JP2000289338A - Heat-sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive recording material free from fixing inhibition when print recording is carried out, providing with the short fixing time and also provided with the superior whiteness of a texture part. SOLUTION: A heat-sensitive recording material containing at least one heat-sensitive recording layer of 90% or less haze value containing a diazonium salt compound decomposed by ultraviolet rays on a substrate composed of a thermoplastic resin layer containing a fluorescent brightening agent and a white pigment and formed on a base layer. In that case, an embodiment, in which the heat-sensitive recording layer contains a binder and particles and the weight ratio between the binder and the particles (binder/particles) is 0.20 or more, is preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material which does not hinder fixing during printing, has a short fixing time, and has excellent whiteness of the background after fixing.

[0002]

2. Description of the Related Art A heat-sensitive recording material containing a diazonium salt compound is heated by a thermal head or the like for printing, and then subjected to a fixing treatment in which a diazonium salt compound not used for printing is decomposed by ultraviolet rays. In order to make the background part look whiter, a fluorescent whitening agent is added to the heat-sensitive recording layer. However, this fluorescent whitening agent absorbs ultraviolet rays and causes fixing inhibition, so that there is a problem that the fixing time is long and the speed cannot be increased. Also, a method has been proposed in which a fluorescent whitening agent having a bis (alkyl-substituted benzoxazolyl) thiophene structure represented by Ubitex OB is added to a thermoplastic resin layer. Bleed out, etc., and there is a problem that the whiteness of the background portion is reduced.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, an object of the present invention is to provide a heat-sensitive recording material which has no fixing hindrance at the time of photographic printing, has a short fixing time, and is excellent in whiteness of a background portion after fixing.

[0004]

Means for solving the above problems are as follows. That is, <1> a support having a thermoplastic resin layer containing a fluorescent whitening agent and a white pigment on a substrate, a diazonium salt compound decomposed by ultraviolet light, and a haze value of 90% or less A heat-sensitive recording material comprising at least one heat-sensitive recording layer. <2> The heat-sensitive recording material according to claim 1, wherein the fluorescent whitening agent is a compound represented by the following structural formula (I). Structural formula (I)

Embedded image However, in the structural formula (I), R ₁ , R ₂ , R ₃ and R
₄ represents a hydrogen atom or a substituent or a substituted atom. <3> The heat-sensitive recording material according to claim 1 or 2, wherein the heat-sensitive recording layer contains a binder and particles, and a weight ratio of the binder to the particles (binder / particle) is 0.20 or more.

In the heat-sensitive recording material of the present invention, a fluorescent whitening agent having a property of absorbing ultraviolet light is contained in the thermoplastic resin layer, so that the ultraviolet light is used for the decomposition treatment of the diazonium salt compound in the heat-sensitive recording layer. It is used efficiently and does not cause fixing hindrance by the fluorescent whitening agent. As a result, the fixing time is shortened. Further, since the fluorescent whitening agent represented by the structural formula (I) is used, bleed out is further reduced. Further, since the haze value of the heat-sensitive recording layer is 90% or less, the heat-sensitive recording layer has high transparency, the thermoplastic resin layer is transparent, and the whiteness of the thermoplastic resin layer is reduced in the background portion. It is noticeable.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The heat-sensitive recording material of the present invention has a heat-sensitive recording layer on a support, and further has other layers as necessary.

(Support) The support is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the support may be formed on both surfaces or one surface (the surface on which the heat-sensitive recording layer is formed) of the substrate. A thermoplastic resin layer formed by melt extrusion is mentioned. Specifically, (1) a thermoplastic resin layer is formed by melt-extruding a thermoplastic resin on a substrate, and (2) a thermoplastic resin layer is appropriately selected on the substrate. A known plastic film is adhered and a thermoplastic resin layer is formed by melt-extruding a thermoplastic resin on the plastic film, or (3) a thermoplastic resin layer is formed by melt-extruding a thermoplastic resin on a substrate. After that, a known plastic film appropriately selected is adhered to the surface thereof.

-Substrate-The substrate is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include paper, plastic film, plastic resin laminated paper, and synthetic paper. These may be used alone or in combination of two or more.

The paper is not particularly limited. For example, natural pulp selected from conifers and hardwoods is used as a main material, and fillers such as clay, talc, titanium oxide, calcium carbonate, and urea resin fine particles are used as necessary. , Alkyl ketene dimer, higher fatty acid, epoxidized fatty acid amide, paraffin wax, sizing agent such as alkenyl succinic acid, paper reinforced agent such as polyacrylamide, starch, polyamide polyamine epichlorohydrin, fixing agent such as sulfate band, cationic polymer, etc. With the addition of
Further, epoxidized fatty acid amides, those to which a softening agent such as a surfactant is added, further, those using synthetic pulp instead of the above natural pulp, those obtained by mixing natural pulp and synthetic pulp at an arbitrary ratio , And the like.

The basis weight of the substrate is 40 to 200 g.
/ M ² is preferred. The substrate preferably has excellent surface smoothness and flatness. Therefore, it is preferable that the substrate is surface-treated by applying heat and pressure using a machine calendar, a soft calendar, a super calendar, or the like.

In the present invention, among the above substrates, those having a surface sizing agent applied to both surfaces thereof are preferable. Examples of the surface sizing agent include an aqueous solution of polyvinyl alcohol and / or a modified product thereof. The application of the surface sizing agent can be performed using, for example, a size press, a tab size, or a gate roll coater.

[0012] Further, starch, CMC,
High molecular compounds such as HEC, sodium alginate and gelatin; metal salts such as calcium chloride, sodium chloride and sodium sulfate; hygroscopic substances such as glycerin and polyethylene glycol; dyes; coloring and brightening substances such as fluorescent whitening agents; A pH control agent such as caustic soda, aqueous ammonia, hydrochloric acid, sulfuric acid, and sodium carbonate may be added. Further, a softening agent such as an epoxidized fatty acid amide and a surfactant may be added, and a pigment or the like may be added as needed.

In the present invention, before the thermoplastic resin is melt-extruded on the substrate to form a thermoplastic resin layer, the adhesive strength between the substrate and the thermoplastic resin layer is strengthened.
Preferably, the substrate is pre-treated.

Examples of the pretreatment include an acid etching treatment using a chromic sulfate mixed solution, a flame treatment using a gas flame, an ultraviolet irradiation treatment, a corona discharge treatment, a glow discharge treatment, and an anchor coat treatment such as alkyl titanate. Among these, corona treatment is preferred from the viewpoint of simplicity. In the case of the corona treatment, the treatment needs to be performed so that the contact angle with water is 70 ° or less.

Examples of the anchor coating agent used in the anchor coating treatment include organic titanium-based, isocyanate-based (urethane-based) polyethyleneimine-based, and polybutadiene-based. As the organic titanium-based,
Examples thereof include alkyl titanates such as tetraisopropyl titanate, tetrabutyl titanate and tetrastearyl titanate; titanium acylates such as butoxytitanium stearate; and titanium chelates such as titanium acetylacetonate. Examples of the isocyanate-based (urethane-based) include toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and hexamethylene diisocyanate (HMD).
I), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI) and the like.

-Thermoplastic resin layer- The thermoplastic resin layer contains a thermoplastic resin, a fluorescent whitening agent and a white pigment, and further contains other components as necessary.

The thermoplastic resin is not particularly restricted but includes polyolefin resins. Examples thereof include homopolymers of α-olefins such as polyethylene and polypropylene, and mixtures of these various polymers, and ethylene and vinyl alcohol. And the like. These may be used alone or in combination of two or more.

As the polyethylene, for example, LD
PE (low density polyethylene), HDPE (high density polyethylene), L-LDPE (linear low density polyethylene)
Is mentioned. In the case of the polyethylene, the melt flow rate before processing is a value measured according to JIS 7201 (condition 4 in Table 1) and is 1.2 to 12 g / 10.
Minutes are preferred.

-Fluorescent Whitening Agent- The above-mentioned fluorescent whitening agent can be classified by a basic chemical structure that emits fluorescence. Specifically, diaminostilbene type, imidazole type, thiazole type, oxazole type, triazole type. , Oxadiazole, thiadiazole, coumarin, naphthalimide, pyrazoline, pyrene, imidazolone, benzidine, diaminocarbazole, oxocyanine, methine, pyridine, anthrapyridazine, distyryl, carbo And styryl compounds. Some of the exemplified optical brighteners are shown below, but are not limited thereto. Imidazole, thiazole, oxazole

[0020]

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[0021]

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[0022]

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Triazole type

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Coumarin type

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[0025]

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Naphthalimide type

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Pyrazolin type

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Others

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Among the exemplified fluorescent whitening agents, a compound represented by the following structural formula (I) is particularly preferred from the viewpoint of less bleeding out of the fluorescent whitening agent from the thermoplastic resin layer.

[0030]

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In the above formula, R ₁ , R ₂ , R ₃ and R ₄ represent a hydrogen atom or a substituent or a substituted atom. Examples of some of the substituents include an alkyl group having 1 to 12 carbon atoms (such as a methyl group, an ethyl group, a propyl group, a butyl group and an octyl group), and an alkoxy group having 1 to 12 carbon atoms (a methoxy group and an ethoxy group). , A propoxy group, a butoxy group, an octyloxy group, etc.), an alkoxycarbonyl group having 2 to 12 carbon atoms (such as a methoxycarbonyl group), an acyloxy group having 2 to 12 carbon atoms (such as an acetyloxy group), An aryl group (phenyl group, tolyl group, etc.), an aryloxy group having 6 to 12 carbon atoms (phenoxy group, phenoxyethoxy group, etc.), an aryloxycarbonyl group having 7 to 12 carbon atoms,
Hydroxy group, nitro group, cyano group, amino group, mono- or dialkylamino group having 1 to 12 carbon atoms (dimethylamino group, diethylamino group, etc.), mono- or diarylamino group having 6 to 12 carbon atoms, 1 to 12 carbon atoms Acylamino group (such as an acetylamino group).

These may further have a substituent, and examples of the substituent include those exemplified above. Examples of further having a substituent include, for example, a benzyl group in which an alkyl group is substituted with an aryl group, a phenethyl group, a benzyloxy group in which an alkoxy group is substituted with an aryl group, and the like. Examples of a part of the substituent atom include a halogen atom (a fluorine atom, a chlorine atom, a bromine atom and the like).

Specific examples of the optical brightener of the structural formula (I) include the following. These may be used in combination of two or more different types. In particular, the following structural formulas (IV) and (V) have less bleed-out,
It is preferable because the fixing time of the diazonium salt compound is short.

[0034]

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The content of these fluorescent brighteners in the thermoplastic resin layer is preferably 0.02 to 0.10% by weight, more preferably 0.04 to 0.08% by weight. When the content is less than 0.02% by weight, the effect of improving the whiteness of the background is small, and when the content is more than 0.10% by weight, bleed out of the fluorescent whitening agent occurs and the whiteness of the background is reduced. There is.

The method for producing the fluorescent whitening agent is not particularly limited, and it can be produced by a conventionally known method. In the present invention, a commercially available fluorescent whitening agent can also be used.

-White Pigment- Examples of the white pigment include titanium oxide, barium sulfate, barium carbonate, calcium carbonate, lithopone, alumina white, zinc oxide, silica antimony trioxide, titanium phosphate and the like. These may be used alone or in combination of two or more. Among them, titanium oxide is particularly preferable in terms of whiteness, dispersibility, and stability. As the content of the white pigment in the thermoplastic resin layer, the type of the white pigment, the type of the thermoplastic resin, the thickness of the thermoplastic resin layer and the like can not be specified unequivocally, but for the thermoplastic resin , Usually 5 to 2
It is about 0% by weight.

The titanium oxide is rutile,
Anatase type may be used, one type may be used alone, or 2
More than one species may be used in combination. Further, it may be one produced by a sulfuric acid method or one produced by a chlorine method. As the titanium oxide, hydrated alumina treatment,
Surface-coated with inorganic substances such as hydrous silicon dioxide treatment or zinc oxide treatment, trimethylolmethane,
Trimethylolethane, trimethylolpropane, 2,
A material that has been surface-coated with an organic substance such as 4-dihydroxy-2-methylpentane or a material that has been treated with siloxane such as polydimethylsiloxane can be used as appropriate.

-Preparation of Thermoplastic Resin Layer- The fluorescent whitening agent and the white pigment are usually prepared by first preparing a so-called compound in which a desired composition ratio is initially contained in a polyolefin resin as the thermoplastic resin. used. To prepare the compound, the compound is kneaded using a conventionally known kneader. As such a kneader,
Examples include a Banbury mixer, a kneader, a kneading extruder, a two-roll kneading machine, and a three-roll kneading machine. Of these, a Banbury mixer and a kneading extruder are preferably used. In addition, you may use these various kneaders in combination of 2 or more types. The compound thus produced is melt-extruded onto the substrate by a conventionally known melt extruder.

The thickness of the thermoplastic resin layer melt-extruded on the substrate is not particularly limited, but is preferably about 10 to 60 μm. In the present invention, known additives such as an antioxidant can be added to the thermoplastic resin layer.

(Thermal Recording Layer) The thermosensitive recording layer contains at least a binder and a color-forming component, and further contains other components as necessary. In the present invention,
The haze value of the heat-sensitive recording layer needs to be 90% or less, preferably from 0 to 80%, particularly preferably from 0 to 70%. When the haze value exceeds 90%, the transparency of the heat-sensitive recording layer decreases, and even if the whiteness of the support is high, it does not appear on the surface of the heat-sensitive recording material, and the whiteness at the background portion is low. It is not preferable because it lowers. on the other hand,
If it is 90% or less, such a case does not occur, and it is preferable in that the whiteness of the background portion of the heat-sensitive recording material can be increased. The haze value can be measured using, for example, a whiteness measuring device, for example, a commercially available haze measuring device.

-Binder-The binder is not particularly limited and can be appropriately selected from known ones according to the purpose. Examples thereof include gelatin, casein, phenol resin, urea resin, melamine resin, and epoxy resin. And various latexes such as polyvinyl alcohol, modified polyvinyl alcohol, methyl cellulose, sodium polystyrene sulfonate, styrene-maleic acid copolymer, and styrene-butadiene latex. These may be appropriately prepared or commercially available, and may be used alone or in combination of two or more.
Among these, gelatin and casein are preferred in view of coatability, and gelatin is particularly preferred.

The content of the binder in the thermosensitive recording layer is preferably such that the weight ratio (binder / particle) to the particles contained in the thermosensitive recording layer is 0.20 or more. If the weight ratio is less than 0.20, the haze value of the heat-sensitive recording layer may exceed 90%,
As a result, the whiteness of the background portion of the heat-sensitive recording material may decrease. On the other hand, when it is 0.20 or more, the haze value can be reduced to 90% or less, and as a result, the whiteness of the background portion of the heat-sensitive recording material can be improved. preferable.

The above-mentioned particles mean components other than the binder in the heat-sensitive recording layer, and specifically, a diazonium salt compound, a coupler,
Examples thereof include a colorless electron-donating dye, an electron-accepting compound, and microcapsules thereof.

The color forming component is not particularly limited.
It can be appropriately selected from known ones, for example,
Examples thereof include a diazonium salt compound, a coupler, a colorless electron-donating dye, and an electron-accepting compound.

-Diazonium Salt Compound- The diazonium salt compound is a coloring component used in the heat-sensitive recording layer, and is a compound represented by the following, and its maximum depends on the position and type of the substituent in the Ar portion in the following formula. The absorption wavelength can be controlled.

[0047]

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In the above formula, Ar represents an aryl group. X
^- represents an acid anion.

