JP3250880B2 - Thermal recording material - Google Patents

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. More specifically, the present invention relates to a heat-sensitive recording material having improved storage stability of an uncolored portion and a colored image.

[0002]

2. Description of the Related Art Heat-sensitive recording materials utilizing a color reaction between an electron-donating color-forming compound and an electron-accepting compound (developing agent) have been well known (for example, Japanese Patent Publication No. Sho 43-4).
No. 160, JP-B-45-14039). Thermosensitive recording materials are widely used in the fields of facsimile machines, recorders, and printers because of their advantages of being relatively inexpensive and having a compact and maintenance-free recording device. In recent years, the fields of application of thermal recording materials have been further expanded and diversified, and further expanded to applications under harsh environments (eg, labels, prepaid cards). However, conventionally known heat-sensitive recording materials using 2,2-bis (4′-hydroxyphenyl) propane [“bisphenol A”], 4-hydroxybenzoic acid benzyl ester, etc. as electron-accepting compounds have been used under severe environments. (E.g., oils, solvents, fats,
Under contact with writing instruments such as highlighters or in humid environments)
Then, the uncolored part is significantly contaminated (dirt),
In addition, there are disadvantages such as fading of the color image. At present, there is a demand for a heat-sensitive recording material having excellent storage stability of uncolored portions and color images.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material having improved storage stability of uncolored areas and color images.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies on a heat-sensitive recording material in order to meet the above-mentioned demands, and have reached the present invention. That is, the present invention relates to a heat-sensitive recording material containing an electron-donating color-forming compound and an electron-accepting compound, wherein at least one compound represented by the general formula (1) or (2) is contained as the electron-accepting compound. The present invention relates to a heat-sensitive recording material.

[0005]

Embedded image (In the formula, X represents a sulfur atom or a sulfonyl group .
And 4,4'-bis (p-hydroxyphenylsulfo
Nyl) excluding diphenylsulfone. )

In the general formula (1), X represents a sulfur atom or a sulfonyl group. In the general formula (1), the substitution position of the hydroxyl group is at the para, meta or ortho position with respect to X, and more preferably at the para or meta position. Specific examples of the compound represented by the general formula (1) include, for example, 4,4′-bis (p-hydroxyphenylthio) diphenylsulfone, 4,4′-bis (m-hydroxyphenylthio) diphenylsulfone, 4,
4'-bis (o-hydroxyphenylthio) diphenylsulfone, 4- (p-hydroxyphenylthio)-
4 ′-(m-hydroxyphenylthio) diphenylsulfone , 4,4′-bis (m-hydroxyphenylsulfonyl) diphenylsulfone, 4,4′-bis (o
-Hydroxyphenylsulfonyl) diphenylsulfone and the like.

The compound represented by the general formula (1) can be produced by a known method, for example, a method described in US Pat. No. 4,306,055. That is, in the general formula (1), a compound in which X is a sulfur atom can be produced, for example, by reacting 4,4′-dichlorodiphenylsulfone with a mercaptophenol in the presence of a base. Further, in the general formula (1), the compound in which X is a sulfonyl group can be produced by, for example, oxidizing a compound in which X is a sulfur atom with hydrogen peroxide. The heat-sensitive recording material of the present invention contains an electron-donating color-forming compound and at least one compound represented by the general formula (1) as an electron-accepting compound. The compounds represented by the general formula (1) may be used alone or in combination. In the heat-sensitive recording material of the present invention, the amount of the electron-accepting compound is usually 50 to 70 parts by weight per 100 parts by weight of the electron-donating color-forming compound.
It is desirable to use 0 parts by weight, preferably 100 to 500 parts by weight.

In the heat-sensitive recording material of the present invention, the colorless or pale-color electron-donating color-forming compound used includes triarylmethane compounds, vinylphthalide compounds, and the like.
Examples include a diarylmethane compound, a rhodamine-lactam compound, a fluoran compound, a pyridine compound, a spiro compound, and a fluorene compound. Some specific examples of these compounds include, as triarylmethane compounds, 3,3-bis (4-dimethylaminophenyl) -6-dimethylaminophthalide ["
Crystal violet lactone "], 3,3-bis (4-dimethylaminophenyl) phthalide, 3- (4-
Dimethylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (1,
2-dimethylindol-3-yl) phthalide, 3-
(4-dimethylaminophenyl) -3- (2-methylindol-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) -6-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide,
3- (4-dimethylaminophenyl) -3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide and the like.

