JPH07149046A - Thermal recording body - Google Patents

Abstract

PURPOSE:To enhance light resistance of a printing part and to control discoloration of a texture part by incorporating a benzotriazole-based ultraviolet absorbent shown in a specified formula into a thermal recording layer or a protective layer in a thermal recording body in which the thermal recording layer and the protective layer if necessary are provided on a supporting body. CONSTITUTION:A thermal recording body is constituted by successively providing a thermal recording layer containing both a colorless or light-colored basic dye and a colorant and a protective layer on a supporting body. A recording image is obtained by utilizing the color reaction of the basic dye and the colorant and allowing both coloring substances to come into contact through heat. In the case, a compound shown in a general formula stated elsewhere, namely 2,2-methylenebis(4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazole-2-yl )phenol) is added into the thermal recording layer or the protective layer as an ultraviolet absorbent. Further hydroxydiphenylsulfone derivative or 4,4'-bis(p- toluenesulfonyl aminocarbonylamino)diphenyl-methane is used as the colorant.

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 is excellent in light stability of a recorded image and suppression of discoloration of a background portion.

[0002]

2. Description of the Related Art A heat-sensitive recording material which utilizes a color reaction between a colorless or light-colored basic dye and an organic or inorganic coloring agent to bring both color-forming substances into contact with each other by heat to obtain a recorded image is well known. Are known. Such a thermal recording material is relatively inexpensive,
Since the recording device is compact and easy to maintain, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields. One of the fields of application is the POS (point of sales) of retail stores.
Thermal recording paper for the system can be mentioned. Along with the expansion of the system, the uses attached to products are increasing. However, depending on the product, the attached heat-sensitive recording paper is often exposed to room light or sunlight, which has a drawback that the recorded image is easily discolored.

Conventionally, in order to improve the light resistance of a recorded image, a method of adding an antioxidant or an ultraviolet absorber in the heat-sensitive recording layer has been disclosed in JP-A-49-54040 and JP-A-50-.
Although it is described in 104650 public information, JP-A-60-48395, etc., there is a problem in background discoloration and stability of recorded images with time.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording material excellent in light resistance, which has very little discoloration of the background portion and fading of a recorded image when exposed to a fluorescent lamp or sunlight for a long time. It is provided.

[0005]

Means for Solving the Problems The present inventors have
In a thermal recording medium in which a support is provided with a thermosensitive recording layer containing a colorless or light-colored basic dye and a coloring agent, and a protective layer if necessary, in the thermal recording layer or the protective layer, the following general formula ( By including the benzotriazole-based ultraviolet absorber represented by 1), it was found that it is possible to improve the light resistance of the printed part and suppress discoloration of the background part, and completed the present invention.

[Chemical 2]

[0006]

In the present invention, the above-mentioned general formula (1) is used as an ultraviolet absorber in a heat-sensitive recording layer containing a colorless or light-colored basic dye and a coloring agent, or in a protective layer provided on the heat-sensitive recording layer if necessary. ), That is, 2,2-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6-
(2H-benzotriazol-2-yl) phenol]
The addition of the compound improves the discoloration of the background and the light fastness of the recorded image. Especially, a hydroxydiphenyl sulfone derivative or 4,4'-bis (p
An excellent effect is obtained for -toluenesulfonylaminocarbonylamino) diphenylmethane. The specific ultraviolet absorber is contained in the heat-sensitive recording layer or the protective layer, but is preferably contained in the recording layer from the viewpoint of effect.

Specific examples of the hydroxydiphenyl sulfone derivative used as a color former include 2,4 '
-Dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-
Isopropyloxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 3,4-dihydroxydiphenyl sulfone, 3,4-dihydroxy-
4'-methyldiphenyl sulfone and the like are exemplified. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

The amount of the ultraviolet absorber represented by the general formula (1) and the hydroxydiphenyl sulfone derivative used is not particularly limited, but generally, a specific ultraviolet absorber is added to 100 parts by weight of the basic dye. 10 to 500 parts by weight, preferably 20 to 200 parts by weight of the agent
It is desirable that the amount of the hydroxydiphenyl sulfone derivative is 50 to 500 parts by weight, preferably 100 to 300 parts by weight.

