GB2178183A - Heat-sensitive recording material - Google Patents

Heat-sensitive recording material Download PDF

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Publication number
GB2178183A
GB2178183A GB08618256A GB8618256A GB2178183A GB 2178183 A GB2178183 A GB 2178183A GB 08618256 A GB08618256 A GB 08618256A GB 8618256 A GB8618256 A GB 8618256A GB 2178183 A GB2178183 A GB 2178183A
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GB
United Kingdom
Prior art keywords
recording material
heat
protective layer
copolymer
electron
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB08618256A
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GB8618256D0 (en
Inventor
Akihiro Shimomura
Kenji Ikeda
Akira Igarashi
Hiroshi Kawakami
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Fujifilm Holdings Corp
Original Assignee
Fuji Photo Film Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP60164974A external-priority patent/JPS6225083A/en
Priority claimed from JP60172020A external-priority patent/JPH0662004B2/en
Priority claimed from JP60175397A external-priority patent/JPS6235877A/en
Priority claimed from JP60194640A external-priority patent/JPS6255189A/en
Application filed by Fuji Photo Film Co Ltd filed Critical Fuji Photo Film Co Ltd
Publication of GB8618256D0 publication Critical patent/GB8618256D0/en
Publication of GB2178183A publication Critical patent/GB2178183A/en
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
    • B41M5/42—Intermediate, backcoat, or covering layers
    • 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
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
    • B41M5/323—Organic colour formers, e.g. leuco dyes
    • B41M5/327—Organic colour formers, e.g. leuco dyes with a lactone or lactam ring
    • 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
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
    • B41M5/333—Colour developing components therefor, e.g. acidic compounds
    • B41M5/3333—Non-macromolecular compounds
    • B41M5/3335—Compounds containing phenolic or carboxylic acid groups or metal salts thereof
    • 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
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
    • B41M5/337—Additives; Binders
    • B41M5/3375—Non-macromolecular compounds
    • 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
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
    • B41M5/323—Organic colour formers, e.g. leuco dyes
    • B41M5/327—Organic colour formers, e.g. leuco dyes with a lactone or lactam ring
    • B41M5/3275—Fluoran compounds
    • 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
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
    • B41M5/333—Colour developing components therefor, e.g. acidic compounds
    • B41M5/3333—Non-macromolecular compounds
    • B41M5/3335—Compounds containing phenolic or carboxylic acid groups or metal salts thereof
    • B41M5/3336—Sulfur compounds, e.g. sulfones, sulfides, sulfonamides
    • 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
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
    • B41M5/42—Intermediate, backcoat, or covering layers
    • B41M5/423—Intermediate, backcoat, or covering layers characterised by non-macromolecular compounds, e.g. waxes
    • 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
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
    • B41M5/42—Intermediate, backcoat, or covering layers
    • B41M5/426—Intermediate, backcoat, or covering layers characterised by inorganic compounds, e.g. metals, metal salts, metal complexes
    • 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
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
    • B41M5/42—Intermediate, backcoat, or covering layers
    • B41M5/44—Intermediate, backcoat, or covering layers characterised by the macromolecular compounds

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Heat Sensitive Colour Forming Recording (AREA)

Abstract

A heat-sensitive recording material comprises a heat-sensitive color forming layer containing a colorless to lightly colored electron-donating dye precursor and an electron-accepting compound capable of reacting with the precursor upon heating to develop a color, and having thereon a protective layer which contains (a) a polymer whose degree of swelling in triethanolamine is not less than 10% by weight; or (b) inorganic pigment particles having an oil absorption of not more than 50 ml/100 g; or (c) an alkali salt of a styrene-maleic acid copolymer; or (d) a water-soluble polymeric binder and a pigment, and the material has a back-coat layer containing colloidal silica on the back-side of a support. The recording material does not suffer color formation reaction on the white background and discoloration of the recorded area even when contacted with writing inks containing a solvent having a boiling point of 150 DEG C or higher, has a solvent-resistant protective layer which exhibits satisfactory running properties and is free from aqueous ink blot, is resistant to water, chemicals and oils and does not fog.

