JPH0768936A - Thermosensitive recording material and method for producing hydrate of zinc salt of benzoic acid derivative - Google Patents

Abstract

(57) [Summary] [Object] To provide a heat-sensitive recording material having excellent storage stability, and a method for producing a hydrate of a zinc salt of a benzoic acid derivative useful as an electron-accepting compound for the heat-sensitive recording material. In a heat-sensitive recording material containing an electron-donating color forming compound and an electron-accepting compound, at least one hydrate of a zinc salt of a benzoic acid derivative represented by the general formula (1) is used as the electron-accepting compound. Thermal recording material containing. [Chemical 1] (In the formula, R represents an alkyl group having 1 to 4 carbon atoms, a halogen atom or a nitro group) and a zinc salt anhydride of a benzoic acid derivative represented by the general formula (1) is heat-treated in the presence of water. A method for producing a hydrate of a zinc salt of a benzoic acid derivative.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat-sensitive recording material.
Furthermore, it relates to a method for producing a hydrate of a zinc salt of a benzoic acid derivative useful as an electron-accepting compound for a heat-sensitive recording material.

[0002]

2. Description of the Related Art Conventionally, a heat-sensitive recording material utilizing a color reaction between an electron-donating color-forming compound and an electron-accepting compound (developing agent) is well known (for example, Japanese Patent Publication No. 43-4).
160, JP-B-45-14039). The heat-sensitive recording material is relatively inexpensive and has the advantage that the recording device is compact and maintenance-free, and is therefore widely used in the fields of facsimiles, recorders and printers. In recent years, the fields of use of thermal recording materials have further expanded and diversified, and have expanded to applications (eg, labels, prepaid cards, etc.) under more severe environments.

Conventionally, phenolic compounds have been widely used as electron-accepting compounds. For example, 2,2-
Bis (4'-hydroxyphenyl) propane [bisphenol A], 4-hydroxybenzoic acid esters (JP-A-56-144193, JP-B-1-30640) and the like are used as electron-accepting compounds. Thermal recording materials are known. However, a heat-sensitive recording material using bisphenol A, 4-hydroxybenzoic acid benzyl ester or the like as an electron-accepting compound is, for example, in a harsh environment (for example, in contact with oil, solvent, plasticizer, etc. or under high temperature and high humidity). In the environment), there are drawbacks such that the uncolored part is significantly contaminated (ground stain), and the color image is discolored.

As a method for improving the storage stability of a color image, for example, a heat-sensitive recording material containing a zinc salt of a benzoic acid derivative of several kinds as an electron accepting compound or a color image stabilizer has been proposed. . For example, zinc salt of 4-chlorobenzoic acid (Japanese Patent Publication No. 4-17157),
Zinc salt of 4-nitrobenzoic acid (Japanese Patent Publication No. 2-39994), zinc salt of 4-methylbenzoic acid (Japanese Patent Publication No. 2-26)
No. 874) is known.

However, these publications do not disclose the method for producing a zinc salt of a benzoic acid derivative and the properties of the zinc salt. The present inventors have investigated and found that an anhydride of a zinc salt of a benzoic acid derivative, for example, 4-
For example, a heat-sensitive recording material using an anhydride of a zinc salt of nitrobenzoic acid as an electron-accepting compound has a problem in storage stability (for example, heat resistance) of an uncolored portion and has practically sufficient performance. It is hard to say that At present, there is a strong demand for a thermal recording material having excellent storage stability that overcomes the above-mentioned problems.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat sensitive recording material having improved storage stability. Furthermore, it is to provide a method for producing a hydrate of a zinc salt of a benzoic acid derivative useful as an electron-accepting compound for the heat-sensitive recording material.

[0007]

The inventors of the present invention have arrived at the present invention as a result of extensive studies to meet the above-mentioned demand. That is, the present invention provides a hydrate of a zinc salt of a benzoic acid derivative represented by the general formula (1) as an electron-accepting compound in a heat-sensitive recording material containing an electron-donating color-forming compound and an electron-accepting compound. The present invention relates to a heat-sensitive recording material containing at least one kind.

[0008]

[Chemical 3] (In the formula, R represents an alkyl group having 1 to 4 carbon atoms, a halogen atom or a nitro group.) Furthermore, an anhydride of a zinc salt of a benzoic acid derivative represented by the general formula (1) is added in the presence of water. The present invention relates to a method for producing a hydrate of a zinc salt of a benzoic acid derivative represented by the general formula (1), which is heat-treated with.

In the benzoic acid derivative represented by the general formula (1), R represents an alkyl group having 1 to 4 carbon atoms, a halogen atom or a nitro group. Specific examples of R include methyl group, ethyl group, n-propyl group, isopropyl group and n-
Butyl group, isobutyl group, sec-butyl group, tert-butyl group, fluorine atom, chlorine atom, bromine atom, iodine atom,
A nitro group can be mentioned, and a methyl group, a chlorine atom and a nitro group are more preferable.

In the benzoic acid derivative represented by the general formula (1), the substitution position of R is an ortho position, a meta position or a para position with respect to the carboxyl group, and more preferably a para position.

