JPH0872408A - Thermal recording - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a thermosensitive recording medium having excellent transparency, less background fog, and high recording sensitivity. [Structure] Dye layer coating liquid containing a leuco dye and an adhesive dissolved in an organic solvent on a support, and a color developing agent layer coating containing a color former and an adhesive dissolved in an organic solvent. In a thermosensitive recording medium in which a dye layer and a color developing agent layer are provided by applying and drying a liquid, the melting point is 40 to 1 between the dye layer and the color developing agent layer.
A heat-sensitive recording material having a sensitizer layer formed by applying a sensitizer layer coating liquid containing a sensitizer, an adhesive, water or an organic solvent at 20 ° C. and drying.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material utilizing a color-developing reaction between a leuco dye and a color-developing agent, and more particularly to a heat-sensitive recording material having excellent transparency, little background fog and high recording sensitivity. is there.

[0002]

2. Description of the Related Art A thermosensitive recording medium is known, in which a color-forming substance is brought into contact with heat to obtain a recorded image by utilizing a color reaction between a colorless or light-colored leuco dye and an organic or inorganic coloring agent. There is. Recently, with the remarkable progress of the thermal recording system, its fields of use and forms are diversifying, and not only as a recording medium for a thermal facsimile or a thermal printer, but also a magnetic thermal paper or a POS label, and a ticket card that requires forgery prevention. There is a rapid increase in the use for new applications such as products, prepaid cards, and sealless fixed terms.

Further, by increasing the transparency of the thermosensitive recording medium, it can be used as an OHP sheet and an X-ray film. For this purpose, a method of coating a dye and a color developing agent in a solvent system (JP-A-4-239688), a method of making fine particles of a heat-sensitive recording layer composition, and the like have been dealt with. However, a satisfactory transparent heat-sensitive recording material has not been obtained because of fog, insufficient transparency, poor sensitivity, and defects.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording medium which is excellent in transparency, has less background fog and has high recording sensitivity.

[0005]

SUMMARY OF THE INVENTION The present invention comprises:
Dye layer coating liquid containing a leuco dye and an adhesive dissolved in an organic solvent, and a color developing agent layer coating liquid containing a color developing agent and an adhesive dissolved in an organic solvent is applied and dried to obtain a dye. In a thermosensitive recording medium provided with a layer and a color developing agent layer, a sensitizing agent containing a sensitizer having a melting point of 40 to 120 ° C., an adhesive, water or an organic solvent between the dye layer and the color developing agent layer. The above problems have been solved and found by applying a coating solution for the agent layer and drying it to form a sensitizer layer.

[0006]

The present invention comprises a support, a dye layer coating solution containing a leuco dye and an adhesive dissolved in an organic solvent, and a coloring agent and an adhesive dissolved in an organic solvent. In a thermosensitive recording medium in which a dye layer and a color former layer are provided by coating and drying a colorant layer coating liquid, a sensitizer having a melting point of 40 to 120 ° C. and adhesion between the dye layer and the color former layer. It is characterized in that a sensitizer layer-coating liquid containing a sensitizer, water or an organic solvent is applied and dried to form a sensitizer layer. With such a constitution, the transparency is excellent, the background fog is small, and the recording sensitivity is high. High thermal recording material.

By providing a sensitizer layer containing a sensitizer having a melting point of 40 to 120 ° C., a barrier can be formed between the dye layer and the color developing agent layer, and the fog phenomenon can be suppressed. Further, if the melting point of the sensitizer is less than 40 ° C., fog tends to occur during storage, and if it exceeds 120 ° C., the recording sensitivity decreases. The sensitizer is added to the sensitizer layer in an amount of 35 based on the total solid amount.
The content of ˜70% by weight creates a place where the dye and the color developing agent are likely to come into contact with each other, so that a heat-sensitive recording material having high sensitivity can be obtained. If the amount of the sensitizer is less than 35% by weight, the recording sensitivity is lowered, and if it exceeds 70% by weight, the transparency may be lowered. It is also possible to further add a sensitizer to the dye layer or the color developing agent layer.

When the leuco dye, the color former, and the sensitizer contained in each layer are dissolved in an organic solvent, the particles do not scatter and the transparency is remarkably improved. Further, when the sensitizer layer is provided by a coating solution using water as a solvent, the dye layer or the color former layer provided on the sensitizer layer is uniformly applied. Further, even if the leuco dye, the colorant, and the sensitizer are not dissolved in the organic solvent, the constituent particles are often hydrophobic, so that the particles and the binder are well compatible with each other, and by filling the voids, Transparency is improved compared to the case of water system. At that time, a thermosensitive recording material having high transparency can be obtained by setting the average particle size of the dye, the color former, and the sensitizer to 0.7 μm or less.

