JP2005047251A - Thermal recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal recording material which is excellent in coated-surface uniformity as well as chemical resistance and enables an image of high dignity to be formed. <P>SOLUTION: The thermal recording material has at least a thermal recording layer and a protection layer on a support. The protection layer contains compounds represented in the following general formula (1) and /or (2). The surface tension of the coating liquid of the protection layer is 20 to 35 mN/m. General formula (1) is shown by R-O(CH<SB>2</SB>CH<SB>2</SB>O)<SB>n</SB>-PO(OH)<SB>2</SB>, wherein, R represents an alkyl group of 4-20C, an alkyl aryl group of 6-20C or an alkyl phenoxy group of 6-20C, and n represents an integer of 1-50. General formula (2) is shown by äR-O(CH<SB>2</SB>CH<SB>2</SB>O)<SB>n</SB>-}<SB>2</SB>-PO(OH), wherein, R and n have the same definition as of the ones in general formula (1). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

  In the thermal recording method, (1) no development is required, (2) when the support is paper, the paper quality is close to ordinary paper, (3) easy handling, (4) high color density, ( 5) Since the recording apparatus is simple and inexpensive, and (6) there is an advantage such as no noise during recording, the application is expanding to the fields of facsimiles and printers, labels such as POS, and the like.

  Also, in recent years, a thermal recording layer on a transparent support that can be directly recorded by a thermal head for projecting an image or the like with an overhead projector or directly observing the image or the like on a light table. Development of a heat-sensitive recording material provided with is desired. In particular, transparent thermosensitive recording materials have attracted attention as those for forming medical diagnostic images.

  Such a transparent heat-sensitive recording material has good transparency, but has a problem that sticking and noise are likely to occur when printing is performed with a heat-sensitive recording device such as a heat-sensitive printer. In particular, when transparent thermosensitive recording materials are used for medical purposes, a high transmission density is required, so the thermal energy applied by the thermal head increases, and problems such as sticking, noise during recording, and thermal head wear become serious. To do. Therefore, for the purpose of improving sticking and noise, a protective layer mainly composed of a pigment, a lubricant, and a binder is provided on the heat-sensitive recording layer.

  For example, as a heat-sensitive recording material for the purpose of improving transparency and thermal head suitability (sticking property, printing sound), a material provided with a protective layer containing a surface treatment of a pigment with a higher fatty acid salt is disclosed. (For example, refer to Patent Document 1). For the purpose of improving chemical resistance, sticking resistance and antistatic effect, a water-soluble resin layer containing a specific amount of alkylsulfosuccinate and a fluorosurfactant is provided as a protective layer. A recording material is disclosed (for example, see Patent Document 2).

  In addition to the protective layer, a gas blocking layer, an undercoat layer, an ultraviolet filter layer, an antireflection layer, and the like are also provided as appropriate. In order to provide these layers on the support, in addition to a method of sequentially forming each layer on the support, a method in which all the layers are uniformly applied by an extrusion die method or the like is known (for example, patents). Reference 3).

However, a heat-sensitive recording material that is sufficiently satisfactory with respect to the uniformity of the coated surface has not yet been obtained. For example, there is a problem that the surface condition of the coating is deteriorated due to the organic solvent remaining in the applied heat-sensitive recording layer, and such a problem is remarkable when multi-layer coating is applied. It was. In particular, when a medical diagnostic image is formed using a transparent heat-sensitive recording material, an accurate diagnosis cannot be made unless a clear image is formed in detail. Also from such a viewpoint, the above-described deterioration of the surface condition in the heat-sensitive recording material adversely affects image formation and becomes a problem. In addition, when the heat-sensitive recording material is used for medical purposes, it is particularly required to have resistance to chemicals.
Accordingly, there is a demand for a heat-sensitive recording material that is suitable for medical recording media and the like, has a good coated surface, is excellent in chemical resistance, and can form a high-quality image. The current situation is not reached.
JP-A-6-340179 JP-A-6-328849 Japanese Patent Laid-Open No. 4-97886

An object of the present invention is to solve the above problems and achieve the following object.
That is, an object of the present invention is to provide a heat-sensitive recording material that is excellent in uniformity of the coated surface, has chemical resistance, and enables high-quality image formation.

The above-mentioned problems of the present invention are solved by providing the following thermal recording material.
<1> A thermal recording material having at least a thermal recording layer and a protective layer on a support,
The protective layer contains a compound represented by the following general formula (1) and / or general formula (2), and the surface tension of the coating liquid of the protective layer is 20 to 35 mN / m. It is a heat sensitive recording material.
R—O (CH ₂ CH ₂ O) _n —PO (OH) ₂ general formula (1)
[In General Formula (1), R represents a C4-C20 alkyl group, a C6-C20 alkylaryl group, or a C6-C20 alkylphenoxy group. n represents an integer of 1 to 50. ]
_{(R-O (CH 2 CH} 2 O) n -) 2 -PO (OH) formula (2)
[In General Formula (2), R and n are synonymous with R and n in General Formula (1). ]

  <2> The heat-sensitive recording material according to <1>, wherein the compound represented by the general formula (1) and / or the general formula (2) is a polyoxyethylene alkyl ether phosphate. .

  <3> The heat-sensitive recording material according to <1> or <2>, wherein the heat-sensitive recording layer and the protective layer are applied in multiple layers.

  According to the present invention, it is possible to provide a heat-sensitive recording material that is excellent in uniformity of the coated surface, has chemical resistance, and enables high-quality image formation.

Hereinafter, the heat-sensitive recording material of the present invention will be described in detail.
The heat-sensitive recording material of the present invention has a heat-sensitive recording layer and a protective layer in this order on a support, and further has an undercoat layer, an intermediate layer and other layers as necessary.

[Protective layer]
The protective layer of the present invention is formed on the heat-sensitive recording layer, or when the intermediate layer is provided on the heat-sensitive recording layer as another layer, and is formed on the intermediate layer, and the following general formula (1) and / or general formula ( 2), and the surface tension of the coating solution for the protective layer is 20 to 35 mN / m.

R—O (CH ₂ CH ₂ O) _n —PO (OH) ₂ general formula (1)
In the general formula (1), R represents an alkyl group having 4 to 20 carbon atoms, an alkylaryl group having 6 to 20 carbon atoms, or an alkylphenoxy group having 6 to 20 carbon atoms. n represents an integer of 1 to 50.

  As a C4-C20 alkyl group represented by said R, a C8-C16 alkyl group is more preferable. Specific examples include an octyl group, a decyl group, a dodecyl group, a myristyl group, a cetyl group, and a 2-ethyl-hexyl group.

  As a C6-C20 alkylaryl group represented by said R, a C14-C18 alkylaryl group is more preferable. Specific examples include octylphenyl group, decylphenyl group, dodecylphenyl group, and the like.

The alkylphenoxy group having 6 to 20 carbon atoms and represented by R is more preferably an alkylphenoxy group having 14 to 18 carbon atoms and 6 to 20 carbon atoms. Specific examples include octylphenoxy group, decylphenoxy group, laurylphenoxy group, and the like.
R may further have a substituent.

  Said n represents the integer of 1-50, and it is more preferable that it is 6-20.

_{(R-O (CH 2 CH} 2 O) n -) 2 -PO (OH) formula (2)
In the general formula (2), R has the same meaning as R in the general formula (1), and the preferred range and specific examples are also the same.
Moreover, in General formula (2), n is synonymous with n in General formula (1), and its suitable range is also the same.

  As the compounds represented by the general formula (1) and the general formula (2), commercially available products can be applied. For example, Neoscore CM57 (manufactured by Toho Chemical Co., Ltd.), Prisurf A217E (manufactured by Daiichi Kogyo Co., Ltd.), Disparon DA-375 (manufactured by Enomoto Kasei Co., Ltd.), Adeka Coal TS, Adeka Coal CS (Asahi Denka Co., Ltd.) Etc.) are preferably used.

  The compound represented by the general formula (1) and / or the general formula (2) contained in the protective layer is more preferably a polyoxyethylene alkyl ether phosphate.

  The compound represented by the general formula (1) and / or the general formula (2) contains a compound represented by the following general formula (1) and / or the general formula (2), and is a coating liquid for the protective layer. The surface tension of 20 to 35 mN / m may be used alone or in combination of two or more.

As content of the compound represented by the said General formula (1) and / or General formula (2) in a protective layer, 0.01-1.0 g / m < ² > is preferable, 0.02-0.3 g / m ² is more preferable.

  The surface tension of the coating solution for the protective layer is 20 to 30 mN / m, preferably 25 to 33 mN / m, and more preferably 28 to 32 mN / m.

  Moreover, you may add another surfactant to the protective layer in the range which does not impair the effect of this invention. Examples of the other surfactants include sulfosuccinic acid-based alkali metal salts, fluorine-containing surfactants, and the like, specifically, di- (2-ethylhexyl) sulfosuccinic acid, di- (n-hexyl) sulfosuccinic acid, and the like. Sodium salt, potassium salt or ammonium salt, acetylene glycol derivative, sodium perfluoroalkyl sulfate, potassium salt or ammonium salt, perfluoroalkyl betaine compound and the like.

Other components contained in the protective layer will be described.
The protective layer usually contains a binder, a pigment, a lubricant, a dispersant, a fluorescent brightener, a metal soap, a hardener, an ultraviolet absorber, a crosslinking agent and the like.

<Binder>
The binder used for the protective layer is preferably a water-soluble resin, and can be appropriately selected from known water-soluble resins. Examples of water-soluble resins include polyvinyl alcohol, silicon-modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, starch and derivatives thereof, casein, sodium alginate, polyvinyl pyrrolidone, sodium polyacrylate, polyacrylamide, and styrene maleic acid polymer. Examples include salts, polyurethane resins, urea resins, melamine resins, and the like.

<Pigment>
The pigment contained in the protective layer is usually added for the purpose of suppressing the occurrence of sticking or abnormal noise during recording with a thermal head, and organic and / or inorganic pigments are used.
There are no particular restrictions on the type of pigment used, and publicly known organic and inorganic pigments can be mentioned, but in particular inorganic pigments such as calcium carbonate, titanium oxide, kaolin, aluminum hydroxide, amorphous silica, and zinc oxide. Organic pigments such as urea formalin resin and epoxy resin are preferred. Of these, kaolin, aluminum hydroxide, and amorphous silica are more preferable. These pigments may be used alone or in combination of two or more. Of these, the surface may be 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 acid include stearic acid, palmitic acid, myristic acid, lauric acid and the like.
These pigments include, for example, sodium metametaphosphate, partially saponified or fully saponified polyvinyl alcohol, polyacrylic acid copolymer, various surfactants and other dispersing aids, preferably partially saponified or fully saponified polyvinyl alcohol, polyacrylic. In the presence of an acid copolymer ammonium salt, it is preferably used after being dispersed to the above-mentioned average particle size by a known disperser such as a dissolver, a sand mill, or a ball mill. That is, the pigment is preferably used after being dispersed until the 50% volume average particle size is in the range of 0.1 to 5.0 μm.

  The average particle diameter of the pigment, specifically, the average particle diameter of the pigment particles corresponding to 50% volume in the pigment measured by a 50% volume average particle diameter (Laser diffraction particle size distribution measuring apparatus LA700, manufactured by Horiba, Ltd.) measured by a laser diffraction method. Diameter, hereinafter simply referred to as “average particle diameter”. ) Is preferably from 0.10 to 5 μm, particularly from the viewpoint of preventing sticking or abnormal noise between the thermal head and the thermal recording material when recording with a thermal head, and from the viewpoint of transparency. The 50% volume average particle size is more preferably in the range of 0.20 to 0.50 μm. When the 50% volume average particle size is in the range of 0.10 to 5.0 μm, the effect of reducing friction with respect to the thermal head is great, and as a result, the thermal head and the protective layer of the thermal recording material adhere to each other at the time of printing. Sticking can be effectively prevented.

<Lubricant>
In addition, it is preferable to add a lubricant to the protective layer, for example, stearamide (melting point 100 ° C.), methylol stearamide (melting point 101 ° C.), polyethylene wax (melting point 110 ° C. or less), melting point 50 to 90 ° C. Paraffin wax, glycerin-12-hydroxystearate (melting point 88 ° C.), oleic acid amide (melting point 73 ° C.), zinc oleate (melting point 75 ° C.), lauric acid amide (melting point 84 ° C.), aluminum stearate (melting point 102) ° C), manganese stearate (melting point 112 ° C), zinc stearate (melting point 125 ° C), calcium stearate (melting point 160 ° C), ethylene bisstearamide (melting point 140 ° C), magnesium stearate (melting point 132 ° C), palmitic Magnesium oxide (melting point 122 ° C), myristic acid mug Siumu (mp 131 ° C.), and the like. The lubricant may be used alone or in combination of two or more.

When the lubricant is insoluble in water, it is added to the protective layer in the form of a dispersion or emulsion. When the lubricant is solid, 1) In the form of an aqueous dispersion dispersed with a known disperser such as a homogenizer, dissolver, sand mill in the presence of a water-soluble polymer such as polyvinyl alcohol or a dispersant such as various surfactants. 2) Used in the form of an emulsion emulsified with a known emulsifier such as a homogenizer, dissolver or colloid mill in the presence of a dispersant such as a water-soluble polymer or various surfactants after being dissolved in a solvent. It is done. When the lubricant is a liquid, it is used in the form of an emulsion as described above. A preferable average particle size of the dispersion and the emulsion is 0.1 to 5.0 μm, and more preferably 0.1 to 2.0 μm. The average particle diameter here refers to a 50% average particle diameter measured with a transmittance of 71 ± 1% by Horiba, Ltd., a laser diffraction particle size distribution analyzer LA-700.
In the case of water-soluble lubricants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl ether acetate, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl ether phosphate, etc. , Can be dissolved in any concentration and added to the protective layer.

<Other ingredients>
The protective layer may contain a known hardener or the like. Examples of the hardener include dialdehyde derivatives represented by the following structural formula (001) in addition to inorganic compounds such as boric acid, borax, and colloidal silica.

  In addition, metal oxide fine particles, inorganic electrolytes, polymer electrolytes, and the like may be added to the protective layer for the purpose of preventing electrification of the thermosensitive recording material.

The protective layer may have a single layer structure or a laminated structure of two or more layers. The dry coating amount of the protective layer is preferably ^{0.2~7g / m 2, 1~4g / m} 2 is more preferable.

[Thermosensitive recording layer]
The heat-sensitive recording layer according to the present invention contains at least a coloring component and further contains other components as required.

(Coloring component)
The heat-sensitive recording layer can be used in any composition as long as it has excellent transparency when not processed and has a property of being colored by heating.
As such a heat-sensitive recording layer, a so-called two-component heat-sensitive recording layer containing a substantially colorless coloring component A and a substantially colorless coloring component B that reacts with the coloring component A to develop a color. The coloring component A or the coloring component B is preferably encapsulated in microcapsules. Examples of the combination of the two components constituting the two-component heat-sensitive recording layer include the following (a) to (m).
Examples of combinations of coloring components that can be applied to the heat-sensitive recording layer according to the present invention include the following combinations (a) to (m).

