JP4717546B2 - Particle movement type display device - Google Patents

Description

  The present invention relates to an electrophoretic display device, a toner display, or the like that changes the amount of transmitted light for each display unit by moving colored charged particles between a display surface for each display unit and a rising surface of a partition wall surrounding the display surface. More particularly, the present invention relates to a thin film electrode structure disposed on a display surface.

  In recent years, with the development of information equipment, development research on wearable PCs, electronic notebooks, electronic papers, electronic books, etc. has progressed, and as an information output device that can be used outdoors, low power consumption, high definition, high contrast, thin and lightweight Image display device is required. As one of such image display devices, a particle movement type display device including an electrophoretic display device has been proposed.

  The particle movement type display device is an image display device that performs pixel display by moving charged particles between electrodes arranged facing a moving space of charged particles. The particle movement type display device can maintain the pixel display for a while after the electric field is released, does not require a polarizing plate that impairs the light source light by 50% or more, enables high-contrast pixel display with colored charged particles, has a simple structure and operation, etc. There are many advantages over conventional liquid crystal display devices.

  Patent Document 1 discloses an electrophoretic display device in which a planar display electrode is provided on a display surface surrounded by a partition wall and a partition electrode is provided on a rising surface of the partition wall, and is set between the display electrode and the partition electrode. The charged particles are moved between the display surface and the standing surface by the potential polarity. Here, when the display surface is colored white, black charged particles are used and the charged particles are collected on the display surface, the pixels are displayed in black, while when the charged particles are collected on the standing surface, the display surface is exposed. The pixel is displayed in white.

JP 9-2111499 A

  Since the electrophoretic display device of Patent Document 1 has a flat display electrode facing the moving space of the charged particles, the inclination of the electric field is vertical in the vicinity of the center of the display electrode, and the charged particles are horizontally aligned along the display electrode. It cannot move efficiently in the direction. In view of this, an electrophoretic display device has been proposed in which black charged particles are moved radially from the surrounding partition wall surface toward the center of the display electrode, with the entire rising surface of the partition wall surrounding the display electrode as the electrode surface (FIG. 6). reference).

  Here, when the charged particles are collected in the partition wall and the display electrode is exposed, if the potential polarity of the electrode surface and the display electrode is reversed, the charged particles move along the electric lines of force from the partition wall to the display electrode, The display electrode is gradually covered toward the center by the particles.

  However, even in this case, in the vicinity of the center of the flat display electrode having high conductivity, the moving speed of the charged particles in the horizontal direction is extremely reduced as compared with the peripheral portion. This is because the electric field is concentrated in the area where the display electrode and the partition wall are adjacent to each other, and a large horizontal potential difference is formed in the horizontal direction.At the center of the display electrode, the electric field is sparse and the gradient of the space potential is gentle. Since a space potential difference is formed in the vertical direction, effective horizontal acceleration cannot be performed on the charged particles (see FIG. 7).

  Therefore, although there is no problem in performing black and white two-color inversion display over a sufficient period of time, if an intermediate gradation display is to be performed, the central portion of the display electrode cannot be sufficiently covered with charged particles, so that the pixel display Low contrast, long time to complete covering the center of the display electrode with charged particles, resulting in poor pixel display responsiveness, and charged particle responsiveness is different between the periphery and the center of the display electrode. Problems such as low gradation controllability and low reproducibility remained.

  An object of the present invention is to provide a highly responsive particle migration display device capable of efficiently moving charged particles in the horizontal direction even near the center of the display surface.

The particle movement type display device of the present invention includes a first substrate, a second substrate, a partition wall that keeps a predetermined distance between the first substrate and the second substrate , the first substrate , the second substrate , Insulating liquid containing charged particles filled in the pixels partitioned by the partition walls, a display electrode disposed in the center of the pixel of the first substrate, and the upper surface of the first substrate connected to the display electrode A resistance layer disposed on the partition wall and a partition wall electrode disposed on the partition wall, wherein the resistance layer and the partition wall electrode are separated from each other, and a voltage is applied to the display electrode to cause the charged particles to move to the first electrode. In a particle movement type display device that performs display by moving in a direction along a substrate, the sheet resistance of the resistance layer is such that a potential gradient generated in the resistance layer when a voltage is applied to the display electrode is It is a sheet resistance that can continue according to the travel time of
Further, the particle movement type display device of the present invention includes a first substrate, a second substrate, a partition wall that keeps a predetermined distance between the first substrate and the second substrate, the first substrate, and the second substrate. An insulating liquid containing charged particles filled in a pixel partitioned by a substrate and the partition, a display electrode disposed on the first substrate, and disposed on the display electrode, An insulating layer having a provided contact hole; a resistance layer disposed on the insulating layer and connected to the display electrode through the contact hole of the insulating layer; and a partition electrode disposed on the partition A particle movement type display device that separates the resistance layer and the partition wall electrode and applies a voltage to the display electrode to move the charged particles in a direction along the first substrate. The sheet resistance of the resistance layer is the display voltage. Potential gradient generated in the resistive layer when a voltage is applied to the can, but the a correspondingly be continued sheet resist movement time of the charged particles.

A particle migration type display device of the present invention, upon applying a voltage signal to between the septal wall electrodes and the display electrodes, the surface of the resistance layer, transient surface potential slope is formed, adjacent to the display surface In the moving space, a transient surface space potential difference corresponding to the surface potential gradient is formed. In the case of a highly conductive electrode member (see FIG. 6), the transient surface potential gradient is canceled out instantaneously, and the transient of the moving space is accelerated without accelerating the charged particles in the direction along the first substrate. spatial difference also disappears, but if the resistor layer sheet resistance is set as described above, since the electric moving speed is slow, transient surface potential slope along the first substrate continue to charged particles Contributes to moving the direction .

