JP2003255401A - Device and method for picture displayer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a picture displayer in which particles fly ideally when an electric field is formed and a favorable picture can be obtained stably with a sufficient contrast in the picture display device for displaying a picture by filling the particles of two or more kinds of colors and electrification characteristics between a transparent substrate and a counter substrate, and making the particles flight-moving by applying an electric field to the particles from two kinds of electrodes at different potentials. <P>SOLUTION: An absolute value of a difference between surface charge density of two kinds of particles measured by the blow-off method using the same kind of carriers is made to be not less than 5 μC/m<SP>2</SP>and not more than 150 μC/m<SP>2</SP>. <P>COPYRIGHT: (C)2003,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 apparatus and method capable of repeatedly displaying and erasing an image as particles fly and move using Coulomb force or the like.

[0002]

2. Description of the Related Art As an image display device replacing liquid crystal (LCD), an image display device (display) 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 image display devices are considered as next-generation inexpensive display devices because they have a wider viewing angle than ordinary printed matter, lower power consumption, and a memory function than LCDs. Therefore, it is expected to be applied to displays for mobile terminals and electronic papers.

Recently, an electrophoretic method has been proposed in which a dispersion liquid composed of dispersed particles and a coloring solution is formed into microcapsules and the microcapsules are arranged between opposed substrates. However, the electrophoretic method has a problem that the response speed is slow due to the viscous resistance of the liquid because the particles migrate in the liquid. Further, since particles having a high specific gravity such as titanium oxide are dispersed in a solution having a low specific gravity, there is a problem in that they easily settle, it is difficult to maintain the stability of the dispersed state, and the stability of image repetition is lacking. Even in the case of microencapsulation, the cell size is set to the microcapsule level, and such defects are apparently difficult to appear, and no essential problem is solved.

In contrast to the electrophoretic method utilizing the behavior in a solution as described above, recently, a solution is not used, and an electrostatic field is applied between two kinds of particles having different colors and different charging polarities. A display device has also been proposed in which the substrates are attached to the substrates in different directions by flying. Since this method is a dry method as compared with the electrophoresis method, it has the advantage that the movement resistance of particles is small and the response speed is fast. The operation mechanism of such a dry display device is that a mixture of two kinds of particles having different colors and charged polarities is sandwiched between electrode plates, and a voltage is applied to the electrode plates to generate an electric field between the electrode plates to polarize them. It is used as a display element by flying differently charged particles of different directions in different directions. However, in a dry display device, particles may not ideally fly when an electric field is formed, and the contrast of a displayed image may be insufficient, so that a good image may not be stably obtained.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been earnestly studied in view of the above circumstances, and in a dry image display device of a type that causes particles to fly, ideal flight of particles when an electric field is formed. It is an object of the present invention to provide an image display device and method capable of stably obtaining a good image with sufficient contrast.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that the surface charge densities of two types of particles measured by a blow-off method using the same type of carrier. The absolute value of the difference is 5 μC / m ² or more 1
The present invention has been found out that when it is 50 μC / m ² or less, the flight of particles due to the application and reversal of an electric field ideally follows, and a satisfactory image with a sufficient contrast can be stably obtained.

That is, the present invention provides the following image display device and method. 1. An image display in which two or more types of particles having different colors and different charging characteristics are enclosed between a transparent substrate and a counter substrate, and an electric field is applied to the particles from two types of electrodes having different potentials to cause the particles to fly and move to display an image. In the apparatus, the absolute value of the difference between the surface charge densities of two types of particles measured by the blow-off method using the same type of carrier is 5 μC / m ² or more 15
An image display device, which is 0 μC / m ² or less. 2. The surface charge density of at least one particle is 5 in absolute value.
The image display device according to 1 above, wherein the image display device has a density of 150 μC / m ² . 3. The image display device according to 1 or 2 above, wherein the average particle size d _{0.5 of the} particles is 0.1 to 50 μm. 4. The image display device according to any one of 1 to 3 above, wherein the particles are insulating particles having a volume resistivity of 1 × 10 ¹⁰ Ω · cm or more. 5. The maximum value of the surface potential after 0.3 seconds when the particles are charged with a corona discharge by applying a voltage of 8 KV to a corona discharger arranged at a distance of 1 mm from the surface to generate corona discharge. The image display device according to any one of 1 to 4 above, wherein the particles are larger than 300V. 6. An image display in which two or more types of particles having different colors and different charging characteristics are enclosed between a transparent substrate and a counter substrate, and an electric field is applied to the particles from two types of electrodes having different potentials to cause the particles to fly and move to display an image. In the apparatus, the absolute value of the difference between the surface charge densities of two types of particles measured by the blow-off method using the same type of carrier is 5 μC / m ² or more 15
And 0μC / m ² or less, an image display method, wherein a surface charge density of at least one of the particles is in absolute value 5~150μC / m ^2.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The image display device of the present invention has two or more kinds of particles enclosed between a transparent substrate and a counter substrate,
An electric field is applied to the particles from two types of electrodes with different potentials,
It is an image display device that displays an image by causing particles to fly and move by Coulomb force or the like. Here, the force exerted on the particles may be a force attracting each other by Coulomb force between particles, an intermolecular force, a Coulomb force with an electrode plate, a liquid bridge force, gravity, and the like. Due to the relative relationship between these total forces and the force exerted on the particles by the electric field, the particles themselves fly when the force due to the electric field exceeds, but here the charge amount of the particles themselves is generated by the electric field. It is the most important parameter when controlling the force of adhesion and the adhesion force between particles or between electrode plates. Here, if the charge amount of the particles is not sufficiently high, ideal flight is not performed when an electric field is formed, and the device does not function as a good display device.
Further, in order for the two particles to ideally follow the electric field reversal, it is necessary to mutually optimize the charge amounts of the two particles.

The charge amount of the particles naturally depends on the measurement conditions, but the charge amount of the particles in the image display device is almost the same as the initial charge amount, the contact with the substrate, the contact with particles of different types, and the charge with the passage of time. It has been found that the "contact with particles of different types", that is, the saturation value of the charging behavior associated with the contact between two particles, is the controlling factor depending on the attenuation. Therefore, it is important to know the difference in the charging characteristics between the two particles, that is, the difference in the work function in the charge amount, but this is difficult to perform by simple measurement. As a result of intensive studies, the present inventors have found that the same carrier can be used in the blow-off method, and the relative charge can be evaluated by measuring the charge amount of each particle. It was found that the charge amount of particles suitable for a display device can be predicted. Although the measuring method will be described later in detail, the amount of charge per unit weight of the particles can be measured by bringing the particles and the carrier particles into sufficient contact by the blow-off method and measuring the saturated amount of charge. Then, the surface charge density of the particles can be calculated by separately determining the particle size and the specific gravity of the particles.

In the image display device, since the particle size of the particles used is small and the influence of gravity is small enough to be ignored, the specific gravity of the particles does not affect the movement of the particles. However, regarding the charge amount of the particles, even if the particles having the same particle size have the same average charge amount per unit weight, the charge amount held when the specific gravity of the particles is two times different will be two times different. Therefore, it was found that it is preferable to evaluate the charging characteristics of the particles used in the image display device by the surface charge density (unit: μC / m ² ) irrelevant to the specific gravity. When there is a sufficient difference in the surface charge density between the particles, the two types of particles hold different amounts of charges of different polarities due to contact with each other, and the function of moving due to an electric field. Here, the surface charge density needs to have a certain difference in order to make the charging polarities of the two particles different, but the larger the surface charge density, the better. In an image display device based on particle movement, when the particle size is large, the electric image force tends to be a factor that mainly determines the flight electric field (voltage). Therefore, it is necessary to move the particles at a low electric field (voltage). The lower the charge amount, the better. In addition, when the particle size is small, non-electrical forces such as intermolecular force and liquid bridging force are often determinants of the flight electric field (voltage), so this particle is moved by a low electric field (voltage). The higher the charge amount, the better. However, this largely depends on the surface properties (material, shape) of the particles and cannot be unconditionally defined by the particle size and the charge amount. The present inventors have found that the average particle diameter d _0.5 is 0.1.
In the case of particles of ˜50 μm, the absolute value of the difference between the surface charge densities of the two types of particles measured by the blow-off method using the same type of carrier is 5 μC / m ² or more and 150 μC / m ² or more.
It has been found that particles having a particle size of m ² or less can be used as an image display device.

In the dry image display device, as shown in FIG. 1, two or more kinds of particles having different colors and different charging characteristics are moved in the direction perpendicular to the substrate, and one type as shown in FIG. Although there is a display method in which color particles are moved in a direction parallel to the substrate, the present invention is applied to the former method shown in FIG. 1 and has high stability. FIG. 3 is an explanatory diagram showing an example of the structure of the image display device, which includes the opposing substrate 1,
The partition wall 4 is formed by the substrate 2 and the particles 3, and if necessary, the partition wall 4
Is provided.

Regarding the substrate, at least one of the substrate 1 and the substrate 2 is a transparent substrate from which the color of particles can be confirmed from the outside of the device, and a material having a high visible light transmittance and a high heat resistance is suitable. Whether or not the image display device is flexible is appropriately selected depending on the application. For example, for an application such as electronic paper, a flexible material, a mobile phone, a PDA, and a display of a portable device such as a notebook computer are used. An inflexible material is used.

Examples of the substrate material include polyethylene terephthalate, polyether sulfone, polyethylene,
Examples include polymer sheets such as polycarbonate and inorganic sheets such as glass and quartz. Substrate thickness is 2-5
000 μm, preferably 5 to 1000 μm is suitable, and when it is too thin, it becomes difficult to maintain strength and uniformity of spacing between substrates, and when it is too thick, sharpness as a display function and deterioration of contrast occur. It lacks flexibility in paper applications.

The electrodes are made of a transparent and patternable conductive material on a transparent substrate, such as aluminum, silver,
A thin film of a metal such as nickel, copper or gold, or a transparent conductive metal oxide such as ITO, conductive tin oxide or conductive zinc oxide formed by a sputtering method, a vacuum deposition method, a CVD method, a coating method, or the like, 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, and conductive zinc oxide, tin oxide and indium oxide. Fine powder or the like is used. The electrode thickness is
It is sufficient if the conductivity can be secured and the light transmittance is not hindered. 3-1
000 nm, preferably 5 to 400 nm is suitable.
Although a transparent electrode material can be used on the counter substrate, a non-transparent electrode material such as aluminum, silver, nickel, copper, or gold can also be used. In this case, the external voltage may be applied by superimposing DC or AC on it. It is preferable to form an insulating coat layer on each electrode so that the charges of the charged particles do not escape. In this coat layer, it is particularly preferable to use a resin having a positive charging property for the negatively charged particles and a resin having a negative charging property for the positively charged particles because it is difficult for the charge of the particles to escape.

It is preferable that the partition walls are provided on the four circumferences of each display element. The partition walls can be provided in two parallel directions. 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, for example, a screen printing method in which paste is applied in a predetermined position using a screen plate, or a partition material having a desired thickness is solidly coated on a substrate to form a partition wall. After coating the resist pattern only on the part to be left on the partition wall material, a blasting material is sprayed to remove the partition wall material other than the partition wall by sandblasting, or a resist pattern is formed on the substrate using a photosensitive resin. , A lift-off method (additive method) in which the resist is removed after the paste is embedded in the resist recesses, or a photosensitive resin composition containing a partition material is applied onto the substrate, and a desired pattern is obtained by exposure and development. Paste method or a mold forming method of forming barrier ribs by applying a paste containing a barrier rib material on the substrate, and then pressure-bonding and pressure-molding a mold or the like having irregularities. Various methods are employed. Further applying the mold forming method, using the relief pattern provided by the photosensitive resin composition as a mold,
The relief stamping method is also adopted.

The particles are preferably spherical particles, which fly and move by Coulomb force, and it is important to use particles having the following characteristics. That is, the absolute value of the difference between the surface charge densities of the two types of particles measured by the blow-off method using the same type of carrier is 5
by applying an electric field-reversed by the [mu] C / m ² or more 150μC / m ² or less may be flying particles ideally follow. In this blow-off method, a mixture of powder and carrier is placed in a cylindrical container having meshes on both ends, high-pressure gas is blown from one end to separate the powder and carrier, and only the powder is opened from the mesh opening. To blow off. At this time, a charge amount opposite to the charge amount of the powder carried away from the container remains in 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 of the powder can be calculated as Q =
It is obtained as CV (C: capacitor capacity, V: voltage across capacitor). When the absolute value of the difference in surface charge density between two particles of different types whose surface charge density is determined from this charge amount and the average particle diameter and specific gravity of the particles separately measured is less than 5 μC / m ^2. Even when an electric field is applied, the force exerted on the particles is weak, and it is necessary to apply a very large voltage to achieve the flight of the particles. Also, the surface charge density has a distribution for each type of particle,
When the absolute value of the difference between the surface charge densities of the two particles is less than 5 μC / m ² , the surface charge density distributions of the two particles overlap each other. Under such a condition, the two particles cannot be ideally separated into both electrodes by the voltage application, and the display device cannot exhibit sufficient performance.

Furthermore, by setting the absolute value of the surface charge density of at least one of the particles to 5 to 150 μC / m ² , a better situation can be obtained in the flight of the particles due to the application and reversal of the electric field. That is, when the absolute value of the surface charge density of one of the particles is 5 to 150 μC / m ² ,
Since the particles ideally fly by the electric field, the other particles are physically excluded from the electrode surface, and as a result, they sufficiently function as a display device. Since the particles are required to retain the charged electric charge, insulating particles having a volume resistivity of 1 × 10 ¹⁰ Ω · cm or more are preferable, and insulating particles having a volume resistivity of 1 × 10 ¹² Ω · cm or more are particularly preferable.

The average particle diameter d _0.5 of the particles is 0.1 to 50.
μm is preferable, and 1 to 30 μm is particularly preferable. 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 becomes poor. In the present invention, the average particle diameter d _0.5 (μm)
Is a Mastersizer2000 (Malvern instruments Ltd.) put each particle into a measuring machine and use the attached analysis software (software that calculates the particle size distribution and particle size based on the volume standard distribution) It is a numerical value expressed in μm that the particle size is larger and 50% is smaller than this.

Further, the particles are more preferably particles having a slow charge decay property evaluated by the method described below. That is, the particles are separately formed into a film having a thickness in the range of 5 to 100 μm by pressing, heat melting, casting, etc., and a voltage of 8 KV is applied to a corona discharger arranged at a distance of 1 mm from the film surface. Corona discharge is generated to charge the surface, and the change in the surface potential is measured and judged.
In this case, the maximum value of the surface potential after 0.3 seconds is 30
It is desirable to select and prepare the particle constituent material so as to be higher than 0 V, and preferably higher than 400 V.
The surface potential can be measured by, for example, the device (CRT2000 manufactured by QEA) shown in FIG. In the case of this device, both ends of the roll shaft having the above-mentioned film arranged on the surface are held by the chuck 21,
A measuring unit having a small corotron discharger 22 and a surface electrometer 23, which are separated from each other by a predetermined distance, is arranged opposite to the surface of the film with a distance of 1 mm, and the measuring unit is kept with the roll shaft stationary. A method of measuring the surface potential while applying the surface charge by moving the roller from one end to the other end of the roll shaft at a constant speed is preferably adopted. The measurement environment is a temperature of 25 ± 3 ° C. and a humidity of 55 ± 5 RH%.

The particles are prepared by using the required resin, charge control agent,
Colorants and other additives may be kneaded and ground, or may be polymerized from monomers, or existing particles may be coated with resins, charge control agents, colorants, and other additives. 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 resin, styrene. Acrylic resin, polyolefin resin, butyral resin, vinylidene chloride resin, melamine resin, phenol resin, fluororesin, polycarbonate resin, polysulfone resin, polyether resin, polyamide resin, etc. are mentioned, especially for controlling the adhesion to the substrate. Therefore, acrylic urethane resin, acrylic silicone resin, acrylic fluororesin, acrylic urethane silicone resin, acrylic urethane fluororesin, fluororesin, and silicone resin are preferable. It is also possible to mix two or more kinds.

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 a nigrosine dye, a triphenylmethane compound, a quaternary ammonium salt compound, a polyamine resin, and an imidazole derivative. 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.

As the colorant, various organic or inorganic pigments and dyes of various colors can be used as shown below. 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, Hansa yellow G, Hansa yellow 10G, benzidine yellow G, benzidine yellow GR, quinoline. Yellow rake, permanent yellow NCG, tartrazine rake, etc. 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.

Examples of red pigments include red iron oxide, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, resole red, pyrazolone red, watching red, calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine. Rake B, Alizarin Rake, Brilliant Carmine 3B, etc. Examples of purple pigments include manganese purple, fast violet B, and methyl violet lake.
Examples of blue pigments include dark 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, chrome oxide, pigment green B, malachite green lake, and final yellow green G.

Examples of extender pigments include barite powder, barium carbonate, clay, silica, white carbon, talc, and alumina white. Further, various dyes such as basic dyes, acid dyes, dispersion dyes and direct dyes include nigrosine, methylene blue, rose bengal, quinoline yellow and ultramarine blue. These colorants can be used alone or in combination.

The distance between the transparent substrate and the counter substrate in the image display device of the present invention is adjusted so that particles can fly and move and the contrast can be maintained, but it is usually adjusted to 10 to 5000 μm, preferably 10 to 500 μm. The volume occupancy of the particles in the space between the opposing substrates is preferably 10 to 80%, more preferably 10 to 60%. If it exceeds 80%, the movement of particles may be hindered, and if it is less than 10%, the contrast tends to be unclear.

The image display device of the present invention is an image display unit of a mobile device such as a notebook computer, a PDA, a mobile phone, an electronic book, an electronic paper such as an electronic newspaper, a signboard,
It is used for posters, bulletin boards such as blackboards, copiers, rewritable paper as a substitute for printer paper, calculators, image display parts of home appliances, and image display parts of point cards.

[0027]

EXAMPLES Next, the present invention will be described more specifically by showing examples. However, the present invention is not limited to the following examples. In each Example and Comparative Example,
Particle characteristics and display function evaluation were performed as follows. (1) Average particle size d _{0.5 Using a} Mastersizer2000 (Malvern instruments Ltd.) measuring machine, particles were put into a nitrogen stream, and attached analysis software (particle size distribution based on volume standard distribution using Mail theory, The average particle size (μm) is defined as the numerical value expressed in μm, that is, 50% of the particles are larger than 50% and 50% are smaller than this, using software for calculating the particle size. (2) Surface charge density (μC / m ² ) As a blow-off powder charge amount measuring device, TB-200 manufactured by Toshiba Chemical Co., Ltd. was used. Two types of carriers, positively charged and negatively charged, were used, and the charge density per unit area (unit: μC / m ² ) in each case was measured. That is, F963-2535 manufactured by Powder Tech Co., Ltd. is used as a positively chargeable carrier (a carrier that makes a partner positively charged and is easily negatively charged by itself), and a negatively charged carrier (a partner is negatively charged and made positive by itself). As the carrier (which is easily charged), powder tech particles F921-2535 were used. The surface charge density was determined from the measured charge amount and the separately measured average particle diameter and specific gravity of the particles. The average particle diameter is determined by the above-described method, and the specific gravity is determined by a specific gravity meter (trade name: multi-volume densitometer H manufactured by Shimadzu Corporation).
130). (3) Evaluation of display function By applying 500 V to the manufactured display device and inverting the polarity, black-white display was repeated. For the evaluation of the display function, a black and white display is used for the reflection image densitometer (M
It was measured using RD918 manufactured by acbeth. Here, the contrast ratio is the reflection density at the time of black display with respect to the time of white display (contrast ratio = reflection density at the time of black display / reflection density at the time of white display). Further, the unevenness at the time of full-screen display was judged according to the following criteria. ◯: The entire surface is colored 100% black / white. B: Some white is mixed in black display, or vice versa. X: The display is a mixture of black and white.

Example 1 Particle A was prepared by adding ethanol to a charge control agent: Bontron E84.
(Orient Chemical: salicylic acid type metal complex) 5% by weight
Was dissolved in a mixer, and undissolved components were removed by filtration. Then, Pernock CFB200W-40 (white urethane particles: made by Dainippon Ink) was added to the filtrate and stirred, and the resulting mixed liquid was filtered with 5C filter paper. Filtered and dried at 110 ° C. Particle B is a charge control agent for ethanol: Bontron N
21 (manufactured by Orient Chemical Co., Ltd.) was dissolved in a mixer by 5% by weight, undissolved components were removed by filtration, and then urethane particles: Pernock CFB620C-40 (black urethane particles: manufactured by Dainippon Ink) were added to the filtrate and stirred. Then, the obtained mixed solution was filtered through a 5C filter paper and dried at 110 ° C. Next, the display device was manufactured as follows. That is, about 50
Particles A and B are put between a pair of glass substrates provided with 0Å indium oxide electrodes and adjusted with a spacer so that the distance between them is 200 μm, and the periphery of the glass substrates is bonded with an epoxy adhesive. At the same time, the particles were enclosed to manufacture a display device. The mixing ratios of the particles A and the particles B were the same weight, and the volume occupancy ratio of the particles between the glass substrates was adjusted to be 60% by volume. Table 1 shows the evaluation results of the particle characteristics and the display function.

Example 2 A particle and a display device were produced in the same manner as in Example 1 except that an aminosilane coupling agent (A1120 manufactured by Nippon Unicar) was used in place of the charge control agent for the particle B in Example 1. . Table 1 shows the evaluation results of the particle characteristics and the display function.

Example 3 A particle and a display device were produced in the same manner as in Example 1 except that the charge control agent for the particle A in Example 1 was not used. Table 1 shows the evaluation results of the particle characteristics and the display function.

Comparative Example 1 A particle and a display device were produced in the same manner as in Example 1 except that the charge control agent for particle A in Example 2 was not used. Table 1 shows the evaluation results of the particle characteristics and the display function.

[0032]

[Table 1]

[0033]

According to the image display device of the present invention, two or more kinds of particles having different colors and different charging characteristics are enclosed between a transparent substrate and a counter substrate, and an electric field is applied to the particles from two kinds of electrodes having different electric potentials. In an image display device for displaying an image by moving particles by flying, the absolute value of the difference between the surface charge densities of two types of particles measured by the blow-off method using the same type of carrier is 5 μC / m ² or more and 150 μC / m ² or more. ^Although it is ² or less, by controlling the charge amount between two particles in this way, ideal flight of particles is performed when an electric field is formed, and a good image with sufficient contrast and no unevenness is obtained. Can be obtained stably.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a display system in an image display device.

FIG. 2 is an explanatory diagram showing a display system in the image display device.

FIG. 3 is an explanatory diagram showing an example of a structure of an image display device.

FIG. 4 is an explanatory diagram showing a method of measuring a surface potential.

[Explanation of symbols]

1, 2: substrate 3: Particle 4: Partition wall 21: Chuck 22: Coroton discharger 23: Surface electrometer

Continued front page    (72) Inventor Yakushiji Manabu             3-2- 6-408 Ogawahigashi-cho, Kodaira-shi, Tokyo (72) Inventor Hajime Kitano             3-5-5 Ogawahigashi-cho, Kodaira-shi, Tokyo (72) Inventor Yoshitomo Masuda             3-5-28 Shinmeidai, Hamura-shi, Tokyo (72) Inventor Takahiro Kawagoe             1302-57 Aobadai, Tokorozawa, Saitama Prefecture

Claims (6)

[Claims] 1. An image in which two or more kinds of particles having different colors and different charging characteristics are enclosed between a transparent substrate and a counter substrate, and an electric field is applied to the particles from two kinds of electrodes having different electric potentials to cause the particles to fly and move. In an image display device that displays, the same type of carrier was used to measure by the blow-off method.
The absolute value of the difference in the surface charge densities of the different types of particles is 5 μC / m
An image display device, characterized in that at least ^two 150μC / m ² or less. 2. The image display device according to claim 1, wherein the surface charge density of at least one of the particles is 5 to 150 μC / m ² in absolute value. 3. The average particle diameter d _{0.5 of the} particles is 0.1 to 50.
The image display device according to claim 1, wherein the image display device has a thickness of μm. 4. The particles have a volume resistivity of 1 × 10 ¹⁰ Ω · cm.
The image display device according to claim 1, wherein the image display device comprises the above insulating particles. 5. When the particles are charged with a voltage of 8 KV to generate a corona discharge to a corona discharger arranged at a distance of 1 mm from the surface of the particles to charge the surface,
The image display device according to claim 1, wherein the maximum value of the surface potential after 3 seconds is particles larger than 300V. 6. An image in which two or more types of particles having different colors and different charging characteristics are enclosed between a transparent substrate and a counter substrate, and an electric field is applied to the particles from two types of electrodes having different potentials to cause the particles to fly and move. In an image display device that displays, the same type of carrier was used to measure by the blow-off method.
The absolute value of the difference in the surface charge densities of the different types of particles is 5 μC / m
² or more and 150 μC / m ² or less, and the surface charge density of at least one particle is 5 to 150 μC / m ^{2 in} absolute value.