As long as the effects of the present invention are not impaired, various other known color developing agents can be used.
For example, activated clay, attapulgite, colloidal silica, inorganic acidic substances such as aluminum silicate, 4-tert-butylphenol, 4-hydroxydiphenoxide, α-
Naphthol, β-naphthol, 4-hydroxyacetophenol, 4-tert-octylcatechol, 2,2′-
Dihydroxydiphenol, 4,4'-isopropylidene bis (2-tert-butylphenol), 4,4'-se
c-butylidene diphenol, 4-phenylphenol, 4,4'-isopropylidenediphenol, 4,
4'-dihydroxydiphenyl-2,2-butane, 4,
4'-dihydroxydiphenylmethane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane,
2,2'-methylenebis (4-chlorophenol), hydroquinone, 4,4'-cyclohexylidene diphenol, 4,4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone , 2,4,4'-trihydroxybenzophenone,
2,2 ', 4,4'-tetrahydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, 4
-Hydroxybenzoic acid-sec-butyl, 4-hydroxybenzoic acid pentyl, 4-hydroxybenzoic acid phenyl,
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, terephthalaldehyde acid, 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, 3-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3- ( α-methylbenzyl) salicylic acid, 3-chloro-5- (α-methylbenzyl) salicylic acid, 3,5
-Di-tert-butylsalicylic acid, 3-phenyl-5-
Aromatic carboxylic acids such as (α, α-dimethylbenzyl) salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, bis (3-tert- Butyl-4-hydroxy-6-methylphenyl) sulfide, bis (2-methyl-4-hydroxy-6-tert-butylphenyl) sulfide, bis (4-hydroxy-3-methylphenyl)
Sulfide derivatives such as sulfide, further, these phenolic compounds, aromatic carboxylic acids and the like, for example, zinc,
Salts with polyvalent metals such as magnesium, aluminum, calcium, titanium, manganese, tin and nickel, and further zinc thiocyanate antipyrine complex and 4,4 ^,
Examples thereof include organic acidic substances such as -bis (p-tolylsulfonylurea) diphenylmethane. Among these, the hydroxydiphenyl sulfone derivative is preferable because it is able to obtain an extremely excellent effect in color development and background fog.

The basic dye used in the present invention includes:
Various known colorless or pale basic dyes may be mentioned, and specifically, for example, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p-dimethylamino). Phenyl) 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-dimethylamino Triallylmethane dyes such as phthalide and 3-p-dimethylaminophenyl-3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydryl Diphenylmethane dyes such as benzyl ether, N-halophenyl-leuco auramine, N-2,4,5-trichlorophenyl leuco auramine, thiazine dyes such as benzoyl leuco methylene blue and p-nitrobenzoyl leuco methylene blue, 3-methyl- Spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran,
3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho-
Spiro dyes such as (6′-methoxybenzo) spiropyran and 3-propyl-spiro-dibenzopyran, lactam dyes such as rhodamine-B anilinolactam, rhodamine (p-nitroanilino) lactam and 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-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, -Dibutylamino-7- (o-chlorophenylamino) fluorane, 3-pyrrolidino-6-methyl-7
-P-Butylphenylaminofluorane, 3-diethylamino-7- (o-fluorophenylamino) fluorane, 3-dibutylamino-7- (o-fluorophenylamino) fluorane, 3-dibutylamino-6-methyl-7 -Phenylaminofluorane, 3- (N-methyl-
Nn-amyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-Nn-amyl)
Amino-6-methyl-7-phenylaminofluorane,
3- (N-ethyl-N-iso-amyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-methyl-Nn-hexyl) amino-6-methyl-7-phenylaminofluor Oran, 3- (N-ethyl-N-n-hexyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-N-β-ethylhexyl)
Amino-6-methyl-7-phenylaminofluorane,
Examples thereof include fluorane dyes such as 3- [N- (3-ethoxypropyl) -N-ethyl] amino-6-methyl-7-anilinofluorane.

Two or more kinds of these basic dyes can be used in combination, if necessary. The use ratio of the basic dye and the color developing agent is appropriately adjusted depending on the types of the basic dye and the color developing agent to be used.
50 to 500 parts by weight, preferably 10 parts by weight, relative to 0 parts by weight
About 0 to 300 parts by weight of a coloring agent is used. The coating liquid for the heat-sensitive recording layer containing these substances is generally prepared by dispersing it with a stirring medium such as a ball mill or a sand mill using water as a dispersion medium.