  In other words, the combination of the appropriate sheet resistance (material, additive, film thickness, stacking conditions, etc.) of the resistive thin film layer according to its capacitance structure and the appropriate voltage signal waveform makes the transient transition of the resistive thin film layer The surface potential gradient is continued to such an extent that it can be used for the movement of charged particles.

  Therefore, when a voltage signal is applied between the electrode surface of the partition wall and the power supply unit, the power supply unit moves from the electrode surface to the electrode surface, or vice versa, depending on the potential polarity. The charged particles are accelerated and moved in the direction along the display surface.

  When the transient surface potential gradient is canceled by the electron movement through the resistive thin film layer, the electric field is the same as in the case of a highly conductive electrode member, and the charged particles are pressed against the display surface or the electrode surface. In addition, intermolecular attractive force or physical engagement of the charged particles with respect to the display surface or the electrode surface is likely to occur, and the property of retaining the charged particles at the interface is enhanced.

  In other words, immediately after the voltage signal is applied between the electrode surface and the power feeding unit, a transient space potential difference along the display surface is formed in the moving space adjacent to the display surface, and the charged particles move along the display surface. Therefore, the responsiveness of pixel display is improved. Thereafter, when the transient space potential difference disappears, the charged particles are pressed perpendicularly to the electrode surface or display surface of the movement destination, and the affinity of the interface becomes easy to work, so that the memory performance of pixel display is improved.

  Hereinafter, reflective electrophoretic display devices 100 to 300 that are embodiments of the present invention will be described in detail with reference to the drawings. Although the electrophoretic display devices 100 to 300 are of a reflective type that does not have a backlight, the present invention may be implemented as a transmission type device in which a backlight is provided adjacent to the rear substrate 1. The electrophoretic display devices 100 to 300 are active matrix types in which switching elements formed for each pixel are dynamically controlled by a large number of data lines and a large number of trigger lines arranged in a grid pattern. A pixel driving method other than the active matrix type may be employed.

  The electrophoretic display devices 100 to 300 are image display devices in which innumerable pixels are arranged in a grid pattern, but in FIG. 1 to FIG. 9, one pixel (unit display) is representatively illustrated. Further, the general structure, general manufacturing method, surface treatment, and the like of the display device disclosed in Patent Document 1 are different from the gist of the present invention, and some illustrations are omitted to avoid complications. Detailed description is also omitted.

  Further, the particle movement type display device of the present invention can be implemented both when a charged particle is interposed between a pair of substrates and when a charged particle dispersed in an insulating liquid is interposed. Since the essence of the embodiments is the same, a typical embodiment of the latter electrophoretic display device will be described below.

<First Embodiment>
1 is an explanatory diagram of a cross-sectional configuration of the electrophoretic display device of the first embodiment, FIG. 2 is an explanatory diagram of a planar configuration of the electrophoretic display device of the first embodiment, and FIG. 3 is a diagram of a transient electric field change in a moving space. It is explanatory drawing. In FIG. 3, (a) is immediately after voltage application, (b) is after 100 msec voltage application, (c) is after 200 msec voltage application, and (d) is after 400 msec voltage application.

As shown in FIG. 1, the electrophoretic display device 100 according to the first embodiment includes a partition wall 6 between a rear substrate 1 (first substrate) and a front substrate 2 (second substrate) so that a moving space 50 is formed. The moving space 50 is filled with the insulating liquid 3 in which the charged particles 4 are dispersed. The front substrate 2 is made of a light-transmitting plate such as transparent glass or a transparent film, but the rear substrate 1 is not necessarily transparent, and may be a film substrate, a metal substrate, or the like.

  A display surface forming body 8 is formed on the rear substrate 1. The display surface forming body 8 is formed using a transparent material or a material colored with a desired color. For example, plastic materials such as acrylic resin, epoxy resin, silicon resin, or glass can be used, and these materials are mixed with inorganic oxide pigments and dyes such as titanium oxide, zinc oxide, aluminum oxide, and colored. You may make it light-scatter.

  Display electrodes 5 are formed on the display surface forming body 8. As the display electrode 5, not only the ITO film but also a metal film such as an Al film may be used. The size of the display electrode 5 is 30% or less of the pixel area, and may be any shape. The display electrode 5 is connected to a drive circuit (not shown) and supplied with a voltage.

  As shown in FIG. 2, the electrophoretic display device 100 according to the first embodiment has a 5 μm × 5 μm square display at the center of a square pixel (display surface) with a pixel pitch of 50 μm surrounded by a grid-like partition wall 6. An electrode 5 is formed. Therefore, the ratio of the display electrode 5 to the display surface is approximately 1%.

As shown in FIG. 1, the partition wall 6 keeps the distance between the rear substrate 1 (first substrate) and the front substrate 2 (second substrate) at a predetermined distance, and moves the movement space 50 and the movement space 50 of the adjacent pixel. Separate. The thickness of the partition wall 6 is generally about 5 μm to 30 μm. As the partition wall 6, a resist material, a thermoplastic material, an ultraviolet curable material, or the like that is generally used can be used. On the surface of the partition wall 6, a partition electrode 7 constituting an upright electrode surface is formed. The partition electrode 7 may be formed of not only a metal film such as Al and Ti but also an ITO film.

  And the resistance layer 9 is formed so that the surface of the display electrode 5 and the surface of the display surface formation body 8 may be covered. The display electrode 5 and the resistance layer 9 are electrically connected to each other at an overlapping portion, and the overlapping portion serves as a power feeding portion from the display electrode 5 to the resistance layer 9.

  The resistance layer 9 may not be provided on the partition wall 6, but may be provided as long as it is separated from the resistance layer on the display surface and electrically insulated from the partition wall electrode 7 as shown in FIG. In FIG. 1, after the resistance layer 9 is integrally formed, the resistance layer 9 is removed at the contour portion 6a along the partition wall electrode 7 by using a photolithography technique. Hereinafter, the resistance layer 9 formed on the partition wall 6 is referred to as a partition resistance layer 9a, and the resistance layer 9 formed on the display surface formation body 8 is referred to as a display surface resistance layer 9b.

