JPH1158949A - Heat sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sensitive recording material favorable in color developing texture in the heat sensitive recording material, which is produced by providing an intermediate layer including non-intumescent minute hollow particles between a support and a heat sensitive coloring layer and, when necessary, an over layer is provided on the heat sensitive coloring layer. SOLUTION: In a heat sensitive recording material, which is formed by providing an intermediate layer and a heat sensitive coloring layer on a support, the support has a smoothness according to JIS P-8119 of 30 or less and an absorption coefficient according to J. TAPPI No. 51 of 0.40 or more. In addition, the intermediate layer includes a plastic minute hollow filler having an average particle diameter of 2-10 μm and a porocity of 80% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is widely applied to computer output, printers such as calculators, recorders for medical measurement, low-speed and high-speed facsimile, automatic ticket vending machines, POS system labels, and the like. It relates to a heat-sensitive recording material to be used.

[0002]

2. Description of the Related Art In recent years, with the diversification of information and the expanding needs, various recording materials have been researched, developed, and put into practical use in the information recording field. (2) The required mechanism of the device is simple and compact, and the recording material is easy to handle and inexpensive.
It has the advantage of such as. In recent years, demand for this heat-sensitive recording material in various fields has been expanding, and higher performance (small size, high speed) of devices has been further demanded. Therefore, there is a demand for high-sensitivity and high-definition heat-sensitive recording materials that can cope with a reduction in printing energy accompanying a reduction in the size and speed of the apparatus.

A thermosensitive recording material is usually produced by applying a thermosensitive coloring layer solution containing a coloring component capable of causing a coloring reaction upon heating onto a support such as paper or a synthetic resin film and drying the coating. The thus obtained thermosensitive recording material is heated with a hot pen or a hot head to form a color image.

Among such heat-sensitive recording materials, those using paper as a support are widely used for POS labels, tickets, and the like, and are required to have a uniform printing quality, particularly a formation at the time of coloring. Have been. As such a support, high-quality paper suitable for uniform coating with a smooth surface has been generally used. However, in recent years, the shortage of paper and the increase in recycled paper due to the spread of ecological environmental conservation (virgin paper) Due to the decrease in pulp paper), it is expected that obtaining suitable paper for coating will become more and more difficult in the future.

[0005] As a conventional technique, a method of using various fine hollow particles (resin, glass, aluminosilicate type, etc.) on a support for an intermediate layer (JP-A-59-5093, JP-A-59-225987). Gazette) has been proposed,
In these cases, the surface was likely to be uneven, and the effect was insufficient to obtain a uniform image.

[0006]

Under such circumstances, the present inventors have proposed a method of using a paper which has poor surface smoothness and a support which is not suitable for coating a thermosensitive recording paper such as a paper having a large permeation property. However, as a result of intensive studies on measures for uniformly forming the heat-sensitive recording layer and obtaining a uniform image, the present invention was completed. Therefore, the present invention provides a heat-sensitive recording material comprising an intermediate layer containing non-expandable fine hollow particles provided between a support and a heat-sensitive coloring layer, and a heat-sensitive coloring layer and, if necessary, an overcoat layer provided thereon. Accordingly, it is an object of the present invention to provide a heat-sensitive recording material having good color formation.

[0007]

The object of the present invention is to provide an intermediate layer and a heat-sensitive recording material which develops color by heat when the support has a smoothness of 30 or less according to JIS P-8119. Yes, and J. TAPPI No. 5
1 is 0.40 or more, and the intermediate layer is a plastic fine hollow filler (average particle size of 2 to 1).
0 μm, hollow ratio of 80% or more). (2) "The thermosensitive recording material as described in (1) above, wherein the plastic hollow microfiller in the intermediate layer has an average particle diameter of 3 to 5 µm."
(3) “The plastic hollow filler has an average particle size smaller than that of the plastic hollow filler (0.1 μm to 10 μm).
μm) a mixture of two or more different types with a plastic hollow filler, wherein
2. The heat-sensitive recording material according to item 1. (4) "A mixture of two or more different types of the plastic hollow filler and the plastic hollow filler having a smaller average particle size than the plastic hollow filler, and the mixing ratio (weight ratio) is 1:
(3) wherein the ratio is 0.1 to 1: 0.5.
2. The heat-sensitive recording material according to item 1. Is resolved.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the contents of the present invention will be described in more detail. In the present invention, the leuco dye used in the thermosensitive coloring layer is applied alone or as a mixture of two or more, and as such a leuco dye, those applied to this kind of thermosensitive material are arbitrarily applied. And, for example, triphenylmethane, fluoran, phenothiazine,
Leuco compounds of dyes such as auramine, spiropyran and indolinophthalide are preferably used. Specific examples of such leuco dyes include, for example, those shown below. 3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal biolettolactone), 3,3-bis ( p-dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) -phthalide, 3- Cyclohexylamino-6-chlorofluoran, 3-dimethylamino-
5,7-dimethylfluorane, 3-N-methyl-N-isobutyl-6-methyl-7-anilinofluoran, 3-
N-ethyl-N-isoamyl-6-methyl-7-anilinofluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7-methylfluoran, 3
-Diethylamino-7,8-benzfluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3
-(Np-tolyl-N-ethylamino) -6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 2- {N- (3'-trifluoro) Rumethylphenyl) amino} -6-diethylaminofluoran, 2- {3,6-bis (diethylamino)
-9- (o-Chloranilino) xanthylbenzoic acid lactam}, 3-diethylamino-6-methyl-7- (m-
Trichloromethylanilino) fluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-
Dibutylamino-7- (o-chloroanilino) fluoran, 3-N-methyl-N-amylamino-6-methyl-
7-anilinofluoran, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6 Methyl-7-
(2 ′, 4′-dimethylanilino) fluoran, 3-
(N, N-diethylamino) -5-methyl-7- (N,
N-dibenzylamino) fluoran, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-3'-methoxy-benzoindolino-spiropyran, 3- (2 '
-Hydroxy-4'-dimethylaminophenyl) -3-
(2′-methoxy-5′-chlorophenyl) phthalide,
3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2'-methoxy-5'-nitrophenyl)
Phthalide, 3- (2'-hydroxy-4'-diethylaminophenyl) -3- (2'-methoxy-5'-methylphenyl) phthalide, 3- (2'-methoxy-4'-dimethylaminophenyl)- 3- (2'-hydroxy-
4'-chloro-5'-methylphenyl) phthalide, 3-
Morpholino-7- (N-propyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7-trifluoromethylanilinofluoran, 3-diethylamino-
5-chloro-7- (N-benzyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7- (di-p
-Chlorophenyl) methylaminofluoran, 3-diethylamino-5-chloro-7- (α-phenylethylamino) fluoran, 3- (N-ethyl-p-toluidino) -7- (α-phenylethylamino ) Fluoran,
3-diethylamino-7- (o-methoxycarbonylphenylamino) fluoran, 3-diethylamino-5-
Methyl-7- (α-phenylethylamino) fluoran, 3-diethylamino-7-piperidinofluoran,
2-chloro-3- (N-methyltoluidino) -7- (p
-N-butylanilino) fluoran, 3- (N-methyl-N-isopropylamino) -6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-
Anilinofluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3,6-bis (dimethylamino) fluorenespiro (9,3 ′)-6′-dimethylaminophthalide, 3- ( N-benzyl-N-cyclohexylamino) -5,6-benzo-7-α-naphthylamino-4′-bromofluoran, 3-diethylamino-
6-chloro-7-anilinofluoran, 3-N-ethyl-N- (2-ethoxypropyl) amino-6-methyl-
7-anilinofluoran, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-mesitidino-4 ′, 5′-benzo Fluoran, 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-butadien-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-naphthalenesulfonylmethane, bis- (p-dimethylaminostyryl) -1-p-tolyl Sulfonylmethane, etc.

In the present invention, various compounds having an electron-accepting property, for example, a phenolic compound, a thiophenolic compound, a thiourea derivative, and an organic acid, which cause the leuco dye to develop a color as a developer when the thermosensitive coloring layer is heated. And metal salts thereof can be used in combination, and specific examples thereof include the following. 4,4′-isopropylidenebisphenol, 4,4′-isopropylidenebis (o-methylphenol), 4,4′-secondarybutylidenebisphenol, 4,4′-isopropylidenebis (2-tert-butylphenol), 4,
4′-cyclohexylidene diphenol, 4,4′-isopropylidenebis (2-chlorophenol), 2,
2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 4,4'-
Butylidenebis (6-tert-butyl-2-methylphenol), 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-isopropoxy-4'-hydroxydiphenylsulfone, 4-benzyloxy -4'-hydroxydiphenyl sulfone,
4,4′-diphenolsulfoxide, isopropyl P-hydroxybenzoate, benzyl P-hydroxybenzoate, benzyl protocatechuate, stearyl gallate,
Lauryl gallate, octyl gallate, 1,7-bis (4-hydroxyphenylthio) -3,5-dioxaheptane, 1,5-bis (4-hydroxyphenylthio)
-3-oxapentane, 1,3-bis (4-hydroxyphenylthio) -propane, 1,3-bis (4-hydroxyphenylthio) -2-hydroxypropane, N,
N'-diphenylthiourea, N, N'-di (m-chlorophenyl) thiourea, salicylanilide, 5-chloro-
Salicylanilide, 2-hydroxy-3-naphthoic acid,
2-hydroxy-1-naphthoic acid, 1-hydroxy-2
-Naphthoic acid, metal salts of hydroxynaphthoic acid such as zinc, aluminum and calcium, bis- (4-hydroxyphenyl) acetic acid methyl ester, bis- (4-hydroxyphenyl) acetic acid benzyl ester, 1,3-bis (4
-Hydroxycumyl) benzene, 1,4-bis (4-hydroxycumyl) benzene, 2,4′-diphenolsulfone, 3,3′-diallyl-4,4′-diphenolsulfone, α, α- Bis (4-hydroxyphenyl)-
α-methyltoluene, tetrabromobisphenol A,
Tetrabromobisphenol S, 4,4-thiobis (2
-Methylphenol), 4,4-thiobis (2-chlorophenol), and the like.

As the binder for binding the intermediate layer on the support in producing the heat-sensitive recording material of the present invention, various conventional binders can be used as appropriate, and specific examples thereof include water-soluble binders. In addition to the resin and the aqueous emulsion, a hydrophobic resin, an ultraviolet curable resin, an electron beam curable resin and the like are included. Specific examples of the water-soluble resin include polyvinyl alcohol, modified polyvinyl alcohol such as carboxy-modified polyvinyl alcohol, starch and derivatives thereof, cellulose derivatives (carboxymethylcellulose, methylcellulose, methoxycellulose, hydroxyethylcellulose, etc.), casein, gelatin, polyacryl. Acid soda, polyvinylpyrrolidone, styrene-maleic anhydride copolymer, diisobutylene-maleic anhydride copolymer,
Examples include polyacrylamide, modified polyacrylamide, methyl vinyl ether-maleic anhydride copolymer, carboxy-modified polyethylene, polyvinyl alcohol / acrylamide block copolymer, melamine-formaldehyde resin, and urea-formaldehyde resin. Examples of the resin or the hydrophobic resin for the aqueous emulsion include polyvinyl acetate, polyurethane, styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer, polyacrylate, and vinyl chloride / vinyl acetate copolymer. , Polybutyl methacrylate, ethylene / vinyl acetate copolymer and the like.

Acrylamide / acrylic acid ester copolymers, acrylamide / acrylic acid ester / methacrylic acid terpolymers, styrene / maleic anhydride copolymer alkali salts, ethylene / maleic anhydride copolymer alkali salts, Isobutylene / maleic anhydride copolymer alkali salts, water-soluble polymers such as polyacrylamide and sodium alginate, as well as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylate, vinyl chloride /
Emulsions such as vinyl acetate copolymer, polybutyl methacrylate, and ethylene / vinyl acetate copolymer, and latexes such as styrene / butadiene copolymer and styrene / butadiene / acrylic copolymer can be given.
These may be used alone or as a mixture, and if necessary, a curing agent may be added to cure the resin.

