JP3373263B2 - Thermosensitive agent dispersion - Google Patents

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 excellent in heat-resistant yellowing of the background, suitability for wrapping, image storability and color development sensitivity.

[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 machines, labels and ticket vending machines.

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 characteristics such as good feel, high color density, and various color hues, the thermosensitive color part (recorded image part) contacts plastic such as polyvinyl chloride and is Loss of storage due to plasticizers and additives contained in, disappearing easily by contact with chemicals contained in foods and cosmetics, or fading easily after exposure to sunlight for a short time The present situation is that the application is subject to certain restrictions due to this drawback, and improvement thereof 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 containing an aromatic isocyanate and a heat-sensitive agent mainly containing an imino compound.

However, these thermal recording materials are
Although the recorded image is excellent in storability, there is a problem that discoloration easily occurs due to heat of the non-image portion, that is, the background. In addition, there is a problem in that when the heat-sensitive recording material comes into contact with a vinyl chloride wrap, the background portion is colored.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording material which is less likely to cause discoloration due to heat of the background and is excellent in yellowing of the background, and is excellent in wrapping aptitude, image storability and color development sensitivity. And

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to obtain a heat-sensitive recording material excellent in heat yellowing of the background and excellent in image storability and color development sensitivity. It was found that by selecting the type of polyvinyl alcohol used to disperse the aromatic isocyanate compound, there is little yellowing due to the heat of the background, and a highly sensitive thermosensitive recording material that can obtain a sufficiently colored image even at low energy can be obtained. The present invention has been completed.

That is, the present invention is as follows. 1. Aromatic isocyanate compounds with a degree of saponification of 81
% Or more and the degree of polymerization is 1000 or more and 2000 or less
Thermal dispersion for heat-sensitive recording material having dispersed in an aqueous solution containing that polyvinyl alcohol. 2. A dispersion obtained by dispersing an aromatic isocyanate compound in an aqueous solution containing polyvinyl alcohol, a heat-sensitive material obtained by coating a support with a dispersion of an imino compound capable of reacting with the aromatic isocyanate compound and developing a color. A heat-sensitive recording material comprising the recording material, wherein the heat-sensitive agent dispersion described in (1) is used as a dispersion obtained by dispersing the aromatic isocyanate compound in an aqueous solution containing polyvinyl alcohol.

The thermal recording material will be described in detail below. In order to obtain a heat-sensitive recording material which is excellent in yellowing due to heat of the background, and which is excellent in image storability and color development sensitivity, saponification of polyvinyl alcohol in an aqueous polyvinyl alcohol solution used to disperse the aromatic isocyanate compound contained in the heat-sensitive recording layer. The degree must be 81% or more, preferably 85% or more. When the degree of saponification of polyvinyl alcohol is 81% or more, there is little discoloration due to heat,
A heat-sensitive recording material with less wrapping can be obtained. The polyvinyl alcohol aqueous solution is usually prepared so as to be 1 to 20% by weight, and the aqueous solution is used to prepare the aromatic isocyanate compound 10
It is preferable to use 50 to 1000 parts by weight, more preferably 100 to 400 parts by weight, based on 0 parts by weight.

The degree of polymerization of polyvinyl alcohol is 100.
A value of 0 or more and 2000 or less is used. Degree of polymerization is 1000
When the above polyvinyl alcohol is used, a dry heat recording material which is particularly less yellowed by the heat of the background can be obtained. If polyvinyl alcohol having a high degree of polymerization is used, the viscosity of this aqueous solution will be high, but if it is used at a low concentration, the amount of the aqueous solution will be large and it will be difficult to operate, but there is no problem.

The aromatic isocyanate compound used in the present invention refers to a colorless or light-colored aromatic isocyanate compound or a heterocyclic isocyanate compound which is solid at room temperature. For example, one or more of the following isocyanate compounds may be used. 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, bilen-3,8-di Isocyanate, naphthalene-1,3,7-triisocyanate, biphenyl-
2,4,4'-triisocyanate, 4,4 ', 4 "-
Triisocyanato-2,5-dimethoxytriphenylamine, 4,4 ', 4 "-triisocyanatotriphenylamine, 4,4'-diisocyanato-2,5dimethoxytriphenylamine, 4,4', 4" -Triisocyanato-2,5-diethoxytriphenylamine, p-dimethylaminophenylisocyanate, tris (4-phenylisocyanato) thiophosphate and the like. These isocyanates are phenols,
Lactams, which are addition compounds with oximes, may be used in the so-called block isocyanate form,
It may be used in the form of diisocyanate dimers, for example, isocyanurate, which is a dimer and trimer of 1-methylbenzene-2,4-diisocyanate, and is adducted with various polyols. It can also be used as a polyisocyanate.

Of these, the triphenylamine derivative isocyanate is particularly preferable, and 4,4 ',
4 "-triisocyanato-2,5-dimethoxytriphenylamine, 4,4 ', 4" -triisocyanatotriphenylamine, 4,4'-diisocyanato-2,5-dimethoxytriphenylamine, 4,4 ', 4 "-Triisocyanato-2,5 diethoxytriphenylamine is preferred.

To prepare a heat-sensitive recording material, one or more kinds of these aromatic isocyanates are made into a dispersion liquid and coated on a support together with other necessary components to form a heat-sensitive recording layer. The dispersion is prepared by finely pulverizing one or more of these aromatic isocyanates in an aqueous solution containing polyvinyl alcohol having a saponification degree of 81% or more. It is preferably pulverized in an aqueous solution containing polyvinyl alcohol having a saponification degree of 85% or more. At this time, it is desirable that the pulverization time is short and the temperature is low to reduce the production of impurities. The particle size of the aromatic isocyanate compound after fine pulverization is preferably 4 μm or less, and more preferably 2 μm or less. When the particle size is 4 μm or less, sufficient color developing sensitivity is obtained, which is preferable. A more desirable dispersion is prepared by dry-milling the raw material to a required particle size, and then saponification degree of 81% or more, preferably 85%.
% Is to disperse only in a short time in an aqueous solution containing polyvinyl alcohol. For dry pulverization, for example, a dry pulverizer such as a ball mill, a vibrating ball mill, an attritor, a jet mill, a sand mill, a bin mill and a turbo mill can be used. The degree of polymerization of polyvinyl alcohol used for dispersion is 600.
It is more preferable that the above is satisfied.

The imino compound used in the present invention is a colorless or light-colored compound having at least one imino group represented by C═NH and represented by the general formula shown in the following chemical formula 1 and solid at room temperature. One or more of the following specific examples are used.

[0015]

[Chemical 1]

(Φ is an aromatic compound residue capable of forming a conjugated system with adjacent C = N.) Specific examples are shown below. 3-iminoisoindoline-1-
On, 3-imino-4,5,6,7-tetrachloroisoindoline-1-one, 3-imino-4,5,6,7-
Tetrabromoisoindoline-1-one, 3-imino-
4,5,6,7-Tetrafluoroisoindoline-1-
On, 3-imino-5,6-dichloroisoindoline-
1-one, 3-imino-4,5,7-trichloro-6-
Methoxy-isoindoline-1-one, 3-imino-
4,5,7-Trichloro-6-methylmercapto-isoindoline-1-one, 3-imino-6-nitroisoindoline-1-one, 3-imino-isoindoline-1
-Spiro-dioxolane, 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-4,5,6,7-tetrabromoisoindoline,
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 [3,4b] 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-iminoisoindoline, 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-dithia Tetrahydroisoindoline, 1-
[(Cyanobenzimidazolyl-2 ')-methylene]-
3-imino-5,6-dimethyl-4,7-pyradiisoindoline, 1-[(1'-methyl-3'-n-butyl)
-Barbituric 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-methylmercaptobenzoic acid imide, 3-imino-
1-sulfonaphthoic acid imide, 3-imino-1-sulfo-5-bromonaphthoic acid imide, 3-imino-2-methyl-4,5,6,7-tetrachloroisoindoline-1
-There is an on.

Among these, iminoisoindoline derivatives are particularly preferable, and 1,3-diimino-4,
5,6,7-Tetrachloroisoindoline, 3-imino-4,5,6,7-tetrachloroisoindoline-1-
On, 1,3-diimino-4,5,6,7-tetrabromoisoindoline is preferred. In order to coat these imino compounds on a support to form a heat-sensitive recording layer material, it is necessary to form a dispersion liquid like the aromatic isocyanate compound.
The dispersion can be prepared by finely pulverizing one or more of these imino compounds in an aqueous solution containing a compound having a dispersing ability such as a water-soluble polymer and a surfactant. There are no particular restrictions.

