JP2001242806A - Display medium and writing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display medium in which desired resolution can be obtained and which has a simple structure so that the production process can be simplified, and which has high visibility, small consumption of the electric power and excellent display stability. SOLUTION: In the display medium, a material or a group of materials which reversibly changes its optical characteristics by the effect of an electric field is held between a pair of substrates at least one of which has an electrode patterned into stripes, dots or similar forms. In this device, the width W' (mm) of the stripe or the length of one side line of the dot, the vertical distance d' (mm) between the substrates and the display dot density D' (dpi) satisfy the relation of formula (1): 17/D'<=W'+d'<=44/D'.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display medium comprising a substance or a group of substances whose optical characteristics are reversibly changed by the action of an electric field, in particular, a colored dispersion medium having a color different from that of the dispersion medium. A display medium capable of changing the distribution state of particles by applying an electric field to a dispersion liquid in which a plurality of migrating particles are dispersed, thereby changing the viewing state reversibly, and being at least close to the display medium at the time of writing And a detachable writing device.

[0002]

2. Description of the Related Art There is a growing expectation for a reflective display device from the viewpoint of reducing power consumption and reducing the burden on the eyes. As one of them, an electrophoretic display device as shown in FIG. 3 is known. Reference numerals 1 and 8 denote a transparent substrate made of glass or the like and a transparent electrode formed on one surface thereof in a required pattern. A pair of the transparent electrodes 8 disposed opposite to each other is dispersed in a colored dispersion medium. A dispersion liquid 4 in which a plurality of migrating particles having a color different from the color of the medium is dispersed is enclosed. The migrating particles are charged on the surface in the dispersion medium, and when a voltage opposite to the charge of the migrating particles is applied to one of the transparent electrodes 8, the migrating particles accumulate there and the color of the migrating particles is observed. When a voltage is applied in the same direction as the charge of the migrating particles, the migrating particles move to the opposite side, and the color of the dispersion medium is observed. Thus, display can be performed.

Here, in a structure in which the dispersion liquid 4 is simply sealed between the electrodes 8, display unevenness may occur due to the aggregation or adhesion of the migrating particles. By disposing the perforated spacers 7, the dispersion liquid 4 is divided discontinuously to stabilize the display operation.

However, in the case of such a structure, there has been a problem that it is difficult to uniformly enclose the dispersion liquid, or it is difficult to obtain reproducibility due to a change in the characteristics of the dispersion liquid during encapsulation. . Therefore, Japanese Patent No. 2551783 solves the above-mentioned problem by forming a large number of microcapsules enclosing a dispersion and disposing them between electrode plates.

However, in these conventional display devices, no detailed study has been made on the thickness of a layer related to display, and a desired display resolution may not be obtained in some cases. Further, in these conventional display devices, a drive circuit for applying a signal for displaying an image to each electrode is connected. Since such a display device can easily perform two-dimensional driving in the form of a matrix, high-speed and high-resolution writing can be performed particularly by employing active matrix driving. However, it is practically impossible to separate the display medium from the driving unit. Because it is impossible, the display medium becomes large,
In addition, it becomes expensive and is not suitable for applications such as carrying around easily like paper or viewing a plurality of sheets side by side.

[0006]

SUMMARY OF THE INVENTION The present invention solves such problems and (1) provides a display medium capable of obtaining a desired resolution (claim 1). To provide a display medium that is simple and can simplify the manufacturing process (Claim 2), (3) To provide a display medium that can obtain a desired resolution and can be removed from a writing device (Claim 2). 3), (4) To provide a display medium which can be detached from a writing device, has a simple structure, and can simplify a manufacturing process.
(5) To provide a display medium with high visibility, low power consumption and excellent display stability (claims 5 and 6).
To provide a writing device capable of removing a display medium from a writing device while maintaining a display state. (Claim 6) To provide a writing device capable of displaying an image in a shorter writing time than in (7). Item 7),
(8) It is an object of the present invention to provide a writing device capable of displaying an image in a shorter writing time. Further, the present invention provides (9) a display medium having good adhesion between microcapsules and between a microcapsule and a substrate, and (10) a display medium having good display uniformity and easy production. To provide, (1
1) Another object is to provide a writing device that can display a clear image even with an image accompanied by a halftone.

[0007]

A first feature of the present invention is as follows.
A display medium in which a substance or a group of substances whose optical characteristics are reversibly changed by the action of an electric field is sealed between a pair of substrates having electrodes patterned in at least one of a stripe shape or a dot shape and a similar shape. , The width of the stripe or 1 of the dot
The length of the side is W '(mm), and the vertical distance between the substrates is d'
(Mm) and the display dot density is D ′ (dpi = dots p
er inch), the display medium has a relationship represented by the following equation (1). 17 / D'≤W '+ d'≤44 / D' (1)

[0008] Substances or substance groups (display substances) whose optical properties are reversibly changed by the action of an electric field include polymer-dispersed liquid crystals, bistable cholesteric liquid crystals, and reversible coloring and decoloring by oxidation-reduction reactions. (Electrochromic element) composed of a film made of a material to be performed and an electrochromic element in contact with the film, and a plurality of electrophoretic particles having a color different from the color of the dispersion medium dispersed in a colored dispersion medium (electrophoresis) Element) and the like.

As a method of encapsulating these display materials between a pair of substrates having electrodes patterned in at least one of a stripe shape or a dot shape and a similar shape, a mesh-like or porous material is formed on one of the substrates. After inserting the display substance into the hole, the other substrate is superimposed, and a spacer material (for example, plastic beads) is scattered on one substrate, and the other substrate is superimposed. A method of injecting the display substance, enclosing the display substance in a number of microcapsules, arranging them on one substrate, and superimposing the other substrate can be adopted.

The width of a stripe of an electrode patterned on at least one substrate or the length of one side of a dot is W ′ (mm), and the vertical distance between the substrates is d ′.
(Mm) and the display dot density is D ′ (dpi), a desired resolution can be obtained by satisfying the relationship of 17 / D ′ ≦ W ′ + d ′ ≦ 44 / D ′. it can. Although this relationship itself does not depend on the value of d ', it is particularly effective when d' is not negligible compared to W ', specifically when W' / d'≤4. ).

A pair of substrates having electrodes patterned at least one of a substance or a group of substances (display substances) whose optical characteristics are reversibly changed by the action of the electric field is formed in a stripe shape or a dot shape and the like. As a method of sealing between them, it is desirable to enclose the display substance in a number of microcapsules and to arrange them between a pair of substrates. Each of the above-mentioned display substances has fluidity at room temperature, but can be handled as a powdery solid by microencapsulation, so that it can be used as a blade coat, a wire bar coat, a spray coat, a spin coat, a dip coat, and a screen. Since the alignment can be performed on the substrate by using a method such as printing or roll coating, the manufacturing process is simplified (claim 2).

A second feature of the present invention is that a substance or a group of substances whose optical characteristics are reversibly changed by the action of an electric field is provided between a substrate provided with a common electrode and an opposing surface at a predetermined distance. In the display medium sealed in the gap, the length of one side of the equipotential portion formed on the surface of the display medium by means (writing device) capable of applying a potential to an arbitrary portion of the surface of the display medium is determined. W (mm), and the vertical distance from the surface of the common electrode to the surface of the display medium is d.
(Mm) and the display or writing dot density is D
(Dpi = dots per inch), the following equation (2)
A display medium characterized by having the following relationship: 17 / D ≦ W + d ≦ 44 / D (2)

As the substance or substance group (display substance) whose optical characteristics are reversibly changed by the action of an electric field, the same substances as those having the first characteristic can be used. As a method for encapsulating these display substances in the gap between the substrate provided with the common electrode and the opposing surface separated by a certain distance, a mesh-like or porous material is provided on the substrate provided with the common electrode. A hole spacer is placed, and after inserting the display substance into the hole, an opposing substrate (for example, a plastic film) is superimposed. A spacer material (for example, plastic beads) is sprayed on a substrate provided with a common electrode, and an opposing substrate (for example, A plastic film), and then injecting the display substance, enclosing the display substance in a number of microcapsules and aligning them on a substrate provided with a common electrode. .

The length of one side of the equipotential portion formed on the surface of the display medium by means (writing device) capable of applying a potential to an arbitrary portion of the surface of the display medium is W (m
m), the vertical distance from the common electrode surface to the display medium surface is d (mm), and the display or write dot density is D (dpi), 17 / D ≦ W + d ≦ 44 / D
, A desired resolution can be obtained. Note that this relationship itself does not depend on the value of d, but is particularly effective when d is not negligible compared to W, specifically when W / d ≦ 4 (claim 3).

A substance or a group of substances (display substances) whose optical characteristics are reversibly changed by the action of the electric field is placed in the gap between the substrate provided with the common electrode and the opposing surface at a predetermined distance. As a method of encapsulation, it is desirable to enclose a display substance in a large number of microcapsules and fix them on a substrate provided with a common electrode. All of the above display substances have fluidity at room temperature, but can be handled as a powdery solid by microencapsulation,
Blade coat, wire bar coat, spray coat, spin coat, dip coat, screen printing,
Since the alignment can be performed on the substrate by using a method such as roll coating, the manufacturing process is simplified. Further, in the above configuration, since the microcapsules are fixed on the substrate provided with the common electrode, only one substrate is used, and the common electrode does not usually need to be patterned, so that the display medium is very inexpensive. Can be produced (claim 4).

Among the substances or substance groups whose optical characteristics are reversibly changed by the action of the electric field, the polymer dispersed liquid crystal and the bistable cholesteric liquid crystal display white by scattering, but the scattering ability is so high. However, there is a drawback that a sufficient white density cannot be obtained because of the absence of the above. The electrochromic element is superior to the liquid crystal in viewability of display, but has a drawback that a current flows at the time of writing and power consumption is increased because of utilizing an electrochemical reaction. In terms of visibility and power consumption, it is desirable to use a dispersion medium in which a plurality of electrophoretic particles having a color different from the color of the dispersion medium are dispersed in a colored dispersion medium (electrophoretic element). In this case, since the dispersion liquid is divided into minute regions by the microcapsule walls by microencapsulation, there is an additional advantage that aggregation and adhesion of the migrating particles hardly occur and a stable display can be performed ( Claim 5).

It is desirable that the plurality of microcapsules be fixed on the one substrate or a substrate provided with a common electrode so as to form one layer together with a binder material filling the gap. The binder material acts to increase the adhesion between the microcapsules and between the microcapsules and the common electrode.

It is preferable that an overcoat layer is provided on a large number of microcapsules and / or binder materials fixed on the one substrate or the substrate provided with the common electrode. The overcoat layer serves to smooth the surface and to protect the microcapsules when an external force is applied to the display medium.

A third feature of the present invention is that in a writing device capable of displaying visible information on the display medium, the display medium and the writing device are detachable so that they can be brought close at least at the time of writing. In addition, the writing device includes an electrode array having a mechanism capable of applying an electric field to the display medium in accordance with an image signal and relatively changing a planar positional relationship with the display medium. There is provided a writing device.

In such a writing device, the common electrode of the display medium is set to the ground potential, and the electrode array is brought into close contact with the surface opposite to the substrate, so that a potential corresponding to the image signal can be applied to a predetermined portion. And thereby an electric field can be applied to the dispersion in the display medium.
Since the electrode array can relatively change the planar positional relationship with the display medium, visible information can be displayed on the entire surface of the display medium. In addition, once this display medium is displayed, it can maintain the display state without the action of an electric field, so it can be easily carried around by removing it from the writing device,
By preparing a plurality of display media, a plurality of images can be easily viewed side by side.

According to a fourth feature of the present invention, in a writing device capable of displaying visually recognizable information on the display medium, the display medium and the writing device are detachable so that they can be brought close at least at the time of writing. In addition, the writing device includes an ion gun array having a mechanism capable of imparting electric charge to the surface of the display medium in accordance with an image signal and relatively changing a planar positional relationship with the display medium. And a writing device.

In this writing apparatus, the electrode array of the writing apparatus according to the third aspect is changed to an ion gun array. In such a writing device, by setting the common electrode of the display medium to the ground potential and bringing the ion gun array close to the surface on the side opposite to the substrate, it is possible to apply a charge corresponding to the image signal to a predetermined portion, This allows an electric field to act on the dispersion in the display medium.
Since the ion gun array can relatively change the planar positional relationship with the display medium, visible information can be displayed on the entire surface of the display medium. Since the charge given to the surface of the display medium by the ion gun is discharged by the time constant of the material constituting the display medium, if the charge is longer than the moving time (response time) of the particles, the action time of the ion gun is reduced to the response time. It can be shorter and therefore the writing speed can be faster. Similarly to the display device of the third aspect, the display medium is easily removed from the writing device and easily carried around, or a plurality of images are prepared, so that a plurality of images can be easily viewed side by side.

According to a fifth feature of the present invention, in a writing device capable of displaying visually recognizable information on the display medium, the display medium and the writing device are detachable so that they can be brought close to each other at least during writing. The writing device further includes a plurality of signal electrodes and scanning electrodes, and a switching element that can apply an electric field to a display medium in accordance with an image signal at an intersection thereof,
The writing device is configured to display an image on the display medium.

According to the above arrangement, since the two-dimensionally arranged electric field applying means has the switching elements, the electric charge given to a certain portion at the time of selection by the action thereof is the time constant of the material constituting the display medium at the time of non-selection. Due to the discharge, if it is longer than the particle transit time (response time), the selection time can be shorter than the response time, and therefore the writing speed can be faster. Further, similarly to the display device having the third and fourth features, it is possible to easily carry a plurality of images side by side by removing the display medium from the writing device and carrying it easily, or preparing a plurality of the display media. 8).

As the switching element, it is desirable to use a thin film device which can be easily manufactured in a large area, particularly a thin film transistor. The thin film transistor applies a scan pulse from a scan electrode connected to the gate, and in synchronization with this, a pulse modulated by an image signal from a signal electrode connected to the source is applied to the display medium from an individual electrode connected to the drain. You. Since the thin film transistor is a three-terminal element, the thin film transistor has high switching performance and can provide a clear display even in a case where a halftone is involved. In order to further increase the writing speed, a storage capacitor may be provided in an equivalent circuit in parallel with the display medium.

[0026]

Next, a first embodiment (corresponding to claims 1, 2 and 5) of the present invention will be described below with reference to FIG. FIG. 8 shows an example of the display medium of the present invention.
1 is a substrate made of glass, plastic, etc., and has a thickness of 1
The thickness is preferably about 0 μm to 1 mm, and more preferably about 25 to 500 μm to have sufficient mechanical strength and light weight. When used on the viewing side, a transparent material is selected, but when used on the non-viewing side, it may be colored. This color (reflection color) may be used as a part of the display color, or the reflectance may be reduced. By increasing the contrast, the contrast ratio can be improved.

9 is a metal, ITO, SnO ₂ , ZnO: A
electrode made of a conductive thin film such as
It is formed by a vacuum deposition method, a CVD method, a coating method, or the like. Substrate 1
When ITO is used on the viewing side, ITO, Sn
A transparent material such as O ₂ , ZnO: Al or the like is selected, but if it is used on the side that is not visible, it may be colored. By increasing the contrast ratio, the contrast ratio can be improved. At least one of the electrodes 9 is patterned in a stripe shape or a dot shape and a similar shape.

Reference numeral 3 denotes a microcapsule, which contains a dispersion 4. 5 is a binder material, polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, polycarbonate, polyarylate, polysulfone, polyimide, polyamide, polystyrene,
Polyester, polyurethane, polyacrylate, polymethacrylate, acrylic copolymer, maleic copolymer, fluororesin, epoxy resin, alkyd resin, silicone resin, phenol resin, urea resin, melamine resin, polyvinyl alcohol,
It is made of a film-forming material such as polyethylene oxide, polypropylene oxide, methylcellulose, ethylcellulose, and gelatin. In order for an electric field applied from the outside to effectively act on the microcapsule portion, it is desirable to use a binder material having a dielectric constant equal to or higher than that of the dispersion. In order to adjust the dielectric constant, a compound such as an alcohol, a ketone, or a carboxylate may be mixed in the binder material in addition to the main resin. Further, by mixing colored particles or ions, the color (reflection color) can be used as a part of the display color, and the contrast ratio can be improved by increasing the reflectance.

The dispersion liquid 4 contains aromatic hydrocarbons such as benzene, toluene, xylene and naphthenic hydrocarbons, aliphatic hydrocarbons such as hexane, cyclohexane, kerosene and paraffinic hydrocarbons, trichloroethylene, tetrachloroethylene and trichlorofluoroethylene. Oil-soluble dyes such as anthraquinones and azo compounds or carbon black in an organic solvent having high resistivity such as halogenated carbon (hydrogen) s such as ethyl bromide, fluorine-containing ether compounds and fluorine-containing ester compounds; Colored fine particles such as iron oxide and organic pigments are used in an amount of 0.01 to 20 wt. % Of an electrophoretic particle made of an inorganic pigment such as titanium dioxide, zinc oxide or zinc sulfide, or an organic pigment such as diarylide yellow or phthalocyanine blue.

The electrophoretic particles have the same specific gravity as the dispersion medium.
Alternatively, the surface may be coated with another substance or complexed with another substance in order to prevent aggregation and enhance dispersibility. The particle size is preferably about 0.01 to 10 μm.

As the wall material of the microcapsule 3, urea-formaldehyde resin, melamine-formaldehyde resin, urethane resin, gelatin-gum arabic and the like can be used. Microcapsules are manufactured by interfacial polymerization, In-Sit
It is formed by a u polymerization method, a coacervation method, or the like. It is possible to produce a capsule diameter of 1 to 1000 μm, but it has been experimentally found that the capsule diameter needs to be 5 μm or more in order to obtain a sufficient display contrast. It has been experimentally found that the upper limit is preferably 200 μm or less from the viewpoint of the strength of the capsule. Furthermore, in order to obtain a desired resolution, the width of the stripe of the electrode 9 or the length of one side of the dot is W ′ (mm), and the vertical distance between the substrates is d ′ (m).
m), and when the display dot density is D ′ (dpi), 17 / D ′ ≦ W ′ + d ′ ≦ 44 / D ′.
Needless to say, the capsule diameter must be d 'or less.

The microcapsules formed by the above-described method are generally in the form of a slurry containing water. It is also possible to dry this into a powder, but as the binder material 5, polyvinyl alcohol, polyethylene oxide, methyl cellulose, gelatin, polyethylene polyacrylamide, polyacrylic acid, urea-formaldehyde, melamine-formaldehyde, isobutylene-anhydride When a water-soluble polymer (or prepolymer) material such as a maleic acid copolymer or an aqueous emulsion of a silicone resin or an acrylic resin is used, a microcapsule slurry is mixed with an aqueous solution of a binder material to form a coating solution. May be prepared. This is applied to the electrode 9 by a technique such as blade coating, wire bar coating, spray coating, spin coating, dip coating, screen printing, and roll coating.
Is applied to one of the substrates provided with and the microcapsules and the binder material form a single layer, and are fixed on the one of the substrates provided with the electrodes 9. A display medium is completed by bonding the other substrate to the substrate via an adhesive. A desired image can be displayed by connecting each electrode to a drive circuit and a power supply and applying a voltage pulse corresponding to an image signal.

The in-plane arrangement of the microcapsules can take various forms such as a matrix form, a hexagonal close-packed form, and a single layer or a multi-layered arrangement in the vertical direction. And other various forms. It is effective to use microcapsules having a center value of two or more capsule diameter distributions in order to increase the filling rate of the microcapsules in the layer.

Next, a second embodiment (corresponding to claims 3, 4, and 5) of the present invention will be described below with reference to FIG.
FIG. 1 shows another example of the display medium of the present invention. 1 is a substrate made of glass, plastic, etc., and has a thickness of 10 μm.
The thickness is desirably about m to 1 mm, and more desirably about 25 to 200 μm in order to have sufficient mechanical strength and flexibility. When used on the viewing side, a transparent material is selected, but when used on the non-viewing side, it may be colored. This color (reflection color) may be used as a part of the display color, or the reflectance may be reduced. By increasing the contrast, the contrast ratio can be improved.

2 is metal, ITO, SnO ₂ , ZnO: A
1 and a common electrode made of a conductive thin film, such as a sputtering method, a vacuum evaporation method, a CVD method, or a coating method. When the substrate 1 is used on the viewing side, the common electrode 2
Transparent materials such as O, SnO ₂ , and ZnO: Al are selected, but when used on the side not visible, they may be colored, and this color (reflection color) may be used as part of the display color, The contrast ratio can be improved by increasing the reflectance. It is not necessary to pattern the common electrode 2 in particular, but a repetitive pattern such as a dot shape or a stripe shape may be formed in order to make the electric field distribution for each display dot more uniform and obtain a sharp display. Reference numeral 3 denotes a microcapsule, which contains a dispersion 4. 5 is a binder material which is made of polyvinyl chloride, polyvinyl acetate, or vinyl chloride.
Vinyl acetate copolymer, polyvinyl butyral, polycarbonate, polyarylate, polysulfone, polyimide, polyamide, polystyrene, polyester, polyurethane, polyacrylate, polymethacrylate, acrylic copolymer, maleic copolymer, It is made of a film-forming material such as a fluororesin, an epoxy resin, an alkyd resin, a silicone resin, a phenol resin, a urea resin, a melamine resin, polyvinyl alcohol, polyethylene oxide, polypropylene oxide, methyl cellulose, ethyl cellulose, and gelatin. In order for an electric field applied from the outside to effectively act on the microcapsule portion, it is desirable to use a binder material having a dielectric constant equal to or higher than that of the dispersion. In order to adjust the dielectric constant, a compound such as an alcohol, a ketone, or a carboxylate may be mixed in the binder material in addition to the main resin. Further, by mixing colored particles or ions, the color (reflection color) can be used as a part of the display color, and the contrast ratio can be improved by increasing the reflectance.

The dispersion liquid 4 contains aromatic hydrocarbons such as benzene, toluene, xylene and naphthenic hydrocarbons, aliphatic hydrocarbons such as hexane, cyclohexane, kerosene and paraffinic hydrocarbons, trichloroethylene, tetrachloroethylene and trichlorofluoroethylene. Oil-soluble dyes such as anthraquinones and azo compounds or carbon black in an organic solvent having high resistivity such as halogenated carbon (hydrogen) s such as ethyl bromide, fluorine-containing ether compounds and fluorine-containing ester compounds; Colored fine particles such as iron oxide and organic pigments are used in an amount of 0.01 to 20 wt. % Of an electrophoretic particle made of an inorganic pigment such as titanium dioxide, zinc oxide or zinc sulfide, or an organic pigment such as diarylide yellow or phthalocyanine blue. The electrophoretic particles may be coated with another substance on its surface or complexed with another substance in order to match the specific gravity with the dispersion medium or to prevent aggregation and enhance dispersibility.

The particle size is preferably about 0.01 to 10 μm. In addition, stearic acid, oleic acid, linoleic acid, sodium dioctyl sulfosuccinate, polyethylene oxide, polymethyl methacrylate, silane coupling agents, titanium coupling agents Etc. may be added. In addition, each material constituting these dispersions may be used as a mixture of two or more as necessary.

As the wall material of the microcapsule 3, urea-formaldehyde resin, melamine-formaldehyde resin, urethane resin, gelatin-gum arabic and the like can be used. Microcapsules are manufactured by interfacial polymerization, In-Sit
It is formed by a u polymerization method, a coacervation method, or the like. It is possible to produce a capsule diameter of 1 to 1000 μm, but it has been experimentally found that the capsule diameter needs to be 5 μm or more in order to obtain a sufficient display contrast. It has been experimentally found that the upper limit is preferably 200 μm or less from the viewpoint of the strength of the capsule. Further, in order to obtain a desired resolution, the length of one side of an equipotential portion formed on the surface of the display medium by the writing device is W (mm), and the vertical distance from the surface of the common electrode to the surface of the display medium (display D)
(Mm) and the display or writing dot density is D
When (dpi) is set, 17 / D ≦ W + d ≦ 44 / D, but it goes without saying that the capsule diameter needs to be d or less.

The microcapsules formed by the above method are generally in the form of a slurry containing water. It is also possible to dry this into a powder, but as the binder material 5, polyvinyl alcohol, polyethylene oxide, methyl cellulose, gelatin, polyethylene polyacrylamide, polyacrylic acid, urea-formaldehyde, melamine-formaldehyde, isobutylene-anhydride When a water-soluble polymer (or prepolymer) material such as a maleic acid copolymer or an aqueous emulsion of a silicone resin or an acrylic resin is used, a microcapsule slurry is mixed with an aqueous solution of a binder material to form a coating solution. May be prepared. This is coated on a substrate provided with the common electrode 2 by a method such as blade coating, wire bar coating, spray coating, spin coating, dip coating, screen printing, roll coating, and the like. The layers are firmly fixed to the substrate on which the common electrode 2 is provided.

The in-plane arrangement of the microcapsules can take various forms such as a matrix form, a hexagonal close-packed form, and a single layer or a multi-layered arrangement in the vertical direction. And other various forms. It is effective to use microcapsules having a center value of two or more capsule diameter distributions in order to increase the filling rate of the microcapsules in the layer.

Next, a third embodiment of the present invention will be described below with reference to FIG. FIG. 2 shows another example of the display medium of the present invention. 1 to 5 are manufactured by the same material and forming method as in the second embodiment. Reference numeral 6 denotes an overcoat layer, which is an inorganic substance such as SiO ₂ or DLC (Diamond Like Carbon), polyvinyl chloride, polyvinyl acetate,
Vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, polycarbonate, polyarylate, polysulfone, polyimide, polyamide, polystyrene, polyester, polyurethane, polyacrylate, polymethacrylate, acrylic copolymer, maleic copolymer Organic substances such as polymers, fluororesins, epoxy resins, alkyd resins, silicone resins, phenolic resins, urea resins, melamine resins, polyvinyl alcohol, polyethylene oxide, polypropylene oxide, methylcellulose, ethylcellulose, gelatin, and various hardeners and crosslinks It is made up of an additive. Curing agent,
Examples of the crosslinking agent include a compound having an isocyanate group, a polyamide epichlorohydrin resin, a compound having an epoxy group, glyoxal, and the like. These can be produced by a vapor phase method such as a sputtering method or a CVD method, or a coating method such as a blade coat, a wire bar coat, a spray coat, a spin coat, a dip coat, a screen print, a roll coat and the like.

Further, an ultraviolet curable resin or an electron beam curable resin can be used for the overcoat layer. Specifically, a polymerization reaction is caused by irradiation with ultraviolet rays or electron beams, and a monomer or oligomer which is cured to be a resin is formed.
In some cases, a photopolymerization initiator is mixed and applied, and is formed by irradiating an ultraviolet ray or an electron beam.

Examples of such a monomer or oligomer include (poly) ester acrylate, (poly) urethane acrylate, epoxy acrylate, polybutadiene acrylate, silicone acrylate, melamine acrylate, and (poly) phosphazene methacrylate. As a photopolymerization initiator, acetophenones such as dichloroacetophenone and trichloroacetophenone, 1-hydroxycyclohexyl phenyl ketone, benzophenone, Michler's ketone, benzoyl, benzoin alkyl ether, benzyl dimethyl ketal, monosulfide, thioxanthones, azo compounds, diallyliodonium salts, Triallylsulfonium salts, bis (trichloromethyl) triazine compounds and the like.

The thickness of the overcoat layer is desirably as thin as possible within a range that does not impair the function as a protective layer, from the viewpoint of display resolution, preferably from 0.1 to 60 μm, more preferably from 0.3 to 30 μm. .

In order for an electric field applied from the outside to effectively act on the microcapsule portion, it is desirable that the overcoat layer has a large dielectric constant. Specifically, the thickness of the overcoat layer is d _o , the dielectric constant is ε _o, and the thickness of the layer (approximately a dispersion) comprising the microcapsules and the binder is d _o
m , and the dielectric constant is ε _m , (ε _o / d _o )> (ε _m / d _m )
It is desirable that the relationship is The refractive index of the overcoat layer is preferably smaller than the refractive indexes of the microcapsule wall material and the binder material from the viewpoint of reducing surface reflection.

Further, surface reflection is more positively reduced.
Single or multi-layer anti-reflective on top of overcoat layer
A stop film may be provided. For example, in the case of a two-layer film, air refraction
Rate n_a, The refractive index of the overcoat layer is n_o, First layer
The refractive index of the (air side layer) is n₁And the film thickness d₁, The second layer (E
The refractive index of_TwoAnd the film thickness is d_TwoTo be
And n₁d₁= N_Twod_TwoAnd n_an_Two ^Two= N_on₁ ^Two, N₁d₁
= N_Twod_TwoAnd n₁n_Two= N _an_oOr satisfy it
Close combinations are effective. Material with relatively small refractive index
MgF_Two, CaF_TwoEtc. are S
iOx, CeO_TwoEtc. can be suitably used. These are vacuum
By ordinary thin film forming means such as vapor deposition method and sputtering method
Can be produced.

It is desirable that the extinction time (time constant) of the externally applied electric field (charge) be longer from the viewpoint of the writing speed.
For this purpose, it is desirable that the specific resistance of the overcoat layer is large. Specifically, the thickness of the overcoat layer is represented by d _o ,
The specific resistance and [rho _o, a thickness d _m of the layer made of the microcapsules and a binder (Dispersion in approximately the), the dielectric constant and [rho _m, a relationship of _{ρ o d o> ρ m d} m It is desirable.

By mixing colored particles or ions in the overcoat layer, the color (reflection color) can be used as a part of the display color. The overcoat layer may be a layer composed of two or more layers as necessary.

In the first, second and third embodiments, an undercoat layer is provided on the substrate provided with the electrode 9 and the common electrode 2 in order to further enhance the adhesion of the microcapsules or the binder material. Is also good. The same material as the overcoat layer can be used as the material for the undercoat layer. Further, it is desirable that the physical properties such as the thickness, the dielectric constant, the specific resistance and the like of the microcapsule and the layer made of the binder material conform to the above-mentioned overcoat layer. The undercoat layer may be a layer composed of two or more layers as necessary.

Next, a fourth embodiment (corresponding to claim 6) of the present invention will be described below with reference to FIG. FIG. 4 shows an example of the writing device of the present invention. Reference numeral 10 denotes a display medium having, for example, the structure shown in FIG. Reference numeral 11 denotes an electrode array, which is a switching circuit 1 mounted integrally with an electrode rod 13 formed on a substrate 12 by screen printing or the like.
4 are arranged in an array in the direction perpendicular to the paper surface. Reference numeral 15 denotes a power supply circuit, which outputs a voltage pulse corresponding to an image signal via the switching circuit 14 to the electrode rod 1
Supply 3 Reference numeral 16 denotes a feed mechanism. In this case, by moving the display medium, visible information can be displayed on the entire surface. Instead, a mechanism for fixing the display medium and moving the electrode array may be used. Reference numerals 11, 15 and 16 are housed in a housing (not shown) and function as a writing device.

An example of the display operation will be described below. First,
When a voltage (for example, a negative voltage) having a polarity opposite to the surface charge of the migrating particles in the display medium is applied to the electrode rod 13, the migrating particles move to the surface and the color of the migrating particles is observed. When the voltage is reversed, the migrating particles move to the common electrode side, and the color of the dispersion medium is observed from the surface. In terms of driving, it is easier to invert the selected dot according to the image signal (writing operation) after displaying the entire surface once (erasing operation), rather than changing the polarity for each dot. In this example,
The length W (mm) of one side of the equipotential portion formed on the display medium surface by the writing device according to the present invention is substantially equal to the width of the electrode rod 13.

Next, a fifth embodiment (corresponding to claim 7) of the present invention will be described below with reference to FIG. FIG. 5 shows another example of the writing device of the present invention. Reference numeral 10 denotes a display medium having, for example, the structure shown in FIG. 2
Reference numeral 1 denotes an ion gun array comprising a corona wire 22, a discharge frame 23, and control electrodes 24a and 24b, which are arranged in a large number in a direction perpendicular to the plane of the paper to form an array. 26
Is a high voltage power supply for corona ion generation, and 27 is a power supply for ion flow control. Reference numeral 28 denotes a feed mechanism. In this case, by moving the display medium, visible information can be displayed on the entire surface. Instead, fix the display medium,
A mechanism for moving the ion gun array may be used.

An example of the display operation will be described below. First,
A voltage (for example, a negative voltage) having a polarity opposite to the surface charge of the migrating particles in the display medium is applied to the corona wire 22 to supply a negative charge to the surface of the display medium. Then, the migrating particles move to the surface by the electric field formed between the electric charge and the common electrode 2, and the color of the migrating particles is observed. Next, a positive voltage is applied to the corona wire 22 to control the control electrode 2 according to the image signal.
The polarity and magnitude of the voltage applied to 4a are changed. That is, when a positive voltage is applied, the ion current passes through the aperture 25 and a positive charge is supplied to the surface of the display medium, so that the migrating particles move to the common electrode side, and the color of the dispersion medium from the surface. Is observed. When a negative voltage is applied, since the ion current cannot pass through the aperture 25, no charge is supplied to the surface of the display medium, the migration of the migrating particles does not occur, and the color of the migrating particles is observed from the surface. 21, 2
6, 27 and 28 are housed in a housing (not shown) and function as a writing device. In this example,
The length W (mm) of one side of the equipotential portion formed on the display medium surface by the writing device according to the present invention is substantially equal to the opening width of the aperture 25.

Next, a sixth embodiment (corresponding to claim 8) of the present invention will be described below with reference to FIG. FIG. 6 shows another example of the display device of the present invention. Reference numeral 10 denotes a display medium having, for example, the structure shown in FIG. A writing device 31 has a plurality of signal electrodes and scanning electrodes on its surface, and has a switching element at an intersection thereof capable of applying an electric field to a display medium according to an image signal. 4
Reference numeral 0 denotes a power supply circuit for supplying a signal corresponding to an image to the writing device.

An example of the surface structure of the writing device will be described with reference to FIG. This is a case where a thin film transistor is used as a switching element. As the substrate 32, an insulator such as glass or a metal whose surface is insulated is used. A scanning electrode 33 also serves as a gate electrode and is made of a thin metal film such as Ta, Mo, W, or Al. 34 is a gate insulating film, which is SiN
x, SiOx, etc. 35 is a-S
a channel made of a semiconductor thin film such as i, Poly-Si,
36 is a signal electrode also serving as a source electrode, and 37 is a drain electrode, each of which is made of a metal thin film of Al, Cr or the like. 38
Are the individual electrodes Al, Cr, ITO, SnO ₂ , ZnO:
It is made of a conductive thin film such as Al. 39 is SiO ₂ , DLC
The protective layer is made of an inorganic substance such as (Diamond Like Carbon) or an organic substance such as polyimide, polyvinyl alcohol, epoxy resin, or acrylic resin. These can be produced by a known method combining a thin film forming technique such as a sputtering method, a CVD method, and a coating method with a patterning technique such as a wet etching method and a dry etching method. FIG. 7 shows one unit of the switching element, and the same pattern is repeatedly formed in the X direction and the Y direction according to the size of the display screen and the pixel density (resolution). In this example, the length W (mm) of one side of the equipotential portion formed on the surface of the display medium by the writing device according to the present invention is one of the individual electrodes 38.
It is almost equal to the length of the side.

[0056]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples.

Example 1 The display medium shown in FIG. 2 was manufactured as follows. 0.5 wt. % Blue dye (Macrolex Blue R)
R: Bayer Co., Ltd. was dissolved, and titanium dioxide (CR60: Ishihara Sangyo Co., Ltd.) having an average particle size of 0.21 μm and having a surface treated with Al was used as the migrating particles. These particles and oleic acid were each used as a dispersion medium in an amount of 10 wt. % And 0.5w
t. % To obtain a dispersion liquid 4. Microcapsules containing this dispersion were prepared as follows.

An aqueous gelatin solution and an aqueous gum arabic solution were mixed and heated to 50 ° C., and the pH was adjusted to 9 by adding an aqueous sodium hydroxide solution. The dispersion 4 was added thereto, and the mixture was stirred and emulsified. Further, the pH was gradually lowered to 4 to precipitate a concentrated solution of gelatin / gum arabic at the interface of the dispersion, and then the temperature was lowered to gel the film, which was then cured by adding an aqueous glutaraldehyde solution. Thus, the gelatin
A slurry of microcapsules using arabic gum as a wall material was obtained. The emulsification conditions were controlled so that the capsule diameter was in the range of 50 μm to 150 μm on average.

Using a 100 μm thick PET as the substrate 1, an ITO thin film was formed by a sputtering method to form a common electrode 2. On top of this, polyvinyl alcohol (PV
A-117: Kuraray Co.) A 10% aqueous solution to which the same weight of the above microcapsule slurry was added was applied by a blade coater and dried to form a single layer of the microcapsules and polyvinyl alcohol to form a common electrode 2
Was fixed to the substrate provided with. After a commercially available two-component epoxy adhesive was vacuum-defoamed thereon, it was applied with a blade coater and heated to 60 ° C. to form an overcoat layer 6 having a thickness of about 5 μm. At this time, the display layer total thickness d is set to 0.
065 mm (65 μm) to 0.191 mm (191 μm)
m) were obtained.

(Writing experiment 1) An Al film was deposited on a glass substrate, and five stripes having a width of 100 μm were formed at a pitch of 300 μm by etching (electrode substrate 1).
Was prepared. This is pressed against the surface of the overcoat layer of the display medium, the common electrode 2 is set to the ground potential, and a DC voltage of -300 V is applied to all lines of the electrode substrate for 1 second. Was measured (average of 5). FIG. 9 shows the relationship between the display layer total thickness d and the line width increase (writing line width−electrode width W). From the figure, it can be seen that the amount of increase in the line width is substantially equal to the total thickness d of the display layer.

(Writing Experiment 2) An Al film was deposited on a glass substrate and the following pattern was formed by etching (electrode substrate 2). These are fixed at line (L) + space (S) = 250 μm and L
The width (S width) is changed so that a set of writing portions / non-writing portions can be repeatedly formed at a pitch of 250 μm. It is expected that the pattern width written on the display medium is different from the electrode width.
μm (= 0.125 mm = 25 mm (≒ 1 inch) / 20
0) L & S pattern of width is formed, ie, 200
1 line (1 dot) of lpi (lines per inch≡dpi)
It is assumed that L & S is formed (in an actual writing apparatus, writing is performed every other dot using a 200 dpi line head to form an L & S pattern or a staggered pattern). 15 μm line / 235 μm space L & S 20 μm line / 230 μm space L & S 30 μm line / 220 μm space L & S 60 μm line / 190 μm space L & S 75 μm line / 175 μm space L & S 100 μm line / 150 μm space L & S 125 μm line / 125 μm space / 125 μm space L / S of line / 100μm space

The electrode substrate is pressed against the surface of the overcoat layer of the display medium, the common electrode 2 is set to the ground potential, a DC voltage of -200 V is applied to all the lines of the electrode substrate for 1 second, and the writing (white portion) state (L & S Was secured or not). Table 1 shows the results. As the display medium, those having a total display layer thickness d of 0.065 mm (65 μm) and 0.095 mm (95 μm) were used.

[0063]

[Table 1]

From the results in Table 1, 0.085 mm ≦ d + W ≦
A range of 0.220 mm is preferable, and 0.095 mm ≦ d
The range of + W ≦ 0.155 mm is more preferable. As described above, this write pattern is D = 200 lpi (≡d
pi) The preferred range is 1 because it corresponds to L & S.
7 / D ≦ d + W ≦ 44 / D, more preferably 19 /
It can be expressed as D ≦ d + W ≦ 31 / D. In addition,
It is clear that the results in Table 1 are caused by an experimental result (write experiment 1) in which the write line width is increased by almost the display layer total thickness d as compared with the electrode width W.
It can be easily analogized that even if D changes, the relational expression in a preferable range is similarly established.

Example 2 The display medium shown in FIG. 1 was manufactured as follows. The dispersion 4 used was the same as in Example 1. Microcapsules containing this dispersion were prepared as follows. Dispersion 4 was added to the aqueous protective colloid solution, and the mixture was stirred and emulsified. Add sodium carbonate to pH
After adjusting the pH to 9, the urea-formaldehyde prepolymer was added, and the pH was adjusted to 4 by adding acetic acid.
By reacting at 0 ° C. for 2 hours, the prepolymer was polymerized at the interface of the dispersion to form a urea-formaldehyde resin film. Thus, a slurry of microcapsules using urea-formaldehyde resin as a wall material was obtained. The emulsification conditions were controlled so that the capsule diameter was 50 μm on average.

A 100 μm thick PET was used as the substrate 1, and an ITO thin film was formed by a sputtering method to form a common electrode 2. On top of this, polyvinyl alcohol (PV
A-117: Kuraray Co.) A 10% aqueous solution to which the same weight of the above microcapsule slurry was added was applied by a blade coater and dried to form a single layer of the microcapsules and polyvinyl alcohol to form a common electrode 2
Was fixed to the substrate provided with. Display layer total thickness d is 0.06m
m (60 μm).

Example 3 Writing was performed on the display medium of Example 1 (display area: 10 cm × 10 cm, d = 0.065 mm) by a writing apparatus having the electrode array shown in FIG. The electrode array used had 800 electrode rods arranged at a pitch of 125 μm. The width W of the electrode rod 13 is 20 μ
m, 60 μm, and 120 μm. First,
Scanning was performed in a state where -300 V was supplied to the electrode bar 13, and the entire surface was displayed in white. Next, the polarity of the power supply was reversed, and a voltage of +300 V was applied to the electrode rod 13 via the switching circuit 14 in accordance with the image signal (staggered pattern and solid pattern). The pulse width of the application was 20 ms. By moving the display medium by the roller feeding mechanism 16, an image could be displayed on the entire surface. Feed speed is 6.25m
m / sec. When the width W of the electrode rod 13 was 60 μm, both staggered and solid images could be displayed well, but when the width was 20 μm, the solid density was slightly insufficient, and when it was 120 μm, the staggered pattern was slightly blurred.

Example 4 Writing was performed on the display medium of Example 2 (display area 10 cm × 10 cm, d = 0.06 mm) using a writing apparatus having an ion gun array shown in FIG. The ion gun array used had 800 ion guns arranged at a pitch of 125 μm. Aperture 25
The three types of opening width W of 30 μm, 60 μm, and 120 μm were prepared. First, a voltage of -5 kV was applied to the corona wire 22 to display white on the entire surface of the display medium. next,
A voltage of +5 kV was applied to the corona wire 22, and a voltage of +150 V (blue display) or -150 V (white display) was applied to the control electrode 24a in accordance with the image signal (staggered pattern and solid). The pulse width of the application was 10 ms. By moving the display medium by the roller feeding mechanism 28, an image could be displayed on the entire surface. Feed speed is 1
2.5 mm / sec. When the aperture width W of the aperture 25 was 60 μm, both staggered and solid images could be displayed satisfactorily, but when the aperture width W was 30 μm, the solid density was slightly insufficient,
In the case of, the zigzag pattern was slightly blurred.

Example 5 Writing was performed on the display medium of Example 1 (display area 10 cm × 10 cm, d = 0.065 mm) using the writing apparatus shown in FIG. Writing device 3
1, the thin film transistor shown in FIG.
× 800 pieces (inter-electrode pitch: 125 μm) were used. The length W of one side of the individual electrode 38 is 20 μm, 60
μm and 120 μm were prepared. Assuming that the selection time per scanning line is 0.1 ms, writing of all lines (staggered pattern and solid) (time required: 0.1 ms × 8)
00 = 80 ms). The voltage for white display on the common electrode side was +20 V, and the voltage for blue display was −20 V.
Shortly after the writing was completed, the full screen display was completed. When the length W of one side of the individual electrode 38 was 60 μm, the staggered pattern and the solid pattern could be displayed satisfactorily. However, when the length W was 20 μm, the solid density was slightly insufficient. When the length W was 120 μm, the staggered pattern was slightly blurred.

Example 6 The display medium shown in FIG. 8 was manufactured as follows. Microcapsules 3 were produced in the same manner as in Example 1. The emulsification conditions were controlled so that the capsule diameter was 50 μm on average. A 100 μm-thick PET is used as the substrate 1, a 0.5 μm-thick SiO ₂ film is formed as a barrier layer on both sides by a plasma CVD method, and then an ITO thin film is formed as an electrode 9 by a sputtering method, and a 60 μm-wide stripe is formed. Fifty patterns were formed at a pitch of 125 μm (the connection with the driver IC was enlarged to a pitch of 330 μm). On this substrate, a 10% aqueous solution of polyvinyl alcohol (PVA-117: Kuraray Co., Ltd.) to which an equal weight of the above microcapsule slurry was added was applied by a blade coater, dried, and then a commercially available two-part epoxy adhesive was used. Was applied, and the other substrate having the same pattern formed thereon was overlapped so that the stripes of both substrates were orthogonal to each other, and heated at 80 ° C. for 2 hours. Each electrode was connected to a driver IC to display a staggered pattern and a solid pattern.

[0071]

According to the first aspect of the present invention, it is possible to provide a display medium having a desired display resolution.
According to the display medium of the second aspect, in addition to the above, a low-cost display medium can be provided because the structure is simple and the manufacturing process can be simplified. According to the display medium of the third aspect, it is possible to provide a display medium that can obtain a desired resolution and can be removed from the writing device. According to the display medium of the fourth aspect, in addition to the above, a low-cost display medium can be provided because the structure is simple and the manufacturing process can be simplified. According to the display medium of claim 5, in addition to the above, it is possible to provide a display medium having high visibility, low power consumption, and excellent display stability. According to the writing device of the sixth aspect, the display medium can be detached from the writing device while the display state is maintained, so that it is easy to carry around or view a plurality of images side by side. According to the writing device of claim 7, in addition to the above, an image can be displayed in a short writing time. According to the writing device of the eighth aspect, an image can be displayed in a shorter writing time. According to another display medium of the present invention, in addition to the above, the adhesion between the microcapsules and the adhesion between the microcapsules and the substrate are improved, so that a highly reliable display medium can be provided. According to another display medium of the present invention, in addition to the above, it is possible to provide a display medium which has improved display uniformity due to increased surface smoothness, and has less wear and excellent durability. . According to another writing apparatus of the present invention, in addition to the above, a clear display can be performed even for an image accompanied by a halftone.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of a display medium according to the present invention.

FIG. 2 is a cross-sectional view schematically showing another example of the display medium according to the present invention.

FIG. 3 is a cross-sectional view schematically showing a conventional display device.

FIG. 4 is a cross-sectional view schematically showing one example of a display device according to the present invention.

FIG. 5 is a cross-sectional view schematically showing another example of the display device according to the present invention.

FIG. 6 is a cross-sectional view schematically showing another example of the display device according to the present invention.

FIG. 7 is a diagram schematically showing the vicinity of the surface of an example of the writing device according to the present invention.

FIG. 8 is a cross-sectional view schematically showing another example of the display medium according to the present invention.

FIG. 9 is a diagram showing a relationship between a display layer thickness and a line width increase (write line width−electrode width).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Common electrode 3 Microcapsule 4 Dispersion liquid 5 Binder material 6 Overcoat layer 7 Perforated spacer 8 Transparent electrode 9 Electrode 10 Display medium 11 Electrode array 12 Substrate 13 Electrode rod 14 Switching circuit 15 Power supply circuit 16 Feed mechanism 21 Ion gun Array 22 Corona wire 23 Discharge frame 24a Control electrode 24b Control electrode 25 Aperture 26 High voltage power supply for corona ion generation 27 Power supply for ion flow control 28 Feed mechanism 31 Writer 32 Substrate 33 Scan electrode (also gate electrode) 34 Gate insulating film 35 Semiconductor Thin film 36 Signal electrode (also source electrode) 37 Drain electrode 38 Individual electrode 39 Protective layer 40 Power supply circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C094 AA05 AA06 AA13 AA15 AA22 AA43 AA44 AA45 AA54 BA03 BA09 BA41 BA75 CA19 CA23 CA25 DA06 DA12 DB02 DB08 EA04 EA05 EA10 EB02 EC03 ED13 ED20 FA01 FA02

Claims (8)

[Claims] 1. A substance or group of substances whose optical characteristics are reversibly changed by the action of an electric field, at least one of which is enclosed between a pair of substrates having electrodes patterned in a stripe or dot shape and a similar shape. In the display medium described above, the width of the stripe or the length of one side of the dot is W ′ (mm), the vertical distance between the substrates is d ′ (mm), and the display dot density is D ′.
(Dpi), wherein the display medium has a relationship represented by the following expression (1). 17 / D'≤W '+ d'≤44 / D' (1) 2. A method according to claim 1, wherein a substance or group of substances whose optical characteristics are reversibly changed by the action of an electric field is encapsulated in a number of microcapsules, and these microcapsules are arranged between a pair of substrates. The display medium according to claim 1, wherein: 3. A substance or group of substances whose optical properties are reversibly changed by the action of an electric field are enclosed in a gap between a substrate provided with a common electrode and an opposing surface separated by a predetermined distance. In the display medium, the length of one side of an equipotential portion formed on the surface of the display medium by means capable of applying a potential to an arbitrary portion of the surface of the display medium is W (mm).
The vertical distance from the common electrode surface to the display medium surface is d (mm), and the display or write dot density is D
(Dpi), wherein the display medium has a relationship represented by the following expression (2). 17 / D ≦ W + d ≦ 44 / D (2) 4. A substance or group of substances whose optical properties are reversibly changed by the action of an electric field are encapsulated in a large number of microcapsules, and these microcapsules are fixed on a substrate provided with a common electrode. 4. The display medium according to claim 3, wherein: 5. A dispersion in which a plurality of migrating particles having a color different from the color of the dispersion medium are dispersed in a colored dispersion medium, wherein the substance or the substance group whose optical characteristics are reversibly changed by the action of the electric field is dispersed. The liquid is a liquid.
The display medium according to any one of the above. 6. A writing device capable of displaying visually recognizable information on the display medium according to claim 3, wherein the display medium and the writing device are:
At least at the time of writing, it can be attached and detached so as to be close to each other, and furthermore, the writing device can apply an electric field to the display medium in accordance with an image signal, and relatively change a planar positional relationship with the display medium. A writing device comprising an electrode array having a changeable mechanism. 7. A writing device capable of displaying visible information on the display medium according to claim 3, wherein the display medium and the writing device are:
At least at the time of writing, it can be attached and detached so as to be close to each other, and furthermore, the writing device can apply a charge to the surface of the display medium in accordance with an image signal, and the relative position of the plane with the display medium can be relatively adjusted. A writing apparatus, comprising: an ion gun array having a mechanism that can be changed into a writing mode. 8. A writing device capable of displaying visible information on the display medium according to claim 3, wherein the display medium and the writing device are:
At least at the time of writing, it can be attached and detached so as to be close to each other, and furthermore, the writing device includes a plurality of signal electrodes and scanning electrodes, and can apply an electric field to the display medium according to an image signal at an intersection thereof. A writing device comprising a switching element, wherein the writing device is configured to display an image on the display medium.