JPH10217618A - Reversible recording medium and image erasing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reversible record indicating medium applicable to a transparent type onto which a user can write a character at an arbitrary writing speed or writing pressure, i.e., can indicate an image, and a convenient image erasing method applicable thereto. SOLUTION: The reversible recording medium comprises a fluid substance 14 wetted in the air gap of a porous layer 12 laminated, on the back thereof, with a transparent support 14. When printing is performed according to image information using a printer having a pressure serial head 20, the fluid substance 14 held in the air gap of the porous layer 12 migrates from the part applied with the printing pressure to the periphery. Consequently, an unfilled air gap 12A appears in the porous layer 12 to bring about a light scattering state and an image is displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet-like recording medium capable of reversibly changing light transmittance and reflectivity, and a method for erasing an image displayed thereon. A reversible recording medium that can be used for recording and erasing images and that can be freely handwritten and retouched, and can be applied to a reversible OHP (overhead projector) sheet, a clean reversible blackboard with a simple structure having a large screen, and the like. The present invention relates to a simple image erasing method that can be performed.

[0002]

2. Description of the Related Art Heretofore, several sheet-shaped recording and display media capable of reversibly changing light transmittance and reflectance have been proposed. For example, a reversible thermosensitive recording medium in which display recording is performed by dispersing an organic low-molecular compound in a polymer resin and controlling transmission and scattering by a heating temperature (Japanese Patent Laid-Open No. 7-1011)
61) or a method of controlling the phase separation by controlling the cooling rate of the polymer liquid crystal after heating and controlling the transmission and scattering to perform display recording (JP-A-6-18866), or a colorless electron-donating dye precursor. There is known a light-transmissive reversible thermosensitive recording film (Japanese Patent Laid-Open No. Hei 6-270540) 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. Have been. Normally, recording is performed on these recording and display media by controlling heating in pixel units using a thermal head or the like. In the former type of recording medium, in which a low molecular weight organic compound is dispersed in a polymer resin, the heated printing portion can be controlled to be white or cloudy depending on the heating temperature, but it is generally applied as a reversible OHP sheet. When the printing is performed, the printing unit is used in a mode in which the printing unit is clouded. In the case of a polymer liquid crystal, when printing is performed with a thermal head, the state is rapidly cooled after heating, and the portion becomes transparent, so that in the case of transmission, a negative image is obtained.

Further, a reversible image recording and display system and a recording medium utilizing a phenomenon that a light-scattering porous body is filled with a substance having a close refractive index and the region is made transparent are also known. A light-scattering sheet medium having voids inside the particles bound with a resin so as to have sufficient mechanical strength,
An image-forming sheet material (Japanese Patent Publication No. 4-84) in which a transparent liquid having a refractive index close to the refractive index of the particles is infiltrated from the outside to form an image, and the image is erased by volatilizing the infiltrating liquid.
48349) is a typical example. When this medium is used for transmission, as in the case of using the above-described polymer liquid crystal, the printing portion is in a transparent state, so that ordinary OHP is used.
It becomes the opposite negative image.

When the former three conventional reversible recording and display media are used as transmissive OHP sheets, printing is performed by a heating device such as a thermal head. However, if information is to be added by handwriting, Special devices such as hot pens had to be developed. However,
In the previous term, the conventional reversible recording medium has limited heating conditions necessary for printing, so if the user writes at a free writing speed and writing pressure, the heating amount on the medium will be irregular and vary widely. It was practically difficult to add handwriting. On the other hand, in the case of the recording medium using the refractive index matching, handwriting can be performed with a pen such as a magic that can infiltrate the liquid from the pen tip into the medium, but the image to be written is written in the porous medium of the liquid. There is a problem that an image having a coarser resolution than an image written on an OHP with a normal pen is caused by the spread of penetration. On a normal irreversible OHP medium, writing is often performed by handwriting with a felt-tip pen or the like while projecting, and the inability to do so has been a major cause of the inability to use an OHP capable of reversible display.

[0005]

SUMMARY OF THE INVENTION 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 can be applied to a transmission type. It is an object of the present invention to provide a reversible recording / display medium and a simple image erasing method applicable to the medium.

[0006]

Means for Solving the Problems As a result of diligent studies, the present inventors utilize changes in light transmittance and reflectance caused by applying pressure to a porous body filled with a flowable liquid. As a result, it has been found that a suitable reversible recording medium can be achieved, and the present invention has been completed.

