JPH07242061A - Thermal recording material - Google Patents

Abstract

PURPOSE:To reduce the labor or cost in the recovery of a label such as paper when a thermal recording material is bonded, for example, as a label by providing a thermal color forming layer containing a colorless or light-colored color forming compd., a coupling compd. capable of allowing the color forming compd. to develop a color at the time of heating and a binder on a support made of polystyrene. CONSTITUTION:A thermal color forming layer containing a colorless or light- colored color forming compd., a coupling compd. capable of allowing the color forming compd. to develop a color at the time of heating and a binder is provided on a support made of polystyrene in a coating amt. of 5-15g/m<2> on a dry wt. basis so that the color forming compd. is 1-50wt.% and the coupling compd. is 5-80wt.%. The color forming compd. may be one generally used in pressure-sensitive recording paper or thermal recording paper and, as the binder, a styrenic polymer is pref. The respective components are mixed to be applied to a support by a bar coater or a blade coater to be dried. This thermal recording material is bonded to a PSP container or a polystyrene receiving bag to be used as a label.

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 which is effective in reducing the cost of collecting and recycling a labeled polystyrene container, storage bag or the like. is there.

[0002]

2. Description of the Related Art A heat-sensitive recording material using a colorless or light-colored color-forming substance and a color-developing substance capable of coloring the color-forming substance under heat is disclosed in JP-B-43-4160 and JP-B-451403.
It was announced in No. 9 and has been put to practical use. Generally, in a heat-sensitive recording material, a leuco dye and a color developer such as a phenolic substance are separately dispersed in fine particles, and then both are mixed, and a binder, a sensitizer, a filler, a lubricant, etc. are added thereto. It forms a coating liquid by adding an agent and is applied to a support such as paper, film, synthetic paper, etc. Color recording by a chemical reaction that occurs when one or both of the leuco dye and the developer melt and contact by heating. And a sheet-like heat-sensitive recording material is usually prepared. A thermal printer or the like having a built-in thermal head is used for color development of such a thermal recording sheet. Compared to other recording methods, this heat-sensitive recording method is (1) no noise is generated during recording, (2) there is no need for developing and fixing, (3) maintenance-free, (4)
It is widely used in the field of facsimiles, computer output, printers such as calculators, recorders for medical measurement, ticket vending machines, thermosensitive recording labels, etc. due to the fact that machines are relatively inexpensive. .

Among these fields of use, the use of labels accompanying the spread of POS systems in retail stores, supermarkets, etc., particularly the measurement of fresh products such as fresh food and bento,
It is an indispensable recording material for price display. As a common example in everyday life, a paper or synthetic paper label is affixed directly or on a wrap film to a tray made of expanded polystyrene (polystyrene) containing foods, a bowl, a lunch box container and the like. By the way, as environmental problems are becoming more serious on a global scale, with the ever-increasing demand for the careful use of limited resources and the minimization of waste, the collection and recycling of the above food containers Commercialization has already started in supermarkets and large retail stores. This expanded polystyrene food container is also called a PSP container. It is made by foaming polystyrene raw material 10 to 15 times, so it is much lighter and tougher than paper, has excellent heat insulation, is water resistant, and has a tray. It is widely used because of its characteristics such as the combustion energy per sheet and the small amount of carbon dioxide and water generated during combustion. However, a label made of (synthetic) paper indicating the product name, price, etc. is attached to such a container, but when collecting and reusing it, the label of the attached paper or synthetic paper is attached. Removal is a problem.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the prior art. That is,
Another object of the present invention is to provide a heat-sensitive recording material for solving the problem of removing the sticky paper or synthetic paper label, which is a problem when collecting PSP containers used for food containers and polystyrene storage bags.

