JPH06166265A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material which is excellent in a head matching ability, a writing ability, and a sealable property. CONSTITUTION:In a thermal recording material wherein a thermal recording layer having a leuco dye and a developer as main components and a protective layer are successively provided on a base material, an organic particulate of 150 deg.C or higher in softening point and 150ml/100g or over in oil absorption is contained in the protective layer. A thermal recording material is preferable wherein the particulate is an agglomerate of at most 2.0mum in mean diameter of primary particle or a content of the particulate in the protective layer is at least 20wt.% and a stuck amount of the protective layer is 1-5g/m<2>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, particularly excellent in matching property with a thermal head, excellent in writability on the surface of the heat-sensitive recording material with a pencil or the like and imprintability on the surface of the heat-sensitive recording material with a stamp or the like. Thermal recording material.

[0002]

2. Description of the Related Art Conventionally, a colorless or light-colored leuco dye is provided on a support such as paper, synthetic paper, and plastic film.
Various recording materials are provided which are provided with a thermosensitive recording layer containing, as a main component, a color developer that develops a color when the leuco dye is brought into contact with the leuco dye and a color development reaction between the leuco dye and the color developer due to heat or pressure. Proposed. This type of heat-sensitive recording material does not require complicated processing such as development and fixing, can record in a relatively short time in a relatively simple device, generates less noise, and has a lower cost. Therefore, it is useful not only for copying books and documents but also as various recording materials for electronic computers, facsimiles, ticket vending machines, label printers, recorders and the like. As the color-forming dye used in the heat-sensitive recording material, for example, a colorless or light-colored leuco dye having a lactone, lactam or spiropyran ring, and as a developer, an organic acid, a phenolic substance or the like has been conventionally used. The heat-sensitive recording material using the leuco dye and the developer has a clear color tone of the obtained image,
It is widely used because of its high image density, high whiteness of the background, and excellent image durability.

However, when the heat-sensitive recording material receives heat from the thermal head, the thermal melt contained in the recording material is melted and adheres to the thermal head, which is a phenomenon of so-called dust adhesion, which causes printing for a long time. If the dust is present, the dust may obstruct the heat transfer to the recording material, and the print may be blurred.

In order to solve this problem, addition of various fine particles has been conventionally proposed (for example, Japanese Patent Laid-Open No. 1-3).
No. 01368), for example, calcium carbonate, kaolin, talc, silica, alumina, titanium oxide and the like are used as the fine particles. However, although these fine particles have an effect on dust adhesion, when a thermal recording material containing these fine particles is used and printing is performed for a long time, the surface of the thermal head is abraded. There is a new problem of disappearing.

In recent years, there has been a demand for a higher printing speed, and in order to improve the thermal efficiency of the thermal head, the protective film on the surface of the thermal head tends to become thin. There is also the problem of becoming weak. Therefore, it is required for the thermal recording material that the thermal head is hard to be worn. On the other hand, when the particles, which have been conventionally proposed to reduce the adhesion of dust, are contained, head wear progresses, and the prevention of dust adhesion and the prevention of head wear are not compatible.

Further, conventionally, a pencil has been attached to the surface of the heat-sensitive recording material,
When attempting to write with a ball-point pen or the like, there are problems that the written image is not clear and writing is difficult as compared with general paper that is not a heat-sensitive recording material. Further, when a stamp is imprinted on the surface of the heat-sensitive recording material, if the imprint portion is rubbed with a finger immediately after imprinting, there is a problem that the stamp image is blurred or the stamp ink adheres to the finger.

[0007]

DISCLOSURE OF THE INVENTION The present invention has an improved matching property with a thermal head, that is, there is little residue of dust and head wear, and a heat-sensitive recording material excellent in imprintability with a writable stamp such as a pencil or a ballpoint pen. The purpose is to provide.

[0008]

According to the present invention, a heat-sensitive recording layer containing, as a main component, a leuco dye and a developer capable of developing the color of the leuco dye when heated is provided on a support, and a protective layer is further provided thereon. In a thermosensitive recording material provided with a layer, the protective layer has a softening point of 150 ° C. or higher and an oil absorption of 150 ml.
/ 100 g or more of organic fine particles are contained in the heat-sensitive recording material, and the organic fine particles form aggregates, and the average diameter of primary particles of the organic fine particles is 2.0 μm. The heat-sensitive recording material is provided below, and further, the organic fine particles are contained in the protective layer in an amount of 20% by weight or more, and the adhesion amount of the protective layer is 1 to 5 g / m ^2. A heat-sensitive recording material according to claim 1 is provided.