[0007] The reversible recording sheet of the present invention provides a light-scattering porous body having a porous structure in which at least holes are open to an open space with a refractive index substantially equal to the refractive index of the material constituting the porous body. It has a structure in which a fluid material is infiltrated, and pressurizes the porous body in which the fluid material is infiltrated, and moves the fluid material in the pressurized portion to a portion other than the portion, thereby forming an image. (Image display) means for changing the light transmittance, and image erasing means for filling the voids in the porous material caused by the movement of the fluid material again with the fluid material and returning to the original transparent state. It is characterized in that an image is displayed and erased by using it. That is, the reversible recording sheet of the present invention has a light-scattering porous body having a porous structure in which at least holes are open to an open space, and has a refractive index substantially equal to the refractive index of a material constituting the porous body. Having a structure in which a fluid material is infiltrated, pressurizing the transparent porous body in which the fluid material is infiltrated, and moving the fluid material of the pressurized portion to a region other than the pressurized portion, The image is displayed by making the portion in a light scattering state, the voids in the porous material generated by the movement of the flowable material due to the pressurization are filled with the flowable material again, and the image is returned to the transparent state. Is erased.

In the method for erasing an image on a reversible recording medium according to the present invention, as a means for refilling a void in the porous material with a fluid material and returning the porous material to its original transparent state, the porous layer is wetted by heating. It is characterized in that the viscosity of the flowing material is reduced, and the gap is 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 material with the flowable material and returning to the original transparent state, a flowable material is newly supplied to the porous layer from the outside to fill the voids in the light scattering state. For example, it is preferable that a heating means is not necessary for erasing an image, and energy consumption is reduced. This is another feature.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the reversible recording medium of the present invention are shown below.

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

The porous material 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 a part of the pores is 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. . Normally, the writing pressure of various pens for adults is approximately in the range of 50 g to 500 g, so that mechanical strength that can 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 a method for forming a porous layer using an organic resin include a phase inversion method, a stretching method, and a filler filling method.

The phase inversion method is a method of dissolving an organic resin in a solvent, casting and developing the solution on a flat plate, and evaporating a part of the solvent to form a film in a bath. This is a method in which a porous layer is formed by immersion and solidification. The filler filling method uses an organic resin as a binder, disperses a filler that is soluble in a solution in which the support substrate and the binder do not react and dissolve in the binder, applies this solution on the support substrate, and removes only the filler from the solvent. This is a method for forming a porous layer. In the stretching method, after forming a crystalline organic resin, heat or adding a plasticizer to a plasticized state to stretch the film uniaxially or biaxially, thereby giving a strain to the film to form pores. This is a method of forming a porous layer by opening.

As specific materials satisfying the characteristics required for the porous body, organic resins formed by a phase inversion method or a filler filling method include, for example, cellulose, acetylcellulose, nitrocellulose, polyamide, Examples include polymethyl methacrylate, polycarbonate, polyvinyl alcohol, and polyurethane. 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 porous layer can be formed by combining an organic resin and a filler. As the filler used at this time, a material such as silica, polymerized melamine, or calcium carbonate having a refractive index close to that of the organic resin is preferably used.
The size of the filler is preferably from 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 size is larger than 5 μm, the turbidity of the porous layer will be reduced. When the porous layer is formed by combining the organic resin of the porous layer and the filler, the porous layer can be formed by the above-described phase exchange method of the membrane. Mixing ratio of filler to organic resin is 5% to 70% by weight
Is preferred. If the filler content is less than 5% or greater than 70%, the effect of increasing the strength of the porous layer is reduced.

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.
μm is preferred in terms of cloudiness. Porosity is 2
If it is 0% or less, the degree of white turbidity decreases, and it becomes difficult to display a high contrast. When the porosity is 80% or more, the opacity increases, but the strength of the display recording layer decreases.
It becomes difficult to maintain stable image recording and images.

The average pore diameter of the voids in the porous layer is 0.01 μm to 10 μm, more preferably 0.1 μm to 10 μm.
A range of 5 μm is preferred. If the average pore diameter is smaller than 0.01 μm or larger than 10 μm, the turbidity decreases, and high-contrast display becomes difficult. Even if the thickness and the pore diameter of the porous layer are within the preferred ranges, the relationship between the two is that the average pore diameter of the voids is smaller than the thickness of the porous layer. This means that if the average pore diameter of the voids is larger than the thickness of the porous layer, the porous layer, which is the light scattering layer, will have at least a portion of the porous layer having a through hole through which light can pass straight, and is displayed. This is because the image density and sharpness of the resulting image are reduced.

Such a porous layer can be used alone as long as it can be produced so as to have sufficient strength to be capable of self-support. However, such a porous layer is difficult to handle as a hard copy medium. In this respect, it is desirable to form it on some kind of support substrate in which the strength and thickness can be easily controlled. As such a support 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 an OHP or the like, it is preferable to use a transparent organic resin film. When the reversible recording medium 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 a displayed image is obtained. A colored film having the same can also be used.

Further, a fluid material having a refractive index substantially equal to the refractive index of the material constituting the porous body infiltrated into the voids of the porous body (hereinafter, simply referred to as a fluid material as appropriate)
Any material can be used as long as it has good transparency and has wettability that naturally penetrates into the porous material by capillary force, irrespective 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 a difference in refractive index between the porous material and the fluid material of 0.1 or less, preferably 0.05 or less. Indicates a combination. If the refractive index difference between the porous material and the flowable material is larger than 0.1, even if the flowable material is infiltrated into the porous layer, light refraction and reflection occur at the interface between the two, and the transparency decreases. Would. As the range of the refractive index close to the refractive index of the porous layer material described above, n = 1.3 to
The range is about 1.6. In the case of a combination with the above-described porous layer material, it is necessary to select a fluid material satisfying the conditions.

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

If the fluid material has a high volatility, the fluid material is volatilized from the voids opened in the open space and the amount thereof is reduced.

In addition to the above-mentioned required characteristics, from the viewpoint of safety, a material which is added to food is particularly preferable, and such a material includes 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, palm oil, Tsubaki oil and the like. Also,
Materials that can be used in cosmetics, such as ethylene glycol, glycerin, and liquid paraffin, are also safe, colorless and transparent liquids having appropriate viscosity and refractive index at room temperature, and can be preferably used. In addition, these materials can be used after adjusting the viscosity by using a suitable solvent having a refractive index substantially equal.

Each of the above-mentioned fluid materials has the property that the viscosity decreases as the temperature rises. Therefore, by heating and heating the entire or necessary part of the reversible display medium, The image can be easily erased by utilizing the increase in the capillary force accompanying the decrease in the viscosity. From the viewpoint of ease of image erasure by heating, of 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 the image erasing of the reversible recording medium of the present invention will be described. This medium changes the light transmittance in an image-like manner by applying pressure to the porous body impregnated with the fluid material and moving the fluid material in the pressurized portion to a region other than the pressurized portion. An image forming method is employed, and an image is recorded by applying pressure. This pressurization can be performed using a known printing means. As a 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, using a metal thin and tough wire used for a dot matrix printer, a normal dot impact of several tens of dots is applied to a porous layer in which a fluid material is infiltrated.
By applying a pressure of about one-half, the part is in a light scattering state and printing is performed. Also, by pressing an object such as a rubber stamp made into a character shape, the character can be written in a light-scattering state faithfully in that shape.

Further, without using special printing means (apparatus and the like), recording is performed by applying pressure by handwriting using a pen having a rounded tip, a rod-shaped body formed of resin, glass or the like. Image display). At this time, it is necessary to press the recording medium with a writing pressure that does not cause irreversible damage to the surface of the recording medium.

Further, as a method for erasing an image displayed on the reversible recording medium of the present invention, the voids in the porous material may be filled with a fluid material again to return to the original transparent state. A method can be used in which the viscosity of the flowable material wetted in the porous layer by heating is reduced, and the void is filled again by utilizing the increase in the capillary force of the flowable material itself. This method is preferable because reversible use can be easily achieved only by repeating pressurization and heating.

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 flowable material, a sponge body or the like impregnated with the flowable material is used, and the image display portion, that is, the portion where the flowable material is not infiltrated into the voids is used. This is a method in which a fluid material is injected into a void from a void that is open to an open space on the surface of a part of the porous body.
As a means for injecting the fluid material, any material and structure may be applied as long as the material can hold the fluid material. For example, it may be a gel, a porous body, a cloth, or a nonwoven fabric. In the case of a porous body or a cloth, or a non-woven fabric, it is necessary that the pores have a size that does not cause the permeated flowable material to flow away, and further, properties that can adhere to the porous layer, for example, the surface has a porous layer. It is necessary that the surfaces have the same form, that the surfaces have elasticity and flexibility, and that the surfaces have physical properties such that the surfaces adhere to each other when pressed. Such a material may be the same as the light-scattering porous layer described above,
Further, a cloth, a nonwoven fabric, or a flocked body made of a natural fiber, a synthetic fiber, a metal fiber, or a glass fiber may be used. In addition, paper, porous rubber, resin or ceramic having pores formed by microfabrication or the like, organic or inorganic fine particles and sintered bodies thereof can be used, among others, flexible sponge,
Suitable examples include urethane foam, fiber mass, and woven or non-woven fabric having a thickness. Here, if the means for injecting the fluid material from the outside is made of a porous material having a weaker capillary force than the light-scattering porous layer, the porous material is brought into close contact with the porous layer, so that the porous material is made of ink. It acts like a blotter and allows the flowable material to be naturally incorporated into its voids. Furthermore, if this porous body is used, it is possible to absorb and retain excess fluid material leached on the surface of the porous layer. Can be.

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

[0029]

EXAMPLES The present invention will be specifically described below by way of 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 this reversible recording medium 10, a fluid material 14 is moistened in voids of a porous layer 12, and the back surface of the porous layer 12 has a transparent support 1
4 are laminated. The surface of the porous layer 12 is provided with a transparent protective layer 18 in which a large number of small holes are formed to maintain the opening of the void opened in the open space of the porous layer 12 in order to protect the layer.

The structure of the reversible recording medium 10 will be described in detail. Acetyl cellulose as a material for forming the porous layer 12 was dissolved in methyl isobutyl ketone (MIBK) to prepare a 15% by weight coating solution. This coating solution is applied to a 75 μm thick PET (polyethylene terephthalate) film support substrate 16 in a wet film thickness of about 500 μm.
m, and without providing a drying step, the coating film together with the supporting substrate was coated with a methyl alcohol / ethyl alcohol mixed solution (6 /
It was immersed in 1) for 5 minutes. After 5 minutes, the support substrate was pulled up from the mixed solution and dried, whereby a display recording medium in which the porous layer 12 having a dry film thickness of 50 μm was formed on the support substrate 16 was prepared.

The acetylcellulose porous layer (refractive index: 1.470) 12 has a fluid material
Vegetable oil [seed oil: refractive index 1.470 to 1.47]
2. Viscosity 25 cps (25 ° C.)]), make it transparent, and then absorb excess fluid material 14 on the surface with a paper having good absorbency to expose the frosted surface. Was adjusted. At this time, it was estimated from the weight measurement before and after wiping the liquid on the surface that the average void filling rate of the porous layer was in the range of about 80 to 90%. Next, a 25 μm-thick PET having a transparent adhesive layer on one side as a surface protective layer on the surface of the porous layer 12.
(Polyethylene terephthalate) A reversible recording medium 10 was prepared by laminating a film 18 on the porous layer 12 whose inside was wet with the fluid material 14 with the adhesive layer inside.
At this time, the polyethylene film 18 is provided with two-dimensionally arranged fine air holes in advance so as not to impair the transparency, and the pressure inside the porous layer 12 is constantly reduced to the external pressure. Is to be equal.

Next, a method of displaying an image on the reversible recording medium 10 will be described. For the reverse recording medium 10 having the above-described configuration, a pressurized serial head 20 composed of a 6 × 8 dot matrix for one character as used in a dot matrix printer is used. Printing was performed in accordance with image information using a printing device (not shown) adjusted to about 1 kgf / cm ² . As a result, as shown in FIG. 2A, the flowable material 14 held in the voids of the porous body 12 at the portion where the pressure is applied by printing moves to the periphery thereof. Voids (unfilled voids not wet by the flowable material) 1
2A was generated, the light scattering state was established, 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. FIG.
(B) shows a reversible recording medium 10 on which an image is displayed.
FIG. Thus, even when printing is completed and no pressure is applied, the flowable material 14
It was confirmed that the image in the light scattering state caused by the deviation was retained.

As shown in FIG. 3, a pen 22 in the form of a writing implement having a rounded tip is applied to the medium on which this image is recorded.
When handwriting was performed by using, the handwritten portion was in a light scattering state like an image printed by the pressurized serial head 20, following an arbitrary writing pressure and writing speed, and the trajectory of writing was changed. , As a reflection image with good contrast. FIG. 3 shows this reversible recording medium 10.
FIG. 7 is a model diagram showing a state in which an image is written by hand using a writing implement pen 22.

The reversible recording medium 10 on which an image has been formed in this manner is inserted into the transmission image projecting device 24 as shown in FIG.
As a result, a light-scattered portion generated by pressurization became a black portion, and a transmission image with good contrast was obtained. Thus, 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 entire 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 rises, the liquid moves so that the bias of the infiltration state in the porous layer becomes uniform, and all the images including the handwritten images are erased,
It quickly returned to its original transparent state.

It was confirmed that the image display by pressurizing and the image erasing by heating can be repeated many times. (Example 2) A black PET film supporting 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 a fluid material 14. A material obtained by mixing 5 parts of ethylene glycol [refractive index: 1.473, viscosity: about 35 cp (25
C)))] to form a reversible recording medium 30.
In Example 2, the porous surface was not provided with a protective layer or the like, but was left open so that the fluid material could be externally supplied and excess portions could be wiped off freely. The reversible recording medium 30 was incorporated in a frame to form a reversible blackboard 32 as shown in FIG.

When rewriting is performed by handwriting on the reversible blackboard 32 using the pen 22 having a rounded tip, a display record similar to that of a normal blackboard is obtained in which a white background appears on a black background. Could be done.

Further, as shown in FIG. 7, the flowable material 14 is moved from the outside of the surface of the porous layer 12 to the cloudy region where the liquid filling rate is low due to the movement of the flowable material 14 to the surroundings due to the pressurization.
4 was brought into contact with a cloth blackboard eraser-like tool 34 which was held and moistened.
4 and the excess liquid 14 was absorbed by the blackboard eraser-like tool 34, so that the image could be easily erased and returned to the initial state. As a result, a clean blackboard in which chalk or ink residue does not occur at the time of erasure as in a normal blackboard or whiteboard can be realized.

As is clear from the above-described embodiment, the reversible recording medium of the present invention is a reversible recording-displayable OHP sheet or a reversible recording display which allows a user to write a character even at a free writing speed and writing pressure. Can provide a reversible blackboard.

By employing the image erasing method as in the first embodiment, the liquid is prevented from seeping out from the surface, and the image written by pressure is spontaneously performed by utilizing the viscosity change of the liquid itself due to heating. This is suitable for batch erasure processing. On the other hand, by adopting the image erasing method as described in Embodiment 2, the image can be repeatedly written and erased without requiring any special device or energy for erasing. Becomes possible.

[0041]

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, according to the image erasing method of the present invention, there is 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 the drawings]

FIG. 1 is a schematic sectional view illustrating a reversible recording medium according to a first embodiment of the present invention.

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

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

FIG. 4 is a diagram in which the reversible recording medium of the first embodiment is used for an image projection device.

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

FIG. 6 is a perspective view illustrating the entire reversible blackboard incorporating the reversible recording medium of Example 2.

FIG. 7 is a schematic cross-sectional view illustrating an image erasing state of a reversible recording medium using a blackboard eraser-like tool holding a fluid material.

[Description of Signs] 10 Reversible recording medium 12 Porous layer 14 Fluid material 16 Support (PET film) 18 Surface protective layer 20 Pressurizing head 12A Porous layer not filled with fluidic material 22 Pressurizing pen 24 Permeation -Type image projection device 26 Heating device for image erasure 30 Reversible recording medium 32 Reversible blackboard 34 Means for supplying a fluid material from outside (blackboard eraser tool impregnated with fluid material)

Claims (4)

[Claims] 1. A fluid scattering material having a refractive index substantially equal to a refractive index of a material constituting the porous body is infiltrated into a light scattering porous body having a porous structure in which at least a hole is opened in an open space. Pressure is applied to the transparent porous body in which the fluid material is infiltrated, the fluid material in the pressurized portion is moved to a region other than the pressurized portion, and the portion is in a light scattering state. To display an image, filling the voids in the porous material caused by the movement of the flowable material by the pressurization again with the flowable material, and returning to a transparent state, thereby erasing the image. Characteristic reversible recording medium. 2. A material whose viscosity decreases by heating is used as the fluid material, and the voids in the porous material are filled with the fluid material again to return to a transparent state. 2. The reversible recording medium according to claim 1, wherein the gap is filled by utilizing an increase in the capillary force of the fluid material itself. 3. An image displayed on the reversible recording medium according to claim 1, wherein the image is heated by heating the reversible recording medium.
A reversible recording medium characterized by lowering the viscosity of a flowable material, utilizing the increase in the capillary force of the flowable material itself, filling the voids in the porous material with the flowable material again, and returning to a 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 material. A method for erasing an image on a reversible recording medium, comprising filling and returning to an original transparent state.