JP2584847B2 - Display device and drive device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device, and more particularly to a ferroelectric liquid crystal display device suitable for moving display such as a cursor and a mouse.

(Prior art)

CRT (cathode ray tube), which forms an image using the afterglow characteristics of the phosphor, and TN (twisted nematic) LCD, which forms an image using the amount of transmitted light according to the driving voltage effective value Liquid crystal element), 1
It is necessary to keep the frame frequency, which is the screen forming frequency, above a certain value. It is generally 30 Hz or higher,
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 interlaced method (interlaced scanning of every other line) and a non-interlaced method (non-interlaced scanning) are known. Other methods are limited to a pairing method and an LCD, but a screen is divided and a simultaneous parallel scanning method is proposed and put to practical use. According to the NTSC standard, the horizontal scanning time is about 63.5 μsec and the number of scanning lines is about 480 (the number of effective display lines) in a 2-field / frame interlaced system with a frame frequency of 30 Hz. The TN type LCD employs a non-interlaced system with 200 to 400 scanning lines and a frame frequency of 30 Hz or more. The CRT also uses a non-interlaced system with a frame frequency of about 40 to 60 Hz, which is different from the NTSC standard, and the number of scanning lines is about 200 to 1,000.

Here, tentatively, a CRT of 1920 (vertical (scanning lines) x 2560 pixels in width)
And driving about TN type LCD. When the frame frequency is 30 Hz and the interlace method is used, the horizontal scanning time is about 17.5 μsec, and the horizontal dot clock frequency is about 147 MHz (the horizontal flyback time in the CRT is not considered). In the case of 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 the electron gun in the picture tube, and even if scanning at 17.5 μsec, it is not possible to accurately image . In the case of a TN type LCD, driving 1920 scan lines is equivalent to a duty ratio of 1920, which is the current maximum duty ratio.
It cannot be displayed because it greatly exceeds about 400. Considering that the horizontal scanning time is set to a realistic value and driving, the frame frequency will be lower than 30 Hz, and the scanning state will be visually recognized or flicker will occur. Significant damage. Thus, CRT and TN type LCD
At present, the screen size and density have been flattened out because the number of scanning lines cannot be sufficiently increased due to the display principle and the limitations of driving elements.

By the way, in recent years, Clark and Lagerwell have disclosed a ferroelectric liquid crystal device having a high-speed response and a memory property (bistability) in US Pat.

This ferroelectric liquid crystal device generally has a chiral smectic C phase (SmC ^* ) or H phase (SmH ^* ) in a specific temperature range.
^* ), And in this state, takes one of the first optical stable state and the second optical stable state in response to an applied electric field, and maintains that state when no electric field is applied. Therefore, it has a phase stability and a quick response to a change in an electric field, and is expected to be widely used as a high-speed and storage type display element.

However, in general, a ferroelectric liquid crystal device is unlikely to have bistability as proposed by Clark et al. And tends 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 the substrate is advantageous. A ferroelectric liquid crystal element that has been subjected to such uniaxial alignment treatment on a substrate and alignment is controlled,
In some cases, permanent bistability did not occur. An alignment state that does not cause this permanent bistability. The so-called monostable orientation state has a property that the biaxial orientation when an electric field is applied is changed to the uniaxial orientation when no electric field is applied in a range of several msec to several hours.
For this reason, in the display device using this monostable ferroelectric liquid crystal element, there is a problem that the image written once is lost when the electric field is released. In particular, at the time of multiplexing driving, there is a problem that the writing state of the pixels on the scanning lines that are not accessed gradually disappears.

To solve this 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, and the period for sequentially selecting the scanning line is set to one. When a frame or one field is set, a driving method (refresh driving) in which writing is performed by repeating this cycle is considered. By adopting such a refresh driving method, the fluctuation of the amount of transmitted light of the non-selected pixels is extremely small, and even when the frame frequency is lower than 30 Hz, the write scan line is visually recognized (the scan write line is compared with other lines). (High brightness can be easily discriminated visually.) The occurrence of flicker can be eliminated. 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.

The above facts solve the problems of large-screen and high-definition, which had arisen from the above-mentioned requirement of driving at a frame frequency of 30 Hz or more, which is a limitation of CRT and TN type LCD. It is effective to do.

However, as described above, when refresh driving is performed at a low frame frequency, so-called moving image display such as character editing, smooth scrolling on a graphics screen, or moving a cursor is slow, and the display performance is degraded. In recent years, the development of computers and their peripheral circuits and software has been remarkable. Particularly for large screens and high-definition displays, a display method called a multi-window, in which a plurality of screens are superimposed and displayed in a display area, has become widespread. I have. Display devices using ferroelectric liquid crystal devices have a much larger screen than conventional display devices (CRT, TN type LCD, etc.).
Although the display device is capable of high definition, the frame frequency becomes low with the enlargement and high definition of the screen, and there is a problem that the speed of smooth scrolling and cursor movement becomes slower.

[Summary of the Invention]

An object of the present invention is to provide a display device which solves the above-mentioned problems, and in particular, to move and display a cursor movement and a mouse movement under a low frame frequency scanning drive such as a frame frequency of 30 Hz or less at a high speed. It is an object of the present invention to provide a display device which enables the above.

The present invention provides a display panel having a display screen provided with a plurality of scan electrodes and a plurality of information electrodes intersecting the scan electrodes, a first means for applying a scan selection signal to the scan electrodes, and And a driving unit having a second unit for applying an information signal to the information electrode. In the case where all the scanning electrodes on the display screen are sequentially selected for scanning, when one scanning electrode is selected in one vertical scanning period, In order to execute the first routine of performing the above-mentioned scan selection by skipping the scanning electrodes and performing the second routine of non-jump-selection of the scanning electrodes of the part when rewriting a part of the display screen. Means,
Is provided.

In the present invention, in the first routine, a plurality of scan electrodes may be skipped in one vertical scan period, and scan electrodes which are not adjacent to each other between two consecutive vertical scans may be selected.

Further, in the present invention, the scan selection signal includes an erasing pulse and a pulse having a polarity opposite to the erasing pulse following the erasing pulse, and the information signal includes a pulse having one polarity and a pulse having a phase before and after the pulse. Preferably includes two pulses of opposite polarities.

In the present invention, a memory for storing image information to be displayed on the display screen is provided, and when a part of the image information stored in the memory is rewritten during execution of the first routine, It is preferable to execute the second routine after one vertical scan based on the image information before rewriting is completed.

In the present invention, a memory for storing image information to be displayed on the display screen is provided, and when a part of the image information stored in the memory is rewritten during the execution of the first routine, It is preferable to shift to the second routine and return to the first routine when the number of scan electrodes selected for scanning in the second routine exceeds a predetermined value.

In the present invention, it is preferable that a period for executing the first routine and a period for executing the second routine are alternately set.

In the present invention, a memory for storing image information to be displayed on the display screen, and a flag memory capable of setting rewrite data for each corresponding scan electrode in accordance with rewriting of the image information stored in the memory. And the first
It is preferable that the flag memory is accessed every vertical scanning by the above-mentioned retin, and the second routine is executed in accordance with the rewritten data, and the scan electrode corresponding to the rewritten data is selected by scanning.

In the present invention, the display panel is preferably a ferroelectric liquid crystal element in which a ferroelectric liquid crystal is disposed between the scanning electrode and the information electrode.

(Detailed description of embodiments of the invention)

A. Signal Transfer Method FIG. 1 is a configuration diagram of a liquid crystal display device and a main unit that supplies a display information signal. FIG. 2 shows a timing chart of the display information signal. The display panel 11 has a scanning electrode 12C (4
A matrix structure of (00) × information electrodes 13D (800) is filled with a ferroelectric liquid crystal, a scanning electrode driving circuit 12 is connected to a scanning electrode 12C, and an information electrode driving circuit 13 is connected to an information electrode 13D.
Connect. The scan electrode drive circuit 12 includes a decoder 12A and an output stage 12B, and 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 and video data designating scan electrode 12C are output from main unit 14 to control circuit 15 through four signal lines PD0, PD1, PD2 and PD3. In this embodiment, the scan electrode address data (A0, A1, A2, A3, A4, A5, A6, A
7, A8, A9, A10, A11) and video data (D0, D1, D2, D3, ... D798,
D799) is transmitted on the same transmission line of each of the signal lines PD0 to PD3, so that it is necessary to distinguish between the scan electrode address data and the video data. In this example, A / is provided as a signal for identification. When the A / signal is at a high level, it indicates that it is scan electrode address data, and when the A / signal is at a low level, it is that it is video data. As shown, each relationship is defined. Further, the A / signal has a meaning as a transfer start signal in transferring the display information.

When the scan electrode address data is provided to the scan electrode drive circuit 12 and the video data is provided to the information electrode drive circuit 13, the scan electrode address data A0 to A11 and the video data D0 to D799 are serially arranged on the signal lines PD0 to PD3. Therefore, a circuit for distributing the scan electrode address data A0 to A11 and the video data D0 to D799 or the scan electrode address data A0 to A11
A circuit for extracting the data is required.
Perform at The control circuit 15 extracts the scan electrode address data A0 to A11 arranged on the signal lines PD0 to PD3,
When temporarily storing and driving the designated scanning electrode 12C,
Output to the scan electrode drive circuit 12 during the horizontal scanning period. The scan electrode address data A0 to A11 are
And the scanning electrode 12C is selected through the decoder 12A.

On the other hand, the video data D0 to D799 are inputted to the shift register 13A in the information electrode drive circuit 13, and are inputted by the transfer clock CLK.
The image data D0 to D799 of the number of pixels corresponding to the information electrodes 13D (800 lines) are separated by shifting each pixel. When the shift register 13A completes the shift for one scanning line in the horizontal direction, the video data on the shift register 13A of these 800 circuits is
D0 to D799 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
Since the generation of the scan electrode address data A0 to A11 and the video data D0 to D799 are performed asynchronously, it is necessary to synchronize the control circuit 15 and the main unit 14 when transferring the display information. This synchronization signal is a signal Sync, which is generated by the control circuit 15 every horizontal scanning.

This signal Sync performs an operation related to A /. The main unit 14 constantly monitors the Sync signal.
If the signal is at a low level, display information is transferred. Conversely, if the signal is at a high level, transfer is not performed after transfer of display information for one horizontal scan is completed. That is, in FIG.
The moment the nc signal goes low, the A / 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 has elapsed from the point A (point B), the level is returned to the low level. If the main unit 14 continuously transfers display information at the point B, that is, when the next scan electrode is driven, A / A
The signal is set to the high level to start the transfer. In this embodiment, since the refresh drive is used, the drive is performed continuously in a line-sequential manner.

The one horizontal scanning period (corresponding to one scanning selection period) is determined due to the characteristics of the ferroelectric liquid crystal and the driving method, and a desired application time is considered in consideration of various optimum driving conditions. And this is determined as one horizontal scanning period. In this embodiment, one horizontal scanning period is set to about 250 μsec at room temperature. Therefore, the frame frequency was about 10 Hz. Also, the transfer clock CLK is 5 MHz,
Transfer time of scan electrode address data and video data is about 4
0.8 μsec. The waiting time in Figure 2 is about 209.2
μsec. The control signal CNT in FIG. 2 is a control signal for generating a desired drive waveform. This is the control circuit 15
Are output to the respective drive circuits 12 and 13. The output timing of the CNT is the same as the timing of outputting the scan electrode address data A0 to A11 from the control circuit 15 to the scan electrode drive circuit 12, and the same as the timing of transferring the video data of the shift register 13A to the line memory 13B.

