JP2000171839A - Electrophoretic display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a high memory holding power by stacking a 1st and a 2nd electrode on a 1st substrate so that they shift in position from the 1st substrate in a necessary direction, making the 1st and 2nd electrodes overlap with the 1st substrate, and giving the necessary surfaces of the 1st and 2nd electrodes steps with the 1st substrate in a necessary direction. SOLUTION: A 1st electrode 8 and a 2nd electrode 7 which is applied with a different voltage from that of the 1st electrode 8 are provided shifted horizontally and vertically from the 1st substrate 3, and an electric field which controls the space distribution in the device is produced. Consequently, colored electrostatically charged electrophoretic particles 2 are able to migrate between the 1st electrode 8 and 2nd electrode 7 in parallel and perpendicular to the 1st substrate 3. The 1st electrode 8 and 2nd electrode 7 are provided with areas horizontally overlapping with the 1st substrate 3. Further, the surfaces of the 1st electrode 8 and 2nd electrode 7 which contact insulating liquid 1 are given vertical steps with the 1st substrate 3. Consequently, the colored electrostatically charged electrophoretic particles 2 are adsorbed because of an increase in the surface area resulting from the formation of the steps.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophoretic display device which performs display by moving electrophoretic particles between electrodes.

[0002]

2. Description of the Related Art In recent years, with the development of information equipment, needs for low power consumption and thin display devices have increased, and research and development of display devices meeting these needs have been actively conducted. Among them, a liquid crystal display device is capable of electrically controlling the arrangement of liquid crystal molecules and changing the optical characteristics of liquid crystal, and has been actively developed and commercialized as a display device capable of meeting the above needs.

However, these liquid crystal display devices have not yet sufficiently solved the difficulty in seeing characters on the screen due to the angle at which the screen is viewed or reflected light, and the burden on vision caused by flickering and low brightness of the light source. For this reason, research on a display device with a small burden on vision is being actively studied.

[0004] Reflective display devices are expected from the viewpoints of low power consumption and reduction of the burden on the eyes. As one of them,
Harold D. Lee
An electrophoretic display device (US Pat. No. 3,612,758) invented by s) is known. In addition, an electrophoretic display device is disclosed in JP-A-9-185087.

FIG. 7 shows the above-mentioned conventional electrophoretic display device and its operating principle. The electrophoretic display device 75 includes a charged electrophoretic particle 73 and an insulating liquid 7 in which a coloring dye is dissolved.
4 and a pair of electrodes 71 and 72 facing each other with the dispersion layer interposed therebetween. By applying a voltage to the dispersion layer through the electrodes 71 and 72, the electrophoretic particles 73
Is attracted to an electrode having the opposite polarity to the charge of the particle itself. The display shows the color of the migrating particles 73 and the migrating particles 7.
Insulating liquid 74 in which a coloring pigment is dissolved unlike the hue of No. 3
Is done by the color.

That is, when the first electrode 71 is used as a negative electrode and the second electrode 72 is used as a positive electrode, the positively charged electrophoretic particles 73 move to the surface of the first electrode 71 close to the observer, and 7
1 and the color of the migrating particles 73 is displayed (FIG. 7).
(B)).

Conversely, when the first electrode 71 is a positive electrode and the second electrode 72 is a negative electrode, the positively charged particles 73 move to the surface of the second electrode 72 far from the observer, and And the color of the coloring pigment contained in the insulating liquid 74 is displayed (see FIG. 7A).

However, the conventional electrophoresis apparatus shown in FIG. 7 has the following problems. First, it is essential that the insulating liquid be colored or made opaque. For this reason, it is difficult for the insulating liquid to be composed of a single component, and it has been necessary to mix some colored particles in the insulating liquid or dissolve the coloring dye.

[0009] Further, the reflectance due to the adverse effect of adsorption of the dye dissolved in the insulating liquid to the electrophoretic particles and invasion of the insulating liquid containing the dye between the electrode surface to which the electrophoretic particles adhere and the electrophoretic particles. And the problem that high contrast cannot be obtained arises.

In addition, the presence of such colored particles (dye) tends to act as an instability factor in the electrophoretic operation, and has the disadvantage that the performance, life, and stability of the display device are significantly reduced.

Therefore, Japanese Patent Application Laid-Open No. Hei 9-212499,
Japanese Patent Publication No. 6-52358 proposes an electrophoretic display device for performing display using a transparent insulating liquid in which colored particles are not mixed or a colored dye is not dissolved.

An electrophoretic display device disclosed in Japanese Patent Application Laid-Open No. 9-212499 and its operation principle will be described with reference to FIG. In this electrophoretic display device, a first electrode 104 is formed on a first substrate 101, and a second electrode 105 is formed on a side wall surface of a spacer substrate 103 at right angles to the first electrode 104. And spacer substrate 103
And a transparent insulating liquid 1 in which charged colored electrophoretic particles 108 are dispersed in a closed space formed by the second substrate 10.
Is filled. A dielectric layer 106 is provided on the surfaces of the first electrode 104 and the second electrode 105 to protect the electrodes. First electrode 104, dielectric layer 1
06, the first substrate 101 is colored. First electrode 10
4. By applying a voltage to the dispersion layer via the second electrode 105, the electrophoretic particles 108 are attracted to the electrode having the opposite polarity to the charge of the particles themselves, and the display is performed by the electrophoretic particles 1
08, and the color of the first electrode 104, the dielectric layer 106, and the first substrate 101 different from the hue. Further, since the positions of the first electrode 104 and the second electrode 105 are far from the observer side, the space between them is always exposed. Therefore, the shielding layer 111 is required.

