JPH08136899A - Driving device for antiferroelectric liquid crystal element - Google Patents

Abstract

PURPOSE: To prevent a flicker to be generated at the time of the noninterlace of a still picture from occurring. CONSTITUTION: This device is provided with a liquid crystal cells 1 having n lines of row electrodes and m lines of column electrodes and in which mn pieces of display pixels are formed by sealing antiferroelectric liquid crystal in which one antiferroelectric state and two ferroelectric states are formed according to impressed voltages, matrix driving means (22, 23, 24) imparting a first driving signal making an arbitrary pixel on one row electrode an ON-display by switching in between ferroelectric states of liquid crystal and a second driving signal making remaining pixels on the same row electrode OFF-displays (holding them in antiferroelectric states) and a means imparting DC signals having voltages equivalent almost to the center of a prescribed range in one polarity succedingly to the first and second driving signals in between row electrodes and column electrodes. Moreover, row electrodes are devided into two groups of odd numbered row electrodes and even numbered row electrodes and then writings on odd numbered row electrodes are performed in the selection period of the first field of an NTSC signal and writings on even numbered row electrodes are performed in the selection period of the second field of the signal.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an antiferroelectric device (AFLC
More particularly, the present invention relates to an antiferroelectric liquid crystal element drive device that can prevent flicker that occurs when a still image is non-interlaced scanned.

[0002]

2. Description of the Related Art A liquid crystal display device utilizing an electric field induced phase transition generated in an antiferroelectric liquid crystal is described in detail in JP-A-2-153322. According to it, the electric field induced phase transfer observed in this type of liquid crystal is, for example, when observed between crossed Nicols, as electro-optical characteristics, (1) double hysteresis characteristic of voltage-transmittance, (2) direct current threshold and ( 3) It shows a high-speed response, and if these characteristics are effectively used, it is possible to use conventional nematic liquid crystal or JP-A-56-107216.
It is stated that a liquid crystal display device of higher quality can be realized as compared with the liquid crystal display device using the ferroelectric liquid crystal described in the publication. A matrix driving method that effectively utilizes the characteristics of the antiferroelectric liquid crystal is proposed in JP-A-2-230117 or JP-A-2-173734. According to the driving method proposed there, it is possible to obtain a high-contrast display that fully utilizes the characteristics of the antiferroelectric liquid crystal.

Further, there is a method of preventing an afterimage caused by a structural change of the smectic layer and reducing the number of voltage levels required for driving a display image.
No., published in Japanese Unexamined Patent Publication No. There, an afterimage is generated due to the structural change of the smectic layer when the same display is performed for a long time, so that it is possible to avoid the restriction that only a specific one can be applied as an alignment control film for aligning liquid crystal molecules. Therefore, the afterimage is prevented from occurring due to the structural change of the smectic layer. Further, according to the principle of alternating-current driving the liquid crystal, the hysteresis loop in the positive polarity voltage range and the hysteresis loop in the negative polarity voltage range are alternately used temporally to drive the liquid crystal. In order to drive one display pixel, it is necessary to select at least five kinds of voltages to the scanning electrodes and at least three voltages to the signal electrodes, and to select them at appropriate times. This makes it impossible to increase the degree of integration of the drive ICs that drive the liquid crystal display device, and ultimately leads to an increase in the cost of the liquid crystal display device. In order to avoid this cost increase, the number of voltage levels required to drive the display pixels is reduced.

[0004]

However, in the antiferroelectric liquid crystal of the drive device for the antiferroelectric liquid crystal element, the afterimage can be prevented and the number of voltage levels is reduced, which is used for the liquid crystal display. In this case, non-interlaced scanning is adopted. Therefore, in the case of a still image, a black-and-white blinking line is generated when looking at a part at the boundary between white and black, which causes flicker and deteriorates display quality. .

Therefore, in view of the above problems, it is an object of the present invention to provide a drive device for an anti-ferroelectric liquid crystal element which can prevent flicker due to interlaced scanning of a still image.

[0006]

The present invention adopts the following technical constitution in order to solve the above problems. That is, at least one anti-ferroelectric state and two ferroelectric states are applied to a voltage application between both electrode substrates in which n row electrodes and m row electrodes are arranged in parallel so as to face each other in a lattice row. Between the n row electrodes and the m row electrodes and the n row electrodes and m column electrodes, the liquid crystal cell in which mn display pixels are formed by enclosing the antiferroelectric liquid crystal stably formed with each other. Of the display pixels, a first drive signal for ON display of an arbitrary pixel on the selected row electrode and a second drive signal for OFF display of the remaining pixels on the selected row electrode are applied. As described above, in the matrix type liquid crystal display device provided with the matrix driving means for selectively scanning each row electrode every 1 / n of one screen display time, the antiferroelectric state is applied by the applied voltage as the antiferroelectric liquid crystal. And two strengths that can be controlled by the direction of the electric field Antiferroelectric which can switch between electric states and has a light transmittance of the antiferroelectric liquid crystal having at least a hysteresis sufficient for matrix driving according to increase or decrease of an applied voltage within a predetermined voltage. Liquid crystal is employed, and the driving means is formed as an AC-changing bipolar pulse that switches between two ferroelectric states as the first driving signal, and the second driving signal is changed from the antiferroelectric state to the ferroelectric state. Formed as an alternating-current bipolar pulse with a voltage in a range where switching to a state is not performed, and
After the second drive signal, a DC signal having a voltage corresponding to approximately the center of a predetermined voltage range of one polarity is applied between the n row electrodes and the m column electrodes. To complete a single screen display, or after repeating the above-mentioned operation a plurality of times, the driving means applies a voltage in which the voltage polarities of the first and second driving signals and the DC signal following them are all opposite polarities. Is applied between the n row electrodes and the m column electrodes by the same operation as described above, and the row electrodes are divided into two groups of odd row electrodes and even row electrodes. Is an antiferroelectric liquid crystal element driving device configured to write in the first field of the NTSC signal and write in the even-numbered row electrodes in the second field.

Further, the row electrodes in which the selection periods appear in chronological order may be alternately positive and negative. When the row electrodes in which the selection periods appear in time order are alternately set to the positive polarity and the negative polarity, as the drive waveform pattern applied to the liquid crystal cell, the polarities of the adjacent row electrodes, that is, the even-numbered row electrodes and the odd-numbered electrodes are set. The drive waveforms that are reversed may be combined.

Further, the number of times the output signal is output to the column electrodes is halved, and the data for the odd row electrodes in the first field and the data for the even row electrodes in the second field are output twice as long. The selection period of the row electrodes may be doubled accordingly. Also, the number of times of outputting the output signal to the column electrodes is halved, and the data for the odd row electrodes is set to 2 in the first field and the data for the even row electrodes is set to 2 in the second field.
Double the time output and the row electrode selection period is 2
Alternatively, the row electrodes in which the selection periods appear in chronological order may be alternately positive and negative.