The solid content of the coating liquid for the heat-sensitive recording layer is 10 to 10.
About 40% by weight, and more preferably about 15 to 30% by weight of binders are blended. Specific examples of the binders include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose,
Gelatin, casein, gum arabic, polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene -Acrylic acid copolymer salts, styrene-acrylic acid copolymer salts, styrene-butadiene copolymer emulsions, urea resins, melamine resins, amide resins and the like.

Further, a preservative improving agent can be used in combination for the purpose of further preserving the preservability of the recorded image according to the purpose unless the effects of the present invention are impaired. Specific examples of such a shelf life improver include 1,4-diglycidyloxybenzene, 4,4'-diglycidyloxydiphenyl sulfone, diglycidyl terephthalate, 4-benzyloxy-
4 '-(2-methyl-2,3-epoxypropyloxy) diphenyl sulfone, 2,2'-dithiodibenzoic acid, 2,2'-methylenebis (4-methyl-6-tert-
Butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-ethylidenebis (4,6-di-tert-butylphenol),
4,4'-thiobis (3-methyl-6-tert-butylphenol), 4,4'-thiobis (2-methyl-6-te
rt-butylphenol), 4,4'-butylidenebis (6-tert-butyl-m-cresol), 2,5-di (tert-butyl) hydroquinone, 2,5-di (tert-
Amyl) hydroquinone, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl)
Butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,4'-
Thiobis (3-methylphenol), 4,4'-dihydroxy-3,3 ', 5,5'-tetrabromodiphenyl sulfone, 4,4'-dihydroxy-3,3', 5
5'-tetramethyldiphenyl sulfone, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis Hindered phenol compounds such as (4-hydroxy3.5-dimethylphenyl) propane, 1- [α-methyl-α- (4′-hydroxyphenyl) ethyl] -4- [α ′, α′-bis (4 "-Hydroxyphenyl) ethyl] benzene, N,
N'-di-2-naphthyl-p-phenylenediamine,
Examples thereof include 2,2-methylenebis (4,6-di-tert-butylphenyl) phosphoric acid soda, a copolymer of glycidyl methacrylate and styrene, and tris (2,3-epoxypropyl) isocyanurate.

Various kinds of auxiliaries can be added to the coating liquid, if necessary, such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, and the like.
In addition to the dispersant such as lauryl alcohol sulfate / sodium salt and fatty acid metal salt, the above-mentioned specific ultraviolet absorber, an ultraviolet absorber such as bezophenone series, an antifoaming agent, a fluorescent dye, a coloring dye, etc. are appropriately added. . Further, if necessary, waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, kaolin, clay, talc, calcium carbonate, calcined kaolin, titanium oxide, diatomaceous earth, and fine anhydrous silica. It is also possible to add an inorganic pigment such as activated clay or the like, and a sensitizer may be used in combination depending on the purpose.

Specific examples of the sensitizer include stearic acid amide, stearic acid methylenebisamide, oleic acid amide, palmitic acid amide, coconut fatty acid amide and other fatty acid amides, 2,2'-methylenebis (4-methyl-amide). 6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-3-methylphenol), 2,2'-methylenebis (4-ethyl-6-tert)
-Butylphenol), 2,4-di-tert-butyl-3
-Hindered phenols such as methylphenol, 2-
Ultraviolet absorbers such as (2'-hydroxy-5'-methylphenyl) benzotriazole and 2-hydroxy-4-benzyloxybenzophenone, p-benzylbiphenyl, 1,2-di (3-methylphenoxy) ethane, 1,
2-diphenoxyethane, 1- (2-methylphenoxy) -2- (4-methoxyphenoxy) ethane, naphthylbenzyl ether, benzyl-4-methylthiophenyl ether, oxalic acid dibenzyl ester, oxalic acid-
Di-p-methyl-benzyl ester, oxalic acid-di-p
-Chloro-benzyl ester, terephthalic acid dimethyl ester, terephthalic acid dibutyl ester, terephthalic acid dibenzyl ester, isophthalic acid dibutyl ester,
Examples thereof include 1-hydroxynaphthoic acid phenyl ester, benzyl-4-methylthiophenyl ether, and various known heat-fusible substances.

In the heat-sensitive recording material of the present invention, among these sensitizers, 1,2-di (3-methylphenoxy) ethane, 1,2-diphenoxyethane and 1- (2
-Methylphenoxy) -2- (4-methoxyphenoxy) ethane is preferably used. Further, it is generally desirable to adjust the amount of the sensitizer to be used in the range of about 400 parts by weight or less based on 100 parts by weight of the color developing agent.