Conventionally, fine particles of calcium carbonate, kaolin, talc, silica, alumina, titanium oxide and the like have been used to reduce the adhesion of dust, but the organic fine particles of the present invention are used in comparison with the case of using these fine particles. When adopted, the head wear is remarkably reduced, and the thermal head debris is extremely adhered, so that the printed image does not drop out or blur even during long-term printing and recording. It is speculated that this is because the fine particles used in the present invention are organic.

Further, the higher the softening point of the organic fine particles used in the present invention (that is, the softening point is 150 ° C. or higher), the more remarkable the effect is. Few. Further, the larger the oil absorption amount (that is, the oil absorption amount of 150 ml / 100 g or more), the more remarkable the effect is, and conversely, if it is less than 150 ml / 100 g, the effect is small. Further, in order to prevent dust adhesion, the organic fine particles are preferably contained in the protective layer in an amount of 20 wt% or more, and the adhesion amount of the protective layer is 1 to 5 g / m ² , more preferably 25 wt% of the organic fine particles in the protective layer. % Or more, and the adhesion amount of the protective layer is 1.5 to 4.5 g / m ² .

Further, when the thermosensitive recording material of the present invention is used to write on the surface with a pencil, a ballpoint pen or the like, the written image is clear and the writing is easy. It is speculated that this is because the organic fine particles used in the present invention form an aggregate and the average primary particle diameter of the organic fine particles is 2.0 μm or less. As in the present invention, the average diameter of the primary particles is 2.0.
When the protective layer contains organic fine particles having a particle size of less than or equal to μm and forming an aggregate, an appropriate friction coefficient for the writing instrument and an appropriate surface shape are formed on the surface of the heat-sensitive recording material. Guessed. In order to ensure good writability, it is preferable that the organic fine particles are contained in the protective layer in an amount of 20 wt% or more, and the amount of the protective layer attached is 1 to 5 g / m ² .

Furthermore, when a stamp is imprinted on the surface of the heat-sensitive recording material of the present invention, immediately after imprinting, rubbing the imprinted portion with a finger causes a problem that the stamp image is blurred or the stamp ink adheres to the finger. Few. The oil absorption of the organic fine particles used in the present invention is 150 ml / 100.
It is presumed that this is due to the formation of aggregates in the amount of g or more. In order to secure good imprintability, the organic fine particles are contained in the protective layer in an amount of 20 wt% or more, and the amount of adhesion of the protective layer is 1
It is preferably ˜5 g / m ² .

The oil absorption is measured according to JIS K5101.
Obeyed. The softening point was measured by a drop-type flow tester. Further, the presence or absence of aggregate formation and the measurement of the primary particle size were carried out by observation with an electron microscope.