Further, as shown in FIG. 2, the output timing of the CNT signal is 1 after the transfer time (40.8 μsec) has elapsed from the low level start (point A) of the Sync signal and from the start of the immediately preceding access. It switches when the horizontal scanning period has elapsed. In this embodiment, the next Sync signal is low level (point B).
Is set to a constant value between the time before and after the end of the transfer time.

The above communication is performed between the drive circuits 12 and 13 and between the control circuit 15 and the main unit 14, and the display panel is driven at the above-described timing.

B. Display Scanning Method In the present invention, refresh driving is performed by the following interlace scanning method, and partial rewriting driving is performed by the non-interlace scanning method. The refresh drive is as described above, and the partial rewrite drive applies a scan selection signal to only a scan electrode corresponding to the partial area (rewrite area) when rewriting a partial area of the entire display screen. Scanning line scanning "is performed.

1. Interlaced scanning method Within one vertical scanning period (corresponding to one field period), the scanning electrode is supplied with a scanning selection signal every other line, preferably four lines or less.
An interlace is applied at intervals of more than every 20 lines (or less than every 20 lines), and one screen scan (corresponding to one frame scan) is performed by N + 1 times (N = number of interlaces) of field scan. In particular, in the present invention, when one vertical scanning drive is performed on the scanning electrodes of the entire display screen, interlaced scanning is selected for every two or more scanning electrodes, and non-adjacent scanning is performed in at least two continuous one vertical scanning. It is preferable to scan and select the electrodes.

FIG. 3A shows a scanning selection signal S _S and a scanning non-selection signal.
S _N, represents the white information signal I _W and a black data signal I _B. Third
FIG. 2B shows a voltage (I) at a selected pixel (a pixel to which the white information signal _IW is applied) among pixels (intersections between the scan electrode and the information electrode) on the scan selection electrode to which the scan selection signal is applied. _W −S _S )
Voltage but applied voltage waveforms applied to applied) to the non-selected pixel on the same scan selection electrode is applied (black level signal I _B voltage (I _B -S _S pixel applied)) The waveform and the voltage waveform applied to two kinds of pixels on the scanning non-selection electrode to which the scanning non-selection signal is applied are shown. Fig. 3 (A)
According to (B), a voltage is applied to the pixels on the scanning electrode selected at the phase t ₁ , regardless of the type of the information signal, to cause one of the alignment states of the ferroelectric liquid crystal. The ferroelectric liquid crystal is erased to a black state based on one orientation state (in this example, the crossed Nicols of the pair of polarizers are set so that the black state is not erased. that may be in the manner.) in the subsequent phase t _2, the selected pixel on the selected scanning electrode (I _W -S _S), resulting white state based on the other orientation state of the ferroelectric liquid crystal voltage (V ₂ + V ₃₎ which is applied, a voltage that does not change the black state in the phase t ₁ to the other pixel _{(V 2 -V 3 = V 3} ) is applied. On the other hand, scanning the pixels on the scanning electrode non-selection signal S _N is applied, the ferroelectric threshold voltage below the voltage ± V ₃ of the liquid crystal is applied. Therefore, in this example, the pixels on the scanning electrodes selected in phase t ₁ and t ₂ is made white or black writing, even in a state in which subsequent scanning non-selection signal S _N is applied, before The write state at the time of writing is maintained as it is.

Further, in the present embodiment, the voltage of opposite polarity is applied from the information electrode to the information signal in the phase t ₃ by the writing phase t _2.
Therefore, as shown in FIG. 3 (C), an AC voltage is applied to the pixels when scanning is not selected, and the threshold characteristics of the ferroelectric liquid crystal can be improved. Referred signal applied from the information electrode at such a phase t ₃ is the auxiliary signal is described in detail in U.S. Pat. No. 4,655,561 publication.

FIG. 3 (C) shows a timing chart of the voltage waveform when a certain display state is caused. In this example, the scan selection signal is skipped and applied to the scan electrodes every three lines, and the scan selection signal is applied to the scan electrodes in four consecutive fields. In this example, every third scanning electrode is selected,
By performing one frame scan (one screen scan) with four field scans, the scan selection period (t ₁ + t ₂ + t ₃ ) is set to be long at a low temperature, and as a result, scan drive at a low frame frequency (for example, 5 (Up to 10 Hz frame frequency), it is possible to significantly suppress the occurrence of flicker caused by low frame frequency scanning drive, and to select non-adjacent scan electrodes in four consecutive field scans. By applying the scan selection signal to the image data, the image deletion can be effectively eliminated.

FIG. 3 (D) is an example using the driving waveform of FIG. 3 (A). In this example, every five scanning electrodes are interleaved and selected by continuous six field scans. A scan selection signal was applied so as to select a scan electrode that was not used.

FIGS. 4A and 4B show another example of driving used in the present invention. According to FIG. 4 and (A) (B), in all or a predetermined number of pixels on the scanning electrode a scanning selection signal S _S regardless phase T ₁ of the type of information signal is applied, black simultaneously A voltage for erasing is applied to the state, and a voltage (V ₂ + V ₃ ) for selectively inverting and writing to the white state is applied to the selected pixel (I _W −S _S ) on the line at phase t _3. is applied, the other pixel (I _B
−S _S ) includes a voltage (V ₂ −V ₃ ) that does not change the black state at the phase T _1.
= V ₃ ) is applied. The phase t ₂ and t ₄ is an auxiliary signal applied from the information electrode as being an AC voltage is applied to the pixel during the scanning non-selection similarly to the previous example.

FIG. 4C is a timing chart for producing a certain display state when using the driving waveforms of FIGS. 4A and 4B. According to the driving example shown in FIG. 4 (C), the scan selection signal is applied to the scan electrodes every four lines, and one frame scan is completed in five field scans. Also in this example, a scan selection signal is applied to non-adjacent scan electrodes in five consecutive field scans.

The present invention is not limited to the above-described example. In particular, the scanning selection signal can be skipped and applied to every other scanning electrode or more, preferably every 4 to 20 scanning electrodes. In the present invention, the peak values of the voltage signals V ₁ , −V ₂ and ± V ₃ are | V ₁ | = |
−V ₂ |> | ± V ₃ |, preferably | V ₁ | = | −V ₂ |> 2 | ± V ₃ | The pulse width of these voltage signals is generally 1 μsec to 1 msec, preferably 10 μsec to 100 μsec.
It is preferable to set the pulse width at low temperature to be longer than the pulse width at high temperature.

The partial rewriting drive used in the present invention is performed by interrupting the entire display screen scanning by the refresh drive described above. Accordingly, the operational relationship between partial scanning line scanning and full display screen scanning used in partial rewriting drive is defined below.

(1) When a request for rewriting a part of the display screen is generated during the entire display screen scanning by the refresh driving, the partial scanning line scanning drive is performed after completing the field scanning at the time of occurrence.

(2) Partial rewrite driving by partial scanning line scanning is performed by non-interlace driving.

(3) The maximum number of partial scanning lines is set to a value equal to the number of scanning lines for all scanning lines (the number of scanning lines for one frame) on the entire display screen. In other words, when the number of partial scan line scans exceeds the number of full scan line scans of the entire display screen, the partial scan line scan is interrupted and the entire display screen scan drive is performed.

(4) When the number of partial scan lines scanned is smaller than the maximum number of scans in the above item (3), the partial scan line is completed, and the next field scan is performed immediately after the field scan performed immediately before the partial scan line scan drive. , The field scanning drive is sequentially performed from the leading scanning line.

(5) Rewriting of image information in VRAM (memory for storing image information) does not depend on the rewriting speed of the display panel.

(6) The image information transferred to the display panel when scanning the entire display screen is the image information at the time of transfer.

FIG. 5 shows a circuit configuration for performing the above operations (1) to (6). FIG. 5 shows the main unit 14 shown in FIG.
It includes a CPU unit 51, a VRAM unit 52, and a sequencer unit 53.

The CPU 51 is a control center of the main unit 14 and serves as an instruction source for generating image information.

The VRAM unit 52 includes a “VRAM” 521 and a “VRAM timing generator” 522, and is a memory that stores image information.

The sequencer 53 includes a first address switch 531, a second address switch 532, a 400 line counter (400 line count) 533, a scan counter (8 line count) 534, a 50 line counter (50 line count) 535, and a flag memory 5
36, a sequencer 537, an input / output port 538, and an 800 dot counter 539. The sequencer unit 53 is
The VRAM unit 52 controls access to the VRAM unit 52 and transfer of image information to the display panel 11.

The VA signal for accessing the address of VRAM521 is
This signal is selected as one of the BA signal, the ADR signal, and the RA signal by the first address switching 531.

(1) BA signal: VRAM address signal for accessing partial rewriting drive of display panel 11 (2) ADR signal: VRAM address signal when image information is generated from CPU 51 (3) RA signal: entire display screen of display panel VRAM Address Signal for Accessing Scanning Drive The above-mentioned BA signal, ADR signal and RA signal are selected by the first address switch 531 and are generated as a VRAM address VR signal. The first address switching 531 is controlled by the sequencer circuit 537.

The scanning counter 534 is a counter that determines a scanning method,
The scanning order of the interlaced scanning lines of the refresh driving is counted. In this example, the scanning lines are interlaced every seven lines. The 50-line counter 535 determines the number of scanning lines per field of refresh driving. In this example, every 400 scanning lines are interleaved and eight field scanning is performed. The number of fields was counted by line counting. The 400 line counter 533 counts a predetermined number of scanning lines (set to 400 line counting in this example). In scanning the entire display screen, it functions as a frame counter. At the time of partial rewrite driving, scan line address data for partial scan line scanning is generated, and a VRAM address is accessed.

The second address switching 532 is based on the flag memory address (F
Since the access in A) is performed in two ways, the BA signal and the ADR signal, this circuit selects one of them. The signals for the two types of flag memory addresses are selected by the sequencer circuit 537.

The flag memory 536 is a memory for allocating data of one bit to one scanning electrode. Below this 1b
The data of it is called a “flag”. This flag is
This occurs when the image information from 1 is written to the VRAM 521.
A VRAM address signal (ADR) generated at the time of rewriting operation of the VRAM 521 of the CPU 51 is sampled and converted into an address corresponding to one scan electrode, and then the address signal (F
Write the flag “0” or “1” to the flag memory 536 based on A). That is, from the image information writing operation of the CPU 51, the location of the scan electrode to be rewritten is detected, and the detected data is written to the flag memory 536 as a flag. Then, in the partial rewriting drive of the display panel 11, the flag information in the flag memory 536 is compared with the BA signal from the 400 line counter 533, and the flag is set to “0” (= “O”).
FF ") and" 1 "(=" ON "), and designates only the scanning line at the time of partial rewrite driving.

The 200 dot counter 539 is a circuit that counts the transfer data amount of video data in one horizontal scan and controls the input / output port 538. In this embodiment, since the data amount of 800 dots is transferred by 4 bits (PD0, PD1, PD2, PD3), 800/4 = 200
It is defined as a count.

The “input / output port 538” has image information PD0, PD1, PD2, PD3, CLKA /
Is transferred to the control circuit 15, and the Sync signal from the control circuit 15 is received.

C. Operational Relationship Between Display Information Generation, Transfer Timing, and Display Panel FIG. 6 is a flowchart showing the operational relationship between full display screen scan drive and partial rewrite scan drive. FIG. 7 is a flowchart of the partial rewriting scanning drive operation. FIG. 8 is a flowchart of the whole display screen scanning drive.

In FIG. 6, first, in "selection of RA for first address switching", VRAM address signal (RA) is supplied to VRAM 521 from scan counter 534 and 50 line counter 535, which are all display screen scan drive counters. Give as VA. Next, after waiting for the “L” level of the Sync signal, the scan electrode address data VA and the video data in the VRAM specified by the VA signal are read and transferred to the display panel 11. Then, the 50 line counter 535 is incremented by one.
At the time of the increment, if the count is 49, the process jumps to the “partial rewriting routine”.
Wait for signal “L” level. The operation up to this point is the one-field scanning drive operation.

