JPS59158178A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To realize flicker-free display of good picture quality through simple constitution by combining two groups of matrixes so that their row lines or column lines cross each other, and obtaining the 1st and the 2nd signals at some timing or timing opposite to it. CONSTITUTION:Matrix circuits (denoted together with dashes in symbol) equal to switching elements M1-Mm and M11-Mnm and liquid crystal cells C11- Cnm are arranged vertically in alternate combination of row lines. A video signal Sv shown in a figure A is supplied to an input terminal 1 as it is. Then, swtiches 5 and 6 are changed over to supply signals a video signal and a signal wherein a DC potential appears alternately at the opposite timing at intervals of one field as shown in figures B and C to the switching elements M1-Mm and M3'-Mm'. Those signals are sampled and held at, for example, a point Tji of time to impress a voltage VLC which varies about the target potential at a termianl 3 as shown in a figure E to opposite terminals of liquid crystal.

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.

Background Art and Problems Displaying television images using liquid crystals has been proposed.

In FIG. 1, (1) is an input terminal to which a television video signal is supplied, and the signal from this input terminal (1) is transmitted to each switching element M1. M2...Mm are supplied to lines LX, L2...Lm in the °ζ vertical (Y-axis) direction. 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 this shift register (2) receives a clock signal φ m times the horizontal frequency.
IHr Φ2H is supplied and this shift register (2
) from each output terminal of the clock signal Φi)(+φ2H
Drive pulse signals φH and φH2 are sequentially scanned by
...φH111 is supplied to each control terminal of the switching elements M1 to Mm. Note that the shift register (2) is supplied with a low potential (Vss) and a crystal potential (Voo), and these two
A drive pulse of two potentials is formed.

Further, each line L1 to Lm includes switching elements Mi't+ M21...Mnx, M12°M22...Mn2.・ ・ ・M engineering, 1M2I
One end of the element constituting each column line of 11. . . 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 to Mnm are respectively connected to the liquid crystal cells C□1. Connected to the target terminal (3) through C21...Cnm.

Furthermore, an n-stage shift register (4) is provided, and this shift register (4) receives a horizontal frequency clock signal ΦIV.
, Φ2v are supplied, and the drive pulse signal φVl+ φ■2・ is sequentially scanned by the clock signal ΦΦIV+ Φ2v from each output terminal of this shift register (4).
...φvn is each row line (Mzt~Mxm) of the switching elements Ml'l~Mnm in the X-axis direction, (M:
u to M2m) ... (Mni to Mnm) are respectively supplied to control terminals. Note that the shift register (
4) as well as shift register (2), Vss and ■, )
I, is supplied.

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

(4) As shown in FIG. 2A and B, the lock signal φi
H, φ2H1φIV+φ2v are supplied. The shift register (2) outputs φH1 to φHm for each pixel period as shown in Figure 2C, and the shift register (4) outputs φH1 to φHm for each horizontal period as shown in Figure 2C. φv1 to φvn are output. Furthermore, input terminal (1)
is supplied with a signal similar to that shown in FIG. 2E-.

When φV1+φH1 is output, switching elements M1 and M11 to MIB are turned on, and input terminal (1) → M1= L1 → M14 → C1'1
→A current path of the target terminal (3) is formed, and the potential difference between the signal supplied to the input terminal (1) and the target terminal (3) is supplied to the liquid crystal cell C1'i. Therefore, the charge corresponding to the potential difference due to the signal of the first pixel is sampled and held in the capacitance of this cell C1'1. The light transmittance of the liquid crystal changes depending on the amount of charge. The same process is performed sequentially for cells C12 to Cnm, and when the next field signal is supplied, each cell C1
The amount of charge from 1 to Cnm can be recalled.

In this way, the light transmittance of the liquid crystal cells C1'1 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, in displaying a television image, (1) the video signal is inverted every vertical period, and a signal to which a required DC potential is added is supplied to the input terminal (1). That is, input terminal +11 is supplied with a signal which is inverted every vertical period and has a DC potential added thereto, as shown in FIG. 2E.

Here, a video signal as shown in FIG. 2 is generally formed by a circuit as shown in FIG. 3. In the figure, transistor C;
11. Two sets of differential amplifiers consisting of transistors Q2, Ql and Q4 are provided, and the bases of transistors Q1, Q4 and Q2. Video signals Sv of opposite phases are supplied to the bases of Ql. Also, transistor Q1. Q2 and Ql, Q
Transistors Qs and Q6 are connected to the collector current paths of 4 and 4, respectively.
A continuous field pulse Pf is supplied to the terminals of the transistors Qs and Ql, respectively.

The emitters of transistors L+, Ql and Q2, Q4 are connected to each other, and Q2. An output is taken out from the connection point of the emitter of Q4 via a load resistor.

However, in this circuit, the waveform of the output signal is as shown in Figure 2E.
The emitter-collector voltage of transistor Q4 differs by Vp from field to field.

Therefore, the collector current flowing through the transistor Q4 is modulated by the Early effect, making it impossible to obtain an output waveform that is symmetrical to human power. This is each liquid crystal cell C1l~Cnm
This corresponds to the fact that the applied effective voltage differs from field to field, causing flicker in the image.

Also, since this circuit is configured as a tuple-balanced type,
The circuit was relatively complex.

Further, as such a liquid crystal display device, a conventional method has been proposed.

In FIG. 4, the outputs of the shift register (4) are connected to the switching elements MV1. MV2...Mvn are connected to the control terminals of each row of switching elements M u to Mr+m in the X-axis direction, and this connection point is connected to the switching elements M yl , M y2 . . .
- Connected to power supply terminal Vss through Mx7. and switching elements Mv1 to Mvn and Ml, 11 to Ml
? Pulses Pf, which are inverted for each field, are supplied to the control terminals in opposite phases to each other. The rest is the same as in FIG.

In this device, the terminal Fll has an L 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, in a state where field pulse Pf'IJ<surface potential is supplied to switching elements Mv1 to Mνn, φH1,
φV.

When is output, the video signal is sampled and held in the liquid crystal cell cji. This signal is held for two field periods, and a new frame of video signal is input with the next field pulse Pf at 18+ potential.

In this device, the equivalent circuit of the circuit constituting one pixel is shown in FIG. In the figure, RLCXCLC is the equal+tli resistance and capacitance of the liquid crystal, and CDC is the DC blocking W [capacitance] present 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.

Here, if sample and hold is performed on the video signal Sv such as A at each time Tji in one frame, the level of this signal will be changed by the resistance RLC.
Due to the leakage through the signal, the effective signal level also decreases.

Therefore, it is necessary to increase the level of the input video signal Sv in consideration of this level drop, which increases the load on the input circuit described above and also requires an increase in the withstand voltage of the Suisson tink element. Furthermore, this level drop caused flicker.

OBJECTS OF THE INVENTION The present invention takes these points into account and enables flicker-free, high-quality image display with a simple configuration.

Summary of the Invention The present invention provides a liquid crystal display device that displays an image by sequentially supplying a video signal to liquid crystal cells arranged in a matrix, in which two sets of the above matrices are arranged such that their row lines or column lines alternate. The video signal to be supplied is switched to a predetermined DC potential for each field with negative timing, and the first signal is switched to a predetermined DC potential for each field with reverse timing. A liquid crystal display device that forms a DC potential of 1 and a switched second signal, supplies these two signals to the two sets of matrices, and drives the two sets of matrices with the same drive signal. According to this, a good image without warping can be displayed with a simple configuration.

Example In FIG. 8, switching elements M1 to Mm.

Matrix circuits equivalent to Mu to Mnm and liquid crystal cells C11 to Cnm (marked with a dash and a box) are provided, and are arranged in combination in L1-, which intersects perpendicularly to each row line, as shown in the figure. . This switching element Ms'~M
The control terminals of m', M11' to M- are connected in common to each other, and are connected to the shift register (2), f4]. Furthermore, the signal input terminals of the switching elements Ms to Mm and Ms' to Mm are respectively connected in common.

Further, the input terminal (1) is connected to one of the fixed contacts of the switch (5) and the other fixed contact of the switch (6). A DC voltage 1lliI (7) of a predetermined voltage VOC is connected to the other fixed contact of the switch (5) and one of the fixed contacts of the switch (6). These switches +5), , +6) are simultaneously switched to one and the other fixed contact by field pulse Pf. And this switch +51. +6) respectively from switching elements M1 to Mm and Ml' to M
It is supplied to the signal input terminal of nl.

In this device, the video signal Sv is directly supplied to the input terminal (1) as shown in FIG. 9A.

By switching the switches (51, (61), the video signal and the DC potential are alternately applied to the switching elements M1 to Mm and Ml' to Mm' for each field as shown in FIG. 9B and C, respectively. A signal is provided which appears with the opposite timing, for example at the instant Tj
Every time the signal is sampled and held at i, a voltage (Lc') in which the signal voltage Vs and the DC voltage VDC alternate as shown in FIG. 9 appears on the output side of the switching element M in the equivalent circuit of FIG. Then, each time this voltage VLC' is DC-blocked by the capacitor Coc, the opposite end of the liquid crystal has a voltage VLC' centered around the target potential of terminal (3) T as shown in Figure 9E. Voltage VLC is applied.

Therefore, the effective voltage V L applied to the opposite ends of the C/& crystal
CtlIS becomes ~vLC1'1llS-"'4- (Vs Voc), and even if the input video signal is applied as signal-DC-1 signal-DC for each field, the information is converted into image information.

The image is displayed in this way. In this case, the input circuit 13 has only one polarity, which simplifies the configuration of the input circuit. Note that although the imaging width needs to be doubled, the level remains the same, and there is no need to increase the load on the circuit or the withstand voltage of the switching element.

Furthermore, since the signal is only one polarity, modulation due to Early effects and the like does not occur, and flicker does not occur due to this. Furthermore, since the voltage applied to the opposite end of the liquid crystal varies around the target potential and is sampled for each field, flicker due to leakage is also reduced.

Furthermore, FIG. 10 shows another example A, in which switching elements M1' to M,', Mtr=M- and liquid crystal cells C1l' to Cn- are combined in the horizontal direction for each column line. Placed. Also, at the input terminal (1), III! A delay circuit (8) for 8I elements is provided, and a switch (9) controlled by a field pulse Pf outputs a signal only during the period when a video signal is supplied to the liquid crystal cell C1; -C- provided on the left side. is delayed. Note that (101 is a video signal amplifier, which performs the general amplification. The other components are the same as in FIG. 8.

In this circuit as well, a video signal and a DC potential are applied to the liquid crystal cells C1'l to Cnl11 and C11' to Cnl alternately for each field at opposite timings. Further, the video signals applied to the left liquid crystal cells Cxr to Cn are delayed by one pixel to adjust the horizontal position of the leather image.

The specific configuration of the input terminal (1) to the amplifier αω is as follows.
This is done as shown in Figure 1. In the figure, (11) is a clamp circuit. In this circuit, the amplifier α0) is not driven by alternating current, so the configuration is simple.

Furthermore, the delay for one pixel can be performed using a sample and hold circuit, for example. In that case, sampling can be performed using the clock signal φIH, as shown in FIG. 12, for example. Note that FIG. 13 shows a specific example of the configuration for this purpose.

Furthermore, as shown in FIG. 14, three sample and hold circuits (8a), (8b), and (8c) are provided,
The circuit (8a) may perform sampling using the clock signal Φ1 day, and the circuits (8b) and (8c) may perform sampling using the clock signal 4)2H.

FIG. 15 shows still another example. In this example, there are four matrix circuits including switching elements M+ to Mm, M11 to Mnm, and liquid crystal cells C11=Cnm (
They are provided with the suffixes a, b, c, and d, respectively, and are arranged in alternating combinations both horizontally and vertically. Then, the signal from the input terminal fll is supplied to one of the switches (5d) and the other of the switches (5b), and the signal from the delay circuit (8) is supplied to one of the switches (5C) and the other of the switches (5d).
the other of the switches (5a) (5c),
Direct/current/potential is supplied to one of (5b) and (5d), and each switch (5a) to (5d)
The signals from are fed to the matrix circuits with the same suffix.

In this circuit as well, a video signal and a DC potential are alternately applied to each liquid crystal cell at predetermined timings for each field, and alignment in the horizontal direction is also performed.

In this example as well, the delay circuit (8) may be a sample hold circuit similar to that shown in FIGS. 12 and 14.

Furthermore, on each of the above-mentioned sides, the switching element M can be configured with a MOSFET using a silicon substrate. Alternatively, it can be constructed by laminating a thin film transistor and liquid crystal using amorphous silicon, polysilicon, silicon on sapphire, etc., which is particularly effective since deterioration due to leakage is particularly severe.

Effects of the Invention According to the present invention, a flicker-free and good I
i! It is now possible to display one image.

[Brief explanation of the drawing]

1 to 7 are diagrams for explaining a conventional device, FIG. 8 is a configuration diagram of an example of the present invention, FIG. 9 is a diagram for explaining the same, and FIG. 10 is a configuration diagram of another example. 11 to 14 are diagrams for explaining the same, and FIG. 15 is a configuration diagram of still another example. 11 is an input terminal, (2) is a shift register, (51, (
Reference numeral 61 represents a switch, (7) a DC voltage source, M a Swiss-tinck element, and C a liquid crystal cell. Figure 5

Claims (1)

[Claims] In a liquid crystal display device in which image No. 16 is sequentially supplied to liquid crystal cells arranged in a matrix to perform image display, two sets of the above-mentioned matrices are combined so that the dot lines or column lines are alternate. The video signal to be supplied is switched to a predetermined DC potential for each field with a negative timing, and the first signal is switched to a predetermined DC potential for each field with a reverse timing. Second
, and convert these two signals into the above two signals.
A liquid crystal display device that supplies signals to two sets of matrices and drives the two sets of matrices with the same drive signal.