JP3740268B2 - Electrophoretic display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophoretic display device that performs display by moving electrophoretic particles.
[0002]
[Prior art]
In recent years, with the development of information equipment, the need for low power consumption and thin display devices is increasing, and research and development of display devices that meet these needs are being actively conducted. Above all, liquid crystal display devices can change the optical characteristics of liquid crystals by electrically controlling the arrangement of liquid crystal molecules, and are actively developed and commercialized as display devices that can meet the above needs. However, in these liquid crystal display devices, the visual burden caused by the angle at which the screen is viewed, the difficulty in seeing characters on the screen due to reflected light, the flickering of the light source, low luminance, etc. has not been sufficiently solved. For this reason, research on display devices with less visual burden has been actively studied.
[0003]
Reflective display devices are expected from the viewpoints of low power consumption and reduced burden on the eyes. For example, Harold D. An electrophoretic display device invented by Lees et al. (US Pat. No. USP3612758) is known. In addition, an electrophoretic display device is disclosed in Japanese Patent Laid-Open No. 9-185087.
[0004]
FIG. 8 shows the conventional electrophoretic display device and its operating principle. The device 85 includes a dispersion layer composed of charged electrophoretic particles 81 and an insulating liquid 82 in which a coloring pigment is dissolved, and a pair of electrodes 83 and 84 facing each other with the dispersion layer interposed therebetween. By applying a voltage to the dispersion layer via the electrodes 83 and 84, the migrating particles 81 are attracted to an electrode having a polarity opposite to the charge of the particles themselves. The display is performed by the color of the electrophoretic particles 81 and the color of the insulating liquid 82 in which the coloring pigment is dissolved unlike the hue of the electrophoretic particles 81.
[0005]
That is, when the first electrode 83 is used as the negative electrode and the second electrode 84 is used as the positive electrode, the positively charged migrating particles 81 move to the surface of the first electrode 83 close to the observer and adhere to the first electrode 83. Then, the color of the migrating particles 81 is displayed (FIG. 8B).
[0006]
Conversely, when the first electrode 83 is the positive electrode and the second electrode 84 is the negative electrode, the positively charged migrating particles 81 move to the surface of the second electrode 84 far from the observer and adhere to the second electrode 84. The color of the coloring pigment contained in the insulating liquid 82 is displayed (FIG. 8A).
[0007]
However, the conventional electrophoretic display device of FIG. 8 has the following problems. First, it was essential that the insulating liquid be colored or opaque. For this reason, it is difficult to constitute the insulating liquid with a single component, and it has been necessary to mix some colored particles in the insulating liquid or dissolve the coloring pigment.
[0008]
In addition, the reflectance decreases due to adverse effects such as adsorption of the dye dissolved in the insulating liquid onto the electrophoretic particles and penetration of the insulating liquid containing the dye between the electrode surface on which the electrophoretic particles adhere and the electrophoretic particles. This causes a problem that high contrast cannot be obtained.
[0009]
Further, the presence of such colored particles and coloring pigments tends to act as an unstable factor in the electrophoresis operation, and has a drawback that the performance, life and stability as a display device are remarkably lowered.
[0010]
In view of this, an electrophoretic display device that performs display using a transparent insulating liquid in which colored particles are not mixed or colored pigments are not dissolved is disclosed in Japanese Patent Application Laid-Open No. 9-2111499, Japanese Patent Publication No. 6-52358, and the like. Has been proposed.
[0011]
An electrophoretic display device disclosed in Japanese Patent Laid-Open No. 9-2111499 and its operating principle will be described with reference to FIG.
[0012]
When a voltage is applied by the electric circuit 110 so that the first electrode 104 has a different polarity from the electrophoretic particle 108 and the second electrode 105 has the same polarity as the electrophoretic particle 108, the electrophoretic particle 108 is It moves to the dielectric layer 106 which coats the electrode 104, and covers its surface. At this time, an observer watching the apparatus from the outside of the transparent substrate 102 visually recognizes the color of the electrophoretic particles 108. Next, when the polarity of the voltage applied to the first electrode 104 and the second electrode 105 is reversed by the electric circuit 110, the electrophoretic particles 108 are contained in the second electrode 105 in the region concealed by the concealing layer 111. Is moved to the dielectric layer 107 covering the surface, and the surface thereof is covered. Since the electrophoretic particles 108 are in the region concealed by the concealing layer 111, the observer can compare the color of the dielectric layer 106, the first electrode 104, or the first substrate 101 with the electrophoretic particles 108. Visualize the color.
[0013]
[Problems to be solved by the invention]
However, the conventional electrophoretic display device of FIG. 11 has the following problems.
[0014]
Since the shielding layer 111 is provided to conceal the electrophoretic particles 108, the aperture ratio is reduced and the light utilization efficiency is reduced. Therefore, the contrast of the display device is also reduced.
[0015]
[Means for Solving the Problems]
SUMMARY An advantage of some aspects of the invention is to provide an electrophoretic display device with improved light utilization efficiency and high contrast.
[0016]
This objective is achieved by:
[0017]
The display device of the present invention includes a first electrode, a second electrode to which a voltage different from the first electrode is applied, a plurality of colored charged electrophoretic particles moving between the first electrode and the second electrode, and a first substrate. And arranged to face the first substrate Transparent with concave structure on the surface toward the first substrate A second substrate; By the concave structure Between the first board and the second board Space that occurs in Met The In an electrophoretic display device comprising a transparent insulating liquid that holds a plurality of colored charged electrophoretic particles,
The refractive index of the transparent insulating liquid is larger than the refractive index of the second substrate, The first electrode is Attract multiple colored electrophoretic particles In the center of the first board To collect And the second electrode is Attract multiple colored electrophoretic particles At the end of the first substrate To collect Of the second substrate Concave structure Is Light incident on the transparent insulating liquid through the second substrate In the center of the first board Gather The configuration is such a shape.
[0020]
Preferably, the outer surface of the second substrate is configured to collect light at the center of the first substrate.
[0021]
Preferably, the outer surface of the second substrate has a concave structure toward the first substrate.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
1A and 1B are cross-sectional views of the display device of this embodiment.
[0023]
In the display device of this embodiment, the colored charged electrophoretic particles 4 perform display by moving horizontally between the first electrode 5 and the second electrode 6.
[0024]
In the present embodiment, the inner surface of the second substrate 2 is shaped so that light gathers at the center of the first substrate 1. Therefore, since the incident light 8 can be condensed, the light use efficiency can be improved and the effect of improving the display contrast can be obtained.
[0025]
For example, the inner surface of the second substrate 2 has a concave structure toward the first substrate 1. The first substrate 1 and the second substrate 2 are bonded via a concave space, and the space is filled with a transparent insulating liquid 3 and colored charged electrophoretic particles 4. The first substrate 1 is formed with a first electrode 5, a second electrode 6, and an insulating layer 7. The first electrode 5 is located on the entire bottom surface or the center of the concave space, and the second electrode 6 is a concave space. Located in the periphery of the bottom.
[0026]
In addition to the concave configuration of the inner surface of the second substrate 2 toward the first substrate 1, the light-transmitting insulating liquid 3 in the concave space has a high refractive index with respect to the material constituting the second substrate 2. You may use the material which has. Thereby, it is possible to further enhance the light collecting effect of collecting the incident light 8 from the second substrate 2 side at the central portion in the concave space.
[0027]
Furthermore, a material having a higher refractive index than that of the insulating liquid 3 such as the insulating layer 7 and the first substrate 1 may be used. Furthermore, the light utilization efficiency can be improved.
[0028]
Next, the charging mechanism of the colored charged electrophoretic particles 4 will be described.
[0029]
It is known that the colored electrophoretic particles in the transparent insulating liquid 3 are charged and transferred between the colored electrophoretic particles and the insulating liquid to form an electric double layer, and the colored electrophoretic particles are positively or negatively charged. ing. That is, positive ion particles or negative ion particles are specifically adsorbed from the insulating liquid to the surface of the colored migrating particles, and the colored migrating particles are charged to a positive charge or a negative charge.
[0030]
Next, the first display method of this embodiment will be described.
[0031]
The colored electrophoretic particles 4 in the insulating liquid 3 can be moved on both electrodes by changing the polarity of the voltage applied to the first electrode 5 and the second electrode 6.
[0032]
For example, if the first electrode 5 is a positive electrode and the second electrode 6 is a negative electrode with respect to the positively charged colored charged electrophoretic particles 4, the colored charged electrophoretic particles 4 are placed on the second electrode 6 by electrostatic attraction. The colored electrophoretic particles 4 are attracted and gathered on the second electrode 6 at the periphery of the bottom of the concave space (FIG. 1A).
[0033]
On the contrary, if the first electrode 5 is a negative electrode and the second electrode 6 is a positive electrode, the colored charged electrophoretic particles 4 are attracted onto the first electrode 5 by electrostatic attraction, and the colored charged electrophoretic particles 4 are in the bottom of the concave space. Are gathered on the first electrode 5 in the central part (FIG. 1B). By utilizing this phenomenon, display can be performed.
[0034]
For example, when the colored charged electrophoretic particles 4 are collected on the first electrode 5 in the center, the color of the colored charged electrophoretic particles 4 is observed from the observation side (second substrate 2 side) due to the concave condensing effect.
[0035]
On the contrary, if it collects on the 2nd electrode 6 in the peripheral part of a concave space bottom face, the colored layer arrange | positioned on the insulating layer 7, the 1st electrode 5, the 1st board | substrate 1, or the 1st board | substrate by the concave shape condensing effect For example, the color of the colored layer having optical characteristics (hue, reflectance, etc.) different from those of the colored charged electrophoretic particles 4 can be observed from the observation side (second substrate 2 side). When the colored layer is formed, it may be formed by patterning or over the entire surface. Further, a light reflecting layer may be provided below the colored layer.
[0036]
For example, when the positively charged colored electrophoretic particles 4 are black and the first electrode 5 is white, monochrome display is possible. However, the second substrate 2 and the insulating layer 7 are transparent.
[0037]
In addition, the colored charged electrophoretic particles 4 and the colors of the first electrode 5, the insulating layer 7, and the first substrate 1 that have different optical characteristics (hue, reflectance, etc.) from the colored charged electrophoretic particles 4 are colored (for example, yellow, Cyan, magenta, etc.) enables color display.
[0038]
Further, the condensing effect due to the concave shape can be enhanced by processing the outer surface of the second substrate 2 into a concave shape toward the first substrate 1. FIG. 2 shows a cross-sectional view.
[0039]
Further, in the present embodiment, the first electrode 5 and the second electrode 6 have a region overlapping with the first substrate 1 in the horizontal direction.
[0040]
Referring to FIG. 1, since the first electrode 5 and the second electrode 6 are in contact with each other through the insulating layer 7, the capacitance can be increased evenly over a wide area. In other words, since the capacitor formation area can be increased structurally, it also has the effect of maintaining a strong memory retention.
[0041]
Next, the second display method of this embodiment will be described with reference to FIG.
[0042]
In the present embodiment, since the colored charged electrophoretic particles 4 are moved horizontally from side to side in the horizontal direction with respect to the display surface, the gradation of the display color can be structurally expressed. 3, the same reference numerals as those used in FIG. 1 denote the same members as those used in FIG.
[0043]
The gradation expression can be achieved by partially moving the colored charged electrophoretic particles 4 from one electrode to the other electrode as shown in FIG. For example, when gradation representation is performed by pulse width modulation, a part of the colored charged electrophoretic particles 4 can be moved by shortening the voltage application time, reducing the applied voltage, or colored charged electrophoretic particles 4 having different charging capabilities. Are mixed and used, and colored charged electrophoretic particles 2 having different sizes are mixed and used.
[0044]
That is, the moving amount of the colored charged electrophoretic particles 2 that move is controlled by adjusting the magnitude of the voltage applied to the electrode, the length of time for applying the voltage applied to the electrode, and the like. That is, an area gradation is realized by controlling the area of the colored electrophoretic particles 2 covering the first electrode 8 and the second electrode 7.
[0045]
Furthermore, in addition to the above-described configuration, the colored display electrophoretic particles 4 having different charging capabilities are mixed and used, and the colored display electrophoretic particles 4 having different sizes can be mixed to improve the gradation display characteristics. it can.
[0046]
In FIG. 3, it is assumed that the colored charged electrophoretic particles 4 in the transparent insulating liquid 3 are positively charged.
[0047]
When the second electrode 6 is a negative electrode and the first electrode 5 is a positive electrode, the positively charged colored charged electrophoretic particles 4 move onto the second electrode 6, and the positively charged colored charged electrophoretic particles 4 are on the second electrode 6. The color of the layer colored in a color different from the hue of the colored charged electrophoretic particles 4 such as the insulating layer 7, the first electrode 5, or the first substrate 1 is observed from the observer (second substrate 2 side). (Displayed) (FIG. 3A).
[0048]
On the other hand, by changing the polarity of the voltage applied to the electrode and adjusting the magnitude of the voltage applied to the first electrode 5 and the magnitude of the voltage applied to the second electrode 6, positive charges moving on the first electrode 5 The amount of the colored charged electrophoretic particles 4 is controlled.
[0049]
That is, the area of the colored positively charged electrophoretic particles 4 occupying the first electrode 5 is controlled. Depending on the size of the occupied area, the observer (the second substrate 2 side) gives the color of the positively charged colored electrophoretic particles 4 and the color of the second electrode 6 and the insulating layer 7 or the first electrode 5 or the first substrate. A mixed color in which the colors of the layers colored in a color different from the hue of the colored charged electrophoretic particles 4 such as 1 is mixed is observed (FIG. 3B). For example, if the colored electrophoretic particles 4 are black and the first electrode 5 is white, black and white gradation display is possible. However, the insulating layer 7 is transparent.
[0050]
When the second display method of the present embodiment is used, the amount of movement of the colored charged electrophoretic particles 4 from the electrode to the other electrode can be controlled, so that an area gradation display can be realized.
[0051]
(Another embodiment)
The reason for covering the first electrode 5 and the second electrode 6 with the insulating layer 7 is that an electrochemical reaction occurs between the first electrode 5 and the second electrode 6 and the insulating liquid 3, resulting in an insulating property. This is to prevent the liquid 3 from deteriorating.
[0052]
However, it is possible to prevent the insulating liquid 3 from deteriorating by selecting materials for the colored charged electrophoretic particles 4 and the first electrode 5 and the second electrode 6. Therefore, the second electrode 6 may be exposed and the colored charged electrophoretic particles 4 may directly adhere to the second electrode 6. Further, the first electrode 5 may be exposed, and the colored charged electrophoretic particles 4 may directly adhere to the first electrode 5.
[0053]
Another embodiment will be described with reference to FIG. 9, the same reference numerals as those used in FIG. 1 denote the same members as those used in FIG. The first electrode 5 and the second electrode 6 are arranged with their positions shifted only in the horizontal direction of the first substrate 1. That is, the first electrode 5 and the second electrode 6 are arranged in parallel and do not have a region overlapping the horizontal direction of the first substrate 1. Even if the structure of FIG. 9 is taken, since the inner surface of the second substrate 2 is a concave structure toward the first substrate 1, a light condensing effect can be obtained and light utilization efficiency can be increased.
[0054]
(Manufacturing method of this embodiment)
Hereinafter, an example of this embodiment will be described in detail.
