JPH0583890B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display device composed of a nonlinear element and a liquid crystal optical switch, and particularly relates to a driving method.

A 2-terminal element is provided for each pixel of a matrix type liquid crystal display panel in which pixels are arranged two-dimensionally.
The terminal type active matrix method has a simple manufacturing process and is promising as a low-cost, high-quality display device.

[Conventional technology and problems]

FIG. 1 shows the configuration of a conventional two-terminal active matrix liquid crystal display device. Reference numeral 1 denotes an input signal, and 2 a control section, which sends a control signal to the scanning electrode drive section 4 and the signal electrode drive section 3 in accordance with the input signal. 5
6 is a scanning electrode, and 6 is a signal electrode. A nonlinear element 7 and a liquid crystal element 8 are arranged at each intersection of the scanning electrode and the signal electrode. The nonlinear element 7 is an element having nonlinear voltage-current characteristics 11 and 12 as shown in FIG. 2, where 9 indicates a voltage axis and 10 indicates a current axis. The element is pn
It is formed by a junction diode, a metal-insulator-metal diode, etc.

A conventional drive waveform is shown in FIG. A solid line 241 is a scanning electrode voltage waveform, and a dotted line 241 is a signal electrode voltage waveform. Drive is positive selection period 16, negative selection period 1
8, a positive bias period 17 and a negative bias period 19. 20 is a positive selection voltage, 21 is a positive bias voltage, 22 is a negative selection voltage, and 23 is a negative bias voltage. The signal electrode voltage waveform 24 is composed of an off voltage 25, an on voltage 26, or an intermediate voltage between the two.

The display operation is as follows. Positive selection period 1
At 6, a voltage corresponding to 15 in FIG. 2 is applied to the nonlinear element 7, the resistance of the nonlinear element is reduced, and positive charges depending on the display content are accumulated in the liquid crystal element.
In the subsequent positive bias period 17, a voltage corresponding to 13-14 in FIG. 2 is applied to the nonlinear element 7,
The nonlinear element has a high resistance and prevents positive charges from flowing out of the liquid crystal element. In the next negative selection period 18, a voltage corresponding to 16 in FIG. 2 is applied to the nonlinear element,
Negative charges depending on the displayed content are accumulated in the liquid crystal element. In the subsequent negative bias period 23, as in the positive bias period, the nonlinear element 7 has a voltage 13- in FIG.
A corresponding voltage is applied between 14 and 14 to maintain the negative charge of the liquid crystal element. During the positive selection period and negative selection period, charges of opposite signs are injected into the liquid crystal element to create AC drive, and by holding the charge in the liquid crystal element during periods other than the selection period, display characteristics comparable to static drive of the liquid crystal element are guaranteed. do.

A drawback of the conventional drive waveform shown in FIG. 3 is that the voltage amplitude is large. When a MiM diode with a tantalum-tantalum pentoxide-chromium configuration is used as the nonlinear element, the positive selection period 20 is 10 volts and the negative selection voltage 22 is -10 volts. The scan electrode voltage amplitude was 10 - (-10) = 20 volts, which exceeded the 15 volt breakdown voltage of normal ICs, necessitating the use of high-cost, high-voltage ICs with large chip areas.

[Purpose of the invention]

An object of the present invention is to provide a small, low-cost liquid crystal display device by reducing the voltage amplitude.

[Structure of the invention]

In the present invention, by simultaneously varying the potential of the scanning electrode voltage waveform and the signal electrode voltage waveform,
Reduce the drive voltage amplitude.

[Embodiments of the invention]

(Example 1) FIG. 4 shows the drive waveform of the present invention. The solid line is the scanning electrode voltage waveform, and the dotted line is the signal electrode voltage waveform.
30 is a synchronization signal, which is a vertical synchronization signal in the case of TV display. 27 is a waveform applied to the scan electrode 5-1, 28 is a waveform applied to the scan electrode 5-2, and 29 is a waveform applied to the scan electrode 5-N. The hatch part in Figure 4 (311, 3
12, 313, 331, 332, 333, etc.) is the scan electrode selection period. The selection electrode changes sequentially at fixed time intervals. In the case of TV display, it is every time corresponding to the horizontal synchronization signal. 311 is a positive selection voltage, 32 is a positive bias voltage, 331 is a negative selection voltage, 34 is a negative bias voltage, 39 is a negative retrace interval voltage, and 40 is a positive retrace interval voltage. 35 and 37 are off voltages of the signal electrodes, and 36 and 38 are on voltages of the signal electrodes. 41 and 42 are retrace section voltages of the signal electrodes.

Each voltage level is as follows. Let V _T be the threshold voltage of the liquid crystal element 8, and V _S be the saturation voltage.
Let 39,331 be the zero level. 36 is almost V _T ,
35 is approximately V _S and 32 is V _S +V _T . 311,
If the voltage level of 40 is V _M , then 38 is V _M −
V _T , 37 is V _M −V _S , and 34 is V _M −(V _S +V _T ). Typical values are V _T =1 volt and V _S =4 volt if the liquid crystal element 8 is of the guest-host type.
V _M is V _M =10 volts using a typical MiM device. 41 is the voltage between 35 and 36, 42 is 3
A voltage between 7 and 38 is desirable.

The feature of this embodiment is that the scan electrode voltage and the signal electrode voltage are changed at regular intervals (in the case of TV display, every vertical synchronization signal) almost simultaneously, while maintaining almost the voltage difference between the two. In this embodiment, the voltage amplitude required for driving is approximately 1/2 that of the conventional one.

(Example 2) The drive waveform of the present invention is shown in FIG. 68, 69
is a synchronization signal; in the case of TV display, 68 is a vertical synchronization signal, and 69 is a horizontal synchronization signal. A solid line 431 of the voltage waveforms 43, 44, 45 indicates the scanning electrode 5.
-1, 5-2, 5-N scanning electrode voltage waveforms. Dotted lines 43, 44, and 45 are signal electrode voltage waveforms. The short dotted line is the off voltage, and the long dotted line is the on voltage. The rightward hatching portion 101 and the leftward hatching portion 102 are scanning electrode selection periods. The selection electrodes are sequentially moved at regular intervals. TV
In the case of display, it is for each time corresponding to the horizontal synchronization signal. The left hatched portion is a positive selection period in which the liquid crystal element 8 is charged with positive charges. The rightward hatched portion is a negative selection period in which the liquid crystal element 8 is charged with negative charge. The period between the positive selection period and the negative selection period is a positive bias period.

Further, the period between the negative selection period and the positive selection period is a negative bias period. The crosshatch area is the retrace section. The feature of this embodiment is that each time the selection electrode moves, it alternates between a positive selection state and a negative selection state, thereby averaging the signal electrode voltage level and reducing crosstalk. , the scanning electrode voltage and the signal electrode voltage are varied simultaneously while maintaining almost the difference between the two, thereby reducing the driving voltage.

46 is a positive selection voltage, 47 and 48 are positive bias voltages, 49 is a negative selection voltage, and 50 and 51 are negative bias voltages. 55, 57 are the off voltages of the signal electrodes,
54 and 56 are on-voltages of the signal electrodes. In the case of gradation display, a voltage between an off voltage and an on voltage is applied to the signal electrodes depending on the display content. 60,6
1, 62, 63, 64, 65, 66, and 67 are scan electrode voltages during the retrace period. 52,53,5
8 and 59 are signal electrode voltages during the retrace period. As for the voltage level, the voltage of each number is 60 = 49,6
1=51, 62=46, 63=48, 64=4
It is desirable that 8,65=46,66=51,67=49. Voltages 52 and 59 are voltages 54 and 5
Voltage level between 5, voltage 53, 58 is 56 and 5
Voltage levels between 7 and 7 are desirable. Each voltage value is the same as in Example 1. In this embodiment, as in the first embodiment, the voltage amplitude required for driving is approximately 1/2 that of the conventional one.

〔Effect of the invention〕

As described above, in the present invention, by changing the scan electrode voltage and the signal electrode voltage almost simultaneously while maintaining the voltage difference between the two, the drive voltage amplitude of the display panel can be reduced to about half that of the conventional one. The IC withstand voltage was sufficient. As a result, a small, low-cost liquid crystal display device that does not require a high-cost, high-voltage IC with a large chip area is provided.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of a liquid crystal display device. Figure 2 is a voltage-current characteristic diagram of the MiM diode. FIG. 3 is a conventional drive waveform diagram. 4 and 5 are drive waveform diagrams according to the present invention. 7...Nonlinear element, 8...Liquid crystal element.

Claims (1)

[Scope of Claims] 1. A plurality of scanning electrodes, a plurality of signal electrodes substantially perpendicular to the scanning electrodes, and a series circuit of a nonlinear element and a liquid crystal element arranged at each intersection of both electrodes, and the two electrodes are coupled at each intersection. A positive selection period driving waveform that sequentially selects the scanning electrodes corresponding to the liquid crystal elements to be charged with positive charge at a first constant time interval, and following the positive selection period, the scanning electrode voltage is equal to the ON voltage of the signal electrode. a positive bias period drive waveform having a value greater than the intermediate value of two off-voltages; and a negative selection period drive waveform that sequentially selects scan electrodes corresponding to liquid crystal elements charged with negative charges at first fixed time intervals. , following the negative selection period, a negative bias period drive waveform in which the scan electrode voltage is smaller than the intermediate value of the two voltages of the on voltage and off voltage of the signal electrode, and a negative bias period common to all scan electrodes and signal electrodes. In a liquid crystal display device driven by a drive waveform consisting of a retrace period drive waveform set at every second constant time, the scanning electrode voltage and the signal electrode voltage are applied almost simultaneously at every third constant time.
A liquid crystal display device characterized in that the voltage difference between the two is substantially maintained and varied. 2. The liquid crystal display according to claim 1, wherein the first fixed time is an integral multiple of the horizontal scanning time of the TV signal, and the second and third fixed times are the vertical scanning time of the TV signal. Device. 3. The first fixed time is an integral multiple of the horizontal scanning time of the TV signal, the second fixed time is the vertical scanning time of the TV signal, and the third fixed time is an integral multiple of the first fixed time. A liquid crystal display device according to claim 1.