The heat-sensitive recording layer 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,
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,
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
Examples include butanediol phenyl ether and dimethyl terephthalate.

The above-mentioned heat-fusible substances may be used alone or in 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 preferable to use 0% by weight, and further 20 to 250
It is more preferable to use the weight percent. Further, the heat-sensitive recording material according to the present invention can contain an aniline derivative having at least one amino group, and 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'-
And tetraaminobenzophenone.

These heat fusible substances and aniline derivatives also need to be in the form of dispersion liquids, like the imino compounds. The dispersion is prepared in the same manner as in the case of the imino compound, but the dispersant used at this time is not limited. The dispersion liquid of the aromatic isocyanate compound, the dispersion liquid of the imino compound and the dispersion liquid of other additives thus obtained are mixed with a binder or the like to prepare a heat-sensitive coating liquid. The heat-sensitive recording material of the present invention 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.

The heat-sensitive recording material according to the present invention is, as described above, provided with a heat-sensitive recording layer for coloring by heating on a support. Paper is mainly used as the support, but in addition to paper, various non-woven fabrics, synthetic resin films, laminated paper,
Synthetic paper, metal foil, or a composite sheet in which these are combined can be arbitrarily used according to the purpose. 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, the heat-sensitive recording layer contains 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. , 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 dye, and the like may be contained.

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

[0026]

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

[0027]

Example 1 4,4 ', 4 "-triisocyanato-2,
5-dimethoxytriphenylamine was milled on a jet mill. 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. 2 g of these particles was used as 2.5 wt% polyvinyl alcohol (PVA-110 manufactured by Kuraray Co., Ltd., saponification degree 98.5).
%, Polymerization degree 1000) 8 g of an aqueous solution, and further dispersed with a paint shaker for 15 minutes together with 2.5 g of a 15 wt% aqueous solution of polyvinyl alcohol used as a binder. The particle size of the dispersion was 1.5 μm.

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% polyvinyl alcohol aqueous solution. After dispersion, 2.5 g of a 15 wt% polyvinyl alcohol aqueous solution 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 and dispersed with 8 g of a 2.5 wt% polyvinyl alcohol aqueous solution in a paint shaker for 4 hours, 2.5 g of a 15 wt% polyvinyl alcohol aqueous solution was further added as a binder, and the mixture was dispersed in a paint shaker for 15 minutes to obtain a dispersion liquid. In addition, 2-methoxy-5-N, N-
2 g of diethylsulfamoylaniline was pulverized and dispersed in a paint shaker for 4 hours together with 8 g of a 2.5 wt% polyvinyl alcohol aqueous solution, and then 2.5 g of a 15 wt% polyvinyl alcohol aqueous solution was added as a binder and dispersed for 15 minutes in a paint shaker. A dispersion was obtained.

2.5 g of calcium carbonate (2 g) by weight
After pulverizing and dispersing with a paint shaker for 4 hours together with 8 g of polyvinyl alcohol aqueous solution, 2.5 g of 15 wt% polyvinyl alcohol aqueous solution 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-2,5-dimethoxytriphenylamine dispersion 10
Parts by weight, 15 parts by weight of 1,3-diimino-4,5,6,7-tetrachloroisoindoline dispersion, 20 parts by weight of 2-benzyloxynaphthalene dispersion, 2-methoxy-3-
20 parts by weight of N, N-diethylsulfamoylaniline dispersion liquid, 50 parts by weight of calcium carbonate dispersion liquid, and 15 parts by weight of zinc stearate dispersion liquid having a solid content of 16% by weight are stirred and mixed to obtain a coating liquid. It was

This coating solution was coated on a base paper having a weight of 50 g / m ² with a bar coater, rod number 16, and after drying, it was processed with a super calendar to obtain a heat-sensitive recording material. The sensitivity was evaluated with a printing tester manufactured by Okura Electric Co., Ltd., and the thermal head was KJT-256-8MGF1 manufactured by Kyocera.
The color density was measured with an RD917 densitometer manufactured by th company.
The result was a good optical density of 1.0.

The degree of discoloration of the background due to heat was evaluated by visually observing the discoloration of the background by allowing the thermosensitive recording material to stand at 60 ° C. for 24 hours. The results were good with very little discoloration. In addition, the evaluation of the wrap coverage is performed by using the thermal recording material as High Wrap KMA-W.
It was sandwiched between (manufactured by Mitsui Toatsu Co., Ltd.) and left at 40 ° C. for 24 hours, and then the discoloration of the background was visually evaluated. The result was good with little discoloration of the background. Collectively shown in Table 1.

