JPH06135150A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material excellent in recording sensitivity and the reproducibility of halftone image quality. CONSTITUTION:In a thermal recording material wherein a recording layer containing a leuco dye and a coupler is provided on a support composed of paper or a synthetic resin film, secondary flocculated granular pigment of which the cumulated content of particles having a particle size of 15mum or more is 15% or less in measurement due to a laser diffraction method is added to the recording layer and/or the intermediate layer provided between the support and the recording layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive recording medium having a support made of synthetic paper or synthetic resin film.

[0002]

2. Description of the Related Art A thermosensitive recording medium is known in which a colored or light-colored leuco dye and an organic or inorganic coloring agent are used to obtain a recorded image by contacting both coloring substances with heat. Has been. Since such a thermosensitive recording medium is relatively inexpensive, the recording device is compact, and its maintenance is easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields. For example, such fields of use include video printers and CAD.
There is a thermal recording medium for plotter output. In particular, a thermal recording medium having a synthetic paper or a synthetic resin film as a support has better smoothness than the thermal recording medium having a paper as a support, and the dot reproducibility of the heating resistor is remarkably excellent. -Or CAD plotter is used as output paper.

However, in recent years, the recording speed of printers and plotters has improved, and there has been a tendency toward lower energy consumption for improving the durability of heat generating resistors. Therefore, synthetic paper or synthetic resin having excellent smoothness as a support is used. In a thermal recording medium using a film, missing dots or spot-like defects occur in halftone recording, and a uniform recorded image cannot be obtained. It is generally said that dot reproducibility depends strongly on the contact state between the heating resistor and the surface of the thermosensitive recording medium. Therefore, in order to significantly improve the contact between the heat-sensitive layer surface or the overcoat layer and the heat-sensitive resistor head, it is conceivable that the smoothness of the heat-sensitive layer surface is extremely improved by using a super calender or the like. However, there are limits to improving the uniformity of halftone images. That is, if the smoothness is extremely improved, dot omission will be reduced to some extent, but sticking between the surface of the thermal recording medium and the thermal head during recording, sticking to the recording head, and blocking during roll finishing, etc. It becomes a factor of occurrence.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a thermal recording material using a synthetic paper or a synthetic resin film as a support, which has excellent recording sensitivity and reproducibility of halftone images. is there.

[0005]

DISCLOSURE OF THE INVENTION The present inventors have proposed a thermosensitive recording medium in which a recording layer containing a leuco dye and a color developer is provided on a support made of synthetic paper or a synthetic resin film. And / or an intermediate layer provided between the support and the recording layer, in the measurement by the laser diffraction method,
It has been found that the above object can be achieved by containing a secondary agglomerated particle-based pigment having a cumulative content of particle diameters of μm or more of 15% or less, and has completed the present invention.

[0006]

As a means for improving the reproducibility of a halftone image on a thermosensitive recording medium, there is a method of increasing the smoothness of the recording medium surface. In the thermal paper using fine paper as a support, the reproducibility of the halftone image is improved to some extent depending on the smoothness of the thermal paper surface.
There is a limit to obtaining high gradation image quality. When using synthetic paper or synthetic resin film, which has higher smoothness than paper, as the support,
The smoothness of the surface of the recording medium as seen in macro is also necessary, but rather, the height of the convex portion that is isolated and protrudes from the surface of the recording medium,
It was found that the width and the number greatly affect the image quality.

Further, in the case of a thermal recording head in which the resistor portion of the heat-sensitive heating element is recessed with respect to the surface of the recording element, and the heat-generating resistor of 100 μ width is 8 dots per 1 mm,
The width of the protruding portion between each heating resistor is 25μ, and it deforms because it is pressed by the platen roll through the thermosensitive recording medium, so that it is pressed to some extent uniformly, and as a result, synthetic paper or synthetic resin film is used as a support. The smoothness of the surface of the thermosensitive recording medium, which is seen in the macro, is not considered to have much effect. Therefore, it is considered that the contact between the heat-sensitive heating element and the surface of the heat-sensitive recording material changes depending on rather fine surface irregularities.

The secondary agglomerate particle type pigment excellent in heat insulation and oil absorption is added to the recording layer or the intermediate layer in order to improve the recording sensitivity and sticking of the thermal recording material. In the case of a synthetic resin film, if a secondary agglomerated particle-based pigment with a cumulative content of particles of 15 μm or more of more than 15% is added to the recording layer or the intermediate layer, even if it is subjected to strong smoothing treatment with a super calender etc. Key record reproducibility is low. However, when a secondary agglomerated particle-based pigment having a cumulative content of particles having a particle size of 15 μm or more and 15% or less is added to the recording layer or the intermediate layer, a thermosensitive recording material having excellent recording sensitivity and reproducibility of halftone recording is obtained.

As the pigment forming the specific secondary agglomerated particles in the present invention, amorphous silica, light calcium carbonate, urea-formalin resin filler and the like are used, and the volume average particle diameter thereof is 1 to 8 μm (laser diffraction method). ), Preferably in the range of 1 to 5 μm.
When the volume average particle diameter is less than 1 μm, the adhesive strength and recording sensitivity of each layer are lowered, and when it exceeds 8 μm, the reproducibility of halftone image quality is deteriorated. The amount of the specific secondary agglomerated particle-based pigment used is not particularly limited, but it may be 5 to 50% by weight based on the total solid amount of the recording layer in the recording layer, and the total solid amount of the intermediate layer in the intermediate layer. On the other hand, it is preferably used in the range of 30 to 90% by weight. Further, the maximum particle size of the specific secondary agglomerated particle-based pigment is configured to be equal to or less than the film thickness of the coating layer, since the secondary agglomerated particle-based pigment does not protrude as much as possible on the surface of the thermal recording material,
Halftone dot reproducibility is significantly improved.

The synthetic paper used as the support of the present invention is produced by coating the surface of a synthetic resin film with a white pigment, or by adding a filler, a foaming agent or the like to the synthetic resin film to make it opaque. It is of fiber type.
Examples of the synthetic resin film used as the support in the present invention include known polyester films, polyolefin films, cellulosic films, polyamide films and the like. These supports may be subjected to corona treatment or surface treatment for surface roughening in advance,
It is desirable to form an anchor coat layer.

In the present invention, various known colorless or pale basic dyes can be used as the basic dye constituting the recording layer. Specifically, for example, 3,3-bis (p-
Dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl)
-3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3-diethylamino-7-dibenzylamino-benzo [a] fluorane, 3- (N-ethyl-
N-p-tolyl) amino-7-N-methylanilinofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3,6-bis (diethylamino) fluorane -Γ
-Anilinolactam, 3-cyclohexylamino-6-
Chlorofluorane, 3-diethylamino-6-methyl-
7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N
-Methyl-N-cyclohexyl) amino-6-methyl-
7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-di (n-butyl)
Amino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (o-chlorophenylamino) fluorane, 3- Di (n-butyl) amino-7- (o-chlorophenylamino) fluorane, 3-
Diethylamino-7- (o-fluorophenylamino)
Fluorane, 3-di (n-butyl) amino-7- (o-
Fluorophenylamino) fluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p- Truizino) Fluoran, 3- (N-
Ethyl-N-furfurylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-
7-anilinofluorane, 3- (N-methyl-Nn-)
Propylamino) -6-methyl-7-anilinofluorane, 3,3-bis [1- (4-methoxyphenyl) -1
-(4-Dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3
-Bis [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,
6,7-Tetrachlorophthalide, 3,3-bis [1,1
-Bis (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrabromophthalide, 3-p
-(P-anilinoanilino) anilino-6-methyl-7
-Chlorofluorane, 2,2-bis {4- [6 '-(N
-Cyclohexyl-N-methylamino) -3'-methylspirophthalide-3,9'-xanthen-2'-ylamino] phenyl} propane, 3,6, -bis (methylamino) fluorene-9-spiro-3 Examples include ′-(6′-dimethylamino) phthalide and the like. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

In the present invention, specific examples of the color former constituting the recording layer include the following known color formers. 4-tert-butylphenol, α-naphthol, β
-Naphthol, 4-acetylphenol, 4-tert-octylphenol, 4,4'-sec-butylidene diphenol, 4-phenylphenol, 4,4'-dihydroxy-diphenylmethane, 4,4'-isopropylidenediphenol (bisphenol A), hydroquinone,
4,4'-cyclohexylidene bisphenol, 4,
4 '-[1,4-phenylenebis (1-methylethylidene)] bisphenol, 4,4'-[1,3-phenylenebis (1-methylethylidene)] bisphenol,
4,4 '-(1,3-dimethylbutylidene) bisphenol, 2,2-bis (4-hydroxyphenyl) -4-
Methyl-pentane, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis (6-tert-butyl-3-methylphenol), 4,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-methyldiphenyl Sulfone, 4-hydroxy-4'-methoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-3 ', 4'-
Trimethylene diphenyl sulfone, 4-hydroxy-
3 ', 4'-tetramethylene diphenyl sulfone, 3,
4-dihydroxy-4'-methyldiphenyl sulfone,
Bis (3-allyl-4-hydroxyphenyl) sulfone, 1,3-di [2- (4-hydroxyphenyl) -2
-Propyl] benzene, hydroquinone monobenzyl ether, bis (4-hydroxyphenyl) acetic acid butyl ester, 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone, 2,2 ', 4 , 4'-tetrahydroxybenzophenone, dimethyl 4-hydroxyphthalate,
Methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, sec-butyl 4-hydroxybenzoate, pentyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, 4-hydroxybenzoic acid Benzyl, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, phenethyl 4-hydroxybenzoate, p-chlorobenzyl 4-hydroxybenzoate, 4-hydroxybenzoic acid-p- Methoxybenzyl, bis (4-hydroxyphenyl) acetic acid-2-phenoxyethyl ester, p-hydroxy-N- (2-
Phenoxyethyl) benzenesulfonamide, dimethyl 4-hydroxyphthalate, 1,5-bis (4-hydroxyphenylthio) -3-oxa-pentane, 1,7-bis (4-hydroxyphenylthio) -3,5- Dioxa-heptane, 1,8-bis (4-hydroxyphenylthio) -3,6-dioxa-octane, (4-hydroxyphenylthio) acetic acid-2- (4-hydroxyphenylthio) ethyl ester, novolac type phenol resin , Phenolic compounds such as phenolic polymers, 4- [2-
Aromatic carboxylic acids such as (p-methoxyphenoxy) ethyloxy] salicylic acid and 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, and zinc salts of these aromatic carboxylic acids.

In the heat-sensitive recording material of the present invention, a sensitizer can be added to the recording layer according to the purpose. Specific examples of the sensitizer include stearic acid amide and methoxycarbonyl-N-stearic acid. Benzamide, N-benzoylstearic acid amide, N-eicosanoic acid amide, ethylenebistearic acid amide, behenic acid amide, methylenebisstearic acid amide, N-methylolstearic acid amide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, Benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate, oxalate-di-p-methylbenzyl, oxalate-di-p-chlorobenzyl, 2-naphthylbenzyl ether, m- Terphenyl, p-benzylbiphenyl, tri Biphenyl ether, di (p- methoxyphenoxy) ether, 1,2-di (3-
Methylphenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane, 1,2-diphenoxy Ethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane,
p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetotoluidide, p-
Examples include acetophenetide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like. The amount of these sensitizers used is not particularly limited, but it is generally desirable to adjust the amount within the range of about 4 parts by weight or less relative to 1 part by weight of the color developing agent.

Further, other preservative improving agents may be used in combination depending on the purpose in order to further enhance the preservability of the recorded image as long as the effect is not impaired. Specific examples of such a storage stability improver include, for example, 2,2'-methylenebis (4-methyl-).
6-tert-butylphenol), 2,2′-ethylenebis (4-methyl-6-tert-butylphenol) 2,
2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-methylenebis (4,6-di-te)
rt-butylphenol), 2,2'-ethylidenebis (4,6-di-tert-butylphenol), 2,2'-
Ethylidene bis (4-methyl-6-tert-butylphenol), 2,2'-ethylidene bis (4-ethyl-6-)
tert-butylphenol), 2,2 '-(2,2-propylidene) bis (4,6-di-tert-butylphenol), 2,2'-methylenebis (4-methoxy-6-te)
rt-butylphenol), 2,2'-methylenebis (6
-Tert-butylphenol), 4,4'-thiobis (3
-Methyl-6-tert-butylphenol), 4,4'-
Thiobis (2-methyl-6-tert-butylphenol), 4,4'-thiobis (5-methyl-6-tert-butylphenol), 4,4'-thiobis (2-chloro-)
6-tert-butylphenol), 4,4'-thiobis (2-methoxy-6-tert-butylphenol), 4,
4'-thiobis (2-ethyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-m-cresol), 1,1,3-tris (2-methyl-4-hydroxy-) 5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,4′-thiobis (3-methylphenol), 4,4′- Dihydroxy-3,3 ', 5,5'-tetrabromodiphenyl sulfone, 4,4'-dihydroxy-3,3', 5,5'-
Tetramethyldiphenyl sulfone, 2,2-bis (4-
Hydroxy-3,5-dibromophenyl) propane,
2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-3,
Hindered phenol compounds such as 5-dimethylphenyl) propane, 1- [α-methyl-α- (4′-hydroxyphenyl) ethyl] -4- [α ′, α′-bis (4 ″)
-Hydroxyferroxyphenyl) ethyl] -4-
[Α ', α'-bis (4 "-hydroxyphenyl) ethyl] benzene, N, N'-di-2-naphthyl-p-phenylenediamine, 2,2'-methylenebis (4,6-di-tert- Butylphenyl) sodium phosphate and the like.

In order to prepare a coating liquid for a recording layer containing these substances, water is generally used as a dispersion medium, and a basic dye, terephthalaldehyde acid and other aromas are mixed with a stirring / grinding machine such as a ball mill, attritor or sand mill. A composite zinc salt of a group carboxylic acid, and further, a sensitizer and the like added as necessary are dispersed together or separately to 3 μm or less to prepare a coating liquid.

In the coating liquid, starch, hydroxyethyl cellulose, methyl cellulose,
Carboxymethyl cellulose, gelatin, casein, arabic gum, polyvinyl alcohol, diisobutylene
A maleic anhydride copolymer salt, a styrene / maleic anhydride copolymer salt, an ethylene / acrylic acid copolymer salt, a styrene / acrylic acid copolymer salt, a styrene / butadiene copolymer emulsion or the like has a total solid content of 10 -40% by weight, preferably about 15-30% by weight. Furthermore, various auxiliaries can be added to the coating liquid, for example, disodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, lauryl alcohol sulfate / sodium salt, alginate, fatty acid metal salt, and other dispersants. , Benzophenone-based and triazole-based ultraviolet absorbers, defoaming agents, fluorescent dyes, coloring dyes and the like. In addition, if necessary, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, inorganic pigments such as kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, and activated clay. It is also possible to add.

In the intermediate layer-forming coating material containing the specific secondary agglomerated particle system pigment, the adhesive used in the recording layer is used as an adhesive in an amount of 10 to 40% by weight based on the total solid amount of the intermediate layer, preferably. Is used in an amount of about 15 to 30% by weight. Further, various auxiliaries can be added to the coating for forming the intermediate layer, for example, sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate / sodium salt, alginate, fatty acid metal salt and the like. And other defoaming agents, fluorescent dyes, coloring dyes and the like.

The method for forming the recording layer and the intermediate layer is not particularly limited. For example, an air knife coater, a variber blade coater, a pure blade coater, a short dwell coater, or the like can be used to apply each coating material to a support or a support. It is formed by coating and drying on the intermediate layer formed above. The coating amount of each coating liquid is not particularly limited, and the intermediate layer is usually 2 to 15 g / dry weight.
m ² , preferably 3 to 10 g / m ² , and 1 for the recording layer
It is adjusted in the range of about 10 to 10 g / m ² , preferably about ² to 7 g / m ² .

It is preferable to provide a protective layer on the recording layer because the storage stability of recording is further improved. Examples of the water-soluble or water-dispersible polymer used for forming the protective layer include polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, and carboxy. Methylcellulose, starch and its derivatives, casein, sodium alginate, polyvinylpyrrolidone, polyacrylamide, styrene-maleic acid copolymer salt, polyurethane resin, urea resin, melamine resin, polyamide resin, epichlorohydridone modified polyamide resin, styrene-butadiene emulsion Examples thereof include synthetic polymer emulsions such as styrene / acrylic ester emulsions and acrylic ester emulsions. Of course, two or more kinds of these polymer compounds may be mixed and used.
Of these polymer compounds, acetoacetyl group-modified polyvinyl alcohol and silicon-modified polyvinyl alcohol are preferably used because they form a strong resin film.

A pigment may be added to the protective layer,
Specific examples thereof include inorganic pigments such as calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined kaolin, calcined clay, and colloidal silica. Examples thereof include styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and organic pigments such as raw starch particles.
It is generally desirable to adjust the amount used in the range of about 20 to 500 parts by weight with respect to 100 parts by weight of the polymer compound.

Furthermore, in the coating liquid for forming the protective layer, zinc stearate, calcium stearate,
Lubricants such as polyethylene wax, carnauba wax, paraffin wax and ester wax, surfactants such as sodium dioctyl sulfosuccinate, and various auxiliaries such as defoaming agents can be appropriately added. Further, a curing agent such as glyoxal, boric acid, dialdehyde starch, or an epoxy compound can be added to further improve water resistance. The dry weight of the protective layer is 1 to 10 g / m ² ,
It is preferably adjusted in the range of ^{2 to} 7 g / m ² , and the like.

[0022]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.
In the examples, parts and% are “parts by weight” unless otherwise specified.
"% By weight" is shown. [Examples 1 to 4, Comparative Examples 1 to 3] Preparation of Liquid A 20 parts of secondary agglomerated particle type pigment of amorphous silica, 5 parts of 10% aqueous solution of sodium polyacrylate, 20% aqueous solution of polyvinyl alcohol [ Trade name: PVA-205, manufactured by Kuraray Co., Ltd.] 15 parts of a composition and 60 parts of water are mixed and stirred, and the particle size distribution shown in Table 1 [Product name: Microtrac particle size distribution meter Moddel 7995-30 SPA (laser Flanhofer diffraction method of forward scattered light), Leeds & North
Rup] was obtained.

Preparation of Solution B 3-di (n-butyl) amino-6-methyl-7-anilinofluorane 10 parts, 1,2-di (3-methylphenoxy) ethane 20 parts, 5% methylcellulose aqueous solution 5 parts ,
A composition comprising 65 parts of water and water was pulverized with a sand mill until the average particle size became 2 μm.

Preparation of Solution C A composition consisting of 30 parts of 4-hydroxy-4′-isopropyloxydiphenylsulfone, 5 parts of a 5% aqueous solution of methylcellulose, and 65 parts of water was pulverized with a sand mill until the average particle diameter became 2 μm.

Preparation of Solution D 200 parts of 10% acetoacetyl group-modified polyvinyl alcohol aqueous solution, 100 parts of kaolin [trade name: UW-90, manufactured by EMC], 30 parts of 30% zinc stearate dispersion,
A composition consisting of 3 parts of a 10% aqueous solution of glyoxal and 100 parts of water was mixed and stirred to prepare a coating liquid.

Formation of Thermosensitive Recording Medium 100 parts of A solution, 100 parts of B solution, 100 parts of C solution, and 10 parts
% Polyvinyl alcohol aqueous solution (80 parts), and the resulting coating solution is mixed and stirred so that the coating amount after drying is 5 g / m ² [Product name: YUPO FPG-80, manufactured by Oji Yuka Co., Ltd.]
A recording layer was formed by coating and drying on the above. D on this recording layer
The solution was applied and dried so that the applied amount after drying was 3 g / m ^2, and then calendered to obtain each heat-sensitive recording material.

[Example 5] Synthetic paper [Product name: YUPO FPG
-80, manufactured by Oji Yuka Co., Ltd.], except that the solution A used in Example 1 was applied and dried to a solid amount of 6 g / m ² .
A thermal recording material was obtained in the same manner as in Example 1.

[Comparative Example 4] A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 100 parts of the liquid A was omitted from the formation of the recording layer in Example 1.

The following 9 types of heat-sensitive recording materials thus obtained were evaluated, and the results are shown in Table 1.
The evaluation method of each evaluation item is as follows. [Reproducibility of halftone image quality] Each thermal recording medium is recorded at a low voltage with a video printer [Product name: PT-1, manufactured by Sony Corporation],
The reproducibility of the obtained halftone image quality was visually judged. ⊚: Reproducibility of halftone image quality is very good. ○ ・ ・ ・ ・ ・ 〃 Excellent. △ ・ ・ ・ ・ ・ 〃 A little inferior. × ・ ・ ・ Inferior [Recording density] Thermal recording material evaluation machine [Product name: TH-PM
D, manufactured by Okura Electric Co., Ltd., and applied energy of 0.3 mJ
Each thermosensitive recording medium was subjected to color development at / dot, and the color density of the obtained recorded image was measured with a Macbeth densitometer [RD-100R type, manufactured by Macbeth Co.]. [Sticking] Recording was performed with an applied energy of 0.4 mJ / dot using the above-mentioned thermal recording medium evaluation device, and the state of sticking was visually judged. ◎ ・ ・ ・ No sticking ○○ 〃 Almost none. ×: Yes.

[0030]

[Table 1]

[0031]

As is clear from the results of Table 1, the thermosensitive recording medium of the present invention was a thermal recording medium excellent in recording sensitivity and reproducibility of halftone image quality.

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[Procedure amendment]

[Submission date] November 11, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

Claims (2)

[Claims] 1. A thermosensitive recording medium comprising a support comprising a synthetic paper or a synthetic resin film and a recording layer containing a leuco dye and a color former, the recording layer and / or between the support and the recording layer. In the intermediate layer provided in, the cumulative content of particles having a particle size of 15 μm or more is 1 when measured by a laser diffraction method.
A heat-sensitive recording material, characterized by containing 5% or less of a secondary aggregate particle pigment. 2. The volume average particle system of the secondary agglomerated particle system pigment is 1
The thermal recording material according to claim 1, which has a thickness of from 8 to 8 μm.