Further, the number of times of outputting the output signal to the column electrodes is halved, and the data for the odd row electrodes in the first field and the data for the even row electrodes in the second field are output twice as long. When the selection period of the row electrodes is doubled accordingly, and the row electrodes in which the selection periods appear in time order are alternately set to the positive polarity and the negative polarity, the driving waveform pattern applied to the liquid crystal cell is set to the adjacent rows. The electrodes, that is, the even-numbered electrodes and the odd-numbered electrodes may be combined with drive waveforms having opposite polarities.

Further, the odd-numbered row electrodes may be written during the selection period of the second field, and the even-numbered row electrodes may be written during the selection period of the first field.
In addition, in the odd-numbered row electrodes and the even-numbered electrodes, the first
The polarity may be the same in the field and the second field, and the selection period may be in the first field in the case of odd row electrodes and in the second field in the case of even row electrodes.

If the display of a still image does not change for a certain period of time, the nth field may be written once. In addition, TFT / LCD, STN / LCD
The display may be performed using an NTSC signal such as.

[0012]

In the matrix type liquid crystal display device of the present invention having the structure as described above, the row electrodes are further divided into two groups of odd row electrodes and even row electrodes, and the odd row electrodes are the groups of the NTSC signal. Write in one field,
By writing in the second field of the even-numbered row electrodes, the integration degree of the driving IC is improved to secure a high contrast, the afterimage due to the structural change of the smectic layer of the antiferroelectric liquid crystal is prevented, and one of the electrodes is It becomes possible to cancel the 30 Hz flicker caused by the decrease in the transmittance caused by using only the field data by the even-row electrode and the odd-row electrode. That is, assuming that two adjacent lines are one line, there is no difference in transmittance between fields, and flicker can be reduced as a whole.

Further, by alternately setting the row electrodes in which the selection periods appear in time order to have the positive polarity and the negative polarity, it is possible to cancel the 15 Hz flicker due to the mismatch of the transmittance between the even electrodes and the odd electrodes. Further, the number of times of outputting the output signal to the column electrode is halved, and the data for the odd-numbered row electrode in the first field and the data for the even-numbered row electrode in the second field are output twice as long, so that the row electrode is output. By doubling the selection period in accordance with this, it becomes possible to prevent the decrease in the transmittance in the non-selection period.

Further, the number of output signals to the column electrodes is halved, and the data for the odd-row electrodes in the first field and the data for the even-row electrodes in the second field are output twice as long. In addition, the selection period of the row electrodes is doubled accordingly, and the row electrodes in which the selection periods appear in time sequence are alternately set to the positive polarity and the negative polarity, thereby reducing the transmittance and causing flicker of 30 Hz and 15 Hz due to mismatch. In addition, it is possible to prevent a decrease in transmittance during the non-selected period at the same time.

When the display such as a still image does not change for a certain period of time, the selection period can be increased by n times by writing once in the nth field, and in the low temperature region where the response time of the liquid crystal becomes slow. effective. Also,
By performing display using an NTSC signal such as TFT / LCD or STN / LCD, it can be applied to all liquid crystal elements.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A concrete configuration example of a driving device for an antiferroelectric liquid crystal element according to the present invention and a driving method thereof will be described in detail below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing the overall configuration of an antiferroelectric liquid crystal element driving device according to an embodiment of the present invention, and FIG. 2 is a liquid crystal cell 1 used in the present invention.
It is sectional drawing which shows the structural example of 0. As shown in FIG.
Row electrodes (Y1, Y2 ... Yn) and m row electrodes (X1,
(X2 ... Xm) are arranged between the two electrode substrates 11 and 12 arranged side by side so as to face each other in a grid pattern (see FIG. 2), and at least one antiferroelectric state and two ferroelectric states are applied when a voltage is applied. Antiferroelectric liquid crystal 1 in which states and states are stably formed
Liquid crystal cell 10 in which 3 is enclosed to form mn display pixels
And the n row electrodes and the m column electrodes form a liquid crystal panel 1, and ON display of any pixel on one row electrode selected from the mn display pixels is performed between the electrodes. The first drive signal and the remaining pixels on the selected row electrode are OF
Antiferroelectric liquid crystal provided with matrix driving means (22, 23, 24) for selectively scanning each row electrode every 1 / n of one screen display time so as to give a second drive signal for F display. In the device driving device, the antiferroelectric liquid crystal can be switched between the antiferroelectric state by an applied voltage and two ferroelectric states that can be controlled by the direction of the electric field, and a predetermined applied voltage can be applied. An antiferroelectric liquid crystal 13 having a light transmittance of the antiferroelectric liquid crystal having at least a hysteresis sufficient for matrix driving in accordance with increase or decrease in voltage is adopted, and the driving means uses two as the first driving signal. Formed as an alternating alternating bipolar pulse switching between ferroelectric states,
A means for generating a bipolar pulse that changes in an alternating manner at a voltage in a range where switching from the antiferroelectric state to the ferroelectric state is not performed as the second drive signal, and an antiferroelectric characteristic is used as the second drive signal. Means for generating an alternating-current bipolar pulse with a voltage in a range in which switching from the state to the ferroelectric state is not performed, and further, a predetermined one polarity after the first and second drive signals. A DC signal having a voltage corresponding to approximately the center of the voltage range is applied between the n-row electrode and the m-row column electrode to complete one-screen display.

After that, or after the signal generating operation by each means is repeated a plurality of times, the driving means applies a voltage in which the voltage polarities of the first and second drive signals and the DC signal following them are all opposite polarities. A means for generating is provided, whereby a voltage having a polarity different from the polarity of the voltage in the previous operation is applied between the n-row electrode and the m-row column electrode by the same operation as described above. It is configured to be done.

Furthermore, it depends on the difference in the transmittance based on the hysteresis asymmetry between the first field driven by using the positive voltage range hysteresis and the second field driven by the negative voltage range hysteresis. The anti-ferroelectric liquid crystal element driving device is configured to superimpose an offset voltage on the row electrode or the column electrode during one period of the first field or the second field.

The driving device for the anti-ferroelectric liquid crystal element of the present invention will be described more specifically. As shown in FIG. 1, the liquid crystal display device of this embodiment has a liquid crystal panel 1 in which an antiferroelectric liquid crystal is sealed, and m column electrodes X1 of the liquid crystal panel 1 based on a video signal input from the outside. , X2 ... Xm and n row electrodes Y1, Y2 ... Yn are applied with a voltage to drive the liquid crystal panel 1, and a control device 4 for displaying an image according to a video signal on the liquid crystal panel 1. Composed of.

Here, in the liquid crystal panel 1, as shown in FIG. 2, the antiferroelectric liquid crystal 13 is provided between the two electrode substrates 11 and 12.
Is enclosed and is created as follows. That is, as shown in FIG. 2, the electrode substrate 11 is made of ITO (Indium Tin Oxid) along the inner surface of the transparent glass plate 11a.
e) Alternatively, the conductive film 11b made of tin oxide is formed, and the conductive film 11b is vertically spaced from each other, so that the n-row electrode Y1, Y2 ... Yn shown in FIG.
Are formed so as to project in parallel with each other in the left-right direction. Further, the electrode substrate 12 is processed in the same manner as the electrode substrate 11, and the m row column electrodes X1, X2 ... Xm shown in FIG. Is formed so as to project. Each of the row electrodes Y1, Y2 ... Yn
And the column electrodes X1, X2 ... Xm, the liquid crystal panel 1
, As shown in FIG. 1, m × n display pixels G1, G2
... G (mn) is formed.

Polymer films 16 and 17 are attached to the inner surfaces of the conductive films 11a and 11b, respectively. Polymer film 16, 1
At least one of the surfaces of 7 has liquid crystal molecules 13a.
However, the rubbing process is performed so as to be parallel to the upper and lower substrates and aligned in the direction perpendicular to the normal P. In addition, each conductive film 11a, 1
Instead of the polymer films 16 and 17, a thin film of an inorganic material such as an oblique vapor deposition film of silicon oxide may be attached to the inner surface of 1b.

In enclosing the antiferroelectric liquid crystal in the liquid crystal cell 10, first, the rubbing directions of the polymer films 16 and 17 are parallel to the conductive films 11b and 12b (that is, the normal line P).
The electrode substrates 11 and 12 are combined in parallel so that they are perpendicular to each other. After that, the antiferroelectric liquid crystal 13 such as 4-
(1-Trifluoromethylheptoxycarbonylphenyl) -4'-octyloxycarbonylphenyl-4-
The carboxylate is overheated to be an isotropic liquid, which is injected between both electrode substrates 11 and 12 by utilizing a capillary phenomenon, and then the entire liquid crystal cell 10 is gradually cooled at about 1 ° C. per minute to obtain antiferroelectricity. The liquid crystal phase (SmCA · phase) is cooled.

As a result of such cooling, the antiferroelectric liquid crystal 13 having a layered structure is oriented along the rubbing direction of the polymer films 16 and 17. This state is a stable state in which it is quenched (first stable state) when observed under orthogonal Nicols, but the recent study by Chandani et al. {Jpn.J.Appl.Phys.Vol.28, (198
9) p.1261}, it was clarified that there is an antiferroelectric structure in which polarization is canceled between layers.

In the liquid crystal cell 10 manufactured as described above, the polarizing plates 14 and 15 are arranged so that their polarization axes are orthogonal to each other.
The liquid crystal is attached so as to match the extinction position when no electric field is applied to the liquid crystal. In the liquid crystal panel 1 having the above configuration, when an electric field is applied between the electrode substrates 11 and 12 in the direction from the electrode substrates 11 to 12, liquid crystal molecules 13 are generated.
Since the permanent dipole moment of a is aligned with the electric field direction, an array change occurs (that is, an electric field-induced antiferroelectric phase-ferroelectric phase transition), and the extinction position shifts by an angle θ. At this time, due to the birefringence of the liquid crystal, the extinction state (dark state) changes to a bright state where light is transmitted. When an electric field in the opposite direction to the above is applied, a bright state is obtained by the same principle, but the direction in which the extinction position shifts is −θ, which is the opposite direction to the above. Here, the liquid crystal 13
When the voltage-transmittance characteristic when a triangular wave voltage was applied to was confirmed, sufficient hysteresis characteristics were obtained as follows.

FIG. 3 is a diagram showing the relationship between the relative light transmittance of the antiferroelectric liquid crystal used in the present invention and the applied voltage. The horizontal axis of this figure shows the applied voltage, and the vertical axis shows the relative transmittance in which the relative transmitted light intensity is displayed in percentage. That is, when the threshold value of the relative transmittance of 90% or more is defined as a bright state and the threshold value of 10% or less is defined as a dark state, first, the liquid crystal cell is in a dark state at an applied voltage of 0 V, and then the applied voltage is positive. When it is increased in the direction, the alignment of the molecules of the liquid crystal begins to change based on the electric field effect E and the spontaneous polarization of the liquid crystal, and the light transmission starts at the threshold voltage + V1 and the complete light transmittance is reached when the saturation voltage + V2 is exceeded. It will be 100%.

That is, the threshold voltage is defined as the voltage at which the relative transmittance changes by 10% from the initial value, and the saturation voltage is defined as the voltage at which the relative transmittance changes by 90% from the initial value. The liquid crystal cell is switched from the dark state to the bright state while changing to a voltage equal to or higher than the saturation voltage. On the contrary, when the applied voltage is changed from a voltage of + V2 or higher, the hysteresis characteristic as shown in FIG. 3 is exhibited without showing the same change as when the voltage is increased.

That is, when the voltage of the liquid crystal cell changes from the bright state to the threshold value + V3 or less, the molecules of the liquid crystal start to change, and the saturation voltage becomes equal to or less than + V4, so that the liquid crystal cell changes to the dark state. Change. That is, when the applied voltage is changed from the threshold voltage to the saturation voltage, the liquid crystal cell is switched from the bright state to the dark state.

Such a state is the same when the applied voltage is a negative voltage, and thresholds are respectively set in the dark state to the bright state and in the change from the bright state to the dark state of the liquid crystal cell. It has -V1, -V3 and saturation voltages -V2, -V4, respectively. Therefore, the applied voltage is +/- V1
If the above setting is made, the liquid crystal will be in a bright state, and if the applied voltage is set to +/- V3 or less, the liquid crystal cell will be in a dark state.

Further, if the voltage is applied between them, the state of the liquid crystal cell does not change, and the state immediately before that is maintained. Next, the control device 4 that drives the liquid crystal panel 1 will be described. As shown in FIG. 1, a control device for driving the liquid crystal panel 1 with the drive waveform of the present invention based on the line-sequential scanning system is a frame memory that captures and stores a video signal input from the outside as image data. 21, a control circuit 22 as control means for reading out image data from the frame memory 21, generating and outputting various control signals such as clock signals, and a control signal from the control circuit 22 to receive the display pixels G.
Each of the row electrodes Y1, Y2, ... Using the voltage (Va or -Va) for selecting the ON or OFF state and the voltage (Vo or -Vo) for holding the selected ON or OFF state as scanning signals. A row drive circuit 23 as a row drive means to be applied to Yn, and a control voltage for controlling each display pixel into an ON or OFF state by receiving a control signal from the control circuit 22 and each column electrode X1, X2.・ ・
A column drive circuit 24 is provided as a column drive means for applying to Xm.

The row drive circuit 23 comprises a shift register 31, a data latch circuit 32, and a drive circuit 33. The column drive circuit 24 has a shift register 41.
And a data latch circuit 42 and a drive circuit 43. FIG. 4 is a diagram showing an example of drive signal waveforms of the liquid crystal panel used in the control device 4. The drive waveform shown in the figure is composed of a first field driven by using the hysteresis characteristic of the positive polarity voltage range and a second field driven by using the hysteresis characteristic of the negative polarity range of FIG. Y1, Y2 ... Yn and column electrodes X1, X
2 consists of 8 basic signals applied to Xm. FIG.
4A shows a group of scanning signals applied to the row electrodes Y1, Y2 ... Yn, and FIG. 4B shows a group of control signals applied to the column electrodes X1, X2. These are output from the control device 4 at appropriate times.

The detailed configuration and operation of the control device 4 will be described below. A row drive circuit 23 that receives a control signal from the control circuit 22 and outputs a scanning signal to the row electrodes Y1, Y2 ... Yn will be described below. FIG. 5 shows a row electrode drive circuit 2 of a drive device for an antiferroelectric liquid crystal element according to the present invention.
It is a figure which shows one specific example of 3. FIG. 6 is a time chart of each signal in the row electrode drive circuit 23 shown in FIG. As shown in FIG. 5, in the shift register 31 of the row drive circuit 23, Va, Vo,
2-bit data (hereinafter referred to as scan signal data) D1 and D2 corresponding to four scan signal levels of -Va and -Vo
And a clock signal CL1 synchronized with this data are input, and the shift register 31 is, as shown in FIG.
Scan signal data D1 and D2 are generated by this clock signal CL1.
Sequentially take in.

Further, as shown in FIG. 5, the data latch circuit 32 is supplied with a clock signal CL2 from the control circuit 22 having one cycle of n clock signals CL1 shown in FIG. The data latch circuit 32 latches the data by the clock signal CL2 every time when the scanning signals D1 and D2 of all the row electrodes Y1, Y2 ... Yn are taken into the shift register 31.

On the other hand, the drive circuit 33, as shown in FIG.
N analog switches 33a1, 33a2, ... 33an provided corresponding to each row electrode Y1, Y2, ... Yn.
And n level shifters 33b1, 33b2, ... 33
bn and. Also, analog switch 3
.. 33an, four kinds of scanning signals to be applied to the row electrodes Y1, Y2 ,.
That is, since Va, Vo, -Va, -Vo are supplied, the analog switches 33a1, 33a2, ...
33an is provided with four switch elements so that one of these four kinds of scanning signals can be selectively applied to the row electrodes Y1, Y2, ..., Yn. The level shifters 33b1, 33b2, ... 33bn level-shift the scanning signal data for each row electrode Y1, Y2, ... Yn accumulated in the data latch circuit 32, and the corresponding analog switches 33a1, 33a2 ,. ..By outputting drive signals to 33an, analog switches 33a1 and 33a
The scanning signals applied to the row electrodes Y1, Y2, ... Yn by 2, ... 33an correspond to the scanning signal data.

As described above, the row driving circuit 23 sequentially takes in the scanning signal data D1 and D2 for the respective row electrodes Y1, Y2, ... Yn output from the control circuit 22 by the clock signal CL1, and all row electrodes Y1, Y2. Each time the scanning signals D1 and D2 corresponding to Yn are fetched (that is, every one cycle of the clock signal CL2), the voltage applied to each row electrode Y1, Y2 ... Yn is changed in accordance with the scanning signal data.

On the other hand, the control circuit 22 is shown in FIG.
As shown in, the scanning signal data D1 and D2 are sequentially output from the row electrode Y1 of the first row to the final row electrode Yn within one cycle of the clock signal CL2. Of the scanning signal data D1 and D2 to be output,
For the scanning signal data D1 and D2 other than the specific row electrode (hereinafter referred to as the selection electrode) whose display is to be changed, a third voltage (Vo or −) which is an intermediate voltage of the hysteresis characteristic of the antiferroelectric liquid crystal is used. Vo) is set, and the first and second voltages Va or −Va capable of switching the ON / OFF state of the display pixel are set only for the scanning signal data D1 and D2 of the selection electrode.

Further, the control circuit 22 is shown in FIG.
As shown in FIG. 6B, the selection electrode is sequentially changed from the first row electrode Y1 every two cycles of the clock signal CL2, and as shown in FIG. 6A, the scanning signal for the selection electrode is changed. The first of the clock signal CL2 is used as the data D1 and D2.
The first voltage and the second voltage −V in the cycle and the second cycle, respectively.
a or Va is set, respectively. In addition, after applying the second voltage to the selection electrode, the control circuit 22 applies the second voltage to the selection electrode until the selection electrode is changed to another row electrode by the next clock signal CL2 and the selection electrode becomes the selection electrode again. The polarity of the applied third voltage is set to the same polarity as the polarity of the second voltage. That is, as shown in FIG. 6A, if the second voltage of the selection electrode is a positive voltage, then the positive third voltage Vo is applied to the electrode and the second voltage of the selection electrode is negative. If the voltage is −Va, then the negative third voltage −Vo is applied to the electrode.

Further, the control circuit 22 further comprises a first
The control for changing the applied voltage from the row electrode Y1 of the row is executed, but each time the control for the row electrode Yn of the first row to the last row is finished, that is, for one screen of the liquid crystal panel 1. Each time the scanning is completed, each row electrode Y1, Y2 ... Yn
Change the polarity of the applied voltage to the polarity different from the previous one. Next, a column drive circuit 24 which receives a control signal from the control circuit 22 and applies a control voltage to the column electrodes X1, X2 ... Xm.
Will be described.

FIG. 7 is a block diagram showing a specific example of the column electrode drive circuit of the drive device for an antiferroelectric liquid crystal element according to the present invention. As shown in this figure, the column electrode drive circuit 2
In the shift register 41 of No. 4, from the control circuit 22, m display pixels formed at the intersections of the selection electrodes and the respective column electrodes X1, X2 ... Xm are turned on or off.
The ON / OFF data DG indicating whether the state is set is sequentially input for each column electrode, and the clock signal CL3 is input in synchronization with the input timing.

FIG. 8 is a timing chart of each signal in the column electrode drive circuit shown in FIG. This figure (b)
As shown in, the ON / OFF data and the clock signal CL3 are (1/1) of one cycle of the clock signal CL2.
m), the shift register 41 receives the ON / OFF data DG of all the column electrodes X1, X2 ... Xm per one cycle of the clock signal CL2 by the clock signal CL3.
Take in.

Further, as shown in FIG. 7, the data latch circuit 42 includes a clock signal CL from the control circuit 22.
2 is input, and at the same time, the field signal F1 indicating the polarity of the voltage applied to the selection electrode is input. Then, the data latch circuit 42 turns on all the column electrodes X1, X2 ... Xm from the shift register 41 by the clock signal CL2.
The OFF signal DG is taken in and the field signal F
Based on 1, the ON / OFF data DG of each column electrode X1, X2 ... Xm is converted into control voltage data and stored according to the polarity of the voltage applied to the selected electrode.

Here, the control circuit 22 converts the ON / OFF data DG for each column electrode into the image data read from the frame memory 21 every time the selection electrode is changed, that is, every two cycles of the clock signal CL2. It is designed to be changed based on this O as shown in FIG.
When the N / OFF data DG represents the ON command of the display pixel, the data latch circuit 42 outputs the field signal F1.
Is ON, that is, when the polarity of the voltage applied to the selection electrode is positive, the control voltage data of the first cycle of the clock signal CL2 is + Vb and the control voltage data of the second cycle is -Vb. If OFF, that is, if the polarity of the voltage applied to the selection electrode is negative, the first of the clock signal CL2
The control voltage data of the second cycle is set to -Vb and the control voltage data of the second cycle is set to + Vb.

Although not shown in the figure, the ON / OFF data DG from the control circuit 22 is OFF for the display pixel.
In the case of indicating a command, conversely to the above, if the field signal F1 is ON, that is, if the polarity of the voltage applied to the selected electrode is positive, the control voltage data of the first cycle of the clock signal CL2 is − Vb, the control voltage data of the second cycle is +
If the field signal F1 is OFF, that is, if the polarity of the voltage applied to the selection electrode is negative, the control voltage data of the first cycle of the clock signal CL2 is + Vb, the control voltage data of the second cycle. Is set to -Vb.

On the other hand, the drive circuit 43, as shown in FIG.
43m provided on the column electrodes X1, X2, ... Xm corresponding to m analog switches 43a1, 43a2 ,.
And n level shifters 43b1, 43b2, ... 43
bn and. Also, each analog switch 4
.. 43an are provided with two switching elements so that one of these three kinds of control voltages can be selectively applied to the column electrodes X1, X2 ,. .

Each level shifter 43b1, 43b2,
... 43bn level-shifts the control voltage data for each column electrode X1, X2, ... Xm stored in the data latch circuit 42, and the corresponding analog switches 43a1, 43bn.
By outputting a drive signal to a2, ... 43an,
A control voltage corresponding to the control voltage is supplied from the analog switches 43a1, 43a2, ... 43an to the column electrodes X1, X2 ...
・ Apply to Xm simultaneously.

That is, to summarize the operation of the column electrode circuit 24, first, the row drive circuit 23 outputs 1 of the clock signal CL2.
The polarity of the applied voltage (that is, the second voltage (Va)) of the selection electrode Yj (j: 1 to n) to which the first voltage (-Va) → the second voltage (Va) is sequentially applied in each cycle is positive. At this time, when the display pixel G formed by the selection electrode Yj and the column electrode Xi (i: 1 to m) is turned on, the column drive circuit 24 causes the column electrode Xi to operate.
On the other hand, + Vb → − for each cycle of the clock signal CL2
When Vb is applied and the display pixel is turned off, the column driving circuit 24 supplies the clock signal CL2 to the column electrode Xi.
+ Vb → −Vb is applied every 1 cycle of.

When the polarity of the voltage applied to the selection electrode Yj is negative, when the display pixel G formed by the selection electrode Yj and the column electrode Xi (i: 1 to m) is turned on, The column driving circuit 24 supplies the clock signal C to the column electrode Xi.
When −Vb → + Vb is applied every one cycle of L2 and the display pixel is turned off, the column driving circuit 24 sets the column electrode X.
For i, + Vb → − for each cycle of the clock signal CL2
Apply Vb.

The operation of the antiferroelectric liquid crystal 13 according to the drive waveform of the present invention formed as described above will be described. FIG. 9 is a partially enlarged view of row electrodes and column electrodes used in the driving device for the anti-ferroelectric liquid crystal element according to the present invention. As shown in the figure, the hatched pixel is (for example, (1.2)) OF.
The F display pixel and the others (eg (1.1)) are ON display pixels.

FIG. 10 is a diagram for explaining the voltage signal waveform actually applied between both electrodes of the liquid crystal cell of the antiferroelectric liquid crystal element driving device according to the present invention. In this figure (a), ON
The waveform applied to the display pixel is shown. Regarding each voltage level, in relation to the hysteresis characteristic of FIG. 3, Vo is a voltage value at the center of the hysteresis width (for example, defined by V1 ⁺ -V3 ⁺ ), and Va and Vb are the following three conditions Va + Vb> V2 ⁺ ... ( ^{1) Va-Vb> V1 +} ... (2) 2 · Vb ≦ V1 + -V3 + ... is set so as to satisfy (3). And each pulse width t
Indicates the switching time when a voltage (Va + Vb) is applied to the antiferroelectric liquid crystal 13. At this time, the liquid crystal 13 is changed to a bright state in which the extinction position is deviated by θ by a voltage (Va + Vb) pulse after the extinction position is deviated by −θ in the first voltage − (Va + Vb) pulse in the selection period. To do. The voltage applied during the non-selection period (Vo
The bright state is maintained by + Vb) or (Vo-Vb). This relationship is exactly the same for voltages of opposite polarities. The change in optical transmittance showing this state is shown in FIG. Next, the waveform applied to the OFF display pixel is shown in FIG.
0 (c). This voltage waveform is originally OF
The liquid crystal in the F state (antiferroelectric state, that is, dark state) does not respond and remains in dark display. Further, even when excited in the ON state (bright state of -θ) in the waveform of the above ON display, it does not change with the first pulse of voltage-(Va-Vb) during the selection period, but it continues with the opposite polarity and the brightness of + θ. By the pulse of the voltage (Va-Vb) that cannot be changed to the state, the bright state of -θ returns to the antiferroelectric state (dark state). The change in optical transmittance showing this state is shown in FIG.

As described above, the matrix liquid crystal cell 10 is dynamically driven by controlling the voltage of the row electrode side 4 level and the column electrode side 2 level, and high contrast display can be obtained. Further, the present driving method has the following advantages. The smectic layer of the antiferroelectric liquid crystal 13 shown in FIG. 3 has a chevron structure which is bent in a "dogleg" as shown in the drawing. This layer structure changes to a bookshelf with an extended "dogleg" when an electric field is applied to bring it into a ferroelectric state. This situation was investigated by X-ray diffraction method,
The results are explained below.

FIG. 11 is a diagram for explaining changes in the bookshelf structure. When the electric field is zero as shown in this figure (a), the smectic layer has a "dog-legged pattern" inclined by about 11 ° C. When an electric field is applied, the voltage does not change at the voltage before it changes to the ferroelectric phase (see this figure (b)), but at the voltage at which it changes to the ferroelectric phase, it changes to a bookshelf structure without inclination of the smectic layer (this figure (c). )reference). When the electric field is made zero again, it returns to a chevron structure with a smaller angle than the initial one. These facts are
Johno et al; Jpn.J.Appl.Phys., Vol.28, (1989) L119 or Y.Yamada et al: Jpn.J.Appl.Phys., Vol.29, (19)
90) pp 1757-1764 and other papers. That is, the antiferroelectric liquid crystal 13 is accompanied by a layer structure change (called layer switching) when switching between an antiferroelectric state (dark state) and a ferroelectric state (bright state). According to our experiments, excessive switching causes an afterimage (a phenomenon called display burn-in) when used as a display device. In the conventional driving method,
Since there is a voltage zero period in the selection signal, the liquid crystal of the ON display pixel undergoes, for example, a negative voltage ferroelectric state → an antiferroelectric state → a positive voltage ferroelectric state or a reverse path state change in each field cycle. . Then, layer switching is occurring accordingly. Then, for example, when a still image is displayed as in a computer terminal, only the liquid crystal of a specific pixel, that is, the ON display pixel has excessive layer switching, and the liquid crystal of the OFF display pixel does not perform layer switching. Therefore, this difference appears as image sticking.

