JPH0872407A - Production of thermal recording material - Google Patents

Abstract

PURPOSE: To produce a thermal recording material excellent in transparency, reduced in background fog and having high recording sensitivity. CONSTITUTION: A thermal recording material is produced by coating a support with a dye layer coating soln. prepared by dissolving a leuco dye and an adhesive in an org. solvent A and drying the coated support to form a dye layer and applying a coupler layer coating soln. prepared by dissolving a coupler and an adhesive in an org. solvent B to the dye layer and drying the coating layer to form a coupler layer.

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-forming reaction between a leuco dye and a coloring agent, and more particularly to a method for producing a heat-sensitive recording material having a heat-sensitive recording layer having excellent transparency.

[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 method for producing 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:
An organic solution which does not dissolve the leuco dye, and which is coated with a dye layer coating liquid containing an organic solvent A that dissolves the leuco dye and the adhesive, and dried to form a dye layer, on which the colorant and the adhesive are dissolved. The above problems have been solved and found by applying a colorant layer coating solution containing the solvent B and drying the solution to form a colorant layer.

[0006]

For example, a dye layer coating liquid containing an organic solvent A which dissolves a leuco dye and an adhesive on a support, and an organic solvent B (which dissolves a color former and an adhesive and does not dissolve a leuco dye) When a leuco dye dissolves in the organic solvent B when a dye layer and a colorant layer are provided by coating and drying a colorant layer coating solution containing 5 g / 100 ml or less of solubility at room temperature),
Since a color development layer is formed on the dye layer and color is developed (background fog) at the same time, it is necessary to provide a barrier layer between the dye layer and the color development layer, and as a result, recording sensitivity and transparency are reduced. To do

According to the present invention, since the solvent in the coating liquid for forming each layer dissolves the constituent components, there is no irregular reflection of light by the particles, so that a highly transparent thermal recording medium can be obtained. Further, by using an organic solvent which does not dissolve the color-forming component of the undercoat layer in the upper layer, the background fog hardly occurs. Further, in order to improve the background fog, it is desirable to sufficiently dry the previously formed layer and reduce the residual solvent.

The thermosensitive recording medium obtained by the production method of the present invention may be provided with a protective layer on the uppermost layer, and by providing the protective layer, discoloration or fading due to chemicals or plasticizers may occur. This is one of the preferred embodiments because a body having a small number and excellent mechanical suitability can be obtained.

The organic solvent used in the present invention is not particularly limited. For example, when the dye layer is provided before the color developing agent layer, the organic solvent A used in the dye layer coating liquid is used.
An organic solvent that dissolves the leuco dye and the adhesive is used as the organic solvent B used in the colorant layer coating liquid. An organic solvent that dissolves the colorant and the adhesive and does not dissolve the leuco dye is used. If As such an organic solvent, for example, hydrocarbons, halogenated hydrocarbons, alcohols, ethers, acetals, ketones, esters are used alone or as a mixed organic solvent.

Specific examples of the hydrocarbons include benzene, toluene, xylene, cyclohexane, methylcyclohexane, cyclopentane, petroleum ether, ethylene and naphthalene, and specific examples of the halogenated hydrocarbons include chloroform. , Methyl chloride, carbon tetrachloride, chlorobenzene, dichlorobenzene and the like, specific examples of alcohols include, for example, methanol, ethanol, propanol, isopropanol, butanol and the like, and specific examples of ethers include, for example, ethyl ether, isopopyropene. Specific examples of acetals such as ruether and the like include, for example, diethyl acetal, and specific examples of ketones include, for example, acetone, methyl ethyl ketone,
Specific examples of the esters such as diethyl ketone include ethyl acetate, methyl acetate, methyl propionate, etc., but are not limited to these.
For example, specific examples of the organic solvent A include benzene, toluene, xylene, methyl ethyl ketone and the like.
Specific examples of the organic solvent B include methanol, ethanol,
Examples include propanol, isopropanol, butanol and the like.

In the present invention, the adhesive used for each layer is not particularly limited as long as it is a resin soluble in an organic solvent, but a thermoplastic resin is particularly preferably used, and the adhesive can be used in the organic solvent as described above. A soluble thermoplastic resin is more preferably used, and specific examples thereof include polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, polybutyl acrylate, polystyrene, acrylic ester / styrene copolymer, polyester resin, Examples thereof include poly α-methylstyrene, ABS resin, coumarone resin, nitrocellulose, and ethylene / vinyl acetate copolymer, but of course, the present invention is not limited to these, and two or more kinds of resins can be used in combination.

The amount of the adhesive used in each layer is not particularly limited, but is adjusted within the range of 1 to 90% by weight, preferably 5 to 60% by weight based on the total solid amount of the coating liquid. It is desirable to do.

Various known dyes can be used as the colorless or pale leuco dye used in the present invention. 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) benzhydrylbenzyl ether, N-halophenyl-leukoauramine, 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.

As the color former used in the present invention, various known color formers can be used. 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, in the heat-sensitive recording material of the present invention, in order to obtain high-speed recording property, it is desirable to use various heat-fusible substances as a recording sensitivity improving agent. Examples of such a heat-fusible substance 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 stearin. Acid anilide, N-methyl oleic 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.

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. Further, stearic acid ester wax, polyethylene wax, carnauba wax, microcrystalline wax, carboxy-modified paraffin wax, zinc stearate, calcium stearate, silicone oil are used to prevent the thermal recording material from sticking due to contact with recording equipment or recording head. Etc. can also be added. If necessary, kaolin, clay, talc, calcium carbonate, magnesium carbonate, calcined clay, titanium oxide, to the extent that transparency is not impaired in order to improve dust adhesion to the recording head,
It is also possible to add pigments such as diatomaceous earth, fine anhydrous silica and activated clay.

As the support, paper, plastic film, synthetic paper, woven fabric molding, etc. are used.
Especially excellent transparency polyethylene, polypropylene, polyethylene terephthalate, nylon, polystyrene,
A resin film such as polyvinyl chloride is preferably used.

In the present invention, the support is not necessarily a colorless and transparent body, but is, for example, an opaque body that is colored or has an image, and is used as a heat-sensitive recording body that makes the best use of the condition of the base. It is also effective when doing.

As the method for forming the heat-sensitive recording layer and the protective layer,
Known publicly known coating methods such as blade coating, bar coating, and gravure coating can be appropriately adopted.

The dye layer, the coating amount of the color developer 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. Further, when a 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 about 1 to 10 g / m ² . Incidentally, it is of course possible to provide an antistatic layer or an EB 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. Various well-known techniques in the field of producing a thermal recording material, such as applying a coating, can be added.

[0023]

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 Dye Layer Coating Liquid 3- (N-Ethyl-N-isoamylamino) -6-methyl-7-phenylaminofluorane 15 parts, vinyl chloride-vinyl acetate copolymer 15 parts, 1, A composition consisting of 10 parts of 2-bis (3-methylphenoxy) ethane was dissolved in 60 parts of methyl ethyl ketone to obtain a coating liquid.

Preparation of Coloring Agent Layer Coating Liquid A composition liquid consisting of 15 parts of 4-hydroxy-4′-isopropoxydiphenyl sulfone and 15 parts of butyral resin was dissolved in 70 parts of ethanol to obtain a coating liquid.

Production of thermal recording material A dye PET coating liquid and a color developer layer coating liquid were applied on a transparent PET film of 75 g / m ^{2 so} that both of them would have a dry weight of 4.0 g / m ^2, and dried. A dye layer and a coloring agent layer were sequentially provided to obtain a heat-sensitive recording material.