[0055]
FIG. 4 shows a sectional view of the manufacturing process. First, the first electrode 5 pattern is formed on the first substrate 1 (FIG. 4A). As the material of the first substrate 1, a material having high heat resistance is used. Polymer films such as polyethylene terephthalate (PET) and polyethersulfone (PES), or inorganic materials such as glass and quartz can be used. Next, the insulating layer 7 is formed on the first electrode 5, and the second electrode 6 pattern is formed thereon. As materials used for the first electrode 5, the insulating layer 7, and the second electrode 6, generally used insulating materials and electrode materials can be used. In the present invention, these material colors are directly displayed colors. Therefore, in order to display a desired color, it is necessary to consider the combination. That is, for a layer having a desired color, it is desirable that the layer closer to the viewer than the layer is as colorless and transparent as possible. The layer having a desired color may be the color of the electrode material, the insulating layer, or the substrate itself, and the coloring material layer may be formed between the layers or on the front surface or the back surface of the substrate. Further, it may be formed on the entire surface, a part thereof, or a combination of a plurality of colors. Further, in addition to the colored layer, as viewed from the observer, a light reflecting layer may be formed below the colored layer to improve the reflectance. The electrode layer is formed by a method such as sputtering deposition, and is patterned by photolithography. The first electrode 5 is formed in a line shape, and the second electrode 6 is also formed in a line shape via an insulating layer 7. The second electrode 6 has a circular or elliptical hole in the line. The pitch of the electrode lines is usually about 5 to 200 μm.
[0056]
An insulating layer 7 is formed on the second electrode 6 layer, and a heat sealing layer 9 is formed on the bonding surface with the first substrate 1 (FIG. 4B).
[0057]
Next, the second substrate 2 is produced. The second substrate 2 uses the same material as the first substrate 1. Any method may be used as a method of forming the concave shape of the second substrate 2. For example, there are a method in which the substrate is softened by applying heat to the substrate (hot press molding), a method in which a mask is formed by photolithography, and etching is performed. A thermal fusion layer 9 is formed on the bonding surface with the first substrate 2 (FIG. 4C).
[0058]
Next, the insulating liquid 3 and the colored charged electrophoretic particles 4 are filled into the concave holes of the second substrate 2. As the insulating liquid 3, diiodomethane, chloronaphthalene, bromobenzene, tetrabromomethane or the like can be used as a high refractive index material. In addition, toluene, xylene, silicone oil, and high purity petroleum zone can be used. As the colored charged electrophoretic particles 4, a material that can be charged in the insulating liquid 3 is used. For example, a resin such as polyethylene or polystyrene mixed with carbon is used. As the size of the particles, those having a size of about 0.1 μm to 50 μm are usually used.
[0059]
After the colored charged electrophoretic particles 4 and the insulating liquid 3 are filled in the recesses of the second substrate 2, the first substrate 1 and the second substrate 2 are bonded together. Lamination is performed by heat fusion or adhesive. A display device can be manufactured by providing a voltage applying means (not shown) (FIG. 4D).
[0060]
The display device manufactured by the above method can perform two-color display, color display, and gradation expression, and can realize a high viewing angle and a high contrast.
[0061]
【Example】
The present invention will be described below with reference to examples.
[0062]
Example 1
This embodiment will be described with reference to FIG. An ITO electrode 5 was formed on a light-transmitting first substrate 1 made of a PES film having a thickness of 150 μm, and patterned into a line shape by photolithography and wet etching (FIG. 4A). On top of this, a titanium oxide fine particle-containing resin layer showing a white color was formed by irregularly reflecting light as the insulating layer 7. Further, a titanium carbide film was formed as the second electrode 6 and formed into a line shape by photolithography and dry etching, and further, only the first electrode 5 was etched in a circular shape to make a hole. On the second electrode 6, a highly transparent polyimide layer was further formed as an insulating layer 7. Next, the heat-fusible adhesive layer 9 was formed in a pattern on the joint portion of the second substrate 2 (FIG. 4B).
[0063]
A concave shape was formed on the light-transmitting second substrate 2 made of a PES film by hot press molding, and a heat-fusible adhesive layer 9 was formed on the adhesive portion with the first substrate 1 in the same manner as the first substrate 1. (FIG. 4 (c)).
[0064]
Next, the concave portion of the second substrate 2 was filled with the transparent insulating liquid 3 and the colored charged electrophoretic particles 4. As the insulating liquid 3, diiodomethane having a refractive index larger than that of the PES film as the second substrate 2 material was used. As the colored charged electrophoretic particles 4, black particles having a particle size of about 1 μm to 2 μm and a mixture of polystyrene and carbon were used. After the filling, the positions of the adhesive layers 9 of the first substrate 1 and the second substrate 2 were aligned and bonded by applying heat. This was provided with a voltage application circuit (not shown) to form a display device (FIG. 4D).
[0065]
Next, display was performed using the manufactured display device. The applied voltage was ± 50V. When a voltage is applied so that the first electrode 5 becomes a positive electrode and the second electrode 6 becomes a negative electrode, the positively charged colored charged electrophoretic particles 4 are present at the peripheral portion of the bottom surface of the concave structure of the second substrate 2. Moved up. When this is observed from the second substrate 2 side, the concave structure of the second substrate 2 acts as a lens, so that light is collected at the center of the first substrate 1 and incident on the exposed white insulating layer 7. The entire lens was white.
[0066]
On the other hand, when the polarity is reversed so that the voltage is applied so that the first electrode 5 becomes the negative electrode and the second electrode 6 becomes the positive electrode, the colored charged electrophoretic particles 4 gather in the central portion, and the entire lens is formed of the colored charged electrophoretic particles 4. A black color was exhibited. The response speed at this time was 20 msec or less, and a display device capable of displaying two colors could be produced.
[0067]
(Example 2)
This embodiment will be described with reference to FIG.
[0068]
As in Example 1, an ITO electrode pattern was formed as a first electrode 5 on a light-transmitting first substrate 1 made of a 150 μm thick PES film (FIG. 6A), and a highly transparent polyimide was formed thereon. An insulating layer 7 made of 3 μm was formed. Further, an ITO electrode pattern was formed as the second electrode 6. The second electrode 6 pattern was etched into a rectangular shape with rounded corners only on the first electrode 5. An insulating layer 7 made of highly transparent polyimide was further formed on the second electrode 6 (FIG. 6B). Further, a cyan, yellow, and magenta colored layer 10 is formed on the back side of the first substrate 1 at a location corresponding to the etched portion of the second electrode 6, and titanium oxide fine particle-containing resin showing white color by irregularly reflecting light on the colored layer 10. Layer 11 was formed. On the front side of the first substrate 1, a heat-fusible adhesive layer 9 was formed in a pattern at the joint with the second substrate 2 (FIG. 6C).
[0069]
Next, as the second substrate 2, a PET film was formed by hot press molding so that the inside of the second substrate 2 was formed into a concave shape, and the outside of the second substrate 2 was formed into a concave shape. A heat-fusible adhesive layer 9 was formed on the bonded portion of the produced second substrate 2 to the first substrate 1 in the same manner as the first substrate 1 (FIG. 6D).
[0070]
Next, the concave portion of the first substrate 1 was filled with the insulating liquid 3 and the colored charged electrophoretic particles 4. Silicone oil was used as the insulating liquid 3, and a mixture of polystyrene and carbon was used as the colored charged electrophoretic particles 4, and the particle size was about 1 μm to 2 μm. After the filling, the positions of the adhesive layers 9 of the first substrate 1 and the second substrate 2 were aligned and bonded by applying heat. This was provided with a voltage application circuit (not shown) to form a display device (FIG. 6 (e)).
[0071]
Next, display was performed using the manufactured display device. The applied voltage was ± 50 V, and the voltage application time was 20 msec. When a voltage is applied so that the first electrode 5 becomes a positive electrode and the second electrode 6 becomes a negative electrode, the positively charged colored charged electrophoretic particles 4 are present at the peripheral portion of the bottom surface of the concave structure of the second substrate 2. Moved up. When this is observed from the second substrate 2 side, since the concave structure of the second substrate 2 acts as a lens, the entire lens exhibits the color of the colored layer 10.
[0072]
On the other hand, when the polarity is reversed so that the voltage is applied so that the first electrode 5 becomes the negative electrode and the second electrode 6 becomes the positive electrode, the colored charged electrophoretic particles 4 gather in the central portion, and the entire lens is formed of the colored charged electrophoretic particles 4. A black color was exhibited. The response speed was 20 msec or less, and good color display could be performed.
[0073]
Next, when it was driven with an applied voltage of ± 50 V and a voltage application time of 5 msec, the brightness of reflected light from each colored layer could be reduced to about half. Multi-level gradation expression can be performed by variously selecting the voltage application time. As described above, a color display device capable of expressing gradation can be manufactured.
[0074]
Example 3
This embodiment will be described with reference to FIG. As in Example 1, an ITO electrode pattern was formed as the first electrode 5 on the light-transmitting first substrate 1 made of a PES film having a thickness of 150 μm (FIG. 7A). On this, an insulating layer 7 made of highly transparent polyimide was formed to 3 μm. Further, a titanium carbide film was formed as the second electrode 6 and formed into a line shape by photolithography and dry etching, and further, only the first electrode 5 was etched in a circular shape to make a hole. On the second electrode 6, a highly transparent polyimide layer was further formed as an insulating layer 7 (FIG. 7B). Further, a titanium oxide fine particle-containing resin layer 11 showing white color by irregularly reflecting light was formed on the entire back surface of the first substrate 1. On the front side of the first substrate 1, a heat-fusible adhesive layer 9 was formed in a pattern at the joint with the second substrate 2.
[0075]
Next, a concave shape was formed on the second substrate 2 by hot press molding, and cyan, yellow, and magenta colored filter layers 12 were formed at locations corresponding to the concave portions on the non-processed surface. A transparent protective layer 12 was formed thereon. A heat-fusible adhesive layer 9 was formed on the adhesive part of the produced second substrate 2 with the first substrate 1 on the concave shape side as in the case of the first substrate (FIG. 7C).
[0076]
Next, the concave portion of the second substrate 2 was filled with the insulating liquid 3 and the colored charged electrophoretic particles 4. Silicone oil was used as the insulating liquid 3, and a mixture of polystyrene and carbon was used as the colored charged electrophoretic particles 4, and the particle size was about 1 μm to 2 μm. After the filling, the positions of the adhesive layers 9 of the first substrate 1 and the second substrate 2 were aligned and bonded by applying heat. This was provided with a voltage application circuit (not shown) to form a display device (FIG. 7D).
[0077]
Next, display was performed using the manufactured display device. The applied voltage was ± 50 V, and the voltage application time was 20 msec. When a voltage is applied so that the first electrode 5 becomes a positive electrode and the second electrode 6 becomes a negative electrode, the positively charged colored charged electrophoretic particles 4 are present at the peripheral portion of the bottom surface of the concave structure of the second substrate 2. Moved up. When this is observed from the second substrate 2 side, since the concave structure of the second substrate 2 acts as a lens, the entire lens exhibits the color of the colored filter layer 12.
[0078]
On the other hand, when the polarity is reversed so that the voltage is applied so that the first electrode 5 becomes the negative electrode and the second electrode 6 becomes the positive electrode, the colored charged electrophoretic particles 4 gather in the central portion, and the entire lens is formed of the colored charged electrophoretic particles 4. A black color was exhibited. The response speed was 20 msec or less, and good color display could be performed.
[0079]
Next, when it was driven with an applied voltage of ± 50 V and a voltage application time of 5 msec, the brightness of reflected light from each colored layer could be reduced to about half. Multi-level gradation expression can be performed by variously selecting the voltage application time. As described above, a color display device capable of expressing gradation can be manufactured.
[0080]
(Example 4)
FIG. 10 shows a schematic configuration of an example of a display device using the first embodiment. FIG. 10A is a cross-sectional view (a cross-sectional view taken along the broken line AA ′ in FIG. 10B) of the display device 82 of this embodiment, and FIG. 10B is a plan view thereof.
[0081]
A gray pigment layer was formed on the entire surface of the first substrate 1 made of a PET film.
[0082]
Thereafter, as in Example 1, a cell 83 having the first electrode 5, the insulating layer 7, the second electrode 6, the colored charged electrophoretic particles 4, the insulating liquid 3, and the second substrate 2 having a concave structure was formed.
[0083]
Thereafter, a partition wall 81 was formed on the surface of the first substrate 1 as shown in FIG.
[0084]
Thereafter, the pulse generator 84 was connected to the second electrode 6 to obtain a display device 82. The first electrode 5 is grounded. Although it is necessary to select the shape and size of the cell 83 in accordance with a desired resolution, in this embodiment, for the sake of simplicity, a 7-segment type in which 7 cells 83 are arranged in an 8-shape is used. It was.
[0085]
Display was performed using the manufactured display device 82. A rectangular wave having a peak value of minus 50 V and a pulse width of 10 ms was applied to all the second electrodes 5. Since the colored charged electrophoretic particles 4 used in this example were positively charged in diiodomethane, they moved onto the black second electrode 6 to which a negative voltage of minus 50 V was applied by voltage application. As a result, all the cells 83 viewed from the second substrate 5 (observation side) were in a grayish white state. On the other hand, when an arbitrary one of the second electrodes 6 is selected by a switch (not shown), a pulse of reverse polarity, a square wave having a peak value plus 50 V and a pulse width of 10 ms is applied to the second electrode 6. Since the colored charged electrophoretic particles 4 move on the white insulating layer 7, the selected cell 83 is in a black state and is displayed using a combination of segment shapes (numerical display from 0 to 9 or one of the alphabets). It was confirmed that (partial display) is possible. The response speed was 20 msec or less.
[0086]
For example, when all the second electrodes 6 are selected by a switch and a pulse of reverse polarity, a rectangular wave with a peak value plus 50 V and a pulse width of 10 ms is applied to the second electrode 6, all the cells 83 are in a black state. The number 8 can be displayed in black.
[0087]
【The invention's effect】
As described above in detail, the present invention has the following effects.
-Since it has a lens structure, high contrast display is possible even with a display method in which migrating particles are moved in the horizontal direction of the display surface.
-Since the migrating particles are driven in the lens, the apparatus can be made thinner than when the lens structure is laminated on the substrate.
・ Since the structure is extremely simple, it is extremely easy to make a large screen display device.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a display device of the present invention.
FIG. 2 is a cross-sectional view of another display device of the present invention.
FIG. 3 shows a diagram of a gray scale expression method for a display device of the present invention.
FIG. 4 shows an example of a method for manufacturing a display device of the present invention.
FIG. 5 is a diagram illustrating the principle of a conventional electrophoretic display device.
FIG. 6 shows an example of a method for manufacturing a display device of the present invention.
FIG. 7 shows an example of a method for manufacturing a display device of the present invention.
FIG. 8 is a diagram illustrating the principle of a conventional electrophoretic display device.
FIG. 9 is a cross-sectional view of another display device of the present invention.
10 shows a cross-sectional view of a display device used in Example 4. FIG.
[Explanation of symbols]
1 First substrate
2 Second substrate
3 Insulating liquid
4 Colored electrophoretic particles
5 First electrode
6 Second electrode
7 Insulation layer
8 Incident light
9 Heat-fusion layer
10 Colored layer
11 Light reflection layer
12 Colored filter layer
81 Bulkhead
82 Display device
83 cells
84 Pulse generator

Claims (3)

A first electrode, a second electrode to which a voltage different from the first electrode is applied, a plurality of colored charged electrophoretic particles moving between the first electrode and the second electrode, the first substrate, and the first substrate facing each other and a transparent second substrate having a concave structure towards the first substrate disposed surface, fills the space formed between the first substrate and the second substrate by the concave structure, said plurality of colored electrophoretic particles In an electrophoretic display device comprising a transparent insulating liquid that holds
The refractive index of the transparent insulating liquid is larger than the refractive index of the second substrate, the first electrode is disposed so as to attract a plurality of colored charged electrophoretic particles and collect them in the center of the first substrate, and the second electrode is A plurality of colored charged electrophoretic particles are arranged to attract and collect at the end of the first substrate, and the concave structure of the second substrate allows light incident on the transparent insulating liquid through the second substrate to be centered on the first substrate. An electrophoretic display device characterized in that the shape is collected in a part.   The display device according to claim 1, wherein an outer surface of the second substrate has a shape such that light is collected at a central portion of the first substrate.   The electrophoretic display device according to claim 1, wherein an outer surface of the second substrate has a concave structure toward the first substrate.

Images