In order to produce the heat-sensitive recording material of the present invention,
When the leuco dye and the developer are bound and supported on the support, various conventional binders can be appropriately used, and specific examples thereof include specific examples of the binder for binding the intermediate layer on the support. Selected from

As described above, in the present invention,
A protective layer is provided on the heat-sensitive coloring layer, if necessary, to improve chemical resistance, water resistance, friction resistance, light resistance, and head matching with a thermal head. This protective layer has a function of maintaining the image quality even when an expensive support is not used.

The protective layer provided as required includes a coating mainly formed of a water-soluble resin or a hydrophobic resin, a coating mainly formed of an ultraviolet curable resin or an electron beam curable resin, and the like. You. By forming such a protective layer, it is possible to obtain a recording medium having no practical problem even by contact with an organic solvent, a plasticizer, oil, sweat, water and the like. Further, by containing an organic or inorganic filler and a lubricant, it is possible to obtain a thermosensitive recording medium excellent in reliability and head matching without problems such as sticking caused by contact with a thermal head or the like.

Next, the protective layer provided as required in the present invention will be described in detail. The binder resin used in the protective layer of the present invention includes, in addition to a water-soluble resin, an aqueous emulsion, a hydrophobic resin, an ultraviolet curable resin, and an electron beam curable resin. Specific examples of the water-soluble resin include, for example, polyvinyl alcohol, modified polyvinyl alcohol, cellulose derivatives (methylcellulose, methoxycellulose, hydroxyethylcellulose, etc.), casein, gelatin, polyvinylpyrrolidone, styrene-maleic anhydride copolymer, diisobutylene- Maleic anhydride copolymer, polyacrylamide, modified polyacrylamide, methyl vinyl ether-maleic anhydride copolymer,
Carboxy-modified polyethylene, polyvinyl alcohol /
An acrylamide block copolymer, a melamine-formaldehyde resin, a urea-formaldehyde resin and the like can be mentioned. Examples of the resin for the aqueous emulsion or the hydrophobic resin include polyvinyl acetate, polyurethane, styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer, polyacrylic acid, polyacrylate, vinyl chloride / acetic acid. Examples include a vinyl copolymer, polybutyl methacrylate, and an ethylene / vinyl acetate copolymer. These may be used alone or as a mixture, and if necessary, a curing agent may be added to cure the resin. Further, a polyester urethane resin can be used for the purpose of improving the adhesiveness and flexibility of the recording layer.

The UV curable resin and the electron beam curable resin used as the protective layer of the present invention will be described. The UV curable resin used for forming the protective layer undergoes a polymerization reaction upon irradiation with ultraviolet light and cures to cure. The type is not limited as long as it is a monomer or oligomer (or a prepolymer), and all known various ones can be used. Examples of such a monomer or oligomer include (poly) ester acrylate, (poly) urethane acrylate, epoxy acrylate, polybutadiene acrylate, silicone acrylate, and melamine acrylate. As the (poly) ester acrylate, 1,6-
Examples thereof include those obtained by reacting polyhydric alcohols such as hexanediol, propylene glycol (as propylene oxide) and diethylene glycol with polybasic acids such as adipic acid, phthalic anhydride and trimellitic acid and acrylic acid.

When an ultraviolet curable resin is used, a solvent may be used. Examples of the solvent include tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, isopropyl alcohol, and acetic acid. Organic solvents such as ethyl, butyl acetate, toluene, and benzene are exemplified. Instead of these solvents, a photopolymerizable monomer can be used as a reactive diluent to facilitate handling.

In order to improve the head matching property, inorganic and organic fillers and lubricants can be added to the protective layer within a range that does not reduce the surface smoothness. The particle size of the filler in the present invention is preferably 0.3 μm or less.
As a pigment in this case, oil supply of 30 ml / 100 g or more,
Preferably, the one with 80 ml / 100 g or more is selected. As these inorganic and / or organic pigments, one or more of pigments commonly used in this type of heat-sensitive recording medium can be selected. Specific examples thereof include calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, kaolin, talc, surface-treated inorganic pigments such as calcium carbonate and silica, and urea-formalin resin. And organic pigments such as styrene / methacrylic acid copolymer and polystyrene resin. The method for applying the protective layer is not particularly limited, and can be applied by a conventionally known method. The preferred protective layer thickness is 0.1 to 20 μm, more preferably 0.5 to 10 μm
It is. If the protective layer is too thin, the function as a protective layer such as storage stability and head matching of the recording medium is insufficient,
If the thickness is too large, the thermal sensitivity of the recording medium decreases, which is disadvantageous in cost.

Further, in the present invention, various heat-fusible substances can be used as a sensitivity improver, and specific examples thereof include, but are not limited to, the following. Fatty acids such as stearic acid and behenic acid, fatty acid amides such as stearic acid amide and palmitic acid amide, zinc stearate, aluminum stearate, calcium stearate, zinc palmitate,
Metal salts of fatty acids such as zinc behenate, p-benzylbiphenyl, m-terphenyl, triphenylmethane, benzyl p-benzyloxybenzoate, β-benzyloxynaphthalene, phenyl β-naphthoate, 1-hydroxy-
Phenyl 2-naphthoate, methyl 1-hydroxy-2-naphthoate, diphenyl carbonate, dalayacol carbonate, dibenzyl terephthalate, dimethyl terephthalate, 1,4-dimethoxynaphthalene, 1,4-ethoxynaphthalene, 1,4- Dibenzyloxynaphthalene,
1,2-diphenoxyethane, 1,2-bis (3-methylphenoxy) ethane, 1,2-bis (4-methylphenoxy) ethane, 1,4-diphenoxy-2-butene,
1,2-bis (4-methoxyphenylthio) ethane, dibenzoylmethane, 1,4-diphenylthiobutane,
1,4-diphenylthio-2-butene, 1,3-bis (2-vinyloxyethoxy) benzene, 1,4-bis (2-vinyloxyethoxy) benzene, p- (2-vinyloxyethoxy) biphenyl, p-aryloxybiphenyl, p-propargyloxybiphenyl, dibenzoyloxymethane, dibenzoyloxypropane, dibenzyldisulfide, 1,1-diphenylethanol,
1,1-diphenylpropanol, p-benzyloxybenzyl alcohol, 1,3-diphenoxy-2-propanol, N-octadecylcarbamoyl-p-methoxycarbonylbenzene, N-octadecylcarbamoylbenzene, 1,2-bis (4-methoxy Phenoxy) propane, 1,5-bis (4-methoxyphenoxy) -3
-Oxapetan, dibenzyl oxalate, bis (4-methylbenzyl) oxalate, bis (4-chlorobenzyl) oxalate, and the like.

In the present invention, together with the leuco dye and the developer, if necessary, auxiliary additives commonly used in this type of heat-sensitive recording material, for example, fillers, surfactants, lubricants, pressure coloring. An inhibitor or the like can be used in combination. In this case, as the filler, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, kaolin,
In addition to inorganic fine powders such as talc and surface-treated calcium and silica, organic fine powders such as urea-formalin resin, styrene / methacrylic acid copolymer, polystyrene resin, and vinylidene chloride resin can be given. Examples of the lubricant include higher fatty acids and metal salts thereof, higher fatty acid amides, higher fatty acid esters, various kinds of animal, vegetable, mineral or petroleum waxes.

In the present invention, a layer containing a pigment, a binder, a heat-fusible substance or the like can be provided between the intermediate layer and the heat-sensitive coloring layer, if necessary, as another intermediate layer. Further, the heat-sensitive recording material of the present invention may be provided with a protective layer on the heat-sensitive coloring layer of the present invention for the purpose of improving the head matching property at the time of printing, and improving the writing property and the marking property on the recording material. Yes, but in this case,
As the components constituting the protective layer, the above-mentioned pigments, binders, and heat-fusible substances can be used.

[0022]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. The “parts” and “%” shown below are all based on weight. Difference in surface properties of cardboard Table 1 shows the smoothness (JIS P-8119) and Bristow absorption coefficient (J. TAPPI No. 51) of the cardboard used.

[0023]

[Table 1]

Preparation of Intermediate Layer Forming Solution Plastic Particulate Hollow Particle Dispersion 100 parts (Table 1; solids concentration 20%) Styrene / butadiene copolymer latex 25 parts (solids concentration 40%) 10% aqueous solution of polyvinyl alcohol 20 Part Water 15 parts (solid content 20% under liquid) The mixture having the composition of the intermediate layer forming liquid was mixed and stirred to prepare an intermediate layer coating liquid.

Preparation of heat-sensitive recording layer forming liquid (dispersion liquid A) 3- (N-dibutyl) amino-6-methyl-7-anilinofluoran 20 parts Polyvinyl alcohol 10% aqueous solution 20 parts Water 33 parts (dispersion liquid Solution B) 4-Hydroxy-4'-isopropoxydiphenyl sulfone 10.0 parts Silica 10.0 parts Polyvinyl alcohol 10% aqueous solution 25 parts Water 30 parts Each mixture having the above composition was adjusted to have an average particle diameter of 2 µm or less. Dispersion A and dispersion B were prepared by dispersion using a sand mill.

Preparation of Thermosensitive Layer Forming Solution 6.3 parts of Dispersion A 40 parts of Dispersion B 3 parts of a zinc stearate dispersion (solid content concentration: 30%) 3 parts of the thermosensitive layer forming liquid prepared as described above was prepared. . After the dried layer of the leuco dye is adjusted on the surface of the paper coated with the intermediate layer so as to have a dry amount of 0.5 g / m ² , the solid content is adjusted, and then the coating is dried to form a thermosensitive coloring layer. The heat-sensitive recording material of the present invention was obtained by performing a super calender treatment so that the Bekk smoothness became 500 to 600 seconds.

Formation Evaluation Method Using Stamprint SP-30F manufactured by Elcos Co., Ltd., heat-sensitive coloring was performed, and the coloring formation formation was visually evaluated. Rank 1: Very poor (base paper unevenness is very noticeable) Rank 2: Bad (base paper unevenness is noticeable) Rank 3: Normal (base paper unevenness is slight) Rank 4: Good (base paper unevenness is not noticeable) Rank 5: Very good (uniform formation without unevenness of base paper) From the results shown in Table 1, it can be seen that the heat-sensitive recording material of the present invention is excellent in color formation.

[0028]

As described above, according to the present invention, an intermediate layer containing non-foamable fine hollow particles is provided between a support and a thermosensitive coloring layer. A heat-sensitive recording material comprising a heat-sensitive coloring layer and, if necessary, an overcoat layer, which has a smoothness of 30 or less according to JIS P-8119. TAPPI. N
o. Since the absorption coefficient according to No. 51 is 0.40 or more, even when a support that is not suitable for coating a thermosensitive recording paper such as a paper having a poor surface smoothness or a paper having a large permeation property is used, the thermosensitive recording layer can be used. Can be formed uniformly, color formation can be improved, and a uniform image can be obtained.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Mitsuru Morita 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (4)

[Claims] In a heat-sensitive recording material which develops a color by heat with an intermediate layer on a support, the support has a smoothness of 30 or less according to JIS P-8119. TAPPI. N
o. 51 has an absorption coefficient of 0.40 or more; and
A heat-sensitive recording material, wherein the intermediate layer contains a plastic fine hollow filler (average particle diameter: 2 to 10 µm, hollow ratio: 80% or more). 2. The heat-sensitive recording material according to claim 1, wherein the plastic fine hollow filler in the intermediate layer has an average particle size of 3 to 5 μm. 3. The plastic hollow filler has a smaller average particle diameter than the plastic hollow filler (0.1 μm).
m-10 μm) 2 different from plastic hollow filler
3. A mixture of two or more types.
2. The heat-sensitive recording material according to item 1. 4. A mixture of two or more different types of the plastic hollow filler and a plastic hollow filler having an average particle size smaller than the plastic hollow filler, and the mixing ratio (weight ratio) is 1: 0.1 to 1: 1. The heat-sensitive recording material according to claim 3, wherein: 0.5.