Thermally recording medium, method for producing thermally recording medium, and medical article comprising the thermally recording medium

Abstract

A thermally recording medium includes a support and a thermally recording layer on the support. The thermally recording layer includes a compound represented by the following general formula (I) and 1,3-diphenylurea: where, in the formula, each of R1 to R3 independently represents a hydrogen atom, a halogen atom, a C1 to C6 alkyl group, a C1 to C6 alkoxy group, or a C1 to C6 fluoroalkyl group.

Description

THERMALLY RECORDING MEDIUM, METHOD FOR PRODUCING THERMALLY RECORDING MEDIUM, AND MEDICAL ARTICLE COMPRISING THE THERMALLY RECORDING MEDIUM

[0001] The present invention relates to a thermally recording medium, a method for producing the thermally recording medium, and a medical article.

[0002] With a thermally recording medium, it is possible to record quickly, easily, and at low cost with relatively simple equipment, so that this may be used widely, for example, in the POS field for a fresh food, a boxed lunch, a prepared food, and the like; in the photocopying field for a book, a document, and the like; in the communication field such as a facsimile; in the issuing machine field for a ticket, a receipt, a voucher, and the like; in the aviation field for an airport baggage tag and the like; and in the medical field for a pill case, a pill bottle, and the like.

[0003] The thermally recording medium contains an electron-donating dye (hereinafter sometimes referred to as a leuco dye) and an electron-accepting developer (hereinafter sometimes referred to as a developer). There are a phenol type developer having a phenol skeleton, such as 4,4'-isopropylidenediphenol, and a developer not having a phenol skeleton (hereinafter sometimes referred to as "non-phenol type developer"). Among these, the use of the phenol type developer is of concern because this may fall into the category of an endocrine disruptor. Therefore, from the viewpoint of environmental and health considerations, the thermally recording medium using a non-phenol type developer is being studied.

[0004] As for the thermally recording medium using the non-phenol type developer, it is proposed the thermally recording medium whose coloring properties, among others, are enhanced by using, for example, a N-phenylureido-phenyl-benzenesulfonamide as the non-phenol type developer (see, for example, PTL 1 and PTL 2).

[0005] Also, the thermally recording medium has been proposed in which in addition to N-phenylureido-phenyl-benzenesulfonamide, a diphenylsulfone-crosslinked compound having a specific structure and a urea urethane compound having a specific structure are used together as the developer (see, for example, PTL 3).

[0006] Workers and others working in a hospital and other medical facilities generally protect their skin with a skin protectant such as a hand cream, a hand lotion, and a hand sanitizer after disinfecting their hands with an alcohol. When the thermally recording medium containing N-phenylureido-phenyl-benzenesulfonamide in the thermally recording layer is used for a label on a medical container such as a pill bottle used in a hospital and so forth, like in the case of a conventional thermally recording medium, there is a problem in that the printed image on the label fades when the thermally recording medium comes into contact with a skin protectant applied to the hands of those workers and others, even if the coloring sensitivity thereof is good.

[0007] An object of an aspect of the present invention is to provide a thermally recording medium having an excellent coloring sensitivity as well as an excellent image preservation of a printed area against a skin protectant, an oil, and heat.

[0008] A thermally recording medium according to an aspect of the present invention includes a support, and a thermally recording layer on the support. The thermally recording layer comprises a compound represented by the following general formula (I) and 1,3-diphenylurea: where, in the formula, each of R1to R3independently represents a hydrogen atom, a halogen atom, a C1 to C6 alkyl group, a C1 to C6 alkoxy group, or a C1 to C6 fluoroalkyl group.

[0009] According to an aspect of the present invention, it is possible to provide a thermally recording medium having an excellent coloring sensitivity as well as an excellent image preservation of the printed area against a skin protectant, an oil, and heat.

[0010] Fig. 1 is a cross-sectional view of one example of a thermally recording medium according to one embodiment.Fig. 2 is an example schematic diagram of an article having the thermally recording medium according to one embodiment.

[0011] Hereinafter, details of embodiments according to the present invention will be described. The embodiments are not restricted by the following description, and may be modified as appropriate as far as such modification will not depart from the gist of the present invention. In this specification, "to" indicating a numerical value range means that the numerical values listed before and after this word include the lower and upper limits thereof, unless otherwise specifically mentioned.

[0012] <Thermally Recording Medium> The thermally recording medium in one embodiment has a support and a thermally recording layer on the support, and may have other layers as needed.

[0013] The inventors of the present applied invention noticed that in the thermally recording medium having the support and the thermally recording layer, when the thermally recording layer uses N-phenylureido-phenyl-benzenesulfonamide as the non-phenol type developer, it is difficult to be used in the medical field and the like because it is low in a durability to a skin protectant and an oil resistance. After the inventors of the present applied invention carefully examined, the inventors studied the concurrent use of N-phenylureido-phenyl-benzenesulfonamide and 1,3-diphenylurea as the non-phenol type developer in the thermally recording layer. In this way, the inventors have found that it is possible to enhance the durability to a skin protectant, the oil resistance, and the heat resistance when the thermally recording layer does not contain the phenol type developer, which might fall into the category of an endocrine disruptor. As a result, the inventors of the present applied invention found that the thermally recording medium had an excellent image preservation of the printed area against a skin protectant, an oil, and heat, as well as an excellent coloring sensitivity without using a phenol type developer.

[0014] The skin protectant is a substance that protects or relieves a skin from an irritating ingredient such as an alcohol, a soap, a surfactant, and other irritants; here, the skin protectant may be a composition containing this substance. The skin protectant may include, for example, a substance that prevents a fat from being excessively removed by an alcohol, a soap, a surface-active agent, or the like by providing a fat to a skin, a skin substance that protects a skin from a lipolytic substance, and a moisture retention agent that prevents a skin from drying. Illustrative examples of the skin protectant include, glycerin, glucomannan, maltodextrin, kaolin, a fatty acid ester, a fatty acid alkylolamide, isopropanolamide laurate, a coconut fatty acid diethanolamide, monoethanolamide stearate, monoethanolamide myristate, monoethanolamide oleate, monoethanolamide undecylate, a coconut palm oil, a palm oil, a castor oil, a sesame oil, a soybean oil, a sunflower seed oil, a tallow, a kamille extract, a pine and oak extract, a seaweed extract, sodium lactate, glycerin, propylene glycol, butanediol, hexylene glycol, a honey, a invert sugar solution, a sorbitol solution, silicone, a 2-pyrrolidone-5-carboxylic acid alkali salt, a polysaccharide, polyethylene glycol, and a low-molecular weight polyglyceride. Specifically, illustrative examples of the skin protectant include a hand cream, a hand lotion, and a hand sanitizer. The form of the skin protectant is not particularly restricted; and it may be, for example, in the form of powder, liquid, gel, solid, or the like.

[0015] (Thermally Recording Layer) The thermally recording layer formed in the thermally recording medium according to one embodiment contains a leuco dye and a developer, in which as the developer, it contains non-phenol type developers including at least one specific urea compound and 1,3-diphenylurea.

[0016] (Leuco Dye) There is no particular restriction in the leuco dye; this may be chosen as appropriate from those used for the thermally recording medium in accordance with the purpose thereof. Preferable examples thereof include leuco dye compounds such as triphenylmethane, fluoran, phenothiazine, auramine, spiropyran, and indolinophthalide.

[0017] There is no particular restriction in the leuco dye, so that they may be chosen as appropriate in accordance with the purpose thereof. Illustrative examples thereof include 3,3-bis(p-dimethylaminophenyl)-phthalide, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (different name: crystal violet lactone), 3,3-bis(p-dimethylaminophenyl)-6-diethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)-6-chlorophthalide, 3,3-bis(p-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6-chlorofluoran, 3-dimethylamino-5,7-dimethylfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7-methylfluoran, 3-diethylamino-7,8-benzofluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-(N-p-tolyl-N-ethylamino)-6-methyl-7-anilinofluoran, 2-{N-(3'-trifluoromethylphenyl)amino}-6-diethylaminofluoran, 2-{3,6-bis(diethylamino)-9-(o-chloroanilino)xanthylbenzoic acid lactam}, 3-diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran, 3-diethylamino-7-(o-chloroanilino)fluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-di-n-butylamino-7-o-chloroanilino)fluoran, 3-N-methyl-N,n-amylamino-6-methyl-7-anilinofluoran, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-(N,N-diethylamino)-5-methyl-7-(N,N-dibenzylamino)fluoran, benzoyl leucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-3'-methoxy-benzoindolino-spiropyran, 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)phthalide, 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-nitrophenyl)phthalide, 3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl)phthalide, 3-(2'-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5'-methylphenyl)phthalide, 3-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl-7-anilinofluoran, 3-N-ethyl-N-(2-ethoxypropyl)amino-6-methyl-7-anilinofluoran, 3-N-methyl-N-isobutyl-6-methyl-7-anilinofluoran, 3-morpholino-7-(N-propyl)-trifluoromethylanilino)fluoran, 3-pyrrolidino-7-trifluoromethylanilinofluoran, 3-diethylamino-5-chloro-7-(N-benzyl-trifluoromethylanilino)fluoran, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluoran, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluoran, 3-(N-ethyl-p-toluidino)-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-(o-(methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-piperidinofluoran, 2-chloro-3-(N-methyltoluidino)-7-(p-n-butylanilino)fluoran, 3-di-n-butylamino-6-methyl-7-anilinofluoran, 3,6-bis(dimethylamino)fluorenspiro(9,3')-6'-dimethylaminophthalide, 3-(N-benzyl-N-cyclohexylamino)-5,6-benzo-7-α-naphthylamino-4'-bromofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-diethylamino-6-methyl-7-mesitidino-4',5'-benzofluoran, 3-N-methyl-N-isopropyl-6-methyl-7-anilinofluoran, 3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(2',4'-dimethylanilino)fluoran, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluoran, 3-pyrrolidino-7-trifluoromethylanilinofluoran, 3-diethylamino-5-chloro-7-(N-benzyl-trifluoromethylanilino)fluoran, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluoran, 3-diethylamino-5-chloro-(α-phenylethylamino)fluoran, 3-(N-ethyl-p-toluidino)-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-(o-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-piperidinofluoran, 2-chloro-3-(N-methyltoluidino)-7-(p-N-butylamino)fluoran, 3,6-bis(dimethylamino)fluorenspiro(9,3')-6'-dimethylaminophthalide, 3-(N-benzyl-N-cyclohexylamino)-5,6-benzo-7-α-naphthylamino-4'-bromofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-N-ethyl-N-(-2-ethoxypropyl)amino-6-methyl-7-anilinofluoran, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-mesitidino-4',5'-benzofluoran, 3-p-dimethylaminophenyl)-3-{1,1-bis(p-dimethylaminophenyl)ethylene-2-yl}phthalide, 3-(p-dimethylaminophenyl)-3-{1,1-bis(p-dimethylaminophenyl)ethylene-2-yl}-6-dimethylaminophthalide, 3-(p-dimethylaminophenyl)-3-(1-p-dimethylaminophenyl-1-phenylethylene-2-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(1-p-dimethylaminophenyl-1-p-chlorophenylethylene-2-yl)-6-dimethylaminophthalide, 3-(4'-dimethylamino-2'-methoxy)-3-(1"-p-dimethylaminophenyl-1"-p-chlorophenyl-1",3"-butadiene-4"-yl)benzophthalide, 3-(4'-dimethylamino-2'-benzyloxy)-3-(1"-p-dimethylaminophenyl-1"-phenyl-1",3"-butadiene-4"-yl)benzophthalide, 3-dimethylamino-6-dimethylamino-fluoren-9-spiro-3'-(6'-dimethylamino)phthalide, 3,3-bis(2-(p-dimethylaminophenyl)-2-p-methoxyphenyl)ethenyl)-4,5,6,7-tetrachlorophthalide, 3-bis{1,1-bis(4-pyrrolidinophenyl)ethylene-2-yl}-5,6-dichloro-4,7-dibromophthalide, bis(p-dimethylaminostyryl)-1-naphthalenesulfonylmethane, and bis(p-dimethylaminostyryl)-1-p-tolylsulfonylmethane. These may be used singly or in a combination of two or more of them.

[0018] The mass ratio of the leuco dye relative to 100% by mass of the total mass of the thermally recording layer may be in the range of 3 to 30% by mass.

[0019] (Developer) The developer included in the thermally recording layer of the thermally recording medium according to one embodiment is a non-phenol type developer. The non-phenol type means the type not having a phenol skeleton. The thermally recording medium according to one embodiment is excellent in terms of an environmental impact because it includes a non-phenol type developer and does not need to include a phenol type developer, which may fall into the category of an endocrine disruptor.

[0020] The developer includes, as the non-phenol type developer, at least one urea compound that is a compound represented by the following general formula (I), and 1,3-diphenylurea.

[0021] (In the formula, each of R1to R3independently represents a hydrogen atom, a halogen atom, a linear C1 to C6 alkyl group, a C1 to C6 alkoxy group, and a C1 to C6 fluoroalkyl group.)

[0022] In one embodiment, the urea compound represented by the above general formula (I) preferably includes a compound represented by the following formula (1). Formula (1) below is a compound in which R1, R2, and R3in the general formula (I) above are all hydrogen atoms.

[0023]

[0024] In one embodiment, it is preferable that the further non-phenol type developer in the thermally recording layer includes a developer represented by the following general formula (II).

[0025] (In the formula, each of R1to R5independently represents a hydrogen atom, a halogen atom, a C1 to C6 alkyl group, a linear C1 to C6 alkoxy group, and a linear C1 to C6 fluoroalkyl group.)

[0026] The urea compound represented by the above general formula (II) may include the urea compound represented by the following formula (2).

[0027]

[0028] The content ratio of 1,3-diphenylurea in the thermally recording layer relative to 1 part by mass of the urea compound (NKK) is preferably in the range of 0.01 to 3.00 parts by mass, more preferably in the range of 0.05 to 2.50 parts by mass, still more preferably in the range of 0.05 to 1.50 parts by mass, and most preferably in the range of 0.25 to 0.50 parts by mass.

[0029] In the thermally recording layer, the content ratio of the developer to 1 part by mass of the leuco dye is preferably in the range of 1 to 20 parts by mass, and more preferably in the range of 2 to 10 parts by mass.

[0030] The thermally recording layer may include other non-phenol type developer to the extent that it does not interfere with the effect of the thermally recording medium according to one embodiment. The non-phenol type developer is less in its type than the phenol type developer. Illustrative examples of the other non-phenol type developer include compounds represented by the following general formula (III), compounds represented by the following general formula (IV), compounds represented by the following general formula (V), compounds represented by the following general formula (VI), compounds represented by the following general formula (VII), compounds represented by the following general formula (VIII), compounds represented by the following general formula (IX), and compounds represented by the following general formula (X).

[0031] (In the formula, R1represents an unsubstituted or a substituted phenyl, naphthyl, or C1to C20alkyl. X represents a -C=NH- group, a -CS- group, or a -CO- group. A represents an unsubstituted or a substituted phenylene, naphthylene, or C1to C12alkylene, or an unsubstituted or a substituted heterocyclic group. B represents a bonding group of -O-SO2-, -SO2-O-, -NH-SO2-, -SO2-NH-, -S-SO2-, -O-CO-, -O-CO-NH-, -NH-CO-, -NH-CO-O-, -S-CO-NH-, -S-CS-NH-, -CO-NH-SO2-, -O-CO-NH-SO2-, -NH=CH-, -CO-NH-CO-, -S-, -CO-, -O-, -SO2-NH-CO-, -O-CO-O-, or -O-PO-(OR2)2. R2represents an unsubstituted or a substituted aryl or benzyl or C1to C20alkyl, and when B is not the -O-SO2- bonding group, R2represents an unsubstituted or a substituted phenyl, naphthyl, or C1to C8alkyl.)

[0032] (In the formula, each of X and Z independently represents an aromatic compound residue, a heterocyclic compound residue, or an aliphatic compound residue; each residue may have a substituent group; and Y0represents one group selected from the group consisting of a tolylene group, a xylylene group, a naphthylene group, a hexamethylene group, and a -φ-CH2-φ- group. Note that -φ- represents a phenylene group.)

[0033] (In the formula, each of X and Y independently represents an aromatic compound residue, a heterocyclic compound residue, or an aliphatic compound residue, in which each residue may have a substituent group.)

[0034] (In the formula, each of X and Y independently represents an aromatic compound residue, a heterocyclic compound residue, or an aliphatic compound residue; α represents a residue having a valency of two or more; n represents an integer of two or more; and each residue may have a substituent group.)

[0035] (In the formula, each of Z and Y independently represents an aromatic compound residue, a heterocyclic compound residue, or an aliphatic compound residue; β represents a residue having a valency of two or more; n represents an integer of two or more; and each residue may have a substituent group.)

[0036] (In the formula, the hydrogen atom in the benzene ring may be substituted by an aromatic, an aliphatic, or a heterocyclic compound residue, in which each residue may have a substituent group. γ represents any one selected from the group consisting of -SO2-, -O-, -(S)n-, -(CH2)n-, -CO-, -CONH-, -O-φ-C(CH3)2-O-φ-O-, -C(CH3)2-φ-C(CH3)2-, -O-φ-O-, -O-φ-φ-O-, and -O-φ-SO2-φ-O-, or none of them is present; and n represents 1 or 2.)

