WO1992005963A1 - Thermal recording medium - Google Patents

Abstract

A thermal recording medium comprising a support and, provided thereon, a thermal recording layer containing a colorless or pale basic dye and a color developing agent which can develop color upon contact with the dye when heated, wherein the thermal recording layer contains at least one phosphate selected among 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate represented by formula (1) and salts thereof with alkali metal, ammonium and polyvalent metal, wherein R represents tert-butyl.

Description

 Specification

 Thermal recording medium

 Technical field

 The present invention relates to a thermosensitive recording medium, and more particularly, to a thermosensitive recording medium having excellent preservability of a recorded image.

 Background art

 Conventionally, heat-sensitive recording materials that use a reaction between a colorless or pale-colored basic dye and a color former and contact the basic dye and the color former with heat to obtain a recorded image are well known. I have. Such a thermosensitive recording medium generally has a disadvantage that the preservability of the recorded image is not sufficient and the recorded image fades with time. In particular, if a thermosensitive recording medium is stored under high humidity or high temperature conditions, the recorded image will be lost in a relatively short time, and there is a strong demand for improvement.

 In order to improve the storage stability of such recorded images, thermal recording media to which various preservability improvers have been added have been proposed. There are also new drawbacks, such as the occurrence of force adhesion to steel, and thus satisfactory results have not always been obtained.

 Disclosure of the invention

In view of this situation, the present inventors have intensively studied a storage stability improving agent contained in the recording layer. As a result, The inclusion of 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate, its alkali metal salts, ammonium salts, polyvalent metal salts or mixtures thereof in the recording layer introduces new disadvantages. Without this, it has been found that a thermosensitive recording medium having excellent storage stability of a recorded image can be obtained. The present invention has been completed based on this finding.

 That is, the present invention

 (a) a support, and

 (b) a heat-sensitive recording layer provided on the support and containing a colorless or light-colored basic dye and a colorant capable of forming a color when contacted with the dye when heated.

Wherein the heat-sensitive recording layer has the following general formula (1):

 [Wherein, R represents a tert-butyl group. ]

Selected from 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphite and its alkali metal, ammonium and polyvalent metal salts And at least one kind of thermal compound.

 According to one embodiment of the present invention, the heat-sensitive recording layer is composed of 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphite represented by the general formula (1), and an alkali metal salt thereof. And at least one of its ammonium salts.

 According to another embodiment of the present invention, the thermosensitive recording layer contains at least one polyvalent metal salt of 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphite. I do.

 Hereinafter, each embodiment of the present invention will be described.

Embodiment (I)

 According to one embodiment of the present invention, the heat-sensitive recording layer comprises a 2,2′-methylenebis (4,6-di-tut-butylphenyl) phosphate represented by the above general formula (1), an alkali metal salt thereof, and an ammonium salt. Contains at least one phosphite compound selected from salts. Preferably, the thermosensitive recording layer contains at least one of 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate and an alkali metal salt thereof.

The thermosensitive recording medium according to this embodiment has a storage stability of a recorded image. The heat-sensitive recording layer has a high whiteness and is generally resistant to color fog.

 Specific examples of the compound of the above general formula (1), its alkali metal salt or its ammonium salt include, for example, 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphate, 2,2 ′ '-Methylenebis (4,6-di-tert-butylphenyl) phosphate sodium salt, 2,2'-Methylenebis (4,6-di-tert-butylphenyl) phosphate calcium salt, 2, 2'-methylenebis

 (4,6-Gee tert-butylphenyl) Phosphate ammonium salt. Of course, these compounds can be used as a mixture of two or more, if necessary. The particle size of the compound of the above general formula (1), its alkali metal salt or its ammonium salt is not particularly limited. Is from 0.1 to: L about 0 m, preferably about 0, l to 3 m.

In addition, these compounds may be adsorbed on an inorganic pigment such as talc, clay, kaolin, silica, or the like beforehand or mixed with the inorganic pigment, and then added to a coating solution for forming a thermosensitive recording layer. Can also. A form in which at least one of the 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphite, an alkali metal salt thereof and an ammonium salt thereof is adsorbed to the inorganic pigment, or an inorganic pigment When used in the form of a mixture with, the ratio of the amounts of the two is not particularly limited, but the 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate described above is used. The weight ratio of the alkali metal salt and the ammonium salt to at least one kind of the (A) inorganic pigment (B) is about A _: B-80: 20 to 2080, especially 70:30 to 30:70. It is desirable to adjust so that it is within the range. In order to adsorb at least one of the compound represented by the general formula (1), its alkali metal salt and its ammonium salt to the inorganic pigment, various commonly used methods can be used. ), At least one of its alkali metal salt and its ammonium salt is dissolved in a small amount of a solvent such as methanol, mixed with an inorganic pigment, dried, and, if necessary, pulverized. Just do it. Although the particle size of the inorganic pigment is not particularly limited, it is usually preferable that the average particle size is about 0, 05 to: L 5. In addition, when the phosphite compound is used in a form adsorbed on the inorganic pigment or mixed with the inorganic pigment, if necessary, It is preferable to use these fine particles having a mean particle size of about 0.1 to 10, preferably about 0.1 to 3 by wet pulverization or the like.

 The use amount of at least one of the above 2,2′-methylenebis (4,6-ditert-butylphenol) phosphite, its alkali metal salt and its ammonium salt is not particularly limited, Generally, it is used in an amount of preferably about 1 to 300 parts by weight, more preferably about 1 to 100 parts by weight, based on 100 parts by weight of the coloring agent.

Embodiment (Π)

 According to another embodiment of the present invention, the heat-sensitive recording layer contains at least one polyvalent metal salt of 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphite. . The heat-sensitive recording medium according to this embodiment is excellent in storage stability of a recorded image, hardly causes color fogging, and has a characteristic that, in particular, there is little scum adhesion.

Although the particle size of the polyvalent metal salt is not particularly limited, it is usually preferable that the average particle size is about 0.1 to 10 m, preferably about 0.1 to 3. Examples of the metal constituting such a polyvalent metal salt include zinc, magnesium, barium, calcium, aluminum, tin, titanium, nigel, cobalt, manganese, and iron. The preparation of the polyvalent metal salt of 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphite can be carried out by various methods, for example, (i) 2,2′-meth (Ii) 2,2,2, a method of reacting an alkali metal salt of Tylenebis (4,6-di-tert-butylphenyl) phosphite with a water-soluble salt containing a polyvalent metal as described above in water to effect salt exchange; '-Methylenebis (4,6-di-tert-butylphenyl) phosphate and salt exchange method by dry or wet milling at least one of alkali metal salts with polyvalent metal compounds .

 The polyvalent metal compound that can be used in the above method (ii) is selected from the group consisting of zinc, magnesium, zinc, calcium, aluminum, tin, titanium, nickel, cobalt, manganese, and iron. Oxides, hydroxides, sulfides, halides, carbonates, phosphates, silicates, sulfates, nitrates or aluminates of the selected polyvalent metal, surface with a substance containing the polyvalent metal Examples include treated silica, higher fatty acid salts of the polyvalent metal, and mixtures of two or more of these compounds.

More specifically, (a) For example, zinc oxide, zinc hydroxide, zinc sulfide, zinc chloride, zinc carbonate, zinc phosphate, zinc silicate, zinc sulfate, zinc nitrate, zinc aluminate, magnesium oxide, magnesium hydroxide , Magnesium sulfide, magnesium chloride Magnesium, magnesium carbonate, magnesium phosphate, magnesium silicate, magnesium sulfate, magnesium nitrate, magnesium aluminate, barium chloride, calcium carbonate, barium sulfate, calcium oxide, calcium hydroxide, calcium chloride , Calcium carbonate, calcium silicate, aluminum oxide, aluminum hydroxide, aluminum hydroxide, aluminum silicate, aluminum silicate, titanium oxide, etc. (b) Polyvalent metals such as zinc, magnesium, balium, calcium and aluminum the including materials such silica mosquitoes were surface treated with a calcium carbonate or oxide Aruminiumu, (c) higher fatty acids, especially C E _n ~

Examples thereof include polyvalent metal salts of C ₂ G higher fatty acids, such as zinc stearate, magnesium stearate, barium stearate, calcium stearate, and aluminum stearate.

 Among these preparation methods, the method according to the above (ii) involves the preparation of a polyvalent metal salt of 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphite and the treatment for fine particle formation at the same time. In particular, the method using wet pulverization is more preferable because the salt exchange proceeds smoothly and a more uniform micronization treatment can be performed.

The wet pulverization is carried out by the above-mentioned 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate. And at least its alkali metal salts (such as sodium salts)

100 parts by weight of one kind together with about 1 to 500 parts by weight of the polyvalent metal compound is used in the presence of water in the presence of water using a conventional pulverizer, for example, a sand mill, to obtain a particle diameter of 0.1 l. It may be ground to about 10 ^ m, preferably about 0, 1 to 3m.

 In addition, when the wet grinding treatment is carried out, if the sulfonated polyvinyl alcohol is used as a dispersing aid, the atomization treatment can be performed efficiently, and as a result, the preservation of the recorded image is excellent, and the adhesion of residue is less. It is more preferable because a thermal recording medium can be obtained.

Such a sulfone group-modified polyvinyl alcohol is a known compound, and is formed by copolymerizing ethylene sulfonic acid, arylsulfonic acid, methanolylsulfonic acid, or other such olefinsulfonic acid or a salt thereof (for example, a sodium salt) with butyl acetate. It is prepared by a method of forming a polymer, or a method in which polyvinyl alcohol is treated with bromine or the like and then heated in an aqueous solution of sodium acid sulfite, and a sulfonic acid group and / or a salt thereof (for example, (Alkaline metal salts such as sodium salts). The ratio (modification degree) of the monomer-unit containing a sulfonic acid group or a salt thereof to the total monomer unit is about 1 to 10 mol%, the saponification degree is about 60 to 100 mol%, and the polymerization degree is 10 Approximately 0 to 100% sulfone group-modified polyvinyl Alcohol is preferably used. The amount of the sulfonate-modified polyvinyl alcohol to be used is at least 100 parts by weight of at least one of 2,2′-methylene phosphite (4,6-di-tert-butylphenyl) phosphate and its alkali metal salt. The amount is preferably about 0.05 to 50 parts by weight, more preferably about 0.5 to 25 parts by weight.

 In this embodiment, it is more preferable to use a mixture of polyvalent metal salts composed of two or more different metal species, since particularly excellent properties are exhibited in the desired effects of the present invention.

 Among the above polyvalent metal salts, a polyvalent metal salt in which the polyvalent metal is magnesium, calcium, norium, zinc or aluminum is particularly preferably used.

 The amount of at least one polyvalent metal salt of the compound represented by the general formula (1) is not particularly limited, but is generally preferably 1 to 300 parts by weight based on 100 parts by weight of the coloring agent. The amount is more preferably about 1 to 100 parts by weight.

 Next, other components contained in the heat-sensitive recording layer of the present invention will be described. The following description applies to both of the above embodiments (I) and (II).

In the present invention, the colorless or light-colored basic dye constituting the recording layer includes various known dyes commonly used in this field. Dyes can be used, and for example, the following are exemplified.

1,3-bis (p-dimethylaminophenyl) phthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) Phenyl) -3- (1,2-dimethylindole-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindole-3-yl) lid Lido, 3,3-bis (1,2, dimethylindole-1-3-yl) 1,5-dimethylaminophthalide, 3,3, bis (1,2, dimethylindole) -3 1- 6-dimethylaminophthalide, 3, 3-bis (9-ethylcarnozo-l 3-yl) 1- 6-dimethylaminophthalide, 3, 3-bis 2-Phenylindole-13-yl) -1-6-dimethylaminophthalide, 3-p-dimethylamino Triphenyl 3- (1-methyl virol 1-3-yl) -16-dimethyl triamino phthalide and other trimethane dyes, 4,4'-bisdimethyl benzoyl hydride Diphenylene-based dyes such as norbenzinoleether, N-noperophenylenoleoi-couramin, N-2,4,5-trichloro- mouth phenylloycouramin, benzylloycomene replenisher, thiazine dyes such as p-nitrobenzoylroy-cometylenepur, 3 -methylspirodinaphthovirane, 3 -ethinolace bilozinaphthovirane, 3 -phenyl —Spirodinaphthopyran, 3—penzinolace pillow dinaphthopyran, 3—methyrinaphtho (6′—methoxybenzo) spiropyran, 3 —spiro dyes such as prospirospirodibenzoviran, rhodami Lactam-based dyes such as B-anilino lactam rhodamine (p-nitroanilino) lactam, rhodamine (o-chloroanilino) lactam, 3-dimethylamino 7-methoxyfluoran, 3 —Jetylamino 6—Methoxyfluoran, 3—Jetylamino 1 7—Methoxyfluoran, 3—Jetylamino 7—Chlorofluoran, 3—Jetylamino 6—Methyl-7—Black mouth Fluorora 6-, 7-Dimethylfluoran, 3- (N-ethyl-p-toluinino) 1-methyl Luoran, 3—Jetylamino 7— (N—Cetylamino N—Methylamino) Fluoran, 3—Jetylamino 7—N—Methylaminofluoran, 3—Jetylamino 1-7 —Dibenzylamino fluoran, 3—Jetylamino 7— (N-methyl-N—benzylamino) fluoran, 3—Jetylamino 7— (N-chloroethyl N-methylamino) fluoran, 3—Jethylamino 7—Jethylaminofluoran, 3— (N—ethylyl p—toluinino) 1 6—Methyl7—phenylaminofluoran, 31 (N—ethylon p—toluinino) 1 6 — methyl — 7— (p—toluinino) fluoran, 3-dimethylamino 6-methyl-7-phenylaminofluoran, 3-getylamino6-methyl-7-phenylaminofluoran, 3—n —Ptylamino 6—Methyl-7—Phenylaminofluoran, 3-G n—Pentylamino 6—Methyl 1 7—Phenylaminofluoran, 3—Jethylamino 7— (2—Power Toxiphenylamino) Fluoran, 3-(N-cyclohexyl N-methylamino) 1 6 -methyl 7 -phenylamino fluoran, 3-pyrrolidino 6 -methyl 7 —Phenylaminofluoran, 3—piperidino 6—methyl-7—phenylaminofluoran, 3—getylamino 6—methyl-7—xylidinofluoran, 3—Jetylamine 7— (o—Chlorophenylamino) Fluoran, 3—Gen n—Ptylamine 7— (o—Chlorophenylamino) Fluoran, 3—Pyrrolidine 6 — methyl 7 — p — butylphenylamino fluoran, 3— (N—methyl N — n — amil) amino 6 — methyl 7 monophenylamino fluoran, 3 — (N— 6-Methyl-7-phenylaminofluoran, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-phenylamino Nofluoran, 3- (N-methyl-N-n-hexyl) amino 6-methyl 7-hue Nilamino fluoran, 3- (N-ethyl-N-n-hexyl) amino 6-methyl-7-phenylamino fluoran, 3- (N-ethyl-N-ethylhexyl) amino-6-methyl-7 —Phenylaminofluoran, 3— (N-ethyl-N-tetrahydrofurfuryl) amino 6-methyl-7-phenylaminofluoran, 3- (N-ethyl-1-N-cyclopentyl) amino 6-methyl-7-phenyl Ruminofluoran, 2,2-bis {4-1- (6 '-(N-cyclohexyl-N-methinoleamino) -13'-Methylspiphate (phthalide 3,9'-xanthene) 1-2'-Iluamino Fluorinated dyes such as propane. Of course, it is not limited to these dyes, and two or more dyes can be used in combination.

 Among these dyes, 3-di-n-butylamino 6-methyl-7-phenylamino fluoran and 3-di-n-butylamino 7- (o-chlorophenylamino) fluoran are particularly useful for whiteness of white paper. It is more preferably used because a thermosensitive recording medium having a high density can be obtained.

 As the colorant used in combination with the above basic dye, various compounds commonly used in this field can be used.

4 tert-butyl phenol, naphthyl naphthol, β Thor, 4-acetylphenol, 4-tert-octylphenol, 4,4'-sec-butylidene didiphenol, 4-phenylphenol, 4,4 'dihydroxydiphenylmethane, 4,4'isopropylene Dendiphenol, hydroquinone, 4,4'-cyclohexylidenediphenol, 4,4 '-(1,3-dimethylbutylidene) bisphenol, 2,2-bis (4-hydroxyphenyl) 1-4 —Methylpentane, 4,4′-dihydroxydiphenylsulfide, 4,4′-thiobis (6-tert-butyl-3-methylphenol), 4,4′-dihydroxydiphenylsulfone, 2,4 ′ —dihyd Droxydiphenylsulfone, 4-hydroxy-1 4'-methinolesif Eninoresnorrenone, 4-t 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy3 ', 4'trimethylenediphenylsulfone, 4-hydroxy3', 4'-tetramethylenediphenylsulfone, 3,4-dihydroxy-4'-methyldiphenylsulfone, bis (3-aryl-1-hydroxyphenyl) sulfone, 1,3-di [2- (4-hydroxyphenyl) 1-2-propyl Benzene, hydroxyquinone monobenzyl ether, bis (4-hydroxyphenyl) acetic acid butyl ester, 4-hydroxybenzobenzophenone, 2,4- Dihydroxybenzophenone, 2,4,4'-Trihydroxybenzophenone, 2,2 ', 4,4'-Tetrahydroxybenzophenone, 4-Hydroxydimethyl phthalate, 4-Hydroxybenzoate Methyl 4-ethyl hydroxybenzoate, 4-hydroxypropyl benzoate, 4-hydroxybenzoic acid see —butyl, 4-hydroxypentyl benzoate, 4-phenyl hydroxybenzoate phenyl, 4-hydroxy benzoate Benzyl hydroxybenzoate, trihydroxy 4-benzoate, chlorophenyl 4-hydroxybenzoate, phenyl propyl 4-hydroxy benzoate, phenyl 4-hydroxy benzoate, 4-hydroxy benzoate p-methyl benzyl, 4-hydroxybenzoic acid mono-p-methoxybenzyl, nopolak-type phenol resin, phenol polymer, etc. Phenolic compound, 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-butylsalicylic acid, 3-benzylsalicylic acid, 3- (1-methylbenzyl) Salicylic acid, 3-chloro-1- (benzyl) salicylic acid, 3-phenyl-5- (a, na-dimethylbenzyl) Lithylic acid, 3,5-di-methylbenzyl salicylic acid, 4- (2-p-methoxyphenoxyethoxy) salicylic acid, 4- (3-p-tolylsulfonylpropyloxy) salicylic acid, 5 — [P— (2-p-methoxyphenoxyethoxy) cumyl] aromatic carboxylic acids such as salicylic acid and their phenolic compounds, aromatic carboxylic acids and zinc, magnesium, aluminum, calcium, titanium, Organic acidic substances such as salts with polyvalent metals such as manganese, tin and nickel. Of course, two or more of the above colorants can be used in combination as needed.

 The ratio of the basic dye and the colorant used should be appropriately selected according to the type of the basic dye and the colorant to be used, and is not particularly limited, but is generally 100 parts by weight of the basic dye. The coloring agent is used in an amount of about 100 to 700 parts by weight, preferably about 150 to 400 parts by weight.

 The heat-sensitive recording layer of the heat-sensitive recording medium of the present invention comprises at least one of the compound represented by the above general formula (1), its alkali metal salt, its ammonium salt, and its polyvalent metal salt (hereinafter simply referred to as “storage modification”). It is formed by preparing a coating solution containing a basic dye and a color former, applying it to a support, and drying.

The above coating liquid is generally prepared by using water as a dispersion medium, a ball mill, It is prepared by an inadvertent method such as dispersing the preservative improver, basic dye and color former together or separately with a stirrer / pulverizer such as a triter or a sand mill.

 A binder is usually added to such a coating solution. Examples of binders include starches, hydroxyshethyl cellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxyl-modified polypinyl alcohol, and sulfone-modified poly. Vinyl alcohol, gay-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, vinyl alcohol, vinyl acetate-vinyl acetate copolymer and graft copolymer of acrylamide, acrylic acid, 7-yl acetate Styrene, maleic anhydride copolymer salt, styrene-acrylic acid copolymer salt, styrene ♦ butadiene copolymer salt, emulsion, etc., which are commonly used in this field, are used. In the above coating liquid, these binders are usually blended in an amount of about 2 to 40% by weight, preferably about 5 to 25% by weight of the total solids of the coating liquid.

Various auxiliaries can be further added to the coating solution. For example, sodium octyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate Dispersants such as stream salts and fatty acid metal salts, 9 Other defoamers, fluorescent dyes, coloring dyes and the like.

 In addition, in order to improve the adhesion of scum to the recording head, various pigments commonly used in the field of thermal recording media, such as silicon oxide pigments, kaolin, clay, talc, calcium carbonate, and magnesium carbonate Inorganic pigments such as calcium silicate, magnesium silicate, calcined clay, titanium oxide, diatomaceous earth, and activated clay, styrene microballs, nylon powder, polyethylene powder, urea-formalin resin filler, and organic pigments such as starch particles. It can also be added. The particle size of these pigments is not particularly limited, but usually those having an average particle size of about 0.1 to 15 μm are preferred.

In addition, among these various pigments, when an alkaline pigment such as calcium carbonate, magnesium carbonate, calcium silicate, or magnesium silicate is used, the relationship with the storage stability improver such as the compound of the general formula (I) can be reduced. In particular, it is preferable because a heat-sensitive recording material with little color development can be obtained. Among these alkaline pigments, calcium carbonate and magnesium carbonate are particularly excellent in terms of effect, and calcium carbonate is most preferred because it is inexpensive. The amount of the pigment used is not particularly limited, but is preferably about 1 to 30% by weight based on the total solid content of the coating solution for forming the heat-sensitive recording layer. About 15% by weight is more preferable. Of course, these alkaline pigments can be used in combination with the other pigments described above. When the alkaline pigment is used in combination with the above-mentioned other pigments, the amount of these pigments used is adjusted in the range of about 5 to 50% by weight based on the total solid content of the coating liquid for forming the heat-sensitive recording layer. Is preferred.

 In addition, stearic acid, polyethylene, carnapaulo, and pho are used to prevent sticking due to contact with recording equipment and recording heads. A dispersion such as raffin wax, zinc stearate, calcium stearate, or esterx, or an emulsion can also be added.

Furthermore, in the heat-sensitive recording medium of the present invention, for example, stearyl acid amide, methylene bisamide stearate, oleic acid amide, palmitic acid amide, and coconut fatty acid are provided as long as the desired effects of the present invention are not impaired. Fatty acid amides such as amides, 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 4,4′butylidenebis (6-tert-butyl-3-methylphenol), 1,1,3— Hindered phenols such as tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3, tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, p —Benzylbiphenyl, p— (4-trioxy) biphenyl and other biphenyls, 1,5-bis (4-Methoxyphenoxy) 1-3-year-old xerpentane, 1,2-bis (phenoxy) ethane, 1,2-bis (4-methylphenoxy) ethane, 1,2-bis (3-methylphenoxy) ethane, 1 1- (2-methylphenoxy) 1-2- (4-methoxyphenoxy) ethane, ethers such as 2-naphthylbenzyl ether, dibenzyl terephthalate,

1-Hydroxy-2-esters such as 2-phenyl phenyl naphthoate, dibenzyl oxalate, di (4-methylbenzyl) oxalate, di (4-monomethylbenzyl) ester oxalate, 2- (2'-Hydroxy 5'-methyl phenyl) Benzotriazole, 2-Hydroxy 41 UV absorbers such as benzyloxybenzofuunone and various known heat-fusible substances are used in combination as sensitizers. You can also.

Among these heat-fusible substances, 1,2-bis (3-methylphenoxy) ethane, 1,2-bis (phenoxy) ethane, and 1- (2-methylphenoxy) 1-2- (4-methoxyphenoxy) Ethane, dibenzyl oxalate, di (4-methylbenzyl) oxalate, di (4-methylbenzyl) oxalate, p-benzyldiphenyl, p- (4-trioxy) biphenyl, and 1,5-I-bis (4-methoxyphenoxy) -13-oxa-pentane is particularly excellent in relation to the above-mentioned storage stability improver. It is more preferable to exhibit a sensation effect. These are as required

Two or more kinds can be used as a mixture.

 When a heat-fusible substance is used, the amount used is not particularly limited, but is generally 50 to 100 parts by weight based on 100 parts by weight of the basic dye. Is preferred,

More preferably, it is used in the range of 100 to 500 parts by weight. Paper, plastic film, synthetic paper, etc. are used as the support, but paper is preferably used in terms of price and applicability o

In the present invention, the method for forming the recording layer is not particularly limited, and it can be formed according to a conventionally known and commonly used technique. For example, a coating solution for a heat-sensitive recording layer is coated on a support with an air knife coater or a plate. Coating and drying using a suitable coating device such as Doco coater, Barco overnight, gravure coater, curtain coater, Short durco overnight, etc. Further, the invention is not limited to Japanese also coated amount of the coating liquid, generally dry weight. 2 to 1 2 gm ^2, is preferably adjusted in the range of 2~8 g Z m ^2. It is also possible to provide an overcoat layer on the recording layer for the purpose of protecting the recording layer, for example, by providing a protective layer on the back surface of the support, or by applying an undercoat between the support and the thermosensitive recording layer. Of course, it is also possible to provide a layer, 2 Various known techniques in the field of thermal recording medium production can be added.

 Example

 Hereinafter, the present invention will be described in more detail with reference to Examples, but it is needless to say that the present invention is not limited thereto. Parts and% in the examples are parts by weight and% by weight, respectively, unless otherwise specified.

 Example I

 ① Preparation of solution A

 3-(N-ethyl-N-isoamyl) amino

 6-methyl-7-phenylaminofluoran 10 parts methylcellulose 5% aqueous solution 5 parts water 40 parts This composition was ground with sandmill until the average particle diameter became 10 m.

 ② Preparation of B solution

 4-Benzyl hydroxybenzoate 20 parts Methyl cellulose 5% aqueous solution 5 parts Water 55 5 parts This composition was ground with sand mill until the average particle diameter became 15 m.

③ Preparation of C solution 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate sodium salt 3 parts Methylcellulose 5% aqueous solution 3 parts Water 25 parts This composition has a mean particle size of 1. And crushed until

の Formation of recording layer

55 parts of liquid A, 80 parts of liquid B, 31 parts of liquid C, 15 parts of silicon oxide pigment (oil absorption 180 m1100 g), 15 parts, 50 parts of 20% polyvinyl alcohol aqueous solution, and 10 parts of water The mixture was stirred to obtain a coating liquid. The resulting coating weight of dry燥後onto the base paper coating liquid basis weight 50 gZm ² is then applied and dried such that the 6 gZin ² to obtain a heat-sensitive recording paper.

Example I I 2

 In the preparation of solution C, instead of the sodium salt of 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate, 2,2'-methylenebis (4,6-di-tert-butylphenyl) A thermosensitive recording paper was obtained in the same manner as in Example I-11 except that phosphate was used.

Example I-1

In the preparation of solution C, sodium 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate A thermosensitive recording paper was obtained in the same manner as in Example I-1, except that a potassium salt of 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphate was used instead of the salt. Example I

① D solution preparation

 3-(Ν-ethyl-isoamyl) amino

 6-Methyl-7-phenylaminofluoran 10 parts 1,2, bis (3-methylphenoxy) ethane 25 5 parts Methylcellulose 5% aqueous solution 5 parts Water 50 parts This composition was sand-milled to an average particle diameter of 10 m. Crushed until no more.

 ② Preparation of liquid

 4,4'-Isopropylidene diphenol 20 parts Methyl cellulose 5% aqueous solution 5 parts Water 55 5 parts This composition was ground with a sand mill until the average particle diameter became 1.5 m.

 ③ Preparation of solution F

Mixture of 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphite sodium salt and silica (mixing ratio: 60/40) 6 parts This composition was pulverized by a sand mill until the average particle diameter became 15 m.

の Formation of recording layer

90 parts of D solution, 80 parts of E solution, 34 parts of F solution, 15 parts of silicon oxide pigment (oil absorption 180 m1 100 g), 15 parts of 20% polyvinyl alcohol aqueous solution, and 10 parts of water are mixed and coated with stirring. Liquid. The resulting coating weight of dry燥後onto the base paper coating liquid basis weight 50 gZm ² is then applied and dried such that the 6 gZm ² to obtain a heat-sensitive recording paper.

Example I-1

 In the preparation of solution F, instead of the mixture of sodium salt of 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate and silicic acid (mixing ratio: 60Z40), 2,2'-methylenebis (4,6-di-tert-butylphenyl) A heat-sensitive recording paper was obtained in the same manner as in Example I-14, except that a mixture of phosphite and silicide (mixing ratio: 60/0) was used.

 Example I-1 6

In the preparation of solution E, instead of 4,4'-isopropylidenediphenol, 4-hydroxy 4'-isopropoxy was used. A thermosensitive recording paper was obtained in the same manner as in Example I-14, except that 2 sidipenylsulfone was used.

 Example I-1 7

 In the preparation of solution A, except that 3- (n-ethyl-N-isoamyl) amino 6-methyl-7-phenylamino fluoran was used in place of 3- (n-butylamino) 6-methyl-7-phenylamino fluoran A thermosensitive recording paper was obtained in the same manner as in Example I-11.

Example I-1 8

① G solution preparation

 3—Gee n—Butylami No 6—Methyl

 7—Phenylaminofluorane 10 parts

1,2-bis (3-methylphenoxy) ethane 25 parts Methylcellulose 5% aqueous solution 5 parts Water 50 parts This composition was pulverized by a sand mill until the average particle diameter became 1. O ^ m.

② Formation of recording layer

90 parts of liquid G, 80 parts of liquid E, 31 parts of liquid C, 15 parts of silicon oxide pigment (oil absorption 180 m1 100 g) 15 parts, 50 parts of 20% polyvinyl alcohol aqueous solution, and 10 parts of water Liquid. Dry the resulting coating liquid onto the base paper grammage 50 gZm ² Coating and drying were performed so that the coating amount after drying was 6 gZm ² to obtain a thermosensitive recording paper.

Example I-1 9

 A heat-sensitive recording paper was obtained in the same manner as in Example I-18, except that 34 parts of solution F was used instead of 31 parts of solution C in Example I-18. .

Example I-1 10

 ① H solution preparation

 3-di-n-butylamino 6-methyl

 7—Phenylaminofluoran 10 parts

1,2-bis (phenoxy) ethane 25 parts 5% aqueous solution of methylcellulose 5 parts Water 50 parts This composition was ground with a sand mill until the average particle diameter became 10 m.

 ② Formation of recording layer

90 parts of liquid H, 80 parts of liquid E, 31 parts of liquid C, 15 parts of silicon oxide pigment (oil absorption 180 m1 100 g), 15 parts of a 20% aqueous polyvinyl alcohol solution, and 10 parts of water And The resulting coating weight of dry燥後onto the base paper coating liquid basis weight 50 gZm ² is then applied and dried such that the 6 gZm ² to obtain a heat-sensitive recording paper. Example I I 1 1

 A heat-sensitive recording paper was obtained in the same manner as in Example I-110 except that in Example I-110, 34 parts of solution F was used instead of 31 parts of solution C.

 Example I-1 12

 ① Preparation of solution I

 3-Gee n-Butylamino 6-Methyl-

 7-Phenylamino fluoran 10 parts Dibenzyl oxalate 25 parts Methylcellulose 5% aqueous solution 5 parts Water 50 parts This composition was ground with a sand mill until the average particle diameter became 10 m.

 ② Formation of recording layer

90 parts of liquid I, 80 parts of liquid E, 31 parts of liquid C, 15 parts of oxidized silica pigment (oil absorption 180 m1 / 100 g) 15 parts, 50 parts of 20% polyvinyl alcohol aqueous solution, and 10 parts of water This was used as a coating solution. The resulting coating weight of dry燥後onto the base paper coating liquid basis weight 50 gZm ² is then applied and dried such that the 6 gZm ² to obtain a heat-sensitive recording paper.

Example I-1 13

In Example I-12, instead of 31 parts of liquid C, liquid F A thermosensitive recording paper was obtained in the same manner as in Example I-12 except that 34 parts were used.

Example I-1 14

 ① J solution preparation

 3—Gee n—Butylamino 6—Methyl

 7-Furaminofluorane 10 parts Di (4-methylbenzyl) oxalate 25 parts Methylcellulose 5% aqueous solution 5 parts Water 50 parts This composition was ground with a sand mill until the average particle diameter became 1.0 m. .

 ② Formation of recording layer

90 parts of liquid J, 80 parts of liquid E, 31 parts of liquid C, 15 parts of silicon oxide pigment (oil absorption 18 Om1 100 g), 15 parts of 20% polyvinyl alcohol aqueous solution, and 10 parts of water And The resulting coating weight of dry燥後onto the base paper coating liquid basis weight 50 gZm ² is then applied and dried such that the 6 gZm ² to obtain a heat-sensitive recording paper.

Example I-I 15

 In Example I-14, instead of 31 parts of solution C, solution F

A thermosensitive recording paper was obtained in the same manner as in Example I-14 except that 34 parts were used. 3 Example I-1 16

 ① Preparation of K solution

 3—Gee n—Ptyla Minor 6—Methyl

 7-Phenylaminofluoran 10 parts 1- (2-methylphenoxy) 1-2- (4-1-Methoxyphenoxy) ethane 25 parts Methylcellulose 5% aqueous solution 5 parts Water 50 parts This composition is averaged with a sand mill. It was pulverized until the particle diameter became 10 m.

 ② Formation of recording layer

90 parts of liquid K, 80 parts of liquid E, 31 parts of liquid C, 15 parts of silicon oxide pigment (oil absorption 18 Om 1 Z 100 g), 15 parts, 50 parts of a 20% polyvinyl alcohol aqueous solution, and 10 parts of water are mixed and stirred. To make a coating solution. The obtained coating wave was applied on a base paper having a basis weight of 50 gZm ² and dried so that the coating amount after drying was 6 gZm ² , to obtain a thermosensitive recording paper.

Example I-I 17

 A heat-sensitive recording paper was obtained in the same manner as in Example I-16, except that 34 parts of Liquid F was used instead of 31 parts of Liquid C in Example I-16.

Example I-1 18 Two

① L solution preparation

 3—Gee n—Ptyla Minor 6—Methyl

 7-Phenylaminofluoran 10 parts p-Benzylbiphenyl 25 parts Methylcellulose 5% aqueous solution 5 parts Water 50 parts This composition was ground by a sand mill until the average particle diameter became 10 m.

 ② Formation of recording layer

90 parts of liquid L, 80 parts of liquid E, 31 parts of liquid C, 15 parts of silicon oxide pigment (oil absorption 18 Om1 / 100 g), 50 parts of 20% polyvinyl alcohol aqueous solution, and 10 parts of water Liquid. The obtained coating solution was applied onto a base paper having a basis weight of 50 g / m ² and dried so that the coating amount after drying was 6 gZm ^2, and a thermosensitive recording paper was obtained.

Example I-1 19

 A heat-sensitive recording paper was obtained in the same manner as in Example I-118, except that 34 parts of Liquid F was used instead of 31 parts of Liquid C.

 Example I-20

 ① M solution preparation

3—Gee n—Butylamino 6—Methyl 7—Phenylaminofluoran 10 parts

1, 5-bis (4-methoxyphenoxy)

 3-oxa-pentane 25 parts Methylcellulose 5% aqueous solution 5 parts Water 50 parts This composition was ground with a sand mill until the average particle diameter became 10 m.

 ② Formation of recording layer

90 parts of liquid M, 80 parts of liquid E, 31 parts of liquid C, 15 parts of silicon oxide pigment (oil absorption 18 Om 1 100 g) 15 parts, 50 parts of 20% aqueous polyvinyl alcohol solution, and 10 parts of water Liquid. The obtained coating solution was applied onto a base paper having a basis weight of 50 g / m ² and dried so that the coating amount after drying was 6 gZm ^2, and a thermosensitive recording paper was obtained.

Example I- 21

 A heat-sensitive recording paper was obtained in the same manner as in Example I-120, except that 34 parts of Liquid F was used instead of 31 parts of Liquid C.

Example I-1 22

 A thermosensitive recording paper was obtained in exactly the same manner as in Example I-18 except that the used amount of the solution C was changed to 10 parts.

Example I 23 Thermal recording paper was obtained in exactly the same manner as in Example I-18, except that the amount of the solution C was changed to 60 parts.

Example I-1 24

 A thermosensitive recording paper was obtained in the same manner as in Example I-18 except that the amount of the solution C was changed to 100 parts.

Example I-I 25

 A thermosensitive recording paper was obtained in the same manner as in Example I-14, except that in forming the recording layer of Example I-14, 55 parts of solution A was used instead of 90 parts of solution D.

Example I-26

 A heat-sensitive recording paper was obtained in the same manner as in Example I-114, except that light calcium carbonate (oil absorption: 90 m1Z, 100 g) was used instead of the silicon oxide pigment in forming the recording layer. Example 1-27

 In the preparation of solution C, instead of the sodium salt of 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate, 2,2'-methylenebis (4,6-di-tert-butylphenyl) A heat-sensitive recording paper was obtained in the same manner as in Example I-114, except that ammonium phosphate of phosphate was used.

Comparative Example I-1

Same as Example I-11 except that solution C was not used A thermosensitive recording paper was obtained.

 Comparative Example I 1 2

 A heat-sensitive recording paper was obtained in the same manner as in Example I-14, except that the solution F was not used.

 Comparative Example I 1 3

 A heat-sensitive recording paper was obtained in the same manner as in Example I-16, except that the solution F was not used.

Comparative Example I 1 4

 A heat-sensitive recording paper was obtained in the same manner as in Example I-17, except that the solution C was not used.

Comparative Example I-1 5

 A heat-sensitive recording paper was obtained in the same manner as in Example I-18 except that the solution C was not used.

Comparative Example I-6

 A thermosensitive recording paper was obtained in the same manner as in Example I-10, except that the liquid C was not used.

Comparative Example I-1 7

 A thermosensitive recording paper was obtained in the same manner as in Examples 1-12, except that the liquid C was not used.

Comparative Example I-1 8

In the preparation of solution C, sodium 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate A thermosensitive recording paper was obtained in the same manner as in Example I-18, except that 1,1,3, -tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane was used instead of the salt. Was.

Comparative Example I-1 9

 In the preparation of solution C, instead of the sodium salt of 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate, 4,4'butylidenebis (6-tert-butyl-m-cresol) was used. Except for the above, a thermal recording paper was obtained in the same manner as in Example I-18.

 The 36 types of heat-sensitive recording paper thus obtained were evaluated by the following methods, and the results are shown in Table 1.

 [Recording density]

 The thermosensitive recording paper is recorded by a thermal facsimile (Panafax UF-60, manufactured by Matsushita Denshisha), and the recording density (Dj) is measured by a Macbeth densitometer (RD-914, manufactured by Macbeth). It was measured.

 (Moisture resistance of recorded image)

The printed thermosensitive recording paper was left in an atmosphere of 40% and 90% RH for 24 hours, and the recording density (D ₂ ) was measured again using a Macbeth densitometer. The recording density residual ratio () was determined by the following equation.

Recording density remaining rate-(D ₂ ) X 100 (Heat resistance of recorded image)

 Place the heat-sensitive recording paper after printing in an atmosphere of 60 ° C and 10% RH.

After standing for 24 hours, the recording density (D ₃ ) of the printed portion was measured again using a Macbeth densitometer. In addition, the recording density residual ratio (%) was determined by the following equation.

Recording density residual rate-(D ₃ ) X 100

 (Whiteness)

 The whiteness of the thermal recording paper before printing was measured with a Hunter whiteness meter.

 (Capri coloring)

After leaving the thermal recording paper in an atmosphere of 40 and 90% RH or in an atmosphere of 60 and 10% RH for 24 hours, the Capri color density of the blank paper was measured using a Macbeth densitometer. It was measured. Table 1 shows the Capri color density when processed in an atmosphere of 40 C and 90% RH as F〗, and the Capri color density when processed in an atmosphere of 10 and 10% RH at 60. displaying the concentration as F _2.

(Continued)

Record density Remaining rate Power

D ₃ Do / Ό _χ

^D l ^D 2. 2, ^D 1 ^F l ^F 2 Ref. 18 1.24 0.93 0.98 75 79 83.7 0.08 0.13 Ref. 19 1.21 0.91 0. 7 75 80 83.5 0.08 0.13 Ref. 20 1.27 1.12 1.07 88 84 84.4 0.08 0.13 Ref. 21 1.23 1.09 1.05 89 85 83.9 0.08 0.13 Ref. 22 1.33 1.08 1.05 81 79 85.7 0.08 0.08 Ref. 1-23 1.32 1.15 1.15 87 87 85.0 0.10 0.09 Fiber -24 1.32 1.12 1.19 85 90 83.0 0.13 0.14 notes -25 0.78 0.64 0.70 82 90 85.6 0.09 0.08 腳-26 1.28 1.23 1.22 96 95 86.5 0.07 0.07

■ -27 1.28 1.20 1.18 94 92 83.8 0.10 0.11 腳 -1 1.27 0.42 0.77 33 61 86.8 0.10 0.17 Fiber 2 1.31 1.16 0.93 89 71 84.6 Π \ λ ϋ, 丄 U. 14 Customer:> 1.25 1.05 0.79 84 63 0 t 0.09 0.10 listen -4 1.28 0.34 0.70 27 55 86.4 0.09 0.08 customer 5 1.33 1.00 0.74 75 56 85.7 0.08 0.08 腳 -6 1.34 1.02 0.71 76 53 85.5 0.09 0.09 sound 7 1.33 0.93 0.67 70 50 85.2 0.11 0.14 note 8 1.34 1.01 0.81 75 60 83.5 0.10 0.10 腳 -9 1.33 1.00 0.75 75 56 84.2 0.09 0.09 As is clear from the results in Table 1, the thermosensitive recording medium of the present invention was an excellent recording medium having excellent storage stability of a recorded image and hardly producing any force due to the improvement in storage stability.

Example Π-1

① Preparation of solution A

 3—Gee n—Ptyla Minor 6—Methyl

 7—Phenylaminofluoran 10 parts

1,2-bis (3-methylphenoxy) ethane 25 parts Methylcellulose 5% aqueous solution 5 parts Water 50 parts This composition was ground with sandmill until the average particle diameter became 1.0 m.

 ② Preparation of B solution

 4,4'-Isopropylidene diphenol 20 parts Methyl cellulose 5% aqueous solution 5 parts Water 55 parts This composition was ground with a sand mill until the average particle diameter became 15 m.

 ③ Preparation of C solution

2, 2'-Methylene bis (4,6-di-tert-butyl) sodium salt of phosphite 3.9 parts Magnesium gayate 2.1 parts Polysulfonic acid modified with sulfone group

 (Product Name: Goceran L-1 3266,

 5% aqueous solution of Nippon Synthetic Chemical Industry Co., Ltd. 3 parts Water 25 parts This composition was pulverized with a sand mill until the average particle size became 1.5 ^ m. It was confirmed that the mixture after the pulverization was salt-exchanged to a magnesium salt of 2,2′-methylenebis (4,6-ditert-butylphenyl) phosphite.

の Formation of recording layer

Liquid A 90 parts, Liquid B 80 parts, Liquid C 34 parts, silicon oxide pigment (oil absorption 180 ml Z100 g) 7 parts, light calcium carbonate (oil absorption 90 m 1/100 g) 8 parts, 20% polyvinyl alcohol A coating liquid was obtained by mixing and stirring 50 parts of an aqueous solution, 15 parts of a 30% aqueous zinc stearate dispersion, and 10 parts of water. The obtained coating solution is weighed SO

Was coated and dried so that the coated amount after drying was 6 g / m ² , to obtain a thermosensitive recording paper. Example Π-2

 In the preparation of solution C, a thermosensitive recording paper was obtained in the same manner as in Example 1 except that calcium gayate was used instead of magnesium gayate.

Example Π-3 In the preparation of Solution A, use 3-di-n-butylamino 7- (o-chlorophenylamino) fluoran instead of 3-di-n-butylamino-6-methyl-7-phenylaminofluoran. Using di (4-methylbenzyl) ester oxalate instead of 1,2-bis (3-methylphenoxy) ethane. In the preparation of solution C, magnesium gayate and calcium carbonate were used instead of magnesium gayate. : 1 Thermal recording paper was obtained in the same manner as in Example II-1, except that the mixture was used.

Example Π-4

 In the preparation of solution A, dibenzyl oxalate was used in place of di (4-methylbenzyl) oxalate, and in the preparation of solution B, 4-hydroxypropyl was used in place of 4,4'-isopropylidenediphenol. Performed except using 4 'monoisopropoxydiphenylsulfone and using a 1: 1 mixture of zinc chloride and calcium carbonate instead of a 1: 1 mixture of magnesium silicate and calcium carbonate in the preparation of Solution C. Thermal recording paper was obtained in the same manner as in Example III-3.

Example Π-5

In the preparation of solution C, heat was applied in the same manner as in Example II-1, except that 3 parts of a 5% aqueous solution of methylcellulose was used instead of 3 parts of a 5% aqueous solution of a polyvinyl alcohol modified with a sulfone group. Recording paper was obtained.

 Example Π-6

 Example II-1 and Example II-1 except that in forming the recording layer, 15 parts of a silicon oxide pigment (oil absorption 180 m1 / 100 g) was used instead of 7 parts of the silicon oxide pigment and 8 parts of light carbonic acid ruthenium. In the same manner, a thermosensitive recording paper was obtained.

 Example Π-7

 A thermosensitive recording paper was obtained in the same manner as in Example I-1, except that 8 parts of magnesium carbonate was used instead of 8 parts of light calcium carbonate in forming the recording layer.

Comparative Example Π-1

 In the preparation of Solution C, instead of the sodium salt of 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate and magnesium gayate, 1,1,3-tris (5-cyclohexane A heat-sensitive recording paper was obtained in the same manner as in Example I-1, except that 6 parts of xylol 4-hydroxy-2-methylphenyl) butane was used.

 The eight types of heat-sensitive recording paper thus obtained were evaluated by the following methods, and the results are shown in Table 2.

 [Recording density]

A thermal paper color tester (made by Okura Electric, TH-PMD, applied voltage: 16 V, pulse cycle: 0.51) ms) with a pulse width of 0.30 ms, and the recorded density was measured with a Macbeth densitometer (RD-914, manufactured by Macbeth).

 (Moisture resistance of recorded image)

After printing, the thermal recording paper was left in an atmosphere of 90% RH at 40 for 48 hours, and the recording density (D ₂ ) was measured again using a Macbeth densitometer. The recording density remaining rate (%) was determined by the following equation.

Residual recording density = (D ₂ / Dj) x 100

 (Heat resistance of recorded image)

 After leaving the thermal recording paper after printing in an atmosphere of 60 ° C and 10% RH for 48 hours, the recording density (!) Of the printed portion was measured again using a Macbeth densitometer. In addition, the recording density residual ratio (%) was determined by the following equation.

Residual recording density = (D ₃ j) 100

 (Whiteness)

 The whiteness of the thermal recording paper before printing was measured with a Hunter whiteness meter.

 (Capri coloring)

After leaving the thermosensitive recording paper at 40 and 90% RH in an atmosphere of 60% and 10% RH for 48 hours, use a Macbeth densitometer to caprite the blank paper. The color density was measured. Table 2 shows the Capri color density when processed in an atmosphere of 40 ° C and 90% RH as F i, and when processed in an atmosphere of 60 ° C and 10% RH. Capri color density of the display as F _2.

 (Waste adhesion)

 Using a thermal paper color tester (manufactured by Okura Electric, TH-PMD type, applied voltage: 16 V, pulse cycle: 0.51 ms). Thermal recording of A4 size under the condition of pulse width 0.3 Oms After 100% printing on three sheets of paper, the amount of scum adhering near the heat-sensitive head was observed.

 Evaluation criteria

 A: Almost no scum adheres.

 B: Small amount of scum adhered, but no practical problem.

C: Adhesion of scum is remarkable.

Table 2

■ t Recording Concentration Persistence 77> Re 74

 White

^D l ^D 2 D ₃ Do j ^F l ^F 2 sticking

 A

瞧 -1 1.33 1.10 1.06 83 80 85 0.10 U.11 A-2 1.33 1.12 1.08 84 81 η in 012 A Π Π-3 1.30 1.13 1.11 87 85 85 0.10 0.12 A -4 1.28 1.14 1.10 89 86 83 0.13 0.14 A -5 1.32 1.07 1.03 81 78 84 0.11 0.12 B Nada -6 1.34 1.10 1.06 82 79 80 0.13 0.14 A 鑭 HT 1.32 1.10 1.06 83 80 86 0.09 0.10 A H-1 1.27 0.80 0.68 63 54 84 0.08 0.10 C

As is clear from the results in Table 2, the heat-sensitive recording material of the present invention was excellent in storage stability of the recorded image, and hardly caused any adhesion of force due to the improvement in storage stability.

Claims

48 Claims

 1 (a) support, and

 (b) a heat-sensitive recording layer provided on the support and containing a colorless or pale-colored basic dye and a colorant capable of forming a color when contacted with the dye when heated.

Wherein the heat-sensitive recording layer comprises a 2,2′-methylenebis (4,6-di-teri-butylphenyl) phosphate represented by the following general formula (1), an alkali metal salt thereof, A heat-sensitive recording material comprising at least one phosphate compound selected from an ammonium salt and a polyvalent metal salt.

 [Wherein, R represents a terbutyl group. ]

 2 Phosphate compound is 2,2'-methylenebis

2. The heat-sensitive recording material according to claim 1, which is (4,6-di-tert-butylphenyl) phosphate and an alkali metal salt thereof.

3 If the alkali metal salt is sodium or potassium salt The thermal recording medium according to claim 2, wherein the thermal recording medium is 49.

 2. The thermosensitive recording material according to claim 1, wherein the phosphate compound is a polyvalent metal salt of 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphate.

 5. The thermal recording medium according to claim 4, wherein the polyvalent metal salt is a magnesium salt, a calcium salt, a barium salt, a zinc salt or an aluminum salt.

 6. The thermosensitive recording material according to claim 4, wherein the polyvalent metal salt is used in the form of a mixture of at least two kinds of polyvalent metal salts.

 7. The heat-sensitive recording material according to claim 1, wherein the phosphorous compound is used in an amount of about 1 to 300 parts by weight based on 100 parts by weight of the color former.

 8. The heat-sensitive recording material according to claim 1, wherein the heat-sensitive recording layer further contains at least one kind of a heat-fusible substance.

 The heat-fusible substance is 1,2-bis (3-methylphenoxy) ethane, 1,2-bis (phenoxy) ethane,

(2-methylbenzyloxy) -1- (4-methoxyphenoxy) ethane, dibenzyl oxalate, dioxalate

(4-methylbenzyl) ester, oxalic acid di- (4-cyclobenzyl) ester, p-benzylbifurnil, p-

The group consisting of (4-tolyloxy) biphenyl and 1,5-bis (4-1-methoxyphenoxy) -13-oxa-pentane 9. The thermosensitive recording medium according to claim 8, wherein at least one kind is selected from the group consisting of:

 9. The heat-sensitive recording material according to claim 8, wherein the heat-fusible substance is used in an amount of about 50 to 100 parts by weight based on 100 parts by weight of the basic dye.

 11. The thermosensitive recording medium according to claim 1, wherein the thermosensitive recording layer further contains at least one kind of alkaline pigment.

 12. The thermosensitive recording material according to claim 11, wherein the pigment is calcium carbonate, magnesium carbonate, calcium silicate, or magnesium silicate.

 13. The thermosensitive recording medium according to claim 12, wherein the pigment is calcium carbonate or magnesium carbonate.

 14. The thermosensitive recording medium according to claim 13, wherein the alkaline pigment is calcium carbonate.

 The thermal recording medium according to claim 11, wherein the alkaline pigment is used in an amount of about 1 to 30% by weight based on the total solid content of the thermal recording layer.