JP2007072349A - Particle movement type display device and method for manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a particle movement type display device 100 in which memory property of image display can be improved without decreasing necessary properties and substantial functions of a layer such as a resistance layer 7 which is conventionally exposed to a movement space 20 of charge particles 9. <P>SOLUTION: A display electrode 5 is disposed in the center of a display screen, and a resistance layer 7 is formed to cover together a barrier wall electrode 6 formed on a barrier wall 3, the display screen and the display electrode 5. A surface layer 8 is formed to cover the entire surface of the resistance layer 7. The surface layer 8 is made of a material that is suitable for adsorption of charge particles 9 from the viewpoint of surface energy and surface roughness compared to the resistance layer 7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophoretic display device, a toner display, etc., 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 to transmit and / or reflect light for each display unit. More particularly, the present invention relates to an interface structure of a moving space of charged particles.

  As a non-light emitting display device, a particle movement type display device is known that performs display by moving charged particles by the action of an electric field. The particle movement type display device is an image display device that performs pixel display by moving charged particles between a pair of electrodes arranged facing a moving space of charged particles. The particle movement type display device 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, and is more than conventional liquid crystal display devices. Has the advantage of The particle movement type display device has been attracting attention as a low power consumption image display device because it can maintain a pixel display for a while after the electric field is released and can display memory without requiring electric power to maintain the gradation display of the pixel. .

  Patent Document 1 discloses an electrophoretic display device in which a planar display electrode is provided on a display surface for each display unit, and a partition electrode is provided on a rising surface of a partition wall surrounding the display surface, and between the display electrode and the partition electrode. The charged particles are moved between the display surface and the standing surface according to the potential polarity set to. 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.

  In Patent Document 2, a plurality of writing signal lines and a plurality of scanning signal lines are arranged on a display-side substrate so as to intersect three-dimensionally, and each display unit corresponds to the intersection position of the writing signal line and the scanning signal line. An electrophoretic display device in which the switching elements are arranged is shown. Then, after resetting the display of all the pixels at once, supplying the scanning signal to the corresponding scanning signal line while applying individual writing signals to the plurality of writing signal lines, the display screen is displayed one by one. An image display is formed by outputting an image.

JP 9-2111499 A JP 2004-163596 A

  In the electrophoretic display device disclosed in Patent Document 1, since the display electrode of the metal thin film is exposed at the interface of the moving space, the binding force to the charged particles is strong and the charged particles are fixed to the display electrode. The state cannot be rewritten.

  In addition, since the exposed metal surface is likely to cause electron exchange, when a voltage signal is applied to the display electrode or when it is released, the insulating liquid that fills the moving space of the charged particles is altered or the display electrode is changed. There is a possibility that the charged particles that come into contact cause atomic exchange and electron exchange with the electrode surface, resulting in deterioration of display quality.

  Therefore, it has been proposed to cover the display electrode with an insulating layer and isolate the metal surface from the insulating liquid, but this time, as the voltage signal is applied to and released from the display electrode repeatedly, the surface or interface of the insulating layer is proposed. It has been found that a residual charge is generated in the insulating liquid, and the residual charge causes a so-called burn-in phenomenon that disturbs the behavior of the charged particles and varies the gradation expression for the same voltage signal. This residual charge may diffuse charged particles to be constrained on the electrode surface and impair the memory performance of the pixel display.

  In addition, when color filter layers having different wavelength absorption characteristics are arranged on a plurality of adjacent display surfaces to perform full color display of one pixel by gradation balance of a plurality of display units, a color filter layer of a thick insulating layer Residual charges are likely to be generated and the level of residual charges is large, so that a large image deterioration is caused by a burn-in phenomenon or a loss of memory performance.

  Therefore, in recent years, the applicant of the present application has covered the surface of the display electrode and the surface of the partition wall electrode with a resistive layer so that the residual charge generated in the insulating layer and the moving space can be quickly released to the display electrode and the partition wall electrode. An interface structure was proposed. This is because it has been found that by disposing a resistance layer having a sheet resistance value in a limited range, the residual charge can be eliminated with a practical time constant while eliminating the aging of the charged particles and the insulating liquid.

  However, when the material of the thin film layer is selected with priority given to the resistance, in many cases, the surface energy, the surface potential, and the surface unevenness necessary for ensuring the memory performance of image display cannot be ensured optimally. It is not easy to ensure the long-term stability necessary for the interface layer and the property of stably and repeatedly collecting and separating charged particles. A material capable of optimally displaying the memory performance of image display cannot secure a necessary range of sheet resistance, and thus cannot realize an optimal resistance layer.

  The present invention provides a particle movement type display device that can improve the memory performance of image display without impairing the necessary properties and essential functions of layers that have been exposed to the movement space of charged particles, such as a resistance layer. It is intended to provide.

  The particle movement type display device of the present invention is a particle movement type display comprising: a display side substrate on which a display surface for each display unit is set; and a partition wall that surrounds the display surface and partitions a moving space of charged particles. The apparatus further includes a surface control layer disposed on an interface of the moving space so as to cover the display surface and the rising surface of the partition wall, and the surface control layer includes at least one of surface energy, surface potential, and surface unevenness. One is different from the lower layer to enhance the restraining performance of the charged particles at the interface.

  In the particle movement type display device of the present invention, necessary optical properties and essential functions such as a resistance layer, an electrode surface, an insulating layer, and a color filter layer are entrusted to the lower layer, and the property of improving the memory performance of the pixel display. Since the surface control layer is exclusively responsible for the necessary functions as the interface layer, the material selection, film formation method, and film that give priority to the property to improve the memory performance of pixel display, ignoring the properties and functions imposed on the lower layer Compared with the case where the thickness or the like is selected and the surface control layer is not provided, it is possible to improve the difficulty in burning the pixel display and the memory performance.

  The surface control layer is composed of a material different from the lower layer, applied, a layer with the same material as the lower layer, a different additive, a layer with the same material as the lower layer, with different film formation conditions, and the surface of the lower layer formed. It can be formed on the lower layer by processing or the like.

  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 planar configuration when the display unit is a rectangle. FIG. 4 is an explanatory diagram of a cross-sectional configuration when the partition wall electrode is directly disposed on the display surface forming body, FIG. 5 is an explanatory diagram of a driving circuit of a display unit of the electrophoretic display device, and FIG. FIG. 7 is a block diagram of a drive circuit of the display device, and FIG. 7 is an explanatory diagram of drive waveforms in one display unit of the electrophoretic display device. In FIG. 1, (a) is black display and (b) is white display. 3A shows a case where the display electrodes are linear, and FIG. 3B shows a case where the display electrodes are plural. In FIG. 7, (a) is the display electrode potential, (b) is the resistance layer potential at point A, and (c) is the optical response.

  As shown in FIG. 1, the electrophoretic display device 100 according to the first embodiment has a partition wall 3 disposed between a rear substrate 1 and a front substrate 2 so that the rear substrate 1 and the front substrate 2 are spaced at a desired constant interval. While maintaining, one display unit 45 is separated from the adjacent display unit. A moving space 20 on the display surface forming body 4 partitioned by the partition walls 3 is filled with an insulating liquid 10 in which charged particles 9 are dispersed.

  As shown in FIG. 1, the display surface forming body 4 is disposed on the rear substrate 1, and the display electrode 5 is disposed at the center of the display surface on the display surface forming body 4. As shown in FIG. 2, the display electrode 5 is formed in the center of the plane of the display unit 45 partitioned by the partition 3 so as to occupy an area of about 1% of the display surface.

  A three-dimensional structure of the partition walls 3 is disposed on the display surface forming body 4, and partition wall electrodes 6 are formed on the standing surfaces of the partition walls 3. The partition wall electrode 6 is configured to cover the partition wall 3. A resistance layer 7 and a surface control layer 8 are laminated so as to integrally cover the display electrode 5, the display surface forming body 4, and the partition wall electrode 6. The surface control layer 8 has a surface potential having a polarity opposite to that of the charged particles 9, strengthens the attractive force with the charged particles 9, and improves display memory properties.

In the electrophoretic display device 100 of the first embodiment, as shown in FIG. 2, the display unit 45 is a square, the pixel pitch is 50 μm, and the display electrode 5 is a square of 5 μm × 5 μm. The sheet resistance of the resistance layer 7 is adjusted to 10 ¹² Ω / □, and the film thickness of the resistance layer 7 is 100 nm.

  The charged particles 9 are colored black and are positively charged. On the other hand, the display surface forming body 4 is a white scattering layer. Accordingly, the charged particles 9 move between the partition wall 3 and the display surface (the surface of the display surface forming body 4) according to the potential polarity of the voltage signal applied between the partition wall electrode 6 and the display electrode 5. Then, as shown in FIG. 1A, the display surface forming body 4 is covered with the charged particles 9 to display black, and the charged particles 9 are collected in the partition 3 as shown in FIG. Thus, white display is performed by exposing the display surface forming body 4. In addition, by controlling at least one of the voltage of the voltage signal, the number of pulses, and the application time, the amount and distribution of the charged particles 9 covering the display surface forming body 4 are led to an intermediate state, so that an intermediate gradation (gray) is obtained. Can be displayed.

