JP2012048227A - Image display element and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display element capable of performing a high quality display with little color mixture and to provide an image display device including the image display element.SOLUTION: An image display element comprises: a cell which has an opening plane and includes electrophoretic liquid; a first driving electrode 1 and second driving electrodes 2 which can independently control electric potential against the electrophoretic liquid and which are arranged side by side; and a transparent third electrode 3 which is arranged facing the first driving electrode 1 and the second driving electrodes 2. An electric field distribution when the first driving electrode 1 and the second driving electrodes 2 are kept at different voltage is rotationally symmetrical in the opening plane of the cell.

Description

  The present invention relates to an image display element and an image display apparatus using an electrophoretic liquid.

  In recent years, with the development of information equipment, information processing such as document creation has been performed on a computer, on a display terminal such as a CRT (Cathode Ray Tube) that displays characters, still images, moving images, etc., a liquid crystal display, etc. Opportunities to read texts have increased significantly. The display terminal can instantly display and rewrite digital data, but it is difficult to carry. In addition, since the device is a self-luminous device, there are problems such as eye fatigue due to long-time work and display failure when the power is turned off.

  On the other hand, when distributing or storing characters, still images, etc., they are recorded on a paper medium using a printer. When a paper medium is used, reflection due to multiple scattering is observed, so that visibility is better than that of a self-luminous device, and eyes are not fatigued. Further, since the paper medium is lightweight, it can be carried and read in a free posture. However, the paper medium has a problem of being discarded after use. At this time, some paper media are recycled, but this requires a lot of labor and cost.

  As an image display medium having the advantages of both a display terminal and a paper medium, an image display element using a polymer dispersed liquid crystal, a bistable cholesteric liquid crystal, an electrochromic element, an electrophoretic element, or the like is known. ing. These image display elements are attracting attention because they are reflective display type and capable of bright display and have a memory property. Among these, an image display element using an electrophoretic element is excellent in terms of display quality and power consumption during display operation.

  For example, Japanese Patent Application Laid-Open No. 2009-9092 proposes a color reflective display. An electrophoretic liquid in which three types of dispersed particles having different optical characteristics and charging characteristics are dispersed in a solvent. Specifically, the first dispersed particles have no charge, and the second dispersed particles are electrophoretic particles having a positive charge. The third dispersed particle has a cell containing an electrophoretic liquid that is a negatively charged electrophoretic particle, and a transparent electrode is disposed on the display surface side of the cell, and two electrodes are disposed on the opposite side of the display surface. . In the first and second color displays, the second electrophoretic particles or the third electrophoretic particles are attracted to the transparent electrode on the display surface side of the cell, and the color of each particle is displayed. In the third color display, voltages having different polarities are applied to the two electrodes, the second positive electrophoretic particles and the third negative electrophoretic particles are attracted to the respective electrodes, and the first non-charged first Displays the color of the dispersed particles.

  Next, in the color reflection display of Patent Document 2 (Japanese Patent Publication No. 2006-520012), an electrophoretic liquid in which charged particles having white optical characteristics are dispersed in a colored nonpolar solvent, and colored in black. With the two electrodes at the bottom, white display, black display, and nonpolar solvent color display are performed. In the first color display, white particles are drawn by attracting white particles to the transparent electrode on the display surface side. In the second color display, white particles are attracted to the two electrodes at the bottom, and the color display of the nonpolar solvent is performed using the scattering of the white particles. In the third color display, white particles are attracted to the outer electrodes of the bottom two electrodes, and black display is performed using absorption of the central black electrode.

Here, in Patent Document 1, particles are moved between two electrodes arranged on the opposite side to the display surface. However, particularly when performing the third color display, the two electrodes are set to different potentials. It is necessary to hold and attract the positive and negative charged particles to the respective electrodes. However, since the two electrodes are arranged so as to divide the cell into two, an in-plane distribution of the electric field on the opening surface (color display surface) of the cell is generated in the electrode dividing direction, and the in-plane of the electric field Particle bias occurs along the distribution. As a result, the positive and negative charged particles are not held on the two electrodes, but the particles diffuse into the solvent, resulting in a third color display in which the colors of the positive or negative charged particles are mixed.
An object of the present invention is to solve the above-described problems and provide an image display element that can display a high-quality image with little color mixing, and an image display device including the image display element.

  In order to solve the above problems, the image display element and the image display device according to the present invention specifically have the technical features described in the following (1) to (8).

(1): a cell having an open surface and containing an electrophoretic liquid; a first driving electrode and a second electrode, the electric potential of which can be controlled independently of each other and the electrophoretic liquid; And a transparent third electrode disposed to face the first driving electrode and the second driving electrode, the first driving electrode, and the first driving electrode, The image display element is characterized in that the electric field distribution when the two driving electrodes are held at different voltages is rotationally symmetric within the opening surface of the cell.

  With the configuration described in (1) above, the positive and negative charged particles are held on the two electrodes (the first driving electrode and the second driving electrode) by moving the particles symmetrically in the cell. can do.

(2): The shape of the opening surface of the cell is rotationally symmetric, the shape of the first driving electrode is the same rotational symmetry as the shape of the opening surface of the cell, and the rotational symmetry of the opening surface of the cell. And the center of rotational symmetry of the first drive electrode coincide with each other, and the second drive electrode is disposed so as to surround the first drive electrode and has a constant width. The image display element according to (1) above, wherein

  With the configuration described in (2) above, the electric field distribution when the first driving electrode and the second driving electrode are held at different voltages is within the opening surface of the cell containing the electrophoretic liquid. , It can be rotationally symmetric.

(3): The shape of the opening surface of the cell is rotationally symmetric, the shape of the first driving electrode is rotationally symmetric, the center of rotational symmetry of the opening surface of the cell, and the first driving And the second drive electrode is arranged in pairs so as to sandwich the first electrode and has a constant width. The image display element according to (1) above.

  With the configuration described in (3) above, the electric field distribution when the first driving electrode and the second driving electrode are held at different voltages is within the opening surface of the cell containing the electrophoretic liquid. , It can be rotationally symmetric.

(4): wherein the area _{A 1} of the first driving electrode, wherein the area _{A 2} of the second driving electrodes, said to satisfy the relationship of _{A 2} ≦ 0.5A ₁ (1 The image display device according to any one of (3) to (3).

  With the configuration described in (4) above, when the two drive electrodes (the first drive electrode and the second drive electrode) are held at different potentials, the positive and negative charged particles are respectively It can be integrated into the electrode.

(5): The electrophoretic liquid encapsulated in the cell is composed of three types of dispersible particles having different optical characteristics and charging characteristics dispersed in a nonpolar solvent, and the first dispersible particles have a charge. The second dispersible particles are electrophoretic particles having a positive charge, and the third dispersible particles are electrophoretic particles having a negative charge. It is an image display element of any one of these.

  With the configuration described in (5) above, when the two drive electrodes (the first drive electrode and the second drive electrode) are held at different potentials, the second dispersible particles and the first Three dispersible particles can be accumulated on each electrode to display the color of the first dispersible particles.

(6): The electrophoretic liquid encapsulated in the cell comprises three kinds of dispersible particles having different charging characteristics dispersed in a colored transparent nonpolar solvent, and the first dispersive particles have optical characteristics. Is a white electrophoretic particle having a positive or negative charge, and the second dispersible particle is an electrophoretic particle having a black optical characteristic and having a charge opposite to that of the first dispersible particle. The image display device according to any one of (1) to (4), wherein the particles are dispersible particles having optical characteristics of white and no charge.

  With the configuration described in (6) above, when the two driving electrodes (the first driving electrode and the second driving electrode) are held at different potentials, the first dispersible particles and the first Two dispersible particles can be accumulated on each electrode to display the color of a colored transparent nonpolar solvent.

(7): The electrophoretic liquid encapsulated in the cell is composed of three types of dispersible particles having different optical characteristics or charging characteristics in a colored transparent nonpolar solvent, and the first dispersible particles are: The electrophoretic particles have white and positive or negative optical characteristics, and the second dispersive particles are opposite to the first dispersive particles whose optical characteristics absorb light in a specific wavelength region in the visible light region. The electrophoretic particles having a polar charge, and the third dispersive particle is an electrophoretic particle having an optical property that is white and having the same polarity as the second dispersible particle, and the colored transparent nonpolar solvent. Any one of the above (1) to (4), wherein the optical characteristic has a characteristic of transmitting light in a specific wavelength region absorbed by the second dispersible particles and absorbing other light. The image display element according to item.

  With the configuration described in (7) above, when the two driving electrodes (the first driving electrode and the second driving electrode) are held at different potentials, the first dispersible particles, The dispersible particles 2 and the third dispersible particles are each accumulated on the electrode having the opposite potential, and the color of the colored transparent nonpolar solvent or black can be displayed.

(8): An image display device comprising the image display element described in any one of (1) to (7) above.

  With the configuration described in (8) above, it is possible to provide an image display device with good color display quality.

  ADVANTAGE OF THE INVENTION According to this invention, an image display element which can display a high quality with few color mixing, and an image display apparatus provided with this image display element can be provided.

1 is a schematic diagram illustrating a configuration example of a first embodiment of a first drive electrode 1 and a second drive electrode 2 that constitute a part of an image display element according to the present invention. It is the schematic which shows the structural example of 2nd Embodiment of the 1st drive electrode 1 and the 2nd drive electrode 2 which comprise some in the image display element which concerns on this invention. It is the schematic which shows the structural example of 3rd Embodiment of the 1st drive electrode 1 and the 2nd drive electrode 2 which comprise some in the image display element which concerns on this invention. It is the schematic which shows the structural example of 4th Embodiment of the 1st drive electrode 1 and the 2nd drive electrode 2 which comprise some in the image display element which concerns on this invention. It is the schematic which shows the structural example of 5th Embodiment of the 1st drive electrode 1 and the 2nd drive electrode 2 which comprise some in the image display element which concerns on this invention. It is the schematic which shows the structural example of 6th Embodiment of the 1st drive electrode 1 and the 2nd drive electrode 2 which comprise a part in the image display element which concerns on this invention. It is the schematic which shows the structural example of 7th Embodiment of the 1st drive electrode 1 and the 2nd drive electrode 2 which comprise a part in the image display element which concerns on this invention. It is the schematic which shows the structural example in one Embodiment of the image display apparatus which concerns on this invention. It is the schematic which shows the structural example in Embodiment A of the image display element which concerns on this invention. It is the schematic which shows the structure of the 1st drive electrode 1 and the 2nd drive electrode 2 which comprise a part in the image display element of a comparative example. It is the schematic which shows the structural example in Embodiment B of the image display element which concerns on this invention. It is the schematic which shows the structural example in Embodiment C of the image display element which concerns on this invention.

<Display element>
The image display element according to the present invention includes a cell having an opening surface and containing an electrophoretic liquid, and a first drive in which the electric potential can be independently controlled with respect to the electrophoretic liquid and arranged side by side. Electrode 1 and second drive electrode 2, and transparent third electrode 3 disposed opposite to the first drive electrode 1 and second drive electrode 2, The electric field distribution when the first driving electrode 1 and the second driving electrode 2 are held at different voltages is rotationally symmetric within the opening surface of the cell.

Here, the rotational symmetry in the present invention will be supplementarily described.
When n is an integer of 2 or more, and rotates around a certain center (in the case of a two-dimensional figure) or axis (in the case of a three-dimensional figure) by (360 / n) °, the property of overlapping with itself is n-fold symmetry, or n It is called phase symmetry or (360 / n) degree symmetry, and such symmetry is generally called rotational symmetry. However, when n is 1, it is obvious that it overlaps with itself at 360 degrees, so the one-time symmetry is not regarded as symmetry.

In addition, although it illustrates below about the material which comprises the image display element which concerns on this invention, this invention is not limited to these at all, and uses various well-known materials in the range which does not impair the effect of this invention. Can do.
Examples of the transparent conductive material (third electrode) include ITO, SnO ₂ , and ZnO / Al.
Examples of the electrode material (first driving electrode, second driving electrode) include ITO, SnO ₂ , ZnO / Al, Au, Ag, Al, and Cr.
Examples of the cell partition material include polymethyl methacrylate, novolak resin, and polystyrene.
Examples of the film material for sealing the opening of the cell into which the electrophoretic solution has been injected include PET, PEN, and PES. In addition, as the sealing adhesive material used at that time, polyurethane, polyurea, polyurea-polyurethane, urea-formaldehyde resin, melamine-formaldehyde resin, polyamide, polyester, polysulfonamide, polycarbonate, polysulfinate, epoxy resin, Examples thereof include polyacrylic acid ester, polymethacrylic acid ester, polyvinyl acetate, and gelatin.

Next, the image display element according to the present invention will be described in more detail.
Although the embodiments described below are preferred embodiments of the present invention, various technically preferable limitations are attached thereto, but the scope of the present invention is intended to limit the present invention in the following description. Unless otherwise described, the present invention is not limited to these embodiments.

[First Embodiment]
FIG. 1 shows a configuration example of the first embodiment of the first driving electrode 1 and the second driving electrode 2 constituting a part of the image display element according to the present invention.
In the present embodiment, the opening shape (the shape of the opening surface) of the cell (the space partitioned by the partition walls) for containing the electrophoresis solution is a rectangle. These cells are arranged in the plane to constitute an image display element. FIG. 1 shows one cell. The opening surface of the cell in FIG. 1 is two-fold symmetric, and the first driving electrode 1 is also a two-fold symmetric rectangle, and the centers thereof coincide with each other. Four second driving electrodes 2 are arranged side by side so as to surround the first driving electrode 1. The widths of the second drive electrodes 2 are all the same. With the configuration of the first driving electrode 1 and the second driving electrode 2 as described above, the electric field distribution on the cell opening surface when different potentials are held becomes symmetrical in the horizontal direction and the vertical direction. It becomes symmetric. The area of the driving electrode is larger than that of the second driving electrode. By having such an area relationship, it becomes easier to hold the positively and negatively charged electrophoretic particles to the respective driving electrodes.
The transparent third electrode 3 (not shown) is provided to face the first driving electrode 1 and the second driving electrode 2. (The same applies to the embodiments described below.)

[Second Embodiment]
FIG. 2 shows a configuration example of the second embodiment of the first drive electrode 1 and the second drive electrode 2 constituting a part of the image display element according to the present invention.
In the present embodiment, the opening shape of the cell for containing the electrophoresis solution is rectangular. The opening surface of the cell in FIG. 2 is two-fold symmetric, and the first driving electrode 1 is also a two-fold symmetric rectangle, and the centers thereof coincide with each other. A second drive electrode 2 is arranged so as to surround the first drive electrode 1. The second drive electrode 2 has a rectangular shape with a central portion missing, and is symmetric twice with the cell opening surface and the first drive electrode 1, and the rotationally symmetric centers coincide. ing. The width of the second drive electrode 2 is also constant. With the configuration of the first driving electrode 1 and the second driving electrode 2 as described above, the electric field distribution on the cell opening surface when different potentials are held becomes symmetrical in the horizontal direction and the vertical direction. It becomes symmetric. The area of the driving electrode is larger than that of the second driving electrode. By having such an area relationship, it becomes easier to hold the positively and negatively charged electrophoretic particles to the respective driving electrodes.

  In the present invention, the second drive electrode 2 may be divided or integrated as shown in FIGS. 1 and 2.

[Third to fifth embodiments]
3, FIG. 4, and FIG. 5 illustrate configuration examples of the third to fifth embodiments of the first driving electrode 1 and the second driving electrode 2 that constitute a part of the image display element according to the present invention. Shown in
3 is an example of three-fold symmetry, FIG. 4 is an example of four-fold symmetry, and FIG. 5 is an example of six-fold symmetry. In these, the second driving electrode 2 is integrated, but may be divided as in the first embodiment shown in FIG. In the case of rotational symmetry of 7 times or more, the cell becomes a regular heptagon or more, and it is impossible to arrange the cells in a planar shape. However, the case of a circle with n = ∞ times belongs to the scope of the present invention.

[Sixth Embodiment]
FIG. 6 shows a configuration example of the sixth embodiment of the first drive electrode 1 and the second drive electrode 2 constituting a part of the image display element according to the present invention.
In the present embodiment, the opening shape of the cell for containing the electrophoresis solution is rectangular. The opening surface of the cell in FIG. 2 is two-fold symmetric, and the first driving electrode 1 is also a two-fold symmetric rectangle, and the centers thereof coincide with each other. The second driving electrode 2 is disposed on both the left and right sides of the first driving electrode 1 in FIG. At this time, the second drive electrode 2 is not disposed on the upper and lower sides of the first drive electrode 1 in FIG. The width of the second drive electrode 2 is constant. With the configuration of the first driving electrode 1 and the second driving electrode 2 as described above, the electric field distribution on the cell opening surface when different potentials are held becomes symmetrical in the horizontal direction and the vertical direction. It becomes symmetric. The area of the driving electrode is larger than that of the second driving electrode. By having such an area relationship, it becomes easier to hold the positively and negatively charged electrophoretic particles to the respective driving electrodes.

[Seventh Embodiment]
FIG. 7 shows a configuration example of the seventh embodiment of the first drive electrode 1 and the second drive electrode 2 constituting a part of the image display element according to the present invention.
In FIG. 6, the order of symmetry of the cell and the order of symmetry of the first drive electrode 1 are the same, but it is not always necessary to match. Such an example is shown in FIG.
In the present embodiment, the opening shape of the cell for containing the electrophoretic solution is a regular hexagon and is 6-fold symmetrical. On the other hand, the first driving electrode 1 is rectangular and symmetrical twice. However, the centers of symmetry are coincident. The second drive electrode 2 is disposed on both the left and right sides of the first drive electrode 1 in FIG. At this time, the second drive electrode 2 is not disposed on both the upper and lower sides of the first drive electrode 1 in FIG. In other words, the second driving electrode 2 includes a pair of electrodes, and is arranged in pairs so as to sandwich the first electrode 1 in a predetermined direction.
The width of the second drive electrode 2 is constant. With the configuration of the first driving electrode 1 and the second driving electrode 2 as described above, the electric field distribution on the cell opening surface when different potentials are held becomes symmetrical in the horizontal direction and the vertical direction. It becomes symmetric.
Further, the area of the driving electrode is larger than that of the second driving electrode. By having such an area relationship, it becomes easier to hold the positively and negatively charged electrophoretic particles to the respective driving electrodes.

In the image display device according to the present invention, the area A ₁ of the first driving electrode, and the area A ₂ of the second driving electrode, by satisfying the relation of A ₂ ≦ 0.5A _1, When the first drive electrode and the second drive electrode are held at different potentials, it is preferable because positive and negative charged particles can be accumulated on the respective electrodes.

<Image display device>
FIG. 8 shows a configuration example in an embodiment of an image display device according to the present invention.
8 includes an image display element 11 as an image display medium, information input means 12 for inputting image information to the image display medium, a housing 13, a drive circuit (not shown), an arithmetic circuit (not shown), An internal memory (not shown), a power supply means (not shown) for supplying power to the image display medium 11 and the information input means 12 are provided. Any of the image display elements of the present invention described above is used for the image display element 11.
The image display device 100 displays an image by causing the designated pixels of the image display medium 11 to develop color. As the power supply means, internal power such as a battery may be provided, or a power receiving device such as an outlet receiving power from an external power source may be provided.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. In addition, this invention is not limited to the example shown below at all.

[Example 1]
FIG. 9 shows a configuration example in Embodiment A of the image display element according to the present invention. The image display element is composed of a plurality of cells, and a cross-sectional view of one of the cells is shown in FIG.
The transparent substrate 4 on which the transparent third electrode 3 is formed, and the thin film transistor substrate 5 on which the first driving electrode 1 and the second driving electrode 2 are formed at a predetermined interval are provided as an electrophoretic liquid. Further, they are arranged to face each other through the partition wall 7.
The electrophoretic liquid contained in the cell is an electrophoretic liquid in which three kinds of dispersible particles (8, 9, 10) having different optical characteristics and charging characteristics are dispersed in the nonpolar solvent 6. The first dispersible particles 8 have no charge and are white. The second dispersible particles 9 are electrophoretic particles having a positive charge and are black. The third dispersible particles 10 are electrophoretic particles having a negative charge and have a magenta color. However, the color of each dispersed particle may be other colors, and the present invention is not limited to the aspect of the first embodiment.

  White polyvinyl naphthalene particles were used as the first dispersible particles 8, black carbon black was used as the second positively charged dispersed particles 9, and red disperse particles were used as the third negatively charged dispersible particles 10. Polyvinyl naphthalene particles were obtained by subjecting 2-vinyl naphthalene to Isopar G (trade name: manufactured by Exxon Mobil, isoparaffin hydrocarbon) and dispersion polymerization using a silicon macromonomer as a dispersant to produce fine particles. The carbon black was surface-modified by heteroaggregating an amino group-containing polymer on the surface. The amino group-containing polymer may be a polymer obtained by copolymerizing dimethylaminoethyl methacrylate and silicon macromer. Disperse red particles are mixed in a solution in which Isopar G, lauryl methacrylate, glycidyl methacrylate, allyl methacrylate, methacrylic acid, and a peroxide polymerization initiator are stirred in advance, and dispersed with a ball mill, and then surface treatment is performed. went.

  An electrophoretic liquid was produced using the produced polyvinyl naphthalene particles, carbon black, and disperse particles. Solsperse 17000 (trade name: manufactured by Avicia) was used as a charge control agent, and sorbitan trioleate was used as a surfactant for controlling dispersion. The solvent was a non-polar solvent IsoparG (trade name: manufactured by ExxonMobil, isoparaffinic hydrocarbon), which was a colorless solvent. The mixing ratio of the electrophoresis solution is shown in Table 1.

  A cell for containing the electrophoresis solution having the configuration shown in FIG. 4 was prepared. On the substrate on which the TFT circuit is formed, the side length of the first driving electrode 1 is 200 μm, the length of the inner side of the second driving electrode 2 is 230 μm, and the length of the outer side is 270 μm. The electrode to be formed was made of Ag. A cell was produced on this substrate by a photoresist process using SU-8 (trade name: manufactured by Kayaku Microchem). The cell size was prepared such that the opening was 275 × 275 μm, the partition wall 7 was 25 μm thick, and the height was 70 μm. At this time, the area ratio of the first drive electrode 1 and the second drive electrode 2 is about 2: 1.

The electrophoretic solution prepared in advance in Table 1 was poured into the prepared cell, and sealed with a PET film on which an ITO film as the third transparent electrode 3 was formed. Sealing was performed by applying an ultraviolet curable adhesive in advance on the surface of the ITO film, covering the cell onto which the electrophoretic solution was poured, and irradiating with ultraviolet rays to perform adhesion.
In the manufactured image display element, the cells were arranged in a square lattice, the pitch between the cells was 300 μm, and the size of the display portion was about 1 × 1 cm.

The operation of one cell of the manufactured image display element will be described.
FIG. 9A shows a schematic diagram of black display. A voltage of +15 V is applied to the first drive electrode 1 and the second drive electrode 2. The positively charged second dispersible particles 9 move to the third transparent electrode 3 on the display surface side, resulting in black display. Similarly, in the red display, a voltage of −15 V is applied to the first driving electrode 1 and the second driving electrode 2, and the negatively charged third dispersive particles 10 are third transparent on the display surface side. It moves to the electrode 3 and becomes red display.

Next, a method for displaying the color of the first dispersible particles 8 will be described.
From the black display state of FIG. 9A, the first driving electrode 1 is changed from +15 V to 0 V, and the third dispersive particles 10 are moved to the second driving electrode 2. At this time, the second dispersible particles 9 are separated from the third transparent electrode 3. (See FIG. 9B.) Further, the voltage of the second drive electrode 2 is changed from +15 V to +10 V, the first drive electrode 1 is changed from 0 V to −10 V, and the second dispersible particles 9 are changed to the first. To the driving electrode 1. Since the first dispersible particles 8 are white and light is scattered, a white display is obtained. (See FIG. 9 (c).)

[Comparative Example]
The white display when the cell shown below is used as the electrophoresis solution of Example 1 is compared with Example 1.
A cell for containing the electrophoresis solution having the configuration shown in FIG. 10 was prepared. An electrode having a first driving electrode 1 of 270 × 125 μm and a second driving electrode 2 of 270 × 125 μm was formed of Ag on the substrate on which the TFT circuit was formed. A cell was produced on this substrate by a photoresist process using SU-8 (trade name: manufactured by Kayaku Microchem). The cell size was prepared such that the opening was 275 × 275 μm, the partition wall 7 was 25 μm thick, and the height was 70 μm.

  An electrophoretic solution prepared in advance in Table 1 was poured into the produced cell, and sealing was performed with a PET film on which an ITO film was formed as the third transparent electrode 3. Sealing was performed by applying an ultraviolet curable adhesive in advance on the surface of the ITO film, covering the cell onto which the electrophoretic solution was poured, and irradiating with ultraviolet rays to perform adhesion.

  In the manufactured image display element, the cells were arranged in a square lattice, the pitch between the cells was 300 μm, and the size of the display portion was about 1 × 1 cm.

  White display was performed in the same procedure as the white display of Example 1. From the black display state, the first driving electrode 1 is changed from +15 V to 0 V, and the third dispersible particles 10 are moved to the second driving electrode 2. Next, the voltage of the second drive electrode 2 is changed from +15 V to +10 V, the first drive electrode 1 is changed from 0 V to −10 V, and the second dispersible particles 9 are moved to the first drive electrode 1. .

In the comparative example, an asymmetry occurs in the electric field in the direction in the display surface during white display. When the cell was observed with a microscope, the second dispersible particles 9 and the third dispersible particles 10 were not stably held by the first driving electrode 1 and the second driving electrode 2, Convection of dispersible particles was confirmed. Due to this convection, a white display in which black and red are mixed is obtained. The white reflectance is about 30 to 35% when all the cells in the 1 × 1 cm display section are displayed in white.
On the other hand, in Example 1, the convection of the electrophoretic liquid generated in the comparative example is not observed, and the black or red color mixture is reduced during white display. The white reflectance is about 40 to 45% when all cells in the 1 × 1 cm display section are displayed in white.

[Example 2]
FIG. 11 shows a configuration example in Embodiment B of the image display element according to the present invention. The image display element is composed of a plurality of cells, and a cross-sectional view of one of the cells is shown in FIG.
The thin film transistor substrate 5 on which the transparent substrate 4 on which the transparent third electrode 3 is formed and the first driving electrode 1 and the second driving electrode 2 are formed at a predetermined interval is provided as an electrophoretic liquid. Further, they are arranged to face each other through the partition wall 7.

  The electrophoretic liquid contained in the cell is an electrophoretic liquid in which three types of dispersible particles (8, 9, 10) having different charging characteristics are dispersed in a colored transparent nonpolar solvent 6. The first dispersible particles 8 are electrophoretic particles having white optical characteristics and negative charges. The second dispersible particles 9 are positively charged electrophoretic particles having a black optical characteristic. The third dispersible particle 10 is a dispersible particle having white optical characteristics and no charge. Furthermore, the nonpolar solvent 6 is colored blue with a dye. However, the color of the dye may be other colors, and the present invention is not limited to the embodiment 2.

  Titanium oxide particles were used as the first negatively charge dispersible particles 8, carbon black was used as the second positively charge dispersible particles 9, and white polyvinyl naphthalene particles were used as the third dispersible particles 10. The titanium oxide particles were surface-treated with 3- (trimethoxysilyl) propyl methacrylate, and then lauryl methacrylate was graft-polymerized on the surface of the titanium oxide particles. The carbon black was surface-modified by heteroaggregating an amino group-containing polymer on the surface. As the amino group-containing polymer, a polymer obtained by copolymerizing dimethylaminoethyl methacrylate and silicon macromer was used. Polyvinyl naphthalene particles were obtained by subjecting 2-vinyl naphthalene to Isopar G (trade name: manufactured by Exxon Mobil, isoparaffin hydrocarbon) and dispersion polymerization using a silicon macromonomer as a dispersant to produce fine particles.

  An electrophoretic solution was produced using the produced polyvinyl naphthalene particles, carbon black, and titanium oxide particles. Solsperse 17000 (trade name: manufactured by Avicia) was used as a charge control agent, and sorbitan trioleate was used as a surfactant for controlling dispersion. The solvent was a non-polar solvent Isopar G (trade name: manufactured by ExxonMobil, isoparaffinic hydrocarbon) and colored blue with oil blue N to obtain a blue colored solvent (6). The mixing ratio of the electrophoresis solution is shown in Table 2 below.

  A cell for containing the electrophoresis solution having the configuration shown in FIG. 4 was prepared. On the substrate on which the TFT circuit is formed, the side length of the first driving electrode 1 is 200 μm, the length of the inner side of the second driving electrode 2 is 230 μm, and the length of the outer side is 270 μm. The electrode to be formed was made of Ag. A cell was produced on this substrate by a photoresist process using SU-8 (trade name: manufactured by Kayaku Microchem). The cell size was prepared such that the opening was 275 × 275 μm, the partition wall thickness was 25 μm, and the height was 70 μm. At this time, the area ratio of the first drive electrode 1 and the second drive electrode 2 is about 2: 1.

The electrophoretic solution prepared in advance in Table 2 was poured into the prepared cell and sealed with a PET film on which an ITO film as the third transparent electrode 3 was formed. Sealing was performed by applying an ultraviolet curable adhesive in advance on the surface of the ITO film, covering the cell onto which the electrophoretic solution was poured, and irradiating with ultraviolet rays to perform adhesion.
In the manufactured image display element, the cells were arranged in a square lattice, the pitch between the cells was 300 μm, and the size of the display portion was about 1 × 1 cm.

The operation of one cell of the manufactured image display element will be described.
FIG. 11A shows a schematic diagram of black display. A voltage of +15 V is applied to the first drive electrode 1 and the second drive electrode 2. The positively charged second dispersible particles 9 move to the third transparent electrode 3 on the display surface side, resulting in black display. Similarly, in the white display, a voltage of −15 V is applied to the first driving electrode 1 and the second driving electrode 2, and the negatively charged first dispersive particles 8 are third transparent on the display surface side. It moves to the electrode 3 and becomes white display.

Next, a method for displaying the color of the nonpolar solvent 6 colored in blue will be described.
From the black display state of FIG. 11A, the first driving electrode 1 is changed from +15 V to 0 V, and the first dispersive particles 8 are moved to the second driving electrode 2. At this time, the second dispersible particles 9 are separated from the third transparent electrode 3. (See FIG. 11B.) Further, the voltage of the second drive electrode 2 is changed from +15 V to +10 V, the first drive electrode 1 is changed from 0 V to −10 V, and the second dispersible particles 9 are moved to the first. To the driving electrode 1. Since the third dispersible particles 10 are white and scatter visible light (400 to 700 nm), and the nonpolar solvent colored blue absorbs light of 500 to 700 nm, blue display is obtained. (See FIG. 11 (c).)

Example 3
FIG. 12 shows a configuration example in Embodiment C of the image display element according to the present invention. The image display element is composed of a plurality of cells, and a cross-sectional view of one cell among them is shown in FIG.
The thin film transistor substrate 5 on which the transparent substrate 4 on which the transparent third electrode 3 is formed and the first driving electrode 1 and the second driving electrode 2 are formed at a predetermined interval is provided as an electrophoretic liquid. Further, they are arranged to face each other through the partition wall 7.

  The electrophoretic liquid contained in the cell is an electrophoretic liquid in which three kinds of dispersible particles (8, 9, 10) having different optical characteristics or charging characteristics are dispersed in a colored transparent nonpolar solvent 6. The first dispersible particles 8 are electrophoretic particles having white optical characteristics and negative charges. The second dispersible particles 9 are positively charged electrophoretic particles having an optical characteristic of cyan. The third dispersible particles 10 are electrophoretic particles having a white optical property and a positive charge. Furthermore, the nonpolar solvent 6 is colored red with a dye. However, the color of the second dispersible particles 9 and the color of the dye may be other colors, and the present invention is not limited to the embodiment 3.

  Titanium oxide particles were used as the first negatively charge dispersible particles 8, phthalocyanine pigments were used as the second positively charge dispersible particles 9, and titanium oxide particles were used as the third positively charge dispersible particles 10. The negatively charged titanium oxide particles were surface-treated with 3- (trimethoxysilyl) propyl methacrylate, and then lauryl methacrylate was graft-polymerized on the surface of the titanium oxide particles. The positively charged phthalocyanine pigment was subjected to surface treatment with 4-vinylaniline, and then 2-ethylhexyl methacrylate was subjected to graft polymerization treatment on the surface of the phthalocyanine pigment. The positively charged titanium oxide particles were subjected to surface treatment with 3- (trimethoxysilyl) propyl methacrylate and then subjected to graft polymerization treatment of 2-ethylhexyl methacrylate on the surface of the titanium oxide particles.

  An electrophoretic liquid was produced using the produced negatively charged titanium oxide particles, positively charged phthalocyanine particles, and positively charged titanium oxide particles. Solsperse 17000 (trade name: manufactured by Avicia) was used as a charge control agent, and sorbitan trioleate was used as a surfactant for controlling dispersion. As a solvent, IsoparG (trade name: manufactured by ExxonMobil, isoparaffinic hydrocarbon) was used, and the solvent was colored red with Sudan Red 7B and Oil Red 5B to obtain a red colored solvent (6). The mixing ratio of the electrophoresis solution is shown in Table 3 below.

  A cell for containing the electrophoresis solution having the configuration shown in FIG. 6 was produced. On the substrate on which the TFT circuit was formed, an electrode having a first driving electrode 1 of 220 × 235 μm and a second driving electrode 2 of 220 × 25 μm was formed of Ag. A cell was produced on this substrate by a photoresist process using SU-8 (trade name: manufactured by Kayaku Microchem). The cell size was prepared such that the opening was 225 × 325 μm, the partition wall thickness was 25 μm, and the height was 70 μm. At this time, the area ratio of the first drive electrode 1 and the second drive electrode 2 is about 4.5: 1.

The prepared electrophoretic solution shown in Table 3 above was poured into the produced cell, and sealed with a PET film on which an ITO film as the third transparent electrode 3 was formed. Sealing was performed by applying an ultraviolet curable adhesive in advance on the surface of the ITO film, covering the cell onto which the electrophoretic solution was poured, and irradiating with ultraviolet rays to perform adhesion.
In the manufactured image display element, the cells were arranged in a lattice pattern, the horizontal pitch between the cells was 350 μm, the vertical pitch was 250 μm, and the size of the display portion was about 1 × 1 cm.

The operation of one cell of the manufactured image display element will be described.
FIG. 12A shows a schematic diagram of cyan display. A voltage of +15 V is applied to the first drive electrode 1 and the second drive electrode 2. The positively charged second dispersible particles 9 and the third dispersible particles 10 move to the third transparent electrode 3 on the display surface side. At this time, the third dispersible particle 10 is white and scatters visible light (400 to 700 nm), and the second dispersible particle 9 absorbs light of 600 to 700 nm.

  FIG. 12B shows a schematic diagram of white display. A voltage of −15 V is applied to the first drive electrode 1 and the second drive electrode 2, and the negatively charged first dispersive particles 8 move to the third transparent electrode 3 on the display surface side, and white Display.

  FIG. 12C shows a schematic diagram of black display. From the cyan display state of FIG. 12A, the first driving electrode 1 is changed from +15 V to 0 V, and the first dispersive particles 8 are moved to the second driving electrode 2. At this time, the second dispersible particles 9 and the third dispersible particles 10 are separated from the third transparent electrode 3. Next, the voltage of the second driving electrode 2 is changed from +15 V to +10 V, the first driving electrode 1 is changed from 0 V to −10 V, and the second dispersible particles 9 and the third dispersible particles 10 are set to the first. To the driving electrode 1. Since the second dispersible particle 9 absorbs light of 600 to 700 nm and the nonpolar solvent colored red absorbs light of 400 to 600 nm, black display is obtained. At this time, since the area of the first drive electrode 1 is larger than the area of the second drive electrode 2, the second dispersive particles 9 and the third disperse particles 9 held by the first drive electrode 1 are used. The optical properties of the dispersible particles 10 determine the color display of the cell.

FIG. 12D shows a schematic diagram of color display of the nonpolar solvent 6 colored red.
From the white display state of FIG. 12B, the first driving electrode 1 is changed from −15 V to 0 V, and the second and third dispersible particles 10 are moved to the second driving electrode 2. At this time, the first dispersible particles 8 are separated from the third transparent electrode 3. Next, the voltage of the second drive electrode 2 is changed from −15 V to −10 V, the first drive electrode 1 is changed from 0 V to +10 V, and the first dispersive particles 8 are moved to the first drive electrode 1. Let Since the first dispersible particles 8 are white and scatter visible light (400 to 700 nm) and the nonpolar solvent 6 colored red absorbs light of 400 to 600 nm, a red display is obtained. At this time, since the area of the first driving electrode 1 is larger than the area of the second driving electrode 2, the optical characteristics of the first dispersive particles held on the first driving electrode 1 are Determine the color display.

  According to Examples 1 to 3 and Comparative Example described above, it was confirmed that the present invention can provide an image display element capable of displaying high quality with little color mixture, and an image display device including the image display element. .

DESCRIPTION OF SYMBOLS 1 1st drive electrode 2 2nd drive electrode 3 3rd transparent electrode 4 Transparent substrate 5 Thin film transistor substrate 6 Nonpolar solvent 7 Partition 8 1st dispersible particle 9 2nd dispersible particle 10 3rd Dispersible particles

JP 2009-9092 A JP 2006-520012 Gazette

Claims (8)

A cell having an open surface and containing an electrophoresis solution;
A first driving electrode and a second driving electrode, the potentials of which can be independently controlled with respect to the electrophoretic solution, and arranged side by side;
A transparent third electrode disposed to face the first driving electrode and the second driving electrode, and
An image display element characterized in that an electric field distribution when the first driving electrode and the second driving electrode are held at different voltages is rotationally symmetric within the opening surface of the cell. . The shape of the opening surface of the cell is rotationally symmetric,
The shape of the first driving electrode is rotationally symmetric with the shape of the opening surface of the cell,
The rotationally symmetric center of the opening surface of the cell coincides with the rotationally symmetric center of the first driving electrode,
The image display element according to claim 1, wherein the second driving electrode is disposed so as to surround the first driving electrode and has a constant width. The shape of the opening surface of the cell is rotationally symmetric,
The shape of the first driving electrode is rotationally symmetric,
The rotationally symmetric center of the opening surface of the cell coincides with the rotationally symmetric center of the first driving electrode,
The image display element according to claim 1, wherein the second driving electrodes are arranged in pairs so as to sandwich the first electrode and have a constant width. The area A ₁ of the first driving electrode, wherein the area A ₂ of the second driving electrodes, one of the claims 1 to 3, characterized in that satisfies the relationship A ₂ ≦ 0.5A ₁ The image display element according to claim 1. The electrophoresis solution encapsulated in the cell comprises three kinds of dispersible particles having different optical characteristics and charging characteristics dispersed in a nonpolar solvent,
The first dispersible particles have no charge,
The second dispersible particles are electrophoretic particles having a positive charge,
The image display element according to claim 1, wherein the third dispersible particles are electrophoretic particles having a negative charge. The electrophoretic solution encapsulated in the cell comprises three types of dispersible particles having different charging characteristics dispersed in a colored transparent nonpolar solvent,
The first dispersible particles are electrophoretic particles having white or positive or negative optical properties,
The second dispersible particles are electrophoretic particles having a black optical property and having a charge opposite to that of the first dispersible particles.
The image display element according to claim 1, wherein the third dispersible particle is a dispersible particle having white optical characteristics and no charge. The electrophoresis solution encapsulated in the cell is composed of three types of dispersible particles having different optical characteristics or charging characteristics in a colored transparent nonpolar solvent,
The first dispersible particles are electrophoretic particles having white or positive or negative optical properties,
The second dispersible particle is an electrophoretic particle having a charge opposite to that of the first dispersible particle, the optical property of which absorbs light in a specific wavelength region in the visible light region,
The third dispersible particles are electrophoretic particles having an optical property of white and the same polarity as the second dispersible particles,
The optical characteristic of the colored transparent nonpolar solvent has a characteristic of transmitting light in a specific wavelength region absorbed by the second dispersible particles and absorbing other light. 5. The image display element according to any one of 4 above.   An image display device comprising the image display element according to claim 1.

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