Liquid crystal display device

Abstract

The present invention allows a liquid crystal display device to perform an image display of high quality by suppressing lowering of image quality which is generated attributed to an AC driving method. In a liquid crystal display device of the present invention, each pixel includes a pixel electrode and a counter electrode. Assuming a state in which a video voltage of a potential higher than a potential of a counter voltage applied to the counter electrode is applied to the pixel electrode as a drive state of positive polarity and a state in which the video voltage of the potential lower than the potential of the counter voltage applied to the counter electrode is applied to the pixel electrode as a drive state of negative polarity, the drive circuit changes the drive state of each pixel, for every m(m≧1) frame, from the drive state of positive polarity to the drive state of the negative polarity or from the drive state of the negative polarity to the drive state of the positive polarity and, at the same time, inverts a phase of the drive state of each pixel for every N(N≧m) frame, and the drive circuit outputs gray scale correction display data which differs from inputted display data in the first frame immediately after the phase inversion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the schematic constitution of a display control circuit 4 of a liquid crystal display module of an embodiment 1 according to the present invention;

FIG. 2 is a graph showing a brightness change quantity of a first frame immediately after a phase inversion in the liquid crystal display module of the embodiment 1 of the present invention and a brightness change quantity of a first frame immediately after the phase inversion in a conventional liquid crystal display module;

FIG. 3 is a graph showing one example of the relationship between inputted display data and gray scale correction display data in the liquid crystal display module of the embodiment 1 according to the present invention;

FIG. 4 is a view which schematically expresses the pixel voltage and the pixel polarity of one pixel for every frame with respect to video voltages of white and black in the liquid crystal display module of the embodiment 1 according to the present invention;

FIG. 5 is a block diagram showing the schematic constitution of a display control circuit 4 of a liquid crystal display module of an embodiment 2 according to the present invention;

FIG. 6 is a block diagram showing the schematic constitution of a conventional liquid crystal display module;

FIG. 7 is a view showing an equivalent circuit of a pixel part of the liquid crystal display panel shown in FIG. 6;

FIG. 8 is a view showing a voltage waveform outputted to the scanning line from the gate driver part and a voltage waveform of the video voltage on the video line outputted from the source driver part in a conventional liquid crystal display module;

FIG. 9 is a schematic view which simply expresses the pixel polarity and the pixel voltage level of one pixel when white and black are alternately displayed for every frame in the conventional liquid crystal display module;

FIG. 10 shows pixel polarity for every frame when a phase of the pixel polarity is inverted at a fixed cycle (period A, period B) in the AC driving method shown in FIG. 9; and

FIG. 11 is a schematic view which simply expresses the pixel polarity and the pixel voltage level of one pixel when white and black are alternately displayed for every frame in a phase inversion driving method.

Claims

1. A liquid crystal display device comprising: a liquid crystal display panel having a plurality of pixels; anda drive circuit which drives each pixel out of the plurality of pixels, each pixel including a pixel electrode and a counter electrode, wherein assuming a state in which a video voltage of a potential higher than a potential of a counter voltage applied to the counter electrode is applied to the pixel electrode as a drive state of positive polarity and a state in which the video voltage of the potential lower than the potential of the counter voltage applied to the counter electrode is applied to the pixel electrode as a drive state of negative polarity, the drive circuit changes the drive state of each pixel, for every m(m≧1) frame, from the drive state of positive polarity to the drive state of the negative polarity or from the drive state of the negative polarity to the drive state of the positive polarity and, at the same time, inverts a phase of the drive state of each pixel for every N (N>m) frame, wherein the drive circuit outputs gray scale correction display data which differs from inputted display data in the first frame immediately after the phase inversion.

2. A liquid crystal display device according to claim 1, wherein the gray scale correction display data is display data corresponding to gray scales lower than gray scales corresponding to the inputted display data.

3. A liquid crystal display device according to claim 2, wherein the difference between the inputted display data and the gray scale correction display data is set such that the display data of intermediate gray scales is larger than the high gray-scale display data or low gray-scale display data.

4. A liquid crystal display device according to claim 1, wherein the liquid crystal display device includes a memory for storing a correction quantity for every inputted display data, and the drive circuit generates and outputs the gray scale correction display data by subtracting the correction quantity stored in the memory from the inputted display data.

5. A liquid crystal display device according to claim 1, wherein the liquid crystal display device includes a memory which stores the gray scale correction display data for every inputted display data, and the drive circuit generates and outputs the gray scale correction display data by reading the gray scale correction display data corresponding to the inputted display data from the memory.

6. A liquid crystal display device according to claim 4, wherein the memory is an EPROM.

7. A liquid crystal display device according to claim 1, wherein the “m” is 1.

8. A liquid crystal display device according to claim 1, wherein the counter voltage applied to the counter electrode is a fixed voltage.

9. A liquid crystal display device according to claim 1, wherein the liquid crystal display panel includes a pair of substrates which sandwiches liquid crystal therebetween, and the pixel electrode and the counter electrode are formed on one substrate out of the pair of substrates.