Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/165—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field
  • G02F1/166—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field characterised by the electro-optical or magneto-optical effect
  • G02F1/167—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field characterised by the electro-optical or magneto-optical effect by electrophoresis
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/165—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field
  • G02F1/1675—Constructional details
  • G02F1/16757—Microcapsules

Definitions

• the present invention relates to an electrophoretic display (apparatus) for performing display by moving charged electrophoretic particles (charged migrating particles) and a process for producing the electrophoretic display.
• FIG 11 shows an embodiment of a structure of the electrophoretic display D2.
• the electrophoretic display D2 of the type includes a pair of substrates la and lb oppositely disposed with a predetermined spacing, an insulating liquid 2 filled between these substrates la and lb, a multitude of colored and charged electrophoretic particles 3 dispersed in the insulating liquid 2, and electrodes 14 and 15 disposed for each pixel A so as to be along the substrates la and lb, respectively.
• the colored and charged electrophoretic particles are electrically charged to a positive or negative polarity, so that the particles are adsorved on either one of the electrodes 14 and 15 depending on a polarity of a voltage applied to the electrodes 14 and 15.
• the insulating liquid 2 and the charged electrophoretic particles 3 are respectively colored different colors, so that in the case where the charged electrophoretic particles 3 are adsorbed on the electrode 15 on a viewer side, the color of the charged electrophoretic particles 3 is visually recognized as shown in Figure 11(a). On the other hand, in the case where the charged electrophoretic particles 3 are adsorbed on the other (opposing) electrode 14, the color of the insulating liquid 2 is visually recognized as shown in Figure 11(b).
• JP-B Japanese Patent Publication
• JP-B Japanese Patent Publication No. 2551783 has disclosed a method wherein a disperse system comprising the insulating liquid 2 and the colored and charged electrophoretic particles 3 is encapsulated to form microcapsules within which the disperse system has been encapsulated in advance, and a binder material filling a space between microcapsules and being sealed together with the microcapsules between the pair of substrates, and can remedy the above-described display irregularity problem.
• this micro-encapsulation method it becomes possible to simplify a time-consuming and troublesome production process such that a volatile disperse system is uniformly encapsulated between the pair of substrate, thereby to realize a reduction in production costs.
• FIG. 12(a) and (b) each shows a sectional structure of a pixel of such a display scheme, and Figure 12(c) shows a corresponding plan view.
• Figures 12(a) and (b) are views illustrating a state that electrophoretic particles 50 are collected on the surface of a narrower electrode 30 and a state that the electrophoretic particles 50 are distributed over the surface of a wider electrode 40, respectively.
• the electrophoretic particles 50 By disposing one microcapsule 20 for one pixel, it is possible to cause the electrophoretic particles 50 to migrate in a lateral direction (along the substrate surface). As a result, when an electrophoretic liquid is transparent, it becomes possible to realize a black-and-white or color display based on a colored electrode surface. In the case of the black-and-white display, it is possible to switch a display mode by moving the electrophoretic particles 50 which are colored black within the microcapsules between a black-colored electrode 30 and a white-colored electrode 40.
• the insulating liquid is required to be colored by mixing a color former, such as dyes or ions, into the insulating liquid.
• a color former such as dyes or ions
• the conventional electrophoretic displays employ the transparent insulating liquid 25 as shown in Figure 12 but include a substrate on which each pixel is constituted by arranging two electrodes 30 and 40.
• the electrode 30 identical in color to the charged electrophoretic particles is required to occupy a predetermined planar area in which a brightness of a display surface is impaired, thus also resulting in less realization of high contrast state.
• a plurality of pixels each having a such a structure are arranged, so that the electrodes 30 and 40 create an electric field also with electrodes 30 and 40 of an adjacent pixel. More specifically, an electric field created within one microcapsule is leaked to an adjacent microcapsule, thus adversely affecting movement of the charged electrophoretic particles within the microcapsules.
• An object of the present invention is to provide an electrophoretic display which is excellent in display stability and is capable of realizing high- contrast display.
• Another object of the present invention is to provide a production method of the electrophoretic display.
• an electrophotographic display comprising: a plurality of microcapsules each encapsulating therein an insulating liquid and a plurality of charged electrophoretic particles dispersed in the insulating liquid, a first substrate and a second substrate disposed opposite to each other so as to sandwich the plurality of microcapsules, and a plurality of electrodes capable of being supplied with a voltage, wherein a voltage is applied between the plurality of electrodes to move the charged electrophoretic particles between a first internal wall portion of each microcapsule an external surface of which contacts the first substrate and a second internal wall portion of each microcapsule an external surface of which is substantially out of contact with both the first and second substrates, thereby to switch a display state.
• the plurality of electrodes comprise a first electrode disposed along the first substrate and a second electrode which is electrically isolated from the first electrode and is disposed at least a part of a space enclosed with the first and second substrates and the surfaces of microcapsules.
• an electrophoretic display including a plurality of microcapsules each encapsulating therein an insulating liquid and a plurality of charged electrophoretic particles dispersed in the insulating liquid, a first substrate and a second substrate disposed opposite to each other so as to sandwich the plurality of microcapsules, a first electrode disposed along the first substrate and a second electrode which is electrically isolated from the first electrode and is disposed at least a part of a space enclosed with the first and second substrates and the surfaces of microcapsules; the process comprising:
• an electrophoretic display including a plurality of microcapsules each encapsulating therein an insulating liquid and a plurality of charged electrophoretic particles dispersed in the insulating liquid, a first substrate and a second substrate disposed opposite to each other so as to sandwich the plurality of microcapsules, a first electrode disposed along the first substrate and a second electrode which is electrically isolated from the first electrode and is disposed at least a part of a space enclosed with the first and second substrates and the surfaces of microcapsules; the process comprising: a first step of preparing a laminated structure including an insulating layer and a projection-shaped electroconductive member, as the second electrode, disposed on the insulating layer by forming the electroconductive member at a recess of a mold substrate, laminating the insulating layer on the electroconductive member, and removing the laminated structure from the mold substrate, a second step of disposing the plurality of microcapsules so that the projection
• 4(a), 4(b), 4(c), 5(a), 5(b), 6(a) and 6(b) are respectively a schematic sectional view showing an embodiment of a representative structure of the electrophoretic display according to the present invention.
• Figures 7(a) - 7(d), 8(a) and 8(b), 9(a) - 9(c), and 10(a) - 10(e) are respectively schematic sectional views for illustrating an embodiment of a representative production method of the electrophoretic display of the present invention.
• Figures 11(a) and 11(b) are schematic sectional views showing an embodiment of a conventional display apparatus (electrophoretic display) .
• Figures 12(a) - 12(c) are schematic views showing a sectional structure (a) and (b) and a planar structure (c) of , another embodiment of the conventional display apparatus.
• the electrophoretic display includes two pixels consisting of pixel A and pixel B, a pair of substrates la and lb disposed opposite to each other with a predetermined spacing, and a plurality of microcapsules 8 disposed between the substrates la and lb.
• an insulating liquid 2 and a plurality of charged electrophoretic particles 3 dispersed in the insulating liquid are encapsulated.
• a first electrode 4 capable of applying a voltage to each pixel is disposed on and along either one of the substrate la or lb (the substrate la in this embodiment).
• the substrate on which the first electrode 4 is disposed is referred to as a "first substrate la" and the other substrate is referred to as a "second substrate lb".
• the first electrode 4 is colored white and a second electrode and the charged electrophoretic particles 3 are colored black, in advance.
• the first electrode 4 is made transparent and the second electrode and the charged electrophoretic particles 3 are made opaque.
• the display mode of the electrophoretic display according to the present invention is not limited to these display modes. Other display modes applicable to the present invention are described later.
• the plurality of microcapsules 8 are disposed along the first substrate la, i.e., are arranged side by side i one layer without overlapping each other, and the second electrode is disposed in a space 5 enclosed or defined by the outer surfaces of adjacent microcapsules 8 and the first and second substrates la and lb (indicated by oblique lines in Figure 1).
• the second electrode is formed with an electroconductive member filled in the space 5 between the plurality of microcapsules 8.
• the microcapsules 8 are ordinarily spherical, so that such a space 5 is left inevitably when the microcapsules 8 are sandwiched by the first and second substrate la and lb.
• an electric field is created only within each microcapsule 8 at the time of applying a voltage to the electrodes, so that the resultant electric field can be utilized in the most effective manner possible.
• the applied voltage is not required to be a higher value than is necessary.
• the second electrode is not limited to such a structure but may be modified into those described later.
• the electrophoretic display of the present invention is characterized in that a display mode is switched by moving the charged electrophoretic particles 3 between an internal wall portion of each microcapsule 8 a corresponding surface of which contacts the first substrate la and an internal wall portion of each microcapsule 8 a corresponding surface of which is substantially out of contact with both the first and second substrates la and lb and constitutes a side wall portion of the microcapsule 8.
• the "external surface of which is substantially out of contact with both the first and second substrates la and lb" principally refers to an external or outer surface portion corresponding to a side wall portion of each microcapsule 8 located between the first and second substrates la and lb but may inclusively refer to such an external surface portion that a direction and strength of electric field thereat are substantially identical to those at the external surface portion corresponding to the microcapsule side wall portion even when the portion almost contacts the first substrate la or the second substrate lb.
• the microcapsules 8 are ordinarily formed in a spherical shape in its preparation step but when the microcapsules 8 are disposed on the substrate and are compressed between the pair of first and second substrate la an lb, the resultant microcapsules 8 are deformed to assume a (partially) flattened shape. At that time, a part of the external surface of the respective microcapsules 8 contacts the first substrate la, another part thereof contacts the second substrate lb, and a remaining part of the 1 external surface, of the respective icrocapsules 8, which is substantially out of contact with both the first and second substrates la and lb, contacts the electroconductive member 6 as the second electrode.
• the first electrode In the case where the charged particles are attracted to the first electrode, the first electrode is disposed on the first substrate in a wider area, so that the charged particles are distributed over a corresponding internal wall portion.
• the charged particles come into sight in such a state that the charged particles gather in a narrower area at a peripheral side wall portion of each microcapsule when viewed from the display surface side. Accordingly, it becomes possible to realize a high-contrast display using these two display states.
• the second electrode is disposed in the space surrounding the side wall portion of each microcapsule, so that a strong electric field is also created in the vicinity of the second substrate to hold the charged electrophoretic particles at a corresponding internal wall portion of each microcapsule .
• the charged electrophoretic particles are moved to an internal wall portion of microcapsule, an external surface of which contacts the first substrate, the charged electrophoretic particles are distributed widely over the internal wall portion, so that an area occupied by the charged electrophoretic particles becomes larger when the electrophoretic display is viewed in the display direction, i.e., in a direction perpendicular to the substrate.
• one mode allows such a display state that the charged electrophoretic particles are distributed for display in the widest area possible and the other mode allows such a state that the charged electrophoretic particles are accumulated for display in the narrowest area possible. For this reason, the area for displaying white is made larger, thus achieving a bright display state. Further, a contrast, i.e., a ratio between the two display states can be made maximum in a scheme wherein a display state is switched by moving the charged electrophoretic particles in the substrate surface direction.
• the electrodes 30 and 40 are disposed on the same substrate surface, so that an electric field is very weak at an internal wall portion of microcapsule opposite to that closer to the attract and hold the charged electrophoretic particles.
• the charged electrophoretic particles are held only in the vicinity of the electrodes, so that a degree of overlapping is lesser than the state shown at the pixel B of Figure 1 even when the charged electrophoretic particles are accumulated on the narrower electrode 30 as shown in Figure 12(a), thus resulting in a wider planar area occupied by the charged electrophoretic particles. Consequently, a planar area of the other wider electrode 4 becomes narrower, so that a brightness in the bright state is not increased when compared with the pixel structure of Figure 1, thus failing to increase a contrast.
• the color of the charged electrophoretic particles is visually recognized through the transparent insulating liquid (at the pixel A). Further, when the charged electrophoretic particles covering the first electrode are moved to the side wall of the microcapsule, the color of the first electrode or the first substrate is visually recognized (at the pixel B) .
• the charged electrophoretic particles are colored black and the first electrode is colored white, it is possible to realize the black-and-white display (hereinafter, for convenience of explanation, the charged electrophoretic particles are in the black-colored state and the first electrode is in the white-colored state, unless otherwise specified) .
• the combination of coloring is not limited thereto but may be modified appropriately.
• the charged electrophoretic particles are colored black and the first electrode is appropriately colored red, green, blue, cyan, magenta or yellow.
• the coloring method of the first electrode may include:
• the charged electrophoretic particles which are appropriately colored red, green, blue, cyan, magenta and/or yellow.
• the number of microcapsules disposed for one pixel is one but is not limited thereto.
• the number of microcapsules disposed for each pixel may be changed to two as shown in Figure 2(a) or three or more.
• microcapsules used in the present invention may preferably be formed in a (partially) flattened shape along the substrates, whereby at the time of white display (at the pixel B of Figure 1), it is possible to increase a planar areal ratio between the white display electrode and the black charged electrophoretic particles when viewed from a viewer on the substrate lb side. As a result, a high-contrast display can be realized.
• the second electrode used in the present invention is disposed in a space between a microcapsule and an adjacent microcapsule, so that the second electrode may also function as a second electrode for the adjacent microcapsule. Accordingly, a potential of the second electrode may ordinarily be set to a level in common with all the pixels, whereby it is possible to prevent an occurrence of interference in terms of movement of charged electrophoretic particles between adjacent microcapsules due to leakage of an electric field from the microcapsule to the adjacent microcapsule.
• the second electrode is disposed in a space between plural microcapsules in the present invention but may be disposed in the entire space between the microcapsules or disposed on a part of the space only or one of the substrates. In the latter case, an effect of attracting the charged electrophoretic particles to the entire side walls of the microcapsules becomes smaller but an effect of electrically shielding adjacent microcapsules is sufficiently ensured. Further, the second electrode may be formed as a separate member in the space between the adjacent, microcapsules without being filled in the space or disposed in any position in the neighborhood of the substrate(s) . Further, the constitution (structure) of the second electrode is also not particularly limited.
• Figure 2(a) shows a structure of the electrophoretic display wherein the second electrode is formed with a electroconductive member which is filled in the entire space between the plurality of microcapsules.
• the electroconductive member is colored black similarly as in the charged electrophoretic particles but may be colored another color in the case of color display.
• the second electrode is made optically transparent in some cases in order to improve a viewing angle characteristic.
• the second electrode may be filled in not only the entire space between the microcapsules as shown in Figures 1 and 2(a) but also a part of the space as shown in Figure 2(b).
• the second electrode may be formed at all or a part of an external wall of the microcapsule side wall portion.
• the second electrode may be formed on the surface of the first substrate which defines the space between the adjacent microcapsules as shown in Figure 3(a).
• the second electrode may also be formed in a projected shape toward the second substrate side on the first substrate surface defining the space between the adjacent microcapsules as shown in Figure 3(b). The projected shape of the second electrode is not restricted to that shown in Figure 3(b).
• the second electrode may be formed, on the first substrate surface defining the space between the adjacent microcapsules, with an electroconductive member filled between the space as a part of the electroconductive member, as shown in Figure 3(c).
• an electroconductive member filled between the space as a part of the electroconductive member as shown in Figure 3(c).
• the second electrode formed on the first substrate it is possible to form the electroconductive member in the space between the microcapsules according to electroplating.
• a projected-shaped member is formed on the first substrate surface which contacts the space between the plurality of microcapsules, and the second electrode may be formed on, under or within the projected-shaped member as shown in Figures 4(a), 4(b) and 4(c), respectively.
• the shape of the projected member is not limited to those shown in Figures 4(a) - 4(c).
• the second electrodes and the projected-shaped members including the second electrodes lb shown in Figures 3(a) to 3(c) and 4(a) to 4(c) may be formed on the second substrate in place of the first substrate la. In these cases, it is necessary to effect a positional alignment
• the second electrode is not necessarily disposed at the space between all the microcapsules.
• a plurality of microcapsules are disposed within one pixel (pixel A or pixel B) and the second electrode may be disposed at a boundary between the adjacent pixels A and B.
• the first electrode is ia planar electrode disposed along the first substrate surface, but as shown in Figure 5(b), al or a part of the first electrode may be formed in a projected shape toward the second substrate side.
• the projected shape of the first electrode is not particularly limited so long as it is such a shape that the central electric field vector of the first electrode is directed in the direction of the second electrode.
• a minimum height of the projected shape may preferably be not less than 0.5 um, more preferably not less than 2 ⁇ m.
• a maximum height thereof may very depending on a distance (gap) between the first and second substrate but may preferably be not more than the gap between the substrates, more preferably be not more than 2/3 of the gap between the substrates. (Arrangement of microcapsules)
• the electrophoretic display of the present invention it is essentially unnecessary to positionally align each microcapsule with a corresponding first electrode and also to uniformize the size of microcapsules as shown in Figures 6(a) and 6(b). As shown in these figures, in the present invention, the microcapsules can be disposed irrespective of the position of the first electrode, thus being advantageous in terms of ease of prqduction.
• the position of a microcapsule may be in alignment with that of an associated first electrode.
• an occurrence of operation failure within a microcapsule disposed over adjacent two first electrode can be minimized.
• the microcapsules in the case where the second electrode is formed in the shape projected toward the second substrate side or formed on or within the projected-shaped member, the microcapsules can be readily disposed in alignment with a predetermined position.
• a predetermined position For example, when the microcapsules are disposed in a predetermined position by an ink jet method, positioning of the microcapsules in the predetermined position can readily be performed based on the prpjected shape of the sep ⁇ nd elept.rpde used, thus being remarkably improved in positioning efficiency.
• the positioning of the microcapsules can be effected by using printing techniques such as screen printing and gravure printing, or a technique such as FSA (fluidic self-assembly).
• FSA fluidic self-assembly
• the electrophoretic display of the present invention it is preferable to dispose a third electrode on the second substrate. If the charged electrophoretic particles are moved in the direction of the second substrate and are attached to the side walls of the microcapsules which contact the second substrate, a resultant display contrast is lowered. In order to suppress the lowering in contrast, it is possible to prevent movement of the charged electrophoretic particles in the second substrate direction by applying a voltage of a polarity identical to the charged electrophoretic particles to the third electrode. For example, in the case where the charged electrophoretic particles are positively charged, a positive-polarity voltage is applied to the third electrode on the second substrate, whereby the movement of the charged electrophoretic particles toward the second substrate can effectively be suppressed.
• first substrate la and the second substrate lb it is possible to use inorganic materials inclusive of polymer films, such as polyethylene terephthalate (PET) and polyether sulfone (PES); glass; and quartz.
• PET polyethylene terephthalate
• PES polyether sulfone
• glass glass
• quartz quartz
• the first electrode 4 it is possible to use any material if it is an electroconductive material capable of being patterned.
• the insulating layer 7 which covers the first electrode 4 it is preferable to use a low-dielectric constant material which does not readily cause pinh ⁇ le even if it is formed in a thin film, specifically amorphous fluorine-containing resin, high transparent polyimide, PET, etc.
• a colorless transparent liquid such as silicone oil, toluene, xylene or high-purity petroleum, may be used.
• the charged electrophoretic particles 3 it is possible to use particles of a material, which exhibits a good charge characteristic in the insulating liquid 2, such as polyethylene or polystyrene.
• carbon black may preferably be mixed in the above resin.
• a particle size of the charged electrophoretic particles 3 is not particularly limited but may preferably be 0.5 - 10 ⁇ m.
• the insulating liquid 2 and the plurality of the charged electrophoretic particles 3 dispersed in the insulating liquid 2 are micro-encapsulated by an appropriate method, such as interfacial polymerization, insolubilization reaction, phase separation or interfacial precipitation.
• the size of the microcapsules may preferably be several ten microns to several hundred microns.
• a first production process for the electrophoretic display (display apparatus) of the present invention is shown in Figures 7(a) to 7(c).
• the first electrode 4 is formed on the first substrate la and is coated with the insulating layer 7 by using a known method, such as printing or photolithography.
• the microcapsules 8 are disposed on the first substrate la ( Figure 7(a)).
• the microcapsules 8 are disposed in positional alignment with the first electrode while keeping a predetermined space between adjacent microcapsules by using a method, such as an ink jet method, a screen printing method or a gravure printing method.
• the second substrate lb is placed to sandwich the microcapsules 8 between the first and second substrates la and lb, and an appropriate pressure is applied between the pair of substrates la and lb.
• the microcapsules 3 are deformed in a flattened form and are caused to approach each other so as to leave a predetermined space ( Figure 7(b)).
• a liquid electroconductive member 5 is filled by utilizing a capillary action ( Figure 7(c)).
• the electroconductive member 5 may be formed only with an electroconductive material or by mixing the electroconductive material into an insulating base material.
• the electroconductive material it is preferable to use an electroconductive polymeric material which is liquid and exhibits fluidity or the electroconductive polymeric material colored with a dye. It is further preferable to impart a property of being curable by heating or light irradiation to the electroconductive member 5.
• the curable electroconductive member 5 is appropriately cured by heating or light irradiation to form the second electrode.
• a second production process of the electrophoretic display of the present invention includes a step shown in Figure 7(d) in addition to the first production process described above.
• the microcapsules 8 are disposed on the first substrate la and sandwiched between the first and second substrate la and lb by placing the second substrate lb on the microcapsules 8 ( Figure 7(a)). Thereafter, the microcapsules 8 are partially flattened by applying ah appropriate pressure between the pair of substrates la and lb ( Figure 7(b)).
• the electroconductive member 5 is filled in the space between adjacent microcapsules created in the first step under the action of capillary phenomenon ( Figure 7(c)).
• FIGs 8(a) and 8(b) show a third production process of the electrophoretic display of the present invention.
• Each of microcapsules 8 is disposed between the first and second substrates la and lb and either one or both of the first and second substrates la and lb are provided with an injection port 9 for the electroconductive member 5 ( Figure 8(a)).
• the injection port 9 is located in the space between adjacent microcapsules 8 arranged along the first substrate la. Then, from the injection port 9, the electroconductive member ⁇ is injected in the space between adjacent microcapsules 8 to form the second electrode ( Figure 8(b)). (Production process 4)
• Figures 9(a) to 9(c) show a fourth production process of the electrophoretic display of the present invention.
• a plurality of microcapsules 8 are disposed on the first substrate la.
• a plating electrode 51 has been formed, in advance, in addition to the first electrode 4 and the insulating layer 7 ( Figure 9(a)).
• the resultant structure is then immersed into a plating liquid to cause metal plating using the electrode 51 as an electrode for metal plating, thus forming therein the second electrode 5 ( Figure 9(b)).
• a metal capable of being formed through plating such as Ni, Au, Pt, Ag, Cu or Cr may suitably be used.
• the second substrate lb is bonded to the structure ( Figure 9(c)).
• a second substrate lb On a second substrate lb, an electrode and a plurality of microcapsules 8 are disposed, followed by metal plating similarly as in Production process 4 to form a second electrode. Thereafter, a first substrate la on which a first electrode is formed is bonded to the first substrate lb so as to sandwich the microcapsules 8 therebetween. (Production process 6)
• a projected-shaped second electrode is formed in advance on a mold substrate and each microcapsule is disposed between the adjacent second electrodes.
• a mold substrate 10 provided with recess portions 52 disposed so as to correspond to a space between adjacent microcapsules to be formed, is prepared ( Figure 1(a)).
• an electroconductive layer 5 to be used as the second electrode is formed on the mold substrate 10.
• an insulating layer 71 is formed ( Figure 10(b) ) .
• the microcapsules 8 are disposed ( Figure 10(d)).
• the structure 11 in which the microcapsules 8 are disposed is bonded to a first substrate la or which a first electrode 4 and an insulating layer 7 are formed in advance ( Figure 10(e)).
• the first substrate on which the first electrode has been formed in advance may be disposed and ponded onto the insulating layer 71.
• the second electrode by patterning a lamination layer comprising the insulating layer 71 and the electroconductive layer 5 through a photolithographic process without using the mold substrate as described in Example 2 appearing hereinafter and removing the electroconductive layer by etching so as to only leave the second electrode portion.
• the electroconductive layer is made thick, it is possible to form such a structure that the second electrode is protruded from the first substrate in a projected- shape as shown in Figure 3(b).
• the structure is bonded to the second substrate provided with no electrode to prepare an electrophoretic display having a structure as shown in Figure 3(b) or Figure 4. (Driving method)
• the second electrode is grounded as a common electrode for all the pixels and a voltage is applied to the first electrode of each pixel, whereby it is possible to move the charged electrophoretic particles which have been electrically charged to a positive polarity or a negative polarity.
• the charged electrophoretic particles are moved to a position which covers thb first electrode, the color of the charged electrophoretic particles is visually recognized through the transparent insulating liquid.
• the charged electrophoretic particles which have covered the first electrode are moved to the side wall surface side of a microcapsule where the microcapsule contacts or crates a space with its adjacent microcapsule, the color of the first display electrode or the first substrate is visually recognized.
• the second electrode is disposed in a space defined or enclosed by the outer surfaces of adjacent microcapsules and the upper and lower (second and first) substrates, and a voltage is applied between the first and second electrodes to cause the charged electrophoretic particles to migrate between the side wall portion of each microcapsule, i.e., the internal wall surface of each microcapsule an external (outer) surface of which does not contact both the first and second substrates, and the internal wall portion of each microcapsule an external surface of which contacts the first substrate.
• a voltage is applied between the first and second electrodes to cause the charged electrophoretic particles to migrate between the side wall portion of each microcapsule, i.e., the internal wall surface of each microcapsule an external (outer) surface of which does not contact both the first and second substrates, and the internal wall portion of each microcapsule an external surface of which contacts the first substrate.
• the second electrode disposed between adjacent microcapsules is grounded as the common electrode for all the pixels, whereby an electric field applied to each pixel (each microcapsule) can be prevented from leaking to its adjacent pixel (adjacent microcapsule).
• the second electrode functions as a shield electrode.
• the charged electrophoretic particles encapsulated in each microcapsule is controlled only by a voltage applied to the associated microcapsule without being adversely affected by a voltage applied to an adjacent microcapsule, thus realizing stable display without causing display disorder or lowering in contrast.
• the above-mentioned shield effect of the second electrode becomes noticeable in such a structure that the electroconductive member is filled in the space between adjacent microcapsules as shown in Figure 1, and is one of significant characteristic features of the electrophoretic display according to the present invention.
• Example 1 An electrophoretic display having a structure shown in Figure 1 was prepared by the above-mentioned
• first substrate la As a first substrate la, an aluminum thin film was formed on a surface of a (200 ⁇ m-thick) PET film, followed by patterning through a photolithographic or wet etching process to form a plurality of first electrodes 4.
• White coloring layers were formed so as to cover these first electrodes 4.
• These white coloring layers 4 were formed of an acrylic resin and a white pigment, such as titanium oxide (use in this example) or alumina, dispersed in the acrylic resin.
• an insulating layer 7 of an acrylic resin was formed so as to cover the white coloring layers.
• Microcapsules 8 were prepared by a combined coacervation method.
• isoparaffin trade name: "Isopar”, mfd. by Exxon Corp.
• charged electrophoretic particles 3 particles of polystyrene-polymethyl methacrylate copolymer resin containing carbon black and having a particle size of ca. 1 - 2 ⁇ m were used.
• succinimide trade name: "OLOA 1200", mfd. by Shevron Corp.
• the resultant charged electrophoretic particles 3 exhibited a positive chargeability.
• the microcapsules 8 were arranged on the first substrate la and were flattened, while being sandwiched between the first substrate la and a second substrate lb (200 ⁇ m-thick PET film) with a roll laminator, by applying an appropriate pressure between the first and second substrates la and lb, so as to bring each microcapsule near to its adjacent microcapsule.
• an electroconductive member As the electroconductive member, an electroconductive polymeric material containing metal (used in this example), metal oxide, polypyrrole, polyaniline, polythiophene, its derivative, etc., was used.
• a display operation was performed by using the thus-prepared electrophoretic display to measure a display characteristic. More specifically, a voltage applied to the second electrode 5 as a common electrode for all the pixels was set to 0 V, and a voltage applied to the first electrode 4 for each pixel was fluctuated between ⁇ 20 V. As a result, a good and stable black-and-white (monochrome) display characteristic was obtained. Further, it was also confirmed that a fluctuation in contrast was not observed and a stable display contrast was achieved even when different black and white display states were employed between adjacent pixels. (Example 2)
• An electrophoretic display having a structure shown in Figure 3(b) was prepared in the following manner.
• each (one) pixel was set to 180 ⁇ m x 180 ⁇ m.
• first substrate la As a first substrate la, an aluminum thin film was formed on a surface of a (180 ⁇ m-thick) PES film, followed by patterning through a photolithographic or wet etching process to form a plurality of first electrodes 4.
• White coloring layers were formed so as to cover these first electrodes 4.
• These white coloring layers 4 were formed of an acrylic resin and a white pigment, such as titanium oxide (used in this example) or alumina, dispersed in the acrylic resin.
• an insulating layer 7 of an acrylic resin was formed so as to cover the white coloring layers.
• an electroconductive resist was applied, followed by patterning in a shape shown in Figure 3(b) to form a second electrode having a width of 5 ⁇ m and a height of 15 ⁇ m.
• the electroconductive resist it is possible to use these containing, as a skeleton (main chain) or a side chain, an electroconductive polymeric substance such as thiophene, acetylene pyrrole thiazyl, azulene, indene, indole, p-phenylene, naphthylene, anthracene, aniline, phthalocyanine, carbazole ferrocene, TCNQ complex and their derivatives. In this example, thiophene was used. Microcapsules 8 were prepared in the same manner as in Example 1.
• the microcapsules 8 were positioned in alignment with the position of the first electrodes 4. At this time, based on the projection-shaped second electrode 5, it was possible to enhance an efficiency of accommodating the microcapsules 8 in a predetermined position. Thereafter, a second substrate lb (180 ⁇ m-thick PES film) was disposed opposite from the first substrate la, and an appropriate pressure was applied between the first and second substrates la and lb to flatten the microcapsules 8. A display operation was performed by using the thus-prepared electrophoretic display to measure a display characteristic.
• a voltage applied to the second electrode 5 as a common electrode for all the pixels was set to 0 V, and a voltage applied to the first electrode 4 for each pixel was fluctuated between ⁇ 20 V.
• An electrophoretic display having a structure shown in Figure 3(c) was prepared by the fifth production process shown in Figure 9.
• the size of each (one) pixel was set to 180 ⁇ m x 180 ⁇ m.
• first substrate la As a first substrate la, an aluminum thin film was formed on a surface of a (1.1 mm-thick) glass substrate, followed by patterning through a photo- lithographic or wet etching process to form a plurality of first electrodes 4.
• White coloring layers were formed so as to cover these first electrodes 4.
• These white coloring layers 4 were formed of an acrylic resin and a white pigment, such as titanium oxide (used in this example) or alumina, dispersed in the acrylic resin.
• an insulating layer 7 of an acrylic resin was formed so as to cover the white coloring layers. Then, on the surface of the insulating layer
• an ITO (indium tin oxide) film was formed, followed by patterning through a photolithographic or wet etchipg process to form a plating electrode 51 having a width of 5 ⁇ m.
• Microcapsules 8 were prepared in the same manner as in Example 1 and were encapsulated between the first substrate la and a second substrate lb (1.1 mm-thick glass substrate), followed by flattening of the microcapsules 8 by applying an appropriate pressure between the first and second substrates la and lb. Then, the second substrate lb was once removed, and an electroconductive member 5 for forming a second electrode was formed in the space between adjacent microcapsules by electroplating with the plating electrode 51. Thereafter, the second substrate lb was again bonded to the resultant strudture.
• a second substrate lb 1.1 mm-thick glass substrate
• a display operation was performed by using the thus-prepared electrophoretic display to measure a display characteristic. More specifically, a voltage applied to the second electrode 5 as a common electrode for all the pixels was set to 0 V, and a voltage applied to the first electrode 4 for each pixel was fluctuated between +20 V. As a result, a good and stable black-and-white (monochrome) display characteristic was obtained. Further, it was also confirmed that a fluctuation in contrast was not observed and a stable display contrast was achieved even when different black and white display states were employed between adjacent pixels.

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