JPS63193131A - Driving method for liquid crystal cell - Google Patents

Abstract

PURPOSE:To execute switching of a throttle operation and a light non- transmission state at a high speed, and also, to reduce the deterioration of a liquid crystal by using the liquid crystal whose dielectric anisotropy is reversed by a frequency, applying a high frequency voltage, and executing the throttle operation by a low frequency voltage. CONSTITUTION:A liquid crystal between the upper plate 2 and the lower plate of a cell 1 shows a positive dielectric anisotropy and goes to a light non- transmission state, when for instance, the voltage of a low frequency of <=10kHz is applied, and shows a negative dielectric anisotropy and goes to a light transmission state, when a voltage of a high frequency of >=10kHz is applied. At the time of operation, power sources 14, 15 are grounded, and a power source 13 generates a low frequency voltage, and sets the cell to the light non- transmission state. Subsequently, when the power source 13 is set to a high frequency of about 10V-scores of V, and the power source 14 is set to above the voltage of the power source 13, and the power source 15 is set to below the voltage of the power source 13, a throttle operation is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving a liquid crystal cell that is capable of area modulation using liquid crystal.

[Conventional technology]

Conventionally, liquid crystals have been used not only for display purposes, but also as optical shutters that control the transmission of light.1 Among these, when used as optical shutters that control the transmission of light, liquid crystals are used to either transmit light or not. It is generally used for these two values.

[Problem that the invention seeks to solve]

In this way, liquid crystals are only used for binary values because the voltage width at which the transition process that changes the alignment state of liquid crystals to other states occurs is relatively narrow, and the light-transmitting and non-light-transmitting parts must be operated at high speed. Because it is difficult to do this, there has not been much research into controlling the amount of light transmission or reflection to an intermediate level by going beyond this transition process.

The present inventors have previously proposed a liquid crystal cell that uses liquid crystal to control the amount of light transmission and reflection at an intermediate stage. The two electrodes are set at ground voltage, and the other electrode is applied with a voltage of a lower frequency (hereinafter referred to as low frequency) than the point of change at which the dielectric anisotropy of the liquid crystal used is reversed (hereinafter referred to as change point). Next, when the light transmission window is in the aperture state, a low frequency unipolar voltage is applied to one of the two electrodes on one plate, and a similar lower voltage is applied to the other electrode. At the same time, this is a driving method in which a frequency higher than the point of change (hereinafter referred to as high frequency) is applied to the other plate. In this case, there is a problem in that the voltage applied to the liquid crystal is biased toward one polarity, resulting in rapid deterioration of the liquid crystal.

[Means for solving problems]

In the method for driving a liquid crystal cell according to the present invention, when the liquid crystal cell is placed in a non-light transmitting state, a low frequency voltage is applied between the transparent electrode of one plate and the transparent electrode of the other plate, and the liquid crystal cell is squeezed. To achieve this, a high-frequency voltage is applied to the transparent electrode on the other plate, a unipolar low-frequency voltage at the same voltage or different voltages is applied to the two electrodes on one plate, and the subsequent photoinhibition is applied. When creating a transparent state, a bipolar low-frequency voltage is applied to the transparent electrode on one plate and the transparent electrode on the other plate, and the voltage with the opposite polarity to the voltage applied to the two electrodes on one plate is narrowed down. A signal that continues for the same time as the state (t1) or a signal divided into multiple parts corresponding to the signal is added to the period in which the non-light transmitting state continues, and in the aperture state, two of the plates on one side are The product (T1) of the voltage (v1) and time (t1) applied to the liquid crystal by each voltage applied to the electrodes is opposite in sign and has the same absolute value as the voltage (V2) and time (t2).
) is applied to each of the two electrodes on one plate.

[Effect]

In this invention, a liquid crystal whose dielectric anisotropy is reversed depending on the frequency is used, and a high-frequency voltage is applied and the aperture operation is performed by a low-frequency voltage, so that switching between the aperture operation and the non-light transmitting state is performed at high speed.

Furthermore, in the method for driving a liquid crystal cell of the present invention, the magnitude of the aperture operation can be controlled by two methods: a method of controlling the low frequency voltage, and a method of controlling the duty by setting the low frequency wave height to a constant value. , the latter is suitable for digital circuits.

Further, when using a digital circuit, it is preferable to use a driving method that controls a uni-polar, binary voltage such as positive polarity and ground voltage, or negative polarity and ground voltage. The driving method of the present invention enables unipolar control of image signals, which account for the majority of circuits, and when combined with the aforementioned duty control, enables control using unipolar binary signals, which is most suitable for digital control. I have to. Also,
When using a unipolar signal, if a high frequency signal is used, as the duty increases, the voltage of the low frequency component in the high frequency increases, and when the duty is 100%, the high frequency properties are lost. Only low frequency components will be present. However, when a low frequency signal is used, the duty is 10
Even at 0%, the low frequency properties are preserved. For this reason,
As in this invention, the method of creating a voltage gradient using unipolar low frequency waves can use a substantially lower voltage than the method of creating voltage gradients using unipolar high frequency waves, and is effective for economical use of power supplies and circuits. be.

