JPH02298915A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To display an image of high quality while reducing the influence of wiring impedance upon the picture quality by uniting counter electrode signal lines and auxiliary capacity elements every picture element to obtain plural-line wiring structures, and providing them with driving circuits, respectively. CONSTITUTION:In the liquid crystal display device which has TFTs 16 arranged at intersections of plural scanning signal lines Y and video signal lines X, one- terminal sides of auxiliary capacity elements 18 and counter electrodes 17b are connected by the picture elements 17, and the respective signal lines 19 for driving the elements are parallel to the video signal lines X and connected to counter electrode and auxiliary capacity element driver 15 and driver amplifier 15a respectively without being short-circuited between signal lines 19. Consequently, wiring is fractionized, so the current consumption of a single amplifier is reduced to 1/N as large as that when all picture elements are driven. Further, the common impedance is reduced, so crosstalk between adjacent picture element is reduced, a voltage which is close to a prescribed value can be applied to picture elements, and the contrast of the display image is improved.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a liquid crystal display device.

(Prior Art) Liquid crystal display devices are used in various fields because they can be made thinner and smaller than conventional CRT (cathode ray tube) displays. Color display is possible.

In particular, in active matrix liquid crystal display devices,
Image signals within one horizontal scanning period are sampled and held in correspondence with pixels, and the data is applied to the pixel electrodes all at once within the horizontal blanking period, giving a twist angle to the liquid crystal molecules of each pixel, and the liquid crystal The structure is such that the transmitted light from the back of the panel is deflected by the above-mentioned twist angle of the liquid crystal molecules and the deflection plate, and the transmitted light is modulated by a color filter arranged for each pixel of the liquid crystal panel and visually recognized from the front of the liquid crystal panel. has been done.

The counter electrode in this conventional active matrix liquid crystal display device is formed of a transparent electrode over all the pixels, taken out from two or three places on the device, and further connected to a single wire on an external substrate. Furthermore, the wiring at one end of the auxiliary capacitance provided for each pixel is connected in adjacent pixels and all connected at the end of the glass substrate and taken out. Generally, the voltage on the counter electrode side is kept at a constant value, and one end of the auxiliary capacitor is grounded, but depending on the drive method, the counter electrode and one end of the auxiliary capacitor are connected to each other, and the voltage applied to the pixel electrode side is always constant. An alternating driving method is adopted in which a driving pressure rb is applied such that the potential difference is maintained and the polarity is reversed.

This method is a driving method that has received particular attention in recent years because it can reduce the burden on the video signal line driver and at the same time, by appropriately selecting the inversion period, it can significantly reduce flicker.

Examples of such liquid crystal display devices include the following.

Fig. 4 is an equivalent model diagram during alternating drive in a conventional liquid crystal display device, Fig. 5 is a diagram showing an example of wiring within the liquid crystal device, and Fig. 6 is an equivalent model diagram when writing to the liquid crystal device in Fig. 4. be.

In these figures, 1 is a timing controller that controls switching of video signals and scanning signals, and 2 is R, G, B.
3 is a sample hold and video signal line driver; 3a is a video signal line driver amplifier; 4 is a scanning signal line driver; and 5 is a counter electrode and auxiliary capacitor drive circuit. In addition, 6 is an active element T
P.T.

7 is a pixel, and 8 is an auxiliary capacitance element. Note that in the pixel 7, a pixel electrode 7a and a counter electrode 7b are formed.

Since voltages are individually set at one end of the counter electrode 7b and the auxiliary capacitance element 8, each end is wired separately to both ends of the device, connected vertically, and further connected via a through hole to the opposite side of the glass substrate. An extraction pad was provided on the side to connect to the mounting board.

Therefore, the number of wiring lines was multilined on the pixel side, but it was changed to a single line on the external board and connected to the counter electrode and the auxiliary capacitor drive circuit 5, so the current was concentrated on the single line wiring. Due to the impedance of the wiring, it is susceptible to voltage fluctuations, and a considerable amount of noise is introduced into the wiring on the multi-line pixel side.

Moreover, such a state unnecessarily increases the number of wiring lines, which is a factor that hinders performance improvements in terms of manufacturability, closure rate, etc. Furthermore, in order to drive the single wire 7 with a - circuit,
The counter electrode and auxiliary capacitance drive circuit is required to process the current equivalent to the current flowing through a plurality of pixels into tlt-, so there are restrictions on the elements to be used.

(Generally, in the active matrix method, a current equivalent to one line flows in.) In this way, in the above drive method, a video signal line side driver is provided for each video signal line, whereas the counter electrode signal There is only one driver on the line side, and the resistivity of the transparent electrode material (ITO) used for the counter electrode signal line is high.In addition, there is a loss due to the through hole for bonding, and the wiring is reduced to one on the external board. Due to the occurrence of crosstalk due to common impedance, the voltage across the pixel electrode significantly deviates from the specified value. The same applies to one end of the auxiliary capacitor.

Furthermore, as mentioned above, the counter electrode signal line and the auxiliary capacitor one end signal line are usually integrated into one and a single drive circuit is used, so the maximum allowable power of the drive circuit is large, the output impedance is sufficiently low, and the speed is high. There are restrictions on the elements and circuits used due to conditions such as the ability to switch. Even if the drive circuit could be configured ideally, as described above, there are problems such as reduction in contrast and pixel deterioration such as luminance variation due to wiring impedance and the like.

(Problem to be Solved by the Invention) As described above, in the wiring configuration of the counter electrode signal line and the auxiliary capacitor one end signal line in the conventional liquid crystal display device, and in the drive circuit of these two lines, the contrast decreases due to the impedance of the wiring. There are problems such as deterioration of pixel quality such as brightness and brightness variations.

The present invention is intended to solve the above-mentioned conventional problems,
It is an object of the present invention to provide a liquid crystal display device that can display high-quality images by improving the influence of wiring impedance on image quality.

[Structure of the Invention (Means for Solving the Problems) The present invention provides a matrix wiring in which a plurality of scanning signal lines and a plurality of video signal lines intersect with each other, and a matrix wiring installed at the intersection of the matrix wiring. A switching element, a liquid crystal display pixel made of liquid crystal sandwiched between a pixel electrode connected to the matrix wiring via the switching element, and a counter electrode facing the upper electrode of the pixel 7, and each of the liquid crystal display pixels. an auxiliary capacitance element that assists in the capacitance of the auxiliary capacitance element; a counter electrode drive circuit provided via a counter electrode signal line to apply a predetermined voltage to each of the counter electrodes; In this liquid crystal display device, the counter electrode signal line and the auxiliary capacitor signal line are connected to a plurality of lines corresponding to the video signal line, respectively. The wiring structure is characterized in that each of these counter electrode signal lines is provided with a counter electrode drive circuit, and each of these auxiliary capacitance element signal lines is provided with an auxiliary capacitance element drive circuit.

(Function) In the present invention, the counter electrode signal line and the auxiliary capacitance element signal line each have a wiring structure of a plurality of lines corresponding to the video signal line, and each of these counter electrode signal lines is provided with a counter electrode drive circuit, A storage capacitance element drive circuit is provided for each of these storage capacitance element signal lines to drive the counter electrode and storage capacitance element, respectively, so that the influence of wiring impedance on image quality is improved and high-quality image display is achieved. be able to.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an equivalent model diagram during alternating drive in a liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of wiring within the liquid crystal device, and FIG. 3 is a diagram showing the liquid crystal device shown in FIG. 1 during writing. It is an equivalent model diagram of .

In these figures, 11 is a timing controller that controls switching of video signals and scanning signals, and 12 is R, G
, a color order switching circuit for switching the color order of the B signal, 13 a sample hold and video signal line driver for the video signal lines X1 to XN, 14 a scanning signal line driver for the scanning signal lines Y1 to YN, and 15 a counter electrode and an auxiliary electrode. 15a with capacitive element driver
are each driver amplifiers. Further, 16 is a TPT which is an active element, 17 is a pixel, and 18 is an auxiliary capacitance element. Note that the pixel 17 includes a pixel electrode 17a and a counter electrode 1.
7b is formed.

Here, one end of the auxiliary capacitor 18 and the counter electrode 17b are connected to each pixel 17, and each signal line 1 that drives these
9 are parallel to the video signal lines X1 to XN, respectively, and are connected to the counter electrode and the driver amplifier 15a of the auxiliary capacitive element driver 15 without being short-circuited between the signal lines 19. The ratings of these driver amplifiers 15a are equal to the ratings of the video signal line driver amplifier 13a, and these are sufficient. That is, since the wiring is coarsely divided, the current consumption of a single amplifier is reduced to 1/N of that when all pixels are driven (the conventional case shown in FIG. 6).

Further, as shown in FIG. 3, since the common impedance is reduced, crosstalk between adjacent pixels is reduced, and a voltage close to a specified value can be applied to the pixels without loss.

[Effects of the Invention] As explained above, in the liquid crystal display device of the present invention, the counter electrode signal line and the auxiliary capacitor one end signal line are made into one for each pixel, and at the same time, they are separated in the video signal line direction, and each of them is provided with a drive circuit. By providing this, the impedance from the drive circuit to the counter electrode side can be lowered, and the pixel applied voltage can be transmitted without loss, which can greatly contribute to improving the contrast of displayed images and improving brightness unevenness.

[Brief explanation of drawings]

FIG. 1 is an equivalent model diagram during alternating drive in a liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of wiring within the liquid crystal device, and FIG. 3 is a diagram showing the liquid crystal device shown in FIG. 1 during writing. 4 is an equivalent model diagram of a conventional liquid crystal display device during alternating drive, FIG. 5 is a diagram showing an example of wiring within the liquid crystal device, and FIG. 6 is a diagram of the liquid crystal device shown in FIG. 4 during writing. It is an equivalent model diagram of . X1 to XN... Video signal line, Y1 to YN... Scanning signal line, 15... Counter electrode and auxiliary capacitance element driver,
15a... Driver amplifier, 16... TFT, 17
... Pixel, 17a... Pixel electrode, 17b... Counter electrode, 18... Storage capacitance element, 19... Signal line.

Claims (1)

[Claims] (1) A matrix wiring in which a plurality of scanning signal lines and a plurality of video signal lines are arranged to intersect, a switching element installed at the intersection of this matrix wiring, and a connection to the matrix wiring via this switching element. a liquid crystal display pixel made of liquid crystal sandwiched between a pixel electrode and a counter electrode facing the pixel electrode; an auxiliary capacitance element for supplementing the capacitance of each of the liquid crystal display pixels; a counter electrode drive circuit provided via a counter electrode signal line to apply a voltage; and an auxiliary capacitive element drive circuit provided via an auxiliary capacitive element signal line to apply a predetermined voltage to each of the auxiliary capacitive elements. In the liquid crystal display device, the counter electrode signal line and the auxiliary capacitor signal line each have a wiring structure of a plurality of lines corresponding to the video signal line, and each of the counter electrode signal lines is provided with a counter electrode drive circuit. A liquid crystal display device characterized in that a storage capacitance element drive circuit is provided for each of these storage capacitance element signal lines.