  As shown in FIG. 5, on the rear substrate 1, write signal lines 48 and scanning signal lines 47 arranged in a three-dimensional cross like a lattice are arranged, and at each intersection of the write signal lines 48 and the scanning signal lines 47. Correspondingly, a pixel TFT 46 (Thin Film Transistor) which is a thin film transistor element for each display unit 45 is arranged.

  The pixel TFT 46 is a switching element for active matrix drive display composed of n-type transistors, and is covered with an interlayer insulating layer (not shown) formed on the rear substrate 1. The display electrode 5 is connected to the drain electrode of the pixel TFT 46 by a contact hole (not shown) formed through the display surface forming body 4 (FIG. 1) and the interlayer insulating layer. In the drain electrode, a capacitor 50 as an auxiliary capacitance is formed between the auxiliary capacitance line 51 and the auxiliary capacitance of all the pixels is connected to the auxiliary capacitance line 51 of the voltage Vcs.

  The scanning signal line 47 that is a scanning line is connected to the gate electrode of the pixel TFT 46, and the writing signal line 48 that is a data line is connected to the source electrode of the pixel TFT 46. The partition wall electrode 6 of the display unit 45 is connected to all the pixels in common and is connected to the common electrode 49 having the voltage Vcom.

  As shown in FIG. 6, a panel controller 41, a source driver 43, and a gate driver 42 are arranged outside the display unit in which the display units 45 on the rear substrate 1 are arranged in a grid pattern. The panel controller 41 generates control signals such as a field synchronization signal, a horizontal synchronization signal, a data capture clock, and display data based on the input image data, and transfers them to the source driver 43 and the gate driver 42.

  The source driver 43 supplies a signal voltage to the display unit 45 through the write signal line 48. The gate driver 42 supplies a scanning signal to the display unit 45 through the scanning signal line 47. The source driver 43 and the gate driver 42 display an image for each scanning line on the display unit 45 of the display unit 44 according to the control signal and display data received from the panel controller 41.

  An operation of the electrophoretic display device 100 according to the first embodiment will be described. Hereinafter, in order to facilitate understanding, a case where the scanning signal line 47 is fixed to ON and the signal voltage is continuously applied to the display electrode 5 will be described. The potential of the partition wall electrode 6 is fixed to 0V. Further, the case where the charged particles 9 are positively charged will be described as an example. However, even when the charged particles 9 are negatively charged, the same explanation will be given if the migration direction of the charged particles 9 is opposite to the electric field. can do.

  As shown in FIG. 1A, since the resistance layer 7 is formed so as to integrally cover the display electrode 5, the display surface forming body 4, and the partition wall electrode 6, the resistance layer 7 includes the display electrode 5 and the partition wall. The electrode 6 is electrically connected. When a negative voltage signal is applied to the display electrode 5, a surface potential gradient that rises toward the partition wall 3 with the display electrode 5 at the bottom is generated in the resistance layer 7 on the display surface forming body 4. Due to this potential gradient, the charged particles 9 on the display surface forming body 4 are accelerated toward the display electrode 5 and move radially. When a positive voltage signal is applied to the display electrode 5 in a state where the display surface forming body 4 is covered with the charged particles 9, the charged particles 9 are accelerated from the center toward the outer side and are directed toward the partition wall 3. Move quickly.

  On the other hand, when the resistance layer 7 covering the display surface forming body 4 is insulated from the partition wall electrode 6 (or in the case of a metal electrode that covers the display surface and is insulated from the partition wall electrode 6), the electrode surface is uniform. When the negative voltage signal is applied to the display electrode 5, the charged particles 9 are simply pressed onto the display surface forming body 4 to form the display surface. Thus, the charged particles 9 are not accelerated in the radial direction.

  Therefore, in the electrophoretic display device 100 according to the first embodiment, the charged particles 9 on the display surface forming body 4 are efficiently moved by the configuration in which the barrier layer electrode 6 and the display electrode are connected by the resistance layer 7. The setting response speed has been increased.

  As shown in FIG. 7A, a period from time t1 to time t2 corresponds to a reset period, and a period from time t2 to time t3 corresponds to a writing period. In the reset period, a negative reset voltage Vr is applied in order to collect the charged particles 9 on the display surface and display black as shown in FIG. At this time, the potential of the resistance layer 7 at the point A shown in FIG. 1B becomes an intermediate potential between the display electrode 5 (Vr) and the partition electrode 6 (0 V) due to the resistance voltage division.

  Thereafter, when the writing period starts, a positive writing voltage Vw is applied to the display electrode 5, the charged particles 9 on the display surface forming body 4 move toward the partition wall 3, and the display surface forming body 4 is gradually exposed. Then, as shown in FIG. 7C, the amount of reflected light increases. At this time, as shown in FIG. 7B, the potential of the resistance layer 7 also changes, and becomes a potential lower than the potential of the display electrode 5 due to the resistance voltage division.

  After completion of writing, the potential of the display electrode 5 is set to 0 V, and the display state maintaining period is started. Here, the resistance in the normal direction of the resistance layer 7 on the display electrode 5 and the resistance in the normal direction of the resistance layer 7 on the partition electrode 6 are the resistance of the electrophoretic liquid between the display electrode 5 and the partition electrode 6. If the voltage is sufficiently lower than that, the residual electric charge is not generated greatly. Therefore, the electric field in the reverse direction is not generated immediately after the voltage is lowered to 0 V, and the display state is not impaired.

<Description of components>
Hereinafter, the components of the electrophoretic display device 100 of the first embodiment will be described individually. The front substrate 2 serving as an observation surface is made of a material having a high visible light transmittance. For example, polymer films such as polyethylene terephthalate (PET), polyethersulfone (PES), polyimide (PI), polyethylene naphthalate (PEN), polycarbonate (PC), or inorganic materials such as glass and quartz can be used. . The rear substrate 1 is not necessarily transparent, and in addition to the above materials, a metal substrate such as SUS, aluminum, titanium, or a film substrate can be used.

An inorganic or organic material can be used for the partition 3, and examples thereof include SiO ₂ , an acrylic resin, an epoxy resin, a norbornene resin, and a fluorine resin. It is also possible to form the partition 3 with a conductive material. When the partition 3 is formed of a conductive material, the partition 3 itself functions as the partition electrode 6, so that the step of forming the partition electrode 6 after forming the three-dimensional structure of the partition 3 can be omitted. Further, the effect of suppressing the electric field interference between the display units 45 is improved, and the generation of residual charges in the partition 3 can be reduced.

Examples of the conductive material include organic substances such as polysilane, polysiloxane, and polyacetylene, or composites thereof, copolymer carbon-containing films, inorganic films such as ITO, AZO, SnO ₂ , and ZnO, or semiconductor films such as silicon, or Conductive fillers (fillers), for example, conductive fine particles such as ITO, ATO, Pb ₂ O ₅ , conductive polymers such as polythiophene-based conductive polymers, ionic conductive materials, etc. are used as epoxy resins, polypropylene resins, etc. A conductive film formed by blending can be used.

  Examples of the method for forming the partition walls 3 include exposure / etching to a photosensitive resin, printing lamination method, thick film printing method, molding method, ink jet method, transfer method, and the like. There is no particular limitation as long as it is a technique that can form the filling partition 3.

  The display surface forming body 4 is formed using an insulating transparent material or a material colored with a desired color. As long as insulation between the display electrode 5 and the partition wall electrode 6 can be obtained, the resistivity and the film thickness are not particularly limited, but the film thickness is 0.1 μm to 5 μm. The display surface forming body 4 has a transmittance different from that of the charged particles 9 or a different color so that the charged particles 9 are spread uniformly on the display surface (FIG. 1A). Contrast can be obtained when moved to the partition 3 ((b) of FIG. 1).

  For the display surface forming body 4, a plastic material such as polyimide resin, polyester resin, polyacrylate resin, polymethacrylate resin, polycarbonate resin, epoxy resin, norbornene resin, urethane resin, silicon resin, or glass can be used. In addition, inorganic oxide pigments and dyes such as titanium oxide, zinc oxide, and aluminum oxide may be mixed with these to be colored and light scattered.

  The display electrode 5 and the resistance layer 7 are connected at the center of the plane of the display unit 45, which is a pixel cell. The connection area may be any shape as long as it is 90% or less of the area of the display surface. good. The shape of the display electrode 5 is not limited to a square, and may be a circle, a star, or the like. As shown to (a) of FIG. 3, when the display unit 45 is a rectangle, you may make the distance to the partition 3 equal as the linear display electrode 5L. Further, as shown in FIG. 3B, a plurality of display electrodes 5 may be arranged. The plurality of display electrodes 5 are commonly connected below the display surface.

