Thermosensitive recording medium

Abstract

To provide a thermal recording medium having good color developing sensitivity, printing running properties (especially head scum adhesion resistance) and scratch resistance and good printing fineness at the time of high speed printing, and its manufacturing method.SOLUTION: The thermosensitive recording body is obtained by providing a primer layer, a thermosensitive recording layer containing a colorless or light-colored electron-donating leuco dye, an electron-accepting developer and a sensitizing agent, and a protective layer in this order on a support, wherein the total content (solid content) of the leuco dye, the developer and the sensitizing agent in the thermosensitive recording layer is ≥ 70.0 wt.%, and the coating amount of the thermosensitive recording layer is ≤ 2.5g / m2.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a thermosensitive recording medium that utilizes a color-developing reaction between a colorless or pale-colored electron-donating leuco dye (hereinafter also referred to as "leuco dye") and an electron-accepting developer (hereinafter also referred to as "developer"). [Background technology]

[0002] Generally, a thermal recording medium is prepared by applying a coating liquid containing a colorless or pale-colored leuco dye and a color developer to a support such as paper, synthetic paper, film, or plastic, and the color develops through an instantaneous chemical reaction when heated with a thermal head, hot stamp, thermal pen, laser light, etc. Thermal recording media are widely used as recording media for facsimiles, computer terminal printers, automatic ticket vending machines, measurement recorders, receipts from supermarkets and convenience stores, etc.

[0003] In recent years, the use of thermal recording media has expanded to include a wide variety of applications, such as various tickets, receipts, labels, bank ATMs, gas and electricity meter reading, and cash vouchers for car and horse racing betting. As a result, various performance characteristics are required, such as water resistance, plasticizer resistance in the image area, heat resistance and oil resistance in the blank area, and storage stability of the image and blank areas under harsh conditions.

[0004] In such applications, stable printing on thermal recording media is required. However, frequent printing can cause recording paper to stick to the print head or head residue to accumulate on the print head, preventing proper printing. To solve these problems, a technique is known in which a phosphate ester compound is blended into the outermost layer, such as a protective layer (Patent Document 1, etc.). Also known is a thermosensitive recording medium in which the color development sensitivity is improved by simultaneously coating and drying a thermosensitive recording layer and a protective layer by a multi-layer curtain coating method (Patent Document 2, etc.). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-56184 [Patent Document 2] Patent No. 5626218 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0006] However, even with such conventional techniques, it has been difficult to achieve both color development sensitivity and print runnability (resistance to head residue adhesion and sticking). Therefore, an object of the present invention is to provide a thermosensitive recording medium that has good color development sensitivity, print running properties (particularly resistance to head residue adhesion), and abrasion resistance, and also has good print resolution during high-speed printing. [Means for solving the problem]

[0007] After extensive research, the inventors discovered that color development sensitivity improves when the total content (solid content) of leuco dye, developer, and sensitizer in the thermosensitive recording layer is 70.0% by weight or more. However, a protective layer was provided to prevent head residue and sticking from occurring when the content of leuco dye, etc. in the thermosensitive recording layer is high. Furthermore, providing a protective layer improves scratch resistance. Furthermore, when the coating weight of the thermosensitive recording layer is 2.5 g / m 2 It was found that by reducing the density to the following level, print resolution during high-speed printing can be improved.

[0008] That is, the present invention provides a thermosensitive recording medium comprising a support, an undercoat layer, a thermosensitive recording layer containing a colorless or light-colored electron-donating leuco dye, an electron-accepting developer and a sensitizer, and a protective layer, in this order, wherein the total content (solid content) of the leuco dye, the developer and the sensitizer in the thermosensitive recording layer is 76.0% by weight or more, and the coating amount of the thermosensitive recording layer is 2.5 g / m 2 the coating amount of the protective layer is 2.5 g / m or less 2 Below 0.4g / m 2 The above is true, and the thermosensitive recording layer does not contain a lubricant, while the protective layer contains a lubricant. [Effects of the Invention]

[0009] According to the present invention, a thermosensitive recording medium can be obtained which has good color development sensitivity, print running properties (particularly resistance to head residue adhesion) and abrasion resistance, and further has good print definition during high-speed printing. DETAILED DESCRIPTION OF THE INVENTION

[0010] The thermosensitive recording medium of the present invention is a thermosensitive recording medium comprising a support, an undercoat layer, a thermosensitive recording layer containing a colorless or light-colored electron-donating leuco dye, an electron-accepting developer and a sensitizer, and a protective layer, in this order, wherein the total content (solid content) of the leuco dye, developer and sensitizer in the thermosensitive recording layer is 70.0% by weight or more, and the coating amount of the thermosensitive recording layer is 2.5 g / m 2 The following is the result.

[0011] Examples of various materials that can be used in the thermal recording layer of the thermal recording medium of the present invention are given below, but binders, crosslinking agents, pigments, etc. can also be used in each coating layer provided as needed, as long as they do not impair the desired effects on the above-mentioned problems.

[0012] <Undercoat layer> The thermosensitive recording medium of the present invention has an undercoat layer on the support. The primer layer consists primarily of a binder and a pigment. The binder used in the undercoat layer may be any commonly used emulsion of a water-soluble or hydrophobic polymer. Specific examples include cellulose derivatives such as polyvinyl alcohol, polyvinyl acetal, hydroxyethyl cellulose, methyl cellulose, and carboxymethyl cellulose; starch and its derivatives; sodium polyacrylate; polyvinylpyrrolidone; acrylic acid amide / acrylic acid ester copolymers; acrylic acid amide / acrylic acid ester / methacrylic acid copolymers; styrene / maleic anhydride copolymer alkali salts; isobutylene / maleic anhydride copolymer alkali salts; polyacrylamide; sodium alginate; gelatin; and casein; and emulsions of hydrophobic polymers such as polyvinyl acetate, polyurethane, styrene / butadiene copolymers, polyacrylic acid, polyacrylic acid esters, vinyl chloride / vinyl acetate copolymers, polybutyl methacrylate, ethylene / vinyl acetate copolymers, and styrene / butadiene / acrylic copolymers. These binders may be used alone or in combination.

[0013] The pigment used in the undercoat layer may be any known pigment that has been commonly used in the past, such as calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, magnesium hydroxide, calcined kaolin, clay, talc, or other inorganic pigments. These pigments may be used alone or in combination. 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. The coating liquid for the undercoat layer may contain various auxiliary agents such as dispersants, plasticizers, pH adjusters, antifoaming agents, water-retaining agents, preservatives, coloring dyes, and ultraviolet protection agents, as needed.

[0014] <Thermal recording layer> The heat-sensitive recording layer contains a colorless or pale-colored electron-donating leuco dye, an electron-accepting developer and a sensitizer. The leuco dye used in the present invention can be any known leuco dye in the field of conventional pressure-sensitive or heat-sensitive recording paper, and is not particularly limited. However, preferred examples include triphenylmethane compounds, fluoran compounds, fluorene compounds, and divinyl compounds. Specific examples of typical colorless or pale-colored dyes (dye precursors) are shown below. These dye precursors may be used alone or in combination.

[0015] <Triphenylmethane 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)

[0016] <Fluoran-based leuco dyes> 3-Diethylamino-6-methylfluoran, 3-Diethylamino-6-methyl-7-anilinofluoran, 3-Diethylamino-6-methyl-7-(o,p-dimethylanilino)fluoran, 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-fu (fluoroanilino)fluoran, 3-diethylamino-6-methyl-7-(m-methylanilino)fluoran, 3-diethylamino-6-methyl-7-n-octylanilinofluoran, 3-diethylamino-6-methyl-7-n-octylaminofluoran, 3-diethylamino-6-methyl-7-benzylaminofluoran, 3-diethylamino-6-methyl-7-dibenzylaminofluoran, 3-diethylamino-6-chloro-7-methylfluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-diethylamino-6-chloro o-7-p-methylanilinofluoran, 3-diethylamino-6-ethoxyethyl-7-anilinofluoran, 3-diethylamino-7-methylfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7-(m-trifluoromethylanilino)fluoran, 3-diethylamino-7-(o-chloroanilino)fluoran, 3-diethylamino-7-(p-chloroanilino)fluoran, 3-diethylamino-7-(o-fluoroanilino)fluoran, 3-diethylamino-benzo[a]fluoran, 3-diethylamino -benzo[c]fluoran, 3-dibutylamino-6-methyl-fluoran, 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-trifluoromethylanilino)fluoran,3-dibutylamino-6-methyl-7-chlorofluoran, 3-dibutylamino-6-ethoxyethyl-7-anilinofluoran, 3-dibutylamino-6-chloro-7-anilinofluoran, 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)fluoran, 3-Di-n-pentylamino-6-chloro-7-anilinofluoran, 3-Di-n-pentylamino-7-(p-chloroanilino)fluoran, 3-Pyrrolidino-6-methyl-7-anilinofluoran, 3-Piperidino-6-methyl-7-anilinofluoran, 3-(N-methyl-N-propylamino)-6-methyl-7-anilinofluoran, 3-(N-methyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran (N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-xylamino)-6-methyl-7-(p-chloroanilino)fluoran, 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isobutylamino) -6-methyl-7-anilinofluoran, 3-(N-ethyl-N-ethoxypropylamino)-6-methyl-7-anilinofluoran, 3-cyclohexylamino-6-chlorofluoran, 2-(4-oxahexyl)-3-dimethylamino-6-methyl-7-anilinofluoran, 2-(4-oxahexyl)-3-diethylamino-6-methyl-7-anilinofluoran, 2-(4-oxahexyl)-3-dipropylamino-6-methyl-7-anilinofluoran, 2-methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluoran,2-Methoxy-6-p-(p-dimethylaminophenyl)aminoanilinofluoran, 2-chloro-3-methyl-6-p-(p-phenylaminophenyl)aminoanilinofluoran, 2-chloro-6-p-(p-dimethylaminophenyl)aminoanilinofluoran, 2-nitro-6-p-(p-diethylaminophenyl)aminoanilinofluoran, 2-amino-6-p-(p-diethylaminophenyl)aminoanilinofluoran, 2-diethylamino-6-p-(p-diethylaminophenyl)aminoanilinofluoran, 2-phenyl-6-methyl-6-p-(p-phenylaminophenyl)aminoanilinofluoran 2-benzyl-6-p-(p-phenylaminophenyl)aminoanilinofluoran, 2-hydroxy-6-p-(p-phenylaminophenyl)aminoanilinofluoran, 3-methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluoran, 3-diethylamino-6-p-(p-diethylaminophenyl)aminoanilinofluoran, 3-diethylamino-6-p-(p-dibutylaminophenyl)aminoanilinofluoran, 2,4-dimethyl-6-[(4-dimethylamino)anilino]-fluoran,

[0017] <Fluorene-based leuco dye> 3,6,6'-Tris(dimethylamino)spiro[fluorene-9,3'-phthalide], 3,6,6'-tris(diethylamino)spiro[fluorene-9,3'-phthalide]

[0018] <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

[0019] <Other> 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-(3'-nitro)anilinolactam (amino)fluoran-γ-(4'-nitro)anilinolactam, 1,1-bis-[2',2',2'',2''-tetrakis-(p-dimethylaminophenyl)-ethenyl]-2,2-dinitrileethane, 1,1-bis-[2',2',2'',2''-tetrakis-(p-dimethylaminophenyl)-ethenyl]-2-β-naphthoylethane, 1,1-bis-[2',2',2'',2''-tetrakis-(p-dimethylaminophenyl)-ethenyl]-2,2-diacetylethane, bis-[2,2,2',2'-tetrakis-(p-dimethylaminophenyl)-ethenyl]-methylmalonic acid dimethyl ester

[0020] Examples of color developers that can be used in the present invention include inorganic acidic substances such as activated clay, attapulgite, colloidal silica, and 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, and 2,4'-dihydroxydiphenyl sulfone. Phenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-n-propoxydiphenyl sulfone, bis(3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxyphenyl-4'-benzyloxyphenyl sulfone, 3,4-dihydroxyphenyl-4'-methylphenyl sulfone, 1-[4-(4-hydroxyphenylsulfonyl)phenoxy]-4-[4-(4-isopropoxyphenylsulfone] phenyl)phenoxy]butane, phenol condensation compositions described in JP-A-2003-154760, aminobenzenesulfonamide derivatives described in JP-A-8-59603, bis(4-hydroxyphenylthioethoxy)methane, 1,5-di(4-hydroxyphenylthio)-3-oxapentane, butyl bis(p-hydroxyphenyl)acetate, methyl bis(p-hydroxyphenyl)acetate, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 1,4-bis[α-methyl-α-(4'-hydroxyphenyl) [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), 4,4'-bis(3-(phenoxycarbonylamino)methylphenylureido)diphenyl sulfone, compounds described in WO02 / 081229 or JP2002-301873A, and N,Examples of suitable aromatic carboxylic acids include thiourea compounds such as N'-di-m-chlorophenylthiourea, p-chlorobenzoic acid, stearyl gallate, zinc bis[4-(n-octyloxycarbonylamino)salicylate] dihydrate, 4-[2-(p-methoxyphenoxy)ethyloxy]salicylic acid, 4-[3-(p-tolylsulfonyl)propyloxy]salicylic acid, and 5-[p-(2-p-methoxyphenoxyethoxy)cumyl]salicylic acid, as well as salts of these aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel, as well as antipyrine complexes of zinc thiocyanate and complex zinc salts of terephthalaldehyde acid and other aromatic carboxylic acids.

[0021] These color developers can be used alone or in combination. 1-[4-(4-hydroxyphenylsulfonyl)phenoxy]-4-[4-(4-isopropoxyphenylsulfonyl)phenoxy]butane is available, for example, from API Corporation under the trade name JKY-214, and the phenol condensation composition described in JP 2003-154760 A is available, for example, from API Corporation under the trade name JKY-224. The compounds described in WO02 / 081229 and the like are available under the trade names NKK-395 and D-100 manufactured by Nippon Soda Co., Ltd. In addition, metal chelate color-developing components such as higher fatty acid metal double salts and polyvalent hydroxy aromatic compounds described in JP-A-10-258577 can also be contained.

[0022] The developer may contain a urea compound represented by the following general formula (Chemical Formula 1): This urea compound does not contain bisphenol A or bisphenol S. [ka] (wherein X represents —O— or —NH—; R 1 is a hydrogen atom or -SO2-R 3 represents R 3represents a substituted or unsubstituted alkyl group, aralkyl group, or aryl group, and R 2 represents a hydrogen atom or an alkyl group, and m represents 0 or 1.

[0023] As the color developer, the above-mentioned color developer and this urea compound may be used in combination, or the urea compound may be used alone as the color developer.

