JPS59153388A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To attain the display of excellent picture without flicker with simple constitution by switching a video signal applied to liquid crystal cells arranged in matrix with a prescribed DC potential at each field. CONSTITUTION:A TV video signal is applied from a terminal 1 and this signal is applied to vertical lines L1-Lm through switching SW elements M1-Mm. The elements M1-Mm are scanned sequentially by phiH1-phiHm from a shift register SR2 of m-stage. Further, the SW elements M11-Mnm are connected in matrix to the lines L1-Lm and the elements M11-Mnm are connected to a target terminal 3 through liquid crystal cells C11-Cnm. Each liquid crystal cell is scanned by drive pulses phiV1-phiVn in horizontal frequency from an SR4 of n-stage. The excellent picture without flicker is displayed on the liquid crystal cells by switching altenately the input TV signal and a DC power supply 6 by a field pulse Pf by means of a switch 5.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal display device used, for example, in a viewfinder of a television camera.

α-viewing technology and its problems Displaying television images using liquid crystals has been proposed.

In FIG. 1, reference numeral (1) denotes an input terminal to which a television video signal is supplied, and each signal from this input terminal (1) is connected to a switching element M1. M2... Line L1 in the walking (Y) direction through Mm. L2...supplied to Lm. Note that m is a number corresponding to the number of pixels in the horizontal (X-axis) direction. Furthermore, an m-stage shift register (2) is provided, and a clock signal ΦII (+Φ2H) of m times the horizontal frequency is supplied to this shift I register (2), and each output of this shift 1 register (2) ～Clock from terminal (W 4Φ11
4. Drive pulse signal φ scanned sequentially by Φ2H
□5. φ□,...ψ)1111 is the switching element M
1 to each control terminal of Mm. Note that the shift register (2) has a low potential (V ss ) and a 1tJJ potential (
■4. l, ) are supplied, and drive pulses of these two potentials are formed.

Further, each of the lines L1 to Lrn is provided with a switching element M I'r consisting of, for example, an N-channel FET.

M1...Mn12MENG22M...Ml)2.・
...Mlm, M2□...One end of Mnm is connected. Note that n is a number corresponding to the number of horizontal scanning lines. The other ends of the switching elements M1'1 to Mnm are respectively the liquid crystal cells CI'1. C11 . . . is connected to Targetera 1 terminal (3) through Cnm.

Furthermore, an n-stage shift register (4) is provided, and each shift register (4) receives a horizontal frequency clock signal Φi.
drive pulse signal φVl+ which is sequentially scanned by clock signal φiV, middle 2v from each output terminal of shift 1 to register (4).
φv2...ψvn is the switching element M1's
Each column in the X-axis direction of ~Mnm (M1] ~Mzm),
(M2i to M2m)...(Mn1 to Mnm) are respectively supplied to control terminals. Note that the shift register (
4) as well as the shift register (2) ■gs and VDI
) is supplied.

That is, in this circuit, the shift register (2).

(4) As shown in Fig. 2A and B, the lock signal ΦI
t(+Φ2H1φiV, Φ2v are supplied. Then, as shown in FIG. 2C, the shift register (2) outputs φ□, ~φHm for each pixel period, and the shift register (4) outputs the As expected, φv1 to φvn are output every horizontal period, exactly 4 times.Furthermore, the input terminal (
1) is supplied with a signal similar to that shown in Figure 2.

When ψVI+ φ8□ is output, switching elements M1, M11 to M, and Ill are turned on, and the input terminal (tl + M1-"l-1→M1'
A current path from 1 to C1'1 to the target terminal (3) is formed, and the potential difference between the signal supplied to the input terminal fl) and the target terminal (3) is supplied to the liquid crystal cell C11.

Therefore, the capacitance of this cell C11 corresponds to the potential difference due to the signal of the first pixel! The load is sample vaulted. The light transmittance of the liquid crystal is changed corresponding to this voltage (iij9).A similar process is performed sequentially for cells C12 to Cnm, and when the next field signal is supplied, each cell Cr1 to Cnm is changed. The turtle (iij) is called out.

In this manner, the light transmittance of the liquid crystal cells Co to Cnm is changed corresponding to each pixel of the video signal, and this is sequentially repeated to display a television image.

By the way, when displaying with a liquid crystal, AC drive is generally used to improve its reliability and lifespan. For example, when displaying a television image, the video signal is inverted every vertical period, and a signal obtained by adding a DC potential of 1] is fed to the input terminal (11).In other words, the input terminal (1) is As shown in FIG. 2E, a signal inverted and added with a DC potential is supplied during one walking period.

A video signal as shown in FIG. 2E is generally formed by a circuit as shown in FIG. 3. In the figure, 1-transistor Q1
．． Two sets of differential amplifiers consisting of Q2, Q3, and Q4 are provided, and the transistors Q1 and Q1 and Q2
, Q3 are each supplied with a video signal Sv of opposite phase. In addition, transistors (Y1. (Y2 and Q3.
Transistors Qs and Q are connected to the collector current path of Q4, respectively.
6 is provided, and this transistor Q5. QG Heath G
A field pulse Pf with an inverted phase is supplied. and 1-transistor Q1. QB and Q2, Q4
The Emi ivy of the Q2. Output is taken out from the connection point of Q4's emitter and ivy via a negative (iS) resistor.

However, in this circuit, the waveform of the output signal (as shown in FIG. 2E), and the emitter-collector voltage of the transistor Q4 differs by G and Vp from field to field.

Therefore, the collector current flowing through transistor Q4 is modulated by the Early effect, making it impossible to obtain an output waveform that is symmetrical to the input.
~Cnm corresponds to the fact that the applied effective current j varies from field to field, causing flicker in the image.

Also, since this circuit is configured in a double-harance type,
The circuit was relatively complex.

In such a liquid crystal display device iQl;
,)'(.

A so-called field skip display is performed in which only the images of every other field are displayed. The following devices have been proposed in the past as devices for this purpose.

In FIG. 4, the outputs of C and shift L-registers (4) are respectively connected to switching elements MV1. MV2...M is connected to the control terminal of each column in the X-axis direction of the switching elements M+'+ to Mnm through the terminals, and this connection point is connected to the switching elements My+, MV2...M, respectively.
It is connected to the power supply terminal Vss through v'o. Pulses Pf, which are inverted for each field, are supplied to the control terminals of the switching elements Mv, .about.M.nu.n and Myl.about.MV'n, respectively, in opposite phases. The rest is the same as in FIG.

In this device, one frame (
A video signal Sv that is inverted every 2 fields) is supplied. Further, the signals of each part are as shown in FIG.

Then, when the field pulse Pf supplied to the switching elements MV1 to Mvn has a surface potential, φH4 and φV.

When is output, the video signal is sampled and bolded to the liquid crystal cell Cjj. This signal is held for two fields, and a new frame of video signal is input with the next field pulse Pf at the previous potential.

In this device, the equivalent blue circuit of the circuit constituting one pixel is as shown in FIG. In the figure, RLCXCLC represents equal filti resistance and capacitance of the liquid crystal, and C9C represents a DC barrier stitch existing at the interface between the switching element M and the liquid crystal. In this circuit, the voltage VLC applied to the opposite end of the liquid crystal
The waveform of is shown in FIG.

For example, when a video signal Sv such as a video signal Sv is sampled and held in the capacitor CLC at each time Tji in one frame, the level of this signal is reduced by the voltage B due to leakage through the resistor RLC. As a result, the effective signal level also decreases.

Therefore, it is necessary to increase the level of the input video signal Sv in consideration of the low level of 1. This increases the burden on the human power circuit described above, and also increases the size of 11+41F of the suissonching element. There is. In addition, this level of low sluggishness occurred (about 7 times)
There was ζ.

OBJECTS OF THE INVENTION The present invention takes these points into consideration, and is capable of displaying good flicker-free images with a simple configuration. V.

Summary of the Invention The present invention provides a liquid crystal display device in which a video signal is sequentially supplied to liquid crystal cells arranged in a matrix to display an image. This is a liquid crystal display device in which the DC potential is switched to a predetermined DC potential for each field, and according to this device, a good image without flicker can be displayed with a simple configuration.

In the embodiment shown in FIG. 8, a switch (5) is installed at the manual terminal +11. This switch (5) is supplied with the image (1'i -'+Sν) from the input terminal (1) and a predetermined voltage vnc from the DC voltage source (6). is switched to alternating current by field pulse Pf.Others are the same as in FIG.

In this device, the video signal Sv is supplied as is to the input terminal (1). By switching the switch (5), the switching elements Mi to Mm- are supplied with a signal in which a blurred video signal and a DC potential appear alternately for each field. For example, by sample-holding the I signal at time Tji, the output side of the switching element M in the equivalent circuit of FIG. B
:', an alternating voltage V LC' of V nc appears.

Then, as the voltage VL[' is DC-blocked by the capacitor C8C, the terminal (3) potential VT is applied to the opposite end of the liquid crystal as shown in Figure C. A center varying voltage LC is applied.

Therefore, the effective voltage V LC applied to the opposite end of the liquid crystal
rills becomes V LCrms (V s -V oc ), and the input video signal is transformed into a DC signal for each field (even if it is applied, the information is converted to image information.

The image is displayed in this way. And in this case,
Since the input video signal has only one polarity, the configuration of the input circuit becomes simple. Note that although the amplitude needs to be doubled, the level is the same, and there is no need to increase the load on the circuit or control the switching elements.

Further, since the signal is only unipolar, no modulation due to Early effect or the like occurs, and therefore no flicker of 41° occurs. Further, since the voltage applied to the opposite end of the liquid crystal varies around the voltage potential and is sampled for each field, the occurrence of flicker due to leakage is also reduced.

Effects of the Invention According to the present invention, it has become possible to display a good image without flicker with a simple configuration.

[Brief explanation of drawings]

Figures 1 to 7 are illustrations of the conventional equipment He";
FIG. 8 is a configuration diagram of an example of the present invention, and FIG. 1J is a diagram for explaining the same. (1) is an input terminal, (2) is a shift register, (5) is a switch, (6) is a DC voltage source, M is a switching element, and C is a liquid crystal cell. ``yl'yv5゜21st I

Claims (1)

[Claims] In a liquid crystal display device that displays images by sequentially supplying video signals to liquid crystal cells arranged in a matrix,
The liquid crystal display device described above (in which the JL-supplied video signal is switched to a predetermined DC potential for each field).