JPS61241796A - Driving of liquid crystal display unit - 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 "Industrial Application Field" The present invention relates to a method for driving a liquid crystal display device, and in particular to a liquid crystal display device that is a composite element of a nonlinear element having nonlinear voltage-current characteristics and a liquid crystal. The present invention relates to a driving method.

"Conventional Example" and "Problems to be Solved by the Invention" Varistors, diodes, metal-insulator-metal elements (hereinafter M
A method of driving a liquid crystal display device by incorporating an element having non-linear voltage-current characteristics such as an IM element to form a composite element is already known (for example, Japanese Patent Laid-Open No. 86092/1983). .

That is, a liquid crystal panel using the above composite element has a small time constant τ when a driving voltage is applied to both electrodes of the panel. , charges the equivalent capacitance between the electrodes, and when the applied voltage is turned off, a large time constant τ occurs. Since the discharge is started at FF (τ ), the selection time t is short after the drive voltage is turned on, as shown in FIG. The liquid crystal is charged with N and maintains a sufficient voltage FF for a long time even after being turned off. As a result, the selection time t. The applied voltage at N determines the effective value of the drive voltage, and the normal TN (
The effective value ratio of ON and OFF can be made larger than that of the twisted nematic (twisted nematic) type liquid crystal display element, and high-density driving of the liquid crystal display device can be realized without reducing the contrast.

n % n + 1 ) (column II), the potential difference Vsl-VDP between the scanning electrode s1 and each data electrode (column m), and the voltage applied to the liquid crystal layer of the lit pixel (column VtoNr).

Further, FIG. 5(a) shows in one diagram the voltage VLO (column 2 in FIG. 8) applied to the liquid crystal layer in the above eight patterns.

As is clear from the above eight figures, when all pixels are lit (Figure 8 (a) and Figure 5 A), the effective value of the voltage VtO applied to the liquid crystal layer of that column is the largest. Become,
When one pixel is lit (Figure 8(b) and Figure 6B)
When the effective value of the voltage VLO becomes the smallest and the interlaced lighting state (Fig. 8 (C) and Fig. 5 C) occurs, the effective value of the voltage vLc becomes equal to the effective value of the above-mentioned two lighting states. Take an intermediate value.

Therefore, in the conventional driving method, the effective voltage applied to the liquid crystal layer differs depending on the display pattern as described above, resulting in variations in contrast between each lit pixel, and the display quality of the liquid crystal display device. However, when the above-mentioned liquid crystal display device is driven by the voltage averaging method at a frequency of 120Hz to 200Hz as in the past, the following problems occur depending on the states of other pixels on the same data electrode. The voltage (vLo) applied to the liquid crystal layer of the lit pixel changed [7], causing contrast variation.

The state of change in this voltage vLo will be explained with reference to FIGS. 2, 8, and 5(a). First, FIG. 2 shows a lighting pattern in which lit pixels are indicated by black circles and non-lit pixels are indicated by white circles, and all pixels on the data electrode Dn-1 are in the lit state (hereinafter referred to as
Only one pixel of the pixels on the data electrode iDn is lit (hereinafter referred to as the one-pixel lighting state), and the pixels on the data electrode D are in the one-pixel lighting state.
A state in which every pixel (n+1) is lit (hereinafter referred to as an intermittent lighting state)
8(a) to (c) show the voltage v applied to the scanning electrode S1 in each of the lighting states.
(column I), each data electrode Dn-1, Dn' Dn
−fl The voltage v Dp (p : n
This caused the problem that s deteriorated.

[Means for Solving the Problems] The present invention has been made in view of the above circumstances, and provides a method for driving a liquid crystal display device that can reduce variations in contrast between each lit pixel. The purpose is to

In order to achieve the above object, the present invention provides a liquid crystal display device in which an element having nonlinear characteristics is incorporated in at least one substrate constituting the liquid crystal display panel.
It is characterized by being driven by pulses of 00Hz to 400Hz.

When the frame frequency exceeds 400 Hz, the drive voltage increases due to the frequency characteristics of the composite element of the nonlinear element and the liquid crystal, while when the frame frequency is 300 Hz or less,
As described above, variations in contrast occur between each lit pixel.

"Example" Figure 4 shows a liquid crystal display device equipped with a composite element of a nonlinear element and a liquid crystal at a driving voltage frequency (frame frequency) of 300.
The voltage waveforms of various parts for each lighting pattern in FIG. 2 when driven at Hz to 400 Hz are shown in correspondence with FIG. 8. As in the case of FIG.
ii Voltage Vst H column is data electrode voltage VDP II
The I column shows the difference between the scan electrode voltage v81 and the data electrode voltage VDP, and the ■ column shows the liquid crystal layer voltage vLc. Moreover, FIG. 5(b) shows a waveform diagram of the voltage '/lo applied to the liquid crystal 1- in each lighting pattern of FIG. As shown in the figure, A indicates an all-pixel lighting state, B indicates a one-pixel lighting state, and C indicates an intermittent lighting state, as in the case of FIG. 3(a). Figures 2, 4, and 5 above
As you can see from figure (b), the frame frequency is set to 300Hz~
At 400 Hz, the variation in the voltage VLO applied to the liquid crystal layer in each lighting pattern is smaller than the variation due to the conventional driving method (FIG. 5(a)). This is because the non-selection period tOFF is shortened by increasing the frame frequency within an appropriate range, and the difference in the lighting pattern is caused by the bias portion of the voltage application waveform (non-selection period (FIG. 4, column I)). This is due to the smaller cutoff of the voltage waveform acting on the

On the other hand, when the frame frequency is set to 400 Hz or more, the driving voltage increases to 20 V or more due to the frequency characteristics of a liquid crystal display device made of composite elements. Further, power consumption also increases, which is not preferable.

On the other hand, when the frame frequency is set to 300 Hz or less, the effective value of the voltage vLc applied to the liquid crystal layer differs depending on the lighting pattern, and the contrast variation between ON selected pixels becomes 0.5 or more. Display quality deteriorates.

Table 1 shows a comparison of the frame frequencies described above and the characteristics of a composite liquid crystal display element consisting of a nonlinear element and a liquid crystal. The characteristics comparison shown in the same table was performed using a drive waveform with a duty ratio of 1/100.1/8 bias, and the ○ mark in the evaluation column indicates a usable level, and the X mark indicates an unusable level. There is.

Table 1 "Effects of the Invention" As explained above, the method for driving a liquid crystal display device according to the present invention uses a liquid crystal display device in which an element having nonlinear characteristics is incorporated in at least one substrate constituting a liquid crystal display panel. Drive frequency (frame frequency) 300Hz ~ 40
Drive at 0Hz without significantly increasing drive voltage.
Variations in contrast between lit pixels (between ON selected pixels) can be suppressed to a small level, and therefore a liquid crystal display device with high display quality can be provided.

[Brief explanation of the drawing]

FIG. 1 shows an example of a voltage waveform applied to the liquid crystal component of a composite liquid crystal element, FIG. 2 shows an example of a lighting pattern of the liquid crystal element, and FIG. 8 shows an example of a scanning electrode sl etc. in each lighting state. FIG. 4 shows the scanning voltage tM in each lighting state when driven by the method according to the present invention.
FIG. 5 is a diagram comparing the voltage vLc applied to the liquid crystal layer in an embodiment of the present invention with the voltage VLO in the conventional method. In the figure, St...scanning electrode, Dn-1IDnIDn+bi data electrode. Applicant (504) Sharp Corporation 7:; ゛・ Agent Patent Attorney Yutaka Habai -”,. Figure 2 Figure 3 1 ■ 4th 1 1V

Claims (1)

[Claims] (1) In a method for driving a liquid crystal display device in which an element having nonlinear characteristics is incorporated in at least one substrate constituting the liquid crystal display panel, the driving frequency (frame frequency) is set to 3.
A method for driving a liquid crystal display device, characterized in that the frequency is set to 00Hz to 400Hz.