JP3625421B2 - Electrophoretic display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention performs display by moving charged electrophoretic particles. Electrophoretic display device About.
[0002]
[Prior art]
In recent years, along with the development of information equipment, the amount of data of various types of information has been steadily expanding, and information is output using various forms. In general, the output of information can be roughly divided into display display using a cathode ray tube or liquid crystal, and hard copy display on paper by a printer or the like. In display display, the need for low power consumption and thin display devices is increasing, and liquid crystal display devices are being actively developed and commercialized as display devices that can meet such needs. However, the current liquid crystal display devices still have a sufficient resolution of the visual burden caused by the angle at which the screen is viewed and the reflected light, making it difficult to see the characters on the screen and the flickering and low brightness of the light source. Not. In contrast, a display using a cathode ray tube has sufficient contrast and brightness as compared with a liquid crystal display, but cannot be said to have sufficient display quality compared to a hard copy display described later, such as flickering. Moreover, since the apparatus is large and heavy, portability is extremely low.
[0003]
On the other hand, hard copy display is thought to be unnecessary due to the digitization of information, but in reality, a huge amount of hard copy output is still being performed. The reason for this is that when information is displayed on the display, in addition to the above-mentioned problems related to display quality, the resolution is generally about 120 dpi at the maximum, compared to printing out on paper (usually 300 dpi or more). Considerably low. Therefore, the visual burden on the display is greater than that on the hard copy display. As a result, even if it can be confirmed on the display, hard copy output is often performed once. In addition, information that is hard-copied can be arranged in large numbers without limiting the display area to the size of the display, as in the case of a display, or can be rearranged without performing complicated device operations, and can be checked in order. What can be done is also a major reason why hard copy display is used in combination even if display can be displayed. Furthermore, the hard copy display does not require energy for holding the display and has excellent portability that information can be confirmed anytime and anywhere as long as the amount of information is not extremely large.
[0004]
As described above, unless moving image display or frequent rewriting is required, hard copy display has various advantages different from display display, but has a drawback of consuming a large amount of paper. Therefore, in recent years, development of a rewritable recording medium (a recording medium that can perform a high-visibility image recording / erasing cycle many times and does not require energy to maintain display) has been actively promoted. A rewritable third display method that inherits the characteristics of such hard copy is called a paper-like display.
[0005]
The necessary conditions for a paper-like display are that it can be rewritten, does not require energy to hold the display or is sufficiently small (memory property), has excellent portability, and has excellent display quality. . At present, as a display method that can be regarded as a paper-like display, for example, an organic low molecular weight / high molecular resin matrix system that records and erases with a thermal printer head (for example, Japanese Patent Laid-Open Nos. 55-154198 and 57-82086). And a reversible display medium using Japanese Laid-open Patent Publication No. This system is partly used as a display part of a prepaid card, but has a problem that the contrast is not so high and the number of recording / erasing repetitions is relatively small, such as about 150 to 500 times.
[0006]
In addition, as a display method usable as another paper-like display, Harold D. et al. An electrophoretic display device (US Pat. No. 3,612,758) invented by Lees et al. Is known. In addition, an electrophoretic display device is disclosed in Japanese Patent Laid-Open No. 9-185087.
[0007]
This display device includes a dispersion system in which colored charged electrophoretic particles are dispersed in an insulating liquid, and a pair of electrodes facing each other with the dispersion system interposed therebetween. By applying a voltage to the dispersion system through the electrode, the colored charged electrophoretic particles are adsorbed on the side of the electrode having the opposite polarity to the electric charge of the particles by the Coulomb force using the electrophoretic properties of the colored charged electrophoretic particles. Is. The display is performed using the difference between the color of the colored charged electrophoretic particles and the color of the stained insulating liquid. That is, when the colored charged electrophoretic particles are adsorbed on the light-transmitting first electrode surface close to the observer, the color of the colored charged electrophoretic particles is observed, and conversely adsorbed on the second electrode surface far from the observer. In this case, the color of the insulating liquid dyed so as to have an optical characteristic different from that of the colored charged electrophoretic particles is observed.
[0008]
However, in such an electrophoretic device, a coloring material such as a dye or ion must be mixed in the insulating liquid, and the presence of such a coloring material causes electrophoresis in order to transfer new charges. It is easy to act as an unstable factor in operation, and there are cases where the performance, life and stability as a display device are lowered.
[0009]
In order to solve such a problem, there is disclosed a display device in which an electrode pair including a first display electrode and a second display electrode is disposed on the same substrate, and colored charged electrophoretic particles are moved horizontally as viewed from an observer. No. 49-5598 and Japanese Patent Application No. 10-005727. Display by moving colored charged electrophoretic particles in a transparent insulating liquid horizontally between the first display electrode surface and the second electrode surface using the electrophoretic characteristics and the substrate surface. It is.
[0010]
In the horizontal movement type electrophoretic display device, the insulating liquid is transparent, and when viewed from the viewer side, the first display electrode and the second display electrode exhibit different colors, and one of the colors is changed to the electrophoretic particle. It matches the color. For example, if the color of the first display electrode is black, the color of the second display electrode is white, and the color of the migrating particles is black, the second display electrode is exposed and white when the migrating particles are distributed on the first electrode. When the migrating particles are distributed on the second display electrode, the migrating particle color is black.
[0011]
By the way, as a method of electrically addressing a display device in which pixels are arranged in a matrix, there are roughly two methods, an active matrix method and a simple matrix method.
[0012]
In the active matrix method, a switching element such as a thin film transistor (TFT) is formed for each pixel, and a voltage applied to each pixel is controlled independently for each pixel. If this method is used, it is possible to drive a horizontal movement type electrophoretic display device with high display contrast. However, the active matrix method has problems such as high process cost and high process temperature of the thin film transistor, which makes it difficult to form the thin film on a polymer substrate. This problem is particularly important in a paper-like display that aims at a low-cost and flexible display. In order to solve these problems, a formation process of a thin film transistor using a polymer material to which a printing process can be applied has been proposed, but the possibility of practical use is still unknown.
[0013]
The simple matrix system is low cost and can be easily formed on a repolymer substrate because only the XY electrode lines are necessary for addressing. When a write voltage is applied to the selected pixel, a voltage corresponding to the write voltage may be applied to the X electrode line and the Y electrode line that intersect with the selected pixel. However, when the horizontal movement type electrophoretic display device is driven by the simple matrix method, a so-called crosstalk phenomenon occurs in which a part of the pixels around the selected pixel is written, and the display contrast is significantly deteriorated. . This is a problem that inevitably occurs because the horizontal movement type electrophoretic display device does not have a clear threshold characteristic with respect to the writing voltage.
[0014]
In order to solve such a problem, in electrophoretic display having no threshold in principle, a proposal has been made to realize a simple matrix drive by a three-electrode structure by introducing a control electrode in addition to a display electrode. Most proposals regarding the three-electrode structure have been made with respect to upper and lower electrode type electrophoretic display, for example, Japanese Patent Laid-Open No. 54-085699 (US Pat. No. 4,203,106).
[0015]
The only proposal of a three-electrode structure in a horizontal movement type electrophoretic display device has been made in Japanese Patent Publication No. 8-507154 (US Pat. No. 5,345,251). However, in JP-A-8-507154, it is considered that the dispersion is colored rather than transparent, and the above-mentioned JP-A-49-5598, JP-A-10-005727, and the present invention are intended. This is different from the horizontal movement type electrophoretic display device characterized in that the dispersion liquid is transparent.
[0016]
JP-T-8-507154 discloses two configurations regarding the arrangement of control electrodes. FIG. 18 is a cross-sectional view of the display device having the two configurations. The first configuration is a type in which a control electrode 5a is disposed as a third electrode on the second substrate 2 side of the horizontal movement type electrophoresis apparatus (see FIG. 18A), and the second configuration is the first substrate. This is a type in which a control electrode 13 a is arranged as a third electrode between the first display electrode 4 and the second display electrode 3 on the first side. (See FIG. 18 (b))
[0017]
In both types of the first configuration and the second configuration, a fork-shaped first display electrode in which a plurality of line electrodes are assembled in one pixel and a plurality of lines arranged between the lines of the first display electrode. A fork-shaped second display electrode in which the electrodes are assembled is disposed on the first substrate. A thick chromium film is provided on the second display electrode 3, and as a result, a step 22 of about 0.3 μm is formed at the boundary between the first display electrode 4 and the second display electrode 3. In the first configuration, the control electrode 5a is formed on the entire surface of the pixel on the second substrate 2 arranged to face the first substrate 1 at an interval of 25 to 116 μm. In the second configuration, the control electrode 13a is It arrange | positions between each line of the 1st display electrode 4 and the 2nd display electrode 3 on a 1st board | substrate. In FIG. 18, for convenience of explanation, the case where both the first display electrode and the second display electrode are configured by one line is shown.
[0018]
Next, the write operation in Japanese Patent Publication No. 8-507154 will be described with reference to FIGS. FIG. 19 shows the operating state of the migrating particle, and FIG. 20 shows the applied pulse and the change in reflectance. The cell configuration is the same as that in FIG. 18A (however, one pixel).
[0019]
The applied voltage value described in the following description is a condition obtained by an experiment actually conducted by the present inventor and does not necessarily match the condition described in Japanese Patent Publication No. 8-507154. This is largely due to physical properties such as the charge polarity and charge amount of the migrating particles used. In the following description, in order to facilitate the comparison with the description of the operation of the present invention described later, the applied voltage value in the experimental result with the migrating particles used by the present inventor will be described.
[0020]
In JP-A-8-507154, it is considered that a colored liquid is used as the insulating liquid. However, in the following description, the present invention is described in order to facilitate comparison with the operation description of the present invention described later. The present invention uses a transparent insulating liquid independently, and the present invention also presents a method of developing display contrast in which the present inventors independently set the migrating particles to black, the first display electrode to black, and the second display electrode to white. Since the configuration of the system similar to that of the embodiment has been described, the description will be given.
[0021]
The charged polarity of the migrating particles 6 is positive, the second display electrode 3 is a common electrode, and the drive voltage Vd is applied to the first display electrode 4 and the control voltage Vc is applied to the control electrode 5a with reference to the ground potential of the second display electrode 3. It shall be.
[0022]
The period Ta is in the white display holding state. In FIG. 19, an arrow indicates an outline of the electric field vector in the cell. The migrating particles 6 collected on the first display electrode 4 are restrained from moving toward the second display electrode 3 by the step 22 provided between the first display electrode 4 and the second display electrode 3, and the first display electrode 4. The display is stabilized by being pressed to the display electrode side by the holding voltage Vc = + 250 V applied between the display electrode 4 and the control electrode 5a, and a white display state having a reflectance (R) of about 70% is held. Vd = 5 V applied in the holding state plays a role of suppressing the tendency that the migrating particles near the step easily move to the first display electrode side in the black display state.
[0023]
In the writing period Tb, Vd = + 50 v and Vc = + 50 V are applied. Since the first display electrode 4 and the control electrode 5a are set to the same potential, the pressing by the control voltage is released, and all the migrating particles 6 move over the step along the display electrode surface and move horizontally to the second display electrode side. Then, the reflectance R decreases rapidly.
[0024]
In the period Tc in which the black display is maintained, the display electrode is pressed by the holding voltage Vc = + 250 V, and the black display state having a reflectivity of about 5% is maintained.
[0025]
Next, a simple matrix driving method disclosed in JP-T-8-507154 will be described with reference to FIGS. Consider a horizontally-moving electrophoretic display device having an m × n matrix in which pixels are arranged in m columns in the X direction and n rows in the Y direction. Along the pixel arrangement, m signal electrode lines are arranged in the column direction and n signal electrode lines are arranged in the row direction so as to be orthogonal to each other, and at each intersection, the signal electrode lines are control electrodes of each pixel. In 5a, the scanning electrode line is wired to the first display electrode 4 in each pixel. The second display electrode 3 is a common electrode and is fixed to the ground potential.
[0026]
First, Vd = −50 V is applied to all scanning lines and Vc = 0 V is applied to all signal lines, and all the migrating particles 6 are collected on the first display electrode (FIG. 21A, entire surface erasure). Next, scanning lines are selected and written sequentially from the top in the Y direction. In the selection period (writing period), Vd = + 50 V is applied to the scanning line, Vc = + 50 V is applied to the signal line corresponding to the selected pixel, and Vc = + 250 V is applied to the line corresponding to the non-selected pixel. In the selected pixel, the drive voltage Vd = + 50 V applied between the display electrodes causes the migrating particles to move over the step and move to the second display electrode side to perform writing (FIG. 21B). Although the drive voltage Vd = + 50 V is also applied to the non-selected pixels, in the first configuration, the migrating particles are pressed against the first display electrode by the control voltage of Vc = + 250 V to prevent movement (writing) ( FIG. 21 (c)).
[0027]
On the other hand, in the non-selection period, Vd = + 5V is applied to the scanning line, and Vc = + 50V or + 250V is applied to the signal line (FIGS. 22D to 22G). In either case, the migrating particles are pressed against the display electrode surface by the control voltage, and the display state does not change.
[0028]
In this way, display writing using the simple matrix driving method is realized in a horizontal movement type electrophoresis apparatus having no threshold characteristic.
[0029]
[Problems to be solved by the invention]
However, the horizontal movement type electrophoresis apparatus disclosed in JP-A-8-507154 has the following problems. The problem will be described below with reference to FIG.
[0030]
In the first configuration, there is a limitation that the step cannot be set so high. If the level difference is made too high, some of the migrating particles remain in the bottom of the level difference in the movement of the charged electrophoretic particles during the selection period, and the display contrast decreases (FIG. 23 (a)). In order not to cause the residue at the bottom of the step, it is necessary to limit the height of the step to around the electrophoretic particle diameter.
[0031]
Since the height of the step is limited, the effect of suppressing migration of the migrating particles due to the step is insufficient. For this reason, in the state where the drive voltage Vd is applied during the selection period, when the control voltage Vc is applied to the non-selected pixel to suppress the movement of the migrating particles (FIG. 21C), the difference in level is low. As a result, an important problem arises in that the display contrast deteriorates due to a crosstalk phenomenon (FIG. 23B).
[0032]
If the control voltage Vc is sufficiently large, it is possible to suppress the migrating particles to some extent. In this case, however, the applied voltage is increased, and the high voltage is injected into the insulating member in the element. A new problem arises in that the charge remains after the voltage is released and the operating state of the migrating particle becomes unstable due to an unintended electric field caused by the residual charge.
[0033]
There are other adverse effects that limit the height of the step. Since the height of the step is not sufficient, the area difference between the first display electrode and the second display electrode cannot be set so large. This is because if the area difference is set large, the electrophoretic particles overflow even if the electrophoretic particles are collected on the electrode surface having a small area (FIG. 23C). Since the display contrast is determined by the area ratio between the first display electrode and the second display electrode, the display contrast is limited as a result.
[0034]
Furthermore, in the first configuration, the movement suppression effect due to the step is limited to the direction from the lower stage side to the upper stage side, and the movement from the upper stage side to the lower stage side is rather accelerated. Therefore, the writing direction is limited to only one direction, and the driving method is such that first, the electrophoretic particles of the entire screen are collected on the lower side and the entire surface is reset, and then writing in one direction is performed. Writing cannot be performed bidirectionally, and driving that selectively rewrites only a part of the screen is not possible.
[0035]
On the other hand, in the second configuration, during the selection period, it is possible to prevent migration of the migrating particles in both directions by applying a voltage between the display electrode and the control electrode for the non-selected pixels. In addition, for the selected pixel, by moving the voltage between the display electrode and the control electrode to 0 V, the migrating particles can be moved smoothly. In this case, the step is not necessarily an essential component.
[0036]
However, in the second configuration, the control electrode can only block the movement between the display electrodes and cannot control the movement in the display electrode plane. For this reason, the control voltage applied between the display electrode and the control electrode during the non-selection period causes the migrating particles that are uniformly dispersed in the display electrode surface to move in a direction repelling from the control electrode, 24 (a) and 24 (b) cause a distribution deviation, and the display contrast is remarkably lowered.
[0037]
The present invention has been made in order to solve such problems of the prior art, and can suppress the occurrence of crosstalk, can be driven by a simple matrix capable of obtaining a good display contrast, and can be used for colored charged electrophoretic particles. Horizontal movement type that can greatly reduce the control voltage required for holding Electrophoretic display device Is intended to provide.
[0038]
Further, according to the present invention, the area ratio between the first display electrode and the second display electrode can be set larger than the conventional one, and the improvement in contrast is realized. Electrophoretic display device Is intended to provide.
[0039]
In addition, the present invention can perform bidirectional writing driving and can perform partial rewriting for rewriting only a part of the display screen. Electrophoretic display device Is intended to provide.
[0040]
[Means for Solving the Problems]
The inventor has analyzed the above-mentioned problems and intensively studied,
(A) The first configuration and the second configuration described above have completely different types of problems,
(B) It has been found that each problem can be solved by introducing the configuration of the other party.
[0041]
Therefore, in order to solve the above-described problems, the present invention has a novel configuration described below. Electrophoretic display device Propose.
[0042]
The present invention A first substrate, a first display electrode and a second display electrode disposed on the first substrate, a second substrate disposed opposite the first substrate, and applying a desired voltage to each electrode Each of the pixels arrayed in a matrix, comprising: a transparent insulating liquid filled between the first substrate and the second substrate; and a plurality of colored electrophoretic fine particles dispersed in the transparent insulating liquid. By moving the colored charged electrophoretic particles between the first display electrode and the second display electrode by simple matrix driving, using the first display electrode and the second display electrode as the first scan electrode and the second scan electrode, respectively. In an electrophoretic display device that switches display,
As an electrode for controlling the movement of the colored charged electrophoretic particles, Perpendicular to scan electrode direction A first control electrode disposed on the second substrate; Similarly, perpendicular to the scan electrode direction, A second control electrode disposed on a boundary portion between the first display electrode and the second display electrode on the first substrate; Pixels to which a scanning bias is sequentially selected and a driving bias for moving the colored charged electrophoretic particles is applied to either the first scanning electrode or the second scanning electrode, and the display on the selected scanning line is to be maintained The second control electrode is applied with a voltage in a direction separating the colored charged electrophoretic particles from the second control electrode on the first and second display electrodes. The colored charged electrophoretic particles are pressed against the first and second display electrodes against the first control electrode Direction Voltage Apply This is an electrophoretic display device.
[0043]
It is preferable that a barrier or a step is provided at a boundary portion between the first display electrode and the second display electrode, and the second control electrode is disposed at a tip portion of the barrier or an edge portion of the step.
[0044]
The colored charged electrophoretic particles can enter and exit the display electrode surface located on the upper side adjacent to the step, and a shielding space is formed that is invisible to the display surface observer. Is preferred.
[0045]
A voltage signal applied to the first display electrode, the second display electrode, the first control electrode, and the second control electrode in order for the colored charged electrophoretic particles to move between the display electrodes causes the colored charged electrophoretic particles to be controlled in the second control. The composite signal is preferably composed of a first period for moving to the electrode and a second period for moving the colored charged electrophoretic particles concentrated on the second control electrode to the target display electrode.
[0047]
In order to cause the migration of colored electrophoretic particles consisting of the above two processes,
(A) In the case of positively charged colored charged electrophoretic particles, “the potential of both display electrodes and the potential of the first control electrode> the potential of the second control electrode” in the first process, “in the second process,“ The potential of the display electrode before movement and the potential of the first control electrode ≧ the potential of the second control electrode> the display electrode of the movement destination ”
(B) In the case of negatively charged colored electrophoretic particles, “the potential of both display electrodes and the potential of the first control electrode <the potential of the second control electrode” in the first process, and “the potential of the second control electrode” in the second process. In order to satisfy the relationship of the potential of the display electrode before movement and the potential of the first control electrode ≦ the potential of the second control electrode <the display electrode of the movement destination ”
It is preferable to apply a voltage to the first display electrode, the second display electrode, and the control electrode.
[0048]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the electrophoretic display device (hereinafter referred to as a display device) of the present invention will be described in order.
[0049]
(Basic configuration and operation of typical embodiment)
FIG. 1 is a cross-sectional view showing a typical example of the display device of the present invention. FIG. 1 shows a configuration composed of two pixels for convenience of explanation. A first display electrode 4 and a second display electrode 3 are disposed on the first substrate 1, and a second substrate 2 is disposed opposite to the first substrate 1 with a partition wall 10 interposed therebetween. A prominent feature of the present invention is that it has two control electrodes. The first control electrode 5 is disposed on the second substrate, and the second control electrode 13 is disposed at the boundary between the first display electrode 4 and the second display electrode 3 on the first substrate. A voltage can be applied independently to each control electrode. A space formed by both the substrates and the partition walls is filled with a transparent insulating liquid 7, and colored charged electrophoretic particles 6 are dispersed in the transparent insulating liquid. Reference numeral 20 denotes a drive driver. In this embodiment, it is preferable to use, for example, a colorless and transparent insulating liquid as the transparent insulating liquid.
[0050]
The planar shape of the display electrode is not particularly limited, and an arbitrary shape such as a square shape (FIG. 2B) or a closed loop shape such as a circle can be applied in addition to a typical stripe shape (FIG. 2A). . In any shape, the second control electrode 13 is formed in the boundary region between the first display electrode 4 and the second display electrode 3.
[0051]
The specific size of the configuration of FIG. 1 includes, for example, a pixel size of 100 μm × 100 μm, an electrophoretic particle diameter of 5 μm, a distance between the first substrate and the second substrate of 70 μm, and an area ratio of each electrode to the total pixel area. A display electrode of 25%, a second display electrode of 70%, and a second control electrode of about 5% are preferable.
[0052]
The color arrangement of the cell constituent members can be arbitrarily combined. For example, the electrophoretic particles 6 are black, the first display electrode 4 is black, the second display electrode 3 is white, the second control electrode 13 is white, and the first control electrode 5 When combined with transparent, white display and black display can be switched. Colored display can also be performed by arranging pixels in which the coloring of the second display electrode 3 and the second control electrode 13 is RGB.
[0053]
The features of the present invention will be described below with reference to FIGS. 3 and 4 and a simple matrix driving method for the configuration of this embodiment.
In the following description, the charged polarity of the migrating particles 6 is positive, the drive voltage Vdl is applied to the first display electrode 4, the drive voltage Vd2 is applied to the second display electrode 3, the control voltage Vcl is applied to the first control electrode 5, and the control voltage Vcl is applied to the second control electrode 13. It is assumed that the control voltage Vc2 is applied. In the figure, an arrow indicates an outline of an electric field vector in the cell.
[0054]
Consider a horizontally-moving electrophoretic display device having an m × n matrix in which pixels are arranged in m columns in the X direction and n rows in the Y direction. Along the pixel arrangement, m signal electrode lines are arranged in the column direction and n signal electrode lines are arranged in the row direction so as to be orthogonal to each other, and at each intersection, the signal electrode lines are control electrodes of each pixel. The first scanning electrode line is wired to the first display electrode in each pixel, and the second scanning electrode line is wired to the second display electrode in each pixel.
[0055]
First, Vdl = −50V is applied to the first display electrode, Vd2 = 0V is applied to the second display electrode, Vcl = 0V is applied to the first control electrode, and Vc2 = 0V is applied to the second control electrode. The entire surface collected on one display electrode 4 is reset to a white display state (FIG. 3A).
[0056]
Next, scanning lines are selected and written in order from the top in the Y direction. First, in the selection period, Vdl = + 50 V is applied to the first scan line, Vd2 = 0 V is applied to the second scan line, a drive bias is generated between the display electrodes, and at the same time, a selected pixel to be switched to black display (FIG. 3 ( Vcl = + 60V is applied to the first signal line corresponding to b)), and Vc2 = 50V is applied to the second signal line. By setting the second control electrode 13 to the same potential as the first display electrode 4, the migrating particles 6 are moved to the second display electrode according to the driving bias in the same manner as in the conventional example (FIG. 24B). The first control electrode is applied with a voltage Vcl = + 60V which is + 10V higher than Vdl and Vcl for the holding operation in the non-selected line. The influence of this control bias (+ 10V) on the migration of the migrating particles due to the drive bias is Almost no.
[0057]
Further, Vcl = + 120 V is applied to the first signal line corresponding to the non-selected pixels, and Vc2 = 70 V is applied to the second signal line (FIG. 3C). Since Vdl <Vc2, the migrating particles 6 are driven to move to the second display electrode 3 as shown in FIG. 23 (c), which was a problem in the first configuration of JP-A-8-507154. There is no bias. On the other hand, as was a problem in the second configuration of JP-A-8-507154 (FIG. 24A), the migrating particles 6 are placed on the first display electrode by a bias of Vdl−Vc2 = −20V. In the present invention, since the electric field vector component in the direction of pressing against the display electrode surface is generated by Vcl = + 120 V applied to the first control electrode in the present invention, migration occurs. The particles 6 can stably maintain the white display state without moving.
[0058]
On the other hand, in the non-selection period, Vdl = Vd2 = + 50 V is applied to both the first scan line and the second scan line. At the same time, Vcl = + 60 V is applied to the first signal line and Vc2 = 50 V is applied to the second signal line to the first signal line corresponding to the selected pixel column (FIGS. 4D and 4F). In this state, the migrating particles 6 are gently pressed against the display electrode surface by the +10 V control bias generated between the first control electrode 5 and each electrode on the first substrate, and the display state is maintained.
[0059]
Further, Vcl = + 120 V is applied to the first signal line corresponding to the non-selected pixel column, and Vc2 = + 70 V is applied to the second signal line (FIGS. 4E and 4G). As in the case of FIG. 3C, the migrating particles 6 try to move in the direction away from the second control electrode on each display electrode by the bias of Vdl−Vc2 = −20V. Since the electric field vector component in the direction of pressing against the display electrode surface is generated by Vcl = + 120 V applied to the control electrode, the migrating particles 6 can stably hold each display state without moving.
[0060]
As described above, in the present invention, the different types of problems of the first configuration and the second configuration disclosed in Japanese Patent Publication No. 8-507154 regarding the display holding operation of the non-selected pixels are solved. By introducing each other, it becomes possible to complement each other and effectively solve the problem.
[0061]
In the present invention, the control voltage required to hold the migrating particles can be greatly reduced. In the first configuration of JP-A-8-507154, even if the control voltage Vc is + 250V, it was insufficient. can do.
[0062]
In this way, in the horizontal movement type electrophoresis apparatus according to the present invention, display with high contrast can be formed without crosstalk by performing simple matrix driving.
[0063]
(Configuration and operation of other representative embodiments)
Next, FIG. 5 shows a cross-sectional view of another typical configuration of the present invention. FIG. 5 shows a configuration composed of two pixels for convenience of explanation. In FIG. 5, the first display electrode and the second display electrode are disposed on the first substrate, the second substrate 2 is disposed to face the first substrate through the partition wall 10, and the second substrate 2 is disposed on the second substrate 2. One control electrode 5 is formed. Between the 1st display electrode 4 and the 2nd display electrode 3, the barrier 11 which is the characteristics of this structure is arrange | positioned, and the 2nd control electrode 13 is arrange | positioned at the front-end | tip part of this barrier 11. FIG. A space formed by both the substrates and the partition walls is filled with a transparent insulating liquid 7, and colored charged electrophoretic particles 6 are dispersed in the transparent insulating liquid 7. The color arrangement of the cell constituent members is the same as in FIG.
[0064]
A prominent feature of the configuration in the present embodiment is that the barrier 11 has a height of several times to several tens of times, preferably 3 to 10 times the particle diameter of the migrating particles. By providing a sufficiently high barrier, it is possible to substantially prevent the migrating particles 6 from moving horizontally between the display electrodes along the electrode surface. In addition, the high barrier allows the migrating particles to be held without overflowing even when the area of the display electrode is small, so that a large area difference can be set between the first display electrode and the second display electrode, and the display contrast is greatly increased. It can be improved.
[0065]
The particle diameter of the migrating particles is 0.1 to 20 μm, preferably 0.5 to 10 μm.
[0066]
Although it is desirable that the area ratio between the first display electrode 4 and the second display electrode 3 is larger, the display electrode having the smaller area (the first display electrode 4 in the case of FIG. 5), the barrier 11, and the partition 10 (or barrier). It is necessary that all the migrating particles in the pixel are stored in the enclosed space. Accordingly, the area ratio can be increased and the display contrast can be increased as the barrier 11 is increased.
[0067]
Specific sizes of the configuration of FIG. 5 include, for example, a pixel size of 100 μm × 100 μm, an electrophoretic particle diameter of 5 μm, an interval between the first substrate and the second substrate of 80 μm, a barrier height of 40 μm, and an area ratio with respect to the total pixel area. For example, the first display electrode is 15%, the second display area is 80%, and the barrier is about 5%.
[0068]
Next, the writing operation, which is a prominent feature of the driving method of the present invention, will be described with reference to FIGS. FIG. 6 shows the operating state of the migrating particles in each process, and FIG. 7 shows the applied pulse and the reflectance change in each process. The cell configuration is the same as in FIG. 5 (however, one pixel).
[0069]
In the following description, the charged polarity of the migrating particles 6 is positive, the drive voltage Vdl is applied to the first display electrode 4, the drive voltage Vd2 is applied to the second display electrode 3, the control voltage Vcl is applied to the first control electrode 5, and the control voltage Vcl is applied to the second control electrode 13. It is assumed that the control voltage Vc2 is applied.
[0070]
The period Ta is in the white display holding state. In FIG. 6, an arrow indicates an outline of the electric field vector in the cell. All the migrating particles 6 are accommodated in a space surrounded by the first display electrode 4, the barrier 11, and the partition wall 10, and are applied by a holding voltage applied between the first display electrode 4 and the first control electrode 5. Pressed against the display electrode side, the white display state with a reflectance of about 85% is stably maintained.
[0071]
In the present invention, the direct horizontal movement of the migrating particles to the second display electrode 3 side is almost completely prohibited by the barrier 11, so that the migrating is compared with the configuration of JP-A-8-507154. It is possible to greatly reduce the control voltage for prohibiting the movement of particles and maintaining the display state.
[0072]
Writing is performed in the periods Tbl and Tb2. First, in the period Tbl, Vdl = vd2 = Vcl = 0V and Vc2 = −50V are applied, and all the migrating particles 6 are moved to the second control electrode arranged at the tip of the barrier 11.
[0073]
Next, Vdl = Vcl = + 100 V, Vc2 = + 50 V, and Vd2 = 0 V are applied in the period Tb2, and the migrating particles 6 collected on the second control electrode in the period Tbl are moved to the second display electrode. At this time, since a bias of +50 V is applied to the first display electrode 4 with respect to the second control electrode 13, all the migrating particles 6 do not return to the first display electrode side and pass over the barrier 11. It moves to the second display electrode side, and the reflectance R decreases rapidly.
[0074]
The period Tc is in the black display holding state, and the migrating particles 6 that have moved to the second display electrode side are pressed to the display electrode side by the holding voltage applied between the second display electrode 3 and the first control electrode 5, A black display state with a reflectance of about 10% is stably maintained.
[0075]
Next, a simple matrix driving method according to this embodiment will be described with reference to FIGS. Consider a horizontally-moving electrophoretic display device having an m × n matrix as in FIGS. In FIG. 3 and FIG. 4, the case where the scanning line is wired to the display electrode, the signal line is wired to the control electrode, the entire surface is initially reset, and writing is performed for each line in only one direction has been described. In the aspect, the first scan line is wired to the first control electrode, the second scan line is wired to the second control electrode, the first signal line is wired to the first display electrode, and the second signal line is wired to the second display electrode. A case where writing is performed bidirectionally for each line will be described. In this case, an initial full reset is unnecessary.
[0076]
Writing is performed by selecting scanning lines in order from the top in the Y direction and applying a signal voltage for white display or black display according to display data.
[0077]
In the selection period, Vcl = 0 V (period Tb1) / + 100 V (period Tb2) is applied to the first scan line, and Vc2 = −50 V / + 50 V is applied to the second scan line. At the same time, Vdl = 0V / + 100V is applied to the first signal line corresponding to the pixel (FIG. 8A) that performs black display writing, and Vd2 = 0V / 0V is applied to the second signal line. Further, Vdl = 0V / 0V is applied to the first signal line corresponding to the pixel (FIG. 8B) that performs white display writing, and Vd2 = 0V / + 100V is applied to the second signal line. The write operation is already described in FIG. 6 and FIG.
[0078]
On the other hand, in the non-selection period, Vcl = + 50 V / + 150 V is applied to the first scan line, and Vc2 = 0 V / + 100 V is applied to the second scan line. As for the signal line, Vdl = 0V / + 100V is applied to the first signal line and Vd2 = 0V / 0V is applied to the second signal line as the black display write signal as in the selection period (FIGS. 9C and 9C). d)). Further, Vdl = 0V / 0V is applied to the first signal line and Vd2 = 0V / + 100V is applied to the second signal line as white display write signals (FIGS. 10E and 10F). In any case, the migrating particles 6 stably hold the display state by the holding voltage biased between the first control electrode and each display electrode.
[0079]
(Configuration variations)
The configuration of the present invention is not limited to the type shown in FIG. Hereinafter, configurations effective in the present invention will be described in order with reference to the drawings.
[0080]
FIG. 11A shows a type in which the barrier is a step. The second control electrode is disposed at the edge of the step. The driving method is the same as in FIG. 5, but writing is limited to only one direction. The height of the step 12 is several times to several tens of times the diameter of the migrating particles, specifically 3 to 10 times, and is characterized by having a function of substantially prohibiting horizontal movement of the migrating particles. The height difference and the function are different from the level difference proposed in Table 8-8507154.
[0081]
FIG. 11B shows a configuration in which the second display electrode surface 3 having a large area is arranged at a position higher than the first display electrode surface 4 as a modification of FIG. When the display electrode surface is observed obliquely in the configuration of FIG. 5, a region where the barrier 11 blocks the field of view occurs on the display electrode surface. This is particularly noticeable on the second display electrode surface 3 where the distance between the tip of the barrier 11 where the second control voltage is disposed and the upper end of the filling surface of the migrating particles 6 is large. The barrier 11 and the second control electrode are connected to the transparent member. Even if it comprises, it may affect the display viewing angle characteristic somewhat. By disposing the second display electrode surface 3 having a large area at a position higher than the l-th display electrode surface 4, the distance between the upper end of the filling surface and the barrier tip in the second display electrode surface 3 is approximately the same as that of the first display electrode. It becomes possible to align. This configuration also has the effect of making the migrating particles 6 on the outermost surfaces of the first display electrode surface 4 and the second display electrode surface 3 difficult to move in the horizontal direction.
[0082]
FIG. 12 shows a variation of the step type shown in FIG. Filling the migrating particles on the first display electrode surface by forming a shielding space 15 that is invisible to the viewer of the display surface on the stepped wall surface on the lower side of the second display electrode surface 3 located on the upper side. Simultaneously with increasing the volume, the effective area ratio between the first display electrode 4 and the second display electrode 3 can be apparently increased to improve display contrast. For example, the shielding space 15 can be formed by a configuration in which the step cross section has an inverted taper shape (FIG. 12A) and an overhang shape (FIG. 12B).
[0083]
In the above description, for the sake of convenience of explanation, a configuration in which a pair of the first display electrode and the second display electrode is arranged in one pixel has been shown. However, in the present invention, the number of electrodes in one pixel is not particularly limited. It goes without saying that a configuration in which a plurality of display electrode pairs is arranged is possible. FIG. 13 shows a configuration in which two electrode pairs are arranged in one pixel. 13A corresponds to the type of FIG. 1, and FIG. 13B corresponds to the type of FIG. In either case, the second control electrode and the barrier are formed at all boundaries between the first display electrode and the second display electrode.
[0084]
(Constituent materials and manufacturing methods)
Hereinafter, the manufacturing method of the display apparatus of this embodiment is demonstrated using FIG.
First, the first display electrode 4 and the second display electrode 3 are formed on the first substrate 1 and patterned. Similarly, the first control electrode 5 is formed on the second substrate 2 and patterned. As a substrate material, a polymer film such as polyethylene terephthalate (PET) or polyethersulfone (PES) or an inorganic material such as glass or quartz can be used. The display electrode material may be any conductive material that can be patterned, and a transparent electrode such as indium tin oxide (ITO) is used as the first control electrode material.
[0085]
Next, an insulating layer is formed on the display electrode. As a material for the insulating layer, a thin film is difficult to form pinholes and a low dielectric constant material is preferable. For example, amorphous fluororesin, highly transparent polyimide, PET, or the like can be used. The thickness of the insulating layer is preferably about 100 nm to 1 μm.
[0086]
Subsequently, the second control electrode 13 is formed on the insulating layer and patterned. The second control electrode material may be any conductive material that can be patterned. For example, a transparent electrode such as indium tin oxide (ITO) is used. The color of the second control electrode 13 may be transparent, but may be matched with either the first display electrode or the second display electrode.
[0087]
For the coloring of the display electrode surfaces 3 and 4 and the second control electrode surface 13, the color of the electrode material or the insulating layer material itself formed on the electrode material may be used, or a material layer of a desired color may be used. You may form on an electrode, an insulating layer, and a substrate surface. Further, a coloring material may be mixed in the insulating layer or the like.
[0088]
Next, insulating layers 8 and 9 are formed on the first control electrode 5 and the second control electrode 13, respectively. The material and film thickness of the insulating layer are as described above.
[0089]
Next, the partition 10 is formed on the second substrate. Although there is no restriction | limiting in the arrangement | positioning of the partition 10, It is good to arrange | position so that the periphery of each pixel may be surrounded so that the migrating particle 6 may not move between pixels. Polymer resin is used as the partition wall material. Any method may be used to form the partition walls. For example, after applying a photosensitive resin layer, a method of performing exposure and wet development, a method of bonding a separately produced barrier, a method of forming by a printing method, or a mold on the surface of a light-transmitting first substrate. For example, a method of forming them can be used.
[0090]
Next, the transparent insulating liquid 7 and the colored charged electrophoretic particles 6 are filled in each pixel space surrounded by the partition walls. As the insulating liquid 7, a colorless transparent liquid such as silicone oil, toluene, xylene, high-purity petroleum or the like is used. As the black charged electrophoretic particles 6, a material that exhibits good charging characteristics in an insulating liquid is used. For example, a resin such as polyethylene or polystyrene mixed with carbon is used. Although there is no restriction | limiting in the particle size of the migrating particle 6, Usually, about 0.1-20 micrometers, Preferably about 0.5-10 micrometers is used.
[0091]
Finally, after an adhesive layer is formed on the bonding surface of the first substrate 1 to the second substrate 2, the first substrate and the second substrate are aligned and bonded by applying heat. A voltage application means is connected to this to complete the display device.
[0092]
Next, it supplements about the manufacturing method of a structure with a barrier or a level | step difference as shown in FIG.5, FIG.11, FIG.12. After forming the display electrode and the insulating layer on the first substrate, the barrier 11 or the step 12 is formed. The barrier or the step can be formed using a material and a formation method similar to those for forming the partition wall. However, the second control electrode 13 and the second display electrode 3 need to be formed on the barrier tip or on the upper surface of the step.
[0093]
For example, in the case of a barrier, the barrier thick film, the second control electrode film, and the resist film are sequentially formed on the entire surface, and then the uppermost resist film is patterned, and the second control electrode film and the step thick film are sequentially dried. Etching or wet etching may be performed. As the second display electrode film, ITO may be formed at a low temperature by a magnetron sputtering method, or an organic conductive material such as polyaniline may be formed by a printing method.
[0094]
In the case of a step, after forming the step thick film, the second display electrode film and the second control electrode film are formed and patterned, and then a resist film is newly formed and patterned, thereby forming the step thick film. May be dry-etched or wet-etched. Further, by adjusting the etching method and conditions, a step having a cross-section with an inverse taper shape (FIG. 12A) or an overhang shape (FIG. 12B) as shown in FIG. 12 is formed. Can do.
[0095]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples.
[0096]
Example 1
In the present embodiment, a 3 × 3 matrix display cell was created using the cell configuration shown in FIG. 1, and simple matrix driving by one-way writing was performed.
[0097]
FIG. 14 shows a plan view of the created 3 × 3 matrix display cell. One pixel size was 1 mm × 1 mm, and the area ratio of the first display electrode, the second control electrode, and the second display electrode was 20: 5: 75.
[0098]
Hereinafter, a method for manufacturing a cell will be briefly described with reference to FIGS. On the first substrate 1 made of a PET film having a thickness of 200 μm, an insulating colored layer made of an acrylic resin in which a white pigment such as alumina was dispersed was first formed on the entire surface. Next, ITO was deposited at a low temperature as the second display electrode 3 and patterned into a shape shown in FIG. 14 by photolithography and dry etching. Next, a dark black titanium carbide film was formed as the first display electrode 4 and patterned in the same manner.
[0099]
Next, an insulating layer made of acrylic resin was formed on the display electrode to a thickness of 1 μm. Subsequently, a dark black titanium carbide film was formed as the second control electrode 13 and patterned in the same manner. Next, an insulating layer 8 made of amorphous fluororesin was formed to a thickness of 200 nm on the entire surface.
[0100]
Subsequently, ITO was deposited at a low temperature as the control electrode 5 on the second substrate 2 made of a PET film, and then patterned into the shape shown in FIG. Next, an insulating layer 9 made of amorphous fluororesin was formed to a thickness of 200 nm on the entire surface. On this, the partition 10 was formed. The partition wall 10 was formed by applying a photosensitive epoxy resin, and then performing exposure and wet development to a height of 70 μm. The formed partition walls were filled with the transparent insulating liquid 7 and the black charged electrophoretic particles 6.
[0101]
As the insulating liquid 7, silicone oil was used. As the black charged electrophoretic particles 6, a mixture of polystyrene and carbon having an average particle size of about 5 μm was used. The migrating particles 6 in the silicone oil showed positive charge polarity. Next, a heat-bonding adhesive layer pattern is formed on the adhesive surface of the first substrate 1 to the second substrate 2, and the first substrate 1 is placed on the partition wall of the second substrate 2 while performing alignment. Laminate with heat. A voltage application circuit (not shown) was connected to this to obtain a display device.
[0102]
Hereinafter, the driving method in the present embodiment will be described.
The first display electrode is the first scan line (S11 to S13), the second display electrode is the second scan line (S21 to S23), the first control electrode is the first signal line (I11 to I13), and the second control electrode is The second signal lines (I21 to I23) were used.
[0103]
FIG. 15A shows a time chart of drive pulses applied to each scanning line and signal line, and FIG. 15B shows a change in display state in each period. One scanning line selection period (TR, Tl, T2, T3) was set to 50 msec.
[0104]
In the driving, first, the entire surface is reset to white display, and then, for each scanning line, the selected pixels (1, 2), (2, 1), (2, 3), (3 corresponding to the set display pattern. , 2), writing was performed in one direction (white display → black display). In this embodiment, writing is performed by the driving method described with reference to FIGS. The detailed operation of the migrating particles at the time of writing is the same as in FIGS.
[0105]
Hereinafter, the driving method will be described in order according to the time chart. In the period TR, Vdl = −50V for all the first scan lines Sll to S13, Vd2 = 0V for all the second scan lines S21 to S23, and for all the first signal lines I11 to I13. Vcl = 0V, Vc2 = 0V was applied to all the second signal lines I21 to I23, and all the pixels were reset to white display.