[0033]

Example 2 4,4 ', 4 "-triisocyanato-2,
Heat treatment was performed in the same manner as in Example 1 except that PVA-117 (manufactured by Kuraray Co., Ltd., saponification degree: 98.5%, polymerization degree: 1700) was used as the polyvinyl alcohol used to disperse 5-dimethoxytriphenylamine. A recording material was obtained.

When the sensitivity was measured under the same conditions as in Example 1, the color density was good. Further, when the discoloration of the background due to heat was examined at the same time as Example 1, it was satisfactory.
Further, when a lap covering test was carried out at the same time as in Example 1, the background color was good with little color development. Collectively shown in Table 1.

[0035]

Comparative Example 1 4,4 ′, 4 ″ -triisocyanato-2,
Heat treatment was carried out in the same manner as in Example 1, except that the polyvinyl alcohol used to disperse 5-dimethoxytriphenylamine was PVA-205 (Kuraray Co., Ltd., saponification degree 88%, polymerization degree 500). A recording material was obtained.

When the sensitivity was measured under the same conditions as in Example 1, the color density was good. Moreover, when the discoloration of the background due to heat was examined at the same time as the heat-sensitive recording material of Example 1, it was satisfactory. Further, when a lap covering test was conducted at the same time as in Example 1, the color development of the background was slightly small and good.
Collectively shown in Table 1.

[0037]

Comparative Example 2 4,4 ′, 4 ″ -triisocyanato-2,
Polyvinyl alcohol used in the dispersion of 5-dimethoxytriphenylamine and 1,3-diimino-4,5,6,7-tetrachloroisoindoline is PVA-405.
A thermal recording material was obtained in the same manner as in Example 1, except that the saponification degree was 80% and the polymerization degree was 500, manufactured by Kuraray Co., Ltd.

When this was examined at the same time as the heat-sensitive recording material of Example 1 for the discoloration of the background due to heat, discoloration occurred and it was defective. Further, when a lap covering test was conducted at the same time as in Example 1, color development of the background occurred and it was defective. Table 1
Shown in.

[0039]

Comparative Example 3 4,4 ′, 4 ″ -triisocyanato-2,
The polyvinyl alcohol used in the dispersion of 5-dimethoxytriphenylamine and 1,3-diimino-4,5,6,7-tetrachloroisoindoline dispersion was L-8.
A thermal recording material was obtained in the same manner as in Example 1, except that the saponification degree was 71.0% (manufactured by Kuraray Co., Ltd.).

When this was examined for discoloration of the background due to heat at the same time as the heat-sensitive recording material of Example 1, discoloration occurred and it was defective. Further, when a lap covering test was conducted at the same time as in Example 1, color development of the background occurred and it was not good. Table 1
Shown in.

[0041]

[Table 1]

[0042]

EFFECTS OF THE INVENTION It is possible to obtain a heat-sensitive recording material which is excellent in image storability and color development sensitivity, and which is excellent in yellowing of the background due to heat and suitability for wrapping.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-262049 (JP, A) JP-A-5-229260 (JP, A) JP-A-2-95886 (JP, A) JP-A-61- 205183 (JP, A) JP 59-135189 (JP, A) JP 4-348988 (JP, A) JP 4-270680 (JP, A) JP 4-62089 (JP, A) JP-A-6-171233 (JP, A) JP-A-6-48041 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B41M 5 / 28-5 / 34

Claims (2)

(57) [Claims] 1. An aromatic isocyanate compound having a saponification degree of 81% or more and a polymerization degree of 1,000 or more and 2,000.
A heat-sensitive agent dispersion liquid for a heat- sensitive recording material, which is dispersed in an aqueous solution containing the following polyvinyl alcohol. 2. A dispersion obtained by dispersing an aromatic isocyanate compound in an aqueous solution containing polyvinyl alcohol,
In a heat-sensitive recording material comprising a support and a dispersion liquid of an imino compound capable of reacting with the aromatic isocyanate compound to form a color, and a binder, the aromatic isocyanate compound is dispersed in an aqueous solution containing polyvinyl alcohol. A heat-sensitive recording material comprising the heat-sensitive agent dispersion according to claim 1 as the dispersion.