JP2001018528A - Two-color developing thermosensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-color developing thermosensitive recording material being excellent in separability of two colors in heat printing and excellent in the matching property with a thermal head. SOLUTION: In a two-color developing thermosensitive recording material having a structure wherein first and second thermosensitive coloring layers differing in coloring energy and coloring in different color tones are laminated on a substrate so that the layer of the smaller coloring energy is the upper, an intermediate layer is provided between the two thermosensitive coloring layers and made to contain a thermally fusible substance of which the average particle size is 1.0 μm or below and the melting point 90 deg.C or above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-color heat-sensitive recording material having a color-forming layer that develops different colors. More specifically, the present invention relates to a two-color heat-sensitive recording material having excellent color tone and two-color separability and excellent matching with a thermal head.

[0002]

2. Description of the Related Art A heat-sensitive recording material utilizing a colorless or pale-colored color-forming substance and a color-developing substance capable of coloring the color-forming substance when heated is disclosed in JP-B-43-4160 and JP-B-45-140.
No. 39, etc., which are widely used. In general,
The heat-sensitive recording material is prepared by separately dispersing a developer such as a leuco dye and a phenolic substance into fine particles, and then mixing the two, and then adding additives such as a binder, a sensitizer, a filler, and a lubricant. Is added to form a coating liquid, coated on a support such as paper, film, synthetic paper, etc., and one or both of the leuco dye and the developer are melted by heating, and a color reaction record is formed by a chemical reaction caused by contact. The heat-sensitive recording material is usually prepared in the form of a sheet. A thermal printer or the like having a built-in thermal head is used for coloring the heat-sensitive recording sheet. This thermal recording method, compared to other recording methods,
(1) No noise during recording, (2) No need for development and fixing, (3) Simple recording method and compact device, (4) Maintenance-free, (5) Machine Features such as relatively inexpensive, facsimile field, computer output, printers such as calculators, recorders for medical measurements, automatic ticket vending machines,
Widely used in the field of thermosensitive label.

[0003] In these fields, in particular, there is an attempt to promote sales by changing the color of POP characters in food POS labels, and the demand for a two-color heat-sensitive recording material is increasing. A conventional two-color heat-sensitive recording material is generally formed by stacking two types of high-temperature and low-temperature color-forming layers that develop different colors with different coloring energies on a support such as paper or film. It can be roughly classified into the following two types.

[0004] One of the methods is to obtain a high-temperature coloring image through a low-temperature coloring image to obtain a high-temperature coloring image having a color tone different from the color tone of the low-temperature coloring layer. . The other is to use a decoloring agent for erasing the low-temperature coloring layer when the high-temperature coloring layer is colored, thereby suppressing the coloring of the low-temperature coloring layer and obtaining the color tone of the high-temperature coloring layer.

However, the type using the decoloring agent has a complicated mechanism as compared with the simply laminated type, and the decolorizing agent acts over time, causing a reduction in color density and a problem in recording preservation. Was. Therefore, Japanese Patent Application Laid-Open No. 61-215086
Japanese Patent Application Laid-Open Publication No. H11-163, the disclosure of which limits the amount of color developer in the low-temperature coloring layer in order to maximize the decoloring effect,
Storage stability was insufficient. Also, in the case of the laminated type, the degree of color mixing varies with printing conditions during heating printing, so that there is a disadvantage that it is difficult to obtain an image having a constant and stable color tone. Further, in the case of high-temperature printing, a region having the same temperature as that of low-temperature printing always occurs around the periphery thereof, so that there is a disadvantage that a low-temperature coloring region is generated around a high-temperature printing image (the two-color separation is poor). ).

Accordingly, Japanese Patent Application Laid-Open No. Hei 5-169802 states that if an intermediate layer containing a heat-fusible substance is provided, the separation properties of the respective color-forming layers are excellent, but the problem remains that the matching property with the thermal head is poor. . Japanese Patent Application Laid-Open No. 8-156409 discloses a technique using an intermediate layer of styrene butadiene latex.
With only styrene-butadiene latex, the heat separation effect at the time of low-temperature coloring was insufficient, and a clear printed image was not obtained.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a two-color heat-sensitive recording material which has improved the above-mentioned drawbacks, that is, has excellent two-color separation during heating printing and excellent matching with a thermal head. Is to do.