The thermal recording material obtained by the production method of the present invention may have a constitution in which the above-mentioned uppermost layer is provided with a protective layer. By providing the protective layer, discoloration or fading due to chemicals or plasticizers is reduced, This is one of the preferred embodiments because a thermosensitive recording medium excellent in mechanical suitability can be obtained.

The melting point used in the sensitizer layer is 40 to 120.
Examples of the sensitizer at ° C include caproic acid amide, capric acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, erucic acid amide, linoleic acid amide, linolenic acid amide, N-methylstearic acid amide, and stearic acid. Anilide, N-methyloleic acid amide, benzanilide, linoleic acid anilide, N-ethylcapric acid amide, N-butyllauric acid amide, N
-Octadecylacetamide, N-oleinacetamide, N-oleylbenzamide, N-stearylcyclohexylamide, polyethylene glycol, 1-benzyloxynaphthalene, 2-benzyloxynaphthalene,
1-Hydroxynaphthoic acid phenyl ester, 1,2-
Diphenoxyethane, 1,4-diphenoxybutane,
1,2-bis (3-methylphenoxy) ethane, 1,2
-Bis (4-methoxyphenoxy) ethane, 1-phenoxy-2- (4-chlorophenoxy) ethane, 1-phenoxy-2- (4-methoxyphenoxy) ethane, 1-
(2-Methylphenoxy) -2- (4-methoxyphenoxy) ethane, terephthalic acid dibenzyl ester, oxalic acid dibenzyl ester, oxalic acid di-p-methylbenzyl ester, p-benzyloxybenzoic acid benzyl ester, p- Benzylbiphenyl, 1,5-bis (p-
Methoxyphenoxy) -3-oxa-pentane, 1,4
Examples thereof include compounds such as -bis (2-vinyloxyethoxy) benzene, p-biphenyl p-tolyl ether, and benzyl-p-methylthiophenyl ether.

The coating amount of the sensitizer layer is not particularly limited, and is usually adjusted in the range of about 0.5 to 5 g / m ² , preferably about 1 to 3 g / m ^{2 in} dry weight. When the coating amount of the sensitizer layer is large, the recording sensitivity may be lowered or a clear image may not be obtained.

In the present invention, the organic solvent for dissolving the adhesive in the dye layer and the color developing agent layer is not particularly limited, but for example, benzene, toluene, xylene, cyclohexane, methylcyclohexane, cyclopentane, petroleum ether. , Ethylene, methyl chloride, carbon tetrachloride, chlorobenzene, dichlorobenzene, methanol,
Examples thereof include, but are not limited to, ethanol, propanol, isopropanol, butanol, ethyl ether, isopropyl ester, diethyl acetal, acetone, methyl ethyl ketone, diethyl ketone, ethyl acetate, methyl acetate and methyl propionate. The organic solvent for dissolving each of the leuco dye, the color former, and the sensitizer may be appropriately selected from the above organic solvents and the like. However, when an organic solvent system is used for all layers, it is desirable to sequentially select a solvent that does not dissolve the constituent components of the lower layer.

In each layer, the adhesive used in an organic solvent system is not particularly limited as long as it is a resin soluble in an organic solvent, but a thermoplastic resin is particularly preferably used,
The organic solvent-soluble thermoplastic resin as described above is more preferably used, and specific examples thereof include polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, polybutyl acrylate, polystyrene, and acrylic acid ester.・ Styrene copolymer, polyester resin,
Poly α-methyl styrene, ABS resin, coumarone resin,
Nitrocellulose, ethylene / vinyl acetate copolymer, vinyl chloride
Examples thereof include vinyl acetate copolymer, butyral resin, and the like, but the present invention is not limited to these, and two or more kinds of resins can be used in combination.

When the sensitizer layer is provided from an aqueous coating solution, the adhesive may be starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol,
Acetoacetyl group-modified polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion, urea resin,
Acrylic resin, amide resin, melamine resin, etc. are used.

The amount of the adhesive used is not particularly limited, but is the total solid amount of the coating liquid in any of the recording layer forming coating liquids, that is, organic solvent type and aqueous type. 1 to 90% by weight, preferably 5 to 60% by weight
It is desirable to adjust within the range. When used for the coating liquid for protective layer, it is 5 to the total solid amount of the coating liquid for protective layer.
It is desirable to adjust in the range of 95% by weight, preferably 20 to 95% by weight.