(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.
(C) A combination of an organic metal salt such as silver behenate or silver stearate and a reducing agent such as protocatechinic acid, spiroindane or 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, etc. such as acetic acid, stearic acid, palmitic acid, and alkaline earths such as calcium sulfide, strontium sulfide, potassium sulfide, etc. A combination of a metal sulfide or a combination of the organic acid heavy metal salt and an organic chelating agent such as s-diphenylcarbazide or diphenylcarbazone.
(F) A combination of a (heavy) metal sulfate such as silver sulfide, lead sulfide, mercury sulfide, or sodium sulfide and a sulfur compound such as Na-tetrathionate, sodium thiosulfate, or thiourea. (G) A combination of an aliphatic ferric salt such as ferric stearate and an aromatic polyhydroxy compound such as 3,4-dihydroxytetraphenylmethane.
(H) A combination of an organic noble metal salt such as silver oxalate or mercury oxalate and an organic polyhydroxy compound such as polyhydroxy alcohol, glycerin or glycol.
(I) A combination of an aliphatic ferric salt such as ferric pelargonate or ferric laurate, and a thiocesylcarbamide or isothiocecilcarbamide derivative.
(J) A combination of an organic acid lead salt such as lead caproate, lead pelargonate or lead behenate and a thiourea derivative such as ethylenethiourea or N-dodecylthiourea.
(K) A combination of a higher fatty acid heavy metal salt such as ferric stearate or copper stearate and zinc dialkyldithiocarbamate.
(L) A substance that forms an oxazine dye such as a combination of resorcin and a nitroso compound.
(M) A combination of a formazan compound and a reducing agent and / or a metal salt.

  Among these, 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, and (c) an organic It is preferable to use a combination of a metal salt and a reducing agent, and it is particularly preferable to use a combination of the above (a) and (b).

  Next, the composition combinations (a, b, c) that are preferably used in the heat-sensitive recording layer will be described in detail below.

<(A) Combination of electron donating dye precursor and electron accepting compound>
The electron-donating dye precursor preferably used in the present invention is not particularly limited as long as it is substantially colorless, but it develops color by donating electrons or accepting protons such as acids. In particular, it has a partial skeleton such as lactone, lactam, sultone, spiropyran, ester, amide, etc., and when this is contacted with an electron accepting compound, these partial skeletons are opened or cleaved. A colorless compound is preferred.

  Examples of the electron-donating dye precursor include triphenylmethane phthalide compounds, fluoran compounds, phenothiazine compounds, indolyl phthalide compounds, leucooramine compounds, rhodamine lactam compounds, triphenylmethane compounds. Examples thereof include compounds, triazene compounds, spiropyran compounds, fluorene compounds, pyridine compounds, pyrazine compounds.

Specific examples of the phthalides include U.S. Reissue Patent No. 23,024, U.S. Pat. Nos. 3,491,111, 3,491,112, and 3,491. Examples thereof include compounds described in Nos. 116 and 3,509,174.
Specific examples of the fluorans include U.S. Pat. Nos. 3,624,107, 3,627,787, 3,641,011, and 3,462,828. No. 3,681,390, No. 3,920,510, No. 3,959,571 and the like.
Specific examples of the spiropyrans include compounds described in US Pat. No. 3,971,808.
Examples of the pyridine-based and pyrazine-based compounds include compounds described in US Pat. Nos. 3,775,424, 3,853,869, 4,246,318, and the like. Is mentioned.
Specific examples of the fluorene 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 aminofluorane] is particularly preferable.

  Specifically, for example, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-N-cyclohexyl-N-methylaminofluorane, 2-p-chloroanilino-3- Methyl-6-dibutylaminofluorane, 2-anilino-3-methyl-6-dioctylaminofluorane, 2-anilino-3-chloro-6-diethylaminofluorane, 2-anilino-3-methyl-6-N- Ethyl-N-isoamylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N-dodecylaminofluorane, 2-anilino-3-methoxy-6-dibutylaminofluorane, 2-o-chloroanilino -6-dibutylaminofluorane, 2-p-chloroanilino-3-ethyl-6-N-ethyl-N-isoamylaminophen Oran, 2-o-chloroanilino-6-p-butylanilinofluorane, 2-anilino-3-pentadecyl-6-diethylaminofluorane, 2-anilino-3-ethyl-6-dibutylaminofluorane, 2-o -Toluidino-3-methyl-6-diisopropylaminofluorane, 2-anilino-3-methyl-6-N-isobutyl-N-ethylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N -Tetrahydrofurfurylaminofluorane, 2-anilino-3-chloro-6-N-ethyl-N-isoamylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N-γ-ethoxypropylamino Fluorane, 2-anilino-3-methyl-6-N-ethyl-N-γ-ethoxypropylaminofluorane, 2-anilino 3-methyl -6-N-ethyl--N-.gamma. propoxypropyl aminofluoran like.

Examples of the electron-accepting compound that interacts with the electron-donating dye precursor include acidic substances such as phenol compounds, organic acids or metal salts thereof, and oxybenzoic acid esters. For example, JP-A-61-291183. Can be mentioned.
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, -Bis (4'-hydroxyphenyl) -2-ethyl-hexane, 1,1-bis (4'-hydroxyphenyl) dodecane, 1,4-bis (p-hydroxyphenylcumyl) benzene, 1,3-bis Bisphenols such as (p-hydroxyphenylcumyl) benzene, bis (p-hydroxyphenyl) sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, bis (p-hydroxyphenyl) acetic acid benzyl ester;

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

Or a polyvalent metal salt thereof (in particular, zinc or aluminum is preferable); p-hydroxybenzoic acid benzyl ester, p-hydroxybenzoic acid-2-ethylhexyl ester, β-resorcinic acid- (2-phenoxyethyl) ester, etc. Oxybenzoates; phenols such as p-phenylphenol, 3,5-diphenylphenol, cumylphenol, 4-hydroxy-4'-isopropoxy-diphenylsulfone, 4-hydroxy-4'-phenoxy-diphenylsulfone Is mentioned.
Among these, bisphenols are particularly preferable from the viewpoint of obtaining good color development characteristics.
Moreover, said electron-accepting compound may be used individually by 1 type, and may use 2 or more types together.

<(B) Combination of photodegradable diazo compound and coupler>
The photodegradable diazo compound is a compound that reacts with a coupler as a coupling component, which will be described later, to develop a desired color, decomposes when receiving light in a specific wavelength region before the reaction, and is no longer coupled. It is a photodegradable diazo compound that does not have a coloring ability even in the presence of a component.
The hue in this color developing system is determined by a diazo dye formed by the reaction of a diazo compound and a coupler. Accordingly, the color hue can be easily changed by changing the chemical structure of the diazo compound or coupler, and an arbitrary color hue can be obtained depending on the combination.

Examples of the photodegradable diazo compound preferably used in the present invention include aromatic diazo compounds, and specifically include aromatic diazonium salts, diazosulfonate compounds, diazoamino compounds and the like.
Examples of the aromatic diazonium salt include, but are not limited to, compounds represented by the following general formula. The aromatic diazonium salt is preferably used since it has excellent photofixability, little generation of colored stain after fixing, and a stable color developing portion.
Ar-N ₂ ⁺ X ^-
In the above formula, Ar represents a substituted or unsubstituted aromatic hydrocarbon ring group, N ₂ ⁺ represents a diazonium group, and X ⁻ represents an acid anion.

  As the diazosulfonate compound, many compounds have been known in recent years, and each diazonium salt can be obtained by treating each diazonium salt with a sulfite, and can be suitably used for 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, etc. It can be suitably used for the heat-sensitive recording material of the invention.
Details of these diazo compounds are described in detail, for example, in JP-A-2-136286.

  On the other hand, examples of couplers that undergo a coupling reaction with the above-mentioned diazo compound include those described in JP-A-62-146678, including resorcin, in addition to 2-hydroxy-3-naphthoic acid anilide. It is done.

In the thermosensitive recording layer, when using a combination of a diazo compound and a coupler, these coupling reactions can be further promoted by performing them in a basic atmosphere. Basic substances may be added.
Examples of the basic substance include water-insoluble or hardly soluble basic substances and substances that generate alkali by heating, such as inorganic or organic ammonium salts, organic amines, amides, urea, thiourea or derivatives thereof, Nitrogenous compounds such as thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidazolines, triazoles, morpholines, piperidines, amidines, forimazines or pyridines. .
Specific examples thereof include those described in JP-A No. 61-291183.

<(C) Combination of organometallic salt and reducing agent>
Next, (c) a combination of an organic metal salt and a reducing agent will be described.
Specific examples of the organic metal salts include silver salts of long chain aliphatic carboxylic acids such as silver laurate, silver myristate, silver palmitate, silver stearate, silver arachidate or silver behenate; benzotriazole silver Silver salts of organic compounds having an imino group such as salts, benzimidazole silver salts, carbazole silver salts or phthalazinone silver salts; silver salts of sulfur-containing compounds such as s-alkylthioglycolates; aromas such as silver benzoate and silver phthalate A silver salt of an aromatic carboxylic acid; a silver salt of a sulfonic acid such as silver ethanesulfonate; a silver salt of a sulfinic acid such as silver o-toluenesulfinate; a silver salt of a phosphoric acid such as silver silver phenylphosphate; a silver barbiturate; Examples include silver saccharinate, silver salt of salicyl asdoxime, or any mixture thereof.
Of these, long-chain aliphatic carboxylic acid silver salts are preferable, and silver behenate is more preferable. Further, behenic acid may be used together with silver behenate.

The reducing agent can be appropriately used based on the description in JP-A-53-1020, page 227, lower left column, line 14 to page 229, upper right column, line 11. Among them, mono, bis, tris or tetrakisphenols, mono or bisnaphthols, di or polyhydroxynaphthalenes, di or polyhydroxybenzenes, hydroxy monoethers, ascorbic acids, 3-pyrazolidones, pyrazolines, pyrazolones It is preferable to use reducing sugars, phenylenediamines, hydroxylamines, reductones, hydroxamic acids, hydrazides, amide oximes, N-hydroxyureas and the like.
Of the above, aromatic organic reducing agents such as polyphenols, sulfonamidophenols or naphthols are particularly preferred.

(Microcapsule)
Next, the manufacturing method of a microcapsule is explained in full detail.
There are an interfacial polymerization method, an internal polymerization method, an external polymerization method and the like in the production of microcapsules, and any method can be adopted.
As described above, the heat-sensitive recording material of the present invention preferably includes an electron-donating dye precursor or a photodegradable diazo compound in a microcapsule, and in particular, an electron-donating dye precursor or a light that becomes the core of the capsule. An oil phase prepared by dissolving or dispersing a degradable diazo compound in a hydrophobic organic solvent is put into an aqueous phase in which a water-soluble polymer is dissolved, emulsified and dispersed by stirring means such as a homogenizer, and then heated. Therefore, it is preferable to employ an interfacial polymerization method in which a polymer forming reaction is caused at the oil droplet interface to form a microcapsule wall made of a polymer substance.

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

  For example, when polyurea is used as a capsule wall material, polyisocyanates such as diisocyanate, triisocyanate, tetraisocyanate, and polyisocyanate prepolymer, polyamines such as diamine, triamine, and tetraamine, two or more amino acids A microcapsule wall can be easily formed by reacting a prepolymer having a group, piperazine or a derivative thereof, or a polyol with the interfacial polymerization method in the aqueous phase.

  In addition, for example, a composite wall made of polyurea and polyamide or a composite wall made of polyurethane and polyamide is made of, for example, polyisocyanate and a second substance (for example, acid chloride, polyamine, or polyol) that forms a capsule wall by reacting with it. It can be prepared by mixing in a water-soluble polymer aqueous solution (aqueous phase) or an oily medium to be encapsulated (oil phase), emulsifying and dispersing them, and then heating. Details of the method for producing the composite wall comprising polyurea and polyamide are described in JP-A-58-66948.

As the polyisocyanate compound, a compound having a trifunctional or higher isocyanate group is preferable, but a bifunctional isocyanate compound may be used in combination.
Specifically, diisocyanates such as xylene diisocyanate and hydrogenated products thereof, hexamethylene diisocyanate, tolylene diisocyanate and hydrogenated products thereof, isophorone diisocyanate and the like, and dimers thereof. Alternatively, in addition to a trimer (burette or isocyanurate), a polyfunctional adduct of a polyol such as trimethylolpropane and a bifunctional isocyanate such as xylylene diisocyanate, a polyol such as trimethylolpropane and a xylylene Examples thereof include a compound in which a high molecular weight compound such as polyether having active hydrogen such as polyethylene oxide is introduced into an adduct with a bifunctional isocyanate such as range isocyanate, and a formalin condensate of benzene isocyanate.
The compounds described in JP-A-62-212190, JP-A-4-26189, JP-A-5-317694, and Japanese Patent Application No. 8-268721 are preferable.

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

Specific examples of polyols and / or polyamines that react with the polyisocyanate and are added to the water phase and / or the oil phase as one of the components of the microcapsule wall include propylene glycol, glycerin, trimethylolpropane, Examples include ethanolamine, 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.
Polyisocyanates, polyols, reaction catalysts, polyamines for forming a part of the wall agent, etc. are well known in the book (Polyurethane Handbook, Nikkan Kogyo Shimbun (1987) edited by Keiji Iwata).

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

Furthermore, it is preferable to use a plasticizer suitable for the polymer used as the wall material in order to make the wall of the microcapsule excellent in material permeability even under a lower temperature and rich in color development. 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 these, those that are 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, a carbamic acid ester compound, an aromatic alkoxy compound, an organic sulfonamide compound, an aliphatic amide compound, an arylamide compound, or the like is preferably used.

In the preparation of the oil phase, an organic solvent having a boiling point of 100 to 300 ° C. is used as the hydrophobic organic solvent used when the electron donating dye precursor or the photodegradable diazo compound is dissolved to form the core of the microcapsule. preferable.
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, tritoluylmethane, toluyldiphenylmethane), terphenyl compound (eg, terphenyl), alkyl compound, alkylated diphenyl ether (For example, propyl diphenyl ether), hydrogenated terphenyl (for example, hexahydroterphenyl), diphenyl ether, and the like. Among these, it is particularly preferable to use esters from the viewpoint of emulsion stability of the emulsion dispersion.

  Examples of the esters include phosphate esters such as triphenyl phosphate, tricresyl phosphate, butyl phosphate, octyl phosphate, cresyl phenyl phosphate; dibutyl phthalate, 2-ethylhexyl phthalate, ethyl phthalate, Phthalic acid esters such as octyl phthalate and butyl benzyl phthalate; Dioctyl tetrahydrophthalate; Benzoic acid esters such as ethyl benzoate, propyl benzoate, butyl benzoate, isopentyl benzoate and benzyl benzoate; Ethyl abietic acid, abietic acid Abietic acid esters such as benzyl; dioctyl adipate; isodecyl succinate; dioctyl azelate; oxalic acid esters such as dibutyl oxalate and dipentyl oxalate; diethyl malonate; dimethyl maleate, diethyl maleate, di maleate Maleic acid esters such as chill; Tributyl citrate; Sorbic acid esters such as methyl sorbate, ethyl sorbate, and butyl sorbate; Sebacic acid esters such as dibutyl sebacate and dioctyl sebacate; Formic acid monoesters and diesters, butyric acid monoesters And ethylene glycol esters such as diester, lauric acid monoester and diester, palmitic acid monoester and diester, stearic acid monoester and diester, oleic acid monoester and diester; triacetin; diethyl carbonate; diphenyl carbonate; ethylene carbonate; propylene carbonate And boric acid esters such as tributyl borate and tripentyl borate.

  Among these, in particular, when tricresyl phosphate is used alone or in combination, the stability of the emulsion is most favorable, which is preferable. It is also possible to use the above oils in combination with other oils.

  When the electron-donating dye precursor to be encapsulated or the photodegradable diazo compound has poor solubility in the hydrophobic organic solvent, a low-boiling solvent having high solubility can be supplementarily used together. Preferred examples of such a low boiling point solvent include ethyl acetate, isopropyl acetate, butyl acetate, and methylene chloride.

When the electron donating dye precursor or the photodegradable diazo compound is contained in the heat sensitive recording layer of the heat sensitive recording material, the content of the electron donating dye precursor is 0.1 to 5.0 g / m ^2. Preferably, 0.5 to 4.0 g / m ² is more preferable. Moreover, as content of a photodegradable diazo compound, 0.02-5.0 g / m < ² > is preferable and 0.10-4.0 g / m < ² > is more preferable from the point of coloring density.
When the content of the electron-donating dye precursor is in the above range, a sufficient color density is obtained, and when the content of both is within 5.0 g / m ² , the color density is sufficiently maintained, and The transparency of the thermosensitive recording layer can be maintained.

  On the other hand, an aqueous solution in which a water-soluble polymer is dissolved as a protective colloid is used for the aqueous phase to be used, and after the oil phase is added thereto, emulsification and dispersion are performed by means of a homogenizer or the like. It acts as a dispersion medium that makes the aqueous solution emulsified and dispersed stable. 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. A known emulsifying surfactant can be used as the surfactant. 0.1-5% is preferable with respect to the mass of an oil phase, and, as for the addition amount of surfactant, 0.5-2% is more preferable.

As the surfactant to be contained in the aqueous phase, an anionic or nonionic surfactant that does not cause precipitation or aggregation by acting with the protective colloid can be suitably selected and used.
Preferable surfactants include, for example, sodium alkylbenzene sulfonate, sodium alkyl sulfate, dioctyl sulfosuccinate sodium salt, polyalkylene glycol (for example, polyoxyethylene nonyl phenyl ether) and the like.

  For emulsification, means used for normal fine particle emulsification such as high-speed stirring, ultrasonic dispersion, etc., for example, a homogenizer, a manton gory, an ultra-phase, an oil phase containing the above components and an aqueous phase containing a protective colloid and a surfactant. It can be easily carried out using a known emulsifying device such as a sonic disperser, a dissolver, a teddy mill or the like. After emulsification, the emulsion is preferably heated to 30 to 70 ° C. in order to promote the capsule wall formation reaction. Further, during the reaction, in order to prevent aggregation between the capsules, it is preferable to add water to reduce the collision probability between the capsules or perform sufficient stirring.

  Further, a dispersion for preventing aggregation may be added again during the reaction. Generation of carbon dioxide gas is observed as the polymerization reaction proceeds, and the end of the generation can be regarded as an approximate end point of the capsule wall formation reaction. Usually, the target microcapsule can be obtained by reacting for several hours.

(Emulsified dispersion)
When an electron donating dye precursor or a photodegradable diazo compound is encapsulated as a core substance, the electron accepting compound or coupler to be used is, for example, a water-soluble polymer and an organic base, other color forming aids, etc. At the same time, it can be used as a solid dispersion by means of a sand mill or the like. However, after previously dissolving in a high-boiling organic solvent that is hardly soluble or insoluble in water, this is used as a protective colloid with a surfactant and / or a water-soluble polymer. It is more preferable to use as an emulsified dispersion mixed with the aqueous polymer solution (aqueous phase) contained and emulsified with a homogenizer or the like. In this case, a low boiling point solvent can be used as a dissolution aid, if necessary.
Further, the coupler and the organic base can be emulsified and dispersed separately, or mixed and then dissolved in a high boiling point organic solvent to be emulsified and dispersed. A preferable emulsified and dispersed particle size is 1 μm or less.

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

The water-soluble polymer contained as the protective colloid can be appropriately selected from known anionic polymers, nonionic polymers, and amphoteric polymers, and has a solubility in water at the temperature to be emulsified. A water-soluble polymer of 5% or more is preferable, and specific examples thereof include polyvinyl alcohol or a modified product thereof, polyacrylic acid amide or a derivative thereof, ethylene-vinyl acetate copolymer, styrene-maleic anhydride copolymer, ethylene -Maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyvinylpyrrolidone, ethylene-acrylic acid copolymer, vinyl acetate-acrylic acid copolymer, cellulose derivatives such as carboxymethylcellulose, methylcellulose, casein, gelatin, Starch derivatives, arabic gum, sodium alginate, etc. And the like.
Among these, polyvinyl alcohol, gelatin, and cellulose derivatives are particularly preferable.

  Moreover, 0.02-0.6 are preferable and, as for the mixing ratio (oil phase mass / aqueous phase mass) with respect to the water phase of an oil phase, 0.1-0.4 are more preferable. When the mixing ratio is in the range of 0.02 to 0.6, an appropriate viscosity can be maintained, the production suitability is excellent, and the coating solution stability is excellent.

When an electron-accepting compound is used in the heat-sensitive recording material of the present invention, the electron-accepting compound is preferably 0.5 to 30 parts by mass with respect to 1 part by mass of the electron-donating dye precursor, and 1.0 to 10 parts by mass is more preferable.
Further, 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 thermal recording layer)
The thermal recording layer coating liquid can be prepared, for example, by mixing the microcapsule liquid prepared as described above and 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 are used as a binder in the thermosensitive recording layer. Function. In addition to these protective colloids, a binder may be added and mixed to prepare a thermal recording layer coating solution.

The binder to be added is generally water-soluble, and polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, epichlorohydrin-modified polyamide, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer. , Isobutylene-maleic salicylic anhydride copolymer, polyacrylic acid, polyacrylamide, methylol-modified polyacrylamide, starch derivative, casein, gelatin and the like.
Further, for the purpose of imparting water resistance to these binders, a water-proofing agent may be added, or a hydrophobic polymer emulsion, specifically, a styrene-butadiene rubber latex, an acrylic resin emulsion, or the like may be added.

  When applying the thermal recording layer coating solution on the support, known coating means used for aqueous or organic solvent coating solutions are used. In this case, the thermal recording layer coating solution is applied safely and uniformly. In addition, in order to maintain the strength of the coating film, in the heat-sensitive recording material of the present invention, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, starches, gelatin, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, polyacrylamide, polystyrene or a copolymer thereof , Polyester or copolymer thereof, polyethylene or copolymer thereof, epoxy resin, acrylate resin or copolymer thereof, methacrylate resin or copolymer thereof, polyurethane resin, polyamide resin, polyvinyl butyral resin, etc. be able to.

(Other ingredients)
Hereinafter, other components that can be used in the thermosensitive recording layer will be described.
Other components that can be suitable for the heat-sensitive recording layer are not particularly limited and may be appropriately selected depending on the purpose. For example, known heat-fusible substances, ultraviolet absorbers, antioxidants and the like can be mentioned.

The heat-fusible substance can be contained in the heat-sensitive recording layer for the purpose of improving the thermal response.
Examples of the heat-fusible substance include aromatic ethers, thioethers, esters, aliphatic amides, and ureidos. Examples of these are disclosed in JP-A Nos. 58-57989, 58-87094, 61-58789, 62-109682, 62-132673, 63-151478, and 63-235961. It is described in Japanese Laid-Open Patent Publication Nos. 2-184289 and 2-215585.

  Preferred examples of the UV absorber include benzophenone UV absorbers, benzotriazole UV absorbers, salicylic acid UV absorbers, cyanoacrylate UV absorbers, and oxalic acid anilide UV absorbers. Examples of these are disclosed in JP-A-47-10537, 58-111942, 58-21284, 59-19945, 59-46646, 59-109555, 63-53544, JP-A 36-10466, 42-26187, 48-30492, 48-31255, 48-41572, 48-54965, and 50-10726, U.S. Pat. No. 086, No. 3,707,375, No. 3,754,919, No. 4,220,711, and the like.

  Preferable examples of the antioxidant include hindered amine antioxidants, hindered phenol antioxidants, aniline antioxidants, and quinoline antioxidants. Examples of these are described in JP-A Nos. 59-155090, 60-107383, 60-107384, 61-137770, 61-139481, 61-160287, and the like. Yes.

The coating amount of the other ingredients, preferably about ^{0.05~1.0g / m 2, 0.1~0.4g / m} 2 is more preferable. The other component may be added inside the microcapsule or may be added outside the microcapsule.

Further, the heat-sensitive recording material of the present invention is an image having excellent transparency by constituting the heat-sensitive recording layer so as to lower the haze value calculated from (diffuse transmittance / total light transmittance) × 100 (%). Can be obtained. The haze value is an index representing the transparency of the material, and is generally calculated from the total light transmission amount, diffuse transmission light amount, and parallel transmission light amount using a haze meter.
In the present invention, as a method for reducing the haze value, for example, the 50% volume average particle size of both the coloring components A and B contained in the heat-sensitive recording layer is 1.0 μm or less, preferably 0.6 μm or less. And a method in which a binder is contained in the range of 30 to 60% by mass of the total solid content of the heat-sensitive recording layer, one of the color developing components A and B is microencapsulated, and the other is coated and dried to be a substantially continuous layer. For example, a method of using it as an emulsion (emulsified dispersion or the like). It is also effective to make the refractive index of the component used for the thermosensitive recording layer as close to a constant value as possible.

The heat-sensitive recording layer is preferably applied so that the dry coating amount after application and drying is 1 to 25 g / m ² , and the thickness of the layer is preferably 1 to 25 μm. . Two or more heat-sensitive recording layers can be laminated and used. In this case, it is preferable that the coating amount of the entire heat-sensitive recording layer and the dry coating amount after drying are 1 to 25 g / m ² .

[Support]
As the support, both a transparent support and an opaque support such as paper can be used depending on the purpose and application. In the present invention, it is preferable to use a transparent support.
Examples of the transparent support include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, cellulose triacetate films, and synthetic polymer films such as polyolefin films such as polypropylene and polyethylene. Can be used together.

  In the case of medical use, the transparent support may be colored with a blue dye (for example, dye-1 described in Examples of JP-A-8-240877) or may be uncolored. The support is preferably primed with gelatin or water-soluble polyester. Regarding the undercoat layer, for example, those described in JP-A Nos. 51-11420, 51-123139, and 52-65422 can be used. The thickness of the support is preferably 25 to 250 μm, more preferably 50 to 210 μm.

  The synthetic polymer film may be colored in an arbitrary hue. As a method of coloring a polymer film, a method of forming a film by kneading a dye into a resin before forming a resin film, preparing a coating solution in which a dye is dissolved in an appropriate solvent, and preparing this as a colorless transparent resin Examples of the coating method include a known coating method on the film, for example, a gravure coating method, a roller coating method, a wire coating method, and the like. Among them, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate kneaded with a blue dye is preferably formed into a film and subjected to heat treatment, stretching treatment, and antistatic treatment.

  In particular, when the heat-sensitive recording material of the present invention is observed from the support side on a shears ten, the shakasten light transmitted through the transparent non-image portion may cause illusion and make the image difficult to see. Therefore, from the viewpoint of avoiding this, A (x = 0.2805, y = 0.3005), B (x = 0.2820, y) on the chromaticity coordinates defined by the method described in JIS-Z8701. = 0.2970), C (x = 0.2885, y = 0.015), and D (x = 0.2870, y = 0.04040) are colored blue in a rectangular region formed by four points. It is particularly preferable to use a synthetic polymer film.

[Other layers]
In the heat-sensitive recording material of the present invention, an intermediate layer, an undercoat layer, an ultraviolet filter layer, a back layer and the like can be provided as other layers on the support.

(Middle layer)
The intermediate layer is provided to prevent mixing of the layers and to block a gas (oxygen or the like) harmful to image storage stability, and the intermediate layer is preferably formed on the heat-sensitive recording layer.

In the present invention, it is a more preferable embodiment that the compound represented by the general formula (1) and / or the general formula (2) is contained in the intermediate layer in addition to the protective layer. By including the compound in the intermediate layer, the excellent effects of the present invention, such as uniformization of the coated surface and chemical resistance, can be further exhibited.
The content when the compound represented by the general formula (1) and / or the general formula (2) is contained in the intermediate layer is preferably 0.005 to 1.0 g / m ² , and 0 0.01 to 0.5 g / m ² is more preferable.

The binder used for the intermediate layer is not particularly limited, and polyvinyl alcohol, gelatin, polyvinyl pyrrolidone, cellulose derivatives, and the like can be used depending on the system.
Among them, gelatin has fluidity at high temperatures, but has a property (set property) that loses fluidity and gels at low temperatures (for example, 35 ° C. or lower), so that a plurality of layers are formed on a support. In the case of providing the layer by applying and drying a coating solution for forming, the two adjacent layers may be applied by a method of applying and drying a plurality of layers sequentially or by a method of applying and drying a multilayer by an extrusion die method or the like. It is effectively prevented that the layers mix with each other. Therefore, the surface shape of the obtained heat-sensitive recording material is improved, and a heat-sensitive recording material capable of forming a high-quality image can be obtained, and is particularly suitable for medical diagnosis that needs to form a clear image in detail. It is. Furthermore, even if it is dried at a high wind speed, the surface condition is not deteriorated, so that the production efficiency is improved.

As such gelatin, unmodified (untreated) gelatin or modified (treated) gelatin can be used without any problem. Examples of modified gelatin include lime-processed gelatin, acid-processed gelatin, phthalated-processed gelatin, deionized-processed gelatin, and enzyme-processed low-molecular-weight gelatin. Further, various surfactants may be added for imparting coatability. In order to further improve the gas barrier properties, inorganic fine particles such as mica may be added to the binder in an amount of 2 to 20% by mass, more preferably 5 to 10% by mass. The binder concentration of the intermediate layer coating solution is 3 to 25% by mass, preferably about 5 to 15% by mass. Dry coating amount of addition the intermediate layer is 0.1 to 6 g / m ^2, and preferably is 0.5-4 g / m ² suitably.

(Undercoat layer)
In the heat-sensitive recording material of the present invention, for the purpose of preventing the heat-sensitive recording layer from peeling off from the support, an undercoat layer is formed on the support before applying a heat-sensitive recording layer containing microcapsules or the like and an antireflection layer. Can be provided. As the undercoat layer, an acrylate copolymer, polyvinylidene chloride, SBR, aqueous polyester or the like can be used, and the thickness of the layer is preferably 0.05 to 0.5 μm.
When applying a heat-sensitive recording layer on the undercoat layer, the undercoat layer may swell due to water contained in the heat-sensitive recording layer coating solution, and the image recorded on the heat-sensitive recording layer may deteriorate. It is preferable to harden using dialdehydes such as glutaraldehyde and 2,3-dihydroxy-1,4-dioxane and a hardener such as boric acid. The amount of these hardeners can be appropriately added in accordance with the desired degree of curing in the range of 0.2 to 3.0% by mass depending on the mass of the undercoat material.
With respect to the undercoat layer, for example, those described in JP-A Nos. 51-11420, 51-123139, and 52-65422 can be used.

(UV filter layer)
In the heat-sensitive recording material of the present invention, a light blocking layer may be provided to prevent discoloration and background fogging of the image. The light blocking layer is obtained by uniformly dispersing an ultraviolet absorber in a binder, and the uniformly dispersed ultraviolet absorber effectively absorbs ultraviolet light, whereby the background is discolored by the ultraviolet light or the image is displayed. Prevents parts from discoloring or fading. As the method for preparing the light blocking layer and the compounds used, those described in JP-A-4-197778 can be used in addition to benzotriazole-based, benzophenone-based, hindered amine-based UV absorbers, and the like.

(Back layer))
The heat-sensitive recording material in the present invention is preferably a single-sided light-sensitive material having a heat-sensitive recording layer containing microcapsules on one side of the support and a back layer on the other side. A matting agent is preferably added to the back layer for the purpose of imparting transportability and preventing light reflection. By adding a matting agent, the glossiness measured at an incident light angle of 20 ° is preferably 50% or less, and more preferably 30% or less.
Examples of the matting agent include fine particles such as starch obtained from barley, wheat, corn, rice, beans, etc., 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 viscosity, inorganic substances such as aluminum hydroxide, silica, zinc oxide Examples thereof include fine particles. The average particle size of the matting agent is 0.5 to 20 μm, preferably 0.5 to 10 μm. The mat materials 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 preferably in the range of 1.4 to 1.8. Various dyes (for example, CI Pigment Blue 60, CI Pigment Blue 64, CI Pigment Blue 15: 6) can be used for the back layer from the viewpoint of improving the hue. Further, a hardener may be used for the back layer. Examples of the hardener include T.W. H. There are various methods described in “THE THEORY OF THE PHOTOGRAPHIC PROCESS 4th EDITION” by James (pages 77 to 87), and vinyl sulfone compounds are preferred.

[Preparation of thermal recording material]
Hereinafter, the method for producing the heat-sensitive recording material of the present invention will be described.
Each layer constituting the heat-sensitive recording material of the present invention is prepared by adjusting a coating solution for forming a plurality of layers including the above-described heat-sensitive recording layer, intermediate layer, protective layer, etc., and applying the coating solution on a support. It is formed by applying multiple layers sequentially or simultaneously and drying.
The heat-sensitive recording material of the present invention provides a coated surface with excellent uniformity even when each layer is formed by multi-layer coating, and thus has excellent characteristics such as chemical resistance and high-quality image formability. Can be demonstrated. Therefore, multilayer coating can be suitably used in the method for producing the heat-sensitive recording material of the present invention.

  As the support used here, the above-described support can be used. In addition, as the coating liquid for forming each layer such as the thermal recording layer coating liquid, the intermediate layer coating liquid, and the protective layer coating liquid, those described in the explanation of each layer can be used.

  In the method for producing a heat-sensitive recording material of the present invention, a blade coating method, an air knife coating method, a gravure coating method, a roll are used to sequentially form an undercoat layer, a heat-sensitive recording layer, an intermediate layer, a protective layer, etc. on a support. Known coating methods such as a coating coating method, a spray coating method, a dip coating method, and a bar coating method are used. An example of a method for applying a plurality of layers simultaneously is an extrusion die method.

  Specific coating methods include various coating methods including extrusion coating, slide coating, curtain coating, knife coating, dip coating, flow coating or extrusion coating using a hopper of the type described in US Pat. No. 2,681,294. It is done. Among them, the extrusion coating or slide coating described in “LIQUID FILM COATING” (CHAPMAN & HALL 1997), pages 399 to 536 by Stephen F. Kistler and Petert M. Schwaizer is preferably used, and slide coating is particularly preferably used. .

An example of the shape of a slide coater used for slide coating is described in Fogure 11b.1 on page 427 of the same document. If desired, a coating solution for a heat-sensitive recording layer may be formed on the support using the method described on pages 399 to 536 of the same document, the method described in US Pat. No. 2,761791 and British Patent No. 837095. By simultaneously applying the coating liquids in multiple layers, the heat-sensitive recording layer, the protective layer, and other layers (intermediate layer, etc.) can be formed simultaneously.
Drying is performed with dry air having a dry bulb temperature of 20 to 65 ° C, preferably 25 to 55 ° C, and a wet bulb temperature of 10 to 30 ° C, preferably 15 to 25 ° C.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “part” means “part by mass”, “%” means “mass%”, and “molecular weight” means “weight average molecular weight” unless otherwise specified.

(Example 1)
<Preparation of electron-donating dye precursor-encapsulated microcapsule solution>
14 g of 2-anilino-3-methyl-6-N-ethyl-N-sec-butylaminofluorane as an electron-donating dye precursor, 0.6 g of tinuvin P (manufactured by Ciba-Gaigi) as an ultraviolet absorber, and capsule wall 10 g of Takenate D-110N (manufactured by Takeda Pharmaceutical Co., Ltd.) and 10 g of Sumidur N3200 (manufactured by Sumitomo Chemical Co., Ltd.) were dissolved in 20 g of ethyl acetate. This solution was mixed with 112 g of an aqueous solution of 5% polyvinyl alcohol (trade name: PVA217C, manufactured by Kuraray Co., Ltd.), emulsified with an ace homogenizer (manufactured by Nippon Seiki Co., Ltd.) at 8000 rpm, and 142 g of water was further added. An electron donating dye precursor-containing microcapsule solution having a capsule size of 0.7 μm was prepared by reacting at 55 ° C. for 3 hours.

<Preparation of developer emulsified dispersion>
The developer represented by the following structural formula (a) 7 g, (b) 7 g, (c) 16 g, (d) 11 g, tricresyl phosphate 1.7 g, diethyl maleate 0.8 g Dissolved in 38 g of ethyl. The obtained developer solution was mixed with an aqueous solution of 100 g of 8% polyvinyl alcohol (PVA205C: manufactured by Kuraray Co., Ltd.), 150 g of water, and 0.5 g of sodium dodecylbenzenesulfonate, and an ace homogenizer ( Nippon Seiki Co., Ltd.) was used and emulsified at 10,000 rpm at room temperature for 5 minutes to obtain a developer emulsified dispersion having an average particle size of 1.0 μm.

<Preparation of thermal recording material>
<Formation of thermal recording layer>
The above-mentioned electron-donating dye precursor-encapsulated microcapsule solution 5.0 g, developer emulsion 10.0 g, and water 5.0 g were stirred and mixed to prepare a thermosensitive recording layer coating solution. A heat-sensitive recording layer was formed on one side of a polyethylene terephthalate support so that the solid content was 10 g / m ² and dried.

