Heat-sensitive recording body

Abstract

Disclosed is a heat-sensitive recording body which comprises, on a supporting body, at least a heat-sensitive recording layer that contains a leuco dye, a developer, and an adhesive. The heat-sensitive recording body is characterized in that the heat-sensitive recording layer contains, as a main first developer, an N, N'-diarylurea-based compound represented by general formula (1) (wherein R2 represents an alkyl group having 1 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms, the aralkyl group and the aryl group may be substituted by an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a halogen atom, and the plurality of R2 moieties may be the same or different, A1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and the plurality of A1 moieties may be the same or different), and contains, as a second developer, at least one compound that is selected from the group consisting of a urea urethane compound represented by general formula (2) and 5-(N-3-methylphenyl-sulfonamide)-N',N"-bis-(3-methylphenyl)-isophthalic acid diamide.

Description

Thermal recording device

[0001] This invention relates to a thermal recording material.

[0002] Thermal recording media that record colored images using the heating-induced color reaction between colorless or light-colored leuco dyes and phenols or organic acids are widely used. Because such thermal recording media form colored images simply by heating, they offer advantages such as compact recording devices, easy maintenance, and low noise generation. Therefore, thermal recording media are widely used as information recording materials in various applications, including label printers, automatic ticket vending machines, CD / ATM machines, order slip output machines in restaurants, and data output machines for scientific research equipment.

[0003] Because the color reaction is reversible, it is known that the colored image fades over time. This fading reaction is accelerated in high-temperature, high-humidity environments and proceeds rapidly upon contact with oils, plasticizers, etc., sometimes causing the recorded image to fade to the point of being unreadable. In recent years, disinfection and sterilization with alcohol have become commonplace in daily life, especially for the prevention of infectious diseases. In addition, food labels are sometimes heated in microwave ovens, which can cause the background to change color. Furthermore, labels used in hospitals may come into contact with chlorine bleach, which can also cause the background to change color. In other words, there is a growing demand for improved performance of thermal recording materials, such as preventing the blank areas from changing color when in contact with alcohol, preventing the printed areas from fading, and preventing the blank areas from changing color when heated in a microwave oven or in contact with chlorine bleach.

[0004] For example, Patent Documents 1 and 2 propose a thermal recording material using a diarylurea derivative and N-[2-(3-phenylureido)phenyl]benzenesulfonamide or 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate as a color developer. However, the thermal recording materials described in Patent Documents 1 and 2 have insufficient heat resistance and bleach resistance, and there is room for improvement.

[0005] Patent No. 6960562 Patent No. 6971434

[0006] The main objective of this invention is to provide a thermal recording body that exhibits excellent alcohol resistance in the recording section and the base section, heat resistance (microwave oven suitability) in the base section, and bleach resistance.

[0007] In view of the above-mentioned prior art, the present inventors have conducted extensive research and have succeeded in solving the above-mentioned problems. That is, the present invention relates to the following thermal recording body.

[0008] Item 1: A thermal recording body comprising a thermal recording layer on a support containing at least a leuco dye, a color developer, and an adhesive, wherein the main first color developer of the thermal recording layer is the following general formula (1): (In the formula, R ２ R represents an alkyl group having 1 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and the aralkyl group and aryl group may be substituted with an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a halogen atom, and multiple R ２ They may be the same or different. A １ A represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and there are multiple A １ The two compounds may be the same or different. The two compounds contain an N,N'-diarylurea compound represented by ( ), and the second color developer is the following general formula (2): A thermal recording body characterized by containing at least one selected from the group consisting of a urea urethane compound represented by the formula (1) and 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide. Item 2: The thermal recording body according to Item 1, wherein the thermal recording layer contains the urea urethane compound represented by the general formula (2) as a second color developer. Item 3: The thermal recording body according to Item 2, wherein the urea urethane compound represented by the general formula (2) is contained in 1 to 80 parts by mass per 100 parts by mass of the N,N'-diarylurea compound represented by the general formula (1). Item 4: The thermal recording body according to Item 1, wherein the thermal recording layer contains 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide as a second color developer. Item 5: The thermal recording body according to Item 4, wherein 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide is contained in 1 to 50 parts by mass per 100 parts by mass of the N,N'-diarylurea compound represented by the general formula (1). Item 6: The thermal recording body according to Item 4, wherein 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide is contained in 1 to 33.0 parts by mass per 100 parts by mass of the N,N'-diarylurea compound represented by the general formula (1). Item 7: The thermal recording body according to Item 1, wherein the thermal recording layer contains a urea urethane compound represented by the general formula (2) and 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide as a second color developer. Item 8: The thermal recording body according to Item 7, wherein 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide is contained in 1 to 50 parts by mass per 100 parts by mass of the N,N'-diarylurea compound represented by the general formula (1). Item 9: The thermal recording body according to Item 7, wherein 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide is contained in 1 to 33 parts by mass per 100 parts by mass of the N,N'-diarylurea compound represented by the general formula (1).Item 10: A thermal recording body according to any one of items 7 to 9, wherein the urea urethane compound represented by general formula (2) is contained in an amount of 1 to 80 parts by mass per 100 parts by mass of the N,N'-diarylurea compound represented by general formula (1). Item 11: A thermal recording body according to item 7, wherein the urea urethane compound represented by general formula (2) and 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide are contained in an amount of 1 to 80 parts by mass and 1 to 50 parts by mass, respectively, per 100 parts by mass of the N,N'-diarylurea compound represented by general formula (1). Item 12: The thermal recording body according to Item 7, wherein the urea urethane compound represented by the general formula (2) and 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide are contained in amounts of 1 to 80 parts by mass and 1 to 33 parts by mass, respectively, per 100 parts by mass of the N,N'-diarylurea compound represented by the general formula (1). Item 13: The thermal recording body according to any one of Items 1 to 12, wherein the support is synthetic paper. Item 14: The thermal recording body according to any one of Items 1 to 12, wherein the support is paper, and a primer layer containing an inorganic pigment and an adhesive is provided between the support and the thermal recording layer. Item 15: The thermal recording body according to Item 14, wherein the primer layer further contains hollow particles. Item 16: The thermal recording body according to Item 15, wherein the primer layer contains foamed hollow particles as hollow particles.

[0009] The thermal recording material of the present invention exhibits excellent alcohol resistance in the recording section and the base section, heat resistance (microwave oven suitability) and bleach resistance (especially to chlorine-based bleaches) in the base section.

[0010] In this specification, the expression "includes" includes the concepts of "includes," "substantially consist of," and "consisting only of." In this specification, numerical ranges expressed using "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits. In the present invention, latex includes the state of a gel or dried film formed by drying a dispersion medium.

[0011] The present invention relates to a thermal recording medium provided with a thermal recording layer containing at least a leuco dye, a developer, and an adhesive on a support. As the main first developer of the thermal recording layer, the following general formula (1): (In the formula, R ２ represents an alkyl group having 1 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. The aralkyl group and the aryl group may be substituted with an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a halogen atom. A plurality of R ２ may be the same or different. A １ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. A plurality of A １ may be the same or different.) containing an N,N'- diarylurea compound represented by the formula, and as the second developer, the following general formula (2): characterized by containing at least one selected from the group consisting of a ureauurethane compound represented by the formula, and 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide.

[0012] [Support] The support in the present invention has no particular limitation on its type, shape, dimensions, etc. For example, paper such as high-quality paper (acid paper, neutral paper), medium-quality paper, coated paper, art paper, cast-coated paper, glassine paper, resin laminated paper, synthetic paper such as polyolefin-based synthetic paper, synthetic fiber paper, non-woven fabric, synthetic resin film, and various transparent supports, etc., can be appropriately selected and used. Among them, synthetic paper and paper are preferred. The thickness of the support is not particularly limited, and is usually about 20 to 200 μm. Also, the density of the support is not particularly limited, and about 0.60 to 0.85 g / cm ３ is preferred.

[0013] [Thermal Recording Layer] (Leuco Dye) The thermal recording layer in the thermal recording medium of the present invention can contain various known colorless or light-colored leuco dyes. Specific examples of such leuco dyes are given below.

[0014] Specific examples of leuco dyes include, for example, blue-colored dyes such as 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylamino-2-methylphenyl)-3-(4-dimethylaminophenyl)-6-dimethylaminophthalide, fluorane, 3-(N-ethyl-N-p-tolyl)amino-7-N-methylanilinofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, and rhodamine B-anilinolactam. Green coloring dyes such as 3,6-bis(diethylamino)fluoran-γ-anilinolactam, 3-cyclohexylamino-6-chlorofluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-7-chlorofluoran, red coloring dyes such as 3-(N-ethyl-N-isoamyl)amino-6-methyl-7-anilinofluoran, 3-(N-methyl-N-cyclohexyl)amino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3 -di(n-butyl)amino-6-methyl-7-anilinofluorane, 3-di(n-pentyl)amino-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluorane, 3-diethylamino-7-(m-trifluoromethylanilino)fluorane, 3-(N-isoamyl-N-ethylamino)-7-(o-chloroanilino)fluorane, 3-(N-ethyl-N-2-tetrahydrofurfurylamino)-6-methyl-7-anilinofluorane, 3-( N-n-hexyl-N-ethylamino)-6-methyl-7-anilinofluorane, 3-[N-(3-ethoxypropyl)-N-ethylamino]-6-methyl-7-anilinofluorane, 3-[N-(3-ethoxypropyl)-N-methylamino]-6-methyl-7-anilinofluorane, 3-diethylamino-7-(2-chloroanilino)fluorane, 3-di(n-butylamino)-7-(2-chloroanilino)fluorane, 4,4'-bis-dimethylaminobenzhydrinbenzylether, N-2,4,5-Trichlorophenylleucoauramine, 3-Diethylamino-7-butylaminofluorane, 3-Ethyl-tolylamino-6-methyl-7-anilinofluorane, 3-Cyclohexyl-methylamino-6-methyl-7-anilinofluorane, 3-Diethylamino-6-chloro-7-(β-ethoxyethyl)aminofluorane, 3-Diethylamino-6-chloro-7-(γ-chloropropyl)aminofluorane, 3-Diethylamino-6-methyl-7-anilinofluorane, 3-(N-I Soamyl-N-ethylamino)-6-methyl-7-anilinofluorane, 3-dibutylamino-7-chloroanilinofluorane, 3-diethylamino-7-(o-chlorophenylamino)fluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-(p-toluidino)fluorane, 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluorane, 3-diethylamino -6-chloro-7-anilinofluorane, 3-dimethylamino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 2,2-bis{4-[6'-(N-cyclohexyl-N-methylamino)-3'-methylspiro[phthalide-3,9'-xanthene-2'-ylamino]phenyl}propane, 3-diethylamino-7-(3'-trifluoromethylphenyl)aminofluorane, etc. Chromochemical dyes, 3,3-bis[1-(4-methoxyphenyl)-1-(4-dimethylaminophenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide, 3,3-bis[1-(4-methoxyphenyl)-1-(4-pyrrolidinophenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide, 3-p-(p-dimethylaminoanilino)anilino-6-methyl-7-chlorofluoran, 3-p-(p-chloroanilino)anilino-6-methyl-7-chlorofluoran, 3,Examples include dyes with absorption wavelengths in the near-infrared region, such as 6-bis(dimethylamino)fluorene-9-spiro-3'-(6'-dimethylamino)phthalide. Of course, the examples are not limited to these, and two or more compounds can be used in combination as needed.

[0015] The content of such leuco dye is not particularly limited, but is preferably about 3 to 30% by mass, more preferably about 5 to 25% by mass, and even more preferably about 7 to 20% by mass, of the total solid content of the thermal recording layer. By setting it to 3% by mass or more, the color development ability can be enhanced and the recording density can be improved. By setting it to 30% by mass or less, the heat resistance can be improved.

[0016] (Color Developer) In this invention, the color developer contains an N,N'-diarylurea compound represented by the above general formula (1) (first color developer) and a urea urethane compound and / or 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide represented by the above general formula (2) (second color developer). This enables excellent alcohol resistance of the recording area and the background, heat resistance of the background (microwave oven suitability), and bleach resistance (especially to chlorine-based bleaches).

[0017] R ２ The C1-C12 alkyl group may be linear, branched, or alicyclic, preferably a C1-C6 alkyl group, more preferably a C1-C3 alkyl group. Examples of C1-C12 alkyl groups include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, cyclopentyl, hexyl, cyclohexyl, 2-ethylhexyl, and lauryl groups. The alkyl group here also includes the alkyl portion of an alkoxy group having C1-C12.

[0018] An aralkyl group refers to an arylalkyl group. Examples of aralkyl groups with 7 to 12 carbon atoms include the benzyl group, 1-phenylethyl group, 2-phenylethyl group, and 3-phenylpropyl group.

[0019] An aryl group refers to a monocyclic or polycyclic group consisting of a five- or six-membered aromatic hydrocarbon ring. Examples of aryl groups with 6 to 12 carbon atoms include the phenyl group, 1-naphthyl group, and 2-naphthyl group. The aryl portion of an aralkyl group is also included in the definition of an aryl group.

[0020] Examples of halogen atoms include fluorine, chlorine, bromine, and iodine.

[0021] In general formula (1), multiple R ２ -SO ３ The substitution position of - may be the same or different. The substitution position is preferably at position 3, position 4, or position 5, with position 3 being more preferred. Also, R ２ The number of substituents on the aralkyl group having 7 to 12 carbon atoms and the aryl group having 6 to 12 carbon atoms is not particularly limited, and can be, for example, 1 to 4.

[0022] A １ The alkyl group having 1 to 4 carbon atoms may be linear or branched, and examples include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, t-butyl group, etc.

[0023] Multiple A １ The substitution position may be the same or different. The substitution position is preferably the 3rd, 4th, or 5th position.

[0024] The N,N'-diarylurea compound represented by the general formula (1) is not particularly limited, but N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(o-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(mesitylenesulfonyloxy)phenyl]urea, N,N'-di-[3-(4-ethylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(2-naphthalenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzylsulfonyloxy)phenyl]urea, N,N'-di-[3-(ethanesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-toluenesulfonyloxy)-4-methyl-phenyl]urea, N,N'-di-[4-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[4-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(ethanesulfonyloxy)phenyl]urea, and at least one selected from the group consisting of N,N'-di-[2-(p-toluenesulfonyloxy)phenyl]urea are preferred. Among these, N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea is preferred.

[0025] The content of the N,N'-diarylurea compound is not particularly limited and may be adjusted according to the leuco dye used. Generally, 0.5 parts by mass or more is preferable, 0.8 parts by mass or more is more preferable, 1 part by mass or more is further preferable, 1.2 parts by mass or more is even more preferable, and 1.5 parts by mass or more is particularly preferable with respect to 1 part by mass of the leuco dye. On the other hand, the content of the N,N'-diarylurea compound is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, further preferably 4 parts by mass or less, and particularly preferably 3.5 parts by mass or less with respect to 1 part by mass of the leuco dye. By setting it to 0.5 parts by mass or more, the recording performance can be enhanced. On the other hand, by setting it to 10 parts by mass or less, background fogging under high-temperature environments can be effectively suppressed.

[0026] In the heat-sensitive recording layer of the present invention, as the second developer, further, 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenyl sulfone represented by the above general formula (2), 4,4'-bis[(2-methyl-5-phenoxycarbonylaminophenyl)ureido]diphenyl sulfone, 4-(2-methyl-3-phenoxycarbonylaminophenyl)ureido-4'-(4-methyl-5-phenoxycarbonylaminophenyl)ureido diphenyl sulfone, and other ureaurethane compounds, and 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide are contained, and at least one selected from the group consisting of these is contained.

[0027] When the heat-sensitive recording layer of the present invention contains the ureaurethane compound represented by the above general formula (2) as the second developer, the content of the ureaurethane compound is preferably about 1 to 80 parts by mass, more preferably about 1 to 50 parts by mass, still more preferably about 1 to 20 parts by mass, and particularly preferably about 1 to 18 parts by mass with respect to 100 parts by mass of the N,N'- diarylurea compound as the first developer. By setting it to 1 part by mass or more, the alcohol resistance of the recording part can be improved. By setting it to 80 parts by mass or less, the alcohol resistance of the background part can be improved.

[0028] When the heat-sensitive recording layer of the present invention contains 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide as the second developer, the content of the 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide is preferably about 1 to 50 parts by mass, more preferably about 1 to 33 parts by mass, still more preferably about 1 to 30.0 parts by mass, and particularly preferably about 1 to 25 parts by mass with respect to 100 parts by mass of the N,N'- diarylurea compound as the first developer. By setting it to 1 part by mass or more, the alcohol resistance of the recording part can be improved. By setting it to 50 parts by mass or less, the bleach resistance can be improved.

[0029] When the thermal recording layer of the present invention contains a urea urethane compound represented by the above general formula (2) and 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide as a second color developer, the content of 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide is preferably about 1 to 50 parts by mass, more preferably about 1 to 33 parts by mass, even more preferably about 1 to 30.0 parts by mass, and particularly preferably about 1 to 25 parts by mass, per 100 parts by mass of the N,N'-diarylurea compound as the first color developer. Furthermore, the content of the urea urethane compound is preferably about 1 to 80 parts by mass, more preferably about 1 to 50 parts by mass, even more preferably about 1 to 20 parts by mass, and particularly preferably about 1 to 18 parts by mass, per 100 parts by mass of the N,N'-diarylurea compound used as the first color developer. Furthermore, the content of the urea urethane compound and 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide is preferably about 1 to 80 parts by mass and 1 to 50 parts by mass, respectively, per 100 parts by mass of the N,N'-diarylurea compound used as the first color developer, more preferably about 1 to 80 parts by mass and 1 to 33 parts by mass, even more preferably about 1 to 20 parts by mass and 1 to 30.0 parts by mass, and particularly preferably about 1 to 18 parts by mass and 1 to 25 parts by mass, respectively.

[0030] Other color developers may be included as long as they do not impair the effects of the present invention. Specific examples of other color developers include, for example, 4-tert-butylphenol, 4-acetylphenol, 4-tert-octylphenol, 4,4'-sec-butylidenediphenol, 4-phenylphenol, 4,4'-dihydroxydiphenylmethane, 4,4'-isopropylidenediphenol, 4,4'-cyclohexylidenediphenyl, 4,4'-cyclohexylidenediphenol, 1,1-bis(4-hydroxyphenyl)-ethane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, and 4,4'-bis (p-tolylsulfonylaminocarbonylamino)diphenylmethane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 2,2'-bis[4-(4-hydroxyphenyl)phenoxy]diethyl ether, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis(3-methyl-6-tert-butylphenol), 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 2,4'-dihydroxydiphenyl Lufon, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-n-propoxydiphenyl sulfone, 4-hydroxy-4'-allyloxydiphenyl sulfone, 4-hydroxy-4'-benzyloxydiphenyl sulfone, 3,3'-diallyl-4,4'-dihydroxydiphenyl sulfone, bis(p-hydroxyphenyl)acetate butyl, bis(p-hydroxyphenyl)acetate methyl, hydroquinone monobenzyl ether, bis(3-allyl-4-hydroxyphenyl)sulfone, 4-hydroxy-4' -Methyldiphenylsulfone, 4-allyloxy-4'-hydroxydiphenylsulfone, 3,4-dihydroxyphenyl-4'-methylphenylsulfone, 4-hydroxybenzophenone, 4-dimethyl hydroxyphthalate, 4-methyl hydroxybenzoate, 4-propyl hydroxybenzoate, 4-sec-butyl hydroxybenzoate, 4-phenyl hydroxybenzoate, 4-benzyl hydroxybenzoate, 4-benzyl ester hydroxybenzoate, 4-tolyl hydroxybenzoate, 4-chlorophenyl hydroxybenzoate, 4,Phenolic compounds such as 4'-dihydroxydiphenyl ether, or aromatic carboxylic acids such as benzoic acid, p-chlorobenzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, salicylic acid, 3-tert-butylsalicylic acid, 3-isopropylsalicylic acid, 3-benzylsalicylic acid, 3-(α-methylbenzyl)salicylic acid, 3,5-di-tert-butylsalicylic acid, 4-[2-(p-methoxyphenoxy)ethyloxy]salicylic acid, 4-[3-(p-tolylsulfonyl)propyloxy]salicylic acid, 5-[p-(2-p-methoxyphenoxyethoxy)cumyl]salicylic acid, 4-[3-(p-tolylsulfonyl)propyloxy]zinc salicylate, and these phenolic compounds, aromatic carboxylic acids and polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel. Organic acidic substances such as salts, as well as antipyrine complexes of zinc thiocyanate, complex zinc salts of terephthalaldehyde and other aromatic carboxylic acids, thiourea compounds such as 4,4'-bis(N-p-tolylsulfonylurea)diphenylmethane, 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, N-p-toluenesulfonyl-N'-3-(p-toluenesulfonyloxy)phenylurea, N-p-toluenesulfonyl-N'-p-butoxycarbonylphenylurea, N-p-tolylsulfonyl-N'-phenylurea, N,N'-di-m-chlorophenylthiourea, N-(p-toluenesulfonyl)carbamoylate p-cumylphenyl ester, N-(p-toluenesulfonyl)carbamoylate p-benzyloxyphenyl ester, N-(o-toluyl)-p-toluenesulfamide, etc., with -SO in the molecule. ２ Examples include organic compounds having NH- bonds, activated clay, attapulgite, colloidal silica, and inorganic acidic substances such as aluminum silicate. The content ratio of other colorants is not particularly limited, but it is preferably 0.2 parts by mass or less, and more preferably 0.1 parts by mass or less, per 1 part by mass of the N,N'-diarylurea compound used as the first colorant.

[0031] In the present invention, the thermal recording layer may further contain a preservation improver, mainly to further enhance the preservation of the color image. Examples of such preservation improvers include 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,1-bis(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisphenol, and 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisphenol At least one compound selected from phenolic compounds such as 4-benzyloxyphenyl-4'-(2-methyl-2,3-epoxypropyloxy)phenylsulfone, 4-(2-methyl-1,2-epoxyethyl)diphenylsulfone, 4-(2-ethyl-1,2-epoxyethyl)diphenylsulfone, and isocyanuric acid compounds such as 1,3,5-tris(2,6-dimethylbenzyl-3-hydroxy-4-tert-butyl)isocyanuric acid can be used. Of course, it is not limited to these, and two or more compounds can be used in combination as needed.

