JPH01263079A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a negative-type thermal recording material which can be produced with favorable stability and has excellent transparency, by providing a thermal recording material by a method wherein a coating liquid comprising a partially saponified polyvinyl alcohol- containing emulsified or dispersed material obtained by dissolving a basic dye precursor and a color developer in an organic solvent and emulsifying or dispersing the resultant solution and also comprising a decolorant-containing microcapsules is applied to a support, followed by drying. CONSTITUTION:A thermal recording material comprises at least a thermal recording layer on a support. The thermal recording layer is provided by a method wherein a partially saponified polyvinyl alcohol-containing emulsified or dispersed material obtained by dissolving a colorless or light-colored dye precursor and a color developer in an organic solvent insoluble or difficultly soluble in water and emulsifying or dispersing the resultant solution and also comprising decolorant-containing microcapsules is applied to the support, followed by drying. When a transparent film is used as the support, the thermal recording material ensures that the recording material on which information received by a facsimile or the like is recorded thereon can be set directly on an overhead projector to view a negative-type image. The coating liquid has favorable emulsion or dispersion stability, so that the reproducibility as to the transparentness of the recording layer is favorable, and the transparency is extremely excellent.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a negative heat-sensitive recording material, and particularly to a heat-sensitive recording material with excellent transparency stability.

(Prior art) Thermosensitive recording materials (1) do not require development, (2) when the support is paper, the paper quality is similar to ordinary paper, (3) easy handling, and (4) color density. (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 has become popular in the field of labels such as PO3 etc. The uses of thermal recording are also expanding.

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

On the other hand, conventional OHP film sheets used to be thermal copying methods using heat-reactive substances, and more recently,
A method in which the film itself or a resin layer coated on the film is distorted by heat, a method in which colored powder is fixed on a transparent support by xerography, or a facsimile printer (thermal transfer type using an ink sheet) There are some that form images.

However, all of the images produced by these conventional thermal methods are positive type, and negative type images, such as ``white-out images on the ground'', which have been particularly prized in the field of slides in recent years, have been prized in recent years because they reduce eye fatigue. OHP films are not common, especially negative-type OHP heat-sensitive films that can be easily recorded with thermal heads widely used in facsimile printers and the like.

Therefore, the inventors of the present invention investigated the possibility of developing a negative-type OHP heat-sensitive film, and found that a leuco dye and an acidic compound were brought into contact with each other to form a color, and a coloring agent and a decoloring agent were coated on a transparent film support. It has been found that the above-mentioned negative type heat-sensitive film for OHP can be produced by this method, and has already been proposed (Japanese Patent Application No. 62-60646).

(Problems to be Solved by the Invention) However, the above-mentioned heat-sensitive recording material has a disadvantage in that the transparency and stability thereof tend to vary.

As a result of intensive studies aimed at solving the above-mentioned drawbacks, the present inventors found that the transparency of the heat-sensitive layer depends on the stability of the emulsified dispersion in the coating solution, and that this stability depends on the partial hydration of polyvinyl alcohol in the coating solution. The present invention was achieved by discovering that the addition of a chemical compound significantly improves the temperature.

Therefore, an object of the present invention is to provide a negative heat-sensitive recording material that can be produced with good stability and has excellent transparency.

(Means for Solving the Problems) The above object of the present invention is to provide a heat-sensitive recording material having at least a heat-sensitive layer on a support, in which the heat-sensitive layer contains a colorless or light-colored basic dye precursor and a color developer in water. By applying and drying a coating solution containing an emulsified dispersion containing a partially saponified polyvinyl alcohol and microcapsules containing a decolorizing agent, which has been emulsified and dispersed after being dissolved in an organic solvent that is sparingly soluble or insoluble in This was achieved by means of a heat-sensitive recording material characterized in that it was formed.

In the heat-sensitive recording material according to the present invention, the unheated portion is colored by a reaction product of a colorless or light-colored basic dye precursor and a color developer, and the heated portion is colored by the reaction product that passes through the thermoresponsive capsule wall. Since the above-mentioned coloring is bleached by the agent, when an overhead projector is used, the background is colored and the image area is colorless or light-colored on a white screen.

Moreover, when the coating material of the present invention is applied to a paper support, it becomes a negative-tone thermal paper.

The transparent film support used is polyester,
Acrylic resins, styrene/acrylic copolymers, cellulose acetate, and the like are suitable, but are not particularly limited.

Next, the heat-sensitive layer of the heat-sensitive recording material of the present invention will be described in detail.

As the basic dye precursor used in the present invention, a colorless or light-colored one is appropriately selected from known compounds that develop color by donating electrons or accepting protons such as acids. 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.

The color developer that causes a color reaction with the basic colorless dye used in the present invention can be appropriately selected from known ones and used. For example, color developers for leuco dyes include phenolic compounds, sulfur-containing phenolic compounds, carboxylic acid compounds, sulfone compounds, urea-based or thiourea-based compounds, etc. For details, see, for example, Paper and Pulp Technology Times. (1985) pp. 49-54 and 65
- described on page 70. Among these, those with a melting point of 50°C to 250°C are particularly preferable, especially those with a melting point of 60°C.
Phenols and organic acids that are sparingly soluble in water and have a temperature of 200°C to 200°C are preferred. 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 (1) to (V).

(1) Cff1 R2ll,.

I (III R, represents an alkyl group, an aryl group, or an aralkyl group, and a methyl group, an ethyl group, and a butyl group are particularly preferred.

(III) R3 R1 is an alkyl group, especially a butyl group, a pentyl group,
Heptyl and octyl groups are preferred.

R1 is a hydrogen atom or a methyl group, and n is 0-2.

(IV) R4 is an alkyl group or an aralkyl group.

(V) R3 and R6 represent hydrogen, halogen, hydroxyl group, nitro group, alkyl group, allyl group, aralyl group, or alkylaryl group.

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.

In the present invention, a basic dye precursor and a color developer are dissolved in an organic solvent that is sparingly soluble or insoluble in water, and then mixed with an aqueous phase containing a surfactant and a water-soluble polymer as a protective colloid. and used in the form of an emulsified dispersion.

The organic solvent for dissolving the basic dye precursor and color developer can be appropriately selected from esters with a boiling point of 150°C or higher or those commonly used as pressure-sensitive oils. Compounds represented by the following general formulas (Vl) to [■] having two or more benzene rings and a certain number or less of heteroatoms, and triallylmethane (e.g. tritolylmethane, tolyl di phenylmethane), terphenyl compounds (e.g. terphenyl), alkylated diphenyl ethers (e.g.
(propyl diphenyl ether), hydrogenated terphenyl (eg, hexahydro terphenyl), diphenyl ether, etc. are preferred, and esters are particularly preferred from the viewpoint of stability of the emulsified dispersion.

(VI) In the formula, R' represents hydrogen or an alkyl group having 1 to 18 carbon atoms, and R2 represents an alkyl group having 1 to 18 carbon atoms. p +
, q l represents an integer of 1 to 4, and the total number of alkyl groups is 4 or less.

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

[■]

In the formula, R3 represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, R4 represents an alkyl group having 1 to 12 carbon atoms, and n represents 1 or 2.

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

(■) In the formula, R5 and R6 represent a hydrogen atom or the same or different alkyl groups having 1 to 18 carbon atoms.

m represents an integer from 1 to 13. p', (13 is 1~
represents an integer of 3, and the total number of alkyl groups is 3 or less.

In addition, the alkyl group of R5 and R6 is particularly preferably an alkyl group having 2 to 4 carbon atoms.

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

Examples of the compound represented by formula [■] include dimethylbiphenyl, diethylbiphenyl, diisopropylbiphenyl, and diisobutylbiphenyl.

Examples of compounds represented by formula [■] include l-methyl-
1-dimethylphenyl-1-phenylmethane, ■-ethyl-1-dimethylphenyl-1-phenylmethane, 1-
Propyl-1-dimethylphenyl-1-phenylmethane is mentioned.

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 (
Diptyl oxalate, dipentyl chelate), 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, lauric acid monoesters and diesters, valmitic 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, a low boiling point auxiliary solvent may be added to the above organic solvent as a solubilizing agent. Preferred examples of such auxiliary solvents include ethyl acetate, isopropyl acetate, butyl acetate, and methylene chloride.

The water-soluble polymer is contained as a protective colloid in the aqueous phase that is mixed with the oil phase in which the basic dye precursor and color developer are dissolved.
Although it can be appropriately selected from known anionic polymers, nonionic polymers, and amphoteric polymers, polyvinyl alcohol, gelatin, cellulose mR form, etc. are preferable.

Among these, partially saponified polyvinyl alcohol, particularly those with a degree of saponification of 75 to 90%, are preferred.

(Function) In particular, when a partially saponified polyvinyl alcohol is used as a protective colloid, it stabilizes the emulsified dispersion of the basic dye precursor and color developer, for reasons that are not clear. In this case, the transparency of the heat-sensitive recording material layer can be made extremely good. In order to make the effect of this partially saponified polyvinyl alcohol most effective, it is preferable to use it during emulsification.
It is also possible to add partially saponified polyvinyl alcohol after emulsification with another protective colloid.

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 alkylbenzenesulfonic acid sorter (eg, sodium dodecylbenzenesulfonate), sodium alkylsulfate, dioctyl sodium sulfosuccinate, polyalkylene glycol (eg, polyoxyethylene nonylphenyl ether), and the like. I can do it.

The emulsified dispersion of a basic dye precursor and a color developer containing partially saponified polyvinyl alcohol in the present invention comprises an oil phase containing a basic dye precursor and a color developer, and a water phase containing a protective colloid and a surfactant. phase by high-speed stirring, ultrasonic dispersion, etc.
It can be easily obtained by mixing and dispersing using the means used for ordinary fine particle emulsification.

A compound having the function of a glass transition point regulator for the capsule wall can be added to the second emulsified dispersion. Such compounds include, for example, and droxy compounds,
Carbamate ester compounds, sulfonamide compounds,
There are aromatic methoxy compounds and the like, the details of which are described in, for example, Japanese Patent Application No. 59-244190.

These compounds can be appropriately 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.

The color developer is applied in a range of 0.05 to 8 g/m'', and the basic dye precursor is applied in a range of 0.02 to 4 g/m''.

The color erasing agent in the present invention has a color erasing effect on the coloring system of a basic dye and a color developer, and examples thereof are shown below.

a) Alkylene oxide adduct of bisphenols (JP-A-54-139741) 0- (C, H2, O), -H where A is methylene or alkylidene, b) Melting point 11
0°C or higher methylolamide and bisamide (JP-A-55-7449), C) long-chain 1,2-glycol (JP-A-55-27217), d) ethylene oxide adduct of terephthalic acid (JP-A-55-27217); 1972-
25306), e) Solid alcohols (especially Publication No. 50-17865) f) Polyoxydecamethylene, polyoxymethylene, polyethylene oxide, trimethylene oxide polymer,
°1. Polyethers such as 3-dioxolane polymers, polyoxyethylene alkylamine, sorbitan monostearate, polyoxyethylene oleyl ether, polyethylene glycol monostearate, polyoxyethylene alkylamide, oxyethylene alkylamine, etc. Polyethylene glycol derivatives (Special Publication of 1970)
-17867 and Japanese Patent Publication No. 17868) g) Acetamide, stearamide, phthalonitrile,
m-Nitroaniline, β-naphthylamine (Special Publication No. 1983
-19991) h) 1,3-dicyclohexyl-2-phenylguanidine, 1,3-dicyclohexyl-2-naphthylguanidine, 2,3-dicyclohexyl-1-phenylguanidine, 1,2. Guanidine g1 such as 3-triphenylguanidine (Japanese Patent Publication No. 51-29024) i) Hexadecylamine, tribenzylamine, N, N
, N', N'-tetrabenzylethylenediamine,
Tricyclohexylamine, dioctadecylamine, 2
-Amine or quaternary ammonium salt such as aminobenzoxazole, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride (Japanese Patent Application Laid-Open No. 18048/1983) A decoloring agent is sufficient to erase the pigment generated from the basic dye. The appropriate amount can be determined experimentally, but it is usually 0.05 to 8.
It is preferable to use the decoloring agent within the range of "g/m. It is possible to improve the raw storage property and the recording storage property.In this case, by selecting the wall material and manufacturing method of the microcapsule, the image contrast during recording can be increased.

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 preferably microencapsulated by emulsifying a core material containing a reactive substance such as a decolorizing agent, and then forming a wall of a polymer material around the oil droplets. In this case, a reactant forming a polymeric substance is added inside the oil droplet and/or outside 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.

In addition to the decolorizing agent, an organic solvent can be added to the core material of the microcapsule. The organic solvent used is the same as that used to dissolve the basic dye precursor and the color developer.

In addition, in order to make the thermal printing part highly transparent, the refractive index of the core material of the microcapsules should be close to the refractive index of the oil phase in which the basic dye precursor and color developer are dissolved. preferable.

In the present invention, the size of the microcapsules is preferably 4 microns or less, as measured by the volume average particle size measured, for example, by the measurement method described in JP-A No. 60-214990.

The preferred microcapsules produced as described above are not ruptured by heat or pressure as used in conventional recording materials, and the reactive substances contained in the core and outside of the microcapsules are It can penetrate through the capsule wall and react.

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

As a binder, polyvinyl alcohol, methylcellulose, carboxymethylcellulose, sodium alginate, hydroxypropylcellulose, gum arabic, gelatin, polyvinylpyrrolidone, casein, sodium alginate, styrene-butadiene latex, acrylonitrile-butadiene latex, polyvinyl acetate,
Various emulsions such as polyacrylic ester and ethylene-vinyl acetate copolymer can be used.

The amount used is 0.5 to 5 g/rd as solid content.

The heat-sensitive recording material of the present invention is produced by preparing a coating solution containing microcapsules containing a decolorizing agent, a dispersion in which at least a basic dye precursor and a color developer are emulsified and dispersed, and other additives such as a binder. Bar coating, blade coating, air knife coating, gravure coating, roll coating coating, spray coating,
It is manufactured by coating and drying by a coating method such as dipping coating to provide a heat-sensitive layer having a solid content of 2.5 to 25 g/bo.

The heat-sensitive layer of the heat-sensitive recording material thus produced has extremely good transparency.

In order to maintain the transparency of such a heat-sensitive layer, scratch resistance,
In order to improve solvent resistance and the like, it is preferable to provide a protective layer with good transparency on top of the heat-sensitive layer.

Water-soluble polymers are mainly used as the binder for the protective layer of the present invention, and a protective layer containing silicon-modified polyvinyl alcohol and colloidal silica as main components is particularly preferred in order to maintain the transparency of the heat-sensitive layer.

Pigments, metal soaps, wax, crosslinking agents, and the like are added to the protective layer for the purpose of improving matching with a thermal head during thermal printing and improving the water resistance of the protective layer.

Pigments include zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, Rouseki, kaolin, aluminum hydroxide, amorphous silica, styrene beads, urea-melamine resin, etc., and the amount of these added depends on the total amount of the polymer. The amount is 0.05 to 2 times the weight, particularly preferably 0.1 to 0.5 times the weight. If the amount is less than 0.05 times, it is ineffective in improving the matching property with the head, and if the amount is more than 2 times, the transparency and sensitivity of the heat-sensitive recording material will be significantly reduced, impairing its commercial value.

Examples of metal soaps include emulsions of higher fatty acid metal salts such as zinc stearate, calcium stearate, and aluminum stearate. It is added in Waxes include emulsions such as paraffin wax, microcrystalline wax, carnauba wax, methylol stearamide, stearic acid amide, polyethylene wax, and silicone.
．． It is added in an amount of 5 to 40% by weight, preferably 1 to 20% by weight. The particle size of these fillers is preferably 2μ or less, more preferably 1μ or less. If the particle size is 2 μm or more, the transparency will be greatly reduced, which is not preferable.

Further, a hardening agent of the same kind as that added to the undercoat layer described later may be added to the protective layer.

Further, in order to uniformly form a protective layer on the heat-sensitive layer, a surfactant is added to the coating solution for forming the protective layer. Surfactants include sulfosuccinic acid-based alkali metal salts, fluorine-containing surfactants, etc. Specifically, di(2-ethylhexyl)sulfosuccinic acid, di(n-hexyl)sulfosuccinic acid, etc. There are sodium salts, ammonium salts, etc.

Furthermore, a surfactant, a polymer electrolyte, etc. may be added to the protective layer to prevent charging of the heat-sensitive recording material. The solid content coating amount of the protective layer is usually preferably 0.2 to 5 g/rd, more preferably 1 g to 3 g/n.

In the present invention, an intermediate layer may be further provided between the heat-sensitive layer and the protective layer in order to prevent blocking and improve scratch resistance.

The heat-sensitive recording material of the present invention can be coated on a support such as paper or a synthetic resin film by bar coating, plate coating, air knife coating, etc.
It is manufactured by coating and drying using coating methods such as gravure coating, roll coating, spray coating, and dip coating. The heat-sensitive layer of the heat-sensitive recording material of the present invention produced in this manner has extremely good transparency.

As the support for the heat-sensitive recording material of the present invention, both a transparent support and an opaque support such as paper can be used depending on the purpose and use.

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 liquid from penetrating into the paper and improve the contact between the thermal recording head and the thermal recording layer, Japanese Patent Application Laid-Open No. 57-116687
The paper described in the above-mentioned issue and having a Bekk smoothness of 90 seconds or more is advantageous.

In addition, 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,
Paper with a density of 0°9 g/cm' or less and an optical contact ratio of 15% or more, described in JP-A No. 8-69097, JP-A-58-690
Canadian standard freeness described in No. 97 (JIS P812
Paper made from valves beaten to 400 cc or more in 1) to prevent penetration of coating liquid, JP-A-58-65
695, the glossy side of base paper made by a Yankee machine is used as the coated surface to improve the color density and resolution, and the method described in JP-A-59-35985, 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.

It is preferable to use a transparent support in the heat-sensitive recording material of the present invention. By using this transparent support, the recorded matter can be used for OHP sheets and the like.

The transparent supports mentioned here include polyester films such as polyethylene terephthalate and polybutylene terephthalate, cellulose derivative films such as cellulose triacetate films, polystyrene films, polypropylene films, polyolefin films such as polyethylene, etc. It can be used alone or in combination.

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

The support may be provided with perforations so that the support can be conveyed with high precision during printing.

In the present invention, an undercoat layer can be provided between the transparent support and the heat-sensitive 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 0.
It is preferably in the range of 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/rn", the adhesion between the support and the heat-sensitive layer will not be sufficient, and even if it is increased to more than 2.0 g/rn", the adhesion between the support and the heat-sensitive layer will reach saturation. This is disadvantageous in terms of cost.

If the undercoat layer swells due to the water contained in the heat-sensitive layer when the heat-sensitive layer is coated thereon, the image quality of the heat-sensitive layer may deteriorate, so a hardening film as shown below is used. It is desirable to cure the resin using an agent.

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

■2.4-dichloro-6-hydroxy-8-triazine sodium salt, 2.4-dichloro-6-medoxy S
-) Riazine, 2,4-dichloro-6-(4-sulfoanilino)-s-triazine sodium salt, 2,4-dichloro-6-(2-sulfoethylamino)-S-triazine, N-No-bis (2-chloroethylcarbamyl)
Active halogen compounds such as piperazine.

■Bis(2,3-epoxypropyl)methylpropylammonium P-)luenesulfonate, 1,4-bis(2',3'-epoxypropyloxy)butane,
1,3.5-1-liglycidyl isocyanurate, 1.
Epoxy compounds such as 3-diglycidyl-5-(T-acetoxy β-oxypropyl) isocyanurate.

■2,4.6-1-lyethylene-5-) riazine, 1.
6-hexamethylene-N,N'-bisethyleneurea,
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-)dimethylaminopropyl)carbodiimide-p-)rienesulfonate, 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, chromium acetate, and zirconium borate.

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

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

■Dialdehydes such as glutaraldehyde, glyoxal, dimethoxyurea, and 2,3-dihydroxy-1,4-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 220% by weight, the degree of curing will be insufficient no matter how long it is left, and the undercoat layer will swell when applying the heat-sensitive layer, and conversely, if it is more than 3.0% by weight, the curing will be insufficient. If the adhesive strength is too high, the adhesion between the undercoat layer and the support deteriorates, and the undercoat layer becomes film-like and peels off from the support.

Depending on the curing agent used, if necessary, the pH of the solution can be made alkaline by adding caustic soda, or the pH of the solution can be made acidic by 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 support by a known method.

Activation treatment methods include acid enquenching treatment,
Flame treatment using a gas burner, corona treatment, glow discharge treatment, etc. are used, but from the viewpoint of cost or simplicity, US Pat. No. 2,715.075 and US Pat.
No. 846,727, No. 3,549.406, No. 3
．． 590. The corona discharge treatment described in No. 107 and the like is most preferably used.

In the heat-sensitive recording material of the present invention, in addition to providing one heat-sensitive layer on one side of a transparent or opaque support, for example, a double-sided heat-sensitive recording material can be prepared by providing one heat-sensitive layer on each side of an opaque support. .

(Effects of the Invention) In the heat-sensitive recording material of the present invention, when a transparent film is used as a support, the content received by facsimile etc. can be directly applied to an OHP to view a negative image. Since the emulsion dispersion stability of the liquid is good, not only the reproducibility of the transparency of the heat-sensitive layer is good, but also the transparency is extremely excellent.

Furthermore, since the stability of the coating liquid is good, workability during the production of heat-sensitive materials can be improved, and production efficiency can also be increased.

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

[Preparation of basic dye precursor and developer emulsion dispersion]

Color developer represented by the following structural formula (a) 2 g, (b)
1 g, (c) 8 g, and basic dye precursor (d) 2
g was dissolved in 5 g of diethyl maleate and 10 g of ethyl acetate.

The obtained solution was mixed with 40 g of 8% polyvinyl alcohol (PVA205 manufactured by Kuraray ■: degree of saponification 87-89%), 50 g of water, and 0.5 g of sodium dodecylbenzenesulfonate.
Mixed with an aqueous solution of
An emulsified dispersion with a particle size of 0°5μ was obtained.

Color developer (a) Color developer (b) Color developer (C) H Basic dye precursor (d) [Preparation of decolorizer capsule liquid] Decolorizer (e) below Log, 1-phenyl-1 -xylylethane 20g, ethyl acetate 10g, Takenate D-1
A solution containing 25g of 1ON (capsule wall agent manufactured by Takeda Pharmaceutical ■) was mixed with 8% polyvinyl alcohol PVA2172.
Mix 60g and 20g of water in an aqueous solution, and mix with Nippon Seiki's Ace homogenizer for 10. The mixture was emulsified at OOOrpm for 5 minutes, 150 g of water was added, and the mixture was reacted at 40°C for 3 hours to mix a capsule liquid with a capsule size of 0.7μ.

Erasing agent (e) (Preparation of heat-sensitive material) A coating liquid was prepared by stirring and mixing 5.0 g of the above capsule liquid, 10.0 g of a basic dye precursor and color developer emulsified dispersion, and 5.0 g of water. . When this coating liquid was allowed to stand for one hour and the state of the coating liquid was observed, the stability of the coating liquid was confirmed. As described above, the coating solution after being left for - hours was applied onto a transparent polyethylene terephthalate (PET) support with a thickness of 70 .mu.m so that the solid content was 10 g/m@2 and dried. next,
A protective layer having the following composition was coated on the heat-sensitive layer at a solid content of 3 g/m 2 and dried to prepare a transparent heat-sensitive film.

[Composition of protective layer]

Silica-modified polyvinyl alcohol 2 parts by weight (PVA R2105 manufactured by Kuraray ■) (Solid content) Colloidal silica 3 parts by weight (Nissan Chemical ■
Snowtex 30) (solid content) Zinc stearate
0.1 part by weight (Hydrin Z manufactured by Middle East Oil & Fats)
-7) (Solid content) Paraffin wax
1 part by weight (Cellosol 428 manufactured by Middle East Oil and Fat ■) (solid content)
The transparency of the resulting transparent thermosensitive film was confirmed by Nippon Seimitsu Kogyo■
Measurement using a manufactured integrating sphere HTR meter demonstrated that it had extremely good transparency.

Example 2 In place of the polyvinyl alcohol manufactured by Kuraray (PVA205: saponification degree 87-89%) used in Example 1 when preparing the basic dye precursor and color developer emulsion dispersion,
Polyvinyl Al manufactured by Kuraray Co., Ltd.:! -ru (P'VA217
E: The same test as in Example 1 was conducted except that the saponification degree was 87 to 89%. As with Example 1, the stability of the coating liquid and the transparency of the coated film were extremely good.

Example 3 In place of the polyvinyl alcohol manufactured by Kuraray ■ (PVA205: saponification degree 87-89%) used in preparing the color developer emulsion dispersion in Example 1, polyvinyl alcohol manufactured by Kuraray ■ (PVA420: saponification degree 87-89%) was used. degree 79.5~83.
The same test as in Example 1 was conducted except that 5% was used. As with Example 1, the stability of the coating liquid and the transparency of the coated film were extremely good.

Comparative Example 1 In Example 1, polyacrylamide was used instead of polyvinyl alcohol manufactured by Kuraray (PVA205: saponification degree 87-89%) used when preparing the color developer emulsion dispersion. <The test was conducted in the same manner as in Example 1. As a result, the coating solution was so unstable that it separated, and even if it was applied to a transparent film before separation, the film became opaque during the drying process.

Comparative example 2. ~5° Instead of the polyacrylamide used in Comparative Example 1, ■
Maleic anhydride/styrene copolymer (Comparative Example 2), ■Maleic anhydride/isobutylene copolymer (Comparative Example 3), ■
Completely saponified poval (PVA105 manufactured by Kuraray Corporation: Saponification degree 98-99%) (Comparative example 4) and ■Completely saponified Poval (PVA117 manufactured by Kuraray Co., Ltd.: Saponification degree 98-99%)
When (Comparative Example 5) was used, the same results as in Comparative Example 1 were obtained.

These results demonstrate that partially saponified polyvinyl alcohol is particularly effective in improving the dispersion stability of color developer emulsion dispersions.

Claims (1)

[Scope of Claims] 1) A heat-sensitive recording material having at least a heat-sensitive layer on a support, in which the heat-sensitive layer contains a colorless or light-colored basic dye precursor and a color developer in an organic solvent that is sparingly soluble or insoluble in water. A heat-sensitive product characterized by being formed by applying and drying a coating solution containing an emulsified dispersion containing partially saponified polyvinyl alcohol and microcapsules containing a decolorizing agent, which are dissolved and then emulsified and dispersed, onto a support. Recording materials. 2) Saponification degree of partially saponified polyvinyl alcohol is 7
The heat-sensitive recording material according to claim 1, which has a content of 5 to 90%.