JPH06227132A - Thermal recording - Google Patents

Abstract

(57) [Summary] [Purpose] A recorded image can be stably maintained even under a high temperature condition without a decrease in whiteness of a white paper portion, and a recording layer having a low viscosity and a high concentration in a manufacturing process. Provided is a thermosensitive recording medium which can prepare a coating liquid and can obtain excellent coating suitability. [Structure] In a thermosensitive recording medium provided with a recording layer containing a basic dye and a coloring agent, a compound represented by the following general formula [Chemical Formula 1], polyvinyl alcohol and (acrylamide / acrylic acid) are further contained in the recording layer. A thermal recording material containing a graft polymer with an acrylonitrile) copolymer. [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. ]

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, which can maintain a recorded image in a stable manner without deteriorating the whiteness of a white paper portion even under a high temperature condition. The present invention relates to a heat-sensitive recording material which can prepare a low-viscosity and high-concentration coating liquid for a recording layer and can obtain excellent coating suitability.

[0002]

2. Description of the Related Art A thermosensitive recording medium is 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 by heat 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 the compound represented by the following general formula [Chemical Formula 1] is used as a storage stability improver and a specific polymer water-soluble compound is used in combination, the whiteness is lowered even when stored under high temperature conditions. It has been found that there is no new defect and that it exhibits an extremely excellent effect in improving the storage stability of a recorded image. However, most of water-soluble polymers containing acidic molecular species cause thickening of the coating solution when preparing the heat-sensitive layer coating solution, making it difficult to smear at high concentration and remarkably reducing operability. Met.

The present inventors have conducted further research to improve the above-mentioned drawbacks, and as a result, polyvinyl alcohol and (acrylamide / acrylic acid / acrylonitrile) have been obtained.
By using a graft polymer with a copolymer and a compound represented by [Chemical Formula 1] in combination, recording without causing defects such as decrease in whiteness even when stored under high temperature conditions It was found that an extremely excellent effect of improving the storage stability of an image was obtained, and that the heat-sensitive layer coating liquid prepared by this combination had an extremely low viscosity and was capable of being smeared at a high concentration, thus completing the present invention. Came to.

[0007]

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:
A heat-sensitive recording material comprising a compound represented by the following formula and a graft polymer of polyvinyl alcohol and a (acrylamide / acrylic acid / acrylonitrile) copolymer.

[0008]

[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. ]

[0010]

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 amount of the compound represented by the general formula [Chemical Formula 1] used is not particularly limited, but generally 1 to 300 parts by weight, preferably about 1 to 300 parts by weight, of the compound is used with respect to 100 parts by weight of the color developing agent. It is desirable to adjust in the range of about 1 to 100 parts by weight.

Further, in the heat-sensitive recording material of the present invention, polyvinyl alcohol and (acrylamide / acrylic acid.
The water-soluble polymer compound is generally used as a binder, but can also be used as a dispersion aid, although it is characterized by containing a graft polymer with an acrylonitrile) copolymer.

In the present invention, various known dyes can be used as the colorless or light-colored basic dye which constitutes 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-leukoauramine, N-2,4,5-trichlorophenylleucoaamine, 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,
A combination of two or more dyes is also possible.

Among these dyes, 3-dibutylamino-7- (o-chlorophenylamino) fluorane,
3-diethylamino-7- (o-chlorophenylamino) fluorane, 3- (N-ethyl-p-toluidino)
-6-Methyl-7-phenylaminofluorane is 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 compounds such as phenolic polymers, 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 ratio of the basic dye to the color developing agent to be used should be appropriately selected according to the type of the basic dye or the color developing agent to be used and is not particularly limited, but the basic dye 1 is generally 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.

The preparation of a coating liquid containing them 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. Further, if necessary, starches, 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. should be used together as a binder or dispersion aid. You can also
In the above coating liquid, these binder components are usually blended 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.

In addition, kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine anhydrous silica, for improving the adhesion of dust to the recording head,
Inorganic pigments such as activated clay, styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and organic pigments such as raw starch particles can also be added. In addition, stearic acid, which prevents sticking due to contact with the recording equipment and recording head,
It is also possible to add a dispersion liquid or emulsion of polyethylene, carnauba wax, paraffin wax, zinc stearate, calcium stearate, ester wax or the like.

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 solution 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 underside, and various known techniques in the field of manufacturing a thermosensitive recording medium such as adhesion processing or magnetic recording layer on the back surface can be added.

