JP3010761B2 - Driving method of liquid crystal electro-optical element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving method for a liquid crystal electro-optical element, and more particularly to a driving method capable of gradation display.

[0002]

2. Description of the Related Art As a method of improving crosstalk by a driving method capable of displaying gradation by pulse width modulation by multiplex driving by a conventional voltage averaging method, Japanese Patent Application No. 63-30.
There is a driving method shown in FIG.

[0003]

In such a conventional driving method, the pulse width of the correction voltage pulse is determined based on the number of gradation data to be displayed for each scanning electrode.
However, even if the data displayed on a certain scanning electrode is the same, the data displayed on the other electrodes are different, and the whole display screen is bright (when liquid crystal molecules are standing) and the whole display screen is dark (liquid crystal). (When the molecules are lying), the difference in the magnitude of the spike voltage pulse generated in the scan electrode waveform due to the change in the capacitance of the entire display screen, depending on the number of each gradation data displayed on one scan electrode Correct correction cannot be performed by the method of determining the correction amount.

[0004]

According to a method of driving a liquid crystal electro-optical element of the present invention, a liquid crystal is sandwiched between a substrate on which a plurality of scanning electrodes are formed and a substrate on which a plurality of signal electrodes are formed. In the method for driving a liquid crystal electro-optical element, a scan electrode waveform is applied to the plurality of scan electrodes, and a signal electrode waveform based on gradation data is applied to the plurality of signal electrodes. A correction pulse for correcting a waveform deformation occurring in the scan electrode waveform is added in accordance with a count value obtained by counting the number of grayscale data for one scanning period for each grayscale, and each grayscale of the grayscale data is predetermined. And the gradation data for one display screen is replaced with a weighted value and added, and the correction amount by the correction pulse is adjusted according to the added value. Further, the added value indicates the brightness of the entire display screen. In addition, one frame before the frame in which the gradation data is actually displayed, the gradation data is replaced with a weighted value and added.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments will be described below in detail. In this embodiment, the description will be made on the assumption that the liquid crystal electro-optical element becomes dark when no voltage is applied and becomes bright when a voltage is applied. (Embodiment 1) FIG. 1 is a diagram showing an example of a scanning electrode waveform according to the driving method in Embodiment 1, and FIG. 2 is a block diagram of a correction circuit.

In the diagram showing the electrode pattern of the liquid crystal display of FIG. 3, when the pixels indicated by oblique lines are bright and the other pixels are dark (pattern A), the waveform applied to the signal electrode 302 is not shown. 4 signal electrode waveform 402
The waveform applied to the signal electrode 303 is the signal electrode waveform 403 in FIG. The state of the spike voltage pulse generated at the scan electrode at this time is indicated by the scan electrode waveform 40.
1 (a waveform applied to the scanning electrode 301).

In the diagram showing the electrode pattern of the liquid crystal display of FIG. 3, when the pixels indicated by oblique lines are dark and the other pixels are bright display patterns (pattern B),
The waveform applied to the signal electrode 302 is signal electrode waveform 4 in FIG.
At 05, the waveform applied to the signal electrode 303 is the signal electrode waveform 406 of FIG. A state of the spike voltage pulse generated at the scan electrode at this time is a scan electrode waveform 404 (a waveform applied to the scan electrode 301).

[0008] Comparing the capacities of the entire liquid crystal panel module in the A pattern and the B pattern, the B pattern has a larger capacity than the A pattern, so that there is a difference in the magnitude of the spike voltage pulse. As shown in the figure, B has a larger spike voltage pulse than A.

Therefore, the amount of the correction voltage pulse is adjusted by the correction circuit of FIG. Hereinafter, the correction circuit of FIG. 2 will be described.

The display circuit 201 is decoded by a decoder circuit 202, and the number of gradation data in one scanning period is counted by an addition circuit section 203 for each gradation data. When the data of the scanning lines is counted, the data is latched by the latch circuit unit 204 indicated by the latch circuits 0 to 15.

Also, the display data 201 is converted into a weighting circuit 2
07 and weighted for each gradation data. In the present embodiment, the weighting ratio is set to 1 when the display data is 0000 (when the display is the darkest) and about 1.6 when the display data is 1111 (when the display is the brightest). The halftone display data between them is set to a value equally divided between 1 and 1.6. Then, the weighted data is added to the addition circuit 20.
8, and when the data for one screen is added, the result of the addition is latched in the latch circuit 209. In this way,
By weighting and adding data for one screen, the change in brightness (capacity of liquid crystal) of the entire screen is digitized and divided into four stages. Then, the data of the latch circuit 209 is converted to the data of the latch circuit unit 204 by the data conversion circuit 2.
05 is input to create pulse data. In this embodiment, a ROM is used as the data conversion circuit 205. The data conversion circuit 205 is divided into four blocks according to the brightness of the screen, and pulse data corresponding to the number of each gradation data in one scanning period is written in each block, and the latch circuit is used. The number of each gradation data latched by the unit 204 and the data indicating the brightness of the entire screen latched by the latch circuit 209 are input to an address bus of the ROM, and the number of each gradation data and the brightness of the entire screen are input. The pulse data corresponding to the data is read. The pulse data is input to the correction pulse generation circuit 206 to generate a correction pulse 212 corresponding to the pulse data, and the analog switches 210 and 211 are switched by the correction pulse, and the non-selection voltage CV1 with the correction voltage pulse is applied.
And CV2 are input to the non-selection voltage of the liquid crystal driver to generate a scan electrode waveform with a correction voltage pulse. An example of the scanning electrode waveform when displaying the pattern A is shown at 101 in FIG. 1, and an example of the scanning electrode waveform when displaying the pattern B is shown at 102. In this way, the correction voltage pulse is generated in the opposite polarity to the spike voltage pulse to cancel the spike voltage pulse. Then, comparing part A of 101 with part B of 102,
As shown in the figure, the pulse width of the part B is longer than that of the part A. This is because, even if the number of gradation data in one scanning period is the same, the magnitude of the spike voltage pulse differs depending on whether the entire screen is bright (the liquid crystal capacity is large) or dark (the liquid crystal capacity is small). The pulse width of the correction voltage pulse is adjusted in accordance with the spike voltage pulse so that optimum correction can always be performed.

As described above, in determining the pulse width of the correction voltage pulse, the optimum value is determined according to the number of each gradation data in one scanning period and the brightness of the whole screen (capacity of the liquid crystal) to cancel the spike voltage pulse. Like that.

In this embodiment, the correction for the brightness of the entire screen causes a time delay of one frame, but this delay hardly adversely affects the display quality.
There is virtually no problem. Further, in order to prevent the correction of the brightness of the entire screen from being delayed by one frame, the data for correcting the brightness of the entire screen is faster by one frame than the actually displayed data. The correction method other than that may be the same as that of the present embodiment.
The correction amount of the correction voltage pulse is adjusted only by the pulse width. However, the correction based on the number of each gradation data in one scanning period is a pulse width, and the correction based on the brightness of the entire screen is correction based on the voltage of the correction voltage pulse. Alternatively, a method in which the pulse width is fixed and the correction is performed only by the voltage is also possible. Also, 1
Although the description has been given by taking the six-gradation display as an example, any number of gradations may be used, and the correction amount for the brightness of the entire screen is divided into four blocks. The ratio of the weighting for each gradation data in the weighting circuit 207 is set to 1 when the display data 0000 is set to 1.
Although the value of 111 is set to be 1.6, the optimal value is set according to each condition because the weighting ratio varies depending on the thickness of the liquid crystal panel and the driving duty. do it.

[0014]

As described above, according to the present invention, the correction for correcting the waveform deformation occurring in the scanning electrode waveform in accordance with the count value obtained by counting the number of gradation data for each gradation for one scanning period. In addition to adding a pulse to the scan electrode waveform, each gradation of the gradation data is weighted to a predetermined value, and the gradation data for one display screen is replaced with a weighted value and added. By adjusting the amount of correction by the correction pulse, the brightness of the screen can be appropriately quantified in the liquid crystal electro-optical device for displaying gray scales, and the spike voltage pulse generated by the gray scale data and the magnitude according to the brightness of the screen For different spike voltage pulses,
Appropriate correction can be made.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a scan electrode waveform of the present invention.

FIG. 2 is a block diagram illustrating an example of a correction circuit according to the present invention.

FIG. 3 is a diagram showing an example of an electrode configuration of a liquid crystal display.

FIG. 4 is a diagram illustrating an example of a signal electrode waveform and a state in which a spike voltage pulse is generated in a scanning electrode waveform.

[Explanation of symbols]

101 Scanning electrode waveform with correction pulse (for pattern A) 102 Scanning electrode waveform with correction pulse (for pattern B) 103 Enlarged view of correction pulse 201 Display data 202 Decoder circuit 203 Addition circuit section 204 Latch Circuit part 205 Data conversion circuit 206 Correction pulse generation circuit 207 Weighting circuit 208 Addition circuit 209 Latch circuit 210, 211 Analog switch 212 Correction pulse 301 Scan electrode 302, 313 Signal electrode 401 Scan electrode waveform (for A pattern) 402, 403 Signal Electrode waveform (for pattern A) 404 Scanning electrode waveform (for pattern B) 405, 406 Signal electrode waveform (for pattern B) 407 Enlarged view of spike voltage pulse t1 1 frame period t2 selection period t3 non-selection period

Claims (3)

(57) [Claims] 1. A driving method for a liquid crystal electro-optical element comprising a liquid crystal sandwiched between a substrate on which a plurality of scanning electrodes are formed and a substrate on which a plurality of signal electrodes are formed, wherein the scanning electrode has a scanning electrode waveform. And applying a signal electrode waveform based on grayscale data to the signal electrode. The scan electrode waveform is based on a count value obtained by counting the number of the grayscale data for one scanning period for each grayscale. A correction pulse for correcting a waveform deformation occurring in the scan electrode waveform is added, and each gradation of the gradation data is weighted to a predetermined value, and a value obtained by weighting the gradation data for one display screen is obtained. A method for driving a liquid crystal electro-optical element, characterized in that the correction pulse is adjusted in accordance with the added value by replacing and adding. 2. The method of driving a liquid crystal electro-optical element according to claim 2, wherein the added value indicates the brightness of the entire display screen. 3. The method according to claim 1, wherein, prior to a frame in which the gradation data is actually displayed, the gradation data is replaced with a weighted value and added. Driving method of a liquid crystal electro-optical element.