Description

SPECIFICATION Heat-sensitive recording material This invention relates to a heat-sensitive recording material and, more particularly, to a heatsensitive recording material making use of a color forming reaction between a colorless to lightly colored electron-donating dye precursor and an electron-accepting compound.
The so-called two-component system heat-sensitive recording materials utilizing a color forming reaction between a colorless to lightly colored electron-donating dye precursor and an electron-accepting compound are disclosed in Japanese Patent Publication Nos. 14039/70 and 4160/68, etc. The two-component color formation system heat-sensitive recording materials are produced by making a dispersion of a colorless to lightly colored electron-donating dye precursor and an electron-accepting compound in the form of fine particles, mixing a binder with the dispersion, and coating the dispersion on a support in such a manner that these two heat reactive compounds are isolated from each other via a binder, etc. Either one or both of the two heat reactive compounds is/are melted upon heating so that they contact with each other to cause a color forming reaction, thereby achieving recording.These two-component color formation system heat-sensitive recording materials have a great utility value owing to advantages such that: (1) the color formation is a first-order system, and no development is necessary; (2) paper quality is near to general paper; (3) handling is easy; (4) the color density is high; (5) heatsensitive recording materials developing a variety of hues can easily be produced; and the like.
From these considerations, they are now most largely employed as heat-sensitive recording materials. In particular, application of these heat-sensitive recording materials to the fields of facsimiles, recorders and printers has recently become noticeable. With a broadening of their application in the field of facsimiles, speeding up of recording has been attempted. Improvements of the heat-sensitive recording materials also have been in high demand so as to have capability of developing a color upon receipt of a short pulse, i.e., low energy, to have improved heat reactivity.
On the other hand, these heat-sensitive recording materials have a disadvantage in that reaction between an electron-donating dye precursor and an electron-accepting compound takes place not only by heat but also with solvents, etc. because the color formation is of a first-order system.
This disadvantage arises from the fact that any of these heat-sensitive recording materials is an organic substance having high solubility in solvents, so that they are subject to reaction in solvents. Therefore, upon contact with stationary containing a solvent, such as aqueous ink pens, oily ink pens, fluorescent pens, diazo developers, adhesives, adhesive pastes, etc., the white background of the heat-sensitive materials undergoes color formation or the recorded area loses its developed color, thus resulting in serious impairment of commercial value.
Further, in general, use of heat-sensitive recording paper as paper for recording has an advantage in that a recording device can be lightened and small-sized, and has rapidly developed in recent years. On the other hand, defects of the heat-sensitive recording paper lie in disappearance of a recorded image or generation of fog when various chemicals, oil, etc. adhere thereto.
This defect forms a serious problem in practical use, and improvements have been demanded.
As a countermeasure, efforts have been made by, for example, providing a solvent-resistant protective layer on a heat-sensitive color forming layer as disclosed in Japanese Patent Publication No. 27880/69, Japanese Patent Applications (OPI) Nos. 27253/80, 30437/73 and 31958/73 (the term "OPl" as used herein refers to a published unexamined Japanese patent application). Japanese Patent Publication No. 27880/69 proposes that a layer comprising a water-soluble high polymer, e.g., polyvinyl alcohol, etc., having dispersed therein a lubricating tack-free wax that is melted at a temperature below an operating temperature is formed on a heat-sensitive color forming layer so as to prevent contamination of a surface of a sign (head) on heating. According to this process, however, resistance to various chemicals, oils, etc. and water resistance are still insufficient.
In order to overcome the above-described problems associated with heat-sensitive recording paper having a protective layer, i.e., poor resistance to various chemicals and water, stickiness, pressure marks, adhesion of work-up, and the like, it has been proposed to use hydrophobic polymeric (high molecular weight) compounds, various water-soluble polymers, water-resistanceimparting agents or fillers in combination (cf. Japanese Patent Applications (OPI) Nos 30437/73, 31958/73, 19840/78, 14751/79, 53545/79, 11837/79, 128349/79, 126193/81, 139993/81, 10530/82, 29491/82, 1053925/82, 115391/82, 144793/82. 107884/82, 53484/83 and 193189/83.).
However, these proposals have disadvantages in that: resistance to various chemicals, oils or water is still unsatisfactory; sensitivity is reduced; the protective layer undergoes blocking when water adheres thereto because, in most cases, the main component of the protective layer is a water-soluble polymer; or the production involves complicated steps or entails high cost. From all these considerations together, they are not very satisfactory from an industrial standpoint.
Further, by providing a back coat layer comprising a water-soluble polymeric binder and an organic or inorganic pigment on the back side of a support, not only running properties on a recording machine are improved, but also sheet curling can be corrected and chemical resistance of the back side can be imparted to therby ensure a commercial value of the above-described heat-sensitive paper having a protective layer.
However, the conventional back coat layer has a disadvantage of poor water resistance because of the water-soluble polymeric binder contained therein. Under a high humidity condition, adhesion between a surface side and a back side (hereinafter referred to as blocking) occurs due to swelling of the back coat layer, and the like, resulting in impairment of a commercial value. As a countermeasure, use of an alkali salt of an isobutylene-maleic anhydride copolymer has been disclosed (cf. Japanese Patent Application (OPI) No. 9091/84), but it is unsatisfactory in terms of water resistance.
Accordingly, one subject of this invention is to obtain a heat-sensitive recording material which is free from problems such as color formation reaction on the white background and discoloration of the recorded area even when contacted with writing inks containing a solvent having a boiling point of 1500C or higher, e.g., commercially available fluorescent pens.
Another object of this invention is to obtain a heat-sensitive recording material having a solvent-resistant protective layer on a heat-sensitive color forming layer, which exhibits satisfactory running properties and is free from acqueous ink blotting.
A third object of this invention is to provide a heat-sensitive recording material which exhibits excellent resistance to various chemicals and oils, does not undergo fog, color disappearance, etc., and is free from blocking even if water is adhered thereto.
A fourth object of this invention is to overcome the aforesaid disadvantage of the conventional backing layer and to provide heat-sensitive recording material which is excellent in water resistance and less subject to blocking and has improved anticurling and running properties.
These and other objects have been achieved by providing a heat-sensitive recording material comprising a heat-sensitive color forming layer containing a colorless to lightly colored electrondonating dye precursor and an electron-accepting compound capable of reacting with said electron-donating dye precursor upon heating to develop a color, which is characterized in that a protective layer containing a polymer whose degree of swelling in triethanolamine is not less than 10% by weight is provided on said heat-sensitive color forming layer.
In a second embodiment of this invention, a heat-sensitive recording material is provided comprising a heat-sensitive color forming layer containing a colorless to lightly colored electrondonating dye precursor and an electron-accepting compound capable of reacting with said electron-donating dye precursor upon heating to develop a color, which is characterized in that a protective layer provided on said heat-sensitive color forming layer contains inorganic pigment particles having an oil absorption of not more than 50 ml/100 g.
A third embodiment of this invention provides a heat-sensitive recording material comprising a support having thereon a heat-sensitive color forming layer containing a colorless or lightly colored electron-donating dye precursor and an electron-accepting compound capable of reacting with said electron-donating dye precursor upon heating to develop a color, which is characterized in that a protective layer containing an alkali salt of a styrenemaleic acid copolymer as a main component is provided on the heat-sensitive color forming layer.
A fourth embodiment of this invention provides a heat-sensitive recording material comprising a support having provided thereon a heat-sensitive recording layer comprising a colorless to lightly colored electron-donating dye precursor and an electron-accepting compound capable of reacting with said electron-donating dye precursor upon heating to develop a color and further provided thereon a protective layer containing a water-soluble polymeric binder and a pigment, which is characterized in that a back coat layer containing colloidal silica is provided on the back of the support.
The degree of swelling as referred to in the first embodiment of the present invention can be determined as follows. A dry film of a polymer to be measured weighing about 1 g is immersed in 500 g of triethanolamine for 1 hour. The sample is taken out, washed with acetonitrile to remove the solvent on its surface and weighed (A). Then, the solvent within the sample is evaporated at 1500C under reduced pressure, and the weight is measured when a constant weight is reached (B). The degree of swelling is calculated from the following equation: Degree of Swelling (%)=(B-A)/AX100 (%) Polymers whose degree of swelling in triethanolamine is 10% by weight or more, which can be used in this invention, include, for example, polyvinyl pyrrolidone, an alkyl ketene dimer, sodium caseinate, hydroxypropyl cellulose, polyacrylic acid, polyacrylates or, copolymers containing maleic acid. Among the maleic acid-containing copolymers, a styrene/maleic acid copolymer, particularly preferred. These polymers may be used individually or in combination with other polymers. The preferred amount of the polymer having the above swelling degree of not less than 10% by weight to be coated is about 10 to 100% by weight per 100% by weight of the protective layer.
For the purpose of improving matching property with a thermal head, water resistance and the like, the protective layer of the invention may contain pigments, metal soaps, waxes or like water-resistance-imparting agents.
The pigment is preferably used in an amount from 0.5 to 4 times, and more preferably from 0.8 to 3.5 times, the total weight of polymers. Amounts less than the above range are ineffective to improve the matching property with a thermal head, and amounts more than that seriously reduce sensitivity to impair the commercial value. Pigments to be used include zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, agalmatolite, kaolin, aluminum hydroxide, silica, amorphous silica, colloidal silica, etc.
Metal soaps to be used include higher fatty acid metal salts, such as emulsions of zinc stearate, calcium stearate, aluminum stearate, etc., with zinc stearate being particularly preferred.
The amount to be added preferably ranges from 0.5 to 20%, and more preferably from 1 to 10%, based on the total weight of the protective layer. Waxes to be used include emulsions of paraffin wax, microcrystalline wax, carnauba wax, methylolstearamide, stearamide, polyethylene wax, polystyrene wax, etc. The amount to be added preferably ranges from 1 to 20%, and more preferably from 1 to 10%, based on the total weight of the protective layer.
Further, in order to obtain a uniform protective layer by coating on a heat-sensitive color forming layer, a surface active agent may be added. The surface active agent which can be used includes alkali metal salts of sulfosuccinic acids, fluorine-containing surface active agents, and the like. Specific examples are sodium or ammonium salts of di-(2-ethylhexyl)sulfosuccinate, di-(nhexyl)sulfosuccinate, etc., and aimost every anionic surface active agent is effective.
The protective layer of the second embodiment of the present invention can be formed by coating the heat-sensitive color forming layer with a coating layer containing inorganic pigment particles having an oil absorption of not more than 50 ml/100 g. The above-recited pigment preferably includes zinc oxide, barium sulfate, titanium oxide, agalmatolite, heavy kaolin and aluminum hydroxide. Heat-sensitive recording materials which are free from aqueous ink blot and also has improved slipperiness can be obtained by incorporating the above-described inorganic pigments into a protective layer. The amount of the pigment in the protective layer is preferably from 20% to 150% based on a binder.
The pigment preferably has a particle size of from 1 jum to 5 ,um.
Binders to be contained in the protective layer preferably include methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, starches, gelatin, gum arabic, casein, a hydrolyzate of a styrene-maleic anhydride copolymer, a hydrolyzate of an ethylene-maleic anhydride copolymer, a hydrolyzate of an isobutylene-maleic anhydride copolymer, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, polyacrylamide, and the like.
In the present invention, metal soaps, waxes, etc. may further be added to a coating composition in addition to the above-described binders. The metal soaps and waxes and amounts thereof are the same as those described above for the first embodiment of the present invention.
In the coating of the uniform protective layer on a heat-sensitive color forming layer, a surface active agent as described above for the first embodiment of the present invention may be added.
The protective layer according to the third embodiment of the invention can be formed by coating a heat-sensitive color forming layer with a coating layer containing an alkali salt of a styrene-maleic acid copolymer.
The alkali salt of a styrene-maleic acid copolymer which can be used in the protective layer of the invention includes a sodium salt, potassium salt, ammonium salt, etc. of a styrene-maleic acid copolymer, with an ammonium salt of a styrene-maleic acid copolymer being preferred.
These salts may be present in combination.
The alkali salt of a styrene-maleic acid copolymer preferably has a degree of polymerization of from 500 to 5,000, and more preferably from 1,500 to 2,500.
The proportion of styrene in the styrene-maleic acid copolymer alkali salt is preferably from 50% by weight to 80% by weight, and more preferably from 50% by weight to 55% by weight.
A part of the ammonium salt may be esterified, with a preferred degree of esterification being from 35% to 50%.
The protective layer to be used in the third embodiment of the present invention produces effects to prevent various chemicals, oils, etc., when adhered to a surface of the protective layer, from penetrating into a heat-sensitive color forming layer; to protect the heat-sensitive color forming layer against influences of various chemicals, oils, etc.; or to prevent the surface of the protective layer from becoming sticky to cause blocking of the heat-sensitive paper between the surface and the back when water is attached thereto.
The amount of the styrene-maleic acid copolymer alkali salt to be coated usually ranges from 0.3 to 5.0 g/m2, and preferably from 0.5 to 3.0 g/m2.
With a low coverage, resistance to various chemicals, that is an object of the invention, is reduced; and with a high coverage, heat-responding properties of the heat-sensitive color forming layer are deteriorated. Therefore, the coverage can be determined depending on requirements for both properties.
If necessary, the protective layer can contain various auxiliary components in addition to the styrene-maleic acid copolymer alkali salt.
For example, the protective layer can contain other water-soluble polymers or polymeric latices for controlling film strength of the protective layer, or organic or inorganic pigments and lubricants for prevention of adhesion to a thermal head.
These additives are described below in more detail.
The water-soluble high polymers which can be used include generally employed conventional binders, such as polyvinyl alcohol, methyl cellulose, starch, carboxymethyl cellulose, diisobutylene-maleic acid copolymer alkali salts, styrene-acrylic acid copolymer alkali salts, polyamide resins, polyacrylamide resins, and the like. These polymers can be used according to necessity in a proportion of from 5 to 50% by weight based on the styrene-maleic acid copolymer alkali salt.
The polymer latices include styrene-butadiene copolymer latices, carboxy-modified styrenebutadiene coplymer latices, styrene-butadiene-vinylpyridine terpolymer latices, acrylic ester copolymer latices, modified acrylic ester copolymer latices, styrene copolymer latices, vinyl acetate copolymer latices, vinyl acetate-acrylic acid copolymer latices, vinyl acetate-ethylene copolymer latices, acrylic acid-butadiene copolymer latices, acrylic acid-styrene-butadiene copolymer latices, and so on, with styrene-butadiene copolymer latices, modified acrylic ester copolymer latices, etc. being preferred. They can be used according to necessity in a proportion of from 5 to 50% by weight based on the styrene-maleic acid copolymer alkali salt.
The inorganic pigments include zinc oxide, calcium carbonate, kaolin, barium sulfate, titanium oxide, lithopone, talc, agalmatolite, aluminum hydroxide, calcined kaolin and silica fine powders.
Examples of the organic pigments are urea-formalin resins and polyethylene fine powders These pigments can be used according to necessity in an amount of from 10 to 200% based on the styrene-maleic acid copolymer alkali salt.
The lubricants to be used include animal waxes, vegetable waxes, petroleum waxes, e.g., paraffin or micro-wax, polyolefin waxes, and other synthetic waxes, such as higher fatty acids, aliphatic alcohols, fatty acid amides and fatty acid esters, and higher fatty acid metal salts as metal soaps. These lubricants are used in the form of a fine powder or an emulsion in an amount of from 3 to 30% based on the styrene-maleic acid copolymer alkali salt as determined according to necessity.
The protective layer according to the fourth embodiment of the present invention can be formed by coating a coating composition comprising a water-soluble polymeric binder and an organic or inorganic pigment on the heat-sensitive color forming layer.
The water-soluble polymeric binder includes polyvinyl alcohol, methyl cellulose, starch, carboxymethyl cellulose, a styrene-maleic acid copolymer, a diisobutylenemaleic acid polymer, a polyamide resin and a polyacrylamide resin and derivatives thereof.
Pigments to be used include inorganic pigments, e.g., zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, agalmatolite, kaolin, calcined kaolin or aluminium hydroxide, and organic pigments, e.g., a urea-formalin resin or a polyethylene powder.
The protective layer in all embodiments is coated to a coverage (dry weight) of from 0.2 to 5.0 g/m2, and preferably from 0.5 to 3 g/m2.
With a low coverage, resistance to various chemicals, that is an object of the present invention, is reduced; and with a high coverage, heat-responding properties of the heat-sensitive color forming layer are deteriorated. Therefore, the coverage can be determined depending on requirements for both properties.
The heat-sensitive color forming layer of the present invention can be formed by coating a paper such as neutral paper, fine paper, etc. or a synthetic resin film base such as a plastic film with a coating composition containing a colorless to lightly colored electron-donating dye precursor (color former) and an electron-accepting substance (developer) capable of reacting with the electron-donating dye precursor to develop a color, and, if desired, a heat-fusible substance, an organic or inorganic pigment, a binder, and so on, that are usually employed in the art, and drying.
The color former and the developer are separately dispersed in a water-soluble polymer (binder) by means of a ball mill, etc. The heat-fusible substance, when used, according to the present invention is similarly dispersed, or it is previously mixed with the color former or developer and subjected to dispersion together. Dispersion is carried out until a volume average particle size is reduced to 5 ,lim or less, and preferably to 2 ,um or less. After completion of the dispersion, the dispersions are mixed to obtain a heat-sensitive coating composition.
The colorless to lightly colored electron-donating dye precursor (color former) which can be used in the present invention includes triarylmethane compounds, diphenylmethane compounds, xanthene compounds, thiazine compounds, spiropyran compounds and the like. Specific examples of these compounds are those described, e.g., in Japanese Patent Application (qPI) No. 27253/80.Illustrative examples are triarylmethane compounds, such as 3,3-bis(dimethy- laminophenyl)-6-dimethylaminophthalide (i.e., Crystal Violet Lactone), 3,3-bis(dimethylaminophe- nyl)-phthalide, 3-(p-dimethylaminophenyl)-3-(1,3-dimethylindol-3-yl)phthalide, 3-(dimethylamino- phenyl)-3-(2-methylindol-3-yl)phthalide, etc.; diphenylmethane compounds, such as 4,4'-bis-dimethylaminobenzhydrinbenzyl ether, an N-halophenylleucoauramine, N-2,4,5-trichlorophenylleucoauramine, etc.; xanthene compounds, such as Rhodamine B-anilino lactam, rhodamine (nitrino)lac- tam, rhodamine (pnitroanilino)-lactam, Rhodamine B ( chloroanilino)lactam, 2-dibenzyiamino-6 diethylaminofluoran, 2-anilino-6-diethylaminofluoran, 2-anilino-3-methyl-6-diethylaminofluoran, 2-an ilino-3-methyl-6-N-cyclohexyl-N-methylaminofluoran, 2-anilino-3-methyl-6-N-ethyl-N-isoamylaminofluoran, 2-o-chloroanilino-6-diethylaminofluoran, 2-mchloroanilino-6-diethylaminof luoran. 2-octylamin-6-diethylaminofluoran, 2-dihexylamino-6-diethylaminofluoran, 2-m-trichloromethylanilino-6-diethylaminofluoran, 2-butylamino-3-chloro-6-diethylaminofluoran, 2-ethoxyethylamino-fl-chloro-6-di- ethylaminofluoran, 2-anilino-3-chloro-6-diethylaminofluoran, 2-diphenylamino-6-diethylaminofluoran, 2-anilino-3-methyl-6-diphenylaminofluoran, 2-anilino-3-methyl-5-chloro-6-diethylaminofluoran, 2-anilino-3-methyl-6-diethylamino-7-methylfluoran, 2-anilino-3-methoxy-6-dibutylaminofluoran, 2- > chlo- roanilino-6-dibutylaminofluoran, 2-p-chloroanilino-3-ethoxy-6-diethylaminofluoran, 2-phenyl-6-diethylaminofluoran, 2-o-chloroanilino-6-p-butylanilinofluoran, 2-anilino-3-pentadecyl-6-diethylaminofluoran, 2-anilino-3-ethyl-6-dibutylaminofluoran, 2-anilino-3-ethyl-6-N-ethyl-N-isoamylaminofluoran, 2-anilino-3-methyl-6-N-ethyl-N-y-methoxypropylaminofluoran, 2-anilino-3-phenyl-6-diethylaminofluoran, 2-diethylamino-3-phenyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-N-isoamyl-N-ethylaminofluoran, 2-dibenzylan::jno)fluornn 2-phenylamino-6-diethylaminofluoran, 2-(o-chloroanilino)-6diethylaminofluoran, 2-(3 ,4-dichloroanilino)-6-diethylaminofluoran, 2-anilino-3-methyl-6-piperidinofluoran, 2-phenyl-6-diethylaminofluoran, etc.; thiazine compunds, such as Benzoyl Leucomethylene Blue, n-Nitrobenzyl Leucomethylene Blue, and spiropyran compounds, such as 3-methyl-spirodinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3 ,3'-dichloro-spiro-dinaphthopyran, 3-benzylspiro-dinaphthopyran, 3-methyl-naphtho(3-methoxybenzo)-spiropyran, 3-propyl-spirodibenzopyran. These compounds are used either individually or in combinations thereof.Of these, triarylmethane compounds (e.g., Crystal Violet Lactone) and xanthene compounds are preferred electron-donating dye precursors since many of them generate less fog and provide high color densities. The more preferred among them include xanthene compounds represented by the following formula (I):
wherein R, and R2 each represents an alkyl group having from 1 to 10 carbon atoms or a cycloalkyl group; R3 represents an aryl group; and X represents an alkyl group having from 1 to 10 carbon atoms or a halogen atom.
In the above-described formula (I), the alkyl group as represented by R1 or R2 may be straight or branched, and may have a substituent. The aryl group as represented by R3 preferably has from 6 to 20 carbon atoms, and a phenyl group and a substituted phenyl group are more preferred. The substituent for the phenyl group preferably includes an alkyl group having from 1 to 10 carbon atoms.
Of the dye precursors represented by the formula (I), those particularly preferred are represented by the following formula (all):
wherein R'1 and R; each represents an alkyl group having from 1 to 10 carbon atoms; R4 represents a hydrogen atom or an alkyl group having from 1 to 8 carbon atoms; and X represents an alkyl group having from 1 to 8 carbon atoms or a chlorine atom.
In the above-described formula (it), the alkyl group as represented by R', or R'2 may form a ring and may have a substituent.
Among the compounds of the formula (II), those wherein X' is a methyl group or a chlorine atom are particularly preferred.
Specific but non-limiting examples of the colorless or lightly colored electron-donating dye precursors are shown below: 2-Anilino-3-methyl-6-dimethylaminofluoran, 2-anilino-3-methyl-6-N-methyl-N-ethylaminofluoran,2-anilino-3-methyi-6-N-methyl-N-(isopropyi)aminofluoran, 2-anilino-3-methyl-6-N-methyl-N-pentylaminofluoran, 2-anilino-3-methyl-6-N-methyl-N-cyclohexylaminofluoran, 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-chloro-6-dimethylaminofluoran, 2-anilino-3-methyl-6-N-ethyl-N-isoamylaminofluoran, 2-anilino-3-methyl-6-N-methyl-N-isoamylaminofluoran, 2-anilino-3-chloro-6-diethylaminofluoran, 2-anilino-3-chloro-6-N-methyl-N-ethylaminofluoran, 2-anilino-3-chloro-6-N-methyl-N-(isopropyl)aminofluoran, 2-anilino-3-chloro-6-N-methyl-N-pentylaminofluoran, 2-anilino-3-chloro-6-Nmethyi-N-cyclohexylaminofluoran, 2-anilino-3-methyl-6-N-ethyl-N-pentylaminofluoran, 2-anilino-3chloro-6-N-ethyl-N-pentylaminofluoran, 2-(p-methylanilino)-3-methyl-6-dimethylaminofluoran, 2-(pmethylanilino)-3-methyl-6-diethylaminofluoran, 2-(p-methylanilino)-3-methyl-6-N-methyl-N-ethylaminofluoran, 2-(p-methylanilino)-3-methyl-6-N-methyl-N-(isopropyl)aminofluoran, 2-(p-methylanilino)-3methyl-6-N-methyl-N-pentylaminofluoran, 2-(p-methylanilino)-3-methyl-6-N-methyl-N-cyclohexylami- nofluoran, 2-(p-methylanilino)-3-methyl-6-N-ethyl-N-pentylaminofluoran, 2-(pmethylanilino)-3- chloro-6-dimethylaminofluoran, 2-(methylanilino)-3-chloro-6-diethylaminofluoran, 2-(pmethylanil- ino)-3-chloro-6-N-methyl-N-ethylaminofluoran, 2-(p-methyíaniíino)-3-chloro-6-N-methyl-N-(isopropy- I)aminofluoran, 2-(Rmethylanilino)-3-chloro-6-N-methyl-N-cycloheXylaminofluoran, 2-(methylanil- ino)-3-chloro-6-N-methyl-N-pentylaminofluoran, 2-(p-methylanilino)-3-chloro-6-N-ethyl-N-pentylaminofluoran, 2-anilino-3-methyl-6-N-methyl-N-furylmethylaminofluoran, 2-aniiino-3-ethyl-6-N-methyl-Nfurylmethylaminofluoran, etc. These compounds may be used individually, and mixtures of two or more thereof may also be used for the purpose of controlling color tone or preventing discoloration of a color-developed image. The preferred amount of these color formers coated is about 0.1 to 1 g/m2.
The electron-accepting compounds (developer) which can be used in the present invention preferably are compounds represented by the following formulae (III) tQ (VII):
wherein X represents.S, 0, SO2, or
I represents 0 or an integer of from 1 to 3; Rs and R6 each represents a hydrogen atom or an alkyl group having from 1 to 8 carbon atoms, or R5 and R8 are bonded together to form a cycloalkyl group; and R represents a straight chain or branched alkyl group having from 1 to 8 carbon atoms or a halogen atom.
wherein Y represents a hydrogen atom, -CH3 or -OH; R7 represents
or a straight chain or branched alkyl group having from 1 to 6 carbon atoms; m and n each represents 0 or an integer of from 1 to 3; and Z represents a hydrogen atom, a halogen atom or -CH3.
