JPH0615954A - Method and apparatus for erase of image - Google Patents

Abstract

PURPOSE:To make it possible to obtain a uniform transparent condition even when heating time is short by heating at a specified temp. from both the heat- sensitive layer side of a reversible heat-sensitive recording medium and the opposite side of the heat-sensitive layer by means of a heating member. CONSTITUTION:A reversible heat-sensitive recording medium having a heat- sensitive layer with a reversibly changable transparency by heating on a substrate is formed. A transparent condition is obtd. by heating both faces, namely, the heat-sensitive layer of this reversible heat-sensitive recording medium and the opposite side of the heat-sensitive layer by means of a heating member and making the temp. of the heating member for the face of the heat-sensitive layer side lower than the temp. of the heating member for the face of the opposite side to the heat-sensitive layer. As the result, even when the heating time is shortened, it is not necessary to make the temp. of the heating source so high as to give a burden to the surroundings and a uniform transparent condition can be obtd. As the heating member, a heat roll, a hot plate, a heat belt etc., can be cited and practically, there exists a heat roller with a built-in infrared lamp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention utilizes the reversible change in transparency depending on the temperature of a thermosensitive layer to form an image using a reversible thermosensitive recording medium capable of repeatedly recording and erasing. Regarding the erasing method.

In recent years, reversible recording materials have been used everywhere in which a primary image formation can be performed and the image can be erased when it becomes unnecessary.
As a typical example thereof, there is known a reversible thermosensitive recording material having a thermosensitive layer in which an organic low molecular weight substance such as a higher fatty acid is dispersed in a resin matrix such as a vinyl chloride resin (Japanese Patent Laid-Open No. Sho 61-206). 54-119377, JP-A-55-1541
No. 98, etc.). However, these have a narrow density width of 2 to 4 ° C. for making the opaque part transparent, and therefore when making the recording material entirely opaque or forming a transparent image on the recording material opaque as a whole. Was difficult to control.

The present inventors previously proposed a reversible thermosensitive recording material capable of widening the temperature range for making an opaque part transparent by changing the material (Japanese Patent Laid-Open No. 63-63).
39378, JP-A-63-178079, JP-A-6
3-14754, etc.). According to these proposed reversible thermosensitive recording materials, although the intended purpose can be achieved, even if the speed of the heat roller or the like is increased and the heating temperature is shortened to make the material transparent, a uniform transparency is not always required. It was recognized that there was no guarantee that the

Further, in order to solve the above-mentioned inconvenience, the present inventors have obtained a transparent state of this reversible thermosensitive recording material.
A method of heating from the surface of the support opposite to the surface on which the heat sensitive layer is formed (Japanese Patent Laid-Open No. 142279/1993) has been proposed. According to this method, a uniform transparent state can be obtained even if the speed with a heat roller or the like is increased and the heating time is shortened.

[0005]

SUMMARY OF THE INVENTION However, Japanese Unexamined Patent Publication No.
Also in the method described in Japanese Patent No. 142279, when the speed is increased and the heating time is shortened, the heat capacity is insufficient due to heating from the back side, and sufficient transparency cannot be obtained, or the heat capacity is insufficient. If the heating source is heated to a high temperature to compensate, problems such as mechanical load of the power source and heat resistance of the material of the heating means itself such as heat rolls, hot plates, and heat belts will increase. It had been.

Therefore, an object of the present invention is to eliminate the above-mentioned inconvenience and shorten the heating time for transparency,
Provided are an image forming and erasing method and an apparatus used for the same, in which not only mechanical and electrical loads on surrounding devices but also heat resistance problems such as a material of a heat source are small. To do.

[0007]

That is, according to the present invention,
In a method of forming and erasing an image using a reversible thermosensitive recording medium having a thermosensitive layer whose transparency is reversibly changed by heat on a support, in order to obtain a transparent state, the reversible thermosensitive recording medium has a thermosensitive layer side. An image erasing method characterized in that heating is performed from both surfaces opposite to the heat sensitive layer by a heating member, and the temperature of the heating member on the surface facing the heat sensitive layer is lower than the temperature of the heating member on the surface opposite to the heat sensitive layer. Will be provided.

The detailed reason why the present method can provide a uniform transparent state without raising the temperature of the heating source to the extent that it imposes a burden on the surroundings even if the heating time is shortened is explained. I don't know yet. However, when heating only from the opposite side of the heat-sensitive layer, the heating member must heat the support of the recording medium to a temperature above which the heat-sensitive layer becomes transparent because of its heat diffusion, but heat from both sides. As a result, the temperature of the heating source on the opposite side of the heat-sensitive layer can be lower than in the case of heating only from the opposite side of the heat-sensitive layer, and the heat capacity does not become insufficient even when the speed is increased. Also, when heating only from the heat sensitive layer side and shortening the heating time, the temperature of the heating source is lower than when heating only from the opposite side of the heat sensitive layer, but a certain high temperature is still necessary to obtain a transparent state. Therefore, the heat is not uniformly propagated due to the fine contact caused by the unevenness of the surface of the reversible thermosensitive recording material and the surface of the heating member. Therefore, the temperature of the heat-sensitive layer is difficult to reach a uniform temperature and does not become a uniform transparent state, but by heating from both sides, the temperature of the heat source on the heat-sensitive layer side is low, and the heat-sensitive layer itself is heated from the support side. Combined with this, even if a fine contact failure occurs between the heat sensitive layer and the heating member, the gradient of the heat distribution inside the heat sensitive layer is small and a uniform transparent state can be obtained.

Further, as is apparent from the above reason, the temperature of the heating member on the heat sensitive layer side is lower than the temperature of the heating member on the side opposite to the heat sensitive layer due to the necessity of making the gradient of the heat distribution inside the heat sensitive layer smaller. It is presumed that it is more preferable.

For the above reasons, it is considered that the method of the present invention can obtain a uniform transparent state without raising the temperature of the heating source to the extent that it burdens the surroundings even when the heating time is shortened. .

Further, in order to prevent the erasing device from being continuously used for a long time, the reversible recording medium being heated more than necessary depending on the ambient temperature, or the erasing failure caused by insufficient heating, or the like. It is preferable that a stable transparent state can be maintained by detecting and controlling the heating temperature (use of the apparatus of claim 2). Further, it is more preferable that the stable transparent state can be maintained by detecting the environmental temperature and controlling the heating time and the heating temperature accordingly (use of the apparatus according to claim 3). Another method for maintaining a stable transparent state is to detect the transparency of an erased image and control the heating time or heating temperature accordingly (use of the apparatus of claim 4).

The present invention will now be described with reference to the accompanying drawings.
Further details will be described. The basic structure of the reversible thermosensitive recording material used in the present invention is shown in FIG. This reversible heat-sensitive recording material 1 has a heat-sensitive layer 3 on a support 2 whose main component is an organic low-molecular substance dispersed in a resin matrix and whose transparency reversibly changes depending on temperature. The protective layer 4 is formed on the upper surface thereof.

A typical image erasing method of the present invention using this recording material is shown in FIGS. As the heating member, a heat roll, a hot plate, a heat belt, etc. are considered,
FIG. 2 (a) uses heat rollers 5 and 6 having infrared lamps 7 and 8 therein, and the reversible thermosensitive recording material 1 passes between the heat rollers 5 and 6. When the heat roller 5 is on the heat sensitive layer side,
The temperature of the heat roller 5 is set lower than that of the heat roller 6, and if the heating temperature can be controlled by using the temperature detecting element 9 and the temperature control device 10 as shown in FIG. preferable. 2 (b) is shown in FIG.
Two heat rollers 5 and 6 of (a) arranged side by side on the heat sensitive layer side and on the opposite side (11a, 11b, 11c, 11).
Since it is d) and the heating time can be lengthened, the time taken for the reversible thermosensitive recording material 1 to pass can be made faster. Further, the temperature of the heat roller 11b is lower than that of the heat roller 11a,
By making the temperature of d lower than that of the heat roller 11c, the time for keeping the temperature in the heat sensitive layer constant is prolonged, or the recording material 1 is heated and then rapidly cooled due to the temperature difference from the ambient temperature. It is easy to set the conditions for obtaining the best transparent state, since it is possible to set various temperature conditions. 2A, the temperature of the heat roller 11a is lower than that of the heat roller 11c, and the temperature of the heat roller 11b is the same as that of the heat roller 11c.
As described above, it is set lower than that of d.

FIG. 2 (c) shows a case where a heat plate is used. The reversible thermosensitive recording material 1 is stopped between the heat plates and the heat plate 12
It is sandwiched between a and 12b and heated. In this method, the reversible thermosensitive recording material 1 is once stopped, so that the passing speed cannot be increased so much, but FIGS. 2 (a) and 2 (b) and FIG.
Since there is no "sliding while heating" when the recording material is conveyed as in (d), it is possible to prevent a burden on the recording material, particularly a scratch caused by entrapping dust or dust on the protective layer. I can. Also in this case, the temperature of the hot plate 12a is set lower than that of the hot plate 12b. FIG. 2D uses the heat belts 13a and 13b. Since the heating time can be longer than that in the case of FIG. 2B, the transport speed can be further increased. Further, 14 is a drive roll, and the temperature of the heat belt 13a is set lower than that of 13b, which is the same as before.

FIG. 3A shows a case where the ambient temperature is detected by the ambient temperature detecting element 15 in FIG. 2A and the heating temperature is controlled accordingly, FIG. 3B shows the drive roll. This is an example in which the controller 16 changes the speed of the drive roll to control the heating time. Further, FIG. 3C is an example of the case where the transparency is detected and the heating temperature is controlled, and this erasing apparatus uses a reversible thermosensitive recording material as an endless film, such as an overhead projector as shown in FIG. It is especially effective when applied to a device. In FIG. 3C, 17 is a light source, 18 is a photomar, and 19 is a light source.
Indicates a CPU, respectively. Also, in FIG.
Is a platen roller, 21 is a writing thermal head, 2
2 is a reflection mirror, 23 is a projection lamp, 24 is a collection reflection mirror, 25 is a projection lens, 26 is protective glass, 27
Is a Fresnel lens, and 28 is an erasing device.

For the heat roller and hot plate, various metals having good thermal conductivity, such as Al, Cu and Ni, are used, and the surface thereof is made of silicone in order to improve contact with the reversible thermosensitive recording medium. It is desirable to provide an elastic material such as rubber. The heat belts 13a and 13b are sheet-shaped resistance heating elements processed into endless belt shapes, and are thin-film resistors inserted between two heat-resistant films, for example.

Next, the materials used for the reversible thermosensitive recording layer of the reversible thermosensitive recording medium used in the present invention will be described. The reversible thermosensitive recording material used in the present invention may be any one as long as its transparency is changed by heat, but a material in which the transparent state and the cloudy state are reversibly changed by heating is preferably used. Specifically, it is composed of a polymer blend (described in JP-A-61-258853), a liquid crystal polymer, a resin base material and an organic low molecular weight substance dispersed in the resin base material, and becomes transparent by heat. Those that change reversibly with the cloudy state, and the like.

Among these, the reversible thermosensitive recording materials of the above-mentioned type which are excellent in repeated durability and have a high rate of change will be described below. This reversible thermosensitive recording material utilizes the change in transparency (transparent state, cloudy opaque state) as described above, and the difference between this transparent state and cloudy opaque state is presumed as follows. That is, in the case of (i) transparent, the particles of the organic low-molecular substance dispersed in the resin base material are composed of large particles of the organic low-molecular substance, and the light incident from one side is not scattered. It appears to be transparent because it penetrates to the opposite side, and (ii) in the case of 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. This is because the crystal axes are oriented in various directions, so that light incident from one side is repeatedly refracted and scattered at the crystal interface of the organic low molecular weight substance particles, and thus appears white.

In FIG. 5 (representing the change in transparency due to heat), a thermosensitive layer mainly composed of a resin base material and an organic low molecular weight substance dispersed in the resin base material is, for example, T
It is cloudy and opaque at room temperature below ₀ . This is the temperature T ₂
When it is heated to ₀ , it becomes transparent, and even if it is returned to room temperature below T _{0 in} this state, it remains transparent. This is the temperature T ₂ to T ₀
It is conceivable that the organic low-molecular-weight substance undergoes a semi-molten state until the following, and the crystal grows from a polycrystal to a single crystal. Upon further heating to T ₃ or more temperature becomes translucent state intermediate between the maximum transparency and the maximum opacity. Next, when this temperature is lowered, the first cloudy opaque state is restored without taking the transparent state again. It is considered that this is because when the organic low molecular weight substance is melted at a temperature of T ₃ or higher and then cooled, a polycrystal is precipitated. 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. Further, even if the material becomes transparent at room temperature, it is returned to the cloudy opaque state again when heated to a temperature of T ₃ or higher and then returned to room temperature. That is, both opaque and transparent forms at room temperature and intermediate forms thereof can be obtained.

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

The reversible thermosensitive recording material can be produced, for example, by forming the thermosensitive layer as a film on the support or molding it into a sheet by the following method. 1) A method in which a resin base material and an organic low molecular weight substance are dissolved in a solvent, which is applied onto a support member, and the solvent is evaporated to form a film or sheet. 2) The resin base material is dissolved in a solvent that dissolves only the resin base material, and the organic low molecular weight substance is pulverized or dispersed therein by various methods, and this is applied onto a support member, and the solvent is evaporated to form a film. Or the method of making a sheet.

The solvent for preparing the heat-sensitive layer or the heat-sensitive recording material 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,
Even when a solution is used, the organic low molecular weight substance is precipitated as fine particles and exists in a dispersed state in the obtained heat sensitive layer.

The resin used as the resin base material of the thermosensitive layer of the reversible thermosensitive recording material is preferably a resin which can form a film or a sheet, has good transparency and is mechanically stable. Such resins include polyvinyl chloride; vinyl chloride /
Vinyl chloride copolymers such as vinyl acetate copolymers, vinyl chloride / vinyl acetate / vinyl alcohol copolymers, vinyl chloride / vinyl acetate / maleic acid copolymers, vinyl chloride / acrylate copolymers; polyvinylidene chloride, Vinylidene chloride / vinyl chloride copolymers, vinylidene chloride / acrylonitrile copolymers and other vinylidene chloride copolymers; polyesters; polyamides; polyacrylates or polymethacrylates or acrylate / methacrylate copolymers; silicone resins and the like. These may be used alone or in admixture of two or more.

On the other hand, as the organic low molecular weight substance, any substance that changes from polycrystal to single crystal due to heat in the recording layer (changes within the temperature range of T _{1 to} T ₃ shown in FIG. 5) may be used. A melting point of generally 30 to 200 ° C., preferably 50 to 15
The thing of about 0 degreeC is used. Such organic low molecular weight substances include alkanols; alkane diols; halogen alkanols or halogen alkane diols; alkylamines; alkanes; alkenes; alkynes; halogen alkanes; halogen alkenes; halogen alkynes; cycloalkanes; cycloalkenes; cycloalkynes; 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; halogen arylcarboxylic acids Or their esters, amides or ammonium salts; thioalcohols; thiocarboxylic acids or their esters, amines or ammonium salts; Acid ester and the like. These may be used alone or in admixture of two or more. The carbon number of these compounds is 10
60, preferably 10-38, particularly 10-30 are preferred. 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, -COOR, -N.
_{H, -NH 2, -S -,} - S-S -, - O-, is preferably a compound containing a halogen and the like.

More specifically, these compounds include lauric acid, dodecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, stearic acid, behenic acid, nonadecanoic acid, aragic acid, henicosanoic acid, tricosanoic acid, lignoceric acid, pentacosan. Higher fatty acids such as acids, cerotic acid, heptacosanoic acid, montanic acid, melissic acid, oleic acid; esters of higher fatty acids such as methyl stearate, tetradecyl stearate, octadecyl stearate, octadecyl laurate, tetradecyl palmitate, and dodecyl behenate. _{; C 16 H 33 -O-C} 16 H 33,
_{C 16 H 33 -S-C 16} H 33, C 18 H 37 -S-C 18 H
_{37, C 12 H 25 -S-} C 12 H 25, C 19 H 39 -S-C
₁₉ H ₃₉ , C ₁₂ H ₂₅ -S-S-C ₁₂ H ₂₅ , Etc., such as ether or thioether. Among these, higher fatty acids, particularly palmitic acid, pentadecanoic acid, nonadecanoic acid, arachidic acid, henicosanoic acid, tricosanoic acid, lignoceric acid, stearic acid, behenic acid and the like, are preferably higher fatty acids having 16 or more carbon atoms and having 16 to 24 carbon atoms.
And higher fatty acids are more preferable.

Further, in order to widen the range of temperature at which the material can be made transparent, the organic low molecular weight substance may be appropriately combined or such an organic low molecular weight substance may be combined with another material having a different melting point. These are disclosed, for example, in JP-A-63-39378,
Japanese Patent Laid-Open No. 63-130380 and Japanese Patent Application No. 63-14
No. 754, Japanese Patent Application No. 1-140109, and the like, but are not limited thereto.

The weight ratio of the organic low molecular weight substance to the resin base material in the heat sensitive layer is preferably about 2: 1 to 1:16, more preferably 1: 1 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 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-phosphate
Ethylhexyl, triphenyl phosphate, tricresyl phosphate, butyl oleate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, di-n-octyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate , Dioctyldecyl phthalate, diisodecyl phthalate, butylbenzyl phthalate,
Dibutyl adipate, di-n-hexyl adipate, di-2-ethylhexyl adipate, di-2 azelaate
-Ethylhexyl, dibutyl sebacate, di-2-ethylhexyl sebacate, diethylene glycol dibenzoate, triethylene glycol di-2-ethyl butyrate, methyl acetylricinoleate, butyl acetylricinoleate, butylphthalylbutyl glycolate, acetylcitric acid Tributyl.

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 adducts 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 Ca, Ba or Mg salt of phosphoric acid mono- or di-ester; low degree of sulfated oil; poly long chain alkyl acrylate; acrylic orgomer; poly long chain alkyl methacrylate; long chain alkyl methacrylate / amine containing mono Chromatography copolymers; styrene / maleic anhydride copolymer; olefin / maleic anhydride copolymer.

When the image of this recording material is used as a reflection image, if a layer that reflects light is provided on the back surface of the recording layer, the contrast can be increased even if the thickness of the recording layer is reduced. Specifically, vapor deposition of Al, Ni, Sn and the like can be mentioned (described in JP-A No. 64-14079).

A protective layer may be provided on the heat-sensitive layer to protect the heat-sensitive layer. Protective layer (thickness 0.1-5
(μm), silicone rubber, silicone resin (described in JP-A-63-221087), polysiloxane graft polymer (JP-A-63-31738).
5)), an ultraviolet curable resin, an electron beam curable resin (described in JP-A-2-566), and the like.

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 and the organic low molecular weight substance in the heat sensitive layer. Examples of the solvent that hardly dissolves the resin of the heat-sensitive layer and the organic low-molecular 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.

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 monomer components of the protective layer-forming liquid (JP-A-1-13378).
No. 1). As the material for the intermediate layer, the following thermosetting resins and thermoreversible resins can be used in addition to those listed as the resin base material in the thermosensitive layer. That is, specifically, 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 varies depending on the use, but is 0.1 to
About 2 μm is preferable. If it is less than this, the protective effect is lowered, and if it is more than this, the thermal sensitivity is lowered.

[0034]

EXAMPLES The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto. In addition, both parts and% are based on weight.

Example On white PET having a thickness of about 188 μm, 10 parts of γ-Fe ₂ O ₃ vinyl chloride / vinyl acetate / vinyl alcohol copolymer 2 parts (UCGH VAGH) coronate (10% toluene solution) 2 parts Methyl ethyl ketone 40 parts Toluene 40 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.

A special acrylic UV-curing resin 10 parts (Unidick C7-164, 49% butyl acetate solution manufactured by Dainippon Ink and Chemicals, Inc.) and a solution of toluene 4 parts were applied with a wire bar and dried by heating. 80
Ultraviolet rays were irradiated for 5 seconds by a W / cm ultraviolet lamp to provide a smooth layer having a thickness of about 1.5 μm. Further, Al was vacuum-deposited to a thickness of about 400 Å to provide a light reflection layer.

Furthermore, behenic acid 6 parts hexadecanedioic acid 4 parts diallyl phthalate 2 parts vinyl chloride / vinyl acetate / phosphate ester copolymer 20 parts (Denka vinyl # 1000P manufactured by Denki Kagaku Kogyo KK) THF 200 parts The resulting solution was applied and dried by heating to provide a heat-sensitive layer (reversible heat-sensitive recording layer) having a thickness of about 5 μm.

A solution consisting of 10 parts of polyamide resin (CM8000 manufactured by Toray Co., Ltd.) and 90 parts of ethyl alcohol was applied on it with a wire bar and dried by heating to provide an intermediate layer of about 0.5 μm thickness, and further on it. Butyl acetate solution of urethane acrylate UV curable resin (Unidick 17-824-manufactured by Dainippon Ink and Chemicals, Inc.
9) is applied with a wire bar and heated and dried to 80 W / cm
UV rays were irradiated for 5 seconds with the UV lamp of No. 2 to provide an overcoat layer having a thickness of about 2 μm to prepare a reversible thermosensitive recording material.

This reversible thermosensitive recording material was placed in a thermostat bath at 110 ° C. for 10 minutes and then left at room temperature to make it cloudy.
Using a heat roller [Fig. 2 (a)] whose temperature and speed can be controlled by modifying the fixing unit of the copying machine, the temperature of the heat roller on the heat sensitive layer side is 20 mm / se.
c, fixed at 80 ° C at 40 mm / sec, 80 mm /
At the time of sec, the temperature of the heat roller on the side opposite to the heat sensitive layer is 90.
The temperature of the heat roller on the side of the heat-sensitive layer is 80, 90, and 95 ° C. at 100 ° C., 100 ° C., and 105 ° C., respectively.
Fixed at 120 ℃ / 120mm / sec, the temperature of the heat roller on the opposite side of the heat sensitive layer is 110 ℃, 120 ℃, 125 ℃
At that time, the heat roller temperature on the heat sensitive layer side is 100 ° C.,
110 ° C. and 115 ° C. When the temperature of the heat roller on the side opposite to the heat-sensitive layer is 125 ° C. or higher, it is fixed at 120 ° C. and the reversible heat-sensitive recording material is heated while changing the temperature of the heat roller on the side opposite to the heat-sensitive layer. Heated through a roller. After cooling this to room temperature, Macbeth reflection densitometer RD914
The reflection density was measured with. The result is shown in FIG.

Comparative Example 1 A reversible thermosensitive recording material prepared in the same manner as in Example 1 was prepared by changing the temperature of the heat roller on the heat sensitive layer side of the support without heating the heat roller on the side opposite to the heat sensitive layer. When the reflection density was measured by passing through a heat roller and cooling at room temperature in the same manner as in, the results shown in FIG. 7 were obtained.

Comparative Example 2 A reversible thermosensitive recording material prepared in the same manner as in Example 1 was used, except that the temperature of the heat roller on the side opposite to the heat sensitive layer of the support was changed and the heat roller on the side of the heat sensitive layer was not heated. Similarly, when passing through a heat roller and cooled at room temperature, the reflection density was measured, and the results shown in FIG. 8 were obtained.

[0042]

As is apparent from the examples, the image erasing method according to the first aspect of the invention heats the reversible thermosensitive recording medium from both the heat-sensitive layer side and the side opposite to the heat-sensitive layer side, Since the temperature of the heating member on the side of the heat-sensitive layer is set lower than the temperature of the heating member on the side opposite to the heat-sensitive layer, even if the heating time is shortened, the temperature of the heating source will not be burdened to the surroundings. It is possible to obtain a uniform transparent state without making it so high. Further, this effect is more remarkable as the heating time is shorter.

Since the image erasing apparatus of the present invention comprises the means for detecting the heating temperature and the means for controlling the heating temperature by the means, the present apparatus requires a reversible thermosensitive recording medium. It is possible to prevent inconveniences such as heating above or causing erasing failure due to insufficient heating, and it is possible to easily obtain a stable transparent state.

Since the image erasing apparatus according to the third aspect of the present invention comprises the means for detecting the ambient temperature and the means for controlling the heating temperature and / or the heating time by the means, it is more stable. A transparent state can be easily obtained.

Since the image erasing apparatus according to the present invention comprises a means for detecting the transparency of the transparentized reversible thermosensitive recording medium and controlling the heating temperature and / or the heating time accordingly, According to this device, a more stable transparent state can be easily obtained.

[Brief description of drawings]

FIG. 1 is a schematic sectional view having a basic structure of a reversible thermosensitive recording material used in the present invention.

FIG. 2 is a schematic view of four typical examples of heating means in the present invention.

FIG. 3 is a schematic view of another typical three examples of the heating means in the present invention.

FIG. 4 is a schematic view of an apparatus when the erasing method of the present invention is applied to an overhead projector apparatus.

FIG. 5 is a diagram showing changes in transparency of a reversible thermosensitive recording material used in the present invention due to heat.

FIG. 6 is a graph showing the relationship between the surface temperature of the heat roller and the reflection density in the example.

FIG. 7 is a graph showing the relationship between the surface temperature of the heat roller and the reflection density in Comparative Example 1.

FIG. 8 is a graph showing the relationship between the surface temperature of the heat roller and the reflection density in Comparative Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reversible thermosensitive recording material 2 Support 3 Reversible thermosensitive layer 4 Protective layer 5, 6 Heat roller 7, 8 Infrared lamp 9 Temperature detection element 10 Temperature control device 11a-11d Heat roller 12a, 12b Heat plate 13a, 13b Heat Belt 14 Driving roll 15 Environmental temperature detecting element 16 Driving roll control device 17 Light source 18 Photographic lens 19 CPU 20 Platen roller 21 Writing thermal head 22 Reflecting mirror 23 Projecting lamp 24 Condensing reflecting mirror 25 Projection lens 26 Protective glass 27 Fresnel lens 28 Eraser unit

Claims (4)

[Claims] 1. In a method of forming and erasing an image using a reversible thermosensitive recording medium having a thermosensitive layer whose transparency is reversibly changed by heat on a support, in order to obtain a transparent state, a thermosensitive recording medium is used. The heating member is heated from both sides of the layer side and the side opposite to the heat sensitive layer, and the temperature of the heating member on the side of the heat sensitive layer is lower than the temperature of the heating member on the side opposite to the heat sensitive layer. How to erase images. 2. An image erasing apparatus according to claim 1, comprising means for detecting a heating temperature and means for controlling the heating temperature thereby. 3. The image erasing apparatus according to claim 2, further comprising a means for detecting an ambient temperature and a means for controlling a heating temperature and / or a heating time by the means. 4. An image erasing apparatus according to claim 2, further comprising means for detecting transparency of the transparentized reversible thermosensitive recording medium and controlling heating temperature and / or heating time accordingly. .