JP2004258618A - Display device and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems that methods of holding display characteristics by impressing the same square wave electric fields to the entire area of a display region and peeling the particles sticking to substrates and of applying vibrations together with the impression of the electric field for improving the flow property of the particles and to assure the display characteristics in order to rewrite the display of the image display device using the particles are proposed heretofore but it takes time to rewrite the display and therefore such methods are not practicable and in addition the transmission of the high vibration energy to the particles is not possible with the impression of the vibrations from the outside. <P>SOLUTION: A vibration generating section is sealed together with the particles into the display device and the erasure of the display is carried out at a high speed by generating the vibrations simultaneously with impression of the electric field for driving the particles and further the deterioration in display at the time of a plurality of times of image rewriting is prevented by peeling the particles sticking to the substrate and disintegrating the particle aggregate. Further, the electric power consumption can be drastically reduced as compared to the time when the vibrations are used in combination with the electric field for driving the particles by erasing the display with use of the vibrations alone. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a display device that includes a display element that performs display by moving a plurality of colored particles between a pair of opposed substrates by an electric field and that can be repeatedly rewritten, and a method for manufacturing the same.

  DESCRIPTION OF RELATED ART Conventionally, as a thin and low power consumption display element used for a portable information terminal, a twist nematic liquid crystal (hereinafter, referred to as a TN liquid crystal) display element, an organic electroluminescence (hereinafter, referred to as an organic EL) element, and the like are known. Have been. In the TN liquid crystal display device, the alignment state of the liquid crystal molecules in the liquid crystal layer changes only when a voltage is applied, whereby the transmittance of light passing through the liquid crystal layer is controlled to perform display. Therefore, operating power for display is constantly required, and an image cannot be displayed in a no-power state. In addition, since the organic EL element displays an image using light emission generated when a current or a voltage is applied, the organic EL element cannot display in a no-power state like the TN liquid crystal display element.

  On the other hand, a display element has been proposed which has a characteristic that a voltage or a current is required only at the time of display rewriting, and a once written display image is held in a no-power state until the image is rewritten again. Unlike the TN liquid crystal display element and the organic EL element described above, such an element does not require electric power to hold an image. Therefore, such a display element is used, for example, in a display section of a portable information terminal. This makes it possible to significantly reduce power, downsize equipment, and the like. Further, by making the rewriting device and the display element serving as a display panel detachable, a thin, lightweight, and flexible display element that does not require a driving circuit can be realized. Such an element is effective for portable equipment.

  The display methods of these devices can be roughly classified into a method using mainly fine particles, a method using an electrochemical or photochemical reaction such as a solution, and a reflected light control method using an electromechanical action. .

  As an example of a display device using fine particles, an electric field is applied to a system in which charged colored fine particles are dispersed in a colored solution filled between a pair of substrates provided with a pair of electrodes, and the particles are applied. 2. Description of the Related Art A display element which displays by electrophoresis in a solution (electrophoresis phenomenon) has been studied. In such a display element, for example, there is a configuration in which, of the two types of particles, two-color display is performed by migrating negative polarity particles to the positive electrode side and positive polarity particles to the negative electrode side. Further, as another configuration, the coloring particles in the coloring solution are electrophoresed according to the polarity, and when the particles move to the observer side, the color of the particles is observed, while when the particles move to the opposite side to the observation, There is also a configuration in which the color of the coloring solution is observed. Further, as another configuration, a configuration for performing multi-color display by using two or more types of colored particles and a colored solution is also conceivable.

  In another example using the above-described electrophoresis principle, an electrode is formed on the same surface of a substrate, and a multi-color is obtained by collecting particles on the electrode and dispersing the particles in the surface. There is a way to display. For example, on one transparent substrate surface, a narrow linear thin wire electrode and a wide plate electrode are formed, and the charged particles are adhered and collected on the fine wire electrode, and on the plate electrode. There is a display method for performing multi-color display by controlling the state in which charged particles are adhered to and dispersed on the display. There is also a display method called a twist ball method, in which spherical or cylindrical particles coated in at least two colors are rotated by an electric field to perform multicolor display.

  As described above, in a display element that performs display by causing particles to migrate in a solution, the migration speed of the particles is affected by the viscosity of the solution. In other words, when particles move in a highly viscous solution, the migration speed of the particles becomes slow, and the display speed (response speed) of the element becomes slow. In addition, since there is no threshold for the voltage at which particles start to move, an active matrix is required for the driving circuit. Therefore, it is costly.

  Therefore, a method of moving particles in a gas phase in which the moving speed of particles is higher than in a solution has been proposed. In this method, at least one kind of charged colored particles is dispersed in a gas phase, and the particles are moved between opposite polarity electrodes by the Coulomb force of an electric field applied in the gas phase. In a gaseous phase, there is no viscous resistance of a moving medium as in a liquid phase, so that the moving speed of particles is increased. Therefore, the display speed is increased, and a high-speed response is possible. The method of moving particles in the gas phase as described above uses a structure in which charged conductive toner particles and uncharged insulating particles are used to move charged particles by Coulomb force (for example, Patent Document 1). And two types of particles having different polarities are used to move these particles by Coulomb force (for example, see Patent Document 2).

  As described above, a display element that performs display by moving particles in a liquid phase and a gas phase requires a gap that serves as a space for moving particles. Such a gap is formed by supporting a pair of substrates arranged opposite to each other by a spacer serving as a gap holding member.

  FIG. 17 is a schematic diagram showing the configuration of such a display element. As shown in FIG. 17, in the display element, a substrate 51 having an electrode 53 formed on an inner surface thereof and a substrate 52 having an electrode formed thereon are supported by spacers 56 and opposed to each other, whereby a gap 55 is formed. You. In the gap 55, for example, a plurality of black particles 57 negatively charged and a plurality of white particles 58 positively charged are sealed, and the gap 55 becomes a moving space 55 'for the colored particles. The moving space 55 'is in a liquid phase or a gas phase depending on the display method. In such a configuration, the moving space 55 'for the colored particles is partitioned by the spacer 56, and the spacer 56 serves as a partition in the space (hereinafter, the spacer 56 is referred to as a partition 56').

  Here, in the moving space 55 ', when the colored particles 57, 58 having different polarities move in the space toward the electrodes 53, 54 in accordance with the polarity, the particles have different polarity. A large number of contact causes a phenomenon that the particles aggregate. As a result, display unevenness occurs in the pixels of the display element. In a rewritable display element, the display is rewritten many times, so that the number of contacts between particles increases with the number of rewrites. Therefore, such a cohesion phenomenon causes a reduction in the quality of a displayed image. In particular, in the movement of particles in the gas phase, it is known that movement is mainly suppressed by contact between particles having different charging characteristics, and therefore, when the fluidity of particles having different charging characteristics is low. Causes a cohesion phenomenon, which degrades the quality of the displayed image.

  In addition, in the moving space 55 'partitioned by the partition 56', the particles adhere to the partition surface by a force such as a mirror image force or coagulate around the partition. For this reason, display unevenness is seen around the partition. When the black particles 57 and the white particles 58 are encapsulated and dispersed in each of the moving spaces 55 ′ partitioned by the partition walls 56 ′, aggregation may occur due to electrostatic force between particles having different polarities, or Aggregation occurs due to Van der Waals' force between the particles, so that the particles are not uniformly dispersed and unevenness is observed. Such uneven dispersion of particles causes display unevenness.

  On the other hand, regarding the above problem, various methods for pulverizing a group of aggregated particles and dissociating them into individual particles have been proposed. There is a method of dissociating particles. For example, there is disclosed a display element in which a vibration applying unit is arranged on the back surface side of a substrate (that is, on the side opposite to a moving space of particles) (for example, see Patent Documents 3 to 5). The vibration applying means has a configuration for applying vibration to the display element itself or a configuration for causing particles to vibrate by an electric field or the like.

  However, the configuration in which the vibration applying means is separately provided in the display element is not advantageous in terms of cost. Also, for example, the higher the rigidity of the substrate, the better the vibration generated by the vibration applying means is transmitted from the substrate to the particles in the moving space. However, it is necessary to increase the amplitude of the vibration according to the rigidity. is there. For this reason, the size of the vibration applying means is increased, and thus a housing structure for preventing the vibration energy from the vibration applying means from decreasing is required. As a result, the cost of the display element increases.

Further, in the configuration including the vibration applying means, a voltage to be applied to the vibration applying means for generating vibration is required in addition to the image signal voltage to be applied for rewriting the display image. Here, when the particles are moved between the opposite polarity electrodes according to the polarity, the Coulomb force of the electric field given by the application of the image signal voltage causes the adhesion force between the particles attached to one electrode and this electrode ( (Specifically, the van der Waals force and the mirror image force) cannot separate particles from this electrode and move them to the other electrode. A large operating voltage is required. Therefore, in a display element that requires a further operating voltage of the vibration applying means, the operating voltage is further increased, and when the applied voltage is low, the contrast is reduced and display unevenness occurs.
JP 2000-347483 A JP 2001-313225 A JP 2002-131789 A JP-A-3-53224 JP 2002-174828 A

  The present invention has been made in order to solve the above-described problems, and provides a display device that achieves good display by preventing display unevenness and a decrease in contrast and has a reduced operating voltage, and a method of manufacturing the same. It is intended to be.

  In order to solve the above-described problems, a display device according to the present invention includes a pair of opposed substrates, each having an electrode formed on at least one surface and at least one of which is translucent; A spacer that holds a space having a width of at least one kind of charged particles sealed in a space between the substrates, and an electric field given by an image signal voltage applied to the electrodes of the substrate. A display device in which an image corresponding to the image signal voltage is displayed by moving the particle group in a space between substrates, wherein the particle utilization promoting means for preventing a decrease in the number of particles contributing to display is provided, It is provided facing the space in which the group moves.

  For example, a pair of substrates disposed at least one surface on which electrodes are formed and at least one of which is translucent and opposed to each other, a spacer formed between the substrates to hold a space having a desired width, And at least one kind of particle group of chargeability enclosed in a space, wherein the particle group moves in the space between the substrates by an electric field given by an image signal voltage applied to the electrode of the substrate, and the image is formed. A display device for displaying an image corresponding to a signal voltage, wherein a vibration generator is provided facing the space in which the particle group moves.

  Generally, the dispersion method of the aggregated fine particles includes a dispersion method using an air current, collision with an obstacle, and a mechanical pulverization method. Among them, a mechanical pulverization method is most suitable for a display device configured to perform display using particles. Mechanical pulverization can be realized by, for example, imparting vibration to the aggregated particle group.Specifically, when high frequency vibration is applied to the aggregated particle group, the vibration energy is transmitted to the particle and the particle is The vibration energy is received, so that the aggregated particles dissociate and the particles are dispersed.

  In the configuration of the present invention, since the vibration generating portion is provided on the space side formed between the pair of substrates supported by the spacer, the vibration generating portion is formed outside the substrate, that is, on the side opposite to the space. It is possible to apply vibration to the particle group more directly and effectively than in the case. Therefore, the effect of dispersing particles can be improved. As described above, according to the configuration of the present invention, even if aggregation of a different scale occurs in each pixel, the aggregation is eliminated by generating vibrations by the vibration generation unit and applying the vibrations to the aggregated particle group. Therefore, the occurrence of display unevenness and a decrease in contrast are improved.

  Further, since the particles attached to the substrate can be separated by vibration, the displayed image can be erased by vibration without applying a voltage for moving the particles between the electrodes. Further, since the peeled particle group can be effectively used for display, display unevenness and contrast are improved.

  Furthermore, in such a configuration, since the dissociation of the particles aggregated by the vibration and the detachment of the attached particles can be performed, the voltage required for the dissociation and detachment at the time of displaying an image is reduced. Therefore, it is possible to reduce the applied voltage for moving the particles, and power saving of the display device can be achieved.

  Further, the amount of charge of the particles, which decreases with the passage of time, can be recovered by friction or the like by applying vibration. For this reason, it is possible to keep the charge amount of the particles constant, and thus it is possible to perform stable and good display.

  The first electrode and the second electrode to which the image signal voltage is applied may be formed on one of the substrates, and the first electrode is formed on one of the pair of substrates and the second electrode May be formed on the other substrate of the pair of substrates.

  In the configuration in which the first and second electrodes are formed on one substrate, a lateral electric field is applied to the vibration of the vibration generating section, and therefore, the vibration intensity can be increased.

  The vibration generator includes an electrode and a vibration generator, and a vibration is generated in the vibration generator by an electric field formed by the electrode, and the electrode provided on the substrate, specifically, the first electrode and At least one of the second electrodes may also serve as an electrode of the vibration generating section.

  According to this configuration, the cost can be reduced, and the display device can be reduced in thickness and weight. Further, if a vibration is generated in the vibration generating section by applying an electric field having an appropriate frequency and intensity between the first and second electrodes, image display and vibration generation are performed using a common electrode. Therefore, the cost can be further reduced, and the device can be made thinner and lighter.

  The vibration generator may include an electrode and a vibration generator, and the vibration generator may generate vibration by an electric field formed by the electrode, and the vibration generator may constitute the spacer.

  Here, in a display device having a configuration in which particles are moved by an electric field, a partition is generally provided in each pixel in order to prevent display unevenness due to a difference in particle density in a display region. Therefore, in the display device according to the present invention, the spacer is used as a partition, and the partition is used as a vibration generating unit. Specifically, a third electrode is provided in the vicinity of, for example, a side surface of a partition mainly composed of a vibration generator, and a vibration is generated in the vibration generator by applying a voltage between the third electrodes of adjacent pixels. The configuration may be such that Further, a third electrode may be provided at both ends in the length direction of the vibration generator, and a vibration may be generated in the vibration generator by applying a voltage between the third electrodes. In these configurations, an insulating medium is arranged between the third electrode and the first and second electrodes to be insulated.

  The space in which the particle group moves may be a gas phase space.

  According to this configuration, since the particles move in the gas phase, the moving speed of the particles is not affected by the viscosity of the solution as in the case where the particles move in the liquid phase. The movement speed of the particles is improved as compared with the case where the particles move inside. Therefore, the response speed of the display device can be improved. Further, in the configuration in which the particles move in the gas space, the threshold voltage for moving the particles is higher than in the case of moving in the liquid space. Therefore, it is possible to prevent particles from moving due to a crosstalk voltage or the like. Therefore, a passive matrix drive type, which has been difficult to realize in a configuration in which particles are moved in a liquid phase space due to a problem of crosstalk voltage, can be easily realized.

  The space in which the particle group moves may be a liquid space filled with an insulating solvent.

  Particles are relatively easily dispersed in the insulating solvent, but when the particle diameter of the particles is reduced, the probability of contact increases as the movement between the electrodes is repeated. On the other hand, as the particle size of the particles becomes smaller, the intermolecular force (Van der Waals force), which is the adsorption force between the particles, becomes relatively larger than the dispersing force (for example, electrostatic repulsion). For this reason, in a display device in which particles for high resolution are miniaturized, aggregation of particles is particularly likely to occur, and display unevenness and a decrease in contrast are likely to occur.

  Therefore, in the present invention, as described above, the dissociation of the aggregated particles and the separation of the particles attached to the substrate are performed by applying the vibration generated by the vibration generating section to the particles in the insulating medium. Thereby, it is possible to prevent the occurrence of display unevenness and the reduction of contrast.

  A capsule in which the particles and the insulating solvent are sealed may be arranged in the gap between the substrates. In such a configuration, since the particle group is sealed in the capsule, the particle group moves in a limited moving space. Therefore, a structure in which the particle concentration does not change in the display area can be realized.

  The particle group may be arranged by an electric field applied between the electrodes of the substrate according to the image signal voltage. For example, the plurality of particles constituting the particle group may be electric field array particles arranged along the electric field.

  For particles having a dielectric constant, polarization occurs within the particle along the electric field vector. This polarization acts on nearby particles as a kind of attraction, whereby the particles are arranged and displayed. In the particles arranged by the electric field, the polarization is maintained by the interaction of the particles even when the electric field is removed, so that the display is maintained without applying a voltage. On the other hand, when the vibration is generated in the vibration generating section, the vibration is applied to the arranged particles. When the vibration energy becomes larger than the holding energy (that is, the interaction force between the particles), the arrangement of the particles is canceled and the particles are uniformly dispersed in the space. Thereby, the image is erased.

  Normally, since an insulator has a dielectric constant, particles of an insulator move in space according to the charge due to the relative relationship between the Coulomb force due to the charge of the particles and the Coulomb force due to polarization. Or the arrangement in space according to the polarization. In the former, the particles move in the direction of the electrode having a polarity opposite to the polarity of the charged particles, and in the latter, the particles are arranged according to the electric field distribution. The present invention is particularly applicable to a display device having a configuration using particles having a small charge amount and arranged by an electric field.

  The particle group may be colored in at least one color. For example, when two kinds of particles having different electric characteristics are used, if the particles are colored differently, it is possible to display at least two colors by a driving method, and colorization is realized.

  The vibration generator may be made of a piezoelectric material. In such a configuration, it is possible to easily generate vibration by applying a voltage to the piezoelectric body to generate a piezoelectric effect.

  The vibration generating section may also serve as at least one substrate. When a material such as a polymer is used for the vibration generating unit, the vibration generating unit has a certain strength, so that the vibration generating unit itself can be used as a substrate. For example, a configuration may be employed in which a pair of vibration generating sections are supported by a spacer and arranged to face each other, and particles are sealed in a space formed between the vibration generating sections. With such a configuration, the thickness and weight of the image display element can be reduced. In addition, flexibility and bending strength are more advantageous than hard substrates such as glass.

  The display of the display device includes at least first and second display states. In the first display state, a first image signal voltage is applied to the electrode provided on the substrate, and a first electric field is applied. Is formed, and in the second display state, a second image signal voltage is applied to the electrode provided on the substrate to form a second electric field having a direction different from the first electric field, and the second electric field is formed. When rewriting from one display state to the second display state, an operation of applying a high-frequency rectangular wave voltage or a high-frequency sine wave voltage to the vibration generating unit, and the second image signal to the electrode of the substrate The operation of applying a voltage may be performed.

  Usually, when rewriting a display image, a rectangular wave voltage corresponding to the image signal voltage is applied to the entire surface of the display element to move the particles. However, with this voltage application, the particles attached to the substrate and the aggregated particles cannot be completely separated and dissociated, and as a result, a problem occurs in the display characteristics after rewriting. In particular, in a display device in which particles are dispersed in a gas phase, since the area where particles contact each other increases, adhesion between particles and particles and between particles and substrates are large, and this should be ignored. Can not. Further, also in a display device having a configuration in which particles are dispersed in a liquid phase, particles attached to a substrate or aggregated particles cause deterioration in display characteristics. Therefore, in the present invention, in addition to the application of the image signal voltage as described above, a high-frequency rectangular wave voltage or a high-frequency sine wave voltage is further applied to the vibration generating unit. Since mechanical vibration can be generated in the vibration generating unit by applying a voltage to such a vibration generating unit, it is possible to perform dissociation of aggregated particles and separation of attached particles using this vibration.

  The operation of applying the high-frequency rectangular wave voltage or the high-frequency sine wave voltage and the operation of applying the image signal voltage may be performed simultaneously, or may be performed at staggered timings. For example, when rewriting an image, first, the voltage is applied to the vibration generating unit, and the particles are separated and dissociated using the generated mechanical vibration to erase the image. Thereafter, an image signal voltage is applied, and particles are moved to a desired electrode side by a DC electric field to perform display. In such a rewriting operation, since the image is erased by the vibration and the aggregation and adhesion of the particles are eliminated, the voltage required for the exfoliation and dissociation of the particles is not required in the image signal voltage applied thereafter. Therefore, good display characteristics can be realized with a low operating voltage, and the driving voltage of the display device can be reduced.

  At least one of the particles may be a porous particle.

  Generally, the adhesive force of the particles includes a liquid crosslinking force, a Van der Waals force, an electrostatic force, and the like. Among them, the liquid crosslinking power can be prevented by creating a certain dry state. On the other hand, the Van der Waals force between particles or between particles and an object to be attached, and the electrostatic force of particles are determined by the properties of the particles themselves, and therefore, it is necessary to consider the material properties of the particles.

  Therefore, if the configuration is such that the porous particles are used as the particles, the molecular weight of each particle is reduced, and it is expected that the van der Waals force between the particles and between the particles and the object to be attached can be reduced. This is because the van der Waals force is obtained by integrating the attractive force between the molecules constituting the particle with respect to all the molecules constituting the whole particle. This is because it is expected that the integrated value of the above-described particles as a whole becomes smaller than that of ordinary particles. If the van der Waals force can be reduced, the adhesion of the particles can be reduced. As a result, the movement of the particles is facilitated, the operating voltage is reduced, and the adhesion of the particles to the partition walls can be reduced. In addition, since the porous particles are light in weight, sedimentation of the particles can be delayed, and therefore, it is possible to realize a floating state without completely adhering the particles to the adhered object. In such a floating state, when moving the particles, there is no need to apply an electric field that generates a Coulomb force larger than the adhesion force to separate the particles from the adhesion target. For this reason, the operating voltage can be further reduced, and a high-speed response can be achieved.

  At least one of the particles has a core particle and a diameter of about 1/1000 to 1/100 of the diameter of the core particle, and the core particle covers the surface of the core particle. Composite particles composed of fine particles fixed to the surface.

  The aforementioned van der Waals force attenuates as the distance between the particles and the distance between the particles and the attached object increase, and rapidly attenuates in inverse proportion to the square of the distance. Therefore, if the configuration is such that the fine particles are attached to the core particles, the distance between the core particles, which are the main components of the particles, and the distance between the core particles and the attachment target can be increased. Therefore, it is expected that van der Waals force can be reduced. Here, if the size of the fine particles is too small, the distance between the core particles and the distance between the core particles and the attachment target cannot be increased. On the other hand, if the size of the fine particles is too large, the interaction between the fine particles and between the fine particles and the attachment target increases. Therefore, it is preferable that the diameter of the fine particles be in the above range. By thus forming the particles as composite particles, the interaction between the particles, and the interaction between the particles and the object to be attached can be reduced, and therefore, the adhesion of the particles to the partition walls can be suppressed. And the electric field intensity required for the movement of the particles is reduced, so that the operating voltage can be reduced. Further, the response speed is improved by improving the mobility of the particles, and the particle packing ratio is also improved.

  A water-repellent treatment may be applied to at least a part of the surface of the particles or the surface of the member to which the particles adhere.

  In such a configuration, for example, a water-repellent treatment may be performed by forming a water-repellent film. For example, when particles adhere to the surface of a partition or a substrate via water, the adhesion of the particles is increased by the surface tension of the water droplets, and therefore, a higher operating voltage is required to separate the particles. On the other hand, in the configuration subjected to the water-repellent treatment, since the surface tension does not act when the particles are separated from the surface of the partition or the substrate, the operating voltage can be reduced.

  In a method for manufacturing a display device according to the present invention, a pair of substrates that are provided with electrodes formed on at least one surface and at least one of which is light-transmissive, and a gap having a desired width formed between the substrates is formed. A spacer for holding, a group of at least one kind of chargeable particles sealed in a gap between the substrates, and a vibration generating unit provided facing a space in which the group of particles moves, and a voltage applied to the electrode. A method of manufacturing a display device in which the particles are moved in the gap between the substrates by an electric field provided by the image signal voltage, and an image corresponding to the image signal voltage is displayed. After enclosing the particle group, vibration is generated in the vibration generating section.

  According to such a configuration, the particles generated in the gap can be uniformly and uniformly dispersed by the vibration generated by the vibration generating unit. Therefore, it is possible to realize a display device in which the occurrence of display unevenness is suppressed.

  ADVANTAGE OF THE INVENTION According to the display apparatus and its manufacturing method which concern on this invention, it becomes possible to implement | achieve favorable display by preventing generation | occurrence | production of display unevenness and a fall of contrast, and to aim at reduction of operating voltage.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram of a display device according to Embodiment 1 of the present invention. FIGS. 2A to 2C are schematic diagrams showing a configuration of a pixel constituting a display element of the display device of FIG. 1, and a cross section perpendicular to a display surface (hereinafter, referred to as a vertical cross section). Is shown.

  As shown in FIGS. 1 and 2A to 2C, the display device includes a display element 70 in which a display unit is a display panel. As shown in FIGS. 2A to 2C, the display element 70 has a lower substrate 6 and an upper substrate 16, and both substrates 6, 16 are supported by the spacer 3 'and have a desired distance. Are arranged facing each other. Thereby, a space 17 is formed between the substrates 6 and 16. Since the space 17 is defined by the spacer 3 ′, the spacer 3 ′ is referred to as a partition 3 here. Each area of the space 17 defined by the partition 3 corresponds to one pixel 100. The space 17 may be a gas phase or a liquid phase. Here, the space 17 is a gas phase. In this space 17, white particles 5A and black particles 5B are sealed.

  The first electrode 2 is provided on the inner surface of the lower substrate 6, and the second electrode 12 is provided on the inner surface of the upper substrate 16. Although not shown in FIGS. 2A to 2C which are vertical cross sections of the display element 70, the first electrode 2 provided on the lower substrate 6 and the first electrode 2 provided on the upper substrate 16 are not shown. The two electrodes 12 intersect in a plan view, and an operating voltage is applied to the intersection. The intersection where the operation voltage is applied and display is performed corresponds to one pixel 100 which is a structural unit of the display element 70. On the other hand, at a portion where the first electrode 2 and the second electrode 12 do not intersect, the voltage is lower than the threshold value, so that no display is performed. The display element 70 is configured by arranging a plurality of pixels 100 partitioned by the partitions 3 as described above in a matrix. The first electrode 2 is arranged so as to extend in the horizontal direction of the display element 70, and the second electrode 12 is arranged so as to extend in the vertical direction of the display element 70. As described above, the display device of this embodiment is a passive matrix drive type.

  Around the display element 70, a first electrode driver 82 for driving the first electrode 2 is provided, and a second electrode driver 81 for driving the second electrode 12 is provided. ing. Further, an external input device 80 that controls the first electrode driver 82 and the second electrode driver 81 according to an external input signal is provided. In the display device configured as described above, the external input device 80 transmits a control signal to the first electrode driver 82 and the second electrode driver 81 according to an image signal input to the signal input unit 83 from outside. Output each. Then, the first electrode driver 82 applies a predetermined voltage to the first electrode 2, while the second electrode driver 81 applies a voltage corresponding to the image signal to the second electrode 12 in accordance with the timing. Applied to the second electrode 12. Thereby, as described later, in each pixel 100, the white particles 5A and the black particles 5B move in the space 17 between the lower substrate 6 and the upper substrate 16. As a result, an image corresponding to the image signal appears in the eyes of a person observing the display device.

  Next, a detailed configuration of the display element 70 in FIG. 1 will be described with reference to FIGS.

  As shown in FIGS. 2A to 2C, the upper substrate 16 has the second substrate 11. Since the upper substrate 16 side is the observation side, the second substrate 11 needs to have translucency, and is made of a material having a high light transmittance, such as a glass substrate or a polyethylene terephthalate (PET) sheet. . Then, on the second substrate 11, a second electrode 12 made of a conductive material is provided. The second electrode 12 needs to have translucency like the second substrate 11, and is made of a material having a high light transmittance, for example, ITO (Indium-Tin-Oxide). As will be described later, the second electrode 12 is connected to a first common wiring (not shown) for each pixel 100 partitioned by the partition 3. The constituent materials of the second substrate 11 and the second electrode 12 are not limited to the above-mentioned materials, and may be other materials.

  On the other hand, the lower substrate 6 has the first substrate 1. The first substrate 1 may have a large thickness, or may be a glass substrate, a polyethylene terephthalate sheet, a stainless film, or the like. From the viewpoint of durability, a material having flexibility is desirable. The material forming the first substrate 1 may be translucent or non-translucent. On the first substrate 1, a third electrode 4, a piezoelectric body 20, and a first electrode 2 are arranged in this order. With the configuration in which the piezoelectric body 20 is sandwiched between the first and third electrodes 2 and 4, the vibration generating section 21 is formed on the first substrate 1. The first and third electrodes 2, 4 are made of a conductive material, which may be translucent or non-translucent. For example, the first and third electrodes 2 and 4 may be made of the same material as the second electrode 12, in which case the material cost can be reduced.

  The piezoelectric body 20 of the vibration generating unit 21 is made of, for example, quartz, a single crystal such as LiTaO3, a thin film such as ZnO, a piezoelectric ceramic, a piezoelectric polymer film such as polyvinylidene fluoride (PVDF), or the like. The configuration of the vibration generation unit 21 including the piezoelectric body 20 is multilayered. Here, the vibration generation unit 21 is disposed inside the display element 70 and directly transmits vibration to the black particles 5B and the white particles 5A in the space 17. Since it is possible, the vibration is transmitted to the black particles 5B and the white particles 5A as compared with the case where the vibration generating unit 21 is provided outside the display element 70 (for example, the surface opposite to the space 17 of the first substrate 1). It's easy to do. Therefore, the vibration generating section 21 may have any number of layers capable of transmitting vibration to particles in the space 17, and can be made thinner than a case where the vibration generating section 21 is provided outside the display element 70.

  Such a piezoelectric body 20 may be divided (patterned) for each pixel 100, or may be provided in common for each pixel 100. Here, a case where the vibration generating unit 21 is provided only on the lower substrate 6 side will be described, but a configuration in which the vibration generating unit 21 is provided on both the upper substrate 16 and the lower substrate 6 is also possible. Further, here, the vibration generating unit 21 is provided on the first substrate 1, but a configuration in which the vibration generating unit 21 including the piezoelectric body 20 also serves as the first substrate 1 is also possible. Can significantly reduce the thickness and weight of the display element 70.

  The lower substrate 6 and the upper substrate 16 are arranged to face each other such that the first electrode 2 and the second electrode 12 face each other, whereby a space 17 is formed between the substrates 6 and 16. A spacer 3 'is provided between the upper substrate 16 and the lower substrate 6 as a space holding member to support the substrates 6, 16, whereby the distance between the substrates (that is, the width of the space 17) is reduced. It is kept constant. By arranging the spacers 3 ′ extending from the lower substrate 6 to the upper substrate 16 in this manner, the space 17 is partitioned by the spacers 3 ′, and each partitioned region corresponds to each pixel 100. As described above, the spacer 3 ′ not only functions as a space holding member, but also functions as a partition for dividing the space 17 into the pixels 100, and the second electrode 12 formed on the upper substrate 16 and the lower substrate 12. 6 has a function of insulating the first electrode 2 formed on the second electrode 6. Hereinafter, the spacer 3 ′ is referred to as a partition 3.

  The spacer 3 ′ needs to be made of an insulating material that does not significantly change the electrical characteristics (for example, charging characteristics) of the white particles 5 </ b> A and the black particles 5 </ b> B described later, for example, polyethylene terephthalate, polyester film, silicon rubber sheet, Alternatively, it is constituted by casting polycarbonate. For example, in the spacer 3 'formed by laminating insulating films, a space 17 having a desired width can be created by the laminating process of the insulating films.

  A plurality of black particles 5B and a plurality of white particles 5A are sealed in a space 17 defined for each pixel 100. It is desirable that the black particles 5B and the white particles 5A have different electric and magnetic characteristics. Here, the black particles 5B are negatively charged insulating particles, and the white particles 5A are positively charged insulating particles. Particles. The white particles 5A and the black particles 5B are both porous particles, and have a core particle having a large diameter and a diameter of about 1/1000 to 1/100 of the diameter of the core particle. And fine particles fixed to the surface of the core particle so as to cover the surface of the particle. Such black particles 5B have substantially the same size, white particles 5A have substantially the same diameter, and black particles 5B and white particles 5A have substantially the same size.

  The first electrode 2, the second electrode 12, and the third electrode 4 are connected to a power supply unit 86 via a switching element 85 that can switch a voltage application path. Here, the second electrode driver 81 (FIG. 1) includes a power supply unit 86 and a switching element 85, and switches the switching element 85 according to an image signal. The power supply unit 86 and the switching element 85 apply a DC voltage between the first and second electrodes 2 and 12 according to an image signal and generate a vibration in the vibration generation unit 21 as described later. For this purpose, a high-frequency rectangular wave voltage or a high-frequency sine wave voltage can be applied between the first and third electrodes 2 and 4.

  Next, a display operation (that is, a driving method of the display device) in the display device will be described with reference to FIGS. 2B and 2C, focusing on one pixel 100 which is a constituent unit of the display element 70. I do. In each of the plurality of pixels 100, an operation described below is separately performed, and thereby an image is displayed.

  FIG. 2B illustrates a display operation during black display, and FIG. 2C illustrates a display operation during white display. Here, a case where rewriting is performed from black display to white display will be described.

  As shown in FIG. 2B, at the time of black display, first, a signal voltage corresponding to an image signal is applied between the first electrode 2 and the second electrode 12. This signal voltage is a DC voltage. Here, the switching element 85 switches the voltage application path so that the potential Vb of the first electrode 2 becomes negative and the potential Va of the second electrode 12 becomes positive. The switching element 85 switches the voltage application path so that no voltage is applied between the first electrode 2 and the third electrode 4. By applying a voltage to the first and second electrodes 2, 12, an electric field determined from the voltage of (Va−Vb) is applied between the two electrodes 2, 12. Here, since (Va−Vb) is positive, an electric field is applied in a direction from the lower substrate 6 toward the upper substrate 16, and the first electrode 2 becomes a negative electrode and the second electrode 12 becomes a positive electrode. It becomes. Therefore, the negatively charged black particles 5B move toward the positive electrode, the second electrode 12, and adhere to the electrode surface, and the positively charged white particles 5A are the negative electrode, the first electrode It moves toward 2 and adheres to the electrode surface. As a result, when viewed from the upper substrate 16 side, the display surface is covered with the black particles 5B and black display is performed.

  After the signal voltage is applied between the first and second electrodes 2 and 12 as described above, the power supply unit 86 is controlled to stop the application of the voltage and to be in a no-voltage state. Even in such a non-voltage state, the adhesion of the black particles 5B to the second electrode 12 is maintained by an adhesion force such as a van der Waals force between particles and between the particles and the electrode 12, or an image force. Is done. Further, the adhesion of the white particles 5A to the first electrode 2 is similarly maintained. Therefore, in this state, the black display is maintained.

  Subsequently, rewriting is performed from the black display to the white display shown in FIG. At this time, before performing the white display operation, first, the vibration is generated by the vibration generating unit 21 and the displayed image (here, the black display image) is erased using the vibration. Hereinafter, the details will be described.

  As described above, when the black particles 5B and the white particles 5A are moved toward the respective electrodes 12 and 2 in the space 17 for display as described above, the black particles 5B and the white particles 5B having different charging characteristics can be obtained. Contact occurs between the white particles 5A, and therefore, aggregation of the particles occurs. Further, the black particles 5B and the white particles 5A adhere to the surface of the partition wall 3 due to the image force or the like, and the particles aggregate around the partition wall 3. As a result, the number of particles used for display is reduced. For example, in the above black display, when the number of black particles 5B used for display decreases, a gap is formed in the area covered with the black particles 5B, and the color of the white particles 5A or the lower substrate 16 is observed from the gap. Is done. As a result, display unevenness occurs and the contrast is reduced.

  Here, in order to prevent the occurrence of such display unevenness and a decrease in contrast, vibration is applied to the black and white particles 5B and 5A, whereby the aggregated particles are crushed and dissociated, and the partition walls are separated. The particles attached to 3 are peeled off. Then, the dissociated and separated black and white particles 5B and 5A are dispersed in the space 17.

  Specifically, as described above, the switching element 85 is switched from the black display state in which the black particles 5B adhere to the second electrode 12 and the white particles 5A adhere to the first electrode 2 without voltage. As a result, the voltage application path is switched so that an electric field is applied between the first electrode 2 and the third electrode 4, and the first and third electrodes 2 and 4 are connected to the power supply unit 86. You. Then, a high-frequency sine wave voltage or a high-frequency rectangular wave voltage is applied between the first and third electrodes 2 and 4. Here, a high-frequency rectangular wave voltage is applied. At this time, no voltage is applied between the first and second electrodes 2 and 12. By applying such a voltage to the first and third electrodes 2 and 4, a piezoelectric effect is generated in the piezoelectric body 20 sandwiched between the first and third electrodes 2 and 4, whereby the vibration generator 21 Vibration occurs.

  The vibration generated by the vibration generation unit 21 is transmitted to the black and white particles 5B and 5A in the space 17. By the application of such vibrations, the black and white particles 5B and 5A are separated from the surfaces of the first and second electrodes 2, 12 and the partition walls 3 to which the black and white particles 5A have adhered, and the aggregated particles are pulverized. Dissociated. The dissociated and separated black and white particles 5B and 5A are dispersed in the space 17. Thereby, the black display image is erased. In addition, when vibration is applied, friction occurs between the particles, so that it is possible to increase the charge amount of the black and white particles 5B and 5A, which decreases with the lapse of the display time.

  After the vibration is generated by the vibration generating unit 21 to erase the image as described above, a white display operation is performed, and rewriting to white display is performed. In the white display operation, as shown in FIG. 2C, a signal voltage corresponding to an image signal is applied between the first electrode 2 and the second electrode 12. Here, contrary to the above-described black display, the voltage application system is switched by the switching element 85 so that the potential Vb of the first electrode 2 becomes positive and the potential Va of the second electrode 12 becomes negative. The path is switched, and a DC voltage is applied between the first and second electrodes 2 and 12. At this time, the switching element 85 switches the voltage application system so that no voltage is applied to the first and third electrodes 2 and 4. By applying a voltage to the first and second electrodes 2 and 12, an electric field determined from the voltage (Va−Vb) is applied between the electrodes 2 and 12. Here, since (Va−Vb) is negative, an electric field is applied in a direction from the upper substrate 16 side to the lower substrate 6 side, and the first electrode 2 becomes a positive electrode and the second electrode 12 becomes It becomes a negative electrode. Therefore, the negatively charged black particles 5B move toward the first electrode 2, which is a positive electrode, and adhere to the electrode surface, while the positively charged white particles 5A are charged with the second electrode, a negative electrode. It moves toward 12 and adheres to the electrode surface. As a result, when viewed from the upper substrate 16 side, the display surface is covered with the white particles 5A and white display is performed.

  In such a white display operation, the display is performed using the black and white particles 5B and 5A which are dissociated and separated by the application of vibration and dispersed in the space 17 as described above. The number is prevented from decreasing, and the proportion of particles contributing to display is increased. Therefore, here, the display surface can be covered with the white particles 5A without gaps, and it is possible to prevent the color of the black particles 5B and the color of the lower substrate 6 from being observed from the gaps between the white particles 5A. Therefore, the occurrence of display unevenness and a decrease in contrast are prevented.

  In addition, since the white and black particles 5A and 5B attached to the first and second electrodes 2 and 12 are separated from the surfaces of the electrodes by vibration in advance, when the black and white particles 5A and 5B are moved, It is not necessary to separate the white and black particles 5A and 5B from the first and second electrodes 2 and 12, and since the aggregated white and black particles 5A and 5B are dissociated in advance by vibration, In addition, there is no need to dissociate the aggregated particles. Therefore, the operating voltage required for particle movement can be reduced.

  After the voltage is applied between the first and second electrodes 2 and 12 as described above, the power supply unit 86 is controlled to stop the application of the voltage and to be in a non-voltage state. Even in such a non-voltage state, the adhesion of the black particles 5B to the first electrode 2 and the adhesion of the white particles 5A to the second electrode 12 are caused by van der Waals forces between the particles and between the particles and the electrode. Or by an adhesive force such as a mirror image force. Therefore, white display is maintained.

  When rewriting the display from white display to black display, a high-frequency rectangular wave voltage is applied between the first and third electrodes 2 and 4 as in the case of rewriting from black display to white display. To erase the display, and then perform the black display operation.

  By performing desired display in each pixel 100 in this manner, an image is displayed on the display device. By the way, when a high-frequency rectangular wave voltage is applied between the first and third electrodes 2 and 4 to generate vibrations in the vibration generating unit 21, only the pixels 100 that need to be rewritten are rewritten. Vibration may be generated by applying a voltage. For example, in a configuration in which the piezoelectric body 20 is divided (patterned) for each pixel 100 and the third electrode 4 is connected to a common wiring (not shown) for each pixel 100, a pixel for which display rewriting is required Vibration is generated by applying a voltage only to the first and third electrodes 2 and 4 of the pixel 100, while a configuration in which no vibration is generated in the pixel 100 that does not require rewriting can be realized.

  In the display device of the present embodiment, the vibrations generated by the vibration generation unit 21 can dissociate the aggregated particles and separate the particles adhered to the partition walls 3. Even if rewriting of a proper display is repeatedly performed, it is possible to suppress aggregation and adhesion of particles. Therefore, it is possible to prevent the occurrence of favorable display unevenness and the decrease in contrast by increasing the utilization rate of the particles, and as a result, it is possible to realize favorable display characteristics. In addition, by applying the vibration, it is possible to prevent a decrease in the charge amount of the black and white particles 5B and 5A, and thus it is possible to perform a stable and good display. Further, after the display is once erased, the black and white particles 5B and 5A are moved between the first and second electrodes 2 and 12 to perform the display operation. In the display operation, the aggregated particles are dissociated and dispersed. Energy for removing the black and white particles 5B and 5A from the first and second electrodes 2 and 12 and the partition 3 is not required. Accordingly, the operating voltage can be reduced, and power consumption of the display device can be reduced.

  Further, in such a display device, since the first electrode 2 to which a signal voltage for display is applied also serves as an electrode of the vibration generating unit 21, the cost is reduced and the device is made thinner and lighter. Is achieved. Furthermore, since the vibration generation unit 21 is arranged inside the display element 70 (that is, on the space 17 side), it is possible to directly transmit vibration to the black particles 5B and the white particles 5A in the space 17. For this reason, the vibration is easily transmitted to the black and white particles 5B and 5A, so that the amplitude width of the vibration can be reduced. Therefore, the operating voltage of the vibration generation unit 21 is reduced, and power saving can be achieved.

  In addition, since the space 17 between the upper substrate 16 and the lower substrate 6 is partitioned by the partition 3 for each pixel 100, it is possible to suppress the movement of the black particles 5B and the white particles 5A to the adjacent pixels 100. This makes it possible to prevent the black and white particles 5B and 5A from concentrating on a specific region. Therefore, the total amount of particles in each pixel 100 can be kept constant. Further, here, when the display device is manufactured, the high-frequency rectangular wave voltage or the high-frequency sine wave is applied between the first and third electrodes 2 and 4 after the black and white particles 5B and 5A are sealed in the space 17. By applying the voltage, the vibration generated in the vibration generating section 21 is applied to the enclosed black and white particles 5B and 5A. Here, a high-frequency rectangular wave voltage is applied. Thereby, it is possible to uniformly disperse the black and white particles 5B and 5A on the substrate surface in the pixel 100 using the vibration. Therefore, the dispersion of the particles in the pixel 100 is made uniform. As a result, display unevenness can be further reduced.

  Further, since the black particles 5B and the white particles 5A are porous and are composite particles of the core particles and the fine particles, the interaction between the particles, and the Can be reduced, and as a result, an operating voltage can be reduced and a high-speed response can be achieved.

 That is, since the black particles 5B and the white particles 5A are porous, the specific gravity of the particles is small and the molecular weight is small. Therefore, it can be expected that the van der Waals force between the particles and between the electrode as the attachment target and the particles can be reduced. When the van der Waals force is reduced as described above, it is possible to reduce the adhesive force between a plurality of particles and the adhesive force between an electrode and a particle. In addition, because of its light weight, it is possible to delay the sedimentation of the particles and bring them into a floating state. In such a floating state, there is no need to peel the particles from the electrodes or the like, so that the particles can be quickly moved at a low voltage. Also, here, as described above, the particles of the same color have the same size, and the particles of the different colors have the same size. There is no need to apply a voltage to detach small particles that have become non-uniform or stick to large particles. Furthermore, since the black particles 5B and the white particles 5A are composite particles, the presence of the fine particles causes the distance between the core particles to move in the space 17 and directly participate in display, and It is possible to increase the distance between the body particles and the electrode serving as the attachment target by the minute particles. Therefore, the van der Waals force can be reduced, and the adhesive force can be reduced.

  In the above description, the configuration in which the black and white particles 5B and 5A are in direct contact with the surfaces of the first and second electrodes 2 and 12 has been described. It is desirable to form an insulating film on the surface in contact with the 12 particles. When an insulating film is provided, the insulating film forms a capacitor, so that long-term retention characteristics are improved. It is desirable that such an insulating film does not significantly change the electrical characteristics and magnetic characteristics of the particles.

  In addition, the surfaces of the first and second electrodes 2 and 12 and the partition wall 3 in contact with the space 17 and the surfaces of the black and white particles 5B and 5A may be subjected to a water-repellent treatment. A water-repellent film may be formed. When water droplets exist on the surfaces of the first and second electrodes 2 and 12 and the partition walls 3 due to aggregation of water in the space 17 and the like, the surfaces of the first and second electrodes 2 and 12 and the partition walls via the water droplets. The adhesive force of the black and white particles 5B and 5A attached to the surface of No. 3 is increased by the surface tension of the water droplet. Therefore, a higher operating voltage is required when moving the particles 5B and 5A by applying an electric field of opposite polarity, respectively. On the other hand, a water-repellent film is formed on the surfaces of the black particles 5B and the white particles 5A, the surfaces of the first and second electrodes 2 and 12, and the surfaces of the partition walls 3 and subjected to a water-repellent treatment. In this case, the surface tension of the water droplet does not act during the movement of the particles, so that the operating voltage can be further reduced.

Also, in the above description, the case where the vibration is generated in the vibration generating unit 21 at a timing shifted from the movement of the black and white particles 5B and 5A for display and the display is once erased has been described. The movement of the particles may be performed simultaneously, that is, the movement of the particles may be performed while the vibration is generated by the vibration generating unit 21.
(Example)
In an example, a method for manufacturing a display element according to this embodiment will be specifically described. Here, a glass substrate having a thickness of 1.1 mm is used as the first and second substrates 1 and 11. First, an ITO film, which is a light-transmitting conductive material, is formed as a second electrode 12 on one surface of a glass substrate that is the second substrate 11. Then, after cleaning the glass substrate with the ITO film, a polycarbonate thin film is formed on the ITO film. Here, polycarbonate having high hardness was used. Then, the polycarbonate is dissolved in tetrahydrofuran, thereby forming an insulating film made of polycarbonate having a thickness of 2 to 5 μm. Here, it is more ideal that the polycarbonate is modified with a terminal group in order to improve the adhesion to ITO. As described above, the upper substrate 16 in which the second electrode 12 and the insulating film (not shown) are formed on the second substrate 11 is manufactured.

  On the other hand, when manufacturing the lower substrate 6, first, an ITO film as the third electrode 4 is formed on the glass substrate as the first substrate 1 by the same method as described above. Then, a piezoelectric body 20 made of lead zirconate titanate (PZT) is formed on the ITO film. Further, an ITO film is formed as the first electrode 2 on the piezoelectric body 20, and a polycarbonate film is formed as an insulating film on the first electrode 2 by the same method as described above. As described above, the lower substrate 6 on which the third electrode, the piezoelectric body 20, the first electrode 2, and the insulating film (not shown) are formed on the first substrate 1 is manufactured.

  Subsequently, the spacer 3 'is arranged on the surface of the lower substrate 6 or the surface of the upper substrate 16 formed as described above. Here, a lattice-shaped polyethylene terephthalate sheet having a square hole of 1 cm square was disposed as a spacer 3 ′ on the first electrode 2 of the lower substrate 6. The thickness of this sheet is 100 μm. The region above the first substrate 1 defined by the spacers 3 'thus arranged corresponds to one pixel region.

  A plurality of black particles 5B and white particles 5A are filled in the space 17 on the first electrode 2 defined by the spacer 3 ', that is, the space 17 in one pixel 100. Here, those obtained by modifying the surface of 5 μm acrylic particles containing carbon black are used as the black particles 5B. The surface-modified 5-μm acrylic particles containing titanium oxide are used as white particles 5A. A mixture of the same amount of the black particles 5B and the white particles 5A is sufficiently stirred with a Henschel mixer and uniformly mixed. Thereby, the black particles 5B are negatively charged, and the white particles 5A are positively charged. Then, 6 mg of the mixed particles is uniformly and uniformly sieved into the space 17 of each pixel 100. Then, the space 17 is sealed by overlapping the upper substrate 16 on the spacer 3 ′ disposed on the lower substrate 6, and the lower substrate 6 and the upper substrate 16 are fixed by sandwiching them with double clips. Thereafter, the first, second, and third electrodes 2, 12, and 4 are connected to the power supply unit 86, and the voltage application system is adjusted.

  Thereafter, in order to uniformly disperse the black and white particles 5B and 5A in the substrate surface, a high-frequency rectangular wave voltage is applied between the first electrode 2 and the third electrode 4, and the piezoelectric effect of the piezoelectric body 20 is applied. Causes the vibration generator 21 to generate vibration. The application of such a voltage is performed, for example, immediately before shipping a display device as a finished product. The vibration generated by the vibration generating unit 21 is transmitted to the black particles 5B and the white particles 5A in the space 17, whereby the black particles 5B and the white particles 5A are evenly and uniformly dispersed on the substrate surface of each pixel 100. It becomes possible. For example, as described above, if such a voltage application is performed once immediately before shipment of the display device to uniformly disperse the black and white particles 5B and 5A, the effect is maintained thereafter. Therefore, in the display device, display unevenness can be prevented. In addition, by imparting the vibration to the black and white particles 5B and 5A, the particles that are not sufficiently charged are again stirred and mixed, so that the black and white particles 5B and 5A have good charging characteristics. Become stable.

  Subsequently, in the display element 70 manufactured by the above method, a voltage is applied between the first and second electrodes 2 and 12 to apply an electric field. At this time, when an electric field (here, an electric field of 2 V / μm) from the first electrode 2 side to the second electrode 12 side is applied, the second electrode 12 becomes a positive electrode and the first electrode 2 becomes a negative electrode. Thus, the negatively charged black particles 5B move toward the second electrode 12, and the positively charged white particles 5A move toward the first electrode 2. Therefore, when the display element 70 is viewed from the observer side, the display becomes black. On the other hand, when an electric field (here, an electric field of −2 V / μm) is applied from the second electrode 12 side to the first electrode 2 side, the first electrode 2 becomes a positive electrode and the second electrode 12 becomes a negative electrode. Therefore, the negatively charged black particles 5B move to the first electrode 2 side, and the positively charged white particles 5A move to the second electrode 12 side. Therefore, when the display element 70 is viewed from the observer side, the display becomes white.

  When rewriting display, first, a high-frequency rectangular wave voltage is applied between the first electrode 2 and the third electrode 4. Thereby, the vibration is generated in the vibration generating section 21 by the piezoelectric effect generated in the piezoelectric body 20. When the vibration is transmitted to the black and white particles 5B and 5A in the space 17, the particles attached to the surfaces of the upper substrate 16 and the lower substrate 6 are separated, and the aggregated particles are dissociated. Then, the separated and dissociated particles are stirred and dispersed to erase the display.

  As described above, after the display is erased using the vibration generated by the vibration generating unit 21, the electric field (2 V / μm for black display and −2 V / μm for white display) necessary for displaying a new image is first applied. And between the second electrodes 2 and 12 to move the black and white particles 5B and 5A to newly display. In this way, the display image is rewritten. In the display image rewritten as described above, the display unevenness on the image display surface is improved, and the reflection density and the contrast can be improved.

(Embodiment 2)
FIG. 3 is a schematic cross-sectional view showing a configuration of a pixel forming a display element of the display device according to Embodiment 2 of the present invention. As shown in FIG. 3, the display element of the present embodiment
It has the same configuration as the display element of the first embodiment, except that the black particles 5 </ b> B have conductivity and the electron transport layer 7 serving as a charge transport layer is formed on the first and second electrodes 2 and 12. The point is different.

  In the first embodiment, the case where both the colored particles have insulating properties has been described. However, as long as at least one kind is insulating, one kind may be conductive. When the colored particles are conductive, it is necessary to form a thin film containing a charge transport material or an insulating film on the surfaces of the first and second electrodes 2 and 12 that come into contact with the particles. Hereinafter, the details will be described.

  For example, when the black particles 5B have conductivity and the electron transport layer 7 as the charge transport layer is not formed on the surfaces of the first and second electrodes 2 and 12, as shown in FIG. When the black particles 5B reach the second electrode 12 during black display, and when the black particles 5B reach the first electrode 2 during white display as shown in FIG. ) Leaks from the first and second electrodes 2, 12, and receives charges (here, holes) from the first and second electrodes 2, 12 and is charged to the same polarity as the destination electrode. Therefore, the black particles 5B repel from the reached electrode and start moving to the other electrode having the opposite polarity to the destination electrode. The repetition of this operation causes the black particles 5B to reciprocate between the lower and upper substrates 6 and 16, thereby making display difficult.

  Therefore, in the present embodiment, the electron transport layer 7 is formed on the first and second electrodes 2 and 12. With such a configuration, when the black particles 5B adhere to the second electrode 12 via the electron transport layer 7 during the black display shown in FIG. 2B, the electron transport layer 7 selectively blocks the passage of holes. And let only electrons pass. For this reason, it is possible to prevent the transfer of holes from the second electrode 12 to the black particles 5B, and to enable the transfer of electrons from the second electrode 12 to the black particles 5B. Therefore, in this case, the polarity (positive polarity) of the black particles 5B is not opposite to the original polarity (negative polarity), and the charge amount is kept uniform even if the black particles 5B are conductive. To maintain negative polarity. Therefore, the black particles 5B are held on the side of the second electrode 12, which is the positive electrode. Further, in the white display shown in FIG. 2C, the electron transport layer 7 is formed on the first electrode 2, so that the positive electrode 1 No holes are transferred to the black particles 5B, and only electrons are transferred to the black particles 5B. Therefore, the black particles 5B are maintained in a negative polarity with the charge amount being kept uniform, and thus are held on the first electrode 2 side which is a positive electrode. Therefore, according to the configuration in which the electron transport layer 7 is formed on the first and second electrodes 2 and 12, even if the black particles 5B having conductivity, the reciprocating vibration motion of the black particles 5B is prevented. It is possible to perform stable and good display. In this example, the same effect as described above can be obtained.

  Examples of the electron transporting material constituting the electron transporting layer 7 include benzoquinone-based, tetracyanoethylene-based, tetracyanoquinodimethane-based, fluorenone-based, xanthone-based, phenanthraquinone-based, phthalic anhydride-based, diphenoquinone-based, and the like. May be used.

  In addition, although the case where the negatively charged black particles 5B have conductivity has been described above, as a modification of the present embodiment, the positively charged white particles 5A may have conductivity. . In this case, a hole transport layer 7 is provided as a charge transport layer instead of the electron transport layer 7 described above. Thereby, the transfer of electrons from the first and second electrodes 2 and 12 to the white particles 5A is prevented and the holes are transferred, so that the positive charge of the white particles 5A can be held. Examples of the material constituting such a hole transport layer 7 include pyrene-based, carbazole-based, hydrazone-based, oxazole-based, oxadiazole-based, pyrazoline-based, arylamine-based, arylmethane-based, benzidine-based, and thiazole-based materials. , Stilbene-based, butadiene-based, low-molecular-weight compounds such as butadiene-based compounds, poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, pyrene-formaldehyde resin, ethyl High molecular compounds such as carbazole-formaldehyde resin, triphenylmethane polymer and polysilane are used.

(Embodiment 3)
FIG. 4 is a schematic cross-sectional view showing a configuration of a pixel forming a display element of the display device according to Embodiment 3 of the present invention. As shown in FIG. 3, in the display element of the present embodiment, the partition wall 3 functions as the vibration generation unit 21.

  When manufacturing the display element of the present embodiment, for example, two glass substrates are used as the first and second substrates 1 and 11, and the first and second electrodes 2 are provided on the surface of each glass substrate. , 12 are formed, and a polycarbonate film, for example, is formed as an insulating film 22 on the ITO film. Thereby, the upper substrate 16 and the lower substrate 6 are manufactured.

  Next, a sheet-shaped piezoelectric body 20 (hereinafter, referred to as a piezoelectric sheet 20) whose front and back surfaces are covered with ITO films as vibration generating electrodes 4A and 4B on the surface of the manufactured lower substrate 6 or upper substrate 16 is formed. Is arranged. The piezoelectric sheet 20 is a lattice-like sheet having a plurality of holes, and the vibration sheet 21 is formed by the piezoelectric sheet 20. Here, the piezoelectric sheet 20 also serves as the spacer and the partition 3, and a region partitioned by the piezoelectric sheet 20 corresponds to one pixel region. After arranging the piezoelectric sheet 20 in this way, the black and white particles 5A and 5B are put in the space 17 of each pixel 100 and sealed with the other substrate. Thereafter, the first and second electrodes 2 and 12 and the vibration generating electrodes 4A and 4B are connected to the power supply unit 86 to prepare a voltage application system. Here, a DC voltage is applied between the first and second electrodes 2 and 12, and a high-frequency rectangular wave voltage or a high-frequency sine wave voltage is applied between the vibration generating electrodes 4A and 4B of the vibration generating unit 21. The power supply unit 86 and the voltage application system are configured so as to be operated. In this case, a high-frequency rectangular wave voltage is applied between the vibration generating electrodes 4A and 4B. The first and second electrodes 2 and 12 are insulated from the vibration generating electrodes 4A and 4B by the insulating film 22.

  In the display element manufactured as described above, as described above in the first embodiment, for example, a high-frequency rectangular wave voltage is applied between the vibration generating electrodes 4A and 4B before shipment of a product or the like, and the vibration generating section 21 is applied. Generates vibrations, and the vibrations make the particle distribution in the pixels 100 uniform.

  In the present embodiment having such a configuration, by applying a high-frequency rectangular wave voltage between the vibration generating electrodes 4A and 4B, the vibration can be generated by the vibration generating unit 21. Using this vibration, the same operation as in the first embodiment is performed, and the display operation and the display erasing operation are performed. Therefore, effects similar to the effects described above in the first embodiment can be obtained. Further, in such a configuration, since the vibration generating section 21 also serves as the spacer and the partition wall 3, the cost can be reduced.

(Embodiment 4)
FIG. 5 is a schematic cross-sectional view showing a configuration of a pixel forming a display element of the display device according to Embodiment 4 of the present invention. As shown in FIG. 5, in the display element of the present embodiment, the vibration generating section 21 functions as the spacer and the partition wall 3 as in the case of the third embodiment.

  In the present embodiment, the piezoelectric body 20 is sandwiched between the first and second electrodes 2 and 12 with the insulating medium 23 interposed therebetween. Accordingly, the space 17 is held by the piezoelectric body 20, that is, the piezoelectric body 20 functions as a spacer, and is divided for each pixel 100 by the piezoelectric body 20, that is, the piezoelectric body 20 functions as the partition wall 3. Also, on the surface of the piezoelectric body 20 that comes into contact with the space 17, the vibration generating electrodes 4A and 4B are provided. The vibration generating electrodes 4A and 4B are formed, for example, by covering the surface of the hole of the sheet-shaped piezoelectric body 20 having a plurality of holes with a conductive film such as an ITO film. As described above, the vibration generating section 21 is formed by the configuration in which the piezoelectric body 20 is sandwiched between the vibration generating electrodes 4A and 4B. The first and second electrodes 2 and 12 and the vibration generating electrodes 4A and 4B are connected to a power supply unit 86, where a DC voltage is applied to the first and second electrodes 2 and 12, and The voltage application system and the power supply unit 86 are configured to apply a high-frequency rectangular wave voltage or a high-frequency sine wave voltage to the vibration generating electrodes 4A and 4B. Here, it is configured to apply a high-frequency rectangular wave voltage to the vibration generating electrodes 4A and 4B. Further, a voltage application path to the vibration generating electrodes 4A, 4B is configured so that the potentials of the vibration generating electrodes 4A, 4B are opposite between the adjacent pixels 100.

  The vibration generating electrodes 4A and 4B and the piezoelectric body 20 are insulated from the first and second electrodes 2 and 12 by an insulating medium 23. The insulating medium 23 may be an insulating film, but preferably has a configuration capable of suppressing transmission of the vibration generated by the vibration generating section 21 to the upper substrate 16 and the lower substrate 6. By suppressing the transmission of vibration to the substrate, it is possible to transmit vibration to the black and white particles 5B and 5A in the space 17 more efficiently.

  In the present embodiment having such a configuration, by applying a high-frequency rectangular wave voltage between the vibration generating electrodes 4A and 4B, the vibration can be generated in the vibration generating section 21 by the piezoelectric effect of the piezoelectric body 20. Become. Using this vibration, the same operation as in the first embodiment is performed, and the display operation and the display erasing operation are performed. Therefore, effects similar to the effects described above in the first embodiment can be obtained. In addition, the vibration generating electrodes 4A and 4B can be used in combination as electrodes that are not affected by the electric field of the adjacent pixels 100 and have an effect of reducing particle adhesion to the partition 3.

(Embodiment 5)
In the first to fourth embodiments, the case where the space 17 is in the gas phase is described, but the space 17 may be in the liquid phase.

  FIG. 6 is a schematic cross-sectional view showing a configuration of a pixel forming a display element of the display device according to Embodiment 5 of the present invention. As shown in FIG. 6, the display element of the present embodiment has the same configuration as that of the first embodiment except that the space 17 is in a liquid phase. Specifically, a space 17 formed between the upper substrate 16 and the lower substrate 6 is filled with an insulating solvent 24 such as silicon oil, for example, so that the space 17 is in a liquid phase. Although not shown in detail here, the display element of the present embodiment is an active matrix drive type element, and a thin film transistor (TFT) is formed as a switching element on the lower substrate 6 for each pixel 100. ing.

  In the present embodiment having such a configuration, the black display (FIG. 2B) and the white display are performed by the electrophoresis phenomenon of the black and white particles 5B and 5A in the insulating solvent 24, as in the first embodiment. The display (FIG. 2C) is performed. Further, by transmitting the vibration generated in the vibration generating section 21 to the black and white particles 5B and 5A in the insulating solvent 24, the display is erased as in the first embodiment. Therefore, also in the present embodiment, the same effect as in the first embodiment can be obtained. Further, in the present embodiment, the specific gravity of the black and white particles 5B and 5A is matched with the specific gravity of the insulating solvent 24, so that the vibration generated by the vibration generating unit 21 allows the particles to aggregate more efficiently. Can be dissociated, and particles can be separated from the substrate surface or partition wall surface.

  In addition, here, the configuration in which the space 17 is a liquid phase is described as the basic configuration similar to the first embodiment, but the configuration in which the space 17 is a liquid phase is based on the configuration of the second to fourth embodiments. It may be.

(Embodiment 6)
FIG. 7 is a schematic cross-sectional view illustrating a configuration of a pixel forming a display element of a display device according to Embodiment 6 of the present invention.

  As shown in FIG. 7, in the display element of the present embodiment, a space 17 is formed between an upper substrate 16 and a lower substrate 6 having the same configuration as in the first embodiment. In this space 17, spherical capsules 25 in which black and white particles 5B and 5A and an insulating solvent 24 are sealed are densely arranged over the entire surface of the substrate in a line in the thickness direction of the display element. I have. Thus, in the display element of the present embodiment, the capsules 25 are uniformly arranged in the image display area. Since the capsule 25 also functions as a support member for the space 17, a spacer is not required in such a configuration. Further, since the black and white particles 5B and 5A are sealed in the capsule 25, the particles do not move between the pixels 100, so that the partition is not required.

  In the display device having such a configuration, the black and white particles 5B and 5A are electrophoresed in the capsule 25, whereby the black display operation (FIG. 2B) and the white display operation (FIG. 2B) described in the first embodiment are performed. (C)) and the display erasing operation by the vibration generated by the vibration generating unit 21 is performed in the capsule 25. Therefore, in the present embodiment, the same effect as in the first embodiment can be obtained. In addition, in the present embodiment, since a spacer and a partition are not necessary as described above, the cost can be reduced, and a highly flexible display element can be easily realized by using a flexible substrate. It becomes.

(Embodiment 7)
In the first to sixth embodiments, the pair of electrodes to which the signal voltage for the display operation is applied, that is, the first and second electrodes 2 and 12 are provided on the upper substrate 16 and the lower substrate 6, respectively. Although the case where the first and second electrodes 2 and 12 are opposed to each other has been described, a configuration in which the first and second electrodes 2 and 12 are arranged on one substrate side may be adopted.

  FIG. 8 is a schematic cross-sectional view showing a configuration of a pixel forming a display element of the display device according to Embodiment 7 of the present invention.

  As shown in FIG. 8, in the display element of the present embodiment, the upper substrate 16 is constituted only by the second substrate 11, and the first and second electrodes 2 and 12 are provided on the lower substrate 6 side. Have been. Specifically, the first electrode 2 and the piezoelectric body 20 are formed in this order on the first substrate 1, and the second electrode 12 is formed in a rectangular shape in a predetermined region on the surface of the piezoelectric body 20. To form a lower substrate 6. The first and second electrodes 2 and 12 are connected to a power supply unit 86 via a voltage application path including a switching element 85. Here, a DC voltage as an image signal voltage and a high-frequency rectangular wave voltage or a high-frequency sine wave voltage as a vibration generation voltage can be applied between the first and second electrodes 2 and 12. , A voltage application system and a power supply unit 86. Here, it is configured such that a high-frequency rectangular wave voltage is applied as the vibration generation voltage. Further, the display element of the present embodiment is of an active matrix drive type, and a thin film transistor (TFT), not shown, is provided for each pixel 100 on the lower substrate 6 as a switching element. Thus, a voltage can be applied to each pixel 100. An insulating solution 24 is sealed in a space 17 formed between the lower substrate 6 and the upper substrate 16, and the black particles 5 </ b> B are dispersed in the insulating solution 24.

  As described above, in the present embodiment, since the piezoelectric body 20 is arranged between the first and second electrodes 2 and 12, the first and second electrodes 2 and 12 and the piezoelectric body 20 The vibration generator 21 is configured. Thus, here, the display electrode is configured to also serve as the vibration generation electrode.

  In the display element of this embodiment having such a configuration, a DC voltage, which is an image signal voltage, is applied between the first and second electrodes 2 and 12 during a display operation. The black particles 5 </ b> B move according to the charging characteristics due to the electric field applied between the first and second electrodes 2 and 12 by this voltage application. For example, when an electric field is applied from the first electrode 2 to the second electrode 12, the first electrode 2 becomes a negative electrode and the second electrode 12 becomes a positive electrode. At this time, the negatively charged black particles 5B move toward the second electrode 12 and adhere to the surface of the second electrode 12. For this reason, as shown in the pixel 100a, when observed from the upper substrate 16 side, which is the observation side, the color of the piezoelectric body 20 is mainly observed, or the color of the first electrode 2 transmitted through the piezoelectric body 20. Is observed. For example, if the piezoelectric body 20 is white, white display is performed.

  On the other hand, when an electric field is applied from the second electrode 12 to the first electrode 2, the first electrode 2 becomes a positive electrode and the second electrode 12 becomes a negative electrode. At this time, the negatively charged black particles 5B move toward the first electrode 2 and adhere to the surface of the piezoelectric body 20 disposed above the first electrode 2. For this reason, as shown in the pixel 100b and the pixel 100c, when viewed from the upper substrate 16 side, which is the observation side, the color of the black particles 5B is mainly observed and black display is performed.

  When rewriting an image in the display element of the present embodiment, first, a high-frequency rectangular wave voltage is applied between the first and second electrodes 2 and 12. By this voltage application, a piezoelectric effect occurs in the piezoelectric body 20 disposed between the first and second electrodes 2, 12, whereby the vibration is generated in the vibration generator 21. When this vibration is transmitted to the black particles 5B, the aggregated black particles 5B are dissociated, and the black particles 5B attached to the surface of the second electrode 12 and the surface of the piezoelectric body 20 are separated from the surface. Then, the dissociated and peeled black particles 5B are uniformly dispersed in the space 17. As described above, the image is erased using the vibration generated by the vibration generating unit 21. Subsequently, an image signal voltage corresponding to a new image is applied to the first and second electrodes 2 and 12, whereby the above-described display operation is performed and the image is rewritten.

  As described above, in the present embodiment having such a configuration, vibration can be generated in the vibration generating section 21 to dissociate the aggregated particles and separate the particles from the attachment surface. Is obtained. Further, since the electrodes used for display and the electrodes used for generating vibration are the same here, the cost can be reduced and the device can be made thinner and lighter. In this case, since the piezoelectric body 20 is in direct contact with the space 17, the vibration transmitted from the piezoelectric body 20 to the black particles 5B is increased. Therefore, the dissociation effect of the agglomerated particles and the separation effect from the adhered surface are further increased, and the operating voltage for generating vibration is reduced.

  Further, as a modified example of the present embodiment, as shown in FIG. 9, the first and second electrodes 2 and 12 are arranged in a comb shape on the first substrate 1 at intervals. You may. In such a configuration, the first electrode 2 and the second electrode 12 are insulated, so that when a voltage is applied between the first and second electrodes 2 and 12, the first and second electrodes 2 and 12 are insulated. An electric field is applied between the electrodes 2, 12.

  In this example, when a DC voltage, which is an image signal voltage, is applied between the first and second electrodes 2, 12, the electric field applied between the first and second electrodes 2, 12 by this voltage application Thereby, the black particles 5B move according to the charging characteristics. When the first electrode 2 is the negative electrode and the second electrode 12 is the positive electrode, as shown in the pixel 100b ′, the negatively charged black particles 5B move to the region above the second electrode 12, and It adheres to the surface of the piezoelectric body 20 arranged above the electrode 12. For this reason, when observed from the upper substrate 16 side, which is the observation side, mainly the color of the piezoelectric body 20 above the first electrode 2 or the color of the first electrode 2 passing therethrough and passing through the piezoelectric body 20. Color is observed. For example, if the piezoelectric body 20 is white, white display is performed. On the other hand, when the first electrode 2 is a positive electrode and the second electrode 12 is a negative electrode, as shown by 100a ′, the negatively charged black particles 5B move to the region above the first electrode 2. , Adhere to the surface of the piezoelectric body 20 disposed above the first electrode 2. For this reason, when observed from the upper substrate 16 side, which is the observation side, the color of the black particles 5B is mainly observed and black display is performed.

  When rewriting an image, as described above, first, a high-frequency rectangular wave voltage is applied between the first and second electrodes 2 and 12 to generate vibrations in the vibration generation unit 21 so as to generate an image. Is erased, and then the above-described display operation is performed. Therefore, also in this example, the same effect as in the first embodiment can be obtained.

  Although the case where the space 17 is in the liquid phase has been described above, in the configuration of the present embodiment in which the display electrodes are provided on the same substrate, the space 17 may be in the gas phase. Further, a configuration in which a partition is provided for each pixel 100 may be employed.

(Embodiment 8)
FIG. 10 is a schematic cross-sectional view showing a configuration of a pixel forming a display element of a display device according to Embodiment 8 of the present invention.

  As shown in FIG. 10, in the present embodiment, a rectangular second electrode 12 is formed on the first substrate 11 of the upper substrate 16 for each pixel 100, and the second electrode 12 A rectangular first electrode 2 is formed on the piezoelectric body 20 of the lower substrate 16 corresponding to the position. Although not shown here, the display element of the present embodiment is of an active matrix drive type, and a thin film transistor (TFT) is provided as a switching element for each pixel 100 on the lower substrate 6. I have. Thus, a voltage can be applied to each pixel 100.

  The electric field array particles 5 </ b> C are sealed in the space 17 filled with the insulating solvent 24. Here, the electric field array particles 5C are particles composed of a material having a high dielectric constant and easy to be polarized, for example, particles composed of composite particles in which silica particles are coated around core particles of an acrylic polymer. It is. Here, the electric field array particles 5C are polarized by the electric field applied between the first and second electrode electrodes 2 and 12. Further, the electric field array particles 5C have a configuration in which light incident from the upper substrate 16 side is scattered and irregularly reflected.

  In the display element having such a configuration, the display provided by the state in which the electric field array particles 5C are arranged between the first and second electrodes 2 and 12 (that is, the state of A in the drawing) and the electric field array particles 5C are arranged in the space 17. And the display provided by the state dispersed in the inside (that is, the state of B in the figure).

  Specifically, when a voltage corresponding to an image signal is applied between the first and second electrodes 2 and 12 to apply an electric field, the electric field polarizes the electric field array particles 5C. In the electric field array particles 5C polarized as described above, an attractive force is generated between the particles depending on the positional relationship. As a result, the electric field array particles 5C dispersed in the space 17 are arranged between the first and second electrodes 2 and 12 along the electric field (state A in the figure). In this state, as shown in the pixel 100a, the color of the piezoelectric body 20 is observed, or the third electrode 4 that passes through the piezoelectric body 20 below it or the first substrate 4 therebelow. One color is observed. Therefore, display in these colors is performed. The state of the particles arranged in this manner is maintained even when the voltage application to the first and second electrodes 2 and 12 is stopped and the electric field is removed.

  When rewriting the display in the state where the electric field array particles 5C are arranged, first, a high-frequency rectangular wave voltage or a high-frequency sine wave voltage is applied between the first and third electrodes 2 and 4. Here, a high-frequency rectangular wave voltage is applied. As a result, a piezoelectric effect is generated in the piezoelectric body 20, and vibration is generated in the vibration generating unit 21, and the vibration is transmitted to the arranged electric field array particles 5C. When the vibration energy larger than the interaction force between the particles is applied, the attractive force between the particles is eliminated in the arranged electric field array particles 5C. As a result, as shown by the pixel 100b, the arrangement state of the electric field array particles 5C is broken, and the electric field array particles 5C are dispersed in the space 17 (state B in the figure). In this state, light incident on the inside of the display element from the upper substrate 16 side is scattered and reflected by the electric field array particles 5C. Therefore, when viewed from the upper substrate 16 side, the display looks white due to the reflected light.

  The display element of the present embodiment is configured such that voltage application to the first and second electrodes 2 and 12 and voltage application to the first and third electrodes 2 and 4 can be performed for each pixel 100. Therefore, a desired display can be performed by controlling the distribution state of the electric field array particles 5C in the space 17 for each pixel 100. Thus, the display element can display a desired image.

  Although the case where the space 17 is in the liquid phase has been described above, in the configuration of the present embodiment in which display is performed using the electric field array particles, the space 17 may be in the gas phase. Further, a configuration in which a partition is provided for each pixel 100 may be employed.

(Embodiment 9)
FIG. 11 is a schematic diagram showing a configuration of a pixel forming a display element of a display device according to Embodiment 9 of the present invention. FIG. 11A shows a cross section perpendicular to the display surface (that is, a vertical cross section). FIG. 11B shows a cross section parallel to the display surface (hereinafter, referred to as a horizontal cross section).

  As shown in FIGS. 11A and 11B, the display element of the present embodiment is, like the display element of the first embodiment, an upper substrate supported by a spacer 3 ′ (corresponding to the partition wall 3). A space 17 is formed between the lower substrate 16 and the lower substrate 6, and the space 17 is filled with black particles 5B and white particles 5A. Here, the lower substrate 6 has a configuration in which the first electrode 2 is formed on the first substrate 1. A third electrode 4 is provided on the surface of the partition wall 3 constituted by the spacer 3 '. The third electrode 4 is arranged without a direct contact with the first and second electrodes 2 and 12 and is spaced apart from the first and second electrodes 2 and 12. The electrodes 2 and 12 are insulated. Although the gap between the first and second electrodes 2 and 12 and the third electrode 4 is exaggerated in the drawing, the gap may be minute.

  In the horizontal cross section of the display element, as shown in FIG. 11B, the partition wall 3 has a mesh shape that defines a hexagonal hole, and the hole corresponds to a region of each pixel 100. A third electrode 4 is provided along the surface of the hole of the partition wall 3. Therefore, the outer periphery of each pixel 100 is surrounded by the partition 3 and the third electrode 4 disposed on the surface thereof. Here, the third electrode 4 of each pixel 100 is connected to a common wiring (not shown). By forming the pixels 100 in such a hexagonal shape, it is possible to realize a display device which is extremely strong against pressure from the front of the display surface, and to improve the pixel density. A plurality of black particles 5B and a plurality of white particles 5A are sealed in a space 17 defined for each pixel 100.

  The first electrode 2 and the second electrode 12 are connected to a DC power supply 23 via a switching element 20 that can switch a voltage application path. Further, the third electrode 4 is connected to the DC power source 23 which is common to the first and second electrodes via a switching element 21 which can switch a voltage application path. Here, the second electrode driver 81 (FIG. 1) has a DC power supply 23 and switching elements 20 and 21, and switches between the switching elements 20 and 21 according to an image signal.

  Next, a method for manufacturing the display element having the above configuration will be described. Here, a glass substrate having a thickness of 1.1 mm is used as the first and second substrates 1 and 11. A first electrode 2 is formed on a first substrate 1 by forming a transparent and conductive ITO (Indium-Tin-Oxide) film. Thereby, the lower substrate 6 is formed. Further, an ITO film is formed on the second substrate 11 to form the second electrode 12. Thereby, the upper substrate 16 is formed.

  Subsequently, the partition walls 3 are formed on the surface of the lower substrate 6 or the surface of the upper substrate 16 formed as described above. Here, for example, a mesh-like sheet made of insulating polyethylene terephthalate (PET) and partitioning a plurality of hexagonal holes is disposed as the partition 3 on the first electrode 2 of the lower substrate 6. Established. The thickness of the sheet is 110 μm. Then, a third electrode 4 is formed by patterning a conductive electrode material, for example, aluminum or the like by a method such as a vacuum evaporation method so as to cover the surface of the hole of the partition 3. Here, as described above, the third electrode 4 needs to have a gap between the first and second electrodes 2 and 12 when the lower substrate 6 and the upper substrate 16 are bonded to each other. For this reason, the third electrode 4 is formed excluding predetermined regions at the upper and lower ends of the partition wall 3. The region above the first substrate 1 divided by the partition walls 3 arranged in this way corresponds to one pixel region. That is, each pixel 100 has a hexagonal shape, and the width (distance between a pair of opposing apex angles) is about 10 μm.

  A plurality of black particles 5B and white particles 5A are filled in the space 17 on the first electrode 2 defined by the partition walls 3, that is, the space 17 in one pixel 100. Here, as the black particles 5B, a negatively charged polymerized toner having an insulating property is used. In addition, non-charged insulating particles (for example, Techpolymer: 20 μm, manufactured by Sekisui Chemical Co., Ltd.) were used as the white particles 5A. These black and white particles 5B and 5A are porous composite particles as described above. In each pixel 100, a mixture of the black and white particles 5B and 5A evenly and uniformly mixed on a medicine packaging paper or the like by 2 mg is sieved into the space 17. At this time, the first substrate 1 is slightly vibrated to spread the particles 5A and 5B uniformly on the substrate surface. Then, the lower substrate 6 and the upper substrate 16 are adhered and fixed by an adhesive or the like. Thereafter, the first, second, and third electrodes 2, 12, and 4 are connected to the DC power supply 23, and the voltage application system is adjusted.

  Thereafter, in order to uniformly disperse the black and white particles 5 </ b> B and 5 </ b> A within the substrate surface, an alternating voltage of a rectangular wave is applied between the first electrode 2 and the second electrode 12, Apply an electric field. The application of such a voltage is performed, for example, immediately before shipping a display device as a finished product. The amplitude of the applied AC voltage is approximately ± 150 V, and the frequency is 3 to 1000 Hz. Here, the lower the frequency, the longer the time required for the black and white particles 5B and 5A to spread uniformly on the substrate surface. On the other hand, when the frequency is high, the particles 5A and 5B are quickly and uniformly dispersed, but when a voltage is further applied in a state where the particles 5A and 5B are uniformly dispersed, the particles 5A and 5B collide with each other and come into contact with each other. The dispersion becomes uneven. Therefore, the frequency of the applied AC voltage is particularly preferably about 3 to 10 Hz, whereby the white and black particles 5A and 5B can be evenly dispersed on the substrate surface of each pixel 100. It becomes. Therefore, it leads to prevention of occurrence of display unevenness. As described above, for example, if such a voltage application is performed once immediately before the display device is shipped to uniformly disperse the particles 5A and 5B, the effect is maintained thereafter.

  Next, a display operation in the display element will be described focusing on one pixel 100 which is a constituent unit. In each of the plurality of pixels 100, an operation described below is separately performed, and thereby an image is displayed.

  12A and 12B are schematic cross-sectional views illustrating a display operation in the pixel 100. FIG. 12A illustrates a display operation during black display, and FIG. 12B illustrates a display operation during white display. 3 shows the display operation. FIG. 13A is a schematic waveform diagram showing signal voltages applied to the first, second, and third electrodes 2, 12, and 4 during a display operation. The signal voltage is shown, and frame 2 shows the signal voltage at the time of white display. Here, the potential of the first electrode is Vb, the potential of the second electrode is Va, and the potential of the third electrode is Vc.

  As shown in frame 1 of FIG. 12A and FIG. 13A, at the time of black display, first, a signal voltage corresponding to an image signal is applied between the first electrode 2 and the second electrode 12. You. Here, the switching element 20 switches the voltage application path so that the potential Vb of the first electrode 2 becomes negative and the potential Va of the second electrode 12 becomes positive. Here, the switching element 21 is switched so that no voltage is applied to the third electrode 4, and the potential Vc of the third electrode 4 is 0 (period A). By such voltage application, an electric field determined from the voltage of (Va−Vb) is applied between the two electrodes 2 and 12. Here, since (Va−Vb) is positive, an electric field is applied in a direction from the lower substrate 6 toward the upper substrate 16, and the first electrode 2 becomes a negative electrode and the second electrode 12 becomes a positive electrode. It becomes. Therefore, the negatively charged black particles 5B move toward the second electrode 12, which is the positive electrode, and adhere to the electrode surface. As a result, when observed from the upper substrate 16 side, the white particles 5A which are not charged and thus float in the space are covered by the black particles 5B.

  Here, when the black particles 5B move, the black particles 5B adhere to the partition walls 3 covered with the third electrode 4 due to the image force or the like. In addition, aggregation of the black particles 5B occurs around the partition walls 3. When the black particles 5B adhere to the partition walls 3 or aggregate around the partition walls 3, the number of the black particles 5B adhering to the second electrode 12 decreases, so that a gap is formed in the area covered with the black particles 5B, and a white color is formed from the gap. Particles 5A are observed. Therefore, in such a state, display unevenness occurs and the contrast is reduced. In order to prevent the occurrence of such display unevenness, the black particles 5B adhering to and aggregating around the partition 3 are separated from the partition 3 and moved to the second electrode 12 side by the following method.