As the leuco dye used in the present invention, generally, leuco dyes known in this type of leuco recording material are applied alone or in combination of two or more kinds. For example, triphenylmethanephthalide type, trile type Allylmethane-based, Fluoran-based, Phenothiazine-based, Thioferouran-based, Xanthene-based, Indophthalyl-based, Spiropyran-based, Azaphthalide-based, Chromenopyrazole-based,
Leuco compounds of dyes such as methine type, rhodamine anilinolactam type, rhodamine lactam type, quinazoline type, diazaxanthene type and bislactone type dyes are preferably used. Specific examples of such leuco dyes include, for example,
The following may be mentioned. 3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-dimethylaminophenyl) -6
-Dimethylaminophthalide (also known as crystal bioleptlactone), 3,3-bis (p-dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide 3,3-bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,7-dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-
Diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3- (Np
-Tolyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- {N- (3'-trifluoromethylphenyl) Amino} -6-diethylaminofluorane, 2- {3,6-bis (diethylamino) -9- (o
-Chloranilino) xanthyl benzoate lactam}, 3
-Diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7
-(O-chloranilino) fluorane, 3-dibutylamino-7- (o-chloranilino) fluorane, 3-
N, N-di-N-amylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N-amylamino-
6-methyl-7-anilinofluorane, 3-N-methyl-N-iso-propylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl- 7-anilinofluoran, 3-
(N-methyl-N-isoamylamino) -6-methyl-
7-anilinofluorane, 3- (N-methyl-N-isobutylamino) -6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3- ( 2'-hydroxy-4'-dimethylaminophenyl) -3- (2'-methoxy-5'-nitrophenyl) phthalide, 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluorane, 3- Pyrrolidino-7-trifluoromethylanilinofluorane,
3-diethylamino-5-chloro-7- (N-benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluorane, 3-diethylamino-5-chloro-7 −
(Α-phenylethylamino) fluorane, 3- (N-
Ethyl-p-toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (o-
Methoxycarbonylphenylamino) fluorane, 3-
Diethylamino-5-methyl-7- (α-phenylethylamino) fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3- (N-methyltoluidino) -7- (pn-butylanilino ) Fluoran, 3- (N-ethyl-N-cyclohexylamino)
-5,6-benzo-7-α-naphthylamino-4'-bromofluorane, 3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-7-α-naphthylamino-4'- Bromofluorane, 3- (p-dimethylaminophenyl) -3- {1,1-bis (p-dimethylaminophenyl) ethylene-2-yl} phthalide, 3- (p
-Dimethylaminophenyl) -3- {1,1-bis (p
-Dimethylaminophenyl) ethylene-2-yl} -6
-Dimethylaminophthalide, 3- (p-dimethylaminophenyl) -3- (1-p-dimethylaminophenyl-
1-phenylethylene-2-yl) phthalide, 3- (p
-Dimethylaminophenyl) -3- (1-p-dimethylaminophenyl-1-p-chlorophenylethylene-2
-Yl) -6-dimethylaminophthalide, 3- (4'-
Dimethylamino-2'-methoxy) -3- (1 ''-p-
Dimethylaminophenyl-1 ''-p-chlorophenyl-
1 ″, 3 ″ -butadiene-4 ″ -yl) benzophthalide, 3- (4′-dimethylamino-2′-benzyloxy) -3- (1 ″ -p-dimethylaminophenyl-1 ″
-Phenyl-1 ", 3" -butadiene-4 "-yl) benzophthalide, 3-dimethylamino-6-dimethylamino-fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide, 3 , 3-bis {2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl} -4,5,6,7-tetrachlorophthalide, 3-bis {1,1-bis (4 -Pyrrolidinophenyl) ethylene-2-yl} -5,6-dichloro-4,7-dibromophthalide, bis (p-dimethylaminostyryl) -1-p
-Tolylsulfonylmethane and the like.

In the present invention, various electron-accepting compounds such as a phenolic compound, a thiophenolic compound, a thiourea derivative, an organic acid and a metal salt thereof can be applied as a developer, and the specific examples thereof can be applied. Examples include the following. 4,4'-isopropylidene bisphenol, 3,4'-isopropylidene bisphenol, 4,4'-isopropylidene bis (o-methylphenol), 4,4'-secondary butylidene bisphenol 4,4'-isopropylidene bisphenol (O-tert-butylphenol), 4,4′-cyclohexylidenediphenol, 4,4′-isopropylidenebis (2-chlorophenol), 2,2′-methylenebis (4-methyl-6-tert-butylphenol) 2,2'-methylenebis (4-ethyl-6-tert-butylphenol),
4,4'-butylidene bis (6-tert-butyl-2
-Methyl) phenol, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) ) Butane, 4,4′-thiobis (6-tert-butyl-2-methyl) phenol, 4,4′-diphenolsulfone, 4,2′-diphenolsulfone, 4-isopropoxy-4′-hydroxydiphenyl Sulfone, 4-benzyloxy-4'-hydroxydiphenyl sulfone, 4,4'-diphenol sulfoxide, stearyl gallate, 1,7-bis (4-hydroxyphenylthio) -3,5-dioxaheptane, 1,
5-bis (4-hydroxyphenylthio) -3-oxapentane, 1,3-bis (4-hydroxyphenylthio) -propane, 2,2'-methylenebis (4-ethyl-
6-tert-butylphenol, 1,3-bis (4
-Hydroxyphenylthio) -2-hydroxypropane, N, N'-diphenylthiourea, salicylanilide,
5-chloro-salicylanilide, salicyl-o-chloroanilide, zinc salt of 1-acetyloxy-2-naphthoic acid, zinc acid of 2-acetyloxy-1-naphthoic acid, methyl bis- (4-hydroxyphenyl) acetate ester,
4- {β- (p-methoxyphenoxy) ethoxy} salicylic acid, 2,4′-diphenol sulfone, 3,3′-diallyl-4,4′-diphenol sulfone, α, α-bis (4-hydroxyphenyl) ) -Α-Methyltoluene, tetrabromobisphenol A, tetrabromobisphenol A, tetrabromobisphenol S, 4,4′-thiobis (2-methylphenol) 3,4′-hydroxy-
4'-methyl-diffel sulfone, 1,3,5-tris (4-tert-butyl-3-vidroxy-2,6-dimethylbenzyl) isocyanuric acid, 2,2-bis (3,3)
4'-dihydroxyphenyl) propane, bis (4-hydroxy-3-methylphenyl) sulfide and the like.

In order to obtain the heat-sensitive recording material of the present invention, a leuco dye, a developer and an auxiliary component described below may be bound and supported on a support. As the binder in this case, various conventional binders can be appropriately used. Specific examples of such a binder include the followings. Polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as methoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, sodium polyacrylate,
Polyvinylpyrrolidone, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide In addition to water-soluble polymers such as sodium alginate, gelatin and casein, polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, polymethacrylic acid ester, vinyl chloride / vinyl acetate copolymer, ethylene / vinyl acetate copolymer Emulsions of polymers and latexes such as styrene / butadiene copolymers and styrene / butadiene / acrylic copolymers.

When the heat-sensitive recording material is obtained according to the present invention, various heat-fusible substances can be used in combination as the sensitivity improver, and the specific examples thereof include the following compounds. Fatty acids such as stearic acid and behenic acid, fatty acid amides such as stearic acid amide and palmitic acid amide, fatty acid metal salts such as zinc stearate, aluminum stearate, calcium stearate, zinc palmitate and zinc behenate, p-benzyl Biphenyl, terphenyl, triphenylmethane, p-benzyloxybenzoic acid benzyl, β-benzyloxynaphthalene, β-naphthoic acid phenyl ester, 1-hydroxy-2-naphthoic acid phenyl ester, 1-hydroxy-2-naphthoic acid methyl ester Ester, diphenyl carbonate, dareyacol carbonate, terephthalic acid dibenzyl ester, terephthalic acid dimethyl ester, 1,4-dimethoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dibenzyloxynaphthalene 1,2-bis (phenoxy)
Ethane, 1,2-bis (3-methylphenoxy) ethane, 1,2-bis (4-methylphenoxy) ethane,
1,4-bis (phenoxy) butane, 1,4-bis (phenoxy) -2-butene, 1,2-bis (4-methoxyphenylthio) ethane, dibenzoylmethane, 1,4-
Bis (phenylthio) butane, 1,4-bis (phenylthio) -2-butene, 1,2-bis (4-methoxyphenylthio) ethane, 1,3-bis (2-vinyloxyethoxy) benzene, 1,4 -Bis (2-vinyloxyethoxy) benzene, p- (2-vinyloxyethoxy)
Biphenyl, p-aryloxybiphenyl, p-propargyloxybiphenyl, dibenzoyloxymethane,
1,3-dibenzoyloxypropane, dibenzyl disulfide, 1,1-diphenylethanol, 1,1-diphenylpropanol, p- (benzyloxy) benzyl alcohol, 1,3-diphenoxy-2-propanol, N-octadecylcarbamoyl -P-methoxycarbonylbenzene, N-octadecylcarbamoylbenzene, oxalic acid dibenzyl ester, oxalic acid bis (4-methylbenzyl), oxalic acid bis (4-chlorobenzyl), 1,5-
Bis (p-methoxyphenyloxy) -3-oxapentane, 1,2-bis (4-methoxyphenoxy) propane and the like.

Further, in the present invention, if necessary, an auxiliary additive component commonly used in this kind of heat-sensitive recording material, for example,
A surfactant, a lubricant, a pressure color-developing inhibitor, etc. can be used in combination. In this case, examples of the lubricant include higher fatty acids and metal salts thereof, higher fatty acid amides, higher fatty acid esters, various waxes of animal, vegetable, mineral or petroleum type.

In the heat-sensitive recording material of the present invention, as described above, a protective layer containing organic fine particles having a softening point of 150 ° C. or more and an oil absorption of 150 ml / 100 g or more is provided on the heat-sensitive recording layer. It is a thing. The organic fine particles used in the present invention include polymethylmethacrylate, styrene / methacrylic acid copolymer, styrene / methacrylic acid ester copolymer, polystyrene resin, urea-
Organic fine particles composed of formalin resin, fluorine resin, styrene / maleic anhydride copolymer, polyimide resin, higher alkylene / maleic anhydride copolymer, vinylidene chloride resin and the like can be mentioned. As the other component constituting the protective layer, the binder, the heat-fusible substance and the like used in the case of the heat-sensitive recording layer can be used.

In the present invention, as a support for the thermal recording paper, synthetic paper, plastic film or the like can be optionally used.

In the present invention, the amounts of the leuco dye, the color developer and the sensitizer used are 0.5 to 10.0 parts by weight of the developer and 0.5 to 10 parts by weight of the sensitizer per 1 part by weight of the leuco dye. 10.0 parts by weight, preferably 1-5 parts by weight.

Regarding the layer structure, if necessary, an intermediate layer may be provided between the support and the heat-sensitive recording layer, or a back layer may be provided on the opposite side of the support from the heat-sensitive recording layer. is there. Further, it is possible to provide another layer between the thermal recording layer and the protective layer.

The coating method for coating the coating solution for the heat-sensitive recording layer on the support, coating the coating solution for the protective layer on the heat-sensitive recording layer and the like include blade coating method, air knife coating method and gravure coating method. Conventionally known coating methods such as a roll coating method, a spray coating method, a dip coating method, a bar coating method and an extrusion coating method can be used.

[0024]

EXAMPLES Next, the present invention will be described in more detail by way of examples. All parts and% shown below are based on weight.

Example 1 [Solution A] 3- (N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane 10 parts 10% aqueous solution of polyvinyl alcohol 20 parts water 60 parts [solution B] p -Benzyl hydroxybenzoate 10 parts Calcium carbonate 10 parts 2,2'-methylene bis (4-methyl-6-tert-butylphenol) 5 parts 10% aqueous solution of polyvinyl alcohol 20 parts water 55 parts Grind and disperse for 2 to 4 hours with a granulator to prepare [Solution A] and [Solution B.] Furthermore, [Solution A] and [Solution B] were mixed and stirred so that the weight ratio was 1: 3, and heat was applied. the recording layer coating solution was prepared, the heat-sensitive recording layer coating already paper by coating and drying in the laboratory coating rod such dried coating amount of the 5.4~5.6g / m ² in a commercial fine paper And. The next resultant heat-sensitive recording layer coating already paper, the following [C liquid] After dry coating amount was applied so that 3.0 g / m ^2, and the calendering treatment, heat-sensitive of the present invention A recording material was obtained [Liquid C] 10% aqueous solution of polyvinyl alcohol 50 parts Epichlorohydrin-based cross-linking agent 1 part Zinc stearate 0.5 part Polymethylmethacrylate fine particles 3 parts Water 50 parts The above polymethylmethacrylate fine particles Softening point is 21
At 0 ° C., oil absorption was 200 ml / 100 g, aggregates were formed, and the average diameter of primary particles was about 0.8 μm.

Examples 2 to 7 The following solutions [D] to [I] were used in place of the solution [C] of Example 1, and the solutions [D] to [I] were used respectively. The same heat-sensitive recording layer-coated paper as in No. 1 was applied and calendered to obtain heat-sensitive recording materials of Examples 2 to 6. Example 2 [Solution D] 10% aqueous solution of polyvinyl alcohol 50 parts Epichlorohydrin-based cross-linking agent 1 part Zinc stearate 0.5 part Urea formalin resin fine particles 2.5 parts Water 50 parts The softening point of the urea formalin resin fine particles is 220
C., oil absorption was 300 ml / 100 g, aggregates were formed, and the average diameter of primary particles was about 0.5 μm. The liquid D was applied to the same paper coated with the thermosensitive recording layer as in Example 1 so as to have a coating amount of 2.0 g / m ² after drying, and was subjected to a calendar treatment to obtain a sample of Example 2.

