JPH06297858A - Heat-sensitive recording material - Google Patents

Abstract

PURPOSE:To improve keeping properties and image stability by a method wherein organic sulfonate compound of the specified benzimidazole derivative is employed as developer in the material concerned prepared by providing heat- sensitive coloring layer mainly made of leuco dye and the developer on support. CONSTITUTION:In the heat-sensitive recording material concerned prepared by providing heat-sensitive coloring layer mainly made of leuco dye and developer, which colors the leuco dye under heat, on support, organic sulfonate compound of benzimidazole represented at least with the general formula noted elsewhere, is employed as the developer. By employing the above-mentioned developer, the leuco dye can be colored by emitting protons by heating, resulting in allowing to obtain image, which hardly fades by oil and valence stock. In the formula, R1 represents hydrogen atom, alkyl group, aryl group, halogen atom or the like, R represents hydrogen atom, alkyl group, aryl group, alkoxy group or the like X represents hydrogen atom or alkyl group.

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 in which an image stability in oil or a plasticizer is remarkably improved.

[0002]

2. Description of the Related Art Generally, a heat-sensitive recording material is mainly composed of a support such as paper, synthetic paper, plastic film and the like. A thermosensitive color developing agent is provided, and a colored image can be obtained by heating with a hot pen, a thermal head, a laser beam, a strobe lamp, or the like. Compared with other recording materials, this recording material can obtain recording in a short time with a relatively simple device without performing complicated processing such as development and fixing, has little noise and environmental pollution, and has a low cost. Due to its low price, it is used for copying books, documents, etc., electronic calculators, facsimile ticket vending machines,
It is useful as various recording materials such as labels and recorders.

Color-forming dyes used in heat-sensitive recording materials are, for example, colorless or light-colored leuco dyes having a lactone, lactam or spiropyran ring, and phenol compounds are conventionally used as color developers. The recording material using the color former and the developer is widely used because of its high image density and high whiteness of the background.

However, an image formed by such a leuco dye and a phenol-based color developer has poor storage stability because the color development is a reversible process, and if the printed image is left as it is for a long time, the image is formed. Disappears.
Further, there is a drawback that the image is easily discolored even when it comes into contact with water, oil, a plasticizer or the like. In order to improve the storability of such a leuco dye-based color image, various studies have been made on the color developer. For example, Japanese Patent Application Laid-Open No. 57-199686 proposes to improve the plasticizer resistance by using a benzophenone derivative having a sulfonyl group. However, such a sulfonic acid type color developing agent is used in the non-image area. It is hard to say that it is not practical and has poor storability.

Japanese Patent Laid-Open No. 59-185693 proposes a method of improving the plasticizer resistance by using a metal salt of an aromatic carboxylic acid and an aliphatic carboxylic acid. It cannot be said that the coloring property is sufficient and it is not practical. In JP-A-63-45087, a sulfonium compound is used, and in JP-A-1-294088, a sulfonium compound of a type having a benzyl group as one of the substituents and an aromatic ammonium organic acid salt are used as developers. A heat-sensitive recording material has been proposed which has improved image stability with respect to a plasticizer and in which color development in a non-image area due to an organic solvent is prevented. It is considered that such a type of developer develops an electron-donating leuco dye by generating a cation species such as a benzyl cation by thermal decomposition during heating.

However, since such a thermal decomposition process requires a considerable amount of heat energy, it cannot be said that the heat source used for ordinary heat-sensitive recording has a poor coloring property and is practical. Further, JP-A-59-109388 and JP-A-1-
Japanese Patent No. 178489 proposes to use a sulfonic acid ester derivative as a color developing agent, but it cannot be said that the color developing property and image strength are sufficient and it is not practical. Further, in JP-A-1-178489, it is proposed that a plasticizer is improved together with color developability by using a developer having a hydrogen bond molecular complex formed between bisphenol A and another phenolic compound or an amine compound. However, in such a system, since the phenolic compound such as bisphenol A acts as a developer, the plasticizer of the image is not fundamentally improved and it is not practical at present. Is.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording material in which the storability of a color image and non-image area, particularly the image stability against oil and plasticizer, is remarkably improved as compared with the prior art. .

