JPH07186552A - Method and apparatus for erasing image of reversible thermal recording medium - Google Patents

Abstract

PURPOSE:To completely erase an image by conducting a plurality of times heating erasing operations having different heating erasing temperatures, heating erasing times and/or heating erasing pressures. CONSTITUTION:Transparency or color-tone detecting and measuring sensors (e.g. transparency detecting sensors 2) are provided at front and rear sides of a heating erasing member 1. A change of an image erasing temperature range to be predicted is obtained by a controller 3 according to number of recording by a magnetic recording layer and transparency or color-tone data at the time of inserting a reversible thermal recording material, and the image is again erased in its temperature range. In this case, a plurality of times of heating erasing operations having different heating erasing temperatures, heating erasing times and/or heating erasing pressures are sequentially shifted to lower temperature range, shorter erasing time and/or lower pressure. Or, at least one of the plurality of times of the heating erasing temperature, heating erasing time and heating erasing pressure is varied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image erasing method and apparatus for repeatedly forming and erasing an image on a reversible thermosensitive recording medium.

[0002]

2. Description of the Related Art In recent years, temporary image formation (recording) can be performed and the image can be erased when it is no longer needed.
Moreover, reversible thermosensitive recording media that can be repeatedly recorded and erased have been receiving attention. As a typical example thereof, a reversible thermosensitive recording medium in which a resin base material such as a vinyl chloride resin and an organic low molecular weight substance such as a higher fatty acid are dispersed is known (JP-A-55-15498). . However, in such a conventional image erasing method by heating the reversible thermosensitive recording medium, the image is erased by one heat erasing at a constant temperature, pressure and time, so that the image erasing temperature range becomes plural over time. There is a problem that it can not be erased sufficiently because it comes or shifts. Therefore, in order to prevent the image erasing temperature range from changing over time, we have optimized the erasing temperature and printing energy, but in reality it is impossible to completely eliminate this change in the image erasing temperature range. Is.

[0003]

SUMMARY OF THE INVENTION The object of the present invention is not to prevent the image erasing temperature range of the reversible thermosensitive recording medium as described above from becoming plural or deviated over time, but the image erasing temperature thereof. It is intended to provide a method and apparatus for completely erasing an image by performing a heat erasing operation a plurality of times according to the extent to which the range is made plural or the extent to which the area is displaced.

[0004]

The first aspect of the present invention is a method for erasing an image by heating a reversible thermosensitive recording medium having a thermosensitive layer whose transparency or color tone is reversibly changed by heat on a support. It is characterized in that the heat erasing operation is performed a plurality of times with different heat erasing temperature, heat erasing time and / or heat erasing pressure.

In the method of the present invention, it is desirable to adopt the following means (a), (b) and (c). (B) Heat erasing temperature, heat erasing time and / or
Alternatively, the heating and erasing operations with different heating and erasing pressures are sequentially moved to a low temperature region, a short erasing time and / or a low pressure. (B) At least one of the heating erasing temperature, the heating erasing time and the heating erasing pressure is changed a plurality of times. (C) A magnetic recording layer is provided on the reversible thermosensitive recording medium,
When the image erasing operation is performed on this recording medium, the number of times of use and the transparency or color tone recorded on the magnetic recording layer are detected or measured, and the number of times the image is erased is controlled accordingly, and the image erasing operation is performed again to completely erase the image. Repeatedly erase the image.

A second aspect of the present invention is a reversible thermosensitive recording medium erasing device, which has means for conveying the reversible thermosensitive recording medium, heating or heating / pressurizing means, and means for detecting or measuring transparency or color tone. Moreover, it is characterized by having a control device for these means.

In the device of the present invention, it is advantageous to adopt the following means (d) and (e). (D) One or a plurality of the above-mentioned conveying means, heating or heating / pressurizing means, transparency or color tone detecting or measuring means. (E) A magnetic reading means is further provided, which is also controlled by the control device.

As a result of examining the image erasing of the reversible thermosensitive recording medium from various angles, the present inventors found that the erasing temperature range at the time of erasing a heated image is as shown in FIGS. As shown in Fig. 1, the temperature range shifts to the high temperature side as shown in Fig. 2 only by changing the heating and erasing conditions, or the erasing temperature region becomes plural as shown in Fig. 3 due to long-term use. It has been found that the lower limit value of the erasing temperature range shifts as shown in FIG. 4 due to environmental preservation. When the image erasing temperature range shifts, or particularly when the image erasing temperature range becomes plural, it is difficult to completely erase the image by one heat erasing operation. In addition, FIG. 1 shows the image erasing temperature range (condition: 1) immediately after the reversible thermosensitive recording medium is manufactured.
gf, 60 seconds), and FIG. 2 also shows the image erasing temperature range (conditions 500 gf, 0.2) immediately after the production of the reversible thermosensitive recording medium.
3), FIG. 3 shows a plurality of image erasing temperature regions due to long-term use of the reversible thermosensitive recording medium (conditions: 500 gf, 0.2
4), FIG. 4 shows the deviation of the image temperature range due to long-term storage of the reversible thermosensitive recording medium (condition: storage at 50 ° C., 500 gf, 0.
2 seconds) respectively.

Therefore, as shown in FIG. 5, a transparent or color tone detecting or measuring sensor (for example, a transparency detecting sensor 2) is provided before and after the heat erasing member 1 so as to insert a reversible thermosensitive recording material into the magnetic recording layer. The change in the image erasing temperature range expected by the control device 3 is obtained from the number of times of use recorded and the transparency or color tone data, and the image erasing is performed again within the temperature range. Further, as shown in FIG. 6, a plurality of heat blocks (heating erasing members) 1 are provided, the erasing conditions predicted from the information obtained by the magnetic reading unit 4 are set in advance, and the image erasing process is sequentially performed. The method of going may be adopted. 5 and 6,
Reference numeral 7 represents a pressing roller, 8 represents a reversible thermosensitive recording medium feed roller (a roller whose rotational speed can be changed), and 9 represents a moving direction of the reversible thermosensitive recording medium.

In carrying out this method, it should be noted that the temperature, the pressure and the time are set so that, in principle, the first time is the highest, the longest, the gradually lower and the shorter. That is. This is unavoidable because, for example, if the image is erased in the low temperature region for the first time and then the image is erased again in the high temperature region, the once erased portion may become cloudy or have a color. As described above, the factors that can control the image erasing include temperature, pressure, and time, and it becomes difficult to control in the order of time, pressure, and temperature. If there is a large temperature difference, it can be covered by controlling the time and pressure. In particular, for long-term environmental preservation changes, the heating pressure of the image erasing conditions is high, and by increasing the time, the change in the image erasing temperature lower limit value can be considerably reduced, so not only the temperature but also the pressure and time are changed. It controls effectively, and it also controls quickly.

By the way, the "reversible thermosensitive recording material" of the reversible thermosensitive recording medium of the present invention is a material which 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 reversible thermosensitive layer in which an organic low molecular weight substance such as a higher alcohol or a higher fatty acid is dispersed in a resin base material such as polyester, as described in the prior art and as has been repeatedly described so far. As. As a typical example, a leuco thermosensitive recording material having enhanced reversibility can be mentioned.

The reversible thermosensitive layer of the type which causes the change in transparency is mainly composed of a resin base material and an organic low molecular weight substance dispersed in the resin base material. The reversible thermosensitive recording material here has a temperature range in which it becomes transparent. Therefore, the reversible thermosensitive layer can be selectively heated by selectively applying heat to form a cloudy image on a transparent background or a transparent image on a cloudy background, and the change can be repeated many times. is there. By arranging a colored sheet on the back surface of such a reversible thermosensitive layer, an image of the color of the colored sheet or a white image of the background of the colored sheet can be formed on a white background. 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. Further, when the image of the reversible thermosensitive recording material is used as a reflection image, if a layer that reflects light is provided on the back surface of the reversible thermosensitive layer, the contrast can be increased even if the thickness of the reversible thermosensitive layer is reduced. Specifically, vapor deposition of Al, Ni, Sn and the like can be mentioned.

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 For example, a dispersion liquid in which at least one kind of organic low molecular weight substance is not dissolved is used, and a dispersion liquid in which the organic low molecular weight substance is finely dispersed is applied to, for example, a support and dried to form a reversible thermosensitive layer. Good.

The reversible heat-sensitive layer or the solvent for preparing the recording medium can be variously selected depending on the kind of the resin base material and the organic low molecular weight substance, and for example, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene, Examples thereof include benzene. Of course, when using the dispersion,
In the reversible thermosensitive layer obtained even when a solution is used, the organic low molecular weight substance is precipitated as fine particles and exists in a dispersed state.

The resin base material used in the reversible thermosensitive 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 the time of maximum transparency. Therefore, the resin base material is preferably a resin having good transparency, mechanical stability, and good film forming property. Examples of 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-acrylate copolymer. Vinyl chloride-based copolymers such as coalesce; polyvinylidene chloride; vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-based copolymers such as vinylidene chloride-acrylonitrile copolymers; polyesters; polyamides; polyacrylates or polymethacrylates or acrylates -
Methacrylate copolymers; silicone resins 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 changes from polycrystal to single crystal by heat in the reversible thermosensitive layer may be used. Generally, a substance having a melting point of 30 to 200 ° C., preferably about 50 to 150 ° C. is used. It Alkanols; alkane diols; halogen alkanols or halogen alkane diols; alkylamines;
Alkanes; alkenes; alkynes; halogen alkanes; halogen alkenes; halogen alkynes; cycloalkanes;
Cycloalkene; cycloalkyne; saturated or unsaturated mono- or dicarboxylic acid or ester, amide or ammonium salt thereof; saturated or unsaturated halogen fatty acid or ester, amide or ammonium salt thereof; arylcarboxylic acid or ester, amide thereof or Ammonium salts; halogenallyl carboxylic acids or their esters, amides or ammonium salts; thioalcohols; thiocarboxylic acids or their esters, amines or ammonium salts; carboxylic acid esters of thioalcohols 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-, -CO.
_{OR, -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 weight ratio of the organic low molecular weight substance to the resin base material in the reversible thermosensitive layer is preferably about 2: 1 to 1:16, and more preferably 1: 2 to 1: 8. 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 can be added to the reversible thermosensitive 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 salts; low-sulfated oils; poly long-chain alkyl acrylates; acrylic orgomers; poly long-chain alkyl methacrylates; long-chain alkyl methacrylate-amine-containing monomer copolymers; styrene-maleic anhydride copolymers;
Olefin-maleic anhydride copolymer. Further, the reversible thermosensitive layer may be crosslinked by heat, UV, EB, etc., whereby the durability can be repeatedly improved. Of these, crosslinking by EB is preferable.

As described above, a protective layer may be provided on the reversible thermosensitive layer to protect the reversible thermosensitive layer. Materials for the protective layer (thickness: 0.1 to 5 μm) include silicone rubber, silicone resin (JP-A-63-221087),
Examples thereof include polysiloxane graft polymers (described in Japanese Patent Application No. 62-152550), ultraviolet curable resins, electron beam curable resins (described in Japanese Patent Application No. 63-310600), and the like. An organic or inorganic filler, silicone oil, etc. may be contained in the protective layer. 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. Examples of the solvent that hardly dissolves the resin of the reversible thermosensitive layer and the organic low molecular weight substance include n-hexane, methyl alcohol, ethyl alcohol, isopropyl alcohol and the like, and the alcohol solvent is particularly preferable from the viewpoint of cost.

Further, an intermediate layer may be provided between the protective layer and the reversible heat-sensitive layer in order to protect the reversible 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, polyvinyl alcohol, polyvinyl butyral, polyurethane, saturated polyester, unsaturated polyester, epoxy resin, phenol resin, polycarbonate, polyamide and the like can be mentioned. The thickness of the intermediate layer is 0.1-2
About μm is preferable.

Subsequently, the reversible thermosensitive layer (where the recording position is formed) is formed by the reversible thermochromic composition utilizing the color-forming reaction between the electron-donating color-forming compound and the electron-accepting compound. I will describe what is done.
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 instantaneously develops color upon heating, and the color development state thereof is stable even at room temperature. On the other hand, the composition in the color development state is instantaneously heated at a temperature below 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 thermal recording medium 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 ₆ or higher, C is the density at a temperature of T ₅ or lower in the completely colored state, and D is T ₅ It shows the concentration when heat erasing is performed at a temperature between T _{6 and} T ₆ .

This composition according to the invention is in the colorless state (A) at temperatures below T ₅ . To perform recording (image formation), a color image (B) is formed by heating to a temperature of T ₆ 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 ₅ or less 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 _{5 and} T _{6 which} is lower than the color development temperature to obtain a colorless state (D). In this state, the colorless state (A) is maintained as it is even if the temperature is returned to T ₅ or lower. 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 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 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 ₆ or higher and then decolored, the particles of the color-developing agent and the color-developing agent are restored to form a new color-forming state. Is advantageous to.

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 having 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, 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 is in 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 former. 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 developing and decoloring behaviors observed in the thermochromic composition are the mutual solubility of the color former and the color developer by heating and melting, the strength of both actions in the color developing state, and the color developer. 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 developers preferably used in the present invention are exemplified as follows. As described above, the color developers 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) Representing a group) 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 linear or branched alkyl group or 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 Acid, etc.

The color former used here is a compound exhibiting an electron-accepting property, and is itself a colorless or light-colored dye precursor and is not particularly limited.
There are triphenylmethanephthalide-based compounds, fluoran-based compounds, phenothiazine-based compounds, leucoauramine-based compounds, rhodamine-lactam-based compounds, spiropyran-based compounds, indolinophtalide-based compounds, and the like. To be 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-diethylaminofluorane, 2- {3,6-
Bis (diethylamino) -6- (o-chloroanilino)
Xanthyl benzoate lactam}, 3-diethylamino-
6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) 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, benzo Leucomethylene 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) fluorane, 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)
Fluoran, 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, anilino) 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-methoxy Carbonylphenylamino) 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) fluorene spiro (9,3 ')-6'-dimethylaminophthalide, 3- ( N-benzyl-N-cyclohexylamino) -5,6-benzo-7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6
-Chlor-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'-benzofur Oran, 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 formed as a reversible thermosensitive layer on a support and used as a reversible thermosensitive recording medium. In this case, the reversible heat-sensitive layer 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 this on a substrate.

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, various additives such as a dispersant, a surfactant, a filler, which are used in ordinary thermal recording paper, are used for the purpose of improving coating properties or recording properties as required.
It is also possible to add a color image stabilizer, an antioxidant, a light stabilizer, a lubricant and the like. 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 long, endless, or even card-shaped.

[0043]

EXAMPLES The present invention will be described in more detail with reference to the following examples. Parts herein are by weight.

(Common Example) White PE about 188 μm thick
Liquid containing 10 parts of γ-Fe ₂ O ₃ on T, vinyl chloride-vinyl acetate-vinyl alcohol copolymer 2 parts (UCC: VAGH) Coronate L (10% toluene solution) 2 parts methyl ethyl ketone 43 parts toluene 43 parts Is applied with a wire bar and dried by heating to about 1
A magnetic recording layer having a thickness of 0 μm was provided.

Next, a solution of urethane acrylate-based UV curable resin 75% acetic acid 10 parts butyl solution (manufactured by Dainippon Ink and Chemicals, Inc .: Unidick C7-164) MEK 10 parts solution was applied with a wire bar and heated and dried. 80
It was cured with a w / cm UV lamp to provide a smooth layer with a temperature of about 3 μm, and Al was vacuum-deposited to a thickness of about 400 Å thereon.

Furthermore, behenic acid (NAF-22S manufactured by NOF CORPORATION) 6 parts Niicosane diacid (SL-20 manufactured by Okamura Oil Co., Ltd.) 4 parts Diisodecyl phthalate 3 parts Vinyl chloride-vinyl acetate-phosphoric acid Ester copolymer 35 parts (manufactured by Denki Kagaku Kogyo KK: # 1000p) THF 150 parts A solution consisting of 15 parts toluene was applied with a wire bar and dried by heating to provide a heat sensitive layer having a thickness of about 15 μm.

A solution consisting of 10 parts of polyamide resin (CM8000, manufactured by Toray Industries, Inc.) and 90 parts of methanol was further applied on it with a wire bar and dried by heating to form an intermediate layer having a thickness of about 1 μm.

Further thereon, a solution containing 10 parts of 75% acetic acid of urethane acrylate UV curable resin in butyl solution (manufactured by Dainippon Ink and Chemicals: Unidick C7-157) and 10 parts of IPA was applied with a wire bar, 80 after heating and drying
A reversible thermosensitive recording medium was prepared by curing with a w / cm ultraviolet lamp and providing an overcoat layer having a thickness of about 5 μm. This reversible thermosensitive recording medium was heated to 80 ° C. to make the thermosensitive layer transparent.

Example 1 Using the reversible thermosensitive recording medium obtained in the common example, recording with a thermal head and erasing with the image erasing device shown in FIG. 6 were repeated 500 times. The conditions of the first heat block of the image erasing device at this time are 95 ° C. and 500 g
f, 0.2 sec, the condition of the second heat block is 80 ° C., 500 gf, 0.2 sec, and 500
The second printing and erasing density measurement were performed. The results are summarized in Table 1.

Example 2 Using the reversible thermosensitive recording medium obtained in the common example, recording paper with a thermal head was repeatedly erased 500 times with the image erasing device shown in FIG. Was measured. The conditions of the image erasing apparatus at this time are the same as those of the first embodiment, but only the first heat block is variable, and the magnetic reader when the recording medium is inserted reads the number of times of use and the period of use, and is predicted in FIG. The image was erased after increasing the lower limit by the amount. The results are summarized in Table 1
Shown in.

Example 3 The same operation as in Example 2 was performed, but instead of performing magnetic reading, the transparency was detected by a transparency detection sensor, and if insufficient, the image erasing temperature remained constant. The pressure was increased at 1, and the time was increased, and then they were gradually lowered and / or shortened to perform erasing over and over again until completely transparent. The results are summarized in Table 1.

Comparative Example 1 Using the reversible thermosensitive recording medium obtained in the common example, recording was carried out by a thermal head, and a heat block was heated at 95 ° C., 500 gf, 0.2 sec by the image erasing apparatus shown in FIG. Repeatedly recording and erasing 500 times under certain conditions, 50 times
The 0th printing and erasing density measurements were performed. The results are summarized in Table 1.

[0053]

[Table 1]

[0054]

According to the first, second and third aspects of the present invention, good image erasing can be performed depending on the state of the reversible thermosensitive recording medium. According to the invention of claim 4, the image can be erased quickly. According to the fifth and sixth aspects of the invention, the image can be easily erased. According to the invention of claim 7, useless operation is avoided.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between image erasing temperature range and density of a reversible thermosensitive recording medium immediately after production.

FIG. 2 is a diagram showing a relationship between an image erasing temperature range and density of a reversible thermosensitive recording medium immediately after manufacturing.

FIG. 3 is a diagram showing a plurality of image erasing temperature regions due to long-term use of a reversible thermosensitive recording medium.

FIG. 4 is a diagram showing a plurality of image erasing temperature regions due to long-term storage of a reversible thermosensitive recording medium.

FIG. 5 is a diagram showing an outline of an image erasing device of the present invention.

FIG. 6 is a diagram showing an outline of an image erasing device of the present invention.

FIG. 7 is a diagram showing how the color tone of the reversible recording heat-sensitive medium of the present invention changes depending on temperature.

[Explanation of symbols]

 1 Heat erasing member (heat block) 2 Transparency detection sensor 3 Control device 4 Magnetic reading unit 7 Holding roller 8 Feed roller 9 Reversible thermosensitive recording material Moving direction of thermosensitive recording medium

Claims (7)

[Claims] 1. A method of erasing an image by heating a reversible thermosensitive recording medium having a thermosensitive layer whose transparency or color tone is reversibly changed by heat on a support, in a method of erasing by heating, erasing time by heating and / or heating. An image erasing method for a reversible thermosensitive recording medium, characterized in that a heat erasing operation with different erasing pressures is performed plural times. 2. The heat erasing operation in which the heat erasing temperature, the heat erasing time and / or the heat erasing pressure are different for a plurality of times,
The image erasing method for a reversible thermosensitive recording medium according to claim 1, wherein the temperature is gradually shifted to a low temperature region, a short erasing time and / or a low pressure. 3. The image erasing method for a reversible thermosensitive recording medium according to claim 1, wherein at least one of the heating erasing temperature, the heating erasing time and the heating erasing pressure is changed a plurality of times. 4. A magnetic recording layer is provided on a reversible thermosensitive recording medium, and the number of times of use and the transparency or color tone recorded on the magnetic recording layer in the image erasing operation of this recording medium are detected or measured to thereby erase the image. 4. The image erasing method for a reversible thermosensitive recording medium according to claim 1, wherein the image erasing operation is performed again by controlling the number of times, and the image erasing operation is repeatedly performed until the image is completely erased. 5. A reversible sensation having a reversible thermosensitive recording medium conveying means, heating or heating / pressurizing means, means for detecting or measuring transparency or color tone, and a control device for these means. Image erasing device for thermal recording medium. 6. An image erasing apparatus for a reversible thermosensitive recording medium according to claim 5, wherein said conveying means, heating or heating / pressurizing means, transparency or color tone detecting or measuring means are one or more. 7. The image erasing device for a reversible thermosensitive recording medium according to claim 5, further comprising magnetic reading means, which is also controlled by the control device.