Example 2 On the color former layer obtained in Example 1, as a protective layer, the following protective layer coating liquid was applied onto the heat-sensitive recording layer at a rate of 3 g / m ² , dried and protected. A thermosensitive recording medium having layers was obtained. Preparation of protective layer coating liquid 30 parts of butyl methacrylate-methyl methacrylate copolymer, 10 parts of silicone oil, and 60 parts of methylcyclohexane were mixed and stirred to obtain a protective layer coating liquid.

Example 3 Preparation of Coloring Agent Layer Coating Liquid 4-Hydroxy-4'-isopropoxydiphenylsulfone 15 parts, vinyl chloride-vinyl acetate copolymer 15 parts, 1,2-bis (3-methylphenoxy) ethane A composition consisting of 10 parts was dissolved in 60 parts of methyl ethyl ketone to obtain a coating liquid.

Preparation of Dye Layer Coating Liquid 3- (N-Ethyl-N-isoamylamino) -6-methyl-7-phenylaminofluorane 15 parts and polybutyl methacrylate 15 parts in a composition of 70 parts toluene. It melt | dissolved and the coating liquid was obtained.

Production of thermal recording material A coating liquid for coloring agent layer and a coating liquid for dye layer were applied on a transparent PET film of 75 g / m ^{2 so} that both of them would have a dry weight of 4.0 g / m ^2, and dried. A color former layer and a dye layer were sequentially provided to obtain a thermosensitive recording medium.

Comparative Example 1 Preparation of coating liquid for heat-sensitive recording layer 4-hydroxy-treated by pulverization to an average particle size of 1 μm
50 parts of a 30% aqueous dispersion of 4'-isopropoxydiphenyl sulfone, the average particle size of which was pulverized to 0.8 μm 3-
(N-ethyl-N-isoamylamino) -6-methyl-
30% aqueous dispersion of 7-phenylaminofluorane 50
Parts, 30 parts of a styrene-butadiene copolymer emulsion (solid concentration 50%), 33 parts of a 30% aqueous dispersion of 1,2-bis (3-methylphenoxy) ethane crushed to an average particle size of 0.8 μm. , 70 parts of water were mixed and stirred to obtain a coating liquid.

Production of thermal recording material A transparent PET film of 75 g / m ² having a dry weight of 4.0
The thermosensitive recording layer coating liquid was applied so as to be g / m ² and dried to obtain a thermosensitive recording material.

Comparative Example 2 Preparation of Coloring Agent Layer Coating Liquid 4-Hydroxy-4'-isopropoxydiphenylsulfone 15 parts, styrene-ethyl acrylate copolymer 10
Part of the composition was dissolved in 75 parts of toluene to obtain a coating liquid.

Preparation of Dye Layer Coating Liquid 30% aqueous dispersion of 3- (N-ethyl-N-isoamylamino) -6-methyl-7-phenylaminofluorane pulverized to an average particle size of 0.5 μm 50 parts, styrene-butadiene copolymer emulsion 1,2-bis (3
-Methylphenoxy) ethane (solid concentration 50%) 30
Parts, a composition consisting of 33 parts of a 30% aqueous dispersion pulverized to an average particle size of 0.5 μm and 70 parts of water was mixed and stirred to obtain a coating liquid.

Production of Thermosensitive Recording Material A coating solution for coloring agent layer and a coating solution for dye layer were applied on a transparent PET film of 75 g / m ^{2 so} that both of them would have a dry weight of 4.0 g / m ^2, and dried. A color former layer and a dye layer were sequentially provided to obtain a thermosensitive recording medium.

Comparative Example 3 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that methyl ethyl ketone was used in place of ethanol in the preparation of the coloring agent layer coating liquid of Example 1.

Comparative Example 4 A thermosensitive recording medium was obtained in the same manner as in Example 2 except that tetrahydrofuran was used instead of toluene in the preparation of the dye layer coating liquid of Example 3.

The heat-sensitive recording material thus obtained was subjected to the following evaluation tests, and the results are shown in Table 1. [Transparency] Transparency was measured with a haze meter [Model TC-H IV / Tokyo Denshoku Co., Ltd.]. The smaller the value, the higher the transparency. [Coloring Density] A 110 ° C. hot plate was brought into close contact with the plate for 10 seconds to develop color, and the coloring density was measured with a transmission densitometer [DM-500 type, manufactured by Screen Co.].

[Background Fog] and [OHP Suitability] Fog and OHP suitability were visually determined. The evaluation criteria are shown below. [Evaluation Criteria] O: Excellent. Δ: Slightly inferior X: Inferior

[0040]

[Table 1]

[0041]

As is apparent from the results shown in Table 1, the thermosensitive recording medium obtained by the production method of the present invention has high transparency and is excellent in practicality.

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[Procedure amendment]

[Submission date] April 4, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

[0005]

SUMMARY OF THE INVENTION The present invention comprises:
An organic solution which does not dissolve the leuco dye, and which is coated with a dye layer coating liquid containing an organic solvent A that dissolves the leuco dye and the adhesive, and dried to form a dye layer, on which the colorant and the adhesive are dissolved. A leuco dye layer is provided by coating and drying a colorant layer coating liquid containing the solvent B, or a colorant and an adhesive are dissolved.
Coloring agent layer coating liquid containing organic solvent B is applied and dried
Is provided, the leuco dye and the adhesive are dissolved on it, and
Apply the dye layer coating liquid containing the organic solvent A that does not dissolve the coloring agent.
The above problems have been solved and found by providing a dye layer by drying the cloth .

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

The organic solvent used in the present invention is not particularly limited, but when the dye layer is provided prior to the color developing agent layer, for example, the organic solvent A used in the dye layer coating liquid is used.
An organic solvent that dissolves the leuco dye and the adhesive is used as the organic solvent B used for the colorant layer coating liquid, and an organic solvent that dissolves the colorant and the adhesive and does not dissolve the leuco dye. If In addition, the coloring agent layer is a dye
When it is provided before the layer, it may be used in the coloring agent layer coating liquid.
As the machine solvent B, an organic solvent that is used as an adhesive with a color developing agent is used.
The organic solvent A used for the dye layer coating liquid is
Dissolve the iko dye and the adhesive, and do not dissolve the coloring agent.
Any organic solvent will do. As such an organic solvent , hydrocarbons, halogenated hydrocarbons, alcohols, ethers, acetals, ketones, esters are used alone or as a mixed organic solvent .

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

In the present invention, the adhesive used for each layer is not particularly limited as long as it is a resin soluble in an organic solvent , but a thermoplastic resin is particularly preferably used and can be applied to the organic solvent as described above. Soluble thermoplastic resins are more preferably used, and specific examples thereof include polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, polybutyl acrylate, polystyrene, acrylate / styrene copolymers, polyester resins, poly Examples thereof include α-methylstyrene, ABS resin, coumarone resin, nitrocellulose, and ethylene / vinyl acetate copolymer, but the present invention is not limited to these and two or more kinds of resins can be used in combination.

Claims (2)

[Claims] 1. A dye layer coating liquid containing an organic solvent A capable of dissolving a leuco dye and an adhesive is applied on a support and dried to form a dye layer, on which a color former and an adhesive are provided. A method for producing a thermosensitive recording medium, which comprises applying a colorant layer coating liquid containing an organic solvent B which dissolves and does not dissolve a leuco dye, and which is dried to form a colorant layer. 2. A colorant layer coating solution containing an organic solvent C capable of dissolving a colorant and an adhesive is applied on a support and dried to form a colorant layer, on which a leuco dye and A method for producing a heat-sensitive recording material, which comprises applying a dye layer coating solution containing an organic solvent D which dissolves an adhesive and does not dissolve a color developing agent, and drying to form a dye layer.