[0008]

Means for Solving the Problems The present inventors have intensively studied to improve the above-mentioned disadvantages of the two-color heat-sensitive recording material and completed the present invention. That is, the present invention relates to a two-color heat-sensitive recording method in which first and second thermosensitive coloring layers having different coloring energies and different colors are formed on a support such that the lower coloring energy layer is the upper layer. In the material, between the two thermosensitive coloring layers,
This can be achieved by forming an intermediate layer containing a heat-fusible substance having an average particle diameter of 1.0 μm or less and a melting point of 90 ° C. or more as a main component, and further containing a styrene-butadiene latex. Since the intermediate layer improves the color separation, the styrene-butadiene latex improves the elasticity of the entire heat-sensitive recording layer and also improves the matching property (adhesion, etc.) with the thermal head.

The object of the present invention is to provide (1) the first and second thermosensitive coloring layers having different coloring energies on the support and having different color tones, respectively. In the two-color heat-sensitive recording material stacked so as to be an upper layer, an intermediate layer is provided between the two heat-sensitive color forming layers, the average particle size is 1.0 μm or less, and the melting point is 90 ° C.
(2) The use of an emulsified dispersion of polyethylene wax or a higher fatty acid compound as the heat-fusible substance of the intermediate layer, wherein the heat-fusible substance contains the above-mentioned heat-fusible substance. (2) The two-color heat-sensitive recording material according to the above (1), wherein the intermediate layer contains a styrene-butadiene latex. And the two-color heat-sensitive recording material described in the item.

The two-color heat-sensitive recording material of the present invention comprises a support, a first heat-sensitive color-forming layer, an intermediate layer, and a second heat-sensitive color-forming layer which forms a color with an energy smaller than that of the first heat-sensitive color-forming layer. An under layer mainly composed of hollow particles for improving the color developing property of the first color forming layer may be provided on the support.

Normally, in a two-color thermosensitive recording paper of a laminated type, an intermediate layer mainly composed of a heat-fusible substance is provided between the first thermosensitive coloring layer and the second thermosensitive coloring layer. Thus, a clear color image can be obtained at the time of heating printing (2).
It is known that color separation is excellent). However, in this case, if a heat-fusible substance having a low melting point (60 ° C. to 80 ° C.) is used for the intermediate layer, the layer is destroyed by heat at the time of heating printing, and the matching property is deteriorated. Be impaired. Also, when a heat-fusible substance having a large average particle size (1.0 μm or more) is used for the intermediate layer, the interlayer binding property is deteriorated, and the plasticizer property and other preservability are poor. So 2
As a result of studying a means for improving the matching property while maintaining the color separation property, the present invention was achieved.

In the present invention, the first thermosensitive coloring layer and the second thermosensitive coloring layer
It is possible to form an intermediate layer comprising a heat-fusible substance having an average particle size of 1.0 μm or less and a melting point of 90 ° C. or more as a main component, more preferably a styrene-butadiene latex, between the heat-sensitive coloring layer and the thermosensitive coloring layer. is necessary. As the heat-fusible substance of the present invention used for the intermediate layer, those described below that are hardly involved in natural or synthetic color development are used,
It is necessary to satisfy the average particle size and melting point, and an emulsified dispersion of polyethylene wax and a higher fatty acid compound is preferable. Further, the amount of use is suitably 30% to 95% of the total weight of the intermediate layer from the viewpoint of the heat control function as the intermediate layer. According to the present invention, the styrene-butadiene latex is used by adding it to the intermediate layer.
To 50%, preferably 5% to 30%, and if it is too large, the two-color separability will be reduced. The intermediate layer has a dry weight of 5 g / m ² or less, preferably 0.5 to ³ g, on a support.
/ M ² . The first thermosensitive coloring layer has a dry weight of 3 to 10 g / m ² , preferably 4 to 7 g / m ² ,
The second thermosensitive coloring layer 1-8 g / m ² by weight of the dry, preferably can be provided respectively 2 to 6 g / m ^2.

In order to increase the sensitivity of the first color forming layer,
It is also possible to provide an under layer mainly composed of hollow particles. As the hollow particles, those used in ordinary thermosensitive recording materials can be used, and the weight when dried is 2 to 2.
10 g / m ^2, preferably can be provided in a range of 2.5~7g / m ^2.

The protective layer can be made of the same material as that of a normal thermosensitive recording material, and is provided in the range of ^{2 to} 8 g / m ² , preferably 2.5 to 5 g / m ² . Examples of the color-forming compound used in the first heat-sensitive color-forming layer having a large color-forming energy serving as the lower layer are selected from blue / green or black colors generally used in pressure-sensitive recording paper and thermosensitive recording paper. However, for the purpose of utilizing for food POS, those that develop black color are most preferable. Specific examples thereof include, for example, fluoran compounds, triarylmethane compounds, spiro compounds, diphenylmethane compounds, thiazine compounds, lactam compounds, fluorene compounds, and the like. Preferably have at least one maximum absorption wavelength between 550 and 1000 nm.

Among them, fluoran compounds include, for example, 3-diethylamino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3- (N-methyl- N-cyclohexylamino) -6-methyl-7-anilinofluoran, 3
-(N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluoran, 3- (N-isobutyl-
N-ethylamino) -6-methyl-7-anilinofluoran, 3- [N-ethyl-N- (3-ethoxypropyl) amino] -6-methyl-7-anilinofluoran,
3- (N-ethyl-N-hexylamino) -6-methyl-7-anilinofluoran, 3-dipentylamino-6
-Methyl-7-anilinofluoran, 3- (N-methyl-N-propylamino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-N-tetrahydrofurylamino) -6 Methyl-7-anilinofluoran, 3-
Diethylamino-6-methyl-7- (p-chloroanilino) fluoran, 3-diethylamino-6-methyl-7
-(P-fluoroanilino) fluoran, 3- (p-toluidinoethylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (p
-Toluidino) fluoran, 3-diethylamino-7-
(3,4-dichloroanilino) fluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro-7-ethoxyethylaminofluoran, 3-diethylamino-6-chloro- 7-anilinofluoran, 3-diethylamino-7-phenylfluoran, 3- (p-toluidinoethylamino) -6
Methyl-7-phenethylfluoran and the like.

Further, as the tolylmethane compound,
For example, 3,3-bis (p-dimethylaminophenyl)-
6-dimethylaminophthalide (alias: crystal violet lactone or CVL), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,2-dimethylaminoindole -3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl)
Phthalide, 3- (p-dimethylaminophenyl) -3-
(2-phenylindol-3-yl) phthalide, 3,
3-bis (1,2-dimethylindol-3-yl)-
5-dimethylaminophthalide, 3,3-bis (1,2-
Dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazole-3)
-Yl) -5-dimethylaminophthalide, 3,3- (2
-Phenylindol-3-yl) -5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-
(1-methylpyrrol-2-yl) -6-dimethylaminophthalide and the like.

Further, as the spiro compound, for example, 3
-Methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-propylspirobenzopyran, 3-methylnaphtho- (3-methoxybenzopyran ) Spiropyran, 1,3,3-trimethyl-6
-Nitro-8'-methoxyspiro (indoline-2,
2′-benzopyran) and the like as diphenylmethane-based compounds, for example, N-halophenyl-leukoauramine, 4,4-bis-dimethylaminophenylbenzhydryl benzyl ether, N-2,4,5-trichlorophenylleucoura As a thiazine-based compound, for example, benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue, and as a lactam-based compound, for example, rhodamine B anilinolactam,
Rhodamine B-p-chloroanilinolactam and the like are fluorene-based compounds, for example, 3,6-bis (dimethylamino) fluorenespiro (9,3 ′)-6′-dimethylaminophthalide, 3,6-bis (Dimethylamino)
Fluorene spiro (9,3 ')-6'-pyrrolidinophthalide, 3-dimethylamino-6-diethylaminofluorene spiro (9,3')-6'-pyrrolidinophthalide and the like. These coloring compounds are used alone or in combination.

Examples of the red-based leuco dye used in the second thermosensitive coloring layer include 3-diethylamino-6-methyl-7-chlorofluorane, 3-cyclohexylamino-6-chlorofluoran, Diethylamino-benzo [α] fluoran, 3-dibutylamino-benzo [α] fluoran, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluoran, 3-N-ethyl-N-isoamylamino- Benzo [α] fluoran, 3-N-ethyl-N-p-methylphenylamino-7-methylfluoran, 3-diethylamino-6,8-dimethylfluoran, 3-dibutylamino-6-methyl-7-bromo Fluoran, 3,6-bis (diethylaminofluoran) -γ- (4′-nitro)
Anilinolactam, bis (1-n-butyl-2-methylindol-3-yl) phthalide, bis (1-ethyl-
2-methylindol-3-yl) phthalide and the like.

Further, a leuco dye which emits blue, green, yellow or the like can be used.
-Diethylaminophenyl) -3- (1-ethyl-2-
Methylindolyl-3-yl) phthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4- Diethylaminophenyl) -3-
(1-Methyl-2-methylindolyl-3-yl) phthalide, 3- (4-diethylamino-2-methylphenyl) -3- (1-ethyl-2-methylindolyl-3-
Yl) phthalide, 3,3-bis (4-dimethylaminophenyl) -6-diethylaminophthalide, 3,7-bis (4-dimethylamino) -10-benzolylphenothiazine, 3,3-bis (4-diethylamino -6-ethoxyphenyl) -4-azaphthalide, 3-diethylamino-7-dianilinofluoran, 3-N-ethyl-N-4
-Methylphenylamino-7-N-methylanilinofluoran, 3-diethylamino-7-N-dibenzylaminofluoran, 3,6-dimethoxyfluoran, 3,6
-Dibutoxyfluorane, 3'-methoxy-4-lanoxyphenyl-2-cytyrylquinoline, 2 ', 4'-dioctoxyphenyl-2-cytyrylquinoline and the like.

The color-developing compound is not particularly limited as long as it is generally used in pressure-sensitive recording paper or heat-sensitive recording paper. When used in the second color-forming layer, the color-forming property, color reproducibility, and storage From the viewpoint of stability, it is preferable to use bis (3-allyl-4-hydroxyphenyl) sulfone. Other specific examples include, for example, α-naphthol, β-naphthol, p-octylphenol, 4-t-octylphenol, pt-butylphenol, p-phenylphenol, 1,1-bis (p-hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl) propane (alias: bisphenol A or BPA), 2,2-bis (p-hydroxyphenyl) butane, 1,1-bis (p-hydroxyphenyl) cyclohexane, 4,4 '
-Thiobisphenol, 4,4'-cyclohexylidenediphenol, 2,2 '-(2,5-dibromo-4-hydroxyphenyl) propane, 4,4-isopropylidenebis (2-t-butylphenol), 2, 2'-methylenebis (4-chlorophenol), 4,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-methoxydiphenylsulfone, 4-hydroxy-4'-ethoxydiphenylsulfone, 4-hydroxy-4'-iso Propoxydiphenyl sulfone, 4-hydroxy-
4'-butoxydiphenyl sulfone, methyl bis- (4-hydroxyphenyl) acetate, butyl bis- (4-hydroxyphenyl) acetate, benzyl bis- (4-hydroxyphenyl) acetate, 2,4-dihydroxy-2'-methoxy Phenolic compounds such as benzanilide, benzyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, dibenzyl 4-hydroxyphthalate, dimethyl 4-hydroxyphthalate, ethyl 5-hydroxyisophthalate, 3,5-di-t -Butylsalicylic acid, 3,5-di-
An aromatic carboxylic acid derivative such as α-methylbenzylsalicylic acid, an aromatic carboxylic acid, a metal salt and the like can be mentioned.

A binder and a filler are used in the under layer, the coloring layer, the intermediate layer, and the protective layer, if necessary. Examples of fillers that can be used include calcium carbonate, magnesium carbonate,
Examples include magnesium oxide, silica, white carbon, talc, clay, alumina, magnesium hydroxide, aluminum hydroxide, aluminum oxide, barium sulfate, polystyrene resin, and urea-formalin resin. Further, as the hollow particles used in the under layer in the present invention, those made of an acrylic resin such as an acrylate ester or acrylonitrile, a styrene resin such as styrene, or a copolymer resin thereof can be used.

Examples of the binder include methylcellulose, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, cellulose, polyvinyl alcohol (PVA), carboxyl group-modified polyvinyl alcohol, sulfonic acid group-modified polyvinyl alcohol, polyvinylpyrrolidone, and the like. Polyacrylamide, polyacrylic acid,
Water-soluble or poly such as starch and its derivatives, casein, gelatin, water-soluble isoprene rubber, alkali salt of styrene / maleic anhydride copolymer, alkali salt of iso (or diiso) butylene / maleic anhydride copolymer, etc. Vinyl acetate, vinyl chloride / vinyl acetate copolymer, polystyrene, polyacrylate, polyurethane, styrene / butadiene (SB) copolymer, carboxylated styrene / butadiene (SB) copolymer, styrene / butadiene / acrylic acid Examples thereof include copolymers, hydrophobic polymer emulsions such as composite particles of colloidal silica and an acrylic resin, and the like.

In the second color-forming layer, a heat-fusible compound called a sensitizer is used if necessary for the purpose of improving sensitivity. Examples of heat-fusible compounds that can be used include, for example, 1-
Benzyloxynaphthalene, 2-benzyloxynaphthalene, 1-hydroxynaphthoic acid phenyl ester and the like,
1,2-diphenoxyethane, 1,4-diphenoxyethane, 1,2-bis (3-methylphenoxy) ethane,
1,2-bis (4-methoxyphenoxy) ethane and the like,
1,2-bis (3,4-dimethylphenyl) ethane, 1
Phenoxy-2- (4-chlorophenoxy) ethane,
Benzyl p-hydroxybenzoate, such as 1-phenoxy-2- (4-methoxyphenoxy) ethane,
Benzyloxybenzoic acid benzyl ester, terephthalic acid dibenzyl ester, etc., p-toluenesulfonic acid phenyl ester, phenyl mesitylene sulfonate, 4-
Diphenyl carbonate, dibenzyl oxalate, dioxalate (4-methylphenyl mesitylene sulfonate, etc.)
P-benzylbiphenyl, p-allyloxybiphenyl, 4-acetylbiphenyl, m-methylbenzyl) ester, oxalic acid di (4-chlorobenzyl) ester, etc.
Terphenyl and the like.

In addition to the above-mentioned heat-fusible substance, the following heat-fusible substance called wax, which hardly contributes to the color-forming property, can be added to the second color-forming layer. Examples thereof include waxes such as animal and vegetable waxes and synthetic waxes, higher fatty acids, higher fatty acid amides, higher fatty acid anilides, and acetylated aromatic amines. Among them, higher fatty acid amides are most suitable for the storage stability of the first color forming layer during immersion in water.

As other waxes, for example, wood wax,
Carnauba wax, shellac, montan wax, paraffin oxide, polyethylene wax, polyethylene oxide and the like, higher fatty acids such as stearic acid and behenic acid, and higher fatty acid amides such as stearamide, oleic acid amide and N- Methyl stearamide, erucamide, methylolbehenamide,
Methylol stearic acid amide, methylene bis stearic acid amide, ethylene bis stearic acid amide, etc., as higher fatty acid anilide, for example, stearic acid anilide, linoleic acid anilide, etc., as acetylated aromatic amine, acetotoluidide, etc. Is exemplified.

A lubricant such as zinc stearate, calcium stearate, aluminum stearate, etc., various surfactants, an antifoaming agent and the like may be added to the coloring layer and the protective layer as required. The heat-sensitive recording material of the present invention is prepared by using the above-mentioned materials by, for example, the following method. That is, first, a basic leuco dye for the first thermosensitive coloring layer, a basic leuco dye for the second thermosensitive coloring layer, a developer and the like are separately bonded or a ball mill together with other additives as necessary. After pulverizing and dispersing with a dispersing machine such as an attritor or a sand mill (usually using water as a medium when the pulverizing and dispersing are performed by a wet method), they are mixed and coated with the first thermosensitive coloring layer coating solution and the second thermosensitive coloring layer coating solution. Each solution is prepared.
Separately, an under layer coating solution, an intermediate layer coating solution, and a protective coating solution are respectively prepared using a binder or other additives as necessary. When an under layer is provided on a support such as paper, plastic sheet, synthetic paper, etc.
Coating and drying are repeated in the order of forming the first thermosensitive coloring layer, the intermediate layer, the second thermosensitive coloring layer, and the protective layer to obtain the thermosensitive recording material of the present invention.

