JP7413085B2 - heat sensitive recording material - Google Patents

Description

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"). A heat-sensitive recording material that has sufficient water resistance against rain and other moisture when used outdoors, and has excellent color development sensitivity, oil resistance, heat resistance, ink adhesion, and solvent resistance. Regarding the body.

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 tickets 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 material (patent document 1) and a urea compound (Patent Document 2) as a color developer for improving required performances such as color density, whiteness, and storage stability of a printed area of a heat-sensitive recording material (Patent Document 2).
In addition, in order to improve the storage stability of heat-sensitive recording materials, a method of providing a protective layer on the heat-sensitive recording layer has been used. It is known that it improves head wear during printing and improves the image storage stability and water resistance of heat-sensitive recording media (Patent Documents 3 and 4, etc.).

JP2015-80852 International publication WO2019/044462 Japanese Patent Publication No. 5-574 JP2000-238432

Therefore, among the various performances required of a heat-sensitive recording medium, the present invention has sufficient water resistance against water and moisture such as rain when used outdoors, as well as coloring sensitivity, oil resistance, heat resistance, and ink resistance. The purpose of the present invention is to provide a heat-sensitive recording material having excellent adhesion and solvent resistance.

（式中、Ｒ^１は、置換若しくは無置換のアルキル基、アラルキル基又はアリール基を表し、Ｒ^２は、水素原子又はアルキル基を表す。）、該保護層が、シラン変性アクリル系樹脂を含有し、該シラン変性アクリル系樹脂が、下記（ａ１）、（ａ２）及び（ａ３）を（ｂ）の存在下で重合させて成る共重合体Ａから成るコアと、下記（ａ１）及び（ａ２）を（ｂ）の存在下で重合させて成る共重合体Ｂから成るシェルとから成るコアシェル型粒子の水性エマルジョンである感熱記録体である。
（ａ１）少なくとも１種の（メタ）アクリル酸エステル
（ａ２）アルコキシシリル基及びエチレン性二重結合を有する単量体
（ａ３）カルボキシル基及びエチレン性二重結合を有する単量体
（ｂ）アリル基及びポリオキシエチレン鎖を有する硫酸塩を含有する重合性界面 As a result of extensive studies, the present inventors have found that the above-mentioned problems can be solved by incorporating two specific types of color developers into the heat-sensitive recording layer, and have completed the present invention.
That is, the present invention provides a heat-sensitive recording material in which a heat-sensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting color developer is provided on a support, and a protective layer is provided on the heat-sensitive recording layer. wherein the heat-sensitive recording layer contains a urea compound represented by the following general formula (Chemical formula 1) as an electron-accepting color developer,

(In the formula, R ¹ represents a substituted or unsubstituted alkyl group, aralkyl group, or aryl group, and R ² represents a hydrogen atom or an alkyl group.), the protective layer contains a silane-modified acrylic resin. The silane-modified acrylic resin comprises a core made of a copolymer A obtained by polymerizing the following (a1), (a2) and (a3) in the presence of (b), and the following (a1) and (a2). ) and a shell made of copolymer B obtained by polymerizing copolymer B 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) Allyl Polymerizable interface containing sulfate groups and polyoxyethylene chains

According to the present invention, the thermal recording material has sufficient water resistance against moisture such as rain when used outdoors, and has excellent color development sensitivity, oil resistance, heat resistance, ink adhesion, and solvent resistance. can be provided.

The heat-sensitive recording material of the present invention is a heat-sensitive recording material in which a heat-sensitive recording layer containing a colorless or light-colored leuco dye and a color developer is provided on a support, and a protective layer is provided on the heat-sensitive recording layer. The recording layer contains a urea compound represented by the above general formula (Chemical formula 1) as a color developer, and the protective layer contains a specific silane-modified acrylic resin that is an aqueous emulsion of core-shell type particles. It is characterized by
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.

The urea compound used in the present invention is represented by the following formula (Chemical formula 1).

In the general formula (Formula 1), R ¹ 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. 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. Further, a plurality of R ¹ 's may be the same or different.
The position of R ¹ - SO ₂ -O- in the benzene ring of general formula (Formula 1) may be the same or different, and is preferably the 3rd, 4th or 5th position.

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.

Examples of the aralkyl group include 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-tolyl Examples include unsubstituted or aralkyl groups such as benzyl group and p-chlorobenzyl group, alkyl groups, alkoxy groups, aralkyl groups, aryl groups, and aralkyl groups substituted with halogen atoms.

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, pi-propylphenyl group, pt-butylphenyl group, p-methoxyphenyl group, 3,4-dimethoxy Unsubstituted or alkyl groups, alkoxy groups, aralkyl groups, aryl groups or halogen atoms such as phenyl group, p-ethoxyphenyl group, p-chlorophenyl group, 1-naphthyl group, 2-naphthyl group, t-butylated naphthyl group, etc. Examples include substituted aryl groups.

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 a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group. , isobutyl group, sec-butyl group, t-butyl group, etc.
The position of R ² in the benzene ring of the general formula (Formula 1) may be the same or different, and is preferably the 3rd, 4th or 5th position.