<Formation of protective layer>
-Preparation of pigment dispersion-
60 g of water, 5 g of 10% polyvinyl alcohol (trade name: PVA205, manufactured by Kuraray Co., Ltd.), 2 g of 2% sodium dodecylbenzenesulfonate, stearic acid-treated aluminum hydroxide (trade name: Hydylite H42S, Showa Denko) 15 g) was added and dispersed so that the average particle size was 0.7 μm.

A coating solution for a protective layer was prepared so as to have the following composition with a solid content, and coated on the heat-sensitive recording layer so that the solid content was 2.5 g / m ² .

Polyvinyl alcohol (trade name: PVA124, manufactured by Kuraray Co., Ltd.) 7 parts Pigment dispersion 12 parts Zinc emulsion (trade name: Hi-micron F115, manufactured by Chukyo Yushi Co., Ltd.) 0.2 part ・ Polyoxyethylene alkyl ether phosphate ester (trade name: Neoscore CM57, manufactured by Toho Chemical Co., Ltd.) 0.05 part

  As described above, the heat-sensitive recording material of Example 1 was produced.

(Example 2)
On the thermosensitive recording layer obtained in the same manner as in Example 1, an intermediate layer of 0.5 g / m ^{2 was} formed so as to have the following composition. Further, a protective layer similar to that of Example 1 was formed thereon, and a thermosensitive recording material of Example 2 was produced.

・ 10 parts of polyvinyl alcohol (trade name: PVA124, manufactured by Kuraray Co., Ltd.)
・ 0.05 parts of polyoxyethylene alkyl ether phosphate (trade name: Neoscore CM57, manufactured by Toho Chemical Co., Ltd.)
・ Straight-chain sodium dodecylbenzenesulfonate 0.05 parts (trade name: Neoperex G-15, manufactured by Kao Corporation)

(Example 3)
In Example 1, the polyoxyethylene alkyl ether phosphate ester (trade name: Neoscore CM57, manufactured by Toho Chemical Co., Ltd.) used in the protective layer was replaced with bispolyoxyethylene alkyl ether phosphate ester (trade name: Prisurf A217E). The heat-sensitive recording material of Example 3 was produced in the same manner as in Example 1 except that it was changed to Daiichi Kogyo Co., Ltd.

(Example 4)
The same procedure as in Example 2 was performed except that polyoxyethylene alkyl ether phosphate ester (trade name: Neoscore CM57, manufactured by Toho Chemical Co., Ltd.) was changed to polyoxyethylene alkyl phenyl ether phosphate ester in Example 2. The heat-sensitive recording material of Example 4 was produced.

(Example 5)
In Example 1, instead of using 0.05 part of polyoxyethylene alkyl ether phosphate (trade name: Neoscore CM57, manufactured by Toho Chemical Co., Ltd.) alone, polyoxyethylene alkyl ether phosphate (product) Name: Neoscore CM57, manufactured by Toho Chemical Co., Ltd.) 0.025 parts and bispolyoxyethylene alkyl ether phosphate ester (trade name: Prisurf A217E, manufactured by Daiichi Kogyo Co., Ltd.) 0.025 parts A heat-sensitive recording material of Example 5 was produced in the same manner as in Example 1 except that it was used in combination.

(Example 6)
A heat-sensitive recording material of Example 6 was produced by simultaneously applying a heat-sensitive recording layer and a protective layer having the same composition as in Example 1 on top of each other.

(Example 7)
A heat-sensitive recording material of Example 7 was produced by simultaneously applying a heat-sensitive recording layer, an intermediate layer, and a protective layer having the same composition as in Example 2 on top of each other.

(Comparative Example 1)
In Example 1, except that the polyoxyethylene alkyl ether phosphate ester was replaced by sulfosuccinic acid 2-ethylhexyl ester sodium salt (trade name: Rapisol B-90, manufactured by NOF Corporation), the same as in Example 1. The thermosensitive recording material of Comparative Example 1 was produced by the method described above.

(Comparative Example 2)
In Example 2, the polyoxyethylene alkyl ether phosphate ester was compared in the same manner as in Example 2 except that it was replaced with sodium butyl naphthalene sulfonate (trade name: Perex NB-L, manufactured by Kao Corporation). The heat-sensitive recording material of Example 2 was produced.

(Comparative Example 3)
In Example 2, the thermal sensitivity of Comparative Example 3 was changed in the same manner as in Example 2 except that the polyoxyethylene alkyl ether phosphate ester was replaced with perfluoroalkyl betaine (trade name: Surflon S131, manufactured by Asahi Glass Co., Ltd.). A recording material was prepared.

(Comparative Example 4)
In Example 1, except that the polyoxyethylene alkyl ether phosphate ester was changed to polyethylene glycol alkyl phenyl ether (trade name: Neugen EA-160, Daiichi Kogyo Co., Ltd.), the same method as in Example 1 was used. A heat-sensitive recording material of Comparative Example 4 was produced.

  The surface tension of the coating solution for the protective layer produced as described above was measured with a plate type surface tension meter (manufactured by Kyowa Interface Chemical Co., Ltd.). Further, each sample of the thermal recording material was printed with a thermal imager FTI1000 (manufactured by Fuji Photo Film Co., Ltd.) and evaluated for printing sound, sticking performance, image quality, and chemical resistance. Evaluation methods and evaluation criteria are as follows. The results are shown in Table 1.

<Evaluation of printing sound>
The printing sound during printing was evaluated according to the following criteria.
○: There is almost no sound.
Δ: A level that sounds but does not matter.
X: The level is loud and unpleasant.

<Evaluation of sticking performance>
The sticking performance during printing was evaluated according to the following criteria.
○: No white stripes occurred.
Δ: Slight white stripes are generated.
X: White stripes frequently occur.

<Evaluation of image quality>
Each sample after printing was visually observed and evaluated according to the following criteria.
A: Density unevenness is not observed at all.
○: Density unevenness is hardly observed.
Δ: Density unevenness is observed.
X: Image missing due to repelling.

<Evaluation of chemical resistance>
After applying ethanol to the sample surface with a cotton swab soaked in ethanol, the discoloration of the background portion was visually observed and evaluated according to the following criteria.
(Double-circle): There is no discoloration in a background part and it is beautiful.
○: Almost no discoloration in the background.
Δ: Moyamura is observed on the background.
X: Fog is generated on the background portion.

  As shown in Table 1, it was found that the heat-sensitive recording material of the present invention was excellent in runnability and printing quality in an actual machine, and did not cause discoloration due to chemicals. Further, it was found that the heat-sensitive recording material of the present invention was able to obtain the same performance as the sequential coating when the multilayer coating was applied. The above results are considered to be due to the excellent uniformity of the coated surface of the heat-sensitive recording material of the present invention.

Claims (3)

A thermal recording material having at least a thermal recording layer and a protective layer on a support,
The protective layer contains a compound represented by the following general formula (1) and / or general formula (2), and the surface tension of the coating liquid of the protective layer is 20 to 35 mN / m. Heat-sensitive recording material.
R—O (CH ₂ CH ₂ O) _n —PO (OH) ₂ general formula (1)
[In General Formula (1), R represents a C4-C20 alkyl group, a C6-C20 alkylaryl group, or a C6-C20 alkylphenoxy group. n represents an integer of 1 to 50. ]
_{(R-O (CH 2 CH} 2 O) n -) 2 -PO (OH) formula (2)
[In General Formula (2), R and n are synonymous with R and n in General Formula (1). ]   The heat-sensitive recording material according to claim 1, wherein the compound represented by the general formula (1) and / or the general formula (2) is a polyoxyethylene alkyl ether phosphate.   The heat-sensitive recording material according to claim 1 or 2, wherein the heat-sensitive recording layer and the protective layer are applied in multiple layers.