  The entire surface of the partition wall 3 is preferably covered with a continuous film of the partition wall electrode 6, but the partition wall electrode 6 may cover a part of the partition wall. The partition wall electrode 6 may be disposed between the partition wall 3 and the display surface forming body 4 as shown in FIG. In this case, the resistance layer 7 covering the partition wall 3 is electrically connected to the thin film side surface of the partition wall electrode 6 to form an upstanding electrode surface. The entire resistance layer 7 becomes equipotential with the partition wall electrode 6, and the entire partition wall 3 becomes an electrode surface having an equipotential surface.

  However, when the resistance layer 7 has a high resistance, the partition 3 is preferably made of a conductive material in order to suppress inter-pixel interference due to electric field leakage. When the partition 3 is formed of a conductive material and has a resistivity that can be used as an electrode, the partition 3 can also serve as the partition electrode 6.

  For the display electrode 5 and the partition electrode 6, inorganic and organic conductive materials can be used. Each electrode can be formed by plating, vapor deposition, an inkjet method, a screen printing method, or the like. As electrode materials, Au, Ag, Al, Ti, TiC, Cu, ITO, ATO, FTO, AZO, ZnO, and other metals known as conductive film materials, conductive nitride, conductive boride, organic A conductive material or the like can be used.

The material of the resistance layer 7 is not particularly limited as long as it is a light-transmitting material having resistance. However, the sheet resistance is desirably 10 ⁹ Ω / □ to 10 ¹⁴ Ω / □, and the film thickness is preferably 1 nm to 1 μm. . As long as the display electrode 5 and the partition wall electrode 6 are electrically connected via the resistance layer 7, the material, form, formation method, and the like of the resistance layer 7 are not particularly limited. As a forming method, a vacuum deposition method, a molecular beam epitaxy method, an ion plating method, a sputtering method, a CVD method, a casting method, an electric field polymerization method, a spin coating method, or the like can be selected.

The resistance layer 7 includes organic substances such as polysilane, polysiloxane, and polyacetylene, or composites thereof, copolymer carbon-containing films, inorganic films such as ITO, AZO, SnO ₂ , and ZnO, or semiconductor films such as silicon, or Conductive fillers (fillers), for example, conductive fine particles such as ITO, ATO, Pb ₂ O ₅ , conductive polymers such as polythiophene-based conductive polymers, ionic conductive substances, etc., epoxy resin, acrylic resin, urethane A conductive film that can be blended with resin, polypropylene resin or the like can be used.

  The surface control layer 8 is a light-transmitting material and desirably has a film thickness of 100 nm or less. In the first embodiment, as shown in FIG. 1A, the surface control layer 8 is formed so as to cover the entire resistance layer 7, but the entire surface of the resistance layer 7 is in contact with the surface control layer 8. Need not be stacked. It is necessary that at least a region where the surface control layer 8 is formed is present at a position farther from the display electrode 5 and the partition wall electrode 6 than the resistance layer 7. The surface control layer 8 is preferably formed so as to cover the entire outermost surface of all structures formed on the rear substrate 1, but the region where the surface control layer 8 is formed is the surface of the outermost surface. It may be a part.

  The surface control layer 8 is defined from at least one physical property value of surface energy, surface potential, and surface unevenness, and is selected so as to enhance the driving stability of the charged particles 9 and the positional stability of the charged particles 9 during the image holding operation. it can. For example, in order to increase the positional stability of the charged particles 9 during the image holding operation, when setting a stronger adhesion state between the charged particles 9 and the surface control layer 8, the charged particles 9 and the surface control layer 8 are set. The surface control value is set to be large, the surface potential of the charged particles 9 and the surface control layer 8 are set to opposite polarities, and the surface control layer 8 that is difficult to adsorb additives contained in the electrophoresis solution is selected. A method of increasing the surface unevenness of the layer 8 or providing an uneven structure having the same curvature as the particle diameter of the charged particles 9 can be selected.

  The surface energy of the surface layer can be measured and managed using a contact angle method or the like, the surface potential can be measured using a Kelvin probe or the like, and the surface unevenness can be measured and managed using SEM, TEM or the like. The surface control layer 8 can also be used as another component constituting the display unit 45 as long as desired surface layer characteristics are obtained. For example, the partition 3, the partition electrode 6, and the resistance layer 7 can be used as the surface control layer 8.

  The material used for the surface control layer 8 is not particularly limited as long as it has the desired values of surface energy, surface potential, and surface unevenness, but is not limited to vapor-deposited films of organic and inorganic materials, sputtered films, electrodeposition films, LB films, A SAM film, an adsorption film, a spray film, or the like can be used. Also, surface modification such as plasma treatment, corona discharge, sputter etching treatment, ion beam, chemical treatment, solvent treatment, coupling agent treatment, surfactant treatment, steam treatment, surface grafting, etc. to obtain desired properties Techniques can be used.

  The charged particles 9 have a transmittance different from that of the display surface forming body 4 or a different coloring. The average particle diameter of the charged particles 9 is not particularly limited, but is preferably in the range of 0.1 μm to 10 μm, and more preferably 0.1 μm to 3 μm. This is because if it is less than 0.1 μm, the handling property is lowered, and if it exceeds 3 μm, the display resolution is lowered. The average particle diameter of the charged particles 9 can be controlled within the above range by a known method such as dry classification or wet classification, if necessary.

  The concentration of the charged particles 9 dispersed in the insulating liquid 10 is not particularly limited, but is preferably 0.1 wt% or more and 30 wt% or less. The charged particles 9 may be used by mixing two or more kinds having different transmittances or different colors. In this case, the concentration of the charged particles 9 in the insulating liquid 10 is 0.1 wt% or more and 50 wt% or less. Is preferred.

  The charged particles 9 are not limited to any of inorganic particles, polymer resin particles, or composite particles thereof. When the charged particles 9 are inorganic particles, titanium dioxide, graphite, carbon black, silica, alumina, or the like can be used. These inorganic particles can be used as the charged particles 9 of the first embodiment by classifying those obtained from a granulation method, a pulverization method, or a sol-gel method, but the production method is not limited to the above method. .

  Further, when the charged particles 9 are polymer resin particles, they can be obtained from known methods such as suspension polymerization method, dispersion polymerization method, seed polymerization, or emulsion polymerization method, but the production method is limited to these methods. Not. When the charged particles 9 are composite particles, the polymer used is not particularly limited. For example, polystyrene, polyethylene, polyester, polymethacrylate, polyacrylate, polyacrylate ester, polyethylene-acrylic acid copolymer And polymer materials such as polyethylene resins such as polyethylene-methacrylic acid copolymer, polyethylene-vinyl acetate copolymer, and other polyvinyl chloride resins, nitrocellulose, phenol resins, and polyamide resins. These materials may be used alone or in combination of two or more.

  In addition, as the charged particles 9 in the first embodiment, commercially available particles can be used. For example, Micropearl (manufactured by Sekisui Chemical Co., Ltd.), Natoko Spacer Particles (manufactured by Natco Co., Ltd.), Epocolor Particles (manufactured by Nippon Shokubai Chemical Industry Co., Ltd.), Chemisnow (manufactured by Soken Chemical Co., Ltd.), Tospearl ( GE Toshiba Silicone Co., Ltd.), techpolymer (Sekisui Chemicals Co., Ltd.) and the like are mentioned, but not particularly limited.

  Further, the surface of the charged particles 9 can be coated in order to give the charged particles 9 desired surface characteristics. Specifically, the polymer particles are coated with a polymer through a coupling group of a coupling agent by a seed polymerization method, a graft polymerization method, or a polymer polymerization method on the core particles. Examples thereof include a method, a method in which a charged particle surface is coated with a solution in which a polymer is dissolved in a solvent and the solvent is removed, and a method in which the charged particle surface is subjected to plasma treatment.

  The charged particles 9 can be colored according to the display method of the electrophoretic display device to be used. Although it does not specifically limit as a coloring agent, For example, dyes, such as pigments, such as carbon black and a titanium oxide, Orient Oil Black [made by Orient Chemical Co., Ltd.] are mentioned. A pigment that can be used alone as the charged particles 9 such as carbon black and titanium oxide may be used without being colored.

  As a method of preparing composite particles in which a high molecular polymer is combined with a plurality of pigment particles and dyes, emulsion polymerization is performed by adding pigment particles and dyes in the polymerization process of the high molecular polymer (including monomer charging), There are methods of performing dispersion polymerization, suspension polymerization, or seed polymerization. Other methods include dyeing the polymer particles themselves with a dye, melting and kneading the pigment particles with the polymer, and pulverizing the pigment particles, or adding the pigment particles or dye to a solution in which the polymer is dissolved in a solvent. Thereafter, the solvent can be removed, the temperature of the solution can be lowered, or reprecipitation using a poor solvent can be performed to precipitate and granulate the composite particles.

  The polymer or dye constituting the composite particle may be subjected to a crosslinking treatment or an immobilization treatment for the purpose of insolubilization in a solvent. Depending on the required degree of coloration of the composite particles, pigment particles and dyes can be mixed and used.

  The material of the insulating liquid 10 is not particularly limited, but a colorless and highly light transmissive material is desirable. Various additives can be added to the insulating liquid 10 in order to obtain desired characteristics of the insulating liquid 10 serving as a dispersion medium for the charged particles 9. A charge control agent for imparting charge to the charged particles 9 or increasing the charge, a charge stabilizer for stabilizing the charge of the charged particles 9, a dispersion stabilizer for improving the dispersibility of the charged particles 9, and the charged particles 9 You may add at least 1 type of adhesion preventing agent for preventing adhering to the inner wall face.

  The viscosity of the insulating liquid 10 is preferably 0.1 cp or more and 30 cp or less. Examples of the insulating liquid 10 include aromatic hydrocarbon solvents such as benzene, toluene, xylene, and naphthenic hydrocarbons, and aliphatic hydrocarbons such as hexane, cyclohexane, kerosene, paraffin hydrocarbon solvents, and isoparaffin hydrocarbons. And various solvents such as fluorine-based solvents such as silicon solvents, halogenated hydrocarbon solvents, silicon oil, high-purity petroleum, fluoroethylene, octafluorocyclopentane, and hydrofluoroether. These solvents can be used as a single species or as a mixture of a plurality of species.

  The charge control agent is not particularly limited as long as it is soluble in a solvent, and examples thereof include anionic surfactants such as carboxylate, sulfonate, sulfate ester salt, phosphate ester salt, aliphatic amine salt, and the like. Cationic surfactants such as quaternary ammonium salts, aromatic quaternary ammonium salts, heterocyclic quaternary ammonium rims, amphoteric surfactants such as carboxybetaines, sulfobetaines, aminocarboxylates, imidazoline derivatives, ether types, ether esters Type, ester type, nitrogen-containing nonionic surfactant, metal soap, fluorine-based surfactant, reactive surfactant, block-type polymer, graft-type polymer, and the like. These may be used alone or in combination of two or more.

  The rosin ester or rosin derivative used as the charge stabilizer is not particularly limited as long as it is soluble in a solvent. For example, gum rosin, wood rosin, tall oil rosin, rosin modified maleic acid, rosin modified pentaerythritol, rosin glycerin ester, Examples thereof include maleic acid-modified rosin ester, fumaric acid-modified rosin ester, acrylic acid-modified rosin ester, and the like.

  Specifically, for example, neotol (Harima Kasei), pencel, ester gum, superester (all of which are Arakawa Chemical Industries) can be mentioned. When the rosin ester or rosin derivative is not contained in the solvent, the charged particles may not be stably charged, and the charge polarity may be reversed or the particles may not be electrophoresed. The rosin ester or rosin derivative can be contained in the range of 0.01 to 5 parts by mass, preferably 0.05 to 3 parts by mass with respect to 100 parts by mass of the solvent.

  The dispersion stabilizer and the adhesion inhibitor are not particularly limited as long as they are compatible with the solvent. For example, polyacrylamide, polyvinyl alcohol, polyethylene, polystyrene, polybutadiene, polydimethylsiloxane, polypropylene, polymethyl methacrylate, polytetrafluoroethylene, polyvinyl chloride, polyisoprene, polybutene, styrene butadiene copolymer, styrene isoprene copolymer Styrene maleic anhydride copolymer, fluorine polymer, norbornene resin, and polyethylene wax can be used.

  Further, polymers such as polyvinyl alcohol and polyvinyl pyrrolidone having various saponification degrees and molecular weights, surfactants, fluorine-based surfactants such as perfluoroalkyl group-containing oligomers, and the like can also be used. Among them, styrene butadiene copolymer is preferable, and commercially available materials include E-SBR, S-SBR (manufactured by JSR), NIPOL 1502, NIPOL 1712, NIPOL NS112, NIPOL NS116, NIPOL 1006, NIPOL 1009 (Japan) Zeon Co., Ltd.), Tuffden, Taffeprene, Asaprene (Asahi Kasei Co., Ltd.), Sumitomo SBR (Sumitomo Chemical Co., Ltd.) and the like can be used. These components can be used alone or in admixture of two or more.

Second Embodiment
FIG. 8 is an explanatory diagram of a cross-sectional configuration in the electrophoretic display device of the second embodiment, FIG. 9 is an explanatory diagram of a cross-sectional configuration when the partition wall electrodes are directly arranged on the display surface forming body, and FIG. 10 is a second embodiment. It is explanatory drawing of the drive waveform of one display unit in. In FIG. 10, (a) is the display electrode potential, (b) is the resistance layer potential at point A, and (c) is the optical response.

  The electrophoretic display device 200 according to the second embodiment is the same as the electrophoretic display device 100 according to the first embodiment except that the display surface forming body 4 is formed of a color filter layer and the resistance layer 7 is disposed below the partition wall 3. It is configured in the same way. Therefore, in FIGS. 8 and 9, the same reference numerals are given to the same components as those in FIG. 1, and detailed description thereof will be omitted.

  As shown in FIG. 8, the display electrode 5 for each display unit 45 has the same area as the display unit 45 and is disposed on the rear substrate 1, and the surface is whitened to serve as a reflection surface. The display surface forming body 4 formed on the display electrode 5 is painted with different colors in three adjacent display units 45. The display surface forming body (colored layer) 4 is composed of color filter layers 4a, 4b, and 4c made of an insulating material in which pigments of red (R), green (G), and blue (B) are dispersed and colored, respectively. Yes. In the electrophoretic display device 200 according to the second embodiment, gradations of three adjacent display units 45 are set, and one pixel is displayed in full color.

The resistance layer 7 is formed so as to uniformly cover the rear substrate 1 on which the display surface forming body 4 is formed, and is positioned between the display electrode 5 and the partition 3. Since the resistance layer 7 electrically connects the display electrode 5 and the partition wall electrode 6 as in the first embodiment, when a voltage signal is applied to the display electrode 5, a uniform potential is generated in the resistance layer 7. A gradient occurs. The resistance layer 7 is an acrylic resin in which a conductive filler is dispersed, and has a sheet resistance of 10 ¹² Ω / □ and a film thickness of 200 nm.

  The contact hole 11 is formed at the center of the display surface, and the resistance layer 7 and the display electrode 5 are electrically connected by the contact hole 11. The display electrode 5 may be formed in a shape and area different from the shape of the contact hole 11. By forming the contact hole 11 at a position farthest from the partition wall electrode 6, that is, at the center portion of the display surface, the potential difference between the center portion of the display surface and the partition wall electrode 6 is most uniform and large. As a result, an electric field in the direction along the display surface toward the center of the display surface is generated during black display, and as a result, migration of the charged particles 9 toward the center of the display surface is accelerated, and the response speed is improved.

  The surface control layer 8 is formed of a continuous film so as to cover the entire resistance layer 7 and the partition wall electrode 6, and the surface control layer 8 is maintained so that the charged particles 9 are in stable contact with the surface control layer 8. The surface of the charged particles 9 is made of methacrylic resin, and an appropriate difference is provided between the surface energy of the surface control layer 8 and the charged particles 9.

  As a tendency, when the surface energy difference between the surface control layer 8 and the charged particles 9 is made larger, the state where the charged particles 9 are in contact with the surface control layer 8 is kept more stable, but the surface energy difference is set larger. If too much is applied, even if a voltage for the migration of the charged particles 9 is applied, the migration does not occur and the charged particles 9 may be fixed, and an appropriate relationship setting is important. Also in this respect, it is effective that the surface control layer 8 can be designed freely.

  In order to increase the stability in the contact state between the charged particles 9 and the surface control layer 8, a carboxylate is added as a charge control material, and polyisobutylene is added as an adhesion preventing agent. In the second embodiment, since the resistance layer 7 is formed on the display surface forming body 4 with small surface irregularities before the partition 3 is formed, the resistance layer 7 is formed on the partition 3 as in the first embodiment. Compared with the case where it forms, the more uniform resistance layer 7 can be formed and the restriction | limiting with respect to film-forming conditions can be made small. Therefore, in addition to the various film forming methods described in the first embodiment, a lower cost method such as a slit coating method, a screen printing method, a transfer method, an ink jet method, or a dispenser coating method is adopted for forming the resistance layer 7. It is also possible.

  As shown in FIG. 9, the partition electrode 6 can be formed between the resistance layer 7 and the partition 3 as shown in FIG. At this time, the partition 3 is preferably formed of a conductive material. The reason is as described in the first embodiment.

  Next, the operation of the electrophoretic display element according to this embodiment will be described. In the second embodiment, the driving circuit is configured in the same manner as described in the first embodiment, and a writing period is set after the reset period, and then the pixel display is held by moving to the voltage off transition period.

  As shown in FIG. 10A, at time t <b> 1, a negative reset voltage Vr is applied to the display electrode 5 to cover the display surface with the charged particles 9. Immediately after application of the negative reset voltage Vr, the potential of the resistance layer 7 at the point A in FIG. 8 is the ratio between the capacitance between the resistance layer 7 and the display electrode 5 and the capacitance between the display surface formation body 4 and the display electrode 5. The voltage is substantially the same as the applied voltage. However, after that, the voltage settles to a predetermined voltage due to the resistance voltage division of the resistance layer 7. This time constant can be adjusted by the resistance value of the resistance layer 7 and the capacitance formed between the resistance layer 7 and the display electrode 5.

  Thereafter, when the writing period starts at time t <b> 2, the positive writing voltage Vw is applied to the display electrode 5. At this time, the potential of the resistance layer 7 at the point A in FIG. 8 becomes equal to or higher than the voltage Vw due to the capacitive voltage division, but settles to a predetermined voltage of the resistance voltage division with the same time constant as during the reset period. Then, as shown in FIG. 10 (c), after the display surface reaches a predetermined gradation level, the voltage off transition period starts from time t3.

  Here, when the voltage is set to 0 V immediately after the time t3, an electric field having a reverse polarity is generated by the electric charge accumulated between the resistance layer 7 and the display electrode 5, and the memory property is deteriorated. Therefore, if the potential of the display electrode 5 is gradually changed to 0 V with a time constant longer than the time constant of the display unit 45, the generation of an electric field of reverse polarity can be suppressed, and the memory performance can be maintained. It becomes possible.

  In other words, after applying the write voltage Vw for gradation display to the display electrode 5, by changing the voltage to 0 V with a time constant larger than the time constant determined by the capacitance of the display surface formation body 4 and the resistance layer 7, The applied voltage is reduced to 0 V with a time constant longer than the time constant of the residual charge accumulated in the display surface forming body 4, so that no residual charge remains in the moving space 20. As a result, application of a reverse polarity voltage to the insulating liquid 10 is suppressed, and the charged particles 9 do not move in the reverse direction, and good memory performance can be obtained.

<Driving of display unit with scanning>
FIG. 11 is an explanatory diagram of drive waveforms in display unit drive with scanning. In FIG. 11, (a) is a scanning signal, (b) is a writing signal, (c) is a display electrode potential, and (d) is an optical response.

  In the second embodiment, the case where the constant write voltage Vw is continuously applied to the display electrode 5 has been described with reference to FIG. 10. However, when the drive circuit shown in FIGS. 5 and 6 is used, a plurality of scanning signals are used. Since the scanning signals are sequentially applied to the lines 47, the write voltage Vw is actually supplied to the display electrode 5 for only a very short time during one scanning period.

  As shown in FIG. 5, a scanning signal is periodically applied to the scanning signal line 47 to turn on the pixel TFT 46, while the writing signal line 48 has a unique writing voltage for each display unit 45 in synchronization with the scanning signal. Vw is applied. Therefore, as shown in FIGS. 11A and 11B, after the write voltage Vw is supplied to the display electrode 5 at the timing of the scan signal, the write voltage Vw is not replenished until the next scan signal. The potential of the display electrode 5 gradually decreases due to the leakage current through the resistance layer 7 and the like.

  Then, as shown in FIG. 11C, the potential of the resistance layer 7 that gradually decreases changes the distribution state of the charged particles 9 covering the surface of the display surface forming body 4, and is shown in FIG. 11D. As described above, the gradation of the display unit 45 changes.

  As shown in FIG. 11, the driving period is composed of three periods: a reset period, a writing period, and a voltage off transition period. In the following, the case where each period is composed of two fields will be described. However, the same effect can be obtained when the number of fields in each period is different or when the number of fields is composed of two or more fields. The potential of the partition wall electrode 6 is 0V.

  In the reset period, as shown in FIG. 11B, when the reset voltage Vr1 is applied in synchronization with the scanning signal and the voltage Vr1 is written to the display electrode 5, the voltage is maintained during the subsequent field period. The At this time, since the display electrode 5 and the partition wall electrode 6 are connected via the resistance layer 7, the potential of the display electrode 5 changes according to the time constant determined by the resistance value of the resistance layer 7 and the auxiliary capacitance 50. To do. The amount of change in the display electrode potential 5 can be reduced by adjusting the sheet resistance of the resistance layer 7 and the auxiliary capacitance 50.

  Here, as indicated by a broken line in FIG. 11C, the potential of the resistance layer 7 at the point A in FIG. 8 becomes the potential Vr1 immediately after the reset, and then settles on the resistance partial pressure of the resistance layer 7. The resistance partial pressure of the resistance layer 7 itself gradually decreases according to the potential change of the display electrode 5. Thus, the surface potential distribution formed in the resistance layer 7 can alleviate the electric field concentration in the vicinity of the partition walls 3 and can realize acceleration in the radiation direction effective for the movement of the charged particles 9.

  In the next field during the reset period, the voltage Vr1 is written to the display electrode 5 again. Since the display electrode potential change at this time is small, the potential fluctuation of the resistance layer 7 at point A in FIG. 8 is also small. Thereafter, the potential drops as in the previous field.

  Next, when the writing period starts, the voltage Vw1 is written to the display electrode 5, and then the voltage is held, and the display state changes from black to white by the movement of the charged particles 9. At this time, the potential of the resistance layer 7 at the point A in FIG. 8 is instantaneously higher than Vw1 because the potential change is substantially equal to the potential difference from Vr1 to Vw1, but thereafter, the resistance component of the resistance layer 7 Settle down to pressure. The potential change in the next field is the same as in the second field during the reset period.

  Next, in the voltage off transition period, the ramp voltage Vs1 is written to the display electrode 5 in the first field, and the ramp voltage Vs2 is written in the second field. The potential of the resistance layer 7 at point A in FIG. 8 is determined by the resistance partial pressure of the resistance layer 7 and changes according to the potential change of the display electrode 5.

  Here, if the voltage is changed to 0 V immediately after the end of the writing period, the electric potential accumulated in the display surface forming body 4 causes the potential of the resistance layer 7 to have a reverse polarity, and an electric field in the reverse direction is generated. As a result, the covering state of the display surface forming body 4 changes and the memory performance of the display is hindered. Therefore, by gradually lowering the potential of the display electrode 5 while satisfying the relationship of Vw1> Vs1> Vs2, the time until the potential of the display electrode 5 is attenuated to 0V is set to the resistance value of the resistance layer 7 and the display surface forming body. It is longer than the time constant determined by the capacity of 4.

Specifically, when the display surface forming body 4 has a film thickness of 1 μm, the display surface forming body 4 has a dielectric constant of 3, and the pixel size is 50 μm × 50 μm, the display is sandwiched between the resistance layer 7 and the display electrode 5. The capacitance of the surface forming body 4 is about 0.13 pF per pixel except for the contact hole portion 11. When the resistance layer 7 is formed so that the resistance between the partition wall electrode 6 and the display electrode 5 is 10 ¹² Ω, the time constant for eliminating the residual charge is about 13 msec. Therefore, as shown in FIG. 11, when the potential of the display electrode 5 is attenuated to 0 V in the time of 2 fields 100 ms, an electric field having a reverse polarity is not generated.

  Thus, by setting the time until the potential of the display electrode 5 is attenuated to 0 V longer than the time constant determined by the capacitance of the display surface forming body 4 and the resistance of the resistance layer 7, an electric field of reverse polarity is obtained. Thus, the potential of the display electrode 5 and the potential of the resistance layer 7 can be lowered to 0 V without causing the optical response after the writing period to change. In actual use, the display switching speed is desirably 1 second or less, and the potential decay time of the display electrode 5 is desirably 1 second or less. As long as the time constant determined by the display surface forming body 4 and the resistance layer 7 does not exceed the decay time, the values of the film thickness, dielectric constant, and resistance of the resistance layer 7 of the display surface forming body 4 are any values. May be.

  That is, according to the driving method described above, the electric field non-uniformity in the vicinity of the partition wall 3 can be improved without generating an electric field in the reverse direction, so that the memory performance, contrast, and display quality of the electrophoretic display panel can be improved. It becomes possible to greatly improve.

<Third Embodiment>
FIG. 12 is an explanatory diagram of a cross-sectional configuration in the electrophoretic display device of the third embodiment, and FIG. 13 is an explanatory diagram of a cross-sectional configuration when the partition wall electrode is directly disposed on the insulating layer. The electrophoretic display device 300 of the third embodiment is the same as the electrophoretic display device 200 of the second embodiment, except that the resistance layer 7 on the display surface forming body 4 is divided by the insulating layer 12 for each display unit 45. It is constituted similarly. Therefore, in FIG. 11 and FIG. 12, the same reference numerals are given to the same constituent members as those in FIG.

  As shown in FIG. 12, the resistance layer 7 is divided by the insulating layer 12 for each display unit 45, and is electrically cut between the display units 45. Further, the resistance layer 7 is electrically connected to the display electrode 5 through a contact hole filled with the connection material 13 in each display unit 45.

  A highly conductive material is used for the connection material 13 to reduce the surface step of the resistance layer 7 due to the contact hole 11. Further, the problem that the physical depression is eliminated and the charged particles 9 are caught or stuck on the step of the contact hole portion is solved. As the connection material 13, a material lower than the resistance of the resistance layer 7 is desirable, and metals such as Al and Ti, ITO, ATO, conductive resin, and the like can be used.

  Further, since the insulating layer 12 is thicker than the resistance layer 7 and the partition wall 3 having the partition electrode 6 formed on the insulating layer 12 is disposed, the resistance layer 7 on the display surface forming body (colored layer) 4 is The partition wall electrode 6 is insulated. Accordingly, when a signal voltage is applied to the display electrode 5, the potential of the resistance layer 7 is uniformly the same as the potential of the display electrode 5 as a whole, and functions as an equipotential surface in each display unit 45. The partition electrode 6 and the resistance layer 7 are insulated, and the migration control of the charged particles 9 is performed by the potential of the resistance layer 7 that forms the pixel surface and the potential of the partition electrode 6 that covers the entire partition 3. .

In the configuration in which the resistance layer 7 and the partition wall electrode 6 are insulated and used as independent electrode surfaces as in the third embodiment, the resistance layer 7 has a sheet resistance of 10 ² Ω / □ to 10 ¹³ Ω / □. It is desirable that In the configuration in which the migration of the charged particles 9 is controlled between the potential surface of the resistance layer 7 electrically connected to the display electrode 5 and the potential surface of the partition wall electrode 6 insulated from the resistance layer 7, the resistance The layer 7 has a sheet resistance of 10 ² Ω / □ to 10 ¹⁴ Ω / □, and a lower sheet resistance is preferable. In the third embodiment, the resistance layer 7 is an inorganic oxide film, and the sheet resistance is 10 ³ Ω / □.

  The surface control layer 8 of the third embodiment is formed of an acrylic resin so as to cover the entire resistance layer 7 and the partition wall electrode 6, and the diameter of the charged particles 9 is increased on the surface in order to improve the capturing performance of the charged particles 9. Innumerable irregularities smaller than that are formed.

  As shown in FIG. 13, the partition wall electrode 6 can be formed between the partition wall 3 and the insulating layer 12. At this time, the partition 3 is preferably formed of a conductive material. In the configuration of FIG. 12, the uneven structure of the surface control layer 8 covering the partition wall 3 can be formed on the partition wall 3.

<Drive circuit>
FIG. 14 is an explanatory diagram of another driving circuit of the electrophoretic display device of the second embodiment, and FIG. 15 is an explanatory diagram of driving waveforms of the display electrodes. In FIG. 15, (a) is a scanning signal, (b) is a writing voltage signal, (c) is a driving potential Vdd of the driving power supply line, (d) is a display electrode potential, and (e) is an optical response.

  As shown in FIG. 8, in the electrophoretic display device 200 of the second embodiment, since the display electrode 5 and the partition wall electrode 6 are connected to each other by the resistance layer 7, if the current supply to the display electrode 5 is interrupted, the control electrode The voltage of 5 falls quickly. Therefore, as described with reference to FIG. 11, the write voltage signal is repeatedly applied to the display electrode 5 through the write signal line 48 (FIG. 5) at intervals of one cycle of the scanning signal. Compared with the case where the constant write voltage signal described with reference to FIG. 6 is applied, the reproducibility of the density expression in the display unit 45 is deteriorated due to the voltage fluctuation.

  Therefore, in the drive circuit shown in FIG. 14, the write voltage signal read from the write signal line 48 is stored in the capacitor 50 at the scanning signal input timing. Then, by controlling the voltage control TFT 53 with the write voltage accumulated in the capacitor 50, a write voltage signal is formed from the drive power supply voltage Vdd and is continuously applied to the display electrode 5. The write voltage accumulated in the capacitor 50 is reset by writing a negative reset signal. In this manner, as described with reference to FIG. 10, a constant write voltage signal can be continuously applied to the display electrode 5.

  As shown in FIG. 14, in another drive circuit for driving the electrophoretic display device 200 of the second embodiment, a drive power supply line 52 and a voltage control TFT 53 are added to the drive circuit shown in FIG. . The voltage control TFT 53 is an n-type transistor similar to the pixel TFT 46. The drive power line 52 and the display electrode 5 (FIG. 8) of the pixel 45 are connected to the source electrode and the drain electrode of the voltage control TFT 53, respectively, and the drain electrode of the pixel TFT 46 is connected to the gate electrode. The drive power supply line 52 is commonly connected to all the display units 45, and + Vdd and -Vdd are alternately applied as shown in FIG. The potential of the partition wall electrode 6 is a common 0V.

  As shown in FIGS. 15A and 15B, the writing voltage signal is applied in synchronization with the scanning signal. In the reset period in which the display unit 45 is displayed in black, the source driver 43 outputs a pulse Vt1 to the write signal line 48, the potential Vt1 is held in the capacitor 50, and the gate of the voltage control TFT 53 is held at the voltage Vt1. At this time, as shown in FIG. 15C, since the voltage of the drive power supply line 52 is −Vdd, a current flows from the gate of the voltage control TFT 53, the voltage control TFT 53 is turned on, and the display electrode 5 of the display unit 45 is As shown in (c) of FIG. 15, the reset voltage Vr <b> 1 is immediately achieved.

  In other words, the source-drain resistance of the voltage control TFT 53 is controlled by the gate voltage, and the resistance when the voltage Vt1 is applied is sufficiently lower than the resistance of the resistance layer 7 between the partition wall electrode 6 and the display electrode 5. Therefore, the potential of the display electrode 5 becomes approximately −Vdd due to the resistance voltage division while the potential difference −Vdd is applied between the partition wall electrode 6 and the drive power supply line, and the reset operation of the charged particles 9 can be performed.

  In the next cycle (field) of the scanning signal, a voltage Vt0 lower than −Vdd is written to the capacitor 50, and the voltage control TFT 53 is turned off. As a result, −Vdd of the drive power supply line 52 is cut off, and the potential of the display electrode 5 is gently induced to 0 V by the leakage current from the partition wall electrode 6 to the display electrode 5 through the resistance layer 7.

  In other words, turning off the voltage control TFT 53 means that the resistance between the source and drain of the voltage control TFT 53 is higher than the resistance of the resistance layer 7, and the potential of the display electrode 5 is the partition electrode as a result of the resistance voltage division. It approaches the potential of 6.

  Thereafter, after the voltage control TFT 53 is cut off and the voltage of the drive power supply line 52 changes to + Vdd, the analog voltage writing Vt2 necessary for writing the predetermined gradation is written into the capacitor 50 at the timing of the scanning signal. Since the voltage control TFT 53 continues to connect the display electrode 5 to the drive power supply line 52 while the current flows from the gate by the write voltage Vt2 of the capacitor 50, the potential of the display electrode 5 is held at the write voltage Vt2. Strictly speaking, the potential of the display electrode 5 is maintained at a potential obtained by subtracting its threshold voltage Vth from the write voltage Vt2.

  In other words, the voltage Vt2 is written to the gate of the voltage control TFT 53, and the resistance between the source and drain of the voltage control TFT 53 decreases. Here, since the potential of the display electrode 5 is controlled by the gate voltage of the voltage control TFT 53 by the resistance voltage division, the voltage Vt2 for obtaining the desired gradation voltage Vw1 may be applied. Here, the reason why the voltage Vt2 becomes higher than Vt1 is that the voltage control TFT is an n-type transistor, and the positive voltage + Vdd is written, and the source-drain resistance is high.

  Thereafter, the reset negative voltage Vt0 is written to the capacitor 50 at the timing of the next scanning signal, and the voltage control TFT 53 is turned off. As a result, Vdd of the drive power supply line 52 is cut off, and the potential of the display electrode 5 is gently induced to 0 V by the leakage current from the partition wall electrode 6 to the display electrode 5 through the resistance layer 7.

  According to the drive circuit shown in FIG. 14 and the signal control shown in FIG. 15, even when the pixel TFT 46 is off, the display electrode 5 can be maintained at a stable and constant potential by resisting the leakage current of the resistance layer 7. Good pixel display with high reproducibility can be obtained.

<Electrophoretic display device of comparative example>
FIG. 16 is an explanatory diagram of a cross-sectional configuration of an electrophoretic display device of a comparative example, and FIG. 17 is an explanatory diagram of a cross-sectional configuration of an electrophoretic display device of another comparative example. In FIG. 16, (a) is black display and (b) is white display.

  As shown in FIG. 16, the electrophoretic display device 500 of the comparative example displays an image by arranging a large number of display areas 145 in a grid pattern and performing pixel display in each display area 145. An insulating liquid 110 in which a large number of charged particles 109 are dispersed is filled between the rear substrate 101 and the front substrate 102 which are held at a predetermined distance by the partition wall 103.

  A display surface is set at the bottom of the moving space 120 partitioned by the partition wall 103, and display electrodes 105 for each display unit (pixel) are arranged on the display surface. On the surface of the partition wall 103, the partition electrode 106 commonly connected to all the display units 145 is disposed. An insulating display surface forming body 104 is laminated on the rear substrate 1 so as to cover the display electrode 105.

  Here, when the charged particles 109 are colored black and are positively charged, when the partition electrode 106 is set to 0 V and a negative voltage is applied to the display electrode 105, as shown in FIG. Covers the display electrode 105. As a result, the display surface viewed from the front substrate 102 side is displayed in black, which is the color of the charged particles 109.

  On the contrary, when the partition electrode 106 is set to 0 V and a positive voltage is applied to the display electrode 105, the charged particles 109 which are positively charged move onto the partition electrode 106 as shown in FIG. The color of the pixel electrode 105 is observed from the substrate 102 side. Therefore, by utilizing the difference between the color of the display electrode 105 and the color of the charged particles 109, it is possible to perform reverse display and halftone display.

  In the electrophoretic display device 500 of the comparative example, since the display electrode 105 is isolated from the moving space 120 of the charged particles 109 by the display surface forming body 104, the display electrode 105 can electrolyze an insulating liquid or charged particles. There is no worry of losing the charge. However, when a voltage is applied between the display electrode 105 and the partition wall electrode 106, even if the voltage is set to OFF, residual charges are generated in the display surface formation body 104 disposed between the display electrode 105 and the partition wall electrode 106. For this reason, the charged particles 109 at the writing position move according to the residual charge, and the written image is destroyed or burn-in occurs.

  By the way, in the colorization of the electrophoretic display device 500, the simplest method is to display one pixel in full color in three adjacent display units in which three primary color filter layers are arranged. If a color filter layer is formed on the display electrode 105, it is possible to avoid a misalignment problem that occurs when the color filter layer is provided on the front substrate 102 side, and a decrease in aperture ratio due to the black matrix.

  However, if a thick color filter layer is disposed on the display electrode 105, a residual charge is likely to be generated in the color filter layer over the display surface forming body 104, and the written image is distorted and burned in.

  As shown in FIG. 17, in an electrophoretic display device 600 of another comparative example, a display electrode 105 is formed on a rear substrate 101, and a partition wall 103 is disposed so as to surround the display electrode 105. A partition wall electrode 106 is formed on the rising surface of the partition wall 103 so as to face the display electrode 105. The display electrode 105 and the partition wall electrode 106 are individually covered with an insulating layer 111 so that the metal electrode surface does not come into contact with the charged particles 109 or the insulating liquid 110.

  In the electrophoretic display device 600 of another comparative example, since the display electrode 105 is covered with the insulating layer 111, there is no concern that the display electrode 105 causes the insulating liquid to be electrolyzed or the charged particles are lost. . However, even when a write voltage is applied between the display electrode 105 and the partition wall electrode 106 for image display and then the voltage is turned off next time, a residual voltage is generated between the display electrode 105 and the partition wall electrode 106 and charging is performed. The position of the particles 109 is not stabilized, leading to display unevenness.

  In recent years, in order to provide the display memory characteristic that is characteristic of an electrophoretic display device that does not require power to maintain display after image writing once, the characteristic relationship of materials constituting the electrophoretic display device has been changed. Various methods for defining have been proposed. In various methods, the surface characteristics of the inner wall surface of the moving space 120 defined by the rear substrate 101, the front substrate 102, and the partition wall 103 may impede display memory performance. Even if the residual charge is lowered, the charged particles 109 at the writing position cannot be kept in place, and the writing state is destroyed.

<Correspondence with Invention>
The electrophoretic display device 100 of the first embodiment includes a rear substrate 1 on which a display surface for each display unit 45 is set, and a partition wall 3 that surrounds the display surface and partitions the moving space 20 of the charged particles 9. . And it has the surface layer 8 arrange | positioned in the interface of the movement space 20 covering the display surface and the standing surface of the partition 3, and the surface layer 8 has at least one of surface energy, surface potential, and surface unevenness | corrugation. Unlike the lower layer, the restraining performance of the charged particles 9 at the interface is enhanced.

  Therefore, the necessary optical properties and essential functions such as the resistance layer, electrode surface, insulating layer, and color filter layer are left to the lower layer, and the necessary qualities as an interface layer including the property to improve the memory performance of pixel display and Since only the function is assigned to the surface layer 8, the material selection, the film formation method, the film thickness, etc. are selected with the highest priority on the property to improve the memory performance of the pixel display, ignoring the property and function to be laid on the lower layer. As compared with the case where the surface layer 8 is not provided, it is possible to improve the difficulty in burning the pixel display and the memory performance.

  In other words, the residual charge generated by the voltage applied between the display electrode 5 and the partition wall electrode 6 is reduced, and it is possible to suppress the collapse and burn-in of the written image due to electrical elements generated in the electrophoretic display device 100. It becomes possible.

  In addition, since the display memory property is given by the relational definition of the material characteristics constituting the electrophoretic display device 100, a stable memory property can be set. In addition, since electrical variation for each display unit 45 is also suppressed, the writing level is stabilized and the stability of gradation display is enhanced.

  Further, by adopting the element configuration and manufacturing method of the resistance layer 7 and the surface layer 8, it becomes possible to select various film forming methods, and in addition to being able to obtain manufacturability and a large area, the substrate Since the degree of freedom of selection of materials is widened, the electrophoretic display device 100 can be easily made flexible.

  In addition, once the image is written by electrical addressing, the image continues to be displayed stably without supplying display maintenance power, so no power is required except when rewriting the display image. Can be used for electronic paper, reading terminals, etc.

  In the electrophoretic display device 100 of the first embodiment, the resistance layer 7 covering the display surface is disposed as the lower layer. Therefore, various effects by the resistance layer 7 can be realized.

  The electrophoretic display device 100 according to the first embodiment includes a display electrode 5 disposed in the center of the plane of the display surface, and the resistance layer 7 is disposed so as to integrally cover the display electrode 5 and the display surface.

  The electrophoretic display device 200 according to the second embodiment includes the display electrode 5 for each display unit 45 disposed below the display surface, and the insulating display surface forming body 4 disposed on the display electrode 5. The resistance layer 7 is connected to the display electrode 5 and is disposed so as to cover the display surface forming body 4. Therefore, prevention of charging of the moving space 20 is realized.

  In the electrophoretic display device 200 of the second embodiment, the resistance layer 7 and the display electrode 5 are connected by a contact hole 11 disposed in the center of the display surface. Therefore, the resistance layer 7 functions as an electrode surface to collect and disperse the charged particles 9.

  In the electrophoretic display device 200 of the second embodiment, the display surface forming body 4 is formed as color filter layers 4a, 4b, and 4c having different absorption wavelength characteristics in a plurality of adjacent display surfaces. One pixel is displayed in color.

  In the electrophoretic display device 100 according to the first embodiment, a resistance layer 7 is disposed so as to be connected to the electrode surface formed on the standing surface of the partition wall 3 and the display electrode 5, and the electrode surface of the partition wall 3 and the display electrode 5 are arranged. When a voltage signal is applied between them, a potential gradient is generated in the resistance layer 7 on the display surface. Accordingly, the moving speed of the charged particles 9 near the center of the display surface is increased.

  In the electrophoretic display device 100 according to the first embodiment, the electrode surface formed on the rising surface of the partition wall 3 and the resistance layer 7 on the display surface may be electrically separated.

  In the electrophoretic display device 100 according to the first embodiment, the resistance layer 7 and the surface layer 8 may be formed of a continuous film in which physical properties and part of the material are changed during the film formation process. The surface layer 8 is formed by laminating and coating a material different from the lower layer, laminating the same material as the lower layer with different additives, laminating the same material as the lower layer with different film formation conditions, and the surface of the lower layer formed. It can be formed on the lower layer by processing or the like.

  As shown in FIG. 5, the electrophoretic display device 100 according to the first embodiment scans a plurality of write signal lines 48, a plurality of scan signal lines 47 three-dimensionally intersecting the write signal lines 48, and the write signal lines 48. It has pixel TFTs 46 for each display unit 45 arranged corresponding to the position of intersection with the signal line 47. Then, at the timing when the voltage of the scanning signal line 47 changes, the writing voltage signal supplied to the display electrode 5 is taken from the writing signal line 48 through the pixel TFT 46.

