JP3417242B2 - Reversible recording medium and image erasing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet-shaped recording medium capable of reversibly changing light transmittance and reflectance and a method for erasing an image displayed thereon, which is under a pressure condition. A reversible recording medium that can be used for a reversible OHP (overhead projector) sheet or a clean reversible blackboard with a large screen and a simple structure, which allows free handwriting and rewriting of images, and its application A simple image erasing method that can be performed.

[0002]

2. Description of the Related Art Heretofore, there have been proposed some sheet-like recording and displaying media capable of reversibly changing the transmittance and reflectance of light. For example, a reversible thermosensitive recording medium in which an organic low molecule is dispersed in a polymer resin, and transmission and scattering are controlled by heating temperature to perform display recording (JP-A-7-1011).
61) or a polymer liquid crystal in which phase separation is controlled and transmission and scattering are controlled depending on the cooling rate after heating (JP-A-6-18866), or a usually colorless electron-donating dye precursor And a light-transmissive reversible thermosensitive recording film containing a dye and an electron-accepting compound that causes a reversible color change in the dye precursor due to a difference in cooling rate after heating (JP-A-6-270540). Has been. Recording is usually performed on these recording and display media by controlling heating in pixel units using a thermal head or the like. The recording medium of the type in which low molecular weight organic molecules are dispersed in the former polymer resin can control the heated print part to be cloudy or transparent depending on the heating temperature, but it is generally applied as a reversible OHP sheet. When it is done, it is used in a mode in which the printing section becomes cloudy. In the case of a high-molecular liquid crystal, when printing is performed with a thermal head, it becomes a rapidly cooled state after heating, and that portion becomes transparent, so that a negative image is obtained in the case of transmission.

Further, there is also known a reversible image recording / displaying system or recording medium which utilizes a phenomenon in which a substance having a close refractive index is filled in a light-scattering porous body to make the region transparent. To a light-scattering sheet medium having voids inside, which is obtained by binding particles with a resin so as to have sufficient mechanical strength,
An image-forming sheet material (see Japanese Examined Patent Publication (Kokoku) No. 4) that externally infiltrates a transparent liquid having a refractive index close to that of the particles to form an image, and volatilizes the infiltrating liquid to erase the image.
48349) is a typical example. When this medium is used transparently, as in the case of using the above-mentioned polymer liquid crystal, the printing portion is in a transparent state, and therefore, a normal OHP is used.
The negative image is the opposite of.

When the former three conventional reversible recording display media are used as a transmissive OHP sheet, printing is performed by a heating device such as a thermal head. However, if it is attempted to add information by handwriting, It was necessary to develop a special device such as a hot pen. However,
Since the conventional reversible recording medium in the previous term has limited heating conditions for printing, when the user writes at a free writing speed and writing pressure, the heating amount for the medium changes irregularly and widely. It was practically difficult to write by hand. Further, in the latter recording medium using refractive index matching, handwriting can be performed with a pen such as a magic pen that allows liquid to be infiltrated into the medium from the pen tip, but the image to be written is in a porous liquid. Due to the spread of the penetration, there is a problem that the image has a coarser resolution than the image written on the OHP with a normal pen. Writing on an ordinary irreversible OHP medium is often performed by handwriting with a felt-tip pen or the like while projecting, and the inability to use this has been a major cause of difficulty in using the OHP capable of reversible display.

[0005]

In view of the above problems, the present invention can write characters, that is, display an image even if the user writes at a free writing speed and writing pressure, and is also applicable to a transmission type. Another object of the present invention is to provide a reversible recording display medium and a simple image erasing method applicable thereto.

[0006]

Means for Solving the Problems As a result of intensive investigations by the present inventors, changes in light transmittance and reflectance caused by applying pressure to a porous body filled with a fluid liquid are utilized. As a result, they have found that a suitable reversible recording medium can be achieved, and completed the present invention.

In the reversible recording sheet of the present invention, a light-scattering porous body having a porous structure in which at least pores are opened in an open space has a refractive index substantially equal to the refractive index of the material constituting the porous body. The porous material having a structure in which the fluid material has been infiltrated, the porous material infiltrated with the fluid material is pressed, and the fluid material in the pressed portion is moved to a portion other than that portion, thereby forming an image A printing (image display) means for changing the light transmittance, and an image erasing means for refilling the voids in the porous material generated by the movement of the fluid material with the fluid material to restore the original transparent state. The feature is that the image is displayed and erased by using it. That is, the reversible recording sheet of the present invention has, in at least a light-scattering porous body having a porous structure in which pores are opened in an open space, having a refractive index substantially equal to the refractive index of the material forming the porous body. Having a structure in which a fluid material is infiltrated, pressure is applied to the transparent porous body in which the fluid material is infiltrated, and the fluid material in the pressed portion is moved to a region other than the pressed portion, An image is displayed by putting the portion into a light-scattering state, and the voids in the porous material caused by the movement of the fluid material due to the pressurization are filled with the fluid material again, and then returned to the transparent state. Is erased.