That is, when the first electrode 104 is used as a negative electrode and the second electrode 105 is used as a positive electrode, the positive electrophoretic particles 108 move to the surface of the first electrode 104 close to the observer, and
04 and the color of the electrophoretic particles 108 is displayed.

When the first electrode 104 is used as a positive electrode and the second electrode 105 is used as a negative electrode, the positive electrophoretic particles 108
Move to the surface of the electrode 105, adhere to the second electrode 105,
The colors of the first electrode 104, the dielectric layer 106, and the first substrate 101 are displayed.

[0015]

However, the conventional electrophoretic display shown in FIG. 8 has the following problems. 8, the power supply circuit 110 and the first electrode 1
04 and the second electrode 105 are disconnected, the dielectric layer 10 of the electrophoretic particles 108 is still owing to the van der Waals force.
Adsorption to 6, 107 continues, but its adsorption power is weak.
With the suction force by the Van der Waals force, the memory property is insufficient.

In the apparatus shown in FIG. 8, the first electrode 104 is formed on the first substrate 101, and the second electrode 105 is formed on the side wall surface of the spacer substrate 103 at right angles to the first electrode 104. . First electrode 104 and second electrode 105
Means that there is no region overlapping the first substrate 101 in the horizontal direction.

Therefore, the area for forming the capacitor of both electrodes is substantially limited to the end face of the first electrode 104 closest to the second electrode 105 and the face of the second electrode 105 close to the first electrode 104. In the apparatus of FIG. 8, the capacitor formation area was structurally small, and the capacitance was insufficient.

Accordingly, since the memory retention force is rapidly attenuated, the power supply circuit 110 and the first electrode 104 and the second electrode 10
When the electrical connection of No. 5 is disconnected, the problem that the adsorption of the electrophoretic particles 2 to the dielectric layer 106 or 107 does not continue occurs, and the problem that power consumption must be spent to maintain the display state occurs.

The insulating liquid 109 and the electrophoretic particles 1
There is a problem that a material having a relatively large density difference of 08 cannot be used. Further, the display device disclosed in Japanese Patent Application Laid-Open No. Hei 9-212499 is normally a binary display, and it is difficult to perform a so-called gradation display for displaying an intermediate color.

The present invention has been made in order to solve the above problems, and has as its object to provide an electrophoretic display device having a strong memory holding power.

[0021]

The object of the present invention is attained by the following constitution. The present invention provides a first substrate, a second substrate disposed to face the first substrate, a first electrode provided on one of the first substrate and the second substrate, A second electrode to which different voltages are applied;
An electrophoretic display device comprising: a plurality of colored charged electrophoretic particles moving between the first electrode and the second electrode; and a transparent insulating liquid holding the plurality of colored charged electrophoretic particles. The two electrodes are stacked on the first substrate so as to be displaced in the horizontal direction and the vertical direction with respect to the first substrate, and the first electrode and the second electrode have a region overlapping the first substrate in the horizontal direction,
In addition, a surface of the first electrode and the second electrode that is in contact with the transparent insulating liquid has a step in a direction perpendicular to the first substrate.

Preferably, the first electrode and the second electrode are arranged in the display area, and the magnitude of the voltage applied to the first electrode and the second electrode and the voltage applied to the first electrode and the second electrode And a means for controlling the area of the colored charged electrophoretic particles covering the first electrode and the second electrode by controlling at least one of the voltage application times.

[0023] Preferably, at least one of the charging ability of the plurality of colored charged electrophoretic particles and the size of the plurality of colored charged electrophoretic particles is different. Preferably, a structure including an insulating layer disposed on the first substrate so as to cover the first electrode and the second electrode is adopted.

Preferably, at least one of the first electrode, the second electrode, the first substrate, and the insulating layer is colored in a different color from the colored electrophoretic particles. Preferably, a configuration is adopted in which a colored layer and a light reflecting layer having optical characteristics different from those of the colored charged electrophoretic particles are laminated on the surface of the first substrate.

Preferably, the light reflecting layer is colored in a color having optical characteristics different from those of the colored electrophoretic particles. Preferably, a magnetic layer is formed in the first substrate or on the surface of the first substrate. Preferably, a configuration is adopted in which the first substrate and the second substrate are polymer films. Preferably, the second electrode and the colored electrophoretic particles are configured to be black or dark black.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a display device and a display method according to an embodiment of the present invention will be described. FIG. 1 is a sectional view of one embodiment of the electrophoretic display device of the present invention. In this embodiment,
As the insulating liquid 1, a transparent insulating liquid in which no colored particles are mixed or in which a coloring dye is not dissolved is used.

The transparent insulating liquid 1 and the colored electrophoretic particles 2 are formed on the insulating layer 4 on the first substrate 3, the second substrate 5 and the partition 6.
Is held in the space surrounded by. A second electrode 7 is partially formed below the insulating layer 4, and a first electrode 8 is formed via the insulating layer 4.

The display device according to the present embodiment includes a first electrode 8,
By disposing the first electrode 8 and the second electrode 7 to which a voltage different from that applied is shifted in the horizontal and vertical directions with respect to the first substrate 3 to form an electric field for controlling the spatial distribution in the device, The colored charged electrophoretic particles 2 are moved between the first electrode 8 and the second electrode 7 in the horizontal and vertical directions with respect to the first substrate 3. If the insulating layer 4 or the first electrode 8 or the first substrate 3 is colored so as to have different optical characteristics (hue, reflectivity, etc.) from the colored charged electrophoretic particles 2, a two-color display such as a monochrome display is performed. Can be realized.

Further, in the present embodiment, the first electrode 8 and the second electrode 7 have a region overlapping the first substrate 3 in the horizontal direction.

Referring to FIG. 1, since the first electrode 8 and the second electrode 7 are in contact with each other via the insulating layer 4, the capacitance can be increased uniformly over a wide area. In other words, a large capacitor formation area can be obtained structurally. Therefore, when the positively charged colored electrophoretic particles 2 adhere to the second electrode 7 as the negative electrode (FIG. 1A), the electric connection between the power supply circuit and the first electrode 8 and the second electrode 7 is cut off. Even when the first electrode 8 and the second electrode 7 overlap, the positively charged colored electrophoretic particles 2 are attracted onto the second electrode 7 by the electrostatic attraction generated by the capacitance generated in the area where the first electrode 8 and the second electrode 7 overlap. Hold. In the case where the positively charged colored electrophoretic particles 2 are attached to the first electrode 8 which is a negative electrode (FIG. 1).
(B)) Even when the electrical connection between the power supply circuit and the first electrode 8 and the second electrode 7 is cut off, the electrostatic force (repulsive force) due to the capacitance generated in the region where the first electrode 8 and the second electrode 7 overlap. ), The positively charged colored electrophoretic particles 2 repelled by
The state of staying on the electrode 8 is maintained.

Therefore, it is possible to maintain a strong memory retention force in which the colored electrophoretic particles 2 adhere to the electrodes, and to reduce power consumption. In addition, there is an effect that the material selection of the insulating liquid 1 and the colored electrophoretic particles 2 can be widened.

The surfaces of the first electrode 8 and the second electrode 7 which are in contact with the transparent insulating liquid 1 have a step in the direction perpendicular to the first substrate 3. With such a configuration, the charged electrophoretic particles 2 are adsorbed even in an increase in the surface area formed by the step, so that the area of the second electrode 7 can be further reduced when observed from the observer side. As a result, the aperture ratio can be increased, and high contrast can be realized.

Next, the charging mechanism of the colored electrophoretic particles 2 will be described. It is known that the colored electrophoretic particles 2 in the transparent insulating liquid 1 transfer electric charge 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. Have been. That is, positive ion particles or negative ion particles are specifically adsorbed on the surface of the colored electrophoretic particles from the insulating liquid, and the colored electrophoretic particles are charged to a positive charge or a negative charge.

Hereinafter, the first embodiment of the present invention will be described with reference to FIG.
An example of the display method will be described. Here, it is assumed that the colored electrophoretic particles 2 in the transparent insulating liquid 1 are positively charged. The colored electrophoretic particles 2 of the present embodiment may be in a negatively charged form.

When the second electrode 7 is used as a positive electrode and the first electrode 8 is used as a negative electrode, the positively charged colored electrophoretic particles 2 move onto the first electrode 8 by Coulomb force, and the positively charged colored electrophoretic particles 2 move. Are collected on the first electrode 8, and the first electrode 8 is covered with the black colored electrophoretic particles 2. Observer (second substrate 5
From the side), the color of the colored charged electrophoretic particles 2 and the color of the second electrode 7 are observed (displayed) (FIG. 1B).

On the other hand, the polarity of the voltage applied to the first electrode 8 and the second electrode 7 is changed, and the colored charged electrophoretic particles 2 are caused to move on the second electrode 7 and between the first electrode and the second electrode by the Coulomb force. To move the colored electrophoretic particles 2 of positive charge to the second
When collected on the electrode 7, the layer colored in a color different from the color of the black colored electrophoretic particles 2 and the hue of the colored particles such as the insulating layer 4 or the first electrode 8 or the first substrate 3 becomes the observation side (the second side). This is observed from the substrate 5 side (FIG. 1A).

For example, if both the second electrode 7 and the positively charged colored electrophoretic particles 2 are black and the first electrode 8 is white, monochrome display is possible. If a colored coloring layer (for example, yellow, cyan, magenta, etc.) is provided, color display is also possible. It is desirable that the second electrode 7 and the colored electrophoretic particles 2 have the same or similar colors. The colored layer having optical characteristics different from those of the colored electrophoretic particles 2 may be the first electrode 8, the insulating layer 4, the first substrate 3 if observable from the observer side.
It may be formed on the back surface of the first substrate 3 or the like, may be formed on the entire surface, or may be formed on a part. Here, the colored particles, electrodes, insulating layers, and the like may be the colors of the materials themselves, or may be those obtained by laminating and mixing other materials on the surfaces of those materials. The colored electrophoretic particles 2 may be composed of one or more materials. Further, in the present invention, since the second electrode and the colored charged electrophoretic particles can be set to the same or similar colors, the shielding layer 111 as in the conventional example shown in FIG. 8 is not required. For this reason, it is not necessary to perform fine positioning in bonding the second substrate.