Specific examples of the benzoic acid derivative represented by the general formula (1) include 4-methylbenzoic acid, 4-ethylbenzoic acid, 4-n-propylbenzoic acid, 4-isopropylbenzoic acid and 4 -N-Butylbenzoic acid, 4-isobutylbenzoic acid, 4-tert-butylbenzoic acid, 4-fluorobenzoic acid, 4-chlorobenzoic acid, 4-bromobenzoic acid, 4-iodobenzoic acid, 3-methylbenzoic acid , 3-chlorobenzoic acid, 3-nitrobenzoic acid, 2-methylbenzoic acid, 2-chlorobenzoic acid, 2-nitrobenzoic acid, and more preferably 4-methylbenzoic acid, 4
-Chlorobenzoic acid and 4-nitrobenzoic acid, particularly preferably 4-chlorobenzoic acid and 4-nitrobenzoic acid.

The hydrate of the zinc salt of the benzoic acid derivative represented by the general formula (1) according to the present invention is produced from the benzoic acid derivative represented by the general formula (1) by, for example, a metathesis method. It That is, for example, a water-soluble salt of a benzoic acid derivative represented by the general formula (1) such as an alkali metal salt, an amine salt or an ammonium salt of a benzoic acid derivative represented by the general formula (1) and a water-soluble salt The zinc compound can be reacted in the presence of water to produce a hydrate of a sparingly water-soluble or water-insoluble zinc salt of a benzoic acid derivative.

These water-soluble salts of the benzoic acid derivative represented by the general formula (1) are usually used in an amount of 0.8 to 1% with respect to 1 equivalent of the benzoic acid derivative represented by the general formula (1). 2 equivalents, preferably 1.0 to 1.1 equivalents of an alkali metal compound (for example, lithium hydroxide, sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, sodium hydrogen carbonate), or an amine compound (for example, It can be produced by reacting methylamine, ethylamine, dimethylamine, diethylamine, trimethylamine, triethylamine, ethanolamine, isopropanolamine, triethanolamine, 2-dimethylaminoethanol, morpholine, ammonia) in the presence of water.

At this time, in addition to water, a water-soluble organic solvent, for example, an alcohol solvent such as methanol, isopropanol, methyl cellosolve or ethylene glycol,
Ether solvents such as tetrahydrofuran and dioxane,
A ketone-based solvent such as acetone, an aprotic polar solvent such as dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, and sulfolane may be allowed to coexist.

As the water-soluble zinc compound, for example,
Examples thereof include zinc sulfate, zinc chloride, zinc bromide, zinc acetate and zinc nitrate. The amount of these zinc compounds used is 0.8 to 1.5 equivalents, preferably 1.0, relative to 1 equivalent of the alkali metal salt of the benzoic acid derivative represented by the general formula (1).
~ 1.2 equivalents.

The method of reacting the zinc compound with the alkali metal salt of the benzoic acid derivative represented by the general formula (1) in the presence of water is not particularly limited, and examples thereof include benzoic acid. The zinc compound may be added to an aqueous solution of an alkali metal salt of an acid derivative, or the aqueous solution of an alkali metal salt of a benzoic acid derivative may be added to an aqueous solution of a zinc compound. At this time, heating may be carried out as desired, and an organic solvent other than water may coexist. After the metathesis, the precipitated zinc salt hydrate is taken out by a known method (for example, filtration) and dried to obtain a benzoic acid derivative zinc salt hydrate represented by the general formula (1). be able to.

The hydrate of the zinc salt of the benzoic acid derivative represented by the general formula (1) is stable under atmospheric pressure and near room temperature, and its state does not change. But,
Under harsh conditions, such as above 100 ° C,
Since the hydrate of the zinc salt of the benzoic acid derivative represented by the general formula (1) gradually loses water and may be converted into an anhydride, no water is lost during drying. It is performed under moderate conditions (for example, room temperature to a temperature of about 90 ° C.).

As described above, the zinc salt of the benzoic acid derivative represented by the general formula (1) includes an anhydride and a hydrate, but the zinc salt of the benzoic acid derivative represented by the general formula (1) The hydrate of the zinc salt of the benzoic acid derivative represented by the general formula (1) can be produced by heat treating the anhydrous zinc salt in the presence of water.

The anhydrous zinc salt of the benzoic acid derivative represented by the general formula (1) is sparingly soluble or insoluble in water,
The anhydrous zinc salt is dispersed in an aqueous medium without being substantially dissolved, and as a method of heat treatment, an aqueous medium containing the anhydrous zinc salt is used at a temperature of room temperature or higher, preferably Is
A method of heating to 50 to 100 ° C. and stirring can be applied.
Although the heat treatment time depends on the temperature, most of the anhydride can be converted to a hydrate by performing the heat treatment for about 30 minutes or more. Whether or not the anhydride has been converted into a hydrate can be determined by a known analysis means such as an X-ray diffraction method, and thus the heat treatment time can be determined by these analysis means. Although long-time heat treatment does not have a bad effect, spending a long time itself
It only brings about a decrease in work efficiency, production efficiency, etc., and is usually 30 minutes to 20 hours, more preferably 1 hour to 1
A heat treatment time of 5 hours is sufficient.

The hydrate of the zinc salt of the benzoic acid derivative represented by the general formula (1) produced as described above contains a specific number of water molecules per zinc atom. Each of them has a unique crystal form characterized by a powder X-ray diffraction pattern of Cu-Kα radiation. The water content in the hydrate can be determined by known analysis means such as thermogravimetric analysis, elemental analysis or Karl Fischer analysis.

The method for producing the hydrate of the zinc salt of the benzoic acid derivative represented by the general formula (1) of the present invention is as follows:
It is characterized in that the anhydride of the zinc salt of the benzoic acid derivative represented by the general formula (1) is heat-treated, but in addition to water, a water-soluble organic solvent such as methanol,
Alcohol solvents such as isopropanol, methyl cellosolve and ethylene glycol, ether solvents such as tethydrofuran and dioxane, ketone solvents such as acetone, dimethylformamide, dimethylacetamide, N
An aprotic polar solvent such as -methyl-2-pyrrolidone, dimethyl sulfoxide and sulfolane may coexist. When the proportion of the water-soluble organic solvent is high, the recovery rate of the hydrate of the zinc salt of the benzoic acid derivative represented by the general formula (1) produced decreases. The amount of soluble organic solvent is preferably 60% by weight or less, and more preferably 40% by weight or less.

The stirring device is not particularly limited, but the zinc salt of the benzoic acid derivative represented by the general formula (1) is necessary for maintaining the state of being dispersed in the aqueous medium. Preference is given to using a device with stirring capacity.

Although the use of a large amount of the aqueous medium does not impede the effect of the present invention, the use of an excessive amount of the medium itself requires a large apparatus and a container, which lowers the production efficiency. It is clear that it usually brings
It is preferable to perform heat treatment in an aqueous medium of 0.5 to 100 times (volume / weight) with respect to the anhydride of the zinc salt of the benzoic acid derivative represented by the general formula (1), and more preferably 1 to
50 times (volume / weight).

The hydrate of the zinc salt of the benzoic acid derivative represented by the general formula (1) produced by the method of the present invention is
It is possible to easily filter and isolate from the reaction system by a known means and device without using a special device. After filtration, it is dried under the condition that it does not change to an anhydride,
Dispersed by the method, or without a drying step,
A dispersion liquid of the electron-accepting compound for the heat-sensitive recording material can be prepared by directly dispersing after filtration.

Examples of the hydrate of the zinc salt of the benzoic acid derivative represented by the general formula (1) according to the present invention include, for example, a hydrate of zinc salt of 4-methylbenzoic acid and a zinc salt of 4-chlorobenzoic acid. And a hydrate of 4-nitrobenzoic acid zinc salt can be specifically mentioned. Hereinafter, hydrates of these zinc salts of benzoic acid derivatives will be described in detail.

Hydrate of 4-methylbenzoic acid zinc salt is 1
Contains two water molecules for one zinc ion (hereinafter,
It is referred to as the dihydrate of 4-methylbenzoic acid zinc salt). This 4-methylbenzoic acid zinc salt dihydrate has an X-ray diffraction pattern showing strong peaks at diffraction angles (2θ) of 6.8 ° and 17.3 ° in a powder X-ray diffraction method of Cu-Kα line. Indicates.

Hydrate of 4-chlorobenzoic acid zinc salt is 1
Contains two water molecules for one zinc ion (hereinafter,
Referred to as the dihydrate of 4-chlorobenzoic acid zinc salt). This 4-chlorobenzoic acid zinc salt dihydrate has a diffraction angle (2θ) of 17.5 ° in a powder X-ray diffraction method using Cu-Kα radiation.
An X-ray diffraction diagram showing a strong peak is shown.

Hydrate of 4-nitrobenzoic acid zinc salt is 1
Contains two water molecules for one zinc ion (hereinafter,
It is referred to as the dihydrate of 4-nitrobenzoic acid zinc salt). This 4-nitrobenzoic acid zinc salt dihydrate has a diffraction angle (2θ) of 7.0 ° in a powder X-ray diffraction method using Cu-Kα radiation.
An X-ray diffractogram showing a strong peak at 14.0 ° and relatively strong peaks at 17.0 °, 24.8 ° and 27.7 ° is shown.

The display of the diffraction angle (2θ) usually has an error of about ± 0.2 °.

The heat-sensitive recording material of the present invention is a heat-sensitive recording material containing an electron-donating color forming compound and an electron-accepting compound, and a zinc salt of a benzoic acid derivative represented by the general formula (1) as the electron-accepting compound. The hydrate of the zinc salt of the benzoic acid derivative represented by the general formula (1) may be used alone or in combination.

In the heat-sensitive recording material of the present invention, usually,
50 to 700 parts by weight of electron-accepting compound, preferably 100 to 5 parts by weight, relative to 100 parts by weight of electron-donating color forming compound.
It is desirable to use 100 parts by weight.

Examples of the colorless or light-colored electron-donating color forming compound used in the present invention include triarylmethane compounds, diarylmethane compounds, rhodamine-lactam compounds, fluorane compounds, indolylphthalide compounds, divinyl. Examples thereof include phthalide compounds, pyridine compounds, spiro compounds, fluorene compounds and thiazine compounds.

Some specific examples of these compounds include 3,3-triarylmethane compounds.
Bis (4-dimethylaminophenyl) -6-dimethylaminophthalide ["Crystal Violet Lactone"], 3,3-bis (4-dimethylaminophenyl)
Phthalide, 3- (4-dimethylaminophenyl) -3-
(4-Diethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazole-3)
-Yl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (1-methylpyrrole-
3-yl) -6-dimethylaminophthalide and the like.

The diarylmethane compound is 4,
4-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl-leuco auramine, N-2,
Examples include 4,5-trichlorophenylleuco auramine.

As the rhodamine-lactam compound,
Rhodamine-B-anilinolactam, Rhodamine- (4
-Nitroanilino) lactam, rhodamine-B- (2-
Chloroanilino) lactam etc.

Fluoran compounds include 3,6-dimethoxyfluorane, 3-diethylamino-6-methoxyfluorane, 3-dimethylamino-7-methoxyfluorane, 3-diethylamino-7-methylfluorane,
3-N-cyclohexyl-Nn-butylamino-7-
Methylfluorane, 3-N-ethyl-N-isopentylamino-7-methylfluorane, 3-diethylamino-
7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7
-Chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3,6-bis (diphenylamino)
Fluoran,

3-diethylamino-7-dibenzylaminofluorane, 3-di-n-butylamino-7-dibenzylaminofluorane, 3-diethylamino-7-di-
n-hexylaminofluorane, 3-diethylamino-
7-n-octylaminofluorane, 3-diethylamino-7-anilinofluorane, 3-N-ethyl-N-isopentylamino-7-anilinofluorane,

3-Diethylamino-7- (2'-chlorophenylamino) fluorane, 3-diethylamino-7
-(3'-chlorophenylamino) fluorane, 3-diethylamino-7- (2 ', 3'-dichlorophenylamino) fluorane, 3-diethylamino-7- (3'-
Trifluoromethylphenylamino) fluorane, 3-
Di-n-butylamino-7- (2′-chlorophenylamino) fluorane,

3-Diethylamino-6-chloro-7-anilinofluorane, 3-di-n-butylamino-6-chloro-7-anilinofluorane, 3-diethylamino-
6-methoxy-7-anilinofluorane, 3-di-n-
Butylamino-6-ethoxy-7-anilinofluorane,

3-Pyrrolidino-6-methyl-7-anilinofluorane, 3-morpholino-6-methyl-7-anilinofluorane, 3-dimethylamino-6-methyl-7
-Anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-di-n-butylamino-6-methyl-7-anilinofluorane, 3-di-n
-Pentylamino-6-methyl-7-anilinofluorane, 3-di-n-octylamino-6-methyl-7-anilinofluorane, 3-N-n-propyl-N-methylamino-6- Methyl-7-anilinofluorane, 3-N
-N-butyl-N-methylamino-6-methyl-7-anilinofluorane, 3-N-n-butyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-N-
Isobutyl-N-methylamino-6-methyl-7-anilinofluorane, 3-N-isobutyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-Nn
-Pentyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-N-isopentyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-N-
n-hexyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-N-n-octyl-N-ethylamino-6-methyl-7-anilinofluorane,

3-N-cyclopentyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-N-cyclohexyl-N-methylamino-6-methyl-7-anilinofluorane, 3-N -Cyclohexyl-N-n-
Propylamino-6-methyl-7-anilinofluorane, 3-N-cyclohexyl-Nn-butylamino-
6-methyl-7-anilinofluorane, 3-N-cyclohexyl-Nn-hexylamino-6-methyl-7-
Anilinofluorane, 3-N-cyclohexyl-Nn
-Octylamino-6-methyl-7-anilinofluorane,

3-N- (2'-methoxyethyl) -N-
Isobutylamino-6-methyl-7-anilinofluorane, 3-N- (2'-ethoxyethyl) -N-ethylamino-6-methyl-7-anilinofluorane, 3-N-
(3'-Methoxypropyl) -N-methylamino-6-
Methyl-7-anilinofluorane, 3-N- (3'-methoxypropyl) -N-ethylamino-6-methyl-7
-Anilinofluorane, 3-N- (3'-ethoxypropyl) -N-methylamino-6-methyl-7-anilinofluorane, 3-N- (3'-ethoxypropyl) -N
-Ethylamino-6-methyl-7-anilinofluorane, 3-N- (2'-tetrahydrofurfuryl) -N-
Ethylamino-6-methyl-7-anilinofluorane,
3-N- (4'-methylphenyl) -N-ethylamino-6-methyl-7-anilinofluorane,

3-Diethylamino-6-ethyl-7-anilinofluorane, 3-diethylamino-6-methyl-
7- (3'-methylphenylamino) fluorane, 3-
Diethylamino-6-methyl-7- (2 ', 6'-dimethylphenylamino) fluorane, 3-di-n-butylamino-6-methyl-7- (2', 6'-dimethylphenylamino) fluorane, 3 -Di-n-butylamino-
7- (2 ', 6'-dimethylphenylamino) fluorane, 2,2-bis [4'-(3-N-cyclohexyl-
N-methylamino-6-methylfluorane) -7-ylaminophenyl] propane, 3- [4 ′-(4-phenylaminophenyl) aminophenyl] amino-6-methyl-7-chlorofluorane, etc. .

As the indolylphthalide compound,
3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide,
3,3-bis (1-ethyl-2-methylindole-3
-Yl) phthalide, 3,3-bis (1-octyl-2-
Methylindol-3-yl) phthalide, 3- (4-dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (4-dimethylaminophenyl) -3- (2- Methylindol-3-yl) phthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide, 3- (2-ethoxy-4-dibutyl) Aminophenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-octyl-2-methylindol-3-yl) ) There are phthalides.

As the divinylphthalide compound, 3,
3-bis [2,2-bis (4-dimethylaminophenyl) ethenyl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [2,2-bis (4-pyrrolidinophenyl) Ethenyl] -4,5,6,7-tetrabromophthalide, 3,3-bis [2- (4-methoxyphenyl)-
2- (4-dimethylaminophenyl) ethenyl] -4,
5,6,7-Tetrachlorophthalide, 3,3-bis [2
-(4-methoxyphenyl) -2- (4-pyrrolidinophenyl) ethenyl] -4,5,6,7-tetrachlorophthalide and the like.

