JPS62289892A - Driving of optical modulation element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for driving an optical modulation element for a display panel, and more specifically, the present invention relates to a method for driving an optical modulation element for a display panel, and more particularly, the present invention relates to a method for driving an optical modulation element for a display panel. This invention relates to a method for driving a display panel using dielectric liquid crystal, particularly a liquid crystal optical element suitable for gradation display.

[Prior Art] In a liquid crystal television panel using a conventional active matrix driving method, thin film transistors (TPTs) are arranged in a matrix for each pixel, and a gate-on pulse is applied to the TPTs to bring the source and drain into a conductive state. At this time, a video image signal is applied from the source and stored in the capacitor, and a liquid crystal (for example, twisted nematic; TN-liquid crystal) is driven in response to this stored image signal, and at the same time, the voltage of the video signal is modulated. Gradation display is performed by.

[Problems to be solved by the invention] However, in active matrix drive type television panels using such TN liquid crystals, the TPT used is
Because TPT has a complicated structure, it requires a large number of structural steps and high manufacturing costs, and it is difficult to spread the thin film semiconductor (e.g. polysilicon, amorphous silicon) that makes up TPT over a large area. There are problems such as difficulty in forming a film over the entire area.

On the other hand, a passive matrix drive type display panel using TN liquid crystal is known as a device that can be manufactured at low manufacturing cost, but in this display panel, as the number of scanning lines (N) increases, one screen (one frame) 1 while scanning
The time during which an effective electric field is applied to one selection point (duty ratio) decreases at a rate of 1/N, which causes crosstalk and has the disadvantages of not providing a high-contrast image. Moreover, when the duty ratio becomes low, it becomes difficult to control the gradation of each pixel by voltage modulation, making it unsuitable for display panels with a high density of wiring, especially liquid crystal television panels.

In view of these problems, an object of the present invention is to provide a method for driving a display panel having high-density pixels over a wide area, and in particular, a method for driving an optical modulation element suitable for gradation display. be.

[Means for Solving the Problems] The present invention provides a first substrate having a first conductive film and two or more striped power transmission electrodes on the conductive film, and a first substrate that faces the power transmission electrodes so as to intersect with each other. a second substrate having a disposed second conductive film and two or more striped transmission electrodes on the conductive film; an optical modulation material disposed between the first substrate and the second substrate; This is a method of driving an optical modulation element having a gradation signal, and includes a point sequential drive in which an information signal voltage corresponding to a gradation signal is simultaneously applied to two transmission electrodes, and a line sequential drive in which it is applied only to the transmission electrode of the second substrate. It is characterized by switching control.

The optical modulating substance used in the present invention has a first optically stable state (for example, a bright state) and a second optically stable state (for example, a dark state) depending on the applied electric field. ), i.e. has at least two stable states with respect to an electric field, in particular liquid crystals having such properties are used.

As a liquid crystal having bistability that can be used in the driving method of the present invention, a chiral smectic liquid crystal having ferroelectricity is most preferable, and among these, chiral smectic C phase (SmCI), H phase (SmH), I phase (S
Suitable is a liquid crystal with one m, F phase (SmF gloss or G phase (SmG)).
OυRNAL DE PHYSIQUELETTERS
) Volume 36 (L-89) 1975 “Ferroelectric Liquid Crystals” (rFer
roelectric Liquid Crystal
s J ); “Applied physics Letter
``S'') Volume 36, No. 11, 1980 ``Submicro Second Hastiple Electro-Optic Switching in Liquid Crystals J (r Submicr.

5econd B15table Electroop
tic Switching 1nLiquid Cr
ystalsJ); “Solid State Physics” I8 (141
), 1981 "Liquid Crystal", etc., and the ferroelectric liquid crystal disclosed therein can be used in the present invention.

More specifically, an example of a ferroelectric liquid crystal compound used in the method of the present invention is decyloxyhenzylidene-p'-amino-2-methylbutylcinnamate (DOBAMBC).
), hexyloxybenzylidene=p'-amino-2
-Chloropropyl cinnamate (HOBACPC) and 4-o-(2-methyl)-butylresolsiliten-4
'-octylaniline (MBRA 8) and the like.

When constructing an element using these materials, the liquid crystal compound may be 5taC", SmH", Sml-5IIF',
In order to maintain the temperature in SmC, the element can be supported by a copper block or the like in which a heater is embedded, if necessary.

FIG. 16 schematically depicts an example of a ferroelectric liquid crystal cell. 101 and 101' are In203, 5n
It is a substrate (glass plate) coated with a transparent electrode such as 02 or ITO (indium tin oxide), and an SmC'' phase liquid crystal with a liquid crystal molecular layer 102 oriented perpendicular to the glass surface is sealed between the substrates (glass plates). A thick line 103 represents a liquid crystal molecule, and this liquid crystal molecule 10
3 is the dipole moment (P
y) has 104. When a voltage higher than a certain threshold is applied between the electrodes on the substrates 101 and 101', the liquid crystal molecules 1
The helical structure of 03 unravels, creating a dipole moment) (P)
The alignment direction of the liquid crystal molecules 103 can be changed so that all of the liquid crystal molecules 104 are oriented in the direction of the electric field. The liquid crystal molecules 103 have an elongated shape and exhibit refractive index anisotropy in the long axis direction and the short axis direction. Therefore, for example, if polarizers are placed above and below the glass surface in a crossed nicol positional relationship, It is easily understood that the liquid crystal optical modulation element is a liquid crystal optical modulation element whose optical characteristics change depending on the polarity of applied voltage.

Furthermore, if the thickness of the liquid crystal cell is made sufficiently thin (for example, l
In u), even when no electric field is applied, the helical structure of the liquid crystal molecules unravels (non-helical structure), and its dipole moment P or P' points upward (11
4) or downward (114').

When an electric field E or E' of different polarity above a certain threshold value is applied to such a cell as shown in FIG. The orientation is changed, and the liquid crystal molecules are accordingly aligned to either the first stable state 113 (bright state) or the second stable state 113' (dark state).

There are two advantages to using such a ferroelectric liquid crystal as an optical modulation element. First, the response speed is extremely fast.
Second, the alignment of liquid crystal molecules has a bistable state. To explain the second point with reference to FIG. 17, for example, when an electric field E is applied, liquid crystal molecules are oriented in a first stable state 113, but this first stable state 113 is maintained even when the electric field is turned off. , and when an electric field E' in the opposite direction is applied, the liquid crystal molecules align to the second stable state 113' and change the orientation of the molecules, but they remain in this state even after the electric field is cut off, and each stable state remains unchanged. It has a memory function. In order to effectively realize such fast response speed and bistability, it is preferable for the cell to be as thin as possible, and generally, the thickness is 0.5 μm to 20 μm, especially 1 μm to 5 μm. Are suitable. A liquid crystal-electro-optical device having a matrix electrode structure using ferroelectric liquid crystals of this type has been proposed, for example, by Clark and Ragaval in US Pat. No. 4,387,924.

[Function] That is, the present invention includes a first substrate having a first conductive film, a second substrate having a second conductive film facing the first conductive film, and the first substrate. an optical modulation substance disposed between the first conductive film and the second conductive film, and a potential gradient is formed in the plane of the first conductive film and the second conductive film; The method of driving the optical modulation element is characterized by applying a signal having gradation information to the optical modulation element. That is, the present invention applies a potential gradient in both planes of two opposing conductive films constituting one pixel, and applies a pulse signal having a peak value corresponding to the gradation to those conductive films or a pulse signal having a peak value corresponding to the gradation. The gradation is expressed by applying a signal with a different pulse width or number of pulses, and forming areas within the pixel where the inversion threshold voltage is exceeded and areas where the inversion threshold voltage is not exceeded. The signal voltages are two orthogonally arranged so as to cross each other.
Since the control is switchable between dot-sequential driving in which voltage is applied to two transmission electrodes simultaneously and line-sequential driving in which voltage is applied only to one electrode, gradation display corresponding to the content of image data is realized.

[Example] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing one embodiment of an optical modulation element used in the present invention. In FIG. 1, 1 is one substrate, and 2 is a display conductive film laminated on the substrate 1. In FIG. Reference numeral 3 denotes transmission electrodes made of a low-resistance metal film, which are laminated in parallel on the display conductive film 2 at equal intervals. Further, another substrate 4 is opposed to the substrate l, and a counter groove TL film 5 is laminated on the counter substrate 4, and furthermore, the counter conductive film Il! On top of 25, other transmission electrodes 6 are made of the same material as the transmission electrodes 3 and are arranged in parallel stripes at equal intervals. A pixel area A is formed at the intersection of the two transmission electrodes. Between the display conductive film 2 and the counter conductive film 5,
The optical modulating material is sandwiched.

In the liquid crystal optical element configured as described above, the transmission electrode 3
By applying a potential gradient in the plane of the display conductive film 2 by the signal voltage applied to the display conductive film 2, a potential difference gradient is generated in the electric field between the display conductive film 2 and the counter electrode 6. At this time, the transmission electrodes 3a and 3c are connected to the reference potential point VE (for example, O port),
When a predetermined signal voltage Va is applied to another transmission electrode 3b,
As shown in FIG. 2(a), between the transmission electrodes 3a and 3b,
In-plane length directions L1 and L2 of the conductive film 2 between 3b and 3c
A potential gradient of Va can be applied to. Similarly, for the transmission electrode 6 provided on the counter substrate 4, by applying a potential gradient in the plane of the counter conductive film 5 using the applied signal voltage, the gradient of potential difference between the transmission electrode 6 and the transmission electrode 3 can be reduced. bring about At this time, the transmission electrodes 6a and 6C are connected to the reference point VE (for example, O port), and the voltage is applied to the transmission electrode 6b.
When a signal voltage vb having the same potential as a is applied, the conduction between the transmission electrodes 6a and 6b or 6b and 6c as shown in FIG. 2(b). [v in the longitudinal direction L1 and L2 in the plane of 5
A potential gradient of b can be applied. At this time, if both the voltages Va and vb have a potential higher than the potential that is 1/2 of the inversion threshold voltage vth of the ferroelectric liquid crystal, the signal voltage applied to the ferroelectric liquid crystal is as shown in FIG.
As shown in C), Va and Vb are applied as potentials with different polarities, and the absolute value of the voltage is a potential of Va+Vb that is applied to the liquid crystal. On this occasion,
When the potential of Va+Vb becomes equal to or higher than vth, the in-plane length directions M, , M2 and ml of the conductive film 2 and the counter conductive film 5
, the inversion threshold voltage vt for the ferroelectric liquid crystal corresponding to 32
A potential difference Va' + Vb' of more than h is applied, and the regions corresponding to Ml, M2 and the shoe 19 layer 2 can be reversed from a bright state to a dark state, for example.

Therefore, according to the present invention, gradation can be expressed by applying the same voltage to Va and vb in accordance with the gradation for each pixel. At this time, the voltage values of the voltage signals Va and Vb applied to the transmission electrode 3 and the counter electrode 6 may be modulated according to the gradation information, or the pulse width thereof may be modulated according to the gradation information. The gradation can also be controlled by modulating the number of pulses.

Furthermore, prior to applying the gradation signal, an erasing step is performed to put the pixel into either a bright state or a dark state, and then an inversion voltage for reversing that state is controlled according to the gradation. It is necessary to apply the voltage to the ferroelectric liquid crystal.

Further, preferred specific examples of the present invention will be described.

A transparent conductive film of 5n02 with a thickness of about 20 OA was formed on the glass substrate 1 in FIG. Next, 100O
Aj) with a thickness of A was vacuum-deposited on the 5n02 film and patterned again to form a plurality of electrical transmission electrodes 3 as shown in FIG. In this embodiment, the interval between the transmission electrodes 3 is set to 23
It was set to 0k. The sheet resistance of this transmission electrode 3 is approximately 0.4
Ω/mouth, and its width was approximately 20μ. On the other hand, for the counter substrate 4, a counter conductive film 5 and a counter electrode 6 are formed using the same method and materials as described above, so that both substrates have exactly the same configuration, and are arranged opposite to the transmission electrode 3 of the substrate 1. The counter electrodes 6 of the substrate 4 are arranged so as to cross each other and face each other.

