Driving method for a liquid crystal display device

• US 5,953,002 A
• Filed: 04/17/1996
• Issued: 09/14/1999
• Est. Priority Date: 08/23/1994
• Status: Expired due to Term

• Current Assignee: Optrex Corporation (Kyocera Corporation)
• Original Assignee: Asahi Glass Company, Limited (AGC, Inc.)
• Inventors: Nagai, Makoto, Nakazawa, Akira, Hirai, Yoshinori, Kawaguchi, Kazuyoshi, Kuwata, Takeshi, Motegi, Hiroyuki
• Primary Examiner(s): Hjerpe, Richard A.
• Assistant Examiner(s): Nguyen, Francis N.
• Application Number:
  US08/628,634
• Time in Patent Office: 1,245 Days
• Field of Search: 345/89, 345/100, 345/95, 345/94, 345/204, 345/147, 345/93, 345/210, 345/148, 345/211, 345/149
• US Class Current: 345/204
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/3622 using a passive matrix G09G3/3674 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3625 using active addressing

Abstract

A driving method for a direct addressing type liquid crystal display device for displaying gradation by changing the amplitude of voltages applied to pixels, wherein a series of voltage pulses, as signal voltages, composed of a plurality of different voltage levels are applied in order to display a specified gradation, and for a display, a plurality kinds of gradation in which a part of the voltage levels is commonly used are selected.

Claims

1. A driving method for a liquid crystal display device having accessible display portions forming pixels, using a multiplex driving method which comprises:

applying to said pixels groups of voltage pulses having respective group pulse heights which vary in at least two different groups depending on gradation levels of data to be displayed, at least two of said respective group pulse heights having a different absolute magnitude in at least one of the at least two of the groups with the respective group pulse heights in the groups including components having a value such that RMS voltages applied to said pixels on scanning electrodes in a non-selection state are effectively made constant in a display frame period, and

using at least one common pulse height in the at least two of the groups, whereby the number of pulse heights used in all of the groups to cause display of all desired gradation levels is reduced.

2. A driving method according to claim 1, further comprising the step of displaying said gradation levels in association with a frame modulation or a pulse width modulation.

3. A driving method according to claim 1 further comprising simultaneously selecting a plurality of scanning electrodes and applying display inducing pulses to the selected scanning electrodes defined by a selection matrix having a substantial orthogonality.

4. A driving method according to claim 3, further comprising adding at least one imaginary scanning electrode to the simultaneously selected scanning electrodes, and determining data for the imaginary scanning electrode so that the number of voltage levels to be applied to data electrodes is reduced.

5. A driving method for a liquid crystal display device having accessible display portions forming pixels, and using a multiplex driving method which comprises:

applying to said pixels groups of voltage pulses, wherein at least one of the groups has at least two pulses with different absolute magnitude pulse heights, wherein each of the groups correspond to one of a plurality of achievable display gradation data levels provided as including components having variable levels such that RMS voltages applied to said pixels on scanning electrodes in a non-selection state are effectively made constant in a display frame period, and

using a part of the divided gradation data commonly relative to at least the at least two groups to provide at least two different display gradation data levels for display.

6. A driving method according to claim 5, further comprising displaying said display gradation data levels in association with a frame modulation or a pulse width modulation.

7. A driving method according to claim 5, further comprising obtaining said display gradation data levels in at least said at least two groups as at least two voltage pulses including pulse heights which vary depending on the display gradation data levels to be displayed and correspond to at least a part of a range of levels from -1 to +1 divided into substantially equal intervals.

8. A driving method according to claim 5, wherein said gradation data levels d span a range from -1, which indicates ON, to 1, which indicates OFF, said gradation data levels being effectively displayed by displaying first and second divided gradation data d±

√

1-d² .

9. A driving method according to claim 5, wherein a plurality of scanning electrodes are simultaneously selected, and pulses applied to the selected scanning electrodes are defined by a selection matrix having a substantial orthogonality.

10. A driving method according to claim 9, wherein the data electrodes corresponding to the simultaneously selected scanning electrodes are applied with signals which are obtained by transforming the divided gradation data with said selection matrix.

11. A driving method according to claim 9, wherein said gradation data levels d span a range from -1, which indicates ON, to 1, which indicates OFF, said gradation data levels being effectively displayed by displaying first and second divided gradation data d±

√

1-d² gradation data ±

d√

-1-d² , wherein.

12. A driving method according to claim 11, wherein when the intermediate gradation data are displayed, signals which are applied to the data electrodes in response to selection pulses in a time period wherein all the scanning electrodes are applied with at least one selection pulse include in a mixed state at least one signal which is obtained by the orthogonal transformation of a data element having the absolute value exceeding 1 among the divided gradation data and at least one signal which is obtained by the orthogonal transformation of a data element having the absolute value less than 1.

13. A driving method according to claim 11, wherein when the intermediate gradation data are displayed, signals which are applied to the data electrodes in response to selection pulses applied once to a simultaneously selected scanning electrode group include in a mixed state at least one signal which is obtained by the orthogonal transformation of a data element having the absolute value exceeding 1 among the divided gradation data and at least one signal which is obtained by the orthogonal transformation of a data element having the absolute value less than 1.

14. A driving method according to claim 9, wherein when signals are applied to the data electrodes with respect to a simultaneously selected scanning electrode group, the signals are formed by the orthogonal transformation of all the divided gradation data necessary for displaying a predetermined gradation data, and the signals are successively applied as a group for each of column vectors of the selection matrix, to the column electrodes in response to a timing of the application of the selection pulses.

15. A driving method according to claim 9, wherein at least one imaginary scanning electrode is added to the simultaneously selected scanning electrodes, and data are determined for the imaginary scanning electrode so that the number of voltage levels to be applied to data electrodes is reduced.

16. A driving method according to claim 15, wherein the display data corresponding to the simultaneously selected scanning electrodes, which include at least one imaginary scanning electrode are divided into plural groups of display data having different absolute values;

and data are determined for the at least one imaginary scanning electrode so that the number of display data included in each of the groups takes a predetermined discrete integer value.

17. A driving method according to claim 15, wherein the product of the column vector elements in the selection matrix takes a predetermined sign, and data are determined for the imaginary scanning electrodes so that the product of the display data elements corresponding to the simultaneously selected scanning electrodes, which include at least one imaginary scanning electrode, takes a predetermined sign.

18. A method for driving a liquid crystal display device so that the number of voltage levels applied to data electrodes is reduced, comprising:

simultaneously selecting a plurality of scanning electrodes;

applying signals to data electrodes corresponding to the simultaneously selected scanning electrodes, said signals being obtained by transforming gradation data with a substantially orthogonal selection matrix, the gradation data being composed of at least two kinds of data elements having different absolute values;

adding at least one imaginary scanning electrode to the simultaneously selected scanning electrodes;

determining gradation data for the at least one imaginary scanning electrode to be one of the at least two kinds of data elements and the number of each data element being one of a predetermined discrete integer.

19. A driving method according to claim 18, wherein a product of column vector elements in the selection matrix has predetermined sign, and data are determined for the at least one imaginary scanning electrode so that the product of the display data elements corresponding to the simultaneously selected scanning electrodes and the at least one imaginary scanning electrode has a predetermined sign.