JP2005346010A - Display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophoretic display element capable of improving display contrast and reducing drive voltage and response time.
An insulating layer is provided in a gap between a first electrode and an insulating liquid, and at least partially has a relative dielectric constant smaller than that of the insulating liquid, and is insulated from a second electrode. By providing at least one of the insulating layers 9 provided in the gap between the insulating liquids 4 and having at least a part of the relative dielectric constant larger than that of the insulating liquid 4, The lines of electric force are refracted so that the component parallel to the substrate 2 becomes large at the interface between the layers 7 and 9.
[Selection] Figure 1

Description

  The present invention relates to a display element that performs display by moving charged electrophoretic particles in an insulating liquid.

  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. In particular, liquid crystal display devices have been actively developed and commercialized as display devices that can meet such needs. However, the current liquid crystal display device has problems that it is difficult to see the characters on the screen due to the angle at which the screen is viewed and reflected light, and that the burden on the vision caused by flickering of the light source, low brightness, etc. is heavy. Is still not fully resolved. For this reason, a reflective display device is expected from the viewpoint of low power consumption and reduction of visual burden.

  Here, as an example of such a reflective display device, there is an electrophoretic display device that performs display by moving charged electrophoretic particles in an insulating liquid. Such electrophoretic display devices are of various types. Has been proposed.

  FIG. 13A is a diagram showing an example of the structure of a conventional electrophoretic display element provided in the electrophoretic display device, and the electrophoretic display element is a pair arranged with a predetermined gap therebetween. The substrates 31 and 32, the insulating liquid 33 filled between the substrates 31 and 32, a large number of colored electrophoretic particles 34 dispersed in the insulating liquid 33, and the substrates 31 and 32. In this way, display electrodes 35 and 36 arranged in each pixel are provided. A partition wall 37 is provided between the pixels, and the partition wall 37 prevents the colored charged electrophoretic particles 34 from moving to other pixels so as to maintain a uniform display.

  In this electrophoretic display element, since the colored charged electrophoretic particles 34 are charged to a positive polarity or a negative polarity, any one of the display electrodes 35, 36 is selected depending on the polarity of the voltage applied to the display electrodes 35, 36. It is adsorbed by 36. Here, since the insulating liquid 33 and the colored charged electrophoretic particles 34 are colored in different colors, when the colored charged electrophoretic particles 34 are adsorbed to the display electrode 35 on the viewer side, When the color is visually recognized (see FIG. 13B) and the colored electrophoretic particles 34 are adsorbed by the display electrode 36 on the other side, the color of the insulating liquid 33 is visually recognized (FIG. 13 ( a)). Therefore, various images can be displayed by controlling the polarity of the applied voltage for each pixel. Hereinafter, this type of apparatus is referred to as “up and down movement type”.

  However, in such an up-and-down electrophoretic display element, a coloring material such as a dye or ion must be mixed in the insulating liquid 33, and the presence of such a coloring material gives and receives a new charge. Therefore, it tends to act as an instability factor in the electrophoresis operation, and the performance, life and stability as a display element may be lowered.

  Therefore, as a solution to such a problem, Patent Document 1 discloses an electrophoretic display element of the type shown in FIG. Such an electrophoretic display element is dispersed in a pair of substrates 31 and 32 arranged with a predetermined gap therebetween, an insulating liquid 33 filled between the substrates 31 and 32, and the insulating liquid 33. In addition, a large number of colored charged electrophoretic particles 34 and two electrodes 35 and 36 arranged in each pixel are provided. The pair of electrodes 35 and 36 is an insulating liquid as in the above-described vertical movement type. The first electrode 35 is disposed along the rear substrate 32, and the second electrode 36 is concealed by a shielding layer 37 provided on the front substrate 31. It is formed in the part.

  Here, in the case of such an electrophoretic display element, the insulating liquid 33 only needs to be transparent, and it is not necessary to mix a coloring material. Therefore, the above-described problems can be avoided. In such an electrophoretic display element, the first electrode 35 or the surface thereof is colored in a different color from the charged electrophoretic particles 34. When the first electrode 35 is transparent, a colored layer colored in a different color from the charged electrophoretic particles 34 is provided behind the first electrode 35.

  Then, the charged electrophoretic particles 34 move according to the polarity of the voltage applied to the electrodes 35 and 36, and when the charged electrophoretic particles 34 are adsorbed by the second electrode 36 below the shielding layer 37, the electrophoretic particles are received from the observer. Since 34 is hidden under the shielding layer 37, the color of the charged electrophoretic particles 34 is not visible, and the color of the first electrode 35 plus the shielding layer 37 is visible. On the other hand, when the charged electrophoretic particles 34 are adsorbed on the first electrode 35, the color of the charged electrophoretic particles 34 plus the color of the shielding layer 37 is visually recognized. Therefore, an image can be displayed by controlling the polarity of the applied voltage for each pixel.

JP 9-2111499 A

  In an electrophoretic display element as an example of a conventional display device, as shown in FIG. 14, a first electrode 35 is provided in a planar shape on a rear substrate 32, and a second electrode 36 is a shielding layer around it. 37 has a structure provided below. In this configuration, when an electric field is applied to both electrodes 35 and 36 in order to move the charged electrophoretic particles 34, the electric field is the most in the first electrode surface with the second electrode 36, as is apparent from FIG. It concentrates on the near part, that is, its end.

  Therefore, for example, when the charged electrophoretic particles 34 that have been on the second electrode are moved onto the first electrode, most of the charged electrophoretic particles 34 gather at the end of the first electrode 35 and the center. It is difficult for particles to reach the area, so that the display contrast is lowered.

  Further, when the charged electrophoretic particles 34 located at the center of the first electrode 35 are moved onto the second electrode, most of the charged electrophoretic particles 34 come into contact with the display side substrate, and therefore the display side. A decrease in contrast or a decrease in response speed has occurred due to adsorption to the substrate 31.

  The present invention includes first and second substrates disposed with a gap therebetween, a partition wall that holds the gap constant and partitions the gap to define pixels, an insulating liquid disposed in the gap, A plurality of charged electrophoretic particles dispersed in the insulating liquid; a first electrode disposed in each pixel along the first substrate; and a second electrode disposed along at least a side surface of the partition wall. A display device that performs display by applying a voltage between the first electrode and the second electrode to move the charged electrophoretic particles between the first electrode and the second electrode, A first insulating layer provided between the first electrode and the insulating liquid, wherein at least a part of the relative dielectric constant is smaller than that of the insulating liquid; and the second electrode and the insulating liquid At least part of the dielectric constant provided between the insulating liquid Of the second insulating layer is larger than the relative dielectric constant, it is characterized in that it comprises at least one.