The method of forming the recording layer is not particularly limited, and the heat-sensitive recording layer forming coating liquid is applied to the support by a suitable coating method such as air knife coating, varibar blade coating, pure blade coating, short dwell coating. It is formed by a method such as drying. The coating amount of the coating liquid is not particularly limited, 2~12g / m ² is usually dry weight, preferably 3 to 10 g / m ²
Adjusted in a range of degrees.

In the heat-sensitive recording material of the present invention, by providing a protective layer on the heat-sensitive recording layer, it is possible to further suppress discoloration of the background portion and improve the storability of recorded prints. When the above-mentioned specific ultraviolet absorber is added to the protective layer, the amount is preferably 0.5 to 50% by weight based on the total solid amount of the protective layer. The protective layer is generally formed by using a water-soluble or water-dispersible polymer as a main component, and specific examples of such a polymer include various binders as described above. Among these, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol are particularly preferably used because they have excellent effects as a protective layer.

In order to further improve the water resistance of the protective layer, glyoxal, formalin, glycine, glycidyl ester, glycidyl ether, dimethylol urea,
Ketene dimer, dialdehyde starch, melamine resin, polyamide resin, polyamide-epichlorohydrin resin,
A curing agent such as a ketone-aldehyde resin, borax, boric acid, ammonium zirconium carbonate, or an epoxy compound may be used in combination.

Further, in the protective layer, in order to further improve printability and sticking, for example, calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, Inorganic pigments such as kaolin, clay, calcined kaolin, and colloidal silica, and organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and raw starch particles can be blended as necessary. The amount of such a pigment blended is 5 to 500 with respect to 100 parts by weight of the binders.
It is desirable to adjust within the range of about parts by weight.

In the coating liquid for forming the protective layer, if necessary, a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax and a surfactant such as sodium dioctylsulfosuccinate ( Various auxiliaries such as a dispersant, a lubricant) and an antifoaming agent can be added as appropriate.

The coating solution for protective layer thus prepared is coated on the thermosensitive recording layer by a suitable coating device, but when the coating amount exceeds 20 g / m ² on a dry weight basis, the recording sensitivity of the thermosensitive recording material decreases. Generally, 0.1-20 g /
It is desirable to adjust in the range of about m ² , preferably 0.5 to 10 g / m ² .

If necessary, a protective layer may be provided on the back side of the thermosensitive recording medium to further improve the storability. Furthermore, providing an undercoat layer on the support,
If necessary, various publicly known techniques in the field of heat-sensitive recording material production can be added, such as processing the back surface of the recording material with an adhesive to process it into an adhesive label. As a support,
Paper, plastic film, synthetic paper, etc. are used,
Paper is most preferably used in terms of price, coating suitability and the like.

[Examples] 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, "part" and "%" in an example show "weight part" and "weight%", respectively, unless there is particular notice.

Example 1 Formation of Undercoat Layer Calcined clay [trade name: Ansilex, manufactured by EMC] 1
00 parts, styrene-butadiene copolymer latex (solid content: 50%) 15 parts, polyvinyl alcohol 10%
A composition comprising 30 parts of an aqueous solution and 200 parts of water was mixed and stirred to prepare a coating liquid for undercoat layer. The obtained coating solution was applied to a high-quality paper of 70 g / m ² and the coating amount after drying was 7 g
The undercoat layer was formed by applying and drying so that the undercoat layer had a thickness of / m ² .

Preparation of Solution A 10 parts of 3-dibutylamino-6-methyl-7-phenylaminofluorane, 20 parts of 1,2-bis (3-methylphenoxy) ethane, 5% aqueous solution of methylcellulose 10
Parts and 50 parts of water were pulverized with a sand mill until the average particle diameter became 0.8 μm.

Preparation of Solution B 30 parts of 4-hydroxy-4′-isopropyloxydiphenylsulfone, 5% aqueous solution of methylcellulose 10
Parts and 50 parts of water were pulverized with a sand mill until the average particle size was 1.2 μm.

Preparation of Solution C 2,2-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazole-2
-Yl) phenol] 10 parts, 5% of methyl cellulose
A composition consisting of 5 parts of an aqueous solution and 15 parts of water was pulverized with a sand mill until the average particle size became 1.5 μm.

