JP3161199B2 - Image erasing method for reversible thermosensitive recording material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for erasing an image of a reversible thermosensitive recording material which can repeatedly form and erase an image by heating.

[0002]

2. Description of the Related Art In recent years, rewritable materials have been demanded as heat-sensitive recording materials for saving resources of paper. As the most influential material, there is provided, on a support, a heat-sensitive layer in which organic low-molecular substances such as higher alcohols and higher fatty acids are dispersed in a resin such as polyester.
These are known from 119377, 55-154198, and the like. This type of recording using a reversible thermosensitive recording material, that is, image formation and erasing, uses a change in transparency due to the temperature of the thermosensitive layer. As with conventional irreversible thermosensitive recording materials, image formation using a thermal head or hot stamp is not possible. It is possible and erasable.

Recently, attention has been paid to the use of reversible thermosensitive recording materials as display media for cards such as prepaid cards and credit cards. As an image erasing device for this card, a heat roller or a thermal head can be used, but at present, hot stamping is suitable because only a part of the card can be heated and high-speed and uniform heating is possible. ing. This type of reversible thermosensitive recording material, for example, when an image is erased by a hot stamp or the like after forming an image with a thermal head or the like, usually, the erasing temperature of the reversible thermosensitive recording material takes into account variations in machinery and environmental conditions. Then, it is set near the center of the erasing temperature range, and is used many times. However, during use, erasing becomes difficult on the high energy side compared to the initial erasing temperature range, and even if a surface image formed by a thermal head or the like is erased by a hot stamp, a faint image remains as an afterimage. There was a problem.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks and reduces the erasing density at the time of erasing an image even if image formation and erasing are repeated several times with a heating element such as a thermal head and a hot stamp. It is an object of the present invention to provide an image erasing method for a reversible thermosensitive recording material which can maintain a high-contrast image without performing.

According to the present invention,The following invention is provided.  (1) Reversible heat-sensitive, capable of forming and erasing images by heating
Image erasing method that heats the recording material to erase the image
hand,As the reversible thermosensitive recording material, a resin base material is provided on a support.
And two or more organic low-molecular substances dispersed in a resin matrix
Transparency changes reversibly depending on temperature, based on quality
Using a heat-sensitive layerErasing energy
Erasable energy during image erasure of an inverse thermosensitive recording material
Energy on the lower energy side than the central energy value in the range
Characteristically performs image erasureReversible feeling
Thermal recording materialImage erasing method. (2) An image for erasing an image by heating the reversible thermosensitive recording material
Using a hot stamp as an image erasing means,
Wherein the image is erased for 0.1 seconds or more.
1Of reversible thermosensitive recording materialImage erasing method. (3) An image for erasing an image by heating the reversible thermosensitive recording material.
A hot stamp is used as an image erasing means, and 0.1 kg /
cm^TwoPress with the above pressure and simultaneously heat to erase the image
2. The reversible thermosensitive recording material as described in 1 above,
Image erasing method. (4) An image to be erased by heating the reversible thermosensitive recording material
As an image erasing means, a metal organic compound
It is characterized by using a hot stamp with a cushioning material
2. The method according to 1 aboveOf reversible thermosensitive recording materialImage erasing method. (5)TheReversible thermosensitive recording materialFrom reversible thermosensitive recording materials
LayerAnd a card having a magnetic recording layer.
5. The method according to any one of 1 to 4,Of reversible thermosensitive recording material
Image erasing method.

The present inventors have studied from various angles to achieve the above object, and as a result, have found that the reversible thermosensitive recording material can be used to form an image by a heating means such as a thermal head, a hot plate or a heat roll. When the image is repeatedly used for erasing, the image is erased many times by performing the image erasing on the lower energy side from the center energy value of the erasable energy range of the reversible thermosensitive recording material as an image erasing method. It has been found that a high-contrast image can be obtained without lowering the erasing density even if the formation and erasing are repeated, and in this case, a hot stamp is used as a means for erasing the image formed on the reversible thermosensitive recording material. , the heating time is 0.1 seconds or more, or pressed with 0.1 kg / cm ² or more pressure, row the image erasing by heating at the same time By disposing a buffer made of a high-molecular organic compound on the entire surface of the metal of the hot stamp, heat transfer from the hot stamp to the reversible thermosensitive recording material becomes uniform, and the heat of the reversible thermosensitive recording material becomes uniform. It has been found that the distribution is uniform and a good transparent state can be obtained, and a high-contrast image can be obtained, and the present invention has been completed.

