JP2000075839A - Driving method of liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent crosstalk from occurring. SOLUTION: In the driving method of the liquid crystal display device, a liquid crystal panel of a simple matrix system where plural scanning electrodes and plural signal electrodes are intersected and the intersections are made to be pixels, is provided with a correction pulse impression means for impressing a correction pulse to make a selection pulse on the scanning electrode at the previous stage to be non-selective according to the difference between the number a of turned-on pixels on the scanning electrodes of the previous stage and the number b of turned-on pixels on the following scanning electrodes, and if a>b, the correction pulse is increased in width, while, if a<b, the correction pulse is decreased in width.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a liquid crystal display device having a simple matrix type liquid crystal panel.

[0002]

2. Description of the Related Art In a simple matrix type liquid crystal display device, a scanning substrate and a signal substrate are opposed to each other so that a plurality of transparent electrodes arranged therein intersect with each other. To form a display area, and an image is displayed by applying a voltage to the transparent electrode on the scanning side (scanning electrode) and the transparent electrode on the signal side (signal electrode) by a voltage averaging method. .

[0003]

However, in a liquid crystal display panel of a simple matrix system, a capacitance is generated in a pixel which is an intersection of a scanning electrode and a signal electrode. Display unevenness was occurring.

FIG. 6 shows a typical example of a crosstalk display pattern. In the entire display area of the liquid crystal display panel, when a rectangular black portion is displayed against the plain (c) as a background, the occurrence of crosstalk on the entire screen is indicated by (a) and (b). Both are the width of one line of the scanning electrode.

On the scanning electrode side, crosstalk occurs along the boundary (the upper side of the black portion) where the number of white (lighting) pixels decreases, and pixels constituted by the scanning electrodes on the side with the higher number of lightings are more likely. It becomes bright. On the other hand, it also occurs along the boundary where the number of white (lit) pixels increases (the lower side of the black portion)
Pixels formed by the scanning electrodes on the side with the smaller number of lightings become darker. That is, when the number of illuminated pixels on the scanning electrode changes, if the change in the scanning direction indicates that the pre-change scan electrode is the previous scan electrode and the post-change scan electrode is the next scan electrode, the previous scan electrode has a higher turn-on number. When there are many pixels, the pixels on the preceding scanning electrodes become brighter, and when the number of lightings of the preceding scanning electrodes is smaller, the preceding scanning electrodes become darker.

[0006] The crosstalk as described above is caused by the distortion of the waveform of the liquid crystal drive voltage. The signal voltage changes synchronously at the time of rising or falling of the scanning selection voltage pulse, and thus the scanning selection voltage pulse is changed. Is induced by capacitive coupling, which causes a distortion in the waveform of the drive voltage and causes crosstalk.

Accordingly, an object of the present invention is to prevent crosstalk from occurring or to reduce the influence thereof.

[0008]

According to the driving method of the liquid crystal display device of the present invention, a simple matrix type liquid crystal panel in which a plurality of scanning electrodes and a plurality of signal electrodes are crossed and the crossing portions are pixels is provided. Lighting number a of pixels in the preceding scanning electrode a
And a correction pulse applying means for applying a correction pulse for deselecting a selection pulse in the previous scanning electrode according to a difference between the lighting number b of the pixel in the next scanning electrode and
When a> b, the width of the correction pulse is widened, and when a <b, the width of the correction pulse is narrowed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to FIGS. FIG. 1 shows a schematic configuration of a liquid crystal display device, and FIG.
Indicates the timing of the signal waveform. FIG. 3 is a circuit block diagram of the DISP signal control circuit, and FIG. 4 shows a timing chart of the DISP signal control circuit. FIG. 5 is a schematic diagram showing an example of the lighting display.

In FIG. 1, reference numeral 1 denotes a liquid crystal panel, 2 denotes a signal electrode driving circuit, and 3 denotes a scanning electrode driving circuit. According to the liquid crystal panel 1, signal electrodes X1, X2,.
n and scanning electrodes Yl, Y2 ... Yn-1, Yn
Are arranged orthogonally in a matrix. The signal electrodes X1, X2,..., Xn-1, Xn are driven by the signal electrode driving circuit 2, and the other scanning electrodes Y1, Y2
,... Yn−1, Yn.

In such a simple matrix type liquid crystal display device, a transparent electrode group (scanning electrodes Y1, Y2... Yn-1, Yn...) Arranged on a scanning substrate and a transparent electrode group arranged on a signal substrate are arranged. Transparent electrode group (signal electrodes X1, X2
.. Xn-1, Xn...), And TN or STN liquid crystal is sealed between the scanning substrate and the signal substrate to form a display area. Then, the signal electrode driving circuit 2 and the scanning electrode driving circuit 3 apply a voltage by a voltage averaging method.

The scanning electrodes Y1, Y2,...
1, Yn... And signal electrodes X1, X2.
The white and black circles shown at the intersections of Xn...
The white circles are lit, and the black circles are non-lighted. For example, all the lines driven by the scanning electrode Yl are turned on, and all the lines driven by the scanning electrode Y2 are not turned on.

The signal electrode drive circuit 2 receives a liquid crystal display data signal DATA, a shift clock CP for taking the liquid crystal display data signal DATA into an internal shift register, a signal LOAD for latching data of the shift register to an output circuit, and a display enable signal DISPIN. I do. These signals are output from a liquid crystal panel control circuit (not shown).

The scanning electrode driving circuit 3 has scanning electrodes Yl, Y
The input data signal FRAM of the shift register and the shift clock LOAD of the shift register for selecting 2 ... Yn-1, Yn ... are input from a liquid crystal panel control circuit (not shown). Note that LOAD input to the scan electrode drive circuit 3 and the signal electrode drive circuit 2 are the same signal.

The scan electrode drive circuit 3 receives a DISPOUT signal from the DISP signal control circuit 5. DI
The clock signal CLK from the oscillation circuit 4 is supplied to the SP signal control circuit 5.
Enter Further, the DISP signal control circuit 5 receives a DISPIN signal from a liquid crystal panel control circuit (not shown). Note that the DISPIN signal input to the liquid crystal panel control circuit 5 and the signal electrode drive circuit 2 is the same.

FIG. 2 shows timings of signal waveforms in the liquid crystal display device having the above configuration. The selection pulse of the scan electrode is at the voltage V2 during the non-selection period, and becomes the voltage V0 between the fall and the fall of LOAD during the selection period. For the signal electrode, the latched DATA
When the signal is high (H), its output is at voltage V3,
When the latched DATA signal is low (L), its output is at the voltage level Vl.

With respect to the voltage actually applied to the liquid crystal during the selection period, when the latched DATA signal is L, V
It turns on at 0-V3 and turns off at V0-V1. For example, since all the lines selected by Y1 in FIG.
1, X2... Xn-1, Xn.
3 is output and all the lines selected by Y2 are in the non-lighting state.
Xn... Xn-1, Xn... All output the voltage V1. Also, during the period when Yn-1 is selected, the signal electrodes X1 and X2 output Vl, and the signal electrodes Xn-1 and Xn output V0.

FIG. 3 shows a circuit block of the DISP signal control circuit. The accumulator circuit block receives the input DAT
The A signal is latched at the falling edge of the CP signal, and only the L level of the latched DATA signal is added. Similarly, only the latch of the DATA signal and the L level are added at the fall of the next CP. At the same time, the previous CP
Is added to the addition result at the falling edge of. Repeat this 1
Cumulative addition of L data for the line is performed. The cumulative addition result for one line is stored in the latch circuit 1. As a latch clock to the latch circuit 1, a pulse generated by counting the CP signal for one line by a counter is used. The result of the latch circuit 1 is latched by the latch circuit 2 at the next fall of the LOAD signal. When the result of one line of the accumulating circuit is latched in the latch circuit 1, the output of the latch circuit 1 and the output of the latch circuit 2 are compared by a comparison circuit. This comparison is performed by subtracting the output of the latch circuit 2 from the output of the latch circuit 1. The output from the comparison circuit is composed of positive and negative polarity signals and an absolute value output. Then, the result of the comparison is decoded by the decoder circuit to the number of clocks of the correction pulse width.

DISP as the correction pulse applying means
Pulse timing circuit (DISP correction pulse control circuit)
Is supplied with a clock CLK generated by the oscillation circuit. Also, there is a counter which starts counting the clock CLK based on the latch clock of the latch circuit 1, and compares the count value with the output result of the decode circuit to generate a pulse having the width of the output result period of the decode circuit. I do. This pulse and a normal DISP signal are superimposed, and the DISP signal is set to L level during the period of the output result of the decoding circuit.

FIG. 4 shows a timing chart of the DISP signal control circuit. The L level of DATA driven by Yn-1 is added and latched at the end of the data input period of Yn. Next, in the data input period of Yn, Y
L level of DATA driven by n is cumulatively added, and Y
Latched at the end of the n data input period. At the same time, the cumulative addition result of the Yn-1 L level data and the cumulative addition result of the Yn L level data are compared, and as a result,
A pulse having a width of an appropriate number of clocks is used as a correction pulse,
Immediately after the n data input period, it is superimposed on the DISPOUT signal.

According to the driving method having the above structure, the scanning electrode Y
The n-1 selection pulse is V2 during the period of the correction pulse.
The level is selected and acts in the direction of decreasing the effective voltage applied to the liquid crystal. By adjusting the width of this correction pulse in accordance with the change in the number of lightings, that is, as shown in FIG. In the relationship between the lighting number a of the pixel and the lighting number b of the pixel in the next scanning electrode, the width of the correction pulse is increased when a> b, and the width of the correction pulse is narrowed when a <b. As a result, a good display without crosstalk was obtained.

[0022]

As described above, according to the driving method of the liquid crystal display device of the present invention, the lighting number a of the pixel in the preceding scanning electrode and the lighting of the pixel in the next scanning electrode are provided in the simple matrix type liquid crystal panel. Correction pulse applying means for applying a correction pulse for making the selection pulse in the preceding scanning electrode non-selective according to the difference from the number b is provided. When a> b, the width of the correction pulse is increased, and a <b By narrowing the width of the correction pulse, the effective voltage applied to the liquid crystal could be controlled, and as a result, a favorable display without crosstalk was obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a liquid crystal display device.

FIG. 2 is a timing chart of a signal waveform.

FIG. 3 is a circuit block diagram of a DISP signal control circuit.

FIG. 4 is a timing chart of a DISP signal control circuit.

FIG. 5 is a schematic diagram showing an example of a lighting display of the liquid crystal display device and a correction pulse.

FIG. 6 is a schematic diagram illustrating occurrence of crosstalk.

Claims (1)

[Claims] 1. A simple matrix type liquid crystal panel in which a plurality of scanning electrodes and a plurality of signal electrodes intersect and the intersections are pixels, the number of pixels a of the preceding scanning electrodes is lit.
And a correction pulse applying means for applying a correction pulse for deselecting a selection pulse in the previous scanning electrode according to a difference between the lighting number b of the pixel in the next scanning electrode and
A driving method of a liquid crystal display device in which the width of the correction pulse is increased when a> b, and the width of the correction pulse is narrowed when a <b.