[0032] When using a preservation improver, the amount used should be sufficient to improve preservation, and is usually preferably about 1 to 25% by mass of the total solid content of the thermal recording layer, and more preferably about 5 to 20% by mass.

[0033] The thermal recording layer in the present invention may also contain a sensitizer. This can increase the recording sensitivity. Examples of sensitizers include stearic acid amide, methoxycarbonyl-N-stearate benzamide, N-benzoyl stearate amide, N-eicosanoic acid amide, ethylenebisstearate amide, behenamide, methylenebisstearate amide, N-methylol stearate amide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, diphenyl sulfone, p-benzyl oxybenzoate benzyl, 1-hydroxy-2-naphthoate phenyl, 2-naphthylbenzyl ether, m-terphenyl, p-benzylbiphenyl, di-p-chlorobenzyl oxalate, di-p-methylbenzyl oxalate, dibenzyl oxalate, p-tolylbiphenyl ether, di(p-methoxyphenoxyethyl) ether, 1,2-di(3-methylphenoxy Examples include ethane, 1,2-di(4-methylphenoxy)ethane, 1,2-di(4-methoxyphenoxy)ethane, 1,2-di(4-chlorophenoxy)ethane, 1,2-diphenoxyethane, 1-(4-methoxyphenoxy)-2-(3-methylphenoxy)ethane, p-methylthiophenylbenzyl ether, 1,4-di(phenylthio)butane, p-acetoluidide, p-acetophenetidide, N-acetoacetyl-p-toluidine, 1,2-diphenoxymethylbenzene, di(β-biphenylethoxy)benzene, p-di(vinyloxyethoxy)benzene, 1-isopropylphenyl-2-phenylethane, di-o-chlorobenzyl adipate, 1,2-bis(3,4-dimethylphenyl)ethane, 1,3-bis(2-naphthoxy)propane, diphenyl, benzophenone, etc. Among these, 1,2-di(3-methylphenoxy)ethane is preferred. These can be used in combination to the extent that it does not cause any problems. The content ratio of the sensitizer should be an amount that is effective for sensitization, and usually, 2 to 25% by mass, more preferably 5 to 20% by mass, and even more preferably 5 to 15% by mass, of the total solid content of the thermal recording layer.

[0034] Other components of the thermal recording layer include adhesives, and if necessary, auxiliary agents such as pigments, crosslinking agents, waxes, metal soaps, water-resistant agents, dispersants, colored dyes, and fluorescent dyes may be used.

[0035] Examples of adhesives include water-soluble polymer materials such as polyvinyl alcohol and its derivatives, starch and its derivatives, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, olefin-acrylic acid copolymer salt, acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin and their derivatives, as well as emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, and ethylene-vinyl acetate copolymer, or water-insoluble polymer latex such as styrene-butadiene copolymer and styrene-butadiene-acrylic copolymer. Among these, polyvinyl alcohol and latex are preferred. The content of the adhesive can be selected from a wide range, but generally it is preferably about 5 to 35% by mass, and more preferably about 10 to 30% by mass, of the total solid content of the thermal recording layer.

[0036] By incorporating a crosslinking agent into the thermal recording layer, the water resistance of the thermal recording layer can be improved. Examples of crosslinking agents include aldehyde compounds such as glyoxal, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, dimethylolurea compounds, aziridine compounds, and blocked isocyanate compounds; inorganic compounds such as ammonium persulfate, ferric chloride, magnesium chloride, sodium tetraborate, and potassium tetraborate; boric acid, triester borate, boron-based polymers, hydrazide compounds, and glyoxylates. These may be used individually or in combination of two or more. The amount of crosslinking agent used is preferably about 0.1 to 5% by mass of the total solid content of the thermal recording layer.

[0037] The thermal recording layer is formed on the undercoat layer by, for example, using water as the dispersion medium, dispersing leuco dyes and color developers separately or together with sensitizers or preservatives as needed using various stirring and wet grinding machines such as ball mills, co-ball mills, attritors, and vertical and horizontal sand mills, along with water-soluble synthetic polymer compounds such as polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, methylcellulose, styrene-maleic anhydride copolymer salts, and other surfactants to obtain dispersions, then finely grinding them to an average particle size of 2 μm or less, mixing in an adhesive, and adding auxiliary agents as needed. The coating for the thermal recording layer is then applied and dried. The amount of thermal recording layer applied is not particularly limited, and the amount applied after drying is 1 to 12 g / m². ２ A suitable degree is 2 to 10 g / m ２ More preferably, 2.5 to 8 g / m ２ More preferably, 3 to 5.5 g / m ２ This is particularly preferable. The thermal recording layer can be formed in two or more layers as needed, and the composition and coating amount of each layer may be the same or different.

[0038] [Undercoat layer] The thermal recording material of the present invention may also include an undercoat layer between the support and the thermal recording layer (especially when the support is paper). The undercoat layer preferably contains an inorganic pigment and an adhesive, and more preferably contains hollow particles.

[0039] (Inorganic Pigments) The undercoat layer may contain oil-absorbing pigments and / or thermally expandable particles as pigments, with an oil absorption capacity of 70 ml / 100 g or more, particularly 80 to 150 ml / 100 g. Here, the above oil absorption capacity is a value determined according to the method of JIS K 5101.

[0040] Various oil-absorbing pigments can be used, but specific examples include inorganic pigments such as calcined kaolin, amorphous silica, light calcium carbonate, talc, and clay. The average particle size of the primary particles of these oil-absorbing pigments is preferably about 0.01 to 5 μm, and particularly preferably about 0.02 to 3 μm. The amount of oil-absorbing pigment used can be selected from a wide range, but generally it is preferably about 20 to 80% by mass, and more preferably about 25 to 75% by mass, of the total solid content of the undercoat layer.

[0041] (Adhesives) Examples of adhesives include water-soluble polymer materials such as polyvinyl alcohol and its derivatives, starch and its derivatives, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, carboxymethylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin and their derivatives, as well as emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, and ethylene-vinyl acetate copolymer, or water-insoluble polymer latex such as styrene-butadiene copolymer and styrene-butadiene-acrylic copolymer. Among these, it is preferable to use an adhesive containing latex. The content of the adhesive can be selected from a wide range, but generally it is preferable to have about 15 to 70% by mass of the total solid content of the undercoat layer, and more preferably about 25 to 60% by mass.

[0042] The glass transition temperature (Tg) of the adhesive is not particularly limited, but is preferably -10°C or lower. A glass transition temperature of -10°C or lower allows for improved image quality even in the low-energy range. A glass transition temperature of -30°C or lower is more preferable because it can further improve image quality in the low-energy range. On the other hand, a temperature of -40°C or higher is preferable because stickiness occurs below -50°C, which is undesirable.

[0043] (Hollow particles) The hollow particles are preferably made of organic resin from the viewpoint of improving cushioning properties. A primer layer containing hollow particles has high heat insulation properties, which prevents the diffusion of heat applied to the thermal recording layer and can improve the sensitivity of the thermal recording material.

[0044] Hollow particles made of organic resin can be classified into foamed and non-foamed types depending on the manufacturing method. Of these two types, foamed hollow particles generally have a larger average particle diameter and a higher hollowness ratio than non-foamed hollow particles. Therefore, foamed hollow particles provide better sensitivity and image quality than non-foamed hollow particles.

[0045] Non-foaming hollow particles can be manufactured by polymerizing seeds in a solution, then polymerizing another resin to surround the seeds, and finally swelling and dissolving the internal seeds to remove them, thereby forming a cavity inside. When swelling and dissolving the internal seeds, an alkaline aqueous solution is used. Non-foaming hollow particles with a relatively large average particle size can also be obtained by alkali swelling treatment of core-shell particles, in which alkali-swellable core particles are coated with a shell layer that does not swell with alkali.

[0046] Foamed hollow particles can be manufactured by creating particles in which a volatile liquid is sealed inside a resin, and then heating the resin to soften it while simultaneously vaporizing and expanding the liquid inside the particles.

[0047] Foamed hollow particles, through the heating and expansion of their internal liquid during the manufacturing process, have a high hollowness ratio and thus high thermal insulation properties. This can improve the sensitivity of the thermal recording material and increase the recording density. Improved sensitivity is particularly important when developing colors in the mid-tone region where less thermal energy is applied to the thermal recording layer. Furthermore, forming the thermal recording layer via a highly thermally insulating undercoat layer prevents the diffusion of heat applied to the thermal recording layer, resulting in excellent image uniformity and improved image quality. Therefore, in this embodiment, it is preferable to use foamed hollow particles that are excellent at improving the thermal insulation properties of the undercoat layer.

[0048] Resins that can be used for foamed hollow particles include thermoplastic resins such as styrene-acrylic resin, polystyrene resin, acrylic resin, polyethylene resin, polypropylene resin, polyacetal resin, chlorinated polyether resin, polyvinyl chloride resin, polyvinylidene chloride resin, acrylic resin (for example, acrylic resin with acrylonitrile as a component), styrene resin, vinylidene chloride resin, and copolymer resins mainly composed of polyvinylidene chloride and acrylonitrile. Common gases contained inside foamed hollow particles include propane, butane, isobutane, and air. Among the various resins listed above, acrylonitrile resin and copolymer resins mainly composed of polyvinylidene chloride and acrylonitrile are preferred for use in hollow particles from the viewpoint of strength to maintain the shape of the foamed particles.

[0049] In the present invention, the maximum particle diameter of the hollow particles is preferably 10 to 40 μm, more preferably 10 to 30 μm, and even more preferably 15 to 25 μm. The maximum particle diameter is also referred to as D100. When the maximum particle diameter of the hollow particles is 10 μm or more, the cushioning properties of the undercoat layer are improved, which improves the adhesion of the thermal recording material to the thermal head during printing, resulting in a high-quality thermal recording material. This high quality can lead to an improvement in the recording density in the midtones, which are colored with lower energy than that that gives the maximum recording density (Dmax). On the other hand, when the maximum particle diameter of the hollow particles is 40 μm or less, the smoothness of the undercoat layer is improved, which allows for the uniformization of the thermal recording layer provided via the undercoat layer, resulting in a thermal recording material that is less prone to white spots in the image.

[0050] In the present invention, the average particle diameter of the hollow particles is preferably 4.0 to 15 μm, more preferably 5.0 to 15 μm. Here, the average particle diameter is the median diameter, which is the diameter at which the volume occupied by the larger particles and the smaller particles are equal when the particles are divided into two groups by particle diameter, i.e., the particle diameter at which the 50% volume frequency occurs, and is also referred to as D50. When the average particle diameter of the hollow particles is 4.0 μm or more, the cushioning properties of the undercoat layer are improved, which improves the adhesion of the thermal recording material to the thermal head during printing, resulting in a high-quality thermal recording material. This high quality can lead to an improvement in the recording density in the midtones, which are colored with lower energy than that that gives the maximum recording density (Dmax). On the other hand, when the average particle diameter of the hollow particles is 15 μm or less, the smoothness of the undercoat layer is improved, which allows for the uniformization of the thermal recording layer provided via the undercoat layer, resulting in a thermal recording material that is less prone to white spots in the image.

[0051] The maximum particle diameter (D100) and average particle diameter (D50) of hollow particles can be measured using a laser diffraction particle size distribution analyzer. Alternatively, the particle diameters can be measured from particle images (SEM images) using an electron microscope and the average value of 10 values ​​can be shown.

[0052] The ratio D100 / D50, which is the ratio of the maximum particle diameter (D100) to the average particle diameter (D50) of hollow particles, is an indicator of the degree of particle size distribution. This ratio D100 / D50 is preferably 1.8 to 3.0, and more preferably 2.0 to 2.8. When the D100 / D50 of hollow particles is 1.8 or higher, the hollow particles foam sufficiently, the maximum particle diameter becomes sufficiently large, the hollowness ratio increases, and the heat insulation of the undercoat layer can be improved. On the other hand, when the D100 / D50 of hollow particles is 3.0 or lower, the size of the hollow particles becomes uniform, the smoothness of the undercoat layer increases, and white spots in the image can be suppressed.

[0053] In the particle size distribution determined by a laser diffraction particle size distribution analyzer, it is preferable that the volume percentage of hollow particles with a particle diameter of 2.0 μm or less is 1% or less. Furthermore, it is preferable that the volume percentage of hollow particles with a particle diameter of 2.0 μm or less is 0.5%, and it is even more preferable that they are not present at all. Hollow particles with a particle diameter of 2 μm or less are considered to have an extremely small contribution to thermal insulation because their particle size is too small to provide a sufficient hollow region. By setting the volume percentage of hollow particles with a particle diameter of 2 μm or less in the undercoat layer to 1% or less, the recording density, image quality, etc., can be improved.

[0054] The hollow particles preferably have a hollowness ratio of 80 to 98%, and more preferably 90 to 98%. When the hollowness ratio of the hollow particles is 80% or more, high heat insulation can be imparted to the undercoat layer containing the hollow particles. On the other hand, when the hollowness ratio of the hollow particles is 98% or less, the strength of the film surrounding the hollow portion can be improved, making it possible to create hollow particles that do not collapse during the formation of the undercoat layer.

[0055] The hollowness ratio of hollow particles is determined by measuring the true specific gravity using the IPA method and then calculating the true specific gravity value as follows: (1) Sample pretreatment - Dry the sample at 60°C overnight to prepare the sample. (2) Reagent - Isopropyl alcohol (IPA: reagent grade) (3) Measurement method - Accurately weigh the volumetric flask (W1). - Take approximately 0.5 g of the dried sample into the volumetric flask and weigh it accurately (W2). - Add approximately 50 mg of IPA and shake well to completely remove air from outside the capsule. - Add IPA to the mark and evaluate (W3). - Add only IPA to the mark in the volumetric flask as a blank and evaluate (W4). (4) Calculation of true specific gravity True specific gravity = {(W2 - W1) × ((W4 - W1) / 100)} / {(W4 - W1) - (W3 - W2)} (5) Calculation of hollow ratio Hollow ratio (%) = {1 - 1 / (1.1 / true specific gravity)} × 100

[0056] Furthermore, the hollow ratio is given by the following formula (d ３ / D ３ This value can also be obtained by multiplying by ) × 100. In this formula, d represents the inner diameter of the hollow particle, and D represents the outer diameter of the hollow particle.

[0057] In this invention, the content of hollow particles is preferably 3 to 40% by mass, and more preferably 5 to 35% by mass, of the total solid content of the undercoat layer. When the content of hollow particles is 3% by mass or more, the heat insulation properties of the undercoat layer can be improved. On the other hand, when the content of hollow particles is 40% by mass or less, problems in terms of coating properties, etc., are less likely to occur, a uniform undercoat layer can be easily formed, and the recording density can be improved. In addition, the coating strength of the undercoat layer can be increased.

[0058] The undercoat layer is formed on the support by applying an undercoat coating, prepared by mixing inorganic pigments and adhesives, and optionally hollow particles and auxiliary agents, using water as a medium, and then drying it. The amount of undercoat coating applied is not particularly limited, but is 2 to 20 g / m² by dry mass. ２ A suitable degree is 2-12 g / m ２ A more moderate degree is preferable.

[0059] [Protective Layer] In thermal recording media, a protective layer may be provided on the thermal recording layer as needed. The protective layer preferably contains a pigment and an adhesive. Furthermore, the protective layer preferably contains a lubricant such as polyolefin wax or zinc stearate to prevent sticking to the thermal head, and may also contain an ultraviolet absorber. In addition, providing a glossy protective layer can increase the added value of the product.

[0060] The pigments contained in the protective layer are not particularly limited and include, for example, inorganic pigments such as amorphous silica, kaolin, clay, light calcium carbonate, heavy calcium carbonate, calcined kaolin, titanium dioxide, magnesium carbonate, aluminum hydroxide, colloidal silica, and synthetic layered mica, as well as plastic pigments such as urea-formaldehyde resin fillers.

[0061] The adhesive contained in the protective layer is not particularly limited, and water-soluble or water-dispersible aqueous adhesives can be used. The adhesive can be appropriately selected from those that can be used in the thermal recording layer. Among these adhesives, various modified polyvinyl alcohols such as acetoacetyl-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and diacetone-modified polyvinyl alcohol are more preferably used.

[0062] The protective layer is formed on the thermal recording layer by applying a protective coating, prepared by mixing a pigment, adhesive, and auxiliary agents as needed with water as the dispersion medium, and then drying it. The amount of protective coating applied is not particularly limited, but is approximately 0.3 to 15 g / m² by dry mass. ２ A degree of 0.3 to 10 g / m is preferable. ２ A more preferable degree is 0.5 to 8 g / m ２ A more preferable degree is 1 to 8 g / m ２ A degree of 1-5 g / m is particularly preferred. ２ A higher degree is preferable. The protective layer can be formed in two or more layers as needed, and the composition and application amount of each layer may be the same or different.

[0063] [Other Layers] In the present invention, it is preferable to have an adhesive layer on at least one side of the support. This can increase the added value of the thermal recording material. As the adhesive layer, for example, by applying an adhesive, re-wettable adhesive, delayed-tack type adhesive, etc. to one side, adhesive paper, re-wettable adhesive paper, delayed-tack paper, etc. can be made. Alternatively, the side of the support opposite to the thermal recording layer can be used to provide functions such as thermal transfer paper, inkjet recording paper, carbonless paper, electrostatic recording paper, or zeography paper, making it possible to create recording paper that can record on both sides. Of course, it is also possible to make a double-sided thermal recording material. Furthermore, a back layer can be provided to suppress the penetration of oil and plasticizer from the back surface of the thermal recording material, to control curl, or to prevent static charge. It is also possible to make a linerless label that does not require release paper by applying a release layer containing silicone on the protective layer and applying an adhesive to one side.

[0064] [Thermal Recording Material] A thermal recording material can be manufactured by forming the above-mentioned layers on a support. Any known coating method can be used to form the above-mentioned layers on the support, such as the air knife method, blade method, gravure method, roll coater method, spray method, dip method, bar method, curtain method, slot die method, slide die method, or extrusion method. In addition, each coating material may be applied and dried one layer at a time to form each layer, or the same coating material may be applied in two or more layers. Furthermore, simultaneous multilayer coating may be performed by applying two or more layers at the same time. In addition, after each layer has been formed, or at any stage after all layers have been formed, a smoothing treatment can be performed using a known method such as a supercalender or softcalender.

[0065] The method for recording an image on the thermal recording medium of the present invention is not particularly limited and can be appropriately selected depending on the purpose. Examples of image recording methods include a thermal head printer and laser light (e.g., carbon dioxide laser, UV laser, semiconductor laser light, YAG laser light, fiber laser light, solid-state laser light, dye laser light, etc.). The wavelength of the laser light used is not particularly limited and can be appropriately selected depending on the purpose.

[0066] The present invention will be described in more detail by reference to examples, but the present invention is not limited thereto. Unless otherwise specified, "parts" and "%" refer to "parts by mass" and "% by mass," respectively.

[0067] (1) Preparation of leuco dye dispersion (Solution A) 40 parts of 3-di-(n-butyl)amino-6-methyl-7-anilinofluorane, 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization 500, degree of saponification 88%), and 20 parts of water were mixed and ground using a sand mill (AIMEX, sand grinder) until the median diameter measured by a laser diffraction particle size analyzer SALD2200 (Shimadzu Corporation) was 0.5 μm to obtain leuco dye dispersion (Solution A).

[0068] (2) Preparation of color developer dispersion (Solution B) 40 parts of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization 500, degree of saponification 88%), and 20 parts of water were mixed and ground using a sand mill (AIMEX, sand grinder) until the median diameter measured by a laser diffraction particle size analyzer SALD2200 (Shimadzu Corporation) was 1.0 μm to obtain the color developer dispersion (Solution B).

[0069] (3) Preparation of color developer dispersion (Solution C) 40 parts of 4,4-bis(4-methyl-3-phenoxycarbonylaminophenylurea)diphenylsulfone, 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization 500, degree of saponification 88%), and 20 parts of water were mixed and ground using a sand mill (AIMEX, sand grinder) until the median diameter measured by a laser diffraction particle size analyzer SALD2200 (Shimadzu Corporation) was 1.0 μm to obtain the color developer dispersion (Solution C).

[0070] (4) Preparation of color developer dispersion (Solution D) 40 parts of 5-(N-3-methylphenyl-sulfonylamide)-(N',N''-bis-(3-methylphenyl)-isophthalic acid diamide), 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization 500, degree of saponification 88%), and 20 parts of water were mixed and ground using a sand mill (manufactured by AIMEX, sand grinder) until the median diameter measured by a laser diffraction particle size analyzer SALD2200 (manufactured by Shimadzu Corporation) was 1.0 μm to obtain the color developer dispersion (Solution D).

[0071] (5) Preparation of color developer dispersion (Solution E) 40 parts of N-p-tolylsulfonyl-N'-3-(N-p-trisulfonyloxy)phenylurea, 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization 500, degree of saponification 88%), and 20 parts of water were mixed and ground using a sand mill (AIMEX, sand grinder) until the median diameter measured by a laser diffraction particle size analyzer SALD2200 (Shimadzu Corporation) was 1.0 μm to obtain the color developer dispersion (Solution E).

[0072] (6) Preparation of color developer dispersion (Solution F) 40 parts of N-[2-(3-phenylureido)phenyl]benzenesulfonamide, 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization 500, degree of saponification 88%), and 20 parts of water were mixed and ground using a sand mill (AIMEX, sand grinder) until the median diameter measured by a laser diffraction particle size analyzer SALD2200 (Shimadzu Corporation) was 1.0 μm to obtain the color developer dispersion (Solution F).

[0073] (7) Preparation of color developer dispersion (Solution G) 40 parts of 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization 500, degree of saponification 88%), and 20 parts of water were mixed and ground using a sand mill (AIMEX, sand grinder) until the median diameter measured by a laser diffraction particle size analyzer SALD2200 (Shimadzu Corporation) was 1.0 μm to obtain the color developer dispersion (Solution G).

[0074] (8) Preparation of color developer dispersion (Solution H) 40 parts of 4,4'-bis(N-p-tolylsulfonylurea)diphenylmethane, 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization 500, degree of saponification 88%), and 20 parts of water were mixed and ground using a sand mill (AIMEX, sand grinder) until the median diameter measured by a laser diffraction particle size analyzer SALD2200 (Shimadzu Corporation) was 1.0 μm to obtain the color developer dispersion (Solution H).

[0075] (9) Preparation of sensitizer dispersion (Solution I) 40 parts of 1,2-di(3-methylphenoxy)ethane, 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization 500, degree of saponification 88%), and 20 parts of water were mixed and ground using a sand mill (AIMEX, sand grinder) until the median diameter measured by a laser diffraction particle size analyzer SALD2200 (Shimadzu Corporation) was 1.0 μm to obtain the sensitizer dispersion (Solution I).

[0076] (10) Preparation of Pigment Dispersion (Solution J) 100 parts of hydrated kaolin, 1.3 parts of dispersant (product name: Aron T-50, manufactured by Toagosei Co., Ltd., solid content concentration 40%), and 66.3 parts of water were mixed and ground using a sand mill (manufactured by AIMEX, sand grinder) until the median diameter measured by a laser diffraction particle size analyzer SALD2200 (manufactured by Shimadzu Corporation) was 0.9 μm to obtain the pigment dispersion (Solution J).

[0077] (11) Preparation of pigment dispersion (Solution K) 100 parts of calcined kaolin, 0.8 parts of a dispersant (product name: Aron T-50, manufactured by Toagosei Co., Ltd., solid content concentration 40%), and 127 parts of water were mixed and stirred to obtain a pigment dispersion (Solution K).

[0078] (Example 1) (12) Preparation of coating solution for thermal recording layer 45.5 parts of solution A, 56.8 parts of solution B, 1.1 parts of solution C, 45.5 parts of solution I, 5 parts of pigment (product name: Nip Seal E-743, manufactured by Tosoh Silica Co., Ltd.), 28 parts of olefin-acrylic acid copolymer salt (product name: Hi-Tec S-3121, manufactured by Toho Chemical Co., Ltd.), 15 parts of a 10% aqueous solution of polyvinyl alcohol (product name: JF-05, manufactured by Nippon Vitamin Vinegar & Polyvinyl Alcohol Co., Ltd.), 41.7 parts of styrene butadiene latex (product name: L-1571, manufactured by Asahi Kasei Corporation, solid content concentration 48%), 0.5 parts of adipic acid dihydrazide (manufactured by Otsuka Chemical Co., Ltd.), 10 parts of a 10% aqueous solution of sodium dioctyl sulfosuccinate (product name: Sanmorin OT-70, manufactured by Sanyo Chemical Industries, Ltd.), and 100 parts of water were mixed and stirred to obtain a coating solution for thermal recording layer.

[0079] (13) Preparation of protective coating solution 58 parts of liquid J, 208 parts of a 12% aqueous solution of acetoacetyl-modified polyvinyl alcohol (product name: Gosenex Z-200, manufactured by Mitsubishi Chemical Corporation), 20.8 parts of zinc stearate (product name: Hydrin Z-9-36, manufactured by Chukyo Oil & Fat Co., Ltd., solid content concentration 36%), 45 parts of polyester polyurethane resin (product name: Hydran AM-1, manufactured by DIC Corporation, solid content concentration 20%), 10 parts of a 10% aqueous solution of sodium dioctyl sulfosuccinate (product name: Sanmorin OT-70, manufactured by Sanyo Chemical Industries, Ltd.), and 150 parts of water were mixed and stirred to obtain a protective coating solution for the protective recording layer.

[0080] (14) Preparation of thermal recording material Basis weight 73 g / m² ２On one side of synthetic paper (FPH80, manufactured by Yupo Corporation), the coating amount for the thermal recording layer and the coating amount for the protective layer were applied at a dry rate of 3.3 g / m² each. ２ , 2.2 g / m ２ The material was coated and dried to sequentially form a thermal recording layer and a protective layer, and then the surface was smoothed with a supercalender to obtain a thermal recording body.

[0081] (Example 2) A thermal recording body was obtained in the same manner as in Example 1, except that the amount of liquid C was changed from 1.1 parts to 2.3 parts in the preparation of the coating solution for the thermal recording layer in Example 1.

[0082] (Example 3) A thermal recording body was obtained in the same manner as in Example 1, except that the amount of liquid C was changed from 1.1 parts to 4.5 parts in the preparation of the coating solution for the thermal recording layer in Example 1.

[0083] (Example 4) A thermal recording body was obtained in the same manner as in Example 1, except that the amount of liquid C was changed from 1.1 parts to 11.4 parts in the preparation of the coating solution for the thermal recording layer in Example 1.

[0084] (Example 5) (15) Preparation of primer coating liquid 56.6 parts of hollow particles (product name: Lowpake SN-1055, manufactured by Dow, median diameter (D50) 1.0 μm, maximum particle diameter (D100) 1.8 μm, hollowness 55%, solid content concentration 26.5%), 20.8 parts of styrene butadiene latex (product name: L-1571, manufactured by Asahi Kasei Corporation, solid content concentration 48%), 16 parts of a 25% solution of oxidized starch (product name: Petrocoat C-8, manufactured by Nippon Denki Chemical Co., Ltd.), 1.1 parts of carboxymethylcellulose (product name: SG AG Gum, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content concentration 95%), 70 parts of K solution, and 100 parts of water were mixed and stirred to obtain a primer coating liquid.

[0085] Basis weight 60g / m ２ On one side of the high-quality paper, apply the above-mentioned undercoat coating solution, with a dry application amount of 6.0 g / m². ２ The coating was applied and dried to form a base coat layer, and a support for the thermal recording body was obtained. A thermal recording body was obtained in the same manner as in Example 1, except that the same thermal recording layer coating liquid as in Example 4 was applied to the base coat layer surface of the support.

[0086] (Example 6) (16) Preparation of primer coating liquid 45.5 parts of foamed particles (average particle size 5.5 μm, hollowness 98%, manufactured by Matsumoto Oil & Fat Pharmaceutical Co., Ltd., solid content concentration 33.0%), 72.9 parts of styrene butadiene latex (product name: L-1571, manufactured by Asahi Kasei Corporation, solid content concentration 48%), 16 parts of a 25% solution of oxidized starch (product name: Petrocoat C-8, manufactured by Nippon Denki Chemical Co., Ltd.), 1.1 parts of carboxymethylcellulose (product name: SG AG Gum, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content concentration 95%), 45 parts of K solution, and 100 parts of water were mixed and stirred to obtain a primer coating liquid.

[0087] Basis weight 60g / m ２ On one side of the high-quality paper, apply the above-mentioned undercoat coating solution, with a dry application amount of 6.0 g / m². ２ The material was applied and dried to form a base coat layer, and a support for the thermal recording body was obtained. A thermal recording body was obtained in the same manner as in Example 1, except that the same thermal recording layer coating liquid as in Example 4 was applied to the base coat layer surface of the support.

[0088] (Example 7) A thermal recording body was obtained in the same manner as in Example 1, except that the amount of liquid C was changed from 1.1 parts to 19.9 parts in the preparation of the coating solution for the thermal recording layer in Example 1.

[0089] (Example 8) A thermal recording body was obtained in the same manner as in Example 1, except that the amount of liquid C was changed from 1.1 parts to 28.4 parts in the preparation of the coating solution for the thermal recording layer in Example 1.

[0090] (Example 9) A thermal recording body was obtained in the same manner as in Example 1, except that in the preparation of the coating solution for the thermal recording layer in Example 1, 11.4 parts of solution D were used instead of 1.1 parts of solution C.

[0091] (Example 10) A thermal recording body was obtained in the same manner as in Example 1, except that in the preparation of the coating solution for the thermal recording layer in Example 1, 1.1 parts of solution C were replaced with 17.0 parts of solution D.

[0092] (Example 11) A thermal recording body was obtained in the same manner as in Example 1, except that in the preparation of the coating solution for the thermal recording layer in Example 1, 11.4 parts of solution C and 11.4 parts of solution D were used instead of 1.1 parts of solution C.

[0093] (Example 12) A thermal recording body was obtained in the same manner as in Example 1, except that the amount of liquid C was changed from 1.1 parts to 56.8 parts in the preparation of the coating solution for the thermal recording layer in Example 1.

[0094] (Example 13) A thermal recording body was obtained in the same manner as in Example 1, except that in the preparation of the coating solution for the thermal recording layer in Example 1, 39.8 parts of solution D were used instead of 1.1 parts of solution C.

[0095] (Comparative Example 1) A thermal recording body was obtained in the same manner as in Example 1, except that in the preparation of the coating solution for the thermal recording layer in Example 1, 1.1 parts of solution C were replaced with 0 parts of solution C.

[0096] (Comparative Example 2) A thermal recording body was obtained in the same manner as in Example 1, except that in the preparation of the coating solution for the thermal recording layer in Example 1, 11.4 parts of solution E were used instead of 1.1 parts of solution C.

[0097] (Comparative Example 3) A thermal recording body was obtained in the same manner as in Example 1, except that in the preparation of the coating solution for the thermal recording layer in Example 1, 11.4 parts of liquid F were used instead of 1.1 parts of liquid C.

[0098] (Comparative Example 4) A thermal recording body was obtained in the same manner as in Example 1, except that in the preparation of the coating solution for the thermal recording layer in Example 1, 11.4 parts of liquid G were used instead of 1.1 parts of liquid C.

[0099] (Comparative Example 5) A thermal recording body was obtained in the same manner as in Example 1, except that in the preparation of the coating solution for the thermal recording layer in Example 1, 11.4 parts of solution H were used instead of 1.1 parts of solution C.

[0100] The above examples and comparative examples were evaluated using the following method. The results are shown in Table 1.

[0101] [Alcohol Resistance] Using a thermal recording evaluation machine (product name: TH-PMD, manufactured by Okura Electric Co., Ltd.), each thermal recording material was recorded with an applied energy of 0.25 mJ / dot (high gradation). After coloring, samples of each thermal recording material were immersed in 100% ethanol for 1 hour, and the optical density of the blank paper area and the printed area after treatment was measured using a spectrophotometer (X-riteeXact, manufactured by X-rite Co., Ltd.). The evaluation criteria were as follows: (Blank paper area) Optical density 0.10 or less: No background color development, very good. Optical density greater than 0.10 and 0.20 or less: Slight background color development occurs, but is good. Optical density greater than 0.20 and 0.30 or less: Background color development is observed, but there is no practical problem. Optical density greater than 0.30: Background color development is significant, and there is a practical problem. (Printed area) Optical density 1.00 or more: Very good. Optical density less than 1.00 but 0.80 or higher: Slight fading occurs, but the quality is excellent. Optical density less than 0.80 but 0.60 or higher: Fading is observed, but there are no practical problems. Optical density less than 0.60: Fading is significant, and there are practical problems.

[0102] [Heat Resistance (Microwave Suitable)] Samples with acrylic adhesive applied to the back of each thermal recording material were attached to the lid of a plastic container. 50 ml of water was added to the plastic container, the lid was closed, and the container was placed in a microwave oven. The sample was heated at 500W for 1 minute, and the optical density of the blank paper area after treatment was measured using a spectrophotometer (X-riteeXact, manufactured by X-rite). The evaluation criteria were as follows: (Blank paper area) Optical density 0.10 or less: No scalp discoloration, excellent. Optical density greater than 0.10 and 0.20 or less: Slight scalp discoloration occurs, but excellent. Optical density greater than 0.20 and 0.30 or less: Scalp discoloration is observed, but there is no practical problem. Optical density greater than 0.30: Scalp discoloration is significant, and there is a practical problem.

[0103] [Chlorine-based bleach resistance] Samples of each thermal recording material were immersed in 1% volume kitchen bleach for 1 hour. The b* value of the white paper area after treatment was measured using a colorimeter (CR-400, Konica Minolta) with a D65 light source, and the Δb* value was calculated by subtracting the b* value before treatment from the b* value after treatment. The evaluation criteria were as follows: (Δb* value) b* value of 1.0 or less: Excellent. b* value greater than 1.0 and 2.0 or less: Slight yellowing is observed, but excellent. b* value greater than 2.0 and 4.0 or less: Yellowing is observed, but no practical problems. b* value greater than 4.0: Strong yellowing, practical problems.

[0104]

Claims

1. A thermal recording body comprising a thermal recording layer on a support containing at least a leuco dye, a color developer, and an adhesive, wherein the main first color developer of the thermal recording layer is the following general formula (1): (In the formula, R ２ R represents an alkyl group having 1 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and the aralkyl group and aryl group may be substituted with an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a halogen atom, and multiple R ２ They may be the same or different. A １ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and multiple A １ The two compounds may be the same or different. The two compounds contain an N,N'-diarylurea compound represented by ( ), and the second color developer is the following general formula (2): A thermal recording body characterized by containing a urea urethane compound represented by and at least one selected from the group consisting of 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide.

2. The thermal recording body according to claim 1, wherein the thermal recording layer contains a urea urethane compound represented by the general formula (2) as a second color developer.

3. The thermal recording body according to claim 2, wherein the urea urethane compound represented by the general formula (2) is contained in 1 to 80 parts by mass per 100 parts by mass of the N,N'-diarylurea compound represented by the general formula (1).

4. The thermal recording body according to claim 1, wherein the thermal recording layer contains 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide as a second color developer.

5. The thermal recording body according to claim 4, wherein 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide is contained in 1 to 50 parts by mass per 100 parts by mass of the N,N'-diarylurea compound represented by the general formula (1).

6. The thermal recording body according to claim 4, wherein 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide is contained in 1 to 33.0 parts by mass per 100 parts by mass of the N,N'-diarylurea compound represented by the general formula (1).

7. The thermal recording body according to claim 1, wherein the thermal recording layer contains, as a second color developer, a urea urethane compound represented by the general formula (2) and 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide.

8. The thermal recording body according to claim 7, wherein 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide is contained in 1 to 50 parts by mass per 100 parts by mass of the N,N'-diarylurea compound represented by the general formula (1).

9. The thermal recording body according to claim 7, wherein 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide is contained in 1 to 33 parts by mass per 100 parts by mass of the N,N'-diarylurea compound represented by the general formula (1).

10. The thermal recording body according to claim 7, wherein the urea urethane compound represented by the general formula (2) is contained in 1 to 80 parts by mass per 100 parts by mass of the N,N'-diarylurea compound represented by the general formula (1).

11. The thermal recording body according to claim 7, wherein the urea urethane compound represented by the general formula (2) and 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide are contained in amounts of 1 to 80 parts by mass and 1 to 50 parts by mass, respectively, per 100 parts by mass of the N,N'-diarylurea compound represented by the general formula (1).

12. The thermal recording body according to claim 7, wherein the urea urethane compound represented by the general formula (2) and 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide are contained in amounts of 1 to 80 parts by mass and 1 to 33 parts by mass, respectively, per 100 parts by mass of the N,N'-diarylurea compound represented by the general formula (1).

13. The thermal recording body according to any one of claims 1 to 12, wherein the support is synthetic paper.

14. The thermal recording body according to any one of claims 1 to 12, wherein the support is paper, and a primer layer containing an inorganic pigment and an adhesive is provided between the support and the thermal recording layer.

15. The thermal recording body according to claim 14, wherein the undercoat layer further contains hollow particles.

16. The thermal recording body according to claim 15, wherein the undercoat layer contains foamed hollow particles as hollow particles.

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