As the vinylphthalide compound, 3,3
-Bis [1,1-bis (4-dimethylaminophenyl)
Ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6 , 7-
Tetrabromophthalide, 3,3-bis [1- (4-dimethylaminophenyl) -1- (4-methoxyphenyl)
Ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1- (4-pyrrolidinophenyl) -1- (4-methoxyphenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide and the like. Examples of the diarylmethane compound include 4,4-bis-dimethylaminobenzhydrin benzyl ether, N
-Halophenyl-leuco auramine, N-2,4,5-
Trichlorophenylleuco auramine and the like. Rhodamine-lactam compounds include rhodamine-B-
Anilinolactam, rhodamine- (4-nitroanilino) lactam, rhodamine-B- (4-chloroanilino) lactam and the like.

The fluoran compounds include 3,6-dimethoxyfluorane, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran, 3-diethylamino-7-methoxyfluoran, Diethylamino-7-chlorofluoran, 3-
Diethylamino-6-methyl-7-chlorofluoran,
3-diethylamino-6,7-dimethylfluoran, 3
-N-cyclohexyl-NN-butylamino-7-methylfluoran, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-octylaminofluoran, 3-diethylamino-7-di-n −
Hexylaminofluoran, 3-diethylamino-7-
Anilinofluoran, 3-diethylamino-7- (2 ′
-Chlorophenylamino) fluoran, 3-diethylamino-7- (3'-chlorophenylamino) fluoran, 3-diethylamino-7- (2 ', 3'-dichlorophenylamino) fluoran, 3-diethylamino-7
-(3'-trifluoromethylphenylamino) fluoran, 3-di-n-butylamino-7- (2'-chlorophenylamino) fluoran, 3-N-isopentyl-
N-ethylamino-7- (2′-chlorophenylamino) fluoran,

3-Nn-hexyl-N-ethylamino-7- (2'-chlorophenylamino) fluoran;
-Diethylamino-6-chloro-7-anilinofluoran, 3-di-n-butylamino-6-chloro-7-anilinofluoran, 3-diethylamino-6-methoxy-
7-anilinofluoran, 3-di-n-butylamino-
6-ethoxy-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-morpholino-6-methyl-7-anilinofluoran, 3-dimethylamino-6-methyl- 7-anilinofluoran, 3
-Diethylamino-6-methyl-7-anilinofluoran, 3-di-n-butylamino-6-methyl-7-anilinofluoran, 3-di-n-pentylamino-6-methyl-7-ani Linofluoran, 3-N-ethyl-N-
Methylamino-6-methyl-7-anilinofluoran,
3-NN-propyl-N-methylamino-6-methyl-7-anilinofluoran, 3-NN-propyl-N
-Ethylamino-6-methyl-7-anilinofluoran, 3-NN-butyl-N-methylamino-6-methyl-7-anilinofluoran, 3-NN-butyl-N
-Ethylamino-6-methyl-7-anilinofluoran,

3-N-isobutyl-N-methylamino-
6-methyl-7-anilinofluoran, 3-N-isobutyl-N-ethylamino-6-methyl-7-anilinofluoran, 3-N-isopentyl-N-ethylamino-
6-methyl-7-anilinofluoran, 3-Nn-hexyl-N-methylamino-6-methyl-7-anilinofluoran, 3-N-cyclohexyl-N-ethylamino-6-methyl- 7-anilinofluoran, 3-N-cyclohexyl-Nn-propylamino-6-methyl-
7-anilinofluoran, 3-N-cyclohexyl-N
-N-butylamino-6-methyl-7-anilinofluoran, 3-N-cyclohexyl-NN-hexylamino-6-methyl-7-anilinofluoran, 3-N-cyclohexyl-NN -Octylamino-6-methyl-
7-anilinofluoran, 3-N-2′-methoxyethyl-N-methylamino-6-methyl-7-anilinofluoran, 3-N-2′-methoxyethyl-N-ethylamino-6 Methyl-7-anilinofluoran, 3-N-
2'-methoxyethyl-N-isobutylamino-6-methyl-7-anilinofluoran, 3-N-2'-ethoxyethyl-N-methylamino-6-methyl-7-anilinofluoran, 3- N-2′-ethoxyethyl-N-ethylamino-6-methyl-7-anilinofluoran,

