JPH10193784A - Reversible recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reversible recording medium of a simple construction which can display a stable and high-grade image with a sharp contrast and also can erase the display image easily whenever such an erasure is desired. SOLUTION: This reversible recording medium is equipped with a light scattering porous layer 12A and a transparent material holding layer 14A consisting of a porous form colored in black, and the transparent material holding layer 14A has a transparent material 16A with a close refractive index to that of a material constituting the photoscattering porous layer penetrating through the layer 14A. When this transparent material 16A is packed into the internal space of the porous layer 12A, an image is displayed and this image is erased by causing it to move from the porous layer 12A to the transparent material holding layer 14A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a recording medium technology capable of reversibly recording and erasing an image. In particular, the present invention relates to a structure of a reversible recording medium having a high black-and-white contrast and a method of erasing and printing an image. The present invention is also an effective method as a display principle of an electronic display.

[0002]

2. Description of the Related Art Research is being actively conducted on rewritable marking technology that replaces paper for reasons such as the preservation of the global environment such as the protection of forest resources, and the improvement of the office environment such as space saving. In particular, research on rewritable marking technology using heat has been actively conducted, and a leuco dye / amphoteric color reducing agent system (Watanabe, Shimizu, Hino: JP-A-2-188293, Hino, Watanabe: Japan Hardcopy '90,
147 (1990), Uchiyama, Tanno: JP-A-5-9
2661, Tanno, Hasegawa, Yatsushige, Uchiyama, Sugiyama, Asabe, Inoue: Japan Hardcopy '94,
129 (1994)), leuco dye / color developer / polar organic compound system (Kito, Nakasuji, Kataoka, Inagaki, Shibashi: JP-A-60-264285), leuco dye / long-chain alkyl color reducer system (Kawamura, Others: JP-A-4-247895,
Tsutsui, Yamaguchi: Polymer Preprints,
Japan, 736, vol. 42, no. 7
(1993); Yokota, M .; Ik
eda, S.E. Hiraish: IS &T's
9th NIP Technologies, 413
(1993)), leuco dye / developer / reversible material system (Takayama, Fujioka, Miyamoto, Nishizawa, Sugiuchi, Naito: Japan H
ardcopy '95, 99 (1995)). The method using these leuco dyes is a chemical change type utilizing color change caused by opening and closing of the lactone ring, and it is difficult at present to achieve both high black-and-white contrast and image maintainability. On the other hand, there has been proposed a physical change type system in which image maintainability is relatively easy to obtain. Polymer / long-chain alkyl low molecular weight system (W.
Dabisch et al. : DP 2907352
(1980), Maruyama, Hotta, Kubo, Takiguchi:
−117888, Yoshihiko Hotta, Keiji Kubo: Proceedings of the 4th Non-impact Printing Technology Symposium, 57
(1987)), a polymer / liquid crystal system (Y. Takaha).
shi, N .; Tamaki, Y .; Komi
ya, Y. Hieda, K .; Koseki,
T. Yamaoka: J. Appl. Phys
s. 74, 4158 (1993)), polymer blends (Kazuhiko Maeda, Akira Kawada: JP-A-61-2588)
53), polymer liquid crystal system (T. Ueno, T. Na)
kamura, C.I. Tani: Japan D
display '86, 290 (1986), Akashi, Ninomiya: JP-A-7-234393, Ninomiya, Morikawa, Akashi: Japan Hardcopy '94, 125
(1994), Akashi, Inoue: Proceedings of the 2nd Polymer Material Forum, 99 (1993), J. Amer. W
atanabe, M .; Goto, T .; Naga
se: Macromolecules, 20, 2
98 (1987)) and crystalline polymer systems (Steel Seikagaku, Nikkei Sangyo Shimbun 1967.8.6).

[0003] The polymer / long-chain alkyl low molecular weight system is a system in which the internal voids are changed by heating temperature to control the light scattering property. The polymer / liquid crystal system and the polymer blend system change the microphase separation state by the cooling rate. It is a method of controlling the light scattering by changing it. The liquid crystal polymer system and the crystalline polymer system are systems in which the crystallinity is changed mainly by a cooling rate to control light scattering. However, these methods of controlling the light scattering property easily maintain the image, but the image density is low and the application range of the product is limited.

[0004] In contrast to the above-described method of forming a visible image by applying energy such as heat, there is known a method of performing reversible display of a visible image by moving a substance into and out of a medium. For example, a method in which a liquid is penetrated and volatilized into a porous light scatterer to reversibly display the background color by refractive index matching (product “Mizuki Calligraphy” (Shiken), product “Mizuki Writing Practice Book” (P
ILOT), Allens, Robert B.
48349, Allens, Robert Bee: 3-3
1211, Allens, Robert B: 4-7
2709). The principle of this method will be described. Since the porous layer constituting the medium has a large number of voids therein, strong light scattering usually occurs and the medium is clouded. When a liquid having a refractive index substantially the same as the refractive index of the substance constituting the porous body is impregnated into the porous body having the voids, the part becomes an optically homogeneous structure in which the solid-air interface has disappeared. And the transmittance increases. In other words, a partially transparent area (optically homogeneous structure area) is generated in the cloudy area (light scattering area having voids), and information can be displayed and recorded by the contrast. Using a light scattering control method by liquid permeation into the porous body, when performing display with a black background, compared to the light scattering control method, the addition of a substance that fills the porous body voids, High black and white contrast display is possible by the removal.

[0005] However, these known systems are chosen so that the permeating liquid evaporates in a normal environment,
You can delete the display image when you want to delete it, and if you want to keep the display image, you can display it for the desired period,
The basic function of the reversible recording medium is not satisfied. Conversely, if a liquid that hardly volatilizes or does not volatilize penetrates into such a medium, display can be maintained, but repeated use becomes difficult. That is, in order to remove the infiltrated liquid, it is possible to take a method such as suctioning, flowing with running water, or washing with a solvent, etc. There is a problem that it takes time to remove. Even if the permeated liquid can be easily removed, it is not easy to reuse the permeated liquid. Further, in this method, although the image quality is excellent, since the liquid to be penetrated is added from outside the recording medium, the liquid to be penetrated needs to be managed, and both a printing device and an erasing device are required.

As described above, erasing is not easy if it is designed to have a beautiful image quality with high black-and-white contrast and sufficient maintainability as in the case of the ordinary recording technique. There is a problem that it becomes difficult to maintain a beautiful image if the device becomes large-scale, and it is difficult to maintain the beautiful image with a design that can be easily erased, that is, it can be easily used repeatedly. At present, a reversible recording medium satisfying all the above conditions has not been proposed.

[0007]

However, the conventional reversible recording system has the above-mentioned problems, and a new reversible recording medium which solves these disadvantages has been desired.

[0008] That is, an object of the present invention is to provide a reversible recording medium which can display a stable, high-contrast, high-quality image, can easily erase a displayed image at a desired time, and has a simple structure. It is in.

[0009]

According to the present invention, there is provided a reversible recording medium comprising a thin or thin light-scattering porous layer, a transparent material, and a transparent material. A thin or thin film-shaped colored transparent substance holding layer capable of making the light scattering porous layer substantially transparent by permeating the transparent substance into the light scattering porous layer. A reversible recording medium having the reversible recording medium, wherein the transparent substance moves between the light-scattering porous layer and the transparent substance holding layer to reversibly display or erase an image. .

The reversible recording medium according to claim 2 is
A light-scattering porous layer in the form of a thin plate or a thin film, a transparent material, a thin or thin film-like substantially transparent transparent material holding layer capable of holding the transparent material, and a thin plate or the thin-film colored layer. A reversible recording medium having physical properties capable of making the light-scattering porous layer substantially transparent by permeating the light-scattering porous layer with the transparent material, wherein the transparent material has the light-scattering property. The image is reversibly displayed or erased by moving between the porous layer and the substantially transparent transparent material holding layer.

According to a third aspect of the present invention, there is provided a reversible recording medium comprising a thin plate or a thin film light-scattering porous layer, a thin plate or a thin film colored porous colored layer, a transparent material, and a transparent material. A transparent material holding layer in the form of a thin plate or a thin film capable of holding the transparent material, the transparent material penetrating into the light-scattering porous layer to have a property of making the light-scattering porous layer substantially transparent. A reversible recording medium characterized in that an image is reversibly displayed or erased by moving the transparent substance between the light-scattering porous layer and the transparent substance holding layer.

In the reversible recording medium of the present invention, when the transparent substance moves and penetrates imagewise from the transparent substance holding layer to the light-scattering porous layer, the refractive index of the porous layer and that of the transparent substance are close to each other. The material layer becomes substantially transparent, and an image is formed at a difference from a place where white light is not scattered and light is scattered. At this time, an image having a high contrast can be obtained due to the difference between the colored layer disposed below the porous layer and the light scattering white portion.

The transparent substance used here is preferably solid at room temperature from the viewpoint of image maintenance. Further, it is preferable that the movement of the transparent substance is performed by applying an electric field when the transparent substance is in a liquid state.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The reversible recording medium of the present invention (hereinafter, appropriately referred to as a medium) comprises at least a thin or thin light-scattering porous layer and a transparent material holding layer laminated and arranged. Moves between the two layers. Both layers may not necessarily be directly laminated, and may be laminated via another layer as long as the movement of the transparent substance between the layers is not hindered.

When the transparent substance moves and penetrates imagewise from the transparent substance holding layer to the light scattering porous layer, the porous layer becomes almost transparent and penetrates when the refractive index of the porous layer and the transparent substance are close to each other. An image is formed at a difference from a place where light is not scattered in white. When the transparent substance holding layer is non-colored like a light-scattering porous layer and is a substance that looks white in a light-scattering state,
Even if the transparent substance moves to the light-scattering porous layer, the transparent substance holding layer in the moved area becomes white in the light-scattering state, and the contrast cannot be obtained. Therefore, when the transparent material holding layer is colored, or when the transparent material holding layer is transparent or substantially transparent, it is necessary to have another colored layer. As long as the transparent material holding layer has a layer colored with a coloring material, the transparent material holding layer can always display the colored color regardless of the presence or absence of the transparent material. On the other hand, the light-scattering porous layer becomes transparent when the transparent substance has penetrated, and becomes white when the transparent substance has not penetrated. If these layers are stacked, good contrast can be obtained.

It should be noted that if the light-scattering porous layer and the transparent substance holding layer can have sufficient strength to support themselves in the laminated state, they can be used as they are. In order to improve the ease of handling, these layers may be formed on any supporting substrate whose thickness and waist are easily controlled.

Further, a transparent protective layer for preventing direct contact with the light-scattering porous layer may be provided. It is not preferable to adopt a closed structure in which the reversible recording medium obstructs the ingress and egress of the atmosphere, because it obstructs the flow of the transparent substance. Therefore, it is desirable that the support substrate and the protective layer also have a structure in which the support substrate and the protective layer are laminated with a gap or a gap.

First, the light-scattering porous layer which is a main component of the present invention will be described in more detail. As the material for forming the light-scattering porous layer according to the present invention, those having good light-transmitting properties are preferably used. When a light-scattering porous layer is made of a material having poor light-transmitting properties, the transparency of the transparent material penetrating into the light-scattering porous layer is reduced, and the contrast between the density of the transparent part and the background of the cloudy part is reduced. Worsens. The light-scattering porous layer of the present invention may be formed by any method using a material satisfying the above-mentioned required characteristics. As a method of forming a light-scattering porous layer using an organic resin, for example, there are a phase change method, a stretching method, a filler filling method, and the like. Describing each method, the phase inversion method is a method in which an organic resin is dissolved in a solvent, cast and spread on a flat plate to form a film. A part of the solvent is evaporated, immersed in a bath and solidified to form a light-scattering porous layer. 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 light-scattering porous layer. In the stretching method, a crystalline organic resin is formed into a film, and then heat is applied or a plasticizer is added to make the film plasticized.
This is a method of forming a light-scattering porous layer by stretching the film in a biaxial or biaxial manner and imparting strain to the film to form holes.

As specific materials satisfying the characteristics required for the porous layer, organic resins formed by a phase inversion method or a filler filling method include, for example, cellulose, nitrocellulose, acetylcellulose, polyamide , Polymethyl methacrylate, polycarbonate, polyvinyl alcohol, polyurethane and the like. Examples of the organic resin formed by the stretching method include polypropylene and polyethylene.

Further, in order to increase the strength of the light-scattering porous layer, an organic resin and a filler may be combined to form a light-scattering porous layer. 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 light-scattering porous layer. If the filler is larger than 5 μm, the turbidity of the light-scattering porous layer will be reduced. When the light-scattering porous layer is formed by combining the organic resin of the light-scattering porous layer and the filler, the light-scattering porous layer can be formed by a phase inversion method. The mixing ratio of the filler to the organic resin is preferably 5% to 70% by weight. If the filler content is less than 5% or greater than 70%, the effect of increasing the strength of the light-scattering porous layer is reduced.

In the present invention, the thin or thin porous layer includes a thin plate having a flexibility of several tens of μm to a thin film of a submicron order. The thickness of the porous layer is preferably 50 μm or less. It is more preferably in the range of 5 μm to 50 μm, and still more preferably 10 μm to 30 μm. If it is 5 μm or less, the porous layer which is a light scattering layer is too thin, so that the turbidity is reduced and the display quality is reduced. Also, 50μ
If the thickness is greater than m, the viewing angle dependence of the display will increase, and the display quality will deteriorate, making it difficult to display high quality images. When the thickness of the light-scattering porous layer is 5 μm to 50 μm, the volume of voids in the porous layer, that is, the porosity is 20 to 85%,
And the average pore diameter of the voids in the porous layer is 0.01 μm to 1 μm.
The thickness is preferably 0 μm from the viewpoint 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 85% or more, the turbidity increases, but the strength of the medium decreases, and it becomes difficult to handle the medium as a paper-like display recording medium.
The average pore diameter of the voids in the light-scattering porous layer is 0.1.
01 μm to 10 μm, more preferably 0.1 μm to 5 μm
The range of m 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.

Such a light-scattering porous layer formed on a supporting substrate together with a transparent substance holding layer or a colored layer as described above has better handleability for the strength and thickness of the medium. This is preferable for controlling the state. As a support substrate material, various organic resin films such as polyethylene, polyester, and polyethylene terephthalate, and paper are used. Needless to say, the structure may be such that the transparent substance holding layer or the colored layer also serves as the supporting substrate. The thickness of the supporting substrate is 20 μm to 150 μm.
Is preferred. If the thickness of the supporting substrate is less than 20 μm, the strength of the medium itself decreases, and the durability deteriorates. On the other hand, if the thickness is larger than 150 μm, the flexibility of the medium itself is impaired, and the handling property as a hard copy-like display recording medium is deteriorated. Even if the thickness and the pore diameter of the porous layer are within the above-mentioned 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 This is because the whiteness decreases.

The transparent material holding layer used in the reversible recording medium of the present invention may be of any material and structure as long as it can hold the transparent material penetrating the light-scattering porous layer. For example, it may be a gel, a porous body, a cloth or a non-woven fabric. Porous or cloth-like,
Alternatively, in the case of a non-woven fabric, the pores need to be large enough to prevent the permeated transparent substance from moving due to a weak external force. Even if the transparent substance swells in the transparent substance holding layer, the transparent substance holding layer can be used as a holding layer. Such a material may be the same as the light-scattering porous layer described above, and may be a cloth, a nonwoven fabric, or a flocking made of natural fiber, synthetic fiber, metal fiber, or glass fiber. You may. Further, paper, porous rubber, resin or ceramic, porous or organic fine particles or fine particles of organic or inorganic fine particles, and sintered bodies thereof, which are formed by fine processing or the like, can also be used.

In the reversible recording medium of the present invention, an image is displayed and erased by moving the transparent substance between the at least two layers. Here, a transparent substance that can make the light-scattering porous layer substantially transparent by penetrating the light-scattering porous layer has a refractive index substantially equal to the refractive index of the substance forming the porous layer. Must. The refractive index substantially equal to the refractive index of the material forming the porous layer refers to a combination of materials having a difference in refractive index between the porous material and the transparent material of 0.1 or less, preferably 0.05 or less. When the refractive index difference between the porous material and the transparent substance is larger than 0.1, light scattering increases at the interface between the porous material and the transparent substance, and the transparency decreases,
High contrast display becomes difficult.

As described above, when a transparent substance penetrates into the light-scattering porous layer, the light-scattering porous layer becomes transparent due to the refractive index matching between the porous layer and the transparent substance, and becomes porous. If there is a colored layer under the layer, the color of the colored layer is observed.
That is, an image is formed. Conversely, erasing is performed by moving from the light-scattering porous layer to the transparent substance holding layer.

FIG. 1 shows the relationship between the filling ratio of the transparent substance in the voids (holes) of the porous layer and the optical density of the black colored layer observed by the transparency. Here, an average pore diameter of 3.0 μm formed on black polyethylene terephthalate (PET) was used.
An example in which glycerin having a refractive index of 1.47 is permeated into a porous layer made of cellulose acetate having a refractive index of 1.47 adjusted to a thickness of 100 μm and a thickness of 100 μm is shown. It shows a similar tendency. In this example, when the filling rate exceeds 60%, the material rapidly becomes transparent (black), and
If it is 0% or less, it becomes almost white. That is, printing of an image is performed by moving the transparent substance from the transparent substance holding layer to the light scattering porous layer until the filling rate becomes 60% or more, and erasing is performed from the light scattering porous layer to the light scattering porous layer. This is achieved by transferring the transparent substance to the substance holding layer until the filling rate of the porous layer becomes 40% or less.

Further, the transparent substance is preferably solid at room temperature. Here, a transparent substance that is solid at room temperature refers to a substance having a melting point of 40 ° C. or higher. In particular, considering the magnitude of energy at the time of printing and the environmental dependence of image display, the preferable melting point range of these substances is 50 ° C to 120 ° C.
C, more preferably 60 ° C to 80 ° C. In terms of quick penetration into the light-scattering porous layer, and ease of movement to the transparent material holding layer because it is difficult to bind inside the light-scattering porous layer during cooling, Instead of a high-molecular resin having a high melt viscosity, a low-molecular-weight crystalline material having a relatively low melt viscosity is preferably used. Specific examples of these materials include natural waxes such as vegetable waxes such as microcrystalline wax, carnauba wax and rice wax, petroleum waxes such as candelilla wax and paraffin wax, and mineral waxes such as montan wax. ,
Synthetic hydrocarbons such as polyethylene wax, montan wax derivatives, paraffin wax derivatives, microcrystalline wax derivatives, modified waxes such as polyethylene wax derivatives, and hydrogenated waxes such as hydrogenated castor oil and hydrogenated jojoba oil. Waxes, other fatty acids such as stearic acid, palmitic acid, myristic acid, and behenic acid; fatty acid amides such as oleic acid amide and stearamide; fatty acid esters such as polyol esters and dibasic acid esters; fatty acid derivatives such as fatty acid ketones; and stearyl alcohol And aliphatic glycerols such as monoglycerol stebrate, vinyl ether, polymer complex ester, and urea. Further examples include glycol ethers such as polyethylene glycol, and aromatic amides such as benzamide and phenacetin. Further, the composition may be a composition obtained by mixing substances selected from these.

As described above, the preferable transparent substance to be filled is not a liquid at room temperature but a solid substance. Therefore, it is possible to cool and solidify the transparent substance in a state of being filled in the light-scattering porous layer. The image can have as good a maintainability as a normal hard copy.

The transfer of the transparent substance from the porous layer to the transparent substance receiving layer can be performed by applying an electric field while the transparent substance is in a liquid state. In this case, it is considered that the movement of the transparent substance between the light-scattering porous layer and the transparent substance holding layer mainly occurs by an electrokinetic phenomenon. Needless to say, the transparent material needs to be liquid at least during the movement. Using a force of an electric field, for example, by applying a mechanical pressure to move the transparent substance from the light-scattering porous layer to the transparent substance holding layer more reliably and efficiently. Can be.
One of the reasons is that, unlike mechanical pressure, the electric field is a remote force, so that a moving force acts on the entire transparent material. In addition, since the electric field can exert a force in a non-contact manner in principle, there is little possibility that the reversible recording medium is damaged or broken. Further, even if there is no protective layer or the like, the possibility of impurities being mixed into the transparent material can be minimized as long as driving can be performed in a non-contact manner. The electric field is (1) a reversible recording medium is sandwiched between electrodes, (2) an image is charged on the surface of the medium with an ion head, etc., and (3) a photoconductor on which an electrostatic latent image is formed in the electrophotographic process. (4)
It can be applied by a method such as contact with a dielectric on which an electrostatic latent image is formed in an ionographic process. (1) In the method using electrodes, the electrodes may be provided on the reversible recording medium itself. As a method, for example, a support substrate or a colored layer may also serve as one electrode.

As described above, the reversible recording medium of the present invention comprises at least a light-scattering porous layer and a transparent material holding layer, and the transparent material is held in these layers. I) having a structure of (a) a porous layer and (b) a laminate of a transparent substance holding layer, wherein a light-scattering porous layer, a substantially transparent transparent substance holding layer, and a colored layer Are laminated, that is, (II) (a) a porous layer;
Sufficient contrast can be obtained for the same reason as described above even if it has the structure of (b ′) a substantially transparent transparent substance holding layer and (c) a laminate of a colored layer. The arrangement of each layer of such a reversible recording medium is, for example, in order from the top (display surface side),-a light-scattering porous layer, a substantially transparent transparent substance holding layer, a colored layer, or- A substantially transparent transparent substance holding layer, a light-scattering porous layer, and a colored layer may be used in this order. The colored layer may be porous so as not to have a closed structure as described above.

The reversible recording medium of the present invention comprises a thin plate or thin film light-scattering porous layer, a thin plate or thin film colored porous coloring layer, and the light scattering porous layer. (III) including a transparent substance that makes the light-scattering porous layer substantially transparent by penetrating into a transparent substance, and a thin-plate or thin-film transparent substance retaining layer capable of retaining the transparent substance.
(A) a porous layer, and (c ′) a colored porous layer;
The same effect can be obtained even with a structure having the structure of (b) a laminate with a transparent substance holding layer.

As in the case of (III), if the coloring layer is porous, the transparent substance can pass through the coloring layer. In the case where the coloring layer does not hinder the movement of the transparent substance, the layers are arranged in order from the top (display surface side), for example, a light-scattering porous layer, a coloring layer, and a transparent substance holding layer. It can be a layer.

Hereinafter, another layer configuration will be described. As the above-mentioned substantially transparent transparent substance holding layer, a colored material capable of absorbing light or a light scattering structure having a fine pore structure cannot be used. The term “substantially transparent” as used herein means that a black colored layer having an optical density of 2.0 (by 404A manufactured by X-Rite) is placed under a substantially transparent transparent material holding layer, and the transparent material is not penetrated. Means that the optical density measured from the substantially transparent transparent material holding layer side is 0.7 or more. As with the light-scattering porous layer, a material with a high light-transmitting property is used, but the porosity and pore diameter are different from those of the light-scattering porous layer. Must be designed. When an amorphous porous structure is employed, the porosity is 5 to 30%, or 80 to 9%.
5%, the average pore diameter of the voids is 0.2 μm or less or 8
It is desirable that it is not less than μm. When a regular porous structure such as perforated metal, woven fabric, or stitch is adopted, even if the porosity is in the range of 20 to 85% or the average pore diameter is 0.01 μm to 10 μm. It can be made almost transparent. The thickness of the substantially transparent transparent substance holding layer is desired to be as thin as possible in order to maintain transparency.However, the voids of the light-scattering porous layer are formed by the filling rate of the transparent substance into the voids and the transparency. The thickness cannot be extremely thin because the transparent substance must be retained in an amount greater than that disclosed in the description of the relationship with the optical density of the observed image. Therefore, in consideration of the thickness and porosity of the light-scattering porous layer and the porosity of the substantially transparent transparent material holding layer, the thickness is usually designed to be 5 μm to 70 μm.

[0035]

【Example】

(Embodiment 1) A schematic sectional view of the reversible recording medium 10 of Embodiment 1 is shown in FIG. Thickness 60 μm, average pore diameter 1.0 μm,
80% porosity nitrocellulose microporous membrane filter (Microporous)
a light-scattering porous layer 12A composed of a membrane filter, and a black colored black layer having a thickness of 60 μm.
m, an average pore size of 1.0 μm, and a porosity of 80%, made of nitrocellulose, made of a microporous membrane filter (Microporous membrane filter).
er), the colored transparent substance holding layer 14A was adhered with low-concentration glue to obtain a reversible recording medium 10. If carefully adhered by glue, the light-scattering porous layer 12A and the porous colored transparent material holding layer 14A will not be in a disconnected state in which the flow of the transparent material is prevented by the adhesive layer.

The whole of the colored transparent substance holding layer 14A is covered with polyethylene glycol (HO (CH ₂ CH ₂ O)).
_n H _n-4) 16A and impregnated, further reversible recording medium 1
0 was sandwiched between ITO-evaporated transparent electrodes 18 and 19. While observing from the light scattering porous layer 12A side, the transparent electrode 18,
During the 19th, when a voltage of 250 V was applied so that the colored transparent material holding layer 14A side became negative, the whole became white. The optical density at this time was 0.15. When a voltage was applied with the polarity reversed, the polyethylene glycol (HO (CH ₂ CH ₂ O) _n H _n-4 ) 16A moved from the colored transparent substance holding layer 14 to the light scattering porous layer 12A, Turned black. The optical density at this time was 1.7. (Embodiment 2) FIG. 3 is a schematic sectional view of the reversible recording medium 18 of Embodiment 2. Fine straight holes were opened in irregular positions by a discharge breakdown method in a PET film (manufactured by Toray) having a thickness of 25 μm to form a substantially transparent transparent substance holding layer 20. The average pore size is 8.00 μm, and the pore density is about 5 × 10 ⁵ pores / cm ⁵ . This substantially transparent transparent substance holding layer 2 made of PET film
0 is almost transparent and slightly cloudy. Next, as a light-scattering porous layer forming material, nitrocellulose was dissolved in methyl isobutyl ketone (MIBK) to prepare an 8% by weight coating solution. This coating solution was applied to a support substrate / colored layer 22 made of black PET film (manufactured by Toray) having a thickness of 75 μm.
Then, the coating film was coated with the supporting substrate and the colored layer 22 in a hexane solution which is a poor solvent for nitrocellulose for 5 minutes without providing a drying step. 5
After a minute, the support substrate / colored layer 22 is pulled up from the hexane solution, and the substantially transparent transparent substance holding layer 20 made of a PET film is laid on the nitrocellulose coated side in an undried state.
Let dry. The reversible recording medium 18 thus obtained
Is, in order from the top, a substantially transparent transparent substance holding layer 20 made of a PET film, a light-scattering porous layer 12B made of nitrocellulose having a dry film thickness of 20 μm, and a support substrate / coloring layer 22 made of a black PET film. Structure.

On the substantially transparent transparent material holding layer 20 side of this reversible recording medium 18, oleic amide (Alflow E-10: manufactured by NOF CORPORATION, melting point 70 to
(78 ° C.) 16B was infiltrated while heating the entire support substrate / coloring layer 22 to 95 ° C. Further, the reversible recording medium 18 is coated with a plate-shaped stainless steel electrode 2 having a thickness of 0.6 mm.
4 and 25, and while heating to 95 ° C. with the heater 26, the substantially transparent transparent material holding layer 20 side is used as a negative electrode for 150 minutes.
A voltage of V was applied for 60 seconds, the electrodes 24 and 25 were removed, and the optical density was measured. When sandwiched between the electrodes 24 and 25 again, and a voltage of 150 V was applied for 60 seconds with the polarity reversed, the oleamide 16B was dispersed from the substantially transparent transparent substance holding layer 20 to the light scattering porous layer 12B.
And the light-scattering porous layer 12B became transparent. The optical density at this time was 1.4.

In the case where the transparent substance flows due to both the electric field and the thermal stimulus, a printing method in which one of the stimuli is applied uniformly to the entire reversible recording medium 18 and the other addressing is performed. Can be taken. For example, an image may be written by a needle electrode or the like by heating the whole, or a uniform electric field may be applied to the entire reversible recording medium 18 and printing may be performed by a thermal head. (Embodiment 3) FIG. 4 is a schematic sectional view of a reversible recording medium 28 of Embodiment 3. Acetylcellulose was used as a porous layer forming material and dissolved in cyclohexanone to prepare a 10% by weight coating solution for a porous layer. Apply this coating solution to PE
About 400 μm of a wet film thickness was applied on the T film, and the coating film together with the supporting substrate was immersed in a hexane solution for 5 minutes without providing a drying step. After 5 minutes, the supporting substrate was taken out of the hexane solution and dried, and the acetylcellulose porous layer was carefully peeled off from the PET film to obtain a 30 μm-thick light-scattering porous layer 12C. Similarly, using acetyl cellulose, 70 parts of acetyl cellulose was mixed with 30 parts of carbon black, dissolved in cyclohexanone, and pulverized by a paint shaker for 60 minutes to prepare a 13% by weight coating solution for a porous layer.
Apply this coating solution on a PET film with a wet film thickness of about 7
The coating film was applied with a thickness of 00 μm, and the coating film together with the supporting substrate was immersed in a hexane solution for 5 minutes without providing a drying step. After 5 minutes, the supporting substrate was taken out of the hexane solution, dried, and peeled off from the PET film to obtain a porous colored layer 30 having a thickness of 60 μm. Next, a polyacrylate film having a thickness of 40 μm was processed in the same manner as in Example 2 to obtain an average pore diameter of 10.0 μm and a pore density of about 5 × 10 ⁵ holes / cm ^2.
The porous substantially transparent transparent substance holding layer 20 was obtained. next,
Each layer of the formed light-scattering porous layer 12C, the substantially transparent transparent substance holding layer 20, and the porous colored layer 30 is laminated in this order, and the acrylic ultraviolet curable resin (DPCA120 manufactured by Nippon Kayaku Co., Ltd.) is used. After being immersed in a isopropyl alcohol solution by weight, pulled up and dried, and cured for 30 seconds with a UV curing device of 120 W / cm output, the reversible recording medium 2
8 was obtained.

When oleic acid amide 16B was permeated into the reversible recording medium 28 in the same manner as in Example 2, and an electric field was further applied, it was confirmed that the optical density changed according to the polarity of the electric field. The optical density was 1.6 for black and 0.14 for white. (Embodiment 4) FIG. 5 is a schematic sectional view of a reversible recording medium 32 of Embodiment 4. Fibrillated polyethylene fiber 3
0 parts and 70 parts of cellulosic synthetic fibers were mixed, dried under no pressure, heat-treated at 150 ° C., and thermally bonded to obtain a 100 μm-thick sheet-shaped transparent substance holding layer 34. Next, a polyethylene film 36 having a thickness of 20 μm was laminated as a protective layer on one surface of the transparent substance holding layer 34 by heating. The light-scattering porous layer 12C and the porous colored layer 30 formed in the same manner as in Example 3 were superimposed on the surface of the transparent substance holding layer 34 without the polyethylene film 36 in this order from the top. Bonding was performed in the same manner as in Example 3 to obtain a reversible recording medium 32.

Decanediol (mp = 7) as a transparent substance
(2 to 74 ° C) 16C was infiltrated by heating from the light-scattering porous layer 12C side. In the same manner as in Example 3, a voltage of 300 V was applied for 30 seconds so that the transparent material holding layer 34 side became negative while heating the whole, and the reversible recording medium 32 turned white. Further, the transparent electrode 38 of the glass substrate patterned imagewise by ITO is placed on the light-scattering porous layer 12C side by the stainless steel electrode 2.
5 was brought into contact with the transparent material holding layer 34 side, and 300 V was applied so that the light-scattering porous layer 12C side became a negative electrode, and an image appeared according to the ITO pattern. When the direction of the electric field was reversed again, the image was erased. The optical density of the image was 1.5 and the background density was 0.15. (Embodiment 5) Schematic sectional view 4 of the reversible recording medium of Embodiment 5.
0 is shown in FIG. Fine straight holes are opened in irregular positions by a discharge breakdown method in a 25 μm thick black PET film,
A colored layer / transparent substance holding layer 14B was obtained. The average pore size is 8.
The pore density is about 8 × 10 ⁵ pores / cm ² .
Next, as a light-scattering porous layer forming material, nitrocellulose was dissolved in methyl isobutyl ketone (MIBK) to prepare an 8% by weight coating solution. This coating solution is applied to a PET film 42 having a thickness of 25 μm in a wet film thickness of about 250 μm, and the coating film is immersed together with the PET film 42 into a hexane solution which is a poor solvent for nitrocellulose for 5 minutes without a drying step. did. Five minutes later, the PET film 42 was pulled up from the hexane solution, and the coloring layer / transparent substance holding layer 14B was placed on the nitrocellulose coated side in an undried state, and then dried. The reversible recording medium 40 thus obtained is composed of a PET film 42 and a light-scattering porous layer 1 made of nitrocellulose having a dry film thickness of 20 μm from the top.
2B and a structure in which a colored layer and a transparent material holding layer 14B are laminated.

From the side of the colored layer / transparent substance holding layer 14B, polyethylene glycol (HO (CH ₂ CH ₂ O))
After impregnated with _n H _n-4) 16A, reversible recording medium 40
Was sandwiched between stainless steel electrodes, and a voltage of 150 V was applied such that the colored layer / transparent substance holding layer 14B side became a negative electrode. All of the polyethylene glycol 16A moved to the colored layer / transparent substance holding layer 14B side and turned white.
Next, the reversible recording medium 40 was placed on the stainless steel electrode 25, and negative ions were irradiated imagewise onto the PET film 42 while applying an ion acceleration voltage 45 between the reversible recording medium 40 and the ion recording head 44. The ion recording head 44 used here is of a type that extracts ions generated by corona discharge with the aid of airflow. The distance between the ion outlet of the ion recording head 44 and the surface of the reversible recording medium 40 (the surface of the PET film 42) is 800 μm, and the ion acceleration voltage 45 is 1200V.
At this time, the charge density of the ions irradiated on the PET film 42 was about 10 ^-4 C / m ² . FIG.
Reference numeral 46 denotes an ion flow control electrode, and 47 denotes a corona wire. Due to the electric field between the irradiated ions and the electrode 25, the polyethylene glycol 16A moved imagewise from the colored layer / transparent substance holding layer 14B to the light scattering porous layer 12B, and a clear image could be obtained. . The image density was 1.
8. The background density was 0.3. As is clear from each of the above Examples, the reversible recording medium of the present invention has a light scattering porous layer in which a transparent substance having a refractive index almost equal to that of a porous layer is penetrated, so that it is equal to or more than a normal hard copy. Good black-and-white contrast is stably obtained. In such an image forming method, since a transparent liquid containing no coloring material is used for forming an image, the transparent substance is used as a light-scattering porous layer and a transparent substance holding layer when printing or erasing. Even when the recording medium is repeatedly moved, a highly reliable reversible recording medium with no adhesion or coloring of the coloring material and no disappearance can be provided. In addition, regarding the transparent substance and the material for forming the porous layer, it is sufficient to pay attention to the refractive index in principle, and the refractive index is in a normal range for an organic material, and the light scattering porous layer and the transparent substance Since no special characteristics are required for the material of the transparent substance holding layer, a wide range of materials can be selected, and safety and cost reduction are excellent.

When a reversible recording medium is composed of a light-scattering porous layer and a colored transparent substance holding layer as in Example 1, the responsiveness of image display and erasure is improved because the layer structure is simple. Since the light-scattering porous layer is directly laminated on the colored layer, a high-density image can be obtained.

If the reversible recording medium is composed of a light-scattering porous layer, a substantially transparent transparent substance holding layer and a colored layer as in Example 2, the functions of the respective layers are separated, and the The range of choices becomes wider.

When the light-scattering porous layer, the colored porous layer and the transparent material holding layer are formed as in Example 3, the light-scattering porous layer and the colored transparent material holding layer are used. As in the case of forming the reversible recording medium with the layers, a structure in which the light-scattering porous layer is directly laminated on the coloring layer can be adopted, so that a high-density image can be obtained. Further, since the functions of the respective layers are separated from each other, a wider range of materials can be selected.

If a solid material at room temperature, such as oleamide or decanediol, is used as the transparent material used for recording, the image will not disappear due to mechanical impact or the like, and the reliability can be improved. . Furthermore, even without having an overcoat layer on the surface of the reversible recording medium,
Since the transparent substance is solid, there is no stickiness or the like, and it can be handled with the same texture as a normal hard copy.

When the movement of a transparent substance is controlled by utilizing the electro-fluid phenomenon for recording or erasing an image on these reversible recording media, restrictions on the material selection are somewhat increased, but the ordinary reversible recording medium is not used. As compared to addressing by heat,
Since the flow direction of the transparent substance can be accurately controlled, a high-definition image can be obtained. In addition, since the non-contact control can be performed, the medium is not damaged. In addition, the use of electrostatic latent images in electrophotography and ionography processes and the effective use of existing recording technologies such as ion heads and multi-stylus heads minimize new investments. it can. Further, the present invention can be used as an electronic display by providing a medium with electrodes, and has a wide range of applications.

[0047]

The reversible recording medium of the present invention has the advantages that a stable, high-contrast, high-quality image can be displayed, the displayed image can be easily erased at a desired time, and the configuration is simple. Have.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a filling rate of a transparent substance in a porous layer and an optical density.

FIG. 2 is a schematic sectional view showing a reversible recording medium of Example 1.

FIG. 3 is a schematic cross-sectional view illustrating a reversible recording medium according to a second embodiment.

FIG. 4 is a schematic sectional view showing a reversible recording medium according to a third embodiment.

FIG. 5 is a schematic sectional view showing a reversible recording medium of Example 4.

FIG. 6 is a schematic sectional view showing a reversible recording medium according to a fifth embodiment.

[Explanation of symbols]

Reference Signs List 10 reversible recording medium 12A light-scattering porous layer (membrane filter) 14A colored transparent substance holding layer (black membrane filter) 16A transparent substance (polyethylene glycol) 18, 19 electrode 18 reversible recording medium 20 substantially transparent transparent substance Retaining layer 22 Supporting substrate / coloring layer 12B Light-scattering porous layer (nitrocellulose porous film) 16B Transparent substance (oleic acid amide) 24, 25 Stainless steel electrode 26 Heating means (heater) 28 Reversible recording medium 12C Light Scattering porous layer (acetylcellulose porous film) 30 Porous colored layer 32 Reversible recording medium 34 Transparent substance holding layer 16C Transparent substance (decanediol) 36 Polyethylene film 38 Transparent electrode 40 Reversible recording medium 42 PET film 44 ion recording head 45 ion recording Voltage 46 ion flow control electrodes 47 Corona wire

Claims (5)

[Claims] 1. A thin or thin light-scattering porous layer, a transparent substance, and a thin or thin colored transparent substance holding layer capable of holding the transparent substance. A reversible recording medium having properties capable of making the light-scattering porous layer substantially transparent by permeating a substance into the light-scattering porous layer, wherein the transparent substance is formed of the light-scattering porous layer. A reversible recording medium characterized by reversibly displaying or erasing an image by moving between the recording material and the transparent material holding layer. 2. A thin plate or thin film light-scattering porous layer, a transparent material, a thin plate or thin film substantially transparent transparent material holding layer capable of holding the transparent material, and a thin plate or thin film A reversible recording medium having physical properties capable of making the light-scattering porous layer substantially transparent by permeating the light-scattering porous layer with the transparent material, Reversibly displays or erases an image by moving between the light-scattering porous layer and the substantially transparent transparent substance holding layer. 3. A thin plate or thin film light-scattering porous layer, a thin plate or thin film colored porous colored layer, a transparent material, and a thin plate or thin film capable of holding the transparent material. A transparent material holding layer, wherein the transparent material penetrates the light-scattering porous layer, whereby the light-scattering porous layer has a property of being substantially transparent, the reversible recording medium, A reversible recording medium, wherein a transparent substance moves between the light-scattering porous layer and the transparent substance holding layer to reversibly display or erase an image. 4. The reversible recording medium according to claim 1, wherein said transparent substance is solid at room temperature. 5. The reversible recording medium according to claim 1, wherein the movement of the transparent substance is performed by applying an electric field when the transparent substance is in a liquid state.