  As in the present invention, the first insulating layer is provided between the first electrode and the insulating liquid and has at least a part of the relative dielectric constant smaller than that of the insulating liquid, and the second electrode and the insulating liquid. By providing at least one of the second insulating layers provided between the liquids and having at least a part of the relative dielectric constant of the insulating liquid larger than that of the insulating liquid, The lines of electric force can be refracted so that a component parallel to the substrate becomes large at the interface, thereby improving display contrast and reducing drive voltage and response time.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an electrophoretic display element which is an example of a display device according to an embodiment of the present invention. As shown in FIG. 1, the electrophoretic display element has a predetermined gap. A display-side substrate 1 and a rear-side substrate 2 which are a pair of substrates arranged in a state, a partition wall 3 for forming a gap between the substrates 1 and 2, and a space surrounded by the substrates 1 and 2 and the partition wall 3 Insulating liquid 4 disposed therein, and a plurality of colored charged electrophoretic particles 5 dispersed in insulating liquid 4 are provided. The partition wall 3 also has a function of preventing the movement of the charged electrophoretic particles 5 between adjacent pixels.

  Here, the first electrode 6 is disposed on the surface of the rear substrate 2 which is the first substrate, which faces the display substrate 1 which is the second substrate. That is, a pixel is defined. At least a part of the surface of the first electrode 6 is covered with an insulating layer 7 that is a first insulating layer having a relative dielectric constant smaller than that of the insulating liquid 4. That is, the insulating layer 7 is provided between the first electrode 6 and the insulating liquid 4.

  On the other hand, the second electrode 8 is formed either on the surface or inside of the partition wall 3, for example, the side wall of the partition wall 3, that is, the insulating liquid 4 side, between the partition wall 3 and the display-side substrate 1, It is arranged in The second electrode 8 may be inside the partition wall 3, on the display side substrate 1 in contact with the partition wall 3, on the rear side substrate 2, or inside one of the substrates 1 and 2. In addition, when forming on a board | substrate, you may protrude from the partition 3 to the 1st electrode direction. In any of the above arrangements, the charged electrophoretic particles 5 can be moved between the first electrode 6 surface and the side surface of the partition wall 3 and the vicinity thereof.

  An insulating layer 9, which is a second insulating layer having a relative dielectric constant larger than that of the insulating liquid 4, is disposed between the surface of the second electrode 8, that is, between the second electrode 8 and the insulating liquid 4. Has been. Further, the relative permittivity of the display side substrate 1 is larger than the relative permittivity of the insulating liquid 4.

  Here, in the electrophoretic display element, by applying a voltage between the first electrode 6 and the second electrode 8, the charged electrophoretic particles 5 are placed on the surface of the first electrode 6 and its vicinity, and on the side surface of the partition wall 3 and its vicinity. It is comprised so that a display may be performed by moving between.

  For example, when the second electrode 8 is formed on the side surface of the partition wall 3 and the first electrode surface is colored white and the black electrophoretic particles 5 are used, for example, as shown in FIG. White display is performed by attracting the side surface of the partition wall 3, and black display is performed by moving the charged electrophoretic particles 5 so as to cover the first electrode 6 as shown in FIG.

  For example, when the second electrode 8 is formed between the partition 3 and the rear substrate 2 as shown in FIG. 3, the charged electrophoretic particles 5 are attracted to the side of the partition 3 as shown in FIG. Thus, white display is performed, and black display is performed by moving the charged electrophoretic particles 5 so as to cover the first electrode 6 as shown in FIG.

  In any of FIG. 1, FIG. 2, or FIG. 3, the partition 3 is formed so as to be separated from adjacent pixels. Since it is not preferable that the voltage applied to the second electrode 8 affects the display state of the adjacent pixels, the second electrode 8 provides a common constant potential in the adjacent pixels as a common electrode for display. Is preferably applied to the first electrode 6.

  Incidentally, in such an electrophoretic display element, an electric field formed in the insulating liquid 4 by applying a voltage between the first electrode 6 and the second electrode 8 is as shown in FIG. It is represented by an electric field line 20.

  Here, the lines of electric force 20 are emitted obliquely upward from the vicinity of the center of the first electrode 6 and enter the second electrode 8 through the insulating layer 7, the insulating liquid 4, and further the insulating layer 9. However, at this time, the electric lines of force 20 are refracted toward the rear substrate 2 at the interface between the insulating layer 7 having a smaller relative dielectric constant and the insulating liquid 4 having a larger relative dielectric constant. Furthermore, the electric lines of force 20 are refracted toward the display-side substrate 1 at the position facing the first electrode 6 at the interface between the insulating liquid 4 having a smaller relative dielectric constant and the larger insulating layer 9. .

  For this reason, the electric lines of force 20 passing through the insulating liquid 4 are smaller in angle with the substrate surface than in the case where there is no refraction as described above. That is, the arc-shaped electric force lines 20 distributed in the insulating liquid 4 are deformed so as to have a flatter arc shape.

  Then, the insulating layer 7 is provided on the first electrode 6 and the insulating layer 9 is provided on the second electrode 8 as described above, and the electric lines of force 20 passing through the insulating liquid 4 have a flattened arc shape ( Distribution), the following effects can be obtained.

  (1) As a result of the electric force lines 20 extending into the insulating liquid 4 having a flatter shape, the electric lines of force that have been detoured into the display-side substrate 1 are insulated by the repulsive action of the electric force lines. As a result, the density of the electric field lines 20 in the insulating liquid 4, that is, the electric field strength is increased. As a result, the moving speed of the charged electrophoretic particles 5 is increased, and the driving voltage is further reduced.

  (2) Even when attention is paid to a single line of electric force, for example, the line of electric force passing through the uppermost portion of the second electrode 8 is more resistant to the first electrode than when there is no refraction as described above. It is possible to reach the vicinity of the center of 6. Thus, when writing from white display to black display, the charged electrophoretic particles 5 present on the side surfaces of the partition walls 3 can reach the vicinity of the center of the first electrode 6 more. As a result, at the time of black display, the charged electrophoretic particles 5 can be more uniformly distributed on the first electrode 6 and the display contrast is increased.

  (3) In the lines of electric force emitted from the vicinity of the center of the first electrode 6, the component perpendicular to the substrate decreases, so that when writing from black display to white display, it collides with the display side substrate 1. The number of charged electrophoretic particles 5 can be reduced. As a result, adhesion of the charged electrophoretic particles 5 to the display-side substrate 1 can be suppressed, and the contrast is increased.

  FIG. 5 is a conceptual diagram visually showing a theory relating to refraction of electric lines of force at the interface between two dielectric layers having different relative dielectric constants.

  Now, assuming that the electric force lines 20 are incident on the two-layer dielectric interface having different relative dielectric constants at an incident angle θ1 with the perpendicular line 52 of the interface 53 and are emitted at an output angle θ2, the dielectric on the incident side. When the relative dielectric constant of ε1 is ε1 and the relative dielectric constant of the output-side dielectric is ε2, the relationship tan θ1 / tan θ2 = ε1 / ε2 holds, and θ1 <θ2 when ε1 <ε2. That is, when the relative dielectric constant of the incident-side dielectric material is smaller than the relative dielectric constant of the output-side dielectric material, the electric lines of force 20 increase the component in the direction parallel to the interface at the interface 53 of both dielectrics. It can be seen that the light is refracted.