3-N-3'-methoxypropyl-N-methylamino-6-methyl-7-anilinofluoran;
-N-3'-methoxypropyl-N-ethylamino-6
-Methyl-7-anilinofluoran, 3-N-3'-ethoxypropyl-N-methylamino-6-methyl-7-
Anilinofluoran, 3-N-3′-ethoxypropyl-N-ethylamino-6-methyl-7-anilinofluoran, 3-N-2′-tetrahydrofurfuryl-N-ethylamino-6-methyl -7-anilinofluoran, 3
-N- (4'-methylphenyl) -N-ethylamino-
6-methyl-7-anilinofluoran, 3-diethylamino-6-ethyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (3'-methylphenylamino) fluoran, 3-diethylamino- 6-methyl-7- (2 ', 6'-dimethylphenylamino) fluoran, 3-di-n-butylamino-6-methyl-7-
(2 ′, 6′-dimethylphenylamino) fluoran, 3
-Di-n-butylamino-7- (2 ', 6'-dimethylphenylamino) fluoran, 2,2-bis [4'-
(3-N-cyclohexyl-N-methylamino-6-methylfluoran) -7-ylaminophenyl] propane, 3- [4 '-(4-phenylaminophenyl) aminophenyl] amino-6-methyl-7 -Chlorofluorane and the like.

Examples of the pyridine compound include 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-octyl-2-methylindol-3-yl) -4 or 7-azaphthalide, Ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4 or 7-azaphthalide, 3-
(2-hexyloxy-4-diethylaminophenyl)
-3- (1-Ethyl-2-methylindol-3-yl) -4 or 7-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-
2-phenylindol-3-yl) -4 or 7-azaphthalide, 3- (2-butoxy-4-diethylaminophenyl) -3- (1-ethyl-2-phenylindol-3-yl) -4 or 7- Azaphthalide and the like. As spiro compounds, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran,
3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho- (3
-Methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran and the like.

As the fluorene-based compound, 3,6-bis (dimethylamino) fluorene-9-spiro-3'-
(6′-dimethylamino) phthalide, 3,6-bis (diethylamino) fluorene-9-spiro-3 ′-(6 ′
-Dimethylamino) phthalide. Of course, it is not limited to these electron-donating color-forming compounds,
These electron-donating color-forming compounds may be used alone or in combination of two or more. The heat-sensitive recording material of the present invention is characterized by containing at least one compound represented by the general formula (1) as an electron-accepting compound, as long as the desired effects of the present invention are not impaired. It is also possible to use other electron accepting compounds in combination. In this case, the proportion of the compound represented by the general formula (1) in all the electron accepting compounds is usually 10% by weight or more, preferably 20% by weight.
As described above, it is more preferable to adjust the content to 30% by weight or more.

Examples of the electron accepting compound other than the compound represented by the general formula (1) include organic electron accepting compounds such as phenol derivatives, organic acids or metal salts and complexes thereof, and urea derivatives; And receptive compounds. Some specific examples of these compounds include 4-tert-butylphenol, 4-tert-octylphenol, 4-phenylphenol, 1-naphthol, 2-naphthol, hydroquinone, resorcinol, 4-tert-octylcatechol, , 2'-dihydroxybiphenyl, 4,4'-dihydroxydiphenyl ether, 2,2-bis (4'-hydroxyphenyl)
Propane [“bisphenol A”], 1,1-bis (4′-hydroxyphenyl) cyclohexane, 2,2
-Bis (4'-hydroxy-3'-methylphenyl) propane, 1,3-bis (4'-hydroxycumyl) benzene, 1,4-bis (4'-hydroxycumyl) benzene, 5-tris (4'-hydroxycumyl) benzene,

Ethyl 2,2-bis (4'-hydroxyphenyl) acetate, n-butyl 4,4- (4'-hydroxyphenyl) pentanoate, benzyl 4-hydroxybenzoate, 4-hydroxybenzoate Acid phenethyl ester, 2,4-dihydroxybenzoic acid phenoxyethyl ester, 4-hydroxyphthalic acid dimethyl ester, gallic acid-n-propyl ester, gallic acid-n-octyl ester, gallic acid-n-dodecyl ester, gallic acid- n-octadecyl ester, hydroquinone monobenzyl ether, bis (3-methyl-4-hydroxyphenyl) sulfide, bis (2-methyl-4-hydroxyphenyl) sulfide, bis (3
-Phenyl-4-hydroxyphenyl) sulfide, bis (3-cyclohexyl-4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfoxide, bis (4-hydroxyphenyl) sulfone, bis (3-allyl-4-hydroxy Phenyl) sulfone,
Bis (3-phenyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4′-methyldiphenylsulfone, 4-hydroxy-4′-tert-butyldiphenylsulfone, 4-hydroxy-4′-chlorodiphenylsulfone,

