JPH01113794A - Driving of liquid crystal display - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving a liquid crystal display, and particularly to a method for driving a liquid crystal display that is effective for improving the image quality of a large, high-duty liquid crystal matrix display.

[Conventional technology]

In conventional high-duty liquid crystal matrix displays, a voltage averaging method as shown in Japanese Patent Publication No. 57-57718 is used, and scanning ffi poles are sequentially scanned as shown in Japanese Patent Application Publication No. 59-204887 and FIG. , was to be displayed.

[While the invention is trying to solve the problem - the point of view]

However, in the conventional technology described above, the output voltage of the drive circuit cannot be uniformly transmitted to all pixels due to the distributed capacitance formed in the liquid crystal panel and the resistance of the transparent electrode, resulting in a difference in the effective voltage applied to each pixel. As shown in Japanese Patent Application Laid-open No. 59-204887, shadows are created around lit pixels in the direction of the signal electrode, causing a stalk and deteriorating image quality. In addition, in the conventional scanning method, when the scanning period approaches the flickering period of the fluorescent lamp, movement of horizontal stripes with different shades of light and flicker occurs according to the attenuation characteristic of the amount of transmitted light shown in FIG. In particular, when a large-screen liquid crystal panel is viewed from an angle relative to the R-appropriate viewing angle, unpleasant flickering tends to occur under fluorescent lighting. This has been prevented by increasing the frame frequency, which increases the operating frequency of the entire liquid crystal display system, increasing current consumption, radiation noise, and increasing the cost of electronic circuits.

Therefore, the present invention aims to solve these problems.
The aim is to improve the LCD drive method by improving the LCD driving method without changing the conventional LCD panel.
The object of the present invention is to provide a liquid crystal display device with higher image quality than before.

(Means for Solving the Problems) The liquid crystal driving method of the present invention divides adjacent scanning electrodes into groups of m (m≧4) each, and sets a certain number of scanning electrodes at equal positions within the group. The present invention is characterized in that interlaced scanning (field scanning) is performed between the groups in order so that all scanning electrodes are scanned within a certain period of time.

[Effect]

According to the above method of the present invention, since one frame is divided into multiple fields and driven, the scanning frequency for each pixel does not change, but the driving frequency increases by the number of fields when scanning around the viewpoint on the liquid crystal panel. , the flicker is canceled out, and the flicker can be visually reduced. In addition, by reversing the AC polarity for each field, the driving polarity of adjacent scanning electrodes is reversed, so that the deviation of the effective voltage applied to each pixel can be easily corrected before the response time of the liquid crystal. It is possible to reduce talk.

〔Example〕

FIG. 1 shows scan electrode side drive waveforms showing an example of the liquid crystal drive method according to the present invention. The figure shows an example in which 400 lines of scanning electrodes are divided into groups of 6 and liquid crystal panels are divided into groups of m-100 lines, and one frame is interlaced with 4 fields. However, due to the nature of the drawings, the time axis is not shown accurately. The signal PR indicates the polarity of the AC drive voltage of the liquid crystal, and when FR is "H", the voltage applied to the lit pixel is positive or "L" with respect to the scanning electrode.
, the reverse is shown, and the same applies to other figures. The scanning electrode numbers are numbered from 1 from the top according to the physical positional relationship in the liquid crystal panel shown in FIG.

Now, the driving method according to the present invention is performed in the following scanning order, and is different from the conventional line sequential driving method.

1st field: 1→5→9→・・・・・・→397
2nd field: →2→8-+10→...→398 3rd field: groan 3→7→11...→388 4th field: →4→8→12→...→400 Below this repetition.

That is, the 40+1st (n is a positive integer) scan electrode is scanned three at a time from scan electrode 1. At this time, it goes without saying that display data matching the scanning electrode is applied to the signal electrode from the VRAM to the signal side drive circuit. 3
After scanning the 87th electrode, all scanning ffi poles are set to non-selected polarities and the liquid crystal drive polarity is reversed. Then, immediately from the second scanning electrode, 40+
The second electrode is interlaced and scanned, and when the 378th electrode is scanned, it is brought into a non-selected state and the liquid crystal drive polarity is reversed. The scanning of the first frame is completed in the same manner for the following *3 and 4 fields.

In the m2 frame, the AC drive polarity of each field is simply reversed from the first frame because the liquid crystal is AC driven.
The scanning order is exactly the same as the wXl frame. By the way, the reversal of the drive polarity described above is performed between fields.
However, it goes without saying that it may be reversed multiple times within the field.

In Figure 1, the waveforms shown by broken lines superimposed on the scan electrodes 1, 2, and 3.4 are signal electrode waveforms that indicate lighting points, all lights on, all lights off, and lighting every 2 lines on odd-numbered lines, respectively. be. What should be noted here is that the drive waveform on the signal side when lighting odd lines, which is said to have particularly severe driving conditions in the conventional Ia [next drive system], is almost the same as the waveforms for all lights on and all lights off. . This means that in the driving method of the present invention, when odd-numbered lines are turned on, almost the same image quality as with all-on or all-off waveforms can be obtained. On the other hand, a particularly severe driving condition in the driving method shown in FIG. 1 is lighting every two lines. In this case, at the highest drive frequency where the signal electrode potential changes for each scan, the drive waveform is difficult to be accurately transmitted within the liquid crystal panel, which is a distributed constant circuit of the CR, and pixels far from the drive circuit cannot be scanned. The effective voltage applied to the liquid crystal tends to deviate from the ideal value due to the voltage impact from the electrodes. However, in the driving method of the present invention, the driving polarity of adjacent scanning electrodes is reversed.
Since the driving polarity is reversed in a shorter time than before,
Even if a deviation occurs in the effective value, it will be offset in the next field. Therefore, if one field time is set within the optical response time of the liquid crystal (the time during which the amount of light changes slightly by changing the drive voltage), the deviation in the effective value will be corrected before the liquid crystal responds, making it possible to Compared to the line sequential drive method, the above-mentioned crosstalk can be reduced.

FIG. 2 shows that the driving method shown in FIG. 1 can also be used as a countermeasure against 7 problems. FIG. 2(a) is a diagrammatic representation of FIG. The X-axis is time, and the Y-axis is scanning electrode number. The numbers in the table indicate the scanning order in the i-frame, and the symbols indicate the drive polarity. Figure 2(b) shows the liquid crystal panel at R'll for a scanning type tail of 2°3.4.
It shows the amount of transmitted light when viewed from the viewing angle. Second
Figure (C) shows the amount of transmitted light when the liquid crystal panel is viewed obliquely with respect to the scanning electrodes 1, 2, and 3.4. FIGS. 3(a), 3(b), and 3(c) show conventional driving methods for comparison with FIG. 2.

In the case of a large LCD screen, the viewing angle is wider than that of a small screen, so flicker when viewed from an oblique direction (large screen flicker)
is easily noticeable. As shown in Figure 2 (C), this means that the optical response frequency when viewed from an angle is 1 of the frame frequency.
72, which is the frequency that is perceived visually. For this reason, conventionally, the frame frequency has been increased to around 80H2. Moreover, as shown in Figure 3 (C), with the conventional driving method, the peak of the optical response is concentrated near the visual field, so under fluorescent lighting, the amount of transmitted light varies depending on the timing of the flickering, so the visual The contrast would flicker and change, causing discomfort.

- With the driving method invented by Rikiki, the optical response frequency near the field of view is four times that of the conventional method, and twice as high when obliquely.Furthermore, the peak of the optical response is dispersed, so the frequency of the optical response of each pixel is Although the flicker is the same as before, the flicker is reduced because it is visually canceled out.

Next, we will outline the circuit means for realizing the driving method of the present invention! This will be explained using Figures 4 and 5.8. FIG. 4 shows an embodiment of the drive circuit configuration. In the figure, display data XD is serially parallel-converted by a shift register 44, periodized by a latch 43 into a signal LP, and driven by a driver 41 via a level shifter 42, which is a known configuration.

The output of the driver 41 is connected to each signal electrode of the liquid crystal panel 40. On the other hand, each scan f12 fi of the liquid crystal panel 40
The shift register 48 clocks a signal YSCL different from the signal LP, and the shift register 48 clocks the signal YSCL, which is different from the signal LP.
and level shifter 46, LS7 is opened and closed by signal LD.
The point is that a latch 47 equivalent to 5 is provided.

In FIG. 5, the number of scanning electrodes of the liquid crystal panel 40 in FIG. 4 is 40.
It shows the timing relationship of the signals that control the drive circuit that realizes the drive method of the present invention when the number of lines is zero. In the case of FIG. 5, since one frame is divided into four fields, four clocks of YSCL are input during the signal LPI clock period, instead of one clock in the past. Further, at the end of one field, additional timing (401 to 404) for one scanning time is provided, and the polarity of the PR multiplied signal is switched and a start pulse for the shift register 48 is generated. The reason for providing this additional timing is to prevent harmonic components of the drive waveform from increasing and horizontal lines from occurring when switching the polarity of the FR. Therefore, in this embodiment, a 400-line liquid crystal panel is driven at a duty of 1/404, but the difference in image quality is slight compared to the case of a duty of 1/400.

Next, in FIG. 6, the circuit configuration of the controller section that generates the signals shown in FIG. 4 will be outlined. The major difference in the circuit configuration from the conventional line-sequential driving method in the figure is that in order to perform interlaced scanning, display data is synchronized with VRA.
Address generation circuit 9 for discontinuous reading from M87
This is the configuration of 4. In this embodiment, a register addition method is used for this address generation circuit. This will be explained below. A dot counter 62 receives the signal from the timing generator 61, counts the number of display dots for one address, and generates a shift clock X5CL for the signal side drive circuit. The output 90 of the dot counter 62 is input to a character counter 63 to count the number of horizontally displayed addresses. Further, the output 90 generates a shift clock YSCL via a frequency divider 64 (1/20 frequency division), and is connected to a start pulse generation circuit of the scanning side shift register. The IH signal generation circuit 65 divides the output of the frequency divider 64 into 1/4, and changes the generation timing of the start pulse YD with respect to the latch pulse LP according to the value of the programmable register 66. The output of the 1-to-1 signal generation circuit 65 is
- It gives a scanning time, and the frequency is divided by 1/101, and this output and the output of the IH signal generation circuit 66 are connected via an AND gate 68 to generate a start pulse YD at the 101st frequency division.

The output 95 of the frequency dividing circuit 67 is 172 frequency dividing circuit 69.7
It produces outputs 96, 97, 138 which give the field timing □ through 0.71. Outputs 96 and 98 are E
The X-OR gate 72 generates a liquid crystal alternating current signal PR.

Next, address generation circuit 94 will be explained. start·
Address register? 3,74,75°76 is LS7
This register stores the start address of each field composed of 7 lip-flops equivalent to 4. This register may be a ROM type storage means. Raster start □ address registers 77 and 78 are registers for storing the start address of each scanning line. In the case of one screen configuration, only register 77 functions. In the screen configuration, register 78 also functions as the lower screen raster start priority address register.

To generate the raster address for each field, the output of register 73 and character counter 63 is output 95.98.
．． The selection is made at 97 using multiplexers 81 and 82, the adder 84 equivalent to LS83A calculates the sum, and the output is once held for each address by latch 85 equivalent to LS74, and the flow described below is repeated. latch 85
The output 93 is applied to an address input terminal of a VRAM 87 storing display data via an output circuit 8G. As a result, display data is read out from the VRAM 87 for each raster e address.

(2): Repeated for each last row (2): The display data that moves to the rough field after the end of the relevant field is converted into a format for the liquid crystal drive circuit by the display data output circuit 89 via the input circuit 88, and is output as serial data XD.

In the embodiment Z of FIG. 6, by changing the contents of the register 66, the star traverse position of each field can be changed as shown in FIG. An interlaced scanning method can be used. In the scanning method shown in Fig. 7, if the number of scanning electrodes in each block is large (n), the scanning direction is not set to one direction, so the optical scanning distribution within each block becomes uniform and flicker is visually reduced. Also, Fig. 6 shows an example where one frame has four fields, but if this is divided into many fields of four or more fields and driven,
It has extensibility that allows for easy programmable expansion of the corresponding parts of the color/register registers.

The driving method of the present invention improves the image quality deterioration caused by the dynamic characteristics of the liquid crystal and the non-ideal surface of the transparent electrode, so it is applicable not only to passive type LCDs but also to TPT and M
Active type LCD1 such as IM, and even FDP
It is applicable to other flat displays such as ELF and ELF.

〔Effect of the invention〕

As described above, according to the present invention, by dividing one frame into a plurality of fields and performing interlace scanning, the following effects are achieved.

a) A display with less flicker can be obtained on a large screen without increasing the scanning frequency.

b) Therefore, the operating margin of the drive circuit system can be maximized, and current consumption can be reduced.

C) High-quality display with less crosstalk in the direction of signal electrodes can be obtained without changing the liquid crystal panel.

d) Since the driving method of the present invention can be realized by only slightly changing the conventional driving circuit, it is easy to maintain compatibility with conventional liquid crystal display devices.

[Brief explanation of the drawing]

FIG. 1 is a scanning electrode driving waveform diagram showing an embodiment of the liquid crystal driving method of the present invention. FIGS. 2(a) to 2(C) are diagrams showing attenuation characteristics of transmitted light of liquid crystal in the driving method of the present invention. FIGS. 3(a) to 3(C) are diagrams showing the attenuation characteristics of transmitted light of a liquid crystal according to a conventional driving method. FIG. 4 is a configuration diagram of a drive circuit for realizing the drive method of the present invention. FIG. 5 is a diagram showing the timing relationship of signals controlling the drive circuit of FIG. 4. FIG. 6 is a configuration diagram of a controller that generates the signals shown in FIG. 5. FIGS. 7(a) to 7(C) are diagrams showing other embodiments of the present invention. Applicant Seiko Epson Co., Ltd. Agent Patent Attorney Tsutomu Mogami and 1 other person Figure 2 Figure 3 R

Claims (3)

[Claims] (1) In a liquid crystal matrix display device in which picture elements are formed at opposing portions of scanning electrodes and signal electrodes, adjacent scanning electrodes are divided into groups of m (m≧4) each, and equal A method for driving a liquid crystal display, characterized in that interlaced scanning (field scanning) is performed between the groups in a fixed order for each scanning electrode at a position, so that all scanning electrodes are scanned within a fixed period. (2) When one field scan is completed, the polarity of the AC drive voltage is reversed and another field scan electrode is scanned, so that all scan electrodes are scanned within a certain period of time. A method for driving a liquid crystal display according to claim 1. (3) In a driving method of a liquid crystal matrix display device in which picture elements are formed in opposing portions of scanning electrodes and signal electrodes, the scanning electrodes are divided into a plurality of fields by scanning intermittently at a fixed number of intervals, and each field is divided into a plurality of fields. Selectively from a plurality of means for storing the start address of a field, a means for storing the number of addresses for interlaced scanning, a means for counting the number of display addresses in the horizontal direction, and a means for storing the display start address in the horizontal direction. A means for reading out address data and calculating and outputting a read address from the display data RAM is used to skip between the means for sending the display data from the display data RAM to the signal side drive circuit and the selection output of the scanning side drive circuit. 1. A method for driving a liquid crystal display, comprising means for sending clocks of the same number as the number of scanning electrodes to a scanning side driving circuit, and interlacing scanning of a liquid crystal panel in a fixed order.