JP2007293233A - Electrochromic display device and display drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochromic display device capable of preventing excessive decoloration and to provide a display drive device used for the display device. <P>SOLUTION: When decoloration drive of a display segment is performed by applying a constant current to the display segment, a decoloration pulse intermittently outputting the constant current is repeatedly applied to an electrode of the display segment from a constant current applying circuit 20, a voltage value in response to electromotive force generated in the display segment is detected by a voltage detection circuit 20-4 when the constant current in the decoloration pulse is not applied, and application of the decoloration pulse by the constant current applying circuit 20 is ended when the output of the voltage detection circuit 20-4 exceeds a preset reference value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrochromic display device and a display driving device.

  Various display devices (hereinafter referred to as electrochromic display devices) have been proposed that utilize a phenomenon in which a solute in an electrolytic solution is precipitated or dissolved by an oxidation-reduction reaction by injecting electric charge into the electrolytic solution. For example, in the case of an electrochromic display device using bismuth (Bi) as a main raw material, when a negative charge is injected into the electrolyte from a transparent electrode such as indium tin oxide (ITO), Bi ions in the electrolyte are reduced. It deposits on the transparent electrode, and the part develops a black color. Conversely, when a positive charge is injected from the transparent electrode into the electrolytic solution, Bi deposited on the transparent electrode is oxidized and dissolved in the electrolytic solution, and the portion is decolored.

  In this type of electrochromic display device, the amount of solute deposited depends on the amount of charge injected into the electrolyte, so the larger the display area, the greater the amount of solute deposited by injecting more charges. Must.

  In order to inject charges according to the area of the display portion in this manner, conventionally, charges are injected by applying a rectangular wave voltage pulse, or applying a triangular wave or sawtooth wave voltage pulse. Yes. For example, in Patent Document 1, coloring and decoloring are performed by applying a rectangular wave voltage pulse to the display unit. Here, when a rectangular wave pulse for a certain period of time is applied to the display unit from a display drive device that performs display drive of the display unit, if the wiring resistance to the display unit can be ignored, the resistance value in the display unit during color development is the display area. It is known to be inversely proportional. It is also known that the resistance value is inversely proportional to the display area in the same manner as in the color development until the color erase is completed even at the time of color erase. Therefore, if a constant voltage is applied for a certain period of time, it is possible to inject an amount of charge that is substantially proportional to the display area.

  By the way, the method of simply applying a certain amount of voltage waveform has a problem that it is difficult to keep the balance between the amount of solute to be precipitated and the amount of solute to be dissolved, and the operating life is short. In other words, if the coloration and decolorization are repeated many times, the balance between the amount of precipitation and the amount of dissolution will be lost, excessive precipitation will result in the disappearance of part of the color development part, or the dissolution of the solute will progress too much in the electrolyte. Other substances (such as iodine) are likely to cause problems such as discoloration of the electrolyte. In particular, when the time from the color development step to the color erasing step becomes long, the color erasure naturally occurs, so that the over color erasure easily occurs.

In order to solve such a problem of over-erasing, in Patent Document 2, when a decoloring current is applied to the display unit by applying a constant voltage, the current change is detected and the current value is detected. There has been proposed a method for ending the decoloring drive when the value of the color becomes less than a certain value, that is, when the apparent resistance value of the display unit becomes greater than a certain value.
JP 2000-142223 A Japanese Patent Publication No. 5-46953

  In the case of color erasing, unlike the case of color development, it is known that the resistance value changes and the current decreases when the color erasure proceeds to some extent. In order to compensate for the decrease in the amount of charge due to the decrease in current, it is necessary to make the voltage in the case of decoloring higher than in the case of color development or to increase the voltage application time. . At this time, since the voltage drop occurs due to the wiring resistance between the display unit and the display driving device, the contact resistance between the circuits, etc., the flowing current changes greatly. Need to be adjusted. However, generally, the values of wiring resistance, contact resistance between circuits, and the like vary greatly, and it is not easy to make these values constant. That is, with the method of applying a constant voltage, it is difficult to perform display driving in consideration of the influence of the wiring resistance, contact resistance, and the like. Therefore, a method of performing display driving by applying a constant current to the display unit is conceivable. However, the method of Patent Document 2 detects a current value, and when the current value becomes a certain value or less, a constant voltage is detected. Therefore, it is difficult to apply to the constant current driving method. In addition, although the method of Patent Document 2 needs to detect a current value, the detection of the current value is less accurate than the detection of the voltage value, and the cost on the circuit is increased.

  The present invention has been made in view of the above circumstances, and provides an electrochromic display device capable of preventing over-erasing in an electrochromic display device and a display driving device used for such a display device. With the goal.

  In order to achieve the above object, an aspect of the electrochromic display device of the present invention includes an electrolytic solution and an electrode for injecting an electric charge into the electrolytic solution, and through the electrode by an oxidation-reduction reaction. Display means having at least one display portion that is colored when an electric charge is injected into the electrolytic solution and decolored when an electric charge having a polarity opposite to the electric charge is injected into the electrolytic solution; At the time of color, at least a decoloring pulse that intermittently outputs a constant current is repeatedly output at a predetermined application interval, and the decoloring pulse is applied to the electrode of the display unit to charge the electrolyte with the reverse polarity. And at least one constant current applying unit having a unit for injecting a voltage, and detecting a voltage value corresponding to an electromotive force generated in the electrode of the display unit when the decoloring pulse is not applied during the decoloring Voltage detection with means And when the voltage value detected by the voltage detection means exceeds a preset reference value at the time of the color erasing, to the electrode of the display section of the color erasing pulse by the constant current application means And a control means for terminating the application of.

  In order to achieve the above object, an aspect of the display driving device of the present invention includes an electrolyte solution and an electrode for injecting electric charge into the electrolyte solution, and the electrode is formed by an oxidation-reduction reaction. Display driving of display means in which at least one display unit is arranged that develops color by injecting electric charge into the electrolytic solution and discolors by injecting electric charge of opposite polarity to the electric charge into the electrolytic solution A display driving device that performs at least a constant current intermittently output at a predetermined application interval at the time of the color erasing, and applies the color erasing pulse to the electrode of the display unit And at least one constant current applying means having means for injecting the charge of the opposite polarity into the electrolyte solution, and generated at the electrode of the display unit when the decoloring pulse is not applied during the decoloring Detects the voltage value corresponding to the electromotive force Voltage detecting means having means for decoloring, and when the voltage value detected by the voltage detecting means exceeds a preset reference value during the decoloring, the decoloring pulse of the constant current applying means Control means for terminating the application of the display portion to the electrodes.

  According to the present invention, in an electrochromic display device and a display driving device used in such a display device, a decoloring pulse for intermittently outputting a constant current is repeatedly output at the time of decoloring and is applied to an electrode of a display unit. Applied and driven, detects the voltage value corresponding to the electromotive force generated in the display unit when the decoloring pulse is not applied, and terminates the decoloring operation when the voltage value exceeds a predetermined reference value Thus, it is possible to prevent over-erasing.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration of an electrochromic display device to which the display driving device according to the first embodiment of the present invention is applied. FIG. 2 is a diagram illustrating an arrangement example of display segments of the display panel. The electrochromic display device shown in FIG. 1 includes a display panel 10, a constant current application circuit 20, a segment profile memory 30, and a system interface 40. In the electrochromic display device according to the present embodiment, as shown in FIG. 1, the display panel 10 has a plurality of display segments, and each display segment is driven by applying a constant current from a constant current applying circuit 20. In particular, the current value of the current applied to each display segment is set to a current value proportional to the area of each display segment based on the value stored in the segment profile memory 30. Yes.

  The display panel 10 as a display means is a segment type display panel, and a plurality of display segments as a display unit are arranged, for example, as shown in FIG. Here, the example of FIG. 2 is an arrangement example of display segments when the display panel 10 is used as a display panel for displaying a display pattern such as alphabets and numbers, and includes seven display segments (display segments 10). -1 to 10-7) are arranged in an 8-character form. Note that the shape, number, and arrangement of the display segments are not limited to those shown in FIG. 2, and can be appropriately changed according to the specifications required for the display panel.

  FIG. 3 is a cross-sectional view taken along the line AA for explaining the configuration of the display segment of FIG. Here, the cross-sectional view of FIG. 3 is a cross-sectional view of the display segment 10-1, but the configuration of the other display segments is basically the same as that described in FIG.

  As shown in FIG. 3, in the display segment, two electrodes (electrodes 10-11 and 10-12) are arranged in parallel, and an electrolytic solution 10-13 is interposed between the electrodes 10-11 and 10-12. It is satisfy | filled and these are sealed and comprised by the sealing material 10-14. Furthermore, the glass substrate 10-15 for protecting a display segment is affixed on the back surface of the electrode 10-11. Here, the electrode 10-11 is a transparent electrode having transparency, and for example, an indium tin oxide (ITO) electrode is used. The electrode 10-12 may be a transparent electrode or an opaque electrode. For example, a copper (Cu) electrode is used as the electrode 10-12. Furthermore, the electrolytic solution 10-13 is an electrolytic solution in which, for example, Bi and Cu are dissolved. In addition, the material shown here is an example and can be changed suitably. For example, the solute dissolved in the electrolytic solution is not limited to Bi, but may be silver (Ag) or the like. Further, not only metals but also organic substances such as viologen compounds can be used. Various solutions such as odorous acid, hydrochloric acid, and iodic acid can be used for dissolving Bi and Cu. Furthermore, as the electrolytic solution 10-13 between the electrode 10-11 and the electrode 10-12, a wet cake sheet holding the electrolytic solution may be used.

  When a negative charge is injected into the display segment configured as shown in FIG. 3, Bi ions in the electrolytic solution are reduced and deposited on the electrode 10-11. As a result, the display segment is colored black. Conversely, when a positive charge is injected into the display segment, Bi deposited on the electrode 10-11 is oxidized and dissolved in the electrolytic solution. As a result, the display segment that has been colored black is erased.

  The constant current application circuit 20 is provided corresponding to each of the plurality of display segments constituting the display panel 10 by the number of display segments. By applying a constant current to each display segment, the display segments are colored or erased. An electric charge for injecting is injected. Here, as shown in FIG. 1, the constant current application circuit 20 includes a coloring pulse generator 20-1, an erasing pulse generator 20-2, a constant current driver 20-3, and a voltage detection circuit 20-4. It consists of and. Each circuit of the constant current application circuit 20 and its operation will be described in detail later.

  The segment profile memory 30 stores the value of the area of each display segment, or the current value designation data necessary for appropriate color development corresponding to the area of each display segment, corresponding to each display segment. It is a memory for. In the following description, it is assumed that the current value designation data corresponding to the area of each display segment is stored in the segment profile memory 30, but the value of the area of each display segment is stored, for example, the coloring pulse generator 20 -1 and the decoloring pulse generator 20-2 may have a function of converting into corresponding current value designation data. Then, the segment profile memory 30 receives the address signal from the system interface 40, and converts the current value designation data stored in the address into the coloring pulse generator in the constant current application circuit 20 connected to the corresponding display segment. 20-1 and the decoloring pulse generator 20-2. The segment profile memory 30 is preferably a nonvolatile memory such as an EPROM or a flash ROM. By configuring the segment profile memory 30 with a non-volatile memory, it is possible to retain the stored contents even when the circuit power is turned off.

  The system interface 40 receives an instruction to display or hide the display panel 10 from a CPU as a control unit (not shown), and develops or erases a display segment corresponding to the instruction. For this purpose, the system interface 40 outputs the pulse width designation data to the coloring pulse generator 20-1 and the decoloring pulse generator 20-2 in the corresponding constant current application circuit 20, and also displays the display segment for coloring or decoloring. The address signal corresponding to the address where the current value designation data corresponding to is stored is output to the segment profile memory 30.

Next, the constant current application circuit 20 will be described in more detail.
FIG. 4 is an example of a circuit block diagram in the case where the decoloring pulse generator 20-2 is configured by a sequential logic circuit. As shown in FIG. 4, the decoloring pulse generator 20-2 includes a pulse width register 20-21, a current value register 20-22, a DA converter 20-23, a down counter 20-24, and an analog switch 20. -25.

  The pulse width register 20-21 receives pulse width designation data for designating the pulse width of the decoloring pulse from the system interface 40 and holds the data.

  The current value register 20-22 receives current value designation data corresponding to each display segment from the segment profile memory 30, and holds the data. The DA converter 20-23 converts the current value designation data held in the current value register 20-22 into an analog voltage signal.

  The down counter 20-24 receives a START pulse from the system interface 40 at the time of decoloring, reads the value held in the pulse width register, and counts down this value at regular time intervals, and sends an ON or OFF signal to the analog switch 20- To 25. That is, the down counter 20-24 outputs an ON signal when the count value is not 0, and outputs an OFF signal when the count value becomes 0. The analog switch 20-25 is connected to the DA converter 20-23 and the positive power source + V, and is turned on when receiving an ON signal from the down counter 20-24, and the output of the DA converter 20-23 is constant current driver 20-. 3 and when the OFF signal is received, the voltage value + V is input to the constant current driver 20-3.

  With such a configuration, the analog switch 20-25 is turned on only while the down counter 20-24 is counting, so that the voltage value and pulse width designation data obtained by the DA converter 20-23 are designated as a result. A decoloring pulse having a predetermined pulse width is input to the constant current driver 20-3. When the down counter 20-24 finishes counting, the analog switch 20-25 is turned OFF, and the voltage value + V is input to the constant current driver 20-3.

  Although FIG. 4 shows the configuration of the decoloring pulse generator 20-2, the coloring pulse generator 20-1 can also be realized with a circuit configuration substantially similar to that of the decoloring pulse generator 20-2. However, in the coloring pulse generator 20-1, the power source connected to the analog switch is not a positive power source but a negative power source -V. The coloring pulse generator 20-1 can change the pulse width so that the display segment can be colored not only in a completely colored state and a completely decolored state, but also in an intermediate state. As a result, gray scale display is possible.

  Note that the functions of the coloring pulse generator 20-1 and the decoloring pulse generator 20-2 may be realized by arithmetic processing such as a microcomputer.

  FIG. 5 is a diagram illustrating an example of a circuit constituting the constant current driver 20-3 and the voltage detection circuit 20-4. FIG. 6 is a diagram showing the wiring resistance between the constant current application circuit and the display segment. The constant current driver 20-3 includes a negative direction constant current applying unit including an operational amplifier 20-31, a MOS transistor 20-32, and a resistor 20-33, an operational amplifier 20-34, and a MOS transistor 20-35. And a positive direction constant current applying means comprising resistors 20-36. Further, the voltage detection circuit 20-4 is constituted by, for example, an AD converter.

  In FIG. 5, the output (coloring pulse or -V) from the coloring pulse generator 20-1 is input to the non-inverting input terminal of the operational amplifier 20-31. The output terminal of the operational amplifier 20-31 is connected to the gate of the MOS transistor 20-32. The source of the MOS transistor 20-32 is connected to the inverting input terminal of the operational amplifier 20-31 and one end of the resistor 20-33. ing. Furthermore, the other end of the resistor 20-33 is connected to a negative power source -V. Further, the output (erasing pulse or + V) from the decoloring pulse generator 20-2 is input to the non-inverting input terminal of the operational amplifier 20-34. The output terminal of the operational amplifier 20-34 is connected to the gate of the MOS transistor 20-35, and the source of the MOS transistor 20-35 is connected to the inverting input terminal of the operational amplifier 20-34 and one end of the resistor 20-36. ing. Further, the other end of the resistor 20-36 is connected to a positive power supply + V.

  The drains of the MOS transistors 20-32 and 20-35 are commonly connected to the output terminal of the constant current driver 20-3. The output terminal of the constant current driver 20-3 is connected to a display segment, for example, the display segment 10-1, as shown in FIG. 6, and is also connected to the voltage detection circuit 20-4. The resistance indicated by reference numeral 10-16 in FIG. 6 is resistance due to wiring resistance, contact resistance, or the like between the constant current driver 20-3 and the display segment 10-1.

  Hereinafter, the operation of the constant current driver 20-3 will be described. Note that the negative direction constant current applying means and the positive direction constant current applying means are the same in the basic operation except that the polarity of the input voltage and the direction of the output current are opposite. Only the operation of the constant current applying means will be described.

  In the configuration shown in FIG. 5, when the display segment is decolored, the decoloring pulse from the decoloring pulse generator 20-2 is input to the non-inverting input terminal of the operational amplifier 20-31. By the input of the decoloring pulse, the output of the operational amplifier 20-34 is applied to the gate of the MOS transistor 20-35, and the MOS transistor 20-35 is turned on. Thereby, the current corresponding to the voltage value of the decoloring pulse is directed from the output terminal of the constant current driver 20-3 toward the positive power supply + V (that is, from the display segment 10-1 toward the constant current driver 20-3). ) Flowing.

  Here, as shown in FIG. 5, since the positive direction constant current applying means constitutes a constant current driver, the positive direction constant current applying means is applied to the display segment 10-1 regardless of the voltage change in the display segment 10-1. The amount of current is constant. In this way, positive charges are injected into the display segment 10-1.

  When + V is input from the decoloring pulse generator 20-2, the output of the operational amplifier 20-31 becomes 0. Accordingly, the MOS transistor 20-35 is turned off, and the constant current driver. The current output from 20-3 becomes zero.

  When a coloring pulse is input from the coloring pulse generator 20-1 to the negative direction constant current applying means, the output terminal of the constant current driver 20-3 is directed to the negative power source -V (that is, the constant current). Current flows from the driver 20-3 toward the display segment 10-1.

  In addition, the voltage detection circuit 20-4 configured by an AD converter, for example, displays a display segment at the time of decoloring when no decoloring pulse is applied, that is, when no current is output from the constant current driver 20-3. A voltage corresponding to the electromotive force generated in the circuit is detected, and the voltage value is input to a CPU (not shown) via the system interface 40. That is, it is known that the electrochromic display device has a characteristic that the electrical resistance of the display segment increases as the color disappears, and a characteristic that an electromotive force is generated in the display segment. Among these, the electromotive force is detected as a voltage value by the voltage detection circuit 20-4.

  FIG. 7 is a timing chart showing the current applied from the constant current application circuit 20 to the display segment and the change in voltage generated by this current during color development and color erasing. In the figure, the upper side of the drawing is the positive direction and the lower side of the drawing is the negative direction.

In the present embodiment, the coloring pulse is applied to the display segment as one coloring pulse having a continuous constant current, for example. This coloring pulse is a negative constant current (current in the direction from the display segment 10-1 to the constant current driver 20-3) designated by the pulse width designated by the pulse width designation data and the current value designation data. When such a color development pulse is applied to the display segment, negative charges corresponding to the applied current × application time are injected into the display segment, and color development occurs. Here, the amount of electric charge necessary for appropriately coloring the display segment is about 30 mC / cm ² in the case of an electrolyte containing Ag or Bi as a main material. In the first embodiment, however, the display segment It is possible to accurately control the amount of charge injected into the display segment by changing the application time of the constant current applied to the display segment.

  The decoloring pulse is a plurality of current pulses in which application of a constant current is repeated intermittently. In this case, each current pulse has a constant pulse width designated by the pulse width designation data and a constant positive constant current designated by the current value designation data (direction from the constant current driver 20-3 to the display segment 10-1). Current). The decoloring pulse is repeatedly applied at regular intervals, for example. However, the decoloring pulse interval is not limited, and the decoloring pulse interval may be appropriately changed. When such a decoloring pulse is applied to the display segment, a positive charge corresponding to the applied current × application time × number of times of application is injected into the display segment, causing decoloration. In the present embodiment, as an example, the application time of each current pulse is 10 ms. Further, it is assumed that the next pulse is applied across the non-application state of 20 ms, and in accordance with the timing, a decoloring pulse generator 20-2 of the constant current application circuit 20 from a CPU (not shown) via the system interface 40. A START pulse is applied to the.

  That is, from a CPU (not shown), the pulse width designation data corresponding to 10 ms is written to the pulse width register 20-21 of the decoloring pulse generator 20-2 via the system interface 40, and the START pulse is erased. -2 to the down counter 20-24. As a result, as described above, the analog switch 20-25 is turned on only while the down counter 20-24 is counting the pulse width designation data corresponding to the 10 ms. As a result, the DA converter 20-23 obtained the analog switch 20-23. A decoloring pulse having a voltage value is input to the constant current driver 20-3. When the down counter 20-24 finishes counting, the analog switch 20-25 is turned OFF, and the voltage value + V is input to the constant current driver 20-3. Therefore, a constant current is applied to the display segment for 10 ms. The pulse width designation data and the START pulse are output from the CPU with a non-application interval of 20 ms, that is, by supplying the pulse width designation data and the START pulse every 30 ms, as shown in FIG. A decoloring pulse is applied to the display segment.

  Note that the amount of current that flows during color development or color erasure is the limit that the voltage generated in the display segment by this current is higher than the voltage required to color or color the display segment, and the display segment is not destroyed. The voltage is made lower than the limit voltage, which is a voltage.

In this embodiment, the end of the decoloring process is determined as follows.
The display segment has a characteristic that the electrical resistance value of the display segment increases as the color disappears and a characteristic that an electromotive force is generated. In the present embodiment, the characteristic that an electromotive force is generated is used, and the completion of the decoloring process is detected based on the value of the electromotive force.

  That is, at the time of erasing, when a current pulse is repeatedly applied at the above interval, as shown in FIG. 7, the voltage generated in the display segment also moves up and down according to the application state. When the decoloring does not proceed, the voltage generated in the display segment when no current pulse is applied returns to almost 0 volts. Further, when the current pulse is repeatedly applied at the above intervals, the resistance value of the display segment increases when the decoloring progresses to some extent, and the voltage rises as shown in FIG. An electromotive force generated in the display segment appears as a voltage when no pulse is applied. Therefore, when no current pulse is applied, for example, immediately before the next current pulse is applied, the voltage value of this electromotive force generated in the display segment is detected by the voltage detection circuit 20-4. Then, when the detected voltage value becomes equal to or higher than the decoloring process end voltage Vr, which is a preset reference value, the CPU (not shown) determines that the decoloring is completed and ends the application of the decoloring pulse. Let

  Next, an example of a method for setting the decoloring process end voltage Vr, which is the reference value, will be described with reference to FIG.

  When setting the erasing process end voltage Vr, a current pulse having the same current value and application time as the erasing pulse is applied once to the display segment in a state where the initial characteristics are maintained. Here, the state in which the initial characteristics are maintained ideally includes an initial state in which no current is applied after manufacturing, but it is accumulated by, for example, grounding the electrodes of the display segment for a predetermined time or more. It also includes a display segment that has been restored to its initial characteristics by sufficiently discharging the charge. In such a state where the initial characteristics are maintained, the coloring process has not been performed, so that even when the current pulse is applied once, an over-erased state occurs and an electromotive force is generated in the display segment. Then, a voltage value detected by the voltage detection circuit 20-4 after a predetermined time (= application interval between two decoloring pulses in the decoloring process as shown in FIG. 7 described above: 20 ms in the present embodiment). Is adopted as the decoloring step end voltage Vr. This is performed for each display segment, and the decoloring process end voltage Vr is set for each display segment. That is, in the decoloring process of each display segment, when the voltage value detected by the voltage detection circuit 20-4 becomes the decoloring process end voltage Vr, the display segment is in a state where the decoloring is completed. Therefore, this time is the end of decoloring.

  The erasing process end voltage Vr is stored in an internal memory of a CPU (not shown) or a memory accessible by the CPU. Alternatively, it may be stored in the segment profile memory 30 and read out from the segment profile memory 30 for use by the CPU at the start of the decoloring process.

  With such a method, the decoloring process end voltage Vr can be set for each display segment.

  As described above, according to the first embodiment, the erasing current that flows during the erasing process is not a continuous constant current application, but a plurality of current pulses in which a constant current is repeatedly output intermittently. As a result, the state of the electromotive force generated in the display segment when no constant current is applied can be observed, and the end of the decoloring process is determined according to this electromotive force. Even when the time until the color erasing process is long and natural color erasure occurs, the end of the color erasing process can be appropriately determined.

[Second Embodiment]
Next, a second embodiment of the present invention will be described.

  Since the configuration of the display driving apparatus according to the second embodiment is the same as that of the first embodiment, illustration and description thereof are omitted. However, in the present embodiment, the voltage detection circuit 20-4 uses the current flowing from the output terminal of the constant current driver 20-3 toward the positive power source + V and the constant current driver 20 when a constant current is applied in the decoloring pulse. -3 is also detected in accordance with the load (display segment resistance, wiring resistance, etc.) connected to -3, and the voltage value is input to the CPU (not shown) via the system interface 40. Of course, as in the first embodiment, when no constant current is applied in the decoloring pulse, that is, when no current is output from the constant current driver 20-3, this corresponds to the electromotive force generated in the display segment. The voltage is detected, and the voltage value is input to a CPU (not shown) via the system interface 40. That is, in the second embodiment, the voltage detection circuit 20-4 generates an electric resistance of the display segment that increases as the decoloring progresses and an electromotive force generated in the display segment as the decoloring progresses. Detect as voltage value.

  FIG. 9 is a timing chart showing changes in current and voltage in the decoloring process by the display driving apparatus according to the second embodiment. The coloring process is the same as in the first embodiment.

  In the second embodiment, as a decoloring pulse, a constant current is continuously applied at the initial stage of the decoloring process, that is, at a portion where the resistance value change of the display segment is small, and at a portion where the resistance value variation is large, A current pulse that outputs a constant current as in the first embodiment is intermittently repeatedly applied. Thereby, when the charge amount injected into the display segment in the decoloring process is the same, the time required for the decoloring process can be made shorter than that in the first embodiment.

  Here, switching from the continuous constant current application to the intermittent application of the current pulse is performed when the voltage value at the time of application of the constant current detected by the voltage detection circuit 20-4 is the resistance value of the display segment. This is performed when a preset threshold value Vb is exceeded in accordance with the change.

  An example of a method for setting the threshold value Vb will be described with reference to FIG. When setting the threshold value Vb, first, coloring is performed for an arbitrary time to precipitate a solute in the electrolytic solution. Next, the voltage generated in the display segment is decolored while being detected by the voltage detection circuit 20-4, and the voltage value of the portion where the resistance value change is small (for example, the portion indicated by reference numeral 100 in FIG. 10) is detected. . In addition to this voltage value, a limit voltage at which the display segment is not destroyed is detected, and a predetermined number of times that the resistance value change is small is set to a threshold value Vb based on conditions such as a ratio of these voltages and a noise component of the detected voltage. And In the experiment of the present applicant, it is preferable that the threshold value Vb is set to about 1.15 times the voltage of the portion where the resistance value change is small.

  With such a method, the threshold value Vb can be set for each display segment. Further, the voltage generated in the display segment is detected in a state including the influence of the wiring resistance to the display segment. Therefore, by setting the threshold value Vb by the method as described above, it is not necessary to calculate the wiring resistance for each display segment and set the threshold value Vb.

  In the above example, the threshold value Vb is set by multiplying the voltage value of the portion where the resistance value change is small by a predetermined number, but by adding the predetermined voltage value to the voltage value of the portion where the resistance value change is small. May be set.

  The threshold value Vb may be set within the initial setting process when the display driving device is turned on. However, the state of the display driving device changes due to changes in the surrounding environment such as temperature. As a result, the threshold value Vb also needs to be changed. Therefore, the threshold value Vb is preferably set every time decoloring is performed.

  Alternatively, the threshold value Vb may be set once every predetermined number of times of decoloring.

[Third Embodiment]
Next, a third embodiment of the present invention will be described.

  Since the configuration of the display driving apparatus according to the third embodiment is the same as that of the second embodiment, illustration and description thereof are omitted. However, in the present embodiment, two types of current values i 1 and i 2 are stored in the segment profile memory 30.

  FIG. 11 is a timing chart showing changes in current and voltage in the decoloring process by the display driving apparatus according to the third embodiment. The coloring process is the same as in the first embodiment.

  In the second embodiment, as the decoloring pulse, a constant current is continuously applied in a portion where the resistance value change of the display segment is small, and a current pulse that repeatedly outputs a constant current is intermittently output in a portion where the resistance value change is large. Applied. On the other hand, as shown in FIG. 11, in the third embodiment, when the current pulse is intermittently repeatedly output, the current value i2 is the current value when the constant current is continuously applied. It should be smaller than i1.

  According to the third embodiment, the voltage increases with an increase in the resistance value of the display segment. However, the constant current value is lowered in a portion where such a change in the resistance value is large. It is possible to reliably prevent the display segment from being destroyed by the voltage increase.

  The current values i1 and i2 are both stored in the segment profile memory 30, but may be stored in a storage device different from the segment profile memory 30.

  Although the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications and applications are naturally possible within the scope of the gist of the present invention.

  For example, each of the above-described embodiments describes a segment type display panel, but the method of each of the above-described embodiments can also be applied to a dot matrix type display panel. However, in the case of the dot matrix method, the area of each display unit is the same, so the segment profile memory 30 is not necessarily required. In this case, the decoloring process end voltage Vr may be a common value for each display segment.

  Also, the application time of the current pulse in the decoloring pulse is 10 ms, and the application interval (non-application time) 20 ms between the two current pulses in the decoloring pulse is an example, and the present invention is not limited thereto.

  Furthermore, the embodiments described above include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be extracted as an invention.

1 is a block diagram illustrating a configuration of an electrochromic display device to which a display driving device according to a first embodiment of the present invention is applied. It is a figure which shows the example of arrangement | positioning of a display segment. It is sectional drawing for demonstrating the structure of a display segment. It is an example of a circuit block diagram when the decoloring pulse generator is configured by a sequential logic circuit. It is a figure which shows an example of the circuit which comprises a constant current driver and a voltage detection circuit. It is a figure shown about wiring resistance between a constant current application circuit and a display segment. It is a timing chart which shows the change of the electric current applied to a display segment from a constant current application circuit at the time of color development and erasing, and the voltage which generate | occur | produces with this electric current. It is a figure for demonstrating the setting method of the erasing process end voltage Vr. It is a timing chart which shows the change of the current and voltage at the time of decoloring by the display drive device concerning a 2nd embodiment of the present invention. It is a figure for demonstrating the setting method of the threshold value Vb. It is a timing chart which shows the change of the current and voltage at the time of decoloring by the display drive device concerning a 3rd embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Display panel 10-1 to 10-7 ... Display segment 10-11, 10-12 ... Electrode 10-13 ... Electrolytic solution 10-14 ... Sealing material 10-15 ... Glass substrate 20 ... Constant current application circuit 20- DESCRIPTION OF SYMBOLS 1 ... Color development pulse generator 20-2 ... Decoloration pulse generator 20-3 ... Constant current driver 20-4 ... Voltage detection circuit 20-21 ... Pulse width register 20-22 ... Current value register 20-23 ... DA converter 20 -24 ... down counter 20-25 ... analog switch 20-31, 20-34 ... operational amplifier 20-32, 20-35 ... MOS transistor 20-33, 20-36 ... resistor 30 ... segment profile memory 40 ... system interface.

Claims (20)

An electrolyte and an electrode for injecting electric charge into the electrolytic solution, and color is generated by injecting electric charge into the electrolytic solution through the electrode by oxidation-reduction reaction, and the electric charge is injected into the electrolytic solution. Display means in which at least one display section that is erased by injecting a charge having a polarity opposite to that of the display means,
At the time of the decoloring, at least a decoloring pulse for intermittently outputting a constant current is repeatedly output at a predetermined application interval, and the decoloring pulse is applied to the electrode of the display unit so that the reverse polarity is applied to the electrolyte solution. At least one constant current applying means having means for injecting a charge of
Voltage detecting means having means for detecting a voltage value corresponding to an electromotive force generated in the electrode of the display unit when the decoloring pulse is not applied during the decoloring;
When the voltage value detected by the voltage detection means exceeds a preset reference value during the color erasing, the constant current application means applies the color erasing pulse to the electrode of the display unit. Control means to terminate;
An electrochromic display device comprising: The constant current applying means further includes means for continuously applying the constant current to the electrodes of the display unit during the decoloring,
The voltage detection means further includes means for detecting a voltage value generated in the electrode of the display unit by application of the constant current by the constant current application means,
The control unit applies the constant current continuously to the electrodes of the display unit at the time of the decoloration, and the voltage value detected by the voltage detection unit according to the continuous application of the constant current. 2. The electrochromic display according to claim 1, wherein the constant current application unit is controlled to be switched so that the constant current is intermittently applied by the decoloring pulse when the threshold value exceeds a preset threshold value. apparatus.   The current value of the constant current applied to the display unit from the constant current application unit is further provided with a current value setting unit that makes the value proportional to the area of the electrode of the display unit. The electrochromic display device described in 1.   The control means sets the current value of the constant current when intermittently output by the decoloring pulse from the constant current application means to a value smaller than the current value of the constant current when continuously output The electrochromic display device according to claim 2, further comprising:   The reference value is obtained by applying the decoloring pulse once to the electrode of the display unit in a state where the display unit maintains initial characteristics, and the application of the decoloring pulse is completed. The electrochromic display device according to any one of claims 1 to 4, wherein the electrochromic display device is set to a voltage value corresponding to an electromotive force generated in the display unit after a time corresponding to an application interval has elapsed. . The display unit is a display segment for forming a predetermined display pattern, and a plurality of the display units are arranged on the display unit.
6. The electrochromic display device according to claim 1, wherein the reference value is set for each display segment.   The threshold value is based on a voltage value generated in the display unit during a period when the resistance value change of the display unit is small during a period in which the constant current is continuously applied to the electrode of the display unit during the decoloring. The electrochromic display device according to claim 2, wherein the electrochromic display device is set.   The electrochromic display device according to claim 7, wherein the threshold value is set to a value obtained by multiplying the voltage value generated in the display unit by a predetermined number in a period in which the resistance value change of the display unit is small.   The electrochromic display according to claim 7, wherein the threshold value is set by adding a predetermined value to the voltage value generated in the display unit in a period in which the resistance value change of the display unit is small. apparatus.   The electrochromic display device according to claim 7, wherein the threshold value is set every time the decoloring is performed.   The electrochromic display device according to claim 7, wherein the threshold value is set every time the decoloring is performed a predetermined number of times. The display unit is a display segment for forming a predetermined display pattern, and a plurality of the display units are arranged on the display unit.
The electrochromic display device according to claim 7, wherein the threshold is set for each display segment. An electrolyte and an electrode for injecting electric charge into the electrolytic solution, and color is generated by injecting electric charge into the electrolytic solution through the electrode by oxidation-reduction reaction, and the electric charge is injected into the electrolytic solution. A display driving device that performs display driving of display means in which at least one display unit that is decolored by injecting a charge of the opposite polarity to
At the time of the decoloring, at least a decoloring pulse for intermittently outputting a constant current is repeatedly output at a predetermined application interval, and the decoloring pulse is applied to the electrode of the display unit to apply the reverse polarity to the electrolyte. At least one constant current applying means having means for injecting a charge of
Voltage detecting means having means for detecting a voltage value corresponding to an electromotive force generated in the electrode of the display unit when the decoloring pulse is not applied during the decoloring;
When the voltage value detected by the voltage detection means exceeds a preset reference value during the color erasing, the constant current application means applies the color erasing pulse to the electrode of the display unit. Control means to terminate;
A display driving device comprising: The constant current applying means further includes means for continuously applying the constant current to the electrodes of the display unit during the decoloring,
The voltage detection means further includes means for detecting a voltage value generated in the electrode of the display unit by application of the constant current by the constant current application means,
The control unit applies the constant current continuously to the electrodes of the display unit at the time of the decoloration, and the voltage value detected by the voltage detection unit according to the continuous application of the constant current. The display driving device according to claim 14, wherein when the value exceeds a preset threshold value, the constant current is controlled to be intermittently applied by the decoloring pulse.   The current value setting means for making the current value of the said constant current applied to the said display part from the said constant current application means into the value proportional to the area of the electrode of the said display part is further provided, It is characterized by the above-mentioned. The display drive device described in 1.   The control means sets the current value of the constant current when intermittently output from the constant current applying means by the decoloring pulse to a value smaller than the current value of the constant current when continuously output. The display driving device according to claim 14, further comprising: means.   The reference value is obtained by applying the decoloring pulse once to the electrode of the display unit in a state where the display unit maintains initial characteristics, and the application of the decoloring pulse is completed. The display driving device according to claim 13, wherein the display driving device is set to a voltage value corresponding to an electromotive force generated in the display unit after a time corresponding to the application interval has elapsed.   The threshold value is set based on a voltage value generated in the display unit during a period when the resistance value change of the display unit is small during the period in which the constant current is continuously applied during the decoloring. The display driving device according to claim 14, wherein the display driving device is a display driving device.   The display driving apparatus according to claim 18, wherein the threshold value is set every time the color erasing is performed.   The display driving apparatus according to claim 18, wherein the threshold is set every time the decoloring is performed a predetermined number of times.

Images