JPH0442658B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for driving a matrix type liquid crystal optical device.

(Prior Art) Ferroelectric liquid crystals have recently been attracting attention as an alternative to TN liquid crystals, and optical devices using them are being developed.

The optical modes of the ferroelectric liquid crystal are a birefringent optical mode and a guest-host optical mode. When driving these, unlike conventional TN-type liquid crystals, the optical response state (brightness and darkness) is controlled by the direction of electric field application, so the driving method used for TN-type liquid crystals cannot be used, and special driving methods are required. It requires a method.

Furthermore, considering the lifespan of the optical device, it is undesirable for a DC component to be applied to the pixels for a long period of time, and a driving method that takes this point into account is required.

One of the driving methods that does not apply this DC component for a long time is "SID'85Digest" (1985) (P.131
~P.134) There are several driving methods. Furthermore, JP-A-61-
Publication No. 230197 includes a write pulse that brings the pixel into a desired optical response state, and after application of this write pulse there is no pulse that changes the optical response state of the pixel, and all positive polarity pulses A pulse group in which there are pulses of negative polarity with respect to
There is a method in which an alternating current pulse is applied to the pixel in a time-division manner, and when the pulse group is not applied, an alternating current pulse is applied to maintain the pixel in the optical response state. Furthermore, Japanese Patent Application Laid-Open No. 116925/1983 discloses a driving method in which the AC pulse for maintaining the above-mentioned optical response state is an AC pulse in which a high-frequency AC pulse is superimposed on an AC pulse having a pulse height lower than that of the write pulse. It is shown.

(Problems to be Solved by the Invention) The electrical signals shown in the above driving method are all formed by voltage levels of four or more values, and the circuit for obtaining the electrical signals becomes complicated. A resistor division method or the like is used to obtain each voltage level, but there are problems such as variations in the voltage level due to variations in resistance values and increased power consumption. This means that the voltage dividing resistor is 2 times the load resistance.
This is because the voltage value will change due to changes in load unless it is set an order of magnitude smaller.

Therefore, the purpose of the present invention is to simplify the circuit configuration,
The object of the present invention is to easily respond to temperature changes and to extend the life of an optical device.

(Means for Solving the Problems) A feature of the present invention is that a liquid crystal whose molecules are oriented differently depending on the direction of application of an electric field is interposed between a plurality of scanning electrodes and a plurality of control electrodes. The signals that form the pixel and are supplied to each electrode are all formed by binary voltages, a first pulse group that brings the pixel into a desired optical response state, and a second pulse group that maintains the optical response state of the pixel. The above object is achieved by making each of the pulse groups have negative polarity pulses with symmetrical waveforms with respect to all the positive polarity pulses.

Furthermore, by using an initialization signal, the scanning time can be shortened.

(Example) In FIG. 1, a ferroelectric liquid crystal is interposed between scanning electrodes L1 to Ln and control electrodes R1 to Rx facing thereto to form a pixel at the intersection of each electrode. From the selection circuit SE, a selection signal S1 (Fig. 2) that sequentially selects the scanning electrodes L1 to Ln in a time-division manner is provided.
is generated, and when this selection signal is not supplied, a non-selection signal NS1 is generated. In addition, from the drive control circuit DR, a response signal D1 or a reverse response signal RD shown in FIG.
1 is generated as a data signal, and the control electrode R1~
Supplied to Rx. i.e. response state (e.g.
A response signal D1 is supplied to the control electrode of a pixel for which a light transmission state is desired, and a reverse response signal D1 is supplied to a control electrode of a pixel for which a reverse response state (for example, a light blocking state) is desired.
It supplies RD1.

Now, assuming that the pulse width of the write pulse to put the pixel into a saturated response state or a saturated reverse response state is 1, the selection signal S1 has a voltage of 0 at intervals corresponding to pulse width 1, a voltage of V at pulse width 2, and a pulse width of The interval corresponding to 1 consists of a voltage of 0. Also non-select signal
NS1 is pulse width 2/3, voltage V followed by pulse width 1/3
The pulses of the voltage V are made up of a group of pulses successive at intervals as shown in FIG. The response signal D1 consists of a pulse group of voltage V pulses with a pulse width of 1/3 successive at intervals, and finally a pulse group of voltage V pulses with a pulse width of 1. The reverse response signal RD1 consists of a pulse group of pulses of voltage V with a pulse width of 1, voltage V with a pulse width of 2/3, and voltage V with a pulse width of 1/3, successive at intervals as shown in FIG. All of these signals are formed by binary voltages with a voltage level of 0 or V.

By supplying the above-mentioned signals, the first pulse group P1 is applied to the pixel for which a response state is desired due to the potential difference between the response signal D1 and the selection signal S1, and the first pulse group P1 is applied to the pixel for which a reverse response state is desired. The first pulse group P is determined by the potential difference between the response signal RD1 and the selection signal S1.
2 is applied.

In the first pulse group P1, the voltage is 0 for the interval corresponding to 1/3 of the pulse width, the voltage is 0 for the interval corresponding to the pulse width 2/3, the voltage is 0 for the interval corresponding to the pulse width 2/3, and the voltage is 0 for the interval corresponding to the pulse width 2/3.
A pulse of voltage -V is applied with a pulse width of 1/3, but
The liquid crystal does not respond to any of these pulses, and then enters a reverse saturation response state (light cutoff state) for the first time with a pulse of voltage -V with a pulse width of 1, but immediately writes a voltage of V with a pulse width of 1. A saturation response state (light transmission state) is achieved by the pulse.

In addition, in the first pulse group P2, first the pulse width is 1.
The pixel enters a light transmitting state with a pulse of voltage V, but immediately enters a light blocking state with a write pulse of voltage -V with a pulse width of 1. The liquid crystal does not respond to the next pulse of voltages -V and V with a pulse width of 1/3, and the light-blocking state is maintained. In this way, the pulse group P2 causes the pixel to maintain the light-blocking state for a long time after a short light-transmitting state, so that the light-blocking state can be obtained without substantially lowering the dark level.

After the selection signal S1 is applied, the scanning electrode L1
The non-selection signal NS1 is applied to ~Ln, but the second pulse group P3 is applied to the pixel due to the potential difference between the non-selection signal and the response signal, and the potential difference between the non-selection signal and the reverse response signal. All of the pulses included in the second pulse group P4 applied to the pixels have a pulse width of 1/3, and do not include write pulses for bringing the pixels into a saturated response state or a saturated reverse response state. Therefore, the response (light transmitting state) or reverse response (light blocking state) state when the selection signal is applied is maintained as it is.

In the second diagram, the pulses in pulse groups P3 and P4 that occur when the non-selection signal NS1 is applied are set to a duty of 1/3, but if this is set to a duty of 1/2, the non-selection from the selection signal is set to 1/3. When transitioning to the signal or vice versa, the pulse width 1/
2, two pulses of voltage V or two pulses of voltage -V may continue, and the optical response state may change. Therefore, in order to eliminate this kind of thing, it is desirable that the duty is 1/3 or less. However, if the duty of the non-selection signal is made too small, the pulse width of pulses other than the write pulse at the time of selection becomes large, so it is desirable that the duty is 1/8 or less. The voltage V and pulse width vary depending on the thickness of the liquid crystal cell, the magnitude of spontaneous polarization of the ferroelectric liquid crystal, etc., but are appropriately determined so as to provide a saturated response or an inverse saturated response.

Further, in both the first pulse group and the second pulse group, there are negative polarity pulses with symmetrical waveforms with respect to all positive polarity pulses, so they are completely AC driven and have a long life.

The third diagram shows another example of each signal waveform, in which a selection signal S2 formed by a binary voltage, a response signal D2 which is a data signal, and an inverse response signal.
The first pulse group P caused by the potential difference with RD2
5 and P6, it is possible to drive with the same response and reverse response as in the case shown in the second diagram. However, in this example, the second
An example is shown in which the pulse width in the pulse groups P7 and P8 is set to duty 1/4. For this reason, fluctuations in contrast when not selected are reduced.

Incidentally, in each of the embodiments described above, when the pulse group at the time of non-selection is switched, pulses of the same polarity may be continuously applied. For example, in Figure 3,
When pulse group P8 is applied after pulse group P7 is applied, the last pulse of pulse group P7 and pulse group P8
Since the first pulses of both are of the same polarity, the contrast may be slightly unstable.

The fourth illustration shows an example for solving the above-mentioned drawbacks, in which each electric signal of the selection signal S2', the response signal D2' as a data signal, the reverse response signal RD2' and the non-selection signal NS2' is Although narrow pulses are added to the beginning and end of each signal shown in Figure 3, both are formed with binary voltages. These signals cause the first pulse group P5', P
6' and a second pulse group P7', P8' are obtained,
By preventing pulses of the same polarity from continuing when non-selected, fluctuations in contrast when non-selected are further reduced, and high contrast can be obtained.

In FIG. 5, instead of the non-selection signal NS2 shown in FIG. 3,
In this example, a non-selected new word NS2'' is generated by a high frequency component, and this signal causes the second pulse group P7'', P
8" is obtained, and the aim is to reduce the fluctuation in contrast when not selected. This is particularly effective for ferroelectric liquid crystals with dielectric anisotropy of Δε<O due to the AC smoothing effect. High frequency AC The pulse width of the pulse is preferably 1/8 or less of the write pulse, and is appropriately determined so that the optical response state can be stably maintained.

In addition, as a non-selection signal in the case shown in the fourth figure, the fifth
It is also possible to use a signal containing a high frequency component similar to that shown in the figure.

In FIG. 6a, the selection signal S3 formed of a binary voltage, the response signal D3 as a data signal, the reverse response signal RD3, and the non-selection signal NS3,
The first pulse group P9, P10 and the second pulse group P11, P12 are applied to the pixel to drive the pixel in the same manner as shown in the second to fifth diagrams, but in this example, the pixel is in a reverse response (light blocking) state. Since the first pulse group P10 for obtaining the image does not include a pulse for making the light transmitting state, a good dark level can be obtained and high contrast can be obtained. Pulse group P in this example
The width of the pulses in P11 and P12 is 1/4 of the width of the write pulse.

Figure 6b is an example in which a non-selection signal NS3' containing a high frequency component is used instead of the non-selection signal NS3 shown in figure 6a, and the second pulse group P generated when non-selection is used.
11' and P12', the same effect as shown in FIG. 5 can be obtained. In this example, similarly to the fourth illustration,
Add narrow pulses at the beginning and end of each signal,
It is also effective to prevent the same polarity from continuing.

FIG. 7 shows that the optical response state of the pixel is once initialized at the timing before supplying the selection signal,
An example is shown in which the state is subsequently changed or maintained. That is, as shown in FIG. 7a, the scanning electrode L
An initialization signal RS formed by a binary voltage is supplied to some or all of the scanning electrodes R1 to Ln, a non-initialization signal NRS is supplied to the other scan electrodes, and an initialization control signal is supplied to the control electrodes R1 to Rx. CR is supplied, thereby temporarily initializing part or all of the screen to a reverse response (light blocking) state. The number of initialized lines is 1.
By increasing the number of books for each book, the time required to rewrite one screen can be shortened. After initialization, the optical response state is written by selecting each scanning electrode. That is, as shown in Figure 7b, a selection signal S formed by a binary voltage is applied to a pixel on a selected scanning electrode.
4, a response signal D4 which is a data signal, and a reverse response signal.
Due to the potential difference with RD4, the first pulse group P1
5 or P16 is applied, and the non-selection signal NS4 is applied to the pixel in the non-selected scanning electrode, and the response signal D4 is applied.
The second pulse group P17 or P18 is applied depending on the potential difference with the reverse response signal RD4. The pulse group P15 has a pulse width of 1 and is composed of voltages -V and V, and includes a positive polarity write pulse in the latter half and a negative polarity pulse whose waveform is symmetrical to this write pulse. For this reason, the pixel becomes a light-transmitting state after being in a light-blocking state, and the light-transmitting state is written therein. However, since the pulse group P16 does not include a write pulse, the liquid crystal does not respond, and the light-blocking state due to initialization is maintained. The pulses in the second pulse group P17 and P18 have a pulse width that is 1/4 of the write pulse, thereby maintaining the optical response state of the pixel at the time of selection. 7b is an example in which a non-selection signal NS4' containing a high frequency component is used instead of the non-selection signal NS4 shown in 7c, and the fifth Effects similar to those shown in the figure can be obtained. In this example, the fourth
It is also effective to add narrow pulses to the beginning and end of each signal to prevent the same polarity from continuing, as shown in the figure.

The method shown in Figure 8 is a method of selecting one scan electrode and simultaneously initializing the next scan electrode in advance, and this is an example in which no additional time is required for initialization and the screen rewriting time can be shortened. is shown. That is, as shown in Figure 8a, the scan electrodes are supplied with initialization signals RS1 and RS2, selection signal S5, and non-selection signal.
NS5 is sequentially supplied, and a response signal D5 or a reverse response signal RD5 is supplied as a data signal to the control electrode in synchronization with the selection signal. Initialization signal RS1,
In response to RS2 and response signal D5 or reverse response signal RD5, initialization pulse P19 or P20 of voltage V and initialization pulse P21 or P22 of voltage -V are sequentially applied to the pixel, and a group of these initialization pulses is applied to the pixel. After the pixel is in the light transmitting state, a light blocking state is written to the pixel and the pixel is initialized to the light blocking state.

Subsequently, selection signal S5, non-selection signal NS5, response signal D5, and reverse response signal RD are supplied at the time of selection.
5 are the same as those shown in Figure 7b, so the resulting first pulse groups P23, P24 and second pulse groups P25, P26 are also the same as the first pulse groups P15, P16 and P16 shown in Figure 7b, respectively. The second pulse group P17 and P18 are the same, and the light transmission state is written in the same way by the first pulse group P23, but the liquid crystal does not respond to the pulse group P24, and light is blocked by initialization. State is preserved. The figure 8b shows the non-selection signal NS5 shown in the figure 8a.
is the non-selection signal NS5' containing a high frequency component, and the second pulse group P25' generated thereby is
The effect of P26' is also the same as that shown in FIG. In this example as well, it is effective to add narrow pulses to the beginning and end of each signal so that the same polarity does not continue, as in the case shown in FIG.

The method shown in FIG. 9 is a further development of the method of selecting one scan electrode and simultaneously initializing the pixels of the next scan electrode in advance, similar to the method shown in FIG. The liquid crystal does not respond to just one pulse of any of the initialization pulses P27 to P38 with a pulse width of 1 and a voltage of v, but when three pulses of the same polarity continue, it enters a saturated response state or a saturated reverse response state. is set to . That is, as shown in FIG. 9a, the initialization signal is applied to the scanning electrode.
RS3 to RS8, selection signal S6, non-selection signal NS6
are sequentially supplied, and a response signal D6 or a reverse response signal RD6 is supplied as a data signal to the control electrode in synchronization with the selection signal. Initialization signal RS3 to RS8
and response signal D6 or reverse response signal RD6, the liquid crystal does not respond to initialization pulse P27 or P28, but responds to initialization pulse P29 or P3.
0, P31 or P32 and P33 or P3
4, it becomes a saturated reverse response state and is initialized to a light blocking state, and is initialized to a response state below the threshold value by the subsequent initialization pulse P35, P36, P37, or P38. Next, when the selection signal S6 is supplied at the time of selection, and the first pulse group P39 is applied due to the potential difference with the response signal D6, a saturation response state is entered by the pulse of the voltage v with the initial pulse width 1. written in a light-transmissive state,
At the next pulse width of 1 and voltage v, the liquid crystal does not respond.
Further, the liquid crystal does not respond to the voltage OP40 due to the potential difference between the selection signal S6 and the reverse response signal RD6, and the light-blocking state due to initialization is maintained. Non-selection signal NS
The liquid crystal is not sensitive to the second pulse group P41 and P42 of 6, and the state at the time of selection is maintained.
With this driving method, the scanning time can be further shortened and the driving voltage can be lowered. 9b shows the second pulse group P4 using the non-selection signal NS6 shown in FIG. 9a as the non-selection signal NS6' with a high frequency component.
1', P42', and the effect is similar to that shown in FIG.

In addition, in the above explanation, it was said that a response is caused by a voltage on the + side and a reverse response is caused by a voltage on a - side.
Since responses and counter-responses are two sides of the same coin,
Conversely, it may be called a reverse response with a voltage on the + side and a response with a voltage on the - side.

By the way, the signals supplied to each electrode are the above O, V
The present invention is not limited to this, and may be formed using only binary voltages.

Furthermore, in the above embodiment, a matrix display as shown in FIG. Needless to say, the present invention can also be applied to driving a liquid crystal shutter array.

(Effects of the Invention) According to the present invention, since the signals supplied to the electrodes are formed using binary voltages, the circuit configuration is simplified and it is possible to easily respond to temperature changes. In addition, the pulses applied to the pixels have negative polarity pulses with symmetrical waveforms for all positive polarity pulses, or the voltage is O, so there is no blackening of the transparent electrode or deterioration of the liquid crystal, and the pulse is long. We can provide optical devices with a long lifespan. Furthermore, by using the initialization signal, it is possible to initialize the pixels in the next scan electrode at the same time as writing the pixels in one scan electrode.
The time required for rewriting can be shortened.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an example of a matrix type liquid crystal optical device, Fig. 2 is an explanatory diagram showing an example of a voltage waveform for realizing the present invention, and Figs. 3 to 9b are illustrations each realizing the present invention. FIG. 4 is an explanatory diagram showing another waveform example for the purpose of the present invention. R1-Rx...Control electrode, L1-Ln...Scanning electrode, S1-S6...Selection signal, NS1-NS6'...
...Non-selection signal, RS~RS8...Initialization signal, D1
~D6...data signal, RD1~RD6...data signal, P1, P2...first pulse group, P5,
P6...first pulse group, P5', P6'...first
pulse group, P9, P10...first pulse group,
P15, P16...first pulse group, P23, P
24... first pulse group, P39, P40... first pulse group, P3, P4... second pulse group,
P7, P8...second pulse group, P7', P8'...
...Second pulse group, P7'', P8''...Second pulse group, P11, P12...Second pulse group, P1
1', P12'...second pulse group, P17, P1
8...Second pulse group, P17', P18'...Second pulse group, P25, P26...Second pulse group, P25', P26'...Second pulse group, P4
1, P42...second pulse group, P41', P4
2'... Second pulse group, P13... Initialization pulse group, P19-P22... Initialization pulse group, P2
7 to P38... Initialization pulse group.

Claims (1)

[Scope of Claims] 1. A matrix in which a liquid crystal whose molecular orientation changes depending on the direction of application of an electric field is interposed between a plurality of scanning electrodes and a plurality of control electrodes, and pixels are formed at the intersections of each electrode. In a method for driving a type liquid crystal optical device, a selection signal is sequentially supplied to each scanning electrode, a non-selection signal is supplied when the selection signal is not supplied, and data is supplied to each control electrode in synchronization with the supply of the selection signal. applying a first group of pulses to the pixel to achieve a desired optical response state by applying a first pulse group to the pixel due to the potential difference between the selection signal and the data signal;
The second pulse group is applied to the pixel to maintain the optical response state of the pixel, and the selection signal, the non-selection signal, and the data signal are all formed by binary voltages, and the first pulse group is applied to the pixel. The second group of pulses includes a write pulse that brings the pixel into a desired optical response state, and for every positive pulse there is a negative pulse with a symmetrical waveform; 1. A method for driving a matrix type liquid crystal optical device, comprising pulses that maintain the optical response state of pixels, and in which there are pulses of negative polarity having a symmetrical waveform with respect to all pulses of positive polarity. 2. Driving a matrix-type liquid crystal optical device in which a liquid crystal whose molecular orientation changes depending on the direction of electric field application is interposed between a plurality of scanning electrodes and a plurality of control electrodes, and pixels are formed at the intersections of each electrode. In the method, each scan electrode is sequentially supplied with an initialization signal and a subsequent selection signal, a non-selection signal is supplied when the initialization signal and selection signal are not supplied, and each control electrode is supplied with a selection signal. A data signal is supplied in synchronization with the initialization signal, and the potential difference between the initialization signal and the data signal causes
A group of initialization pulses is applied to the pixel to optically initialize it, and a first group of pulses or a voltage O is applied to the pixel to bring it into a desired optical response state depending on the potential difference between the selection signal and the data signal. Due to the potential difference between the selection signal and the data signal,
The second pulse group is applied to the pixel to maintain the optical response state of the pixel, and the initialization signal, selection signal, non-selection signal, and data signal are all formed by binary voltages. , the initialization pulse group puts the pixel into a light transmitting state or a light blocking state, and there is a negative polarity pulse with a symmetrical waveform with respect to all the positive polarity pulses, and the first pulse The group includes pulses that maintain the state initialized by the write pulse or initialization pulse group that changes the pixel to the desired optical response state, and has a negative polarity waveform that is symmetrical for all positive polarity pulses. The second pulse group consists of pulses that maintain the optical response state of the pixel, and there are negative polarity pulses with a symmetrical waveform to all the positive polarity pulses. be. A method for driving a matrix type liquid crystal optical device, characterized in that: