JP2633191B2 - Display control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display control device.

[0002]

2. Description of the Related Art A CRT (Card Ray Tube) for forming an image using the afterglow characteristics of a phosphor and a T for forming an image using a transmitted light amount characteristic corresponding to an effective driving voltage value.
N (twisted nematic) type LCD (liquid crystal element)
In view of the display principle, it is necessary to keep the frame frequency, which is one screen forming frequency, at a certain value or more. It is generally 30
Hz or more, and this frame frequency can be expressed by the reciprocal of the product of the number of scanning lines constituting the display unit and the horizontal scanning time for scanning the same. At present, as a scanning method, an interlace method and a non-interlace method are known. Other methods are limited to the pairing method and the LCD, but have been proposed and put to practical use, such as a simultaneous parallel scanning method in which a fraction is divided. In the NTSC standard, two fields / frame frequency 30 Hz /
With frame interlacing, horizontal scanning time is about 6
This is 3.5 μsec, and the number of scanning lines is about 480 (the number of effective display lines). The TN type LCD employs a non-interlaced system with 200 to 400 scanning lines and a frame frequency of 30 Hz or more. In addition, the CRT has a frame frequency of 40-60 Hz separately from the NTSC standard.
A non-interlaced system is also used, and the number of scanning lines is about 200 to 1,000.

Here, let us consider driving a CRT and a TN type LCD having 1920 (vertical) (scanning lines) × 2560 pixels in the horizontal direction. When the frame frequency is 30 Hz and the interlace method is used, the horizontal scanning time is about 17.5 μm.
sec, and the horizontal dot clock frequency is about 147
MHz (the horizontal retrace time in the CRT is not taken into account). In the case of a CRT, the horizontal dot clock frequency of 147 MHz has a very high beam scanning speed, which greatly exceeds the current maximum electron beam modulation frequency of an electron gun in a picture tube, so that an image can be accurately formed even when scanning at 17.5 μsec. Can not. 192 in case of TN type LCD
Zero scanning line drive corresponds to the duty ratio 1920, and the current maximum duty ratio greatly exceeds about 400, and the display cannot be performed. Considering that the horizontal scanning time is set to a realistic value and driving is performed, the frame frequency is now 3
The frequency is lower than 0 Hz, so that the scanning state is visually recognized or flickering occurs, and display quality is significantly impaired. As described above, at present, the increase in the screen size and the density of the CRT and the TN type LCD have reached a plateau because the number of scanning lines cannot be sufficiently increased due to the display principle and the restriction of the driving elements.

In recent years, Clark and Lagerwell have disclosed a ferroelectric liquid crystal device having high-speed response and memory properties in US Pat. No. 4,367,924.

This ferroelectric liquid crystal device generally has a chiral smectic C phase (SmC ^* ) in a specific temperature range.
Or an H phase (SmH ^* ), in which state one of the first optical stable state and the second optical stable state is taken in response to an applied electric field and no electric field is applied. Has a property of maintaining its state, that is, has bistability, and has a quick response to a change in electric field, and is expected to be widely used as a high-speed and storage-type display element.

However, ferroelectric liquid crystal devices are generally difficult to have bistability as proposed by Clark et al. And tend to have a monostable state. Clark et al. Used an orientation control method by applying shear force by shearing or applying a magnetic field in order to realize permanent bistability, but from the viewpoint of production technology, as an orientation control method, A method in which a uniaxial orientation treatment such as a rubbing treatment or an oblique deposition treatment is applied to a base is advantageous. A ferroelectric liquid crystal element in which such a uniaxial alignment treatment is applied to a substrate to control the alignment may not produce permanent bistability. An alignment state that does not cause permanent bistability, a so-called monostable alignment state, is in a range from several msec to several hours.
It has the property that biaxial orientation when an electric field is applied changes to uniaxial orientation when no electric field is applied. For this reason, in the display device using this monostable ferroelectric liquid crystal element, the image written once is
There is a problem that the electric field disappears with the release of the electric field. In particular, at the time of multiplexing driving, the writing state of the pixels on the scanning lines that have not been accessed may gradually disappear.

In view of the above problem, a voltage signal that causes "black" and a voltage signal that causes "white" are selectively applied to the pixels on the selected scanning line to sequentially select the scanning line. When the period is set to one frame or one field, a driving method (refresh driving) in which writing is performed by repeating this period has been considered. By adopting such a refresh driving method, the fluctuation of the amount of transmitted light of the non-selected pixels is very small, and even when the frame frequency is lower than 30 Hz,
It was possible to eliminate the occurrence of the visual recognition of the writing scanning line (the scanning writing line has a higher luminance than other lines and can be easily visually recognized) and flickering. At this time, according to the study by the present inventors, it was confirmed that the same effect was obtained even at a frame frequency of about 5 Hz.

[0008] The above facts point out that the above-mentioned restrictions on the CRT and TN type LCDs, which must be driven at a frame frequency of 30 Hz or more, have caused the problems of large screen and high definition. It is effective for breaking at once.

[0009]

However, in the case where refresh driving is performed at a low frame frequency as described above, the display speed is low in order to perform a so-called moving image display such as smooth crawl or cursor movement on character editing or a graphics screen. Is slow, and the display performance may decrease.
For example, in a display device using a ferroelectric liquid crystal element, a display device capable of realizing a large screen and high definition far exceeding conventional display devices (CRT, TN type LCD, etc.) is used. -The frame frequency has become lower with higher definition, and as a result, the speed of smooth scrolling and cursor movement may become slower.

In recent years, for a large screen and a high-definition display, a method called a multi-window, in which a plurality of screens are overlapped and displayed in a display area, has become widespread. If so, the display quality of the background portion outside the window may be degraded.

[0011]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems, and in particular, to provide a stable still image display even in a display device using a ferroelectric liquid crystal element which easily exhibits monostability. The present invention provides a display device, a drive control device, and a display method for substantially speeding up moving image display such as cursor movement, smooth scrolling and multi-window display or video moving image display even under a low frame frequency (30 Hz or less). It is in.

A display control device according to the present invention comprises a display panel on which a plurality of scanning electrodes and a plurality of information electrodes are arranged in a matrix, a scanning electrode drive circuit for selecting the scanning electrodes, and an information signal applied to the information electrodes. A display control device for forming a display image on a display means having an information electrode driving circuit to be applied; and a refresher for sequentially selecting the plurality of scanning electrodes and repeatedly applying a signal to the plurality of information electrodes. A memory for storing information of all pixels displayed by driving, a means for changing a part of the information stored in the memory, and an address for selecting only a scan electrode corresponding to a pixel for which the changed information is to be displayed Means for generating a signal and an image information signal for rewriting a display image of the pixel, wherein only the scanning electrode selected by the address signal is selected and The scan electrode drive circuit and the information electrode drive circuit alternately perform the refresh drive period for performing the refresh drive and the partial rewrite period so that the partial rewrite operation for rewriting the image on the scan electrode does not continue beyond a predetermined period. And controlling the circuit.

[0013]

According to the present invention, when partial rewriting is repeatedly performed, a phenomenon in which the display quality of a portion that is not partially rewritten is reduced is prevented by inserting a refresh operation at a predetermined timing. In this way, even if the display screen is partially rewritten, the display quality of the background is maintained, and at the same time, the speed of rewriting the image is increased.

[0014]

FIG. 1 is a block diagram of a liquid crystal display device according to the present invention and a main unit for controlling driving. FIG. 2 shows a timing chart of the display information signal. The display panel 11 has scanning electrodes 12C (1920 lines) × information electrodes 13D (2560).
In the matrix structure of (1), a ferroelectric liquid crystal is sealed in the matrix structure, and a scan electrode drive circuit 12 is connected to the scan electrode 12C.
The information electrode drive circuit 13 is connected to the information electrode 13D. The scan electrode drive circuit 12 includes a decoder 12A and an output stage 12B.
The information electrode drive circuit 13 includes a shift register 13A, a line memory 13B, and an output stage 13C.

