JPH08169184A - Thermosensitive color coupler and thermosensitive recording sheet - Google Patents

Abstract

PURPOSE: To obtain a heat sensitizer which attains multicoloration in addition to a known chromogenic system ranging from orange to red as developable colors with outstanding image preservability by constituting the heat sensitizer of an imino compound and an aromatic isocyanate compound shown respectively by specific formulae as main components. CONSTITUTION: This heat sensitizer is composed mainly of an imino compound shown by formula I and an aromatic isocyanate compound shown by formula II. In the formula I, A is C=O or C=NH; X is a substituent with Hammett's σvalue (para) is +0.2 or less; and n is an integer of 1-4, if n is 2 or more, X may be different from each other. On the other hand, in the formula II, X is halogen, an alkyl group, an aryl group, N,N-dialkylamino group. Further, a-c each is an integer to meet the following relationship; 1<=a<=6, 0<=b<=5, 0<=c<=5 and (a+b+c)=6, wherein if 2<=b, X may be different from each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive agent and a heat-sensitive recording sheet having excellent image storability. For more information,
The present invention relates to a heat-sensitive agent composed of an imino compound and an aromatic isocyanate compound, and a heat-sensitive recording sheet provided with a color forming layer containing these.

[0002]

2. Description of the Related Art In recent years, for example, in a variety of information devices such as facsimiles, printers, recorders, etc., a heat-sensitive recording system for recording by heat energy has been widely adopted. The mainstream of these recording methods is to use a recording sheet in which a color-forming layer containing a two-component chemical color-forming agent is provided on a support, and heat is applied as recording energy to this to form a color-forming agent component on the recording sheet. It is a method of recording colors by contacting each other. Among them, as a color former,
Many use leuco dyes and acidic substances.

Recording sheets using these conventionally known leuco dyes have a high whiteness, an appearance and a feeling close to those of plain paper.
It has many excellent characteristics such as good recording suitability such as color development sensitivity, and the thermal recording sheet has advantages such as small device size, maintenance-free and no noise generation. Applications have expanded to a wide range of fields such as facsimiles, printers, computer terminals, labels, ticket vending machines, and other vending machines. On the other hand, recording sheets using these leuco dyes are represented by, for example, a thermal paper (see US Pat. No. 3,539,375) having crystal violet lactone and 4,4′-isopropylidenediphenol (bisphenol A) as a coloring agent. As described above, since the recorded portion obtained by coloring has poor chemical resistance, the recording material is easily erased by contact with a plasticizer contained in a plastic sheet or an eraser or a chemical contained in food or cosmetics, In addition, since the light resistance of the recording portion is poor, the recording has a drawback that it is inferior in the storage stability of the record, such as fading or even disappearing of the recording by exposure to sunlight for a relatively short period of time. At present, the application is subject to certain restrictions, and its improvement is strongly desired.

As a heat-sensitive recording material capable of obtaining a recorded image having a good storability in response to such a demand, for example, Japanese Patent Laid-Open Publication No.
8-38733, JP-A-58-54085, JP-A-58-104959, JP-A-58-149388,
JP-A-59-115887, JP-A-59-11588
No. 8 and U.S. Pat. No. 4,521,793 disclose a recording sheet comprising a combination of a heat sensitive agent mainly containing an aromatic isocyanate and a heat sensitive agent mainly containing an imino compound.

This heat-sensitive agent produces a colored product by a two-component contact reaction, and this colored product has excellent chemical resistance and light resistance. However, hitherto, as disclosed in JP-A-61-205183, a heat-sensitive agent having a purple coloring hue and a tea having a color close to this have been used.
Many of the hues of purple are known, but few of them exhibit multicolor recording, for example, red, orange, and yellow.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a heat-sensitive agent which is excellent in image storability and has a hue capable of forming a color of orange to red, which enables multi-coloring in addition to a conventionally known coloring system. A heat-sensitive recording sheet using the heat-sensitive agent is provided.

[0007]

That is, the present invention provides an imino compound represented by the general formula (I) (in the formula (I), A represents C = O or C = NH, and X represents a Hammett σ value. (Para) represents a substituent of +0.2 or less, and n is 1
It represents an integer of 4 or more and 4 or less. When n is 2 or more, X may be different from each other. ) And an aromatic isocyanate compound represented by the general formula (II), and a heat-sensitive recording sheet having the heat-sensitive agent as a color forming layer provided on a support.

[0008]

Embedded image

[0009]

[Chemical 4]

In the formula (II), X is halogen, an alkyl group, an aryl group, an alkoxyl group, a hydroxyl group,
Represents an N, N-dialkylamino group. a, b, and c are integers and satisfy the following relationships. l ≦ a ≦ 6, 0 ≦ b ≦ 5, 0 ≦ c ≦ 5, a + b + c = 6 where 2 ≦ b, X may be different from each other. It is preferable that A in the formula (I) is C = NH and X is a methyl group or a methoxy group.

The imino compound used in the present invention is 25
It is a colorless or pale compound that is solid at ℃. Examples of the substituent include an amino group, N-alkylamino group, N, N-dialkylamino group, N-arylamino group, N, N-diarylamino group, hydroxyl group, alkoxyl group,
Examples include a phenoxy group, an alkyl group, an aryl group, and a trialkylsilyl group. Specific examples of the compound are shown below. It is also possible to use two or more types of imino compounds in combination depending on the purpose. For example, 1,3-diimino-5-methylisoindolenine, 1,3-diimino-5-methoxyisoindolenine, 1,3-diimino-5-phenoxyisoindolenine, 1,3-diimino-5- ( N, N-diethylamino) isoindolenine, 1,3-diimino-5,
6-dimethylisoindolenine, 1,3-diimino-
5,6-dimethoxyisoindolenine, 1,3-diimino-5,6-di- (N, N-diethylamino) isoindolenine, 3-imino-5-methylisoindolenine-
1-one, 3-imino-5-methoxyisoindolenin-1-one, 3-imino-5- (N, N-diethylamino) isoindolenin-1-one, 3-imino-5,6
-Dimethylisoindolenin-1-one, 3-imino-
5,6-dimethoxyisoindolenin-1-one, 3-
Imino-5,6-di- (N, N-diethylamino) isoindolenin-1-one and the like.

The aromatic isocyanate compound used in the present invention refers to a colorless or light-colored aromatic isocyanate compound which is solid at 25 ° C., and for example, one or more of the following isocyanate compounds are used. 2,6-dichlorophenyl isocyanate, p-chlorophenyl isocyanate, 1,3-phenylene diisocyanate, 1,
4-phenylene diisocyanate, 1,3-dimethylbenzene-4,6-diisocyanate, 1,4-dimethylbenzene-2,5-diisocyanate, 1-methoxybenzene-2,4-diisocyanate, 1-methoxybenzene-2,5-diisocyanate, 1-ethoxybenzene-2,4-diisocyanate, 2,5-dimethoxybenzene-1,4-diisocyanate, 2,5-diethoxybenzene-1 , 4-diisocyanate, 2,5-dibutoxybenzene-1,4-diisocyanate and the like. These isocyanates may be used in the form of so-called block isocyanates, which are addition compounds with phenols, lantams, oximes and the like, if necessary, and dimers of diisocyanate, for example, 1 -Methylbenzene-2,4-diisocyanate may be used in the form of a dimer or trimer of isocyanurate, or may be used as a polyisocyanate adducted with various polyols. Is.

The heat-sensitive recording sheet according to the present invention may contain a heat-fusible substance in order to improve its sensitivity. Those having a melting point of 60 ° C. to 180 ° C. are preferable, and those having a melting point of 80 ° C. to 140 ° C. are particularly preferable. For example, benzyl p-benzyloxybenzoate, stearic acid amide, palmitic acid amide, N-methylol stearic acid amide, β-naphthylbenzyl ether, N-stearyl urea, N, N′-distearyl urea, and β-naphthoic acid phenyl. Ester, 1-hydroxy-2-naphthoic acid phenyl ester, β-naphthol (p-methylbenzyl) ether, 1,4-dimethoxynaphthalene, 1-methoxy-4-benzyloxynaphthalene, N-stearoylurea, 4-benzylbiphenyl , 1,2-di (m-methylphenoxy) ethane, 1-
Phenoxy-2- (4-chlorophenoxy) ethane,
1,4-butanediol phenyl ether, dimethyl terephthalate, metaterphenyl, dibenzyl oxalate, oxalic acid (p-chlorobenzyl) ester and the like can be mentioned.

The above-mentioned heat-fusible substances may be used alone or as a mixture, and in order to obtain a sufficient heat response, the heat-fusible substance is contained in an amount of 10 to 30 relative to the aromatic isocyanate compound.
It is preferably 0% by weight, more preferably 20 to 250% by weight. Further, the heat-sensitive recording sheet according to the present invention can contain an aniline derivative having at least one amino group, which is more effective in preventing background fog.