wherein R8 represents a benzyl group, a benzyl group, a benzyl group substituted with a halogen atom or a straight chain or branched alkyl group having from 1 to 8 carbon atoms or a straight chain or branched alkyl group having from 1 to 8 carbon atoms.
wherein R9 and Rla each represents an alkyl group having from 1 to 8 carbon atoms.
wherein R,l represents an alkylene group having from 1 to 5 ether linkages.
Specific examples of the compounds represented by the above formulae (Ill) to (VII) are 2,2bis(4'-hydroxyphenyl)propane, 2,2-bis(4'-hydroxyphenyl)pentane, 2,2-bis(4'-hydroxy-3',5'-dichlorophenyl)propane, 1,1 -bis(4'-hydroxyphenyl)cyclohexane, 2,2-bis(4'-hydroxyphenyi)hexane, 1,1 bis (4'-hydroxyphenyl)propane, 1,1 -bis(4'-hydroxyphenyl)butane, 1,1 -bis(4'-hydroxyphenyl)pentane, 1,1 -bis(4'-hydroxyphenyl)-hexane, 1,1 -bis(4'-hydroxyphenyl)heptane, 1,1 -bis(4'-hydroxyphenyl)oc- tane, 1,1 -bis(4'-hydroxyphenyl)-2-methylpentane, 1,1 -bis(4-hydroxyphenyl)-2-ethylhexane, 1,1 bis(4'-hydroxphenyl)dodecane, 3,3-bis(4-hydroxyphenyl)pentane, 1 ,2-bis(4'-hydroxyphenyl)ethane, 1,1 -bis(4'-hydroxyphenyl)-sulfide, 1,1 -bis(4'-hydroxyphenyl)sulfone. 1,1 -bis(4'-hydroxyphenyl)ether, 2,2-bis(4'-hydroxy-3',5-dichlorophenyl)-butane, phenyl 2,4-dihydroxybenzoate, phenyl 2,4-dihydroxy-4'-methylbenzoate, phenyl 2,4-dihydroxy-4'-chlorobenzoate, phenyl 2,4-dihydroxy-6-methylbenzoate, phenyl 2,4,6-trihydroxybenzoate, phenyl 2,4-dihydroxy-6,4'-dimethylbenzoate, phenyl 2,4-dihydroxy-6-methyl-4'-chlorobenzoate, benzyl 2,4-dihydroxybenzoate, benzyl 2,4-dihydroxy-4'- methylbenzoate, benzyl 2,4-dihydroxy-4'-chlorobenzoate, benzyl 2,4-dihydroxy-6-methylbenzoate, benzyl 2,4,6-trihydroxybenzoate, benzyl 2,4-dihydroxy-6,4'-dimethylbenzoate, benzyl 2,4-dihydoxy-6'-methyl-4'-chlorobenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, isopropyl 4-hydoxybenzoate, benzyl 4-hydroxybenzoate, 2-ethylhexyl 4-hydroxybenzoate, benzyl 4-hydroxy4'-chlorobenzoate, benzyl 4-hydroxy-4'-methylbenzoate, benzyl 4-hydroxy-4'-ethylbenzoate, dimethyl 3-hydroxy-m-phthalate, diethyl 3-hydroxy-m-phthalate, methylethyl 3-hydroxy-m-phthalate, dibutyl 3-hydroxy-m-phthalate, dimethyl 3-hydroxy-o-phthalate, diethyl 3-hydroxy-o-phthalate, etc.
Specific examples of the compounds represented by the formula (VII) are shown below:
Examples of preferred electron-accepting compounds other than those represented by the above formulae (III) to (VII) include bis-hydroxycumylbenzenes or bis-hydroxy-a-methylbenzylbenzenes, such as 1 ,4-bis-p-hydroxycumylbenzene, 1,4-bis-m-hydroxycumylbenzene, 1,3-bis-p-hydroxycumylbenzene, 1,3-bis-m-hydroxycumylbenzene, 1 ,4-bis-o-hydroxycumyl-benzene, 1,4-bis-phydroxy-a-methylbenzylbenzene, 1 ,3-bis-p-hydroxy-a-methylbenzylbenzene, etc.; salicyclic acid derivatives, such as salicyclic acids, e.g., 3,5-di-a-methylbenzylsalicyclic acid, 3,5-di-t-butylsalicyclic acid. 3-a,a-dimethylbenzylsalicyclic acid, etc. and polyvalent metal salts thereof (zinc or aluminum salts are particularly preferred), etc.; and phenols, such as p-phenylphenol, 3,5-diphenylphenol, cumylphenol, etc. However, these examples are not limitative.
The above-described electron-accepting compound is preferably used in an amount of from 50 to 1000% by weight, and more preferably from 100 to 500% by weight, based on the electrondonating dye precursor. They may be used either individually or in combination of two or more thereof. The preferred amount of these developers coated is about 0.1 to 5 g/m2.
In order to improve heat-responding properties of the heat-sensitive recording materials of this invention, a heat-fusible substance can be added to the heat-sensitive color forming layer.
Examples of preferred heat-fusible substances include compounds represented by the following formulae (VIII) to (XIII):
R.6NHCONH2 (Xl) Rl7CONH-Rl8 (XII) wherein R12, R,3, R,4 and R,5 each represents a phenyl or benzyl group or a phenyl or benzyl group substituted with a lower alkyl group, a halogen atom, a hydroxyl group or an alkoxy group; R,6 and R" each represents an alkyl group having from 12 to 24 carbon atoms; and R,8 represents a hydrogen atom or a phenyl group.
In the formulae (VIII) to (X), when the phenyl or benzyl group as represented by R12, R,3, R,4 or R,s is substituted with a lower alkyl group, such an alkyl group has from 1 to 8, and preferably from 1 to 3, carbon atoms. When it is substituted with a halogen atom, a preferred halogen atom is a chlorine atom or a fluorine atom.
wherein R,g represents a divalent group, preferably an alkylene group, an alkylene group having an ether linkage, an alkylene group having a carbonyl group, an alkylene group having a halogen atom or an alkylene group having an unsaturated bond, and more preferably an alkylene group or an alkylene group having an ether linkage; and X", Y", Z", X", Y"' and Z"', which may be the same or different, each represents a hydrogen atom, an alkyl group, a lower alkoxy group, a lower aralkyl group, a halogen atom, an alkyloxycarbonyl group or an aralkyloxycarbonyl group.
The compounds of the above formulae (VIII) to (XIII) preferably have a melting point of from 70" to 1500C, and more preferably from 80" to 1300C.
Specific examples of these compounds include benzyl p-benzyloxybenzoate, fi-naphthylbenzyl ether, stearamide, palmitamide, N-phenylstearamide, N-stearylurea, phenyl ss-naphthoate, phenyl 1-hydroxy-2-napthoate, fl-napthol(p-chlorobenzyl)ether, fl-napthol(p-methylbenzyl)ether, a-napthylbenzyl ether, 1 ,4-butanediol-p-methylphenyl ether, 1 ,4-propanediol-p-methylphenyl ether, 1,4-butanediol-p-isopropylphenyl ether, 1 ,4-butanediol-p-octylphenyl ether, 2-phenoxy- 1 -p-tolyloxyeth- ane, 1 -phenoxy-2-(4-ethylphenoxy)-ethane, 1 -phenoxy-2-(4-chlorophenoxy)ethane, 1,4-butanediolphenyl ether, etc.
The above-described heat-fusible substances may be used either individually or in combinations thereof. They are preferably used in an amount of from 10 to 200% by weight, and more preferably from 20 to 150% by weight, based on the electron-accepting compound for obtaining sufficient heat-responding properties.
In the two-component system heat-sensitive recording materials using an electron-donating dye precursor and an electron-accepting compound, a recorded image is generally liable to discoloration by influences of external conditions, such as humidity, heat, etc.
In order to prevent such discoloration and to make a formed image fast in the heat-sensitive recording materials of the invention, it is preferable to incorporate a compound which inhibits discoloration into the heat-sensitive color forming layer.
Effective discoloration inhibitors include phenol derivatives, and particularly hindered phenol compounds. Examples of preferred discoloration inhibitors include compounds represented by the following formulae (XIV) to (XVII):
wherein R20 represents a branched alkyl group having from 3 to 8 carbon atoms; R2, represents a hydrogen atom or a branched alkyl group having from 3 to 8 carbon atoms; R22 represents a hydrogen atom or an alkyl group having from 1 to 3 carbon atoms; R23 represents a hydrogen atom or an alkyl group having from 1 to 8 carbon atoms;R24, R25 and R28 each represents a hydrogen atom or an alkyl group having from 1 to 3 carbon atoms; and R27 represents a hydrogen atom or an alkyl group having from 1 to 8 carbon atoms.
wherein R28 and R30 each represents a branched alkyl group having from 3 to 8 carbon atoms; R9 and R31 each represents an alkyl group having from 1 to 8 carbon atoms; X"" represents S, o, SO2, S2
a cyclopentylene group or a cyclohexylene group; q represents 0 or an integer of from 1 to 3; and R32 and R33 each represents a hydrogen atom or an alkyl group having from 1 to 8 carbon atoms.
wherein R34 and R37 each represents a branched alkyl group having from 3 to 8 carbon atoms; R35 R36' R38 and R39 each represents a hydrogen atom or an alkyl group having from 5 to 8 carbon atoms; Y"" represents S, O, SO2, S2 or
represents 0 or an integer of from 1 to 3; and R, and R4, each represents a hydrogen atom or an alkyl group having from 1 to 8 carbon atoms, or R, and R4, are bonded together to form a cyclic pentamethylene group.
wherein R42 and R43 each represents a branched alkyl group having from 3 to 8 carbon atoms; Z"" represents -NH-, -O(CH2)k-, wherein k represents an integer of from 1 to 5; i represents an integer of from 1 to 4; and W represents an alkyl group having from 1 to 18 carbon atoms when i=1, or W represents S, 0,
wherein R44 and R4, each represents a hydrogen atom or an alkyl group having from 1 to 8 carbon atoms, and j represents 0 or an integer of from 1 to 8, when i=2, or W represents I, c-R46, wherein R46 represents a hydrogen atom or an alkyl group having from 1 to 8 carbon atoms, when i=3, or W represents -c- when i=4.
Typical examples of the phenol derivatives represented by the above formulae (XIV) to (XVII) are shown below: (A) Examples of the phenol derivatives represented by the formula (XIV) are 1,1 ,3-tris(2- methyl-4-hydroxy-5-t-butylphenyl)butane, 1,1 ,3-tris(2-ethyl-4-hydroxy-5-t-butylphenyl)butane, 1,1 ,3-tris(3,5-di-t-butyl-4-hydroxyphenyl)butane, 1,1 ,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)propane, etc.
(B) Examples of the phenol derivatives represented by the formula (XV) are 2,2'-methylenebis(6-t-butyl-4-methylphenol), 2,2'-methylene-bis(6-t-butyl-4-ethylphenol), etc.
(C) Examples of the phenol derivatives represented by the formula (XVI) are 4,4'-butylidenebis(6-t-butyl-3-methylphenol), 4,4'-thio-bis(3-methyl-6-t-butylphenol), etc.
(D) Examples of the phenol derivatives represented by the formula (XVII) are
tBu o 'CHrCH2COClsHJ7 r tBS tsu {HOCH2CH20ClOCH2CH2 i2s tBu tBu [HO > CH2CH2COCH2 0 4C and the like.
The amount of these phenol compounds of the formulae (XIV) to (XVII) to be used preferably ranges from 1 to 200% by weight, and more preferably from 5 to 50% by weight, based on the electron-accepting compound.
If necessary, an antioxidant or an ultraviolet absorbent may be added to the coating composition.
The recording layer of the - heat-sensitive recording materials of the present invention generally contains a polymer as a binder, in addition to modified polyvinyl alcohol or modified polyvinyl alcohol and starch. The polymer to be used is desirably a compound having a solubility in water at 25"C of at least 5%. Specific examples of such a polymer includes methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, starches, gelatin, gum arabic, casein, a hydrolyzate of a styrene-maleic anhydride copolymer, a hydrolyzate of an ethylene-maleic anhydride copolymer, a hydrolyzate of an isobutylene-maleic anhydride copolymer, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, polyacrylamide, and the like. The preferred amount of the binder used is about 3 to 50% by weight (as a solid) per 100% by weight of the heat-sensitive recording layer.
If desired, the recording layer of the heat-sensitive recording materials of this invention furthermore contains pigments, water-insoluble binders, metal soaps, waxes, surface active agents, fluorescent brightening agents, and so on.
Oil-absorbing pigments which can be used include inorganic pigments such as zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, agalmatolite, kaolin, aluminum hydroxide, calcined kaolin, silica, amorphous silica, and the like. Organic pigments include ureaformalin resins, polyethylene powders, and the like.
Water-insoluble binders to be used generally include synthetic rubber latices and synthetic resin emulsions, such as a styrene-butadiene rubber latex, an acrylonitrile-butadiene rubber latex, a methyl acrylate-butadiene rubber latex, a vinyl acetate emulsion, and the like.
Metal soaps to be used include higher fatty acid metal salts, such as emulsions of zinc stearate, calcium stearate, aluminum stearate, etc.
Waxes to be used include emulsions of paraffin wax, microcrystalline wax, carnauba wax, methylolstearamide, polyethylene wax, polystyrene wax, fatty acid amides and the like.
Surface active agents to be used include alkali metal salts of sulfosuccinic acids, fluorinecontaining surface active agents, and the like.
For the purpose of preventing curling of the heat-sensitive paper and imparting chemical resistance to the back side, a back coat layer can be provided on the back side of a support of the heat-sensitive recording paper of the invention.
The back coat layer can be formed by coating the back side of a support with a coating layer containing a water-soluble polymer.
The water-soluble polymer to be used in the back coat layer according to the present invention is preferably a compound having a solubility in water of 25"C of at least 5%. Specific examples of such a compound include methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, starches, gelatin, gum arabic, casein, an alkali salt of a styrene-maleic acid copolymer, an alkali salt of an ethylene-maleic acid copolymer, an alkali salt of an isobutylene-maleic acid copolymer, an alkali salt of a styrene-acrylic acid copolymer, polyvinyl alcohol, carboxy-modified poly vinyl alcohol, silicon-modified polyvinyl alcohol, and the like, with an alkali salt of a styrenemaleic acid copolymer being particularly preferred.
Further, according to the forth embodiment of the invention, the back coat layer can be formed by coating a composition containing colloidal silica on the back of a support in all embodiments. The colloidal silica preferably has a particle size of from 1 to 100 ,um and more preferably from 10 to 50 ,um.
The back coat layer of the heat-sensitive paper of the invention preferably contains a binder.
Binders to be used include dispersions of water-soluble polymers, such as methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, starches, gelatin, gum arabic, casein, a hydrolyzate of a styrene-maleic anhydride copolymer, a hydrolyzate of an ethylene-maleic anhydride copolymer, a hydrolyzate of an isobutylene-maleic anhydride copolymer, polyvinyl alcohol, or a carboxy-modified polyvinyl alcohol, and hydrophobic polymers, such as a styrene-butadiene rubber latex, an acrylic resin emulsion, or a vinyl acetate emulsion. The particularly preferred among them are water-soluble polymers. The amount of the binder to be used is preferably not more than twice the weight of colloidal silica.
Both of the back coat layers of the heat-sensitive recording paper of the invention preferably further contain a pigment. The pigment to be used preferably includes inorganic pigments, such as zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, agalmatolite, kaolin, calcined kaolin, aluminum hydroxide, etc., and organic pigments, such as urea-formalin resins, polyethylene, etc. The first mentioned back coat layer can also contain silica as a preferred inorganic pigment.
The coverage (dry basis) of the back coat layer is from 0.2 to 5.0 g/m2, and preferably from 0.2 to 3.0 g/m2.
In order to satisfy running properties on an actual machine, the back coat layer containing colloidal silica preferably has a degree of smoothness of from 30 to 500 seconds (JIS P8119), and more preferably from 80 to 150 seconds (JIS P8119).
Surface active agents may be added to the coating composition containing colloidal silica for the sake of stability and defoaming after dispersing.
Examples are given below, but the present invention is not limited thereto.
FIRST EMBODIMENT Materials used in heat-sensitive color forming layers according to the first embodiment of the present invention are shown in Table 1. Twenty grams of each of the electron-donating dye precursor, electron-accepting compound, heat-fusible substance and discoloration inhibitor were dispersed together with 100 g of a 5% aqueous solution of polyvinyl alcohol (Kuraray PVA-105) in a ball mill for one day so as to have a volume average particle size of 3 CL or smaller. Eighty grams of the pigment were dispersed together with 160 g of a 0.5% solution of sodium hexametaphosphate in a homogenizer. Five grams of the electron-donating dye precursor dispersion, 10 g of the electron-accepting compound dispersion, 5 g of the heat-fusible substance dispersion, 2 g of the discoloration inhibitor dispersion, and 22 g of the pigment dispersion were mixed, and to the mixture were added 3 g of a 21% emulsion of zinc stearate and 5 g of a 2% aqueous solution of sodium di(2-ethylhexyl)-sulfosuccinate. The resulting coating composition was coated on fine paper having a basis weight of 50 g/m2 with a wire bar, followed by drying in an oven at 50 C to obtain Heat-sensitive Color Forming Layers (A) to (K) as shown in Table 1.
Table 1 Heat Sensitive Electron Color Form- Electron-Donating Accepting Heat-Fusible Discoloration ing Layer Dye Precursor Compound Substance Inhibitor Pigment A Crystal Violet Lactone 2,2-bis(p- stearamide none calcium hydroxydi- carbonate phenyl)propane B 2-Anilino-3-chloro-6-di- " " none " ethyl amino fluoran C 1:1 (by weight) mixture of " ss-naphthyl- none " 2-anilino-3-chloro-6-di- benzyl ether ethyl amino fluoran and 2anilino-3-methyl-6-N-methyl N-cyclohexyl amino fluoran D 1:1 (by weight) mixture of " phenyl 1- 1,1,3-tris(2- " 2-anilino-3-chloro-6-di hydroxy-2- methyl-4ethyl amino fluoran and 2- naphthoate hydroxy-5-tanilino-3-methyl-6-N-ethyl- butylphenyl) N-isoamyl amino fluoran butane E 1::1 (by weight) mixture of 1,1-bis(4'- 1-phenoxy-2- " calcined 2-anilino-3-chloro-6-di- hydroxy- (4-ethyl- kaolin ethyl amino fluoran and 2- phenyl)- phenoxy)ethane anilino-3-methyl-6-N-ethyl- cyclohexane N-furylmethyl amino fluoran Table 1 (cont'd) Heat Sensitive Electron Color Form- Electron-Donating Accepting Heat-Fusible Discoloration ing Layer Dye Precursor Compound Substance Inhibitor Pigment F 1::1 (by weight) mixture of 1,4-bis(p- ss-naphthyl- 1,1,3-tris(2- calcined 2-anilino-3-chloro-6-di- hydroxy- benzyl ether methyl-4- kaolin ethyl amino fluoran and 2- cumyl)ben- hydroxy-5-tanilino-3-methyl-6-N-ethyl- zene butyl phenyl) N-isoamyl amino fluoran butane G 2-Anilino-3-methyl-6-N- benzyl 4- none 2,2'-methyl- aluminum methyl-N-cyclohexyl amino- hydroxy- ene-bis(6-t hydroxide fluoran benzoate butyl-4-methylphenol) H 2-Anilino-3-methyl-6-N- " phenyl 1- 4,4'-thio- calcium methyl-N-cyclohexyl amino- hydroxy-2- bis(3-methyl- carbonate fluoran naphthoate 6-t-butylphenol) I 1::1 (by weight) mixture of dimethyl 3- " 1,1,3-tris- amorphous 2-anilino-3-chloro-6-di- hydroxy-o- (2-methyl-4- silica ethyl amino fluoran and 2- phthalate hydroxy-5-tanilino-3-methyl-6-N-ethyl- butyl phenyl) N-furylmethyl amino fluoran butane J 2-Anilino-3-methyl-6-N- bis-(2-(4- 1-phenoxy-2- 4,4'-butyl- calcium methyl-N-cyclohexyl amino- hydroxyphe- (4-ethoxy- idene-bis(6- carbonate fluoran nylthio)- phenoxy)- t-butyl-3ethoxy)me- ethane methylphenol thane Table 1 (cont'd) Heat Sensitive Electron Color Form- Electron-Donating Accepting Heat-Fusible Discoloration ing Layer Dye Precursor Compound Substance Inhibitor Pigment K 1::1 (by weight) mixture of 1,1-bis(4'- ss-naphthyl- 1,1,3-tris(2- calcium 2-anilino-3-chloro-6-di- hydroxyphe- benzyl ether methyl-4-hy- carbonate ethyl amino fluoran and 2- nyl)cyclo- droxy-5-tanilino-3-methyl-6-N-methyl- hexane butyl phenyl) N-cyclohexyl amino fluoran butane Note: Calcium carbonate: Brilliant-15, produced by Shiraishi Kogyo K.K.
Calcined kaolin: Ansilex-93, produced by Engel Halt Co.
Aluminum hydroxide: Haijiraito-H42M, produced by Showa Keikinzoku K.K.
Amorphous silica: Mizukosil P-527, produced by Mizusawa Kagaku K.K.
EXAMPLES 1 TO 20 A hundred grams of a 5% solution of the polymer of the invention shown in (A) of Table 2 or 100 g of a mixture comprising a 5% solution of the polymer shown in (A) of Table 2 and a 5% solution of the polymer shown in (B) of Table 2 was mixed with 15 g of a dispersion of the pigment shown in Table 3 (the dispersion was prepared in the same manner as in the preparation of the heat-sensitive color forming layer), 4 g of a 21% emulsion of zinc stearate and 1 g of a 2% aqueous solution of sodium di-(2-ethylhexyl)sulfosuccinate to prepare a coating composition.The resulting composition was coated on each of the above-prepared heat-sensitive color forming layers with a wire bar to a dry coverage of 2 g/m2, dried in an oven at 50"C, followed by supercalendering so as to have a Bekk's degree of surface smoothness of 800 seconds or more to thereby obtain a heat-sensitive recording material according to the present invention.
COMPARATIVE EXAMPLE 1 TO 10 A coating composition using the polymer shown in (B) of Table 2 was coated on each of the heat-sensitive color forming layers as prepared above in the same manner as in above Examples.
Writing was made on each of the thus obtained samples with a commercially available fluorescent pen, andcolor formation reaction on the white background and discoloration of recorded letters of the heat-sensitive recording material were visually observed. Evaluations were made according to the following standards.
Color Formation Reaction on Discoloration of Evaluation White Background Recorded Letters No color formation was No discoloration was observed at all observed at all substantially no color Substantially no dis O formation was observed coloration was ob served Color formation was ob- Discoloration was ob A served, but the color served, but the let of the fluorescent pen ters were recognizable was recognizable X Color formation took Discoloration took place to make the color place to make the of the fluorescent pen letters unrecognizable unrecognizable The results of evaluation are shown in Table 5.
It can be seen from the results of Table 5 that the samples according to the present invention exhibit extremely excellent resistance to writing with a fluorescent pen.
Table 2 Degree of Swelling to Polymer Used in Table 3 Trade Name Maker Triethanol amine (wt%) Group (A) alkyl ketene dimer Aquapel AKD Kao Atlas Co., Ltd. 12 polyvinyl pyrrolidone K-30 Tokyo Kasei K.K. 45 diisobutylene-maleic HR-303 Hitachi Chemical Co., 18 anhydride copolymer Ltd.
hydroxypropyl HPC Nippon Soda K.K. 29 cellulose polyamidepolyurea Epinox Dic-Hercules Co. 16 formaldehyde styrene-maleic acid Polymalon 385 Arakawa Kagaku K.K. 12 copolymer NH4 salt sodium caseinate Casein Wako Pure Chemical 16 Industries, Ltd.
reactive acrylic Aron S4002 Toa Gosei Chemical 14 ester Industry Co., Ltd.
styrene-maleic acid SR-402 Sumitomo Chemical Co., 13 copolymer Na salt Ltd.
Table 2 (cont'd) Degree of Swelling to Polymer Used in Table 3 Trade Name Maker Triethanol amine (wt%) Group (B) completely saponified PVA 117 Kuraray Co., LTd. 2 polyvinyl alcohol incompletely saponi- PVA 217 Kuraray Co., Ltd. 4 fied polyvinyl alcohol silicon - modified R-2105 Kuraray Co., Ltd. 2 polyvinyl alcohol polyacryl amide F-007 Showa Denko K.K. 7 oxidized starch MS 3800 Japan Maize Product 2 Co., Ltd.
hydroxyethyl BL-15 Fuji Chemical K.K. 3 cellulose Table 3 Pigment Ratio of Color Used in Polymer Example Forming Protective Polymer-(1) Used Polymer-(2) Used Used No. Layer Layer in Protective Layer in Protective Layer (1)/(2) 1 A aluminum alkyl ketene dimer - 1/0 hydroxide 2 B calcium polyvinyl pyrrolidone - 1/0 carbonate 3 C amorphous diisobutylene-maleic - 1/0 silica anhydride copolymer 4 D kaolin hydroxypropyl cellulose - 1/0 5 E calcined polyamidepolyurea- - 1/0 kaolin formaldehyde 6 F aluminum styrene/maleic acid - 1/0 hydroxide copolymer NH4 salt 7 G amorphous sodium caseinate - 1/0 silica 8 H kaolin reactive acrylic ester - 1/0 9 I calcined hydroxypropyl cellulose - 1/0 kaolin 10 J calcium styrene-maleic acid - 1/0 carbonate copolymer Na salt Table 3 (cont'd) Pigment Ratio of Color Used in Polymer Example Forming Protective Polymer-(1) Used Polymer-(2) Used Used No. Layer Layer in Protective Layer in Protective Layer (1)/(2) 11 K kaolin styrene-maleic acid - 1/0 copolymer NH4 salt 12 C kaolin alkyl ketene dimer oxidized starch 9/1 13 D aluminum polyvinyl pyrrolidone polyacryl amide 6/4 hydroxide 14 E calcium hydroxypropyl cellulose hydroxyethyl cellulose 9/1 carbonate 15 F kaolin diisobutylene-maleic hydroxyethyl cellulose 8/2 anhydride copolymer 16 G kaolin styrene-maleic acid oxidized starch 7/3 copolymer Na salt 17 H aluminum styrene-maleic acid silicon-modified poly- 8/2 hydroxide copolymer Na salt vinyl alcohol 18 I kaolin sodium caseinate completely saponified 9/1 polyvinyl alcohol 19 J amorphous reactive acrylic ester completely saponified 8/2 silica polyvinyl alcohol Table 3 (cont'd) Pigment Ratio of Color Used in Polymer Example Forming Protective Polymer-(1) Used Polymer-(2) Used Used No. Layer Layer in Protective Layer in Protective Layer (1)/(2) 20 K kaolin styrene-maleic acid incompletely saponified 9/1 copolymer NH4 salt polyvinyl alcohol Note: Aluminum hydroxide: "Haijiraito H42M" produced by Showa Keikinzoku K.K.
Calcium carbonate: "Brilliant 15" produced by Shiraishi Kogyo K.K.
Kaolin: "Kaobrite" produced by Georgia Pacific Co.
Calcined kaolin: "Ansilex 93" produced by Engel Halt Co.
Amorphous silica: "Mizukosil P-527" produced by Mizusawa Kagaku K.K.
Table 4 Compara- Pigment Ratio of tive Color Used in Polymer Example Forming Protective Polymer-(1) Used Polymer-(2) Used Used No. Layer Layer in Protective Layer in Protective Layer (1)/(2) 1 A aluminum completely saponified - 1/0 hydroxide polyvinyl alcohol 2 B calcium incompletely saponi- - 1/0 carbonate fied polyvinyl alcohol 3 C amorphous silicon-modified - 1/0 silica polyvinyl alcohol 4 D kaolin polyacryl amide - 1/0 5 E calcined oxidized starch - 1/0 kaolin 6 F calcined hydroxyethyl cellulose - 1/0 kaolin 7 G kaolin completely saponified oxidized starch 1/1 polyvinyl alcohol 8 H kaolin completely saponified silicon-modified poly- 1/1 polyvinyl alcohol vinyl alcohol 9 I calcium polyacryl amide oxidized starch 1/2 carbonate 10 J amorphous hydroxyethyl cellulose completely saponified 8/2 silica polyvinyl alcohol 11 K kaolin silicon-modified poly- hydroxyethyl cellulose 8/2 vinyl alcohol Table 5
Discoloration with Example Foa with Fluorescent Pen ~ Fluorescent Pen No. Yellow *1 Yellow *2 Yellow *3 Pink *9 Brown *5 0 0 0 Go 2 O O O t 0 3 0 0 0 0 0 4 0 Go 0 Go 5 t 0 o o o 6 Q Go O 7 t 0 0 A 8 Qo 0 9 0 0 O Go 10 0 Qo G9 Go 0 11 0 O O O 0 12 0 0 O 13 0 0 O 0 14 0 0 o 15 0 0 0 0 16 0 Go Qo 0 17 Go Q Q O 18 < 0 0 A 19 0 Qo 0 0 20 0 QO Qo Go 0 Table 5 (cont'd) Comparative Discoloration with Example Foa with Fluorescent Pen Fluorescent Pen No. Yellow *1 Yellow *2 Yellow *3 Pink @*4 Brown *5 1 X # X A X 2 X X X X X 3 X X # X X 4 X A A A 5 X # X X X 6 X X X X X 7 X X X X X 8 X A A A 9 X X X X X 10 X A A A A 11 X X X X X Note: 1: Made by Pilot Ink Co., Ltd.
*2: Made by Pentel Co., Ltd.
*3: Made by Zebra Co., Ltd.
*4: Made by Pentel Co., Ltd.
*5: Made by Zebra Co., Ltd.
SECOND EMBODIMENT Heat-Sensitive Color Forming Layer: Twenty grams each of 2-anilino-3-methyl-6-N-methyl-N-cyclohexylaminoflSoran as an electrondonating dye precursor, benzyl 4-hydroxybenzoate as an electron-accepting compound, phenyl 1hydroxy-2-naphthoate as a heat-fusible substance, and 4,4'-thio-bis(3-methyl-6-butylphenol) as a discoloration inhibitor were dispersed together with 100 g of a 5% aqueous solution of polyvinyl alcohol (Kuraray PVA-105) in a ball mill for one day so as to have a volume average particle size of 3 ,um or smaller.
Eighty grams of calcium carbonate (Unibur 70, produced by Shiraishi Kogyo K.K.) as a pigment were dispersed together with 160 g of a 0.5% solution of sodium hexametaphosphate in a homogenizer. Five grams of the 2-anilino-3-methyl-6-N-methyl-N-cyclohexylaminofluoran dispersion, 10 g of the benzyl 4-hydroxybenzoate dispersion, 5 g of the phenyl 1-hydroxy-2-naphthoate dispersion, 2 g of the 4,4'-thio-bis(3-methyl-6-t-butylphenol) dispersion and 22 g of the calcium carbonate dispersion were mixed, and 3 g of a 21% emulsion of zinc stearate and 5 g of a 2% aqueous solution of sodium di(2-ethylhexyl)sulfosuccinate were added to the mixture to prepare a coating composition.The resulting coating composition was coated on fine paper having a basis weight of 50 g/m2 with a wire bar to a dry coverage of 5 g/m2, followed by drying in an oven at 500C to obtain a heat-sensitive color forming layer.
EXAMPLE 21 A coating composition obtained by mixing 100 g of a 5% aqueous solution of polyvinyl alcohol (Kuraray PVA-105), 15 g of a dispersion of heavy kaolin (Kaobrite, produced by Shiraishi Kogyo K.K.; oil absorption: 35 my/100 g), 3 g of a 21% emulsion of zinc stearate and 1 g of a 2% aqueous solution of sodium di(2-ethylhexyl)sulfosuccinate was coated on a heat-sensitive color forming layer as obtained by the above-described method with a wire bar to a dry coverage of 2 g/m2, followed by drying in an over at 50"C. The coated layer was then subjected to supercalendering so as to have a Bekk degree of surface smoothness of 800 seconds or more, to thereby obtain a heat-sensitive recording material according to the second embodiment of the present invention.
EXAMPLE 22 A heat-sensitive recording material was obtained in the same manner as in Example 21 but replacing the heavy kaolin with aluminum hydroxide (Haijiraito H-43, produced by Showa Denko K.K.; oil absorption: 22 my/100 g).
EXAMPLE 23 A heat-sensitive recording material was obtained in the same manner as in Example 21 but changing the amount of the heavy kaolin dispersion to 10 g.
EXAMPLE 24 A heat-sensitive recording material was obtained in the same manner as in Example 21 but changing the amount of the heavy kaolin with dispersion to 5 g.
COMPARA TIVE EXAMPLE 11 A heat-sensitive recording material was obtained in the same manner as in Example 21 but replacing the heavy kaolin with calcined kaolin (Ansilex-93; oil absorption: 78 ml/100 g).
COMPARATIVE EXAMPLE 12 A heat-sensitive recording material was obtained in the same manner as in Example 21 but replacing the heavy kaolin with amorphous silica (Mizukosil P-832; oil absorption 140 ml/100 g).
COMPARATIVE EXAMPLE 13 A heat-sensitive recording material was obtained in the same manner as in comparative Example 11 but changing the amount of the calcined kaolin dispersion to 10 g.
The running property was evaluated by obtaining 100 or more copies of Test Chart No. 2 according to The Image Electronics Institute by using a high-speed facsimile (UF-2, produced by Matsushita Denso K.K.). The anti-blot property was evaluated by visually observing ink blots on both the recorded area and the white background of the heat-sensitive recording material upon application of an aqueous ink pen.
The results obtained are shown in Table 6.
Table 6
Running Anti-Blot Example Property on Property to No. Facsimile * Aaueous Ink* Example 21 Go Go 22 Qo 0 " 23 0 Go " 0 0 Comparative Example 11 X A 12 A X " 13 X X Note: *: 6 : very excellent excellent acceptable for practical use X : unacceptable for practical use THIRD EMBODIMENT EXAMPLE 25 Preparation of Heat-Sensitive Recording Layer Coating Composition: Twenty grams of 2-anilino-3-methyl-6-N-cyclohexyl-N-methylaminofluoran as a color former and 100 g of a 5% aqueous solution of polyvinyl alcohol (saponification degree: 98%; degree of polymerization: 1,000; produced by Kuraray Co., Ltd.) were dispersed in a ball mill for one day to obtain Dispersion (A').
Similarly, 10 g of benzyl p-hydroxybenzoate, 5 g of 2,2'-methylene-bis(4-methyl-6-t-butylphe- nol) and 75 g of a 5% aqueous solution of polyvinyl alcohol were dispersed in a ball mill for one day to prepare Dispersion (B').
Fourty grams of calcium carbonate (Brilliant 15 produced by Shiraishi Kogyo K.K.) as a pigment was dispersed together with 60 g of a 1.0% solution of sodium hexametaphosphate in a homogenizer to obtain Dispersion (C').
Dispersion (A'), Dispersion (B') and Dispersion (C') were mixed at a weight ratio of 1:3:1, and to 200 g of the resulting mixture was added 20 g of a 21% dispersion of zinc stearate, followed by sufficiently dispersing to prepare a heat-sensitive coating composition.
The thus prepared coating composition was coated on base paper having a basis weight of 49 g/m2 to a solid coverage of 5 g/m2 and dried at 60"C for 1 minute to prepare a basic heatsensitive recording paper.
A protective layer coating composition having the following formulation was coated on the heatrsensitive color forming layer to a solid coverage of 2.5 g/m2, followed by drying at 50"C for 2 minutes to form a protective layer. The resulting material was subjected to calendering to obtain heat-sensitive recording paper having a degree of smoothness of 1,000 seconds (JIS P8119).
Protective Layer Coating Composition: Thirty-five grams of a 10% ammonium salt of a styrene-maleic acid copolymer (Polymalon 385 produced by Arakawa Kagaku K.K.; degree of polymerization: 2,000), 6 g of a 40% kaolin dispersion (Kaobrite), 1.5 g of a 21% zinc stearate dispersion and 7 g of water were mixed and dispersed to obtain a protective layer coating composition.
Onto the back side of the thus obtained heat-sensitive recording paper was coated a back coat coating composition having the following formulation to a solid coverage of 2.5 g/m2 and dried at 50"C for 2 minutes to form a back coat layer, thereby to obtain heat-sensitive recording paper according to the present invention.
Back Coat Coating Composition: Fifteen grams of a 25% aqueous solution of an ammonium salt of a styrene-maleic acid copolymer, 12.5 g of a 50% calcium carbonate dispersion and 12.5 g of water were mixed and dispersed to obtain a back coat coating composition.
EXAMPLE 26 Heat-sensitive recording paper was obtained in the same manner as in Example 25 but using the following protective layer coating composition.
Thirty-five grams of a 10% styrene-maleic acid copolymer sodium salt (Sumirezresin SR-402, produced by Sumitomo Chemical Co., Ltd.), 6 g of a 40% kaolin dispersion, 1.5 g of a 21% zinc stearate dispersion and 7 g of water were mixed and dispersed to obtain a protective layer coating composition.
EXAMPLE 27 Heat-sensitive recording paper was obtained in the same manner as in Example 25 but using the following protective layer coating composition.
Twenty-eight grams of a 10% styrene-maleic acid copolymer ammonium salt, 7 g of a 10% aqueous solution of polyvinyl alcohol (PVA-217, produced by Kuraray Co., Ltd.; saponification degree: 87%; degree of polymerization: 1,700), 6 g of a 40% kaolin dispersion, 1.5 g of a 21% zinc stearate dispersion and 7 g of water were mixed and dispersed to obtain a protective layer coating composition.
EXAMPLE 28 Heat sensitive recording paper was obtained in the same manner as in Example 25 but using the following protective layer coating composition.
Thirty-five grams of a 10% styrene-maleic acid copolymer ammonium salt partially esterified product (SMA 1440, produced by ARCO Chemical Co., Ltd.; degree of polymerization: 1,000), 6 g of a 40% kaolin dispersion, 1.5 g of a 21% zinc stearate dispersion and 7 g of water were mixed and dispersed.
COMPARATIVE EXAMPLE 14 Heat-sensitive recording paper was obtained in the same manner as in Example 25 but using the following protective layer coating composition.
Thirty-five grams of a 10% polyvinyl alcohol (PVA-110, produced by Kuraray Co., Ltd.; saponification degree: 98%; degree of polymerization: 500), 6 g of a 40% kaolin dispersion, 1.5 g of a 21% zinc stearate dispersion and 7 g of water were mixed and dispersed to obtain a protective layer coating composition.
COMPARATIVE EXAMPLE 15 Heat-sensitive recording paper was obtained in the same manner as in Example 25 but using the following protective layer coating composition.
Thirty-five grams of a 10% starch (MS-3800, produced by Nisshoku K.K.), 6 g of a 40% kaolin dispersion, 1.5 g of a 21% zinc stearate dispersion and 7 g of water were mixed and dispersed to obtain a protective layer coating composition.
COMPARATIVE EXAMPLE 16 Heat-sensitive recording paper was obtained in the same manner as in Example 25 but using the following protective layer coating composition.
Thirty-five grams of a 10% diisobutylene-maleic acid copolymer ammonium salt (Isobam 04, produced by Kuraray Co., Ltd.), 6 g of a 40% kaolin dispersion, 1.5 g of a 21% zinc stearate dispersion and 7 g of water were mixed and dispersed to obtain a protective layer coating composition.
COMPARATIVE TEST 1 Comparative tests were conducted on the heat-sensitive recording paper samples obtained in the foregoing examples and comparative examples as follows: (1) Blocking qn a surface of the heat-sensitive recording paper was dropped 0.5 ml of water, and base paper was superposed thereon. After air-drying for 1 hour, the base paper was peeled apart to observe adhesiveness between the heat-sensitive recording paper and the base paper. The less adhesive, the better. The results of evaluation were graded "excellent", "good" or "poor".
(2) Solvent Resistance The heat-sensitive recording paper was evaluated for fog with a fluorescent pen (Keiko Pen 2, produced by ZEBRA Co., Ltd.; and Spot Writer produced by Pilot Ink Co., Ltd.) or magic ink.
The results of evaluation were graded "0" "d" or "X". Those samples which did not generate fog were graded "0"; those which generated fog but whose original color could be identified were graded "A"; and samples whose original color could not be identified due to fog were graded "X".
These results are shown in Table 7. It can be seen therefrom that the heat-sensitive recording paper in accordance with the present invention are excellent in anti-blocking property and chemical resistance.
Table 7 Example Anti- chemical Resistance No. Blocking Keiko Pen Spot Writer Magic Ink Example 25 excellent G O G 26 26 excellent 0 G G 27 excellent G G G 28 excellent 0 G G Comparative Example 14 poor X X O 15 poor X A X 16 poor A A G FOURTH EMBODIMENT EXAMPLE 29 Preparation of Heat-Sensitive Recording Layer Coating Composition:: Ten grams of 2-anilino-3-methyl-6-N-cyclohexyl-N-methylaminofluoran as a color former, 25 g of a 10% aqueous solution of polyvinyl alcohol (saponification degree: 98%; degree of polymerization: 1,000) and 25 g of water were dispersed in a ball mill for one day to obtain Dispersion (A"). Similarly, 10 g of benzyl p-hydroxybenzoate, 5 g of 2,2'-methylene-bis(4-methyl-6-t-butylphenol), 15 g of calcium carbonate (Brilliant 15, produced by Shiraishi Kogyo K.K.), 25 g of a 10% aqueous solution of polyvinyl alcohol (saponification degree: 98%; degree of polymerization: 1,000) and 50 g of water were dispersed in a ball mill for one day to obtain Dispersion (B").
Dispersion (A") and Dispersion (B") were mixed at a weight ratio of 1:3, and to 200 g of the resulting mixture was added 15 g of a 21% dispersion of zinc stearate, followed by sufficiently dispersing to prepare a heat-sensitive coating composition.
The thus prepared coating composition was coated on base paper having a basis weight of 47 g/m2 to a dry coverage of 5 g/m2 and dried at 60"C for 1 minute to prepare basic heatsensitive recording paper.
A protective layer coating composition having the following formulation was coated on the heat-sensitive color forming layer to a solid coverage of 2.5 g/m2 and dried at 500C for 2 minutes to form a protective layer, which was then subjected to calendering to obtain heatsensitive recording paper having a degree of smoothness of 850 seconds (JIS) P8119).
Protective Layer Coating Composition: A mixture of 100 g of a 10% polyvinyl alcohol, 25 g of 40% kaolin (Kaobrite) and 40 g of water was dispersed to obtain a protective layer coating composition.
A back coat layer coating composition having the following formulation was coated on the back of the thus obtained heat-sensitive recording paper to a solid coverage of 2.5 g/m2, followed by drying at 50"C for 2 minutes to form a back coat layer, thereby obtaining heatsensitive recording paper according to the present invention.
Back Coat Layer Coating Composition: 20% Colloidal silica (Snowtex 20, produced by Nissan Chemicals Industries, Ltd.; particle size: 10 to 20 ,um; pH 9.5 to 10).
EXAMPLE 30 Heat-sensitive recording paper was obtained in the same manner as in Example 29 but using the following backing layer: 20% Colloidal silica (Snowtex C, produced by Nissan Chemicals Industries, Ltd.; particle size: 10 to 20 Am; pH 8.5 to 9.0).
EXAMPLE 31 Heat-sensitive recording paper was obtained in the same manner as in Example 29 but using the following backing layer: A 25% styrene-maleic acid copolymer ammonium salt (Polymalon 385, produced by Arakawa Kagaku, K.K.; degree of polymerization: 2,000) (1.5 g) and 25 g of 20% colloidal silica (Snowtex C, produced by Nissan Chemicals Industries, Ltd.) were mixed and dispersed to form a dispersion.
COMPARATIVE EXAMPLE 17 Heat-sensitive recording paper was obtained in the same manner as in Example 29 but using the following backing layer: Thirty grams of 10% polyvinyl alcohol (produced by Kuraray Co., Ltd.; saponification degree: 98%; degree of polymerization: 1,000), 10 g of a 40% dispersion of kaolin (Kaobrite) produced by Shiraishi Kogyo K.K.) and at least 32.5 g of water were mixed to obtain a dispersion.
COMPARATIVE EXAMPLE 18 Heat-sensitive recording paper was obtained in the same manner as in Example 29 but using the following backing layer: Fifteen grams of a 25% isobutylene-maleic acid copolymer ammonium salt (Isobam 04, produced by Kuraray Co., Ltd.), 12.5 g of 50% calcium carbonate and at least 12.5 g of water were mixed and dispersed.
COMPARATIVE EXAMPLE 19 Heat-sensitive recording paper was obtained in the same manner as in Example 29 but using the following backing layer: Ten grams of 20% starch (MS-4600, produced by Nisshoku K.K.), 6 g of 50% calcium carbonate, and at least 17 g of water were mixed and dispersed.
COMPARATIVE TEST 2 The heat-sensitive recording paper samples obtained in the foregoing examples and comparative examples were subjected to comparative test as follows: (1) Blocking On a surface of the heat-sensitive recording paper was dropped 0.5 ,a1 of water, and base paper was superposed thereon. After air-drying for 1 hour, the base paper and the heat-sensitive recording paper were peeled apart to observe adhesiveness therebetween. The less adhesive, the better. The results of evaluation were graded "excellent", "good" or "poor".
(2) Sheet Curling A4-sized recording paper was conditioned in a thermo-hygrostat at 30 C, 90% for 1 hour, at 25"C, 65% for 1 hour, and then at 20"C, 35% for 1 hour. Thereafter, curling was evaluated by measuring the heights of the four corners of the recording paper and obtaining an average. The evaluation was expressed by the following symbols: -# # #+ curling toward almost no curling toward the back coat curling the heat-sensi tive color form ing layer (3) Running Property Recording was performed on the heat-sensitive recording paper by the use of a heat-sensitive facsimile (UF-920, produced by Matsushita Denso, K.K.) to observe sticking or adhesion to a platen roll.
The results obtained are shown in Table 8 below. It can be seen therefrom that the heat sensitive recording paper in accordance with the present invention is excellent in anti-stick property, anti-block property and anti-curling property.
Table 8 Anti-Stick Anti-Block Anti-Curling Property Property Property Example 29 excellent excellent Example 30 excellent excellent Example 31 excellent excellent Comparative Example 17 excellent poor Example 18 good poor + Example 19 good poor +

Claims (25)

1. A heat-sensitive recording material comprising a support having provided thereon a heatsensitive color forming layer containing a colorless to lightly colored electron-donating dye precursor and an electron-accepting compound capable of reacting with said electron-donating dye precursor upon heating to develop a color, which is characterized in that a protective layer containing a polymer whose degree of swelling in triethanolamine is not less than 10% by weight is provided on said heat-sensitive color forming layer.
2. A heat-sensitive recording material comprising a support having provided thereon a heatsensitive color forming layer containing a colorless to lightly colored electron-donating dye precursor and an electron-accepting compound capable of reacting with said electron-donating dye precursor upon heating to develop a color, which is characterized in that a protective layer provided on said heat-sensitive color forming layer contains inorganic pigment particles having an oil absorption of not more than 50 my/100 g.
3. A heat-sensitive recording material comprising a support having provided thereon a heatsensitive color forming layer containing a colorless to lightly colored electron-donating dye precursor and an electron-accepting compound capable of reacting with said electron-donating dye precursor upon heating to develop a color, which is characterized in that a protective layer containing an alkali salt of a styrene-maleic acid copolymer is provided on said heat-sensitive color forming layer.
4. A heat-sensitive recording material comprising a support having provided thereon a heatsensitive color forming layer containing a colorless to lightly colored electron-donating dye precursor and an electron-accepting compound capable of reacting with said electron-donating dye precursor upon heating to develop a color and further provided thereon a protective layer containing a water-soluble polymeric binder and a pigment, which is characterized in that a back coat layer containing colloidal silica is provided on the back side of the support.
5. A heat-sensitive recording material of any one of claims 1, 2 or 3, which is characterized in that a back coat layer containing colloidal silica is provided on the back side of a support.
6. A recording material according to Claim 1, wherein said protective layer polymer is polyvinyl pyrrolidone, an alkyl ketene dimer, sodium caseinate, hydroxypropyl cellulose, polyacrylic acid, a polyacrylate or a copolymer containing maleic acid.
7. A recording material according to Claim 1 or 6, wherein the protective layer contains a pigment and/or a metal soap or a wax.
8. A recording material according to Claim 7, wherein the amount of pigment is 0.5 to 4 times the weight of the polymer.
9. A recording material according to Claim 7 or 8, wherein the pigment is zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, agalmatolite, kaolin, aluminium hydroxide, silica amorphous silica or colloidal silica.
10. A recording material according to Claim 2, wherein the pigment has a particle size of 1 to 5 millimicrons.
11. A recording material as claimed in Claim 2 or 10, wherein the pigment is zinc oxide, barium sulfate, titannium oxide, agalmatolite, heavy kaolin or aluminium hydroxide.
12. A recording material according to Claim 2, 10 or 11, wherein the amount of pigment is 20 to 150% by weight of the weight of binder in the layer.
13. A recording material according to Claim 2, 10, 11 or 12, wherein the protective layer contains a metal soap or a wax.
14. A recording material according to Claim 3, wherein the salt in the protective layer has a degree of polymerisation of 500 to 5000.
15. A recording material according to Claim 3 or 14, wherein the proportion of styrene in the salt is 50 to 80 wt%.
16. A recording material according to Claim 3, 14 or 15, wherein the protective layer includes a water-soluble polymer or polymeric latex, and/or a pigment or lubricant.
17. A recording material according to Claim 16, wherein the polymer or latex comprises polyvinyl alcohol, methyl cellulose, starch, carboxymethyl cellulose, an alkali salt of a copolymer of diisobutylene and maleic acid, or of a copolymer of styrene and acrylic acid, a polyamide resin, on a polyacrylamide resin.
18. A recording material according to Claim 16, wherein the polymeric latex comprises a latex of a styrene-butadiene copolymer, carboxy-modified styrene-butadiene copolymer, styrenebutadiene-vinylpyridine terpolymer, acrylic ester copolymer, modified acrylic ester copolymer, styrene copolymer, vinyl acetate copolymer, vinyl acetate-acrylic acid copolymer, vinyl acetateethylene copolymer, acrylic acid-butadiene copolymer or acrylic acid-styrene-butadiene copolymer.
19. A recording material according to Claim 16, 17 or 18, wherein the polymer or latex is present in a proportion of from 5 to 50% by weight based on the weight of the copolymer alkali salt.
20. A recording material according to Claim 16, wherein the pigment in the protective layer is zinc oxide, calcium carbonate, kaolin, barium sulfate, titanium oxide, lithopone, talc, agalmatolite, aluminium hydroxide, calcined kaolin or a silica powder.
21. A recording material according to Claim 4 or 5, wherein the polymeric binder is polyvinyl alcohol, methyl cellulose, starch, carboxymethyl cellulose, a styrene-maleic acid copolymer, a diisobutylene-maleic acid copolymer, a polyamide resin or a polyacrylamide resin.
22. A recording material according to Claim 4, 5 or 21, wherein the pigment is zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, agalmatolite, kaolin, calcined kaolin, aluminium hydroxide, a urea-formaldehyde resin or a polyethylene powder.
23. A recording material according to any preceding claim, wherein the protective layer is coated at a dry coverage of 0.2 to 5.0 grams per square meter.
24. A heat-sensitive recording material as claimed in any of Claims 1 to 5, substantially as hereinbefore described with reference to any of Examples 1 to 31.
25. A recording made by iocally heating the recording layer of a material as claimed in any preceding claim.
GB08618256A 1985-07-25 1986-07-25 Heat-sensitive recording material Withdrawn GB2178183A (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP60164974A JPS6225083A (en) 1985-07-25 1985-07-25 Thermal recording material
JP60172020A JPH0662004B2 (en) 1985-08-05 1985-08-05 Thermal recording paper
JP60175397A JPS6235877A (en) 1985-08-09 1985-08-09 Thermal recording paper
JP60194640A JPS6255189A (en) 1985-09-03 1985-09-03 Thermal recording material

Publications (2)

Publication Number Publication Date
GB8618256D0 GB8618256D0 (en) 1986-09-03
GB2178183A true GB2178183A (en) 1987-02-04

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GB08618256A Withdrawn GB2178183A (en) 1985-07-25 1986-07-25 Heat-sensitive recording material

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0405946A2 (en) * 1989-06-30 1991-01-02 New Oji Paper Co., Ltd. Method for producing a heat-sensitive recording material
EP0408339A2 (en) * 1989-07-13 1991-01-16 Fuji Photo Film Co., Ltd. Heat-sensitive recording material
FR2670435A1 (en) * 1990-12-17 1992-06-19 Ricoh Kk Heat-sensitive recording material
EP0941867A1 (en) * 1998-03-09 1999-09-15 Fuji Photo Film Co., Ltd. Heat-sensitive recording material having a protective layer
EP1084860A2 (en) * 1999-09-17 2001-03-21 The Pilot Ink Co., Ltd. Thermochromic microencapsulated pigments
WO2005108102A1 (en) * 2004-04-27 2005-11-17 Hewlett-Packard Development Company, L.P. Multilayered color-forming compositions and imaging methods

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2094496A (en) * 1981-03-05 1982-09-15 Ricoh Kk Thermosensitive recording materials
GB2110399A (en) * 1981-11-18 1983-06-15 Dainippon Printing Co Ltd Thermosensitive recording material
GB2114767A (en) * 1982-02-05 1983-08-24 Ricoh Kk Thermosensitive recording sheets
EP0111335A2 (en) * 1982-12-11 1984-06-20 Kanzaki Paper Manufacturing Company Limited Heat-sensitive recording material
GB2147428A (en) * 1983-09-27 1985-05-09 Sanyo Kokusaku Pulp Co Heat-sensitive recording material
GB2162651A (en) * 1984-07-27 1986-02-05 Ricoh Kk Two-colour thermosensitive recording labels

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2094496A (en) * 1981-03-05 1982-09-15 Ricoh Kk Thermosensitive recording materials
GB2110399A (en) * 1981-11-18 1983-06-15 Dainippon Printing Co Ltd Thermosensitive recording material
GB2114767A (en) * 1982-02-05 1983-08-24 Ricoh Kk Thermosensitive recording sheets
EP0111335A2 (en) * 1982-12-11 1984-06-20 Kanzaki Paper Manufacturing Company Limited Heat-sensitive recording material
GB2147428A (en) * 1983-09-27 1985-05-09 Sanyo Kokusaku Pulp Co Heat-sensitive recording material
GB2162651A (en) * 1984-07-27 1986-02-05 Ricoh Kk Two-colour thermosensitive recording labels

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0405946A2 (en) * 1989-06-30 1991-01-02 New Oji Paper Co., Ltd. Method for producing a heat-sensitive recording material
EP0405946A3 (en) * 1989-06-30 1991-05-02 Kanzaki Paper Manufacturing Co., Ltd. Method for producing a heat-sensitive recording material
EP0408339A2 (en) * 1989-07-13 1991-01-16 Fuji Photo Film Co., Ltd. Heat-sensitive recording material
EP0408339A3 (en) * 1989-07-13 1991-07-31 Fuji Photo Film Co., Ltd. Heat-sensitive recording material
FR2670435A1 (en) * 1990-12-17 1992-06-19 Ricoh Kk Heat-sensitive recording material
US5189007A (en) * 1990-12-17 1993-02-23 Ricoh Company, Ltd. Thermosensitive recording material
EP0941867A1 (en) * 1998-03-09 1999-09-15 Fuji Photo Film Co., Ltd. Heat-sensitive recording material having a protective layer
US6197724B1 (en) 1998-03-09 2001-03-06 Fuji Photo Film Co., Ltd. Heat-sensitive recording material
EP1084860A2 (en) * 1999-09-17 2001-03-21 The Pilot Ink Co., Ltd. Thermochromic microencapsulated pigments
EP1084860A3 (en) * 1999-09-17 2001-10-04 The Pilot Ink Co., Ltd. Thermochromic microencapsulated pigments
US6494950B1 (en) 1999-09-17 2002-12-17 The Pilot Ink Co., Ltd. Thermochromic microencapsulated pigments
WO2005108102A1 (en) * 2004-04-27 2005-11-17 Hewlett-Packard Development Company, L.P. Multilayered color-forming compositions and imaging methods

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