JP5535811B2 - Display device - Google Patents

Description

  The present invention relates to a low power consumption display device including a display panel having a memory property for performing display by movement of charged particles.

  Conventionally, as thin display devices, liquid crystal display devices have been widely used in various electronic devices, and in recent years, they have also been used as large color displays such as computers and televisions. Plasma displays are also used as large color displays for televisions. However, although liquid crystal display devices and plasma displays are much thinner than CRT display devices, they are still not thin enough for some applications and cannot be bent. Moreover, when using as a display of a portable device, further reduction of power consumption is desired.

  Therefore, as a display device that realizes further thinning and low power consumption, a display panel called an electronic paper using an electrophoretic display element has been developed. An electronic book, an electronic newspaper, an electronic advertisement signboard, and a guidance display board are developed. Attempts have been made to use it. A display panel (display device) using the electrophoretic display element is provided with an image display layer in which charged particles are sealed between a pair of substrates each having an electrode on an opposing surface, and is applied between the electrodes of the pair of substrates. In accordance with the polarity of the voltage applied, the charged particles move by electrophoresis and display is performed.

  This electrophoretic display panel has a memory property because the charged particles do not move even if the drive voltage applied between the electrodes is removed, and the display state can be maintained even when the drive power is zero. The display period in which this display state is maintained may last from several seconds to several hours or months. For this reason, since this electrophoretic display panel can be driven with extremely little power, it is promising as a display device for portable devices such as wrist watches and mobile phones that require low power consumption.

[Description of configuration and operation of electrophoretic display panel]
Here, although it is publicly known, it helps to understand the present invention, so the configuration and operation of a conventionally known electrophoretic display panel will be outlined below with reference to FIGS. FIG. 9 shows an example of a cross section of the electrophoretic display panel, which is shown as a display panel 50. The display panel 50 is the same as the display panel used in the embodiment of the present invention.

  In the display panel 50, a transparent common electrode (common electrode) COM made of an ITO (indium tin oxide) film is formed on the entire back surface of a transparent resin substrate 51, and a microcapsule display layer also called electronic ink is formed thereon. 53 is formed. A flexible printed circuit board (hereinafter abbreviated as FPC) 55 having a segment electrode SEG for each pixel formed on the surface of the microcapsule display layer 53 is adhered and configured by an adhesive layer 54.

In the microcapsule display layer 53, a large number of microcapsules 60 having a diameter of about several tens of μm are dispersed in a mixture such as a binder, a surfactant, a thickener, and pure water. That is, in the display panel 50, a transparent resin substrate 51 and an FPC 55 are disposed as a pair of substrates, a common electrode COM is formed on one of the opposing surfaces, a segment electrode SEG is formed on the other surface, and a microelectrode is interposed therebetween. A capsule 60 is enclosed.

Next, the operation principle of the display panel 50 will be described with reference to FIG. In FIG. 10, a microcapsule 60 has white particles 63a made of titanium oxide or the like as charged particles and black particles 63b made of carbon black or the like as charged particles in a capsule shell 61 made of transparent methacrylic resin or the like. It is encapsulated in a state of being dispersed in a transparent dispersion medium 62 having a high density. The white particles 63a are negatively charged, and the black particles 63b are positively charged.

  Of the electrodes arranged so as to sandwich the microcapsule display layer 53, one of the entire common electrodes COM is grounded (0 V), and a negative voltage is applied to the segment electrode SEG on the other FPC 55. Since the negatively charged white particles 63a in the microcapsule 60 are moved to the transparent common electrode COM side by the electric field, and the positively charged black particles 63b are moved to the segment electrode SEG side, the viewing side (direction of arrow A) Looks white when viewed from above. On the other hand, in the portion where a positive voltage is applied to the segment electrode SEG, the black particles 63b positively charged in the microcapsule 60 by the electric field in the opposite direction are transferred to the transparent common electrode COM side, and the white particles 63a negatively charged are segmented. Since it moves to the electrode SEG side, it looks black when viewed from the viewing side.

  Further, as in the central microcapsule 60 in FIG. 10, in the microcapsule 60 at a position straddling the segment electrode SEG to which the negative voltage is applied and the segment electrode SEG to which the positive voltage is applied, one of the white particles 63a is present. The portion moves to the common electrode COM side, the rest moves to the segment electrode SEG side, a part of the black particles 63b moves to the segment electrode SEG side, and the rest moves to the common electrode COM side. However, detailed display is also possible.

  Therefore, the display panel 50 can change the display state to white or black depending on the polarity of the voltage applied between the common electrode COM and the segment electrode SEG. At this time, the white particles 63a and the black particles 63b move in the dispersion medium 62 by electrophoresis. However, since the dispersion medium 62 has a high viscosity, the display state is changed by applying a voltage, and then the application of the voltage is stopped. Even so, the intermolecular force of each particle can provide a memory effect that maintains its display state. As a result, the display panel 50 only has to apply a drive voltage only when the display is changed, and thus the power consumption is extremely small.

  Next, FIG. 11 shows an example in which characters such as numbers are displayed on the display panel 50 described above. In FIG. 11, the display panel 50 is composed of a display body that represents a seven-segment character SC consisting of segments S0 to S6 by one digit. Further, the surrounding area S7 of the segments S0 to S6 represents the background area of the seven segment character SC.

  The display panel 50 has one common electrode COM and eight segment electrodes as electrodes. The eight segment electrodes are the segment electrodes SEG0 to SEG6 corresponding to the segments S0 to S6 and the segment electrode SEG7 corresponding to the surrounding region S7. Further, the nine lines coming out from the lower part of the display panel 50 are lead wires connected to the common electrode COM and the eight segment electrodes SEG0 to SEG7, and each lead wire is connected to each segment to be connected. The same name as the electrode is shown. Each lead wire is connected to a driving means described later.

  Next, FIG. 12 shows a case where the seven segment character SC by the display panel 50 shown in FIG. 11 is changed from a state where the number “2” of (A) is displayed to a state where the number “3” of (B) is displayed. Show. In FIG. 12, in the first display state (A), the segments S0, S1, S3, S4 and S6 are black, and the segments S2 and S5 and the surrounding area S7 are white. In the changed display state (B), the segments S0, S1, S2, S3 and S6 are black, and the segments S4 and S5 and the surrounding area S7 are white.

In order to change the display from the number “2” in (A) to the number “3” in (B), the common electrode COM is always grounded (that is, 0 V), and is temporarily applied to the segment electrode SEG2 that changes from white to black. A positive drive voltage is applied, and a negative voltage is temporarily applied to the segment electrode SEG4 that changes from black to white. After that, the segment electrodes SEG2 and SEG4 return to 0V, which is the same potential as the common electrode COM, and the segment electrodes SEG0, SEG1, SEG3, SEG5, SEG6 and the segment electrode SEG7 in the surrounding area continue to be applied with 0V. .

  In this way, a positive or negative driving voltage is temporarily applied to the segment electrode to be rewritten to black or white, and 0 V having the same potential as that of the common electrode COM is continuously applied to the other segment electrodes whose display does not change. This is because, as described above, the display panel 50 has a memory property, so that the previous display state can be maintained as it is.

  However, in such an electrophoretic display panel, if a voltage is not applied for a long time after applying a driving voltage to make the display black or white, the charged particles in the display layer flow slightly but freely. As a result, the display density of white or black tends to change and approaches gray, and there is a problem that the contrast of display gradually decreases and visibility deteriorates. In addition, if the display voltage of a segment changes when the contrast decreases and the display rewrite voltage is applied to the segment electrode, the normal black or white density is not displayed and the display density varies. There is also a problem that the display quality deteriorates. Such a phenomenon is called an afterimage phenomenon and is one problem of the electrophoretic display panel.

  FIG. 13 is a graph showing an example of contrast reduction of the electrophoretic display panel. In FIG. 13, the horizontal axis represents elapsed time, and the vertical axis represents the light reflectance of the display panel. Here, a negative voltage is applied to the segment electrode of the electrophoretic display panel to display white (high light reflectance), and a positive voltage is applied to the other segment electrode to display black (low light reflectance). Then, the change in the light reflectance with the elapsed time after the drive voltage was set to zero (that is, no voltage applied state) was measured.

  As is apparent from FIG. 13, immediately after the drive voltage is applied, for example, the light reflectance of white display is about 40%, but decreases with the lapse of time, and the light reflectance after 10 hours is nearly 30%. It has dropped to. The light reflectance of black display is initially 5% or less, but increases along with the elapsed time, and the light reflectance after 10 hours increases to nearly 10%. Here, since the ratio of the light reflectance of white display and black display is contrast, it can be understood that the contrast decreases with the elapsed time. Since the decrease in contrast due to the elapsed time deteriorates the display quality of the display panel as described above, improvement is demanded.

  Against this background, in order to reduce the decrease in contrast due to the elapsed time after display rewriting, a display inversion pulse that rewrites the display is output when the display changes, and an overwrite pulse that overwrites the display is output when the display does not change A display device is disclosed (see, for example, Patent Document 1).

  Hereinafter, an outline of the driving voltage of the conventional electrophoretic display panel disclosed in Patent Document 1 will be described with reference to FIG. Here, the drive voltage shown in FIG. 14 indicates the segment drive voltage VS20-23 applied to any of the segment electrodes SEG of the display panel 50 shown in FIG. 9, and the voltage applied to the common electrode COM is 0V. The illustration is omitted because it exists.

In FIG. 14, the segment drive voltage VS20 is a drive voltage when the display is white and does not change (white → white), and the segment drive voltage VS21 is a drive when the display is black and does not change (black → black). The segment drive voltage VS22 is a drive voltage when the display changes from white to black (white to black), and the segment drive voltage VS23 is a case where the display changes from black to white (black to white). Drive voltage.

  The segment drive voltages VS20 and VS21 have a pre-period T10 for outputting a pre-pulse and an overwrite period T11 for outputting an overwrite pulse. The segment drive voltages VS22 and VS23 have a pre-period T10 for outputting a pre-pulse and a display inversion period T12 for outputting a display inversion pulse. The display period T13 is a period in which the drive voltage continues to be 0 V, and is a period for maintaining the display state.

  Here, the segment drive voltage VS20 that is output when the display transition is white → white is the negative voltage −V overwriting pulse P20m is output during the overwriting period T11, and the positive voltage is opposite in polarity to the overwriting pulse P20m. A + V pre-pulse P21p is output during the pre-period T10. In the display inversion period T12 (excluding T11) and the display period T13, which are other periods, 0 V having the same potential as that of the common electrode COM is output.

  The segment drive voltage VS21 that is output when the display transition is black → black is the positive voltage + V overwrite pulse P20p that is output during the overwrite period T11, and the negative voltage −V that is opposite in polarity to the overwrite pulse P20p. The pre-pulse P21m is output in the pre-period T10. In the display inversion period T12 (excluding T11) and the display period T13, which are other periods, 0 V having the same potential as that of the common electrode COM is output.

  The segment drive voltage VS22 output when the display transition is from white to black is output as a positive voltage + V display inversion pulse P22p in the display inversion period T12, and is negative in polarity opposite to the display inversion pulse P22p. A pre-pulse P23m having a voltage of −V is output in the pre-period T10. In the display period T13, 0 V having the same potential as that of the common electrode COM is output.

  Further, the segment drive voltage VS23 output when the display transition is black → white, the display inversion pulse P22m of negative voltage −V is output in the display inversion period T12, and the polarity is opposite to that of the display inversion pulse P22m. A pre-pulse P23p having a positive voltage + V is output in the pre-period T10. In the display period T13, 0 V having the same potential as that of the common electrode COM is output.

  Here, the overwriting pulses P20m and P20p change the display density of white or black when the voltage non-application state, which is a characteristic of the electrophoretic display panel having memory properties, is continued, and approaches the gray, thereby causing the display contrast. Is applied to reduce the phenomenon of gradually decreasing. That is, when the segment of the display panel 50 holds white and gradually approaches white to gray, the display state is brought to a normal white density by applying the negative voltage −V overwrite pulse P20m that becomes white again. Since it returns, the reduction in contrast can be reduced.

  Similarly, when the segment of the display panel 50 holds black and gradually approaches black to gray, the display state is changed to the normal black density by applying the positive voltage + V overwrite pulse P20p that becomes black again. The reduction in contrast can be reduced. In this way, the overwrite pulses P20m and P20p are applied with the voltage polarity in the direction that increases the density of the display state of the display panel 50 being selected, so even if there is a display portion where the display content does not change for a long time. It has been shown to prevent a reduction in display contrast.

Further, the pre-pulse output in the pre-period T10 will be described. The pre-pulse P21p of the segment drive voltage VS20 (white → white) is a positive voltage + V, and the overwrite pulse P20m output after that is negative. The voltage is -V. Here, when an overwrite pulse P20m having a negative voltage −V is periodically applied to the electrophoretic display panel, a direct current component of the negative voltage −V is slightly accumulated on the panel, and the electrophoretic display panel is viewed over a long period. There is a problem that it deteriorates and the reliability decreases. However, by applying the pre-pulse P21p having the opposite polarity in the pre-period T10 before the application of the overwrite pulse P20m, a reverse current flows between the electrodes of the electrophoretic display panel, and the driving is close to AC driving. And the integration of the DC component is reduced.

  Similarly, also in the segment drive voltage VS21, the pre-pulse P21m having the opposite polarity is applied before the overwrite pulse P20p to drive the electrophoretic display panel close to alternating drive. This indicates that the deterioration of the display panel can be reduced.

  The segment drive voltages VS22 and VS23 output a pre-pulse P23m before the display inversion pulse P22p, and output a pre-pulse P23p before the display inversion pulse P22m. The operation of the pre-pulses P23m and P23p at this time is such that the white or black display density changes in the display period T13 and approaches gray, and then the normal white or black density is temporarily returned by the pre-pulse. Therefore, there is an effect of rewriting to the target black or white density by the display inversion pulse and setting the density after rewriting to a normal level. Thereby, it is shown that the uneven density of display can be reduced.

  Here, an example in which the contrast of the display panel is improved by the driving voltage disclosed in Patent Document 1 (see FIG. 14) will be described with reference to FIG. FIG. 15 shows how the above-described example of contrast reduction (see FIG. 13) of the electrophoretic display panel is improved. In FIG. 15, the horizontal axis represents elapsed time, and the vertical axis represents the light reflectance of the display panel 50. Here, for example, in the case of a segment that displays white for a long time, such as the surrounding area S7 of the seven segment character SC in FIG. 11 described above, an overwrite pulse is synchronized with the timing each time a display rewrite signal for rewriting the display is received. When P20m (see FIG. 14) is applied, white display is repeatedly overwritten with white. As a result, as shown in the figure, the white display segment returns to the normal white density (for example, around the light reflectivity of 38%) at the timing of the display rewrite signal, so that a reduction in contrast can be prevented.

  Similarly, even if the seven segment character SC in FIG. 11 is displayed in reverse video and the surrounding area S7 is displayed in black for a long time, the overwrite pulse P20p (see FIG. 14) is applied, the black display is repeatedly overwritten with black. As a result, as shown in the figure, the black display segment returns to the normal black density (for example, around 5% of the light reflectance) at the timing of the display rewrite signal, so that a reduction in contrast can be prevented.

JP 2009-48077 A (pages 14 to 15, FIG. 5)

  However, the actual time of each period in Patent Document 1 is presented as an overwriting period T11 of about 16 mS, a display inversion period T12 of about 300 mS, and a pre-period T10 of ½ or less of the overwriting period T11. As a result of various experiments using the electrophoretic display panel, the inventor of the present invention significantly deteriorated the electrophoretic display panel when the voltage imbalance drive with different overwrite pulse width and pre-overwrite pulse width is frequently performed for a long time. Turned out to be invited. In addition, when alternating drive is performed with the pulse widths of the overwrite pulse and the pre-overwrite pulse being equal, in the region where the pulse width is short, the effect of the overwrite pulse is not fully exhibited, the contrast is not improved, and the pulse width is It was found that the contrast is good in a long region.

  FIG. 16 is a graph showing an example of experimental results of transition of the light reflectance R of the display panel with respect to the difference in pulse width between the overwrite pulse and the pre-overwrite pulse performed by the inventors of the present invention. In FIG. 16, the horizontal axis represents the pulse width (mS) of the applied overwrite pulse and the pre-overwrite pulse, and the vertical axis represents the light reflectance R of the display panel. In this experiment, a drive voltage is applied to the segment electrode of the electrophoretic display panel under a predetermined condition to display white (high light reflectance), and a drive voltage is applied to the other segment electrode under a predetermined condition to generate black. Display (low light reflectivity), and then make the pulse width of the pre-overwrite pulse and the overwrite pulse equal, apply over a predetermined period from a short pulse width to a long pulse width, and overwrite the white display segment. The light reflectance of each black display segment was measured. Here, Rw is the reflectance for white display, and Rb is the reflectance for black display.

  As is apparent from FIG. 16, when the pulse width of the overwrite pulse and the pre-overwrite pulse is 50 mS or less, the effect of the overwrite pulse is not exhibited, and the ratio of the light reflectance of white display and black display on the display panel. Contrast drops sharply. In addition, it can be understood that when the pulse width of the overwrite pulse and the pre-overwrite pulse is 100 mS or more, the region has a high contrast. In addition, although this cannot be expressed in FIG. 16, when the pulse width of the overwrite pulse and the pre-overwrite pulse becomes 150 mS or more, flickers appear on the display panel due to the effect of the pre-overwrite pulse, and the user can see it. It turned out to be uncomfortable and uncomfortable.

  An object of the present invention is to solve the above-described problems and provide a display device using an electrophoretic display panel that has a good contrast, does not notice flickering, and can operate for a long life.

  In order to solve the above problems, the display device of the present invention employs the following configuration.

In the display device of the present invention, a charged particle is sealed between a pair of substrates each having an electrode on an opposing surface, and a display panel having a memory property for performing display by movement of the charged particle, and display by inputting display data Driving means for applying a driving voltage to the electrodes of the panel, wherein the driving means stores a control unit that stores input display data, a waveform parameter unit that stores various waveforms of the driving voltage, A drive pulse generation unit that generates a drive pulse by selecting a waveform signal from the waveform parameter unit based on display data stored in the control unit, the drive pulse generation unit when the display data changes Outputs a display reversal pulse that rewrites the display to the electrode, and if the display data does not change, outputs an overwrite pulse that overwrites the electrode, before outputting the display reversal pulse. Outputs pre Reversible pulse display inversion pulse and different polarities, before outputting the overwrite pulse outputs置上writing pulse before overwriting pulse and polarity is divided into a plurality of different, and from 100ms and for 200ms The pulse width of the overwrite pulse is made equal to the pulse width obtained by adding a plurality of pre-overwrite pulses , and the pre-overwrite pulse has a longer pulse width than the pre-display inversion pulse.

  In addition, a pause period is provided between the overwrite pulse and the pre-overwrite pulse.

  Further, a temperature sensor for measuring the ambient temperature is provided, and the control unit controls to change the pulse widths of the overwrite pulse and the pre-overwrite pulse based on temperature information from the temperature sensor.

  The display panel is an electrophoretic display panel in which charged particles move by electrophoresis according to the polarity of a voltage applied between the electrodes of a pair of substrates, and the electrode of one of the pair of substrates is It is a plurality of segment electrodes, the electrode on the other substrate is one common electrode facing the plurality of segment electrodes, and the drive means drives each segment electrode.

  As described above, according to the present invention, since the display panel is completely AC driven by equalizing the pulse width of the overwrite pulse and the pre-overwrite pulse, the application of DC voltage to the display panel is not integrated by the overwrite pulse, It is possible to provide a long-life display device that prevents deterioration of the display panel and has excellent reliability. In addition, by increasing the pulse width of the pre-overwrite pulse relative to the pre-display inversion pulse, the problem that the display contrast gradually decreases can be surely solved by the overwrite pulse, and the display device has good contrast and excellent visibility. Can be realized.

  Further, the flickering phenomenon of the display panel can be reduced by dividing the pre-overwrite pulse into a plurality of parts. As a result, even if the pulse width of the overwrite pulse and the pre-overwrite pulse is increased to about 200 mS, the flicker becomes inconspicuous.

  Further, by providing a pause period between the overwrite pulse and the pre-overwrite pulse, even if the pulse widths of the overwrite pulse and the pre-overwrite pulse are shortened, the reduction in contrast can be prevented to some extent. Thus, by dividing the pre-overwrite pulse into a plurality of portions and providing a pause period between the overwrite pulse and the pre-overwrite pulse, a display device with good contrast and less flicker can be provided. Further, since the allowable range of the pulse width of the overwrite pulse and the pre-overwrite pulse can be widened, it is possible to provide a display device with stable display appearance by preventing the influence of temperature change and display panel lot-to-lot variation.

  Further, by changing the pulse width of the overwrite pulse and the pre-overwrite pulse in accordance with the ambient temperature, a display device with excellent visibility that is hardly affected by temperature changes can be realized. Thereby, it is suitable as a display device for a mobile phone or a wristwatch that is easily affected by the ambient temperature.

It is a block diagram which shows schematic structure of the display apparatus of the 1st Embodiment of this invention. It is a timing chart explaining an example of basic operation of a display of a 1st embodiment of the present invention. It is a timing chart explaining an example of operation of a display of a 2nd embodiment of the present invention. It is a timing chart explaining an example of operation of a display of a 3rd embodiment of the present invention. It is a graph of the light reflectance with respect to the pulse width of the overwrite pulse explaining the effect of the 3rd Embodiment of this invention. It is a graph explaining the temperature characteristic with respect to the pulse width of the overwrite pulse of a display panel, and a front overwrite pulse. It is a block diagram which shows schematic structure of the display apparatus of the 4th Embodiment of this invention. It is a flowchart explaining operation | movement of the display apparatus of the 4th Embodiment of this invention. It is sectional drawing explaining the electrophoretic display panel used with the display apparatus of this invention. It is an expanded sectional view explaining the principle of operation of the electrophoretic display panel used with the display apparatus of this invention. It is a top view which shows an example which displays the numerical character of the electrophoretic display panel used with the display apparatus of this invention. It is explanatory drawing in the case of changing from the state which displayed the number "2" to the state which displays the number "3" on the electrophoretic display panel used with the display apparatus of this invention. It is a graph which shows an example of the change of the light reflectivity in the white display and black display of the conventional electrophoretic display panel. It is a timing chart explaining operation | movement of the display apparatus which drives the conventional electrophoretic display panel. It is a graph explaining the effect of the overwrite pulse by the conventional display apparatus. It is a graph explaining the change of the light reflectance with respect to the pulse width of the overwrite pulse of a conventional electrophoretic display panel, and a pre-overwrite pulse.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[Features of each embodiment]
The first embodiment is characterized in that the pulse widths of the overwrite pulse and the pre-overwrite pulse applied when the display panel by electrophoresis is not rewritten for a long time are made equal, and the pulse width is changed to the pre-display inversion pulse width. By making the length longer, the deterioration of the display panel is prevented and the display contrast is improved. A feature of the second embodiment is that display flickering is reduced by dividing the pre-overwrite pulse into a plurality of parts.

  The feature of the third embodiment is that a pause period is provided between the overwrite pulse and the pre-overwrite pulse, thereby widening the pulse width range of the over-write pulse and the pre-overwrite pulse that allow the contrast. The feature of the fourth embodiment is to provide a display device that is less susceptible to temperature changes by varying the pulse widths of the overwrite pulse and the pre-overwrite pulse in accordance with the ambient temperature.

[Description of Configuration of First Embodiment: FIG. 1]
The configuration of the display device according to the first embodiment will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes a display device as the first embodiment. The display device 1 includes a display panel 50 that performs display by moving charged particles, and a drive IC 10 that serves as a drive unit that drives the display panel 50. Here, since the display panel 50 has the same configuration as the display panel 50 shown in FIGS. 9 to 12 described above, the same reference numerals are given in FIG.

That is, in the display panel 50, the charged particles 63 are sealed between the common electrode COM and the segment electrode SEG formed on the opposing surfaces of the pair of substrates by the transparent resin substrate 51 and the FPC 55, and the common electrode COM and the segment electrode SEG are enclosed. This is an electrophoretic display panel in which charged particles 63 move by electrophoresis according to the polarity of an applied voltage. As described above with reference to FIG. 10, the charged particles 63 are composed of white particles 63 a and black particles 63 b enclosed in the microcapsules 60, and the microcapsules 60 are dispersed in the microcapsule display layer 53. However, detailed illustration and description are omitted here.

  Next, the drive IC 10 includes a control unit 11, a waveform parameter unit 12, a drive pulse generation unit 20, an output driver 30, and the like. Further, a clock circuit for generating the clock signal CLK and a power supply circuit for generating the positive voltage + V and the negative voltage -V are also provided, but they are not shown because they are not special circuits.

  Here, although not shown, the control unit 11 has a register and an arithmetic circuit inside, inputs and stores display data P1 from the outside, and outputs a control signal P3 for controlling the drive voltage. Further, a start signal ST is output.

  The waveform parameter unit 12 includes a group of registers, stores waveform parameter information of the drive voltage, and outputs a waveform signal P4. This waveform signal P4 includes time information of each period of the drive voltage to be output and voltage polarity information of each period.

  The drive pulse generator 20 receives the control signal P3 and the waveform signal P4, and also receives the clock signal CLK and the start signal ST. Here, the drive pulse generator 20 selects the waveform signal P4 from the waveform parameter unit 12 by the control signal P3, is activated by the start signal ST, and counts the clock signal CLK by an internal counter (not shown). Drive pulse P10 to be output.

  That is, the drive pulse generator 20 determines the time of each period of the drive voltage and the voltage polarity of each period from the information of the selected waveform signal P4, and generates the drive pulse P10 that is the basis of the drive voltage applied to the display panel 50. Generate and output. As a result, the drive pulse generator 20 outputs drive pulses of an overwrite pulse, a pre-overwrite pulse, a display inversion pulse, and a pre-display inversion pulse, which will be described later.

  Next, the output driver 30 has a number of level shift circuits (not shown) corresponding to the number of output terminals, inputs a driving pulse P10, and has three values of positive voltage + V, 0V, and negative voltage −V. Are provided with a plurality of output terminals OUT for outputting a driving voltage. Here, the number of output terminals is arbitrarily set according to the display panel to be driven, but in this embodiment, the eight output terminals are exemplified by driving the eight segment electrodes of the display panel 50 described above. OUT1 to OUT8 are provided.

  The output terminals OUT <b> 1 to OUT <b> 8 are connected to the segment electrodes SEG of the display panel 50, although a part of the illustration is omitted. The output terminal OUTC is an output connected to the common electrode COM of the display panel 50. Since the common electrode COM is always grounded to 0V, the output terminal OUTC is connected to 0V inside the driving IC 10.

  The internal configuration of the drive IC 10 is not limited to FIG. 1. For example, the control unit 11 may be disposed outside the drive IC 10.

[Description of Basic Waveform of Driving Voltage of First Embodiment: FIGS. 1 and 2]
Next, the basic waveform of the drive voltage output from the display device of the first embodiment will be described based on the timing chart of FIG. The configuration of the first embodiment is based on the assumption that the display panel 50 is driven with reference to FIG.

  In FIG. 2, four types of segment drive voltages VS 1, VS 2, VS 10, and VS 11 are drive voltages applied to the segment electrodes SEG of the display panel 50. Here, the segment drive voltages VS1 and VS2 are drive voltages for applying an overwrite pulse for preventing the contrast from being lowered because the display is not rewritten. The segment drive voltage VS1 overwrites white when the display segment displays white (white → white), and the segment drive voltage VS2 overwrites black when the display segment displays black (black → black). The segment drive voltages VS1 and VS2 are synchronized with the start signal ST, the pre-overwriting period T1 for outputting the pre-overwriting pulse, the overwriting period T2 for outputting the overwriting pulse, and the display for maintaining the display state. It consists of a period with a period T0.

  The segment drive voltages VS10 and VS11 are drive voltages for applying a display inversion pulse when changing the display. The segment drive voltage VS10 rewrites the display segment from white to black, and the segment drive voltage VS11 is Rewrite the display segment from black to white. The segment drive voltages VS10 and VS11 maintain the display state in synchronization with the start signal ST, the pre-display inversion period T3 for outputting the pre-display inversion pulse, the display inversion period T4 for outputting the display inversion pulse, and the display state. For the display period T0. Note that the common electrode COM of the display panel 50 is always applied with a driving voltage of 0 V, and is not shown.

  Here, as for the segment drive voltage VS1 (white to white), a pre-overwrite pulse P11p with a positive voltage + V is output in the pre-overwrite period T1, and subsequently, an overwrite pulse P12m with a negative voltage −V is output in the overwrite period T2. In the subsequent display period T0, 0 V having the same potential as that of the common electrode COM is applied.

  The segment drive voltage VS2 (black to black) is output in the pre-overwrite period T1 with a negative voltage −V pre-overwrite pulse P11m, and subsequently with the over-write pulse P12p with a positive voltage + V in the over-write period T2. In the subsequent display period T0, 0 V having the same potential as the common electrode COM is applied.

  That is, when the display does not change, overwrite pulses P12m and P12p for overwriting the display are output, and pre-overwrite pulses P11p and P11m having different polarities are output before the overwrite pulses P12m and P12p. These pre-overwrite pulses P11p and P11m and the overwrite pulses P12m and P12p are generated by the drive pulse generator 20 (see FIG. 1).

  Here, the pre-overwriting period T1 and the overwriting period T2 are set equal to each other, so that the pulse widths of the pre-overwriting pulse P11p and the overwriting pulse P12m of the segment drive voltage VS1 are the same, and before the segment driving voltage VS2 The pulse widths of the overwrite pulse P11m and the overwrite pulse P12p are also the same. Further, as described above with reference to FIG. 16, the lower limit of the pulse width is that when the pulse width becomes 50 mS or less, the contrast sharply decreases. Therefore, 50 mS or more is required at room temperature, and the display contrast is good. It is good that it is 100 mS or more which becomes a large area. The upper limit of the pulse width is preferably 150 mS or less because flickering of the display is noticeable when the pulse width exceeds 150 mS.

  Here, the overwrite pulses P12m and P12p output when the display does not change are displayed in white or black when the voltage non-application state, which is a characteristic of the electrophoretic display panel having memory characteristics, is continued as described above. The object is to reduce the phenomenon in which the density changes and approaches gray, and the display contrast gradually decreases.

  That is, when the display segment holds white and gradually approaches white to gray, the display state returns to the normal white density by reapplying the overwrite pulse P12m of the negative voltage −V that becomes white. Can be reduced. Similarly, when the segment holds black and gradually approaches black to gray, the display state returns to the normal black density by applying the positive voltage + V overwrite pulse P12p that becomes black again. Can be reduced. Therefore, by periodically applying the overwrite pulse P12m or the overwrite pulse P12p with the segment drive voltages VS1 (white → white) and VS2 (black → black), the contrast is lowered and the afterimage phenomenon ( Display unevenness).

  Further, the pre-overwrite pulse P11p of the segment drive voltage VS1 (white → white) output in the pre-overwrite period T1 will be described. The pre-overwrite pulse P11p is a positive voltage + V and is overwritten after that. The pulse P12m is a negative voltage −V. Here, when an overwrite pulse P12m having a negative voltage −V is periodically applied to the electrophoretic display panel, a direct current component of the negative voltage −V is accumulated little by little on the panel. There is a problem that it deteriorates and the reliability decreases.

  However, by applying the pre-overwrite pulse P11p having the same pulse width and the opposite polarity before the application of the over-write pulse P12m, the display panel is completely driven by alternating current, and the reverse direction is applied between the electrodes of the display panel. The current flows repeatedly and the application of the DC component is canceled. As a result, it is possible to realize a long-life display panel with excellent reliability by preventing the deterioration of the electrophoretic display panel. The same applies to the pre-overwrite pulse P11m of the segment drive voltage VS2 (black to black), and the electrophoretic display panel can be driven in an alternating manner in combination with the overwrite pulse P12p.

  The segment drive voltage VS10 (white → black) is a drive voltage output when the display segment is rewritten from white display to black display. For this segment drive voltage VS10 (white → black), a pre-display inversion pulse P13m with a negative voltage −V is output during the pre-display inversion period T3, and then a display inversion pulse with a positive voltage + V is applied to make the display black. P14p is output in the display inversion period T4, and 0V having the same potential as the common electrode COM is applied in the subsequent display period T0.

  The segment drive voltage VS11 (black → white) is a drive voltage output when the display segment is changed from black display to white display. For this segment drive voltage VS11 (black → white), a front display inversion pulse P13p with a positive voltage + V is output during the front display inversion period T3, and then a display inversion pulse with a negative voltage −V is applied to make the display white. P14m is output in the display inversion period T4, and 0V having the same potential as the common electrode COM is applied in the subsequent display period T0. Here, since the display inversion pulses P14p and P14m are drive pulses for inverting the display (rewriting the display), a predetermined length is required, and is about 300 mS as an example.

  Further, the operation of the pre-display inversion pulses P13m and P13p of the segment drive voltages VS10 and VS11 will be described. The state in which the display period T0 continues and the white or black display density changes and approaches gray is displayed. There is an effect that the normal white or black density is once returned by the pulse and then the target black or white density is rewritten by the display inversion pulses P14p and P14m, so that the density after rewriting is set to the normal level. As a result, display shading unevenness can be reduced. A pulse width of 10 mS or less is sufficient as the pulse width of the pre-display inversion pulses P13m and P13p. If the pulse width of the pre-display inversion pulses P13m and P13p is longer than necessary, the display flickers. It is not preferable because it looks.

These pre-display inversion pulses P13m and P13p and display inversion pulses P14p and P14
m is generated by the aforementioned drive pulse generator 20 (see FIG. 1).

  Here, the pulse widths of the drive pulses of the first embodiment are summarized. The pre-overwrite pulses P11p, P11m and the overwrite pulses P12m, P12p have the same pulse width, and the recommended pulse width is the lower limit of the pulse width at room temperature. Is about 100 mS from the contrast, and the upper limit of the pulse width is about 150 mS from the display flicker (see FIG. 16). Further, the pulse width of the pre-display inversion pulses P13m and P13p is about 10 mS or less. The display inversion pulses P14p and P14m have a pulse width of about 300 mS. Accordingly, the pulse widths of the overwrite pulses P12m and P12p are wider than the pulse widths of the front display inversion pulses P13m and P13p.

  That is, the drive voltage of the first embodiment equalizes the pulse widths of the pre-overwrite pulse and the overwrite pulse, and the lower limit value of the pulse width of the pre-overwrite pulse and the overwrite pulse is an area where the display contrast does not decrease. The upper limit value of the pulse width is determined in an area where display flicker is not noticeable. This is also applied to the second to fourth embodiments described later.

  Note that the pre-overwrite pulse and the pulse width of the overwrite pulse may be selected within the range of the lower limit value and the upper limit value according to the request of the application displayed on the display device. For example, in an application where display flicker is relatively acceptable, the pulse width is selected to be a value close to the upper limit value. As a result, it is possible to realize a display with better contrast. In applications that require display flicker to be inconspicuous, the pulse width is selected to be close to the lower limit. Thereby, it is possible to realize a good display in which flickering is not noticeable.

  As described above, according to the first embodiment, by making the pulse widths of the overwrite pulse and the pre-overwrite pulse equal to each other, the display panel is driven with complete alternating current. Accordingly, it is possible to realize a long-life display device that prevents deterioration of the display panel and has excellent reliability. In addition, it is possible to make the display contrast higher than before by configuring the pulse width of the overwrite pulse and the pre-overwrite pulse longer than the conventional example and making it longer than the pre-display inversion pulse. It is possible to provide a display device with excellent appearance.

[Description of Configuration of Second Embodiment: FIG. 1]
Next, the display device of the second embodiment will be described. Since the configuration of the display device of the second embodiment is the same as that of the first embodiment, detailed description of the configuration of the second embodiment will be omitted with reference to FIG. Here, the second embodiment is different from the first embodiment in that the pre-overwrite pulse is divided into a plurality of parts. The pre-overwrite pulse divided into a plurality of waveforms has the waveform shown in FIG. Since it is obtained by changing the waveform parameters stored in the parameter unit 12, there is no difference in configuration as a block diagram.

[Description of Driving Voltage of Second Embodiment: FIGS. 1 and 3]
Next, the drive voltage output from the display device of the second embodiment will be described with reference to the timing chart of FIG. Since the configuration of the second embodiment is the same as the configuration of the first embodiment as described above, the configuration is illustrated in FIG.

In FIG. 3, four types of segment drive voltages VS3, VS4, VS10, and VS11 are drive voltages applied to the segment electrodes SEG of the display panel 50 (see FIG. 1). Here, the segment drive voltages VS3 and VS4 are drive voltages for applying an overwrite pulse for preventing the contrast from being lowered because the display is not rewritten. The segment drive voltage VS3 overwrites white when the display segment displays white (white → white), and the segment drive voltage VS4 overwrites black when the display segment displays black (black → black). The segment drive voltages VS3 and VS4 are synchronized with the start signal ST, the pre-overwrite periods T1a, T1b, and T1c for outputting a plurality of pre-overwrite pulses, the overwrite period T2 for outputting the overwrite pulses, and the display state The display period T0 is maintained for maintaining the period.

  The segment drive voltages VS10 and VS11 are drive voltages for applying a display inversion pulse when changing the display, and are the same as the segment drive voltages VS10 and VS11 of the first embodiment. Description is omitted.

  Here, as for the segment drive voltage VS3 (white → white), a plurality of pre-overwrite pulses P11pa, P11pb, P11pc having a positive voltage + V are output to the pre-overwrite periods T1a, T1b, T1c, and subsequently a negative voltage −V. The overwriting pulse P12m is output in the overwriting period T2, and 0V having the same potential as that of the common electrode COM is applied in the subsequent display period T0.

  The segment drive voltage VS4 (black to black) is output with a plurality of pre-overwrite pulses P11ma, P11mb, and P11mc having a negative voltage −V in the pre-overwrite periods T1a, T1b, and T1c, and then overwriting with a positive voltage + V. The pulse P12p is output in the overwriting period T2, and 0V having the same potential as that of the common electrode COM is applied in the subsequent display period T0.

  Here, the total pulse width of the pre-overwrite pulses P11pa, P11pb, and P11pc of the segment drive voltage VS3 is equal to the pulse width of the overwrite pulse P12m, and the pre-overwrite pulses P11ma, P11mb, and P11mc of the segment drive voltage VS4. The total pulse width is equal to the pulse width of the overwrite pulse P12p.

Further, as described above with reference to FIG. 16, the lower limit of the pulse width is that the contrast sharply decreases when the pulse width of the overwrite pulse is 50 mS or less, so that 50 mS or more is required at room temperature. It is good that it is 100 mS or more, which is a region with good contrast. Further, the upper limit of the pulse width is that the flickering phenomenon of the display panel can be reduced by dividing the pre-overwrite pulse into a plurality of parts. Flickering is less noticeable.

  Here, the reason why the flickering phenomenon of the display panel is reduced by dividing the pre-overwrite pulse into a plurality of parts is that the electrophoretic display panel 50 shown in FIG. 10 described above has internal white particles 63a and black particles. It is considered that 63b moves in the dispersion medium 62 by electrophoresis, but the movement of the charged particles cannot respond to the short pulse width of each divided pre-overwrite pulse. The number of divisions of the pre-overwrite pulse is not limited. However, if the number of divisions is too large (individual pulse widths are too short), a plurality of pulses are substantially integrated to reduce the division effect.

  Similarly to the driving voltage of the first embodiment, the overwrite pulses P12m and P12p change to gray when the display density of white or black changes when the voltage non-application state, which is a characteristic of the electrophoretic display panel, is continued. The object is to reduce the phenomenon that the display contrast gradually decreases.

  Also, for the plurality of pre-overwrite pulses P11pa, P11pb, P11pc, and P11ma, P11mb, and P11mc, a pre-overwrite pulse having a polarity different from that of the overwrite pulse is applied as in the drive voltage of the first embodiment. The purpose is to drive the AC and prevent the display panel from deteriorating.

  Here, the pulse widths of the drive pulses of the second embodiment are summarized. The total pulse width of the pre-overwrite pulses P11pa, P11pb, and P11pc, the total pulse width of P11ma, P11mb, and P11mc, and the overwrite pulses P12m and P12p The pulse widths are equal to each other, the lower limit of the pulse width is about 100 mS at normal temperature from the contrast, and the upper limit of the pulse width is about 200 mS because the flicker phenomenon is reduced. The pulse widths of the pre-display inversion pulses P13m and P13p of the segment drive voltages VS10 and VS11 and the display inversion pulses P14p and P14m are the same as in the first embodiment. Accordingly, the pulse widths of the overwrite pulses P12m and P12p are wider than the pulse widths of the front display inversion pulses P13m and P13p. However, one pulse in the divided pre-overwrite pulses P11pa, P11pb, P11pc, and P11ma, P11mb, and P11mc does not necessarily have a longer pulse width than the pre-display inversion pulse.

  As described above, according to the second embodiment, the flickering phenomenon of the display panel can be reduced by dividing the pre-overwrite pulse into a plurality of parts. The upper limit can be set longer. As a result, the allowable pulse width range of the overwrite pulse and the pre-overwrite pulse is widened, so that it is possible to provide a display device that maintains a stable display with little influence of temperature change and display panel manufacturing variation. .

[Description of Configuration of Third Embodiment: FIG. 1]
Next, the display device of the third embodiment will be described. Since the configuration of the display device of the third embodiment is the same as that of the first embodiment, detailed description of the configuration of the third embodiment will be omitted with reference to FIG. Here, the third embodiment is different from the first embodiment in that a pause period is provided between the overwrite pulse and the pre-overwrite pulse. However, the overwrite pulse and the pre-overwrite pulse provided with the pause period are different. Is obtained by changing the waveform parameters stored in the waveform parameter section 12 shown in FIG. 1, and therefore there is no structural difference as a block diagram.

[Description of Driving Voltage of Third Embodiment: FIGS. 1, 4, and 5]
Next, the drive voltage output by the display device of the third embodiment will be described with reference to the timing chart of FIG. Since the configuration of the third embodiment is the same as the configuration of the first embodiment as described above, the configuration is illustrated in FIG.

  In FIG. 4, four types of segment drive voltages VS5, VS6, VS10, and VS11 are drive voltages applied to the segment electrodes SEG of the display panel 50 (see FIG. 1). Here, the segment drive voltages VS5 and VS6 are drive voltages for applying an overwrite pulse for preventing the contrast from being lowered because the display is not rewritten. The segment drive voltage VS5 overwrites white when the display segment displays white (white → white), and the segment drive voltage VS6 overwrites black when the display segment displays black (black → black). The segment drive voltages VS5 and VS6 include a pre-overwrite period T1 for outputting a pre-overwrite pulse, an overwrite period T2 for outputting an overwrite pulse, and a pause period T5 between the pre-overwrite period T1 and the overwrite period T2. And a display period T0 for maintaining the display state.

  The segment drive voltages VS10 and VS11 are drive voltages for applying a display inversion pulse when changing the display, and are the same as the segment drive voltages VS10 and VS11 of the first embodiment. Description is omitted.

Here, the segment drive voltage VS5 (white → white) is output from the pre-overwrite pulse P11p of the positive voltage + V in the pre-overwrite period T1, and then the negative voltage − The V overwrite pulse P12m is output in the overwrite period T2, and 0 V having the same potential as the common electrode COM is applied in the subsequent display period T0.

  The segment drive voltage VS6 (black → black) is output as a negative voltage −V pre-overwrite pulse P11m during the pre-overwrite period T1, and then after a predetermined length of the pause period T5, the positive voltage + V The overwriting pulse P12p is output in the overwriting period T2, and 0 V having the same potential as that of the common electrode COM is applied in the subsequent display period T0.

  Here, the pulse width of the pre-overwrite pulse P11p of the segment drive voltage VS5 is equal to the pulse width of the over-write pulse P12m, and the pulse width of the pre-overwrite pulse P11m of the segment drive voltage VS6 and the pulse width of the overwrite pulse P12p. Are equally configured.

  The lower limit of the pulse width is that a pause period T5 is provided between the overwrite pulse and the pre-overwrite pulse, so that the reduction in contrast due to the decrease in the pulse width is alleviated and the allowable pulse width range can be expanded. If the pulse width is 70 mS to 80 mS or more, the region has good contrast. The upper limit of the pulse width is preferably 150 mS or less because flickering of the display is noticeable when the pulse width of the overwrite pulse exceeds 150 mS.

  Here, the reason why the decrease in display contrast is mitigated by providing the pause period T5 between the overwrite pulse and the pre-overwrite pulse is that the charge that has started to move due to the pre-overwrite pulse is provided by providing the pause period T5. After the particles are once stabilized, an overwrite pulse having an opposite polarity is applied, so that it is considered that the effect of the overwrite pulse is sufficiently exhibited. Therefore, even if the pulse widths of the overwrite pulse and the pre-overwrite pulse are relatively short, the reduction in contrast can be improved.

  FIG. 5 is a graph for explaining the effect of the drive voltage of the third embodiment in which the pause period T5 is provided. In FIG. 5, the horizontal axis represents the pulse width (mS) of the overwrite pulse and the pre-overwrite pulse, and the vertical axis represents the light reflectance R of the display panel. In the graph, the reflectances Rw and Rb indicated by solid lines are the same as the light reflectance in FIG. 16 described above, and the change in the light reflectance with respect to the pulse width of the overwrite pulse and the pre-overwrite pulse when there is no pause period T5. is there. The light reflectance Rw ′ indicated by a broken line is a light reflectance in white display provided with a predetermined pause period T5, and the light reflectance Rb ′ indicated by a broken line is indicated in black display provided with a predetermined pause period T5. Light reflectivity. From FIG. 5, it can be understood that the display contrast is good up to a region having a relatively short pulse width by providing the pause period T5 between the pre-overwriting period T1 and the overwriting period T2.

  The purpose of the overwrite pulses P12m and P12p and the pre-overwrite pulses P11p and P11m are the same as those in the first and second embodiments.

  Here, when the pulse widths of the drive pulses of the third embodiment are summarized, the pulse widths of the pre-overwrite pulses P11p and P11m of the segment drive voltages VS5 and VS6 and the overwrite pulses P12m and P12p are equal. The lower limit of the pulse width may be about 70 to about 80 mS at room temperature due to the effect of the present embodiment, and the upper limit of the pulse width is about 150 mS in consideration of flicker. The pulse widths of the pre-display inversion pulses P13m and P13p of the segment drive voltages VS10 and VS11 and the display inversion pulses P14p and P14m are the same as in the first embodiment. Accordingly, the pulse widths of the overwrite pulses P12m and P12p are wider than the pulse widths of the front display inversion pulses P13m and P13p.

As described above, according to the third embodiment, by providing a pause period between the overwrite pulse and the pre-overwrite pulse, the contrast can be reduced even if the pulse width of the overwrite pulse and the pre-overwrite pulse is shortened. Thus, the lower limit value of the pulse width of the overwrite pulse and the pre-overwrite pulse can be set short. This increases the range of allowable pulse widths, so
It is possible to provide a display device that maintains a stable display with little influence of temperature change and manufacturing variation of the display panel.

  Further, by combining the division of the pre-overwrite pulse of the second embodiment and the provision of a pause period between the overwrite pulse and the pre-overwrite pulse of the third embodiment, the overwrite pulse and the pre-overwrite can be further combined. Since the allowable pulse width range of the pulse can be widened, it is possible to provide a display device with excellent contrast and excellent visibility with little flicker by eliminating the influence of temperature change and display panel lot-to-lot variation.

[Description of temperature characteristics of electrophoretic display panel: FIG. 6]
Next, the display device of the fourth embodiment will be described. The fourth embodiment is an example in which the pulse widths of the overwrite pulse and the pre-overwrite pulse are varied according to the ambient temperature. This is because the electrophoretic display panel corrects the characteristic that the contrast changes depending on the temperature. This is an example for the purpose. In order to understand this embodiment, first, the temperature characteristics of the electrophoretic display panel will be described.

FIG. 6 shows an example of the temperature characteristics of the electrophoretic display panel based on the graph of the transition of the light reflectance with respect to the difference between the pulse widths of the overwrite pulse and the pre-overwrite pulse of the electrophoretic display panel shown in FIG. It is the graph which showed. In FIG. 6, the horizontal axis represents the pulse width (mS) of the overwrite pulse and the pre-overwrite pulse, and the vertical axis represents the light reflectance of the display panel. On the graph, the solid line is the light reflectance (Rw, Rb) for white display and black display at room temperature (25 ° C.), and the rough broken line is the light reflectance for white display and black display at low temperature (0 ° C.). The broken line represents the light reflectance of white display and black display at high temperature (50 ° C.).

  As can be seen from this graph, in the electrophoretic display panel, when the pulse width of the overwrite pulse and the pre-overwrite pulse becomes 100 mS or less at a low temperature, the contrast rapidly decreases. Moreover, even when the pulse width approaches 50 mS at high temperatures, the contrast is not so much reduced. Thus, it can be understood that the contrast of the drive voltage with respect to the pulse width is affected by the temperature in the electrophoretic display panel. The cause of this temperature characteristic is that the response speed of the electrophoretic display panel with respect to the driving voltage varies depending on the temperature. That is, the charged particles of the electrophoretic display panel have a low response speed with respect to the drive voltage at a low temperature and a high response speed with respect to the drive voltage at a high temperature.

[Description of Configuration of Fourth Embodiment: FIG. 7]
Next, the configuration of the display device according to the fourth embodiment will be described with reference to FIG. The basic configuration of the display device according to the fourth embodiment is the same as the configuration according to the first embodiment (FIG. 1). To do. In FIG. 7, reference numeral 40 denotes a display device as the fourth embodiment. The display device 40 includes a display panel 50 that performs display by moving charged particles, a drive IC 10 that serves as a drive unit that drives the display panel 50, and a temperature sensor 41. Here, since the display panel 50 has the same configuration as the display panel 50 shown in FIGS. 9 to 12 described above, the same reference numerals are also given in FIG.

  The temperature sensor 41 is configured by a temperature detection element such as a thermistor, and outputs a temperature signal P2 that is analog information according to the ambient temperature and inputs the temperature signal P2 to the control unit 11 of the drive IC 10. The control unit 11 of the drive IC 10 receives the temperature signal P2, converts it into digital information by an internal AD converter circuit (not shown), outputs the temperature control signal P6, and inputs it to the waveform parameter unit 12. Since the other configuration of the driving IC 10 is the same as that of the first embodiment, the description thereof is omitted.

[Description of Operation of Fourth Embodiment: FIGS. 7 and 8]
Next, the basic operation of the display device 40 of the fourth embodiment will be described based on the flowchart of FIG. The configuration of the display device 40 is shown in FIG. In FIG. 8, the driving IC 10 of the display device 40 receives the temperature signal P2 from the temperature sensor 41 as the first display operation, and converts it into digital information by an AD conversion circuit (not shown) inside the control unit 11. (Step ST1).

  Next, the control unit 11 of the drive IC 10 determines whether the ambient temperature of the display device 40 is in the normal temperature range, the low temperature range, or the high temperature range (step ST2). Here, as an example, the normal temperature range is 15 ° C. to 35 ° C., the low temperature range is 15 ° C. or less, and the high temperature range is 35 ° C. or more. The setting of the temperature range is not limited and may be arbitrary.

  Next, based on the determined temperature range, the control unit 11 outputs the temperature control signal P6 and inputs it to the waveform parameter unit 12 in order to select the pulse width of the drive pulse along the temperature range (step ST3). .

  Next, the waveform parameter unit 12 of the drive IC 10 receives the temperature control signal P6 and outputs a waveform signal P4 that is a waveform parameter of the drive voltage based on the temperature information (step ST4).

  Next, the drive pulse generation unit 20 of the drive IC 10 receives the control signal P3 from the control unit 11 and the waveform signal P4 from the waveform parameter unit 12, selects the waveform signal P4 based on the control signal P3, and selects an internal counter ( (Not shown) counts the clock signal CLK and outputs a drive pulse P10 based on the selected waveform signal P4. Further, the output driver 30 receives the drive pulse P10 and outputs a drive voltage composed of three values of positive voltage + V, 0V, and negative voltage −V (step ST5).

[Description of Driving Voltage of Fourth Embodiment: FIG. 2]
Next, the drive voltage output by the display device of the fourth embodiment will be described. The basic waveform of the drive voltage of the fourth embodiment is the same as the drive voltage (see FIG. 2) of the first embodiment. is there. If the pre-overwriting period T1 and the overwriting period T2 are set to 100 mS as an example when the temperature is in the normal temperature range, for example, when the temperature is in the low temperature range, the waveform parameter unit 12 sets it to 120 mS, When the temperature is in the high temperature range, for example, it is set to 80 mS. Thereby, the pulse width of the pre-overwrite pulse and the overwrite pulse can be changed according to the temperature change, so that the temperature characteristics of the electrophoretic display panel can be corrected.

  As described above, according to the fourth embodiment, by changing the pulse width of the overwrite pulse and the pre-overwrite pulse according to the ambient temperature, the contrast is good even when the ambient temperature changes, and visibility is improved. An excellent display device can be realized. Thereby, it is suitable as a display device for a mobile phone or a wristwatch that is easily affected by the ambient temperature. In the fourth embodiment, control is performed to vary the pulse width by setting three ranges of ambient temperature as low temperature, normal temperature, and high temperature. However, the present invention is not limited to this control. The switching may be performed more finely, or depending on the case, it may be performed in only two stages of low temperature and high temperature. Needless to say, the fourth embodiment can be applied to the second embodiment or the third embodiment.

  In the present embodiment, the case of using segment-shaped segment electrodes has been described. However, the same effect can be obtained even in matrix display using active elements or the like as electrodes. Further, the block diagrams, timing charts, flowcharts, and the like shown in the embodiments of the present invention are not limited thereto, and may be arbitrarily changed as long as they satisfy the gist of the present invention.

1, 40 Display device 10 Drive IC
DESCRIPTION OF SYMBOLS 11 Control part 12 Waveform parameter part 20 Drive pulse generation part 30 Output driver 41 Temperature sensor 50 Display panel 51 Resin board 55 Flexible printed circuit board (FPC)
60 Microcapsule 63 Charged particle COM Common electrode SEG Segment electrode P1 Display data P2 Temperature signal P3 Control signal P4 Waveform signal P6 Temperature control signal P10 Drive pulse P11p, P11m Pre-overwrite pulse P12p, P12m Overwrite pulse P13p, P13m Pre-display inversion Pulse P14p, P14m Display inversion pulse CLK Clock signal ST Start signal T0 Display period T1 Pre-overwrite period T2 Overwrite period T3 Pre-display inversion period T4 Display inversion period T5 Rest period VS1 to VS6, VS10, VS11 Segment drive voltage

Claims (4)

A charged particle is enclosed between a pair of substrates each having an electrode on the opposite surface, and a display panel having a memory property for performing display by movement of the charged particle, and display voltage is input to the display panel electrode to drive voltage A display device comprising:
The drive means includes a control unit that stores the input display data, a waveform parameter unit that stores various waveforms of the drive voltage, and a waveform parameter unit based on the display data stored in the control unit. A drive pulse generator that selects a waveform signal of and generates a drive pulse,
The drive pulse generation unit outputs a display inversion pulse for rewriting the display to the electrode when the display data changes, and outputs an overwrite pulse for overwriting the electrode when the display data does not change. Before the display inversion pulse is output, a pre-display inversion pulse having a polarity different from that of the display inversion pulse is output. Before the overwriting pulse is output, the display inversion pulse is divided into a plurality of polarities different from those of the overwrite pulse. A pre-overwrite pulse is output, the pulse width of the over-write pulse between 100 ms and 200 ms is made equal to the pulse width obtained by adding the pre-over-write pulses , and the pre-overwrite pulse is displayed in the pre-display A display device characterized in that a pulse width is set longer than an inversion pulse. The display device according to claim 1 , wherein a pause period is provided between the overwrite pulse and the pre-overwrite pulse. Further provided a temperature sensor for measuring the ambient temperature, wherein the control unit, wherein the controller controls so as to change the pulse width of the front置上writing pulse and the overwrite pulses based on temperature information from said temperature sensor Item 3. The display device according to Item 1 or 2 . The display panel is an electrophoretic display panel in which the charged particles move by electrophoresis according to the polarity of a voltage applied between the electrodes of the pair of substrates.
Of the pair of substrates, an electrode of one substrate is a plurality of segment electrodes, an electrode of the other substrate is a common electrode facing the plurality of segment electrodes, and the driving means includes the segment electrodes. The display device according to claim 1 , wherein each of the display devices is driven.

Images