JP3842567B2 - Electrophoretic display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophoretic display device using a dispersion liquid containing an insulating liquid and a plurality of electrophoretic particles.
[0002]
[Prior art]
Expectations for reflective display devices are increasing from the standpoint of reducing power consumption and reducing the burden on the eyes. Until now, an electrophoretic display device as described in, for example, US Pat. No. 3,668,106 has been known as one of reflection type display devices.
[0003]
This electrophoretic display device is composed of a dispersion liquid having charged electrophoretic particles and an insulating liquid, and a pair of electrodes facing each other with the dispersion liquid interposed therebetween, and an electric field is applied to the dispersion liquid through the electrodes. Thus, display is performed by moving the electrophoretic particles onto an electrode having a polarity opposite to the charge. The contrasting color of the electrophoretic particles is borne by the insulating liquid in which the dye is dissolved.
[0004]
More specifically, if the electrophoretic particles adhere to the surface of the electrode close to the observation surface, the electrophoretic display device displays the color of the electrophoretic particles, while the electrophoretic particles are on the surface of the second electrode far from the observation surface. If it adheres, the color carried by the electrophoretic particles is concealed by the insulating liquid, and the electrophoretic display device displays the color of the insulating liquid.
[0005]
For example, Proc. As described in SID 18, 267 (1977), although it has the advantages of wide viewing angle, high contrast, and low power consumption, there is no threshold characteristic between applied voltage and display color characteristic, so it is simple. There was a problem that matrix drive was not possible.
[0006]
For this reason, each pixel electrode must be provided with a switching element. However, a necessary applied voltage is high, and the thin film transistor technology used in a liquid crystal display or the like cannot be used. Therefore, the circuit of the switching element of each pixel must be provided on a substrate different from the display panel, and the display panel and the substrate must be connected by a plurality of wirings, and the number of wirings increases as the number of pixels increases. It was not feasible.
[0007]
In addition, Proc. As described in SID, 18, 255 (1977) and SID 00 DIGEST, 24 (2000), there is an example in which simple matrix driving is possible by devising the cell structure, but the cell structure is complicated. This increases the cost of the display device and hinders high resolution.
[0008]
In the structure for driving the simple matrix, a partition for providing a control electrode in the cell exists. In the future, even if the resolution of the display device becomes higher and the cell size becomes smaller, there is a limit to the reduction in the thickness of the partition wall.
[0009]
[Problems to be solved by the invention]
In an electrophoretic display device having a high resolution and a large number of pixels, there is a demand to use simple matrix driving. However, the conventional technology has led to an increase in the cost of the display device due to the complicated structure.
[0010]
An object of the present invention is to provide an electrophoretic display device that realizes simple matrix driving with a simple structure.
[0011]
[Means for Solving the Problems]
In view of the above circumstances, the first of the present invention is a first substrate having a first surface, first and second electrodes formed in parallel with each other near the first surface, and a second facing the first surface. A second substrate having a surface; a third electrode formed in the vicinity of the second surface and intersecting the first and second electrodes; and a first and second electrode in a region where the first and second electrodes intersect with the third electrode. A dispersion liquid containing an insulating liquid and a plurality of electrophoretic particles having charges of the same polarity sandwiched between substrates, an initial voltage, a first holding voltage, and an initial voltage and a first holding voltage A first power supply that applies a rewrite voltage between the initial voltage, the rewrite voltage, and the first holding voltage in this order; a second power supply that applies an intermediate voltage between the initial voltage and the rewrite voltage to the second electrode; The three electrodes are synchronized with the color display voltage different from the intermediate voltage and the first holding voltage Providing an electrophoretic display device, characterized in that it comprises a third power source for applying a second holding voltage between the voltages.
[0012]
In the first invention, before the elapse of time necessary for movement of the electrophoretic particles from the first electrode to the second or third electrode. It is also possible to apply the first and second holding voltages by controlling the first and third power sources.
[0013]
In the first invention, the fourth and fifth electrodes formed in parallel to each other on the third surface located on the opposite side of the second surface of the second substrate, and the fourth surface facing the third surface are further provided. A plurality of third substrates, a sixth electrode formed on the fourth surface and intersecting the fourth and fifth electrodes, and sandwiched between the second and third substrates, and each having an insulating liquid and charges of the same polarity. A dispersion containing electrophoretic particles, the first and fourth electrodes are commonly connected to the first power source, the second and fifth electrodes are commonly connected to the second power source, and the third and sixth electrodes are connected to the first power source. You may connect in common to 3 power supplies.
