JP2001188267A - Display medium and write-in device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display medium which can write in easily image information of high uniformity, the high resolution, the high contrast, the high gradation characteristic, and high reliability with a small write-in device at high speed when writing reversibly the image information in the display medium which can be used like the paper bendablely thinly, and can be rewritten the image information reversibly with the write-in device separable from this medium. SOLUTION: In the display medium which has a surface-like portion which has a display part capable of the visual recognition state changing by applying the voltage or the electric current, at least a portion of the member which forms the top of at least one side of the display part is the portion which consists of the material large in the electric conductivity rather than at least one member disposed on the lower part and the circumscription, and the portion which consists of the material large in this electric conductivity is the driving means in which the voltage or the electric current is applied, and the separable display medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display medium capable of reversibly changing a visual state by the action of a voltage or a current and a writing device therefor, and more particularly to a rewritable electronic paper, a digital paper, and a web as a substitute for paper. The present invention relates to a display medium such as paper and a writing device therefor.

[0002]

2. Description of the Related Art Liquid crystal, electrochromic devices, electrophoretic devices, gyricons, and the like are known as display media capable of reversibly changing the visual state by the action of an electric field. The display medium includes a pair of electrode substrates and a display element inserted therebetween, and a drive circuit for applying a signal for displaying an image to each electrode is connected. In addition to nematic liquid crystals and cholesteric liquid crystals, various display elements using liquid crystals such as polymer-dispersed liquid crystals and discotic liquid crystals have been proposed, and those utilizing the memory properties of liquid crystals. Various proposals have been made.

Further, this display medium is not used as a display device, but is used as a bendable planar display medium such as paper. As shown in the specification of “writing sheet and writing system” described in 188489, a voltage of 100 V or more can be generated by using a display medium capable of reversibly changing the viewing state by the action of a voltage. Some image information is written by moving a simple electrode array with respect to the display medium.

However, in the above display medium, a diameter of 25 μm is used.
When 100 V is used for the sphere of m, it takes 3 msec. When writing A4 data at a density of 400 dpi, it takes 10 msec.
It is calculated that it takes more than seconds, and the writing time is long,
It is expected that high-speed writing will be difficult. Furthermore, when writing is performed by an electrode array at a voltage lower than the voltage using discharge, as in an electrostatic plotter, the unevenness of the surface of the electrode causes the portion that cannot be in contact with the electrode and the formed portion to change the voltage applied to the display medium. Variations occur and cause variations in image quality. If the voltage is increased until it can be discharged, the reversibility tends to decrease.

On the other hand, one of the pair of substrates sandwiching the display medium is made of an insulator without electrodes, and the outer surface thereof is charged with an ion stream by means of an ion irradiation means or the like, thereby applying an electric field. The method is known (for example, JP-A-62-34187, JP-A-4-86).
784, JP-A-6-202168). This method is the same as the above-mentioned method using the electrode array in that it is difficult to arrange the ion irradiating means at a high density and two-dimensionally, so that a mechanical scan is required for writing. For writing, the substantial voltage application time can be lengthened. If the threshold value is not steep, the applied voltage can be reduced to reduce the load on the electric drive circuit. Writing is also possible.
However, it is difficult to control the resolution and shape of the flow of ions and the voltage application time due to the loss of charge, and it is difficult to improve the resolution and gradation.

In addition, the size of the writing device is increased, so that it is not used for a display medium on a bendable surface such as paper.
A display device in which writing means is integrated has been proposed. In JP-A-4-86784, an electrophoretic display liquid is used as a display material, and the volume resistivity is set to 6 × 10 ¹⁰ (Ω).
cm) or more, which has a dielectric constant of 19.5 × 10
^A time constant of 12 (msec) is given to ^-12 (F / m), taking into account the voltage application time by the charging method.

[0007] In addition, as a display device which is not a bendable display medium such as paper but is capable of changing the visual state reversibly by the action of an electric field and a writing unit, For example, a display device having a driving circuit provided for each pixel and having an electrode connected to the driving circuit (Japanese Patent Laid-Open No.
202168). Although a low-resistance independent full-surface electrode is provided corresponding to a display location, a driving circuit, that is, a writing unit and a display device are integrated. When such an active element is provided in the display medium,
Although the image quality can be improved, the response speed can be reduced, so that high-speed writing can be performed.

Further, there is a display device (JP-A-5-61421) in which a display material is sealed in the gap between the opposed electrodes and an insulating layer is provided on the surface of the opposed electrode. this is,
Although the withstand voltage and time constant of the insulating film are taken into account, the long-term life due to the direct current flowing through the electrophoretic liquid is reduced. In addition, as an equivalent circuit, the insulator does not substantially pass a current. Therefore, when a sufficiently long pulse voltage is applied, the voltage is applied to the electrophoretic liquid but becomes substantially zero. I will. Similarly, there is a display device in which one of the opposing electrodes is provided on the outer surface (Japanese Patent Application Laid-Open No. 5-34710). These are based on the premise that a drive circuit is connected to each display location, and the drive means and the display device are integrated. In addition, the time constant of the display part is taken into account, but basically the resistance is treated as infinity in the capacitor model and only the inside of the power supply and the wiring resistance are taken into account. are doing.

Further, as a device using a microcapsule, there is a display device described in Japanese Patent Application Laid-Open No. 10-119118, in which a substrate and an electrode are arranged in advance so as to face each other. Are provided with a microcapsule containing an electrophoretic display liquid and a binder, and by making the dielectric constant of the electrophoretic display liquid and the dielectric constant of the binder substantially the same, it is possible to suppress the migration of the electrophoretic particles at the top of the capsule.

However, any of these methods is still not enough to realize reliable high-speed writing with a small-sized apparatus while improving image quality such as resolution, image density, and high gradation. There are many sufficient points, and the configuration tends to be complicated, low in reliability, and expensive.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a display medium which can be used like thinly bent paper and which can rewrite image information reversibly. When writing image information reversibly by a writing device that can be separated from this, high uniformity, high resolution, high contrast, high gradation, and high reliability image information can be easily written at high speed with a small writing device. An object of the present invention is to provide a writable display medium. More specifically, the following is the subject of the present invention. An object of claim 1 of the present invention is to provide a display medium which is excellent in uniformity of image quality of the display medium, is highly reliable, and can be written by a simple and small device. Another object of the present invention is to provide a simple and high-resolution display medium for the display medium. It is another object of the present invention to provide a display medium on which image information can be written more quickly and more easily. It is another object of the present invention to provide a display medium capable of writing image information at a high speed with a relatively low voltage even if it has a multilayer structure. It is another object of the present invention to provide a display medium capable of writing image information at a relatively high speed with a relatively low voltage even if it has a multilayer structure. It is another object of the present invention to provide a writing device capable of writing image information on a display medium at high speed and more easily. Another object of the present invention is to provide a display medium with more uniform image quality, to provide a more reliable display medium, and to provide a higher resolution display medium. I do.

[0012]

A first aspect of the present invention is an electric power supply system.
Visual state changes by applying pressure or current
Display medium having a planar portion having a display portion capable of
In the body, the uppermost part on at least one side of the display location
At least a portion of the member forming
Higher conductivity than at least one member arranged on the side
This part is made of a high-performance material and has high conductivity.
A driver made of material that applies voltage or current
It can be separated from the step. Claim 2 of the present invention
Is made of a material having a large electric conductivity in the above-described configuration.
The shape of the part is substantially rectangular and the four corners of this rectangle
A song whose radius is a quarter of the length of the short side of the rectangle
Curve shape smaller than the ratio or chamfered shape equivalent to this
It is characterized by having. Claim 3 of the present invention provides the above structure.
The lower portion of the portion made of a material having high conductivity
At least one part located in
The dielectric constant of the part_b0, Conductivity σ_b0, The table
Set the writing speed of the recording medium to X (sec / dot) or Y (sec / lin).
e), X ≦ ε_b0/ Σ_b0Or Y ≦ ε_b0
/ Σ_b0It is characterized by being. Claim 4 of the present invention
Is made of a material having a large electric conductivity in the above-described configuration.
At least one part located below the part and
The dielectric constant of the part where the_b0, Conductivity σ
_b0, Thickness D_b0And made of a material having a large electric conductivity.
At least one and no more than n
The conductivity of other parts is ε_bx, Conductivity σ_bx,thickness
To D_bx(Where x is a positive number, 0 <x ≦
n), σ_bx≦ 1.0 × 10^-Four(S / cm)
Σ for all x_b0/ D_b0≧ σ_bx/ D_bxor
Is ε_b0/ D_b0≤ε_bx/ D_bxIt is especially true that
Sign. Claim 5 of the present invention is the above configuration,
A small element placed below the part made of a material with high conductivity
Invite at least one part and the part whose visibility changes
The electric power is ε_b, Conductivity σ_b0, Thickness D_b0And the conductive
The lower part located below the part made of high-rate material
The conductivity of one or more and n or less other parts
ε _bx, Conductivity σ_bx, Thickness D_bxAnd when
(Where x is a positive number, 0 <x ≦ n), σ_bx≦ 1.0 ×
10^-FourFor all x in the case of (S / cm), σ
_b0/ D_b0≧ Σσ_bx/ D_bxOr 1 / (ε_b0/ D
_b0) ≧ Σ (1 / ε_bx/ D_bx)
Sign. Claim 6 of the present application is the table according to any of the above.
Driving means for applying a voltage or current to a display portion of a display medium
In the writing device having, the writing device,
Apply a voltage or current that can touch the display
Electrode, and the state of contact between this electrode and the display location
It is characterized by having means capable of changing further,
The display medium of the present invention, in the above configuration, has a large conductivity.
Σ_aAnd σ_a
≧ 1.0 × 10^-Four(S / cm) and / or
Is disposed below the portion made of the material having high conductivity.
The conductivity of at least one of the_bAnd when
σ_b≦ 1.0 × 10^-Ten(S / cm), and
And / or on the periphery of the portion made of the material having high conductivity
The conductivity of at least one of the arranged portions is represented by σ_cMade
Then σ_c≦ 1.0 × 10 ^-6(S / cm)
Features.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the display medium of the present invention will be described in detail. The display medium of the present invention has a planar portion having a display portion whose visual state can be changed by applying a current or a voltage, and the current or voltage applied to the display portion is different from this. Can be given by using an electrical drive means of a separable writing device. The inventors of the present invention have found a structure after intensive studies,
As a result, the uniformity of the image information on the display medium is improved, the reliability and the resolution are improved, and the display medium can be written at high speed with a simple and small writing device.

First, a conventional embodiment to be compared with the present invention will be described. A display medium capable of displaying an arbitrary image on a plane is formed of display pixels of a size corresponding to the resolution or a size smaller than the resolution or an equivalent material, and by changing a visibility state of any display pixel. , Any image can be displayed. These display pixels have substantially the same meaning as the above-described display portions when the display medium is viewed from the vertical direction. A substantial display portion of the display pixel is a display location. When the display pixel applies a voltage between the opposing scanning line and the signal line by using a driving circuit, the display pixel is generally arranged corresponding to coordinates shown on vertical coordinates,
In the case of full-color display, the three pixels of the configuration reference colors RGB are further arranged in an array such as the horizontal direction for the OA and the polygonal shape for the television.

When such a display medium is used like paper, image information can be displayed using another writing device, and the mechanical absolute position of the display medium and the writing device is different. Is extremely difficult because it is required to have an accuracy lower than the resolution, and the position is detected to change the absolute write position or to write with emphasis on the relative position. Such a structure is highly useful in that an image can be written by applying a voltage or current to a display medium at a predetermined resolution, but the writing speed is likely to be reduced from the following points.

The size of the electrode array is about 1 times as large as the size of the pixel dot derived from the resolution, and it can be used in either writing using the electrode array as a solid-state scanning head or writing using the electrode array as a raster operation head. However, when a display medium transport type writing device is configured, the writing speed depends on the size of the pixel dot.
(Dot length) / (1 dot voltage application time).
For this reason, it is effective to reduce the voltage application time for one dot in a normal resolution. This is because, as described in the above-mentioned Japanese Patent Application Laid-Open No. 3-188489, when one dot voltage application time takes 3 ms, A4 data is converted to 400 dpi.
It can be understood from the fact that it takes 10 seconds or more when writing at a density of. In order to shorten the voltage application time, it is straightforward to increase the voltage. However, in this case, there is a problem that the selection and structure of a driving IC that switches at 100 V or more and a surrounding insulating material are difficult and the cost is high, and the electric field is easily leaked from the wiring portion to the electrode array. However, there is also a problem that the resolution of the image may be reduced. Also, 30
When the voltage is 0 V or more, air discharge is likely to occur, and besides the effective applied voltage or current value decreases,
An electrical load is generated on C and peripheral circuits, and the reliability is reduced.
Further, in order to ensure reliability against high pressure, the size of the apparatus is increased, the number of parts is increased, and the cost is increased. However, since charge can be written to a display medium by air discharge, writing can be performed at a higher speed than the actual voltage increase. Further, non-uniformity of image information due to non-uniformity of voltage or current at a non-contact portion between the electrode and the display medium, which is caused by unevenness of the display medium due to discharge, can be reduced. However, when the state of occurrence of air discharge is not made uniform, unevenness due to the size of unevenness is likely to occur.

Here, one of the embodiments according to the invention of the present inventors and filed as a patent application separately from the present application will be described below with reference to FIGS. 7 and 8.

FIG. 7 shows an example of the writing device.
FIG. 8 shows an example of a display medium written by this writing device. This display medium is a display medium similar to the one that can be written by the writing device of the present invention, and is an example of a display medium in which image information can be rewritten with a voltage that can be handled like paper.

In FIG. 7, reference numeral 10 denotes a display medium, 11 denotes an electrode array, and a switching circuit 14 integrally mounted on an electrode rod 13 formed on a substrate 12 by screen printing or the like.
These are arranged in a large number in the direction perpendicular to the paper surface to form an array. 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 13.
To supply. 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, fix the display medium,
A mechanism for moving the electrode array may be used. 1
1, 15, and 16 are housed in a housing (not shown) and function as a writing device.

In FIG. 8, reference numeral 1 denotes a substrate made of glass, plastic, or the like. When used on the viewing side, a transparent material is selected. 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
A transparent material such as O, SnO ₂ , ZnO: Al is selected. Reference numeral 3 denotes a microcapsule, which contains a dispersion 4. Reference numeral 5 denotes a binder material made of an acrylic, urethane, epoxy, or ester resin, and reference numeral 6 denotes a coating material.

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 coloring fine particles such as carbon black, iron oxide, and organic pigments are added to an organic solvent having a high resistivity such as halogenated carbon (hydrogenated) such as ethyl bromide and the like. 0.01-20 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 fluid 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. Further, stearic acid, oleic acid, linoleic acid, sodium dioctylsulfosuccinate, polyethylene glycol, a titanium coupling agent, or the like may be added for the purpose of controlling the surface charge amount of the migrating particles or increasing dispersibility.

As the wall material of the microcapsule 3, urea resin, melamine resin, urethane resin, gelatin 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. Capsule diameter is 1 to 1000 μm, preferably 5 to 200 μm
It is said. The microcapsules formed by the above method are generally in the form of a slurry containing water. It is possible to dry this to make a powder, but the binder material 5
As polyvinyl alcohol, polyacrylamide,
When using a water-soluble polymer (or prepolymer) material such as polyacrylic acid, urea-formalin type, melamine-formalin type, isobutylene-maleic anhydride type, the microcapsule slurry is added to the aqueous solution of the binder material. What is necessary is just to mix and produce a coating liquid. This is applied onto the common electrode 2 by a method such as blade coating, screen printing, roll coating and the like, and dried, whereby the microcapsules and the binder material form a single layer and are firmly fixed on the common electrode 2. You.

Reference numeral 6 denotes a coating layer for reducing the irregularities of the capsule. The coating layer is made of an organic material such as an acrylic resin, a urethane resin, an epoxy resin, an ester resin, polyvinyl alcohol, or polyimide, or SiO ₂ or DLC (Diamond Like Carbon).
And the like. These can be produced by a coating method such as blade coating, screen printing, or roll coating, or a gas phase method such as a sputtering method or a CVD method. The thickness of this layer is preferably about 1 to 50 μm.

Another embodiment of the present invention, which is a patent application separate from the present invention, is described below with reference to FIG.

FIG. 9 shows an example of a display device based on a principle similar to that of the display medium of the present invention. Reference numeral 10 denotes a display medium having, for example, a structure shown in FIG. Reference numeral 21 denotes an ion gun array which includes a corona wire 22, a discharge frame 23, and control electrodes 24a and 24b, and a large number of these are arranged in a direction perpendicular to the paper surface 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, a mechanism for fixing the display medium and 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 accommodated in a housing (not shown) and function as a writing device.

Next, one embodiment of the present invention will be described below with reference to FIGS. 1 and 2 (claims 1 and 3). FIGS. 1 and 2 show an example corresponding to the display medium of FIG. FIG. 2 is a cross-sectional view and a schematic diagram of an upper surface. In FIG. 1, 31 is I
A high-conductivity member made of TO, 1, 2, 3, 4,
5 and 6 have the same names as in FIG. Here, reference numeral 6 denotes a coating layer formed mainly for flattening the upper surface of the capsule, and the same material as 5 is used as the material. In FIG. 2, reference numeral 32 denotes a region where the state of visibility from the top surface has changed due to electrophoresis of particles in the microcapsules. In practice, the microcapsules are densely arranged in a plane.

A display medium having an ITO member having a higher conductivity than the lower part and the periphery of the upper part in FIG. By electrophoresing the particles in the capsule, the pigment particles can move to the top surface,
At this time, the observer of the display medium observes the color of the pigment particles. Conversely, by applying a voltage, the pigment particles can move to the lower surface, and the color of the dye in the dispersion medium can be observed.

As shown in FIG. 2, although depending on the voltage application conditions and the structure of the display medium, since the lower part is a common electrode,
The particles in the microcapsules are electrophoresed in a range slightly larger than that of the ITO member having high conductivity, and the visual recognition state changes. This range becomes smaller as the distance between the electrodes in the vertical and horizontal directions becomes smaller, and the variation depending on the thickness of the microcapsules decreases as the microcapsules become smaller.

In the case where a highly conductive member made of ITO is provided on the upper surface of the display medium adjacent to the electrode array by applying a voltage corresponding to the image information, in this case, a pressure of a certain level or more is applied between the two. Thereby, a part of the tip surface of the electrode array and a part of the ITO can be easily brought into contact. At this time, since the ITO has a high conductivity, the voltage loss of the electrode array can be uniformly transmitted to the members below the ITO while reducing the loss. This makes it possible to effectively apply a highly reliable voltage that does not depend on the unevenness of the display medium to a material such as a microcapsule or the like whose visual state changes due to the action of a voltage, with a simple electrode array structure. . This is based on the following reasons.

The display medium can be formed by using solvent coating or vacuum film formation. In order to coat the surface evenly, leveling by gravity is performed using a coating solution with low viscosity like resist coating such as spin coater or roll coater, or temperature is increased by vacuum film formation There are various methods such as reducing the speed. And a method of using a dense film. There is also a method of smoothing the surface of a thermoplastic material by heat-treating the surface with a smooth roller.

However, these methods not only limit the method of manufacturing the display medium but lower the function, but also lower the yield and increase the cost, making it difficult to spread the practical use as a paper-like display medium. There is a point. Further, surface irregularities generally tend to increase when the number of coating layers is increased. However, if there are irregularities on the surface to some extent,
A gap is formed between the display medium and the electrode array in combination with the unevenness of the electrode array. Although it is difficult to eliminate the gap unless the pressure is considerably increased, the microcapsules of the display medium are deformed or broken by such pressure, and the display quality is rather deteriorated. Display media for writing by direct contact include heat-sensitive (thermal) paper using leuco dye and heat (thermal).
Although there is a combination with a printer, in this case, heat is efficiently transferred from the contact point of the convex portion of the unevenness to the adjacent concave portion, and the structure has no practical problem.

Further, since the thermal paper can be formed by coating a thin leuco dye layer on a thin substrate mainly composed of paper, the flexibility is large and the unevenness between the thermal printer head and the thermal paper is affected by pressure. It is considerably reduced from the initial state without pressure.

On the other hand, the display medium of the present invention, which changes the display state by applying a voltage, uses a plastic material for the substrate, and furthermore, the member whose visual state changes to reduce the influence of the resolution degradation by the substrate. A conductive film is formed between the substrate and the substrate. For this reason, besides the flexibility of the substrate is smaller than that of the thermal paper, the substrate is less likely to be deformed by pressure, so that the electrode is less likely to be directly contacted by the unevenness of the display medium. A voltage cannot be substantially applied to a portion where the display medium and the electrode do not directly come into contact with each other due to high air resistance. The degradation of image quality due to this effect is much greater than with thermal printers. Conventionally, there is a method of reducing the influence of the unevenness by writing at such a large voltage as to generate air discharge. However, as described above, the writing device tends to be expensive and large. Also, by giving the electrodes elastic properties, it is possible to reduce the increase in resistance due to air in order to make the electrodes conform to the unevenness of the display medium, but in this case, deterioration and reliability of the electrodes are problematic. Becomes

However, according to the present invention, the potential of the electrode can be transmitted to the entire shape of the ITO on the display medium through a part of the ITO which is easily in contact with a part of the front end face of the electrode array, thereby displaying the image. By applying a voltage between the common electrode and the microcapsules whose visual state changes depending on the voltage that is a part of the medium, an almost uniform electric field intensity that reduces the influence of the unevenness of the display medium surface is obtained. And the image quality can be made uniform. Further, since it is not necessary to write at a high voltage for air discharge, the load on the display medium and the driving IC is reduced, so that the reliability can be improved and a simple writing device can be used.

In the present invention, the high-conductivity member made of ITO on the surface of the display medium is provided by providing an independent ITO or conductive member on the surface of the display medium even if the display medium does not have a common electrode of the substrate. It can also be realized by In this case, although the strength is reduced by the omission of the substrate, by increasing the flexibility of the display medium, it is possible to approximate the feeling of paper use.

Hereinafter, each configuration and each member will be described in detail. A portion made of a material having a higher conductivity than a member disposed below or around the uppermost portion on one side of the display medium, or a conductive layer provided directly on the substrate is not limited to ITO. A conductive layer using an electron conductive pigment as a conductive agent can be used. As the electron conductive pigment, a conductive inorganic pigment, that is, an inorganic pigment is used as a base material, and the base material alone or a needle-like or particulate pigment whose surface is further coated with a conductive material is used. Here, the acicular conductive pigment is potassium titanate, titanium oxide, barium sulfate,
Aluminum borate, calcium carbonate, etc. as a base material, or those whose surface is coated with antimony, tin oxide, etc., and particulate conductive pigments are zinc oxide, titanium oxide, calcium carbonate, calcium sulfate, and even metals, A semiconductor whose base material is a semiconductor or the like, or whose surface is coated with antimony, tin oxide, or aluminum can be used. Further, a metal oxide, a metal colloid, or the like can be used.

Further, the member having a large electric conductivity can be formed by using the above-mentioned electron conductive pigment and a binder. Examples of the binder used here include vinyl chloride resin, vinyl acetate resin, acrylic resin, polyester resin, urethane resin, butyral resin, nitrocellulose, styrene-butadiene copolymer, polyvinyl alcohol, hydroxyethyl cellulose, gelatin, starch, and casein. Water-soluble resins, water-dispersible resins, and organic solvent-based resins can be used. In addition, the ITO of this embodiment
Can be easily produced by sputtering.

The display portion of the present invention may be any display portion whose liquid crystal, electrochromic, electrophoretic, organic EL, inorganic EL, LED, etc., whose visibility can be changed by the action of voltage or current. Voltage or current to light,
It is similarly effective for the case where the magnetic field, heat, pressure and the like are used supplementarily.

Further, a display medium capable of retaining a displayed image even after erasing the electric field, that is, a display medium having a memory property is preferable. Ferroelectric liquid crystal, memory polymer dispersed liquid crystal, bistable cholesteric liquid crystal, electrochromic element , An electrophoretic element and the like, but are not limited to these, and may use a combination of light, heat, magnetic field, pressure and the like. In the case where the display medium does not have a memory property, the display medium is used alone and the erasing step is performed at the same time, so that its use is limited. Therefore, when it is desired to use the display medium in the same manner as paper, it is necessary to provide a power supply or a structure for retaining some memory property in the display medium.
However, in the case of having a memory property, image data can be held without requiring any special means, as in the case of the above-mentioned paper, which is particularly effective.

Even if the display material is not encapsulated in a microcapsule, it can be used as it is, applied alone or with another material, inserted into a flat plate, or sealed in a space formed by a flat plate and partition walls. Or you may.

Furthermore, these writings are not limited to one time, and by performing the writing a plurality of times, the resolution and contrast can be further improved.

Further, a charge removing means may be provided as a capacitor in order to remove charges generated at a display portion. The charge removing roller or blade serving as the charge removing means preferably does not have a large resistance in order to remove electric charge, and is preferably an elastic body in order not to damage a display portion.
These do not need to be made of a single material, and a composite of an elastic body and a conductive pigment can be used.

The electrode array for applying a voltage to the high-conductivity member made of ITO according to the present embodiment is driven by a driving IC or an electric circuit for applying a voltage. By applying a pulse voltage or a pulse voltage obtained by changing the voltage, a voltage can be applied according to the display medium.

Further, since the range in which the voltage acts depends not on the shape of the electrode array but on the shape of the high-conductivity member of the display medium, the shape of the electrode array can be designed relatively freely, and the frictional force can be reduced. Small spheres / elliptical spheres or cylinders can also be used.

The conductivity σ as the material of the high conductivity member
_a (S / cm) depends on the thickness of the high conductivity member, but is preferably σ _a = 1.0 × 10 ⁻⁴ (S / cm) or more, and more preferably σ _a = 1.0 × 10 ² (S / cm)
More preferably, σ _a = 1.0 × 10 ⁴ (S / c
m) or more. This is based on the following reasons.

When the thickness of the high conductivity member is d and the distance between the high conductivity member and the lower common electrode is D, the conductivity of the high conductivity member is not less than D / d with respect to the lower member. If there is a ratio, the resistance in the horizontal direction can be reduced. However, in consideration of the uniformity of the lower member in the thickness direction and the voltage distribution at the resistance ratio, it has been experimentally found that about 1/100 or less is preferable. The minimum value of D is 10 μm
Assuming that the maximum value of d is 5 μm, the minimum conductivity ratio is 50 times, but the actual practical configuration is that when D is small, high resolution and high electric field strength are required. In general, D / d is 1/10 or less, and a conductivity ratio of 3 digits or more is preferable. On the other hand, the lower resistance value is preferably such that the conductivity σ _b is small in the case where the side effect due to the current is reduced by making the action dependent on the voltage mainly, and the power consumption is further reduced. Is effectively σ _b = 1.0
× 10 ⁻⁷ (S / cm) or less is preferable. From these, σ
_It can be seen that _a = 1.0 × 10 ⁻⁴ (S / cm) or more is preferable. These are the minimum conductivity values at which the effects of the present invention can be found. However, since this value generally corresponds to a material that is not an insulator but a region that is separated from a semiconductor, many materials can be applied. The configuration of the present invention can be manufactured at a low cost by a simple method.

By the way, a material for changing the visibility of the lower part
Material, prescription, film thickness, conductivity or resistance
When the current value increases, the partial unevenness of the material
The effect also affects the effect of the voltage drop. others
Need to be less affected by the current value
There is. To do this, the conductivity must be determined from the semiconductor material value.
It is necessary to have conductivity that has conductive properties.
Has σ_a= 1.0 × 10 ¹(S / cm) or more
Is preferred. In general, the conductivity called a conductor is σ_a=
1.0 × 10^Four(S / cm) or more,
In this case, it is not necessary that the conduction levels match completely instantaneously.
And effectively generate a uniform electric field between the bottom surface
Σ_a= 1.0 × 10^Two(S / cm) or more
Then you can see that the effect is fully found
Was.

As described above, the conductivity of the high conductivity member is represented by σ _a
= 1.0 × 10 ⁻⁴ (S / cm) or more, and σ _a =
By setting it to 1.0 × 10 ² (S / cm) or more, it was possible to improve the reliability and improve the uniformity of the image.

The conductivity σ _{b at} the lower portion is σ _b ≦ 1.0 × 10 ⁻⁷ (S _b) when the display quality and cycle deterioration due to the side effect of the current are reduced and the power consumption is reduced.
/ Cm) has been stated it is preferable, to increase the effect of the first aspect, at least conductivity σ _{b =} 1.0 × 10 ^{-1 0} to at least a portion of the bottom of the high conductivity member
(S / cm) It is more preferable to have a member that is not more than (S / cm).

This is applicable when the lower part has a multilayer structure.
Because the combined resistance of
If there is a relatively conductive material inside,
The resistance of one layer is sufficiently large for
Of the combined resistance due to the relatively high conductivity layer in the bottom
The increase in the current value due to the decrease
_b= 1.0 × 10^-Ten(S / cm) or less
And can be reduced. In other words, the bottom
Inside σ_b= 1.0 × 10^-7Conductivity larger than (S / cm)
Material with three orders of magnitude larger than this even if there is a member of the rate
By providing the material, the material having a smaller conductivity can be used.
Even if the thickness is about 100 times smaller,
Series resistance can be increased,
Current value can be reduced to reduce the voltage drop.
This conductivity is σ_b= 1.0 × 10 ^-Ten(S / cm) or less
Is a voltage distribution due to the resistance ratio
It is a material that can change the visual recognition state by
It is preferable to use AC voltage or DC pulse
Optimizing voltage application methods such as voltage and material design values
To increase the efficiency of the effective voltage applied to the viewing state
Can be. Of course, the conductivity of any of the lower members is σ_b
= 1.0 × 10^-7(S / cm)
The effect of equalizing the voltage action by the high conductivity member in the part
Σ_b= 1.0 × 10^-Ten(S / cm) or less
It is preferable to have a member that becomes

As described above, the lower conductivity is σ _b = 1.0 ×
By using a member of 10 ^-10 (S / cm) or less, the resistance value of the display medium can be increased without depending only on the material type, the prescription, and the layer structure of the member whose visual state changes, so that the image quality can be improved. Can improve the stability and cycle characteristics, and can improve the reliability.

Next, another embodiment of the present invention will be described below with reference to FIG. FIG. 3 is a schematic diagram showing an example corresponding to the display medium of FIG. FIG.
In the figure, 31 is a high conductivity member coated with a conductive paint, and 33 is a low conductivity member made of a polymer material which is practically embedded in the gap between the conductive paints. 1,
2, 3, 4, 5, and 6 have the same names as in FIG. Here, reference numeral 6 denotes a coating layer formed mainly for flattening the upper surface of the capsule, and the same material as 5 is used as the material. In FIG. 3, 31 and 33 can be produced using screen printing.

In many cases, the conductivity of the conductive paint is lower than that of ITO or the like. At this time, steps due to unevenness of the coated surface may cause poor contact with the electrode array, roughness of the display medium,
Although a problem is caused by adhesion of dirt, etc., by printing a material having a small conductivity in the gap in the same manner, the surface can be smoothed, voltage application by the electrode array can be performed uniformly, and at the same time, the high conductivity can be obtained. Steps due to members can be reduced.

The conductivity σ _c of the peripheral portion depends on the configuration of the display medium, but is preferably σ _c = 1.0 × 10 ⁻⁶ (S
/ Cm) or less, and σ _c = 1.0 × 10 ⁻⁷ (S /
cm) or less is particularly preferred. The reason will be described below.

If the conductivity of the peripheral member between adjacent high-conductivity members is smaller than the conductivity of the high-conductivity member, the short-circuit between the high-conductivity members is less than that between the high-conductivity members. Can be reduced, and the influence of adjacent display locations can be reduced. This is especially true for σ _c =
The reason is preferably 1.0 × 10 ⁻⁷ (S / cm) or less. However, in practice, even with a higher conductivity, the influence between adjacent high-conductivity members is further reduced to reduce crosstalk. It was found that it could be reduced. Of course, depending on the distance between the adjacent highly conductive members, the peripheral portion needs to have a certain degree of conductivity or less. Generally, it is also correlated with the size of the gap between the highly conductive member and the common electrode, but since there is a spread of the electric field that effectively acts at a size of 1/5 or more of the size of the gap. In addition, there is a need for a gap between the high conductivity members, and there is also the simplicity of production due to the accuracy of printing and simple photolithography, so that the thickness is 5 μm or more. In this case, assuming that a low voltage of 10 V, a material having an effective value of σ _b = 1.0 × 10 ⁻⁸ (S / cm) is used, and a voltage is applied to an image dot having a thickness of 10 μm and equivalent to 600 dpi, A current of about 10 nA flows. On the other hand, the peripheral part has a length of 5
μm and the effective thickness is 1 μm, σ _c = 1.0
At × 10 ⁻⁶ (S / cm), a current value of 1/10 or less flows compared to the above-mentioned about 10 nA, and crosstalk between dots can be reduced. Of course, usually, the interval is usually 5 μm or more and the effective thickness is usually 1 μm or less, so that σ _c = 1.0 × 10 ⁻⁶ (S / c
It can be seen that m) or less is almost sufficient. The larger the size of the image dot, the higher the conductivity may be. Also, the thickness of the image dot portion needs to be small, and although it is affected by the conductivity, σ _c = 1.0 × 10
It was found that a relatively low resistance material having a conductivity of ^-6 (S / cm) or less can sufficiently reduce crosstalk. This makes it possible to easily provide a display medium with excellent resolution.

The visual recognition state at the bottom of the high conductivity member
Changes the conductivity of the material whose_b0The dielectric constant
ε_b0And the writing speed of the display medium is X (sec / dot)
Or Y (sec / line), X ≦ ε_b0
/ Σ_b0Or Y ≦ ε_b0/ Σ _b0By having
Voltage can be applied to the material that effectively changes to the visible state,
Writing can be performed.

Assuming that the portion visually recognized on the high conductivity member and the common electrode is simply a parallel circuit of CR, these time constants are τ _b0 = CR = ε _b0 / σ _b0 . By setting this time constant at least as long as the time required for the writing speed of one dot or one line, the writing of the electric charge is used to actually increase the electrode array in spite of the writing by the electrode array. The voltage can be applied to the material whose visual state changes for a time longer than the time of contact with the conductive member, and the material can be applied at a high speed despite having a low voltage even if it has a multilayer structure.

When a DC voltage is applied between the high conductivity member of the display medium and the common electrode, and when the voltage of the external circuit is sufficiently smaller than that of the display medium, the applied voltage is immediately applied to the microcapsules. Is done. Thereafter, when the application of the voltage is immediately terminated, that is, when the resistance of the electrode array is infinite or sufficiently large with respect to the display medium, the voltage is attenuated by the time constant of τ _b0 . By making τ _b0 longer than the time required for writing, the electrophoretic particles in the microcapsules can be moved at the effective time of τ _b0 and writing can be performed at high speed. Therefore, X ≦
It is particularly preferable in ensuring a sufficient voltage action time is 4.tau _b0 or Y ≦ 4.tau _b0. The same thing is described in a part of Japanese Patent Application Laid-Open No. 4-86784 in a display device that performs writing by an ion flow method.

However, in a display medium having a paper-like shape as in the present invention and separable from a writing device, X ≦ ε _b0 / σ without providing a high conductivity member.
_{Even if b0} or Y ≦ ε _b0 / σ _b0 , it is difficult to increase the effective time applied to the microcapsules. This is because, when the electrode array contacts the relatively low-conductivity member 6 of the display medium to perform writing, at least a part of the electrode array is substantially slightly pressed to the display medium. Contact is maintained somewhere on the surface of the electrode array and display medium. For this reason, even if a voltage is applied by the drive IC of the electrode array and then the voltage is turned off, the surface of the display medium becomes a continuous dielectric material having a low conductivity, and the electric charge stays in the portion where the voltage is applied to the electrode array. Instead, a part thereof is dragged by the electrode array, which is a conductor, and moves so as to lower its potential. This is similar to the phenomenon of shorting another capacitor at a different location. However, since the high-conductivity member of the present invention can have a role as a conductor electrode when the display medium is a capacitor, the switch is suddenly switched at the moment when the electrode array comes into contact with the high-conductivity member. Is opened, and the charge as a capacitor of the display medium can be held as it is. However, since there is a possibility that an adjacent high conductivity member is short-circuited by the electrode array, it is necessary to appropriately design the interval between the high conductivity members and the size of the electrode array.

There are two ways to increase τ _b0 , namely, to increase ε _b0 and to decrease σ _b0. However, ε _b0 is limited to the range of 2 to 4 in many organic materials. Therefore, it is preferable to reduce σ _b0 . Specifically, when 10 ppm is written at 400 dpi, the time required for one dot is 2.5 ms. To set a time constant longer than this, the relative dielectric constant of the dispersion medium of the microcapsule must be 2.82. Σ _c = 1.0
It is preferable that the concentration be not more than × 10 ⁻⁸ (S / cm). Further, the time constant is preferably set to a time sufficient for the electrophoretic particles to move, and although depending on the mobility of the electrophoretic particles, the mobility is μ = 4.0 × 10 ⁻¹⁰ (m × m / V × s)
Assuming that 20 V is applied, when a microcapsule of s = 30 μm is used, the voltage application time is t = s
^{Since 2} / V / μ = 113 ms is required, τ _min = 2 × t
Σ _cmin = (2.5 / (2 × 112)) ×
1.0 × 10 ⁻⁸ = approximately 1.0 × 10 ⁻¹⁰ (S / cm), and therefore it is preferable that σ _c = 1.0 × 10 ⁻⁸ (S / cm) or less. These naturally change depending on the voltage application conditions and the like. In practice, the time constant τ of the microcapsule is
Although τ _b0 has a large influence, it is not determined by this alone, so that it is also affected by the shape and material of the microcapsule, the conductivity and dielectric constant of the binder, the structure, the thickness, and the like. Therefore, it is preferable to design these optimally. In addition, in order to remove an adverse effect due to the charge remaining for a long time, it can be easily eliminated by providing means such as a charge removing roller, a blade, and a brush.

Next, another embodiment of the present invention will be described below with reference to FIG. 4 (Claim 2). FIG. 4 shows a state where a voltage is applied to the display medium of FIG. FIG. In FIG.
a is the case where the shape of the high conductivity member is substantially rectangular and the corner is a right angle. This right angle is a radius of curvature of 1 μm within a range that can be normally confirmed as a right angle by optical microscope observation.
Indicates an arc or chamfered shape corresponding to less than. 35b
Is a schematic diagram of a region where the visual recognition state has changed when a voltage is applied to 34a. 34b is a case where the rectangular corner of the high-conductivity member has a radius of curvature of 1/24 of its short side, and 35b is a schematic diagram of a region where the visual state has changed when a voltage is applied to this 34a. . Similarly, 34
c, 34d, and 34e are cases where the rectangular corners of the high-conductivity member have radii of curvature of 1/12, 1/6, and 1/4 of their short sides, and 35c, 35d, and 35e represent voltages corresponding thereto. FIG. 4 is a schematic diagram of a region where the visual recognition state has changed when is applied.

As shown in FIG. 4, when the shape of the electrode is rectangular and the corner is substantially a right angle, the electric field is concentrated on the corner. In other words, the electric field strength is specifically increased only at the corners, and the electrophoretic particles are electrophoresed and aggregated in the vicinity of the corners, so that the visible state changes to an extra area compared to the original electrode shape. I will. Furthermore, since the electric field intensity in this part is larger than that in the other parts, the cycle characteristics of this part are easily deteriorated, and the reliability of the display quality is also lowered. However, by making the corners of the rectangle slightly curved as in the case of 34b, it is possible to reduce the portion of the region in which the visual state is changed as in the case of 35b, which is extra than the original shape. Further, since the portion where the electric field intensity is unusually large can be eliminated, the cycle characteristics of the peripheral portion are improved, and the background stain is reduced. However, as the curvatures of the corners 34c, d, and e are increased, the area in which the viewing state is changed correspondingly changes the original shape, and the corners are rounded. For this reason, depending on the distance between the high-conductivity materials, if the curvature is larger than 1/4 of the short side of the rectangle, the cycle characteristics are improved, but the region that changes the visibility state becomes conspicuous, and the contrast is increased. Therefore, it is preferable to have a corner having a curvature of 1/4 or less and a substantially non-perpendicular angle with respect to the short side of the rectangle.

The corners of the high conductivity member need not be perfect arcs but may be any shape that reduces the concentration of the electric field, and may be elliptic curves, hyperbolas, trigonometric curves, quadratic curves, or higher-order curves. May be replaced with a right angle by a plurality of straight lines having a chamfered shape.

As described above, the high-conductivity member is substantially rectangular, and the four corners of the rectangle are smaller than the curvature having a radius equal to one-fourth of the length of the short side of the rectangle, or a curved shape having a smaller radius. Has a chamfered shape corresponding to that, it is possible to reduce the area where the viewing state changes near the corner due to the electric field concentration, and it is possible to increase the resolution of the display medium and at the same time to improve the reliability due to the high electric field. Can also be reduced.

Next, another embodiment of the present invention will be described below with reference to FIGS. 5 and 6 (claims 4 and 5). FIG. 5 shows an example corresponding to the display medium of FIG. FIG. FIG. 6 is an equivalent circuit diagram in the case of the configuration corresponding to FIG. In FIG. 5, reference numeral 31 denotes a high conductivity member formed by applying a conductive paint, and 36 denotes an overcoat layer formed of a low conductivity member. 1, 2, 3, 4, 5, and 6 are shown in FIG.
It has the same name as. In FIG. 6, R (ITO)
Is the resistance of the high conductivity portion, R (OC) is the resistance of the overcoat (OC) layer, C (OC) is the corresponding capacitance, and R (vis) is the layer (vi) whose visual state changes.
s) and C (vis) is the corresponding capacitance. Although the common electrode on the lower surface actually has some resistance, the equivalent circuit is approximated on the assumption that it is generally sufficiently smaller than R (OC) and R (vis). Furthermore, when a material that changes the visibility is encapsulated in the microcapsule,
Although its substantial length differs depending on the position with respect to the microcapsule, this is approximated by the diameter of the central position which is the maximum length. It is assumed that the thickness of the microcapsule portion of the layer 6 whose main purpose is planarization is smaller than that of the others.

In FIG. 5 and FIG.
When an overcoat layer is provided between the electrode array and the common electrode 1 other than the microcapsules, the voltage applied between the electrode array and the common electrode 1 is divided into respective members. At this time, when the electric conductivity of the high-conductivity member 31 is sufficiently large as compared with the lower portion as in the present invention, the resistance R (ITO) of the high-conductivity member is approximately good even if it is ignored. It becomes an equivalent circuit composed of a layer and a microcapsule layer. At this time, when the voltage V is applied to the whole, the voltage V (vis) applied to the microcapsule is:
It changes with respect to time t as follows. V (vis) = V × (R (vis) / (R (vis) +
R (OC))) × (1-A × e ^B ), where τ = R (vis) × R (OC) (C (vis)
+ C (OC)) / (R (vis) + R (OC)) A = (τ−R (OC) × C (OC)) / τ B = −t / τ Therefore, at t = 0, V (vis ) = V × (C (O
C) / (C (vis) + C (OC)), and at t = ∞, V (vis) = V × (R (vis) / (R (vi)
s) + R (OC))).

On the other hand, the resistance R is inversely proportional to the conductivity σ and proportional to the layer thickness D. The capacitance C is proportional to the dielectric constant ε,
It is inversely proportional to the layer thickness D. Considering these, at t = 0, V (vis) = V × (C (OC) / (C (vis)
+ C (OC)), and at t = ∞, V (vis) = V
× (R (vis) / (R (vis) + R (OC))). As the conductivity σ, the dielectric constant ε, and the thickness D, the subscripts as the display medium and the overcoat layer are (vis), respectively.
(OC), and K and K ′ are constants, and the following expression is obtained. At t = 0, V (vis) = K × V × ((D (OC) /
ε (OC)) / (D (vis) / ε (vis) + D
(OC) / ε (OC))) At t = ∞, V (vis) = K ′ × V × ((D (vi
s) / σ (vis)) / ((D (vis) / σ (vi
s) + (D (OC) / σ (OC)))

Now, let the dielectric constant of the portion where the visual recognition state changes be ε
and _b0, the conductivity and sigma _b0, a thickness D _{b 0,} the conductivity of the portion disposed at the bottom of the high conductivity member and epsilon _bx, the conductivity sigma _bx, the thickness and D _bx. At this time,
When writing is performed in a time smaller than the time constant, the above-mentioned capacity mainly has a large effect. At this time, ε _b0 /
By setting D _b0 ≦ ε _bx / D _bx , the applied voltage V
Can be applied to the microcapsule, and the voltage utilization efficiency can be increased to 50% or more.

When writing is performed in a time smaller than the time constant, the above-described resistance mainly has a large effect.
By setting σ _b0 / D _b0 ≧ σ _bx / D _bx , a voltage equal to or more than _の of the applied voltage can be applied to the microcapsule, and the voltage use efficiency can be increased to 50% or more. However, if the writing method mainly depends on one of the phenomena, it is sufficient to hold for at least one of the phenomena. For example, when a DC pulse voltage of 5 ms is applied to a display medium having a time constant of 300 ms, it is sufficient to satisfy only the relational expression based on the dielectric constant and the thickness. Even when a direct current is applied for 100 ms, the effective formula to be satisfied differs between the case where the direct current is applied and the case where the pulse is applied.

In general, materials that operate with a DC voltage can be classified into those that can operate with an AC voltage and those that can only operate with a DC voltage. A twisted nematic liquid crystal material is an example of a material that can operate even with an alternating current, and a display using electrophoretic particles is an example of a material that can operate only with a direct current. However, even a device that can operate only with this DC voltage can be operated by applying a DC pulse. When the applied voltage of one or more DC pulses is made smaller than the time constant, it is preferable to satisfy the relationship of σ _b0 / D _b0 ≧ σ _bx / D _{b x} described above.

Further, these may be satisfied at the same time. When the above conditions are satisfied at the same time, a display medium which does not depend on the writing method, the time, or the time constant of the display medium determined by the material or configuration can be manufactured. For this reason, it is possible to provide writing compatible with different types of writing devices and different types of display media. In addition, since a voltage is applied to a material whose viewing state changes efficiently, the response speed can be increased, the writing speed can be increased, and the voltage can be reduced.

In these cases, a material other than the microcapsules, which changes the visual state, may be used. And the relationship between them and other layers is important. An object whose thickness varies depending on the position, such as a microcapsule, must satisfy at least one of the average thickness, the maximum thickness, and the minimum thickness. This is the same for the thicknesses of the other layers.

In the case of having a multilayer structure, it is necessary that at least each of the layers be satisfied.
If even one does not hold, the voltage application efficiency will be lower than 50%, and it will be necessary to reduce the writing speed or increase the driving voltage. However, among these layers, the σ _bx of the high conductivity layer or the like as an intermediate layer for applications such as the above-mentioned high conductivity member or shield, etc.
When there is a layer having a conductivity of ≦ 1.0 × 10 ⁻⁴ (S / cm), the above equation, particularly the equation of the dielectric constant, does not need to be satisfied for this layer.

Further, in the case of having a multilayer structure (x is an integer, 0 <x ≦ n), σ _bx ≦ 1.0 × 10 ⁻⁴ (S / c
For all x in case m), σ _b0 / D _b0 ≧ Σ
σ _{b x} / D _bx or 1 / (ε _b0 / D _b0 ) ≧ Σ (1 /
By _satisfying ε _bx / D _bx ), writing on the display medium can be performed at a higher speed (claim 5). Here, Σ indicates the sum of the values.

This is because when all the layers are RC equivalent circuits, after a time sufficiently larger than the time constant,
By satisfying σ _b0 / D _b0 ≧ Σσ _bx / D _bx , the entire voltage utilization efficiency can be made 50% or more. Also, during a time smaller than the time constant, 1 / (ε
By satisfying _b0 / _Db0 ) ≧ Σ (1 / _εbx / _Dbx ), the overall voltage utilization efficiency can be increased to 50% or more.

As a result, the action of the voltage can be efficiently applied to the material whose visual state changes, so that the image information can be displayed on the display medium at a relatively low voltage at a higher speed than when the conditions for each layer are satisfied. Can be applied.

Further, according to the present invention, by providing means for changing the contact state between the electrode of the writing device for applying a voltage or a current capable of coming into contact with the display portion and the display portion, contact, non-contact, and By changing the contact pressure in the contact state according to the state of the action of the voltage or current, it is possible to instantaneously open the circuit between the high conductivity member and the electrode and at the same time physically move away from it. Reduces crosstalk and effective voltage reduction due to leakage, charge transfer, electric field leakage, etc. due to contact with a low conductivity member or a high conductivity member of an adjacent display pixel. Data can be written by the array and the low-voltage drive circuit. Further, the effective contact area is changed by the pressure change, the contact resistance with the high conductivity member is reduced, and the influence of the current leakage to the periphery can be reduced.

[0080]

EXAMPLES Specific examples of the present invention will be described below.

(Example 1) (Claim 1) A reversibly rewritable display medium was manufactured as follows. 0.5 wt.
% Of a blue dye (Macrolex Blue RR: Bayer AG) dissolved therein, and as an electrophoretic particle, the surface was A
l of titanium dioxide having an average particle size of 0.21 µm (C
R60: Ishihara Sangyo Co., Ltd.) was used. These particles and oleic acid were each used as a dispersion medium in an amount of 15 wt. % And 0.6 wt. % 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, the temperature was raised to 50 ° C., and an aqueous sodium hydroxide solution was added to adjust the pH to 9. 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, a slurry of microcapsules using gelatin as a wall material was obtained. The emulsification conditions were controlled so that the capsule diameter was 30 to 50 μm on average, and further classified to adjust the maximum particle size and the minimum particle size.

A common electrode 2 was formed by using a PET having a thickness of about 12 μm as a substrate 1 and forming an ITO thin film by a sputtering method. On top of this, polyvinyl alcohol 10%
A solution obtained by adding an equal weight of the above microcapsule slurry to an aqueous solution was applied by a blade coater and dried to fix the microcapsules and polyvinyl alcohol in one layer to the common electrode 2. In addition, about 1
An overcoat layer was formed by applying a 0000 Cp low-viscosity, quick-drying two-component epoxy resin (Cemedine Kogyo: 1590) using a blade coater to smooth the surface and improve water resistance. At this time, the epoxy resin was used after removing bubbles during mixing by defoaming treatment in a vacuum. From the experiment of the response speed of the change in the reflectance, the mobility of the titanium oxide particles in the microcapsule was about 4.0 × 1.
0 ^-10 ( ^mxm / Vxs).

Thereafter, an ITO thin film is formed by a sputtering method to form a highly conductive layer on the entire surface.
A highly conductive member was formed by etching into a desired shape with an iron solution. Sputtering of ITO as a material for the highly conductive member could be performed at a low temperature by the following method. Using a normal target made of ITO (indium tin oxide),
Magnetron sputtering was performed. At that time, the substrate was heated at a temperature lower than that of a normal one, and a film could be formed at about 90 degrees or less. As the gas, a mixed gas of argon and oxygen is used, the oxygen concentration is set to 1 to 10%, and the total pressure is set to 1 to 10 mT.
Optimized as orr. The film formation rate was about 3 to 15 Å / s. Further, the conductivity was 1.0 × 10 ⁻⁴ (Ωcm) or more in specific resistance in a state where the film was formed well. By performing such low-temperature film formation, it was possible to prevent deterioration of the characteristics of the material that changes the visibility of the display medium at a high temperature. By changing these film forming conditions, a specific resistance of 1.0 × 10 ⁻⁴ (Ωc
m) Higher conductive layers smaller than those were easily prepared. This specific resistance was measured by a film thickness measurement value of a film thickness masking portion and a sheet resistance measurement device (Mitsubishi Kasei MCP-HT450 type).

In the present embodiment, the high conductivity member made of ITO was etched. However, if the water resistance of the base or the water absorption of water is affected, the blocking layer may be made of any material other than epoxy resin. A display element insulating film such as a low-temperature-formed polyimide coat used for a liquid crystal display element may be used.

First, writing was performed on the charge holding member using a writing device having an electrode array substantially similar to that shown in FIG. 7 on this display medium. However, as a driving IC of the switching circuit 14, a relatively low voltage used for EL display or the like was used, and a voltage that would cause air discharge was not applied. The electrode array 13 has 125
The one in which 200 electrode rods were arranged at a pitch of μm was used. The switching circuit 1 generates a voltage pulse corresponding to an image signal.
After passing through No. 4, a negative voltage of, for example, 100 V was applied as a voltage for supplying a white display to the display medium surface supplied to the electrode array 13 by adjusting the pulse width in accordance with the particle diameter of the microcapsules and other conditions. The average transport speed was substantially equal to 1 / (8 × pulse width time) (mm / s), and step transport was performed for each dot so as to reach this average transport speed. The display screen here is the side where the high-conductivity member is located, and a display medium to which a positive voltage has been applied in advance by a roller electrode so that this side is displayed in blue is used.

The optical density of the written white solid display portion is measured with an optical densitometer (DENSITOMETER TC-
6MC). Since the optical density decreases when a portion that does not become white is present in a solid white portion, it is used as one of indices for indirectly indicating uniformity. The optical density of the initialized blue solid display portion is 9 to 10% in a capsule having an average particle size of 30 μm,
It was 8% for capsules having a uniform particle size of 50 μm. Image uniformity In addition, the image resolution is determined in advance by incorporating various vertical, horizontal, and oblique line and space (L & S), lattice, and kanji characters with a large number of strokes into the check pattern B, and output with a Ricoh monochrome laser printer SP10MarkII. Were visually compared (Reference Example 1), and the resolution evaluation value was determined comprehensively. The resolution is one of the indices indicating the uniformity indirectly because roughness due to unevenness of the image deteriorates the resolution. Table 1 shows the evaluation results.

[0088]

[Table 1]

However, ◎ is a very good evaluation, ○ is good, Δ is normal, and × is bad. More specifically, with respect to the resolution of the main 1L & S, those having a sufficient resolution corresponding to 200 dpi output at an electrophotographic printer level of 600 dpi or more and having a blue line thinning within 1.05 times are excellent. It is. ○ indicates 1.
The blue line is narrow within the range of 05 to 1.2 times,
When the blue line is thinner within 1.5 times, x indicates that the blue line is thinner. Regarding image unevenness, ◎ indicates that the image was substantially uniform and a blue background was not recognized on a white character background. O indicates that a blue display part (blue to intermediate color) is recognized on a white background within 10%, Δ indicates that a blue display part is recognized on a white background within 25%, and X indicates a white background. Is recognized in the blue display area. In addition, the overall evaluation is simply a four-level visual evaluation. However, emphasis was placed on the easiness of discrimination of the text characters actually projected, and a plurality of observers performed a relative visual evaluation within the range of the experiment. . However, if the writing speed is slow, this is taken into account. The writing speed is a slow 2.78 mm / sec in A4 vertical conversion.
In the case of c, it takes about 2 minutes, but 5.56 mm / sec.
In this case, it is a practical value of about 1 minute. The reflectance is rounded off to the first decimal place.

Comparative Example 1 Writing was performed in the same manner as in Example 1 using a display medium similar to that of Example 1 shown in FIG. The evaluation method is the same as in the first embodiment. Table 1 shows the results of these evaluations.

Example 2 A display medium similar to that of Example 1 shown in FIG. 1 was used, but writing was performed in the same manner as in Example 1 using a display medium manufactured by changing the conductivity of the high conductivity member. Was done. The evaluation method is the same as in the first embodiment. In the case of ITO, the conductivity of the high-conductivity member is based on increasing the partial pressure of oxygen during film formation, and σ _a ≧ 1.0 × 10
² (S / cm). In addition, in the range below this, a paint was prepared by mixing conductive particles composed of Sb-doped SnO fine particles and a binder composed of polyvinyl butyral in a solvent, and changing the conductivity by changing the mixing ratio. It was prepared by pattern coating and drying. Although methyl ethyl ketone was used as the solvent, gelatin was not damaged due to protection by the epoxy resin on the surface. Table 2 shows the results of these evaluations.

Comparative Example 2 A display medium was prepared in the same manner as in Example 2, but the conductivity of the high conductivity member was reduced by changing the formulation of the conductive particles and the binder. Produced. The evaluation method is the same as in the first embodiment. Table 2 shows the results of these evaluations.

[Table 2]

(Example 3) A display medium similar to that of Example 1 shown in FIG. 1 except that a binder portion made of a high-conductivity member and an epoxy resin is used as an upper binder and the conductivity is changed. Writing was performed in the same manner as in Example 1 using the medium. The evaluation method is the same as in the first embodiment.
The conductivity of the binder was changed by adding conductive fine particles similar to those used for the high conductivity member to the original binder. Table 3 shows these evaluation results.

Comparative Example 3 A display medium was produced in the same manner as in Example 3. A display medium in which the conductivity of a portion made of an epoxy resin was changed was manufactured. The evaluation method is the same as in the first embodiment. Table 3 shows these evaluation results.

[Table 3]

Embodiment 4 A display medium similar to that of Embodiment 1 shown in FIG. 1 is used, except that the display medium manufactured by changing the conductivity of the peripheral portion of the high conductivity member is used. Writing was performed similarly. The evaluation method is the same as in the first embodiment. As in the case of the high-conductivity member of Example 2, the conductivity of the peripheral portion of the high-conductivity member was prepared by mixing a conductive particle composed of Sb-doped SnO fine particles and a binder composed of polyvinyl butyral in a solvent. Then, the one in which the conductivity was changed by changing the mixing ratio was pattern-coated and dried to produce the same. Table 4 shows the evaluation results. Further, as compared with the following comparative example, the surface step was reduced, so that the touch was smooth and the display medium was more paper-like.

[Table 4]

Comparative Example 4 A display medium was manufactured in the same manner as in Example 2, but the conductivity of the peripheral portion of the high conductivity member was reduced by changing the formulation of the conductive particles and the binder. Produced. The evaluation method is the same as in the first embodiment. Table 4 shows the evaluation results.

(Example 5) (Claim 2) A display medium was manufactured in the same manner as in Example 2, except that the shape of the high conductivity member was changed. The evaluation method is the same as in the first embodiment. Table 5 shows the results of these evaluations. The shape of the high-conductivity member was prepared by changing the curvature of a square and its corners and by chamfering (defining the chamfer length by the length of the oblique side).

Comparative Example 5 A display medium was manufactured in the same manner as in Example 5, except that the shape of the high conductivity member was changed. The evaluation method is the same as in the first embodiment. Table 5 shows the results of these evaluations.

[Table 5]

However, in addition to the visual evaluation at the four standard levels of ◎: extremely good, は: good, Δ: normal, ×: bad, a fine pattern and small point characters were printed for the extremely good ◎.目-and ◎, ＋+ (this −- is slightly inferior, ◎ is average, ◎ + is good and high resolution is evaluated in detail). (Good rank).

Example 6 (Claims 3 and 6) A display medium similar to that of Example 1 shown in FIG. 1, but manufactured by changing the conductivity of the high conductivity member and the dispersion medium in the microcapsule. Writing was performed in the same manner as in Example 1 using a display medium that was not used. However, in practice, a pulse voltage corresponding to the transport speed is applied, and the electrode array and the display medium are applied immediately after the application of the pulse voltage shorter than the time per dot calculated from the transport speed by displacing using a piezo element. Was written in a non-contact state. The evaluation method is the same as in the first embodiment. The conductivity of the dispersion medium in the microcapsule is determined by purifying the dispersion medium, tetrachloroethylene and oleic acid, removing the impurities by vacuum drying and dehydrating the titanium oxide and pigment to remove the impurities, and at the same time, reducing the conductivity of the original dispersion medium. Was prepared by mixing a small amount of a solution composed of propylene carbonate having a large dielectric constant and 1M n-butylammonium salt. The conductivity of the dispersion medium in Example 1 was σ = 2.0 × 10 ⁻⁹ (S / cm). Also,
The conductivity was determined from C and R values as a CR equivalent circuit by injecting a mixed dispersion medium into a jig having a narrow gap using an impedance measuring apparatus of Model 1860B manufactured by Solartron. However, with a small amount of propylene carbonate,
The relative dielectric constant of the dispersion medium was almost unchanged at 2.3, as compared with the large change in the conductivity. Table 6 shows the results of these evaluations. However, the linear velocity was 5.56 mm from Example 1.
/ S corresponds to the writing speed required for one dot or one line, 22.5 (ms / dot or line), and the pulse width is almost equal to this value. As a result, the pulse width becomes smaller.

Comparative Example 6 A display medium was produced in the same manner as in Example 6, except that the conductivity of the dispersion medium was reduced by changing the formulation of the dispersion medium. The evaluation method is the same as in the first embodiment. Table 6 shows the results of these evaluations. In addition, the writing method in which the movement by the piezo was substantially stopped and the electrode array was always in contact with the display medium was performed on the same display medium.

[Table 6] However, the write condition of * is that the movement of the piezo is stopped. )

Example 7 A display medium similar to that of Example 1 shown in FIG. 1 and provided with an overcoat layer having a lower conductivity than that of the highly conductive member of Example 1 was used. An evaluation method in which writing is performed in the same manner as in Example 1 is the same as that in Example 1. Table 7 shows the results of these evaluations. The conductivity of the overcoat layer was changed by adding conductive fine particles similar to those used for the high conductivity member to the main material epoxy resin. By controlling the conductivity and controlling the film thickness, a value corresponding to ε _bx / D _bx or σ _bx / D _bx could be adjusted. At this time, (ε _b0 / D _b0 ) /ε=2.3/30×1
0 ⁻⁶ /ε=8.66×10 ¹⁵ , and σ _b0 / D _b0 =
It was fixed at 2.0 × 10 ⁻⁹ / 30 × 10 ⁻⁶ = 6.66 × 10 ⁻⁵ . Here, ε is a vacuum dielectric constant. At this time, D _bx = 45.7 at which ε _bx / D _bx has the same value.
(Μm), and σ _bx = 3.0 × 10 ⁻⁹ where σ _bx / D _bx is the same for the same film thickness. However, since the volume fraction of the epoxy resin itself in the epoxy resin is mainly the epoxy resin, the relative dielectric constant of this layer was calculated as a constant value of 3.5. The actual conductivity of the epoxy resin was prepared in a range considerably larger than σ _bx = 3.0 × 10 ⁻⁹ by mixing conductive fine particles. When the thickness of the epoxy resin is within 100 μm, the flexibility is extremely deteriorated, but the influence of the stress is relatively small, and the epoxy resin can be produced by coating. In addition, writing is performed for 0.5 ms.
It was performed with both a 1 kHz wide DC pulse and a simple constant voltage DC.

[Table 7] Here, “single” indicates a simple constant voltage DC application, and “direct” indicates a DC pulse voltage application. )

(Embodiment 8) A display medium similar to that of Embodiment 7 shown in FIG. An evaluation method in which writing was performed on the medium in the same manner as in the seventh embodiment is the same as that in the first embodiment. Table 7 shows the results of these evaluations. The undercoat layer was produced in the same manner as the overcoat layer. The sum of ε _bx / D _bx of the undercoat layer and the overcoat layer was set to Σ (ε _bx / D _bx ), and similarly, the total sum of σ _bx / D _bx was set to Σ (σ _bx / D _bx ).

[Table 8]

[0104]

According to a first aspect of the present invention, at least a part of a member forming the uppermost portion on at least one side of the display portion has a conductivity higher than that of at least one member disposed at a lower portion or a periphery thereof. Since the portion is made of a large material, it is possible to provide a display device which is excellent in uniformity of image quality of the display medium, is excellent in reliability, and can be written by a simple and small device.

The second aspect of the present invention is that the shape of the portion made of the material having high conductivity is substantially rectangular, and the four corners of the rectangle are one quarter of the length of the short side of the rectangle. Since it has a curved shape smaller than a curvature having a length as a radius or a chamfered shape corresponding to the curved shape, it is possible to provide a simple high-resolution display medium of the display medium.

The third aspect of the present invention relates to a dielectric constant of at least one portion disposed under the portion made of a material having a high conductivity and a portion where the visual state is changed is ε _b0.
When the conductivity is σ _b0 and the writing speed of the display medium is X (sec / dot) or Y (sec / line), X ≦ ε _b0 / σ _b0 or Y ≦ ε _b0 / σ _{b0 respectively.} Therefore, it is possible to provide a display medium on which image information can be written more quickly and more easily.

Further, in the present invention, it is preferable that the dielectric constant of at least one portion disposed under the portion made of the material having high conductivity and the portion where the visual state is changed be ε _b0 and the conductivity be σ _{b b0,} and a thickness of D _b0, the dielectric constant epsilon _bx of at least one n or less of the other portions is disposed below the portion consisting of a material having a large conductive _rate, the conductivity sigma _bx, a thickness _Dbx (where x
Is an integer, 0 <x ≦ n), σ b x ≦ 1.0 × 10 -4 (S /
cm), σ _b0 / D _b0 ≧
Since σ _bx / D _bx or ε _b0 / D _b0 ≦ ε _bx / D _bx is satisfied, it is possible to provide a display medium which can write image information at a high speed with a relatively low voltage even if it has a multilayer structure. Can be.

Further, in the present invention, it is preferable that the dielectric constant of at least one portion disposed under the portion made of the material having high conductivity and the portion where the visual state changes is ε _b ,
The conductivity is σ _b0 , the thickness is D _b0 , the permittivity of at least one or more and n or less other portions disposed below the portion made of the material having high conductivity is ε _bx , and the conductivity is σ _b0 .
_bx and the thickness is D _bx (where x is an integer,
0 <x ≦ n) and σ _b0 / D _b0 ≧ Σσ _bx for all x in the case of σ _bx ≦ 1.0 × 10 ⁻⁴ (S / cm)
/ D _bx or 1 / (ε _b0 / D _b0 ) ≧ Σ (1 / ε _bx
/ D _bx ) is satisfied, so that it is possible to provide a display medium in which image information can be written at a higher speed with a relatively low voltage even if it has a multilayer structure.

According to a sixth aspect of the present invention, there is provided means for changing the contact state between the electrode of the writing device for applying a voltage or a current capable of coming into contact with the display location and the display location. It is possible to provide a writing device that can easily and quickly write image information on a medium.

According to the present invention, when the conductivity of a portion made of a material having a high conductivity is σ _a , σ _a ≧ 1.
By setting it to 0 × 10 ⁻⁴ (S / cm), a display medium with more excellent image quality uniformity can be provided.

According to the present invention, assuming that the conductivity of at least one portion disposed below the portion made of a material having a high conductivity is σ _b , σ _b ≦ 1.0 × 10 ⁻¹⁰
(S / cm) makes it possible to provide a more reliable display medium.

Further, according to the present invention, assuming that the conductivity of at least one portion disposed around the portion made of the material having high conductivity is σ _c , σ _c ≦ 1.0 × 10 ⁻⁶ (S
/ Cm), a higher resolution display medium can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a display medium according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of the display medium of FIG. 1 as viewed from above.

FIG. 3 is a cross-sectional view illustrating a display medium that is another embodiment of the present invention.

FIG. 4 is a schematic view from the top showing a state where a voltage is applied to the display medium of FIG. 1 to perform writing;

FIG. 5 is a cross-sectional view showing a display medium that is another embodiment of the present invention.

FIG. 6 is an equivalent circuit diagram in the case of a configuration corresponding to FIG.

FIG. 7 is a diagram showing a writing device according to one of the embodiments filed in a patent application separate from the present application.

FIG. 8 is a diagram showing a display medium in one of the embodiments filed in a patent application separate from the present application.

FIG. 9 is a diagram showing a display device according to a principle similar to that of the display medium of the present invention, which has been filed with a patent separately from the present application.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Common electrode 3 Microcapsule 4 Dispersion liquid 5 Binder material 6 Coating layer 31 High-conductivity member 32 The area where the state of visibility from the upper surface changed 33 Low-conductivity member

Claims (6)

[Claims] 1. A member that forms the uppermost part on at least one side of a display portion in a display medium having a planar portion having a display portion whose visual state can be changed by applying a voltage or a current. Is a portion made of a material having a higher conductivity than at least one member disposed at a lower portion and a periphery thereof, and the portion made of the material having a higher conductivity is a driving means for applying a voltage or a current. A display medium characterized by being separable from a display medium. 2. The shape of a portion made of a material having a high conductivity is substantially rectangular, and each of the four corners of the rectangle has a radius whose length is a quarter of the length of a short side of the rectangle. The display medium according to claim 1, wherein the display medium has a smaller curved shape or a chamfered shape corresponding to the smaller curved shape. 3. Under the portion made of a material having high conductivity.
At least one part located in the
The permittivity of the changing part is ε_b0, Conductivity σ _b0,
X (sec / dot) or Y (sec / l)
ine), X ≦ ε_b0/ Σ_b0Or Y ≦ ε
_b0/ Σ_b03. The method according to claim 1, wherein
Display medium according to the description. 4. Under the portion made of a material having a high conductivity.
At least one part located in the
The permittivity of the changing part is ε_b0, Conductivity σ _b0,thickness
D_b0And the lower part of the portion made of a material having a high conductivity.
At least one and no more than n other parts arranged in
The dielectric constant of ε_bx, Conductivity σ_bx, Thickness D_bxWhen
(Where x is an integer, 0 <x ≦ n), σ_bx
≦ 1.0 × 10⁻⁴(S / cm) for all x
On the other hand, σ_b0/ D_b0≧ σ_{b x}/ D_bxOr ε_b0/
D_b0≤ε_bx/ D_bxIs characterized by the fact that
The display medium according to any one of claims 1 to 3. 5. The dielectric constant ε _b , the conductivity σ _{b 0} , and the thickness D of at least one portion disposed below the portion made of a material having a high conductivity and a portion where the visibility state changes.
_b0 , the dielectric constant of at least one or more and n or less other parts arranged below the portion made of the material having high conductivity is ε _bx , the conductivity is σ _bx , and the thickness is D _bx (Where x is an integer, 0 <x ≦ n), σ _bx ≦
For all x in the case of 1.0 × 10 ⁻⁴ (S / cm), σ _b0 / D _b0 ≧ Σσ _bx / D _bx or 1 / (ε
The display medium according to claim 1, wherein _b0 / _Db0 ) ≧ Σ (1 / _εbx / _Dbx ) is satisfied. 6. A writing device having driving means for applying a voltage or a current to a display portion of a display medium according to any one of claims 1 to 5, wherein the writing device comprises:
A writing device comprising: an electrode for applying a voltage or a current capable of coming into contact with a display portion; and means for changing a contact state between the electrode and the display portion.