  While the display surface resistance layer 9b is connected to the display electrode 5, the partition surface resistance layer 9a and the display surface resistance layer 9b are planarly separated by the contour portion 6a. Is higher by two digits or more than the resistance value between the outer edge of the display surface resistance layer 9 b and the display electrode 5.

  The resistance layer 9 is light transmissive, has an intermolecular attractive force on the charged particles 4 and has a surface composition and a surface structure in which the charged particles 4 are difficult to bond, and does not deteriorate for a long time in an insulating liquid. A material that does not easily cause electron exchange with the charged particles 4 and that can achieve the necessary sheet resistance described later is employed.

  Specifically, an organic film such as polysilane, polysiloxane, polyacetylene, or a composite or copolymer thereof, a carbon-containing film, indium-tin oxide (ITO), or the like, depending on the type of the charged particles 4 An inorganic film, a semiconductor film such as silicon, or a conductive filler (filler) such as a metal powder, carbon particles, or the like can be used in an epoxy resin, a polypropylene resin, or the like.

These materials may be colored, or may be an organic film in which a red, green, or blue pigment is dispersed. Further, a laminated film of these thin films may be used as the interface member. The sheet resistance of the resistance layer 9 is preferably 10 ² Ω / □ to 10 ¹⁵ Ω / □, and the film thickness is preferably 1 nm to 200 nm.

  An insulating liquid 3 in which charged particles 4 are dispersed is enclosed in the moving space 50 partitioned by the partition walls 6. Examples of the insulating liquid 3 include water, methanol, ethanol, acetone, hexane, toluene, aromatic hydrocarbons such as benzenes having a long-chain alkyl group, and other various oils alone or a mixture thereof. What mix | blended surfactant etc. can be used.

  The charged particles 4 are charged organic or inorganic particles, and have an electrophoretic property of being moved by being driven by a space potential difference in the insulating liquid 3. As the charged particles 4, one or more of black pigments such as aniline black and carbon black, white pigments such as titanium dioxide and antimony trioxide, azo pigments, and other colored pigments can be used.

  Furthermore, these pigments include, as necessary, charge control agents composed of particles of electrolytes, surfactants, resins, rubbers, oils, titanium-based coupling agents, aluminum-based coupling agents, silane-based coupling agents. A dispersing agent such as a lubricant, a lubricant, a stabilizer and the like can be added.

  Next, the operation of the thus configured electrophoretic display device 100 according to the first embodiment will be described. In the following description, the case where the charged particles 4 are positively charged will be described as an example. However, even when the charged particles 4 are negatively charged, the same explanation will be given in consideration of the fact that the moving direction of the charged particles is reversed. be able to.

  On the rear substrate 1, data lines and trigger lines (not shown) arranged in a three-dimensional intersection in a lattice shape are arranged, and switching elements (not shown) for each pixel corresponding to the intersections of the data lines and the trigger lines. ) Is formed. A driving voltage generator (not shown) that controls the trigger line while applying a voltage signal to the data line is disposed outside the image display area of the rear substrate 1.

  The drive voltage generator supplies a voltage signal to the display electrode 5 through a data line and a switching element (not shown). The drive voltage generator applies a voltage signal between the partition wall electrode 7 and the display electrode 5 to generate an electric field in the moving space 50. When a voltage signal is applied to the display electrode 5 by the drive voltage generator, the electric field state of the moving space 50 changes in the order of (a), (b), (c), and (d) in FIG. Indicates. In the figure, the arrow indicates an electric field vector, and the solid line indicates an equal electric field strength line.

  As shown in FIG. 3A, immediately after the negative voltage is applied to the display electrode 5, there is capacitive coupling between the resistance layer 9b and the partition wall electrode 7, so that the potential of the entire resistance layer 9b is immediately The potential is not the same as that of the display electrode 5. At the center of the display surface, the potential immediately becomes a negative voltage as it is, but in the peripheral portion of the display surface resistance layer 9b, the follow-up to the new potential is delayed as the distance from the power feeding portion increases, and the potential becomes transiently different from the center of the display surface.

  At this time, a concentric potential gradient is generated on the surface of the display surface resistance layer 9 b, and the potential of the display surface resistance layer 9 b is lower at the center of the display surface and higher as it is closer to the partition wall electrode 7. Therefore, the potential difference between each position on the surface of the resistance layer 9b and the partition wall electrode 7 is the largest in the power feeding portion farthest from the partition wall 6, and is small in the peripheral portion near the partition wall. As a result, the electric field generated in the moving space 50 is made uniform as compared with the case where the display electrode 5 is on the entire display surface and the display surface has the same potential.

  Further, in the moving space 50, an electric field having a spatial potential inclined in the radial direction is formed, and the horizontal component of the electric field vector becomes strong, and the charged particles 4 are accelerated in the central direction along the display surface, Run toward.

  As time passes, the potential of the display surface resistance layer 9b approaches the potential of the display electrode 5. After a sufficient time has elapsed, the potential of the entire display surface resistance layer 9b is unified with the potential of the display electrode 5. The electric field vector in this process changes in the order of (b), (c), and (d) in FIG.

  As shown in FIG. 3D, when the potential of the entire display surface resistance layer 9b becomes uniform, the transient response is completed, and the force that has moved the charged particles in the radial direction is lost, while the display surface resistance layer 9b is The electric field in the downward direction is strengthened almost on the entire surface, and the charged particles 4 are surely pressed against the display surface. The charged particles 4 are displayed on the display surface by the affinity, cohesive force, and adsorption force between the charged particles 4 and the display surface resistance layer 9b. It stagnates on the surface of the resistance layer 9b, and good memory performance for pixel display is obtained.

  On the other hand, when the surface resistance layer 9b is a highly conductive metal thin film, the potential gradient of the display surface resistance layer 9b when a voltage signal is applied to the display electrode 5 is instantaneously caused by electron movement in the metal thin film. By canceling out, a uniform electric potential distribution is obtained, and there is no time to apply a horizontal force to the charged particles 4, and an electric field state as shown in FIG. Therefore, the charged particles 4 are stagnated on the surface of the display surface resistance layer 9b from the beginning, and the horizontal movement does not proceed slowly.

  In the electrophoretic display device 100 of the first embodiment, two operations of moving the charged particles 4 to the center of the display surface and pressing them against the display surface are obtained before and after, so that the display surface is made of a highly conductive display electrode. The response speed, contrast, and memory performance can be greatly improved as compared with the electrophoretic display device (see FIG. 6).

  When the charged particles 4 are moved to the partition wall 6 to display the pixel in white, a positive voltage signal is applied to the display electrode 5. At this time, too, (a), (b), (c) in FIG. , (D), a transient response of the electric field state occurs in which the electric field vectors are reversed.

  Immediately after the voltage is applied, the electric field vector directed outward in the horizontal direction is strong, so that the charged particles 4 in the center of the display surface are also quickly attracted to the partition electrode 7 and the display surface is covered with a highly conductive display electrode. The response speed of white display is faster than that of the display device (see FIG. 6).

  By the way, it is desirable that the duration of the transient response shown in FIGS. 3A, 3 </ b> B, and 3 </ b> C is secured to the same level as the moving time of the charged particles 4. This is because it is possible to shift to the operation of pressing the charged particles 4 against the display surface immediately after the charged particles 4 migrate to the center of the display surface, so that the operation is not wasteful and the particle migration operation and the memory operation can be completed in a short time. Because.

  The duration of the transient response is determined by the product of the resistance R between the power feeding portion and the periphery of the resistance layer 9b and the capacitance C between the display surface and the partition wall electrode. R is about the same as the sheet resistance of the resistance layer unless the display surface is in an extreme shape.

The electrophoretic display time of a general electrophoretic display device is about several hundred ms from the realistic moving speed of the charged particles 4 and the pixel size. On the other hand, when the dot pitch is 50 μm, the partition electrode size is 5 μm × 5 μm, and the sheet resistance of the resistance layer 9 is 10 ¹³ Ω / □, the transient response period is about 100 ms according to the electric field simulation result, which is almost the same as the migration time. It will be about.

Further, in the electrophoretic display device 100 of the first embodiment, even if the partition wall electrode 7 and the display surface resistance layer 9b are short-circuited, it is difficult to cause a point (pixel) defect. When the sheet resistance of the resistance layer 9 is 10 ¹³ Ω / □ and the size of the short portion is 5 μm × 5 μm, the short resistance is 10 ¹³ Ω. When the auxiliary capacitance mounted on a general active matrix substrate is 0.2 pF per pixel and the driving frequency is 60 Hz, the pixel potential after a potential drop due to a short circuit is V = V0 × exp (−t / (RC )), 99.17%, almost no potential drop. Therefore, even if short-circuited, it does not lead to point defects, and a good display can be obtained.

  Furthermore, when a thin film transistor (hereinafter referred to as TFT) switching element, which is a switching element for active matrix drive display, is used, even if the display electrode and the resistance layer are short-circuited, the sheet resistance of the resistance layer is high. The resistance of the short section increases. Therefore, the pixel potential drop due to leakage can be suppressed depending on the auxiliary capacitance mounted on the pixel and the driving frequency, and a good display with few point defects can be obtained.

  In addition, since the resistance value of the resistance layer 9 is much higher than that of metal, it is difficult for charges to be injected into the charged particles 4, and the resistance layer 9 can be disposed at the interface of the moving space 50. : Refer to FIG. 9), and the process can be simplified.

<Second Embodiment>
FIG. 4 is an explanatory diagram of a cross-sectional configuration of the electrophoretic display device of the second embodiment. The electrophoretic display device 200 of the second embodiment is the same as the electrophoretic display of the first embodiment shown in FIG. 1 except that the display surface forming body 8 is replaced with the colored layer 10 and the display electrode 5 is replaced with the display electrode 12. The configuration is the same as that of the apparatus 100. Therefore, in FIG. 4, the same components as those in FIG.

  As shown in FIG. 4, the electrophoretic display device 200 of the second embodiment sets the gradations of R (red), G (green), and B (blue) in three adjacent display units, respectively. One pixel is displayed in full color.

  The display electrode 12 is an electrode member that also serves as a reflective surface of the metal thin film, and is formed on the upper surface of the uneven portion 13 formed on the rear substrate 1. Here, the uneven | corrugated | grooved part 13 can be formed by performing exposure and wet development, after apply | coating photosensitive resin, for example. Alternatively, a method of making fine irregularities by etching glass, sandblasting, or the like may be used. As a material of the display electrode 12 formed on the concavo-convex portion 13, it is desirable to use a material having high reflectivity such as Al or Ag.

  In addition, by forming the display electrode 12 on the concavo-convex portion 13 in this manner, the display electrode 12 can have a function of diffusing incident light. Further, by controlling the distribution of the inclination angle of the concavo-convex portion 13, the viewing angle can be expanded and the external light can be reflected efficiently, so that the electrophoretic display device 100 of the first embodiment having a flat reflecting surface can be used. A bright and good display can be obtained.

  The colored layer 10 includes colored layers 10 a, 10 b, and 10 c that are red, green, and blue color filter layers, and constitutes an insulating layer that is formed on the display electrode 12. The colored layers 10a, 10b, and 10c are made of, for example, an ultraviolet curable acrylic resin resist in which a red, green, or blue pigment is dispersed. The film thickness of the colored layers 10a, 10b, and 10c is usually about 0.5 μm to 4 μm.

