JPH11180041A - Thermal recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording body with excellent light resistance of recorded parts and unrecorded parts without spoiling basic characteristics of the heat-sensitive recording body and a thermal recording body with excellent color developing properties, plasticizer resistance and oil resistance. SOLUTION: In a thermal recording body wherein a heat-sensitive recording layer contg. an electron-donating compd. and an electron-accepting compd. and if necessary, a protective layer are successively provided on a substrate 2,2'-methylene-bis[4-(2-hydroxyethyl)-6-(2H-benzotriazole-2-yl)phenol] is corporated in at least one of the heat-sensitive recording layer and the protective layer. This electron-receiving compd. is pref. 1,1-bis-(4-hydroxyphenyl)-1-phenylethane.

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 utilizing a color-forming reaction between an electron-donating compound and an electron-accepting compound. The present invention relates to a thermosensitive recording medium having improved heat resistance.

[0002]

2. Description of the Related Art A thermosensitive recording medium in which a recording image is obtained by contacting a plurality of coloring substances with heat is well known.
Such a thermosensitive recording medium is relatively inexpensive, and the recording apparatus is compact and easy to maintain. Therefore, it is used not only as a recording medium for facsimile machines and various computers but also in a wide range of fields.

[0003] As one of the fields of use, for example, POS
(Point of sales) Thermal recording labels for systems can be cited, but with the expansion of the system, apart from food labels that have completed their mission in a short time as before, they have been attached to products for a long time. The use as tag paper to be used or handy terminal paper for collection and delivery, which is often handled outdoors, is increasing. However, in such applications, the image is often exposed to room light or sunlight for a long period of time, and as a result, the recorded image on the heat-sensitive recording medium discolors or the background portion turns yellow, and as a result, the product image becomes poor. Will also be significantly impaired. For this reason, there is a strong demand for a heat-sensitive recording material which is excellent in light fastness with little discoloration of a recorded image or yellowing of a background portion even when exposed to room light or sunlight for a long time.
Further, the thermal recording medium for tag paper or handy terminal paper as described above may adhere to a chemical such as a plasticizer, oil or solvent, or may be exposed to a high temperature environment. Sex is also demanded.

Conventionally, a method of adding a benzotriazole compound to a heat-sensitive recording layer for the purpose of improving the light fastness of a heat-sensitive recording material has been disclosed in JP-B-53-23205 and JP-A-55-205.
55891, JP-A-63-307981, JP-A-3
No. 23986 and Japanese Patent Application Laid-Open No. 5-8545. Further, in order to improve the chemical resistance of the heat-sensitive recording medium, a method of adding a benzotriazole compound to the heat-sensitive recording layer is disclosed in JP-A-58-87093 and JP-A-63-1.
No. 5783 has been proposed. Further, in order to improve the chemical resistance of the heat-sensitive recording medium, a method of providing a protective layer on the heat-sensitive recording layer is disclosed in JP-A-54-128347 and JP-A-5-128347.
No. 9-9909, Japanese Utility Model Publication No. 62-21616 and many others have been proposed. Further, for the purpose of improving the light fastness of the heat-sensitive recording medium, a method of adding a finely pulverized benzotriazole compound to a protective layer formed on the recording layer has been disclosed in JP-A-60-107388 and JP-A-60-108. -11487
And Japanese Patent Application Laid-Open No. 61-193883.

However, the conventionally proposed 2-
When a benzotriazole compound such as (2'-hydroxy-5'-methylphenyl) benzotriazole is contained in the heat-sensitive recording layer to obtain sufficient light resistance, the absorption efficiency of ultraviolet rays, in other words, the shielding of ultraviolet rays. In terms of efficiency, it is necessary to add these compounds in a relatively large amount, which impairs the basic characteristics of the heat-sensitive recording medium, such as a decrease in color developability and a background fog when placed in a high-temperature environment. There is a disadvantage that. On the other hand, a method in which a benzotriazole compound is added to a protective layer formed on a heat-sensitive recording layer can also be achieved by adding a conventionally proposed compound such as 2- (2'-hydroxy-5'-methylphenyl) benzotriazole. When used, such a compound has a relatively low melting point and melts during recording to cause sticking between the thermal head and the protective layer, so that a uniform recorded image cannot be obtained. Compound elutes to impair the original barrier function as a protective layer, and as a result, the chemical resistance of the recorded image is reduced.

[0006]

SUMMARY OF THE INVENTION In view of such circumstances, it is an object of the present invention to provide a heat-sensitive recording medium in which the light resistance of a recorded portion and an unrecorded portion is improved without impairing the basic characteristics of the above-described heat-sensitive recording material. And to provide a heat-sensitive recording material having excellent light resistance in a recorded portion and an unrecorded portion, and excellent in chemical resistance such as plasticizer resistance, oil resistance, and solvent resistance and recording running property. is there.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a heat-sensitive recording medium comprising a support, on which a heat-sensitive recording layer containing an electron-donating compound and an electron-accepting compound and, if necessary, a protective layer, are provided. A thermosensitive recording medium characterized in that at least one of the layer and the protective layer contains 2,2'-methylenebis [4- (2-hydroxyethyl) -6- (2H-benzotriazol-2-yl) phenol]. According to.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a heat-sensitive recording layer comprising an electron-donating compound and an electron-accepting compound on a support and, if necessary, a protective layer. At least one of the protective layers is 2,
2'-methylenebis [4- (2-hydroxyethyl)-
6- (2H-benzotriazol-2-yl) phenol], the light resistance of a recorded portion and an unrecorded portion is remarkably improved as compared with a conventionally proposed benzotriazole compound. . Further, since such a specific benzotriazole compound hardly dissolves in solvents such as a plasticizer, an oil and an organic solvent, when used for a protective layer, even if the surface of the protective layer comes into contact with these solvents, the ultraviolet absorbent may be used. The barrier function does not decrease due to the elution, and the chemical resistance is improved. In addition, there is no sticking or head residue due to melting at the time of recording with the thermal head, and an excellent effect of improving the recording running property can be obtained.

In the present invention, 2,2'-methylenebis [4
-(2-Hydroxyethyl) -6- (2H-benzotriazol-2-yl) phenol] can provide the desired effect if it is contained in either the heat-sensitive recording layer or the protective layer. Of course, it can be contained in both the recording layer and the protective layer, or it can be contained only in the recording layer of the thermosensitive recording medium having the protective layer. In terms of the efficiency of shielding ultraviolet rays, it is better to mix the protective layer in the protective layer than in the recording layer.

2,2'-methylenebis [4- (2-hydroxyethyl) -6- (2H-benzotriazole-2
-Yl) phenol] is preferably pulverized and added to the heat-sensitive recording layer or the protective layer. The method of pulverization is generally to use water as a dispersing medium and additives such as a dispersant and an antifoaming agent. Is added as necessary, and the mixture is dispersed by a stirring / pulverizer such as a ball mill, an attritor, and a sand mill. Finely pulverized 2,2'-methylenebis [4
-(2-hydroxyethyl) -6- (2H-benzotriazol-2-yl) phenol] has an average particle diameter of 2.
0 μm or less is preferable, and especially when it is 1.0 μm or less, not only does the absorption efficiency of ultraviolet rays remarkably improve, but when the particles having this particle size are added to the protective layer, the recorded image is hardly concealed. There is an effect that a clear recorded image is obtained, and in addition, since the film-forming property of the protective layer is improved, a more excellent improvement in chemical resistance is obtained.

The thermal recording system utilizing the color development reaction between an electron donating compound and an electron accepting compound to which the present invention is applied includes, for example, a combination of a leuco dye and a color former, a combination of a diazonium salt and a coupler, Examples include a combination of a chelating compound with a transition element such as iron, and a combination of an aromatic isocyanate compound and an imino compound.However, the combination of a leuco dye and a color former is excellent in terms of color density and recording sensitivity. Hereinafter, a thermosensitive recording medium utilizing a color development reaction between a leuco dye and a color former will be described in detail.

As the leuco dye, various known leuco dyes can be used. Specifically, for example, 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluoran, Diethylamino-7- (m-trifluoromethylanilino) fluoran, 3- (N-ethyl-N-isoamylamino) -7- (o-chloroanilino) fluoran, 3-di-n-pentylamino-6-methyl- 7-anilinofluoran, 3- [N- (3-ethoxypropyl) -N-ethylamino] -6-methyl-7
-Anilinofluoran, 3- [N- (3-ethoxypropyl) -N-methylamino] -6-methyl-7-anilinofluoran, 3- (N-ethyl-p-toluidino)-
6-methyl-7-anilinofluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluoran, 3-diethylamino-6-methyl-
7-anilinofluoran, 3-di-n-butylamino-
6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (2,4-xylidino) fluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-di-n-butyl Amino-7- (o
-Chloroanilino) fluoran, 3-di-n-butylamino-7- (o-fluoroanilino) fluoran, 3-
(N-ethyl-N-cyclopentylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-6
-Chloro-7-anilinofluoran, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, di -Ethylamino-6-methyl-7
-(2,6-xyridino) fluoran, 3- (N-methyl-NN-propylamino) -6-methyl-7-anilinofluoran, 2,2-bis {4- [6 '-(N -Cyclohexyl-N-methylamino) -3'-methylspiro (phthalide-3,9'-xanthen) -2'-ylamino] phenyl} propane, 2,2-bis {4- [6 '
-(N-ethyl-p-toluidino) -3'-methylspiro (phthalide-3,9'-xanthen) -2'-ylamino] phenyl} propane, 3-diethylamino-6
Methyl-7-chlorofluoran, 3-diethylamino-
7-chlorofluorane, 3-diethylamino-6,7-
Dimethylfluoran, 3,3'-bis (1-ethyl-2
-Methylindol-3-yl) phthalide, 3,3-bis (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylamino Phenyl) -6
Dimethylaminophthalide, 3,7-bis (dimethylamino) -10-benzoylphenothiazine, 3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] −4,5,6
7-tetrachlorophthalide, 3,3'-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide, 3-di-n-pentylamino-6,8,8-trimethyl-9-ethyl-8 , 9-Dihydro- (3,2, e)
Pyridofluoran, 3-di-n-butylamino-6,
8,8-trimethyl-9-ethyl-8,9-dihydro-
(3,2, e) pyridfluoran, 3- [1,1-bis (4-diethylaminophenyl) ethylene-2-yl]
-6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) amino-5,7-dimethylfluoran,
3- (4-di-n-butylaminophenyl) amino-6
-Methyl-7-chlorofluoran, 3- (1-methyl-
2-phenylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- (1-methyl-2-phenylindol-3-
Yl) -3- (2-methyl-4-diethylaminophenyl) -4,7-diazaphthalide and the like. Of course, the present invention is not limited to these, and two or more of them can be used in combination as needed. The amount of the leuco dye used is not particularly limited, but may be 5 to the heat-sensitive recording layer.
About 40% by weight is preferable.

Various known colorants can be used in combination with the above-mentioned leuco dye. For example, 4,4'-
Isopropylidene diphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4
-Hydroxyphenyl) -4-methylpentane, 1,1
-Bis (4-hydroxyphenyl) -1-phenylethane, bis (4-hydroxyphenylthioethoxy) methane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 4,4′-dihydroxydiphenyl sulfone,
2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone,
4-hydroxybenzoic acid benzyl ester, bis (4-
(Hydroxyphenyl) butyl acetate, bis (4-hydroxyphenylthioethyl) ether, N- (p-tolylsulfonyl) -N'-phenylurea, 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane, -Zinc salt of [2- (p-methoxyphenoxy) ethoxy] salicylic acid, 4- [3- (p-
Tolylsulfonyl) propyloxy] salicylic acid zinc salt, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid zinc salt, 4-octyloxyacetylaminosalicylic acid zinc salt, zinc thiocyanate antipyrine complex, etc. Is exemplified. Of course, the present invention is not limited to these, and two or more of them can be used in combination as needed.

Among these colorants, a diphenylsulfone derivative represented by the following general formula (1) is preferably used because a heat-sensitive recording material having excellent preservability of a recorded image can be obtained.

Embedded image [Wherein, R ₁ and R ₂ each represent a C ₁ -C ₄ alkyl group, a C ₂ -C ₄ alkenyl group, a C ₁ -C ₄ alkoxyl group, or a halogen atom. m represents an integer of 0 to 2, n represents an integer of 1 to 3, and p and q each represent an integer of 0 to 2. ]

Among the diphenylsulfone derivatives represented by the above general formula, 4-hydroxy-4'-isopropoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone or 2,4'-dihydroxydiphenylsulfone The use of is particularly preferable because a heat-sensitive recording medium having particularly excellent preservability of a recorded image can be obtained.

Further, 1,1'-bis (4-
When (hydroxyphenyl) -1-phenylethane is used, a heat-sensitive recording medium having particularly excellent heat resistance can be obtained, so that it is preferably used.

The ratio of the leuco dye to the colorant is appropriately selected according to the type of the leuco dye and the colorant used, and is not particularly limited. The colorant is used in an amount of 50 to 500 parts by weight, preferably about 100 to 300 parts by weight.
When a specific benzotriazole compound is contained in such a thermosensitive recording layer, its use ratio is not particularly limited, but is generally 10 to 500 parts by weight, preferably 20 to 200 parts by weight, per 100 parts by weight of the leuco dye. Parts. Further, the heat-sensitive recording layer may contain a sensitizer for increasing the recording sensitivity and a storability improving agent for improving the aging stability of the recorded image.

Specific examples of the sensitizer include, for example, stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, ethylenebisstearic acid, methylenebisstearic acid amide, N-methylolstearic acid amide, dibenzyl terephthalate, -Benzylbenzyl benzoate, 2-naphthylbenzyl ether, m-
Terphenyl, oxalic acid dibenzyl ester, oxalic acid-di-p-methylbenzyl ester, oxalic acid-di-p
-Chlorobenzyl ester, p-benzylbiphenyl,
Di (p-methoxyphenoxyethyl) ether, 1,2
-Bis (3-methylphenoxy) ethane, 1,2-bis (4-methylphenoxy) ethane, 1,2-bis (4-
Methoxyphenoxy) ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (3-methoxyphenoxy) ethane, 1-phenoxy-2- (2
-Naphthoxy) ethane, 1,3-bis (2-naphthoxy) propane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-biphenyl-p-tolyl ether, N-acetoacetyl-p- Toluidine, di (β-biphenylethoxy) benzene, p
-Di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like.

Specific examples of the preservability improver include, for example,
2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 4,4'-thiobis (3-methyl-6-tert -Butylphenol), 4,
4'-butylidenebis (3-methyl-6-tert-butylphenol), 1,1,3-tris (2-methyl-4-
(Hydroxy-5-cyclohexylphenyl) butane,
1,1,3-tris (2-methyl-4-hydroxy-5
-Tert-butylphenyl) butane, 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) -2,4,6-trimethylbenzene, 1- [α-methyl-α- (4-hydroxyphenyl) ethyl] -4-
[Α ′, α′-bis (4-hydroxyphenyl) ethyl] benzene, tetrakis (1,2,2,6,6-pentamethyl-4-piperidinyl) -1,2,3,4-butanetetracarboxylate, 1,3,5-tris (4-
tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 4-benzyloxyphenyl-
4 '-(2-methyl-2,3-epoxypropyloxy) phenyl sulfone and the like. Above all, 1,
1,3-Tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane is preferably used because it has an excellent effect on water resistance and hardly causes background fog. The amounts of the sensitizer and the storage stability improver are not particularly limited, but are generally 40 to 100 parts by weight of the colorant.
It is preferable to adjust the amount within a range of 0 parts by weight or less.

The coating solution for the heat-sensitive recording layer containing these substances is
Generally, water is used as a dispersion medium, and additives such as a dispersant and an antifoaming agent are added as necessary, and these substances are dispersed together or separately by a stirring / pulverizing machine such as a ball mill, an attritor, and a sand mill. It is prepared by mixing and stirring.

In the heat-sensitive recording layer coating solution, starch, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin,
Casein, gum arabic, polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene
At least one of an acrylic acid copolymer salt, a styrene / acrylic acid copolymer salt, a styrene / butadiene copolymer emulsion, a urea resin, a melamine resin, an amide resin, and a polyurethane resin, based on the total solid content of the heat-sensitive recording layer About 10 to 40% by weight, more preferably 15 to 30% by weight.

Various auxiliaries can be added to the coating liquid, if necessary. For example, surfactants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, sodium lauryl alcohol sulfate and fatty acid metal salts can be used. Agents, lubricants such as zinc stearate and calcium stearate, waxes such as polyethylene wax, carnauba wax, paraffin wax, ester wax, kaolin, clay, talc, calcium carbonate, aluminum hydroxide, calcined clay, calcined kaolin, titanium dioxide, diatomaceous earth Inorganic pigments such as finely divided anhydrous silica, activated white pigment, amorphous silica, and organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, raw starch particles, etc. Agents, fluorescent dyes, coloring dyes and the like are appropriately added.

The method for forming the heat-sensitive recording layer is not particularly limited, and examples thereof include air knife coating, variver coating, pure blade coating, rod blade coating, short dwell coating, and the like.
It is formed by applying and drying a coating solution for a heat-sensitive recording layer on a support by an appropriate coating method such as curtain coating or die coating. The coating amount of the coating liquid is not particularly limited, and is usually ² to 15 g / m ² , preferably 3 to 15 g / m ² in dry weight.
It is adjusted in the range of 〜１０10 g / m ² . In addition, paper (acid paper, neutral paper), plastic film,
It is appropriately selected from synthetic paper, nonwoven fabric, metal-deposited sheet and the like.

When a specific benzotriazole compound is contained in the protective layer, the content thereof is not particularly limited, but may be 1 to 5 with respect to the total solid content of the protective layer.
The content is preferably in the range of 0% by weight, more preferably 5 to 40%.
% By weight. When the specific benzotriazole compound is less than 1% by weight with respect to the total solid content of the protective layer, the light resistance of the recorded image is reduced. May decrease the chemical resistance.

The protective layer further contains a water-soluble or water-dispersible binder. As such a binder, various binders used in the above-mentioned heat-sensitive recording layer are used. Among them, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol and silicon-modified polyvinyl alcohol are
It is preferably used because it has an excellent effect as a protective layer. Above all, acetoacetyl group-modified polyvinyl alcohol is preferable because it can easily increase the chemical resistance and the water resistance of the protective layer. The acetoacetyl group-modified polyvinyl alcohol is obtained by esterifying polyvinyl alcohol having a polymerization degree of about 200 to 2000 with acetoacetic acid. Acetoacetic esterification of polyvinyl alcohol includes a method of adding diketene to a polyvinyl alcohol resin or transesterifying acetoacetic ester. The content of the binder is desirably about 15 to 80% by weight based on the total solid content of the protective layer.

In the protective layer, in order to improve printability and sticking, for example, calcium carbonate, zinc oxide,
Inorganic pigments such as aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, talc, kaolin, clay, calcined kaolin, and colloidal silica;
Organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, raw starch particles and the like can be blended as required. It is desirable that the amount of such a pigment be adjusted in the range of about 5 to 500 parts by weight with respect to 100 parts by weight of the binders. Furthermore, if necessary, a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax and the like, and a surfactant such as sodium dioctyl sulfosuccinate (dispersant, wetting agent) Agents), an antifoaming agent, and various auxiliaries such as a water-soluble polyvalent metal salt such as potassium alum and aluminum acetate. In order to further improve the water resistance, a curing agent such as glyoxal, boric acid, dialdehyde starch, or an epoxy compound can be used.

The method for preparing the coating liquid for the protective layer is not particularly limited. Generally, water is used as a dispersing medium, and in addition to the aqueous binder, the above-mentioned specific benzotriazole compound, pigment and lubricant which are added as required And the like are mixed and stirred. The method for forming the protective layer is not particularly limited. For example, the protective layer is formed on the heat-sensitive recording layer by applying a coating solution for the protective layer on the heat-sensitive recording layer by various appropriate coating methods as described above. Further, since the coating amount of the protective layer coating solution recording sensitivity of the heat sensitive recording material it exceeds a dry weight 15 g / m ² may be reduced, generally 0.5 to 15 g / m ^2,
Preferably, it is adjusted in the range of about 1 to 7 g / m ² .

If necessary, a protective layer may be provided on the back side of the thermosensitive recording medium to further improve the storage stability. Furthermore, an undercoat layer is provided between the support and the thermosensitive recording layer, a smoothing treatment such as super calendering is performed after each layer is coated, or an adhesive label is formed by applying an adhesive treatment to the back surface of the thermosensitive recording material. Or, providing a magnetic heat-sensitive recording layer or printing coating layer, or even a thermal transfer heat-sensitive recording layer,
Various known techniques in the field of thermal recording medium production can be added as necessary.

[0029]

The present invention will be described in more detail with reference to the following Examples, but it should be understood that the present invention is by no means restricted to such specific Examples. In the examples, "parts" and "%" indicate "parts by weight" and "% by weight", respectively, unless otherwise specified.

Preparation of Solution A 10 parts of 3-di-n-butylamino-6-methyl-7-anilinofluoran, 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 size became 1.5 μm.

Solution B Preparation A composition comprising 20 parts of 4-hydroxy-4'-isopropoxydiphenylsulfone, 10 parts of a 5% aqueous solution of methylcellulose, and 30 parts of water is pulverized by a sand mill until the average particle size becomes 1.5 μm. did.

Preparation of solution C 10 parts of 2,2'-methylenebis [4- (2-hydroxyethyl) -6- (2H-benzotriazol-2-yl) phenol], 5 parts of a 5% aqueous solution of methylcellulose and 15 parts of water Was pulverized with a sand mill until the average particle size became 0.4 μm.

Example 1 Formation of heat-sensitive recording layer 90 parts of solution A, 60 parts of solution B, and 10 parts of polyvinyl alcohol
% Aqueous solution and 35 parts of calcium carbonate are mixed and agitated, and the coating is dried on one side of a high-quality paper of 60 g / m ² so that the coating amount after drying is 6 g / m ² and dried. A recording layer was formed.

Formation of protective layer 30 parts of solution C, 125 parts of a 10% aqueous solution of acetoacetyl group-modified polyvinyl alcohol, kaolin [trade name: UW-
90, manufactured by Engelhard Co.] 30 parts, 2 parts of a 10% aqueous solution of glyoxal, 30% dispersion of zinc stearate 6
Of the protective layer coating liquid obtained by mixing and stirring a composition consisting of 30 parts by weight of water and 30 parts of water, is applied onto the heat-sensitive recording layer in an amount of 5 after drying.
After coating and drying to give g / m ² , a super calender treatment was performed to obtain a thermosensitive recording medium.

Example 2 In the preparation of Solution B of Example 1, 4-hydroxy-4'-
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that bis (3-allyl-4-hydroxyphenyl) sulfone was used instead of isopropoxydiphenylsulfone.

Example 3 In the preparation of Solution B of Example 1, 4-hydroxy-4'-
Instead of isopropoxydiphenyl sulfone,
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 4'-dihydroxydiphenylsulfone was used.

Example 4 In the preparation of Solution B of Example 1, 4-hydroxy-4'-
Instead of isopropoxydiphenyl sulfone, 1,1
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that -bis (4-hydroxyphenyl) -1-phenylethane was used.

Example 5 In the preparation of Solution B of Example 1, 4-hydroxy-4'-
Instead of isopropoxydiphenyl sulfone,
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 4'-isopropylidene diphenol was used.

Example 6 In the preparation of the solution A of Example 1, instead of 3-di-n-butylamino-6-methyl-7-anilinofluoran,
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 3-diethylamino-7- (m-trifluoromethylanilino) fluoran was used.

Example 7 In the preparation of the solution A of Example 1, instead of 3-di-n-butylamino-6-methyl-7-anilinofluoran,
3- (4-dimethylaminophenylamino) -5,7-
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that dimethylfluorane was used.

Example 8 In the preparation of the solution C of Example 1, the average particle size was 0.4 μm.
Instead of grinding until the average particle size is 1.5 μm
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the heat-sensitive recording material was pulverized until the temperature was reduced.

Example 9 In the formation of the heat-sensitive recording layer of Example 1, 60 parts of the liquid C was further added to the coating solution of the heat-sensitive recording layer to form the heat-sensitive recording layer. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the protective layer was formed without using the same.

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 protective layer in Example 1.

Comparative Example 2 In the preparation of the solution C of Example 1, 2 was used instead of 2,2'-methylenebis [4- (2-hydroxyethyl) -6- (2H-benzotriazol-2-yl) phenol].
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that-(2'-hydroxy-5'-methylphenyl) benzotriazole was used.

Comparative Example 3 In the preparation of the liquid C of Example 1, instead of 2,2'-methylenebis [4- (2-hydroxyethyl) -6- (2H-benzotriazol-2-yl) phenol],
2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazole-
2-yl) phenol] was used in the same manner as in Example 1 to obtain a thermosensitive recording medium.

The following evaluation tests were performed on the thus obtained heat-sensitive recording medium, and the results are shown in Table 1.

[Coloring property] Thermal evaluation machine [Product name: TH-P]
MD, manufactured by Okura Electric Co., Ltd.]
Each thermosensitive recording medium was colored at mJ / dot, and the densities of the obtained recorded portions and unrecorded portions were measured using a Macbeth densitometer [RD-9].
14 type, manufactured by Macbeth Co.] in the visual mode.

[Light resistance] A heat meter (trade name: SUNSHIN) in which the heat-sensitive recording medium recorded in the above evaluation of the color development was set under the conditions of a light source: xenon, 63 ° C., 50% RH.
E XENONLONG LIFE WEATHER
METER (manufactured by Suga Test Instruments Co., Ltd.) for 24 hours, and the density of the unrecorded portion and the recorded portion was measured in visual mode using a Macbeth densitometer.

[Heat resistance] The heat-sensitive recording medium recorded in the above evaluation of the color development was left in a hot-air dryer at 70 ° C. for 24 hours.
The density of the unrecorded portion and the recorded portion was measured in a visual mode using a Macbeth densitometer.

[Plasticizer resistance] Wrap film on polycarbonate pulp (40 mmφ tube) [trade name: KMA
-W, manufactured by Mitsui Toatsu Chemicals Co., Ltd.], and the thermosensitive recording medium recorded in the above evaluation of the coloring property is placed thereon, and a wrap film is further wound on it three times at 40 ° C. for 24 hours. After standing for a period of time, the color density was measured with a Macbeth densitometer (visual mode) to evaluate the plasticizer resistance.

[Oil resistance] An edible oil was applied on the heat-sensitive recording medium recorded in the evaluation of the color developing property, and the color developing density after being left at room temperature for 8 hours was measured with a Macbeth densitometer (visual mode). Oil resistance was evaluated.

[Head Matching Property] The degree of contamination (head scum) of the thermal head after continuous recording of 2 m in the evaluation of the coloring property was visually evaluated as follows. Evaluation criteria ：: No head residue, no practical problem. ×: There is a head residue and there is a problem in practical use.

[0053]

[Table 1]

[0054]

As is clear from the results shown in Table 1, the heat-sensitive recording material of the present invention not only has excellent light fastness in the recorded and unrecorded areas, but also has good coloring properties, plasticizer resistance and oil resistance. Excellent,
In addition, it was an excellent thermal recording medium having a head matching property.

Claims (4)

[Claims] 1. A thermosensitive recording medium comprising a support and a thermosensitive recording layer containing an electron-donating compound and an electron-accepting compound and, if necessary, a protective layer, wherein at least one of the thermosensitive recording layer and the protective layer is provided. 2,2'-methylenebis [4- (2-hydroxyethyl) -6- (2H-benzotriazol-2-yl) phenol]. 2. The heat-sensitive recording material according to claim 1, wherein the electron-accepting compound is at least one diphenyl sulfone derivative represented by the following general formula (1). Embedded image [Wherein, R ₁ and R ₂ each represent a C ₁ -C ₄ alkyl group, a C ₂ -C ₄ alkenyl group, a C ₁ -C ₄ alkoxyl group, or a halogen atom. m represents an integer of 0 to 2, n represents an integer of 1 to 3, and p and q each represent an integer of 0 to 2. ] 3. The method according to claim 1, wherein the electron accepting compound is 4-hydroxy-4 '.
-Isopropoxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone or 2,4 '
The thermosensitive recording medium according to claim 2, which is -dihydroxydiphenyl sulfone. 4. The heat-sensitive recording material according to claim 1, wherein the electron accepting compound is 1,1-bis (4-hydroxyphenyl) -1-phenylethane.