Further, in the image erasing method for the reversible recording medium of the present invention, the porous layer is wetted by heating as a means for refilling the voids in the porous body with the fluid material again and restoring the original transparent state. It is characterized in that the viscosity of the flowing material is lowered and the voids are filled again by utilizing the increase in the capillary force of the flowing material itself. Further, as a means for refilling the voids in the porous body with the fluid material again to restore the original transparent state, the fluid material is newly supplied to the porous layer from the outside to fill the voids in the light scattering state. In this case, it is preferable that a heating means is not required for erasing the image and energy consumption is reduced, which is another feature.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Details of the reversible recording medium of the present invention are shown below.

In the reversible recording medium of the present invention, a light-scattering porous body having a porous structure in which at least pores are opened in an open space has a refractive index substantially equal to that of the material forming the porous body. It has a structure that is infiltrated with the fluid material that it has, and is the light transmittance in the state where the fluid material is infiltrated into the voids in the porous structure, and that of the porous body itself when the fluid material is removed. Due to the light-scattering property, it becomes opaque, and the image is displayed.

The porous body used in the reversible recording medium of the present invention has a large number of voids (pores) therein, and has a porous structure in which at least some of these pores are open to an open space. It is necessary. In addition, this porous body,
Any method may be used as long as it has a void inside, exhibits light scattering properties, and has mechanical strength against stress corresponding to the writing pressure of the user. . Usually, the writing pressure of various pens for an adult is in the range of about 50 g to 500 g, so that mechanical strength to withstand the pressure is required.

The porous body is usually made of an organic resin material from the viewpoint of ease of molding and the like. Examples of the method of forming a porous layer using an organic resin include a phase inversion method, a stretching method, and a filler filling method.

Each of the methods will be described. The phase inversion method is a method of dissolving an organic resin in a solvent, casting and spreading on a flat plate to form a film. It is a method of forming a porous layer by immersing it in a solidified layer to solidify it. The filler filling method is an organic resin as a binder, in which a filler that is soluble in a solution that does not react or dissolve in the supporting substrate and the binder is dispersed, this solution is applied on the supporting substrate, and the solvent is removed only from the filler. This is a method of forming a porous layer. In the stretching method, after a crystalline organic resin is formed into a film, heat or a plasticizer is added to make it into a plasticized state, and the film is stretched uniaxially or biaxially to distort the film to form pores. This is a method of opening to form a porous layer.

As a specific material satisfying the properties required for the porous material, organic resins formed by a phase inversion method or a filler filling method include, for example, cellulose, acetyl cellulose, nitrocellulose, polyamide, Examples thereof include polymethyl methacrylate, polycarbonate, polyvinyl alcohol, polyurethane and the like. In addition, examples of the organic resin formed by the stretching method include polypropylene, polyethylene, and polytetrafluoroethylene (PT).
FE) and the like.

Further, in order to increase the strength of the porous layer, the organic resin and the filler may be combined to form the porous layer. As the filler used at this time, materials such as silica, polymerized melamine, and calcium carbonate, which have a refractive index close to that of the above organic resin, are preferably used.
The size of the filler is preferably 0.1 μm to 5 μm. If the size of the filler is less than 0.1 μm, there is no effect of increasing the strength of the porous layer, and if the filler is larger than 5 μm, the white turbidity of the porous layer is reduced. When the organic resin and the filler of the porous layer are combined to form the porous layer, the porous layer can be formed by the above-mentioned phase exchange method of the membrane. Mixing ratio of filler to organic resin is 5% to 70% by weight
Is preferred. If the amount of the filler is less than 5% or more than 70%, the effect of increasing the strength of the porous layer becomes small.

When the thickness of the porous layer is 5 μm to 50 μm, the volume of the voids in the porous layer is 20 to 80% and the average pore diameter of the voids in the porous layer is 0.01 μm to 10 μm.
From the viewpoint of white turbidity, the thickness is preferably μm. Porosity is 2
When it is 0% or less, the white turbidity decreases, and it becomes difficult to display a high contrast. When the porosity is 80% or more, the white turbidity increases, but the strength of the display recording layer decreases,
It becomes difficult to record images stably and maintain images.

The average pore diameter of the voids in the porous layer is 0.01 μm to 10 μm, more preferably 0.1 μm.
The range of 5 μm is preferable. When the average pore diameter is smaller than 0.01 μm or larger than 10 μm, the white turbidity is lowered and high contrast display becomes difficult. Even if the thickness and the pore diameter of the porous layer are within the above-mentioned preferred ranges, the relationship between the two needs to be such that the average pore diameter of the voids is smaller than the thickness of the porous layer. This means that when the average pore diameter of the voids is larger than the thickness of the porous layer, the porous layer that is the light scattering layer has through holes that allow straight light transmission in at least a part of it. This is because the density and sharpness of the image are reduced.

Such a porous layer can be used alone as long as it can be prepared so as to have sufficient strength so that it can be self-supported, but it is easy to handle as a hard copy medium. In view of this, it is preferable to form it on some kind of supporting substrate, whose strength and thickness can be easily controlled. As such a supporting substrate material, various organic resin films such as polyethylene, polyester and polyethylene terephthalate are used. When the reversible recording medium of the present invention is used for OHP or the like, it is preferable to use a transparent organic resin film, and when it is applied to a reversible blackboard or the like, in addition to the transparent film, a color tone that does not impair the contrast of the displayed image is obtained. It is also possible to use a colored film having the same.

Further, a fluid material having a refractive index substantially equal to that of a material forming the porous body that is infiltrated into the voids of the porous body (hereinafter, simply referred to as a fluid material).
As long as it has a good transparency and has a wettability that naturally penetrates into the porous body by a capillary force, it can be used regardless of the presence or absence of polarity and other electrical characteristics. However, the "refractive index close to the refractive index of the substance constituting the porous layer" here means that the difference in refractive index between the porous material and the fluid material is 0.1 or less, preferably 0.05 or less. The combination is shown. If the refractive index difference between the porous material and the fluid material is larger than 0.1, refraction and reflection of light occur at the interface between the fluid material and the transparency even if the fluid material is infiltrated into the porous layer. Will end up. The range of the refractive index which is close to the refractive index of the porous layer material is n = 1.3 to
The range is about 1.6, and in the case of combination with the above-mentioned porous layer material, it is necessary to select a fluid material that satisfies the condition.

Further, it is preferable to use a liquid having a viscosity range of 20 cp to 60 cp at room temperature (25 ° C.) as a viscosity range of the fluid material suitable for use in order to maintain the image formation state. That is, if the viscosity of the fluid material is less than 20 cp, the image maintainability is deteriorated, and if it exceeds 60 cp, the pressure required for printing for image display is increased, which is not preferable. However, this is not the case when the reversible recording medium of the present invention is used in combination with an appropriate temperature control means.

Further, when the fluid material has a high volatility, the fluid material volatilizes from the voids opened in the open space to reduce the amount of the fluid material.

In addition to the above-mentioned required characteristics, from the viewpoint of safety, materials that can be added to foods are particularly preferable. Examples of such materials include edible vegetable oils and fats. Specifically, safflower oil, soybean oil, sunflower oil, niger oil, corn oil, cottonseed oil, sesame oil, rapeseed oil, rice oil, kapok oil, peanut oil, olive oil, palm oil, palm kernel oil, coconut oil, There is camellia oil. Also,
Materials such as ethylene glycol, glycerin, and liquid paraffin that can be used for cosmetics are also safe, have a suitable viscosity and refractive index, and are colorless and transparent liquids at room temperature, which can be preferably used. Also, these materials can be used by adjusting the viscosity using a suitable solvent having a substantially equal refractive index.

Since all of the above-mentioned fluid materials have physical properties whose viscosity decreases as the temperature rises, by heating or heating the entire reversible display medium or a necessary portion thereof, The image can be easily erased by utilizing the increase in the capillary force due to the decrease in the viscosity. From the viewpoint of ease of image deletion by heating, among the above materials,
Viscosity at 60 ° C is 20 cp or less, further 10 cp
The following materials are preferably used.

Next, the image forming method and image erasing of the reversible recording medium of the present invention will be described. This medium pressurizes the porous material infiltrated with the fluid material, and moves the fluid material in the pressurizing portion to a region other than the pressurizing portion, thereby changing the light transmittance in an image form. An image forming method is adopted, and an image is recorded by applying pressure. This pressurization can be performed using a known printing means. As the printing means that can be used here, any structure and method may be adopted as long as pressure can be applied in dot units or character units in accordance with image information. For example, by using a thin and tough wire made of metal used in a dot matrix printer, a typical dot impact of several tens of dots is applied to a porous layer infiltrated with a fluid material.
By applying a pressure of about 1 / min, that part becomes a light scattering state and printing is performed. Also, by pressing something like a rubber stamp made in the shape of a letter, the letter can be written in a light-scattering state faithfully to the shape.

Furthermore, without using a special printing means (device, etc.), a pen having a rounded tip shape, a rod-shaped body formed of resin, glass or the like is used and pressure is applied by handwriting to record ( (Image display) can also be performed. At this time, it is necessary to apply pressure with a writing pressure that does not damage the surface of the recording medium irreversibly.

As a method of erasing the image displayed on the reversible recording medium of the present invention, it is sufficient to refill the voids in the porous material with the fluid material to restore the original transparent state. It is possible to use a method in which the viscosity of the fluid material wetted in the porous layer is reduced by heating and the voids are filled again by utilizing the increase in the capillary force of the fluid material itself. According to this method, it is possible to easily and reversibly use only by repeating pressurization and heating, which is preferable.

As another means for erasing an image, a method in which a fluid material is newly supplied to the porous layer from the outside and the voids in the light scattering state are refilled can be used. Specifically, as a means for supplying the fluid material, a sponge body impregnated with the fluid material is used, and the image display portion, that is, the portion where the fluid material is not infiltrated into the voids, This is a method of injecting a fluid material into the voids through the voids that are open to the open space on the surface of the porous body.
As a means for injecting the fluid material, any material or structure can be applied as long as it can retain the fluid material. For example, it may be a gel, a porous body, or a cloth or non-woven cloth. In the case of a porous body or cloth-like or non-woven cloth-like, it is necessary that the permeated fluid material has voids of a size that does not flow away, and further, a property that can adhere to the porous layer, for example, the surface is a porous layer. It is necessary that the surface has elasticity and flexibility, has the same shape, and has physical properties such that the surfaces are brought into close contact with each other when pressed. Such a material may be the same as the light-scattering porous layer described above,
Further, it may be a cloth, a non-woven fabric, or a flocked body made of natural fibers, synthetic fibers, metal fibers or glass fibers. Further, paper, porous rubber, resin and ceramics formed by microfabrication by microfabrication, organic or inorganic fine particles, or a sintered body thereof can be used. Among them, a sponge having flexibility,
Suitable examples include urethane foam, fiber lumps, woven fabrics and nonwoven fabrics having a thickness. Here, if the means for injecting the fluid material from the outside is made of a porous material having a capillary force weaker than that of the light-scattering porous layer, the porous material can be adhered to the porous layer so that It acts like a blotting paper and can naturally incorporate the flowable material into its voids. Further, by using this porous body, it is possible to absorb and retain the excess fluid material leached on the surface of the porous layer, so that the wet state of the fluid material in the porous layer can be adjusted at the same time. You can

As described above, when the method of injecting the fluid material into the voids from the outside is used, it is preferable that the heating means is not required and therefore the energy consumption at the time of erasing the image is reduced.

[0029]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. (Embodiment 1) FIG. 1 is a schematic sectional view showing a reversible recording medium of Embodiment 1 according to the present invention. In the reversible recording medium 10, the fluid material 14 is wet in the voids of the porous layer 12, and the back surface of the porous layer 12 is the transparent support 1.
4 are laminated and configured. On the surface of the porous layer 12, for protection of the layer, a transparent protective layer 18 having a large number of small holes for maintaining the opening of voids opened in the open space of the porous layer 12 is provided.

The structure of the reversible recording medium 10 will be described in detail. Acetyl cellulose was dissolved in methyl isobutyl ketone (MIBK) as a material for forming the porous layer 12 to prepare a coating solution of 15% by weight. This coating solution was applied to a PET (polyethylene terephthalate) film supporting substrate 16 having a thickness of 75 μm to obtain a wet film thickness of about 500 μm.
The coating film is coated with the supporting substrate in a methyl alcohol / ethyl alcohol mixed solution (6 /
It was immersed in 1) for 5 minutes. After 5 minutes, the supporting substrate was pulled up from the mixed solution and dried to prepare a display recording medium in which the porous layer 12 having a dry film thickness of 50 μm was formed on the supporting substrate 16.

A fluid material 14 having a refractive index substantially equal to that of the acetyl cellulose porous layer (refractive index 1.470) 12.
As vegetable oil [rapeseed oil: refractive index 1.470 to 1.47]
2. Viscosity 25 cps (25 ° C.)]) to a transparent state, and then the excess fluid material 14 on the surface is absorbed by a paper having good absorptivity, so that the frosted surface is exposed. Adjusted to. The average void filling rate of the porous layer at this time was estimated to be in the range of about 80 to 90% from the weight measurement before and after the surface liquid was wiped off. Then, a 25 μm-thick PET having a transparent adhesive layer on one surface as a surface protective layer on the surface of the porous layer 12
The (polyethylene terephthalate) film 18 was laminated on the porous layer 12 whose inside was wet with the fluid material 14 with the adhesive layer inside, to prepare the reversible recording medium 10.
At this time, the polyethylene film 18 has fine air holes that are two-dimensionally arranged in advance so as not to impair the transparency, and the pressure inside the porous layer 12 is constant with the outside pressure. Are to be equal.

Next, an image display method of the reversible recording medium 10 will be described. With respect to the reverse recording medium 10 having the above structure, the press serial head 20 having a matrix of 6 × 8 dots for one character, which is used in a dot matrix printer, is provided, and the printing pressure is Printing was performed according to image information with a printing device (not shown) adjusted to about 1 kgf / cm ² . As a result, as shown in FIG. 2 (A), the fluid material 14 held in the voids of the porous body 12 at the portion where pressure is applied by printing moves to the surroundings, and as a result, inside the porous body 12. Voids (unfilled voids that are not wetted by the fluid material) 1
2A was generated and a light scattering state occurred, and an image was displayed. FIG. 2A is a schematic sectional view showing a state in which an image is displayed (printed) on the reversible recording medium 10. Also, FIG.
(B) is a reversible recording medium 10 in a state where an image is displayed.
It is a schematic sectional drawing which shows. As described above, even when the printing is completed and the pressure is not applied, the fluid material 14
It was confirmed that the image in the light-scattering state caused by the bias of was retained.

Further, as shown in FIG. 3, a writing instrument-like pen 22 having a rounded tip with respect to the medium on which the image is recorded is formed.
When handwriting was performed using, the handwritten portion follows the arbitrary writing pressure and writing speed, and becomes a light-scattering state like the image printed by the pressure serial head 20. It was observed as a reflection image with good contrast. FIG. 3 shows this reversible recording medium 10.
6 is a model diagram showing a state in which an image is being written by hand using a writing instrument-like pen 22. FIG.

As shown in FIG. 4, the reversible recording medium 10 on which the image is formed in this manner is shown in FIG.
As a result, a light-scattering portion generated by pressurization became a black portion, and a transmission image with good contrast was obtained. From this, it was found that the reversible recording medium 10 of the present example can be suitably used as a medium for OHP.

Next, a method of erasing the formed image will be described. As shown in FIG. 5, when the reversible recording medium 10 on which an image is formed is placed on a hot plate 26 heated to 60 ° C. and heated, the viscosity of the infiltrating fluid material 14 decreases. , The capillary force increases, the movement of the liquid occurs so that the unevenness of the infiltration state in the porous layer becomes uniform, and all images including handwritten images are erased,
It quickly returned to its original transparent state.

It was confirmed that the image display by the pressure and the image erasure by the heating can be repeated many times. (Example 2) A black PET film support substrate (Lumirror X-30: manufactured by Panac) 28 was used as a support, a porous layer 12 similar to that of Example 1 was formed, and 7 parts of glycerin was used as the fluid material 14. Material mixed with 5 parts of ethylene glycol [refractive index 1.473, viscosity about 35 cp (25
C.))] was wetted to form a reversible recording medium 30.
Further, in Example 2, a structure such as a protective layer was not provided on the porous surface, and the structure was opened so that the fluid material from the outside can be replenished and the excess portion can be wiped off freely. The reversible recording medium 30 was incorporated into a frame to form a reversible blackboard 32 as shown in FIG.

The reversible blackboard 32 has a writing instrument-like pen 22 with a rounded tip, and when handwriting is performed, a white background appears in a black background, and a display record similar to that of a normal blackboard is obtained. I was able to do it.

Further, as shown in FIG. 7, in the white turbid region where the liquid filling rate is low due to the movement of the fluid material 14 to the surroundings by the pressurization, the fluid material 1 is supplied from the outside of the surface of the porous layer 12.
4 held and moistened with a cloth blackboard eraser-like tool 34, and the traces were brought into contact with each other.
4 was supplied, and the excess liquid 14 was absorbed by the blackboard eraser tool 34, so that the image could be easily erased and the initial state could be restored. As a result, we were able to realize a clean blackboard that does not have chalk or ink residue when erased, like a normal blackboard or whiteboard.

As is apparent from the above-mentioned embodiment, the reversible recording medium of the present invention is an OHP sheet or a reversible recording display on which a character can be written even if the user writes at a free writing speed and writing pressure. Can provide a reversible blackboard.

By adopting the image erasing method as in Example 1, the liquid is prevented from seeping out from the surface, and the image written by pressurization is naturally performed by utilizing the viscosity change of the liquid itself by heating. Therefore, it is suitable for batch erase processing. On the other hand, by adopting the image erasing method as described in the second embodiment, it is possible to repeatedly write and erase the image without requiring a special device or energy for erasing, so that the device can be simplified and downsized. Will be possible.

[0041]

INDUSTRIAL APPLICABILITY The reversible recording medium of the present invention can write characters, that is, display an image even if the user writes at a free writing speed and writing pressure, and is applicable to a transmission type. Further, the image erasing method of the present invention has an advantage that the image displayed on the reversible recording medium can be easily erased without using a complicated device or the like.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a reversible recording medium of Example 1 of the present invention.

2A is a schematic cross-sectional view showing an image display state on the reversible recording medium of Example 1, and FIG. 2B is a schematic cross-sectional view showing an image display state on the reversible recording medium.

FIG. 3 is a model diagram showing a state in which an image is written by handwriting on the reversible recording medium according to the first embodiment.

FIG. 4 is a diagram in which the reversible recording medium of Example 1 is used in an image projection apparatus.

FIG. 5 is a schematic cross-sectional view showing an image erased state of a reversible recording medium by heating.

FIG. 6 is a perspective view showing the entire reversible blackboard in which the reversible recording medium of Example 2 is incorporated.

FIG. 7 is a schematic cross-sectional view showing an image erased state of a reversible recording medium by a blackboard eraser-shaped tool holding a fluid material.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Reversible recording medium 12 Porous layer 14 Fluid material 16 Support (PET film) 18 Surface protective layer 20 Pressurizing head 12A Porous layer fluid material unfilled void 22 Pressurizing pen 24 Transmission type image projection device 26 Image erasing heating device 30 Reversible recording medium 32 Reversible blackboard 34 Means for supplying fluid material from the outside (blackboard eraser tool soaked with fluid material)

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-57-75817 (JP, A) JP-A-61-202882 (JP, A) JP-A-10-44592 (JP, A) JP-A-10- 181197 (JP, A) JP 10-35095 (JP, A) JP 10-193782 (JP, A) JP 10-181196 (JP, A) JP 10-193786 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B41M 5/00 G09F 9/30 G09F 9/37

Claims (4)

(57) [Claims] 1. A light-scattering porous body having a porous structure in which at least pores are opened in an open space is infiltrated with a fluid material having a refractive index substantially equal to that of a material forming the porous body. The porous material in the transparent state having the above-mentioned structure and infiltrated with the fluid material is pressed, the fluid material in the pressed portion is moved to a region other than the pressed portion, and the portion is in a light scattering state. By displaying the image, it is possible to erase the image by refilling the fluid material into the voids in the porous material generated by the movement of the fluid material due to the pressurization and returning to the transparent state. Characteristic reversible recording medium. 2. A material whose viscosity is reduced by heating is used as the fluid material, and the viscosity of the fluid material is heated by heating as a means for refilling the voids in the porous material with the fluid material again and returning to a transparent state. The reversible recording medium according to claim 1, wherein the gap is reduced and the gap is filled by utilizing an increase in the capillary force of the fluid material itself. 3. The image displayed on the reversible recording medium according to claim 1, is heated on the reversible recording medium,
A reversible recording medium characterized by lowering the viscosity of a fluid material and utilizing the increase in the capillary force of the fluid material itself to refill the voids in the porous material with the fluid material to restore the transparent state. Image erasing method. 4. An image displayed on the reversible recording medium according to claim 1, wherein a fluid material is newly supplied to the porous layer from the outside, and the fluid material is again supplied to the voids in the porous layer. An image erasing method for a reversible recording medium, which comprises filling and restoring the original transparent state.