4-hydroxy-4'-methoxydiphenylsulfone, 4-hydroxy-4'-n-propoxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4 '
-N-butoxydiphenylsulfone, 4-hydroxy-4'-benzyloxydiphenylsulfone, 3,4
-Dihydroxy-4'-methyldiphenylsulfone,
2,4'-dihydroxydiphenylsulfone, 2-methoxy-4'-hydroxydiphenylsulfone, 2-
Ethoxy-2'-hydroxydiphenylsulfone, 4
-Hydroxy-3-methyl-4'-n-propoxydiphenylsulfone, bis (2-hydroxy-5-tert-
Butylphenyl) sulfone, bis (2-hydroxy-
5-chlorophenyl) sulfone, bis [4- (3'-
Hydroxyphenyloxy) phenyl] sulfone, 4
-Hydroxybenzophenone, 2,4-dihydroxybenzophenone, 1,7-di (4'-hydroxyphenylthio) -3,5-dioxaheptane, 1,5-di (4 '
Phenol derivatives such as -hydroxyphenylthio) -3-oxapentane,

4- [2 '-(4-methoxyphenoxy)
Ethoxy] salicylic acid, 5- [4 ′-(2- [4-methoxyphenoxy] ethoxy) cumyl] salicylic acid, 4-
[3 ′-(4-methylphenylsulfonyl) propoxy] salicylic acid, 1-naphthoic acid, 1-hydroxy-2
-Naphthoic acid, 2-hydroxy-3-naphthoic acid, 2-
Hydroxy-6-naphthoic acid, 1-acetyloxy-2
-Naphthoic acid, 2-acetyloxy-1-naphthoic acid,
2-acetyloxy-3-naphthoic acid, monobenzyl phthalate, monophenyl phthalate, 4-
Organic acids such as nitrobenzoic acid, 4-chlorobenzoic acid, and 4-formylbenzoic acid, and metal salts thereof (for example,
Metal salts such as nickel, zinc, aluminum and calcium), complexes such as zinc thiocyanate antipyrine complex and acetylacetone molybdate complex, N, N'-diphenylthiourea, and N, N'-di (3-trifluoromethylphenyl) Thiourea, N, N'-di (3-chlorophenyl) thiourea, 1,4-di (3'-chlorophenyl) -3
-Organic electron-accepting compounds such as urea derivatives such as thiosemicarbazide, acid clay, attapulgite, activated clay,
Preferred compounds include inorganic electron-accepting compounds such as aluminum chloride, zinc chloride, and zinc bromide. Of course, the present invention is not limited to these compounds, and these electron-accepting compounds may be used alone or in combination.

Further, the addition of a heat-fusible compound (compound having a melting point of about 70 to 150 ° C., more preferably a compound having a melting point of about 80 to 130 ° C.) as a sensitizer to the heat-sensitive recording material of the present invention, This is preferable for obtaining a thermosensitive recording material compatible with high-speed recording. In this case, usually, 100 parts by weight of the electron-donating color-forming compound is added to the heat-fusible compound 10.
７００700 parts by weight, preferably 20-500 parts by weight. Such heat-fusible compounds include, for example, caproic acid amide, capric acid amide, palmitic acid amide, stearic acid amide, oleic acid amide,
Erucinamide, linoleamide, linolenic amide, N-ethylcapramide, N-butyllauric amide, N-methylstearic amide, N-methyloleic amide, N-stearylcyclohexylamide, N-octadecylacetamide N-olein acetamide, stearyl urea, stearic anilide, benzanilide, linoleic anilide, acetoacetic anilide, o-acetoacetic toluidide, p-acetoacetic anisidide, N-ethylcarbazole, nitrogen-containing compounds such as 4-methoxydiphenylamine, 4-benzyloxybenzoic acid benzyl ester, 2-naphthoic acid phenyl ester, 1-hydroxy-2-naphthoic acid phenyl ester, oxalic acid dibenzyl ester, oxalic acid di (4-methylbenzyl) es Le, oxalic acid di (4-chlorobenzyl) ester, glutaric acid di phenacyl ester, di (4-methylphenyl) carbonate, ester compounds such as terephthalic acid dibenzyl ester,

Hydrocarbon compounds such as 4-benzylbiphenyl, m-terphenyl, fluorene, fluoranthene, 2,6-diisopropylnaphthalene, and 3-benzylacenaphthene; 2-benzyloxynaphthalene;
(4′-methylbenzyloxy) naphthalene, 1,4-
Diethoxynaphthalene, 1,2-diphenoxyethane,
1,2-bis (3′-methylphenoxy) ethane, 1-
Phenoxy-2- (4′-ethylphenoxy) ethane,
1- (4′-methoxyphenoxy) -2-phenoxyethane, 1- (4′-methoxyphenoxy) -2- (3 ′
-Methylphenoxy) ethane, 1- (4'-methoxyphenoxy) -2- (2'-methylphenoxy) ethane,
1,2-bis (4′-methoxyphenylthio) ethane,
1,5-bis (4′-methoxyphenoxy) -3-oxapentane, 1,4-bis (2′-vinyloxyethoxy) benzene, 4- (4′-methylphenoxy) biphenyl, 1,4-bis ( 2'-chlorobenzyloxy) benzene, 4,4'-di-n-butoxydiphenylsulfone, 1,2-diphenoxybenzene, 1,4-bis (2'-chlorophenoxy) benzene, 1,4-bis ( 4′-methylphenoxy) benzene, 1,4-bis (3′-methylphenoxymethyl) benzene, 4-chlorobenzyloxy- (4′-ethoxybenzene), 4,
4′-bis (phenoxy) diphenyl ether, 4,
4'-bis (phenoxy) diphenylthioether,
1,4-bis (4′-benzylphenoxy) benzene,
Ether compounds such as 1,4-bis [(4'-methylphenyloxy) methoxymethyl] benzene, 1,4-diglycidyloxybenzene, 4-benzyloxy-4'-
Epoxy compounds such as (2-methylglycidyloxy) diphenylsulfone, 4- (4-methylbenzyloxy) -4′-glycidyloxydiphenylsulfone, and N-glycidylphthalimide can be exemplified. Of course, it is not limited to these compounds, and these heat-fusible compounds may be used alone or in combination of two or more.

The heat-sensitive recording material of the present invention can be manufactured by a known method without using a special method. In general, the electron-donating color-forming compound, the compound represented by the general formula (1), and the like are each usually dissolved in a water-soluble binder by means such as a ball mill, a sand mill, a horizontal sand mill, an attritor, and a colloidal mill. 3
The coating liquid for the recording layer can be prepared by pulverizing, dispersing, and mixing to a particle size of not more than 2 μm, preferably not more than 2 μm.

Examples of such a water-soluble binder include polyvinyl alcohol, sulfonated polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, modified epichlorohydrin polyamide, ethylene-maleic anhydride copolymer, styrene-
Maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyacrylic acid, polyacrylamide, methylol-modified polyacrylamide, starch derivative, casein, gelatin, methylcellulose, carboxymethylcellulose, gum arabic, carboxyl-modified polyvinyl alcohol, etc. Can be mentioned.

Further, if necessary, the recording layer of the heat-sensitive recording material of the present invention may contain a pigment, a water-insoluble binder, a metal soap, a wax, a surfactant, an ultraviolet absorber, a hindered phenol, a defoaming agent and the like. Is added. As pigments, zinc oxide, zinc carbonate, calcium carbonate, magnesium carbonate, barium carbonate, barium sulfate, titanium oxide, talc, laurite, kaolin, diatomaceous earth, aluminum hydroxide, magnesium hydroxide, alumina, silica, amorphous Silica, urea-formalin filler, polyethylene particles, cellulose filler and the like are used. As the water-insoluble binder, a synthetic rubber latex or a synthetic resin emulsion is generally used, and styrene-butadiene rubber latex, acrylonitrile-butadiene latex, methyl acrylate-butadiene rubber latex, vinyl acetate emulsion, and the like are known. Used accordingly.

