JP2001018522A - Heat-sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To particularly enhance a heat response and storage stability of an image portion by arranging a heat-sensitive recording layer containing a specific dihydroxydiphenylsulfone and a specific diphenylsulfone on a support to form a heat-sensitive recording material. SOLUTION: A heat-sensitive recording layer containing an electron donative dye precursor and an electron acceptive compound for color developing the precursor when heated is laminated on a support to form the heat-sensitive recording material. It is necessary to blend a compound represented by the formula I (wherein R1, R2 are each an H atom, alkyl group, aralkyl group or the like, m is an integer of 1 to 3, and n is an integer of 0 to 2) and a compound represented by the formula II (wherein R3 to R8 are each a halogen atom, an alkenyl group, aryl group or the like) in the recording layer. A content weight ratio of the compound of the formula I to the compound of the formula II is suitably (1:1) to (2:3). It is more preferable to further blend a hydroxybenzoic acid derivative with the record 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, and more particularly to a heat-sensitive recording material having excellent heat responsiveness and storage stability of an image area.

[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.

As the uses and demands of the heat-sensitive recording material have been expanded in various ways, high heat responsiveness and storage stability of the image area have been demanded.

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 that has high thermal responsiveness and color development density, has less background fogging, and is excellent in image storage stability has been 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, the salicylic acid derivative described in this publication is still not enough to improve the storage stability of the image area, and furthermore has low thermal responsiveness and is suitable for practical high-speed recording. It was hard to say a heat-sensitive recording material.

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]

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

[0011]

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 has a heat-sensitive recording layer containing an electron-donating, usually colorless or pale-colored dye precursor, and an electron-accepting compound that reacts upon heating to form the dye precursor. A thermosensitive recording material characterized in that the thermosensitive recording layer contains a compound represented by the general formula (1) and a compound represented by the general formula (2) in the thermosensitive recording layer.

[0012]

Embedded image (In the formula 1, R1 and R2 may be the same or different, and each may be a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aralkyl group, an aryl group, an alkyloxy group, Represents an alkenyloxy group, an aralkyloxy group or an aryloxy group, m represents an integer of 1 to 3, and n represents an integer of 0 to 2.)

[0013]

Embedded image (In the formula 2, R3 to R8 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, an aryl group, an alkoxy group, an alkenyloxy group. Group, an aralkyloxy group, or an aryloxy group.)

A thermosensitive recording material characterized in that the compound represented by the general formula (1) is 4,4'-dihydroxydiphenyl sulfone.

The weight ratio of the compound represented by the general formula (1) to the compound represented by the general formula (2) is 1: 1 to 1: 1.
This is a heat-sensitive recording material characterized by being in the range of 2: 3.

A thermosensitive recording material having a thermosensitive recording layer containing an electron-donating, usually colorless or pale-colored dye precursor and an electron-accepting compound which reacts upon heating to form a color of the dye precursor, A heat-sensitive recording material characterized in that the heat-sensitive recording layer contains a compound represented by the general formula (1), a compound represented by the general formula (2), and a hydroxybenzoic acid derivative.

The weight ratio of the compound represented by the general formula (1) to the hydroxybenzoic acid derivative is from 1: 1 to 5:
1. A heat-sensitive recording material having a range of 1.

[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, a compound represented by the general formula (1) and a hydroxybenzoic acid derivative are used.

[0019]

Embedded image (In the formula 1, R 1 and R 2 may be the same or different substituents, and may be a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aralkyl group, an aryl group, an alkoxy group, an alkenyl Represents an oxy group, an aralkyloxy group, or an aryloxy group, m represents an integer of 1 to 3, and n represents an integer of 0 to 2.)

Specific examples of the preferably used compound represented by the general formula (1) include 4-hydroxy-4'-isopropoxydiphenylsulfone and 4-hydroxy-
4'-n-propoxydiphenyl sulfone, 4,4'-
Dihydroxydiphenylsulfone, 2,4'-hydroxydiphenylsulfone, 4-hydroxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-methoxydiphenylsulfone, 4-hydroxy-4'-ethoxydiphenyl Sulfone, 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-hydroxydiphenyl sulfone, 3,4-dihydroxy-4'-methyldiphenyl sulfone, 3,4,4'-trihydroxydiphenyl sulfone, 3,4,3 ', 4'-tetra Hydroxydiphenylsulfone, 2,3,4-trihydroxydiphenylsulfone, 3-phenylsulfonyl-4
-Hydroxydiphenylsulfone and the like, but are not limited thereto. These hydroxydiphenylsulfone derivatives can be used alone or as a mixture of two or more, if necessary.

Among the compounds represented by the general formula (1), when 4,4'-dihydroxydiphenylsulfone is used, a comparison is made with the case where other compounds represented by the general formula (1) are used. Thus, the storage stability of the image area, especially the storage stability under heat, is excellent.

The heat-sensitive recording material of the present invention has a higher thermal responsiveness by using the compound represented by the general formula (1) in combination with the diphenyl sulfone derivative represented by the general formula (2) as a sensitizer. And further, it became possible to obtain a heat-sensitive recording material having excellent storage stability of the image area against temperature and humidity.

Embedded image (In the formula 2, R3 to R8 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, an aryl group, an alkoxy group, an alkenyloxy group. Group, an aralkyloxy group, or an aryloxy group.)

Specific examples of the compound represented by the general formula (2) include diphenylsulfone, 4,4'-dimethyldiphenylsulfone, 4,4'-diallyloxydiphenylsulfone, and 4,4'-bismethoxy. Carbonylmethyloxydiphenylsulfone, 4,4′-bis (2-acetyloxyethyloxy) diphenylsulfone,
4'-bis (2-benzoyloxyethyloxy) diphenyl sulfone and the like can be mentioned, and these can be used alone or as a mixture of two or more. Of these, diphenyl sulfone and 4,4′-diallyloxydiphenyl sulfone are particularly preferably used.

The weight ratio of the compound represented by the general formula (1) and the compound represented by the general formula (2) in the present invention is preferably in the range of 1: 1 to 2: 3. When the weight ratio of the compound represented by the general formula (1) is too large, in other words, when the weight ratio of the compound represented by the general formula (2) is too small, good thermal responsiveness is obtained. It is hard to be.

Further, as the additive constituting the heat-sensitive recording layer of the heat-sensitive recording material of the present invention, a hydroxybenzoic acid derivative is used. As a result, a practically higher thermal response was obtained. The reason is that the hydroxybenzoic acid derivative acts as an auxiliary electron accepting compound,
This is considered to improve the compatibility between the dye precursor and the electron-accepting compound.

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 the above specific examples of the hydroxybenzoic acid derivative, benzyl 4-hydroxybenzoate is particularly preferably used.

The amount of the hydroxybenzoic acid derivative added in the present invention is preferably in the range of 10% by weight to 100% by weight based on the electron accepting compound. More preferably, it is in the range of 50% by weight to 100% by weight.

If the amount of the hydroxybenzoic acid derivative in the present invention is less than 10% by weight based on the weight of the electron accepting compound, the thermal responsiveness may be insufficient. On the other hand, if it exceeds 100% by weight, the contact between the electron-donating dye precursor and the electron-accepting compound is excessively promoted, which may cause background fogging.

The heat-sensitive recording material of the present invention generally comprises, on a support, an electron-donating, usually colorless or pale-colored dye precursor and an electron-accepting compound, which are dispersed in a binder. By applying a heat-sensitive recording layer and heating it with a thermal head, hot pen, laser light, etc.
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 typically, but not limited to, those used in pressure-sensitive recording materials or heat-sensitive recording materials.

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 thereof include 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran, and 3-propylspirobenzopyran. These dye precursors can be used alone or as a mixture of two or more, if necessary.

The heat-sensitive recording layer of the heat-sensitive recording material of the present invention contains, as a main electron-accepting compound for coloring a dye precursor,
It is characterized by containing a compound represented by the general formula (1). Further, other electron-accepting compounds can be used in the heat-sensitive recording layer in a range that does not impair the effects obtained by the present invention. The electron accepting compound that can be used in combination is generally represented by an acidic substance used in 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'-hydroxydiphenyl ether, 3,3'-dichloro-4,4'-hydroxydiphenyl 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'-
Bis (3- (4-methylphenylsulfonyl) ureido) diphenylmethane, N- (4-methylphenylsulfonyl) -N'-phenylurea, salicylanilide, 5
-Chlorosalicylanilide, salicylic acid, 3,5-di-
Tertiary butyl salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4- [2 ′-(4-methoxyphenoxy) ethyloxy] salicylic acid or metal salts of these salicylic acid derivatives.

The pigment used in the heat-sensitive recording material of the present invention includes diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide,
Inorganic and organic pigments such as zinc oxide, silicon oxide, aluminum hydroxide, and urea-formalin resin.

The binder used in the heat-sensitive recording material of the present invention includes starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose,
Gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylamide / acrylate copolymer, acrylamide / acrylate / methacrylic acid terpolymer,
Water-soluble binders such as alkali salts of styrene / maleic anhydride copolymer, alkali salts of ethylene / maleic anhydride copolymer, polyvinyl acetate, polyurethane, polyacrylate, styrene / butadiene copolymer, acrylonitrile / butadiene Latexes such as copolymers, methyl acrylate / butadiene copolymers, ethylene / vinyl acetate copolymers and the like can be mentioned.

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.

As the support used in the present invention, paper is mainly used, but non-woven fabric, plastic film, synthetic paper, metal foil, etc., 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 dye precursor and the electron-accepting compound, which are coloring components, and is usually 0.1 to 1.0 g / m ^{2 in} terms of the coating amount of the dye precursor. Is appropriate. The amount of the electron accepting compound is usually in the range of 5 to 500% by weight based on the dye precursor.
The range of -400% by weight is a particularly preferable addition amount.

[0044]

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 Thermosensitive 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, 70 parts of 4,4'-hydroxydiphenylsulfone as an electron accepting compound and 70 parts of 4,4'-diallyloxydiphenylsulfone as a sensitizer were pulverized in a sand mill together with 420 parts of a 2.5% aqueous polyvinyl alcohol solution, A dispersion containing an electron-accepting compound having a volume average particle size of 2 μm or less was obtained. 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% 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 coated on 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 4,4'-diallyloxydiphenylsulfone was changed to diphenylsulfone as a sensitizer.

Example 3 In Example 1, the amount of the sensitizer was changed from 70 parts to 105 parts.
A thermosensitive recording material was produced in the same manner as in Example 1 except that the number of parts was changed.

Example 4 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the amount of the sensitizer was changed from 70 parts to 50 parts.

Example 5 In Example 1, the addition amount of the sensitizer was changed from 70 parts to 120 parts.
A thermosensitive recording material was produced in the same manner as in Example 1 except that the number of parts was changed.

Example 6 In Example 1, the addition amount of the electron-accepting compound was changed from 70 parts to 35 parts, and 35 parts of benzyl p-hydroxybenzoate was further added as an auxiliary electron-accepting compound. Example 1 except that the total amount of the compounds was adjusted to 70 parts.
In the same manner as in the above, a heat-sensitive recording material was produced.

Example 7 In Example 1, the addition amount of the electron-accepting compound was changed from 70 parts to 58 parts, and 12 parts of benzyl p-hydroxybenzoate was further added as an auxiliary electron-accepting compound. Example 1 except that the total amount of the compounds was adjusted to 70 parts.
In the same manner as in the above, a heat-sensitive recording material was produced.

Example 8 In Example 1, the addition amount of the electron-accepting compound was changed from 70 parts to 30 parts, and 40 parts of benzyl p-hydroxybenzoate was further added as an auxiliary electron-accepting compound. Example 1 except that the total amount of the compounds was adjusted to 70 parts.
In the same manner as in the above, a heat-sensitive recording material was produced.

Example 9 In Example 1, the amount of the electron-accepting compound was changed from 70 parts to 65 parts, and 5 parts of benzyl p-hydroxybenzoate was further added as an auxiliary electron-accepting compound. A heat-sensitive recording material was produced in the same manner as in Example 1 except that the total amount of the compounds was adjusted to 70 parts.

Comparative Example 1 A heat-sensitive recording material was prepared in the same manner as in Example 1, except that the sensitizer was changed to 2-benzyloxynaphthalene.

The heat-sensitive recording materials prepared in the above Examples and Comparative Examples were calendered so that the Beck smoothness of the heat-sensitive coated surface was 400 to 500 seconds, and then subjected to the following evaluation. The results of the evaluation are shown in Tables 1, 2 and 3.

[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 185Ω, a head voltage of 12 V, a pulse width of 0.8,
And printing for 1.0 millisecond, and the color density was measured with a Macbeth RD-918 reflection densitometer. Table 1 shows the evaluation results. Color density of 0.80 or more at pulse width of 0.8 msec, and color density of 1.0 msec.
05 or more is practically necessary.

The storage characteristics of the image area were evaluated by a heat resistance test,
A heat resistance test, a heat acceleration test, and a water resistance test were performed.

[Heat Resistance Test of Image Area] The heat resistance test was carried out at 0.8 msec used in the evaluation of the thermal responsiveness.
The density of the image portion of each thermosensitive recording material printed at 0 msec and the unprinted background portion after being stored for 24 hours at 60 ° C. were measured with a Macbeth RD-918 reflection densitometer. Table 2 shows the evaluation results of the portions printed at 0.8 msec, and Table 3 shows the evaluation results of the portions printed at 1.0 msec.
Shown in

[Moisture / Heat Resistance Test of Image Area] The moist / heat resistance test was performed using the image area of each thermosensitive recording material printed at 0.8 msec and 1.0 msec used in the evaluation of the thermal response characteristics.
The density after storing the unprinted background portion for 24 hours under the conditions of 40 ° C. and 90% RH was measured using Macbeth RD-91.
It was measured with a type 8 reflection densitometer. Table 2 shows the evaluation results of the portions printed at 0.8 msec, and Table 3 shows the evaluation results of the portions printed at 1.0 msec.

[Heat Acceleration Test of Image Area] The heat acceleration test was carried out in the image area of each thermosensitive recording material printed at 0.8 msec and 1.0 msec used in the evaluation of the thermal response characteristics.
In addition, the density of the unprinted background portion after storing it for 168 hours at 40 ° C. was measured with a Macbeth RD-918 reflection densitometer. Table 2 shows the evaluation results of the portions printed at 0.8 msec, and Table 3 shows the evaluation results of the portions printed at 1.0 msec.

[0063]

[Table 1]

[0064]

[Table 2]

[0065]

[Table 3]

[0066]

As is clear from the examples, the present invention has 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. In the heat-sensitive recording material, by using the compound represented by the general formula (1) and the compound represented by the general formula (2) together in the heat-sensitive recording layer, the heat responsiveness and the storage characteristics of the image area are excellent. Heat-sensitive recording material. Further, by adding the hydroxybenzoic acid derivative of the present invention to this, it is possible to obtain a thermosensitive recording material having a better balance between heat responsiveness and storage characteristics of the image area, and having an excellent balance.

Claims (5)

[Claims] 1. A heat-sensitive recording material having 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. A heat-sensitive recording material characterized in that the heat-sensitive recording layer contains a compound represented by the general formula (1) and a compound represented by the general formula (2). Embedded image (In the formula 1, R 1 and R 2 may be the same or different substituents, and may be a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aralkyl group, an aryl group, an alkoxy group, an alkenyl Represents an oxy group, an aralkyloxy group, or an aryloxy group;
Represents an integer of 1 to 3, and n represents an integer of 0 to 2. ) (In the formula 2, R3 to R8 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, an aryl group, an alkoxy group, an alkenyloxy group. Group, an aralkyloxy group, or an aryloxy group.) 2. The compound represented by the general formula (1) is 4,
2. The heat-sensitive recording material according to claim 1, which is 4'-dihydroxydiphenyl sulfone. 3. The compound represented by the general formula (1) and the compound represented by the general formula (2) in a weight ratio of 1: 1 to 1.
The ratio is in the range of 2: 3.
The heat-sensitive recording material as described. 4. A heat-sensitive recording material having a heat-sensitive recording layer containing an electron-donating, usually colorless or pale-colored dye precursor, and an electron-accepting compound that reacts upon heating to form the dye precursor. A heat-sensitive recording material characterized in that the heat-sensitive recording layer contains a compound represented by the general formula (1), a compound represented by the general formula (2), and a hydroxybenzoic acid derivative. 5. The weight ratio of the compound represented by the general formula (1) to the hydroxybenzoic acid derivative is from 1: 1 to 5: 1.
5. The heat-sensitive recording material according to claim 4, wherein: