JPH068632A - Thermal agent - Google Patents

Abstract

PURPOSE:To provide a thermal agent for producing a thermal recording material excellent in image preservability and the yellowing resistance due to the light of a background. CONSTITUTION:The content of the aromatic urea compd. in a thermal agent mainly composed of an aromatic isocyanate compd. is set to 20wt.% or less and the average particle size of the thermal agent is set to 3mum or less. By this constitution, the yellowing properties against the light of the background of a thermal recording material are reduced.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat-sensitive agent for use in a heat-sensitive recording material which is excellent in yellowing of the background, sensitivity and image storability.

[0002]

2. Description of the Related Art A heat-sensitive recording material generally comprises a support and a heat-sensitive recording layer containing an electron-donating colorless dye precursor and an electron-accepting developer as main components. By heating with a hot pen, laser light or the like, the colorless dye precursor and the developer react instantaneously to obtain a recorded image. JP-B-43-4160 and JP-B-45-140.
No. 39, etc. Such a heat-sensitive recording material has the advantages that recording can be obtained with a relatively simple device, that it is easy to maintain, and that it does not generate noise, and it is a terminal for measuring recorders, facsimiles, printers, and computer terminals. It is used in a wide range of fields such as vending machines, labels, ticket vending machines, etc.

A heat-sensitive recording material using such an electron-donating colorless dye precursor and an electron-accepting color developer has a good appearance.
While it has excellent properties such as good feel, high color density, and various color hues, the thermosensitive color part (recorded image part) is in contact with plastic such as polyvinyl chloride to form plastic. Preservation of records, such as disappearance due to plasticizers and additives contained in it, easy disappearance due to contact with chemicals contained in foods and cosmetics, or fading easily after exposure to sunlight for a short time Is inferior, and due to this drawback, the application is subject to certain restrictions, and its improvement is strongly desired.

Further, in recent years, a high-speed printing apparatus capable of printing in a short time has been developed, and it has excellent thermal response suitable for it.
There has been a demand for a highly sensitive heat-sensitive recording material capable of obtaining a sufficiently colored image even at low energy. Examples of heat-sensitive recording materials capable of obtaining recorded images with good storage stability are, for example, JP-A-58-38733, JP-A-58-54085, JP-A-58-104959, and JP-A-58-149388.
JP-A-59-115888, JP-A-59-115
No. 888 and U.S. Pat. No. 4,521,793 disclose recording materials comprising a combination of a heat-sensitive agent mainly composed of aromatic isocyanate and a heat-sensitive agent mainly composed of imino compound.

However, these thermal recording materials are
Although the recorded image is excellent in storability, discoloration of the non-image portion, that is, the background, due to light is likely to occur, and there is a problem in yellowing of the background.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat sensitive agent for a heat sensitive recording material which is excellent in yellowing of the background, sensitivity and image storability.

[0007]

The inventors of the present invention have conducted intensive studies to obtain a heat-sensitive agent for a heat-sensitive recording material which is excellent in yellowing of the background and has good image storability, and as a result, the content of an aromatic urea compound was found. The present invention was completed by discovering that when a heat-sensitive recording material is prepared using a heat-sensitive agent having a small amount of particles and having an average particle diameter of 3 μm or less, yellowing of the background is reduced.

That is, the present invention is characterized in that in a heat-sensitive agent mainly composed of an aromatic isocyanate compound and having an average particle diameter of 3 μm or less, the aromatic urea compound in the heat-sensitive agent is 20% by weight or less. It is a heat sensitive agent.
The aromatic urea compound in the heat-sensitive agent of the present invention is produced during the synthesis of the aromatic isocyanate compound and during grinding in water, and yellowing can be significantly reduced by reducing the amount of the aromatic urea compound. I found what I could do.

As described in JP-A-3-150190, it is necessary for the heat-sensitive agent to be pulverized to a particle size necessary for improving the sensitivity. Normally, the required particle size is obtained by underwater crushing, but it was discovered that during this underwater crushing process, the amount of aromatic urea compound increased and the yellowing of the background due to light increased. Therefore, the content of aromatic urea compounds is low,
Further, by using a heat-sensitive agent having a small particle size, a heat-sensitive recording material having high sensitivity and less yellowing due to background light can be prepared only by simple water-milling, which simplifies the milling process in water.

The amount of aromatic urea compound in the heat-sensitive agent is 2
It is necessary to be 0% by weight or less, and preferably 12% by weight or less. The amount of the aromatic urea compound in the heat sensitive agent can be measured using liquid chromatography. The particle size of the heat sensitive agent must be 3 μm or less. If it is larger than 3 μm, a heat-sensitive recording material having sufficient sensitivity cannot be obtained. In order to make the heat-sensitive agent have a required particle size, it is pulverized by a dry and / or non-aqueous wet method with a pulverizer such as a ball mill, a sand mill, an attritor, a vibration mill, and a jet mill, or it is refined by dissolution precipitation. Although a method or the like can be used, it is preferable to use a dry type jet mill.

The aromatic isocyanate compound, which is the main component of the heat-sensitive agent used in the present invention, means a colorless or light-colored aromatic isocyanate compound or a heterocyclic isocyanate compound which is solid at room temperature. For example, the following isocyanate compound is used. One or more of 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, azobenzene-4,4'-diisocyanate, diphenyl ether-
4,4'-diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, naphthalene-2,6-diisocyanate, naphthalene-2,7-diisocyanate, 3 , 3'-dimethyl-
Biphenyl-4,4'-diisocyanate, 3,3'-
Dimethoxybiphenyl-4,4'-diisocyanate,
Diphenylmethane-4,4'-diisocyanate, diphenyldimethylmethane-4,4'-diisocyanate,
Benzophenone-3,3'-diisocyanate, fluorene-2,7-diisocyanate, anthraquinone-
2,6-diisocyanate, 9-ethylcarbazole-
3,6-diisocyanate, pyrene-3,8-diisocyanate, naphthalene-1,3,7-triisocyanate, biphenyl-2,4,4'-triisocyanate,
4,4 ', 4 "-triisocyanato-2,5-dimethoxytriphenylamine, 4,4', 4" -triisocyanatotriphenylamine, p-dimethylaminophenylisocyanate, tris (4-phenylisocyanate) Nato) There is thiophosphate etc. If desired, these isocyanates may be used in the form of so-called block isocyanates, which are addition compounds with phenols, lactams, oximes, etc., and dimers of diisocyanate, for example, 1- It may be used in the form of isocyanurate, which is a dimer and trimer of methylbenzene-2,4-diisocyanate, or may be used as a polyisocyanate adducted with various polyols. is there.

In order to obtain a heat-sensitive recording material, it is necessary to coat these on a support together with other necessary components in the form of a dispersion to form a heat-sensitive recording layer. The dispersion is prepared by dispersing one or more of the heat-sensitive agents of the present invention in an aqueous solution containing a compound having a dispersive ability such as a water-soluble polymer and a surfactant. At this time, it is desirable that the dispersion time is short and the temperature is low so that an aromatic urea compound is not formed. It is desirable that these heat-sensing agents are dry-processed and pulverized to a required particle size, and then dispersed only in a short time. For dry grinding, for example, a dry grinder such as a ball mill, a vibrating ball mill, an attritor, a jet mill, a sand mill, a pin mill or a turbo mill can be used.

The imino compound which is the main component of the other heat-sensitive agent used in the heat-sensitive recording material has at least one imino group represented by the following chemical formula 1 and is represented by the general formula shown in the chemical formula 2 below. Such a compound is a colorless or light-colored compound that is solid at room temperature. A specific example is shown below. It is also possible to use two or more types of imino compounds in combination depending on the purpose.

[0014]

[Chemical 1]

[0015]

[Chemical 2]

3-iminoisoindoline-1-one, 3
-Imino-4,5,6,7-tetrachloroisoindoline-1-one, 3-imino-4,5,6,7-tetrabromoisoindoline-1-one, 3-imino-4,5,5
6,7-Tetrafluoroisoindoline-1-one, 3
-Imino-5,6-dichloroisoindoline-1-one, 3-imino-4,5,7-trichloro-6-methoxy-isoindoline-1-one, 3-imino-4,5,5
7-Trichloro-6-methylmercapto-isoindoline-1-one, 3-imino-6-nitroisoindoline-1-one, 3-imino-isoindoline-1-spirodioxolane, 1,1-dimethoxy-3 -Imino-isoindoline, 1,1-diethoxy-3-imino-4,
5,6,7-tetrachloroisoindoline, 1-ethoxy-3-imino-isoindoline, 1,3-diiminoisoindoline, 1,3-diimino-4,5,6,7-tetrachloroisoindoline, 1,3-Diimino-6-methoxyisoindoline, 1,3-Diimino-6-cyanoisoindoline, 1,3-Diimino-4,7-dithia-
5,5,6,6-tetrahydroisoindoline, 7-amino-2,3-dimethyl-5-oxopyrrolo [3,4
b] pyrazine, 7-amino-2,3-diphenyl-5-
Oxopyrrolo [3,4b] pyrazine, 1-iminonaphthalimide, 1-iminodiphenimide, 1-phenylimino-3-iminoisoindoline, 1- (3'-chlorophenylimino) -3-iminoisoindoline, 1
-(2 ', 5'-Dichlorophenylimino) -3-iminoisoindoline, 1- (2', 4 ', 5'-trichlorophenylimino) -3-iminoisoindoline, 1-
(2'-Cyano-4'-nitrophenylimino) -3-
Iminoisoindoline, 1- (2'-chloro-5'-cyanophenylimino) -3-iminoisoindoline, 1
-(2 ', 6'-Dichloro-4'-nitrophenylimino) -3-iminoisoindoline, 1- (2', 5'-
Dimethoxyphenylimino) -3-iminoisoindoline, 1- (2 ', 5'-diethoxyphenylimino)-
3-iminoisoindoline, 1- (2'-methyl-4 '
-Nitrophenylimino) -3-iminoisoindoline, 1- (5'-chloro-2'-phenoxyphenylimino) -3-iminoisoindoline, 1- (4'-N,
N-dimethylaminophenylimino) -3-iminoisoindoline, 1- (3′-N, N-dimethylamino-
4'-methoxyphenylimino) -3-iminoisoindoline, 1- (2'-methoxy-5'-N-phenylcarbamoylphenylimino) -3-iminoisoindoline, 1- (2'-chloro-5'- Trifluoromethylphenylimino) -3-iminoisoindoline, 1-
(5 ', 6'-dichlorobenzothiazolyl-2'-imino) -3-iminoisoindoline, 1- (6'-methylbenzothiazolyl-2'-imino) -3-iminoisoindoline, 1 -(4'-phenylaminophenylimino) -3-iminoisoindoline, 1- (p-phenylazophenylimino) -3-iminoisoindoline, 1
-(Naphthyl-1'-imino) -3-iminoisoindoline, 1- (anthraquinone-1'-imino) -3-iminoisoindoline, 1- (5'-chloroanthraquinone-1'-imino)- 3-iminoisoindoline, 1-
(N-ethylcarbazolyl-3'-imino) -3-iminoisoindoline, 1- (naphthoquinone-1'-imino) -3-iminoisoindoline, 1- (pyridyl-
4'-imino) -3-iminoisoindoline, 1- (benzimidazolone-6'-imino) -3-iminoisoindoline, 1- (1'-methylbenzimidazolone-
6'-imino) -3-iminoisoindoline, 1-
(7'-chlorobenzimidazolone, -5'-imino)
-3-iminoisoindoline, 1- (benzimidazolyl-2'-imino) -3-iminoisoindoline, 1-
(Benzimidazolyl-2'-imino) -3-imino-
4,5,6,7-tetrachloroisoindoline, 1-
(2 ', 4'-Dinitrophenylhydrazone) -3-iminoisoindoline, 1- (indazolyl-3'-imino) -3-iminoisoindoline, 1- (indazolyl-3'-imino) -3-imino- 4,5,6,7-Tetrabromoisoindoline, 1- (indazolyl-3'-
Imino) -3-imino-4,5,6,7-tetrafluoroisoindoline, 1- (benzimidazolyl-2'-
Imino) -3-imino-4,7-dithiatetrahydroisoindoline, 1- (4 ', 5'-dicyanoimidazolyl-2'-imino) -3-imino-5,6-dimethyl-
4,7-Pyradiisoindoline, 1- (cyanobenzoylmethylene) -3-iminoisoindoline, 1- (cyanocarbonamidomethylene) -3-iminoisoindoline, 1- (cyanocarbomethoxymethylene) -3-imino Isoindoline, 1- (cyanocarboethoxymethylene) -3-iminoisoindoline, 1- (cyano-N-
Phenylcarbamoylmethylene) -3-iminoisoindoline, 1- [cyano-N- (3′-methylphenyl)
-Carbamoylmethylene] -3-iminoisoindoline, 1- [cyano-N- (4'-chlorophenyl) -carbamoylmethylene] -3-iminoisoindoline, 1
-[Cyano-N- (4'-methoxyphenyl) -carbamoylmethylene] -3-iminoisoindoline, 1-
[Cyano-N- (3'-chloro-4'-methylphenyl) -carbamoylmethylene] -3-iminoisoindoline, 1- (cyano-p-nitrophenylmethylene)-
3-iminoisoindoline, 1- (dicyanomethylene)
-3-iminoisoindoline, 1- [cyano-1 ',
2 ', 4'-triazolyl- (3')-carbamoylmethylene] -3-iminoisoindoline, 1- [cyanothiazoyl- (2 ')-carbamoylmethylene] -3-iminoisoindoline, 1- [cyanobenzimidazolyl- (2 ')-carbamoylmethylene] -3-iminoisoindoline, 1- [cyanobenzothiazolyl- (2')
-Carbamoylmethylene] -3-iminoisoindoline, 1- [cyanobenzimidazolyl-2 ')-methylene] -3-iminoisoindoline, 1-[(cyanobenzimidazolyl- (2')-methylene] -3-imino −
4,5,6,7-tetrachloroisoindoline, 1-
[(Cyanobenzimidazolyl-2 ')-methylene]-
3-imino-5-methoxyisoindoline, 1-[(cyanobenzimidazolyl-2 ')-methylene] -3-imino-6-chloroisoindoline, 1-[(1'-phenyl-3'-methyl-5 -Oxo) pyrazolidene-
4 ']-3-iminoisoindoline, 1-[(cyanobenzimidazolyl-2')-methylene] -3-imino-
4,7-dithiatetrahydroisoindoline, 1-
[(Cyanobenzimidazolyl-2 ')-methylene]-
3-imino-5,6-dimethyl-4,7-pyradiisoindoline, 1-[(1'-methyl-3'-n-butyl)
Parbituric acid-5 ']-3-iminoisoindoline, 3
-Imino-1-sulfobenzoic acid imide, 3-imino-1
-Sulfo-6-chlorobenzoic acid imide, 3-imino-1
-Sulfo-5,6-dichlorobenzoic acid imide, 3-imino-1-sulfo-4,5,6,7-tetrachlorobenzoic acid imide, 3-imino-1-sulfo-4,5,6,7-
Tetrabromobenzoic acid imide, 3-imino-1-sulfo-4,5,6,7-tetrafluorobenzoic acid imide, 3
-Imino-1-sulfo-6-nitrobenzoic acid imide, 3
-Imino-1-sulfo-6-methoxybenzoic acid imide,
3-imino-1-sulfo-4,5,7-trichloro-6
-Methylmercaptobenzoimide, 3-imino-1-
Sulfonaphthoic acid imide, 3-imino-1-sulfo-5
-Bromonaphthoic acid imide, 3-imino-2-methyl-
4,5,6,7-tetrachloroisoindoline-1-one and the like.

The heat-sensitive recording material may contain a heat-fusible substance in order to improve its sensitivity. 60 ℃ ~
Those having a melting point of 180 ° C. are preferable, and especially 80 ° C.
Those having a melting point of 140 ° C. are preferred. For example, p-
Benzyl 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-stearoylurea, 4-benzylbiphenyl, 1,2-di (m-methylphenoxy) ethane, 1-phenoxy-2
-(4-chlorophenoxy) ethane, 1,4-butanediol phenyl ether, dimethyl terephthalate 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, 10 to 30 relative to the aromatic isocyanate compound.
It is preferable to use 0% by weight, and further 20 to 25%
It is more preferable to use 0% by weight. Further, the heat-sensitive recording material 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, orthosortidine 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'-tetraaminobenzophenone and the like.

A dispersion of a heat-sensitive agent containing an aromatic isocyanate compound as a main component, a dispersion of a heat-sensitive agent containing an imino compound as a main component, a dispersion of other additives and a binder, etc. are thus obtained. Mix to make a heat-sensitive coating liquid. The heat-sensitive recording material can be obtained by applying the heat-sensitive coating liquid on the support by a coating method such as an air knife, a blade or curtain coating to form a heat-sensitive recording layer.

As described above, the heat-sensitive recording material comprises a support and a heat-sensitive recording layer on which a color is developed by heating. Paper is mainly used as the support, but in addition to paper, various non-woven fabrics, synthetic resin films, laminated papers, synthetic papers, metal foils, etc., or composite sheets in which these are combined are arbitrarily used according to the purpose. You can The thermal recording layer may have a single layer structure or a multi-layer structure. In the case of multiple layers, an intermediate layer may be interposed between each layer. Further, a protective layer may be provided on this layer. This recording layer can be obtained by mixing the respective aqueous dispersions obtained by finely pulverizing the respective color-forming components, the binder, etc., and coating and drying on a support. In this case, for example, each color-forming component may be contained in one layer to form a multilayer structure.

As the binder, water-soluble materials such as starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, etc. Examples thereof include latex-based water-insoluble binders such as binders, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers and methyl acrylate-butadiene copolymers.

Further, in the heat-sensitive recording layer, pigments such as diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide and urea-formalin resin, and others. , Higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as paraffin, oxidized paraffin, polyethylene, polyethylene oxide, stearamide, and castor wax for the purpose of preventing head wear and sticking, and dioctylsulfosuccinic acid. A dispersant such as sodium acid salt, a benzophenone-based or benzotriazole-based ultraviolet absorber, a surfactant, a fluorescent paint, and the like may be contained.

Further, a leuco dye or the like may be incorporated for the purpose of adjusting the color tone of the developed color.

[0025]

The present invention will be described in more detail with reference to the following examples.

[0026]

Example 1 4,4 ', 4 "-triisocyanato-2,
5-Dimethoxytriphenylamine (aromatic urea compound content 2.5% by weight) was pulverized with a jet mill to obtain a heat-sensitive agent. The particle size after crushing is PRO700 manufactured by Seishin Enterprise Co., Ltd.
When measured at 0S, the average particle size was 1.4 μm. The amount of aromatic urea compound in the heat-sensitive agent after pulverization is
It was measured using a liquid chromatogram. As the measurement conditions, a temperature of 35 ° C. and a carrier having a composition of acetonitrile and water by volume of 65% acetonitrile and 35% water at a flow rate of 1.0 ml / min are used. Column is GL Sci
using Inertsil ODS-2 manufactured by ences,
The measurement was performed at a detection wavelength of 310 nm. The result was 3% by weight. 2 g of this heat-sensitive agent was added to 8 g of a 2.5 wt% aqueous polyvinyl alcohol solution, and further dispersed with a paint shaker for 15 minutes together with 2.5 g of a 15 wt% polyvinyl alcohol aqueous solution used as a binder.

Separately from this dispersion, 2 g of an imino compound, 1,3-diimino-4,5,6,7-tetrachloroisoindoline, was pulverized with a paint shaker for 4 hours together with 8 g of a 2.5 wt% aqueous polyvinyl alcohol solution. After dispersion, 2.5 g of 15 wt% polyvinyl alcohol was further added as a binder and dispersed for 15 minutes with a paint shaker to obtain a dispersion liquid.

2 g of 2-benzyloxynaphthalene
Was pulverized with a paint shaker for 4 hours together with 8 g of a 2.5% by weight aqueous solution of polyvinyl alcohol, and then 15% by weight of polyvinyl alcohol as a binder.
5 g was added and dispersed for 15 minutes with a paint shaker to obtain a dispersion liquid. Further, 2 g of 2-methoxy-3-N, N-diethylsulfamoylaniline was pulverized and dispersed with a paint shaker for 4 hours together with 8 g of a 2.5 wt% polyvinyl alcohol aqueous solution, and then 15 wt% as a binder.
2.5 g of polyvinyl alcohol was added and dispersed for 15 minutes with a paint shaker to obtain a dispersion liquid.

2.5 g of calcium carbonate 2 g by weight
After pulverizing and dispersing with 8 g of polyvinyl alcohol aqueous solution in a paint shaker for 4 hours, 2.5 g of 15 wt% polyvinyl alcohol was further added as a binder and dispersed for 15 minutes with a paint shaker to obtain a dispersion liquid. These dispersions were mixed with 4,4 ', 4 "-triisocyanato-2,
10 parts by weight of 5-dimethoxytriphenylamine dispersion,
1,3-Diimino-4,5,6,7-tetrachloroisoindoline dispersion 15 parts by weight, 2-benzyloxynaphthalene dispersion 20 parts by weight, ITR dispersion 20 parts by weight, calcium carbonate dispersion 50 parts by weight, Furthermore, solid content concentration 16
A coating liquid was obtained by stirring and mixing 15 parts by weight of a zinc stearate dispersion liquid of 15% by weight.

This coating solution was coated on a base paper having a weight of 50 g / m ² with a rod coater No. 16 and dried and then treated with a super calender to obtain a heat-sensitive recording material. The sensitivity was evaluated with a printing tester manufactured by Okura Electric Co., Ltd., and a thermal head was KJT-256-8MGF1 manufactured by Kyocera, and the color density (OD) was measured at an applied voltage of 24 V and a pulse width of 1.2 msec. The result was a good optical density of 0.92.

To evaluate the degree of discoloration of the background due to light, the thermosensitive recording material was allowed to stand in the sunlight through a glass window for 2 days and visually compared with a portion where the discoloration of the background was not exposed to the sunlight. The results were good with very little discoloration. It is summarized in Table 1.

[0032]

Example 2 4,4 ', 4 "-triisocyanato-2,
5-Dimethoxytriphenylamine (aromatic urea compound content 2.5% by weight) was pulverized with a turbo mill. When the particle size after pulverization was measured by PRO7000S manufactured by Seishin Enterprise Co., Ltd., the average particle size was 3.0 μm. The amount of the aromatic urea compound in the heat-sensitive agent after pulverization was 8% by weight as a result of performing the same conditions as in Example 1. 2g of this particle
Was added to 8 g of a 2.5 wt% polyvinyl alcohol aqueous solution, and further dispersed with a paint shaker for 15 minutes together with 2.5 g of a 15 wt% polyvinyl alcohol aqueous solution used as a binder. The heat-sensitive recording material was obtained in the same manner as in Example 1, except for the above dispersion liquid of the aromatic isocyanate compound.

When the sensitivity was evaluated under the same conditions as in Example 1, the color density was 0.91 which was a good value. Further, when the discoloration of the background due to light was examined at the same time as in Example 1, it was satisfactory. The results are summarized in Table 1.

[0034]

Example 3 4,4 ', 4 "-triisocyanato-2,
5-Dimethoxytriphenylamine (aromatic urea compound content 2.5% by weight) was pulverized with a vibrating ball mill.
When the particle size after pulverization was measured by PRO7000S manufactured by Seishin Enterprise Co., Ltd., the average particle size was 2.1 μm. The amount of the urea compound in the heat-sensitive agent after pulverization was 11% by weight as a result of performing the same conditions as in Example 1. 2g of this particle
Was added to 8 g of a 2.5 wt% polyvinyl alcohol aqueous solution, and further dispersed with a paint shaker for 15 minutes together with 2.5 g of a 15 wt% polyvinyl alcohol aqueous solution used as a binder. The heat-sensitive recording material was obtained in the same manner as in Example 1, except for the above dispersion liquid of the aromatic isocyanate compound.

When the sensitivity was evaluated under the same conditions as in Example 1, the color density was 0.91, which was a good value. Further, when the discoloration of the background due to light was examined at the same time as in Example 1, it was satisfactory. The results are summarized in Table 1.

[0036]

[Comparative Example 1] 4,4 ', 4 "-triisocyanato-2,
5-dimethoxytriphenylamine (aromatic urea compound content 2.5% by weight) was pulverized with a bin mill. When the particle size after pulverization was measured by PRO7000S manufactured by Seishin Enterprise Co., Ltd., the average particle size was 5.8 μm. The amount of the aromatic urea compound in the heat-sensitive agent after pulverization was 5% by weight as a result of performing the same conditions as in Example 1. Polyvinyl alcohol 1 obtained by adding 2 g of the particles to 8 g of a 2.5 wt% polyvinyl alcohol aqueous solution and further used as a binder
1 on a paint shaker with 2.5 g of a 5% by weight aqueous solution
Dispersed for 5 minutes. The heat-sensitive recording material was obtained in the same manner as in Example 1, except for the above dispersion liquid of the aromatic isocyanate compound.

When the sensitivity was evaluated under the same conditions as in Example 1, the color density was 0.86, which was a low value. Further, when the discoloration of the background due to light was examined at the same time as in Example 1, it was satisfactory. The results are summarized in Table 1.

[0038]

Comparative Example 2 4,4 ', 4 "-triisocyanato-2,
2 g of 5-dimethoxytriphenylamine (aromatic urea compound content 2.5% by weight) was pulverized with a paint shaker for 6 hours together with 8 g of a 2.5% by weight polyvinyl alcohol aqueous solution. The particle size after crushing is PRO7 manufactured by Seishin Enterprise Co., Ltd.
When measured at 000S, the average particle size was 0.9 μm. The amount of the aromatic urea compound was 28% by weight as a result of conducting the same conditions as in Example 1. Further, 2.5 g of a 15% by weight aqueous solution of polyvinyl alcohol used as a binder was added and dispersed for 5 minutes to obtain a dispersion liquid. A heat-sensitive recording material was prepared in the same manner as in Example 1, except that the above aromatic isocyanate compound was pulverized.

When the sensitivity was evaluated under the same conditions as in Example 1, the color density was 0.93, which was a good value. When this was examined for discoloration of the background due to light simultaneously with Example 1, a large discoloration was shown. The results are summarized in Table 1.

[0040]

[Comparative Example 3] 4,4 ', 4 "-triisocyanato-2,
8 g of 5-dimethoxytriphenylamine (aromatic urea compound content 2.5% by weight) was pulverized with 32 g of a 2.5% by weight aqueous polyvinyl alcohol solution by Dynomill for 2 hours. The particle size after crushing is PRO7000 manufactured by Seishin Enterprise Co., Ltd.
When measured by S, the average particle size was 0.8 μm.
The amount of the aromatic urea compound after pulverization was 22% by weight as a result of performing the same conditions as in Example 1. Further, 10 g of a 15% by weight aqueous solution of polyvinyl alcohol used as a binder was added and dispersed for 5 minutes to obtain a dispersion liquid. A heat-sensitive recording material was prepared in the same manner as in Example 1, except for the above dispersion liquid of the aromatic isocyanate compound.

When the sensitivity was evaluated under the same conditions as in Example 1, the color density was 0.92, which was a good value. When the discoloration of the background due to light was examined simultaneously with Example 1, a large discoloration was shown. The results are summarized in Table 1.

[0042]

[Table 1]

[0043]

By using the heat-sensitive agent of the present invention, it is possible to obtain a heat-sensitive recording material having high sensitivity and being excellent in yellowing due to background light.

Claims (1)

[Claims] 1. A heat-sensitive agent comprising an aromatic isocyanate compound and having an average particle size of 3 μm or less,
A heat-sensitive agent, wherein the aromatic urea compound in the heat-sensitive agent is 20% by weight or less.