JP2000280618A - Heat sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve color developing sensitivity and preservation stability of an image by incorporating a diphenylsulfone derivative represented by the formula I in an electron acceptive compound and incorporating an ether compound represented by the formula II as an additive. SOLUTION: As an electron acceptive compound for color developing a dye precursor in reaction when heated, a diphenylsulfone derivative represented by the formula I (wherein R1, R2 are each an alkyl group, an alkenyl group, a phenylsulfonyl group or a halogen atom, m is an integer of 1 to 3, n is an integer of 0 to 2, and x, y are each an integer of 0 to 2) is used. As a sensitizer for constituting a heat sensitive recording layer, an ether compound represented by the formula II (wherein R3, R4 are each an alkenyl group, an alkyl group or an alkylcarbonyl group) is used. Thus, color developing sensitivity can be upgraded, and balance of preservation characteristics of an image can be improved.

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 color sensitivity 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. Conventional heat-sensitive recording materials that use an electron-donating, colorless dye precursor and an electron-accepting compound have properties such as high color density, but the recording image area is made of plastic such as polyvinyl chloride. Deterioration due to penetration of plasticizers and additives contained in plastics upon contact with plastic, or decolorization upon contact with chemicals contained in foods and cosmetics ing. In addition, it also has disadvantages such as a decrease in the density of a colored image due to deterioration over time,
At present, certain restrictions are imposed on its use, and improvements have been strongly desired.

As a means for improving the storage characteristics of the recorded image area, a heat-sensitive method using a salicylic acid derivative having a substituent such as an alkyl group, an aralkyl group, an alkyloxy group, an acyl group or a metal salt thereof as an electron accepting compound is used. Recording materials have been proposed. (JP-A-62-169681, JP-A-63-22683, and 63-95977)
No.)

[0004] However, the salicylic acid derivative described in the above publication has insufficient storage characteristics of a color image, has a low color development sensitivity, and cannot be said to be a heat-sensitive recording material suitable for practical high-speed recording. Met.

[0005] In order to improve the color sensitivity, a sensitizer is added as required. 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 the method, 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, the heat-sensitive recording materials produced by these disclosed methods are still insufficient in color density and color sensitivity.

[0007]

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

[0008]

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 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. As a receptive compound, a diphenylsulfone derivative represented by the following general formula 1 is contained.
A heat-sensitive recording material comprising an ether compound represented by the formula:

[0009]

Embedded image (Wherein R1 and R2 are an alkyl group, an alkenyl group, an aralkyl group, an alkoxy group, a benzyloxy group,
Represents a phenylsulfonyl group or a halogen atom. m
Represents an integer of 1 to 3, n represents an integer of 0 to 2, and x and y each represent an integer of 0 to 2. )

[0010]

Embedded image (In the formula, R3 and R4 each represent an alkenyl group, an alkyl group, or an alkylcarbonyl group.)

The ether compound is represented by the following general formula 3
The heat-sensitive recording material is an ether compound represented by the following formula:

Embedded image (In the formula, R5 and R6 each represent an alkenyl group, a lower alkyl group, or a lower alkylcarbonyl group.)

Further, the thermosensitive recording material is characterized in that the ether compound is an ether compound represented by the following general formula 4.

Embedded image

The electron accepting compound is represented by the following general formula 5
Wherein the ether compound is an ether compound represented by the above general formula (4).

Embedded image (In the formula, R7 represents an alkyl group, a benzyl group, or a hydrogen atom.)

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The contents of the present invention will be described more specifically. As the electron-accepting compound for coloring the dye precursor constituting the heat-sensitive recording layer of the heat-sensitive recording material of the present invention, a diphenylsulfone derivative represented by the above general formula 1 is used.