[0008]

According to the present invention, there is provided a thermosensitive recording material having a thermosensitive coloring layer containing a leuco dye and a color developer capable of coloring the leuco dye when heated as a main component on a support. As a developer, at least the following general formula (I)
There is provided a heat-sensitive recording material characterized by using an organic sulfonate compound of a benzimidazole derivative represented by the chemical formula (1).

[Chemical 1] (In the formula, R ₁ represents a hydrogen atom, an alkyl group, a substituted alkyl group, an aryl group, a halogen atom, a nitro group or a carboxyl group, and R ₂ represents a hydrogen atom, an alkyl group, a substituted alkyl group, an aryl group, an alkoxy group, Thioether group,
It represents a hydroxy group, a mercapto group, a guanidyl group, a pyridyl group, a halogen atom or an amino group, X represents a hydrogen atom or an alkyl group, and n is an integer of 1 to 4. Further, according to the present invention, in a thermosensitive recording material provided with a thermosensitive coloring layer containing, as a main component, a leuco dye and a developer which develops a color when the leuco dye is heated on a support, at least the following general developer is used as a developer. Provided is a heat-sensitive recording material comprising an organic sulfonate compound of a benztriazole derivative represented by the formula (II).

[Chemical 2] (In the formula, R ₃ represents a hydrogen atom, an alkyl group, a substituted alkyl group, an aryl group, a halogen atom, a nitro group or a carboxyl group, Y represents a hydrogen atom, a hydroxy group or a carbonic acid ester, and m represents 1 to 4 It is an integer.)

In the present invention, as the organic sulfonate compound of the benzimidazole derivative [general formula (I)] and the benztriazole derivative [general formula (II)] used as the developer, a benzimidazole derivative or a benztriazole derivative is an organic compound. The proton of the organic sulfonic acid is not a kind of complex or a mixture that has an intermolecular interaction with the sulfonic acid, but a proton of the organic sulfonic acid and an unshared electron pair of the heterocyclic nitrogen atom of the benzimidazole or benztriazole derivative. Is a chloride in which a bond is formed with an organic sulfonate ion as the counter ion. This means that in the infrared absorption spectra of these compounds, the absorption characteristic of NH of the tertiary amine salt is 27
It can be deduced from the fact that it is observed near 00 cm ^-1 .

In the present invention, the organic sulfonate compound of the benzimidazole derivative or benztriazole derivative used as a color developer is prepared by mixing an organic solvent solution of the benzimidazole derivative or benztriazole derivative with an organic solvent solution of organic sulfonic acid. The crude product obtained by the reaction can be purified by recrystallization from a suitable solvent. As an example, a method for synthesizing α-naphthalene sulfonate of benzimidazole will be shown below. Benzimidazole (10 g, 0.0
To the acetone solution of 8 mol), an acetone solution of α-naphthalenesulfonic acid (17 g, 0.08 mol) is added dropwise.
After the dropping, α-naphthalene sulfonate of benzimidazole is obtained as a milky white precipitate (25 g, 0.076 mol, yield 90%). The precipitate is recrystallized from nitromethane to give white crystals with a melting point of 168-170 ° C.

In the present invention, the organic sulfonate compound of the above-mentioned benzimidazole derivative and benztriazole derivative used as a color developer can release a proton to a leuco dye during heating to develop a color. Therefore, when the compound of the present invention is used as a color developer, an image which is hardly discolored by oil and a plasticizer can be obtained, unlike the case where a usual phenol type color developer is used.

In the present invention, specific examples of the benzimidazole derivative and the benztriazole derivative capable of forming a color developer (chloride) with an organic sulfonic acid include those shown below. It is not limited to.

<Benzimidazole Derivatives> Benzimidazole, 5-benzimidazolecarboxylic acid, 2-benzimidazoleacetonitrile, 2-chloromethylbenzimidazole, 5-chloro-2-trichloromethylbenzimidazole, 5,6-dimethylbenzimidazole, 2-guadininobenzimidazole, 2-hydroxybenzimidazole, 2-mercaptobenzimidazole, 2-mercapto-5-methylbenzimidazole, 2-mercapto-5-nitrobenzimidazole,
2-methylbenzimidazole, 5-methylbenzimidazole, 2-methylmercaptobenzimidazole,
2-methyl-5-nitrobenzimidazole, 1-methyl-2-phenylbenzimidazole, 5-nitrobenzimidazole, 2-phenylbenzimidazole, 2
-(2-pyridyl) benzimidazole, 2-aminobenzimidazole, 2-amino-5,6-dimethylbenzimidazole,

<Benztriazole Derivatives> Benztriazole, benztriazole-5-carboxylic acid, 5,
6-dimethyl-1H-benztriazole, 1-hydroxybenztriazole, 5-methyl-1H-benztriazole, 5-nitrobenztriazole, allyl-
1-Benztriazole carbonate.

Specific examples of the organic sulfonic acid forming a developer (chloride) with the above-mentioned benzimidazole derivative and benztriazole derivative include those shown below, but the present invention is not limited thereto. Not something. <Organic sulfonic acid> α-naphthalene sulfonic acid, β-naphthalene sulfonic acid, benzene sulfonic acid, paratoluene sulfonic acid.

The leuco dyes used in the present invention may be applied alone or as a mixture of two or more kinds. As such leuco dyes, any one applied to the recording material of this kind may be optionally applied, for example, a trio dye. Leuco compounds such as phenylmethanephthalide type, triallylmethane type, fluorane type, phenothidian type, thioferral type, methine type, rhodamine anilinolactam type, rhodamine lactam type, quinazoline type, diazaxanthene type and bislactone type are preferably used. To be Examples of such compounds include those shown below.

3,3-bis (p-dimethylaminophenyl)-
Phthalide, 3,3-bis (p-dimethylaminophenyl) -6
-Dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis (p-dimethylaminophenyl)
-6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-
Dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,
7-Dimethylfluorane, 3-N-methyl-N-isobutyl-6-
Methyl-7-anilinofluorane, 3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3- (Np-tolyl-N-ethylamino) -6-
Methyl-7-anilinofluorane, 3-pyrrolidino-6-
Methyl-7-anilinofluorane, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluorane, 2- {3,6-bis (diethylamino) -9- (o-
Chloranilino) xanthylbenzoic acid lactam}, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o -Chloranilino) fluorane, 3-N-methyl-N-amylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N
-Cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (2 ', 4'-dimethylanilino ) Fluoran, 3- (N, N-diethylamino) -5
-Methyl-7- (N, N-dibenzylamino) fluorane, benzoyl leuco methylene blue, 6'-chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-
3'-methoxy-benzoindolino-spiropyran, 3-
(2'-hydroxy-4'-dimethylaminophenyl) -3-
(2'-methoxy-5'-chlorophenyl) phthalide, 3- (2 '
-Hydroxy-4'-dimethylaminophenyl) -3- (2 '
-Methoxy-5'-nitrophenyl) phthalide, 3- (2'-
Hydroxy-4'-diethylaminophenyl) -3- (2'-
Methoxy-5'-methylphenyl) phthalide, 3- (2'-methoxy-4'-dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-methylphenyl) phthalide, 3
-Morpholino-7- (N-propyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7- (N-benzyl-trifluoromethyl) Anilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl)
Methylaminofluorane, 3-diethylamino-5-chloro-
7- (α-phenylethylamino) fluorane, 3- (N-ethyl
-p-toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluorane, 3-diethylamino-5-methyl-7-
(α-Phenylethylamino) fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3- (N-methyltoluidino) -7- (pn-butylanilino) fluorane, 3-
(N-methyl-N-isopropylamino) -6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3,6-bis (dimethylamino) fluorene spiro ( 9,3 ')-6'-Dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-7-α
-Naphthylamino-4'-bromofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-N-ethyl-N
-(2-Ethoxypropyl) amino-6-methyl-7-anilinofluorane, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane, 3-diethylamino
-6-methyl-7-mesitidino-4 ', 5'-benzofluorane, 3-
(p-Dimethylaminophenyl) -3- {1,1-bis (p-dimethylaminophenyl) ethylene-2-yl} phthalide, 3- (p-dimethylaminophenyl) -3- {1,1-bis ( p-dimethylaminophenyl) ethylene-2-yl} -6-dimethylaminophthalide,
3- (p-dimethylaminophenyl) -3- (1-p-dimethylaminophenyl-1-phenylethylene-2-yl) phthalide, 3- (p-
Dimethylaminophenyl) -3- (1-p-dimethylaminophenyl-1-p-chlorophenylethylene-2-yl) -6-dimethylaminophthalide, 3- (4'-dimethylamino-2'-methoxy)-
3- (1 ''-p-dimethylaminophenyl-1 ''-p-chlorophenyl-1 '', 3 ''-butadiene-4 ''-yl) benzophthalide, 3-
(4'-Dimethylamino-2'-benzyloxy) -3- (1 ''-p-dimethylaminophenyl-1 ''-phenyl-1 '', 3 ''-butadiene-4 ''-yl) benzophthalide , 3-dimethylamino-6-dimethylamino-fluorene-9-spiro 3 '(6'-dimethylamino) phthalide, 3,3-bis {2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ) Ethenyl} -4,5,6,7-tetrachlorophthalide, 3-bis {1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl} -5,6-dichloro-4,7- Dibromophthalide, bis (p-dimethylaminostyryl) -1-naphthalenesulfonylmethane, bis (p-dimethylaminostyryl) -1
-p-tolylsulfonylmethane and the like.

Further, in the present invention, the organic sulfonate compound of the above-mentioned benzimidazole derivative and benztriazole derivative is used as a developer, but other developer can be used in combination, if necessary. In this case, as the developer to be used in combination, various electron-accepting compounds such as phenolic compounds, thiophenolic compounds, thiourea derivatives, organic acids and metal salts thereof can be used. Examples include, but are not limited to:

4,4'-isopropylidene bisphenol,
4,4'-isopropylidene bis (o-methylphenol),
4,4'-secondary butylidene bisphenol 4,4'-isopropylidene bis (2-tert-butylphenol), 4,4'-cyclohexylidene diphenol,
4,4'-isopropylidene bis (2-chlorophenol),
2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 4,4'-butylidenebis
(6-tert-butyl-2-methylphenol), 1,1,3
-Tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 4,4'-thiobis ( 6-tert-butyl-2-methylphenol),
4,4'-diphenol sulfone, 4-isopropoxy-4'-hydroxydiphenyl sulfone, 4-benzyloxy-4'-hydroxydiphenyl sulfone, 4,4'-diphenol sulfoxide, P-hydroxybenzoic acid isopropyl, P -Benzyl hydroxybenzoate, benzyl protocatechuate, stearyl gallate, lauryl gallate, octyl gallate, 1,7-bis (4-hydroxyphenylthio) -3,
5-dioxaheptane, 1,5-bis (4-hydroxyphenylthio) -3-oxapentane, 1,3-bis (4-hydroxyphenylthio) -propane, 1,3-bis (4-hydroxyphenylthio) ) -2-Hydroxypropane, N, N'-diphenylthiourea, N, N'-di (m-chlorophenyl) thiourea, salicylanilide, 5-chloro-salicylanilide, 2-hydroxy-3-naphthoic acid, 2 -Hydroxy-1
-Naphthoic acid, 1-hydroxy-2-naphthoic acid, metal salts of hydroxynaphthoic acid such as zinc, aluminum and calcium, bis- (4-hydroxyphenyl) acetic acid methyl ester, bis- (4-hydroxyphenyl) acetic acid benzyl ester , 1,3-bis (4-hydroxycumyl) benzene, 1,4
-Bis (4-hydroxycumyl) benzene, 2,4'-diphenol sulfone, 3,3'-diallyl-4,4'-diphenol sulfone, α, α-bis (4-hydroxyphenyl) -α- Methyltoluene, zinc thiocyanate antipyrine complex,
Tetrabromobisphenol A, tetrabromobisphenol S, 4,4'-thiobis (2-methylphenol), 4,4'-
Thiobis (2-chlorophenol) etc.

In order to produce the heat-sensitive recording material of the present invention,
When the leuco dye and the color developer are bound and supported on the support, various commonly used binders can be appropriately used, and specific examples thereof include the following.

Polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose and ethyl cellulose, polyacrylic acid sodium -Da, polyvinylpyrrolidone, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid terpolymer, styrene /
Maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, soda alginate, gelatin, other water-soluble polymers such as casein, polyvinyl acetate, polyurethane, polyacrylic acid, Polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene /
Emulsion such as vinyl acetate copolymer, latex such as styrene / butadiene copolymer and styrene / butadiene / acrylic copolymer.