In the image erasing method of the present invention, the heating time of the hot stamp is, as described above, at least 0.1 second, preferably at least 0.3 second, more preferably at least 1.0 second. is there. The pressurizing pressure is 0.1 kg / cm ² or more as described above, but is preferably 0.3 kg / cm ² or more.
kg / cm ² or more, and more preferably 1.0 kg / cm ² or more.

Further, specific examples of the buffer material comprising a high-molecular organic compound used for the hot stamp of the present invention are as follows. As the material and structure of the cushioning material, in addition to using a so-called rubber-like substance showing elasticity itself in a plate-like form, sponge, steel wool, and even highly heat-conductive and hard materials such as metals and ceramics are used. It can be used in a form that is easily elastically deformed such as a spring,
Further, it can be used in the form of a sponge.
In the case of a sponge-like form, the air in the sponge impedes the conduction of heat, so that it is also effective to fill the sponge with a fluid having high thermal conductivity instead of air. In addition, since the surface of the cushioning material becomes uneven in the sponge-like form, it is also effective to provide a thin film of a soft material such as a vinyl sheet on the surface.

Materials exhibiting rubber-like elasticity are roughly divided into natural rubber and synthetic rubber. Synthetic rubber further includes polyisoprene, polybutadiene and copolymers thereof with other vinyl compounds as diene rubbers. Examples include olefin rubber such as butyl rubber and ethylene-propylene rubber, polyurethane rubber, silicon rubber, and fluorine rubber known under the trade name Viton. Above all, silicon rubber and fluorine rubber are excellent materials for the cushioning material because of their high heat resistance and thermal conductivity. It is also effective to fill a rubber-like substance with a material having high thermal conductivity such as silica to enhance thermal conductivity.

The hardness of such a cushioning material is not more than 75 in terms of spring hardness Hs, preferably in the range of 25 to 75, and more preferably in the range of 25 to 50. The thickness of the cushioning material provided on the metal surface of the hot stamp is preferably 0.2 to 2.0 mm, more preferably 0.2 to 1.0 mm.

With respect to the fact that a high-contrast image can be obtained without lowering the erasure density even if image formation and erasure are repeated many times according to the present invention, the detailed reason is not yet known, but is as follows. Guessed. In order to erase the image formed on the reversible thermosensitive recording material,
Heating the image area with a heat roller, hot stamp, etc., and cooling to room temperature causes the organic low-molecular-weight substance dispersed in the heat-sensitive layer to grow from a polycrystal to a single crystal through a semi-molten state. Have been. However, while the image formed on the reversible thermosensitive recording material is repeatedly erased on the high energy side of the transparent temperature range of the reversible thermosensitive recording material many times, the organic low molecular weight dispersed in the thermosensitive layer is reduced. If the substance is, for example, a mixture of two or more kinds, it is considered that they do not become eutectic and the low-melting-point organic low-molecular substance becomes cloudy.

Next, the reversible thermosensitive recording medium used in the present invention will be described. The reversible thermosensitive recording material used in the present invention is not particularly limited as long as its transparency changes by heat. In particular, a material which changes reversibly between a transparent state and a cloudy state by heating is preferably used. In particular,
A polymer blend (described in JP-A-61-258853), comprising a liquid crystal polymer, a resin matrix and an organic low-molecular substance dispersed in the resin matrix, and reversible between a transparent state and a cloudy state by heat. That change dynamically.

The reversible thermosensitive recording material of the above-mentioned type, which is excellent in repeated durability and has a fast change rate, 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, (i) in the case of transparency,
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 light incident from one side passes through to the other side without being scattered, and thus looks transparent. (Ii) In the case of cloudiness, the particles of the organic low-molecular substance are composed of polycrystals in which fine crystals of the organic low-molecular substance are aggregated, and the crystal axes of the crystals are oriented in various directions. The light incident from one side is refracted many times at the interface between the crystals of the organic low-molecular substance particles, and is scattered.

In FIG. 1 (representing a change in transparency due to heat), a heat-sensitive layer mainly composed of a resin base material and an organic low-molecular substance dispersed in the resin base material is, for example, T
_At a room temperature of ₀ or less, it is cloudy and opaque. This is called temperature T ₂
When the temperature is returned to room temperature below T ₀ , the film remains transparent. This is from temperature T ₂ to T ₀
It is considered that the organic low-molecular substance grows from a polycrystal to a single crystal through a semi-molten state before reaching the following. Upon further heating to T ₃ or more temperature becomes translucent state intermediate between the maximum transparency and the maximum opacity. Next, when the temperature is lowered, the state returns to the original cloudy and opaque state without taking the transparent state again. After this low-molecular organic material at a temperature T ₃ above the melt, by being cooled, it is believed to be because the polycrystalline precipitates. 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 lower than T ₀ , an intermediate state between transparent and opaque can be obtained. Moreover, even those became transparent at the normal temperature, it returned to room temperature after heating again T ₃ or more temperature returns to cloudy opaque state again. That is, both opaque and transparent forms at room temperature and intermediate states thereof can be taken.

Therefore, the heat-sensitive layer can be selectively heated by selectively applying heat to form a cloudy image on a transparent ground and a transparent image on a cloudy ground, and the change can be repeated many times. It is. If a colored sheet is arranged on the back of such a thermosensitive element, a color image of the colored sheet on a white background or a white image on the colored background of the colored sheet can be formed. 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 a thermosensitive layer on a support as a film or by forming it into a sheet by the following method. 1) A method of dissolving a resin base material and an organic low-molecular substance in a solvent, applying this on a support member, and evaporating the solvent to form a film or sheet. 2) The resin base material is dissolved in a solvent in which only the resin base material is dissolved, and the organic low-molecular substance is pulverized or dispersed therein by various methods, applied to a support member, and the solvent is evaporated to form a film. Or a method of forming a sheet.

[0017] As thermal R ₁ or heat-sensitive recording material creation solvent, various can be selected depending on the type of resin matrix and an organic low molecular weight substance, such as tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene , Benzene and the like. It should be noted that, not only when a dispersion is used, but also when a solution is used, the organic low-molecular substance is precipitated as fine particles in the obtained heat-sensitive layer and exists in a dispersed state.

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 copolymer, vinyl chloride / vinyl acetate / vinyl alcohol copolymer, vinyl chloride / vinyl acetate / maleic acid copolymer, and vinyl chloride / acrylate copolymer; polyvinylidene chloride; Vinylidene chloride-based copolymers such as vinylidene chloride / vinyl chloride copolymer and vinylidene chloride / acrylonitrile copolymer; polyester; polyamide; polyacrylate or polymethacrylate or acrylate / methacrylate copolymer; and silicone resin. These may be used alone or as a mixture of two or more.

The organic low-molecular substance may be any substance that changes from polycrystal to single crystal by heat in the recording layer (a substance that changes within the temperature range of T _{1 to} T ₃ shown in FIG. 1). Those having a temperature of 30 to 200 ° C, preferably about 50 to 150 ° C are used. Such organic low molecular weight substances include alkanol; alkane diol; halogen alkanol or halogen alkane diol; alkylamine; alkane; alkene; alkyne; halogen alkane; halogen alkene; halogen alkyne; cycloalkane; cycloalkene; cycloalkyne; 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; allylcarboxylic acids or their esters, amides or ammonium salts; Esters, amides or ammonium salts thereof; thioalcohols; thiocarboxylic acids or their esters, amines or ammonium salts; Carboxylic acid esters, and the like. These may be used alone or in combination of two or more. These compounds have 10 to 60 carbon atoms,
Preferably it is 10-38, especially 10-30. The alcohol group in the ester may be saturated, may not be saturated, and may be halogen-substituted. In any case, organic low molecular weight substances contain oxygen,
At least one of nitrogen, sulfur and halogen, such as -O
H, -COOH, -CONH, -COOR, -NH,-
It is preferable that the compound contains NH ₂ , —S—, —SS—, —O—, halogen, and the like.

More specifically, these compounds include
Uric acid, dodecanoic acid, myristic acid, pentadecane
Acid, palmitic acid, stearic acid, behenic acid, nonadeca
Fatty acids such as acid, araginic and oleic acid; stearic acid
Methyl phosphate, tetradecyl stearate, stearin
Octadecyl acid, octadecyl laurate, palmitin
Of higher fatty acids such as tetradecyl acrylate and dodecyl behenate
Steal; C₁₆H₃₃-OC₁₆H₃₃ , C₁₆H₃₃-SC₁₆H₃₃
 , C₁₈H₃₇-SC₁₈H₃₇ , C₁₂H_{twenty five}-SC₁₂
H_{twenty five} , C₁₉H₃₉-SC₁₉H₃₉ , C₁₂H_{twenty five}-S-
SC₁₂H_{twenty five} , And ether or thioether. In particular, the present invention
Higher fatty acids, especially palmitic acid, stearic acid,
Higher fats with 16 or more carbon atoms such as henic acid and lignoceric acid
Acids are preferred, and higher fatty acids having 16 to 24 carbon atoms are more preferred.
Good.

