JP2009031662A - Display medium and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display medium and a display device, capable of suppressing deterioration in display color densities of colors displayed after repetitive rewriting and in color uneveness of secondary colors or more. <P>SOLUTION: The display medium includes a pair of substrates disposed with a clearance between them, wherein at least one of the substrates is translucent; a dispersion medium sealed in the clearance between the substrates, different kinds of translucent particle groups having different colors and different absolute values of migration potentials for moving and being dispersed in the dispersion medium to move in the electric field formed between the substrates; and a pre-charged film provided on at least one of the opposed surfaces of the substrates and having a plurality of depressed sections opened to the opposite substrate to enable transfer of the particle groups. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display medium and a display device.

Conventionally, an image display medium using colored particles is known as an image display medium that can be repeatedly rewritten (see, for example, Patent Documents 1 and 2).
The image display medium includes, for example, a pair of substrates and a group of particles sealed between the substrates so as to be movable between the substrates in accordance with an electric field formed between the pair of substrates.

  The particle group enclosed between the pair of substrates is a single type of particle group colored in a specific color, or a plurality of types of particle groups having different colors and different electric field strengths required for movement, etc. There is.

  In this image display medium, by moving the encapsulated particles by applying a voltage between a pair of substrates, the color according to the amount of particles moved to one of the substrates and the color of the moved particles Images are displayed. That is, by applying a voltage with a strength for moving the particles to be moved between the substrates in accordance with the color and density of the image to be displayed, the particles to be moved are moved between the pair of substrates. An image corresponding to the color and density of the image to be displayed is displayed by moving to either side.

  In the technique of Patent Document 1, a charged film is disposed on a substrate, a difference in electric field density is generated on a fixing surface on which the charged film is formed, and the electric field density of the charged film is increased by an edge effect. A concave portion formed in a shape in which charged particles do not fit is provided on the fixing surface formed by the film. For this reason, the charged particles are provided to be larger than the recesses.

  In the technique of Patent Document 2, a charged film in which a surface charge having a polarity opposite to that of the charged particles is steadily charged is arranged on the fixing surface where the charged particles are gathered. The surface of this charged film is substantially planar.

JP 2006-215473 A JP 2000-258805 A

  It is an object of the present invention to provide a display medium and a display device capable of suppressing color unevenness of secondary or higher colors as well as suppressing a decrease in color density of a display displayed after repeated rewriting.

The above problem is solved by the following means. That is,
According to the first aspect of the present invention, at least one of the pair of substrates having translucency and disposed with a gap, a dispersion medium enclosed between the pair of substrates, dispersed in the dispersion medium, and transmitting light A plurality of types of particle groups having different properties and moving according to an electric field formed between the substrates, and having different colors and absolute values of moving voltages necessary for moving, and opposing surfaces of the pair of substrates And a precharged charged film having a plurality of recesses that are open on the opposite substrate side and that allow the particle groups to enter and exit the display medium.

  The invention according to claim 2 is the display medium according to claim 1, wherein the concave portion is provided over the entire area of the opposing surfaces of the pair of substrates of the charging film.

  The invention according to claim 3 is the display medium according to claim 1, wherein the depth of the recess is equal to or greater than the volume average primary particle size of at least a plurality of particles in the plurality of types of particle groups. It is.

  According to a fourth aspect of the present invention, the charged film is formed by laminating a second charged film that is charged or uncharged to less than the saturated charge amount on the first charged film that has been charged to a saturated charge amount in advance. The display medium according to claim 1.

  The invention according to claim 5 is a pair of substrates having electrodes, at least one of which is translucent and disposed with a gap, a dispersion medium sealed between the pair of substrates, A plurality of types of particles dispersed in the dispersion medium, having translucency, moving according to an electric field formed between the substrates, and having different absolute values of colors and movement voltages necessary to move with each other A display medium having a group and a precharged charging film provided on at least one of the opposing surfaces of the pair of substrates and having a plurality of recesses that are open on the opposing substrate side and into which the particle group can enter and exit. And a voltage applying means for applying a voltage between the pair of substrates.

  The invention according to claim 6 is characterized in that the plurality of types of particles have a voltage range necessary for moving according to the electric field for each type, and the voltage ranges are different from each other. It is a display apparatus of description.

  According to the first aspect of the present invention, a precharged charged film having a plurality of recesses that are open on the opposite substrate side and into which particles can enter and exit is provided on at least one of the opposed surfaces of the pair of substrates. Therefore, a decrease in color density due to a decrease in the ratio of the area of particles present in the surface direction of the apparent display medium (apparent coverage) viewed from one substrate side of the display medium after repeated rewriting is suppressed. In addition, there is an effect that color unevenness of the secondary or higher color is suppressed.

  According to the second aspect of the present invention, compared with the case where the concave portion is provided only in a partial region of the opposing surfaces of the pair of substrates, a decrease in the apparent coverage after repeated rewriting is further suppressed. As a result, a decrease in color density due to this is suppressed, and color unevenness of secondary or higher colors is suppressed.

  According to the invention of claim 3, the apparent coverage after repeated rewriting is reduced as compared with the case where the depth of the recess is less than the volume average particle diameter of two particles of a plurality of types of particles. As a result, it is possible to suppress the decrease in color density due to the suppression of color and to further suppress the color unevenness of the secondary color or more.

  According to the invention which concerns on Claim 4, compared with the case where a charging film is comprised with a single layer, there exists an effect that the charging intensity | strength of a charging film is adjusted easily.

  According to the fifth aspect of the present invention, the display in which the decrease in the color density due to the suppression of the decrease in the apparent coverage after repeated rewriting is suppressed and the color unevenness of the secondary color or more are suppressed. There exists an effect that an apparatus is provided.

  According to the invention concerning Claim 6, there exists an effect that the color display which suppressed color mixing is made | formed.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol may be provided to the member which an action and a function bears the same function through all drawings, and the overlapping description may be abbreviate | omitted.

  FIG. 1 is a schematic configuration diagram of a display device according to an embodiment.

  As illustrated in FIG. 1, the display device 10 according to the embodiment includes a display medium 12, a voltage application unit 16 that applies a voltage to the display medium 12, and a control unit 18.

The display medium 12 includes a display substrate 20 that serves as an image display surface, a rear substrate 22 that faces the display substrate 20 with a gap, and holds the substrates at a predetermined interval, and between the display substrate 20 and the rear substrate 22. The gap member 24 is configured to include a plurality of cells, a particle group 34 enclosed in each cell, and a reflection member 36 having an optical reflection characteristic different from that of the particle group 34.
Although details will be described later, the particle group 34 is composed of a plurality of types of particle groups having different movement voltages and different absolute values necessary for movement.

  The cell indicates a region surrounded by the display substrate 20, the back substrate 22, and the gap member 24. A dispersion medium 50 is enclosed in this cell. The particle group 34 (described in detail later) is composed of a plurality of particles. The particle group 34 is dispersed in the dispersion medium 50 and passes between the display substrate 20 and the back substrate 22 according to the electric field strength formed in the cell. It moves through the gap of the reflecting member 36.

  In addition, by providing the gap member 24 so as to correspond to each pixel when the image is displayed on the display medium 12 and forming the cell so as to correspond to each pixel, for example, the display medium 12 is provided for each cell. One pixel is displayed. Note that cells may be provided corresponding to a plurality of pixels, that is, a plurality of pixels may be displayed in one cell.

  Further, in this embodiment, in order to simplify the description, the present embodiment will be described using a diagram focusing on one cell. Hereinafter, each configuration will be described in detail.

  The display substrate 20 has a configuration in which display electrodes 40 are stacked on a support substrate 38. The back substrate 22 has a configuration in which a back electrode 46 is laminated on a support substrate 44.

The display substrate 20 or both the display substrate 20 and the back substrate 22 are translucent.
Here, the translucency in the present embodiment indicates that the transmittance of visible light is 60% or more.

  Examples of the support substrate 38 and the support substrate 44 include glass and plastics such as polyethylene terephthalate resin, polycarbonate resin, acrylic resin, polyimide resin, polyester resin, epoxy resin, and polyethersulfone resin.

  For the display electrode 40 and the back electrode 46, oxides such as indium, tin, cadmium and antimon, composite oxides such as ITO, metals such as gold, silver, copper and nickel, organic materials such as polypyrrole and polythiophene are used. can do. These can be used as a single layer film, a mixed film, or a composite film, and can be formed by vapor deposition, sputtering, coating, or the like. Moreover, the thickness is 100-2000 mm normally according to a vapor deposition method and sputtering method. The back electrode 46 and the display electrode 40 may be formed in a desired pattern, for example, a matrix shape or a stripe shape that enables passive matrix driving, by a conventionally known means such as etching of a conventional liquid crystal display medium or a printed circuit board. it can.

  Further, the display electrode 40 may be embedded in the support substrate 38. Further, the back electrode 46 may be embedded in the support substrate 44. In this case, the materials of the support substrate 38 and the support substrate 44 are selected according to the composition of each particle of the particle group 34 and the like.

  Note that the back electrode 46 and the display electrode 40 may be separated from the display substrate 20 and the back substrate 22 and disposed outside the display medium 12.

  In the above description, the case where both the display substrate 20 and the back substrate 22 are provided with electrodes (the display electrode 40 and the back electrode 46) has been described. However, only one of them is provided and active matrix driving is performed. Also good.

  In order to enable active matrix driving, the support substrate 38 and the support substrate 44 may include a TFT (thin film transistor) for each pixel. Since it is easy to laminate wiring and mount components, it is desirable to form the TFT on the back substrate 22 instead of the display substrate.

  As shown in FIGS. 1 and 2, the opposing surfaces of the display substrate 20 and the back substrate 22 (in this embodiment, the opposing surfaces of the display electrode 40 and the back electrode 46) have translucency and are charged in advance. The charged film 27 and the charged film 29 are provided.

  In the present embodiment, the case where the charging film is provided on each of the opposing surfaces of the display substrate 20 and the back substrate 22 will be described. However, the charging film may be provided on only one of them. Although the details will be described later when the charging film is provided at least on the display substrate 20, the decrease in the apparent coverage during repeated display (details will be described later) is suppressed, and the color density decreases. In addition to being suppressed, color unevenness of the secondary color or more is suppressed.

  The charged film 27 and the charged film 29 are films that are charged in advance, and are charged to a predetermined charge amount without being applied with a voltage.

  Since the charging film 27 and the charging film 29 are provided on the display substrate 20 side and the back substrate 22 side, a voltage exceeding the moving voltage at which the particle group 34 moves between the display substrate 20 and the back substrate 22 is applied. As a result, the particle group 34 that has moved to the display substrate 20 side or the back substrate 22 side is stopped after the voltage application between the display substrate 20 and the back substrate 22 is stopped. The deterioration of the image quality retention of the display medium 12 after the voltage application is stopped is suppressed.

  In the present embodiment, the case where the charging film 27 and the charging film 29 are provided on both the display substrate 20 side and the back substrate 22 side will be described. However, the charging film 27 and the charging film 29 are configured to be provided only on one side. There may be. In the case of the configuration provided only on either one side, in the display medium 12, the decrease in the apparent coverage displayed after repeated rewriting is suppressed, the decrease in color density is suppressed, and the secondary color is suppressed. From the viewpoint of further suppressing color unevenness of the above colors, it is preferable to be provided at least on the display substrate 20 side.

  The charge amount of the charge film 27 and the charge film 29 is preferably smaller than the charge amount per area of each particle constituting the particle group 34.

  If the charge amount of the charge film 27 and the charge film 29 is larger than the charge amount of each particle, even if a voltage exceeding the moving voltage at which each type of particle group 34 moves between the display substrate 20 and the back substrate 22 is applied. Electrophoresis while the particle group 34 remains on the charged film 27 side or the charged film 29 side may be suppressed.

  Further, as will be described in detail later, in the display medium 12 that performs multicolor display by electrophoresis of the particle group 34 for each color, the display substrate 20 and the back substrate 22 of each particle group 34 constituting the particle group 34. In order to ensure the display responsiveness without interfering with the movement between the particles, the particles do not overlap in the direction in which the display substrate 20 and the back substrate 22 face each other, but on the surface of the charged film 27 or the charged film 29. In addition, it is a preferable form that they are attached in a single layer. However, when the charge amount of the charge film is larger than the charge amount of each particle of the particle group 34, a plurality of particles are stacked in the facing direction of the display substrate 20 and the back substrate 22, and the surfaces of the charge film 27 and the charge film 29 are respectively. It tends to be in a state of adhering to. For this reason, for example, the movement of the particles in the dispersion medium 50 located closest to the charged film 27 (or charged film 29) in the particle group 34 is stacked on the substrate side opposite to the particles. It may be hindered by the particle group, and the responsiveness of the display will decrease, or the color of the secondary color or more will be displayed along with the decrease in color density due to the decrease in the apparent coverage that is displayed after repeated rewriting Unevenness may occur.

Examples of the material constituting each of the charged film 27 and the charged film 29 include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and polyhexafluorinated polypropylene (FEP-Teflon (registered trademark)). Examples thereof include fluorine-based polymer materials, synthetic polymer materials such as polyethylene terephthalate (PET) and polypropylene (PP). These are easy to mold, and may be cooled after the material is applied in a molten state, or a film-like material may be laminated. Furthermore, inorganic materials such as LiTaO ₃ , PZT, LiNbO ₃ , PbTiO ₃ can also be used. _{SiO 2, Si 3 N 4,} SiO 2 and Si ₃ complex of N ₄ (SION) similar effect constitute an electret of silicon-based inorganic material such as can be expected.

  For the inorganic material, the charged film 27 and the charged film 29 are formed by a known film forming method such as vapor deposition, CVD, sputtering, printing and baking, and patterning.

  The polarity of the charged film 27 and the charged film 29 should be adjusted to the opposite polarity to the polarity of the particle group 34 in order to make maximum use of the electrostatic attractive force with the particles when a plurality of types of particle groups 34 have the same polarity. Is preferred. When the particle group of a plurality of particles includes both positive and negative polarities, since the electretized charging film can generally adsorb both positive and negative polarity particles, the polarity of the charging film may be any polarity.

  Each of the charging film 27 and the charging film 29 has an opening on the opposite substrate side (the display substrate 20 side or the back substrate 22 side), and each particle constituting the particle group 34 can enter and exit through the opening. A plurality of recesses 52 are provided.

  The recess 52 is a pair of substrates (the display substrate 20 and the display substrate 20) of the charging film 27 and the charging film 29 from the viewpoint of further suppressing color unevenness of the secondary color or more displayed after repeated rewriting in the display medium 12. Although it is preferable to be provided over the entire area of the surface facing the back substrate 22), the structure may be provided only in a part of the area.

The concave portion 52 has a surface area on the opposing surface of the display substrate 20 and the back substrate 22 in each of the charging film 27 and the charging film 29 provided with the concave portion 52, and the concave portion 52 is provided in each of the charging film 27 and the charging film 29. It is preferable that the surface area of the opposing surface of the display substrate 20 and the back substrate 22 in the absence is three times or more.
The surface area of each of the charging film 27 and the charging film 29 provided with the recess 52 is set to be three times or more that of each of the charging film 27 and the charging film 29 not provided with the recess 52, thereby forming each particle constituting the particle group 34. The surface area that can be arranged in contact with the charging film 27 and the charging film 29 can be three times or more that of each of the charging film 27 and the charging film 29 not provided with the recess 52.

Here, when each of the charging film 27 and the charging film 29 has a flat configuration in which the concave portion 52 is not provided, the particle group 34 is arranged in the surface direction of the substrate when positioned on the display substrate 20 side or the back substrate 22 side. Will be arranged along. Therefore, when the display medium 12 has a configuration in which the concave portions 52 are not provided in the charging film 27 and the charging film 29, the display medium 12 is arranged in the surface direction when viewed from the display substrate 20 side. When a missing particle occurs in the particle, the portion is visually recognized as a color other than the particle (for example, white). Such missing particles are particularly noticeable when a single color (one kind of particles of the same color) is displayed after a display target color is displayed (that is, a secondary color or more is displayed) using a plurality of color particles. Occurs.
Specifically, for example, in the case where the display medium 12 includes particles of three colors having different colors as the particle group 34, after the tertiary color is displayed by three types of particles, When the primary color is displayed, in the case where the charging film 27 and the charging film 29 have a flat configuration in which the concave portion 52 is not provided, the configuration in which the concave portion 52 is provided as in the present embodiment. In contrast, the ratio of the particle existing area in the surface direction of the apparent display medium 12 viewed from the display substrate 20 side is low, and the color density is low.

  In the present embodiment, the “ratio of the particle existing area in the surface direction of the apparent display medium 12 visually recognized from the display substrate 20 side” will be referred to as “apparent coverage” as appropriate.

  Thus, in the conventional configuration, the apparent coverage is reduced as compared with the configuration of the present invention, and as a result, colors other than particles necessary for expressing the display target color (for example, white) It is considered that the color density is lowered.

  On the other hand, in the display medium 12 of the present embodiment, since the recessed portions 52 are provided in each of the charging film 27 and the charging film 29, an apparent decrease in coverage is suppressed and a decrease in color density is suppressed. . Further, since the concave portions 52 are provided in each of the charging film 27 and the charging film 29, color unevenness when displaying a secondary color or higher is suppressed.

  The depth of the recess 52 is not less than a value obtained by adding the volume average primary particle sizes of at least two or more of the particles constituting the particle group 34, that is, the particles constituting the particle group 34. Is a depth at which two or more particles can be arranged in the depth direction when they are arranged in the depth direction of the recess 52, and is preferably a depth of 1/3 or less of the distance between the opposing substrates. .

  In addition, when the volume average primary particle size of the particle group 34 is different for each type (each color), the volume average of the plurality of types of particle groups 34 having different colors contained in the same cell is the most volume average. The volume average primary particle size of the particles constituting the type of particle group 34 having a large primary particle size and the volume average primary particle size of the particles constituting the type of particle group 34 having the next largest volume average primary particle size are added together. It is preferable that the depth is not less than the above value.

  When the depth of the concave portion 52 is less than the value obtained by adding the volume average primary particle diameters of the two particles constituting the particle group 34, color unevenness when a color of a secondary color or higher is displayed can be suppressed. It becomes difficult. On the other hand, when the depth of the concave portion 52 is equal to or greater than the value obtained by adding the volume average primary particle sizes of the two particles constituting the particle group 34, the depth of the concave portion 52 includes two or more particles constituting the particle group 34. It becomes possible to arrange in the direction, and when the display medium 12 is viewed from the display substrate 20 side, the color due to the subtractive color mixing of two or more particles is visually recognized, and as a result, the decrease in the coverage of the particles is suppressed. Color unevenness when a secondary color or higher is displayed.

  In addition, when the depth of the recess 52 exceeds 1/3 of the distance between the opposing substrates, the thickness of the reflecting member 36 when configured as the display medium 12 may decrease and the white reflectance may decrease.

  The distance (shortest distance) between adjacent recesses 52 formed in each of the charging film 27 and the charging film 29 is preferably smaller than the major axis of the bottom of the recess 52. If the distance between the recesses 52 is larger than the major axis of the bottom of the recess 52, the efficiency of increasing the surface area decreases.

  As shown in FIGS. 2 and 3A, each of the charging film 27 and the charging film 29 is formed by providing the charging film 27 and the charging film 29 on the display electrode 40 and the back electrode 46 having projections and depressions, respectively. The charging film 27 and the charging film 29 having the recess 52 may be configured, but is not limited to such a form.

  For example, as shown in FIG. 3C, the display electrode 40 and the back electrode 46 are formed on the flat support substrate 38 and the support substrate 44, respectively, and the display electrode 40 and the back surface having no unevenness on the surface. A configuration in which the charging film 27 and the charging film 29 each having the recess 52 are laminated on each electrode 46 may be employed.

As shown in FIG. 2 and FIG. 3A, the charging film 27 having the recess 52 is provided by providing the charging film 27 and the charging film 29 respectively on the display electrode 40 and the back electrode 46 having projections and depressions. When the charging film 29 is formed, the thicknesses of the charging film 27 and the charging film 29 are usually 0.1 μm or more and 5 μm or less, preferably 0.5 μm or more and 2 μm or less.
Further, as shown in FIG. 3C, when the charging film 27 and the charging film 29 each having the recess 52 are laminated on the display electrode 40 and the back electrode 46 each having no unevenness on the surface. The thickness of the region corresponding to the bottom of the concave portion 52 of the charging film 27 and the charging film 29 is usually 1 μm or more and 10 μm or less, preferably 3 μm or more and 7 μm or less.

  Further, the shape of the recess 52 of each of the charging film 27 and the charging film 29 may be rectangular or cylindrical as shown in FIGS. 2 and 3A, but as shown in FIG. 3B. It may be trapezoidal. When the recessed part 52 is trapezoidal, it is preferable that the area of the opening of the recessed part 52 is larger than the area of the bottom part of the recessed part 52. By adjusting so that the area of the opening of the recess 52 is larger than the area of the bottom of the recess 52, each particle constituting the particle group 34 that has moved through the dispersion medium 50 passes through the opening of the recess 52. The particles constituting the particle group 34 entering the recess 52 are easily arranged in a single layer in the thickness direction of the recess 52 along the surface of the charged film 27 (or the charged film 29). Become.

  As a method of forming each of the charging film 27 and the charging film 29, as shown in FIGS. 3A and 3B, the charging film 27 and the charging film 27 and the back electrode 46 are formed on the uneven electrodes (the display electrode 40 and the back electrode 46, respectively). When each of the charged films 29 is formed, for example, each of the display electrode 40 and the back electrode 46 having projections and depressions is immersed in a solution obtained by diluting CYTOP manufactured by Asahi Glass Co., Ltd. 5 times with a diluent, and then pulled and dried Examples thereof include a dip coating method for forming a film, a spin coating method, and the like.

In addition, as shown in FIG. 3C, the charging film 27 and the charging film 29 are formed by using the above-described materials in the case where the concave portion 52 is formed by providing irregularities on the charging film 27 and the charging film 29 itself. The charging film 27 and the charging film 29 are formed on the display electrode 40 and the back electrode 46, respectively, using a dip coating method or the like, or the sheet-like charging film 27 and the charging film 29 are respectively formed on the display electrode 40 and the back electrode 46. After the lamination, the recess 52 is formed by using laser processing, for example, a method of forming the recess 52 by a high frequency short pulse method, a screen printing method, a relief printing method, an intaglio printing (gravure printing) method, or the like. A method is mentioned.
Further, it may be formed by an etching method or an imprint method.

  In the etching method, for example, a UV curable resin such as Three Bond 3000 series is applied on each of the display electrode 40 and the back electrode 46, and then irradiated with UV light in accordance with the shape, depth, and position of the recess 52. Is cured to remove a non-cured portion, and a material formed as a material constituting the charging film 27 and the charging film 29 is formed thereon by spin coating or the like.

  In the imprint method, a mold in which a convex portion corresponding to the concave portion 52 is processed using a lithography method or the like, an ultraviolet curable resin such as Toyo Gosei PAK-01 is formed on a substrate by a spin coat method or the like, By irradiating UV light under mold pressure bonding, the concave / convex structure of the mold is transferred and molded on the resin side, and the materials mentioned as the materials constituting the charging film 27 and the charging film 29 are manufactured by spin coating or the like. Formed by filming.

Here, in order to charge the material constituting each of the charging film 27 and the charging film 29 to a predetermined charge amount, the following charging process is performed.
As the charging treatment, an electroelectret method in which a material constituting each of the charging film 27 and the charging film 29 is heated to a softening point or a melting temperature to irradiate a DC corona discharge on the surface of the material constituting each, a gamma ray or an electron beam. The radio electret method etc. which irradiate high energy radiations etc. are applicable. Among these, a charging method using corona discharge, which can be processed in a short time with a simple apparatus and can easily control the region to be charged, is preferable.

  In this charging process, each of the charging film 27 and the charging film 29 may be configured as a single layer film, and the charging process may be performed on the single layer film. It is necessary to adjust the charge amount 29 to a predetermined charge amount.

In the case where each of the charging film 27 and the charging film 29 is formed of a single layer, there are methods of adjusting the film thickness and adjusting the amount to be charged. Therefore, when the thickness is reduced, variation in the distribution of the charge amount may be a problem.
In addition, there is a method in which charging is performed while adjusting the charging amount to a desired amount during the charging process, and the charging process is terminated when the desired charging amount is reached. Since it is performed by the electrodes, it is difficult to uniformly charge a large area simultaneously. For this reason, the progress of charging varies, and it may be difficult to obtain the charging film 27 and the charging film 29 having a uniform charge distribution.
Therefore, each of the charging film 27 and the charging film 29 is preferably configured by the following method. In the following, the configuration of the charging film 27 will be described for the sake of simplicity, but the configuration method of the charging film 29 is the same.

  As shown in FIG. 4A, a first charged film 27A is provided on the display electrode 40. At this time, as the material constituting the first charging film 27A, the materials mentioned as the materials constituting the charging film 27 and the charging film 29 may be used. Then, the charging process is performed so that the first charging film 27A is charged up to the saturation charge amount of the first charging film 27A.

  Here, the saturated charge amount is an average value when the charge amount increase is less than 2% and the in-plane charge amount distribution is within ± 5% when the first charged film 27A is additionally irradiated with corona discharge for 1 minute. The value of

Note that the thickness of the first charging film 27A is preferably such that fluctuations in the charge amount due to partial variations in film thickness are negligible. The “thickness with which the variation in the charge amount due to partial variations in the film thickness is negligible” refers to the measurement result obtained by measuring a plurality of local charge amounts near the center and the periphery of the first charged film 27A. Refers to the thickness that is within 10%.
Specifically, the thickness of the first charging film 27A is preferably, for example, 0.1 μm to 5 μm, and more preferably 0.5 μm to 2 μm.

Then, as shown in FIG. 4B, on the first charging film 27A, a second charging film 27B that is charged to a charge amount less than the saturation charge amount, and preferably uncharged, is formed.
In this manner, the charged film 27 is stacked on the first charged film 27A charged to the saturation charge amount to a charge amount less than the saturation charge amount, preferably the non-charged second charge film 27B. By configuring, the charge of the first charging film 27A charged to the saturation charge amount is partially neutralized by the second charging film 27B, and the charge amount of the entire charging film 27 is easily adjusted.

The second charged film 27B is preferably composed of a compound modified with an acidic group or a basic group. By configuring the second charging film 27B with a polar compound in this way, as shown in FIG. 4B, when the second charging film 27B is laminated on the first charging film 27A, the second charging film 27B. The polar group of the neutralization partly neutralizes the charge of the first charging film 27A, and the charge amount of the entire charging film 27 formed by laminating the second charging film 27B on the first charging film 27A is easy. Adjusted.
The charge amount of the charging film 27 can be easily adjusted by adjusting the number of polar groups of the second charging film 27B.

  The film thickness of the second charging film 27B is preferably 0.5 times or less, more preferably 0.1 times or less the film thickness of the first charging film 27A. Specifically, the thickness of the second charging film 27B is preferably 0.5 μm or less, and more preferably 0.2 μm or less.

  Note that the second charging film 27B functions as a protective layer for the first charging film 27A, and the first charging film 27A does not directly contact the dispersion medium 50. It is suppressed that the charge amount of is deteriorated.

In addition, it is possible to prevent electrophoresis from being suppressed while the particle group 34 remains on the charged film 27 by containing the second charging film 27 </ b> B with a material excellent in peeling characteristics with respect to the particle group 34. it can.
This “material with excellent peeling properties” includes materials with low surface energy and excellent hydrophobicity, such as fluorine-containing polymers, such as various surface treatment agents such as OPTOOL (Daikin Industries) and Novec (Sumitomo 3M). Is mentioned.

  Even if the charge amount of the charge film 27 and the charge film 29 is adjusted to a weak charge amount such as 5 V or less by adopting such a two-layer structure for the charge film 27 and the charge film 29, the charge film 27 In addition, the charge distribution of each of the charge films 29 is uniform, the charge amount is easily adjusted, and the deterioration of the charge amount is suppressed.

  The second charging film 27B can be formed on the first charging film 27A by any method such as a spin coating method, a dip coating method, or a casting method. Since the water in the solvent used for the material constituting the second charged film 27B when the film 27B is provided may cause the charge of the first charged film 27A to disappear, the solvent is a non-aqueous system having a low water content. The solvent is preferably a nonpolar or low polarity solvent.

  The gap member 24 for maintaining a gap between the display substrate 20 and the back substrate 22 is formed so as not to impair the light-transmitting property of the display substrate 20, and is a thermoplastic resin, a thermosetting resin, or an electron beam curing. It can be formed of resin, photo-curing resin, rubber, metal or the like.

The gap member 24 may be integrated with either the display substrate 20 or the back substrate 22. In this case, the support substrate 38 or the support substrate 44 can be manufactured by performing etching processing, laser processing processing, press processing processing, printing processing, or the like using a previously manufactured mold.
In this case, the gap member 24 can be fabricated on either the display substrate 20 side, the back substrate 22 side, or both.

  The gap member 24 may be colored or colorless, but is preferably colorless and transparent so as not to adversely affect the display image displayed on the display medium 12, and in this case, for example, transparent such as polystyrene, polyester, or acrylic Resin or the like can be used.

  The particulate gap member 24 is also preferably transparent, and glass particles can be used in addition to transparent resin particles such as polystyrene, polyester or acrylic.

  Note that “transparent” means having a transmittance of 60% or more with respect to visible light.

The dispersion medium 50 in which the particle group 34 is dispersed is desirably an insulating liquid. Here, “insulating” indicates that the volume resistivity is 10 ¹¹ Ωcm or more. The same applies hereinafter.

  Specific examples of the insulating liquid include hexane, cyclohexane, toluene, xylene, decane, hexadecane, kerosene, paraffin, isoparaffin, silicone oil, dichloroethylene, trichloroethylene, perchloroethylene, high-purity petroleum, ethylene glycol, and alcohols. , Ethers, esters, dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, 2-pyrrolidone, N-methylformamide, acetonitrile, tetrahydrofuran, propylene carbonate, ethylene carbonate, benzine, diisopropylnaphthalene, olive oil, isopropanol, trichloro Trifluoroethane, tetrachloroethane, dibromotetrafluoroethane, etc. and mixtures thereof are preferred. It can be used for.

Moreover, water (so-called pure water) can also be suitably used as the dispersion medium 50 by removing impurities so that the following volume resistance value is obtained. The volume resistance value is preferably 10 ³ Ωcm or more, more preferably 10 ⁷ Ωcm or more and 10 ¹⁹ Ωcm or less, and further preferably 10 ¹⁰ Ωcm or more and 10 ¹⁹ Ωcm or less. By setting the volume resistance value in this range, it is possible to more effectively apply an electric field to the particle group, and the generation of bubbles due to the electrolysis of the liquid due to the electrode reaction is suppressed, The electrophoretic properties of the particles are not impaired, and excellent repeated stability can be imparted.

  The insulating liquid can be added with an acid, alkali, salt, dispersion stabilizer, stabilizer for the purpose of anti-oxidation or UV absorption, antibacterial agent, preservative, etc., if necessary. It is desirable to add so that it may become the range of the specific volume resistance value shown above.

  For insulating liquids, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, fluorosurfactants, silicone surfactants, metal soaps as charge control agents , Alkyl phosphate esters, succinimides and the like can be added.

  More specific examples of the ionic and nonionic surfactants are as follows. Nonionic activators include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, And fatty acid alkylolamide. Examples of the anionic surfactant include alkylbenzene sulfonate, alkylphenyl sulfonate, alkyl naphthalene sulfonate, higher fatty acid salt, sulfate of higher fatty acid ester, sulfonic acid of higher fatty acid ester, and the like. Examples of the cationic surfactant include primary to tertiary amine salts and quaternary ammonium salts. These charge control agents are preferably 0.01% by weight or more and 20% by weight or less, and particularly preferably in the range of 0.05 to 10% by weight, based on the solid content of the particles. If it is less than 0.01% by weight, the desired charge control effect may be insufficient, and if it exceeds 20% by weight, it may cause an excessive increase in the conductivity of the developer, making it difficult to use. Because.

  Note that the particle group 34 enclosed in the display medium 12 is preferably dispersed in a polymer resin as the dispersion medium 50. The polymer resin is preferably a polymer gel, a polymer, or the like.

  As this polymer resin, agarose, agaropectin, amylose, sodium alginate, propylene glycol ester of alginate, isolikenan, insulin, ethylcellulose, ethylhydroxyethylcellulose, curdlan, casein, carrageenan, carboxymethylcellulose, carboxymethyl starch, callose, agar, chitin , Chitosan, silk fibroin, gar gum, quince seed, crown gall polysaccharide, glycogen, glucomannan, keratan sulfate, keratin protein, collagen, cellulose acetate, gellan gum, schizophyllan, gelatin, elephant palm mannan, tunisin, dextran, dermatan sulfate, starch , Tragacanth gum, nigeran, hyaluronic acid, hydroxyethyl cellulose, hydroxy In addition to polymer gels derived from natural polymers such as propylcellulose, pustulan, funolan, decomposed xyloglucan, pectin, porphyran, methylcellulose, methyl starch, laminaran, lichenan, lentinan, locust bean gum, etc. Includes almost all polymer gels.

  In addition, polymers containing functional groups of alcohol, ketone, ether, ester, and amide in the repeating unit are exemplified. For example, polyvinyl alcohol, poly (meth) acrylamide and derivatives thereof, polyvinyl pyrrolidone, polyethylene oxide, and the like. Mention may be made of copolymers containing molecules.

  Among these, gelatin, polyvinyl alcohol, poly (meth) acrylamide and the like are desirably used from the viewpoints of production stability, electrophoretic characteristics and the like.

  These polymer resins are desirably used as the dispersion medium 50 together with the insulating liquid.

  Further, by mixing the following colorant in the dispersion medium 50, a color different from the color of the particle group 34 can be displayed on the display medium 12. For example, when the color of the particle group 34 is black by mixing a colorant showing white as the colorant, white and black can be displayed in the display medium 12.

  Examples of the colorant mixed in the dispersion medium 50 include carbon black, titanium oxide, magnesium oxide, zinc oxide, phthalocyanine copper-based cyan color material, azo-based yellow color material, azo-based magenta color material, quinacridone-based magenta color material, and red. Known colorants such as a color material, a green color material, and a blue color material can be listed. Specifically, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. Blue 15: 1, C.I. I. Pigment Blue 15: 3, etc. can be cited as typical examples.

  Since the particle group 34 moves in the dispersion medium 50, if the viscosity of the dispersion medium 50 is equal to or higher than a predetermined value, the dispersion of the adhesion force to the back substrate 22 and the display substrate 20 is large, and the particle movement with respect to the electric field Since the threshold value cannot be taken, the viscosity of the dispersion medium 50 may be adjusted.

  The viscosity of the dispersion medium 50 is indispensable to be 0.1 mPa · s or more and 100 mPa · s or less in an environment at a temperature of 20 ° C. from the viewpoint of the moving speed of particles, that is, the display speed, and is 0.1 mPa · s. It is preferably 50 mPa · s or less and more preferably 0.1 mPa · s or more and 20 mPa · s or less.

  By setting the viscosity of the dispersion medium 50 in the range of 0.1 mPa · sPa · s to 100 mPa · s, the adhesion force between the particle group 34 dispersed in the dispersion medium 50 and the display substrate 20 or the back substrate 22. And variations in flow resistance and electrophoresis time can be suppressed.

  The viscosity of the dispersion medium 50 can be adjusted by adjusting the molecular weight, structure, composition, and the like of the dispersion medium. In addition, Tokyo Keiki B-8L type | mold viscosity meter can be used for the measurement of this viscosity.

  In the present embodiment, as the particle group 34, a plurality of types of particle groups 34 having different colors and different absolute values of movement voltages necessary for movement are dispersed in the dispersion medium 50. The particle group 34 has at least translucency.

In the present embodiment, as the three types of particle groups 34, the yellow color yellow particle group 34Y, the magenta magenta particle group 34M, and the cyan color cyan particle group 34C are dispersed as the particle groups 34 having different colors. However, it is not limited to three types.
The plurality of types of particle groups 34 are particle groups that perform electrophoresis between substrates, and the absolute value of the movement voltage necessary for moving in accordance with the electric field is different for each color particle group. That is, each color particle group 34 (yellow particle group 34Y, magenta particle group 34M, and cyan particle group 34C) has a voltage range necessary for moving the color particle group 34 for each color. Are different (details will be described later).

  Examples of the particles of the plurality of types of particle groups 34 having different absolute values of the movement voltage necessary for moving in accordance with the electric field include, for example, charge control among materials constituting the particle group 34 described later. By changing the amount of the agent and magnetic powder, the type and concentration of the resin constituting the particles, the size of the particles, etc. can get.

  Each particle of the particle group 34 includes glass beads, insulating metal oxide particles such as alumina, titanium oxide, and the like, thermoplastic or thermosetting resin particles, and a colorant fixed on the surface of these resin particles. And particles containing a colorant in a thermoplastic or thermosetting resin, and metal colloidal particles having a plasmon coloring function.

  Examples of the thermoplastic resin used in the production of particles include styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene, and isoprene, vinyls such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate. Α-methylene aliphatic monocarboxylic acid such as ester, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate Homopolymers or copolymers of vinyl ethers such as acid esters, vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone It can be exemplified.

  In addition, as thermosetting resins used for the production of particles, crosslinked resins mainly composed of divinylbenzene and crosslinked resins such as crosslinked polymethyl methacrylate, phenol resins, urea resins, melamine resins, polyester resins, silicones Examples thereof include resins. Particularly representative binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer. Examples thereof include a polymer, polyethylene, polypropylene, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, and paraffin wax.

  As the colorant, organic or inorganic pigments, oil-soluble dyes, etc. can be used, magnetic powders such as magnetite and ferrite, carbon black, titanium oxide, magnesium oxide, zinc oxide, phthalocyanine copper-based cyan colorant, Known colorants such as an azo yellow color material, an azo magenta color material, a quinacridone magenta color material, a red color material, a green color material, and a blue color material can be given. Specifically, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. Blue 15: 1, C.I. I. Pigment Blue 15: 3, etc. can be exemplified as typical ones.

  The particle resin may be mixed with a charge control agent, if necessary. As the charge control agent, known materials used for toner materials for electrophotography can be used. For example, cetylpyridyl chloride, BONTRON P-51, BONTRON P-53, BONTRON E-84, BONTRON E-81 (above, Quaternary ammonium salts such as Orient Chemical Industry Co., Ltd., salicylic acid metal complexes, phenol condensates, tetraphenyl compounds, metal oxide particles, and metal oxide particles surface-treated with various coupling agents. .

A magnetic material may be mixed in the inside or the surface of the particles as necessary. As the magnetic material, a color-coated inorganic magnetic material or organic magnetic material is used as necessary. Further, a transparent magnetic material, in particular, a transparent organic magnetic material does not hinder the color development of the color pigment, and the specific gravity is smaller than that of the inorganic magnetic material, and is more desirable.
As the colored magnetic powder, for example, a small-diameter colored magnetic powder described in JP-A-2003-131420 can be used. A material provided with magnetic particles serving as nuclei and a colored layer laminated on the surface of the magnetic particles is used. The colored layer may be selected by coloring the magnetic powder opaque with a pigment or the like, but it is desirable to use, for example, a light interference thin film. This optical interference thin film is a thin film having a thickness equivalent to the wavelength of light made of an achromatic material such as SiO ₂ or TiO ₂ , and reflects light in a wavelength selective manner by optical interference in the thin film. is there.

  An external additive may be attached to the surface of the particles as necessary. The color of the external additive is desirably transparent so as not to affect the color of the particles.

  As the external additive, inorganic particles such as metal oxides such as silicon oxide (silica), titanium oxide, and alumina are used. In order to adjust the charging property, fluidity, and environment dependency of the particles, they can be surface-treated with a coupling agent or silicone oil.

  Coupling agents include positively chargeable ones such as aminosilane coupling agents, aminotitanium coupling agents, nitrile coupling agents, and silanes that do not contain nitrogen atoms (consisting of atoms other than nitrogen). There are negatively charged ones such as coupling agents, titanium-based coupling agents, epoxy silane coupling agents, and acrylic silane coupling agents. Silicone oil includes positively charged ones such as amino-modified silicone oil, dimethyl silicone oil, alkyl-modified silicone oil, α-methylsulfone-modified silicone oil, methylphenyl silicone oil, chlorophenyl silicone oil, fluorine-modified silicone. Examples include negatively chargeable oils. These are selected according to the desired resistance of the external additive.

Of the above external additives, well-known hydrophobic silica and hydrophobic titanium oxide are desirable. In particular, the reaction of TiO (OH) ₂ described in JP-A-10-3177 with a silane compound such as a silane coupling agent. The titanium compound obtained in (1) is preferred. As the silane compound, any of chlorosilane, alkoxysilane, silazane, and a special silylating agent can be used. This titanium compound is produced by reacting TiO (OH) ₂ produced in a wet process with a silane compound or silicone oil and drying. Since it does not pass through the firing step of several hundred degrees, a strong bond between Ti is not formed, there is no aggregation, and the particles are in the state of primary particles. Furthermore, since the silane compound or silicone oil reacts directly with TiO (OH) ₂ , the amount of silane compound or silicone oil treated can be increased, and the charging characteristics can be controlled by adjusting the amount of silane compound treated. The charging ability that can be imparted and can be imparted can be significantly improved over that of conventional titanium oxide.

  The primary particles of the external additive are generally 1 nm or more and 100 nm or less, and preferably 5 nm or more and 50 nm or less, but are not limited thereto.

  The mixing ratio of the external additive and the particles is adjusted based on the balance between the particle size of the particles and the particle size of the external additive. When the amount of the external additive added is too large, at least a part of the external additive is liberated from the particle surface and adheres to the surface of the other particle, so that desired charging characteristics cannot be obtained. In general, the amount of the external additive is preferably 0.01 to 3 parts by weight and more preferably 0.05 to 1 part by weight with respect to 100 parts by weight of the particles.

  The external additive may be added to any one of a plurality of types of particles, or may be added to a plurality of types or all types of particles. When an external additive is added to the surface of all particles, it is desirable that the external additive is applied to the particle surface with impact force or the particle surface is heated to firmly fix the external additive to the particle surface. . As a result, the external additive is released from the particles, and the external additive of different polarity is strongly aggregated to prevent the formation of an aggregate of the external additive that is difficult to dissociate with an electric field. Is prevented.

  As a method for producing the particle group 34, any conventionally known method may be used. For example, as described in JP-A-7-325434, a resin, a pigment, and a charge control agent are weighed to a predetermined mixing ratio, and after the resin is heated and melted, the pigment is added, mixed, dispersed, and cooled. Then, a method of preparing particles using a pulverizer such as a jet mill, a hammer mill, a turbo mill, etc., and then dispersing the obtained particles in a dispersion medium can be used. In addition, particles containing a charge control agent are prepared by polymerization methods such as suspension polymerization, emulsion polymerization, dispersion polymerization, coacervation, melt dispersion, emulsion aggregation, and then dispersed in a dispersion medium. A particle dispersion medium may be produced. Furthermore, the resin, the colorant, the charge control agent and the dispersion medium can be plasticized, the dispersion medium does not boil, and the temperature is lower than the decomposition point of the resin, the charge control agent and / or the colorant. There is a method using an appropriate apparatus capable of dispersing and kneading the raw materials. Specifically, the pigment, the resin, and the charge control agent are heated and melted in a dispersion medium with a meteor mixer, a kneader, etc., and the molten mixture is cooled with stirring using the temperature dependence of the solvent solubility of the resin. The particles can be produced by solidification / precipitation.

  Furthermore, the above raw materials are put into a suitable container equipped with granular media for dispersion and kneading, for example, a heated vibration mill such as an attritor or a heated ball mill, and the container is placed in a desired temperature range, for example, 80 A method of dispersing and kneading at ˜160 ° C. can be used. As granular media, steels such as stainless steel and carbon steel, alumina, zirconia, silica and the like are desirably used. In order to produce particles by this method, the raw material that has been previously fluidized is further dispersed in a container by means of granular media, and then the dispersion medium is cooled to precipitate a resin containing a colorant from the dispersion medium. The granular media generates a shear and / or impact to reduce the particle size while maintaining a motion state during and after cooling.

  The content of the particle group 34 (content (% by mass) with respect to the total mass in the cell) is not particularly limited as long as the desired hue is obtained, and the cell thickness (that is, the display substrate 20). It is effective for the display medium 12 to adjust the content by the distance between the substrate and the back substrate). That is, in order to obtain a desired hue, the content decreases as the cell becomes thicker, and the content can increase as the cell becomes thinner. Generally, it is 0.01 mass%-50 mass%.

  The volume average primary particle diameter of each particle constituting the particle group 34 varies depending on the opening diameter of the recess 52, but is preferably 1000 nm or less, more preferably 800 nm, and more preferably 600 nm or less. Further preferred.

  When the volume average primary particle size of each particle constituting the particle group 34 exceeds 1000 nm, there may be a problem that the secondary color display performance when the particles overlap is deteriorated.

  Thus, since the volume average primary particle size of each particle constituting the particle group 34 is set to 600 nm, particles having a smaller volume average primary particle size than the invention described in the cited document 1 cited in the prior art are electrically Since it is used as a migrating particle, the resolution of the display medium 12 can be improved, the dispersion stability of each particle of the particle group 34 is achieved, and the display medium 12 having excellent secondary color display characteristics is provided. Realized.

  In the present embodiment, the volume average primary particle size is measured by irradiating each type, that is, each color particle group 34 with laser light, and calculating the average particle size from the intensity distribution pattern of diffraction and scattered light emitted therefrom. The laser diffraction scattering method is used to measure In addition, the measurement was performed at 25 ° C. using a dynamic light scattering type particle size distribution measuring device (LB-550, Horiba, Ltd.).

  The reflecting member 36 has an optical reflection characteristic different from that of the particle group 34 and has a hole through which the particle group 34 moves.

  The holes provided in the reflecting member 36 are at least holes in the direction of the electric field gradient formed in the display medium 12. In the present embodiment, the display electrode 20 and the back electrode 46 are used to connect the display substrate 20 and the display substrate 20. The holes are at least formed in the direction of the electric field gradient formed between the rear substrate 22, that is, in the direction where the display substrate 20 and the rear substrate 22 face each other. The holes of the reflecting member 36 are configured to have a size such that at least particles constituting the particle group 34 move from one of the display substrate 20 and the back substrate 22 to the other substrate side through the holes. ing.

  The reflection member 36 has “an optical reflection characteristic different from that of the particle group 34” means that the dispersion medium 50 in which only the particle group 34 is dispersed, and the reflection member 36 in which the dispersion medium 50 is permeated into the holes, This means that there is a difference that can distinguish the difference between the two in terms of hue, brightness, freshness, and the like.

  The reflecting member 36 preferably has a function of shielding the particle group 34. Here, “concealment” in the present embodiment means a case where the transmittance is 50% or less with respect to visible light.

  For this reason, when the particle group 34 is closer to the display substrate 20 than the reflecting member 36, the color of the particle group 34 is different. When the particle group 34 is closer to the rear substrate 22 than the reflecting member 36, the color of the reflecting member 36 is larger. Is displayed on the display medium 12.

The color of the reflecting member 36 is preferably white, because the display can be performed with a bright white background, the whiteness is preferably 30% or more, and particularly 40% or more. preferable.
The whiteness is a measure of whiteness, and is specifically a value measured using a Hunter whiteness meter or X-rite colorimeter according to the method described in JIS-P8123.

  The thickness of the reflecting member 36 is desirably at least the volume average primary particle size of the particles constituting the particle group 34. Since the particle group 34 existing on the back substrate 22 side of the reflecting member 36 may be observed from the hole portion of the reflecting member 36, the thickness of the reflecting member 36 is three times the volume average primary particle size of the particle group 34. More preferably, it is more than that.

Specifically, the thickness of the reflective member 36 depends on the distance between the display substrate 20 and the back substrate 22 and the like, but is preferably 1 μm or more and 500 μm or less, and preferably 10 μm or more and 100 μm or less. Further preferred.
If the thickness of the reflective member 36 is less than 1 μm, there may be a problem that sufficient color developability cannot be obtained. If the thickness exceeds 500 μm, the distance between the electrodes increases and a high drive voltage is required. There is.

  As described above, the shape of the reflecting member 36 is not particularly limited as long as it has a hole through which the particle group 34 moves and has an optical reflection characteristic different from that of the particle group 34. Titanium oxide, zinc oxide Such as inorganic material particles composed of materials such as, and organic material particles composed of materials such as methyl methacrylate resin, styrene acrylic resin, silicone resin, and polytetrafluoroethylene resin. Alternatively, a resin sheet or a non-woven fabric may be used.

  When the reflective member 36 is configured as an aggregate of particles, the volume average primary particle size of the particles is not particularly limited, but the reflective member 36 formed of the aggregate of particles is the display substrate 20 and the back substrate. It is desirable that the volume average primary particle size is such that the particle group 34 can pass through the gap between adjacent particles when arranged in the region between the two particles.

  For this reason, the volume average primary particle size of the particles constituting the reflecting member 36 is preferably 10 times or more, and more preferably 25 times or more the volume average primary particle size of the particle group 34. When the volume average primary particle size of the particles constituting the reflecting member 36 is less than 10 times the volume average primary particle size of the particle group 34, the particle group is interposed through gaps (holes) between the plurality of particles constituting the reflecting member 36. It may be difficult for 34 to pass. The upper limit of the volume average primary particle diameter of the particles constituting the reflecting member 36 is not particularly limited, but when the reflecting member 36 is configured as an aggregate of such particles, the space between the reflecting member 36 and the display substrate 20 is not limited. In addition, the filling rate of the particles constituting the reflecting member 36, the number of layers to be laminated, and the like so that a gap having a volume average primary particle size of the particle group 34 is formed between the reflecting member 36 and the back substrate 22. You may adjust according to.

  In the present embodiment, the volume average primary particle size of the particles constituting the reflecting member 36 was measured in the same manner as the particle group 34.

  Further, when the reflecting member 36 is made of a resin sheet or nonwoven fabric, examples of the material constituting the resin sheet or nonwoven fabric include polyethylene, polystyrene, polyester, polyacryl, polypropylene, and polytetrafluoroethylene ( Fluorinated resins such as PTFE) can be applied. Particularly desirable are polypropylene and PTFE resins because the particle group 34 is difficult to adhere. When the reflecting member 36 is composed of a nonwoven fabric, the reflecting member 36 may be configured as an aggregate of fibers made of these materials.

  The porosity of the reflecting member 36 is preferably 50% or more and 80% or less for the reason that both the passing performance through which the particle group 34 passes and the high color developability of the display medium 12 are compatible.

Further, the average pore diameter of the holes of the reflecting member 36 is not particularly limited as long as the particles constituting the particle group 34 can pass through, but the average particle diameter of the particle group 34 is the volume average primary particle diameter of the particle group 34. Is preferably in the range of 2 times to 1000 times, more preferably in the range of 5 times to 200 times.
If the average hole diameter of the holes of the reflecting member 36 is less than twice the volume average primary particle diameter of the particle group 34, it may be difficult for each particle constituting the particle group 34 to move through the hole. If it exceeds 1000 times, there is a case where a problem arises in that color development is lowered due to an increase in the gap.

Further, when the reflecting member 36 is made of a nonwoven fabric, the basis weight of the fibers constituting the nonwoven fabric makes the passage rate of the particle group 34 good and the thickness of the display medium 12 is reduced. m ² or more 100 g / ^{m 2} or less in the range of good, 20 g / ^{m 2} or more 50 g / ^{m 2} or less in the range better.

  The diameter of the fibers constituting the nonwoven fabric is in the range of 0.1 μm to 20 μm, and preferably in the range of 0.1 μm to 3 μm, to ensure a sufficient surface area and physical strength. To preferred.

  The reflective member 36 is sealed between the substrates by, for example, an ink jet method. When the reflecting member 36 is fixed, for example, after the reflecting member 36 is sealed, the particle gap is maintained by heating (and pressing if necessary) to melt the particle group surface layer of the reflecting member 36. To be done.

  In order to fix the display substrate 20 and the back substrate 22 through the gap member 24, fixing means such as a combination of bolts and nuts, a clamp, a clip, and a frame for fixing the substrate can be used. Also, fixing means such as an adhesive, heat melting, and ultrasonic bonding can be used.

  The display medium 12 configured in this way is shared with bulletin boards, circular editions, electronic blackboards, advertisements, signboards, blinking signs, electronic paper, electronic newspapers, electronic books, and copiers / printers that can store and rewrite images. It can be used for document sheets that can be used.

  In the display medium 12 described above, different colors are displayed by changing the voltage values of the voltages applied to the display substrate 20 and the back substrate 22.

  In the display medium 12, each type of particle group 34 moves in accordance with the electric field formed between the display substrate 20 and the back substrate 22, so that image data is obtained for each cell corresponding to each pixel of the display medium 12. The color corresponding to each pixel can be displayed.

  Here, as described above, in the particle group 34 of the present embodiment, the absolute value of the movement voltage necessary for movement differs for each type, that is, for each color.

  In addition, it is preferable that each color particle group 34 has a range of movement voltages different for each color as a movement voltage necessary for movement.

  Here, the “movement voltage range” means the display substrate 20 and the back substrate from the movement voltage necessary for the particles constituting one type of particle group 34 among the plurality of types of particle groups 34 to start moving. The voltage value of the voltage applied between the substrate 22 and the substrate is continuously changed to indicate a range less than the moving voltage at which the other type of particle group 34 starts moving. That is, it is possible to selectively move the specific particle group 34 by applying a voltage within the range of the moving voltage of each type of particle group 34.

  The movement voltage necessary for the particles constituting the particle group 34 to start moving is when the voltage value of the voltage applied between the display substrate 20 and the back substrate 22 is continuously changed. In addition, it is applied between the substrates when the display density of the display medium 12 does not change due to the movement of the particles constituting each type of particle group 34 and the display density changes. The voltage value of the voltage is shown.

  This “change in display density” means that a voltage is applied to the display electrode 40 and the back electrode 46 of the display medium 12 and the voltage value of this voltage is increased or decreased from 0V. Boundary when 20 concentration is measured with a densitometer (X-Rite 404A, manufactured by X-Rite Co., Ltd.), and the concentration change with respect to the concentration before voltage application starts from 0.01 to 0.01 or more Shows the state.

  Next, the relationship between the electric field strength and the change in display density due to the movement of each color particle group 34 between substrates in a plurality of types of particle groups 34 used in the display medium 12 of the present embodiment will be described with reference to FIG. This will be specifically described.

  In this embodiment, as the particle group 34 enclosed in the same cell of the display medium 12, as shown in FIG. 1, a magenta magenta particle group 34M, a cyan cyan particle group 34C, and yellow Three-color particle groups 34 of colored yellow particle groups 34Y are enclosed.

Note that the absolute values of the voltage values Vtc, -Vtc, Vdc, -Vdc, Vtm, -Vtm, Vdm, -Vdm, Vty, -Vty, Vdy, and -Vdy described below are | Vtc | <| Vdc | The description will be made assuming that the relationship is <| Vtm | <| Vdm | <| Vty | <| Vdy |.
In the present embodiment, as shown in FIG. 1, as a plurality of types of particle groups 34 having different absolute values of the moving voltage, a magenta magenta particle group 34M, a cyan cyan particle group 34C, and a yellow color particle group 34C are used. As the absolute value of the moving voltage when the three color particle groups of the yellow particle group 34Y start to move, the magenta magenta particle group 34M is | Vtm |, the cyan cyan particle group 34C is | Vtc |, yellow. The description will be made assuming that the yellow particle group 34Y of the color is | Vty |. Further, even if the voltage applied between the substrates and the voltage application time are further increased from the start of movement of each color particle group 34, the display density does not change and the magenta magenta particles are used as the saturation voltage when the display density is saturated. It is assumed that the group 34M is | Vdm |, the cyan cyan particle group 34C is | Vdc |, and the yellow yellow particle group 34Y is | Vdy |.

  When a voltage of 0 V is applied between the display substrate 20 and the back substrate 22 to gradually increase the voltage value of the applied voltage and a voltage exceeding + Vtc is applied between the substrates, cyan particles in the display medium 12 are applied. The display density starts to change due to the movement of the group 34C. Further, when the voltage value is increased and the voltage value + Vdc is applied between the substrates, the change in display density due to the movement of the cyan particle group 34C in the display medium 12 stops.

  When the applied voltage is further increased and a voltage exceeding + Vtm is applied between the display substrate 20 and the rear substrate 22, a change in display density due to the movement of the magenta particle group 34M starts to appear in the display medium 12. When the voltage value is further increased and a voltage exceeding the voltage value + Vdm is applied between the display substrate 20 and the rear substrate 22, the change in display density due to the movement of the magenta particle group 34M in the display medium 12 stops.

  Further, when the voltage value is increased and a voltage exceeding the voltage value + Vty is applied between the substrates, a change in display density due to the movement of the yellow particle group 34Y starts to appear in the display medium 12. When the voltage value is further increased and a voltage exceeding the voltage value + Vdy is applied between the substrates, the change in display density due to the movement of the yellow particle group 34Y in the display medium 12 stops.

  On the other hand, a negative voltage from 0 V is applied between the display substrate 20 and the back substrate 22 to gradually increase the absolute value of the voltage, and a voltage exceeding the absolute value of the voltage value −Vtc is applied between the substrates. Then, the display density starts to change in the display medium 12 due to the movement of the cyan particle group 34C between the substrates. Furthermore, when the absolute value of the voltage value is increased and a voltage equal to or higher than the absolute value of the voltage value −Vdc is applied between the display substrate 20 and the rear substrate 22, the cyan particle group 34 </ b> C is moved in the display medium 12. The change in display density stops.

  When the negative voltage is further applied by raising the absolute value of the voltage value and a voltage exceeding the absolute value of the voltage value −Vtm is applied between the display substrate 20 and the rear substrate 22, the display medium 12 A change in display density due to the movement of the magenta particle group 34M begins to appear. When the absolute value of the voltage value is further increased and a voltage exceeding the absolute value of the voltage value −Vdm is applied between the display substrate 20 and the rear substrate 22, the magenta particle group 34 </ b> M is moved in the display medium 12. The change in display density stops.

  When the negative voltage is further applied by raising the absolute value of the voltage value and a voltage exceeding the absolute value of the voltage value −Vty is applied between the display substrate 20 and the rear substrate 22, the display medium 12 The display density starts to change due to the movement of the yellow particle group 34Y. When the absolute value of the voltage is further increased and a voltage exceeding the absolute value of the voltage value −Vdy is applied between the substrates, the change in display density due to the movement of the yellow particle group 34Y in the display medium 12 stops.

That is, in the present embodiment, as shown in FIG. 5, the voltage between the display substrate 20 and the back substrate 22 is such that the potential difference between the substrates is in the range of −Vtc to Vtc (potential difference | Vtc | or less). When applied in the meantime, there is no movement of the particles 34 (cyan particle group 34C, magenta particle group 34M, and yellow particle group 34Y) to the extent that the display density of the display medium 12 changes. It can be said.
When a voltage that is equal to or greater than the absolute value of the voltage value + Vtc and the voltage value −Vtc and less than the absolute value of the voltage value + Vtm and the voltage value −Vtm is applied between the substrates, the particle group 34 of the three colors is included. Only the cyan particle group 34 </ b> C causes the movement of particles such that the display density of the display medium 12 changes. Further, when a voltage higher than the absolute value of the voltage value + Vdc and the voltage value −Vdc is applied between the substrates, the display density per unit voltage does not change due to the movement of the cyan particle group 34C.

  Furthermore, when the voltage is changed and a voltage that is greater than or equal to the absolute value of the voltage value + Vtm and the voltage value −Vtm and less than the absolute value of the voltage value + Vty and the voltage value −Vty is applied between the substrates, the three colors The magenta particle group 34M in the particle group 34 moves so much that the display density of the display medium 12 changes. Further, when a voltage equal to or higher than the absolute value of the voltage value + Vdm and the voltage value −Vdm is applied between the substrates, the display density per unit voltage does not change due to the movement of the magenta particle group 34M.

  Further, when the voltage is changed and a voltage equal to or higher than the absolute value of the voltage value + Vty and the voltage value −Vty is applied between the substrates, the yellow particle group 34Y of the three color particle groups 34 is displayed on the display medium 12. The particles move to such an extent that the display density changes. Further, when a voltage higher than the absolute value of the voltage value + Vdy and the voltage value −Vdy is applied between the substrates, the display density per unit voltage does not change due to the movement of the yellow particle group 34Y.

  As described above, the particle group 34 dispersed in the dispersion medium 50 of the display medium 12 has an absolute movement voltage necessary to move between the display substrate 20 and the rear substrate 22 for each color. It is preferable that the values are different, and as described above, the voltage ranges necessary for moving the particle groups 34 of each color (type) are different.

  Next, with reference to FIG. 6, the mechanism of particle movement when an image is displayed on the display medium 12 of the present invention will be described.

  The display medium 12 includes a plurality of types of particle groups having different moving voltages that start moving according to color and electric field, and the yellow particle group 34Y, the magenta particle group 34M, and the cyan particle group described with reference to FIG. It is assumed that 34C is enclosed.

In the following, as described in FIG. 5 above, the absolute value of the moving voltage of the magenta particle group 34M is larger than the absolute value of the moving voltage of the yellow particle group 34Y, and the absolute value of the moving voltage of the magenta particle group 34M. In the following description, it is assumed that the absolute value of the moving voltage of the yellow particle group 34Y is large. A voltage that is equal to or higher than the absolute value of the moving voltage of the cyan particle group 34C and lower than the moving voltage of the magenta particle group 34M is referred to as a “first voltage”, and is equal to or higher than the absolute value of the moving voltage of the magenta particle group 34M. The voltage that is less than the absolute value of the moving voltage is referred to as “second voltage”, and the voltage that is equal to or greater than the absolute value of the moving voltage of the yellow particle group 34Y is referred to as “third voltage”.
That is, although details will be described later, as a summary, when a first voltage is applied between the display substrate 20 and the back substrate 22, the driving voltage among the plurality of types of particle groups 34 is the first. The particle group 34 (cyan particle group 34 </ b> C) having a value less than the voltage moves between the substrates. In addition, when a second voltage is applied between the display substrate 20 and the back substrate 22, among the plural types of particle groups 34, the particle groups 34 whose drive voltage is less than the second voltage move between the substrates. To do. In addition, when a third voltage is applied between the display substrate 20 and the back substrate 22, the drive voltage of the plurality of types of particle groups 34 moves between the particle group 34 substrates having a voltage less than the third voltage. .

  When a voltage higher than that on the rear substrate 22 side is applied to the display substrate 20 side to create a potential difference between the substrates, each voltage is changed to “+ first voltage”, “+ second voltage”, and “+ first voltage”. These are referred to as “three voltages”. Further, when a potential difference is provided between the substrates by applying a higher voltage to the back substrate 22 side than the display substrate 20 side, the respective voltages are set to “−first voltage”, “−second voltage”, and “−first voltage”. These are referred to as “three voltages”.

  As shown in FIG. 6A, when all of the magenta particle group 34M, the cyan particle group 34C, and the yellow particle group 34Y as all the particle groups are positioned on the back substrate 22 side in the initial state, When “+ third voltage” is applied between the display substrate 20 and the rear substrate 22 from the state, the magenta particle group 34M, the cyan particle group 34C, and the yellow particle group 34Y are displayed as the display substrate as all the particle groups. Move to the 20 side. In this state, even if the applied voltage is zero, each particle group does not move while adhering to the display substrate 20 side, and subtractive color mixing (magenta) by the magenta particle group 34M, the cyan particle group 34C, and the yellow particle group 34Y. In this case, the black color is displayed by the subtractive color mixture of cyan and yellow. (See FIG. 6B).

  Next, when a “−second voltage” is formed between the display substrate 20 and the back substrate 22 from the state of FIG. 6B, the magenta particle group 34 </ b> M of all the color particle groups 34, and cyan The particle group 34 </ b> C moves to the back substrate 22 side. For this reason, since only the yellow particle group 34Y is positioned on the display substrate 20 side, yellow display is performed (see FIG. 6C).

  Further, when “+ first voltage” is formed between the display substrate 20 and the back substrate 22 from the state of FIG. 6C, the magenta particle group 34M and the cyan particle group 34C moved to the back substrate 22 side. The cyan particle group 34C moves to the display substrate 20 side. For this reason, the yellow particle group 34Y and the cyan particle group 34C are attached to the display substrate 20 side, and green is displayed by the subtractive color mixture of yellow and cyan (see FIG. 6D).

  6B, when the “−first voltage” is formed between the display substrate 20 and the back substrate 22, the cyan particle groups 34C of all the particle groups 34 move to the back substrate 22 side. To do. For this reason, since the yellow particle group 34Y and the magenta particle group 34M are attached to the display substrate 20, the red display is achieved by additive mixing of cyan and magenta (see FIG. 6I).

  On the other hand, when a “+ second voltage” is formed between the display substrate 20 and the back substrate 22 from the initial state shown in FIG. 6A, all the particle groups 34 (magenta particle group 34M, cyan particle group 34C). , And the yellow particle group 34Y), the magenta particle group 34M and the cyan particle group 34C move to the display substrate 20 side. For this reason, since the magenta particle group 34M and the cyan particle group 34C are attached to the display substrate 20, the blue color is displayed by the subtractive color mixing of magenta and cyan (see FIG. 6E).

When the “−first voltage” is formed between the display substrate 20 and the back substrate 22 from the state of FIG. 6E, the magenta particle group 34M and the cyan particle group 34C attached to the display substrate 20 side. Among them, the cyan particle group 34C moves to the back substrate 22 side.
Therefore, only the magenta particle group 34M is attached to the display substrate 20 side, so that a magenta color is displayed (see FIG. 6F).

When a “−third voltage” is formed between the display substrate 20 and the back substrate 22 from the state of FIG. 6F, the magenta particle group 34M adhering to the display substrate 20 side is moved to the back substrate 22 side. Moving.
For this reason, since nothing is attached to the display substrate 20 side, white is displayed as the color of the reflecting member 36 (see FIG. 6G).

  When the “+ first voltage” is formed between the display substrate 20 and the back substrate 22 from the initial state shown in FIG. 6A, all the particle groups 34 (magenta particle group 34M, cyan particle group) are formed. 34C and the yellow particle group 34Y), the cyan particle group 34C moves to the display substrate 20 side. For this reason, the cyan particle group 34C adheres to the display substrate 20 side, so that a cyan color is displayed (see FIG. 6H).

Further, when a “−third voltage” is formed between the display substrate 20 and the back substrate 22 from the state shown in FIG. 6I, all the particle groups 34 are back as shown in FIG. 6G. Moving to the substrate 22 side, white display is performed.
Similarly, when the “−third voltage” is formed between the display substrate 20 and the back substrate 22 from the state shown in FIG. 6D, all the particle groups 34 are formed as shown in FIG. Moving to the back substrate 22 side, white display is performed.

  As described above, according to the display medium 12 of the present embodiment, a plurality of types of particles having different moving voltages necessary for moving and moving with each other in the dispersion medium 50 between the display substrate 20 and the back substrate 22. By enclosing the group 34 and applying a voltage having an intensity corresponding to the moving voltage of each color particle group 34, the particle group 34 of a desired color is selectively moved, so that particles of a color other than the desired color are dispersed. The movement in the medium 50 can be suppressed, and the color mixture of colors other than the desired color is suppressed.

  Further, as shown in FIG. 6, cyan, magenta, yellow, blue, red, green, and black are displayed by dispersing the three color particle groups 34 of cyan, magenta, and yellow in the dispersion medium 50. In addition, white can be displayed by the white reflecting member 36, and a desired color display can be performed.

  The color display by selective application of the moving voltage as described above is realized by providing the display medium 12 in the image display device 10.

  For example, as shown in FIG. 1, the image display device 10 includes the display medium 12 and the writing device 17 described above. The writing device 17 includes a voltage application unit 16 and a control unit 18.

  The voltage application unit 16 is electrically connected to the display electrode 40 and the back electrode 46. In the present embodiment, a case where both the display electrode 40 and the back electrode 46 are electrically connected to the voltage application unit 16 will be described. However, one of the display electrode 40 and the back electrode 46 is grounded. The other may be connected to the voltage application unit 16.

  The voltage application unit 16 is connected to the control unit 18 so as to be able to exchange signals.

  The control unit 18 stores in advance various programs such as a CPU (Central Processing Unit) that controls the operation of the entire apparatus, a RAM (Random Access Memory) that temporarily stores various data, and a control program that controls the entire apparatus. It is also possible to configure as a microcomputer including a ROM (Read Only Memory).

  The voltage application unit 16 is a voltage application device for applying a voltage to the display electrode 40 and the back electrode 46, and applies a voltage according to the control of the control unit 18 between the display electrode 40 and the back electrode 46.

  The display medium 12 is provided in the writing device 17 and the display device 10 as described above, and a plurality of types are provided between the display substrate 20 and the back substrate 22 as described with reference to FIG. By selectively applying a voltage having a predetermined polarity and voltage value according to the moving voltages of the yellow particle group 34Y, the magenta particle group 34M, and the cyan particle group 34C as the particle group 34, color display is performed. The

  Here, there is no problem in displaying primary colors such as yellow, magenta, and cyan, which are the colors of the yellow particle group 34Y, the magenta particle group 34M, and the cyan particle group 34C, as shown in FIG. However, when displaying a secondary color such as green and red or a tertiary color such as black, since the particles have translucency, the particles of different colors are separated from the display substrate 20 and the back substrate 22. It is preferable that it is visually recognized in a state where they overlap in the opposite direction. However, in the state in which the charging film 27 and the charging film 29 are planar and a plurality of types of particle groups 34 exist on the charging film 27 and the charging film 29 as in the prior art, a more specific type of particle group 34 exists. When an electric field for moving the color particle group 34 is formed between the substrates, the movement of the particle group 34 may be hindered by the particle group 34 that is not the object of movement, and display responsiveness may decrease.

  However, according to the display medium 12 of the present embodiment, as described above, the charging film 27 and the charging film 29 are provided, and each of the charging film 27 and the charging film 29 has the concave portion 52 described above. is doing. Therefore, as shown in FIG. 2 and FIGS. 3A to 3C, the particle groups 34 of the respective colors are arranged in a single layer on the surface of the charging film 27 or the charging film 29 and are displayed. When viewed from the display substrate 20 side of the medium 12 (viewed from the direction of the arrow X in FIG. 3A and FIG. 1), a plurality of particles (particles constituting the particle group 34) are visually recognized.

  For this reason, after repetitive rewriting, especially in the display of the primary color after displaying the secondary color or higher, the same display as when only the single color particle group 34 is dispersed in the cell The density is secured, the apparent decrease in coverage is suppressed, and the color unevenness of the secondary color or more displayed after repeated rewriting is suppressed.

  In addition, the particle group 34 is prevented from adhering to the charging film 27 and the charging film 29 in a stacked state by the concave portions 52 provided in the charging film 27 and the charging film 29, respectively. After that, the responsiveness of the particle group 34 is prevented from being lowered, and the uneven color display of the secondary color displayed after rewriting a plurality of times is suppressed.

  In addition, the recess 52 provided in each of the charging film 27 and the charging film 29 is a member that extends in a direction intersecting with the facing direction of the display substrate 20 and the back substrate 22 such as a porous film or a nonwoven fabric. Is not present, and the charging film 27 and the charging film 29 can be provided regularly, so that display uniformity is improved.

  Therefore, according to the display medium 12 of the present embodiment, the decrease in the apparent coverage after repeated rewriting is suppressed, the decrease in color density is suppressed, and the color unevenness of the secondary color or more displayed is suppressed. Has the effect of being suppressed. In addition, since the charging film 27 and the charging film 29 are charged films, deterioration in image quality retention is also suppressed.

  The present invention will be described below in more detail with reference to examples. However, the present invention is not limited to the following examples.

(Preparation of reflecting member)
The following particles were prepared as reflecting members.
-Preparation of dispersion AA-
The following components were mixed and ball milling was performed for 20 hours with 10 mmφ zirconia balls to prepare dispersion AA.
<Composition>
・ Cyclohexyl methacrylate: 53 parts by weight ・ Titanium oxide 1 (white pigment) (primary particle size 0.3 μm, Type CR63: manufactured by Ishihara Sangyo Co., Ltd.): 45 parts by weight ・ Cyclohexane: 5 parts by weight

-Preparation of charcoal dispersion AB-
The following components were mixed, and finely pulverized with a ball mill in the same manner as above to prepare a charcoal dispersion AB.
<Composition>
・ Calcium carbonate: 40 parts by weight ・ Water: 60 parts by weight

-Preparation of mixture AC-
The following components were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed liquid AC.
<Composition>
・ 2% serogen: 4.3g
Charcoal cal dispersion AB: 8.5g
・ 20% saline solution: 50g

  35 g of dispersion AA, 1 g of divinylbenzene, and polymerization initiator AIBN: 0.35 g were weighed and mixed well, and deaeration was performed for 10 minutes with an ultrasonic machine. This was added to the mixed solution AC and emulsified with an emulsifier. Next, this emulsified liquid was put into a bottle, put into a silicone bottle, used with an injection needle, sufficiently degassed under reduced pressure, and sealed with nitrogen gas. Next, it was reacted at 65 ° C. for 15 hours to prepare particles. After cooling, cyclohexane was removed from the dispersion with a freeze dryer at −35 ° C. and 0.1 Pa for 2 days. The obtained particle powder was dispersed in ion-exchanged water, calcium carbonate was decomposed with hydrochloric acid water, and filtered. Thereafter, it was washed with sufficient distilled water, and passed through a nylon sieve having openings of 12 μm and 25 μm, so that the particle sizes were uniform. This was dried to obtain a group of white particles having an average particle diameter of 12 μm. This was made into the reflective member which consists of a some white particle.

―Preparation of particles―
Two types of particle groups 34 that require different moving voltages for the cyan and magenta colors when starting to move from the state positioned on one side of the display substrate 20 and the rear substrate 22 to the other side. Configured.

-Production of magenta particle group 34M-
As the magenta particle group 34M, magenta particles were adjusted by the following procedure.
Styrene monomer: 53 parts by weight, magenta pigment (Kermin 6B; manufactured by Dainichi Seika Co., Ltd.), 3 parts by weight, charge control agent (SBT-5-0016; manufactured by Orient Kogyo Co., Ltd.), 1.5 parts by weight, magenta-coated magnetite Dispersion A was prepared by carrying out ball milling for 20 hours using 13.3 parts by weight of zirconia balls having a diameter of 10 mm.
Next, calcium carbonate dispersion liquid B was prepared by pulverizing 40 parts by weight of calcium carbonate and 60 parts by weight of water with a ball mill. 2% serogen aqueous solution: 4.3 g, calcium carbonate dispersion B 8.5 g, and 20% saline: 50 g are mixed, deaerated with an ultrasonic machine for 10 minutes, and mixed with an emulsifier. Liquid C was prepared.
35 g of the above dispersion A, 1 g of divinylbenzene, and polymerization initiator AIBN: 0.35 g were sufficiently mixed and deaerated with an ultrasonic machine for 10 minutes. This was put into the above mixed solution C and emulsified with an emulsifier.

Next, this emulsified liquid was put into a bottle, siliconized, and using an injection needle, vacuum deaeration was sufficiently performed, and the mixture was sealed with nitrogen gas. Next, it was made to react at 60 degreeC for 10 hours, and particle | grains were created. The obtained particle powder was dispersed in ion-exchanged water, calcium carbonate was decomposed with hydrochloric acid water, and filtered. Then, it is washed with sufficient distilled water to make the particle size uniform and dried. 2 parts by weight of the obtained particles were added to 98 parts by weight of silicone oil (octamethyltrisiloxane) together with 2 parts by weight of a nonionic surfactant polyoxyethylene alkyl ether, and stirred and dispersed to obtain a mixed solution. When the polarity of the magenta particle group 34M contained in the obtained mixed liquid was measured using a parallel electrode plate, it was positive.
The obtained magenta color particles (magenta particle group 34M) had a volume average primary particle size of 200 nm.

-Production of cyan particle group 34C-
As the cyan particle group 34C, cyan particles were adjusted by the following procedure. Among the procedures for preparing the particles of the magenta particle group 34M, charge control is performed on a magenta pigment coated with a cyan pigment (cyanine blue 4933M; manufactured by Dainichi Seika Co., Ltd.) and a magenta coated magnetite with a cyan color. Cyan particles were prepared in the same manner as the magenta particle group 34M except that the amount of the agent (SBT-5-0016; manufactured by Orient Kogyo Co., Ltd.) was changed to 6.7 parts by weight.

  The resulting cyan particles (cyan particle group 34C) had a volume average primary particle size of 200 nm. Further, when the polarity was measured in the same manner as in the magenta particle group 34M, the polarity of the cyan particle group 34C was positive.

  In addition, the said volume average primary particle diameter was measured with the following measuring method.

<Measurement method of volume average primary particle size>
When the particle diameter to be measured is 2 μm or more, the volume average primary particle size is measured using a Coulter Counter TA-II type (manufactured by Beckman-Coulter), and the electrolyte is ISOTON-II (Beckman-Coulter). Was used to measure the particle size.

  As a measurement method, 0.5 to 50 mg of a measurement sample was added to 2 ml of a 5% aqueous solution of a surfactant, preferably sodium alkylbenzenesulfonate as a dispersant, and this was added to 100 ml or more and 150 ml or less of the electrolytic solution. The electrolytic solution in which the measurement sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 minute. Using the Coulter Counter TA-II type, an aperture having an aperture diameter of 100 μm is used. The particle size distribution of particles in the range of 60 μm was measured. The number of particles to be measured was 50,000.

  For the divided particle size range (channel), the measured particle size distribution is drawn from the small diameter side for each volume and number, and the particle size that is 16% cumulative by volume is accumulated by volume average particle size D16v and number. The cumulative number particle diameter of 16% is defined as D16p. Similarly, a particle diameter that is 50% cumulative in volume is defined as a volume average particle diameter D50v, and a particle diameter that is cumulative 50% in number is defined as a number average particle diameter D50p. Similarly, a particle diameter that is 84% cumulative in volume is defined as a volume average particle diameter D84v, and a cumulative particle diameter that is 84% cumulative in number is defined as D84p. The volume average primary particle diameter is the D50v.

Using these, the volume average particle size distribution index (GSDv) is calculated from (D84v / D16v) ^1/2 , the number average particle size index (GSDp) is calculated from (D84p / D16p) ^1/2 , and the small diameter side number average The particle size index (lower GSDp) is calculated by {(D50p) / (D16p)}.

  On the other hand, when the particle diameter to be measured was less than 2 μm, the particle size was measured using a laser diffraction particle size distribution analyzer (LA-700: manufactured by Horiba, Ltd.). As a measuring method, a sample in a dispersion is adjusted to have a solid content of about 2 g, and ion exchange water is added thereto to make about 40 Ml. This is put into the cell until an appropriate concentration is reached, waits for about 2 minutes, and is measured when the concentration in the cell becomes almost stable. The obtained volume average primary particle diameter for each channel was accumulated from the smaller volume average primary particle diameter, and the volume average primary particle diameter was determined when the accumulation reached 50%.

  When measuring powders such as external additives, 2 g of a measurement sample is added to 50 ml of a 5% aqueous solution of a surfactant, preferably sodium alkylbenzenesulfonate, and 2 with an ultrasonic disperser (1,000 Hz). A sample was prepared by dispersing for a minute, and the measurement was performed in the same manner as the above dispersion.

Example 1
―Preparation of display media―

In this embodiment, a transparent conductive ITO supporting substrate having a size of 70 mm × 50 mm × 1.1 mm is used as the supporting substrate 38, and a line-shaped display electrode having a width of 0.234 mm and an interval of 1 mm is formed on the supporting substrate 38 by etching. A plurality of 40 were created.
On the display electrode 40, the charging film 27 and each were formed as follows.

(Formation of recesses)
As the charging film 27, first, an ultraviolet curable Toyo Gosei PAK-01 is prepared as a resin constituting each of the charging films 27, and a mold (mold) for providing the recess 52 has a diameter of 2 μmφ, a height of 5 μm, A cylindrical structure (made of quartz) having a center interval of 2.5 μm was prepared, and the charging film 27 having the recesses 52 was formed by an imprint method.
Specifically, the UV curable Toyo Gosei PAK-01 was spin-coated at 700 rpm on each of the back electrode 46 and the display electrode 40 to obtain a thin film having a thickness of about 6 μm. The quartz mold is brought into close contact with the thin film, the ultraviolet lamp is irradiated for 30 seconds to cure the thin film, and then the quartz mold is removed so that the recesses 52 are regularly arranged over the entire surface area. The formed thin film (uncharged charged film 27) was formed.

  The depth of the recess 52 was estimated from SEM observation and found to be 5 μm. The major axis of the bottom surface of the recess 52 was 2 μm, and the distance between adjacent recesses 52 (the distance between the centers of the bottom surfaces) was 2.5 μm. Moreover, when the shape of the recessed part 52 was confirmed using SEM, it was cylindrical shape.

  Further, the surface area of the thin film in which the recess 52 was formed (surface area of the surface on which the recess 52 was formed) was obtained by calculation, and compared with the surface area in the case where the recess 52 was not formed, it was 6 times.

  Moreover, the recessed part 52 was formed over the whole area | region of the surface of a thin film, and was arrange | positioned taking the close packing structure with respect to the surface direction of a thin film.

(Charging treatment)
The thin film formed on each of the display electrodes 40 and having the recess 52 formed thereon is coated with a Cytop (manufactured by Asahi Glass) film using a spin coating method under a condition of 1000 rpm × 20 seconds from a 5-fold diluted solution, This film was charged by corona charging.
In the charging process, a charged film 27 having a surface potential of −20 V was obtained by applying a voltage of −4 kV or higher with a wire electrode for 1 minute while the thin film was heated to 100 ° C.

  The surface potential was measured with a non-contact surface potential meter manufactured by TREK.

(Performance evaluation of charged film)
The display substrate 20 on which the charging film 27 is formed is dispersed in the adjusted magenta particle group 34M in silicone oil as a dispersion medium to prepare an electrophoretic solution, and the magenta particle group 34M is formed by permeating the electrophoretic solution. After spontaneously adsorbing to the charged film 27, it was pulled up from the electrophoresis solution.
For comparison, a comparative substrate in which the charging film 27 is formed on the display substrate 20 is prepared in the same manner as described above except that the concave portion 52 is not formed. The gel was allowed to permeate and adsorb naturally, and then pulled up from the electrophoresis solution.

  For each of the display substrate 20 and the comparative substrate on which the charging film 27 having the concave portions 52 is formed, the amount of the magenta particle group 34M attached was measured using an absorption spectrum (U-3300 manufactured by Hitachi). The ratio was 2.5. For this reason, the adhesion amount of the magenta particle group 34M of the charging film 27 in which the concave portion 52 is formed is 2.5 times that of the charged film in which the concave portion 52 is not formed.

  Further, for each of the display substrate 20 and the comparative substrate on which the charging film 27 having the concave portion 52 is formed, the concentration of the substrate is measured using X-Rite (X-Rite 404A, manufactured by X-Rite), and the optical density is measured. When the display substrate 20 on which the charging film 27 having the recess 52 was formed was within ± 5% of the average density, the comparison substrate was measured with respect to the average density. Within ± 10%.

  The in-plane variation of the optical density was obtained by measuring the density at 10 points on each substrate surface to obtain an average value, and calculating the magnification of the maximum density and the minimum density with respect to the average value.

  For this reason, it can be said that unevenness of display density is suppressed as compared with the case where the charging film 27 having the recess 52 and the recess 52 are not provided.

(Observation of particle adhesion to the charged film)
The display substrate 20 on which the charging film 27 is formed is dispersed in the adjusted magenta particle group 34M in silicone oil as a dispersion medium to prepare an electrophoretic solution, which is infiltrated into the electrophoretic solution, and the display on the display substrate 20 is displayed. The electrode 40 was left for 3 seconds while applying a voltage of 10V. Thereafter, the electrophoretic solution was pulled out while being applied with a voltage and washed with silicone oil, and then the application of voltage was stopped and air-dried.

The surface of the charging film 27 (the surface on the side where the recess 52 was formed) of the obtained display substrate 20 was observed by SEM, and the adhesion state of the magenta particle group 34M was confirmed.
As a result, the magenta particle group 34M was adhered to cover the surface of the cylindrical recess 52 provided in the charging film 27. In addition, it was confirmed that the particles of the magenta particle group 34M were hardly overlapped and adhered in a substantially single layer state.

  Similarly, the prepared comparative substrate as the display substrate 20 on which the charged film without the concave portion 52 was formed was also observed by SEM with the magenta particle group 34M attached thereto. Overlapping of a plurality of particles of the magenta particle group 34M was observed.

  For this reason, it has been confirmed that by adopting a configuration in which the concave portion 52 is provided in the charging film, particles that move due to an electric field such as the magenta particle group 34M can be present in a single layer on the surface of the charging film.

  As the back substrate 22, a substrate in which copper having a film thickness of 500 nm was formed on alumina ceramics by a sputtering method was prepared.

  Next, the gap member 24 was provided on the charging film 29 formed on the back substrate 22 as described above, and formed so as to have a height of 50 μm. The gap member 24 was formed so as to be provided with cells (area surrounded by the gap member 24, the display substrate 20, and the back substrate 22) corresponding to each pixel when an image was displayed on the display medium 12.

  The gap member 24 was formed by applying an epoxy resin (SU-8 manufactured by MicroChem Corp.) to the back substrate 22 and then performing exposure and wet etching. The gap member 24 has a size of 20 mm × 20 mm, a height of 50 μm, and a width of 2 mm.

  Here, as the dispersion medium 50, silicone oil (KF-96) manufactured by Shin-Etsu Chemical Co., Ltd. was used.

  The magenta particle group 34M and the cyan particle group 34C produced as described above are dispersed at a volume ratio of 1 to 1 in a volume ratio of each particle group in silicone oil (KF-96) manufactured by Shin-Etsu Chemical Co., Ltd. at 1% by volume. At the same time, a dispersion liquid in which white particles as the reflecting member 36 are dispersed at 70% by volume is filled on the back substrate 22 on which the gap member 24 is formed, thereby dividing each cell (by the gap member 24). Each region) was filled with a dispersion of mixed particles.

  The reflecting member 36 is mixed with 70% by volume of white particles to reflect with a gap through which each particle of the particle group 34 can pass along a direction orthogonal to the facing direction of the display substrate 20 and the back substrate 22. The white particles as the member 36 were arranged and provided in the cell so that the distance between the reflecting member 36 and the display substrate 20 and the back substrate 22 was substantially equal.

  Further, the display substrate 20 provided with the charging film 27 is disposed on the gap member 24 so that the charging film 27 faces the back substrate 22, and the periphery is sealed with an ultraviolet curable adhesive (manufactured by Norland). The display medium 12 was manufactured by irradiating ultraviolet rays after being fixed.

(Evaluation)
When a voltage of 10 V was applied to both electrodes for 3 seconds so that the electrode on the display substrate side of the display medium produced in Example 1 was negative and the electrode on the back substrate side was positive, cyan particle group 34C and magenta particle group Both 34M moved to the display substrate 20 side, and purple was displayed on the display medium.

  About this purple display medium, the concentration was measured with a densitometer (X-Rite 404A, manufactured by X-Rite Co., Ltd.) for 10 points including the end and center of the entire area of the surface substrate surface. The ratio of the maximum density and the minimum density to the average density value of the measurement results was calculated to be 104% and 96%, respectively.

  Next, with the electrode on the display substrate side set as positive and the electrode on the back substrate side set as negative, the applied voltage is gradually increased from 0 V to both electrodes, and display by electrophoresis of each of the cyan particle group 34C and the magenta particle group 34M. When the color change of the medium was confirmed, the display medium changed from purple → red → white.

The above purple, red, and white display is one cycle, the applied voltage is changed and 1000 cycles are repeated. After that, the voltage for displaying purple (10V voltage is applied for 3 seconds so that the display substrate side becomes negative) ) To display purple color, and for the purple-displayed display medium, the concentration is measured at 10 points including the end portion and the central portion of the entire area of the surface substrate surface by a densitometer (X-Rite). X-Rite 404A), and the ratio of the maximum density and the minimum density to the density average value of the measurement result was calculated to be 105% and 96%, respectively. For this reason, it can be said that the display density variation of the secondary color is suppressed before and after the display color is switched a plurality of times.
Also, compared to Comparative Example 1 described later, it can be said that the variation in the density of the secondary color (purple) display after switching the display color a plurality of times is small, and color unevenness is suppressed.

  Furthermore, after repeating the display change for the above 1000 cycles, a voltage for displaying purple was applied, and the sample was left under normal temperature pressure for 24 hours in the state of displaying purple, and then the concentration measurement was performed again in the same manner as described above. When the ratio of the maximum density and the minimum density to the average density value of the measurement results was calculated, they were 105% and 96%, respectively. For this reason, it can be said that the image quality retention is also maintained.

  Next, when a voltage of 10 V was applied to both electrodes so that the electrode on the display substrate side of the display medium produced in Example 1 was negative and the electrode on the back substrate side was positive, the cyan particle group 34C and Both of the magenta particle groups 34M moved to the display substrate side, and purple was displayed on the display medium.

  Next, when the electrode on the display substrate side is positive and the electrode on the back substrate side is negative, the applied voltage is gradually increased from 0 V to both electrodes at a rate of 0.5 V / sec and a voltage of 4 V is applied. When the color change of the display medium was confirmed, red was displayed on the display medium.

  For the display medium displayed in red, the concentration was measured with a densitometer (X-Rite 404A, manufactured by X-Rite Co., Ltd.) at 10 points including the end and center of the entire area of the surface substrate surface. The concentration average value of the measurement results was calculated to be 1.4.

(Comparative Example 1)
In Example 1 described above, the case where the charging film having the recesses 52 is provided on the display substrate has been described. In Comparative Example 1, the display medium provided with the charging film not having the recesses 52 was evaluated.

  In Comparative Example 1, a display medium was produced in the same manner as in Example 1 except that in the production of the display medium in Example 1 above, the process of providing the concave portions 52 in the charging film 27 was not performed.

  When a voltage of 10 V was applied to both electrodes for 3 seconds so that the electrode on the display substrate side of the display medium produced in Comparative Example 1 was negative and the electrode on the back substrate side was positive, cyan particle group 34C and magenta particle group Both 34M moved to the display substrate 20 side, and purple was displayed on the display medium.

  About this purple display medium, the concentration was measured with a densitometer (X-Rite 404A, manufactured by X-Rite Co., Ltd.) for 10 points including the end and center of the entire area of the surface substrate surface. The ratios of the maximum density and the minimum density with respect to the density average value of the measurement results were calculated to be 110% and 92%, respectively.

Next, with the electrode on the display substrate side set as positive and the electrode on the back substrate side set as negative, the applied voltage is gradually increased from 0 V to both electrodes, and display by electrophoresis of each of the cyan particle group 34C and the magenta particle group 34M. When the color change of the medium was confirmed, the display medium changed from purple to white, and no red color was observed.
This is because the display medium produced in Comparative Example 1 does not have a concave portion in the charging film unlike the display medium produced in Example 1, and therefore, two types of particles having different colors (cyan particle group 34C and This is probably because the magenta particle group 34 </ b> M) is stacked in a plurality of layers so as to overlap in the facing direction of the display substrate 20 and the back substrate 22, and the selective detachment from the charging film 29 is inhibited.

Next, the purple → white display is set to one cycle, the applied voltage is changed and the display change is repeated for 1000 cycles, and then the voltage for displaying purple is displayed (a voltage of 10 V is applied for 3 seconds so that the display substrate side is negative). Application) is applied to display purple color, and for the purple-displayed display medium, the concentration is measured at 10 points including the end portion and the central portion of the entire area of the surface substrate surface by a densitometer (X− The ratio of the maximum density and the minimum density with respect to the density average value of the measurement result was calculated by Rite, X-Rite 404A), and they were 115% and 88%, respectively.
Thus, the density variation was larger after the display switching was performed a plurality of times than before the display color was switched a plurality of times.
In addition, as compared with the display medium manufactured in Example 1 above, the variation in the density of the secondary color (purple) display after switching the display color a plurality of times was large.

  Furthermore, after repeating the display change for 1000 cycles, after applying the voltage for displaying purple to display purple, the sample was allowed to stand at room temperature for 24 hours, and the concentration was measured again in the same manner as described above. The ratio of the maximum density and the minimum density to the average density value of the measurement results was calculated to be 115% and 88%, respectively. For this reason, the image quality retention was maintained.

  Next, when a voltage of 10 V was applied to both electrodes so that the electrode on the display substrate side of the display medium produced in Comparative Example 1 was negative and the electrode on the back substrate side was positive, the cyan particle group 34C and Both of the magenta particle groups 34M moved to the display substrate side, and purple was displayed on the display medium.

  Next, when the electrode on the display substrate side is positive and the electrode on the back substrate side is negative, the applied voltage is gradually increased from 0 V to both electrodes at a rate of 0.5 V / sec, and a voltage of 4 V is applied. When the color change of the display medium was confirmed, red was displayed on the display medium.

  For the display medium displayed in red, the concentration was measured with a densitometer (X-Rite 404A, manufactured by X-Rite Co., Ltd.) at 10 points including the end and center of the entire area of the surface substrate surface. It was 0.8 when the density | concentration average value of this measurement result was computed.

  For this reason, in Comparative Example 1, the display color density after displaying the secondary color was lower than that in Example 1.

(Example 2)
In Example 2, a display medium was produced and evaluated in the same manner as in Example 1 except that the charged film was adjusted by a method different from the method for adjusting the charged film used in Example 1.

  In the second embodiment, the charging film 27 has a two-layer structure (a first charging film 27A and a second charging film 27B).

  As the first charging film 27A, first, as a resin constituting the charging film 27A, an ultraviolet curable Toyo Gosei PAK-01 is prepared in the same manner as in Example 1, and in the same manner as in Example 1, a concave portion is formed. A cylindrical structure (made of quartz) having a diameter of 2 μmφ, a height of 5 μm, and a center interval of 2.5 μm is prepared as a mold (mold) for providing 52, and a thin film (not charged) having a recess 52 by an imprint method State of charged film). Furthermore, in the same manner as in Example 1, a thin film having the recess 52 formed thereon was coated with a Cytop (manufactured by Asahi Glass) film using a spin coating method under conditions of 1000 rpm × 20 seconds from a 5-fold diluted solution, This film was charged by corona charging to obtain a first charged film 27A having a surface potential of −20V.

Next, a thin film of an ultraviolet curable fluororesin (Toyo Gosei PAK-01-60) was formed as the second charging film 27B on the first charging film 27A.
The thin film as the second charged film 27B is formed by spin-coating the UV curable Toyo Gosei PAK-01-60 at 2000 rpm to obtain a thin film with a thickness of about 100 nm. The thin film was formed by irradiation.

  When the surface potential of the charging film 27 formed by laminating the second charging film 27B on the first charging film 27A was measured in the same manner as described above, it was -5V. This is presumably because part of the surface charge of the first charging film 27A was canceled by the formation of the second charging film 27B.

In addition, the variation in the in-plane charge distribution of the charging film 27 adjusted in Example 2 was measured with a surface potentiometer, and was within ± 8%. On the other hand, when the variation in the in-plane charge distribution of the charging film 27 adjusted to a low surface potential by adjusting the charging process time by the same method as in Example 1 was measured in the same way, it was found that −4V to −− It became 12V, and there was a variation of 3 times.
For this reason, it can be said that the charging film 27 configured by the adjustment method of the second embodiment has less variation in charge distribution than the charging film 27 configured by the adjustment method of the first embodiment.

(Evaluation)
When a voltage of 10 V was applied to both electrodes for 3 seconds so that the electrode on the display substrate side of the display medium produced in Example 2 was negative and the electrode on the back substrate side was positive, cyan particle group 34C and magenta particle group Both 34M moved to the display substrate 20 side, and purple was displayed on the display medium.

  About this purple display medium, the concentration was measured with a densitometer (X-Rite 404A, manufactured by X-Rite Co., Ltd.) for 10 points including the end and center of the entire area of the surface substrate surface. The ratios of the maximum density and the minimum density with respect to the density average value of the measurement results were calculated to be 105% and 95%, respectively.

  Next, with the electrode on the display substrate side set as positive and the electrode on the back substrate side set as negative, the applied voltage is gradually increased from 0 V to both electrodes, and display by electrophoresis of each of the cyan particle group 34C and the magenta particle group 34M. When the color change of the medium was confirmed, the display medium changed from purple → red → white.

  The above purple, red, and white display is one cycle, the applied voltage is changed and 1000 cycles are repeated. After that, the voltage for displaying purple (10V voltage is applied for 3 seconds so that the display substrate side becomes negative) ) To display purple color, and for the purple-displayed display medium, the concentration is measured at 10 points including the end portion and the central portion of the entire area of the surface substrate surface by a densitometer (X-Rite). X-Rite 404A), and the ratio of the maximum density and the minimum density with respect to the density average value of the measurement results was calculated to be 105% and 95%, respectively. For this reason, it can be said that the density variation is suppressed before and after the display color is switched a plurality of times.

  Furthermore, after repeating the display change for 1000 cycles, after applying the voltage for displaying purple to display purple, the sample was allowed to stand at room temperature for 24 hours, and the concentration was measured again in the same manner as described above. The ratio of the maximum density and the minimum density to the average density value of the measurement results was calculated to be 106% and 94%, respectively. For this reason, it can be said that the image quality retention is also maintained.

  Next, when a voltage of 10 V was applied to both electrodes so that the electrode on the display substrate side of the display medium produced in Example 2 was negative and the electrode on the back substrate side was positive, the cyan particle group 34C and Both of the magenta particle groups 34M moved to the display substrate side, and purple was displayed on the display medium.

  Next, when the electrode on the display substrate side is positive and the electrode on the back substrate side is negative, the applied voltage is gradually increased from 0 V to both electrodes at a rate of 0.5 V / sec, and a voltage of 4 V is applied. When the color change of the display medium was confirmed, red was displayed on the display medium.

  For the display medium displayed in red, the concentration was measured with a densitometer (X-Rite 404A, manufactured by X-Rite Co., Ltd.) at 10 points including the end and center of the entire area of the surface substrate surface. The concentration average value of the measurement results was calculated to be 1.3.

  For this reason, in Example 2, as in Example 1, it was confirmed that the display color density after displaying the secondary color was higher than that in Comparative Example 1, and the decrease in display color density was suppressed. It was done.

1 is a schematic configuration diagram of a display medium and a display device according to an embodiment. It is the schematic diagram which expanded the charging film of the display medium which concerns on this embodiment. (A)-(C) It is the schematic diagram which expanded the charging film of the display medium which concerns on this embodiment. (A) (B) It is a schematic diagram which shows the structure method of a charged film. It is a diagram which shows typically the relationship between the voltage to apply and the moving amount (display density | concentration) of particle | grains. It is a schematic diagram which shows the relationship between the movement of particle | grains and the displayed color in the display medium which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Display apparatus 12 Display medium 16 Voltage application part 18 Control part 20 Display substrate 22 Back substrate 27, 29 Charged film 34M Magenta particle group 34Y Yellow particle group 34C Cyan particle group 34 Particle group 52 Recessed part

Claims (6)

A pair of substrates at least one having translucency and disposed with a gap;
A dispersion medium sealed between the pair of substrates;
A plurality of types of particles dispersed in the dispersion medium, having translucency, moving according to an electric field formed between the substrates, and having different absolute values of colors and movement voltages necessary to move with each other Group,
A precharged charging film provided on at least one of the opposing surfaces of the pair of substrates, having a plurality of recesses that are open on the opposing substrate side and through which the particle group can enter and exit;
A display medium comprising:   The display medium according to claim 1, wherein the concave portion is provided over the entire region of the opposing surfaces of the pair of substrates of the charging film.   2. The display medium according to claim 1, wherein a depth of the concave portion is equal to or greater than a value obtained by adding a volume average primary particle diameter of at least a plurality of particles in the plurality of types of particle groups.   2. The charged film according to claim 1, wherein a second charged film that is charged or uncharged to less than a saturated charge amount is laminated on a first charged film that has been charged to a saturated charge amount in advance. The display medium described. A pair of substrates having electrodes, at least one of which is translucent and disposed with a gap, a dispersion medium sealed between the pair of substrates, and dispersed in the dispersion medium, A plurality of types of particle groups having translucency and moving according to the electric field formed between the substrates, and having different colors and absolute values of moving voltages necessary for moving, and the pair of substrates A display medium having a pre-charged charging film provided on at least one of the opposing surfaces and having an opening on the opposing substrate side and having a plurality of recesses through which the particles can enter and exit,
Voltage applying means for applying a voltage between the pair of substrates;
A display device comprising:   The display device according to claim 5, wherein the plurality of types of particles have a voltage range necessary for moving according to an electric field for each type, and the voltage ranges are different from each other.