JPH0688460B2 - Thermal recording material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention relates to a heat-sensitive recording material.
The present invention relates to a heat-sensitive recording material which has excellent preservability before heat recording, has a high color density at the time of heat recording, and has less background fog.

"Prior art" The thermal recording method (1) does not require development, (2) when the support is paper, the quality of the paper is similar to general paper, (3) is easy to handle, (4) color density It is rapidly popularized in recent years in the fields of facsimiles and printers because of its advantages such as high cost, (5) simple and inexpensive recording device, and (6) no noise during recording.

As a recording material used in the thermal recording method, a leuco color-developing thermal recording material is usually used. However, this heat-sensitive recording material has a drawback that color develops unexpectedly due to severe handling after recording, heating or adhesion of solvents, and the recorded image is stained. As a heat-sensitive recording material without such a defect, diazo color-developing heat-sensitive recording material has been actively researched in recent years. For example, JP-A-57-123086
No., Journal of the Institute of Image Electronics Engineers, 11 , 290 (1982), etc., a recording material containing a diazo compound, a coupling component and a chlorine component (including a substance which becomes basic by heat) is heated. It is recorded and then irradiated with light to decompose the unreacted diazo compound and stop the color development. Certainly, according to this method, it is possible to stop (hereinafter, referred to as fixing) the color development of a portion where recording is unnecessary. However, also in this recording material, pre-coupling gradually progresses during storage, and undesired coloring (fog) may occur.

Also, various new functions are required in such a recording field, and, for example, facsimiles and color printers for transmitting color originals have been developed. An ink jet method and a thermal transfer method are used as these printing methods. However, these have drawbacks such as clogging of ink nozzles and a large amount of unnecessary ink sheets. Thermal paper is known that is capable of multicolor development with a thermal system. For example, there is a reaction product of diazosulfonate, a combination of diazosulfonate and a leuco coloring system, and the like. These are compounds that cause a color-forming reaction and it is necessary to have a difference in thermal responsiveness, so that the color-forming materials that can be used are very limited, and this is greatly restricted in designing and manufacturing recording materials.

In general, character recording is mainly performed for heat-sensitive recording, but in recent years, there has been an increasing demand for image recording with gradation such as a hard copy of a television image. As a method of expressing gradation, a method of changing the recording area while keeping the recording density constant,
There is a method to change the recording density while keeping the recording area constant,
The former is superior to the latter because the resolution is lowered and the halftone expression is limited. However, conventional thermal paper is suitable for the former method, but not so suitable for the latter method. This is because the latter method requires printing with an intermediate density as thermal paper. That is, it is required that the applied energy changes with a certain degree of graduality (the change rate is not too large).

However, the conventional leuco color-developing thermal recording paper is one in which a leuco dye and a phenol-based color developer are finely dispersed in a size of micron order, mixed and applied to a paper support, and heated by a thermal head. The above-mentioned color-forming components are melt-mixed with each other to form a color, but it is not easy to make a difference in temperature characteristics between particles or between coating layer portions.

Therefore, in order to solve these problems, we have proposed a method in which at least one of the components involved in the coloring reaction is contained in the core substance, and a wall is formed around this core substance by polymerization to form microcapsules. (JP-A-58-65043) found an excellent thermal recording material.

By combining a plurality of microcapsules having different thermal responsiveness by changing the wall material of the microcapsules, it is possible to realize the above-described heat-sensitive recording material and / or multicolor heat-sensitive recording material capable of reproducing halftone. Headings, each,
It is presented in Japanese Patent Application No. 59-89781 and Japanese Patent Application No. 59-99489.

"Problems to be Solved by the Invention" However, even in the heat-sensitive recording material produced by the microencapsulation method, unexpected fog often occurs during storage.

Further, it has been desired to further improve the thermochromic property.

"Object of the Invention" Therefore, a first object of the present invention is to provide a heat-sensitive recording material having excellent raw storability and high thermochromic property.

A second object of the present invention is to provide a heat-sensitive recording material excellent in manufacturing suitability.

“Means for Solving Problems” As a result of earnest research by the present inventors, in a heat-sensitive recording material having a heat-sensitive layer composed of a diazo compound and a coupling component, at least one of the diazo compound and the coupling component was selected. The problem has been solved by a heat-sensitive recording material which is encapsulated in a microcapsule together with an organic solvent, and the organic solvent is a compound represented by the following formula.

In the above formula, R represents a cresyl group.

"Function" The microcapsule of the present invention is a reactive substance that is destroyed by heat or pressure and is contained in the core of the microcapsule and a reactive substance outside the microcapsule as used in conventional recording materials. It does not cause a color development reaction by contacting with each other, but by heating the reactive substance existing on the core and the outside of the microcapsule, the reaction mainly passes through the microcapsule wall.

The microcapsules of the present invention are prepared by dissolving the diazo compound or the coupling component encapsulated as the core substance with the organic solvent of the present invention and emulsifying it in water, and then forming the microcapsule wall around the droplets by polymerization. To be done.

The organic solvent of the present invention is a compound represented by the above general formula, and diphenyl cresyl ester phosphate is particularly preferable.

The organic solvent of the present invention has higher solubility than conventional phosphoric acid ester-based compounds, and when used in a heat-sensitive recording material, the occurrence of background fog is small, and the effect on the occurrence of background fog is not clear. It is expected that the solvent will affect the formation of the microcapsule wall. In particular, it is presumed that the density of the microcapsule wall is affected, and as a result, the occurrence of background fog is affected.

The addition amount of the microcapsules of the present invention is 2 parts by weight of the organic solvent of the present invention with respect to 24 parts by weight of microcapsule wall material.
1 to 50 parts by weight of diazo compound or coupling component
It is 50 parts by weight. Still more preferably, the organic solvent 2-30
2 to 15 parts by weight of diazo compound or coupling component.

The diazo compound used in the present invention has the general formula ArN ₂ + X
^- (wherein, Ar represents an aromatic moiety, N ₂ ⁺ represents a diazonium group, X ^-. Is representative of the acid anion) a diazonium salt represented by the color development undergoes a coupling component and a coupling reaction It is a compound that can be decomposed by light.

As the aromatic moiety, specifically, those having the following general formula are preferred.

In the formula, Y represents a hydrogen atom, a substituted amino group, an alkoxy group, an aryloxy group, an arylthio group, an alkylthio group or an acylamino group, and R represents a hydrogen atom, an alkyl group, an alkoxy group, an aryloxy group, an arylamino group or , Halogen (I, Br, Cl, F).

The substituted amino group of Y includes a monoalkylamino group, a dialkylamino group, an arylamino group, a morpholino group,
A piperidino group and a pyrrolidino group are preferred.

Specific examples of the diazonium that forms a salt include 4-diazo-1-dimethylaminobenzene, 4-diazo-1-diethylaminobenze, 4-diazo-1-dipropylaminobenzene, 4-diazo-1-methylbenzylamino. Benzene, 4-diazo-1-dibenzylaminobenzene,
4-diazo-1-ethylhydroxyethylaminobenzene, 4-diazo-1-diethylamino-3-methoxybenzene, 4-diazo-1-dimethylamino-2-methylbenzene, 4-diazo-1-benzoylamino-2, 5-
Diethoxybenzene, 4-diazo-1-monophorinobenzene, 4-diazo-1-morpholino-2,5-diethoxybenzene, 4-diazo-1-morpholino-2,5-dibutoxybenzene, 4-diazo -1-anilinobenzene, 4
-Diazo-1-toluylmercapto-2,5-diethoxybenzene, 4-diazo-1,4-methoxybenzoylamino-2,5-diethoxybenzene, 4-diazo-1-pyrrolidino-2-ethylbenzene and the like. To be

Specific examples of the ^{_{anion, C H F 2H + 1COO- (}} n is 3
9 ^{_{integer), CmF 2 m + 1 SO}} 3 - (m is 2-8 integer), (Cl
_{F 2 l + 1 SO 2)} 2 CH - (l 1 to 18 integer), BF ₄ ^-, PF ₆ ^-, and the like.

In particular, the acid anion contains a perfluoroalkyl group or a perfluoroalkenyl group, or
PF ₆ ^- is preferable because it causes less fog during storage.

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

The coupling component used in the present invention is one that forms a dye by coupling with a diazo compound (diazonium salt) in a basic atmosphere, and a coupling component that promotes color development by a basic substance and a basic substance are used. Even if it is not present, some coupling components have high color density.
Specific examples of the coupling component whose color density is promoted by the basic substance are resorcin, phloroglucin, 2,
Sodium 3-dihydroxynaphthalene-6-sulphonate, 1-hydroxy-2-naphthoic acid morpholinopropylamide, 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 tetradecylamide, acetanilide, acetoacetanilide, benzoylacetanilide, 1-phenyl-3-methyl-5-pyrzolone, 1- (2 ', 4', 6'-
Trichlorophenyl) -3-benzamido-5-pyrazolone, 1- (2 ', 4', 6'-trichlorophenyl) -3
-Anilino-5-pyrazolone, 1-phenyl-3-phenylacetamido-5-pyrazolone and the like.

As a coupling component having a high color density even if there is no basic component, active methylene compounds, aromatic amino compounds, aromatic hydroxy compounds having a basic group in the molecule, etc. , Β-
Ketocarboxylic acid amides (for example, benzoylacetanilide, pivaloylacetanilide, 1,3-bis (benzoylacetamino) toluene, 1,3-bis (pivaloylacetaminomethyl) benzene, etc.), pyrazolones [For example, 3-methyl-1-phenylpyrazolone,
3-hexylcarbamoyl-1-phenylpyrazolone,
3-myristoylamino-1- (2,4,6-trichlorophenyl) pyrzolone, etc.], barbituric acids [eg
1,3-didodecyl barbituric acid, 1,3-dicyclohexyl barbituric acid, 1-octyl-3-stearyl barbituric acid, etc., 1,3-cyclohexanediones (e.g. 5,5-dimethyl-1,3 -Cyclohexanedione, 5,5
-Dimethyl-4-phenyl-1,3-cyclohexanedione, etc.] and the like.

As the aromatic amine compound, α-naphthylamine,
β-naphthylamine, 1-anilino-naphthalene, 2-
Anilino-naphthalene, 3-amino-diphenylamine, 4,4'-diaminodiphenylmethane, N, N-dicyclohexylaniline, 2-aminocarbazole, 2-phenylindole, 1-phenyl-2-methylindole and N, N There are organic acid salts and inorganic acid salts of aromatic amines such as p-toluenesulfonic acid salt of dimethylaniline and α-naphthyluanic acid hydrochloride.

Examples of the aromatic hydroxy compound having a basic group in the molecule include 2-hydroxy-3-naphthoic acid-3'-morpholinopropylamide and 2-hydroxy-3-naphthoic acid-
2'-diethylaminoethylamide, 2-hydroxy-
3-naphthoic acid-3-piperidinopropylamide, 2-
Hydroxy-3-naphthoic acid-3'-piperidinopropylamide, 2-hydroxy-3-naphthoic acid-p-
(3'-N'-cyanoguanidinopropyl nooxyanilide, salicylic acid-p- (3'-morpholinopropyl)
Oxyanilide, 1-naphthol-4-sulfonic acid-
Aromatic hydroxy compounds having residues such as 3'-diethylaminopropylamide, 8-hydroxyquinoline-4-sulfonic acid-2'-diethylaminoethylamide and organic carboxylate salts of amino groups which generate basicity by heating [For example, 2-hydroxy-3-naphthoic acid-3 '
-Trichloroacetic acid salt of morpholinopropylamide, 1-
Naphthol-4-sulfonic acid-3'-diethylaminopropylamide phenylthioacetate, etc.] and the like.
Further, by using two or more of these coupling components in combination, an image of any color tone can be obtained.

In the present invention, a basic substance can be added for the purpose of accelerating thermal color development. As the basic substance, a hardly water-soluble or water-insoluble basic substance or a substance which generates an alkali by heating is used.

As the basic substance, inorganic and organic ammonium salts, organic amines, amides, urea and thiourea and their derivatives, thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidazolines, triazoles. And nitrogen-containing compounds such as morpholines, piperidines, amidines, formazines and pyridines. Specific examples thereof include ammonium acetate, tricyclohexylamine, tribenzylamine, octadecylbenzylamine, stearylamine, allylurea, thiourea, methylthiourea, allylthiourea, ethylenethiourea, 2-benzylimidazole, 4-phenyl. Imidazole, 2-
Phenyl-4-methyl-imidazole, 2-undecyl-imidazoline, 2,4,5-trifuryl-2-imidazoline, 1,2-diphenyl-4,4-dimethyl-2-imidazoline, 2-phenyl-2-imidazoline, 1,2,3-triphenylguanidine, 1,2-ditolylguanidine, 1,2-dicyclohexylguanidine, 1,2,3-tricyclohexyguanidine, guanidine trichloroacetate, N, N'-dibenzylpiperazine, There are 4,4'-dithiomorpholine, morpholinium trichloroacetate, 2-amino-benzothiazole, 2-benzoylhydrazino-benzothiazole. These basic substances can be used in combination of two or more.

The microcapsules of the present invention are produced by emulsifying the diazo compound or coupling component and the organic solvent of the present invention as a core substance, and then forming a wall of a polymer substance around the oil droplets. The reactant forming the polymer substance is added inside the oil droplet and / or outside the oil droplet. Specific examples of the polymer substance include polyurethane, polyurea, polyamide,
Examples thereof include polyester, polycarbonate, urea-formaldehyde resin, melamine resin, polystyrene, styrene methacrylate copolymer, styrene-acrylate copolymer, gelatin, polyvinylpyrrolidone and polyvinyl alcohol.

Two or more polymer substances can be used in combination. Preferred polymeric substances are polyurethane, polyurea, polyamide,
Polyester and polycarbonate, more preferably polyurethane and polyurea.

When emulsifying, the organic solvent of the present invention is used.
An organic solvent having a boiling point of 180 ° C. or higher such as fatty acid amide or alkyl naphthalene, or an auxiliary solvent such as methylene chloride can be used in combination.

As a method of producing the microcapsule wall of the present invention, the effect is particularly large when the microencapsulation method by polymerizing the reactant from the inside of the oil droplet is used. That is, it is possible to obtain capsules having a uniform particle size within a short period of time, which are preferable as a recording material having excellent raw storability.

For this method and specific examples of the compound, US Pat.
726,804 and 3,796,669.

For example, when polyurethane is used as a capsule wall material, a polyisocyanate and a second substance (for example, a polyol) which reacts with the polyisocyanate to form a capsule wall are mixed in an oily liquid to be encapsulated, emulsified and dispersed in water, and then the temperature is increased. By rising, a polymer forming reaction is caused at the oil droplet interface to form a microcapsule wall. At this time, an auxiliary solvent having a low boiling point and a strong dissolving power can be used in the oily liquid.

In this case, regarding the polyisocyanate used and the partner polyol and polyamine which react with it, US Pat. Nos. 3,281,383, 3,773,695, 3,793,268 and JP-B-48-4
0347, 49-24159, JP-A-48-80191, 48-84
No. 086, and they can also be used.

The capsule wall is not limited to the above method, but is preferably a polymer substance formed by a reaction of a polyvalent isocyanate with a polyol, in the present invention. The color development temperature can be changed by a combination of a polyvalent isocyanate and a polyol.

As the polyvalent isocyanate, for example, m-phenylene diisocyanate, p-phenylene diisocyanate,
2,6-tolylene diisocyanate, 2,4-tolylene 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 Diisocyanates such as -1,2-diisocyanate, cyclohexylene-1,2-diisocyanate and cyclohexylene-1,4-diisocyanate, 4,4 ', 4 "-triphenylmethane triisocyanate, toluene-2,4,6- Triisocyanates such as triisocyanates, tetraisocyanates such as 4,4'-dimethyldiphenylmethane-2,2 ', 5,5'-tetraisocyanates, adducts of hexamethylene diisocyanate and trimethylolpropane, 2,4-
There are isocyanate prepolymers such as tolylene diisocyanate and trimethylol propane adducts, xylylene diisocyanate and trimethylol propane adducts, and tolylene diisocyanate and hexane triol adducts.

Examples of polyols include aliphatic and aromatic polyhydric alcohols, hydroxypolyesters, and hydroxypolyalkylene ethers. Preferred polyols include the following (I), (II) and (II
The molecular weight of the group I) or (IV) is 5000.
The following polyhydroxy compounds may be mentioned.

(I) Aliphatic hydrocarbon group having 2 to 8 carbon atoms Here, (II), (III) , Ar is a substituted or a (IV), represents an aromatic moiety of unsubstituted, and aliphatic hydrocarbon group (I), -CnH ₂ n- was a basic skeleton The hydrogen group may be replaced with another element.

Specific examples thereof include (I) ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7- Heptanedinol, 1,8-octanediol,
Propylene glycol, 2,3-dihydroxybutane, 1,2
-Dihydroxybutane, 1,3-dihydroxybutane, 2,2
-Dimethyl-1,3-propanediol, 2,4-pentanediol, 2,5-hexanediol, 3-methyl-1,5-pentakediol, 1,4-cyclohexanedimethanol,
Dihydroxycyclohexane, diethylene glycol,
Examples thereof include 1,2,6-trihydroxyhexane, phenylethylene glycol, 1,1,1-trimethylolpropane, hexanetriol, pentaerythritol, and glycerin.

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

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

Examples of (IV) are 4,4'-dihydroxy-diphenylmethane, 2- (p, p'-dihydroxydiphenylmethyl) benzyl alcohol, an adduct of ethylene oxide with bisphenol A, and propylene oxide with bisphenol A. And the like. The polyol is preferably used in such a manner that the ratio of the hydroxyl group is 0.02 to 2 mol with respect to 1 mol of the isocyanate group.

The polyisocyanate can also react with water to form a polymeric substance.

The water-soluble polymer that can be used when making the microcapsules may be any of water-soluble anionic polymers, nonionic polymers, and amphoteric polymers.
Examples of the anionic polymer, either natural can be used even be synthetic, for example _{^{-COO -, -S ▲ O - 3}} ▼ include those having a group. Specific anionic natural polymers include arabic gum and alginic acid, and semi-synthetic products include carboxymethyl cellulose, phthalated gelatin, sulfated starch, sulfated cellulose,
Lignin sulfonic acid etc.

As synthetic products, maleic oxygen anhydride (including hydrolyzed products) copolymers, acrylic acid-based (including methacrylic acid-based) polymers and copolymers, vinylbenzenesulfonic acid-based polymers and copolymers, carboxy, etc. Modified polyvinyl alcohol and the like.

Examples of the nonionic polymer include polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose and the like.

Examples of amphoteric compounds include gelatin.

These water-soluble polymers are used as 0.01-10 wt% aqueous solutions. The particle size of the microcapsules is adjusted to 20 μm or less. Generally, if the particle size exceeds 20μ, the print quality tends to be poor.

In particular, when heating with a thermal head is performed from the coating layer side, it is preferably 8 μm or less in order to avoid pressure fog.

Any one of the diazo compound and the coupling component which are the main components used in the present invention is used as the core substance of the microcapsule. When two kinds of microcapsules are contained in the core substance of the microcapsules, separate microcapsules may be used. Other components not contained in the core material of the microcapsules are used in the heat-sensitive layer outside the microcapsules.

When making a microcapsule, it can be made from an emulsion containing 0.2 wt% or more of the component to be microencapsulated.

A diazo compound used in the present invention, a coupling component,
The basic substance used as necessary, whether contained in the inside of the microcapsule or in the heat-sensitive layer outside the microcapsule, requires 0.1 to 10 parts by weight of the coupling component per 1 part by weight of the diazo compound. It is preferable to use the basic substance used according to the above in a ratio of 0.1 to 20 parts by weight. The diazo compound is preferably applied in an amount of 0.05 to 5.0 g / m ² .

When the diazo compound used in the present invention, the coupling component and the basic substance used if necessary are not microencapsulated, it is preferable to use them by solid dispersion with a water-soluble polymer by a sand mill or the like. Preferred water-soluble polymers include water-soluble polymers used when making microcapsules. At this time, the concentration of the water-soluble polymer is 2 to 30.
wt%, and the diazo compound, coupling component, and basic substance are added to this water-soluble polymer solution at 5 to 40%, respectively.
It is input so that it becomes wt%.

The dispersed particle size is preferably 10 μm or less.

The heat-sensitive recording material of the present invention contains silica, barium sulfate, titanium oxide, aluminum hydroxide, zinc oxide, for the purpose of preventing sticking to the thermal head and improving the writability.
Pigments such as calcium carbonate and fine powders such as styrene beads and urea-melamine resin can be used.

Similarly, metal soaps can be used to prevent staking. The usage of these is 0.2
~ 7 g / m ² .

Further, in the heat-sensitive recording material of the present invention, a heat-melting substance can be used to increase the heat-recording density. The heat-melting substance is a substance that is solid at room temperature and has a melting point of 50 to 150 ° C. that melts when heated by a thermal head.
It is a substance that dissolves coupling components or basic substances. The heat-fusible substance is dispersed in the form of particles having a particle size of 0.1 to 10 μ and is used in an amount of solid content of 0.2 to 7 g / m ² . Specific examples of the heat-fusible substance include fatty acid amide, N-substituted fatty acid amide, ketone compound, urea compound, ester and the like.

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

As the binder, polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, arabic rubber, gelatin, polyvinyl pyrrolidone, casein, styrene-butadiene latex, acrylonitrile-butadiene latex, polyvinyl acetate, polyacrylic ester, ethylene-vinyl acetate copolymer Various emulsions of polymers can be used. The amount used is 0.5 to 5 g / m ² of solid content.

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

The heat-sensitive recording material of the present invention is prepared by preparing a coating solution containing a diazo compound, a coupling component, a basic substance used if necessary and other additives, and bar coating or blade coating on a support such as paper or a synthetic resin film. , Air knife application,
Solids are dried by coating methods such as gravure coating, roll coating, spray coating, and dip coating.
Provide a heat-sensitive layer of 2.5 to 25 g / m ² . As another method, a coupling component, a basic substance and other additives used as necessary are added as a core substance of microcapsules, or dispersed as a solid, or dissolved as an aqueous solution and mixed to prepare a coating liquid, It is coated on a support and dried to provide a precoat layer having a solid content of ² to 10 g / m ² , and a diazo compound as the main component and other additives are further added as a core substance of the microcapsule on the precoat layer, or It is also possible to apply a coating solution prepared by dispersing it as a solid or dissolving it as an aqueous solution and then mixing it and drying it to obtain a laminated type having a coating layer having a solid content of 1 to 15 g / m ² . In any case, it is necessary to encapsulate one of the diazo compound and the coupling component in microcapsules. The lamination type thermal recording material may be formed by laminating the layers in the reverse order, and the coating method may be sequential coating or simultaneous coating of the layers. This laminated-type heat-sensitive recording material is particularly excellent in long-term storability.

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

In order to prevent the coating liquid from penetrating into the paper and to improve the contact between the recording heat head and the heat-sensitive recording layer, it is described in JP-A-57-116687. Moreover, paper with a smoothness of 90 seconds or more is advantageous.

The optical surface roughness described in JP-A-58-136492 is 8 μm.
Paper having a thickness of 40 to 75 μ, a paper having a density of 0.9 g / cm ³ or less and an optical contact ratio of 15% or more as described in JP-A-58-69091, and JP-A-58-69097. Canadian Standard Water (JIS
P8121) paper made from pulp that has been beaten to 400 c.c. or more to prevent impregnation of the coating liquid, JP-A-58-65695
In order to improve the color density and resolution by using the glossy surface of the base paper produced by the Yankee machine as the coating surface,
The paper described in JP-A-59-35985, which is obtained by subjecting the base paper to corona discharge treatment to improve the coating suitability, is also used in the present invention and gives good results. In addition to these, any of the supports generally 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 facsimiles and electronic calculators that require high-speed recording, and can be fixed by exposing after exposure to heat and decomposing unreacted diazo compounds. . In addition to this, it can also be used as a heat-developing copying paper.

"Examples" Examples will be shown below, but the present invention is not limited thereto. In addition, "part" indicating the addition amount represents "part 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 added to and dissolved in 24 parts of diphenylcresyl phosphate. A solution of this diazo compound was mixed with an aqueous solution in which 3.5 parts of polyvinyl alcohol and 1.7 parts of gelatin were dissolved in 58 parts of water.
It was emulsified and dispersed at ℃.

100 parts of water was added to the obtained emulsion and the mixture was heated to 60 ° C. with stirring and after 2 hours, a capsule liquid having an average particle diameter of 3 μ and containing a diazo compound was obtained.

(Diazo compound) Next, 20 parts of 2-hydroxy-3-naphthoic acid anilide was added to 100 parts of a 5% aqueous polyvinyl alcohol solution and dispersed in a sand mill for about 24 hours to obtain a dispersion having an average particle diameter of 3 μm.

Next, 20 parts of triphenylguanidine was added to 100 parts of a 5% aqueous solution of polyvinyl alcohol and dispersed by a sand mill for about 24 hours to obtain a dispersion having an average particle size of 3μ.

Further, 20 parts of p-benzyloxyphenol is added to 100 parts of a 5% polyvinyl alcohol aqueous solution, and about 24 by a sand mill.
The dispersion was carried out over time to obtain a dispersion having an average particle size of about 3μ.

The diazo compound capsule liquid obtained as described above 50
15 parts of coupling component dispersion, 15 parts of triphenylguanidine dispersion and 30 parts of p-benzyloxyphenol dispersion were added to 10 parts to prepare a coating solution.

This coating solution was applied to a smooth high-quality paper (50 g / m ² ) using a coating grind so as to have a dry weight of 8 g / m ^{2, and} was dried at 40 ° C. for 30 minutes to obtain a thermosensitive recording material. .

(Test method) Thermal recording was performed on the obtained thermal recording material using a GIII mode thermal printer (Hyfax 700; manufactured by Hitachi, Ltd.), and then Ricopy Super Dry 100 (manufactured by Ricoh Co., Ltd.) high pressure mercury lamp (Jetrite). Oak corporation
(Manufactured by Mitsui Chemical Co., Ltd.) was used for the whole surface exposure and fixing. The blue density of the obtained recorded image was measured by a Macbeth reflection densitometer.
In addition, the yellow density of the background part was also measured. The results are shown in Table 1. On the other hand, when heat recording was performed again on the fixed portion, it was confirmed that no image was recorded on any of the fixed portions.

Next, in order to check the raw storability, the background density (background fog) of the thermosensitive recording material and the thermosensitive recording material at 40 ° C and relative humidity
Stored in a dark place for 24 hours under the condition of 90% RH and measured the background fog after conducting a forced deterioration test with a Macbeth reflection densitometer,
I saw changes in the background fog. The results are shown in Table 1.

Comparative Example 1 A thermosensitive recording material was obtained in the same manner as in Example 1 except that 24 parts of tricresyl phosphate was used instead of 24 parts of diphenyl cresyl phosphate of Example 1. The test was conducted in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 2 A thermosensitive recording material was obtained in the same manner as in Example 1 except that 24 parts of dibutyl phthalate was used instead of 24 parts of diphenyl cresyl phosphate of Example 1. The test was conducted in the same manner as in Example 1, and the results are shown in Table 1.

"Effect of the invention" As can be seen from Table 1, the image density of Example 1 using the organic solvent of the present invention is higher than that of Comparative Examples 1 and 2 using the conventional organic solvent, and the background part density is high. Low. Further, after the forced deterioration test, the density of the background portion is lower in the example than in the comparative example.

Claims (1)

[Claims] 1. A heat-sensitive recording material having a heat-sensitive layer comprising a diazo compound and a coupling component, wherein at least one of the diazo compound and the coupling component is encapsulated in a microcapsule together with an organic solvent, and the organic solvent is A thermal recording material, which is a compound represented by the formula: In the above formula, R represents a cresyl group.