LIQUID CRYSTAL DISPLAY APPARATUS AND METHOD FOR DRIVING THE SAME

• US 20090167665A1
• Filed: 04/05/2007
• Published: 07/02/2009
• Est. Priority Date: 04/28/2006
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Kobayashi, Katsutoshi, Sutoh, Seiji, Inoue, Yuichi, Yamaguchi, Hidehiko, Kobayashi, Tetsuya
• Granted Patent: US 8,174,474 B2
• Time in Patent Office: Days
• US Class Current: 345/94
• CPC Class Codes: G02F 1/133305 Flexible substrates, e.g. plastics, organic film
• CPC Class Codes: G09G 2320/0204 Compensation of DC component across the pixels in flat panels
• CPC Class Codes: G09G 2320/0209 Crosstalk reduction, i.e. to reduce direct or indirect influences of signals directed to a certain pixel of the displayed image on other pixels of said image, inclusive of influences affecting pixels in different frames or fields or sub-images which constitute a same image, e.g. left and right images of a stereoscopic display
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/046 Dealing with screen burn-in prevention or compensation of the effects thereof
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3655 Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers

Abstract

A voltage having the positive polarity and a voltage having the negative polarity are alternately applied to a pixel between a counter electrode and a pixel electrode. A counter electrode voltage (Vcom) generating circuit or a source signal generating section is provided each of which controls effective voltages to be applied to the pixel for an identical tone so that an effective voltage having the positive polarity and an effective voltage having the negative polarity are asymmetrically applied to the pixel for all of the tones which can be displayed. The counter electrode voltage (Vcom) generating circuit or the source signal generating section shifts a counter electrode voltage Vcom-A or a source voltage by 0.3 V or more from a voltage causing the effective voltages to be symmetrically applied to the pixel.

Claims

1. A liquid crystal display apparatus in which a voltage having a positive polarity and a voltage having a negative polarity are alternately applied to a pixel between a counter electrode and a pixel electrode, comprising:

an effective voltage control section that controls effective voltages for an identical tone so that an effective voltage having the positive polarity and an effective voltage having the negative polarity have asymmetrical values to be applied to the pixel for all of tones which can be displayed,

wherein the effective voltage control section shifts a counter electrode voltage or a source voltage by 0.3 V or more from a voltage causing the effective voltages in the positive and the negative polarity to be symmetrically applied to the pixel.

2. The liquid crystal display apparatus as set forth in claim 1, wherein:

the effective voltage control section shifts the counter electrode voltage by 0.3 V or more toward the positive polarity from a voltage causing the effective voltage having the positive polarity and the effective voltage having the negative polarity, for an identical tone, to be symmetrically applied to the pixel so that the effective voltage having the negative polarity is higher than the effective voltage having the positive polarity to be applied to the pixel.

11. The liquid crystal display apparatus as set forth in any one claims 1, 3, and 5, wherein:

the effective voltage control section causes the effective voltage having the positive polarity and the effective voltage having the negative polarity, whose white display luminance is not more than 5% or whose transmittance is not more than 5%, to be asymmetrically applied to the pixel in a normally black mode, whereas the effective voltage having the positive polarity and the effective voltage having the negative polarity, whose white display luminance is not less than about 95% or whose transmittance is not less than about 95%, to be asymmetrically applied to the pixel in a normally white mode.

12. The liquid crystal display apparatus as set forth in any one claims 1, 3, and 5, wherein:

the effective voltage control section controls effective voltage by a single polarity driving instead of a polarity inversion driving for a certain pixel voltage region while the effective voltages to be applied to the pixel are asymmetrical.

13. The liquid crystal display apparatus as set forth in any one of claims 1, 3 and 5, wherein;

the effective voltage control section shifts, for every plural frames or for every plural fields, the counter electrode voltage or the source voltage by 0.3 V or more alternately toward the positive polarity and the negative polarity from an effective voltage causing the voltage having the positive polarity and the voltage having the negative polarity to be symmetrically applied to the pixel, in a certain pixel voltage range.

14. The liquid crystal display apparatus as set forth in any one of claims 1, 3, or 5, wherein:

the effective voltage control section shifts the counter electrode voltage or the source voltage alternately toward the positive polarity and the negative polarity at a certain cycle, when the effective voltage having the positive polarity and the effective voltage having the negative polarity are asymmetrically applied.

15. The liquid crystal display apparatus as set forth in any one of claims 1, 3, or 5, wherein:

the effective voltage control section changes the counter electrode voltage or the source voltage in sync with turning on the liquid crystal display panel so that the counter electrode voltage or the source voltage alternately or randomly has a shift toward the positive polarity and a shift toward the negative polarity, so as to perform the asymmetrical application of the effective voltage having the positive polarity and the effective voltage having the negative polarity.

16. The liquid crystal display apparatus as set forth in any one of claims 1, 3, or 5, wherein:

the effective voltage control section shifts the counter electrode voltage or the source voltage alternately toward the positive polarity and the negative polarity, while displaying an entire black display, an entire white display, or an entire gray image which includes an single color display of red (R), green (G), blue (B), or a still image display.

17. The liquid crystal display apparatus as set forth in any one of claims 1, 3, or 5, wherein:

the effective voltage control section shifts the counter electrode voltage or the source voltage alternately toward the positive polarity and the negative polarity in an interval of about one hour to ten days, so that the effective voltage having the positive polarity and the effective voltage having the negative polarity are asymmetrically applied.

18. The liquid crystal display apparatus as set forth in any one of claims 1, 3, or 5, wherein:

the effective voltage control section applies a voltage to a liquid crystal in a pixel between a pair of substrates, i.e., a pixel electrode substrate and a counter substrate in a liquid crystal panel.

3. A liquid crystal display apparatus in which a voltage having a positive polarity and a voltage having a negative polarity are alternately applied to a pixel between a counter electrode and a pixel electrode, comprising:

an effective voltage control section that controls effective voltages for an identical tone so that an effective voltage having the positive polarity and an effective voltage having the negative polarity have asymmetrical values to be applied to the pixel, for the effective voltages of not more than a first effective voltage which is lower than half of a maximum effective voltage,

wherein the effective voltage control section shifts a counter electrode voltage or a source voltage by 0.3 V or more from a voltage causing the effective voltages in the positive polarity and the negative polarity to be symmetrically applied to the pixel, for the effective voltages of not more than the first effective voltage.

4. The liquid crystal display apparatus as set forth in claim 3, wherein:

the effective voltage control section controls the effective voltages for an identical tone so that an effective voltage having the positive polarity and an effective voltage having the negative polarity have asymmetrical values to be applied to the pixel, even for effective voltages of higher than the first effective voltage, and

reduces asymmetricity for voltages of higher than the first effective voltage.

5. A liquid crystal display apparatus in which a voltage having a positive polarity and a voltage having a negative polarity are alternately applied to a pixel between a counter electrode and a pixel electrode, comprising:

an effective voltage control section that controls effective voltages for an identical tone so that an effective voltage having the positive polarity and an effective voltage having the negative polarity are shifted by 0.3 V or more from each other and are asymmetrically applied to the pixel, for a tone at which a minimum effective voltage is applied to the pixel, and

reduces asymmetricity more as a tone is changed from a tone for a lowest effective voltage to a tone corresponding to an effective voltage which is higher than the lowest effective voltage.

6. The liquid crystal display apparatus as set forth in claim 5, wherein:

the effective voltage control section reduces the asymmetricity as the effective voltage is changed from the lowest effective voltage to a second effective voltage which is higher than the lowest effective voltage.

7. The liquid crystal display apparatus as set forth in claim 6, wherein:

the effective voltage control section causes the effective voltage having the positive polarity and the effective voltage having the negative polarity to be symmetrically applied to the pixel for an effective voltage which is higher than the second effective voltage.

8. The liquid crystal display apparatus as set forth in claim 6, wherein:

the effective voltage control section causes the asymmetricity of the effective voltage having the positive polarity and the effective voltage having the negative polarity which are applied to the pixel to become greater from a third effective voltage, which is higher than the second effective voltage and is also higher than half of a maximum effective voltage, to the maximum effective voltage.

9. The liquid crystal display apparatus as set forth in claim 7, wherein:

the effective voltage control section causes the asymmetricity of the effective voltage having the positive polarity and the effective voltage having the negative polarity which are applied to the pixel to become greater from a third effective voltage, which is higher than the second effective voltage and is also higher than half of a maximum effective voltage, to the maximum effective voltage.

10. The liquid crystal display apparatus as set forth in claim 6, wherein:

the effective voltage control section causes the effective voltage having the positive polarity and the effective voltage having the negative polarity to be asymmetrically applied to the pixel while an axis of symmetry is shifted toward the opposite polarity, for a fourth effective voltage which is higher than the second effective voltage, and

causes the asymmetricity to be small, for an effective voltage which is higher than the fourth effective voltage.

19. A method for driving a liquid crystal display apparatus in which a voltage having a positive polarity and a voltage having a negative polarity are alternately applied to a pixel between a counter electrode and a pixel electrode, comprising the steps of:

controlling effective voltages for an identical tone so that an effective voltage having the positive polarity and an effective voltage having the negative polarity have asymmetrical values to be applied to the pixel for all of tones which can be displayed; and

shifting a counter electrode voltage or a source voltage by 0.3 V or more from a voltage causing the effective voltages in the positive polarity and the negative polarity to be symmetrically applied to the pixel.

20. A method for driving a liquid crystal display apparatus in which a voltage having the positive polarity and a voltage having the negative polarity are alternately applied to a pixel between a counter electrode and a pixel electrode, comprising the steps of:

controlling effective voltages for an identical tone so that an effective voltage having the positive polarity and an effective voltage having the negative polarity have asymmetrical values to be applied to the pixel, for the effective voltages of not more than a first effective voltage which is lower than half of a maximum effective voltage; and

shifting a counter electrode voltage or a source voltage by 0.3 V or more from a voltage causing the effective voltages in the positive polarity and the negative polarity to be symmetrically applied to the pixel.

21. A method for driving a liquid crystal display apparatus in which a voltage having a positive polarity and a voltage having a negative polarity are alternately applied to a pixel between a counter electrode and a pixel electrode, comprising the steps of:

controlling effective voltages for an identical tone so that an effective voltage having the positive polarity and an effective voltage having the negative polarity are shifted by 0.3 V or more from each other and are asymmetrically applied to the pixel, for a tone at which a minimum effective voltage is applied to the pixel; and

reducing asymmetricity more as a tone is changed from a tone for a lowest effective voltage to a tone corresponding to an effective voltage which is higher than the lowest effective voltage.