JPS5986092A - Driving of liquid crystal electrooptic apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for driving a liquid crystal electro-optical device in which driving performance is improved by a nonlinear element having nonlinear voltage-current characteristics (V-processability).

By combining nonlinear elements (varistors, diodes, metal-insulator-metal braces (hereinafter abbreviated as M-devices), discharge tubes, etc.) and liquid crystal electro-optical devices, multi-digit driving is realized compared to conventional devices. It is known. This makes it possible to realize liquid crystal display devices that can display a large amount of information, optical switches that can display finer patterns, and the like.

Figure 1 shows the operation of a liquid crystal electro-optical device using nonlinear elements.
6j This is an equivalent circuit for one pixel for simple explanation. The equivalent capacitance QLO and equivalent resistance RLO of the liquid crystal layer are connected to the equivalent resistance RNL of the nonlinear element. RNL has nonlinearity that does not follow Ohm's law as shown in FIG. 2, and has a low resistance RNLON when the voltage is high and a high resistance RNLOFF when the voltage is low. When a voltage E is applied across the equivalent circuit in Figure 1, the equivalent resistance of the nonlinear element is RNI, O
N becomes C! I, 0 is charged. Next, the voltage E
Let E−△E be the drop, then the nonlinear element is RNLOF
F and Of,0 starts discharging. RN L
OF F):) RL O>> RN s, ON
Then, the charging/discharging time constant τ is RNL
They are ONOOLO and RLO/OLO. FIG. 3 shows the voltage waveform applied to the liquid crystal layer at this time. In other words, OLO is charged in a very short write time tw, and the increased voltage VLO is maintained for a sufficiently long time (ttx, o
・OLO friend number m5ec~several 10m5■) Only t k is retained. As a result, the applied voltage during the writing time tw determines the effective value, and a larger effective value ratio between ON and OB'F can be obtained than in a normal liquid crystal ``optical device''. Through such operations, multi-digit driving of several hundred digits is realized.

Although electro-optical devices have such great advantages,
When driving is performed using the voltage averaging method (Fig. 4) of the commonly used two-frame AC system (frame period t, p), the effective voltage applied to the liquid crystal layer due to the influence of other pixels on the same data electrode. A problem arises in that the changes occur. This corresponds to the applied voltage during the holding period tk in FIG.
This is because the discharge curve of O depends. In Figure 4, Tm (
Timing) The applied voltage given by -D n (data) changes variously during the holding period depending on the display pattern of other pixels on the same data electrode, and accordingly the voltage VLO applied to the liquid crystal layer is exceeded. Figure 4 (a) shows the case where the effective voltage of Vr, 0 is the smallest, (h) shows the case where it is the largest, and (C)
shows an example of a general display pattern. As described above, when the effective voltage applied to the liquid crystal changes depending on the display pattern, the display quality deteriorates by 9 halftones.

The present invention eliminates such drawbacks, and its purpose is to provide a driving method in which unnecessary periods for operation and rest periods are provided in the driving waveform to reduce halftones and display unevenness caused by display patterns. No+! This is what we provide.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 5 is an example of a drive waveform obtained by setting a pause period according to the present invention. "Display pattern", as in Figure 4, (σ
] is the minimum effective value, (h) is the M large effective value, and (C) is the general display pattern.

The difference from FIG. 4 is that two rest periods tr are provided within the frame period t F , at the beginning and end of the frame. In the case of FIG. 5, the voltage level during this pause period is such that the data signal is set at the selection level (ON level) and the timing signal is set at the selection level of the data signal, so that the voltage level is applied to the pixel (rlL, TL) at tI. The voltage T--D is 0.

Further, by setting the pause period tI within the frame period tF, the writing time tw is reduced to tF. As shown in Fig. 3, a decrease in tw works to suppress charging to QLO, but if the switching ratio of the nonlinear element, RNLOFF/RNLON, is large, even an extremely short write time tw can sufficiently charge CLO. Therefore, there is no problem in practical use except for multiplex driving with a very large number of digits (i4 digits or more).

Next, the remaining frame period excluding the pause period will be explained for humans. Compare Figures 4 and 5.

If the voltage waveform within tA in FIG. 5 is connected by dividing the rest period tI), it can be seen that the voltage waveform in FIG. 4 matches the waveform compressed in the time axis direction. In other words, the rest period −
1, I is installed, and the conventional drive waveform is pushed into the remaining tA. This increases the multiplicity seen from the frame period, and as mentioned above, of course tW
decreases. In addition, in the drive waveforms during the non-selection period (holding period) other than the tw group, the time interval is reduced similarly to the tw.

The voltage VLO applied to the liquid crystal layer when driven with the drive waveform given in this way is shown as VLO in FIG. Comparing Figures 4 and 5, in the case of the minimum effective value display pattern (a), the effective value increases compared to Figure 4, and C
In the case of the maximum effective value display pattern h), on the contrary, it decreases and (
In the case of the general display pattern C), they are about the same. This state is enlarged and shown in FIG. The broken line is the corner) The conventional example shown in FIG. 4 is the case, and the solid line is the case shown in FIG.

(a), Cb), CC) correspond to the 41st strand and FIG. 5.

The fact that the minimum effective value increases and the maximum effective value decreases means that fluctuations in the effective value of vLO due to the display pattern are suppressed.

In this way, driving can be performed while suppressing the ONOFF shadow pv of other pixels on the same data electrode.

Also, the ratio of the pause period tl to the frame period tp,
The set voltage level during the installation time and rest time can be optimized according to the number of driving multiplexes, the switching performance of the nonlinear elements, the driving voltage, etc. The case of FIG. 5 is an example in which tl is set at the beginning and end of the frame, and the applied voltage 'I' m -D n at tx is set to 0.

FIG. 7 shows the pause period tI at the end of the frame, tl=-Ht.
P, and the applied voltage TmD at t+
n is /av (positive frame period, VO...
This is an example of a drive waveform when a drive peak voltage, a...1/a bias method) is given. fiii single,
Only the case of a general display pattern is shown.

In this way, the setting of the pause period can be changed in various ways.

There is no problem in setting the voltage level during the idle period either on the data side or the timing side, but it is difficult to select it so as not to increase the number of required voltage levels and to reduce power consumption. In addition, by making the effective value applied to the liquid crystal as large as possible, the peak voltage required for driving (Vo in Figure 7) can be lowered, so the applied voltage (Tm-DSL) during the rest period can be made as large as possible. (Positive side frame) It is more advantageous to set this.

Although it is possible to increase the writing peak voltage of the OFF waveform (see the broken line in Figure 7), in practice, V O / a v shown in Figure 7 is not necessary for the t+i pressure level bell. It's the best.

First, the circuit for generating the drive waveform of the present invention will be described.

FIG. 8 shows an example of the drive waveform generating circuit h16 of the present invention, including a non-linear element liquid crystal panel (2), a data driver part (2), a timing driver part (2), and a basic voltage and bell generator part (9). Oscillated control circuit■.

Consists of display memory■. Each of the circuit blocks constituting the drive circuit has the same configuration as that of a normally used liquid crystal drive circuit, except for the control circuit (2).

Data dry no kuichion 6■ is a shift register, a j-sensor selection circuit consisting of 6 latch clusters ■9 level shifter [phase]
, the basic 1 crazy pressure level is turned off (consisting of a demultiplexer λt1, which is made up of a demultiplexer ■), and a timing driver part ■, which also consists of a shift register, as well as a data Drino<-S, a scanning image r6o tv health shifter [phase], Demultiplexer 0) et al.4441.

Mr. 1) The basic voltage generation part 1) uses the basic voltage obtained at the Official Residence 1, etc. to select the data ON and OFF level timings, to select the non-selected level, and to set the 'A', f, and levels. Convert multiplexer 0 to L/.

The control circuit (2) transfers the display data of the display memo 1) to the output) to the selection circuit, sucks it in four times along with the lock, and further outputs a latch pulse. Four data pulses and a scanning clock are sent to the timing driver.

The driving waveform of the present invention can be most easily realized in the case of cocoon weight %) Tamashi Verka (both data and timing signals do not increase (1) as shown in Fig. 7, and the rest period is stored in the display memory. Against engineering! Core, all ON (or all 0F)
It is sufficient to change the display data of F) to 'rAx'q. In other words, this means that the timing 'tbh hr number is 5,
The number of data electrodes and the timing
The number of Ili poles is J4-α, and the number of data electrodes is 4 each b'I for memo 1 and the display data corresponding to the book panel, and the timing when it is not displayed? This means that extra data for 1F and 4J4α is stored in the display memory.

However, the above method of storing data corresponding to the pause period in the display memory wastes the memo IJ-, so it is actually desirable to add (10) to the control circuit. Specifically, the shift register of the timing driver is set to the idle period 1iU 'l''J, and the data driver is also set to the timing σ, )IJ, and specific data is transferred to all data τff+ (VIJ4 (I
I.

All you have to do is give it to them. Is this lj? li-napu J
Realized by a combination of manter and logic.

In this way, the present invention improves the conventional drive (possibly 1t'6) by
This can be easily achieved by making a sudden change.

As described above, the driving method in which a pause period is provided according to the present invention prevents display unevenness and no-ftones in a liquid crystal electro-optical device using a non-linear element. Furthermore, it also has the advantage that the driving margin increases and matching between the liquid crystal layer and the nonlinear element becomes easier.

The present invention provides an innovative driving method in the field of liquid crystal electro-optical devices that handle large amounts of information.

[Brief explanation of the drawing]

FIG. 1 shows an equal number of circuits for one pixel of a liquid crystal electro-optical device using nonlinear elements. FIG. 2 shows the voltage-current characteristics of the nonlinear element. FIG. 3 is a diagram conceptually showing the voltage waveform applied to the liquid crystal layer. (For simplicity, the illustration is for a positive frame.) Figure 4 shows the timing electrode Tm, the data electrode Dn, and the pixels in the ON state (Q, -) in two-frame AC driving with a frame period tF. tTL IT
ET m-D rL, and the voltage applied to the liquid crystal layer ■L O
(rn, rL). (σ) is the minimum effective voltage applied to the liquid crystal, Cb) is the maximum, and (C) is the general display pattern. 1...Nonlinear element liquid crystal panel 2...Data electrode Z1 6...Timing electrode ni. FIG. 5d shows an example of a driving waveform according to the present invention. (12), Cb), and CC) correspond to the same display states as in FIG. FIG. 6 shows the LO waveform of the voltage applied to the liquid crystal layer when driving according to the present invention. The solid line is the one according to the present invention, and the broken line is the one according to the conventional drive. (a),
(1, CC) is Figure 4. This is based on (a), Cb), and CC) in FIG. FIG. 7 shows another example of the drive waveform according to the present invention. The broken line shows the OFF waveform. In addition, FIGS. 4 to 7 are all II! of the present invention! In order to explain the concept, the number of digits of multiplex drive is reduced. FIG. 8 is a block diagram of a drive circuit according to the present invention. 4... Data driver part 5... Timing driver part 6...
Basic voltage level generation section 7...Control circuit 8...Display memory 9...Selection circuit 10...Level shifter 11...Demultiplexer Company Suwa Seikosha Agent Patent Attorney Tsutomu Mogami Figure 1 Figure 2 To F-+I Figure 7 Left Figure 8

Claims (2)

[Claims] (1) When driving a liquid crystal display device in which an element with non-linear characteristics is installed on at least one of the substrates constituting the liquid crystal display panel using a two-frame AC method, a pause period must be provided within the frame period. A method for driving a liquid crystal electro-optical device characterized by: (2) In the method for driving a liquid crystal electro-optical device provided with a non-linear element, the voltage level during the rest period is set to a specific voltage level. Method.