JPH06286313A - Reversible thermal recording material - Google Patents

Abstract

PURPOSE:To provide a reversible thermal recording material capable of repeatedly performing the writing and erasure of an image by heat and forming an image excellent in contrast and enabling recording on both surfaces thereof. CONSTITUTION:A reversible thermal recording layer capable of performing the repeated writing and erasure of an image and based on a usually colorless or light-colored dye precursor and a reversible developer generating a reversible hue change in the dye precursor by the difference of a cooling speed after heating is provided on both surfaces of a support to obtain a reversible thermal recording material.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a reversible thermosensitive recording material capable of forming and erasing an image by controlling thermal energy.

[0002]

2. Description of the Related Art A widely used heat-sensitive recording material has a heat-sensitive recording layer containing, on a support, an electron-donating, usually colorless or light-colored dye precursor and an electron-accepting developer as main components. By heating with a thermal head, a heating pen, a laser beam or the like, a dye precursor and a developer react instantaneously to obtain a recorded image. JP-B-43-4160
And Japanese Patent Publication No. 45-14039.

In such a heat-sensitive recording material, once an image is formed, it is impossible to erase the portion and restore the state before the image is formed again. Therefore, when further information is recorded, the image is not formed. I had no choice but to add to the part. Therefore, when the area of the heat-sensitive recording portion is limited, there is a problem that the recordable information is limited.

Therefore, Japanese Patent Application Laid-Open No. 3-246091 proposes a heat-sensitive recording material in which an ordinary heat-sensitive recording layer is provided on both sides of a base paper so that the back side can be printed and recorded. As a result, it is possible to print on both the front and back sides, and it is possible to record twice as much information as the conventional thermal recording material. However, even with this heat-sensitive recording material, once an image is formed, it is impossible to erase the part and restore the state before the image formation.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a reversible thermosensitive recording material capable of repeatedly writing and erasing an image by heat, excellent in image contrast and capable of recording on both sides.

[0006]

The inventors of the present invention have conducted research to solve this problem, and as a result, reversible thermosensitive recording capable of repeatedly writing and erasing images on both surfaces of the support by heating. The desired reversible thermosensitive recording material could be obtained by providing each layer. In particular, a reversible thermosensitive recording layer containing a colorless or light-colored dye precursor and a reversible developer that causes a reversible color tone change in the dye precursor due to a difference in cooling rate after heating is provided. Thus, a reversible thermosensitive recording material having a good image contrast could be obtained.

As the reversible thermosensitive recording layer, for example, Japanese Patent Laid-Open Publication No.
No. 4,119,377, JP-A-63-39377, and JP-A-63-41186,
A reversible thermosensitive recording material composed of a resin base material and organic low molecular weight particles dispersed in the resin base material can be used. This method is a method in which the transparency of the reversible thermosensitive recording layer is reversibly changed by heat energy, and an organic low molecular weight compound is previously contained in the resin base material to form a film. Therefore, when it is used by utilizing transmitted light, it can be directly used as a film, but in order to be used as the reversible thermosensitive recording material of the present invention, it is also necessary to recognize an image by utilizing reflected light. is there. In this case, it is necessary to use the film by laminating it on a support which is colored or has a colored layer. However, the contrast between the transparent image-unformed area and the opaque image-formed area after printing is insufficient, and image recognition may be difficult depending on the application.

A preferred reversible thermosensitive recording layer is a type which develops a high density color upon heating and is decolorized upon reheating, and has a large image contrast and easy image recognition. As this type, in particular, a reversible thermosensitive recording layer mainly composed of a colorless or light-colored dye precursor and a reversible developer which causes a reversible color tone change in the dye precursor due to a difference in cooling rate after heating. Is preferably used.

The reversible developer used in the present invention is not particularly limited as long as it is a compound capable of causing a reversible color change in the dye precursor by heating, but the present applicant considers it in terms of image contrast, repetition durability and the like. According to Japanese Patent Application No. 4
An electron-accepting compound having an aliphatic hydrocarbon group having 6 or more carbon atoms, which is used in the reversible thermosensitive recording material proposed in No. 347032, is preferable, and a phenolic compound having at least one aliphatic hydrocarbon group having 6 or more carbon atoms is particularly preferable. Is preferred.

Examples of the reversible color developer used in the present invention include those represented by the general formula 1, but the invention is not limited thereto.

[0011]

[Chemical 1]

In Formula 1, n is an integer of 1 or more and 3 or less, and m
Represents an integer of 0 or 1. R1 and R2 represent a substituent selected from an aliphatic hydrocarbon group, an alkoxy group, a halogen atom or a hydrogen atom, and may be the same or different. R3 represents an aliphatic hydrocarbon group. Y is a group represented by Formula 2. In addition, among the compounds represented by Chemical formula 1, R3
It is preferable that the number of carbon atoms in R3 is large, and the one in which the number of carbon atoms in R3 is 5 or less does not have sufficient decoloring effect. In addition, if the carbon number of R3 is 23 or more, the manufacturing cost is high, so R3
Is particularly preferably an aliphatic hydrocarbon group having 6 to 22 carbon atoms.

[0013]

[Chemical 2]

In Formula 2, 11 and 12 each represent an integer of 0 or 1. X1 and X2 each represent a divalent group having at least one hetero atom and may be the same or different from each other. Ar represents an aromatic group which may have a substituent, and the aromatic group represented by Chemical formula 3 is particularly preferable.

[0015]

[Chemical 3]

In Formula 3, k1 and k2 each represent an integer of 0 or 1, and X3 and X4 each represent a divalent group having at least one hetero atom, which may be the same or different. When k1 is 0, R4 is an aliphatic hydrocarbon group,
It represents a substituent selected from an alkoxy group, a halogen atom or a hydrogen atom, and when k1 is 1, R4 represents an aliphatic hydrocarbon group. When k2 is 0, R5 represents a substituent selected from an aliphatic hydrocarbon group, an alkoxy group, a halogen atom or a hydrogen atom, and when k2 is 1, R5 represents an aliphatic hydrocarbon group.

In Formula 3, when R4 and R5 are aliphatic hydrocarbon groups, R4 and R5 are particularly preferably aliphatic hydrocarbon groups having 6 to 22 carbon atoms. Further, in Formulas 1 and 3, when R 1 to R 5 are aliphatic hydrocarbon groups, R 1 to R 5 are particularly preferably alkyl groups, cycloalkyl groups or alkenyl groups.

In formulas 2 to 3, the divalent group having at least one hetero atom represented by X1 to X4 is, for example, an amide bond, a sulfonamide bond, an ester bond, a carbonic acid ester bond, an ether bond or a sulfide. Bond, thioester bond, carbonyl group, amino bond, urea bond,
Examples thereof include a thiourea bond, a urethane bond, and an azomethine bond, and a divalent group selected from an amide bond, a sulfonamide bond, a sulfide bond, a urea bond, and an azomethine bond is particularly preferable, but the present invention is not limited thereto. Not a thing.

Next, specific examples of preferable reversible color developing agents used in the present invention will be given, but the present invention is not limited thereto.

4'-hydroxyheptane anilide, 4 '
-Hydroxy-3-methyloctaneanilide, 4'-hydroxytridecaneanilide, 4'-hydroxynonadecaneanilide, 3'-hydroxynonadecaneanilide,
2 ', 4'-dihydroxyheptadecane anilide, 4'
-Hydroxy-4-hexylbenzanilide, 4'-hydroxy-4-octadecylbenzanilide, 4'-hydroxy-4- (heptylthio) benzanilide, 4 '
-Hydroxy-4-octadecyloxybenzanilide, 4'-hydroxy-4-dodecylsulfonylbenzanilide, 4'-hydroxy-4- (N-heptadecylideneamino) benzanilide, 4'-hydroxy-3,
4-dioctyloxybenzanilide, 4'-hydroxy-3- (heptadecylthio) -5-pentadecyloxybenzanilide, 4'-hydroxy-3-heptadecylcarbonylamino-5-dodecylbenzanilide,
4'-hydroxy-3,5-bis (N-docosylideneamino) benzanilide,

N-cyclohexyl-4-hydroxybenzamide, N-cyclohexylmethyl-4-hydroxybenzamide, N-octadecyl-4-hydroxybenzamide, N-methyl-N-octadecyl-4-hydroxybenzamide, 4-hydroxy-4 '. -Heptylcarbonylaminobenzanilide, 4-hydroxy-4 '
-Octyloxycarbonylaminobenzanilide, N
-Octadecyl-2,3,4-trihydroxybenzamide, N-methyl-3-hydroxy-4'-octadecylbenzanilide, 4- (N-octylsulfonylamino) phenol, 4'-hydroxy-4-cyclohexylbenzenesulfonanilide 4'-hydroxy-4-
Octadecylaminobenzenesulfonanilide, N-octylidene-4- (4-hydroxyphenyl) aminosulfonylaniline, 1- (4-hydroxyphenylthio) dodecane, 1- (4-hydroxyphenylthio) tetracosane,

4'-hydroxy-4-octadecyloxydiphenyl sulfide, N- (4-hydroxyphenyl) -N'-octadecyl urea, N- (3-allyl-4)
-Hydroxyphenyl) -N'-octadecylurea, N
-(4-hydroxyphenyl) -N '-(4-tetradecylphenyl) urea, N- (4-hydroxybenzylidene) octadecylamine, N- (4-hydroxybenzylidene) -4'-tetradecylcarbonyloxyaniline, N -(3-hydroxybenzylidene) dodecylamine, N- (4-hydroxy-α-methylbenzylidene)
-4'-octadecylaniline, N- (4-octadecylcarbonylamino) benzylidene-4'-hydroxyaniline and the like.

The colorless or light-colored dye precursor used in the present invention is typically represented by an electron-donating compound used for pressure-sensitive recording paper, heat-sensitive recording paper, light-sensitive pressure-sensitive paper, electric heat-sensitive recording paper, heat-sensitive transfer paper and the like. However, it is not particularly limited. Specific examples include the followings, but the present invention is not limited thereto.

3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) ) -3- (1,2-Dimethylindol-3-yl)
Phthalide, 3- (p-dimethylaminophenyl) -3-
(2-methylindole-3-i) 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-ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5-dimethylaminophthalide, 3
Triarylmethane compounds such as -p-dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6-dimethylaminophthalide.

Diphenylmethane compounds such as 4,4'-bis (dimethylaminophenyl) benzhydryl benzyl ether, N-chlorophenyl leuco auramine and N-2,4,5-trichlorophenyl leuco auramine.

Rhodamine B anilinolactam, Rhodamine B p-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-phenylflurane. Oran, 3-diethylamino-
7-chlorofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7-
(3,4-dichloroanilino) fluorane, 3-diethylamino-7- (2-chloroanilino) fluorane,

3-Diethylamino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl- 7-anilinofluoran, 3-
(N-ethyl-N-tolyl) amino-6-methyl-7-
Funethylfluorane, 3-diethylamino-7- (4-
Nitroanilino) fluorane, 3-dibutylamino-6
-Methyl-7-anilinofluorane, 3- (N-methyl-N-propyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamylamino-
6-Methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-tetrahydrofuryl) amino-6- Xanthene compounds such as methyl-7-anilinofluorane.

Thiazine compounds such as benzoyl leuco methylene blue and p-nitrobenzoyl leuco methylene blue. 3-Methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran, 3
There are spiro compounds such as propyl spiro benzopyran. These usually colorless to light-colored electron-donating dye precursors may be used either individually or in combination of two or more.

The reversible thermosensitive recording material of the present invention can also change the hue of a colored image at the time of printing of each reversible thermosensitive recording layer provided on both sides of the support. In this case, a reversible thermosensitive recording layer containing the dye precursor that produces different hues by reaction with the reversible color developer may be provided on each surface for use. When an opaque support is used as the support to be used, it is easy to identify the information written on the front and back sides, and when a transparent or semitransparent support is used, it is possible to see from one side. In the form in which the coloring hue is changed such that information displayed in color can be obtained, it is possible to advantageously use it because it is possible to display information for identification, confirmation of superiority, etc. in color.

A binder may be added to the reversible thermosensitive recording layer for the purpose of improving the strength of the reversible thermosensitive recording layer. Specific examples of these binders include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylic acid amide / acrylic acid ester copolymer, and acrylic acid amide. / Acrylic ester / methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, water-soluble polymer such as alkali salt of ethylene / maleic anhydride copolymer, polyvinyl acetate, polyurethane, poly Examples of the latex include acrylates, styrene / butadiene copolymers, acrylonitrile / butadiene copolymers, methyl acrylate / butadiene copolymers, and ethylene / vinyl acetate copolymer latexes, but are not limited thereto. Not.

Further, a heat-fusible substance may be contained in the reversible thermosensitive layer as an additive for controlling the color developing sensitivity and the decoloring temperature of the reversible thermosensitive recording layer. As these heat fusible substances, those having a melting point of 60 ° C. to 200 ° C. are preferable, and those having a melting point of 80 ° C. to 180 ° C. are particularly preferable. Further, a sensitizer used in general thermal recording paper can also be used. Specific examples thereof include waxes such as N-hydroxymethylstearic acid amide, stearic acid amide and palmitic acid amide, naphthol derivatives such as 2-benzyloxynaphthalene, biphenyl derivatives such as p-benzylbiphenyl and 4-allyloxybiphenyl, 1,2-Bis (3-methylphenoxy) ethane, 2,2'-bis (4-methoxyphenoxy) diethyl ether, polyether compounds such as bis (4-methoxyphenyl ether), diphenyl carbonate, dibenzyl oxalate, oxalic acid Examples thereof include carbonic acid such as bis (p-methylbenzyl) ester and oxalic acid diester derivatives. Two or more kinds can be added in combination, but the present invention is not limited thereto.

The reversible thermosensitive recording material of the present invention is heated to
An image is repeatedly written and erased, and a protective layer is preferably provided on the reversible thermosensitive recording layer in order to prevent deterioration of the reversible thermosensitive recording layer. Materials for forming the protective layer include water-soluble polymers, latexes, and polymerizable compounds. Examples thereof include polyurethane resin, polyester resin, epoxy resin, melamine resin, polyvinyl alcohol, nitrocellulose, methacrylic acid ester, acrylic acid oligomer, acrylic acid ester oligomer and the like. If necessary, a crosslinking agent such as an epoxy compound, a urea derivative or a vinyl compound, a curing agent such as a phosphoric acid type, a sulfonic acid type, a polyamide type or an amine type can be added. In addition, in the state of a transparent film such as polyethylene, polyethylene terephthalate in advance,
It is also possible to form a protective layer on the reversible thermosensitive recording layer by means such as bonding. In this case, if necessary, an intermediate layer can be provided between the reversible thermosensitive recording layer and the protective layer.

The reversible thermosensitive recording layer may contain a colorless or light-colored dye precursor and a reversible color developer in the following manner.
A method of dissolving or dispersing each compound alone in water or an organic solvent, a method of dissolving or dispersing each compound in water or an organic solvent, heating and dissolving each compound to homogenize and then cooling, There is a method of mixing respective solutions or dispersions obtained by a method of dissolving or dispersing in water or an organic solvent, printing on a support and coating and drying. In this case, for example, each color-forming component may be contained in one layer to form a multilayer structure, but the invention is not particularly limited thereto.

The layer structure for forming the reversible thermosensitive recording material of the present invention is usually a colorless or light-colored dye precursor on both sides of the support, and a reversible change in color tone of the dye precursor due to the difference in cooling rate after heating. Although it may be only the reversible thermosensitive recording layer mainly containing the reversible color developing agent that causes the above-mentioned phenomenon, it is preferable to provide a protective layer on the reversible thermosensitive recording layer, and an intermediate layer may be provided between the reversible thermosensitive recording layer and the support. It can also be provided. In this case, the protective layer and / or the intermediate layer may be composed of a plurality of layers of 2 layers or 3 layers or more. Further, a layer containing a material capable of electrically, magnetically and optically recording information may be formed in the reversible thermosensitive recording layer and / or on another layer and / or on the reversible thermosensitive recording layer.

Further, the protective layer and / or the reversible thermosensitive recording layer and / or the intermediate layer include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide and aluminum hydroxide. , Urea-formalin resin and other pigments, as well as higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as paraffin, oxidized paraffin, polyethylene, oxidized polyethylene stearate amide and castor wax, and dioctylsulfosuccinic acid. A dispersant such as sodium acid salt, a surfactant, a fluorescent dye, etc. may be contained.

The support used in the present invention includes paper, coated paper, various non-woven fabrics, woven fabrics, laminated paper, synthetic paper, metal foil, synthetic resin, or a white sheet formed by adding a white pigment to synthetic resin to form a film. A foamed sheet or a composite sheet obtained by combining these may be arbitrarily used according to the purpose. These may be opaque, translucent or transparent. The thickness of the support is not particularly limited as long as it can withstand repeated use, but is 30 to 500 μm.
m, preferably about 40 to 300 μm.

The method of forming each layer constituting the reversible thermosensitive recording material of the present invention on the support is not particularly limited, and it can be formed by a conventional method. For example,
It is possible to use a smearing device such as an air knife coater, a blade coater, a bar coater, or a curtain coater, and various printing machines such as planographic printing, letterpress, intaglio printing, flexo, gravure, screen, and hot melt. Further, in addition to the usual drying process, each layer can be held by UV irradiation / EB irradiation. By these methods, it is possible to smear and print both sides of the support simultaneously or separately on one side.

Further, after forming a layer including a reversible thermosensitive recording layer on one surface of each of two identical or different types of supports, the other surface of each of the supports is faced to each other to form an adhesive. It is also possible to provide a reversible thermosensitive recording layer on both sides of the support by laminating with each other or by laminating each other on both sides of the support at the time of laminating.

In the reversible thermosensitive recording material of the present invention, in order to form a color-developed recording image, rapid cooling following heating is required, and in order to erase the recorded image, the cooling rate after heating is slow. Good. For example, the color-developed state can be developed by heating the material by an appropriate method and then rapidly cooling it by pressing a low-temperature metal block or the like. In addition, if a heating is performed for a very short time using a thermal head, a laser beam or the like, the material is cooled immediately after the heating is completed, and thus a color-developed state can be developed. on the other hand,
Suitable heat source (thermal head, laser light, heat roll,
Radiant heat from heat stamps, high frequency heating, electric heaters, and light sources such as tungsten lamps and halogen lamps,
When heated with hot air) for a relatively long period of time, not only the recording layer but also the support and the like are heated, so that the cooling speed is slow even if the heat source is removed, resulting in a decolored state. Therefore, even if the same heating temperature and / or the same heat source is used, the colored state and the decolored state can be arbitrarily expressed by controlling the cooling rate.

The reversible thermosensitive recording material of the present invention can be printed on one side separately, or by printing a plurality of heating means for image recording and printing so as to contact both sides of the reversible thermosensitive recording material. It can also be recorded. Also, when erasing a recorded image, it is possible to erase only one side by heating from one side or simultaneously erase both sides by heating from both sides.

[0041]

The present invention will be described in more detail with reference to the following examples.

Example 1 25 parts of 3-di-n-butylamino-6-methyl-7-anilinofluorane was pulverized with 80 parts of a 2.5% polyvinyl alcohol aqueous solution by a ball mill for 24 hours to obtain a dye precursor dispersion liquid. Got Next, 63 parts of 4'-hydroxy-n-heptaneanilide was pulverized with 200 parts of a 2.5% aqueous solution of polyvinyl alcohol in a ball mill for 24 hours to obtain a reversible developer dispersion. Mix the two dispersions obtained and mix 1
After adding 130 parts of 0% polyvinyl alcohol aqueous solution and stirring sufficiently, a reversible heat-sensitive coating liquid was prepared. The obtained coating liquid was applied to one surface of a 188 µ polyethylene terephthalate (PET) sheet with a Meyer bar so that the solid content was applied in an amount of 4 g / m ² , dried, and treated with a super calendar. Further, smear the surface of the reversible thermosensitive recording layer thus obtained with polyvinyl alcohol to a thickness of 4 μm,
It dried and the protective layer was formed. Next, the reversible thermosensitive coating liquid was smeared on the other surface in the same manner, dried and then treated with a super calendar, and a protective layer was formed in the same manner to obtain a reversible thermosensitive recording material.

When a JAN code was printed on one surface of the obtained reversible thermosensitive recording material with a bar code printer, a clear black bar code was printed and could be read by a bar code reader. Next, when printed on the other side with a word processor, clear black character printing was possible. When the reversible thermosensitive recording material with both sides printed was passed through a heat roll at 120 ° C., the bar code and characters disappeared and both sides returned to the state before printing.

Example 2 25 parts of 3-di-n-ethylamino-6-methyl-7-anilinofluorane was pulverized with 80 parts of a 2.5% aqueous polyvinyl alcohol solution in a ball mill for 24 hours to obtain a dye precursor dispersion liquid. Got Next, 63 parts of N- (4-hydroxyphenyl) -N'-dodecylurea was pulverized with 200 parts of a 2.5% aqueous solution of polyvinyl alcohol in a ball mill for 24 hours to obtain a reversible color developer dispersion. The obtained two kinds of dispersion liquids are mixed, and a 10% polyvinyl alcohol aqueous solution 130
After adding 1 part and stirring sufficiently, the 1st reversible heat-sensitive coating liquid was created. The resulting coating liquid was applied to one side of a 48 μ-quality paper with a Meyer bar so that the solid content was applied in an amount of 4 g / m ² , dried, and treated with a super calendar. Further, a polyacrylic acid ester copolymer was smeared on the surface of the obtained reversible thermosensitive recording layer so as to have a thickness of 4 μm and dried to form a protective layer.

Next, 25 parts of 3-di-n-ethylamino-6-methyl-7-chlorofluorane was crushed together with 80 parts of a 2.5% aqueous polyvinyl alcohol solution in a ball mill for 24 hours to obtain a dye precursor dispersion liquid. It was Then, 63 parts of N- (4-hydroxyphenyl) -N'-dodecylurea was added to 2.5 parts.
% Aqueous solution of polyvinyl alcohol and pulverized with a ball mill for 24 hours to obtain a reversible developer dispersion. The obtained two kinds of dispersions were mixed, 130 parts of a 10% polyvinyl alcohol aqueous solution was added, and after sufficiently stirring, a second reversible heat-sensitive coating liquid was prepared. The obtained coating liquid was applied to one surface of another quality paper of 48 μm by means of a Meyer bar so that the amount of solid content applied was 4 g / m ² , dried, and treated with a super calendar. Further, a polyacrylic acid ester copolymer was smeared on the surface of the obtained reversible thermosensitive recording layer so as to have a thickness of 4 μm and dried to form a protective layer.

Next, an adhesive is applied to each of both surfaces of a 75 μ expanded polyethylene terephthalate (PET) sheet, and the uncoated surfaces of the two types of smeared paper obtained above are made to face each other and bonded together, followed by superimposing. Both sides were treated with a calendar to obtain a reversible thermosensitive recording material.

When a JAN code was printed on one surface of the obtained reversible thermosensitive recording material with a bar code printer, a clear black bar code could be printed and could be read with a bar code reader. Next, when printed on the other side with a word processor, a clear red character was printed. When the reversible thermosensitive recording material with both sides printed was passed through a heat roll at 120 ° C., the bar code and characters disappeared and both sides returned to the state before printing.

[0048]

As described above, the reversible thermosensitive recording layer is provided with a reversible color developing agent capable of reversibly changing the color tone of a dye precursor, which is usually colorless or light-colored, by the difference in cooling rate after heating. By providing a reversible thermosensitive recording layer mainly containing and on both sides of the support, good image contrast,
It was possible to obtain a reversible thermosensitive recording material which can be printed and recorded on both the front and back sides and can be erased as required.
Further, by providing a reversible thermosensitive recording layer that develops different hues on the front and back surfaces, it is possible to distinguish the superiority of information by color and the front and back surfaces.

Claims (3)

[Claims] 1. A reversible thermosensitive recording material in which a reversible thermosensitive recording layer capable of repeatedly writing and erasing an image by heating is provided on both surfaces of a support. 2. The reversible thermosensitive recording layer is mainly composed of a colorless or light-colored dye precursor and a reversible developer which causes the dye precursor to undergo reversible color tone change due to a difference in cooling rate after heating. The reversible thermosensitive recording material according to claim 1, which is a reversible thermosensitive recording layer. 3. The reversible thermosensitive recording material according to claim 1, wherein a protective layer is provided on the reversible thermosensitive recording layer.