JPH071840A - Reversible thermal recording medium - Google Patents

Abstract

PURPOSE:To obtain a reversible thermal recording medium capable of imparting reversible recording display properties even to a medium impossible to coat, capable of forming a high contrast image even when the recording and erasure of an image are repeatedly performed and excellent in repeated durability by bonding a material to be bonded having two-layered constitution to the rear surface of a support through an adhesive layer or self-adhesive layer. CONSTITUTION:A reversible thermal layer 1 reversibly generating a transparency- opacity change or a color development-erasure change in dependence on temp. is provided on a support 3 to obtain a reversible thermal recording medium 12. In this recording medium 12, materials 7, 8 to be bonded having two-layered constitution are bonded to the rear surface of the support 3 through an adhesive layer or self-adhesive layer 4. For example, a light reflecting layer 2 is provided on the surface of the support 3 and the reversible thermal layer 1 is provided thereon. A material to be bonded such as paper or a film 7 is bonded to the rear surface of the reversible thermal recording material 12 through the self-adhesive layer 4 and a material to be bonded composed of a urethane mat 8 is bonded to the rear surface thereof through the self-adhesive layer 4 and, further, release paper 5 is bonded to the rear surface thereof through the self-adhesive layer to constitute a label sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive recording medium, and more specifically, a reversible thermosensitive recording capable of repeatedly forming and erasing an image by utilizing transparency change or color reaction due to temperature. Regarding the medium.

[0002]

2. Description of the Related Art In recent years, reversible heat-sensitive recording materials have been attracting attention because they can form images temporarily and can erase the images when they are no longer needed. As a typical example, the glass transition temperature (Tg) is from 50 to 60 ° C. to 8
A reversible thermosensitive recording material is known in which an organic low molecular weight substance such as a higher fatty acid is dispersed in a resin matrix such as a vinyl chloride-vinyl acetate copolymer having a low glass transition temperature of less than 0 ° C. JP-A-54-119377, JP-A-55-1
54198 and the like).

A method of displaying information on a card by providing a colored portion on the back surface of this recording material (Actual Kaihei 2-387).
6) and a method for displaying information by providing a light reflecting layer on the back surface of the recording material to improve the contrast (Japanese Patent Laid-Open Publication No. 6-58242).
4-14079), a method of providing a thin film layer having a different refractive index on the back surface of this recording material (JP-A-2-175280) and the like. Silicone resin (JP-A-63-221
No. 087), a polysiloxane graft polymer (described in JP-A-63-317385), an ultraviolet curable resin or an electron beam curable resin (described in JP-A-2-566).
There is also proposed a method of providing the.

Recently, on thick vinyl chloride cards such as I
The demand for displaying information on C cards, ID cards, cash cards, etc. is increasing. The uniform coating of the reversible thermosensitive recording material on this PVC-based thick card is 1) dissolving the PVC material with a solvent, and 2) uniform mechanical coating is impossible due to the thick hard sheet. , Etc. are extremely difficult. Also, some thick cards are provided with recesses, and labeling is considered as a method of displaying on these cards.

As one of the methods, there is a method of embedding the display portion in the concave portion of the thick card (Actual No. Sho 58-192066).
If this condition is left as it is, there is a step between the embedding part and the card surface, and if printing is repeated using a heating means such as a thermal head, the card will be deformed by heat and print failure and erasing defects will occur, thus making repeated printing possible. There are no drawbacks. In addition, the thick card requires printing of the thermal head if the pressure of the thermal head is not increased. Therefore, it is necessary to increase the pressure of the thermal head. As a side effect, there are defects such as defective scratches and peeling of the label.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned drawbacks, and by labeling, it is possible to provide reversible recording display even on a medium that cannot be coated, and further Even if the image is repeatedly formed and erased by a heating means such as a thermal head and at a low pressure of the thermal head, an image with high contrast can be formed and the durability is excellent, and scratches and label peeling at the time of repetition are defective. It is another object of the present invention to provide a reversible thermosensitive recording medium that does not have a printout and does not run out even when the card is deformed.

[0007]

The present invention comprises:
A reversible thermosensitive recording medium provided with a thermosensitive layer in which transparent-opaque change or color-decoloring change reversibly depending on temperature is provided, and a two-layer structure is formed on the back surface of the support through an adhesive layer or an adhesive layer. There is provided a reversible thermosensitive recording medium, which is obtained by sticking the adherend. Further, the reversible thermosensitive recording medium is provided, wherein the adherend has one layer made of paper or a film and the other layer made of a layer having a cushioning function. Further, there is provided the above reversible thermosensitive recording medium, wherein the layer having the cushion function is a urethane mat. The tensile properties of the urethane mat are 100% modulus and MDC.
The reversible thermosensitive recording medium is characterized in that the D is 1.5 to 2.5 kg / mm ² . Further, there is provided the above reversible thermosensitive recording medium, characterized in that a light reflecting layer is provided between the support and the thermosensitive layer. Furthermore, the adhesive layer or the adhesive layer interposed between the back surface of the support and the adherend has a non-adhesive portion having air inside, in which an adhesive or a pressure-sensitive adhesive is not applied to a part thereof. Then, the reversible thermosensitive recording medium is provided in which the contact portion is used as a display portion.

The present inventors have used a reversible thermosensitive recording material having a reversible thermosensitive layer provided on a support, and have a high image contrast on a card or the like, and a reversible recording display excellent in durability by repeated use. As a result of earnest studies for imparting the property, adhesion of a two-layer structure (for example, a paper or film layer and a urethane mat layer) on the back surface of the support of the reversible thermosensitive recording material via an adhesive or pressure-sensitive adhesive layer. By adhering the body, it was found that the intended purpose of the present invention can be achieved, and the present invention has been completed.

The present invention will be described in more detail below with reference to the accompanying drawings. 3 to 4 show a label structure of a conventional reversible thermosensitive recording medium. 5 to 6 show the label construction of the reversible thermosensitive recording medium of the present invention. FIG. 5A shows a reversible thermosensitive recording material 12 comprising a light-reflecting layer 2 provided on the surface of a support 3, and a reversible thermosensitive layer 1 further coated on the light-reflecting layer 2, with a pressure-sensitive adhesive layer 4 interposed therebetween. An object to be adhered of paper or film 7 is adhered, and an object to be adhered of urethane mat 8 is adhered to the back surface thereof via adhesive layer 4, and release paper 5 is applied to the back surface thereof via adhesive layer 4 It is the structure of a label sheet that has been adhesively processed. Figure 5
FIG. 5B shows the structure of FIG.
It has the same configuration as (a).

FIG. 6 (a) shows a non-adhesive portion having air inside without a partial adhesive layer on the back surface of a reversible thermosensitive recording material 12 formed by coating a reversible thermosensitive layer on the surface of a support 3. 6 is provided and the contrast is improved by utilizing the reflection of light by the air layer, and is the same as FIG. 5A. Figure 6
6B is a configuration in which the portion having no adhesive layer in FIG. 6A is colored, and the contrast is further improved compared to FIG. 6A, and the other configurations are the same as those in FIG. 6A. . 7 (a),
(B), (c) and (d) show configurations in which the reversible thermosensitive recording medium 10 of the present invention is attached to the card 11. FIG. 7A shows a structure in which the surface of the card 11 is partially attached, FIG. 7B shows a structure in which the surface of the card 11 is made to be a convex portion, and FIG. The card 11 has the same height as the surface of the card 11, and (d) has a structure in which the entire surface of the card 11 is attached.

The reversible thermosensitive recording medium of the present invention has a basic constitution in which a reversible thermosensitive recording layer is provided on a support (reversible thermosensitive recording member). In this case, the support is a polyethylene film, Polypropylene film, polyvinyl chloride film, polyvinylidene chloride film, polyvinyl alcohol film, polyethylene terephthalate film, polycarbonate film, nylon film, polystyrene film, ethylene vinyl acetate copolymer film, ethylene vinyl alcohol copolymer film, polyethylene naphthalate film , Fluorinated ethylene propylene film, aromatic polyamide film, polyarylate film, polyether sulfone film, polyetherimide film, polyimide film, acrylic resin Film, plastic film such as ionomer film is used. The thickness of the support is preferably about 20 to 250 μm, and 50 to 1
88 μm is more preferable.

Further, the basic structure of the label of the reversible thermosensitive recording material of the present invention is such that a paper or film is adhered to the back surface of the reversible thermosensitive recording material via an adhesive layer, and a urethane mat etc. is adhered to the back surface via an adhesive layer. Is attached. In this case, as the paper or film, plain paper, coated paper or the like is used as the paper, and as the film, a plastic film similar to the above support is used. The material of the film used may be the same as the material of the support,
Also, different types may be used. The thickness of paper and film is preferably about 4 to 350 μm.

Further, the urethane mat of the present invention preferably has a cushioning function and high elasticity, and in particular, MD CD having a tensile strength of 100% modulus in view of physical properties.
It is preferably 1.5 to 2.5 kg / mm ² . When the tensile strength is less than the above range, the adherend is easily affected by unevenness, deformation, and the like, and a defect of image breakage occurs. On the other hand, when the size is large, there is a drawback that only the urethane mat comes out from the label of a certain size by repeating the print erasing.

The reversible thermosensitive recording material is adhered to a paper or film via an adhesive layer, further adhered to a urethane mat via an adhesive layer on the back side thereof, and further adhered to a release paper via an adhesive layer on the back side. However, in any case, as the adhesive or pressure-sensitive adhesive forming the adhesive layer or the pressure-sensitive adhesive layer,
A conventionally known adhesive or pressure-sensitive adhesive can be used. Specific examples of the adhesive and the tackifier include urea resin, melamine resin, phenol resin, epoxy resin, vinyl acetate resin, vinyl acetate acrylic copolymer resin, EVA resin, acrylic resin, polyvinyl ether resin. , Vinyl chloride vinyl acetate copolymer resin, polystyrene resin, polyester resin, polyurethane resin, polyamide resin, chlorinated polyolefin resin, polyvinyl butyral resin, acrylic ester copolymer, methacrylic ester copolymer Examples thereof include adhesives such as polymers, natural rubber-based and cyanoacrylate-based copolymers, and adhesives obtained by adding a suitable tackifier to these adhesives. Further, if necessary, a plasticizer, a filler, an antiaging agent and the like can be added.

Among the above-mentioned adhesives, the elastic adhesive containing a synthetic rubber or a siloxane cross-linked polymer as a main component is particularly preferable because it has a large ability to relieve stress. As an elastic adhesive containing a siloxane cross-linking polymer as a main component,
Examples thereof include a liquid polymer containing an amino group capable of reacting with an epoxy group, a main chain structure of which is polyoxypropylene, and a moisture-curable silyl group, and a composition containing an epoxy resin as a main component.

If necessary, water or an organic solvent is added to such an adhesive or pressure-sensitive adhesive to adjust the viscosity, and the composition is coated on a support or paper or film by a conventional method, and further coated on a urethane mat. It is applied to form an adhesive layer or a pressure-sensitive adhesive layer. The thickness of the adhesive layer or the pressure-sensitive adhesive layer is about 1 to 40 μm.
m is preferred.

In the present invention, the reflective film layer provided for improving the image contrast is preferably made of a metal vapor deposition film, for example, made of Al, Zn or the like. The colored layer preferably has a dark color, for example, black.

In the present invention, the reversible thermosensitive recording label is adhesively processed on the support side via an adhesive layer or an adhesive layer, and a commercially available silicone paper is preferred as the release paper to be used.

Further, the heat-sensitive recording layer of the reversible heat-sensitive recording medium of the present invention is repeatedly sandwiched between the thermal head and the platen when forming and erasing an image with a thermal head or the like, and by a guide roll of the conveying section. Be transported. Therefore, if the adhesive force when the label sheet is attached to the adherend is insufficient, the label sheet may peel off during repeated image formation and erasure. Therefore, in the present invention, the adhesive strength between the label sheet and the adherend is,
When expressed by the average value of the tensile load measured by the method of JIS K-6854, 180 degree peeling, 0.5 kgf / 2
5 mm or more is required. When the support side of the reversible thermosensitive recording material is attached to a paper or film and then to a urethane mat, the adhesive force between the support and the paper or film is increased by the adhesive force between the paper or film and the urethane mat. It is preferably 0.5 kgf / 25 mm or more.

The label sheet of the present invention is attached to an adherend, and examples of the adherend include a vinyl chloride card such as a credit card, an IC card, an ID card, a paper, a film, a synthetic paper, a boarding path, A commuter pass and the like can be cited, but the present invention is not limited to these.

Next, the reversible thermosensitive layer in the present invention will be described. That is, the heat-sensitive layer 1 includes a type in which the light-shielding property (transparency) is reversibly changed by changing the heating temperature, and a type in which color development and erasing are reversibly changed by changing the heating temperature. , It does not matter which one of these two. The principle of image formation-erasure in these types of heat-sensitive layers will be described below.

The heat-sensitive layer of the type that causes a change in transparency is mainly composed of a resin base material and an organic low-molecular substance dispersed in the resin base material. The reversible thermosensitive recording material here has a temperature range in which it becomes transparent, as described later. Further, the reversible thermosensitive recording material herein utilizes the transparency change (transparent state, cloudy opaque state) as described above, and the difference between the transparent state and the cloudy opaque state is presumed as follows. That is, in the case of (I) transparent, the particles of the organic low molecular weight substance dispersed in the resin base material are composed of large particles of the organic low molecular weight substance, and the light incident from one side is not scattered. It looks transparent because it penetrates to the other side, and in the case of (II) white turbidity,
Particles of organic low-molecular weight substances are composed of polycrystals of fine crystals of organic low-molecular weight substances, and the crystal axes of the individual crystals point in various directions, so the light incident from one side is the organic low-molecular weight substance particles. It is derived from the fact that it appears white because it is refracted many times at the crystal interface and is scattered.

In FIG. 1 (representing the change in transparency due to heat), a heat-sensitive layer mainly composed of a resin base material and an organic low molecular weight substance dispersed in the resin base material is, for example, T ₀ or less. It is cloudy and opaque at room temperature. When it is heated to a temperature T ₂ , it becomes transparent, and even if it is returned to room temperature below T _{0 in} this state, it remains transparent. It is considered that this is because the organic low-molecular-weight substance undergoes a semi-molten state from the temperature T ₂ to T ₀ or lower and the crystal grows from a polycrystal to a single crystal. Further heating to a temperature of T ₃ or higher results in a semi-transparent state intermediate between maximum transparency and maximum opacity. Next, when this temperature is lowered, the first cloudy opaque state is restored without taking the transparent state again. This is after the organic low molecular weight substance melts at temperature T ₃ or higher,
It is considered that this is because a polycrystal is precipitated by cooling. It should be noted that when this opaque state is heated to a temperature between T _{1 and} T ₂ and then cooled to room temperature, that is, a temperature of T ₀ or lower, an intermediate state between transparent and opaque can be obtained.
In addition, even if the material becomes transparent at room temperature, it is returned to the cloudy opaque state again when heated to a temperature of T ₃ or higher and then returned to room temperature. That is, both opaque and transparent forms at room temperature and intermediate forms thereof can be obtained.

Therefore, the heat sensitive layer can be selectively heated by selectively applying heat to form a cloudy image on a transparent background and a transparent image on a cloudy background, and the change can be repeated many times. It is possible. By arranging a coloring sheet on the back surface of such a heat-sensitive layer, it is possible to form an image of the color of the coloring sheet on a white background or a white image on the background of the color of the coloring sheet. Also, when projected with an OHP (overhead projector) or the like, the cloudy part becomes a dark part, and the transparent part transmits light and becomes a bright part on the screen.

In order to form and erase an image using such a reversible thermosensitive recording material, it is necessary to have two thermal heads for image formation and image erasure, or to change the applied energy conditions. Therefore, it is effective to use a thermal head having a single thermal head for image formation and image deletion.

In the former case, the cost of the apparatus is increased because two thermal heads are required. However, if the reversible thermosensitive recording material is passed once with different energy application conditions for each thermal head, image formation and It can be erased. In the latter case, an image is formed and erased by one thermal head. Therefore, the conditions for applying energy to the thermal head at one time when the thermal recording material passes are adjusted according to the image forming portion and the erasing portion. The operation is complicated, but the operation is complicated, such as changing finely, or erasing the image on the thermal recording material once and then running the thermal recording material again in the opposite direction to form an image under different energy conditions. Therefore, the equipment cost is reduced.

In order to prepare a reversible thermosensitive recording medium according to this type of the present invention, generally, (a) a resin matrix and an organic low molecular weight substance are used.
Dispersion of fine particles of organic low molecular weight substance in a solution of two components or (b) a resin base material solution (a solvent that does not dissolve at least one organic low molecular weight substance is used) Is coated on a support 3 such as a plastic film and dried to form the heat-sensitive layer 1.

The solvent for forming the heat-sensitive layer can be variously selected depending on the type of the resin base material and the organic low molecular weight substance, and examples thereof include tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene and benzene. To be The organic low molecular weight substance is precipitated as fine particles and exists in a dispersed state in the heat-sensitive layer obtained not only when the dispersion liquid is used but also when the solution is used.

The resin base material used for the heat sensitive layer is a material that forms a layer in which an organic low molecular weight substance is uniformly dispersed and held, and has an effect on the transparency at maximum transparency. Therefore, the resin base material is preferably a resin having good transparency, mechanical stability, and good film forming property. As such a resin, a resin that can form a film or a sheet, has good transparency, and is mechanically stable is preferable. Specifically, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-acrylate copolymer, etc. Vinyl chloride copolymers; polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-acrylonitrile copolymers and other vinylidene chloride copolymers; polyesters; polyamides; styrene-butadiene copolymers; polyacrylates Alternatively, polymethacrylate or acrylate-methacrylate copolymer; silicone resin and the like can be mentioned. These may be used alone or in combination of two or more.

On the other hand, as the organic low molecular weight substance, any substance which can be changed from polycrystal to single crystal by heat in the heat-sensitive layer may be used, and those having a melting point of 30 to 200 ° C., preferably about 50 to 150 ° C. are generally used. . Such organic low-molecular substances include alkanols; alkane diols; halogen alkanols or halogen alkane diols; alkylamines; alkanes; alkenes; alkynes; halogen alkanes; halogen alkenes; halogen alkynes; cycloalkanes; cycloalkenes; cycloalkynes; saturated or Unsaturated mono- or dicarboxylic acids or their esters, amides or ammonium salts; saturated or unsaturated halogen fatty acids or their esters, amides or ammonium salts; arylcarboxylic acids or their esters, amides or ammonium salts; halogenallylcarboxylic acids or Thioalcohols; esters, amides or ammonium salts thereof; thiocarboxylic acids or their esters, amines or ammonium salts; thioalcohols Carboxylic acid esters, and the like. These may be used alone or in combination of two or more. The carbon number of these compounds is preferably 10 to 60, preferably 10 to 38, and particularly preferably 10 to 30. The alcohol group moiety in the ester may be saturated or unsaturated, and may be halogen-substituted. In any case, the organic low molecular weight substance is at least one of oxygen, nitrogen, sulfur and halogen in the molecule, for example, -OH, -COOH, -CONH-, -COO.
_{R, -NH -, - NH 2} , -S -, - SS -, - O-, is preferably a compound containing a halogen and the like.

More specifically, as these compounds,
Uric acid, dodecanoic acid, myristic acid, pentadecane
Acid, palmitic acid, stearic acid, behenic acid, nonadeca
Higher fatty acids such as acid, araginic acid and oleic acid; steer
Methyl phosphate, tetradecyl stearate, stearin
Acid octadecyl, octadecyl laurate, palmitin
Of higher fatty acids such as tetradecyl acid acid and dodecyl behenate
Stell; C₁₆H₃₃-O-C₁₆H₃₃ , C₁₆H₃₃-S-C₁₆H₃₃ , C₁₈H₃₇-S-C₁₈H₃₇ , C₁₂H_{twenty five}-S-C₁₂H_{twenty five} , C₁₉H₃₉-S-C₁₉H₃₉ , C₁₂H_{twenty five}-S-S-C₁₂H_{twenty five} ,  Etc., such as ether or thioether. Above all, the present invention
Higher fatty acids, especially palmitic acid, pentadecanoic acid,
Nonadecanoic acid, arachidic acid, henicosanoic acid, Tricosa
Charcoal such as acid, stearic acid, behenic acid, lignoceric acid
Higher fatty acids with a prime number of 16 or more are preferred, and high fatty acids with a carbon number of 16-24.
Further preferred are the primary fatty acids.

The ratio of the organic low molecular weight substance to the resin base material in the heat sensitive layer is preferably about 2: 1 to 1:16 by weight.
The ratio of 1: 2 to 1: 3 is more preferable. When the ratio of the resin base material is less than this, it becomes difficult to form a film in which the organic low molecular weight material is retained in the resin base material. Becomes difficult.

It is also possible to use one of the above-mentioned organic low molecular weight substances as the organic low molecular weight substance and another type of organic low molecular weight substance as the substance for controlling the crystal growth. For example, stearic acid is used as an organic low molecular weight substance, and stearyl alcohol is used as a substance for controlling crystal growth. The weight ratio of the organic low molecular weight substance to the substance that controls the crystal growth of the organic low molecular weight substance is preferably about 1: 0.1 to 1: 0.8. When the substance that controls the crystal growth of the organic low molecular weight substance is below this range, the temperature range or energy range where it becomes transparent cannot be widened, and above this range, the opacity decreases.

The thickness of the heat sensitive layer is preferably 1 to 3 μm, and 2
˜20 μm is more preferred. If the heat-sensitive layer is too thick, heat distribution will occur in the layer and it will be difficult to achieve uniform transparency. On the other hand, if the heat-sensitive layer is too thin, the white turbidity is lowered and the contrast is lowered. Further, the white turbidity can be increased by increasing the amount of the organic low molecular weight substance in the heat sensitive layer.

In addition to the above components, additives such as a surfactant and a high boiling point solvent may be added to the heat-sensitive layer in order to facilitate the formation of a transparent image. Specific examples of these additives are as follows. Examples of high boiling point solvents: tributyl phosphate, tri-2-ethylhexyl phosphate, triphenyl phosphate, tricresyl phosphate, butyl oleate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, diphthalate. -n-octyl, di-2-ethylhexyl phthalate, diisononyl phthalate, dioctyldecyl phthalate, diisodecyl phthalate, butylbenzyl phthalate, dibutyl adipate, di-n-hexyl adipate, di-adipate
2-ethylhexyl, di-2-ethylhexyl azelate, dibutyl sebacate, di-2-ethylhexyl sebacate, diethylene glycol dibenzoate, triethylene glycol di-2-ethyl butyrate, methyl acetylricinoleate, butyl acetylricinoleate, butyl Phthalyl butyl glycolate, tributyl acetyl citrate.

Examples of surfactants and other additives: polyhydric alcohol higher fatty acid ester; polyhydric alcohol higher alkyl ether; polyhydric alcohol higher fatty acid ester, higher alcohol, higher alkylphenol, higher fatty acid higher alkylamine, higher fatty acid amide , Lower olefin oxide adduct of fats and oils or polypropylene glycol; acetylene glycol; Na, Ca, Ba or Mg salt of higher alkylbenzene sulfonic acid; higher fatty acid, aromatic carboxylic acid, higher fatty acid sulfonic acid, aromatic sulfonic acid, sulfuric acid monoester Or phosphoric acid mono- or di-ester Ca,
Ba or Mg salt; low-sulfated oil; poly long-chain alkyl acrylate; acrylic oligomer; poly long-chain alkyl methacrylate; long-chain alkyl methacrylate-amine-containing monomer copolymer; styrene-maleic anhydride copolymer;
Olefin-maleic anhydride copolymer.

When the image of this recording medium is used as a reflection image, if a layer that reflects light is provided on the back surface of the recording layer, the contrast can be increased even if the thickness of the recording layer is reduced. Specifically, vapor deposition of Al, Ni, Sn and the like can be mentioned (described in JP-A-64-14079).

Further, a protective layer can be provided on the heat-sensitive layer in order to prevent the transparency of the transparent portion from being lowered due to the deformation of the surface due to the heat and pressure of the heating means by a writing method such as a thermal head. The thickness of the protective layer is 1 to 15 μm, preferably about 2 to 10 μm. If the thickness of the protective layer is less than 1 μm, the heat-sensitive layer cannot be protected, and if it exceeds 15 μm, the heat sensitivity of the heat-sensitive layer decreases. As the material of the protective layer laminated on the heat-sensitive layer, silicone rubber, silicone resin (described in JP-A-63-221087),
Polysiloxane graft polymer (described in JP-A-63-317385), UV curable resin or electron beam curable resin (JP
2-566). In either case,
A solvent is used at the time of coating, but it is desirable that the solvent is difficult to dissolve the resin of the heat sensitive layer and the organic low molecular weight substance.
Examples of the solvent in which the resin of the heat-sensitive layer 1 and the organic low molecular weight substance are difficult to dissolve include n-hexane, methyl alcohol, ethyl alcohol, isopropyl alcohol and the like, and an alcohol solvent is particularly preferable from the viewpoint of cost. Further, silicone oil, fluororesin, and filler such as calcium carbonate and talc may be added in consideration of transportability and blocking.

Furthermore, an intermediate layer may be provided between the protective layer and the heat-sensitive layer 1 in order to protect the heat-sensitive layer 1 from the solvent and monomer components of the protective layer-forming liquid (Japanese Patent Laid-Open No. 1-13378).
(Described in Publication No. 1). As the material for the intermediate layer, the following thermosetting resins and thermoplastic resins can be used in addition to those listed as the resin base material in the heat sensitive layer. That is, polyethylene, polypropylene, polystyrene, polyvinyl alcohol, polyvinyl butyral, polyurethane, saturated polyester, unsaturated polyester, epoxy resin, phenol resin, polycarbonate, polyamide and the like. The thickness of the intermediate layer is preferably about 0.1 to 2 μm. Although the thickness of the intermediate layer varies depending on the use, it is preferably about 0.1 to 2 μm. If it is less than this, the protective effect is lowered, and if it is more than this, the thermal sensitivity is lowered.

Next, a description will be given of a case where the heat-sensitive layer is formed by a reversible thermochromic composition utilizing a color-forming reaction between an electron-donating color-forming compound and an electron-accepting compound. A thermochromic composition utilizing a color-forming reaction between an electron-donating color-developing compound and an electron-accepting compound has a non-coloring property when the electron-donating color-developing compound and the electron-accepting compound are heated and melt-mixed. When a crystalline chromophore is generated, on the other hand, when the amorphous chromophore is heated at a temperature lower than the melting temperature, the phenomenon that the electron-accepting compound causes crystallization and the chromophore disappears. It was used.

The thermochromic composition instantly develops color upon heating, and the color-developed state thereof is stable even at room temperature. On the other hand, the composition in the color-developed state is instantly heated by heating at a temperature not higher than the color development temperature. The color is erased and the erased state is stable even at room temperature, and such a reversible peculiar coloring / decoloring behavior is a novel and surprising phenomenon that has never been seen before.

The principle of coloring and erasing, that is, image formation and image erasing when this composition is used as a heat-sensitive layer will be described with reference to the graph shown in FIG. In FIG. 2, the vertical axis of the graph represents the color density, the horizontal axis represents the temperature, the solid line represents the image forming process by heating, and the broken line represents the image erasing process by heating. A is the density in the completely erased state, B is the density in the completely colored state when heated to a temperature of T ₅ or higher, C is the density at a temperature of T ₄ or lower in the completely colored state, and D is T ₄ ~ T ₅
It shows the concentration when erased by heating at a temperature between.

This composition according to the invention is in the colorless state (A) at temperatures below T ₄ . To perform recording (image formation), a color image (B) is formed by heating to a temperature of T ₅ or higher with a thermal head or the like to form a recorded image. Even if the recorded image is returned to the temperature of T ₄ or lower according to the solid line, the state (C) is maintained as it is and the recording memory property is not lost.

Next, in order to erase the recorded image, the formed recorded image is heated to a temperature between T _{4 and} T _{5 which} is lower than the coloring temperature, so that a colorless state (D) is obtained. In this state, even if the temperature is returned to T ₄ or lower, the colorless state (A) is maintained as it is. That is, the process of forming the recorded image reaches C by the path of the solid line ABC and the recording is held. Next, in the process of erasing the recorded image, the erased state is maintained by reaching A through the path of the broken line CDA. The behavior characteristic of forming and erasing the recorded image is reversible and can be repeated many times.

The reversible thermochromic composition contains a color former and a color developer as essential components. Then, the coloring state is formed by heating and melting the color-developing agent and the color-developing agent, while the coloring state is erased by heating at a temperature lower than the coloring temperature, and the coloring state and the erasing state exist stably at room temperature. Is. As described above, the mechanism of coloring and decoloring in the composition is such that when the coloring agent and the color developer are heated and melt mixed at the coloring temperature, the composition is amorphized to form a color. This is based on the property that when the developer is heated to a temperature lower than the coloring temperature, the developer of the colored composition causes crystallization to form an erased state of coloring.

A composition comprising an ordinary color-developing agent and a color-developing agent, for example, a leuco compound having a lactone ring, which is a dye precursor widely used in conventional thermal recording paper, and a phenolic compound exhibiting a color-developing action. When this is melt-mixed by heating, it becomes a coloring state based on the ring opening of the lactone ring of the leuco compound. This colored state is an amorphous state in which both are compatible. Although this colored amorphous state is stable at room temperature, it does not crystallize even when heated again, and because the phenolic compound is not separated from the leuco compound, there is no ring closure of the lactone ring and decolorization. I don't.

On the other hand, when the composition of the color former and the developer according to the present invention is also melt-mixed by heating, it becomes a color-developed state, exhibits an amorphous state as in the conventional case, and is stable at room temperature. Exist. However, in the case of the present invention, when the composition in the colored amorphous state is heated at a temperature not higher than the coloring temperature, that is, a temperature at which the molten state is not reached, crystallization of the developer occurs and a compatibility state with the color developing agent occurs. The bond due to can not be retained, and the color developer separates from the color developer. It is considered that due to the crystallization of the color developer from the color developer, the color developer cannot accept electrons from the color developer, and the color developer is decolorized.

The above-mentioned peculiar coloring and decoloring behaviors observed in this thermochromic composition are the mutual solubility of the color former and the color developer by heating and melting, the strength of the action of both in the color developing state, Although the solubility of the colorant in the color former and the crystallinity of the color developer are related, in principle, it causes amorphization due to heating and melting, while on the other hand, it is crystallized by heating at a temperature lower than the coloring temperature. Any color-developing agent / developing agent system that causes the change can be used as the composition component in the present invention. Further, those having such characteristics show endothermic change due to melting and exothermic change due to crystallization in thermal analysis, so that the color former / developer system applicable to the present invention can be easily analyzed by thermal analysis. You can check. Further, the reversible thermochromic composition system according to the present invention may include a third substance,
For example, it has been found that the reversible coloring / decoloring behavior is retained even when a polymer substance is present.

In the thermochromic composition of the present invention, the decoloring is caused by the separation from the color former due to the crystallization of the color developing agent. The choice of is important.

Examples of the color developer preferably used in the present invention are as follows. As described above, the color developer applicable to the present invention can be easily found by thermal analysis.
It is not limited to them. (1) Organic phosphoric acid compound represented by the following general formula (1) R ¹ —PO (OH) ₂ (1) (wherein R ¹ is a linear or branched alkyl group or alkenyl having 8 to 30 carbon atoms) Represents a group.) Specific examples of the organic phosphoric acid compound include the following. Octylphosphonic acid, nonylphosphonic acid, decylphosphonic acid, dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid, docosylphosphonic acid, tetracosylphosphonic acid. (2) Organic acid having a hydroxyl group at the α-position carbon represented by the following general formula (2) R ² —CH (OH) COOH (2) (wherein R ² is a linear or branched chain having 6 to 28 carbon atoms). It represents a branched alkyl group or an alkenyl group.) Specific examples of the organic acid having a hydroxyl group at the α-position carbon include the following. α-Hydroxyoctanoic acid, α
-Hydroxydodecanoic acid, α-hydroxytetradecanoic acid, α-hydroxyhexadecanoic acid, α-hydroxyoctadecanoic acid, α-hydroxypentadecanoic acid, α-hydroxyeicosanoic acid , Α-hydroxydocosanoic acid and the like.

The color former used in the present invention is a compound exhibiting an electron-accepting property, and is a colorless or light-colored dye precursor itself, and is not particularly limited, and conventionally known compounds such as triphenylmethanephthalide compounds are used. There are compounds, fluoran compounds, phenothiazine compounds, leuco auramine compounds, rhodamine lactam compounds, spiropyran compounds, indolinophtalide compounds and the like, and specific examples include the following. 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-chlorofluorane, 3-dimethylamino-5,7-dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7- Methylfluorane, 3-diethylamino-7,8
-Benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3- (Np-tolyl-N-
Ethylamino) -6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylamino Fluoran, 2-
{3,6-bis (diethylamino) -6- (o-chloroanilino) xanthylbenzoic acid lactam}, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- ( o-
Chloranilino) fluorane, 3-dibutylamino-7
-(O-Chloranilino) fluorane, 3-N-methyl-N-amylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N-cyclohexylamino-6
-Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N,
N-diethylamino) -5-methyl-7- (N, N-dibenzylamino) fluorane, benzoleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-2'- 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'-methoxyphenyl) phthalide, 3-morpholino-7- (N-propyl-). Trifluoromethylaniline)
Fluoran, 3-diethylamino-5-chloro-7-
(N-benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluorane, 3-diethylamino-5
-Chloro-7- (α-phenylethylamino) fluorane, 3- (N-ethyl-p-toluidino) -7- (α-
Phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluorane, 3-diethylamino-5-methyl-7- (α
-Phenylethylamino) fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3-
(N-methoxytoluidino) -7- (pn-butylanilino) fluorane, 3- (N-methyl-N-isopropylamino) -6-methyl-7-anilinofluorane,
3-dibutylamino-6-methyl-7-anilinofluorane, 3,6-bis (dimethylamino) fluorenspiro (9,3 ')-6'-dimethylaminophthalide, 3-
(N-benzyl-N-cyclohexylamino) -5,6
-Benzo-7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-N-ethyl-N- (2-ethoxypropyl) amino-6- Methyl-7-anilinofluorane, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-mesitidino-4 ', 5'. −
Benzofluorane, 3-N-methyl-N-isobutyl-
6-methyl-7-anilinofluorane, 3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (2 ',
4'-dimethylanilino) fluorane and the like.

Particularly preferred color formers used in the present invention are those containing halogen as a substituent. Examples of such a thing include the following. 3,3-bis (p-dimethylaminophenyl) -6
-Chlorophthalide, 3-cyclohexylamino-6-chlorofluorane, 3-cyclohexylamino-6-bromofluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-bromofluorane, 3
-Dipropylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-phenylamino-fluorane, 3-pyrrolidino-6-chloro-7-phenylamino-fluorane, 3-diethylamino-6-chloro-7
-(M-trifluoromethylphenyl) amino-fluorane, 3-cyclohexylamino-6-chloro-7- (o
-Chlorophenyl) amino-fluorane, 3-diethylamino-6-chloro-7- (2 ', 3'-dichlorophenyl) amino-fluorane, 3-diethylamino-6-
Methyl-7-chlorofluorane, 3-dibutylamino-
6-chloro-7-ethoxyethylamino-fluorane,
3-diethylamino-7- (o-chlorophenyl) amino-fluorane, 3-diethylamino-7- (o-bromophenyl) amino-fluorane, 3-diethylamino-7- (o-chlorophenyl) amino-fluorane, 3
-Dibutylamino-7- (o-fluorophenyl) amino-fluorane, 6'-bromo-3'-methoxybenzoindolino-pyrrolospirane, 3- (2'-methoxy-
4'-Dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-chlorophenyl) phthalide, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2 '-Methoxy-5'-chlorophenyl) phthalide, 2- {3,6-bis (diethylamino)}-9- (o-chlorophenyl) amino-xanthyl lactam benzoate and the like.

A more preferable color former used in the present invention is a compound represented by the following general formula (3) (formula 1).

[Chemical 1] (However, R ³ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ⁴ is a hydrogen atom or an optionally substituted amino group, X is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or a phenylamino group. , Y represents an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 2 carbon atoms, and m and n each represent an integer of 1 or 2.)

Specific examples of the compound represented by the general formula (3) include the following. 3- (N-
Methyl-N-phenylamino) -7-amino-fluorane, 3- (N-ethyl-N-phenylamino) -7-amino-fluorane, 3- (N-propyl-N-phenylamino) -7-amino- Fluoran, 3- {N-methyl-N- (p-methylphenyl) amino} -7-amino-
Fluorane, 3- {N-ethyl-N- (p-methylphenyl) amino} -7-amino-fluorane, 3- {N-
Propyl-N- (p-methylphenyl) amino} -7-
Amino-fluorane, 3- {N-methyl-N- (p-ethylphenyl) amino} -7-amino-fluorane, 3
-{N-ethyl-N- (p-ethylphenyl) amino}
-7-amino-fluorane, 3- {N-propyl-N-
(P-Ethylphenyl) amino} -7-amino-fluorane, 3- {N-methyl-N- (2 ', 4'-dimethylphenyl) amino} -7-amino-fluorane, 3- {N
-Ethyl-N- (2 ', 4'-dimethylphenyl) amino} -7-amino-fluorane, 3- {N-propyl-
N- (2 ', 4'-dimethylphenyl) amino} -7-amino-fluorane, 3- {N-methyl-N- (p-chlorophenyl) amino} -7-amino-fluorane, 3-
{N-ethyl-N- (p-chlorophenyl) amino}-
7-amino-fluorane, 3- {N-propyl-N-
(P-Chlorophenyl) amino} -7-amino-fluorane, 3- (N-methyl-N-phenylamino) -7-
Methylamino-fluorane, 3- (N-ethyl-N-phenylamino) -7-methylamino-fluorane, 3-
(N-propyl-N-phenylamino) -7-methylamino-fluorane, 3- {N-methyl-N- (p-methylphenyl) amino} -7-ethylamino-fluorane,
3- {N-ethyl-N- (p-methylphenyl) amino} -7-benzylamino-fluorane, 3- {N-methyl-N- (2 ', 4'-dimethylphenyl) amino}-
7-methylamino-fluorane, 3- {N-ethyl-N
-(2 ', 4'-Dimethylphenyl) amino} -7-ethylamino-fluorane, 3- {N-methyl-N-
(2 ', 4'-Dimethylphenyl) amino} -7-benzylamino-fluorane, 3- {N-ethyl-N-
(2 ', 4'-Dimethylphenyl) amino} -7-benzylamino-fluorane, 3- (N-methyl-N-phenylamino) -7-dimethylamino-fluorane, 3- (N
-Ethyl-N-phenylamino) -7-dimethylamino-fluorane, 3- {N-methyl-N- (p-methylphenyl) amino} -7-diethylamino-fluorane,
3- {N-ethyl-N- (p-methylphenyl) amino} -7-diethylamino-fluorane, 3- (N-methyl-N-phenylamino) -7-dipropylaminofluorane, 3- (N- Ethyl-N-phenylamino) -7
-Dipropylaminofluorane, 3- {N-methyl-N
-(P-Methylphenyl) amino} -7-dibenzylamino-fluorane, 3- {N-ethyl-N- (p-methylphenyl) amino} -7-dibenzylamino-fluorane, 3- {N-ethyl -N- (p-methylphenyl)
Amino} -7-di (p-methylbenzyl) amino-fluorane, 3- {N-methyl-N- (p-methylphenyl) amino} -7-acetylamino-fluorane, 3-
{N-ethyl-N- (p-methylphenyl) amino}-
7-benzoylamino-fluorane, 3- {N-methyl-N- (p-methylphenyl) amino} -7- (o-methoxybenzoyl) amino-fluorane, 3- {N-ethyl-N- (p-methyl) Phenyl) amino} -6-methyl-7-phenylamino-fluorane, 3- {N-methyl-N- (p-methylphenyl) amino} -6-methyl-7-phenylamino-fluorane, 3- {N- Methyl-N- (p-methylphenyl) amino} -6-tert
-Butyl-7- (p-methylphenyl) amino-fluorane, 3- (N-ethyl-N-phenylamino) -6-
Methyl-7- (N-ethyl-N- (p-methylphenyl) amino-fluorane, 3- {N-propyl-N-
(P-Methylphenyl) amino} -6-methyl-7-
{N-methyl-N- (p-methylphenyl) amino}-
Fluoran, 3- {N-ethyl-N- (p-methylphenyl) amino} -5-methyl-7-benzylamino-fluorane, 3- {N-ethyl-N- (p-methylphenyl) amino} -5 -Chloro-7-dibenzylamino-fluorane, 3- {N-methyl-N- (p-methylphenyl) amino} -5-methoxy-7-dibenzylamino-
Fluoran, 3- {N-ethyl-N- (p-methylphenyl) amino} -6-methyl-fluorane, 3- {N-
Ethyl-N- (p-methylphenyl) amino} -5-methoxy-fluorane and the like.

The developer is used alone or in combination of two or more kinds. Similarly, the color-developing agent can be applied alone or in a mixture of two or more kinds. The thermochromic composition can be used as a reversible thermosensitive recording material by forming the thermosensitive layer 1 on the support 3. In this case, the color-developing agent and the color-developing agent can be used as they are or by being encapsulated in microcapsules. Such a reversible thermosensitive recording material can be obtained by uniformly dispersing or dissolving a color former and a developer together with a binder in water or an organic solvent according to a conventionally known method, and coating the support on a support. .

As the binder, various conventional binders can be appropriately used, and examples thereof include polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, methoxy cellulose, carboxymethyl cellulose, methyl cellulose, cellulose acetate, gelatin, casein, starch, polyacrylic acid. Soda, polyvinylpyrrolidone, polyacrylamide, maleic acid copolymer, acrylic acid copolymer, polystyrene, polyvinyl chloride, polyvinyl acetate, polyacrylic acid esters, polymethacrylic acid esters, vinyl chloride-vinyl acetate copolymer Coalesce, styrene copolymer, polyester,
There is polyurethane etc.

Microencapsulation of the color former and / or the developer can be carried out by a known method such as a coacervation method, an interfacial polymerization method or an in situ polymerization method. In the present invention, various additives used in ordinary thermal recording paper, such as dispersants, surfactants, fillers, color image stabilizers, and oxidants, are used with the intention of improving coating properties or recording properties as necessary. It is also possible to add an inhibitor, a light stabilizer, a lubricant and the like.

The support 3 is made of paper, synthetic paper,
It may be a plastic film or a composite thereof, and is not particularly limited as long as it is flexible.

Further, as in the case of the heat-sensitive layer of the type described above, a protective layer, an intermediate layer and the like can be provided. In this case, the materials constituting them can be the same as those in the case of the heat sensitive layer of the above type.

The formation of a recorded image is not particularly limited by a hot pen, a thermal head, laser heating, etc. depending on the purpose of use. Similarly, the erasing of the recorded image is not particularly limited as long as the erasing temperature conditions such as the heating roller, the sheet heating element, the constant temperature bath, the warm air, and the thermal head are given. In addition, so-called overwriting is possible in which the recorded image is erased by the thermal head set to the erasing temperature and at the same time the recorded image is formed by another thermal head set to the recording temperature.

[0061]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples. Parts herein are by weight.

Example 1 On a PET film having a thickness of about 50 μm, 500 Å aluminum was vapor-deposited, the surface of which was coated with a solution having the following composition, and dried by heating to form a heat-sensitive layer having a thickness of about 15 μm. Stearic acid 6 parts Eicosane diacid 4 parts Diisodecyl phthalate 2 parts Vinyl chloride-vinyl acetate-phosphorus ester copolymer 20 parts (Denka vinyl # 1000P manufactured by Denki Kagaku Kogyo KK) THF 150 parts Toluene 15 parts Next, on the thermosensitive layer A polyamide resin (Toray, CM8000) 5 parts methyl alcohol 90 parts solution was applied with a wire bar and dried by heating to form an intermediate layer of about 0.3 μm thickness, and further urethane acrylate UV A butyl acetate solution of curable resin (Unidick Ci-157 manufactured by Dainippon Ink and Chemicals, Inc.) is applied with a wire bar, and after heating and drying, an ultraviolet ray of 80 W / cm is irradiated with ultraviolet rays for 3 seconds to form an overcoat of about 3 μm thickness. Layers were provided to make a reversible thermosensitive recording material. Next, a nitrile rubber adhesive (trade name EC766: manufactured by Sumitomo 3M Ltd.) is applied to the back surface of the reversible thermosensitive recording material to give about 40
An adhesive layer of μm is formed, 100 μm-thick high-quality paper is pasted on it, and the same adhesive as above is applied to the opposite surface,
An adhesive layer of about 40 μm was formed, and a 188 μm thick urethane mat (100% modulus tensile strength MD
1.58 kg / mm ² , CD 1.59 kg / mm ² ) and then apply the same adhesive as above to the opposite surface to form an adhesive layer of about 40 μm, and then attach release paper to it. The label sheet of the reversible thermosensitive recording medium of the present invention was prepared by processing and punching into an arbitrary size. This label sheet was adhered on a vinyl chloride card having a thickness of 500 μm.

Example 2 A label sheet for a reversible thermosensitive recording medium of the present invention was prepared in the same manner as in Example 1 except that the aluminum vapor deposition process of Example 1 was processed on the opposite surface of the support, and this label sheet was used. 500
It was adhered on a PVC card having a thickness of μm.

Example 3 In the same manner as in Example 1 except that a reversible thermosensitive recording layer similar to that in Example 1 was provided on a 50 μm PE film and no adhesive layer was provided on a part of the back surface of the reversible thermosensitive recording material. A label sheet for the reversible thermosensitive recording medium of the present invention was prepared, and this label sheet was adhered onto a vinyl chloride card having a thickness of 500 μm.

Example 4 A label sheet of the reversible thermosensitive recording material of the present invention was prepared in the same manner as in Example 1 except that the portion where the adhesive layer was not provided in Example 3 was colored (dark color). To 500
It was adhered on a PVC card having a thickness of μm.

Example 5 The material of the urethane mat of Example 1 was 188 μm thick and 10
A label sheet for the reversible thermosensitive recording medium of the present invention was prepared in the same manner as in Example 1 except that the tensile strength at 0% modulus was changed to 1.0 kg / mm ^2.
It was adhered on a PVC card having a thickness of 00 μm.

Example 6 The material of the urethane mat of Example 1 was 10 mm thick with a thickness of 188 μm.
A label sheet for the reversible thermosensitive recording medium of the present invention was prepared in the same manner as in Example 1 except that the tensile strength at 0% modulus was changed to 3.0 kg / mm ^2.
It was adhered on a PVC card having a thickness of 00 μm.

Example 7 A label sheet for the reversible thermosensitive recording medium of the present invention was prepared in the same manner as in Example 1 except that the quality paper of the adherend of Example 1 was changed to 100 μm thick. 500 μm
Bonded on thick PVC card.

Example 8 A label sheet for a reversible thermosensitive recording medium of the present invention was prepared in the same manner as in Example 1 except that the quality paper of the adherend of Example 1 was changed to 100 μm thick synthetic paper. 5 label sheets
It was adhered on a PVC card having a thickness of 00 μm.

Example 9 Comparative reversible thermosensitive recording was carried out in the same manner as in Example 1 except that the pressure-sensitive adhesive of Example 1 was replaced by a silicon pressure-sensitive adhesive (trade name Trepharm SP4570: manufactured by Toray Dow Corning). Create a label sheet for the material and add this label sheet to 5
It was adhered on a PVC card having a thickness of 00 μm.

Comparative Example 1 A comparative reversible thermosensitive recording medium label sheet was prepared in the same manner as in Example 1 except that the urethane mat of the adherend in Example 1 was removed, and this label sheet was prepared to have a vinyl chloride thickness of 500 μm. Glued on the card.

Comparative Example 2 A comparative reversible thermosensitive recording medium label sheet was prepared in the same manner as in Example 4 except that the urethane mat of the adherend in Example 4 was removed. Glued on the card.

Using the label sheet adhesive card obtained as described above, a card recording device (prototype) having a thermal head of 8 dots / mm was used, and an energy of 0.3 mj was obtained at a thermal head pressure of 1 K / 100 mm width. When the erasure field formation and the erasing were repeated with the hot stamp erasing apparatus, the samples of Comparative Examples 1 and 2 had image breakage and defective erasing at the first time. In Comparative Example 3, the image was not cut and the erasing failure did not occur, but there was a problem that the label was peeled off at the 10th time. With respect to the samples of Examples 1 to 4 and 6 to 8, the label sheet was not peeled off from the PVC card, and the image was not cut and the erasing failure was not observed after the 100th repetition. For the sample of Example 5, image breakage and defective erasing occurred at the 50th time. Regarding the sample of Example 6, there was a defect that the urethane mat came out of the label sheet at the 70th time.

The image density and scratches of the 11 types of reversible thermosensitive recording media were evaluated at the initial stage and after 100 times of repetition. The results are shown in Table 1. The measuring method is as follows. Density measurement Measured with a Macbeth reflection densitometer RD-514. Scratches were visually evaluated. ○: No scratches occurred △: Slight scratches occurred ×: Many scratches occurred

[0075]

[Table 1] ┛

[0076]

In the reversible thermosensitive recording medium of the present invention, the adherend has a two-layer structure, for example, one layer of the adherend is paper or film and the other layer is a urethane mat having a cushioning function. In addition, the pressure of the thermal head can be lowered, and high-quality image formation can be performed without being affected by the unevenness and deformation of the card. Furthermore, the problem of erasing failure can be prevented, and it can be repeated many times. In addition, lowering the thermal head pressure has the effect of preventing scratches on the back surface.

[Brief description of drawings]

FIG. 1 is an illustration showing that an image is formed and erased on a heat sensitive layer according to the present invention.

FIG. 2 is an explanatory diagram showing that an image is formed / erased in another heat-sensitive layer according to the present invention.

3A and 3B are schematic cross-sectional views each showing the basic structure of a conventional label sheet for a reversible thermosensitive recording medium.

FIG. 4 is a schematic cross-sectional view showing the structure of a conventional label sheet for a reversible thermosensitive recording medium.

5 (a) and 5 (b) are each a schematic cross-sectional view showing the basic structure of the label sheet of the reversible thermosensitive recording medium of the present invention.

6 (a) and 6 (b) are schematic cross-sectional views each showing a basic structure of a label sheet of the reversible thermosensitive recording medium of the present invention.

7 (a), (b), (c), and (d) are schematic cross-sectional views showing the configuration of the reversible recording medium card of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reversible thermosensitive recording layer 2 Light reflection layer 3 Support 4 Adhesive layer or adhesive layer 5 Releasing paper 6 Non-adhesive part 7 Adhered body-paper or film 8 Adhered body-Urethane mat 9 Colored layer 10 Reversible thermosensitive layer Label sheet for recording medium 11 Adherend 12 Reversible thermosensitive recording material

Front Page Continuation (72) Inventor Nogori Dori 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (6)

[Claims] 1. A reversible thermosensitive recording medium comprising a support and a thermosensitive layer which reversibly undergoes a transparent-opaque change or a color-decoloring change depending on temperature, wherein an adhesive layer is provided on the back surface of the support. Alternatively, a reversible thermosensitive recording medium having a double-layered adherend adhered via an adhesive layer. 2. The reversible thermosensitive recording medium according to claim 1, wherein one layer of the adherend is paper or a film, and the other layer is a layer having a cushion function. 3. The reversible thermosensitive recording medium according to claim 2, wherein the layer having a cushion function is a urethane mat. 4. The tensile property of the urethane mat is 10
MDCD 1.5% to 2.5 kg / mm with 0% modulus
Reversible thermosensitive recording medium according to claim 3, characterized in that the ^2. 5. The reversible thermosensitive recording medium according to claim 1, wherein a light reflecting layer is provided between the support and the thermosensitive layer. 6. A non-adhesive portion having air inside, wherein an adhesive layer or an adhesive layer interposed between the back surface of the support and the adherend has no adhesive or pressure-sensitive adhesive applied to a part thereof. Have
The contact portion is a display portion,
The reversible thermosensitive recording medium according to 2, 3, 4 or 5.