Heat-sensitive recording material

Abstract

To provide a heat-sensitive recording material which is excellent in terms of high-speed printing performance among various performances required for heat-sensitive recording materials, and which is also excellent in terms of printing runnability, oil resistance, solvent barrier properties and the like.SOLUTION: A heat-sensitive recording material has a heat-sensitive recording layer on a supporting body, the heat-sensitive recording layer containing a colorless or pale electron-donating leuco dye and an electron-accepting color developer, while having a protective layer on the heat-sensitive recording layer. The heat-sensitive recording layer contains, as the electron-accepting color developer, at least one urea compound, and the protective layer contains an acrylic resin.SELECTED DRAWING: None

Description

Technical field

[0001] This invention utilizes a color-forming reaction between a colorless or light-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"). The present invention relates to a heat-sensitive recording material that has excellent high-speed printing properties, as well as excellent printing running properties, oil resistance, solvent barrier properties, etc. [Background technology]

[0002] In general, thermal recording materials are made by coating a support such as paper, synthetic paper, film, or plastic with a coating solution containing a colorless or light-colored leuco dye and a color developer. Color develops through an instant chemical reaction caused by heating with a stamp, thermal pen, laser beam, etc., and a recorded image is obtained. Thermosensitive recording media are widely used as recording media for facsimiles, computer terminal printers, automatic ticket vending machines, measurement recorders, receipts at supermarkets, convenience stores, etc. In recent years, heat-sensitive recording materials have expanded to a variety of uses, including for various tickets, receipts, labels, bank ATMs, gas and electricity meter reading, and cash vouchers such as horse racing tickets. Various performances are now required, such as plasticizer resistance in the image area, heat resistance and oil resistance in the blank area, and storage stability of the image area and the blank area under harsh conditions. In response to these demands, a thermal recording medium (patent document 1) and urea compounds (Patent Documents 2 and 3) are disclosed as color developers for improving the required performance of heat-sensitive recording materials, such as color density, whiteness, and storage stability of printed areas. Further, as a method for improving the storage stability of a heat-sensitive recording material, a method of providing a protective layer on a heat-sensitive recording layer is known. It is known that by containing a silane-modified acrylic resin in this heat-sensitive recording layer or protective layer, head wear during printing can be improved, and image storage stability and water resistance of the heat-sensitive recording medium can be improved (Patent Document 4, 5 etc.). Furthermore, it is known that by containing an acrylic resin whose glass transition point (Tg) is higher than 50°C and lower than 95°C in the protective layer, the heat-sensitive recording material has sufficient water resistance etc. (Patent Reference 6 etc.). [Prior art documents] [Patent document]

[0003] [Patent Document 1] JP2015-80852 [Patent Document 2] International publication WO2019 / 044462 [Patent Document 3] JP2020-066148 [Patent Document 4] Japanese Patent Publication No. 5-574 [Patent Document 5] JP2000-238432 [Patent Document 6] International publication WO2010 / 110209 [Disclosure of the invention] [Problem to be solved by the invention]

[0004] Therefore, an object of the present invention is to provide a heat-sensitive recording material that is excellent in high-speed printing properties among the various performances required of a heat-sensitive recording material, as well as excellent in printing running properties, oil resistance, solvent barrier properties, and the like. [Means to solve the problem]

[0005] As a result of extensive studies, the present inventors solved the above problem by incorporating a specific urea compound as a color developer into the heat-sensitive recording layer and by containing an acrylic resin in the protective layer provided on the heat-sensitive recording layer. We have discovered that this can be done, and have completed the present invention. That is, the present invention provides a heat-sensitive recording material having, on a support, a heat-sensitive recording layer containing a colorless to light-colored electron-donating leuco dye and an electron-accepting color developer, and a protective layer on the heat-sensitive recording layer. The heat-sensitive recording layer contains a urea compound represented by the following (1) or (2) as an electron-accepting color developer, and the protective layer contains an acrylic compound represented by the following (4) or (5). A thermosensitive recording material containing a resin, wherein the content of the acrylic resin in the protective layer is 15.0 to 50.0% by weight, and the minimum film forming temperature (MFT) of the acrylic resin is 0°C to 25°C. It is. (1) a first urea compound represented by the following general formula (Chemical formula 5), [ka] (In the formula, R 2 represents a hydrogen atom or an alkyl group, R 3 may be the same or different, and are groups represented by the following formula (Chemical formula 11), and R in the benzene ring of the general formula (Chemical formula 5) 3 -SO 2 The position of -O- may be the same or different, and is the 3rd, 4th or 5th position. ) [ka] (In the formula, R 4 ~R 8 may be the same or different, and include 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, It represents 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), [ka] (In the formula, R 2 ,R 4 ~R 8 is defined in the same way as above, and m represents an integer from 0 to 2. ) (4) Non-core-shell type acrylic resin with glass transition point (Tg) higher than 50℃ and lower than 95℃ (5) A core consisting of copolymer A obtained by polymerizing the following (a1), (a2) and (a3) ​​in the presence of (b), and the following (a1) and (a2) in the presence of (b). A silane-modified acrylic resin that is an aqueous emulsion of core-shell type particles consisting of a shell made of copolymer B and a shell made of copolymer B. (a1) At least one (meth)acrylic ester (a2) Monomer having an alkoxysilyl group and an ethylenic double bond (a3) Monomer with carboxyl group and ethylenic double bond (b) Polymerizable surfactant containing sulfate having an allyl group and a polyoxyethylene chain

Effect of the invention

[0006] According to the present invention, it is possible to provide a heat-sensitive recording material that has color development performance and good high-speed printing properties, and further provides a heat-sensitive recording material that has good printing running properties, oil resistance, solvent barrier properties, etc. can do. [Form for carrying out the invention]

[0007] The heat-sensitive recording material of the present invention has a heat-sensitive recording layer on a support and a protective layer on the heat-sensitive recording layer, and the heat-sensitive recording layer contains a specific urea compound as an electron-accepting color developer, The protective layer contains an acrylic resin. Examples of various materials used in the heat-sensitive recording layer of the heat-sensitive recording material of the present invention are listed below, and binders, cross-linking agents, pigments, etc. may be added as necessary to the extent that they do not impede the desired effects on the above-mentioned problems. It can also be used in each coating layer.

[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 (Chemical formula 5), [ka] (In the formula, R 2 and R 3 is defined as above. ) (2) a second urea compound represented by the following general formula (Chemical formula 3), [ka] (In the formula, R 2 and m are defined as above, R 4 ~R 8 will be described later. ) (3) Third urea compound represented by the following formula (Chemical formula 4) [ka] (In the formula, R 2 is defined as above and R 4 ~R 8 will be described later. )

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

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

[0011] In the general formula (Chemical formula 5), ​​n represents 0 or 1, preferably 1. In the general formula (Chemical formula 5), ​​R 3 represents an alkyl group, an aralkyl group, or an 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. The aralkyl group preferably has 7 to 12 carbon atoms, and the aryl group preferably has 6 to 12 carbon atoms. Further, when 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 may be the same or different. R in the benzene ring of general formula (Chemical formula 5) 3 -SO 2 The position of -O- may be the same or different, and is preferably the 3rd, 4th or 5th position.

[0012] Examples of this alkyl group 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, and 2-ethyl group. Examples include xyl group and lauryl group.

[0013] This aralkyl group includes benzyl group, 1-phenylethyl group, 2-phenylethyl group, 3-phenylpropyl group, p-methylbenzyl group, m-methylbenzyl group, m-ethylbenzyl group, p-ethylbenzyl group. , p-i-propylbenzyl group, p-t-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, p Examples include unsubstituted or aralkyl groups such as -chlorobenzyl group, alkyl groups, alkoxy groups, aralkyl groups, aryl groups, or aralkyl groups substituted with halogen atoms.

[0014] Examples of the aryl group include 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, p-i-propylphenyl group, p-t-butylphenyl group, p-methoxyphenyl group, 3,4-dimethoxyphenyl group, p -Ethoxyphenyl group, p-chlorophenyl group, 1-naphthyl group, 2-naphthyl group, t-butylated naphthyl group or other unsubstituted aryl group, alkoxy group, aralkyl group, aryl group, or aryl substituted with a halogen atom Examples include groups.

[0015] R 2 represents a hydrogen atom or an alkyl group, preferably a hydrogen atom, and the alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group. group, sec-butyl group, t-butyl group, etc. R in the benzene ring of general formula (Chemical formula 2) 2 The positions of may be the same or different, 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 (Formula 6) is more preferable. [ka] In the general formula (chemical formula 6), R 9 is an alkyl group or an alkoxy group, preferably an alkyl group, and o represents an integer of 0 to 3, preferably 0 to 2, more preferably 0 to 1. The alkyl group has, for example, 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms. R in the benzene ring of general formula (Chemical formula 6) 9 The positions of may be the same or different, preferably the 3rd, 4th or 5th position, preferably the 4th position.

[0017] Further, as the first urea compound of the present invention, for example, N,N'-di-[3-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-4 -Methyl-phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-4-ethyl-phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-5-methyl -phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-4-propyl-phenyl]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-methyl-phenyl]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-(p-t-butyl) benzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(m-methoxybenzenesulfonyloxy)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,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-[3-(p-chlorobenzenesulfonyloxy)phenyl]urea, -[4-(p-Toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(ethanesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzylsulfonyloxy)phenyl ] urea, etc., but are not limited to these.

[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 is defined as above. In the general formula (Chemical formula 3), R 4 ~R 8 is preferably a hydrogen atom, an alkyl group, or an alkoxy group. In particular, R 4 ,R 5 ,R 7 ,R 8 is preferably a hydrogen atom, and R 6 A hydrogen atom or an alkyl group is preferable. R 6 Especially preferred is an alkyl group. This alkyl group (including those included in alkylcarbonyloxy group, alkylcarbonylamino group, alkylsulfonylamino group, monoalkylamino group, dialkylamino group) and aryl group (aryloxy group, arylcarbonyloxy group, aryl (including those contained in the carbonylamino group, arylsulfonylamino group, and arylamino group) are defined in the same manner as the alkyl group and aryl group in the above general formula (Formula 2). 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 -SO 2 The position of the -substituted phenyl group is preferably the 3-position, the 4-position, or the 5-position (the same applies to the following general formulas (Chemical Formula 7) and General Formulas (Chemical Formula 8)). In the general formula (Chemical formula 3), m represents an integer of 0 to 2, preferably 0 to 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 preferable. [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 is defined as above.

[0022] The third urea compound is preferably 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. It is. [ka]

[0023] The content of the urea compound in the heat-sensitive 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, more preferably 10.0 to 60.0 parts by weight. It is. The content of the first urea compound in the heat-sensitive recording layer of the present invention is 1.0 to 50.0% by weight, preferably 5.0 to 40.0% by weight. Further, 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 heat-sensitive recording layer of the present invention may use a color developer other than the first and second urea compounds, such as activated clay, attapulgite, colloidal silica, aluminum silicate, etc. Inorganic acidic substance, 4,4'-isopropylidenediphenol, 1,1-bis(4-hydroxyphenyl)cyclohexane, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 4,4'-dihydroxy Diphenylsulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 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-dihydroxy Phenyl-4'-methylphenylsulfone, 1-[4-(4-hydroxyphenylsulfonyl)phenoxy]-4-[4-(4-isopropoxyphenylsulfonyl)phenoxy]butane, described in JP-A No. 2003-154760 Phenol condensation composition, aminobenzenesulfonamide derivative described in JP-A-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 JP2002-301873, and N,N'-di-m-chlorophenyl Thiourea compounds such as thiourea, p-chlorobenzoic acid, stearyl gallate, bis[4-(n-octyloxycarbonylamino)zinc salicylate] dihydrate, 4-[2-(p-methoxyphenoxy)ethyloxy] Aromatic carboxylic acids of salicylic acid, 4-[3-(p-tolylsulfonyl)propyloxy]salicylic acid, 5-[p-(2-p-methoxyphenoxyethoxy)cumyl]salicylic acid, and zinc of these aromatic carboxylic acids , salts with polyvalent metal salts such as magnesium, aluminum, calcium, titanium, manganese, tin, and nickel, as well as antipyrine complexes of zinc thiocyanate, complex zinc salts of terephthalaldehydic acid and other aromatic carboxylic acids, etc. Can be mentioned. These color developers can be used alone or in combination of two or more. 1-[4-(4-hydroxyphenylsulfonyl)phenoxy]-4-[4-(4-isopropoxyphenylsulfonyl)phenoxy]butane is available, for example, under the trade name JKY-214 manufactured by API Corporation. The phenol condensation composition described in JP-A No. 2003-154760 is available, for example, under the trade name JKY-224 manufactured by API Corporation. Further, the compounds described in WO02 / 081229 and the like are available as trade names NKK-395 and D-100 manufactured by Nippon Soda Co., Ltd. In addition, metal chelate type coloring components such as higher fatty acid metal double salts and polyvalent hydroxy aromatic compounds described in JP-A-10-258577 can also be contained.

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

[0026] As the leuco dye used in the present invention, all those known in the field of conventional pressure-sensitive or heat-sensitive recording paper can be used, and there are no particular restrictions on the leuco dye, including triphenylmethane compounds, fluoran compounds, fluorene compounds, etc. type compounds, divinyl type compounds, etc. are preferred. Specific examples of typical colorless to light-colored dyes (dye precursors) are shown below. Further, these dye precursors may be used alone or in combination of two or more.

[0027] <Triphenylmethane-based leuco dye> 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 leuco dye> 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)fluoran, 3-diethylamino-6-methyl-7-(o-fluoroanilino)fluoran, 3-diethylamino-6-methyl-7-(m-methylanilino)fluoran , 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- Anilinofluoran, 3-dibutylamino-6-methyl-7-(o,p-dimethylanilino)fluoran, 3-dibutylamino-6-methyl-7-(o-chloroanilino)fluoran, 3-dibutylamino- 6-Methyl-7-(p-chloroanilino)fluoran, 3-dibutylamino-6-methyl-7-(o-fluoroanilino)fluoran, 3-dibutylamino-6-methyl-7-(m-trifluoromethyl Anilino)fluoran, 3-dibutylamino-6-methyl-7-chlorofluoran, 3-dibutylamino-6-ethoxyethyl-7-anilinofluoran, 3-dibutylamino-6-chloro-7-anilino Fluoran, 3-dibutylamino-6-methyl-7-p-methylanilinofluorane, 3-dibutylamino-7-(o-chloroanilino)fluoran, 3-dibutylamino-7-(o-fluoroanilino) Fluoran, 3-di-n-pentylamino-6-methyl-7-anilinofluoran, 3-di-n-pentylamino-6-methyl-7-(p-chloroanilino)fluoran, 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)-6-methyl-7 -anilinofluorane, 3-(N-ethyl-N-xylamino)-6-methyl-7-(p-chloroanilino)fluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-ani Linofluorane, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isoamylamino)-6-chloro-7-anilinofluoran Oran, 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluorane Orane, 3-(N-ethyl-N-ethoxypropylamino)-6-methyl-7-anilinofluorane, 3-cyclohexylamino-6-chlorofluorane, 2-(4-oxahexyl)-3-dimethyl Amino-6-methyl-7-anilinofluorane, 2-(4-oxahexyl)-3-diethylamino-6-methyl-7-anilinofluorane, 2-(4-oxahexyl)-3-dipropyl Amino-6-methyl-7-anilinofluorane, 2-methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluorane, 2-methoxy-6-p-(p-dimethylaminophenyl)amino Anilinofluorane, 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 dye> 3,6,6'-tris(dimethylamino)spiro[fluorene-9,3'-phthalide], 3,6,6'-tris(diethylamino)spiro[fluorene-9,3'-phthalide]