[0023]

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. In addition, unless otherwise indicated, the part and% in an example show a weight part and weight%, respectively.

Example 1 Formation of Undercoat Layer Baked 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 applied 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.

Liquid B Preparation 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 size 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 A liquid, 65 parts of B liquid, 33 parts of C liquid, 10 parts of light calcium carbonate, 20 parts of silicon oxide pigment, 15 parts of 30% zinc stearate dispersion liquid, and polyvinyl alcohol (acrylamide). A 15% aqueous solution of a graft polymer with an acrylic acid / acrylonitrile copolymer (Arakawa Chemical Co., Ltd .:
100 parts of polymalon 1560) were mixed and stirred, and water was added so that the concentration of the coating liquid was 30% to obtain a coating liquid. The viscosity of the obtained coating liquid is measured using a B-type viscometer (manufactured by Tokyo Keiki Co., Ltd., model 8M), and then coated and dried on the undercoat layer so that the coating amount after drying is 4 g / m ^2. Then, a thermosensitive recording medium was obtained.

Example 2 Instead of 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane in the preparation of the liquid C of Example 1, 1,1,3-tris ( 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 In the formation of the recording layer of Example 1, a 15% aqueous solution of a graft polymer of polyvinyl alcohol and a (acrylamide / acrylic acid / acrylonitrile) copolymer 100
In place of the parts, acetoacetyl-modified polyvinyl alcohol (Nippon Gosei Kagaku KK, Gocefimer Z-200)
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that was used.

Comparative Example 2 In the formation of the recording layer of Example 1, a 15% aqueous solution of a graft polymer of a polyvinyl alcohol and a (acrylamide / acrylic acid / acrylonitrile) copolymer 100
Instead of parts, polyvinyl alcohol (Kuraray Co., P
80 parts of a 15% aqueous solution of VA-110) and 1 of carboxy-modified polyvinyl alcohol (Kuraray Co., Ltd., HL-75)
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 20 parts of a 5% aqueous solution was used.

Comparative Example 3 In the formation of the recording layer of Example 1, a 15% aqueous solution of a graft polymer of polyvinyl alcohol and (acrylamide / acrylic acid / acrylonitrile) copolymer 100
Instead of parts, polyvinyl alcohol (Kuraray Co., P
80 parts of a 15% aqueous solution of VA-110), 20 parts of a 15% aqueous solution of a graft copolymer of a (vinyl alcohol / vinyl acetate) copolymer and a (acrylamide / acrylic acid / allyl acetoacetate) copolymer were used. A thermal recording material was obtained in the same manner as in Example 1 except for the above.

Comparative Example 4 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 5 In the formation of the recording layer of Example 1, a 15% aqueous solution of a graft polymer of polyvinyl alcohol and a (acrylamide / acrylic acid / acrylonitrile) copolymer 100
Instead of parts, polyvinyl alcohol (Kuraray Co., P
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 100 parts of a 15% aqueous solution of VA-110) was used.

Comparative Example 6 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 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 as a thermosensitive paper color tester (manufactured by Okura Electric Co., Ltd., TM-PMD type, applied voltage: 16).
V, pulse cycle: 0.51 ms) was used, recording was performed with a pulse width of 0.30 ms, and the recording density (D ₁ ) was measured by a Macbeth densitometer (RD-914 type, manufactured by Macbeth Co.).

[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

[Development of Fog Color] Heat sensitive recording paper at 60 ° C. and 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.

[0038]

[Table 1]

[0039]

As is clear from the results of Table 1, the thermosensitive recording medium of the present invention has excellent storage stability of recorded images, and there is very little reduction in whiteness under high humidity conditions with the improvement of storage stability. It was an excellent recording material. Moreover, the coating liquid for the heat-sensitive recording layer was excellent in smearing suitability at a high concentration in the manufacturing process, and the operability could be remarkably improved.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaharu Nojima 4-3-1, Jokoji Temple, Amagasaki City, Hyogo Prefecture Kanzaki Paper Manufacturing Co., Ltd. Kanzaki Mill

Claims (1)

[Claims] 1. A thermosensitive recording medium provided with a recording layer containing a colorless or light basic dye and a coloring agent, wherein the recording layer further contains a compound represented by the following general formula [Chemical Formula 1] and polyvinyl. Alcohol and (acrylamide / acrylic acid /
A heat-sensitive recording material comprising a graft polymer with an acrylonitrile) copolymer. [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. ]