First, scan electrode address data designating scan electrode 12C and video data are divided into four signal lines PD0,
The data is output from the main unit 14 to the control circuit 15 through PD1, PD2 and PD3. In this embodiment, the scan electrode address data (A0, A1, A2, A3, A4, A5, A6,
A7, A8, A9, A10, A11) and video data (D
0, D1, D2, D3,... D2558, D2559) are transferred on the same transmission line of each of the signal lines PD0 to PD3, so that the scan electrode address data and the video data must be distinguished. In this example, A / D is provided as a signal for identification, and when this A / D signal is at a high level, it indicates that it is scan electrode address data.
When low level indicates that it is video data,
Each relationship is defined. Further, the A / D signal has a meaning as a signal for starting the transfer when the display information is transferred.

When the scan electrode address data is supplied to the scan electrode drive circuit 12 and the video data is supplied to the information electrode drive circuit 13, the scan electrode address data A0 to A11 and the video data D0 to D2559 are placed on the signal lines PD0 to PD3. Scan electrode address data A
A circuit for distributing 0 to A11 and video data D0 to D2559 or a circuit for extracting scan electrode address data A0 to A11 is required. This operation is performed by the control circuit 15. The control circuit 15 controls the signal lines PD0 to PD3.
The upper scan electrode address data A0 to A11 are extracted, temporarily stored, and output to the scan electrode drive circuit 12 during the horizontal scanning period when the designated scan electrode 12C is driven. The scan electrode address data A0 to A11 are input to a decoder 12A in the scan electrode drive circuit 12,
The scanning electrode 12C is selected through the decoder 12A.

On the other hand, the video data D0 to D2559 are inputted to the shift register 13A in the information electrode drive circuit 13, and are shifted every four pixels by the transfer clock CLK to obtain the number of pixels corresponding to the information electrodes 13D (2560). Video data D0 to D2559 are separated. Shift register 13
When the shift for one scanning line in the horizontal direction is completed at A, the video data D0 to D2559 on the shift register 13A for 2560 exposures are transferred to the line memory 13B and stored within the horizontal scanning period.

In this embodiment, the driving of the display panel 11 and the scan electrode address data A0 to
A11 and the generation of the video data D0 to D2559 are performed asynchronously.
And the main unit 14 need to be synchronized. This synchronization signal is a signal Sync, which is generated by the control circuit 15 every horizontal scanning.

The signal Sync performs an operation related to the A / D. The main unit 14 constantly monitors the Sync signal. If the Sync signal is at a low level, the main unit 14 transfers display information. If the Sync signal is at a high level, the main unit 14 transfers the display information for one horizontal scan after the transfer is completed. Do not do. That is, in FIG. 2, at the moment when the Sync signal goes low, the A / D signal goes high, and the control circuit 15 returns the Sync signal to high during the display information transfer period. Then, after one horizontal scanning time determined from the point A has passed (point B), the level is returned to the low level. If B
When the main unit 14 continuously transfers display information at the point, that is, when driving the next scan electrode, the A / D
The signal is set to the high level to start the transfer. In the present embodiment, since the refresh driving is performed, continuous driving is performed in a line-sequential manner.

The predetermined one horizontal scanning time is determined due to the characteristics of the ferroelectric liquid crystal and the driving method, and a desired application time is determined in consideration of various optimum driving conditions. , Which is defined as one horizontal scanning time. In this embodiment, one horizontal scanning time (period) is set to about 80 μsec at room temperature. Therefore, the frame frequency was about 6.5 Hz. The transfer clock CLK is set to 12 MHz, and the transfer time of scan electrode address data and video data is about 54 μsec. The waiting time in FIG. 2 is about 26 μsec. The control signal CNT in FIG. 2 is a control signal for generating a desired drive waveform.
This is because the driving circuit 12 and 1
3 is output. The output timing of CNT is the same as the timing of outputting scan electrode address data A0 to A11 to scan electrode drive circuit 12, and shift register 13A
Is transferred to the line memory 13B.

The timing of these CNT signals starts at an arbitrary time within a C period defined between the start of the waiting time and the start of the low level of the Sync signal as shown in FIG. Output as a signal. In this embodiment, since the refresh driving is performed, a certain period of time during the period C starts (access starts) and at the same time, the driving end point of the pre-scanning electrode.

The above communication is performed between the drive circuits 12, 13 and the control circuit 15 and the main unit 14, and the refresh drive is performed at the drive timing as described above.

Next, a display information generating means which is a characteristic configuration of the present invention will be described.

The display information is generated by the main unit 14, and is generated according to the specifications according to the signal transfer described above. Here, this is called an image forming circuit.

FIG. 3 shows a main program for generating display information in the partial write routine. This operation is shown in FIG. CPU
It is determined whether or not new rewrite data comes from the memory. If not, this process is repeated. If so, the previous data in the VRAM is rewritten and new data is written (VRAM is a memory for storing video data. ). Thus, the image forming circuit adds the scanning electrode address data to the video data newly sent from the CPU, and
Transfer to 5.

On the other hand, the entire surface refresh drive is executed at regular intervals as described above. For this reason, the entire program is driven to be refreshed by using an interrupt request to the main program, and the image forming circuit executes the routine shown in FIG. 4 at regular intervals in response to the interrupt request. The operation shown in FIG.
This is interrupted and new data from the CPU is rejected. Then, the display information of the entire screen is transferred to the control circuit 15. Then, a time until the next full refresh driving is set (in this embodiment, it is set to 1 second). Then, new data from the CPU is received.

As described above, the operation of the image forming circuit is determined and the driving method of the present invention is executed.

Next, since the scan electrode address data is an address corresponding to the scan electrode 12C of the display panel 11, it becomes address data unique to the scan electrode. Therefore, in this embodiment, data in the VRAM managed by the image forming circuit is mapped as shown in FIG. First, it was divided into two areas, one of which was allocated to scan electrode address data, and one was allocated to video data. In the scan electrode address data area, one line of video data corresponding to the pixels of the display panel 11 is arranged, and the scan electrode address data is arranged at the head of the one line video data. The data mapping in the VRAM is shown in detail in FIG. The first 16 bits of serial data are scan electrode address data,
560 bits are video data.

As the display information to be sent to the control circuit 15, display information for one scanning line is sent in the data format shown in FIG.

Next, drive signals applied to the display panel 11 will be described.

FIGS. 7 and 8 show driving waveforms used in this embodiment. FIG. 7 shows a scan selection signal S _2n-1 (n = 1, 2, 3,...) Applied to odd-numbered scan electrodes in odd _- numbered frames F _2M-1 and even _- numbered frames F _2M (M = 1, 2, 3,...). ) And the scan selection signal S _2n applied to the even-numbered scan electrodes. According to FIG. 7, the scan selection signal S _2n-1 is composed of the odd frame F _2M-1 and the even frame F _2M (M = 1, 2, 3,...).
Have the same polarity (voltage polarity based on the voltage of the scanning non-selection signal) in the same phase, and the same applies to the scanning selection signal _S2n . Further, the scanning selection signals S _2n-1 and S _2n applied within one frame period have different voltage waveforms, and the voltage polarities of the same phase are opposite to each other.

In the scanning drive waveform example of FIG. 7, a third phase is provided for simultaneously stopping the screen (for example, applying a voltage 0 to all the pixels constituting the screen all at once).
The third phase of the scan selection signal is set to voltage 0 (the same level as the voltage of the scan non-selection signal).

According to FIG. 7, the information signal applied to the signal electrode in the odd frame F _2M-1 is the scanning selection signal S.
The combination of the white signal (scanning selection signal S _2n-1 for _2n-1, 2-th voltage 3V ₀ exceeding a threshold voltage of the ferroelectric liquid crystal phase is applied to form a white pixel ) And a holding signal (a voltage ± V ₀ smaller than the threshold voltage of the ferroelectric liquid crystal is applied to the pixel by combining the scanning selection signal S _2n-1 )
Is selectively applied, and a voltage -3V ₀ exceeding the threshold voltage of the ferroelectric liquid crystal in the second phase due to the black signal (combined with the scanning selection signal S _2n) is applied to the scanning selection signal S _2n . And a holding signal (a voltage ± V ₀ smaller than the ferroelectric liquid crystal is applied to the pixel by combining the scanning selection signal S _2n with the pixel).

In the even-numbered frame F _2M subsequent to the writing of the odd-numbered frame F _2M-1 , the information signal applied to the signal electrode includes a black signal similar to that described above with respect to the scanning selection signal S _2n-1 . The holding signal is selectively applied, and the scanning selection signal S
A white signal and a holding signal similar to those described above are selectively applied to _2n .

FIG. 8 is a timing chart when the display state shown in FIG. 9 is written by the drive waveform shown in FIG. In FIG. 9, ○ indicates a white pixel, and ● indicates a black pixel. 8 is a time-series waveform of a voltage applied to an intersection of the I ₁ -S ₁ scan electrode S ₁ and the signal electrode I ₁ in FIG.
I ₂ -S ₁ is a time series waveform of the voltage applied to the intersection between the scanning electrode S ₁ and the signal electrode I _2.

The present invention also discloses a driving method described in US Pat. No. 4,655,561, German Publication No. 350, in addition to the driving method described above.
Driving methods disclosed in 1982, German Offenlegungsschrift 3644220 and the like can also be used.

FIG. 10 is a timing chart showing the display operation principle of the present invention. The first frame is a full refresh driving period. At this time, if rewrite information is generated, main unit 14 prepares rewrite display information (scan electrode address data + video data) by the above-described means. And from the beginning of the second frame,
The partial write operation is started by the above-described signal transfer means (the signal transfer means is the same regardless of the entire refresh driving state and the partial write state). Partial writing is completed,
The entire surface is refreshed again as soon as a fixed time is reached from the first frame.

Here, when the rewriting information does not cover the entire surface, that is, the partial write scan electrode <the total number of scan electrodes (19
In the case of (20 lines), after the partial writing is completed as shown in FIG.

Next, when the rewriting information covers the entire surface, that is, the number of partial write scan electrodes ≧ the number of full scan electrodes (1920)
In the case of (1), as shown in FIG. 10B, after the full refresh driving in the first frame, the entire writing is continued with the frame frequency of the full refresh driving until the end of the entire writing.

In this embodiment, the entire refresh driving cycle is set to 1 second.

FIG. 11 shows an embodiment of a multi-window screen display. The display screen displays different screens in the display area. Window 1 is a screen that displays a certain tally result in a pie chart. Window 2 is window 1
The screen which expressed the total result of the table. Window 3 is a screen that represents the total result of window 1 in a bar graph. The window 4 performs an operation related to text creation. The background is solid white.

Here, window 4 is the work screen, and the other windows are in a still image state. In other words, the window 4 is in a moving image display state while text is being created. Specific operations in this moving image state include scrolling, insertion, deletion and copying of words and phrases, area movement, and the like. These operations require relatively fast operations. Hereinafter, a display operation example will be described.

First Example--A new character is additionally displayed on an arbitrary line in the window 4. Character font is 16 × 1
There are six configurations. To additionally display one character is to rewrite 16 scanning electrodes. The timing of rewriting only the 16 scan electrodes during the refresh driving is as follows: the number of partial write scan electrodes is 16 <the total number of scan electrodes (1920)
Therefore, the timing is as shown in FIG.
The entire frame is refresh-driven in the first frame, and the driving time of 16 scan electrodes from the beginning of the second frame is 16 × 80 =
Partial writing is performed for 1.28 msec, and after one second from the driving of the first frame, the entire surface is refresh-driven again. After the partial writing is completed, about (1000msec-153.6m
sec-1.28 msec).

Second example: Window 4 is in a smooth scroll state.

The number of scanning electrodes occupied by window 4 is 400
Suppose it is a book. Smooth scroll display is to rewrite 400 lines. The timing for driving the 400 scanning electrodes during the refresh driving is the same as in the first example. The first frame is entirely refresh-driven, and the driving time of 400 scan electrodes from the beginning of the second frame is 4
The partial writing is repeated by repeating 00 × 80 μsec = 32 msec until the next full refresh driving start time comes. At this time, the speed of the smooth scroll is about (1
000 msec-153.6 msec) / 32 msec
= 261ine / sec. The general smooth scroll speed is from 10 to 301 in / sec, and the smooth scroll speed shown in the second example is not low at all.

FIG. 12 schematically shows an example of a ferroelectric liquid crystal cell as a display means of the present invention. Upper and lower electrode substrates (glass substrates) 121 coated with transparent electrodes
A layer 122 composed of ferroelectric liquid crystal molecules is sealed between A and 121B so as to be perpendicular to the electrode substrates 121A and 121B. This ferroelectric liquid crystal exhibits a chiral smectic C or H phase, and is set to a film thickness (for example, 0.5 μm to 5 μm) sufficiently small to eliminate the inherent helical structure of the chiral smectic phase.

When an electric field E (-E) having a certain threshold value or more is applied between the upper and lower electrode substrates 121A and 121B, the liquid crystal molecules 123 change their orientation in the direction of the electric field. Liquid crystal molecules have an elongated shape and exhibit refractive index anisotropy in the major axis direction and the minor axis direction. Therefore, if crossed Nicol polarizing plates (not shown) are placed above and below the glass surface, a liquid crystal modulation element whose optical characteristics are changed by the applied polarity of the electric field E (-E) is obtained. When an electric field E of a certain threshold value or more is applied to such a cell, the liquid crystal molecules 123 are oriented to the first stable state 123A. When an electric field -E in the opposite direction is applied, the liquid crystal molecules 123 are oriented to the second stable state 123B, and the orientation of the molecules can be changed. As long as the applied electric field does not exceed a certain threshold value of E and −E, the respective alignment states are maintained.

The ferroelectric liquid crystal device used in this embodiment has a monostable alignment state, and has a first stable state 123A.
And the second stable state 123B are asymmetric, and after the electric field E or −E is released, they are oriented to one of the stable states or another more stable third stable state.
In the present invention, the application to the ferroelectric liquid crystal element having such a monostable alignment state is preferable.
No. 67,924 discloses a ferroelectric liquid crystal element in an alignment state for exhibiting semi-permanent or permanent bistability, and an alignment state in which a helical structure exists as disclosed in European Patent No. 91661. Application to a ferroelectric liquid crystal element is also possible.

FIGS. 13A and 13B show an embodiment of the liquid crystal element of the present invention. FIG. 13A is a plan view of the liquid crystal element of the present invention, and FIG.
It is A 'sectional drawing.

A cell structure 130 shown in FIG. 13 has a pair of substrates 131A made of a glass plate, a plastic plate or the like.
And 131B are held at a predetermined interval by a spacer 134,
It has a cell structure bonded with an adhesive 136 to seal the pair of substrates, and further has an electrode group including a plurality of transparent electrodes 132A on the substrate 131A (for example, a scanning voltage of a matrix electrode structure). Applying electrode group)
Are formed in a predetermined pattern such as a strip pattern. On the substrate 131B, an electrode group including a plurality of transparent electrodes 132B crossing the above-described transparent electrode 132A (for example, a signal voltage application electrode group in a matrix electrode structure) is formed.

The substrate 1 provided with such a transparent electrode 132B
31B includes, for example, inorganic insulating materials such as silicon monoxide, silicon dioxide, aluminum oxide, zirconia, magnesium fluoride, cerium oxide, cerium fluoride, silicon nitride, silicon carbide, boron nitride, polyvinyl alcohol, polyimide, Polyamide imide, polyester imide, polyparaxylerin, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride,
An alignment control film 135 formed using an organic insulating substance such as polyamide, polystyrene, cellulose resin, melamine resin, urea resin, or acrylic resin can be provided.

The orientation control film 135 is obtained by forming a film of the above-mentioned inorganic insulating material or organic insulating material and then rubbing (rubbing) the surface thereof in one direction with velvet, cloth or paper.

In another preferred embodiment of the present invention, SiO 2
The orientation control film 135 can be obtained by forming a film of an inorganic insulating material such as SiO ₂ or the like on the substrate 131B by an oblique evaporation method.