However, in the driving method of the present invention, ON
Since the liquid crystal of the display pixel does not have the period of zero voltage, only the ferroelectric state of the negative voltage → the ferroelectric state of the positive voltage or the state change of the reverse path occurs every field period. That is, the polarity reversal occurs without passing through the antiferroelectric state. Therefore, no layer switching occurs with this change. After all, according to the driving method of the present invention, the layer switching occurs only when the ON display and the OFF display are switched. Therefore, it is possible to prevent image burn-in because there is no bias of layer switching to a specific pixel as in the conventional driving method. Moreover, by reducing the number of voltage levels required to drive the display pixels, it is possible to obtain a drive device for an anti-ferroelectric liquid crystal element with a simplified drive circuit.

Next, flicker prevention by non-interlaced scanning of a still image will be described. FIG. 12 is a diagram showing an output signal of the row drive circuit 25 and an input / output signal of the column drive circuit 24 of the antiferroelectric liquid crystal element. As shown in this figure, a liquid crystal display including an anti-ferroelectric liquid crystal device has two fields in one frame, and NTSC (National T
In the case of using an (elevision system committee) signal, a driving method called non-interlace is used in which the same row electrodes are written twice within one frame (30 Hz) (first field and second field). As shown in this figure (a), writing to the row electrode is performed in a selection period (63.5 μs) in which there is a selection signal for sequentially selecting each row electrode in each field.
ec), when the output signal of the column drive circuit 24 (signal driver IC) is applied to the column electrodes to turn on / off the display pixels as shown in FIG. The ON / OFF of these display pixels is held. A positive voltage (denoted by a circle + symbol in the figure) is applied in the first field, and a negative voltage (denoted by a circle-symbol in the figure) is applied in the second field.
It has the polarity of the pattern as shown in FIG. It should be noted that the numbers of the input signals of the column drive circuit 24 and the output signals thereof are data corresponding to the electrode numbers (Y1, Y2, Y3, etc.) on the scanning side.

Now, the NTSC signal and its scanning method will be described. The NTSC signal is defined as a domestic television video signal, and all televisions and videos use this signal. NTSC signal is 1 frame (30
The data for 525 rows of electrodes (vertical direction) is sent in (Hz). FIG. 13 is a diagram for explaining interlaced scanning.
Regarding the transmitted data, as in the first field shown in FIG. 7A, a normal television writes the data for the first 263 row electrodes by scanning one screen every other row electrode from the top to the bottom. As in the second field shown in FIG. 3B, the data for the subsequent 262 row electrodes is written by scanning from the top to the bottom between the previously written row electrodes. This scanning method is called interlaced scanning.

However, when interlaced scanning is performed in a liquid crystal display driven by the above-mentioned anti-ferroelectric liquid crystal element driving device, the first problem is that the number of scanning electrodes (the number of row electrodes in the vertical direction) increases and the height thereof increases accordingly. There are a large number of fine pitch terminals and driver ICs. Furthermore, the liquid crystal display must be driven by alternating current in order to avoid deterioration of the liquid crystal material. Therefore, positive and negative voltages are applied for each frame, and if the liquid crystal transmittances at the positive and negative voltages do not match, flickers (flicker) of 15 Hz occur and display quality deteriorates. For this reason, a non-interlaced drive system is adopted in the drive device for the anti-ferroelectric liquid crystal element.

However, the anti-ferroelectric liquid crystal element driving device adopting the non-interlaced driving method has the following problems in the still image due to the non-interlaced scanning. FIG. 14 is a diagram for explaining the occurrence of flicker at the boundary between a white area and a black area in a still image. As shown in this figure (a), consider the case where a white-filled quadrangle is displayed (still image) on a black background as an example. Looking at the boundary portion between black and white in the vertical direction (points A and B in FIG. 10), black and white blinking row electrodes may be visible as shown in FIG. 10B. This results in a flicker of 30 Hz and deteriorates the display quality. This phenomenon occurs due to the data content of the sent NTSC signal. That is, since the NTSC signal is premised on interlaced scanning, the data for the first 263 row electrodes (the first field of non-interlaced scanning) and the data for the subsequent 262 row electrodes (the same second field) are stored. This is because they do not always match.
This will be described in detail below.

The drive waveform of each row electrode at point A shown in FIG. 14A will be described with reference to the waveform shown in FIG. Here, although FIG. 12 shows the third row electrodes from the first row electrode (Y1) for convenience, the row electrodes Yn, Yn + 1, Yn + as shown in FIG. 14B are shown.
Same as the waveform of 2 (only the generation position of the selection period is shifted)
Since it can be considered, the description will be made in correspondence with Y1 to Y3. In Y1, 1 (data for the Y1 first field) and 1 '(data for the Y1 second field) of the signal drive IC input signal (the signal obtained by converting the NTSC signal for driving the liquid crystal) are the same black data. Therefore, black is always displayed. Similarly, Y3 has the same white data for 3 and 3 '. Looking at Y2, 2 is the same black data as 1 and 2'is the same white data as 3.

FIG. 15 is a diagram showing the change with time of the transmittance for one pixel on the Yn + 1 (Y2) row electrode of FIG. As shown in this figure, with respect to one pixel on the Yn + 1 (Y2) row electrode, a region having high transmittance and a region having low transmittance are repeated every 30 Hz, and flicker occurs. The 30 Hz flicker in this figure was a large value of 70%. In summary, in non-interlaced scanning, there is no problem because moving images such as TV image display always have different data for each frame and each field, but still images such as telop have different data for each field. However, there is a problem that flicker of 30 Hz occurs and display quality deteriorates. As a countermeasure against this, a method of storing data of the first field called a frame memory and using the stored data in the second field is considered, but the cost is inevitable because this memory is expensive. As another measure for the problem caused by the non-interlace, the problem can be solved by using only the data of one field, but in this case, 15 Hz flicker occurs as in the second problem of the interlaced scanning. There is a problem of doing. Further, as is clear from the change with time of the transmittance in FIG. 15, the antiferroelectric liquid crystal device shows a decrease in the transmittance after the selection period, and when there is no selection period in the second field, the decrease in the transmittance is further reduced. 30Hz as well as the brightness decreases
Flicker also appears. This is due to the decrease in transmittance.
This is because the field is displayed in black.

Further, in the antiferroelectric liquid crystal element, as shown in FIG.
In the drive waveform of, the contrast is lowered and the display quality is lowered at a low temperature of 20 ° C. or lower (the temperature value varies depending on the liquid crystal material). The reason for this is that the response time of the liquid crystal becomes slow at low temperatures, and the liquid crystal may not be able to sufficiently respond during the selection period of 63.5 μsec. Therefore, at present, the drive voltage in the selection period is increased to compensate for the lack of response time in order to display white, but on the other hand, the transmittance of black (= brightness)
Also increases as the drive voltage increases, and the contrast decreases.

FIG. 16 is a diagram showing a first signal waveform of the driving device for the anti-ferroelectric liquid crystal element which prevents flicker during non-interlaced scanning of a still image. The scanning-side row electrodes of the row drive circuit 23 are divided into two groups of odd row electrodes and even row electrodes. As shown in the signal waveform of the row drive circuit 23 in FIG. 6A, the odd-row electrodes are 63.5 μs in the first field.
Writing is performed during the selection period of ec, the next second field is set to the non-selection period, and the even-row electrodes are set to the 6th of the second field
Writing is performed in the selected period of 3.5 μsec, and the first
The field is a non-selected period.

When the row electrodes in which the selection period appears in this configuration are shown in chronological order, Y1, Y3, Y5 ... Y263, Y2, Y4.
Y6 ... Y262 Corresponding to this, as shown in the signal waveform of the column electrode circuit 24 of this figure (b), the output waveform signal 1 (data for Y1 first field), 3 (data for Y3 first field), 5 (Y5 first field data) 263 (Y263 first field data)
.Output waveform signal 2 '(data for Y2 second field)
4 '(data for Y4 second field), 6' (data for Y6 second field) ... 262 '(Y262 second field)
The data for the field) is output. Here, in the figure,
A circle + indicates a positive field with a selection period, a circle − indicates a negative field of the same, a broken circle + indicates a positive field only in a non-selection period, and a broken circle − indicates a negative field only in a non-selection period. Show.

According to this first signal waveform, it is possible to cancel the 30 Hz flicker caused by the decrease in the transmittance between the even-numbered row electrodes and the odd-numbered row electrodes. That is, assuming that two adjacent lines are one line, there is no difference in transmittance between fields, and flicker can be reduced as a whole. FIG.
FIG. 7 is a diagram showing a second signal waveform of the drive device for the anti-ferroelectric liquid crystal element which prevents flicker during non-interlaced scanning of a still image. Similar to FIG. 16, the scanning side row electrodes of the row drive circuit 23 are divided into two groups of odd row electrodes and even row electrodes. As shown in the signal waveform of the column electrode circuit 24 of this figure (b), the number of times of sampling and output of the input signal of the column electrode circuit 24 is halved, and in the first field, the data for odd row electrodes is The two fields output the data for the even row electrodes twice as long. Along with this, the waveform on the scanning side is also 2 in this way for the selection period of the first signal waveform.
Double it. That is, as shown in the signal waveform of the row drive circuit 23 in FIG. 7A, the odd-numbered row electrode is 1 in the first field.
Writing is performed for a selection period of 27 μsec, the next second field is set as a non-selection period, and even-numbered row electrodes are written for a selection period of 127 μsec for the second field.
The field is a non-selected period.

Similarly to the above, when the row electrodes in which the selection period appears in this configuration are shown in chronological order, Y1, Y3, Y5, ... Y2
63 / Y2 / Y4 / Y6 ... Y262. Corresponding to this, as shown in the signal waveform of the column electrode circuit 24 of this figure (b), the output waveform signal 1 (Y1 first field data)
3 (Y3 first field data) 5 (Y5 first field data) 263 (Y263 first field data) output waveform signal 2 '(Y2 second field data) 4 '(data for Y4 second field), 6' (data for Y6 second field) ... 2
62 '(data for the Y262 second field) is output. The row electrodes arranged in this time sequence are alternately output with positive and negative polarities. For example, Y1, Y5, Y2, and Y6 output a positive waveform in the first frame and a negative waveform in the second frame. The reverse is true for Y3, Y7, Y4, and Y8. This figure (c)
As shown in, the horizontal axis is the time, the vertical axis is the row electrode number,
Waveform pattern applied to the liquid crystal at that time, circle +, circle-,
The table is a circle with a broken line + and a circle with a broken line. The horizontal axis delimiters are for each field, and the horizontal axis delimiters are one-row electrodes. Horizontal axis,
Each of the vertical axes has 4 cells (4 fields = 2 frames, 4 lines) as one set, and this is repeated.

According to this second signal waveform, it is possible to prevent a decrease in the transmittance during the non-selection period by doubling the selection period. However, the decrease in the transmittance during the non-selection period directly depends on the signal waveform of the row electrode circuit 23 depending on the voltage value during the non-selection period, and the liquid crystal is sufficiently turned on or off during the selection period during the doubling of the selection period. This secondarily prevents a decrease in transmittance. This is effective when the liquid crystal does not respond sufficiently in the current selection period due to the increase of the liquid crystal response time such as in the low temperature range.
Further, by alternately outputting the row electrodes arranged in chronological order, the flicker of 15 Hz can be reduced by the same principle as in the case of the first signal waveform.

FIG. 18 is a diagram showing the flicker value of one pixel and the entire screen. As shown in the figure, the flicker of one pixel is reduced by the plurality of row electrodes. As another example, the odd-row electrodes are written during the selection period of the second field,
The even-row electrodes may be written during the selection period of the first field. This is the opposite of the first signal waveform in FIG.

FIG. 19 is a diagram showing another example of the waveform pattern applied to the liquid crystal. As shown in FIG.
The same effect can be obtained by combining drive waveforms in which the polarities of the adjacent row electrodes (even-numbered row electrodes and odd-numbered row electrodes) are reversed with respect to the pattern of No. 6. This is the same as when viewing the LCD panel upside down or upside down. As shown in FIG. 17B, the same effect can be obtained by combining drive waveforms in which the polarities of adjacent row electrodes (even-numbered row electrodes and odd-numbered row electrodes) are reversed with respect to the pattern of FIG. it can. This is the same as when viewing the LCD panel upside down or upside down. When there is no flicker of 15 Hz, it is not necessary to alternately output the row electrodes arranged in chronological order in the positive polarity and the negative polarity as described above, and the drive waveforms of FIGS. Combinations are also possible. Further, as shown in FIG. 19C, the odd-row electrode and the even-row electrode have the same polarity in the first field and the second field, and the selection period is the even-row in the first field in the case of the odd-row electrode. In the case of electrodes, it may be performed in the second field.

Further, when the display of a still image does not change for a certain period of time, the selection period can be increased by n times by writing once in the nth field (second field in FIG. 16). This is effective in the low temperature range where the response time of the liquid crystal is slow. Drive waveforms are different, but TFT / LC
It can be applied to all liquid crystal elements that display using NTSC signals, including D and STN / LCD.

[0067]

The antiferroelectric liquid crystal element driving device according to the present invention employs the above-mentioned configuration, and therefore, the driving IC
In order to secure high contrast by improving the integration degree, prevent the afterimage due to the structural change of the antiferroelectric liquid crystal smectic layer, and use only the data of one field for the non-interlaced scanning of the still image. It is possible to prevent flicker due to this and further prevent a decrease in transmittance during the non-selection period. If the display does not change for a certain period of time such as a still image, writing is performed once in the nth field, so the selection period is set to n.
This is effective in a low temperature region where the response time of the liquid crystal becomes slower. In addition, TFT / LCD, ST
By displaying using an NTSC signal such as N.LCD, it can be applied to all liquid crystal elements.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an overall configuration of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration example of a liquid crystal cell 10 used in the present invention.

FIG. 3 is a diagram showing the relationship between the relative light transmittance of the antiferroelectric liquid crystal used in the present invention and the applied voltage.

FIG. 4 is a diagram showing an example of drive signal waveforms of a liquid crystal panel used in a control device 4.

FIG. 5 is a diagram showing a specific example of a row electrode drive circuit 23 of a drive device for an antiferroelectric liquid crystal element according to the present invention.

6 is a time chart of each signal in the row electrode drive circuit 23 shown in FIG.

FIG. 7 is a block diagram showing a specific example of a column electrode drive circuit of a drive device for an antiferroelectric liquid crystal element according to the present invention.

8 is a timing chart of each signal in the column electrode drive circuit shown in FIG.

FIG. 9 is a partially enlarged view of row electrodes and column electrodes used in the driving apparatus for an antiferroelectric liquid crystal element according to the present invention.

FIG. 10 is a diagram illustrating a waveform of a voltage signal actually applied between both electrodes of a liquid crystal cell of a drive device for an antiferroelectric liquid crystal element according to the present invention.

FIG. 11 is a diagram illustrating a change in the bookshelf structure.

FIG. 12 is a diagram showing an output signal of a row driving circuit 25 and an input / output signal of a column driving circuit 24 of an antiferroelectric liquid crystal element.

FIG. 13 is a diagram illustrating interlaced scanning.

FIG. 14 is a diagram illustrating occurrence of flicker at a boundary between a white area and a black area in a still image.

15 is a diagram showing a change with time in transmittance of one pixel on a Yn + 1 (Y2) row electrode in FIG.

FIG. 16 is a diagram showing a first signal waveform of a drive device for an anti-ferroelectric liquid crystal element that prevents flicker during non-interlaced scanning of a still image.

FIG. 17 is a diagram showing a second signal waveform of a drive device for an anti-ferroelectric liquid crystal element that prevents flicker during non-interlaced scanning of a still image.

FIG. 18 is a diagram showing flicker values for one pixel and the entire screen.

FIG. 19 is a diagram showing another example of the waveform pattern applied to the liquid crystal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Liquid crystal panel 4 ... Control device 10 ... Liquid crystal cell 11, 12 ... Electrode substrate 13 ... Antiferroelectric liquid crystal 14, 15 ... Polarizing plate 16, 17 ... Polymer film 21 ... Frame memory 22 ... Control circuit 23 ... Row electrode Drive circuit 24 ... Column electrode drive circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norio Yamamoto 14 Iwatani, Shimohakaku-cho, Nishio-shi, Aichi Japan Auto Parts Research Institute, Inc. Within Nippon Denso Co., Ltd.

Claims (10)

[Claims] 1. An n-row electrode and an m-column electrode are arranged side by side so as to face each other in a grid, and at least one antiferroelectric state and two Between the liquid crystal cell in which anti-ferroelectric liquid crystal in which the ferroelectric state is stably formed is encapsulated to form mn display pixels, and between the n row electrodes and the m column electrodes, Of the mn display pixels, a first drive signal for ON display of an arbitrary pixel on one selected row electrode and a second drive signal for OFF display of the remaining pixels on the selected row electrode. In an antiferroelectric liquid crystal element driving device provided with a matrix driving means for selectively scanning each row electrode every 1 / n of one screen display time, an applied voltage is applied as the antiferroelectric liquid crystal. Can be controlled by the antiferroelectric state and the direction of the electric field by The two ferroelectric states can be switched to each other, and the light transmittance of the antiferroelectric liquid crystal has at least a hysteresis sufficient for matrix driving depending on an increase or a decrease of an applied voltage within a predetermined voltage. A ferroelectric liquid crystal is adopted, and the driving means is formed as an alternating-current-changing bipolar pulse that switches between two ferroelectric states as the first driving signal, and the anti-ferroelectric state is used as the second driving signal. It is formed as a bipolar pulse alternatingly changing with a voltage in a range in which switching to the ferroelectric state is not performed, and follows the first and second drive signals, and is substantially a predetermined voltage range in one polarity. One screen display is completed by applying a DC signal having a voltage corresponding to the center between the n-row electrode and the m-row electrode, and thereafter, or after the operation described above. After a plurality of times, the driving means applies a voltage in which the voltage polarities of the first and second driving signals and the DC signal following them are all opposite to each other by the same operation as described above, and the n row electrode And m
The row electrodes are divided into two groups of odd row electrodes and even row electrodes, and the odd row electrodes are written in the selection period of the first field of the NTSC signal. Is a drive device for an anti-ferroelectric liquid crystal element, characterized in that writing is performed during the selection period of the second field. 2. The driving device for an anti-ferroelectric liquid crystal element according to claim 1, wherein the row electrodes in which the selection periods appear in time order are alternately made positive and negative. 3. The antiferroelectric liquid crystal according to claim 2, wherein drive waveforms applied to the liquid crystal cell are combined with drive waveforms in which the polarities of the adjacent row electrodes, that is, the even row electrodes and the odd electrodes are reversed. Device driving device. 4. The number of times the output signal is output to the column electrode is 1
/ 2, the data for the odd-numbered row electrodes in the first field and the data for the even-numbered row electrodes in the second field are output twice as long, and the row electrode selection period is also doubled accordingly. The drive device for an antiferroelectric liquid crystal element according to claim 1, which is characterized in that. 5. The number of times the output signal is output to the column electrode is 1
/ 2, the data for the odd-numbered row electrodes in the first field and the data for the even-numbered row electrodes in the second field are output twice as long, and the selection period of the row electrodes is also doubled accordingly. The antiferroelectric liquid crystal element driving device according to claim 4, wherein the row electrodes whose periods appear in chronological order are alternately made positive and negative. 6. The anti-ferroelectric liquid crystal according to claim 4, wherein drive waveform patterns applied to the liquid crystal cells are combined with drive waveforms in which adjacent row electrodes, that is, the even-numbered row electrodes and the odd-numbered electrodes have opposite polarities. Device driving device. 7. The driving of an anti-ferroelectric liquid crystal device according to claim 1, wherein the odd-numbered row electrodes perform writing in the selection period of the second field and the even-numbered row electrodes perform writing in the selection period of the first field. apparatus. 8. The odd-numbered electrode and the even-numbered electrode have the same polarity in the first field and the second field, and the selection period is the first field in the case of the odd-numbered electrode and in the case of the even-numbered electrode. 3. The antiferroelectric liquid crystal element drive device according to claim 1, wherein is in the second field. 9. The drive device for an anti-ferroelectric liquid crystal element according to claim 1, wherein writing is performed once in the nth field when a display such as a still image does not change for a certain period of time. 10. The drive device for an antiferroelectric liquid crystal element according to claim 1, wherein display is performed using an NTSC signal such as TFT / LCD or STN / LCD. Driving device for anti-ferroelectric liquid crystal device.