Specific examples of the diazonium salt compound include 4- (N- (2- (2,4-di-tert-amylphenoxy) butyryl) piperazino) benzenediazonium, 4-dioctylaminobenzenediazonium,
-(N- (2-ethylhexanoyl) piperazino) benzenediazonium, 4-dihexylamino-2-hexyloxybenzenediazonium, 4-N-ethyl-N-
Hexadecylamino-2-ethoxybenzodiazonium, 3-chloro-4-dioctylamino-2-octyloxyobenzenediazonium, 2,5-dibutoxy-
4-morpholinobenzenediazonium, 2,5-octoxy-4-morpholinobenzenediazonium, 2,5-
Dibutoxy-4- (N- (2-ethylhexanoyl) piperazino) benzenediazonium, 2,5-diethoxy-4- (N- (2- (2,4-di-tert-amylphenoxy) butyryl) piperazino) benzene Diazonium, 2,5-dibutoxy-4-tolylthiobenzenediazonium, 3- (2-octyloxyethoxy) -4-
Examples thereof include acid anion salts such as morpholinobenzenediazonium and the following diazonium salt compounds D-1 to D-5.
Of these, hexafluorophosphate salts, tetrafluoroborate salts, and 1,5-naphthalene sulfonate salts are preferred.

[0050]

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In the present invention, among the diazonium salt compounds, a compound which is decomposed by ultraviolet rays having a wavelength of 300 to 400 nm is preferable. Examples of such a compound include 4- (N- (2- (2,4-di-tert)
-Amylphenoxy) butyryl) piperazino) benzenediazonium, 4-dioctylaminobenzenediazonium, 4- (N- (2-ethylhexanoyl) piperazino) benzenediazonium, 4-dihexylamino-2
-Hexyloxybenzenediazonium, 4-N-ethyl-N-hexadecylamino-2-ethoxybenzodiazonium, 2,5-dibutoxy-4- (N- (2-ethylhexanoyl) piperazino) benzenediazonium,
2,5-diethoxy-4- (N- (2- (2,4-di-
tert-amylphenoxy) butyryl) piperazino)
Benzenediazonium and the compounds shown in the specific examples D-3 to D-5 are mentioned. The maximum absorption wavelength of the diazonium salt compound here is 0.1 to 1.0 g of each compound.
/ M ² was measured using a spectrophotometer (Shimadzu MPS-2000, manufactured by Shimadzu Corporation).

-Coupler- In the present invention, a coupler capable of reacting with a diazonium salt compound when heated to form a dye is preferably used as a coloring component used in the heat-sensitive recording layer. Specific examples of the coupler include resorcin, flurgurcine,
Sodium 2,3-dihydroxynaphthalene-6-sulfonate, morpholinopropylamide 1-hydroxy-2-naphthoate, 1,5-dihydroxynaphthalene, 2,
3-dihydroxynaphthalene, 2,3-dihydroxy-
6-sulfanylnaphthalene, 2-hydroxy-3-naphthoic acid anilide, 2-hydroxy-3-naphthoic acid ethanolamide, 2-hydroxy-3-naphthoic acid octylamide, 2-hydroxy-3-naphthoic acid-N-dodecyloxy Purpyramide, 2-hydroxy-3-naphthoic acid tetradecylamide, acetanilide, acetoacetanilide, benzoylacetoanilide, 2-chloro-5-octylacetoacetoanilide, 1-phenyl-3-methyl-5-pyrazolone, 1- (2 '-Octylphenyl) -3-methyl-5-pyrazolone, 1-
(2 ′, 4 ′, 6′-trichlorophenyl) -3-benzamide-5-pyrazolone, 1- (2 ′, 4 ′, 6′-
Trichlorophenyl) -3-anilino-5-pyralone,
Examples thereof include 1-phenyl-3-phenylacetamido-5-pyrazolone, and C-1 to C-6 compounds shown below. These couplers may be used alone or in combination of two or more.

[0053]

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[0054]

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-Basic Substance- In the present invention, a basic substance that promotes the reaction between the diazonium salt compound and the coupler can be preferably used. The basic substance includes an inorganic or organic basic compound, as well as a compound which decomposes upon heating to release an alkaline substance.

Representative examples of the basic substance include organic ammonium salts, organic amines, amides, ureas and thioureas, and derivatives thereof, thiazoles, pyrroles,
Examples include nitrogen-containing compounds such as pyrimidines, piperazines, guanidines, indoles, imidazoles, imidazolines, triazoles, morpholines, piperidines, amidines, formazines, and pyridines.

Specific examples thereof include tricyclohexylamine, tribenzylamine, octadecylbenzylamine, stearylamine, allylurea, thiourea,
Methylthiourea, allylthiourea, ethylenethiourea,
2-benzylimidazole, 4-phenylimidazole, 2-phenyl-4-methylimidazole, 2-undecylimidazoline, 2,4,5-trifuryl-2-imidazoline, 1,2-diphenyl-4,4-dimethyl-
2-imidazoline, 2-phenyl-2-imidazoline,
1,2,3-triphenylguanidine, 1,2-dicyclohexylguanidine, 1,2,3-tricyclohexylguanidine, guanidine trichloroacetate, N, N ′
-Dibenzylpiperazine, 4,4'-dithiomorpholine, morpholinium trichloroacetate, 2-aminobenzothiazole, 2-benzoylhydrazinobenzothiazole and the like. These may be used alone or in combination of two or more.

-Electron-donating colorless dye- As the color-forming component used in the heat-sensitive recording layer, those utilizing a reaction between an electron-donating colorless dye and an electron-accepting compound can also be preferably used. As the electron-donating colorless dye, an electron-donating colorless dye precursor can be used. Examples of the precursor include a triarylmethane compound, a diphenylmethane compound, a thiazine compound, a xanthene compound, and a spiropyran compound. Is mentioned. These may be used alone or in combination of two or more. Among these, a triarylmethane compound and a xanthene compound are preferable in that they have a high coloring density.

Specific examples thereof include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (ie, crystal violet lactone),
3,3-bis (p-dimethylamino) phthalide, 3-
(P-dimethylaminophenyl) -3- (1,3-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindole-
3-yl) phthalide, 3- (o-methyl-p-diethylaminophenyl) -3- (2-methylindole-3-
Yl) phthalide, 4,4'-bis (dimethylamino) benzhydrin benzyl ether, N-halophenylleuco-auramine, N-2,4,5-trichlorophenylleuco-auramine, rhodamine-B-anilinolactam,
Rhodamine (p-nitroanilino) lactam, rhodamine-B- (p-chloroanilino) lactam, 2-benzylamino-6-diethylaminofluoran, 2-anilino-6-diethylaminofluoran, 2-anilino-3
-Methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-cyclohexylmethylaminofluoran, 2-anilino-3-methyl-6-isoamylethylaminofluoran, 2- (ο-chloroanilino)-
6-diethylaminofluoran, 2-octylamino-
6-diethylaminofluoran, 2-ethoxyethylamino-3-chloro-2-diethylaminofluoran, 2
-Anilino-3-chloro-6-diethylaminofluoran, benzoylleucomethylene blue, p-nitrobenzylleucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran,
3,3'-dichloro-spiro-dinaphthopyran, 3-benzylspirodinaphthopyran, 3-propyl-spiro-
Dibenzopyran and the like.

—Electron-Accepting Compound— Examples of the electron-accepting compound include phenol derivatives, salicylic acid derivatives, and hydroxybenzoic acid esters. Among these, bisphenols and hydroxybenzoates are preferred. Specific examples of these include 2,2-bis (p-hydroxyphenyl) propane (ie, bisphenol A), 4,4 ′-(p-phenylenediisopropylidene) diphenol (ie, bisphenol P), 2-bis (p-hydroxyphenyl) pentane, 2,2-bis (p-hydroxyphenyl) ethane, 2,2-bis (p-hydroxyphenyl)
Butane, 2,2-bis (4'-hydroxy-3 ', 5'
-Dichlorophenyl) propane, 1,1- (p-hydroxyphenyl) cyclohexane, 1,1- (p-hydroxyphenyl) propane, 1,1- (p-hydroxyphenyl) pentane, 1,1- (p-hydroxyphenyl) ) -2-ethylhexane, 3,5-di (α-methylbenzyl) salicylic acid and its polyvalent metal salts, 3,5-di (tert-butyl) salicylic acid and its polyvalent metal salts,
3-α, α-dimethylbenzylsalicylic acid and its polyvalent metal salts, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, 2-ethylhexyl p-hydroxybenzoate, p-phenylphenol, p-cumylphenol And the like.

