JP4929646B2 - Display drive device and display drive method for display medium with memory - Google Patents

Description

  The present invention relates to a display drive device and a display drive method for a display medium having a memory property, and more particularly to a method for detecting an image quality abnormality in a display medium having a memory property.

  Conventionally, as a so-called electronic paper that can be repeatedly rewritten, an image display medium having a memory property such as rotating colored particles (Twisting Ball Display), electrophoresis, thermal rewritable, liquid crystal having a memory property, electrochromy, etc. Those using technology are known.

  Among these, an image display medium in which black particles and white particles having different charging characteristics are sealed between sheets facing each other has been proposed as an image display medium that displays using particles (toner) (Patent Document 1). ). Such an image display medium displays an image as the contrast between black particles and white particles by applying a voltage between sheets to form an electric field and moving the particles.

  In an image display medium having a memory property using such particles, the display density may change by rewriting the display repeatedly. One of the causes is a change in threshold value in the drive voltage. Such image defects are not caused by limited single particles, but are caused by a change in the relationship between the drive voltage and the display density in the entire image area.

  FIG. 7 shows the relationship between drive voltage and display density. Originally, when the drive voltage is increased to increase the density, the hysteresis curve is traced along the XABY path, and when the drive voltage is decreased to decrease the density, the hysteresis curve is traced along the YEFX path. The relationship between the drive voltage and the display density changes due to particle deterioration or the like, and a phenomenon occurs that a hysteresis curve spreads along a path of XCDY when the density is increased and YGHX when the density is decreased.

  That is, when the drive voltage of the display medium is in the range up to a, the density remains constant white, the density increases as the drive voltage increases at the boundary of a, and when it exceeds b, the density is constant in black. The particle charge amount changes, and the drive voltage threshold at which the display density changes changes from a and b to c and d. Conversely, the same phenomenon occurs when the color is changed from black to white. As a result, the white display part is covered or the density of the black display part is lowered. In order to prevent such a phenomenon, it is necessary to select a voltage necessary for rewriting.

As a technology for selectively applying a voltage, conductive particles are sealed between a transparent display substrate having an electrotransport property, a medium having a charge transport layer having a minute gap as a surface layer, and a medium to which a voltage can be applied. Then, by selectively applying a voltage, an image forming method for forming an image by selectively attaching conductive particles on the medium, and an electric field is applied between the substrates to move the colored particles. There has been proposed a rewritable image display medium that displays (Patent Document 2).
JP 2001-31225 A JP 2000-347483 A

  However, in rewriting an image on a display medium using an electric field, it is necessary to grasp the electrical characteristics of the particles of the display medium in order to select the optimum voltage necessary for rewriting. There was a problem that it was difficult to grasp each and the error was large.

  The present invention has been made to solve the above-described problems, and accurately detects the particle charge amount of the display medium, selects parameters such as the magnitude of voltage necessary for rewriting, and changes the display density. It is an object to obtain a display drive device and display drive method for a display medium having no memory.

In order to achieve the above object, the display driving device according to claim 1 is an insulating particle in which an image display element of a display medium having a memory property is charged according to a plurality of colors, and an insulating film is applied. A display driving device for applying a voltage to a pair of electrodes arranged to face each other at a pixel position in the display medium in which the particles are sealed between a pair of electrode substrates arranged to face the display medium. A driving power supply for outputting a driving voltage applied to the electrode pair for displaying an image on the display medium and an erasing voltage applied to the electrode pair for erasing the image displayed on the display medium; and the display A potential difference between the electrode pairs remaining in the display medium in a state where a voltage is not applied between the electrode pairs after a predetermined image is displayed on the display medium when a condition including a measurement request for the medium is satisfied. Measure That the potentiometric unit, based on a relationship between the particle charge amount of the display medium and the potential difference, and deriving the particle charge amount of the display medium from the potential difference measured, to the electrode pairs in accordance with the particle charge amount Updating means for updating a predetermined parameter relating to the voltage to be applied.

  The display driving apparatus according to the present invention is a display driving apparatus that applies a voltage to an electrode pair arranged to face each other at a pixel position in a display medium having a memory property, and the electrode pair for displaying an image on the display medium. And a driving power source for outputting an erasing voltage to be applied to the electrode pair in order to erase an image displayed on the display medium.

  The potential difference measuring means is configured to display a predetermined image on the display medium when a condition including a measurement request for the display medium is satisfied, and then the electrode pair remaining on the display medium in a state where no voltage is applied between the electrode pairs. Measure the potential difference. Experiments have confirmed that there is a unique relationship between the residual voltage and the amount of charged particles on the display medium.

  Therefore, the updating unit updates a predetermined parameter regarding the voltage necessary for rewriting and the like based on the charge amount derived from the residual voltage. In this way, display rewriting or the like is performed using appropriate parameters, so that image defects such as density reduction can be prevented.

  In addition, as described in claim 2, when there is a measurement request and the elapsed time from the previous rewrite is a predetermined time or more, or when the display medium moves, or the ambient temperature of the display medium Alternatively, the potential difference may be measured when the value is outside the predetermined range or when the display density of the display medium is outside the predetermined range. Thereby, the selection of the voltage by updating the parameters can be performed at an appropriate timing, and the defect of the display image can be efficiently prevented.

  Further, according to the third aspect of the present invention, the parameters of the present invention include the magnitude of the erase voltage, the magnitude of the drive voltage, the voltage application time of the erase voltage, the voltage application time of the drive voltage, the AC frequency of the erase voltage, and the drive voltage. At least one of the AC frequency, the erase voltage voltage waveform, and the drive voltage voltage waveform.

  According to a fourth aspect of the present invention, an image display element of a display medium having a memory property is an insulating particle charged in accordance with a plurality of colors, and an insulating film is applied and disposed opposite to the display medium. A display driving method of applying a voltage to a pair of electrodes arranged to face each other at a pixel position in the display medium in which the particles are sealed between a pair of electrode substrates, the condition including a measurement request for the display medium Is established, the potential difference between the electrode pairs remaining in the display medium is measured in a state where no voltage is applied between the electrode pairs after displaying a predetermined image on the display medium, and the measured It is characterized in that a particle charge amount of the display medium is derived from a potential difference, and a predetermined parameter relating to a voltage applied to the electrode pair is updated according to the particle charge amount.

  By driving the image display medium by such a display driving method, it is possible to prevent image defects such as density reduction.

  In addition, as described in claim 5, when there is a measurement request and the elapsed time from the last rewrite is a predetermined time or more, or when the display medium moves, or the ambient temperature of the display medium Alternatively, the potential difference may be measured when the value is outside the predetermined range or when the display density of the display medium is outside the predetermined range.

  Further, according to the present invention, the parameters of the present invention include the magnitude of the erase voltage, the magnitude of the drive voltage, the voltage application time of the erase voltage, the voltage application time of the drive voltage, the AC frequency of the erase voltage, and the drive voltage. At least one of the AC frequency, the erase voltage voltage waveform, and the drive voltage voltage waveform.

  As described above, according to the present invention, in a display drive that performs display rewriting with an electric field on a display medium having a memory property, image defects such as a decrease in density due to particle deterioration of the display medium can be prevented and improved. The effect is that an image can be displayed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an image display apparatus 10 according to the present embodiment.

  The image display device 10 includes a display medium 12, a control unit 14, a drive power supply 16, an update unit 18, a potential difference measurement unit 20, a detection switch 22, a column electrode drive circuit 24, a row electrode drive circuit 26, switching elements 28 and 30, And the noise reduction means 32 is comprised.

  Although not shown for simplicity, the control means 14 and the detection switch 22, the control means 14 and the column electrode drive circuit 24, and the control means 14 and the row electrode drive circuit 26 are connected to each other.

  As shown in FIG. 2, the display medium 12 includes a display-side substrate 34 having translucency, and a back-side substrate 36 disposed to face the display-side substrate 34 with a gap therebetween. The gap between the front-side substrate 34 and the back-side substrate 36 is held at a minute and constant interval by a gap holding member (not shown). In this gap, black particles 38 and white particles 40 having different charging characteristics are provided. (For example, the black particles 38 are positively charged and the white particles 40 are negatively charged).

  The black particles 38 and the white particles 40 are made of, for example, insulating particles. However, the present invention is not limited to this, and conductive particles may be used. As the black particles 38 and the white particles 40, for example, the types of particles described in Patent Document 1 can be used.

  Further, on the surface of the display-side substrate 34 facing the back-side substrate 36, a line-shaped (strip-shaped) transparent electrode 42 extending in the first direction (the left-right direction in FIGS. 1 and 2) is a first electrode. A plurality of lines are formed in parallel along a second direction (vertical direction in FIG. 1, direction perpendicular to the paper surface in FIG. 2) perpendicular to the direction. A plurality of line-shaped electrodes 44 extending in the second direction are formed in parallel along the first direction on the surface of the back side substrate 36 facing the display side substrate 34. Thus, the transparent electrode 42 and the electrode 44 are arranged so that the display medium 12 can be driven by a simple matrix method.

  When the display medium 12 is driven by a simple matrix system, the intersection position of the transparent electrode 42 and the electrode 44 functions as a pixel of the display medium 12 and is applied between the transparent electrode 42 and the electrode 44 at each intersection position. According to the magnitude of the electric field generated by the voltage, the movement of the black particles 38 and the white particles 40 at each intersection position, that is, the display density at each intersection position is controlled. Hereinafter, the transparent electrode 42 is referred to as a “row electrode 42”, and the electrode 44 is referred to as a “column electrode 44”.

  The drive power supply 16 generates, for example, a plurality of types of voltages with a single power supply, and divides the power supply voltage with a plurality of voltage dividing resistors and uses a smoothing capacitor provided corresponding to each voltage dividing resistor. The configuration is such that a plurality of stable voltages are generated, and a voltage having a desired potential is selected from these voltages and output. The output voltage is output separately to the column electrode drive circuit 24 and the row electrode drive circuit 26. The potential is selected according to an instruction from the control means 14.

  The control means 14 is a means capable of controlling the output by a rewritable program such as a computer equipped with a CPU, PLD, FPGA, etc., and is operated by the power supplied from the drive power supply 16 and selects the output voltage for the drive power supply 16. At the same time, image information is output to the column electrode drive circuit 24 and the row electrode drive circuit 26. As a result, a voltage corresponding to the image information is applied to the row electrode 42 and the column electrode 44, the particles move, and an image is displayed.

  In addition, after the driving power supply 16 is driven, the control unit 14 sets the electrodes according to the potential difference between the electrodes remaining on the display medium 12 when the detection switch 22 that connects the display medium 12 and the driving power supply 16 is turned off after a certain period of time has elapsed. The updating means 18 is instructed to update a predetermined parameter with respect to the internal voltage.

  The column electrode drive circuit 24 includes the same number of switching elements 28 as the number of column electrodes 44 provided in the display medium 12. By turning on and off the switching elements 28, the column electrode drive circuit 24 receives power from the drive power supply 16. Turns on / off the application of output voltage.

  Although not shown, the individual switching elements 28 of the column electrode drive circuit 24 are connected to the control means 14 and the individual column electrodes 44, and correspond to the image information of the line image supplied from the control means 14. It is turned on and off by the control signal.

  The row electrode driving circuit 26 includes the same number of switching elements 30 as the number of row electrodes 42 provided in the display medium 12, and the driving power supply 16 for the row electrodes 42 is turned on and off. Turns on or off the application of the output voltage from.

  Although not shown, each switching element 30 of the row electrode drive circuit 26 is connected to the control means 14 and each row electrode 42. For example, the first row is controlled by a control signal supplied from the control means 14. The image is rewritten by sequentially turning on the switching elements corresponding to the row electrodes to the switching elements corresponding to the last row electrode.

  The noise reduction means 32 is installed between the control means 14 and the potential difference measurement means 20, and reduces noise so that an accurate potential difference is obtained.

  Next, the operation of the display driving apparatus in the present embodiment will be described along the flowchart shown in FIG.

  First, in step 100, when there is a measurement request at the time of rewriting a display medium having a memory property, a detection mode of the particle charge amount of the display medium starting from the measurement of the potential difference starts.

  In step 102, the drive power supply 16 is driven to apply a voltage to the display medium 12, and the image of the part (the entire display medium) where the particle charge amount is detected is rewritten.

  In step 104, after a predetermined time has elapsed, the detection switch 22 connecting the display medium 12 and the drive power supply 16 is turned off. Thereby, the image display state of the display medium 12 is maintained as it is. Further, when the detection switch 22 is turned off, the particles of the display medium 12 are lifted and floated, so that a potential difference corresponding to the charge amount of the particles is generated although the voltage is weak.

  Note that the detection switch 22 is turned off after a lapse of a certain time because the movement of particles for image display requires a certain amount of time in an instant, and therefore the particles can move over the entire surface of the display medium. By waiting for the passage of time.

  In step 106, the residual voltage is measured by the potential difference measuring means 20. The residual voltage is measured by turning off the detection switch 22 after a predetermined time has elapsed after being driven by the drive power supply 16 and disconnecting from the power supply. An average potential is obtained for a predetermined time after cutting, for example, 5 seconds between 5 seconds and 10 seconds.

  At this time, noise is reduced by installing the noise reduction means 32 between the control means 14 and the potential difference measurement means 20, and a more accurate value is obtained. Specifically, it is preferable to provide a magnetic shield such as a VCCI-compatible ferrite core so that an induction voltage from a commercial power supply and a low-pass filter that removes high-frequency components are not affected.

  FIG. 5 is a graph showing the relationship between the residual voltage and the amount of charged particles obtained here. Thus, it was newly confirmed by experiments that the particle charge amount and the residual voltage are proportional, and that the total particle charge amount increases when the residual voltage is large. For example, in a particle encapsulated substrate having a size of 420 mm × 298 mm, a relationship of a total charge amount of 4 μC is established with respect to a residual voltage of 0.3 V.

  FIG. 6 is a graph showing the relationship between the driving voltage and the particle charge amount. If the charge amount is larger than a certain value, the particles are agglomerated between particles due to a difference in charge amount from adjacent particles and cannot be driven, and electrostatic force that can move the charge amount by an electric field is not generated. Therefore, there is an appropriate charge amount for the particles to move, and if the charge amount is more appropriate, the particles can be driven with a lower driving voltage.

  As an example, it has been confirmed that particles can move if the charge amount is in the range of 2 to 10 μC, and can be driven if the residual voltage in FIG. 5 is in the range of 150 mV to 750 mV.

  In step 108, the charge amount of the particles of the display medium 12 is derived from the residual voltage measured in step 106. The derivation is performed by the control means 14 based on a charge amount derivation table stored in a storage means (not shown) connected to the control means 14. This table includes information representing the correspondence between the measured residual voltage and the charge amount corresponding to the residual voltage. However, the derivation method is not limited to this, and there is also a method in which a conversion formula for obtaining the charge amount from the residual voltage is defined and obtained by calculation.

  In step 110, a predetermined parameter for the voltage to be applied is updated according to the charge amount derived in step 108. Specifically, based on the charge amount obtained in step 108, the drive voltage is derived from the relationship between the charge amount and the drive voltage shown in FIG. The driving voltage is derived by using a table or defining a conversion formula as in the case of the above-described charge amount derivation.

  Regarding the relationship between the charge amount and the drive voltage, the threshold value A shown in FIG. 7 varies as the charge amount changes. However, although the value A in FIG. 7 is uniquely related to the drive voltage V in FIG. 6, the drive voltage is not uniquely related to the charge amount as shown in FIG. Therefore, the drive voltage is obtained from FIG. 6 based on the charge amount value obtained from the residual voltage based on the graph of FIG.

  Therefore, the control can be performed by feeding back the relationship between the A value that is the threshold of the drive voltage in FIG. 7 and the measured residual voltage in FIG.

  Specific methods for updating the parameters include a method of changing the magnitude of the applied voltage by automatically adjusting the input voltage of the boosting amplifier, and a voltage application by changing the drive circuit switch (transistor: not shown) application time. A method of changing the time, a method of changing the AC frequency by applying an alternating voltage by alternately applying a voltage to the display side and the back side, and a sine wave according to the particle state by creating a waveform in the power supply circuit, There is a method of changing a voltage waveform by changing a triangular wave, a rectangular wave and its inclination or frequency.

  In step 112, the display contents are erased by the voltage application method after updating the parameters. In the non-volatile display medium having a memory property according to the present application, when the image is rewritten, if the new image is displayed while the previous image is displayed, it is overwritten. There is. Even when an image is erased, a voltage is applied in the same manner as when displaying, and updating parameters regarding the erase voltage is also effective in preventing image defects caused by a change in charge amount.

  In step 114, the display is rewritten by the voltage application method after updating the parameters. Since the previous display contents are erased in step 112, an image is newly displayed here.

  FIG. 8 is a graph showing the relationship between the drive voltage after the parameter update and the display density. Here, since the drive start voltage is adjusted, the threshold A does not fluctuate, so that the display density is stabilized and image defects such as density reduction do not occur.

  FIG. 4 is a flowchart in the case where the above-described processing is performed by changing a driving sequence according to another embodiment. Here, only when a certain condition is satisfied in addition to the measurement request, the above-described processing from the potential difference measurement to the parameter change is performed, and when the condition is not satisfied, the display is rewritten with a normal potential.

  If there is a measurement request at the time of rewriting a display medium having a memory property in step 100, in order to determine the success or failure of other conditions for starting the particle charge amount detection mode of the display medium starting from the measurement of the potential difference. Proceed to step 202.

  In step 202, it is determined whether or not a predetermined time or more has elapsed since the previous rewriting. If it has elapsed, the process proceeds to step 102, and if not, the process proceeds to step 204. For example, it is determined whether one hour or one day has elapsed since the previous rewriting.

  As shown in FIG. 9, the elapsed time is detected by attaching a timer to the control means 14, installing a time storage means, writing the timer output time to the storage means at the end of rewriting, and outputting the timer output time at the time of a measurement request. This is done by comparing the previous rewrite time read from the storage means.

  In step 204, it is determined whether or not the display medium has been moved. If the display medium has moved, the process proceeds to step 102. If not, the process proceeds to step 206.

  To detect the presence or absence of movement, a movement detection sensor such as a pickup acceleration sensor is mounted, the detection result is output based on voltage information, and the movement is detected by the comparison means in the control means 14 based on whether or not the voltage is above a certain voltage. Alternatively, there is a method of detecting using position information detecting means such as GPS.

  In step 206, if the temperature around the display medium is outside the predetermined range, the process proceeds to step 102, and if it is within the predetermined range, the process proceeds to step 208.

  The ambient temperature is detected by mounting a temperature detection sensor such as a thermoelectric body or an infrared sensor on the control means 14.

  In step 208, the display is rewritten within the detection range of the density detection sensor. This is because it is not necessary to rewrite the entire display medium for density detection, in order to eliminate waste due to rewriting the entire display medium.

  In step 210, the density on the density detection sensor is detected. The display density is detected by mounting a reflection type light detection sensor (equivalent to a toner density sensor) on the control unit 14. If the density is outside the predetermined range, the process proceeds to step 102, and if it is within the predetermined range, step 212 is performed. Proceed to

  FIG. 10 shows a configuration diagram of the detection means (movement detection sensor, temperature detection sensor, concentration detection sensor). All the detection means are configured to mount the detection means on the control device. In addition, as shown in FIG. 11, the installation location does not interfere with the image area of the display medium 12, and therefore it is preferable to install the detection means outside the display area.

  In step 212, since it is not necessary to change the driving voltage from the series of condition determinations described above, the display display is rewritten at a normal potential. In step 214, the time at the end of the rewriting is stored and the process ends.

  If it is determined by the condition determination that the drive voltage needs to be changed, after performing the above-described steps 102 to 112, the time at the end of rewriting is stored in step 214, and the process ends.

It is a figure of an image display apparatus. It is sectional drawing of the image display medium along the AA line of FIG. It is the flowchart (the 1) which showed the flow of the display drive process which concerns on this embodiment. It is the flowchart (the 2) which showed the flow of the display drive process which concerns on this embodiment. It is a graph which shows the relationship between a residual voltage and particle | grain charge amount. It is a graph which shows the relationship between a drive voltage and particle charge amount. It is a graph (the 1) which shows the relationship between a drive voltage and image display density. It is a graph (the 2) which shows the relationship between a drive voltage and image display density. It is a block diagram of a detection means (elapsed time). It is a block diagram of a detection means (medium movement, temperature, density | concentration). It is a figure which shows the installation state of a detection means.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image display apparatus 12 Display medium 14 Control means 16 Drive power supply 18 Update means 20 Potential difference measurement means 22 Detection switch 24 Column electrode drive circuit 26 Row electrode drive circuits 28 and 30 Switching element 32 Noise reduction means 34 Display side board 36 Back side Substrate 38 Black particle 40 White particle 42 Row electrode 44 Column electrode

Claims (6)

The image display element of the display medium having a memory property is an insulating particle charged according to a plurality of colors, and the insulating film is applied between the pair of electrode substrates disposed opposite to each other in the display medium. A display driving device for applying a voltage to a pair of electrodes arranged to face each other at a pixel position in the display medium in which particles are enclosed ,
A driving power source for outputting a driving voltage applied to the electrode pair for displaying an image on the display medium and an erasing voltage applied to the electrode pair for erasing the image displayed on the display medium;
When a condition including a measurement request for the display medium is satisfied, the electrode pair remaining on the display medium in a state where no voltage is applied between the electrode pair after displaying a predetermined image on the display medium. A potential difference measuring means for measuring the potential difference of
Based on the relationship between the potential difference and the particle charge amount of the display medium, a particle charge amount of the display medium is derived from the measured potential difference, and a predetermined voltage is applied to the electrode pair according to the particle charge amount. Updating means for updating the given parameters;
A display drive device comprising: The condition includes the measurement request, and
If the elapsed time from the previous rewriting of the display medium is a predetermined time or more, or if the display medium has moved, or if the temperature around the display medium is outside the predetermined range, or the display If the display density of the medium is outside the specified range,
The display driving apparatus according to claim 1, wherein: The parameter is
The magnitude of the erase voltage, the magnitude of the drive voltage, the voltage application time of the erase voltage, the voltage application time of the drive voltage, the AC frequency of the erase voltage, the AC frequency of the drive voltage, and the voltage waveform of the erase voltage The display driving device according to claim 1, wherein the display driving device is at least one of a voltage waveform of the driving voltage. The image display element of the display medium having a memory property is an insulating particle charged according to a plurality of colors, and the insulating film is applied between the pair of electrode substrates disposed opposite to each other in the display medium. A display driving method for applying a voltage to a pair of electrodes arranged to face each other at a pixel position in the display medium in which particles are enclosed,
When a condition including a measurement request for the display medium is satisfied, the electrode pair remaining on the display medium in a state where no voltage is applied between the electrode pair after displaying a predetermined image on the display medium. Measure the potential difference of
Deriving the particle charge amount of the display medium from the measured potential difference,
A display driving method in which a predetermined parameter relating to a voltage applied to the electrode pair is updated in accordance with the particle charge amount. The condition includes the measurement request, and
When the elapsed time from the last rewriting of the display medium is a predetermined time or more, or when the display medium is moved, or when the temperature around the display medium is outside the predetermined range, or the display If the display density of the medium is outside the specified range,
The display driving method according to claim 4, wherein: The parameter is
The magnitude of the erase voltage, the magnitude of the drive voltage, the voltage application time of the erase voltage, the voltage application time of the drive voltage, the AC frequency of the erase voltage, the AC frequency of the drive voltage, and the voltage waveform of the erase voltage The display driving method according to claim 4, wherein the display driving method is at least one of a voltage waveform of the driving voltage.

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