In another specific example, the surface of the substrate 131B made of glass or plastic or the substrate 131B
After a film of the above-mentioned inorganic insulating material or organic insulating material is formed thereon, the surface of the film is etched by an oblique etching method, whereby an orientation control effect can be imparted to the surface.

It is preferable that the above-mentioned orientation control film 135 also functions as an insulating film at the same time. Therefore, the thickness of the orientation control film 135 is generally set in the range of 100 to 1 μm, preferably in the range of 500 to 5000 °. Can be. This insulating film also has the advantage of preventing generation of current generated due to impurities or the like contained in the liquid crystal layer 133 in a small amount, and therefore does not deteriorate the liquid crystal compound even when the operation is repeated.

Further, in the liquid crystal element of the present invention, a material similar to the above-described alignment control film 135 can be provided on the other substrate 131A.

As the ferroelectric liquid crystal 133, US Pat. No. 4,561,726 and US Pat.
No. 09, U.S. Pat. No. 4,589,996, U.S. Pat. No. 4,592,858, U.S. Pat.
No. 96,667, U.S. Pat. No. 4,613,209 and the like can be used liquid crystal compounds or compositions exhibiting a chiral smectic phase.

In the figure, reference numerals 133 and 138 denote polarizing plates whose polarization axes cross each other, preferably at 90 °. According to the present embodiment, it is possible to stably display a still image of a ferroelectric liquid crystal material having a strong monostable tendency and to speed up the display of a partial moving image at a low frame frequency.

[0059]

As described above, the display means is driven and driven.
By controlling, it is possible to realize both partial writing (rewriting) driving and full-surface refresh driving, and since one horizontal scanning driving time is not related to the number of scanning electrodes, the driving voltage and the optical Image formation is not limited to electro-optical characteristics such as response characteristics, and can be performed in principle without limitation on the number of scanning electrodes of the display panel.

[Brief description of the drawings]

FIG. 1 is a block diagram of a display device of the present invention.

FIG. 2 is a chart showing timings of signal transfer and driving used in the display device of the present invention.

FIG. 3 is a sequence diagram showing a partial write routine.

FIG. 4 is a sequence diagram showing an entire surface refresh driving routine.

FIG. 5 is an explanatory diagram showing data mapping of a VRAM.

FIG. 6 is an explanatory diagram showing a data format of display data of one scanning line.

FIG. 7 is a waveform diagram of a driving waveform used in the present invention.

FIG. 8 is a diagram showing a timing chart.

FIG. 9 is an explanatory diagram showing a display state of a pixel.

FIG. 10 is a timing chart when the number of scan electrodes for partial writing <the number of full scan electrodes and the number of partial write scan electrodes ≧ the number of full scan electrodes;

FIG. 11 is a display screen diagram showing an example of an image display used in the present invention.

FIG. 12 is a perspective view for schematically explaining a ferroelectric liquid crystal element used in the present invention.

FIG. 13 is a plan view of an element used in the present invention and its AA ′ line.
It is a figure showing a section.

Claims (3)

(57) [Claims] A display panel on which a plurality of scanning electrodes and a plurality of information electrodes are arranged in a matrix; a scanning electrode driving circuit for selecting the scanning electrodes; and an information electrode driving circuit for applying an information signal to the information electrodes. A display control device for forming a display image on the display means, wherein the display is performed by refresh driving in which the plurality of scan electrodes are sequentially selected and signals are repeatedly applied to the plurality of information electrodes. A memory for storing information of all pixels;
Means for changing a part of the information stored in the memory, an address signal for selecting only a scan electrode corresponding to a pixel for which the changed information is to be displayed, and an image information signal for rewriting a display image of the pixel. Means for generating only the scan electrode selected by the address signal and rewriting an image on the selected scan electrode so that the partial rewrite operation does not continue beyond a predetermined period. A display control device, wherein a scan electrode drive circuit and an information electrode drive circuit are controlled so that a refresh drive period for performing refresh drive and a partial rewrite period are alternately performed. 2. The display control device according to claim 1, wherein a total period of one refresh driving period and one partial rewriting period is constant. 3. The display control device according to claim 1, wherein said scan electrode drive circuit has a decoder.