JP4899407B2 - Image display medium and image display device - Google Patents

Description

  According to the present invention, an image in which an image is displayed by enclosing a group of positively or negatively charged particles between a transparent front substrate and a rear substrate opposed to the front substrate and applying an electric field. The present invention relates to a display medium and an image display device.

  Conventionally, for example, an image display medium and an image display apparatus described in Patent Document 1 are known as an image display medium and an image display apparatus that perform image display by moving colored particles by an electric field.

Patent Document 1 solves the problem that the density contrast of the image display is unstable together with the problem that the set drive voltage is high in the following features. That is, the image display medium described in Patent Document 1 includes a pair of substrates arranged opposite to each other, and a particle group including two or more kinds of particles having different colors enclosed in a gap between the pair of substrates. The two or more kinds of particles have a property that at least one of them can be positively charged and at least one of the other particles can be negatively charged, and the particles that can be positively and negatively charged have different colors. The shape factor of both the positively and negatively charged particles in the image display medium is shape factor = {(L ² / S) / 4π} × 100 (where L is the particle area and L is the surrounding area) 100 <shape factor ≦ 140.

According to this configuration, density contrast can be obtained between the image portion made up of the positively charged particle group and the image portion made up of the negatively charged particle group due to the different colors. In addition, by setting the shape factor within the above specific range, an appropriate space is created between the particles, the fluidity of the particle group is improved, and the triboelectric charge distribution of both the positively and negatively charged particles is sharpened. can do. On the other hand, the adhesion force between the particle substrate due to the contact between the particles having opposite charging polarities and the substrate is also weakened because an appropriate space exists between the positive and negative particles. For this reason, even if rewriting is repeated over a long period of time, the change in image density is small, the change in density uniformity is small, stable density contrast image display is possible, and the drive voltage required for image display can be reduced. It becomes.
JP 2003-57688 A

  However, at present, there is a demand for further performance improvement, and without affecting the image quality of the displayed image, improvements in image quality maintenance such as image density stability and uniformity, density contrast stability, and dot defect prevention. There is a need for an improvement to further expand the degree of freedom of the means for applying the drive voltage for driving the image display medium.

  In consideration of the above-described facts, the present invention provides an image display medium and an image display device that can improve the image quality maintainability without affecting the image quality of the display image and can improve the drive voltage for driving the image display medium. For the purpose.

According to a first aspect of the present invention, there is provided a transparent front substrate, a rear substrate disposed opposite to the front substrate, a partition member that partitions a plurality of cells between the front substrate and the rear substrate, and the plurality of cells. At least two different surface colors or concentrations, which are enclosed in a cell and are charged positively or negatively in the cell in the direction of the surface substrate or the back substrate depending on the electric field applied between the substrates. A large particle group having a large particle group, and a small particle group which is mixed in the large particle group and has a relatively small diameter and does not contribute to the color or density in the image display, the surface substrate surface or the back substrate surface An image display medium composed of small particle groups smaller than that of the large particle group, and a surface electrode and a back electrode constituting the image display medium by applying a voltage. Between A pair of electrodes for applying the electric field, and a voltage application means for applying the voltage, at least two different surface color display of each cell of the image display medium prior to writing the image to the image display medium Alternatively, in the case of refreshing uniformly with any of the large- diameter particles having a concentration, a first applied voltage for moving only the particles of the small-diameter particle group toward the front substrate or the rear substrate is applied to the pair of electrodes. And then applying a second applied voltage having a larger absolute value than the first applied voltage for moving the particles of the large particle group toward the front substrate or the rear substrate. And a control means for controlling the voltage application means so as to be applied to the power supply.

  Thus, in the first invention, the small diameter particle group that does not contribute to the color or density in the image display mixed with the particle group does not affect the image quality of the display image, and the electric field applied between the substrates. Accordingly, the inside of the cell is moved in the direction toward the front substrate or the rear substrate prior to the large particle group. Large particle groups can easily move so as to follow this movement.

  The first aspect of the invention can improve the image quality maintainability without affecting the image quality of the display image, and can improve the drive voltage for driving the image display medium.

In the first invention, the particle group is characterized in that the small particle group has a smaller mass than the large particle group.

  Furthermore, in the first invention, the large diameter particle group and the small diameter particle group are the same between the large diameter particle group and the small diameter particle group and the surface substrate surface or the back substrate surface in the same electric field space. It is characterized in that the adhesive force acting between them is different.

The small particle group has a smaller particle size and a smaller mass than the large particle group. And in the space of the same electric field, the adhesion force acting between the surface substrate surface or the back substrate surface is different between the small particle group and the large particle group. For this reason, the voltage which produces an electric field when a small particle group starts a movement is small. The effect of the first invention is due to the presence of such a small particle group that is easy to start moving.

