JPH03109524A - Driving method for display panel and display device - Google Patents

Abstract

PURPOSE:To drastically shorten the average renewal time of a screen by using a matrix type bistable display panel and rewriting a display after impressing a prescribed voltage only on an image which must be rewritten. CONSTITUTION:A display data generated by a CPU, etc., is stored in a data memory 20, and in accordance with a display mode, in the case of partial scanning, a renewal data is extracted by a comparison circuit 23 so as to read out the data necessary for a data control circuit 24 from the memory. The writing and the reading out of the data memory 20 are controlled by a memory control circuit 22, and a scanning driver 26 and a signal driver 27 are controlled by a driver control circuit 25 in synchronism with the read-out timing so as to scan only a scanning electrode which needs rewriting. On the other hand, in the case that the display mode displays complete scanning, the data in the data memory 20 is successively read out, and the display panel 28 is completely scanned so as to renew the screen. Thus, the display with high uniformity can be always maintained because of using a partial scanning method and a complete scanning method jointly in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for driving a display panel in which the display panel itself has memory properties, and a display device.

2. Description of the Related Art In recent years, there has been an increasing demand for large-screen, thin display devices in the field of information equipment, mainly computers. As this type of display device, liquid crystal display devices, which are characterized by low power consumption, are becoming widely used. In particular, since the display panel itself has memory properties, ferroelectric liquid crystal panels have the characteristic that display quality does not deteriorate even when the number of scanning lines increases.
It is expected that it will be put into practical use.

Hereinafter, a method for driving a display panel using a conventional ferroelectric liquid crystal panel will be described with reference to the drawings.

FIG. 5 is a schematic diagram showing the electrodes of a matrix panel, and shows an example of a dot matrix panel with m rows and n columns. In Fig. 5, C1, C2, C3°C4,...
, Cn is a signal electrode, R1, R2, R3°R4,...
..., Rm indicates a scanning electrode, and the intersection of the signal electrode and the scanning electrode becomes a pixel.

FIG. 6 is a scanning sequence diagram showing a conventional display panel driving method using a ferroelectric liquid crystal panel.
R2, . . . , Rm indicate scanning electrodes, and the horizontal axis indicates time. In FIG. 6, Tr indicates a reset period, Ts indicates a write period, and in the reset period Tr,
Put the pixel in the first or second stable state and write period T
In s, it is determined whether to invert or maintain the stable state according to the image data, and the image data is written to the pixel. In this example, pixels corresponding to eight scanning electrodes are simultaneously reset during the reset period Tr, and subsequently, the scanning electrodes are scanned one by one during the period Ts to write image data. Thereafter, similar processing is repeated to scan all scanning electrodes to complete one screen (for example, Japanese Patent Laid-Open No. 62-17571
(Described in Publication No. 4 ``Operation method of matrix type ferroelectric liquid crystal panel'').

Problems to be Solved by the Invention However, in the above driving method, the time Tf for rewriting one screen is Tf = (m/8) ・Tr + m - Ts (however, m is 8
be a multiple of ) Therefore, in order to shorten the rewriting time Tf for one screen, it is necessary to make the reset period Tr as similar as possible to the write period Ts. However, when the reset time Tr is shortened, the bistability of the liquid crystal deteriorates, resulting in a problem in that the display contrast deteriorates.

In addition, since the scanning lines are simultaneously reset for each block (eight lines in this case), there is a problem in that display brightness becomes uneven in this block-by-block period.

The present invention solves the above problems and provides a method for driving a display panel and a display device that enable display with excellent quality.

Means for Solving the Problems In order to solve the above problems, the display panel driving method and display device of the present invention uses a bistable matrix type display panel as the display panel, and eliminates pixels that need to be rewritten. This method uses a partial scanning method in which the display is rewritten by applying a predetermined voltage only to the display panel, and a full scanning method in which the entire display panel is scanned to update the display only when rewriting is necessary.

Further, a full-screen update drive is used at predetermined time intervals to update the display by scanning the entire display panel regardless of the necessity of rewriting.

Furthermore, a ferroelectric liquid crystal display panel is used for the display panel.

action The effect of this technical means is as follows.

The present invention uses a bistable display panel to update the display by scanning only the pixels that need to be rewritten, so the average screen update time is significantly shortened, and the entire screen can be scanned as needed. Since the display is also updated using the partial scanning method, the uniformity of the display can be maintained even if the screen is updated at uneven locations due to the partial scanning method.

Further, even if there is no need to rewrite the display, by performing full update drive as necessary, the screen is forcibly updated and the stability of the display can be improved.

Furthermore, by using a ferroelectric liquid crystal display panel for the display panel, a display panel that has stable bistability and can operate at high speed can be easily realized.

EXAMPLE Hereinafter, a method for driving a display panel and a display device according to an example of the present invention will be described with reference to the drawings.

FIG. 1 is a scanning sequence diagram showing a method for driving a display panel according to an embodiment of the present invention. In FIG. 1(a), R1, R2, ..., Rm on the vertical axis are scanning electrodes. shows,
The horizontal axis shows time. Ts indicates a display update period, which is a period during which each scan electrode is rewritten. FIG. 1 (+) shows the timing of a request to rewrite the display, and becomes high level when rewriting is necessary. Figure 1 (C
) indicates the scanning mode, and indicates the state of switching between the partial scanning method and the full scanning method.

As is clear from FIG. 1, in the partial scan mode, necessary scan electrodes are scanned and updated only when there is a rewrite request. On the other hand, in the full-screen update mode, all scan electrodes are scanned in response to a rewrite request, and the entire display area is updated.

As shown in FIG. 1, by normally driving by a partial scanning method and occasionally by a full scanning method, the screen update time can be significantly shortened and display uniformity can be maintained.

FIG. 2 is a block diagram showing a schematic configuration of a display device according to an embodiment of the present invention, in which 20 is a memory for storing display data;
21 is a mode switching circuit for selecting partial scanning or full scanning; 22 is a memory control circuit for controlling memory;
23 is a comparison circuit for extracting updated data during partial scanning;
24 is a data control circuit that controls data to be rewritten; 26
．． 27 is a scan driver and a signal driver that drive the display panel 28; 29 is a drive voltage source that generates a drive voltage; 30
is a scanning mode switching signal generation circuit.

The operation of the display device of the present invention configured as described above will be described below.

Display data generated by the CPU etc. is stored in the data memory 20.
and according to the display mode, for partial scans:
The comparison circuit 23 extracts updated data and reads data necessary for the data control circuit 24 from the memory. The memory control circuit 22 controls writing and reading of the data memory 20, but in synchronization with the reading timing, the driver control circuit 25 controls the scan driver 26 and the signal driver 27, and controls only the scan electrodes that need to be rewritten. scan. On the other hand, when the display mode is full-scale scanning, the data in the data memory 20 is read out sequentially and the display panel 28 is scanned.
FIG. 3 is a block diagram showing another configuration of the mode switching signal generation circuit in a display device according to another embodiment of the present invention, in which 30a indicates a counter and a comparison circuit. The number of rewriting request signals generated based on the result of step 23 is counted, and when a preset number is reached, a scanning mode switching signal is output. With such a configuration, full-scale scanning can be performed after partial scanning has been performed several times, so that highly uniform display can always be maintained.

Further, the configuration of the mode switching signal generation circuit may be a timer as shown in 30b, and a predetermined clock signal may be input to the timer to output a scanning mode switching signal at regular intervals. With this configuration, even if almost no rewriting occurs in the partial scan mode, the entire surface scan is executed periodically and excellent display uniformity can be maintained at all times.

It goes without saying that both the counter 30a and the timer 30b may be used in combination in the configuration of the mode switching signal generation circuit.

FIG. 4 is a voltage waveform diagram when a ferroelectric liquid crystal is used as an example of a method for driving a display panel according to an embodiment of the present invention and a driving voltage waveform for rewriting pixels on one scanning electrode of a display device. and is a graph showing the optical response of a pixel. FIG. 4(a) shows the drive voltage of the rewriting pixel, where 41 is the OFF write voltage waveform, 42 is the ON write voltage waveform, and 43 is the bias voltage waveform when scanning the adjacent scanning electrode, ±Vs is the voltage at which the bistable state of the liquid crystal is reversed,
±Vn is the voltage at which the bistable state is not reversed, and ±vb is the bias voltage.For ferroelectric liquid crystals, ON10F is determined by the final polarity of ±Vs, so see Figure 4 Φ)
As shown in , the optical transmittance becomes Boff due to the write waveform 41.

This state is maintained when a bias voltage or no voltage is applied. Conversely, with the write voltage 42, the transmittance becomes Ban due to the final voltage of +Vs, so a desired display can be achieved by applying a predetermined voltage only to the pixels that need to be rewritten.

Note that the drive voltage waveform shown in FIG. 4 is only one line;
It is not limited to this.

Effects of the Invention As described above, the present invention uses both the partial scanning method and the full scanning method, so even if the partial scanning location is biased to one part, the entire scanning electrode is scanned by the full scanning, so the scanning is always uniform. It is possible to maintain a high quality display.

Further, by performing full-scale scanning driving every time partial scanning driving is performed a predetermined number of times, the effective screen update time can be significantly reduced, and high display uniformity can be maintained. Furthermore, by performing partial scan driving normally and periodically performing full scan driving at predetermined time intervals, display uniformity can be maintained regardless of the display rewriting state.

In addition, since partial scan drive scans only when rewriting is necessary, the drive circuit of the display device can be stopped while the display content does not change, which has the ripple effect of reducing power consumption. .

[Brief explanation of drawings]

FIG. 1 is a scanning sequence diagram showing a method for driving a display panel according to an embodiment of the present invention, FIG. 2 is a block diagram showing a schematic configuration of a display device according to an embodiment of the present invention, and FIG. FIG. 4 is a block diagram showing another configuration of the mode switching signal generation circuit in a display device according to another embodiment, and FIG. A graph showing the drive voltage waveform diagram for rewriting and the optical response of pixels, Figure 5 is a schematic diagram showing the electrodes of a matrix panel, and Figure 6 shows a conventional method of driving a display panel using a ferroelectric liquid crystal panel. FIG. 3 is a scanning sequence diagram. Ts...Writing period, 20...Data memory, 21...Scanning mode switching circuit,
22... Memory control circuit, 23... Comparison circuit, 24... Data control circuit, 25...
...Driver control circuit, 26...Scanning driver, 27...Signal driver, 2nd...
Display panel, 29... Drive voltage source, 30...
...Mode switching, switching signal generation circuit, 30a...
...Counter, 30b...Timer, 41...
...Write voltage waveform of OFF, 42...
ON write voltage waveform, 43...bias voltage, R1, R2,..., Rm...scanning electrode, CI, C2,..., Cn.・・・・・・
signal electrode.

Claims (7)

[Claims] (1) In a matrix-type display panel whose optical characteristics exhibit bistability with respect to an applied electric field, a partial scanning method updates the display by applying a predetermined voltage only to pixels that require rewriting, and a partial scanning method that updates the display by applying a predetermined voltage only to pixels that require rewriting. A method for driving a display panel, characterized in that a desired display is performed by using a full-surface scanning method in which the display is updated by scanning the entire surface of the display panel and applying a predetermined voltage only when the following occurs. (2) The method for driving a display panel according to claim (1), wherein the matrix type display panel uses ferroelectric liquid crystal. (3) Rewriting required a matrix-type display panel whose optical properties showed bistability with respect to an applied electric field, a partial scan control means that updated the display by scanning only the scanning electrodes that required rewriting. The display panel includes a full scanning control unit that scans the entire surface of the display panel to update the display only when the display panel is displayed, and a selection unit that switches between the partial scanning control unit and the full scanning control unit, and according to a predetermined rule, the partial scanning control unit and the full-scale scanning control means to drive the display panel. (4) The display device according to claim 3, wherein the display panel is driven by the full scan control means every time the display panel is driven a predetermined number of times by the partial scan control means. (5) Claim (3) or (4) characterized in that the matrix type display panel uses ferroelectric liquid crystal.
). (6) A matrix-type display panel whose optical characteristics exhibit bistability with respect to an applied electric field, a partial scan control means that updates the display by scanning only the scan electrodes that need to be rewritten, and a display panel that scans the entire surface of the display panel. and a selection means for switching between the partial scan control means and the full-scale update control means, and the display panel is driven by the full-scale update control means at predetermined intervals. A display device characterized by: (7) The display device according to claim (6), wherein the matrix type display panel uses ferroelectric liquid crystal.