一般式（化２）中、Ｒ^３はアルキル基又はアルコキシ基、好ましくはアルキル基であり、ｎは０～３、好ましくは０～２、より好ましくは０～１の整数を表す。このアルキル基の炭素数は、例えば、１～１２、好ましくは１～８、より好ましくは１～４である。
一般式（化２）のベンゼン環中のＲ^３の位置は、同じであっても異なってもよく、好適には３位、４位又は５位、好ましくは４位である。 As the urea compound of the present invention, a urea compound represented by the following general formula (Chemical formula 2) is preferable.

In the general formula (Formula 2), R ³ is an alkyl group or an alkoxy group, preferably an alkyl group, and n 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.
The position of R ³ in the benzene ring of general formula (Chemical formula 2) may be the same or different, and is preferably the 3-position, the 4-position or the 5-position, preferably the 4-position.

Further, as the 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-xylene) sulfonyloxy)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-butylbenzene) sulfonyloxy)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-k) milbenzenesulfonyloxy)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, N,N'-di-[3-(benzylsulfonyloxy)phenyl] Examples include, but are not limited to, urea, and the like.

The content (solid content) of the urea compound represented by the general formula (Chemical formula 1) in the heat-sensitive recording layer of the present invention is 1.0 to 50.0% by weight, preferably 1.0 to 40.0% by weight. Weight%.

In the heat-sensitive recording layer of the present invention, a color developer other than the urea compound represented by the general formula (Chemical formula 1) may be used. Examples of such color developer include activated clay, attapulgite, and colloidal silica. , inorganic acidic substances such as aluminum silicate, 4,4'-isopropylidenediphenol, 1,1-bis(4-hydroxyphenyl)cyclohexane, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 4 , 4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 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-hydroxyphenylsulfonyl)phenoxy]-4-[4-(4-isopropoxyphenylsulfonyl)phenoxy]butane, JP-A-2003- Phenol condensation compositions described in JP-A-154760, aminobenzenesulfonamide derivatives 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), N-[2-(3-phenylureido)phenyl]benzenesulfonamide, WO02/081229 or Compounds described in JP-A No. 2002-301873, thiourea compounds such as N,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, 5-[p-(2-p- Aromatic carboxylic acids such as methoxyphenoxyethoxy)cumyl salicylic acid, salts of these aromatic carboxylic acids with polyvalent metal salts such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel, and further thiocyanic acid. Examples include antipyrine complexes of zinc, complex zinc salts of terephthalaldehydic acid and other aromatic carboxylic acids, and the like. 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.

When the heat-sensitive recording layer of the present invention contains a color developer other than the urea compound represented by the above general formula (Chemical formula 1), all the color developers contained in the heat-sensitive recording layer (the above general formula (Chemical formula The total content (solid content) of the urea compound represented by the general formula (Chemical formula 1) with respect to the urea compound represented by 1) is preferably 50% by weight or more, more preferably 80% by weight or more, More preferably, it is 90% by weight or more.

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.

<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]

<Fluorane-based 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-chlorofluoran, 3-diethylamino-6-methyl-7-(m-trifluoromethylanilino)fluoran, 3-diethylamino-6-methyl-7-(o-chloroanilino)fluoran, 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-methylanilinofluoran, 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)fluoran, 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 Oran, 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 Anilinofluoran, 2-chloro-3-methyl-6-p-(p-phenylaminophenyl)aminoanilinofluoran, 2-chloro-6-p-(p-dimethylaminophenyl)aminoanilinofluoran , 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

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

<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- ]-4,5,6,7-tetrachlorophthalide

<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)fluoran-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

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.

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.

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.

Further, in the present invention, a crosslinking agent can also be used in combination. 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. resin, modified polyamide resin, polyalkylene polyamine urea formalin resin, or polyamine/polyamide resin such as polyalkylene polyamine polyamide polyurea resin, glyoxal, methylol melamine, melamine formaldehyde resin, melamine urea resin, potassium persulfate, ammonium persulfate, Examples include sodium sulfate, ferric chloride, magnesium chloride, borax, boric acid, alum, and ammonium chloride.

In the present invention, it is preferable that the heat-sensitive recording layer contains a carboxyl group-containing resin as a binder, and an epichlorohydrin resin and a polyamine/polyamide resin as a crosslinking agent, since the water resistance becomes particularly good.
In the present invention, when the heat-sensitive recording layer contains a carboxyl group-containing resin as a binder and an epichlorohydrin resin and a polyamine/polyamide resin as a crosslinking agent, the water resistance is particularly improved because of the following reasons. It is assumed that.

A crosslinking reaction (first water resistance) occurs between the carboxyl group of the carboxyl group-containing resin and the amine moiety or amide moiety of the epichlorohydrin resin that is the crosslinking agent. Next, the hydrophilic crosslinking site formed by the carboxyl group-containing resin and epichlorohydrin resin and the hydrophilic site of the polyamine/polyamide resin are attracted to each other. In other words, the hydrophilic crosslinking site is protected from water by the hydrophobic group (second water resistance). Therefore, it is presumed that extremely high hydrophobicity is imparted to the reaction site between the carboxyl group-containing resin and the crosslinking agent, resulting in particularly good water resistance.

The carboxyl group-containing resin used in the heat-sensitive recording layer of the present invention may be any resin as long as it mainly has a carboxyl group, such as methacrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, dimethylamino methacrylate. Examples include acrylic resins containing monofunctional acrylic monomers having carboxyl groups such as ethyl, glycidyl methacrylate, and tetrahydrofurfuryl methacrylate, oxidized starch, carboxymethylcellulose, and carboxy-modified polyvinyl alcohol in which carboxyl groups are introduced into polyvinyl alcohol. Is possible.
In particular, when the carboxyl group-containing resin is carboxy-modified polyvinyl alcohol, it is preferable because the plasticizer resistance of the image area and the heat resistance of the blank area are further improved. This is presumably because, in addition to the above-mentioned crosslinking reaction, the cationic moiety of the polyamine/polyamide resin undergoes a crosslinking reaction with the carboxyl group of the carboxy-modified polyvinyl alcohol.

The carboxy-modified polyvinyl alcohol used in the heat-sensitive recording layer of the present invention is a reaction product of polyvinyl alcohol and a polyhydric carboxylic acid such as fumaric acid, phthalic anhydride, mellitic anhydride, itaconic anhydride, or an ester of these reactants. It is obtained as a saponified product of a copolymer of vinyl acetate and an ethylenically unsaturated dicarboxylic acid such as maleic acid, fumaric acid, itaconic acid, crotonic acid, acrylic acid, or methacrylic acid. Specifically, the manufacturing method illustrated in Example 1 or 4 of JP-A-53-91995 may be mentioned. The degree of saponification of carboxy-modified polyvinyl alcohol is preferably 72 to 100 mol%, and the degree of polymerization is preferably 500 to 2,400, more preferably 1,000 to 2,000.

The epichlorohydrin resin used in the heat-sensitive recording layer of the present invention is a resin characterized by containing an epoxy group in its molecule, and includes the above-mentioned polyamide epichlorohydrin resin, polyamine epichlorohydrin resin, etc. Examples include resins and the like.
As the amine present in the main chain of the epichlorohydrin resin, primary to quaternary amines can be used, and there are no particular limitations. Furthermore, the degree of cationization and molecular weight are preferably 5 meq/g/solid or less (measured value at pH 7) and the molecular weight is preferably 500,000 or more, since water resistance is good. These epichlorohydrin resins can be used alone or in combination of two or more.
Specific examples of epichlorohydrin-based resins used in the heat-sensitive recording layer of the present invention include violet resin 650 (30), violet resin 675A, violet resin 6615 (manufactured by Sumitomo Chemical Co., Ltd.), WS4002, WS4020 , WS4024, WS4030, WS4046, WS4010, CP8970 (all manufactured by Seiko PMC).

The polyamine/polyamide resin used in the heat-sensitive recording layer of the present invention is a resin characterized by not having an epoxy group in its molecule, and includes the aforementioned polyamide urea resin, polyalkylene polyamine resin, and polyalkylene polyamide resin. , polyamine polyurea resin, modified polyamine resin, modified polyamide resin, polyalkylene polyamine urea formalin resin, polyalkylene polyamine polyamide polyurea resin, and the like.
Among these polyamine/polyamide resins, polyamine resins (polyalkylene polyamine resin, polyamine polyurea resin, modified polyamine resin, polyalkylene polyamine urea formalin resin, polyalkylene polyamine polyamide polyurea) have particularly good water resistance. It is preferable to use trees (such as trees). These polyamine/polyamide resins can be used alone or in combination of two or more.
Specific examples of the polyamine/polyamide resin used in the heat-sensitive recording layer of the present invention include Sumiraze Resin 302 (manufactured by Sumitomo Chemical Co., Ltd.: polyamine polyurea resin), Sumiraze Resin 712 (manufactured by Sumitomo Chemical Co., Ltd.: polyamine polyurea resin). ), violet resin 703 (manufactured by Sumitomo Chemical Co., Ltd.: polyamine polyurea resin), violet resin 636 (manufactured by Sumitomo Chemical Co., Ltd.: polyamine polyurea resin), violet resin SPI-100 (manufactured by Sumitomo Chemical Co., Ltd.: modified polyamine resin) , violet resin SPI-102A (manufactured by Sumitomo Chemical Co., Ltd.: modified polyamine resin), violet resin SPI-106N (manufactured by Sumitomo Chemical Co., Ltd.: modified polyamide resin), violet resin SPI-203 (50) (manufactured by Sumitomo Chemical Co., Ltd.) , violet resin SPI-198 (manufactured by Sumitomo Chemical), Printiv A-700 (manufactured by Asahi Kasei), Printiv A-600 (manufactured by Asahi Kasei), PA6500, PA6504, PA6634, PA6638, PA6640, PA6644, PA6646, Examples thereof include PA6654, PA6702, and PA6704 (polyalkylene polyamine polyamide polyurea resin manufactured by Seiko PMC).

Examples of the lubricant used in the present invention include fatty acid metal salts such as zinc stearate and calcium stearate, waxes, and silicone resins.

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. may also be added. In addition, benzophenone-based or triazole-based ultraviolet absorbers, dispersants, antifoaming agents, antioxidants, fluorescent dyes, and the like can be used.

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, and 0.01 to 10 parts by weight of stabilizer. part, and about 0.01 to 10 parts by weight of other components. 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.

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 or alcohol can be used as the solvent for this coating liquid, and the solid content thereof is about 20 to 40% by weight.

The protective layer of the present invention has a pigment and a resin as main components, and contains a silane-modified acrylic resin. 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 made 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 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) Allyl This copolymer A is prepared by adding a styrene monomer to the above (a1), (a2) and (a3) in the presence of (b). and/or copolymer B may be obtained by adding a styrene monomer to (a1) and (a2) and polymerizing in the presence of (b).

Regarding <(a1) At least one type of (meth)acrylic acid ester> In this specification, "(meth)acrylic acid" refers to both acrylic acid and methacrylic acid, and at least one type of acrylic acid and methacrylic acid. It means to include.
"(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.

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.

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.

Regarding <(a2) Monomer having an alkoxysilyl group and an ethylenic double bond> A monomer having an alkoxysilyl group and an ethylenic double bond is a monomer having an alkoxysilyl group and an ethylenic double bond. It refers to a compound capable of imparting a silyl group, and is not particularly limited as long as the aqueous resin emulsion according to the present invention 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. can. Particularly preferred are trimethoxysilyl group and triethoxysilyl group.

As used herein, the term "ethylenic double bond" refers to a double bond between carbon atoms that can undergo a polymerization reaction (radical polymerization). Examples of functional groups having such an ethylenic double bond include vinyl group (CH ₂ =CH-), (meth)allyl group (CH ₂ =CH-CH ₂ - and CH ₂ =C(CH ₃ )- _CH2- ), (meth)acryloyloxy group ( _CH2 =CH-COO- and _CH2 =C( _CH3 )-COO-), (meth)acryloyloxyalkyl group ( _CH2 =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.

As the monomer having an alkoxysilyl group and an ethylenic double bond, a compound represented by the following formula (1) can be exemplified.
R ¹ Si (OR ² ) (OR ³ ) (OR ⁴ ) (1)
In the formula, R ¹ is a functional group having an ethylenic double bond, and R ² , R ³ and R ⁴ are alkyl groups having 1 to 5 carbon atoms. R ² , R ³ and R ⁴ may be the same or different.
Examples of the functional group having an ethylenic double bond for R ¹ 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.

Examples of the alkyl group having 1 to 5 carbon atoms in R ^{2 ,} R ³ and R ⁴ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t- Examples include straight chain or branched alkyl groups such as butyl group and n-pentyl group.
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.

Regarding <(a3) Monomer having a 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.

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

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-[(allyloxymethyl) ) 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 (trade name, polyoxyethylene chain length 10), "Aqualon KH-1025" (trade 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.

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.

<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-stage (actually two-stage) process. The polymerizable unsaturated monomers (a1, a2, a3 and b above) used during polymerization other than the final stage are referred to as polymerizable unsaturated monomer A, and the obtained polymer is referred to as 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.

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 the multi-stage emulsion polymerization includes the polymerizable unsaturated monomer A used in a stage other than the final stage and the polymerizable unsaturated monomer B used in the final stage. 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 preferred, particularly 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.

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 to 0.8% by weight, and the proportion of the a3 polymerizable unsaturated monomer is preferably 1.0 to 10% by weight, more preferably 2.0 to 6.0% by weight. The remainder is the a1 polymerizable unsaturated monomer, but the ratio of the a1 polymerizable unsaturated monomer to the total weight of the a1, a2, and a3 polymerizable unsaturated monomers is preferably is 89 to 99% by weight, more preferably 90 to 98% by weight.
In copolymer B, the ratio 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 is 0.1 to 0.4% by weight, and the remainder is the a1 polymerizable unsaturated monomer, but the above a1 polymerizable unsaturated monomer is based on the total weight of the a1 and a2 polymerizable unsaturated monomers. The proportion of monomers is preferably 85 to 100% by weight, more preferably 95 to 100% by weight.
In addition, in the synthesis of copolymers A and B (i.e., silane-modified acrylic resin), (b) allyl group and polyoxyethylene chain with respect to the total weight of the polymerizable unsaturated monomers a1, a2, and a3. 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.

An example of this multi-stage emulsion polymerization process will be described below.
First, in a reaction vessel, (a1) (meth)acrylic ester, (a2) a monomer having an alkoxysilyl group and an ethylenic double bond, and (a3) a monomer having a carboxyl group are uniformly mixed, 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. .
Monomer emulsion B is prepared 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 an alkoxysilyl group and an ethylenic double bond are uniformly mixed, and a polymerizable unsaturated monomer is formed. 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.

Next, water and (b) a sulfate having an allyl group and a polyoxyethylene group are charged into 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-stage 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.

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, 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, particularly preferably 30 to 50°C. Further, the minimum film forming temperature (MFT) of the silane-modified acrylic resin used in the present invention is preferably 25° C. or lower.
Note that the glass transition point (Tg) and minimum film forming temperature (MFT) of the silane-modified acrylic resin are measured by differential scanning calorimetry (DSC).

Moreover, it is preferable that the protective layer of the present invention further contains a pigment, and it is more preferable that the aspect ratio of the pigment is 30 or more. By adding such a pigment, it is possible to compensate for the plasticizer resistance and solvent resistance, which are disadvantages of acrylic resins having a high Tg. Adding a pigment also has the effect of improving stick resistance.
Examples of the pigment used in the present invention include inorganic or organic fillers such as kaolin, calcined kaolin, aluminum hydroxide, silica, calcium carbonate, diatomaceous earth, talc, and titanium oxide. Particularly preferred pigments used in the protective layer are kaolin and/or aluminum hydroxide. These pigments may be used alone or in combination of two or more.

The content of the silane-modified acrylic resin in the protective layer of the present invention is preferably 10 to 70% by weight, more preferably 30 to 60% by weight, based on the solid content of the protective layer.

As the binder used in the protective layer of the present invention, in addition to the above-mentioned silane-modified acrylic resin, binders that can be used in the above-mentioned heat-sensitive recording layer can be used as appropriate, but the above-mentioned carboxy-modified polyvinyl alcohol and non-core-shell type acrylic resin is preferred. These binders may be used alone or in combination of two or more.
As the crosslinking agent, any crosslinking agent that can be used in the heat-sensitive recording layer described above can be used as appropriate, but the epichlorohydrin resins and polyamine/polyamide resins (contained in the epichlorohydrin resins) can be used as appropriate. ) is preferred.
It is more preferable that the protective layer contains an epichlorohydrin resin and a polyamine/polyamide resin together with carboxy-modified polyvinyl alcohol, thereby further improving the coloring performance.

The glass transition point (Tg) of this non-core-shell type acrylic resin is preferably 95°C or lower, more preferably higher than 50°C. This Tg is measured by differential scanning calorimetry (DSC).
This non-core-shell type acrylic resin contains (meth)acrylic acid and a monomer component copolymerizable with (meth)acrylic acid, and (meth)acrylic acid is 1 part by weight in 100 parts by weight of the non-core-shell type acrylic resin. The amount is preferably 10 parts by weight. (Meth)acrylic acid is alkali-soluble and has the property of making a non-core-shell type acrylic resin 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 per 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 per 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.

When epichlorohydrin resin and polyamine/polyamide resin are used together with carboxy-modified polyvinyl alcohol in the protective layer, the content thereof is preferably 1 to 100 parts by weight per 100 parts by weight of carboxy-modified polyvinyl alcohol. , more preferably 5 to 50 parts by weight, and still more preferably 10 to 40 parts by weight.

The binder content (solid content) in the protective layer is preferably 20% by weight or more, more preferably about 20 to 80% by weight. When the protective layer contains a pigment, the content of the pigment and binder is 100 parts by weight of the pigment. On the other hand, the binder preferably has a solid content of about 30 to 300 parts by weight.
The coating solution for the protective layer may contain crosslinking agents, lubricants, stabilizers, ultraviolet absorbers, dispersants, antifoaming agents, antioxidants, fluorescent dyes, etc. that can be used in the heat-sensitive recording layer as described above. Various auxiliary agents may be blended as appropriate.

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.

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, 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. These binders may be used alone or in combination of two or more.

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 ultraviolet inhibitors may be added to the coating solution for the undercoat layer. good.

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. The coating amount of the protective layer is preferably 0.5 to 5.0 g/m ² in terms of solid content ^.
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.

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.

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) will be 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.

<Polymerizable unsaturated monomer>
Methyl methacrylate (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°C)
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 Fuji Film 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°C)

<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")

[Manufacture 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.

((A) Preparation of monomer emulsion)
As shown in Table 1, (a1-1) 5 parts by mass of MMA, (a1-3) 23 parts by mass of BA, (a1-4) 10 parts by mass of BMA, (a1-5) 10 parts by mass of CHMA, (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).
The above polymerizable unsaturated monomer solution was added to a uniformly mixed solution of 14 parts by mass of water and 0.1 parts by mass of (b) polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate ammonium salt. Then, the mixed solution was stirred with a stirrer to obtain a monomer emulsion (A).

((B) Preparation of monomer emulsion)
(A) As shown in Table 1, (a1-1) 16.6 parts by mass of MMA, (a1-3) 13 parts by mass of BA, (a1-4) 10 parts by mass of BMA, (a1-5) 10 parts by mass of CHMA, ( a2) 0.1 part by mass of 3-methacryloxypropyltrimethoxysilane was mixed uniformly to prepare a polymerizable unsaturated monomer solution.
The above polymerizable unsaturated monomer solution was added to a uniformly mixed solution of 14 parts by mass of water and 0.1 parts by mass of (b) polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate ammonium salt. Then, the mixed solution was stirred with a stirrer to obtain a monomer emulsion (B).

(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 system was purged with nitrogen. After purging with gas, the charge was heated to 80°C.
Thereafter, (A) monomer emulsion (containing 50.3 parts by mass of a polymerizable unsaturated monomer and corresponding to 10.1 parts by mass of the polymerizable unsaturated monomer) is added to the charging liquid. , 2 parts by mass of a 1% by mass sodium persulfate (hereinafter also referred to as "SPS") aqueous solution were added.
After another 10 minutes, while keeping the temperature inside the reactor at 80°C, ) and 4 parts by mass of a 1% aqueous solution of SPS, which is a polymerization catalyst, were each simultaneously added dropwise over 2 hours to obtain a pre-emulsion ((a) an aqueous resin emulsion based on a polymerizable unsaturated monomer).

(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-mentioned (B) monomer emulsion (containing 49.7 parts by mass of unsaturated polymerizable monomer) and a 1% aqueous solution of SPS were added. 4 parts by mass were each simultaneously added dropwise over 2 hours to the above-mentioned pre-emulsion to obtain an aqueous resin emulsion.
The resulting aqueous resin emulsion was adjusted to pH 8.0 with aqueous ammonia. The aqueous resin emulsion consists of (A) a polymerizable unsaturated monomer (copolymer A) with a glass transition temperature of -3.8°C, and (B) a polymerizable unsaturated monomer (copolymer B) with a glass transition temperature of -3.8°C. The temperature was 26.7°C and the solid content concentration was 45% by mass. The solid content is the percentage by weight of the remaining portion after drying in an oven at 105° C. for 3 hours, based on the weight before drying.
The obtained aqueous resin emulsion is called silane-modified acrylic resin 1.

[Production Examples 2 to 5]
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 resulting aqueous resin emulsions are referred to as silane-modified acrylic resins 2 to 5, respectively.

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, trade name: Ansilex 90) 100.0 parts Styrene-butadiene copolymer latex (manufactured by Nippon Zeon,
Product name: ST5526, solid content 48%) 10.0 parts Water 50.0 parts

Color developer dispersion (A1, A2 liquid), leuco dye dispersion (B liquid), and sensitizer dispersion (C liquid) having the following formulations were each separately ground in a sand grinder until the average particle size was 0.5 μm. Wet grinding was performed.

完全ケン化型ポリビニルアルコール水溶液（ＰＶＡ１１７） ５．０部
水 １．５部 Color developer dispersion (A1 liquid)
N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea
6.0 parts fully saponified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd., product name:
PVA117, solid content 10%) 5.0 parts Water 1.5 parts
Color developer dispersion (A2 liquid)
Phenolic compound represented by the following formula (Chemical formula 3) (manufactured by Nippon Soda Co., Ltd., trade name: D90)
6.0 copies

Completely saponified polyvinyl alcohol aqueous solution (PVA117) 5.0 parts Water 1.5 parts

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 Water 1.5 parts
Sensitizer dispersion liquid (C liquid)
1,2-bis-(3-methylphenoxy)ethane (manufactured by Sankosha,
Product name: KS232) 6.0 parts Completely saponified polyvinyl alcohol aqueous solution (PVA117) 5.0 parts Water 1.5 parts

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 (Liquid A1) 10.0 parts Leuco dye dispersion (Liquid B) 5.0 parts Sensitizer dispersion (Liquid C) 3.0 parts Completely saponified polyvinyl alcohol aqueous solution (PVA117) 25. 0 copies

Next, protective layer coating solutions 1 and 2 were prepared by mixing formulations having the following proportions.
<Coating liquid 1 for protective layer>
Aluminum hydroxide dispersion (manufactured by Martinsberg,
Product name: Martyfin OL, solid content 50%) 9.0 parts Silane-modified acrylic resin 1 (Tg 18°C, MFT 22°C, 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

<Coating liquid 2 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 (Nippon Gosei Kagaku Co., Ltd.) (solid content: 40%) 3.0 parts

[Example 1]
After applying the coating solution for the undercoat layer to one side of the support (high-quality paper with a basis weight of 47 g/m ² ) using a bent blade method so that the coating amount in terms of solid content was 10.0 g/m ² , It was dried to obtain an undercoat coated paper.
A heat-sensitive recording layer coating liquid was applied onto the undercoat layer of the undercoat layer-coated paper using a rod blade method in a coating amount of 6.0 g/ ^m2 in terms of solid content, and then dried. A paper coated with a heat-sensitive recording layer was obtained.
Next, on the heat-sensitive recording layer of this heat-sensitive recording layer-coated paper, protective layer coating liquid 1 was applied by a curtain method to a coating amount of 3.0 g/ ^m2 in terms of solid content, and then dried. A heat-sensitive recording material was prepared by processing with a super calender to obtain a smoothness of 100 to 500 seconds.

[Example 2]
N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea in the A1 solution used in the coating solution for the heat-sensitive recording layer was replaced with N,N'-di-[3-(o-toluene). A thermosensitive recording material was produced in the same manner as in Example 1 except that sulfonyloxy)phenyl]urea was used.
[Example 3]
N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea in liquid A1 used in the coating solution for the heat-sensitive recording layer was replaced with N,N'-di-[3-(benzenesulfonyloxy) ) A thermosensitive recording material was produced in the same manner as in Example 1 except that the material was changed to phenyl]urea.

[Example 4]
N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea in liquid A1 used in the coating solution for the heat-sensitive recording layer was replaced with N,N'-di-[3-(mesitylenesulfonyloxy) ) A thermosensitive recording material was produced in the same manner as in Example 1 except that the material was changed to phenyl]urea.
[Example 5]
N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea in liquid A1 used in the coating liquid for heat-sensitive recording layer was replaced with N,N'-di-[3-(2-naphthalene). A thermosensitive recording material was produced in the same manner as in Example 1 except that sulfonyloxy)phenyl]urea was used.

[Example 6]
N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea in liquid A1 used in the coating liquid for the heat-sensitive recording layer was replaced with N,N'-di-[3-(p-methoxy) A heat-sensitive recording material was produced in the same manner as in Example 1 except that benzenesulfonyloxy)phenyl]urea was used.
[Example 7]
N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea in liquid A1 used in the coating solution for the heat-sensitive recording layer was replaced with N,N'-di-[3-(benzylsulfonyloxy) ) A thermosensitive recording material was produced in the same manner as in Example 1 except that the material was changed to phenyl]urea.

[Example 8]
N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea in the A1 liquid used in the coating solution for the heat-sensitive recording layer was replaced with N,N'-di-[3-(ethanesulfonyloxy) ) A thermosensitive recording material was produced in the same manner as in Example 1 except that the material was changed to phenyl]urea.
[Example 9]
N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea in the A1 solution used in the coating solution for the heat-sensitive recording layer was replaced with N,N'-di-[4-(p-toluene). A thermosensitive recording material was produced in the same manner as in Example 1 except that sulfonyloxy)phenyl]urea was used.
[Example 10]
N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea in liquid A1 used in the coating solution for the heat-sensitive recording layer was replaced with N,N'-di-[4-(benzenesulfonyloxy) ) A thermosensitive recording material was produced in the same manner as in Example 1 except that the material was changed to phenyl]urea.

[Comparative example 1]
In Coating Solution 1 for Protective Layer, silane-modified acrylic resin 1 was changed to acrylic resin A (no silane modification, non-core-shell type, styrene acrylic, Tg 2°C, MFT 10°C, solid content 40%). A thermosensitive recording medium was produced in the same manner as in Example 1.
[Comparative example 2]
Examples except that in coating liquid 1 for protective layer, silane-modified acrylic resin 1 was changed to acrylic resin B (no silane modification, core-shell type, styrene acrylic, Tg 92°C, MFT 50°C, solid content 40%). A thermosensitive recording medium was produced in the same manner as in Example 1.
[Comparative example 3]
In coating liquid 1 for protective layer, 10.0 parts of silane-modified acrylic resin 1 was added to acrylic resin C (non-silane modified, non-core shell type, styrene acrylic, Tg 55°C, MFT 18°C, solid content 18%) 22. A thermosensitive recording material was produced in the same manner as in Example 1 except that the number of parts was changed to 2 parts.
[Comparative example 4]
A thermosensitive recording material was produced in the same manner as in Example 1, except that Coating Liquid 1 for protective layer was changed to Coating Liquid 2 for protective layer.
[Comparative example 5]
A heat-sensitive recording material was produced in the same manner as in Example 1, except that the A1 solution used as the coating solution for the heat-sensitive recording layer was changed to A2 solution.

The produced heat-sensitive recording material was evaluated as follows.
<Color development performance (print density)>
The produced thermal recording material was checkered 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. The pattern 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.

<Oil resistance>
The produced thermal recording medium was tested using TH-PMD (thermal recording paper printing tester, manufactured by Okura Electric Co., Ltd.).
A checkered pattern was printed at an applied energy of 0.41 mJ/dot and a printing speed of 50 mm/sec.
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 area was measured with a Macbeth densitometer (RD-914, using an amber filter) and evaluated according to the following criteria.
Excellent: The remaining rate of the printed part is 90% or more. Fair: The remaining rate of the printed part is 70% or more and less than 90%. Poor: The remaining rate of the printed part is less than 70%.

<Heat resistance>
The heat-sensitive recording surface of the produced heat-sensitive recording material was brought into contact with an iron plate at 100° C. for 5 seconds. Measure the density of the non-printed area (blank paper area) with a Macbeth densitometer (RD-914, using an amber filter), calculate the ground color value from the difference between the values before and after processing, and measure the density of the non-printed area (blank paper area) using the following criteria. part) was evaluated for discoloration.
Ground color color value = (density of non-printing area after processing) - (density of non-printing area before processing)
Excellent: Ground color development value is less than 0.1 Acceptable: Ground color development value is 0.1 or more and less than 0.2 Impossible: Ground color development value is 0.2 or more

<Plasticizer resistance>
The produced thermal recording medium was tested using TH-PMD (thermal recording paper printing tester, manufactured by Okura Electric Co., Ltd.).
A checkered pattern was printed at an applied energy of 0.41 mJ/dot and a printing speed of 50 mm/sec.
The printed heat-sensitive recording material was pasted on a paper tube wrapped once with PVC wrap (Hi-Lap KMA manufactured by Mitsui Chemicals), and further wrapped with PVC wrap three times on top of that, and left in an environment of 40°C for 24 hours. After standing still, the print density of the printed portion was measured using a Macbeth densitometer (RD-914, using an amber filter).

<Suitability for high-speed printing>
Regarding the produced thermal recording medium, a barcode (CODE 39) was printed in the vertical direction (the moving direction of the printer head and the barcode After printing the printed barcode on a barcode (orthogonal), a reading test was carried out on the printed barcode using a barcode verification machine (manufactured by Honeywell, QCPC600, light source 640 nm) to evaluate barcode reading suitability. The evaluation results were expressed using ANSI standard symbol grades.
*Symbol grade: The barcode is divided into 10 parts vertically to the bar, a reading test is carried out once for each part, and the average value is graded into 5 grades: (excellent) A, B, C, D, F (poor). Expressed in evaluation.

<Ink adhesion>
The heat-sensitive recording surface of the produced heat-sensitive recording material was printed using offset sheet-fed ink (UV161 ink manufactured by T&K) on a Roland offset sheet-fed printing machine (two colors), and then printed using a UV irradiation machine (I-Graphics Co., Ltd.). UV ink curing treatment was carried out using a UV ink (manufactured by Eye Grandage).
After that, a cellophane tape with a width of 18 mm was pasted on the printed surface, and a roller (diameter 10 cm, width 13 cm, weight 2000 g) was moved back and forth 5 times on the cellophane tape, and then a digital force gauge (Nidec-Shimpo, FGX- 2), the cellophane tape was pulled at a tensile force of 4.9 N and a tensile angle of 90°, and the adhesion of the ink was visually evaluated using the following criteria.
Excellent: Almost no ink comes off. Fair: Ink comes off slightly. Poor: Most of the ink comes off.

<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 for 24 hours under environmental conditions of 23° C. and 50% RH, visual evaluation was performed according to the following criteria.
Excellent: No coloration at all Fair: Slight coloration Poor: Strong coloration

<Water resistance: 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 using the following criteria.
Excellent: There is no peeling of the protective layer or heat-sensitive recording layer. Fair: The protective layer peels off slightly, but there is no peeling of the heat-sensitive recording layer. Poor: The protective layer or heat-sensitive recording layer peels off.

<Water resistance: Water resistant blocking>
For the produced heat-sensitive recording material, 10 ml of tap water was dropped onto the surface of the protective layer, the surface of the protective layer was folded in half so that the surface of the protective layer was on the inside, and a load of 20 gf/cm ² was applied and the material was allowed to stand for 24 hours. Peeling and peeling of the protective layer and heat-sensitive recording layer at the portion where water was dropped was visually evaluated based on the following criteria.
Excellent: No blocking occurs, and there is no peeling of the protective layer or heat-sensitive recording layer. Fair: Blocking occurs, and the protective layer peels off slightly, but there is no peeling of the heat-sensitive recording layer. Poor: Strong blocking occurs, The protective layer and heat-sensitive recording layer are peeled off, or the heat-sensitive recording material is destroyed when peeled off.

<Water resistance: 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: There is no peeling of the protective layer or heat-sensitive recording layer. Fair: The protective layer peels off slightly, but there is no peeling of the heat-sensitive recording layer. Poor: The protective layer or heat-sensitive recording layer peels off.

The results are shown in the table below.

Claims (8)

A heat-sensitive recording material in which a heat-sensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting color developer is provided on a support, and a protective layer is provided on the heat-sensitive recording layer,
The heat-sensitive recording layer contains a urea compound represented by the following general formula (Chemical formula 1) as an electron-accepting color developer,

(In the formula, R ¹ represents a substituted or unsubstituted alkyl group, aralkyl group, or aryl group, and R ² represents a hydrogen atom or an alkyl group.)
The protective layer contains a silane-modified acrylic resin, and the silane-modified acrylic resin is a copolymer A obtained by polymerizing the following (a1), (a2) and (a3) in the presence of (b). A thermosensitive recording material which is an aqueous emulsion of core-shell type particles comprising a core consisting of a core consisting of the following and a shell consisting of a 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) Allyl Polymerizable surfactant containing a sulfate group and a polyoxyethylene chain The thermosensitive recording material according to claim 1, wherein the urea compound has the following general formula (Chemical formula 2).

(In the formula, R ³ represents an alkyl group or an alkoxy group, and n represents an integer from 0 to 3.) 3. In the urea compound, R ³ represents an alkyl group having 1 to 4 carbon atoms, n represents an integer of 0 to 1, and the position of R ³ in the benzene ring is the 4-position. Heat sensitive recording material. The heat-sensitive recording material according to any one of claims 1 to 3, wherein the content (solid content) of the urea compound in the heat-sensitive recording layer is 1.0 to 50.0% by weight. The copolymer A is formed by adding a styrene monomer to the above (a1), (a2) and (a3) and polymerized in the presence of (b), and/or the copolymer B is formed by adding the styrene monomer to the above (a1), (a2) and (a3) and polymerizing the same in the presence of (b) The heat-sensitive recording material according to any one of claims 1 to 4, wherein a styrene monomer is added to (a2) and polymerized in the presence of (b). In the copolymer A, the ratio of the a2 component to the total weight of the a1, a2 and a3 components is 0.05 to 1.0% by weight, and the ratio of the a3 component is 1.0 to 10% by weight. , wherein the proportion of the a2 component in the copolymer B is 0.01 to 1.0% by weight with respect to the total weight of the a1 and a2 components. heat sensitive recording material According to any one of claims 1 to 6, the ratio of component (b) to the total weight of the a1, a2 and a3 components of the copolymers A and B is 0.5 to 5% by weight in total. The heat-sensitive recording medium described above. The heat-sensitive recording material according to any one of claims 1 to 7, wherein the protective layer contains kaolin and/or aluminum hydroxide as a pigment.