Formation of Thermal Recording Layer 90 parts of solution A, 90 parts of solution B, 30 parts of solution C, 160 parts of 10% aqueous solution of polyvinyl alcohol, calcium carbonate 10
Parts, 20 parts of fine particle silicon oxide, 30% of zinc stearate
10 parts of the dispersion liquid and 100 parts of water were mixed and stirred to obtain a coating liquid for the heat-sensitive recording layer. After applying the obtained coating liquid to the above undercoat layer so that the dry weight becomes 3 g / m ^2, and drying,
Supercalendering was performed to obtain a heat sensitive recording material.

Example 2 Example 1 was repeated except that 2,4'-dihydroxydiphenyl sulfone was used in place of 4-hydroxy-4'-isopropyloxydiphenyl sulfone in the preparation of solution B.
A thermosensitive recording medium was obtained in the same manner as described above.

Example 3 In preparation of solution A, 3-dibutylamino-6-methyl-
Instead of 7-phenylaminofluorane, 3- (N-
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane was used.

Example 4 In the preparation of solution B, 4,4'-bis (p-toluenesulfonylaminocarbonylamino) was used instead of 4-hydroxy-4'-isopropyloxydiphenylsulfone.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that diphenylmethane was used.

Example 5 Example 1 was repeated except that 4,4′-isopropylidenediphenol was used in place of 4-hydroxy-4′-isopropyloxydiphenylsulfone in the preparation of solution B. A thermal recording material was obtained in the same manner. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 90 parts of the liquid C was added to the undercoat layer.

Example 6 Formation of Protective Layer 80 parts of a 10% aqueous solution of acetoacetylated polyvinyl alcohol, partially saponified previnyl alcohol (trade name: PV
A-217, manufactured by Kuraray Co., Ltd.), 20 parts of 10% aqueous solution, 20 parts of kaolin, 2 parts of 10% aqueous solution of glyoxal, and 50 parts of water were mixed and stirred to obtain a coating solution on the thermosensitive recording layer of Example 1 above. A thermal recording material having a protective layer was obtained by coating and drying so that the coating amount after drying was 1 g / m ² .

Example 7 A thermosensitive recording medium was obtained in the same manner as in Example 6 except that 50 parts of C liquid was added to the protective layer coating liquid.

Comparative Example 1 In the formation of the recording layer of Example 1, the heat-sensitive recording layer was coated with C.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the liquid was not used.

Comparative Example 2 In the preparation of solution C, 2,2-methylenebis [4- (1,
1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol],
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 2- (2'-hydroxyphenyl) benzotriazole was used.

The following 9 evaluation tests were carried out on the 9 kinds of thermal recording materials thus obtained, and the results are shown in Table 1. [Color density] Thermal recording material evaluation machine (Product name: TH-PM
D, manufactured by Okura Electric Co., Ltd.), applied energy −0.2 mJ
The recording density was measured with a Macbeth densitometer (RD-914 type, manufactured by Macbeth Co.) visual mode.

[Light resistance] Background part A weather meter (trade name: SUNSHIN) in which a heat-sensitive recording material is set under conditions of light source xenon, 63 ° C. and 50% RH.
EXENON LONG LIFE WEATHER
After leaving for 24 hours in METER, manufactured by Suga Test Instruments Co., Ltd., R is measured with a spectral reflectance meter (ELREPHO2000).
₄₅₇ YELLOWNESS and whiteness were measured. Recorded image After recording the heat-sensitive recording paper for 24 hours under the same conditions as the above weather meter, the density of the recorded image was measured with a Macbeth reflection densitometer.

[0040]

[Table 1]

[0041]

As is clear from the results shown in Table 1, the thermosensitive recording materials obtained in the respective examples of the present invention are heat-sensitive recording materials having excellent light resistance, that is, there is little discoloration of the background due to light irradiation and recording. The heat-sensitive recording material was excellent in light stability of the image.

Claims (2)

[Claims] 1. A thermosensitive recording medium comprising a support, a thermosensitive recording layer containing a colorless or light-colored basic dye and a coloring agent, and, if necessary, a protective layer, in the thermosensitive recording layer or the protective layer. A heat-sensitive recording material comprising a compound represented by the following general formula (1) as an ultraviolet absorber. [Chemical 1] 2. The heat-sensitive recording material according to claim 1, wherein the color developing agent is a hydroxydiphenyl sulfone derivative or 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane.