JP2801218B2 - Display device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device having an information processing device, and more particularly, to a display device using a ferroelectric liquid crystal having a memory property.

(Prior art)

2. Description of the Related Art Conventionally, a refresh scan type CRT is mainly used as a computer terminal display device, and a vector scan type CRT partially having a memory property is used for a large and high definition display for CAD. After displaying the vector scan type CRT once, the next screen is not updated until the screen is erased, so the cursor movement display, the information display from the pointing device, the movement display of the mouse and other icons, the display of characters It is not suitable for real-time man-machine interface display devices for editing and displaying sentences (insertion, deletion, movement, copying, etc.). On the other hand, in the case of a refresh-scan CRT, a refresh cycle of 60 Hz or more is required as a frame frequency to prevent flicker (screen flicker), and the visibility of moving information (moving icons) on the screen is required. In order to improve the performance, a non-interlaced method is used (TV is an interlaced method with a 60 Hz field frequency and a 30 Hz frame frequency in terms of simplification of a moving image display and a drive control system). Therefore, the higher the display resolution, the larger the display device, the higher the power required, the larger the drive control, and the higher the cost.

In recent years, flat display panels have appeared
This is due to the inconvenience of increasing the size and power of CRTs.

Currently, there are several types of flat display panels. For example, a high time-division driving method (STN) for twisted nematic liquid crystal, a method (N
TN) or plasma display method, the image data transfer method uses the same method as CRT, and the screen update method uses a non-interlace method with a frame frequency of 60 Hz or more. 40 total lines
No large flat display panels from 0 to 480 or more than 1000 have been obtained. The reason is that these display panels do not have a memory property in terms of the driving principle, so that a refresh cycle of a frame frequency of 60 Hz or more is required in order to prevent flicker, and therefore, one horizontal scanning time is 10 to 50 μsec or less. , And no good contrast can be obtained.

The ferroelectric liquid crystal display device can display a large screen and a high-definition display far exceeding the above-mentioned display device, but because of its low frame frequency drive, the display of the man-machine interface as described above is performed. In order to cope with the device, a partial rewriting scanning (scanning only scanning lines in a rewriting area) system utilizing a memory property is required. This partial rewriting scanning method is described, for example, in U.S. Pat.
It is clarified in the official gazette.

In particular, in the ferroelectric liquid crystal display device, the above-described partial rewriting scanning method is suitable for moving display of a mouse or a cursor, scrolling display of a multi-window, etc., but partial rewriting scanning of two different areas at the same time. In the case of partial rewriting scanning by specifying the partial rewriting scanning start address and end address, it is not possible to move and display the mouse or cursor during multi-window scroll display. there were. For example, when the scroll display of the window and the display of the pointing device are given and the movement is assumed,
First, even if a partial rewrite scan request for window scroll display is generated and the pointing device moves after the partial rewrite scan of the display panel is started,
Since the rewriting scan of the pointing device cannot be started until the scanning of the last scan line address of the window is completed, the pointing device moves discontinuously according to the size of the window (the number of partial rewrite scan lines). As a result, there is a problem that the moving display is obviously unnatural.

[Summary of the Invention]

An object of the present invention is to provide a display device capable of displaying images while maintaining real-time operability as a man-machine interface.

The present invention provides: a. Display means for displaying display contents on a display screen according to image information by scanning drive of a scan electrode and synchronous drive of an information electrode; b. A plurality of different image types (hereinafter referred to as “graphics”). An event))-a display request is generated for each of an item for displaying a moving image such as a moving cursor image and an item for displaying a scrolling image-and the image information of the image information generated based on the display request is generated. Among them, image information for rewriting a part of the display content in the display screen to another display content is generated, and the unaltered image information corresponding to the other part in the display screen among the image information is transferred. Instead, the changed image information corresponding to a part of the display screen is transferred, and the partial rewriting that is driven by scanning the scanning electrode designated by only the transferred image information is performed. First control means for controlling the display means so that a scan drive is performed; and c. At least two different graphic events among the plurality of graphic events are displayed by the partial rewrite scan drive. When screen rewriting is specified to be performed, and a display request based on the two different graphic events occurs at the same time, during transfer of image information generated based on one of the graphic events, The transfer priority between the one graphic event and the other graphic event is specified so that the transfer of image information generated based on the graphic event is interrupted. The partial rewriting scan drive according to the display request generated to display is performed, and during the execution of the scan drive, As not perform a partial rewriting scanning drive according to square display request, the display device is characterized in having a second control means for controlling said first control means.

