Liquid crystal display device

• US 5,818,411 A
• Filed: 04/22/1996
• Issued: 10/06/1998
• Est. Priority Date: 04/24/1995
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Asada, Hiromasa, Sakamoto, Atsushi, Ohba, Toshihiro
• Primary Examiner(s): Hjerpe, Richard A.
• Assistant Examiner(s): CHANG, KENT WU
• Application Number:
  US08/635,700
• Time in Patent Office: 897 Days
• Field of Search: 345/58, 345/77, 345/78, 345/87, 345/88, 345/89, 345/93, 345/94, 345/95, 345/99
• US Class Current: 345/99
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• 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 2320/0223 Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes
• CPC Class Codes: G09G 3/3622 using a passive matrix G09G3/3674 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3692 suitable for passive matrices only
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers

Abstract

A liquid crystal display device includes a liquid crystal panel having a plurality of scanning electrodes including first and second scanning electrodes, a plurality of signal electrodes including a first signal electrode, and a liquid crystal layer. A display is generated based on display data including first and second display data. The liquid crystal display device further includes a scanning electrode driver which outputs a scanning voltage to the first scanning electrode in a first scanning period and outputs a scanning voltage to the second scanning electrode in a second scanning period following the first scanning period. A signal electrode driver outputs a first voltage corresponding to the first display data to the first signal electrode in the first scanning period and outputs a second voltage corresponding to the second display data to the first signal electrode in the second scanning period. The signal electrode driver compares the first display data and the second display data and, when the first display data and the second display data are different, outputs a third voltage for correcting a reduction of an effective voltage of the second voltage for a correction duration in the second scanning period.

Claims

1. A liquid crystal display device comprising a liquid crystal panel having a plurality of scanning electrodes including first and second scanning electrodes, a plurality of signal electrodes including a first signal electrode, and a liquid crystal layer interposed between the plurality of scanning electrodes and the plurality of signal electrodes, display being conducted based on display data including first and second display data, the liquid crystal display device further comprising:

scanning electrode driving means which outputs a scanning voltage to the first scanning electrode in a first scanning line period and outputs a scanning voltage to the second scanning electrode in a second scanning line period following the first scanning line period; and

signal electrode driving means which outputs a first voltage corresponding to the first display data to the first signal electrode in the first scanning line period and outputs a second voltage corresponding to the second display data to the first signal electrode in the second scanning line period,

wherein the signal electrode driving means compares the first display data and the second display data and, when the first display data and the second display data are different, outputs a third voltage for correcting a reduction of an effective voltage of the second voltage for a correction duration in the second scanning line period.

2. A liquid crystal display device according to claim 1, wherein the signal electrode driving means is provided for each of the plurality of signal electrodes.

3. A liquid crystal display device according to claim 1, wherein an absolute value of the third voltage is larger than an absolute value of the second voltage.

4. A liquid crystal display device according to claim 1, wherein the signal electrode driving means comprises power source means for generating voltages including the first, second, and third voltages.

5. A liquid crystal display device according to claim 1, wherein the signal electrode driving means compares the first display data and the second display data and, when the first display data and the second display data are the same, outputs the second voltage to the first signal electrode over the entire second scanning period.

6. A liquid crystal display device according to claim 4, wherein the signal electrode driving means further comprises voltage switching means for selecting the second voltage or the third voltage as an output of the power source means and output switching means for outputting the second voltage or the third voltage to the first signal electrode or putting an output of the signal electrode driving means in a high-impedance state, and the signal electrode driving means compares the first display data and the second display data and, when the first display data and the second display data are the same, puts the output of the signal electrode driving means in the high-impedance state using the output switching means in the correction duration, while outputting the second voltage to the first signal electrode in the second scanning period excluding the correction duration.

7. A liquid crystal display device according to claim 5, wherein the correction duration is as long as the second scanning period.

8. A method for driving a liquid crystal display device comprising a liquid crystal panel having a plurality of scanning electrodes including first and second scanning electrodes, a plurality of signal electrodes including a first signal electrode, and a liquid crystal layer interposed between the plurality of scanning electrodes and the plurality of signal electrodes, display being conducted based on display data including first and second display data, the method comprising the steps of:

(A) allowing scanning electrode driving means to output a scanning voltage to the first scanning electrode in a first scanning line period and output a scanning voltage to the second scanning electrode in a second scanning line period following the first scanning line period;

(B) allowing signal electrode driving means to output a first voltage corresponding to the first display data to the first signal electrode in the first scanning line period and output a second voltage corresponding to the second display data to the first signal electrode in the second scanning line period;

(C) allowing the signal electrode driving means to compare the first display data and the second display data; and

(D) allowing the signal electrode driving means to output a third voltage for correcting a reduction of an effective voltage of the second voltage for a correction duration in the second scanning line period when the first display data and the second display data are different.

9. A method according to claim 8, wherein the steps (B), (C), and (D) are conducted for each of the plurality of signal electrodes.

10. A method according to claim 8, wherein the step (D) includes the step of allowing the signal electrode driving means to output the second voltage to the first signal electrode over the entire second scanning period when the first display data and the second display data are the same.

11. A method according to claim 8, wherein the step (D) includes the step of allowing the signal electrode driving means to put the output of the signal electrode driving means in a high-impedance state in the correction duration when the first display data and the second display data are the same, and the step of allowing the signal electrode driving means to output the second voltage to the first signal electrode in the second scanning period excluding the correction duration when the first display data and the second display data are the same.

12. A liquid crystal display device comprising a liquid crystal panel having a liquid crystal layer between a plurality of signal electrodes and a plurality of scanning electrodes formed to cross each other, the device further comprising:

signal electrode driving means for applying a voltage corresponding to display data for displaying images on the liquid crystal panel to the plurality of signal electrodes;

scanning electrode driving means for applying a scanning voltage to the plurality of scanning electrodes sequentially; and

voltage generating means for supplying voltages required for driving the signal electrode driving means and the scanning electrode driving means to the signal electrode driving means and the scanning electrode driving means, wherein the signal electrode driving means detects whether or not the display data corresponding to a current scanning line period has changed from the display data corresponding to a scanning line period immediately before the current scanning line period for each of the plurality of signal electrodes and outputs, when no change is detected, a normal signal voltage level or, when a change is detected, a correction reference voltage for correcting a reduction of an effective voltage caused by waveform dulling due to the change, to each of the plurality of signal electrodes for a predetermined duration in the current scanning line period.

13. A liquid crystal display device according to claim 12, wherein the voltage generating means is configured so that it can generate at least one level of the correction reference voltage as voltage levels to be supplied to the signal electrode driving means, and

the signal electrode driving means is configured so that output means thereof can selectively output the at least one level of the correction reference voltage, supplied from the voltage generating means, and the signal electrode driving means detects whether or not the display data corresponding to a current scanning period has changed from the display data corresponding to a scanning period immediately before the current scanning period for each of the plurality of signal electrodes and outputs the normal signal voltage level when no change is detected or the correction reference voltage when a change is detected, to each of the plurality of signal electrodes for a predetermined duration in the current scanning period.

14. A liquid crystal display device according to claim 12, wherein the voltage generating means has a function of generating at least one level of the correction reference voltage as voltage levels to be supplied to the signal electrode driving means, and comprises voltage switching means for outputting the correction reference voltage instead of the normal signal voltage level for a predetermined duration in the current scanning period to supply to the signal electrode driving means, and

the signal electrode driving means can select the normal signal voltage level or a high-impedance state as an output, and the signal electrode driving means detects whether or not the display data corresponding to the current scanning period has changed from the display data corresponding to the scanning period immediately before the current scanning period for each of the plurality of signal electrodes and, when no change is detected, put the output in the high-impedance state for a predetermined duration in a scanning period corresponding to a voltage switching period of the voltage generating means or, when a change is detected, selects a signal voltage which is switched to the correction reference voltage level by the voltage switching means for a predetermined duration in the current scanning period.