A polyvinyl alcohol layer of about 50 OA was formed as a liquid crystal alignment film on the surface of each of the two substrates thus created, and a rubbing treatment was performed.

Next, adjust the gap between the two boards to be about 1 tile,
Ferroelectric liquid crystal (p-η-octyloxybenzoic acid-p'
-(2-methylbutyloxy)phenyl ester and p-
Liquid crystal composition containing η-nonyloxybenzoic acid-p'-(2-methylbutyloxy)phenyl ester as a main component)
was injected. The shape of the partial pixel A where the transmission electrode 3 and the counter electrode 6 overlapped was 230×230μ, and the capacitance after the liquid crystal was injected was about 3PF. However, the width of pixel A was set to L+/2+L2/2. Then, polarizing plates are arranged in crossed nicols on both sides of the liquid crystal cell formed in this way,
The optical properties were observed.

FIG. 3 is a cross-sectional view taken along the a-a' plane of FIG. A transmission electrode 3 is disposed thereon, a counter conductive film 5 is formed on a counter substrate 4, and a counter electrode 6 is disposed above it to cross the transmission electrode 3, and a ferroelectric It has a sexual liquid crystal 31. The counter electrode 6 is connected to the first drive circuit 32, and the electric transmission type 8i3 is vcbe connected to the second drive circuit 33.

FIG. 4 shows the signal (a) generated in the drive circuit 32 of FIG.
), and FIG. 5 shows the waveform of the signal (b) generated in the drive circuit 33 of FIG. 3.

Now, as the signal (a), the counter electrodes 6a, 6b,
8c etc. - 12V, 2001j, sec pulse, signal (b) as the transmission electrode 3, la, 3b,
3c is provided with an erase step in which an 8'J, 2004 sec pulse is synchronized in advance (this is called an erase pulse), the liquid crystal is switched to the first stable state,
For example, the entire pixel A becomes a bright state (cross polarizing plates are arranged in this way). Note that the inversion threshold of the liquid crystal used here is assumed to be ±15 to ±16 V for convenience of explanation. From this state, various pulses as shown in FIGS. 4(a) to 4(e) are applied to the counter electrode 6b as signals (b). At this time, the applied opposing electrodes 6a and 6c are at the reference potential point V
E (for example O port). Moreover, the counter electrode 6b
Various pulses shown in FIGS. 5(a) to 5(e) are applied as signals (b) to the transmission electrode 3b in synchronization with the various pulses shown in FIG. 4 applied to . Also at this time, the opposing electrodes 3a and 3c adjacent to the applied opposing electrode 3b are connected to the reference potential point VE (for example, O port). FIG. 6 shows the optical state of pixel A in such a state.

The pulse applied voltage is -2 V as the potential of vb corresponding to FIG. 4(a), and the voltage applied to the opposing transmission electrode 3b corresponding to the potential of vb corresponds to FIG. 5(a). Similarly, when the potential of Va is +2V, -5V corresponding to FIG. 4(b), and +5■ corresponding to FIG. 5(b),
Since the inversion threshold voltage of the liquid crystal is not exceeded, no change occurs from the bright state 61. However, 18 corresponding to Fig. 4(C)
v and +8v corresponding to FIG. 5(C), the transmission electrode 3
The liquid crystal near the intersection where b and the counter electrode 6b are perpendicular to each other is switched to a dark state 62.

Further, the applied voltages are set to 14 V and 5 V as shown in FIG. 4(d).
In the case of +14V corresponding to figure (d), the dark state 6
The area of 2 becomes wider as shown in Fig. 6(C), and when the applied voltage is -20V shown in Fig. 4(e) and +20V corresponding to Fig. 5(e), the area of Fig. 6(d) The entire screen A is switched to a dark state 62, as shown in FIG. In this way, an image with gradation can be formed by applying the voltage corresponding to the gradation signal to the transmission electrode and its opposing electrode as the same voltage.

In the gradation display method of a ferroelectric liquid crystal element according to the present invention, a voltage corresponding to a gradation signal is applied to a transmission electrode and its counter electrode, and switching is started from an intersection point where each electrode intersects at right angles. . Therefore, the changes in the switching area of the liquid crystal in one pixel are shown in Figures 6(a) to (d).
As shown in , the liquid crystal changes from bright to dark in a regular quadrilateral shape from the intersection of the electrodes. Such changes in liquid crystal orientation are important when displaying images with gradation.
This method achieves the same effect as the gradation display method using halftone dot printing, which is generally used for displaying photographs in newspapers and the like. or,
When trying to realize a driving method that causes regional changes in orientation as shown in FIGS. 6(a) to 6(d), for example, in a liquid crystal display panel configured in a matrix, each pixel is In order to write an information signal, the general method is to sequentially apply an information signal with the same potential to the scanning electrode and information electrode corresponding to each pixel, one pixel at a time. This is called sequential drive. The advantage of point-sequential driving is that it is a very effective driving method for displaying images that require high density and high quality, such as photographs and paintings, and it enables high-quality images, especially when displaying gradation images. . However, the speed of writing to one pixel is very fast, for example, when one scanning electrode is 1000 pixels and one scanning line time of the NTSC system of TV is 84) Lsec, if the speed of writing to one pixel is T, then In other words, in dot-sequential driving, as the number of pixels on the display panel increases, high-speed writing is required in proportion to the increase, and high-speed processing in the drive circuit is required.

In contrast to the above-mentioned point sequential driving method, a line sequential driving method is a method in which an arbitrary voltage pulse is applied to the scanning electrode side and an information signal is applied to one scanning electrode at a time to perform writing. This method, compared to the point-sequential driving method,
The writing speed does not depend on the number of electrodes in one scan, and writing can be completed in the time of one scan line. Therefore, for example, when driving according to the NTSC: system of a TV, a writing speed of 84 g 5 ec per scanning line is sufficient, and the high-speed processing of the drive circuit required for dot sequential driving is no longer required.

FIG. 7 is a schematic diagram showing the alignment state of liquid crystals by line sequential driving. In FIG. 7, the counter electrode 6b on the counter substrate
A constant scanning signal voltage vb applied to the electrode 6b
The electrodes 13a and 8c adjacent to each other are connected to a reference potential point VE (for example, O port). At this time, the scanning signal vb is applied to the counter conductor by applying a voltage equal to the inverted dark value voltage vth of the liquid crystal. ! ! A potential gradient is created on the membrane 5. Further, an information signal Va corresponding to the gradation signal is applied to the transmission electrode 3b as an information signal voltage, and the electrodes 3a and 3C adjacent to the transmission electrode 3b are connected to a reference potential point VE (for example, O port).

Similarly, Va applied to the transmission electrode 3b causes a potential difference gradient on the conductive film 2.

Therefore, when vb, which is the same potential as the threshold voltage vth, is applied as a scanning signal and a voltage Va corresponding to the gradation signal is applied as an information signal, the absolute value voltage Va+Vb is applied to pixel B of the liquid crystal.
A voltage is applied. At this time, when a voltage higher than the liquid crystal threshold voltage vth is applied to pixel B, switching occurs,
Although the alignment region changes, in the alignment change of the liquid crystal in FIG. 7, switching of the liquid crystal occurs at an electric field of Vth/2 or more in Va and vb, respectively, and at the electrode 6b, L is the orientation region length,
For the transmission electrode 3b, the electric field region L1 is Vth/2 or more.
and L2 are oriented. Therefore, as a change in the orientation area in pixel B, the information signal V that changes according to the gradation signal
The regions Ll and L2 change from a bright state to a dark state, for example, depending on the potential of a.

As described above, when forming an image display with gradation, the change in the alignment state of the liquid crystal due to line-sequential driving causes the alignment region to have a rectangular shape along the transmission electrode 3b, as shown in pixel B in FIG. Therefore, when displaying an image, for example, a picture, photograph 9 figure, etc., the image will have many frequency components in the L direction in Fig. 7 within the pixel.
It is not suitable for display aiming at high image quality, but is rather effective for displaying characters. Therefore, in the present invention, it is possible to switch the driving method depending on the image pattern, for example, dot-sequential driving for displaying pictures, photographs, figures, etc., and line-sequential driving for displaying characters, etc. This paper proposes a driving method for a liquid crystal display.

The liquid crystal 31 of this embodiment shown in FIG. 3 is a ferroelectric liquid crystal, more preferably a chiral smectic liquid crystal in a bistable state.

Further, as the transmission electrode 3 and the counter electrode 6, metals such as gold, silver, copper, and chromium can be used in addition to aluminum (Ai'), and preferably the sheet resistance thereof is 102
Ω/mouth or less. Furthermore, the conductive film 2 and the counter conductive film 5 to which a potential gradient is applied are IOKΩ/~IMΩ/
A transparent conductive film with a certain sheet resistance can be used.

FIG. 8 is a block diagram specifically showing an example of the method for driving gradation display according to the present invention, in which 81 is a liquid crystal display panel using an optical modulation element, 82 is a line-sequential information side circuit, and 83 are dot sequential information side circuits, and both have pixel memory for one scan. 84 is a line sequential scanning side circuit, 85 is a dot sequential scanning side circuit, 11.12.1= +...IN is an information line, S+
, S2. S3. ...SN is a scanning line.

Reference numeral 86 denotes a control circuit that controls switching between line sequential drive or dot sequential drive, and also outputs an address signal for controlling the output of gradation signals and selecting the information side or scanning side signal line during dot sequential drive; It has a function of outputting a control signal during sequential driving.

A in the figure is an information signal corresponding to a gradation signal.

B in the figure is a switching control signal output from the control circuit 86. When the signal level is "0", the switch Sw+ is connected to a", and the outputs of the point sequential drive circuits 83 and 85 are in a high impedance state. , line sequential driving is performed.In addition, when the signal level is "1", the switch Sw1 is a
', and the outputs of the line sequential drive circuits 82 and 84 are in a high impedance state, resulting in point sequential drive. Regarding the relationship between the signal line selection address signal output from the control circuit 88 and the signal lines C and D when point sequential driving is performed, the signal line C transmits information for point sequential driving to the drive circuit 83. In synchronization with the signal, information line II, 12
゜13, . . . Transmits a signal having a decoding function to sequentially select information lines to be written in IN. The information line on the information side in the point sequential drive in which the address signal by the signal line C is not selected is connected to the reference potential point VE (for example, O port). Similarly, when the dot-sequential scanning side drive circuit 85 performs dot-sequential driving based on the address signal line from the control circuit 86, the scanning side drive circuit 85
1. S2. S3. ...A signal having a decoding function for sequentially selecting SNs is transmitted. The address by the signal line is maintained until the point sequential drive for one scan is completed.

Further, the scanning line of the drive circuit 85, which is not selected by the address signal by the signal line, is connected to the reference potential point VE (for example, O port).

FIG. 9 is a partial block specifically showing one example of the line sequential drive circuit 82. In FIG. 9, 91 is the same display panel as 81, and 92 is the even information line 12° 14, 16 .
. . . , 33 is the odd information line II, 13.15. This is an odd-number side drive circuit that drives... The drive circuits 92 and 93 have memories that are mutually exclusive to each of the even and odd information lines. 94
is a control circuit for line sequential driving, which operates switch Sw2 in synchronization with an information signal corresponding to a gradation signal for line sequential driving at a control level b'' for line sequential driving output from the control circuit 86.
is switched by signal S. The switch Sw2 is set to S' when the control level signal S from the control circuit 94 is "1".
, when it is "0", it is connected to S". Also, the drive circuit 92
and S3, when the control signal line E is "1", the total output of the drive circuit 92 is output at an output level corresponding to the information signal, and the total output of the drive circuit 83 is set to the reference potential point VE (for example, O port). When the control signal line E is 0''', the entire output of the drive circuit 93 is output at an output level corresponding to the information signal, and the entire output of the drive circuit 92 is at the reference potential point VE (for example, O volts). connected to.

Next, when writing an information signal corresponding to a gradation signal to a display panel, assume that the number of pixels for one scanning line is, for example, 256 pixels. Here, one scanning line worth of image data outputted from the control circuit 86 is denoted by d+, A in FIG.
d2. d3. da, d+, d3 are point sequential data, such as a photograph, two pictures, etc., and d2. If da is line sequential data, such as characters, the switching control level for controlling the switch Swl by the control circuit 88 changes as shown in FIG. 11 to I80 corresponding to the information line dl and 1160 corresponding to d3”
Point sequential data is output to 1180, 181 to 1159 corresponding to d2 and 1+s+"12s+ corresponding to d4.
Line sequential data is output to +. Information data dl, d3
Point-sequential driving is performed in the point-sequential driving circuit 83, and the information signal shown at 12 in FIG. 10 is inputted to the point-sequential information side drive circuit 83.

Here, in the data area of dl, the first information signal corresponds to the signal l line 11 in the drive circuit 83, the second corresponds to I2, the third corresponds to I3, and hereafter the 800th I80, the information signal order and the signal line is compatible.

Naturally, they also correspond in 11bo-1+so. Also, since the signal line C in FIG. 8 sequentially selects the signal lines of the drive circuit 83, the address signal for the first information signal written to the signal line I+ is "1". , in case of work 2, 2' is addressed.In other words, the signal line addressed by the signal line C is output.Here, the dot sequential scanning side drive circuit 85 inputs to the information side drive circuit 83. Signals with the same voltage level as the information data to be displayed are sequentially input. In this case, since the data is only for one scanning line, the drive circuit 85
For example, when the signal line for addressing the scanning line becomes "°l", it is addressed while Sl is written for one scanning line. Therefore, the information data is input to Sl in synchronization with the information data input to the drive circuit 83. Here, both the drive circuits 83 and 85 use signal lines C and D for address signals.
The signal line that is not selected is the reference potential point VE (
For example, O Porto).

FIG. 11 is a diagram showing the alignment state of the liquid crystal by dot-sequential writing. At the intersection of I2 and 82, "
a', the same value 'a' is output to the scanning side, and I3 and 5
At the intersection with 2, "b" is output on the information side and the same value "b'" is output on the scanning side, and furthermore, at the intersection between I4 and 82, "C" is output on the information side and the same value is output on the scanning side. "a'" of each is output as an information signal voltage. Then, the sum of the information signal voltages output to the information side and the scanning side is the threshold voltage vth of the liquid crystal (the information side, the scanning side, Vh
The regions a, b, and c exceeding the voltage (voltage t/2 or more) are inverted. The information signal written to one pixel by these liquid crystal driving methods is applied as an information voltage according to the gradation signal to both the information side and the scanning side, and a gradation display image is formed on the liquid crystal display panel by dot-sequential operation. be able to.

Next, a method of writing to the liquid crystal when performing line sequential driving will be described. According to A in FIG. 10, the image data for one operation includes information lines I81 to l159 and 1181''.
Image data d2 and d4 corresponding to 1256, such as character patterns, are output. And the control circuit 8
By switching control B from 6, the data for line sequential drive is connected to a'' and input to the drive circuit 82. In line sequential drive, the information signal (image data) is divided into an odd information signal and an even information signal. The information is separated by switching the switch Sv2 by the line sequential control circuit S4 in FIG. 9. FIG. 12 is a diagram showing the information signals S' and S'' when the switch Sw2 is switched. The odd number side drive circuit 93 has d2 and d4.
odd number signals 81.83.85...181.183...
・255, even number side drive circuit 92 has even number signals 82.84.88...182°184...2 of d2 and d4.
56 are stored consecutively. At this time, since the information signals dl and d3 are input to the dot sequential drive circuit,
The drive circuits 93', 92' are connected to a reference potential point VE (for example, O
Porto) is kept at the same potential. Next, drive circuit 93
After the information signal is stored in ', 92', a voltage of -vb is applied to the drive circuit 84 in FIG.

-vb voltage applied to the scanning line S1 and each drive circuit 93'.

Synthesis V with the information signal corresponding voltage Va output from 92'
Only the region where a+Vb exceeds the threshold voltage vth of the liquid crystal is inverted. FIG. 13 is a timing chart showing that when scanning is performed sequentially using scanning lines Sl and S2, the scanning line S1 is selected and the control signal from the control circuit 86 is applied within time t1 when the scanning signal voltage -vb is applied. By setting the output level control human power E to the °°1 level, in the first period 1z, the odd-numbered total outputs, which are the outputs of the drive circuit 93' in FIG. 12, become the reference potential Vr (for example, O port),
The even-numbered outputs of the drive circuit 92' each have an output voltage Va corresponding to the information signal. Also, the first period 1
In z, by setting the output level control human power E to the "0 par level," the total output of the even-numbered slot which is the output of the drive circuit 92' becomes the base/f8 potential Vr, and the output of the odd-numbered slot which is the output of the drive circuit 93' becomes the base/f8 potential Vr. The output is an output voltage V according to each information signal.
a (for example, O port).

FIG. 14 is a diagram showing the relationship between the output in the two periods mentioned above and the alignment state of the liquid crystal. In the first period (A), an output Va corresponding to the even-numbered information signal is output, and the liquid crystal layer is The alignment state diagram (C) shows that only the region where the voltage Va+Vb exceeds the threshold voltage vth of the liquid crystal is inverted, and similarly for the second period (B), the output Va according to the odd-numbered information signal is is output, and the voltage Va+V applied to the liquid crystal layer
The orientation state (C) shows that only the region where b exceeds the threshold voltage vth of the liquid crystal is inverted. As a result, it is understood that even-numbered gradation information can be written in the first period and odd-numbered gradation information can be written in the second period.

In this way, in the present invention, by switching the driving method according to the image data using the control circuit 86, it is possible to realize a variety of gradation displays. Here, the control circuit 86 may include, for example, a frame memory circuit having a memory for one frame of an image and a control circuit, or may be a small computer terminal device or the like.

The driving method of the above embodiment can be applied not only to black and white gradation display but also to color gradation display and color binary display by using a color filter. It is also possible to use a simple binary display; for example, a flip-flop type shift register is used as a drive circuit for a binary display, and a sample and hold type drive circuit is used for a gradation display as shown in Figure 15. analog memory can be used.

Regarding the optical modulation element, the most preferable example is a ferroelectric liquid crystal, particularly a ferroelectric liquid crystal having at least two stable states, but the present invention is not limited thereto, and may be applied to other optical modulation elements. It can also be applied to twisted nematic liquid crystals, guest host liquid crystals, etc. as modulation elements.

[Effects of the Invention] As explained above, according to the present invention, by switching between point-sequential driving and line-sequential driving for display, point-sequential driving and line-sequential driving are performed, so that high image quality is required, such as photographs and pictures. Optical modulation elements that realize an appropriate driving method depending on the content of image data by sequential driving, or line sequential driving when it is only necessary to identify display contents such as characters, and significantly improve image quality in gradation display. A driving method can be provided.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the basic structure of an optical modulation element that implements the driving method of the present invention, FIG. 2 is a potential gradient diagram thereof, and FIGS. 3, 8, 9, and 15 are wiring diagrams. Figures 4, 5, and 13 are voltage waveform diagrams, Figures 6, 7, and 10~
Figures 12 and 14 are explanatory diagrams of pixels, Figure 16 and Figure 1.
FIG. 7 is a schematic diagram of the orientation of ferroelectric liquid crystal. 1; Substrate, 2: Conductive film, 3; Transmission electrode, 4: Counter substrate, 5: Counter conductive film, 6; Counter electrode, 81, 91; Display panel, 82, 83.84.85.92.93; Start-up circuit, 86
．． 94. control circuit.

Claims (1)

[Claims] (1) A first substrate having a first conductive film and two or more striped transmission electrodes on the conductive film, a second conductive film disposed opposite to the transmission electrodes, and a second conductive film and the conductive film. In a method for driving an optical modulation element having a second substrate having two or more striped transmission electrodes thereon, and an optical modulation material disposed between the first substrate and the second substrate, An optical modulation element characterized by switching control between point-sequential driving in which an information signal voltage corresponding to a modulation signal is applied to two transmission electrodes simultaneously, and line-sequential driving in which it is applied only to the transmission electrodes of a second substrate. Driving method.