JP2009244290A - Display panel and image display device with the display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display panel which changeovers a display color due to variation of attitude of at least one kind of charged particles and does not require power for maintaining the attitude, and an image display device with the display panel. <P>SOLUTION: The display panel 2 includes a container part including a substrate 4 on the side of a display surface 4a for image display and a substrate 6 on the rear side and first charged particles 20 stored in the container part, wherein the first charged particles 20 have a such shape that the size of a projection area on the display surface 4a is changed in accordance with their deposition attitude on the substrate 4 on the side of the display surface 4a. The image display device is provided with the display panel 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention includes a display panel provided with a container part composed of a display surface side substrate and a back surface side substrate for displaying an image, and charged particles contained in the container part, and the display panel. The present invention relates to an image display apparatus.

  2. Description of the Related Art In recent years, an electrophoretic display panel comprising a container portion composed of a display surface side substrate and a back surface side substrate for displaying an image, and charged particles accommodated in the container portion, and the display panel The provided image display apparatus is widely used in various fields including the electronic paper field. Such a display panel requires power only at the time of rewriting the display, and has a memory effect that the display state can be maintained without supplying power after the rewriting.

In such an electrophoretic display panel, electrophoresis is performed using electrophoretic display particles in which liquid crystal is accommodated in microcapsules, two kinds of dichroic dyes are dissolved in the liquid crystal, and fine particles are dispersed. A formula display panel has been proposed (see, for example, Patent Document 1). In the display panel described in Patent Document 1, it is described that the color to be displayed is switched by a change in the posture of one type of display element.
JP 2002-277906 A

  However, in order to maintain the display element in one posture, it is necessary to continuously apply an AC voltage or a DC voltage to the display element. In this case, the display state is maintained without supplying power. The memory effect that can be done is not demonstrated.

  Accordingly, an object of the present invention is to solve the above-described problem, and to switch the color to be displayed by changing the posture of at least one kind of charged particles, and further, a display panel that does not require power to maintain the posture, Another object of the present invention is to provide an image display device including the display panel.

  In order to solve the above-described problem, an embodiment of a display panel according to claim 1 of the present invention includes a container portion configured by a display surface side substrate and a back side substrate for displaying an image, and the container portion. First charged particles contained therein, and the first charged particles have a shape in which the size of the projected area on the display surface changes according to the posture of adhering to the substrate on the display surface side. Features.

  According to this embodiment, the posture of the first charged particles attached to the substrate on the display surface side is easily changed by changing the electric field strength or the direction of the electric field inside the container portion in which the first charged particles are accommodated. Thus, the displayed color can be easily switched. Furthermore, the posture can be maintained, that is, the display can be maintained without requiring electric power by electrostatic force or the like.

  An embodiment of the display panel according to claim 2 of the present invention is characterized in that the first charged particles have a plane-symmetric shape.

  According to this embodiment, since the first charged particles have a plane-symmetric shape, for example, when the symmetry plane is tilted from the state perpendicular to the display plane so that the symmetry plane is horizontal with respect to the display plane. In addition, when the first charged particles are tilted to the left or right side with respect to the symmetry plane, the projected area changes in the same manner. Conversely, when the symmetry plane returns from a horizontal state to a vertical state with respect to the display surface. However, the projected area changes in the same way on the left and right. Therefore, display rewriting with reproducibility can be realized by the same voltage control pattern.

  An embodiment of the display panel according to claim 3 of the present invention is characterized in that the first charged particles have an oval cross section.

  According to this embodiment, since the cross section has an oval shape, the posture can be smoothly changed.

  An embodiment of the display panel according to claim 4 of the present invention is characterized in that the first charged particles have a circular cross section orthogonal to the oval cross section.

  According to the present embodiment, as described above, the posture can be changed smoothly, and the first charged particles have a circular cross section. When displaying with the color of the first charged particles, the gap between the particles can be reduced, and a clear display with excellent shielding properties can be realized.

  In a display panel according to a fifth aspect of the present invention, the first charged particles have a first posture in which the projected area on the display surface is the largest, and a first posture in which the projected area on the display surface is the smallest. It is housed in the container part so as to be able to take two postures.

  According to this embodiment, the first charged particles can take the first posture in which the projected area on the display surface is the largest and the second posture in which the first charged particles are the smallest. Since the color can be clearly changed, high contrast can be obtained.

  An embodiment of the display panel according to claim 6 of the present invention is characterized in that the charged particles are accommodated in the container portion in an amount that covers the entire surface of the display surface with one layer of particles in the first posture. And

  According to this embodiment, since the first charged particles in the first posture can cover the entire display surface, it is possible to display clearly with excellent shielding properties. Further, since the display surface is provided in an amount that covers the entire surface with one layer of particles, a display panel with high contrast can be provided.

  An embodiment of the display panel according to claim 7 of the present invention is characterized in that child particles are externally added to the first charged particles.

  According to this embodiment, since the adhesive force between the first charged particles and the display surface or the like is reduced, the posture of the first charged particles can be changed with a low applied voltage in display rewriting.

In an embodiment of the display panel according to claim 8 of the present invention, spherical second charged particles having a polarity opposite to that of the first charged particles are accommodated in the container portion, and the first charged particles and the second charged particles are Is accommodated in the container part so that it can be selectively adhered to the substrate on the display surface side by moving in the container part.

  According to this embodiment, in addition to the change in the posture of the first charged particles with respect to the display surface, various color displays can be performed by selectively attaching the first charged particles or the second charged particles to a position close to the display surface. And change in gradation can be realized. Note that when the first charged particles and the second charged particles are of similar colors, a change in gradation can be realized. Further, when the colors are not similar, a change in the color of the first charged particle, the color of the second charged particle, and the mixed color of the color of the first charged particle and the color of the second charged particle is realized. be able to.

  An embodiment of the display panel according to claim 9 of the present invention is characterized in that child particles are externally added to the second charged particles.

  According to this embodiment, even if it is necessary to increase the distance between the display surface and the back surface because the first charged particles are not spherical, the child particles are externally added to the second charged particles. By doing so, the adhesive force between the second charged particles and the display surface or the like can be reduced, the applied voltage in the display rewriting can be reduced, and the power consumption can be reduced.

  In an embodiment of the display panel according to claim 10 of the present invention, the first charged particles have a first posture in which the projected area on the display surface is the largest, and a first posture in which the projected area on the display surface is the smallest. It is accommodated in the container so that it can take two postures, and the projected area of the second charged particles on the display surface is larger than the projected area of the first charged particles in the second posture. It is characterized by.

  According to this embodiment, since the projected area of the second charged particles on the display surface is larger than the projected area of the first charged particles in the second posture on the display surface, the first charged particles are in the second posture. In the case of adhering to the display surface side, the second charged particles are less likely to enter the gaps between adjacent particles, and a clear display can be expected.

  An embodiment of the display panel according to claim 11 of the present invention is characterized in that the first charged particles are white and the second charged particles are black.

  According to this embodiment, three colors of white, black, and gray of mixed colors of white and black can be displayed.

  According to a twelfth aspect of the present invention, there is provided an image display apparatus according to any one of the first to eleventh aspects, an electrode for generating an electric field in the container portion, and the display surface. And a control unit for controlling the strength of the electric field generated by the electrode in order to change the size of the projected area of the first charged particles.

  According to this embodiment, the attitude of the first charged particles attached to the substrate on the display surface side can be easily changed by changing the electric field strength and the direction of the electric field inside the container portion. The color to be performed can be easily switched. Furthermore, the posture can be maintained, that is, the display can be maintained without requiring electric power by electrostatic force or the like.

  According to a thirteenth aspect of the present invention, there is provided an image display device according to any one of the eighth to eleventh aspects, an electrode for generating an electric field in the container portion, and the display surface. Controlling the intensity of the electric field generated by the electrode to change the size of the projected area of the first charged particles, and from the display state in which the first charged particles are arranged on the display surface side, A control unit that reverses the direction of the electric field generated by the electrode in order to change the display state in which the second charged particles are arranged on the display surface side.

    According to this embodiment, the first charged particles or the second charged particles are selectively attached to a position close to the display surface in addition to the change in the posture of the first charged particles with respect to the display surface by voltage control by the control unit. As a result, various color displays and gradation changes can be realized. Similarly to the above, when the first charged particles and the second charged particles have similar colors, a change in gradation can be realized. Further, when the colors are not similar, a change in the color of the first charged particle, the color of the second charged particle, and the mixed color of the color of the first charged particle and the color of the second charged particle is realized. be able to.

  In an embodiment of the image display device according to a fourteenth aspect of the present invention, the control unit has a first posture in which the projected area on the display surface is the largest and a second posture in which the projected area on the display surface is the smallest. The strength of the electric field generated by the electrode is controlled so as to change the posture of the first charged particles between the postures.

  According to this embodiment, by controlling the electric field by the control unit, the posture of the first charged particle is changed between the first posture in which the projected area on the display surface is the largest and the second posture in which the projected area is the smallest. be able to. As a result, the displayed color can be clearly changed, so that high contrast can be obtained.

As described above, in the display panel and the display device according to the present invention, by changing the electric field strength and the direction of the electric field inside the container portion in which the first charged particles are accommodated, the display surface side of the first charged particles is changed. The posture of adhering to the substrate can be easily changed, whereby the color to be displayed can be easily switched. Furthermore, the posture can be maintained, that is, the display can be maintained without the need for electric power by electrostatic force or the like.

Embodiments of a display panel according to the present invention and an image display apparatus including the display panel will be described in detail below with reference to the drawings.
(Description of One Embodiment of Display Panel According to the Present Invention)
First, the outline of the structure of one embodiment of the display panel according to the present invention will be described with reference to FIGS.

Here, FIG. 1 is a plan view of the display panel 2 according to the present invention as viewed from the display surface side, and a part of the substrate 4 on the display surface side of the display panel 2 is cut away so that the inside is exposed. It is shown. As is apparent from the cutout portion of FIG. 1, in the display panel 2, the display area surrounded by the outer frame 14 is divided into a plurality of sections 40 by partition walls 8 formed in a lattice shape. In the present embodiment, the grid-like partition walls 8 are continuously formed. However, the present invention is not limited to this, and a structure in which a part of the partition walls 8 is discontinuous and there is a gap between the partition walls 8. Is also possible.
FIG. 2 is a side cross-sectional view as seen from the arrow AA in FIG. 1 and schematically shows the internal structure of the display panel 2. In FIG. 2, the upper surface is the display surface and the lower surface is the back surface.

As shown in FIG. 2, the display panel 2 includes a display surface side substrate (display substrate) 4 provided with a common electrode 10 that is an electrode on the display surface side, and a back surface provided with pixel electrodes 12 that are electrodes on the back side. It is mainly comprised from the container part which has the board | substrate (back substrate) 6 of the side, and the display medium 24 accommodated in this container part and containing the charged particles 20 and 22 in a solvent. Further, as described above, the internal space of the container portion between the display substrate 4 and the back substrate 6 is divided by the partition wall 8 for each pixel, and the pixel electrode 12 is formed for each partition 40 partitioned by the partition wall 8. Is provided. However, the present invention is not limited to this, and the display panel of the present invention includes, for example, a display panel in which the partition area 8 is not provided and the display area is not divided, and a plurality of partitions are provided for each of the plurality of pixels. A display panel having a partition 40 including a plurality of pixels is also included, and a display panel including a plurality of partition walls 8 in one pixel and including pixels including the plurality of partition walls 8 is also included.
In this embodiment, the common electrode 10 and the pixel electrode 12 are provided outside the substrates 4 and 6. However, the present invention is not limited to this. For example, the common electrode 10 and the pixel electrode 12 are provided on the substrate 4. , 6 may be provided inside.

The internal space of the container part between the display substrate 4 and the back substrate 6 contained negatively charged white first charged particles 20 and positively charged black second charged particles 22 in a solvent. A display medium 24 is enclosed.
Regarding the shape of these charged particles 20 and 22, the black second charged particles 22 have a substantially spherical shape. Moreover, the white first charged particles 20 have a shape in which the size of the projected area on the display surface (inner surface) 4a changes according to the posture facing the display surface (inner surface) 4a. To describe this shape in more detail, the charged particle 20 has an oval cross section as shown in FIG. 2, and a cross section orthogonal to the oval cross section is circular. Therefore, the first charged particles 20 have a shape that is plane-symmetric with respect to the maximum surface of the circular cross section (the cross section including the major axis of the ellipse shown in FIG. 2). In the following description, the shape of the first charged particles 20 is simplified and referred to as “disk shape”.

The shape of the 1st charged particle 20 is not restricted to the disk shape shown in FIG. 2, For example, it can also have a shape close | similar to a flat disk. However, in consideration of interference during the movement of the charged particles, a shape constituted by a curved surface is preferable to a shape having a corner such as a rectangle.
As described above, the first charged particles 20 can be realized by a relatively simple shape and structure, and it can be expected that the first charged particles 20 are manufactured at a relatively low manufacturing cost.

In the present embodiment, the disk-shaped first charged particles 20 are colored white and the spherical second charged particles 22 are colored black for the following reasons.
In the case of spherical charged particles, the reversal and change of the moving direction is easier when the specific gravity is smaller at the time of rewriting, but in the case of white particles, the specific gravity is compared due to the influence of the additive substance to make it white. Tend to be larger. Therefore, it is preferable that the black particles having a relatively small specific gravity be the spherical second charged particles 22. In addition, when the disc-shaped first charged particles 20 are white, the specific gravity may be increased, but even in that case, the first charged particles 20 have the least flow resistance and the minimum projected area. Since the surface to be moved moves in a posture that is perpendicular to the moving direction, the direction of movement can be reversed and changed relatively easily.

However, the present invention is not limited to this, and the coloring of the charged particles 20 and 22 may be reversed black and white. The charged particles 20 and 22 can be colored not only in black and white but also in any other color for color display. In addition to the charged particles 20 and 22, the colors of the display medium and the back substrate can be used. Display using can also be performed.
Further, the positive and negative signs may be reversed with respect to the charges charged to the first charged particles 20 and the second charged particles 22.

  As the “display surface”, a display surface (inner surface) 4a on the inner side of the display substrate 4 shown in FIG. 2 and a display surface (outer surface) 4b on the outer side of the display substrate 4 can be considered, but both surfaces are parallel to each other. When “the first charged particles have a shape whose projected area changes with respect to the display surface”, both the display surface (inner surface) 4a and the display surface (outer surface) 4b Corresponds to the display surface. In the following description, the display surface (inner side) 4a is used as a representative display surface.

Next, the charged particles 20 and 22 constituting the display medium 24 and the material of the solvent will be described. In the present embodiment, methacrylic resin (PMMA) is used as the material for the charged particles 20 and 22, but is not limited thereto, and other materials such as fluorinated acrylic resin, polycarbonate (PC), and high-density polyethylene. (HDPE), polypropylene (PP), acrylonitrile butadiene styrene (ABS), polyethylene terephthalate (PET), polyacetal (POM), polystyrene (PS), and the like can be used.
In the present embodiment, the white first charged particles 20 are formed by externally adding silicon oxide (silica) to the surface of the disk-shaped charged particles. However, the present invention is not limited to this. In addition, titanium oxide, alumina, etc. can be externally added. As for the black charged particles 22, black particles can be formed by attaching carbon (carbon black) to a resin material constituting the particles.
Moreover, as a solvent, solvents, such as hydrocarbon and silicone oil which have high insulation, can be used suitably. The present invention is not limited to this, and air, an inert gas such as nitrogen, or the like is appropriately stored as a medium for dispersing the charged particles 20 and 22 in the container instead of the solvent. You may apply to the display panel using. Or you may apply to the display panel which decompressed the inside of a container part to a vacuum state, and accommodated the charged particles 20 and 22 in the container part.

In the display panel 2 configured as described above, by applying a predetermined voltage between the common electrode 10 and the pixel electrode 12 to form an electric field, the disc-shaped white charged particles 20 are displayed on the display surface 4a. The spherical black charged particles 22 can be switched by moving the particles by changing the projected area with respect to or moving the particles. The display switching method will be described in detail below.
As the dimensions of the display panel 2 of the present embodiment, for example, the width of the partition 40, that is, the distance between the adjacent partition walls 8 is 250 μm, and the inter-substrate distance between the display substrate 4 and the back substrate 6 is 40 μm. However, the present invention is not limited to this, and any other dimensions can be adopted.

If the outline of the material of the display panel 2 of this embodiment is described, the display substrate 4 is formed of a material having high transparency and high insulation properties, such as polyethylene naphthalate, polyethersulfone, polyimide, polyethylene terephthalate, etc. These resin materials, glass materials, and the like can be used. The common electrode 10 is made of a material that has high transparency and can be used as an electrode. For example, ITO (Indium Tin Oxide) can be used.
Further, the back substrate 6 is formed of a material having high insulating properties, and for example, an inorganic material such as glass or an insulating metal film, or a resin material such as polyethylene terephthalate can be used. Note that, unlike the display substrate 4, the back substrate 6 may be transparent or opaque. The outer frame 14 can also be made of the same material as the back substrate 6. The pixel electrode 12 is formed of a material having high electrical conductivity such as a copper material.

(Description of One Embodiment of Display Switching Method of Display Panel According to the Present Invention)
Next, with reference to FIG. 3, one embodiment of the display switching method of the display panel 2 according to the present invention will be described. Here, FIG. 3 is a side sectional view schematically showing the display panel 2 in the same manner as FIG. 3 and the subsequent drawings, the illustration of the partition wall 8 is omitted.
In FIG. 3, a predetermined voltage is applied between the electrodes 10, 12, starting from the display state 1 displaying white, going through the display state 2 displaying gray, and finally displaying the black Each step of the display rewriting up to 3 is shown.

<Description of display state 1>
First, the display state 1 for displaying white will be described with reference to FIG. In the display state 1, the disk-shaped white first charged particles 20 are located on the display surface side, and the spherical black second charged particles 22 are located on the back side. Further, the disk-shaped white charged particles 20 are positioned on the display surface side in a first posture that maximizes the projected area with respect to the display surface 4a. As a result, when viewed from the display surface (outer surface) side as indicated by an arrow B, the first charged particles 20 that are almost closely packed can be visually recognized, and white is displayed on the entire display surface.
In the present embodiment, since the first charged particles 20 have a circular cross-sectional shape, the first charged particles 20 can be arranged in a close-packed manner with respect to the display surface 4a. Display can be realized.

In order to form the display state 1, the first display particles 20 that are negatively charged are applied to the display substrate 4 side by applying a predetermined voltage so that the common electrode 10 is a positive electrode and the pixel electrode 12 is a negative electrode. The first posture that moves and finally becomes the most stable with the formed electric field and has the maximum projected area with respect to the display surface 4a. Further, the positively charged second charged particles 22 move to the back side.
When the voltage application between the electrodes 10 and 12 is stopped in this state, the positions and postures of the first charged particles 20 and the second charged particles 22 are maintained by electrostatic force or the like, and the display state 1 for displaying white is maintained. The

<Description of display state 2>
Next, from this display state 1, a voltage equal to or higher than the lowest voltage value (threshold value) capable of rotating the disk-shaped first charged particles 20 is applied so that the common electrode 10 is a negative electrode and the pixel electrode 12 is a positive electrode. . An example of the voltage value to be applied is 20V as shown in # 1 of Table 1 below. By this voltage application, the white first charged particles 20 are rotated by about 90 degrees while maintaining the state of being positioned on the display surface side, and projected onto the display surface 4a as shown in FIG. The orientation is changed to the second posture that minimizes the area. At this time, the black second charged particles 22 located on the back side maintain the position in the vicinity of the back side.

In the display state 2, since the projected area of the white first charged particles 20 onto the display surface 4a is minimized, as viewed from the display surface (outer surface) side as indicated by an arrow B, the white first charged particles 20 are caused by the individual first charged particles 20. There is a larger gap between the white areas than in the display state 1, and the black second charged particles 22 located on the back side can be visually recognized from the gap. Therefore, in the display state 2, gray is displayed on the entire display surface. That is, by changing the electric field formed between the common electrode 10 and the pixel electrode 12, the posture of the first charged particles 20 attached to the display surface 4a can be easily changed. Can be switched easily.
Further, when the voltage application between the electrodes 10 and 12 is stopped in this state, the positions and postures of the first charged particles 20 and the second charged particles 22 are maintained by electrostatic force or the like, and the display state 2 displaying gray is displayed. Maintained. That is, the posture of the first charged particles 20, that is, the display can be maintained without requiring electric power due to electrostatic force or the like.

Here, the gray density to be displayed is determined according to the ratio between the maximum projected area and the minimum projected area of the white first charged particles 20 on the display surface 4a (in addition, the first charged particles 20). It can also be indicated by the ratio of the major axis to the minor axis of the oval cross section). When the ratio between the maximum projected area and the minimum projected area is large, the gap between the first charged particles 20 becomes larger in the display state 2, so that the black second charged particles 22 on the back side The area can be seen larger and darker (close to black) gray is displayed.
In any case, the first charged particles 20 can take a first posture where the projected area on the display surface 4a is the largest and a second posture where the first projected particle 20 is the smallest. Since the color can be clearly changed, high contrast can be obtained.

<Description of particle movement state>
Next, from the display state 2 where the first charged particles 20 are in the second posture, the lowest voltage at which the first charged particles 20 in the second posture can move so that the common electrode 10 is the negative electrode and the pixel electrode 12 is the positive electrode. A voltage higher than the value (threshold) is applied. An example of the voltage value to be applied is 100 V as shown in # 2 of Table 1 below.
By applying this voltage, as shown in FIG. 3C, the white first charged particles 20 are maintained from the display substrate 4 side to the back surface while maintaining the second posture in which the projected area is minimized with respect to the display surface 4a. It moves to the substrate 6 side in a direction substantially perpendicular to the substrates 4 and 6. That is, the 1st charged particle 20 moves in the state where the cross-sectional area of the surface orthogonal to the moving direction that minimizes the flow resistance is minimized.
Further, the black charged particles 22 move from the back substrate 6 side to the display substrate 4 side in a direction substantially perpendicular to the substrates 4 and 6. A state in which these charged particles 20 and 22 are moving is indicated by an arrow in FIG.

<Description of display state 3>
While the above particle movement state is continued, as shown in FIG. 3D, the display state 3 in which the black second charged particles 22 reach the display side and the white first charged particles 20 reach the back side. To. When this state is viewed from the display surface (outer surface) side as shown by an arrow B, the second charged particles 22 that are almost closely packed can be visually recognized, and black is displayed on the entire display surface.
When the voltage application between the electrodes 10 and 12 is stopped in this state, the positions and postures of the first charged particles 20 and the second charged particles 22 are maintained by electrostatic force or the like, and the display state 3 for displaying black is maintained. The

<Description of applied voltage between electrodes>
Next, the voltage value applied between the common electrode 10 and the pixel electrode 12 in display rewriting will be described with reference to Table 1 below. The values shown in Table 1 are values based on test data when display rewriting is actually performed using the display panel 2 shown in FIG.
First, when the display rewriting is performed from the display state 1 displaying white to the display state 2 displaying gray, the projection area is maximized with respect to the display surface 4a as described above. By applying a voltage of 20 V between the electrodes 10 and 12 to the charged particles 20 in the first posture (see # 1 in Table 1), the first charged particles 20 are rotated and shifted to the second posture. Can do. In this case, the black second charged particles 22 maintain the position in the vicinity of the back surface.
Thereby, display rewriting can be performed from white to gray. However, at this voltage value, the first charged particles 20 can be rotated, but cannot be moved away from the display surface side.

Next, a voltage of 100 V is applied between the electrodes 10 and 12 with respect to the first charged particles 20 positioned in the display surface side and in the second posture in which the projected area is minimized with respect to the display surface 4a ( The white first charged particles 20 on the display surface side can be moved to the back side, and the black second charged particles 22 on the back side can be moved to the display surface side. Thereby, display rewriting can be performed from gray to black.
Further, as shown in # 3 of Table 1, between the electrodes 10 and 12 with respect to the first charged particles 20 in the first posture which is located on the display surface side and has the maximum projected area with respect to the display surface 4a. By applying a voltage of 120V to the first charged particle 20, the first charged particle 20 can be rotated to shift to the second posture, and the white first charged particle 20 on the display surface side can be moved to the back surface side. In this case, at the same time, the black second charged particles 22 located on the back side can be moved to the display surface side. Thereby, display rewriting can be performed from white to black.

In addition, by applying a voltage having the opposite polarity to the above to the electrodes 10 and 12, the display is rewritten from the display state 3 displaying black to the display state 2 displaying white through the display state 2 displaying gray. It can be performed. In this case, the positive and negative directions are reversed, but the applied voltage value is the same value.
In the present embodiment, the first charged particle 20 has an oval cross section even when the first charged particle 20 is rotated from the first position to the second position or when the first charged particle 20 is rotated from the second position to the first position. Since it has a shape, the posture can be changed smoothly. Thereby, the power consumption for posture change can also be suppressed.

<Description for color display>
The display rewriting method according to the present invention is not limited to the gradation change in the black and white display as described above, and can be similarly applied to the color display. For example, when the disk-shaped first charged particles are colored yellow and the spherical second charged particles are colored cyan, the following display can be realized.

First, the disk-shaped yellow first charged particles 20 are positioned on the display surface side in the first posture where the projected area is the maximum with respect to the display surface 4a, and spherical cyan second charged particles 22 are formed. In the display state 1 located on the back side, the entire display surface can be displayed in yellow.
Next, the disk-shaped yellow first charged particles 20 are positioned on the display surface side in a second posture in which the projected area is minimized with respect to the display surface 4a, and spherical cyan second charged particles 22 are formed. In the display state 2 located near the back surface, the entire display surface can be displayed in green.
Further, in the display state 3 in which the spherical cyan second charged particles 22 are positioned on the display surface side and the disk-shaped yellow first charged particles 20 are positioned on the back surface side, the entire display surface can be displayed in cyan. .
Even when charged particles of other colors are used, the same display rewriting can be performed.

As described above, in the present embodiment, the first charged particles 20 have a shape in which the size of the projected area on the display surface changes according to the posture facing the display surface 4a. By combining with the second charged particles 22, various color displays and gradation changes can be realized without using charged particles having a complicated structure and without performing complicated control processing.
That is, in addition to the change in the posture of the first charged particle 20 with respect to the display surface 4a, various color displays can be achieved by selectively attaching the first charged particle 20 or the second charged particle 22 to a position close to the display surface 4a. And change in gradation can be realized. If the first charged particle 20 and the second charged particle 22 are similar colors, a change in gradation can be realized. If they are not similar colors, the color of the first charged particles 20 and the second charged particles It is possible to realize a change in the three colors of 22 colors and a mixed color of the colors of the first charged particles 20 and the second charged particles 22.

(Explanation regarding symmetrical shape of first charged particles)
Next, the influence of display rewriting when the first charged particles 20 have a symmetric shape and when the first charged particle 20 does not have a symmetric shape will be described with reference to FIG. Here, FIG. 4A on the upper side shows a case where the first charged particles 20 have a symmetrical shape, and FIG. 4B on the lower side shows that the first charged particles 20 do not have a symmetrical shape. Show the case.
The first charged particles 20 having the symmetrical shape shown in FIG. 4A have an oval cross section and a circular cross section orthogonal to the oval cross section, as in the embodiment shown in FIGS. It has a disk-like shape, and has a shape that is plane-symmetric with respect to the maximum surface of the circular cross section (the cross section including the major axis of the oval) as shown by the dotted line in the center figure. In the first charged particles 20 having this symmetrical shape, when the first charged particles 20 are rotated from the second posture in which the projected area to the display surface 4a shown in the center is the smallest to the first posture in which the projected area is maximized, There are cases where it rotates clockwise as shown in the left figure and there is a case where it rotates counterclockwise as shown in the right figure.

  In this case, since the shape of the curved surface 20a facing the display surface 4a is the same in both the clockwise and counterclockwise directions, the first charged particles 20 are tilted from the second posture to the first posture. In the case of returning from the first posture to the second posture, the applied voltage is the same on the left and right. Therefore, display rewriting can be performed from display state 1 to display state 2 or from display state 2 to display state 1 by always performing constant voltage control. That is, display rewriting with reproducibility can be realized by the same voltage control pattern.

  On the other hand, the first charged particles 20 having no symmetrical shape shown in FIG. 4B are obtained by dividing the first charged particles 20 having the symmetrical shape shown in FIG. have. In the first charged particle 20 having no symmetrical shape, when the particle is rotated from the second posture where the projected area to the display surface 4a shown at the center is the smallest to the first posture where the projected area is the largest, There are cases where it rotates clockwise as shown in the figure and there is a case where it rotates counterclockwise as shown in the right figure.

Here, when it is rotated clockwise as shown in the left figure, the curved surface 20a faces the display surface 4a. On the other hand, when rotated counterclockwise, the flat surface 4b faces or is in contact with the display surface 4a.
Therefore, for example, taking the case where the first charged particles 20 are returned from the second posture to the first posture as an example, than when the left curved surface 20a is returned from the second posture facing the display surface 4a to the first posture. A larger voltage is required when the right plane 20b is returned from the second position in which the right plane 20b faces the display surface 4a to the first position. Therefore, when the display rewriting is performed from the display state 1 to the display state 2, the voltage necessary for the rewriting is not constant, and the voltage control becomes difficult because of the display rewriting.
Therefore, in order to realize reproducible voltage control for display rewriting, it can be said that the first charged particles 20 preferably have a symmetrical shape.

(Explanation regarding preferred content of first charged particles)
Next, the preferable content of the first charged particles 20 contained in the solvent of the display medium 24 will be described with reference to FIG. FIG. 5A is a side cross-sectional view schematically showing the display panel 2 according to the present invention, and FIG. 5B is viewed from the arrow CC in FIG. It is a part of a plan view of the display surface 4a).

  In FIG. 5, the display surface 4 a covers the entire surface of the display surface 4 a in a state where the first charged particles 20 of one layer are most closely focused in the first posture. As a result, the entire display surface 4a can be indicated by the color of the first charged particles 20, and a clear display excellent in shielding properties (that is, having a small gap) is enabled. Further, since the first charged particles 20 are provided in such an amount that the entire surface of the display surface 4a is covered with one layer of particles, the first charged particles 20 interfere with each other due to the presence of the first charged particles 20 in excess. The problem that the first charged particles 20 are mixed into the second charged particles 22 can be prevented in the case where the second charged particles 22 are displayed. Thereby, the display panel 2 with high contrast can be provided.

(Description of charged particles to which child particles are externally added>
Next, the first charged particles 20 to which the child particles are added and the second charged particles 22 to which the child particles are added will be described with reference to FIG. FIG. 6A shows a case where oxide inorganic fine particles such as silicon oxide (silica) are externally added as white child particles 30 to the surface of the disk-shaped white first charged particles 20. As a result, even if the first charged particles are not spherical, even if it is necessary to increase the distance between the display surface and the back surface, the child particles externally added to the surface of the first charged particles 20 By 30, the adhesive force between the first charged particles and the display substrate or the back substrate can be reduced, the applied voltage in the display rewriting can be reduced, and the power consumption can be reduced.
In particular, when display switching is performed from the first posture where the projected area on the display surface is the largest, a large applied voltage is required, so as shown in FIG. 6A, the display surface is opposed to the display surface. It is considered that it is effective to externally add the child particles 30 to the surface.

  FIG. 6B shows a state where oxide inorganic fine particles such as silicon oxide (silica) are externally added as the child particles 32 to the entire surface of the spherical and black second charged particles 22. Accordingly, even if the first charged particles are not spherical and the distance between the display surface and the back surface needs to be increased, the child particles externally added to the surface of the second charged particles 22 By 32, the adhesive force between the 2nd charged particle 22 and a display board | substrate or a back substrate can be reduced, the applied voltage in display rewriting can be reduced, and power consumption can be reduced by extension.

(Explanation regarding preferred size of second charged particles)
Next, a preferred size of the second charged particles with respect to the first charged particles will be described with reference to FIG. FIG. 7 shows a projected figure 120 on the display surface 4a of the first charged particles 20 in the second posture (in which the projected area is minimized). The projected figure 120 has an oval shape. Similarly, a projected figure 122 of the spherical second charged particle 22 on the display surface 4a is shown. The projected figure 122 has a circular shape.
Here, each charged particle 20, 22 is formed such that the area of the projected figure 122 of the second charged particle 22 is larger than the area of the projected figure 120 of the first charged particle 20.

In this case, in the second posture in which the projected area is minimum, the gap between the first charged particles 20 is larger than that in the first posture in which the projected area is maximum. The possibility of becoming larger than the projected figure 120 of the first charged particle 20 in the posture is low. Therefore, when the projected figure 122 is larger than the projected figure 120 of the first charged particle 20, the second charged particle 22 is less likely to pass through the gap between the first charged particles 20 and reach the display surface 4a. .
By determining the size of the second charged particles 22 in this way, for example, in the display state 2 in which the white first charged particles 20 display gray that is positioned on the display surface 4a in the second posture, It is possible to prevent the particles from being mixed on the display surface side and causing unevenness in display or change in gray density, thereby realizing a clear display.

(Description of the display panel device according to the present invention)
A display device that includes the embodiment of the display panel 2 according to the present invention as described above and a control unit that controls an applied voltage between the electrodes 10 and 12 and displays an image on the display panel 2 is also included in the present invention.
Here, the control unit changes the size of the projected area of the first charged particles 20 on the display surface, and selectively arranges the first charged particles 20 or the second charged particles 22 on the display surface side. In addition, the strength of the electric field generated by the electrodes 10 and 12 (applied voltage between the electrodes) can be controlled.

(Description of Other Embodiments of Display Panel and Display Device According to the Present Invention)
Embodiments of the display panel according to the present invention and the display device including the display panel are not limited to the above-described embodiments, and various other embodiments are included in the present invention.

It is the top view which looked at the display panel which concerns on this invention from the display surface side. It is side surface sectional drawing seen from arrow AA of FIG. 1, Comprising: It is the figure which showed typically the internal structure of the display panel. In the display panel which concerns on this invention, it is side surface sectional drawing which shows typically each process in the case of performing display switching. It is the schematic diagram which compared and showed the display rewriting in the 1st charged particle which has a symmetrical shape, and the 1st charged particle which does not have a symmetrical shape. It is side surface sectional drawing and a top view which show preferable content of the 1st charged particle in a display medium. It is a figure which shows typically the 1st charged particle and the 2nd charged particle to which the child particle was externally added. It is the top view which showed the projection figure on the display surface of the 1st charged particle of a 2nd attitude | position, and the projection figure on the display surface of a 2nd charged particle.

Explanation of symbols

2 Display panel 4 Display side substrate (display substrate)
4a Display surface (inner surface)
4b Display surface (outer surface)
6 Back side board (Back side board)
8 Partition 10 Common electrode 12 Pixel electrode 14 Outer frame 20 First charged particle 22 Second charged particle 30 Child particle 32 externally added to the first charged particle Child particle 40 externally added to the second charged particle 40, 120, 122 Projected figure

Claims (14)

A container portion composed of a display-side substrate and a back-side substrate for displaying an image;
First charged particles contained in the container portion;
With
The display panel according to claim 1, wherein the first charged particles have a shape in which a size of a projected area on the display surface changes according to a posture of attaching to the substrate on the display surface side.   The display panel according to claim 1, wherein the first charged particles have a plane-symmetric shape.   The display panel according to claim 1, wherein the first charged particles have an oval cross section.   The display panel according to claim 3, wherein the first charged particles have a circular cross section orthogonal to the oval cross section.   The first charged particles are accommodated in the container so as to be able to take a first posture in which the projected area on the display surface is the largest and a second posture in which the projected area on the display surface is the smallest. The display panel according to any one of claims 1 to 4, wherein the display panel is provided.   6. The display panel according to claim 5, wherein the charged particles are contained in the container portion in an amount that covers the entire surface of the display surface with one layer of particles in the first posture.   The display panel according to claim 1, wherein child particles are externally added to the first charged particles. Spherical second charged particles having a polarity opposite to that of the first charged particles are accommodated in the container part,
The first charged particles and the second charged particles are accommodated in the container portion so that the first charged particles and the second charged particles can be selectively adhered to the substrate on the display surface side by moving in the container portion. The display panel according to any one of claims 1 to 7.   The display panel according to claim 8, wherein child particles are externally added to the second charged particles. The first charged particles are accommodated in the container so as to be able to take a first posture in which the projected area on the display surface is the largest and a second posture in which the projected area on the display surface is the smallest. The display panel according to claim 8 or 9, wherein a projected area of the second charged particles on the display surface is larger than a projected area of the first charged particles in the second posture.   The display panel according to claim 8, wherein the first charged particles are white and the second charged particles are black. A display panel according to any one of claims 1 to 11,
An electrode for generating an electric field in the container part;
A control unit for controlling the intensity of an electric field generated by the electrode in order to change the size of the projected area of the first charged particles on the display surface;
An image display device comprising: A display panel according to any one of claims 8 to 11,
An electrode for generating an electric field in the container part;
The strength of the electric field generated by the electrode is controlled to change the size of the projected area of the first charged particles on the display surface, and the first charged particles are attached to the display surface side. A control unit for reversing the direction of the electric field generated by the electrode in order to change from a display state to a display state in which the second charged particles adhere to the display surface side;
An image display device comprising:   The control unit changes the posture of the first charged particles between a first posture in which the projected area on the display surface is the largest and a second posture in which the projected area on the display surface is the smallest. The image display apparatus according to claim 12, wherein the intensity of the electric field generated by the electrode is controlled as described above.

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