JP2002362029A - Thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording material which reduces sticking and the fouling of a head and is excellent in photographic printing aptitude. SOLUTION: In the thermal recording material in which a thermal recording layer and a protective layer are formed in turn on a support, the protective layer contains polyvinyl alcohol, silica, and fine particles of aluminum hydroxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat-sensitive recording material, and more particularly, to a high-quality heat-sensitive recording material suitable for medical recording media and the like.

[0002]

2. Description of the Related Art Either a substantially colorless coloring component A or a substantially colorless coloring component B which reacts with the coloring component A to form a color is microencapsulated, and the other is formed into an emulsion. There is a heat-sensitive recording material prepared by providing a heat-sensitive recording layer to be formed on a transparent support such as a synthetic polymer film. Such a transparent thermosensitive recording material has good transparency in itself, but when printing with a thermosensitive recording device such as a thermosensitive printer, there is a problem that sticking (the accompanying noise) and head contamination easily occur. is there. In particular, when a transparent thermosensitive recording material is used for medical purposes, a high transmission density is required, so that the thermal energy applied by the thermal head increases, and sticking,
In addition, problems such as head contamination become serious.

For the purpose of improving the sticking and head contamination, an attempt has been made to provide a protective layer mainly composed of a pigment and a binder on the heat-sensitive recording layer and to add various lubricants to the protective layer. , Excessive lubricant may adhere as the head becomes dirty, causing uneven image density.
Particularly, it is not preferable for medical use. On the other hand, for images for medical use, high-energy recording with a high black ratio is performed.
The thermal head wears, and the thermal conductivity from the head heating element changes, causing density unevenness. With respect to the abrasion of the thermal head, it has been proposed to provide a layer having a high hardness and a chemically stable carbon as a main component on the head surface. However, the carbon layer has a characteristic that its surface energy is lower than that of a conventional thermal head surface layer (for example, SiN, SiC), the friction coefficient with the recording material protective layer is increased, and sticking is deteriorated. there were.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned problems, and has been made in consideration of sticking,
Further, it is an object of the present invention to provide a heat-sensitive recording material having excellent printability by reducing dirt on a head.

[0005]

Means for solving the above problems are as follows. <1> A heat-sensitive recording material having a heat-sensitive recording layer and a protective layer sequentially on a support, wherein the protective layer contains polyvinyl alcohol and fine particles of silica and aluminum hydroxide. Recording material. <2> The thermosensitive recording material according to <1>, wherein the support and the thermosensitive recording layer are substantially transparent.

<3> The silica is contained in an amount of 5 to 60% by mass based on aluminum hydroxide, <1> or <2>.
> The heat-sensitive recording material described in <1. <4> The particle size of silica is 5 to 100 nm, and the particle size of aluminum hydroxide is 0.2 to 0.5 μm. <1>
The heat-sensitive recording material according to any one of <1> to <3>. <5> The protective layer contains at least one selected from the group consisting of stearic acid, zinc stearate, stearic acid amide, and a silicone compound as a lubricant.
The heat-sensitive recording material according to any one of 1> to <4>.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the heat-sensitive recording material of the present invention will be described. The heat-sensitive recording material of the present invention has a heat-sensitive recording layer and a protective layer sequentially on a support, and further has other layers as necessary. Hereinafter, the heat-sensitive recording material of the present invention will be described in detail.

[Protective Layer] The protective layer is a layer for sticking the heat-sensitive recording layer and protecting the heat-sensitive recording layer from a solvent or the like, and is provided on the heat-sensitive recording layer or as an intermediate layer as the other layer. Is provided on the heat-sensitive recording layer,
It is formed on an intermediate layer or the like. The protective layer may have a single-layer structure or a laminated structure of two or more layers.
Such a protective layer contains polyvinyl alcohol as a binder and contains fine particles of silica and aluminum hydroxide. When the protective layer contains these two types of inorganic fine particles having different particle diameters, sticking and generation of head contamination can be suppressed. In addition, the generation of noise can be suppressed by suppressing sticking.

Hereinafter, the protective layer will be described in more detail. (Binder) As the binder, polyvinyl alcohol (including completely saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, and modified polyvinyl alcohol) is used from the viewpoint of improving transparency.
Among them, (long chain) alkyl ether-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silica-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, and alkyl-modified polyvinyl alcohol are particularly preferable.

Further, another polymer may be used in combination with the polyvinyl alcohol. Preferred polymers used in combination include silicone-modified polymers, gelatin, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, starches, agar, κ-carrageenan,
Gum arabic, casein, styrene-maleic anhydride copolymer hydrolyzate, ethylene-maleic anhydride copolymer hydrolyzate, isobutylene-maleic anhydride copolymer hydrolyzate and the like can be mentioned. From the viewpoint of ensuring the transparency of the protective layer, the amount of the polymer used in combination is preferably from 2 to 30% by mass, more preferably from 2 to 20% by mass, based on polyvinyl alcohol.

(Inorganic fine particles) As described above, fine particles of silica and aluminum hydroxide are used. As the silica, amorphous silica, colloidal silica, fine powder silica, amorphous silica, surface-treated amorphous silica, and the like are preferable, and among them, colloidal silica is particularly preferable. The content of the fine particles composed of silica and aluminum hydroxide is 50 to the binder.
To 400% by mass, preferably 100 to 300% by mass.
More preferably, it is mass%.

Preferably, the silica is contained in an amount of 5 to 60% by mass based on aluminum hydroxide.
More preferably, the content is 10 to 50% by mass.
More preferably, the content is 30 to 30% by mass. If the silica is not in the above range, head contamination or head wear may occur.

The silica preferably has a particle size of 5 to 100 nm, more preferably 5 to 60 nm, and even more preferably 10 to 40 nm. The particle size of aluminum hydroxide is 0.2 to 0.5 μm
And more preferably 0.2 to 0.35 μm. If the particle size of the silica and aluminum hydroxide is not in the above range, head contamination or head wear may occur.

The protective layer of the heat-sensitive recording material of the present invention may contain organic and / or inorganic pigments (fine particles) other than the above silica and aluminum hydroxide. As the pigment that can be used for the protective layer, its average particle size,
More specifically, a 50% volume average particle size measured by a laser diffraction method (laser diffraction particle size distribution measuring device LA700 (trade name)
Average particle size of pigment particles corresponding to 50% volume in the pigment, as measured by HORIBA, Ltd. Hereinafter, it may be simply referred to as “average particle size”. ) Is 0.10-5.00 μm
In particular, from the viewpoint of preventing the occurrence of sticking, abnormal noise, head contamination, and the like between the head and the heat-sensitive recording material when recording with a thermal head, the 50% volume average particle diameter is 0. .20 to 0.50
More preferably, it is in the range of μm.

The 50% volume average particle size is 0.10-5.
When the thickness is in the range of 00 μm, the effect of reducing abrasion on the thermal head is great, and the effect of preventing welding between the thermal head and the binder in the protective layer is great. As a result, protection of the thermal head and the thermal recording material during printing is achieved. It is possible to effectively prevent so-called sticking that adheres to the layer.

The pigment used in combination with the protective layer is not particularly limited, and includes known organic and inorganic pigments. In particular, pigments such as calcium carbonate, titanium oxide, kaolin, and zinc oxide can be used. Organic pigments such as inorganic pigments, urea formalin resins, and epoxy resins are preferred. Among them, kaolin is more preferable. These pigments may be used alone or in combination of two or more.

Further, these pigments (including silica and aluminum hydroxide) may be surface-coated with at least one selected from the group consisting of higher fatty acids, metal salts of higher fatty acids, and higher alcohols. Examples of the higher fatty acids include stearic acid, palmitic acid, myristic acid, and lauric acid. In addition, these pigments (including silica and aluminum hydroxide) include, for example, sodium hexametaphosphate, partially or completely saponified modified polyvinyl alcohol, polyacrylic acid copolymer, dispersing aids such as various surfactants, Preferably, partially saponified or completely saponified modified polyvinyl alcohol, in the presence of a polyacrylic acid copolymer ammonium salt, disperser, sand mill, a known disperser such as a ball mill, dispersed to the above average particle size It is preferably used.

(Lubricant) The protective layer comprises at least one lubricant selected from the group consisting of stearic acid, zinc stearate, stearic acid amide, and silicone compound.
Preferably, it contains a species. This lubricant is preferably contained in an amount of 2 to 30% by mass, more preferably 5 to 20% by mass, based on all components of the protective layer.
Within this range, there is no problem such as dirt on the head and stickiness of the head surface, and sufficient head matching properties can be obtained. Further, a known lubricant (paraffin wax, another higher fatty acid, another higher fatty acid salt, another higher fatty acid amide, a fluorine-containing compound, or the like) may be further used in the protective layer.

(Other Components) The protective layer may contain a known crosslinking agent (hardening agent) and the like. Examples of the crosslinking agent include vinyl sulfone compounds, aldehyde compounds (formaldehyde, glutaraldehyde, etc.), epoxy compounds, oxazine compounds, triazine compounds, and polymer hardeners described in JP-A-62-234157. Film agents, methylated melamine, blocked isocyanates, methylol compounds, carbodiimide resins and the like can be used. Among these crosslinking agents, vinyl sulfone compounds, aldehyde compounds, epoxy compounds, oxazine compounds, triazine compounds, and polymer hardeners described in JP-A-62-234157 are preferred.

In order to form a protective layer uniformly,
It is preferable to add a surfactant to the coating solution for forming the protective layer. Examples of the surfactant include sulfosuccinic acid-based alkali metal salts and fluorine-containing surfactants. Specific examples thereof include di- (2-ethylhexyl) sulfosuccinic acid and di-sulfosuccinic acid.
Examples thereof include sodium salts or ammonium salts such as (n-hexyl) sulfosuccinic acid. Further, in the protective layer, for the purpose of preventing the heat-sensitive recording material from being charged, metal oxide fine particles,
You may add an inorganic electrolyte, a polymer electrolyte, etc.

It is preferable that the protective layer contains an aliphatic compound derivative having at least a -CONH- structure in a molecule (hereinafter, may be referred to as an amide compound). By containing a specific amide compound in the protective layer, sticking is less likely to occur and the head is sufficient for a thermal head having an uppermost layer having a carbon ratio of 90% or more, which is excellent in wear resistance. Since it has matching properties, it is suitably used particularly in fields requiring high image quality, such as medical recording media.

(Amide compound) The amide compound is represented by the following structural formulas (1) to (3).

[0023]

Embedded image

In the structural formulas (1), (2) and (3), X is
H or CH_TwoOH¹, R ^Two, R^Three, R^FourIs carbon
Even when branched by a saturated or unsaturated alkyl group of Formulas 8 to 24
It may be hydroxylated. R^ThreeAnd R^FourAre the same but different
It may be. L is represented by the following structural formula (4)
You.

[0025]

Embedded image

In the structural formula (4), n + m = 0 to 8.
Among these, the compounds represented by the structural formulas (1) and (3) are particularly preferable, and R ¹ , R ³ and R ⁴ have 12 carbon atoms.
Preferred are -20 saturated or unsaturated alkyl groups. The alkyl group may be branched, and may have a hydroxy group in the structure. n + m is preferably 0 to 4, particularly 2 when h = 0, and preferably 0 to 2 when h = 1.

When the amide compound is a solid, 1) in the presence of a water-soluble polymer such as polyvinyl alcohol and a dispersant such as various surfactants, a known dispersing machine such as a homogenizer, a dissolver, and a sand mill is used to remove the amide compound. 2) After being dissolved in a solvent, used in the form of an emulsion with a known emulsifying device such as a homogenizer, a dissolver, or a colloid mill in the presence of a dispersant such as a water-soluble polymer or various surfactants. Can be When the amide compound is a liquid, the dispersion and the emulsion used in the form of an emulsion as described above preferably have an average particle size of 0.1 to 5.0 μm, more preferably 0.1 to 2 μm. The average particle diameter here is measured by a Horiba Seisakusho laser diffraction particle size distribution analyzer LA700 with a transmittance of 75.
% Refers to a 50% average particle size measured at ± 1%.

The ratio of the amide compound to the total amount of the protective layer is preferably in the range of 0.5 to 10% by mass.
When the content is within this range, sufficient head matching properties can be obtained, and problems such as head contamination and surface stickiness do not occur.
A more preferred range is 1 to 5% by mass.

The protective layer is formed by applying a coating liquid for a protective layer comprising the above binder and inorganic fine particles on a heat-sensitive recording layer or the like described later using a bar coater, an air knife coater, a blade coater, a curtain coater or the like. It is applied and dried. However, the protective layer may be applied simultaneously with the heat-sensitive recording layer by a superposition method, or after the heat-sensitive recording layer or the like is applied,
The thermosensitive recording layer or the like may be dried once and then applied thereon. The drying coating amount of the protective layer is preferably ^{0.2~7g / m 2, 1~4g / m} 2 is more preferable.

[Thermal Recording Layer] The thermosensitive recording layer contains at least a color-forming component and, if necessary, other components.

(Coloring Component) As the heat-sensitive recording layer, those having excellent transparency when not processed and having a property of being colored by heating are preferably used. As such a heat-sensitive recording layer, a so-called two-component type heat-sensitive recording layer containing a substantially colorless color-forming component A and a substantially colorless color-forming component B that forms a color by reacting with the color-forming component A is used. However, the coloring component A or the coloring component B is preferably encapsulated in a microcapsule. Examples of the combination of the two components constituting the two-component type thermosensitive recording layer include the following (a) to (m).

(A) A combination of an electron-donating dye precursor and an electron-accepting compound. (B) Combination of a photodegradable diazo compound and a coupler. (C) an organic metal salt such as silver behenate or silver stearate;
Combination with reducing agents such as protocatechinic acid, spiroindane and hydroquinone. (D) A combination of a long-chain aliphatic salt such as ferric stearate or ferric myristate, and a phenol such as gallic acid or ammonium salicylate. (E) organic acid heavy metal salts such as salts with nickel, cobalt, lead, copper, iron, mercury, silver and the like such as acetic acid, stearic acid and palmitic acid; calcium sulfide and strontium sulfide;
Combination with alkaline earth metal sulfides such as potassium sulfide,
Alternatively, a combination of the organic acid heavy metal salt and an organic chelating agent such as s-diphenylcarbazide and diphenylcarbazone.

(F) Combination of (heavy) metal sulfates such as silver sulfide, lead sulfide, mercury sulfide and sodium sulfide with sulfur compounds such as Na-tetrathionate, sodium thiosulfate and thiourea. (G) an aliphatic ferric salt such as ferric stearate;
Combination with an aromatic polyhydroxy compound such as 4-dihydroxytetraphenylmethane. (H) organic noble metal salts such as silver oxalate and mercury oxalate;
Combination with organic polyhydroxy compounds such as polyhydroxy alcohol, glycerin and glycol. (I) A combination of an aliphatic ferric salt such as ferric pelargonate and ferric laurate with a thiocetyl carbamide or isothiocesyl carbamide derivative. (J) A combination of a lead salt of an organic acid such as lead caproate, lead pelargonate or lead behenate with a thiourea derivative such as ethylenethiourea or N-dodecylthiourea. (K) A combination of a heavy metal salt of a higher fatty acid such as ferric stearate and copper stearate with zinc dialkyldithiocarbamate. (L) A substance that forms an oxazine dye such as a combination of resorcinol and a nitroso compound. (M) A combination of a formazan compound and a reducing agent and / or a metal salt.

Among them, in the heat-sensitive recording material of the present invention, (a) a combination of an electron-donating dye precursor and an electron-accepting compound, (b) a combination of a photodegradable diazo compound and a coupler, or ( c) It is preferable to use a combination of an organometallic salt and a reducing agent, and in particular, the above (a) or (b)
Is more preferable.

The heat-sensitive recording material of the present invention comprises a heat-sensitive recording layer having a haze value calculated from (diffuse transmittance / total light transmittance) × 100 (%), and
An image having excellent transparency can be obtained. The haze value is an index indicating the transparency of the material, and is generally calculated from the total light transmission amount, the diffuse transmission light amount, and the parallel transmission light amount using a haze meter. In the present invention, as a method of lowering the haze value, for example, the 50% volume average particle diameter of both the color forming components A and B contained in the heat-sensitive recording layer is set to 1.0 μm.
m or less, preferably 0.6 μm or less, and a method in which a binder is contained in a range of 30 to 60% by mass of the total solid content of the heat-sensitive recording layer. One of the color-forming components A and B is microencapsulated, For example, there is a method in which the other layer substantially forms a continuous layer after coating and drying, for example, a method of using an emulsion or the like. It is also effective to make the refractive index of the component used in the heat-sensitive recording layer as close to a certain value as possible.

Next, the combinations (a, b, c) of the above-mentioned compositions, which are preferably used in the above-mentioned thermosensitive recording layer, will be described in detail below. First, (a) the combination of the electron-donating dye precursor and the electron-accepting compound will be described. The electron donor dye precursor preferably used in the present invention,
It is not particularly limited as long as it is substantially colorless, but has a property of donating electrons, or having a property of receiving a proton such as an acid to develop color,
It is preferably a colorless compound having a partial skeleton such as lactone, lactam, sultone, spiropyran, ester, amide and the like, and when these partial skeletons are contacted with an electron-accepting compound, these partial skeletons are opened or cleaved.

Examples of the electron-donating dye precursor include a triphenylmethanephthalide compound, a fluoran compound, a phenothiazine compound, an indolylphthalide compound, a leucouramine compound, a rhodamine lactam compound, and a triamine compound. Examples include phenylmethane-based compounds, triazene-based compounds, spiropyran-based compounds, fluorene-based compounds, pyridine-based compounds, and pyrazine-based compounds.

Specific examples of the phthalides are described in US Pat. No. Re. 23,024, US Pat. Nos. 3,491,111, 3,491,112, and 3,491. , 116, and 3,509,174. Specific examples of the fluorans are described in US Pat. No. 3,624,107.
No. 3,627,787, No. 3,641,01
No. 1, No. 3,462,828, No. 3,681,3
No. 90, No. 3,920,510, No. 3,959,
No. 571 and the like. Specific examples of the spiropyrans include US Pat.
71,808 and the like. Examples of the pyridine-based and pyrazine-based compounds include U.S. Patent Nos. 3,775,424 and 3,853,8.
No. 69, No. 4,246,318 and the like. Specific examples of the fluorene-based compound include compounds described in Japanese Patent Application No. 61-240989. Among these, black-colored 2-arylamino-3- [H, halogen, alkyl or alkoxy-6-substituted aminofluoran] is particularly preferable.

Specifically, for example, 2-anilino-3-
Methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-N-cyclohexyl-N-methylaminofluoran, 2-p-chloroanilino-3-methyl-6-dibutylaminofluoran, 2-anilino- 3-
Methyl-6-dioctylaminofluoran, 2-anilino-3-chloro-6-diethylaminofluoran, 2-
Anilino-3-methyl-6-N-ethyl-N-isoamylaminofluoran, 2-anilino-3-methyl-6
N-ethyl-N-dodecylaminofluoran, 2-anilino-3-methoxy-6-dibutylaminofluoran,
2-o-chloroanilino-6-dibutylaminofluoran, 2-p-chloroanilino-3-ethyl-6-N-ethyl-N-isoamylaminofluoran, 2-o-chloroanilino-6-p-butylanilinofur Oran, 2-
Anilino-3-pentadecyl-6-diethylaminofluoran, 2-anilino-3-ethyl-6-dibutylaminofluoran, 2-o-toluidino-3-methyl-6
Diisopropylaminofluoran, 2-anilino-3-
Methyl-6-N-isobutyl-N-ethylaminofluoran, 2-anilino-3-methyl-6-N-ethyl-N
-Tetrahydrofurfurylaminofluoran, 2-anilino-3-chloro-6-N-ethyl-N-isoamylaminofluoran, 2-anilino-3-methyl-6-N-
Methyl-N-γ-ethoxypropylaminofluoran,
2-anilino-3-methyl-6-N-ethyl-N-γ-
Ethoxypropylaminofluoran, 2-anilino-3
-Methyl-6-N-ethyl-N- [gamma] -propoxypropylaminofluoran and the like.

Examples of the electron-accepting compound that acts on the electron-donating dye precursor include phenol compounds, organic acids or metal salts thereof, and acidic substances such as oxybenzoic acid esters. And the compounds described in Japanese Patent Application Publication No.

Specifically, 2,2-bis (4'-hydroxyphenyl) propane (generic name: bisphenol A), 2,2-bis (4'-hydroxyphenyl) pentane, 2,2-bis (4 '-Hydroxy-3', 5'-
Dichlorophenyl) propane, 1,1-bis (4′-hydroxyphenyl) cyclohexane, 2,2-bis (4′-hydroxyphenyl) hexane, 1,1-bis (4′-hydroxyphenyl) propane, 1,1- Bis (4'-hydroxyphenyl) butane, 1,1-bis (4'-hydroxyphenyl) pentane, 1,1-bis (4'-hydroxyphenyl) hexane, 1,1-bis (4'-hydroxyphenyl) Heptane, 1,1-bis (4'-hydroxyphenyl) octane, 1,1-bis (4'-hydroxyphenyl) -2-methyl-pentane, 1,1-bis (4'-hydroxyphenyl) -2-
Ethyl-hexane, 1,1-bis (4′-hydroxyphenyl) dodecane, 1,4-bis (p-hydroxyphenylcumyl) benzene, 1,3-bis (p-hydroxyphenylcumyl) benzene, bis ( Bisphenols such as p-hydroxyphenyl) sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, and bis (p-hydroxyphenyl) acetic acid benzyl ester;

3,5-di-α-methylbenzylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3-
α-α-dimethylbenzylsalicylic acid, 4- (β-p-
Salicylic acid derivatives such as methoxyphenoxyethoxy) salicylic acid;

Or polyvalent metal salts thereof (particularly zinc and aluminum are preferred); benzyl ester of p-hydroxybenzoate, 2-ethylhexyl p-hydroxybenzoate, and 2- (2-phenoxyethyl) -β-resorcinate Oxybenzoic acid esters such as esters; p-phenylphenol, 3,5-diphenylphenol, cumylphenol, 4-hydroxy-4′-isopropoxy-diphenylsulfone, 4-hydroxy-4′-phenoxy-diphenylsulfone, etc. Phenols. Among them, bisphenols are particularly preferable from the viewpoint of obtaining good color-forming properties. The above-mentioned electron accepting compounds may be used alone or in combination of two or more.

Next, the combination (b) of the photodegradable diazo compound and the coupler will be described. The photodegradable diazo compound is a compound that undergoes a coupling reaction with a coupler, which is a coupling component described below, to produce a desired hue, and is decomposed when receiving light in a specific wavelength range before the reaction, and is no longer coupled. It is a photo-degradable diazo compound that does not have a coloring ability even if a component is present. The hue in this color forming system is determined by the diazo dye formed by the reaction between the diazo compound and the coupler. Therefore, the color hue can be easily changed by changing the chemical structure of the diazo compound or the coupler, and depending on the combination,
Any color hue can be obtained.

As the photodecomposable diazo compound preferably used in the present invention, an aromatic diazo compound can be mentioned, and specifically, an aromatic diazonium salt, a diazosulfonate compound, a diazoamino compound and the like can be mentioned. Examples of the aromatic diazonium salt include compounds represented by the following general formula, but are not limited thereto. The aromatic diazonium salt is preferably one having excellent light fixing property, little generation of colored stain after fixing, and a stable coloring part. Ar-N ₂ ⁺ X ^- in the above formulas, Ar has a substituent, or represents an unsubstituted aromatic hydrocarbon ring group, a N ₂ ⁺ diazonium group, X ^-
Represents an acid anion.

Many diazosulfonate compounds are known in recent years, and are obtained by treating each diazonium salt with a sulfite, and can be suitably used in the heat-sensitive recording material of the present invention. .

The diazoamino compound can be obtained by coupling a diazo group with dicyandiamide, sarcosine, methyltaurine, N-ethylanthranic acid-5-sulfonic acid, monoethanolamine, diethanolamine, guanidine or the like. It can be suitably used for the heat-sensitive recording material of the present invention. Details of these diazo compounds are described in detail, for example, in JP-A-2-136286.

On the other hand, examples of the coupler capable of performing a coupling reaction with the above-mentioned diazo compound include, for example, 2-hydroxy-
In addition to 3-naphthoic anilide, resorcinol, and those described in JP-A-62-146678 and the like can be mentioned.

In the case where a combination of a diazo compound and a coupler is used in the heat-sensitive recording layer, the sensitization is carried out from the viewpoint that the coupling reaction is carried out in a basic atmosphere so that the reaction can be further accelerated. A basic substance may be added as an agent. Examples of the basic substance include a water-insoluble or hardly soluble basic substance and a substance that generates an alkali by heating, for example, an inorganic or organic ammonium salt, an organic amine, an amide, urea or thiourea or a derivative thereof, Thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidazolines, triazoles, morpholines, piperidines, amidines,
Nitrogen-containing compounds such as forimazines or pyridines are exemplified. Specific examples of these are described in, for example,
No. 1,291,183, and the like.

Next, (c) a combination of an organic metal salt and a reducing agent will be described. Specific examples of the organic metal salt include silver salts of long-chain aliphatic carboxylic acids such as silver laurate, silver myristate, silver palmitate, silver stearate, silver arachiate or silver behenate; silver benzotriazole Silver salt of an organic compound having an imino group such as salt, silver benzimidazole, silver carbazole or silver phthalazinone; silver salt of a sulfur-containing compound such as s-alkylthioglycolate; fragrance such as silver benzoate and silver phthalate Silver salt of aromatic carboxylic acid; silver salt of sulfonic acid such as silver ethanesulfonate; o
Silver salts of sulfinic acids such as silver toluenesulfinate; silver salts of phosphoric acid such as silver phenylphosphate; silver barbiturates;
Examples include silver saccharinate, silver salt of salicyl asdoxime, or any mixture thereof. Of these, silver salts of long-chain aliphatic carboxylic acids are preferred, and silver behenate is more preferred. Also, behenic acid may be used together with silver behenate.

As the reducing agent, JP-A-53-102 can be used.
No. 0, page 227, lower left column, line 14 to page 229, upper right column, line 11 can be used as appropriate. Among them, mono, bis, tris or tetrakisphenols, mono or bisnaphthols, di or polyhydroxynaphthalenes, di or polyhydroxybenzenes,
Hydroxy monoethers, ascorbic acids, 3-pyrazolidones, pyrazolines, pyrazolones, reducing sugars, phenylenediamines, hydroxylamines, reductones, hydroxamic acids, hydrazides, amide oximes, N-hydroxyurea It is preferable to use a class or the like. Among the above, aromatic organic reducing agents such as polyphenols, sulfonamidophenols and naphthols are particularly preferred.

In order to ensure sufficient transparency of the heat-sensitive recording material, the heat-sensitive recording layer may contain (a) a combination of an electron-donating dye precursor and an electron-accepting compound, or (b) a photo-decomposable diazo compound. It is preferable to use a combination of and a coupler. In the present invention, it is preferable to use one of the color-forming component A and the color-forming component B after microencapsulation, and use the electron-donating dye precursor or the photodecomposable diazo compound after microencapsulation. Is more preferable.

(Microcapsules) The method for producing microcapsules will be described below in detail. The production of microcapsules includes an interfacial polymerization method, an internal polymerization method, an external polymerization method and the like, and any method can be adopted. As described above, the heat-sensitive recording material of the present invention is an electron-donating dye precursor,
Alternatively, it is preferable to microencapsulate the photodegradable diazo compound, particularly, an oil phase prepared by dissolving or dispersing the electron-donating dye precursor serving as the core of the capsule, or the photodegradable diazo compound in a hydrophobic organic solvent. Is mixed in an aqueous phase in which a water-soluble polymer is dissolved, and emulsified and dispersed by means of a homogenizer or the like, and then heated to cause a polymer formation reaction at the oil droplet interface, thereby forming a microcapsule wall of the polymer substance. Is preferably employed.

The reactant forming the polymer substance is added inside and / or outside the oil droplet. Specific examples of the polymer substance include polyurethane, polyurea, polyamide, polyester, polycarbonate, urea-formaldehyde resin, melamine resin, polystyrene, styrene methacrylate copolymer, styrene-acrylate copolymer and the like. Among these, polyurethane, polyurea, polyamide, polyester,
Polycarbonates are preferred, and polyurethanes and polyureas are particularly preferred.

For example, when polyurea is used as a capsule wall material, a polyisocyanate such as diisocyanate, triisocyanate, tetraisocyanate or polyisocyanate prepolymer and a polyamine such as diamine, triamine, tetraamine, etc. The microcapsule wall can be easily formed by reacting the above prepolymer having an amino group, piperazine or a derivative thereof, or a polyol with the above-mentioned aqueous phase by an interfacial polymerization method.

Further, for example, a composite wall composed of polyurea and polyamide or a composite wall composed of polyurethane and polyamide is composed of, for example, polyisocyanate and a second substance which reacts therewith to form a capsule wall (for example, acid chloride or polyamine, Polyol) can be prepared by mixing a water-soluble polymer aqueous solution (aqueous phase) or an oil medium (oil phase) to be encapsulated, emulsifying and dispersing these, and then heating. Details of the method for producing the composite wall composed of polyurea and polyamide are described in JP-A-58-66948.

The polyisocyanate compound includes:
A compound having a trifunctional or higher isocyanate group is preferred, but a bifunctional isocyanate compound may be used in combination. Specifically, diisocyanates such as xylene diisocyanate and its hydrogenated product, hexamethylene diisocyanate, tolylene diisocyanate and its hydrogenated product, and isophorone diisocyanate are used as main raw materials, and dimers of these dimers are used. Alternatively, in addition to a trimer (buret or isocyanurate), a polyfunctional adduct of a polyol such as trimethylolpropane and a bifunctional isocyanate such as xylylene diisocyanate, or a polyol such as trimethylolpropane and xylylene Examples thereof include a compound obtained by introducing a high molecular weight compound such as polyether having active hydrogen such as polyethylene oxide into an adduct with a bifunctional isocyanate such as range isocyanate, and a formalin condensate of benzene isocyanate. JP-A-62-2
Compounds described in JP-A-12190, JP-A-4-26189, JP-A-5-317694, and Japanese Patent Application No. 8-268721 are preferred.

The polyisocyanate is preferably added so that the microcapsules have an average particle size of 0.3 to 12 μm and the thickness of the capsule wall is 0.01 to 0.3 μm. The dispersed particle diameter is generally about 0.2 to 10 μm.

Specific examples of polyols and / or polyamines added to the aqueous phase and / or the oil phase as one of the constituents of the microcapsule wall by reacting with the polyisocyanate include propylene glycol, glycerin, trimethylol Examples include propane, triethanolamine, sorbitol, hexamethylenediamine and the like. When a polyol is added, a polyurethane wall is formed.
In the above reaction, it is preferable to keep the reaction temperature high or to add an appropriate polymerization catalyst from the viewpoint of increasing the reaction rate. The details of polyisocyanates, polyols, reaction catalysts, and polyamines for forming a part of the wall material are described in detail in Polygraphs (Polyurethane Handbook, edited by Keiji Iwata, Nikkan Kogyo Shimbun (1987)).

Further, a charge controlling agent such as a metal-containing dye, nigrosine, or any other optional substance can be added to the microcapsule wall, if necessary. These additives can be included in the capsule wall at the time of wall formation or at any time. In addition, a monomer such as a vinyl monomer may be graft-polymerized in order to adjust the chargeability of the capsule wall surface as needed.

Further, in order to make the microcapsule wall excellent in substance permeability even under a lower temperature condition and rich in coloring, it is preferable to use a plasticizer suitable for the polymer used as the wall material. The plasticizer preferably has a melting point of 50 ° C. or higher, and more preferably has a melting point of 120 ° C. or lower. Among them, those solid at room temperature can be suitably selected and used. For example, when the wall material is made of polyurea or polyurethane, a hydroxy compound,
Carbamate compounds, aromatic alkoxy compounds, organic sulfonamide compounds, aliphatic amide compounds,
Arylamide compounds and the like are preferably used.

In preparing the oil phase, the hydrophobic organic solvent used for dissolving the electron-donating dye precursor or the photo-decomposable diazo compound to form the core of the microcapsule has a boiling point of 100 to 300. Organic solvents at 0 ° C are preferred. Specifically, in addition to esters, dimethylnaphthalene, diethylnaphthalene, diisopropylnaphthalene,
Dimethylbiphenyl, diisopropylbiphenyl, diisobutylbiphenyl, 1-methyl-1-dimethylphenyl-2-phenylmethane, 1-ethyl-1-dimethylphenyl-1-phenylmethane, 1-propyl-1-dimethylphenyl-1-phenylmethane , Triallylmethane (eg, tritolylmethane, toluyldiphenylmethane), terphenyl compound (eg, terphenyl), alkyl compound, alkylated diphenylether (eg, propyldiphenylether), hydrogenated terphenyl (eg, hexahydroterphenyl) , Diphenyl ether and the like. Among these, the use of esters is particularly preferred from the viewpoint of the emulsion stability of the emulsified dispersion.

Examples of the esters include phosphoric esters such as triphenyl phosphate, tricresyl phosphate, butyl phosphate, octyl phosphate and cresyl phenyl phosphate;
Phthalates such as dibutyl phthalate, 2-ethylhexyl phthalate, ethyl phthalate, octyl phthalate, and butyl benzyl phthalate; dioctyl tetrahydrophthalate; ethyl benzoate, propyl benzoate, butyl benzoate, isopentyl benzoate; Benzoic acid esters such as benzyl benzoate; abietic acid esters such as ethyl abietic acid and benzyl abietic acid; dioctyl adipate; isodecyl succinate; dioctyl azelate;
Oxalic esters such as dibutyl oxalate and dipentyl oxalate; diethyl malonate; maleic esters such as dimethyl maleate, diethyl maleate and dibutyl maleate; tributyl citrate; methyl sorbate, ethyl sorbate, butyl sorbate and the like Sorbic acid esters; sebutylic acid esters such as dibutyl sebacate and dioctyl sebacate; monoesters and diesters of formic acid;
Butyric acid monoesters and diesters, lauric acid monoesters and diesters, palmitic acid monoesters and diesters, stearic acid monoesters and diesters,
Ethylene glycol esters such as oleic acid monoesters and diesters; triacetin; diethyl carbonate; diphenyl carbonate; ethylene carbonate; propylene carbonate; and boric esters such as tributyl borate and tripentyl borate.

Of these, the use of tricresyl phosphate alone or in combination is particularly preferred because the stability of the emulsion is the best. It is also possible to use the above oils together or in combination with other oils.

When the solubility of the electron-donating dye precursor or the photo-decomposable diazo compound to be encapsulated in the hydrophobic organic solvent is poor, a low-boiling solvent having high solubility is used in combination. Can also. Preferred examples of such a low-boiling solvent include ethyl acetate, isopropyl acetate, butyl acetate, and methylene chloride.

When the above-mentioned electron-donating dye precursor or photo-decomposable diazo compound is used in the heat-sensitive recording layer of the heat-sensitive recording material, the content of the electron-donating dye precursor is 0.1 to 5.
Preferably ^{0g / m 2, 1.0~4.0g / m} 2 is more preferable. Further, the content of the photodegradable diazo compound is 0.1.
Preferably 02~5.0g / m ^2, more preferably 0.10~4.0g / m ² from the viewpoint of color density.

When the content of the electron-donating dye precursor is 0.1%,
To be in the range of 1~5.0g / m ^2, sufficient color density can be obtained and, when the content of both are within 5.0 g / m ^2, sufficient color density is retained, and, The transparency of the heat-sensitive recording layer can be maintained.

On the other hand, for the aqueous phase to be used, an aqueous solution in which a water-soluble polymer is dissolved as a protective colloid is used, and after the oil phase is added thereto, emulsification and dispersion are carried out by means of a homogenizer or the like. Serves as a dispersion medium for making the dispersion uniform and easy and for stabilizing the emulsified aqueous solution. Here, in order to more uniformly emulsify and disperse and stabilize, a surfactant may be added to at least one of the oil phase and the aqueous phase. As the surfactant, a well-known surfactant for emulsification can be used. The amount of the surfactant added was 0.1 to the mass of the oil phase.
-5% is preferable, and 0.5-2% is more preferable.

As the surfactant to be contained in the aqueous phase, a surfactant which does not cause precipitation or aggregation by acting on the protective colloid is preferably selected from anionic or nonionic surfactants. it can. Preferred surfactants include, for example, sodium alkylbenzenesulfonate, sodium alkylsulfate, dioctyl sodium sulfosuccinate, polyalkylene glycol (eg, polyoxyethylene nonyl phenyl ether) and the like.

In the emulsification, the oil phase containing the above components and the aqueous phase containing the protective colloid and the surfactant are stirred at a high speed.
The emulsification can be easily carried out by using a means commonly used for emulsification of fine particles such as ultrasonic dispersion, for example, a known emulsifying apparatus such as a homogenizer, a Manton-Gawley, an ultrasonic disperser, a dissolver, and a Keddy mill. After the emulsification, the emulsion is preferably heated to 30 to 70 ° C. in order to promote the capsule wall forming reaction. During the reaction, in order to prevent aggregation of the capsules, it is preferable to reduce the probability of collision between the capsules by adding water or to perform sufficient stirring.

During the reaction, a dispersion for preventing aggregation may be added again. Generation of carbon dioxide gas is observed with the progress of the polymerization reaction, and the end of the generation can be regarded as an approximate end point of the capsule wall forming reaction. Usually, by reacting for several hours, the desired microcapsules can be obtained.

(Emulsified Dispersion) When an electron-donating dye precursor or a photo-decomposable diazo compound is encapsulated as a core substance, the electron-accepting compound or coupler to be used is:
For example, together with a water-soluble polymer and an organic base, other color-forming auxiliaries, etc., it can be used as a solid dispersion by means of a sand mill or the like, but after previously dissolved in a hardly water-soluble or insoluble high-boiling organic solvent, This is more preferably mixed with a polymer aqueous solution (aqueous phase) containing a surfactant and / or a water-soluble polymer as a protective colloid and emulsified with a homogenizer or the like and used as an emulsified dispersion. In this case, if necessary, a low boiling point solvent can be used as a dissolution aid. Further, the coupler and the organic base can be separately emulsified and dispersed, or can be mixed and then dissolved in a high boiling organic solvent to be emulsified and dispersed. Preferred emulsified dispersion particle size is 1 μm
It is as follows.

The high boiling organic solvent used in this case is
For example, it can be appropriately selected from the high boiling point oils described in JP-A-2-141279. Among them, the use of esters is preferred from the viewpoint of the emulsion stability of the emulsified dispersion, and tricresyl phosphate is particularly preferred. The above oils can be used together or with other oils.

The water-soluble polymer contained as the above protective colloid can be appropriately selected from among known anionic polymers, nonionic polymers and amphoteric polymers. A water-soluble polymer having a solubility in water of 5% or more is preferable. Specific examples thereof include polyvinyl alcohol or a modified product thereof, polyacrylamide or a derivative thereof, an ethylene-vinyl acetate copolymer, and a styrene-maleic anhydride copolymer. Coalesce, ethylene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyvinylpyrrolidone, ethylene-acrylic acid copolymer, vinyl acetate-acrylic acid copolymer,
Examples include cellulose derivatives such as carboxymethylcellulose and methylcellulose, casein, gelatin, starch derivatives, gum arabic, sodium alginate and the like. Among these, polyvinyl alcohol, gelatin and cellulose derivatives are particularly preferred.

The mixing ratio of the oil phase to the aqueous phase (mass of the oil phase / mass of the aqueous phase) is preferably 0.02 to 0.6.
1 to 0.4 is more preferable. When the mixing ratio is 0.02-0.
When it is in the range of 6, the viscosity can be maintained at an appropriate level, the production suitability is excellent, and the coating liquid stability is excellent.

When an electron-accepting compound is used in the heat-sensitive recording material of the present invention, the amount of the electron-accepting compound is preferably 0.5 to 30 parts by mass, more preferably 1 to 30 parts by mass, per 1 part by mass of the electron-donating dye precursor. 0.0 to 10 parts by mass is more preferable. When a coupler is used in the heat-sensitive recording material of the present invention, the amount of the coupler is preferably 0.1 to 30 parts by mass with respect to 1 part by mass of the diazo compound.

(Coating solution for heat-sensitive recording layer) The coating solution for heat-sensitive recording layer can be prepared, for example, by mixing the microcapsule solution prepared as described above with an emulsified dispersion. Here, the water-soluble polymer used as a protective colloid in the preparation of the microcapsule liquid, and the water-soluble polymer used as a protective colloid in the preparation of the emulsified dispersion, as a binder in the thermosensitive recording layer Function. Further, a coating solution for a heat-sensitive recording layer may be prepared by adding and mixing a binder separately from these protective colloids. As the binder to be added, a water-soluble binder is generally used, and polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, epichlorohydrin-modified polyamide, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer Coalescing,
Isobutylene-maleic salicylic anhydride copolymer, polyacrylic acid, polyacrylamide, methylol-modified polyacrylamide, starch derivatives, casein, gelatin and the like. Further, a water-proofing agent may be added to these binders for the purpose of imparting water resistance, or an emulsion of a hydrophobic polymer, specifically, a styrene-butadiene rubber latex, an acrylic resin emulsion, or the like may be added.

When applying the coating solution for a heat-sensitive recording layer onto a support, a known coating means used for an aqueous or organic solvent-based coating solution is used. In order to uniformly coat and maintain the strength of the coating film, in the heat-sensitive recording material of the present invention, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, starch, gelatin, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, polyacrylamide, polystyrene or The copolymer, polyester or its copolymer, polyethylene or its copolymer, epoxy resin, acrylate resin or its copolymer, methacrylate resin or its copolymer, polyurethane resin, polyamide resin, polyvinyl butyral resin Using etc. It can be.

(Other Components) Hereinafter, other components that can be used in the heat-sensitive recording layer will be described. The other components are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include known heat-fusible substances, ultraviolet absorbers, and antioxidants.

The above-mentioned heat-fusible substance can be contained in the heat-sensitive recording layer for the purpose of improving the thermal response. As the heat-fusible substance, aromatic ether, thioether,
Esters, aliphatic amides, ureides and the like. These examples are described in JP-A-58-57989 and JP-A-58-87.
Nos. 094, 61-58789, 62-10968
No. 1, 62-132677, 63-151478
No. 63-235961, JP-A-2-184489.
And JP-A-2-215585.

Examples of the ultraviolet absorber preferably include a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, a salicylic acid ultraviolet absorber, a cyanoacrylate ultraviolet absorber, and an oxalic acid anilide ultraviolet absorber. Can be These examples are disclosed in
Nos. 7-10537, 58-111942, 58-
No. 212844, No. 59-19945, No. 59-46
No. 646, No. 59-109055, No. 63-5354
No. 4, JP-B-36-10466, 42-26187
No. 48-30492, No. 48-31255, No. 48-41572, No. 48-54965, No. 50-
10726, U.S. Pat. No. 2,719,086
No. 3,707,375, No. 3,754,919
No. 4,220,711.

Examples of the antioxidant include a hindered amine antioxidant, a hindered phenol antioxidant,
An aniline-based antioxidant and a quinoline-based antioxidant are preferably exemplified. These examples are disclosed in JP-A-59-15509.
No. 0, No. 60-107383, No. 60-107384
Nos. 61-137770 and 61-139481
And JP-A-61-160287.

The amount of the other components to be applied is set to 0.1.
About 0.5 to 1.0 g / m ² , preferably 0.1 to 0.4 g / m ^2.
g / m ² is more preferred. The other components are
It may be added inside the microcapsule or outside the microcapsule.

The heat-sensitive recording layer has an energy amount necessary for obtaining a saturated transmission density (DT-max) in order to suppress a density unevenness or the like caused by a slight difference in thermal conduction of a thermal head and to obtain a high-quality image. It is preferable that the thermosensitive recording layer has a wide width, that is, a wide dynamic range. The heat-sensitive recording material of the present invention has a heat-sensitive recording layer as described above,
It is preferable that the heat-sensitive recording layer has a property that a transmission density DT of 3.0 can be obtained with a heat energy amount in a range of 50 mJ / mm ² .

The heat-sensitive recording layer is coated so that the dry coating amount after coating and drying is 1 to 25 g / m ² ;
It is preferable that the coating be performed so that the thickness of the layer is 1 to 25 μm. The heat-sensitive recording layer can be used by laminating two or more layers. In this case, application of the entire thermosensitive recording layer,
The dry coating amount after drying is preferably 1 to 25 g / m ² .

[Support] In the heat-sensitive recording material of the present invention, it is preferable to use a transparent support in order to obtain a transparent heat-sensitive recording material. Examples of the transparent support include a synthetic polymer film such as a polyester film such as polyethylene terephthalate or polybutylene terephthalate, a cellulose triacetate film, or a polyolefin film such as polypropylene or polyethylene, and these may be used alone or in combination. be able to. The thickness of the synthetic polymer film is preferably 25 to 250 μm, and 50 to 250 μm.
200 μm is more preferred.

Further, the above-mentioned synthetic polymer film may be colored in an arbitrary hue. As a method of coloring a polymer film, a method of kneading a resin with a dye before forming a resin film to form a film, a coating solution in which the dye is dissolved in an appropriate solvent is prepared, and this is a colorless transparent resin A known coating method such as a gravure coating method, a roller coating method, a wire coating method, or the like, may be used on the film. Among them, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate in which a blue dye is kneaded is formed into a film, which is subjected to a heat treatment, a stretching treatment, and an antistatic treatment.

In particular, when the transparent heat-sensitive recording material of the present invention is observed from the side of the support on the Schaukasten, the Sakakasten light transmitted through the transparent non-image portion may cause an illusion, resulting in an unsightly image. In order to avoid this, as the transparent support, A (x = 0.2805, y = 0 on the chromaticity coordinates specified by the method described in JIS-Z8701)
0.3005), B (x = 0.2820, y = 0.29)
70), C (x = 0.2885, y = 0.315),
It is particularly preferable to use a synthetic polymer film colored blue in a square region formed by four points of D (x = 0.2870, y = 0.3040).

[Other Layers] The heat-sensitive recording material of the present invention comprises:
On the support, an intermediate layer, an undercoat layer, an ultraviolet filter layer, an antireflection layer, and the like can be provided as other layers.

(Intermediate Layer) The intermediate layer is preferably formed on the heat-sensitive recording layer. The intermediate layer is provided to prevent mixing of the layers and to block gases (such as oxygen) that are harmful to image storability. The binder used is not particularly limited, and polyvinyl alcohol, gelatin, polyvinylpyrrolidone, a cellulose derivative, or the like can be used depending on the system. In addition, various surfactants may be added to impart coating suitability. Further, in order to further enhance gas barrier properties, inorganic fine particles such as mica are used in an amount of 2 to 20% by mass, more preferably 5 to 10% by mass, based on the binder.
It may be added.

(Undercoat layer) In the heat-sensitive recording material of the present invention, in order to prevent the heat-sensitive recording layer from peeling off from the support, before the heat-sensitive recording layer containing microcapsules or the like or the anti-reflection layer is applied. In addition, an undercoat layer can be provided on the support. As the undercoat layer, an acrylate copolymer, polyvinylidene chloride, SBR, aqueous polyester, or the like can be used.
5 to 0.5 μm is preferred.

When the heat-sensitive recording layer is coated on the undercoat layer, the water contained in the heat-sensitive recording layer coating solution may swell the undercoat layer and deteriorate the image recorded on the heat-sensitive recording layer. Glutaraldehyde, 2,
It is preferable to harden using a dialdehyde such as 3-dihydroxy-1,4-dioxane and a hardening agent such as boric acid. The addition amount of these hardeners can be appropriately added in the range of 0.2 to 3.0% by mass according to the mass of the undercoat material in accordance with the desired degree of curing.

(Ultraviolet Filter Layer) An ultraviolet filter layer may be provided on the back side of the support opposite to the surface on which the heat-sensitive recording layer is applied, for the purpose of preventing image fading. The ultraviolet filter layer contains a benzotriazole-based, benzophenone-based, or hindered amine-based ultraviolet absorber.

(Anti-reflection layer) An anti-reflection layer containing fine particles having an average particle diameter of 1 to 20 μm, preferably 1 to 10 μm is provided on the back side of the support opposite to the surface on which the heat-sensitive recording layer is coated. Is also good. By applying this antireflection layer, the glossiness measured at an incident light angle of 20 ° is preferably 50% or less, more preferably 30% or less. Examples of the fine particles contained in the anti-reflection layer include fine particles such as starch obtained from barley, wheat, corn, rice, and beans, cellulose fiber, polystyrene resin, epoxy resin, polyurethane resin, urea formalin resin, poly ( (Meth) acrylate resin, polymethyl (meth) acrylate resin, copolymer resin such as vinyl chloride or vinyl acetate, fine particles of synthetic polymer such as polyolefin, calcium carbonate, titanium oxide, kaolin, smectite clay, aluminum hydroxide, silica, Examples include fine particles of inorganic substances such as zinc oxide. These may be used alone or in combination of two or more. Further, from the viewpoint of improving the transparency of the heat-sensitive recording material, the refractive index is 1.45.
It is preferably a fine particle substance having a particle size of from 1.75 to 1.75.

The heat-sensitive recording material of the present invention can be suitably manufactured by the method for manufacturing a heat-sensitive recording material of the present invention described below, but is not limited thereto, and is manufactured by another manufacturing method. You can also.

Hereinafter, the method for producing the thermosensitive recording material of the present invention will be described. The production method of the heat-sensitive recording material of the present invention,
On the support, a coating solution for forming a heat-sensitive recording layer is applied to form a heat-sensitive recording layer. On the heat-sensitive recording layer, a coating solution for forming a protective layer is applied to form a protective layer. And other layers are formed. Here, the heat-sensitive recording layer and the protective layer may be simultaneously formed, and in that case, the heat-sensitive recording layer-forming coating liquid and the protective layer-forming coating liquid are simultaneously multi-layer coated on the support. The heat-sensitive recording layer and the protective layer can be simultaneously formed thereon.

As the support used here, the above-described support used for the heat-sensitive recording material of the present invention can be used. Further, as the heat-sensitive recording layer-forming coating liquid, the above-described heat-sensitive recording layer coating liquid can be used, and further, the protective layer-forming coating liquid is also used for the protective layer containing the pigment and the binder described above. A coating solution can be used. Examples of the other layer include other layers such as the above-described intermediate layer and undercoat layer. In the method for producing a heat-sensitive recording material of the present invention, in order to sequentially form an undercoat layer, a heat-sensitive recording layer, an intermediate layer, a protective layer, and the like on a support, a blade coating method, an air knife coating method, a gravure coating method, a roll coating method Known coating methods such as a coating method, a spray coating method, a dip coating method, and a bar coating method are used. According to the method for producing a heat-sensitive recording material of the present invention, the above-described heat-sensitive recording material of the present invention can be produced.

[0098]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples.

(Example 1) [Preparation of coating solution for protective layer] (Preparation of pigment dispersion for protective layer) Stearic acid-treated aluminum hydroxide (trade name: Hygilite H42S, Showa Denko 30 g) 3
After stirring for an hour, a dispersion aid (trade name: Poise 53)
2A, manufactured by Kao Corporation) 0.8 g, 10% by mass aqueous solution of polyvinyl alcohol (trade name: PVA105, manufactured by Kuraray Co., Ltd.) 30 g, adjusted to the following structural formula [10
0], and dispersed by a sand mill to obtain a pigment dispersion for protective layer having an average particle size of 0.30 µm. The “average particle size” is obtained by dispersing a pigment to be used in the presence of a dispersing agent, diluting the pigment dispersion immediately after the dispersion to 0.5% by mass with water, and adding a test solution at 40 ° C. And adjusted to have a light transmittance of 75 ± 1.0%, then subjected to ultrasonic treatment for 30 seconds, and measured with a laser diffraction particle size distribution analyzer (trade name: LA700, manufactured by Horiba, Ltd.). The average particle size of the pigment particles corresponding to 50% volume of the total pigment is used, and the “average particle size” described below all represents the average particle size measured by the same method.

[0100]

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(Preparation of Coating Solution for Protective Layer) In 65 g of water, 8 mass% aqueous polyvinyl alcohol solution (trade name: PVA124C, manufactured by Kuraray Co., Ltd.) 90 g 20.5 mass% zinc stearate dispersion (trade name: F115) 5.5 g 21.5 mass% stearic acid amide compound (trade name: G-270, manufactured by Chukyo Yushi Co., Ltd.) 3.8 g 18.0 mass% stearic acid (trade name: Cerosol 920, manufactured by Chukyo Yushi Co., Ltd. 2.8 g 4% aqueous boric acid solution 10 g Pigment dispersion for protective layer (18% by mass) 70 g 35% by mass aqueous silicone oil dispersion (polydimethylsiloxane, trade name: BY22-840) , Toray Dow Corning Co., Ltd.) 4.7 g 10 mass% aqueous solution of sodium dodecylbenzenesulfonate 6.5 g 6 mass% styrene-maleic Acid copolymer ammonium salt aqueous solution (trade name: Polymaron 385, manufactured by Arakawa Chemical Co., Ltd.) 17.5 g 20% colloidal silica (average particle size: 20 nm) (trade name: Snowtex, manufactured by Nissan Chemical Co., Ltd.) 14 g 10 % Surflon S131S (manufactured by Seimi Chemical Co., Ltd.) 16 g Plysurf A217 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 1.1 g 2% acetic acid 8 g was mixed to obtain a coating solution for a protective layer.

[Preparation of Coating Solution for Thermosensitive Recording Layer] Each of a microcapsule coating solution and a developer emulsified dispersion was prepared as follows. (Preparation of Microcapsule Coating Solution A) As a color former, a compound represented by the following structural formula [201] 11.7 g A compound represented by the following structural formula [202] 1.5 g represented by the following structural formula [203] Compound 2.2 g Compound represented by the following structural formula [204] 5.65 g Compound represented by the following structural formula [205] 1.2 g Compound represented by the following structural formula [206] 1.1 g 0.57 g of the compound represented by [207]

[0103]

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[0104]

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[0105]

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Was added to 24.3 g of ethyl acetate.
, And then cooled to 45 ° C. To this, 13.1 g of capsule wall material (trade name: Takenate D140N, manufactured by Takeda Pharmaceutical Co., Ltd.) and 2.3 g of Vernock D750 (manufactured by Dainippon Ink Industries, Ltd.) were added and mixed.

This solution was dissolved in an aqueous solution of 8% by mass of polyvinyl alcohol (trade name: PVA217C, 16 g of water).
(Kuraray Co., Ltd.) was added to the aqueous phase mixed with 48 g,
Emulsification was carried out at 15,000 rpm for 5 minutes using an ace homogenizer (manufactured by Nippon Seiki Co., Ltd.). After 110 g of water and 1.0 g of tetraethylenepentamine were further added to the obtained emulsion, an encapsulation reaction was carried out at 60 ° C. for 4 hours to prepare a microcapsule coating solution having an average particle diameter of 0.35 μm.

(Preparation of Microcapsule B) Compound represented by Structural Formula [201] 12.2 g Compound represented by Structural Formula [202] 1.6 g Compound represented by Structural Formula [203] 2.4 g Structure Compound represented by formula [204] 3.3 g Compound represented by structural formula [205] 1.5 g Compound represented by structural formula [206] 0.2 g Compound represented by structural formula [207] 5 g was added to 21 g of ethyl acetate, heated and dissolved at 70 ° C., and then cooled to 35 ° C. N-Butanol 0.5
g, Takenate D127N (manufactured by Takeda Pharmaceutical Co., Ltd.)
1 g, and Takenate D110N (manufactured by Takeda Pharmaceutical Co., Ltd.)
2.5 g was added, and the temperature was kept at 35 ° C. for 40 minutes.

This solution was dissolved in 16.6 g of water at 8% by mass of polyvinyl alcohol (PVA217C, manufactured by Kuraray Co., Ltd.).
48.1 g was added to the mixed aqueous phase, and emulsified at 15000 rpm for 5 minutes using an ace homogenizer (manufactured by Nippon Seiki Co., Ltd.). Water 112 is further added to the obtained emulsion.
g and 0.9 g of tetraethylenepentamine were added, followed by performing an encapsulation reaction at 60 ° C. for 4 hours to prepare a microcapsule solution having an average particle diameter of 0.35 μm.

(Preparation of Developer Microemulsified Dispersion) A compound represented by the following structural formula [301] 6.7 g as a developer 8.0 g of a compound represented by the following structural formula [302] 8.0 g Compound represented by the following structural formula [305] 5.8 g Compound represented by the following structural formula [304] 1.5 g Compound represented by the following structural formula [305] 2.2 g Compound represented by the following structural formula [306] 0 .8 g Compound represented by the following structural formula [307] 4.3 g

[0111]

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[0112]

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1.0 g of tricresyl phosphate,
15. ethyl acetate together with 0.5 g of diethyl maleate.
5 g and heated to 70 ° C. to dissolve. This solution was treated with 70 g of water, 57 g of an 8% by mass aqueous polyvinyl alcohol solution (PVA217C, manufactured by Kuraray Co., Ltd.), and a 15% by mass aqueous solution of polyvinyl alcohol (trade name: PVA20).
5C, manufactured by Kuraray Co., Ltd.) 20 g, the following structural formula [401]
And 11.5 g of a 2% by mass aqueous solution of a compound represented by the following formula and a compound represented by the following structural formula [402] were added to an aqueous phase, and then added.

