KR920007169B1 - Method for driving a liquid crystal apparatus - Google Patents

Abstract

No content.

Description

Driving Method of Matrix Liquid Crystal Optical Device

1 is an explanatory diagram showing an example of a matrix liquid crystal optical device.

2 is an explanatory diagram showing an example of a voltage waveform for realizing the present invention.

3 is an explanatory diagram showing signal supply timings to scan electrodes L ₁ to L _N.

4 is a waveform diagram showing an example of a pulse added to a pixel.

5, 6, and 7 are explanatory diagrams showing another waveform example for implementing the present invention, respectively.

* Explanation of symbols for main parts of the drawings

R ₁ to R _X : control electrode L ₁ to L _N : scan electrode

RS ₁ to RS ₂ : initialization signal S ₁ to S ₂ : selection signal

NS ₁ , NSi, NS ₂ : non-selective signal D ₁ to D ₂ : data signal

RD ₁ to RD ₂ : data signal C: data signal

C _R : Initialization control signal P ₁ , P ₂ , P ₇ , P ₁₀ : Initialization pulse group

P ₃ , P ₄ , P ₈ , P ₁₂ , P ₁₃ : Initialization pulse group

P ₅ , P ₆ , P ₉ , P ₁₄ , P ₁₅ : second pulse group

The present invention relates to a method of driving a matrix liquid crystal optical device.

In recent years, ferroelectric liquid crystals have been attracting attention instead of TN-type liquid crystals, and development of optical devices using them has been in progress.

As an optical mode of ferroelectric liquid crystal, there exist a birefringent optical mode and a guest host optical mode. When driving these, it is different from the conventional TN type liquid crystal, and since the optical response state (contrast) is controlled by the application direction of an electric field, the driving method used in the TN type liquid crystal is not used, and a special driving method is required. It is.

In consideration of the lifetime of the optical device, it is not preferable that the direct current component is applied to the pixel for a long time, and a driving method considering the point is required.

One driving method in which this DC component is not applied to the pixel for a long time is a driving method of " SID'85 Digests (1985) (p. 131 to p. 134).

Japanese Patent Laid-Open No. 60-176097 also discloses a driving method in which bistable in an optical response state is realized as a driving electric signal by using a ferroelectric liquid crystal having an alternating current stabilizing effect.

However, in the latter driving method, a direct current component is sometimes applied to the pixel for a long time, and the transparent electrode for driving is reduced and blackened, or there is a problem of causing liquid crystals. On the other hand, in the previous driving method, there is no problem of drawing, but if the time T required for rewriting one screen is t, the time required for writing one pixel is t = 4 × t × N (N is the number of scanning lines / screen). There is a problem that the rewriting time T is long and the number of lines is not increased too much, or is not suitable for moving picture display.

According to the present invention, the rewriting time can be shortened and the black side of the transparent electrode and the liquid crystal of the liquid crystal are not caused even if it is driven for a long time.

According to the present invention, a matrix type liquid crystal optical device is formed by a pixel using a liquid crystal having an alternating stabilizing effect by varying the compounding state of the molecules depending on an application direction of an electric field, and optically initialized by adding an initialization pulse group to the pixel. The first pulse group is added to the desired optical response state, and then the second pulse group is used to maintain the optical response state of the pixel by the AC stabilizing effect. The initialization pulse group and the first pulse group are A negative pulse having a symmetrical waveform exists for each of the positive and negative pulses, and the second pulse group has a frequency having an AC stabilizing effect, and a positive pulse and a negative pulse having a symmetrical waveform with this. Is achieved alternately, thereby achieving the above object.

In addition, after the initialization signal is supplied to the plurality of scan electrodes at the same time and the initialization is performed, the initialized pixel can be written in the desired optical response state, thereby reducing the rewriting time, and in accordance with the gradation, The halftone is also obtained by adjusting the amplitude of the high frequency component of the write pulse included in the signal.

In Fig. ₁ , ferroelectric liquid crystals are sandwiched between scan electrodes L ₁ to L _N and control electrodes R ₁ to R _x opposite thereto to form a plurality of pixels at the intersections of the electrodes. From the selection circuit SE, an initialization signal RS ₁ (FIG. 2) for time-divisionally initializing the scan electrodes L ₁ to L _N and a selection signal S ₁ (FIG. 2) for time-divisionally selecting are shown in FIG. It occurs at the timing shown, and when this initialization signal and the selection signal are not supplied, the non-selection signal NS ₁ (FIG. 2) is generated. The initialization signal RS ₁ is formed with voltages V _R ± H and -Vr ± H, the selection signal S ₁ is formed with a voltage ± V, and the non-selection signal NS ₁ is formed with ± H.

