JPH0776170A - Reversible thermal record medium and image forming/ deleting method using the medium - Google Patents

Abstract

PURPOSE:To provide a novel reversible thermal record medium whose deterioration is very little even when images are formed and deleted many times, and provide an image forming/deleting method which uses the record medium. CONSTITUTION:Between a support body and a reversible thermal recording layer, a layer which is heated by irradiation of microwave is provided. The heat from the layer which is heated by the irradiation of the microwave is transmitted to the reversible thermal recording layer and is consumed for forming and deleting images. The reversible thermal recording layer is not deteriorated by the irradiation of the microwave.

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 an image forming / erasing method using the reversible thermosensitive recording medium. The present invention relates to an image recording medium that can be used many times and an image forming / erasing method using the same.

[0002]

2. Description of the Related Art In recent years, reversible thermosensitive recording media have attracted attention because they can temporarily form images and can erase the images when they are no longer needed. A typical example thereof is a reversible thermosensitive recording medium in which an organic low molecular weight substance such as a higher fatty acid and a higher alcohol are dispersed in a resin matrix such as a vinyl chloride-vinyl acetate copolymer or a polyester resin. (JP-A-54-119377, JP-A-55-154198, JP-A-63-31790,
JP-A-63-317385 and the like).

Recording with a reversible thermosensitive recording medium of this kind,
That is, image formation and erasure utilize the transparent change due to the temperature of the heat sensitive layer. Generally, image formation is performed by thermal head printing, and as a method for erasing the image, a means such as a hot roll or a hot plate thermal head is used. However, with these heating means, the surface and the inside of the reversible thermosensitive recording medium are easily deformed by the heat and pressure, and in particular, the organic low molecular weight substance particles inside are deformed, and the formation and deletion of the image are repeated. However, there is a drawback that the deformation gradually accumulates and the transparency of the transparent portion is lowered.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a reversible thermosensitive recording medium which solves the above-mentioned drawbacks and an image forming / erasing method using the same. Another object of the present invention is a reversible thermosensitive recording medium suitable for facilitating this image formation and its erasing (especially, image erasing is extremely easy), and an image recording / recording using the same.
It provides erasure.

[0005]

The first aspect of the present invention is a reversible thermosensitive recording medium. As shown in FIG. 1, as shown in FIG. A reversible thermosensitive recording material layer 3 whose transparency or color tone reversibly changes depending on temperature is provided on the layer 2. The heat generating layer 2 in this case is composed of a conductive layer or a dielectric layer.

A second aspect of the present invention is an image forming method using the first reversible thermosensitive recording medium, wherein the reversible thermosensitive recording medium is imagewise applied or irradiated with a thermal head or a microwave. The reversible thermosensitive recording material layer is directly heated or the reversible thermosensitive recording material layer (heat sensitive layer) is heated by the heat generated by the heat generating layer, and a cloudy or colored image or a transparent or colorless image is formed on the reversible thermosensitive recording material layer. It is characterized in that it is formed.

A third aspect of the present invention is a method for erasing an image recorded on the reversible thermosensitive recording medium by the method according to the second method, wherein the image-formed reversible thermal recording medium is irradiated with microwaves. The heat-generating layer is caused to generate heat, and the heat causes the cloudy or colored image of the reversible thermosensitive recording material layer to be transparent or colorless as in the background.

A fourth aspect of the present invention is another erasing method of the image recorded on the reversible thermosensitive recording medium by the second method, wherein the image-formed reversible thermosensitive recording medium is irradiated with microwaves. The heat-generating layer is caused to generate heat, and the heat causes the transparent or colorless image of the reversible thermosensitive recording material layer to become cloudy or colored as in the background.

In order to achieve the above-mentioned object, the present inventor has
We have studied recording media and recording / erasing methods that use reversible thermosensitive recording materials from various angles. A layer that generates heat between the support and the reversible thermosensitive recording material layer by irradiation with microwaves (hereinafter (Also referred to as "heating layer")
According to the use of the reversible thermosensitive recording medium provided with, the image can be easily erased by irradiation of quichrowave (in the office and at home, microwave induction heating using a microwave is sufficient). The present invention has been made by confirming that image recording (image formation) can be performed by a thermal printer such as a word processor or a facsimile (irradiating a beam-shaped microwave with a digital image may be performed). The present invention will be described in more detail below.

By the way, the "reversible thermosensitive recording material" in the present invention is a material that reversibly causes a visible change due to a temperature change. The visible change can be divided into a change in color state and a change in shape, but the present invention mainly uses a material that causes a change in color state. Changes in the color state include changes in transmittance, reflectance, absorption wavelength, scattering degree, etc., and in actual reversible thermosensitive recording materials, display is performed by a combination of these changes. More specifically, at present, there are two types of systems: materials that reversibly change the transparent state and cloudy state, and materials that chemically change the color, such as dyes.

As a typical example, a resin base material such as polyester having a heat sensitive layer in which an organic low molecular weight substance such as higher alcohol or higher fatty acid is dispersed is provided on the heat generating layer. As a typical example, a leuco thermosensitive recording material having enhanced reversibility can be mentioned.

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 and is opposite. In addition, in the case of (II) white turbidity, the particles of the organic low molecular weight substance are composed of polycrystals of fine crystals of the organic low molecular weight substance, and the crystal axis of each crystal Since the light is directed in various directions, the light incident from one side is refracted many times at the interface of the crystal of the organic low molecular weight substance particles, and is scattered and thus appears white.

In FIG. 2 (representing the change in transparency due to heat), the heat-sensitive layer mainly composed of the resin base material and the organic low-molecular 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, by selectively applying the heat generated in the heat generating layer 2 to the heat sensitive layer 3, the heat sensitive layer 3 can be selectively heated to form a cloudy image on a transparent background and a transparent image on a cloudy background. Can be repeated many times.

The heat generating layer 2 is composed of a conductive layer or a dielectric layer,
Any material may be used as long as it easily generates heat when irradiated with microwaves. Specifically, an organic conductive polymer alone, a metal powder or conductive carbon coated as a plastic resin binder, and a thin film of an inorganic material are used. However, when a single metal layer such as a metal vapor deposition layer is formed, sparks are generated, so that conductivity up to that point is not required. Also,
For the support 1, various types of plastic, paper, glass metal, etc. are used as in the conventional case. The thickness of the support can be arbitrarily selected depending on the application.

To make a reversible thermosensitive recording medium according to this type of the present invention, generally, (1) a solution in which two components of a resin base material and an organic low molecular weight substance are dissolved, or (2) a solution of a resin base material (solvent Is used as a solution in which at least one of the organic low molecular weight substances is not dissolved), a dispersion liquid in which the organic low molecular weight substance is dispersed in the form of fine particles is prepared, and this is placed on a support having a heat generating layer. It may be applied and dried to form a heat-sensitive layer.

The solvent for forming the heat-sensitive layer can be variously selected according to 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. Such resins include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-
Vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinyl chloride copolymer such as acrylate copolymer; polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, Examples thereof include vinylidene chloride-copolymers such as vinylidene chloride-acrylonitrile copolymers; polyesters; polyamides; polyacrylates or polymethacrylates or acrylate-methacrylate copolymers; and silicone resins. 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 changes from polycrystal to single crystal due to heat in the heat sensitive layer may be used, and generally, one having a melting point of about 30 to 200 ° C, preferably about 50 to 150 ° C is 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-C₁₈
H₃₇ , 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, stearic acid,
Higher fatty acids having 16 or more carbon atoms such as henic acid and lignoceric acid
Is preferred, and higher fatty acids having 16 to 24 carbon atoms are more preferred.
Yes.

In order to widen the range of temperature at which the material can be made transparent, the organic low molecular weight substances described in this specification may be appropriately combined, or such organic low molecular weight substances may be combined with other materials having different melting points. . These are, for example, JP-A-63-3
9378, JP 63-130380 and other publications, and Japanese Patent Application 63-14
No. 754, Japanese Patent Application No. 1-140109 and the like are disclosed, but the invention is not limited thereto. The ratio of the organic low molecular weight substance and the resin base material in the heat sensitive layer is 2: 2 by weight.
About 1 to 1:16 is preferable, and 1: 1 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.

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 degree of sulfated oil; poly long chain alkyl acrylate; acrylic orgomer; poly long chain alkyl methacrylate; long chain alkyl methacrylate to amine-containing monomer copolymer; styrene-maleic anhydride copolymer;
Olefin-maleic anhydride copolymer.

A protective layer may be provided on the heat-sensitive layer to protect the heat-sensitive layer. Protective layer (thickness 0.1 to 5μ
Examples of the material of (m) include silicone rubber, silicone resin (described in JP-A-63-221087), polysiloxane graft polymer (described in Japanese Patent Application No. 62-152550), UV curable resin, or electron beam. A cured resin (described in Japanese Patent Application No. 63-310600) can be used. In any 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. As a solvent that does not easily dissolve the resin and organic low-molecular substances in the heat-sensitive layer
Examples thereof include n-hexane, methyl alcohol, ethyl alcohol, isopropyl alcohol and the like, and an alcohol solvent is particularly preferable in terms of cost.

Further, an intermediate layer may be provided between the protective layer and the heat-sensitive layer in order to protect the heat-sensitive layer from the solvent and the monomer component of the protective layer forming liquid. 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,
Examples thereof include polyvinyl alcohol, polyvinyl butyral, polyurethane, saturated polyester, unsaturated polyester, epoxy resin, phenol resin, polycarbonate and polyamide. The thickness of the intermediate layer is preferably about 0.1 to 2 μm.

Next, a description will be given of a case where the heat-sensitive layer is formed of 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 is prepared by heating and melting the electron-donating color-developing compound and the electron-accepting compound. Amorphous chromophores are formed, while when the amorphous chromophore is heated at a temperature lower than the melting temperature, the electron-accepting compound causes crystallization and the chromophore disappears. It utilizes the phenomenon of.

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 color developing and erasing behavior is a novel and surprising phenomenon that has never been seen before.

The principle of coloring and erasing, that is, image forming and image erasing when this composition is used as a heat-sensitive recording material is shown in FIG.
This will be explained with reference to the graph shown in. 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 It shows the concentration when heat erasing is performed at a temperature between T _{5 and} T ₅ .

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 behavioral characteristics of forming and erasing the recorded image are reversible and can be repeated many times.

The reversible thermochromic composition contains a color former and a 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 causes an amorphization and a coloring state. On the other hand, it is based on the property that, when heated at a temperature lower than the coloring temperature, the developer of the colored composition causes crystallization to form an erased state of coloring. However, even in this case, since the heat-sensitive layer is heated to a temperature of T ₅ or higher and then decolored, the particles of the color-developing agent and the color-developing agent are restored to form a new color-developed state. Is advantageous to.

A composition comprising an ordinary color former and a developer, 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 effect. 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, the lactone ring is not closed and decolorized. 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, at a temperature at which the molten state is not reached, crystallization of the developer occurs and the composition is compatible with the color developing agent. The bond due to the state cannot be maintained, 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 color-development behavior observed in the thermochromic composition is the mutual solubility of the color-developing agent and the color-developing agent by heating and melting, the strength of both actions in the color-developing state, and the color-developing agent. Is related to the solubility of the color developing agent, the crystallinity of the developer, etc.
In principle, it causes amorphization by heating and melting, while
Any color former / developer system that causes crystallization by heating at a temperature lower than the color development temperature can be used as a 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 contain a third substance, for example, the reversible decoloring behavior thereof is retained even if a polymer substance is present. Was confirmed. In the thermochromic composition of the present invention, the decolorization is due to the separation from the color former due to the crystallization of the color developer. Therefore, in order to obtain an excellent decoloring effect, the color developer should be selected. is important.

Next, the color developing agents preferably used in the present invention are exemplified as follows. As described above, the color developing agents applicable to the present invention can be easily found by thermal analysis. It is not limited to ones. (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) Specific examples of this 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 straight chain having 6 to 28 carbon atoms) (Representing a branched or 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 Acid, α-hydroxydocosanoic acid, etc.

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 per se, and is not particularly limited, and conventionally known ones, for example, triphenylmethanephthalide series. 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'-dimethyl Aminophenyl) -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.

The color former preferably used in the present invention is a compound represented by the following general formula (3).

[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. , M is an integer of 1 or 2, Y is a carbon number of 1 to 4.
Alkyl group or alkoxy group having 1 to 2 carbon atoms, n is 1
Or represents an integer of 2. )

Specific examples of the compound represented by the general formula (3) include the followings. 3-
(N-methyl-N-phenylamino) -7-amino-fluorane, 3- (N-ethyl-N-phenylamino)-
7-amino-fluorane, 3- (N-propyl-N-phenylamino) -7-amino-fluorane, 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'-dimethyl) Phenyl) 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-
Fluoran, 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 color developers are used alone or in admixture of two or more. 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 medium by forming a thermosensitive layer on the heat generating layer. In this case, the heat-sensitive layer can be obtained by uniformly dispersing or dissolving the color-developing agent and the color-developing agent together with the binder in water or an organic solvent according to a conventionally known method, and applying the resultant onto the heat-generating layer.

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.

In the present invention, for the purpose of improving coating properties or recording properties as necessary, various additives used in ordinary heat-sensitive recording paper, such as dispersants, surfactants, fillers, etc., in the heat generating layer. Colored image stabilizer, antioxidant, light stabilizer,
Lubricants and the like can also be added. Further, as described above, the protective layer and the intermediate layer may be provided if necessary.

In the reversible thermosensitive recording medium of the present invention,
It may be a long one or an endless one.

To actually prepare the reversible thermosensitive recording medium of the present invention, for example, by a coating method using a wire bar,
A heat generating layer and a heat sensitive layer may be sequentially laminated on the support. Further, in order to form a recorded image on the recording medium thus created, the heat sensitive layer may be printed by a thermal head or the like, or microwaves may be irradiated to heat the heat generating layer imagewise.
Then, in order to erase the printed image, the whole thing may be irradiated with microwaves.

[0045]

The present invention will be described in more detail with reference to the following examples. All parts here are parts by weight.

Example 1 A solution consisting of 30 parts of polyvinylbenzyltrimethylammonium chloride solution (ECR34 by Dow Chemical Co.) 100 parts of water was coated on a polyester film having a thickness of about 75 μm with a wire bar and dried by heating to about 20 μm. A thick conductive layer (surface resistance value 3000Ω) was provided. A solution consisting of 8 parts of behenic acid, 8 parts of stearyl stearate, 2 parts of di (2-ethylhexyl) phthalate, 3 parts of vinyl chloride-vinyl acetate copolymer (VYHH manufactured by UCC Co., Ltd.), and 200 parts of tetrahydrofuran was applied to the conductive layer with a wire bar. Then, it was heated and dried to form a heat-sensitive layer having a thickness of about 15 μm. A solution consisting of 5 parts of polyamide resin (CM8000 manufactured by Toray Industries, Inc., CM8000) and 90 parts of methyl alcohol was applied on the heat-sensitive layer with a wire bar, and dried by heating to form an intermediate layer having a thickness of about 0.3 μm. A butyl acetate solution of acrylate-based UV curable resin (Unidik C7-157, manufactured by Dainippon Ink and Chemicals, Inc.) was applied with a wire bar, and after heating and drying, UV rays were irradiated for 3 seconds with an 80 W / cm UV lamp to a thickness of about 3 μm. An overcoat layer was provided to prepare a reversible thermosensitive recording medium of the present invention. Then, it was reheated to 65 ° C. to obtain a transparent recording medium.

