JPH04309920A - Driving method for liquid crystal display device - Google Patents

Abstract

PURPOSE:To eliminate a flicker which is generated at intervals of one field period and to improve numerical aperture by making a preliminary scan on the most adjacent scanning line which is equal in the polarity of an applied voltage when a 1st scanning line is scanned. CONSTITUTION:The polarity of the voltage applied to a liquid crystal composition is inverted at intervals of 1st-4th scanning lines and the preliminary scan on the 2nd most adjacent scanning line which is equal in the polarity to the applied voltage at the time of the scanning of the 1st scanning line is made. Thus, the flicker generated at intervals of a field period T is suppressed by inverting the polarity of the applied voltage at the intervals of the 1st-4th scanning lines. The polarity of the applied voltage is inverted preferably at intervals of one scanning line so as to minimize the flicker, but the flicker can be suppressed sufficiently by inverting the polarity of the applied voltage at the intervals of at least four scanning lines. Further, the scanning lines are scanned preliminarily to hold specific charges on the preliminarily scanned scanning lines in advance.

Description

[Detailed description of the invention]

[Purpose 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, and more particularly to a method for driving a liquid crystal display device having a switching element for each pixel.

0002

2. Description of the Related Art In recent years, liquid crystal display devices have come to be used in various fields by taking advantage of their characteristics of being lightweight, compact, and low power consumption.

Among these, active matrix liquid crystal display devices, in which each pixel is provided with a switching element such as a thin film transistor, have attracted particular attention in recent years because they can provide display quality as good as static drive.

FIG. 1 shows an equivalent circuit diagram of an active matrix liquid crystal display device, in which a plurality of signal electrodes and a plurality of scanning electrodes are formed in a matrix, and the intersections of each signal electrode and scanning electrode are A thin film transistor connected to the pixel electrode is installed in that part. A liquid crystal composition is sandwiched between this pixel electrode and a common electrode facing the pixel electrode, thereby forming an active matrix type liquid crystal display device. In such a liquid crystal display device, each scanning line is sequentially scanned within, for example, one field period (T), and an image is displayed. By the way, the above-mentioned active matrix type liquid crystal display device has the following problems.

That is, in order to improve the aperture ratio of each pixel, it is conceivable to make switching elements such as thin film transistors sufficiently small, but if the switching elements are made small, the channel width of the element also becomes narrow, and one horizontal scanning Sufficient writing to the pixel electrode cannot be performed within the period (H). This is especially noticeable when the voltage applied to the liquid crystal composition swings to the positive polarity.
Insufficient writing to the pixel electrode occurs, causing flicker and deteriorating display quality.

To solve this problem, for example, when the first scanning line is scanned, a second scanning line adjacent to the first scanning line scheduled to be scanned next is pre-scanned, that is, two adjacent scanning lines are scanned. It is known that scanning lines are scanned simultaneously during one horizontal scanning period (H).

[0007] By pre-scanning the second scanning line scheduled for the next scanning in this way, the shortage of writing current to the pixel electrode during actual scanning of the second scanning line is eliminated, and flicker is prevented from occurring. be able to.

[0008]

[Problems to be Solved by the Invention] By the way, it is known that liquid crystal compositions deteriorate when a DC component is applied for a long period of time, and the above-mentioned driving method generally This was done in combination with a method of reversing the polarity of the voltage applied to the liquid crystal composition.

However, although such a driving method solves the problem of insufficient writing to the pixel electrode, the period is shortened because the polarity of the voltage applied to the liquid crystal composition is reversed every one field period (T). There is a problem in that the optical response of the liquid crystal during the two-field period (T) is observed as flicker to the human eye. In order to solve this problem, the period of the optical response must be short enough to be difficult for the human eye to perceive.
That is, it is conceivable to shorten one horizontal scanning period (H), which is the writing time of the switching element, but since it is necessary to complete writing in a short time, this requires increasing the size of the switching element. As a result, there was a problem in that the aperture ratio decreased as the switching element area increased.

The present invention has been developed in view of the above-mentioned problems, and is capable of sufficiently reducing flicker caused by the optical response of liquid crystal, and even if the aperture ratio is improved, there is no problem such as insufficient write current to the pixel electrode. The purpose of the present invention is to provide a method for driving a liquid crystal display device that can obtain good display quality without causing problems. [Structure of the invention]

[0011]

[Means for Solving the Problems] A method for driving a liquid crystal display device according to the present invention includes a liquid crystal display device in which a liquid crystal composition is sandwiched between a pair of electrode substrates. A method for driving a liquid crystal display device that performs scanning by inverting the polarity of the voltage applied to the composition, the method comprising pre-scanning the nearest adjacent second scanning line having the same polarity of the applied voltage when scanning the first scanning line. It is characterized by

0012

[Operation] As described above, the present invention reverses the polarity of the voltage applied to the liquid crystal composition at least every one to four scanning lines, and also reverses the polarity of the voltage applied during scanning of the first scanning line. This is to pre-scan the nearest second scanning line with the same values. By reversing the polarity of the applied voltage every 1 to 4 scanning lines, flicker that occurs every field period (T) can be suppressed.

[0013] In order to minimize flicker, it is preferable to reverse the polarity of the applied voltage every scanning line, but flicker can be sufficiently suppressed by reversing the polarity of the applied voltage at least every four scanning lines. was confirmed by experiment.

Furthermore, by pre-scanning the scan lines to which the polarity of the applied voltage is the same when scanning one scan line, a predetermined charge is held in the pre-scanned scan line in advance. Therefore, when actually scanning the pre-scanned scanning line, sufficient writing can be performed even if a switching element formed with a narrow channel width is used. By performing this preliminary scanning on the nearest adjacent scanning line having the same polarity as the applied voltage during scanning of one scanning line, a sufficient effect of the preliminary scanning can be obtained.

In other words, if the distance between the actual scanning line and the preliminary scanning line is large, the voltage level applied during actual scanning will often differ between the two, and the charge from preliminary scanning will not be useful during actual scanning. It's gone. On the other hand, by selecting the nearest scanning line with the same polarity as the applied voltage during scanning of the actual scanning line and performing a preliminary scanning line, the charges retained during preliminary scanning can be utilized to the maximum during actual scanning. It is possible to write to the pixel electrode at the same time.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific example of the method for driving a liquid crystal display device according to the present invention will be explained in detail below with reference to the drawings.

Liquid crystal display device (1) used in this example
For example, as shown in FIG. 1, a plurality of signal electrodes (11
) and scanning electrodes (15) are formed in a matrix,
A liquid crystal composition (31) is sandwiched between a pixel electrode (25) connected to each intersection via a thin film transistor (21) and a common electrode (27) facing the pixel electrode (25), This common electrode (27) is connected to a common common voltage driving means (51).

Furthermore, as shown in FIG. 2, each scanning electrode (15
) is a scanning electrode drive circuit (61) consisting of a shift register.
Each signal electrode (11) is connected to a signal electrode drive circuit (101).

The specific configuration of the signal electrode drive circuit (101) for realizing an embodiment of the present invention is as shown in FIG.
a serial/parallel conversion circuit (71) that samples and outputs in parallel based on a sampling timing signal (SP);
A latch circuit (8) holds the output from the serial/parallel converter (71) and outputs one line based on the latch signal (LA).
1) and a polarity selection means (91) that inverts the polarity of the output signal from the latch circuit (81) every scanning period (H).
).

The polarity selection means (91) is connected to a system connected to an inverter (95) for inverting the polarity of the output signal from the latch circuit (81), and a system that inverts the polarity of the output signal from the latch circuit (81). and a switching circuit (93) for switching each scanning line in accordance with a switching signal (ST). A method of driving such a liquid crystal display device (1) will be explained with reference to FIG.

[0021] An analog video signal (VD) is inputted to the serial/parallel conversion circuit (71) of the signal electrode drive circuit (101), sampled based on a predetermined sampling timing signal (SP), and sent to the latch circuit (81). Output. Then, the output signal for one scanning line is output to the latch circuit (81
), it is output to the polarity selection means (91) based on the timing of the latch signal (LA).

The output signal from the latch circuit (81) input to the polarity selection means (91) is a switching signal (ST).
Since the system to which the inverter (95) is connected is selected every horizontal scanning period (H) by the switching circuit (93) that performs a switching operation according to the A signal voltage (SV) whose polarity is inverted is input every horizontal scanning period (H).

A shift clock (CK) and a data signal (DIN) are input to the scanning electrode drive circuit (61), and a data signal (DIN) is input at the rise time of the shift clock (CK).
IN) are transferred sequentially. For the data signal (DIN),
As shown in FIG. 3, a first pulse that becomes active for one horizontal scanning period (H) and a second pulse that becomes active two horizontal scanning periods (H) later than this pulse are input.

[0024] This data signal (DIN) is sequentially transferred by a shift clock (CK), and the preliminary scanning gate pulse and the actual scanning gate pulse are applied to each scanning at intervals of one horizontal scanning period (H). The gate voltage (S
X).

For example, the first frame period (
Regarding the first horizontal scanning period (1H) of 1T),
The actual scanning gate pulse is input to the scanning electrode (X1) (15), and the preliminary scanning gate pulse is input to the scanning electrode (X3) (15).

Therefore, an actual scanning gate pulse is input to each pixel electrode (25) connected to the scanning electrode (X1), a positive signal voltage (SV1) is applied, and an image of one scanning line is displayed. The Rukoto.

Further, a preliminary scanning gate pulse is input to each pixel electrode (25) connected to the scanning electrode (X3) (15), and each pixel electrode (25) connected to the scanning electrode (15) When the signal voltage (SV1) of the same positive polarity is applied, preliminary scanning is performed.

In the second scanning period (2H), the scanning electrode (
A negative signal voltage (SV2) is applied to each pixel electrode (25) connected to the scanning electrode (X2) (15), and an image of one scanning line is displayed.
A signal voltage (SV2) of negative polarity is also applied to each pixel electrode (25) connected to the pixel electrode 5) for preliminary scanning.

Furthermore, in the third scanning period (3H), each pixel electrode (25) connected to the scanning electrode (X3) (15)
The gate pulse for actual scanning is input to , and the positive polarity signal voltage (SV3) is applied again to display the image of one scanning line, and each pixel connected to the scanning electrode (X5) (15) A positive signal voltage (SV3) is also applied to the electrode (25) for preliminary scanning.

In this way, by performing preliminary scanning when scanning the nearest adjacent scanning line with the same polarity as the signal voltage (SV) applied to a predetermined scanning line, it is possible to eliminate the write current shortage during actual scanning. Can be done. Furthermore, flicker can be minimized by inverting the polarity of the signal voltage (SV) for each scanning line.

[0031] In the above-described embodiment, a case was shown in which display was performed by inverting the polarity of the signal voltage (SV) for each scanning line, but the present invention is not limited to this;
Good display can be obtained if the polarity of the signal voltage (SV) is inverted within every scanning line.

For example, when display is performed by inverting the polarity of the signal voltage (SV) every four scanning lines, the nearest scanning line to which the signal voltage (SV) with the same polarity is applied, that is, the one selected five scanning periods ago, is displayed. It is a good idea to perform preliminary scanning when selecting a scanning line. By performing preliminary scanning in this way, charges with the same polarity as the signal voltage (SV) that will be applied during actual scanning are held, and it is possible to eliminate the shortage of write current during actual scanning. .

[0033] Furthermore, since the above-mentioned preliminary scanning can eliminate the write current shortage during actual scanning,
It becomes possible to reduce the channel width of the switching element connected to each pixel electrode. Thereby, the aperture ratio of the liquid crystal display device can be improved and good contrast characteristics can be obtained.

[0034]

As described above in detail, according to the method for driving a liquid crystal display device of the present invention, it is possible to eliminate flicker that occurs every one field period (T), and
Even if the aperture ratio is improved, good display quality can be obtained.

Furthermore, since writing is performed by two scans, a preliminary scan and an actual scan, for each scan line, one
Compared to a device that completes writing in one scan, sufficient writing can be performed even with a smaller applied voltage, making it possible to drive with even lower power consumption.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a liquid crystal display device for realizing an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a liquid crystal display device for realizing an embodiment of the present invention.

FIG. 3 is a timing diagram showing drive timing by the liquid crystal display device of FIGS. 1 and 2;

[Explanation of symbols]

(1)...Liquid crystal display device (11)...Signal electrode (15)...Scanning electrode (61)...Scanning electrode drive circuit (101)...Signal electrode drive circuit

Claims (1)

[Claims] Claim 1: At least one to four scanning lines of a liquid crystal display device comprising a liquid crystal composition sandwiched between a pair of electrode substrates.
A driving method of a liquid crystal display device in which the polarity of the voltage applied to the liquid crystal composition is inverted for each scanning line and the polarity of the voltage applied to the liquid crystal composition is inverted for each scanning line. A method for driving a liquid crystal display device characterized by pre-scanning a scanning line.