Examples of the pyridine compound include 3- (2-ethoxy-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-Ethoxy-4-diethylaminophenyl) -3-
(1-octyl-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-n-butoxy-4-diethylaminophenyl) -3- (1-ethyl-2-phenylindol-3-yl) -4 or 7-azaphthalide, 3-
(4-Diethylamino-2-methylphenyl) -3-
(1-Ethyl-2-methylindol-3-yl) -4
Or 7-azaphthalide, 3- (4-diethylamino-
2-Methylphenyl) -3- (1-n-octyl-2-
Methylindol-3-yl) -4 or 7-azaphthalide, 3,3-bis (4-diethylamino-2-methoxyphenyl) -4 or 7-azaphthalide, 3,3-bis (4-diethylamino-2-ethoxyphenyl) ) -4
Or 7-azaphthalide.

The spiro compounds include 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 compound, 3,6-bis (dimethylamino) fluorene-9-spiro-3'-
(6′-Dimethylamino) phthalide, 3-diethylamino-6- (N-allyl-N-methylamino) fluorene-9-spiro-3 ′-(6′-dimethylamino) phthalide, 3,6-bis (dimethyl) Amino) -spiro [fluorene-9,6'-6'H-chromeno (4,3-b) indole], 3,6-bis (dimethylamino) -3'-methyl-spiro [fluorene-9,6 '-6'H-chromeno (4,3-b) indole], 3,6-bis (diethylamino) -3'-methyl-spiro [fluorene-9,
6'-6'H-chromeno (4,3-b) indole] and the like.

Examples of the thiazine compounds include benzoyl leuco methylene blue and 4-nitrobenzoyl leuco methylen blue.

These electron-donating color-forming compounds are independent,
Alternatively, a plurality may be used in combination.

The heat-sensitive recording material of the present invention is characterized by containing at least one hydrate of a zinc salt of a benzoic acid derivative represented by the general formula (1) as an electron-accepting compound. However, it is possible to use other electron-accepting compounds in combination as long as the desired effects of the present invention are not impaired.

In this case, the proportion of the hydrate of the zinc salt of the benzoic acid derivative represented by the general formula (1) in the total electron-accepting compound is usually 10% by weight or more, preferably 20% by weight or more. It is desirable to adjust the amount to 30% by weight or more.

The electron-accepting compounds other than the hydrate of the zinc salt of the benzoic acid derivative represented by the general formula (1) include organic electron-accepting compounds such as phenol derivatives, organic acids or their metal salts, complexes and urea derivatives. Examples thereof include compounds and inorganic electron accepting compounds such as acid clay.

Some specific examples of these compounds are 4-tert-butylphenol, 4-tert-octylphenol, 4-phenylphenol, 1-naphthol, 2-naphthol, hydroquinone, resorcinol, 4-tert-octyl. Catechol, 2,2'-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, 1,3,3 5-tris (4'-hydroxycumyl) benzene, 2,2-bis (4'-hydroxyphenyl) acetic acid ethyl ester, 4,4- (4'-hydroxyphenyl) pentanoic acid-n-butyl ester, 4- Hydroxybenzoic acid benzyl ester, 4-hydroxybenzoic 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 Acid-n-dodecyl ester, gallic acid-n-octadecyl ester, hydroquinone monobenzyl ether Le, 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-hydroxy) Phenyl) sulfoxide, bis (4-hydroxyphenyl) sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone,
4-hydroxy-4′-methyldiphenyl sulfone,
4-hydroxy-4'-tert-butyldiphenylsulfone, 4-hydroxy-4'-chlorodiphenylsulfone, 4-hydroxy-4'-methoxydiphenylsulfone, 4-hydroxy-4'-n-propoxydiphenylsulfone, 4- Hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-n-
Butoxydiphenyl sulfone, 4-hydroxy-4 '
-Benzyloxydiphenyl sulfone, 3,4-dihydroxy-4'-methyldiphenyl sulfone, 2,
4'-dihydroxydiphenyl sulfone, 2-methoxy-4'-hydroxydiphenyl sulfone, 2-ethoxy-2'-hydroxydiphenyl sulfone, 4-hydroxy-3-methyl-4'-n-propoxydiphenyl sulfone, 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-bis (4'-hydroxyphenylthio) -3,5- Dioxaheptane, 1,5-bis (4 '
A phenol derivative such as -hydroxyphenylthio) -3-oxapentane,

Salicylic acid, 3-isopropylsalicylic acid, 3-cyclohexylsalicylic acid, 3,5-di-tert
-Butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 3-methyl-5-α-methylbenzylsalicylic acid, 4- [2 '-(4-methoxyphenyloxy)
Ethyloxy] salicylic acid, 4- [3 ′-(4-methylphenylsulfonyl) propyloxy] salicylic acid, 4
-[3 '-(4-Methoxyphenylsulfonyl) propyloxy] salicylic acid, 5- {4'-[2- (4-methoxyphenyloxy) ethyloxy] cumyl} salicylic acid, 1-naphthoic acid, 2-naphthoic acid, 2 -Hydroxy-3-naphthoic acid, 2-hydroxy-6-naphthoic acid,
Organic acids such as 6-acetoxy-2-naphthoic acid, phthalic acid monobenzyl ester, phthalic acid monophenyl ester and 4-formylbenzoic acid, or metal salts thereof (for example, metal salts such as nickel, zinc, aluminum and calcium). , Zinc thiocyanate antipyrine complex, molybdate acetylacetone complex and other complexes, N, N′-
Organic electron accepting compounds such as urea derivatives such as diphenylthiourea, N, N'-di (3-trifluoromethylphenyl) thiourea, and 1,4-di (3'-chlorophenyl) -3-thiosemicarbazide, acidic White clay, attapulgite, colloidal silica, aluminum silicate, activated clay,
Inorganic electron-accepting compounds such as aluminum chloride, zinc chloride and zinc bromide can be mentioned as preferred compounds. These electron-accepting compounds may be used alone or in combination.

The heat-sensitive recording material of the present invention is further provided with various known formulations (addition of a heat-fusible compound, etc.) for producing a known heat-sensitive recording material, as described below.

In the heat-sensitive recording material of the present invention, a heat-fusible compound (a compound having a melting point of about 70 to 150 ° C., more preferably a melting point of about 80 to 130 ° C.) is optionally added to the heat-sensitive recording material of the present invention. This is preferable for obtaining a heat-sensitive recording material compatible with high speed recording.

In this case, it is usually desirable to use 10 to 700 parts by weight of the heat-fusible compound, preferably 20 to 500 parts by weight, based on 100 parts by weight of the electron-donating color forming compound.

Specific examples of such a heat-fusible compound include:
For example, caproic acid amide, capric acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, erucic acid amide, linoleic acid amide, linolenic acid amide, stearic acid methylenebisamide, stearyl urea, stearic acid anilide, N- Nitrogen-containing compounds such as ethylcarbazole and 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) ester, oxalic acid diester (4-chlorobenzyl) ester, glutaric acid diphenacyl ester, di (4-methylphenyl) carbonate, terephthalic acid dimethyl ester, terephthalic acid di-n-butyl ester, terephthalic acid dibenzyl ester, isophthalic acid di-n- Butyl ester, bis (4-benzyloxycarbonylphenyl) isophthalate, bis [2- (benzoyloxy)]
An ester compound such as ethyl] sulfide,

Hydrocarbon compounds such as 4-benzylbiphenyl, m-terphenyl, fluorene, fluoranthene, 2,6-diisopropylnaphthalene and 3-benzylacenaphthene,

2-benzyloxynaphthalene, 2-
(4'-methylbenzyloxy) naphthalene, 1,4-
Diethoxynaphthalene,

1,2-diphenoxyethane, 1,2-bis (3'-methylphenoxy) ethane, 1,2-bis (4'-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- (4 '
-Methoxyphenoxy) -2-phenoxypropane, 1
-Phenoxy-2- (4'-methoxyphenoxy) propane, 1,2-bis (4'-methoxyphenoxy) propane, 1,3-bis (4'-methoxyphenoxy) propane, 1- (4'-methoxyphenoxy) ) -2- (2 '
-Chlorophenoxy) ethane, 1,4-diphenoxybutane, bis [2- (4'-methoxyphenoxy) ethyl] ether,

4- (4'-methylphenoxy) biphenyl, 1,2-diphenoxybenzene, 1,4-diphenoxybenzene, 1,4-bisbenzyloxybenzene,
1,4-bis (2'-chlorobenzyloxy) benzene, 1,4-bis (2'-chlorophenoxy) benzene, 1,4-bis (4'-methylphenoxy) benzene, 1,4-bis (3 '-Methylphenoxymethyl) benzene, 4- (4'-chlorobenzyloxy) ethoxybenzene, 4,4'-bis (phenoxy) diphenyl ether, 1,4-bis (4'-benzylphenoxy) benzene, 1,4- Bis [(4'-methylphenyloxy) methoxymethyl] benzene,

4- (4'-methoxybenzylthio) anisole, 1-phenoxy-2- (4'-methoxyphenylthio) ethane, 1,2-bis (4'-methoxyphenylthio) ethane, 1- (4 '-Methylphenoxy) -2
-(4'-methoxyphenylthio) ethane, benzyl-
4-methylthiophenyl ether, 4,4'-bis (phenoxy) diphenylthioether, 4,4'-di-n
-Ether compounds such as butoxydiphenyl sulfone, sulfur-containing compounds,

1,4-di (glycidyloxy) benzene, 1,4-diglycidyl terephthalate, 4-glycidyloxy-4'-isopropyloxydiphenyl sulfone, 4-[(2,3-epoxy-2-methyl) propyl Compounds having an epoxy group such as oxy] phenyl-4 ′-(benzyloxy) phenyl sulfone and 4-[(2,3-epoxy) propyloxy] phenyl-4 ′-(4-methylbenzyloxy) diphenylsulfone. Can be mentioned. These heat fusible compounds may be used alone or in combination.

The heat-sensitive recording material of the present invention can be manufactured by a known method without using a special method.

Generally, an electron-donating color-forming compound, a hydrate of a zinc salt of a benzoic acid derivative represented by the general formula (1), and the like are each placed in a water-soluble binder in a ball mill, a sand mill or a horizontal sand mill. A coating liquid for the heat-sensitive recording layer can be prepared by dispersing by a means such as an attritor or colloidal mill, and usually pulverized and dispersed to a particle size of 3 μm or less, preferably 2 μm or less and mixed.

Specific examples of the water-soluble binder include polyvinyl alcohol, sulfonated polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, epichlorohydrin-modified polyamide, ethylene-maleic anhydride copolymer, and styrene-anhydrous. Maleic acid copolymer, isobutylene-maleic anhydride copolymer, polyacrylic acid, polyacrylamide, methylol-modified polyacrylamide, starch derivative, casein, gelatin, methylcellulose,
Examples include carboxymethyl cellulose, gum arabic, and carboxyl group-modified polyvinyl alcohol.

Further, in the recording layer of the heat-sensitive recording material of the present invention, a pigment, a water-insoluble binder, a metal soap, a wax, a surfactant, an ultraviolet absorber, a hindered phenol, an antifoaming agent, etc. may be added, if necessary. Added.

As the pigment, zinc oxide, zinc carbonate, calcium carbonate, magnesium carbonate, barium carbonate, barium sulfate, titanium oxide, talc, wax, 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, synthetic rubber latex or 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 as needed.

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.

As the wax, paraffin wax,
Microcrystalline wax, Carboxy modified paraffin wax, Carnauba wax, Polyethylene wax, Polystyrene wax, Candelia wax,
Examples include montan wax and higher fatty acid esters.

Examples of the surfactant include alkali metal salts of sulfosuccinic acid [eg, sodium salts of di (n-hexyl) sulfosuccinic acid, di (2-ethylhexyl) sulfosuccinic acid], sodium salts of dodecylbenzenesulfonic acid, Examples thereof include sodium salt of lauryl alcohol sulfate and fluorine-containing surfactant.

Examples of UV absorbers 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 can be mentioned.

In the heat-sensitive recording material of the present invention, the method for forming the recording layer is not particularly limited, and the recording layer can be formed according to a conventionally known technique.

For example, the coating liquid for the 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 and a wire bar, and dried to form a recording layer. Can be formed.

The coating amount of the coating liquid is not particularly limited, and is generally 1.5 to 12 g / dry weight.
It is adjusted in the range of m ² , preferably 2.5 to 10 g / m ² .

As the support, paper, plastic sheet,
Synthetic paper or a composite sheet combining these is used.

If necessary, a protective layer (overcoat layer) may be provided on the front surface and / or the back surface of the heat-sensitive recording layer, or a single-layer or multi-layer pigment (for example, kaolin) may be provided between the support and the heat-sensitive recording layer. ) Or synthetic resin (for example,
An undercoat layer (undercoat layer) made of plastic spherical particles, plastic spherical hollow particles, etc. is provided, and a pigment, a binder, etc. are provided between the heat sensitive recording layer and the undercoat layer or between the heat sensitive recording layer and the protective layer. It is of course possible to provide an intermediate layer, and various known techniques in the method for producing a heat-sensitive recording material can be imparted to the back surface of the support, such as adhesion processing.

[0083]

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 the examples,% represents% by weight.

Production Example 1 (Production of Dihydrate of 4-Methylbenzoic Acid Zinc Salt) 4-Methylbenzoic acid 25.2 g of methanol (200 m
l) To the solution, 50 ml of an aqueous solution in which 7.4 g of sodium hydroxide was dissolved was added dropwise at room temperature, and the mixture was further stirred at room temperature for 1 hour. To the suspension solution of 4-methylbenzoic acid sodium salt, 150 ml of an aqueous solution in which 26.6 g of zinc sulfate heptahydrate was dissolved was added dropwise at room temperature over 1 hour. After dropping
After stirring at room temperature for further 2 hours, the precipitated crystals were filtered, washed with water, and dried at 60 ° C. for 24 hours to obtain 30.5 g of 4-methylbenzoic acid zinc salt dihydrate as colorless crystals. . Melting point 75-80 ° C (dec.). As a result of moisture measurement by Karl Fischer analysis, the water content was 9.9% by weight, which was in agreement with the theoretical value of 9.8% by weight.

The powder X-ray diffraction pattern of the hydrate of this zinc salt by Cu-Kα ray is shown in FIG.

Production Example 2 (Production of Dihydrate of 4-Chlorobenzoic Acid Zinc Salt) In Production Example 1, 4-methylbenzoic acid was used in place of 4-methylbenzoic acid.
A dihydrate of zinc 4-chlorobenzoate salt was obtained by the same method as in Example 1 except that chlorobenzoic acid was used.
Melting point 125-135 [deg.] C. As a result of moisture measurement by Karl Fischer analysis, the water content was 8.9% by weight, which was in agreement with the theoretical value of 8.8% by weight. The powder X-ray diffraction pattern of the hydrate of this zinc salt by Cu-Kα ray is shown in FIG.

Production Example 3 (Production of Dihydrate of 4-Nitrobenzoic Acid Zinc Salt) In Production Example 1, 4-methylbenzoic acid was used in place of 4-methylbenzoic acid.
A dihydrate of 4-nitrobenzoic acid zinc salt was obtained in the same manner as in Example 1 except that nitrobenzoic acid was used.
Melting point> 300 ° C. As a result of moisture measurement by Karl Fischer analysis, the water content was 8.6% by weight, which was in agreement with the theoretical value of 8.4% by weight. Cu of this zinc salt hydrate
The powder X-ray diffraction pattern by -Kα ray is shown in FIG.

Reference Example (Production of anhydrous 4-nitrobenzoic acid zinc salt) 4-Nitrobenzoic acid 25.0 g of methanol (200 m
l) To the solution, 50 ml of an aqueous solution containing 6.0 g of sodium hydroxide was added dropwise at room temperature, and the mixture was further stirred at room temperature for 1 hour. To the suspension solution of sodium 4-nitrobenzoate, 150 ml of an aqueous solution in which 21.6 g of zinc sulfate heptahydrate was dissolved was added dropwise at room temperature over 1 hour. After dropping
After further stirring at room temperature for 2 hours, the precipitated crystals were filtered, washed with water, and dried at 120 ° C. for 24 hours to obtain 25.0 g of anhydrous 4-nitrobenzoic acid zinc salt as colorless crystals. Melting point> 300 ° C. As a result of moisture measurement by Karl Fischer analysis, it was confirmed to be an anhydride.

Production Example 1 (Production of 4-nitrobenzoic acid zinc salt dihydrate from anhydrous 4-nitrobenzoic acid zinc salt) Anhydride 2 of 4-nitrobenzoic acid zinc salt produced in Reference Example 2
300 ml of water was added to 5.0 g, and the aqueous dispersion was heated to 80 ° C.
And stirred for 2 hours. After cooling to room temperature, the crystals are filtered and filtered.
It was dried at 0 ° C. for 48 hours to obtain 25.5 g of 4-nitrobenzoic acid zinc salt dihydrate as colorless crystals. The powder X-ray diffraction pattern of the hydrate of this zinc salt by Cu-Kα radiation showed the same diffraction pattern as in FIG.

[Composition of Thermosensitive Recording Paper] (Composition of Liquid A)

[0091]

[Table 1]

[0092]

[Table 2]

[0093]

[Table 3] The above liquids A, B and C were dispersed with a sand grinding mill to an average particle diameter of 1.5 μm to obtain a dispersion liquid.

Examples 1 to 5 A liquid 100 g, liquid B 250 g, and liquid C 250 g dispersion were mixed with 30% paraffin wax 23 g, and the dry coating amount of this was 5.0 g / m ^2. To apply,
It was dried to prepare a thermosensitive recording paper.

Hydration of the zinc salt of the benzoic acid derivative represented by the general formula (1) used as the electron-donating color-forming compound in the solution A and the electron-accepting compound in the solution B used in each example. The products are shown in Table 1.

[0096]

[Table 4] Comparative Example 1 As the electron-donating color forming compound in the liquid A, 3-di-n was used.
-Butylamino-6-methyl-7-anilinofluorane was used, and anhydrous 4-nitrobenzoic acid zinc salt was used as the electron-accepting compound in solution B.
Liquid dispersion (250 g) and liquid C (250 g) were mixed with 30% paraffin wax (23 g), and this was applied to a high-quality paper so that the dry coating amount was 5.0 g / m ^2, and dried to prepare a heat-sensitive recording paper. .

[Evaluation Method of Thermosensitive Recording Paper] (Storage Stability Test of Uncolored Part) Whiteness of each thermal recording paper prepared in Examples and Comparative Examples immediately after coating was measured by a color difference meter (Σ-
80, manufactured by Nippon Denshoku). Furthermore, the heat resistance of the uncolored part of each thermal recording paper was examined. still,
As the heat resistance test, the whiteness of the uncolored portion of each thermosensitive recording paper after being stored at 60 ° C. for 24 hours was examined using a color difference meter. The larger the value, the higher the whiteness and the more excellent the heat resistance of the uncolored part. The evaluation results are shown in Table 2.

[0098]

[Table 5] As is apparent from Table 2, the heat-sensitive recording material using the hydrate of the zinc salt of the benzoic acid derivative represented by the general formula (1) of the present invention as the electron accepting compound is a zinc salt of the benzoic acid derivative. It can be seen that the heat resistance of the uncolored portion is excellent as compared with the heat-sensitive recording material using the above anhydride as an electron-accepting compound.

[0099]

According to the present invention, there are provided a heat-sensitive recording material having excellent storage stability, and a process for producing a hydrate of a zinc salt of a benzoic acid derivative useful as an electron-accepting color forming compound for the heat-sensitive recording material. It became possible to do.

[Brief description of drawings]

FIG. 1 shows an X-ray diffraction pattern (powder) of a hydrate of a zinc salt of 4-methylbenzoic acid.

FIG. 2 shows an X-ray diffraction pattern (powder) of a hydrate of a zinc salt of 4-chlorobenzoic acid.

FIG. 3 shows an X-ray diffraction pattern (powder) of a hydrate of a zinc salt of 4-nitrobenzoic acid.

Continuation of the front page (72) Inventor ▲ Jiro ▼ 1190 Kasamacho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd. (72) Masakatsu Nakatsuka 1190 Kasama-cho, Sakae-ku, Yokohama, Kanagawa Mitsui Toatsu Chem Within the corporation

Claims (2)

[Claims] 1. A thermosensitive recording material containing an electron-donating color forming compound and an electron-accepting compound, wherein at least a hydrate of a zinc salt of a benzoic acid derivative represented by the general formula (1) is used as the electron-accepting compound. A thermal recording material containing one kind. [Chemical 1] (In the formula, R represents an alkyl group having 1 to 4 carbon atoms, a halogen atom or a nitro group.) 2. Hydration of a zinc salt of a benzoic acid derivative represented by the general formula (1), wherein an anhydride of a zinc salt of the benzoic acid derivative represented by the general formula (1) is heat-treated in the presence of water. Method of manufacturing things. [Chemical 2] (In the formula, R represents an alkyl group having 1 to 4 carbon atoms, a halogen atom or a nitro group.)