JPH07104709A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent the generation of the difference in contrast and the difference in resolving power between the entrance side and the terminal end of a video line to excellently uniformize the performance of picture display over a screen by supplying analog image signals from the right and left sides for a displaying screen to the video line. CONSTITUTION:A data line point sequential driving circuit 11 is successively driven from the left to the right on a display screen and inputted to the gate of an analog switch 12. The analog switch 12 performs sampling data from a video line 13 with a prescribed timing and writes them on a data line 15 on a liquid crystal display screen. Here, the video line 13 is wired so as to be inputted from both the left and the right sides of the screen. Thus, since the video line 13 is wired from both sides of the screen in the liquid crystal display, the effect of increase of resistance and capacity of the video line 13 is reduced by half, the performance of display does not become worse only on one side of the screen. Since the video line 13 is driven from the opposite side even when the video line 13 is disconnected on the half-way of upper part of the screen, the defect is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art In an active type liquid crystal display device having a switching element in each pixel, a driving system for supplying data to a data line electrically connected to a source electrode of each pixel transistor every data line is called dot sequential driving. Has been. An equivalent circuit diagram of a conventional liquid crystal display device is shown in FIG. The dot sequential circuit 24 is composed of a shift register circuit and provides a sampling pulse to the gate of the analog switch 25. On the other hand, the analog switch 25 supplies the analog video signal from the video line 26 to the data line 28 during the sampling time. Here, the analog video signal is input to the video line 26 from the left side of the screen in FIG. 2 on the matrix substrate, and the right side of the screen is electrically open. Paying attention to the operation of writing the analog image signal to the data line, the data line 28 at the analog video signal input side end (the left end in FIG. 2) is the wiring resistance from the analog video signal input terminal on the matrix substrate to the upper left of the screen.
It is written in the data line 28 through the wiring capacitance, the conduction resistance of the analog switch, and the capacitance. On the other hand, in FIG. 2, the data line at the right end of the screen is added with the resistance and capacitance applied to the left end of the screen, and the wiring resistance and capacitance of the video line on the upper side of the screen are added. Considering only this write operation as a closed circuit, a wiring resistance, a wiring capacitance, and a parasitic capacitance form a low-pass filter as shown in FIGS. 3 (a) and 3 (b), and an amplitude is large for driving a high-frequency analog video signal. It is possible that it will decrease. This causes a reduction in contrast and resolution in image display, and a fine image cannot be obtained. 3A is an equivalent closed circuit of the data line at the left end of the screen in FIG. 2, and FIG. 3B is a closed circuit of the data line at the right end of the screen in FIG. When these two are compared, there is a difference between the left and right sides of the screen by the wiring resistance, the wiring capacitance and the parasitic capacitance of the video line corresponding to the upper side of the screen, so that there is a difference in the writing capability and the uniformity of the display performance on the left and right sides of the screen is impaired. It will be.

[0003]

As described in the prior art, the problem to be solved by the present invention is that when an analog video signal to the video line is input from only one side of the screen, the data lines are connected to the data lines on the left and right sides of the screen. This is a difference in the data writing ability, which impairs the uniformity of display performance such as contrast and resolution within the screen. The present invention also solves the problem that the video line becomes defective if it is disconnected in the middle of the pixel and the yield is reduced.

[0004]

In order to solve such a problem, according to the present invention, a plurality of pixel electrodes in which an electro-optical substance is enclosed between a pair of substrates and arranged in a matrix on one of the substrates, An image display unit in which a switching transistor connected to the pixel electrode and a plurality of data lines for supplying an image signal to the switching transistor are formed, and a scanning line for supplying a scanning signal to a gate electrode of the switching transistor is formed. An image sampling means for sampling an analog image display signal from a video line and supplying a sampled image signal to the data line; and a drive circuit section on an active matrix substrate having a shift register circuit for supplying the sampling signal. In the constituted liquid crystal display device, the display screen is displayed on the video line. Analog image signal, characterized in that it is supplied from the right sides.

[0005]

FIG. 1 shows an equivalent circuit of an active matrix substrate of a liquid crystal display device as an example of the driving method of the liquid crystal display device of the present invention. The data line dot sequential drive circuit 11 is sequentially driven from left to right as viewed from the display screen, and the analog switch 12 is driven.
Enter into the gate. The analog switch 12 samples data from the video line 13 at a predetermined timing and writes it to the data line 15 in the liquid crystal display screen. What should be noted here is that the video line 13 is wired so as to be input from both the left and right sides of the screen. In recent years, with respect to liquid crystal displays, improvement in image quality has been raised as an issue, and high-definition display performance has come to be emphasized. This is nothing but improvement of the pixel density, and it can be said that an increase in the number of pixels and a reduction in the pixel pitch are the directions of the future technology. In an active matrix substrate that constitutes a liquid crystal display having such high density pixels, the resistance of the data line 15 increases due to the reduction of the wiring width, and the parasitic capacitance of the data line 15 also increases the number of scanning lines and the number of pixels in the scanning line direction. It increases with the increase of. Further, the analog switch 12 that drives the data line 15 needs to have a larger transistor size as the resistance and capacitance of the data line 15 increase. Further, since the number of horizontal pixels also increases, it can be said that the parasitic capacitance applied to the video line 13 increases significantly. The analog switch 12 shown in FIG. 1 is an N-channel transistor only, but in order to increase the driving capability by increasing the resistance and parasitic capacitance of the data line 15 described above, C
It is conceivable to use a transfer gate as a MOS, but in this case as well, a parasitic capacitance double that of the one-channel transistor of FIG. Further, it is considered that the resistance and the capacitance of the video line 15 alone increase as the wiring width and the wiring interval decrease. In such a high-density active matrix substrate, there have been cases where multilayer wiring is used as the structure and wiring density are improved. The video line 13 is also made of a material having low resistance (aluminum) to a material having high resistance (chrome, molybdenum, molybdenum silicide, IT, etc.).
O) may be used, resulting in a significant increase in video line resistance. As described above, increasing the density of pixels causes an increase in the resistance and capacitance of the video line 13. FIG. 2 shows an example of an equivalent circuit diagram of a conventional liquid crystal display device.
The difference from FIG. 1 is that the video line 23 is wired only from one side of the screen. As described above, in a liquid crystal display device having a high pixel density, the resistance and capacitance of the video line are greatly increased. Therefore, the equivalent circuit of the conventional circuit shown in FIG. On one side, the frequency characteristic at the time of writing the data signal is such that the voltage gain decreases on the high frequency side. Since the video frequency used increases as the number of pixels increases, it causes a decrease in resolution and a decrease in contrast on one side of the screen and impairs uniformity of display performance. However, in the liquid crystal display of FIG. 1 of the present invention, since the video lines 13 are wired from both sides of the screen, the effect of increasing the resistance and the capacitance of the video lines is halved, and the display performance deteriorates only on one side of the screen. Absent. Further, even if the video line 13 is broken in the middle of the upper part of the screen, it is driven from the opposite side, so that the defect is prevented, and a redundant design can be expected to improve the yield.

[0006]

As described above, in the liquid crystal display device having a high pixel density, the resistance and the capacitance of the video line are significantly increased. Therefore, the equivalent circuit in FIG. The frequency characteristic at the time of writing a data signal on one side of the screen is such that the voltage gain decreases on the high frequency side. Since the video frequency used increases as the number of pixels increases, it causes a decrease in resolution and a decrease in contrast on one side of the screen, impairing the uniformity of display performance. However, by using the means for solving the problems of the present invention, the display performance does not deteriorate only on one side of the screen. Further, even if the video line is broken in the middle of the upper part of the surface, it is driven from the opposite side, so that the defect is prevented. In this way, it is possible to provide an image with good in-plane uniformity of display performance at a high yield.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram of a liquid crystal display device of the present invention.

FIG. 2 is an equivalent circuit diagram of a conventional liquid crystal display device.

FIG. 3 is a data line equivalent circuit diagram in a conventional liquid crystal display device. (A) Video line input side data line (b) Video line end side data

[Explanation of symbols]

11 --- Dot-sequential drive circuit 12 --- Analog switch 13 --- Video line 14 --- Scan line drive circuit 15 --- Data line 16・ ・ ・ Scan line 17 ・ ・ ・ ・ ・ Pixel transistor 18 ・ ・ ・ Parasitic capacitance 19 ・ ・ ・ ・ ・ Pixel holding capacitance 20 ・ ・ ・ ・ Counter substrate electrode 21 ・ ・ ・・ ・ ・ Analog video signal input 22 ・ ・ ・ ・ ・ Start pulse input 23 ・ ・ ・ ・ ・ ・ Clock signal input 24 ・ ・ ・ ・ ・ ・ Dot sequential drive circuit 25 ・ ・ ・ ・ ・ Analog switch 26 ・ ・ ・··· Video line 27 ··· scanning line drive circuit 28 ··· data line 29 ··· scanning line 30 ··· pixel transistor 31 ···・ Parasitic capacitance 32 ・ ・ ・ ・ Pixel electrode 33 ・ ・ ・ ・ ・ ・ Pixel holding Capacitance 34 ・ ・ ・ ・ ・ Counter electrode 35 ・ ・ ・ ・ ・ Analog video signal input 36 ・ ・ ・ ・ ・ ・ Start pulse input 37 ・ ・ ・ ・ Clock signal input 38 ・ ・ ・ ・ ・ Video wiring Resistance (input terminal-screen entrance) 39 ... Video wiring capacity (input terminal-screen entrance) 40 ... Data line resistance 41 ... Data line capacity 42 ...・ ・ Video wiring resistance (input terminal to screen entrance) 43 ・ ・ ・ ・ ・ ・ Video wiring capacitance (input terminal to screen entrance) 44 ・ ・ ・ ・ ・ ・ Video line resistance (on screen) 45 ・ ・ ・ ・ ・ ・Data line resistance 46 ・ ・ ・ ・ Video line capacitance (on screen) 47 ・ ・ ・ ・ ・ ・ Data line capacitance

Claims (1)

[Claims] 1. A plurality of pixel electrodes in which an electro-optic material is sealed between a pair of substrates and arranged in a matrix on one substrate of the substrates, a switching transistor connected to the pixel electrodes, and the switching transistor. A plurality of data lines for supplying an image signal to the switching transistor, and a plurality of scanning lines for supplying a scanning signal to the gate electrode of the switching transistor, and an analog image display signal is sampled from the video line. In a liquid crystal display device comprising an image sampling means for supplying an image signal sampled to the data line and a drive circuit section on an active matrix substrate having a shift register circuit for supplying the sampling signal, to the video line Analog image signals are supplied from the left and right sides of the display screen. Liquid crystal display device characterized by.