JPH1044592A - Reversible recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reversible recording medium capable of repeatedly displaying and erasing an image having the same contrast and quality feeling as a printing image due to printed matter and having high reliability and excellent preservability in rewritable marking technique. SOLUTION: A reversible recording medium 10 consists of a porous material 12 having a porous structure opened so that at least one surface faces to an open space and an ink material 16 containing one or more kind colorant reversible controlled in flowability and non-flowability within the pores 14 of the porous material 12 and, the contact angle at the contact surface of the ink material 16 and the porous material 12 at a time of the flowability of the ink material is 90 deg. or more and the ink material is made flowable to be moved to the visible region on the surface of the porous material 12 and made non- flowable to form an image and the ink material is again made flowable to be moved to the invisible region in the porous material 12 to erase the image. The ink material can be moved by the pressure from the outside or the application of energy such as an electric field.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible recording medium for reversibly displaying and erasing an image, and more particularly to a reversible recording medium which can be used for a simple reversible display recording apparatus. It can be applied to an electronic display device or a rewritable hard copy device.

[0002]

2. Description of the Related Art While an electronic display as an information display device has been widely used, demand for a paper hard copy has been strong due to readability of information, portability and low cost. However, the conventional hard copy technology using a paper medium applies a color material such as ink or toner on paper in accordance with document information, and is semi-permanent by melting / resolidifying by heat or penetrating / drying into paper fibers. It is assumed that the image is fixed on the image. Therefore, when the use of the document information is completed, the hard copy is almost completely discarded and most of the paper is used only once. In particular, paper documents discharged from offices contain a lot of confidential information.
The bulkiness has increased transportation costs, making it difficult to get on paper recycling routes.

In recent years, in order to minimize such wasteful disposal of paper, a technique has been proposed in which an electrophotographic apparatus peels off toner once fixed on paper and reuses the paper. Yes (Paper / Paper Technical Journal Vol. 47, No. 12, p. 74
-76). In addition, a technique has been proposed in which a toner fixed by an electrophotographic apparatus is also erased by light of a specific wavelength to make the color material colorless and to reuse the paper (Paper Technical Journal No. 48). Vol. 4, p62-65). But,
Basically, when ordinary paper is reused many times as described above, the number of times of use is limited, and in reality, it is a level that can withstand about 10 repetitions.

In view of the above, various types of reversible display recording media have been proposed in which a temporary image can be formed on a new paper medium instead of ordinary paper and can be erased when unnecessary. Among them, the thermosensitive reversible display recording medium has a relatively stable image after recording at room temperature, and a small and inexpensive printing system is realized by using recording device technology such as a thermal head. It has the merit that it can be done, and research on practical use is progressing. The heat-sensitive reversible recording medium is roughly classified into a medium utilizing a chemical change and a medium utilizing a physical change. A typical one of the former is a combination of a leuco dye and a color-reducing agent ( And the representative of the latter is a polymer / organic low molecular weight composite film (JP-A-55-15 / 1995).
4198, JP-A-58-7683, JP-A-63-221
087).

[0005] Reversible recording media of the type using leuco dyes are used to control the difference in the reaction rate of the color development / decoloration reaction and the phase separation due to crystallization of the leuco dye and the developer in the cooling process after melting. The method is intended to be controlled by a method, and the image formed by the black coloration of the colorless leuco dye is excellent in that it has a black-and-white contrast close to that of a normal paper hard copy. However, in the case of a type using a leuco dye, since the color development / decoloration depends on a chemical reaction caused by reversible electron donation / transfer between the leuco dye molecule and the developer / desensitizer molecule, image instability due to decolorization stimulus is caused. In addition, problems such as a decrease in the density of the printed portion due to the deterioration of the reactant and a print residue after erasure are caused.

The polymer / organic low molecular weight composite film utilizes the solidification timing of the polymer and the organic low molecule, which are reversed by the supercooling phenomenon of the organic low molecule depending on the heating temperature, and uses the solidification timing. By controlling the generation of voids around low molecules, a transparent state and a light scattering state are created to display and erase images. This method is excellent in terms of image stability and storability since display is performed by a physical mechanism without involving a chemical reaction. On the other hand, in the type using a polymer / organic low-molecular composite film, whiteness due to light scattering is originally expressed by using the refractive index mismatch in the composite film of a transparent substance.
There is a problem that black-and-white contrast unlike a normal paper hard copy is hardly produced.

In contrast to the above-described method of forming a visible image by applying energy such as heat, a method of performing reversible display of a visible image by entering and exiting a substance from / to a medium is known. A method in which a liquid is infiltrated into a light scatterer from the outside and volatilized to display a background color reversibly by refractive index matching (for example,
JP-A-61-202882, JP-B-4-48349, and the like. In a medium, a transparent liquid having the same refractive index as that of the porous material is infiltrated into the opaque or colored porous material by capillary force. In addition, there is known a technique of lowering the level of a wetting liquid by an electroosmosis phenomenon and reversibly changing the surface reflectance by refractive index matching to display an image.
Nos. 1-59491 and 63-36512). The light scattering control method based on liquid infiltration as described above enables relatively high black and white contrast display as compared with the light scattering control method based on the above-described energy application. However, in the light scattering control method based on liquid infiltration, the liquid to be infiltrated volatilizes not a little, so that the stability of the image is poor, and the durability and the storage stability are poor. Furthermore, the display technology that controls the liquid level wetted by electroosmosis is basically stable in a wet state, and a voltage must be continuously applied for display. Cannot be applied.

[0008]

As described above, the current reversible recording medium systems have the above-mentioned problems, and a new reversible display recording system which solves the disadvantages of these systems is eagerly desired.

That is, an object of the present invention is to provide a simple reversible display / recording apparatus which has the same texture, black-and-white contrast, image stability and storability as ordinary paper hard copy, and which can be used. To provide a dynamic recording medium.

[0010]

The reversible recording medium of the present invention has a porous body having a porous structure in which at least one surface is open so as to face an open space, and is present inside the pores of the porous body. An ink material containing one or more types of color materials whose fluidity and non-fluidity are reversibly controlled, and a contact angle at a contact surface between the ink material and the porous body when the ink material is fluidized. Is 90 degrees or more, and after the ink material is made fluid and moved to the visible region of the porous body surface,
In addition to displaying the image as non-fluid, the image is erased by moving the ink material again into the invisible area inside the porous body as fluid. .

This reversible recording medium forms an image using an ink material containing one or more kinds of coloring materials whose fluidity and non-fluidity are reversibly controlled. By making it non-fluid, the formed image is fixed, and the ink material concealed in the non-image portion does not move to the visible region, thereby realizing image stabilization. Further, since the contact angle at the contact surface between the ink material and the porous body when the ink material is fluidized is 90 degrees or more, the ink material never spontaneously penetrates into the porous body by capillary force, and It is possible to form an image with good contrast and high reliability without adhering or remaining on the wall surfaces of the pores inside the porous body.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The reversible recording medium of the present invention will be described in detail.

The reversible recording medium of the present invention has a porous body having a porous structure in which at least one surface is open to an open space, and reversibly controls the fluidity and non-fluidity existing inside the porous body. An ink material containing one or more kinds of color materials (hereinafter, simply referred to as ink as appropriate), and FIG. 1 schematically shows an example of the reversible recording medium. FIG. 1A shows a reversible recording medium 1.
0 is a schematic cross-sectional view, and FIG.
It is a perspective view showing the state where the image of 0 was displayed. A large number of holes 14 are formed in the porous body 12, and an ink material 16 is present therein. The ink material 16 has a characteristic of reversibly showing fluidity and non-fluidity. When the ink material 16 is moved from the holes 14 on the surface of the porous body 12 to the visible region, an image of the medium 10 is formed. Formed on the surface. At this time, a stable image is formed by making the ink material 16 non-fluid. As shown in FIG.
The hole 14 formed in the porous body 12 has a function of a pixel,
A desired image can be formed by controlling the position of the ink material 16 for each hole 14, that is, whether the ink material 16 exists in the visible region or is hidden in the invisible region.

It is necessary that the material constituting the porous body has a relation of a contact angle of 90 degrees or more on a contact surface with the ink material when fluidized.

The display of the image is performed by making the ink material flowable, moving a desired portion from the inside of the porous body to the visible region of the surface, and then rendering the image non-flowable. The erasing of the formed image is performed by making the ink material flowable again, moving to the invisible area inside the porous body, and concealing it.

The pores formed in the porous material used here are holes penetrating both surfaces of the porous material, so that the fluid ink material can easily move and conceal the fluid ink material. Although it is desirable in terms of ease of use, it does not necessarily have to penetrate, and it is sufficient if it is open on one surface of the porous body. However, at this time, at least the opening of the hole needs to communicate with the open space so as to be a visible region for displaying an image.

Further, as for the arrangement of the openings of the holes, it is more desirable that the openings are regularly arranged at positions corresponding to the minimum pixel density in order to control the resolution and coverage of the display image with high accuracy. However, it need not be regular.

In the structure of the pores inside the porous body, as shown in FIG. 1A, the pores 14 are linearly opened with respect to the surface of the porous body and open independently of the surrounding pores. Is more preferable in order to facilitate the movement of the fluid ink material inside the porous body 12 and to prevent the irregular fluid ink material 16 from spreading around, It does not need to penetrate vertically.

3 (A), 3 (B), 4 (A), 5
FIG. 6 and FIG. 7 are schematic cross-sectional views showing the shape of the hole 14 of the porous body 12 of the present invention.

FIGS. 3A and 3B show a through hole 14.
Is formed obliquely to the surface of the porous body 12. In such a case, since the hole 14 is not opened straight to the surface of the porous body 12, the incident light does not directly reach the coloring material, and the reflected light does not directly return to the eyes of the observer. Therefore, when the observer observes the image formed on the surface of the porous body 12 from the front, the observer does not see the color of the ink 16 hidden inside the porous body 12,
This has the advantage that the contrast between the image part and the non-image part becomes clearer.

FIG. 4A shows that the diameter of the hole 14 differs between the inside of the porous body 12 and the surface opening.
The hole diameter of the surface opening is made smaller than the internal hole diameter. An aspect in which the ink 16 is held in a flowable state including a coloring material inside the porous body 12 is shown.

A specific method for forming a porous body in such a shape is described below with reference to FIG. Prepare a plate with half the thickness of the thin metal plate to be manufactured, apply photoresist on the entire surface of the metal plate, overlay a pattern mask with a hole pattern baked after pre-baking, and perform UV exposure to selectively photoresist After immersion in a developer, development is performed, and baking is performed again. Further, this is immersed in an etching solution, and the metal is dissolved only in the portion of the hole from which the photoresist has been removed to form a pattern. Here, in the etching step, the etching time is set slightly shorter than the time when the hole completely penetrates to the surface on the opposite side according to the size of the hole of the pattern, and the etched hole 14 becomes a mortar shape, and The etching is completed only when it penetrates to the opposite side. In this way, after the plate 18 having two thin mortar-shaped holes etched in the same manner is subjected to a water-repellent treatment, the plates 18 are laminated and bonded so that the wide openings of the mortar are aligned with each other as shown in FIG. Formed.

As another method for forming a porous body in which the pore diameter of the surface opening of the porous body 12 is smaller than the internal pore diameter, as shown in FIG. Two types of plates 3 with holes
Alternatively, one porous plate 20 having a large hole diameter and two porous plates 21 having a small hole diameter may be prepared, and the porous plates 21 may be stacked so that the inside has a large hole diameter 20. Aqueous ink 16 is filled into the pores inside the porous body thus produced while applying pressure from the outside. In this way, even when the aqueous ink filled in the pores with the pore diameter inside the porous body larger than the opening is in a fluidized state such as in a liquid phase, the surface tension of the liquid itself causes the inside of the pores to be filled. The droplets have a diameter larger than the hole diameter of the opening, and do not spontaneously seep outside unless the droplets are pushed out or pulled by some external force.

FIG. 6 shows an example of a porous body in which the pore diameter at the surface opening of the porous body is smaller than the internal pore diameter, and the pore opening is one. In this case, a porous body can be obtained in the same manner as in FIG. 5, except that a plate having no holes is used on the plate on the side facing the visible region.

FIG. 8 shows a filter made of PTFE (ethylene tetrafluoride resin) having a pore diameter of 1 μm as an example of the porous body 24 having an irregular porous structure. Examples of such an irregular porous structure include, for example, a resin matrix in which an infinite number of cavities of irregular size and arrangement are three-dimensionally included in a porous body, or a fibrous material such as paper or nonwoven fabric. May be irregularly entangled with each other while embracing an air layer around the surface, or a structure in which fine particles are dispersed and bound on a porous body.

The pores inside the porous body are shown in FIG.
As shown in FIGS. 5 and 6, the ink material present inside the hole has a space in which a spherical droplet can be formed by its own surface tension, and the hole diameter of the opening of the hole is The porous structure that is provided narrower than the space and is open independently of the surrounding pores inside the porous body has a small size because the ink fluidized in the pores is dispersed in the surrounding pores. This is desirable because droplets having a size as large as possible can be easily formed due to the surface tension of the ink itself without forming droplets.
When an irregular porous body having a space three-dimensionally connected to the surrounding holes inside the porous body as shown in FIG. 8 is used, the opening on the surface of the porous body is placed inside the porous body. A method in which a layer that regulates the diameter of the formed ink droplet to be smaller than the diameter of the formed ink droplet may be overlapped on the surface can also be used.

Regarding the relationship between the porous material and the fluid ink material, the contact angle between the porous material surface and the internal surface of the porous material including at least the fluidized ink material is 90 degrees or more. Therefore, it does not penetrate spontaneously into the porous body by capillary force, there is no wetting on the pore wall surface, and
It is necessary that the solid-air interface inside the porous body is not lost. The ink material is desirably made of water as a medium, for example, one in which water-soluble dye molecules are dissolved in water or one in which colorant particles are dispersed in water, from the viewpoint of safety during use.

In this case, a water-repellent material such as PTFE (tetrafluoroethylene resin) is used as a material constituting the porous body, or a material having a hydrophobic group such as fluorocarbon on the surface of a hydrophilic material. A surfactant or the like may be adsorbed to give water repellency. However, the present invention is not necessarily limited to the use of these combinations, and the contact angle between the ink material and the porous body when exhibiting fluidity is 9%.
Other combinations may be used as long as the angle is 0 degrees or more.
For example, a combination of an ink material using a liquid having a hydrophobic group as a solvent and a porous body whose surface is subjected to an oil-repellent treatment with a perfluoro compound or the like may be used.

Next, the ink material will be described. The ink material used in the reversible recording medium of the present invention is an ink material containing one or more kinds of color materials whose fluidity and non-fluidity are reversibly controlled, and the fluidity and non-fluidity are controlled. Can be performed by applying heating, shearing force, or the like.

When heating is used for fluidization, the ink material containing one or more coloring materials exhibits a solid phase at normal temperature, and a substance which changes phase only upon heating and exhibits fluidity as a component. The reversible recording apparatus is characterized in that the reversible recording apparatus further includes a heating means for causing such a phase change.

As the material which changes its phase depending on the temperature,
More specifically, carnauba wax, beeswax, paraffin wax, natural waxes such as microcrystalline wax can be used as a base, or synthetic waxes such as zazole wax and low molecular weight polyethylene wax containing polymethylene as a component. May be based. Further, these waxes may be used independently as a single substance, or may be used by being mixed at an appropriate ratio.

As another form of the ink material, there is a substance which is non-fluid in a stationary state and which exhibits fluidity when a shear stress is applied.

As described above, there is no fluidity in a stationary state, and fluidity is generated by applying a shear stress.
It contains a so-called thixotropic substance or a plastic fluid substance as a component, and when such an ink material is used, and such a shearing force is applied to a substance having a thixotropic property or a plastic fluid substance. It is characterized by having means for adding.

As the substance which generates fluidity by applying the shear stress, a system in which colloid particles are dispersed in a liquid at a high concentration, a polymer gel material, or the like can be used. In any case, it is a gel state that shows high viscosity and does not flow when left standing, and when a mechanical force such as shearing force is applied to it, the structure that forms the gel is temporarily broken, It becomes a sol state showing properties. Further, the system in which the gel structure is temporarily destroyed as described above loses fluidity again by being left for a certain period of time, and returns to a gel state.

In a reversible recording apparatus using a reversible recording medium, it is necessary to provide a means for controlling the fluidity of a substance constituting such an ink material.

For example, as the heating means for a substance whose phase state changes due to heat, any means capable of uniformly heating a certain area can be used, and specifically, a metal, ceramic, mica plate or fluorine-based material can be used. A heater in which a heating resistor made of a nickel-chromium alloy, iron-chromium alloy foil, or the like is disposed inside or on a plate made of a heat-resistant resin such as a resin is used. In addition, these heaters have excellent thermal responsiveness, are capable of on-demand heating with low power consumption, and have elasticity and flexibility. Is preferable since the degree of adhesion becomes good.
Specifically, a film heater in which a heating resistor made of a nickel-chromium alloy, an iron-chromium alloy foil, or the like is sandwiched between insulating layers made of a silicon resin or a polyimide resin is used. Further, when using these film heaters, the film is wound around a roll having an elastic body such as synthetic rubber as a nucleus, and rotated in the same direction according to the movement of the porous body while being in contact with the porous body. Thereby, heat can be efficiently transmitted. In addition to the above-described means, when a one-dimensional printing heating device in which heat generating elements are integrated like a thermal head is diverted to heat a specific pixel region or one line of the porous body,
There is an effect that the region where the ink is fluidized can be finely controlled. Of course, it is also possible to use a heat roll or a two-dimensional heat generation sheet in contact with each other.

The heating means does not necessarily need to be in contact with the surface of the porous body, and may be in non-contact. Specifically, a ceramic heater that emits far-infrared rays is used. When the porous body is heated by these heaters in a non-contact manner, there is no resistance due to contact with the medium, so that there is an effect that there is no mechanical wear on the contact surface. Further, as other non-contact heating means, a blower for blowing air heated to a predetermined temperature to the porous body may be used. Further, a non-contact heating means such as a heat mode using a laser or high-frequency heating can also be used.

When a component which does not have fluidity in a stationary state and generates fluidity by applying a shearing stress is used as a component, a means for applying a shearing stress to a flowable viscosity includes a high-frequency voltage applied to the piezoelectric element. A method of applying a voltage to cause mechanical deformation and transmitting high-frequency vibration to the porous body by using this as a transmission source is suitable in terms of easy control of the power of the shearing force.

In the reversible recording medium of the present invention, the external force for moving the ink material is as follows:
Heat, light, magnetism, electric field, pressure, etc. can be used.

When a pressure, for example, a pressure difference of air is used as a force for moving the flowable ink material, the reversible recording medium has a sealed structure at least at the time of forming and erasing an image so that the pressure difference can be sensed. Don't be. Specifically, for example, the reversible recording is performed by a printing device having a nozzle having a size corresponding to the size of a pixel that can be suctioned or pressurized for each pixel and an erasing device that can pressurize or suction the entire image surface. Recording and erasing on a medium can be performed. Further, as another example of the printing means for providing such an air pressure difference, a method in which a sheet having fine holes in an image pattern is superimposed on the reversible recording medium and the entire image surface is sucked. Can be According to the method using this pressure, the ink material can be applied to any material as long as the ink material has a flowable physical property, and there is an advantage that the degree of freedom in selecting the ink material is high.

When a liquid that flows when an electric field is applied is used as the ink material that can flow, voltage application can be used as the forcing force. An electrode for applying a voltage may be provided on the reversible recording medium itself, on the printing device side, or on both. In addition, a method of applying an electric field using an electrostatic image created by electrophotography, ion flow control, or the like can also be used. The liquid that flows by applying an electric field,
Although those based on water are more desirable in terms of use environment and safety to the human body, those based on a liquid having a high boiling point and hardly volatilized can be used. As a phenomenon of flowing when an electric field is applied, for example, electroosmosis, electrostatic attraction, electro-wetting, and the like are known, and a known technique can be applied to the present invention. As described above, by using a liquid that flows when an electric field is applied as an ink material, not only printing by applying a voltage from an electrode, but also ink depending on a charged dielectric or a latent image on a photoreceptor is used. Can control the movement of the image, enabling writing of two-dimensional images, and sharing a part of the existing marking technologies such as electrophotography and ionography.
Can be used.

Further, when the ink material contains a substance which responds to a magnetic field as a component, application of a magnetic field can be used as a forcing force for moving the ink material in a flowing state. As such an ink material, a magnetic fluid or the like in which magnetite fine particles are dispersed so as to form a colloid using water as a base liquid is more desirable in terms of use environment and safety for a human body, but has a high boiling point and is hardly volatilized. A liquid based on a hydrophobic liquid (for example, perfluoropolyether) can be used.

[0043]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. (Example 1) A specific embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is a schematic cross-sectional view showing the configuration of a basic reversible recording medium according to a first embodiment of the present invention, and FIG. 1B is a perspective view showing the image formed state.

The reversible recording medium 10 shown here has holes 14 penetrating through both surfaces of the porous body 12, and the openings of the holes 14 communicate with the open spaces. Also, hole 1
The openings 4 are arranged regularly at positions corresponding to the minimum pixel density. The holes inside the porous body 12 are holes 14 linearly opened in a direction substantially perpendicular to the surface of the porous body, and are independent of the surrounding holes 14. These porous bodies 12 can be prepared by the same method as a metal mesh filter used for high-precision sieving of powder or the like. That is, a photoresist is applied to the entire surface of a thin metal plate such as aluminum, a pattern mask having a hole pattern baked after pre-baking is overlaid and exposed to UV, and the photoresist is selectively exposed to light and then immersed in a developing solution and developed. Later, baking is performed again.
Further, this is immersed in an etching solution, and the metal is dissolved only in the portion of the hole from which the photoresist has been removed to form a pattern. At this time, the diameter of the hole is 20 microns, and the pitch between adjacent holes is 60 microns. The non-perforated metal surface is frosted so as not to cause specular reflection to form a white background that can diffusely reflect light. Next, the porous body 12 in which the holes are patterned is subjected to a water-repellent treatment using a fluorine-added silicon-based water-repellent agent. The porous plate was dip-coated with a liquid obtained by appropriately diluting the water-repellent agent, and then suction-filtered immediately after lifting so that the holes were not clogged, so that the water-repellent agent was sufficiently distributed on the inner walls of the holes. In addition, 1
Heat treatment was performed at 00 ° C. for 1.5 hours.

The pores 1 of the porous body 12 produced as described above
The inside of 4 is filled with the ink material 16 which has been made fluid while applying pressure from the outside. In the first embodiment, the ink material 16 filled in the porous body 12 contains a black dye and a hot-melt wax as a base material, and is a solid (non-flowable) at room temperature, but becomes a solid when heated. Transforms into a liquid phase and becomes fluid. Here, the wax used as the base material is mainly composed of linear paraffin, and the melting point of the hot melt ink material 16 containing the same is about 80 ° C. The contact angle between the fluidized ink material and the water-repellent porous body 12 was 125 ° as measured by a contact angle meter.
Met. This ink is injected under pressure into the pores of the porous body in a liquid phase by heating, and solidifies again (non-fluidity) inside the pores.

FIG. 2 is a schematic diagram illustrating the configuration of the entire reversible display recording apparatus to which the reversible recording medium of the first embodiment is applied. First, the area of the hole 14 in which the ink to be fluidized is held in accordance with the image signal is heated from one surface by the heating device 26 to liquefy the solid ink 16 inside the hole 14 to make it flow, and at the same time to the opposite side. According to the pixel signal from the surface, a part of the fluidized ink 16 is exposed to the outside through the opening of the hole. The heating device 2 used at this time was
Reference numeral 6 denotes a plate-shaped heater in which a heating resistor made of an iron-chromium alloy foil is sandwiched between insulating layers made of a silicon resin and arranged on a ceramic plate. The movement of the fluidized ink was performed by reducing the air pressure in the space outside the opening of the hole 14 to an atmospheric pressure or less by a nozzle-shaped suction device 28 whose opening and closing are individually controlled by a valve for each pixel. At this time, a point to be noted is that the ink to be drawn out of the hole is drawn out from the ink body present in the hole 14 to the extent that the ink is not separated. in this way,
The ink whose volume had been partially lifted was rapidly cooled after being exposed to the outside, solidified again, and was able to maintain its state by the frictional force with the hole walls. Further, when a part or the whole of the porous body 12 is heated again by the heating device 18 to a temperature equal to or higher than the melting point of the hot melt wax ink 16 and fluidized, the surface tension of the ink itself causes
A part of the ink exposed to the outside of the hole is subjected to a force to return to a single droplet from the base of the ink remaining in the hole, and the portion of the ink exposed to the outside of the hole is changed to the hole. 14 was drawn into the invisible area inside, and the image was erased. The contact angle between the porous body 12 and the ink material 16 is 125
°, and since the wall surface of the porous body 12 is not wet by the ink material 16, the ink material 16 is
The image is completely erased without remaining on the wall surface of the hole 14 of the porous body 12 near the two surfaces or the visible portion. Further, by controlling the heating and the pressure, it was possible to repeatedly display and erase a desired image. (Embodiment 2) FIG. 8 is a schematic diagram showing a state in which an image is formed on a reversible recording medium by the reversible display recording apparatus of Embodiment 2.

As a moving force of the fluidized ink material 16, a method is used in which the photosensitive member 9 whose surface is charged imagewise is brought close to the porous body, and the fluidized ink is electrostatically sucked from the inside of the porous body. Indicated. The porous body used was the same as in FIG.
The type in which the inner hole diameter shown in (A) has a larger space than the opening on the surface is used. This porous body is shown in FIG.
As shown in (B), two plates 18 etched in a mortar shape are bonded together. The porous body 12 has been subjected to a water-repellent treatment. As the ink material 16, a hydrophilic ink which is in a solid state at room temperature and is based on hot melt wax containing a black dye was used as in the case of Example 1.

The process of recording and erasing an image in this embodiment will be described below. First, the photoconductor 30 is charged by the charging device 32, and a positive charge is held on the photoconductor surface. Exposure is performed thereon by a laser beam 36 in accordance with image information to form a charge distribution on the photoconductor, and the reversible display recording medium is conveyed so as to approach the photoconductor 30. The heating device 26 similar to that used in the first embodiment is brought into contact with the position just on the back surface of the porous body 12 closest to the photosensitive member 30, and
The ink 16 solidified and held inside 4 is melted and brought into a fluid state. At the same time, a part of the ink 16 is electrostatically attracted to the outside of the hole 14 according to the charge distribution on the photoconductor 30. As described above, the ink 16 whose volume has been partially lifted is rapidly cooled after being exposed to the outside, solidifies again, and can maintain its state by the frictional force with the wall of the hole.

In order to erase this image again, only the heating device 26 is used to heat the hot melt wax ink 18 to a temperature higher than the melting point of the hot melt wax ink 18 to liquefy it, and the ink is exposed to the outside of the hole by the surface tension of the ink itself. A force is applied to a part of the ink to return to a single droplet from the ink matrix remaining inside the hole 14, and the part of the ink exposed outside the hole is drawn into the inside of the hole. .
As a result, the image was erased.

(Embodiment 3) FIG. 9 shows the configuration of a reversible recording medium of Embodiment 4. Example 4 shows an example in which a porous body 24 having an irregular porous structure is used. In the present embodiment, a membrane filter 24 made of PTFE (tetrafluoroethylene resin) is used as a porous body, and an ink holding layer 38 mainly containing nitrocellulose, which is a hydrophilic material, is provided inside the porous body 24. Is provided so as to sandwich it. Since PTFE, which is the base material of the porous body 24, has strong water repellency, hot melt wax having a contact angle with PTFE of 90 ° or more when liquefied as in Examples 1 and 2 is used as a component. Ink 16 is used. However, in the present embodiment, since the magnetic field formed by the magnet 40 is used as the moving force of the fluidized ink, the ink has a diameter of 1 in addition to the black dye as a coloring component of the ink.
It is made to be a magnetic fluid containing a high concentration of 00 angstrom magnetite.

Since the porous body 24 of the present embodiment does not have a segment for defining a pixel, the thermal head 42 capable of forming a pixel is used as a heating means for fluidizing the ink 16 from the back side of the display. Used in contact. The thermal head 42 melts the ink 16 that has been solidified and held in the hydrophilic ink holding layer 38 inside the irregular pores and makes the ink 16 flow. At the same time, a part of the ink 16, which is a magnetic fluid, is sucked out of the hole according to the magnetic force lines 44 of the magnet 40. As described above, the ink 16 whose volume has been partially lifted is rapidly cooled after being exposed to the outside, solidifies again, and can maintain its state by the frictional force with the wall of the hole.

In order to erase this image again, only the thermal head for heating 42 is used to heat the hot melt wax ink to a temperature higher than the melting point of the hot melt wax ink to liquefy the ink. Due to the capillary force to 38, a part of the ink 16 exposed to the outside of the hole 14 acts to return to the inside again, and the part of the exposed ink is drawn into the hole. As a result, the image was erased. Fourth Embodiment FIG. 10 shows a reversible recording medium according to a fourth embodiment in which a thixotropic gel ink 16 is used in place of an ink material having hot melt wax as a base material. This gel ink is water-based and has been actively used in recent years for ballpoint pens as writing instruments. In this example, the viscosity was adjusted by mixing an appropriate amount of glycerin with R-PGM for ballpoint pens (trade name) manufactured by SAKURA. The same porous body and printing apparatus as in Example 2 were used. In this embodiment, the fluidization of the ink is performed by applying a high-frequency voltage from a high-frequency power source 48 to the piezoelectric element 46 that is in contact with the back surface of the porous body 12 and applying ultrasonic vibration to the porous body. ing. The contact angle between the fluidized gel ink and the porous body 12 used here was about 120 ° as measured by a contact angle meter.

The process of recording and erasing an image in this embodiment will be described below. First, the photoconductor 30 is charged by the charging device 32, and a positive charge is held on the surface of the photoconductor 30. Exposure is performed thereon by the laser beam 36 in accordance with the image information, and a charge distribution is formed on the photoconductor 30, and the reversible display recording medium is conveyed so as to approach the photoconductor 30. The piezoelectric element 46 is brought into contact with the position of the back surface of the porous body 12 closest to the photoconductor 30 to apply ultrasonic vibration to the porous body. The bonding relationship between the particles inside the ink, which has been solidified and held inside the porosity 14, is temporarily weakened and brought into a fluid state. At the same time, a part of the ink 16 is sucked out of the hole according to the charge distribution on the photoconductor 30. In this manner, the ink 16 whose volume has been partially lifted moves away from the ultrasonic vibration source after being moved to the outside, and becomes a stationary state again. That state could be maintained by the frictional force with the wall.

To erase this image again, the piezoelectric element 4
By using only the ink 6, the ink 16 is fluidized again, and the surface tension of the ink 16 causes a part of the ink 16 exposed to the outside of the hole to return from the ink base remaining in the hole to 1 part again. The force to return to one droplet acts, and the portion of the ink exposed outside the hole is drawn into the inside of the hole 14. As a result, the image was erased.

[0055]

By using the reversible recording medium of the present invention, an image structure very close to that of a normal paper hard copy can be obtained, and the same texture and black-and-white contrast as those of a paper hard copy can be realized. This achieves the effect that the image can be repeatedly displayed and erased, while maintaining both the image quality and the storability of the image.

[Brief description of the drawings]

FIG. 1A is a schematic sectional view showing a basic configuration and an image forming state of a reversible recording medium of the present invention, and FIG. 1B is a perspective view.

FIG. 2 is a schematic diagram illustrating image formation on a reversible recording medium of the present invention.

FIGS. 3A and 3B are schematic sectional views showing modified examples of the pore shape of a porous body used for a reversible recording medium.

FIG. 4A is a schematic cross-sectional view of a porous body having pores in which the pore diameter of the surface opening is smaller than the internal pore diameter,
(B) is a schematic view showing a method for producing the porous body.

FIG. 5 is a schematic cross-sectional view showing another embodiment of a porous body having pores in which the diameter of the surface opening is smaller than that of the inside.

FIG. 6 is a schematic cross-sectional view showing another embodiment of a porous body having holes in which the hole diameter of the surface opening is smaller than the hole diameter of the inside, and having the opening only on the surface.

FIG. 7 is a schematic sectional view showing a porous body having irregular continuous holes.

FIG. 8 is a schematic view illustrating an image forming method for a reversible recording medium according to a second embodiment.

FIG. 9 is a schematic diagram illustrating an image forming method for a reversible recording medium according to a third embodiment.

FIG. 10 is a schematic diagram illustrating an image forming method for a reversible recording medium according to a fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Reversible recording medium 12 Porous body 14 hole 16 Ink material 18 Porous film with mortar-shaped hole 20 Porous film with large pore size 22 Porous film with small pore size 24 Porous film with irregular porous structure 26 Heating Device 28 Nozzle Suction Device 30 Photoreceptor 32 Charging Device 34 Charge Elimination Device 36 Exposure Laser Beam 38 Hydrophilic Ink Retaining Layer 40 Magnet 42 Heating Thermal Head 44 Magnetic Field Line 46 Ultrasonic Vibration Generation Piezoelectric Element 48 High Frequency Power Supply

Claims (7)

[Claims] 1. A porous body having a porous structure in which at least one surface faces an open space, and fluidity and non-fluidity existing inside pores of the porous body are reversibly controlled. An ink material containing at least one type of coloring material, wherein when the ink material is fluidized, the contact angle between the ink material and the porous body at the contact surface is 90 degrees or more; Then, after moving to the visible region of the surface of the porous body, the image is displayed as non-fluid, and the ink material is moved again to the invisible region inside the porous body as fluid. A reversible recording medium for erasing an image. 2. The shape of the pores forming the open porous structure of the porous body is such that the ink material moved to the invisible area inside the pores of the porous body forms spherical droplets due to its own surface tension. 2. The reversible recording medium according to claim 1, wherein the reversible recording medium has a pore size that can be adjusted, and the pore size of the opening of the pore on the surface of the porous body is smaller than the pore size inside the pore. 3. The ink material containing one or more types of coloring materials shows a non-fluidity at room temperature, and contains as a component a substance showing a fluidity by phase change only when heated, and the ink material Heating means for heating the ink material to its fluidization temperature, and an ink material for moving the fluid ink material between a visible region on the surface of the porous body and an invisible region inside the porous body. The reversible recording medium according to claim 1, further comprising: moving means. 4. An ink material containing one or more types of coloring materials, which exhibits a non-fluidity in a stationary state, contains a substance which exhibits a fluidity by applying a shearing stress, and is capable of flowing the ink material. Means for applying sufficient shearing force to allow the ink to flow, and a method for applying a fluid ink material between the visible region on the porous body surface and the invisible region inside the porous body. The reversible recording medium according to claim 1, further comprising: an ink material moving unit for moving. 5. The apparatus according to claim 3, wherein pressure is used as a moving means for moving the fluid ink material.
Or a reversible recording medium according to 4. 6. The reversible recording medium according to claim 3, wherein an electric field is applied as a moving unit for moving the fluid ink material. 7. The method according to claim 3, wherein the ink material includes a substance responsive to a magnetic field as a component, and an application of a magnetic field is used as moving means for moving the fluid ink material. Reversible recording medium.