JPS5866995A - Driving of electrochromic display element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrochromic display device (hereinafter referred to as ICCD).
It is related to a method of driving a device (referred to as an element), and it eliminates unevenness in display contrast and enables display with always uniform contrast.

Generally, it consists of a display electrode and a counter electrode.
In driving the W-CD element, when changing the display,
After the NODCD element is removed from the display cell, a negative voltage is applied to the display electrode and a positive voltage is applied to the counter electrode for a certain period of time to the substrate for writing.

Such a driving method is based on T1. Regardless of the history of each segment of the CD element before display, it can be erased under the same driving conditions.
In order to perform a write operation, each segment cannot be written with the same display contrast, resulting in display contrast unevenness. In other words, if a segment in a written state is rewritten after a display change before display, the writing groove will be darker and the display contrast will be stronger than if a segment in an erased state is newly written after a display change. state. This is because the RODCD element behavior is caused by an electrochemical reaction. That is, the display state of the display electrode is caused by an electrochemical reduction reaction, and the erased state is caused by an electrochemical oxidation state.

In general, the electrochemical reaction of a KCD element using tungsten oxide, an inorganic display material, for the display electrode is explained as follows: [Elimination reaction] HWO, -+4' +e- (Display state) (Erased state) Here, WOS is tungsten oxide, H+ is a hydrogen ion, and e- is an electron.

In this display reaction, the display contrast is proportional to the amount of electricity transferred; the higher the writing voltage, the more
And the longer the writing time, the stronger the display contrast becomes. Moreover, the same thing can be said about the elimination reaction.

Generally, electrochemical reactions tend to become more stable over time. That is, a segment left in the erased state for a long time is likely to have a predetermined display contrast in one write operation.

In addition, segments that have been left in the written state for a long time are difficult to be completely erased with one erase operation, and when they are written continuously, the display contrast tends to be stronger than before the writing change. .

As a result, when changing the display of the ECD element, one display contrast unevenness may occur, resulting in a display that is extremely difficult to understand.

The present invention was made in view of the current situation, and is
This is a very effective driving method for eliminating display contrast unevenness when changing the display of an element.

Hereinafter, the driving method of the present invention will be explained using the drawings of FIGS. 1 to 3.

The basic driving principle according to the present invention is shown in Fig. 1 (a) t (b
), shown in Figure 2 (IL)t (b), and Figure 1 (
&), (b) is when the segment of the EOD element is in the write state before and after rewriting, and from the write state to the write state after rewriting, and Figure 2 (a), Φ) is when the segment of the ECD element is before and after rewriting. , when the state changes from the erased state to the written state after rewriting.

In FIGS. 1 and 2, when the erase voltage is vx, the normal value of V is a constant voltage between about 0.87 and 1.2 mm. Further, if the write voltage is vw, the normal value of V is a constant voltage between about -0.8v and -1.2m. Tmax and Tv indicate the erase pulse time at each time, and this value is usually a constant time between several hundred milliseconds and several seconds [depending on the segment shape and size of the D element] different.

In addition, 71w1 to 'rvv3 indicate the write pulse time at each time, and normally this value ranges from several hundred milliseconds to several hours.
It is a constant time of seconds and varies depending on the segment shape and size of the K(5I) element. TI Kan 1 ~ T Engineering t5
indicates the erase current waveform at each time %TIW1~Ttw
s indicates the write current waveform at each time.

FIGS. 1(&) and 1(b) are diagrams showing the driving force k when a segment in a written state is brought into a display state even after display rewriting, and the number of times of erasing and number of times of writing is three each. That is, this is the case of three erasing display operations. Here, the erase current waveform 'rtxt~Ttt5 is Txgt<T
The relationship ll2<Tll3 holds, and 'I'tx 5 shows the current waveform when the erasure reaction is carried out steadily. On the other hand, write current waveform TXWI~T! , 5 is T
There is a relationship of xwl>Tll2” Tll15% T
X12. 1xws shows the current waveform when the display reaction is performed steadily. That is, the display contrast of the displayed segment of the ECD element always has a predetermined value due to the constant erasing and writing current waveforms.

FIGS. 2(a) and 2(b) are diagrams showing a driving method when a segment in an erased state is brought into a display state after display rewriting, and the number of times of erasure and writing is three times each, that is, three times. This is the case of the display erasing operation.

Here, erase current waveform T! 12t T113 is Tx
There is a relationship of w2>Txzs, and 'rtts indicates a current waveform when the erasing reaction is performed steadily. Note that no erase current flows during the erase pulse time Tvx+, which indicates that the erase current hardly flows through the segment in the erased state. On the other hand, the write current waveform TIWI~T'zv3 is Ttwl<Tll2<
TXws, and T111S indicates a current ferry when the display reaction is performed steadily. That is, the display contrast of the segment of the ECD element displayed by the steady erasing and writing current waveforms always has a predetermined constant value.

Now, from FIGS. 1(a) and 1(b), if we consider driving when a segment in a written state is brought into an erased state after display rewriting, the steady state write current waveform TIW2'
・ After driving ", the segment erase operation is completed by driving with the erase current waveform TlX3 in the steady state. In other words, by driving with the write and erase current waveforms in the steady state, the display The segment of the EOD element whose display has been erased has no remaining display and has been completely erased.

As described above, since the display rewriting operation of the KCD element according to the present invention is performed by the steady write current waveform after the steady erase current waveform, a constant display contrast is always possible and the display is clear. Become something.

Note that here, the erase voltage v1g and the write voltage V.

was kept constant during the display erasing operation, but when it was erased.

Of course, it is possible to vary the write cycles T1 to T5. Also, FIGS. 1(a) and 1(b), and FIG. 2(a).

In (b), the erase and write cycles are explained three times, but of course this can be varied depending on the state of the ECD element.

FIG. 3 is a block diagram showing an example of a driving circuit for carrying out the method for driving an EOD element according to the present invention.

In FIG. 3, an input digital signal Signal coded for EOD element display is input to an input signal change detection section 1, and this input signal change detection section 1 performs a function for temporarily storing the input signal. The input signal is compared with the input signal currently being displayed by the KOD element, which is captured in a certain latch circuit. If it is determined that the input signal has changed as a result of this comparison, the input signal change detection section 1 inputs the ROD element display rewriting signal LL d J/ to the erase signal and write signal generation section 5. do.

The input signal change detection section 1 also sends a KID signal to the decoder section 2.
Digital signal L/ for writing all segments of the element
Enter @ //. The decoder section 2 converts the coded digital signal inputted from the input signal change detection section 1 into R.
It has a decoding function of converting into a digital signal corresponding to each segment in which a writing operation of the OD element is to be performed. The decode signal output “b” output from the decoder section 2 is input to the driver section 3. This driver part 3 has a function of generating erase voltage and write voltage necessary for rewriting the JKCD element in a form corresponding to each segment of the ROD element.

When the ECD element display rewriting signal "d" is inputted from the input signal change detection part 1, the erase signal/write signal generating section 5 outputs the ICCD element erase signal IIO" to the driver section 3 for a certain period of time, and then erases the signal. At the same time as the output of the signal is finished, the XOD element write signal /'61/ is output for a certain period of time.
At the same time as the erase signal is outputted, the counter signal JJflJ is input from the erase/write signal generating section 6 to the counter section 8 in the form of a cycle. The counter section 8 inputs a signal NgLL that measures the number of repetitions of the display erasing operation of the man standard from the counter signal "f".

According to the erase signal L/61/or the write signal 〃θ″ of the erase signal/write signal generator 6, the dry/junior 3
Erase voltage 〃c〃or write voltage'' to ICCD element 4
C'' is input. With this drive output "c", the EOD
Each segment of element 4 performs erase and write operations.

In addition, the erase signal/write signal generation section 6 is configured to generate a counter section 8.
Erase until the reset signal u, u is input from
The write signal //6 LL is sequentially input to the driver part 3. At this time, the decoder 2 (decoder 2 to part 3)
Since the decode signal 'lb〃 from the driver part 3 outputs a signal with contents instructing the EOD element 4 to write all segments, one output of the driver part 3 is output from the IcD element 4.
This means that all segments are erased and written, and all segments are erased and written multiple times, so all segments can be displayed with uniform display contrast, regardless of the history before display rewriting. is in a state.

When the reset signal "g" is output from the counter section 8, the erase signal/write signal generating section 5 sequentially sends the erase signal "e" and write signal "6" of the final cycle to the driver section 3 once. input and end the operation.

During this final cycle, the input signal change detection section 1, which receives the reset signal ngu from the counter section 8 at the same time as the erase signal and the write signal generation section 5, receives a coded input signal for rewriting the display of the IECD element 4. Signal
is taken into the latch circuit, and the encoded digital signal "a" to be newly displayed is output to the decoder section 2. The decoder section 2 sends a decode signal 7'b" corresponding to the segment of the KCD element 4 to be newly written to the driver section 3.
Enter.

As a result, in the final erase/write cycle, the driver part 3 inputs the write voltage to the D element 4 for all the segments to be newly displayed, and all the segments to be newly displayed are uniformly distributed. Finish writing with the appropriate display contrast.

In FIG. 3, the reference clock oscillator 6 and the frequency divider 7 supply clock signals "h" and "i" to the erase signal, the write signal generator 6, and the counter section 8 to maintain the operation timing. It has the function of supplying

As described above, according to the method for driving an ECU element according to the present invention, it is possible to eliminate display contrast unevenness, which is a drawback of the conventional method, and to always perform display with uniform display contrast. This has the effect of being able to completely prevent this.

[Brief explanation of the drawing]

FIGS. 1(IL) and (b) show drive voltage waveforms and drive current waveforms when segments that were displayed before rewriting are still displayed after rewriting in the display rewriting operation in the EOD element driving method according to the present invention. Figure, Figure 2 (
a) j (b) are diagrams showing drive voltage waveforms and drive current waveforms when segments erased before rewriting are displayed after rewriting in the display rewriting operation in the driving method of the present invention; FIG. FIG. 2 is a block diagram showing an example of a drive circuit for implementing the method for driving an ECD element according to the present invention. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure No. 2111

Claims (1)

[Claims] When rewriting the display contents of an electrochromic display element having multiple segments, perform the erase and write operations for all segments multiple times, then perform the erase operation for all segments, and then perform the write operation for the necessary segments. Accordingly, a method for driving an electrochromic display element that terminates a display rewriting operation.