  In the drive circuit shown in FIG. 14, the drive power supply line 52 that supplies the display unit 45 with the power supply voltage + Vdd having an absolute value larger than the write voltage, and the voltage control that supplies the display voltage 5 with the write voltage signal formed from the power supply voltage + Vdd. The TFT includes a capacitor 50 that maintains the write voltage signal at least at the write voltage signal capture interval by holding the captured write voltage signal and controlling the voltage control TFT. Therefore, the display electrode 5 is maintained at a constant potential against current leakage through the resistance layer 7, thereby realizing an image display with good reproducibility and good controllability.

  In the drive circuit shown in FIG. 14, the drive power supply line 52 supplies the display unit 45 with a reset voltage −Vdd that is different from the power supply voltage + Vdd after the end of the period for maintaining the write voltage signal. Therefore, it is possible to reset all the pixels at once and shift to writing.

  The driving method shown in FIG. 10 is applied to the electrophoretic display device 200 in which the display electrode 5 and the partition wall 3 electrode arranged under the insulating display surface forming body 4 are connected by the resistance layer 7. The falling time for releasing the voltage applied between the display electrode 5 and the partition wall 3 electrode is longer than the rising time of the voltage applied between the display electrode 5 and the partition wall 3 electrode. Therefore, charging of the display surface forming body 4 can be prevented.

  The driving method shown in FIG. 15 is applied to the electrophoretic display device 200 in which the display electrode 5 and the partition wall 3 electrode are connected by the resistance layer 7. A voltage control TFT that forms a write voltage signal from the power supply voltage + Vdd supplied to the common drive power supply line 52 and supplies the write voltage signal to the display electrode 5 is provided for each display electrode 5. Then, after resetting the display state by supplying a reset voltage −Vdd that is different from the power supply voltage to the drive power supply line 52, the drive power supply voltage is supplied to the drive power supply line 52, and a write voltage signal by the voltage control TFT is received. Applied to the display electrode 5. Therefore, it is possible to reset all the pixels at once and shift to writing.

  14 and 15, the capacitor 50 for holding the write voltage signal captured at a predetermined capture interval and controlling the voltage control TFT is provided, and the reset voltage −Vdd is supplied to the drive power supply line 52. The write voltage signal of the display electrode 5 is maintained by the capacitor 50. Therefore, the display electrode 5 is maintained at a constant potential against current leakage through the resistance layer 7, thereby realizing an image display with good reproducibility and good controllability.

It is explanatory drawing of the cross-sectional structure in the electrophoretic display device of 1st Embodiment. It is explanatory drawing of the plane structure in the electrophoretic display device of 1st Embodiment. It is explanatory drawing of a plane structure in case a display unit is a rectangle. It is explanatory drawing of a cross-sectional structure when a partition electrode is directly arrange | positioned on a display surface formation body. It is explanatory drawing of the drive circuit of the display unit of an electrophoretic display device. It is a block diagram of the drive circuit of an electrophoretic display device. It is explanatory drawing of the drive waveform of 1 display unit of an electrophoretic display device. It is explanatory drawing of the cross-sectional structure in the electrophoretic display device of 2nd Embodiment. It is explanatory drawing of a cross-sectional structure when a partition electrode is directly arrange | positioned on a display surface formation body. It is explanatory drawing of the drive waveform of one display unit in 2nd Embodiment. It is explanatory drawing of the drive waveform in the drive of the display unit accompanying a scan. It is explanatory drawing of the cross-sectional structure in the electrophoretic display device of 3rd Embodiment. It is explanatory drawing of a cross-sectional structure when a partition electrode is directly arrange | positioned on an insulating layer. It is explanatory drawing of another drive circuit of the electrophoretic display device of 2nd Embodiment. It is explanatory drawing of the drive waveform of a display electrode. It is explanatory drawing of the cross-sectional structure 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.

Explanation of symbols

1 Display board (rear board)
2 Observation side board (front board)
3 Partition 4 Display surface forming bodies 4a, 4b, 4c Colored layer (color filter layer)
5 Display electrode 6 Partition electrode 7 Resistance layer 8 Surface control layer (surface layer)
9 Charged Particle 10 Insulating Liquid 11 Contact Hole 12 Insulating Layer 13 Connection Material 20 Moving Space 41 Panel Controller 42 Gate Driver 43 Source Driver 44 Electrophoretic Display Panel 45 Display Unit (Pixel)
46 Capture transistor element (pixel TFT)
47 Scanning signal line 48 Writing signal line 50 Maintenance circuit (capacitor)
52 Power supply means, power supply line (drive power supply line)
53 Control transistor element (Voltage control TFT)
100, 200, 300 Particle movement type display device (electrophoretic display device)

Claims (16)

A display-side board on which a display surface for each display unit is set, and
In a particle movement type display device comprising a partition wall that surrounds the display surface and partitions a moving space of charged particles,
A surface control layer disposed on an interface of the moving space so as to cover the display surface and the rising surface of the partition;
The surface control layer is characterized in that at least one of surface energy, surface potential, and surface unevenness is different from a lower layer to enhance the restraining performance of the charged particles at the interface. apparatus.   The particle movement type display device according to claim 1, wherein a resistance layer covering the display surface is disposed as the lower layer. Having a display electrode arranged in the center of the plane of the display surface;
3. The particle movement type display device according to claim 2, wherein the resistance layer is disposed so as to integrally cover the display electrode and the display surface. A display electrode for each display unit disposed below the display surface;
An insulating display surface forming layer disposed on the display electrode,
3. The particle movement type display device according to claim 2, wherein the resistance layer is connected to the display electrode and is disposed so as to cover the display surface forming layer.   5. The particle movement type display device according to claim 4, wherein the resistance layer and the display electrode are connected by a contact hole arranged at a central portion of the display surface. The display surface forming layer is formed as a colored layer having different absorption wavelength characteristics between the plurality of adjacent display surfaces,
6. The particle movement type display device according to claim 5, wherein one pixel is displayed in color by the plurality of display surfaces. The resistance layer is disposed in connection with the electrode surface formed on the standing surface and the display electrode,
7. The particle movement type display device according to claim 3, wherein when a voltage signal is applied between the electrode surface and the display electrode, a potential gradient is generated in the resistance layer of the display surface. .   7. The particle movement type display device according to claim 3, wherein the electrode surface formed on the standing surface and the resistance layer on the display surface are electrically separated.   9. The particle movement type display device according to claim 2, wherein the resistance layer and the surface control layer are formed of a continuous film. Multiple write signal lines;
A plurality of scanning signal lines three-dimensionally intersecting the writing signal lines;
A capture transistor element for each display unit arranged corresponding to an intersection position of the write signal line and the scanning signal line,
10. The write voltage supplied to the display electrode is captured from the write signal line through the capture transistor element at a timing when the voltage of the scanning signal line is changed. Particle movement type display device. Power supply means for supplying the display unit with a power supply voltage having an absolute value larger than the write voltage;
A control transistor element for supplying a control voltage formed from the power supply voltage to the display electrode;
11. The particle according to claim 10, further comprising: a maintenance circuit that maintains the control voltage in at least the write voltage capture interval by maintaining the captured write voltage and controlling the control transistor element. Mobile display device.   12. The particle movement type display device according to claim 11, wherein the power supply means supplies a reset voltage, which is different from positive and negative from the power supply voltage, to the display unit after the period for maintaining the control voltage. In the manufacturing method of the particle movement type display device provided with the partition surrounding the display surface,
After forming a resistance layer that integrally covers the surface of the partition and the display surface,
A particle-moving display device characterized in that at least one of surface energy, surface potential, and surface unevenness is superimposed on the resistive layer to be different from that of the resistive layer to enhance the restraining performance of charged particles at the interface. Production method. In the driving method of the particle movement type display device in which the display electrode disposed under the insulating display surface forming layer and the partition wall electrode are connected by the resistance layer,
Particles characterized in that the falling time for releasing the voltage applied between the display electrode and the partition electrode is longer than the rising time of the voltage applied between the display electrode and the partition electrode Driving method of mobile display device In the driving method of the particle movement type display device in which the display electrode and the partition wall electrode are connected by the resistance layer,
A control transistor element that forms a control voltage from a power supply voltage supplied to a common power supply line and supplies the display transistor to the display electrode is provided for each display electrode.
After supplying a reset voltage that is different from the power supply voltage to the power supply line to reset a display state, the power supply voltage is supplied to the power supply line, and the control voltage by the control transistor element is applied to the display electrode. A driving method for a particle movement type display device. A maintenance circuit for controlling the control transistor element by holding a write voltage captured at a predetermined capture interval is provided,
16. The driving method of the particle movement type display device according to claim 15, wherein the control voltage of the display electrode is maintained by the sustain circuit until the reset voltage is supplied to the power line.

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