In addition, the method of creating a voltage gradient using a unipolar voltage causes the polarity of the voltage applied to the liquid crystal to be biased, but by using the charge compensation method of the present invention, the polarity bias is eliminated, and ii
Deterioration of one item is reduced. 1 [Example] FIG. 8 is a perspective view showing an exploded state of a basic cell for liquid crystal used in the present invention. In this figure, 1 is a basic cell, and 2 is one transparent plate (hereinafter, for convenience, 3 is the other transparent plate (hereinafter also referred to as the lower plate), 4 is a spacer,
5 is a transmission hole of the spacer 4; 6 is an electrode of the upper plate 2;
7 and 8 are electrodes of the lower plate 3, and 9 and 10 are main electrodes consisting of transparent electrodes.

Here, polarizing plates are required above the upper plate 2 and below the lower plate 3, but the irons are omitted because the drawing becomes complicated. The basic cell 1 consists of the upper plate 2, the spacer 4, and the lower plate 3 being brought into close contact with each other, and a liquid crystal placed between the upper plate 2 and the lower plate 3 created by the spacer 4. In addition, B, C,
D indicates the terminal of the electrode 6°7.8 (at the same time, the terminal voltage).

Next, the basic operation of this basic cell 1 will be explained.

The inner boundaries of the electrodes 7 and 8 on the lower plate 3 in FIG. 8 are a and b, respectively.
shall be. Further, a signal voltage is input to the electrode 7, and the electrode 8 and the electrode 6 of the upper plate 2 are grounded.

FIG. 9 shows the relationship between the light transmittance when a signal voltage is applied to the electrode 7 in FIG. 8 and the positions a and b in FIG. 8 using the signal voltage as a parameter.

At this time, it is preferable to modulate the signal voltage with an alternating current signal because deterioration of the liquid crystal will be reduced.

Further, the optical plates Oi1 placed above and below the basic cell 1 are shown in a state where they are placed so that their polarization planes are perpendicular to each other.

When the polarization planes of this polarizing plate are parallel, the light transmittance is reversed. Further, an example in which a twisted toy, matic mode liquid crystal (hereinafter referred to as T N 2y crystal) is used as the liquid crystal is used because it is easy to understand the principle.

When 2■ is applied to the electrode 7, the light transmittance near point a partially decreases, and when 5■, almost no light near point a is transmitted. Further, as the voltage increases to 8V and IOV, the non-light transmitting portion moves in the direction of point b, and the area of the light transmitting portion decreases. This phenomenon occurs because when a signal voltage is applied to the electrode 7, a current flows in the direction of the grounded electrode 8, and since the main 1FM 10 acts as a resistor, the main electrode 1o has an almost linear drop from position a to position A. A voltage distribution is formed. On the other hand, a voltage equal to the voltage difference between the voltage distributed and formed on the main electrode 10 of the lower plate 3 and the grounded main electrode 9 of the upper plate 2 is applied to the liquid crystal. On the other hand, with a liquid crystal, the orientation of the liquid crystal changes with a voltage of about 2 cm, and the light transmittance partially changes. For this reason, the signal voltage becomes high, and the position where a voltage of 2 or more is applied to the liquid crystal spreads toward point b, thereby reducing the number of light transmitting parts.

FIG. 10 specifically illustrates changes in the state of the light transmitting window of the cell that transmits light. This state is called an aperture operation (a state in which a light transmitting state and a light non-transmitting state are distributed). In (i) to (1v) in the figure, the voltage B of the electrode 6 is OV, and (
Only v) is for B=10V. When the signal voltage C applied to the electrode 7 is 0 in (1), the entire light transmitting window is in a light transmitting state (hereinafter, this part will be referred to as the light transmitting section 41).
In C-2, 5■ of (ii), there is a part near point a where almost no light transmits (hereinafter, this part will be referred to as the non-light transmitting part 42), and to the right of it, the orientation of the liquid crystal gradually changes. There is a portion 43 (hereinafter this portion will be referred to as a transition portion) where the light transmission gradually increases due to change, and a light transmitting portion 41 is located to the right of the portion 43. (Mountain)
When C=4V, the non-light transmitting part 42 expands, and the transition part 4
3 moves to the right while being slightly pinched, and the light transmitting portion 41 decreases. This tendency became even more remarkable at C=7V in (1v)°. Further, when (V) C=10V and B=10V, no light is transmitted at all.

FIG. 11 shows the case of driving under different conditions, and for easy understanding, the lower plate 3 of the cell with the structure shown in FIG.
Rotate the electrodes 6, 7, 8 (actually, as shown in Figure 8)
is a sectional view and an external circuit diagram.

Furthermore, DC power supplies are used for the power supplies 11 and 12, and are connected to the electrodes 7 and 8 on the lower plate 3. Although the power supplies 11 and 12 are DC power sources for the sake of explanation in FIG. 12, the same effect can be achieved even if the power sources 11 and 12 are AC power sources. Matco, the grounding position is the first
This was chosen to make the explanation of Figure 2 easier to understand.

