JPS6169284A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To reduce the dynamic range of an external circuit by not only inverting the polarity of a picture signal at intervals of a prescribed time but also eliminating DC components to supply the signal to a display panel and providing a clamping circuit to add prescribed DC components. CONSTITUTION:The signal from an external input terminal 11 of video signals is supplied to a polarity inverting circuit 12, and the signal from the inverting circuit 12 and the signal from the input terminal 11 are supplied to a switch 13. The signal from the input terminal 11 is supplied to a synchronizing signal separating circuit 14, and the switch 13 is switched by a signal, whose polarity is inverted in every field, from the circuit 14. The signal from the switch 13 is supplied to an input terminal 1 of a display panel 100 through an amplifier 15 and a capacitor 16. A switch 17 is switched equally to the switch 13, and a horizontal blanking pulse phiHBLK from the synchronizing signal separating circuit 14 is supplied from a switching element 5 to a terminal 7. When a signal shown in a figure A is supplied to the input terminal 1, this signal is clamped at a voltage Vdc1 or Vdc2 in every horizontal period, and an internal signal of the display panel 100 becomes as shown in a figure B. Thus, pictures are displayed well by AC driving.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display device for displaying, for example, television images.

[Conventional technology]

For example, it has been proposed to display television images using liquid crystals.

In FIG. 3, (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 LL, L2...Lm in the 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 ΦIH of m times the horizontal frequency.
pixel switch signals φH11φH2... which are supplied with n Φ2M and are sequentially scanned by clock signals ΦiH+Φ2H from each output terminal of this shift register (2).
- φ) ITII 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 high potential (Voo), and drive pulses of these two potentials are formed.

Further, each of the lines L1 to Lm includes a switching element Mrs, which is formed of, for example, an N-channel FET.

M21...Mo11M121M22...MT121
... Ml, t, M2m... 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 sweep clamp elements Mll to Mnm are connected to the target terminal (3) through the liquid crystal cells C11, C21, . . . Cnm, respectively.

Furthermore, a one-stage shift register (4) is provided, and this shift register (4) receives a horizontal frequency clock signal φiV.
, Φ2v are supplied, and scanning line switch signals φVi + φ are sequentially scanned by clock signals ΦIV and Φ2V from each output terminal of this shift register (4).
v2...φvn is the gate line G1 in the horizontal (X-axis) direction
゜G2...Switching element M11 through Gn
Each row of Mnm in the X-axis direction (M1t to Mtm), (M
21~Mm>... (Ma~Mnm>) are respectively supplied to the control terminals. Note that VSS and VOO are also supplied to the shift register (4) as well as the shift register (2).

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

(4) The lock signal φ1 is as shown in FIG. 4A and B.
81 Φ2H1ΦiV+Φ2v is supplied. The shift register (2) outputs φH~φHm for each pixel period as shown in Figure 4C, and the shift register (4) outputs φHm for each horizontal period as shown in Figure 4. φv1 to φvn are output.

Furthermore, a signal as shown in FIG. 4E is supplied to the input terminal (1).

And when φVi + φH□ is output,
Switching elements M1 and Mll to M11 are turned on, and a current path of input terminal (1) → M1-L1 → M□1 → C11-target terminal (3) is formed, and the current is supplied to the input terminal (1) of liquid crystal cell C11. signal and target terminal (3)
A potential difference between the two is supplied. 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 C1s. The light transmittance of the liquid crystal changes depending on the amount of charge. This is similar to cell C
This is performed sequentially for cells C1s to Cnm, and when the next field signal is supplied, the amount of charge in each cell C1s to Cnm is rewritten.

In this way, the light transmittance of the liquid crystal cells C1L 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 TV image, ■ Input a signal that is an inverted video signal for each field or frame to the input terminal (1).
supply to. That is, the input terminal (1) is supplied with a signal that is inverted for each field or frame as shown in FIG.

Incidentally, in the above-mentioned apparatus, the signals supplied to the input terminal (1) are as shown in FIG.

Therefore, the external circuit that supplies the signal to the input terminal (1) needs to have a sufficient dynamic range to pass the full amplitude of the polarity-inverted signal, for example l0.
The extremely large dynamic range required for VP-P has caused problems in circuit design.

[Problem that the invention seeks to solve]

Conventional devices were constructed as described above. For this reason, in conventional devices, a large dynamic range is required for the circuit, resulting in problems such as a complicated configuration and difficulty in designing.

[Means for solving problems]

The present invention provides switch elements ML1 arranged in a matrix.
〜Mnm, respectively, liquid crystal display cells CLI〜Cn
In a liquid crystal display device configured to display an image using a display panel (100) provided with m, the polarity of the image signal is inverted (12) at predetermined intervals, and the direct current component is removed and the image signal is displayed on the display panel. (100), and a clamp circuit (5) is provided in connection with the display panel (100) to supply predetermined DC components (1B) and (19
) is added to the liquid crystal display device.

[Effect]

According to this device, since the DC component of the signal supplied to the display panel (100) is removed, the amplitude of the polarity-inverted signal is reduced to 1/2 or less, significantly reducing the dynamic range of the external circuit. can do.

〔Example〕

In FIG. 1, switching elements M1 to Mm.

The devices shown in FIG. 3, such as M 11 to M nm and liquid crystal display cells Ctt to Cnm, are formed on a single IC substrate to constitute a display panel (100).

Further, an external input terminal (11) for a video signal from a tuner (not shown) or the like is provided, and a signal from this input terminal (11) is supplied to a polarity inversion circuit (12). The signal from the inverting circuit (12) and the signal from the input terminal (11) are supplied to the switch (13). In addition, the input terminal (11
) is supplied to a synchronous separation circuit (14), and a switch (13) is switched by a signal from this separation circuit (14) that is inverted, for example, every field. A signal from this switch (13) is supplied to the input terminal (1) of the display panel (100) through an amplifier (15) and a capacitor (16).

Furthermore, a switching element (5) for clamping is provided in the signal path from the input terminal (1) in the display pulse (lOO), and the clamping element (5) is connected to the clamp t1 through this switching element (5).
A clamp voltage supply terminal (6) is connected, and a clamp voltage V is connected to this terminal (6) through a switch (17).
dcl and V dcl DC voltage source (18), (
19) is connected.

This switch (17) is switched in the same manner as the above-mentioned switch (13). Also, the gate of the switching element (5) is connected to the terminal (7), and the synchronous component -11 is connected to this terminal (7).
Horizontal blanking pulse φHRLK from circuit (14)
is supplied.

Therefore, in this device, for example, the second
When a signal as shown in Figure A is supplied, this signal is clamped to voltage V dcl or V dcl in each horizontal period, and the signal inside the display panel (100) becomes as shown in Figure 2. As a result, images can be displayed with good AC drive.

In this case, the signal on the outside gH of the display bar (100) and the input side of the capacitor (16) may be a signal from which the DC component is removed, as shown in Figure 2A, and the external circuit The range can be significantly reduced to 1/2 or less. Furthermore, this makes it possible to simplify the circuit configuration and facilitate circuit design.

Note that this device can be applied to an active matrix liquid crystal display device using TPT such as amorphous silicon, polysilicon, silicon on sapphire, and organic semiconductor.

Furthermore, the above-mentioned shift register (2), T4) and switching element (5) are integrated circuits that constitute the display panel (100).
It may be provided outside the

Further, the switches (13) and (17) may be switched every horizontal period.

Furthermore, the display can be applied either point-sequentially or line-sequentially.

〔Effect of the invention〕

According to the present invention, since the DC component of the signal supplied to the display panel (100) is removed, the amplitude of the inverted signal is reduced to 1/2 or less, thereby improving the external circuit's range. It is now possible to make it significantly smaller.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an example of the present invention, FIG. 2 is a diagram for explaining the same, and FIGS. 3 and 4 are diagrams for explaining a conventional device. Cu~Cnrn is a liquid crystal display cell, Mt~Mm, Mt
z~M nm, (5) is a switching element, (11)
is an external input terminal, (12) is a polarity inversion circuit, (13)
, (17) is a switch, (16) is a capacitor, (
1B), (19) is a DC voltage source. Go to -11

Claims (1)

[Claims] In a liquid crystal display device that displays an image using a display panel each having a liquid crystal display cell associated with switch elements arranged in a matrix,
The polarity of the image signal is reversed at predetermined intervals, the DC component is removed, and the image signal is supplied to the display panel, and a clamp circuit is provided in connection with the display panel to add a predetermined DC component. A liquid crystal display device featuring: