JP2010091908A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device in which charged particles are sealed in a gaseous phase, obtaining proper image density and contrast, and obtaining display images of high-definition image quality. <P>SOLUTION: This image display device contains particles in a space, formed by two opposite substrates and a partition joined to the substrates, two or more pairs of electrodes are disposed along the substrates, and the partition is disposed along at least the ends of the substrates. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image display apparatus capable of displaying and erasing an image by moving charged particles in an electric field formed in a gas phase, and more particularly to an image display apparatus capable of making a display screen a cellless structure.

  In the technical field of image display devices, studies on a new display device that is reflective and gentle on eyes, consumes little power during rewriting, and does not consume power for holding a display image have been underway. In such a display device, fine particles of several nanometers to several microns are encapsulated in a liquid phase or the like, and the fine particles are moved using electrophoresis or electrochromic to display an image. There is a technology. In other words, image formation is performed by moving the injected fine particles by the action of an electric field formed in the phase, and it is expected as a technology to replace liquid crystal display devices (LCD) such as display devices for mobile terminal devices and electronic paper. ing. In other words, a wider viewing angle can be obtained compared to a liquid crystal display device, so an image with an image quality close to that of a normal printed matter can be obtained, power consumption is low, and image display continues even after the power is turned off, which is called memory performance. There are advantages such as being able to continue.

  One technique for displaying an image by moving fine particles by the action of an applied voltage is one in which charged particles are enclosed in a gas phase so that the image can be displayed. This technique can solve problems such as liquid leakage, storage stability, and sedimentation of particles, which are problems in the technique of introducing particles into the liquid phase as in the electrophoresis method. Recently, a technique has been studied in which a driving voltage is reduced by coating a fluororesin on the surface of a substrate in contact with particles so that the particles can be charged and moved smoothly even at a low applied voltage (for example, patents). Reference 1, Non-Patent Document 1, etc.).

In addition, a method for manufacturing a display device in which encapsulated charged particles move smoothly and display an image accurately has been studied. A manufacturing method has also been studied (for example, see Patent Document 2).
JP 2003-248247 A JP 2005-3892 A 趙 Kuniaki and three others, “New Toner Display Device (I)”, July 21, 1999, Annual Meeting of the Imaging Society of Japan (83 times in total) “Japan Hardcopy '99”, p. 249-252

  By the way, when displaying image information such as characters and photographs with an image display device, it is required that more information can be displayed on the screen at a time. That is, if the specification is such that more information can be displayed at a time even on a small screen, it is advantageous for the development of, for example, downsizing of the apparatus. For this reason, the image display apparatus prepares a large number of units for fine image display (hereinafter, the unit for fine image display is also referred to as a pixel), and display is performed for each unit of image display. Then, the viewer sees a set of displayed pixels, and as a result, recognition of characters and photographs is performed. In this way, images such as letters and photos are displayed.

  In a conventional image display device in which charged particles are enclosed in a gas phase, each pixel is composed of independent elements finely divided into image forming units called cells, and the cells are divided by partitions called partition walls. Each independence is maintained. Each cell is provided with a pair of electrodes, and by applying a voltage between the electrodes, the movement of the charged particles is realized to form an image. Therefore, the finer the cell, the easier it is to achieve high image quality. However, when the cell size is reduced, the proportion of the partition wall increases relatively, and the image display area decreases. The contrast is lowered and the amount of information that can be displayed on the screen is reduced.

  In view of this, the present inventor has studied to narrow the partition wall width between cells to expand the image display area. However, when the partition wall width is narrowed, high-precision cell and electrode alignment is required in the production process. became. When the alignment between the cells and the electrodes is insufficient, a voltage having a phase shift is applied to each cell, and a uniform image without unevenness cannot be displayed. Further, as the partition wall width becomes narrower, it has become difficult to ensure the durability of the image display device.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image display device in which charged particles are enclosed in a gas phase so that a good image density and contrast can be obtained and a high-definition display image can be obtained. It is what. In addition, the present invention eliminates the labor of aligning the partition wall and the electrode, which required high accuracy in the production process, and easily provides a highly reliable image display device that can obtain a uniform and uniform display image. The purpose is to enable production.

The present inventor has found that the above-described problem can be solved by any of the configurations described below. That is,
The invention described in claim 1
“An image display device comprising particles in a space formed by facing two substrates, at least one of which is transparent,
The image display device includes:
A plurality of pairs of electrodes for applying a voltage to the space are disposed along the two substrates, and
An image display device characterized in that a partition wall for joining the two substrates is disposed along at least an end portion of the substrate. ].

The invention described in claim 2
2. The image display device according to claim 1, wherein the partition wall is disposed only along an end portion of the base body. ].

The invention according to claim 3
The image display apparatus according to claim 1, wherein at least two or more pairs of electrodes are arranged in a region surrounded by the partition walls. ].

  According to the image display device of the present invention, since the partition walls are not arranged between all the electrodes disposed in the display screen, it is possible to suppress the problem of image density and contrast reduction caused by the presence of the partition walls. I can do it now. As the size of the electrode is reduced, the resolution is increased and the image quality is improved. At the same time, the image can be displayed with good image quality and contrast. In particular, according to the present invention, an image display device called a cellless structure in which no partition wall is present in the display screen can be realized.

  In addition, according to the present invention, since an image display device can be manufactured by providing the minimum necessary partition walls, it is not necessary to align the partition walls and electrodes with high accuracy as required in the prior art, It has also become possible to easily produce a highly reliable image display device.

  In order to solve the above-described problems, the present inventor has reviewed the display screen design method. In the prior art, when designing a display screen, the substrate region constituting the display screen is finely divided into pixel levels called cells, a partition is provided around the divided region, and a pair of electrodes are arranged therein to form particles. And so on. In this way, the display screen is designed in the form of an assembly of small pixel-level cells, and the display screen is designed by accurately storing and arranging the constituent materials such as electrodes in a limited narrow space. As a result, the production process was very difficult. In particular, in manufacturing an image display device, in order to align the position of two electrodes and a cell, it was necessary to prepare a highly accurate manufacturing apparatus and bond the electrode and the cell using a complicated process. . In addition, it is necessary to pay attention to fabrication so that each cell constituting the display screen exhibits a predetermined performance.

  The present inventor considers that such a labor for manufacturing is to realize a highly reliable image display device, and does not dare to divide the substrate constituting the display screen, and corresponds to the size of the substrate. A plurality of pairs of electrodes prepared by cutting a pair of electrodes into small pieces were arranged along the substrate. A partition for forming and holding a space for storing image forming particles was provided only at the edge of the substrate, that is, at the edge of the display screen. The present inventor has found that an image display apparatus having this configuration can perform good image display.

  Hereinafter, the present invention will be described in detail.

  First, FIG. 1 shows a typical cross section of an image display device according to the present invention. In the image display device 1 shown in FIG. 1A, electrodes 15a and 15b are provided on substrates 11 and 12, respectively, and an insulating layer 16 is further provided on the surfaces of the electrodes 15a and 15b. In the image display device 1 in FIG. 1A, a plurality of electrodes 15 a are arranged along the base 11, and similarly, a plurality of electrodes 15 b are arranged along the base 12. A plurality of electrodes 15 a and 15 b are arranged to face each other to form a plurality of electrode pairs 15. Here, the plurality of electrodes 15a and 15b are arranged at an angle such that they intersect each other at an angle of 90 ° when viewed from the viewing direction. Further, the image display device shown in FIG. 1B has a structure in which the electrode pair 15 is not arranged in the device, but is the same as that shown in FIG. 1A provided outside the device. A voltage is applied from the plurality of electrode pairs 15 so that the particles 21 and 22 can move. The type shown in FIG. 1B has the merit that the structure of the device can be simplified and the manufacturing process can be shortened because the electrode pair 15 is not provided in the device itself. FIG. 3 shows a state in which the image display apparatus 1 of the type shown in FIG. 1B is set in an apparatus capable of applying a voltage and voltage is applied. The cross-sectional configuration of the image display device according to the present invention is not limited to that shown in FIGS.

  The image display device 1 in FIG. 1 visually recognizes an image from the substrate 11 side as shown in the figure, but the present invention is not limited to the one that visually recognizes an image from the substrate 11 side.

  At the outermost part of the image display device 1 in FIG. 1A, two base bodies 11 and 12 which are casings constituting the image display device are arranged to face each other. The bases 11 and 12 are provided with an electrode pair 15 for applying a voltage on a surface on the side where both face each other, and further, an insulating layer 16 containing a substance having a silicone structure is provided on the electrode 15 pair.

  The substrates 11 and 12 are provided with a plurality of electrode pairs 15 and an insulating layer 16, but the particles 2 exist in a space 18 formed by facing the surfaces having the electrode pairs 15 and the insulating layer 16. To do. In the image display device 1 shown in FIG. 1, two types of particles, black particles 21 and white particles 22, exist in the space 18 as the particles 2. In the image display device 1 of FIG. 1, the space 18 has a structure surrounded by the bases 11 and 12 and the two partition walls 17, and the particles 2 exist in a state of being enclosed in the space 18. Further, it has an image display surface 18 a that is surrounded by a partition wall 17 disposed at the ends of the substrates 11 and 12 and is an area where image display by the particles 2 is performed.

  The thickness of the space 18 is not particularly limited as long as the enclosed particles can move and maintain the contrast of the image, and is usually 10 μm to 500 μm, preferably 10 μm to 200 μm. The volume occupancy of the particles in the space 18 is 5% to 70%, preferably 10% to 60%. By setting the volume occupancy of the particles within the above range, the particles 2 can move smoothly in the space 18 and an image with good contrast can be obtained.

  As shown in FIG. 1, in the image display device according to the present invention, a partition wall 17 that joins two substrates 11 and 12 to form a space 18 is disposed along at least the end portions of the substrates 11 and 12. Is. This structure is different from the structure of a conventional image display device in which the partition wall 17 is arranged around an image forming unit composed of independent elements each having a size of a pair of electrodes called a cell. As described above, in designing the display screen in the prior art, the base region constituting the display screen is finely divided into “cell units”, and a partition wall is provided around the divided region, and a pair of electrodes is provided therein. The image display apparatus was designed by arranging these. With such a design, the cell which is the unit constituting the element and the pixel which is the unit constituting the image correspond to 1: 1. On the other hand, in the present invention, a plurality of driving electrodes are arranged for a unit constituting one element so that a plurality of pixels can be displayed in the unit constituting one element. In order to improve the resolution of the display image, a partition wall is provided around the smaller cell. Therefore, a partition region that cannot contribute to image display must be added to a narrow space, and the density and contrast of the output image are low. The image quality was degraded. Also, technically high difficulty is required for the work of accurately storing and arranging the constituent materials such as electrodes in a narrow cell and accurately bonding the finely divided bases along the partition walls.

  In the present invention, a partition image can be eliminated from the display screen as much as possible, and a display image having high resolution and sufficient image density and contrast can be obtained. Further, the effort for manufacturing the image display device can be greatly reduced as compared with the conventional art by eliminating the partition as much as possible.

  FIG. 2 is a schematic diagram for explaining the arrangement of the partition walls 17 of the image display device 1 according to the present invention. FIG. 3 is a schematic diagram showing the arrangement of the partition walls of the conventional image display device. 2 and 3, the illustration of the particles 21 and 22 contained in the space 18 is omitted. As shown in FIGS. 2A and 2B, in the image display device 1 according to the present invention, the partition wall 17 that joins the base bodies 11 and 12 to form the space 18 extends along at least the end portions of the base bodies 11 and 12. Are arranged. That is, as shown in FIG. 2A, the partition walls 17a are arranged at the ends of the substrates 11 and 12, but the partition walls 17b are sparsely arranged in the display screen so as to surround the pair of electrodes. The partition is not arranged. In FIG. 2B, there is no partition wall other than the partition wall 17a disposed at the end portions of the substrates 11 and 12, and no partition wall is disposed other than the substrate end portion called the “cellless structure”. The screen itself is a single cell. As shown in FIG. 2, the image display device 1 according to the present invention includes a plurality of electrode pairs 15 for applying a voltage to the space 18 in a region surrounded by the partition walls 17a and 17b, in other words, a plurality of pairs. Electrodes 15a and 15b. On the other hand, in the conventional image display device shown in FIG. 3, the partition walls 17 (17a and 17b) are arranged so as to surround each electrode pair 15 (electrodes 15a and 15b), and the partition wall 17b occupying the image display surface 18a. The area ratio is very large compared to the image display device according to the present invention.

  Next, the behavior of the particles 2 in the space 18 of the image display device 1 will be described.

  The image display device according to the present invention performs image display by moving particles by causing particles to exist between two opposed substrates and applying a voltage between the two substrates. . That is, when an electric field is formed by applying a voltage between two substrates, charged particles existing between the substrates move along the direction of the electric field. In this manner, by applying a voltage between the substrates on which the particles are present, the charged particles move between the substrates to perform image display.

The image display in the image display apparatus according to the present invention is performed by the following procedure. (1) The particles used as the display medium are charged by a known method such as frictional charging with a carrier to form charged particles.
(2) Charged particles are sealed between two opposing substrates, and a voltage is applied between the substrates in this state. (3) An electric field is formed between the substrates by applying a voltage between the substrates.
(4) The charged particles are attracted to the surface of the substrate along the direction of the electric field by the action of Coulomb force, so that the charged particles move and image display can be performed.
(5) The moving direction of the charged particles is switched by changing the electric field direction between the substrates. The image display can be changed variously by switching the moving direction.

  In addition, as a method for charging particles by the above-described known method, for example, a method in which particles are brought into contact with a carrier and particles are charged by frictional charging, or two-color particles having different charging properties are mixed and stirred with a shaker. And a method of charging particles by frictional charging between particles.

  Examples of the movement of the particles 2 accompanying the voltage application between the substrates are shown in FIGS. FIG. 4A shows a state before a voltage is applied between the substrates 11 and 12, and positively charged white particles 22 exist in the vicinity of the viewing-side substrate 11 before the voltage is applied. . In this state, the image display device 1 displays a white image. FIG. 4B shows a state after a voltage is applied to the electrode 15. The black particles 21 that are negatively charged by the voltage application move to the vicinity of the substrate 11 on the viewing side, and the white particles 22 represent the substrate. It has moved to the 12th side. In this state, the image display device 1 displays a black image.

  FIG. 5 shows a state before the voltage is applied in this state in which the image display device 1 shown in FIG. The state after a) and a voltage are applied is shown. In the image display device 1 of the type shown in FIG. 1B, the black particles 21 that are negatively charged by voltage application move to the vicinity of the substrate 11 on the viewing side and are positively charged, as in the image display device 1 having the electrodes 15. The white particles 22 have moved to the substrate 12 side.

  The above is a description of the operation of one pixel due to the movement of particles. Even if the image display device 1 shown in FIG. 1A has an electrode, the operation shown in FIG. Even if the image display apparatus 1 shown in the figure does not have an electrode, a portable storage medium can be obtained by using matrix driving having a power source and a driving circuit for a plurality of electrode pairs 15a and 15b. Images such as characters and photos in a personal computer or the like can be displayed. As matrix driving, either passive matrix driving (also called simple matrix driving) or active matrix driving can be used. From the viewpoint of cost reduction of the image display device, it is preferable to use simple matrix driving.

  Next, the bases 11 and 12, the electrodes 15a and 15b (electrode pair 15), the insulating layer 16, the partition wall 17, and the particles 2 (black particles 21 and white particles 22) constituting the image display device 1 according to the present invention. explain.

  First, the substrates 11 and 12 constituting the image display device 1 will be described. In the image display apparatus 1, the observer visually recognizes the image formed by the particles 2 from at least one side of the bases 11 and 12, and therefore the base provided on the side viewed by the observer is required to be made of a transparent material. . Therefore, the substrate used on the side where the viewer visually recognizes the image is preferably a light-transmitting material having a visible light transmittance of 80% or more, for example, and has a visible light transmittance of 80% or more. Sex is obtained. Note that, of the substrates constituting the image display device 1, the material of the substrate provided on the opposite side of the image viewing side is not necessarily transparent.

  The thicknesses of the substrates 11 and 12 are each preferably 2 μm to 5 mm, and more preferably 5 μm to 2 mm. When the thicknesses of the substrates 11 and 12 are in the above range, sufficient strength can be imparted to the image display device 1 and the distance between the substrates can be kept uniform. In addition, by making the thickness of the base within the above range, a compact and lightweight image display device can be provided, and thus the use of the image display device in an expanded field is promoted. Further, by setting the thickness of the base on the side where the image is viewed to be in the above range, the display image can be accurately recognized and the display quality is not hindered.

  Examples of the material having a visible light transmittance of 80% or more include an inorganic material having no flexibility such as glass and quartz, an organic material typified by a resin material described later, a metal sheet, and the like. Among these, organic materials and metal sheets can impart a certain degree of flexibility to the image display device. Examples of the resin material having a visible light transmittance of 80% or more include polyester resins typified by polyethylene terephthalate and polyethylene naphthalate, polycarbonate resins, polyethersulfone resins, and polyimide resins. . In addition, a transparent resin obtained by radical polymerization of a vinyl polymerizable monomer such as an acrylic resin or a polyethylene resin, which is a polymer of acrylic acid ester or methacrylic acid ester represented by polymethyl methacrylate (PMMA). It is done.

  Next, the electrode pair 15 (electrodes 15a and 15b) constituting the image display device 1 will be described. A plurality of electrodes 15 a and 15 b arranged along the surfaces of the bases 11 and 12 are opposed to each other via a space 18 to form a plurality of electrode pairs 15, and a voltage is applied between the substrates, that is, the space 18 by the electrode pairs 15. An electric field is formed by application. In addition, as for the electrodes 15a and 15b, it is necessary to use a transparent one at least on the side where an observer visually recognizes an image, like the above-described base.

  The thickness of the electrode provided on the side for visually recognizing the image is required to ensure conductivity and at a level that does not hinder the light transmittance. Specifically, the thickness is preferably 3 nm to 1 μm, and preferably 5 nm to 400 nm. More preferred. In addition, it is preferable that the visible light transmittance of the electrode provided in the side which visually recognizes an image shall be 80% or more like a base | substrate.

  Note that the thickness of the electrode provided on the side opposite to the side where the image is viewed is also preferably in the above range, but it is not necessary to be transparent.

  Examples of the constituent material of the electrodes 15a and 15b include metal materials, conductive metal oxides, and conductive polymer materials. Specific examples of the metal material include aluminum, silver, nickel, copper, and gold. Specific examples of the conductive metal oxide include indium tin oxide (ITO), indium oxide, and antimony tin. An oxide (ATO), a tin oxide, a zinc oxide, etc. are mentioned. Furthermore, examples of the conductive polymer material include polyaniline, polypyrrole, polythiophene, polyacetylene, and the like.

  As a method for forming the electrodes 15a and 15b on the substrate 11 or 12, for example, when an electrode on a thin film is provided, a sputtering method, a vacuum evaporation method, a chemical vapor deposition method (CVD method; Chemical Vapor Deposition), a coating method is used. Etc. There is also a method of forming an electrode by mixing a conductive material with a solvent or a binder resin and applying the mixture to a substrate.

  Next, the insulating layer 16 constituting the image display device 1 will be described.

  As shown in FIG. 1, the image display device 1 is provided with an insulating layer 16 containing a substance having a silicone structure on the surfaces of a plurality of electrodes 15 a and 15 b arranged along the bases 11 and 12. Therefore, the particles 21 and 22 can be in contact with each other. A typical example of the substance having a silicone structure contained in the insulating layer 16 is a silicone resin. Silicone resin is a general term for polymer compounds whose basic skeleton is a bond of a silicon atom (Si) and an oxygen atom (O) called a siloxane bond, and has an alkyl group or the like in the side chain, and is also called an organosilicon compound Is.

  As shown in FIG. 1, when the insulating layer 16 is formed on the surfaces of the electrodes 15a and 15b, the silicone resin is selected as the resin component for forming the insulating layer. A silicone resin can be contained in the insulating layer by applying. Further, when the electrode 15 has a structure in which conductive fine particles are dispersed in the binder resin, it can be contained on the surfaces of the electrodes 15a and 15b by selecting a silicone resin as a constituent component of the binder resin. Furthermore, in the case of a system in which an electric field is applied from the outside of the image display device 1, the surfaces of the substrates 11 and 12 are surfaces that are in direct contact with the particles 21 and 22. An insulating layer 16 is provided or contained as a constituent component of the substrates 11 and 12.

  When the insulating layer 16 contains a silicone resin, the content of the silicone resin is preferably 10 ppm or more with respect to the entire constituent material of the insulating layer 16. Similarly, when using the electrodes 15a and 15b having a structure in which conductive fine particles are dispersed in the binder resin, it is preferable to contain 10 ppm or more of the silicone resin in the binder resin. Further, when the insulating layer 16 is directly provided on the opposing surfaces of the bases 11 and 12 or when a silicone resin is included as a constituent component of the bases 11 and 12, the insulating layer 16 contains 10 ppm or more, It is preferable to contain 10 ppm or more of silicone resin.

  As a method for adding a silicone resin in the case where a silicone resin is contained as a constituent component of the substrates 11 and 12 or when the electrodes 15a and 15b having a structure in which conductive fine particles are dispersed in a binder resin are used, for example, There are various methods. That is, a method in which a silicone resin is dissolved in a solvent and applied and dried, a method in which a curable raw material is applied and then cured with heat or ultraviolet light, and further, when the substrates 11 and 12 and the electrodes 15a and 15b are manufactured. And a method of forming by adding a silicone resin and its raw material, or a method of coating.

  The thickness of the insulating layer 16 is preferably 0.01 μm or more and 10.0 μm or less. That is, when the thickness of the insulating layer 16 is in the above range, the particles 13 and 14 can be moved without applying a very large voltage between the electrodes 15, and for example, a voltage at a level applied in image formation by electrophoresis is applied. Therefore, it is preferable because an image can be formed.

Next, specific examples of silicone resins that can be used in the present invention will be described. The silicone resin that can be used in the present invention is composed of repeating units represented by the general formula R _n SiO _(4-n) typified by a polysiloxane resin. That is, the basic skeleton is composed of a repeating unit consisting of a bond of a silicon atom (Si) and an oxygen atom (O) called a siloxane bond, and has an organic group such as a methyl group or a phenyl group in the side chain. The polysiloxane resin is obtained by hydrolysis after polymerization of organochlorosilanes as monomers, and has a structure in which n organic groups serving as side chains are bonded to silicon atoms constituting the main chain as shown below. Is.

  Next, the partition wall 17 constituting the image display device 1 according to the present invention will be described. In the image display device according to the present invention, the partition wall 17 joins the bases 11 and 12 to form a space 18. In the present invention, as shown in FIG. 2, at least along the end portions of the substrates 11 and 12. Are arranged. The arrangement of the partition walls 17b in the image display surface 18a is reduced. In particular, the partition walls 17b are not disposed in the image display surface 18a, and the partition walls 17a are disposed only along the end portions of the substrates 11 and 12. Those arranged are preferred.

  The partition wall 17 can be formed, for example, by processing the substrate on the side opposite to the side where the image is viewed using the following method. Examples of the method for forming the partition wall 17 include embossing with a resin material or the like, uneven formation by hot press injection molding, photolithography, screen printing, and the like.

  Next, the particles 2 enclosed in the space 18 will be described. In the image display device of FIG. 1, two types of particles, white particles 22 and black particles 21, are enclosed. In the image display by the movement of the particles, when a voltage is applied to the electrodes 15 provided on the substrates 11 and 12, an electric field is formed in the space 18, and the white particles 22 and the black particles 21 are charged by frictional charging. To move through the space 18. Thus, image display is performed by moving the particles in the space 18 where the electric field is formed. An image with contrast can be obtained by forming an image using the white particles 22 and the black particles 21.

  An electric field application (voltage application) method for driving the particles 2 contained in the space 18 is not particularly limited. For example, the image display device 1 shown in FIG. The electric field is applied to the space 18 through the electrode 15 provided in the circuit 12. On the other hand, the image display device 1 shown in FIG. 1B does not have the electrode 15 in its structure, and such an image display device 1 is an image display device that has an electrode outside the image display device 1. By connecting 1, an electric field can be formed in the space 18 and the particles 2 can be driven.

  In addition, when performing image display with two types of particles, the white particles 22 and the black particles 21, the mobility of the two types of particles can be determined by providing a difference in the chargeability between the white particles 22 and the black particles 21 by a known method. Can be controlled. As specific methods, for example, the particles are designed so as to change the charge order with the carrier, or the external additive is selected so as to change the charge order between the external additive added to the particle surface and the carrier. There is a way.

  The particle diameter of the particles 2 usable in the image display device 1 is preferably 0.1 μm to 50 μm in terms of volume-based median diameter, and by setting the particle diameter of the particles 2 within the above range, a uniform, uniform and clear image can be obtained. An image is obtained. Further, there is no fear of aggregation of particles, and an image having an appropriate image density and contrast can be obtained by smooth movement.

  The volume-based median diameter (D50v diameter) of the particles 2 can be measured and calculated using an apparatus in which a computer system for data processing is connected to Multisizer 3 (manufactured by Beckman Coulter).

  As a measurement procedure, 0.02 g of particles 2 was used in 20 ml of a surfactant solution (for dispersing particles 2, a surfactant solution in which a neutral detergent containing a surfactant component was diluted 10 times with pure water). After soaking, ultrasonic dispersion is performed for 1 minute to prepare a particle dispersion. This particle dispersion is poured into a beaker containing ISOTON II (manufactured by Beckman Coulter) in a sample stand with a pipette until the measurement concentration reaches 10%, and the measurement is performed with a measuring machine count of 2500. The aperture size of the multisizer 3 is 50 μm.

  Next, the constituent material of the particles 2 contained in the space 18 of the substrates 11 and 12 will be described. The particles 2 used in the image display device 1 are required to contain at least a resin and a colorant and develop charging properties by an action such as frictional force. The particles 2 are preferably colored with a colorant because the image display device 1 is required to display an image with contrast. In addition, inorganic compound particles such as titanium oxide, silica, and calcium carbonate can be externally added to the particle surface.

  The resin constituting the particles 2 is not particularly limited, and a polymer called a vinyl resin shown below is typical, and in addition to the vinyl resin, a polyamide resin, a polyester resin, or a polycarbonate resin is used. There are also condensation resins such as epoxy resins. Specific examples of vinyl resins include polystyrene resins, polyacrylic resins, polymethacrylic resins, and polyolefin resins formed from ethylene monomers and propylene monomers.

  In addition to the above-described condensation resins, resins other than vinyl resins include polyether resins, polysulfone resins, polyurethane resins, fluorine resins, and silicone resins.

  The polymer constituting the resin that can be used for the particles 2 is prepared by combining a plurality of types of polymerizable monomers in addition to those obtained by using at least one type of polymerizable monomer that forms these resins. You can also. When a resin is prepared by combining a plurality of types of polymerizable monomers, for example, a method of forming a copolymer such as a block copolymer, a graft copolymer, or a random copolymer, or a mixture of a plurality of types of resins. There is also resin formation by a polymer blending method.

  Next, the colorant contained in the particles 2 is not particularly limited, and a known pigment is used. Among these, examples of the white pigment constituting the white particles 21 include zinc oxide (zinc white), titanium oxide, antimony white, and zinc sulfide. Among these, titanium oxide is preferable. Moreover, as a black pigment which comprises the black particle 22, carbon black, copper oxide, manganese dioxide, aniline black, activated carbon etc. are mentioned, for example, Among these, carbon black is preferable.

The method for producing the particles 2 is not particularly limited. For example, a known method for producing particles containing a resin and a colorant is applied, such as a method for producing toner used for electrophotographic image formation. It is possible to cope with it. Specific methods for producing the particles 2 include, for example, the following methods.
(1) A method of producing particles by kneading a resin and a colorant and then performing pulverization and classification processes.
(2) A so-called suspension polymerization method in which particles are formed by mechanically stirring a polymerizable monomer and a colorant in an aqueous medium to form droplets and then performing polymerization.
(3) A polymerizable monomer is dropped into an aqueous medium containing a surfactant, and a polymerization reaction is performed in a micelle to produce polymer particles of 100 to 150 nm. The so-called emulsion association method in which these particles are added and associated to produce particles.

  Examples of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

1. Production of Image Display Device According to the following procedure, an image display device that performs image display using positively charged white particles and negatively charged black particles was produced.

1-1. Preparation of Particles (1) Preparation of “White Particles 1” The following resin and titanium oxide are charged into a Henschel mixer (Mitsui Miike Mining Co., Ltd.), and the peripheral speed of the stirring blade is set to 25 m / second and mixed for 5 minutes. To make a mixture.

Styrene acrylic resin (weight average molecular weight 20,000) 100 parts by mass Anatase-type titanium oxide (average primary particle size 150 nm) 30 parts by mass After kneading the above mixture with a twin-screw extrusion kneader and then roughly pulverizing with a hammer mill, The mixture was pulverized by a turbo mill pulverizer (manufactured by Turbo Kogyo Co., Ltd.), and further finely classified by an airflow classifier using the Coanda effect to produce white particles having a volume-based median diameter of 8.2 μm.

  Next, 0.6 parts by mass of silica fine particles (average primary particle size 50 nm) treated with an aminosilane coupling agent is added to the white particles, and the number of rotations is determined using a vibratoryzer (manufactured by Nara Machinery Co., Ltd.). Was set at 15,000 rpm and the treatment was performed for 10 minutes. Subsequently, 1.0 part by mass of silica particles having an average primary particle size of 15 nm subjected to the aminosilane coupling agent treatment was added, and the same treatment was performed to produce “white particles 1”.

(2) Preparation of “Black Particle 1” The following resin and carbon black were put into a Henschel mixer (made by Mitsui Miike Mining Co., Ltd.), and the peripheral speed of the stirring blade was set to 25 m / sec. did.

Styrene acrylic resin (weight average molecular weight 20,000) 100 parts by mass Carbon black (average primary particle size 25 nm) 10 parts by mass The above mixture is kneaded with a twin-screw extrusion kneader, then coarsely pulverized with a hammer mill, and then turbo milled. Coarse powder was pulverized by a machine (manufactured by Turbo Kogyo Co., Ltd.), and further finely classified by an airflow classifier utilizing the Coanda effect, to produce black particles having a volume-based median diameter of 8.0 μm.

  Next, 0.6 parts by mass of silica fine particles (average primary particle size 50 nm) treated with an aminosilane coupling agent is added to the above black particles, and the number of rotations is determined using a vibratoryzer (manufactured by Nara Machinery Co., Ltd.). Was set at 15,000 rpm and the treatment was performed for 10 minutes. Subsequently, 1.0 part by mass of silica particles having an average primary particle size of 15 nm subjected to the aminosilane coupling agent treatment was added, and the same treatment was performed to produce “Black Particles 1”.

1-2. Production of “image display device housings 1 to 4” (1) Production of “image display device housing 1” Two glass substrates each having a length of 100 mm, a width of 140 mm, and a thickness of 0.7 mm were prepared on each substrate surface. For this, an electrode made of an indium tin oxide (ITO) film having a thickness of 300 nm was formed by a vapor deposition method. Next, in order to make the said electrode comprised from a some electrode, the electrode was divided | segmented by the well-known method so that it might become a thing of the structure where the 80-micrometer-wide electrode was arranged with a 20 micrometer space | interval. Further, for one glass substrate used at a position not on the viewing side of the two substrates, a partition wall having a width of 80 μm and a height of 50 μm is formed only along the edge of the substrate by a photoresist method, and the image display surface The one without a partition was used.

  A coating solution prepared by dissolving 12 parts by mass of a polycarbonate resin having the following structure having a viscosity average molecular weight of 30,000 in a mixed solvent of tetrahydrofuran and toluene (volume ratio = tetrahydrofuran 80: toluene 20) on the plurality of electrodes thus formed. Was applied by spin coating to form an insulating layer 1. The insulating layer was formed so that the film thickness at the time of drying was 3 μm, and the coating solution was prepared so as to contain 100 ppm of dimethyl silicone resin having a viscosity average molecular weight of 100,000.

  The above-described processing was performed on the two glass substrates to produce a two-image set “image display device housing 1” having a structure in which no partition wall exists in the image display surface shown in FIG.

(2) Production of “image display device housing 2” Two glass substrates larger than the glass substrate used in production of “image display device housing 1” (length 150 mm, width 220 mm, thickness 0.7 mm) And an electrode made of an indium tin oxide (ITO) film having a thickness of 300 nm was formed on each substrate surface by a vapor deposition method.

  Next, the electrodes were divided by a known method so that electrodes having a width of 80 μm square were arranged at intervals of 20 μm. Next, for one glass substrate used at a position not on the viewing side of the two substrates, a partition wall having a width of 80 μm and a height of 50 μm is formed along the edge of the substrate by a photoresist method. Inside, in principle, 16 electrodes were taken as one unit, and a partition wall having a width of 20 μm and a height of 50 μm was formed around it. In this way, a two-sheet “image display device housing 2” having a structure having a partition wall surrounding a plurality of electrodes in the image display surface shown in FIG.

(3) Production of “image display device housing 3” After the electrodes are formed by vapor deposition on two glass substrates having the same dimensions as those used in the production of “image display device housing 2”, the width is 80 μm. The electrodes were divided by a known method so that the four electrodes were arranged at intervals of 20 μm. Next, for one glass substrate used at a position not on the viewing side of the two substrates, a partition is formed by forming a partition wall having a width of 80 μm along the edge of the substrate by a photoresist method, and by dividing processing. A partition wall having a width of 20 μm and a height of 50 μm was formed around all the 80 μm square electrodes formed. In this way, a two-sheet “image display device housing 3” having a structure in which partition walls are also arranged around all the electrodes shown in FIG. 3 was produced.

(4) Production of “image display device housing 4” In the production of “image display device housing 3”, the electrodes are divided by a known method so that electrodes having a width of 60 μm are arranged at intervals of 40 μm. In addition, for one glass substrate used in a position not on the viewing side of the two sheets, a partition wall having a width of 40 μm and a height of 50 μm was formed around each formed 60 μm square electrode. Other than that, the “image display device housing 4” in a set of two sheets having a structure in which partition walls are arranged around all the electrodes shown in FIG.

1-3. Production of “image display devices 1 to 4” Each of the above-mentioned “white particles 1” and “black particles 1” is stirred for 30 minutes with a shaker, and “white particles 1” and “black particles 1” are previously prepared. Frictionally charged, white particles were positively charged and black particles were negatively charged.

  After filling the “image display device casings 1 to 4” with a mixture of “white particles 1” and “black particles 1” so that the occupied volume of white particles is 15% and the occupied volume of black particles is 15%. Two casings were bonded together using a commercially available adhesive so as to face each other along the partition wall. In this manner, “image display devices 1 to 4” were produced. Among these, the “image display device 3” in which a partition wall having a width of 20 μm is formed around all the 80 μm square electrodes formed, requires more labor than the “image display devices 2 and 4” of the same size. did. Specifically, when arranging the adhesive along the partition wall, it was necessary to arrange the adhesive so that the adhesive did not flow from the partition wall toward the electrode.

  Further, when the two glass substrates are bonded, a large number of partition walls on the non-viewing substrate on which a partition wall having a width of 20 μm and a height of 50 μm is formed, and a large number of partition walls formed on the viewing side substrate on which the partition walls are not formed. All the electrode positions could not be aligned. As a result, in some cells, the position of the cell and the position of the electrode provided on the substrate were shifted, and a portion where the phase of the cell and the electrode was not aligned was born. The “image display devices 1 to 4” all have the same number of electrode pairs, but among the “image display devices 1 to 4”, the “image display device 1” has no partition wall in the image display surface. "Is smaller than the other" image display devices 2 to 4 ".

2. Evaluation Experiment The “image display apparatuses 1 and 2” produced by the above procedure were referred to as “Examples 1 and 2,” and the “image display apparatuses 3 and 4” were referred to as “Comparative Examples 1 and 2.”

Display characteristics were evaluated by applying a DC voltage to each image display device according to the following procedure and measuring the reflection density of the image display device obtained by the voltage application. The voltage application was performed according to the following procedure. The applied voltage was changed from 0V to the plus side, then changed to the minus side, and the voltage was applied so as to draw a hysteresis curve of a path returning to 0V again. That is,
(1) Application is performed while changing the voltage from 0V to + 100V at intervals of 20V.
(2) Application is performed while changing the voltage from + 100V to −100V at intervals of 20V.
(3) Application is performed while changing the voltage from −100V to 0V at intervals of 20V.

  When a DC voltage was applied to each image display device according to the above procedure, it was confirmed that the display changes from white to black when a positive voltage is applied to the electrode provided on the substrate on the viewing side in the white display state. It was. In the evaluation, all the electrodes provided on the substrate on the viewing side are connected to one, all the electrodes provided on the substrate on the non-viewing side are connected to one, and the two connections obtained as a result A voltage was applied to the terminals.

  In the evaluation, black density, white density, and contrast were measured as display characteristics, and occurrence of display unevenness was visually evaluated. Here, the black density is the reflection density of the display surface obtained when a voltage of +100 V is applied to the viewing direction electrode of the image display device, and the white density is obtained when a voltage of −100 V is applied by the above hysteresis curve. It shows the reflection density of the display surface.

The contrast is the difference between the black density obtained in (1) and the white density obtained in (2), that is,
Contrast = (black density obtained in (1)) − (white density obtained in (2))
Is defined in

  Each density mentioned above was measured at five locations on the display surface at random using a reflection densitometer “RD-918 (manufactured by Macbeth Co.)”, and the average value was obtained. The white density was 0.55 or less, the black density was 1.25 or more, and the contrast was 0.70 or more.

  The results are shown in Table 1.

  As shown in Table 1, all of the image display devices of “Examples 1 and 2” corresponding to the present invention have values of black density 1.25 or more, white density 0.50 or less, and contrast 0.70 or more. As a result, the passing value specified in the present invention was cleared. On the other hand, in the image display devices of Comparative Examples 1 and 2 that fall outside the present invention, both the white density and the black density become low values, and the image quality deteriorates due to the presence of many partition walls in the image display unit. In particular, in Comparative Example 1, when two substrates were bonded together, the electrodes and the partition walls were displaced between the substrates, and unevenness was observed on the image.

  As described above, “Examples 1 and 2” obtained display characteristics far superior to “Comparative Examples 1 and 2”. From the above results, it was confirmed that an image display device having good image density and contrast can be obtained by the configuration of the present invention. It has also been confirmed that the configuration of the present invention can reduce the trouble of manufacturing the image display device.

It is a schematic diagram which shows the structure cross section of the image display apparatus which concerns on this invention. It is a structure cross-sectional schematic diagram of the image display apparatus which concerns on this invention, and the conventional image display apparatus. It is a structure cross-sectional schematic diagram of the conventional image display apparatus. It is a schematic diagram which shows the example of the movement of the particle | grains by the voltage application between base | substrates. It is a schematic diagram which shows the example of the movement of the particle | grains by the voltage application between base | substrates.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image display apparatus 11, 12 Base body 15 Electrode pair 15a, 15b Electrode 16 Insulating layer 17 (17a, 17b) Partition 18 Space 18a Image display surface 2 Particles 21 Black particle 22 White particle

Claims (3)

An image display device comprising particles in a space formed by facing two substrates, at least one of which is transparent,
The image display device includes:
A plurality of pairs of electrodes for applying a voltage to the space are disposed along the two substrates, and
An image display device, wherein a partition wall for joining the two substrates is disposed at least along an end of the substrate. The image display device according to claim 1, wherein the partition wall is disposed only along an end portion of the base body. The image display device according to claim 1, wherein at least two or more pairs of electrodes are arranged in a region surrounded by the partition walls.

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