JPH03143679A - Thermally sensitive recording material - Google Patents

Abstract

PURPOSE:To enhance the capacity to maintain resistance against damage, chemical, water-proofness and prevent sticking by providing a protecting layer consisting of resin cured by ultraviolet beam on an at least single ply thermally sensitive layer containing an electron-donative dye precursor in a microcapsule. CONSTITUTION:A fog generated during the manufacture of a thermally sensitive record ing material can be prevented by incorporating an electron-donative dye precursor in a microcapsule, and at the same time, the material can be preserved fresh and maintain recorded data in satisfactory condition. Then a protecting layer consisting mainly of resin cured by an ultraviolet beam is provided on a thermally sensitive layer formed on a support for the purpose of giving the capacity to maintain resistance against damage and solvent as well as water-proofness to an obtained thermally sensi tive recording material. The resin component cured by an ultraviolet beam which is used for a protecting layer includes optically polymerizable monomer, prepolymer and an optical polymerization initiator as essential components. When the protecting layer is provide, it is recommended that an intermediate layer of water-soluble polymer be provided from a viewpoint of increasing the strength of a coating and preventing unnecessary color development during the application of a protecting layer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material that has excellent feeding suitability for a thermal head.

(Prior art) The thermal recording method has three advantages: (1) no development is required; (2) when the support is paper, the quality of the paper is similar to that of ordinary paper; (3) it is easy to handle; and (4) color density is high. (5) The recording device is simple and inexpensive, and (6) There is no noise during recording, so it has rapidly become popular in the field of facsimiles and printers in recent years, and the applications of thermal recording are also expanding. are doing.

Against this background, in recent years, in order to adapt to multicolor, overhead projectors (
It has been desired to develop a transparent heat-sensitive recording material that can be directly recorded with a thermal head for use in OHP.

In response to such demands, in recent years, microcapsules containing a colorless or light-colored electron-donating dye precursor and a color developer dissolved in an organic solvent that is sparingly soluble or insoluble in water have been emulsified and dispersed on a support. A heat-sensitive recording material has been proposed that has a transparent heat-sensitive layer formed by coating and drying a coating liquid consisting of an emulsified dispersion.
For example, JP-A-63-45084, JP-A-63-9248
No. 9).

(Problem to be Solved by the Invention) If the transparent heat-sensitive layer produced in this way is scratched and opaque areas are produced, not only will the image quality deteriorate when used as an OHP, but it will also be inconvenient when forming multicolor images. It is. Therefore, at least one protective layer is usually provided on the heat-sensitive layer, but this does not reduce the transparency of the heat-sensitive layer.
It is not easy to realize a protective layer that improves scratch resistance (much less to provide a protective layer that can also contribute to preventing sticking).

On the other hand, a protective layer is also provided for conventional heat-sensitive layers that are not transparent heat-sensitive layers from the viewpoint of water resistance, solvent resistance, etc., and a resin layer cured by ultraviolet rays is used as a protective layer of thermal paper. It is also known to be used (Tokuko Sho 58-3)
No. 5478). However, when such a protective layer is provided on a heat-sensitive layer whose color forming component is a combination of an electron-donating dye precursor and a color developer, there is a drawback that background fogging occurs.

As a result of intensive studies to solve these drawbacks, the present inventors and others have found that when the electron-donating dye precursor is encapsulated in microcapsules, the above-mentioned ground force blur does not occur, and the running suitability for thermal heads is significantly improved. The present inventors have discovered that it is extremely excellent as a retaining LN for the transparent heat-sensitive layer because it has excellent scratch resistance.

Accordingly, a first object of the present invention is to provide a heat-sensitive recording material that has excellent scratch resistance, chemical resistance, water resistance, and anti-sticking ability, and does not cause background fog.

A second object of the present invention is to have a transparent heat-sensitive layer, and
The object of the present invention is to provide a heat-sensitive recording material that has not only scratch resistance and chemical resistance but also excellent runnability with respect to a thermal head.

(Means for Solving the Problems) The above aspects of the present invention are such that a coating solution containing microcapsules containing a colorless or light-colored electron-donating dye precursor and a color developer is coated on a support and dried. A heat-sensitive recording material consisting of at least one heat-sensitive layer formed by a heat-sensitive layer and at least one protective layer provided on the heat-sensitive layer, wherein the protective layer is mainly made of a resin cured by ultraviolet rays. This was achieved using a heat-sensitive recording material.

The present invention will be explained in detail below.