[0114]

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Ace homogenizer (Nippon Seiki Co., Ltd.)
At 10,000 rpm and an average particle size of 0.7
The emulsion was emulsified to a thickness of μm to obtain a developer emulsified dispersion.

(Preparation of Coating Solution A for Thermosensitive Recording Layer) The coating solution A of the microcapsule (solid content: 23% by mass) 12
g, 2.5 g of microcapsule B (24%), 50 g of the developer emulsified dispersion (solid content: 22% by mass), and 0.7 g of a 50% by mass aqueous solution of a compound represented by the following structural formula [403]. 1.8 g of colloidal silica (manufactured by Snowtex Nissan Chemical Industries, Ltd.) was mixed to prepare a coating solution A for a heat-sensitive recording layer.

[0117]

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[Preparation of Coating Solution C for Thermosensitive Recording Layer] Microcapsule A (23%) 2.3 g Microcapsule B (24%) 6.6 g Developer (22%) 33 g Colloidal silica (Snowtex, Nissan Scientific) 1.5 g of the compound represented by the structural formula [403] was mixed to prepare a coating solution B for a heat-sensitive recording layer.

[Preparation of coating solution C for heat-sensitive recording layer] 6% by mass
35 g of an aqueous PVA solution (trade name: PVA124C, manufactured by Kuraray Co., Ltd.), 2 g of a 2% aqueous solution of a compound represented by the following structural formula [404], and microcapsule A (23%) 0.5
g was dissolved in 5 g of water to prepare a coating solution C for a heat-sensitive recording layer.

[0120]

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[Preparation of Coating Solution for BC Layer (Back Layer)] A gelatin dispersion containing 1 kg of lime-processed gelatin and 12% by mass of a spherical PMMA matting agent having an average particle diameter of 5.7 μm was prepared.
57 g, 3,761 g of an emulsion of an ultraviolet absorber containing the compounds represented by the following structural formulas [501] to [505] at the following content (the content of the ultraviolet absorber per kg of the emulsion is represented by the following structural formula [ 501] 9.8 g Compound represented by the following structural formula [502] 8.4 g Compound represented by the following structural formula [503] 9.8 g Compound represented by the following structural formula [504] 13 9.9 g Compound represented by the following structural formula [505] 29.3 g 1,2-benzisothiazolin-3-one 1.75 g Poly (sodium p-vinylbenzenesulfonate) (molecular weight: about 400,000) 64.2 g Compound represented by the formula [506] 10.0 g Polyethyl acrylate latex 20% solution 3,180 ml N, N-ethylene-bis (vinylsulfonylacetate) Bromide) 75.0 g 1,3-bis (added to bring the total amount of water to the above vinylsulfonylacetamido) propane 25.0g was prepared so as to be 62.77 l.

[0122]

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[Preparation of Coating Solution for BPC Layer (Back Protective Layer)] 1 kg of lime-processed gelatin, average particle size 0.70 μm
2,000 g of a gelatin dispersion containing 15% by mass of a spherical PMMA matting agent of m.
1,75-benzisothiazolin-3-one
g, sodium polyacrylate (molecular weight about 100,000)
4.4 g, 54.0 g of poly (sodium p-vinylbenzenesulfonate) (molecular weight: about 400,000), 25.2 g of sodium pt-octylphenoxypolyoxyethylene-ethylsulfonate, N-propyl-N- 5.3 g of sodium polyoxyethylene-perfluorooctanesulfonamidobutylsulfonate, 7.1 g of potassium perfluorooctanesulfonate, p with caustic soda
After adjusting to H = 7.0, water was added to adjust the total amount to 66.79 liters.

A transparent PET support in which the above-mentioned coating solution for the BC layer and the coating solution for the BPC layer were dyed blue with x = 0.2850 and y = 0.29995 in chromaticity coordinates specified by the method described in JIS-Z8701. (Thickness: 180 μm), the coating amounts for the BC layer coating solution and the BPC layer coating solution were 44.0 ml / m ² and 18.5 ml, respectively, from the side closer to the support.
/ M ² and dried.

[Preparation of Thermosensitive Recording Material] The above BC layer, B
On the opposite side of the support on which the PC layer was coated, the application amounts of the thermosensitive coloring layers A, B, and C, and the protective layer coating solution were 50 ml / m ² , respectively, from the side closer to the support. 20 ml / m ² ,
The coating was dried at 25 ml / m ² and 25 ml / m ² to obtain a transparent heat-sensitive recording material of the present invention.

Example 2 A heat-sensitive recording material was produced in the same manner as in Example 1, except that the average particle size of the aluminum hydroxide dispersion was 0.34 μm.

Example 3 A thermosensitive recording material was produced in the same manner as in Example 1, except that the average particle size of the aluminum hydroxide dispersion was 0.26 μm. (Example 4) A heat-sensitive recording material was prepared in the same manner as in Example 1 except that 3 g of 20% colloidal silica was used in the preparation of the coating solution for the protective layer of Example 1.

Example 5 A heat-sensitive recording material was produced in the same manner as in Example 1, except that the average particle size of aluminum hydroxide was 0.7 μm.

Comparative Example 1 A thermosensitive recording material was prepared in the same manner as in Example 1 except that the pigment dispersion was not added in the preparation of the coating solution for the protective layer. (Comparative Example 2) A thermosensitive recording material was prepared in the same manner as in Example 1 except that colloidal silica was not added in the preparation of the coating solution for the protective layer. Comparative Example 3 Example 1 was repeated except that the pigment dispersion and colloidal silica were not added in the preparation of the coating solution for the protective layer.
A heat-sensitive recording material was produced in the same manner as in Example 1.

<Evaluation of print aptitude> A thermal head (trade name: KGT, 260-12M) was applied to the obtained thermal recording material.
PH8, manufactured by Kyocera Corporation) with a head pressure of 10 kg /
cm ^2, and recorded in the recording energy 120 mJ / mm ^2, during printing, was evaluated by visual observation whether cause sticking. After printing 300 sheets of B4 size recording material, the used thermal head was removed from the printing apparatus.
The presence or absence of dirt was visually evaluated. Further, the surface of the thermal head was observed with a reflection type optical microscope, and it was evaluated whether or not there was any stain that could not be visually observed. further,
The same evaluation was performed using the same thermal head in which a carbon layer having a thickness of 2 μm and a carbon ratio of 98% was provided on the uppermost layer by physical vapor deposition. Table 1 shows the results.

[0131]

[Table 1]

[0132] ○: no problem ○ ^×: slightly occurrence to have, but practically no problem △: there is a possibility that the occurrence was observed problem ×: level of practical use on the disabled

As shown in Table 1, in Examples 1 to 5, both ordinary heads and heads provided with a carbon layer provided heat-sensitive recording materials excellent in printability without sticking and head contamination. In particular, Examples 1-3 and 5
Was superior to Example 4 in terms of head contamination. In Examples 1 to 4, the head wear was smaller than that in Example 5. On the other hand, in Comparative Example 1 in which the fine particles of aluminum hydroxide were not contained, sticks that became a practical problem and head contamination that might be a practical problem occurred. Further, in Comparative Example 2 containing no colloidal silica, head dirt was generated to such an extent that it became a practical problem. In Comparative Example 3 in which neither aluminum hydroxide nor colloidal silica was contained, both sticking and head contamination, which were problems in practice, occurred.

[0134]

According to the present invention, it is possible to provide a heat-sensitive recording material which is excellent in printing suitability by reducing sticking and head contamination.

Claims (5)

[Claims] 1. A heat-sensitive recording material having a heat-sensitive recording layer and a protective layer successively on a support, wherein the protective layer contains polyvinyl alcohol, and fine particles of silica and aluminum hydroxide. Thermosensitive recording material. 2. The heat-sensitive recording material according to claim 1, wherein the support and the heat-sensitive recording layer are substantially transparent. 3. The heat-sensitive recording material according to claim 1, wherein the silica is contained in an amount of 5 to 60% by mass based on aluminum hydroxide. 4. The silica has a particle size of 5 to 100 nm,
4. The heat-sensitive recording material according to claim 1, wherein the particle size of the aluminum hydroxide is 0.2 to 0.5 [mu] m. 5. The protective layer comprises: stearic acid as a lubricant;
The heat-sensitive recording material according to any one of claims 1 to 4, further comprising at least one selected from the group consisting of zinc stearate, stearic acid amide, and a silicone compound.