JP4696477B2 - Display medium driving apparatus and method - Google Patents

Description

  The present invention relates to a display medium driving apparatus and method, and more particularly, to a colored charged particle group enclosed between a pair of substrates opposed to each other with a gap, and formed by a voltage applied between the pair of substrates. A display medium driving device for driving a display medium whose display density is changed by moving a colored charged particle group between a pair of substrates in accordance with an electric field, and a display medium applicable to the display medium driving device. The present invention relates to a driving method.

Conventionally, there has been proposed a display medium having a structure in which colored charged particles such as toner (specifically, a plurality of types of particles having different colors and polarities of charge) are enclosed between a pair of substrates arranged with a gap (for example, a plurality of types). (See Patent Documents 1 and 2). In this type of display medium, a pair of substrates are partitioned into a plurality of cells by a gap member, and colored charged particles are enclosed in each cell, and the pair of substrates is a substrate in units of individual pixels. Electrode groups are provided so that a voltage can be applied between them. The display medium is driven by applying a voltage between each pair of electrodes corresponding to each pixel in the same manner as in a liquid crystal display, and the colored charged particles are formed on the substrate by an electric field generated along with the application of the voltage. By applying a Coulomb force that moves between each colored charged particle to the individual colored charged particles and attaching the colored charged particles of the desired color to the substrate on the display surface side to switch the display density, the display medium can be arbitrarily controlled. Images can be displayed.
JP 2001-33833 A JP 2000-165138 A

  By the way, in the above display medium, once an image is written by applying a voltage between a pair of electrodes, the colored charged particles have a predetermined adhesion force (Van del Waals force, electric mirror image force, etc.). The suction force between the two objects) is attached to the substrate and adjacent particles, and the written image is maintained even when the voltage application between the electrode pair is stopped. Although there is an advantage that power for maintaining the displayed state is unnecessary, on the other hand, if the state in which the written image is displayed is continued for a long period of time, each electrode pair is displayed at the time of writing the next image. Even if a voltage is applied between them, the display density does not change in some cells or many pixels because some or most of the colored charged particles do not move between the substrates. Cell or pixel with poor display density change occurs There is a problem.

  On the other hand, since the techniques described in Patent Documents 1 and 2 do not consider the above-described problem, a new image is displayed on a display medium in which a written image is displayed and held for a long period of time. In some cases, a cell or pixel having a poor display density change as described above occurs, and the cell or pixel having a poor display density change may be visually recognized as a deterioration in image quality of a display image.

  The present invention has been made in consideration of the above facts, and even when a new image is written and displayed on a display medium in which the written image is displayed and held for a long period of time, the display medium is also provided. It is an object of the present invention to obtain a display medium driving apparatus and a display medium driving method capable of realizing high image quality of newly displayed images.

  The inventors of the present application have examined the reason why a cell or pixel having a poor display density change occurs, and when the state of displaying the written image is continued for a long time, the charge amount of the colored charged particles gradually decreases during this period. (The Coulomb force that the colored charged particles receive from the electric field also decreases as the charge amount decreases) and the colored charged particles are kept in a certain state for a long period of time. This is because the adhesion force with the particles increases, and the number of colored charged particles that do not move between the substrates without the Coulomb force given by the applied voltage (electric field) exceeding the adhesion force with the substrate or adjacent particles increases. An experiment was conducted to confirm this (details will be described later). As a result, even when the written image is displayed for a long period of time, prior to writing to the display medium, each electrode pair is used to erase the image that has been displayed on the display medium. In the intermittent application or alternating application of voltage, the generation of cells or pixels with poor display density change can be suppressed by extending the period of intermittent application or alternating application of voltage to increase the voltage application time per time. It was confirmed.

Driving device for a display media according to the invention 請 Motomeko 1, at least one is made with colored charged particles between a pair of substrates facing each other across a gap and having a light transmitting property is enclosed, the pair A display medium driving apparatus for driving a display medium in which a display density is changed by moving a colored charged particle group between the pair of substrates in accordance with an electric field formed by a voltage applied between the substrates. An image writing unit that writes the image to be written on the display medium by applying a voltage according to the image to be embedded between the pair of substrates, and an image on the display medium by the image writing unit Prior to writing, after a voltage is intermittently or alternately applied between the pair of substrates in a first period, the second period between the pair of substrates is shorter than the first period . Intermittent application or alternating application in 1 cycle Is characterized with Brighter fresh control means is intermittently applied or alternately applying a voltage lower than the voltage which, further comprising a.

According to a second aspect of the present invention, in the first aspect of the present invention, the information processing apparatus further includes a time measuring unit that measures a display holding time of the image written on the display medium, and the refresh control unit is measured by the time measuring unit. As the display holding time becomes longer, the first cycle is lengthened, and the time during which the voltage is intermittently applied or alternately applied in the first cycle between the pair of substrates is lengthened, and It is characterized in that at least one of increasing the magnitude of the voltage applied intermittently or alternately in the first period between the pair of substrates is performed.

According to a third aspect of the present invention, in the first aspect of the invention, the first period is set to a period in which the frequency is 20 Hz or less or the application time of a voltage having a constant polarity is 50 milliseconds or more. It is characterized by.

According to a fourth aspect of the present invention, in the first or second aspect of the present invention, the gap between the pair of substrates is provided with a gap member that divides the gap into a plurality of cells, and the colored charged particle group Are each enclosed in individual cells defined by the gap member.

According to a fifth aspect of the present invention, in the first or second aspect of the present invention, the pair of substrates is an electrode group capable of applying different voltages between the pair of substrates at a plurality of pixel positions on the substrate. Are provided, and at least the electrode group provided on the substrate side having a light-transmitting property has a light-transmitting property, and by applying a voltage between the opposing electrode pairs at each pixel position, A voltage is applied between the pair of substrates at each pixel position.

According to a sixth aspect of the present invention, in the first or second aspect of the present invention, when a voltage is applied between the pair of substrates, the external electrode pair separate from the display medium sandwiches the pair of substrates. The electrodes are arranged so as to face each other, and a voltage is applied between the pair of substrates by applying a voltage between the pair of external electrodes.

According to a seventh aspect of the present invention, there is provided a display medium driving method comprising: a pair of colored charged particles encapsulated between a pair of substrates, at least one of which is translucent and disposed oppositely with a gap therebetween; A display medium driving method for driving a display medium in which a display density is changed by moving a colored charged particle group between the pair of substrates in accordance with an electric field formed by a voltage applied between the substrates, After intermittently applying or alternatingly applying a voltage between a pair of substrates in a first cycle, intermittently applying a voltage between the pair of substrates in a first cycle with a second cycle shorter than the first cycle. Alternatively, a voltage smaller than a voltage to be alternately applied is intermittently applied or alternately applied, and then a voltage corresponding to an image to be written is applied between the pair of substrates, whereby the writing target is applied to the display medium. Characterized by writing images To have.
According to an eighth aspect of the present invention, in the seventh aspect of the invention, the display holding time of the image written on the display medium is measured by the time measuring means, and the first display holding time becomes longer as the measured display holding time becomes longer. Increasing the period, and increasing the time during which the voltage is intermittently applied or alternating applied between the pair of substrates in the first period, and intermittently applying or alternating between the pair of substrates in the first period It is characterized in that at least one of increasing the magnitude of the applied voltage is performed.

The present invention, when displaying by writing a new image on the display medium of the condition of displaying and holding over the image written to the long-term also, high-quality images to be newly displayed on the display medium It has an excellent effect that can be realized.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an image display apparatus 10 according to the present embodiment. The image display device 10 includes an image display medium 12 as a display medium according to the present invention.

As shown in FIG. 2A, the image display medium 12 includes a display side substrate 14 having translucency, and a back side substrate 16 disposed to face the display side substrate 14 with a gap therebetween. The gap between the rear side substrate 1 6 and the display-side substrate 1 4, the display-side substrate 1 4 and the back side substrate 1 6 holds the gap constant, display the gap-side substrate 1 4 and the rear-side substrate 1 6 A partition wall 17 is provided for partitioning into a plurality of cells along the surface. The partition wall 17 can be formed by, for example, a photolithography method or a printing method. The color of the partition wall 17 can be, for example, a translucent gray, but other colors may be used.

  As shown in FIG. 2B, each cell formed by the partition wall 17 has a basic shape of a rectangle surrounded by a pair of opposing short sides and a pair of short sides, and the length of the short sides is also constant. However, the length of the long side (aspect ratio) is indefinite, and the direction in which the long side extends is also indefinite (vertical direction or horizontal direction). Each cell is a cell in which at least one of the pair of corners located at both ends of at least one of the pair of short sides exists in the direction in which the short side in contact with the corner extends, and is adjacent to each cell. Are arranged at random in the middle of the sides so as to be in contact with the adjacent cells. Thereby, it is possible to prevent the partition walls 17 continuous over a certain length from appearing periodically at a relatively large pitch. And it can suppress that the partition 17 is visually recognized as a linear noise pattern, and the display quality of the image display medium 10 can be improved. Note that the shape and arrangement of the cells in the present invention are not limited to the example shown in FIG. 2B, and any shape and arrangement can be applied.

Further, the surface of the display-side substrate 14 facing the back-side substrate 16 has a line shape (band shape) extending in the first direction (the left-right direction in FIG. 1 and the direction perpendicular to the paper surface in FIG. 2A). A plurality of transparent electrodes 22 are formed along a second direction (vertical direction in FIG. 1, horizontal direction in FIG. 2A) orthogonal to the first direction. A plurality of line-shaped electrodes 24 extending in the second direction are formed on the surface of the back substrate 16 facing the display substrate 14 along the first direction. Thus, the transparent electrode 22 and the electrode 24 are arranged so that the image display medium 12 can be driven by a simple matrix method. The provision of the electrodes 22 and 24 on the substrates 14 and 16 as described above corresponds to the invention described in claim 5, but in this case, a voltage is applied between the image display medium 12 and a separate external electrode pair. Compared to the case, the distance between the electrodes can be shortened, and the applied voltage for generating the same electric field can be reduced, so that power consumption can be reduced.

  In addition, a predetermined amount of black particles 18 and white particles 20 charged with different polarities are encapsulated in each cell as colored charged particles according to the present invention. As the black particles 18 and the white particles 20, for example, particles having a diameter of about 10 μm can be used. As the black particles 18, positively charged particles can be used, and as the white particles 20, negatively charged particles can be used. . In the image display medium 10 according to the present embodiment, each cell is filled with a gas such as air. Instead, charged white particles and black particles are dispersed in a transparent insulating liquid. Things may be filled into the cell. Alternatively, the insulating liquid may be white, for example, and charged black particles may be dispersed in the insulating liquid.

As described above, the gap of the back side substrate 1 6 and the display-side substrate 1 4 is divided into a plurality of cells by partitions 17, encapsulating the black particles 18 and white particles 20 within the individual cells according to claim 4, wherein This corresponds to the invention. In this configuration, the image display medium 12 is used in an upright position (the display-side substrate 14 and the back-side substrate 16 are in a vertical position) because they can move only within the individual cells in which the black particles 18 and the white particles 20 are enclosed. In such a case, the black particles 18 and the white particles 20 can be prevented from being extremely unevenly distributed between the substrates 14 and 16.

When the image display medium 12 is driven by a simple matrix system, the intersection positions of the transparent electrode 22 and the electrode 24 function as pixels (dots) of the image display medium 12, respectively, and between the transparent electrode 22 and the electrode 24 at each intersection position. It is given to the black particles 18 and the substrate 1 4 white particles 20, 1 individual Coulomb force for moving between 6 black particles 18 and white particles 20 by voltage (electric field generated by) applied to the black particles 18 and It is attached either white particles 20 on the display side substrate 1 4 are the switchable display concentration, thereby being possible to display an arbitrary image. Hereinafter, the transparent electrode 22 is referred to as a “row electrode 22”, and the electrode 24 is referred to as a “column electrode 24”.

  In addition, the image display device 10 includes a power supply device 26, a control device 28, a column electrode drive unit 30, and a row electrode drive unit 32. The power supply device 26, the control device 28, the column electrode driving unit 30, and the row electrode driving unit 32 correspond to the display medium driving device according to the present invention. The control device 28 includes a microcomputer and a non-volatile storage means such as an HDD (hard disk drive) or a flash memory. The storage device drives a display medium to be described later. A display medium driving program for performing processing is installed in advance. The control device 28 is connected to the power supply device 26 and is operated by electric power supplied from the power supply device 26. The power supply device 26 and the control device 28 are connected to the column electrode drive unit 30 and the row electrode drive unit 32.

As shown in FIG. 3, the power supply device 26 is provided with a first refresh power supply 34, a second refresh power supply 33, and a drive power supply 35. As shown in FIG. 5A, the first refresh power supply 34 includes DC power supplies 56A and 56B, and the minus terminal of the DC power supply 56A and the plus terminal of the DC power supply 56B are connected to each other and grounded ( Instead, it may be maintained at a reference potential V _CL described later). The DC power sources 56A and 56B can change the output voltage (absolute value thereof), and the control device 28 changes the output voltage of the DC power sources 56A and 56B. Although not shown, a large capacity capacitor for stabilizing the output potential is connected in parallel to the DC power sources 56A and 56B. The plus terminal of the DC power source 56A is connected to one of the two input ends of the switching unit 58, and the other input end is connected to the minus terminal of the DC power source 56B.

The switching unit 58 is configured by a semiconductor switching element (eg, MOSFET) or the like, and is configured to selectively output one of two signals (potentials) input via two input terminals. Yes. Although not shown, the switching unit 58 is connected to the control device 28, and an output signal (potential) is output in a polarity switching cycle T _L (see FIG. 9) set by the control device 28 in a first refresh period to be described later. ) Is switched. Therefore, the first refresh power supply 34 outputs a potential (see also the waveform shown in FIG. 5A) whose polarity is switched in the polarity switching period T _L as the first refresh output.

The second refresh power source 33 is also configured as shown in FIG. The switching unit 58 of the second refresh power supply 33 is also connected to the control device 28, and the configuration shown in FIG. 5A can be employed in the same manner as the first refresh power supply 34. The switching unit 58 of the second refresh power supply 33 has a polarity switching cycle T _S (T _S << T _L : see FIG. 9) in which a signal (potential) to be output is set in advance in a second refresh period to be described later. It is controlled to switch. Accordingly, the second refresh power source 33 outputs a potential at which the polarity is switched in the polarity switching period T _S as the second refresh output.

In the present embodiment, the first refresh power supply 34, the polarity switching period T _L of the first refresh output is longer than the polarity switching period T _S of the second refresh output of the second refresh power supply 33 Along with the setting (T _L >> T _S ), the stability of the generated potential is configured to be higher than that of the second refresh power source 33. The second refresh power source 33 will be described later. As the large current flows during the second refresh period, the capacitance of the capacitors connected in parallel to the DC power sources 56A and 56B is such that the allowable current value becomes larger than that of the first refresh power source 34. The capacity is larger than the refresh power supply 34.

On the other hand, the driving power source 35 includes a first power source unit 35A for generating a potential to be supplied to the column electrode driving unit 30, and a second power source unit 35B for generating a potential to be supplied to the row electrode driving unit 32. It is configured. The first power supply unit 35A generates a reference potential V _CL of the column electrode 24 and a potential difference (V _CH −V _CL ) using the reference potential V _CL as a ground potential to generate a high voltage output. A high-voltage output unit 38 that outputs a potential V _CH and a signal power output unit 40 that outputs a potential (V _CL + TTL) as a signal power source output by generating a potential difference TTL using the reference potential V _CL as a ground potential. . The high-voltage output unit 38 is also connected in parallel with a large-capacity capacitor for stabilizing the output potential.

With the above configuration, the first power supply unit 35A 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 35 </ b> A is connected to the column electrode drive unit 30, and the GND output and the signal power supply output among the outputs are directly supplied to the column electrode drive unit 30. The high voltage output of the first power supply unit 35A is input to the switching unit 60, and the first refresh output of the first refresh power supply 34 and the second refresh output of the second refresh power supply 33 are also input to the switching unit 60. Entered.

  The switching unit 60 is also composed of a semiconductor switching element (for example, a MOSFET) or the like, and the input high voltage output of the first power supply unit 35A, the first refresh output of the first refresh power supply 34, and the second refresh power supply. One of the 33 second refresh outputs is selectively output. The switching unit 60 is connected to the control device 28, and the control device 28 controls which of the high voltage output, the first refresh output, and the second refresh output is output. An output terminal of the switching unit 60 is connected to the column electrode driving unit 30, and the high voltage output or the first refresh output output from the switching unit 60 is supplied to the column electrode driving unit 30.

In addition, the second power supply unit 35B generates a reference potential V _RH of the row electrode 22 and a high potential output by generating a potential difference (V _RL −V _RH ) using the reference potential V _RH as a ground potential. It includes a high-voltage output unit 44 for outputting a potential V _RL as the signal power output unit 46 which outputs a potential (V _RH + TTL) of the reference potential V _RH as the signal power output by generating a potential difference TTL as a ground potential ing. The second power supply unit 35B is connected to the row electrode drive unit 32, and the high voltage output (potential V _RL ), GND output (reference potential V _RH ), and signal power output (potential (V _RH + TTL)) are the row electrode drive unit. 32.

On the other hand, the column electrode drive unit 30 includes the same number of switching elements 50 as the number of column electrodes 24 provided in the image display medium 12, and the GND output (reference potential V _CL ) from the first power supply unit 35A. The high-voltage output, the first refresh output, or the second refresh output from the switching unit 60 is supplied to each switching element 50. In FIG. 3, the switching element 50 is schematically shown as a switch, but the switching element 50 is actually composed of a semiconductor switching element (for example, a MOSFET or the like). The individual switching elements 50 operate using the signal power supply output supplied from the first power supply unit 35A as a power supply and the GND output (reference potential V _CL ) as a reference potential. In the on state, each switching element 50 operates as a high voltage output (or first refresh output). Or the second refresh output), and the GND output (reference potential V _CL ) is output in the off state. The individual switching elements 50 are also supplied with control signals supplied from the control device 28, and the on / off states of the individual switching elements 50 are controlled by the control device 28.

As shown in FIG. 4, the column electrode driving unit 30 is attached to the back side substrate 16 of the image display medium 12, and the individual switching elements 50 of the column electrode driving unit 30 are individually formed on the back side substrate 16. The column electrode 24 is connected. Therefore, the potential of each column electrode 24 of the image display medium 12 is a potential V _CH corresponding to a high voltage output or a potential corresponding to the first refresh output (first potential) according to the on / off state of the connected switching element 50. 1 refresh potential) or a potential corresponding to the second refresh output (second refresh potential) or the reference potential V _CL .

The row electrode driving unit 32 includes the same number of switching elements 52 as the number of row electrodes 22 provided in the image display medium 12, and the high voltage output (potential V _RL ) and the GND from the second power supply unit 35B. The output (reference potential V _RH ) is supplied to each switching element 52. The switching element 52 is actually composed of a semiconductor element (for example, a MOSFET). The individual switching elements 52 operate using the signal power supply output supplied from the second power supply unit 35B as a power supply and the GND output (reference potential V _RH ) as a reference potential. In the on state, each switching element 52 outputs a high-voltage output (potential V _RL ). In the OFF state, the GND output (reference potential V _RH ) is output. A control signal supplied from the control device 28 is also input to each switching element 52, and on / off of each switching element 52 is controlled by the control device 28.

As shown in FIG. 4, the row electrode driving unit 32 is attached to the display side substrate 14 of the image display medium 12, and the individual switching elements 52 of the row electrode driving unit 32 are individually formed on the display side substrate 14. Are connected to the row electrode 22. Therefore, the potential of each row electrode 22 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 52.

  Next, the operation of this embodiment will be described. In the image display medium 12 according to the present embodiment, the position of the intersection of the specific column electrode 24 and the specific row electrode 22 with respect to a change in voltage (electric field) applied between the specific row electrode 22 and the specific column electrode 24. The change in pixel density is shown in FIG. As is apparent from FIG. 6, the image display medium 12 has a small Coulomb force applied to the particles if the applied voltage (electric field) is within the holding voltage range (the voltage range in which the movement of the black particles 18 and the white particles 20 does not occur). For this reason, the concentration does not change, and when the applied voltage (absolute value) exceeds the holding voltage range, the Coulomb force received by the particles exceeds the adhesion force of the individual particles to the substrate and adjacent particles. When the concentration changes with a large slope with respect to the increase in the applied voltage and the applied voltage (absolute value thereof) exceeds a threshold value (the voltage indicated as the display drive voltage in FIG. 6), the concentration with respect to the increase in the applied voltage. It has the characteristic that the slope of the change of the is small.

On the other hand, in the present embodiment, the potential of the column electrode 24 is switched to the potential V _CH or the reference potential V _CL and the potential of the row electrode 22 is switched to the potential V _RL or the reference potential V _RH , thereby displaying an image by a simple matrix method. Since the medium 12 is driven, any one of the voltages V1 to V4 shown in the following Table 1 is applied between the column electrode 24 and the row electrode 22 when the image display medium 12 is driven.

ここで、表１に示す電圧Ｖ２〜Ｖ４は、黒粒子１８及び白粒子２０の移動を生じさせない大きさである必要があるので、画像表示媒体１２における保持電圧の最大値をｘとすると、
|Ｖ２|＜ｘ、|Ｖ３|＜ｘ、|Ｖ４|＜ｘ
よって
|Ｖ_CH−Ｖ_RH|＜ｘ、|Ｖ_CL−Ｖ_RL|＜ｘ、|Ｖ_CL−Ｖ_RH|＜ｘ
となる。また、
|Ｖ２|＝（Ｖ_CH−Ｖ_CL）―（Ｖ_RH−Ｖ_CL）＜ｘ
―ｘ＜（Ｖ_CH−Ｖ_CL）―（Ｖ_RH−Ｖ_CL）＜ｘ
よって、
−２ｘ＜（Ｖ_CH−Ｖ_CL）＜２ｘ
同様に
−２ｘ＜（Ｖ_RH−Ｖ_RL）＜２ｘ
となり、画像表示媒体１２の駆動時における列電極２４の電位Ｖ_CH／Ｖ_CLの電位差、行電極２２の電位Ｖ_RL／Ｖ_RHの電位差は、何れも保持電圧の最大値ｘの２倍が限度となる。従って、画像表示媒体１２の駆動時に列電極２４と行電極２２の間に印加可能な最大電圧（電位差）は、
|Ｖ１|＝（Ｖ_CH−Ｖ_RL）＜２ｘ＋ｘ＝３ｘ
となる（図７も参照）。

Here, the voltages V2 to V4 shown in Table 1 need to be large enough not to cause the movement of the black particles 18 and the white particles 20, so that 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
Thus, the potential difference between the potential V _CH / V _CL of the column electrode 24 and the potential difference between the potential V _RL / V _RH of the row electrode 22 when the image display medium 12 is driven are limited to twice the maximum value x of the holding voltage. It becomes. Therefore, the maximum voltage (potential difference) that can be applied between the column electrode 24 and the row electrode 22 when the image display medium 12 is driven is
| V1 | = (V _CH −V _RL ) <2x + x = 3x
(See also FIG. 7).

As is clear from FIG. 6, the image display medium 12 is applied even when the voltage applied between the column electrode 24 and the row electrode 22 is relatively large (a magnitude exceeding the display drive voltage in FIG. 6). Since the density slightly changes with increasing voltage, the display on the image display medium 12 is erased before writing the image on the image display medium 12 (the display density of all pixels is uniform). The contrast of the displayed image is improved when a higher voltage is applied. For this reason, in the present embodiment, the power supply device 26 is provided with the second refreshing power supply 33, which is higher than the maximum drive voltage V1 (corresponding to the display drive voltage shown in FIG. 6) between the column electrode 24 and the row electrode 22. A potential for applying a large voltage (corresponding to the second refresh voltage shown in FIG. 6) at a relatively high frequency (for example, about several hundred Hz) is generated by the second refresh power source 33 (ie, the second refresh voltage). Maximum refresh output potential >> V _CH ).

However, when the image display medium 12 is in a state where the written image is displayed / held for a long time, the charge amount of the black particles 18 and the white particles 20 gradually decreases during the image display / holding period. while, by the black particles 18 and white particles 20 is placed a long period in a constant state, adhesion between the substrate 1 4 or the substrate 1 6 of the individual particles, adhesion between neighboring particles increases. Therefore, even if a new image is written by applying a voltage after the second refresh voltage is applied alternately at a relatively high frequency to erase the display on the image display medium 12 in the above-described state, the application is applied. A cell or pixel in which the change in display density is insufficient because the coulomb force received by each particle is smaller than the voltage while the adhesion of each particle to the substrate and adjacent particles is increased. And such a cell or pixel may be visually recognized as a deterioration in image quality of a written image (display image).

For this reason, the power supply device 26 according to the present embodiment is also provided with a first refresh power supply 34, and prior to the display erasure of the image display medium 12 by the alternating application of the second refresh voltage, the column electrode 24 and the row power supply 26 are provided. A voltage higher than the maximum drive voltage V1 (corresponding to the display drive voltage shown in FIG. 6) and slightly higher than the second refresh voltage (corresponding to the first refresh voltage shown in FIG. 6) between the electrodes 22 is relatively A potential to be applied at a low frequency (for example, 20 Hz or less) is generated by the first refresh power supply 34 (that is, the maximum potential of the first refresh output> the maximum potential of the second refresh output >> V _CH ).

Then, image data representing the image to be written (for example, image data representing each pixel gradation value of the image to be written in binary (for example, white / black)) from the external device (not shown) to the control device 28. When input, the control device 28 temporarily stores the input image data in a storage unit such as an HDD, and then writes a display medium drive program installed in the storage unit in order to write an image on the image display medium 12. Then, the display medium driving process shown in FIG. 8 is executed. Steps 100 to 126 in the display medium driving process are processes corresponding to the first refresh control unit and the second refresh control unit according to the present invention, together with step 132 described later, and control for executing each of the above processes. device 28, engages lapis fresh control means in the present invention (details refresh control means according to claim 2) will function as a. The display medium driving process also corresponds to the display medium driving method described in claims 7 and 8 .

In this display medium driving process, an elapsed time since the previous image was written to the image display medium 12 as a process for refreshing the image display medium 12 prior to writing the image represented by the input image data to the image display medium 12. After the first refresh voltage is alternately applied to all the pixels of the image display medium 12 with a relatively long polarity switching period T _L set according to the above, all the pixels of the image display medium 12 are applied with a relatively short polarity switching period T _S. The process of alternately applying the second refresh voltage is sequentially performed. That is, in step 100, the writing date and time stored in the memory or the like when the previous image was written to the image display medium 12 is acquired, and the acquired writing is obtained as the elapsed time since the previous image was written to the image display medium 12. Calculate the difference between the date and time and the current date and time.

In the next step 102, based on the elapsed time from the previous image writing calculated in step 100, the polarity switching period T _L , the voltage V, and the number of times of application in the alternating application of the first refresh voltage are set. Although details will be described later, according to an experiment conducted by the inventors of the present application, in order not to generate a cell or a pixel in which a change in display density is insufficient with respect to a voltage applied during image writing, the previous image is not generated. As the elapsed time from writing becomes longer, the polarity switching period T _L (pulse width) in alternating application of the first refresh voltage is lengthened, the number of times of application of the first refresh voltage is increased, and the first refresh voltage It has been confirmed that at least one of increasing the size needs to be performed. For this reason, in step 102, as the elapsed time from the previous image writing becomes longer, the polarity switching period _TL in the alternating application of the first refresh voltage becomes longer, the number of times of application of the first refresh voltage increases, The polarity switching period T _L , the voltage V, and the number of applications are set so that the refresh voltage (voltage V) of 1 is increased.

The polarity switching period T _L , the voltage V, and the number of times of application may be set so as to change continuously with respect to the change in the elapsed time from the previous image writing, or the elapsed time from the previous image writing. You may set so that it may change in steps with respect to this change. Further, it is not always necessary to change each of the polarity switching period T _L , the voltage V, and the number of application times with respect to the change in the elapsed time since the previous image writing. For example, the elapsed time t is t ₁ to t ₂ (t ₂ > t ₁₎ according to the elapsed time t when the value within the range of changing the polarity switching period T _L, the elapsed time t is equal a value in the range of _{t 2 ~t 3 (t 3>} t 2) elapsed time by changing the polarity switching period T _L and the number of applications depending on t, the elapsed time t is _{t 3 ~t 4 (t 4>} t 3) the voltage V according to the elapsed time t when the value within the range of Any setting method can be applied within a range that does not depart from the present invention. In step 104, the output voltages of the DC power supplies 56A and 56B of the first refresh power supply 34 are changed so that the output voltage of the first refresh power supply 34 matches the voltage V set in step 102.

In step 106, the switching unit 58 of the first refresh power supply 34 is switched so that the first refresh output from the first refresh power supply 34 has a predetermined polarity. In step 108, each switching element 50 of the column electrode driver 30 is turned on. In step 110, the first refresh output from the first refresh power supply 34 is supplied to the column electrode driver 30. The switching unit 60 is controlled. Accordingly, the first refresh voltage is applied between the row electrode 22 and the column electrode 24 at a predetermined polarity at each intersection position (each pixel position) between the row electrode 22 and the column electrode 24 of the image display medium 12. In the next step 112, it is determined whether or not the polarity switching period T _L set in the previous step 102 has elapsed, and step 112 is repeated until the determination is affirmed. If the determination in step 112 is affirmed, the routine proceeds to step 114, where it is determined whether or not the first refresh voltage application for the period corresponding to the polarity switching period T _L has been performed the number of times set in the previous step 102. . If the determination is negative, the process proceeds to step 116, where the switching unit of the first refresh power supply 34 is set so that the first refresh output from the first refresh power supply 34 has a polarity opposite to the predetermined polarity. After switching 58, the process returns to step 112.

As a result, as shown as “first refresh period” in FIG. 9 as an example, at each intersection position (each pixel position) between the row electrode 22 and the column electrode 24 of the image display medium 12, A first refresh voltage whose polarity is switched at a relatively long polarity switching period T _L is applied between the column electrodes 24.

  The size, shape, and charge amount of each particle of the image display medium 12 vary, and the adhesion state of each particle to the substrate 14 or 16 and the adhesion state to adjacent particles vary (for example, particles are loosened from the substrate). In some cases, the particles are adhered to the substrate, the particles are densely adhered to the substrate, and the particles are adhered to each other but not to the substrate. For this reason, the magnitude of the adhesion force between the substrate and adjacent particles (the threshold value of the Coulomb force at which the particles begin to move) differs for each particle, and when a first refresh voltage having a certain polarity is applied. First, only the particles whose Coulomb force (the magnitude of the Coulomb force itself changes according to the amount of charge of the particles) exceeding the adhesion force with the substrate and adjacent particles are received by the generation of the electric field. Start moving between. Further, when the particles that have started to move reach one substrate, the particles become particles that are held in a state of being attached to one substrate because the Coulomb force received by the generated electric field does not exceed the adhesion force. The impact force of the collision causes a part of the collided particles to have reduced adhesion to one substrate and adjacent particles, and the adhesion to one substrate and adjacent particles is peeled off to the other substrate. Start moving. Then, when these particles reach the other substrate and collide with the particles adhered and held on the other substrate, the same phenomenon as described above occurs. By repeating this phenomenon, almost all of the particles are moved (this is referred to as “striking effect”).

  Here, when the Coulomb force received by each particle is sufficiently larger than the adhesion force with the substrate and adjacent particles, a large number of particles start moving immediately when the application of the first refresh voltage is started. The time required until almost all particles adhere to the substrate and adjacent particles can be shortened, but when the elapsed time since the previous image was written on the image display medium 12 is long. , While the charge amount of each particle is decreasing, the adhesion of each particle to the substrate and adjacent particles is strong, so some of the particles whose Coulomb force exceeds the adhesion to the substrate and adjacent particles Only, and the difference between the Coulomb force and the adhesion force is also slight. For this reason, the number of particles that start moving when the application of the first refresh voltage is started is small, and the number of particles that are peeled off by the collision of the particles is also small. The time required for the adhesion with the adjacent particles to be peeled off also becomes longer.

In contrast, in this embodiment, in accordance with the elapsed time from the image writing the last longer, the polarity switching period T _L Ri is long in the alternating application of the first refresh voltage, the number of applications of the first refresh voltage many of Ri, as the magnitude of the first refresh voltage (voltage V) increases, the polarity switching period T _L, since the setting of the voltage V, application times, the image display medium 12, written image previous Even when a relatively long time has passed since the release, the first electrode having a certain polarity is maintained until the adhesion of almost all the particles to the substrate and adjacent particles is peeled off. The refresh voltage is continuously applied, and the adhesion with the substrate and adjacent particles can be reliably peeled off for almost all particles.

In the present embodiment, the number of times the first refresh voltage is applied decreases as the elapsed time from the previous image writing decreases, and the second refresh is performed even when the elapsed time from the previous image writing is short. as the magnitude of the voltage is greater than the voltage, than the size of the first refresh voltage (voltage V) is set, the image display medium 12, the image is much time since written last elapsed If the first refresh voltage is not applied, the application of the first refresh voltage can be completed in a short time, and the first refresh period is relatively short, but the substrate and adjacent particles have a strong adhesive force. The attached particles can be surely peeled off.

Thus, in the embodiment according to the elapsed time from the previous image writing, the application time of the first refresh voltage (polarity switching period T _L × number of times of application) is optimized (the invention of claim 2, wherein Therefore, it is possible to surely peel off the particles adhering to the substrate and adjacent particles with a strong adhesive force, while refreshing (application of the first refresh voltage) takes more time than necessary. Can be prevented.

When the application of the first refresh voltage in the period corresponding to the polarity switching period T _L is performed for the preset number of times, the determination in step 114 is affirmed and the process proceeds to step 118, and then the display on the image display medium 12 In order to erase the signal, the switching unit 58 of the second refresh power supply 33 is switched so that the second refresh output from the second refresh power supply 33 has a predetermined polarity. In step 120, the switching unit 60 is controlled so that the second refresh output from the second refresh power supply 33 is supplied to the column electrode driving unit 30. Accordingly, the second refresh voltage is applied between the row electrode 22 and the column electrode 24 at each intersection position (each pixel position) between the row electrode 22 and the column electrode 24 of the image display medium 12. Determines whether the next step 122 in the preset polarity switching period T _S has elapsed, the determination is repeated step 122 until the affirmative. If the determination in step 122 is affirmative, the routine proceeds to step 124, where it is determined whether or not the application of the second refresh voltage for a period corresponding to the polarity switching period T _S has been performed a predetermined number of times. If the determination is negative, the process proceeds to step 126 and the switching unit of the second refresh power supply 33 so that the second refresh output from the second refresh power supply 33 has a polarity opposite to the predetermined polarity. After switching 58, the process returns to step 122.

As a result, as shown as “second refresh period” in FIG. 9 as an example, at each intersection position (each pixel position) between the row electrode 22 and the column electrode 24 of the image display medium 12, between the column electrode 24, will be the second refresh voltage polarity is switched is alternating applied in a relatively short polarity switching period T _S, adhere to the substrate and adjacent particle by the application of the first refresh voltage above The black particles 18 and the white particles 20 that have been peeled off from each other are reciprocated between the substrates 14 and 16 many times by an alternating electric field generated in response to the application of the second refresh voltage. At the same time as the frictional charging of the particles by collision, the particle arrangement is made uniform (the elimination of the density of the particle arrangement in each cell) and the display density uniformity is improved.

When the refresh of the image display medium 12 is completed as described above (application of the first refresh voltage in the polarity switching period T _L to the image display medium 12 and application of the second refresh voltage in the polarity switching period T _S Are performed in order), the determination in step 124 is affirmed and the process proceeds to step 128 to read the image data temporarily stored in the storage means such as an HDD. In step 130, the high voltage output from the first power supply unit 35A is output from the column electrode driving unit while 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 switching unit 60 is controlled so as to be supplied to 30, and the switching elements 50 of the column electrode driving unit 30 and the switching elements 52 of the row electrode driving unit 32 are turned on / off based on the image data read from the storage unit. By doing so, an image is written in the image display medium 12 by a simple matrix method.

That is, the control device 28 first turns on only the switching element 52 connected to the specific row electrode 22 (writing row electrode) among the switching elements 52 of the row electrode driving unit 32 (the other switching elements 52 are Off). Thereby, only the specific row electrode 22 (write row electrode) is switched to the potential V _RH , and the other row electrodes 22 are maintained at the reference potential V _RL . Further, the control device 28 extracts the data of each pixel corresponding to the intersection position of the writing row electrode and each column electrode 24 from the above-described image data, and the gradation value (density) of each pixel represented by the extracted data. ON / OFF of each switching element 50 of the column electrode driving unit 30 is controlled according to whether the switching element 50 is white or black (for example, the switching element 50 is turned on only for a pixel having a black gradation value).

As a result, the column electrode 24 in which the connected switching element 50 is turned on is switched to the potential V _CH , so that the voltage V1 (Table 1) is applied to the pixel located at the intersection of the column electrode 24 and the write row electrode. The black particles 18 and the white particles 20 receive the Coulomb force and move between the substrates 14 and 16 due to the electric field generated by the application of the reference). 14, the display density of the pixel changes. Further, since the column electrode 24 in which the connected switching element 50 is turned off is set to the reference potential V _CL , the voltage V3 is applied to the pixel located at the intersection of the column electrode 24 and the write row electrode. (See Table 1) is applied, and the display density of the pixel does not change.

During this period, each pixel corresponding to the intersection position of each row electrode 22 other than the write row electrode and each column electrode 24 has the column electrode 24 at the potential V _CH or the reference potential V _CL as described above. Since the row electrode 22 is maintained at the reference potential _VRL , the voltage V3 or the voltage V4 is applied (see also FIG. 9), so that each pixel is maintained in a state where the display density does not change. .

The control device 28 repeats the above processing by switching the write row electrode to another row electrode 22 every time a predetermined time elapses after the switching element 52 connected to the specific row electrode 22 is turned on. . As a result, the row electrodes 22 are used as scanning electrodes in the simple matrix system, the column electrodes are used as data electrodes, and an image to be written is written on the image display medium 12. Note that the above-described steps 128 and 130 are processes corresponding to the image writing unit according to the present invention, and the control device 28 that performs the above-described processing functions as the image writing unit according to the present invention. When the writing of the image to the image display medium 12 is completed as described above, the current date and time is stored in the memory or the like as the current image writing date and time in step 132, and then the display medium driving process is terminated. Note that step 132 corresponds to the time measuring means described in claim 2 together with step 100 described above.

Thus, in the present embodiment, a first refresh voltage higher than the display drive voltage V1 is alternately applied between the electrodes 24 and 22 with a relatively long polarity switching period T _L , and the display is performed between the electrodes 24 and 22. Since the image is written after the second refresh voltage higher than the drive voltage V1 is alternately applied with a relatively short polarity switching period T _S , the display density changes with respect to the voltage applied at the time of image writing. The generation of insufficient cells or pixels can be prevented, and the display density of the image display medium 12 at the time of image writing is uniform over the entire surface, so that the image quality of the image displayed on the image display medium 12 can be improved. Can be improved.

Further, in this embodiment, as the elapsed time from the previous image writing becomes longer, the polarity switching period _TL in the alternating application of the first refresh voltage becomes longer, the number of times of application of the first refresh voltage increases, Since the polarity switching period T _L , the voltage V, and the number of times of application are set so that the refresh voltage (voltage V) of 1 is increased, the image display medium 12 is relatively free from the image written last time. Even in a state where a long time has elapsed, the alternating application of the first refresh voltage generates cells or pixels whose display density changes insufficiently with respect to the voltage applied during image writing. This can be surely prevented.

  Note that the first refresh power supply 34 and the second refresh power supply are not limited to the configuration shown in FIG. 5A. For example, as shown in FIG. Or an AC power supply 64 that outputs an AC voltage. Further, when the voltage of the same polarity is intermittently repeatedly applied at the time of display erasure prior to image writing, the image display medium 12 has a slight display density as the number of times of voltage application increases as shown in FIG. It has a characteristic that the contrast of the display image is improved as a result. Based on the above characteristics, the second refresh power supply 34 may be configured so that a voltage having the same polarity can be intermittently and repeatedly applied as the second refresh voltage.

  For example, in the second refresh power supply 33 shown in FIG. 5C, one of the two input terminals is connected to the plus terminal of the DC power supply 66 and the other is grounded, and the input is made via the two input terminals. The switching element 68 that selectively outputs one of the two signals (potential) is controlled by a control unit (not shown) so that the output signal (potential) is periodically switched. . Therefore, the potential output as the second refresh output from the second refresh power source 33 shown in FIG. 5C is alternately switched to a high potential or a ground potential with a certain polarity (shown in FIG. 5C). By also supplying the first refresh output to the column electrode driving unit 30, the second refresh voltage having the same polarity is intermittently repeated on the row electrode 22 and the column electrode 24 of the image display medium 12. Can be applied. It goes without saying that the same refresh voltage may be intermittently repeatedly applied to the first refresh voltage instead of alternating application.

In the above, as the elapsed time from the previous image writing becomes longer, the polarity switching period T _L in the alternating application of the first refresh voltage becomes longer, the number of times of application of the first refresh voltage increases, and the first The polarity switching period T _L , voltage V, and number of times of application of the first refresh voltage are alternately set so that the magnitude of the refresh voltage (voltage V) is increased. However, the present invention is not limited to this. The polarity switching period T _L , the voltage V, and the number of times of application of the first refresh voltage in alternating application may be fixedly determined in advance. The invention described in claim 1 includes this aspect within the scope of the right.

Further, in the above as a refresh of the image display medium 12, after the alternating application of a voltage with a relatively long polarity switching period T _L, it is alternating application of a voltage in a relatively short polarity switching period T _S. Here, the main purpose of alternating voltage application with a relatively short polarity switching period T _S is to make the display density of the image display medium 12 uniform over the entire surface. When some of the particles 20 are attached with strong adhesive force and the substrate or adjacent particles, also be relatively short polarity switching period T _S display density of the image display medium 12 even when the alternating application of a voltage in is not uniform Conceivable. Therefore, as described above, after the voltage is alternately applied with the relatively long polarity switching period T _L , the voltage is alternately applied with the relatively short polarity switching period T _S (the first period is more than the second period). long has been set) that is, after peeling the adhesion between the substrate and the adjacent particles of the colored charged particles have been made, it means that uniformity of display density over the entire surface of the image display medium is performed, The display density can be made uniform with higher accuracy, and a higher image quality of the display image can be realized.

  In the above description, the display medium according to the present invention has been described by way of example of the image display medium 12 provided with electrodes having a structure premised on driving in a simple matrix system. However, the present invention is not limited to this. Needless to say, the present invention can be applied to a display medium having a structure premised on driving in an active matrix system.

In the above description, the image display medium 12 having the configuration in which the electrodes 22 and 24 are formed on the opposing surfaces of the substrates 14 and 16 has been described as an example of the display medium according to the present invention. However, the present invention is not limited to this. You may use the image display medium of the structure by which the electrode is not formed in the board | substrate. In this case, when refreshing and writing the image display medium, an external electrode pair group separate from the image display medium is disposed in the vicinity of the image display medium, and a voltage is applied between the external electrode pair group to Display media can be refreshed and images can be written. Although this aspect corresponds to the invention described in claim 6 , this aspect has an effect that the display medium can be configured at low cost because it is not necessary to provide an electrode group on the display medium.

  Next, the results of experiments conducted by the inventors will be described. In this experiment, a predetermined image is written on an image display medium having a display dot number of 32 × 32 dots, left for a predetermined time (display holding time), and all dots (pixels) of the image display medium are alternating with a predetermined size and frequency. After refreshing the image display medium by applying a voltage for a predetermined number of pulses, writing the predetermined image to the image display medium 12 again and counting the number of dots in which the display density defect has occurred is retained. The test was repeated while changing the time and refresh conditions (the magnitude of the applied voltage, the frequency, and the number of applied pulses). Table 2 below shows the refresh conditions, display holding time, and experimental results (occurrence of dot defects) in this experiment.

表２より明らかなように、画像表示媒体のリフレッシュとして、印加電圧の大きさが±210Ｖで比較的高周波（400Hz）の交番電圧を印加した場合、印加時間(周期（＝極性切替周期×２）×印加パルス数)を変化させたとしても、表示保持時間が６時間以上になると一部のドットに表示濃度不良が生ずる。また、印加電圧の大きさを±280Ｖまで増大させると表示保持時間が６時間のときにはドット不良は生じないものの、表示保持時間が12時間以上になると一部のドットに表示濃度不良が生ずる。また、交番電圧の周波数を30Hzにまで低下させた場合にも、表示保持時間が６時間以上で一部のドットに表示濃度不良が生じており、ドット不良改善効果は認められない。

As is apparent from Table 2, when an alternating voltage having a voltage of ± 210 V and a relatively high frequency (400 Hz) is applied to refresh the image display medium, the application time (period (= polarity switching period × 2) Even if the number of (applied pulses) is changed, a display density defect occurs in some dots when the display holding time is 6 hours or more. Further, when the magnitude of the applied voltage is increased to ± 280 V, a dot defect does not occur when the display holding time is 6 hours. However, when the display holding time is 12 hours or more, a display density defect occurs in some dots. Further, even when the frequency of the alternating voltage is lowered to 30 Hz, a display density defect occurs in some dots when the display holding time is 6 hours or more, and the dot defect improvement effect is not recognized.

  On the other hand, in each refresh condition described as “present invention” in Table 2, the frequency of the alternating voltage is set to 20 Hz or less (the cycle is 50 ms or more). Is recognized. In other words, the condition where the frequency is 20 Hz, the applied voltage is ± 210 V, and the number of applied pulses is 5 pulses is compared with the condition where the frequency is 400 Hz, the applied voltage is ± 280 V, and the applied pulse number is 10 pulses. Thus, it can be understood that the dot defect occurrence situation is the same even though the applied voltage is small, and the dot defect improvement effect is produced. Also, when the frequency is 10 Hz (cycle is 100 ms), the applied voltage is ± 210 V, and the number of applied pulses is 5 pulses, no dot defect occurs even if the display holding time is 12 hours, and the frequency is 1 Hz (cycle) 1 second), under the condition that the applied voltage is ± 210 V and the number of applied pulses is 5 pulses, no dot failure occurs even with a display holding time of 48 hours, the frequency is 1 Hz, and the applied voltage is ± 280 V. Under the condition where the number of applied pulses is 3, no dot defect occurs even when the display holding time is 168 hours, so it is clear that a remarkable dot defect improvement effect is produced.

  Further, the inventors of the present application fixed the magnitude of the applied voltage to ± 210 V, the number of applied pulses to 10 pulses, and the display holding time for each value in order to confirm the frequency of the alternating voltage at which the dot defect improvement effect can be obtained. An experiment was conducted to confirm the maximum frequency (shortest cycle) at which no dot defect occurred. The results of this experiment are shown in FIG. In FIG. 11, the maximum frequency at which no dot defect occurs is shown as a pulse width (= polarity switching period, time during which a voltage with a constant polarity is applied), but the elapsed time after display (display holding time) is 5 hours. If it exceeds, the shortest pulse width at which no dot defect occurs is abruptly changed, and it can be understood that the dot defect cannot be eliminated unless the pulse width is increased to 50 msec (= frequency 20 Hz, period 100 msec) even at the shortest.

Therefore, although depending on conditions such as the tolerance of defective dots, the length of the assumed display holding time, the magnitude of the applied voltage, and the allowable length of time required for refresh, the alternating voltage applied during refresh is, for example, As described in claim 3, it is preferable that the frequency is 20 Hz or less and the pulse width (polarity switching period) is 50 ms or more (≧ 100 ms), the frequency is 10 Hz or less and the pulse width is 100 ms. It is more preferable that the period is as described above (≧ 200 msec). As a result, the colored charged particles are more reliably peeled off from the substrate and adjacent particles during the period in which the alternating voltage is applied, and dot defects are suppressed and display images are further improved in image quality. realizable. In consideration of the fact that it is preferable that the display density of the image display medium is uniform at the time of image writing, as described in the previous embodiment, after applying the low frequency alternating voltage as described above, a relatively high frequency is displayed. It is desirable to further apply an alternating voltage (for example, an alternating voltage having a frequency of 400 Hz, an applied voltage of ± 210 V, and an applied pulse number of 10 pulses).

  Further, the inventors of the present application fixed the frequency of the alternating voltage to 1 Hz in order to confirm the number of applied pulses of the alternating voltage at which the dot defect improving effect is obtained, and no dot defect occurs when the display holding time is each value. Experiments were conducted to confirm the minimum number of applied pulses (the shortest application time) when the applied voltage was ± 210 V and ± 280 V, respectively. The results of this experiment are shown in FIGS. As is clear from FIG. 12 and FIG. 13, when the elapsed time after display (display holding time) exceeds a certain value, the minimum number of applied pulses (shortest applied time) at which dot defects do not occur monotonically increases. In order to suppress the occurrence of dot defects when the elapsed time after display exceeds a certain value, it can be understood that the number of applied pulses is preferably increased in accordance with the increase in elapsed time after display.

  Further, as apparent from comparison of FIG. 13 with FIG. 12, when the magnitude of the applied voltage is increased, the post-display elapsed time in which the minimum number of applied pulses (shortest applied time) does not cause a dot defect occurs monotonically. As the threshold of (display holding time) increases, the minimum number of applied pulses that do not cause dot defects also decreases, and accordingly, the application time of alternating voltage (time required for refresh) also decreases. Therefore, the magnitude of the applied voltage and the number of applied pulses (alternating voltage application time) depend on which one of the conditions of “small applied voltage” and “allowable length of time required for refresh” is prioritized. Can be determined.

It is a schematic block diagram of the image display apparatus which concerns on this embodiment. (A) is sectional drawing of the display medium along the II-II line | wire of FIG. 1, (B) is a top view which shows an example of the shape and arrangement | positioning of the cell in an image display medium. It is a block diagram which shows schematic structure of a power supply part and a drive part. It is a top view which shows the connection state of each electrode and drive part of a display medium. It is the schematic which shows an example of a structure of a 1st refresh power supply / a 2nd refresh power supply, respectively. It is a diagram which shows the relationship between the applied voltage between electrodes in a display medium, and a density | concentration. It is the schematic for demonstrating the magnitude | size of each electric potential for applying the voltage for a drive. It is a flowchart which shows the content of the display medium drive process performed with a control apparatus. It is a diagram which shows an example of transition of the voltage applied to the specific cell (pixel) of a display medium. It is a diagram which shows an example of the relationship between the application frequency of the 2nd voltage for a refresh, and the contrast of a display image. It is a diagram which shows the result (The relationship between the elapsed time after a display and the shortest pulse width which can eliminate a dot defect) which the inventor etc. implemented. It is a diagram which shows the result (relationship between the elapsed time after a display, and the minimum number of applied pulses which can eliminate a dot defect) which the inventor etc. implemented. It is a diagram which shows the result (relationship between the elapsed time after a display, and the minimum number of applied pulses which can eliminate a dot defect) which the inventor etc. implemented.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image display apparatus 12 Image display medium 14 Display side board | substrate 16 Back side board | substrate 18 Black particle 20 White particle 22 Row electrode 24 Column electrode 26 Power supply device 28 Control apparatus 30 Column electrode drive part 32 Row electrode drive part 33 For 2nd refresh Power supply 34 First refresh power supply 35 Drive power supply 38 High voltage output section 60 Switching section

Claims (8)

At least one is light-transmitting and a group of colored charged particles is enclosed between a pair of substrates opposed to each other with a gap therebetween, in accordance with an electric field formed by a voltage applied between the pair of substrates. A display medium driving device for driving a display medium in which a display density is changed by moving a colored charged particle group between the pair of substrates,
Image writing means for writing the image to be written to the display medium by applying a voltage according to the image to be written between the pair of substrates;
Prior to writing an image on the display medium by the image writing means, a voltage is intermittently or alternately applied between the pair of substrates at a first period, and then the first substrate is interposed between the pair of substrates. in a second period shorter than the period, the Brighter fresh control means voltage is intermittently applied or alternately applying less than the voltage for intermittently applied or alternately applied in the first period,
A display medium driving apparatus comprising: Further comprising time measuring means for measuring the display holding time of the image written on the display medium,
The refresh control means lengthens the first period as the display holding time measured by the time measuring means becomes longer, and intermittent application or alternation of voltage between the pair of substrates in the first period. The at least one of increasing the applied time and increasing the magnitude of the voltage that is intermittently applied or alternately applied in the first period between the pair of substrates is performed. The display medium driving device according to claim 1. It said first circumferential-life, the frequency is below 20Hz, or drive device for a display medium of claim 1, wherein the application time of a constant polarity voltage is characterized in that it is set to a period equal to or greater than 50 milliseconds. A gap member that divides the gap into a plurality of cells is provided in the gap between the pair of substrates, and the colored charged particle group is enclosed in each cell partitioned by the gap member. 3. The display medium driving device according to claim 1, wherein the display medium driving device is a display medium driving device. The pair of substrates are each provided with an electrode group so that different voltages can be applied between the pair of substrates at a plurality of pixel positions on the substrate, and at least provided on the substrate side having translucency. The electrode group has translucency, and voltage is applied between the pair of substrates at each pixel position by applying a voltage between a pair of electrodes facing each other at each pixel position. The display medium driving device according to claim 1 or 2 . When a voltage is applied between the pair of substrates, the external electrode pair separate from the display medium is disposed opposite to the pair of substrates, and the pair of substrates is applied by applying a voltage between the pair of external electrodes. 3. The display medium driving device according to claim 1, wherein a voltage is applied between the display medium and the display medium. At least one is light-transmitting and a group of colored charged particles is enclosed between a pair of substrates opposed to each other with a gap therebetween, in accordance with an electric field formed by a voltage applied between the pair of substrates. A display medium driving method for driving a display medium in which a display density is changed by moving a colored charged particle group between the pair of substrates,
After intermittently applying or alternatingly applying a voltage between the pair of substrates at a first period, intermittently at the first period between the pair of substrates at a second period shorter than the first period. Apply a voltage smaller than the voltage to be applied or alternating applied intermittently or alternately applied,
Subsequently, a voltage corresponding to an image to be written is applied between the pair of substrates to write the image to be written on the display medium. The display holding time of the image written on the display medium is measured by the time measuring means,
As the measured display holding time becomes longer, the first cycle is lengthened, and the time during which the voltage is intermittently or alternately applied between the pair of substrates in the first cycle is lengthened, and the pair The display medium driving method according to claim 7 , wherein at least one of increasing a magnitude of a voltage to be intermittently applied or alternately applied in the first period between the substrates is performed .

Images