。
その後得られた顔料組成物と、表1に記載のシリカ液とを、配合表に従い混合し、攪拌機にて5分間攪拌し、本発明の水性顔料分散体を得た。この時得た水性顔料分散体の顔料とシリカの含有量は、配合表に記載した。
なおシリカ液B~Eは、事前にシリカ粉15g、イオン交換水84.7g、塩基性化合物(34質量%水酸化カリウム水溶液)0.3g、の混合液を、同超音波分散機「hielscher社製UP200St 最大出力:200W、周波数:26KHz」により3分間超音波分散した、15質量%濃度シリカ液に調整している。
またシリカ液A,シリカ液F~Iは、もともと分散液であるためイオン交換水を適宜加え、15質量%濃度シリカ液に調整している。
顔料、樹脂A、塩基性化合物(34質量%水酸化カリウム水溶液)、及び水性媒体としてトリエチレングリコールとを、プラネタリーミキサー「愛工舎製作所ACM04LVTJ-B」に配合表に記載の量仕込み、ジャケット温度60℃、攪拌羽根回転数25rpm(公転数80rpm)にて60分間混練を行なった。その後得られた混練物全部を家庭用ミキサー(象印社製ヘルシーミックス)に投入し、イオン交換水を、顔料濃度が15質量%となるように加え密栓し20分間撹拌溶解し、顔料濃度15質量%の顔料組成物を得た。
その後得られた顔料組成物と、表1に記載のヒュームドシリカ液(シリカ濃度はいずれも15質量%である)と、イオン交換水を配合表に従い混合し、攪拌機にて5分間攪拌し、本発明の水性顔料分散体を得た。この時得た水性顔料分散体の顔料とヒュームドシリカの含有量は、後述の配合表に記載した。
得られた水性顔料分散体を、ワイヤーバー#3にて普通紙(PPC用紙High-White)、及びカラーロック紙(HP社製:HPMP)のぞれぞれに塗布した。24時間自然乾燥後、塗布物のODを測定した。測定結果は後述の配合表に記載した。
測定には「Gretag Macbeth Spectro Scan Transmission」(X-Rite社)を使用し、塗布物のODとして、縦3点×横3点の合計9点測定の平均値を採用した。
なお、OD向上率は、下記式により算出し、3%以上の光学濃度の向上があった場合をG、3%以上の光学濃度の向上がなかった場合をNとした。
(なおヒュームドシリカ未添加の水性顔料分散体は比較例でもあるので、各々配合表にそれぞれ使用した比較例名を説明している)
彩度は、前記光学濃度(以下OD)値の測定方法と同様にして、塗布物のL*、a*、b*を測定し、彩度c*(c*=√(a*×a*+b*×b*))を計算した。
なお、彩度向上率は、下記式により算出し、3%以上の彩度向上があった場合をG、3%以上の彩度向上がなかった場合をNとした。
これより、ヒュームドシリカを4質量%添加したブラック水性顔料分散体(表1の実施例1~5)OD向上率は、ヒュームドシリカを添加していないブラック水性顔料分散体(表4の比較例5)に比べ、OD向上率は、プラス3%以上になっており、OD向上効果が有ることを示している。またこの効果は普通紙・カラーロック紙を問わず有効であることもわかる。
次に、シアン顔料の場合も(製法2)混練法により、カーボンブラックをシアン顔料(銅フタロシアニン:DIC社Fastogen Blue TGR-SD)に変えた以外は同様にして顔料濃度15%の水性分散体を得た。その後得られた顔料組成物と、表6に記載のヒュームドシリカ液B(シリカ濃度15質量%)と、イオン交換水を配合表に従い混合し、攪拌機にて5分間攪拌し、本発明の水性顔料分散体を得た。
ヒュームドシリカの「アエロジル130」からなるシリカ液Bを添加したシアン水性顔料分散体(表6の実施例12)はヒュームドシリカを添加していない水性顔料分散体(比較例7)に比べOD向上率・彩度向上率がプラスになっており、OD向上効果・彩度向上効果が有ることを示している。
次に、イエロー顔料の場合も(製法2)混練法により、カーボンブラックをイエロー顔料(Pigment Yellow 74(山陽色素社Fast Yellow 7413 ))に変えた以外は同様にして顔料濃度15%の水性分散体を得た。その後得られた顔料組成物と、表7に記載のヒュームドシリカ液B(シリカ濃度15質量%)と、イオン交換水を配合表に従い混合し、攪拌機にて5分間攪拌し、本発明の水性顔料分散体を得た。
ヒュームドシリカの「アエロジル130」からなるシリカ液Bを添加したイエロー水性顔料分散体(表7実施例13)はヒュームドシリカを添加していない水性顔料分散体(比較例9)に比べOD向上率・彩度向上率がプラスになっており、OD向上効果・彩度向上効果が有ることを示している。
Claims (6)
- 顔料、親水性ヒュームドシリカ、及び水性媒体を含有することを特徴とする水性顔料分散体。
- 前記親水性ヒュームドシリカの平均分散粒子径が250nm以下である請求項1に記載の記録用水性顔料分散体。
- 前記親水性ヒュームドシリカを前記顔料に対して20~300質量%の範囲で含有する請求項1または2に記載の水性顔料分散体。
- 前記顔料を前記水性顔料分散体全量に対して0.5~30質量%の範囲で含有する請求項1~3のいずれかに記載の水性顔料分散体。
- 請求項1~4のいずれかに記載の水性顔料分散体を使用するインクジェット記録用インク。
- 請求項1~4のいずれかに記載の水性顔料分散体を使用した印字物。
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US11613664B2 (en) | 2019-04-25 | 2023-03-28 | Seiko Epson Corporation | Aqueous ink jet ink composition and ink jet printing method |
WO2024029631A1 (ja) * | 2022-08-04 | 2024-02-08 | 御国色素株式会社 | 黒色着色組成物及び黒色顔料分散液 |
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EP4063458A4 (en) * | 2019-11-21 | 2023-11-15 | DIC Corporation | METHOD FOR MANUFACTURING PIGMENT COMPOSITION |
CN111393900A (zh) * | 2020-04-24 | 2020-07-10 | 深圳市崯涛油墨科技有限公司 | 丝网印刷油墨的制备方法以及丝网印刷油墨 |
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