(Detailed description of embodiments of the invention)

FIG. 1 is a block diagram of a ferroelectric liquid crystal display device 101 and a graphics controller 102 provided on a main device such as a personal computer as a supply source of display information. FIG. 2 is a communication timing chart of image information. The display panel 103 has a scanning electrode 1120
This is one in which 1280 information electrodes are arranged in a matrix and ferroelectric liquid crystal is sealed in two glass plates that have been subjected to alignment treatment. The scanning lines are scanning line driving circuits 104, and the information lines are information. Each is connected to the line drive circuit 105.

Hereinafter, the operation will be described with reference to the drawings. The graphics controller 102 converts the scanning line address information for specifying the scanning electrodes and the image information (PD0 to PD3) on the scanning line specified by the address information into the display driving circuit (the scanning line driving circuit 104 (Composed by the line drive circuit 105). In this embodiment, since the image information having the scanning line address information and the display information is transferred through the same transmission line, the two types of information must be distinguished. The signal for this identification is AH / DL,
When H / DL signal is at the Hi level, it indicates that the scanning line address information, when the L ₀ level, indicating a display information.

The scanning line address information is extracted from the image information transferred as the image information PD0 to PD3 on the drive control circuit 111 side in the liquid crystal display device 101, and then scanned in accordance with the timing for driving the designated scanning line. Output to the line drive circuit 104. This scanning line address information is stored in the scanning line driving circuit 10.
4 is input to the decoder 106, and the designated scan electrode of the display panel 103 is supplied to the scan signal generation circuit 1 via the decoder 106.
07, while the display information is
It is led to the shift register 108 in 5 and 4 in the transfer clock
It is shifted on a pixel-by-pixel basis. When the shift for one scanning line in the horizontal direction is completed by the shift register 108, the display information for 1280 pixels is transferred to the line memory 109 provided therewith and stored for one horizontal scanning period to generate an information signal. circuit
From 110, it is output to each information electrode as a display information signal.

In this embodiment, the driving of the display panel 103 in the liquid crystal display device 101 and the generation of the scanning line address information and the display information in the graphics controller 102 are performed asynchronously. /Ten
It is necessary to synchronize 2). The signal that governs this synchronization is S
YNC, which is generated by the drive control circuit 111 in the liquid crystal display device 101 every horizontal scanning period. The graphics controller 102 constantly monitors the SYNC signal, and the SYNC signal is low.
If the level is ₀ , image information is transferred. Conversely, at the Hi level, no transfer is performed after transfer of image information for one horizontal scanning line is completed. That is, in FIG. 2, the the graphics controller 102 side SYNC signal when detecting that became L ₀ level, immediately the AH / DL signal to Hi level to start the transfer of image information of one horizontal scan line . The drive control circuit 111 in the liquid crystal display device 101 sets the SYNC signal to the Hi level during the image information transfer period. Drive control circuit after writing to the display panel 103 has ended through a predetermined one horizontal scanning period (FLCD controller) 111, returned again to the L ₀ level SYNC signal, can receive the image information of the next scan line .

FIG. 3 shows a display screen 3 when a plurality of display requests are made in a multi-window and multi-task system.

Display request 31; Mouse font moves diagonally smoothly Display request 32; A window is selected as the active screen and the part that overlaps with the previous window that was already displayed is displayed on the front Display request 33; Input from the keyboard Display request 34; move the previous character that was already displayed (character movement in the direction of the arrow) display request 35; change the display of the overlap area display request 36; display a non-active window display request 37 ; Scroll display of non-active window display request 38; full scan display Table 1 below shows the display priorities of the graphic events corresponding to the display requests 31 to 38 described above.