As the colorless or pale leuco dye used in the present invention, various known dyes can be used. Specific examples of these leuco dyes include the following. 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p
-Dimethylaminophenyl) phthalide, 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2)
-Methylphenyl) -6-dimethylaminophthalide, 3
-(P-Dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3 , 3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide and other triarylmethane dyes,

Diphenylmethane dyes such as 4,4'-bis (dimethylamino) benzhydryl benzyl ether, N-halophenyl-leuco auramine, and 4,4'-bis (dimethylamino) benzhydryl-p-toluenesulfinic acid ester. , 3,7-bis (diethylamino)
Thiazine-based dyes such as -10-benzoylphenoxazine, benzoylleucomethylene blue, p-nitrobenzoylleucomethylene blue, 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, di-β-
Spiro dyes such as naphthospiropyran and 3-methyl-di-β-naphthospiropyran, lactam dyes such as rhodamine-B-anilinolactam and rhodamine (o-chloroanilino) lactam,

3-diethylamino-6-methylfluorane, 3-dimethylamino-7-methoxyfluorane, 3
-Diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3- (N- Ethyl-p-toluidino) -7-methylfluorane, 3-
Diethylamino-7-diethylaminofluorane, 4-
Benzylamino-8-diethylaminobenzo [a] fluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, 3-dibutylamino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-
N-isoamylamino) -6-methyl-7-phenylaminofluorane, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-phenylaminofluorane, (N-ethyl-N-isobutylamino) ) -6-Methyl-7-phenylaminofluorane, 3-dibutylamino-7- (o-fluorophenylamino) fluorane,
Fluorane such as 2,2′-bis {4- [6 ′-(N-cyclohexyl-N-methylamino) -3′-methylspiro [phthalide-3,9′-xanthene] -2′-ylamino] phenyl} propane Dyes, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'
-Dimethylamino) phthalide, 3-diethylamino-6
Examples thereof include fluorene dyes such as-(N-allyl-N-methylaminofluorene-9-spiro-3 '-(6'-dimethylamino) phthalide, etc. Of course, the dyes are not limited to these dyes, and A combination of two or more dyes is also possible.

Various known colorants can be used as the colorant used in the present invention. Specific examples of such known color formers include the following. 4-tert-butylbenzoic acid, 4-chlorobenzoic acid,
Salicylic acid, 3-isopropylsalicylic acid, 3-phenylsalicylic acid, 3-cyclohexylsalicylic acid, 3,5
-Di-tert-butylsalicylic acid, 3-methyl-5-benzylsalicylic acid, 3-phenyl-5- (α, α-dimethylbenzyl) salicylic acid, 3,5-di- (α-methylbenzyl) salicylic acid, 2-hydroxy -1-benzyl-
Aromatic carboxylic acids such as 3-naphthoic acid; 4,4'-isopropylidenediphenol (bisphenol A), 4,
4'-isopropylidene bis (2-methylphenol), 4,4'-cyclohexylidene bisphenol,
4,4'-Cyclohexylidenebis (2-methylphenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, methyl-4
-Hydroxybenzoate, 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,
2'-dihydroxydiphenyl, 4-hydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-methyl-diphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy- 3 ', 4'-tetramethylene diphenyl sulfone, 2,2'-diallyl-4,
Phenolic compounds such as 4'-dihydroxydiphenyl sulfone; p-phenylphenol-formalin resin,
One or more organic colorants such as phenolic resins such as p-butylphenol-acetylene resin; and further salts of these organic colorants with polyvalent metals such as zinc, aluminum, etc .; of antipyrine complexes of zinc thiocyanate. Such a metal complex compound.

Further, various auxiliaries such as dispersants, UV absorbers such as triazole type, antifoaming agents, fluorescent dyes, coloring dyes and the like can be appropriately added to each layer. Also,
Stearic acid ester wax, polyethylene wax, carnauba wax, microcrystalline wax, carboxy-modified paraffin wax, zinc stearate, calcium stearate, silicone to prevent sticking of the thermosensitive recording medium due to contact with recording equipment or recording head. Oil etc. can also be added. If necessary, kaolin, clay, and kaolin may be added to the extent that transparency is not impaired in order to improve dust adhesion to the recording head.
Pigments such as talc, calcium carbonate, magnesium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine anhydrous silica, and activated clay can also be added.

As the support, paper, synthetic paper, film or the like is used, but a film having excellent transparency is particularly preferable. For example, resin film of polyethylene, polypropylene, polyethylene terephthalate, nylon, polystyrene, polyvinyl chloride or the like. Is mentioned.

As a method of forming each layer, a well-known and publicly-known coating method such as blade coating, bar coating, gravure coating and the like can be appropriately adopted. The drying method is preferably about 40 to 140 ° C. for several seconds to several tens of seconds with a publicly known dryer, and is not particularly limited as long as the heat-sensitive layer does not develop a color.

The coated amount of dye layer and color acceptor layer is not particularly limited, usually 1~12g / m ^2, respectively dry weight, is preferably adjusted in the range of about 2 to 10 g / m ^2. Furthermore,
When the protective layer is provided, the coating amount is not particularly limited, and is usually adjusted to a dry weight of 0.5 to 20 g / m ² , preferably 1 to 10 g / m ² . In addition,
It is of course possible to provide an antistatic layer or a protective layer on the back surface of the support, or to further provide an undercoat layer on the support for the purpose of increasing the recording sensitivity. If necessary, the back surface of the support is appropriately treated with an adhesive. Various known techniques in the field of thermal recording material manufacturing such as the above can be added. In addition, an electron beam curable resin, a UV curable resin or the like may be used for the protective layer.

[0024]

The present invention will be described in more detail by way of the following examples, but the present invention is not limited to these examples. Unless otherwise specified, the parts in the examples represent parts by weight.

Example 1 Preparation of solution A (coating solution for dye layer) 3- (N-ethyl-N-isoamylamino) -6-methyl-7-phenylaminofluorane 15 parts, vinyl chloride-vinyl acetate copolymer 15 And 10 parts of 1,2-bis (3-methylphenoxy) ethane were dissolved in 160 parts of methyl ethyl ketone to obtain a solution A.

Preparation of Liquid B (Coating liquid for sensitizer layer) 1,2-bis (3-methylphenoxy) ethane (melting point:
92 ° C) 20 parts, polystyrene 20 parts, toluene 110
It was dissolved in a part to obtain a liquid B.

Preparation of Solution C (Coating Solution for Coloring Agent Layer) 4-Hydroxy-4′-isopropoxydiphenylsulfone 15 parts, butyral resin 15 parts, ethanol 110
It was dissolved in a part to obtain a liquid C.

Preparation of Liquid D (Coating Liquid for Protective Layer) Butyl Methacrylate-Methyl Methacrylate Copolymer 20
Parts, silicone oil 2 parts, methylcyclohexane 70
It was dissolved in a part to obtain a liquid D.

Production of thermosensitive recording medium Liquid A, liquid B, on a transparent PET film of 80 g / m ²
Liquid C and liquid D were sequentially applied, and the coating amount after drying was 3.0 g /
m ² , 1.5 g / m ² , 3.0 g / m ² , and 2.5
A thermosensitive recording material was obtained by coating and drying so as to be g / m ² .

Example 2 ^On a transparent PET film of 80 g / m ² , C liquid, B liquid,
Liquid A and liquid D were sequentially applied, and the coating amount after drying was 3.0 g /
m ² , 1.5 g / m ² , 3.0 g / m ² , and 2.5
A thermosensitive recording material was obtained by coating and drying so as to be g / m ² .

Example 3 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that bisphenol A was used in place of 4-hydroxy-4'-isopropoxydiphenyl sulfone in the preparation of the liquid C.

Example 4 In solution A of Example 1, 3-di (n-butylamino) -6 was used instead of 3- (N-ethyl-N-isoamylamino) -6-methyl-7-phenylaminofluorane. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that -methyl-7-phenylaminofluorane was used.

Example 5 Preparation of solution F (sensitizer layer coating solution) 50 parts of a 30% dispersion solution of oxalic acid dibenzyl ester (melting point: 80 ° C.) pulverized to an average particle size of 0.6 μm, 20 parts of polyvinyl alcohol % Aqueous solution 50 parts, and water 30
The composition consisting of was mixed and stirred to obtain a liquid F.

Production of Thermal Recording Material A thermal recording material was obtained in the same manner as in Example 1 except that in the production of the thermal recording material of Example 1, the F liquid was used instead of the B liquid.

Example 6 Preparation of G liquid (dye layer coating liquid) 15 parts of 3-di (n-butylamino) -6-methyl-7-phenylaminofluorane, 15 parts of polybutene, 1,2
A composition comprising 10 parts of -bis (3-methylphenoxy) ethane and 160 parts of n-hexane was ground with a sand mill,
Liquid G was obtained.

Production of Thermal Recording Medium A thermal recording medium was obtained in the same manner as in Example 1 except that the liquid G was used in place of the liquid A in the method for manufacturing the thermal recording medium of Example 1.

Comparative Example 1 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that the liquid B (sensitizer layer) was omitted from the production of the thermosensitive recording medium of Example 1.

Comparative Example 2 Example 3 except that dibenzyl terephthalate (melting point: 140 ° C.) was used in place of 1,2-bis (3-methylphenoxy) ethane (melting point: 92 ° C.) in the liquid B of Example 1. A thermal recording material was obtained in the same manner as in 1.

The thermal recording material thus obtained was evaluated as follows, and the results are shown in Table 1. [Transparency] Transparency was measured using a haze meter [Model TC-H IV / Tokyo Denshoku Co., Ltd.]. The smaller the value, the higher the transparency. [Coloring Density] A color was developed by adhering to a hot plate at 80 ° C. and 120 ° C. for 10 seconds, and the coloring density was measured by a transmission densitometer.

[Background Fogging] Fogging was visually evaluated. The evaluation criteria are shown below. [Evaluation Criteria] O: Excellent. X: Inferior

[0041]

[Table 1]

[0042]

The heat-sensitive recording material of the present invention has excellent transparency,
There was little background fog and the recording sensitivity was high.

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[Procedure amendment]

[Submission date] January 10, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title of invention Thermal recording material

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material utilizing a color-developing reaction between a leuco dye and a color-developing agent, and more particularly to a heat-sensitive recording material having excellent transparency, little background fog and high recording sensitivity. is there.

[0002]

2. Description of the Related Art A thermosensitive recording medium is known, in which a color-forming substance is brought into contact with heat to obtain a recorded image by utilizing a color reaction between a colorless or light-colored leuco dye and an organic or inorganic coloring agent. There is. In recent years, with the remarkable progress of the thermal recording system, its fields of application and forms are also diversifying, and not only as a recording medium for a thermal facsimile or a thermal printer, but also as a magnetic thermal recording medium or a POS label or a ticket for which forgery prevention is required. The use for new applications such as cards, prepaid cards, and sealless term is also rapidly increasing.

Further, by increasing the transparency of the thermosensitive recording medium, it can be used as an OHP sheet and an X-ray film. For this purpose, a method of coating a dye and a color developing agent in a solvent system (JP-A-4-239688), a method of making fine particles of a heat-sensitive recording layer composition, and the like have been dealt with. However, a satisfactory transparent heat-sensitive recording material has not been obtained because of fog, insufficient transparency, poor sensitivity, and defects.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording medium which is excellent in transparency, has less background fog and has high recording sensitivity.

[0005]

SUMMARY OF THE INVENTION The present invention comprises:
Dye layer coating liquid containing a leuco dye and an adhesive dissolved in an organic solvent, and a color developing agent layer coating liquid containing a color developing agent and an adhesive dissolved in an organic solvent is applied and dried to obtain a dye. In a thermosensitive recording medium provided with a layer and a color developing agent layer, a sensitizing agent containing a sensitizer having a melting point of 40 to 120 ° C., an adhesive, water or an organic solvent between the dye layer and the color developing agent layer. The above problems have been solved and found by applying a coating solution for the agent layer and drying the solution to provide a sensitizer layer.

[0006]

The present invention comprises a support, a dye layer coating solution containing a leuco dye and an adhesive dissolved in an organic solvent, and a coloring agent and an adhesive dissolved in an organic solvent. In a thermosensitive recording medium in which a dye layer and a color former layer are provided by coating and drying a colorant layer coating liquid, a sensitizer having a melting point of 40 to 120 ° C. and adhesion between the dye layer and the color former layer. Agent, coating a sensitizer layer coating liquid containing water or an organic solvent, characterized by providing a sensitizer layer by drying, excellent transparency by such a configuration,
We have obtained a thermal recording material with low background fog and high recording sensitivity.

By providing a sensitizer layer containing a sensitizer having a melting point of 40 to 120 ° C., a barrier can be formed between the dye layer and the color developing agent layer, and the fog phenomenon can be suppressed. Further, if the melting point of the sensitizer is less than 40 ° C., fog tends to occur during storage, and if it exceeds 120 ° C., the recording sensitivity decreases. The sensitizer is added to the sensitizer layer in an amount of 35 based on the total solid amount.
The content of ˜70% by weight creates a place where the dye and the color developing agent are likely to come into contact with each other, so that a heat-sensitive recording material having high sensitivity can be obtained. If the amount of the sensitizer is less than 35% by weight, the recording sensitivity is lowered, and if it exceeds 70% by weight, the transparency may be lowered. It is also possible to further add a sensitizer to the dye layer or the color developing agent layer.

When the leuco dye, the color former, and the sensitizer contained in each layer are dissolved in an organic solvent, the particles do not scatter and the transparency is remarkably improved. Further, when the sensitizer layer is provided by a coating solution using water as a solvent, the dye layer or the color former layer provided on the sensitizer layer is uniformly applied. Further, even if the leuco dye, the colorant, and the sensitizer are not dissolved in the organic solvent, the constituent particles are often hydrophobic, so that the particles and the binder are well compatible with each other, and by filling the voids, Transparency is improved compared to the case of water system. At that time, when the average particle diameter of the dye, the color former, and the sensitizer is 0.7 μm or less, a heat-sensitive recording material having high transparency can be obtained.

The thermal recording material of the present invention may have a constitution in which a protective layer is provided on the uppermost layer described above, and by providing the protective layer, discoloration or fading due to chemicals or plasticizers is small, and it is excellent in mechanical suitability. This is one of the preferred embodiments because a thermosensitive recording medium can be obtained.

The melting point used in the sensitizer layer is 40 to 120.
Examples of the sensitizer at ° C include caproic acid amide, capric acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, erucic acid amide, linoleic acid amide, linolenic acid amide, N-methylstearic acid amide, and stearic acid. Anilide, N-methyloleic acid amide, benzanilide, linoleic acid anilide, N-ethylcapric acid amide, N-butyllauric acid amide, N
-Octadecylacetamide, N-oleinacetamide, N-oleylbenzamide, N-stearylcyclohexylamide, polyethylene glycol, 1-benzyloxynaphthalene, 2-benzyloxynaphthalene,
1-Hydroxynaphthoic acid phenyl ester, 1,2-
Diphenoxyethane, 1,4-diphenoxybutane,
1,2-bis (3-methylphenoxy) ethane, 1,2
-Bis (4-methoxyphenoxy) ethane, 1-phenoxy-2- (4-chlorophenoxy) ethane, 1-phenoxy-2- (4-methoxyphenoxy) ethane, 1-
(2-Methylphenoxy) -2- (4-methoxyphenoxy) ethane, terephthalic acid dibenzyl ester, oxalic acid dibenzyl ester, oxalic acid di-p-methylbenzyl ester, p-benzyloxybenzoic acid benzyl ester, p- Benzylbiphenyl, 1,5-bis (p-
Methoxyphenoxy) -3-oxa-pentane, 1,4
Examples thereof include compounds such as -bis (2-vinyloxyethoxy) benzene, p-biphenyl p-tolyl ether, and benzyl-p-methylthiophenyl ether.

The coating amount of the sensitizer layer is not particularly limited, and is usually adjusted in the range of about 0.5 to 5 g / m ² , preferably about 1 to 3 g / m ^{2 in} dry weight. When the coating amount of the sensitizer layer is large, the recording sensitivity may be lowered or a clear image may not be obtained.

In the present invention, the organic solvent for dissolving the adhesive in the dye layer and the color developing agent layer is not particularly limited, but for example, benzene, toluene, xylene, cyclohexane, methylcyclohexane, cyclopentane, petroleum ether. , Ethylene, methyl chloride, carbon tetrachloride, chlorobenzene, dichlorobenzene, methanol,
Examples thereof include, but are not limited to, ethanol, propanol, isopropanol, butanol, ethyl ether, isopropyl ester, diethyl acetal, acetone, methyl ethyl ketone, diethyl ketone, ethyl acetate, methyl acetate and methyl propionate. The organic solvent for dissolving each of the leuco dye, the color former, and the sensitizer may be appropriately selected from the above organic solvents and the like. However, when an organic solvent system is used for all layers, it is desirable to sequentially select a solvent that does not dissolve the constituent components of the lower layer.

In each layer, the adhesive used in an organic solvent system is not particularly limited as long as it is a resin soluble in an organic solvent, but a thermoplastic resin is particularly preferably used,
The organic solvent-soluble thermoplastic resin as described above is more preferably used, and specific examples thereof include polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, polybutyl acrylate, polystyrene, and acrylic acid ester.・ Styrene copolymer, polyester resin,
Poly α-methyl styrene, ABS resin, coumarone resin,
Nitrocellulose, ethylene / vinyl acetate copolymer, vinyl chloride
Examples thereof include vinyl acetate copolymer, butyral resin, and the like, but the present invention is not limited to these, and two or more kinds of resins can be used in combination.

When the sensitizer layer is provided from an aqueous coating solution, the adhesive may be starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol,
Acetoacetyl group-modified polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion, urea resin,
Acrylic resin, amide resin, melamine resin, etc. are used.

The amount of the adhesive used is not particularly limited, but is the total solid amount of the coating liquid in any of the recording layer forming coating liquids, that is, organic solvent type and aqueous type. 1 to 90% by weight, preferably 5 to 60% by weight
It is desirable to adjust within the range. When used for the coating liquid for protective layer, it is 5 to the total solid amount of the coating liquid for protective layer.
It is desirable to adjust in the range of 95% by weight, preferably 20 to 95% by weight.

As the colorless or pale leuco dye used in the present invention, various known dyes can be used. Specific examples of these leuco dyes include the following. 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p
-Dimethylaminophenyl) phthalide, 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2)
-Methylphenyl) -6-dimethylaminophthalide, 3
-(P-Dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3 , 3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide and other triarylmethane dyes,

Diphenylmethane dyes such as 4,4'-bis (dimethylamino) benzhydryl benzyl ether, N-halophenyl-leuco auramine, and 4,4'-bis (dimethylamino) benzhydryl-p-toluenesulfinic acid ester. , 3,7-bis (diethylamino)
Thiazine-based dyes such as -10-benzoylphenoxazine, benzoylleucomethylene blue, p-nitrobenzoylleucomethylene blue, 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, di-β-
Spiro dyes such as naphthospiropyran and 3-methyl-di-β-naphthospiropyran, lactam dyes such as rhodamine-B-anilinolactam and rhodamine (o-chloroanilino) lactam,

3-diethylamino-6-methylfluorane, 3-dimethylamino-7-methoxyfluorane, 3
-Diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3- (N- Ethyl-p-toluidino) -7-methylfluorane, 3-
Diethylamino-7-diethylaminofluorane, 4-
Benzylamino-8-diethylaminobenzo [a] fluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, 3-dibutylamino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-
N-isoamylamino) -6-methyl-7-phenylaminofluorane, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-phenylaminofluorane, (N-ethyl-N-isobutylamino) ) -6-Methyl-7-phenylaminofluorane, 3-dibutylamino-7- (o-fluorophenylamino) fluorane,
Fluoran such as 2,2'-bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthene] -2'-ylamino] phenyl} propane Dyes, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'
-Dimethylamino) phthalide, 3-diethylamino-6
Examples thereof include fluorene dyes such as-(N-allyl-N-methylaminofluorene-9-spiro-3 '-(6'-dimethylamino) phthalide, etc. Of course, the dyes are not limited to these dyes, and A combination of two or more dyes is also possible.

Various known colorants can be used as the colorant used in the present invention. Specific examples of such known color formers include the following. 4-tert-butylbenzoic acid, 4-chlorobenzoic acid,
Salicylic acid, 3-isopropylsalicylic acid, 3-phenylsalicylic acid, 3-cyclohexylsalicylic acid, 3,5
-Di-tert-butylsalicylic acid, 3-methyl-5-benzylsalicylic acid, 3-phenyl-5- (α, α-dimethylbenzyl) salicylic acid, 3,5-di- (α-methylbenzyl) salicylic acid, 2-hydroxy -1-benzyl-
Aromatic carboxylic acids such as 3-naphthoic acid; 4,4'-isopropylidenediphenol (bisphenol A), 4,
4'-isopropylidene bis (2-methylphenol), 4,4'-cyclohexylidene bisphenol,
4,4'-Cyclohexylidenebis (2-methylphenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, methyl-4
-Hydroxybenzoate, 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,
2'-dihydroxydiphenyl, 4-hydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-methyl-diphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy- 3 ', 4'-tetramethylene diphenyl sulfone, 2,2'-diallyl-4,
Phenolic compounds such as 4'-dihydroxydiphenyl sulfone; p-phenylphenol-formalin resin,
One or more organic colorants such as phenolic resins such as p-butylphenol-acetylene resin; and further salts of these organic colorants with polyvalent metals such as zinc, aluminum, etc .; of antipyrine complexes of zinc thiocyanate. Such a metal complex compound.

Further, various auxiliaries such as dispersants, UV absorbers such as triazole type, antifoaming agents, fluorescent dyes, coloring dyes and the like can be appropriately added to each layer. Also,
Stearic acid ester wax, polyethylene wax, carnauba wax, microcrystalline wax, carboxy-modified paraffin wax, zinc stearate, calcium stearate, silicone to prevent sticking of the thermosensitive recording medium due to contact with recording equipment or recording head. Oil etc. can also be added. If necessary, kaolin, clay, and kaolin may be added to the extent that transparency is not impaired in order to improve dust adhesion to the recording head.
Pigments such as talc, calcium carbonate, magnesium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine anhydrous silica, and activated clay can also be added.

As the support, paper, synthetic paper, film or the like is used, but a film having excellent transparency is particularly preferable. For example, resin film of polyethylene, polypropylene, polyethylene terephthalate, nylon, polystyrene, polyvinyl chloride or the like. Is mentioned.

As a method of forming each layer, a well-known and publicly-known coating method such as blade coating, bar coating, gravure coating and the like can be appropriately adopted. The drying method is preferably about 40 to 140 ° C. for several seconds to several tens of seconds with a publicly-known dryer, and is not particularly limited as long as the dye layer does not develop color.

The coated amount of dye layer and color acceptor layer is not particularly limited, usually 1~12g / m ^2, respectively dry weight, is preferably adjusted in the range of about 2 to 10 g / m ^2. Furthermore,
When the protective layer is provided, the coating amount is not particularly limited, and is usually adjusted to a dry weight of 0.5 to 20 g / m ² , preferably 1 to 10 g / m ² . In addition,
It is of course possible to provide an antistatic layer or a protective layer on the back surface of the support, or to further provide an undercoat layer on the support for the purpose of increasing the recording sensitivity. If necessary, the back surface of the support is appropriately treated with an adhesive. Various known techniques in the field of thermal recording material manufacturing such as the above can be added. In addition, an electron beam curable resin, a UV curable resin or the like may be used for the protective layer.

[0024]

The present invention will be described in more detail by way of the following examples, but the present invention is not limited to these examples. Unless otherwise specified, the parts in the examples represent parts by weight.

Example 1 Preparation of solution A (coating solution for dye layer) 3- (N-ethyl-N-isoamylamino) -6-methyl-7-phenylaminofluorane 15 parts, vinyl chloride-vinyl acetate copolymer 15 And 10 parts of 1,2-bis (3-methylphenoxy) ethane were dissolved in 160 parts of methyl ethyl ketone to obtain a solution A.

Preparation of Liquid B (Coating liquid for sensitizer layer) 1,2-bis (3-methylphenoxy) ethane (melting point:
92 ° C) 20 parts, polystyrene 20 parts, toluene 110
It was dissolved in a part to obtain a liquid B.

Preparation of Solution C (Coating Solution for Coloring Agent Layer) 4-Hydroxy-4′-isopropoxydiphenylsulfone 15 parts, butyral resin 15 parts, ethanol 110
It was dissolved in a part to obtain a liquid C.

Preparation of Liquid D (Coating Liquid for Protective Layer) Butyl Methacrylate-Methyl Methacrylate Copolymer 20
Parts, silicone oil 2 parts, methylcyclohexane 70
It was dissolved in a part to obtain a liquid D.

Production of thermosensitive recording medium Liquid A, liquid B, on a transparent PET film of 80 g / m ²
Liquid C and liquid D were sequentially applied, and the coating amount after drying was 3.0 g /
m ² , 1.5 g / m ² , 3.0 g / m ² , and 2.5
A thermosensitive recording material was obtained by coating and drying so as to be g / m ² .

Example 2 ^On a transparent PET film of 80 g / m ² , C liquid, B liquid,
Liquid A and liquid D were sequentially applied, and the coating amount after drying was 3.0 g /
m ² , 1.5 g / m ² , 3.0 g / m ² , and 2.5
A thermosensitive recording material was obtained by coating and drying so as to be g / m ² .

Example 3 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that bisphenol A was used in place of 4-hydroxy-4'-isopropoxydiphenyl sulfone in the preparation of the liquid C.

Example 4 In solution A of Example 1, 3-di (n-butylamino) -6 was used instead of 3- (N-ethyl-N-isoamylamino) -6-methyl-7-phenylaminofluorane. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that -methyl-7-phenylaminofluorane was used.

Example 5 Preparation of solution F (sensitizer layer coating solution) 50 parts of a 30% dispersion solution of oxalic acid dibenzyl ester (melting point: 80 ° C.) pulverized to an average particle size of 0.6 μm, 20 parts of polyvinyl alcohol % Aqueous solution 50 parts, and water 30
The composition consisting of was mixed and stirred to obtain a liquid F.

Production of Thermal Recording Material A thermal recording material was obtained in the same manner as in Example 1 except that in the production of the thermal recording material of Example 1, the F liquid was used instead of the B liquid.

Example 6 Preparation of G liquid (dye layer coating liquid) 15 parts of 3-di (n-butylamino) -6-methyl-7-phenylaminofluorane, 15 parts of polybutene, 1,2
A composition consisting of 10 parts of -bis (3-methylphenoxy) ethane and 160 parts of n-hexane was ground with a sand mill,
Liquid G was obtained.

Production of Thermal Recording Medium A thermal recording medium was obtained in the same manner as in Example 1 except that the liquid G was used in place of the liquid A in the production of the thermal recording medium of Example 1.

Comparative Example 1 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that the liquid B (sensitizer layer) was omitted from the production of the thermosensitive recording medium of Example 1.

Comparative Example 2 Example 3 except that dibenzyl terephthalate (melting point: 140 ° C.) was used in place of 1,2-bis (3-methylphenoxy) ethane (melting point: 92 ° C.) in the liquid B of Example 1. A thermal recording material was obtained in the same manner as in 1.

The thermal recording material thus obtained was evaluated as follows, and the results are shown in Table 1. [Transparency] Transparency was measured using a haze meter [Model TC-H IV / Tokyo Denshoku Co., Ltd.]. The smaller the value, the higher the transparency. [Coloring Density] A color was developed by adhering to a hot plate at 80 ° C. and 120 ° C. for 10 seconds, and the coloring density was measured by a transmission densitometer.

[Background Fogging] Fogging was visually evaluated. The evaluation criteria are shown below. [Evaluation Criteria] O: Excellent. X: Inferior

[0041]

[Table 1]

[0042]

The heat-sensitive recording material of the present invention has excellent transparency,
There was little background fog and the recording sensitivity was high.

Claims (3)

[Claims] 1. A dye layer coating liquid containing a leuco dye and an adhesive dissolved in an organic solvent on a support, and a color developing agent containing a color developing agent and an adhesive dissolved in an organic solvent. A thermosensitive recording medium having a dye layer and a color-developing layer formed by applying a layer coating solution and drying the layer has a melting point of 40 or less between the dye layer and the color-developing layer.
A heat-sensitive recording material, characterized in that a sensitizer layer coating solution containing a sensitizer, an adhesive, water or an organic solvent at 120 ° C. is applied and dried to provide a sensitizer layer. 2. The heat-sensitive recording material according to claim 1, wherein the leuco dye, the color former and the sensitizer are each dissolved in an organic solvent. 3. The heat-sensitive recording according to claim 1, wherein the sensitizer layer contains 35 to 70% by weight of a sensitizer having a melting point of 40 to 120 ° C. with respect to the total solid amount of the sensitizer layer. body.