The operation when the count reaches 49 and the process jumps to the “partial rewriting routine” will be described below.

The count 49 indicates that the display information to be transmitted next is the 49th scan electrode within one field, and the "partial rewrite routine" starts from the terminal () shown in FIG. Also, while the “partial rewriting routine” is being performed, the 1-field scanning drive is operating on the display panel, so the time relationship between the “partial rewriting routine” and “1 field scanning driving” is “ "And" Transferring the 50th line ". The transfer of the 49th and 50th lines means the transfer of the scan electrode address data and the video data from the VRAM 521 in the one field scan drive.

In the “BA selection of second address switching”, the flag memory address signal (FA) of the 400 line counter 533 is supplied to the flag memory 536, and 400 times of the flag memory 536 are counted by 400 times.
Read bit data. If there is data of the flag “01” (= “ON”) in the read data, then the “partial rewriting routine” is entered. If the flag is “0” (= “OFF”), the terminal (▲ ▼) Proceed to. Proceeding to the terminal (▲ ▼) means returning to full display screen scanning drive. After the “partial rewriting routine” ends, the scan counter 534 is incremented by one, and an RA signal for accessing the next one-field scan is set. Then, one field scanning drive is performed again.

Here, the flag “1” is the flag memory address (FA)
Means that rewriting occurs in the scanning electrode indicated by.
On the other hand, if there is no rewriting, the flag is set to “0”. The processing from the terminal () to here is performed during the 49th transfer.

Now, the processing in the case where there is a bit of the flag “1” will be described.

Wait for Sync = "L" level, and when the 50th transfer starts,
First, the 400 line counter is cleared ("0"), and 1 bit is read from the flag memory 536. The reading order is from the first in the scanning electrode number. Here, “1” or “0” of the flag memory 536 is also determined. If it is “0”, the 400 line counter 533 is incremented by one, and the next 1-bit read address (FA) is set. At this time, when the increment result is not 400, 1 bit is read from the flag memory 536 again. The processing up to this point is repeated until the bit of the flag “1” is reached.

Immediately after the flag “1” bit is read, the operation of the 400 line counter 533 is interrupted, and the address of the flag “1” bit is held. While the operation of the 400 line counter 533 is suspended, the end of the one-field scanning drive is waited until Sync = “L” level.

On the other hand, the first address switch 531 is set to BA selection, and 1
Following the field scan drive, the address of the flag held in the flag memory 536 becomes the scan electrode address of the partial rewrite scan, and the VRAM specified by the scan electrode address
Transfer video data. Then, at the same time as the transfer, the processing after the above-mentioned "increment the 400 line counter by one" is performed.

Thus, the processing when the flag “1” bit is present is repeated 400 times. Next, when it is repeated 400 times, that is, after the value of the incremented result is determined, it is further determined whether or not the number 400 is equivalent to 400 times of the partial rewriting scan. If the number has not reached 400, the process proceeds to the terminal (▲ ▼) and returns to the partial rewriting routine. If it has reached 400, it proceeds to the terminal (▲ ▼) and jumps to the full display screen scanning routine.

 Next, the operation of the entire display screen scanning routine will be described.

In FIG. 8, starting from the terminal, the RA signal is selected by the first address switching, and waits for the Sync = “L” level. The scan electrode address data determined by the scan counter 534 and the 50-line counter 535 and the designation thereof are performed. Video data in the VRAM to be transferred. And 50 line counter 535
Is incremented by one. This increment value is 50
Is determined, and if it is not 50, the next transfer is started. If it is 50, it is determined that one-field scanning drive has been completed, and the scanning counter 534 is incremented by one.
Set the next field. Further, it is determined whether or not the set value is 8, and if it is not 8, one field scanning drive is performed from the head of the next field. If it is 8, it is determined that the 8-field scanning drive is completed, the scanning drive of one frame is completed, and the process proceeds to the terminal. Then, the whole display screen scanning routine and the partial rewriting routine are performed again as shown in FIG.

From the standpoint of driving the display panel, the above-described processing always drives the entire display screen scanning unless the display screen is rewritten. Search for image rewriting is 1
It is performed every field scanning drive. If rewriting is performed, partial rewriting is continued after one field scanning drive is completed. Here, the scanning method at the time of partial rewriting is a non-interlace method. In the case of partial rewriting, if the number of rewriting exceeds 400 before the next one field scan drive, one frame scan drive is automatically performed. The scanning method at this time is interlace driving. The display panel 11 repeats these series of operations based on image information from the main device 14.

While the image information is generated as shown in FIGS. 6 to 8, the BA signal and the RA signal selected by the first address switch 531 are temporary, and otherwise the ADR signal of the CPU 51 is not used. Selected. That is, the data in the VRAM 521 is always accessible by the CPU 51.

FIG. 9 shows another partial write routine used in the present invention. This operation is shown in FIG. Judge whether new rewriting data comes from the CPU, and if it does not, repeat this. If it does, rewrite the previous data of VRAM and write new data. In this way, main unit 14 adds scan electrode address data to the video data newly sent from the CPU and transfers the data to control circuit 15.

On the other hand, the entire display screen scanning drive is executed at regular intervals. For this reason, the entire display screen scanning drive is performed using an interrupt request to the main program, and the main unit 14 executes the routine shown in FIG. 10 at regular intervals in response to the interrupt request. In the operation of FIG. 10, if partial rewriting is in progress, this is interrupted and new data from the CPU is rejected. Then, the image information of the entire screen is transferred to the control circuit 15. Then, the time until the next whole display screen scanning drive is set (1 second in this embodiment).
Then, new data from the CPU is received.

As described above, the operation of the main device 14 is determined, and the driving method of the present invention is executed.

FIG. 11 is a timing chart showing the display operation principle in the above-described example. The first frame is the entire display screen scanning drive period. At this time, if rewrite information is generated, main unit 14 prepares rewrite image information (scan electrode address data and video data are generated serially) by the above-described means. Then, from the beginning of the second frame, the partial rewriting operation is started with the routine shown in FIGS. 9 and 10. When the partial rewriting is completed, the whole display screen is scanned and driven 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, when the number of scanning electrodes for partial rewriting <the number of scanning electrodes for the entire surface, the eleventh
After the partial rewriting as shown in Fig. (A),
The entire display screen is scanned and driven.

Next, when the number of partial rewriting scans is equal to or greater than the number of scanning lines of the entire display screen (for example, 400), when the number of partial rewriting scans exceeds 400 as shown in FIG. The partial rewriting scan is interrupted and the process proceeds to the next whole display screen scan drive.

In this embodiment, the entire display screen scanning drive cycle is 1 second.

D. Display Operation Example Hereinafter, the present embodiment will be described in more detail with reference to specific examples.

FIG. 12 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 a screen representing the tabulated result of window 1 in a 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, inserting / deleting and copying words / phrases, moving an area, and the like. These operations require relatively fast operations. Hereinafter, a display operation example will be described.

First Example-One additional character is displayed on an arbitrary line in the window 4-A character font has a 16 × 16 configuration. To additionally display one character is to rewrite 16 scanning electrodes. Fifth
At the time of the routine shown in FIG. 8 to FIG.
1 searches the flag memory 536 from the 49th field at the time when one character is additionally rewritten in the VRAM521, detects the 16-bit flag "ON", and continues scanning electrodes after scanning is completed during field scanning driving. Partially rewrite only 16 lines non-interlaced. Then, the next field scanning drive is performed again sequentially from the first scanning electrode. The time required for 16 rewrites is 16 × 250 μsec = 3.8 msec, where one horizontal scanning period is 250 μsec, and partial rewrite is performed at high speed. The time required for field scanning drive is 50 ×
250 μsec = 12.5 msec. Therefore, the time required from when the CPU 51 rewrites the VRAM 521 to when the additional character is displayed on the display panel 11 is at most 16.3 msec. When rewritten to frequency, it becomes about 61Hz, which is a very fast response. Therefore,
By repeatedly and periodically performing the partial scan line scanning drive corresponding to a font such as a cursor or a mouse for each different scan electrode, it is possible to move and display a cursor or a mouse, and to perform such a moving display at a high speed.

Second Example: Scrolling the Whole Using the Routine of FIGS. 5 to 8 The timing of switching from the entire display screen scan drive to the partial rewrite scan drive is the same as in the first example described above. Here, the entire display screen is rewritten instead of partial rewriting, and the scanning is performed for 400 scanning electrodes.
The frame rewrites the entire display screen by scanning 400 scanning electrodes in a non-interlaced scanning method,
The next frame is scanned by the interlaced scanning method. That is, the display screen is rewritten alternately between the non-interlaced scanning method and the interlaced scanning method. Here, even during the interlaced scanning drive, the image information transferred from the VRAM has the latest video data. In this example, the rewriting speed for one screen is 250 μs for one horizontal scanning time.
As ec, 400 × 250 μsec = 100 msec, which is expressed in frequency as a frame frequency of 10 Hz, and the scroll is at a visible level.

Third Example-Smooth scroll state of window 4 using the routines of Figs. 9 to 11-It is assumed that the number of scanning electrodes occupied by window 4 is 200. Smooth scroll display is to rewrite 200 lines. The timing for driving the 200 scanning electrodes during the entire display screen scanning drive is the timing shown in FIG. 1
The frame is driven by scanning the entire display screen, and the driving time of 200 scanning electrodes from the beginning of the 2nd frame is 200 × 250 μsec = 50 ms
ec is repeated until the next whole display screen scanning drive start time comes, and partial writing is continued.

E. Ferroelectric Liquid Crystal Element FIG. 13 schematically illustrates an example of a ferroelectric liquid crystal cell. A layer 132 composed of ferroelectric liquid crystal molecules is sealed between upper and lower electrode substrates (glass substrates) 131A and 131B coated with transparent electrodes so as to be perpendicular to the electrode substrates 131A and 131B. 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) which is small enough to eliminate the inherent helical structure of the chiral smectic phase. I have.

When an electric field E (−E) of a certain threshold value or more is applied between the upper and lower electrode substrates 131A and 131B, the liquid crystal molecules 133 change the alignment direction to the electric field direction. 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 exceeding a certain threshold is applied to such a cell, the liquid crystal molecules 133
Are oriented to the first stable state 133A. Also, the opposite electric field
When E is applied, the liquid crystal molecules 133 are oriented to the second stable state 133B, 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,
Each alignment state is maintained.

The ferroelectric liquid crystal element used in this embodiment has a monostable alignment state, and the first stable state 133A and the second stable state 133B are asymmetric, and the electric field E or -E
Is released, orienting 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 of such a monostable alignment state is preferable, but the ferroelectric liquid crystal of the alignment state that expresses the semi-permanent or permanent bistability disclosed in U.S. Pat.No. 4,367,924. The present invention is also applicable to an element or a ferroelectric liquid crystal element in an alignment state having a helical structure as disclosed in European Patent No. 91,661.

FIGS. 14 (A) and (B) show one embodiment of the liquid crystal element of the present invention. FIG. 14 (A) is a plan view of the liquid crystal element of the present invention, and FIG. 14 (B) is a cross-sectional view along the line AA ′.

A cell structure 140 shown in FIG. 14 includes a pair of substrates 141A and 141B made of a glass plate, a plastic plate, or the like.
It has a cell structure held at a predetermined interval by 144 and bonded with an adhesive 146 to seal the pair of substrates, and further on the substrate 141A, an electrode group including a plurality of transparent electrodes 142A (for example, , A scanning voltage application electrode group of the matrix electrode structure) is formed in a predetermined pattern such as a strip pattern. On the substrate 141B, an electrode group including a plurality of transparent electrodes 142B crossing the above-described transparent electrode 142A (for example, a signal voltage application electrode group in a matrix electrode structure) is formed.

The substrate 141B provided with such a transparent electrode 142B includes, for example, silicon monoxide, silicon dioxide, aluminum oxide, zirconia, magnesium fluoride, cerium oxide, cerium fluoride, silicon nitride, silicon carbide, boron nitride, etc. Inorganic insulating materials and organic materials such as polyvinyl alcohol, polyimide, polyamide imide, polyester imide, polyparaxylerin, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyamide, polystyrene, cellulose resin, melamine resin, urea resin and acrylic resin An alignment control film 145 formed with a film using an insulating material can be provided.

The orientation control film 145 is obtained by forming a film of the above-described inorganic insulating material or organic insulating material, and then rubbing the surface thereof in one direction with velvet, cloth or paper.

In another preferred embodiment of the present invention, the orientation control film 145 can be obtained by forming a film of an inorganic insulating material such as SiO or SiO ₂ on the substrate 141B by an oblique evaporation method.

In another specific example, after the above-mentioned inorganic insulating material or organic insulating material is formed on the surface of the substrate 141B made of glass or plastic or on the substrate 141B, the surface of the film is etched by oblique etching. Thereby, an orientation control effect can be imparted to the surface.

It is preferable that the above-mentioned orientation control film 145 also functions as an insulating film at the same time.
Generally has a thickness of 100Å to 1 、, preferably 500Å to 5000Å.
Can be set in the range. This insulating film is the liquid crystal layer
It also has the advantage of preventing the generation of current generated due to impurities or the like contained in a small amount in 143, so that the liquid crystal compound does not deteriorate even if the operation is repeated.

In the liquid crystal element of the present invention, the same substrate as the above-described alignment control film 145 can be provided on the other substrate 141A.

As the ferroelectric liquid crystal 143, U.S. Pat.No. 4,561,726, U.S. Pat.No. 4,614,609, U.S. Pat.
Publication, U.S. Pat.No. 4,592,858, U.S. Pat.
Liquid crystal compounds or compositions exhibiting a chiral smectic phase disclosed in US Pat. No. 6,667, US Pat. No. 4,613,209, and the like can be used.

In the figure, 143 and 148 are polarizing plates whose polarization axes cross each other, preferably at 90 °.

〔The invention's effect〕

According to the present invention, it is possible to realize both partial rewrite scanning drive and full display screen scanning drive, and to display a still image stably using a ferroelectric liquid crystal material having a strong monostable tendency while maintaining a low frame frequency. Can speed up the partial moving image display.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a display device of the present invention. FIG. 2 is a chart showing the timing of signal transfer and driving used in the display device of the present invention. Fig. 3 (A)
4 (A) to 4 (D) and FIGS. 4 (A) to 4 (C) are waveform diagrams of the drive signals used in the present invention. FIG. 5 is a block diagram of the main unit used in the present invention. FIG. 6 is a flowchart showing an operation routine of the entire display screen scanning drive and the partial rewriting scanning drive. FIG. 7 is a flowchart showing a routine of the partial rewriting scanning drive. FIG. 8 is a flowchart showing a one-frame scanning drive routine. FIG. 9 is a flowchart showing a partial write routine. FIG. 10 is a flowchart showing an entire display screen scanning drive routine. FIG. 11 (A) shows the number of scanning electrodes at the time of partial rewriting scanning <
FIG. 11 (B) is a timing chart in the case of the whole number of scanning electrodes.
FIG. 7 is a timing chart when the number of scanning electrodes at the time of partial rewriting scanning ≧ the number of scanning electrodes over the entire surface. FIG. 12 is a display screen diagram showing one example of an image display used in the present invention. FIG. 13 is a perspective view for schematically explaining the ferroelectric liquid crystal element used in the present invention. FIG. 14 (A) is a plan view of an element used in the present invention, and FIG. 14 (B) is a cross-sectional view taken along the line AA ′.

Continuation of the front page (56) References JP-A-63-63093 (JP, A) JP-A-63-104583 (JP, A) JP-A-61-272724 (JP, A) JP-A-63-65494 (JP) JP-A-61-149933 (JP, A) JP-A-62-272777 (JP, A) JP-A-61-156229 (JP, A) JP-A-63-257794 (JP, A) 62-44797 (JP, A) JP-A-63-116128 (JP, A)

Claims (17)