Examples of specific diphenylsulfone derivatives include 4,4'-dihydroxydiphenylsulfone,
2,4′-dihydroxydiphenylsulfone, 4-hydroxydiphenylsulfone, 4-hydroxy-4′-methyldiphenylsulfone, 4-hydroxy-4′-methoxydiphenylsulfone, 4-hydroxy-4′-ethoxydiphenylsulfone, 4- Hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4 '
-N-propoxydiphenylsulfone, 4-hydroxy-4'-n-butoxydiphenylsulfone, 4-hydroxy-4'-benzyloxydiphenylsulfone, 3,
3'-diallyl-4,4'-dihydroxydiphenylsulfone, 3,3'-dichloro-4,4'-dihydroxydiphenylsulfone, 3,3 ', 5,5'-tetrabromo-4,4'-dihydroxydiphenylsulfone , 3,
3 ', 5,5'-tetrachloro-4,4'-dihydroxydiphenylsulfone, 3-phenylsulfonyl-4-
Hydroxydiphenyl sulfone, 4-hydroxy-4 '
Benzenesulfonyloxydiphenyl sulfone, 3,
4-dihydroxydiphenylsulfone, 3,4-dihydroxy-4′-methyldiphenylsulfone, 3,4
4'-trihydroxydiphenyl sulfone, 3,4
3 ′, 4′-tetrahydroxydiphenyl sulfone,
Examples thereof include 2,3,4-trihydroxydiphenyl sulfone, but are not limited thereto. Further, the diphenylsulfone derivative according to the present invention can be used alone or as a mixture of two or more as needed.

As a sensitizer constituting the heat-sensitive recording layer of the heat-sensitive recording material of the present invention, an ether compound represented by the above general formula 2 is used. Specific examples of ether compounds include bis (4-methoxyphenyl) ether and bis (4) in which R3 and R4 are lower alkyl groups.
-Ethoxyphenyl) ether, bis (4-isopropylphenyl) ether, bis (4-butylphenyl) ether and the like are exemplified by bis (4-
Acryloxyphenyl) ether, bis [4- (2-
Examples of the lower alkylcarbonyl group include bis (4-acetoxyphenyl) ether and bis (4-ethylcarbonyloxyphenyl) ether. However, the present invention is not limited to this. The ether compounds according to the present invention can be used alone or as a mixture of two or more, if necessary.

The heat-sensitive recording material of the present invention uses a diphenyl sulfone derivative represented by the above general formula 1 as an electron accepting compound which reacts upon heating to form a dye precursor, and a sensitizer represented by the above general formula 2 By using the ether compound shown, a heat-sensitive recording material having excellent color-forming sensitivity and excellent storage stability of an image area can be obtained.

Further, when the ether compound represented by the general formula 3 is used as the ether compound represented by the general formula 2, it is possible to obtain a heat-sensitive recording material having particularly excellent color development sensitivity and storage stability of an image area. It became.

When the ether compound represented by the general formula 3 is used as the ether compound and the diphenyl sulfone derivative represented by the general formula 4 is used as the diphenyl sulfone derivative represented by the general formula 1, the color sensitivity,
In addition, a heat-sensitive recording material having excellent storage stability in the image area can be obtained.

The amount of the ether compound represented by the general formula 2 is preferably 10 to 400% by weight based on the diphenylsulfone derivative represented by the general formula 1,
It is more preferable to use 0 to 300% by weight. When the addition amount is less than 10% by weight, the effect of improving sensitivity is insufficient, and when it exceeds 400% by weight, the amount of the heat-fusible substance becomes excessive, resulting in a dilution effect and a reduction in color density. In addition, it is disadvantageous in terms of cost.

The heat-sensitive recording material of the present invention generally comprises, as main components, an electron-donating, usually colorless or pale-colored dye precursor and an electron-accepting compound on a support, and these are dispersed and applied to a binder. By providing a layer and heating with a thermal head, a hot pen, a laser beam or the like, the dye precursor and the electron-accepting compound react instantaneously to obtain a recorded image. In the heat-sensitive recording layer, a pigment, a sensitizer, a binder,
An antioxidant, an anti-sticking agent and the like are added as necessary.

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.

Specific examples are 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,
3,3′-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran, 3-propylspirobenzopyran and the like, and these dye precursors are If necessary, they can be used alone or in combination of two or more.

