JP2001026182A - Heat-sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive recording material excellent in thermal responsiveness and storage stability of image part. SOLUTION: In a heat-sensitive recording material including a normally colorless or pale-colored electron donable dye precursor and an electron acceptable compound, which develops color in the dye precursor through a reaction under heat, the amine salt of a diphenylsulfone derivative is included in a heat- sensitive recording layer. As the diphenylsulfone derivative, a 4, 4'- dihydroxydiphenylsulfone is employed. Further, the amine salt of the diphenylsulfone derivative and the diphenylsulfone derivative are included in the heat-sensitive recording layer. Further, a hydroxybenzoic acid derivative is added to the heat-sensitive recording layer made of the heat-sensitive recording material.

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, and more particularly to a heat-sensitive recording material having excellent heat responsiveness and storage stability of an image portion and a background portion.

[0002]

2. Description of the Related Art A thermosensitive recording material generally comprises a support provided with a thermosensitive recording layer mainly composed of an electron-donating, usually colorless or pale-colored dye precursor, and an electron-accepting developer. Yes, by heating with a thermal head, a hot pen, a laser beam or the like, the dye precursor and the developer react instantaneously to obtain a recorded image. Japanese Patent Publication Nos. 43-4160 and 45-14039 It is disclosed in gazettes and the like.
Such a heat-sensitive recording material has the advantages that recording can be obtained with a relatively simple device, easy maintenance, no generation of noise, etc., a measurement recorder, a facsimile, a printer, a computer terminal, It is used in a wide range of fields, such as label and ticket vending machines.

In recent years, in particular, heat-sensitive recording materials have been used for financial-related recording paper, such as receipts for gas, water, and electricity bills, financial institution ATM usage statements, and various receipts.

[0004] As the applications and demands of the heat-sensitive recording material are expanding in various ways, high heat responsiveness is required.

However, the heat-sensitive recording material obtains a recorded image by heating, and when high sensitivity, that is, thermal responsiveness is realized, when exposed to high temperature and / or high humidity conditions for a long time, There are disadvantages that the recorded image is deteriorated and the discoloration of the uncolored portion, that is, the background fog is increased. Due to the deterioration of the recorded image and the background fog, the contrast between the image portion and the background is lost. Therefore, development of a heat-sensitive recording material having high heat responsiveness, low color fog, low background fog, and excellent image storage stability is desired.

Means for improving the storage stability of the image area include:
As the electron accepting compound, an alkyl group, an aralkyl group,
A heat-sensitive recording material using a salicylic acid derivative having a substituent such as an alkyloxy group or an acyl group, or a metal salt thereof has been proposed. (JP-A-62-169681, JP-A-63-22683, JP-A-63-95977, etc.)

However, it cannot be said that the salicylic acid derivative described in the publication is still sufficient to improve the storage stability of the image area, and furthermore, the thermal response is low, and practical high-speed recording is not possible. The corresponding thermosensitive recording material was hard to say.

On the other hand, a sensitizer is added as needed to improve the thermal response. When the sensitizer itself is melted by the transferred thermal energy, the sensitizer has a function of dissolving or enclosing the nearby dye precursor and the color developer or accelerating the color forming reaction. Increasing the responsiveness, or the compatibility with the dye precursor and the color developer, is also one means for increasing the sensitivity of the heat-sensitive recording material.

As this means, waxes are disclosed in JP-A-48-19231, JP-A-49-34842, JP-A-50-149353, and JP-A-52-1.
JP-A-06746 and JP-A-53-56364 disclose nitrogen-containing compounds and carboxylic acid esters, and JP-A-57-64593 and JP-A-58-87094 disclose naphthol derivatives. JP-A-57-64592, JP-A-57-185187, JP-A-57-185187
In Japanese Patent Application Laid-Open Nos. 191089 and 58-110289, naphthoic acid derivatives are disclosed in Japanese Patent Application Laid-Open Nos. 57-148688, 57-182483, and 58-108.
Japanese Patent Application Laid-Open Nos. 112788 and 58-162379 disclose benzoate derivatives.
No. 93 discloses parabenzylbiphenyl, which is disclosed in
JP-A-56588 discloses an example in which diphenoxyethanes are added. However, even in the heat-sensitive recording materials produced by these disclosed methods, the color density and the thermal response are still insufficient.

[0010] The inventors of the present invention have proposed that a specific diphenylsulfone derivative is previously contained in a heat-sensitive recording layer to thereby provide high heat responsiveness, low background fog while having a high color density, and storage stability of an image. A method for obtaining a thermosensitive recording material having excellent heat resistance was proposed. However, in reality, higher thermal responsiveness is being demanded.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material which is particularly excellent in thermal response and storage stability of an image area.

[0012]

Means for Solving the Problems As a result of intensive studies, the present inventors have invented a heat-sensitive recording material of the present invention which can solve the problems. That is, the heat-sensitive recording material of the present invention is a heat-sensitive recording material comprising a support on a support, which is usually a colorless or pale-color dye-donating dye, and an electron-accepting compound which reacts when heated to form the dye precursor. A heat-sensitive recording material provided with a recording layer, characterized in that the electron-accepting compound contains an amine salt of a diphenylsulfone derivative.

Further, the heat-sensitive recording material of the present invention is a heat-sensitive recording material characterized in that the amine salt of the diphenylsulfone derivative is a compound represented by the general formula 1.

Embedded image (In the formula 1, R1 and R2 may be the same or different substituents, and represent a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aralkyl group, or an aryl group, and n , M represents an integer of 1 to 4, and R3, R4, and R5 may be the same or different, and each may be a hydrogen atom, an alkyl group, an alkenyl group, an aralkyl group, Alternatively, it represents an aryl group.)

Further, in the heat-sensitive recording material of the present invention, the diphenylsulfone derivative used for the amine salt of the diphenylsulfone derivative represented by the above general formula 1 is 4,4'-
A thermosensitive recording material characterized by being dihydroxydiphenyl sulfone.

Further, the heat-sensitive recording material of the present invention comprises an electron-donating, usually colorless or pale-colored dye precursor on a support, and an electron-accepting compound which reacts upon heating to form the dye precursor. A heat-sensitive recording material provided with a heat-sensitive recording layer, which comprises an amine salt of a diphenylsulfone derivative represented by the general formula 1 and a diphenylsulfone derivative represented by the general formula 2.

Embedded image (In the formula 1, R6 and R7 may be the same or different substituents, and each represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aralkyl group, or an aryl group; , Q each represent an integer of 1 to 4.)

The heat-sensitive recording material of the present invention comprises an electron-donating, usually colorless or light-colored dye precursor on a support, and an electron-accepting compound which reacts upon heating to form the dye precursor. A heat-sensitive recording material provided with a heat-sensitive recording layer containing an amine salt of a diphenylsulfone derivative represented by the general formula 1 and a hydroxybenzoic acid derivative.

The heat-sensitive recording material of the present invention comprises an electron-donating, usually colorless or pale-colored dye precursor on a support, and an electron-accepting compound which reacts upon heating to form the dye precursor. A heat-sensitive recording material provided with a heat-sensitive recording layer, comprising: an amine salt of a diphenylsulfone derivative represented by the general formula 1, a diphenylsulfone derivative represented by the general formula 2, and a hydroxybenzoic acid derivative. It is a recording material.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The contents of the present invention will be described more specifically. Constituting the heat-sensitive recording layer of the heat-sensitive recording material of the present invention,
As the electron-accepting compound that forms a color of the dye precursor, an amine salt of a diphenylsulfone derivative is used, and preferably, a compound represented by the general formula 1 is used.

Embedded image (In the formula 1, R1 and R2 may be the same or different substituents, and represent a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aralkyl group, or an aryl group, and n , M represents an integer of 1 to 4, and R3, R4, and R5 may be the same or different, and each may be a hydrogen atom, an alkyl group, an alkenyl group, an aralkyl group, Alternatively, it represents an aryl group.)

Specific examples of the amine salt of the diphenylsulfone derivative include 4,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, and 4-hydroxy-4'-n-propoxydiphenylsulfone. , 2,4'-dihydroxydiphenylsulfone, 4-hydroxydiphenylsulfone, 4
-Hydroxy-4'-methyldiphenylsulfone, 4-
Hydroxy-4′-methoxydiphenylsulfone, 4-
Hydroxy-4′-ethoxydiphenylsulfone, 4-
Hydroxy-4′-n-butoxydiphenyl sulfone,
4-hydroxy-4'-benzyloxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, bis (3,5-dibromo-4-hydroxyphenyl) sulfone, bis (3,5-dichloro-4-) (Hydroxyphenyl) sulfone, 3,4-dihydroxydiphenyl sulfone, 3,4-dihydroxy-4′-methyldiphenyl sulfone, 3,4,4′-trihydroxydiphenyl sulfone, 3,4,3 ′, 4′-tetrahydroxy Examples thereof include amine salts such as diphenylsulfone, 2,3,4-trihydroxydiphenylsulfone, and 3-phenylsulfonyl-4-hydroxydiphenylsulfone, but are not limited thereto. The amine salt of the diphenylsulfone derivative can be used alone or as a mixture of two or more as necessary.