When the display device of this embodiment is used, it is not necessary to use the colored insulating liquid in which the colored particles are mixed or the colored dye is dissolved. The colored particles do not adsorb to the colored electrophoretic particles. Further, the coloring pigment and the colored particles do not enter between the electrode surface to which the colored charged electrophoretic particles are attached and the colored charged electrophoretic particles. In addition, since the step between the first electrode and the second electrode can be used as a surface to which the colored electrophoretic particles are attached, the aperture ratio can be increased because the area of the second electrode can be reduced accordingly. Therefore, there is an effect that a display device capable of realizing high reflectance and high contrast can be provided.

Next, in the second display method according to the embodiment of the present invention, since the colored electrophoretic particles 2 are horizontally moved from side to side in the horizontal direction with respect to the display surface, the gradation of the display color is structurally determined. Expression becomes possible. An example of the display method will be described with reference to FIG. In FIG. 2, the same reference numerals as those used in FIG. 1 indicate the same members as those used in FIG.

The gradation expression can be achieved by partially moving the charged electrophoretic particles 2 from the electrode to the other electrode as shown in FIG. For example, when gradation expression is performed by pulse width modulation, as a method of moving a part of the colored charged electrophoretic particles 2, the voltage application time is shortened, the applied voltage is reduced, and the colored charged electrophoretic particles 2 having different charging capabilities are moved. Are used in combination, and colored electrophoretic particles 2 having different sizes are mixed and used.

That is, the amount of the moving colored charged electrophoretic particles 2 is controlled by adjusting the magnitude of the voltage applied to the electrodes, the length of time for applying the voltage to the electrodes, and the like. That is, the area of the colored electrophoretic particles 2 covering the first electrode 8 and the second electrode 7 is controlled to realize area gradation.

Further, in addition to the above configuration, by using a mixture of colored charged electrophoretic particles 2 having different charging capabilities or a mixture of colored charged electrophoretic particles 2 having different sizes, the characteristics of gradation display can be improved. Can be improved.

In FIG. 2, it is assumed that the colored electrophoretic particles 2 in the transparent insulating liquid 1 are positively charged. Second electrode 7
Is the negative electrode, and the first electrode 8 is the positive electrode, the positively charged colored electrophoretic particles 2 move onto the second electrode 7 and the positively charged colored electrophoretic particles 2 are collected on the second electrode 7, From the observer (the second substrate 5 side), the color of the colored electrophoretic particles 2 and the insulating layer 4
Alternatively, the color of the layer colored differently from the hue of the colored particles such as the first electrode 8 or the substrate 3 is observed (displayed) (FIG. 2).
(A)).

On the other hand, by changing the polarity of the voltage applied to the electrodes,
By adjusting the magnitude of the voltage applied to the first electrode 8 and the magnitude of the voltage applied to the second electrode 7, the amount of the positively charged colored electrophoretic particles 2 moving on the first electrode 8 is controlled.

That is, the area of the colored electrophoretic particles 2 occupying the first electrode 8 is controlled. Depending on the size of the occupied area, the observer (on the second substrate 5 side) may receive the color of the positively charged colored electrophoretic particles 2, the color of the second electrode 7, the insulating layer 4, the first electrode 8, the substrate 3, and the like. A mixed color obtained by mixing the colors of the layers colored differently from the hue of the colored particles is observed (FIG. 2B). For example, if both the second electrode 7 and the positively charged colored electrophoretic particles 2 are made black and the first electrode 8 is made white, monochrome gray scale display is possible. However, in this case, if the capacitance accumulated between the two electrodes is too large, it becomes difficult to control the area. Therefore, when the colored charged electrophoretic particles 2 move by a desired amount, the capacitance between the two electrodes is changed to the colored charge. Keep it low enough that the migrating particles 2 do not move.

Using the second display method of this embodiment,
Since the amount by which the colored electrophoretic particles move from the electrode to the other electrode can be controlled, an area gray scale display can be realized. Also, the reason why the first electrode 8 and the second electrode 7 are covered with the insulating layer 4 is that an electrochemical reaction occurs between the first electrode 8 and the second electrode 7 and the insulating liquid 1, and the insulating property is increased. Liquid 1
This is to prevent the deterioration of.

However, deterioration of the insulating liquid 1 can be prevented by selecting the materials of the colored electrophoretic particles 2 and the first electrode 8 and the second electrode 7. Therefore,
The second electrode 7 may be exposed, and the colored electrophoretic particles 2 may directly adhere to the second electrode 7. Further, the first electrode 8 may be exposed, and the colored electrophoretic particles 2 may directly adhere to the first electrode 8.

In the above description, the second substrate 5 side is the display side, but in the present embodiment, the first substrate 3 side may be the display side. For example, the colored electrophoretic particles 2 and the second electrode 7 are black, the insulating layer 4, the first electrode 8, and the first substrate 3 are transparent, and the second substrate 5 is white. By applying a voltage to the first electrode 8 and the second electrode 7 as described above, a monochrome display can be realized. Further, gradation display is possible by controlling the voltage application time and the magnitude of the applied voltage, or by controlling the size of the colored electrophoretic particles 2 and the magnitude of the charging ability of the colored electrophoretic particles 2.

Further, by using charged electrophoretic particles having magnetism and further forming a magnetic layer on the surface of the first substrate, a threshold can be given in driving the electrophoretic particles.

The display device of the present invention is capable of rewriting the display, does not require energy for holding the display or has a sufficiently small size (memory property), is excellent in portability, has excellent display quality, and has a hard copy ( It can be used as a paper display instead of paper.

Hereinafter, an example of a method for manufacturing the display device of the present embodiment will be described. FIG. 3 shows a process chart of a manufacturing process of the electrophoretic display device of the present invention. First, the first electrode 8 is formed on the first substrate 3 (FIG. 3A). As a material of the first substrate 3, a polymer film such as polyethylene terephthalate (PET) or polyether sulfone (PES), or an inorganic material such as glass or quartz can be used.
The first electrode 8 may be made of any conductive material that can be patterned, and in the case of a transparent electrode, indium tin oxide (ITO) or the like is used.

Next, the insulating layer 4 is formed on the first electrode 8,
Further, the position of the second electrode 7 is shifted with respect to the first electrode 8 in the horizontal direction and the vertical direction with respect to the first substrate 3, and the second electrode 7 has a region overlapping the first electrode 8 and the first substrate 3 in the horizontal direction.
Is formed (FIG. 3B).

The material of the insulating layer 4 is preferably a material having a low dielectric constant, which is difficult to form a pinhole in a thin film.
Amorphous fluorine resin, highly transparent polyimide, acrylic resin and the like can be used. The material of the second electrode 7 is the first electrode 8
The same thing as can be used. After the formation of the second electrode, the insulating layer on the first electrode is removed by etching (FIG. 3C). The insulating layer 4 is formed thinner on the first electrode 8 and the second electrode 7.

Next, a partition 6 is formed on the first substrate 3 (FIG. 3D). A polymer resin is used as the partition wall material. The partition wall may be formed by any method. For example, a method of performing exposure and wet development after applying a photosensitive resin layer, a method of bonding a separately formed partition, a method of forming a mold on the surface of a light-transmitting second substrate, or the like is used. be able to.

Next, an adhesive layer 9 is formed on a part or the entire surface of the joining surface between the second substrate 5 and the partition, and the insulating liquid 1 and the colored electrophoretic particles 2 are filled in the partition 6. As the material of the second substrate 5, a material having high visible light transmittance and high heat resistance is used. Polyethylene terephthalate (PE
T), a polymer film such as polyethersulfone (PES), or an inorganic material such as glass or quartz can be used. As the insulating liquid 1, a colorless transparent liquid such as silicone oil, toluene, xylene, or high-purity petroleum is used. A material that can be charged in the insulating liquid 1 is used as the black charged electrophoretic particles 2. For example, a material obtained by mixing carbon or the like with a resin such as polyethylene or polystyrene is used. Usually, the particle size of the migrating particles 2 is equal to 0. lμm ~
Use the one of about 50 μm. In addition, a charge control agent is added as needed.

As the display color, the color of the electrode material or the insulating layer material itself may be used, or a material layer of a desired color may be formed on the electrode, the insulating layer, or the substrate surface. Further, a coloring material may be mixed into an insulating layer or the like.

Next, the first substrate 3 and the second substrate 5 are stuck and bonded by applying heat (FIG. 3E). A display device is obtained by providing a voltage applying means (not shown) to this. 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.

[0058]

Embodiments of the present invention will be described below.

Example 1 An electrophoretic display device was manufactured by the steps shown in FIG. First of a 200 μm thick light-reflective PET film
An ITO film was formed as the first electrode 8 on the substrate 3 and patterned in a line shape (FIG. 3A). Next, an acrylic resin layer was formed as the insulating layer 4.

Next, a dark black titanium carbide film was formed as the second electrode 7, and was patterned into a line shape by photolithography and dry etching. Line width is 30 μm
(FIG. 3B).

As a result, the first electrode 8 is shifted in the horizontal and vertical directions with respect to the first substrate 3 and has a region overlapping the first electrode 8 and the first substrate 3 in the horizontal direction. Then, the second electrode 7 was formed. Next, the acrylic resin layer on the first electrode was removed by etching (FIG. 3).
(C)).

After an acrylic resin layer was further formed thereon as an insulating layer 4, a partition 6 was formed.
(D)). The partition 6 is formed by applying a photosensitive epoxy resin and then performing exposure and wet development.
The height was 50 μm. After forming the heat-fusible adhesive layer 9 on the joint surface with the second substrate 5, the insulating liquid 1 and the colored electrophoretic particles 2 were filled in the partition walls.

As the insulating liquid 1, silicone oil was used. The black electrophoretic particles 2 are a mixture of polystyrene and carbon and have a particle size of 1 μm to
Those having a size of about 2 μm were used. Next, a pattern of a heat-fusible adhesive layer 9 is formed on the surface of the second substrate 5 to be bonded to the first substrate 3, and the light-transmitting film made of a PET film having a thickness of 200 μm and the partition 6 of the first substrate 3 is formed. The second substrate 5 was bonded by applying heat. A voltage application circuit (not shown) was installed in this to make a display device (FIG. 3E).

Display was performed using the display device thus manufactured.
The applied voltage was ± 80V. Since the black charged electrophoretic particles 2 used in this example were positively charged in the silicone oil, they moved onto the negative electrode by applying a voltage. Accordingly, when the second electrode 7 is used as a positive electrode and the first electrode 8 is used as a negative electrode, the black charged electrophoretic particles 2 move on the first electrode 8 and pass through the transparent first electrode with the black charged electrophoretic particles 2. The first white substrate, which is observed as a result, is covered. The display surface viewed from the second substrate 5 (observation side) was displayed in black.

On the other hand, when the polarity of the voltage applied to the electrodes is replaced and the first electrode 8 is used as a positive electrode and the second electrode 7 is used as a negative electrode, the first electrode 8 is used as a positive electrode and the second electrode 7 is used as a negative electrode. Since the black charged electrophoretic particles 2 move to the surface of the step formed between them, the white surface observed through the transparent first electrode is exposed. The display surface viewed from the second substrate 5 (observation side) was grayish white. The response speed was 30 msec or less.

The method of manufacturing a display device according to the present embodiment has the following functions and effects as compared with the conventional method. First electrode 8,
The insulating layer 4 is formed by depositing the electrode material of the second electrode 7 on a substrate and patterning the film by a photolithography process.
Can be formed by repeating an extremely simple process such as baking after vacuum deposition or spin coating and laminating. Since the process of forming the electrodes and the insulating layer 4 is extremely simple, the occurrence of defects such as short-circuits between the electrodes can be suppressed to a very low level. Further, since an electrode pad for external electrical connection can be formed at the same time, there is no problem of external connection. Since the partition walls 6 can also be formed at once by film formation of a partition wall material and a photolithography process, there is no need for a complicated process of aligning and bonding one by one.

In addition, since the storage of charged electrophoretic particles for white display is performed on the step surface between the first electrode and the second electrode in addition to the storage on the second electrode surface, the area of the second electrode is reduced. be able to. As a result, the aperture ratio can be increased, and the contrast can be increased. In addition, since the second electrode and the colored electrophoretic particles can be set to the same or similar colors, no shielding layer is required. For this reason, it is not necessary to perform fine positioning in bonding the second substrate.

As described above, since the display device of the present invention can be manufactured by an extremely simple process, it can be manufactured with a high yield, a low manufacturing cost, and a high contrast.

Example 2 A display device was manufactured in the same steps as in Example 1. FIG. 4 shows a cross-sectional view of the display device manufactured in this example. Thickness 200
An ITO film was formed as a first electrode 8 on a light-transmissive first substrate 3 made of a PES film having a thickness of μm, and was patterned in a line shape.

Next, a transparent polyimide layer was formed as an insulating layer 4 on the first electrode 8. Furthermore, the second electrode 7
A dark black titanium carbide film was formed, and patterned in a line by photolithography and dry etching. The line width was 30 μm. Next, the polyimide layer on the first electrode was removed by oxygen plasma etching.
The second electrode was overhanged by performing etching sufficiently.

Next, a red pigment layer was formed as a colored layer 10 on the back side of the first substrate 3, and a light reflection layer 11 containing titanium oxide fine particles was formed thereon.

The partition 6 was formed on the front side of the first substrate 3. The partition walls 6 were coated with a photosensitive polyimide varnish, and then subjected to exposure and wet development to form partition walls 6 having a height of 50 μm. After forming the heat-fusible adhesive layer 9 on the joint surface with the second substrate 5, the insulating liquid 1 and the colored electrophoretic particles 2 were filled in the partition walls. As the insulating liquid 1, silicone oil was used. As the colored charged electrophoretic particles 2, a mixture of polystyrene and carbon having a particle size of about 1 μm to 2 μm was used.

Next, the first substrate and the second substrate were bonded by applying heat. A voltage application circuit (not shown) was installed in this to make a display device.

Display was performed using the display device thus manufactured.
The applied voltage was ± 70 V. Since the colored charged electrophoretic particles 2 used in the present example were positively charged in the silicone oil, they were moved on the electrode to which the negative voltage was applied by the voltage application. Thus, when a negative voltage is applied to the first electrode 8,
Since the black charged electrophoretic particles 2 moved onto the colored layer 10, the display surface viewed from the second substrate 5 (observation side) was displayed in black. On the other hand, when a negative voltage is applied to the second electrode 7, the black electrophoretic particles 2 move to the dark black second electrode 7 and to the step formed between the first electrode and the second electrode. On the display surface viewed from the side (the second substrate side), a red layer could be observed, and dark red could be displayed as a whole. Response speed is 30msec
It was below.

When the colored layer 10 was formed by combining three elements of each color of yellow, magenta, and cyan,
Color display could be performed. This will be described in detail below. It is assumed that the configuration in FIG. 4 is one cell (one element). For example, a yellow cell, a magenta cell, and a cyan cell having the configuration shown in FIG. 4 are arranged adjacent to each other, and one pixel is configured by combining three cells. A voltage is applied to the first electrode 8 and the second electrode 7 to perform color display.

Example 3 A display device was manufactured in the same steps as in Example 1. FIG. 5 shows a cross-sectional view of the display device manufactured in this example. First substrate 3
The magnetic layer 12 formed by mixing a magnetic powder with a polymer was formed on the surface of a white PET film. Silicone oil was used for the insulating liquid 1. Colored electrophoretic particles 2
A mixture of polystyrene, carbon and magnetic powder having a particle size of about 0.5 μm to 2 μm was used.

Display was performed using the display device thus manufactured.
The applied voltage was ± 100V. Due to the application of the voltage, the black positively charged electrophoretic particles 2 moved onto the electrode to which the negative voltage was applied. Accordingly, when a positive voltage is applied to the second electrode 7 and a negative voltage is applied to the transparent first electrode 8, the black positively charged electrophoretic particles 2 move on the first electrode 8. The substrate is covered with the black positive electrophoretic particles 2. Second substrate 5
The display surface viewed from the (observation side) was black. on the other hand,
When a positive voltage is applied to the first electrode 8 and a negative voltage is applied to the second electrode 7, the second electrode 7 and the second substrate 7
Since the black positive charge migrating particles 2 move to the steps between the substrates, white of the white first substrate 4 is exposed. The display surface viewed from the second substrate 5 (observation side) was grayish white. The response speed was 30 msec or less.

Next, when the charged electrophoretic particles were driven at an applied voltage of ± 50 V, it was confirmed that the charged electrophoretic particles were not driven and a threshold was formed.

Example 4 A display device was manufactured in the same process as in Example 1, and a display was performed using the manufactured display device. The applied voltage was ± 80V. Since the black charged electrophoretic particles 2 used in this example were positively charged in the silicone oil, they moved onto the negative electrode by applying a voltage. Accordingly, when the second electrode 7 is used as a positive electrode and the first electrode 8 is used as a negative electrode, the black charged electrophoretic particles 2 move on the first electrode 8 and pass through the transparent first electrode with the black charged electrophoretic particles 2. The first white substrate, which is observed as a result, is covered. The display surface viewed from the second substrate 5 (observation side) was displayed in black. On the other hand, when the polarity of the voltage applied to the electrodes is replaced, and the first electrode 8 is used as a positive electrode and the second electrode 7 is used as a negative electrode, on the dark black second electrode 7 and between the first electrode and the second electrode. Since the black charged electrophoretic particles 2 move to the formed step surface, the white surface observed through the transparent first electrode is exposed. The display surface viewed from the second substrate 5 (observation side) was grayish white. The response speed was 30 msec or less.

Next, when the applied voltage is ± 40 V, a positive voltage is applied to the first electrode 8, and a negative voltage is applied to the second electrode 7, the second electrode is applied as compared with the case where the applied voltage is ± 80 V. The amount of the black positive charge migrating particles 2 moving on 7 was reduced, and a part thereof remained on the first electrode 7 and did not move. Therefore, the brightness of the reflected light could be reduced to about half. Compared to when the applied voltage was ± 80 V, a white color closer to gray was observed. By variously selecting the voltage application time,
It was possible to perform multi-step gradation expression. Further, gradation can be similarly expressed by changing the voltage application time while keeping the applied voltage the same. From the above,
A black-and-white display device capable of gradation expression was produced.

Fifth Embodiment FIG. 6 shows a schematic configuration of an example of a display device using the first embodiment. FIG. 6A is a plan view of the display device 82 of this embodiment, and FIG. 6B is a broken line A- of FIG.
It is sectional drawing which follows the A 'line.

An ITO film was formed on a first substrate made of a white PET film and patterned in a line shape.

Next, an amorphous fluororesin was formed on the first electrode 8 as the insulating layer 4. Next, a dark black titanium carbide film was formed as the second electrode 7 and was patterned in a line by photolithography and dry etching. The line width was 50 μm. Next, the insulating layer on the first electrode was removed by oxygen plasma etching to form a step between the first electrode and the second electrode. Next, an amorphous fluororesin layer was formed as the insulating layer 4. Subsequently, the partition 8
1 was formed. The partition wall 81 is coated with an epoxy resin, and then exposed and wet-developed to form an 80 μm.
A partition 81 having a height of m was formed. After forming a heat-fusible adhesive layer (not shown) on the bonding surface with the second substrate 5, the partition walls were filled with the green liquid 1 and the colored electrophoretic particles 2.

As the green liquid 1, silicone oil was used. The black electrophoretic particles 2 are a mixture of polystyrene and carbon and have a particle size of 1 μm to 2 μm.
The thing of about μm was used. Next, a heat-fusible adhesive layer pattern is formed on the adhesive surface between the second substrate 5 and the first substrate 3, and the partition 81 of the first substrate 3 and the light-transmitting second substrate 5 made of a PET film are formed. The positions of the adhesive layers were aligned, and they were bonded by applying heat.

After that, the pulse generator 84 was connected to the second electrode 7 to complete the display device 82. The first electrode 8 is grounded. It is necessary to select the shape and size of the cell 83 according to the desired resolution. However, in this embodiment, for simplicity, a seven-segment type in which seven cells 83 are arranged in a figure-eight shape is used. .

Display was performed using the display device 82 thus manufactured. A rectangular wave having a peak value of minus 80 V and a pulse width of 10 ms was applied to all the second electrodes 7. Since the colored electrophoretic particles 2 used in the present example were positively charged in the silicone oil, the colored electrophoretic particles 2 were applied on the dark black second electrode 7 to which a negative voltage of −80 V was applied by voltage application, and the first electrode and the second electrode It moved to the surface of the step formed between the electrodes. Thereby, the inside of all the cells 83 as viewed from the second substrate 5 (observation side) was in a slightly grayish white state. On the other hand, an arbitrary one of the second electrodes 7 was selected by a switch (not shown), and then a pulse having a reverse polarity, a peak value of +80 V, and a pulse width of 10 ms was applied to the second electrode 7. Since the black electrophoretic particles 2 have moved onto the first electrode, the selected cell 83
The inside was in a black state, and it was confirmed that display using a combination of segment shapes (numerical display of 0 to 9 and partial display of alphabets) was possible. The response speed was 20 msec or less.

Further, all the second electrodes 7 are selected by a switch, and a pulse of the opposite polarity and a peak value plus 80 are applied to the second electrodes 7.
When a rectangular wave having a pulse width of 10 V and a pulse width of 10 ms was applied, all the cells 83 were in a black state, and the numeral 8 could be displayed in black.

[0088]

As described in detail above, the following effects can be obtained by using the electrophoretic display device of the present invention. (1) There is an effect that the memory holding force for the colored charged electrophoretic particles to adhere to the electrode can be maintained strongly, and the power consumption can be reduced. (2) Since the manufacturing process is a repetition of a very simple and general process such as film formation on a substrate plane and patterning by a photolithography process, occurrence of defects such as short-circuit between electrodes is extremely low. Since it can be kept low, the manufacturing cost can be kept very low. (3) Since an electrode pad for external electrical connection can be formed at the same time, there is no problem of external connection. Since the partition walls can also be formed at once by film formation of a partition wall material and a photolithography process, a complicated process of aligning and bonding one by one is not required. (4) Since the storage of charged electrophoretic particles during white display is performed on the step surface between the first electrode and the second electrode in addition to the storage on the second electrode surface, the area of the second electrode can be reduced. The contrast can be increased. (5) Since the second electrode and the colored electrophoretic particles can be set to the same or similar colors, no shielding layer is required. for that reason,
There is no need to perform fine positioning in bonding the second substrate.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an electrophoretic display device of the present invention.

FIG. 2 is an explanatory diagram illustrating an example of the principle of the electrophoretic display device of the present invention.

FIG. 3 is a process chart showing a method for manufacturing an electrophoretic display device of the present invention.

FIG. 4 is a cross-sectional view illustrating an example of the electrophoretic display device of the present invention.

FIG. 5 is a sectional view showing an example of the electrophoretic display device of the present invention.

FIG. 6 is a schematic diagram showing a seven-segment type electrophoretic display device according to a fifth embodiment of the present invention.

FIG. 7 is an explanatory diagram showing the principle of a conventional electrophoretic display device.

FIG. 8 is a schematic view showing a conventional electrophoretic display device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 insulating liquid 2 colored electrophoretic particles 3 first substrate 4 insulating layer 5 second substrate 6 partition 7 second electrode 8 first electrode 9 adhesive layer 10 colored layer 11 light reflective layer 12 magnetic layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C094 AA06 AA12 AA22 AA43 AA44 AA48 AA54 BA09 BA12 BA75 BA76 BA82 BA84 CA24 DA13 DB01 DB02 EA04 EA06 EB02 EC02 EC03 EC04 ED02 ED11 ED13 FA01 FA02 FB03 FB04 FB16

Claims (10)

[Claims] A first substrate; a second substrate disposed to face the first substrate; a first electrode provided on one of the first substrate and the second substrate; A second electrode to which a different voltage is applied, a plurality of colored charged electrophoretic particles moving between the first electrode and the second electrode, and a transparent insulating liquid holding the plurality of colored charged electrophoretic particles. In the electrophoretic display device, the first electrode and the second electrode are stacked on the first substrate while being displaced in the horizontal and vertical directions with respect to the first substrate, and the first electrode and the second electrode are connected to the first electrode. An electric field characterized by having an area overlapping the substrate in a horizontal direction, and a surface of the first electrode and the second electrode in contact with the transparent insulating liquid having a step in a direction perpendicular to the first substrate. Electrophoretic display. 2. The method according to claim 1, wherein the first electrode and the second electrode are disposed in a display area, and a magnitude of a voltage applied to the first electrode and the second electrode and a voltage applied to the first electrode and the second electrode. Controlling at least one of the application times of the applied voltage,
The electrophoretic display device according to claim 1, further comprising a unit configured to control an area of the colored electrophoretic particles covering the first electrode and the second electrode. 3. The electrophoretic display device according to claim 2, wherein at least one of the charging ability of the plurality of colored charged electrophoretic particles and the size of the plurality of colored charged electrophoretic particles is different. 4. The electrophoretic display device according to claim 1, further comprising an insulating layer disposed on the first substrate so as to cover the first electrode and the second electrode. 5. The method according to claim 1, wherein at least one of the first electrode, the second electrode, the first substrate, and the insulating layer is colored to have a different optical property from the colored electrophoretic particles. The electrophoretic display device according to the item. 6. The electrophoretic display device according to claim 1, wherein a color layer and a light reflection layer having optical characteristics different from those of the colored electrophoretic particles are laminated on the surface of the first substrate. . 7. The electrophoretic display device according to claim 6, wherein the light reflection layer is colored in a color having optical characteristics different from those of the colored charged electrophoretic particles. 8. The electrophoretic display device according to claim 1, wherein a magnetic layer is formed in the first substrate or on the surface of the first substrate. 9. The electrophoretic display device according to claim 1, wherein the first substrate and the second substrate are made of a polymer film. 10. The electrophoretic display device according to claim 1, wherein the second electrode and the colored electrophoretic particles are black or dark black.