[0014]
In view of the above circumstances, the second of the present invention includes a first substrate having a first surface, first and second electrodes juxtaposed on the first surface, and a second surface facing the first surface. A second substrate provided, a third electrode formed on the second surface and intersecting the first and second electrodes, and sandwiched between regions where the first and second electrodes and the third electrode intersect between the first and second substrates And an insulating liquid and a dispersion containing a plurality of electrophoretic particles having charges of the same polarity. A third substrate having a fourth surface and a fifth electrode formed in parallel to each other on a third surface located on the opposite side of the second surface of the second substrate; a fourth substrate facing the third surface; Insulating liquid formed on the surface of 4 and sandwiched between the sixth electrode intersecting with the fourth and fifth electrodes and the region between the second and third substrates intersecting with the fourth and fifth electrodes and the sixth electrode And a dispersion containing a plurality of electrophoretic particles having the same polarity of charge, the first and fourth electrodes having an initial voltage, a first holding voltage, and a rewriting voltage between the initial voltage and the first holding voltage. Are applied in the order of an initial voltage, a rewrite voltage, and a first holding voltage, a second power supply that applies an intermediate voltage between the initial voltage and the rewrite voltage to the second and fourth electrodes, A second holding voltage is applied to the sixth electrode in synchronization with the color display voltage and the first holding voltage. And a power source An electrophoretic display device is provided.
[0015]
In the first and second inventions, a microcapsule sandwiched between the first and second substrates and enclosing the dispersion may be provided.
[0016]
In view of the above circumstances, the third aspect of the present invention includes a first substrate having a first surface, first and second electrodes juxtaposed on the first surface, and a second surface facing the first surface. A second substrate provided, a third electrode formed on the second surface and intersecting the first and second electrodes, and sandwiched between the first and second substrates in a region where the first and second electrodes intersect with the third electrode There is provided an electrophoretic display device comprising an insulating liquid and a microcapsule that encloses a dispersion liquid containing a plurality of electrophoretic particles having the same polarity of charge.
[0017]
In the first to third inventions, a protrusion formed on the side of the microcapsule may be provided on the first or second surface. Further, the protrusion formed on the first surface may also serve as the first and second electrodes.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0020]
(First embodiment)
FIG. 1 is a diagram showing a cell cross section of an electrophoretic display device according to a first embodiment of the present invention and the connection between each electrode of the cell and a power source.
[0021]
The electrophoretic display device includes a dispersion 3 containing a colorless and transparent insulating liquid 1 and a plurality of electrophoretic particles 2 having the same polarity. The dispersion 3 is formed by a first substrate 4, a transparent second substrate 5 located closer to the observation surface than the first substrate 4, and a third substrate 6 that supports the first and second substrates 4 and 5. Is held in the space.
[0022]
On the surface of the first substrate 4 on the side of the dispersion, a first electrode 7 located approximately at the center of the bottom of the space in which the dispersion is held and a second electrode 8 are formed in parallel with each other. Has been.
[0023]
A transparent third electrode 9 intersecting with the first and second electrodes 7 and 8 is formed on the surface of the second substrate 5 on the dispersion side.
[0024]
Dielectric layers 10 and 11 are formed on the surfaces of the first to third electrodes 7, 8, and 9, thereby being separated from the dispersion liquid 3. In this embodiment, the dielectric layer 10 is responsible for the contrast color of the electrophoretic particles 2.
[0025]
The first to third electrodes 7, 8 and 9 are connected to a power source 12, and a voltage having a predetermined polarity and a predetermined value is applied by the control of the power source 12.
[0026]
The electrophoretic display device according to the present embodiment can realize simple matrix driving with a simple structure by providing each of the above-described configurations in an array.
[0027]
FIG. 2 is a plan view of the electrophoretic display device in which the above-described configurations are arranged in the plane vertically and horizontally as viewed from the second substrate 5 side.
[0028]
As shown in FIG. 2, the third electrode 9 extends in the horizontal direction on the paper surface, and the first and second electrodes 7 and 8 extend in the vertical direction on the paper surface. A portion surrounded by a thick line in FIG. 2 corresponds to one pixel, and the dispersion 3 is sandwiched as described in FIG.
[0029]
In FIG. 2, an electrophoretic display device having 8 × 8 pixels is shown for simplicity of explanation. The eight first electrodes 7-1, 7-2,... 7-7, 7-8 are applied with the initial voltage, the rewrite voltage, and the first holding voltage by the first power supply 12-1. The second electrode 8 is connected to the second power source 12-2. The eight third electrodes 9 are applied with a rewriting voltage and a holding voltage by the third power source 12-3.
[0030]
In this embodiment, control of the value and timing of the voltage applied to the first to third electrodes 7, 8, 9 is controlled by the control circuit in the second power source 12-2.
[0031]
Next, the operation of the electrophoretic display device according to this embodiment will be described.
[0032]
The rewriting operation is performed in the order of a plurality of pixels in the first electrode 7-1 column, a plurality of pixels in the first electrode 7-2 column,..., A plurality of pixels in the first electrode 7-8 column in order from the left side of FIG. I will rewrite it. FIG. 3 shows a timing chart of voltage application to the first to third electrodes 7, 8, 9.
[0033]
As the first rewriting operation, as shown in the timing (S) of FIG. 3, all the first electrodes 7-1, 7-2,..., 7-7, 7-8 are set to 0V, and the third electrode 9 is set. 15V is applied to the second electrode 8. Then, the positively charged electrophoretic particles 2 gather on the first electrode 7 having a low potential.
[0034]
Next, each pixel is rewritten under voltage control by the power supplies 12-1, 12-2, and 12-3.
[0035]
Timings (7-1), (7-2),..., (7-7), (7-8) in FIG. 3 are the first electrodes (7-1), (7-2), ..., the second pixel column from the left under the control of the first electrode (7-2) at the timing of rewriting the pixel column under the control of (7-7), (7-8) in order from the left An example of rewriting is shown. Further, the voltage to the third electrode 9 shown in FIG. 3 is shown for one of the third electrodes 9 in FIG. 2 corresponding to the cell to be rewritten.
[0036]
Until each pixel column is rewritten, the potential of the first electrode 7 is set to 0 V, and the positively charged electrophoretic particles 2 are held on the first electrode 7 side. Then, when the cell rewrite order comes, the potential of the first electrode 7-2 is raised to 25V.
[0037]
At this time, the potential of the third electrode 9 is set to 0 V when displaying the color (for example, black) of the electrophoretic particles 2 and 30 V when displaying the color (for example, white) of the dielectric layer 10. Then, the value of the first electrode is raised to 50 V in the column where the rewriting has been completed.
[0038]
In the cell of the column after rewriting, the voltage of the first electrode 7 is 50V as shown in FIG. 3, but the voltage of the third electrode 9 is 0V or Fluctuates between 30V. At this time, as shown in FIG. 3, the voltage to the third electrode 9 is provided with a time of 15 V in the time for rewriting each pixel column.
[0039]
In the present embodiment, the time for setting the voltage applied to the third electrode 9 to 0 V or 30 V is 10 msec, and the time for 15 V is 10 msec. In this way, during the first 10 msec, the electrophoretic particles 2 slightly move in a direction different from the desired position due to the voltage value of the third electrode 9, but again during the next 10 msec. Return to the desired position. In this manner, in the cell after rewriting, the electrophoretic particles 2 reciprocate near the desired position, but eventually return to the desired position.
[0040]
Then, as a final operation after rewriting all the cells, the electrophoretic particle 2 is kept in a desired state by maintaining a state of 50 V for the first electrode, 15 V for the third electrode, and 15 V for the second electrode for a certain period of time. It settles on the position electrode. In the present embodiment, this holding time is set to 100 msec.
[0041]
Even if the voltage of each electrode is set to 0 V after rewriting, the electrophoretic particles 2 are held on the moved electrode after rewriting as in the conventional electrophoretic display device, and the screen information can be maintained. .
[0042]
As described above, the movement of the electrophoretic particles 2 can be summarized as shown in FIGS. 4 (a), (b-1), (b-2), (c-1), (c-2), (d-1), As shown in each sectional view of (d-2). In addition, the arrow in each figure of FIG. 4 shows the Coulomb force added to the electrophoretic particle 2. First, the electrophoretic particles 2 are collected on the first electrode 7 at the timing (S) in FIG. 3 as shown in FIG. This voltage setting is maintained until the cell rewriting timing comes, and the electrophoretic particles 2 are held on the first electrode 7.
[0043]
When the timing of rewriting comes and the first electrode 7 rises to 25 V as shown in timing (7-2) in FIG. 3, the electrophoretic particles 2 leave the first electrode and are given to the third electrode 9. Move according to the next voltage value.
[0044]
That is, when 30 V is applied to the third electrode 9, the electrophoretic particles 2 move to the second electrode 8 side as shown in FIG. When 0 V is applied to the third electrode 9, the electrophoretic particles 2 move to the third electrode 9 side as shown in FIG. 4 (b-2).
[0045]
In the middle of moving the electrophoretic particle 2 to a desired position, the moving speed of the electrophoretic particle 2 is accelerated by applying a potential of 50 V to the first electrode 7.
[0046]
In the pixel after rewriting, the voltage of the first electrode 7 is maintained at 50V, but the potential of the third electrode 9 changes to 30V, 15V, or 0V during the rewriting operation of other pixel columns. . At that time, the electrophoretic particles 2 move somewhat as shown in FIGS. 4 (c-1) and 4 (c-2). However, when the third electrode becomes 15 V after rewriting another pixel column, the electrophoretic particle 2 returns to a desired position as shown in FIGS. 4 (d-1) and 4 (d-2).
[0047]
The potential distribution of the cell cross section at this time is as shown in FIG. FIG. 5 shows an equipotential surface when the first electrode 7 is 50V, the second electrode 8 is 15V, and the third electrode 9 is 15V. Although the electrophoretic particles 2 move somewhat at both ends of the cell due to the potential fluctuation of the third electrode 9, the potential distribution shown in FIG. 5 is obtained when each pixel column is rewritten. Return to the electrode 8 or the third electrode 9 side.
[0048]
After the rewriting of all the pixel columns is completed, the electrophoretic particles 2 are applied to the electrodes 7, 8, 9 by applying the voltage shown in the timing (E) of FIG. And the rewrite operation is completed.
[0049]
In this way, during rewriting of the entire screen, the electrophoretic particle 2 reciprocates between a desired position and an intermediate position, and settles to the desired position after rewriting the entire screen. During rewriting of the entire screen, the electrophoretic particles 2 are moving, so the image is not stable and is blurred. However, a still image such as an advertisement display board or electronic paper is displayed. There is no problem in the display device for the purpose.
[0050]
Further, when the electrophoretic particles 2 are collected on the second electrode 8 side, the observer sees the dielectric layer 10, but in the structure of FIG. 1, the electrophoretic particles 2 on the second electrode 8 can also be seen. Thus, the color mixture of the dielectric layer 10 and the electrophoretic particles 2 is seen. In order to prevent this, a shielding layer that shields the electrophoretic particles 2 on the second electrode 8 may be provided on the surface of the second substrate 5.
(Modification)
In the first embodiment, the region surrounded by the first to third substrates 4, 5, 6, that is, the cross section in which the dispersion liquid is sandwiched is rectangular as shown in FIG. 1. On the other hand, as shown in the cell cross section of FIG. 6, the third substrate 6 may have a convex shape with a step.
[0051]
In FIG. 6, two third substrates 61 and 62 having different widths are stacked and sandwiched between the first and second substrates 4 and 5. The third substrate 61 in contact with the first substrate 4 has a width of about 10 μm, and the spacer substrate 62 in contact with the second substrate 5 has a width of about 20 μm.
[0052]
Such a cross-sectional shape makes it difficult for the electrophoretic element 2 to move between the second and third electrodes 8 and 9 when rewriting other pixel columns.
[0053]
That is, as shown in the cell cross-sectional view of FIG. 7A, when another pixel column is rewritten, the electrophoretic particles near the third electrode 9 move slightly toward the second electrode 8. However, it hits the vertical wall surface of the third substrate 62 and cannot move in the direction of the second electrode 8.
[0054]
Similarly, as shown in the cell cross-sectional view of FIG. 7B, the electrophoretic particles 2 in the vicinity of the second electrode 8 may move somewhat toward the third electrode 9, but the third substrate It becomes impossible to move in the direction of the third electrode 9 on the 62 horizontal wall surface.
[0055]
This structure makes simple matrix driving more realistic. The application of voltage by each electrode and the movement of the electrophoretic particles 2 are the same as in the first embodiment.
Example 1
In the electrophoretic display device of the first embodiment, selection, formation, and setting of each member were performed as follows.
[0056]
A transparent glass plate having a thickness of 1 mm was used as the first and second substrates 4 and 5, and a polyimide substrate having a thickness of about 40 μm was used as the third substrate 6. The distance between the first and second substrates 4 and 5 was set to about 40 μm, and the distance between the third substrates 6 was set to about 80 μm.
[0057]
The third electrode 9 was formed by depositing transparent indium oxide to a thickness of about 0.1 μm on the dispersion side surface of the second substrate 5. The first and second electrodes 7 and 8 were formed by sputtering aluminum on the dispersion side of the first substrate 4 and then etching according to the pattern.
[0058]
The dielectric layers 10 and 11 prevent the irreversible adsorption of the electrophoretic particles 2 to the first to third electrodes 7, 8 and 9, and the dielectric layer 10 is responsible for the contrasting color of the electrophoretic particles 2. Be placed. The dielectric layer 10 was formed by spin coating a mixture of fine barium sulfate powder in a fluororesin with a thickness of about 0.5 μm. In addition, the dielectric layer 11 was formed of a transparent fluororesin on a dip coat with a thickness of about 0.5 μm.
[0059]
The dispersion was prepared as follows. First, a black resin toner (particle size: 1 μm) is used as the electrophoretic particles 2 and isopropanol is used as the insulating liquid, and both are mixed so that the mixing weight ratio of the electrophoretic particles 2 is 10%. In order to improve the above, a small amount of a surfactant was added to prepare a dispersion. In this case, the surface of the electrophoretic particle 2 is positively charged.
(Second Embodiment)
In the first embodiment, the first electrode 7 that controls rewriting or holding of the pixel is provided at the center of the bottom of the pixel, and the second electrode 8 that collects the electrophoretic particles is provided at both ends. It doesn't matter.
[0060]
In the following description of the present embodiment, the same components as those described in the first embodiment will be denoted by the same reference numerals, and the detailed description thereof will be made by referring to the first embodiment. Detailed description will be omitted.
[0061]
As shown in the cell cross section and the connection between each electrode and the power source in FIG. 8, the electrophoretic display device according to the present embodiment is provided with the second electrode 8 for collecting the electrophoretic particles below the center of the pixel, First electrodes 7 for controlling rewriting and holding of the pixels are provided at both ends. In this case, the first electrode 7 cannot be shared with adjacent pixels as shown in FIG. 8, and must be divided for each pixel. Application of a voltage to each electrode by each power source, movement of the electrophoretic particles 2 and the like are the same as in the first embodiment.
(Third embodiment)
In the first and second embodiments, the first electrode 7 or the second electrode 8 is provided at the center of the bottom of each pixel, and the two first or second electrodes 7, 8 was provided. In this embodiment, one first electrode 7 and one second electrode 8 are arranged in each pixel, as in the cell cross section shown in FIG.
[0062]
Whether to set the pixel size to any one of the first to third modes is determined by resolution, driving voltage, manufacturing cost, and the like. When the third embodiment is used, the resolution is improved, but the number of the first electrodes 7 and the second electrodes 8 provided on the substrate is increased, and a manufacturing method with higher positional accuracy is adopted for wiring formation. There is a need to. The method of applying a voltage to each electrode, the movement of the electrophoretic particles 2 and the like are the same as in the first embodiment.
(Fourth embodiment)
In the first to third embodiments, the dispersion liquid 3 is partitioned into a desired size by putting the dispersion liquid in a region partitioned by the partition walls. In this embodiment, an electrophoretic display device using a microcapsule 13 containing a dispersion liquid will be described with reference to FIG. 10 showing a cell cross section and connection between each electrode and a power source.
[0063]
FIG. 10 shows a cell cross section in which a microcapsule 13 that encloses the dispersion liquid 3 composed of the electrophoretic particles 2 and the insulating liquid 1 is disposed between the first substrate 4 and the second substrate 5.
[0064]
In this embodiment, one pixel is composed of 2 × 2 four microcapsules 13. This can be substantially determined from the resolution of the display device and the particle size of the microcapsules 13. In this embodiment, the display device has a resolution of 300 dpi and pixels have a pitch of 85 μm. The particle size of the microcapsule 13 is 40 μm, and a total of four microcapsules 13 arranged in two vertical and two horizontal directions form one pixel.
[0065]
The microcapsule 13 was prepared by a well-known coacervation method. First, 11 parts by weight of a dispersion containing electrophoretic particles and an insulating liquid is emulsified with a homogenizer together with 100 parts by weight of pure water and 2 parts by weight of an emulsifier. This emulsified mixed solution is dropped into a 5% gelatin-gum arabic aqueous solution at 40 ° C., and 10% acetic acid is added dropwise with stirring to adjust the pH to 3.5. Thereafter, the temperature is lowered to 5 ° C., 37% formalin is added dropwise, and further a 10% NaOH aqueous solution is added dropwise to adjust the pH to 8.5 to cure the film. Thereafter, it was washed with pure water and filtered through a 1 μm filter to obtain microcapsules 13 having an average particle diameter of 40 μm included in a transparent polymer film.
[0066]
As the microencapsulation technology, in addition to the methods described above, interfacial polymerization method, in situ polymerization method, liquid curing coating method, phase separation method from organic solution system, melt dispersion cooling method, air suspension method, There is a spray drying method or the like, which can be appropriately selected according to the use and form of the recording medium.
[0067]
In addition to gelatin-gum arabic, the coating film of the microcapsule 13 is also a condensation polymer such as melanin resin, epoxy resin, urea resin, phenol resin, furan resin, styrene-divinylbenzene copolymer, methyl methacrylate-vinyl acrylate. A thermosetting resin such as a three-dimensional cross-linked vinyl polymer such as a copolymer can be appropriately used.
[0068]
Moreover, you may form the multilayer film which comprises the microcapsule 13 using 2 or more types selected from said thermosetting resin and thermoplastic resin. In this case, from the viewpoint of improving the thermal stability of the microcapsule 13, it is desirable to use a known thermosetting resin for the outermost shell of the coating.
[0069]
Even in such a configuration, the movement of the electrophoretic particles 2 is controlled by the voltage application method to the first to third electrodes 7, 8, and 9 shown in FIG. 3 as described in the first embodiment. Is possible.
[0070]
The dielectric layers 10 and 11 can be omitted by selecting a known material having the same characteristics as the dielectric layers 10 and 11 on the substrate side as the shell material of the microcapsule 13.
(Fifth embodiment)
In the fourth embodiment, by omitting the third substrate 6 between the first substrate 4 and the second substrate 5, an electrophoretic display device having a simple structure can be realized. However, in the fifth embodiment, a protrusion for determining the position of the microcapsule 13 is formed on the first substrate 4 in order to improve the positional alignment between the electrodes 7, 8, 9 and the microcapsule 13. .
[0071]
FIG. 11 is a cross-sectional view showing a cell cross section of an electrophoretic display device according to the fifth embodiment and the connection between each electrode and a power source. The first and second electrodes 7 and 8 have a length in the direction perpendicular to the paper surface of FIG. 11, and their cross-sectional shapes are substantially triangular.
[0072]
Such an electrode can be formed by a printing technique or an etching technique. In the printing technique, a conductive ink is used, and a projection having a height of about 10 to 20 μm can be formed by screen printing or gravure printing technique. In addition, the etching technique can be formed by etching a substrate on which copper having a thickness of about 15 μm is attached. In this case, the cross section of the electrode does not have to be triangular but may be substantially rectangular.
[0073]
On the first substrate thus formed, 10% of microcapsules dispersed in pure water are applied and then dried at 100 ° C. to remove moisture. When dried, the shells fuse together due to the strength of the shells of the microcapsules, and the gaps between adjacent microcapsules 13 are closed as shown in FIG.
[0074]
Next, FIG. 12 shows a plan view of the positional relationship between the microcapsule 13 and the first and second electrodes 7 and 8 from the second substrate 5 side, as observed from the second substrate 5 side. The cross sections of the first and second electrodes 7 and 8 are triangular, but the width of the bottom surface varies depending on the location. The center of one side of the microcapsule 13 is aligned with the narrowest bottom surface. FIG. 12 shows an example in which the widths of the bases of the first and second electrodes 7 and 8 are periodically changed. As shown in FIG. 13 showing a plan view similar to FIG. It doesn't matter.
[0075]
Moreover, as shown in the cell cross-sectional view of FIG. In FIG. 14, a projection 14 is used for positioning the microcapsule 13, and the first and second electrodes 7 and 8 are provided on the first substrate 4 in a flat plate shape separately from the projection.
[0076]
Furthermore, the protrusion may be provided on the lower surface of the second substrate 5 as shown in the cell sectional view of FIG. In this case, what forms the protrusions is not intended to be used as an electrode, so there is no need for a conductive material and an insulator may be used.
[0077]
Even in such a configuration, the movement of the electrophoretic particles 2 is controlled by applying voltages to the first to third electrodes 7, 8, and 9 shown in FIG. 3 as described in the first embodiment. It is possible.
(Sixth embodiment)
In the electrophoretic display devices according to the first to fifth embodiments, the dispersion liquid 3 including the transparent colorless insulating liquid 1 and the electrophoretic particles 2 is used as the dispersion liquid 3. In the electrophoretic display device according to the sixth embodiment, a dispersion containing a dye coloring solvent and electrophoretic particles is used.
[0078]
In this embodiment, in the state of FIG. 16A in which the electrophoretic particles 2 are located on the first substrate 4 side, the cell changes the color of the dye coloring solvent with respect to the observation from the second substrate 5 side. indicate. Further, in the state of FIG. 16B in which the electrophoretic particles 2 are located on the second substrate 5 side, the cell displays the color of the electrophoretic particles 2. In FIG. 16A, the color of the electrophoretic particles 2 collected on the second electrode can be hidden by setting the dye concentration to an appropriate amount.
[0079]
Even in such a configuration, as described in the first embodiment, the movement of the electrophoretic particles 2 is controlled by voltage application to the first to third electrodes 7, 8, and 9 shown in FIG. 3. It is possible.
(Seventh embodiment)
Next, an electrophoretic display device for multicolor display according to the seventh embodiment will be described.
[0080]
The electrophoretic display device of the present invention can also realize multicolor display by a conventionally known method. That is, a method of providing a color filter on the observation-side transparent substrate, a method of coating the dielectric layer 10 in multiple colors for each pixel, a method of changing the electrophoretic particles to different colors for each pixel, and an insulating property in which a different dye is dissolved for each pixel Multicolor display can be realized by a technique using liquid or the like.
[0081]
However, in any of the above methods, white or black is displayed by color mixture using a plurality of pixels, so that the resolution is lowered and the image quality is particularly deteriorated when displaying text. Moreover, since white display and black display are performed by color mixing, a decrease in whiteness and blackness is observed.
[0082]
In the electrophoretic display device of the present embodiment, each cell is formed of a plurality of layers, so that it is possible to display three or more colors of white, black, and different colors for each pixel. A display device according to the seventh embodiment will be described with reference to a partial cross-sectional view of FIG. 17 and cell cross-sectional views of FIGS. 18 (a), 18 (b), and 18 (c).
[0083]
FIG. 17 shows a structure in which two display cells having the structure used in the first to sixth embodiments are stacked in the vertical direction on the paper surface. In the upper cell, white electrophoretic particles 21 are dispersed in a colorless and transparent insulating liquid 1. In the lower cell, electrophoretic particles 22, 23, and 24 having different colors for each pixel are dispersed in the colorless and transparent insulating liquid 1. Specifically, red, blue, and green electrophoretic particles are used as the electrophoretic particles 22, 23, and 24, respectively, and are regularly arranged in a three-pixel cycle in the plane.
[0084]
Here, as shown in FIG. 18A, when the white electrophoretic particles 21 are collected along the transparent substrate 5 on the observer side, the cell displays white. At this time, the electrophoretic particles 22 in the lower layer cell may exist at an arbitrary place.
[0085]
Then, as shown in FIG. 18B, the white electrophoretic particles 21 are collected on the second electrode 71, and the electrophoretic particles 22 of the lower layer cell are collected along the third electrode 81. At this time, when the dielectric layer 91 of the upper cell is formed of a colorless and transparent material, the cell displays the color of the electrophoretic particles 22.
[0086]
Finally, as shown in FIG. 18C, by collecting the upper white electrophoretic particles 21 and the lower electrophoretic particles 22 on the second electrodes 71 and 72, the cell changes the color of the dielectric layer 92. indicate. By making the dielectric layer 92 black, this pixel can display three colors of white, black, and different colors from white and black. By doing so, it is possible to increase the resolution of white display and black display, and it is possible to prevent image quality degradation during text display.
[0087]
As described above, the electrophoretic display device of the present invention has been described using each embodiment. However, the present invention is not limited to these embodiments, and can be appropriately changed within the scope of the claims.
[0088]
【The invention's effect】
As described above, in the electrophoretic display device of the present invention, since the display color can be changed by simple matrix driving, a low-cost display device can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a cell of an electrophoretic display device according to a first embodiment of the present invention, and a diagram showing a connection between each electrode and a power source.
FIG. 2 is a plan view showing a connection between wirings of first to third electrodes and first to third power supplies of the electrophoretic display device according to the first embodiment.
FIG. 3 is a diagram showing a voltage application sequence according to the first embodiment.
FIG. 4 is a cell cross-sectional view for explaining the Coulomb force applied to the electrophoretic particles accompanying voltage application and the movement of particles accompanying this according to the first embodiment.
FIG. 5 is a cross-sectional view showing a potential distribution in a cell according to the first embodiment.
6A and 6B are diagrams showing a cell cross-section for explaining a modification of the electrophoretic display device according to the first embodiment, and connections between electrodes and a power source.
FIG. 7 is a cross-sectional view of a cell for explaining advantages related to a modified example.
FIG. 8 is a cross-sectional view of a cell showing an electrophoretic display device according to a second embodiment of the present invention, and a diagram showing connections between electrodes and power sources.
FIG. 9 is a partial cross-sectional view showing an electrophoretic display device according to a third embodiment of the present invention, and a diagram showing connections between electrodes and power sources.
FIG. 10 is a diagram showing a cell cross section of an electrophoretic display device using microcapsules according to a fourth embodiment of the present invention, and connections between electrodes and a power source.
FIG. 11 is a diagram showing a partial cross section of an electrophoretic display device using protrusions that define the position of a microcapsule according to a fifth embodiment of the present invention, and the connection between each electrode and a power source.
FIG. 12 is a plan view showing a pattern of protrusions of an electrophoretic display device according to a fifth embodiment.
FIG. 13 is a plan view showing another pattern of protrusions of the electrophoretic display device according to the fifth embodiment.
FIG. 14 is a partial cross-sectional view showing another example of the protrusion of the electrophoretic display device according to the fifth embodiment, and a diagram showing connections between electrodes and a power source.
FIG. 15 is a diagram showing a partial cross-section and connection of electrodes and a power source in still another example of the protrusions of the electrophoretic display device according to the fifth embodiment.
FIG. 16 is a cell cross-sectional view of an electrophoretic display device according to a sixth embodiment of the invention.
FIG. 17 is a partial cross-sectional view of an electrophoretic display device according to a seventh embodiment of the invention.
FIG. 18 is a cell cross-sectional view of an electrophoretic display device according to a seventh embodiment.
[Explanation of symbols]
1 ... insulating liquid,
2 ... electrophoretic particles,
3 ... dispersion,
4 ... 1st board | substrate,
5 ... second substrate,
6 ... Third substrate,
7 ... 1st electrode,
8 ... second electrode,
9 ... third electrode,
10, 11 ... Dielectric layer
12 ... Power supply

Claims (5)

A first substrate having a first surface; first and second electrodes formed in parallel with each other in the vicinity of the first surface; a second substrate having a second surface facing the first surface; and the second A third electrode formed in the vicinity of the surface and intersecting the first and second electrodes, and an insulation sandwiched between the first and second substrates in a region where the first and second electrodes intersect the third electrode And a dispersion liquid containing a plurality of electrophoretic particles having electric charges of the same polarity with each other, an initial voltage, a first holding voltage, and rewriting between the initial voltage and the first holding voltage on the first electrode A first power source that applies a voltage in the order of the initial voltage, the rewrite voltage, and the first holding voltage; and a second power source that applies an intermediate voltage between the initial voltage and the rewrite voltage to the second electrode; The third electrode has a color display different from the intermediate voltage Pressure, and an electrophoretic display device, characterized in that it comprises a third power source for applying a second voltage held between the first holding voltage in synchronization with said initial voltage and said writing voltage. The first and third power sources apply the first and second holding voltages before the time necessary for the movement of the electrophoretic particles from the vicinity of the first electrode to the vicinity of the second or third electrode. The electrophoretic display device according to claim 1. A third substrate having a fourth surface and a fifth electrode formed in parallel to each other on a third surface located on the opposite side of the second surface of the second substrate; and a fourth surface facing the third surface; A plurality of electrophoresis formed on the fourth surface and intersecting the fourth and fifth electrodes, sandwiched between the second and third substrates, and having an insulating liquid and charges of the same polarity. A dispersion containing particles, wherein the first and fourth electrodes are commonly connected to the first power source, the second and fifth electrodes are commonly connected to the second power source, and the third and sixth The electrophoretic display device according to claim 1, wherein the electrode is commonly connected to the third power source. A first substrate having a first surface; first and second electrodes juxtaposed on the first surface; a second substrate having a second surface facing the first surface; and formed on the second surface. A third electrode intersecting with the first and second electrodes, an insulating liquid sandwiched in a region where the first and second electrodes and the third electrode between the first and second substrates intersect, and And a dispersion liquid containing a plurality of electrophoretic particles having charges of the same polarity, and a fourth surface and a fourth surface formed in parallel with each other on a third surface located on the opposite side of the second surface of the second substrate. A third substrate having a fourth surface opposite to the third surface, a sixth electrode formed on the fourth surface and intersecting the fourth and fifth electrodes, and the second and third Insulating liquid sandwiched between regions where the fourth and fifth electrodes and the sixth electrode cross between the substrates And a dispersion liquid containing a plurality of electrophoretic particles each having the same polarity of charge, the first and fourth electrodes having an initial voltage, a first holding voltage, and the initial voltage and the first holding voltage. A first power supply for applying a rewrite voltage between the initial voltage, the rewrite voltage, and the first holding voltage in this order; and an intermediate voltage between the initial voltage and the rewrite voltage for the second and fourth electrodes. A second power voltage to be applied, a color display voltage different from the intermediate voltage, and a second holding voltage between the initial voltage and the rewrite voltage in synchronization with the first holding voltage are applied to the third and sixth electrodes. An electrophoretic display device comprising: a third power source to be applied. The electrophoretic display device according to claim 1, further comprising a microcapsule sandwiched between the first and second substrates and enclosing the dispersion.

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