JP2001249649A - Driving method for liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal driving method excellent for preventing the flicker phenomenon of display which is to be generated especially in reflection type liquid crystal display device because frequencies of light of fluorescent tubes being environmental light depend upon respective power source frequencies and the frequency of the vertical synchronizing frequency of a display device interferes with a certain power source frequency. SOLUTION: In this liquid crystal display driving method, the continuous frequency of the vertical synchronizing signal which is supplied from an external controller is made to be changed irregularly.

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 for displaying characters, images, and the like.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a matrix type liquid crystal display device. The matrix type liquid crystal display device 1 has a matrix type liquid crystal display panel in which p display signal lines 2 and n scan signal lines 3 are arranged in a matrix, and a liquid crystal display element 4 is formed between electrodes at the intersections. 5, a display signal line driving circuit 6 for driving the display signal line 2, a scanning signal line driving circuit 7 for driving the scanning signal line 3, and a driving power supply device 8. The display signal line driving circuit 6 and the scanning signal line driving circuit 7 are formed from a liquid crystal driving controller integrated circuit.

As a method of driving the matrix type liquid crystal display device 1 by the scanning signal line driving circuit 6 and the scanning signal line driving circuit 7, a scanning voltage is sequentially applied to the scanning signal lines 3 and the scanning signal lines 3 are connected. A driving method for applying a selection voltage / non-selection voltage from the display signal line 2 in accordance with the selection / non-selection data of the liquid crystal display element 4 on the selected scanning signal line 3 during the selection period to drive the liquid crystal, that is, A split driving method is generally employed.

The reflection type liquid crystal display device has a configuration in which an external environment light source is reflected by a polarizing plate having a reflection layer attached to a liquid crystal display panel or a reflection electrode provided inside the panel. As the ambient light, artificial lighting such as the sun or a fluorescent light is used.

[0005]

The above-described reflection type liquid crystal display and the above-described time-division driving have the following problems. Generally, the lighting frequency of a fluorescent lamp depends on the power supply frequency of 50 Hz or 60 Hz,
The screen rewriting frequency of the liquid crystal display device is the period of the vertical synchronization signal. When these two periods interfere with each other, a flicker called flicker occurs on the screen of the liquid crystal display device. Although the optimum vertical synchronization signal frequency can be selected for each power supply frequency, it is difficult to select a vertical synchronization signal frequency that can support both power supply frequencies. As a countermeasure, the response speed of the liquid crystal is reduced, but the performance is deteriorated. Further, increasing the frequency of the vertical synchronizing signal frequency leads to an increase in current consumption. Therefore, at present, some flicker is tolerated.

However, in recent reflection type liquid crystal display devices, the reflectivity has been improved by the aluminum reflection layer, and thus the degree of flicker has been visually increased, which has become a serious problem.

[0007]

In order to achieve the above object, a method of driving a liquid crystal display device according to the present invention comprises the steps of: alternating a frequency of a continuous vertical synchronizing signal supplied to the liquid crystal display device;
Alternatively, it is changed randomly.

The operation of the above means is as follows.

[0009] By changing the frequency of the vertical synchronizing signal to a certain value, the frequency is not fixed, the interference with the lighting frequency of the fluorescent lamp can be broken, and flicker of the liquid crystal display device can be reduced.

[0010]

(Embodiment 1) An embodiment 1 of the present invention will be described.

FIG. 1 shows a driving method according to the first embodiment in which two vertical synchronizing signals having different frequencies are alternately supplied.

It is assumed that the frequency of the vertical synchronizing signal changes alternately with the odd number being the frequency A (the number of scanning signal lines Ya) and the even number being the frequency B (the number of scanning signal lines Yb). (60 Hz), which is less likely to interfere with the lighting frequency of the fluorescent lamp. Therefore, display flicker is reduced at any power frequency.

(Embodiment 2) An embodiment 2 of the present invention will be described.

FIG. 2 shows a driving method in which the vertical synchronization signal according to the second embodiment randomly supplies different frequencies.

Since the vertical synchronizing signal is supplied every time with a different frequency in a random manner, interference with the fluorescent lamp lighting frequency can be suppressed, and flicker of display can be reduced.

[0016]

According to the liquid crystal display driving method of the present invention, the vertical synchronizing signal frequency of the reflection type liquid crystal display device hardly interferes with the lighting frequency at each power supply frequency of the fluorescent lamp which is ambient light, and the flicker of display is reduced. It is of great industrial value to be able to do it.

[Brief description of the drawings]

FIG. 1 is a diagram showing a liquid crystal driving waveform according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a liquid crystal driving waveform according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a conventional liquid crystal display device.

FIG. 4 is a diagram showing a conventional liquid crystal driving waveform.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Display signal line 3 Scan signal line 4 Liquid crystal display element 5 Liquid crystal display panel

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Claims (1)

[Claims] 1. A method for driving a liquid crystal display device, wherein an external controller for driving the liquid crystal display device changes a period of a continuous vertical synchronization signal alternately or randomly.