As the electron-donating dye precursor used in the heat-sensitive layer of the present invention, a colorless or light-colored one may be appropriately selected from known compounds that develop color by donating electrons or accepting protons such as acids. can. Such compounds have partial skeletons such as lactones, lactams, sultones, spiropyrans, esters, and amides, and these partial skeletons are ring-opened or cleaved upon contact with a color developer. Preferred compounds include Examples include triarylmethane compounds, diphenylmethane compounds, xanthine compounds, thiazine compounds, and spiropyran compounds.

A particularly preferred compound is represented by the following general formula.

In the formula, R1 is an alkyl group having 1 to 8 carbon atoms, Rt is an alkyl group having 4 to 18 carbon atoms, an alkoxyalkyl group, or a tetrahydrofurfuryl group, and R4 is a hydrogen atom or an alkyl group having 1 to 15 carbon atoms. Alternatively, the halogen atom and R4 represent a substituted or unsubstituted aryl group having 6 to 20 carbon atoms.

As the substituent for R4, an alkyl group having 1 to 5 carbon atoms, an alkoxy group, a halogenated alkyl group, and a halogen atom are preferable.

In the present invention, by encapsulating the above-mentioned electron-donating dye in microcapsules, it is possible to prevent fogging during the production of heat-sensitive recording materials, and at the same time to improve the raw and archival properties of heat-sensitive recording materials. It can be made into a good one. In this case, by selecting the wall material and manufacturing method of the microcapsules, it is possible to increase the image density during recording. The amount of electron-donating dye precursor used is 0°05
It is preferable that it is 5.0 g/%.

Examples of the wall material of the microcapsule include polyurethane, polyurea, polyester, polycarbonate, urea-formaldehyde resin, melamine resin, polystyrene, styrene methacrylate copolymer, styrene-acrylate copolymer, gelatin, polyvinylpyrrolidone, polyvinyl alcohol, etc. . In the present invention, two or more of these polymeric substances can also be used in combination.

In the present invention, among the above-mentioned polymeric substances, polyurethane, polyurea, polyamide, polyester, polycarbonate, etc. are preferable, and polyurethane and polyurea are particularly preferable.

The microcapsules used in the present invention are produced by emulsifying a core material containing a reactive substance such as an electron-donating dye precursor, and then
It is preferable to form a wall of a polymeric material around the oil droplet for microencapsulation, in which case the polymeric material or actant is added to the interior of the oil droplet and/or the exterior of the oil droplet.

Details of microcapsules that can be preferably used in the present invention, such as a preferred method for producing microcapsules, are described in, for example, JP-A-59-222716.

Here, the organic solvent for forming the oil droplets can be appropriately selected from those generally used as pressure-sensitive oils, but in particular, an organic solvent suitable for dissolving the color developer described below is used. In this case, it is preferable because it has excellent solubility in leuco dyes, increases the color density and speed of color development during thermal printing, and reduces fogging.

When using the preferable microcapsules produced as described above, the reactive substances contained in the core and outside of the microcapsules can react by passing through the microcapsule walls, which have become permeable to substances by heating. Can be done.

In the present invention, the wall material of the microcapsule is selected,
If necessary, a glass transition point adjusting agent (for example,
277490) to prepare microcapsules consisting of walls with different glass transition points, and by selecting combinations of electron-donating dye precursors and their color developers with different hues. It is possible to achieve intermediate colors. Therefore, the present invention is not limited to monochrome thermal paper, but can also be applied to two-color or multi-color thermal paper and thermal paper suitable for recording images with gradation.

Further, if necessary, a photofading inhibitor described in, for example, JP-A-61-283589, JP-A-61-283590, and JP-A-61-283591 can be appropriately added.

The color developer that causes a color-forming reaction upon thermal melting with the electron-donating dye precursor used in the present invention can be appropriately used from among known ones.For example, as a color developer for leuco dyes, phenolic compounds , triphenylmethane compounds, sulfur-containing phenol compounds, carboxylic acid compounds, sulfone compounds, urea or thiourea compounds, etc. For details, see, for example, Paper and Pulp Technology Times (1985) 49- 54 and pages 65-70. Among these, especially those with a melting point of 50°C ~
250°C is preferable, especially 60°C to 200°
C, phenols and organic acids that are sparingly soluble in water are desirable.

It is preferable to use two or more color developers in combination because the solubility increases.

Among the color developers used in the present invention, particularly preferred ones are represented by the following general formulas (13 to [■]).

\/ [Summer] CIIHffi#+1 (III) m-0~2, n=2~11 (n) R2 is an alkyl group, especially a butyl group, a pentyl group,
Heptyl and octyl groups are preferred.

(IV) R3 is an alkyl group, an aryl group or an aralkyl group, with methyl, ethyl and butyl groups being particularly preferred.

