|Publication number||US7298353 B2|
|Application number||US 11/032,426|
|Publication date||Nov 20, 2007|
|Filing date||Jan 10, 2005|
|Priority date||Jan 30, 2004|
|Also published as||US20050168434|
|Publication number||032426, 11032426, US 7298353 B2, US 7298353B2, US-B2-7298353, US7298353 B2, US7298353B2|
|Original Assignee||Chi Mei Optoelectronics Corp.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (1), Referenced by (2), Classifications (15), Legal Events (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims the benefit of Taiwan application Serial No. 93102247, filed Jan. 30, 2004, the subject matter of which is incorporated herein by reference.
The invention relates in general to a driving method of a multi-domain vertical alignment (MVA) liquid crystal display (LCD), and more particularly to a driving method for resolving the frame retention problem of an MVA LCD.
Compared with a conventional cathode-ray tube (CRT) display, a flat-panel display has gradually become the main-stream in the display market for lighter and slimmer, high quality frame displays. Of the flat-panel displays, the thin-film-transistor liquid crystal display (TFT LCD) plays an essential role. However, ordinary TFT LCDs have restricted applications due to narrow visual angles.
With the feature of broader visual angles, the multi-domain vertical alignment (MVA) LCD has become a target for the display industry to achieve.
However, when an external driving force, such as an electric field or the user's touch, is applied to the MVA LCD, mura appears on the display screen. The liquid crystal molecules, having received the external driving force, would not be aligned in accordance with original designed directions.
It is therefore an object of the invention to provide a driving method of multi-domain vertical alignment (MVA) liquid crystal display (LCD) preventing the occurrence of mura effect or frame retention.
One embodiment of the present invention is directed to a driving method of a MVA LCD. The LCD, which receives an image signal and displays a frame accordingly, includes a plurality of scan lines. The driving method first enables one of the scan lines, then determines whether to proceed with resetting the scan line. If the scan line is reset, a low voltage is applied to the pixels on the scan line. If the scan line is not reset, the image signal is applied to the pixels on the scan line.
Other objects, features, and advantages of the invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.
When a multi-domain vertical alignment (MVA) liquid crystal display (LCD) receives an external force, for example, touched by a user, mura appears on the screen.
If a low voltage, 0 volts for instance, is applied to the liquid crystal molecules which are at the steady state point B′ and followed by a pixel voltage, 6 volts for instance, then the liquid crystal molecules will return to the steady state of point B. The mura effect caused by the external force would be eliminated, and the screen would return to the normal status. The driving method of the embodiment eliminates the mura effect from the screen according to the above mentioned reset principle.
A conventional liquid crystal screen receives an image signal and displays a frame according to the image signal received. The driving method thereof is to enable a scan line of the liquid crystal screen, and then apply the pixel voltages, generated in response to the image signals, onto the pixels on the enabled scan line via data lines. Each of the scan lines is enabled once sequentially to complete a frame.
In resetting step 330, after a low voltage, 0 volts for instance, is applied onto the pixel, the liquid crystal molecules return to the initial steady state illustrated in the steady state of point A in
The mura can be eliminated in 2 seconds if each of the scan lines is reset within 2 seconds. For a liquid crystal screen with a 60 Hz refresh rate, 60 frames are displayed per second. One way to reset all the scan lines in 2 seconds is to insert a resetting frame formed by the low voltage into any of the 120 frames within the 2 seconds.
Another way to reset all the scan lines in 2 seconds is to reset some of the scan lines each frame with all the scan lines being reset after 120 frames are displayed. For example, the scan lines are divided into an normal group and a reset group, wherein the scan lines of the normal group are driven by the original image signal, while the scan lines of the reset group are driven by the low voltage. With a liquid crystal screen having 1024 scan lines, by resetting 9 different scan lines (1024/(60*2)˜=9) each frame, the mura can be eliminated in 2 seconds. For each frame, 9 scan lines belong to the reset group while the other 1015 scan lines belong to the normal group.
The above embodiment uses 0 volts as the low voltage to reset the scan lines. But in practice the low voltage may not need to be as low as 0 volts to reset the scan lines. The maximum resetting low voltage required is different depending on the grey value of the pixel. A reference table can be created showing the maximum resetting low voltage for each grey value by experimentation. During the driving process, the value of the low voltage required for resetting can be determined by the reference table and the image signal.
The driving method of MVA LCD disclosed in the above preferred embodiment eliminates the mura formed due to an external force to provide a satisfying high quality LCD.
While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US6922183 *||Nov 1, 2002||Jul 26, 2005||Chin-Lung Ting||Multi-domain vertical alignment liquid crystal display and driving method thereof|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US8581878 *||Oct 30, 2009||Nov 12, 2013||Au Optronics Corp.||Method for mitigating pooling mura on liquid crystal display apparatus and liquid crystal display apparatus|
|US20100220068 *||Sep 2, 2010||Au Optronics Corp.||Method for Mitigating Pooling Mura on Liquid Crystal Display Apparatus and Liquid Crystal Display Apparatus|
|U.S. Classification||345/87, 349/123, 345/55, 349/144, 345/84|
|International Classification||G09G3/20, G09G3/36, G02F1/133, G02F1/1337|
|Cooperative Classification||G09G3/3637, G09G2310/062, G09G3/207, G09G3/3681, G09G3/3644|
|Jan 10, 2005||AS||Assignment|
Owner name: CHI MEI OPTOELECTRONICS CORP., TAIWAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:WANG-YANG, LI;REEL/FRAME:016177/0054
Effective date: 20050105
|May 10, 2010||AS||Assignment|
Owner name: CHIMEI INNOLUX CORPORATION,TAIWAN
Free format text: MERGER;ASSIGNOR:CHI MEI OPTOELECTRONICS CORP.;REEL/FRAME:024358/0143
Effective date: 20100318
|May 20, 2011||FPAY||Fee payment|
Year of fee payment: 4
|Apr 3, 2014||AS||Assignment|
Owner name: INNOLUX CORPORATION, TAIWAN
Free format text: CHANGE OF NAME;ASSIGNOR:CHIMEI INNOLUX CORPORATION;REEL/FRAME:032604/0487
Effective date: 20121219
|May 20, 2015||FPAY||Fee payment|
Year of fee payment: 8