  The contact hole 11 is a voltage signal feeder for the display surface resistance layer 9b and is formed at the center of the display surface. The resistance layer 9 is formed so as to integrally cover the surface of the partition wall electrode 7, the surface of the colored layer 10 a (or 10 b, 10 c), and the contact hole 11, and then along the partition electrode 7 by a photolithography technique. The contour portion 6a is removed and the contour is patterned.

  Even in such a configuration, the display surface resistance layer 9b is electrically connected to the display electrode 12 through the contact hole 11, and the resistance value between the display surface resistance layer 9b and the partition wall electrode 7 is the display electrode 12. Therefore, the electrophoretic display device 200 of the second embodiment has the same effect (transient response of the electric field as the electrophoretic display device 100 of the first embodiment). The radial movement of the charged particles 5 used and the subsequent pressing on the display surface are obtained.

  Further, immediately after the voltage is applied, the display electrode 12 and the display surface resistance layer 9b are driven by capacitive coupling via the colored layer 10 to reduce the amount of injected charge necessary for stabilizing the potential of the resistance layer. Therefore, the potential of the display surface resistance layer 9b is stabilized faster than in the first embodiment. In this case, even if the resistance between the outer edge portion of the display surface resistance layer 9b and the display electrode 12 is high, a voltage can be reliably applied to the moving space 50. Defects hardly occur and good display characteristics can be obtained.

  In addition, even if residual DC is formed in the colored layers 10a, 10b, and 10c, the display surface resistance layer 9b releases electric charges, so that burn-in due to the residual DC is improved and the memory performance of pixel display is improved.

<Third Embodiment>
FIG. 5 is an explanatory diagram of a cross-sectional configuration of the electrophoretic display device of the third embodiment. The electrophoretic display device 300 of the third embodiment is the same as that of the second embodiment shown in FIG. 4 except that the partition wall resistance layer 9a and the display surface resistance layer 9b are separated in the height direction at the base portion of the partition wall 6. The configuration is the same as that of the electrophoretic display device 200. Therefore, in FIG. 5, the same reference numerals are given to the same components as those in FIG. 4, and detailed description thereof will be omitted.

  As shown in FIG. 5, a step forming layer 14 is formed between the colored layer 10 a (or 10 b, 10 c) and the partition wall 6. As a material for the step forming layer 14, a metal such as Cr, AL, Ti, or a transparent electrode such as ITO or IZO may be used to serve as a power feeding portion to the partition wall electrode 7. Alternatively, an inorganic insulating film such as SiO 2, or an organic material such as an acrylic resin, an epoxy resin, a silicon resin, an ultraviolet curable acrylic resin resist, or a laminated film of these is used, and the partition electrode 7 is formed thereon. You may form the electrode layer (not shown) used as a electric power feeding part.

  For example, a thin film layer that becomes the step forming layer 14 and an electrode layer that becomes a power feeding portion to the partition wall electrode 7 are formed on the colored layer 10 so as to overlap each other, and the three-dimensional structure of the partition wall 6 is formed thereon. Then, a thin film layer to be the partition electrode 7 is formed on the entire surface of the rear substrate 1 on which the partition 6 is formed, and the contours of the partition electrode 7 and the electrode layer are patterned using a normal photolithography technique performed by applying a resist. Then, the step forming layer 14 on the display surface is exposed. In this state, the ridge structure 6b may be formed by wet-etching the step forming layer 14 and subjecting the portion under the partition wall electrode 7 to side etching.

  In any case, the patterning of the step forming layer 14 is performed after the partition electrode 7 is formed, and can be performed by wet etching, chemical dry etching, or the like, and the width of the step forming layer 14 is narrower than the width of the partition electrode 7. This is very important.

  Thereafter, when the resistance layer 9 is formed by anisotropic sputtering or the like, the partition wall electrode 7 becomes the ridge structure 6b, and the resistance layer 9 is not laminated under the ridge structure 6b, and the display surface resistance layer 9b and the partition resistance layer 9a is automatically divided. As a condition for dividing the resistance layer 9, the width of the step forming layer 14 is smaller than the width of the partition wall electrode 7, and the thickness of the display surface resistance layer 9 b is thinner than the thickness of the step forming layer 14. Can be mentioned.

  Even in such a configuration, the display surface resistance layer 9b is electrically connected to the display electrode 12, and the resistance value between the display surface resistance layer 9b and the partition wall electrode 7 is changed from the display electrode 12 to the display surface resistance layer. Since the resistance value up to the outer edge of 9b can be made higher, the electrophoretic display device 300 of the third embodiment has the same effect as the electrophoretic display device 100 of the first embodiment (charged particles using a transient response of an electric field). 5 in the radial direction and subsequent pressing on the display surface).

  Further, the display surface resistance layer 9b and the partition wall resistance layer 9a are electrically separated simultaneously with the formation of the resistance layer 9 by the eaves structure 6b, so that the display surface resistance as in the electrophoretic display device 200 of the second embodiment. The patterning step of the layer 9b can be omitted.

  By the way, as shown in FIG. 4, in the electrophoretic display device 200 of the second embodiment, the contour of the display surface resistance layer 9b is patterned by a photolithography technique, and the space between the partition wall electrode 7 and the display surface resistance layer 9b. In this case, a gap corresponding to the patterning accuracy (about 3 to 6 μm) is formed. Since the electric field vector in the gap portion is in the horizontal direction, particles cannot be retained in the gap portion during black writing. Therefore, sufficient black cannot be displayed, resulting in a decrease in contrast.

  On the other hand, as shown in FIG. 5, in the electrophoretic display device 300 according to the third embodiment, the etching amount of the step forming layer 14 is controlled, so that the gap between the partition wall electrode 7 and the display surface resistance layer 9b is controlled. It is possible to suppress the gap to 1 μm or less. Therefore, since unnecessary emission light can be reduced from the gap and sufficient black can be displayed, a pixel display having a higher contrast than the electrophoretic display device 200 of the second embodiment can be obtained.

  Furthermore, in the gap between the partition wall electrode 7 and the display surface resistance layer 9b, the insulating colored layer 10a is exposed to generate residual DC. However, since the generated area is very narrow, the influence of the residual DC is also affected. Good pixel display with small image sticking can be obtained.

<Electrophoretic display device of comparative example>
FIG. 6 is an explanatory diagram of a display operation in the electrophoretic display device of the comparative example, and FIG. 7 is an explanatory diagram of a transient electric field change in the moving space in the electrophoretic display device of the comparative example. In FIG. 6, (a) is a black display state and (b) is a white display state. In FIG. 7, (a) is immediately after voltage application, (b) is after 100 msec voltage application, (c) is after 200 msec voltage application, and (d) is after 400 msec voltage application.

  As shown in FIG. 6A, the electrophoretic display device 500 of the comparative example is formed by forming the partition wall 106 surrounding the display surface on the rear substrate 102 and disposing the front substrate 101 on the partition wall 106. The moving space 50 is filled with an insulating liquid 103 in which charged particles 104 are dispersed.

  A display electrode 105 is disposed on the rear substrate 102 so as to occupy the display surface, and the display electrode 105 is covered with a dielectric layer 107 for avoiding direct electron exchange between the charged particles 104 and the display electrode 105. One display electrode 105 is arranged for each display surface, and an individual voltage signal corresponding to an individual pixel density is applied.

  A partition wall electrode 108 is formed on the rising surface of the partition wall 106. The partition wall electrode 108 is commonly connected to all the pixels included in the display device, and 0 V or a predetermined voltage is applied in common. The surface of the display electrode 105 is whitened also as a reflection surface, while the charged particles 104 are black and the insulating liquid 103 is transparent.

  In the electrophoretic display device 500 of the comparative example configured as above, the charged particles 104 are moved between the partition electrode 108 and the display electrode 105 by reversing the voltage polarity between the display electrode 105 and the partition electrode 108. As a result, the light emitted from the display electrode 105 is changed.

  That is, as shown in FIG. 6A, when the charged particles 104 are collected on the display electrode 105 to cover the display electrode 105, incident light to the display electrode 105 and reflected light from the display electrode 105 are applied to the charged particles 104. Absorbed and the display electrode 105 is observed in black.

  Further, as shown in FIG. 6B, when the charged particles 104 are collected on the partition wall electrode 108 and the display electrode 105 is exposed, external light incident from the front substrate 101 reaches the display electrode 105 and is reflected, The display electrode 105 is observed as white light emitted from the front substrate 101. Further, by adjusting the voltage signal applied to the display electrode 105 and changing the amount of the charged particles 104 covering the display electrode 105, a gray intermediate gradation can be displayed.

  In the electrophoretic display element 500 of the comparative example, when a voltage signal is applied between the display electrode 105 and the partition wall electrode 106, the electric field state in the moving space 50 is transient as shown in FIGS. Without generating a response, the state is fixed immediately after the voltage application (the electric field is strong in the adjacent portion of the partition wall electrode 108 and the display electrode 105 and the electric field is weak in the center of the display surface).

  When displaying black, a negative voltage signal is applied to the display electrode 105 to collect the charged particles 104 on the display electrode 105. However, since the electric field toward the center of the display surface is very weak, the charged particles 104 Does not reach the center of the display surface. For this reason, the display electrode 105 cannot be reliably covered with the charged particles 104, so that there is a problem that sufficient contrast cannot be obtained or the response speed of display is remarkably slow.

<Other comparative examples>
FIG. 8 is an explanatory diagram of a cross-sectional configuration in an electrophoretic display device of another comparative example, and FIG. 9 is an explanatory diagram of a cross-sectional configuration in an electrophoretic display device of still another comparative example. As shown in FIG. 8, in an electrophoretic display device 600 of another comparative example, R (red), G (green), and B (blue) color filter layers 109a are respectively formed on three adjacent display electrodes 105. , 109b, 109c are arranged to perform color display of one pixel. The electrophoretic display device 600 is capable of displaying full-color pixels by changing the light intensity balance of the three primary colors by displaying the respective intermediate gradations with the three display electrodes 105.

  By the way, when performing color display of pixels on the electrophoretic display device, a method of forming the color filter layers 109a, 109b, and 109c on the display electrode 105 as in the electrophoretic display device 600 of another comparative example shown in FIG. There is also a method of forming it on the counter substrate 102 side.

  However, in the case where the color filter layer is formed on the counter substrate side, it is necessary to assemble the cells so that the color filter layer and the pixels match. If a positional deviation between the outline of the color filter layer and the pixel occurs, color mixture occurs between adjacent pixels. Therefore, in order to prevent color mixture, it is necessary to provide a black matrix for the alignment margin on the counter substrate side.

  However, when a black matrix is provided on the counter substrate, it is difficult to obtain a high aperture ratio because the black matrix blocks incident light and emitted light. In particular, when a high-definition pixel of 150 ppi or more is formed, or when a plastic substrate having a high thermal expansion coefficient is used, the aperture ratio is remarkably lowered and cannot be practically used.

  On the other hand, since the electrophoretic display device 600 of the comparative example forms the color filter layers 109a, 109b, and 109c on the display electrode 105, a decrease in the aperture ratio due to the black matrix can be suppressed.

  As shown in FIG. 9, in the electrophoretic display device 700 of still another comparative example, the ITO thin film conductive layer 111 is disposed on the surface of the color filter layers 109a, 109b, 109c, respectively, and the color filter layers 109a, 109b, Residual charges generated on the surface 109 c are discharged to the display electrode 105. The conductive layer 111 and the display electrode 105 are connected by a contact hole 110 formed in the center of the plane of the display electrode 105. The conductive layer 111 is covered with a dielectric layer 112 for avoiding direct electron exchange between the charged particles 104 and the conductive layer 111.

