JPS63249825A - Method for driving liquid crystal element - Google Patents

Abstract

PURPOSE:To simplify a circuit constitution, and to display a moving image by changing the width of a driving pulse in accordance with the temperature variation of a liquid crystal element. CONSTITUTION:By a thermistor 121, a temperature variation is converted to a voltage, inputted to a voltage control oscillator 122, oscillated by a high frequency and a low frequency at a high temperature and a low temperature, respectively, and by bringing it to a frequency division by a frequency divider 123, a signal 103 is generated, and inputted to a counter 124. Subsequently, by a counter output and a frame signal 101, and a horizontal synchronizing signal 102, signals 104-106 are generated. By selecting a scanning electrode selecting waveform 107 and '0' volt by a scanning electrode data 110, a scanning electrode waveform 112 is generated, and by selecting waveforms 108, 109 by a signal electrode data 111, a signal electrode waveform 112 is generated, and it is applied to a liquid crystal element 126. In such a way, the circuit constitution is simplified, and the motion of the moving image can be made smooth.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving a liquid crystal element, and particularly to a method for driving an element using ferroelectric liquid crystal.

[Conventional technology]

As a conventional method for driving a ferroelectric liquid crystal element,
There is a drive waveform as shown in No. 0-258181. In this driving method, the liquid crystal element is multiplex driven, and the liquid crystal element is operated depending on whether the voltage applied during the selection period is below the threshold voltage or above the saturation voltage, and is always driven during the non-selection period. This is a driving method in which the state of the liquid crystal element during the selection period can be maintained because only a voltage pulse below the threshold voltage is applied.

[The point at which the invention attempts to solve]

When driving a ferroelectric liquid crystal using the driving method described above, if the driving pulse width changes, the 7 lem period also changes. The optical characteristics of a ferroelectric liquid crystal element are temperature dependent, and as shown in FIG. 4, when the temperature changes, the driving pulse width also changes.

In this manner, when driving a liquid crystal element, there may be cases where the driving pulse width must be changed in response to temperature changes. However, in the conventional driving method, if the pulse width changes, the 7-rem period also changes.
When ferroelectric liquid crystal is used as a personal display or television display,
If the frame period of the video signal and the 7-frame period of the ferroelectric liquid crystal display are not equal, it is necessary to store the video signal data in the 7-frame memory and then read the data from the memory again. The structure becomes complicated. Also, when displaying a moving image as on a television, the motion of the moving image is not smooth. [Means for Solving the Problems] Ferroelectric liquid crystal of the present invention In order to solve the above problems, the device driving method changes the drive pulse width in response to temperature changes in the liquid crystal device, shortens the pulse width in high temperature conditions, and
The selection period and frame period of the liquid crystal element are always constant even if the pulse width is increased and the pulse width is increased in a low temperature state.O [Embodiments] Below, embodiments of the present invention will be described in detail. Figure 1 shows an example of a drive circuit in an embodiment, in which a thermistor 0121 converts temperature changes into voltage and inputs the voltage to a voltage controlled oscillator 122. Oscillate with 123 frequency divider and divide by 10
A signal of 3 is created and input to the counter of 124.

Then, by the counter output of 124, the frame signal of 101, and the horizontal period signal of 102, 104.105
．． Create a signal of 106 and use this signal to switch the transmission gate of 125 to obtain VI%.
'11, V3.74, V5, -v6 voltages are switched, 107 scanning electrode selection waveform, 108 signal electrode O
N waveforms and 109 signal electrode OFF waveforms are created. These 107 waveforms and O volts are selected by 110 scans [polarity data to create 112 scan electrode waveforms, and 112 scan electrode waveforms are created.
The waveforms 108 and 109 are selected according to the signal electrode data 1 to create the signal electrode waveform 113, which is applied to the liquid crystal element 126. A timing chart of the waveforms 101 to 109 is shown in FIG. 2, and a timing chart of the waveforms 112, 113, the composite waveform 301, and the optical response of the liquid crystal element 302 is shown in FIG.

Looking at the eye period in Figure 3, we see that the temperature of the liquid crystal element is in a low temperature state. Therefore, it is necessary to lengthen the driving pulse width, and by lowering the frequency of the oscillator 122 in Figure 1, the liquid crystal element is in a low temperature state. tl4, which is the drive pulse width that allows the element to operate;
The pulse width of tl is 0, and the liquid crystal element is brought into the 0FIF state during 414, and whether the voltage applied to the liquid crystal element during t's is below the threshold voltage or above the saturation voltage. , select whether to leave the liquid crystal element in the 0IFF state or turn it on. During tl6, the voltage applied to the liquid crystal element is zero volts, and during the non-selection period Kuraguchi, t14, t'+s Since only a voltage pulse with a pulse width equal to and below the threshold voltage is always applied, the state of the liquid crystal element during tl5 is maintained.

Also, if we look at the time between t31 in FIG. 3, the temperature of the liquid crystal element is high. Therefore, it is necessary to shorten the driving pulse width, and increase the frequency of the oscillator in FIG. 1 at 122. t is the driving pulse width that allows the liquid crystal element to operate.
, 4, the pulse width is tss. Then, during ts4, the liquid crystal element is turned off, and during t3. Depending on whether the voltage applied to the liquid crystal element is below the threshold voltage or above the saturation voltage during During the non-selection period tss, the voltage applied to the liquid crystal element is zero volts.
During this period, the pulse width is equal to tl4 and tsg, and only voltage pulses below the end voltage are always applied, so tsa
The state of the liquid crystal element is maintained between

Although this embodiment is a binary display example, the voltage of the signal electrode waveform is changed according to the gradation data (9), and the pulse width of the signal electrode waveform is changed according to the gradation data.・Can also show. Also, regarding driving methods other than this embodiment, the driving pulse width may be changed according to the temperature of the liquid crystal element using the same concept, and the driving pulse width may be shortened in a high temperature state and lengthened in a low temperature state. The selection period and the frame period can be kept constant without changing.

〔Effect of the invention〕

As described above, according to the present invention, even if the driving pulse width is changed in response to temperature changes of the liquid crystal element, the selection period and the frame period can be kept constant, so that the selection period and frame period can be kept constant. Even if a ferroelectric liquid crystal element is used in a display, a frame memory is not required and the circuit configuration is simple. Furthermore, when displaying a moving image, it is possible to display a clear moving image because it is synchronized with the video signal.

[Brief explanation of drawings]

Figure 1 is a drive circuit diagram of the present invention, and timing charts of this drive circuit are shown in Figures 2 and 3. Figure 4 is a diagram showing the temperature characteristics of the liquid crystal element. This figure shows how the drive pulse width changes with respect to temperature changes when the temperature is constant. 101...Frame signal 102...Horizontal synchronization signal 107...Scanning! ! Pole selection waveform 108...Signal electrode ON waveform 109...Signal electrode OPP waveform 110...Scanning electrode data 111...Signal electrode data 112...Scanning electrode waveform 113...Signal electrode waveform 121 ...Thermistor 122...Voltage controlled oscillator 123...Frequency divider 124...Counter (741S161) 125...
...Transmission gate 26...Liquid crystal element 301...Synthesized waveform 302 applied to the liquid crystal element...
・Optical response of liquid crystal elements Applicant: Seiko Epson Corporation Figure 2

Claims (1)

[Claims] At least, in a method of driving a liquid crystal element in which a ferroelectric liquid crystal is sandwiched between a substrate on which a scanning electrode is formed and a substrate on which a signal electrode is formed, the driving pulse width is changed in response to temperature changes of the liquid crystal element. A method for driving a liquid crystal element, characterized in that the selection period and frame period of the liquid crystal element are always constant even if the pulse width is shortened in a high temperature state and the pulse width is lengthened in a low temperature state.