JP2003322880A - Image display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display which is of a dry type having a fast response performance, of a simple structure, inexpensive, and excellent in stability, and is also capable of displaying halftone utilizing the display memory property. <P>SOLUTION: When forming an image desired to display, the image display provided with an image display board for displaying the image by enclosing two kinds of particles having different colors and electrification characteristics, i.e., positively electrified electrons 5 in white and negatively electrified electrons 6 in black between a transparent substrate 1 and a counter substrate 2, and applying an electric field to the particles 5, 6 from electrode pairs constituted of display electrodes 3 arranged on the transparent substrate 1 and the counter electrodes 4 arranged on the counter substrate 2, performs halftone display in which the particles 5, 6 are mixed at a desired ratio by adjusting the electric field strength to be applied across the display electrodes and the counter electrodes according to the display density, and also applies a reset electric field for resetting the mixture state of the particles 5, 6 before the halftone display. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device equipped with an image display plate capable of repeatedly displaying and erasing an image as particles fly and move by utilizing Coulomb's force. In particular, the present invention relates to an image display device adapted to perform halftone display.

[Prior art]

Conventionally, as an image display device replacing liquid crystal (LCD), an image display device using a technique such as an electrophoretic system, an electrochromic system, a thermal system, and a two-color particle rotation system has been proposed.

These conventional techniques, when compared with LCDs,
It is considered as a technology that can be used for next-generation inexpensive image display devices because it has advantages such as a wide viewing angle similar to ordinary printed matter, low power consumption, and memory function. It is expected to be applied to image display for mobile terminals and electronic paper. In particular, recently, an electrophoretic method (for example, see Non-Patent Document 1) in which a dispersion liquid composed of dispersed particles and a coloring solution is microencapsulated and the microcapsules are arranged between opposed substrates has been proposed and expected. There is.

However, in the electrophoretic method, there is a problem that the response speed becomes slow due to the viscous resistance of the liquid because the particles migrate in the liquid. Furthermore, since particles of high specific gravity such as titanium oxide are dispersed in a solution of low specific gravity, they tend to settle, and it is difficult to maintain the stability of the dispersed state, and there is a problem of lacking image repeatability stability. . Further, even in the case of microencapsulation, the cell size is set to the microcapsule level to make it difficult for the above-mentioned defects to appear, and no essential problem has been solved.

On the other hand, in contrast to the electrophoretic method utilizing the behavior in a solution, a method in which the conductive particles and the charge transport layer are incorporated in a part of the substrate without using the solution has begun to be proposed.
However, since the structure is complicated by disposing the charge transport layer and further the charge generation layer, it is difficult to constantly inject the charges into the conductive particles, so that there is a problem of lack of stability.

[0006]

[Non-Patent Document 1] Zhao, 3 foreigners, "New Toner Display Device (I)", July 21, 1999,
Annual Meeting of the Imaging Society of Japan (83 times in total) “Japan Hardcop
y'99 ”, p.249-252

[0007]

As a method for solving the above-mentioned various problems, at least one of two transparent substrates has two or more kinds of particles having different colors and different charging characteristics enclosed between them. An image display device including an image display plate that displays an image by applying an electric field to the particles from an electrode pair formed of electrodes provided on one or both of the substrates and causing the particles to fly and move by Coulomb force is known. There is.

This image display device has a display memory property (a property of retaining the display state before power-off even after the power is turned off), but such an image display device having a display memory property is used. In this case, Ea, which is the direction (polarity) of the electric field in which the particle A flies to the display substrate side, and Eb, in which the particle B having a different color and charging characteristic from the particle A flies to the display substrate side, are sequentially switched. It is necessary to form one image. Therefore, when displaying a halftone by this image display device, the particle A / particle B is repeatedly displayed by applying the electric fields Ea and Eb at a frequency at which the eyes do not feel flicker. By adjusting the display time ratio of the particles B, an intermediate color display can be obtained. However, in the halftone display by this method, there is a problem that the characteristic of the image display device, which is the display memory property, cannot be utilized.

The present invention has been made by paying attention to the above-mentioned problems. It is a dry type, has a quick response performance, has a simple structure, is inexpensive and has excellent stability, and can display a halftone while utilizing a display memory property. An image display device is provided.

[0010]

In order to achieve the above object, the image display device of the present invention has two or more kinds of particles having different colors and different charging characteristics enclosed between at least two transparent substrates. An image display device comprising an image display plate for displaying an image by applying an electric field to the particles from an electrode pair formed of electrodes provided on one or both of the substrates and causing the particles to fly and move by Coulomb force. When the image to be displayed is formed, at least one of the strength of the electric field applied between the electrodes, the application time, and the number of times of application is adjusted according to the display density, so that the two or more types of particles are desired. It is characterized in that a display state mixed in a ratio is obtained.

In the image display device of the present invention having the above-described structure, a novel image display device is provided in which image display elements capable of directly applying an electrostatic field to particles and causing the particles to fly and move by Coulomb force are arranged in a matrix. By configuring the above, it is possible to provide an image display device which is dry, has a high response speed, has a simple structure, is inexpensive, and is excellent in stability. Further, as a method for displaying a halftone, instead of using the repeated display of particles A / particles B, at least one of the strength of the electric field applied between the electrodes forming the electrode pair, the application time, and the number of times of application is displayed. The method of obtaining a display state in which the two or more kinds of particles are mixed in a desired ratio by using the above method is used, so that it is possible to display a halftone while utilizing the display memory property.

In the image display device of the present invention, prior to an electric field application process for obtaining a display state in which two or more kinds of particles are mixed in a desired ratio, a reset for resetting the states of the two or more kinds of particles. The electric field is applied by resetting the states of the two or more kinds of particles once prior to the display of the halftone, thereby eliminating the influence of the display state before the halftone display is performed. It is preferable for realizing halftone display with good reproducibility.

Further, in the image display device of the present invention, the reset electric field is an alternating electric field. However, when the particles A and the particles B constituting the two or more kinds of particles fly between the electrodes, the reset electric field is not formed. Since it is possible to create a desired state in which the interaction is minimized, it is preferable for realizing the mixed state of the particles A / particles B by the subsequent voltage application with even higher reproducibility. Further, in the image display device of the present invention, the reset electric field is a pulse electric field,
If there is a limit to the frame scanning time when displaying a moving image,
It is preferable to obtain a desired reset state in a short time by applying a pulse of a reset electric field sufficient for all particles to fly.

The particles in the image display device of the present invention preferably have an average particle diameter of 0.1 to 50 μm. Further, it is preferable that the surface charge density measured by a blow-off method using a carrier of said particles is 5 [mu] C / m ² or more 150μC / m ² or less in absolute value. In addition, when the particles are charged with a voltage of 8 KV to generate a corona discharge in a corona discharger arranged at a distance of 1 mm from the surface, the surface potential after 0.3 seconds is charged. It is preferred that the particles have a maximum value of more than 300V. Further, it is preferable that the color of the particles is white or black. Further, the image display plate in the image display device of the present invention is preferably an image display plate having one or more image display elements in which each electrode pair of the matrix electrodes is separated from each other by a partition wall.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram for explaining an example of an image display element of an image display plate which constitutes an image display device of the present invention and a display driving principle thereof.
In the example shown in (c), 1 is a transparent substrate, 2 is a counter substrate, 3 is a display electrode (transparent electrode), 4 is a counter electrode, 5 is negatively charged particles, 6 is positively charged particles, and 7 is a partition.

FIG. 1A shows a state in which negatively charged particles 5 and positively charged particles 6 are arranged between opposed substrates (transparent substrate 1 and opposed substrate 2). When a voltage is applied to this state such that the display electrode 3 side has a low potential and the counter electrode 4 side has a high potential, as shown in FIG. 1B, the Coulomb force causes the positively charged particles 6 to move to the display electrode 3 side. And the negatively charged particles 5 fly to the counter electrode 4 side. in this case,
When viewed from the transparent substrate 1 side, the display surface looks like the color of the positively charged particles 6. Next, by switching the potentials and applying a voltage so that the display electrode 3 side has a high potential and the counter electrode 4 side has a low potential, the negatively charged particles 5 are displayed by the Coulomb force as shown in FIG. The positively charged particles 6 fly to the electrode 3 side, and fly to the counter electrode 4 side. In this case, the display surface when viewed from the transparent substrate 1 side looks like the color of the negatively charged particles 5.

Between FIG. 1 (b) and FIG. 1 (c), display can be repeated by simply inverting the potential of the power source.
By reversing the potential of the power supply in this way, the color can be reversibly changed. The color of the particles can be chosen at will. For example, the negatively charged particles 5 may be white and the positively charged particles 6 may be black, or the negatively charged particles 5 may be black and the positively charged particles 6 may be black.
Is white, the display is a reversible display between white and black. In this method, once the display is performed, each particle is attached to the electrode by the image force, so that the display image is retained for a long time even after the voltage application is stopped, and the memory retention property is good.

In the present invention, since each charged particle flies in gas, the response speed of image display is fast, and the response speed is 1 ms.
It can be ec or less. Moreover, unlike a liquid crystal display element, an alignment film, a polarizing plate, etc. are not required, and the structure is simple, and the cost and the area can be increased. It is stable against temperature changes and can be used from low temperatures to high temperatures.
Furthermore, it has no viewing angle, has high reflectance, is a reflective type, and is easy to see even in a bright place, and has low power consumption. Since it also has a memory property, it does not consume power when holding an image.

The image display device of the present invention comprises an image display plate in which the above image display elements are arranged in a matrix. 2A and 2B show an example of the schematic diagram.
In this example, a 3 × 3 matrix is shown for convenience of explanation.
By setting the number of each electrode to be n, an arbitrary n × n matrix can be constructed.

In the example shown in FIGS. 2A and 2B, the display electrodes 3-1 to 3-3 arranged substantially parallel to each other and the counter electrodes 4-1 to 4-3 arranged substantially parallel to each other are as follows. They are provided on the transparent substrate 1 and the counter substrate 2 so as to be substantially orthogonal to each other. The voltage selection device 13 is connected to each of the display electrodes 3-1 to 3-3. Similarly, the voltage selection device 13 is connected to each of the counter electrodes 4-1 to 4-3.

Voltage selection device 13 connected to the display electrode side
Respectively, the high voltage from the high voltage generation circuit 8, the low voltage from the low voltage generation circuit 9, and the reset voltage generation circuit 1
It has a function of selectively applying one voltage from the reset voltage from 1 and the inverted reset voltage inverted by passing through the inverter 12 to the display electrodes 3-1 to 3-3. Further, each of the voltage selection devices 13 connected to the counter electrode side has a reset voltage from the reset voltage generation circuit 11 and a plurality of gradations (for example, the same number as the desired gradation number) from the gradation voltage generation device 14. It has a function of selectively applying one voltage from the voltage to the counter electrodes 4-1 to 4-3. The entire voltage selection device 13 constitutes the matrix drive circuit 10. In this example, the partition 7 separates each other to form 3 × 3 image display elements, but the partition 7 is not essential and can be omitted.

In the drive control for the matrix electrodes composed of the display electrodes 3-1 to 3-3 and the counter electrodes 4-1 to 4-3, each is controlled by a sequencer (not shown) according to the image to be displayed. An operation of controlling the operation of the voltage selection device 13 and sequentially displaying 3 × 3 image display elements is executed. This operation basically performs almost the same image display operation as that conventionally known,
In the present invention, in addition to that, an operation for halftone display (gradation display) and a particle state reset operation prior to the halftone display are performed (these operations will be described in detail later).

In the case of display electrodes provided on a transparent substrate, each of the electrodes forming the matrix electrode is formed of a transparent and patternable conductive material. As such a conductive material, a metal such as aluminum, silver, nickel, copper, gold or a transparent conductive metal oxide such as ITO, conductive tin oxide, conductive zinc oxide or the like is formed by a sputtering method, a vacuum deposition method, a CVD method, A thin film formed by a coating method or the like, or a conductive agent mixed with a solvent or a synthetic resin binder and applied is used.

Examples of the conductive agent include cationic polymer electrolytes such as benzyltrimethylammonium chloride and tetrabutylammonium perchlorate, anionic polymer electrolytes such as polystyrene sulfonate and polyacrylate, conductive zinc oxide, and oxides. Tin, indium oxide fine powder or the like is used. The thickness of the electrode may be any thickness as long as the conductivity can be secured and the light transmittance is not hindered, but the thickness is preferably 3 to 1000 nm, and more preferably 5 to 400 nm. On the counter substrate, a transparent electrode material may be used similarly to the display electrode, but aluminum,
Non-transparent electrode materials such as silver, nickel, copper and gold can also be used.

It is preferable to form an insulative coating layer on each electrode so that the charges of the charged particles do not escape.
The coat layer is a resin that is positively charged for negatively charged particles,
It is particularly preferable to use a negatively chargeable resin for the positively charged particles because the charge of the particles is difficult to escape.

The substrate used in the image display device of the present invention will be described below. At least one of the substrates is a transparent substrate in which the color of the particles can be confirmed from the outside of the device, and a material having a high visible light transmittance and good heat resistance is suitable. The presence or absence of flexibility is appropriately selected depending on the application, and for example, a flexible material is suitable for applications such as electronic paper, mobile phones,
Inflexible materials are suitable for applications such as displays for portable devices such as PDAs and notebook computers.

Examples of the material of the substrate include polymer sheets such as polyethylene terephthalate, polyether sulfone, polyethylene, polycarbonate, polyimide and acrylic, and inorganic sheets such as glass and quartz. The opposite substrate may be transparent or opaque. The thickness of the substrate is preferably 2 to 5000 μm, particularly 5 to 100 μm.
0 μm is preferred. If the thickness is too thin, it becomes difficult to maintain the strength and the uniformity of the spacing between the substrates, and if the thickness is too thick, the sharpness as a display function and the decrease in contrast occur,
In particular, it lacks flexibility in electronic paper applications.

Further, as shown in FIG. 2 (a), it is preferable to provide partition walls 7 on the four circumferences of each display element. The partition walls can be provided in two directions parallel to each other. As a result, excessive movement of particles in the direction parallel to the substrate can be prevented, durability repeatability and memory retention can be assisted, and the distance between the substrates can be made uniform and reinforced to increase the strength of the image display plate. The method for forming the partition wall is not particularly limited, but, for example,
After the screen printing method in which the paste is applied repeatedly at a predetermined position using a screen plate, or after the partition material having a desired thickness is solidly coated on the substrate, and only the portion to be left as the partition is coated with the resist pattern on the partition material. , A sandblasting method in which a blasting material is sprayed to remove the partitioning material other than the partitioning material, and a lift-off method in which a resist pattern is formed on a substrate by using a photosensitive resin and the resist is removed after the paste is embedded in the resist recesses. (Additive method), a photosensitive resin composition containing a partition material is applied on a substrate, and a photosensitive paste method for obtaining a desired pattern by exposure and development, or a paste containing a partition material is applied on a substrate. After that, various methods such as a mold forming method of forming partition walls by pressure-bonding / press-molding a mold having irregularities are adopted. further,
A relief embossing method in which a relief pattern formed by applying a mold forming method and using a photosensitive resin composition as a mold is used is also adopted.

The particles used in the image display device of the present invention will be described below. In the present invention, the particles for display may be negatively charged or positively charged colored particles and may be any particles that fly and move by Coulomb force, but spherical particles having a small specific gravity are particularly preferable. The average particle size of the particles is preferably 0.1 to 50 μm, and particularly preferably 1 to 30 μm. When the particle size is smaller than this range, the charge density of the particles is too large and the image force on the electrode or the substrate is too strong, and the memory property is good, but the followability when the electric field is reversed becomes poor. On the contrary, if the particle size is larger than this range, the followability is good, but the memory property is poor.

The method of negatively or positively charging the particles is not particularly limited, but a method of charging the particles such as a corona discharge method, an electrode injection method, or a friction method is used. It is preferable that the surface charge density measured by a blow-off method using a carrier of particles is 5 [mu] C / m ² or more 150μC / m ² or less in absolute value. When the absolute value of the surface charge density is lower than this range, the response speed to changes in the electric field becomes slow and the memory property also becomes low. When the absolute value of the surface charge density is higher than this range, the image force on the electrode or the substrate is too strong, and the memory property is good, but the followability when the electric field is reversed becomes poor. As used in the present invention, necessary for determining the surface charge density,
The charge amount and the particle specific gravity were measured as follows. <Blow-off measurement principle and measurement method> In the blow-off method, a mixture of powder and carrier is placed in a cylindrical container having meshes at both ends, and high-pressure gas is blown from one end to separate the powder and carrier from each other. Blow off (blow off) only the powder from the opening. At this time, the same amount of charge that the powder carried out of the container and the opposite amount of charge remains on the carrier. Then, all of the electric flux due to this electric charge is collected in the Faraday cage, and the capacitor is charged by this amount.
Therefore, by measuring the potential across the capacitor, the charge amount Q of the powder is Q = CV (C; capacitor capacity, V;
The voltage across the capacitor). As a blow-off powder charge amount measuring device, TB-20 made by Toshiba Chemical Co.
0 was used. In the present invention, two types of carriers, positively chargeable and negatively chargeable, were used, and the charge density per unit surface area (unit: μC / m ² ) was measured in each case.
That is, as a positively chargeable carrier (a carrier that makes the other party positively charged and is likely to become negative) F963-2535 manufactured by Powdertech Co., Ltd. As an easy carrier, F921-2535 manufactured by Powder Tech Co. was used. <Particle Specific Gravity Measuring Method> The particle specific gravity was measured with a specific gravity meter manufactured by Shimadzu Corporation and a multi-volume densitometer H1305.

[0031] particles, it is necessary to hold the charge, volume resistivity is preferably ¹ × 10 1 ⁰ Ω · cm or more insulating particles, in particular volume resistivity of 1 × 10 ¹² Ω
-Insulating particles of cm or more are preferable. Further, particles having a low charge decay property evaluated by the method described below are more preferable.

That is, the particles are separately formed into a film having a thickness of 5 to 100 μm by pressing, heat melting, casting or the like. Then, a voltage of 8 KV is applied to a corona discharger arranged at a distance of 1 mm from the film surface to generate corona discharge to charge the surface, and the change in the surface potential is measured and judged. In this case, it is important to select and prepare the particle constituent material so that the maximum value of the surface potential after 0.3 seconds is larger than 300V, preferably larger than 400V.

The surface potential is measured, for example, by using FIG.
Can be carried out by the device shown in (CRT2000 manufactured by QEA). In the case of this apparatus, the chuck 21 is provided on both ends of the shaft of the roll having the above-mentioned film arranged on the surface.
, The small scorotron discharger 22 and the surface electrometer 23 are separated from each other by a predetermined distance, and a measuring unit is placed opposite to the surface of the film with a space of 1 mm, and the film is kept stationary. A method of moving the measuring unit from one end of the film to the other end at a constant speed to measure the surface potential while applying the surface charge is suitably adopted. The measurement environment is temperature 25 ± 3
℃ and humidity 55 ± 5RH%.

The particles may be made of any material as long as the charging performance and the like are satisfied. For example, it can be formed from a resin, a charge control agent, a colorant, an inorganic additive, or the like, or a colorant alone or the like.

Examples of the resin include urethane resin, urea resin, acrylic resin, polyester resin, acrylic urethane resin, acrylic urethane silicone resin, acrylic urethane fluororesin, acrylic fluororesin, silicone resin, acrylic silicone resin, epoxy resin, polystyrene. Resins, styrene acrylic resins, polyolefin resins, butyral resins, vinylidene chloride resins, melamine resins, phenol resins, fluororesins, polycarbonate resins, polysulfone resins, polyether resins, polyamide resins and the like, and two or more types may be mixed. it can.
In particular, acrylic urethane resin, acrylic silicone resin, acrylic fluororesin, acrylic urethane silicone resin, acrylic urethane fluororesin, fluororesin, and silicone resin are preferable from the viewpoint of controlling the adhesive force to the substrate.

The charge control agent is not particularly limited,
Examples of negative charge control agents include salicylic acid metal complexes, metal-containing azo dyes, metal-containing (including metal ions and metal atoms).
Oil-soluble dyes, quaternary ammonium salt compounds, calixarene compounds, boron-containing compounds (boric acid benzyl complex), nitroimidazole derivatives and the like. Examples of the positive charge control agent include nigrosine dyes, triphenylmethane compounds, quaternary ammonium salt compounds, polyamine resins, imidazole derivatives and the like. In addition, ultrafine silica, ultrafine titanium oxide, metal oxides such as ultrafine alumina, nitrogen-containing cyclic compounds such as pyridine and their derivatives and salts, various organic pigments, resins containing fluorine, chlorine, nitrogen, etc. are also charged. It can also be used as a control agent.

Examples of the colorant are as shown below.
Various organic or inorganic pigments and dyes of various colors can be used.

Examples of black pigments include carbon black, copper oxide, manganese dioxide, aniline black and activated carbon. Examples of yellow pigments include yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, banza yellow G, banza yellow 10G,
There are benzidine yellow G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, tartrazine lake and the like. Orange pigments include red yellow lead, molybdenum orange, permanent orange GT
R, pyrazolone orange, vulcan orange, induslen brilliant orange RK, benzidine orange G, induslen brilliant orange GK and the like.
Red pigments include red iron oxide, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R,
Examples include resole red, pyrazolone red, watching red, calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, and brilliant carmine 3B.

Examples of purple pigments include manganese purple, fast violet B, and methyl violet lake.
Examples of blue pigments include navy blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated compound, fast sky blue, and indanthrene blue BC. Examples of green pigments include chrome green, chromium oxide, pigment green B, malachite green lake, and final yellow green G. Examples of white pigments include zinc white, titanium oxide, antimony white, and zinc sulfide.

Examples of extender pigments include barite powder, barium carbonate, clay, silica, white carbon, talc, and alumina white. Also, basic, acidic, dispersion,
Examples of various dyes such as direct dyes include nigrosine, methylene blue, rose bengal, quinoline yellow, and ultramarine blue. These colorants can be used alone or in combination. Particularly, carbon black is preferable as the black colorant, and titanium oxide is preferable as the white colorant.

The method for producing the particles is not particularly limited, but, for example, a pulverization method and a polymerization method, which are similar to those for producing an electrophotographic toner, can be used. Further, a method of coating the surface of the powder of the inorganic or organic pigment with a resin, a charge control agent or the like is also used.

The distance between the transparent substrate and the counter substrate should be such that particles can fly and move and the contrast can be maintained.
It is adjusted to 0 to 5000 μm, preferably 30 to 500 μm. The particle filling amount is 1 with respect to the space volume between the substrates.
It is good to fill so as to have a volume of 0 to 90%, preferably 30 to 80%.

In the display plate used in the image display device of the present invention, a plurality of the above-mentioned display elements are used and arranged in a matrix for display. In the case of black and white, one display element becomes one pixel. When displaying an arbitrary color other than black and white, the particle colors may be appropriately combined. In the case of full color, three types of display elements, that is, display elements each having particles of R (red), G (green) and B (blue) and each having black particles are set as one set, and It is preferable to arrange a plurality of sets to form a display plate.

The image display device of the present invention is an image display unit of a mobile device such as a notebook computer, a PDA and a mobile phone.
It is used for electronic papers such as electronic books and electronic newspapers, signboards, posters, bulletin boards such as blackboards, calculators, home electric appliances, image display parts for automobile articles and the like.

Next, the operation for halftone display (gradation display) executed in the image display apparatus according to the embodiment of the present invention and the particle state reset operation prior to the halftone display will be described with reference to FIG. This will be described with reference to (a), (b) and FIG.

FIG. 4A is a diagram for explaining a reset voltage application method for the particle state reset operation prior to the halftone display in the image display device of the present invention.
(B) is a figure for demonstrating the electric field application method for halftone display in the image display apparatus of this invention. Figure 4
In (a) and (b), the horizontal rectangle is the display electrode 3.
The vertical rectangle corresponds to the counter electrode 4, and the intersection of both rectangles corresponds to the image display element. Now, when a voltage Vs is applied from the display electrode side and a voltage Vd1 is applied from the counter electrode side to the image display element at the left end of the uppermost row in the figure, as shown in FIG. A display state is obtained in which particles A and particles B are mixed at a mixing ratio according to the magnitude (electric field strength) of (Vd1-Vs) / g (g: distance between electrodes). Similarly, the voltage V from the display electrode side is applied to the third image display element from the left in the uppermost row in the figure.
When s is applied and a voltage Vd2 is applied from the counter electrode side, the image display element has an electric field (Vd2-Vs) / g.
A display state is obtained in which particles A and particles B are mixed at a mixing ratio according to the size of (g: distance between electrodes) (electric field strength).

Here, for example, when the particles A are black and the particles B are white, the mixing ratio of the particles A and the particles B is 1.
If it is 00: 0, black is displayed as in the case of applying a normal image forming electric field, and the mixing ratio of particles A and particles B is 0: 1.
If it is 00, it is clear that white display is performed as in the case of applying a normal image forming electric field. Therefore, the electric field (Vd1-Vs) /
If the magnitude of g is set to be close to the magnitude of the electric field at the time of displaying black, the image display element at the left end of the uppermost row in the figure will display a halftone close to black. Similarly, the electric field (Vd2-V
If the magnitude of s) / g is set to be close to the magnitude of the electric field at the time of displaying white, the third image display element from the left in the uppermost row in the figure displays a halftone close to white. Therefore, by adjusting the strength of the electric field applied between the display electrode and the counter electrode according to the desired display density, the particles A
It is possible to obtain a display state in which the particles B are mixed in a desired ratio. Note that, as shown in FIG. 4B, the image display element when the 0 electric field is applied to at least one of the electrodes retains the display color before the voltage application.

In the example described above, halftone display is realized by adjusting the strength of the electric field applied between the display electrode and the counter electrode, but the electric field applied between the display electrode and the counter electrode is adjusted. The application time may be adjusted, the number of times the electric field is applied between the display electrode and the counter electrode may be adjusted, and these three types of adjustment may be performed simultaneously.

FIG. 5 is a diagram for explaining a reset voltage application method for a particle state reset operation prior to halftone display in the image display device according to the embodiment of the present invention. In the present invention, as shown in FIG. 5, the reset voltage application period is inserted between the end of the previous frame and the start of the current frame. During this reset voltage application period, a reset voltage for generating an alternating electric field as a reset electric field is applied. This reset voltage is set so that the voltage value is higher than the respective image forming voltages applied when displaying various images including only particle A, only particle B, and mixed display of particle A / particle B. ing. The application of the reset voltage is
This is performed by applying voltages of opposite phase (reset voltage and inverted reset voltage) between the display electrode and the counter electrode, and the image display element to which this reset voltage is applied (see FIG. 4).
(Indicated by a black square in (a)), the previous state will be reset.

The reason why the reset voltage is applied is that particles A and particles B are used when the halftone display method by adjusting the strength of the applied electric field as shown in FIG. 4B is adopted.
This is to prevent the actual mixing ratio from fluctuating from the desired mixing ratio under the influence of the display condition before halftone display unless the mixing condition is reset once. In this way, by resetting the mixed state of the particles A and the particles B before performing the halftone display, the influence of the display state before performing the halftone display is eliminated, and thus the desired halftone display is performed. Can be realized with good reproducibility.

At that time, since an alternating electric field is used as the reset electric field, the particles A and B fly between the display electrode and the counter electrode, so that the interaction with the surface of the electrode material is minimized. Can be produced, and the mixed state of the particles A / particles B can be realized with higher reproducibility by the subsequent voltage application.

Although the alternating electric field is used as the reset electric field in the above example, a pulse electric field may be used as the reset electric field instead. In that case, even if the frame scanning time is limited such as when displaying a moving image, a desired reset state can be obtained in a short time by applying a reset electric field sufficient for all particles to fly in pulses. Will be possible. In the above-mentioned example, the electrodes (display electrodes, counter electrodes) are used as substrates (transparent substrates, counter substrates).
Although it is provided above, "providing on the substrate" in this case includes "providing the electrode on the substrate" and "providing the electrode apart from the substrate".

[0053]

As described above, according to the image display device of the present invention, image display elements capable of directly applying an electrostatic field to particles and causing the particles to fly and move by Coulomb force are arranged in a matrix. Since a new image display device is configured by using the above, it is possible to provide an image display device that has a fast response speed, a simple structure, is inexpensive, and is excellent in stability. Further, when displaying the halftone, instead of using the repeated display of the particles A / particles B, at least one of the strength of the electric field applied between the electrodes forming the electrode pair, the application time, and the number of times of application is set to the display density. Since a method of obtaining a display state in which the two or more kinds of particles are mixed in a desired ratio by using the above method is used, halftone can be displayed while utilizing the display memory property. Furthermore, since the states of the two or more types of particles are once reset prior to the halftone display, the influence of the display state before the halftone display is eliminated, and the desired halftone display can be reproduced with good reproducibility. Can be realized.

[Brief description of drawings]

1A to 1C are diagrams for explaining an example of a display element of an image display plate used in an image display device of the present invention and a display driving principle thereof.

2A and 2B are schematic views each illustrating an image display plate of the image display device of the present invention.

FIG. 3 is a diagram showing a procedure for measuring the surface potential of particles used in the image display device of the present invention.

4A is a diagram for explaining a reset voltage applying method for a particle state reset operation prior to halftone display in the image display device of the present invention, and FIG. 4B is an image display device of the present invention. FIG. 5 is a diagram for explaining a method of applying an electric field for halftone display in FIG.

FIG. 5 is a diagram for explaining a reset voltage application method for a particle state reset operation prior to halftone display in the image display device of the present invention.

[Explanation of symbols]

1 transparent substrate 2 Counter substrate 3 display electrodes 4 Counter electrode 5 Negatively charged particles 6 Positively charged particles 7 partition 8 High voltage generation circuit 9 Low voltage generation circuit 10 Matrix drive circuit 11 Reset voltage generator 12 inverter 13 Voltage selection device 14 Grayscale voltage generator 21 chuck 22 Scorotron discharger 23 Surface electrometer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/34 G09G 3/34 C (72) Inventor Manabu Yakushiji 3-2-6 Ogawahigashi-cho, Kodaira-shi, Tokyo (72) Inventor Kazuya Murata 3-5-5 Ogawahigashi-cho, Kodaira-shi, Tokyo (72) Inventor Koji Takagi 3-21-33-304 Miyauchi, Nakahara-ku, Kawasaki-shi, Kanagawa (72) Inventor Yoshitomo Masuda Tokyo 3-5-28 Shinmeidai, Hamura-shi (72) Takahiro Kawagoe 1302-57 Aobadai, Tokorozawa-shi, Saitama Prefecture 72-72 Inventor Reiji Hattori F-term, 200-1 Meinohama-cho, Nishi-ku, Fukuoka-shi 5C080 AA13 BB05 DD03 DD08 DD22 EE29 FF12 JJ04 JJ06

Claims (9)

[Claims] 1. Two or more kinds of particles having different colors and different charging characteristics are enclosed between at least one transparent substrate, and an electrode pair consisting of electrodes provided on one or both of the substrates is formed into the particles. An image display device comprising an image display plate for applying an electric field to fly and move the particles to display an image, wherein the intensity of the electric field applied between the electrodes when forming an image to be displayed, At least 1 of the application time and the number of applications
The image display device is characterized in that a display state in which the two or more kinds of particles are mixed in a desired ratio is obtained by adjusting one of the particles according to the display density. 2. Prior to an electric field application process for obtaining a display state in which the two or more kinds of particles are mixed in a desired ratio,
The image display device according to claim 1, wherein a reset electric field for resetting the states of the two or more types of particles is applied. 3. The image display device according to claim 1, wherein the reset electric field is an alternating electric field. 4. The image display device according to claim 1, wherein the reset electric field is a pulse electric field. 5. The average particle diameter of the particles is 0.1 to 50 μm.
The image display device according to any one of claims 1 to 4, wherein m is m. 6. The surface charge density measured by a blow-off method using the carrier of the particles is 5 μC / m in absolute value.
^{It is 2} or more and 150 μC / m ² or less, and the image display device according to claim 1. 7. The particles, when a voltage of 8 KV is applied to a corona discharger arranged at a distance of 1 mm from the surface to generate corona discharge to charge the surface,
The image display device according to claim 1, wherein the particles have a maximum surface potential of more than 300 V after 0.3 seconds. 8. The image display device according to claim 1, wherein the color of the particles is white or black. 9. The image according to claim 1, wherein the image display plate has one or more image display elements in which each electrode pair of a matrix electrode is separated from each other by a partition wall. Display device.