  That is, after the signal voltage for moving the black particles 5 </ b> B is applied between the first and second electrodes 2 and 12 as described above, the third electrode 4 is replaced with a DC power supply instead of the first electrode 2. The switching element 21 is switched so as to be connected to the first electrode 2 (here, connected to the voltage application path of the first electrode 2). Thereby, a voltage is applied between the second electrode 12 and the third electrode 4, the potential Vb of the first electrode 2 becomes 0, the potential Va of the second electrode 12 becomes positive, and the third The potential Vc of the electrode 4 becomes negative. Therefore, an electric field determined from the voltage (Va−Vc) is applied between the two electrodes 12 and 4 by such voltage application. Here, since (Va−Vc) is positive, an electric field is applied in a direction from the third electrode 4 side to the second electrode 12 side, so that the second electrode 12 becomes the positive electrode and the third electrode 12 becomes the third electrode. The electrode 4 becomes a negative electrode (period B). By making the third electrode 4 disposed on the partition wall 3 the same polarity as the black particles 5B attached thereto, the black particles 5B attached to the third electrode 4 and agglomerated around the third electrode 4 are coulomb-bound. It repels the electrode 4 by force, and thus separates from the partition wall 3 and moves toward the second electrode 12. Then, the moved particles 5B adhere to the surface of the second electrode 12, cover the lower white particles 5A, and contribute to display. As described above, by applying a voltage between the second electrode 12 and the third electrode 4 to remove the black particles 5B from the partition walls 3, the black particles 5B are effectively used for display, and the black particles 5B are used. 5A can be prevented from being observed from the gap. Therefore, display unevenness can be suppressed, and high contrast can be achieved.

  After the voltage is applied between the second electrode 12 and the third electrode 4 as described above, the application of the voltage is stopped and the state is set to the non-voltage state. That is, the potentials Vb, Va, and Vc of the first, second, and third electrodes 2, 12, and 4 become 0 (period C). Even in such a non-voltage state, the adhesion of the black particles 5B to the second electrode 12 is maintained by an adhesion force such as a van der Waals force between particles and between the particles and the electrode 12, or an image force. Is done. Therefore, the black display is maintained.

Subsequently, the display is changed from black display to white display. When rewriting to white display,
13B, a signal voltage corresponding to an image signal is applied between the first electrode 2 and the second electrode 12. Here, contrary to the case of the above-described black display, voltage application is performed by the switching element 20 so that the potential Vb of the first electrode 2 becomes positive and the potential Va of the second electrode 12 becomes negative. The system is switched. Here, the switching element 21 is switched so that no voltage is applied to the third electrode 4, and the potential Vc of the third electrode 4 is 0 (period D). By such voltage application, an electric field determined from the voltage of (Va−Vb) is applied between the two electrodes 2 and 12. Here, since (Va−Vb) is negative, an electric field is applied in a direction from the upper substrate 16 side to the lower substrate 6 side, and the first electrode 2 becomes a positive electrode and the second electrode 12 becomes It becomes a negative electrode. Therefore, the negatively charged black particles 5B move toward the first electrode 2, which is the positive electrode, and sink below the white particles 5A and adhere to the electrode surface. Accordingly, when observed from the upper substrate 16 side, the black particles 5B are covered and hidden by the white particles 5A, and white display is performed.

  Here, at the time of the movement of the black particles 5B, the black particles 5B adhere to the partition walls 3 covered with the third electrode 4 due to a mirror image or the like, as in the case of the above-described black display. In addition, aggregation of the black particles 5B occurs around the partition walls 3. When the black particles 5B adhere to the partition wall 3 or aggregate around the partition walls 3, these black particles 5B are observed when observed from the upper substrate 16 side. Therefore, display unevenness occurs and the contrast is reduced. In order to prevent the occurrence of such display unevenness, the black particles 5B adhering to and aggregating around the partition walls 3 are separated from the partition walls 3 and moved to the first electrode 2 side by the following method.

  That is, after the signal voltage for moving the black particles 5 </ b> B is applied between the first and second electrodes 2 and 12 as described above, the third electrode 4 is replaced with the DC power supply 23 instead of the second electrode 12. (Here, the third electrode 4 is connected to the voltage application system of the second electrode). Thereby, a voltage is applied between the first electrode 2 and the third electrode 4, the potential Vb of the first electrode 2 becomes positive, the potential Va of the second electrode 12 becomes 0, and the third The potential Vc of the electrode 4 becomes negative (period E). Accordingly, an electric field determined from the voltage of (Vb−Vc) is applied between the two electrodes 2 and 4 by applying such a voltage. Here, since (Vb−Vc) is positive, an electric field is applied in a direction from the third electrode 4 side to the first electrode 2 side, so that the first electrode 2 becomes a positive electrode and the third The electrode 4 becomes a negative electrode. By making the third electrode 4 disposed on the partition wall 3 the same polarity as the black particles 5B attached thereto, the black particles 5B attached to the third electrode 4 and agglomerated around the third electrode 4 are coulomb-bound. It repels the electrode 4 by force, and thus peels off from the partition wall 3 and moves toward the first electrode 2. Then, the moved particles 5B enter under the white particles 5A and adhere to the surface of the first electrode 2. Thus, by applying a voltage between the first electrode 2 and the third electrode 4 to remove the black particles 5B from the partition walls 3, it is possible to prevent the black particles 5B from being observed. It becomes. Therefore, display unevenness can be suppressed, and high contrast can be achieved.

  After a voltage is applied between the first electrode 2 and the third electrode 4 as described above, the application of the voltage is stopped and a non-voltage state is set. That is, the potentials Vb, Va, and Vc of the first, second, and third electrodes 2, 12, and 4 become 0 (period F). Even in such a non-voltage state, the adhesion of the black particles 5B to the first electrode 2 is maintained by an adhesion force such as a van der Waals force between particles and between the particles and the electrode 2 or a mirror image force. Is done. Therefore, white display is maintained.

  In the display device of the present embodiment, the black display and the white display as described above are repeatedly performed according to the image signal, and the image is rewritten. In the display device according to the present embodiment, as in the first embodiment, it is possible to prevent the occurrence of display unevenness and decrease the contrast, to realize good display characteristics, and to reduce the operating voltage. Is achieved. Specifically, by removing the black particles 5 </ b> B from the partition walls 3, it is possible to perform a favorable display in which display unevenness is suppressed, and to reduce the operating voltage. Further, as described above, by applying an alternating voltage between the first and second electrodes 2 and 12 at the time of manufacturing the display device, the black and white particles 5B and 5A can be uniformly dispersed in the pixel 100. Therefore, display unevenness can be further reduced.

  Further, in this display device, a third electrode 4 is provided on the partition wall 3, and wiring is configured to connect the electrode 4 to a DC power supply 23 to which the first and second electrodes 2 and 12 are connected. Since it can be realized only by itself, it can be easily manufactured. Further, since the common DC power supply 23 is used, the space of the device is saved, and the voltage applied to the first and second electrodes 2 and 12 is also applied to the third electrode 4 by switching the voltage application system. Since the voltage can be applied, power saving of the device can be achieved.

  In the above description, as shown in FIG. 13A, a voltage applied for moving particles directly involved in display and a voltage applied for removing particles from the partition are DC voltages. Although a case has been described, as shown in FIG. 13B, a voltage configured by superimposing a rectangular wave AC voltage having a smaller amplitude than the DC voltage on the DC voltage is applied to the two applications. More preferably, it is applied to at least one of the following. When a voltage in which an AC voltage is superimposed is applied as described above, the particles adhered to the partition walls and the electrodes can be caused to minutely oscillate by the AC voltage, and with this movement, the adhesion of the particles can be weakened. Become. When a DC voltage is applied in such a state, it is possible to easily exfoliate the particles having weakened adhesion and move them to the opposite polarity. Therefore, the DC voltage applied to move the particles is reduced as compared with the DC voltage required when no AC voltage is superimposed. Therefore, it is possible to reduce the overall operating voltage. For example, in FIG. 13B, the signal voltage (period A, period D) applied to the first and second electrodes 2 and 12 at the time of black display includes a DC voltage component having an amplitude of 150 V, 30 to 70 V, For example, it may be composed of an AC voltage component of a rectangular wave having an amplitude of about 50V. In this case, the frequency of the AC voltage component is preferably 100 Hz or more. The optimum value of the frequency is determined by the ratio between the DC voltage component and the AC voltage component.

  As a modification of the present embodiment, an insulating layer may be formed between the first and second electrodes and the third electrode. As a method for forming the insulating layer, for example, a mixture of a polycarbonate resin (manufactured by Mitsubishi Gas Chemical Co., Ltd., bisphenol Z type polycarbonate Z200) at 10 wt% in tetrahydrofuran (THF) is spin-coated on the first and second electrodes. A film having a thickness of about 2 to 3 μm is formed. In the case where an insulating layer is formed, the third electrode may cover the entire upper and lower ends of the partition wall, and may be in direct contact with the insulating layer.

(Embodiment 10)
FIG. 14 is a cross-sectional view schematically showing a configuration of a pixel forming a display element of the display device according to Embodiment 10 of the present invention. As shown in FIG. 14, the pixel of this embodiment has the same configuration as that of the ninth embodiment, but differs from the first embodiment in the following points. The display operation according to the present embodiment is the same as the display operation according to the first embodiment shown in FIGS. 12A and 12B. The voltage applied during the display operation is as shown in FIG. 13A or 13B, as in the first embodiment.

  In the present embodiment, unlike Embodiment 9 in which black particles 5B are insulative, black particles 5B have conductivity. Therefore, as in the case of the second embodiment, as shown in FIG. 14, the electron transport layer 7 as a charge transport layer is formed on the first electrode 2 and the second electrode 12. As described above in the second embodiment, in the present embodiment in which the black particles 5B have conductivity, if the electron transporting layer 7 is not formed, the black particles 5B are kept in the first state while the alternating electric field is generated. And the reciprocating vibration motion is repeated between the second electrodes 2 and 12, and therefore, display becomes difficult. On the other hand, when an insulating layer is formed on the first and second electrodes 2 and 12 instead of the electron transporting layer 7, the black particles 5 </ b> B are charged (holes) from the first and second electrodes 2 and 12. However, in this case, only the charge (electrons) leaks from the black particles 5B, and the black particles 5B do not receive the charges from anywhere. Therefore, the black particles 5B cannot be moved, and the display cannot be performed.

  On the other hand, when the electron transport layer 7 is formed on the first and second electrodes 2 and 12, for example, at the time of black display shown in FIG. When attached to the second electrode 12, the electron transport layer 7 selectively blocks holes from passing and allows only electrons to pass. For this reason, it is possible to prevent the transfer of holes from the second electrode 12 to the black particles 5B, and to enable the transfer of electrons from the second electrode 12 to the black particles 5B. Therefore, in this case, the black particles 5B do not have the opposite polarity (positive polarity) to the original polarity (negative polarity), and even if the particles 5B are conductive, the charge amount is kept uniform. It remains negative and is therefore held on the side of the second electrode 12 which is the positive electrode. Also, in the white display shown in FIG. 13B, the electron transport layer 7 is formed on the first electrode 2, so that the positive electrode of the first electrode 2 becomes the same as in the black display. No holes are transferred to the black particles 5B, and only electrons are transferred to the black particles 5B. Therefore, the black particles 5 </ b> B have a uniform charge amount, remain negative, and are thus held on the first electrode 2 side, which is the positive electrode. Therefore, according to the configuration of the present embodiment in which the electron transport layer 7 is formed on the first and second electrodes 2 and 12, even if the black particles 5 </ b> B having conductivity, the reciprocating vibration of the black particles 5 </ b> B is caused. Exercise can be prevented, and stable and good display can be performed. In this embodiment, the same effects as those described in the ninth embodiment can be obtained.

Examples of the electron transporting material constituting the electron transporting layer 7 include benzoquinone, tetracyanoethylene, tetracyanoquinodimethane, fluorenone, xanthone, phenanthraquinone, phthalic anhydride, diphenoquinone, and the like. May be used.
(Embodiment 11)
FIG. 15 is a cross-sectional view schematically showing a configuration of a pixel forming a display element of the display device according to Embodiment 11 of the present invention. As shown in FIG. 15, the pixel of this embodiment has the same configuration as that of the ninth embodiment, but differs from the ninth embodiment in the following points. The display operation according to the present embodiment is the same as the display operation according to the ninth embodiment shown in FIGS. 12 (a) and 12 (b). The voltage applied during the display operation is as shown in FIG. 13A or FIG. 13B as in the ninth embodiment.

  In the present embodiment, unlike the ninth embodiment in which the partition 3 is made of an insulating material, the partition 13 is made of a conductive material. Here, the partition 13 is made of the same conductive material as the third electrode 4, and therefore, the partition 13 also serves as the third electrode 4. Such a partition 13 preferably has flexibility in terms of the bending strength of the display device. In the configuration in which the partition 13 has conductivity, if the partition 13 is in direct contact with the first and second electrodes 2 and 12, conduction between the two electrodes will occur and an electric field will not be generated. , 12 to ensure insulation.

  In the present embodiment having the above configuration, the same effects as those described in the ninth embodiment can be obtained. Further, here, the partition and the third electrode are formed integrally, so that the manufacture becomes easy.

(Embodiment 12)
FIG. 16 is a cross-sectional view schematically showing a configuration and a display operation of a pixel constituting a display element of a display device according to Embodiment 12 of the present invention, and FIG. FIG. 16B shows the case of white display. In the present embodiment, as shown below, instead of applying a voltage to the electrode 4 provided on the partition 3 to remove the black particles 5B attached to the partition 3, it is necessary to move particles that contribute to display. A voltage is applied to the third electrode 4.

  As shown in FIGS. 16A and 16B, in the present embodiment, a white plate is used for the first substrate 30 of the lower substrate 6 '. In addition, the second electrode is not provided on the upper substrate side. Here, the alternating electric field is generated between the electrode 4 provided on the partition 3 and the electrode 2 on the lower substrate 6 ′. Given. Further, in this case, only one kind of colored particles, that is, only black particles 5B is sealed in the space 17.

  As shown in FIG. 16A, at the time of black display, a signal voltage according to an image signal is applied between the electrode 2 on the lower substrate 6 ′ and the electrode 4 provided on the partition 3, Thereby, the electrode 2 becomes a positive electrode and the electrode 4 becomes a negative electrode. Therefore, the negatively charged black particles 5B move toward the electrode 2, which is the positive electrode, and cover the surface thereof. When the surface of the electrode 2 is covered with the black particles 5B, the white plate (first substrate) 30 disposed below the electrode 2 becomes invisible. Therefore, when observed from the upper substrate side, the color of the white plate 30 is not observed, and black display based on the black particles 5B is performed.

  On the other hand, at the time of white display, as shown in FIG. 16B, a voltage opposite to that at the time of black display is applied between the electrodes 2 and 4, and the electrode 2 becomes a negative electrode and the electrode 4 becomes a positive electrode. Thereby, the black particles 5B move toward the electrode 4 and cover the surface of the electrode 4. Then, as the black particles 5B move, the particles 5B attached to the white plate 30 are removed, and the white plate 30 is exposed. Therefore, when observed from the upper substrate side, the color of the white plate 30 is mainly observed through the transparent electrode 2 and white display is performed.

  Here, the voltage applied between the electrodes 2 and 4 may be a DC voltage as shown in FIG. 13A of the ninth embodiment, but as described above in the ninth embodiment. From the viewpoint of reducing the operating voltage, it is preferable that the voltage is a voltage configured by superimposing a rectangular wave AC voltage on a DC voltage as shown in FIG. Further, at the time of manufacturing the display element of the present embodiment, as in the case of the ninth embodiment, after enclosing the black particles 5B in the space 17, an alternating voltage is applied between the electrode 2 and the electrode 4, Preferably, an electric field is generated. This makes it possible to uniformly disperse black particles 5B in space 17 as in the case of the ninth embodiment.

  In this embodiment, the same effects as those described in the ninth embodiment can be obtained. Here, since the particles moving in the space 17 are one type of the black particles 5B, the particles collide with each other during the movement as in the case where a plurality of types of particles are used, or the particles having the opposite polarity are used. Do not interfere with each other. For this reason, the black particles 5B can move quickly. Therefore, in the display device, the response speed is improved and the operating voltage is reduced.

  In the above description, the case where the first substrate 30 on the lower substrate 6 ′ side is colored is described, but the electrode 2 may be colored instead of the first substrate 30, or A colored layer may be separately provided.

  In the above embodiments 9 to 11, after applying a voltage between the first and second electrodes for the main movement of the particles contributing to the display, the second and the second for removing the particles attached to the partition walls. Although a voltage is applied between the third electrodes, a voltage may be applied between the first and second electrodes after a voltage is previously applied between the first and third electrodes, or Voltage application between the first and second electrodes and voltage application to the first and third electrodes may be performed simultaneously. That is, the voltage application for the main movement of the particles and the voltage application for the removal of the particles from the partition walls may be performed at a shifted timing or may be performed simultaneously. For example, if a voltage is applied between the first and third electrodes in advance, it is possible to prevent the particles from adhering to the partition walls, so that the particles once adhered to the partition walls are separated and removed, The effect can be obtained at a low voltage. In the above embodiment, the case where the voltage applied for the main movement of the particles and the voltage applied for the removal of the particles from the partition walls have the same amplitude has been described. The two applied voltages may be of different magnitudes. The application time of the two voltages may be the same or different.

  In the above-described ninth to twelfth embodiments, the case where the pixel has a hexagonal shape has been described. However, the shape of the pixel is not limited to this, and may have a normal rectangular shape.

  Further, in the above-described ninth to twelfth embodiments, the case has been described where the first electrode and the second electrode are opposed to each other with a space therebetween, and a vertical electric field is generated. As described above, a configuration in which the first and second electrodes are arranged on the same substrate side to generate a lateral electric field may be employed.

  In Embodiments 9 to 11 described above, charging is not limited to black particles 5B, and white particles 5A may be charged. In this case, due to the applied electric field, both particles move in the space according to the polarity, and the color of the particles attached to the second electrode disposed on the upper substrate side serving as the observation side becomes the display color. . Therefore, here, the third electrode provided on the partition has a polarity opposite to that of the second electrode on the display side in order to prevent particles giving the target display color from adhering to the partition. Is applied.

  Further, in the above-described ninth to eleventh embodiments, the case where the third electrode is connected to the same power supply as the first and second electrodes has been described, but the third electrode is configured to be connected to another power supply. May be. Further, the third electrode does not necessarily need to be connected to the first electrode or the second electrode.

  Further, in the above-described Embodiments 9 to 12, the case where the particles move in the gas phase has been described. However, the present invention relates to a display device in which the particles move in the liquid phase, such as an electrophoretic display. It is applicable also in.

  In the ninth to twelfth embodiments, the passive matrix drive type display device has been described. However, the active matrix drive type may be used. The active matrix drive type is suitable for a display requiring a high-speed response such as a moving image. In addition, the passive matrix drive type is suitable when a high-speed response such as a moving image is not required, for example, when displaying a newspaper or the like on a paper display. Here, in a conventional electrophoretic display in which particles are moved in a liquid phase, since the particles move due to a crosstalk voltage or the like, it is difficult to use a passive matrix driving type. With the configuration in which the particles are moved, since the threshold voltage when moving the particles is high, the movement due to the crosstalk voltage or the like can be suppressed, so that a passive matrix drive type can be realized. Further, in the case of the passive matrix drive type, it is not necessary to form a thin film transistor (TFT) as a switching element as in the case of the active matrix drive type, so that manufacturing cost can be reduced, lead time can be reduced, yield can be improved, and the like. .

  Further, the chargeability of the particles contributing to the display is not limited to Embodiments 1 to 12 described above. For example, in the above ninth to twelfth embodiments, the case where the black particles 5B are negatively charged has been described, but the black particles 5B may be positively charged. In this case, a voltage having a polarity opposite to the above-described operation voltage is applied to each of the electrodes 2, 12, and 4, and the potential of each of the electrodes 2, 12, and 4 becomes opposite to that in the above-described case, whereby the above-described operation is performed. Be done. Here, when the black particles 5B are positively charged and conductive, it is necessary to provide a hole transport layer on the surface of the electrode to which the image signal voltage is applied. By providing the hole transport layer, the transfer of electrons from the electrode to the black particles 5B is prevented and holes are transferred, so that the positive charge of the black particles 5B can be held.

  Further, in the above first to twelfth embodiments, the case where black and white display is performed has been described, but the present invention is also applicable to color display. For example, the color display may be realized by providing a color filter on the upper substrate side. Furthermore, by using two or more kinds of colored particles having different moving characteristics for each color and moving the particles by variously changing the direction of the electric field, it is possible to realize a multi-color display according to the number of kinds of the colored particles. Is also possible. In the twelfth embodiment, it is also possible to perform multicolor display by applying different colors to the colored substrate on the lower substrate side.

  In the above first to twelfth embodiments, the case where the colored particles are porous and are composite particles has been described. However, the configuration of the particles is not limited to this, and the case where ordinary particles are used is described. However, the above effects can be obtained. Further, as described above, it is preferable to reduce the operating voltage if the size of the particles is substantially the same, but it is not necessarily required to be the same.

  In the first to twelfth embodiments, the electric field applied between the first and second electrodes, the electric field applied between the first and third electrodes, and the electric field applied between the second and third electrodes Although the case where three electric field distributions of the applied electric field are generated has been described, an electric field can be generated by a combination of the electric fields. In addition, for example, a plurality of electric fields can be further generated by separately providing the third electrode or by separately providing the first and / or second electrodes on the substrate in the pixel. It becomes possible.

  INDUSTRIAL APPLICABILITY The display device according to the present invention is effective as a display device in which the occurrence of display unevenness and a decrease in contrast are prevented and the operating voltage is reduced. This is effective as an electronic paper that can be used as a substitute for the electronic paper.

FIG. 1 is a schematic diagram illustrating a configuration of a display device according to a first embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a configuration and a display operation of a pixel which is a structural unit of a display element of the display device in FIG. FIG. 2B shows an operation in black display, and FIG. 2C shows an operation in white display. FIG. 9 is a schematic cross-sectional view illustrating a configuration of a pixel that is a structural unit of a display element according to Embodiment 2 of the present invention. FIG. 9 is a schematic cross-sectional view illustrating a configuration of a pixel that is a structural unit of a display element according to Embodiment 3 of the present invention. FIG. 13 is a schematic cross-sectional view illustrating a configuration of a pixel that is a structural unit of a display element according to Embodiment 4 of the present invention. FIG. 14 is a schematic cross-sectional view illustrating a configuration of a pixel that is a structural unit of a display element according to Embodiment 5 of the present invention. FIG. 13 is a schematic cross-sectional view illustrating a configuration of a pixel that is a structural unit of a display element according to Embodiment 6 of the present invention. FIG. 14 is a schematic cross-sectional view illustrating a configuration of a pixel that is a structural unit of a display element according to Embodiment 7 of the present invention. FIG. 21 is a schematic cross-sectional view illustrating a configuration of a pixel that is a structural unit of a display element according to a modification of Embodiment 7 of the present invention. FIG. 15 is a schematic cross-sectional view illustrating a configuration of a pixel that is a structural unit of a display element according to Embodiment 8 of the present invention. FIG. 11A is a schematic cross-sectional view illustrating a configuration of a pixel that is a structural unit of a display element according to Embodiment 9 of the present invention. FIG. () Shows a cross section parallel to the display element. 12A and 12B are schematic cross-sectional views illustrating a display operation of the pixel in FIG. 11, wherein FIG. 12A illustrates an operation during black display, and FIG. 12B illustrates an operation during white display. 13A and 13B are diagrams schematically illustrating applied voltages during the display operation of the pixel in FIG. 11, FIG. 13A illustrates a case where only a DC voltage is applied, and FIG. Are superimposed. FIG. 21 is a schematic cross-sectional view showing a configuration of a pixel forming a display element of a display device according to Embodiment 10 of the present invention. FIG. 21 is a schematic cross-sectional view showing a configuration of a pixel forming a display element of a display device according to Embodiment 11 of the present invention. FIG. 21 is a schematic cross-sectional view showing a configuration of a pixel forming a display element of a display device according to Embodiment 12 of the present invention. It is a typical sectional view showing composition of a pixel which constitutes a display element of a conventional display.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1, 11 Transparent resin substrate 2 1st electrode 3 Partition wall 4 3rd electrode 4A, 4B Vibration generation electrode 5A, 5B Colored particle 5C Electric field arrangement particle 6, 6 'Lower substrate 10 Insulating layer 12 Second electrode 15 Insulating layer 16 Upper substrate 17 Space 20 Piezoelectric body 21 Vibration generator 24 Insulating solvent 25 Capsule
100 pixels

Claims (22)

An electrode is formed on at least one surface, and at least one of the substrates is opposed to each other and is translucent.A spacer that holds a space of a desired width formed between the substrates, and a space between the substrates. And at least one kind of charged particle group enclosed therein, wherein the particle group moves in the space between the substrates by an electric field given by an image signal voltage applied to the electrode of the substrate, and the image signal voltage is increased. A display device that displays an image corresponding to
A display device, wherein a vibration generating unit is provided facing the space in which the particle group moves.   The display device according to claim 1, wherein the vibration generating unit is provided on at least one of the substrates on a space side on which the particle group moves.   The display device according to claim 1, wherein the first electrode and the second electrode to which the image signal voltage is applied are formed on one of the substrates.   The first electrode to which the image signal voltage is applied is formed on one of the pair of substrates, and the second electrode to which the image signal voltage is applied is formed on the other substrate of the pair of substrates. The display device according to 1.   The vibration generator includes an electrode and a vibration generator, and vibration is generated in the vibration generator by an electric field formed by the electrode, and the electrode provided on the substrate also functions as an electrode of the vibration generator. The display device according to claim 1.   The display device according to claim 1, wherein the vibration generator includes an electrode and a vibration generator, and the vibration generator generates vibration by an electric field formed by the electrode, and the vibration generator configures the spacer.   7. The display device according to claim 6, wherein an insulating medium is disposed between the electrode of the vibration generating unit and the electrode provided on the substrate, so that the vibration generating unit and the electrode of the substrate are insulated.   The display device according to claim 1, wherein a space in which the particle group moves is a gas phase space.   The display device according to claim 1, wherein the space in which the particle group moves is a liquid space filled with an insulating solvent.   The display device according to claim 9, wherein a capsule in which the particle group and the insulating solvent are sealed is disposed in the gap between the substrates.   The display device according to claim 9, wherein the particle groups are arranged by an electric field applied between the electrodes of the substrate according to the image signal voltage.   The display device according to claim 11, wherein the plurality of particles forming the particle group are electric field array particles arranged along the electric field.   The display device according to claim 1, wherein the particle group is colored in at least one color.   The display device according to claim 1, wherein the vibration generator is formed of a piezoelectric body.   The display device according to claim 1, wherein the vibration generating unit also serves as at least one of the substrates. The display of the display device includes at least first and second display states,
In the first display state, a first image signal voltage is applied to the electrode provided on the substrate to form a first electric field,
In the second display state, a second image signal voltage is applied to the electrode provided on the substrate to form a second electric field having a different direction from the first electric field,
When rewriting from the first display state to the second display state, the operation of applying a high-frequency rectangular wave voltage or a high-frequency sine wave voltage to the vibration generator, and the operation of applying the high-frequency sine wave voltage to the electrode provided on the substrate The display device according to claim 1, wherein the operation of applying a second image signal voltage is performed.   17. The display device according to claim 16, wherein the operation of applying the high-frequency rectangular wave voltage or the high-frequency sine wave voltage and the operation of applying the image signal voltage are performed simultaneously.   17. The display device according to claim 16, wherein the operation of applying the high-frequency rectangular wave voltage or the high-frequency sine wave voltage and the operation of applying the image signal voltage are performed at different timings.   The display device according to claim 2, wherein at least one of the charged colored particles is a porous particle.   At least one of the particles has a core particle and a diameter of about 1/1000 to 1/100 of the diameter of the core particle, and the core particle covers the surface of the core particle. The display device according to claim 1, wherein the display device is a composite particle composed of fine particles fixed to the substrate.   The display device according to claim 1, wherein a water-repellent treatment is applied to at least a part of a surface of the particles or a surface of a member to which the particles adhere. An electrode is formed on at least one surface, and at least one of the substrates is opposed to each other and is translucent.A spacer for holding a gap having a desired width formed between the substrates, It comprises at least one kind of charged charged particle group, and a vibration generating unit provided facing a space in which the particle group moves, and the electric field given by an image signal voltage applied to the electrode, A method for manufacturing a display device in which an image corresponding to the image signal voltage is displayed by moving the particle group in a gap between substrates,
A method of manufacturing a display device, comprising: generating vibration in the vibration generating section after sealing the particle group in a gap between the substrates.

Images