Liquid crystal display device with correction voltage different from video signal applied to data line in display period

• US 8,493,302 B2
• Filed: 03/21/2008
• Issued: 07/23/2013
• Est. Priority Date: 03/29/2007
• Status: Active Grant

• Current Assignee: NLT Technologies, Ltd. (Tianma Microelectronics Company Limited)
• Original Assignee: NLT Technologies, Ltd. (Tianma Microelectronics Company Limited)
• Inventors: Sekine, Hiroyuki
• Primary Examiner(s): Beck, Alexander S
• Assistant Examiner(s): KIYABU, KARIN A
• Application Number:
  US12/052,772
• Publication Number:
  US 20080239180A1
• Time in Patent Office: 1,950 Days
• Field of Search: 345 87-104
• US Class Current: 345/87
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/0237 Switching ON and OFF the backlight within one frame
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/0214 with crosstalk due to leakage current of pixel switch in active matrix panels
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general

Abstract

The present invention aims to reduce flickers of the liquid crystal display device and enable the use of liquid crystal material exhibiting a high response speed, and to enhance light usage efficiency of the field sequential type liquid crystal display device. After writing the video signal to all the pixels in each sub-frame period, a correction voltage signal or an alternating signal having a frequency of greater than or equal to a certain frequency is input to the data line, so that the magnitude of the leakage current of each pixel TFT caused by the difference in polarity of the video signal with respect to the opposing electrode written to the pixel electrode is equalized, and the flickers are greatly reduced.

Claims

1. A liquid crystal display device comprising:

a display panel including a pixel matrix in which pixels each including at least a switching element and a pixel electrode are arranged in matrix near intersection points of data lines and gate lines arranged longitudinally and laterally, and a counter electrode that is arranged to oppose the pixel matrix with a liquid crystal layer interposed therebetween;

a light source for irradiating light onto the display panel; and

a control part for dividing a frame period for displaying a video signal of one screen into a plurality of sub-frame periods and performing display on the display panel;

wherein

the control part divides each of the sub-frame periods into a writing period for writing the video signal to the pixel matrix and a display period for lighting up the light source, and, in the display period, renders all the switching elements non-conductive while simultaneously applying a correction voltage that is different from the video signal to the data line to allow the correction voltage to be applied to the switching elements, and

the correction voltage is an alternating signal having a higher frequency than a frequency at which a liquid crystal molecule of the liquid crystal layer responds.

2. The liquid crystal display device according to claim 1, wherein

a conductive layer separated with an insulation film is arranged between the pixel electrode and the data line;

and

the control part performs voltage control to the conductive layer.

3. The liquid crystal display device according to claim 2, wherein the control part changes a waveform of the voltage that is applied to the conductive layer for each of the sub-frame periods.

4. The liquid crystal display device according to claim 2, wherein the control part applies the voltage to the conductive layer, by changing the voltage depending on polarities of the video signals for the counter electrode.

5. The liquid crystal display device according to claim 1, wherein

the light source comprises different colors, and the control part lights up the light source of different colors for each of the sub-frame periods, and performs a display control of a color image corresponding to the color of the light source.

6. The liquid crystal display device according to claim 1, further comprising a lighting device for irradiating, to the display panel, light of high directivity in two different directions, under the control of the control part.

7. The liquid crystal display device according to claim 6, wherein

the lighting device irradiates the light emitted towards one of the two different directions to a first observing position by transmitting the pixels, and irradiates the light emitted towards the other one of the directions to a second observing position by transmitting the pixels;

and

the control part displays an image for the first observing position or an image for the second observing position in accordance with the directions of the irradiated light through outputting an instruction to the lighting device to irradiate the light emitted towards the two different directions alternately for every continuous two sub-frame periods.

8. The liquid crystal display device according to claim 6, wherein

the lighting device irradiates the light emitted towards one of the two different directions to the right eye of an observer by transmitting the pixels, and irradiates the light emitted towards the other one of the directions to the left eye of the observer by transmitting the pixels;

and

the control part displays an image for a right eye or an image for a left eye in accordance with the directions of the irradiated light through outputting an instruction to the lighting device to irradiate the light emitted towards the two different directions alternately for every continuous two sub-frame periods.

9. A control system for drive controlling a display panel including:

a pixel matrix in which pixels each including at least a switching element and a pixel electrode are arranged in matrix near intersection points of data lines and gate lines arranged longitudinally and laterally, and a counter electrode that is arranged to oppose the pixel matrix with a liquid crystal layer interposed therebetween, the control system comprising;

a light source for irradiating light onto the display panel; and

a control part for dividing a frame period for displaying a video signal of one screen into a plurality of sub-frame periods and performing display on the display panel;

wherein

the control part divides each of the sub-frame periods into a writing period for writing the video signal to the pixel matrix and a display period for lighting up the light source, and, in the display period, renders all the switching elements non-conductive while simultaneously applying a correction voltage that is different from the video signal to the data line to allow the correction voltage to be applied to the switching elements, and

the correction voltage is an alternating signal having a higher frequency than a frequency at which a liquid crystal molecule of the liquid crystal layer responds.

10. The control system according to claim 9, wherein the control part performs voltage control to a conductive layer arranged between the pixel electrode and the data line while being separated with an insulation film.

11. The control system according to claim 10, wherein the control part changes a waveform of the voltage that is applied to the conductive layer for each of the sub-frame periods.

12. The control system according to claim 10, wherein the control part applies the voltage to the conductive layer, by changing the voltage depending on polarities of the video signals for the counter electrode.

13. The control system according to claim 9, wherein

the light source comprises different colors, and

the control part lights up the light source of different colors for each of the sub-frame periods, and performs a display control of a color image corresponding to the color of the light source.

14. The control system according to claim 9, further comprising a lighting device for irradiating, to the display panel, light of high directivity in two different directions, under the control of the control part.

15. The control system according to claim 14, wherein

the lighting device irradiates the light emitted towards one of the two different directions to a first observing position by transmitting the pixels, and irradiates the light emitted towards the other one of the directions to a second observing position by transmitting the pixels;

and

the control part displays an image for the first observing position or an image for the second observing position in accordance with the directions of the irradiated light through outputting an instruction to the lighting device to irradiate the light emitted towards the two different directions alternately for every continuous two sub-frame periods.

16. The control system according to claim 14, wherein

the lighting device irradiates the light emitted towards one of the two different directions to the right eye of an observer by transmitting the pixels, and irradiates the light emitted towards the other one of the directions to the left eye of the observer by transmitting the pixels;

and

the control part displays an image for a right eye or an image for a left eye in accordance with the directions of the irradiated light through outputting an instruction to the lighting device to irradiate the light emitted towards the two different directions alternately for every continuous two sub-frame periods.

17. A driving method for drive controlling a display panel including a pixel matrix in which pixels each including at least a switching element and a pixel electrode are arranged in matrix near intersection points of data lines and gate lines arranged longitudinally and laterally, and a counter electrode that is arranged to oppose the pixel matrix with a liquid crystal layer interposed therebetween, the method comprising:

dividing a frame period for displaying a video signal of one screen into a plurality of sub-frame periods and displaying images on the display panel; and

dividing each of the sub-frame periods into a writing period for writing the video signal to the pixel matrix and a display period for lighting up a light source, and, in the display period, rendering all the switching elements non-conductive while simultaneously applying a correction voltage that is different from the video signal to the data line to allow the correction voltage to be applied to the switching elements, and

the correction voltage is an alternating signal having a higher frequency than a frequency at which a liquid crystal molecule of the liquid crystal layer responds.

18. The driving method according to claim 17, further comprising performing voltage control to a conductive layer arranged between the pixel electrode and the data line.

19. The driving method according to claim 18, wherein a voltage waveform to be applied to the conductive layer is changed for each of the sub-frame periods.

20. The driving method according to claim 18, wherein a different voltage is applied depending on the-polarities of the video signals for the counter electrode.

21. A non-transitory computer readable medium having stored thereon a control program, for drive controlling a display panel including a pixel matrix in which pixels each including at least a switching element and a pixel electrode are arranged in matrix near intersection points of data lines and gate lines arranged longitudinally and laterally, and a counter electrode that is arranged to oppose the pixel matrix with a liquid crystal layer interposed there between;

the control program causing a computer to execute functions of;

dividing a frame period for displaying a video signal of one screen into a plurality of sub-frame periods and displaying images on the display panel; and

dividing each of the sub-frame periods into a writing period for writing the video signal to the pixel matrix and a display period for lighting up the light source, and, in the display period, rendering all the switching elements non-conductive while simultaneously applying a correction voltage that is different from the video signal to the data line to allow the correction voltage to be applied to the switching elements, and

the correction voltage is an alternating signal having a higher frequency than a frequency at which a liquid crystal molecule of the liquid crystal layer responds.