In the present invention, various heat-fusible substances can be used as the sensitivity improver, and specific examples thereof include the followings, but the present invention is not limited thereto. . Fatty acids such as stearic acid and behenic acid, fatty acid amides such as stearic acid amide and palmitic acid amide, fatty acid metal salts such as zinc stearate, aluminum stearate, calcium stearate, zinc palmitate and zinc behenate, p-benzyl Biphenyl, terphenyl, triphenylmethane, benzyl p-benzyloxybenzoate, β-benzyloxynaphthalene, phenyl β-naphthoate, phenyl 1-hydroxy-2-naphthoate, methyl 1-hydroxy-2-naphthoate, diphenyl Carbonate, Greacol Carbonate, Dibenzyl terephthalate, Dimethyl terephthalate, 1,4-Dimethoxynaphthalene, 1,4-Diethoxynaphthalene, 1,4-Dibenzyloxynaphthalene, 1,2-Diphenoxyethane, 1,2 -
Bis (3-methylphenoxy) ethane, 1,2-bis (4-methylphenoxy) ethane, 1,4-diphenoxy-2-butene, 1,2-
Bis (4-methoxyphenylthio) ethane, dibenzoylmethane, 1,4-diphenylthiobutane, 1,4-diphenylthio
-2-butene, 1,3-bis (2-vinyloxyethoxy) benzene, 1,4-bis (2-vinyloxyethoxy) benzene, p- (2
-Vinyloxyethoxy) bifer, p-aryloxypphenyl, p-propargyloxybiphenyl, dibenzoyloxymethane, dibenzoyloxypropane, dibenzyl disulfide, 1,1-diphenylethanol, 1,1-diphenylpropanol, p -Benzyloxybenzyl alcohol, 1,3-phenoxy-2-propanol, N-octadecylcarbamoyl-p-methoxycarbonylbenzene, N-
Octadecylcarbamoylbenzene, 1,2-bis (4-methoxyphenoxy) propane, 1,5-bis (4-methoxyphenoxy) -3-oxapentane, dibenzyl oxalate, bis (4-methylbenzyl) oxalate, oxalic acid Bis (4-chlorobenzyl) and the like.

In the case of obtaining a heat-sensitive recording material according to the present invention, a leuco dye, a color developer, the compound of the present invention and, if necessary, additional components commonly used in this kind of heat-sensitive recording material such as fillers and surface active agents are used. Agents can be used in combination. In this case, as the filler, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide,
In addition to barium sulfate, clay, kaolin, talc, inorganic fine powder such as surface-treated calcium and silica, urea-
Examples include organic fine powders such as formalin resin, styrene-methacrylic acid copolymer, polystyrene resin, and vinylidene chloride resin. Regarding the layer structure, it may be a single layer or multiple layers, and if necessary, an over layer,
An under layer and a back layer can be provided.

[0024]

EXAMPLES Next, the present invention will be described in more detail by way of examples. The parts and% shown below are based on weight.

Example 1 The following mixtures were pulverized with a magnetic ball mill for 2 days to prepare [solution A], [solution B] and [solution C]. [Solution A] 3- (N-methyl-N-cyclohexamino) -6-methyl-7-anilinofluorane 20 parts 10% aqueous solution of polyvinyl alcohol 20 parts water 60 parts [Solution B] Developer: benzimidazole α-naphthalene sulfonate 20 parts 10% aqueous solution of polyvinyl alcohol 20 parts water 60 parts [C liquid] 20 parts silica 5% aqueous solution of methylcellulose 20 parts water 60 parts [A liquid] 10 parts, [B liquid] 30 parts, [C liquid] 30
Parts and 20% of isobutylene / maleic anhydride copolymer
A thermosensitive color forming layer-forming liquid is prepared by mixing 10 parts of an alkaline aqueous solution, and this is applied to a high quality paper having a basis weight of 50 g / m ² so that the amount of dye adhering after drying is 0.5 / m ² and dried to produce a thermosensitive color. After providing the layer, the surface thereof was further calendered to prepare the thermosensitive recording material of Example 1.

Example 2 Example 2 was repeated except that the α-naphthalene sulfonate of benzimidazole, which is the developer of [B liquid], was replaced with p-toluene sulfonate of 5-methylbenzimidazole. A thermal recording material of Example 2 was prepared in the same manner as in Example 1.

Example 3 As Example 1, except that the α-naphthalene sulfonate of benzimidazole, which is the developer of [B liquid], was replaced with the α-naphthalene sulfonate of benztriazole. Similarly, a thermosensitive recording material of Example 3 was prepared.

Example 4 In Example 1, the α-naphthalene sulfonate of benzimidazole, which is the developer of [B liquid], was replaced with the p-toluene sulfonate of 5-methyl-1H-benztriazole. A thermal recording material of Example 4 was prepared in the same manner as in Example 1 except for the above.

Comparative Example 1 In Example 1, 4,4′- was prepared by adding α-naphthalene sulfonate of benzimidazole, which is the developer of [B liquid].
Example 1 except that isopropylidenediphenol was used instead
A thermosensitive recording material of Example 1 was prepared in the same manner as in.

Comparative Example 2 Example 1 was repeated except that the α-naphthalene sulfonate of benzimidazole, which is the developer of [B liquid], was replaced with benzyl p-hydroxybenzoate.
A thermal recording material of Comparative Example 2 was prepared in the same manner as in.

Comparative Example 3 Example 3 was repeated except that the α-naphthalene sulfonate of benzimidazole, which is the developer of [B liquid], was replaced with the compound of the following structural formula (a) (Chemical Formula 3). A thermal recording material of Comparative Example 3 was prepared in the same manner as in Example 1.

[Chemical 3]

With respect to the heat-sensitive recording materials of Examples 1 to 4 and Comparative Examples 1 to 3 obtained as described above, a temperature of 150 ° C. and a pressure of 2 Kg / c were measured using a thermal gradient tester (manufactured by Toyo Seiki Seisakusho).
The image density and the background density are printed under the condition of m ² , 2 seconds, and the image density and the background density are determined by Macbeth densitometer RD-914 (filter: W-10
Measured in 6). Next, the samples after printing were tested for oil resistance and plasticizer resistance as follows. The results are shown in Table 1. The concentration measurement after each of the above-mentioned storage stability tests was also carried out with a Macbeth densitometer RD-914 (filter: W-106). Oil resistance: Cotton seed oil was applied to the printed area and the density of the image area was measured after storing for 16 hours under a drying condition at a temperature of 40 ° C. Plasticizer resistance: Plasticizer (dioctyl adipate,
(DOA) was applied to the printed part, and the density of the image part was measured after storing for 16 hours under a dry condition of 40 ° C.

[0033]

[Table 1] It can be seen from Table 1 that the heat-sensitive recording material of the present invention is extremely excellent in that the image area does not fade due to oil or plasticizer.

[0034]

INDUSTRIAL APPLICABILITY According to the present invention, a thermosensitive recording material provided with a thermosensitive coloring layer containing a leuco dye and a developer capable of coloring the leuco dye when heated as a main component is used as a developer. By using at least one organic sulfonate compound of a benzimidazole derivative or triazole derivative of a specific structure, the storability of the color image and non-image area, especially the image stability against oil and plasticizer, is remarkably improved than before. The material is obtained.

Claims (2)

[Claims] 1. A thermosensitive recording material having a thermosensitive coloring layer containing a leuco dye and a color developer capable of coloring the leuco dye when heated as a main component on a support, wherein at least the following general formula (I ) (1) A heat-sensitive recording material comprising an organic sulfonate compound of a benzimidazole derivative. [Chemical 1] (In the formula, R ₁ represents a hydrogen atom, an alkyl group, a substituted alkyl group, an aryl group, a halogen atom, a nitro group or a carboxyl group, and R ₂ represents a hydrogen atom, an alkyl group, a substituted alkyl group, an aryl group, an alkoxy group, Thioether group,
It represents a hydroxy group, a mercapto group, a guanidyl group, a pyridyl group, a halogen atom or an amino group, X represents a hydrogen atom or an alkyl group, and n is an integer of 1 to 4. ) 2. A thermosensitive recording material comprising a support and a thermosensitive coloring layer containing, as a main component, a leuco dye and a developer for coloring the leuco dye when heated, at least the following general formula (II) is used as the developer. (3) A heat-sensitive recording material comprising an organic sulfonate compound of a benztriazole derivative represented by the formula (2). [Chemical 2] (In the formula, R ₃ represents a hydrogen atom, an alkyl group, a substituted alkyl group, an aryl group, a halogen atom, a nitro group or a carboxyl group, Y represents a hydrogen atom, a hydroxy group or a carbonic acid ester, and m represents 1 to 4 It is an integer.)