In the table, "partial rewriting" is a driving method that scans only the scanning lines of the partial rewriting area, and "multi-field refresh" is mouse interlace scanning by N fields (N = 2, 4, 8,... ^2N ) scanning. This is a one-frame scanning method (a driving method described in Japanese Patent Application No. 62-287172). The “display priority” is a rank specified in advance. In this embodiment, the operability of the man-machine interface is emphasized, and the graphic event 31 (mouse movement display) is set as the highest priority display at the highest level. Then, the priority display order of the graphic events 33, 34, 37 and 38 was set.
The "drawing operation" indicates an internal drawing operation of the graphics processor.

The moving display of the mouse has the highest display priority because the purpose of the pointing device must reflect the intention of the operator most quickly (in real time) on the computer. The next most important thing is character input from the keyboard, which is usually buffered, and although real-time is high, it is lower than a mouse. As a result of this key input, the screen update in the window does not necessarily have to be at the same time as the key input, and the row in which the key is input has a higher priority. Scrolling in other windows and display of overlap area It depends on system settings, but it can of course occur under multitasking, where line scrolling is performed under the active window. It is said that.

In the present invention, the image display control program shown in FIG. 4 receives image display requests 31 to 38 from the outside via the communication means shown in the figure, and sends the request to the ferroelectric liquid crystal display device (FLCD) 101 shown in FIG. Has the function of controlling the transfer of image information. When at least one request for rewriting the already displayed content is made at least once, the image display control program assigns the rewriting area and the rendering process to the VRAM (image information storage memory) necessary for the rewriting to the display priority. The image information to be sent to the display device 101 can be selected and transferred while synchronizing with the display device 101.

The communication procedure shown in FIG. 4 includes a window manager.
41 and Operating System (OS) 42 are used. Operating System (OS) 42
Microsoft "MS-DOS" (trade name), "XENIX" (trade name), AT & T "UNIX" (trade name) and Microsoft "OS / 2" (trade name) As the window manager 41, "MS-Windows ver 1.03" or "ve
r 2.0 ”(both product names), Microsoft Corporation“ O ”
S / 2Presentation Manager "(trade name), Public
The domain "X-Window" or "DEC-Window" (trade name) of Digital Equipment Corporation of the United States is used. The illustrated event imilator 43 includes a set of “MS-DOS & MS-Windows” and “UNIX & X-Window”
Etc. can be used.

The partial rewriting used in the present invention scans only the scanning lines in the partial rewriting area. Since the FLCD has a memory property, high-speed partial rewriting can be performed. In the present invention, it is assumed that it is not instantaneous that the computer system rewrites display information at high speed within the entire screen. For example, information from a pointing device (= mouse or the like) may be displayed at a speed of 30 Hz or less, and at a speed higher than that, human eyes cannot follow. Similarly, the smooth scrolling (scrolling per line), which requires the fastest display of the display, is not noticeable if it is too fast. Rather, in practice, scrolling is often performed not in units of lines but in units of characters or blocks. In computer systems, scrolling is often used when editing programs and sentences, and its purpose is to move from one line to another rather than to smooth scrolling,
There is no practical problem if 10 lines / sec in line units.

If the mouse font is composed of 32 × 32 dots, and if the partial rewriting scan for the FLCD is driven in a non-interlace manner, this can be simply calculated as follows: [Expression 1] 32 lines × 100 μsec / line = 3.2 msec ≒ 312 Hz Response speed becomes possible.

Performing one line / line scroll at 10 lines / sec is equivalent to a non-interlaced image update speed of a frequency of 10 Hz.
Strictly speaking, flicker should occur at a frequency of 10 Hz. However, since the entire screen moves on a line-by-line basis, a change in information is recognized more greatly than flickering, so that there is no actual problem. Therefore, when scrolling in units of rows, the number of scanning lines that can be driven non-interlaced is [Equation 2] (1/10 Hz) / 100 μsec = 1000 (lines).

The present invention relates to a data format and a SY as image information having scanning line address information shown in FIG. 1 and FIG.
By using a communication synchronizing means using NC signals, a liquid crystal display device based on a partial rewriting scanning algorithm on the graphics controller side described below is realized.

The generation of the image information is performed by the graphics controller 102 of the main unit, and is transferred to the display panel 103 according to the signal transfer means shown in FIGS. The graphics controller 102 manages and communicates image information between the host CPU 113 and the liquid crystal display device 101 with a CPU (Central Processing Unit, hereinafter abbreviated as GCPU 112) and a VRAM (memory for storing image information) 114 at the core. And
The control method of the present invention is mainly realized on the graphics controller 102.

FIG. 9 is a partial rewriting algorithm according to the present invention. The image information (pointing device, pop-up menu, etc.) that needs to be partially rewritten by the ferroelectric liquid crystal display device 101 is registered in the GCPU 112 in advance, and the host C
When it is determined that partial rewriting is necessary for the information from the PU 113, the process proceeds to a partial rewriting routine. In the partial rewriting routine, first, the scan line address and the number of scan lines immediately before branching are saved in a register prepared in the GCPU 112 in advance. The GCPU 112 manages a storage start address and an expansion area when the image information that needs partial rewriting from the host CPU 113 is stored in the VRAM 114 of the graphics controller 102, and the display device 101 performs the first rewriting scan for partial rewriting. The image information is transferred to the liquid crystal display device 101 based on the signal transfer method shown in FIGS.

Here, in order to form a data format of image information having scanning line address information, the scanning line address information is VR
Mapping was performed on AM114 as shown in FIG. VRAM114 2
One is assigned to the scanning line address information area and the other is assigned to the display information area. As the information on the VRAM 114 corresponds to the pixel of the display panel 1: 1,
One line of image information is arranged horizontally, and scanning line address information is embedded in the head (left end) of the one line of image information in advance. The GCPU 112 implements a data format of image information having scanning line address information by reading information from the left end of the VRAM 114 in units of one line and sending the information to the liquid crystal display device 101.

The transfer to the liquid crystal display device 101 is performed line by line while the GCPU 112 constantly monitors the scanning line address information mapped on the VRAM 114 and the number of transfer scanning lines. Each time one line is transferred, it is determined whether another partial rewrite request has occurred. If a second partial rewrite request has been generated at that time, and the image information associated with the partial rewrite request is lower-order (lower display priority) information than the currently-processed partial rewrite information, the next partial rewrite request remains unchanged. Scan line line transfer, and conversely, if it is the higher one, the first
The data transfer of the partial rewriting information is interrupted, and the flow branches to a second partial rewriting routine. In the second partial rewriting routine, similarly to the first partial rewriting routine, the scan line address and the number of scan lines immediately before branching are saved in a register prepared in advance in the GCPU 112. After that, the second partial rewrite information is stored in the VRAM 114, and the information is sent to the display device 101 line by line. At this time, the presence / absence of a higher partial rewrite request is checked for each line. If there is no request, image information for the entire area of the second partial rewrite is transferred, and then the second partial rewrite is performed. The process returns to the first partial rewriting routine based on the scanning line address and the number of scanning lines which have been saved before entering. In the first partial rewrite routine, the transfer of the remaining image data is continued while checking again whether a higher-order partial rewrite request has been generated for each line, and is first saved after the transfer of all image information. The scanning line address and the number of scanning lines are returned, and the process returns to the normal refresh routine.

FIG. 11 shows a multi-window display screen 11 according to the present invention.
This is an example of 0. Window 1 is a screen that displays a certain tally result in a pie chart. Window 2 is a screen representing the tabulated result of window 1 in a table. Window 3 is window 1
The screen which expressed the total result of the bar graph. Window 4 is a screen during document creation. Reference numeral 5 denotes a pointing device mouse. It is assumed that the windows 1 to 3 are stationary and the mouse 5 moves while performing document editing operations such as smooth scrolling, insertion / deletion of words / phrases, and area movement in the window 4. Mouse movement is ferroelectric liquid crystal display 101
Is image information that requires partial rewriting scanning. By the way, when 1120 full screens are scanned in one horizontal scanning time = 80 μs, the frame frequency becomes about 10 Hz, and cannot follow normal mouse movement (≧ 30 Hz) at all. By applying the algorithm of the present invention and setting the priority of the partial rewriting by moving the mouse higher than the document editing work in the window 4, even if the mouse moves during the scrolling operation, the mouse part is immediately changed. Branch to the rewrite routine,
You can enter the mouse writing operation. At this time, the time required for branching to the partial rewriting routine of the mouse is within one horizontal scanning time at the longest. For example, as clarified in the above equation (1), the font size of the mouse is set to 32.
If it is × 32 dots, the time required to write the mouse on the display panel 103 is 3.2 msec, and the scroll operation is stopped during this time, but the time is short enough and the effect on the scroll speed is not affected. rare. After writing the mouse, the process returns to the partial rewriting scan of the window 4. When the mouse moves again, the process immediately branches to the partial rewriting routine of the mouse and enters the mouse writing operation.
As described above, in a display driven by a low frame frequency having a memory characteristic such as the ferroelectric liquid crystal display device 101, the priority of the partial rewriting is set in such a manner that the movement of the pointing device (mouse) is most important. This makes it possible to realize a display function such as multi-window multi-task.

FIG. 5 is a block diagram of the graphics controller 102, FIG. 6 is a block diagram of the digital interface, and FIGS. 7 and 8 are timing charts of information transfer.

The major difference between the graphics controller 102 used in the present invention and the conventional graphics controller 102 is that the graphics processor 501 has its own dedicated system memory 502,
It not only manages the RAM 503 and ROM 504, but also executes and manages drawing commands to the RAM 503, and can independently program information transfer from the digital interface 505 to the FLCD controller and management of the FLCD driving method. .

First, the digital interface 505 in FIG.
External synchronization signal from D controller 111
While synchronizing with the drive circuits 104 and 105 of the display panel 103 by ▼ / ▲ ▼, 4bits / cl
The information in VRAM is sent as ock (clock = data transfer clock). FIG. 7 shows the timing when the FLCD rewrites the entire screen, and the parameters in the figure are the same as those in the timing chart at the time of information transfer in FIG. First, 1
The transfer of the image information for the line is indicated by ▲ ▼ in FIG.
Becomes active (low level in this case). Set ▲ ▼ to low for FLCD controller 1
Reference numeral 11 denotes an information request on the panel 103 side. This panel 103
The information request on the side is the graphics processor 501 in FIG.
, And is internally processed at the timing shown in FIG. In the timing chart of FIG. 8, ▲ ▼ of the information request on the panel 103 side is sampled for one cycle of the external video clock (CLKOUT) from the outside (in other words, the low period of VCLK). (In this case, the VCLK is actually input to the graphics processor 501, and the processor 501 is designed to perform sampling during the low period.) Then, after 2.5 clocks of VCLK, the horizontal The counter HCOUNT is cleared, and the parameters HESYNC and HEBLNK shown in FIG. 7 are programmed to immediately before HCOUNT = 1.
▲ ▼ in the figure is disabled (high),
In the circuit of FIG. 6, as shown in FIG. 8, after half a clock of VCLK, DATEN becomes active (high).
After clocking, the next one line of data is 4 bits from VRAM
Every time, it is transferred to the FLCD controller 111.

As shown in the lower right part of FIG. 8, the line information to be transferred in this case is obtained by first sending scanning line address information (ie, corresponding to the scanning line No.) every 4 bits, Is sent for one line. FLCD in this case
The controller 111 uses the AH / DL signal to identify the scanning line address information and the information line address information. When the AH / DL signal is high, it indicates the scanning line address information, and when it is low, the display information is recognized. Therefore, the FLCD selects a scanning line according to the scanning line address information and writes the display information. Therefore, when the scanning line address information from the graphics controller of FIG. The FLCD is driven in an interlace manner when increasing every other, and in a multi-interlace manner when increasing every m lines. Therefore, the display driving method can be controlled.