In order to widen the range of temperatures that can be made transparent,
The organic low-molecular substance described in this specification may be appropriately combined, or such an organic low-molecular substance may be combined with another material having a different melting point. These are disclosed in, for example, JP-A-63-39378 and JP-A-63-130380, and Japanese Patent Application Nos. 63-14754 and 1-14.
0109, JP-A-2-1363, JP-A-3-208
No. 9, but are not limited thereto.

The ratio between the organic low-molecular substance and the resin base material in the heat-sensitive layer is preferably about 2: 1 to 1:16, more preferably 1: 2 to 1: 6 by weight. When the ratio of the resin base material is less than this, it becomes difficult to form an organic low-molecular substance in a film held in the resin base material. Becomes difficult.

The thickness of the heat-sensitive layer is preferably 1 to 30 μm,
2-20 μm is more preferred. If the heat-sensitive layer is too thick, heat distribution within the layer will occur, making it difficult to achieve uniform transparency. On the other hand, if the heat-sensitive layer is too thin, the turbidity decreases and the contrast decreases. Further, the turbidity can be increased by increasing the amount of the organic low-molecular substance in the heat-sensitive layer.

In addition to the above components, additives such as a surfactant and a high-boiling solvent can be added to the heat-sensitive layer in order to facilitate formation of a transparent image. Specific examples of these additives are as follows. Examples of high boiling solvents: tributyl phosphate, tri-2-ethylhexyl phosphate, triphenyl phosphate, tricresyl phosphate, butyl oleate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, diphthalic phthalate -N-octyl, di-2-ethylhexyl phthalate, diisononyl phthalate, dioctyldecyl phthalate, diisodecyl phthalate, butylbenzyl phthalate, dibutyl adipate, di-n-hexyl adipate, di-2-ethylhexyl adipate , Di-2-ethylhexyl azelate, dibutyl sebacate, di-2-ethylhexyl sebacate, diethylene glycol dibenzoate, triethylene glycol di-2-ethyl butyrate, methyl acetyl ricinoleate, butyl acetyl ricinoleate, butyrate Phthalyl butyl glycolate, acetyl tributyl 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 adducts of fats and oils or polypropylene glycol; acetylene glycol; Na, Ca, Ba or Mg salts of higher alkylbenzene sulfonic acids; higher fatty acids, aromatic carboxylic acids, higher fatty acid sulfonic acids, aromatic sulfonic acids, monoesters of sulfuric acid Or Ca, Ba or Mg salts of phosphoric acid mono- or di-esters; low sulfated oils; poly long chain alkyl acrylates; acrylic oligomers;
Poly long chain alkyl methacrylate; long chain alkyl methacrylate-amine-containing monomer copolymer; styrene-maleic anhydride copolymer; olefin-maleic anhydride copolymer.

When a resin used as a resin base material is coated and dried on a support such as a plastic film, glass or metal to form a laminated heat-sensitive layer, some of the resins have poor adhesion to the support. It is also possible to provide an adhesive layer between the thermosensitive layer and the thermosensitive layer so that the thermosensitive layer does not peel off. The resin for the adhesive layer is not particularly limited as long as it has good adhesiveness to the support and does not adversely affect the components of the heat-sensitive recording layer. For example, vinyl chloride resins, polyester resins,
Acrylic resins, polyamide resins, and the like are listed. In particular, a metal or a metal thin film has poor adhesion, and a copolymer or the like containing vinyl chloride and a phosphate ester as main components is suitably used as a material for the adhesive layer. The thickness of the adhesive layer is 0.1
About 5 μm, more preferably about 0.3 to 2 μm.

When an image of the recording material is used as a reflection image, providing a light reflecting layer on the back of the recording layer can increase the contrast even if the thickness of the recording layer is reduced. Specific examples include vapor deposition of Al, Ni, Sn and the like (described in JP-A-64-14079). It is also possible to create a card combining a magnetic recording layer and a reversible thermosensitive layer. In particular, when a reversible thermosensitive layer is provided on the magnetic recording layer, a smooth layer containing a resin as a main component is provided to make the surface smooth, a light-reflecting layer is provided thereon, and further thereon. In some cases, a heat-sensitive layer may be provided via an adhesive layer (Japanese Utility Model Application Laid-Open No. 2-3876).

Further, a protective layer may be provided on the heat-sensitive layer of the present invention in order to prevent the surface from being deformed by the heat and pressure of the heating means by a writing method such as a thermal head and the transparency of the transparent portion being reduced. good. A protective layer (having a thickness of 0.
1-5 μm) as silicone rubber, silicone resin (described in JP-A-63-221087),
Polysiloxane graft polymer (JP-A-63-317)
385), an ultraviolet curable resin or an electron beam curable resin (described in JP-A-2-566).

In each case, a solvent is used at the time of coating, and it is desirable that the solvent does not easily dissolve the resin of the heat-sensitive layer and the organic low-molecular substance. N-hexane, as a solvent that hardly dissolves the resin of the heat-sensitive layer and organic low-molecular substances,
Examples thereof include methyl alcohol, ethyl alcohol, and isopropyl alcohol, and an alcohol-based solvent is particularly desirable in terms of cost.

[0030]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The parts and percentages are based on weight.

Example 1 r-Fe ₂ O ₃ 10 parts Vinyl chloride / vinyl acetate / vinyl alcohol copolymer (VAGH manufactured by UCC) 2 parts Coronate (10% toluene solution) 2 on white PET having a thickness of about 188 μm A part of methyl ethyl ketone 40 parts Toluene 40 parts is coated with a wire bar, and dried by heating to about 1 part.
A magnetic recording layer having a thickness of 4 μm was provided. Then, on the transparent PET opposite to the magnetic recording layer side, about 400-500 mm thick Al
Was vacuum deposited to provide a light reflecting layer. In addition, behenic acid 2 parts eicosane diacid 5 parts lignoceric acid 3 parts vinyl chloride-vinyl acetate copolymer (Kanebuchi Chemical Co., Ltd. polymerization degree 1800, prototype) 40 parts THF 100 parts toluene 50 parts The solution was applied with a wire bar and dried by heating to form a reversible thermosensitive recording layer having a thickness of about 11 μm. Further, a solution consisting of 10 parts of a 75% butyl acetate solution of a urethane acrylate ultraviolet curable resin (Unidick C7-157 manufactured by Dainippon Ink and Chemicals, Inc.) and 12 parts of isopropyl alcohol is applied by a wire bar and heated. 80W after drying
/ Cm and cured with an ultraviolet lamp, and a protective layer having a thickness of about 4 μm was provided to prepare a reversible thermosensitive recording material.

Next, the reversible thermosensitive recording material was left in a thermostat at 120 ° C. for 1 minute and then cooled to room temperature to make it opaque and opaque. The reversible thermosensitive recording material thus prepared was
After heating in a thermostat at 0 ° C to 130 ° C in steps of 2 ° C for 10 minutes, the mixture was cooled to room temperature, and then cooled with a Macbeth reflection densitometer (RD)
−914), the reflection density was measured. At this time, the temperature range when the reflection density value exceeded 0.8 was defined as the transparency temperature range, and the range was defined as the width. Table 1 shows the results.

[Table 1] Next, the reversible thermosensitive recording material of Example 1 was subjected to a durability test 500 times in which image formation and image erasure were repeated as follows. An image was formed using a thermal head printer manufactured by Kyushu Matsushita Electric Co., Ltd. as an image forming apparatus, and the image was erased by leaving it in a constant temperature bath at 82 ° C. for 10 minutes and then cooling to room temperature. Table 5 shows the results of measurement of the cloudy image density and the image erasure density by the Macbeth reflection densitometer (RD-914) for the first and 500th repetitions in the durability test 500 times.
It was shown to.

Example 2 A durability test was repeated 500 times in the same manner as in Example 1 except that the same reversible thermosensitive recording material as in Example 1 was used and the erasing temperature in the thermostatic chamber was 93 ° C. Was. Table 5 shows the results.

Example 3 The same reversible thermosensitive recording material as in Example 1 was used, and the measurement of the clearing temperature range was carried out using an erasing device manufactured by Unique Machinery Co., Ltd. at a pressure of 2 ° C. from 70 ° C. to 130 ° C. Pressure 1.
After heating at 5 kg / cm ² for 1.0 second and cooling to room temperature, the range and width of the clearing temperature were measured in the same manner as in Example 1. Table 2 shows the results.

[Table 2] The erasing apparatus used here is a hot stamping method. An Al block is used for the hot stamping, and a metal sheet having a thickness of 0.2 mm and a thickness of 45 mm with a spring hardness Hs applied to the surface of the metal hot plate is used. used. Next, a durability test was performed 500 times by repeating image formation and image erasure. The image was formed in the same manner as in Example 1. The image was erased using an erasing device manufactured by Unique Machinery, at an erasing temperature of 94 ° C., an applied pressure of 1.5 kg / cm ² , and an application time of 1
sec. Table 5 shows the test results.

