LIQUID CRYSTAL DISPLAY DEVICE AND METHOD OF DRIVING THE SAME

• US 20140085356A1
• Filed: 09/20/2013
• Published: 03/27/2014
• Est. Priority Date: 09/26/2012
• Status: Active Grant

• Current Assignee: Japan Display Incorporated
• Original Assignee: Japan Display Incorporated
• Inventors: TANAKA, Yukio, HIGANO, Toshiyuki, NAKAO, Kenji, WAKEMOTO, Hirofumi
• Granted Patent: US 9,390,673 B2
• Time in Patent Office: Days
• US Class Current: 345/691
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2320/046 Dealing with screen burn-in prevention or compensation of the effects thereof
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers

Abstract

According to one embodiment, a liquid crystal display device includes an array substrate, a counter substrate, a liquid crystal layer and a driving unit. The driving unit is configured to perform polarity inversion driving by applying, to the pixel electrode, positive and negative video signals. When applying the video signals to the pixel electrode, the driving unit superposes a correction signal corresponding to a polarity inversion frequency and the gray level on the video signals in advance.

Claims

1. A liquid crystal display device comprising:

an array substrate comprising a pixel electrode forming a pixel, and a counterelectrode arranged opposite to the pixel electrode with an insulating layer being interposed therebetween and forming the pixel;

a counter substrate arranged opposite to the array substrate;

a liquid crystal layer held between the array substrate and the counter substrate; and

a driving unit configured to perform polarity inversion driving by applying, to the pixel electrode, positive and negative video signals corresponding to a gray level of an image to be displayed by the pixel,

wherein when applying the video signals to the pixel electrode, the driving unit superposes a correction signal corresponding to a polarity inversion frequency and the gray level on the video signals in advance.

2. The device according to claim 1, wherein

in a first mode in which driving is performed at a first polarity inversion frequency, the driving unit superposes a first correction signal corresponding to the first polarity inversion frequency and the gray level on the video signals, and

in a second mode in which driving is performed at a second polarity inversion frequency different from the first polarity inversion frequency, the driving unit superposes a second correction signal corresponding to the second polarity inversion frequency and the gray level and different from the first correction signal on the video signals.

3. The device according to claim 2, wherein

the first correction signal and the second correction signal are bias voltages,

the first polarity inversion frequency is higher than the second polarity inversion frequency, and

a voltage value of the first correction signal is not more than a voltage value of the second correction signal for each gray level.

4. The device according to claim 1, wherein the driving unit is preset to superpose a correction signal corresponding to the polarity inversion frequency and the gray level on the video signals.

5. The device according to claim 1, wherein the correction signal is set such that a change amount of a countervoltage applied to the counterelectrode when an average luminance value of an image which is to be displayed by the pixel into which a first video signal is burned-in and has a first gray level is minimal is equal to a change amount of the countervoltage when an average luminance value of an image which is to be displayed by the pixel into which a second video signal is burned-in and has a second gray level different from the first gray level is minimal, at each polarity inversion frequency.

6. The device according to claim 1, wherein the correction signal is set such that when a first minimal value as a minimum of an average luminance value of an image which is to be displayed by the pixel into which a first video signal is burned-in and has a first gray level is larger than a second minimal value as a minimum of an average luminance value of an image which is to be displayed by the pixel into which a second video signal is burned-in and has a second gray level having a luminance level lower than that of the first gray level, at each polarity inversion frequency, a change amount of a countervoltage applied to the counterelectrode is zero when a luminance of the image having the first gray level takes the first minimal value.

7. The device according to claim 6, wherein

the driving unit superposes the correction signal corresponding to the polarity inversion frequency and the first gray level on the first video signal corresponding to the polarity inversion frequency and the first gray level, such that the change amount of the countervoltage is zero when the luminance of the image having the first gray level takes the first minimal value, and

when the change amount of the countervoltage is zero when the luminance of the image having the first gray level takes the first minimal value, the driving unit superposes the correction signal corresponding to the polarity inversion frequency and the second gray level on the second video signal corresponding to the polarity inversion frequency and the second gray level, such that the luminance of the image having the second gray level takes a predetermined value.

8. The device according to claim 7, wherein the predetermined value is made to deviate from the second minimal value.

9. A method of driving a liquid crystal display device comprising an array substrate comprising a pixel electrode forming a pixel, and a counterelectrode arranged opposite to the pixel electrode with an insulating layer being interposed therebetween and forming the pixel, a counter substrate arranged opposite to the array substrate, a liquid crystal layer held between the array substrate and the counter substrate, and a driving unit, the method comprising:

performing polarity inversion driving by applying, to the pixel electrode, positive and negative video signals corresponding to a gray level of an image to be displayed by the pixel by the driving unit; and

when applying the video signals to the pixel electrode, superposing a correction signal corresponding to a polarity inversion frequency and the gray level on the video signals in advance by the driving unit.

10. The method according to claim 9, wherein

in a first mode in which driving is performed at a first polarity inversion frequency, a first correction signal corresponding to the first polarity inversion frequency and the gray level is superposed on the video signals, and

in a second mode in which driving is performed at a second polarity inversion frequency different from the first polarity inversion frequency, a second correction signal corresponding to the second polarity inversion frequency and the gray level and different from the first correction signal is superposed on the video signals.

11. The method according to claim 10, wherein

the first correction signal and the second correction signal are bias voltages,

the first polarity inversion frequency is higher than the second polarity inversion frequency, and

a voltage value of the first correction signal is not more than a voltage value of the second correction signal for each gray level.

12. The method according to claim 9, wherein the correction signal is set such that a change amount of a countervoltage applied to the counterelectrode when an average luminance value of an image which is to be displayed by the pixel into which a first video signal is burned-in and has a first gray level is minimal is equal to a change amount of the countervoltage when an average luminance value of an image which is to be displayed by the pixel into which a second video signal is burned-in and has a second gray level different from the first gray level is minimal, at each polarity inversion frequency.

13. The method according to claim 9, wherein the correction signal is set such that when a first minimal value as a minimum of an average luminance value of an image which is to be displayed by the pixel into which a first video signal is burned-in and has a first gray level is larger than a second minimal value as a minimum of an average luminance value of an image which is to be displayed by the pixel into which a second video signal is burned-in and has a second gray level having a luminance level lower than that of the first gray level, at each polarity inversion frequency, a change amount of a countervoltage applied to the counterelectrode is zero when a luminance of the image having the first gray level takes the first minimal value.

14. The method according to claim 13, wherein

the correction signal corresponding to the polarity inversion frequency and the first gray level is superposed on the first video signal corresponding to the polarity inversion frequency and the first gray level, such that the change amount of the countervoltage is zero when the luminance of the image having the first gray level takes the first minimal value, and

when the change amount of the countervoltage is zero when the luminance of the image having the first gray level takes the first minimal value, the correction signal corresponding to the polarity inversion frequency and the second gray level is superposed on the second video signal corresponding to the polarity inversion frequency and the second gray level, such that the luminance of the image having the second gray level takes a predetermined value.

15. The method according to claim 14, wherein the predetermined value is made to deviate from the second minimal value.