-Sensitizer- In the present invention, a sensitizer can be suitably added to the heat-sensitive recording layer. As the sensitizer, a low-melting point organic compound having an aromatic group and a polar group in the molecule is preferable, and benzyl p-benzyloxybenzoate,
α-naphthyl benzyl ether, β-naphthyl benzyl ether, β-naphthoic acid phenyl ester, α-hydroxy-β-naphthoic acid phenyl ester, β-naphthol- (p-chlorobenzyl) ether, 1,4-butanediol phenyl ether 1,4-butanediol-p-methylphenyl ether, 1,4-butanediol-p-ethylphenyl ether, 1,4-butanediol-m-methylphenyl ether, 1-phenoxy-
2- (p-tolyloxy) ethane, 1-phenoxy-2
-(P-ethylphenoxy) ethane, 1-phenoxy-
2- (p-chlorophenoxy) ethane, p-benzylbiphenyl, and the like.

-Dispersion of each component-The diazonium salt compound in the thermosensitive recording layer,
There is no particular limitation on the mode of containing the coupler, the basic substance, the electron-donating colorless dye, the electron-accepting compound, the sensitizer, etc., which reacts with the diazonium salt compound to give a color when heated. Can be appropriately selected depending on the purpose. For example, they can be contained by (1) solid dispersion, (2) emulsification dispersion,
(3) a method of containing by polymer dispersion, (4) a method of containing by latex dispersion, and (5) a method of containing by microencapsulation.

Among these, the method of microencapsulation and inclusion is preferable from the viewpoint of storage stability. In the case of utilizing the color development reaction between the diazonium salt compound and the coupler, the diazonium salt compound is microencapsulated. The thermosensitive recording layer is preferably contained in the heat-sensitive recording layer, and in the case of utilizing a color-forming reaction between the electron-donating colorless dye and the electron-accepting compound, the electron-donating colorless dye is microencapsulated to form the heat-sensitive recording layer. It is preferable to contain them.

As a method of the emulsification and dispersion, first, a coloring component such as the diazonium salt compound is dissolved in oil. The oil may be solid or liquid at room temperature, or may be a polymer, and may be a low-boiling auxiliary solvent such as acetate, methylene chloride, cyclohexanone and / or a phosphate, or phthalic acid. Esters, acrylic esters, methacrylic esters, other carboxylic esters, fatty acid amides, alkylated biphenyls, alkylated terphenyls, alkylated naphthalenes, diarylethanes, chlorinated paraffins, alcohols, phenols, ethers, monoolefins system,
Epoxy type, and the like. Specific examples include tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, tricyclohexyl phosphate, dibutyl phthalate, dioctyl phthalate, dilaurate phthalate, dicyclohexyl phthalate, butyl olefin, diethylene glycol benzoate, dioctyl sebacate,
Dibutyl sebacate, dioctyl adipate, trioctyl trimellitate, acetyl triethyl citrate, octyl maleate, dibutyl maleate, isoamyl biphenyl, chlorinated paraffin, diisopropyl naphthalene, 1,1'-ditolyl ethane, 2,4-dita-shalia Milphenol, N, N-dibutyl-2-butoxy-
And high-boiling oils such as 5-tert-octylaniline, 2-ethylhexyl hydroxybenzoate, and polyethylene glycol. These may be used alone or in combination of two or more,
Of these, alcohols, phosphates, carboxylic esters, alkylated biphenyls, alkylated terphenyls, alkylated naphthalenes, and diarylethanes are preferred. In the present invention, the oil
An anti-carbonizing agent such as hindered phenol or hindered amine may be added.

The oil containing a coloring component such as the diazonium salt compound is added to an aqueous solution of a water-soluble polymer, and emulsified and dispersed using a colloid mill, a homogenizer, or ultrasonic waves.

Examples of the water-soluble polymer include polyvinyl alcohol, silanol-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amino-modified polyvinyl alcohol, itaconic acid-modified polyvinyl alcohol,
Styrene-maleic anhydride copolymer, butadiene maleic anhydride copolymer, ethylene maleic anhydride copolymer,
Isobutylene maleic anhydride copolymer, polyacrylamide, polystyrenesulfonic acid, polyvinylpyrrolidone, ethylene-acrylic acid copolymer, gelatin and the like can be mentioned. In the present invention, a surfactant or the like may be added to the water-soluble polymer, if necessary, or an emulsion or latex of a hydrophobic polymer may be used in combination.

When the color-forming components such as the diazonium salt compound are microencapsulated, a conventionally known microencapsulation method can be used. For example, a coloring component such as the diazonium salt compound and the like and a microcapsule wall precursor are dissolved in an organic solvent that is hardly soluble or insoluble in water, added to an aqueous solution of a water-soluble polymer, and emulsified and dispersed using a homogenizer or the like. Then, by forming a wall film on the oil / water interface of the polymer substance which becomes the microcapsule wall when the temperature is raised, microcapsules such as a coloring component such as the diazonium salt compound can be prepared.

Specific examples of the microcapsule wall film include, for example, polyurethane resin, polyurea resin, polyamide resin, polyester resin, polycarbonate resin, aminoaldehyde resin, melamine resin, polystyrene resin, styrene-acrylate copolymer resin, and polystyrene. And a wall film made of a methacrylate copolymer resin, gelatin, polyvinyl alcohol, or the like. Among these, a wall film made of a polyurethane / polyurea resin is preferable.

The microcapsules having a wall film made of the polyurethane / polyurea resin are prepared, for example, by mixing a microcapsule wall precursor such as a polyvalent isocyanate in a core material to be microencapsulated, and adding a water-soluble polymer such as polyvinyl alcohol. It is manufactured by emulsifying and dispersing in an aqueous solution of molecules, raising the liquid temperature and causing a polymer formation reaction at the oil droplet interface.

Specific examples of the polyvalent isocyanate compound include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, naphthalene-1,4-diisocyanate, and diphenylmethane-isocyanate. 4,
4'-diisocyanate, 3,3'-diphenylmethane-4,4'-diisocyanate, xylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2- Diisocyanates such as diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, 4,4 ′, 4 ″ -triphenylmethane triisocyanate, toluene-2, Triisocyanates such as 4,6-triisocyanate; tetraisocyanates such as 4,4'-dimethyldiphenylmethane-2,2 ', 5,5'-tetraisocyanate; hexamethylene diisocyanate; Adduct of trimethylolpropane,
Isocyanate prepolymers such as adducts of 2,4-tolylene diisocyanate and trimethylolpropane, adducts of xylylene diisocyanate and trimethylolpropane, and adducts of tolylene diisocyanate and hexanetriol. These may be used alone or in combination of two or more. Among them, those having three or more isocyanate groups in the molecule are particularly preferable.

In the method of microencapsulation,
As the organic solvent for dissolving the coloring components such as the diazonium salt compound, the oils described in the emulsification and dispersion method can be used. The same applies to a water-soluble polymer.

The average particle size of the microcapsules is preferably 0.1 to 1.0 μm, and 0.2 to 0.7 μm.
m is more preferred.

When the heat-sensitive recording layer has a multilayer structure, a multi-color heat-sensitive recording material can be obtained by changing the hue of each heat-sensitive recording layer. The layer structure in this case is as follows:
There is no particular limitation, and it can be appropriately selected according to the purpose. In the present invention, two kinds of diazonium salt compounds having different photosensitive wavelengths and each of the diazonium salt compounds react with heat to develop a different hue. It is preferable to form a multicolor heat-sensitive recording layer by laminating two heat-sensitive recording layers combining a coupler and a heat-sensitive recording layer combining an electron-donating colorless dye and an electron-accepting compound. That is, on the support, a heat-sensitive recording layer A containing an electron-donating colorless dye and an electron-accepting compound, a diazonium salt compound having a maximum absorption wavelength of 360 ± 20 nm and a hot reaction with the diazonium salt compound are presented. A thermosensitive recording layer B-1 containing a coloring coupler; and a thermosensitive recording layer B- containing a diazonium salt compound having a maximum absorption wavelength of 400 ± 20 nm and a coupler which reacts with the diazonium salt compound when heated to give a color. 2 are laminated in this order, and a multicolor heat-sensitive recording material is preferable.

As a recording method of the multicolor heat-sensitive recording material, first, the heat-sensitive recording layer B-2 is heated, and the heat-sensitive recording layer B-
The color of the diazonium salt compound and the coupler contained in 2 is developed. Next, after irradiating light of 400 ± 20 nm to decompose the unreacted diazonium salt compound contained in the heat-sensitive recording layer B-2, heat sufficient for the heat-sensitive recording layer B-1 to develop a color is applied. In addition, the diazonium salt compound and the coupler contained in the heat-sensitive recording layer B-1 are colored. At this time, the heat-sensitive recording layer B-2 is also strongly heated at the same time, but does not develop color because the diazonium salt compound has already been decomposed and the color-forming ability has been lost. Further, by irradiating light of 360 ± 20 nm, the diazonium salt compound contained in the heat-sensitive recording layer B-1 is decomposed, and finally, sufficient heat for the heat-sensitive recording layer A to develop color is applied to develop the color. At this time, the heat-sensitive recording layer B-
2 and the heat-sensitive recording layer B-1 are also strongly heated at the same time, but do not develop color because the diazonium salt compound has already been decomposed and the color-forming ability has been lost.

Further, in the present invention, a three-layered heat-sensitive recording layer comprising a combination of three kinds of diazonium salt compounds having different photosensitive wavelengths and a coupler which reacts with each of the diazonium salt compounds upon heating and develops a different hue is used. It is also preferable to form a laminated multicolor heat-sensitive recording layer. That is, on the support, the maximum absorption wavelength is 350 nm or less, preferably 34 nm or less.
Heat-sensitive recording layer A-1 containing a diazonium salt compound having a wavelength of not more than 0 nm and a coupler which reacts with the diazonium salt compound when heated to form a color, and has a maximum absorption wavelength of 360 ± 20 nm
Heat-sensitive recording layer B-1 containing a diazonium salt compound having the following formula: and a coupler which reacts with the diazonium salt compound when heated to form a color, a diazonium salt compound having a maximum absorption wavelength of 400 ± 20 nm, Heat-sensitive recording layer B-2 containing a coupler which reacts and develops a color
Are preferably stacked in this order.

In the case of the multicolor heat-sensitive recording layer described above,
If the color hue of each heat-sensitive recording layer is selected so as to be three primary colors, yellow, magenta, and cyan in subtractive color mixing,
Full-color image recording becomes possible.

(Other Layers) The heat-sensitive recording material of the present invention may have other layers appropriately selected according to the purpose, in addition to the support and the heat-sensitive recording layer. Examples of the layer include an undercoat layer, an intermediate layer, a protective layer, a light transmittance adjusting layer, and the like.

(Undercoat layer) In the present invention, it is preferable that an undercoat layer is provided between the support and the thermosensitive recording layer. The undercoat layer is not particularly limited and may be appropriately selected from known ones according to the purpose. Gelatin having a PAGI viscosity of 10 to 30 mP and a PAGI jelly strength of 15 to 70 g is preferred. It is particularly preferable to contain a "gelatin") and a layered inorganic compound. In the present invention, it is preferable that such a layer is provided as the intermediate layer or the like.

The viscosity of the above-mentioned PAGI method and the jelly strength of the above-mentioned PAGI method are described in Pagii method: Photographic gelatin test method, 7th edition (1992)
2 years version). The gelatin can be obtained by reducing the molecular weight of a known gelatin produced by a usual method (hereinafter, referred to as “normal gelatin”). However, the term "normal gelatin" used herein refers to, for example, "raw glue and gelatin (edited by Abiko Yoshihiro, published by Nippon Nippon, Gelatin Industry Association, 1987), such as cow bone, cow hide, and pig hide. Is processed by lime, acid or the like, and has a much higher viscosity and jelly strength than the gelatin.

The above-mentioned ordinary gelatin is characterized by conditions such as a raw material, a processing method (eg, lime treatment, acid treatment) and extraction conditions (temperature, number of extractions). The gelatin may be obtained by reducing the molecular weight based on any gelatin.However, the number of extractions is small, and the one extracted at a low temperature can achieve both low viscosity and jelly strength within the above numerical range. Is preferred. Examples of the method for reducing the molecular weight include a method using an enzyme and a method using heat, and among these, the method using an enzyme is preferable. In the case of the method using heat, when the viscosity is reduced to a preferable value, the jelly strength may be reduced. In addition, as said enzyme, papain is mentioned suitably, for example.

In the gelatin, the viscosity according to the PAGI method is 10 to 30 mP, and the jelly strength according to the PAGI method is 15 to 70 g. However, if the viscosity according to the PAGI method is less than 10 mP, the viscosity of the coating liquid decreases. Becomes larger,
In some cases, the dispersion state of the pigment (mica) in the coating liquid is deteriorated, and when it exceeds 30 mP, the viscosity of the coating liquid increases, and coating failure may easily occur. Further, when the jelly strength of the PAGI method is less than 15 g, the strength of the coating film decreases, and the adhesive strength with the support may decrease. When the jelly strength of the PAGI method is greater than 70 g, the coating strength may decrease. The curl of the film may increase due to environmental changes.

The gelatin may be cross-linked by using a hardening agent, if necessary. In this case, examples of the hardening agent include known ones used as hardening agents for gelatin. For example, a vinyl sulfone compound, an active halogen compound, an isocyanate compound, an epoxy compound and the like can be mentioned. Among these, epoxy compounds are particularly preferred, and as the epoxy compound, for example, the following compounds are suitably mentioned.

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The coating amount of the gelatin in the undercoat layer is preferably 0.5 g / m ² or more from the viewpoint of suppressing Plister (a fine swelling phenomenon due to the heat of the printer thermal head during printing).

As the layered inorganic compound, a swellable inorganic layered compound is preferably exemplified. Specific examples of the swellable inorganic layered compound include bentonite, hectorite, saponite, beaderite, nontronite, stevensite, beidellite, swellable viscosity minerals such as montmorillonite, swellable synthetic mica, swellable synthetic smectite, and the like. No.

These swellable inorganic layered compounds have a laminated structure composed of unit crystal lattice layers having a thickness of about 10 to 15 Å, and the substitution of metal atoms in the lattice is significantly larger than that of other clay minerals. As a result, the lattice layer suffers from a lack of positive charge, and Na ⁺ , C
Cations such as a ²⁺ and Mg ²⁺ are adsorbed. The cations interposed between these layers are called "exchangeable cations" and exchange with various cations. In particular, when the cation between the layers is Li ⁺ , Na ^+, etc., since the ionic radius is small, the bond between the layered crystal lattices is weak, and the layer swells greatly with water. When shear is applied in this state, it is easily cleaved and forms a stable sol in water. Among the specific examples of the swellable inorganic layered compound, bentonite and swellable synthetic mica are preferable because of their strong tendency, and swellable synthetic mica is particularly preferable.

As the swellable synthetic mica, for example, the following compounds are preferably exemplified. Na tetra mica _{NaMg 2.5 (Si 4 O 10)} F 2, Na or Li teniolite _{(NaLi) Mg 2 (Si 4} O 10) F 2, Na or L
i-hectorite (NaLi) _{/ 3} Mg _2/3 Li _1/3 Si ₄ O
₁₀ ) F ₂ , and the like.

The swellable synthetic mica has a thickness of 1 to 50 nm and a plane size of 1 to 20 μm. The thickness is preferably as thin as possible in terms of diffusion control, and the plane size is preferably as large as possible without deteriorating the smoothness and transparency of the coated surface. The aspect ratio of the swellable synthetic mica is usually 100 or more, preferably 200 or more, and more preferably 500 or more.

In the case where the above-mentioned ordinary gelatin is used, if the ratio of mica (to gelatin 1.5 to 10 or more) increases, the viscosity increases and the gelation proceeds at a certain solid content concentration (for example, 5 to 10%). , It is necessary to lower the viscosity. To lower the viscosity, there is a method of lowering the concentration. However, lowering the concentration increases the drying load of the coating film and deteriorates the coated surface state due to thick coating. There is also a method of adding urea, salt, or the like to the coating solution, but the viscosity cannot be sufficiently reduced, and the surface after coating is poor. On the other hand, the gelatin is capable of remarkably reducing the thickening and gelation without causing such adverse effects, and can significantly reduce the thickening and gelation even when used in combination with mica. Is advantageous.

The content of the water-swellable synthetic mica in the undercoat layer was 1 / mica / gelatin weight ratio.
20 to 1/2 is preferred. When the content of the water-swellable synthetic mica is less than 1/20, the undercoat layer may not function sufficiently as an oxygen barrier layer. May worsen.

The amount of mica applied to the undercoat layer is usually 0.01 g / m ² or more, and 0.02 g / m ² or more.
/ M ² or more. When the coating amount of the mica is 0.01
If it is less than g / m ² , the oxygen-blocking ability of the undercoat layer is reduced, and the characteristics of the present invention such as prevention of background coloring or the like may not be exhibited.

(Intermediate Layer) In the present invention, when the thermosensitive recording layer has a laminated structure of thermosensitive coloring layers having different hues, an intermediate layer for preventing color mixing or the like is provided between the thermosensitive recording layers. Is preferred. The intermediate layer is not particularly limited and may be appropriately selected depending on the intended purpose. The intermediate layer can be formed using a water-soluble polymer compound or the like.

Examples of the water-soluble polymer compound include polyvinyl alcohol, modified polyvinyl alcohol, methyl cellulose, sodium polystyrene sulfonate, styrene-maleic acid copolymer, gelatin and / or
Alternatively, those composed of a zetirane derivative, polyethylene glycol and / or a polyethylene glycol derivative are preferred.

The inorganic layered compound can be suitably added to the intermediate layer. When the intermediate layer contains the inorganic layered compound, color mixing can be prevented by suppressing and preventing mass transfer between layers, and raw storage and color image storage are improved by suppressing the supply of oxygen. Can be done.

(Protective Layer) In the present invention, it is preferable to provide a protective layer containing a pigment, a release agent, and the like on the heat-sensitive recording layer in order to protect the heat-sensitive recording layer from sticking and a solvent. . As a pigment to be added to the protective layer,
An inorganic layered compound containing mica or the like can be used, but other pigments may be used in combination. Examples of such pigments include calcium oxide, zinc oxide, titanium oxide, aluminum hydroxide, kaolin, synthetic silicate, amorphous silica,
Urea formalin resin powder and the like.

(Light Transmittance Adjusting Layer) In the present invention, a light transmittance adjusting layer can be suitably provided. It is preferable that at least one light transmittance adjusting layer is provided in the thermosensitive recording material, and it is more preferable that the light transmittance adjusting layer is formed between the thermosensitive recording layer and the protective layer. Note that the light transmittance adjusting layer may be designed so as to double as the protective layer. The light transmittance adjusting layer contains a component that functions as a precursor of an ultraviolet absorber, and does not function as an ultraviolet absorber before irradiation with light having a wavelength in a region necessary for fixing. When the recording layer is fixed, the wavelength in the region required for fixing is sufficiently transmitted, and the transmittance of visible light is high, so that the fixing of the heat-sensitive recording layer does not hinder.

The component functioning as a precursor of the ultraviolet absorber absorbs ultraviolet light by reacting with light or heat after light irradiation of a wavelength necessary for fixing the heat-sensitive recording layer by light irradiation is completed. Began to function as an agent,
Most of the light in the wavelength range necessary for fixing in the ultraviolet region is absorbed by the ultraviolet absorber, and the transmittance is reduced.
Although the light resistance of the heat-sensitive recording material is improved, the visible light transmittance is not substantially changed because there is no visible light absorbing effect. The light transmittance adjusting layer may be provided at least one layer in the heat-sensitive recording material, and is preferably formed between the heat-sensitive recording layer and the protective layer. You may design so that it may also serve as a protective layer.

In the present invention, when the number of the heat-sensitive recording layers is two or more, a multi-color heat-sensitive recording material is obtained by changing the hue of each heat-sensitive recording layer, and the color hue of each heat-sensitive recording layer is reduced. Three primary colors in the mixture, yellow, magenta,
If it is selected to be cyan, full-color image recording becomes possible. In this case, the color-forming component of the heat-sensitive recording layer directly laminated on the support surface (the lowermost layer of the heat-sensitive recording layer) is not limited to a combination of an electron-donating colorless dye and an electron-accepting dye. A diazo coloring system consisting of a coupler that reacts with a diazonium salt to form a color, a base coloring system that forms a color upon contact with a basic compound, a chelate coloring system, and a coloring system that forms a color by reacting with a nucleophile to cause an elimination reaction. Any two heat-sensitive recording layers each containing a diazonium salt compound having a different maximum absorption wavelength and a coupler which reacts with the diazonium salt compound to form a color are provided on the heat-sensitive recording layer. It is preferable to provide a rate adjusting layer and a protective layer sequentially.

In the present invention, the following known antioxidants can be added to the heat-sensitive recording material in order to further improve the light resistance. Such antioxidants include, for example, EP-A-310551, DE-A-3435443, EP-A-310552 and JP-A-3-121.
No. 449, EP-A-594416, JP-A-2-262654, JP-A-2-712.
No. 62, JP-A-63-163351, U.S. Pat. No. 4,814,262, JP-A-54-48535, JP-A-5-61166, JP-A-5-119
No. 449, U.S. Pat. No. 4,980,275, JP-A-63-113536, JP-A-62-26204.
7, European Patent No. 223739,
Examples include antioxidants described in European Patent Publication No. 309402 and European Patent Publication No. 309401, and specific examples include the following.

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Also, Japanese Patent Application Laid-Open No. Sho 60-125470,
JP-A-60-125471, JP-A-60-125
472, JP-A-60-287485, JP-A-60-287486, and JP-A-60-28748.
7, JP-A-62-146680, and JP-A-6-146680.
JP-A-0-287488, JP-A-62-282885, JP-A-63-89877, JP-A-63-8
JP-A-8380, JP-A-63-088381, JP-A-01-239282, JP-A-04-2916
No. 85, JP-A-04-291684, JP-A-05-188687, JP-A-05-188686
JP, JP-A-05-110490, JP-A-05-110490
-1108437, JP-A-05-170361, JP-A-63-203372, JP-A-63-203372
Japanese Patent Application Laid-Open Nos. 224,1989, 63-267594, 63-182484, and 60-1
No. 07384, JP-A-60-107383,
JP-A-61-160287, JP-A-61-185
483, JP-A-61-211079, JP-A-63-251282, JP-A-63-05117
No. 4, JP-B-48-043294, JP-B-4
8-033212, and the like. Specific examples include 6-ethoxy-1-phenyl-
2,2,4-trimethyl-1,2-dihydroquinoline,
6-ethoxy-1-octyl-2,2,4-trimethyl-1,2-dihydroquinoline, 6-ethoxy-1-phenyl-2,2,4-trimethyl-1,2,3,4-tetrahydroquinoline, 6-ethoxy-1-octyl-2,
2,4-trimethyl-1,2,3,4-tetrahydroquinoline, nickel cyclohexanoate, 2,2-bis-4
-Hydroxyphenylpropane, 1,1-bis-4-hydroxyphenyl-2-ethylhexane, 2-methyl-
4-methoxy-diphenylamine, 1-methyl-2-phenylindole and the like. These antioxidants can be added to the heat-sensitive recording layer, the intermediate layer, the light transmittance adjusting layer, and the protective layer.

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EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples. In the following, “parts” means “parts by weight” unless otherwise specified.

(Example 1) <Support> A wood pulp composed of 100 parts of LBKP was beaten to a Canadian freeness of 300 cc with a double disc refiner, and epoxidized behenamide was used.
5 parts, 1.0 part of anionic polyacrylamide, 0.1 part of polyamide polyamine epichlorohydrin, and 0.5 part of cationic polyacrylamide were all added at an absolute dry weight ratio to pulp, and the basis weight was 100 g / m by a fourdrinier paper machine.
^{2 was made into} a base paper, treated with polyvinyl alcohol as a surface sizing agent so that the absolute dry weight was 1.0 g / m ^2, and the density was adjusted to 1.0 g / cm by calendering.
I tried to be ³ . This was used as a substrate.

A corona is provided on the wire side (back side) of the substrate.
After performing discharge treatment, high-density poly
Ethylene coated to a thickness of 36μm
Then, a resin layer consisting of a mat surface was formed (this surface was
Plane "). On this backResin layerCorona discharge treatment
Later, aluminum oxide (Nissan Chemical Industries, Ltd.)
Alumina sol 100 manufactured by Nissan.
Gaku Kogyo Co., Ltd., Snowtex O) = 1/2 (weight)
Is dispersed in water and the weight after drying is 0.2 g / m ^TwoWhen
It applied so that it might become.

After the corona discharge treatment was performed on the felt surface (front surface) of the base paper, the anatase type titanium dioxide 10
MFR (melt flow rate) containing 3.8 wt%, a trace amount of ultramarine blue, and 0.01 wt% (based on polyethylene) of the optical brightener represented by the structural formula (IV) is melted to melt low-density polyethylene. Using an extruder, the resin was melt-extruded to a thickness of 50 μm to form a thermoplastic resin layer having a glossy surface on the substrate. (This surface is called “surface”)

<Undercoat layer> -Preparation of gelatin solution- Enzyme-decomposed gelatin (average molecular weight: 10,000, PAGI
Method viscosity: 15 mP, PAGI method jelly strength: 20 g) 4
0 parts were added to 60 parts of water and dissolved by stirring at 40 ° C. to prepare a gelatin solution. -Preparation of mica dispersion liquid- 8 parts of water-swellable synthetic mica (aspect ratio: 1000, trade name: Somasif ME100, manufactured by Corp Chemical) and water 9
After mixing with 2 parts, the mixture was wet-dispersed with a biscomil to obtain a mica dispersion having an average particle size of 2.0 μm. Water was added to the mica dispersion so that the mica concentration was 5% by weight, and the mixture was uniformly mixed to prepare a desired mica dispersion.

—Formation of Undercoat Layer— 100 parts of the above 40% by weight gelatin solution at 40 ° C. was added with water 1
After 20 parts and 556 parts of methanol were added and sufficiently mixed with stirring, 208 parts of the mica dispersion liquid of 5% by weight were added and mixed with sufficient stirring, and 9.8 parts of 1.66% by weight of an ethylene oxide surfactant was added. Was. Then, the liquid temperature is changed from 35 ° C to 4
6. The gelatin hardener represented by E-1 was maintained at 0 ° C.
3 parts were added to prepare an undercoat layer coating solution (5.7% by weight).

This undercoat layer coating solution was applied onto the support so that the coating amount of mica was 0.2 g / m ² ,
An undercoat layer was formed.

<Preparation of Coating Solution for Thermosensitive Recording Layer A> —Preparation of Electron-donating Colorless Dye Precursor Microcapsule Solution— 3.0 parts of crystal violet lactone as an electron-donating colorless dye precursor was added to 20 parts of ethyl acetate. After dissolution, 20 parts of alkylnaphthalene, which is a high boiling point solvent, was added, and the mixture was heated and uniformly mixed. 20 parts of an xylylene diisocyanate / trimethylolpropane adduct was further added to this solution as a microcapsule wall agent, and the mixture was stirred uniformly to obtain an electron-donating colorless dye precursor solution. Separately, 54 parts of a 6% by weight aqueous solution of gelatin were prepared, and the above-mentioned electron-donating colorless dye precursor solution was added thereto, followed by emulsification and dispersion with a homogenizer. After 68 parts of water was added to the obtained emulsion to homogenize it, the temperature was raised to 50 ° C. while stirring, and a microencapsulation reaction was performed for 3 hours to prepare an electron-donating colorless dye precursor microcapsule liquid. . The average particle size of the microcapsules was 1.6 μm.

—Preparation of Electron-Accepting Compound Dispersion— An electron-accepting compound dispersion was obtained by adding 30 parts of bisphenol A as an electron-accepting compound to 150 parts of a 4% by weight aqueous solution of gelatin and dispersing it in a ball mill for 24 hours. Was. The average particle size of the electron accepting compound in the electron accepting compound dispersion was 1.2 μm.

—Preparation of Coating Solution for Thermosensitive Recording Layer A— Next, the electron-donating dye precursor microcapsule solution and the electron-accepting compound dispersion were mixed with an electron-donating dye precursor / electron-accepting compound. Were mixed so that the ratio was 1/2 to prepare the intended coating solution for the heat-sensitive recording layer A.

<Preparation of coating solution for heat-sensitive recording layer B> -Preparation of microcapsule solution of diazonium salt compound- As the diazonium salt compound, 4- (N- (2- (2,4
Dissolve 2.0 parts of -di-tert-amylphenoxy) butyryl) piperazinobenzenediazonium hexafluorophosphate in 20 parts of ethyl acetate, add 20 parts of alkylnaphthalene which is a high-boiling point solvent, and heat. Mix evenly. 15 parts of an xylylene diisocyanate / trimethylolpropane adduct as a microcapsule wall agent was further added to this solution, and the mixture was stirred uniformly. Separately, 54 parts of a 6% by weight aqueous solution of gelatin were prepared, the above diazonium salt compound solution was added, and the mixture was emulsified and dispersed with a homogenizer. After 68 parts of water was added to the obtained emulsion to homogenize it, the temperature was raised to 40 ° C. while stirring, and a microencapsulation reaction was performed for 3 hours to prepare a desired diazonium salt compound microcapsule liquid. The average particle size of the microcapsules was 1.1 μm.

—Preparation of Coupler Emulsion— 1- (2′-octylphenyl) -3- as a coupler
Methyl-5-pyrazolone 2 parts, 1,2,3-triphenylguanidine 2 parts, l, 1- (p-hydroxyphenyl) -2-ethylhexane 2 parts, 4,4 ′-(p-phenylenediisopropylidene ) 4 parts of diphenol, 4 parts of 2-ethylhexyl-4-hydroxybenzoate, 0.3 part of tricresyl phosphate, 0.1 part of diethyl maleate and 1 part of a 70% calcium dodecylbenzenesulfonate methanol solution in acetic acid This solution was dissolved in 10 parts of ethyl, and this solution was added to 80 parts of an 8% aqueous gelatin solution, emulsified with a homogenizer for 10 minutes, and then ethyl acetate was removed to prepare a desired coupler emulsion.

—Preparation of Coating Solution for Thermosensitive Recording Layer B— Next, the diazonium salt compound microcapsule solution and the coupler dispersion were mixed with a diazonium salt compound /
The mixture was mixed such that the ratio of the couplers became 2/3 to prepare the intended coating solution for the heat-sensitive recording layer B.

<Coating solution for heat-sensitive recording layer C> -Preparation of microcapsule solution of diazonium salt compound- As the diazonium salt compound, 2,5-dibutoxy-4-
Dissolve 3.0 parts of tolylthiobenzenediazonium hexafluorophosphate in 20 parts of ethyl acetate, and further add 20 parts of alkylnaphthalene, which is a high boiling point solvent,
Heat to mix evenly. 15 parts of an xylylene diisocyanate / trimethylolpropane adduct as a microcapsule wall agent was further added to this solution, and the mixture was stirred uniformly. Separately, 54 parts of a 6% by weight aqueous solution of gelatin were prepared, the above diazonium salt compound solution was added, and the mixture was emulsified and dispersed with a homogenizer. After 68 parts of water was added to the obtained emulsion to homogenize it, the temperature was raised to 40 ° C. with stirring, and a microencapsulation reaction was performed for 3 hours to obtain a desired diazonium salt compound microcapsule liquid. The average particle size of the microcapsules was 1.0 μm.

-Preparation of Coupler Dispersion- As a coupler, 2-chloro-5- (3- (2,4-di-
tert-pentyl) phenoxypropylamino) acetoacetanilide 2 parts, 1,2,3-triphenylguanidine 2 parts, 1,1- (p-hydroxyphenyl) -2
-2 parts of ethylhexane, 4 parts of 4,4 '-(p-phenylenediisopropylidene) diphenol, 4 parts of 2-ethylhexyl-4-hydroxybenzoate, 0.3 part of tricresyl phosphate, 0.1 part of diethyl maleate Department,
Then, 1 part of a 70% calcium dotesylbenzenesulfonate methanol solution was dissolved in 10 parts of ethyl acetate, and this solution was added to 80 parts of an 8% aqueous gelatin solution, emulsified with a homogenizer for 10 minutes, and then ethyl acetate was removed. Thus, the desired coupler dispersion was prepared.

—Preparation of Coating Solution for Thermosensitive Recording Layer C— Next, the diazonium salt compound microcapsule solution and the coupler dispersion were mixed with a diazonium salt compound /
The mixture was mixed so that the ratio of the couplers became 4/5 to prepare the intended coating solution for the heat-sensitive recording layer C.

<Light Transmittance Adjusting Layer> —Preparation of Ultraviolet Absorber Precursor Microcapsule Solution— In 30 parts of ethyl acetate, [2-
Allyl-6- (2H-benzotriazol-2-yl)
-4-t-octylphenyl] benzenesulfonate 1
0 parts, 2,5-di-t-octyl-hydroquinone 3
Parts, 2 parts of tricresyl phosphate and 4 parts of α-methylstyrene dimer were dissolved. As a microcapsule wall material, 20 parts of an xylylene diisocyanate / trimethylolpropane adduct was further added to this solution, and the mixture was stirred uniformly. Separately, 200 parts of an 8% aqueous solution of itaconic acid-modified polyvinyl alcohol was prepared, and the ultraviolet absorbent precursor solution was added thereto, followed by emulsification and dispersion with a homogenizer. After 120 parts of water was added to the obtained emulsion to homogenize it, the temperature was raised to 40 ° C. with stirring, and an encapsulation reaction was performed for 3 hours to prepare a desired ultraviolet absorbent precursor microcapsule solution. The average particle size of the microcapsules was 0.3 μm.

—Preparation of Coating Solution for Light Transmittance Adjusting Layer— 2 parts of [4-nonylphenoxytrioxyethylene] was added to 100 parts of the ultraviolet absorbent precursor microcapsule solution.
10 parts of an aqueous solution of sodium butylsulfonate was added to prepare a coating solution for a light transmittance adjusting layer.

<Preparation of Coating Solution for Intermediate Layer> To 100 parts of a 10% aqueous gelatin solution was added 2 parts of sodium 2% (4-nonylphenoxytrioxyethylene) butylsulfonate to prepare a coating solution for an intermediate layer.

<Preparation of Coating Solution for Protective Layer> In 61 parts of 5.0% aqueous solution of ethylene-modified polyvinyl alcohol, 20.5 parts
2.0 parts by weight of a 2% zinc stearate dispersion (Hydrin F115, manufactured by Chukyo Yushi Co., Ltd.), 8.4 parts of a 2% (4-nonylphenoxytrioxyethylene) sodium butylsulfonate aqueous solution, (ME-313,
8.0 parts of Daikin Co., Ltd.) and 0.5 parts of flour starch were added, and the mixture was stirred uniformly to prepare a PVA solution. Separately, 12.5 parts of a 20% by weight chao gloss (manufactured by Shiraishi Industry Co., Ltd.) aqueous solution,
1.25 parts of 0% by weight polyvinyl alcohol (PVA105: trade name of Kuraray Co., Ltd.) was mixed with 0:39 parts of a 2% by weight aqueous solution of sodium dodecylsulfonate, and the mixture was dispersed with a Dynomill to prepare a pigment liquid. 4.4 parts of the pigment liquid was added to 80 parts of the PVA liquid to prepare a coating liquid for a protective layer.

<Coating of Coating Solutions for Each Thermosensitive Recording Layer> On the undercoat layer, the coating solution for the thermosensitive recording layer A, the coating solution for the intermediate layer, the coating solution for the thermosensitive recording layer B, and the coating solution for the intermediate layer. Liquid, the coating liquid for the heat-sensitive recording layer C, the coating liquid for the light transmittance adjusting layer, and the coating liquid for the protective layer in this order at a coating speed of 60 m / min.
%, And a temperature of 40 ° C. and a humidity of 30%, respectively, to obtain a multicolor heat-sensitive recording material.

The solid content coating amount was 6.0 g for the heat-sensitive recording layer A.
/ M ² , the intermediate layer is 3.0 g / m ² , and the heat-sensitive recording layer B is 6.0.
g / m ² , the intermediate layer is 3.0 g / m ² , and the heat-sensitive recording layer C is 5.0 g / m ² .
0 g / m ² , the light transmittance adjusting layer was 3.0 g / m ² , and the protective layer was 1.5 g / m ² . The weight ratio between the binder and the particles in the heat-sensitive recording layer A (binder / particle) was 0.23, and the weight ratio between the binder and the particles in the heat-sensitive recording layer B (binder / particle) was 0.2.
The weight ratio of the binder to the particles in the thermosensitive recording layer C (binder / particle) was 0.20.

The haze value of the thermosensitive recording layer was measured using a haze measuring device (DIGITALHAZE COMPUTER, manufactured by Suga Test Instruments Co., Ltd.). The light-sensitive recording material had an emission center wavelength of 420 nm and an output of 40 W.
Irradiate the UV lamp for 10 seconds, and the emission center wavelength is 3
After irradiating for 15 seconds to an ultraviolet lamp having a power of 65 nm and a power of 40 W, 440 was applied using a color analyzer 607 manufactured by Hitachi.
The reflectance at a wavelength of nm was measured. The obtained reflectance was defined as whiteness (%). As a result, in the heat-sensitive recording material of Example 1, the haze value was 85%, and the whiteness was 84.
5%. Therefore, it was a heat-sensitive recording material having a high whiteness in the background.

The whiteness of the support before coating the heat-sensitive recording layer was measured as a reflectance at a wavelength of 440 nm using a color analyzer 607 manufactured by Hitachi.
%Met. The presence or absence of bleed-out of the fluorescent whitening agent was evaluated as a decrease in whiteness of the support. That is, the support was heat-treated at 120 ° C. for 3 minutes, cooled, and further heat-treated at 100 ° C. for 24 hours. When the decrease in whiteness was visually evaluated, no yellowing was observed. Further, the obtained heat-sensitive recording material was set to have an emission center wavelength of 420 n.
m, irradiation with an ultraviolet lamp with an output of 40 W for 10 seconds, and further irradiation with an emission center wavelength of 365 nm and an ultraviolet lamp with an output of 40 W, the irradiation time at which the optical density of the background became 0.30 was measured, and it was 9 seconds. And it was short.

Example 2 The procedure of Example 1 was repeated except that the weight ratio (binder / particle) of the binder to the particles in the heat-sensitive recording layer A was changed to 0.26. As a result, the haze value was 65%, and the whiteness was 85.3%. Therefore, it was a heat-sensitive recording material having a high whiteness in the background.

Example 3 The procedure of Example 1 was repeated, except that the weight ratio (binder / particle) between the binder and the particles in the heat-sensitive recording layer A was changed to 0.30. As a result, the haze value was 62%, and the whiteness was 85.5%. Therefore, it was a heat-sensitive recording material having a high whiteness in the background.

Comparative Example 1 The procedure of Example 1 was repeated, except that the weight ratio (binder / particle) between the binder and the particles in the thermosensitive recording layer A was changed to 0.19. As a result, the haze value was 93% and the whiteness was 83.9%. Therefore, it was a heat-sensitive recording material in which the whiteness of the background was not sufficient.

[0136]

According to the present invention, the above-mentioned conventional problems can be solved. Further, according to the present invention, excellent fixation time is obtained without fixing inhibition at the time of image recording, the background after fixing is white, there is no bleeding out of the fluorescent brightener from the thermoplastic resin layer, and a good image is obtained. Heat-sensitive recording material can be provided.

Claims (3)

[Claims] 1. A diazonium salt compound which is decomposed by ultraviolet rays on a support having a thermoplastic resin layer containing a fluorescent brightener and a white pigment on a substrate, and has a haze value of 90% or less. A heat-sensitive recording material comprising at least one heat-sensitive recording layer. 2. The heat-sensitive recording material according to claim 1, wherein the fluorescent whitening agent is a compound represented by the following structural formula (I). Structural formula (I) However, in the structural formula (I), R ₁ , R ₂ , R ₃ and R
₄ represents a hydrogen atom or a substituent or a substituted atom. 3. The thermosensitive recording according to claim 1, wherein the thermosensitive recording layer contains a binder and particles, and a weight ratio (binder / particle) between the binder and the particles is 0.20 or more. material.