[0037] (In the formula, the hydrogen atom in the benzene ring may be substituted by an aromatic, an aliphatic, or a heterocyclic compound residue, in which each residue may have a substituent group. δ represents any one selected from the group consisting of -SO2-, -O-, -(S)n-, -(CH2)n-, -CO-, -CONH-, -NH-, -CH(COOR1)-, -C(CF3)2-, and -CR2R3-, in which R1, R2, and R3each represent an alkyl group, or none of them is present, and n represents 1 or 2.)

[0038] (In the formula, R represents an alkyl group and n represents an integer of 0 to 3.)

[0039] The non-phenol type developer may be synthesized as appropriate, or a commercially available product thereof may be used. Illustrative examples of the commercially available product thereof include UU (trade name: urea urethane represented by the following formula (2); manufactured by Chemipro Kasei Kaisha, Ltd.), Pergafast 201 (4-methyl-N-[[[3-[[(4-methylphenyl)sulfonyl]oxy]phenyl]amino]carbonyl]benzenesulfonamide; manufactured by BASF SE), and NKK-1304 (N-[2-[[(phenylamino)carbonyl]amino]phenyl]benzenesulfonamide; manufactured by Nippon Soda Co., Ltd.).

[0040]

[0041] There is no particular restriction in the content of the developer, so that this may be chosen as appropriate in accordance with the purpose. The content of the entire non-phenol type developer relative to 1 part by mass of the leuco dye is preferably in the range of 1 to 20 parts by mass, and more preferably in the range of 2 to 10 parts by mass.

[0042] The content ratio of the additional developer may be chosen as appropriate in accordance with the intended purpose as long as the effects of the thermally recording medium according to one embodiment are not impaired. The combined mass of a compound of the formula (I) or the formula (II) and other developer that is not 1,3-diphenylurea relative to 1 part by mass of leuco dye in the thermally coloring layer is preferably less than 2 parts by mass, and more preferably less than 0.5 parts by mass. In one embodiment, it is not allowed to substantially include, in the thermally recording layer, other developer than the compound of the formula (I) or the formula (II), and 1,3-diphenylurea.

[0043] (Other Ingredients) The thermally recording layer may further include other ingredients as needed, such as a thermally meltable substance, a binder resin, an auxiliary additive, a surfactant, a lubricant, and a filler.

[0044] -Thermally Meltable Substance- Illustrative examples of the thermally meltable substance include fatty acids such as stearic acid and behenic acid; fatty acid amides such as stearic acid amide and palmitic acid amide; fatty acid metal salts such as zinc stearate, aluminum stearate, calcium stearate, zinc palmitate, and zinc behenate; p-benzylbiphenyl, terphenyl, triphenylmethane, benzyl p-benzyloxybenzoate, β-benzyloxynaphthalene, β-naphthoic acid phenyl ester, 1-hydroxy-2-naphthoic acid phenyl ester, 1-hydroxy-2-naphthoic acid methyl ester, diphenyl carbonate, dibenzyl terephthalate ester, dimethyl terephthalate ester, 1,4-dimethoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dibenzyloxynaphthalene, 1,2-bis(phenoxy)ethane, 1,2-bis(3-methylphenoxy)ethane, 1,2-bis(4-methylphenoxy)ethane, 1,4-bis(phenoxy)butane, 1,4-bis(phenoxy)-2-butene, 1,2-bis(4-methoxyphenylthio)ethane, dibenzoylmethane, 1,4-bis(phenylthio)butane, 1,4-bis(phenylthio)-2-butene, 1,2-bis(4-methoxyphenylthio)ethane, 1,3-bis(2-vinyloxyethoxy)benzene, 1,4-bis(2-vinyloxyethoxy)benzene, p-(2-vinyloxyethoxy)biphenyl, p-aryloxybiphenyl, p-propagyloxybiphenyl, dibenzoyloxymethane, 1,3-dibenzoyloxypropane, dibenzyl disulfide, 1,1-diphenylethanol, 1,1-diphenylpropanol, p-(benzyloxy)benzyl alcohol, 1,3-diphenoxy-2-propanol, N-octadecylcarbamoyl-p-methoxycarbonylbenzene, N-octadecylcarbamoylbenzene, oxalic acid dibenzyl ester, and 1,5-bis(p-methoxyphenyloxy)-3-oxapentane. These may be used singly or in a combination of two or more of them.

[0045] -Binder Resin- There is no particular restriction in the binder resin, so that it may be chosen as appropriate in accordance with the purpose thereof. Illustrative examples thereof include polyvinyl alcohol, starch, or its derivatives; cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, and ethyl cellulose; water-soluble polymers such as sodium polyacrylate, polyvinyl pyrrolidone, an acrylamide-acrylate ester copolymer, an acrylamide-acrylate ester-methacrylic acid ternary copolymer, an alkali salt of styrene-maleic anhydride copolymer, an alkali salt of isobutylene-maleic anhydride copolymer, polyacrylamide, sodium alginate, gelatin, and casein; emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, a polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, and ethylene-vinyl acetate copolymer; and latexes such as styrene-butadiene copolymer and styrene-butadiene-acrylic copolymer. These may be used singly or in a combination of two or more of them.

[0046] -Auxiliary Additive- Illustrative examples of the auxiliary additive that may be used include various hindered phenol or hindered amine compounds that are electron-accepting but have a relatively low color developing ability. Specifically, illustrative examples thereof include 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 4,4'-butylidenebis(6-tert-butyl-2-methylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 4,4'-thiobis(6-tert-butyl-2-methylphenol), tetrabromobisphenol A, tetrabromobisphenol S, 4,4'-thiobis(2-methylphenol), 4,4'-thiobis(2-chlorophenol), tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, and tetrakis(1,2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate.

[0047] -Surfactant- There is no particular restriction in the surfactant, so that it may be chosen as appropriate in accordance with the purpose thereof. Illustrative examples thereof include an anionic surfactant, a nonionic surfactant, an amphoteric surfactant, and a fluorinated surfactant. These may be used singly or in a combination of two or more of them.

[0048] Illustrative examples of the anionic surfactant include a polyoxyethylene alkyl ether acetate, a dodecylbenzenesulfonate salt, a laurate salt, and a polyoxyethylene alkyl ether sulfate salt. These may be used singly or in a combination of two or more of them.

[0049] Illustrative examples of the nonionic surfactant include an acetylene glycol type surfactant, a polyoxyethylene alkyl ether, a polyoxyethylene alkyl phenyl ether, a polyoxyethylene alkyl ester, and a polyoxyethylene sorbitan fatty acid ester. These may be used singly or in a combination of two or more of them.

[0050] Illustrative examples of the acetylene glycol type surfactant include 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 3,6-dimethyl-4-octyn-3,6-diol, 3,5-dimethyl-1-hexyn-3-diol, and 2,5,8,11-tetramethyl-6-dodecyn-5,8-diol. These may be used singly or in a combination of two or more of them.

[0051] -Lubricant- Illustrative examples of the lubricant include a higher fatty acid or its metal salt, a higher fatty acid amide, a higher fatty acid ester, an animal wax, a vegetable wax, a mineral wax, and a petroleum wax.

[0052] -Filler- Illustrative examples of the filler include inorganic fine powders such as calcium carbonate, silica, zinc oxide, titanium dioxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, kaolin, talc, surface-treated calcium, and surface-treated silica; and organic fine powders such as a urea-formalin resin, styrene-methacrylic acid copolymer, a polystyrene resin, and a vinylidene chloride resin.

[0053] (Method for Producing Thermally Recording Layer) There is no particular restriction in the method for producing the thermally recording layer, so that the thermally recording layer may be formed by a generally known method. To produce the thermally recording layer, for example, a leuco dye, a developer, and other ingredients are pulverized and dispersed by a ball mill, an attritor, a sand mill, or other dispersing machine until the dispersed particle diameter becomes in the range of 0.1 μm to 3 μm, and then the resulting dispersion is mixed with a sensitizer and, as need, a filler to prepare the coating liquid for the thermally recording layer. The thermally recording layer may be formed by applying the coating liquid for the thermally recording layer on the support followed by drying it.

[0054] There is no particular restriction in the application method, so that it may be chosen as appropriate in accordance with the purpose thereof. Illustrative examples of the application method include a blade coating method, a gravure coating method, a gravure offset coating method, a bar coating method, a roll coating method, a knife coating method, an air knife coating method, a comma coating method, a U comma coating method, an AKKU coating method, a smoothing coating method, a micro-gravure coating method, a reverse roll coating method, a 4- or a 5-roll coating method, a dip coating method, a single-layer curtain coating method, a multi-layer simultaneous curtain coating method, a slide coating method, and a die coating method.

[0055] In the production of the thermally recording medium according to one embodiment, from the viewpoint of an economic requirement and an improvement of uniformity of the coat layer, it is preferable to use the method for applying the thermally recording layer and other layers such as a protective layer to be described later by the multi-layer simultaneous curtain method, or the method for forming at least one intermediate layer between the thermally recording layer and the other layer followed by applying them by the multi-layer simultaneous curtain method.

[0056] There is no particular restriction in the attached amount of the thermally recording layer after drying, so that this may be chosen as appropriate in accordance with the purpose thereof. For example, it is preferable in the range of 0.5 g / m2to 20.0 g / m2, and more preferably in the range of 1.0 g / m2to 10.0 g / m2.

[0057] (Other Layers) There is no particular restriction in other layers that are included in the thermally recording medium according to one embodiment, so that this may be chosen as appropriate in accordance with the purpose thereof. Illustrative examples of the other layers that may be used include a protective layer, a back layer, an undercoat layer, an intermediate layer, and an adhesive layer.

[0058] (Protective Layer) A protective layer may be formed above the thermally recording layer. The protective layer may include a binder resin and a crosslinking agent, as well as other ingredients as needed.

[0059] -Binder Resin- There is no particular restriction in the binder resin included in the protective layer, so that this may be chosen as appropriate in accordance with the purpose thereof. Illustrative examples thereof include a water-soluble resin, a water-soluble resin emulsion, a hydrophobic resin, a UV-curable resin, and an electron beam-curable resin.

[0060] Illustrative examples of the water-soluble resin include polyvinyl alcohol, a modified polyvinyl alcohol, starch or a derivative thereof, cellulose derivatives such as methoxycellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, and ethyl cellulose, as well as sodium polyacrylate, polyvinyl pyrrolidone, an acrylamide-acrylate ester copolymer, an acrylamide-acrylate ester-methacrylate ternary copolymer, an alkali salt of styrene-maleic anhydride copolymer, an alkali salt of isobutylene-maleic anhydride copolymer, polyacrylamide, a modified polyacrylamide, methyl vinyl ether-maleic anhydride copolymer, a carboxy-modified polyethylene, polyvinyl alcohol-acrylamide block copolymer, a melamine-formaldehyde resin, a urea-formaldehyde resin, sodium alginate, gelatin, and casein. These may be used singly or in a combination of two or more of them. Among these, a modified polyvinyl alcohol is preferable.

[0061] Illustrative examples of the modified polyvinyl alcohol include diacetone-modified polyvinyl alcohol; acetoacetyl-modified polyvinyl alcohol; and carboxylic acid-modified polyvinyl alcohols such as itaconic acid-modified polyvinyl alcohol and maleic acid-modified polyvinyl alcohol.

[0062] -Crosslinking Agent- There is no particular restriction in the crosslinking agent as far as it can react with a water-soluble resin so as to reduce the solubility thereof in water. This may be chosen as appropriate in accordance with the purpose thereof. Illustrative examples of the crosslinking agent include a glyoxal derivative, a methylol derivative, epichlorohydrin, a polyamide epichlorohydrin, an epoxy compound, an aziridine compound, hydrazine, a hydrazide derivative, an oxazoline derivative, and a carbodiimide derivative. These may be used singly or in a combination of two or more of them. Among these, a polyamide epichlorohydrin is particularly preferable because of its safety in handling and short curing time required for making it water-resistive.

[0063] There is no particular restriction in the content of the polyamide epichlorohydrin, so that this may be chosen as appropriate in accordance with the purpose thereof. The content thereof relative to 100 parts by mass of the binder resin is preferably in the range of 10 to 60 parts by mass, and more preferably in the range of 20 to 50 parts by mass or less.

[0064] A pigment (filler), an auxiliary additive ingredient, and the like may be included as other ingredients in addition to the binder resin and the crosslinking agent.

[0065] Illustrative examples of the pigment used in the protective layer include inorganic pigments such as zinc oxide, calcium carbonate, barium sulfate, titanium dioxide, lithopone, talc, wax stone, kaolin, aluminum hydroxide, and calcined kaolin; and organic pigments such as a crosslinked polystyrene resin, a urea resin, a silicone resin, a crosslinked polymethyl methacrylate resin, and a melamine-formaldehyde resin.

[0066] Illustrative examples of the auxiliary additive ingredient used in the protective layer include a surfactant, a thermally meltable substance, a lubricant, an inhibitor of coloration by pressure, and other auxiliary additive ingredients that have been commonly used from the past.

[0067] There is no particular restriction in the method for producing the protective layer, so that a generally known method may be used.

[0068] There is no particular restriction in the average thickness of the protective layer, so that the thickness may be chosen as appropriate in accordance with the purpose thereof. It is preferably in the range of 0.5 μm to 5 μm, and more preferably in the range of 1 μm to 3 μm.

[0069] (Back Layer) The back layer may be formed, as needed, on the side of the support not having the thermally recording layer. The back layer contains a filler and a binder resin, and may further contain, as needed, other ingredients such as a lubricant and a color pigment.

[0070] For example, inorganic or organic fillers may be used as the filler.

[0071] Illustrative examples of the inorganic filler include a carbonate salt, a silicate salt, a metal oxide, and a sulfate compound.

[0072] Illustrative examples of the organic filler include a silicone resin, cellulose, an epoxy resin, a nylon resin, a phenol resin, a polyurethane resin, a urea resin, a melamine resin, a polyester resin, a polycarbonate resin, a styrene resin, an acrylic resin, a polyethylene resin, a formaldehyde resin, and a polymethyl methacrylate resin.

[0073] There is no particular restriction in the binder resin, so that this may be chosen as appropriate in accordance with the purpose thereof. For example, the same binder resins as those used for the thermally recording layer described before may be used.

[0074] There is no particular restriction in the average thickness of the back layer, so that the thickness may be chosen as appropriate in accordance with the purpose thereof. This is in the range of 0.1 μm to 20 μm, and more preferably in the range of 0.3 μm to 10 μm.

[0075] (Undercoat layer) The undercoat layer may be formed between the support and the thermally recording layer. There is no particular restriction in the undercoat layer, so that this may be chosen as appropriate in accordance with the purpose thereof. It is preferable to include an adhesive resin, a thermoplastic hollow resin particle, and the like, and furthermore, other ingredients as needed.

[0076] The thermoplastic hollow resin particle is the micro hollow particle having a thermoplastic resin shell in which a gas such as air or other gases is included thereby having already been in a foamed state.

[0077] There is no particular restriction in the average particle diameter (mean particle diameter) of the thermoplastic hollow resin particle, so that the average diameter may be chosen as appropriate in accordance with the purpose thereof. This is preferably in the range of 0.2 μm to 20 μm, and more preferably in the range of 2 μm to 5 μm. When the average particle diameter is 0.2 μm or more, the thermoplastic hollow resin particle having a hollow structure may be formed technically, thereby realizing the function as an undercoat layer. When the average particle diameter is 20 μm or less, deterioration in the surface smoothness after application and drying can be suppressed, allowing for uniform application of the thermally recording layer thereby suppressing the application of more than the necessary amount of the coating liquid for the thermally recording layer required to achieve the uniformity. Therefore, it is preferable that the average particle diameter of the thermoplastic hollow resin particle is within the above range, and at the same time, that the particles have the uniform distribution peak of the particle diameter with less variance.

[0078] The average particle diameter of the thermoplastic hollow resin particle is the average value of the particles' outer shape diameters of the thermoplastic hollow resin particles. The average particle diameter refers to the volume-average particle diameter based on the effective diameter. The average particle diameter is the particle diameter (median diameter) when the integrated amount in the particle size distribution becomes 50% on a cumulative volume basis from the smallest particle in the particle size distribution curve obtained by measuring the particle sizes of the thermoplastic hollow resin particles using a laser diffraction and scattering method, a dynamic light scattering method, or the like.

[0079] There is no particular restriction in the hollow ratio of the thermoplastic hollow resin particle, so that this may be chosen as appropriate in accordance with the purpose thereof. This is preferably in the range of 50% to 95%, and more preferably in the range of 80% to 95%. When the hollow ratio is 30% or more, the insulation property is sufficient to suppress the release of thermal energy from a thermal head to the outside of the thermally recording medium through the support, thereby ensuring the sensitivity enhancement effect. The hollow ratio is the ratio between the outer diameter and the inner diameter (diameter of the hollow portion) of the hollow particle, and is expressed by the following formula. Hollow ratio [%] = (Inner diameter of hollow particle / outer diameter of hollow particle) × 100

[0080] The thermoplastic hollow resin particle has a thermoplastic resin shell, as described above. There is no particular restriction in the thermoplastic resin, so that the resin may be chosen as appropriate in accordance with the purpose thereof. Illustrative examples thereof include a styrene-acrylic resin, a polystyrene resin, an acrylic resin, a polyethylene resin, a polypropylene resin, a polyacetal resin, a chlorinated polyether resin, a polyvinyl chloride resin, and a copolymer resin mainly composed of vinylidene chloride and acrylonitrile. Among these, a styrene-acrylic resin and a copolymer resin mainly composed of vinylidene chloride and acrylonitrile are preferable because of their higher hollow ratio, smaller variance in the particle diameter, and suitability for a blade coating.

[0081] There is no particular restriction in the thermoplastic substance, so that this may be chosen as appropriate in accordance with the purpose thereof. Illustrative examples thereof include a phenol-formaldehyde resin, a urea-formaldehyde resin, a melamine-formaldehyde resin, a furane resin, an unsaturated polyester resin formed by addition polymerization, and a crosslinked MMA resin.

[0082] There is no particular restriction in the coating amount of the plastic hollow particle, so that this may be chosen as appropriate in accordance with the purpose thereof. From the viewpoint of sensitivity and maintaining the coating uniformity, the amount per 1 m2of the support is in the range of 1 g to 3 g. When the coating amount is 1 g or more per 1 m2of the support, a sufficient sensitivity may be obtained, and when the coating amount is 3 g or less per 1 m2of the support, the bonding of the layers may be ensured.

[0083] (Intermediate Layer) The intermediate layer may be formed, for example, between the protective layer and the thermally recording layer. The intermediate layer usually includes at least a binder, and each may include an inorganic filler and a surfactant.

[0084] The binder for the intermediate layer(s) may be chosen as appropriate without any restriction in accordance with the purpose thereof, and the same binder in the intermediate layers or different binders in the layers may be used. Illustrative examples of the binder that may be used for the intermediate layer include polyvinyl alcohol, modified polyvinyl alcohol, starch, and a derivative thereof; a cellulose derivative, polyvinylpyrrolidone, polyethyleneimine, sodium alginate, gelatin, and casein; and an acrylic binder.

[0085] A hydrophobic resin may also be used as the binder for the intermediate layer. The hydrophobic resin that may be used as the binder for the intermediate layer may include those provided as an emulsion and as a water-soluble form. Illustrative examples of the hydrophobic resin that may be used as the binder for the intermediate layer include a urethane resin, an epoxy resin, a vinyl acetate (co)polymer, a vinylidene chloride (co)polymer, a vinyl chloride (co)polymer, and styrene-butadiene copolymer. As for the especially preferable binder for the intermediate layer, polyvinyl alcohol or modified polyvinyl alcohol may be mentioned.

[0086] The thickness of the intermediate layer is preferably in the range of 0.2 μm to 10 μm, and more preferably in the range of 0.5 μm to 5 μm. When a plurality of the intermediate layers are used, the total thickness of all the intermediate layers after drying is preferably 5 μm or less.

[0087] (Adhesive Layer) The adhesive layer may be formed, for example, on the surface of the support opposite the surface where the protective layer of the thermally recording layer is formed.

[0088] There is no particular restriction in the material to be used to form the adhesive layer, so that this may be chosen as appropriate in accordance with the purpose thereof. Illustrative examples of the adhesive layer include a urea resin, a melamine resin, a phenol resin, an epoxy resin, a vinyl acetate resin, a vinyl acetate-acrylic copolymer, an ethylene-vinyl acetate copolymer, an acrylic resin, a polyvinyl ether resin, a vinyl chloride-vinyl acetate copolymer, a polystyrene resin, a polyester resin, a polyurethane resin, a polyamide resin, a chlorinated polyolefin resin, a polyvinyl butyral resin, an acrylate ester copolymer, a methacrylate ester copolymer, a natural rubber, a cyanoacrylate resin, and a silicone resin. These may be used singly or in a combination of two or more of them.

[0089] In the usual use of the thermally recording medium according to one embodiment, the adhesive layer serves to attach the thermally recording medium, for example, to a food package. Therefore, the thermally recording medium according to one embodiment can have an adhesive surface attached to the support or to the back layer, making it a useful thermally recording medium for providing a label that has the adhesive layer. The adhesive layer may be attached with a peelable liner, which may be removed prior to the final attachment to a labeled product. The adhesive layer may have an antistatic property.

[0090] The method for forming the viscous layer is not particularly restricted. General coating and laminating methods may be used to form the viscous layer.

[0091] There is no particular restriction in the average thickness of the adhesive layer, so that this may be chosen as appropriate in accordance with the purpose thereof; this may be in the range of 0.1 μm to 20 μm.

[0092] There is no particular restriction in the method for producing the thermally recording medium according to one embodiment, so that this may be produced by a generally known method. In the method for producing the thermally recording medium according to one embodiment, from the viewpoint of an economic requirement and an improvement of uniformity of the coat layer, it is preferable to use the method for applying the thermally recording layer and other layers such as the protective layer by the multi-layer simultaneous curtain method, or the method for forming at least one intermediate layer between the thermally recording layer and the other layer followed by applying them by the multi-layer simultaneous curtain method.

[0093] As described above, the thermally recording medium according to one embodiment has the support and the thermally recording layer, which includes the urea compound represented by the above general formula (I) and 1,3-diphenylurea. This allows the thermally recording medium according to one embodiment to make the thermally recording layer more durable to a skin protectant, an oil, and heat. Accordingly, the thermally recording medium according to one embodiment can have an excellent image preservation of the printed area against a skin protectant, an oil, and heat, as well as can have an excellent coloring sensitivity.

[0094] The thermally recording medium according to one embodiment may further include as the non-phenol type developer a developer represented by the above general formula (II) in the thermally recording layer. This allows the thermally recording medium according to one embodiment to further enhance the durability of the thermally recording layer against a skin protectant and an oil, resulting in further enhancement of the image preservation in the printed area against a skin protectant and an oil.

[0095] In the thermally recording medium according to one embodiment, the content of 1,3-diphenylurea relative to 1 part by mass of the compound represented by the general formula (I) may be made in the range of 0.01 to 3.00 parts by mass. This allows the thermally recording medium according to one embodiment to further enhance the durability of the thermally recording layer against a skin protectant and an oil, resulting in further enhancement of the image preservation in the printed area against a skin protectant and an oil.

[0096] The thermally recording medium according to one embodiment may have a back layer on the opposite side of the support having the thermally recording layer. This allows the thermally recording medium according to one embodiment to enhance the strength as well as the shape stability.

[0097] The thermally recording medium according to one embodiment may have the undercoat layer between the support and the thermally recording layer. This allows the thermally recording medium according to one embodiment to exhibit a thermal insulating property, which suppresses the release of thermal energy transferred to the support to the outside of the thermally recording medium through the support, thereby realizing the enhancement of the sensitivity thereof.

[0098] The thermally recording medium according to one embodiment may include the hollow particles in the undercoat layer. This makes it easier to ensure that the thermally recording medium according to one embodiment exhibits the thermal insulating property, which suppresses the release of thermal energy transferred to the support to the outside of the thermally recording medium through the support, thereby realizing enhancement of the sensitivity thereof.

[0099] The thermally recording medium according to one embodiment may have the protective layer on the thermally recording layer. This allows the thermally recording medium according to one embodiment to protect the thermally recording layer from the outside, thereby realizing enhancement of the durability of the thermally recording layer.

[0100] There is no particular restriction in the form of the thermally recording medium according to one embodiment, so that this may be chosen as appropriate in accordance with the purpose thereof. For example, the thermally recording medium according to one embodiment may be used as a label as it is, or it may have, on the protective layer or on the support, a layer having information such as a letter, a mark, a picture, and a two-dimensional code such as a bar code or a QR code (registered trademark) printed thereon. The thermally recording medium according to one embodiment may also be provided with the adhesive layer on the opposite side of the support from the side on which the thermally recording layer is formed.

[0101] There is no particular restriction in the form of the thermally recording medium according to one embodiment, so that the form may be chosen as appropriate in accordance with the purpose thereof. The form of the thermally recording medium according to one embodiment includes, for example, a label, a sheet, and a roll.

[0102] The followings are specific examples of aspects of the thermally recording medium according to one embodiment.

[0103] (Thermally Recording Label) The thermally recording medium according to one aspect is a thermally recording label in which the support has the adhesive layer formed on the side opposite the side having the thermally recording layer, and a release paper formed on the adhesive layer, and other layers as needed. The adhesive layer may be coated on the whole label or only on a portion thereof.

[0104] (Linerless Thermally Recording Medium) A linerless thermally recording medium may be used in an aspect having a release layer (a type with a release layer) or without having a release layer (a type without a release layer).

[0105] (Type with Release Layer) The thermally recording medium according to one aspect is the linerless thermally recording medium in which the support has the release layer on the top layer of the side having the thermally recording layer (front side) and further has the adhesive layer on the side opposite the side having the thermally recording layer (back side). Other layers may be formed as needed.

[0106] It is preferable that the release layer is the layer formed from a material that has a good release property from the adhesive layer, and it is especially preferable that the layer contains silicone.

[0107] The linerless thermally recording medium according to one aspect may be handled as a roll form that is rolled such that the adhesive layer overlaps on the release layer.

[0108] (Type without Release Layer) The thermally recording medium according to one aspect is the linerless thermally recording medium in which the support further has an adhesive layer on the opposite side of the surface having the thermally recording layer, and the adhesive layer is the thermally adhesive layer that exhibits an adhesiveness upon heating, and may further have other layers as needed.

[0109] The thermally adhesive layer contains a thermoplastic resin and a thermally meltable substance, and may further contain a tackifier as needed.

[0110] The thermoplastic resin provides an adhesion force and a bonding force. The thermally meltable substance is solid at room temperature and does not impart plasticity to the resin, but it melts upon heating, causing the resin to swell or soften, and thereby exhibiting the adhesiveness. The tackifier works to enhance the adhesiveness. The thermoplastic resin, the thermally meltable substance, and the tackifier may be a thermoplastic resin, a thermally meltable substance, and a tackifier, which are generally used.

[0111] (Heat-sensitive Magnetic Recording Paper) The thermally recording medium according to one aspect is a heat-sensitive magnetic recording paper in which the support has a magnetic recording layer on the opposite side of the surface having the thermally recording layer, and further has other layers as needed.

[0112] The magnetic recording layer may be formed by the method in which iron oxide, barium ferrite, or the like, as well as a vinyl chloride resin, a urethane resin, a nylon resin, or the like are applied onto the support, or by the method in which the magnetic recording layer is formed by vapor deposition or sputtering without using a resin. The magnetic recording layer is preferably formed on the side of the support opposite the side having the thermally recording layer, but may be formed between the support and the thermally recording layer as well. The magnetic recording layer may be formed at least partially on the thermally recording layer.

[0113] (Recording Method) There is no particular restriction in the recording method using the thermally recording medium according to one embodiment, so that the method may be chosen as appropriate in accordance with the purpose thereof. For example, the method using a thermal head, a laser, or the like may be used.

[0114] There is no particular restriction in the shape, structure, size, and the like of the thermal head, so that these may be chosen as appropriate in accordance with the purpose thereof.

[0115] There is no particular restriction in the type of the laser, so that this may be chosen as appropriate in accordance with the purpose thereof. For example, a CO2laser, a semiconductor laser, or the like, with a wavelength of 9.3 μm to 10.6 μm, may be used.

[0116] (Use) The thermally recording medium according to one embodiment has high coloring sensitivity and image density, and does not use a phenol type developer, and has an excellent durability against a skin protectant such as a hand cream, an oil, and heat, so that this may be used widely. Illustrative examples of the use thereof include those in the POS field for a fresh food, a boxed lunch, a prepared food, and the like; in the photocopying field for a book, a document, and the like; in the communication field such as a facsimile; in the issuing machine field for a ticket a receipt, a voucher, and the like; in the aviation field for an airport baggage tag and the like; and in the medical field for a drug container such as a pill case and a pill bottle. In particular, the thermally recording medium according to one embodiment may be suitably used in the medical field because this is excellent in skin protectant.

[0117] (Article) An article according to one embodiment has the thermally recording medium according to one embodiment. As for the thermally recording medium, the thermally recording medium according to one embodiment may be suitably used. Having the thermally recording medium according to one embodiment means the state in which the thermally recording medium according to one embodiment is affixed, attached, or the like. Fig. 1 is a cross-sectional view of one example of the thermally recording medium according to one embodiment. As illustrated in Fig. 1, a thermally recording medium 1 according to one embodiment has an adhesive layer 11, a back layer 12, a support 13, an undercoat layer 14, a thermally recording layer 15, an intermediate layer 16, and a protective layer 17 in this order. Fig. 2 is a schematic diagram of one example of the article having the thermally recording medium according to one example.

[0118] There is no particular restriction in the article according to one embodiment as far as the article includes the thermally recording medium according to one embodiment, so that the article may be chosen as appropriate in accordance with the purpose thereof. Illustrative examples of the article according to one embodiment include a packing material, a packaging material, and a wrapping paper. More specifically, illustrative examples thereof include packaging materials for a fresh food, a boxed lunch, a prepared food, a book, a document, and the like as well as the medical articles such as a pill case and a pill bottle. In particular, the thermally recording medium according to one embodiment has an excellent durability against a skin protectant, so that this may be suitably used for a medical article used in the medical field.

[0119] As can be seen above, embodiments have been described as examples; thus, the present invention is not limited by the embodiments described above. The above embodiments may be carried out in a variety of other forms; thus, various combinations, omission, substitution, change, and the like may be made as far as they do not depart from the gist of the present invention. These embodiments and variations thereof are included in the scope and gist of the present invention as well as in the inventions stipulated in the scope of the claims and the equivalents thereof.

[0120] The following Examples and Comparative Examples are described to further specifically illustrate the embodiments; however, the embodiments are not limited by these Examples and Comparative Examples.

[0121] <Preparation of Coating Liquids> (Preparation of Coating Liquid for Undercoat Layer) The coating liquid for the undercoat layer was prepared by mixing and stirring the following composition. - Hollow particles (copolymer of acrylonitrile, methacrylonitrile, and isobonyl methacrylate; hollow ratio of 90%; volume-average particle diameter of 4.4 μm; solid concentration of 33% by mass): 20 parts by mass - Styrene / butadiene copolymer latex (solid concentration of 47.5% by mass): 20 parts by mass - Aqueous solution of 10% by mass of polyvinyl alcohol (PVA117; manufactured by Kuraray Co., Ltd.,): 20 parts by mass - Ion-exchanged water: 40 parts by mass

[0122] (Preparation of Coating Liquid for Thermally Recording Layer) The leuco dye dispersion liquid [Liquid A], the main developer dispersion liquid [Liquid B], the auxiliary developer dispersion liquids [Liquid C1] to [Liquid C4], and the sensitizer dispersion liquid [Liquid D], each having the following composition, were dispersed and prepared respectively using a sand grinder such that the volume-average particle diameter became 0.5 μm in [Liquid A], 1.0 μm in [Liquid B], 1.0 μm in [Liquid C1] to [Liquid C4]; and 1.0 μm in [Liquid D].

[0123] Next, the coating liquid for the thermally recording layer was prepared by mixing and stirring predetermined amounts of [Liquid A], [Liquid B], [Liquid C1] to [Liquid C4], [Liquid D], and an aqueous solution of 10% by mass of itaconic acid-modified polyvinyl alcohol. The contents of [Liquid A], [Liquid B], [Liquid C1] to [Liquid C4], [Liquid D], and the aqueous solution of 10% by mass of the itaconic acid-modified polyvinyl alcohol in each of Examples and Comparative Examples are listed in Table 1.

[0124] (Composition of [Liquid A] (Leuco Dye Dispersion Liquid)) - Leuco dye (3-dibutylamino-6-methyl-7-anilinofluoran): 20 parts by mass - Aqueous solution of 10% parts by mass of itaconic acid-modified polyvinyl alcohol (25-88KL; manufactured by Kuraray Co., Ltd.): 40 parts by mass - Surfactant (Newcol 290; manufactured by Nippon Nyukazai Co., Ltd.; solid concentration of 100% by mass): 0.2 parts by mass - Ion-exchanged water: 40 parts by mass

[0125] (Composition of [Liquid B] (Main Developer Dispersion Liquid)) - N-[2-(3-phenylureido)phenyl]benzenesulfonamide (NKK-1304; manufactured by Nippon Soda Co., Ltd.): 20 parts by mass - Aqueous solution of 10% parts by mass of itaconic acid-modified polyvinyl alcohol (25-88KL; manufactured by Kuraray Co., Ltd.): 20 parts by mass - Amorphous silica (Mizukasil P527; manufactured by Mizusawa Industrial Chemicals, Ltd.): 15 parts by mass - Surfactant (PD-001; manufactured by Nissin Chemical Co., Ltd.; solid concentration of 100% by mass): 0.2 parts by mass - Ion-exchanged water: 65 parts by mass

[0126] (Composition of [liquid C1] (Auxiliary Developer Dispersion Liquid)) - 1,3-Diphenylurea: 20 parts by mass - Aqueous solution of 10% parts by mass of sulfone-modified polyvinyl alcohol (GOHSERAN L-3266; manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.): 20 parts by mass - Surfactant (PD-001; manufactured by Nissin Chemical Co., Ltd.; solid concentration of 100% by mass): 0.2 parts by mass - Ion-exchanged water: 35 parts by mass

[0127] (Composition of [Liquid C2] (Auxiliary Developer Dispersion Liquid)) - Urea compound represented by the chemical formula (II) (TG-MD; manufactured by Nippon Kayaku Co., Ltd.): 20 parts by mass - Aqueous solution of 10% by mass of sulfone-modified polyvinyl alcohol (GOHSERAN L-3266; manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.): 20 parts by mass - Surfactant (PD-001; manufactured by Nissin Chemical Co., Ltd.; solid concentration of 100% by mass): 0.2 parts by mass - Ion-exchanged water: 35 parts by mass

[0128] (Composition of [Liquid C3] (Auxiliary Developer Dispersion Liquid)) - Urea compound represented by the chemical formula (II) (TG-MD; manufactured by Nippon Kayaku Co., Ltd.): 20 parts by mass - Aqueous solution of 10% parts by mass of itaconic acid-modified polyvinyl alcohol (25-88KL; manufactured by Kuraray Co., Ltd.): 20 parts by mass - Amorphous silica (Mizukasil P527; manufactured by Mizusawa Industrial Chemicals, Ltd.): 15 parts by mass - Surfactant (PD-001; manufactured by Nissin Chemical Co., Ltd.; solid concentration of 100% by mass): 0.2 parts by mass - Ion-exchanged water: 65 parts by mass

[0129] (Composition of [liquid C4] (Auxiliary Developer Dispersion Liquid)) - Urea-urethane compound (UU; manufactured by Chemipro Kasei Kaisha, Ltd.): 20 parts by mass - Aqueous solution of 10% parts by mass of itaconic acid-modified polyvinyl alcohol (25-88KL; manufactured by Kuraray Co., Ltd.): 20 parts by mass - Amorphous silica (Mizukasil P527; manufactured by Mizusawa Industrial Chemicals, Ltd.): 15 parts by mass - Surfactant (PD-001; manufactured by Nissin Chemical Co., Ltd.; solid concentration of 100% by mass): 0.2 parts by mass - Ion-exchanged water: 65 parts by mass

[0130] (Composition of [Liquid D] (Sensitizer Dispersion Liquid)) - 1,2-Bis(3-methylphenoxy)ethane (KS-232; manufactured by SANKO Co., Ltd.): 10 parts by mass - Aqueous solution of 10% parts by mass of sulfone-modified polyvinyl alcohol (GOHSERAN L-3266; manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.): 10 parts by mass - Surfactant (PD-001; manufactured by Nissin Chemical Co., Ltd.; solid concentration of 100% by mass): 0.1 parts by mass - Ion-exchanged water: 25 parts by mass

[0131] (Preparation of [Liquid F] (Coating Liquid for Protective Layer)) Thirty parts by mass of aluminum hydroxide, 30 parts by mass of an aqueous solution of 10% by mass of itaconic acid-modified polyvinyl alcohol (25-88KL; manufactured by Kuraray Co., Ltd.), and 40 parts by mass of ion-exchanged water were stirred and dispersed using a sand grinder to obtain [Liquid E] having a volume-average particle diameter of 0.5 μm.

[0132] The coating liquid for the protective layer [liquid F] was prepared by mixing and stirring the composition described below. (Composition of [Liquid F] (Coating Liquid for Protective Layer)) - [Liquid E]: 30 parts by mass - Aqueous solution of 10% parts by mass of itaconic acid-modified polyvinyl alcohol (25-88KL; manufactured by Kuraray Co., Ltd.): 50 parts by mass - Crosslinking agent liquid (polyamide epichlorohydrin resin; solid concentration of 25% by mass): 8 parts by mass - Dispersion liquid of montanate ester wax (solid concentration of 30% by mass): 5 parts by mass - Ion-exchanged water: 15 parts by mass

[0133] <Preparation of Thermally Recording Material> (Example 1) (Content of Each Ingredient in the Coating Liquid for Thermally Recording Layer) In the coating liquid for the thermally recording layer, the content of each liquid are as follows: [Liquid A] = 20 parts by mass, [Liquid B] = 35 parts by mass, [Liquid C1] = 22 parts by mass, [Liquid D] = 10 parts by mass, and the aqueous solution of 10% by mass of itaconic acid-modified polyvinyl alcohol = 20 parts by mass.

[0134] (Preparation of Thermally Recording Material) On the surface of paper with a basis weight of 60 g / m2as the support, the coating liquid for the undercoat layer was applied such that the attached amount thereof after drying was 3.0 g / m2, which was then followed by drying to form the undercoat layer. On the undercoat layer, the coating liquid for the thermally recording layer was applied such that the attached amount thereof after drying was 3.0 g / m2, which was then followed by drying to form the thermally recording layer. On the thermally recording layer, the coating liquid for the protective layer was applied such that the attached amount thereof after drying was 2.5 g / m2, which was then followed by drying to form the protective layer.

[0135] The content of 1,3-diphenylurea in the thermally recording layer relative to 1 part by mass of N-[2-(3-phenylureido)phenyl]benzenesulfonamide was calculated. This content was calculated from the content of 1,3-diphenylurea in [Liquid C1] and the content of N-[2-(3-phenylureido)phenyl]benzenesulfonamide in [Liquid B], these liquids being included in the coating liquid for the thermally recording layer.

[0136] Next, the surface treatment was conducted by supercalendering to bring a surface smoothness in the range of 1,500 seconds to 2,500 seconds; then, this was cured in a sealed bag made of a high-density polyethylene in an environment at 40°C for a predetermined period of time.

[0137] (Example 2) The thermally recording material was prepared in the same manner as in Example 1, except that the content of [Liquid C1] used in the coating liquid for the thermally recording layer in Example 1 was changed from 22 parts by mass to 1 part by mass, and that 22 parts by mass of [Liquid C2] was added.

[0138] (Example 3) The thermally recording material was prepared in the same manner as in Example 2, except that the content of [Liquid C1] used in the coating liquid for the thermally recording layer in Example 2 was changed from 1 part by mass to 5.5 parts by mass.

[0139] (Example 4) The thermally recording material was prepared in the same manner as in Example 2, except that the content of [Liquid C1] used in the coating liquid for the thermally recording layer in Example 2 was changed from 1 part by mass to 11 parts by mass.

[0140] (Example 5) The thermally recording material was prepared in the same manner as in Example 2, except that the content of [Liquid C1] used in the coating liquid for the thermally recording layer in Example 2 was changed from 1 part by mass to 22 parts by mass.

[0141] (Example 6) The thermally recording material was prepared in the same manner as in Example 2, except that the content of [Liquid C1] used in the coating liquid for the thermally recording layer in Example 2 was changed from 1 part by mass to 33 parts by mass.

[0142] (Example 7) The thermally recording material was prepared in the same manner as in Example 2, except that the content of [Liquid C1] used in the coating liquid for the thermally recording layer in Example 2 was changed from 1 part by mass to 44 parts by mass.

[0143] (Example 8) The thermally recording material was prepared in the same manner as in Example 2, except that the content of [Liquid C1] used in the coating liquid for the thermally recording layer in Example 2 was changed from 1 part by mass to 55 parts by mass.

[0144] (Example 9) The thermally recording material was prepared in the same manner as in Example 2, except that the content of [Liquid C1] used in the coating liquid for the thermally recording layer in Example 2 was changed from 1 part by mass to 66 parts by mass.

[0145] (Comparative Example 1) The thermally recording material was prepared in the same manner as in Example 1, except that [Liquid C1] used in the coating liquid for the thermally recording layer in Example 1 was not used.

[0146] (Comparative Example 2) The thermally recording material was prepared in the same manner as in Example 1, except that in place of 35 parts by mass of [Liquid B] used in the coating liquid for the thermally recording layer in Example 1, 35 parts by mass of [Liquid C3] was used.

[0147] (Comparative Example 3) The thermally recording material was prepared in the same manner as in Example 1, except that in place of 35 parts by mass of [Liquid B] used in the coating liquid for the thermally recording layer in Example 1, 35 parts by mass of [Liquid C4] was used.

[0148] In each of Examples and Comparative Examples, the types and contents of the dispersion liquids used in the preparation of the coating liquid for the thermally recording layer and the content of 1,3-diphenylurea relative to 1 part by mass of N-[2-(3-phenylureido)phenyl]benzenesulfonamide are listed in Table 1. In Table 1, N-[2-(3-phenylureido)phenyl]benzenesulfonamide is denoted as "NKK".

[0149] <Evaluation of Characteristics> Next, the characteristics of each thermally recording material prepared were evaluated. The characteristics of the thermally recording material were evaluated with regard to the durability against a hand lotion (hand lotion resistance), the oil resistance, and the heat resistance. The evaluation results for each characteristic are listed in Table 1.

[0150] (Hand Lotion Resistance) Pre-test image samples were prepared by printing at 2 kg / cm2for 2.0 seconds in a thermal block at the temperature at which each sample exhibited a saturated image density using a thermal tilt tester manufactured by Toyo Seiki Seisaku-sho, Ltd., and the printed density was measured using a Macbeth densitometer RD-914. Next, a cotton pad impregnated with a hand lotion (3M Cavilon Hand Moisture Lotion: manufactured by 3M Company) was applied once over the image and non-image areas of the pre-test image sample so as to allow the density measurement to be taken; then, the hand lotion-impregnated pre-test image sample was placed in a constant temperature chamber at 40°C and 90% RH for 24 hours. The image density after 24 hours was measured with a Macbeth densitometer to determine the residual percentage of the image density remaining after the test relative to the pre-test image density value. Based on the obtained residual image density, the hand lotion resistance was evaluated according to the following evaluation criteria. Residual image density [%] = (Image density after test) / (image density before test) × 100 (Evaluation Criteria) S: Residual image density is 98% or more. A: Residual image density is 90% to less than 98%. B: Residual image density is 80% to less than 90%. C: Residual image density is 70% to less than 80%. D: Residual image density is less than 70%.

[0151] (Oil Resistance) Pre-test image samples were prepared by printing at 2 kg / cm2for 2.0 seconds in a thermal block at the temperature at which each sample exhibited a saturated image density using a thermal tilt tester manufactured by Toyo Seiki Seisaku-sho, Ltd., and the printed density was measured using a Macbeth densitometer RD-914. A cotton pad impregnated with a cottonseed oil was applied once over the image and non-image areas of the pre-test image sample to allow the density measurement to be taken; then, this was placed in a constant temperature chamber at 80°C for 24 hours. The image density after 24 hours was measured with a Macbeth densitometer to determine the residual percentage of the image density remaining after the test relative to the pre-test image density value. Based on the obtained residual image density, the oil resistance was evaluated according to the following evaluation criteria. Residual image density [%] = (Image density after test) / (image density before test) × 100 (Evaluation Criteria) S: Residual image density is 95% or more. A: Residual image density is 80% to less than 95%. B: Residual image density is 50% to less than 85%. C: Residual image density is 20% to less than 50%. D: Residual image density is less than 20%.

[0152] (Heat Resistance) Pre-test image samples were prepared by printing at 2 kg / cm2for 2.0 seconds in a thermal block at the temperature at which each sample exhibited a saturated image density using a thermal tilt tester manufactured by Toyo Seiki Seisaku-sho, Ltd., and the printed density was measured using a Macbeth densitometer RD-914. The pre-test image sample was placed in a constant temperature chamber at 100°C for 1 hour, and then, the image density was measured with a Macbeth densitometer. The residual image density after the test was measured relative to the pre-test density value. Based on the obtained residual image density, the heat resistance was evaluated according to the following evaluation criteria. Residual image density [%] = (Image density after test) / (image density before test) × 100 (Evaluation Criteria) S: Residual image density is 95% or more. A: Residual image density is 90% to less than 95%. B: Residual image density is 80% to less than 90%. C: Residual image density is 70% to less than 80%. D: Residual image density is less than 70%.

[0153] (Coloring Sensitivity) Characters were printed on the thermally recording medium prepared using a thermal printer (model: MP-104T; manufactured by MARKPOINT Printer AB) at a printing speed of 100 mm / s, with the printing energy varying in the range of 0.96 mJ / mm2to 13.00 mJ / mm2. The image density was measured using a Macbeth reflection densitometer (model: RD-914; manufactured by Macbeth Corp.) to determine the printing energy at which the image density reached 1.0, and then, the senfsitivity factor was obtained by applying the following formula with the printing energy of Example 1 as the standard. The higher the value of the sensitivity factor, the higher the sensitivity (thermal response). Sensitivity factor = (Printing energy of Comparative Example 1) / (printing energy of each thermally recording material) Evaluation Criteria S: Sensitivity factor is 1.05 or more. A: Sensitivity factor is 1.00 to less than 1.05. B: Sensitivity factor is 0.95 to less than 1.00. C: Sensitivity factor is 0.90 to less than 0.95. D: Sensitivity factor is 0.9 or less.

[0154] (Comprehensive Evaluation) The comprehensive evaluation was made based on the following evaluation criteria. The evaluation was judged "S" when the hand lotion resistance, the oil resistance, the heat resistance, and the sensitivity were all S; "A" when the evaluation items were S and A; "B" when the evaluation items were A and B; "C" when at least one evaluation item was C; "D" when two or more evaluation items were C; and "E" when at least one evaluation item was D. (Evaluation Criteria) S: Most superior A: Very good B: Good C: Slightly better than conventional D: Inferior to conventional E: Not practical

[0155]

[0156] From Table 1, it was recognized that the thermally recording materials of Examples 1 to 9 all met the requirements for use regarding the hand lotion resistance, the oil resistance, and the heat resistance, and that they were superior to conventional materials. In contrast, it was recognized that the thermally recording materials in Comparative Examples 1 to 3 did not meet the requirements for use regarding at least the hand lotion resistance and the oil resistance, and that they were inferior to conventional materials.

[0157] Therefore, unlike the thermally recording materials of Comparative Examples 1 to 3, the thermally recording materials of Examples 1 to 4 contain specific benzenesulfonamide and 1,3-diphenylurea as the non-phenol type developers, so that they are excellent in the hand lotion resistance, the oil resistance, the heat resistance, the coloring property, and the antistatic stability. Accordingly, it can be said that it is possible to provide the thermally recording materials of Examples 1 to 4 as the thermally recording medium having excellent image preservation of the printed area against a skin protectant with high oil resistance and heat resistance, as well as an excellent coloring sensitivity.

[0158] Embodiments of the present invention are, for example, as follows. <1> A thermally recording medium uncluding: a support; and a thermally recording layer on the support, in which the thermally recording layer includes a compound represented by the following general formula (I) and 1,3-diphenylurea: where, in the formula, each of R1to R3independently represents a hydrogen atom, a halogen atom, a C1 to C6 alkyl group, a C1 to C6 alkoxy group, or a C1 to C6 fluoroalkyl group. <2> The thermally recording medium as described in <1>, in which the thermally recording layer further includes a developer represented by the following general formula (II) as a non-phenol type developer <3> The thermally recording medium as described in <1> or <2>, including 0.01 to 3.00 parts by mass of 1,3-diphenylurea relative to 1 part by mass of the compound represented by the general formula (I). <4> The thermally recording medium as described in any one of <1> to <3>, including a back layer formed on the opposite side of the support to the thermally recording layer. <5> The thermally recording medium as described in any one of <1> to <4>, inclduing an undercoat layer between the support and the thermally recording layer. <6> The thermally recording medium as described in <5>, in which the undercoat layer includes a hollow particle. <7> The thermally recording medium as described in any one of <1> to <6>, in which the protective layer is a top protective layer, and the thermally recording medium including one or more lower protective layers between the thermally recording layer and the top protective layer. <8> The thermally recording medium as described in any one of <1> to <7>, in which the thermally recording layer and the protective layer are layers formed by simultaneous coating using a curtain coating method.

[0159] 1 Thermally recording medium 11 Adhesive layer 12 Back layer 13 Support 14 Undercoat layer 15 Thermally recording layer 16 Intermediate layer 17 Protective layer 2 Pill case

[0160] Japanese Patent No. 5887423Japanese Patent No. 7143952Japanese Patent No. 5939209

Claims

1. A thermally recording medium comprising: 　　a support; and 　　a thermally recording layer on the support, 　　wherein the thermally recording layer comprises a compound represented by the following general formula (I) and 1,3-diphenylurea: 　　where, in the formula, each of R1to R3independently represents a hydrogen atom, a halogen atom, a C1 to C6 alkyl group, a C1 to C6 alkoxy group, or a C1 to C6 fluoroalkyl group.

2. The thermally recording medium according to claim 1, further comprising a developer represented by the following general formula (II) as a non-phenol type developer in the thermally recording layer: .

3. The thermally recording medium according to claim 1, comprising 0.01 to 3.00 parts by mass of 1,3-diphenylurea relative to 1 part by mass of the compound represented by the general formula (I).

4. The thermally recording medium according to claim 1, comprising a back layer on an opposite side of the support to the thermally recording layer.

5. The thermally recording medium according to claim 1, comprising an undercoat layer between the support and the thermally recording layer.

6. The thermally recording medium according to claim 5, wherein the undercoat layer comprises a hollow particle.

7. The thermally recording medium according to claim 1, comprising a protective layer on the thermally recording layer.

8. A method for producing a thermally recording medium comprising forming a thermally recording layer comprising a compound represented by the following general formula (I) and 1,3-diphenylurea on a support: 　　where, in the formula, each of R1to R3independently represents a hydrogen atom, a halogen atom, a C1 to C6 alkyl group, a C1 to C6 alkoxy group, or a C1 to C6 fluoroalkyl group.

9. The method for producing the thermally recording medium according to claim 8, comprising forming a back layer on an opposite surface of the support to a surface having the thermally recording layer.

10. A medical article comprising the thermally recording medium according to claim 1.

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