JPS58209787A - Driving of electrooptic 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 a driving method that improves the responsiveness of an electro-optical element such as a liquid crystal display element or an electrochromic display element.

Conventionally, for example, as a driving method for a liquid crystal display element, there has been a method of applying an effective value voltage that changes over time as shown in FIG.

This is the period T during which the liquid crystal display element should be turned on. The driving voltage ■ is higher than the threshold value vT8 by 3. N is applied, and no other voltage is applied during the non-lighting period Tott.

Application of such a voltage is, for example, a liquid crystal display element of the type shown in FIG. .

A drive frequency signal S is generated by a two-digit drive frequency generating means. This is an exclusive OR gate that outputs the drive voltage (segment electrode drive voltage) X of the three segment electrodes 1b based on the state of the content a to be displayed and the state of the drive frequency signal S. This is digital data that should be displayed in four digits.

Two drive frequency generating means supply a drive frequency signal bv to the common electrode 1a as a common electrode drive voltage.

In addition, the segment electrode drive voltage X is, in detail, xi+X
21... Consisting of XN. Similarly, the content a to be displayed also consists of all az, --, aN in detail.

In this circuit, the voltage applied to the liquid crystal material 16 is the difference between the drive frequency signal applied to each of the common electrode 1a and the segment electrode 1b and the segment electrode drive voltage X -
Since x, we take into account the relationship between the contents a and the like to be displayed and make the display as shown in Fig. 3.

The time change of the effective value (b-X) of this applied voltage is also shown in the same figure.

The conventional method for driving the liquid crystal display element 1 is as described above, but it has the drawback that sufficiently fast response of the liquid crystal display element 1 cannot be obtained. In order to improve this, a bias voltage VB lower than the threshold value v1 is applied, and when the lighting is to be performed, a driving voltage V equal to or higher than the threshold value VTI is applied. A driving method that applies N has been proposed. FIG. 4 shows the change over time in the effective value of the applied voltage in this case. However, kneading improves the rise but worsens the rise.

The present invention has been made in order to eliminate the drawbacks of the conventional methods as described above, and specifically provides a method for driving an electro-optical element such as a liquid crystal display element that speeds up the rising response without deteriorating the falling response. It is an object. The invention will now be described. FIG. 5 shows the change over time in the effective value of the voltage applied to the liquid crystal display element according to the first embodiment of the invention. During the period when the light should not be lit, the period is T'.

Bias voltage V for ff, ? : Lowering.

FIG. 6 shows the change over time in the effective value of the voltage applied to the liquid crystal display element according to the second embodiment of the invention. In addition to lowering the -H bias voltage v11 for a certain period of time T'att during which the light should not be lit, the level of the driving voltage is reduced to V for a certain period of time T'ON during which the light should be turned on. N to V
I have raised it to ONI.

In the first embodiment, when the liquid crystal display element is turned on, the threshold value v? A bias voltage VB of 3 or less is applied, and when lighting is to be performed, a driving voltage voN of a threshold [VTg or more] is applied. When turning off the light, lower the bias voltage V to a sufficiently low voltage (including voltage 0),
When the liquid crystal display element has almost fallen, apply the original bias voltage v111 again.This is because the falling response is not slow because the bias voltage is low, and the bias voltage v3
This takes advantage of the fact that the rise response can be made faster by applying .

In the second embodiment, the drive voltage vo is equal to or higher than the threshold value 7711.
N is applied, but once the driving voltage V is at a high level,
. N1 is applied, and when the liquid crystal display element rises to a low level of driving voltage V. Lower it to N. This takes advantage of the fact that when the driving voltage V)N is high, the rising response is fast. From a different perspective, the driving voltage V. N
It takes advantage of the fact that the lower the value, the faster the fall response. This embodiment is the same as the first embodiment in that it takes advantage of the fact that the lower the bias voltage V, the faster the falling response, and the faster the rising response when the bias voltage vIl is applied. FIGS. 7 and 8 show how the response changes depending on the drive voltage voN and how the response changes depending on the bias voltage (3), respectively.

In FIGS. 7 and 8, curve I indicates a rising response, and curve II indicates a falling response. According to these, it is better for the drive voltage voN to be higher for the rising response and lower for the falling response, and for the bias voltage vB, it is better to be higher for the rising response and lower for the falling response. I understand. However, in reality, these values approach the threshold value kH (and there is a limit in terms of optical response), so an appropriate value naturally exists.

The driving methods of the first and second embodiments can be realized, for example, by a circuit as shown in FIG.

In FIG. 9, numeral 1 is a liquid crystal display element, which is the same as in FIG. 1 is an applied voltage generating means that generates a plurality of voltages with respect to the potential of the common electrode 1a. This configuration uses resistors to divide the voltage of an alternating current power source, which is configured to be switched automatically. Contents to be displayed in 6 digits (digital data)
It is a change detection means for detecting the point in time when a change occurs, and is composed of, for example, a register that stores the content to be displayed last time, and a digital comparator that compares the content of this register with the content to be displayed this time. This is a monostable oscillation (timer) means that outputs a signal ω that is active for a fixed period of time approximately equal to the response time of the liquid crystal display element 1 from the time fj is detected by the seven-digit change detection means 6. Based on the urgent state of the signal ω outputted by the monostable oscillation means 7, the applied voltage generating means 50 selects one of the plurality of alternating current voltages generated by the applied voltage generating means 50. This is means for selecting an applied voltage to be supplied to the segment electrode 1b, which is connected to a demultiplexer such as a transmission gate, for example. These connections are made as shown in the truth tables shown in Tables 1 and 2. Table 1 shows the case of the first embodiment shown in FIG. 5, and Table 2 shows the case of the 6th embodiment.
This is the case of the second embodiment shown in the figure.

Table 1 Table 2 Next, the operation of the circuit shown in FIG. 9 will be explained with reference to the waveform diagram in FIG. 10.

B) When there is a change in the content to be displayed aK, the output of the change detection means 6 becomes active.

(10) Using this active state as a trigger, the output of the monostable oscillation means 7 becomes active for a predetermined fixed time.

(→ The voltage generated by the applied voltage generation means 5 is selectively supplied to the segment electrode 1b by the applied voltage selection means 8 based on the state of the content to be displayed and the state of the output of the monostable oscillation means T. be done.

) Based on the truth tables in Tables 1 and 2, in the first embodiment, when the content a to be displayed is ``1'', voN is a
is 10" and the output ω of the change detection means 6 is 11", then the addition
However, when a is "O" and ω is ``O'', vlI is applied to the corresponding segment of the liquid crystal display element 1. In the second embodiment, when the content a to be displayed is l'' and the output ω of the change detection means 6 is 11'', ■. N1 is ω when a is “l”
When is "0", but when a is 0' and ω is 1", 0 is
When a is 0" and ω is "O", vlI is the liquid crystal display element 1
is applied to the corresponding segment of.

As a result, a driving method in which the applied voltage changes over time as shown in FIGS. 5 and 6 is achieved.

In the above embodiment, a case was explained in which a liquid crystal display element was driven as an electro-optical element. However, even when driving a certain type of electrochromic display element having a threshold@ The driving method of the invention produces effects similar to those of the above embodiments.

As described in detail above, since the present invention drives the device so that the bias voltage is temporarily lowered during the falling response, it is possible to improve the rising response without sacrificing the falling response of the electro-optical element.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the change over time in the effective value of the applied voltage according to the conventional driving method for liquid crystal display elements, Figure 2 is a circuit diagram implementing the conventional driving method, and Figure 3 is the circuit shown in Figure 2. Figure 4 shows the time changes of the signals of each part, the voltages applied to the liquid crystal display element, and their effective values over time. The diagram showing the changes, the faS diagram, and FIG. 6 are the first diagrams of this invention. A diagram showing the change over time in the effective value of the applied voltage in the method for driving a liquid crystal display element in the second embodiment,
7 and 8 are diagrams showing the drive voltage dependence and bias voltage dependence of the response time of a liquid crystal display element, and FIG. A diagram showing an example of a circuit implementing the driving method of the second embodiment, and FIG. 10 is a waveform diagram of the driving voltage, bias voltage, etc. generated by the applied voltage generating means in the circuit shown in FIG. 9. . In the figure, 1 digit liquid crystal display element, 1 a common electrode, 1 b segment electrode, 1 c liquid crystal material, 2 digit drive frequency generating means, 3 an OR gate, 4 digital data of contents to be displayed, 5 digits. Applied voltage generation means, 6-digit change detection means, T
8 monostable oscillation means and 8 applied voltage selection means. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Shin Kuzuno - (1 other person) Figure 1 Figure 2 Figure 4 Figure 0
−−−− −−□ Time Figure 5 Figure 6 □ Time Figure 7 Bias voltage Va + Figure 9 Figure 10 0 D / 1 piece supplementary subtraction (spontaneous) ↑'I' + i'l' l□ J length 1'l' Itfx1
°1111 force table small 1119 river 1. 'i 5
7-94242 No. 2, '; Name Electro-optical element driving method;
゛ Item 23S; name +4;
Rinto fI Tokoro Heavy Industries; [Toriyo 111-ku Marunouchi-
No. 1-112, No. 3, J-5, Claims column 1 of the specification subject to amendment 1 Detailed description of the invention column and drawings 6, Contents of the amendment (1) Claims of the specification attached, Correct as shown below. (2) Replace rla, la, ICJ on page 2, line 6 of the specification with Na, 1b, +cJ. (3) Similarly, delete the part "and each of segment 'tun h1b'" in the first line of page 3. (4) Similarly, in the 4th line of the 3rd page, the phrase ``It will be as shown.'' should be supplemented with ``It will be as shown in J.'' (5) Similarly, in the 4th member, line 19, ``Bias pressure ” is supplemented with “bias voltage Va J. do. (7) Similarly, on page 8, line 15, replace ``Contents to be displayed'' with ``Contents to be displayed a.'' (8) Correct the figures 2 and 6 of the 1-plane as shown in the attached sheet. 1-2, Claim (1) An electro-optic device having a threshold value, always applying a bias voltage lower than the threshold value described in ii7 above, and applying a driving voltage higher than the threshold value to the driving pin. 7↓, an electro-optical element driving method characterized in that in the r-driving method, when non-direct lighting is desired, . Power method.

Claims (1)

[Claims] In an electro-optical element driving method in which the electro-optical element has a threshold value, a bias voltage lower than the threshold value is always applied, and a drive voltage higher than the threshold value is applied during driving, the electro-optical element should be displayed on the electro-optical element. An electro-optical element driving method characterized in that the bias voltage is lowered for a certain period of time after the content changes to non-lighting.