[0024] The urea compound is preferably the following (1) or (2): (1) A first urea compound represented by the following general formula (Chemical Formula 2): [ka] (In the formula, R 1 , R 2 and R 3 is defined as above.) (2) A second urea compound represented by the following formula (Chemical Formula 3): [ka] (In the formula, R 2 is defined as above, and R 4 ~R 8 The definition of will be explained later.)

[0025] The first urea compound used in the present invention is preferably represented by the following formula (Chemical Formula 4). [ka]

[0026] In the general formula (Chemical Formula 2) and the general formula (Chemical Formula 4), R 3 represents an alkyl group, an aralkyl group, or an aryl group, which may be substituted or unsubstituted, and is preferably a substituted or unsubstituted aryl group. 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. 3 may be the same or different. R in the benzene ring of general formula (Chemical formula 2) 1 The positions of -O- may be the same or different, and are preferably the 3-, 4- or 5-positions. R in the benzene ring of general formula (chemical formula 2) and general formula (chemical formula 4) 3 The positions of -SO2-O- may be the same or different, and are preferably the 3-, 4- or 5-positions.

[0027] The alkyl group is, for example, a linear, branched, or alicyclic alkyl group, and preferably has 1 to 12 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a t-butyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a 2-ethylhexyl group, and a lauryl group.

[0028] The number of carbon atoms in this aralkyl group is preferably 7 to 12. Examples of this aralkyl group include unsubstituted or aralkyl groups substituted with an alkyl group, an alkoxy group, an aralkyl group, an aryl group, or a halogen atom, such as a benzyl group, 1-phenylethyl group, 2-phenylethyl group, 3-phenylpropyl group, p-methylbenzyl group, m-methylbenzyl group, m-ethylbenzyl group, p-ethylbenzyl group, pi-propylbenzyl group, pt-butylbenzyl group, p-methoxybenzyl group, m-methoxybenzyl group, o-methoxybenzyl group, m,p-di-methoxybenzyl group, p-ethoxy-m-methoxybenzyl group, p-phenylmethylbenzyl group, p-cumylbenzyl group, p-phenylbenzyl group, o-phenylbenzyl group, m-phenylbenzyl group, p-tolylbenzyl group, m-tolylbenzyl group, o-tolylbenzyl group, and p-chlorobenzyl group.

[0029] The number of carbon atoms in this aryl group is preferably 6 to 12. Examples of this aryl group include unsubstituted aryl groups or aryl groups substituted with an alkyl group, an alkoxy group, an aralkyl group, an aryl group, or a halogen atom, such as a phenyl group, a p-tolyl group, a m-tolyl group, an o-tolyl group, a 2,5-dimethylphenyl group, a 2,4-dimethylphenyl group, a 3,5-dimethylphenyl group, a 2,3-dimethylphenyl group, a 3,4-dimethylphenyl group, a mesitylene group, a p-ethylphenyl group, a p-propylphenyl group, a p-butylphenyl group, a p-methoxyphenyl group, a 3,4-dimethoxyphenyl group, a p-ethoxyphenyl group, a p-chlorophenyl group, a 1-naphthyl group, a 2-naphthyl group, or a t-butylated naphthyl group.

[0030] In the above general formulas (Chemical Formulas 1, 2, and 4), R 3 is preferably a group represented by the following formula: [ka] In the above formula, R 4 ~R 8 may be the same or different and represent a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, or an arylamino group.

[0031] 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, an isobutyl group, a sec-butyl group, or a t-butyl group. R in the benzene ring of general formula (Chemical formula 2) 2 may be the same or different, and is preferably the 3rd, 4th or 5th position.

[0032] As the first urea compound of the present invention, a urea compound represented by the following general formula (Chemical Formula 6) is more preferred. [ka] In the general formula (chemical formula 6), R 9 represents 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, preferably 1 to 8, more preferably 1 to 4 carbon atoms. R in the benzene ring of general formula (Chemical Formula 6) 9 may be the same or different, and is preferably the 3rd, 4th or 5th position, more preferably the 4th position.

[0033] Furthermore, examples of the first urea compound of the present invention include 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-(pt-butylbenzenesulfonyloxy)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,Examples of such urea include, but are not limited to, N'-di-[3-(p-cumylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(o-phenylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-phenylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-chlorobenzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(ethanesulfonyloxy)phenyl]urea, and N,N'-di-[3-(benzylsulfonyloxy)phenyl]urea.

[0034] The second urea compound used in the present invention 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. [ka]

[0035] The sensitizer used in the present invention may be a conventionally known sensitizer. Examples of 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- Examples include 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)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.

[0036] The total content (solid content) of the leuco dye, developer, and sensitizer in the thermosensitive recording layer of the present invention is 70.0% by weight or more. When the total content (solid content) is 70.0% by weight or more, color development sensitivity is improved. The total content (solid content) of the leuco dye, developer, and sensitizer in the thermosensitive recording layer is preferably 72.0% by weight or more, more preferably 79.0% by weight. The upper limit of the total content (solid content) is 90% by weight or less.

[0037] The coating amount of the heat-sensitive recording layer of the present invention is 2.5 g / m 2 Preferably, it is 2.4 g / m or less. 2 or less, more preferably 2.1 g / m 2As described above, by setting the total content (solid content) of the leuco dye, developer, and sensitizer in the thermosensitive recording layer to 70.0% by weight or more, the coating amount of the thermosensitive recording layer can be set to 2.5 g / m or less. 2 Even if the sensitivity is reduced to below this level, it is possible to maintain a sensitivity that is acceptable for practical use. The lower limit of the coating amount of the thermal recording layer is, for example, 1.2 g / m 2 The coating weight of the thermal recording layer is 1.4 to 2.4 g / m 2 It is more preferable that:

[0038] It is preferable that the thermosensitive recording layer of the present invention does not contain an inorganic pigment. If the thermosensitive recording layer contains an inorganic pigment, the total content (solid content) of the leuco dye, developer, and sensitizer described above will be reduced accordingly, and color development sensitivity may be reduced. Examples of inorganic pigments include kaolin, calcined kaolin, calcium carbonate, aluminum oxide, titanium oxide, magnesium carbonate, aluminum silicate, magnesium silicate, calcium silicate, aluminum hydroxide, and silica.

[0039] It is preferable that the thermosensitive recording layer of the present invention does not contain a lubricant. If the thermosensitive recording layer contains a lubricant, the total content (solid content) of the leuco dye, developer, and sensitizer described above will be reduced accordingly, and color development sensitivity may be reduced. Examples of the lubricant include fatty acid metal salts such as zinc stearate and calcium stearate, waxes, and silicone resins.

[0040] Binders that can be used in the heat-sensitive recording layer include polyvinyl alcohols such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, olefin-modified polyvinyl alcohol, nitrile-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, and other modified polyvinyl alcohols; silane-modified acrylic resins; and high-Tg acrylic resins (preferably non-core-shell type acrylic resins, the glass transition point (Tg) of which is higher than 50°C and not higher than 95°C). This Tg can be determined by differential scanning calorimetry (DS). C). Examples of such polymers include (meth)acrylic acid and other acrylic resins composed of monomer components copolymerizable with (meth)acrylic acid (excluding olefins), cellulose derivatives such as hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, ethyl cellulose, and acetyl cellulose, starches such as oxidized starch, etherified starch, and esterified starch, styrene-maleic anhydride copolymers, styrene-butadiene copolymers, casein, gum arabic, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylic acid esters, polyvinyl butyral, polystyrose, and their copolymers, polyamide resins, silicone resins, petroleum resins, terpene resins, ketone resins, and coumarone resins. These polymeric substances can be used by dissolving them in solvents such as water, alcohols, ketones, esters, and hydrocarbons, or by dispersing them in water or other media in an emulsified or paste-like form, and these can also be used in combination depending on the required quality.

[0041] In the present invention, stabilizers such as 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, and 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane can be added to improve the oil resistance of image areas within a range that does not impair the desired effects for solving the above problems. In addition, benzophenone-based or triazole-based ultraviolet absorbers, dispersants, antifoaming agents, antioxidants, fluorescent dyes, etc. can be used in the thermal recording layer.

[0042] The types and amounts of leuco dye, developer, sensitizer, and other components used in the thermosensitive recording layer of the present invention are determined according to the required performance and recording suitability and are not particularly limited, but typically, 0.5 to 10 parts by weight of developer, 0.1 to 10 parts by weight of sensitizer, 0.01 to 10 parts by weight of stabilizer, and 0.01 to 10 parts by weight of other components are used per part by weight of leuco dye. The binder content is suitably about 5 to 25% by weight of the solid content of the thermosensitive recording layer. In the present invention, the total content (solid content) of the leuco dye, developer, and sensitizer is 70.0% by weight or more, so it is desirable to reduce the binder content. However, if the binder content is less than 5% by weight, the coating properties, particularly the curtain film suitability, will be reduced, so the lower limit is preferably 5% by weight or more.

[0043] In the present invention, the leuco dye, developer, and other optional additives are pulverized to particle sizes of several microns or less using a grinder such as a ball mill, attritor, or sand grinder, or an appropriate emulsifier, and then a binder and various additives depending on the purpose are added to prepare a coating liquid. The solvent used in this coating liquid can be water or alcohol, and the solid content is about 20 to 40% by weight.

[0044] <Protective layer> The thermosensitive recording medium of the present invention has a protective layer on the surface of the thermosensitive recording layer. The thermosensitive recording layer of the present invention has a total content (solids content) of leuco dye, developer, and sensitizer of 70.0% by weight or more. As a result, the absolute amount of color former that melts during printing increases, increasing the area of ​​direct contact between the head and the color former and relatively reducing the material that absorbs the melted color former, which tends to deteriorate print runnability and stick resistance. Therefore, in the present invention, it is essential to provide a protective layer in order to obtain a thermosensitive recording medium with good print runnability (especially resistance to head residue adhesion) and stick resistance. This protective layer mainly comprises a binder and a pigment, and may further contain a lubricant. As the binder, any of the binders that can be used in the above-mentioned thermosensitive recording layer can be used appropriately.

[0045] Examples of pigments include inorganic pigments such as kaolin, calcined kaolin, calcium carbonate, aluminum oxide, titanium oxide, magnesium carbonate, aluminum silicate, magnesium silicate, calcium silicate, aluminum hydroxide, and silica. In particular, when the protective layer contains an inorganic pigment with an aspect ratio of 30 or more, the surface smoothness of the protective layer is improved, and the print running properties (particularly, resistance to head residue adhesion) are improved. An example of an inorganic pigment with an aspect ratio of 30 or more is kaolin. The aspect ratio is expressed as the maximum diameter of the pigment divided by its thickness (minimum length).

[0046] Examples of the lubricant include fatty acid metal salts such as zinc stearate and calcium stearate, waxes, and silicone resins. When the protective layer contains a lubricant, the surface smoothness of the protective layer is improved, and the print running properties (particularly, resistance to head residue adhesion) are improved. As mentioned above, in the present invention, in order to increase the total content (solid content) of leuco dye, developer and sensitizer in the thermosensitive recording layer to 70% by weight or more, it is preferable not to include a lubricant in the thermosensitive recording layer, but to include a lubricant in the protective layer in order to ensure smoothness as a thermosensitive recording medium.

[0047] 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 solid content, and the amount of binder is preferably about 30.0 to 300.0 parts by weight per 100 parts by weight of pigment. The coating solution for the protective layer may contain various auxiliary agents such as stabilizers, ultraviolet absorbers, dispersants, antifoaming agents, antioxidants, fluorescent dyes, etc., which can be used in the above-mentioned thermosensitive recording layer, as needed.

[0048] The coating weight of the protective layer is 2.5 g / m 2 It is preferably 2.3 g / m or less, and more preferably 2.3 g / m 2 Below 2.0 g / m, most preferably 2 It can be as follows: The lower limit of the coating amount of the protective layer is, for example, 0.4 g / m 2 The coating weight of the protective layer is 0.7 to 2.5 g / m 2 It is more preferable that:

[0049] <Support> Examples of the support include paper, synthetic paper, film, and plastic sheet.

[0050] In the present invention, the means for applying the thermosensitive recording layer and the coating layers other than the thermosensitive recording layer, i.e., the protective layer, undercoat layer, etc., is not particularly limited, and they can be applied according to well-known conventional techniques. For example, an off-machine coater or an on-machine coater 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, or a curtain coater can be appropriately selected and used. Furthermore, various known techniques in the field of thermosensitive recording media can be added as necessary and appropriate, such as smoothing treatment such as supercalendering after coating each coating layer.

[0051] In particular, when the above-mentioned thermosensitive recording layer and protective layer are formed by applying the coating liquid for the thermosensitive recording layer and the coating liquid for the protective layer by a multi-layer curtain coating method and drying, the coating amount is 2.5 g / m 2Even at low coating weights below this, the coverage of the thermosensitive recording layer and protective layer is good, so the surface smoothness of the thermosensitive recording layer and protective layer is high, and print running properties (especially resistance to head residue adhesion) are further improved. The coating method is preferably a simultaneous multilayer curtain coating method. [Example]

[0052] The present invention will be illustrated by the following examples, but is not intended to limit the scope of the present invention. In each example and comparative example, "parts" means "parts by weight" and "%" means "% by weight" unless otherwise specified.

[0053] [Example 1] The following ingredients were stirred and dispersed to prepare a coating liquid for the undercoat layer. Undercoat layer coating liquid 1 Calcined kaolin (Engelhard Co., Ltd. product name: Ansilex 90, <Oil absorption amount 90cc / 100g>) 100 parts Styrene-butadiene copolymer latex (48% solids) 35.4 parts 45 parts of 10% aqueous polyvinyl alcohol solution Water 157.1 parts Next, the undercoat layer coating solution was applied to the support (54 g / m 2 After blade coating on one side of the base paper, the paper is dried to a dry coating weight of 4.0 g / m 2 Thus, a coated paper with a primer layer was obtained.

[0054] The developer dispersions (Liquids A1 to A5), leuco dye dispersion (Liquid B), and sensitizer dispersions (Liquids C1 to C3) having the following formulations were each wet-ground in a sand grinder until the average particle size reached 0.5 microns. A1 liquid (developer dispersion liquid) 4,4'-dihydroxydiphenyl sulfone 5.7 parts Polyvinyl alcohol 10% aqueous solution 5.1 parts Water 9.9 parts A2 liquid (developer dispersion liquid) 4-Hydroxy-4'-benzyloxydiphenyl sulfone (Nicca Chemical Co., Ltd.) Product name: BPS-MA3) 6.0 copies Polyvinyl alcohol 10% aqueous solution 11.3 parts 6.5 parts water A3 liquid (developer dispersion liquid) 4,4'-bis(3-(phenoxycarbonylamino)methylphenylureido)diphenyl sulfone (Fine Ace UU) 3.5 parts 7.4 parts of 10% aqueous polyvinyl alcohol solution 3.3 parts water A4 liquid (developer dispersion liquid) N-[2-(3-phenylureido)phenyl]benzenesulfonamide (Product name NKK1304) 6.0 copies 7.5 parts of 10% aqueous polyvinyl alcohol solution Water 9.0 parts A5 liquid (developer dispersion liquid) N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea (Product name S-176) 3.5 parts 4.4 parts of 10% aqueous solution of polyvinyl alcohol Water 5.3 parts Solution B (leuco dye dispersion) 3-Dibutylamino-6-methyl-7-anilinofluoran (ODB-2) 2.85 copies 4.8 parts of 10% aqueous solution of polyvinyl alcohol 3.5 parts water C1 liquid (sensitizer dispersion liquid) Diphenyl sulfone (manufactured by Sankosha, trade name: DPS) 5.7 parts 7.1 parts of 10% aqueous polyvinyl alcohol solution Water 8.6 parts C2 liquid (sensitizer dispersion liquid) 5.7 parts stearic acid amide (manufactured by Fine Ace Co., Ltd., trade name: Finawax) Polyvinyl alcohol 10% aqueous solution 14.3 parts 3.8 parts water C3 liquid (sensitizer dispersion liquid) 1,2-bis-(3-methylphenoxy)ethane (manufactured by Sankosha, trade name: KS232) 0.5 part 0.6 parts of 10% aqueous solution of polyvinyl alcohol Water 0.8 parts

[0055] Next, the dispersions were mixed in the following proportions to prepare a coating liquid for the heat-sensitive recording layer. Coating liquid for thermal recording layer A1 liquid (developer dispersion liquid) 20.7 parts Solution B (leuco dye dispersion) 11.1 parts C1 solution (sensitizer dispersion) 21.4 parts C2 liquid (sensitizer dispersion) 23.8 parts 32 parts of 10% aqueous polyvinyl alcohol solution

[0056] Then, the following mixture was mixed in the following ratio to prepare a coating liquid for the protective layer. Coating liquid for protective layer Flat kaolin (50% dispersion, IMERYS product name: Contour1500, aspect ratio: 30) 7.0 copies 30 parts of 10% aqueous polyvinyl alcohol solution Polyamide epichlorohydrin resin (Seiko PMC Corporation, product name: WS4030, Solid content 25%) 4.0 parts Modified polyamine resin (manufactured by Taoka Chemical Co., Ltd., product name: Sumirez Resin SPI-102A, Solids content 45%) 2.2 parts Zinc stearate (trade name: Hydrin Z-7-30, solids content 30%) Particle size 5.5 microns, Chukyo Yushi) 1.7 parts Next, a coating film of the coating liquid for the thermosensitive recording layer and the coating liquid for the protective layer was formed on the undercoat layer of the undercoat-coated paper using a slide curtain coating device, from the bottom side, and the coating film was simultaneously multi-layered and curtain coated at a coating speed of 600 m / min. After drying, the film was subjected to a supercalendering process to obtain a dry coating weight of 1.8 g / m. 2 Thermal recording layer, dry coating weight 0.7g / m 2 A heat-sensitive recording material having a protective layer of the formula (I) was obtained.

[0057] [Color development sensitivity] Printing was performed on the prepared thermal recording medium with an applied energy of 0.35 mJ / dot or 0.42 mJ / dot using a TH-PMD manufactured by Okura Electric Co., Ltd. The image density after printing was measured with a Macbeth densitometer (using an amber filter). <Solvent resistance> Ethanol (50.0%) was applied to the blank area of ​​the thermal recording medium with a cotton swab and then stored at 23°C x After leaving the sample to stand for 24 hours under 50% RH environmental conditions, the sample was visually evaluated according to the following criteria. ○: No color development at all △: Slight color development, but no practical problem ×: Strong color development

[0058] <Printing runnability (head residue resistance)> A 10 cm long grid pattern was printed on the prepared thermal recording medium using a Sato label printer (Resply R-8), and the residue (head residue) adhering to the thermal head after printing was visually evaluated according to the following criteria. ◯: Almost no adhesion of head residue was observed. Δ: A small amount of head residue was observed, but the formed image was not void or blurred, and was of a level that was not problematic for practical use. x: A large amount of head residue was observed, and voids and blurring were observed in the formed image.

[0059] <Stick resistance> The prepared thermosensitive recording medium was subjected to 100 mm solid printing in a 0° C. environment using a thermosensitive handy terminal printer (HT180 manufactured by Canon), and the printed matter was visually evaluated. ○: No white streaks in the printed area △: Several white streaks appear in the printed area ×: Numerous white streaks appear in the printed area [Printing loss rate] The prepared thermal recording medium was used to print the Arabic numerals '2' and '3' in solid form using a Zebra label thermal printer (product name 140XiIIIPlus) at a printing speed of 8 inch / s and 2 inch / s, and the printing loss rate was calculated using the following formula. Print defect rate = 100 - (colored area at a printing speed of 8 inches / s / colored area at a printing speed of 2 inches / s) (%) The color-developed area was measured by capturing the printed image as digital data, determining the pixels corresponding to grayscale levels 0 to 97 as the color-developed area, and integrating the total number of color-developed pixels to determine the color-developed area. The smaller the print defect rate, the finer the printing during high-speed printing, and a print defect rate of 35% or less is considered good.

[0060] [Example 2] Dry coating weight of the thermal recording layer: 2.1 g / m 2 A thermosensitive recording medium was prepared in the same manner as in Example 1, except that the above was replaced with the above. [Example 3] A thermosensitive recording medium was prepared in the same manner as in Example 1, except that the total content (solid content) of the leuco dye, developer and sensitizer in the thermosensitive recording layer was changed to 70.0% by weight. [Example 4] A thermosensitive recording medium was prepared in the same manner as in Example 1, except that the total content (solid content) of the leuco dye, developer and sensitizer in the thermosensitive recording layer was changed to 85.0% by weight.

[0061] [Example 5] Dry coating weight of protective layer: 1.0 g / m 2 A thermosensitive recording medium was prepared in the same manner as in Example 1, except that the above was replaced with the above. [Example 6] A thermosensitive recording medium was prepared in the same manner as in Example 1, except that no lubricant was added to the protective layer. [Example 7] A thermosensitive recording medium was prepared in the same manner as in Example 1, except that the inorganic pigment in the protective layer was replaced with aluminum hydroxide. [Example 8] A thermal recording medium was prepared in the same manner as in Example 1, except that the developer dispersion in the thermal recording layer was changed to 23.8 parts of A2 liquid and 14.2 parts of A3 liquid, the sensitizer dispersion was changed to 1.9 parts of C3 liquid, and the leuco dye blending ratio was changed to 5.0 parts. [Example 9] A thermosensitive recording medium was prepared in the same manner as in Example 8, except that the developer dispersion in the thermosensitive recording layer was changed to 22.5 parts of A4 liquid and 13.2 parts of A5 liquid.

[0062] [Comparative Example 1] A thermosensitive recording medium was prepared in the same manner as in Example 1, except that the total content (solid content) of the leuco dye, developer and sensitizer was changed to 46.0% by weight by incorporating an inorganic pigment into the thermosensitive recording layer. Comparative Example 2 A thermosensitive recording medium was prepared in the same manner as in Example 1, except that no protective layer was provided.

[0063] The results are shown in Tables 1 and 2. [Table 1]

[0064] [Table 2]

[0065] As shown in Table 1, the thermosensitive recording medium of the present invention had excellent color development sensitivity and print running properties. Furthermore, it also had excellent print definition (print defect rate) during high-speed printing. In each example in which kaolin having an aspect ratio of 30 or more was used as the inorganic pigment in the protective layer, the color development sensitivity was further improved compared to Example 7 in which aluminum hydroxide was used as the inorganic pigment. In the case of Example 9, in which the developer contained the urea compound (NKK1304 and S176) represented by the general formula (1) described above, the solvent resistance was improved compared to the other Examples.

[0066] On the other hand, in the case of Comparative Example 1, in which the total content (solid content) of the leuco dye, developer, and sensitizer in the thermosensitive recording layer was less than 70.0% by weight, the coating amount of the thermosensitive recording layer was 2.5 g / m 2 In addition, the print resolution (print defect rate) during high-speed printing was poor, which is thought to be due to the reduced sensitivity. In the case of Comparative Example 2 in which no protective layer was provided, the color development sensitivity was good, but the print running properties were poor.

Claims

1. A thermosensitive recording medium comprising a support, an undercoat layer, a thermosensitive recording layer containing a colorless or light-colored electron-donating leuco dye, an electron-accepting developer and a sensitizer, and a protective layer, in this order; the total content (solid content) of the leuco dye, the color developer, and the sensitizer in the thermosensitive recording layer is 76.0% by weight or more; The coating amount of the thermosensitive recording layer is 2.5 g / m ２ is as follows: The coating amount of the protective layer is 2.5 g / m ２ 0.4g / m or less ２ That's all, A thermosensitive recording medium, wherein the thermosensitive recording layer does not contain a lubricant, and the protective layer contains a lubricant.

2. The coating amount of the protective layer is 2.0 g / m ２ 2. The thermosensitive recording medium according to claim 1, wherein:

3. 3. The thermosensitive recording material according to claim 1, wherein the thermosensitive recording layer does not contain an inorganic pigment.

4. 3. The thermosensitive recording material according to claim 1, wherein the developer contains a urea compound represented by the following general formula (1): 【Chemistry 1】 (wherein X represents —O— or —NH—; R １ is a hydrogen atom or —SO ２ -R ３ represents R ３ represents a substituted or unsubstituted alkyl group, aralkyl group, or aryl group; R ２ represents a hydrogen atom or an alkyl group, and m represents 0 or 1.

5. 3. The thermosensitive recording material according to claim 1, wherein the protective layer contains an inorganic pigment having an aspect ratio of 30 or more.

6. 3. The thermosensitive recording material according to claim 1, wherein the print defect rate, as expressed by the following formula, is 35% or less. 100 - (Coloring area at a printing speed of 8 inches / s / Coloring area at a printing speed of 2 inches / s) (%)

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