These compounds include methyl p-aminobenzoate, ethyl p-aminobenzoate, n-propyl p-aminobenzoate, and p-aminobenzoic acid-iso-.
Propyl, butyl p-aminobenzoate, dodecyl P-aminobenzoate, benzyl p-aminobenzoate, o-aminobenzophenone, m-aminoacetophenone, p-aminoacetophenone, m-aminobenzamide, o-aminobenzamide, p- Aminobenzamide, p-amino-N-methylbenzamide, 3-amino-4-methylbenzamide, 3-amino-4-methoxybenzamide, 3-amino-4-chlorobenzamide, p- (N-
Phenylcarbamoyl) aniline, p- [N- (4-chlorophenyl) carbamoyl] aniline, p- [N-
(4-Aminophenyl) carbamoyl] aniline, 2-
Methoxy-5- (N-phenylcarbamoyl) aniline, 2-methoxy-5- [N- (2'-methyl-3'-
Chlorophenyl) carbamoyl] aniline, 2-methoxy-5- [N- (2'-chlorophenyl) carbamoyl] aniline, 5-acetylamino-2-methoxyaniline, 4-acetylaminoaniline, 4- (N-methyl-N-). Acetylamino) aniline, 2,5-diethoxy-4- (N-benzoylamino) aniline, 2,5-dimethoxy-4- (N-benzoylamino) aniline, 2
-Methoxy-4- (N-benzoylamino) -5-methylaniline, 4-sulfamoylaniline, 3-sulfamoylaniline, 2- (N-ethyl-N-phenylaminosulfonyl) aniline, 4-dimethylamino Sulfonylaniline, 4-diethylaminosulfonylaniline, sulfathiazole, 4-aminodiphenylsulfone, 2-chloro-5-N-phenylsulfamoylaniline, 2-methoxy-5-N, N-diethylsulfamoylaniline, 2 , 5-Dimethoxy-4-N-phenylsulfamoylaniline, 2-methoxy-5-benzylsulfonylaniline, 2-phenoxysulfonylaniline, 2- (2'-chlorophenoxy) sulfonylaniline, 3-anilinosulfonyl-4. -Methylaniline, bis [4- (m-amido Phenoxy) phenyl] sulfone, bis [4-(p-aminophenoxy) phenyl] sulfone, bis [3-methyl-4-(p-aminophenoxy) phenyl] sulfone, 3,3'-dimethoxy-4,
4'-diaminobiphenyl, 3,3'-dimethyl-4,
4'-diaminobiphenyl, 2,2'-dichloro-4,
4'-diamino-5,5'-dimethoxybiphenyl,
2,2 ', 5,5'-tetrachloro-4,4'-diaminobiphenyl, ortho-tolidine sulfone, 2,4'-
Diaminobiphenyl, 2,2'-diaminobiphenyl,
4,4'-diaminobiphenyl, 2,2'-dichloro-
4,4'-diaminobiphenyl, 3,3'-dichloro-
4,4'-diaminobiphenyl, 2,2'-dimethyl-
4,4'-diaminobiphenyl, 4,4'-thiodianiline, 2,2 'dithiodianiline, 4,4'-dithiodianiline, 4,4'-diaminodiphenyl ether, 3,
3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, bis (3-amino-4-chlorophenyl) sulfone, bis (3,4-diaminophenyl) ) Sulfone, bis (4-aminophenyl) sulfone, bis (3-aminophenyl)
Sulfone, 3,4'-diaminodiphenyl sulfone,
3,3'-diaminodiphenylmethane, 4,4'-ethylenedianiline, 4,4'diamino-2,2'-dimethyldibenzyl, 4,4'-diamino-3,3'-dichlorodiphenylmethane, 3,3 ′ -Diaminobenzophenone, 4,4′-diaminobenzophenone, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4
-Aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 9,9-bis (4-aminophenyl) fluorene, 2,2-bis (4-aminophenoxyphenyl) propane, 4,4 ' -Bis (4-aminophenoxy) diphenyl, 3,3 ', 4,4'-tetraaminodiphenyl ether, 3,3', 4,4'-tetraaminodiphenyl sulfone, 3,3'4,4'-tetraamino Examples thereof include benzophenone.

Further, from the viewpoints of background fogging and thermal responsiveness, N-stearyl-N '-(2-hydroxyphenyl) urea, N-stearyl-N'-(3-hydrococyphenyl) urea, N-stearyl. -N '-(4-hydroxyphenyl) urea, p-stearoylaminophenol, o-stearoylaminophenol, p-lauroylaminophenol, p-butyrylaminophenol, m-acetylaminophenol, o-acetylaminophenol, p -Acetylaminophenol, o-butylaminocarbonylphenol, o-stearylaminocarbonylphenol, p-stearylaminocarbonylphenol, 1,1,3-tris (3-tert.
-Butyl-4-hydroxy-6-methylphenyl) butane, 1,1,3-tris (3-tert.-butyl-4)
-Hydroxy-6-ethylphenyl) butane, 1,1,
3-tris (3,5-di-tert.-butyl-4-hydroxyphenyl) butane, 1,1,3-tris (3-
tert. -Butyl-4-hydroxy-6-methylphenyl) propane, 1,2,3-tris (3-tert.
-Butyl-4-hydroxy-6-methylphenyl) butane, 1,1,3-tris (3-phenyl-4-hydroxyphenyl) butane, 1,1,3-tris (3-cyclohexyl-4-hydroxy-5) -Methylphenyl) butane, 1,1,3-tris (3-cyclohexyl-4-hydroxy-6-methylphenyl) butane, 1,1,3-
Tetra (3-phenyl-4-hydroxyphenyl) propane, 1,1,3,3-tetra (3-cyclohexyl-)
4-hydroxy-6-methylphenyl) propane, 1,
1-bis (3-tert.-butyl-4-hydroxy-
It is also possible to add phenol compounds such as 6-methylphenyl) butane and 1,1-bis (3-cyclohexyl-4-hydroxy-6-methylphenyl) butane.

For the purpose of adjusting the color tone of the image and improving the image density, a colorless or pale basic dye is used as the color developing agent and an inorganic or organic acid is used as the color developing agent to the extent that the image storability is not impaired. A substance can also be used as a color-forming component. In this case, the color former and / or the developer can be contained in the layer containing the aromatic isocyanate compound and the aromatic imino compound, or can be provided as a separate layer.

Specific examples of the color former are shown below. (1) As a triarylmethane compound, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,
3-bis (p-dimethylaminophenyl) phthalide, 3
-(P-Dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3 -(P-Dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindole-
3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazole-3-) Yl) -5-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrole-2) -Yl) -6-dimethylaminophthalide and the like.

(2) As a diphenylmethane compound,
4,4-bis-dimethylaminophenyl benzhydryl benzyl ether, N-halophenyl leuco auramine, N-2,4,5-trichlorophenyl leuco auramine and the like can be mentioned. (3) Rhodamine B anilinolactam, rhodamine B-p-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino as xanthene compounds -7-phenylfluorane,
3-diethylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-
Diethylamino-7- (3,4-dichloroanilino) fluorane, 3-diethylamino-7- (2-chloroanilino) fluorane, 3-diethylamino-6-methyl-
7-anilinofluorane, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-anilinofluorane, 3
-Piperidino-6-methyl-7-anilinofluoran,
3- (N-ethyl-N-tolyl) amino-6-methyl-
7-phenethylfluorane, 3-diethylamino-7-
(4-nitroanilino) fluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3- (N-
Methyl-N-propyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamyl)
Amino-6-methyl-7-anilinofluorane, 3-
(N-Methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-
And tetrahydrofuryl) amino-6-methyl-7-anilinofluorane.

(4) Examples of thiazine compounds include benzoyl leuco methylene blue and p-nitrobenzoyl leuco methylene blue. (5) As a spiro compound, 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3-
Examples thereof include dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran, and 3-propylspirobenzopyran.