FIG. 12 is a diagram showing the positions on the main electrode 1o in FIG. 11 and the voltage difference between electrodes 7 and 8 at each position.

The solid lines (1) and (11) in the figure are the voltage distribution of the main electrode 10 when voltage is applied by the power supplies 11 and 12, and the actual 6% (ii) is when the output of the power supply 12 is OV. . On the other hand, the broken line is the threshold voltage at which the liquid crystal changes from the transparent state to the non-light transmitting state via the transition state, and the dotted line is the boundary between the transition state and the non-light transmitting state, which exist in both polarities. Here, the area closer to the electrode 8 than the part where the solid lines (i) and (11) intersect with the broken line forms a light transmitting part 41, and the part closer to the electrode i7 passes through a transition part 43 and becomes a light non-transmitting part 42. However, the 12th
In the figure, only the light transmission distribution formed by the solid line (1) is shown in the range indicated by the arrow. In this case, the distribution of the light transmitting portions 41 actually formed is similar to (1v) in FIG. 10.

The difference between these solid lines (i) and (ii) is that even if the voltage of the power supply 11 is the same, the case where the voltage is applied by the power supply 12 and the case where the voltage is applied by the power supply 12 are
In the case of V, the position across the threshold voltage shown by the dotted line is different, and the range of the light transmitting portion 41 is narrower in the solid line (1). At this time, the power consumed by the main electrode 1o is characterized by being smaller in the solid line (1) than in the solid line (II). but,
A disadvantage is that the range where the solid line (i) intersects between the broken line and the dotted line increases, and the area of the transition portion 43 increases. These operations will produce similar results even if bipolar alternating current voltages are used.

The above is the basic operation of this invention. In this method using T N ill crystal, the speed of changing from an optically rotating state to a non-optically rotating state is as high as about 0.1 to 10 milliseconds, but conversely, The speed at which the state changes from the optically active state to the optically active state is one to two orders of magnitude slower than that. For this reason, it has the disadvantage of slow operation when used as an optical switch for an optical printer, which will be described later. On the other hand, when the frequency of the alternating current of the drive power source is low, it exhibits positive dielectric anisotropy, and when the frequency is high, it exhibits negative dielectric anisotropy.By changing the frequency using a liquid crystal, high-speed operation becomes possible. .

FIG. 13 shows an example of the characteristics of liquid crystal showing dielectric anisotropy with respect to driving frequency, which is positive below 10 KHz.

Above that point, negative dielectric anisotropy is exhibited. This boundary point will hereinafter be referred to as the transition point.

Next, a driving method of the present invention for driving a cell using this will be explained.

When a low frequency voltage below the change point is applied, a positive dielectric anisotropy is exhibited, and the liquid crystal assumes a home-first lobbing arrangement and becomes non-light-transmissive.

On the other hand, when a high-frequency voltage is applied above the change point, negative dielectric anisotropy is exhibited, and the liquid crystal becomes homogeneously aligned and enters a light-transmitting state. By utilizing this, it is possible to increase the speed at which the state changes alternately between the non-light transmitting state and the light transmitting state.

A specific example will be explained by using an ECB liquid crystal exhibiting an electric field controlled birefringence effect as the liquid crystal having the characteristics shown in FIG. 13 to fabricate a cell and using the external circuit shown in FIG. 14.

The cell shown here is a cell under the same conditions as in FIG. 11, but with power supplies 13, 14 and 15 connected to electrodes 6, 7 and 8, respectively.

Here, the light sweeping plates installed above and below the cell were placed so that their polarization planes were perpendicular to each other. The power source 13 can alternately output low frequency and high frequency alternating current, and when operated, the power source 13 enters a non-light transmitting state when low frequency is applied, and becomes a light transmitting state when switching to high frequency. On the other hand, the power supplies 14 and 15 each output low-frequency alternating current whose wave height is controllable.

Next, the actual operation will be explained.

First, as a first step, the power supplies 14 and 15 are grounded, and the power supply 13 generates a low frequency voltage to make the cell non-light transmitting. At this time, the power supplies 14 and 15 generate low frequency waves having the same phase, and even if the power supply 13 is in the grounded state, the cell similarly enters the non-light transmitting state. Next, in the second step, the power source 13 is set to a high frequency of about IOV to several tens of volts, the power source 14 is set at a voltage higher than the voltage of the power source 13, and the power source 15 is set at a voltage lower than the voltage of the power source 13.The aperture operation is similar to that shown in FIG. will be done. This is because, as shown in the voltage distribution diagram of FIG. 15, the gradient shown by the actual ti(i) due to the low frequency voltage decreasing from electrode 7 to electrode 8 with respect to the high frequency shown by the broken line (ii) is Formed bipolar. At this time, the region where the low frequency voltage is lower than the high frequency voltage becomes the light transmitting section 41, and the opposite region becomes the light non-transmitting section 42, and an aperture operation is performed.

The feature of this method is that both the aperture action and the closing action are 0.1 to 2
The point is that it can operate at high speeds of about milliseconds.

The range of this operating speed depends on the applied voltage, and the larger the difference between the effective voltages between high and low frequencies, the faster the operation. Therefore, the operating speed is fastest near the electrode 8, and the operating speed is slowest near the intersection of the broken lines (R and B) in FIG.

Here, as shown in the voltage distribution diagram of FIG. 15, the voltage distribution of the broken line (11) due to the high frequency voltage and the voltage distribution due to the low frequency voltage,
For example, a voltage gradient (solid line (1)) that decreases from electrode 7 to electrode 8 was formed, but the relationship between low frequency and high frequency is reversed, and the broken line (11) is set to be low frequency, and the voltage gradient is also set to high frequency. Perform the aperture operation. Here, the method of B will be called the high-frequency gradient method, and the method of this invention will be called the low-frequency gradient method, to distinguish between the two.

By the way, in this cell array, heat is generated because a voltage gradient is provided on one plate and a current is passed through the transparent electrode. For this reason, it is necessary to increase the specific resistance of the transparent electrode as much as possible.

However, since a liquid crystal cell forms a kind of flat capacitor and has a capacitance, increasing the resistance of the transparent electrode increases the time constant of the circuit (which makes it difficult for high frequency voltages to be applied to the cell). Therefore, the lower the frequency of the alternating current applied to the transparent electrode that forms the voltage gradient, the higher the resistance of the transparent electrode can be.For this reason, the low frequency gradient method of this invention is better at high frequency This method has the advantage of being able to form cell arrays that generate less heat than the gradient method.

Next, in the third step, when a voltage under the same conditions as in the first step is applied, the cell rapidly returns to the non-light transmitting state.

In this way, it is possible to cause the aperture operation to occur at any timing.

An embodiment of the method for driving a liquid crystal cell according to the present invention will be described below using a liquid crystal cell array.

FIG. 1 is a partial plan view showing one embodiment of a liquid crystal cell array used in the present invention, in which the wiring between an upper plate 2 and a lower plate 3 is used to construct a liquid crystal cell array having a plurality of light transmitting windows. 10 and 21 and main electrodes 9 and 10, which are used to form a liquid crystal cell in the same manner as in FIG. 10 to form a liquid crystal cell array. In addition, in the following explanation, subscripts by alphabetical characters (-) will not be used for each code unless it is necessary to indicate them individually.

By the way, as explained so far (Fig. 8), the lower plate 3 of this cell has electrodes 7°8 on both sides of the main electrode 1o, and the upper plate 2 has one electrode 6, for a total of three electrodes. Electrodes and three drive circuits are required. Therefore, if these cells are simply arranged in an array, three electrodes and drive circuits are required for each cell, which reduces the yield in manufacturing the cell array.

Also, the increase in the number of drive circuits causes uneconomical effects.

On the other hand, in the configuration of the cell array shown in FIG. 1 and thereafter, the electrodes on the lower plate 3 can drive image signals using wiring and a drive circuit in which one cell is added to the number of cells.
Since the upper plate 2 can control a common signal using only two electrodes and two drive circuits, it is characterized by easy manufacturing and economical use of drive circuits.

Next, FIG. 1 will be explained in detail.

Here, the main electrodes shown at 10-a to 10-e of the lower plate 3 shown in this figure overlap with the main electrodes 9- to 9-E of the upper plate 2, and each of them is connected to the light transmitting window 23-. The following explanation will be given assuming that cell arrays a to 23-e (not shown; generally, 23 is used) are formed. Also, 20-a
-20-d show the wiring of the main electrodes 10-a to 10-e.

Next, a driving waveform for independently driving each light transmission window 23 will be explained. Here, as an example, the light transmitting windows 23-b and 23 of the cell array formed by the upper plate 2 and lower plate 3 in FIG.
A method of independently driving -C will be explained.

01 and 02 in FIG. 2 are the respective configurations f+121A in FIG. 1.

This is the voltage waveform for the common signal input to 21B, and is the voltage waveform for the common signal input to D1. Dt and Ds are examples of waveforms for the wirings 20-b, 20-a, and 20-c of the board in FIG. 1, and F in FIG. This is a diagram showing the range for

In the range S□ when the light transmission window 23 is closed, a low frequency voltage waveform C! and 02 are input with the same phase. On the other hand, the voltage waveform is D2. The voltage of D3 is 0■.

Next, the light transmitting window 23-
b4! When the throttle state is established, the voltage waveform C1 is a high frequency voltage, and the voltage waveform C2 is in the same low frequency voltage application state as Sl. Furthermore, voltage waveform D1. D2 applies a necessary low frequency voltage. In addition, the voltage waveform is the light transmission window 23-
A voltage waveform according to the aperture state d is applied, but since it is unnecessary for the explanation here, detailed explanation will be omitted. Here, the high frequency is indicated by a rectangular figure with an X mark. The same applies to the following explanations.

In this range of 11, the voltage gradient due to low frequency is
3-b and 23-e, but 1. Light transmission window 23-c
Since all the voltages applied to are low frequency voltages, the state of not transmitting light is maintained. However, in the light transmitting window 23-b to which the voltage of the voltage waveform C1 is applied, the low frequency generates a voltage gradient while the high frequency is uniformly applied.
A voltage distribution as shown in the figure is formed, and the aperture is in an operating state.

Next, the light transmission window 23 closes from the aperture operation S.

In the range , the state is the same as S8, and therefore the light does not transmit at high speed. In this case as well, switching between the diaphragm state and the non-light transmitting state is fast.

Next, in the range I2 where the light transmission window 23-c is in the aperture state, the voltage waveform C2 is set to a high frequency, and the voltage waveform C1 is set to the same low frequency application state as S2, and the voltage waveforms are as follows.

Apply low frequency to. This allows only the light transmitting window 23-c to be in the aperture state while the light transmitting window 23-b remains in the non-light transmitting state. At this time, the voltage waveform D2 is
A voltage waveform according to the aperture state of 3-a is applied. Similar to the case of the range 11, a detailed explanation of this will be omitted. By such a method, it is possible to perform the aperture operation on the other light transmitting windows in the same way, and the magnitude of the aperture operation can be arbitrarily changed by controlling the low frequency voltage.

Up to this point, we have explained how to form the aperture state in the range of I By setting each of the voltage waveforms D 2 , , D 2°Ds to a voltage lower than the high frequency of the voltage waveform C1 or C2, it is possible to completely open each light transmission window.

In addition, the light transmitting windows 23-b and 23-c are
In order to completely close each light transmission window at timing 2, by setting the voltage waveforms Du-Dt and Ds to a higher voltage than the high frequency of voltage waveform C8 or C2, the light transmission window can be completely closed. It is possible to make it transparent.

In the previous explanation, the magnitude of the aperture operation was controlled by controlling the wave height of the voltage waveform. On the other hand, the magnitude of the aperture operation can be changed by keeping the voltage constant and changing the pulse width (duty) of the high frequency. Therefore, this method is applicable to the methods described above even if pulse width control is used.

In this way, the method of changing the area of the aperture operating section by controlling the actual voltage application time is easy to control using a digital circuit using a constant voltage. This has the advantage that the drive circuit is simpler than the alternative method.

Furthermore, while a method for controlling the aperture operation using bipolar signals has been described so far, a method for controlling the aperture operation using unipolar signals will be described next.

For the voltage waveforms D 1p D 2 - D 3 in FIG. 2, it is necessary to use a waveform that is a combination of three levels of signals: Ov, positive polarity signal, and negative polarity signal even if the pulse width control described above is used. However, this three-level signal is a positive polarity signal and an OV
Or compared to two level signals like positive and negative polarity w
A disadvantage is that the drive circuit becomes complicated. This drawback is not a particular problem when the number of drive circuits is small, but it has a significant effect when the number of windows in the seven-channel array is several hundred or more, as in the present invention. For this reason, a method of controlling the aperture operation using unipolarity, which is suitable for making the drive circuit more economical, is shown in Figure 3 'rjA! This will be explained using the a waveform.

CI and 02 in FIG. 3 are the respective wirings 21A in FIG. 1.

This is the voltage waveform input to 21B, and is D8°D in Fig. 3.
, D are the respective wirings 21-a and 20-b of the board in FIG.
, 20-c, and F in FIG. 2 is a diagram showing a range for explanation.

In the range 81 in which the light transmission window 23 is closed, low frequency bipolar voltage waveforms C1 and 02 are input with the same phase.

On the other hand, the voltage waveforms ,D, ,D are OV.

Next, perform the aperture operation in the range shown in 1.
When b is brought into the narrowed state, the voltage waveform C1 is a bipolar high frequency voltage as in FIG. 2, and the voltage waveform C2 is in the same low frequency voltage application state as S□. Furthermore, the voltage waveform, D2
A unipolar low frequency voltage is applied as follows. In this range □, a voltage gradient due to low frequency is formed in the light transmission window 23-b. At this time, the light transmitting window 23-c enters a non-light transmitting state because all the input signals are of low frequency.

Next, in the range S2 in which the light transmitting window 23 closes from the aperture operation, it quickly enters the non-light transmitting state as in FIG. 2.

Next, the light transmission window 23-eli! Range I2 for aperture state
Here, the voltage waveform C2 is set to a high frequency, the voltage waveform C1 is set to the same low frequency application state as S2, and the voltage waveform D1. Unipolar low frequency is applied to D2. This allows only the light transmitting window 23-c to be in the aperture state while the light transmitting window 23-b remains in the non-light transmitting state. By using this method, it is possible to make the other light transmitting windows have the same fringing action.
Furthermore, by controlling the low frequency voltage, the magnitude of the aperture operation can be changed arbitrarily.

Further, as in the case of FIG. 2, each light transmission window can be completely opened or closed.

By the way, when a unipolar signal is used in combination with the duty control described above to form a voltage gradient, in the high frequency gradient method, when the duty is 100%, only the low frequency component is generated, and the high frequency component is lost. On the other hand, the low frequency gradient method of the present invention has only low frequency components even at 100% duty, and is characterized in that its properties are fully utilized.

Therefore, when using unipolar duty control, the low frequency gradient method of the present invention is suitable.

However, when a unipolar voltage waveform is used, the polarity of the voltage applied to the liquid crystal in the liquid crystal cell shifts to one side each time the aperture operation is performed. As a result, the liquid crystal deteriorates, and when driven with a voltage waveform without bias as shown in FIG. 2, there is a problem that the life of the liquid crystal becomes shorter than that of the liquid crystal. This problem can be resolved by modifying the applied voltage waveform.

FIG. 4 is a partial plan view showing another embodiment of the liquid crystal cell array used in the present invention, which differs from the liquid crystal cell array of FIG. 1 in that the arrangement 120 is provided above and below the main electrode 10.

FIG. 5 shows the voltage waveform C1 output by the power supply 13 in FIG.
This is a diagram showing voltage waveforms A and A2 that are applied to the liquid crystal in the liquid crystal cell when considering voltage waveforms D1 and D2 and Dl and D2 as reference voltages, respectively, showing an example of the voltage waveforms output by the power supplies 14 and 15. be. Further, F is a diagram showing the range of explanation.

In the range shown by Sl and 82, only the power supply 13 outputs a low frequency, and the voltage waveform applied to the liquid crystal is AI.

Both A2 have the same waveform as C1, and the liquid crystal is in a non-light transmitting state. In the range indicated by ■, voltage waveform C outputs high frequency;
2 is an example in which a diaphragm operation is performed by outputting a unipolar intermediate voltage. In the range indicated by J, the voltage waveform C1 outputs a negative output for a certain period of time. As for this time, it is basic to make the range ■ and J equal, but it is a value that changes by dividing J into two or more ranges or by changing the voltage output within the range J. Furthermore, the output voltage of voltage waveforms D1 and D2 in range J is from the maximum voltage (Vo) output by voltage waveforms D1 and D2 in range I to range I
The value obtained by subtracting the voltage (VO) output at (V7 = V
0 Vo ).

In this way, the solid lines showing the effective voltages of voltage waveforms A and A2 applied to the liquid crystal are voltages that are symmetrical to each other in the ranges I and J, and in reality, a biased voltage is applied to the liquid crystal. Things will go away. By the way, in the waveforms of A1 and A2, the high frequency is shown by a broken line in order to clearly distinguish it from the effective voltage. This relationship holds true in all locations between electrodes 7 and 8 in FIG. 14, and is characterized by the fact that voltage bias does not occur in all areas. By the way, in the explanation so far, range J has been set to be the simplest, but in reality, the voltage waveform output by power supply 13 in range J and power supplies 14 and 15 are
It is not necessary that the voltages are output at exactly the same time; the effect is the same even if the voltages are output at different times. Also, M(T) of the voltage (v1) applied to the liquid crystal and its duration (t□) in the range of ■ is the same as the voltage (v2) and its duration (t, ) applied to the liquid crystal in the range of J. It is sufficient that the absolute values of the products (I2) are equal and opposite signs, and the voltages v1 and v2
Even if the duration time txkt* is different in voltage or time, the effect is the same.

The voltage waveforms in FIG. 6 are waveforms for driving the cell array explained in FIG. The voltage waveforms A and A2 are the phosphor pressure applied to the liquid crystal at the intersection of the wiring 21A or 21B and the wiring 20 in the cell array when the voltage waveforms A and A2 are referenced.

The range indicated by S1 and S 2p 3 M is a range where a low frequency is applied to the liquid crystal, as in the previous explanation, and the liquid crystal becomes in a non-light transmitting state. ■, and the range of I2 are each wiring 21
The windows above A and 21B are ranges indicating the aperture state, and C, C2, and D in these ranges have waveforms similar to those in FIG. 3, respectively. In the J8 and J2 ranges, the voltage is applied to correct the biased voltage waveform to the liquid crystal due to the waveforms in the 1 and 12 ranges, respectively. Voltage waveforms C1 and 02 have negative polarity, and D has the low polarity of C8 and 02. If the frequency and high frequency voltages are equal, the fifth
As in the explanation of the figure, ■, and 11 from the maximum voltage in the range of I2.
Alternatively, a voltage obtained by subtracting the voltage of I2 is applied. In this way, in the waveforms of AI and A2, the shaded area shown in range 11 and the shaded area shown in range Jl have opposite polarities and the product of voltage and time is the same, and the shaded area shown in range 2 The shaded area shown in the range J2 and the shaded area J2 have a similar complementary relationship, and the unevenness of voltage application can be eliminated. Here, the timing of providing the ranges J1 and J2 does not have to be at the positions shown in FIG. 6 (although the same effect can be obtained by appropriately changing the timing).

In addition, the voltages corresponding to ranges J1 and J2 are applied in divided parts, and the sum of the products of those voltages and time is equal to the opposite sign of the sum of the products of voltage and time in ranges 11 and I2, and the voltage application is It would be good if the relationship was such that the imbalance could be resolved.

In addition, although the signal D is set to have a positive polarity, it is also possible to set it to a negative polarity. In that case, in the voltage waveforms c1 and C2, the signals output at times in the ranges J and J are set to have a positive polarity. The same effect can be obtained by doing so.

Here, we have so far described the case of electric field controlled birefringence mode as a liquid crystal, but these driving methods can also be applied to other modes such as twisted nematic mode and kestohost mode that can be driven at two frequencies.

In addition, the wiring lines 20° 21 constituting the liquid crystal cell array are arranged in the same direction as the arrangement direction of the light transmitting windows 23 (in (i) of FIG. 1).
Up to this point, we have explained a cell array in which light-transmitting windows are lined up for aperture operation from the lateral direction), but in addition to this, we can also use cell arrays such as (A) in Figure 4 and (
A seven cell array is fabricated using a lower plate 3 as shown in the arrangement diagram of wiring and transparent electrodes shown in B), and performs a diaphragm operation in which the horizontal and vertical directions are sewn together, and a diaphragm operation in the vertical direction. can be similarly driven by the driving method of the present invention.

Next, an example of application of this cell will be explained.

FIG. 7 is a configuration diagram in which the liquid crystal cell array described above is applied as an optical switch for an optical printer.

The light emitted from the light source 25 is focused by a lens 26, passes through a polarizing plate 27, and reaches the exposure light switch array 22. Here, the light is polarized according to the front light distribution of the light transmission window 23. The light passing through the exposure light switch A 22 is transmitted to the substrate 2.
4 and the polarizing plate 29, and only the light having the same polarization plane passes through the polarizing plate 29. This light is focused onto the photoreceptor 31 by the self-focusing fiber 3o.

When the exposure light switch array 22 using the cell of this invention is used, the light whose light distribution within one pixel is controlled is transmitted to the photoreceptor 31.
This results in an area-modulated image similar to halftone dot printing in printing. Here, as the photoreceptor 31,
Silver halide photography, electronic photography.

Examples include diazo photographs. In addition, although only a light-transmitting liquid crystal cell has been described in the above description, it is clear that the present invention can also be applied to a light-reflecting liquid crystal cell.

Next, a specific example will be explained.

[Specific Example 1] A cell having the configuration shown in FIG. 8 was created as follows. The main electrode 9 is an indium oxide film with a surface resistance of 50Ω.
o is a tin oxide film with a surface resistance of 300Ω, and electrodes 6 and 7
．． 8 was formed by aluminum vapor deposition. Furthermore, the size of the window was 1 cm square. A 6 μm polyester spacer 4 was used between the upper plate 2 and the lower plate 3, and a liquid crystal (NTTF-01 manufactured by Chisso Corporation) was placed in the gap formed by the spacer 4 to form a liquid crystal cell array. Further, the polarizing plates were placed in two places, one above the upper plate 2 and the other below the lower plate 3, so that the polarizing planes were perpendicular to each other in order from the top. An independent drive circuit was connected to each electrode 6, 7.8.

Kakeru! As the p11 waveform, voltage waveform 01 of FIG. 5 was applied to electrode 6, DI to electrode 7, and D2 to electrode 8.

The frequency of the low frequency used for the waveform C□ in Figure 5 is 2KHz.
The frequency of the high frequency was 100 KHz, and the wave heights of the low frequency and high frequency were ±25V. In addition, the frequency of the low and high frequencies of Dl and D2 in Fig. 15 is 4K jl z, and the wave height is O.
The light transmission window was controlled as V~±30V. The pulse width of the aperture operation range ■ and the correction signal application range J is 1 ms.
As a result, the light transmitting state of the light transmitting window becomes a diaphragm operation, and as the voltages of the voltage waveforms D and D2 increase, the light non-transmitting part 4
The width of 2 has become narrower. Also, the time to change from the non-light transmitting state to the aperture state is approximately o,s < less seconds, and the time to change to the non-light transmitting state again is Oe 6 <!J seconds. showed that.

Further, no significant deterioration was observed even after the operation was repeated 107 times.

[Specific Example 2] A cell array having the configuration shown in FIG. 1 was created as follows. The main electrode 9 was an indium oxide film with a surface resistance of 50Ω, the main electrode 1o was a tin oxide film with a surface resistance of 100KΩ, and the wirings PI&20.21 were formed by chromium and gold vapor deposition. Further, each window had a size of 250 μ square. A 6 μm polyester spacer 4 is used between the upper plate 2 and the lower plate 3.
Liquid crystal (NTTF) is placed in the gap formed by this surface 4.
-01 manufactured by Chisso Corporation) to form a liquid crystal cell array. In addition, the polarizing plates are placed in two places, above the upper plate 2 and below the lower plate 3, and the polarizing plane is ili! I decided to go to 32'.

Each distribution s20, 21 has an independent drive! g1 circuit was connected.

The waveform shown in Fig. 6 is applied as the wA dynamic waveform, and each wiring 20
The waveforms applied to each were controlled according to the signals. The frequencies of the waveforms C1, 02, and D in FIG. 6 were set to the same conditions as in Example 1.

As a result, each light transmission window performed an aperture operation with an arbitrary size, and no significant change was observed even after repeated use 107 times.

[Specific Example 3] The aperture operation was performed using the same cell array and drive conditions as those in Specific Example 2. At this time, duty control for controlling the effective voltage by controlling the pulse width was used as a signal having the waveform shown in FIG.

Other driving conditions were the same as in Example 1, and Example 1
Similarly, the aperture operation and non-light transmission state are repeated at high speed,
A similar aperture operation was possible using duty control.

Further, no significant change in properties was observed even after repeated use 107 times.

〔Effect of the invention〕

As explained above, according to the liquid crystal cell and liquid crystal cell array driving method of the present invention, it is possible to increase the resistance of the transparent electrode that forms a voltage gradient among the transparent electrodes that constitute the window, and it is possible to increase the resistance of the transparent electrode that forms the voltage gradient, resulting in an element that generates less heat. can be formed. In addition, since a low frequency signal is used as a signal for forming a voltage gradient, a unipolar No. 18 signal can be used, making it easy to make the drive circuit economical, and enabling duty control that modulates the pulse width.

Further, since the driving method of the present invention controls and applies low-frequency and high-frequency voltages, it is possible to perform a high-speed aperture operation and a clear aperture operation.

In addition, by applying a unipolar signal, a correction voltage is applied that prevents voltages of unbalanced polarity from being applied to the liquid crystal, so there is no deterioration of the liquid crystal even after repeated use many times. .

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an upper plate and a lower plate showing an embodiment of a liquid crystal cell array of this invention, and FIGS. 2, 3, 5, and 6 show waveforms for performing wArJIJ on the cell array of this invention. FIG. 4 is a configuration diagram of an upper plate and a lower plate showing another embodiment of a liquid crystal cell array of the present invention, FIG. 7 is a schematic cross-sectional view of an optical printer, and FIG. 8 is a basic diagram of the liquid crystal cell array of this invention. FIG. 9 is a perspective view showing the disassembled state of the cell; FIG. 9 is a diagram showing the relationship between the voltage and light transmittance in the basic cell; FIG. 10 is a diagram showing the applied voltage and the state of the light transmitting window that transmits light; FIG. 12 and 15 are voltage distribution diagrams, and FIG. 13 is a diagram showing the driving frequency of the liquid crystal used in this invention. FIG. 14 is a diagram showing the relationship between dielectric anisotropy, and is a cross-sectional view and a diagram showing a drive circuit for explaining another embodiment of the present invention. In the figure, 1 is a basic cell, 2 is an upper plate, 3 is a lower plate, 4 is a spacer, 6 to 8 are electrodes, 9 and 1o are main electrodes, 11 to 15 are power supplies, 20 and 21 are wiring, and 23 is a light In the transparent window, 41 is a light transmitting part, 42 is a light non-transmitting part, and 43 is a transition part. Figure 1 20.21: 2 Figure 2 F 1--5+-1-1+-I-5z-1-h-÷-
53□One hour Figure 3 FFSt-←■1±S2+12→-53-←One hour Figure 4 Figure 5 F S+-→--I →'' - to -52□□
Ginseki Figure 6 FSt-)-1+-+-52→12-+-Jl+Jz-
-F-1111-s code □Time Fig. 7 Fig. 8 Fig. 9 Fig. 11 Fig. 12 Fig. 13 Fig. 14 Fig. 15) -42-Code 41-I

Claims (2)

[Claims] (1) One plate with two electrodes on both sides of the transparent electrode,
When the liquid crystal cell is made into a non-light transmitting state in a liquid crystal cell having a liquid crystal whose dielectric anisotropy is reversed depending on the frequency and which is sandwiched between the plates and the other plate having a window forming portion made of a transparent electrode. When a bipolar low frequency voltage is applied to the transparent electrode of the one plate and the transparent electrode of the other plate to put the liquid crystal cell in the aperture state, a bipolar low frequency voltage is applied to the transparent electrode of the other plate. When applying a high frequency voltage of A bipolar low frequency voltage is applied to the transparent electrode of the plate and the transparent electrode of the other plate, and a voltage of opposite polarity to the voltage applied to the two electrodes of the one plate is applied for the duration of the constriction state. A signal that continues for the same time as (t_1) or a signal divided into a plurality of signals corresponding to the signal is added to the period during which the non-light transmitting state continues, and in the aperture state, the two plates of the one plate are The voltage (V_1) applied to the liquid crystal by each voltage applied to the electrode and the time (t_
A voltage waveform capable of applying a product (T_2) of voltage (V_2) and time (t_2) whose sign is opposite to the product (T_1) of 1) and equal in absolute value to the liquid crystal is applied to each of the two plates on one of the plates. A method for driving a liquid crystal cell, characterized in that a voltage is applied to an electrode of the liquid crystal cell. (2) The method for driving a liquid crystal cell according to claim (1), wherein the low frequency voltage applied to the two electrodes of one plate has a voltage waveform with pulse width control.