An FLCD generally requires a driving time of about 100 μsec for one scanning line. Suppose now that the driving time for one scan line is 100 μsec.
Assuming that the lowest frequency at which flicker does not occur is 30 Hz, in the non-interlace drive method of this FLCD, [Equation 3] (1/30 Hz) / 100 μsec ≒ 333 (book) In the interlace drive method, [Equation 4] (1 / 30Hz) × 2 / 100μsec ≒ 666 (lines) In the case of m multi-interlace, scan (scan / drive) the scanning line of (Equation 5) (1 / 30Hz) × m / 100μsec ≒ 333 × m (lines) Does not produce flicker as a still image. According to the experiment of the present invention, m = 32
However, it was confirmed that flicker did not occur. That is, [Equation 6] The display panel 103 having (1/30 Hz) × 32/100 μsec ≒ 333 × 32 = 10656 (lines) can be displayed without flicker, which is exactly the same as the conventional flat display panel. The high-definition that is not possible is numerically possible.

The "74AS161A", "74AS74", and "74ALS2"
57, 74ALS878, and 74AS257 are I
The C number represents the pin number, and the numbers in the figure each represent the pin number.

FIG. 12 is an example of a driving waveform of the multi-interlace driving method used in the present invention.

FIG. 12 shows (4M-3) field F _4M-3 , (4M-2) field F _4F-2 , (4M-1) field F _4M-1 and 4M field F _4M (where 1 field is One vertical scanning period, where M = 1, 2, 3,..., And a scan selection signal S _4n-3 (n = 1, 2, 3,...), 4n applied to the 4n-3rd scan electrode
A scan selection signal S _4n-2 , 4n- applied to the second scan electrode
A scan selection signal _S4n-1 applied to the first scan electrode and a scan selection signal _S4n applied to the 4nth scan electrode are shown. According to FIG. 12, the scanning selection signal S _4n-3 is (4M−
3) Field F _4M-3 and (4M-1) Field F _4M-1 (M
= 1, 2, 3,...) (Voltage polarities based on the voltage of the scanning non-selection signal) are opposite to each other, and the (4M-2) fields F _4M-2 and 4M Scanning is not performed in the field _F4M , and the same applies to the scan selection signal _S4n-1 . Further, the scanning selection signals S _4n-3 and S _4n-1 applied within one field period have different voltage waveforms, and the voltage polarities of the same phase are opposite to each other.

Similarly, the scan selection signal signal S _4n-2 has the opposite voltage polarity (voltage polarity based on the voltage of the scan non-selection signal) in the same phase of the (4M-2) field F _4M-2 and the 4M field F _4M. Polarity and (4M-3) field F
_{The 4M-3} and (4M-1) fields F _4M-1 do not scan, and the scanning selection signal S _4n is also the same. Further, the scanning selection signal S applied within one field period
_4n-2 and S _4n have different voltage waveforms from each other,
The voltage polarities of the same phase are opposite to each other.

In the scanning drive waveform example of FIG. 12, a third phase is provided for stopping the screen all at once (for example, applying a voltage 0 to all the pixels constituting the screen all at once). The third phase is set to voltage 0 (the same level as the voltage of the scanning non-selection signal).

According to FIG. 12, the (4M-3) th field F
_The information signal applied to the signal electrode in _4M-3 is a white signal (in combination with the scanning selection signal _S4M-3 , the ferroelectric liquid crystal in the second phase is applied to the scanning selection signal _S4n-3) . A voltage ± V ₀ smaller than the threshold voltage of the ferroelectric liquid crystal is applied to the pixels by combining the voltage of 3V ₀ exceeding the threshold voltage to form a white pixel and the holding signal (scan selection signal S _4n-3 ). Is applied)
Is selectively applied, and a black signal (a voltage exceeding the threshold voltage of the ferroelectric liquid crystal in the second phase due to synthesis with the scanning selection signal _S4n-1) is applied to the scanning selection signal _S4n-1 . the synthesis of -3 V ₀ is applied to form a black pixel) and the hold signal (scanning selection signal S _4n-1, the voltage ± V ₀ smaller than the ferroelectric liquid crystal in the pixel is applied) and selective Is applied. Since the scanning non-selection signal is applied to the (4n-2) th and (4n) th scanning electrodes, the information signal is applied as it is.

Following the writing of the above (4M-3) field F _4M-3 (4
M-2) In the field _F4M-2 , as an information signal to be applied to the signal electrode, a black signal and a holding signal similar to those described above are selectively applied to the scanning selection signal _S4n-2 , A white signal and a holding signal similar to those described above are selectively applied to the scanning selection signal _S4n . Since the scanning non-selection signal is applied to the (4n-3) th and (4n-1) th scanning electrodes, the information signal is applied as it is.

In the (4M-1) field F _4M-1 following the (4M-2) field F _4M-2 , the information signal applied to the signal electrode is the same as described above for the scanning selection signal S _4n-3 . Black signal and the holding signal are selectively applied, and the scanning selection signal S _4n-1
, A white signal and a holding signal similar to those described above are selectively applied. Since the scanning non-selection signal is applied to the (4n-2) th and 4nth scanning electrodes, the information signal is applied as it is.

The information signal applied to the signal electrode in the 4M field F _4M following the (4M-1) field F _4M-1 is the scanning selection signal S
_{For 4n-2} , the same black signal and holding signal as described above are selectively applied, and for the scanning selection signal _S4n , the same white signal and holding signal as described above are selectively applied. Is done. Since the scanning non-selection signal is applied to the (4n-3) th and (4n-1) th scanning electrodes, the information signal is applied as it is.

FIGS. 13 (A), (B) and (C) show timing charts when the display state shown in FIG. 13 (D) is written by the drive waveforms shown in FIG. Fig. 13 (D)
In the figure, ○ indicates a white pixel, and ● indicates a black pixel. or,
I ₁ -S ₁ in FIG. 13 (B) is a time series waveform of the voltage applied to the intersection of the scanning electrode S ₁ and the signal electrode I ₁ . I ₂ −S ₁ is a time-series waveform of the voltage applied to the intersection of the scanning electrode S ₁ and the signal electrode I ₂ . Similarly, I ₁ −S ₂ is the scanning electrode S ₂ and the signal electrode I ₁
5 is a time-series waveform of a voltage applied to an intersection with the above. I ₂ −S ₂
Also is a time-series waveform of the voltage applied to the intersection between the scanning electrode S ₂ and the signal electrode I _2, the present invention is not limited to the driving waveform example described above, for example, four every scanning line, Every 5th, every 6th,
Scanning can be performed every seven lines, preferably every eight or more lines. The scanning selection signal may have a waveform whose polarity is inverted for each field as shown in FIG. 12, or may have the same waveform for each field.

FIG. 14 schematically illustrates an example of a ferroelectric liquid crystal cell. 141a and 141b are substrates (glass plates) coated with a transparent electrode such as In ₂ O ₃ , SnO ₂ or ITO (indium-tein-oxide), between which the liquid crystal molecular layer 142 is perpendicular to the glass surface The liquid crystal of the SmC ^* phase which is oriented likewise is sealed. A bold line 143 represents a liquid crystal molecule, and the liquid crystal molecule 143 has a dipole moment (P⊥) 144 in a direction perpendicular to the molecule. Substrate 141a
When a voltage equal to or higher than a certain threshold is applied between the electrodes on the electrodes 141b and 141b, the helical structure of the liquid crystal molecules 143 is released, and the orientation direction of the liquid crystal molecules 143 is changed so that all dipole moments (P⊥) 144 are directed to the electric field direction. be able to. The liquid crystal molecules 143 have an elongated shape, exhibit refractive index anisotropy in the major axis direction and the minor axis direction, and therefore, for example, if a polarizer arranged in a crossed Nicols positional relationship above and below the glass surface is placed. ,
It is easily understood that the liquid crystal optical modulation element whose optical characteristics change depending on the voltage application polarity. Further, when the thickness of the liquid crystal cell is made sufficiently thin (for example, 1 μm), the helical structure of the liquid crystal molecules is released even when no electric field is applied as shown in FIG. 15, and the dipole moment Pa or Pb of the liquid crystal molecule becomes It takes either the upward (154a) or downward (154b) state. When an electric field Ea or Eb having a different polarity or more than a certain threshold is applied to such a cell for a predetermined period of time as shown in FIG. The orientation is changed, and the liquid crystal molecules are accordingly aligned in one of the first stable state 153a and the second stable state 153b.

