JPH05278333A - Thermal recording material - Google Patents

Abstract

PURPOSE:To raise a retentive property of a recording image by a method wherein a recording layer which contains a basic dye, a coloration agent, a retentive property improving agent expressed by a specific general formula, and water-soluble containing an acid molecular species, is provided onto a base material. CONSTITUTION:An application liquid for thermal recording layer is prepared by dispersing respective specific amounts of a colorless or light colored basic dye, a coloration agent, a compound expressed by the formula I (R1, R2, R3 represent a hydrogen atom, a C1-C8 alkyl group, a C5-C8 cycloalkyl group, and R4-R8 represents a hydrogen atom, a C1-C8 alkyl group), and a water-soluble compound containing an acid molecular species in a water-soluble binder by grinding with a ball mill or the like. The application liquid is applied onto a base material of paper, a plastic film, synthetic paper, etc., dried to form a thermal recording layer, and a thermal recording material is obtained. As the abovementioned water soluble high molecular compound containing the acid molecular species, a graft copolymer or the like of a vinyl alcohol and vinyl acetate copolymer and an acrylic amide, acrylic acid and allyl acetate copolymer is exemplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and in particular, it has excellent suitability for high-speed recording and storability of recorded images, and can maintain stable recorded images without lowering the whiteness of white paper. The present invention relates to a thermosensitive recording medium.

[0002]

2. Description of the Related Art A thermosensitive recording medium is well known in which a reaction between a colorless or light-colored basic dye and a coloring agent is used to bring both color-forming substances into contact with each other to obtain a recorded image.
Since such a thermosensitive recording medium is relatively inexpensive and the recording device is compact and its maintenance is relatively easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields. ..

In general, a thermal recording material is required to have not only suitability for high-speed recording but also quality characteristics such as stability of a recorded image under high temperature and high humidity conditions and unnecessary reduction of fog on a white paper portion. .

[0004]

In order to improve the storage stability of a recorded image, a thermal recording material containing various storability improving agents has been proposed. Satisfactory results have not always been obtained because of new defects such as a large decrease in whiteness when stored.

In view of the above situation, the inventors of the present invention have earnestly studied the preservability improving agent to be contained in the recording layer.
When a compound represented by the following general formula [Chemical Formula 1] is used as a preservability improver and a specific polymer water-soluble compound is used in combination, the whiteness is lowered even when stored under high temperature conditions. The present invention has been completed based on the finding that it does not have any new defects and exhibits an extremely excellent effect in improving the storage stability of a recorded image.

[0006]

The present invention provides a thermosensitive recording medium provided with a recording layer containing a colorless or light-colored basic dye and a coloring agent, and the recording layer further has the following general formula:
And a water-soluble polymer compound containing an acidic molecular species.

[0007]

[Chemical 1]

[In the formula, R ₁ , R ₂ and R ₃ each represent a hydrogen atom, a C _{1 to} C ₈ alkyl group or a C _{5 to} C ₈ cycloalkyl group. R ₄ , R ₅ , R ₆ , R ₇ , R
₈ are each a hydrogen atom, an alkyl group of C ₁ -C _8. ]

[0009]

Specific examples of the compound represented by the above general formula [Chemical formula 1] include 1,1,3-tris (2-methyl-4)
-Hydroxy-5-tert-butylphenyl) butane,
1,1,3-tris (2-ethyl-4-hydroxy-5)
-Tert-butylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) propane, 1,1,3-tris (2-ethyl-4)
-Hydroxy-5-tert-butylphenyl) propane,
1,1,3-tris (2-methyl-4-hydroxy-5)
-Cyclohexylphenyl) butane, 1,1,3-tris (2-ethyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-)
4-hydroxy-5-cyclohexylphenyl) propane, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclopentylphenyl) butane, 1,1,3-
Examples thereof include tris (2-ethyl-4-hydroxy-5-cyclopentylphenyl) butane and 1,1,3-tris (2-methyl-4-hydroxy-5-cyclopentylphenyl) propane.

The water-soluble polymer compound containing an acidic molecular species used in the heat-sensitive recording material of the present invention includes, for example, a compound having an acidic molecular species in its molecule.・ Vinyl acetate) copolymer (acrylamide / acrylic acid / allyl acetoacetate)
Examples thereof include graft copolymers with copolymers, acetoacetyl group-modified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, sulfo group-modified polyvinyl alcohol, and the like. Above all (vinyl alcohol / vinyl acetate)
The graft copolymer of the copolymer and the (acrylamide / acrylic acid / allylacetoacetate) copolymer is preferably used because it exhibits particularly remarkable effects. Although these water-soluble polymer compounds are generally used as a binder, they can also be used as a dispersion aid. The amount of the compound represented by the general formula [Chemical Formula 1] used is not particularly limited, but is generally about 1 to 300 parts by weight, preferably 1 to 100 parts by weight of the compound with respect to 100 parts by weight of the color developing agent. It is desirable to adjust within the range of about parts by weight.

