Liquid crystal display device, and method and circuit for driving liquid crystal display device

Abstract

A liquid crystal display device includes a display section, an image signal drive circuit, a scan signal drive circuit, a common electrode potential control circuit, and a synchronous circuit. The display section has scan electrodes, image signal electrodes, a plurality of pixel electrodes arranged in a matrix, a plurality of switching elements for transmitting an image signal to the pixel electrodes, and a common electrode. The common electrode potential control circuit changes an electric potential of the common electrode into a pulse shape, after the scan signal drive circuit has scanned all the scan electrodes and the image signal has been transmitted to the pixel electrodes. Otherwise, the image signal is overdriven. Otherwise, torque for returning to a no-voltage-application state is increased.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystal display device, and a method and a circuit for driving the liquid crystal display device. In particular, the present invention relates to a liquid crystal display device which can respond at high speed with high efficiency, and a method and a circuit for driving the liquid crystal display device. [0003] 2. Description of the Related Art [0004] With the progression of the age of multimedia, various types of liquid crystal display devices, from a small one used in a projector device, a cellular phone, a viewfinder, and the like to a large one used in a notebook PC, a monitor, a television, and the like, have rapidly become widespread. A medium-sized liquid crystal display device has become essential in electronic equipment such as a viewer and a PDA, and in a game instrument such as a portable game machine and a pachinko (Japanese pinball game) machine. The liquid crys...

AI Technical Summary

Benefits of technology

[0058] A third effect of the present invention is to be able to obtain a liquid crystal display device with high light-use efficiency and low electric power consumption. This is because, first, the liquid crystal rapidly reaches stable transmittance due to the speedup of the liquid crystal response. Second, a voltage necessary for overdriving the image signal at a high frequency is low due to the two steps of overdrive, so that electric power consumption is reduced as compared with a conventional overdrive method.

[0059] A fourth effect of the present invention is to be able to obtain a liquid crystal display device which can stabilize an image within one frame, and does not degrade the image (variations in gray level and flicker) by the effect of a history. This is because delay in a response such as a bounce and delay does not occur. Also, an image signal for realizing a desired display state is generated by a comparison calculator and a lookup table.

[0060] A fifth effect of the present invention is to be able to provide a liquid crystal display device which does not bring blurriness in a moving image. This is because a combination of field sequential drive and drive according to the present invention can provide favorable display.

[0061] A sixth effect of the present invention is to be able to realize an overdrive type of display device with simple system structure at low cost. This is because it is not necessary to compare all color data of a previous screen with all color data of the next screen by applying a field sequential method. It is enough to compare specific color (or one color synthesized from a plurality of colors) da

Problems solved by technology

When the conventional TN liquid crystal display element is driven by simple matrix drive, display quality is not high, and the number of scanning lines is limited.

The STN liquid crystal display device, however, is not suited for displaying moving images because the response speed thereof is slow.

The following problems occur in such high speed nematic liquid crystal.

Also, means for storing previously written information such as the frame memory becomes unnecessary.

The foregoing liquid crystal display devices, that is, the display device by the overdrive, the display device by the reset drive, the display device disclosed in a document such as Japanese National Publication No. 2001-506376, however, have several problems.

A first problem is that the rising response speed of the liquid crystal can be increased in the overdrive method, but the response speed is confined from several tens milliseconds to a dozen or so milliseconds under the constraint of a material.

As to the falling response speed, it cannot be much increased.

Thus, it is difficult to increase/decrease the viscosity, dielectric anisotropy, and elastic constants to predetermined values or more/less.

Furthermore, it is extremely difficult to largely change only each physical value itself, so that it is difficult to realize the effect of speedup assumed by the equations.

Therefore, improvement at a few tens percent or more is impossible, though slight adjustment is possible.

A method of increasing the applied voltage value according to (4), on the other hand, receives severe constraint from the viewpoints of electric power consumption and the high cost of a high voltage driving circuit.

At the same time, when the active element such as a thin-film transistor is provided in the display device and driven, the withstand voltage of the element adds constraints to the display device

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