JPH05173507A - Method for driving liquid crystal element and display device therefor - Google Patents

Abstract

PURPOSE:To improve display quality by displaying gradation with the combination of (n) kinds of on-pulses to one gradation and making (n) kinds of on-pulses at every gradation on one scanning electrode in the same timing roughly equal number. CONSTITUTION:Respective scanning electrode waveforms outputted from scanning electrode drivers are applied to respective scanning electrodes and respective signal electrode waveforms outputted from signal electrode drivers are applied to respective signal electrodes. At this time, when the signal electrode waveforms 102, 103 are compared in a timing t4, the on-pulse width of the waveform 103 is longer than the same of the waveform 102. In such a manner, 16-gradation is displayed by combining two kinds of gradation pulse waveforms at the time of displaying a certain gradation. Then, respective signal electrode waveforms in one scanning period are constituted so that the on-pulse width of a first group between two kinds of waveforms indicating respective gradations is long and the on-pulse width of a second group is short and the number of the first group is nearly equal as the number of the second group.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art FIG. 8 shows an example of a conventional driving method by pulse width modulation in multiplex driving by a voltage averaging method.

[0003]

In such a driving method, when the display on a certain scan electrode is almost the same, as shown by A in FIG. 8, the timing of the rise or fall of the signal electrode waveform is changed. Since the number of coincidence is large, the spike voltage generated in the scan electrode waveform becomes large,
Crosstalk due to the influence becomes severe and the display quality deteriorates.

[0004]

According to a method of driving a liquid crystal element of the present invention, there are n (n is a positive number) kinds of on-tone for one gradation.
It is characterized in that it is displayed by a combination of pulses, and the number of n kinds of on-pulses for each gradation on one scanning electrode is substantially the same at the same timing. In addition, the signal electrode waveform applied to the liquid crystal element is
The number of waveforms A and B is substantially the same.

[0005]

[Embodiment] In this embodiment, a case of displaying 16 gradations will be described.

(Embodiment 1) In the embodiment 1, o for each gradation
FIG. 4 shows the gradation pulse waveform for each gradation at that time when there are two kinds of n pulses, and the width of the on pulse shown at t7 is 17 kinds from 1 to 17 and 1 is the width of the on pulse. It is assumed that the width of the on pulse is gradually narrowed to 2 and 3 and becomes long, and the width of the on pulse of 17 is the longest.

FIG. 1 is a timing chart showing an example of drive waveforms in the first embodiment of the present invention. Then, in the liquid crystal module shown in FIG. 7, a case where all pixels have the same display will be described.

Each scan electrode waveform output from the scan electrode driver 701 of FIG. 7 is applied to each scan electrode, and each signal electrode waveform output from the signal electrode driver 702 is applied to each signal electrode. Then, the scan electrode waveform 101 is applied to 703, and the signal electrode waveform 102 is applied to 704, 706, 70.
8 and the signal electrode waveforms 103 are 705, 707,
709 is applied. At this time, comparing the signal electrode waveforms 102 and 103 in the period of t4 in FIG.
The width of the on pulse of 103 becomes longer than the width of the on pulse of 2, and assuming that the pulse widths at this time are 15 and 16 in FIG. 4, the signal electrode waveform 102 changes during the period t6 of the next frame. In the waveform shown by 16, 103 has a waveform shown by 15. Then, looking at the gradation pulse waveforms applied to the pixels of A to R of FIG. 7 for each frame, it becomes as shown in FIG.
7 corresponds to the pixels of A to R in FIG. 7, 1 to 5 indicate the respective frames, and the gradation pulse waveforms of the respective pixels in the 1 to 5th frames are shown. Regarding the pixel A, the waveform of 16 in FIG. 4 is used for the first frame, and the waveform of 15 is used for the second frame.
The 15th waveform in FIG. 4 is 16th in the second frame.
The waveform is. Further, the gradation pulse waveform applied to each of the pixels A to R in FIG. 7 can be set as shown in FIG.

As described above, two kinds of gradation pulse waveforms are combined to display a certain gradation, and 1 and 2, 2 and 3, 3 and 4, to 14 and 15, 15 and 16, 16 of FIG. 4 are combined. 16 gradations are displayed in each of the combinations of and. And
Each signal electrode waveform in one scanning period represents 2 for each gradation.
The first group has a long on-pulse width, the second group has a short on-pulse width, and the numbers of the first group and the second group are approximately the same.

By using such a driving waveform, the generation of the spike voltage is dispersed at two or more places as shown by A in FIG. 1, the magnitude of the spike voltage can be reduced, and the crosstalk is reduced.

In the above embodiment, 17 types of gradation pulse waveforms of 1 to 17 in FIG. 4 are used, but 1 to 2, 1 to 3 are defined as 16 types of gradation pulse waveforms of 1 to 16. Two
And 3,3 and 4,4 and 5,5 and 6,6 and 7,7 and 8,8 and 9,9 and 10,10 and 11,11 and 12,12 and 13,
The number of gradation pulse waveforms can be reduced by using combinations of gradation pulse waveforms such as 13 and 14, 14 and 15, and 15 and 16. The combination of the gradation pulse waveforms may be other than the above, and two kinds are combined.

(Embodiment 2) In Embodiment 2, o for each gradation
FIG. 4 shows the gradation pulse waveform for each gradation in the case of three kinds of n pulses, and the width of the on pulse indicated by t7 is 18 kinds from 1 to 18, and 1 is the width of the on pulse. It is assumed that the width of the on pulse is gradually narrower and becomes 2 and 3, and the width of the on pulse of 18 is the longest.

FIG. 2 is a timing chart showing an example of drive waveforms in the second embodiment of the present invention. Then, in the liquid crystal module shown in FIG. 7, a case where all pixels have the same display will be described.

Each scan electrode waveform output from the scan electrode driver 701 of FIG. 7 is applied to each scan electrode, and each signal electrode waveform output from the signal electrode driver 702 is applied to each signal electrode. Then, the scan electrode waveform 201 is applied to 703, the signal electrode waveform 202 is applied to 704 and 707, the signal electrode waveform 203 is applied to 705 and 708, and the signal electrode waveform 204 is applied to 706 and 709. At this time, the signal electrode waveform 2 during the period of t4 in FIG.
Comparing 02, 203 and 204, the width of the on pulse of 204 is the longest, the next is 202 and the shortest is 203. If the pulse widths at this time are 16 and 15 and 14 in FIG. 4, the next frame is t6. In the period of, the signal electrode waveform 202 is the waveform shown by 14, the waveform 203 is shown by 16, and the waveform 204 is shown by 15. Then, in FIG.
Looking at what the gradation pulse waveform applied to each pixel up to R is for each frame, it becomes as shown in FIG. 6A, and A to R indicates A to R in FIG. 1 to 5 indicate each frame, and the gradation pulse waveform of each pixel in the 1 to 5 frames is shown. Regarding the pixel A, the waveform of 16 in FIG. 4 is shown in the first frame, the waveform of 15 is shown in the second frame, and the waveform of 14 is shown in the third frame. Regarding the pixel B, 15 is shown in FIG. 4 in the first frame. Waveform, the second frame has 14 waveforms, the third frame has 16 waveforms, and regarding the pixel C, the 14th waveform in FIG. 4 in the first frame, the 16th waveform in the second frame, and the 15th waveform in the third frame It has a waveform of. Further, the gradation pulse waveform applied to each of the pixels A to R in FIG. 7 can be set as shown in FIG. 6B.

As described above, three kinds of gradation pulse waveforms are combined to display a certain gradation, and 1 and 2 and 3, 2 in FIG. 4 are combined.
And 3 and 4, 3 and 4, 5 and 14 to 15 and 16, 15 and 1
Sixteen gradations are displayed by combinations of 6 and 17, 16 and 17 and 18, respectively. In each of the signal electrode waveforms in one scanning period, the first group has the longest on pulse width, the second group has the shortest on pulse width, and the third group has the third group among the three types of waveforms representing the respective gradations. Has an on pulse width intermediate between the first and second groups so that the numbers of the first group, the second group and the third group are substantially the same.

By using such a driving waveform, the generation of spike voltage is dispersed at three or more places as shown by A in FIG. 2, the magnitude of spike voltage can be reduced, and crosstalk is reduced.

(Third Embodiment) In the third embodiment, as in the second embodiment, three types of on-pulses for each gray scale are applied and substantially the same number of waveforms A and B are applied in one scanning period. ..

FIG. 3 is a timing chart showing an example of drive waveforms in the third embodiment of the present invention. Then, in the liquid crystal module shown in FIG. 7, a case where all pixels have the same display will be described.

Each scan electrode waveform output from the scan electrode driver 701 of FIG. 7 is applied to each scan electrode, and each signal electrode waveform output from the signal electrode driver 702 is applied to each signal electrode. Then, the scan electrode waveform 301 is applied to 703, and the signal electrode waveform 302 is 704 and 303 is 70.
5, 304 is 706, 305 is 707, and 306 is 70
8, 307 are applied to 709, respectively. At this time, when comparing the signal electrode waveforms 302 to 307 in the period of t4 in FIG. 3, the width of the on pulse of 304 and 307 is the longest, the next is 302 and 305, and 303 and 306 are the shortest, and 302, 304, 306 Is the waveform B in FIG.
Thus, 303, 305, and 307 are waveform A in FIG. The pulse width at this time is 16 and 15 and 1 in FIG.
4, the gradation pulse waveform applied to each pixel is as shown in FIGS. 6A and 6B as in the second embodiment.

As described above, three kinds of gradation pulse waveforms are combined to display a certain gradation, and 1 and 2 and 3 and 2 in FIG. 4 are combined.
And 3 and 4, 3 and 4, 5 and 14 to 15 and 16, 15 and 1
Sixteen gradations are displayed by combinations of 6 and 17, 16 and 17 and 18, respectively. In each of the signal electrode waveforms in one scanning period, the first group has the longest on pulse width, the second group has the shortest on pulse width, and the third group has the third group among the three types of waveforms representing the respective gradations. Is an on pulse width intermediate between the first and second groups so that the numbers of the first group, the second group and the third group are almost the same, and the waveform A shown in FIG. The waveform B is set to be almost the same. With such a drive waveform, the generation of spike voltage is dispersed at six or more locations as shown by A in FIG. 3, the magnitude of spike voltage can be reduced, and crosstalk is reduced.

In Embodiments 2 and 3, the gradation pulse waveforms are 18 kinds of 1 to 18 in FIG. 4, but the gradation pulse waveforms are 16 kinds of 1 to 16 and 1
And 2 and 3, 1 and 2 and 4,2 and 3 and 4,3 and 4 and 5,4 and 5 and 6,5 and 6 and 7,6 and 7 and 8,7 and 8 and 9,8 and 9
And 10, 9 and 10 and 11, 10 and 11 and 12, 11 and 1
2 and 13, 12 and 13 and 14, 13 and 14 and 15, 14
It is also possible to reduce the number of gradation pulse waveforms by combining gradation pulse waveforms such as 15 and 16, 13 and 15 and 16. The combinations of the gradation pulse waveforms are not limited to the above, and three kinds are combined.

Further, in the first, second, and third embodiments, 16 gradation display is explained, but the gradation number may be any gradation, and the combination of gradation pulse waveforms is only 2 or 3. No, 4 types, 5 types ... n types, any number,
The number of gradations can be increased by changing the combination of each gradation pulse waveform, and 32 gradations or 64 gradations can be displayed, and 64 gradations or more can be supported depending on the number and combination of gradation pulse waveforms. ..

[0023]

As described above, according to the present invention, the rising or falling positions of the signal electrode waveform are dispersed in several places, and the spike voltage is reduced accordingly.
Crosstalk is reduced and display quality is improved.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an example of drive waveforms of the present invention.

FIG. 3 is a diagram showing an example of drive waveforms of the present invention.

FIG. 4 is a diagram showing each gradation pulse waveform.

FIG. 5 is a diagram showing an example of a combination of gradation pulse waveforms applied to each pixel by the driving method of the present invention.

FIG. 6 is a diagram showing an example of a combination of gradation pulse waveforms applied to each pixel by the driving method of the present invention.

FIG. 7 is a block diagram showing an example of a configuration of a liquid crystal driver and electrodes of a liquid crystal panel module.

FIG. 8 is a diagram showing an example of drive waveforms according to a conventional drive method.

[Explanation of symbols]

101 Examples of Scan Electrode Waveforms 102, 103 Examples of Signal Electrode Waveforms 104 Examples of Scan Electrode Waveforms on Scan Electrodes 201 Examples of Scan Electrode Waveforms 202, 203, 204 Examples of Signal Electrode Waveforms 205 Scan Electrode Waveforms on Scan Electrodes 301 Scan electrode waveform example 302, 303, 304, 305, 306, 307 Signal electrode waveform example 308 Scan electrode waveform on scan electrode 701 Scan electrode driver 702 Signal electrode driver 703 Scan electrode waveform 704, 705, 706, 707 , 708, 709 signal electrode waveform 710 signal electrode 711 scan electrode t1 first frame period t2 selection period t3 non-selection period t5 second frame period

Claims (3)

[Claims] 1. A method for performing multiplex driving of a liquid crystal element in which a liquid crystal is sandwiched between at least a substrate on which a scanning electrode is formed and a substrate on which a signal electrode is formed, and n (n is a positive value) for one gradation. A method for driving a liquid crystal element, wherein the number of kinds of on-pulses is displayed and the number of n kinds of on-pulses for each gradation on one scanning electrode is substantially the same at the same timing. 2. A signal electrode waveform applied to a liquid crystal element,
2. The method for driving a liquid crystal element according to claim 1, wherein the waveforms A and B have substantially the same number at the same timing. 3. A display device using a liquid crystal element according to the driving method according to claim 1.