  Therefore, as shown in FIG. 1 described above, by arranging the insulating layer 7 having a relative dielectric constant smaller than that of the insulating liquid 4 on the first electrode 6, the electric lines of force are generated at the interface between the two layers. Refracts to increase the component parallel to the substrate. Therefore, the electric field strength in the insulating liquid 4 increases, and further, the component parallel to the substrate of the electric field increases.

  Further, by disposing the insulating layer 9 having a relative dielectric constant larger than that of the insulating liquid 4 on the second electrode 8, the electric lines of force increase the component parallel to the substrate at the interface between the two layers. Refract. Therefore, the electric field strength in the insulating liquid 4 increases, and the component parallel to the substrate of the electric field increases.

  Further, when the relative permittivity of the display side substrate 1 is made larger than the relative permittivity of the insulating liquid 4, the distribution of the electric lines of force 20 in the pixel is as shown in FIG. That is, the electric lines of force 23 incident on the display side substrate 1 at the interface between the display side substrate 1 and the insulating liquid 4 and both layers are refracted so that a component parallel to the substrate increases. As a result, the repulsive action of the electric lines of force 23 occurs, the electric field strength in the insulating liquid 4 increases, and the component of the electric field parallel to the substrate increases.

  Thus, by optimizing the relative dielectric constant of the insulating layer 7 disposed on the first electrode 6, the insulating layer 9 disposed on the second electrode 8, and further the display-side substrate 1, the insulating property is improved. The intensity of the electric field passing through the liquid 4 can be increased, and the component parallel to the substrate can be increased.

  1, 2, or 3, the second insulating layer 10 is formed as the third insulating layer on the surface of the insulating layer 7 on the first electrode 6 as shown in FIG. 6A, for example. May be. Further, as shown in FIG. 6B, an insulating layer 11 may be formed as a third insulating layer as another insulating layer (insulating layer) on the surface of the insulating layer 9 on the second electrode 8. Further, as shown in FIG. 6C, an insulating layer 12 that is in contact with the insulating liquid 4 and has a relative dielectric constant larger than that of the insulating liquid 4 is formed on the surface of the display-side substrate 1. May be.

  6A to 6C, the dielectric constant of the insulating layer 7 on the surface of the first electrode 6 is smaller than the dielectric constant of the insulating liquid 4, and the second electrode 8 is used. The relative dielectric constant of the insulating layer 9 on the surface is larger than the relative dielectric constant of the insulating liquid 4.

  FIG. 7 is a conceptual diagram visually showing a theory relating to refraction when electric lines of force pass through three layers of dielectrics having different relative dielectric constants.

  Now, the electric lines of force 20 are incident on the three layers of dielectrics having different relative dielectric constants at an incident angle θ1 with the perpendicular line 52 of the interface 53, and are emitted at an outgoing angle θ2. Further, if the light is incident on the interface 54 at an incident angle θ2 and is emitted at an output angle θ3, in this case, the relationship of tan θ1 / tan θ3 = ε1 / ε3 holds, and when ε1 <ε3, θ1 <θ3. Become.

  That is, when the relative dielectric constant of the incident side dielectric material is lower than the relative dielectric constant of the output side dielectric material, it can be seen that the electric field lines 20 are refracted so as to increase the component in the direction parallel to the interface. . Furthermore, it can be seen that the relative dielectric constant ε2 of the intermediate layer does not affect the incident angle θ1 and the outgoing angle θ3.

  Therefore, even when the second insulating layers 10 and 11 having different relative dielectric constants are disposed on the surface of the insulating layer 7 or the insulating layer 9, the electric field strength in the insulating liquid 4 as described above is parallel to the substrate of the electric field. It can be seen that the effect of increasing the number of components can be obtained, improving the display contrast, further increasing the moving speed of the charged electrophoretic particles, and reducing the driving voltage.

  By the way, when the component parallel to the substrate 2 of the electric field near the bottom of the partition 3 is too large, when switching from white display to black display, for example, as shown in FIG. In some cases, it may not be possible to uniformly distribute on one electrode 6. In this case, the display contrast is slightly lowered.

  Therefore, in order to prevent such a decrease in display contrast, the insulating layer 7 should have a relative dielectric constant distribution or a different relative dielectric constant in a direction parallel to the substrate 2 as shown in FIG. Is more preferable. For example, in this case, the relative dielectric constant of the insulating layer 7b around the bottom of the partition wall is made larger than that of the insulating liquid 4, and the relative dielectric constant of the insulating layer 7a in the center of the pixel is made smaller than that of the insulating liquid 4.

  In the electrophoretic display element shown in FIG. 8A, an electric field formed in the insulating liquid 4 by applying a voltage between the first electrode 6 and the second electrode 8 is shown in FIG. ) And electric field lines 20 and 21 as shown in FIG. In FIG. 8, reference numeral 21 denotes electric lines of force near the bottom of the partition wall 3.

  Here, as shown in FIG. 8, the electric lines of force 20 emitted from the first electrode 6 near the center of the pixel are refracted toward the rear substrate 2 side at the interface between the insulating liquid 4 and the insulating layer 7a. Yes. The electric lines of force 21 emitted from the first electrode 6 near the bottom of the partition wall are refracted toward the display-side substrate 1 at the interface between the insulating liquid 4 and the insulating layer 7b. That is, the electric lines of force 21 are refracted in the vicinity of the bottom of the partition wall 3 so as to increase the component perpendicular to the substrate. Therefore, since the charged electrophoretic particles 5 can be moved also on the first electrode and in the vicinity of the bottom of the partition wall 3 during black display, the display contrast is further improved.

  Incidentally, it is desirable that the insulating layer 9 disposed on the surface of the second electrode 8 also has a relative permittivity distribution or a different relative permittivity in a direction parallel to the surface of the second electrode 8.

  FIG. 9 is a diagram showing a schematic configuration of the electrophoretic display element having such a configuration. In this electrophoretic display element, the relative dielectric constant of the insulating layer 9 a in the vicinity of the bottom of the partition wall 3 is smaller than that of the insulating liquid 4. The relative dielectric constant of the insulating layer 9 b in the other part (upper part) is made larger than that of the insulating liquid 4.

  FIG. 10 shows an electric force line distribution indicating an electric field formed in the insulating liquid 4 when a voltage is applied between the first electrode 6 and the second electrode 8 in such an electrophoretic display element. Is. In FIG. 10, reference numeral 22 denotes electric lines of force near the bottom of the partition wall 3.

  Here, as shown in FIG. 10, the electric lines of force 22 incident on the surface of the second electrode 8 located in the vicinity of the bottom of the partition wall are directed to the rear substrate 2 side at the interface between the insulating liquid 4 and the insulating layer 9a. Refracted. Further, the electric lines of force 20 incident on the other (upper) portion of the second electrode 8 disposed on the partition wall 3 are refracted toward the display-side substrate 1 at the interface between the insulating liquid 4 and the insulating layer 9b. doing. That is, the electric lines of force 22 are refracted in the vicinity of the bottom of the partition wall 3 so as to increase a component horizontal to the substrate. Therefore, the charged electrophoretic particles 5 can be moved to the vicinity of the bottom of the partition wall 3 on the first electrode during black display, so that the display contrast is further improved.

  FIG. 11 is a diagram showing different display states in the two pixels a and b of the electrophoretic display element according to the present embodiment.

  In FIG. 11, reference numeral 13 denotes a switching element such as a thin film transistor for active matrix driving, and the switching element 13 is formed corresponding to each pixel a and b. Other elements necessary for display, such as wiring or driver ICs, are not shown, but are arranged around the display element.

  A signal is supplied to the first electrode 6 of each pixel a, b through the switching element 13. The second electrodes 8 of the pixels a and b are preferably connected to each other and supplied with the same signal.

  As shown in FIG. 11, the second electrode 8 is disposed on the side surface of the partition wall 3, that is, on the insulating liquid 4 side, but between the partition wall 3 and the display side substrate 1 or between the partition wall 3 and the rear side substrate 2. You may make it arrange | position between. Further, the second electrode 8 may be inside or on the surface of the partition wall 3, and as shown in FIGS. 12A to 12C, the second electrode 8 is interposed between the partition wall 3 and other layers. It may be provided on the substrate 1 or on the rear substrate 2 or inside the substrate.

  As described above, the second electrode 8 is formed on one or more of the side surface, the bottom surface, and the top surface of the partition wall 3 or on the inside thereof. As a method for forming the second electrode 8, the second electrode 8 is formed on the rear substrate 2. After the formation, the partition 3 may be formed, or the second electrode 8 layer may be formed on the surface of the partition 3 formed on the substrate. Further, the partition 3 on which the second electrode 8 layer is formed may be disposed on the substrate.

  Here, as described above, the electrophoretic display element applies the voltage between the first electrode 6 and the second electrode 8 so that the charged electrophoretic particles 5 are separated from the first electrode 6 surface, the partition wall 3 side surface, The display is performed by moving between the vicinity.

  For example, when positively charged migrating particles are used, a positive voltage is applied to the first electrode 6 in a configuration in which the second electrode 8 is formed in the gap between the partition wall 3 and the insulating liquid 4, that is, on the side surface of the partition wall 3; When the second electrode 8 is grounded, the charged electrophoretic particles 5 are collected in the portion of the pixel b in FIG. 11, that is, the portion surrounded by the side surface of the partition wall 3 and the rear side substrate 2 excluding the first electrode 6 surface. Thus, the observer can observe the first electrode 6 surface. Here, if the surface of the first electrode 6 is white, a white display is obtained.

  In this white display, the charged electrophoretic particles 5 are collected in a portion surrounded by the rear substrate 2 except for the surfaces of the partition walls 3 and the first electrodes 6, and the charged electrophoretic particles 5 are located in a portion close to the rear substrate 2. Therefore, the influence of the viewing angle of the observer can be extremely reduced. Even when the second electrode 8 is formed on the side surface of the partition wall 3, the influence of the viewing angle does not increase.

  Thus, in the present electrophoretic display element, most of the colored charged particles gather on the surface of the partition wall 3 when displaying white, so that the area occupied by the colored charged particles when viewed vertically from the display side substrate 1 side is reduced. The brightness of the white display is increased and the contrast is improved.

  Further, when a negative voltage is applied to the first electrode 6 and the second electrode 8 is grounded, the charged electrophoretic particles 5 are spread on the portion of the pixel a, that is, on the surface of the first electrode 6 in FIG. This allows the observer to observe the charged electrophoretic particle color on the first electrode 6 surface. Here, when the color of the second electrode 8 and the color of the charged electrophoretic particles 5 are substantially matched, a clearer display can be performed. For example, high blackness can be obtained by setting both the charged electrophoretic particle color and the second electrode 8 to black.

In the above description, the colored electrophoretic particles 5 are black and the first electrode 6 surface is white. However, the present invention is not limited to this, and any combination of colors can be used. When performing color display, the colored charged electrophoretic particles 5 are preferably black, and the first electrode 6 surface is suitably red, green, blue, or the like. As a method of coloring,
・ Method of coloring the electrode itself ・ Method of providing a colored layer separately from the electrode ・ Method of using an insulating layer formed so as to cover the electrode (for example, using coloring of the insulating layer itself or mixing a coloring material into the insulating layer) Method)
Etc.

  The material of the partition 3 may be the same material as the substrate, or a photosensitive resin such as acrylic. In addition, any method may be used for forming the partition wall, for example, by applying a photosensitive resin layer, and then performing exposure and wet development, or a method of adhering a separately created partition wall, and further a printing method. A forming method or the like can be used.

  The rear substrate 2 may be made of glass, quartz, or the like, in addition to a plastic film such as polyethylene terephthalate (PET), polycarbonate (PC), or polyethersulfone (PES). The rear substrate 2 may be colored with polyimide (PI) or the like.

  The first electrode 6 and the second electrode 8 may be made of any conductive material that can be patterned. For example, a metal such as titanium (Ti), aluminum (Al), copper (Cu), carbon or silver paste, or an organic conductive film can be used. In addition, when using the 1st electrode 6 also as a light reflection layer, material with high light reflectivity, such as silver (Ag) or Al, is used suitably. When the first electrode 6 is used for white display, surface irregularities are provided so that light is irregularly reflected on the electrode surface itself, or a light scattering layer is formed on the electrode.

  For the insulating liquid 4, it is desirable to use isoparaffin, silicone oil and a transparent nonpolar solvent such as xylene and toluene.

  As the charged electrophoretic particles 5, it is preferable to use a material that is colored and has good positive or negative charge characteristics in the insulating liquid 4. For example, various inorganic pigments, organic pigments, carbon black, or resins containing them may be used. A particle having a particle size of about 0.01 μm to 50 μm can be usually used, but preferably about 0.1 to 10 μm.

  In addition, it is preferable to add a charge control agent for controlling and stabilizing the charge of the charged electrophoretic particles 5 in the insulating liquid 4 and the charged electrophoretic particles 5 described above. As such a charge control agent, a metal complex salt of a monoazo dye, salicylic acid, an organic quaternary ammonium salt, a nigrosine compound, or the like may be used.

  Further, a dispersing agent for preventing aggregation of the charged electrophoretic particles 5 and maintaining a dispersed state may be added to the insulating liquid 4. As such a dispersing agent, polyvalent metal phosphates such as calcium phosphate and magnesium phosphate, carbonates such as calcium carbonate, other inorganic salts, inorganic oxides, or organic polymer materials can be used.

  The insulating layer 7 covering the surface of the first electrode 6 is made of a material that has a relative dielectric constant smaller than that of the insulating liquid 4 and is difficult to form pinholes even in a thin film. Specific examples of such a material include organic porous materials such as borazine-silicon polymer and methylsiloxane polymer porous material, but are not limited thereto. A material having a dielectric constant of about 1.1 to 3.1 is preferably used as the dielectric constant of the insulating layer 7, and a smaller relative dielectric constant is more preferable.

  In the display pixel, the lines of electric force are distributed in an arc shape. Therefore, as the film thickness of the insulating layer 7 increases, the lines of electric force enter the interface between the insulating liquid 4 and the insulating layer 7 with a larger incident angle, and the refraction angle also increases. That is, although it is desirable that the insulating layer 7 is thick, in reality, there are problems such as a decrease in film thickness uniformity, a decrease in transmittance, and an increase in driving voltage. Therefore, the insulating layer 7 is usually used with a film thickness of about 0.01 to 20 μm, preferably about 0.1 to 10 μm.

  The insulating layer 7 preferably has an action of preventing charge injection from the first electrode 6 to the charged electrophoretic particles 5 and an adhesive action of the charged electrophoretic particles 5 for imparting memory properties to the display. Furthermore, the insulating layer 7 may have a function as a colored layer for performing color display or a function as a light scattering layer.

  Insulating layers having different relative dielectric constants may be formed on the surface of the insulating layer 7. In addition, insulating layers having the same relative dielectric constant may be formed.

  In addition, the insulating layer 7 may be an insulating layer having a distribution of relative permittivity in a direction parallel to the substrate or a different relative permittivity as shown in FIG. 8, for example. As a method, there is a method of sequentially forming insulating layers having different relative dielectric constants in a plurality of patterning steps. As described above, when the insulating layer 7 has a distribution of relative permittivity, the relative permittivity of the insulating layer on the center of the first electrode 6 (the insulating layer 7a in FIG. 8) is higher than that of the insulating liquid 4. It is desirable to reduce the relative dielectric constant of the insulating layer (insulating layer 7b in FIG. 8) in the vicinity of the bottom of the partition wall 3 to be larger than that of the insulating liquid 4.

  In addition, the insulating layer 9 covering the surface of the second electrode 8 is made of a material having a relative dielectric constant larger than that of the insulating liquid 4 and difficult to form pinholes even in a thin film. Specifically, a photosensitive acrylic resin or the like can be used, but is not limited thereto. It is preferable to use a material having a relative dielectric constant of 3.1 or more as the dielectric layer 9.

  Similar to the insulating layer 7 on the first electrode 6, the insulating layer 9 has a function of preventing charge injection from the electrode to the charged electrophoretic particles 5, and further, the charging electrophoretic particles 5 for providing a display with a memory property. It is desirable to have an adhesive action. Furthermore, insulating layers having different relative dielectric constants may be formed on the surface of the insulating layer 9. In addition, insulating layers having the same relative dielectric constant may be formed.

  Furthermore, the insulating layer 9 may be, for example, an insulating layer having a distribution of relative permittivity in a direction parallel to the surface of the second electrode 8 or a different relative permittivity as shown in FIG. As a method for realizing the above, there is a method of sequentially forming insulating layers having different relative dielectric constants in a plurality of patterning steps. In this way, when the insulating layer 9 has a relative dielectric constant distribution, the insulating layer near the bottom of the partition wall 3 (the insulating layer 9a in FIG. 9) has a relative dielectric constant smaller than that of the insulating liquid 4, The other dielectric constant of the insulating layer (insulating layer 9b in FIG. 9) on the surface of the second electrode 8 is preferably larger than that of the insulating liquid 4.

  A material having a relative dielectric constant larger than that of the insulating liquid 4 is used for the display-side substrate 1. As the relative dielectric constant of the display side substrate 1, it is desirable to use a material of 4.0 or more. Specifically, glass, quartz, or a plastic film having a relatively large relative dielectric constant can be used. Further, it is necessary to use a transparent material for the display side substrate 1.

  Further, when an insulating layer in contact with the insulating liquid 4 is disposed on the surface of the display side substrate 1, the relative dielectric constant of the insulating layer is made larger than the relative dielectric constant of the insulating liquid 4.

  According to the present embodiment, when the relative dielectric constant of the insulating liquid 4 is used as a reference, the insulating layer 7 having a smaller relative dielectric constant is disposed on the first electrode 6, and the second electrode 8 is formed on the surface of the second electrode 8. An insulating layer 9 having a higher relative dielectric constant is disposed. Further, the relative permittivity of the display side substrate 1 itself or the insulating layer disposed on the surface thereof is larger. With this structure, the electric lines of force are refracted so that the electric field strength in the insulating liquid 4 and the component parallel to the substrate of the electric field increase at the interface between the insulating liquid 4 and each insulating layer. As a result, the display contrast can be improved, and the drive voltage and response time can be reduced.

(Example)
Examples of the present invention will be described below.

(Example 1)
In this example, as the electrophoretic display element having the configuration shown in FIG. 1, an electrophoretic display element having a size of one pixel of 120 × 120 μm and 200 × 200 pixels was manufactured. Here, each pixel is surrounded by a partition wall having a width of 10 μm and a height of 20 μm. The first electrode is located at the center of the portion surrounded by the partition wall, and the length of one side is 100 μm. The second electrode is disposed on the side surface of the partition wall.

  Next, a method for manufacturing the electrophoretic display element according to this example will be described.

  A glass substrate having a thickness of 1.1 mm is used for the rear substrate 2, and a switching element, other wiring necessary for driving, a driver IC, and the like are formed on the rear substrate.

  Next, the first electrode 6 is formed on the rear substrate. The first electrode 6 is connected to a switching element on the rear substrate. As the material of the first electrode 6, aluminum having a high light reflectance is used. Next, the first electrode is covered with an insulating layer 7 made of an organic porous material having a relative dielectric constant smaller than that of the insulating liquid 4. The insulating layer material may contain titanium oxide fine particles to have a light scattering effect.

  Acrylic resin is patterned at the boundary portion of each pixel by exposure and development, and this is used as the partition 3. Next, patterning is performed on the side surface of the partition wall 3 using titanium as a material to form the second electrode 8. Further, a photosensitive acrylic resin having a relative dielectric constant larger than that of the insulating liquid is patterned on the surface of the second electrode to form and cover the insulating layer 9.

  Next, each pixel is filled with an insulating liquid 4 and charged electrophoretic particles 5. Isoparaffin (trade name: Isopar, manufactured by Exxon) is used for the insulating liquid 4, and a polystyrene-polymethylmethacrylate copolymer resin containing carbon black having a particle size of about 1 to 2 μm is used for the charged electrophoretic particles 5. . Isoparaffin contains succinimide (trade name: OLOA 1200, manufactured by Shepron) as a charge control agent. Next, a glass substrate having a relative dielectric constant larger than that of the insulating liquid 4 is disposed on the partition as the display side substrate 1.

  The electrophoretic display device manufactured by the above method includes the insulating layer 7 and the insulating liquid 4 on the first electrode, the insulating layer 9 and the insulating liquid 4 on the second electrode, and the display side substrate 1 and the insulating liquid. At the interface between the liquid 4 and the above three, the lines of electric force refract so as to increase the electric field strength in the insulating liquid and further increase the component parallel to the substrate. As a result, for example, more charged electrophoretic particles 4 can move to the center of the pixel during black display, so that the display contrast is improved. Furthermore, the response time can be shortened and the drive voltage can be reduced by increasing the electric field strength.

(Example 2)
In this example, as the electrophoretic display element having the configuration shown in FIG. 3, an electrophoretic display element having a size of one pixel of 120 × 120 μm and 200 × 200 pixels was manufactured. Here, each pixel is surrounded by a partition wall having a width of 10 μm and a height of 20 μm. The first electrode is located at the center of the portion surrounded by the partition wall, and the length of one side is 100 μm. The second electrode is disposed on the bottom surface of the partition wall.

  Next, a method for manufacturing the electrophoretic display element according to this example will be described.

  A glass substrate having a thickness of 1.1 mm is used for the rear substrate 2, and a switching element, other wiring necessary for driving, a driver IC, and the like are formed on the rear substrate.

  Next, the first electrode 6 is formed on the rear substrate. The first electrode 6 is connected to a switching element on the rear substrate. As the material of the first electrode 6, aluminum having a high light reflectance is used. Next, the first electrode is covered with an insulating layer 7 made of an organic porous material having a relative dielectric constant smaller than that of the insulating liquid 4. The insulating layer material may contain titanium oxide fine particles to have a light scattering effect.

  Next, the second electrode 8 is formed by patterning titanium at the boundary portion of each pixel. Thereafter, an acrylic resin having a relative dielectric constant larger than that of the insulating liquid is patterned on the second electrode by exposure and development, and this is used as the partition 3. Further, the surface of the partition wall is patterned with a photosensitive acrylic resin having a relative dielectric constant larger than that of the insulating liquid 4 to form an insulating layer 9 and cover it.

  Next, each pixel is filled with an insulating liquid 4 and charged electrophoretic particles 5. Isoparaffin (trade name: Isopar, manufactured by Exxon) is used for the insulating liquid 4, and a polystyrene-polymethylmethacrylate copolymer resin containing carbon black having a particle size of about 1 to 2 μm is used for the charged electrophoretic particles 5. . Isoparaffin contains succinimide (trade name: OLOA 1200, manufactured by Shepron) as a charge control agent. Next, a glass substrate having a relative dielectric constant larger than that of the insulating liquid 4 is disposed on the partition as the display side substrate 1.

  The electrophoretic display device produced by the above method includes the insulating layer 7 and the insulating liquid 4 on the first electrode, the insulating layer 9 and the insulating liquid 4 on the second electrode, and the display side substrate 1 and the insulating material. At the interface between the liquid 4 and the above three, the lines of electric force refract so as to increase the electric field strength in the insulating liquid and further increase the component parallel to the substrate. As a result, for example, more charged electrophoretic particles 5 can move to the center of the pixel during black display, so that the display contrast is improved. Furthermore, the response time can be shortened and the drive voltage can be reduced by increasing the electric field strength.

(Example 3)
In this example, an electrophoretic display element having a size of one pixel of 120 × 120 μm and 200 × 200 pixels was manufactured as the electrophoretic display element having the configuration shown in FIG. Here, each pixel is surrounded by a partition wall having a width of 10 μm and a height of 20 μm. The first electrode is located at the center of the portion surrounded by the partition wall, and the length of one side is 100 μm. The second electrode is disposed on the side surface of the partition wall.

  Next, a method for manufacturing the electrophoretic display element according to this example will be described.

  A glass substrate having a thickness of 1.1 mm is used for the rear substrate 2, and a switching element, other wiring necessary for driving, a driver IC, and the like are formed on the rear substrate.

  Next, the first electrode 6 is formed on the rear substrate. The first electrode 6 is connected to a switching element on the rear substrate. As the material of the first electrode 6, aluminum having a high light reflectance is used. Next, the first electrode is covered with an insulating layer 7 made of an organic porous material having a relative dielectric constant smaller than that of the insulating liquid 4. The insulating layer material may contain titanium oxide fine particles to have a light scattering effect. Further, the surface of the insulating layer on the first electrode is covered with another second insulating layer 10 made of a photosensitive acrylic resin. The second insulating layer 10 may also have a light scattering effect.

  Acrylic resin is patterned at the boundary portion of each pixel by exposure and development, and this is used as the partition 3. Next, patterning is performed on the side surface of the partition wall 3 using titanium as a material to form the second electrode 8. Further, a photosensitive acrylic resin having a relative dielectric constant larger than that of the insulating liquid is patterned on the surface of the second electrode to form and cover the insulating layer 9.

  Next, each pixel is filled with an insulating liquid 4 and charged electrophoretic particles 5. Isoparaffin (trade name: Isopar, manufactured by Exxon) is used for the insulating liquid 4, and a polystyrene-polymethylmethacrylate copolymer resin containing carbon black having a particle size of about 1 to 2 μm is used for the charged electrophoretic particles 5. . Isoparaffin contains succinimide (trade name: OLOA 1200, manufactured by Shepron) as a charge control agent. Next, a glass substrate having a relative dielectric constant larger than that of the insulating liquid 4 is arranged on the partition as a display side substrate.

  The electrophoretic display element produced by the above method includes the second insulating layer 10 and the insulating liquid 4 on the first electrode, the insulating layer 9 and the insulating liquid 4 on the second electrode, and the display-side substrate 1. In the insulating liquid 4, at the above three interfaces, the lines of electric force are refracted so as to increase the electric field strength in the insulating liquid and further increase the component parallel to the substrate. As a result, for example, more charged electrophoretic particles can move to the center of the pixel during black display, so that the display contrast is improved. Furthermore, the response time can be shortened and the drive voltage can be reduced by increasing the electric field strength.

Example 4
In this example, an electrophoretic display element having a size of one pixel of 120 × 120 μm and 200 × 200 pixels was manufactured as the electrophoretic display element having the configuration shown in FIG. 6B. Here, each pixel is surrounded by a partition wall having a width of 10 μm and a height of 20 μm. The first electrode is located at the center of the portion surrounded by the partition wall, and the length of one side is 100 μm. The second electrode is disposed on the side surface of the partition wall.

  Next, a method for manufacturing the electrophoretic display element according to this example will be described.

  A glass substrate having a thickness of 1.1 mm is used for the rear substrate 2, and a switching element, other wiring necessary for driving, a driver IC, and the like are formed on the rear substrate.

  Next, the first electrode 6 is formed on the rear substrate. The first electrode 6 is connected to a switching element on the rear substrate. As the material of the first electrode 6, aluminum having a high light reflectance is used. Next, the first electrode is covered with an insulating layer 7 made of an organic porous material having a relative dielectric constant smaller than that of the insulating liquid 4. The insulating layer material may contain titanium oxide fine particles to have a light scattering effect.

  Acrylic resin is patterned at the boundary portion of each pixel by exposure and development, and this is used as the partition 3. Next, the second electrode 8 is formed on the side surface of the partition wall 3 by patterning with titanium as a material. Further, the surface of the second electrode is patterned with a photosensitive acrylic resin having a relative dielectric constant larger than that of the insulating liquid 4 to form an insulating layer 9 and cover it. Further, the surface of the insulating layer on the second electrode is covered with a second insulating layer 11 made of another photosensitive acrylic resin.

  Next, each pixel is filled with an insulating liquid 4 and charged electrophoretic particles 5. Isoparaffin (trade name: Isopar, manufactured by Exxon) is used for the insulating liquid 4, and a polystyrene-polymethylmethacrylate copolymer resin containing carbon black having a particle size of about 1 to 2 μm is used for the charged electrophoretic particles 5. . Isoparaffin contains succinimide (trade name: OLOA 1200, manufactured by Shepron) as a charge control agent. Next, a glass substrate having a relative dielectric constant larger than that of the insulating liquid 4 is arranged on the partition as a display side substrate.

  The electrophoretic display element produced by the above method includes the insulating layer 7 and the insulating liquid 4 on the first electrode, the second insulating layer 11 and the insulating liquid 4 on the second electrode, and the display-side substrate 1. In the insulating liquid 4, at the above three interfaces, the lines of electric force are refracted so as to increase the electric field strength in the insulating liquid and further increase the component parallel to the substrate. As a result, for example, more charged electrophoretic particles can move to the center of the pixel during black display, so that the display contrast is improved. Furthermore, the response time can be shortened and the drive voltage can be reduced by increasing the electric field strength.

(Example 5)
In this example, an electrophoretic display element having a size of one pixel of 120 × 120 μm and 200 × 200 pixels was manufactured as the electrophoretic display element having the configuration shown in FIG. Here, each pixel is surrounded by a partition wall having a width of 10 μm and a height of 20 μm. The first electrode is located at the center of the portion surrounded by the partition wall, and the length of one side is 100 μm. The second electrode is disposed on the side surface of the partition wall.

  Next, a method for manufacturing the electrophoretic display element according to this example will be described.

  A glass substrate having a thickness of 1.1 mm is used for the rear substrate 2, and a switching element, other wiring necessary for driving, a driver IC, and the like are formed on the rear substrate.

  Next, the first electrode 6 is formed on the rear substrate. The first electrode 6 is connected to a switching element on the rear substrate. As the material of the first electrode 6, aluminum having a high light reflectance is used. Next, the first electrode is covered with an insulating layer 7 made of an organic porous material having a relative dielectric constant smaller than that of the insulating liquid 4. The insulating layer material may contain titanium oxide fine particles to have a light scattering effect.

  Acrylic resin is patterned at the boundary portion of each pixel by exposure and development, and this is used as the partition 3. Next, patterning is performed on the side surface of the partition wall 3 using titanium as a material to form the second electrode 8. Further, a photosensitive acrylic resin having a relative dielectric constant larger than that of the insulating liquid is patterned on the surface of the second electrode to form and cover the insulating layer 9.

  Next, each pixel is filled with an insulating liquid 4 and charged electrophoretic particles 5. Isoparaffin (trade name: Isopar, manufactured by Exxon) is used for the insulating liquid 4, and a polystyrene-polymethylmethacrylate copolymer resin containing carbon black having a particle size of about 1 to 2 μm is used for the charged electrophoretic particles 5. . Isoparaffin contains succinimide (trade name: OLOA 1200, manufactured by Shepron) as a charge control agent. Next, a glass substrate in which an insulating layer 12 having a relative dielectric constant larger than that of the insulating liquid 4 is formed on the surface in contact with the insulating liquid 4 as the display side substrate 1 is disposed on the partition wall.

  The electrophoretic display element produced by the above method includes the insulating layer 7 and the insulating liquid 4 on the first electrode, the insulating layer 9 and the insulating liquid 4 on the second electrode, and the insulating layer of the display-side substrate 1. 11 and the insulating liquid 4. At the above three interfaces, the electric lines of force refract so as to increase the electric field strength in the insulating liquid and further increase the component parallel to the substrate. As a result, for example, more charged electrophoretic particles can move to the center of the pixel during black display, so that the display contrast is improved. Furthermore, the response time can be shortened and the drive voltage can be reduced by increasing the electric field strength.

(Example 6)
In this example, an electrophoretic display element having a size of one pixel of 120 × 120 μm and 200 × 200 pixels was manufactured as the electrophoretic display element having the configuration shown in FIG. Here, each pixel is surrounded by a partition wall having a width of 10 μm and a height of 20 μm. The first electrode is located at the center of the portion surrounded by the partition wall, and the length of one side is 100 μm. The second electrode is disposed on the side surface of the partition wall.

  Next, a method for manufacturing the electrophoretic display element according to this example will be described.

  A glass substrate having a thickness of 1.1 mm is used for the rear substrate 2, and a switching element, other wiring necessary for driving, a driver IC, and the like are formed on the rear substrate.

  Next, the first electrode 6 is formed on the rear substrate. The first electrode 6 is connected to a switching element on the rear substrate. As the material of the first electrode 6, aluminum having a high light reflectance is used. Next, an acrylic resin is patterned by exposure and development at the boundary portion of each pixel and the vicinity thereof, and the insulating layer 7b is formed of a photosensitive acrylic resin having a relative dielectric constant larger than that of the insulating liquid 4.

  At this time, the length of the insulating layer 7b protruding from the bottom surface of the partition wall 3 was set to the length of several charged electrophoretic particles, specifically, the length of three. Further, the portion of the first electrode surface not covered with the insulating layer 7 b is covered with an insulating layer 7 a made of an organic porous material having a relative dielectric constant smaller than that of the insulating liquid 4. Titanium oxide fine particles may be included in the material of the insulating layers 7a and 7b to have a light scattering effect.

  Acrylic resin is patterned at the boundary portion of each pixel by exposure and development, and this is used as the partition 3. Next, patterning is performed on the side surface of the partition wall 3 using titanium as a material to form the second electrode 8. Further, the surface of the second electrode is covered with a second insulating layer 9 made of a photosensitive acrylic resin having a relative dielectric constant larger than that of the insulating liquid 4.

  Next, each pixel is filled with an insulating liquid 4 and charged electrophoretic particles 5. Isoparaffin (trade name: Isopar, manufactured by Exxon) is used for the insulating liquid 4, and a polystyrene-polymethyl methacrylate copolymer resin containing carbon black having a particle diameter of about 1 to 2 μm is used for the charged electrophoretic particles 4. . Isoparaffin contains succinimide (trade name: OLOA 1200, manufactured by Shepron) as a charge control agent. Next, a glass substrate having a relative dielectric constant larger than that of the insulating liquid 4 is disposed on the partition as the display side substrate 1.

  The electrophoretic display device produced by the above method includes the insulating layer 7 and the insulating liquid 4 on the first electrode, the insulating layer 9 and the insulating liquid 4 on the second electrode, and the display side substrate 1 and the insulating material. At the interface between the liquid 4 and the above three, the lines of electric force refract so as to increase the electric field strength in the insulating liquid and further increase the component parallel to the substrate. As a result, for example, more charged electrophoretic particles can move to the center of the pixel during black display, so that the display contrast is improved. Furthermore, the response time can be shortened and the drive voltage can be reduced by increasing the electric field strength.

(Example 7)
In this example, as the electrophoretic display element having the configuration shown in FIG. 9, an electrophoretic display element having a size of one pixel of 120 × 120 μm and 200 × 200 pixels was manufactured. Here, each pixel is surrounded by a partition wall having a width of 10 μm and a height of 20 μm. The first electrode is located at the center of the portion surrounded by the partition wall, and the length of one side is 100 μm. The second electrode is disposed on the side surface of the partition wall.

  Next, a method for manufacturing the electrophoretic display element according to this example will be described.

  A glass substrate having a thickness of 1.1 mm is used for the rear substrate 2, and a switching element, other wiring necessary for driving, a driver IC, and the like are formed on the rear substrate.

  Next, the first electrode 6 is formed on the rear substrate. The first electrode 6 is connected to a switching element on the rear substrate. As the material of the first electrode 6, aluminum having a high light reflectance is used. Next, the first electrode is covered with an insulating layer 7 having a relative dielectric constant smaller than that of the insulating liquid 4. The insulating layer material may contain titanium oxide fine particles to have a light scattering effect.

  Acrylic resin is patterned at the boundary portion of each pixel by exposure and development, and this is used as the partition 3. Next, patterning is performed on the side surface of the partition wall 3 using titanium as a material to form the second electrode 8. Next, an insulating layer 9a made of an organic porous material having a relative dielectric constant smaller than that of the insulating liquid 4 is formed in the vicinity of the bottom of the partition wall on the second electrode surface. Furthermore, an insulating layer 9b made of a photosensitive acrylic resin having a relative dielectric constant larger than that of the insulating liquid is formed on a portion of the second electrode surface that is not covered with the insulating layer 9a.

  Next, each pixel is filled with an insulating liquid 4 and charged electrophoretic particles 5. Isoparaffin (trade name: Isopar, manufactured by Exxon) is used for the insulating liquid 4, and a polystyrene-polymethylmethacrylate copolymer resin containing carbon black having a particle size of about 1 to 2 μm is used for the charged electrophoretic particles 5. . Isoparaffin contains succinimide (trade name: OLOA 1200, manufactured by Shepron) as a charge control agent. Next, a glass substrate having a relative dielectric constant larger than that of the insulating liquid 4 is disposed on the partition as the display side substrate 1.

  The electrophoretic display element produced by the above method includes the insulating layers 7a and 7b on the first electrode and the insulating liquid 4, the insulating layers 9a and 9b on the second electrode and the insulating liquid 4, and the display-side substrate. 1 and the insulating liquid 4, at the above three interfaces, the lines of electric force are refracted so as to increase the electric field strength in the insulating liquid and further increase the component parallel to the substrate. As a result, for example, more charged electrophoretic particles can move to the center of the pixel during black display, so that the display contrast is improved. Furthermore, the response time can be shortened and the drive voltage can be reduced by increasing the electric field strength.

1 is a diagram showing a schematic configuration of an electrophoretic display element which is an example of a display device according to an embodiment of the present invention. FIG. 6 illustrates a display operation of the electrophoretic display element. FIG. 10 is another diagram illustrating a display operation of the electrophoretic display element. The figure which shows distribution of the electric force line in the said electrophoretic display element. The conceptual diagram which shows the type | formula regarding the refraction | bending of the said electric force line | wire visually. The figure which shows the other schematic structure of the said electrophoretic display element. The conceptual diagram which shows the type | formula regarding the refraction | bending of the said electric force line | wire visually. The figure which shows the other schematic structure of the said electrophoretic display element. The figure which shows the other schematic structure of the said electrophoretic display element. The figure which shows distribution of the electric force line of the said electrophoretic display element. The figure which shows a different display state in two pixels of the said electrophoretic display element. The figure which shows the other schematic structure of the said electrophoretic display element. FIG. 10 is a diagram illustrating a display operation of a conventional electrophoretic display element. The figure which shows schematic structure of the conventional electrophoretic display element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Display side board | substrate 2 Back side board | substrate 3 Partition wall 4 Insulating liquid 5 Charged electrophoretic particle 6 1st electrode 7 Insulating layer 7a Insulating layer 7b of pixel center part Insulating layer 8 around the partition wall bottom part 2nd electrode 9 Insulating layer 9a Near partition wall bottom part Insulating layer 9b Insulating layer 10 above partition wall 2nd insulating layer 11 2nd insulating layer 12 Insulating layer 13 Switching element 20 Electric field lines 21 Electric field lines 23 Electric field lines a and b Pixel

Claims (11)

First and second substrates disposed with a gap therebetween, partition walls that hold the gap constant and partition pixels to define pixels, an insulating liquid disposed in the gap, and the insulating liquid A plurality of charged electrophoretic particles dispersed in the first substrate, a first electrode disposed in each pixel along the first substrate, and a second electrode disposed along at least a side surface of the partition wall, A display device that performs display by applying a voltage between one electrode and a second electrode to move the charged electrophoretic particles between the first electrode and the second electrode,
A first insulating layer provided between the first electrode and the insulating liquid and having at least a portion of a relative dielectric constant smaller than that of the insulating liquid; and the second electrode and the insulating liquid A display element comprising at least one of a second insulating layer provided between the second insulating layers and having a relative dielectric constant of at least a part larger than that of the insulating liquid.   The display element according to claim 1, wherein the first insulating layer and the second insulating layer are in contact with the first electrode and the second electrode, respectively.   3. The display element according to claim 1, wherein a third insulating layer having a relative dielectric constant different from that of the first insulating layer is provided between the first insulating layer and the insulating liquid.   The display element according to claim 1, wherein a relative dielectric constant of at least a part of the second substrate is larger than a relative dielectric constant of the insulating liquid.   The insulating layer in contact with the insulating liquid is provided on the second substrate, and the relative dielectric constant of at least a part of the insulating layer is larger than the relative dielectric constant of the insulating liquid. The display element as described.   The first insulating layer provided in at least a part between the first electrode and the insulating liquid has a relative permittivity distribution or a different relative permittivity in a direction parallel to the first substrate. The display element according to claim 1, wherein the display element is a display element.   The display element according to claim 6, wherein the relative dielectric constant of the first insulating layer is the smallest at the center of the pixel and increases as the partition wall is approached.   The relative dielectric constant of the central portion of the pixel of the first insulating layer is smaller than the relative dielectric constant of the insulating liquid, and the relative dielectric constant becomes larger than the relative dielectric constant of the insulating liquid as it approaches the partition. The display element according to claim 7.   The second insulating layer provided in at least a part between the second electrode and the insulating liquid has a relative dielectric constant distribution or a different relative dielectric constant in a direction parallel to the partition wall. The display element according to claim 1.   10. The display element according to claim 9, wherein the relative dielectric constant of the second insulating layer is the smallest at the first substrate side end of the side wall of the partition wall and increases as the partition wall approaches the second substrate side. The relative dielectric constant at the first substrate side end of the second insulating layer is smaller than the relative dielectric constant of the insulating liquid, and the relative dielectric constant becomes larger than the relative dielectric constant of the insulating liquid as it approaches the second substrate. The display element according to claim 10.

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