JPS6255188A - Thermal recording material - Google Patents

Abstract

PURPOSE:To prevent scummings when a diazo compound is fixed by light exposure and to store a recording image also in a good condition, by a method wherein a micro-capsule contains a diazo compound along with a compound generating free radicals on light irradiation. CONSTITUTION:On a substrate, a recording layer containing a diazo compound and a coupling ingredient is formed. Furthermore, a micro-capsule contains the diazo compound along with at least one of compounds generating free radicals on light irradiation. The diazo compound can create a coupling reaction with the coupling ingredient to develop color and can be dissolved by light irradiation. The coupling ingredient is divided into tow sorts; one which couples with the diazo compound under basic atmosphere to accelerate forming of coloring matter, and the other which can couple with the diazo compound in the absence of a basic substance acting as a coupling assistant. The diazo compound used as a coupler can be fixed by fully exposing the thermally recorded material. In this case, the free radical generator can prevent scummings.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a heat-sensitive recording material, and particularly to a fixable diazo compound-based heat-sensitive recording material.

(Prior Art) As a recording material used in a heat-sensitive recording method, a leuco color-forming heat-sensitive recording material is usually used. However, this heat-sensitive recording material has the disadvantage that color develops in unexpected places due to harsh handling, heating, or adhesion of solvents after recording, which stains the recorded image. In recent years, research has been actively conducted on diazo color-forming heat-sensitive recording materials as heat-sensitive recording materials that do not have these drawbacks. For example, Japanese Patent Application Laid-open No. 57-123086, Journal of the Institute of Image Electronics Engineers, 11°290
(1982), etc., thermal recording is performed on a recording material using a diazo compound, a coupling component, and a basic component (including substances that become basic when heated), and then light irradiation is performed to record the raw material. It decomposes the diazo compound in the reaction and stops color development.

It is true that this method can stop color development in areas that do not require recording (hereinafter referred to as fixation), but this recording material also undergoes pre-coupling gradually during storage, resulting in undesirable coloring (fogging). may occur. To this end, it has been attempted to prevent contact between the components and prevent pre-coupling by making one of the coloring components exist in the form of discontinuous particles (solid dispersion). However, the storage stability (hereinafter referred to as "raw storage stability") is still insufficient, and the thermochromic color development property is also deteriorated. On the other hand, in order to minimize contact between the components, it is known to separate the diazo compound and the coupling component as separate layers (for example, as described in JP-A-57-123086 mentioned above).

Although this method improves raw storage stability, the thermal coloring properties are greatly reduced, and it cannot respond to high-speed recording with short pulse widths, making it impractical. Furthermore, as a method to satisfy both raw storage stability and thermochromic properties, either the coupling component or the basic substance is replaced with a non-polar waxy substance (Japanese Patent Application Laid-Open No. 57-441
41, JP-A No. 57-142636) or encapsulation with a hydrophobic polymer substance (JP-A-57-192944) to isolate it from other components.

However, these encapsulation methods involve dissolving wax or polymeric substances in their solvents, and dissolving or dispersing color-forming components in these solutions to form capsules, and the surroundings of the core substance are This differs from the concept of a normal capsule that is covered with a shell, so when a capsule is formed by dissolving a coloring component, the coloring component does not become the core material of the capsule, but mixes uniformly with the encapsulating material. For this reason, pre-coupling gradually progresses at the wall interface of the capsule during storage, and the raw storage stability is not fully satisfied. In addition, when a color-forming component is dispersed and formed, the color-forming reaction does not occur unless the walls of the capsule are thermally melted, resulting in a decrease in thermal color-forming properties. Furthermore, there was a manufacturing problem in that the wax or the solvent used to dissolve the polymer substance had to be removed after the capsules were formed, and the material was not fully satisfactory as a heat-sensitive recording material.

In order to solve these problems, at least one of the components involved in the coloring reaction is contained in the core material, and a wall is formed around the core material by polymerization to form microcapsules (Japanese Patent Application Laid-Open No. 59-1999-1). 190886) was disclosed.

(The problem that the invention is trying to solve) However,
Even in the heat-sensitive recording material using the above-mentioned microencapsulation, it was not possible to avoid the drawback that the background portion (portion other than the recorded image) becomes slightly yellowish when thermally recorded and then photofixed.

Therefore, the first object of the present invention is to provide a heat-sensitive recording material which has a white background tone, has excellent shelf life, and has high thermochromic properties.

A second object of the present invention is to provide a heat-sensitive recording material that can be fixed by photodecomposing unreacted diazo compounds after heat recording.

A third object of the present invention is to provide a heat-sensitive recording material that is easy to manufacture.

(Means for Solving the Problems) The above aspects of the present invention are such that in a heat-sensitive recording material provided with a recording layer containing at least a diazo compound and a coupling component on a support, the diazo compound is irradiated with light. This has been achieved by a heat-sensitive recording material characterized in that it is contained in microcapsules together with at least one compound that generates free radicals.

The heat-sensitive recording material of the present invention can be thermally colored and then uniformly irradiated with light to photodecompose the uncolored diazo compound, thereby stopping thermal coloring.

Further, after imagewise exposure, the diazo compound in the unexposed area can be thermally colored by uniform heating.

The diazo compound used in the heat-sensitive recording material of the present invention is a diazonium salt represented by the general formula ArN2+X-,
It is a compound that can develop a color by causing a coupling reaction with a coupling component, and can be decomposed by light irradiation.

(In the formula, Ar represents a substituted or unsubstituted aromatic moiety, and N
2+ represents a diazonium group, and X- represents an acid anion. ) The aromatic moiety is represented by the following general formula.

, R 2 doo, -Y-- In the formula, Y represents a substituted amino group, alkoxy group, arylthio group, alkylthio group, or acylamino group, and R represents an alkyl group, an alkoxy group, an arylamino group, or a halogen (1, Br, C1, F).

Preferred examples of the substituted amino group for Y include a monoalkylamino group, dialkylamino group, arylamino group, morpholino group, piperidino group, and pyrrolidino group.

Specific examples of diazonium that forms salts include 4-diazo-1-dimethylaminobenzene, 4-diazo-1-diethylaminobenzene, 4-diazo-1-dipropylaminobenzene, and 4-diazo-1-methylbenzylamino. Benzene, 4-diazo-1-dibenzylaminobenzene, 4-diazo-1-ethylhydroxyethylaminobenzene, 4-diazo-1-diethylamino-3-methoxybenzene, 4-diazo-1-dimethylamino-2-methyl Benzene, 4-diazo-1-benzoylamino-2,
5-jethoxybenzene, 4-diazo-1-morpholinobenzene, 4-diazo-1-morpholino-2,5-jethoxybenzene, 4-diazo-1-morpholino-2,5
-dibutoxybenzene, 4-diazo-1-anilinobenzene, 4-diazo-1-)ruylmerkabuto 2.5-
Examples include jetoxybenzene, 4-diazo-1,4-methoxybenzoylamino-2,5-jethoxybenzene, and the like.

Specific examples of acid anions include CnF2n+IC0O-
(n is an integer from 3 to 9), CmF2m+ISO3- (m is an integer from 2 to 8), (CJ!F2to1SO2)2CH-(
J! is an integer from 1 to 18), C13H27C0NH 15H31 CIIH23CO N-(CH2)2 Coo - 63H7' can be mentioned.

In particular, as an acid anion, /R-fluoroal /14
or) containing a fluoroalkenyl group or T
ry P Fe- has less increase in fog during raw storage (preferable).

Specific examples of the diazo compound (diazonium salt) include the following examples.

0C4H9 QC,)L.

QC4) L9 C2H5 0C2)15 0C2H5C(CH3n.

0C4)L9 QC4)19 The coupling components used in the present invention include those that promote the formation of a dye by coupling with a diazo compound (diazonium salt) in a basic atmosphere, and a base as a coloring aid. Some coupling occurs even in the absence of a sexual substance.

Specific examples of coupling components in which a basic substance is preferably present include resorcinol, phloroglucin, 2.3-
Sodium dihydroxynaphthalene-6-sulfonate,
1.5-dihydroxynaphthalene, 2.3-dihydroxynaphthalene, 2゜3-dihydroxy-6-sulfanylnaphthalene, 2-hydroxy-3-naphthoic acid anilide, 2-hydroxy-3-naphthoic acid-2''-methylanilide, 2-hydroxy-3-naphthoic acid ethanolamide, 2-hydroxy-3-naphthoic acid octylamide, 2-hydroxy-3-naphthoic acid-N-dodecyl-oxy-propylamide, 2-hydroxy-3-naphthoic acid tetradecyl Amide, etc.

Coupling components that do not require the presence of a basic substance include compounds having active methylene in the molecule, aromatic amine compounds, aromatic hydroxy compounds having a basic group in the molecule, and the like.

Examples of active methylene compounds include β-ketocarboxylic acid amides [e.g., benzoylacetanilide, pivaloylacetanilide, 1,3-bis(benzoylacetamino)toluene, 1,3-bis(pivaloylacetaminomethyl)benzene; etc.], pyrazolones [e.g. 3-methyl-1-phenylpyrazolone, 3-hexylcarbamoyl-1-phenylpyrazolone, 3-myristoylamino-1-(2,4,6-)lichlorophenyl)pyrazolone, etc.], Barbir Acids [e.g. 1,3-didodecylbarbital acid, 1,3-dicyclohexylbarbital acid, 1-octyl-3-stearylbarbital acid, etc.], 1,3-cyclohexanediones [For example, 5.5-
dimethyl-1°3-cyclohexanedione, 5,5-dimethyl-4-phenyl-1,3-cyclohexanedioff, etc.).

As aromatic amine compounds, α-naphthylamine,
β-naphthylamine, 1-anilino-naphthalene, 2-
Anilino-naphthalene, 3-aminodiphenylamine, 4,4-diaminodiphenylmethane, N,N-
dicyclohexylaniline, 2-aminocarbazole,
Organic acid salts and inorganic acids of aromatic amines such as 2-phenylin F-Az, l-phenyl-2-methylindole and N,N-dimethylaniline p-toluenesulfonate, α-naphthylamine hydrochloride, etc. There is salt, etc.

Examples of aromatic hydroxy compounds having a basic group in the molecule include 2-hydroxy-3-naphthoic acid-3'-morpholinopropylamide, 2-hydroxy-3-naphthoic acid-2'-diethylaminoethylamide, and 2-hydroxy-3-naphthoic acid-2'-diethylaminoethylamide. -3-naphthoic acid-3-piperidinopropylamide,
2-Hydroxy-3-naphthoic acid-3'-piperidinopropylamide, 2-hydroxy-3-naphthoic acid-P
-(3°-N'-cyanoguanidinopropyl)oxyanilide, salicylic acid-P-(3°-morpholinopropyl)oxyanilide, 1-naphthol-4-sulfonic acid-3'-diethylaminopropylamide, 8-hydroxyquinoline- Aromatic hydroxy compounds having residues such as 4-sulfonic acid-2°-diethylaminoethylamide and organic carboxylic acid salts of amines that generate basicity upon heating [e.g. 2-hydroxy-3-naphthoic acid-3°] -trichloroacetate of morpholinopropylamide, phenylthioacetate ring of 1-ninaphthol-4-sulfonic acid-3'-diethylaminopropylamide, and the like.

In the present invention, an image of any color tone can be obtained by using two or more of the above-mentioned coupling components in combination.

In the present invention, water-releasable or water-insoluble basic substances, substances that generate alkali upon heating (hereinafter referred to as basic substances), and the like can be used as color development aids. The basic substances used as such coloring aids are:
inorganic and organic ammonium salts, organic amines and amides,
Urea and thiourea and their derivatives, thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidacillins, triazoles, morpholines, piperidines, amidines,
Nitrogen-containing compounds such as formazines and pyridines, and specific examples thereof include ammonium acetate, tricyclohexylamine, tribenzylamine, octadecylbenzylamine, stearylamine, allyl urea, thiourea, methylthiourea, Allylthiourea, ethylenethiourea, 2-benzylimidazole, 4-phenylimidazole, 2-phenyl-4-methyl-imidazole, 2-undecyl-imidacillin, 2.4.5-
Trifuryl-2-imidacillin, 1゜2-diphenyl-
4,4-dimethyl-2-imidacyline, 2-phenyl-
2-Imidacillin, 1゜2.3-) Riphenylguanidine, 1.2-Ditolylguanidine, 1.2-Dicyclohexylguanidine, 1.2.3-) Dicyclohexylguanidine, Guanidine trichloroacetate, N ,N'
-dibenzylpiperazine, 4,4'-dithiomorpholine, morpholinium trichloroacetate, 2-amino-
Examples include benzothiazole, 2-benzoylhydrazino-benzothiazole, and the like. Two or more of these basic substances can also be used in combination.

The coupling agent and/or the basic substance can be contained in a separate microcapsule from the diazo compound or simply added to the layer of the microcapsule containing the diazo compound. When not included in microcapsules,
It is preferable to finely disperse it in the form of particles. Incidentally, in the case of a coupling agent that can couple with a diazo compound only in a basic atmosphere, it is natural that the diazo compound and the camping agent can be contained in the same microcapsule.

In the present invention, the coating amount of the diazo compound is 0°05~
It is preferably 5.0 g/rd, and it is preferable to use the force/knobling agent in a ratio of 0.1 to 10 parts by weight and the basic substance in a ratio of 0 to 20 parts by weight per 1 part by weight of the diazo compound.

In the present invention, a compound that generates a *U group by light irradiation is encapsulated in a microcapsule together with a diazo compound (
Free radical generators (hereinafter referred to as free radical generators) are well known in the field of graphic arts.

They are widely used as photopolymerization initiators in photopolymerizable compositions, and photosensitive materials are produced using various image forming systems.

Particularly preferred examples of the free radical generator used in the present invention include the following compounds. Aromatic ketones (e.g. benzophenone, 4゜4゜-bis(dimethylamino)benzophenone, 4.4゜-bis(diethylamino)benzophenone, 4-methoxy-4゛ (
dimethylamino)benzophenone, 4,4°-dimethoxybenzophenone, 4-dimethylaminobenzophenone, 4-methoxy-3,3'-dimethylbenzophenone, 1-hydroxycyclohexyl phenyl ketone, 4-
Dimethylaminoacetophenone, 2-methyl-1-(4
-(Methylthio)phenyl2-morpholino-propanone-1-acetophenone, benzyl, cyclic aromatic ketones (e.g. fluorenone, anthrone, xanthone, thioxanthone, 2-chlorothioxanthone, 2.4
-dimethylthioxanthone, 2,4-diethylthioxanthone, acridone, N-ethyl acridone, benzanthrone), quinones (e.g. benzoquinone, 2.3
．． 5-) Tsumethyl-6-promobenzoquinone, 2.6-
di-n-decylbenzoquinone, 1,4-naphthoquinone,
2-isopropoxy-1,4-naphthoquinone, 1.2-
naphthoquinone, anthraquinone, 2-chloro-anthraquinone, 2-methylanthraquinone, 2-tert-butylanthraquinone, phenanthraquinone), benzoin, benzoin ethers (e.g. benzoin methyl ether, benzoin ethyl ether, 2,2-dimethoxy-2 -phenylacetophenone, α-methylolbenzoin methyl ether), aromatic polycyclic hydrocarbons (e.g. naphthalene, anthracene, phenanthrene, pyrene), azo compounds (e.g. azobisisobutyronitrile, α-azo-1-cyclohexane) carbonitrile, azobisvaleronitrile), organic disulfides (e.g. thiuram disulfide), acyloxime esters (e.g. benzyl-(〇-ethoxycarbonyl)-α)
-monoxime).

(Function) When a diazo compound is used as a color former as in the present invention, fixation can be achieved by exposing the entire surface of the recording material after thermal recording to light. In this case, the skin becomes stained brown due to the decomposition of the diazo compound, but the free radical generator used in the present invention can prevent the above-mentioned skin from becoming stained, although the details of its action are not clear.

The amount of the free radical generator added is preferably in the range of 0.01 part to 5 parts, particularly 0.1 part to 1 part, per 1 part of the diazonium salt.

In the present invention, by dissolving at least a part of the diazo compound contained in the microcapsules in a water-insoluble organic solvent, the reactivity during heating recording can be increased and the color density of the recording material can be improved. . Organic solvents that can be used for this purpose include boiling points of 18
It is preferable to use a temperature of 0° C. or higher because evaporation loss during raw storage is small.

Next, the microcapsules used in the present invention will be explained in detail.

Microcapsules that can be used in the present invention can be appropriately selected from known microcapsules, but
In particular, it is preferable to select a material that is difficult to be destroyed by heat or pressure, from the viewpoint of the storage stability of the recording material and its ease of handling.

Such preferable microcapsules are those in which reactive substances present in the core and outside of the microcapsules are heated so that they permeate through the microcapsule walls and react.

Therefore, the capsule walls of the microcapsules used in the present invention do not necessarily need to be melted by heat, and it is preferable that the walls have a higher melting point because they have better shelf life.

Furthermore, as the size of the microcapsules increases, the thermal contact between the core substance of the microcapsules and other substances decreases with short heating, resulting in a decrease in color density.
The average particle size is preferably 20μ or less, particularly preferably 8μ or less.

Next, a method for manufacturing the microcapsules used in the present invention will be described in detail.

The microcapsules used in the present invention are preferably made by emulsifying a core material containing a diazo compound and then forming a wall of a polymer material around the oil droplets. In this case, the reactant forming the polymeric substance is added to the interior of the oil droplet and/or to the exterior of the oil droplet. Specific examples of such polymeric substances include polyurethane, polyurea, polyamide, polyester, polycarbonate, urea-formaldehyde resin, melamine resin, polystyrene, styrene methacrylate copolymer, styrene-acrylate copolymer, gelatin, polyvinylpyrrolidone, Examples include polyvinyl alcohol.

Two or more of these polymeric substances can also be used in combination.

Among the above-mentioned polymeric substances, polyurethane, polyurea, polyamide, polyester, and polycarbonate are preferred in the present invention, and polyurethane and polyurea are particularly preferred.

The microcapsule wall using the above-mentioned polymeric substance is particularly effective when using a microencapsulation method by polymerizing a glue actant from inside the oil droplet. That is, when this method is used, capsules having a uniform particle size and excellent shelf life can be obtained in a short period of time and are suitable as recording materials.

Such techniques and specific examples of compounds are described in U.S. Pat. Nos. 3,726,804 and 3,796.669.

For example, when polyurethane is used as a capsule wall material, a polyvalent isocyanate and a second substance that reacts with it to form the capsule wall (such as a polyol) are mixed into the oily liquid to be encapsulated, emulsified and dispersed in water, and then By increasing the temperature, a polymer formation reaction occurs at the oil droplet interface, forming a microcapsule wall. At this time, an auxiliary solvent with a low boiling point and strong melting power can be used in the oily liquid.

In this case, the polyisocyanate used and the polyol and polyamine to be reacted with it are described in U.S. Pat. No. 3,135,716 and 3.・No. 281.383,
No. 3,468,922, No. 3.773,695, No. 3
, No. 793.268, Special Publication No. 48-40347, No. 4
No. 9-24159, JP-A-48-80191, JP-A No. 48
-84086, and they can also be used.

Furthermore, a tin salt or the like can also be used in combination to promote the urethanization reaction. Note that polyvalent isocyanate can react with water to form a polymer film.

Furthermore, by combining polyvalent isocyanate, which is the first wall-forming substance, and polyol, which is the second wall-forming substance, the thermal permeability of the reactive substance can be changed arbitrarily.

In the present invention, examples of the polyvalent isocyanate as the first wall film-forming substance include m-phenylene diisocyanate, p-phenylene diisocyanate, 2.6-
1-lylene diisocyanate, 2.4-)lylene diisocyanate, naphthalene-1,4-diisocyanate,
diphenylmethane-4,4'-diisocyanate, 3.
3'-dimethoxy-4,4°-biphenyl-diisocyanate, 3,3°-dimethyldiphenylmethane-
4゜4゛-diisocyanate, xylylene-1,4-diisocyanate), 4.4゜-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1゜2-diisocyanate,
Diisocyanates such as cyclohexylene-1゜2-diisocyanate and cyclohexylene-1゜4-diisocyanate; triisocyanates such as 4゜4',4''-triphenylmethane triisocyanate and toluene-2,4,6-1 diisocyanate. , addition of tetraisocyanates such as 4,4'-dimethyldiphenylmethane-2,2',5.5'-tetraisocyanate, hexamethylene diisocyanate and trimethylolpropane!, 2.4-) Addition of lylene diisocyanate and trimethylolpropane Isocyanate prepolymers such as trimethylol propane, adducts of xylylene diisocyanate and trimethylolpropane, and adducts of tolylene diisocyanate and hexanetriol can be used.

On the other hand, the polyol that is the second wall film-forming substance is
Examples include aliphatic and aromatic polyhydric alcohols, hydroxy polyesters, and hydroxy polyalkylene ethers. Preferred polyols include 2
It has the following group (1), (II), (I
0 or less polyhydroxy compounds.

(1) Aliphatic hydrocarbon group having 2 to 8 carbon atoms, where (I[
), (I[[), Ar in (IV) represents a substituted or unsubstituted aromatic moiety, and the aliphatic hydrocarbon group in (1) is
The basic skeleton is -CnH2n-, and hydrogen atoms may be substituted with other elements.

Examples of (I) include ethylene glycol, l.

3-propanediol, 1.4-butanediol, 1.
5-bentanediol, 1,6-hexanediol, 1
, 7-hebutanediol, 1,8-octanediol,
Propylene glycol, 2゜3-dihydroxybutane-
1,2-dihydroxybutane, 1,3-dihydroxybutane, 2,2-dimethyl-1,3-propanediol,
2.4-bentanediol, 2,5-hexanediol, 3-methyl-1,5-bentanediol, 1,4-cyclohexane dimetatool, dihydroxycyclohexane, diethylene glycol, 1,2゜6-trihydroxyhexane, phenyl Ethylene glycol, 1.1.1
-) Limethylolpropane, hexanetriol, pentaerythritol, glycerin and the like.

Examples of (II) include condensation products of aromatic polyhydric alcohols and alkylene oxides such as 1,4-di(2-hydroxyethoxy)benzene and resorcinol dihydroxyethyl ether.

Examples of (III) include p-xylylene glycol,
Examples include m-xylylene glycol, α,α'-dihydroxy-p-diisopropylbenzene, and the like.

Examples of (IV) include 4,4'-dihydroxy-diphenylmethane, 2-(p,p'-dihydroxydiphenylmethyl)benzyl alcohol, adduct of bisphenol A and ethylene oxide, bisphenol A
Examples include adducts of and propylene oxide.

The polyol should be used in a ratio of 0.02 to 2 moles of hydroxyl groups per mole of isocyanate groups.

preferable.

When producing microcapsules as described above, water-soluble polymers can be used. Here, water-soluble polymers include water-soluble anionic polymers, nonionic polymers, and amphoteric polymers. As anionic polymers, both natural and synthetic polymers can be used. For example, −
Examples include those having a coo-1-s03- group.

Specific anionic natural polymers include gum arabic and alginic acid, while semi-synthetic products include carboxymethyl cellulose, phthalated gelatin, sulfated starch, sulfated cellulose, and lignin sulfonic acid.

Synthetic products include maleic anhydride-based (including hydrolyzed) copolymers, acrylic acid-based (including methacrylic acid) polymers and copolymers, and vinylbenzenesulfonic acid-based polymers and copolymers. and carboxy-modified polyvinyl alcohol.

Examples of nonionic polymers include polyvinyl alcohol, hydroxyethyl cellulose, and methyl cellulose.

Examples of amphoteric compounds include gelatin.

These water-soluble polymers are used as a 0.01 to 10% by weight water-soluble liquid.

When making microcapsules, they can be made from an emulsion containing 0.2% by weight or more of the component to be microencapsulated.

The microcapsules containing the diazo compound and free radical generator used in the present invention as a core material are prepared by dissolving or dispersing the core material in a water-insoluble organic solvent and emulsifying it, and then forming a microcapsule wall around it by polymerization. Form. Examples of organic solvents used in this case include phosphoric acid esters, phthalic acid esters, other carboxylic acid esters, fatty acid amides, alkylated biphenyls, alkylated terphenyls, chlorinated paraffins, alkylated naphthalenes, diarylethanes, etc. with a boiling point of 180. ℃ or higher is preferable. Specific examples of these preferred organic solvents include tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, tricyclohexyl phosphate, diptyl phthalate, dioctyl phthalate, dilaurate phthalate, dicyclohexyl phthalate, butyl oleate,
Diethylene glycol dibenzoate, dioctyl sebacate, diptyl sebacate, dioctyl adipate,
trioctyl trimellitate, acetyltriethyl citrate, octyl maleate, dibutyl maleate, isopropylbiphenyl, isoamyl biphenyl, chlorinated paraffin, diisopropylnaphthalene 1.1. I'-
Ditolylethane, 2,4-di-tert-aminophenol, N.

Examples include N-dibutyl-2-butoxy-5-tert-octylaniline. Among these, ester solvents such as diethyl phthalate, dibutyl phthalate, tricresyl phosphate, and diptyl maleate are particularly preferred. still,
The organic solvent is used as a core material to form emulsified droplets (diazo compounds,
It is preferably contained in an amount of 10 to 70% by weight, particularly 20 to 55% by weight, in a vinyl monomer, an organic solvent, a capsule wall-forming substance, etc.

As mentioned above, the microcapsules produced as described above are destroyed by heat and pressure, such as those used in conventional recording materials, and react with the reactive substance contained in the core of the microcapsules and the outside of the microcapsules. This method does not cause a coloring reaction by bringing a reactive substance into contact with it, but rather by heating the reactive substance present in the core and outside of the microcapsule, the reaction mainly occurs through the microcapsule wall. In this case, if the recording layer contains a compound that lowers the glass transition point of the wall material in order to promote softening of the wall of the microcapsule during heating and make it easier for the reactant to pass through, color development is possible. The temperature can be reduced substantially.

Such a glass transition point adjusting agent is preferably one that lowers the glass transition point of the wall material of the microcapsules to 80 to 150°C, particularly one that lowers it to 100 to 130°C.
Specific examples include hydroxy compounds, carbamate ester compounds, aromatic methoxy compounds, and the like.

Some of these compounds not only lower the glass transition point of the microcapsule wall material, but also lower the melting points of cambling components and basic substances. This is particularly effective as the temperature is further reduced.

These compounds are introduced into the recording layer in the same way as basic substances.

The heat-sensitive recording material of the present invention contains silica, barium sulfate, titanium oxide, aluminum hydroxide, zinc oxide,
Pigments such as calcium carbonate, fine powders such as styrene beads and urea-melamine resin can be added.

Similarly, metal stones M may be added to prevent sticking. The amount used is 0.2 to 7
It is glrd.

Furthermore, a heat-melting substance can be added to the heat-sensitive recording material of the present invention in order to increase the heat recording speed. Such thermofusible substances are solid at room temperature, but melt when heated with a thermal head, and have a melting point of 50°C to 150°C.
It is a substance that melts diazo compounds, coupling agents, or basic substances. 0.1 for thermofusible substances
Dispersed in ~10μ particles, solid content 0.2~1g1r
used in an amount of d. Specific examples of heat-melting substances include:
Fatty acid amide, N-substituted fatty acid amide, ketone compound, N
Examples include substituted carbamate compounds, urea compounds, and esters.

Substances not contained in microcapsules are preferably used after being dispersed in solid form using a sand mill or the like. In this case, each is separately dispersed in a water-soluble polymer solution. Preferred water-soluble polymers include water-soluble polymers used when making microcapsules. In this case, the concentration of the water-soluble polymer is 2 to 30% by weight, and the amount of the material to be dispersed in the water-soluble polymer solution is 5 to 40% by weight. Preferably, the dispersed particle size is 10 microns or less.

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 0.5 to 5 g/rrr as solid content.

In the present invention, in addition to the above materials, citric acid is used as an acid stabilizer.
Tartaric acid, oxalic acid, boric acid, phosphoric acid, pyrophosphoric acid, etc. can be added.

The heat-sensitive recording material of the present invention is prepared by preparing a coating liquid by dispersing microcapsules containing a diazo compound and an organic solvent and other components in a solid state (which can also be microcapsulated) or by melting them as an aqueous solution and then mixing them. , coated on a support such as paper or synthetic resin film by a coating method such as bar coating, blade coating, air knife coating, gravure coating, roll coating, spray coating, dip coating, etc., and dried to a solid content of 2.5. Produced by providing a heat sensitive layer of ~15 g/rrf.

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)
It is advantageous in terms of storage stability over time.

In addition, in order to prevent the coating liquid from penetrating the paper and 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 with an optical surface roughness of 8μ or less as described in JP-A No. 58-136492, and paper with a density of 0.9 g/cm3 or less and an optical contact ratio of 15% or more as described in JP-A-58-69091. , JP-A-58-65695, a paper made from pulp beaten to 400 cc or more with Canadian standard freeness (JIS P8121), described in JP-A-58-69097, which prevents penetration of coating liquid. JP-A-59-359, described in JP-A-59-359, uses the glossy side of base paper made by a Yankee machine as the coating surface to improve color density and resolution.
The paper described in No. 85, in which the base paper is subjected to a corona discharge treatment to improve its applicability, can also be used in the present invention and gives 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 heat-sensitive recording material of the present invention can be used as printer paper for facsimile machines and electronic computers that require high-speed recording, and can be fixed by exposing it to light after printing by heating to decompose unreacted color formers. . In addition, it can also be used as a heat-developable copying paper.

(Effects of the Invention) The heat-sensitive recording material of the present invention has at least a diazo compound in microcapsules, so the recording material has good shelf life, and since the free radical generator coexists with the diazo compound, Since the background is not smudged when photofixed, the recorded image can be stored in good condition after recording.

It goes without saying that these effects of the present invention can be similarly obtained in multicolor thermosensitive recording materials using one or more color formers.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto. Note that "parts" indicating the amount added represent "parts by weight."

Example 1 4 parts of the following diazo compound and 18 parts of a (3:1) adduct of xylylene diisocyanate and trimethylolpropane were mixed with 24 parts of tricresyl phosphate, 0.5 part of 2-dimethoxy-2-phenylacetophenone, and 6 parts of dichloromethane. was added to a mixed solvent and dissolved. This diazo compound solution was added to an aqueous solution containing 5.2 parts of polyvinyl alcohol dissolved in 58 parts of water, and emulsified and dispersed at 20°C to obtain an emulsion having an average particle size of 2.5 μm. 100 parts of water was added to the obtained emulsion and heated to 60° C. with stirring, and after 2 hours, a capsule liquid containing a diazo compound in the core substance was obtained.

(Diazo compound) C4Hg C4H9 Next, 10 parts of 2-hydroxy-3-naphthoic acid 3'-morpholinopropylamide and 15 parts of p-benzyloxyphenol were added to 100 parts of a 5% polyvinyl alcohol aqueous solution, and dispersed in a sand mill for about 24 hours. A dispersion of a coupling component and p-penzyloxyphenol having an average particle size of 2 μm was obtained.

Capsule liquid of diazo compound obtained as above 5
48 parts of a dispersion of a coupling component and p-benzyloxyphenol were added to 0 parts to prepare a coating liquid. Dry this coating solution on smooth high-quality paper (50g/rd) using Coach-in-Blonde! Apply so that ffilog/d is 40
It was dried at ℃ for 30 minutes to obtain a heat-sensitive recording material.

(Test method) Heat recording was performed on the obtained heat-sensitive recording material using a Gmode thermal printer (Hifax 700: Hitachi (Yokosaki)), and then the entire surface was recorded using a high-pressure mercury lamp (Jet Light: made of oak wood). It was exposed to light and fixed.The blue density of the resulting recorded image was measured using a Macbeth reflection density needle.

In addition, the yellow density of the background portion was also measured in the same manner. The results are shown in Table 1. Further, when thermal recording was performed again on the fixed portions, no image was recorded on any of them, and it was confirmed that they were fixed.

Next, in order to examine raw storage stability, we examined the background density (fog) of the heat-sensitive recording material and the heat-sensitive recording material at 40°C and relative humidity of 9.
Table 1 shows the results of fogging measured with a Macbeth reflection densitometer after storage in a dark place under 0% RH conditions for 24 hours and a forced deterioration test.

Example 2. ~7゜Practice 1 Heat-sensitive recording materials 2 to 7 were obtained in the same manner as in Example 1, except that the free radical generator shown in the table below was used in place of 2,2-dimethoxy-2-phenylacetophenone in Example 1. Ta.

The obtained recording material was tested in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 1 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 2,2-dimethoxy-2phenylacetophenone was removed.

The obtained recording material was tested in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 2 A heat-sensitive recording material was obtained in the same manner as in Comparative Example 1, except that tricresyl phosphate was omitted and 24 parts of diptyl phthalate was used instead. The results are shown in Table 1.

Example 8 The dispersion composition of the coupling components used in Example 1 was changed to 10 parts of 2-hydroxy-3-naphthoic acid anilide, 10 parts of triphenylguanidine, and p- as a color accelerator.
A heat-sensitive recording material was obtained in the same manner as in Example 1, except that 15 parts of benzyloxyphenol was added to 100 parts of 5% polyvinyl alcohol to make 1 lilN.

Table 1 As is clear from Table 1, the background yellow density of Comparative Examples 1 and 2 is high, whereas Examples 1 to 1 of the present invention
In the case of No. 8, it was demonstrated that the yellow density in the background area could be kept low without causing any other performance deterioration.

Claims (1)

[Claims] In a heat-sensitive recording material provided with a recording layer containing at least a diazo compound and a coupling component on a support,
A heat-sensitive recording material characterized in that the diazo compound is contained in microcapsules together with at least one compound that generates free radicals when irradiated with light.