On the other hand, from the drive control circuit DR, in response to the desired optical response state of the pixel in the scan electrode supplied with the selection signal S ₁ , the response signal D ₁ or the reverse response signal RD ₁ in FIG. 2 is generated and controlled as a data signal. It is supplied to the electrodes R ₁ to R _x . That is, a response signal D ₁ is supplied to a control electrode that desires a response state (e.g., a light transmission state), and a reverse response signal RD is provided to a control electrode that desires a reverse response state (e.g., a light blocking state). To supply. The reverse response signal RD ₁ includes a high frequency component corresponding to the frequency at which the liquid crystal exhibits an AC stabilizing effect.

By supplying the above signals, the initialization pulse group P ₁ or P ₂ is _first applied to the pixel in which the response state is desired by the supply of the initialization signal RS ₁ to become the saturation response state, and then initialized to the saturation reverse response state. Thereafter, the first pulse group P ₃ is applied by the selection signal S ₁ and the response signal D ₁ . In the pulse group P ₃ , since the high frequency AC pulse component is 0, there is no AC stabilizing effect, and the saturation reverse response state is maintained by the voltage -V, and the saturation response state is then written by the write pulse of the voltage + V. Thereafter, the high frequency AC pulses of the second pulse group P ₅ or P ₆ are applied by the supply of the non-selection signal NS ₁ , so that the response state is stably maintained by the AC stabilization effect.

On the other hand, in the pixel in which the reverse response is desired, after the saturation response state is applied by applying the pulse group P ₁ or P ₂ , the pixel is initialized to the saturation reverse response state, and then the first pulse is selected by the selection signal S ₁ and the reverse response signal RD ₁ . Group P ₄ is added. The pulse group P ₄ superimposes a low frequency AC pulse having a voltage of ± V and a high voltage high frequency AC pulse of a voltage of ± 2H. The pulse group P ₄ does not become a saturation response state due to an AC stabilization effect of ± 2H. will be. Therefore, after the application of the pulse group P ₄ , the second pulse group P ₅ or P ₆ is applied, and the saturation region response state is maintained by the AC stabilization effect.

FIG. 4 shows examples of voltage waveforms applied to pixels for which these responses and inverse responses are desired.

Thus initialization pulse groups P _1, P ₂ and the first pulse group P _3, according to P ₄ pulses, respectively, to the negative polarity pulse of the symmetrical waveform exists for every positive pulse, the second pulse group P ₅ In P ₆ , since a positive pulse and a negative pulse having a symmetrical waveform are alternately generated, the DC voltage is not biased and added to the pixel, causing a confusion of the transparent electrode, or a sharpening of the liquid crystal. This disappears.

In addition, the introduction of the initialization signal allows the initialization of the next line at the same time as the supply of the selection signal, thereby reducing the rewriting time of the screen. In this example, the rewrite time T is 1/2 of the conventional T = 2 × t × N.

Again, since the second pulse groups P ₅ and P ₆ added at the time of non-selection do not contain low frequency pulse components, the holding force of the optical response state is strong and high contrast is realized.

In the first pulse group P ₃ , the frequency of the pulse and the pulse height V are appropriately determined so that the saturation region response state and the saturation response state can be obtained in relation to the magnitude of the spontaneous polarization of the ferroelectric liquid crystal and the liquid crystal cell thickness.

In the second pulse groups P ₅ and P ₆ , the frequency of the high-frequency alternating current pulse is preferably two times or more (preferably four times or more integer times) in the first pulse group P ₃ , and the pulse height. H is suitably determined so that the optical response state remains stable in relation to the magnitude of the dielectric anisotropy of the ferroelectric liquid crystal.

Again, the initializing response voltage V _R of the initializing pulse group P ₁ or P ₂ is determined so that the high frequency AC pulses of ± H are superimposed so as to be sufficiently response or reverse response.

Next, an example of realizing halftones will be described. 5 is to melt the example of FIG. 2 to realize the intermediate bath. The method of claim 5, also, the initialization signal RS ₁ and the selection signal S ₁ is one to control due to manufacturing the voltage ± h of the control signal C to be supplied to the control electrode R ₁ to R _x as the second assist, as a data signal.

In FIG. 5, the initialization pulse group P ₇ is applied to the pixel by the supply of the initialization signal RS ₁ and the control signal C to be initialized to the saturation reverse response state with respect to the saturation response state, and then by the supply of the selection signal S ₁ . The first pulse group P ₈ is applied. The first half of the pulse group P ₈ is formed by a pulse superimposed with a high frequency AC pulse on the voltage -V, and the saturated reverse response state initialized by the pulse group acting as a reverse response state is maintained, but ± h is applied to the latter voltage V. The unsaturated response state (midtone) is realized by applying the write pulse to the unsaturated state in which the high frequency AC pulses are superimposed.

In other words, only the pulse of voltage V is in the saturation response state, but the unsaturated response state is obtained by controlling the AC stabilization effect by the amplitude of the high frequency AC pulse superimposed thereon.

Therefore, after that, the high frequency alternating current pulse P _0, which is the second pulse group, is applied by the non-selection signal NS ' ₁ and the control signal C to maintain the above optical response state. In addition, the non-selection signal NS ' ₁ is a signal which is out of phase with the non-selection signal NS' ₁ in FIG. 2 in order to further stabilize the AC stabilization effect at the time of non-selection.

However, we initialized the saturation inverse response state before the pulse of the intermediate group, but this is important. The application of the pulse for giving halftone only changes the optical response state after the pulse portion is applied by the previous optical response state, so that stable halftone is not realized, but in the example of FIG. Because it initializes to a state, a stable halftone can be produced despite the previous optical response state.

Next, a description will be given of a method of simultaneously initializing each of a plurality of scan electrodes (for example, M blocks), and then driving the time-divisionally selected scan electrodes in the initialized block in sequence.

Figure 6, 7 also in, first voltage ± V _R Reset signal RS ₂ (FIG. 6) for instance a first-degree scan electrodes L ₁ of to L _N, a plurality of (for example, formed by L ₁ to L _M to the The non-initialized signal NRS (FIG. 6) is supplied to the other scan electrode. The control electrode group and R ₁ to R _x is supplied to the reset control signal _R C (Figure 6).

By supplying the above signals, the pixels in the M scan electrodes supplied with the initialization signal RS ₂ are initialized to the saturated reverse response state after the initialization pulse group P ₁₀ is applied to the saturated response state and the other pixels. The high frequency AC pulse P ₁₁ is applied to the optical response state.

Subsequently, a selection signal S ₂ (Fig. 7), which is formed at a voltage ± V, is supplied to the initialized scan electrode described above, and a non-selection signal NS ₂ (which is formed at a voltage ± H is supplied to a scan electrode that is not supplied with a selection signal. 7) is supplied.

On the other hand, to the control electrodes R ₁ to R _x , the response signal D ₂ or the reverse response signal RD ₂ in FIG. 7 is supplied as the data signal in response to the desired optical response state of the pixel in the scan electrode supplied with the selection signal S _2. do.

The first pulse group P ₁₂ is applied to the pixel for which a response is desired by supplying the above signal, and the saturation response state is maintained by the pulse of voltage -V, and then the saturation response state is generated by the write pulse of voltage + V. After writing, the high frequency AC pulse P ₁₄ or P ₁₅ as the second pulse group is applied, and the response state is maintained. On the other hand, the first pulse group P ₁₃ is applied to the pixel for which the reverse response is desired by the selection signal S ₂ and the reverse response signal RD ₂ . The pulse group P ₁₃ has a high voltage high frequency AC pulse having a voltage of ± 2H superimposed on a low frequency AC pulse having a voltage of ± V. It is maintained. After the addition of the pulse group P ₁₃ , the saturated reverse response state is maintained by the pulse group P ₁₄ or P ₁₅ .

Therefore, when M time-division scans are finished, the next M blocks are initialized and time-division scans are performed in sequence.

In this example, in the ultra-initialization pulse group P ₁₀ and the first pulse groups P ₁₂ and P ₁₃ , the negative pulses of symmetrical waveforms exist for all the positive pulses, and the second pulse groups P ₁₄ and P _{15 are present.} In, since a positive pulse and a negative pulse having a symmetrical waveform are alternately generated, a bias DC voltage ratio is not added.

In addition, the rewriting time T of one screen is T = (2 × t × N / M) + (2 × t × N) = E × t (N + N / M), and the rewriting time is made by taking M large. Can shorten.

Again, as in the above example, it is also possible to obtain a halftone by controlling the amplitude of the high frequency AC pulse superimposed on the low frequency pulse.

In addition, in the above description, the response is referred to as the response by the voltage on the positive side and the response by the voltage on the negative side. However, since the response and the reverse response are a bunch, the reverse response and the negative side of the voltage on the positive side are reversed. The response may be referred to as a voltage.

By the way, the signal supplied to each electrode is not limited to the above thing, Various changes are possible, and you may make it apply a bias voltage suitably as needed.

In the above-described embodiment, the matrix optical device as shown in FIG. 1 has been described above. However, the present invention is not limited thereto, and the optical shutter array provided in a line shape is divided into a plurality of blocks, and the matrix optical device is connected in a matrix. Needless to say, the same applies to the driving of the liquid crystal shutter array. In this case, if the reverse response state is set to the dark (light cutoff) state, high contrast can be taken.

According to the present invention, by using the initialization signal, the pixel can be initialized in the next scan electrode at the time of writing the pixel in one scan electrode, so that the rewriting time of the pixel can be shortened, and further, the pixel is added to the pixel. The pulses to be generated are negative pulses with respect to all positive pulses, or positive pulses and negative pulses having a symmetrical waveform are alternately generated, so that a biased direct current voltage is not applied. Even if it does, it has many effects, such as black-and-white of a transparent electrode and no hardening of liquid crystal. In addition, by controlling the amplitude of the high frequency component included in the write pulse, a stable optical response state including the halftone is obtained.

In addition, after initializing the pixels in the plurality of scan electrodes at the same time, the desired optical response state can be written, thereby reducing the rewriting time.

Claims (6)

The liquid crystal optical device of the matrix type liquid crystal device comprising a liquid crystal having an alternating state of molecules depending on an application direction of an electric field and sandwiching a liquid crystal having an alternating current stabilizing effect between a plurality of scan electrodes and a plurality of control electrodes to form pixels at the intersections of the electrodes. In the driving method, each scan electrode is supplied with an initialization signal and a selection signal subsequent thereto, and a non-selection signal is supplied when the initialization signal and the selection signal are not supplied, and the liquid crystal exhibits an AC stabilizing effect to each control electrode. A data signal containing a high frequency component corresponding to a frequency to be emitted or a data signal not containing this high frequency component is supplied in synchronization with the supply of a selection signal, and an initialization pulse group is supplied to the pixel by a potential difference between the initialization signal and the data signal. Applied and optically initialized, and the pixel is caused by the potential difference between the selection signal and The first pulse group is applied to the desired optical response state, and the second pulse group is applied to the pixel by the potential difference between the unselected signal and the data signal, thereby maintaining the optical response state of the pixel by the AC stabilizing effect. In this case, the initializing pulse group causes the pixel to be in a light transmission state or a light blocking state, and a negative symmetric waveform pulse exists from all the positive pulses, and the first pulse group desires the pixel. Including the pulse which maintains an initialization state by the write pulse or initialization pulse group which change to the optical response state to be said, and the negative pulse of a symmetrical waveform exists with respect to all the positive pulses, The 2nd pulse group is It is characterized by the fact that a positive pulse and a negative pulse having a symmetrical waveform are generated alternately with a frequency having an alternating current stabilizing effect. Matrix type driving method of the liquid crystal optical device. The method of driving a matrix liquid crystal optical device according to claim 1, wherein the liquid crystal is a ferroelectric liquid crystal showing negative dielectric anisotropy in the frequency range of an alternating pulse in the second pulse group. The liquid crystal optical device comprising a liquid crystal having an alternating stabilization effect depending on the direction in which an electric field is applied is sandwiched between a plurality of scan electrodes and a plurality of control electrodes to form pixels at the intersections of the electrodes. In the driving method, each scan electrode is supplied with an initialization signal and a selection signal subsequent thereto, and a non-selection signal is supplied when the initialization signal and the selection signal are not supplied, and the liquid crystal is AC stabilizing effect to each control electrode. A data signal containing a high frequency component corresponding to a frequency generating the signal is supplied in synchronization with the supply of the selection signal, and is optically initialized to apply an initialization pulse group to the pixel by a potential difference between the initialization signal and the data signal, The desired optical response state by applying the first pulse group to the pixel by the potential difference between By setting the potential difference between the non-selection signal and the data signal, the second pulse group of the pixel is added to maintain the optical response state of the pixel by the AC stabilization effect. Or a light blocking state, and a negative pulse having a symmetrical waveform exists for all positive pulses, and the first pulse group includes a high frequency component to change the pixel into a desired optical response state. The symmetrical waveform of the negative pulse exists for all the positive pulp, including the pulse which maintains the state initialized by the pulse or the initialization pulse group, and the 2nd pulse group has the frequency which produces the AC stabilization effect. In addition, positive pulses and negative pulses having a symmetrical waveform are alternately generated. Method of driving a matrix type liquid crystal optical device, characterized in that to obtain an optical state in response to the desired hameuroseo change the amplitude of the wave component by adjusting the amplitude of the high-frequency component of the write pulse, includes a half tone. 4. The method for driving a matrix type liquid crystal optical device according to claim 3, wherein the liquid crystal is a ferroelectric liquid crystal showing negative dielectric anisotropy in a frequency range of an alternating pulse in the second pulse group. The matrix type liquid crystal optical device comprising a liquid crystal having an alternating stabilization effect depending on a direction in which an electric field is applied to sandwich a liquid crystal having an alternating current stabilizing effect between a plurality of scan electrodes and a plurality of control electrodes to form pixels at the intersections of the electrodes. In the driving method, after supplying an initialization signal to a plurality of scan electrodes simultaneously, a selection signal is supplied to each scan electrode to which the initialization signal is supplied, and a non-selection signal is supplied when the initialization signal and the selection signal are not supplied. Each control electrode is supplied with an initialization control signal in synchronization with the supply of an initialization signal, and includes a high frequency component or a high frequency component corresponding to a frequency at which the liquid crystal exhibits an AC stabilizing effect in synchronization with the supply of the selection signal. Supplying a data signal that does not include the voltage difference between the initialization signal and the initialization control signal By applying an initialization pulse group to the pixel, and optically initializing, by applying the first pulse group to the pixel by the potential difference between the selection signal and the data signal, the non-selection signal and data signal and The second pulse group is added to the pixel by the potential difference of and the optical response state of the pixel is maintained by the AC stabilizing effect. The initialization pulse group causes the pixel to be in the light transmission state or the light blocking state, and all the positive electrodes The negative pulse of the symmetrical waveform exists with respect to the positive pulse, and the first pulse group supplies the selection signal following the initialization pulse group as the write pulse for changing the pixel to the desired optical response state, and the initialization signal and the selection signal. When not supplied, the non-selection signal is supplied, and each control electrode is supplied with an initialization control signal in synchronization with the supply of the initialization signal. In synchronization with the supply of the selection signal, a data signal containing a high frequency component corresponding to a frequency at which the liquid crystal exhibits an AC stabilizing effect is supplied, and the initialization pulse group is applied to the pixel by a potential difference between the initialization signal and the initialization control signal. The first pulse group is applied to the pixel by the potential difference between the selection signal and the data signal by applying and optically initialized to the desired optical response state. The potential difference between the non-selection signal and the data signal is applied to the pixel. The second pulse group is added to maintain the optical response state of the pixel by the AC stabilization effect. The initialization pulse group causes the pixel to be in a light transmission state or a light blocking state, and also has a symmetrical waveform for all positive pulses. The negative pulse of is present, and the first group of pulses includes a high frequency component to change the pixel into a desired optical response state. The negative pulses of the symmetrical waveform exist for all the positive pulses, including the pulses maintained in the state initialized by the write pulses or the initialization pulse groups, and the second pulse group produces the AC stabilizing effect. A pulse having a frequency and a positive pulse and a negative pulse having a symmetrical waveform are alternately generated. The gray level changes the amplitude of the high frequency component of the data signal, thereby adjusting the amplitude of the high frequency component of the write pulse. A method of driving a matrix type liquid crystal optical device, characterized by obtaining a desired optical response state including a halftone. 6. The method for driving a matrix liquid crystal optical device according to claim 5, wherein the liquid crystal is a ferroelectric liquid crystal showing negative dielectric anisotropy in the frequency range of an alternating pulse in the second pulse group.

Images