These color formers can be used alone or in combination of two or more kinds. As the developer, an electron-accepting substance generally used in thermal paper is used, and a phenol derivative, an aromatic carboxylic acid derivative or a metal compound thereof, an N, N-diarylthiourea derivative and the like are particularly preferable.
Particularly preferred are phenol derivatives. As a specific example, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) butane,
2,2-bis (4-hydroxyphenyl) pentane,
2,2-bis (4-hydroxyphenyl) heptane,
1,1-bis (4-hydroxyphenyl) cyclohexane, bis (4-hydroxyphenyl) butyl acetate, benzyl bis (4-hydroxyphenyl) acetate, bis (4-
Hydroxyphenyl) sulfone, bis (3-methyl-4)
-Hydroxyphenyl) sulfone, 4-hydroxyphenyl-4'-methylphenyl sulfone, 3-chloro-4
-Hydroxyphenyl-4'-methylphenyl sulfone, 3,4-dihydroxyphenyl-4'-methylphenyl sulfone, 4-isopropylphenyl-4'-hydroxyphenyl sulfone, 4-isopropyloxyphenyl-4'-hydroxyphenyl sulfone, Screw (2-
Allyl-4-hydroxyphenyl) sulfone, 4-hydroxyphenyl-4′-benzyloxyphenyl sulfone, 4-isopropylphenyl-4′-hydroxyphenyl sulfone, bis (2-methyl-3-tert.-butyl-4-hydroxy) Phenyl) sulfide, ethyl 4-hydroxybenzoate. Benzyl 4-hydroxybenzoate. 4-Hydroxybenzoic acid (4'-chlorobenzyl), 1,2-bis (4'-hydroxybenzoic acid) ethyl, 1,5-bis (4'-hydroxybenzoic acid) benzyl, 1,6 bis (4 ') -Hydroxybenzoic acid) hexyl, dimethyl 3-hydroxyphthalate, stearyl gallate, lauryl gallate and the like.

In addition, diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin, etc. are contained in the heat-sensitive recording layer as pigments. You can also Also, for the purpose of preventing head wear and sticking, higher fatty acid metal salts such as zinc stearate and calcium stearate, paraffin,
Waxes such as paraffin oxide, polyethylene, polyethylene oxide, stearic acid amide, castor wax, dispersants such as sodium dioctyl sulfosuccinate, UV absorbers such as benzophenone and benzotriazole, surfactants, fluorescent dyes. Etc. can be contained as needed.

As the binder used in the heat-sensitive recording layer, various binders that are commonly used can be used. Examples of the binder include starches, hydroxyethyl cellulose, methyl cellulose,
Carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer Water-soluble binders such as alkali salts of ethylene, alkali salts of ethylene / maleic anhydride copolymers, etc., and water-insoluble latex systems such as styrene / butadiene copolymers, acrylonitrile / butadiene copolymers, methyl acrylate / butadiene copolymers Examples thereof include binders.

The heat-sensitive recording sheet according to the present invention comprises a support having thereon a heat-sensitive recording layer for color development by heating. Paper is mainly used as the support, but various woven fabrics, non-woven fabrics, synthetic resin films, laminated papers, synthetic papers, metal foils, or composite sheets in which these are combined are arbitrarily used in addition to the paper. be able to. The thermal recording layer may be composed of a single layer or plural layers. For example, each color-forming component may be contained in each layer to form a multi-layer structure. A protective layer composed of one or more layers may be provided on the thermosensitive recording layer, or an intermediate layer composed of one or more layers may be provided between the support and the thermosensitive recording layer. Good. This heat-sensitive recording layer can be obtained by mixing each aqueous dispersion obtained by finely pulverizing each color forming component or other component with a binder, coating on a support and drying.

[0025]

Example 1 2 g of 1,3-diimino-5-methylisoindolenin was dispersed and pulverized for 4 hours with a paint shaker together with 8 g of a 2.5 wt% polyvinyl alcohol aqueous solution,
Further, 2.5 g of a 15 wt% polyvinyl alcohol aqueous solution was added and dispersed for 15 minutes to obtain an aqueous dispersion. 2,5-
2 g of diethoxybenzene-1,4-diisocyanate was added to 4 g of a 2.5% by weight polyvinyl alcohol aqueous solution and 3
An aqueous dispersion was obtained by dispersing and pulverizing with a paint shaker for 4 hours together with 4 g of a 1% by weight aqueous ethanol solution, further adding 2.5 g of a 15% by weight aqueous polyvinyl alcohol solution and dispersing for 15 minutes. 2 g of 2-benzyloxynaphthalene
Was dispersed and pulverized with a paint shaker for 4 hours together with 8 g of a 2.5 wt% polyvinyl alcohol aqueous solution, and further 15%
Weight polyvinyl alcohol aqueous solution 2.5g 15
It was dispersed for a minute to obtain an aqueous dispersion. Also, 2-methoxy-3
2 g of -N, N-diethylsulfamoylaniline was added to 2.
A 5% by weight polyvinyl alcohol aqueous solution (8 g) was used to disperse and pulverize for 4 hours with a paint shaker. Further, 15% by weight polyvinyl alcohol aqueous solution (2.5 g) was added and dispersed for 15 minutes to obtain an aqueous dispersion. Further, 2 g of calcium carbonate was dispersed and pulverized with a paint shaker for 4 hours together with 8 g of a 2.5% by weight polyvinyl alcohol aqueous solution, 2.5 g of a 15% by weight polyvinyl alcohol aqueous solution was further added and dispersed for 15 minutes to obtain an aqueous dispersion. . Add these dispersions to 1,3-
Diimino-5-methylisoindolenin dispersion 0.75
g, 2,5-diethoxy-1,4-diisocyanate dispersion liquid 0.5 g, 2-benzyloxynaphthalene dispersion liquid 1
g, 2-methoxy-3-N, N-diethylsulfamoylaniline dispersion 1 g, calcium carbonate dispersion 2.5
g, and 0.75 g of a zinc stearate dispersion having a solid content concentration of 16% by weight was mixed with stirring to obtain a coating liquid. This liquid was put on a base paper having a weight of 50 g / m ² and rod number 1
It was coated with a No. 6 bar coater, dried and processed with a super calendar to obtain a heat-sensitive recording sheet. Sensitivity was evaluated with a printing tester made by Okura Electric Co., Ltd. and a thermal head was KJC KJ
After printing with an applied voltage of 24 V and a pulse width of 1.3 ms using T-256-8MGF1, a Macbeth densitometer RS9
The print density was measured at 17. The print density was 0.4 and the color tone was reddish orange.

[0026]

Example 2 A heat-sensitive recording sheet as in Example 1 except that 1,3-diimino-5-methylisoindolenin was replaced by 1,3-diimino-5-methoxyisoindolenine. It was created. When the sensitivity was measured under the same conditions as in Example 1, the print density was 0.4 and the color tone was reddish orange.

[0027]

Example 3 2,5-diethoxybenzene of Example 1
A thermal recording sheet was prepared in the same manner as in Example 1 except that 2,5-dibutoxybenzene-1,4-diisocyanate was used instead of 1,4-diisocyanate. When the sensitivity was measured under the same conditions as in Example 1, the print density was 0.4 and the color tone was reddish orange.

[0028]

Example 4 2,5-diethoxybenzene of Example 2
A thermal recording sheet was prepared in the same manner as in Example 2 except that 2,5-dibutoxybenzene-1,4-diisocyanate was used instead of 1,4-diisocyanate. When the sensitivity was measured under the same conditions as in Example 2, the print density was 0.4 and the color tone was reddish orange.

[0029]

[Comparative Example 1] Example 1 was repeated except that 4,5,6,7-tetrachloro-1,3-diiminoisoindolenine was used in place of 1,3-diimino-5-methylisoindolenine of Example 1. A thermal recording sheet was prepared in the same manner as in Example 1. Example 1
When the sensitivity was measured under the same conditions as above, the print density was 1.1 and the color tone was magenta. The results of these Examples and Comparative Examples are summarized in Table 1.

[0030]

[Table 1]

[0031]

INDUSTRIAL APPLICABILITY As compared with the conventional heat-sensitive agent and heat-sensitive recording material composed of an imino compound and an isocyanate compound, storage stability can be obtained and an orange to red coloring hue can be obtained.

Claims (3)

[Claims] 1. An imino compound represented by the general formula (I) (in the formula (I), A represents C═O or C═NH, and X is a substitution having a Hammett σ value (para) of +0.2 or less. Represents a group, and n represents an integer of 1 or more and 4 or less, and when n is 2 or more, X may be different from each other) and the general formula (I
A heat-sensitive agent which is mainly composed of an aromatic isocyanate compound represented by I). Embedded image Embedded image In formula (II), X represents a halogen, an alkyl group, an aryl group, an alkoxyl group, a hydroxyl group, or an N, N-dialkylamino group. a, b, and c are integers and satisfy the following relationships. l ≦ a ≦ 6, 0 ≦ b ≦ 5, 0 ≦ c ≦ 5, a + b + c = 6 where 2 ≦ b, X may be different from each other. 2. A heat-sensitive recording sheet comprising a heat-sensitive agent containing the imino compound according to claim 1 and an aromatic isocyanate compound as a color forming layer on a support. 3. The heat-sensitive agent according to claim 1, wherein A in the formula (I) is C═NH and X is a methyl group or a methoxy group.