[0027]

EXAMPLES The present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. In the examples, "parts" indicates parts by weight. (Example 1) [Preparation of first thermosensitive coloring layer] A mixture having the following composition was pulverized and dispersed using a sand grinder so that the average particle diameter became 1 µm or less, and [A] solution and [B] solution were respectively obtained. Prepared. [A] solution: 3- (N-ethyl-N-4-methylphenylamino) -6-methyl-7-anilinofluoran 20 parts 10% PVA aqueous solution 20 parts water 60 parts [B] solution: bis (3 -Allyl-4-hydroxyphenyl) sulfone 10 parts Silica (P-603 manufactured by Mizusawa Chemical) 10 parts 10% PVA aqueous solution 20 parts Water 60 parts Then, each prepared solution was used for 10 parts of [A] solution and 50 parts of [B] solution. To prepare a first thermosensitive coloring layer coating solution, and
It was applied to a high-quality paper of 0 g / m ^{2 so} as to have a dry weight of about 5 g / m ^2, and dried to form a first thermosensitive coloring layer of black color.

(Formation of Intermediate Layer) An intermediate layer solution having the following composition was prepared.
And a weight of about 2 g / m when dried on the first thermosensitive coloring layer. ^Two
And dried to form an intermediate layer. 5 parts of 10% PVA aqueous solution, 20 parts of 40% zinc stearate emulsion (Himilokun F-930, manufactured by Chukyo Yushi, average particle size: 0.9 μm, melting point: 145 ° C)

(Formation of the second thermosensitive coloring layer) A mixture having the following composition was pulverized and dispersed using a sand grinder so as to have an average particle diameter of 1 μm or less, and each of the liquid [C]
Solutions [D] and [E] were prepared. [C] solution: bis (3-allyl-4-hydroxyphenyl) sulfone 20 parts 10% PVA aqueous solution 20 parts water 60 parts [D] solution: 3-diethylamino-7-chloroanilinofluoran 20 parts 10% PVA aqueous solution 20 parts water 60 parts [E] solution: oxalic acid di (4-methylbenzyl) ester 10 parts silica (P-603 manufactured by Mizusawa Chemical) 10 parts water 60 parts Then, each prepared solution was mixed with 10 parts of solution [C] and [D]. ] 10 parts of liquid,
[E] A solution of the second thermosensitive coloring layer was prepared by mixing 20 parts of the solution, and the weight of the intermediate layer after drying was about 4 g / d
m ² and dried to form a red-colored second thermosensitive coloring layer.

(Formation of Protective Layer) A mixture having the following composition was pulverized and dispersed using a sand grinder so that the average particle diameter became 1 μm or less, to thereby prepare liquids [F]. [F] solution: 20 parts of aluminum hydroxide 20 parts of a 10% PVA aqueous solution 20 parts of water 40 parts Next, a protective layer solution [G] solution having the following composition was prepared and weighed about 3 g / m on the second thermosensitive coloring layer when dried. to form a protective layer was coated and dried to be ^2. [G] solution: [F] solution 10 parts 10% PVA aqueous solution 20 parts 12.5% epichlorohydrin aqueous solution 5 parts 30% zinc stearate (Chukyo Yushi Hydrin Z-730) 2 parts Further calender treatment is performed, and the surface is treated. With the use of an Oken-type smoothness meter, 2000 s, a two-color-developed thermosensitive recording paper of the present invention was obtained.

Example 2 In Example 1, 30% zinc stearate emulsion of the intermediate layer solution was used instead of 30%.
% Polyethylene wax (Hoechst Synthetic T-531)
(a: average particle size: 0.11, melting point: 105 ° C.) A two-color heat-sensitive recording paper of the present invention was obtained in the same manner except that the above-mentioned conditions were used.

(Example 3) A two-color heat-sensitive recording paper of the present invention was obtained in the same manner as in Example 1, except that 1 part of 50% styrene-butadiene latex was added to the coating solution for the intermediate layer.

Example 4 A two-color heat-sensitive recording paper for comparison was obtained in the same manner as in Example 3, except that 20 parts of the solution [C] was added to the coating solution for the intermediate layer.

Comparative Example 1 A two-color heat-sensitive recording paper for comparison was obtained in the same manner as in Example 3 except that the 40% zinc stearate emulsion of the intermediate layer liquid was omitted.

(Comparative Example 2) In Example 1, 30% zinc stearate emulsion of the intermediate layer solution was used instead of 30%.
% Paraffin wax (Hydrin D-33 made by Chukyo Yushi)
8: An average particle size of 0.8 μm and a melting point of 77 ° C. were used in the same manner as above to obtain a two-color heat-sensitive recording paper for comparison.

(Comparative Example 3) In Example 1, 30% zinc stearate emulsion of the intermediate layer solution was used instead of 30%.
% Of zinc stearate emulsion (Hydrin Z-730, manufactured by Chukyo Yushi Co., Ltd .; average particle size: 4.0 μm, melting point: 145 ° C.).

(Comparative Example 4) In Example 1, 30% zinc stearate emulsion of the intermediate layer liquid was replaced with 30%.
% Methylol stearic acid amide emulsion (Hydrin D-757 manufactured by Chukyo Yushi Co., Ltd .; average particle size 2.7 μm, melting point 110 ° C.) was used in the same manner to obtain a two-colored thermosensitive recording paper for comparison.

(Comparative Example 5) In Example 4, a 40% zinc stearate emulsion of the intermediate layer liquid was added from 20 parts to 4 parts.
The same two-color thermosensitive recording paper was obtained in the same manner except that the number of parts was changed. Table 1 shows the quality performance of the heat-sensitive recording papers of the present invention and the comparative two-colored heat-sensitive recording paper obtained as described above.

[0039]

[Table 1]

1) Matching test: Using a thermal printing apparatus TH-PMD manufactured by Okura Electric Co., Ltd., and using a head energy of 1.2
A printing test was performed under the conditions of mj / dot, a printing speed of 4 ms / line, and a platen pressure of 6 kgf / line, and the surface of the printing surface was visually observed using an optical microscope to make a judgment. (Judgment Criteria) ：: No layer peeling and good matching. ：: Little layer peeling is observed. Δ: The second coloring layer was peeled off, and the first coloring layer was confirmed. X: The first color-forming layer was almost turned up. 2) Two-color separation test: Thermal printing device TH-P manufactured by Okura Electric
Using MD, head energy 0.30 mj / dot
Perform a print test on the low temperature side under the conditions
The coloring of the coloring layer was determined. (Judgment criteria) ：: Clear red. ×: Red mixed with blackness.

[0041]

As is apparent from the above detailed and specific description, the two-color heat-sensitive recording material of the present invention has excellent matching properties and excellent color-forming properties (two-color separation properties) for each color. It has excellent effects.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tomoyuki Kugo 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (Reference) 2H026 AA07 AA13 AA28 DD34 DD48 DD56 FF13

Claims (3)

[Claims] 1. Two-color heat-sensitive recording in which first and second thermosensitive coloring layers having different coloring energies and different colors are formed on a support such that the lower coloring energy is the upper layer. A two-color heat-sensitive material, characterized in that an intermediate layer is provided between the two heat-sensitive coloring layers, and the material contains a heat-fusible substance having an average particle size of 1.0 μm or less and a melting point of 90 ° C. or more. Recording material. 2. The two-color heat-sensitive recording material according to claim 1, wherein an emulsified dispersion of polyethylene wax and a higher fatty acid compound is used as the heat-fusible substance of the intermediate layer. 3. The two-color heat-sensitive recording material according to claim 1, wherein the intermediate layer contains a styrene-butadiene latex.