R1 is an alkyl group, an aryl group or an aralkyl group.

In the present invention, a color developer is dissolved in an organic solvent that is sparingly soluble or insoluble in water, and then mixed with an aqueous phase containing a surfactant and having a water-soluble polymer as a protective colloid to emulsify and disperse it. It is preferable to use it in the form of a dispersion in order to improve transparency.

The organic solvent for dissolving the color developer can be appropriately selected from those commonly used as pressure-sensitive oils.
In particular, high-boiling point esters and the following general formulas (V) to (
■) and triallylmethane (e.g.
tritolylmethane, tolyl diphenylmethane),
terphenyl compounds (e.g., terphenyl), alkylated diphenyl ethers (e.g., eva, propyl diphenyl ether), hydrogenated terphenyl (e.g., hexahydroterphenyl), diphenyl ether, etc., which have two or more benzene rings and have a hetero atom It is preferable to use an oil in which the number of is equal to or less than the basic constant.

In the formula, R1 is hydrogen or an alkyl group having 1 to 18 carbon atoms,
R2 represents an alkyl group having 1 to 18 carbon atoms lIP'%
q' represents an integer of 1 to 4, and the total number of alkyl groups is 4 or less.

In addition, the alkyl group of R1 and Rz is preferably an alkyl group having 1 to 8 carbon atoms.

(V1) (V) In the formula, R3 is a hydrogen atom or 7/Iz having 1 to 12 carbon atoms
-1-l group = R' is an alkyl group having 1 to 12 carbon atoms, and n represents 1 or 2;

p R and q t represent integers of 1 to 4; when n=1, the total number of alkyl groups is 4 or less; when n=2, the total number of alkyl groups is 6 or less.

(■) In the formula, R', R'' is a hydrogen atom or a carbon number of 1 to 18,
Represents the same or different alkyl groups.

m represents an integer of 1 to 13, ρ3 and q3 represent integers of 1 to 3, and the total number of alkyl groups is 3 or less.

In addition, the alkyl group of R5 and R' is particularly preferably an alkyl group having 2 to 4 carbon atoms.

Examples of the compound represented by formula (V) include dimethylnaphthalene, diethylnaphthalene, diisopropylnaphthalene, and the like.

Examples of the compound represented by formula (V1) include dimethylbiphenyl, diethylbiphenyl, diisopropylbiphenyl, diisobutylbiphenyl, and the like.

Examples of compounds represented by formula (■) include 1-methyl-1-dimethylphenyl-1-phenylmethane, 1-ethyl-1-dimethylphenyl-1-phenylmethane, 1-
Examples include propyl-1-dimethylphenyl-1-phenylmethane.

Examples of esters include phosphate esters (e.g., triphenyl phosphate, tricresyl phosphate, butyl phosphate, octyl phosphate, talesyl diphenyl phosphate), phthalate esters (
Dibutyl phthalate, 2-ethylhexyl phthalate, ethyl phthalate, octyl phthalate, butylbenzyl phthalate), dioctyl tetrahydrophthalate, benzoate ester (ethyl benzoate, propyl benzoate, butyl benzoate, isopentyl benzoate, benzyl benzoate),
Abietate ester (ethyl abietate, benzyl abietate), dioctyl adipate, isodecyl succinate, dioctyl azelaate, oxalate ester (
dibutyl oxalate, dipentyl oxalate), diethyl malonate, maleate esters (dimethyl maleate, diethyl maleate, dibutyl maleate), tributyl citrate, sorbate esters (methyl sorbate, ethyl sorbate, butyl sorbate) , sebacate ester (dibutyl sebacate, dioctyl sebacate),
Ethylene glycol esters (formic acid monoesters and diesters, butyric acid monoesters and diesters, laurate monoesters and diesters, palmitic acid monoesters and diesters, stearic acid monoesters and diesters, oleic acid monoesters and diesters)
, triacetin, diethyl carbonate, diphenyl carbonate, ethylene carbonate, propylene carbonate, boric acid esters (tributyl borate, tripentyl borate), and the like.

It is also possible to use the above oils together or with other oils.

In the present invention, an auxiliary solvent may be added to the above-mentioned organic solvent as a low boiling point dissolution aid. Particularly preferred examples of such co-solvents include ethyl acetate, isopropyl acetate, butyl acetate and methylene chloride.

The water-soluble polymer to be contained as a protective colloid in the aqueous phase to be mixed with the oil phase in which the color developer is dissolved can be appropriately selected from known anionic polymers, nonioleic polymers, and amphoteric polymers. However, polyvinyl alcohol, gelatin, cellulose derivatives, etc. are preferred.

Further, as the surfactant to be contained in the aqueous phase, one can be appropriately selected from anionic or nonionic surfactants that do not cause precipitation or aggregation by interacting with the above-mentioned protective colloid. .

Preferred surfactants include sodium alkylbenzenesulfonate (eg, sodium lauryl sulfate), dioctyl sodium sulfosuccinate, polyalkylene glycol (eg, polyoxyethylene nonylphenyl ether), and the like.

The emulsified dispersion of a color developer in the present invention is produced by mixing an oil phase containing a color developer and an aqueous phase containing a protective colloid and a surfactant by means commonly used for fine particle emulsification, such as high-speed stirring and ultrasonic dispersion. It can be easily mixed and dispersed using.

A melting point depressant for a color developer may be added to this emulsified dispersion as appropriate. Some of these melting point depressants are
It also functions as a glass transition point regulator for the capsule wall. Examples of such compounds include hydroxy compounds, carbamate ester compounds, sulfonamide compounds, aromatic methoxy compounds, etc. For details, see
For example, it is described in Japanese Patent Application No. 59-244190.

These melting point depressants can be used in an amount of 0.1 to 2 parts by weight, preferably 0.5 to 1 part by weight, per 1 part by weight of the color developer that lowers the melting point. It is preferable to use the color developer and the like that lower the melting point at the same location.When adding the melting point lowering agent into the microcapsule or the microcapsule wall,
It is preferable to add 1 to 3 times the amount added above.

The heat-sensitive recording material of the present invention can be coated using a suitable binder.

Binders include polyvinyl alcohol, methylcellulose, carboxymethylcellulose, hydroxypropylcellulose, gum arabic, gelatin, polyvinylpyrrolidone, casein, styrene-butadiene latex, acrylonitrile-butadiene latex, polyvinyl acetate, polyacrylic acid ester, ethylene-vinyl acetate, etc. Various emulsions such as polymers can be used. The amount used is 0.2 to 5 g/n (solid content).

The heat-sensitive recording material of the present invention can be produced by preparing a coating solution containing microcapsules encapsulating at least an electron-donating dye precursor, a dispersion in which at least a color developer is emulsified and dispersed, and other additives such as a binder. Bar coating, blade coating, air knife coating on supports such as resin films, etc.
It is manufactured by coating and drying by a coating method such as gravure coating, roll coating, spray coating, or dip coating to provide a heat-sensitive layer having a solid content of 2.5 to 25 g/rd.

The paper used for the support is heat extracted pH 6 sized with a neutral sizing agent such as an alkyl ketene dimer.
~9 Neutral paper (described in JP-A-55-14281)
The use of is advantageous in terms of storage stability over time.

In order to prevent the coating from penetrating the paper and to improve the contact between the recording heat head and the heat-sensitive recording layer, Japanese Patent Application Laid-Open No. 57-1166
The paper described in No. 87 and having a Bekk smoothness of 90 seconds or more is advantageous.

Also, paper having an optical surface roughness of 8μ or less and a thickness of 40 to 75μ, described in JP-A-58-136492, JP-A-58-136492.
- Density 0 as described in No. 69097. Paper with an optical contact rate of 9 g/cm' or less and an optical contact rate of 15% or more, JP-A-58-690
Canadian standard freeness described in No. 97 (JIS P812
Paper made from pulp beaten to 400 cc or more in 1) to prevent penetration of coating liquid, JP-A-58-656
No. 95, the glossy side of base paper made by a Yankee machine is used as the coating surface to improve color density and resolution, and JP-A No. 59-35985 describes a method in which the base paper is subjected to corona discharge treatment. Papers with improved coating suitability may also be used in the present invention with good results. In addition to these, any support commonly used in the field of heat-sensitive recording paper can be used as the support of the present invention.

The synthetic resin film used as a support in the present invention has excellent abrasion resistance, water resistance, and chemical resistance, and has a thickness and/or rigidity to the extent that it does not curl when coated with a heat-sensitive layer, etc. during thermal recording. The material may be arbitrarily selected from known materials that do not deform even when heated and have dimensional stability. Examples of such films include polyester films such as polyethylene terephthalate and polybutylene terephthalate, cellulose derivative films such as cellulose triacetate films, polystyrene films, polypropylene films, and polyolefin films such as polyethylene. It can be used as

The thickness of the support used is 20 to 200 .mu.m, particularly preferably 50 to 100 .mu.m.

In the present invention, an undercoat layer may be provided between the synthetic resin film and the photosensitive layer in order to enhance adhesion between the two layers.

Gelatin, synthetic polymer latex, nitrocellulose, etc. are used as the material for the undercoat layer. The coating amount of the undercoat layer is preferably in the range of 0.1 g/m" to 2.0 g/m", particularly preferably in the range of 0.2 g/m" to 1.0 g/m". If it is less than 0.1 g/m", the adhesion between the film and the photosensitive layer will not be sufficient, and even if it is increased to 2.0 g/m" or more, the adhesion between the film and the photosensitive layer will reach saturation, so it is cost-effective. It will be disadvantageous.

The undercoat layer may swell due to the water contained in the heat-sensitive layer when the heat-sensitive layer is applied thereon.
It is desirable to harden using a hardening agent.

As hardeners that can be used in the present invention, the following can be mentioned.

■Divinylsulfone-N,N'-ethylenebis(vinylsulfonylacetamide), 1,3-bis(vinylsulfonyl)-2-propatol, methylenebismaleimide, 5-acetyl-1,3-diacryloyl- xahydro-5-) liazine, 1.3.5-) lyacryloyl-
Active vinyl compounds such as hexahydro-8-triazine, 1,3.5-)rivinylsulfonyl-hexahydro-5-)lyazine.

■2.4-dichloro-6-hydroxy-5-triazine sodium salt, 2,4-dichloro-6-medoxys
-triazine, 2,4-dichloro-6-(4-sulfoanilino)-s-) riazine sodium salt, 2,4-dichloro-6-(2-sulfoethylamino)-S-) riazine, N-N'- Active halogen compounds such as bis(2-chloroethylcarbamyl)piperazine.

■Bis(2,3-epoxypropyl)methylpropylammonium p-toluenesulfonate, 1,4-bis(2" 3°-epoxypropyloxy)butane,
1,3.5-)liglycidyl isocyanurate, 1.3
-Epoxy compounds such as diglycidyl-5-(T-acetoxy-β-oxypropyl)isocyanurate.

■2,4.6-doriethylene-s-)riazine, ■,6
-hexamethylene-N, N'-bisethylene urea,
Ethylenimino compounds such as bis-β-ethyleneiminoethylthioether.

■1.2-di(methanesulfonoxy)ethane, 1.4
- Methanesulfonic acid ester compounds such as di(methanesulfonoxy)butane and 1°5-di(methanesulfonoxy)pentane.

■Dicyclohexylcarbodiimide, 1-cyclohexyl-3-(3-trimethylaminopropyl)carbodiimide-P-trienesulfonate, 1-ethyl-3-(
3-dimethylaminopropyl) carbodiimide hydrochloride.

■2.5-dimethylisoxazole perchlorate, 2
Isoxazole compounds such as -ethyl-5-phenylisoxazole-3°-sulfonate and 5,5'-(paraphenylene)bisisoxazole.

■Inorganic compounds such as chromium alum and chromium acetate.

■N-carboethoxy-2-isopropoxy-1,2-
Dihydroquinoline, N-(1-morpholinocarboxy)
Dehydration condensation type peptide reagents such as -4-methylpyridinium chloride; active ester compounds such as N,N'-aziboyldioxydisuccinimide and N,N'terephthaloyldioxydisuccinimide.

[Co., Ltd.] Toluene-2,4-diisocyanate, 1゜6-
Isocyanates such as hexamethylene diisocyanate.

■Dialdehydes such as glutaraldehyde, glyoxal, dimethoxyurea, and 2,3-dihydroxy-14-dioxane.

Among these, dialdehydes such as glutaraldehyde and 2°3-dihydroxy 1,4-dioxane, and boric acid are particularly preferred.

The amount of these hardeners added is based on the weight of the base coat material.
An appropriate addition amount can be selected in the range of 0.20% by weight to 3.0% by weight depending on the coating method and desired degree of curing.

If the amount added is less than 0.2% by weight, the degree of curing will be insufficient no matter how long it is allowed to last, and the undercoat layer will swell when the heat-sensitive layer is applied. If the amount is too high, the degree of curing will progress too much, and the adhesion between the undercoat layer and the support will deteriorate, resulting in the disadvantage that the undercoat layer will become film-like and peel off from the film. Depending on the hardening agent used, if necessary, caustic soda, etc. may be added to make the pH of the solution alkaline.
Alternatively, the pH of the liquid can be made acidic using citric acid or the like.

It is also possible to add an antifoaming agent to eliminate foam generated during coating, or to add an activator to improve liquid leveling and prevent coating streaks.

Moreover, it is also possible to add an antistatic agent if necessary.

Furthermore, before applying the undercoat layer, it is desirable to activate the surface of the film by a known method. Examples of the activation treatment include etching treatment with acid, flame treatment with a gas burner, or corona treatment. Discharge treatment, glow discharge treatment, etc. are used, but from the point of view of cost or simplicity, U.S. Pat.
6.727, 3,549,406, 3,5
The corona discharge treatment described in No. 90107 and the like is most preferably used.

The heat-sensitive layer in the present invention can be coated using a suitable binder.

As binders, various emulsions such as polyvinyl alcohol, methylcellulose, carboxymethylcellulose, hydroxypropylcellulose, gum arabic, gelatin, polyvinylpyrrolidone, casein, styrene-butadiene latex, polyvinyl acetate, polyacrylic acid ester, and ethylene-vinyl acetate copolymer are used. can be used. The amount used is 0.5-20g/rr in terms of solid content.
f, preferably 0.5 to 5 g/i.

In the present invention, in addition to the above materials, citric acid, tartaric acid, oxalic acid, boric acid, phosphoric acid, pyrophosphoric acid, etc. can be added as acid stabilizers.

In the present invention, ultraviolet rays are mainly applied to the heat-sensitive layer formed on the support using the above materials for the purpose of imparting scratch resistance, water resistance, and solvent resistance to the resulting heat-sensitive recording material. A protective layer made of hardened resin is provided.

The resin component that is cured by ultraviolet rays and used in the protective layer of the present invention contains a photopolymerizable monomer, a prepolymer, and a photopolymerization initiator as essential components.

Examples of the photopolymerizable monomer include monofunctional acrylate monomers such as 2-ethylhexyl acrylate, tetrahydrofurfuryl acrylate, phenoxyethyl acrylate, and 1,3-dioxolane acrylate, and/or hexanediol acrylate and neopentyl glycol diacrylate. , low viscosity monomers such as difunctional acrylate monomers such as neopenkel glycol hydroxypivalate.

In addition, as a prepolymer, for example, adipic acid 1.6-
Hexanediol/acrylic acid, phthalic anhydride/propylene oxide/acrylic acid, trimellitic acid/diethylene glycol/acrylic acid, trimethylolpropane/
Such as adipic acid, hydrogenated castor oil fatty acids, etc.
, polyester acrylate with (meth)acryloyl group introduced into polyester obtained from polyhydric alcohol and polybasic acid, and bisphenol A/epichlorohydrin/
Examples include epoxy resins modified with acrylic acid, methacrylic acid, and epoxy acrylates such as phenol novolak/epichlorohydrin/acrylic acid.

Since polyester alone has insufficient photocurability, a mixture of epoxy acrylates and polyesters is preferably used. A preferred mixing ratio of polyesters: epoxy acrylates is 1=1O to 2:1, more preferably 1:5 to 1:1.

The photopolymerizable monomer is mixed as appropriate from the viewpoint of improving the coating suitability or printing suitability of the protective layer. Furthermore, a polymer that does not have photopolymerizability can also be mixed.

As a photopolymerization initiator, benzophenone, 4-chlorobenzophenone, 4.4"bis(diethylamino)benzophenone, 2-methylbenzophenone, 4-methylbenzophenone, β-naphthylphenyl ketone, 2-benzoylthiophene, methylorthobenzoylbenzoic acid Benzyl photopolymerization initiators such as methyl, 2-benzoylpyridine, and 4-methylbenzyl, xanthone photopolymerization initiators such as xanthone, 2-chloroxanthone, 2-methylxanthone, and 2-isopropylxanthone, thioxanthone, 2 - Thioxanthone-based photopolymerization initiators such as chlorothioxanthone, 2-methylthioxanthone, and 2-propylthioxanthone; anthraquinone-based photopolymerization initiators such as anthraquinone, 2-methylanthraquinone, 2ethylanthraquinone, 1-chloroanthraquinone, and 9-fluorene; agent, acetophenone, 4-methylacetophenone, 4-diethylaminoacetophenone, 4-chloroacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-dimethoxyacetophenone, 2.
2.2-) Acetophenone photopolymerization initiator such as dichloro-4°-t-butylacetophenone, 2.2-dichloro-4"-phenyloxyacetophenone, l-phenyl-1,2 propanedione-2 Examples include oxime-based photopolymerization initiators such as -(o-benzoyl)oxime, and benzoin-based photopolymerization initiators such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin butyl ether.

Pigments are contained in the protective layer for the purpose of improving matching with the thermal head during thermal printing and improving the water resistance of the protective layer.
Metal soap, wax, etc. can also be added.

Pigments include organic substances such as zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, Rouseki, kaolin, aluminum hydroxide, amorphous silica, styrene resin, formalin condensate, fluoroethylene resin, and urea resin. Yes, the amount added is 0.05 to 1 of the total weight of the polymer.
The amount is particularly preferably 0.1 to 0.5 times. If the amount is 1 times or more, the transparency and sensitivity of the heat-sensitive recording material will be significantly reduced, impairing its commercial value.

