JPS63236012A - Driving method of electro-optical device - Google Patents

Abstract

PURPOSE:To display a picture which is varied at a high speed, by setting an address time of an address signal applied successively to a scanning electrode group, shorter than a response time of a ferroelectric liquid crystal itself. CONSTITUTION:In the case of driving an electro-optical device of a structure which has a first substrate provided with plural picture element electrodes placed in a matrix shape and plural active elements corresponding to each of them, and a second substrate provided with counter electrodes opposed to the picture element electrodes, and has inserted and held a ferroelectric liquid crystal having a bistable state to an electric field between the picture element electrode and the counter electrode, an address time of an address signal applied successively to a scanning electrode group 1 is set shorter than a response time of the ferroelectric liquid crystal itself. In such a way, a display of a large picture having a large number of picture elements can be moved at a high speed, and also, a TV image can be displayed by a time gradation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving an electro-optical device using liquid crystal. More specifically, the present invention relates to active matrix driving of electro-optical devices such as optical shutter arrays, image display devices, and character display devices using ferroelectric liquid crystals.

[Conventional technology]

Regarding a liquid crystal electro-optical device having a matrix electrode structure using a ferroelectric liquid crystal having bistability, for example, US Pat. No. 43,3792 by Clark et al.

It is stated in No. 4. Further, an electro-optical device combining the ferroelectric liquid crystal and an active element is also described in, for example, Japanese Patent Laid-Open No. 61-0625. The driving method of this electro-optical device is to selectively and periodically apply address signals to a group of scanning electrodes, and selectively apply predetermined information signals in parallel to a group of signal electrodes in a manner that corresponds to the address. It used a split drive.

[Problem that the invention seeks to solve]

In the above method for driving an electro-optical device using an active element, the address signals sequentially applied to the scanning electrode group are applied for a time longer than the response time of the ferroelectric liquid crystal itself.

Therefore, the time required to scan one screen of an electro-optical device is equal to or more than (response time of ferroelectric liquid crystal) x (number of scanning lines). 640X400
For displays with dots, the response time is 150
If a microsecond ferroelectric liquid crystal was used, the scanning time for one screen would be 60 to 120 m5, making it impossible to display a screen that changes at high speed.

[Means for solving problems]

In order to solve the above problems, the present invention provides (1) a first substrate having a plurality of pixel electrodes arranged in a matrix and a plurality of active elements corresponding to each of the pixel electrodes; and a counter electrode facing the pixel electrodes. In the driving method of an electro-optical device having a structure in which a ferroelectric liquid crystal having a bistable state with respect to an electric field is sandwiched between the pixel electrode and the counter electrode, the second substrate is provided with a scanning electrode group. The present invention is characterized in that the address time of the applied address signal is shorter than the response time of the ferroelectric liquid crystal itself.

Hereinafter, a method for driving an electro-optical device using an active element and a ferroelectric liquid crystal according to the present invention will be described with reference to Examples.

[Example 1] FIG. 1 is a circuit diagram showing a part of an active matrix using a nonlinear element having a metal-insulator-metal structure (hereinafter referred to as MIM) according to the present invention. Group 2 is connected to MI'M3 by a capacitance 4 of the liquid crystal on the pixel electrode to form a matrix. This MI
M is such that when a voltage V is applied across the element, the current I flowing through the element is 1: KV @ exp (βv'''''>
This shows the bidirectional diode characteristics expressed by .

Here, the first factor is the ease of current flow, and β is a coefficient representing nonlinearity. In order to display a part of the matrix shown in FIG. 1 as a display status information as shown in FIG. 2, it is sufficient to apply signals as shown in FIG. 3, for example. 31st; Zl(a) is the scanning signal applied to the scanning electrode group 1 (Cn to Cn+, ), and FIG. 3(1)) is the signal electrode IT'2 (Sm-3m+
* ), and as a result, a signal waveform shown in FIG. 3(C) is applied to each pixel.

Ta Tat with pixel count E340x400 dots
A cell with a gap of 2 μm was made using a matrix substrate using MIM of Os CtlMN, and CS-1015 manufactured by Chisso Corporation, which has a response of about 1 ms at 20@C, ±5■, was used as a ferroelectric liquid crystal. It was sealed to form an electro-optical device. In this electro-optical device, the selection time t-80 shown in FIG.
When a drive signal of voltage Vp-p=50V was applied to a pixel portion of 32m51 for a period of 1 μs, that is, 1 frame, the device operated normally and a contrast ratio of 1:30 was obtained.

Although MIM was used in this example, other two-layer elements such as bidirectional diodes using amorphous silicon,
It is clear that an element with nonlinearity, such as a Varisf using zinc oxide, operates in a similar manner.

[Embodiment 2] FIG. 4 is another embodiment of the present invention, and is a circuit diagram showing a part of an active matrix using TPT as an active element, in which the scanning electrode group 5 and the signal electrode group 6 are arranged on the same substrate. A matrix is formed through the gate and source electrodes of T I” T7, and the capacitance of liquid crystal on the pixel electrode is
is connected to the common electrode 10 on the counter substrate O. Fifth
The figure shows the structure of the TET panel used in this example, which includes a polysilicon 12 formed on a quartz substrate 11-A, a gate insulating film 13 obtained by thermally oxidizing the polysilicon 12,
An S s Ox interlayer insulating film 15 is formed on the T I”T formed by the polysilicon gate 14 .Furthermore, contact poles are opened, and the signal line 10 and the pixel electrode 17 are formed.
is formed to form a TPT substrate. This TPT substrate and a counter substrate 10 provided with a counter electrode 9 are used as a cell with a gap of 2 μm maintained, and a liquid crystal 18 is injected into the cell. Polarizing plates 19 and 20 are pasted on both outer sides of the cell to form an electro-optical device.

In order to soften the display of a part of the 320×240 dot electro-optical device shown in FIG. 2 with the above structure tQ, the selection time [=lOμs1 data voltage ±5μ] as shown in FIG.
When the following driving waveform was applied, a contrast ratio of 1:50 was obtained.

[Example 3].

A driving waveform as shown in FIG. 7 was applied to the electro-optical device used in Example 2. That is, selection IR time t:==12
．． When using G3us and changing the number of consecutive same polarity pulses from 0 to 11 with ll frames as one set, 1
Two gradations were confirmed. From this result, it was found that gradation display for normal TV can be performed using 1-interval gradation.

[Example 4] Second, CM was applied to a silicon wafer using a normal IC process.
OS-FET is formed, and the pixel electrode is made of AI (X
1+i, pixel pitch G3.5XO3, 5μmv pixel number 320X240F, diagonal dimension 25, /1
It was made into an active matrix substrate of mm.

Using this substrate, a reflective panel with a cell thickness of 1 μm was made, liquid crystal was injected, and a single polarizing plate was pasted on the top surface to create a single-digit electro-optical device. This electro-optical device was selected for a time t=8.
When driven at E3ms, 16 gradations could be displayed.

〔Effect of the invention〕

By using the method for driving an electro-optical device using the ferroelectric liquid crystal of the present invention, which is composed of the above-mentioned It becomes possible to display.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a part of the MIM active matrix used in the present invention. FIG. 2 is a diagram showing an example of display according to the present invention. FIG. 3 is a diagram showing an example of a drive waveform for obtaining the display example shown in FIG. 2. FIG. 4 is a diagram showing a part of the T l"T active matrix of the present invention, with no part shown. FIG. 5 is a diagram showing an example of +1+rI construction of a panel using T P T.
The figure which shows the example of a drive waveform of the panel using T. FIG. 7 is a diagram showing an example of a driving waveform for displaying gradation according to the present invention. ■...Scanning electrode group 2...Signal electrode group 3...MIM element 4...Liquid crystal capacitance on pixel electrode 5...Scanning electrode group 6...Signal electrode group 7... TPT 8...capacitance of liquid crystal on pixel electrode 9...counter substrate 10...counter electrode 11...quartz substrate 12...polysilicon 13...gate insulating film 14...polysilicon Gate 15...Interlayer insulating film 1G...Signal line 17...More than pixel electrode SS S, +IS Uraya 2 Figure 2 Figure 3 (a) Figure 3 (b) %+1 qh+2
Figure 3 (C) To Figure 6 Flip Figure 7

Claims (3)

[Claims] (1) A first substrate provided with a plurality of pixel electrodes arranged in a matrix and a plurality of active elements corresponding to each of the pixel electrodes, and a second substrate provided with a counter electrode facing the pixel electrodes; In a method for driving an electro-optical device having a structure in which a ferroelectric liquid crystal having a bistable state with respect to an electric field is sandwiched between an electrode and a counter electrode, the address time of an address signal sequentially applied to a group of scanning electrodes is A method for driving an electro-optical device characterized by a response time shorter than that of a dielectric liquid crystal itself. (2) The method for driving an electro-optical device according to claim 1, wherein the active element is a nonlinear element having a two-terminal structure. (3) The method for driving an electro-optical device according to claim 1, wherein the active element is a FET.