  In the electrophoretic display device 600 of another comparative example shown in FIG. 8, residual DC that is a cause of image sticking may occur on the exposed surfaces of the color filter layers 109a, 109b, and 109c. Then, there is a problem that the memory performance of the pixel is impaired by the residual DC.

  However, in the electrophoretic display device 700 shown in FIG. 9, the conductive layer 111 is formed on the color filter layers 109a, 109b, and 109c, and the generated residual DC flows from the conductive layer 111 to the display electrode 105 through the contact hole 110. Since the battery is discharged, the disturbance of the pixel display due to the residual DC is suppressed, and a good memory property of the pixel display can be ensured.

  However, in such a configuration, the process becomes complicated, and the transmittance decrease due to the conductive layer 111 of the ITO electrode is large, so that the reflectivity of the electrophoretic display device 700 is lowered. Further, since the distance between the partition wall electrode 107 and the conductive layer 111 is narrow, a point (pixel) defect due to a short circuit is likely to occur.

<Correspondence with Invention>
As shown in FIG. 1, the electrophoretic display device 100 according to the first embodiment includes a partition electrode disposed on an upstanding surface of a partition 6 in the electrophoretic display device 100 including a rear substrate 1 on which a display surface for each pixel is set. 7, the display electrode 5 disposed on the display surface forming body 8 at a distance from the partition wall electrode 7, the display electrode 5 connected to the display electrode 5 to cover the display surface forming body 8, and electrically separated from the partition wall electrode 7. The sheet resistance of the display surface resistance layer 9b is that the potential gradient generated in the display surface resistance layer 9b when a voltage signal is applied to the display electrode 5 is caused by the movement of the charged particles 4. Since it is set in a range that can be continued according to time, the charged particles 4 move in the direction along the display surface immediately after the voltage signal is applied.

  The electrophoretic display device 100 according to the first embodiment includes a rear substrate 1 in which a display surface for each pixel is set, and a partition wall 6 that has a partition electrode 7 on an upright surface surrounding the display surface and partitions a moving space 50 of charged particles 4. A display electrode 5 disposed in the center of the display surface, a display surface resistance layer 9b that covers the display electrode 5 and the display surface integrally and is electrically separated from the partition wall electrode 7, The sheet resistance of the surface resistance layer 9b is set in a range in which the potential gradient generated in the display surface resistance layer 9b when a voltage signal is applied to the display electrode 5 can be continued according to the moving time of the charged particles 4. Therefore, immediately after the voltage signal is applied, the charged particles 4 move in the direction along the display surface.

  In any case, when a voltage signal is applied between the partition wall electrode 7 and the display electrode 5, a transitional surface potential gradient is formed on the surface of the display surface resistance layer 9b. A transient space potential difference in the radial direction according to the inclination is formed. As shown in FIG. 6, in the case of the display electrode 105 having high conductivity, the transient surface potential gradient is instantaneously canceled, and the transient space potential difference of the moving space 50 is also increased without accelerating the charged particles 104. Although disappears, in the case of the display surface resistance layer 9b, since the electron moving speed in the layer is slow, the transient surface potential gradient continues and contributes to the movement of the charged particles 4.

  In other words, a combination of an appropriate sheet resistance (material, additive, film thickness, stacking condition, etc.) of the display surface resistance layer 9b corresponding to the capacitance structure and an appropriate voltage signal waveform results in the display surface resistance layer 9b. The transient surface potential gradient is continued to such an extent that it can be used for the movement of the charged particles 4.

  Therefore, when a voltage signal is applied between the partition electrode 7 and the display electrode 5, the display electrode 5 is directed toward the partition electrode 7 or vice versa, depending on the potential polarity. Toward 5, the charged particles 4 are accelerated and moved in the radial direction.

  When the transient surface potential gradient is canceled by electron movement through the display surface resistance layer 9b or the like, the same electric field state as that of the display electrode 105 (FIG. 6) with high conductivity is obtained, and the display surface (potential Depending on the polarity, the charged particles 4 are pressed against the surface of the partition wall electrode 7, so that intermolecular attractive force and physical engagement of the charged particles 4 with respect to the display surface (surface of the partition wall electrode 7) are likely to occur, and the charged particles 4 are brought into the interface. The property to fasten is enhanced.

  In other words, immediately after the voltage signal is applied between the partition wall electrode 7 and the display electrode 5, a transient space potential difference along the display surface is formed in the moving space 50, and the charged particles 4 follow the display surface. Since it moves in the radiation direction, the responsiveness of pixel display is enhanced. Thereafter, when the transient space potential difference disappears, the charged particles 4 are pressed perpendicularly to the destination display surface (the partition wall electrode 7 surface), and the interface affinity becomes easy to work, so that the memory performance of pixel display is improved.

  In the electrophoretic display device 100 according to the first embodiment, since the partition electrode 7 surface and the display surface are covered with the common resistance layer 9, the property common to the partition electrode 7 surface and the display surface, that is, charged particles. Quality, performance, etc. as an electrophoretic display device, such as an affinity with 4, a property that the charged particles 4 are difficult to bind, a property that does not oxidize and change for a long time in the insulating liquid 3, and a property that does not easily cause electron exchange with the charged particles 4. The property which improves durability can be provided.

  In the electrophoretic display device 300 of the third embodiment, the step forming layer 14 disposed at the base of the partition wall 6 is moved back toward the center of the partition wall 6 so that the partition wall resistance layer 9a and the display surface resistance layer 9b are in the height direction. Therefore, it is possible to achieve electrical separation from the partition wall electrode 7 without patterning the contour of the display surface resistance layer 9b. In addition, since the partition wall resistance layer 9a and the display surface resistance layer 9b are divided in the height direction, a planar gap as in the case of dividing in the horizontal direction and a region where the charged particles 4 cannot be covered are not formed on the display surface.

  The electrophoretic display device 200 according to the second embodiment includes a display electrode 5 that is arranged on a display surface and to which a voltage signal is applied, and an insulating colored layer 10 that is arranged on the display electrode 5. Since the display surface resistance layer 9b on 10 and the display electrode 5 are connected by the contact hole 11, the display electrode 5 can be used as a reflection surface.

  In the electrophoretic display device 200 of the second embodiment, since the reflective surface is formed on the surface of the display electrode 5, the reflective electrophoretic display device 200 can be realized.

  In the electrophoretic display device 200 according to the second embodiment, different transmission wavelength characteristics of R (red), G (green), and B (blue) are imparted to the colored layers 10 of three adjacent display units, respectively, and three displays are provided. Since each pixel is set to R (red), G (green), and B (blue) gradations to display one pixel in full color, a color image can be displayed.

  In the electrophoretic display device 100 of the first embodiment, the display surface resistance layer 9b is disposed on the display surface forming body 8 surrounded by the partition wall electrode 7, and the display electrode 5 is disposed at the center of the display surface resistance layer 9b. In the driving method of the electrophoretic display device 100, a voltage signal is applied between the partition wall electrode 7 and the display electrode 5 to generate a transient radial surface potential difference in the display surface resistance layer 9b. 50, by generating a transient electric field change and moving the charged particles 4 in the radiation direction of the display surface, a driving method using a voltage signal of a gradual voltage rise that does not cause a transient radial surface potential difference, Compared to a driving method in which the transient radial surface potential difference disappears instantaneously, both the time for covering the display surface with the charged particles 4 and the time for removing the charged particles 4 from the display surface can be shortened.

It is explanatory drawing of the cross-sectional structure of the electrophoretic display device of 1st Embodiment. It is explanatory drawing of the plane structure of the electrophoretic display device of 1st Embodiment. It is explanatory drawing of the transient electric field change of movement space. It is explanatory drawing of the cross-sectional structure in the electrophoretic display device of 2nd Embodiment. It is explanatory drawing of the cross-sectional structure in the electrophoretic display device of 3rd Embodiment. It is explanatory drawing of the display operation in the electrophoretic display device of a comparative example. It is explanatory drawing of the transient electric field change of the movement space in the electrophoretic display apparatus of a comparative example. It is explanatory drawing of the cross-sectional structure in the electrophoretic display device of another comparative example. It is explanatory drawing of the cross-sectional structure in the electrophoretic display device of another comparative example.

Explanation of symbols

1 Display board (rear board)
2 Front substrate 3 Insulating liquid 4 Charged particles 5 and 11 Feeding part (display electrode, contact hole)
6 partition wall 6a contour portion 6b ridge structure 7 partition electrode 8, 10, 10a, 10b, 10c insulating layer (display surface forming body, colored layer)
9, 9a, 9b Resistive thin film layer (resistance layer, partition wall resistance layer, display surface resistance layer)
13 Concave and convex portion 14 Step forming layer

Claims (10)

A first substrate, a second substrate, a partition that maintains a predetermined distance between the first substrate and the second substrate, and a pixel defined by the first substrate , the second substrate, and the partition are filled. An insulating liquid containing charged particles, a display electrode disposed in the center of a pixel of the first substrate, a resistance layer connected to the display electrode and disposed on the first substrate, and the partition wall And the barrier layer electrode is separated, and a voltage is applied to the display electrode to move the charged particles in a direction along the first substrate for display. In a particle movement type display device for performing
The sheet resistance of the resistance layer is a sheet resistance in which a potential gradient generated in the resistance layer when a voltage is applied to the display electrode can be continued according to a moving time of the charged particles. Particle movement type display device. A first substrate, a second substrate, a partition that keeps a predetermined distance between the first substrate and the second substrate, and a pixel defined by the first substrate , the second substrate, and the partition are filled. An insulating liquid containing charged particles, a display electrode disposed on the first substrate, an insulating layer disposed on the display electrode and having a contact hole provided in a central portion of the pixel, A resistance layer disposed on an insulating layer and connected to the display electrode through the contact hole of the insulating layer; and a partition electrode disposed on the partition; the resistance layer and the partition electrode In a particle movement type display device that performs display by applying a voltage to the display electrode to move the charged particles in a direction along the first substrate,
The sheet resistance of the resistance layer is a sheet resistance in which a potential gradient generated in the resistance layer when a voltage is applied to the display electrode can be continued in accordance with a moving time of the charged particles. Particle movement type display device. Particle migration type display device according to claim 1 or 2, wherein the sheet resistance of the resistive layer is in the range of ^{10 2 Ω / □ 10 15 Ω} / □ of the. The particle movement according to any one of claims 1 to 3 , wherein a layer separated from the resistance layer and having the same composition as the resistance layer is disposed on the surface of the partition wall. Type display device. The particle movement type display device according to claim 1, wherein the display electrode is a metal film . The resistive layer, polysilanes, polysiloxanes, particle migration type display device according to the organic film or 1, wherein any one of claims 1 to 5, characterized in that a complex or a copolymer thereof of those polyacetylene. The particle movement type display device according to claim 1, wherein the resistance layer is a semiconductor film . 6. The particle movement type display device according to claim 1, wherein the resistance layer is a conductive resin film in which metal powder or carbon particles are blended with an epoxy resin or a polypropylene resin . Particle migration type display device according to claim 2, characterized in that to form the resistive layer transgressions electrical capacitance between the display electrode overlapping through the insulating layer. Particle migration type display device according to claim 2 or 9, characterized in that the reflecting surface to the surface of the display electrode is formed.

Images