Metal soaps include emulsions of higher fatty acid metal salts such as zinc stearate, calcium stearate, and aluminum stearate, and the proportion thereof is 0.1 to 10% by weight, preferably 0.3 to 5% by weight of the total weight of the protective layer. is added in an amount of Waxes include emulsions such as paraffin wax, microcrystalline wax, carnauba wax, methylolstearamide, polyethylene wax, and silicone, and account for 0.1 to 20% by weight of the total weight of the protective layer.
, preferably in a proportion of 0.2 to 10% by weight.

Furthermore, a surfactant, a polymer electrolyte, etc. may be added to the protective layer to prevent charging of the heat-sensitive recording material.

The protective layer is coated on the heat-sensitive layer by a known method after preparing a coating solution diluted with an organic solvent if necessary. The solid content coating amount of Hoi1M is usually 0. It is preferably 2 to 5 g/m", more preferably 1 to 3 g/m".

When providing the protective layer of the present invention, it is preferable to provide an intermediate layer made of a water-soluble polymer from the viewpoint of improving the strength of the coating film and preventing unnecessary color development when applying the protective layer. Specific examples of polymers include methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, starches, gelatin, gum arabic, casein, styrene-maleic anhydride copolymer hydrolyzate, styrene-maleic anhydride copolymer half ester hydrolyzate. , polyvinyl alcohol, carboxy-modified polyvinyl alcohol, polyacrylamide derivatives, polyvinylpyrrolidone, sodium polystyrene sulfonate, sodium alginate, and the like.

The coating amount of the intermediate layer is preferably 0.1 to 5 g/m'',
In particular, it is preferably 0.5 to 3 g/m''.

When producing the heat-sensitive recording material of the present invention, generally well-known coating methods are used, such as dip coating, air knife coating, curtain coating, roller coating, doctor coating, wire barcoding, slide coating, and gravure coating. Act, or U.S. Pat. No. 2,681,
The extrusion coating method using a hopper described in the specification of No. 294, etc. can be employed. In addition, as necessary, U.S. Patent No. 2,761,791, U.S. Patent No. 3.508.947, U.S. Patent No. 2,941,898, and U.S. Pat. It is also possible to coat two or more layers at the same time using the method described in "Coating Engineering", page 253 (published by Asakura Shoten, 1973), etc., and apply the appropriate method depending on the amount of coating, coating speed, etc. You can choose.

In the present invention, a back layer may be provided on the back surface of the support for the purpose of curl correction, antistatic properties, and improved slipperiness. As the constituent components of the back layer, it is preferable to use the same components as those of the protective layer.

(Effects of the Invention) The heat-sensitive recording material of the present invention is easy to handle since it has a protective layer particularly excellent in scratch resistance and anti-sticking ability. Furthermore, since it has high thermal sensitivity, it is possible to form images using a thermal head such as a facsimile machine, so by using a transparent film as a support, it is possible to use information received by facsimile and directly apply it to OHP. .

(Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 [Preparation of capsule liquid] 14 g of crystal violet lactone (leuco pigment)
, 60 g of Takenate D-11ON (capsule wall material manufactured by Takeda Pharmaceutical Co., Ltd.) and 2 g of Sumisorb 200 (ultraviolet absorber manufactured by Sumitomo Chemical ■) were added to a mixed solvent of 55 g of 1-phenylene/L/-1-xylylethane and 55 g of methylene chloride. Added and dissolved. A solution of this leuco dye was mixed with 100 g of an 8% aqueous polyvinyl alcohol solution, 40 g of water, and 1°4 of 2% sodium salt of dioctyl sulfosuccinate (dispersing agent).
g of an aqueous solution, emulsified for 5 minutes at 10.00 (lypm) using an Ace homogenizer manufactured by Nippon Seiki ■, and further added 150 g of water and reacted at 40'C for 3 hours to form capsules with a capsule size of 0.7μ. liquid was produced.

[Preparation of developer emulsion dispersion]

Color developer represented by the following structural formula (a) 8 g, (b)
4 g and 30 g of (C) were dissolved in 8.0 g of 1-phenyl-1-xylylethane and 30 g of ethyl acetate. The obtained developer solution was mixed with an aqueous solution of 100 g of 8% polyvinyl alcohol aqueous solution, 150 g of water, and 0.5 g of sodium dodecylbenzenesulfonate, and Nippon Seiki ■
10,000γp using an Ace homogenizer manufactured by
The mixture was emulsified at room temperature for 5 minutes to obtain an emulsified dispersion with a particle size of 0.5 μm.

Color developer (a) Color developer, etc.) Color developer (C) H [Preparation of heat-sensitive recording material] 5.0 g of the above capsule liquid, 1010 g of color developer emulsion dispersion
and 5 g of water were stirred and mixed, and the solid content was Log
/m” and dried, then coated with 2 of the following composition.
A protective layer of μ was provided and cured with a 340 nm tJ V lamp to produce a transparent thermosensitive film.

[Composition of protective layer]

Irgacure 651 (photopolymerization initiator manufactured by Ciba Geigy) 5 parts Ebecryl 440 (polyester acrylate manufactured by UCB)
: 15 parts Lipoxy 5P15
19X-2 (epoxy acrylate manufactured by Showa Kobunshi ■)
:20 parts The obtained heat-sensitive recording material had good stinking properties and was also almost satisfactory in scratch resistance, water resistance, and chemical resistance. Furthermore, transparency was also good.

Example 2゜0.5μ polyvinyl alcohol (PVA
A transparent heat-sensitive film was prepared in exactly the same manner as in Example 1, except that an intermediate layer (manufactured by -217 Kuraray ■) was provided.

The resulting heat-sensitive recording material had good sticking properties and was even better in scratch resistance, water resistance, chemical resistance, etc. than in Example 1. Moreover, transparency was also good.

Comparative Example 1 A heat-sensitive recording material was obtained in exactly the same manner as in Example 1, except that a protective layer having the following composition was used.

[Protective layer composition]

Silica-modified polyvinyl alcohol (PVA manufactured by Kuraray)
R2105) 10% by weight aqueous solution: 15 parts Colloidal silica (Snowtex 30 manufactured by Nikki Kagaku ■) 30% by weight
Aqueous solution: 8.5 parts Stair, zinc phosphate (Hydrin Z7 manufactured by Middle East Oil Co., Ltd.) 30% by weight aqueous solution
: 0.42 parts Paraffin wax (Cellosol D130 manufactured by Middle East Oil Co., Ltd.) 22% by weight aqueous solution = 0.54
Titanium oxide (Tiebake A-100 manufactured by Ishiya Sangyo) 3
3% by weight aqueous dispersion: 1.9 parts were mixed to obtain a protective layer liquid.

The obtained heat-sensitive recording material had good sticking properties, but its scratch resistance was somewhat poor, and its water resistance and chemical resistance were insufficient. Furthermore, the transparency was also insufficient.

Comparative Example 2 [Preparation of heat-sensitive recording liquid] In 100 parts by weight of a 5% aqueous solution of water-soluble binder PVA, 7 parts by weight of black leuco dye (PSD-T, !I, manufactured by Shin Nisso Kako ■) and 10 parts by weight of clay. part and stearic acid amide powder 3
A liquid obtained by mixing parts by weight and dispersing for 5 hours in a centrifugal rotary ball mill was used as component A, and separately 10% aqueous solution of PVA, the same binder as above.
0 parts by weight, 7 parts by weight of bisphenol A, 10 parts by weight of clay, and 3 parts by weight of stearic acid amide powder were mixed and dispersed in a centrifugal rotating ball mill for 5 hours.
, and B were mixed and stirred at a ratio of 1:3 to obtain a uniformly dispersed paint.

[Preparation of heat-sensitive recording material]

The above heat-sensitive recording liquid was applied to a transparent polyethylene terephthalate (PET) support with a thickness of 75 μm, and the solid content was 10 g/rr.
After coating and drying, the protective layer of Example 1 was applied to a thickness of 2 μm.
The thickness was set to .

The obtained heat-sensitive material had good sticking properties, and its scratch resistance, water resistance, and chemical resistance were generally satisfactory.
There was insufficient transparency. In addition, fogging occurred on the entire surface.

Claims (1)

[Scope of Claims] 1) Microcapsules containing a colorless or light-colored electron-donating dye precursor and at least one heat-sensitive layer formed by coating and drying a coating solution containing a color developer on a support; ,
A heat-sensitive recording material comprising at least one protective layer provided on the heat-sensitive layer, wherein the protective layer is mainly made of a resin cured by ultraviolet rays. 2) The color developer is contained in the coating liquid as an emulsified dispersion obtained by dissolving the color developer in an organic solvent that is sparingly soluble or insoluble in water and then emulsifying and dispersing it. Heat-sensitive recording material. 3) The heat-sensitive recording material according to claim 1, further comprising an intermediate layer mainly composed of a water-soluble polymer between the heat-sensitive layer and the protective layer.