JP3218539B2 - Thermal recording material - Google Patents

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, and more particularly to a heat-sensitive recording material having improved properties by providing an intermediate layer between a support and a heat-sensitive coloring layer.

[0002]

2. Description of the Related Art Recently, various recording materials have been researched, developed, and put to practical use in the information recording field in accordance with social demands such as diversification and increase of information, resource saving, and non-pollution. Above all, the heat-sensitive recording material is (1) that a color image is recorded only by heating, and a complicated developing step is not required; (2) recording can be performed using a relatively simple and compact apparatus; (3) In many cases, paper is used as a support. In this case, not only the cost of the support is low but also the feeling of the obtained recording material. Because of the advantages of being close to plain paper, such as computer output, printers such as calculators, recorders for medical measurement, low and high-speed facsimile, automatic ticket vending machines, thermal copying, POS systems Are widely used in the label field and the like of the beam.

The above-mentioned thermosensitive recording material is usually produced by applying and drying a thermosensitive coloring layer solution containing a coloring component capable of causing a coloring reaction by heating on a support such as paper, synthetic paper or synthetic resin film. The heat-sensitive recording material thus obtained is heated by a hot pen or a thermal head to record a color image. Conventional examples of such a heat-sensitive recording material include, for example, Japanese Patent Publication No. 43-4160.
Or the heat-sensitive recording material disclosed in JP-B-45-14039. However, such a conventional heat-sensitive recording material has, for example, a low thermal response, and does not provide a sufficient color density during high-speed recording. . As a method for remedying such a defect, for example, Japanese Patent Application Laid-Open No. S49-38424 discloses the use of a nitrogen-containing compound such as acetamide, stearamide, m-nitroaniline, dinitrile phthalate, etc.
No. 06746 discloses an acetoacetic anilide disclosed in
JP-A-3-11036 discloses N, N-diphenylamine derivatives, benzamide derivatives and carbazole derivatives, and JP-A-53-39139 discloses alkylated biphenyls and biphenylalkanes and JP-A-56-144193.
In the publication, a p-hydroxybenzoic acid ester derivative,
Methods for increasing the speed and increasing the sensitivity by adding each of them are disclosed, but at present, no satisfactory results have been obtained by any of the methods. As another method, Japanese Patent Application Laid-Open No. 56-164890 discloses a method in which a leuco dye having a high melting point is made amorphous to lower the melting point and increase the sensitivity. However, since the surface of the amorphized dye is activated and has high reactivity, there is a problem that the fogging or background fog of the thermosensitive coloring liquid or the thermosensitive recording material is large and the whiteness is poor.

Therefore, in order to suppress background fog and enhance dynamic color development sensitivity, the thermal conductivity of the support is set to 0.04 Kca.
1 / mh ° C. or lower (Japanese Patent Laid-Open No. 55-164192) or providing a layer mainly composed of fine hollow sphere particles on a support (Japanese Patent Laid-Open Nos. 59-5093 and 59-225).
No. 987) and the use of non-expandable fine hollow particles of 5 μm or less made of a thermoplastic resin for the intermediate layer (Japanese Patent Application Laid-Open No. 62-5886).
And an average particle diameter of 0.2 to 1.5 μm and a hollowness of 4
It has been proposed to use 0 to 90% of plastic spherical hollow particles for the under layer (JP-A-1-113282).

[0005]

However, the heat-sensitive recording materials proposed in the above-mentioned JP-A-55-164192 and JP-A-59-5093 have insufficient foaming properties and are not suitable for wall materials. In some cases, the thermal head may not have sufficient heat insulating properties, or the thermal head may have insufficient adhesion to the heat-sensitive recording material. The thermal recording materials proposed in JP-A-62-5886, JP-A-1-113282 and the like do not produce satisfactory results.

Accordingly, it is an object of the present invention to provide a heat-sensitive recording material having high sensitivity and excellent dot reproducibility and head matching.

[0007]

According to the present invention, an intermediate layer and a heat-sensitive recording layer mainly composed of a leuco dye and a developer which causes the leuco dye to develop color when heated are successively laminated on a support. In the heat-sensitive recording material, the intermediate layer is made of a thermoplastic resin, has an average particle diameter of 2 to 10 μm, and has a hollow ratio of 90.
% Or more of hollow fine particles and an inorganic or / and organic pigment having an oil absorption of 30 ml / 100 g or more, or the intermediate layer has an average particle diameter of 2 to 4 made of a thermoplastic resin.
From a laminate of a first intermediate layer mainly composed of fine hollow particles having a hollow ratio of 10% or more and a hollow ratio of 90% or more and a second intermediate layer mainly composed of an inorganic or / and organic pigment having an oil absorption of 30 ml / 100 g or more. A thermosensitive recording material is provided.

The intermediate layer mainly composed of fine hollow particles having an average particle diameter of 2 to 10 μm and having a hollow ratio of 90% or more made of the thermoplastic resin of the present invention acts as a heat insulating layer, and heat energy from a thermal head or the like. The color development sensitivity is improved by the efficient utilization of color. In addition, the heat-sensitive recording material having an intermediate layer containing the fine hollow particles as a main component is rich in elasticity and excellent in dot reproducibility.

When the intermediate layer contains an inorganic or / and organic pigment having an oil absorption of 30 ml / 100 g or more together with the fine hollow particles, the intermediate layer functions as a heat insulating layer, and the heat from a thermal head or the like is applied. It not only improves the color sensitivity by efficient use of energy, but also has the effect of adsorbing the heat-sensitive coloring component in the heated and melted state, and prevents the heat-sensitive coloring component from sticking to heating recording equipment such as a thermal head. Show. Therefore, the intermediate layer enables the thermal energy applied for image recording to be effectively used in the heat-sensitive recording layer, and also provides a heat-sensitive recording material excellent in matching with a thermal pad or the like.

When the intermediate layer has a laminated structure of the first intermediate layer mainly composed of the fine hollow particles and the second intermediate layer mainly composed of the inorganic and / or organic pigment,
The intermediate layer functions as a heat insulating layer, and the second intermediate layer exhibits an effect of adsorbing the heat-sensitive coloring component in a heated and molten state.

The hollow particles used in the present invention are fine hollow particles having a thermoplastic resin as a shell and containing air or other gas therein, and are already in a foamed state. Those having a size of 10 μm are used. If the average particle diameter (particle outer diameter) is smaller than 2 μm, there is a problem in production such as difficulty in obtaining an arbitrary hollow ratio, which is difficult in terms of cost. Since the smoothness of the surface after coating and drying is reduced, the adhesion to the thermal head is reduced, and the effect of improving sensitivity is reduced. Therefore, it is desirable that such a particle distribution is such that the particle diameter is within the above-mentioned range and the distribution peak with little variation is uniform.

Further, the minute hollow particles used in the present invention have a hollow ratio of 90% or more, and those having a hollow ratio of less than 90% have insufficient heat insulating properties, so that thermal energy from a thermal head is not sufficient. Is released through the support to the outside of the heat-sensitive recording material, and the effect of improving sensitivity is insufficient. In addition,
Here, the hollow ratio is a ratio between the outer diameter and the inner diameter of the hollow particles, and is represented by the following equation.

The fine hollow particles used in the present invention have a shell of a thermoplastic resin as described above, and the resin is preferably a copolymer resin mainly containing vinylidene chloride and acrylonitrile. .

In the present invention, the intermediate layer or the second
Inorganic or / and organic pigments are used for the intermediate layer, and in this case, the pigment may have an oil absorption of 30 ml / 100 g or more,
Preferably, the one with 80 ml / 100 g or more is selected. As a result, the ability to adsorb the thermosensitive coloring component in the heated and melted state is imparted, and the matching property with the thermal head or the like is improved.

As the above-mentioned inorganic and organic pigments having an oil absorption of 30 ml / 100 g or more, one or more of pigments commonly used in this type of heat-sensitive recording material can be appropriately selected. Specific examples thereof include calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, surface-treated inorganic pigments such as calcium and silica, and urea-formalin resin. And organic pigments such as styrene / methacrylic acid copolymer and polystyrene resin.

In order to provide the intermediate layer on a support, the fine hollow particles are dispersed in water together with a known binder such as a water-soluble polymer or an aqueous polymer emulsion, and the dispersion is applied to the surface of the support. Obtained by drying. In this case, the coating amount of the fine hollow particles is at least 1 g, preferably about ^{2 to} 15 g per 1 m ² of the support, and the coating amount of the binder resin may be an amount that strongly bonds the intermediate layer to the support. Usually, it is 2 to 50% by weight based on the total amount of the hollow microparticles and the binder resin.

When forming an intermediate layer containing the fine hollow particles and the pigment, the fine hollow particles and the pigment are dispersed in water together with a binder, applied to the surface of a support, and dried. Obtained by In this case, the amount of the inorganic or / and organic pigment used is determined by the fine hollow particles 1
It is in the range of 0.05 to 10 parts by weight, and particularly preferably in the range of 0.1 to 5 parts by weight with respect to parts by weight. This ratio is 0.0
When the amount is less than 5 parts by weight, the effect of excellent head matching properties is not sufficiently exhibited, and when the amount is more than 10 parts by weight, the coloring sensitivity becomes insufficient.

When the intermediate layer has a laminated structure of the first intermediate layer containing the fine hollow particles as a main component and the second intermediate layer containing the pigment as a main component, first, the support is carried out as described above. An intermediate layer containing the fine hollow particles as a main component (first
After the intermediate layer is provided, a second intermediate layer containing the pigment as a main component is provided thereon. The second intermediate layer, the pigment is dispersed in water together with a known water-soluble polymer, a binder such as an aqueous polymer emulsion, and applied to the surface of the support,
Obtained by drying. In this case, the coating amount of the pigment is at least 1 g, preferably about ^{2 to} 15 g per 1 m ^{2 of} the first intermediate layer, and the coating amount of the binder resin is such that the second intermediate layer is strongly bonded to the first intermediate layer. The amount is usually 2 to 50% by weight based on the total amount of the pigment and the binder resin.

In the present invention, the binder used for forming the intermediate layer is appropriately selected from conventionally known water-soluble polymers and / or aqueous polymer emulsions. Specific examples thereof include, as water-soluble polymers, for example, polyvinyl alcohol, starch and derivatives thereof, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, cellulose derivatives such as ethylcellulose, sodium polyacrylate,
Polyvinylpyrrolidone, acrylamide / acrylate copolymer, acrylamide / acrylate /
Examples include methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, alkali salt of isobutylene / maleic anhydride copolymer, polyacrylamide, sodium alginate, gelatin, casein and the like. Examples of the aqueous polymer emulsion include latexes such as styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer, vinyl acetate resin, vinyl acetate / acrylic acid copolymer, and styrene / acrylic acid ester copolymer. And emulsions of acrylate resin, polyurethane resin and the like.

In the intermediate layer of the present invention, if necessary, an auxiliary additive component commonly used in this type of heat-sensitive recording material, for example, a heat-sensitive recording material, together with the fine hollow particles, (possibly a pigment) and a binder. A fusible substance, a surfactant and the like can be used in combination. In this case, specific examples of the heat-fusible substance include various substances described below in relation to the heat-sensitive recording layer component.

Since the surface of the intermediate layer formed on the support as described above has considerable irregularities, the surface may be smoothed by calendering after the formation of the intermediate layer.

The leuco dye used in the heat-sensitive recording layer of the present invention may be used alone or as a mixture of two or more kinds. As such a leuco dye, those applied to this kind of heat-sensitive material may be arbitrarily applied. For example, leuco compounds of dyes such as triphenylmethane type, fluoran type, phenothiazine type, auramine type, spiropyran type and indolinophthalide type 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 violet lactone), 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 -Dimethylfluoran, 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'-trifluoromethylphenyl) amino} -6-diethylaminofluoran, 2- {3 6-bis (diethylamino)-
Lactam 9- (o-chloroanilino) xanthylbenzoate, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-di- n-butylamino-7- (o-chloroanilino) fluoran, 3-N-methyl-N, n-amylamino-6-
Methyl-7-anilinofluoran, 3-N-methyl-N
-Cyclohexylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 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-
(N-ethyl-N-tetrahydrofurfuryl) amino-
6-methyl-7-anilinofluoran, 3-N-ethyl-N- (2-ethoxypropyl) amino-6-methyl-
7-anilinofluoran, 3-N-methyl-N-isobutyl-6-methyl-7-anilinofluoran 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluoran, 3-pyrrolidino- 7-m-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- (pn-
Butylanilino) fluoran, 3- (N-methyl-N-
Isopropylamino) -6-methyl-7-anilinofluoran, 3-di-n-butylamino-6-methyl-7-
Anilinofluoran, 3,6-bis (dimethylamino)
Fluorene spiro (9,3 ')-6'-dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-7-α-naphthylamino-4'
-Bromofluorane, 3-diethylamino-6-chloro-7-anilinofluoran, 3-diethylamino-6
Methyl-7-mesitidino-4 ′, 5′-benzofluoran, 3-N-methyl-N-isopropyl-6-methyl-
7-anilinofluoran, 3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (2 ′, 4′-dimethylanilino) fluoran etc.

Further, as the color developer used in the heat-sensitive recording layer of the present invention, various compounds having an electron-accepting property or a oxidizing agent which develop the color of the leuco dye upon contact are applied. Such materials are conventionally known, and specific examples thereof include the following.

4,4'-isopropylidene diphenol, 4,4'-isopropylidenebis (o-methylphenol), 4,4'-secondarybutylidenebisphenol 4,4'-isopropylidenebis (2-tertiary) Butylphenol), zinc p-nitrobenzoate,
1,3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 2,2- (3,4'-dihydroxydiphenyl) propane, bis (4-hydroxy-3 -Methylphenyl) sulfide, 4- {β- (p-methoxyphenoxy) ethoxy} salicylic acid, 1,7-bis (4-hydroxyphenylthio) -3,5-dioxaheptane, 1,5-bis (4- (Hydroxyphenylthio) -5-oxapentane, monobenzyl phthalate monocalcium salt,
4,4'-cyclohexylidenediphenol, 4,4 '
-Isopropylidenebis (2-chlorophenol),
2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4'-butylidenebis (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-isopropoxy-4'-hydroxydiphenylsulfone, 4-benzyloxy-4'-hydroxydiphenylsulfone, 4,4 '-Diphenol sulfoxide, isopropyl P-hydroxybenzoate,
Benzyl P-hydroxybenzoate, benzyl protocatechuylate, stearyl gallate, lauryl gallate, octyl gallate, 1,3-bis (4-hydroxyphenylthio) -propane, N, N′-diphenylthiourea,
N, N'-di (m-chlorophenyl) thiourea, salicylanilide, methyl bis- (4-hydroxyphenyl) acetate, benzyl bis- (4-hydroxyphenyl) acetate, 1,3-bis (4-hydroxycumyl) )benzene,
1,4-bis (4-hydroxycumyl) benzene, 2,
4'-diphenol sulfone, 2,2'-diallyl-4,
4'-diphenolsulfone, 3,4-dihydroxyphenyl-4'-methyldiphenylsulfone, zinc 1-acetyloxy-2-naphthoate, 2-acetyloxy-
Zinc 1-naphthoate, zinc 2-acetyloxy-3-naphthoate, α, α-bis (4-hydroxyphenyl)-
α-methyltoluene, antipyrine complex of zinc thiocyanate, tetrabromobisphenol A, tetrabromobisphenol S, 4,4′-thiobis (2-methylphenol), 4,4′-thiobis (2-chlorophenol) and the like.

In the heat-sensitive recording layer of the present invention, in order to apply the leuco dye and the color developing agent on the intermediate layer, various conventional binders can be appropriately used. And the same as those exemplified in the application of the intermediate layer.

Further, in the heat-sensitive recording layer of the present invention, together with the leuco dye and the developer, if necessary, an auxiliary additive component commonly used in this type of heat-sensitive recording material, for example, a pigment, a heat-fusible material, Substances, surfactants and the like can be used in combination. In this case, as the pigment, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc,
In addition to inorganic fine powders such as calcium and silica surface-treated, organic fine powders such as urea-formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin can be used. As, for example, in addition to higher fatty acids or their esters, amides or metal salts,
Various waxes, condensates of aromatic carboxylic acids and amines, phenyl benzoate, higher linear glycols,
50 to 20 such as 3,4-epoxy-dialkyl hexahydrophthalate, higher ketone, and other heat-fusible organic compounds
Those having a melting point of about 0 ° C. are mentioned.

In the present invention, a layer containing a pigment, a binder, a heat-fusible substance or the like may be provided as an additional intermediate layer between the intermediate layer and the heat-sensitive recording layer, if necessary. In this case, specific examples of the pigment, the binder, and the heat-fusible substance include those similar to those exemplified in relation to the heat-sensitive recording layer or the intermediate layer.

Further, in the heat-sensitive recording material of the present invention, a protective layer can be provided on the heat-sensitive recording layer for the purpose of improving the matching property of a thermal head or the like and further improving the preservability of a recorded image. In this case, as the components constituting the protective layer, the above-mentioned pigments, binders, surfactants, and heat-fusible substances can also be used.

The heat-sensitive recording material of the present invention is produced, for example, by applying the above-mentioned coating liquid for forming each layer on a suitable support such as paper, synthetic paper, plastic film or the like, and drying. Applied in the recording field.

[0031]

Next, the present invention will be described in more detail with reference to examples. The parts and percentages shown below are based on weight.

Example 1 (Reference Example) [Solution A] 20 parts of 3- (N-methyl-3-N-cyclohexyl) amino 20 parts of a 10% aqueous solution of 6-methyl-7-anilinofluoran polyvinyl alcohol 20 parts Water 60 Department

[Solution B] 1,5-bis (4-hydroxyphenylthio) -3-oxapentane 10 parts Polyvinyl alcohol 10% aqueous solution 25 parts Calcium carbonate 15 parts Water 50 parts

The mixture composed of the above composition was dispersed using a sand mill so that the average particle diameter was 2 μm or less and 2.5 μm or less, respectively, to prepare [Solution A] and [Solution B].

[Liquid C] Fine hollow particle dispersion (copolymer resin mainly composed of vinylidene chloride and 30 parts of acrylonitrile) (solid content: 32%, average particle diameter: 5 μm, hollow ratio: 92%) Styrene / butadiene copolymer Combined latex 10 parts (solid content 47.5%) Water 60 parts

The mixture having the above composition was stirred and dispersed to prepare a liquid for forming an intermediate layer.
/ M ² ), and then dried and coated to a weight of 5 g / m ² to obtain an intermediate layer coated paper.

Next, the above [Solution A] and [Solution B] were mixed and stirred at a weight ratio of 1:10 to prepare a heat-sensitive recording layer forming solution, which was coated on the surface of the above-mentioned intermediate layer coated paper. After drying, a heat-sensitive recording layer is formed by applying the heat-sensitive recording layer to a weight of 5 g / m ² and then subjected to a super calender treatment so that the Beck smoothness is 600 to 700 seconds. Obtained.

Example 2 (Reference Example) Instead of the fine hollow particle dispersion in [C solution] of Example 1, another fine hollow particle dispersion (a copolymer resin mainly composed of vinylidene chloride and acrylonitrile; solid) The heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the partial concentration was 30%, the average particle diameter was 9 μm, and the hollow ratio was 93%.

Comparative Example 1 Instead of the fine hollow particles in [C solution] of Example 1,
Fine hollow fine particles having a hollow ratio of 75% and an average particle diameter of 0.4 μm (OP-62, manufactured by Rohm and Haas Co., solid content concentration: 3)
7.5%) to obtain a comparative thermosensitive recording material in the same manner as in Example 1.

Comparative Example 2 Instead of the fine hollow particles in [C solution] of Example 1,
Plastic spherical solid particles (Mitsui Toatsu: SPMM
-HS, solids concentration 47%)
In the same manner as in the above, a heat-sensitive recording material for comparison was obtained.

Example 3 [Liquid D] Fine hollow particle dispersion (copolymer resin mainly composed of vinylidene chloride and acrylonitrile) 25 parts (solid content: 32%, average particle diameter: 5 μm, hollow ratio: 92%) Inorganic pigment (Silica; oil absorption 135 ml / 100 g) 2 parts Styrene / butadiene copolymer latex (solid content concentration 47.5%) 8 parts Water 80 parts

An intermediate layer forming liquid was prepared by stirring and dispersing the mixture having the above-mentioned composition.
/ M ² ), and then dried and coated to a weight of 5 g / m ² to obtain an intermediate layer coated paper. Thereafter, the heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 using the obtained intermediate layer coated paper.

Example 4 [E liquid] 15 parts of fine hollow particle dispersion (copolymer resin mainly composed of vinylidene chloride and acrylonitrile) (solid content: 32%, average particle diameter: 5 μm, hollow ratio: 92%) Inorganic pigment (Silica; oil absorption 135 ml / 100 g) 5 parts Styrene / butadiene copolymer latex (solid content concentration 47.5%) 8 parts Water 80 parts

A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 3, except that [Solution E] was used instead of [Solution D].

Example 5 Instead of the inorganic pigment in [D solution] of Example 3, an organic pigment (OP-62, manufactured by Rohm and Haas Co., solid content concentration: 3) was used.
7.5%) to obtain a heat-sensitive recording material of the present invention in the same manner as in Example 3.

Example 6 Instead of the inorganic pigment in [E solution] of Example 4, an organic pigment (OP-62, manufactured by Rohm and Haas Co., solid content concentration: 3) was used.
7.5%) to obtain a heat-sensitive recording material of the present invention in the same manner as in Example 4.

Example 7 [Solution F] Inorganic pigment (silica: oil absorption 135 ml / 100 g) 10 parts Styrene / butadiene copolymer latex (solid content concentration 47.5%) 10 parts Water 80 parts

The mixture having the above-mentioned composition was stirred and dispersed to prepare a pigment-containing intermediate layer forming solution, which was dried on the surface of the intermediate layer coated paper obtained in Example 1 to a weight of 5 g / m ² after drying. And dried as described above to provide a second intermediate layer. Since then
Using the obtained first and second interlayer coated papers, a heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1.

Example 8 Instead of the inorganic pigment in [F solution] of Example 7, an organic pigment (OP-62, manufactured by Rohm and Haas Co., solid concentration: 3) was used.
7.5%) to obtain a heat-sensitive recording material of the present invention in the same manner as in Example 7.

Each of the heat-sensitive recording materials obtained as described above was tested for dynamic color sensitivity, dot reproducibility and head matching. Table 1 shows the results. The test was performed as follows.

Dynamic color development: A thermal power test apparatus having a thin film head manufactured by Matsushita Electronic Parts Co., Ltd.
Printing was performed with pulse widths of 0.3, 0.4, 0.5 and 0.6 msec under the conditions of 5 w / dot, 1 line recording time of 20 msec / 1, and scanning line density of 8 × 3.85 dots / mm.
The print density was measured with a Macbeth densitometer RD-914.

Dot reproducibility: Images obtained by the test method of dynamic color development sensitivity were visually evaluated. …: Excellent, Δ: slightly inferior (slightly pinhole generated), x: inferior.

Head matching property: Judgment was made based on the amount of scum adhering to the thermal head after the printing test and the stick sound. …: Excellent, ×: inferior.

[0054]

[Table 1]

From the results shown in Table 1, it can be seen that the heat-sensitive recording material of the present invention has high dynamic color sensitivity and excellent dot reproducibility. In addition, it can be seen that those containing the pigment in the intermediate layer are also excellent in head matching.

[0056]

According to the first aspect of the present invention, there is provided a heat-sensitive recording material comprising a thermoplastic resin between a support and a heat-sensitive recording layer.
Since an intermediate layer mainly composed of fine hollow particles having a hollow ratio of 10% or more and a hollow ratio of 90% or more is provided, the dynamic coloring sensitivity is high and the dot reproducibility is excellent.

The heat-sensitive recording material according to claims (2) and (3) further comprises an inorganic or / and organic pigment having an oil absorption of 30 ml / 100 g or more in the intermediate layer, or contains the pigment as a main component. Since the second intermediate layer is laminated on the intermediate layer containing the fine hollow particles as a main component, an effect that the head matching property is further improved is added.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shuji Miyamoto 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP 4-129797 (JP, A) JP 4-201481 (JP, A) JP-A-4-219275 (JP, A)

Claims (3)

(57) [Claims] 1. A heat-sensitive recording material comprising a support, on which an intermediate layer and a heat-sensitive recording layer containing a leuco dye and a developer for causing the leuco dye to develop color upon heating are successively laminated.
The intermediate layer is made of a thermoplastic resin and has an average particle diameter of 2 to 10.
Micro hollow particles with a hollow ratio of 90% or more and an oil absorption of 3 μm
A heat-sensitive recording material comprising, as a main component, 0 ml / 100 g or more of an inorganic and / or organic pigment. 2. A heat-sensitive recording material comprising a support, on which an intermediate layer and a heat-sensitive recording layer mainly containing a leuco dye and a color developing agent which causes the leuco dye to develop color when heated are sequentially laminated.
The intermediate layer is made of a thermoplastic resin and has an average particle diameter of 2 to 10.
From a laminate of a first intermediate layer mainly composed of fine hollow particles having a hollow ratio of 90% or more and a second intermediate layer mainly composed of an inorganic or / and organic pigment having an oil absorption of 30 ml / 100 g or more. A heat-sensitive recording material characterized in that: 3. A heat-sensitive recording material according to claim 1 or 2 wherein the thermoplastic resin is a copolymer resin composed mainly of vinylidene chloride and acrylonitrile.