[0030] <Divinyl leuco dye> 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] <Others> 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-( 1-Octyl-2-methylindol-3-yl)-4-azaphthalide, 3-(4-cyclohexylethylamino-2-methoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)- 4-Azaphthalide, 3,3-bis(1-ethyl-2-methylindol-3-yl)phthalide, 3,6-bis(diethylamino)fluoran-γ-(3'-nitro)anilinolactam, 3,6 -Bis(diethylamino)fluorane-γ-(4'-nitro)anilinolactam, 1,1-bis-[2',2',2'',2''-tetrakis-(p-dimethylaminophenyl)- ethenyl]-2,2-dinitrile ethane, 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]-methylmalonic acid dimethyl ester

[0032] As the sensitizer used in the present invention, conventionally known sensitizers can be used. Such sensitizers include fatty acid amides such as stearic acid amide and palmitic acid amide, ethylene bisamide, montanic acid wax, polyethylene wax, 1,2-bis-(3-methylphenoxy)ethane, p-benzylbiphenyl, 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-naphthyl carbonate, 1,4-diethoxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, o-xylene-bis -(phenyl ether), 4-(m-methylphenoxymethyl)biphenyl, 4,4'-ethylenedioxy-bis-benzoic acid dibenzyl ester, dibenzoyloxymethane, 1,2-di(3-methylphenoxy) Examples include ethylene, bis[2-(4-methoxy-phenoxy)ethyl]ether, methyl p-nitrobenzoate, phenyl p-toluenesulfonate, o-toluenesulfonamide, and p-toluenesulfonamide. These sensitizers may be used alone or in combination of two or more.

[0033] Examples of pigments used in the present invention include kaolin, calcined kaolin, calcium carbonate, aluminum oxide, titanium oxide, magnesium carbonate, aluminum silicate, magnesium silicate, calcium silicate, aluminum hydroxide, and silica. They can also be used together.

[0034] The 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, and olefin-modified polyvinyl alcohol. Polyvinyl alcohol, nitrile-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, other modified polyvinyl alcohols, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer, styrene-butadiene copolymer, and Cellulose derivatives such as ethylcellulose, acetylcellulose, casein, gum arabic, oxidized starch, etherified starch, dialdehyde starch, esterified starch, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylate ester, polyvinyl butyral, polystyrose Examples include copolymers thereof, polyamide resins, silicone resins, petroleum resins, terpene resins, ketone resins, coumaron resins, and the like. These polymeric substances are used by dissolving them in solvents such as water, alcohol, ketones, esters, and hydrocarbons, or by emulsifying them or dispersing them in paste form in water or other media to meet the required quality. They can also be used together depending on the situation.

[0035] The lubricant used in the present invention includes fats such as zinc stearate and calcium stearate. Examples include acid metal salts, waxes, and silicone resins.

[0036] In the present invention, 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. In addition, benzophenone-based or triazole-based ultraviolet absorbers, dispersants, antifoaming agents, antioxidants, fluorescent dyes, and the like can be used.

[0037] The types and amounts of the leuco dye, color developer, sensitizer, and other various components used in the heat-sensitive recording layer of the present invention are determined according to the required performance and recording suitability, and are not particularly limited. Usually, per 1 part by weight of leuco dye, 0.5 to 10 parts by weight of color 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. Use parts by weight. The binder is suitably used in an amount of about 5 to 25% by weight based on the solid content of the heat-sensitive recording layer.

[0038] In the present invention, the leuco dye, color developer, and materials added as necessary are atomized to a particle size of several microns or less using a pulverizer such as a ball mill, attritor, or sand glider, or an appropriate emulsifying device, and then the binder A coating liquid is prepared by adding various additive materials depending on the purpose. Water, alcohol, or the like can be used as a solvent for this coating liquid, and the solid content thereof is about 20 to 40% by weight.

[0039] In the heat-sensitive recording material of the present invention, a protective layer is further provided on the heat-sensitive recording layer, and this protective layer contains an acrylic resin. In the present invention, a silane-modified acrylic resin or a high Tg acrylic resin is preferably used as the acrylic resin.

[0040] The silane-modified acrylic resin used in the present invention is an aqueous resin emulsion obtained by multi-step emulsion polymerization of a plurality of types of polymerizable unsaturated monomers in the presence of a surfactant. This silane-modified acrylic resin has a core consisting of copolymer A obtained by polymerizing the following (a1), (a2), and (a3) ​​in the presence of (b), and the following (a1) and (a2). This is an aqueous emulsion of core-shell type particles consisting of a shell made of copolymer B polymerized in the presence of (b). (a1) At least one (meth)acrylic ester (a2) Monomer having an alkoxysilyl group and an ethylenic double bond (a3) Monomer with carboxyl group and ethylenic double bond (b) Polymerizable surfactant containing a sulfate having an allyl group and a polyoxyethylene chain This copolymer A may be formed by adding a styrene monomer to the above (a1), (a2) and (a3) ​​and polymerizing it in the presence of (b), and / or the copolymer B A styrene monomer may be added to (a1) and (a2) and polymerized in the presence of (b).

[0041] About <(a1) At least one (meth)acrylic acid ester> As used herein, "(meth)acrylic acid" refers to both acrylic acid and methacrylic acid, and means containing at least one of acrylic acid and methacrylic acid. "(Meth)acrylic acid ester" refers to an ester of (meth)acrylic acid, that is, (meth)acrylate. (Meth)acrylate refers to both acrylate and methacrylate, and means containing at least one of acrylate and methacrylate. Note that vinyl esters having a structure in which a vinyl group and oxygen are bonded, such as vinyl acetate, are not included in (meth)acrylate in this specification.

[0042] Specific examples of (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and pentyl (meth)acrylate. ) acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, octadecyl (meth)acrylate, (meth)acrylic acid (Meth)acrylic acid alkyl esters such as behenyl and docosyl (meth)acrylate; (meth)acrylic acids such as 2-hydroxyethyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, etc. Examples include hydroxyalkyl esters. These can be used alone or in combination of two or more.

[0043] In the embodiment of the present invention, (meth)acrylic acid esters are preferably (meth)acrylic acid alkyl esters, and specifically, methyl methacrylate (MMA), 2-ethylhexyl acrylate (2EHA), acrylic acid n Examples include, but are not limited to, -butyl (n-BA), n-butyl methacrylate (n-BMA), cyclohexyl methacrylate (CHMA), and the like.

[0044] Regarding <(a2) Monomer having an alkoxysilyl group and an ethylenic double bond> The monomer having an alkoxysilyl group and an ethylenic double bond refers to a compound capable of imparting an alkoxysilyl group to an aqueous resin emulsion resin obtained by an emulsion polymerization reaction, and refers to a compound capable of imparting an alkoxysilyl group to an aqueous resin emulsion resin obtained by an emulsion polymerization reaction. There is no particular restriction as long as it can be obtained. A monomer having an alkoxysilyl group and an ethylenic double bond has both an alkoxysilyl group and an ethylenic double bond, and the alkoxysilyl group and an ethylenic double bond are, for example, an ester bond, an amide bond, and an alkylene bond. They may be bonded via other functional groups such as groups. Here, the term "alkoxysilyl group" refers to a silicon-containing functional group that provides a hydroxyl group (Si-OH) bonded to silicon upon hydrolysis. Examples of the "alkoxysilyl group" include alkoxysilyl groups such as trimethoxysilyl group, triethoxysilyl group, dimethoxysilyl group, dimethoxymethylsilyl group, diethoxysilyl group, monoethoxysilyl group, and monomethoxysilyl group. I can give an example. Particularly preferred are trimethoxysilyl group and triethoxysilyl group.

[0045] As used herein, the term "ethylenic double bond" refers to a double bond between carbon atoms that can undergo a polymerization reaction (radical polymerization). As a functional group having such an ethylenic double bond, for example, a vinyl group (CH 2 =CH-), (meth)allyl group (CH 2 =CH-CH 2 - and CH 2 =C(CH 3 )-CH 2 -), (meth)acryloyloxy group (CH 2 =CH-COO- and CH 2 =C(CH 3 )-COO-), (meth)acryloyloxyalkyl group (CH 2 =CH-COO-R- and CH 2 =C(CH 3 )-COO-R-) and -COO-CH=CH-COO-. Note that monomers having an alkoxysilyl group and an ethylenic double bond are not included in the above-mentioned (meth)acrylic acid ester.

[0046] As the monomer having an alkoxysilyl group and an ethylenic double bond, a compound represented by the following formula (1) can be exemplified. R 11 Si(OR 12 )(OR 13 )(OR14 ) (1) In the formula, R 11 is a functional group having an ethylenic double bond, and R 12 ,R 13 and R 14 is an alkyl group having 1 to 5 carbon atoms. R 12 ,R 13 and R 14 may be the same or different from each other. R 11 Examples of functional groups having an ethylenic double bond include vinyl group, (meth)allyl group, (meth)acryloyloxy group, 2-(meth)acryloyloxyethyl group, 2-(meth)acryloyloxypropyl group, Examples include 3-(meth)acryloyloxypropyl group, 2-(meth)acryloyloxybutyl group, 3-(meth)acryloyloxybutyl group, and 4-(meth)acryloyloxybutyl group.

[0047] R 12 ,R 13 and R 14 Examples of the alkyl group having 1 to 5 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t-butyl group, and n-pentyl group. Examples include straight chain or branched alkyl groups such as. Examples of the "monomer containing an alkoxysilyl group and having an ethylenic double bond" include vinyltrialkoxysilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltri-n-butoxysilane. Specifically, 3-(meth)acryloyloxypropyltrimethoxysilane and 3-(meth)acryloyloxypropyltriethoxysilane are preferred, and 3-methacryloyloxypropyltrimethoxysilane is particularly preferred. These monomers containing an alkoxysilyl group and having an ethylenic double bond can be used alone or in combination.

[0048] Regarding <(a3) Monomer having carboxyl group and ethylenic double bond> Examples of the monomer having a carboxyl group include (meth)acrylic acid. As mentioned above, (meth)acrylic acid means both acrylic acid and methacrylic acid. It is particularly preferable to use acrylic acid as the (meth)acrylic acid. The "ethylenic double bond" is as described above.

[0049] Regarding <(b) Polymerizable surfactant containing sulfate having allyl group and polyoxyethylene chain> Examples of sulfates having an allyl group and a polyoxyethylene group include sulfate ammonium salts having an allyl group and a polyoxyethylene group, sulfate ester sodium salts having an allyl group and a polyoxyethylene group, and sulfate ester sodium salts having an allyl group and a polyoxyethylene group. Examples include sulfate ester potassium salts having Specifically, polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate ammonium salt, polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate sodium salt, polyoxyethylene-1-(allyloxy Methyl)alkyl ether sulfate potassium salt; α-[1-[(allyloxy)methyl]-2-(nonylphenoxy)ethyl]-ω-polyoxyethylene sulfate ammonium salt, α-[1-[(allyloxy)methyl ]-2-(nonylphenoxy)ethyl]-ω-polyoxyethylene sulfate ester sodium salt, α-[1-[(allyloxy)methyl]-2-(nonylphenoxy)ethyl]-ω-polyoxyethylene sulfate ester potassium Examples include salt; etc. These sulfates may be used alone or in combination.

[0050] As the sulfate having an allyl group and a polyoxyethylene group in the present invention, an ammonium sulfate salt is preferable, namely, polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate ammonium salt, α-[1-[(allyloxy )Methyl]-2-(nonylphenoxy)ethyl]-ω-polyoxyethylene sulfate salt is preferred for the present invention, and polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate ammonium salt is particularly preferred for the present invention. Most desirable. As a commercially available sulfate having an allyl group and a polyoxyethylene group, for example, "Aqualon KH-10" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., which is a polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate ammonium salt (Product name, polyoxyethylene chain length 10), "Aqualon KH-1025" (Product name, 25% aqueous solution of "Aqualon KH-10"); α-[1-[(allyloxy)methyl]-2-(nonyl) Examples include "Adecaria Soap (trademark) SR-1025" manufactured by Asahi Denka Kogyo Co., Ltd., which is a phenoxy)ethyl]-ω-polyoxyethylene sulfate ester salt.

[0051] Note that this polymerizable unsaturated monomer may contain "other monomers" as long as the desired aqueous resin emulsion can be obtained. "Other monomers" refer to monomers other than (meth)acrylic acid esters, monomers having an alkoxysilyl group and ethylenic double bonds, and (meth)acrylic acid. Examples of "other monomers" are shown below, but are not limited to the following. Styrenic monomers such as styrene and styrene sulfonic acid; unsaturated carboxylic acids and their esters such as itaconic acid, fumaric acid, and maleic acid; and acrylamides such as (meth)acrylamide and diacetone (meth)acrylamide.

[0052] <Multi-step emulsion polymerization> The silane-modified acrylic resin (aqueous resin emulsion) of the present invention is obtained by multi-stage emulsion polymerization of polymerizable unsaturated monomers in the presence of a surfactant. In one embodiment of the present invention, the polymerizable unsaturated monomer is emulsion polymerized in a multi-step (actually two-step) process. The polymerizable unsaturated monomers (a1, a2, a3 and b above) used during polymerization other than the final stage are called polymerizable unsaturated monomer A, and the obtained polymer is called copolymer A. The polymerizable unsaturated monomers (a1, a2 and b above) used during the step polymerization are referred to as polymerizable unsaturated monomer B, and the resulting polymer is referred to as copolymer B. The aqueous resin emulsion finally obtained by multi-stage emulsion polymerization is obtained by polymerizing the polymerizable unsaturated monomer B into a pre-emulsion obtained by polymerizing the polymerizable unsaturated monomer A.

[0053] The aqueous resin emulsion obtained by multi-stage emulsion polymerization has a multilayer structure (core-shell). In the present invention, the polymerizable unsaturated monomer A used in multi-stage emulsion polymerization includes polymerizable unsaturated monomer A used in steps other than the final step and polymerizable unsaturated monomer B used in the final step. and the mass ratio of polymerizable unsaturated monomer B and polymerizable unsaturated monomer A (polymerizable unsaturated monomer B / polymerizable unsaturated monomer A) is 30 / 70 to 70 / 30. is preferable, and particularly preferably 40 / 60 to 60 / 40. By setting the mass ratio of polymerizable unsaturated monomer B and polymerizable unsaturated monomer A to the above ratio, the aqueous resin composition (aqueous resin emulsion) of the present invention has excellent coating properties and durability ( It has an excellent balance of water resistance and solvent resistance.

[0054] In copolymer A, the proportion of the a2 polymerizable unsaturated monomer to the total weight of the a1, a2 and a3 polymerizable unsaturated monomers is preferably 0.05 to 1.0% by weight, more preferably 0.4 ~0.8% by weight, and the proportion of the a3 polymerizable unsaturated monomer is preferably 0.5 to 10% by weight, more preferably 2.0 to 6.0% by weight, and the remainder is the a1 polymerizable unsaturated monomer. However, the ratio of the a1 polymerizable unsaturated monomer to the total weight of the a1, a2, and a3 polymerizable unsaturated monomers is preferably 89 to 99% by weight, more preferably 90 to 98% by weight. %. In copolymer B, the proportion of the a2 polymerizable unsaturated monomer to the total weight of the a1 and a2 polymerizable unsaturated monomers is preferably 0.01 to 1.0% by weight, more preferably 0.1 to 0.4. The balance is the a1 polymerizable unsaturated monomer, but the ratio of the a1 polymerizable unsaturated monomer to the total weight of the a1 and a2 polymerizable unsaturated monomers is preferably is 85 to 99.9% by weight, more preferably 95 to 99.9% by weight. In addition, in the synthesis of copolymers A and B (i.e., silane-modified acrylic resin), (b) allyl group and polyoxyethylene chain relative to the total weight of the polymerizable unsaturated monomers a1, a2, and a3 above. The proportion of the polymerizable surfactant containing the sulfate having the formula is preferably 0.5 to 5% by weight based on the total amount in the synthesis step. The silane-modified acrylic resin (aqueous resin emulsion) of the present invention is available, for example, from Henkel Japan Ltd. under the trade name AQUENCE EPIX BC 21066.

[0055] An example of this multi-stage emulsion polymerization process will be described below. First, (a1) (meth)acrylic acid ester, (a2) a monomer having an alkoxysilyl group and an ethylenic double bond, and (a3) ​​a monomer having a carboxyl group are uniformly mixed in a reaction container, A mixture of polymerizable unsaturated monomers A is prepared. Water (or an aqueous medium) is added to a sulfate having an allyl group and a polyoxyethylene group to form an aqueous solution, and a mixture of polymerizable unsaturated monomers A is added to this aqueous solution to prepare a monomer emulsion A. . Prepare monomer emulsion B separately from monomer emulsion A in a separate container. The preparation of monomer emulsion B may be the same as the preparation of monomer emulsion A. Specifically, (a1) (meth)acrylic acid ester and (a2) a monomer having a monomer having an alkoxysilyl group and an ethylenic double bond are uniformly mixed, and the polymerizable unsaturated monomer is Prepare mixture B. A mixture of polymerizable unsaturated monomers B is added to an aqueous solution of a sulfate having an allyl group and a polyoxyethylene group to obtain a monomer emulsion B.

[0056] Next, water and (b) a sulfate having an allyl group and a polyoxyethylene group are placed in a reactor equipped with a stirrer, a thermometer, etc., and a portion of the monomer emulsion A and a catalyst are added. . While maintaining the temperature inside the reactor at an appropriate temperature, the remaining monomer emulsion A and the catalyst are further added dropwise to prepare a pre-emulsion. Monomer emulsion B and a catalyst are added dropwise to this pre-emulsion and polymerized, thereby synthesizing the final product, an aqueous resin emulsion, by multi-step emulsion polymerization. Examples of the catalyst used here include ammonium persulfate, sodium persulfate, potassium persulfate, t-butylperoxybenzoate, 2,2-azobisisobutitonitrile (AIBN), and 2,2-azobis(2-amidinopropane). ) dihydrochloride, and 2,2-azobis(2,4-dimethylvaleronitrile), among others, ammonium persulfate, sodium persulfate, and potassium persulfate are particularly preferred.

[0057] The glass transition point (Tg) of the silane-modified acrylic resin used in the present invention is preferably -10°C or more and 50°C or less, more preferably 0°C or more and 50°C or less. Further, the glass transition temperature of copolymer A is preferably lower than that of copolymer B. Further, the glass transition temperature of copolymer A is preferably -20 to 20°C, more preferably -10 to 20°C, and particularly preferably -10 to 15°C. Further, the glass transition temperature of copolymer B is preferably 10 to 50°C, more preferably 25 to 50°C, and particularly preferably 30 to 50°C. Further, the minimum film forming temperature (MFT) of the acrylic resin used in the present invention is preferably 25°C or lower, more preferably 0°C to 25°C. When the minimum film forming temperature (MFT) is 0°C to 25°C, the solvent barrier properties are particularly good. Note that the glass transition point (Tg) and minimum film forming temperature (MFT) of the acrylic resin are measured by differential scanning calorimetry (DSC).

[0058] The high Tg acrylic resin used in the present invention is a non-core-shell type acrylic resin, and its glass transition point (Tg) is higher than 50°C and lower than 95°C. This Tg is measured by differential scanning calorimetry (DSC). This high Tg acrylic resin contains (meth)acrylic acid and a monomer component copolymerizable with (meth)acrylic acid, and (meth)acrylic acid is 1 to 100 parts by weight of the non-core-shell type acrylic resin. Preferably it is 10 parts by weight. (Meth)acrylic acid is alkali-soluble and has the property of turning a non-core-shell type acrylic resin into a water-soluble resin by adding a neutralizing agent. By changing the non-core-shell type acrylic resin to a water-soluble resin, the bonding property to the pigment is significantly improved, especially when the protective layer contains a pigment, and the protective layer has excellent strength even when containing a large amount of pigment. can be formed. Examples of components copolymerizable with (meth)acrylic acid include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, By alkyl acrylate resins such as pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, epoxy resin, silicone resin, styrene or its derivatives. Examples include modified alkyl acrylate resins such as the above-mentioned modified alkyl acrylate resins, (meth)acrylonitrile, acrylic esters, and hydroxyalkyl acrylic esters, but in particular, (meth)acrylonitrile and / or methyl methacrylate should be blended. is preferred. (Meth)acrylonitrile is preferably blended in an amount of 15 to 70 parts in 100 parts of the non-core-shell type acrylic resin. Furthermore, it is preferable that methyl methacrylate be contained in an amount of 20 to 80 parts in 100 parts of the non-core-shell type acrylic resin. When containing (meth)acrylonitrile and methyl methacrylate, mix 15 to 18 parts of (meth)acrylonitrile to 100 parts of non-core-shell acrylic resin, and 20 to 80 parts of methyl methacrylate to 100 parts of non-core-shell acrylic resin. It is preferable.

[0059] Other binders that can be 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, Polyvinyl alcohols such as olefin-modified polyvinyl alcohol, nitrile-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, and other modified polyvinyl alcohols, (meth)acrylic acid, and monomers copolymerizable with (meth)acrylic acid. Acrylic resins (excluding the above silane-modified acrylic resins and high Tg acrylic resins) consisting of body components (excluding olefins), cellulose derivatives such as hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, ethyl cellulose, and acetyl cellulose, oxidized Starches such as starch, etherified starch, and esterified starch, styrene-maleic anhydride copolymer, styrene-butadiene copolymer, casein, gum arabic, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylic ester, Examples include polyvinyl butyral, polystyrose and copolymers thereof, polyamide resins, silicone resins, petroleum resins, terpene resins, ketone resins, and coumaron resins. These polymeric substances are used by dissolving them in solvents such as water, alcohol, ketones, esters, and hydrocarbons, or by emulsifying them or dispersing them in paste form in water or other media to meet the required quality. They can also be used together depending on the situation.

[0060] The protective layer of the present invention contains a binder (including the above-mentioned silane-modified acrylic resin and high Tg acrylic resin), and may optionally contain optional components such as the pigments shown for the heat-sensitive recording layer. good. The amount of binder or the total amount of binder and pigment in the protective layer is usually 80.0 to 100.0% by weight, preferably 90.0 to 100.0% by weight in terms of solid content, and the binder is 30.0 to 300.0 parts by weight per 100 parts by weight of pigment. It is preferable that the degree of The content of the acrylic resin in the protective layer of the present invention is preferably 5.0 to 80.0% by weight, more preferably 5.0 to 60.0% by weight, and still more preferably 15.0 to 50.0% by weight. Further, the content of the silane-modified acrylic resin in the protective layer of the present invention is preferably 10.0 to 70.0% by weight, more preferably 30.0 to 60.0% by weight, and the content of the high Tg acrylic resin in the protective layer is preferably 10.0 to 70.0% by weight, more preferably 30.0 to 60.0% by weight. The amount is preferably 5.0 to 50.0% by weight, more preferably 10.0 to 40.0% by weight. Each of the other components does not exceed 15.0% by weight, preferably 10.0% by weight, in the protective layer.

[0061] Moreover, a crosslinking agent can also be used in the protective layer of the present invention. 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, and modified polyamines. resins, modified polyamide resins, polyalkylene polyamine urea formalin resins, or polyamine / polyamide resins such as polyalkylene polyamine polyamide polyurea resins, glyoxal, methylol melamine, melamine formaldehyde resins, melamine urea resins, potassium persulfate, ammonium persulfate, Sodium sulfate, ferric chloride, magnesium chloride, borax, boric acid, alum, ammonium chloride Examples include um. In the present invention, it is preferable to contain an epichlorohydrin resin and a polyamine / polyamide resin as crosslinking agents in the protective layer, since water resistance becomes particularly good.

[0062] The heat-sensitive recording material of the present invention has a heat-sensitive recording layer on a support, but an undercoat layer may be provided between the support and the heat-sensitive recording layer.

[0063] This undercoat layer mainly consists of a binder and a pigment. As the binder for the undercoat layer, commonly used emulsions of water-soluble polymers or hydrophobic polymers can be used as appropriate. Specific examples include polyvinyl alcohol, polyvinyl acetal, cellulose derivatives such as hydroxyethylcellulose, methylcellulose, and carboxymethylcellulose, starch and its derivatives, sodium polyacrylate, polyvinylpyrrolidone, acrylic acid amide / acrylic ester copolymer, and acrylic acid. Water-soluble polymers such as amide / acrylic acid ester / methacrylic acid copolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein, etc. Polyvinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylic ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer, styrene / butadiene / acrylic copolymer Emulsions of hydrophobic polymers such as polymers can be used. One type or two or more types of these binders may be used.

[0064] Pigments used in the undercoat layer include commonly used known pigments, such as calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, magnesium hydroxide, calcined kaolin, clay, and talc. Inorganic pigments and the like can be used. These pigments may be used alone or in combination of two or more. The amount of pigment in the undercoat layer is usually 50 to 95 parts by weight, preferably 70 to 90 parts by weight, based on 100 parts by weight of the total solid content. If necessary, various auxiliary agents such as dispersants, plasticizers, pH adjusters, antifoaming agents, water retention agents, preservatives, coloring dyes, and UV inhibitors may be added to the coating solution for the undercoat layer. good.

[0065] In the present invention, the means for applying the heat-sensitive recording layer and coating layers other than the heat-sensitive recording layer, such as the protective layer and the undercoat layer, are not particularly limited, and can be applied according to well-known and commonly used techniques. For example, an off-machine coating machine or an on-machine coating machine equipped with various coaters such as an air knife coater, a rod blade coater, a bent blade coater, a bevel blade coater, a roll coater, and a curtain coater is appropriately selected and used. The coating amount of the heat-sensitive recording layer and coating layers other than the heat-sensitive recording layer is determined according to the required performance and recording suitability, and is not particularly limited, but the general coating amount of the heat-sensitive recording layer is solid. 2~12g / m in minutes 2 The coating amount of the protective layer is 0.5~5.0g / m in solid content. 2 is preferred. Further, various known techniques in the field of heat-sensitive recording materials can be added as necessary, such as applying a smoothing treatment such as super calendering after coating each coating layer.

Example

[0066] Hereinafter, the present invention will be illustrated by Examples, but they are not intended to limit the present invention. In each of the Examples and Comparative Examples, "part" means "part by weight" and "%" means "% by weight" unless otherwise specified.

[0067] [Silane-modified acrylic resin] In the following production examples, aqueous emulsions were prepared from (A) a monomer emulsion (copolymer A) and (B) a monomer emulsion (copolymer B). The polymerizable unsaturated monomer, surfactant, and each additive for producing (A) and (B) are described below. In addition, the homopolymer Tg of the polymerizable unsaturated monomer is a literature value, and (a) the Tg of the copolymer of the polymerizable unsaturated monomer and (b) the copolymer of the polymerizable unsaturated monomer. The Tg of coalescence is a value calculated using a theoretical calculation formula.

[0068] <Polymerizable unsaturated monomer> Methyl methacrylate (hereinafter referred to as "MMA", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., homopolymer Tg = 105°C) 2-ethylhexyl acrylate (2-ethylhexyl acrylate, hereinafter referred to as "2EHA", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., homopolymer Tg = -70°C) n-Butyl acrylate (n-butyl acrylate, hereinafter referred to as "n-BA", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., homopolymer Tg = -54℃) n-Butyl methacrylate (n-butyl methacrylate, hereinafter referred to as "n-BMA", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., homopolymer Tg = 20°C) Cyclohexyl methacrylate (cyclohexyl methacrylate, hereinafter referred to as "CHMA", manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., homopolymer Tg = 83°C) 3-methacryloxypropyltrimethoxysilane (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) Acrylic acid (hereinafter referred to as "AA", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., homopolymer Tg = 106°C) Styrene (hereinafter referred to as "St", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., homopolymer Tg = 100℃)

[0069] <Surfactant> Polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfuric acid ester ammonium salt (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Aqualon KH10) (hereinafter referred to as "b")

[0070] [Manufacturing example 1] A monomer emulsion was prepared from a plurality of polymerizable unsaturated monomers, a pre-emulsion was then prepared from the monomer emulsion, and an aqueous resin emulsion was synthesized from the pre-emulsion. The specific steps are as follows.

[0071] ((A) Preparation of monomer emulsion) As shown in Table 1, (a1-1) MMA5 parts by mass, (a1-3) BA23 parts by mass, (a1-4) BMA10 parts by mass, (a1-5) CHMA10 parts by mass, (a2) 3-methacrylate 0.3 parts by mass of roxypropyltrimethoxysilane and 2 parts by mass of (a3)AA were uniformly mixed to prepare a polymerizable unsaturated monomer solution (50.3 parts by mass). Adding the above polymerizable unsaturated monomer solution to a uniformly mixed solution of 14 parts by mass of water and 0.1 part by mass of (b) polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate ammonium salt, These mixed solutions were stirred with a stirrer to obtain a monomer emulsion (A).

[0072] ((B) Preparation of monomer emulsion) (A) As shown in Table 1, (a1-1) MMA16.6 parts by mass, (a1-3) BA13 parts by mass, (a1-4) BMA10 parts by mass, (a1-5) CHMA10 parts by mass, ( a2) 0.1 part by mass of 3-methacryloxypropyltrimethoxysilane was mixed uniformly to prepare a polymerizable unsaturated monomer solution. Adding the above polymerizable unsaturated monomer solution to a uniformly mixed solution of 14 parts by mass of water and 0.1 part by mass of (b) polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate ammonium salt, These mixed solutions were stirred with a stirrer to obtain a monomer emulsion (B).

[0073] (Synthesis of pre-emulsion) A reactor equipped with a stirrer, a condenser, and a thermometer was charged with 78 parts by mass of water and 1.25 parts by mass of (b) polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate ammonium salt, and the inside of the system was heated with nitrogen gas. After displacement, the charge was heated to 80°C. Thereafter, 1% by mass of (A) monomer emulsion (containing 50.3 parts by mass of polymerizable unsaturated monomer and corresponding to 10.1 parts by mass of the polymerizable unsaturated monomer) was added to the charging solution. 2 parts by mass of an aqueous solution of sodium persulfate (hereinafter also referred to as "SPS") were added. After another 10 minutes, while maintaining the temperature inside the reactor at 80°C, the remaining monomer emulsion (A) (a portion corresponding to 40.2 parts by mass of (a) polymerizable unsaturated monomer) and 4 parts by mass of a 1% aqueous solution of SPS, which is a polymerization catalyst, was simultaneously added dropwise over 2 hours to obtain a pre-emulsion ((a) an aqueous resin emulsion based on a polymerizable unsaturated monomer).

[0074] (Synthesis of water-based resin emulsion) The temperature inside the reactor was maintained at 80°C, and 30 minutes after the completion of the dropwise addition, the above monomer emulsion (B) (containing 49.7 parts by mass of unsaturated polymerizable monomer) and 4 parts by mass of a 1% aqueous solution of SPS were added. 2 parts were simultaneously added dropwise to the above-mentioned pre-emulsion over 2 hours to obtain an aqueous resin emulsion. The resulting aqueous resin emulsion was adjusted to pH 8.0 with aqueous ammonia. In the aqueous resin emulsion, (A) the polymerizable unsaturated monomer (copolymer A) has a glass transition temperature of -3.8°C, and (B) the polymerizable unsaturated monomer (copolymer B) has a glass transition temperature of -3.8℃. The temperature was 26.7°C, and the solid content concentration was 45% by mass. The solids content is the weight percentage of the remaining portion after drying in an oven at 105° C. for 3 hours, relative to the weight before drying. The obtained aqueous resin emulsion is called silane-modified acrylic resin 1.

[0075] [Manufacturing examples 2-3] Synthesis was carried out in the same manner as in Production Example 1 using the raw material monomers shown in Table 1. The numbers related to formulations in the table represent parts by weight. The obtained aqueous resin emulsions are respectively referred to as silane-modified acrylic resins 2 and 3.

[0076]

table 1

[0077] On the other hand, in order to produce a heat-sensitive recording material, each dispersion liquid and coating liquid were prepared as follows. [Preparation of each coating fluid] A coating solution for an undercoat layer was prepared by stirring and dispersing a composition having the following composition. <Coating liquid for undercoat layer> Calcined kaolin (manufactured by BASF, product name: Ansilex 90) 100.0 copies Styrene-butadiene copolymer latex (manufactured by Nippon Zeon Co., Ltd., Product name: ST5526, solid content 48%) 10.0 parts Water 50.0 parts

[0078] Each dispersion liquid and coating liquid were prepared as follows. A coating solution for an undercoat layer was prepared by stirring and dispersing a composition having the following composition. <Coating liquid for undercoat layer> Calcined kaolin (manufactured by BASF, product name: Ansilex 90) 100.0 copies Styrene-butadiene copolymer latex (manufactured by Nippon Zeon Co., Ltd., Product name: ST5526, solid content 48%) 10.0 parts Water 50.0 parts

[0079] The developer dispersion (A1 to A4 solutions), leuco dye dispersion (B solution), and sensitizer dispersion (C solution) of the following composition were wet-grinded separately using a sand grinder until the average particle size was 0.5 μm. It was prepared by grinding.

[0080] Color developer dispersion (A1 liquid) N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea (Hereinafter referred to as "urea compound 1".) 6.0 parts Completely saponified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd., product name: PVA117, solid content 10%) 5.0 parts 1.5 parts water Color developer dispersion (A2 liquid) N-[2-(3-phenylureido)phenyl]benzenesulfonamide (Hereinafter referred to as "urea compound 2".) 6.0 parts Completely saponified polyvinyl alcohol aqueous solution (PVA117) 5.0 parts 1.5 parts water Color developer dispersion (A3 liquid) Urea compound represented by the following chemical formula (Chemical formula 9) (Hereinafter referred to as "urea compound 3".) 6.0 parts [ka] Completely saponified polyvinyl alcohol aqueous solution (PVA117) 5.0 parts 1.5 parts water

[0081] Color developer dispersion (A4 liquid) Urea urethane compound represented by formula (Chemical formula 13) (UU manufactured by Fine Ace) 6.0 parts [ka] Completely saponified polyvinyl alcohol aqueous solution (PVA117) 5.0 parts 1.5 parts water Color developer dispersion (A5 liquid) 4-Hydroxy-4'-isopropoxydiphenylsulfone (Mitsubishi Chemical Corporation system, NYDS) 6.0 copies Completely saponified polyvinyl alcohol aqueous solution (PVA117) 5.0 parts 1.5 parts water

[0082] Leuco dye dispersion (liquid B) 3-dibutylamino-6-methyl-7-anilinofluorane (Manufactured by Yamamoto Kasei Co., Ltd., product name: ODB-2) 6.0 parts Completely saponified polyvinyl alcohol aqueous solution (PVA117) 5.0 parts 1.5 parts water

[0083] Sensitizer dispersion (C liquid) 1,2-di(3-methylphenoxy)ethane (Manufactured by Sankosha, product name: KS232) 6.0 copies Completely saponified polyvinyl alcohol aqueous solution (PVA117) 5.0 parts 1.5 parts water

[0084] Next, each dispersion liquid was mixed in the following proportions to prepare a coating liquid for a heat-sensitive recording layer. <Coating liquid for heat-sensitive recording layer> Color developer dispersion (A1 liquid) 18.0 parts Color developer dispersion (A2 liquid) 18.0 parts Leuco dye dispersion (liquid B) 18.0 parts Sensitizer dispersion (C solution) 9.0 parts Completely saponified polyvinyl alcohol aqueous solution (PVA117) 25.0 parts

[0085] Next, protective layer coating solutions 1 to 3 were prepared by mixing formulations having the following proportions. <Coating liquid 1 for protective layer> Aluminum hydroxide dispersion (manufactured by Martinsberg, Product name: Marty Fin OL, solid content 50%) 9.0 parts Silane-modified acrylic resin 1 (Tg18℃, MFT22℃, Solid content 40%) 10.0 parts Zinc stearate (manufactured by Chukyo Yushi Co., Ltd., product name: Hydrin Z-7-30, Solid content 30%) 2.0 parts

[0086] <Coating liquid 2 for protective layer> Aluminum hydroxide dispersion (Martifin OL) 9.0 parts Non-core shell type acrylic resin (no silane modification, styrene acrylic, Tg55℃, MFT18℃, solid content 18%) 22.2 parts Zinc stearate (Hydrin Z-7-30) 2.0 parts <Coating liquid 3 for protective layer> Aluminum hydroxide dispersion (Martifin OL) 9.0 parts Completely saponified polyvinyl alcohol aqueous solution (PVA117) 40.0 parts Zinc stearate (Hydrin Z-7-30) 2.0 parts Glyoxal aqueous solution (manufactured by Nippon Gosei Kagaku Co., Ltd., solid content 40%) 3.0 parts <Coating liquid 4 for protective layer> Carboxy-modified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd., product name: KL118, solid content 10%<polymerization degree: approx. 1700, saponification degree: 95-99 mol%, sodium acetate: 3% or less) 40.0 parts Polyamide epichlorohydrin resin (manufactured by Seiko PMC, product name: WS4020, solids 25%) 4.0 parts Modified polyamine resin (manufactured by Taoka Chemical Co., Ltd., product name: violet resin) SPI-102A, solids content 45%) 2.2 parts Aluminum hydroxide dispersion (Martifin OL) 9.0 parts Zinc stearate (Hydrin Z-7-30) 2.0 parts

[0087] [Reference example 1] Support (basis weight 47g / m 2 Coating liquid for undercoat layer is applied to one side of (high-quality paper) at a solid content of 10.0 g / m 2 After coating by the bent blade method so as to obtain the following, drying was performed to obtain an undercoat coated paper. On the undercoat layer of this undercoat layer-coated paper, apply the coating liquid for the heat-sensitive recording layer at a coating amount of 6.0 g / m2 in terms of solid content. 2 After coating by the rod blade method so as to obtain the following, drying was performed to obtain a heat-sensitive recording material. Next, on the heat-sensitive recording layer of this heat-sensitive recording layer-coated paper, protective layer coating solution 1 was applied in a coating amount of 3.0 g / m2 in terms of solid content. 2 After coating by a curtain method so as to have the following properties, it was dried and treated with a supercalender to give a smoothness of 100 to 500 seconds to obtain a heat-sensitive recording layer. [Reference example 2] A thermosensitive recording material was produced in the same manner as in Reference Example 1, except that silane-modified acrylic resin 1 was changed to silane-modified acrylic resin 2 in coating liquid 1 for protective layer.

[0088] [Reference example 3] A thermosensitive recording material was produced in the same manner as in Reference Example 1, except that silane-modified acrylic resin 1 was changed to silane-modified acrylic resin 3 in coating liquid 1 for protective layer. [Reference example 4] A heat-sensitive recording material was produced in the same manner as in Reference Example 1, except that liquid A2 was replaced with liquid A3 in the coating liquid for the heat-sensitive recording layer. [Reference example 5] A heat-sensitive recording material was produced in the same manner as in Reference Example 1, except that the A1 solution was changed to A3 solution in the heat-sensitive recording layer coating solution. [Reference example 6] A thermosensitive recording material was produced in the same manner as in Reference Example 1, except that Coating Liquid 1 for protective layer was changed to Coating Liquid 2 for protective layer. [Reference example 7] A heat-sensitive recording material was produced in the same manner as in Reference Example 1, except that in the heat-sensitive recording layer coating solution, the number of parts of the A1 solution was changed to 9 parts, and 9 parts of the A4 solution was added. [Example 8] A heat-sensitive recording material was produced in the same manner as in Reference Example 1, except that the A2 solution was not blended in the heat-sensitive recording layer coating solution and the A1 solution was changed to 36 parts. [Example 9] A heat-sensitive recording material was produced in the same manner as in Reference Example 1, except that in the coating liquid for a heat-sensitive recording layer, liquid A1 was not blended and the number of parts of liquid A2 was changed to 36 parts. [Reference example 10] A heat-sensitive recording material was produced in the same manner as in Reference Example 1, except that in the coating liquid for a heat-sensitive recording layer, liquid A1 and liquid A2 were not blended, and 36 parts of liquid A3 was added.

[0089] [Comparative example 1] A thermosensitive recording material was produced in the same manner as in Reference Example 4, except that Coating Liquid 1 for protective layer was changed to Coating Liquid 3 for protective layer. [Comparative example 2] A heat-sensitive recording material was produced in the same manner as in Reference Example 4, except that Coating Liquid 1 for protective layer was changed to Coating Liquid 4 for protective layer. [Comparative example 3] A thermosensitive recording material was produced in the same manner as in Reference Example 4 except that the protective layer was not provided. [Comparative example 4] A thermosensitive recording material was produced in the same manner as in Example 8 except that the protective layer was not provided. [Comparative example 5] A thermosensitive recording material was produced in the same manner as in Reference Example 1 except that no protective layer was provided. [Comparative example 6] A thermosensitive recording material was produced in the same manner as in Reference Example 5 except that no protective layer was provided. [Comparative example 7] A heat-sensitive recording material was produced in the same manner as in Reference Example 1, except that in the coating liquid for a heat-sensitive recording layer, liquid A1 and liquid A2 were not blended, and 36 parts of liquid A5 was added.

[0090] The produced heat-sensitive recording material was evaluated as follows. <Color development performance (print density)> The produced thermal recording material was printed in a checkerboard pattern using a TH-PMD manufactured by Okura Electric Co., Ltd. (thermal recording paper printing tester, equipped with a thermal head manufactured by Kyocera Corporation) at a printing speed of 50 mm / sec and an applied energy of 0.41 mJ / dot. was printed. The print density of the printed area was measured using a Macbeth densitometer (RD-914, using an amber filter), and the color development performance (print density) was evaluated. <Print running performance (head debris resistance)> The produced thermal recording material was printed with a grid of 60 cm in length using a SATO label printer (Lesprit R-8), and the residue (head residue) attached to the thermal head after printing was visually evaluated according to the following criteria. did. Excellent: Hardly any head residue was observed. Fair: A small amount of head residue was observed, but no missing or blurred images were observed, and the level was not a problem for practical use. Unsatisfactory: A lot of head debris was observed, and the formed image was missing and faded.

[0091] <High-speed printing suitability> The produced thermal recording medium was printed with a barcode (CODE39) in the vertical direction (the direction of movement of the printer head) using a Zebra label printer 140XiIII at a printing level of +10 and a printing speed of 25.4 cm / sec (10 inches / sec). The barcode was printed at right angles. Next, a reading test was performed on the printed barcode using a barcode verification machine (manufactured by Honeywell, QCPC600, light source 640 nm) to evaluate barcode reading aptitude. The evaluation results were recorded using ANSI standard symbol grades. Symbol grade: The barcode is divided into 10 parts vertically and a reading test is carried out once for each part, and the average value is evaluated in 5 stages: (excellent) A, B, C, D, F (poor). Expressed as <Oil resistance> A checkered pattern was printed on the produced thermal recording material using a TH-PMD manufactured by Okura Electric Co., Ltd. (thermal recording paper printing tester, equipped with a thermal head manufactured by Kyocera) at an applied energy of 0.41 mJ / dot and a printing speed of 50 mm / sec. I printed it. Salad oil was applied to the printed thermosensitive recording material with a cotton swab, and after leaving it for 24 hours, the print density of the printed portion was measured using a Macbeth densitometer (RD-914, using an amber filter).

[0092] <Solvent barrier properties> Ethanol (99.5%) was applied with a cotton swab to the blank area of ​​the produced heat-sensitive recording material, and after standing under environmental conditions of 23° C. and 50% RH for 24 hours, visual evaluation was performed according to the following criteria. Excellent: No color at all Acceptable: Slightly colored Impossible: Strongly colored <Wet friction> Regarding the produced heat-sensitive recording material, the surface of the protective layer was rubbed back and forth 80 times with tap water applied to the finger, and peeling of the protective layer and the heat-sensitive recording layer was visually evaluated according to the following criteria. Excellent: No peeling of the protective layer or heat-sensitive recording layer. Fair: The protective layer peels off slightly, but the heat-sensitive recording layer does not peel off. Not possible: The protective layer and heat-sensitive recording layer will peel off.

[0093] <Waterproof blocking> For the produced heat-sensitive recording material, drop 10ml of tap water on the surface of the protective layer, fold it in half so that the surface of the protective layer is on the inside, and add 20gf / cm. 2 The protective layer and heat-sensitive recording layer were peeled off after being left standing for 24 hours under a load of 100.degree. Excellent: No blocking occurs at all, and there is no peeling of the protective layer or heat-sensitive recording layer. Acceptable: Blocking occurs and the protective layer peels off slightly, but the heat-sensitive recording layer does not peel off. Impossible: Strong blocking occurs and the protective layer and heat-sensitive recording layer peel off. Or, the heat-sensitive recording material is destroyed when peeling it off. <Immersion friction> The produced heat-sensitive recording material was immersed in tap water for 10 minutes, the surface of the protective layer was rubbed back and forth with a finger 20 times, and peeling of the protective layer and the heat-sensitive recording layer was visually evaluated using the following criteria. Excellent: No peeling of the protective layer or heat-sensitive recording layer. Fair: The protective layer peels off slightly, but the heat-sensitive recording layer does not peel off. Not possible: The protective layer and heat-sensitive recording layer will peel off.

[0094] The results are shown in the table below. [Table 2]

Claims

1. A thermosensitive recording medium having a support, a thermosensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer, and a protective layer on the thermosensitive recording layer, wherein the thermosensitive recording layer contains a third urea compound represented by the following (3) as the electron-accepting developer, the protective layer contains an acrylic resin represented by the following (4) or (5), the content of the acrylic resin in the protective layer is 15.0 to 50.0% by weight, and the minimum film-forming temperature (MFT) of the acrylic resin is 0°C to 25°C. (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.) (4) A non-core-shell acrylic resin having a glass transition point (Tg) of more than 50° C. and not more than 95° C. (5) A silane-modified acrylic resin which is an aqueous emulsion of core-shell type particles comprising a core made of copolymer A obtained by polymerizing the following (a1), (a2) and (a3) ​​in the presence of (b), and a shell made of copolymer B obtained by polymerizing the following (a1) and (a2) in the presence of (b): (a1) at least one (meth)acrylic acid ester (a2) Monomer having an alkoxysilyl group and an ethylenic double bond (a3) Monomer having a carboxyl group and an ethylenic double bond (b) Polymerizable surfactant containing a sulfate having an allyl group and a polyoxyethylene chain

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 according to claim 1, wherein the acrylic resin content (solid content) in the protective layer is 15.0 to 50.0% by weight.

Images