Example 4 Using the same reversible thermosensitive recording material as in Example 1, the transparency temperature range was measured using a thermal gradient tester manufactured by TOYOSEIKI Co., Ltd., at 90 ° C. to 140 ° C. at 2 ° C. increments. After heating at a pressure of 1.5 kg / cm ² for 1.0 second and cooling to room temperature, the range and width of the clearing temperature were measured in the same manner as in Example 1. Table 3 shows the results.

[Table 3] Next, a durability test was performed 500 times by repeating image formation and image erasure. The image was formed in the same manner as in Example 1. The image was formed using a thermal gradient tester manufactured by TOYOSEIKI, at an erasing temperature of 108 ° C. and an applied pressure of 1.5 kg.
/ Cm ² and an application time of 0.1 second. Table 5 shows the test results.

Example 5 The same reversible thermosensitive recording material as in Example 1 was used, and the measurement of the clearing temperature range was performed in the same manner as in Example 3 except that the applied pressure was 0.1 kg / cm ² and the application time was 2 seconds. Similarly, the range and width of the clearing temperature were measured. Table 4 shows the results.

[Table 4] Next, a durability test was performed 500 times by repeating image formation and image erasing. The erasing temperature during image erasing was 91 ° C., and the applied pressure was 0.1 k.
The procedure was performed in the same manner as in Example 3 except that g / cm ² and the application time were 2 seconds. Table 5 shows the results.

COMPARATIVE EXAMPLE 1 A durability test was conducted 500 times in the same manner as in Example 1 except that the erasing temperature was changed to 103 ° C. Table 5 shows the results.

Comparative Example 2 A durability test was repeated 500 times in the same manner as in Example 3 except that the erasing temperature was changed to 110 ° C. Table 5 shows the results.

Comparative Example 3 A durability test was repeated 500 times in the same manner as in Example 5 except that the erasing temperature was 105 ° C. Table 5 shows the results.

[0040]

[Table 5]

[0041]

As is clear from the results of Examples 1 to 5 and Comparative Examples 1 to 3, the image erasing method of the present invention does not lower the erasure density even if the image formation and erasure are repeated many times. In addition, a high-contrast image can be maintained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a change in transparency due to heat.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takao Igawa 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Kunichika Moroboshi 1-3-6 Nakamagome, Ota-ku, Tokyo (56) References JP-A-63-173684 (JP, A) JP-A-4-21485 (JP, A) JP-A-3-160067 (JP, A) JP-A-5-96852 (JP, A) Japanese Patent Laid-Open No. 5-169841 (JP, A) International Publication No. 90/11898 (WO, A1)

Claims (5)

(57) [Claims] 1. An image erasing method for erasing an image by heating a reversible thermosensitive recording material capable of forming and erasing an image by heating, wherein the reversible thermosensitive recording material comprises a resin on a support.
Two or more kinds of organic bases dispersed in a fat matrix and a resin matrix
Mainly composed of molecular substance, transparency is reversible depending on temperature
The image erasing is performed by using the one having a heat-sensitive layer which changes to the above, and using the erasing energy as energy on the lower energy side than the central energy value in the erasable energy range at the time of erasing the image of the reversible thermosensitive recording material. Yes, characterized
An image erasing method for an inverse thermosensitive recording material . 2. The image erasing method according to claim 1, wherein a hot stamp is used as an image erasing means for erasing the image by heating the reversible thermosensitive recording material, and the heating time is set to 0.1 second or more to erase the image. Image erasing method for reversible thermosensitive recording material . 3. A hot stamp is used as an image erasing means for erasing an image by heating the reversible thermosensitive recording material.
^2. The reversible feeling according to claim 1, wherein the image is erased by pressing at a pressure of 1 kg / cm < ² > or more and heating at the same time .
An image erasing method for a thermal recording material . 4. An image erasing means for erasing an image by heating said reversible thermosensitive recording material, wherein a hot stamp is used by disposing a buffer made of a high molecular weight organic compound on a metal surface. An image erasing method for the reversible thermosensitive recording material as described above. Wherein said reversible thermosensitive recording material is a reversible thermosensitive recording
5. A reversible thermosensitive device according to claim 1, wherein the card has a layer made of a material and a magnetic recording layer.
A method for erasing images on recording materials .