Heat-sensitive recording material

Abstract

To provide a heat-sensitive recording material which is excellent in terms of high-speed printing performance among various properties required for heat-sensitive recording materials, which is also excellent in terms of oil resistance, plasticizer resistance, printing runnability and the like.SOLUTION: A heat-sensitive recording material has a primer coating layer on a supporting body, and also has a heat-sensitive recording layer on the primer coating layer, the heat-sensitive recording layer containing a colorless or pale electron-donating leuco dye and an electron-accepting color developer. The heat-sensitive recording layer contains, as the electron-accepting color developer, a urea compound. The primer coating layer contains 50-95 wt.% of a pigment in terms of solid content, while containing 50 wt.% or more of plastic hollow particles relative to the pigment in terms of solid content.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a thermal recording material that utilizes a color-developing reaction between a colorless or pale-colored electron-donating leuco dye (hereinafter also referred to as "leuco dye") and an electron-accepting color developer (hereinafter also referred to as "color developer"), and which has excellent high-speed printing properties, as well as excellent oil resistance, plasticizer resistance, printability, etc. [Background technology]

[0002] Generally, thermal recording media are made by coating a support material such as paper, synthetic paper, film, or plastic with a coating solution containing a colorless or light-colored leuco dye and a developer. The material develops color through an instantaneous chemical reaction caused by heating using a thermal head, hot stamp, thermal pen, or laser light, resulting in a recorded image. Thermal recording media are widely used as recording media in fax machines, computer terminal printers, automatic ticket vending machines, measurement recorders, and receipts in supermarkets and convenience stores. In recent years, thermal recording materials have expanded to a wide range of applications, including tickets, receipts, labels, bank ATMs, gas and electricity meter readings, and money vouchers such as betting tickets for cars and horse racing. As a result, various performance characteristics are required, such as water resistance, plasticizer resistance in the image area, heat resistance and oil resistance in the blank area, and the ability to preserve both the image and blank areas under harsh conditions. In response to such requirements, thermal recording materials (Patent Document 1) have been disclosed that improve water resistance, plasticizer resistance of the image area, and heat resistance of the blank area by using a combination of two specific color developers, and urea compounds as color developers (Patent Documents 2 and 3) have been disclosed to improve the required performance of thermal recording materials, such as color density, whiteness, and preservation of the printed area. Furthermore, as a method to improve the sensitivity and print quality of thermal recording materials, it has been proposed to provide an undercoat layer containing hollow particles between the support and the thermal recording layer (Patent Documents 4, 5, etc.). [Prior art documents] [Patent Documents]

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Disclosure of the Invention

Problems to be Solved by the Invention

[0004] Therefore, an object of the present invention is to provide a thermal recording medium that is excellent in high-speed printing performance among various performances required for a thermal recording medium, and is further excellent in oil resistance, plasticizer resistance, printing running performance, and the like.

Means for Solving the Problems

[0005] As a result of intensive studies, the present inventors have found that by incorporating a specific urea compound as a developer in a thermal recording layer provided on a support, providing an undercoat layer between the support and the thermal recording layer, and incorporating a specific amount of plastic hollow particles in the undercoat layer, the above problems can be solved, and the present invention has been completed. That is, the present invention is In a thermal recording medium provided with an undercoat layer on a support and a thermal recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer on the undercoat layer, the thermal recording layer contains, as an electron-accepting developer, a urea compound represented by the following (1) or (2), the undercoat layer contains a binder and a pigment, the pigment contains 50 to 95% by weight of the solid content, and the pigment contains plastic hollow particles, and the plastic hollow particles in the pigment contain 50% by weight or more of the solid content, which is a thermal recording medium. (1) A first urea compound represented by the following general formula (Chemical Formula 5), [Chemical Formula] (In the formula, R2 represents a hydrogen atom or an alkyl group, and R 3 may be the same or different and is a group represented by the following formula (Chemical Formula 11), and R in the benzene ring of the general formula (Chemical Formula 5) 3 -SO2-O- may be in the same or different positions and is the 3-position, 4-position or 5-position.) [Chemical Formula] (In the formula, R 4 ~R 8 may be the same or different and represent a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, or an arylamino group.) (2) A second urea compound represented by the following general formula (Chemical Formula 3) [Chemical Formula] (In the formula, R 2 , R 4 ~R 8 are defined as above, and m represents an integer from 0 to 2.) [Advantages of the Invention]

[0006] According to the present invention, it is possible to provide a thermal recording medium having coloring performance and good high-speed printing property, and further, it is possible to provide a thermal recording medium having good oil resistance, plasticizer resistance, printing running property, etc. [Embodiments for Carrying Out the Invention]

[0007] The thermal recording medium of the present invention has a thermal recording layer on a support and an undercoat layer between the support layer and the thermal recording layer, the thermal recording layer contains a specific urea compound as an electron-accepting color developer, and the undercoat layer contains a specific amount of plastic hollow particles. Hereinafter, various materials used in the heat-sensitive recording layer of the heat-sensitive recording medium of the present invention will be exemplified. However, binders, crosslinking agents, pigments, etc. can also be used in the undercoat layer and each coating layer provided as necessary, as long as they do not inhibit the desired effects on the above problems.

[0008] The urea compound of the present invention is selected from the following (1) to (2). (1) A first urea compound represented by the following general formula (Formula 5), [Chemical formula] (In the formula, R 2 and R 3 are defined as above.) (2) A second urea compound represented by the following general formula (Formula 3), [Chemical formula] (In the formula, R 2 and m are defined as above, and R 4 to R 8 will be described later.) (3) A third urea compound represented by the following formula (Formula 4) [Chemical formula] (In the formula, R 2 is defined as above, and R 4 to R 8 will be described later.)

[0009] Furthermore, the urea compound used in the present invention is selected from the urea compounds represented by the above (1) to (2).

[0010] The first urea compound used in the present invention is represented by the following formula (Formula 5). [Chemical formula]

[0011] In general formula (Formula 5), n represents 0 or 1, preferably 1. In general formula (Formula 5), R 3R represents an alkyl group, aralkyl group, or aryl group, which may be substituted or unsubstituted. This alkyl group is, for example, a linear, branched, or alicyclic alkyl group, and preferably has 1 to 12 carbon atoms. This aralkyl group preferably has 7 to 12 carbon atoms, and this aryl group preferably has 6 to 12 carbon atoms. Furthermore, if these are substituted, the substituent is preferably 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. Also, multiple R 3 They may be the same or different. R in the benzene ring of general formula (Chemical Formula 5) 3 The position of -SO2-O- may be the same or different, preferably at position 3, 4, or 5.

[0012] Examples of alkyl groups include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, cyclopentyl group, hexyl group, cyclohexyl group, 2-ethylhexyl group, and lauryl group.

[0013] Examples of aralkyl groups include unsubstituted groups such as benzyl group, 1-phenylethyl group, 2-phenylethyl group, 3-phenylpropyl group, p-methylbenzyl group, m-methylbenzyl group, m-ethylbenzyl group, p-ethylbenzyl group, pi-propylbenzyl group, pt-butylbenzyl group, p-methoxybenzyl group, m-methoxybenzyl group, o-methoxybenzyl group, m,p-di-methoxybenzyl group, p-ethoxy-m-methoxybenzyl group, p-phenylmethylbenzyl group, p-cumylbenzyl group, p-phenylbenzyl group, o-phenylbenzyl group, m-phenylbenzyl group, p-tolylbenzyl group, m-tolylbenzyl group, o-tolylbenzyl group, and p-chlorobenzyl group, or aralkyl groups substituted with alkyl groups, alkoxy groups, aralkyl groups, aryl groups, or halogen atoms.

[0014] Examples of aryl groups include unsubstituted groups such as phenyl group, p-tolyl group, m-tolyl group, o-tolyl group, 2,5-dimethylphenyl group, 2,4-dimethylphenyl group, 3,5-dimethylphenyl group, 2,3-dimethylphenyl group, 3,4-dimethylphenyl group, mesitylene group, p-ethylphenyl group, pi-propylphenyl group, pt-butylphenyl group, p-methoxyphenyl group, 3,4-dimethoxyphenyl group, p-ethoxyphenyl group, p-chlorophenyl group, 1-naphthyl group, 2-naphthyl group, and t-butylated naphthyl group, or aryl groups substituted with alkyl groups, alkoxy groups, aralkyl groups, aryl groups, or halogen atoms.

[0015] R 2 represents a hydrogen atom or an alkyl group, preferably a hydrogen atom. The alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, such as a methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, t-butyl group, etc. R in the benzene ring of general formula (Chemical Formula 2) 2 The position may be the same or different, and is preferably the 3rd, 4th, or 5th position.

[0016] As the first urea compound of the present invention, a urea compound represented by the following general formula (Chemical Formula 6) is even more preferred. [ka] In the general formula (chemical formula 6), R 9 is an alkyl group or alkoxy group, preferably an alkyl group, and o represents an integer from 0 to 3, preferably 0 to 2, more preferably 0 to 1. The number of carbon atoms in this alkyl group is, for example, 1 to 12, preferably 1 to 8, more preferably 1 to 4. R in the benzene ring of general formula (Chemical Formula 6) 9 The position may be the same or different, preferably the 3rd, 4th, or 5th position, and preferably the 4th position.

[0017] Furthermore, as the first urea compound of the present invention, for example, N,N'-di-[3-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-4-methylphenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-4-ethylphenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-5-methylphenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-4-propylphenyl]urea, N,N'-di-[3-(o-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(m-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-toluenesulfonyloxy)-4-methylphenyl]urea, N,N'-di-[3-(p-xylenesulfonyloxy)phenyl]urea, N,N'-di-[3-(m-xylenesulfonyloxy)phenyl]urea, N,N'-di-[3-(mesitylenesulfonyloxy)phenyl]urea, N,N'-di-[3-(1-naphthalenesulfonyloxy)phenyl]urea, N, N'-di-[3-(2-naphthalenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-ethylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-propylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-isopropylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(pt-butylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(m-methoxybenzenesulfonyloxy)phenyl]urea [phenyloxy)phenyl]urea, N,N'-di-[3-(o-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(m,p-dimethoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-ethoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-propoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-butoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-cumylbenzylsulfonyloxy)phenyl]urea, N,Examples include, but are not limited to, N'-di-[3-(p-cumylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(o-phenylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-phenylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-chlorobenzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(ethanesulfonyloxy)phenyl]urea, and N,N'-di-[3-(benzylsulfonyloxy)phenyl]urea.

[0018] The second urea compound used in the present invention is represented by the following formula (Chemical Formula 3). [ka]

[0019] In the general formula (Chemical formula 3), R 2 , R 4 ~R 8 R is defined in the same way as above. In the general formula (Chemical Formula 3), R 4 ~R 8 R is preferably a hydrogen atom, an alkyl group, or an alkoxy group. In particular, 4 , R 5 , R 7 , R 8 For example, a hydrogen atom is preferred, R 6 A hydrogen atom or an alkyl group is preferred. 6 Alkyl alkyl groups are particularly preferred. These alkyl groups (including alkylcarbonyloxy groups, alkylcarbonylamino groups, alkylsulfonylamino groups, monoalkylamino groups, and dialkylamino groups) and aryl groups (including aryloxy groups, arylcarbonyloxy groups, arylcarbonylamino groups, arylsulfonylamino groups, and arylamino groups) are defined in the same way as the alkyl and aryl groups in the general formula (Chemical Formula 2) above. This alkoxy group is, for example, a linear, branched, or alicyclic alkoxy group, and preferably has 1 to 12 carbon atoms. -O-(CONH) in the benzene ring of general formula (Chemical Formula 3) m The position of the -SO2-substituted phenyl group is preferably at the 3rd, 4th, or 5th position (the same applies to general formulas (Chemical Formula 7) and (Chemical Formula 8) below). In the general formula (Chemical Formula 3), m represents an integer between 0 and 2, preferably between 0 and 1.

[0020] As the second urea compound of the present invention, a urea compound represented by the following general formula (Chemical Formula 7) or the following general formula (Chemical Formula 8) is preferred. [ka] [ka]

[0021] The third urea compound used in the present invention is represented by the following formula (Chemical Formula 4). [ka] In the general formula (Chemical formula 4), R 2 , R 4 ~R 8 It is defined in the same way as above.

[0022] The preferred third urea compound is N-[2-(3-phenylureido)phenyl]benzenesulfonamide, which is represented by the following formula and is available, for example, from Nippon Soda Co., Ltd. under the trade name NKK1304. [ka]

[0023] The content of the urea compound in the thermal recording layer of the present invention (solid content, total amount if multiple urea compounds are included) is 1.0 to 70.0% by weight, preferably 5.0 to 65.0% by weight, and more preferably 10.0 to 60.0 parts by weight. The content of the first urea compound in the thermal recording layer of the present invention is 1.0 to 50.0% by weight, preferably 5.0 to 40.0% by weight. The content of the second urea compound is 5.0 to 50.0% by weight, preferably 5.0 to 40.0% by weight.

[0024] The thermal recording layer of the present invention may use color developers other than the first and second urea compounds described above. Examples of such color developers include inorganic acidic substances such as activated clay, attapulgite, colloidal silica, and aluminum silicate, as well as 4,4'-isopropylidenediphenol, 1,1-bis(4-hydroxyphenyl)cyclohexane, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, and 4-hydroxybenzoic acid. Benzyl, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4'-n-propoxydiphenylsulfone, bis(3-allyl-4-hydroxyphenyl)sulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxyphenyl-4'-benzyloxyphenylsulfone, 3,4-dihydroxyphenyl-4'-methylphenylsulfone, 1-[4-(4-Hyd [(4-(4-isopropoxyphenylsulfonyl)phenoxy]-4-[4-(4-isopropoxyphenylsulfonyl)phenoxy]butane, phenol condensation composition described in Japanese Patent Publication No. 2003-154760, aminobenzenesulfonamide derivative described in Japanese Patent Publication No. Hei 8-59603, bis(4-hydroxyphenylthioethoxy)methane, 1,5-di(4-hydroxyphenylthio)-3-oxapentane, bis(p-hydroxyphenyl)butyl acetate, bis(p-hydroxyphenyl)methyl acetate, 1,1-bis( 4-Hydroxyphenyl)-1-phenylethane, 1,4-bis[α-methyl-α-(4'-hydroxyphenyl)ethyl]benzene, 1,3-bis[α-methyl-α-(4'-hydroxyphenyl)ethyl]benzene, di(4-hydroxy-3-methylphenyl) sulfide, 2,2'-thiobis(3-tert-octylphenol), 2,2'-thiobis(4-tert-octylphenol), compounds described in WO02 / 081229 or Japanese Patent Publication No. 2002-301873, and N,Examples include thiourea compounds such as N'-di-m-chlorophenylthiourea, p-chlorobenzoic acid, stearyl gallate, bis[4-(n-octyloxycarbonylamino)zinc salicylate]dihydrate, 4-[2-(p-methoxyphenoxy)ethyloxy]salicylic acid, 4-[3-(p-tolylsulfonyl)propyloxy]salicylic acid, and 5-[p-(2-p-methoxyphenoxyethoxy)cumyl]salicylic acid, as well as salts of these aromatic carboxylic acids with polyvalent metal salts such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel, and also antipyrine complexes of zinc thiocyanate and complex zinc salts of terephthalaldehyde and other aromatic carboxylic acids. These color developers can be used individually or in mixtures of two or more. 1-[4-(4-hydroxyphenylsulfonyl)phenoxy]-4-[4-(4-isopropoxyphenylsulfonyl)phenoxy]butane is available, for example, as product name JKY-214 from API Corporation, and the phenol condensation composition described in Japanese Patent Publication No. 2003-154760 is available, for example, as product name JKY-224 from API Corporation. Furthermore, compounds described in WO02 / 081229, etc., are available as product names NKK-395 and D-100 from Nippon Soda Co., Ltd. In addition, metal chelate-type coloring components such as higher fatty acid metal double salts and polyvalent hydroxyaromatic compounds described in Japanese Patent Publication No. 10-258577 can also be included.

[0025] When the thermal recording layer of the present invention contains a color developer other than the first and second urea compounds, the total content (solid content) of the first and second urea compounds used relative to the total color developer (including the first and second urea compounds) contained in the thermal recording layer is preferably 50% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more.

[0026] All leuco dyes known in the field of conventional pressure-sensitive or thermal recording paper can be used as leuco dyes in this invention and are not particularly limited, but triphenylmethane compounds, fluorane compounds, fluorene compounds, and divinyl compounds are preferred. Specific examples of typical colorless or light-colored dyes (dye precursors) are shown below. These dye precursors may be used individually or in mixtures of two or more.

[0027] <Triphenylmethane-based leuco dyes> 3,3-Bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-Bis(p-dimethylaminophenyl)phthalide (also known as malachite green lactone)

[0028] <Fluorane-based leuco dyes> 3-Diethylamino-6-methylfluorane, 3-Diethylamino-6-methyl-7-anilinofluorane, 3-Diethylamino-6-methyl-7-(o,p-dimethylanilino)fluorane, 3-Diethylamino-6-methyl-7-chlorofluorane, 3-Diethylamino-6-methyl-7-(m-trifluoromethylanilino)fluorane, 3-Diethylamino-6-methyl-7-(o-chloroanilino)fluorane, 3-Diethylamino-6-methyl-7-(p-chloroanilino)fluorane, 3-Diethylamino-6-methyl-7-(o- (Luoroanilino)fluorane, 3-diethylamino-6-methyl-7-(m-methylanilino)fluorane, 3-diethylamino-6-methyl-7-n-octylanilinofluorane, 3-diethylamino-6-methyl-7-n-octylaminofluorane, 3-diethylamino-6-methyl-7-benzylaminofluorane, 3-diethylamino-6-methyl-7-dibenzylaminofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-diethylamino-6-chloro 7-p-methylanilinofluorane, 3-diethylamino-6-ethoxyethyl-7-anilinofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-(m-trifluoromethylanilino)fluorane, 3-diethylamino-7-(o-chloroanilino)fluorane, 3-diethylamino-7-(p-chloroanilino)fluorane, 3-diethylamino-7-(o-fluoroanilino)fluorane, 3-diethylamino-benzo[a]fluorane, 3-diethylamino -Benzo[c]fluorane, 3-dibutylamino-6-methyl-fluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-(o,p-dimethylanilino)fluorane, 3-dibutylamino-6-methyl-7-(o-chloroanilino)fluorane, 3-dibutylamino-6-methyl-7-(p-chloroanilino)fluorane, 3-dibutylamino-6-methyl-7-(o-fluoroanilino)fluorane, 3-dibutylamino-6-methyl-7-(m-trifluoromethylanilino)fluorane,3-Dibutylamino-6-methyl-7-chlorofluorane, 3-Dibutylamino-6-ethoxyethyl-7-anilinofluorane, 3-Dibutylamino-6-chloro-7-anilinofluorane, 3-Dibutylamino-6-methyl-7-p-methylanilinofluorane, 3-Dibutylamino-7-(o-chloroanilino)fluorane, 3-Dibutylamino-7-(o-fluoroanilino)fluorane, 3-Di-n-pentylamino-6-methyl-7-anilinofluorane, 3-Di-n-pentylamino-6-methyl-7-(p-chloroanilino)fluorane, 3-di-n-pentylamino-7-(m-trifluoromethylanilino)fluorane, 3-di-n-pentylamino-6-chloro-7-anilinofluorane, 3-di-n-pentylamino-7-(p-chloroanilino)fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-(N-methyl-N-propylamino)-6-methyl-7-anilinofluorane, 3-(N-methyl-N-cyclohexylamino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-cyclohexylamino) Xylamino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-xylamino)-6-methyl-7-(p-chloroanilino)fluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isoamylamino)-6-chloro-7-anilinofluorane, 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isobutylamino) -6-methyl-7-anilinofluorane, 3-(N-ethyl-N-ethoxypropylamino)-6-methyl-7-anilinofluorane, 3-cyclohexylamino-6-chlorofluorane, 2-(4-oxahexyl)-3-dimethylamino-6-methyl-7-anilinofluorane, 2-(4-oxahexyl)-3-diethylamino-6-methyl-7-anilinofluorane, 2-(4-oxahexyl)-3-dipropylamino-6-methyl-7-anilinofluorane, 2-methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluorane,2-Methoxy-6-p-(p-dimethylaminophenyl)aminoanilinofluorane, 2-chloro-3-methyl-6-p-(p-phenylaminophenyl)aminoanilinofluorane, 2-chloro-6-p-(p-dimethylaminophenyl)aminoanilinofluorane, 2-nitro-6-p-(p-diethylaminophenyl)aminoanilinofluorane, 2-amino-6-p-(p-diethylaminophenyl)aminoanilinofluorane, 2-diethylamino-6-p-(p-diethylaminophenyl)aminoanilinofluorane, 2-phenyl-6-methyl-6-p-(p- Phenylaminophenyl)aminoanilinofluorane, 2-benzyl-6-p-(p-phenylaminophenyl)aminoanilinofluorane, 2-hydroxy-6-p-(p-phenylaminophenyl)aminoanilinofluorane, 3-methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluorane, 3-diethylamino-6-p-(p-diethylaminophenyl)aminoanilinofluorane, 3-diethylamino-6-p-(p-dibutylaminophenyl)aminoanilinofluorane, 2,4-dimethyl-6-[(4-dimethylamino)anilino]-fluorane,

[0029] <Fluorene-based leuco dyes> 3,6,6'-Tris(dimethylamino)spiro[fluorene-9,3'-phthalide], 3,6,6'-Tris(diethylamino)spiro[fluorene-9,3'-phthalide]

[0030] <Divinyl leuco dyes> 3,3-Bis-[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethenyl]-4,5,6,7-tetrabromophthalide, 3,3-Bis-[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethenyl]-4,5,6,7-tetrachlorophthalide, 3,3-Bis-[1,1-bis(4-pyrrolidinophenyl)ethylene-2-yl]-4,5,6,7-tetrabromophthalide, 3,3-Bis-[1-(4-methoxyphenyl)-1-(4-pyrrolidinophenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide

[0031] <Other> 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-octyl-2-methylindole-3-yl)-4-azaphthalide, 3-(4-cyclohexylethylamino-2-methoxyphenyl)-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalide, 3,3-bis(1-ethyl-2-methylindole-3-yl)phthalide, 3,6-bis(diethylamino)fluoran-γ-(3'-nitro)anilinolactam, 3,6-bis(diethyl Mino)fluoran-γ-(4'-nitro)anilinolactam, 1,1-bis-[2',2',2'',2''-tetrakis-(p-dimethylaminophenyl)-ethenyl]-2,2-dinitrileethane, 1,1-bis-[2',2',2'',2''-tetrakis-(p-dimethylaminophenyl)-ethenyl]-2-β-naphthoylethane, 1,1-bis-[2',2',2'',2''-tetrakis-(p-dimethylaminophenyl)-ethenyl]-2,2-diacetylethane, bis-[2,2,2',2'-tetrakis-(p-dimethylaminophenyl)-ethenyl]-methylmalonate dimethyl ester

[0032] Conventional known sensitizers can be used as sensitizers in the present invention. Such sensitizers include fatty acid amides such as stearic acid amide and palmitic acid amide, ethylenebisamide, montanic acid wax, polyethylene wax, 1,2-bis-(3-methylphenoxy)ethane, p-benzyl biphenyl, β-benzyloxynaphthalene, 4-biphenyl-p-tolyl ether, m-terphenyl, 1,2-diphenoxyethane, dibenzyl oxalate, di(p-chlorobenzyl) oxalate, di(p-methylbenzyl) oxalate, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, di-p-tolyl carbonate, phenyl-α- Examples of sensitizers include naphthyl carbonate, 1,4-diethoxynaphthalene, phenyl 1-hydroxy-2-naphthoate, o-xylene-bis-(phenyl ether), 4-(m-methylphenoxymethyl)biphenyl, 4,4'-ethylenedioxy-bis-benzoate dibenzyl ester, dibenzoyloxymethane, 1,2-di(3-methylphenoxy)ethylene, bis[2-(4-methoxyphenoxy)ethyl] ether, p-methyl p-nitrobenzoate, phenyl p-toluenesulfonate, o-toluenesulfonamide, and p-toluenesulfonamide. These sensitizers may be used individually or in combination of two or more.

[0033] Examples of pigments used in this invention include kaolin, calcined kaolin, calcium carbonate, aluminum oxide, titanium dioxide, magnesium carbonate, aluminum silicate, magnesium silicate, calcium silicate, aluminum hydroxide, and silica, and these can be used in combination depending on the required quality.

[0034] Examples of binders used in the present invention include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, olefin-modified polyvinyl alcohol, nitrile-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, other modified polyvinyl alcohols, hydroxyethylcellulose, methylcellulose, ethylcellulose, carboxymethylcellulose, styrene-maleic anhydride copolymer, styrene-butadiene copolymer, and cellulose derivatives such as ethylcellulose and acetylcellulose, casein, gum arabic, oxidized starch, etherified starch, dialdehyde starch, esterified starch, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylic acid ester, polyvinyl butyral, polystyrene and copolymers thereof, polyamide resins, silicone resins, petroleum resins, terpene resins, ketone resins, coumarone resins, and the like. These polymeric substances can be used dissolved in solvents such as water, alcohol, ketones, esters, and hydrocarbons, or dispersed in water or other media in an emulsified or paste-like state, and can be used in combination depending on the required quality.

[0035] The lubricants used in this invention include zinc stearate, calcium stearate, and other fatty acids. Examples include metal oxide salts, waxes, and silicone resins.

[0036] In the present invention, to the extent that the desired effects for the above-mentioned problems are not inhibited, 4,4′-butylidene(6-t-butyl-3-methylphenol), 2,2′-di-t-butyl-5,5′-dimethyl-4,4′-sulfonyldiphenol, 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, etc. can also be added as stabilizers to improve the oil resistance of the image portion, etc. In addition, benzophenone-based or triazole-based ultraviolet absorbers, dispersants, defoamers, antioxidants, fluorescent dyes, etc. can be used.

[0037] The types and amounts of leuco dyes, developers, sensitizers, and other components used in the thermal recording layer of the present invention are determined according to the required performance and recording suitability and are not particularly limited, but typically, about 0.5 to 10 parts by weight of developer, 0.1 to 10 parts by weight of sensitizer, 0.5 to 20 parts by weight of pigment, 0.01 to 10 parts by weight of stabilizer, and 0.01 to 10 parts by weight of other components are used per 1 part by weight of leuco dye. The binder is suitable at about 5 to 25% by weight of the solid content of the thermal recording layer.

[0038] In this invention, the leuco dye, color developer, and any additional materials as needed are pulverized to a particle size of a few microns or less using a pulverizer such as a ball mill, attritor, or sand grinder, or a suitable emulsifier, and then a binder and various additive materials are added as needed to form a coating solution. Water or alcohol can be used as the solvent for this coating solution, and its solid content is approximately 20-40% by weight.

[0039] The thermal recording body of the present invention includes an undercoat layer between the support and the thermal recording layer. This undercoat layer consists mainly of a binder and a pigment. As the binder used for the undercoat layer, any binder suitable for use with the thermal recording layer described above can be used as appropriate. One or more types of these binders may be used.

[0040] The pigment used in the undercoat layer contains hollow plastic particles. The hollow plastic particles used in this invention are micro-hollow particles that are already in a foamed state, with a thermoplastic resin shell containing air or other gases inside. Examples of thermoplastic resins include polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyacrylic acid ester, polyacrylonitrile, polybutadiene, or copolymers thereof. Styrene-based resins such as polystyrene, acrylic-based resins such as polyacrylic acid ester and polyacrylonitrile, copolymers thereof, or copolymer resins mainly composed of polyvinylidene chloride and polyacrylonitrile are particularly preferred. Such organic hollow particles are available as SX8782 from JSR Corporation, MH5055 and MH8108A from Nippon Zeon Corporation, Rohm & Haas Japan Co., Ltd., and Microsphere from Matsumoto Oil & Fat Co., Ltd. The volumetric hollowness of the plastic hollow particles used in this invention is preferably about 40-95%. By setting the volumetric hollowness to 40% or more, the heat insulation performance can be improved and the color development performance can be further enhanced. On the other hand, by setting it to 95% or less, the strength of the shell of the hollow particles is increased, the hollow state is effectively maintained, and it becomes easier to obtain a primer layer with good surface strength. Here, the volumetric hollowness is a value that can be obtained by (d3 / D3) × 100. In this formula, d represents the inner diameter of the organic hollow particle, and D represents the outer diameter of the organic hollow particle.

[0041] The undercoat layer may contain pigments other than plastic hollow particles. For example, inorganic pigments such as calcium carbonate, silica, zinc oxide, titanium dioxide, aluminum hydroxide, magnesium hydroxide, kaolin, calcined kaolin, clay, and talc, or organic pigments such as plastic hollow particles can be used. One or more of these pigments may be used. As a pigment other than plastic hollow particles, calcined kaolin is preferred. The pigment content in the undercoat layer is typically 50-95% by weight, preferably 70-90% by weight, relative to the undercoat layer (solid content). The content of hollow plastic particles in the undercoat layer is 50% or more by weight, preferably 70-100% by weight, more preferably 80-100% by weight, relative to the pigment (solid content) in the undercoat layer. The primer coating liquid may contain various auxiliary agents as needed, such as dispersants, plasticizers, pH adjusters, defoamers, water-retaining agents, preservatives, coloring dyes, and UV-blocking agents.

[0042] The thermal recording material of the present invention may further have a protective layer on the thermal recording layer. This protective layer mainly consists of a binder and a pigment, and a crosslinking agent may be added to it. As this binder, any binder suitable for use in the thermal recording layer described above can be used as appropriate, but carboxylated polyvinyl alcohol and non-core-shell type acrylic resins with a glass transition temperature (Tg) higher than 50°C are preferred. One or more of these binders may be used. Examples of crosslinking agents include epichlorohydrin resins such as polyamine epichlorohydrin resin and polyamide epichlorohydrin resin, polyamide urea resins, polyalkylene polyamine resins, polyalkylene polyamide resins, polyamine polyurea resins, modified polyamine resins, modified polyamide resins, polyalkylene polyamine urea formalin resins, or polyalkylene polyamine polyamide polyurea resins, as well as polyamine / polyamide resins such as glyoxal, methylolmelamine, melamine formaldehyde resin, melamine urea resin, potassium persulfate, ammonium persulfate, sodium persulfate, ferric chloride, magnesium chloride, borax, boric acid, alum, and ammonium chloride. It is preferable to include epichlorohydrin resins and polyamine / polyamide resins as crosslinking agents in the protective layer, as this results in particularly good water resistance. The amount of binder in the protective layer, or the total amount of binder and pigment, is usually 80.0 to 100.0% by weight in terms of solids, preferably 90.0 to 100.0% by weight, and it is preferable that the amount of binder is about 30.0 to 300.0 parts by weight per 100 parts by weight of pigment. The protective coating liquid may, as needed, contain various auxiliary agents suitable for use in the aforementioned thermal recording layer, such as lubricants, stabilizers, UV absorbers, dispersants, defoamers, antioxidants, and fluorescent dyes.

[0043] In the present invention, the means for applying the thermal recording layer and coating layers other than the thermal recording layer, i.e., protective layers, undercoat layers, etc., are not particularly limited and can be applied according to well-known and conventional techniques. For example, off-machine coating machines or on-machine coating machines equipped with various coaters such as air knife coaters, rod blade coaters, vent blade coaters, bevel blade coaters, roll coaters, and curtain coaters can be appropriately selected and used. The coating amounts for the thermal recording layer and other coating layers are determined according to the required performance and recording suitability, and are not particularly limited. However, the general coating amount for the thermal recording layer is 2 to 12 g / m² in terms of solid content. 2 The amount of protective layer coating is approximately 0.5 to 5.0 g / m² in terms of solid content. 2 It is preferable. Furthermore, various known techniques in the field of thermal recording materials can be added as needed, such as applying a smoothing treatment like supercalendering after coating each coating layer. [Examples]

[0044] The present invention will be illustrated below with examples, but this is not intended to limit the present invention. In each example and comparative example, unless otherwise specified, "parts" refers to "parts by weight" and "%" refers to "% by weight".

[0045] For the manufacture of the thermal recording material, each dispersion and coating solution was prepared as follows. [Preparation of each coating solution] The following formulations were stirred and dispersed to prepare primer coating liquids 1 to 4. <Primer coating liquid 1> Calcined kaolin (BASF product name: Ansilex 90) 40.0 parts Hollow plastic particles (manufactured by Zeon Corporation, product name: Nipol) MH8108A, hollow rate 50%, solid content 27%) 222.2 parts Styrene-butadiene copolymer latex (manufactured by Zeon Corporation) Product name: ST5526, solid content 48%) 10.0 parts <Primer coating liquid 2> Calcined kaolin (Ansilex 90) 30.0 parts Plastic hollow particles (Nipol MH8108A) 259.3 parts Styrene-butadiene copolymer latex (ST5526) 10.0 parts <Primer coating liquid 3> Calcined kaolin (Ansilex 90) 20.0 parts Plastic hollow particles (Nipol MH8108A) 296.3 parts Styrene-butadiene copolymer latex (ST5526) 10.0 parts <Primer coating liquid 4> Calcined kaolin (Ansilex 90) 10.0 parts Plastic hollow particles (Nipol MH8108A) 333.3 parts Styrene-butadiene copolymer latex (ST5526) 10.0 parts

[0046] <Primer coating liquid 5> Plastic hollow particles (Nipol MH8108A) 370.0 parts Styrene-butadiene copolymer latex (ST5526) 10.0 parts <Primer coating liquid 6> Calcined kaolin (Ansilex 90) 60.0 parts Plastic hollow particles (Nipol MH8108A) 148.1 parts Styrene-butadiene copolymer latex (ST5526) 10.0 parts <Primer coating liquid 7> Calcined kaolin (Ansilex 90) 50.0 parts Plastic hollow particles (Nipol MH8108A) 185.1 parts Styrene-butadiene copolymer latex (ST5526) 10.0 parts Water 50.0 parts <Primer coating liquid 8> Calcined kaolin (Ansilex 90) 100.0 parts Styrene-butadiene copolymer latex (ST5526) 10.0 parts Water 50.0 parts

[0047] The developer dispersions (Solutions A1-5), leuco dye dispersion (Solution B), and sensitizer dispersion (Solution C) were each wet-ground separately using a sand grinder until the average particle size was 0.5 μm.

[0048] Chromogen dispersant (Solution A1) N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea (Hereinafter referred to as "Urea Compound 1.") Part 6.0 Fully saponified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd., product name: PVA117, solids content 10%) 5.0 parts 1.5 parts water

[0049] Chromogen dispersant (Solution A2) Urea compounds represented by the following chemical formula (Chemical Formula 9) (Hereinafter referred to as "Urea Compound 2.") Part 6.0 [ka] 5.0 parts of fully saponified polyvinyl alcohol aqueous solution (PVA117) 1.5 parts water Chromolytic agent dispersion (A3 solution) N-[2-(3-phenylureido)phenyl]benzenesulfonamide (Hereinafter referred to as "Urea Compound 3.") Part 6.0 5.0 parts of fully saponified polyvinyl alcohol aqueous solution (PVA117) 1.5 parts water

[0050] Chromolytic agent dispersion (A4 solution) Urea urethane compound represented by chemical formula (Chemical Formula 13) (Fine Ace Co., Ltd.) (Manufactured by UU) 6.0 copies [ka] 5.0 parts of fully saponified polyvinyl alcohol aqueous solution (PVA117) 1.5 parts water

[0051] Chromogenizer dispersion (A5 solution) 4-Hydroxy-4'-Isopropoxydiphenylsulfone (Manufactured by Mitsubishi Chemical Corporation, product name: NYDS) 6.0 parts 5.0 parts of fully saponified polyvinyl alcohol aqueous solution (PVA117) 1.5 parts water

[0052] Leuco dye dispersion (Solution B) 3-Dibutylamino-6-methyl-7-anilinofluorane (Yamamoto Chemical Co., Ltd.) (product name: ODB-2) 6.0 copies 5.0 parts of fully saponified polyvinyl alcohol aqueous solution (PVA117) 1.5 parts water

[0053] Sensitizer dispersion (Solution C) 1,2-Bis-(3-methylphenoxy)ethane (manufactured by Sanko Co., Ltd.) Product name: KS232) 6.0 copies 5.0 parts of fully saponified polyvinyl alcohol aqueous solution (PVA117) 1.5 parts water

[0054] Next, the dispersions were mixed in the following proportions to prepare a coating solution for the thermal recording layer. <Coating liquid for thermal recording layer> 36.0 parts of developer dispersion (Solution A1) Leuco dye dispersion (Solution B) 18.0 parts Sensitizer dispersion (Solution C) 5.0 parts 25.0 parts of fully saponified polyvinyl alcohol aqueous solution (PVA117)

[0055] Next, a protective coating liquid was prepared by mixing the following formulations. <Protective coating liquid> Aluminum hydroxide dispersion (manufactured by Martinsberg, Product name: Martiffin OL, 50% solids, 9.0 parts Carboxylated polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd., product name: KL318, polymerization degree: about 1800, saponification degree: 85~90mol%, 30.0 parts (10% solids) Polyamide epichlorohydrin resin (manufactured by Seikoh PMC, product name: WS4030, solids content 25%) 4.0 parts Modified polyamine resin (manufactured by Taoka Chemical Co., Ltd., product name: Sumire's Resin SPI) -102A, 45% solids) 2.2 parts Zinc stearate (manufactured by Chukyo Oils Co., Ltd., product name: Hydrin Z-7-30) 2.0 parts (30% solids)

[0056] [Example 1] Support (basis weight 47g / m 2 On one side of the high-quality paper, apply primer coating liquid 1, with a solid content coating amount of 10.0 g / m². 2 After coating using the bent blade method, the paper was dried to obtain a base coat layer. On this undercoat layer of coated paper, a thermal recording layer coating liquid is applied at a solid content rate of 6.0 g / m². 2 After coating using the rod-blade method, the material was dried and then processed with a supercalender to achieve a smoothness of 100-500 seconds to produce a thermal recording material. [Example 2] A thermal recording body was prepared in the same manner as in Example 1, except that coating liquid 3 for the undercoat layer was used instead of coating liquid 1 for the undercoat layer, the amount of liquid A1 in the coating liquid for the thermal recording layer was changed to 18 parts, and 18 parts of liquid A4 were added to the coating liquid for the thermal recording layer.

[0057] [Example 3] A thermal recording body was prepared in the same manner as in Example 1, except that coating liquid 3 for the undercoat layer was used instead of coating liquid 1 for the undercoat layer, and liquid A2 was used instead of liquid A1 in the coating liquid for the thermal recording layer. [Reference example 4] A thermal recording body was prepared in the same manner as in Example 1, except that coating liquid 3 for the undercoat layer was used instead of coating liquid 1 for the undercoat layer, and liquid A3 was used instead of liquid A1 in the coating liquid for the thermal recording layer. [Reference example 5] A thermal recording body was prepared in the same manner as in Example 1, except that coating liquid 4 for the undercoat layer was used instead of coating liquid 1 for the undercoat layer, the amount of liquid A1 in the coating liquid for the thermal recording layer was changed to 18 parts, and 18 parts of liquid A2 were added to the coating liquid for the thermal recording layer. [Reference example 6] A thermal recording body was prepared in the same manner as in Example 1, except that coating liquid 2 for the undercoat layer was used instead of coating liquid 1 for the undercoat layer, the amount of liquid A1 in the coating liquid for the thermal recording layer was changed to 18 parts, and 18 parts of liquid A3 were added to the coating liquid for the thermal recording layer. [Reference example 7] A thermal recording body was prepared in the same manner as in Example 1, except that coating liquid 3 for the undercoat layer was used instead of coating liquid 1 for the undercoat layer, the amount of liquid A1 in the coating liquid for the thermal recording layer was changed to 18 parts, and 18 parts of liquid A3 were added to the coating liquid for the thermal recording layer.

[0058] [Reference example 8] A thermal recording body was prepared in the same manner as in Example 1, except that coating liquid 5 for the undercoat layer was used instead of coating liquid 1 for the undercoat layer, the amount of liquid A1 in the coating liquid for the thermal recording layer was changed to 18 parts, and 18 parts of liquid A3 were added to the coating liquid for the thermal recording layer. [Reference example 9] A protective coating liquid is applied to the thermal recording layer of thermal recording paper at a solid content rate of 2.0 g / m².2 A thermal recording material was prepared in the same manner as in Reference Example 8, except that after coating using the rod-blade method, it was dried and then treated with a supercalender to achieve a smoothness of 100-500 seconds. [Reference example 10] A thermal recording body was prepared in the same manner as in Example 1, except that coating liquid 3 for the undercoat layer was used instead of coating liquid 1 for the undercoat layer, the amount of liquid A1 in the coating liquid for the thermal recording layer was changed to 18 parts, and 9 parts each of liquid A3 and A4 were added to the coating liquid for the thermal recording layer. [Reference example 11] A thermal recording body was prepared in the same manner as in Example 1, except that coating liquid 3 for the undercoat layer was used instead of coating liquid 1 for the undercoat layer, liquid A1 was omitted from the coating liquid for the thermal recording layer, and 18 parts of liquid A2 and 18 parts of liquid A3 were added.

[0059] [Comparative Example 1] A thermal recording body was prepared in the same manner as in Example 1, except that the undercoat coating liquid 1 was changed to undercoat coating liquid 6. [Comparative Example 2] A thermal recording body was prepared in the same manner as in Example 3, except that a primer layer was not applied. [Comparative Example 3] A thermal recording body was prepared in the same manner as in Example 3, except that the undercoat coating liquid 3 was changed to undercoat coating liquid 8. [Comparative Example 4] A thermal recording device was prepared in the same manner as in Reference Example 4, except that the undercoat coating liquid 3 was changed to undercoat coating liquid 6.

[0060] [Comparative Example 5] A thermal recording body was prepared in the same manner as in Reference Example 5, except that the undercoat coating liquid 4 was changed to undercoat coating liquid 6. [Comparative Example 6] A thermal recording material was prepared in the same manner as in Reference Example 5, except that a primer layer was not applied. [Comparative Example 7] A thermal recording device was prepared in the same manner as in Reference Example 5, except that the undercoat coating liquid 4 was changed to undercoat coating liquid 8. [Comparative Example 8] A thermal recording material was prepared in the same manner as in Reference Example 6, except that a primer layer was not applied. [Comparative Example 9] A thermal recording device was prepared in the same manner as in Reference Example 6, except that the undercoat coating liquid 2 was changed to undercoat coating liquid 8. [Comparative Example 10] A thermal recording material was prepared in the same manner as in Reference Example 11, except that a primer layer was not applied.

[0061] [Comparative Example 11] A thermal recording device was prepared in the same manner as in Reference Example 11, except that the undercoat coating liquid 3 was changed to undercoat coating liquid 8. [Comparative Example 12] A thermal recording body was prepared in the same manner as in Example 1, except that the undercoat coating liquid 1 was changed to undercoat coating liquid 7, and in the thermal recording layer coating liquid, liquid A1 was not included, and 36.0 parts of liquid A5 were included. [Comparative Example 13] A thermal recording body was prepared in the same manner as in Example 1, except that undercoat coating liquid 1 was changed to undercoat coating liquid 3, and in the thermal recording layer coating liquid, liquid A1 was not included, and 36.0 parts of liquid A5 were included.

[0062] The following evaluations were performed on the fabricated thermal recording material. <Color reproduction performance (print density)> The fabricated thermal recording material was printed with a checkerboard pattern at a printing speed of 50 mm / sec and an applied energy of 0.41 mJ / dot using a TH-PMD (thermal recording paper printing tester, manufactured by Okura Electric Co., Ltd., equipped with a Kyocera thermal head). The print density of the printed area was measured using a Macbeth densitometer (RD-914, using an amber filter) to evaluate the color development performance (print density).

[0063] <Suitable for high-speed printing> The prepared thermal recording material was printed with a barcode (CODE39) in both the vertical (perpendicular to the direction of the printer head movement) and horizontal (parallel to the direction of the printer head movement) directions using a Zebra 140XiIII label printer at a print level of +10 and a print speed of 30.4 cm / second (12 inches / second). Next, the printed barcodes were tested using a barcode verification machine (Honeywell QCPC600, 640nm light source) to evaluate their readability. The evaluation results are recorded using ANSI standard symbol grades. Symbol Grade: The barcode is divided into 10 sections perpendicular to the bar, and a reading test is performed on each section once. The average value is expressed on a 5-point scale: (Excellent) A, B, C, D, F (Poor). <Heat resistance of the blank area> The prepared thermal recording material was treated under environmental conditions of 80°C for 24 hours, and then left to stand for 3 hours under environmental conditions of 23°C × 50%RH. The density of the non-printed area (white paper area) was measured using a Macbeth densitometer (RD-914, using an amber filter), and the background color development value was calculated from the difference in values ​​before and after processing. The heat resistance of the non-printed area (white paper area) was evaluated according to the following criteria. Background color value = (Density of unprinted area after processing) - (Density of unprinted area before processing) Excellent: Base color development value is less than 0.3 Acceptable: Base color development value is 0.3 or higher and less than 0.5 Not acceptable: Base color value is 0.5 or higher

[0064] <Plasticizer resistance> The fabricated thermal recording material was printed with a checkerboard pattern using an Okura Electric TH-PMD (thermal recording paper printing tester, equipped with a Kyocera thermal head) at an applied energy of 0.41 mJ / dot and a printing speed of 50 mm / sec. The printed thermal recording material was attached to a paper tube that had been wrapped once with PVC wrap (Hi-Wrap KMA, manufactured by Mitsui Chemicals), and then wrapped three more times with PVC wrap. The tube was left undisturbed for 24 hours under environmental conditions of 40°C. The print density of the printed area was measured using a Macbeth densitometer (RD-914, using an amber filter), and the remaining percentage was calculated from the values ​​before and after treatment to evaluate the plasticizer resistance. Remaining percentage (%) = (Print density of the printed area after processing / Print density of the printed area before processing) × 100 Excellent: Survival rate of 90% or higher Acceptable: Remaining rate of 70% or more, but less than 90% Unacceptable: Remaining rate less than 70% <Printing performance (head load resistance)> The fabricated thermal recording material was printed with a 10cm grid pattern using a Sato Corporation label printer (Lesprit R-8), and the residue (head residue) adhering to the thermal head after printing was visually evaluated according to the following criteria. Excellent: Almost no head residue was observed. Acceptable: Although there was some head residue, there were no gaps or blurring in the formed image, and it was not a problem for practical use. Unacceptable: There was a lot of head residue attached, and the resulting image was incomplete and blurry.

[0065] The results are shown in the table below. [Table 1]

[0066] [Table 2]

Claims

1. A thermosensitive recording medium comprising an undercoat layer provided on a support, and a thermosensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer provided on the undercoat layer, wherein the thermosensitive recording layer contains a urea compound represented by the following formula (3) as the electron-accepting developer, the undercoat layer contains a binder and a pigment, the pigment content being 50 to 95% by weight in terms of solid content, and the pigment contains hollow plastic particles, the hollow plastic particles accounting for 50% by weight or more in terms of solid content. (3) A third urea compound represented by the following general formula (Chemical Formula 4): 【Chemistry 4】 (In the formula, R 2 represents a hydrogen atom or an alkyl group, and R 4 to R 8 may be the same or different and represent a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, or an arylamino group.)

2. 2. The thermosensitive recording material according to claim 1, wherein the third urea compound is N-[2-(3-phenylureido)phenyl]benzenesulfonamide.

3. A thermal recording medium as described in claim 2, in which a barcode (CODE 39) is printed vertically (the barcode is perpendicular to the moving direction of the printer head) at a printing speed of 25.4 cm / sec (10 inches / sec), the barcode is read by a barcode verifier, and the average value expressed in ANSI standard symbol grade is B or higher (wherein symbol grade is the average value when the barcode is divided into 10 parts perpendicular to the bar and a reading test is conducted once for each part, and is expressed on a 5-level scale of A, B, C, D, F from best to worst).

4. A thermal recording medium described in any one of claims 1 to 3, wherein the total content (solid content) of the urea compound in the thermal recording layer is 1.0 to 70.0 weight %.

5. A thermal recording medium described in any one of claims 1 to 4, wherein the volumetric hollowness of the plastic hollow particles is 40 to 95%.

6. The undercoat layer, (i) The pigment contains 50 to 95% by weight of solid content, and the pigment contains 80 to 100% by weight of hollow plastic particles in terms of solid content, or (ii) The heat-sensitive recording material according to claim 1, wherein the pigment is contained in an amount of 70 to 90% by weight in terms of solid content, and the pigment contains hollow plastic particles in an amount of 70 to 100% by weight in terms of solid content.

7. A thermal recording medium as described in claim 1 or 6, wherein when the undercoat layer contains a pigment other than plastic hollow particles, the pigment contains calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, magnesium hydroxide, kaolin, calcined kaolin, clay, or talc.

8. A thermal recording medium according to claim 1, wherein the undercoat layer contains 70 to 100% by weight of the hollow plastic particles in the pigment in terms of solid content.

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