(57) [Claims] 1. A display panel having a display screen provided with a plurality of scanning electrodes and a plurality of information electrodes intersecting the scanning electrodes, and first means for applying a scanning selection signal to the scanning electrodes. And a driving unit having a second unit for applying an information signal to the information electrode. In the display device, when sequentially scanning and selecting all the scanning electrodes on the display screen, within one vertical scanning period, A first routine is executed for skip-selecting one or more scan electrodes, and a second routine is executed for non-jump scan-selection of some of the scan electrodes when rewriting a part of the display screen. A display device comprising: 2. A display panel having a display screen provided with a plurality of scanning electrodes and a plurality of information electrodes intersecting the scanning electrodes, and first means for applying a scanning selection signal to the scanning electrodes. And a driving unit having a second unit for applying an information signal to the information electrode. In the display device, when sequentially scanning and selecting all the scanning electrodes on the display screen, within one vertical scanning period, A first routine is executed in which one or more scan electrodes are skipped and scanning is selected, and a second routine is executed in which, when rewriting a part of the display screen, non-interlaced scanning of some of the scan electrodes is performed. The scanning selection signal includes an erasing pulse and a subsequent pulse of the opposite polarity to the erasing pulse, wherein the information signal includes a pulse of a single polarity and the pulse having a phase before and after the pulse. Are two of opposite polarity Display device characterized by including a pulse. 3. A display panel having a display screen provided with a plurality of scanning electrodes and a plurality of information electrodes intersecting the scanning electrodes, and a first means for applying a scanning selection signal to the scanning electrodes. And a driving unit having a second unit for applying an information signal to the information electrode. In the display device, when sequentially scanning and selecting all the scanning electrodes on the display screen, within one vertical scanning period, A first routine is executed for skip-selecting one or more scan electrodes, and a second routine is executed for non-jump scan-selection of some of the scan electrodes when rewriting a part of the display screen. A memory for storing image information to be displayed on the display screen;
When part of the image information stored in the memory is rewritten during execution of the first routine, after one vertical scan based on the image information before rewriting is completed, A display device for executing the second routine. 4. A display panel having a display screen provided with a plurality of scanning electrodes and a plurality of information electrodes intersecting the scanning electrodes, and a first means for applying a scanning selection signal to the scanning electrodes. And a driving unit having a second unit for applying an information signal to the information electrode. In the display device, when sequentially scanning and selecting all the scanning electrodes on the display screen, within one vertical scanning period, A first routine is executed for skip-selecting one or more scan electrodes, and a second routine is executed for non-jump scan-selection of some of the scan electrodes when rewriting a part of the display screen. And a memory for storing image information to be displayed on the display screen. A part of the image information stored in the memory is rewritten during the execution of the first routine. When the second luch Proceeds to, when the number of scanning electrodes to be scanned selected by the second routine exceeds a predetermined value, a display device, characterized in that the transition into the first routine. 5. A display panel having a display screen provided with a plurality of scanning electrodes and a plurality of information electrodes intersecting with the scanning electrodes, and first means for applying a scanning selection signal to the scanning electrodes. And a driving unit having a second unit for applying an information signal to the information electrode. In the display device, when sequentially scanning and selecting all the scanning electrodes on the display screen, within one vertical scanning period, A first routine is executed for skip-selecting one or more scan electrodes, and a second routine is executed for non-jump scan-selection of some of the scan electrodes when rewriting a part of the display screen. A period for executing the first routine and a period for executing the second routine are alternately set. 6. A display panel having a display screen provided with a plurality of scanning electrodes and a plurality of information electrodes intersecting the scanning electrodes, and a first means for applying a scanning selection signal to the scanning electrodes. And a driving unit having a second unit for applying an information signal to the information electrode. In the display device, when sequentially scanning and selecting all the scanning electrodes on the display screen, within one vertical scanning period, A first routine is executed for skip-selecting one or more scan electrodes, and a second routine is executed for non-jump scan-selection of some of the scan electrodes when rewriting a part of the display screen. Means for storing image information to be displayed on the display screen, and a flag memory capable of setting rewriting data for each corresponding scan electrode in accordance with rewriting of the image information stored in the memory. Accessing the flag memory for each vertical scan by the first routine, shifting to the second routine according to the rewritten data, and scanning and selecting a scan electrode corresponding to the rewritten data. A display device characterized by the above-mentioned. 7. The display device according to claim 1, wherein said display panel is a ferroelectric liquid crystal element having a ferroelectric liquid crystal disposed between said scanning electrode and said information electrode. 8. The display device according to claim 1, wherein said first means is a scan electrode drive circuit having a decoder, and said second means is an information electrode drive circuit having a shift register. 9. A display panel having a display screen provided with a plurality of scanning electrodes and a plurality of information electrodes intersecting the scanning electrodes, and a first means for applying a scanning selection signal to the scanning electrodes. And a driving unit having a second unit for applying an information signal to the information electrode. In the display device, when sequentially scanning and selecting all the scanning electrodes on the display screen, within one vertical scanning period, When a first routine is executed for skipping a plurality of scan electrodes and scanning and selecting a scan electrode that is not adjacent between two consecutive vertical scans, and rewriting a part of the display screen, the scan electrode of the part is changed. Means for executing a second routine for non-interlaced scanning selection. 10. The scanning selection signal comprises an erasing pulse followed by a pulse of the opposite polarity to the erasing pulse, wherein the information signal is a pulse of one polarity and the pulse of the pulse is in the opposite phase of the pulse. The display device according to claim 9, comprising two pulses having polarities. 11. The display device according to claim 1, further comprising a memory for storing image information to be displayed on the display screen, and rewriting a part of the image information stored in the memory during execution of the first routine. 10. The display device according to claim 9, wherein the second routine is executed after one vertical scanning based on the image information before rewriting has been completed when the occurrence of the error occurs. 12. The display device has a memory for storing image information to be displayed on the display screen, and rewrites a part of the image information stored in the memory during execution of the first routine. When the number of scan electrodes selected for scanning in the second routine exceeds a predetermined value, the process proceeds to the first routine. Item 10. The display device according to Item 9. 13. The display according to claim 9, wherein a period for executing the first routine and a period for executing the second routine are set alternately. apparatus. 14. A memory for storing image information to be displayed on the display screen, and a flag memory capable of setting rewriting data for each corresponding scanning electrode in accordance with rewriting of the image information stored in the memory. Accessing the flag memory for each vertical scan by the first routine, shifting to the second routine according to the rewritten data, and scanning and selecting a scan electrode corresponding to the rewritten data. The display device according to claim 9, wherein: 15. The display device according to claim 9, wherein said display panel is a ferroelectric liquid crystal element in which a ferroelectric liquid crystal is disposed between said scanning electrode and said information electrode. 16. The display device according to claim 9, wherein said first means is a scan electrode drive circuit having a decoder, and said second means is an information electrode drive circuit having a shift register. 17. A driving apparatus for a display panel having a display screen provided with a plurality of scanning electrodes and a plurality of information electrodes intersecting the scanning electrodes, wherein a first signal for applying a scanning selection signal to the scanning electrodes is provided. Means for applying an information signal to the information electrode, and a driving means having a second means for applying an information signal to the information electrode. When a first routine is executed to select a non-adjacent scan electrode between two successive vertical scans and rewrite a part of the display screen, non-jump scan selection of the part of the scan electrode is performed. And a means for executing a second routine.