Specific examples of amine salts include butylamine, hexylamine, octylamine, decylamine, dodecylamine (laurylamine), tetradecylamine, octadecylamine, 2-ethylhexylamine, benzylamine, cyclohexylamine, dibutylamine , Dicyclohexylamine, hexanediamine,
Examples include, but are not limited to, amines such as isophorone diamine. Among these, when an aliphatic amine is used, the effect of improving the thermal responsiveness tends to be large, and thus, a linear aliphatic amine is particularly preferable.

As compared with the case where a diphenylsulfone derivative is used as the electron-accepting compound for forming a color of the dye precursor, the use of the amine salt of the diphenylsulfone derivative according to the present invention significantly improves the thermal response. This is considered to be the result of lowering the melting point by converting the diphenyl sulfone derivative into an amine salt.

By employing an amine salt of 4,4'-dihydroxydiphenylsulfone as an amine salt of the diphenylsulfone derivative, the storage stability of the image area, particularly the heat storage stability, is lower than in other cases. Is preferable since it becomes possible to obtain a heat-sensitive recording material having improved.

Further, in the present invention, by adding the diphenyl sulfone derivative represented by the general formula 2 together with the amine salt of the diphenyl sulfone derivative represented by the general formula 1, the saturation concentration is improved in addition to the thermal responsiveness. .

Embedded image (In the formula 1, R6 and R7 may be the same or different substituents, and each represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aralkyl group, or an aryl group; , Q each represent an integer of 1 to 4.)

Specific examples of diphenylsulfone derivatives include 4,4'-dihydroxydiphenylsulfone,
4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4'-n-propoxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone , 4-hydroxy-4'-methoxydiphenylsulfone, 4-hydroxy-4'-ethoxydiphenylsulfone, 4-hydroxy-4'-n-butoxydiphenylsulfone, 4-hydroxy-4'-benzyloxydiphenylsulfone, bis ( 3-allyl-4-hydroxyphenyl) sulfone, bis (3,5-dibromo-4-hydroxyphenyl) sulfone, bis (3,5-dichloro-4-hydroxyphenyl) sulfone, 3,4-dihydroxydiphenyl sulfone, 3 , 4-dihydroxy- '-Methyldiphenylsulfone, 3,4,4'-trihydroxydiphenylsulfone, 3,4,3', 4'-tetrahydroxydiphenylsulfone, 2,3,4-trihydroxydiphenylsulfone, 3-phenylsulfonyl-4 -Hydroxydiphenylsulfone and the like, but are not limited thereto. These diphenylsulfone derivatives can be used alone or as a mixture of two or more, if necessary.

When the amine salt of the diphenylsulfone derivative and the diphenylsulfone derivative are used together in the heat-sensitive recording material of the present invention, the content ratio by weight of each is preferably in the range of 1: 1 to 1:10. When the amount of the diphenylsulfone derivative is smaller than the amount of the amine salt of the diphenylsulfone derivative, the improvement in the saturation concentration is small. Conversely, when the amount exceeds 10 times the amount of the amine salt of the diphenylsulfone derivative, the effect of improving the thermal responsiveness is reduced.

In the heat-sensitive recording material of the present invention, the hydroxybenzoic acid derivative is added to the heat-sensitive recording layer of the heat-sensitive recording material, wherein the amine salt of the diphenylsulfone derivative is a compound represented by the above general formula 1. By adding the compound, it becomes possible to obtain a heat-sensitive recording material exhibiting higher thermal responsiveness and further having excellent storage stability of the image area against temperature and humidity.

In the heat-sensitive recording material of the present invention, the general formula 1
In the heat-sensitive recording layer of a heat-sensitive recording material, characterized by containing an amine salt of a diphenylsulfone derivative represented by
By adding a hydroxybenzoic acid derivative, it is possible to obtain a thermosensitive recording material that exhibits higher thermal responsiveness and greater improvement in saturation concentration, and furthermore has excellent storage stability of the image area against temperature and humidity. Becomes

Specific examples of hydroxybenzoic acid derivatives include ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, butyl 4-hydroxybenzoate,
Benzyl 4-hydroxybenzoate and the like can be mentioned, and these can be used alone or in combination of two or more. Among them, particularly, when benzyl 4-hydroxybenzoate is used, the thermal responsiveness and the saturation concentration are very good, the fogging of the background portion is small, and the quality characteristics such as the storage stability of the image portion are improved. Is preferred because a good heat-sensitive recording material can be obtained.

In the present invention, when the hydroxybenzoic acid derivative is added to the heat-sensitive recording layer, the amount of the amine salt of the diphenylsulfone derivative and the amount of the hydroxybenzoic acid derivative, or the amount of the hydroxybenzoic acid derivative and the diphenylsulfone derivative are combined. The weight ratio of the content to the added amount is preferably in the range of 1: 1 to 1:10. When the total amount of hydroxybenzoic acid or the hydroxybenzoic acid derivative and the diphenylsulfone derivative is smaller than the amount of the amine salt of the diphenylsulfone derivative, the effect of improving the saturation concentration is reduced. Conversely, when the amount exceeds 10 times the amount of the amine salt of the diphenylsulfone derivative, the improvement in thermal responsiveness is small. As described above, the hydroxybenzoic acid derivative is an excellent additive, but when the addition amount is excessive, the density of the image area tends to decrease in the heat resistance test, and fine crystals are generated on the surface of the image area. As a result, care must be taken because a quality defect called powder blowing is likely to occur, in which the color tone becomes cloudy and the density is reduced.

The heat-sensitive recording material of the present invention generally comprises, as a main component, an electron-donating, usually colorless or light-colored dye precursor on a support, and an electron-accepting compound which reacts upon heating to form the dye precursor. And, after dispersing these in a binder, coated on a support to provide a thermosensitive recording layer, a thermal head,
By heating with a hot pen, laser light or the like, the dye precursor and the electron-accepting compound react instantaneously to obtain a recorded image. Further, a pigment, a sensitizer, a binder, an antioxidant, an anti-sticking agent and the like are added to the heat-sensitive recording layer as needed.

The dye precursor used in the heat-sensitive recording material of the present invention is typified by those generally used in pressure-sensitive recording materials or heat-sensitive recording materials, but is not limited thereto.

A specific example is as follows. (1) Triarylmethane compound: 3,3-bis (p
-Dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p
-Dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindole-3-
Yl) phthalide, 3- (p-dimethylaminophenyl)
-3- (2-Phenylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-
Yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide,
3,3-bis (2-phenylindol-3-yl)-
5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6
-Dimethylaminophthalide, etc.

(2) Diphenylmethane compound: 4,
4'-bis (dimethylaminophenyl) benzhydryl benzyl ether, N-chlorophenyl leuco auramine, N-2,4,5-trichlorophenyl leuco auramine, etc.

(3) Xanthene compound: rhodamine B
Anilinolactam, rhodamine B-p-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-octylaminofluoran, 3-diethylamino-7-phenylfluoran, 3-diethylamino -7-chlorofluoran, 3
-Diethylamino-6-chloro-7-methylfluoran, 3-diethylamino-7- (3,4-dichloroanilino) fluoran, 3-diethylamino-7- (2-chloroanilino) fluoran, 3-diethylamino-6
Methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3-
(N-ethyl-N-tolyl) amino-6-methyl-7-
Anilinofluoran, 3-piperidino-6-methyl-7
-Anilinofluoran, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-phenethylfluoran,
3-diethylamino-7- (4-nitroanilino) fluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-propyl) amino-6-methyl-7-anilino Fluoran, 3- (N-
Ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluoran,
3- (N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-anilinofluoran and the like

(4) Thiazine compounds: benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, etc.

(5) Spiro compounds: 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran,
Examples include, but are not limited to, 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran, and 3-propylspirobenzopyran. Not something. These dye precursors can be used alone or as a mixture of two or more, if necessary.

In the heat-sensitive recording layer of the heat-sensitive recording material of the present invention, as the electron-accepting compound for forming a color of the dye precursor, an amine salt of a diphenylsulfone derivative alone or a mixture of an amine salt of a diphenylsulfone derivative and a diphenylsulfone derivative is used. It is a heat-sensitive recording layer characterized by containing a hydroxybenzoic acid derivative to these heat-sensitive recording layers. In the heat-sensitive recording layer, other electron-accepting compounds can be used in combination as long as the effects expected from the present invention are not impaired. The electron-accepting compound that can be used in combination is typically represented by an acidic substance used for a pressure-sensitive recording material or a heat-sensitive recording material, but is not limited thereto. Examples thereof include phenol derivatives, aromatic carboxylic acid derivatives, N, N'-diarylthiourea derivatives, arylsulfonylurea derivatives, and polyvalent metal salts such as zinc salts of organic compounds.

A specific example is as follows.
That is, p-phenylphenol, p-hydroxyacetophenone, 4-hydroxy-4'-benzenesulfonyloxydiphenylsulfone, 1,1-bis (p-hydroxyphenyl) propane, 1,1-bis (p-hydroxyphenyl) pentane 1,1-bis (p-hydroxyphenyl) hexane, 1,1-bis (p-hydroxyphenyl) cyclohexane, 2,2-bis (p-hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl) ) Hexane, 1,1-bis (p-hydroxyphenyl) -2-ethylhexane, 2,2-bis (3
-Chloro-4-hydroxyphenyl) propane, 1,1
-Bis (p-hydroxyphenyl) -1-phenylethane, 1,3-di- [2- (p-hydroxyphenyl)-
2-propyl] benzene, 1,3-di- [2- (3,4
-Dihydroxyphenyl) -2-propyl] benzene,
1,4-di- [2- (p-hydroxyphenyl) -2-
Propyl] benzene, 4,4'-dihydroxydiphenyl ether, 3,3'-dichloro-4,4'-dihydroxydiphenyl sulfide, methyl 2,2-bis (4-hydroxyphenyl) acetate, 2,2-bis (4- (Hydroxyphenyl) butyl acetate, 4,4'-thiobis (2-
Tert-butyl-5-methylphenol), dimethyl 4-hydroxyphthalate, benzyl gallate, stearyl gallate, N, N'-diphenylthiourea, 4,
4'-bis (3- (4-methylphenylsulfonyl) ureido) diphenylmethane, N- (4-methylphenylsulfonyl) -N'-phenylurea salicylanilide,
5-chlorosalicylanilide, salicylic acid, 3,5-di-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4- [2 ′-(4-methoxyphenoxy) ethyloxy] salicylic acid or a derivative of these salicylic acids But are not limited to these.

In the heat-sensitive recording material of the present invention, a heat-fusible substance can be contained in the heat-sensitive recording layer in order to improve the thermal response. In this case, those having a melting point of 60 ° C to 180 ° C are preferable, and those having a melting point of 80 ° C to 140 ° C are more preferable.

Specifically, stearic acid amide, N-hydroxymethyl stearic acid amide, N-stearyl stearic acid amide, ethylenebisstearic acid amide,
N-stearyl urea, β-naphthyl benzyl ether,
m-terphenyl, 4-benzylbiphenyl, 2,2 ′
-Bis (4-methoxyphenoxy) diethyl ether,
α, α′-diphenoxyxylene, bis (4-methoxyphenyl) ether, diphenyl adipate, dibenzyl oxalate, di (4-chlorobenzyl) oxalate, dimethyl terephthalate, dibenzyl terephthalate, phenyl benzenesulfonate, bis Known heat-fusible substances such as (4-allyloxyphenyl) sulfone, 4-acetylacetophenone, acetoacetic anilides, and fatty acid anilides are exemplified. These compounds can be used alone or in combination of two or more. Further, in order to obtain a sufficient thermal response, in the total solid content of the heat-sensitive recording layer,
Preferably, the fusible material accounts for 5 to 50% by weight.

The pigments used in the heat-sensitive recording material of the present invention include diatomaceous earth, talc, kaolin, calcined kaolin, heavy calcium carbonate, precipitated calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, aluminum hydroxide, and hydroxide. Inorganic pigments such as magnesium, titanium dioxide, barium sulfate, zinc sulfate, amorphous silica, amorphous calcium silicate, and colloidal silica; organic pigments such as melamine resin filler, urea-formalin resin filler, polyethylene powder, and nylon powder. Can be used.

As the binder used in the heat-sensitive recording layer, various binders used in ordinary coating can be used.

Specifically, starches, hydroxymethylcellulose, methylcellulose, ethylcellulose,
Carboxymethylcellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium alginate, polyvinylpyrrolidone, polyacrylamide, acrylamide / acrylate copolymer,
Acrylamide / acrylic acid ester / methacrylic acid terpolymer, alkaline salt of polyacrylic acid, alkaline salt of polymaleic acid, alkaline salt of styrene / maleic anhydride copolymer, alkaline salt of ethylene / maleic anhydride copolymer Water-soluble binder such as alkali salt of isobutylene / maleic anhydride copolymer, and styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, acrylonitrile / butadiene / styrene terpolymer Water-dispersible binders such as polymers, polyvinyl acetate, vinyl acetate / acrylate copolymers, ethylene / vinyl acetate copolymers, polyacrylates, styrene / acrylate copolymers, and polyurethanes. But limited to this Not to.

Other additives include metal salts of higher fatty acids such as zinc stearate and calcium stearate, paraffin, paraffin oxide, polyethylene, polyethylene oxide, and stearamide for the purpose of preventing abrasion or sticking of a heated print head. , Waxes such as custard wax, dispersants such as dioctyl sodium sulfosuccinate, benzophenone,
A benzotriazole-based ultraviolet absorber, a surfactant, a fluorescent dye, and the like can be added as needed.

The method for forming the heat-sensitive recording layer is not particularly limited, and it can be formed according to a conventionally known technique. Specific examples include various printing methods,
A thermosensitive recording layer can be formed by applying a coating liquid to a support by a method such as air knife coating, rod blade coating, bar coating, blade coating, gravure coating, or curtain coating, and drying. .

As the support used in the present invention, paper is mainly used, but non-woven fabric, plastic film, synthetic paper, metal foil and the like, or a composite sheet combining these can be used arbitrarily. Further, an overcoat layer consisting of a single layer or a plurality of layers is provided to protect the heat-sensitive recording layer, or an undercoat layer consisting of a single layer or a plurality of pigments or resins is provided between the heat-sensitive recording layer and the support. For example, various known techniques in the production of heat-sensitive recording materials can be used.

The coating amount of the heat-sensitive recording layer is determined by the amounts of the electron-donating dye precursor and the electron-accepting compound, which are color-forming components, and is usually 0.1 to 1.0 g based on the coating amount of the dye precursor. / m ²
Is appropriate. The amount of the electron-accepting compound is usually added in the range of 5 to 400% by weight with respect to the dye precursor, but the range of 20 to 300% by weight is particularly preferable.

If necessary, the image quality can be improved by applying a super calender treatment after the application of the undercoat layer, the application of the heat-sensitive recording layer, or the application of the overcoat layer.

[0049]

Next, the present invention will be described in more detail by way of examples. However, it is not limited to these.
The parts and percentages shown below are based on weight, and the coating amounts are absolutely dry coating amounts.

Example 1 (A) Preparation of coating solution for forming heat-sensitive recording layer Dye precursor having a black color tone, 3- (N, N'-)
30 parts of (dibutylamino) -6-methyl-7-anilinofluoran were ground together with 69 parts of a 2.5% aqueous solution of polyvinyl alcohol in a ball mill for 24 hours to obtain a dye precursor dispersion. Next, stearylamine salt of 4,4'-dihydroxydiphenyl sulfone 70 as an electron accepting compound
Parts and 70 parts of β-benzyloxynaphthalene as a sensitizer were added to a 2.5% aqueous solution of polyvinyl alcohol 420
The resultant mixture was pulverized with a sand mill together with a portion to obtain a dispersion containing an electron-accepting compound having a volume average particle size of 2 μm or less. After mixing the above two dispersions, the following additives are added under stirring,
The mixture was mixed well to prepare a coating solution for forming a heat-sensitive recording layer. 50% aqueous calcium carbonate dispersion 180 parts 40% zinc stearate aqueous dispersion 25 parts 10% polyvinyl alcohol aqueous solution 272 parts water 300 parts

(B) Preparation of heat-sensitive coated paper A coating liquid having the following composition was applied to a high-quality paper having a basis weight of 40 g / m ^{2 so} as to have a solid content of 9 g / m ² and dried. Thus, a heat-sensitive coated paper was produced. Calcined kaolin 100 parts 50% styrene butadiene latex aqueous dispersion 24 parts Water 200 parts

(C) Preparation of heat-sensitive recording material The coating solution for forming a heat-sensitive recording layer prepared in (A) was coated on the heat-sensitive coating paper prepared in (B) at a solid content of 4 g / m ^2.
The coating was dried to give a heat-sensitive recording material.

Example 2 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the amount of the electron-accepting compound and the amount thereof were changed to 70 parts of dibutylamine salt of 4,4'-dihydroxydiphenylsulfone. Was prepared.

Example 3 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the amount of the electron-accepting compound and the amount thereof were changed to 70 parts of a butylamine salt of 4,4'-dihydroxydiphenylsulfone. Produced.

Example 4 In Example 1, the amount of the electron-accepting compound and the amount thereof were changed to 35 parts of dicyclohexylamine salt of 4,4'-dihydroxydiphenylsulfone and 35 parts of 4,4'-dihydroxydiphenylsulfone. A heat-sensitive recording material was produced in the same manner as in Example 1 except for the above.

Example 5 In Example 1, the amount of the electron-accepting compound and the amount thereof were changed to 35 parts of cyclohexylamine salt of 4,4'-dihydroxydiphenylsulfone and 35 parts of 4,4'-dihydroxydiphenylsulfone. A heat-sensitive recording material was produced in the same manner as in Example 1 except for the above.

Example 6 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the amount of the electron-accepting compound and the amount thereof were changed to 70 parts of octylamine salt of 4,4'-dihydroxydiphenylsulfone. Was prepared.

Example 7 In Example 1, the amount of the electron-accepting compound and the amount thereof were changed to 35 parts of the octylamine salt of 4,4'-dihydroxydiphenylsulfone and 35 parts of 4,4'-dihydroxydiphenylsulfone. A heat-sensitive recording material was produced in the same manner as in Example 1 except for the above.

Example 8 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the amount of the electron-accepting compound and the amount thereof were changed to 70 parts of decylamine salt of 4,4'-dihydroxydiphenylsulfone. Produced.

Example 9 Example 9 was repeated except that the electron-accepting compound and the amount thereof were changed to 35 parts of decylamine salt of 4,4'-dihydroxydiphenylsulfone and 35 parts of 4,4'-dihydroxydiphenylsulfone. In the same manner as in Example 1, a thermosensitive recording material was produced.

Example 10 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the amount of the electron-accepting compound and the amount thereof were changed to 70 parts of a benzylamine salt of 4,4'-dihydroxydiphenylsulfone. Was prepared.

Example 11 In Example 1, the amount of the electron-accepting compound and the amount thereof were changed to 35 parts of a benzylamine salt of 4,4'-dihydroxydiphenylsulfone and 35 parts of 4,4'-dihydroxydiphenylsulfone. A heat-sensitive recording material was produced in the same manner as in Example 1 except for the above.

Example 12 Example 12 was repeated except that the electron-accepting compound and the amount thereof were changed to 35 parts of stearylamine salt of 4,4'-dihydroxydiphenylsulfone and 35 parts of benzyl hydroxybenzoate. A heat-sensitive recording material was produced in the same manner as in Example 1.

Comparative Example 1 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the amount of the electron-accepting compound and the amount thereof were changed to 70 parts of 4,4'-dihydroxydiphenylsulfone.

The heat-sensitive recording materials prepared in the above Examples and Comparative Examples were coated with a heat-sensitive recording layer having a Beck smoothness of 400 to 5 on the coated surface.
After calendering to 00 seconds, it was subjected to the following evaluation. Table 1 shows the results of the evaluation.

[Thermal Responsiveness Test] A print test was performed using a facsimile tester TH-PMD manufactured by Okura Electric. Using a thermal head with a dot density of 8 dots / mm and a head resistance of 818 Ω, a head voltage of 14 V, a pulse width of 0.8,
Printing was performed by applying current at 1.0 and 1.2 msec, and the color density was measured with a Macbeth RD-918 reflection densitometer.
Table 1 shows the evaluation results. It is practically necessary that the color density is 0.80 or more at a pulse width of 0.8 msec and the color density is 1.05 or more at a pulse width of 1.0 msec.

The evaluation of the storage characteristics of the image area was performed by a heat resistance test,
In addition, the test was performed in a wet heat resistance test. In Table 2, Dm
ax represents the density of the image portion of the thermosensitive recording material printed at 1.2 msec, and Dmin represents the density of the unprinted portion.

[Heat Resistance Test of Image Area] In the heat resistance test, the image area of the heat-sensitive recording material printed at 1.2 msec used in the evaluation of the thermal response characteristics and the unprinted background area were measured at 60 msec.
The concentration after storage for 24 hours under the condition of
It measured with the D-918 type reflection densitometer. Table 2 shows the evaluation results.
Shown in

[Moisture / Heat Resistance Test of Image Area] In the moist / heat resistance test, the image area of the thermosensitive recording material printed at 1.2 msec used in the evaluation of the thermal response characteristics and the unprinted background area were measured at 40.degree. The density after storage for 24 hours under the condition of% RH was measured with a Macbeth RD-918 reflection densitometer. Table 2 shows the results of the evaluation.

[0070]

[Table 1]

[0071]

[Table 2]

[0072]

As is clear from the examples, a heat-sensitive recording layer containing an electron-donating, usually colorless or pale-colored dye precursor and an electron-accepting compound which reacts upon heating to form the dye precursor is provided. By adding an amine salt of a diphenylsulfone derivative to the heat-sensitive recording layer of the heat-sensitive recording material, it is possible to obtain a heat-sensitive recording material having excellent heat responsiveness without impairing other characteristics. Further, the coloring density is improved by containing the amine salt of the diphenylsulfone derivative and the diphenylsulfone derivative. It is also found that adding a hydroxybenzoic acid derivative to the heat-sensitive recording layer of the heat-sensitive recording material makes it possible to obtain a heat-sensitive recording material having higher heat responsiveness.

[Procedure amendment]

[Submission date] November 2, 1999 (1999.11.
2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0050

[Correction method] Change

[Correction contents]

Example 1 (A) Preparation of coating liquid for forming heat-sensitive recording layer 30 parts of 3-dibutylamino-6-methyl-7-anilinofluoran, a dye precursor having a black color tone, was added to 2.
The mixture was ground with a ball mill for 24 hours together with 69 parts of a 5% aqueous polyvinyl alcohol solution to obtain a dye precursor dispersion. Next, 70 parts of a stearylamine salt of 4,4'-dihydroxydiphenylsulfone as an electron accepting compound and 70 parts of β-benzyloxynaphthalene as a sensitizer were used.
It was pulverized with a sand mill together with 420 parts of a 5% aqueous polyvinyl alcohol solution to obtain a dispersion containing an electron-accepting compound having a volume average particle diameter of 2 μm or less. After mixing the above two dispersions, the following additives were added under stirring and mixed well to prepare a coating liquid for forming a thermosensitive recording layer. 50% calcium carbonate dispersion 180 parts 40% zinc stearate aqueous dispersion 25 parts 10% polyvinyl alcohol aqueous solution 272 parts water 300 parts

Claims (6)

[Claims] 1. A heat-sensitive recording layer containing an electron-donating dye precursor, which is usually colorless or light-colored, and an electron-accepting compound which reacts upon heating to develop the dye precursor, is provided on a support. A heat-sensitive recording material, wherein the heat-sensitive recording layer contains an amine salt of a diphenylsulfone derivative. 2. The heat-sensitive recording material according to claim 1, wherein the amine salt of the diphenyl sulfone derivative is a compound represented by the general formula 1. Embedded image (In the formula 1, R1 and R2 may be the same or different substituents, and represent a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aralkyl group, or an aryl group, and n , M represents an integer of 1 to 4, and R3, R4, and R5 may be the same or different, and each may be a hydrogen atom, an alkyl group, an alkenyl group, an aralkyl group, Alternatively, it represents an aryl group.) 3. A heat-sensitive recording layer containing a colorless or light-colored electron-donating dye precursor having electron-donating properties and an electron-accepting compound which reacts upon heating to develop the color of the dye precursor is provided on a support. In a thermosensitive recording material, an amine salt of a diphenylsulfone derivative represented by the general formula 1 is contained in the thermosensitive recording layer;
And a heat-sensitive recording material containing a diphenylsulfone derivative represented by the general formula 2. Embedded image (In the formula 2, R6 and R7 may be the same or different substituents, and represent a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aralkyl group, or an aryl group; , Q each represent an integer of 1 to 4.) 4. A heat-sensitive recording layer containing an electron-donating dye precursor, which is usually colorless or light-colored, and an electron-accepting compound which reacts upon heating to form the dye precursor, is provided on a support. In a thermosensitive recording material, an amine salt of a diphenylsulfone derivative represented by the general formula 1 is contained in the thermosensitive recording layer;
And a heat-sensitive recording material containing a hydroxybenzoic acid derivative. 5. A heat-sensitive recording layer containing an electron-donating dye precursor, which is usually colorless or light-colored, and an electron-accepting compound which reacts upon heating to form the dye precursor, is provided on a support. In a thermosensitive recording material, an amine salt of a diphenylsulfone derivative represented by the general formula 1 is contained in the thermosensitive recording layer;
A heat-sensitive recording material comprising a diphenylsulfone derivative represented by the general formula 2 and a hydroxybenzoic acid derivative. 6. The diphenylsulfone derivative used in the amine salt of the diphenylsulfone derivative is 4,4 ′
6. The heat-sensitive recording material according to claim 2, which is -dihydroxydiphenyl sulfone.