[0106]
Next, in the period Tl, Vdl = + 50V and Vd2 = 0V are applied to the selected scanning lines Sll and S21, and Vdl = + 50V and Vd2 = 0V are applied to the non-selected scanning lines Sl2, S22, S13, and S23. Then, Vcl = + 60V is applied to the first signal line I12 corresponding to the selected pixel (1,2), Vc2 = + 50V is applied to the second signal line I22, and the non-selected pixels (1,1), (1,3) are applied. Vcl = + 120V was applied to the corresponding first signal lines I11 and I13, and Vc2 = + 70V was applied to the second signal lines I21 and I23. As a result, only the selected pixel (1, 2) on the selected scanning line is rewritten to black display, and white display is performed on the non-selected pixel (1, 1), (1, 3) and each pixel on the non-selected scanning line. Retained.
[0107]
Hereinafter, as a result of performing the same driving in accordance with the selected pixel pattern in the periods T2 and T3, the target display pattern was obtained with good contrast. In the obtained display, there is no crosstalk phenomenon, no deterioration of contrast due to poor migration and retention of the migrating particles, and the average contrast of white display and black display shows a high value of about 10: 1. It was. The maximum control voltage required for driving was + 120V.
[0108]
Example 2
In this embodiment, a 3 × 3 matrix display cell having the cell configuration shown in FIG. 5 was created, and simple matrix driving by bidirectional writing was performed. Since the configuration of FIG. 5 is used, the movement of the electrophores in the horizontal direction can be prohibited in both directions, and therefore writing is performed in both directions of black display → white display and white display → black display. Can do. Bidirectional writing drive is difficult with the first configuration disclosed in Japanese Patent Laid-Open No. 8-507154, and is one of the features of the present invention in which the barrier structure is symmetric.
[0109]
FIG. 16 shows a plan view of the created 3 × 3 matrix display cell. One pixel size was 1 mm × 1 mm, and the area ratio of the first display electrode, the second control electrode, and the second display electrode was 18: 5: 77.
[0110]
Hereinafter, a method for manufacturing a cell will be briefly described with reference to FIGS. On the first substrate 1 made of a PET film having a thickness of 200 μm, an insulating colored layer made of an acrylic resin in which a white pigment such as alumina was dispersed was first formed on the entire surface. Next, ITO was deposited at a low temperature as the second display electrode 3 and patterned into the shape shown in FIG. 16 by photolithography and dry etching. Next, a dark black titanium carbide film was formed as the first display electrode 4 and patterned in the same manner.
[0111]
Next, an epoxy resin is applied to a thickness of 30 μm, a dark black titanium carbide film is subsequently formed as a second control electrode film, and then a resist film is applied to form a pattern as shown in FIG. Ning and finally CF ₄ And O ₂ Reactive dry etching with gas was performed to form a structure in which the second control electrode 13 made of titanium carbide was disposed on the barrier 11 having a height of 30 μm. Next, an insulating layer 8 made of amorphous fluororesin was formed to a thickness of 200 nm on the entire surface.
Since the following process is the same as that of Example 1, description is abbreviate | omitted.
[0112]
Next, the driving method in the present embodiment will be described.
The first control electrode is the first scan line (S11 to S13), the second control electrode is the second scan line (S21 to S23), the first display electrode is the first signal line (I11 to I13), and the second display electrode is The second signal lines (I21 to I23) were used (FIG. 16).
[0113]
FIG. 17A shows a time chart of drive pulses applied to each scanning line and signal line, and FIG. 17B shows a change in display state in each period. In this embodiment, writing is performed by the driving method described with reference to FIGS. The selection period per scan line was 30 msec in the first half of the period and 30 msec in the second half of the period. Detailed operation of the migrating particles at the time of writing is the same as in FIGS.
[0114]
In this embodiment, since bidirectional writing is possible, it is not necessary to reset the entire surface as an initial operation. Therefore, a pattern shown in the period T0 is given as an initial display pattern, and all pixels are displayed in reverse for each scanning line (S1 to S3).
[0115]
Hereinafter, the driving method will be described in order according to the time chart. In the period Tl, the first scanning line is selected, and Vcl = 0 V (first half period Tll) / + 100 V (second half period Tl2) is applied to S1l, and Vc2 = −50 V / + 50 V is applied to S21. Vcl = + 50 / + 200V is applied to a certain Sl2, S13, Vc2 = 0V / + 100V is applied to S22, S23, and at the same time, a first signal corresponding to the pixels (1,1), (1,3) Vdl = 0V / 0V and Vd2 = 0V / + 100V are applied to the lines I11 and I13 and the second signal lines I21 and I23 as white display write pulses, respectively, and the first signal line corresponding to the pixel (1,2) Vdl = 0V / + 100V and Vd2 = 0V / 0V are applied to I12 and the second signal line I22 as black display write pulses, respectively. It was. As a result, all the pixels on the selected scanning line in the first row were rewritten and displayed in reverse video. In addition, the initial display state is maintained in each pixel on the non-selected scanning lines in the second and third rows.
[0116]
Hereinafter, as a result of performing the same driving in the periods T2 and T3, the intended reverse display pattern was obtained with good contrast. In the obtained display, there is no crosstalk phenomenon, no deterioration in contrast due to poor migration or retention of migrating particles, and the average contrast of white display and black display shows a high value of about 12: 1. It was. The maximum control voltage required for driving was + 200V.
[0117]
Comparative Example 1
As Comparative Example 1, a 3 × 3 matrix display cell was created with the cell configuration shown in FIG. 18A disclosed in JP-A-8-507154, and simple matrix driving by one-way writing was performed.
[0118]
A plan view of the created 3 × 3 matrix display cell is shown in FIG. One pixel size is 1 mm × 1 mm, the area ratio of the first display electrode to the second display electrode is 35:65, the distance between the first substrate and the second substrate is 70 μm, the step height is 5 μm, and the positively charged electrophoretic particles have an average particle diameter of 5 μm. Was used. The color arrangement of the display electrode and the migrating particles is the same as in FIG.
[0119]
Hereinafter, a method for manufacturing a cell will be briefly described with reference to FIGS. On the first substrate 1 made of a PET film having a thickness of 200 μm, an insulating colored layer made of an acrylic resin in which a white pigment such as alumina was dispersed was first formed on the entire surface. Next, a dark black titanium carbide film was formed as the first display electrode 4 and patterned into the shape shown in FIG. 25 by photolithography and dry etching.
[0120]
Next, an epoxy resin was applied to a thickness of 5 μm, and then an ITO thin film was formed as a second display electrode at a low temperature by a magnetron sputtering method. Subsequently, a resist film is applied and patterned into a shape as shown in FIG. ₄ And O ₂ Reactive dry etching with gas was performed to form a structure in which a second display electrode made of ITO was disposed on a step having a height of 5 μm. Next, the green layer 8 made of amorphous fluororesin was formed to a thickness of 200 nm on the entire surface.
[0121]
Subsequently, after forming ITO as a control electrode 5a at a low temperature on the second substrate 2 made of PET film, it is patterned into the shape shown in FIG. 25, and then an insulating layer 9 made of amorphous fluororesin is formed on the entire surface with a thickness of 200 nm. Formed. On this, the partition 10 was formed. The partition wall 10 was formed by applying a photosensitive epoxy resin, followed by exposure and wet development, and had a height of 70 μm. The formed partition walls were filled with the transparent insulating liquid 7 and the black charged electrophoretic particles 6.
[0122]
Silicone oil was used as the transparent insulating liquid 1. The black charged electrophoretic particles 6 were a mixture of polystyrene and carbon as in Example 1 and had an average particle size of about 5 μm. The migrating particles 6 in the silicone oil showed positive charge polarity. Next, a heat-bonding adhesive layer pattern is formed on the adhesive surface of the first substrate 1 to the second substrate 2, and the first substrate 1 is placed on the partition wall of the second substrate 2 while performing alignment. Laminate with heat. A voltage application circuit (not shown) was connected to this to obtain a display device.
[0123]
Hereinafter, the driving method will be described. The first display electrode was a scan line (S1 to S3), the control electrode was a signal line (I1 to I3), and the second display electrode was fixed to a ground potential as a common electrode.
[0124]
FIG. 26A shows a time chart of drive pulses applied to each scanning line and signal line, and FIG. 26B shows a change in display state in each period. One scanning line selection period (TR, Tl, T2, T3) was set to 50 msec.
[0125]
In the driving, first, the entire surface is reset to white display, and then, for each scanning line, the selected pixels (1, 2), (2, 1), (2, 3), (3 corresponding to the set display pattern. , 2), writing was performed in one direction (white display → black display). In this comparative example, writing was performed by the driving method described with reference to FIGS. 19, 20, 21, and 22. Detailed operations of the migrating particles at the time of writing are the same as those in FIGS.
[0126]
Hereinafter, the driving method will be described in order according to the time chart. In the period TR, Vd = −50 V is applied to all the scanning lines S1 to S3, Vc = 0 V is applied to all the signal lines I1 to I3, and all pixels are reset to white display.
[0127]
Next, in a period Tl, Vd = + 50 V is applied to the selected scanning line S1 and Vd = + 5 V is applied to the non-selected scanning lines S2 and S3, and the signal line corresponding to the selected pixel (1, 2). 12 was applied with Vc = + 50 V, and Vc = + 250 V was applied to the signal lines I1 and I3 corresponding to the non-selected pixels (1, 1) and (1, 3). As a result, only the selected pixel (1, 2) of the selected scanning line S1 is rewritten to black display, and the non-selected pixels (1, 1), (1, 3) and each pixel in the non-selected scanning lines S2, S3 are rewritten. The white display was retained. However, in the non-selected pixels (1, 1) and (1, 3), the migrating particles are not sufficiently suppressed by the control voltage Vc = + 250V, and some of the migrating particles are not shown in FIG. It moved to the 2nd display electrode side, and it became a grayish display as shown in FIG.26 (b).
[0128]
Hereinafter, as a result of performing the same drive according to the selected pixel pattern in the periods T2 and T3, the target display pattern was obtained, but the white display was generally grayish and the display contrast was poor. The average contrast between white display and black display was about 3: 1. Moreover, although the control voltage used in this comparative example was + 250V, it was still insufficient and needed to be further increased.
[0129]
【The invention's effect】
As described above in detail, the present invention has the following effects.
First, a simple matrix drive capable of obtaining a good display contrast without a crosstalk phenomenon in a horizontal movement type electrophoresis apparatus was realized. This is because the occurrence of crosstalk due to defective holding of electrophoretic particles in non-selected pixels, which has been a problem in the past, has been almost completely suppressed by the novel configuration and driving method.
[0130]
Second, by introducing two different control electrodes, the control voltage required to hold the migrating particles can be greatly reduced.
Thirdly, in a configuration in which a high barrier or a step is introduced, the area ratio between the first display electrode and the second display electrode can be set larger than in the past. As a result, a further improvement in contrast was realized for reasons other than crosstalk suppression.
[0131]
Fourth, it has become possible to perform bidirectional write driving. For this reason, there is no need for an initial full-reset, and partial rewriting driving for rewriting only a part of the display screen can be performed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a typical example of a display device of the present invention.
FIG. 2 is a plan view showing a typical example of a display device of the present invention.
FIG. 3 is a diagram showing an example of a simple matrix driving method of the display device of the present invention.
4 is a diagram showing another part of the simple matrix driving method of the display device of FIG. 3; FIG.
FIG. 5 is a cross-sectional view showing another example of the display device of the present invention.
FIG. 6 is a diagram illustrating an example of a driving method and an operation state of a display device of the present invention.
7 is a diagram showing another part of the driving method and operation state of the display device of FIG. 6; FIG.
FIG. 8 is a diagram showing another example of the simple matrix driving method of the display device of the present invention.
9 is a diagram showing another part of the simple matrix driving method of the display device of FIG. 8. FIG.
10 is a diagram showing another part of the simple matrix driving method of the display device of FIG. 8. FIG.
FIG. 11 is a cross-sectional view showing another example of the display device of the present invention.
FIG. 12 is a cross-sectional view showing another example of the display device of the present invention.
FIG. 13 is a cross-sectional view showing another example of the display device of the present invention.
14 is a plan view showing a 3 × 3 matrix created in Example 1 of the present invention. FIG.
FIG. 15 is a diagram showing a time chart and display pattern of driving performed in Example 1 of the present invention.
FIG. 16 is a plan view showing a 3 × 3 matrix created in Example 2 of the present invention.
FIG. 17 is a diagram showing a time chart and a display pattern of driving performed in Example 2 of the present invention.
FIG. 18 is a cross-sectional view showing a display device in a conventional example.
FIG. 19 is a diagram illustrating a driving method and an operation state of a display device in a conventional example.
20 is a diagram showing another part of the driving method and the operation state of the display device of FIG. 19;
FIG. 21 is a diagram showing a simple matrix driving method of a display device in a conventional example.
22 is a diagram showing another part of the simple matrix driving method of the display device of FIG. 21. FIG.
FIG. 23 is an explanatory diagram showing a problem of a display device in a conventional example.
FIG. 24 is an explanatory diagram showing another problem of the display device in the conventional example.
25 is a plan configuration diagram showing a 3 × 3 matrix created in Comparative Example 1. FIG.
FIG. 26 is a diagram showing a time chart and display pattern of driving performed in Comparative Example 1;
[Explanation of symbols]
1 First substrate
2 Second substrate
3 Second display electrode
4 First display electrode
5 First control electrode
5a Control electrode
6 Electrophoretic particles
7 Transparent insulating liquid
8, 9 Insulating film
10 Bulkhead
11 Barrier
12 steps
13 Second control electrode
13a Control electrode
15 Shielded space
20 Drive driver
22 steps

Claims (1)

A first substrate, a first display electrode and a second display electrode disposed on the first substrate, a second substrate disposed opposite to the first substrate, and a desired voltage are applied to each electrode. Each of the pixels arranged in a matrix comprising means, a transparent insulating liquid filled between the first substrate and the second substrate, and a plurality of colored charged electrophoretic particles dispersed in the transparent insulating liquid The first display electrode and the second display electrode are used as the first scan electrode and the second scan electrode, respectively, and the colored charged electrophoretic particles are moved between the first display electrode and the second display electrode by simple matrix driving. In an electrophoretic display device that switches between
As an electrode for controlling the movement of the colored electrophoretic particles, and a first control electrode perpendicular to the scanning electrode direction is disposed on the second substrate, likewise perpendicular to the scanning electrodes direction, on the first substrate A second control electrode disposed at a boundary between the first display electrode and the second display electrode, and sequentially selecting a scanning line and charging the colored charge to either the first scanning electrode or the second scanning electrode. A driving bias for moving the migrating particles is applied, and the second control electrode of the pixel whose display on the selected scanning line is to be maintained includes the colored charging electrophoresis on the first and second display electrodes. that is applied in the direction of voltage separating the particles from the second control electrode, the first control electrode of the same pixel, applying a direction of a voltage to press the colored electrophoretic particles in the first and second display electrodes An electrophoretic display device.

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