KR19990074540A - Liquid crystal display - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, wherein a pixel electrode is formed in a pixel region defined by a plurality of gate lines and data lines on a thin film transistor substrate, and is separated from the pixel electrode at a boundary portion of the pixel region. An ITO film for this is formed. In addition, a common electrode is formed on the entire surface of the color filter substrate facing the thin film transistor substrate. In the case where the same voltage as the common voltage is applied to the black matrix ITO film, the portion corresponding to the black matrix ITO film always shows a dark state in the normally black mode. In the normally white mode, when an inverted voltage is applied to the black matrix ITO film to form a sufficient electric field to drive the liquid crystal molecules, the portion corresponding to the black matrix ITO film always shows a dark state. do. Therefore, since the part corresponding to this black-matrix ITO film | membrane is always dark, it replaces a black matrix.

Description

Liquid crystal display

The present invention relates to a liquid crystal display device and a manufacturing method thereof.

In general, a liquid crystal display includes a pair of transparent glass substrates on which transparent electrodes are formed, a liquid crystal material between two glass substrates, two polarizers attached to an outer surface of each glass substrate to polarize light, and a light emitting device that emits light. It consists of a back light.

In such a liquid crystal display, one of two substrates is a color filter substrate in which a red, green, and blue color filter for displaying a desired color and a black matrix for blocking a part of light are formed, and the other substrate is a plurality of pixels. A thin film transistor substrate on which a pixel electrode for displaying a data signal and a thin film transistor (TFT) for driving the pixel electrode through switching are formed, respectively.

On the thin film transistor substrate, a plurality of pixel electrodes for displaying operation are formed in a display area formed of a set of unit pixels, and the pixel electrodes are driven by a signal applied through a wiring. The wirings include gate lines and data lines that cross each other to define a unit pixel region, and the wirings are connected to the pixel electrodes through switching elements such as thin film transistors. At this time, the switching element switches the image signal from the data line in accordance with the scanning signal from the gate line and applies it to the pixel electrode.

The common electrode forming an electric field corresponding to the pixel electrode is formed on one of the thin film transistor substrate and the color filter substrate according to the type of the liquid crystal display.

Next, a liquid crystal display according to the related art will be described with reference to the accompanying drawings.

1 is a cross-sectional view illustrating a structure of a unit pixel in a liquid crystal display according to the related art.

As shown in FIG. 1, in the liquid crystal display device according to the related art, the gate electrode 2, the gate insulating film 3 thereon, and the gate electrode 2 are disposed on the first substrate 1. A thin film transistor (TFT) including the semiconductor layer 4, the source electrode 5, and the drain electrode 6 is formed, and the drain electrode 6 is disposed on the drain electrode 6 side of the TFT. Is connected to the pixel electrode 7. This is called a thin film transistor substrate.

On the other hand, a black matrix 9 having an opening in a portion corresponding to the pixel region P is formed on the second substrate 8, and the pixel electrode 7 of the first substrate 1 is formed. The color filter 10 is formed above the second substrate 8. In addition, a common electrode 11 is formed over the entire surface of the second substrate 8. This second substrate 8 is called a color filter substrate.

In the liquid crystal display according to the related art, the black matrix 9 is formed between the color filters 10 to improve contrast ratio and blocks light that does not pass through the color filter 10. In addition, a portion 91 of the wide black matrix 9 blocks light C incident from the outside into the thin film transistor TFT so that leakage current due to the photoelectric effect does not occur, thereby thin film transistor TFT. To prevent deterioration of the function.

On the other hand, in the manufacturing method of such a liquid crystal display device, it is an important subject to reduce manufacturing cost. To this end, a method of reducing a photo process is being developed.

The present invention provides a liquid crystal display device with low manufacturing cost.

1 is a cross-sectional view illustrating a structure of one unit pixel in a liquid crystal display according to the related art.

2 is a plan view illustrating a structure of a thin film transistor substrate for a liquid crystal display according to an exemplary embodiment of the present invention.

FIG. 3 is a cross-sectional view taken along line AA ′ in FIG. 2.

In the thin film transistor substrate for a liquid crystal display device according to the present invention for achieving such a problem, an ITO film for black matrix is formed on a portion other than the pixel electrode formed in the pixel region.

In such a black matrix ITO film, a voltage equal to a common voltage applied to a common electrode formed on an upper color filter substrate is applied, or an inverted voltage is applied to the common voltage. That is, in the normally black mode in the dark state when no electric field is applied, when the common voltage is applied, the portion covered by the black matrix ITO film is always in the dark state because the common voltage is the same as that of the common electrode. In the normally white mode, which is bright when no electric field is applied, when an inverted voltage is applied to the common voltage, the potential is always different from the common electrode. Therefore, the part covered by the black matrix ITO film is always dark. do.

In this case, a light blocking film may be further formed at a portion where light leaks between the black matrix ITO film and the pixel electrode.

Next, embodiments of the liquid crystal display according to the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present invention pertains can easily practice the present invention.

The color filter substrate for a liquid crystal display device according to the present invention has no black matrix, and the ITO film for black matrix formed on the thin film transistor substrate replaces the function of the black matrix. Hereinafter, a thin film transistor substrate for a liquid crystal display according to the present invention will be described in detail.

2 is a plan view illustrating a structure of a thin film transistor substrate for a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 3 is a cross-sectional view taken along line A-A 'of FIG. 2.

2 and 3, a gate line 200 and a branched gate electrode 210 are formed in a horizontal direction on the transparent insulating substrate 100. On the upper edge of the pixel region P, the storage capacitor horizontal electrode 220 is formed in the horizontal direction, separated from the gate line 200, and the horizontal capacitance electrode on the both sides of the pixel region P in the vertical direction. The storage capacitor vertical electrodes 230 and 240 connected to the 220 are formed in parallel with each other. In addition, a first light blocking layer 250 is formed in the pixel region P adjacent to the gate electrode 210.

A gate insulating layer 300 is formed on the substrate 100 to cover the gate line 200, the gate electrode 210, the horizontal and vertical electrodes 220, 230, and 240 for the storage capacitor, and the first light blocking layer 250. have.

On the gate insulating layer 300, a vertical data line 400 crossing the gate line 200 and defining a pixel area P and a source electrode 410, which is a branch thereof, overlap the gate electrode 210. It is extended as much as possible. In addition, one end overlaps the gate electrode 210, and the other end has a drain electrode 420 extending to the pixel region P. Here, the drain electrode 420 is separated from the source electrode 410, and a part of the drain electrode 420 overlaps the first light blocking film 250. In addition, an upper portion of the drain electrode 420 has a second light blocking layer 430 formed in a horizontal direction at both ends of the horizontal electrode 220 for the storage capacitor and the upper end of the first light blocking layer 250, respectively. On the left side of the drain electrode 420, a third light blocking layer 440 is formed at both ends of which the storage capacitor horizontal electrode 220 and the lower end of the first light blocking layer 250 overlap each other. A fourth light blocking layer 450 is parallel to the gate line 200 at the lower edge of the pixel electrode P, and both ends thereof overlap the ends of the vertical storage electrodes 230 and 240, respectively, in the horizontal direction. Formed.

A passivation layer 600 is formed on the gate insulating layer 300 to cover the data line 400, the source / drain electrodes 410 and 420, and the second, third and fourth light blocking layers 430, 440, and 450. In this case, a contact hole 800 exposing a part of the drain electrode 420 is formed in the passivation layer 600.

A pixel electrode 700 formed of ITO (indium tin oxide), which is connected to the drain electrode 420 through the contact hole 800, is formed in the pixel area P on the passivation layer 600. In this case, the pixel electrode 700 is formed to overlap the edges of the first, second, third and fourth light blocking layers 250, 430, 440, and 450 and the storage capacitor electrodes 220, 230, and 240. have. A portion of the gate line 200, the data line 400, the gate electrode 210, the source electrode 410, and the drain electrode 420 is also covered on the passivation layer 600, and is separated from the pixel electrode 700. The black matrix ITO film 710 is formed along the boundary line of the pixel electrode 700 with the first, second, third and fourth light blocking films 250, 430, 440, and 450 and the storage capacitor electrodes 220, 230, and the like. It is formed to overlap with the edge portion of 240.

In the liquid crystal display device according to the present invention, since the black matrix ITO film 710 is made of a transparent conductive material, the black matrix ITO film 710 acts as a black matrix by displaying the dark state using the characteristics of the liquid crystal rather than blocking light by itself. To do it.

The first method is a method in which the same voltage as the common voltage applied to the common electrode is applied by connecting the black matrix ITO film 710 to the common electrode (see FIG. 1) formed on the color filter substrate. In this case, since the ITO film 710 and the common electrode are always in the equipotential state, the liquid crystal molecules therebetween are always along the alignment direction without being affected by an electric field even if a signal applied to the gate line 200 and the data line 400 changes. Are arranged. Therefore, in the normally black mode in which the dark state is displayed when no electric field is applied, the portion corresponding to the black matrix ITO film 710 always displays the dark state.

The second method is a method applied in a normally white mode that displays a bright state when no electric field is applied, and applies an inverted voltage to the common voltage applied to the common electrode to the black matrix ITO film 710. It is. Then, an electric field capable of sufficiently driving the liquid crystal molecules is always formed between the black matrix ITO film 710 and the common electrode, so that a portion corresponding to the black matrix ITO film 710 always displays a dark state.

The voltage applied to the ITO film 710 for the black matrix may be a voltage capable of making an electric field capable of sufficiently driving the liquid crystal molecules even if the voltage is not inverted with respect to the common voltage.

In the thin film transistor substrate for a liquid crystal display according to the present invention, the first, second, third, and fourth light blocking films 250, 430, 440, and 450 are formed of the black matrix ITO film 710 and the pixel electrode 700. They are formed to block the light leaking in between, and they are all floating.

There is no additional process for manufacturing the thin film transistor substrate for a liquid crystal display according to the present invention, the black matrix ITO film 710 is formed at the same time when forming the pixel electrode 700, the first light blocking film 250 ) May be formed in the gate line 200, and the second, third and fourth light blocking layers 430, 440, and 450 may be formed when the data line 400 is formed.

Accordingly, in the liquid crystal display according to the present invention, the black matrix ITO film is formed, and the corresponding portion is displayed in a dark state to replace the function of the black matrix, thereby reducing the manufacturing cost of the liquid crystal display.

Claims (3)

A pixel electrode, a thin film transistor, and a pixel electrode formed in a plurality of pixel regions defined by gate lines and data lines crossing each other, are separated from each other, and a transparent conductive film for a black matrix is formed at a boundary of the pixel region except for the pixel electrode. First substrate, A second substrate facing the first substrate and having a common electrode formed on a front surface thereof; Liquid crystal display comprising a. In claim 1, The transparent conductive film for the black matrix is made of ITO, and the same voltage as that applied to the common electrode or a voltage inverted is applied. In claim 2, And a light blocking layer between the pixel electrode and the black matrix.