There are two advantages of using such a ferroelectric liquid crystal as the optical modulation element. First, the response speed is extremely fast, and second, the orientation of the liquid crystal molecules has a bistable state. The second point will be described with reference to FIG. 15, for example. When an electric field Ea is applied, the liquid crystal molecules are oriented to a first stable state 153a. This state is stable even when the electric field is turned off. When the electric field Eb in the opposite direction is applied, the liquid crystal molecules are brought into the second stable state 15.
Orientation to 3b changes the orientation of the molecule, but it remains in this state even after the electric field is turned off. As long as the applied electric field Ea does not exceed a certain threshold value, each orientation state is maintained. In order to effectively realize such a high response speed and bistability, it is preferable that the cell is as thin as possible, generally 0.5 μm to 20 μm, particularly 1 μm to
5μ is suitable.

〔The invention's effect〕

As described above, in the partial rewriting scan for a display device having a memory property such as a ferroelectric liquid crystal display device, the area of the partial rewrite is defined by the rewrite start scanning line address and the number of rewrite scan lines, and the image data to be transferred is defined. In the case where another partial rewriting request occurs during one partial rewriting process, the priority of the display information associated with the partial rewriting request is determined, and processing with a higher priority (for example, Advanced display application software such as cursor, pointing device movement, multi-window multi-tasking, etc., even in a display driven by a low frame frequency, by performing partial rewriting scanning in order from the movement of the pointing device). Can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a liquid crystal display device and a graphics controller, and FIG. 2 is a timing chart of image information communication between the liquid crystal display device and the graphics controller. FIG. 3 is a display screen diagram schematically showing a plurality of graphic events. FIG. 4 is a block diagram of a display control program used in the present invention. Fifth
FIG. 6 is a block diagram of a graphics controller used in the present invention, and FIG. 6 is a block diagram of a digital interface. FIG. 7 is an interface timing chart for the display driving device used in the present invention.
FIG. 8 is an interface timing chart for the FLCD controller. FIG. 9 is a sequence diagram showing an algorithm for partial rewriting used in the present invention. FIG. 10 is an explanatory diagram showing data mapping of scanning line address information and display information on a VRAM used in the present invention. FIG. 11 is a diagram of a multi-window display screen in this embodiment. FIGS. 12 (A) and (B) are driving waveform diagrams used in the present invention, FIGS. 13 (A) to (C) are timing charts thereof, and FIG. 13 (D) is a display of pixels at that time. It is a schematic diagram which shows a state. FIG. 14 and FIG. 15 are perspective views of the ferroelectric liquid crystal cell used in the present invention.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-257197 (JP, A) JP-A-63-63093 (JP, A) JP-A-60-130794 (JP, A) 53794 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) G09G 3/36 G02F 1/133 G09G 3/20 G09G 5/36 G09G 1/02 G06F 3/14 350

Claims (3)

(57) [Claims] A. Display means for displaying display contents on a display screen in accordance with image information by scanning drive of a scan electrode and synchronous drive of an information electrode; b. Display for each of a plurality of different image types. Generating a request, of the image information generated based on the display request, generating image information for rewriting a part of the display content in the display screen to another display content, among the image information,
Unchanged image information corresponding to another part of the display screen is not transferred, and changed image information corresponding to a part of the display screen is transferred, and is specified only by the transferred image information. As the partial rewriting scanning drive, which is driven by scanning the scanning electrodes, is performed,
First control means for controlling the display means, and c. At least two different image types among the plurality of image types are designated such that rewriting of a display screen by the partial rewriting scanning drive is executed. And when the display requests based on the two different image events occur simultaneously, during the transfer of the image information generated based on one of the image events,
The transfer priority between the one image item and the other image item is specified so that the transfer of the image information generated based on the other image item is interrupted. A partial rewriting scan drive according to a display request generated for displaying is executed, and during the execution of the scan drive, the first control means for controlling the first control means so as not to execute a partial rewrite scan drive according to the other display request. 2. A display device comprising: 2. The display device according to claim 1, wherein said display means is an element having a ferroelectric liquid crystal. 3. The display device according to claim 1, wherein said one image item is an item for displaying a moving image, and the other image item is an item for displaying a scroll image in a window.