According to a second aspect of the present invention, there is provided a transparent front substrate, a rear substrate opposed to the front substrate, a partition member that partitions a plurality of cells between the front substrate and the rear substrate, and the plurality of cells. At least two different surface colors or concentrations, which are enclosed in a cell and are charged positively or negatively in the cell in the direction of the surface substrate or the back substrate depending on the electric field applied between the substrates. A large-diameter particle group , and a small-diameter particle group that is mixed in the large-diameter particle group and has a relatively small diameter and does not contribute to color or density in the image display , the surface substrate surface or An image display medium composed of a small particle group having an adhesion force acting between the rear substrate surface and that of the large particle group, and a surface constituting the image display medium by applying a voltage. Electrodes and spine Between the electrodes, and a pair of electrodes for applying the electric field, and a voltage application means for applying the voltage, the magnetizable means capable of moving the surface on the substrate in a state in which a magnetized, the magnetization means magnetic Control is performed so as to move on the surface substrate in a tinged state, and then an applied voltage for moving the particles of the large particle group toward the surface substrate or the back substrate is applied to the pair of electrodes. Control means for controlling the voltage application means .

  Since the second invention includes the image display medium that operates in the same manner as the first invention, the image quality maintenance can be improved without affecting the image quality of the display image as in the first invention, and the image can be improved. The driving voltage for driving the display medium can be improved.

  As described above, the present invention provides an image display medium and an image display apparatus that can improve image quality maintainability without affecting the image quality of the display image and can improve the drive voltage for driving the image display medium. It has an excellent effect.

(First embodiment)
FIG. 1 shows an image display apparatus according to a first embodiment of the present invention.

  The image display device 10 is roughly configured by an image display medium 12 that displays an image, and a voltage application unit 30 that applies a voltage to the image display medium 12 to apply an electric field.

  First, details of the image display medium 12 will be described. The image display medium 12 mainly includes a partition member 26 that partitions the display substrate 14 having the transparent electrode 16 and the dielectric layer 18 and the back substrate 20 having the electrode 22 and the dielectric layer 24.

  The image display medium 12 is configured such that display contents can be seen from the direction of the display substrate 14, and the back substrate 20 disposed so as to face the display substrate 14, and between the display substrate 14 and the back substrate 20. Between the display substrate 14 and the back substrate 20, and a partition member 26 that forms a plurality of cells by partitioning in a direction parallel to the display substrate 14 and the back substrate 20. It is configured with a small interval.

  White particles 28A and black particles 28B as large diameter particles mainly contributing to image display are enclosed in the minute intervals. Further, small particles 28C having an action of promoting the smoothness of movement of the white particles 28A and the black particles 28B at the intervals are mainly enclosed in the minute space (the small particle 28C will be described in detail later). ).

  The display substrate 14 is transparent and is a transparent belt-like transparent electrode 16 and a member that protects the transparent electrode 16 and stabilizes the charging characteristics of the white particles 28A, the black particles 28B, and the small-diameter particles 28C. The dielectric layer 18 thus formed is laminated. The transparency in the first embodiment is preferably as high as possible, but may be translucent or colored and transparent.

  The transparent electrode 16 is formed using a transparent conductive material, or formed thin enough to be translucent.

  Moreover, although the transparent electrode 16 of 1st Embodiment is set as the structure provided in one cell, in order to raise the resolution, you may provide multiple pieces.

  The dielectric layer 18 has transparency. In addition, the dielectric layer 18 is provided so that the white particles 28A, the black particles 28B, and the small-diameter particles 28C attached to the display substrate 14 are kept charged even after the voltage application to the transparent electrode 16 is finished. In addition, an insulating or semiconductive material is used.

  The dielectric layer 18 can contain a charge transport substance in the insulating material according to the charging characteristics of the white particles 28A, the black particles 28B, and the small diameter particles 28C to be encapsulated. By including the charge transporting substance, the white particles 28A, the black particles 28B, and the small diameter particles 28C are improved in chargeability, and the white particles 28A, the black particles 28B, and the small diameter particles 28C are stabilized in the charge amount. Obtainable.

  On one side of the back substrate 20, a strip-like electrode 22 disposed in parallel with a predetermined interval in the direction perpendicular to the paper surface, and a dielectric layer 24 that protects the electrode 22 and stabilizes the charging characteristics of the white particles 28A. And is configured. In addition, the dielectric layer 24 is provided so that the white particles 28A, the black particles 28B, and the small-diameter particles 28C attached to the back substrate 20 side are kept charged even after the voltage application to the electrode 22 is finished. As with the dielectric layer 18, an insulating or semiconductive material is used.

  Similar to the transparent electrode 16, a plurality of the electrodes 22 may be provided instead of one per cell.