In the present invention, various kinds of known dyes can be used as the colorless or light-colored basic dye constituting the recording layer, and specific examples thereof include the following.
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 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,
3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -6-dimethylaminophthalide,
3,3-bis (2-phenylindol-3-yl)-
6-Dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-3-yl) -6
-Triarylmethane dyes such as dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoauramine, N-2,4,5-trichlorophenylleucoalamin, etc. Diphenylmethane dyes, benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene blue and other thiazine dyes, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-
Phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho (6'-methoxybenzo) spiropyran, 3-propyl-spiro-
Spiro dyes such as dibenzopyran, lactam dyes such as rhodamine-B-anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine (o-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluorane, 3- Diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane,
3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-
Diethylamino-6,7-dimethylfluorane, 3-
(N-ethyl-p-toluidino) -7-methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino- 7-dibenzylaminofluorane, 3-diethylamino-7-N
-Methyl-N-benzylaminofluorane, 3-diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-diethylaminofluorane, 3- (N-ethyl-p-toluidino) −
6-methyl-7-phenylaminofluorane, 3- (N
-Ethyl-p-toluidino) -6-methyl-7- (p-
Toluidino) fluorane, 3-dimethylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, 3
-Di-n-butylamino-6-methyl-7-phenylaminofluorane, 3-di-n-pentylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-7- (2-carbomethoxy -Phenylamino) fluorane, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-phenylaminofluorane, 3
-Pyrrolidino-6-methyl-7-phenylaminofluorane, 3-piperidino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-
Xylidinofluorane, 3-diethylamino-7- (o
-Chlorophenylamino) fluorane, 3-di-n-butylamino-7- (o-chlorophenylamino) fluorane, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluorane, 3- (N-methyl-) N-n-
Amyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-Nn-amyl) amino-
6-methyl-7-phenylaminofluorane, 3- (N
-Ethyl-N-isoamyl) amino-6-methyl-7-
Phenylaminofluorane, 3- (N-methyl-Nn)
-Hexyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-Nn-hexyl) amino-6-methyl-7-phenylaminofluorane, 3
-(N-ethyl-N-β-ethylhexyl) amino-6
-Methyl-7-phenylaminofluorane, 3- (N-
Ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-N-cyclopentyl) amino-6-methyl-7-phenylaminofluorane, 2,2-bis {4- [6'-
(N-Cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthene] -2 '
Fluorane dyes such as -ylamino] phenyl} propane. Of course, it is not limited to these dyes,
It is also possible to use two or more dyes in combination. Among these dyes, 3-dibutylamino-7- (o-chlorophenylamino) fluorane and 3-diethylamino-7- (o
-Chlorophenylamino) fluorane and 3- (N-ethyl-p-toluidino) -6-methyl-7-phenylaminofluorane are more preferably used because a thermosensitive recording medium having a particularly high whiteness in the white paper portion can be obtained.

Various compounds are known as colorants used in combination with the above basic dyes, and the following are exemplified. 4-tert-butylphenol, α-
Naphthol, β-naphthol, 4-acetylphenol, 4-tert-octylphenol, 4,4′-sec −
Butylidene diphenol, 4-phenylphenol,
4,4'-dihydroxy-diphenylmethane, 4,4 '
-Isopropylidenediphenol, hydroquinone,
4,4'-cyclohexylidene diphenol, 4,4 '
-(1,3-dimethylbutylidene) bisphenol,
2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis (6-tert-butyl-3-methylphenol), 4,4'- Dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-4'-methoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy -3 ', 4'-trimethylene diphenyl sulfone, 4-hydroxy-3', 4'-tetramethylene diphenyl sulfone, 3,4-dihydroxy-4'-methyldiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) ) Sulfone, 1,3-di [2- (4-hydroxyphenyl) Phenyl) -2-propyl] benzene, hydroquinone monobenzyl ether, bis (4
-Hydroxyphenyl) acetic acid butyl ester, 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, 4-hydroxyphthalic acid Dimethyl, methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, 4
-Propyl hydroxybenzoate, -sec-butyl 4-hydroxybenzoate, pentyl 4-hydroxybenzoate,
Phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, phenethyl 4-hydroxybenzoate, 4-hydroxybenzoic acid-p. -Chlorobenzyl,
4-hydroxybenzoic acid-p-methoxybenzyl, novolac type phenolic resin, phenolic compound such as phenolic polymer, benzoic acid, p-tert-butylbenzoic acid,
Trichlorobenzoic acid, terephthalic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-
Hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3,5-di-tert-
Butyl salicylic acid, 3-benzyl salicylic acid, 3- (α
-Methylbenzyl) salicylic acid, 3-chloro-5- (α
-Methylbenzyl) salicylic acid, 3-phenyl-5-
Aromatic carboxylic acids such as (α, α-dimethylbenzyl) salicylic acid and 3,5-di-α-methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids and, for example, zinc, magnesium, aluminum, calcium, titanium, Examples thereof include organic acidic substances such as salts with polyvalent metals such as manganese, tin and nickel. As a matter of course, two or more kinds of the above-mentioned color developing agents can be used in combination.

The use ratio of the basic dye and the color developing agent should be appropriately selected according to the types of the basic dye and the color developing agent to be used and is not particularly limited, but in general, the basic dye 1 is used.
About 100 to 700 parts by weight, preferably about 150 to 400 parts by weight, of the coloring agent is used with respect to 00 parts by weight. In the present invention, the use ratio of the substance represented by the general formula [Chemical Formula 1] to the coloring agent is generally 1 to 1000 parts by weight, preferably 10 to 300 parts by weight, relative to 100 parts by weight of the coloring agent. Is compounded in.

The preparation of a coating liquid containing these is generally represented by a basic dye, a coloring agent, and a general formula [Chemical formula 1] by using a stirring and crushing machine such as a ball mill, an attritor, and a sand mill with water as a dispersion medium. It is prepared by dispersing the compound or the like together or separately.

As described above, according to the present invention, acetoacetyl group-modified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, sulfone group-modified polyvinyl alcohol, (vinyl alcohol / vinyl acetate) copolymer and (acrylamide / acrylic acid / allyl acetoacetate). )
It is essential to use a water-soluble polymer compound containing an acidic molecular species such as a graft copolymer with a copolymer as a binder or a dispersion aid. , Hydroxyethyl cellulose,
Methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene / maleic anhydride copolymer salt, styrene /
Acrylic acid copolymer salt, styrene-butadiene copolymer emulsion, etc. can be used together as a binder or a dispersion aid. Then, these binder components are usually blended in the above coating liquid so as to be in the range of 2 to 40% by weight, preferably 5 to 25% by weight based on the total solids of the coating liquid.

Further, various auxiliaries can be added to the coating liquid, for example, dioctylsulfosuccinic acid sodium salt, dodecylbenzenesulfonic acid sodium salt,
Examples thereof include dispersants such as lauryl alcohol sulfate / sodium salt and fatty acid metal salt, defoaming agents, fluorescent dyes, and coloring dyes. Further, in order to improve the adhesion of dust to the recording head, inorganic pigments such as kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, particulate anhydrous silica, activated clay, styrene microballs, nylon powder, polyethylene. Powder, urea
Organic pigments such as formalin resin filler and raw starch particles can also be added. Furthermore, a dispersion liquid or emulsion of stearic acid, polyethylene, carnauba wax, paraffin wax, zinc stearate, calcium stearate, ester wax or the like may be added so that sticking does not occur due to contact with a recording device or recording head.

Further, in the heat-sensitive recording material of the present invention, fatty acid amides such as stearic acid amide, stearic acid methylenebisamide, oleic acid amide, palmitic acid amide, and coconut fatty acid amide are used as long as the desired effects of the present invention are not impaired. , 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-3-methylphenol), 1,1,3-tris (2-methyl) -4-Hydroxy-5-tert-butylphenyl) butane and other hindered phenols, p-benzylbiphenyl, p- (4-tolyloxy) biphenyl, 1,5-bis (4-methoxyphenoxy) -3-oxa- Pentane, 1,2-bis (phenoxy) ethane, 1,2-bis (4-methylphenoxy) ethane, 1,2-bi (3-methylphenoxy) ethane, 1- (2-methylphenoxy) -2- (4
-Methoxyphenoxy) ethane, ethers such as 2-naphtholbenzyl ether, dibenzyl terephthalate, 1-hydroxy-2-naphthoic acid phenyl ester, oxalic acid dibenzyl ester, oxalic acid di (4-methylbenzyl) ester, oxalic acid Esters such as di (4-chlorobenzyl) ester, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2-
An ultraviolet absorber such as hydroxy-4-benzyloxybenzophenone and various known heat-fusible substances can also be used together as a sensitizer. The amount of the heat-fusible substance used is not particularly limited, but is generally 50 to 1000 parts by weight, preferably 100 to 500 parts by weight, based on 100 parts by weight of the basic dye. Is desirable.

As the support, paper, plastic film, synthetic paper or the like is used, but paper is preferably used in terms of cost and coating suitability. In the present invention, the method for forming the recording layer is not particularly limited, and it can be formed according to a conventionally well-known and conventional technique. For example, a coating liquid for a heat-sensitive recording layer is formed on a support by an air knife coater or a blade. Examples of the method include coating and drying with a suitable coating device such as a coater, bar coater, gravure coater, curtain coater, and short dwell coater. Also, there are no particular limitation on the coating amount of the coating liquid, generally dry weight 2~12g / m ^2, it is adjusted preferably in the range of 2 to 8 g / m ^2.

An overcoat layer may be provided on the recording layer for the purpose of protecting the recording layer, and a protective layer may be provided on the back surface of the support or between the support and the heat-sensitive recording layer. It is of course possible to provide an undercoat layer on the above, and various known techniques in the field of manufacturing a thermosensitive recording medium can be added, such as adhesion processing or magnetic recording layer on the back surface.

[0020]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The parts and% in the examples are parts by weight and% by weight, respectively, unless otherwise specified.

Example 1 Formation of Undercoat Layer Fired clay (trade name: Ansilex, manufactured by EMC)
100 parts, styrene / butadiene copolymer latex (solid content: 50%) 15 parts, 10% polyvinyl alcohol aqueous solution 30 parts, and water 20 parts were mixed and stirred to prepare a coating liquid for the undercoat layer. 50 g of the obtained coating liquid
/ M ² of high-quality paper was coated and dried so that the coating amount after drying was 10 g / m ² to form an undercoat layer. Preparation of Solution A 3-di-n-butylamino-6-methyl-7-phenylaminofluorane 10 parts, 1,2-di (3-methylphenoxy) ethane 25 parts, 5% aqueous solution of methylcellulose 5 parts, and water 50 parts were pulverized with a sand mill until the average particle diameter became 0.7 μm.

Preparation of Liquid B 20 parts of 4,4′-isopropylidenediphenol, 5 parts of a 5% aqueous solution of methylcellulose, and 40 parts of water were pulverized with a sand mill until the average particle diameter became 1.1 μm. Preparation of liquid C 1,1,3-tris (2-methyl-4-hydroxy-5)
10 parts of -cyclohexylphenyl) butane, 3 parts of a 5% aqueous solution of polyvinyl alcohol, and 20 parts of water were pulverized with a sand mill until the average particle size became 1.2 µm.

Formation of Recording Layer 90 parts of solution A, 65 parts of solution B, 33 parts of solution C, 10 parts of light calcium carbonate, 20 parts of silicon oxide pigment, 15 parts of 30% zinc stearate dispersion, and (vinyl alcohol / acetic acid A coating solution was obtained by mixing and stirring 100 parts of a 15% aqueous solution of a graft copolymer of a vinyl) copolymer and a (acrylamide / acrylic acid / allylacetoacetate) copolymer. The obtained coating liquid is applied onto the undercoat layer to give a coating amount of 4 g / m after drying.
^A thermosensitive recording medium was obtained by applying and drying so that the amount became ² .

Example 2 In the formation of the recording layer of Example 1, a 15% aqueous solution of a graft copolymer of a (vinyl alcohol / vinyl acetate) copolymer and a (acrylamide / acrylic acid / allylacetoacetate) copolymer. Example 1 except that acetoacetyl-modified polyvinyl alcohol (Nippon Gosei Kagaku Co., Ltd., Gocefimer Z-200) was used instead of 100 parts.
A thermosensitive recording medium was obtained in the same manner as described above.

Example 3 In the formation of the recording layer of Example 1, a 15% aqueous solution of a graft copolymer of a (vinyl alcohol / vinyl acetate) copolymer and a (acrylamide / acrylic acid / allylacetoacetate) copolymer. Except that 100 parts of 80 parts of 15% aqueous solution of polyvinyl alcohol (Kuraray Co., Ltd., PVA-110) and 20 parts of 15% aqueous solution of carboxy-modified polyvinyl alcohol (Kuraray Co., Ltd., HL-75) were used. A thermal recording material was obtained in the same manner as in Example 1.

Example 4 In the formation of the recording layer of Example 1, a 15% aqueous solution of a graft copolymer of a (vinyl alcohol / vinyl acetate) copolymer and a (acrylamide / acrylic acid / allylacetoacetate) copolymer. Instead of using 100 parts, 80 parts of a 15% aqueous solution of polyvinyl alcohol (Kuraray Co., Ltd., PVA-110) and 20 parts of a 15% aqueous solution of sulfone modified polyvinyl alcohol (Nippon Gosei Chemical Co., Ltd., Gocelan L-3266) were used. In the same manner as in Example 1, a thermal recording material was obtained.

Example 5 In the preparation of the liquid C of Example 1, 1,1,3-tris (instead of 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane was used. 2-
Methyl-4-hydroxy-5-tert-butylphenyl)
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that butane was used.

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the liquid C was not used in forming the recording layer of Example 1.

Comparative Example 2 In the formation of the recording layer of Example 1, a 15% aqueous solution of a graft copolymer of a (vinyl alcohol / vinyl acetate) copolymer and a (acrylamide / acrylic acid / allylacetoacetate) copolymer. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 100 parts of a 15% aqueous solution of polyvinyl alcohol (PVA-110 manufactured by Kuraray Co., Ltd.) was used instead of 100 parts.

Comparative Example 2 In the preparation of the liquid C of Example 1, 10 parts of 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane was replaced with 4,4'-thiobis. (6-t-butyl-m-cresol) (Kawaguchi Kasei Co., Ltd.)
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 10 parts were used.

The seven kinds of thermal recording papers thus obtained were evaluated by the following methods, and the results are shown in [Table 1]. [Recording Density] A thermosensitive recording paper was used with a thermosensitive paper coloring tester (TM-PMD type, manufactured by Okura Electric Co., Ltd., applied voltage: 16 V, pulse cycle: 0.51 ms), and pulse width was 0.30 ms.
The recorded density (D ₁ ) was recorded with a Macbeth densitometer (R
It was measured with a D-914 type, manufactured by Macbeth.

[Temperature Resistance of Recorded Image] After printing the heat-sensitive recording paper in an atmosphere of 60 ° C. and 10% RH for 72 hours,
The recording density (D ₂ ) was measured again using a Macbeth densitometer. Further, the recording density residual rate (%) was determined by the following formula. Recording density residual rate = D ₂ / D ₁ × 100

[Fog color development] Heat-sensitive recording paper at 60 ° C for 10
After left in an atmosphere of% RH for 72 hours, the fog color density (F) of the white paper portion was measured using a Macbeth densitometer.

[0034]

[Table 1]

[0035]

As is clear from the results of Table 1, the thermosensitive recording medium of the present invention is excellent in the storage stability of recorded images, and further, the whiteness under the high humidity condition is extremely decreased due to the improvement of the storage stability. There were few excellent recording materials.

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[Procedure amendment]

[Submission date] April 2, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

The eight kinds of thermal recording papers thus obtained were evaluated by the following methods, and the results are shown in [Table 1]. [Recording Density] A thermosensitive recording paper was used with a thermosensitive paper coloring tester (TM-PMD type, manufactured by Okura Electric Co., Ltd., applied voltage: 16 V, pulse cycle: 0.51 ms), and pulse width was 0.30 ms.
The recorded density (D ₁ ) was recorded with a Macbeth densitometer (R
It was measured with a D-914 type, manufactured by Macbeth.

Claims (6)

[Claims] 1. A heat-sensitive recording material comprising a recording layer containing a colorless or light-colored basic dye and a coloring agent, wherein the recording layer further contains a compound represented by the following general formula [Chemical Formula 1] and an acid. A heat-sensitive recording material containing a water-soluble polymer compound containing the above-mentioned molecular species. [Chemical 1] [In the formula, R ₁ , R ₂ and R ₃ are each a hydrogen atom, C ₁
An alkyl group or a cycloalkyl group of C ₅ -C ₈ of -C _{8. R 4, R 5, R 6} , R 7, R 8 are each a hydrogen atom, an alkyl group of C ₁ -C _8. ] 2. The water-soluble polymer compound containing an acidic molecular species is a compound containing an acidic molecular species in its molecule.
The heat-sensitive recording material described. 3. A water-soluble polymer compound containing an acidic molecular species is a (vinyl alcohol / vinyl acetate) copolymer and (acrylamide / acrylic acid / allyl acetoacetate).
The heat-sensitive recording material according to claim 2, which is a graft copolymer with a copolymer. 4. The heat-sensitive recording material according to claim 2, wherein the water-soluble polymer compound containing an acidic molecular species is acetoacetyl group-modified polyvinyl alcohol. 5. The heat-sensitive recording material according to claim 2, wherein the water-soluble polymer compound containing an acidic molecular species is a carboxyl group-modified polyvinyl alcohol. 6. The heat-sensitive recording material according to claim 2, wherein the water-soluble polymer compound containing an acidic molecular species is a sulfo group-modified polyvinyl alcohol.