As the metal soap, higher fatty acid metal salts are used, and zinc stearate, calcium stearate,
Aluminum stearate, zinc oleate and the like are used. Examples of the wax include paraffin wax, microcrystalline wax, modified carboxy paraffin wax, carnauba wax, polyethylene wax, polystyrene wax, canderia wax, montan wax, and higher fatty acid esters. As the surfactant, a sulfosuccinic acid-based alkali metal salt [for example, di (n-hexyl) sulfosuccinic acid,
Sodium salt such as di (2-ethylhexyl) sulfosuccinic acid], sodium salt of dodecylbenzenesulfonic acid, sodium salt of lauryl alcohol sulfate,
Examples include a fluorine-containing surfactant. Examples of the ultraviolet absorber include cinnamic acid derivatives, benzophenone derivatives, and benzotriazolylphenol derivatives.

The hindered phenol is preferably a phenol derivative in which at least one of the ortho positions of the phenolic hydroxyl group is substituted with a branched alkyl group.
3-tris (2-methyl-4-hydroxy-5-tert-
Butylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl)
Butane, 1,1,3-tris (2-ethyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3
-Tris (3,5-di-tert-butyl-4-hydroxyphenyl) butane, 1,1,3-tris (2-methyl-
4-hydroxy-5-tert-butylphenyl) propane, 2,2′-methylene-bis (6-tert-butyl-4)
-Methylphenol), 2,2′-methylene-bis (6
-Tert-butyl-4-ethylphenol), 1,3,5
-Trimethyl-2,4,6-tris (3,5-di-tert
-Butyl-4-hydroxybenzyl) benzene, 1,
3,5-tris (4-tert-butyl-3-hydroxy-
2,6-dimethylbenzyl) isocyanuric acid, 1,3
5-tris (4-tert-butyl-3-hydroxy-2-
Methyl-6-ethylbenzyl) isocyanuric acid, bis (2-methyl-4-hydroxy-5-tert-butylphenyl) sulfide and the like.

In the heat-sensitive recording material of the present invention, the method for forming the recording layer is not particularly limited, and it can be formed according to a conventionally known technique. For example, a coating solution for a heat-sensitive recording layer is coated on a support with an appropriate coating device such as an air knife coater, a blade coater, a bar coater, a gravure coater, a curtain coater, a wire bar, and the like, and dried to form a recording layer. be able to. Also, the amount of the coating liquid applied is not particularly limited, and is generally 1.5 to 12 g / dry weight.
m ² , preferably in the range of 2.5 to 10 g / m ² . As the support, paper, plastic sheet, synthetic paper, or a composite sheet obtained by combining these is used. If necessary, a protective layer (overcoat layer) may be provided on the front and / or back surface of the heat-sensitive recording layer, or a single layer or a plurality of layers of pigment (for example, kaolin) or Providing an undercoat layer (undercoat layer) made of a synthetic resin (eg, plastic spherical particles, plastic spherical hollow particles),
It is of course possible to provide an intermediate layer made of a pigment, a binder or the like between the heat-sensitive recording layer and the undercoat layer, or between the heat-sensitive recording layer and the protective layer. Various known techniques in a method for producing a thermosensitive recording material can be provided.

[0028]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In Examples,% represents% by weight. [Preparation of thermosensitive recording paper] Liquids A, B, and C shown below were each dispersed by a sand grinding mill so that the average particle diameter became 1.5 µm to prepare a dispersion liquid. (Solution A composition) Electron-donating color-forming compound 10 g 10% aqueous polyvinyl alcohol solution (Kuraray-117) 10 g Water 80 g total 100 g (Solution B composition) Electron-accepting compound 20 g Light calcium carbonate (Okutama Kogyo, TP-123) 40 g 10% aqueous solution of polyvinyl alcohol (Kuraray-117) 60 g Water 130 g Total 250 g (Composition of liquid C) Heat-fusible compound (2-benzyloxynaphthalene) 20 g 10% Polyvinyl alcohol aqueous solution (Kuraray-117) 10 g Water 220 g Total 250 g

Examples 1 to 3 A dispersion of 100 g of solution A, 250 g of solution B, and 250 g of solution C, and 23 g of 30% paraffin wax were mixed, and the mixture was applied to wood free paper at a dry coating amount of 5 g / m ² . It was coated so as to be dried and dried to prepare a thermosensitive recording paper. The electron-donating color-forming compound and the electron-accepting compound used in each Example are shown in Table 1 (Table 1).

[0030]

[Table 1]

Comparative Examples 1-2 A dispersion of 100 g of solution A, 250 g of solution B, and 250 g of solution C, and 23 g of 30% paraffin wax were mixed, and the mixture was applied to a high quality paper at a dry coating amount of 5 g / m ² . It was coated so as to be dried and dried to prepare a thermosensitive recording paper. In Comparative Examples 1 and 2, 3-di-n-butylamino-6-methyl-7-anilinofluoran was used as the electron-donating color-forming compound in Solution A. As the electron accepting compound in the solution B, bisphenol A was used in Comparative Example 1 and Comparative Example 2 was used.
Used benzyl 4-hydroxybenzoate.

[Evaluation of Thermosensitive Recording Paper] (Storage Stability Test of Uncolored Area) For each of the thermosensitive recording papers produced in Examples and Comparative Examples, the whiteness of the uncolored area (background) immediately after coating was measured by a color difference meter. (Σ-80, manufactured by Nippon Denshoku). In addition, the storage stability test was performed by a heat and moisture resistance test, an oil resistance test and a writing instrument test, and the whiteness of the uncolored portion of each thermosensitive recording paper after each test was examined. In the wet heat resistance test, the whiteness of each heat-sensitive recording paper after being stored at 60 ° C. and 90% relative humidity for 24 hours was measured using a color difference meter. The oil resistance test was performed by superimposing a capsule-coated paper containing dioctyl phthalate on each heat-sensitive recording paper, passing the paper through a pressure roll, and storing the paper at 25 ° C. for one week using a color difference meter. It was measured. The larger the numerical value, the higher the whiteness and the better the storage stability of the uncolored portion. -As a writing instrument test, after writing the uncolored portion with a fluorescent pen, the whiteness after standing at 25 ° C for 72 hours was visually observed. ◎ indicates a state of high whiteness without stains, and X indicates a state of stained black gray. The results are shown in Table 2 (Table 2).

[0033]

[Table 2] From the results shown in Table 2, the heat-sensitive recording material of the present invention using the compound represented by the general formula (1) as an electron-accepting compound is as follows:
It can be seen that, in comparison with a heat-sensitive recording material prepared by using a conventional electron-accepting compound, a writing instrument test of an uncolored portion is extremely excellent.

(Storage Stability Test of Colored Image) A Macbeth densitometer (TR-524 type) was applied to each of the thermal recording papers produced in the Examples and Comparative Examples using a thermal paper coloring apparatus (TH-PMD manufactured by Okura Electric Co., Ltd.). ) Is 0.9.
After forming a colored image, a storage stability test was performed. In the storage stability test, a moist heat resistance test, an oil resistance test, and a writing instrument test were performed, and the image storage stability of each thermosensitive recording paper after each test was examined. In the wet heat resistance test, the color image density after each heat-sensitive recording paper was stored at 60 ° C. and 90% relative humidity for 24 hours was measured using a Macbeth densitometer to determine the residual ratio of the color image. The oil resistance test was performed by superposing a capsule-coated paper containing dioctyl phthalate on each heat-sensitive recording paper, passing through a pressure roll, and storing the color image density after storage at 25 ° C. for one week, using a Macbeth densitometer. And the residual ratio of the color image was determined. In addition, the residual ratio was calculated by the following equation. The larger the value, the better the storage stability of the color image. -As a writing instrument test, after writing a color image with a fluorescent pen, the degree of the residual ratio of the color image after standing at 25 ° C for 72 hours was visually observed. ◎ indicates a state without decoloration,
X shows the state where the color was erased. The results are shown in Table 3 (Table 3).

[0035]

[Table 3] From the results shown in Table 3, the heat-sensitive recording material of the present invention using the compound represented by the general formula (1) as an electron-accepting compound,
It can be seen that the storage stability (moisture heat resistance, oil resistance and writing implement resistance) of the color image is very excellent as compared with the heat-sensitive recording material prepared using the conventional electron-accepting compound.

[0036]

According to the present invention, it has become possible to provide a heat-sensitive recording material which is very excellent in storage stability of an uncolored portion and a color image.

Claims (1)

(57) [Claims] 1. A thermosensitive recording material containing an electron-donating color-forming compound and an electron-accepting compound, wherein the electron-accepting compound contains at least one compound represented by the general formula (1) (formula 1). A heat-sensitive recording material characterized in that: Embedded image (In the formula, X represents a sulfur atom or a sulfonyl group .
And 4,4'-bis (p-hydroxyphenylsulfo
Nyl) excluding diphenylsulfone. )