Example 3 [Solution E] 10% aqueous solution of polyvinyl alcohol 50 parts Epichlorohydrin type crosslinking agent 1 part Zinc stearate 0.5 part Urea formalin resin fine particles 2.5 parts Water 50 parts The above urea formalin resin fine particles are used. Softening point is 220
The oil absorption was 350 ml / 100 g, aggregates were formed, and the average diameter of the primary particles was about 0.3 μm. The solution E was applied to the same paper coated with the thermosensitive recording layer as in Example 1 so that the coating amount after drying was 2.0 g / m ² and calendering was performed to obtain a sample of Example 3. .

Example 4 [F liquid] 10% aqueous solution of polyvinyl alcohol 50 parts Epichlorohydrin-based cross-linking agent 1 part Zinc stearate 0.5 part Styrene / methacrylic acid copolymer fine particles 3.0 parts Water 50 parts The above styrene / Methacrylic acid copolymer fine particles had a softening point of 200 ° C., an oil absorption amount of 250 ml / 100 g, formed aggregates, and had an average primary particle diameter of about 0.2 μm. The solution F was applied to the same paper coated with the thermosensitive recording layer as in Example 1 so that the coating amount after drying was 2.0 g / m ² and calendered to obtain the sample of Example 4. .

Example 5 [G Liquid] 10% aqueous solution of polyvinyl alcohol 50 parts Epichlorohydrin type crosslinking agent 1 part Zinc stearate 0.5 part Styrene / methacrylic acid copolymer fine particles 2 parts Water 50 parts The above styrene / methacryl The acid copolymer fine particles had a softening point of 200 ° C., an oil absorption amount of 220 ml / 100 g, formed aggregates, and had an average primary particle diameter of about 2.8 μm. The liquid G was applied to the same paper coated with the thermosensitive recording layer as in Example 1 so that the coating amount after drying was 3.0 g / m ² , and calendering was performed to obtain a sample of Example 5. .

Example 6 [Liquid H] 10% aqueous solution of polyvinyl alcohol 50 parts Epichlorohydrin-based cross-linking agent 1 part Zinc stearate 0.5 part Styrene / butyl methacrylate copolymer particles 0.5 part Water 50 parts Styrene / butyl methacrylate copolymer fine particles have a softening point of 170 ° C., an oil absorption of 190 ml / 100 g,
Formed aggregates, the average diameter of the primary particles is about 3.5μ
It was m. The solution H was applied to the same paper coated with the thermosensitive recording layer as in Example 1 so that the applied amount was 0.8 g / m ² after drying, and calendering was performed to obtain a sample of Example 6. .

Example 7 [Liquid I] 10% aqueous solution of polyvinyl alcohol 50 parts Epichlorohydrin type crosslinking agent 1 part Zinc stearate 0.5 part Urea-formalin resin fine particles 3 parts Water 50 parts The above urea-formalin resin fine particles Softening point is 220
C., oil absorption was 300 ml / 100 g, aggregates were formed, and the average diameter of primary particles was about 0.5 μm. Solution I was applied to the same paper coated with the thermosensitive recording layer as in Example 1 so that the coating amount after drying was 0.5 g / m ² , and calendered to give the thermosensitive recording material of Example 7. Got

Comparative Examples 1 to 4 Instead of the [C liquid] of Example 1, the following [J liquid] to [M]
Liquid], and heat sensitive recording materials of Comparative Examples 1 to 5 were obtained in the same manner as in Example 1 except that each liquid was used. Comparative Example 1 [Liquid J] 10% aqueous solution of polyvinyl alcohol 50 parts Epichlorohydrin-based crosslinking agent 1 part Zinc stearate 0.5 part Styrene / butyl methacrylate copolymer particles 2.5 parts Water 50 parts The above styrene / methacryl The butyl acid copolymer fine particles have a softening point of 130 ° C., an oil absorption of 200 ml / 100 g,
Formed aggregates, the average diameter of the primary particles is about 1.0μ
It was m. Liquid J was applied to the same paper as in Example 1 on which a thermosensitive recording layer had been applied, so that the coating amount after drying was 3.0 g / m ² , and the mixture was calendered to obtain the thermosensitive recording material of Comparative Example 1. Got

Comparative Example 2 [K Solution] 10% aqueous solution of polyvinyl alcohol 50 parts Epichlorohydrin-based cross-linking agent 1 part Zinc stearate 0.5 part Silica 2.5 parts Water 50 parts The softening point of the above silica is a descending flow. It cannot be measured with a tester, the oil absorption is 150 ml / 100 g, no aggregates are formed, and the average diameter of the primary particles is about 0.8 μm.
Met. Liquid K was applied to the same paper coated with the thermosensitive recording layer as in Example 1 so that the coating amount after drying was 2.5 g / m ² , and the mixture was calendered to obtain the thermosensitive recording material of Comparative Example 2. Got

Comparative Example 3 [Liquid L] 10% aqueous solution of polyvinyl alcohol 50 parts Epichlorohydrin type crosslinking agent 1 part Zinc stearate 0.5 part Aluminum hydroxide fine particles 3 parts Water 50 parts The softening point of the above aluminum hydroxide fine particles Cannot be measured with a drop-down flow tester, and oil absorption is 130 m
1/100 g, a loose aggregate was formed, and the average diameter of the primary particles was about 0.5 μm. The amount of L liquid applied to the paper coated with the thermosensitive recording layer similar to that in Example 1 was 2.
The heat-sensitive recording material of Comparative Example 3 was obtained by applying 5 g / m ² and calendering.

Comparative Example 4 [M Liquid] 10% aqueous solution of polyvinyl alcohol 50 parts Epichlorohydrin-based cross-linking agent 1 part Zinc stearate 0.5 part Polymethylmethacrylate resin fine particles 1 part Water 50 parts The above polymethylmethacrylate resin The softening point of the fine particles was 110 ° C., the oil absorption was 200 ml / 100 g, aggregates were formed, and the average diameter of the primary particles was about 1.5 μm. The solution M was applied to a paper coated with the same thermal recording layer as in Example 1 so that the coating amount after drying was 2.5 g / m ² , followed by calendering, and the thermal recording material of Comparative Example 4 was used. Got

Evaluation Method for Debris Adhesion and Head Wear In a thermal printing experimental apparatus having a thin film head, head voltage 0.6 W / dot, 1 line recording time 10 msec /
Under the conditions of 1, scanning density 8 × 7.7 dots / mm, pulse width was 0.8 msec, printing test was conducted for each sample of Examples and Comparative Examples by 20 km, and the thermal head was observed after the printing test. The results are shown in Table 1. Debris adhesion ○: Almost no debris adhered on the head, and there is no print blur due to debris adhesion. Δ: Scrap adhered to the head, but the print was not faded. ×: Scrap adhered to the head, and print fading due to the scrap adherence also occurred. Head wear ○: Almost no head wear. ×: Head wear occurred, but the print was not lost. XX: Print missing due to head wear. Evaluation of Writability Evaluated by image density when written on the surface of each sample with an HB pencil. Good density on ordinary paper. Δ: The density is slightly lower than that of ordinary paper. ×: The density is much lower than that of ordinary paper. Evaluation of imprintability An aqueous stamp with a red pigment as a colorant was imprinted on the surface of each sample, and after about 10 seconds, when the imprinted area was rubbed with a finger, the extent of bleeding of the stamp ink was evaluated. … Slightly bleeding occurs ×… Bleeding occurs extensively

[0037]

[Table 1]

[0038]

The heat-sensitive recording material of the present invention contains the organic fine particles having a softening point of 150 ° C. or more and an oil absorption of 150 ml / 100 g or more in the protective layer provided on the heat-sensitive color developing layer. Excellent matching with thermal head, writing on the surface of thermal recording material and imprinting. The organic fine particles have an average primary particle diameter of 2.0 μm.
The following effects are particularly remarkable when the content of the organic fine particles in the protective layer is 20% by weight or more and the amount of the protective layer attached is 1 to 5 g / m ² .

Claims (3)

[Claims] 1. A heat-sensitive recording material comprising a support, on which a heat-sensitive recording layer containing a leuco dye and a color developer capable of coloring the leuco dye under heating as a main component is provided, and further a protective layer is provided thereon. A heat-sensitive recording material, characterized in that the protective layer contains organic fine particles having a softening point of 150 ° C. or higher and an oil absorption of 150 ml / 100 g or higher. 2. The heat-sensitive recording material according to claim 1, wherein the organic fine particles form an aggregate, and the average diameter of primary particles of the organic fine particles is 2.0 μm or less. 3. The organic fine particles are contained in the protective layer in an amount of 20% by weight or more, and the amount of adhesion of the protective layer is 1 to 5 g / m ^2.
The heat-sensitive recording material according to claim 1, wherein