[0005]

The present inventor has completed the present invention as a result of various studies to achieve the above object. That is, the present invention provides (1) a thermosensitive color-forming layer containing a colorless or light-colored color-forming compound, a color-developing compound capable of coloring the color-forming compound when heated, and a binder on a support made of polystyrene. A heat-sensitive recording material, (2) a heat-sensitive recording material according to (1), wherein a surface tension of a polystyrene support is 40 dyn / cm or more,
(3) The heat-sensitive recording material according to (1), wherein the binder is a styrene polymer.

In the heat-sensitive recording material of the present invention, a color-forming compound as shown below on a polystyrene support,
It is prepared by providing a thermosensitive coloring layer containing a color-developing compound, a binder and optionally a filler, a heat-fusible compound, a lubricant, a surfactant and the like. In the present invention, the thermosensitive color-developing layer is formed by coating the coating solution of the above material on the support so that the dry weight is 1 to 40 g / m ^2, preferably 5 to 15 g / m ² . Further, an intermediate layer may be provided between the support and the thermosensitive coloring layer, and a protective layer may be provided on the thermosensitive coloring layer. The component ratio of the thermosensitive coloring layer is 1 to 50% by weight for the color forming compound, 5 to 80% by weight for the color developing compound, 1 to 90% by weight for the binder, and 0 to 0 for the filler and the heat-fusible compound. 80% by weight, other lubricants, surfactants and the like are used in arbitrary proportions. The material for forming the intermediate layer and the protective layer can be appropriately selected from a binder and a filler, if necessary, and is provided in a range of 6 g / m ² or less by dry weight.

The polystyrene support used in the present invention is polystyrene or one containing polystyrene as a main component, and preferably the same material as the polystyrene container or wrap film. The shape is not particularly limited, but a sheet shape such as a film is preferable. The polystyrene film is preferably a stretched film base such as polystyrene resin or polystyrene resin containing an inorganic pigment. The thickness is preferably about 10 μm-500 μm. Further, the polystyrene support has a surface wetting tension of 40 dyn / cm or more, preferably 44 dyn / cm or more, in view of the necessity of providing a thermosensitive coloring layer. The surface of an ordinary polystyrene support has a wetting tension of 37 dyn / cm or less, and by subjecting this to corona treatment or coating with a surfactant, preferably corona treatment, a substrate having the above wetting tension can be obtained.

Examples of the color-forming compound may be those generally used for pressure-sensitive recording paper and heat-sensitive recording paper,
There is no particular limitation. Specific examples include, for example, fluoran compounds, triarylmethane compounds, spiro compounds, diphenylmethane compounds, thiazine compounds, lactam compounds, fluorene compounds and the like.

Examples of fluoran compounds include 3-
Diethylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-anilino Fluoran, 3- (N
-Ethyl-N-isopentylamino) -6-methyl-7
-Anilinofluorane, 3-isobutylethylamino-
6-Methyl-7-anilinofluorane, 3- [N-ethyl-N- (3-ethoxypropyl) amino] -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-
Hexylamino) -6-methyl-7-anilinofluorane, 3-dipentylamino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-propylamino)
-6-Methyl-7-anilinofluorane, 3- (N-ethyl-N-tetrahydrofurylamino) -6-methyl-
7-anilinofluorane, 3-diethylamino-6-methyl-7- (p-chloroanilino) fluorane, 3-diethylamino-6-methyl-7- (p-fluoroanilino) fluorane, 3- (p-toluidi Noethylamino)
-6-Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (p-toluidino) fluorane, 3-diethylamino-7- (o-chloroanilino)
Fluoran, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-diethylamino-7- (3,
4-dichloroanilino) fluorane, 3-diethylamino-7- (o-fluoroanilino) fluorane, 3-dibutylamino-7- (o-fluoroanilino) fluorane, 3-pyrrolidino-6-methyl-7-ani Rinofluorane, 3-diethylamino-6-chloro-7-ethoxyethylaminofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-diethylamino-
7-chlorofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7-
Methylfluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-phenylfluorane, 3- (p-toluidinoethylamino) -6
-Methyl-7-phenethylfluorane and the like can be mentioned.

Examples of triarylmethane compounds include 3,3-bis (p-dimethylaminophenyl) -6.
-Dimethylaminophthalide (also known as 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 can be mentioned.

Examples of the spiro compound include 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran, 3-
Benzylcypyrodinaphthopyran, 3-propylspirobenzopyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran, 1,3,3-trimethyl-6-nitro-8'-methoxyspiro (indoline-2,2'- Examples of the diphenylmethane compound include N-halophenyl-leukoauramine, 4, and the like.
4-bis-dimethylaminophenylbenzhydrylbenzyl ether, N-2,4,5-trichlorophenyl leuco auramine and the like, and thiazine compounds such as benzoyl leuco methylene blue and p-nitrobenzoyl leuco methylene blue are lactams. Examples of the system compound include rhodamine B anilinolactam and rhodamine B-p-chloroanilinolactam, and examples of the fluorene compound include 3,6-bis (dimethylamino) fluorenspyro (9,3 ′)-6- 'Dimethylaminophthalide, 3,6-bis (dimethylamino) fluorenspyro (9,3')-6'-pyrrolidinophthalide,
Examples thereof include 3-dimethylamino-6-diethylaminofluorene spiro (9,3 ′)-6′-pyrrolidinophthalide. These color-forming compounds may be used alone or in admixture of two or more.

As the color-developing compound, those which are generally used for pressure-sensitive recording paper and heat-sensitive recording paper can be used and are not particularly limited. Specific examples include 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 (also known as bisphenol A or BPA),
2,2'-bis (p-hydroxyphenyl) butane,
1,1′-bis (p-hydroxyphenyl) cyclohexane, 4,4′-thiobisphenol, 4,4′-cyclohexylidene diphenol, 2,2 ′-(2,5-dibromo-4-hydroxyphenyl) propane , 4, 4 '
-Isopropylidenebis- (2-t-butylphenol), 2,2'-methylenebis- (4-chlorophenol), 4,4'-sulfonyldiphenol, 4,4'-
Sulfonyl-bis- (2-allylphenol), 4-hydroxy-4'-methoxydiphenyl sulfone, 4-hydroxy-4'-ethoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone,
4-hydroxy-4'-butoxydiphenylyl sulfone,
Methyl bis (4-hydroxyphenyl) acetate, bis (4
-Hydroxyphenyl) butyl acetate, bis (4-hydroxyphenyl) benzyl acetate and other phenolic compounds,
Benzyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, dibenzyl 4-hydroxyphthalate, 4-
Dimethyl hydroxyphthalate, ethyl 5-hydroxyisophthalate, 3,5-di-t-butylsalicylic acid, 3,
Examples thereof include aromatic carboxylic acid derivatives such as 5-di-α-methylbenzylsalicylic acid, aromatic carboxylic acids, and metal salts thereof.

The binder contained in the thermosensitive color developing layer is preferably a styrene polymer, examples of which include styrene / maleic anhydride copolymer, polystyrene, styrene / acrylic ester copolymer, and styrene / acrylonitrile copolymer. Examples thereof include hydrophobic polymer emulsions such as polymer, styrene / butadiene copolymer, carboxylated styrene / butadiene copolymer, styrene / butadiene / acrylic acid copolymer, colloidal silica and styrene copolymer composition. Further, if necessary, methyl cellulose, methoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, polyvinyl alcohol (PVA), carboxy group modified polyvinyl alcohol, sulfonic acid group modified polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, Starch and its derivatives,
Casein, gelatin, aqueous isoprene rubber, water-soluble substances such as alkali salts of iso (or diiso) butylene / maleic anhydride copolymer, or polyvinyl acetate, vinyl chloride / vinyl acetate copolymer, polyacrylic ester, Hydrophobic polymer emulsions such as polyurethane, colloidal silica and acrylic resin composition are used.

Examples of usable fillers include calcium carbonate, magnesium carbonate, magnesium oxide, silica, white carbon, talc, clay, alumina, magnesium hydroxide, aluminum hydroxide, aluminum oxide, barium sulfate, polystyrene resin, urea- Formalin resin etc. are available.

Examples of the heat-fusible compound that can be used include waxes such as animal and vegetable wax, polyethylene wax, and synthetic wax, and higher fatty acids, higher fatty acid amides, higher fatty acid metal salts, acetylated aromatic amines, and aromatic ethers. Compounds, aromatic sulfonic acid esters, biphenyl derivatives and the like that are solid at room temperature and have a melting point of about 80 ° C. or higher can be used.

Specific examples of these heat-fusible compounds include caproic acid amide, capric acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, erucic acid amide, linoleic acid amide, and N-methylstearic acid amide. , Stearic acid anilide, N-methyl oleic acid amide, benzanilide, linoleic acid anilide,
N-ethylcaprylic acid amide, N-butyllauric acid amide, N-octadecylacetamide, N-oleinacetamide, N-oleinbenzamide, N-stearylcyclohexylamide, erucic acid amide, methylolbehenic acid amide, methylolstearic acid amide, methylenebis Stearic acid amide, ethylenebis stearic acid amide, p-acetotoluidide, polyethylene glycol, 1-benzyloxynaphthalene, 2-benzyloxynaphthalene, 1-hydroxynaphthoic acid, 1,2-
Bis (3-methylphenoxy) ethane, 1,2-bis (4-methoxyphenoxy) ethane, 1,2-bis (3,4-dimethylphenyl) ethane, 1-phenoxy-2- (4-chlorophenoxy) ethane , 1-phenoxy-2- (4-methoxyphenoxy) ethane, 1- (2
-Methylphenoxy) -2- (4-methoxyphenoxy) ethane, terephthalic acid dibenzyl ester, oxalic acid dibenzyl ester, oxalic acid di (4-methylbenzyl) ester, p-benzyloxybenzoic acid benzyl ester, p-benzyl Biphenyl, m-terphenyl,
1,5-bis (p-methoxyphenoxy) -3-oxa-pentane, 1,4-bis (2-vinyloxyethoxy) benzene, p-biphenyl-p-tolyl ether,
Examples include compounds such as benzyl-p-methylthiophenol, phenylmesitylene sulfonate, and 4-methylphenylmesitylene sulfonate.

In addition, lubricants such as zinc stearate, calcium stearate and aluminum stearate, various surfactants, antifoaming agents, ultraviolet absorbers and the like are added as required.

The heat-sensitive recording material of the present invention is prepared using the above-mentioned material by the following method, for example. That is, by a conventional method, a color-developing compound, a color-developing compound, a binder, and optionally other additives are separately pulverized and dispersed by a dispersing machine such as a ball mill, attritor, or sand mill (wet dispersion). In this case, usually, water is used as a medium so that the proportion of solid components is adjusted to 10 to 50% by weight), and then the respective components are mixed and optionally additives are added to the heat-sensitive coloring layer aqueous coating solution. Was prepared and coated on a polystyrene support by a bar coater, a blade coater, etc. so that the dry weight is usually ¹ to 40 g / m ² (the ratio of the color forming compound to the color developing compound is usually a dry weight). The ratio is 2: 1 to 1:10) to obtain the heat-sensitive recording material of the present invention.

If desired, an intermediate layer may be provided between the thermosensitive color developing layer and the support as described above, or a protective layer may be provided on the thermosensitive color developing layer. The thermosensitive recording material of the present invention in which a thermosensitive coloring layer is provided on a polystyrene support is usually used as a label having a pressure-sensitive adhesive layer provided on the back side, which is attached to a polystyrene container such as a PSP container and a polystyrene storage bag. By doing so, separation of paper or synthetic paper labels that become foreign matter in collecting and recycling PSP containers and polystyrene storage bags, etc. in which conventional (synthetic) paper labels are used,
The cleaning work is omitted and the cost is greatly reduced.

[0020]

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 addition,
In the examples, "part" indicates part by weight.

Example 1 A mixture [A] liquid, a [B] liquid and a [C] liquid were prepared by pulverizing and dispersing a mixture having the following composition using a sand grinder so that the average particle diameter was 2 μm or less. did. [A] liquid: 3-dibutylamino-6-methyl-7-anilinofluorane 25 parts 25% PVA aqueous solution 20 parts water 55 parts [B] liquid: bisphenol A 25 parts 25% PVA aqueous solution 20 parts water 55 parts [ C] liquid: methylol stearic acid amide 20 parts 25% PVA aqueous solution 20 parts water 60 parts

Next, the respective preparation solutions are mixed in the following ratios to prepare an aqueous coating solution for the thermosensitive color developing layer, which is subjected to corona treatment in advance and a transparent polystyrene film having a surface wetting tension of 50 dyn / cm (trade name: OPS film, thickness). is 50 [mu] m, Asahi Chemical Industry Co., Ltd.) coated to approximately 13 g / m ² by weight of the dry was formed on the thermosensitive coloring layer was dried. [A] liquid 6 parts [B] liquid 24 parts [C] liquid 22 parts 50% calcium carbonate dispersion liquid 20 parts 50% carboxylated styrene-butadiene copolymer latex 6 parts Further, a coating liquid having the following ratio is used. Was coated on the heat-sensitive color-developing layer (2) so that the dry weight was about 2 g / m ^2, and dried to obtain the heat-sensitive recording material of the present invention. 25% PVA aqueous solution 60 parts 50% calcium carbonate dispersion 6 parts water 20 parts

Example 2 Instead of the transparent polystyrene film of Example 1, corona treatment was performed in advance and a white polystyrene film having a surface wetting tension of 45 dyn / cm (trade name: Optisite, thickness 65 μm, polystyrene was kneaded with an inorganic pigment) Crowded,
A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that Asahi Chemical Industry Co., Ltd. was used.

Example 3 A white polystyrene film having a surface wetting tension of 50 dyn / cm after being subjected to corona treatment in advance in place of the transparent polystyrene film of Example 1 (trade name: Peachcoat SG
A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that -115F, a thickness of 130 μm, a polystyrene film having an inorganic pigment layer on the surface thereof, and Nisshinbo Co., Ltd. were used.

Example 4 A mixture [D] and a solution [E] were prepared by pulverizing and dispersing a mixture having the following composition using a sand grinder so that the average particle diameter was 2 μm or less. Liquid [D]: 4,4′-sulfonyl-bis- (2-allylphenol) 25 parts 25% PVA aqueous solution 20 parts water 55 parts Liquid [E]: meta-terphenyl 25 parts 25% PVA aqueous solution 20 parts water 55 Parts Then, the respective preparation solutions were mixed in the following ratios to prepare an aqueous coating solution for the thermosensitive color developing layer, and a corona treatment was carried out in advance to obtain a transparent polystyrene film having a surface wetting tension of 50 dyn / cm (trade name: OPS film, thickness 50 μm). , Asahi Kasei Co., Ltd.
(Manufactured by Mitsui Chemicals Co., Ltd.) so as to have a dry weight of about 13 g / m ^2, and dried to form a thermosensitive color developing layer. [A] liquid 6 parts [D] liquid 24 parts [E] liquid 15 parts 50% calcium carbonate dispersion 20 parts 50% carboxylated styrene-butadiene copolymer latex 6 parts Further, a protective layer was formed in the same manner as in Example 1. The thermal recording material of the present invention was obtained by overcoating.

Example 5 Instead of the liquid [A] of Example 4, pulverization was carried out in the same manner as in Example 4,
25% 3-dibutylamino-7- (o-obtained by dispersion
Example 4 using chloroanilino) fluorane dispersion
A thermal recording material of the present invention was obtained in the same manner as in.

Example 6 Instead of the liquid [A] of Example 4, pulverization was carried out in the same manner as in Example 4,
25% 3,6-bis (dimethylamino) obtained by dispersion
Using the fluorene-9-spiro-3 '-(6'-dimethylaminophthalide) dispersion, the thermal recording material of the present invention was obtained in the same manner as in Example 4.

A quality performance test was conducted on the thermal recording material of the present invention obtained as described above, and the results are shown in Table 1.

Table 1 Quality performance test results Example 1 Background 2 Color density 3 Heat resistance 4 Water resistance 5 Plasticizer resistance 6 Adhesion 1 0.06 1.42 90% 85% 85% ○ / ○ 2 0.04 1.45 95% 90% 83% ○ / ○ 3 0.04 1.45 95% 90% 83% ○ / ○ 4 0.06 1.47 100% 95% 99% ○ / ○ 5 0.05 1. 45 98% 92% 98% ○ / ○ 6 0.05 1.64 97% 90% 89% ○ / ○

1) Background: A value (reflection density) obtained by measuring the uncolored portion of the sample with a Macbeth reflection densitometer RD-914 type. 2) Color density: Macbeth reflection density of the image portion printed by a thermal printer (D-805P) manufactured by Ishida Koki. 3) Heat resistance: 6 samples of color developed by the above printer
Remaining rate (%) of the density of the image area after standing for 24 hours in a thermostat at 0 ° C. 4) Water resistance: The residual ratio (%) of the density of the image area after the sample developed by the printer was immersed in tap water at room temperature for 24 hours. 5) Plasticizer resistance: The sample colored by the above printer was P
The residual rate (%) of the density of the image area after leaving the VC wrap film on both sides and leaving it at 25 ° C. for 24 hours under a load of 30 g / cm ² . 6) Adhesiveness: The sample was observed by hand with the removal of the thermosensitive coloring layer, adhesion of cellophane tape, and peeling of the thermosensitive coloring layer due to peeling (hand-rubbing / cellophane tape). ○ / ○ = No dropout /
No peeling.

As is apparent from the table, the heat-sensitive recording material of the present invention is excellent in storage stability such as heat resistance, water resistance and plasticizer resistance and has a large color density.

[0032]

The PSP container used as a food container, the polystyrene storage bag, and the like are excellent in storage stability and color sensitivity of a color image formed of a polystyrene film support for easy recovery and recycling. A thermosensitive recording material was obtained. Usually, a thermosensitive color developing layer is formed by applying an aqueous thermosensitive color developing layer coating liquid to a paper support, but simply replacing the support with a hydrophobic polystyrene one causes cissing and unevenness. A satisfactory thermosensitive coloring layer may not be obtained, and the adhesion between the support and the thermosensitive coloring layer may be poor. In this case, the surface of the support made of polystyrene is treated so that the wetting tension of the surface is 40 dyn / cm or more, and the thermosensitive coloring layer formed on the support made of polystyrene is further made to contain a styrene copolymer. It is possible to solve the above-mentioned drawbacks that occur when the above support is used. As a result, a PSP container used as a food container, a polystyrene wrap film or a storage bag, and a thermosensitive recording material whose support film is the same polystyrene as those materials are attached as a label, for example, to recover the conventional material. It is possible to omit the work of sorting and washing paper or synthetic paper labels that sometimes become foreign substances, and it is very effective in saving labor and cost for recovery and recycling.

Claims (3)

[Claims] 1. A thermosensitive color-forming layer containing a colorless or light-colored color-forming compound, a color-developing compound capable of coloring the color-forming compound when heated, and a binder on a polystyrene support. Heat sensitive recording material 2. The heat-sensitive recording material according to claim 1, wherein the surface tension of the support made of polystyrene is 40 dyn / cm or more. 3. The binder is a styrenic polymer.
Thermal recording material.