  The dielectric layer 24 may be a colored layer, for example, a layer formed by applying a coloring material to the back substrate 20 or attaching a film. In this case, three colors can be displayed together with the two colors of the white particles 28A and the black particles 28B. In order to display the color of the back substrate 20 on the screen, by applying an alternating voltage of a predetermined frequency between the electrodes corresponding to the target cell, particles existing in the target cell are retreated to the periphery, and the white color is formed on the colored layer. The particles 28 </ b> A and the black particles 28 </ b> B do not exist so that the color of the back substrate 20 can be seen through the display substrate 14.

  In the partition member 26 formed on the dielectric layer 24 of the back substrate 20, the end surface of the partition member 26 formed on the dielectric layer 24 and the dielectric layer 18 on the display substrate 14 side are joined by an adhesive. The

  In FIG. 1, only one cell is shown, but in reality, the transparent electrode 16 and the electrode 22 are arranged so as to intersect each other, and a large number of cells are arranged in a two-dimensional array. A voltage is applied to the cell between the transparent electrode 16 and the electrode 22 by matrix driving.

  Next, details of the voltage application unit 30 will be described. The voltage application unit 30 includes an alternating voltage generation unit (not shown) that generates an alternating voltage for initialization, and a DC voltage generation unit that generates a DC voltage for performing two-color display using the white particles 28A and the black particles 28B ( A control device 34 connected to the power supply device 32, an electrode drive unit 36 that drives the electrode 22, and a transparent electrode drive unit 38 that drives the transparent electrode 16. The control device 34 is operated by electric power supplied from the power supply device 32. Further, the power supply device 32 and the control device 34 are connected to an electrode driving unit 36 and a transparent electrode driving unit 38.

  The alternating voltage generation unit included in the power supply device 32 is used to attach an initial state, for example, the white particles 28A to one substrate side and the black particles 28B to the other substrate side, and has a predetermined frequency (for example, , 200 Hz to 10 kHz) of alternating voltage (for example, ± 100 V to 300 V) is applied to all the cells.

  On the other hand, the DC voltage generator included in the power supply device 32 outputs a DC voltage (for example, + 140V to + 210V or −140V to −210V) and performs two-color display using the white particles 28A and the black particles 28B. It has come to be used.

  The control device 34 includes, for example, a CPU, a ROM, a RAM, an input / output interface (I / F) circuit, and the like (not shown). The CPU selects and operates one of the alternating voltage generator and the DC voltage generator in accordance with a control program stored in the ROM, and based on the image data from the image storage unit (not shown), A voltage is applied to the electrode 22.

  Incidentally, in order to improve the contrast of the display image on the image display medium 12, the display density of each cell of the image display medium 12 is uniformly set to white or black prior to image writing (hereinafter referred to as “refresh”). ")" Is confirmed to be effective.

  As shown in FIG. 2, the power supply device 32 is provided with a refresh power supply 40 and a drive power supply 42.

By the way , even when the voltage applied between the electrode 22 and the transparent electrode 16 is relatively large, the density (display image contrast) of the image display medium 12 slightly changes as the applied voltage increases. It has characteristics. On the other hand, when the display of the image display medium 12 is refreshed before the image is written to the image display medium 12 (the display density of all the cells is set to white or dark black having a lower density), the contrast of the display image is improved. Can be achieved. At this time, the contrast of the display image is improved by applying a higher voltage. Therefore, in the first embodiment, the power supply device 32 is provided with the refresh power supply 40.

  The refresh power supply 40 can employ, for example, the configuration shown in FIG.

In the configuration shown in FIG. 3, DC power sources 62A and 62B are provided, and the minus terminal of the DC power source 62A and the plus terminal of the DC power source 62B are connected to each other and grounded. Instead of this, a reference potential V _CL described later may be maintained. The DC power supplies 62A and 62B are connected in parallel with a large-capacity capacitor (not shown) for stabilizing the output potential. Furthermore, the plus terminal of the DC power supply 62A is connected to one of the two input ends of the switching unit 64, and the other input end is connected to the minus terminal of the DC power supply 62B.

  The switching unit 64 is configured by a semiconductor switching element (for example, MOSFET) or the like, and is configured to selectively output one of two signals (potentials) input via two input terminals. ing. The switching unit 64 is connected to the control device 34 (not shown), and is controlled so that the output signal (potential) is switched at a constant cycle. Therefore, the refresh power supply 40 outputs a potential (see also the waveform shown in FIG. 3) whose polarity is switched at a constant cycle as a refresh output.

  As a result, as in the refresh period shown as an example in FIG. 4, at each intersection position (each cell position) between the transparent electrode 16 and the electrode 22 of the image display medium 12, a fixed period is provided between the transparent electrode 16 and the electrode 22. Thus, a refresh voltage whose polarity is switched is applied, and white particles 28A and black particles 28B enclosed in a gap between the display substrate 14 side and the back substrate 20 side by an alternating electric field generated by the application of the refresh voltage. Moves greatly, and the display density of the entire surface of the image display medium 12 is switched from dark black to lower white density to dark black.

  A refresh drive sequence performed during the refresh period is determined in advance.

On the other hand, the driving power source 42 includes a first power source unit 42A for generating a potential to be supplied to the electrode driving unit 36 and a second power source unit 42B for generating a potential to be supplied to the transparent electrode driving unit 38. It is configured. The first power supply unit 42A outputs a high voltage output by generating a reference potential generation unit 44 that generates the reference potential V _CL of the electrode 22 and a potential difference (V _CH −V _CL ) using the reference potential V _CL as a ground potential. A high voltage output unit 48 and a signal power output unit 50 that outputs a potential (V _CL + TTL) as a signal power output by generating a potential difference TTL with the reference potential V _CL as a ground potential. Note that a large-capacity capacitor for stabilizing the output potential is also connected in parallel to the high-voltage output unit 48.

With the above configuration, the first power supply unit 42A outputs a high voltage output (potential V _CH ), a GND output (reference potential V _CL ), and a signal power supply output (potential (V _CL + TTL)). The first power supply unit 42A is connected to the electrode drive unit 36, and the GND output and the signal power supply output among the outputs are directly supplied to the electrode drive unit 36. The high voltage output of the first power supply unit 42A is input to the switching unit 60, and the refresh output of the refresh power supply 40 is also input to the switching unit 60.

  The switching unit 60 is also composed of a semiconductor switching element (eg, MOSFET) or the like, and is configured to selectively output one of the input high-voltage output of the first power supply unit 42A and the refresh output of the refresh power supply 40. Has been. The switching unit 60 is connected to the control device 34, and the control device 34 controls which of the high voltage output and the refresh output is output. The output end of the switching unit 60 is connected to the electrode driving unit 36, and the high voltage output or the refresh output output from the switching unit 60 is supplied to the electrode driving unit 36.

The second power supply unit 42B generates a reference voltage V _RL of the transparent electrode 16 and a high voltage output by generating a potential difference ( V _RH −V _RL ) using the reference potential V _RL as a ground potential. and a signal power output unit 54 for outputting a high-voltage output section 52, the potential of the reference potential V _RL as the signal power output by generating a potential difference TTL as a ground potential (V _RL + TTL) for outputting a voltage V _RH as ing. The second power source 42B is connected to the transparent electrode driver 38, and the high voltage output (potential V _RH ), GND output (reference potential V _RL ), and signal power source output (potential ( V _RL + TTL)) are transparent electrode driver. 38.

On the other hand, the electrode drive unit 36 includes the same number of switching elements 56 as the number of electrodes 22 provided in the image display medium 12, and the GND output (reference potential V _CL ) from the first power supply unit 42 </ b> A and switching The high voltage output from the unit 60 or the refresh output is supplied to each switching element 56.

  In FIG. 2, the switching element 56 is schematically shown as a switch. However, the switching element 56 is actually composed of a semiconductor switching element (for example, a MOSFET).

The individual switching elements 56 operate using the signal power supply output supplied from the first power supply unit 42A as the power supply and the GND output (reference potential V _CL ) as the reference potential, and in the on state, the high-voltage output (or refresh output). In the OFF state, the GND output (reference potential V _CL ) is output. A control signal supplied from the control device 34 is also input to each switching element 56, and on / off of each switching element 56 is controlled by the control device 34. .

As shown in FIG. 1, the electrode driving unit 36 is attached to the back substrate 20 side of the image display medium 12, and the individual switching elements 56 of the electrode driving unit 36 are individually formed on the back substrate 20 side. The electrode 22 is connected. Therefore, the potential of each electrode 22 of the image display medium 12 is a potential V _CH corresponding to a high voltage output, a potential corresponding to a refresh output, or a reference potential V according to the on / off state of the connected switching element 56. It will be switched to _CL .

Further, the transparent electrode driving unit 38 includes the same number of switching elements 58 as the number of transparent electrodes 16 provided in the image display medium 12, and the high-voltage output (potential V _RH ) and the GND from the second power supply unit 42B. The output (reference potential V _RL ) is supplied to each switching element 58. The switching element 58 is also actually composed of a semiconductor element (for example, a MOSFET). The individual switching elements 58 operate using the signal power supply output supplied from the second power supply unit 42B as the power supply, the GND output (reference potential V _RL ) as the reference potential, and the high voltage output (potential V _RH ) in the on state. In the OFF state, the GND output (reference potential V _RL ) is output. The individual switching elements 58 are also supplied with control signals supplied from the control device 34, and the on / off states of the individual switching elements 58 are controlled by the control device 34.

As shown in FIG. 1, the transparent electrode driver 38 is attached to the display substrate 14 side of the image display medium 12, and each switching element 58 of the transparent electrode driver 38 is formed on the display substrate 14 side. The individual transparent electrodes 16 are connected. Therefore, the potential of each transparent electrode 16 of the image display medium 12 is switched to the potential V _RL or the reference potential V _RH depending on the on / off state of the connected switching element 58.

Since the potential of the electrode 22 is switched to the potential V _CH or the reference potential V _CL and the potential of the transparent electrode 16 is switched to the potential V _RL or the reference potential V _RH , the image display medium 12 is driven by a simple matrix method. One of the voltages V1 to V4 shown in the following Table 1 is applied between the electrode 22 and the transparent electrode 16 when the image display medium 12 is driven.

  The movement of the white particles 28A and the black particles 28B occurs when the voltage V1 is applied. Thus, the display density of the cell changes when the voltage V1 is applied.

On the other hand, the voltages V2 to V4 shown in Table 1 (that is, other than the voltage V1) need to have a magnitude that does not cause the movement of the white particles 28A and the black particles 28B. Therefore, when the maximum value of the holding voltage in the image display medium 12 is X,
| V2 | <X, | V3 | <X, | V4 | <X
Therefore, | V _CH −V _RH | <X, | V _CL −V _RL | <X, | V _CL −V _RH | <X
It becomes. Also,
| V2 | = (V _CH −V _CL ) − (V _RH −V _CL ) <X
−X <(V _CH −V _CL ) − (V _RH −V _CL ) <X
Therefore,
-2X <(V _CH -V _CL ) <2X
Similarly _{-2X <(V RH -V RL)} <2X
Therefore, the potential difference between the potential V _CH / V _CL of the electrode 22 and the potential V _RL / V _RH of the transparent electrode 16 when the image display medium 12 is driven are limited to twice the maximum value X of the holding voltage. It has become. Therefore, the maximum voltage (potential difference) that can be applied between the electrode 22 and the transparent electrode 16 when the image display medium 12 is driven is
| V1 | = (V _CH −V _RL ) <2X + X = 3X
It becomes.

  Next, each of the white particles 28A, the black particles 28B, and the small diameter particles 28C will be described.

  The white particles 28 </ b> A and the black particles 28 </ b> B are charged with different polarities by frictional charging due to mutual friction. Here, the white particles 28A are negatively charged, and the black particles 28B are positively charged.

The small-diameter particles 28C are conductive particles like the white particles 28A and the black particles 28B, and are formed of metal particles, metal oxide particles, or the like . In the first embodiment, since the same material is used for the white particles 28A, the black particles 28B, and the small diameter particles 28C, the difference in particle diameter is proportional to the difference in mass of the particles. Thus, the small-diameter particles 28C are formed so as to have a smaller particle diameter and a smaller mass than the white particles 28A and the black particles 28B.

Since the particle diameter is small and the mass is small, the small particle 28C starts to move first before the white particles 28A and the black particles 28B when a DC voltage is applied. Thus, the movement of the small diameter particles 28C is easy.

By the way, when the particles move between the substrates according to the electric field formed between the substrates, the voltage at which the particles start moving is the Coulomb force due to the electric field strength acting on the particles, which acts between the particles and the substrate surface. Since it is a time when the adhesion force (electrostatic force, van der Waals force) is overcome, that the movement is easy to start means that this adhesion force is weak. As a mechanism that facilitates the movement of the particles encapsulated between the substrates, the particles that move easily, that is, the small-sized particles 28C that are easy to start moving because they are formed so that the particle diameter is small and the mass is small are first moved. These become so-called “priming water” and collide with other white particles 28A and black particles 28B, which are relatively difficult to start moving, to start moving at substantially the same voltage, and the movement starting voltage as a whole It is thought that the reduction of As a result, the voltage at which the many white particles 28A, the black particles 28B, and the small-diameter particles 28C move and the image display density is almost saturated can be lowered, and the drive voltage for driving the image display medium 12 can be reduced. Reduction can be achieved.

  In addition, when the image display is repeated, the movement start voltage increases, and the white particles 28A, the black particles 28B, and the small diameter particles 28C are aggregated to be difficult to move, or the triboelectric charge amount is decreased. It is known that a dot defect or the like will occur. However, as in the first embodiment, by adding and mixing the small-diameter particles 28C, the dot defect is prevented and the number of repetitions of image display while maintaining the image quality is increased. Increase is possible.

  The small diameter particles 28C are characterized by being easy to start moving and having low adhesion to the transparent electrode 16 and the electrode 22. As the small particle 28C, a particle obtained by mirror-coating the surface of the small particle is used. By mirror coating the particle surface of the small particle 28C, the color of the small particle 28C is assimilated with the surrounding color. Therefore, the image quality of the display image does not deteriorate due to the presence of the small diameter particles 28C.

  By the way, it is necessary to add and mix more small-diameter particles 28C as the difference in the above-mentioned characteristics or the ease of movement start between the white particles 28A and the black particles 28B and the small-diameter particles 28C is small. In addition, it is better to add a small amount of small-diameter particles 28C having a large particle size difference between white particles 28A and black particles 28B than to add a large amount of white-particles 28A and black particles 28B and small-diameter particles 28C having a small particle size difference. This is preferable in that a larger effect can be expected.

  The small diameter particles 28C may be particles formed of a material such as transparent glass. When formed of a transparent material such as glass, the small-diameter particles 28C themselves become transparent and cannot be seen. Therefore, the image quality of the display image does not deteriorate due to the presence of the small diameter particles 28C.

  In the first embodiment, a mixture of white and black two types of white particles 28A and black particles 28B is shown, but not limited to two types, three or more types (red, blue, etc.) It may be. Further, two or more kinds of small-diameter particles 28C may be mixed.

  Next, the operation of the image display device 10 according to the first embodiment will be described.

  In the state where the entire surface of the image display medium 12 has a predetermined display density (for example, a display density corresponding to white having a lower density), the control device 34 outputs the high voltage output from the first power supply unit 42A to the electrode driving unit. The switching unit 60 is controlled so as to be supplied to 36, and the switching elements 56 of the electrode driving unit 36 and the switching elements 58 of the transparent electrode driving unit 38 are turned on and off based on the input image data. Thus, the image is written on the image display medium 12 by the simple matrix method.

That is, the control device 34 first turns on only the switching element 58 connected to the specific transparent electrode 16 (the transparent electrode 16 to be written) among the switching elements 58 of the transparent electrode driving unit 38 (other switching elements). 58 is turned off). As a result, only the transparent electrode 16 to be written is switched to the potential _VRH , and the other transparent electrodes 16 are maintained at the reference potential _VRL . Further, the control device 34 extracts data of each cell corresponding to the intersection position of the transparent electrode 16 to be written and each electrode 22 from the above-described image data, and the gradation value (density) of each cell represented by the extracted data. ) Controls on / off of each switching element 56 of the electrode drive unit 36 according to whether it is white or black (for example, the switching element 56 is turned on only for a cell having a black gradation value).

As a result, the electrode 22 with the connected switching element 56 turned on is switched to the potential V _CH , so that the voltage V1 (Table 1) is applied to the cell located at the intersection of the electrode 22 and the transparent electrode 16 to be written. When the reference is applied, the white particles 28A and the black particles 28B move, and the display density of the cell changes (for example, the density changes from white to black having a lower density). Further, since the electrode 22 where the connected switching element 56 is turned off is set to the reference potential V _CL , the voltage V3 is applied to the cell located at the intersection of the electrode 22 and the transparent electrode 16 to be written. (See Table 1) is applied, and the display density of the cell does not change.

During this time, in each cell corresponding to the intersection position of each transparent electrode 16 other than the transparent electrode 16 to be written and each electrode 22, the electrode 22 is set to the potential V _CH or the reference potential V _CL as described above. Since the transparent electrode 16 is maintained at the reference potential V _RL , the voltage V3 or the voltage V4 is applied, so that each cell is maintained in a state where the display density does not change.

  The control device 34 performs the above processing by switching the transparent electrode 16 to be written to another transparent electrode 16 every time a predetermined time elapses after the switching element 58 connected to the specific transparent electrode 16 is turned on. repeat. Thus, the transparent electrode 16 is used as a scanning electrode in the simple matrix system, the electrode 22 is used as a data electrode, and an image to be written is written on the image display medium 12.

  Even if the application of voltage to the transparent electrode 16 and the electrode 22 is stopped, the electrostatic adhesion force between the white particles 28A, the black particles 28B, and the small diameter particles 28C and the dielectric layers 18 and 24 is maintained. The white particles 28A, the black particles 28B, and the small-diameter particles 28C are held while adhering to the inner surfaces of the dielectric layers 18 and 24, and a black and white image is displayed for a long time.

  In the initial state, the control unit operates the alternating voltage generating unit of the voltage applying unit 30 to apply an alternating voltage (for example, ± 210 V) of a predetermined frequency (for example, 400 Hz) to the transparent electrode 16. By applying an alternating voltage (for example, ± 210 V) having an opposite phase to the electrode 22 and applying a positive DC voltage to the transparent electrode 16 as the final pulse, for example, the white particles 28 </ b> A are formed on the dielectric layer of the display substrate 14. The black particles 28B adhere to the entire inner surface of the dielectric layer 24 of the back substrate 20 and return to the initial state. At this time, when the image display medium 12 is viewed from the display substrate 14 side, only a white screen by the white particles 28A is visible.

  Next, a refresh driving sequence for the small-diameter particles 28C will be described with reference to the flowchart of FIG.

As shown in FIG. 5 , first, in step 100, small-diameter particle refresh is performed. Here, the small-diameter particle refresh is refresh performed by applying the voltage V2 described above between the display substrate 14 and the back substrate 20. As described above, even when the voltage V2 is applied between the substrates, the movement of the white particles 28A and the black particles 28B does not occur. However, the small particle 28C having a small particle diameter and a small mass also moves when the voltage V2 is applied, and comes into contact with the white particles 28A and the black particles 28B by the movement. And by the said contact, the small diameter particle 28C destroys aggregation of the white particle 28A and the black particle 28B, and restores the triboelectric charge amount of the white particle 28A and the black particle 28B to an appropriate level by friction due to the contact.

  Next, the process proceeds to step 102 and normal refresh is performed. Here, the normal refresh is a refresh performed by applying the voltage V1 described above between the substrates, and the normal refresh causes the white particles 28A, the black particles 28B, and the small diameter particles 28C to move.

  Thus, in the refresh drive sequence, first, the small-diameter particle refresh causes movement of the small-diameter particles 28C, destroying the aggregation of the white particles 28A and the black particles 28B, and increasing the triboelectric charge amount. As a result, the refresh effect of the image display medium 12 can be improved by applying a voltage lower than the refresh performed conventionally for the white particles 28A and the black particles 28B.

The image display on the image display medium 12 is performed after a predetermined time has elapsed since the application of the normal refresh voltage.
(Modification 1 of refresh drive sequence)
FIG. 6 shows a flowchart of Modification 1 of the refresh drive sequence.

  First, “1” is assigned to n (n is an integer) (step 120).

  Next, the above-described normal refresh of only the nth cell is performed (step 122), and an image is written only in the nth cell (step 124).

  Next, in step 126, “1” is added to n such that n = n + 1.

Next, in step 128, whether or not n exceeds “N” (“N” is the number of all cells), that is, whether or not all the cells are normally refreshed and the image is written. Is judged. If the result is affirmative exceeding N, the flow ends. If the result is negative in step 118, the process proceeds to step 120.
(Modification 2 of refresh drive sequence)
FIG. 7 shows a flowchart of Modification 2 of the refresh drive sequence.

  First, “L (L is an integer not less than“ 1 ”and not more than“ N ”)” is substituted for n (n is an integer) (step 130).

  Next, the normal refresh described above is performed only on the nth cell (step 132), and an image is written only in the nth cell (step 134).

  Next, in step 136, “1” is added to n as n = n + 1.

Next, in step 138, whether or not n exceeds “M (“ M ”is an integer not less than“ L ”and not more than“ N ”)”, that is, specified (“L” or more and “M” It is determined whether or not the following cells are normally refreshed and an image is written. If “M” is exceeded and the result is affirmed, the flow ends. If the result is “No” in step 138, the process proceeds to step 130.
(Modification 3 of refresh drive sequence)
FIG. 8 shows a flowchart of Modification 3 of the refresh drive sequence.

  In the third modification, first, the above-described normal refresh is performed on all cells (step 140), and then an image is written on all cells (step 142).

  In the first embodiment, the pair of electrodes (the electrode 22 and the transparent electrode 16) are provided on the pair of substrates (the display substrate 14 and the back substrate 20). However, the pair of electrodes is the image display medium 12. You may provide outside. This is desirable in that the transparency of the display substrate 14 is increased. The pair of electrodes may be a full-surface electrode and a cell electrode, or a combination of cell electrodes.

  As described above, the white particles 28A, the black particles 28B, and the small diameter particles 28C in the first embodiment are mixed particles obtained by mixing the white particles 28A, the black particles 28B, and the small diameter particles 28C at a predetermined ratio. A group. In this way, in the first embodiment, since the particle diameter of the small particle 28C is small, even if it is mixed with the white particle 28A and the black particle 28B, it is difficult to stand out, and the dot image can be prevented without affecting the image quality of the display image. Deterioration of the image quality of the displayed image can be prevented.

  In addition, since the voltage at which the display density is substantially saturated can be lowered, the voltage applied from the driving power supply 42 can be reduced.

Furthermore, a plurality of types of particles can be used for the small-diameter particles 28C.
(Second Embodiment)
The second embodiment of the present invention will be described below. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description of the configuration is omitted.

  A feature of the second embodiment resides in that magnetic particles that start moving by a magnetic field formed are applied to the small-diameter particles 28C.

  As shown in FIG. 9, the image display medium 70 of the second embodiment includes a magnetic head 72 that can move the surface of the display substrate 14 as indicated by an arrow 10A. The magnetic head 72 includes a magnetic coil (not shown) and is moved on the surface of the display substrate 14, so that small-diameter particles enclosed in a minute space between the display substrate 14 and the back substrate 20. 28C is vibrated.

  Thus, in the second embodiment, the image display medium 12 is refreshed by the vibration of the small diameter particles 28C. The refresh drive sequence is the same as in the first embodiment.

  Thus, the second embodiment can obtain the same effects as those of the first embodiment by employing magnetic particles as the small-diameter particles 28C.

It is a figure which shows schematic structure of the image display apparatus which concerns on 1st Embodiment. It is a block diagram which shows schematic structure of the power supply device which concerns on 1st Embodiment, an electrode drive part, and a transparent electrode drive part. 2 shows an example of a configuration of a refresh power supply according to the first embodiment. It is a diagram which shows an example of transition of the voltage applied to the specific cell of the image display medium which concerns on 1st Embodiment. A refresh drive sequence according to the first embodiment is shown. The flow of Modification 1 of the refresh drive sequence according to the first embodiment is shown. The flow of modification 2 of the refresh drive sequence according to the first embodiment is shown. The flow of Modification 3 of the refresh drive sequence according to the first embodiment is shown. It is a figure which shows schematic structure of the image display medium based on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image display apparatus 12 Image display medium 14 Display substrate 16 Transparent electrode 18 Dielectric layer 20 Back substrate 22 Electrode 24 Dielectric layer 26 Partition member 28 Particle 30 Voltage application part 32 Power supply apparatus 34 Control apparatus 36 Electrode drive part 38 Transparent electrode drive Unit 40 refresh power source 42 drive power source 42A first power source unit 42B second power source units 44 and 46 reference potential generators 48 and 52 high voltage output units 50 and 54 signal power source output units 56 and 58 switching element 60 switching units 62A and 62B DC power supply 64 switching unit 70 image display medium 72 magnetic head

Claims (3)

A transparent front substrate, a rear substrate opposed to the front substrate, a partition member that partitions a plurality of cells between the front substrate and the rear substrate, and enclosed in the plurality of cells; Large particle group having positive or negative charge moving in the cell direction or the back substrate direction in accordance with an electric field applied between the substrates and having at least two different surface colors or concentrations And a small particle group which is mixed in the large particle group and has a relatively small diameter and does not contribute to the color or density in the image display, and acts between the surface substrate surface or the back substrate surface. An image display medium composed of a small particle group having an adhesion force smaller than that of the large particle group;
A pair of electrodes for applying the electric field between a front electrode and a rear electrode constituting the image display medium by applying a voltage;
Voltage applying means for applying the voltage;
Prior to the writing of an image on the image display medium, in the case of refreshing in which the display of each cell of the image display medium is made uniform by any one of the large diameter particles having at least two different surface colors or densities, A first applied voltage for moving only the particles of the small particle group in the direction of the surface substrate or the back substrate is applied to the pair of electrodes, and then the particles of the large particle group are applied in the direction of the surface substrate or the back surface. Control means for controlling the voltage application means so as to apply a second applied voltage having a larger absolute value than the first applied voltage to be moved in the substrate direction to the pair of electrodes;
An image display device comprising:   The image display device according to claim 1, wherein the small particle group has a mass smaller than that of the large particle group. A transparent front substrate, a rear substrate opposed to the front substrate, a partition member that partitions a plurality of cells between the front substrate and the rear substrate, and enclosed in the plurality of cells; Large particle group having positive or negative charge moving in the cell direction or the back substrate direction in accordance with an electric field applied between the substrates and having at least two different surface colors or concentrations And a small-diameter particle group that is mixed in the large-diameter particle group and has a relatively small diameter and does not contribute to the color or density in the image display, the surface substrate surface or the back substrate surface An image display medium composed of small particle groups having an adhesion force acting between them smaller than that of the large particle groups;
A pair of electrodes for applying the electric field between a front electrode and a rear electrode constituting the image display medium by applying a voltage;
Voltage applying means for applying the voltage;
Magnetization means capable of moving on the surface substrate in a magnetized state;
The magnetizing means is controlled so as to move on the surface substrate in a magnetized state, and thereafter, an applied voltage for moving the particles of the large particle group in the surface substrate direction or the back substrate direction is applied to the pair of pairs. Control means for controlling the voltage application means to apply to the electrodes;
An image display device comprising: