KR920007128B1 - Method for driving a liquid crystal optical 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 and 4 show voltage waveforms for implementing the present invention.

3 and 5 are waveform diagrams showing examples of pulses applied to pixels.

* Explanation of symbols for main parts of the drawings

L ₁ to L ₇ : scanning electrode R ₁ to R ₅ : control electrode

S ₁ , S ₂ : Selection signal NS ₁ , NS ₂ : Unselection signal

C ₁ , C ₂ : Data signal RS: Initialization signal

P ₁ : first pulse group P ₂ : second pulse group

P ₃ : Initialization pulse P ₄ : Write pulse

P ₅ : second pulse group

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

In recent years, ferroelectric liquid crystal has attracted attention instead of the TN type liquid crystal, and development of an optical device using the same has been advanced.

Examples of the optical mode of the strong dielectric liquid crystal include a birefringent optical mode and a guest host optical mode. When driving these, it differs 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 for the TN type liquid crystal is not used, and a special driving method is required. will be.

In consideration of the lifetime of the liquid crystal, 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 a pixel for a long time is a driving method of "SID 85 Digest" (1985) (P.131 to P.134). Japanese Patent Application Laid-Open No. 60-176097 also discloses a driving method capable of realizing bi-stable stability of an optical response state using a ferroelectric liquid crystal having an alternating current stabilization effect as a driving electric signal.

However, in any driving method, a stable halftone is not obtained, and in the driving method in which a direct current component is applied to a pixel for a long time like the latter driving method, the transparent electrode for driving is reduced to black, or causes liquid crystals to be hardened. There was a problem.

It is an object of the present invention to provide a method of driving a matrix liquid crystal optical device which can reduce the time required for rewriting even when the transparent electrode is not blackened, the liquid crystal is not instantiated even after long driving.

According to the present invention, a plurality of pixels are formed by a liquid crystal having an alternating current stabilizing effect, and an initializing pulse is first applied to the pixels to optically initialize them, and then a write pulse containing a high frequency component is applied to the desired optical response state. After that, the optical response state is maintained by applying the second pulse group of the frequency having the AC stabilizing effect, and the desired optical response including the halftone is adjusted by adjusting the amplitude of the high frequency component of the write pulse according to the gray scale. The above object is achieved by obtaining a state.

In Fig. ₁ , a plurality of pixels are formed at the intersections of the electrodes with a ferroelectric liquid crystal having an alternating current stabilizing effect interposed between the control electrodes R ₁ to R ₅ facing the frequency electrodes L ₁ to L ₇ . From the selection circuit SE, a selection signal S ₁ (FIG. 2) which sequentially selects scan electrodes L ₁ to L ₇ in time division is generated, and a non-selection signal NS ₁ is generated when this selection signal is not supplied. The selection signal S ₁ is composed of voltage ± V, and the non-selection signal NS ₁ is composed of voltage ± H.

On the other hand, from the drive control circuit, the control signal C ₁ formed by the voltage 0 in FIG. 2 and the voltage ± h according to the desired halftone is supplied to the control electrodes R ₁ to R ₅ as data signals. Control signal C is _1, and the liquid crystal containing a high-frequency component that an AC stabilization effect.

By supplying the above signals, the first pulse group P ₁ is _first applied to the pixel as shown in FIG. In the pulse group P ₁ , an initialization pulse of voltage -V is first applied, and once initialized to a saturation reverse response state, a write pulse in which a high frequency AC pulse of ± h is superimposed on a DC voltage V is applied to the high frequency AC pulse height. The halftone based on this is realized. In other words, when the pulse height h is 0, the saturation response state is caused by the direct current voltage v, and as the h becomes larger, the unsaturated response state (midtone) is obtained by the AC stabilization effect.

After the application of the above-mentioned pulse group P _{1, the} high frequency AC pulse P _2, which is the second pulse group, is applied by the non-selection signal NS ₁ to maintain the intermediate tone.

Here, in the first pulse group P ₁ , the average voltage value of the initialization pulse has the same absolute value and different polarity as the average voltage value of the write pulse, and the second pulse group P ₂ has a frequency that produces an AC stabilizing effect. In addition, since positive pulses and negative pulses having symmetrical waveforms are generated alternately, black edges of the transparent electrodes, exemplification of the liquid crystal, and the like are eliminated.

In addition, a stable halftone is realized by initializing the saturated reverse response state before the write perks are applied. In other words, when only an unsaturated response pulse is applied to produce an intermediate tone, even if the same unsaturated response pulse is affected by the preceding response state, it becomes another intermediate tone and a stable intermediate tone cannot be obtained.

In addition, the pulse width and the pulse height V of the initialization pulse are appropriately determined so as to obtain a saturation response state and a saturation response state in relation to the magnitude of the spontaneous polarization of the ferroelectric liquid crystal and the cell thickness. In addition, the pulse width of the high frequency AC pulse is preferably 1/4 or less of the initialization pulse width, and the pulse height H is appropriately determined so that the response state remains stable in relation to the magnitude of the dielectric anisotropy of the ferroelectric liquid crystal.

Next, an example of supplying a signal for initializing the pixel at the timing before supplying the selection signal will be described in detail. The method of claim 4, also, short of the selection signal S ₂ is formed of a voltage -V H ± sequentially supplied to the first-degree scan electrodes L ₁ to L _7, initialization is formed of a voltage ± V H in the timing signal before that RS To supply. In the case of non-selection, the non-selection signal NS ₂ formed with the voltage ± H is supplied.

On the other hand, to the control electrodes R ₁ to R ₅ , a control signal C ₂ , which is formed at a voltage ± h of a desired halftone, is supplied as a data signal. The control signal C ₂ is, and the liquid crystal containing a high-frequency component that the stabilizing effect.

The pixel arrangement, as shown in FIG. 5, first, applying a set-up pulse P _3. Pulse P ₃ is a superposition of high-frequency AC pulse ± (hH) on DC voltage -V, initialized to saturation response by the application of pulse P ₃ , and then write write pulse P ₄ to write halftone, Thereafter, the high frequency pulse P ₅ as the second pulse group is applied to maintain the halftone.

According to this example, in order to use the initialization signal, the pixel can be initialized in the next scan electrode when the pixel is written in one scan electrode, so that the supply time of each signal is 1/2 of the above example. Therefore, the number of digits that can be scanned within the same time can be doubled. In other words, if the same number of digits is scanned, the rewriting speed of one screen can be doubled.

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 those of the front and back, the reverse response and the voltage on the negative side are reversed. You may call it answering.

In addition, as the pulse for realizing the halftone, the halftone may be provided by applying the applied width (duty) modulation of ± h, not limited to the modulation of the voltage ± h.

By the way, the signal supplied to each electrode and the application method of a signal are not limited to the said thing, A various change is possible.

According to the present invention, halftone can be realized by controlling the amplitude of the high frequency component of the write pulse, and stable halftone can be realized by initializing the pixel once before the write pulse to write the halftone. In addition, since the average voltage value of the initialization pulse applied to the pixel has the same absolute value as the average voltage value of the write pulse, the polarity is inverse. In the second pulse group, the positive pulse and the symmetric waveform negative pulse are alternately generated. Even if it drives for a long time, a transparent electrode does not blacken or a liquid crystal hardens. By introducing the initialization signal, the pixel can be initialized in the next scan electrode when the pixel is written in one scan electrode, and the time required for rewriting the optical response state of the pixel can be shortened. The number of scans that can be injected within the same time can be increased.

Claims (4)

The matrix type liquid crystal optical device comprising a liquid crystal having an alternating stabilization effect depending on an application direction of an electric field and interposing a plurality of scan electrodes and a plurality of control electrodes to form pixels at the intersections of the electrodes. In the driving method, a selection signal is sequentially supplied to each scan electrode, and a non-selection signal is supplied when the selection signal is not supplied, and a high frequency component corresponding to the frequency at which the liquid crystal exhibits an AC stabilizing effect is supplied to each control electrode. The data signal to be supplied is supplied in synchronization with the supply of the selection signal, and the first pulse group is applied to the pixel by the potential difference between the selection signal and the data signal, thereby bringing the desired optical response state to the non-selection signal and data. By the potential difference with the signal, the second pulse group is applied to the pixel to maintain the optical response state of the pixel by the AC stabilizing effect. The first pulse group is composed of an initialization pulse for bringing a pixel into a light transmission state or a light blocking state, followed by a write pulse for changing the pixel to a desired optical response state, the write pulse comprising a high frequency component. In addition, the average voltage value is the same as the absolute voltage value of the initialization pulse and the polarity is different, and the second pulse group has a frequency which produces an alternating current stabilizing effect, and the positive pulse and this and the waveform are symmetrical. Phosphorous negative pulses are generated alternately, and according to the gradation, the amplitude of the high frequency component of the data signal is adjusted, thereby adjusting the linear width of the high frequency component of the write pulse to obtain a desired optical response state including the halftone. A method of driving a matrix liquid crystal optical device. The method according to claim 1, wherein the liquid crystal is a ferroelectric liquid crystal displaying negative dielectric anisotropy in the frequency range of the AC pulse. Matrix liquid crystal optical device comprising liquid crystals having an alternating stabilization effect depending on the direction in which an electric field is applied, interposed between a plurality of scan electrodes and a plurality of control electrodes, and forming pixels at the intersections of the electrodes. In the driving method of the above, each scan electrode is supplied with an initializing signal followed by a selection signal following this, a non-selection signal is supplied when the initialization signal and the selection signal are not supplied, and the liquid crystal is stabilized alternatingly with each control electrode. A data signal containing a high frequency component corresponding to the frequency to be effected is supplied in synchronization with the supply of the selection signal, and an initializing pulse is applied to the pixel and optically initialized by the potential difference between the initialization signal and the data signal. By the potential difference between the signal and the data signal, a write pulse having the same pulse width as the initialization pulse is applied to the pixel. For example, an alternating pulse is applied to the pixel by the potential difference between the non-selection signal and the data signal to maintain the optical response state of the pixel by the AC stabilization effect. It is a transmission state or a light blocking state, and a write pulse is a pulse which changes to a desired optical response state, and contains a high frequency component, and the average voltage group has the same absolute value as that of the initialization pulse and has different polarity. The alternating current pulse has an alternating frequency and a positive polarity pulse and a negative polarity wave whose polarity is symmetrical. By adjusting the amplitude of the high frequency component of the write pulse, the desired optical response state including the halftone is obtained. The drive method of the matrix type liquid crystal optical device. 4. A method according to claim 3, wherein the liquid crystal is a ferroelectric liquid crystal displaying negative dielectric anisotropy in the frequency range of the alternating current pulse.