JP2010223876A - Time display device and method of driving time display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a time display device provided with an electrophoresis display panel, avoiding deterioration of display characteristics of the electrophoresis display panel, and having a time precision measurement mode. <P>SOLUTION: In the time precision measurement mode, rewriting of display is performed in a rewriting period Ta (a first half Ta1, a latter half Ta2) at timing M10. A segment 5D (not shown) corresponding a segment 5XA is displayed in black color. After a stoppage period Tb', a first drive voltage (0 V) of mutually the same phases and same potential and a second drive voltage (+12 V) of potential different from the first drive voltage being mutually the same phases and same potential on each segment electrode 14 and common electrode 25 (referring to Fig.4) are synchronized on a reference signal CL to be alternately repeatedly applied by drive signals SEG1, SEG2, SEG3 and a drive signal COM in a period Tc from timing M20 to timing M30. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a time display device using an electrophoretic display panel and a driving method of the time display device.

In recent years, display devices including an electrophoretic display panel using an electrophoretic phenomenon have been proposed.
In this type of electrophoretic display panel, for example, an electrophoretic layer (hereinafter also referred to as an electrophoretic element) in which white and black electrophoretic particles are enclosed is provided between electrodes, and a drive voltage having a positive potential or a negative potential is provided between the electrodes. Is applied to move any of the black and white electrophoretic particles to the display surface side, and the display color of the display surface can be set to white or black.
A display device including the above-described electrophoretic display panel is also used as a time display device such as a wristwatch (see, for example, Patent Document 1).

JP 2007-79170 A

By the way, the time display device has a time accuracy measurement mode (also called a rate measurement mode) for measuring the time accuracy, which is the degree of advance or delay of the displayed time, by a time accuracy measuring device called a quartz tester or the like. There is something to have.
For example, in a time display device equipped with a liquid crystal display panel, in this time accuracy measurement mode, in order to continuously generate a stable electric field for time accuracy measurement, the time display device is shifted to the normal display mode. In the meantime, the AC drive voltages having opposite phases are continuously applied between all the electrodes, so that all the display portions are continuously lit.

However, in an electrophoretic display panel, in general, opposite driving voltages having opposite phases and in-phase are applied to opposing electrodes when rewriting a display.
Therefore, when continuous driving as in the time accuracy measurement mode described above is applied to a time display device equipped with an electrophoretic display panel, the following problems may occur.
(1) Originally, due to the holdability of the display, the opposite-phase and in-phase alternate drive voltages are continuously applied to the opposing electrodes of the electrophoretic display panel that need to be applied only when the display is rewritten. When the display portion is continuously displayed, it becomes a burn-in state, and display characteristics such as responsiveness and contrast (hereinafter simply referred to as display characteristics) of the electrophoretic display panel are remarkably deteriorated.
(2) When a drive voltage in the same direction is continuously applied to one electrode and each display portion is continuously displayed and driven in the same color such as white or black, the DC balance of the electrophoretic display panel As a result, the transparent electrode such as an ITO (Indium-Tin-Oxide) film constituting the electrode is corroded, and the display characteristics of the electrophoretic display panel are significantly deteriorated.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  [Application Example 1] A time display device according to this application example includes an electrophoretic display panel having an electrophoretic element between opposed electrodes, and a driving voltage for driving the electrophoretic element applied to both electrodes. A display control unit for controlling the display of the electrophoretic display panel to display at least the time, and a time standard source serving as a reference for the time, and in synchronization with a reference signal generated from the time standard source, the display The control unit alternately applies a first drive voltage having the same phase and the same potential to the electrodes and a second drive voltage having the same phase and the same potential but different from the potential of the first drive voltage. It has a time accuracy measurement mode to be applied.

According to this, in the time display device, in synchronization with the reference signal generated from the time standard source, the display control unit applies the first drive voltage having the same phase and the same potential to each electrode, and the same phase and the same potential. In addition, a time accuracy measurement mode in which the second drive voltage having a different potential from the first drive voltage is applied alternately.
For this reason, the time display device does not cause a potential difference between the electrodes of the electrophoretic display panel in the time accuracy measurement mode, so that a state like the above-mentioned burn-in or a transparent ITO film such as an ITO film due to a DC balance breakdown is obtained. Corrosion of the electrodes is suppressed, and deterioration of display characteristics of the electrophoretic display panel can be avoided.
In addition, the time display device alternately applies the first drive voltage and the second drive voltage having a potential different from the potential of the first drive voltage to both electrodes of the electrophoretic display panel. In the entire electrophoretic display panel, an electric field is generated due to a potential difference between the potential of the first drive voltage and the potential of the second drive voltage.
Thereby, the time display device can perform time accuracy measurement by the time accuracy measuring instrument in the time accuracy measurement mode.

  Application Example 2 In the time display device according to the application example, it is preferable that the electrophoretic display panel is a segment display panel or an active matrix display panel.

  According to this, in the time display device, since the electrophoretic display panel is a segment display panel or an active matrix display panel, various display forms can be selected.

  Application Example 3 In the time display device according to the application example, in the time accuracy measurement mode, it is preferable that information indicating the time accuracy measurement mode is displayed on the electrophoretic display panel.

  According to this, since the information indicating that it is the time accuracy measurement mode is displayed in the time accuracy measurement mode, the time display device can more reliably make it known that it is the time accuracy measurement mode.

  Application Example 4 In the time display device according to the application example, it is preferable that the display of the electrophoretic display panel is rewritten at a predetermined cycle in the time accuracy measurement mode.

  According to this, since the display of the electrophoretic display panel is rewritten at a predetermined cycle in the time accuracy measurement mode, the time display device can avoid deterioration of the display state of the electrophoretic display panel.

  Application Example 5 In the time display device according to the application example described above, in the time accuracy measurement mode, the first drive voltage and the second drive voltage applied to the electrodes of the electrophoretic display panel are obtained. It is preferable that the potential difference is larger than the potential difference between the drive voltages in the normal mode which is a normal display state.

According to this, in the time display device, in the time accuracy measurement mode, the potential difference between the first drive voltage and the second drive voltage applied to both electrodes is larger than the potential difference between the drive voltages in the normal mode.
Therefore, in the time display device, the electric field generated in the entire electrophoretic display panel is stronger than in the normal mode, so that the time accuracy measurement by the time accuracy measuring device is performed more reliably.

  Application Example 6 A driving method of a time display device according to this application example includes an electrophoretic display panel having an electrophoretic element between opposed electrodes, and a driving voltage for driving the electrophoretic element applied to both electrodes. A display control unit for controlling display of the electrophoretic display panel to display at least the time, and a time standard source serving as a reference for the time, the driving method of the time display device comprising the time display device Has a time accuracy measurement mode, a first step of shifting from the normal mode, which is a normal display state, to the time accuracy measurement mode, and a reference signal generated from the time standard source in the time accuracy measurement mode. In synchronization, the display control unit applies a first driving voltage having the same phase and the same potential to the two electrodes, and a second driving voltage having the same phase and the same potential but different from the potential of the first driving voltage. A second step of applying a dynamic voltage alternately, and having a third step of migrating from the time accuracy measurement mode to the normal mode.

  According to this, the driving method of the time display device has the effects described in Application Example 1.

The figure which shows the external appearance structure of the wristwatch as a time display apparatus concerning 1st Embodiment. The figure explaining the structure of the display panel of a wristwatch. Sectional drawing which shows typically the time display unit of a wristwatch. Sectional drawing explaining the structure of a display panel. The block diagram which shows the electric constitution of a time display unit. The timing chart which shows the display control operation at the time of normal mode. The timing chart which shows the display control operation | movement at the time precision measurement mode. The figure which shows the external appearance structure of the wristwatch as a time display apparatus concerning 2nd Embodiment. The figure which shows the structure of the display panel of a wristwatch, and a display drive circuit. The timing chart which shows the display control operation | movement at the time precision measurement mode. The schematic diagram which shows the example of a display of a display panel. The timing chart which shows another display control operation | movement at the time accuracy measurement mode.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram illustrating an external configuration of a wristwatch as a time display device according to the first embodiment, and FIG. 2 is a diagram illustrating a configuration of a display panel of the wristwatch.
As shown in FIG. 1, the wristwatch 1 includes a watch case 2 and a pair of watch bands 3 attached to the watch case 2 and wound around the wrist of the user. The timepiece case 2 is formed with a time display window 4 for displaying time and the like on the front, and a display panel 5 for displaying time and the like can be viewed from the time display window 4.

The time display window 4 is fitted with a cover body 6 formed of a transparent resin or transparent glass, and the display panel 5 is protected by the cover body 6.
Further, the watch case 2 has a time correction, a mode change (transition) from a normal mode which is a normal display state to a time accuracy measurement mode for time accuracy measurement using an external time accuracy measuring instrument, and the like. Operation buttons 8 are provided for performing various instructions.

As shown in FIG. 2, a segment display panel that displays various information by a plurality of segments is applied to the display panel 5, and a display area 5 </ b> R of the display panel 5 is used to display numbers 0 to 9. Four rows of segments (so-called 7 segments) 5A are arranged.
On the display panel 5, "hour" of the time is displayed by the left two columns of segments 5A, and "minute" is displayed by the right two columns of segments 5A. Further, between the “hour” segment 5A and the “minute” segment 5A, a circular segment 5B for displaying a “colon” indicating a separation of “hour” and “minute” is arranged.

Each of the segments 5A and 5B is provided with a background segment 5C for displaying the background, and for each character (number and colon) displayed by each of the segments 5A and 5B, the background segment 5C The background (black or white background) is displayed.
In the upper right portion of the display area 5R, a character string (L / G) segment 5D is provided as information indicating the time accuracy measurement mode in the time accuracy measurement mode described later.
In the present embodiment, an electrophoretic display panel is used as the display panel 5, and the detailed configuration thereof will be described later. Moreover, in the following description, when it is not necessary to distinguish each of the segments 5A to 5D, it is expressed as a segment 5X.

FIG. 3 is a cross-sectional view schematically showing a time display unit of a wristwatch.
As shown in FIG. 3, a time display unit 10 configured integrally with the display panel 5 is disposed in the watch case 2. The time display unit 10 includes a circuit board 11A, a display frame 11B, a display board 11C, a transparent board 11D, and a circuit presser 13 for holding them.
The display substrate 11C is provided with a segment electrode 14 corresponding to each of the segments 5A to 5D and a common electrode segment electrode 15 on the upper surface thereof.

A circuit board 11A is arranged on the lower surface of the display board 11C via a display frame 11B. On the circuit board 11A, an element 16 constituting a display drive circuit 40, a control part 50, etc. as a display control part is mounted. Has been.
A contact 11A1 wired to the element 16 (display drive circuit 40, etc.) is provided on the upper surface of the circuit board 11A, and a segment electrode 14 and a common electrode segment electrode 15 are provided on the lower surface of the display board 11C. A contact 11C1 connected by wiring is provided, and the contact 11A1 and the contact 11C1 are electrically connected via a connection connector 17 penetrating the display frame 11B.

Further, a switch electrode 18 is provided on the side surface of the circuit board 11A. The switch electrode 18 is configured to be conductive through a leaf spring 19 provided on the circuit holding member 13, and the leaf spring 19 is When it is deformed by the pressing operation of the operation button 8, it conducts through the deformed leaf spring 19. This conduction / non-conduction is detected by the element 16 (the control unit 50 in this embodiment).
A battery (power source) 20 for supplying driving power to the element 16 is detachably provided on the lower surface of the circuit board 11A. Further, a circuit frame 21 covering the element 16 is fixed to the circuit board 11A, and the element 16 is protected by the circuit frame 21. In addition, although the button battery which is a primary battery is applied to the said battery 20, not only this but a secondary battery may be applied.

  The transparent substrate 11D is provided with a transparent common electrode 25 formed of an ITO film or the like on the surface on the display substrate 11C side. Between the transparent common electrode 25 and the segment electrode 14 of the display substrate 11C, An electrophoretic layer 30 as an electrophoretic element is provided. Further, a common electrode conductive material 26 is interposed between the common electrode 25 and the common electrode segment electrode 15. The common electrode conducting material 26 is formed of, for example, conductive rubber, and the conductive rubber is deformed in accordance with the gap between the common electrode 25 and the common electrode segment electrode 15, thereby the common electrode 25. Thus, conduction between the common electrode segment electrodes 15 is reliably ensured.

FIG. 4 is a cross-sectional view illustrating the configuration of the display panel.
As shown in FIG. 4, a configuration called a two-color powder fluid system is applied to the electrophoretic layer 30. The electrophoretic layer 30 is composed of a plurality of microcapsules 31, and an electrophoretic dispersion liquid 33 is enclosed in these microcapsules 31.
In the electrophoretic dispersion liquid 33, black electrophoretic particles (hereinafter also referred to as black particles) 34 and white electrophoretic particles (hereinafter also referred to as white particles) 35 are mixed.
The black particles 34 and the white particles 35 are charged with different polarities. In this embodiment, the black particles 34 are positively charged and the white particles 35 are negatively charged.

Therefore, the display drive circuit 40 applies a drive voltage of 0 V potential to the common electrode 25 via the common electrode segment electrode 15 (see FIG. 3), and a positive drive voltage is applied to the predetermined segment electrode 14. When applied, an electric field from the segment electrode 14 toward the common electrode 25 is generated, the positively charged black particles 34 in the microcapsule 31 move to the common electrode 25 side, and the negatively charged white particles 35 become segment electrode. Move to the 14th side.
As a result, since the microcapsule 31 visually recognized from the transparent substrate 11D side (in the direction of arrow A) becomes black, the segment 5X displays black.

On the contrary, when a drive voltage having a positive potential is applied to the common electrode 25 by the display drive circuit 40 and a drive voltage having a 0 V potential is applied to the predetermined segment electrode 14, the display electrode 40 becomes negative in the microcapsule 31. The charged white particles 35 move to the common electrode 25 side, and the positively charged black particles 34 move to the segment electrode 14 side.
As a result, since the microcapsule 31 visually recognized from the transparent substrate 11D side becomes white, the segment 5X displays white.

When no potential difference is generated between the common electrode 25 and the segment electrode 14, no electric field is generated, and the black particles 34 and the white particles 35 do not move, so that the display color of the segment 5X does not change. The previous state is maintained.
In the present embodiment, the display drive circuit 40 has a built-in booster circuit, boosts the voltage (eg, 3V) supplied from the battery 20 to generate a + 12V voltage, and the + 12V voltage and the 0V voltage A voltage is applied to the segment electrode 14 and the common electrode 25 as a drive voltage.

FIG. 5 is a block diagram showing an electrical configuration of the time display unit.
The control unit 50 is electrically connected to the display drive circuit 40 and the battery 20 through a wiring pattern provided on the display substrate 11C.
The control unit 50 includes a timer circuit 51, an input / output circuit (I / O) 52, a voltage control circuit 53, an operation control circuit 54, and a control circuit 57.

The time measuring circuit 51 measures time by dividing an oscillation pulse of a predetermined frequency such as a crystal resonator as a time standard source in the oscillation circuit 51a by a frequency dividing circuit 51b and counting it by a time counting counter 51c. is there. The timer circuit 51 is connected to the display drive circuit 40 via the input / output circuit 52.
The voltage control circuit 53 supplies power supplied from the battery 20 to each unit in the control unit 50 and the display drive circuit 40, and the operation control circuit 54 detects conduction / non-conduction of the switch electrode 18. Thus, the operation of the operation button 8 is detected, and the detection result is notified to the control circuit 57.

The control circuit 57 centrally controls the entire time display unit 10 and includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. By executing the stored control program, the operation of each unit of the control unit 50 is controlled, and various signals are output to the display drive circuit 40 via the input / output circuit 52.
The display driving circuit 40 is a circuit for driving the display panel 5, acquires information such as time information timed by the time measuring circuit 51 under the instruction of the control circuit 57, and displays the display panel 5 at the instructed rewriting interval. And the time and the like are displayed on the display panel 5.

By the way, the control circuit 57 is a normal display state in which the mode of the wristwatch 1 is a normal display state in which the time information displayed on the display panel 5 is rewritten at the time update interval (in this embodiment, 1 minute interval). And a function for switching between a mode and a time accuracy measurement mode which is a display state for time accuracy measurement using an external time accuracy measuring instrument.
This mode switching (transition) is performed by a predetermined operation (short press, long press, simultaneous press, etc.) of a predetermined operation button 8 by the user.

Here, a display control operation as a driving method of the wristwatch 1 in each mode will be described.
First, the display control operation in the normal mode will be described.
FIG. 6 is a timing chart showing the display control operation in the normal mode. In FIG. 6, the timing at which the display rewrite instruction signal is output from the control circuit 57 to the display drive circuit 40 is M1, and the timing after 1 minute has passed from M1 is M2.

In FIG. 6, the drive signal for supplying the drive voltage applied to the common electrode 25 is COM, and the drive signals for supplying the drive voltage applied to each of the three segment electrodes 14 are SEG1, SEG2, and SEG3, respectively. .
In addition, when it is not necessary to particularly distinguish each drive signal that supplies the drive voltage applied to the segment electrode 14, it is expressed as a drive signal SEG.
Here, a case will be described in which, among the three segments 5X, the first display color is rewritten to black, the second display color is rewritten to white, and the third display color does not change.
In order to distinguish these segments 5X from each other, the first is denoted as segment 5XA, the second is denoted as segment 5XB, and the third is denoted as segment 5XC.

As shown in FIG. 6, during the period T (1 minute) from the timing M1 at which the display rewrite instruction signal is input to the display drive circuit 40 to the timing M2 at which the next display rewrite instruction signal is input, A period Ta and a pause period Tb are provided.
During the rewrite period Ta, the display drive circuit 40 applies a drive voltage to the common electrode 25 and each segment electrode 14 by the drive signal COM and the drive signal SEG to change or maintain the display color of each segment 5X, thereby displaying the time display. Is the period for rewriting.
The rewriting period Ta is composed of a first half Ta1 and a second half Ta2. The first half Ta1 and the second half Ta2 are substantially equal in length, and the reverse rewriting operation is performed between the first half Ta1 and the second half Ta2 in order to achieve DC balance.

The suspension period Tb is a period of waiting until the timing M2 when the next display rewrite instruction signal is input after the time display is rewritten. The display driving circuit 40 sets the operation state to the power saving state during the idle period Tb.
In the idle period Tb, the output terminal for outputting the drive signal COM and the drive signal SEG of the display drive circuit 40 is in a high impedance state (denoted as HI-Z).
Therefore, no potential difference occurs between the common electrode 25 and each segment electrode 14 during the rest period Tb. From this, the display color of each segment 5X is maintained in the color in the second half Ta2 of the rewriting period Ta.

As shown in FIG. 6, in the rewriting period Ta, for the segment 5XA in which the display color is rewritten to black, a driving voltage of 0V is applied in the first half Ta1 and a driving voltage of + 12V is applied in the second half Ta2 by the driving signal SEG1. Apply.
Further, for the segment 5XB in which the display color is rewritten to white, a drive voltage of + 12V is applied in the first half Ta1 and a drive voltage of 0V is applied in the second half Ta2 by the drive signal SEG2. For the segment 5XC in which the display color does not change, the drive signal SEG3 applies the same drive voltage as the drive signal COM described later for both the first half Ta1 and the second half Ta2.

To the common electrode 25, a driving voltage of 0V and a driving voltage of + 12V are alternately applied in the form of a pulse that repeats at a constant cycle by a driving signal COM.
The pulse width W of one pulse of the drive signal COM is set based on a frequency-divided signal having a period (for example, 125 ms, 62.5 ms, etc.) that can be generated by the frequency-dividing circuit 51b (see FIG. 5). For the common electrode 25, a driving voltage having a pulse number sufficient to change the display color of each segment 5X with the driving signal SEG using the pulse train P having the pulse width W by the driving signal COM. Applied.

As a result, in the first half Ta1 of the rewrite period Ta, when the drive voltage applied to the common electrode 25 by the drive signal COM is + 12V, the same as the segment electrode 14 of the segment 5XA to which the drive voltage of 0V is applied by the drive signal SEG1. An electric field is generated between the electrodes 25.
As a result, the black particles 34 move to the segment electrode 14 side, the white particles 35 move to the common electrode 25 side, and the display color of the segment 5XA slightly changes to white.

Next, when the drive voltage applied to the common electrode 25 by the drive signal COM is 0V, an electric field is generated between the segment electrode 14 of the segment 5XB to which the drive voltage of + 12V is applied by the drive signal SEG2 and the common electrode 25. appear.
As a result, the black particles 34 move to the common electrode 25 side, the white particles 35 move to the segment electrode 14 side, and the display color of the segment 5XB slightly changes to black.
Thereafter, similarly, the black particles 34 and the white particles 35 move little by little between the common electrode 25 and the segment electrode 14 according to the time-series change of the drive voltage applied to the common electrode 25 by the drive signal COM. As a result, the display colors of the segments 5XA and 5XB change stepwise.

  As a result, in the first half Ta1 of the rewriting period Ta, the display color of the segment 5XA is white and the display color of the segment 5XB is black.

Similarly, in the second half Ta2 of the rewriting period Ta, when the drive voltage applied to the common electrode 25 by the drive signal COM is 0V, the segment electrode 14 of the segment 5XA to which the drive voltage of + 12V is applied by the drive signal SEG1 An electric field is generated between the common electrode 25.
As a result, the black particles 34 move to the common electrode 25 side, the white particles 35 move to the segment electrode 14 side, and the display color of the segment 5XA changes slightly to black.

Next, when the drive voltage applied to the common electrode 25 by the drive signal COM is + 12V, an electric field is generated between the segment electrode 14 of the segment 5XB to which the drive voltage of 0V is applied by the drive signal SEG2 and the common electrode 25. appear.
As a result, the black particles 34 move to the segment electrode 14 side, the white particles 35 move to the common electrode 25 side, and the display color of the segment 5XB slightly changes to white.
Thereafter, similarly, the black particles 34 and the white particles 35 move little by little between the common electrode 25 and the segment electrode 14 according to the time-series change of the drive voltage applied to the common electrode 25 by the drive signal COM. As a result, the display colors of the segments 5XA and 5XB change stepwise.

  As a result, in the second half Ta2 of the rewriting period Ta, the display color of the segment 5XA is black and the display color of the segment 5XB is white.

  In addition, since the drive voltage applied by the drive signal SEG3 is the same as the drive voltage applied to the common electrode 25 by the drive signal COM, the segment 5XC has a gap between the segment electrode 14 and the common electrode 25 of the segment 5XC. No electric field is generated and the display color does not change.

Then, after the rewriting period Ta has elapsed, the display driving circuit 40 stands by until the timing M2 when the next display rewriting instruction signal is input.
When the display rewrite instruction signal is input at timing M2, the display drive circuit 40 changes or maintains the display colors of the segments 5XA, 5XB, and 5XC in the rewrite period Ta in the same manner as described above. .

Next, the display control operation in the time accuracy measurement mode will be described.
FIG. 7 is a timing chart showing the display control operation in the time accuracy measurement mode.
[First step]
First, the normal mode is shifted to the time accuracy measurement mode by a predetermined operation of the predetermined operation button 8 by the user.

[Second step]
Next, as shown in FIG. 7, in the time accuracy measurement mode, the display is rewritten by the display control operation similar to the normal mode in the rewrite period Ta at the timing M10 when the mode is shifted to the time accuracy measurement mode.
At this time, the segment 5D (see FIG. 2) indicating the time accuracy measurement mode corresponding to the segment 5XA is displayed in black.

Next, in the period Tc from the timing M20 to the timing M30 for shifting to the normal mode after the pause period Tb ′, the reference signal CL generated by dividing the oscillation pulse of the crystal resonator or the like by the frequency dividing circuit 51b is used. In synchronism, the display drive circuit 40 causes the segment electrodes 14 and the common electrode 25 to have a first drive voltage having the same phase and the same potential and a potential different from the first drive voltage and having the same phase and the same potential. The second drive voltage is applied alternately and repeatedly.
Note that here, the potential of the first drive voltage is 0 V, and the potential of the second drive voltage is +12 V.

That is, in the period Tc, the display drive circuit 40 synchronizes the drive voltage applied to each segment electrode 14 and the common electrode 25 by the drive signals SEG1, SEG2, SEG3 and the drive signal COM to 0 V in synchronization with the reference signal CL. The display panel 5 is driven by setting the potential to alternately change to a potential of + 12V and a potential of + 12V.
Thereby, in the period Tc, no potential difference is generated between each segment electrode 14 and the common electrode 25, so that there is no display change in all the segments 5X.

At this time, in the display panel 5 as a whole, an electric field is generated due to a potential difference between the first drive voltage that is a potential of 0V and the second drive voltage that is a potential of + 12V.
Note that it is preferable to use 16 Hz or the like as the reference signal CL at this time.

[Third step]
Next, a transition from the time accuracy measurement mode to the normal mode is made by a predetermined operation of the predetermined operation button 8 by the user, as in the first step. In addition, it is good also as a setting which transfers automatically from time accuracy measurement mode to normal mode, for example, after predetermined time of about 3 to 10 minutes progress.

  As described above, the wristwatch 1 according to the first embodiment has the time accuracy measurement mode. In the time accuracy measurement mode, the segment electrode 14 and the common electrode 25 are synchronized with the reference signal CL by the display drive circuit 40. In addition, the first drive voltage (0V) having the same phase and the same potential and the second drive voltage (+ 12V) having the same phase and the same potential but different from the first drive voltage are alternately repeated. Applied.

According to this, in the time accuracy measurement mode, the wristwatch 1 does not cause a potential difference between the segment electrode 14 and the common electrode 25 of the display panel 5, so that the above-described burn-in state or DC balance is lost. Corrosion of the common electrode 25 made of an ITO film or the like is suppressed, and deterioration of display characteristics of the display panel 5 can be avoided.
In addition, since the wristwatch 1 alternately applies the first drive voltage and the second drive voltage having a potential different from the first drive voltage to both electrodes of the display panel 5, the display panel 5 as a whole. An electric field is generated by a potential difference between the first drive voltage and the second drive voltage.

  Thereby, in the time accuracy measurement mode, the wristwatch 1 generates an electric field in synchronization with the reference signal CL generated by frequency-dividing an oscillation pulse such as a crystal resonator as a time standard source serving as a time reference. Therefore, it is possible to measure time accuracy with a time accuracy measuring instrument such as a quartz tester.

  Further, since the segment 5D indicating that the wristwatch 1 is in the time accuracy measurement mode is displayed in the time accuracy measurement mode, the user can be surely informed of the time accuracy measurement mode.

In the time period Tc in the time accuracy measurement mode, the wristwatch 1 may rewrite the display on the display panel 5 at a predetermined cycle that is not synchronized with the measurement cycle of the time accuracy measuring device, similarly to the rewrite period Ta. .
According to this, the wristwatch 1 rewrites the display of the display panel 5 during the period Tc in the time accuracy measurement mode, and thus the display state of the display panel 5 is deteriorated due to the continuation of the period Tc. Can be avoided.

  In the time accuracy measurement mode, the wristwatch 1 has a potential difference between the first drive voltage and the second drive voltage applied to both electrodes of the display panel 5 between the drive voltages in the normal mode in the normal display state. The potential of the second drive voltage may be higher than + 12V, for example, + 15V, + 18V, or the like so as to be larger than the potential difference (12V).

According to this, in the wristwatch 1, the potential difference between the first drive voltage and the second drive voltage applied to both electrodes in the time accuracy measurement mode is larger than the potential difference between the drive voltages in the normal mode.
From this, the time accuracy measurement by the time accuracy measuring device is more reliably performed in the wristwatch 1 because the electric field generated in the entire display panel 5 becomes stronger than in the normal mode.

  Further, the driving method of the wristwatch 1 includes the first step of shifting from the normal mode to the time accuracy measurement mode by a predetermined operation of the operation button 8, and the display drive circuit 40 in synchronization with the reference signal CL in the time accuracy measurement mode. A first drive voltage having the same phase and the same potential and a second drive voltage having the same phase and the same potential but different from the potential of the first drive voltage are applied to each segment electrode 14 and the common electrode 25. The second step of alternately applying repeatedly and the third step of shifting from the time accuracy measurement mode to the normal mode by a predetermined operation of the operation button 8 or the like.

  According to the driving method of the wristwatch 1, the wristwatch 1 can be switched between the normal mode and the time accuracy measurement mode. In the time accuracy measurement mode, the time accuracy measurement is performed by a time accuracy measuring instrument such as a quartz tester. Is possible.

Note that the wristwatch 1 does not have to be rewritten in the rewriting period Ta in the time accuracy measurement mode. That is, the wristwatch 1 may not have a display indicating the time accuracy measurement mode by the segment 5D.
This is because, since the time accuracy measurement by the time accuracy measuring device is performed in the period Tc, there is no technical problem in the time accuracy measurement even if the time accuracy measurement mode is not displayed by the segment 5D.
Needless to say, it is preferable to display the time accuracy measurement mode from the viewpoint of usability.

(Second Embodiment)
FIG. 8 is a diagram illustrating an external configuration of a wristwatch as a time display device according to the second embodiment. In addition, the same code | symbol is attached | subjected to a common part with 1st Embodiment, and the description is abbreviate | omitted.

As shown in FIG. 8, an active matrix display panel that displays various information such as time as images using a plurality of matrix-like pixels 102 is applied to the display panel 205 in the wristwatch 101 of the second embodiment. ing.
Here, the description will focus on the periphery of the display panel 205, which is different from the wristwatch 1 of the first embodiment.

FIG. 9 is a diagram illustrating a configuration of a display panel and a display driving circuit of a wristwatch. FIG. 9A is a diagram showing the overall configuration, and FIG. 9B is a diagram showing the configuration of each pixel.
As shown in FIG. 9, the display driving circuit 140 includes a scanning line driving circuit 106, a data line driving circuit 107, a common power supply modulation circuit 108, and a controller 110.

In the display panel 205, m pixels 102 are formed in a matrix form along the Y axis direction and n pixels along the X axis direction. The scanning line driving circuit 106 is connected to the pixel 102 through a plurality of scanning lines 104 (Y1, Y2,..., Ym) extending along the X-axis direction on the display panel 205.
The data line driving circuit 107 is connected to the pixel 102 via a plurality of data lines 105 (X1, X2,..., Xn) extending along the Y-axis direction on the display panel 205.
The common power supply modulation circuit 108 includes a first control line 111, a second control line 112, a first power supply line 113 (Vdd), a second power supply line 114 (Vss), and a common electrode power supply wiring 115. It is connected to the pixel 102.

The scanning line driving circuit 106, the data line driving circuit 107, and the common power supply modulation circuit 108 are controlled by the controller 110. The display drive circuit 140 is controlled by the control circuit 57 (see FIG. 5).
The first control line 111, the second control line 112, the first power supply line 113, the second power supply line 114, and the common electrode power supply wiring 115 are used as a common wiring in all the pixels 102.

  The pixel 102 includes a driving TFT (Thin Film Transistor) 124, an SRAM (Static Random Access Memory) 125, a switch circuit 135, a pixel electrode 121 and a common electrode 122 as opposed electrodes, and an electricity as an electrophoretic element. The electrophoresis layer 30 is provided.

The driving TFT 124 is configured by an N-MOS (Negative Metal Oxide Semiconductor). A scanning line 104 is connected to the gate portion of the driving TFT 124, a data line 105 is connected to the source side, and an SRAM 125 is connected to the drain side.
The driving TFT 124 connects the data line 105 and the SRAM 125 by connecting the data line 105 and the SRAM 125 during a period in which the selection signal is input from the scanning line driving circuit 106 via the scanning line 104. Is used to input the image signal input to the SRAM 125.

The SRAM 125 includes two P-MOS (Positive Metal Oxide Semiconductors) 125p1 and 125p2 and two N-MOSs 125n1 and 125n2. A first power supply line 113 is connected to the source sides of the P-MOSs 125p1 and 125p2, and a second power supply line 114 is connected to the source sides of the N-MOSs 125n1 and 125n2.
Therefore, the source side of the P-MOS 125p1 and the P-MOS 125p2 is the high potential power terminal PH of the SRAM 125, and the source side of the N-MOS 125n1 and the N-MOS 125n2 is the low potential power terminal PL of the SRAM 125.

The switch circuit 135 includes a first transfer gate 136 and a second transfer gate 137. The first transfer gate 136 includes a P-MOS 136p and an N-MOS 136n. The second transfer gate 137 includes a P-MOS 137p and an N-MOS 137n.
The source side of the first transfer gate 136 is connected to the first control line 111, and the source side of the second transfer gate 137 is connected to the second control line 112. The drain sides of the first transfer gate 136 and the second transfer gate 137 are connected to the pixel electrode 121.

The SRAM 125 includes an input terminal N1 connected to the drain side of the driving TFT 124, and a first output terminal N2 and a second output terminal N3 connected to the switch circuit 135.
The drain side of the P-MOS 125p1 and the drain side of the N-MOS 125n1 of the SRAM 125 function as the input terminal N1 of the SRAM 125.
The input terminal N1 is connected to the drain side of the driving TFT 124 and to the second output terminal N3 of the SRAM 125 (the gate portion of the P-MOS 125p2 and the gate portion of the N-MOS 125n2).
Further, the second output terminal N3 is connected to the gate portion of the N-MOS 136n of the first transfer gate 136 and the gate portion of the P-MOS 137p of the second transfer gate 137.

The drain side of the P-MOS 125p2 and the drain side of the N-MOS 125n2 of the SRAM 125 function as the first output terminal N2 of the SRAM 125.
The first output terminal N2 is connected to the gate portion of the P-MOS 125p1 and the gate portion of the N-MOS 125n1, and the N-- of the P-MOS 136p of the first transfer gate 136 and the N-gate of the second transfer gate 137. It is connected to the gate portion of the MOS 137n.

The SRAM 125 holds the image signal sent from the driving TFT 124 and is used to input the image signal to the switch circuit 135.
The switch circuit 135 functions as a selector that selectively selects one of the first control line 111 and the second control line 112 based on the image signal input from the SRAM 125 and connects to the pixel electrode 121. . At this time, only one of the first transfer gate 136 and the second transfer gate 137 operates according to the level of the image signal.

Specifically, when a high level is input to the input terminal N1 of the SRAM 125 as an image signal, a low level is output from the first output terminal N2, so that the transistor connected to the first output terminal N2 Of these, the P-MOS 136p operates.
Further, the N-MOS 136n connected to the second output terminal N3 (input terminal N1) operates to drive the first transfer gate 136.
Therefore, the first control line 111 and the pixel electrode 121 are electrically connected.

On the other hand, when a low level is input as an image signal to the input terminal N1 of the SRAM 125, a high level is output from the first output terminal N2. Therefore, among the transistors connected to the first output terminal N2, N -MOS 137n operates.
Further, the P-MOS 137p connected to the second output terminal N3 (input terminal N1) operates to drive the second transfer gate 137.
Therefore, the second control line 112 and the pixel electrode 121 are electrically connected.
Then, the first control line 111 or the second control line 112 is electrically connected to the pixel electrode 121 via the operated transfer gate (the first transfer gate 136 or the second transfer gate 137), and the pixel electrode A drive voltage is applied to 121.
The common electrode 122 is electrically connected to the common electrode power supply wiring 115.

As described above, the electrophoretic layer 30 is configured to display the image by moving the white and black electrophoretic particles according to the potential difference between the pixel electrode 121 and the common electrode 122.
Here, the outline of the operation of the electrophoretic layer 30 will be described again.
A driving voltage is applied to the pixel electrode 121 and the common electrode 122 so that the potential of the common electrode 122 becomes relatively high. Then, as shown in FIG. 9B, the positively charged black particles 34 are attracted to the pixel electrode 121 side in the microcapsule 31.
On the other hand, the negatively charged white particles 35 are attracted toward the common electrode 122 in the microcapsule 31.
As a result, the white particles 35 are collected on the display surface side (the common electrode 122 side) in the microcapsule 31, and the color (white) of the white particles 35 is displayed on the display surface.
The viewing direction here is the direction of arrow B.

Conversely, a drive voltage is applied between the pixel electrode 121 and the common electrode 122 so that the potential of the pixel electrode 121 is relatively high. Then, the negatively charged white particles 35 are attracted to the pixel electrode 121 side.
On the other hand, the positively charged black particles 34 are attracted to the common electrode 122 side.
As a result, the black particles 34 gather on the display surface side in the microcapsule 31, and the color (black) of the black particles 34 is displayed on the display surface.

Here, a display control operation in the time accuracy measurement mode as a driving method of the wristwatch 101 will be described.
FIG. 10 is a timing chart showing the display control operation in the time accuracy measurement mode. In FIG. 10, S1 indicates a potential as a drive voltage of the first control line 111, S2 indicates a potential as a drive voltage of the second control line 112, and COM indicates a drive of the common electrode power supply wiring 115. The potential as a voltage is shown. CL indicates a reference signal to be described later.
Since the first step and the third step are the same as those in the first embodiment, description thereof is omitted.

[Second step]
As shown in FIG. 10, in the time accuracy measurement mode, at the timing M10 when the normal mode is shifted to the time accuracy measurement mode, first, in the rewriting period Ta, the time accuracy measurement mode is performed by the display control operation similar to the normal mode. The display is rewritten to indicate this.
(In the normal mode, the period T (see FIG. 6) including the following rewriting period Ta and the rest period Tb ′ is set to 1 minute, and display rewriting is performed every minute in synchronization with the change of the minute of time. Is done.)

Here, a pixel 102 whose image signal is at a high level displays black, a pixel 102 whose image signal is at a low level displays white, and an image in which various information such as time is displayed in black on a white background is correct. An image is defined, and an image obtained by reversing the monochrome display is defined as an inverted image.
In the rewriting period Ta, a reverse image is displayed in the first half Ta1 and a normal image is displayed in the second half Ta2 in order to achieve DC balance.

Specifically, in the first half Ta1 of the rewriting period Ta, a low-level (potential: 0 V) driving voltage is supplied from the common power supply modulation circuit 108 to the first control line 111 (S1), while the second control line 112 is supplied. A drive voltage at a high level (potential: + 15V) is supplied to (S2).
At this time, in the pixel 102 whose image signal is high level, the potential of the first output terminal N2 of the SRAM 125 is low level, and the potential of the second output terminal N3 (input terminal N1) is high level. Accordingly, the first transfer gate 136 is driven to connect the pixel electrode 121 and the first control line 111. As a result, a driving voltage having a low level potential is applied to the pixel electrode 121.

Further, the common electrode 122 is alternately supplied with a high level (potential: +15 V) period and a low level (potential: 0 V) period from the common power supply modulation circuit 108 via the common electrode power supply wiring 115 (COM). A pulsed drive voltage that is repeated at a constant period is applied.
When the potential of the driving voltage applied to the common electrode 122 is at a high level, a potential difference (15 V) is generated between the pixel electrode 121 and the common electrode 122, and the white particles 35 are attracted to the common electrode 122 side. The black particles 34 are attracted to the pixel electrode 121 side.
As a result, white is displayed on the pixel 102 whose image signal is at a high level.

  On the other hand, in the pixel 102 whose image signal is at a low level, the potential of the first output terminal N2 of the SRAM 125 is at a high level, and the potential of the second output terminal N3 (input terminal N1) is at a low level. Accordingly, the second transfer gate 137 is driven to connect the pixel electrode 121 and the second control line 112. As a result, a driving voltage having a high level potential is applied to the pixel electrode 121.

Further, the common electrode 122 has a high level (potential: +15 V) period and a low level (potential: 0 V) period alternately at a constant cycle from the common power supply modulation circuit 108 via the common electrode power supply wiring 115. A repetitive pulsed driving voltage is applied.
When the potential of the driving voltage applied to the common electrode 122 is at a low level, a potential difference (15 V) is generated between the pixel electrode 121 and the common electrode 122, and the white particles 35 are attracted to the pixel electrode 121 side. The black particles 34 are attracted to the common electrode 122 side.
As a result, black is displayed on the pixel 102 whose image signal is at a low level.
With the display control operation described above, in the first half Ta1 of the rewriting period Ta, an inverted image of white display is displayed on a black background.

In the second half Ta2 of the rewrite period Ta, on the contrary to the above, a high level drive voltage is supplied from the common power supply modulation circuit 108 to the first control line 111, while a low level drive voltage is applied to the second control line 112. Supply. The common electrode power supply wiring 115 is supplied with a driving voltage similar to that of the first half Ta1.
Accordingly, in the pixel 102 in which the image signal is at a high level, a driving voltage having a high level potential is applied to the pixel electrode 121 via the first control line 111, and in the pixel 102 in which the image signal is at a low level, A driving voltage having a low level potential is applied to the pixel electrode 121 through the second control line 112.
As a result, in the second half Ta2 of the rewriting period Ta, the display color of each pixel 102 is opposite to that of the first half Ta1, black is displayed on the pixel 102 whose image signal is high level, and the pixel 102 whose image signal is low level. When white is displayed on the screen, a black-colored normal image is displayed on the white background.

In the rewriting period Ta, an image 205D as information indicating the time accuracy measurement mode is displayed on the display panel 205 as shown in a schematic diagram showing a display example of the display panel of FIG.
FIG. 11 shows a normal image display in the second half Ta2 of the rewriting period Ta, and displays a time (10:08) and a character string (L / G) indicating a time accuracy measurement mode.

Returning to FIG. 10, after the end of the rewriting period Ta, a predetermined pause period Tb ′ is provided.
Next, in a period Tc from the timing M20 at which the pause period Tb ′ ends to the timing M30 at which the normal mode is entered, an oscillation pulse such as a crystal resonator is frequency-divided by the frequency dividing circuit 51b (see FIG. 5). In synchronization with the generated reference signal CL, the display drive circuit 140 applies a first drive voltage having the same phase and the same potential to the pixel electrode 121 and the common electrode 122, and a first drive voltage having the same phase and the same potential. And a second driving voltage having a different potential are applied alternately and repeatedly.
Note that here, the potential of the first drive voltage is 0 V, and the potential of the second drive voltage is +15 V.

That is, the display drive circuit 140 supplies a first drive voltage at a low level (potential: 0 V) from the common power supply modulation circuit 108 to the first control line 111, the second control line 112, and the common electrode power supply line 115, and A second driving voltage of high level (potential: +15 V) is supplied alternately and repeatedly in synchronization with the reference signal CL.
As a result, in the period Tc, the drive voltage applied to the pixel electrode 121 and the drive voltage applied to the common electrode 122 are independent of the level state (high level or low level) of the image signal for each pixel 102. There is no potential difference.
Accordingly, there is no display change in all the pixels 102 in the period Tc.

  At this time, as the entire display panel 205, the first drive voltage and the second drive voltage are alternately and repeatedly applied in synchronization with the reference signal CL. An electric field is generated in synchronization with the reference signal CL due to a potential difference (15 V) between the drive voltage and the second drive voltage which is a potential of + 15V.

Thereby, similarly to the wristwatch 1 of the first embodiment, the wristwatch 101 of the second embodiment suppresses corrosion of the common electrode 122 due to the state of burn-in or the collapse of the DC balance in the time accuracy measurement mode. In addition, it is possible to avoid deterioration of display characteristics of the display panel 205 and to measure time accuracy using a time accuracy measuring device such as a quartz tester.
As the reference signal CL, 16 Hz or the like is preferably used as in the first embodiment.

In addition, as described above, the wristwatch 101 uses the drive voltage applied to the pixel electrode 121 and the drive voltage applied to the common electrode 122 regardless of the level state of the image signal for each pixel 102 during the period Tc. There is no potential difference between them.
Thereby, the wristwatch 101 can also eliminate the need to transmit the image signal from the driving TFT 124 to each pixel 102 in the period Tc.

  For example, when the image signal of all the pixels 102 is set to the high level or the low level in the pause period Tb ′, a display like a timing chart showing another display control operation in the time accuracy measurement mode of FIG. A control operation may be performed.

  More specifically, when the image signals of all the pixels 102 are set to the high level, as shown in FIG. 12A, the first control line 111 and the common electrode power supply wiring 115 from the common power supply modulation circuit 108 in the period Tc, as shown in FIG. Only the first driving voltage and the second driving voltage may be alternately and repeatedly supplied in synchronization with the reference signal CL.

According to this, when the image signal of the pixel 102 is at a high level, as described above, the pixel electrode 121 and the first control line 111 are connected, so that the drive voltage supplied to the second control line 112 is No potential difference occurs between the drive voltage applied to the pixel electrode 121 and the drive voltage applied to the common electrode 122, regardless of the potential (0 V in this case).
Therefore, the wristwatch 101 does not change the display on the display panel 205 during the period Tc.

  On the other hand, when the image signals of all the pixels 102 are set to the low level, as shown in FIG. 12B, only the second control line 112 and the common electrode power supply line 115 are supplied from the common power supply modulation circuit 108 in the period Tc. The first drive voltage and the second drive voltage may be alternately and repeatedly supplied in synchronization with the reference signal CL.

According to this, when the image signal of the pixel 102 is at the low level, as described above, the pixel electrode 121 and the second control line 112 are connected, so that the drive voltage supplied to the first control line 111 is No potential difference occurs between the drive voltage applied to the pixel electrode 121 and the drive voltage applied to the common electrode 122, regardless of the potential (0 V in this case).
Therefore, the wristwatch 101 does not change the display on the display panel 205 during the period Tc.

  In addition, although the system called 9T system is applied to the configuration (circuit configuration) of each pixel of the wristwatch 101 shown in FIG. 9B, the display control operation in the time accuracy measurement mode is the same as described above. Other methods may be applied as long as they are performed, for example, a method called a 1T method.

Note that the wristwatch 101 can reliably notify the user of the time accuracy measurement mode by displaying the character string (L / G) indicating the time accuracy measurement mode in the time accuracy measurement mode. For the same reason as in the first embodiment, the character string (L / G) may not be displayed without providing the rewriting period Ta in the time accuracy measurement mode.
Similarly to the first embodiment, in the time accuracy measurement mode, the wristwatch 101 rewrites the display on the display panel 205, which is performed in the rewrite period Ta, in the period Tc, and the measurement period of the time accuracy measuring instrument. It may be performed in a predetermined cycle that is not synchronized.

Similarly to the first embodiment, the wristwatch 101 has a potential difference between the first drive voltage and the second drive voltage applied to both electrodes of the display panel 205 in the time accuracy measurement mode. The potential of the second drive voltage may be higher than + 15V, for example, + 18V so as to be larger than the potential difference between the drive voltages (here, 15V).
According to these, the wristwatch 101 can obtain the same effects as the wristwatch 1 of the first embodiment.

In each of the above embodiments, since the segment display panel or the active matrix display panel is used for the display panels 5 and 205, the wristwatch 1 and 101 can perform various time accuracy measurements with a time accuracy measuring instrument. Various display modes can be selected.
Note that the time display device is not limited to a wristwatch, but is a mobile phone, a portable music player, a portable game machine, an electronic desk calculator, an electronic dictionary, an electronic notebook, an electronic viewer, digital It may be a camera.

  CL: reference signal, COM, SEG1, SEG2, SEG3 ... drive signal, M10, M20, M30 ... timing, P ... pulse train, Ta ... rewrite period, Ta1: first half of rewrite period, Ta2 ... second half of rewrite period, Tb '... Pause period, Tc: period from M20 to M30, W: pulse width.

Claims (6)

An electrophoretic display panel having an electrophoretic element between opposing electrodes;
A display control unit configured to control the display of the electrophoretic display panel by applying a driving voltage for driving the electrophoretic element to the electrodes, and to display at least the time;
A time standard source serving as a reference for the time,
In synchronization with the reference signal generated from the time standard source, the display control unit applies the first driving voltage having the same phase and the same potential to the both electrodes, and the first driving voltage having the same phase and the same potential. A time display device having a time accuracy measurement mode in which a drive voltage and a second drive voltage having a different potential are applied alternately.   2. The time display device according to claim 1, wherein the electrophoretic display panel is a segment display panel or an active matrix display panel.   3. The time display device according to claim 1, wherein in the time accuracy measurement mode, information indicating that the time accuracy measurement mode is being displayed is displayed on the electrophoretic display panel. apparatus.   4. The time display device according to claim 1, wherein the display of the electrophoretic display panel is rewritten at a predetermined cycle in the time accuracy measurement mode. 5. .   5. The time display device according to claim 1, wherein, in the time accuracy measurement mode, the first drive voltage and the second drive applied to the electrodes of the electrophoretic display panel. 6. A time display device characterized in that a potential difference from a voltage is larger than a potential difference between the drive voltages in a normal mode which is a normal display state. An electrophoretic display panel having an electrophoretic element between opposing electrodes, and a display for controlling the display of the electrophoretic display panel by applying a driving voltage for driving the electrophoretic element to both the electrodes and displaying at least the time A method for driving a time display device comprising a control unit and a time standard source serving as a reference for the time,
The time display device has a time accuracy measurement mode,
A first step of shifting from the normal mode, which is a normal display state, to the time accuracy measurement mode;
In the time accuracy measurement mode, in synchronization with the reference signal generated from the time standard source, the display control unit applies a first drive voltage having the same phase and the same potential to the both electrodes and the same phase and the same potential. A second step of alternately applying a second drive voltage having a different potential from the potential of the first drive voltage;
And a third step of shifting from the time accuracy measurement mode to the normal mode.

Images