JPH08169183A - Heat sensitizer and thermosensitive recording sheet - Google Patents

Abstract

PURPOSE: To obtain a heat sensitizer which shows high image preservability with developable color of purplish black and high sensitivity by using an imino compound and an aromatic isocyanate compound which are 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 an electron attractive group with Hammett's σ value (para) is, at least, +0.25; n is an integer of 1-4 if n is or more 2, X may be different from each other. On the other hand, in formula II, Z is either of -OH-, -CR- (R is an alkyl group or an aryl group), X1 to X3 is respectively halogen, an alkyl group, an aryl group, N, N dialkylamino group, etc.; a1 -c3 is an integers.

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, the hue of this color-developed product can be varied over a wide range depending on the selection of the imino compound and aromatic isocyanate compound used, but is often reddish, orangedish, or yellowish, for example, in many cases during recording. Regarding the required black coloration, it is often reddish black. It is relatively difficult to produce a blackish purple color. JP 61
No. 205183 discloses a thermosensitive recording sheet having a hue of purple, but it has a problem in sensitivity.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a heat-sensitive agent which is excellent in image storability and which has a purple-black hue and high sensitivity, and a heat-sensitive recording sheet comprising the heat-sensitive agent. is there.

[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 an electron withdrawing group of +0.25 or more.
n represents an integer of 1 or more and 4 or less. When n is 2 or more, X
May differ from each other. ) And an aromatic isocyanate compound represented by the general formula (II), and a heat-sensitive recording sheet in which the heat-sensitive agent is provided as a color-forming layer on a support.

[0008]

Embedded image

[0009]

[Chemical 4]

In the formula (II), Z is --CH-- or --CR--.
(R is an alkyl group or an aryl group), -N-, -P-
Represents either X _{1 to} X ₃ are halogen, an alkyl group,
Aryl group, alkoxyl group, hydroxyl group, N, N
-Represents a dialkylamino group. a _{1 to} c ₃ are integers and satisfy the following relationships. 0 ≦ a ₁ , b ₁ , c ₁ ≦ 5, a ₁ + b ₁ + c ₁ = 50 0 ≦ a ₂ , b ₂ , c ₂ ≦ 5, a ₂ + b ₂ + c ₂ = 50 0 ≦ a ₃ , b ₃ , c ₃ ≦ 5, a ₃ + b ₃ + c ₃ = 5, where a ₁ + a ₂ + a ₃ ≠ 0 where 2 ≦ b ₁ , 2 ≦ b ₂ , and 2 ≦ b ₃ , X _{1 to} X ₃ are respectively They may be different from each other. A in formula (I)
Is preferably C = NH and X is a nitro group or a cyano group.

The imino compound used in the present invention is 25
It is a colorless or pale compound that is solid at ℃. As a substituent, it is preferable to use a nitro group, a methylsulfonyl group or a cyano group having a relatively strong electron withdrawing property, and it is more preferable to have two or more of these substituents on the aromatic ring. It is also possible to use two or more types of imino compounds in combination depending on the purpose. As a specific example, 5-cyano-1,3-
Diiminoisoindolenine, 1,3-diimino-5-nitroisoindolenine, 1,3-diimino-5-methylsulfonylisoindolenine, 5,6-dicyano-1,
3-diiminoisoindolenine, 1,3-diimino-
5,6-dinitroisoindolenine, 1,3-diimino-5,6-di (methylsulfonyl) isoindolenine,
5-cyano-3-iminoisoindolenin-1-one,
3-imino-5-nitroisoindolenin-1-one,
3-imino-5-methylsulfonylisoindolenin-
1-one, 5,6-dicyano-3-iminoisoindolenin-1-one, 3-imino-5,6-dinitroisoindolenin-1-one, 3-imino-5,6-di (methylsulfonyl) ) 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. 4, 4 ',
4 ''-triisocyanatotriphenylamine, 4,
4 ', 4 "-triisocyanato-2-methoxytriphenylamine, 4,4', 4" -triisocyanato-
2,5-dimethoxytriphenylamine, 4,4 ′,
4 ″ -triisocyanato-2,2 ′, 5,5′-tetramethoxytriphenylamine and the like. These isocyanates may be used in the form of so-called block isocyanates, which are addition compounds with phenols, lantams, oximes, etc., if necessary, and uretdione which is a dimer of diisocyanate. , And isocyanurate, which is a trimer,
It can also be used as a polyisocyanate adducted with various polyols.

The heat-sensitive recording sheet according to the present invention may contain a heat-fusible substance in order to improve its sensitivity. The melting point of the heat-fusible substance is preferably 60 ° C to 180 ° C, particularly preferably 80 ° C to 140 ° C. As specific examples, benzyl p-benzyloxybenzoate, stearic acid amide, palmitic acid amide, N-methylol stearic acid amide, β-naphthylbenzyl ether, N-
Stearyl urea, N, N'-distearyl urea, 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
-Stearoyl urea, 4-benzyl biphenyl, 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-chloro) Benzyl) ester and the like.

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 5,6-dicyano-1,3-diiminoisoindolenin was dispersed and pulverized for 4 hours with a paint shaker together with 8 g of a 2.5 wt% polyvinyl alcohol aqueous solution, and then a 15 wt% polyvinyl alcohol aqueous solution 2 was added. ．
5 g was added and dispersed for 15 minutes to obtain an aqueous dispersion. Separately, 2 g of 4,4 ′, 4 ″ -triisocyanato-2,5-dimethoxytriphenylamine was dispersed and pulverized in a paint shaker for 4 hours together with 4 g of a 2.5 wt% polyvinyl alcohol aqueous solution and 4 g of a 31 wt% ethanol aqueous solution. , 15% by weight polyvinyl alcohol aqueous solution 2.5
g was added and dispersed for 15 minutes to obtain an aqueous dispersion. Also, 2
2 g of benzyloxynaphthalene was dispersed and pulverized with a paint shaker for 4 hours together with 8 g of a 2.5% by weight aqueous solution of polyvinyl alcohol, and 2.5 g of a 15% by weight aqueous solution of polyvinyl alcohol was added and dispersed for 15 minutes to obtain an aqueous dispersion. . Further, 2-methoxy-3-N, N-diethylsulfamoylaniline (2 g) was dispersed and pulverized with a paint shaker for 4 hours together with a 2.5% by weight polyvinyl alcohol aqueous solution (8 g). In addition, the mixture was dispersed for 15 minutes to obtain an aqueous dispersion.

2.5 g of calcium carbonate 2% by weight
An aqueous polyvinyl alcohol solution (8 g) was dispersed and pulverized with a paint shaker for 4 hours, and 15% by weight aqueous polyvinyl alcohol solution (2.5 g) was added and dispersed for 15 minutes to obtain an aqueous dispersion. These dispersions were mixed with 5,6-dicyano-
0.75 g of 1,3-diiminoisoindolenine dispersion,
4,4 ′, 4 ″ -triisocyanato-2,5-dimethoxytriphenylamine dispersion 0.5 g, 2-benzyloxynaphthalene dispersion 1 g, 2-methoxy-3-N,
N-diethylsulfamoylaniline dispersion 1 g, calcium carbonate dispersion 2.5 g, and solid content concentration 16% by weight
The zinc stearate dispersion liquid of 0.75 g was mixed with stirring to obtain a coating liquid. This liquid was applied on a base paper having a weight of 50 g / m ² by a bar coater with a rod number of 16,
After drying, it was processed with a super calendar to obtain a heat-sensitive recording sheet. The sensitivity was evaluated with a printing tester manufactured by Okura Electric Co., Ltd., the thermal head was KJT-256-8MGF1 manufactured by Kyocera, and the printing was carried out with an applied voltage of 24 V and a pulse width of 1.3 ms. did.
The print density was 1.0 and the color tone was black.

[0027]

Example 2 Instead of 5,6-dicyano-1,3-diiminoisoindolenin of Example 1, 5-nitro-1,3 was used.
A thermosensitive recording sheet was prepared in the same manner as in Example 1 except that diiminoisoindolenin was used. When the sensitivity was measured under the same conditions as in Example 1, the print density was 1.3 and the color tone was black purple.

[0028]

[Example 3] The same as Example 1 except that 5-methylsulfonyl-1,3-diiminoisoindolenine was used in place of 5,6-dicyano-1,3-diiminoisoindolenine of Example 1. Similarly, a thermosensitive recording sheet was prepared. When the sensitivity was measured under the same conditions as in Example 1, the print density was 1.2 and the color tone was black purple.

[0029]

Example 4 In place of 4,4 ′, 4 ″ -triisocyanato-2,5-dimethoxytriphenylamine of Example 1, 4,4 ′, 4 ″ -triisocyanatotriphenylamine was used. A heat-sensitive recording sheet was prepared in the same manner as in Example 1 except that it was used. When the sensitivity was measured under the same conditions as in Example 1, the print density was 1.0 and the color tone was black.

[0030]

Example 5 In place of 4,4 ′, 4 ″ -triisocyanato-2,5-dimethoxytriphenylamine of Example 2, 4,4 ′, 4 ″ -triisocyanatotriphenylamine was used. A thermosensitive recording sheet was prepared in the same manner as in Example 2 except that it was not used. When the sensitivity was measured under the same conditions as in Example 2, the print density was 1.3 and the color tone was black purple.

[0031]

Example 6 In place of 4,4 ′, 4 ″ -triisocyanato-2,5-dimethoxytriphenylamine of Example 3, 4,4 ′, 4 ″ -triisocyanatotriphenylamine was used. A thermosensitive recording sheet was prepared in the same manner as in Example 3 except that the above was used. When the sensitivity was measured under the same conditions as in Example 3, the print density was 1.2 and the color tone was black purple.

[0032]

Comparative Example 1 In place of 5,6-dicyano-1,3-diiminoisoindolenin of Example 1, 4,5,6,7-tetrachloro-1,3-diiminoisoindolenin was used. A thermal recording sheet was prepared in the same manner as in Example 1 except for the above. When the sensitivity was measured under the same conditions as in Example 1, the print density was 1.2 and the color tone was magenta.

[0033]

Comparative Example 2 A thermosensitive recording sheet similar to that of Example 1 except that 1,3-diiminoisoindolenine was used in place of 5,6-dicyano-1,3-diiminoisoindolenine of Example 1. It was created. When the sensitivity was measured under the same conditions as in Example 1, the print density was 0.7 and the color tone was brown. The results of these Examples and Comparative Examples are summarized in Table 1.

[0034]

[Table 1]

[0035]

As compared with the conventional heat-sensitive agent and heat-sensitive recording material prepared by the reaction of an imino compound and an isocyanate compound,
It was stable in storage and the coloring hue was close to black.

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 represents an electron having a Hammett σ value (para) of +0.25 or more). Represents a suction group, and n represents an integer of 1 or more and 4 or less.
When is 2 or more, X may be different from each other. ) And an aromatic isocyanate compound represented by the general formula (II). Embedded image Embedded image In formula (II), Z represents any one of -CH-, -CR- (R is an alkyl group or an aryl group), -N-, and -P-. X _{1 to} X ₃ represent a halogen, an alkyl group, an aryl group, an alkoxyl group, a hydroxyl group or an N, N-dialkylamino group. a _{1 to} c ₃ are integers and satisfy the following relationships. 0 ≦ a ₁ , b ₁ , c ₁ ≦ 5, a ₁ + b ₁ + c ₁ = 50 0 ≦ a ₂ , b ₂ , c ₂ ≦ 5, a ₂ + b ₂ + c ₂ = 50 0 ≦ a ₃ , b ₃ , c ₃ ≦ 5, a ₃ + b ₃ + c ₃ = 5, where a ₁ + a ₂ + a ₃ ≠ 0 where 2 ≦ b ₁ , 2 ≦ b ₂ , and 2 ≦ b ₃ , X _{1 to} X ₃ are respectively They may be different from each other. 2. A heat-sensitive recording sheet having a heat-sensitive agent containing the imino compound according to claim 1 and an aromatic isocyanate compound provided 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 nitro group or a cyano group.