JPH02111920A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To correct the unequal contrast and brightness and to uniformize the display over the entire part of the screen, by the increased size of a display screen by providing leader electrodes which apply an optimum voltage to each of the band of electrodes and regulating the voltages between the counter electrodes divided to a band shape and picture element electrodes so as to uniformize the contrast and brightness over the entire part of the screen. CONSTITUTION:The TFT-LCD (thin-film transistor type liquid crystal display device) is constituted of picture elements 2, a TFT substrate 3, gate wirings 4, and the counter electrodes 1. The counter electrodes 1 are divided to the band shape in the form of intersecting orthogonally with the gate wirings 4 at the three picture element widths. Whether there is a need for adjusting the voltage for each of the band-shaped picture element electrodes 1 of what picture element width to meet the resistance of the gate wirings and the number of gradations of the gradation display or not is determined. The resistance value is adjusted by laser trimming the thin-film resistors 12 respectively connected to the divided counter electrodes, by which the voltage is adjusted. The uniform image display having no unequal contrast and brightness over the entire part of the screen is possible in this way.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a three-film transistor type liquid crystal display device (hereinafter abbreviated as TPT-LCD) used in liquid crystal televisions, etc.
Regarding TPT-LC, which has a function to correct uneven display contrast and brightness that occurs due to larger size and larger capacity.
Regarding D.

<Conventional technology> FIG. 2 shows a schematic diagram of a conventional TPT-LCD.

On the TFT substrate (2), a pixel (2) shown in the schematic diagram of one pixel in FIG. 3, a gate line (2), a thin film transistor (2), and a source line (2) are arranged in an array as shown in FIG. Also, ``■'' is a liquid crystal layer, and ``■'' is a counter electrode that is solid on the entire surface. As the size increases, the wiring length of the gate wiring (2) becomes longer, and the gate wiring resistance and capacitance increase. As a result, the gate wiring resistance is small in the pixels [phase] near the gate signal feeding end ■, and sufficient voltage is applied to the liquid crystal, and the contrast and brightness are high, but in the pixels [phase] far away from the feeding end ■, the gate wiring resistance,
The gate signal is distorted due to the capacitance, and sufficient voltage is not applied to the liquid crystal, resulting in a decrease in contrast and brightness.

In other words, the contrast and brightness of the LCD screen gradually deteriorate along the gate line (2).

As a countermeasure, it is considered to use a low-resistance material for the gate wiring (2), make it 2N, make it thicker, etc. However, due to the double layering and thickening of the gate wiring (2), the source wiring (2) that intersects with it is likely to be disconnected due to the step difference in the gate wiring (2). On the other hand, it is difficult to find a material with low resistance that can withstand strong acid treatment for removing attached organic matter.

<Problems to be Solved by the Invention> The present invention solves unevenness in contrast and brightness due to enlargement of display screens by adjusting the voltage of a counter electrode divided into strips each having a width of several to several tens of pixels. To provide a TPT-LCD with N capability to modify and make the display uniform across the screen.

Means for Solving the Problems> The present invention is a liquid crystal display device in which a counter electrode is divided into strips with a width of a plurality of pixels (several to several tens) in a direction perpendicular to the wiring direction of the gate wiring. An extraction voltage (ball) is provided to provide the optimum voltage for each strip of the electrode, and the voltage between the opposing type i divided into strips and the pixel electrode is adjusted so that the contrast and brightness of the entire screen are uniform. .

As described above, by dividing the counter electrode into strips in the direction perpendicular to the gate wiring and applying an optimal voltage to each of the strip-shaped counter electrodes, it is possible to reduce the It is also possible to obtain images with even contrast and brightness.

<Embodiments of the Invention> FIG. 1 is a schematic diagram showing an example of a TPT-LCD embodying the present invention. In Figure 1, the TPT-LCD has pixels (transparent conductive film ITO) almost the same as Figure 2 (conventional product).
etc.), TPT substrate (glass), gate wiring (chrome metal), and counter electrode (transparent conductive film, ITO, etc.). In FIG. 1, the counter electrode (2) is divided into strips having a width of three pixels and is perpendicular to the gate wiring. Depending on the gate wiring resistance and the number of gradations for image gradation display, it is determined how many pixel widths the voltage needs to be adjusted for each band-shaped counter electrode. Usually, it is in the form of a band with a width of several tens to hundreds of pixels.

(Method for adjusting voltage 1) Voltage is adjusted by adjusting the resistance value of the variable resistor @ connected to each of the divided counter electrodes ①, as shown in Fig. 4 (al).

(Voltage adjustment method 2) As shown in Fig. 4 (bl), the resistance value is adjusted by laser trimming the thin film resistors @° connected to the divided counter electrodes, respectively, and the electrician is set to J!1. As a result, uniform image display without contrast or even one-degree unevenness is possible over the entire screen (r≧).

<Effects of the Invention> As explained above, according to the present invention, by dividing the counter electrode into strips of several to ten blocks in a direction perpendicular to the gate wiring direction and adjusting the voltage of each,
It can correct contrast and brightness unevenness that occurs on large screens with a large number of pixels.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a thin film transistor type liquid crystal display device according to the present invention, and FIG. 2 is a schematic diagram showing an example of a conventional thin film transistor type liquid crystal display device. FIG. 3 is a schematic diagram of one pixel of a thin film transistor type liquid crystal display device. FIGS. 4(a) and 4(b) are schematic diagrams of voltage adjustment of the strip-shaped counter electrodes. 1 divided counter electrode 2: pixel 3: TPT base 4: gate wiring 5: 1 layer 6; counter electrode 7: TFT (:1 copy transistor) 8: source wiring 9: gate power supply end 10 : Pixel near the power supply end 11: Pixel different from the power supply end 12: Variable resistance 12°: ;n1llI resistance 13: Counter electrode supply power 14: Counter extraction electrode 15: Counter group) Image Patent Applicant Representative of Toppan Printing Co., Ltd. Kazuo Suzuki Figure 2 Figure 3 Figure 4 (a)

Claims (2)

[Claims] (1) The counter electrode of a thin film transistor type liquid crystal display device is divided into strips having multiple pixel widths in the direction perpendicular to the gate wiring, and the voltage applied to the liquid crystal layer is controlled by controlling the voltage of each of the counter electrodes divided into strips. A liquid crystal display device characterized by nearly uniform effective voltage. (2) A liquid crystal display device characterized in that, in order to adjust the voltage, the resistance value of a chip or thin film resistor provided on each counter electrode is adjusted.