A white turbid image was formed on this recording medium by using a thermal head with heat of 0.5 mJ / dot.
When the microwave was irradiated for 20 seconds with a household microwave oven (manufactured by Sanyo), the printed image could be erased. Furthermore, when this was repeated 100 times, an image that was completely the same as the initial image was obtained.

Example 2 A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the conductive layer was replaced by a conductive layer (surface resistance value 700Ω) formed by the following formulation. (Conductive layer formulation) Conductive carbon 3 parts PVA 10 parts Dispersant 0.1 part Water 100 parts Subsequently, image formation / erasure was performed as in Example 1 (however, microwave irradiation was performed for 5 seconds). When I went, 1
An image which was almost the same as the initial image was obtained even after the repetition of 00 times.

Example 3 The same procedure as in Example 1 was repeated except that the conductive layer formed by the following formulation (surface resistance value 450 Ω) was used instead of the conductive layer, and finally reheated at 100 ° C. to give a cloudy reversible sensation. I made a thermal recording medium. Al metal powder 2 parts PVA 10 parts Dispersant 0.1 part Water 100 parts This recording medium was 0.35 mJ using a thermal head.
/ Dot heat to form a transparent image, followed by Example 1
When microwave was applied for 8 seconds in the same manner as above, the whole was opaque and the transparent printed image was erased. Further, even if this was repeated 100 times, an image which was almost the same as the initial image was obtained.

After replacing the conductive layer with a commercially available conductive film (Electrister 500Ω: an ITO thin film is formed on a polyester film having a thickness of about 75 μm), the same heat-sensitive layer as in Example 1 was provided on the conductive layer side. The recording medium was reheated at 100 ° C. to form a cloudy recording medium. When this recording medium was repeatedly tested, almost the same results as in Example 3 were obtained.

[0051]

According to the first or second aspect of the present invention, a reversible thermosensitive recording medium can be obtained in which images can be repeatedly formed / erased by an easy means and which is durable. According to the invention of claim 3, a clear image can be obtained. According to the inventions of claims 4 and 5, the image can be erased neatly.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a reversible thermosensitive recording medium of the present invention.

FIG. 2 is a diagram for explaining the characteristics of another reversible thermosensitive recording material used in the present invention.

FIG. 3 is a diagram for explaining characteristics of another reversible thermosensitive recording material used in the present invention.

[Explanation of symbols]

 1 Support 2 Heating Layer 3 Thermosensitive Layer (Reversible Thermosensitive Recording Material Layer)

Claims (5)

[Claims] 1. A reversible thermosensitive recording material layer having a layer that generates heat upon irradiation with microwaves is provided on a support, and a reversible thermosensitive recording material layer that reversibly changes transparency or color tone depending on temperature is provided on the heating layer. Characteristic reversible thermosensitive recording medium. 2. The reversible thermosensitive recording medium according to claim 1, wherein the heat generating layer comprises a conductive layer or a dielectric layer. 3. A reversible thermosensitive recording medium according to claim 1, wherein a thermal head or microwave is applied or irradiated in an image form,
Heating the reversible thermosensitive recording material layer directly or by heating the exothermic layer to form a cloudy or colored image or a transparent or colorless image on the reversible thermosensitive recording material layer. Characteristic image recording method. 4. The reversible thermosensitive recording medium according to claim 1 is irradiated with microwaves to generate heat in the heat generating layer, and the heat causes the cloudy or colored image of the reversible thermosensitive recording material layer to be the same transparent or colorless as the background. An image erasing method characterized by the above. 5. The reversible thermosensitive recording medium according to claim 1 is irradiated with microwaves to generate heat in the heating layer, and the heat causes the transparent or colorless image of the reversible thermosensitive recording material layer to become cloudy or colored the same as the background. An image erasing method characterized by the above.