The electron-accepting compound used in the heat-sensitive recording material of the present invention is characterized by containing a diphenylsulfone derivative represented by the general formula 1, and is expected to be obtained by the present invention. Other electron-accepting compounds can be used in combination as long as the sufficient effect is not impaired. As the electron accepting compound that can be used in combination,
Generally, it is represented by an acidic substance used for a pressure-sensitive recording material or a heat-sensitive recording material, but is not limited thereto. For example, phenol derivatives, aromatic carboxylic acid derivatives, N, N'-diarylthiourea derivatives, and polyvalent metal salts such as zinc salts of organic compounds can be given.

A specific example is as follows.
That is, p-phenylphenol, p-hydroxyacetophenone, 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,
4-di- [2- (p-hydroxyphenyl) -2-propyl] benzene, 4,4′-dihydroxydiphenyl ether, 3,3′-dichloro-4,4′-dihydroxydiphenyl sulfide, 2,2-bis ( Methyl 4-hydroxyphenyl) acetate, butyl 2,2-bis (4-hydroxyphenyl) acetate, 4,4′-thiobis (2-t-
Butyl-5-methylphenol), benzyl p-hydroxybenzoate, chlorobenzyl p-hydroxybenzoate, dimethyl 4-hydroxyphthalate, benzyl gallate, stearyl gallate, salicylanilide, 5-chlorosalicylanilide, salicylic acid, 3 , 5-di-ter
Examples thereof include t-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4- [2 ′-(4-methoxyphenoxy) ethyloxy] salicylic acid, and 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 and the like, or a composite sheet combining these can be used arbitrarily. Also, an overcoat layer may be provided to protect the heat-sensitive recording layer,
Such as providing a single layer or a plurality of undercoat layers made of pigment or resin between the heat-sensitive recording layer and the support,
Various known techniques in the production of heat-sensitive recording materials can be used.

The amount of smear of the heat-sensitive recording layer is determined by the amounts of the dye precursor and the electron-accepting compound, which are color-forming components, and is usually from 0.1 to 1.0 g / m ^{2 as the} amount of smear of the dye precursor. It is. The amount of the electron-accepting compound is 5 to 400% by weight based on the dye precursor.
% By weight is a preferable addition amount.

[0035]

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

Example 1 (A) Preparation of coating liquid for forming heat-sensitive recording layer Dye precursor having a black color tone, 3- (N, N'-)
35 parts of (dibutylamino) -6-methyl-7-anilinofluorane were ground together with 80 parts of a 2.5% aqueous solution of polyvinyl alcohol in a ball mill for 24 hours to obtain a dye precursor dispersion. Next, 40 parts of 4-hydroxy-4′-isopropoxydiphenyl sulfone as an electron accepting compound and 60 parts of bis (4-methoxyphenyl) ether as a sensitizer were added to a 2.5% aqueous solution of polyvinyl alcohol 300
The resulting mixture was pulverized with a Dynomill (a sand mill manufactured by WEB Co.) to obtain a dispersion containing an electron-accepting compound having a volume average particle diameter of 2 μm or less and a sensitizer. After mixing the above two dispersions, the following additives were added under stirring and mixed well to prepare a coating solution for forming a thermosensitive recording layer. 50% aqueous calcium carbonate dispersion 100 parts 40% zinc stearate aqueous dispersion 25 parts 10% polyvinyl alcohol aqueous solution 200 parts Water 280 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.

Comparative Example 1 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that benzyl-β-naphthyl ether was used instead of (4-methoxyphenyl) ether.

Comparative Example 2 In place of 4-hydroxy-4'-isopropoxydiphenylsulfone in Example 1, 2,2-bis (4-
Example 1 except that (hydroxyphenyl) propane was used.
In the same manner as in the above, a heat-sensitive recording material was produced.

The heat-sensitive recording materials prepared in the above Examples and Comparative Examples were calendered so that the Bekk smoothness of the heat-sensitive coated surface was 400 to 500 seconds, and then subjected to the following evaluation. Table 1 shows the results of the evaluation.

[Coloring Sensitivity Test] A printing 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 1290Ω, a head voltage of 21 V and a pulse width of 0.
Printing was performed by supplying electricity for 7, and 1.0 milliseconds, and the color density was measured with a Macbeth RD-918 reflection densitometer. It is practically necessary that the color density be 0.60 or more at a pulse width of 0.7 msec and the color density be 1.15 or more at a pulse width of 1.0 msec.

The storage characteristics of the image area were evaluated by a heat resistance test,
And a lap resistance test.

[Heat Resistance Test of Image Area] In the heat resistance test, the image area of each heat-sensitive recording material printed with a pulse of 1.0 msec used in the evaluation of the color development sensitivity was examined at 60 ° C. for 2 hours.
The density after storage for 4 hours was measured with a Macbeth RD-918 reflection densitometer. In addition, the residual ratio% obtained by dividing the measured concentration value by the concentration value measured before the heat resistance test.
Are also shown in parentheses.

[Moisture / Heat Resistance Test of Image Area] In the moist / heat resistance test, the image area of each thermosensitive recording material printed with a pulse of 1.0 msec used in the evaluation of the color development sensitivity characteristic was subjected to a temperature of 60 ° C.
The density after storage for 24 hours in an environment with a relative humidity of 90% was measured with a Macbeth RD-918 reflection densitometer. In addition, the residual ratio% obtained by dividing the measured concentration value by the concentration value measured before the moist heat resistance test is also shown in parentheses.

[Lap resistance test of image area] The lap resistance test was conducted by covering the image area of each thermosensitive recording material printed with a pulse of 1.0 msec used in the evaluation of the color sensitivity characteristics with a commercially available wrap, and weighing 2 g from the top. The density after storing for 24 hours in a 40 ° C. environment with a load of / cm ² was measured with a Macbeth RD-918 reflection densitometer. In addition, the residual rate% obtained by dividing the measured density value by the density value measured before the lap resistance test is also shown in parentheses.

[0047]

[Table 1]

As shown in Table 1, Example 1 was superior to Comparative Examples 1 and 2 in both the color development sensitivity characteristics and the image storage characteristics. Comparative Example 1 had good image storage characteristics, but was inferior in color sensitivity, and Comparative Example 2 had good color sensitivity, but was inferior in image storage characteristics.

[0049]

As is clear from the examples, the present invention relates to a heat-sensitive recording material 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. By adopting a diphenylsulfone derivative represented by the general formula 1 as the electron-accepting compound and containing an ether compound represented by the general formula 2 as an additive, the color development sensitivity and the storage characteristics of the image area are balanced. It is possible to obtain an excellent thermosensitive recording material.

Claims (4)

[Claims] 1. A heat-sensitive recording material 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 comprising a diphenylsulfone derivative represented by Formula 1 and an ether compound represented by General Formula 2 as an additive. Embedded image (Wherein R1 and R2 are an alkyl group, an alkenyl group, an aralkyl group, an alkoxy group, a benzyloxy group,
Represents a phenylsulfonyl group or a halogen atom. m
Represents an integer of 1 to 3, n represents an integer of 0 to 2, and x and y each represent an integer of 0 to 2. ) (In the formula, R3 and R4 each represent an alkenyl group, an alkyl group, or an alkylcarbonyl group.) 2. The method according to claim 1, wherein the ether compound is an ether compound represented by the following general formula 3.
The heat-sensitive recording material as described. Embedded image (In the formula, R5 and R6 each represent an alkenyl group, a lower alkyl group, or a lower alkylcarbonyl group.) 3. The compound according to claim 2, wherein said ether compound is an ether compound represented by the following general formula 4.
The heat-sensitive recording material as described. Embedded image 4. The heat-sensitive recording material according to claim 3, wherein the electron accepting compound is a diphenyl sulfone derivative represented by the following general formula 5. Embedded image (In the formula, R7 represents an alkyl group, a benzyl group, or a hydrogen atom.)