Thermal recording medium, method of preparing thermal recording medium, and medical article including thermal recording medium

Abstract

The thermal recording medium includes a support and a thermal recording layer on the support. The thermal recording layer includes a compound represented by the following general formula (I) and 1, 3-diphenylurea: # imgabs0 # wherein in the formula, each of R1 to R3 independently represents a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group, or a C1-C6 fluoroalkyl group.

Description

Technical Field

[0001] The present invention relates to a thermal recording medium, a method for preparing the thermal recording medium, and a medical article. Background Art

[0002] Thermal recording media enable quick, easy, and low-cost recording with relatively simple equipment, so they can be widely used in POS applications such as fresh food, boxed lunches, and prepared foods; copying of books and documents; communications such as fax; ticket machines for issuing tickets, receipts, and vouchers; aviation such as airport luggage tags; and medicine such as medicine boxes and bottles.

[0003] Thermal recording media contain an electron-donating dye (sometimes referred to as a leuco dye) and an electron-accepting developer (sometimes referred to as a developer). There are phenolic developers with a phenolic backbone, such as 4,4'-isopropylidene diphenol, and developers without a phenolic backbone (sometimes referred to as "non-phenolic developers"). The use of phenolic developers is a cause for concern, as they may be considered endocrine disruptors. Therefore, from environmental and health perspectives, research is underway into thermal recording media using non-phenolic developers.

[0004] Regarding thermal recording media using non-phenolic developers, there have been proposed thermal recording media whose coloring properties and the like are improved by using, for example, N-phenylureido-phenyl-benzenesulfonamide as a non-phenolic developer (see, for example, PTL 1 and PTL 2).

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

[0006] Technical issues

[0007] Staff and other people working in hospitals and other medical institutions typically protect their skin with skin protectants (such as hand creams, hand lotions, and hand disinfectants) after disinfecting their hands with alcohol. When thermal recording media containing N-phenylureido-phenyl-benzenesulfonamide in the thermal recording layer are used for labels on medical containers (such as medicine bottles used in hospitals), as with conventional thermal recording media, there is a problem that the printed image on the label fades when the thermal recording medium comes into contact with the skin protectant applied to the hands of these staff and other people, even if the coloring sensitivity is good.

[0008] An object of one aspect of the present invention is to provide a thermal recording medium having excellent coloring sensitivity and excellent image preservation of the printed area against skin protectants, oil, and heat.

[0009] Technical Solution

[0010] A thermal recording medium according to one aspect of the present invention includes a support and a thermal recording layer on the support. The thermal recording layer contains a compound represented by the following general formula (I) and 1,3-diphenylurea:

[0011]

[0012] Among them, in the formula, R 1 to R 3 Each of 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.

[0013] Favorable technical effects

[0014] According to one aspect of the present invention, there can be provided a thermal recording medium having excellent coloring sensitivity and excellent image preservation of a printed area against a skin protectant, oil, and heat. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a cross-sectional view of an example of a thermal recording medium according to an embodiment.

[0016] Figure 2 is an exemplary schematic diagram of an article having a thermal recording medium according to one embodiment. DETAILED DESCRIPTION

[0017] Hereinafter, details of embodiments according to the present invention will be described. The embodiments are not limited to the following description and may be modified as appropriate, as long as such modifications do not deviate from the gist of the present invention. In this specification, unless otherwise specified, the term "to" indicating a numerical range means that the numerical values ​​listed before and after the term include the lower and upper limits.

[0018] <Thermal Recording Medium>

[0019] In one embodiment, the thermal recording medium has a support and a thermal recording layer on the support, and may have other layers as needed.

[0020] The inventors of the present invention noted that thermal recording media comprising a support and a thermal recording layer, when using N-phenylureido-phenyl-benzenesulfonamide as a non-phenolic developer, had difficulty using the thermal recording layer in medical applications due to its low durability against skin protectants and oil resistance. After careful examination, the inventors investigated the simultaneous use of N-phenylureido-phenyl-benzenesulfonamide and 1,3-diphenylurea as non-phenolic developers in the thermal recording layer. This discovery revealed that when the thermal recording layer does not contain phenolic developers, which may be classified as endocrine disruptors, it can improve durability against skin protectants, oil resistance, and heat resistance. As a result, the inventors discovered that the thermal recording medium exhibits excellent printed area image preservation against skin protectants, oil, and heat, as well as excellent coloring sensitivity, without the use of phenolic developers.

[0021] A skin protectant is a substance that protects or relieves the skin from the effects of irritating ingredients such as alcohol, soap, surfactants, and other irritants; herein, the skin protectant may be a composition containing such a substance. Skin protectants may include, for example, substances that prevent excessive removal of fat by alcohol, soap, surfactants, etc. by providing fat to the skin, skin substances that protect the skin from fat-decomposing substances, and moisturizers that prevent dry skin. Illustrative examples of skin protectants include glycerin, glucomannan, maltodextrin, kaolin, fatty acid esters, fatty acid alkanolamides, lauric acid isopropyl alcoholamide, coconut fatty acid diethanolamide, stearic acid monoethanolamide, myristic acid monoethanolamide, oleic acid monoethanolamide, undecanoic acid monoethanolamide, coconut palm oil, palm oil, castor oil, sesame oil, soybean oil, sunflower oil, animal fats, chamomile extract, pine and oak extracts, seaweed extract, sodium lactate, glycerin, propylene glycol, butylene glycol, hexylene glycol, honey, invert sugar solution, sorbitol solution, silicone, 2-pyrrolidone-5-carboxylic acid alkali salt, polysaccharide, polyethylene glycol and low molecular weight polyglycerol. Specifically, examples of skin protectants include hand creams, hand lotions and hand disinfectants. The form of the skin protectant is not particularly limited; for example, it can be in the form of powder, liquid, gel, solid, etc.

[0022] (Thermal recording layer)

[0023] The thermal recording layer formed in the thermal recording medium according to one embodiment contains a leuco dye and a developer, wherein as the developer, it contains a non-phenolic developer including at least one specific urea compound and 1,3-diphenylurea.

[0024] (leuco dye)

[0025] The leuco dye is not particularly limited; it can be appropriately selected from those used for thermal recording media according to its purpose. Preferred examples thereof include leuco dye compounds such as triphenylmethane, fluoran, phenothiazine, auramine, spiropyran, and indolinephthalide.

[0026] The leuco dye is not particularly limited and can be appropriately selected according to its purpose. Illustrative examples thereof include 3,3-bis(p-dimethylaminophenyl)phthalide,

[0027] 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone),

[0028] 3,3-bis(p-dimethylaminophenyl)-6-diethylaminophthalide,

[0029] 3,3-bis(p-dimethylaminophenyl)-6-chlorophthalide,

[0030] 3,3-Bis(p-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6-chlorofluoran,

[0031] 3-dimethylamino-5,7-dimethylfluoran, 3-diethylamino-7-chlorofluoran,

[0032] 3-diethylamino-7-methylfluoran, 3-diethylamino-7,8-benzofluoran,

[0033] 3-diethylamino-6-methyl-7-chlorofluoran,

[0034] 3-(N-p-tolyl-N-ethylamino)-6-methyl-7-anilinofluoran,

[0035] 2-{N-(3'-trifluoromethylphenyl)amino}-6-diethylaminofluoran,

[0036] 2-{3,6-bis(diethylamino)-9-(o-chloroanilino)xanthenylbenzoic acid lactam},

[0037] 3-diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran,

[0038] 3-diethylamino-7-(o-chloroanilino)fluoran, 3-pyrrolidinyl-6-methyl-7-anilinofluoran,

[0039] 3-di-n-butylamino-7-(o-chloroanilino)fluoran,

[0040] 3-N-Methyl-N-pentylamino-6-methyl-7-anilinofluoran

[0041] 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran,

[0042] 3-Diethylamino-6-methyl-7-anilinofluoran,

[0043] 3-(N,N-diethylamino)-5-methyl-7-(N,-N-dibenzylamino)fluoran, benzoyl leuco-methylene blue, 6'-chloro-8'-methoxy-benzoindoline spiropyran,

[0044] 6'-Bromo-3'-methoxy-benzoindoline spiropyran,

[0045] 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)phthalide,

[0046] 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-nitrophenyl)phthalide,

[0047] 3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl)phthalide,

[0048] 3-(2'-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5'-methylphenyl)phthalide, 3-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl-7-anilinofluoran,

[0049] 3-N-ethyl-N-(2-ethoxypropyl)amino-6-methyl-7-anilinofluoran,

[0050] 3-N-methyl-N-isobutyl-6-methyl-7-anilinofluoran,

[0051] 3-morpholinyl-7-(N-propyl)-trifluoromethylanilino)fluoran,

[0052] 3-pyrrolidinyl-7-trifluoromethylanilinofluoran,

[0053] 3-diethylamino-5-chloro-7-(N-benzyl-trifluoromethylanilino)fluoran,

[0054] 3-pyrrolidinyl-7-(di-p-chlorophenyl)methylaminofluoran,

[0055] 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluoran,

[0056] 3-(N-ethyl-N-p-toluidinyl)-7-(α-phenylethylamino)fluoran,

[0057] 3-diethylamino-7-(o-methoxycarbonylanilino)fluoran,

[0058] 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluoran,

[0059] 3-Diethylamino-7-piperidinylfluoran,

[0060] 2-chloro-3-(N-methyltoluidino)-7-(p-butylanilino)fluoran,

[0061] 3-di-n-butylamino-6-methyl-7-anilinofluoran,

[0062] 3,6-bis(dimethylamino)fluorenespiro(9,3')-6'-dimethylaminophthalide,

[0063] 3-(N-benzyl-N-cyclohexylamino)-5,6-benzo-7-α-naphthylamino-4'-bromofluoran,

[0064] 3-Diethylamino-6-chloro-7-anilinofluoran,

[0065] 3-diethylamino-6-methyl-7-mesitylidinyl-4',5'-benzofluoran,

[0066] 3-N-methyl-N-isopropyl-6-methyl-7-anilinofluoran,

[0067] 3-N-ethyl-N-isopentyl-6-methyl-7-anilinofluoran,

[0068] 3-diethylamino-6-methyl-7-(2',4'-dimethylanilino)fluoran,

[0069] 3-morpholinyl-7-(N-propyl-trifluoromethylanilino)fluoran,

[0070] 3-pyrrolidinyl-7-trifluoromethylanilinofluoran,

[0071] 3-diethylamino-5-chloro-7-(N-benzyl-trifluoromethylanilino)fluoran,

[0072] 3-pyrrolidinyl-7-(di-p-chlorophenyl)methylaminofluoran,

[0073] 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluoran,

[0074] 3-(N-ethyl-N-p-toluidinyl)-7-(α-phenylethylamino)fluoran,

[0075] 3-diethylamino-7-(o-methoxycarbonylanilino)fluoran,

[0076] 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluoran,

[0077] 3-Diethylamino-7-piperidinylfluoran,

[0078] 2-chloro-3-(N-methyltoluidinyl)-7-(p-butylamino)fluoran,

[0079] 3,6-bis(dimethylamino)fluorenylspiro[9,3']-6'-dimethylaminophthalide,

[0080] 3-(N-benzyl-N-cyclohexylamino)-5,6-benzo-7-α-naphthylamino-4'-bromofluoran,

[0081] 3-Diethylamino-6-chloro-7-anilinofluoran,

[0082] 3-N-ethyl-N-(-2-ethoxypropyl)amino-6-methyl-7-anilinofluoran,

[0083] 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluoran,

[0084] 3-diethylamino-6-methyl-7-mesitylidinyl-4',5'-benzofluoran,

[0085] 3-(p-dimethylaminophenyl)-3-{1,1-bis(p-dimethylaminophenyl)ethylene-2-yl}phthalide,

[0086] 3-(p-dimethylaminophenyl)-3-{1,1-bis(p-dimethylaminophenyl)ethylene-2-yl}-6-dimethylaminophthalide,

[0087] 3-(p-dimethylaminophenyl)-3-(1-p-dimethylaminophenyl-1-phenylethylene-2-yl)phthalide,

[0088] 3-(p-dimethylaminophenyl)-3-(1-p-dimethylaminophenyl-1-p-chlorophenylethylene-2-yl)-6-dimethylaminophthalide,

[0089] 3-(4'-dimethylamino-2'-methoxy)-3-(1"-p-dimethylaminophenyl-1"-p-chlorophenyl-1",3"-butadiene-4"-yl]benzophthalide,

[0090] 3-(4'-dimethylamino-2'-benzyloxyphenyl)-3-[1"-p-dimethylaminophenyl-1"-phenyl-1",3"-butadien-4"-yl]benzophthalide,

[0091] 3-dimethylamino-6-dimethylamino-fluorene-9-spiro-3'-(6'-dimethylamino)phthalide,

[0092] 3,3-bis[2-(p-dimethylaminophenyl)-2-p-methoxyphenyl)vinyl]-4,5,6,7-tetrachlorophthalide,

[0093] 3-bis{1,1-bis(4-pyrrolidinylphenyl)ethylene-2-yl}-5,6-dichloro-4,7-dibromophthalide, bis(p-dimethylaminophenyl)-1-naphthalenesulfonylmethane and

[0094] Bis(p-dimethylaminophenyl)-1-p-toluenesulfonylmethane These may be used alone or in combination of two or more.

[0095] The mass ratio of the leuco dye relative to 100 mass % of the total mass of the thermal recording layer may be in the range of 3 to 30 mass %.

[0096] (Developer)

[0097] The developer included in the thermal recording layer of a thermal recording medium according to one embodiment is a non-phenolic developer. Non-phenolic refers to a type that does not have a phenolic skeleton. The thermal recording medium according to one embodiment is excellent in terms of environmental impact because it includes a non-phenolic developer and does not need to include a phenolic developer (which may belong to the category of endocrine disruptors).

[0098] The developer includes at least one urea compound and 1,3-diphenylurea as a non-phenolic developer, the urea compound being a compound represented by the following general formula (I).

[0099]

[0100] (In the formula, R 1 to R 3 Each independently represents a hydrogen atom, a halogen atom, a linear C 1 to C 6 Alkyl, C 1 to C 6 Alkoxy and C 1 to C 6 Fluoroalkyl.)

[0101] In one embodiment, the urea compound represented by the above general formula (I) preferably includes a compound represented by the following formula (1). The following formula (1) is R 1 、R 2 and R 3 All of them are hydrogen atoms.

[0102]

[0103] In one embodiment, it is preferred that another non-phenolic developer in the thermal recording layer includes a developer represented by the following general formula (II).

[0104]

[0105] (Where R 1to R 5 Each independently 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.

[0106] The urea compound represented by the above-mentioned general formula (II) may include a urea compound represented by the following formula (2).

[0107]

[0108] The content ratio of 1,3-diphenylurea in the thermal 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.

[0109] In the thermal 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, more preferably in the range of 2 to 10 parts by mass.

[0110] According to one embodiment, the thermal recording layer may include other non-phenolic developers as long as they do not interfere with the effect of the thermal recording medium. The types of non-phenolic developers are less than phenolic developers. Illustrative examples of other non-phenolic developers 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 (IX), and compounds represented by the following general formula (X).

[0111]

[0112] (wherein, R1 represents an unsubstituted or substituted phenyl, naphthyl or C1 to C 20 Alkyl. X represents a -C=NH- group, a -CS- group or a -CO- group. A represents an unsubstituted or substituted phenylene, naphthylene or C1-C 12 alkylene, or an unsubstituted or 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. R2 represents an unsubstituted or substituted aryl or benzyl or a C1 to C20 alkyl, and when B is not an -O-SO2- bonding group, R2 represents an unsubstituted or substituted phenyl, naphthyl or C1 to C8 alkyl.)

[0113]

[0114] (In the formula, X and Z each independently represent an aromatic compound residue, a heterocyclic compound residue, or an aliphatic compound residue; each residue may have a substituent; and Y0 represents a group selected from tolylene, xylylene, naphthylene, hexamethylene, and -φ-CH2-φ- groups. Note that -φ- represents a phenylene group.)

[0115]

[0116] (In the formula, X and Y each independently represent an aromatic compound residue, a heterocyclic compound residue, or an aliphatic compound residue, each of which may have a substituent.)

[0117]

[0118] (In the formula, X and Y each independently represent an aromatic compound residue, a heterocyclic compound residue, or an aliphatic compound residue; α represents a residue having a valence of 2 or more; n represents an integer of 2 or more; and each residue may have a substituent.)

[0119]

[0120] (In the formula, Z and Y each independently represent an aromatic compound residue, a heterocyclic compound residue, or an aliphatic compound residue; β represents a residue having a valence of 2 or higher; n represents an integer of 2 or greater; and each residue may have a substituent.)

[0121]

[0122] (In the formula, the hydrogen atoms in the benzene ring may be substituted by aromatic, aliphatic or heterocyclic compound residues, each of which may have a substituent. γ represents a group selected from -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- and -O-φ-SO2-φ-O-, or none of them exists; and n represents 1 or 2. )

[0123]

[0124] (In the formula, the hydrogen atoms in the benzene ring may be substituted by aromatic, aliphatic or heterocyclic compound residues, each of which may have a substituent. δ represents a compound selected from -SO2-, -O-, -(S) n -, -(CH2)n-, -CO-, -CONH-, -NH-, -CH(COOR1)-, -C(CF3)2- and -CR2R3-, wherein R1, R2 and R3 each represent an alkyl group, or none of them are present, and n represents 1 or 2.)

[0125]

[0126] (In the formula, R represents an alkyl group, and n represents an integer from 0 to 3.)

[0127] The non-phenolic developer can be synthesized as needed, or a commercially available product thereof can be used. Illustrative examples of commercially available products thereof include UU (trade name: ureaurethane represented by the following formula (2); manufactured by Chemipro Kasei Kaisha, Ltd.), Pergavest 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.).

[0128]

[0129] The content of the developer is not particularly limited and can be appropriately selected depending on the intended purpose. The content of the entire non-phenol developer is preferably 1 to 20 parts by mass, more preferably 2 to 10 parts by mass, relative to 1 part by mass of the leuco dye.

[0130] The content ratio of the additional developer can be appropriately selected depending on the intended purpose, as long as it does not impair the effectiveness of the thermal recording medium according to one embodiment. The combined mass of the compound of formula (I) or (II) and other developers other than 1,3-diphenylurea is preferably less than 2 parts by mass, and more preferably less than 0.5 parts by mass, relative to 1 part by mass of the leuco dye in the thermal coloring layer. In one embodiment, the thermal recording layer is not permitted to contain a significant amount of developers other than the compound of formula (I) or (II) and 1,3-diphenylurea.

[0131] (Other ingredients)

[0132] The thermal recording layer may further include other components such as a hot-melt substance, a binder resin, auxiliary additives, a surfactant, a lubricant, and a filler, as necessary.

[0133] -Hot-melt substances-

[0134] Illustrative examples of the hot-melt 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-phenyl naphthoate, phenyl 1-hydroxy-2-naphthoate, methyl 1-hydroxy-2-naphthoate, diphenyl carbonate, dibenzyl terephthalate, dimethyl terephthalate, 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-vinyloxyethylthio)benzene, p-(2-vinyloxyethoxy)biphenyl, p-aryloxybiphenyl, p-propargyloxy These may be used alone or in combination of two or more.

[0135] -Binder resin-

[0136] The binder resin is not particularly limited and can be appropriately selected depending on the intended purpose. Examples include polyvinyl alcohol, starch, or its derivatives; cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose; water-soluble polymers such as sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylate copolymers, acrylamide-acrylate-methacrylic acid terpolymers, alkali metal salts of styrene-maleic anhydride copolymers, alkali metal salts of isobutylene-maleic anhydride copolymers, polyacrylamide, sodium alginate, gelatin, and casein; emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylates, vinyl chloride-vinyl acetate copolymers, polybutyl methacrylate, and ethylene-vinyl acetate copolymers; and latexes such as styrene-butadiene copolymers and styrene-butadiene-acrylic acid copolymers. These can be used alone or in combination of two or more.

[0137] -Auxiliary additives-

[0138] Illustrative examples of usable auxiliary additives include various hindered phenol or hindered amine compounds, which are electron-accepting but have relatively low color-developing ability. Specifically, illustrative examples thereof include 2,2′-methylenebis(4-ethyl-6-tert-butylphenol), 4,4′-butylenebis(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-piperidinyl)-1,2,3,4-butanetetracarboxylate, and tetrakis(1,2,2,6,6-tetramethyl-4-piperidinyl)-1,2,3,4-butanetetracarboxylate.

[0139] -Surfactants-

[0140] The surfactant is not particularly limited and can be appropriately selected according to its purpose. Illustrative examples thereof include anionic surfactants, nonionic surfactants, amphoteric surfactants, and fluorinated surfactants. These can be used alone or in combination of two or more.

[0141] Illustrative examples of anionic surfactants include polyoxyethylene alkyl ether acetates, dodecylbenzenesulfonates, laurate salts, and polyoxyethylene alkyl ether sulfates. These may be used alone or in combination of two or more.

[0142] Illustrative examples of nonionic surfactants include acetylene glycol surfactants, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, and polyoxyethylene sorbitan fatty acid esters. These can be used alone or in combination of two or more.

[0143] Illustrative examples of acetylene glycol-based surfactants include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyne-3-diol, and 2,5,8,11-tetramethyl-6-decyne-5,8-diol. These can be used alone or in combination of two or more.

[0144] -Lubricant-

[0145] Illustrative examples of the lubricant include higher fatty acids or metal salts thereof, higher fatty acid amides, higher fatty acid esters, animal waxes, vegetable waxes, mineral waxes, and petroleum waxes.

[0146] -filler-

[0147] 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 urea-formaldehyde resin, styrene-methacrylic acid copolymer, polystyrene resin, and vinylidene chloride resin.

[0148] (Method for producing thermal recording layer)

[0149] There are no particular limitations on the method for producing the thermal recording layer, and the thermal recording layer can be formed using known methods. To produce the thermal recording layer, for example, the leuco dye, developer, and other ingredients are pulverized and dispersed using a ball mill, grinder, sand mill, or other dispersing machine until the dispersed particles have a diameter ranging from 0.1 μm to 3 μm. The resulting dispersion is then mixed with a sensitizer and, if necessary, a filler to prepare a coating liquid for the thermal recording layer. The thermal recording layer can be formed by applying the coating liquid for the thermal recording layer onto a support, followed by drying.

[0150] The coating method is not particularly limited and can be appropriately selected according to its purpose. Illustrative examples of the coating method include blade coating, gravure coating, gravure offset coating, rod coating, roll coating, knife coating, air knife coating, comma coating, U comma coating, AKKU coating, smooth coating, micro gravure coating, reverse roll coating, 4-roll or 5-roll coating, dip coating, single-layer curtain coating, multi-layer simultaneous coating, slide coating, and die coating.

[0151] In the production of a thermal recording medium according to one embodiment, from the viewpoint of economic requirements and improvement of coating uniformity, it is preferable to use a method of applying the thermal recording layer and other layers (such as a protective layer described later) by a multi-layer simultaneous curtain method, or a method of forming at least one intermediate layer between the thermal recording layer and other layers and then applying them by a multi-layer simultaneous curtain method.

[0152] The amount of the thermal recording layer adhered after drying is not particularly limited and can be appropriately selected according to its purpose. For example, it is preferably 0.5 g / m 2 Up to 20.0g / m 2 range, more preferably 1.0 g / m 2 Up to 10.0g / m 2 range.

[0153] (Other layers)

[0154] The other layers included in the thermal recording medium according to one embodiment are not particularly limited and thus can be appropriately selected according to their purpose. Illustrative examples of usable other layers include a protective layer, a back layer, an undercoat layer, an intermediate layer, and an adhesive layer.

[0155] (Protective layer)

[0156] A protective layer may be formed over the thermal recording layer. The protective layer may include a binder resin and a crosslinking agent, as well as other components as required.

[0157] -Binder resin-

[0158] The binder resin contained in the protective layer is not particularly limited and can be appropriately selected according to its purpose. Illustrative examples thereof include water-soluble resins, water-soluble resin emulsions, hydrophobic resins, UV-curable resins, and electron beam-curable resins.

[0159] Illustrative examples of water-soluble resins include polyvinyl alcohol, modified polyvinyl alcohol, starch or its derivatives, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose and ethylcellulose, as well as sodium polyacrylate, polyvinyl pyrrolidone, acrylamide-acrylate copolymer, acrylamide-acrylate-methacrylate terpolymer, alkali salts of styrene-maleic anhydride copolymer, alkali salts of isobutylene-maleic anhydride copolymer, polyacrylamide, modified polyacrylamide, methyl vinyl ether-maleic anhydride copolymer, carboxyl-modified polyethylene, polyvinyl alcohol-acrylamide block copolymer, melamine-formaldehyde resin, urea-formaldehyde resin, sodium alginate, gelatin and casein. These can be used alone or in combination of two or more. Among them, modified polyvinyl alcohol is preferred.

[0160] Illustrative examples of the modified polyvinyl alcohol include diacetone-modified polyvinyl alcohol; acetoacetyl-modified polyvinyl alcohol; and carboxylic acid-modified polyvinyl alcohol, such as itaconic acid-modified polyvinyl alcohol and maleic acid-modified polyvinyl alcohol.

[0161] - Cross-linking agent -

[0162] The cross-linking agent is not particularly limited, as long as it can react with the water-soluble resin to reduce its solubility in water. This can be appropriately selected according to its purpose. Illustrative examples of cross-linking agents include glyoxal derivatives, methylol derivatives, epichlorohydrin, polyamide epichlorohydrin, epoxy compounds, aziridine compounds, hydrazine, hydrazine derivatives, oxazoline derivatives and carbodiimide derivatives. These can be used alone or in combination of two or more. Among them, polyamide epichlorohydrin is particularly preferred because it is safe to handle and has a short curing time required for waterproofing.

[0163] The content of the polyamide epichlorohydrin is not particularly limited and can be appropriately selected according to its purpose. The content is preferably in the range of 10 to 60 parts by mass, more preferably 20 to 50 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0164] In addition to the binder resin and the crosslinking agent, a pigment (filler), auxiliary additive components, etc. may be included as other components.

[0165] 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 cross-linked polystyrene resins, urea resins, silicone resins, cross-linked polymethyl methacrylate resins and melamine-formaldehyde resins.

[0166] Illustrative examples of auxiliary additive components used in the protective layer include surfactants, hot-melt substances, lubricants, pressure coloration inhibitors, and other auxiliary additive components commonly used in the past.

[0167] There is no particular limitation on the method for producing the protective layer, and thus a publicly known method can be used.

[0168] The average thickness of the protective layer is not particularly limited, and thus the thickness can be appropriately selected depending on its purpose, preferably within the range of 0.5 μm to 5 μm, and more preferably within the range of 1 μm to 3 μm.

[0169] (Back layer)

[0170] If necessary, the back layer may be formed on the side of the support that does not have the thermal recording layer. The back layer contains a filler and a binder resin, and may further contain other components such as a lubricant and a color pigment if necessary.

[0171] For example, inorganic or organic fillers can be used as fillers.

[0172] Illustrative examples of the inorganic filler include carbonates, silicates, metal oxides, and sulfate compounds.

[0173] Illustrative examples of the organic filler include silicone resins, cellulose, epoxy resins, nylon resins, phenolic resins, polyurethane resins, urea resins, melamine resins, polyester resins, polycarbonate resins, styrene resins, acrylic resins, polyethylene resins, formaldehyde resins, and polymethyl methacrylate resins.

[0174] The binder resin is not particularly limited and can be appropriately selected according to its purpose. For example, the same binder resin as that used for the thermal recording layer described above can be used.

[0175] The average thickness of the back layer is not particularly limited, and thus can be appropriately selected depending on its purpose. It ranges from 0.1 μm to 20 μm, and more preferably from 0.3 μm to 10 μm.

[0176] (Base coating)

[0177] The undercoat layer may be formed between the support and the thermal recording layer. The undercoat layer is not particularly limited and can be appropriately selected according to its purpose. It preferably includes a binder resin, thermoplastic hollow resin particles, etc., and further includes other components as needed.

[0178] Thermoplastic hollow resin particles are micro hollow particles having a thermoplastic resin shell, in which gas such as air or other gas is contained and thus already in a foamed state.

[0179] The average particle diameter (average particle diameter) of thermoplastic hollow resin particles is not particularly limited, so the average diameter can be appropriately selected according to its purpose. This is preferably in the range of 0.2 μm to 20 μm, more preferably in the range of 2 μm to 5 μm. When the average particle diameter is 0.2 μm or larger, thermoplastic hollow resin particles with a hollow structure can be technically formed, thereby realizing the function as an undercoat layer. When the average particle diameter is 20 μm or smaller, the deterioration of the surface smoothness after application and drying can be suppressed, thereby allowing the thermal recording layer to be applied uniformly, thereby suppressing the application of the coating liquid exceeding the thermal recording layer required for achieving uniformity. Therefore, the average particle diameter of the preferred thermoplastic hollow resin particles is within the above range, and the particles have a uniformly distributed particle diameter peak value with less variance.

[0180] The average particle size of the thermoplastic hollow resin particles is the average value of the particle outer diameters of the thermoplastic hollow resin particles. The average particle size refers to the volume average particle size based on the effective diameter. The average particle size is the particle size (median diameter) at which the integral volume in the particle size distribution becomes 50% based on the cumulative volume starting from the smallest particle in the particle size distribution curve obtained by measuring the particle size of the thermoplastic hollow resin particles using a laser diffraction and scattering method, a dynamic light scattering method, or the like.

[0181] The hollow ratio of the thermoplastic hollow resin particles is not particularly limited and can be appropriately selected depending on the intended purpose. It is preferably in the range of 50% to 95%, more preferably in the range of 80% to 95%. When the hollow ratio is 30% or greater, the insulating properties are sufficient to suppress the release of heat energy from the thermal head through the support to the exterior of the thermal recording medium, thereby ensuring the effect of increased sensitivity. The hollow ratio is the ratio of the outer diameter to the inner diameter (diameter of the hollow portion) of the hollow particle and is expressed by the following formula.

[0182] Hollow ratio [%] = (hollow particle inner diameter / hollow particle outer diameter) × 100

[0183] As mentioned above, thermoplastic hollow resin particles have a thermoplastic resin shell. There is no particular limitation on the thermoplastic resin, so the resin can be appropriately selected according to its purpose. Illustrative examples thereof include styrene-acrylic resin, polystyrene resin, acrylic resin, polyethylene resin, polypropylene resin, polyacetal resin, chlorinated polyether resin, polyvinyl chloride resin and a copolymer resin mainly consisting of vinylidene chloride and acrylonitrile. Among them, styrene-acrylic resin and a copolymer resin mainly consisting of vinylidene chloride and acrylonitrile are preferred because their hollow ratio is higher, particle size variation is smaller, and they are suitable for blade coating.

[0184] The thermoplastic substance is not particularly limited and can be appropriately selected according to its purpose. Illustrative examples thereof include phenolic resins, urea-formaldehyde resins, melamine-formaldehyde resins, furan resins, unsaturated polyester resins formed by addition polymerization, and cross-linked MMA resins.

[0185] The coating amount of the plastic hollow particles is not particularly limited and can be appropriately selected according to the purpose. From the viewpoint of sensitivity and maintaining coating uniformity, the coating amount per 1m 2 The amount of the support is in the range of 1 g to 3 g. 2 When the support is 1 g or more, sufficient sensitivity can be obtained, and when the coating amount is per 1 m 2 When the support is 3 g or less, the bonding of the layers can be ensured.

[0186] (Middle layer)

[0187] For example, the intermediate layer may be formed between the protective layer and the thermal recording layer.The intermediate layer generally includes at least a binder, and each binder may include an inorganic filler and a surfactant.

[0188] The binder of the intermediate layer can be appropriately selected according to its purpose without any limitation, and the same binder in the intermediate layer or different binders in the layers can be used. Illustrative examples of binders that can be used in the intermediate layer include polyvinyl alcohol, modified polyvinyl alcohol, starch and its derivatives; cellulose derivatives, polyvinyl pyrrolidone, polyethyleneimine, sodium alginate, gelatin and casein; and acrylic binders.

[0189] Hydrophobic resin also can be used as the binding agent of intermediate layer.The hydrophobic resin that can be used as intermediate layer binding agent can comprise the hydrophobic resin that provides with emulsion and water-soluble form.The illustrative example of the hydrophobic resin that can be used as the intermediate section binding agent comprises polyurethane resin, epoxy resin, vinyl acetate (to) polymer, vinylidene chloride (to) polymer, vinyl chloride (co) polymer and butadiene-styrene copolymer.For particularly preferred intermediate layer binding agent, can mention polyvinyl alcohol or modified polyvinyl alcohol.

[0190] The thickness of the intermediate layer is preferably in the range of 0.2 μm to 10 μm, more preferably in the region of 0.5 μm to 5 μm. When multiple intermediate layers are used, the total thickness of all intermediate layers after drying is preferably 5 μm or less.

[0191] (Adhesive layer)

[0192] The adhesive layer may be formed on, for example, the surface of the support opposite to the surface on which the protective layer of the thermal recording layer is formed.

[0193] The material for forming the adhesive layer is not particularly limited and can be appropriately selected according to its purpose. Illustrative examples of the adhesive layer include urea resins, melamine resins, phenolic resins, epoxy resins, vinyl acetate resins, vinyl acetate-acrylic acid copolymers, ethylene-vinyl acetate copolymers, acrylic resins, polyvinyl ether resins, vinyl chloride-vinyl acetate copolymers, polystyrene resins, polyester resins, polyurethane resins, polyamide resins, chlorinated polyolefin resins, polyvinyl butyral resins, acrylate copolymers, methacrylate copolymers, natural rubber, cyanoacrylate resins, and silicone resins. These can be used alone or in combination of two or more.

[0194] In typical use of a thermal recording medium according to one embodiment, the adhesive layer is used to attach the thermal recording medium to, for example, food packaging. Thus, a thermal recording medium according to one embodiment can have an adhesive surface that adheres to a support or backing layer, making it a useful thermal recording medium for providing a label having an adhesive layer. The adhesive layer can be attached with a removable liner that can be removed prior to final attachment to the labeled product. The adhesive layer can have antistatic properties.

[0195] The method for forming the adhesive layer is not particularly limited. General coating and lamination methods can be used to form the adhesive layer.

[0196] The average thickness of the adhesive layer is not particularly limited and can be appropriately selected according to its purpose; it may be in the range of 0.1 μm to 20 μm.

[0197] The method for producing a thermal recording medium according to one embodiment is not particularly limited, and thus it can be produced by a known method. In the method for producing a thermal recording medium according to one embodiment, from the perspective of economic requirements and improving coating uniformity, it is preferable to use a method in which a thermal recording layer and other layers (such as a protective layer) are applied by a multi-layer simultaneous curtain method, or a method in which at least one intermediate layer is formed between the thermal recording layer and other layers and then they are applied by a multi-layer simultaneous curtain method.

[0198] As described above, a thermal recording medium according to one embodiment includes a support and a thermal recording layer comprising a urea compound represented by the aforementioned general formula (I) and 1,3-diphenylurea. This allows the thermal recording medium according to one embodiment to have a thermal recording layer that is more durable against skin protectants, oils, and heat. Consequently, the thermal recording medium according to one embodiment can exhibit excellent image preservation of the printed area against skin protectants, oils, and heat, and can also exhibit excellent coloring sensitivity.

[0199] The thermal recording medium according to one embodiment may further include a developer represented by the above-mentioned general formula (II) as a non-phenolic developer in the thermal recording layer. This allows the thermal recording medium according to one embodiment to further improve the durability of the thermal recording layer against skin protectants and oils, thereby further improving the image preservation of the printed area against skin protectants and oils.

[0200] In the thermal recording medium according to one embodiment, the content of 1,3-diphenylurea may be in the range of 0.01 to 3.00 parts by mass relative to 1 part by mass of the compound represented by general formula (I). This allows the thermal recording medium according to one embodiment to further improve the durability of the thermal recording layer against skin protectants and oils, thereby further improving the image preservation of the printed area against skin protectants and oils.

[0201] The thermal recording medium according to one embodiment may have a back layer on the opposite side of the support having the thermal recording layer. This allows the thermal recording medium according to one embodiment to improve strength and shape stability.

[0202] The thermal recording medium according to one embodiment may have an undercoat layer between the support and the thermal recording layer. This allows the thermal recording medium according to one embodiment to exhibit heat insulation properties, which inhibits the thermal energy transferred to the support from being released to the outside of the thermal recording medium through the support, thereby achieving an improvement in its sensitivity.

[0203] The thermal recording medium according to one embodiment may include hollow particles in the undercoat layer. This makes it easier to ensure that the thermal recording medium according to one embodiment exhibits heat insulation performance, which suppresses the heat energy transferred to the support from being released to the outside of the thermal recording medium through the support, thereby achieving an improvement in its sensitivity.

[0204] The thermal recording medium according to one embodiment may have a protective layer on the thermal recording layer. This allows the thermal recording medium according to one embodiment to protect the thermal recording layer from external influences, thereby achieving improved durability of the thermal recording layer.

[0205] The form of the thermal recording medium according to an embodiment is not particularly limited, and therefore can be appropriately selected according to its purpose. For example, the thermal recording medium according to an embodiment can be used as a label as it is, or it can have a layer on a protective layer or a support, on which information such as letters, marks, pictures, and two-dimensional codes such as bar codes or QR codes (registered trademarks) are printed. The thermal recording medium according to an embodiment can also be provided with an adhesive layer on the side of the support opposite to the side on which the thermal recording layer is formed.

[0206] The form of the thermal recording medium according to one embodiment is not particularly limited, and thus the form can be appropriately selected according to its purpose. The form of the thermal recording medium according to one embodiment includes, for example, a label, a sheet, and a roll.

[0207] The following are specific examples of aspects of the thermal recording medium according to one embodiment.

[0208] (Thermal Recording Label)

[0209] According to one aspect, a thermal recording medium is a thermal recording label, wherein a support has an adhesive layer formed on the side opposite to the side having the thermal recording layer, a release paper formed on the adhesive layer, and other layers as needed. The adhesive layer can be applied to the entire label or only to a portion thereof.

[0210] (linerless thermal recording medium)

[0211] The linerless thermal recording medium can be used in an aspect with a release layer (a type with a release layer) or without a release layer (a type without a release layer).

[0212] (Type with peeling layer)

[0213] According to one aspect, the thermal recording medium is a linerless thermal recording medium in which the support has a release layer on the top layer on the side (front surface) having the thermal recording layer, and further has an adhesive layer on the side (back surface) opposite to the side having the thermal recording layer. Other layers may be formed as needed.

[0214] It is preferable that the release layer is a layer formed of a material having good release properties from the adhesive layer, and it is particularly preferable that the layer contains silicone.

[0215] The linerless thermal recording medium according to one aspect may be handled in the form of a roll that is rolled up such that the adhesive layer overlaps the release layer.

[0216] (Type without peeling layer)

[0217] A thermal recording medium according to one aspect is a linerless thermal recording medium in which a support further has an adhesive layer on the side opposite to the surface having the thermal recording layer, the adhesive layer being a thermal adhesive layer exhibiting adhesiveness when heated, and may further have other layers as needed.

[0218] The thermal adhesive layer contains a thermoplastic resin and a hot-melt substance, and may further contain a tackifier as needed.

[0219] Thermoplastic resins provide adhesion and bonding. Hot melts are solid at room temperature and do not impart plasticity to the resin, but they melt when heated, causing the resin to expand or soften, thus exhibiting adhesion. Tackifiers enhance adhesion. Thermoplastic resins, hot melts, and tackifiers can be commonly used.

[0220] (Thermal magnetic recording paper)

[0221] A thermal recording medium according to one aspect is a thermosensitive magnetic recording paper in which a support has a magnetic recording layer on the opposite side to a surface having a thermal recording layer, and further has other layers as needed.

[0222] The magnetic recording layer can be formed by applying iron oxide, barium ferrite, or the like, and vinyl chloride resin, polyurethane resin, nylon resin, or the like to a support, or by forming the magnetic recording layer by vapor deposition or sputtering without using a resin. The magnetic recording layer is preferably formed on the side of the support opposite to the side having the thermal recording layer, but may also be formed between the support and the thermal recording layer. The magnetic recording layer may be formed at least partially on the thermal recording layer.

[0223] (Recording method)

[0224] According to one embodiment, the recording method using the thermal recording medium is not particularly limited, and thus the method can be appropriately selected according to the purpose. For example, a method using a thermal head, a laser, or the like can be employed.

[0225] The shape, structure, size, etc. of the thermal head are not particularly limited, and thus these can be appropriately selected according to the purpose.

[0226] The type of laser is not particularly limited and can be appropriately selected according to its purpose. For example, a CO2 laser having a wavelength of 9.3 μm to 10.6 μm, a semiconductor laser, or the like can be used.

[0227] (use)

[0228] The thermal recording medium according to one embodiment has high coloring sensitivity and image density, does not use phenolic developers, and exhibits excellent resistance to skin protectants such as hand creams, oils, and heat, making it suitable for a wide range of applications. Illustrative examples of its use include point-of-sale (POS) applications for fresh food, boxed lunches, and prepared foods; copying applications for books and documents; communications applications for fax machines; ticket machines for issuing tickets, receipts, and vouchers; aviation applications for airport luggage tags; and medical applications for pharmaceutical containers such as medicine boxes and bottles. In particular, the thermal recording medium according to one embodiment is particularly suitable for use in the medical field due to its excellent performance as a skin protectant.

[0229] (thing)

[0230] An article according to an embodiment has a thermal recording medium according to a specific embodiment. As the thermal recording medium, the thermal recording medium according to an embodiment can be appropriately used. Having a thermal recording medium according to an embodiment means that the thermal storage medium according to an embodiment is in a state of being pasted, attached, etc.

[0231] Figure 1 is a cross-sectional view of an example of a thermal recording medium according to an embodiment. Figure 1 As shown, a thermal recording medium 1 according to one embodiment has an adhesive layer 11, a backing layer 12, a support 13, an undercoat layer 14, a thermal recording layer 15, an intermediate layer 16, and a protective layer 17 in this order. Figure 2 is a schematic diagram of an example of an article having a thermal recording medium according to an example.

[0232] The article according to one embodiment is not particularly limited, as long as it includes the thermal recording medium according to one embodiment. Thus, the article can be appropriately selected depending on its intended use. Illustrative examples of the article according to one embodiment include wrapping materials, packaging materials, and wrapping paper. More specifically, illustrative examples include packaging materials for fresh food, boxed lunches, prepared foods, books, documents, and the like, as well as medical items such as medicine boxes and bottles. In particular, the thermal recording medium according to one embodiment exhibits excellent resistance to skin protectants, making it suitable for use in medical articles used in the medical field.

[0233] As described above, the embodiments have been described as examples; therefore, the present invention is not limited to the above-described embodiments. The above-described embodiments can be implemented in various other forms; therefore, various combinations, omissions, substitutions, modifications, etc. can be made without departing from the gist of the present invention. These embodiments and their variations are included in the scope and spirit of the present invention, as well as in the inventions specified in the claims and their equivalents.

[0234] Example

[0235] In order to more specifically illustrate the embodiment, the following Examples and Comparative Examples are described; however, the embodiment is not limited to these Examples and Comparative Examples.

[0236] <Preparation of coating solution>

[0237] (Preparation of Undercoat Layer Coating Liquid)

[0238] A coating liquid for the undercoat layer was prepared by mixing and stirring the following composition.

[0239] - Hollow particles (copolymer of acrylonitrile, methacrylonitrile and isobornyl methacrylate; hollow ratio 90%; volume average particle size 4.4 μm; solid concentration 33% by mass): 20 parts by mass

[0240] - Styrene / butadiene copolymer latex (solid concentration 47.5% by mass): 20 parts by mass

[0241] - Aqueous solution of 10% by mass polyvinyl alcohol (PVA117; manufactured by Kuraray Co., Ltd.): 20 parts by mass

[0242] - Ion-exchanged water: 40 parts by mass (Preparation of thermal recording layer coating solution)

[0243] A colorless dye dispersion [Liquid A], a primary developer dispersion [Liquid B], auxiliary developer dispersions [Liquid C1] to [Liquid C4], and a sensitizer dispersion [Liquid D], each having the following composition, were dispersed and prepared separately using a sand mill so that the volume average particle diameter in [Liquid A] was 0.5 μm, the volume average particle diameter in [Liquid B] was 1.0 μm, the volume average particle diameter in [Liquid C1]-[Liquid C4] was 1.0 μm; and the volume average particle diameter in [Liquid D] was 1.0 μm.

[0244] Next, a coating liquid for a thermal recording layer was prepared by mixing and stirring predetermined amounts of [Liquid A], [Liquid B], [Solution C1] to [Liquid C4], [Liquid D], and a 10% by mass aqueous solution of itaconic acid-modified polyvinyl alcohol. Table 1 lists the contents of [Liquid A], [Liquid B], [Liquid C1] to [Liquid C4], [Liquid D], and a 10% by mass aqueous solution of itaconic acid-modified polyvinyl alcohol in each of Examples and Comparative Examples.

[0245] (Composition of [Liquid A] (Leuco dye dispersion))

[0246] - Leuco dye (3-dibutylamino-6-methyl-7-anilinofluoran): 20 parts by mass

[0247] - 10% by mass itaconic acid-modified polyvinyl alcohol aqueous solution (25-88 KL; manufactured by Kuraray Co., Ltd.): 40 parts by mass

[0248] - Surfactant (Newcol 290; manufactured by Nippon Nyukazai Co., Ltd.; solid concentration: 100% by mass): 0.2 parts by mass

[0249] - Ion-exchanged water: 40 parts by mass (composition of [Liquid B] (primary developer dispersion))

[0250] -N-[2-(3-phenylureido)phenyl]benzenesulfonamide (NKK-1304; manufactured by Nippon Soda Co., Ltd.): 20 parts by mass

[0251] - 10% by mass itaconic acid-modified polyvinyl alcohol aqueous solution (25-88 KL; manufactured by Kuraray Co., Ltd.): 20 parts by mass

[0252] - Amorphous silica (Mizukasil P527; manufactured by Mizusawa Industrial Chemicals, Ltd.): 15 parts by mass

[0253] - Surfactant (PD-001; manufactured by Nissin Chemical Co., Ltd.; solid concentration 100% by mass): 0.2 parts by mass

[0254] - Ion-exchanged water: 65 parts by mass (composition of [Liquid C1] (auxiliary developer dispersion))

[0255] -1,3-Diphenylurea: 20 parts by mass

[0256] - 10% by mass sulfone-modified polyvinyl alcohol aqueous solution (GOHSERAN L-3266; manufactured by Nippon Synthetic Chemical Industry Co., Ltd.): 20 parts by mass

[0257] - Surfactant (PD-001; manufactured by Nissin Chemical Co., Ltd.; solid concentration 100% by mass): 0.2 parts by mass

[0258] - Ion-exchanged water: 35 parts by mass (composition of [Liquid C2] (auxiliary developer dispersion))

[0259] - Urea compound represented by chemical formula (II) (TG-MD; manufactured by Nippon Kayaku Co., Ltd.): 20 parts by mass

[0260] - 10% by mass aqueous solution of sulfone-modified polyvinyl alcohol (GOHSERAN L-3266; manufactured by Nippon Synthetic Chemical Industry Co., Ltd.): 20 parts by mass

[0261] - Surfactant (PD-001; manufactured by Nissin Chemical Co., Ltd.; solid concentration 100% by mass): 0.2 parts by mass

[0262] - Ion-exchanged water: 35 parts by mass (composition of [Liquid C3] (auxiliary developer dispersion))

[0263] - Urea compound represented by chemical formula (II) (TG-MD; manufactured by Nippon Kayaku Co., Ltd.): 20 parts by mass

[0264] - 10% by mass itaconic acid-modified polyvinyl alcohol aqueous solution (25-88 KL; manufactured by Kuraray Co., Ltd.): 20 parts by mass

[0265] - Amorphous silica (Mizukasil P527; manufactured by Mizusawa Industrial Chemicals, Ltd.): 15 parts by mass

[0266] - Surfactant (PD-001; manufactured by Nissin Chemical Co., Ltd.; solid concentration 100% by mass): 0.2 parts by mass

[0267] - Ion-exchanged water: 65 parts by mass (composition of [Liquid C4] (auxiliary developer dispersion))

[0268] - Urea-polyurethane compound (UU; manufactured by Chemipro Kasei Kaisha, Ltd.): 20 parts by mass

[0269] - 10% by mass itaconic acid-modified polyvinyl alcohol aqueous solution (25-88 KL; manufactured by Kuraray Co., Ltd.): 20 parts by mass

[0270] - Amorphous silica (Mizukasil P527; manufactured by Mizusawa Industrial Chemicals, Ltd.): 15 parts by mass

[0271] - Surfactant (PD-001; manufactured by Nissin Chemical Co., Ltd.; solid concentration 100% by mass): 0.2 parts by mass

[0272] - Ion-exchanged water: 65 parts by mass (composition of [Liquid D] (sensitizer dispersion))

[0273] -1,2-bis(3-methylphenoxy)ethane (KS-232; manufactured by SANKO Co., Ltd.): 10 parts by mass

[0274] - 10% by mass sulfone-modified polyvinyl alcohol aqueous solution (GOHSERAN L-3266; manufactured by Nippon Synthetic Chemical Industry Co., Ltd.): 10 parts by mass

[0275] - Surfactant (PD-001; manufactured by Nissin Chemical Co., Ltd.; solid concentration: 100% by mass): 0.1 part by mass

[0276] - Ion-exchanged water: 25 parts by mass (Preparation of [Liquid F] (Protective layer coating liquid))

[0277] 30 parts by mass of aluminum hydroxide, 30 parts by mass of an aqueous solution of 10% by mass 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 mill to obtain [Liquid E] having a volume average particle diameter of 0.5 μm.

[0278] A protective layer coating liquid [Liquid F] was prepared by mixing and stirring the following composition.

[0279] (Composition of [Liquid F] (Protective Layer Coating Liquid))

[0280] -[Liquid E]: 30 parts by mass

[0281] 10% by mass aqueous solution of itaconic acid-modified polyvinyl alcohol (25-88KL; manufactured by Kuraray Co., Ltd.): 50 parts by mass

[0282] - Cross-linking agent liquid (polyamide-epichlorohydrin resin; solid concentration 25% by mass): 8 parts by mass

[0283] -Montanic acid ester wax dispersion (solid concentration: 30% by mass): 5 parts by mass

[0284] - Ion exchange water: 15 parts by mass

[0285] <Preparation of Thermal Recording Material>

[0286] (Example 1)

[0287] (Contents of Each Component in the Thermal Recording Layer Coating Liquid)

[0288] In the thermal recording layer coating liquid, the content of each liquid is 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 10% by mass itaconic acid-modified polyvinyl alcohol aqueous solution = 20 parts by mass.

[0289] (Preparation of Thermal Recording Material)

[0290] The basis weight of the support is 60 g / m 2 On the surface of the paper, the primer coating liquid is applied so that the adhesion amount after drying is 3.0 g / m 2 , and then dried to form an undercoat layer. On the undercoat layer, a thermal recording layer coating liquid was applied so that the coating amount after drying was 3.0 g / m 2 , and then dried to form a thermal recording layer. On the thermal recording layer, a protective layer coating liquid is applied so that the adhesion amount after drying is 2.5 g / m 2 , and then dried to form a protective layer.

[0291] The content of 1,3-diphenylurea in the thermal recording layer was calculated per 1 part by mass of N-[2-(3-phenylureido)phenyl]benzenesulfonamide. 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], which were contained in the coating liquid for the thermal recording layer.

[0292] Next, the surface was treated by super calendering to make the surface smoothness within a range of 1500 seconds to 2500 seconds; and then, it was cured in a sealed bag made of high-density polyethylene in an environment of 40° C. for a predetermined time.

[0293] (Example 2)

[0294] A thermal recording material was prepared in the same manner as in Example 1 except that the content of [Liquid C1] used in the thermal recording layer coating liquid in Example 1 was changed from 22 parts by mass to 1 part by mass and 22 parts by mass of [Liquid C2] was added.

[0295] (Example 3)

[0296] A thermal recording material was prepared in the same manner as in Example 2, except that the content of [Liquid C1] used in the thermal recording layer coating liquid in Example 2 was changed from 1 part by mass to 5.5 parts by mass.

[0297] (Example 4)

[0298] A thermal recording material was prepared in the same manner as in Example 2, except that the content of [Liquid C1] used in the thermal recording layer coating liquid in Example 2 was changed from 1 part by mass to 11 parts by mass.

[0299] (Example 5)

[0300] A thermal recording material was prepared in the same manner as in Example 2, except that the content of [Liquid C1] used in the thermal recording layer coating liquid in Example 2 was changed from 1 part by mass to 22 parts by mass.

[0301] (Example 6)

[0302] A thermal recording material was prepared in the same manner as in Example 2, except that the content of [Liquid C1] used in the thermal recording layer coating liquid in Example 2 was changed from 1 part by mass to 33 parts by mass.

[0303] (Example 7)

[0304] A thermal recording material was prepared in the same manner as in Example 2, except that the content of [Liquid C1] used in the thermal recording layer coating liquid in Example 2 was changed from 1 part by mass to 44 parts by mass.

[0305] (Example 8)

[0306] A thermal recording material was prepared in the same manner as in Example 2, except that the content of [Liquid C1] used in the thermal recording layer coating liquid in Example 2 was changed from 1 part by mass to 55 parts by mass.

[0307] (Example 9)

[0308] A thermal recording material was prepared in the same manner as in Example 2, except that the content of [Liquid C1] used in the thermal recording layer coating liquid in Example 2 was changed from 1 part by mass to 66 parts by mass.

[0309] (Comparative Example 1)

[0310] A thermal recording material was prepared in the same manner as in Example 1 except that the [Liquid C1] in the thermal recording layer coating liquid in Example 1 was not used.

[0311] (Comparative Example 2)

[0312] A thermal recording material was prepared in the same manner as in Example 1, except that 35 parts by mass of [Liquid C3] was used instead of 35 parts by mass of [Liquid B] used in the thermal recording layer coating liquid in Example 1.

[0313] (Comparative Example 3)

[0314] A thermal recording material was prepared in the same manner as in Example 1, except that 35 parts by mass of [Liquid C4] was used instead of 35 parts by mass of [Liquid B] used in the thermal recording layer coating liquid in Example 1.

[0315] Table 1 lists the type and content of the dispersion used to prepare the thermal recording layer coating solution in each Example and Comparative Example, as well as the content of 1,3-diphenylurea relative to 1 part by mass of N-[2-(3-phenylureido)phenyl]benzenesulfonamide. In Table 1, N-[2-(3-phenylureido)phenyl]benzenesulfonamide is represented by "NKK."

[0316] <Characteristics Evaluation>

[0317] Next, the properties of each prepared thermal recording material were evaluated. The thermal recording material properties were evaluated with respect to durability against hand lotion (hand lotion resistance), oil resistance, and heat resistance. Table 1 lists the evaluation results for each property.

[0318] (Hand lotion resistance)

[0319] The images were measured at a temperature of 2 kg / cm2 in a heat block at a temperature at which each sample showed a saturated image density by using a thermal tilt tester manufactured by Toyo Seiki Seisaku-sho, Ltd. 2 The pre-test image sample was prepared by printing for 2.0 seconds, and the print density was measured using a Macbeth densitometer RD-914. Next, a cotton pad soaked in hand lotion (3M Caviar Hand Lotion: manufactured by 3M Company) was applied once to the image and non-image areas of the pre-test image sample for density measurement; the pre-test image sample soaked in hand lotion was then placed in a constant temperature chamber at 40°C and 90% RH for 24 hours. The image density after 24 hours was measured using a Macbeth densitometer to determine the remaining percentage of the image density remaining after the test relative to the pre-test image density value. Based on the obtained remaining image density, the hand lotion resistance was evaluated according to the following evaluation criteria.

[0320] Remaining image density [%] = (image density after test) / (image density before test) × 100

[0321] (Evaluation Criteria)

[0322] S: The remaining image density is 98% or higher.

[0323] A: The remaining image density is 90% to less than 98%.

[0324] B: The remaining image density is 80% to less than 90%.

[0325] C: The remaining image density is 70% to less than 80%.

[0326] D: The remaining image density is less than 70%.

[0327] (Oil resistance)

[0328] The images were measured at a temperature of 2 kg / cm2 in a heat block at a temperature at which each sample showed a saturated image density by using a thermal tilt tester manufactured by Toyo Seiki Seisaku-sho, Ltd. 2 A pre-test image sample was prepared by printing for 2.0 seconds, and the print density was measured using a Macbeth densitometer RD-914. A cotton pad soaked in cottonseed oil was applied once to the image and non-image areas of the pre-test image sample for density measurement; the sample was then placed in a constant temperature chamber at 80°C for 24 hours. The image density after 24 hours was measured using a Macbeth densitometer to determine the percentage of image density remaining after the test relative to the pre-test image density value. Based on the remaining image density obtained, oil resistance was evaluated according to the following evaluation criteria.

[0329] Remaining image density [%] = (image density after test) / (image density before test) × 100

[0330] (Evaluation Criteria)

[0331] S: The remaining image density is 95% or higher.

[0332] A: The remaining image density is 80% to less than 95%.

[0333] B: The remaining image density is 50% to less than 85%.

[0334] C: The remaining image density is 20% to less than 50%.

[0335] D: The remaining image density is less than 20%.

[0336] (Heat resistance)

[0337] The images were measured at a temperature of 2 kg / cm2 in a heat block at a temperature at which each sample showed a saturated image density by using a thermal tilt tester manufactured by Toyo Seiki Seisaku-sho, Ltd. 2 A pre-test image sample was prepared by printing for 2.0 seconds, and the print 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 using 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, heat resistance was evaluated according to the following evaluation criteria.

[0338] Remaining image density [%] = (image density after test) / (image density before test) × 100

[0339] (Evaluation Criteria)

[0340] S: The remaining image density is 95% or higher.

[0341] A: The remaining image density is 90% to less than 95%.

[0342] B: The remaining image density is 80% to less than 90%.

[0343] C: The remaining image density is 70% to less than 80%.

[0344] D: The remaining image density is less than 70%.

[0345] (Coloring Sensitivity)

[0346] Characters were printed on the prepared thermal recording medium using a thermal printer (model: MP-104T; manufactured by MARKPOINT Printer AB) at a printing speed of 100 mm / s and a printing energy of 0.96 mJ / mm 2 Up to 13.00mJ / mm 2 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. The sensitivity factor was then obtained by applying the following formula using the printing energy of Example 1 as a standard. The higher the value of the sensitivity factor, the higher the sensitivity (thermal response).

[0347] Sensitivity factor = (printing energy of Comparative Example 1) / (printing energy of each thermal recording material)

[0348] Evaluation Criteria

[0349] S: Sensitivity factor is 1.05 or greater.

[0350] A: The sensitivity factor is 1.00 to less than 1.05.

[0351] B: The sensitivity factor is 0.95 to less than 1.00.

[0352] C: The sensitivity factor is 0.90 to less than 0.95.

[0353] D: Sensitivity factor is 0.9 or less.

[0354] (Comprehensive Assessment)

[0355] Comprehensive evaluation is conducted based on the following criteria. When hand lotion resistance, oil resistance, heat resistance, and sensitivity are all rated S, the evaluation is determined as "S"; when both evaluation items are S and A, the evaluation is determined as "A"; when both evaluation items are A and B, the evaluation is determined as "B"; when at least one evaluation item is rated C, the evaluation is determined as "C"; when two or more evaluation items are rated C, the evaluation is determined as "D"; and when at least one evaluation item is rated D, the evaluation is determined as "E".

[0356] (Evaluation Criteria)

[0357] S: Most superior

[0358] A: Very good

[0359] B: OK

[0360] C: Slightly better than normal

[0361] D: Below average

[0362] E: Impractical

[0363] Table 1

[0364]

[0365] As can be seen from Table 1, the heat-sensitive recording materials of Examples 1 to 9 meet the requirements for use in terms of hand lotion resistance, oil resistance, and heat resistance, and are superior to conventional materials. In contrast, the heat-sensitive recording materials of Comparative Examples 1 to 3 do not meet the requirements for use in terms of at least hand lotion resistance and oil resistance, and are inferior to conventional materials.

[0366] Thus, unlike the thermal recording materials of Comparative Examples 1 to 3, the thermal recording materials of Examples 1 to 4 contain specific benzenesulfonamide and 1,3-diphenylurea as non-phenolic color developers, resulting in excellent hand lotion resistance, oil resistance, heat resistance, coloring performance, and antistatic stability. Therefore, it can be said that the thermal recording materials of Examples 1 to 4 can serve as thermal recording media with excellent image preservation performance for skin protection agents in the printed area, high oil resistance and heat resistance, and excellent coloring sensitivity.

[0367] The embodiments of the present invention are as follows, for example.

[0368] <1> A thermosensitive recording medium comprising:

[0369] a support; and

[0370] A thermal recording layer on a support, wherein

[0371] The thermal recording layer contains a compound represented by the following general formula (I) and 1,3-diphenylurea:

[0372]

[0373] Among them, in the formula, R 1 to R 3 Each of them independently represents a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group or a C1-C6 fluoroalkyl group.

[0374] <2> like <1> The thermal recording medium, wherein the thermal recording layer further comprises a developer represented by the following general formula (II) as a non-phenolic developer

[0375]

[0376] <3> like <1> or <2> The thermal recording medium contains 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).

[0377] <4> like <1> to <3> The thermal recording medium according to any one of the preceding claims, comprising a back layer formed on the side of the support opposite to the thermal recording layer.

[0378] <5> like <1> to <4> The thermal recording medium described in any one of the preceding claims, comprising an undercoat layer between the support and the thermal recording layer.

[0379] <6> like <5> The thermal recording medium, wherein the undercoat layer comprises hollow particles.

[0380] <7> like <1> to <6> The thermal recording medium according to any one of the preceding claims, wherein

[0381] This protective layer is the top protective layer, and

[0382] The thermal recording medium includes one or more lower protective layers between the thermal recording layer and the top protective layer.

[0383] <8> like <1> to <7> The thermal recording medium as described in any one of the preceding claims, wherein the thermal recording layer and the protective layer are layers formed by simultaneous coating using a curtain coating method.

[0384] [Reference Signs List]

[0385] 1 Thermal recording medium

[0386] 11 Adhesive layer

[0387] 12 back layers

[0388] 13 support body

[0389] 14 base coat

[0390] 15 Thermal recording layer

[0391] 16 middle layer

[0392] 17 protective layers

[0393] 2 medicine boxes

[0394] [Citation List]

[0395] [Patent Document]

[0396] [PTL 1] Japanese Patent No. 5887423

[0397] [PTL 2] Japanese Patent No. 7143952

[0398] [PTL 3] Japanese Patent No. 5939209

Claims

1. A thermal recording medium comprising: Support body; and The thermal recording layer on the support, wherein the thermal recording layer comprises a compound represented by the following general formula (I) and 1,3-diphenylurea: Among them, in the formula, R 1 to R 3 Each of them independently represents a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group or a C1-C6 fluoroalkyl group.

2. The thermal recording medium according to claim 1, further comprising a developer represented by the following general formula (II) as a non-phenolic developer in the thermal recording layer: 3 . The thermal 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 thermal recording medium according to claim 1 , comprising a back layer on a side of the support opposite to the thermal recording layer. 5 . The thermal recording medium according to claim 1 , comprising an undercoat layer between the support and the thermal recording layer. The thermal recording medium according to claim 5 , wherein the undercoat layer comprises hollow particles. 7 . The thermal recording medium according to claim 1 , comprising a protective layer on the thermal recording layer.

8. A method for preparing a thermal recording medium, comprising forming a thermal recording layer comprising a compound represented by the following general formula (I) and 1,3-diphenylurea on a support: in, In the formula, R 1 to R 3 Each of them independently represents a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group or a C1-C6 fluoroalkyl group. 9 . The method for producing a thermal recording medium according to claim 8 , comprising forming a back layer on a surface of the support opposite to a surface having the thermal recording layer. 10 . A medical article comprising the thermal recording medium according to claim 1 .

Images