JPH0431371B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active matrix display device, such as a liquid crystal display or an electrochromic display device, which has a built-in drive circuit.

[Conventional technology]

2. Description of the Related Art Conventionally, an active matrix liquid crystal display device, as shown in the circuit diagram of FIG. 2, is known in which a thin film transistor is provided as a switching element for each pixel on a transparent insulating substrate. In FIG. 2, an active matrix liquid crystal display device 13 includes an active matrix array 1 composed of thin film transistors.
It has 4. The drive circuit includes a gate line drive circuit 15 that drives the gate line and a drain line drive circuit 16 that drives the drain line. The drain line drive circuit 16 has a sample hold circuit 17 and a shift register 18. The video signal corresponding to one scanning line is sequentially written into the sample hold circuit 17 by the shift register 18 and held. The gate line drive circuit 15 sequentially scans the gate lines in the vertical direction and writes video signals line by line. The structure of active matrix array 14 is shown in the equivalent circuit diagram of FIG. Each pixel consists of a thin film transistor 19, a video signal holding capacitor 20, and a liquid crystal cell 21, and has a drain line Yi in the vertical direction and a drain line Yi in the horizontal direction.
They are connected to the gate line Xj and arranged in an array. When the gate line Xj is on, the video signal is written to the video signal holding capacitor 20 via the drain lines Yi, Yi+1, etc., and even after the gate line Xj is turned off, the voltage is maintained and the next video signal is The voltage continues to be applied to the liquid crystal cell 21 until the voltage is applied. In this way, the liquid crystal cell 21 is capable of static operation, so compared to conventional matrix liquid crystal display devices,
This enables high-quality display with high contrast and wide viewing angles.

[Problem that the invention seeks to solve]

However, when displaying a TV image with a frame frequency of 60Hz using a conventional active matrix display device, for example, using pixels in a matrix of about 240 x 240 (vertically x horizontally), the clock frequency of the drain line drive circuit is 1 to 4MHz. becomes. In this case,
The operating speed of the drive circuit that can be realized using thin film transistors is as slow as about 100 KHz, so it is difficult to provide the drive circuit on the same substrate as the active matrix display device. For this reason, there was a drawback that wire bonds had to be made at hundreds of locations in order to connect to an external drive circuit.

Therefore, in order to solve these conventional drawbacks, the present invention aims to provide an active matrix display device with a built-in drive circuit that can be realized even by using thin film transistors with slow operating speeds.

[Means for solving problems]

In order to solve the above problems, the present invention provides an active matrix display device with a
A plurality of drain drive circuits each made of thin film transistors that divide and drive a plurality of drain lines are provided, and each of the video signals for one scanning line divided according to the number of the plurality of N drain line drive circuits is simultaneously transmitted. I made it work in parallel.

[Effect]

As mentioned above, by dividing the drive circuit, the clock frequency of the divided drive circuit is reduced to 1/
(For example, in the case of a drive circuit that requires a clock frequency of 4 MHz, N = 10, that is, the drive circuit needs 10
(If divided, a clock frequency of 400KHz would actually be sufficient.) Even with slow-operating thin film transistors, the drive circuit can be integrated on the same substrate as the switching element.

〔Example〕

Embodiments of the present invention will be described below based on the drawings. In FIG. 1, an active matrix liquid crystal display device 1 includes an active matrix array 2 shown in FIG. 3 consisting of thin film transistors, a gate line drive circuit 3 for driving a gate line, and three drain line drivers for driving a drain line. Circuits 4, 5, and 6 are formed. The gate line driving circuit 3 sequentially scans the gate lines in the vertical direction in synchronization with the G-clock signal. Vv1, Vv2, and Vv3, which are divided video signals for one scanning line, are applied as serial data to the drain line drive circuits 4, 5, and 6, respectively, in synchronization with the D-clock signal. Drain line drive circuits 4, 5, and 6 each correspond to 1/3 of one screen.
drive the drain line. The clock frequency of the D-clock signal is 1 with only one shift register.
It only takes 1/3 the time compared to scanning a scanning line.

An example of the external drive circuit of the active matrix liquid crystal display device 1 includes a shift register 7, a sample hold circuit 8, a sample hold circuit 9, shift registers 10, 11, 12, etc., as shown in FIG. The video signal is sequentially written into the sample hold circuit 8 by the shift register 7 and held. When scanning of the next scanning line begins, the video signal written in the sample and hold circuit 8 is transferred to the sample and hold circuit 9. The video signal held in the sample hold circuit 9 is transferred to the shift register 1
The data is divided into 1/3 of one scanning line by 0, 11, and 12 and written as serial data to the drain line drive circuits 4, 5, and 6 in synchronization with the D-clock signal. Drain line drive circuit 4, 5,
6 simultaneously and in parallel drive the drain lines of the three divided areas of the screen.

In the above description, the drain line drive circuit of the active matrix liquid crystal display device 1 is divided into three parts, but if the number of divisions is made ten, for example, the clock frequency is further reduced to 1/10. In this case, the number of input signals to the active matrix liquid crystal display device 1 does not increase compared to the three-division method because the D-clock signal is common to all drain line drive circuits, and the number of signals input to the active matrix liquid crystal display device 1 does not increase. Increase at most 7
It's just a book.

In the above description, the unit display pixel is an active matrix liquid crystal display device using liquid crystal, but the present invention can also be applied to an active matrix display device using EL, electrochromic, or the like. The thin film transistor used in the present invention may be a thin film transistor using amorphous silicon, polysilicon, Te, etc. as a semiconductor material.
Insulated gate field effect transistors are common. Furthermore, it is clear that the present invention is applicable not only to black and white display, but also to liquid crystal color display using a color filter.

〔Effect of the invention〕

As explained above, by dividing the video signal drive circuit into multiple parts, the clock frequency of the video signal drive circuit can be significantly reduced without significantly increasing the number of input terminals, thereby increasing the operating speed. Even if slow thin film transistors are used, it is possible to realize an active matrix display device in which the drive circuit is built on the same substrate as the active matrix display device.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an active matrix liquid crystal display device according to the present invention, FIG. 2 is a circuit diagram of a conventional active matrix liquid crystal display device, and FIG.
The figure is an equivalent circuit diagram of an active matrix array. 1... Active matrix liquid crystal display device, 2
... Active matrix array, 3... Gate line drive circuit, 4, 5, 6... Drain line drive circuit, Yi, Yi+1... Drain line.

Claims (1)

[Claims] 1. One substrate provided with a plurality of drain lines and a plurality of gate lines perpendicular to the drain lines, and on which thin film transistors are formed at each intersection of the drain lines and the gate lines; In an active matrix display device, the one substrate has a common electrode placed opposite to the other substrate, and is driven by scanning the gate lines line-by-line and applying a video signal to the drain line. , a plurality of drain line drive circuits made of thin film transistors that divide and drive the plurality of drain lines, and a gate line drive circuit that drives the plurality of gate lines, and a plurality of drain line drive circuits that drive the plurality of drain lines. A common clock signal is applied to each of them, and each of the video signals for one scanning line divided according to the number of the plurality of drain line drive circuits is synchronized with the clock signal as serial data. An active matrix display device characterized in that a voltage is applied to the active matrix display device.