KR19980072227A - LCD - Google Patents

Abstract

The liquid crystal display device of the present invention is composed of a plurality of domains in which the alignment films have different alignment directions. An opaque metal layer is formed in the boundary region between the domains at the same time as the gate wiring to prevent light leakage from the boundary between the domains and to stabilize the voltage applied to the pixel. The alignment direction of the alignment layer is determined by applying an organic material such as polyimide and rubbing or applying a photoreactive substance and then irradiating light.

Description

LCD

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having improved image quality and aperture ratio by forming a metal layer for storage capacitance at the boundary of domains having different alignment directions in a pixel.

Recently, a twisted nematic liquid crystal display device, which is mainly used as a flat panel display device, has a property that light transmittance at each gray level is changed by the birefringence effect of the liquid crystal. In particular, the light transmittance is distributed symmetrically with respect to the viewing angle in the left and right directions, but the light transmittance is distributed asymmetrically with respect to the vertical direction. .

In order to solve the above problems, two domain TN LCDs and Domain Divided TN LCDs have been proposed. In TDTN LCD, each domain has two LC directiors opposite to each other in the pretilted direction so that the liquid crystal directors in these two domains are inclined in opposite directions when the gray scale display voltage is applied. As a result, the average light transmittance in the vertical direction is compensated to widen the viewing angle. In DDTN, a plurality of alignment films composed of materials having different pretilt angles, for example, an organic alignment film or an inorganic alignment film, are formed on a substrate to compensate for the viewing angle by making the average alignment angle in each alignment film different.

1 is a diagram illustrating the above-described multi-domain LCD, in which FIG. 1 (a) is a plan view and FIG. 1 (b) is a cross-sectional view taken along line AA ′ of FIG. 1 (a). As shown in the figure, the pixel is defined by the gate wiring 7 and the data wiring 9 extending longitudinally and horizontally on the first substrate 1, and the intersection of the gate wiring 7 and the data wiring 9 described above. A thin film transistor which is a switching element is disposed in the gate electrode, and the gate electrode 5 is connected to the gate wiring 7 and the source / drain electrode 3 is connected to the data wiring 3. The liquid crystal display device is a storage on gate type liquid crystal display device using a portion of the gate wiring as an electrode for a storage capacitor, and the metal layer 13 is formed on the gate wiring 7 to stabilize the applied voltage. Be sure to In each pixel area, the first alignment layer 17 and the second alignment layer 18 are aligned to be divided into four domains having different alignment directions.

As described above, when the pixel is composed of a plurality of domains, the liquid crystal molecules 26 of the respective domains are oriented in opposite directions or in different directions from the liquid crystal molecules of the adjacent domains, as shown in FIG. A discontinuous surface of orientation occurs. Therefore, when light enters the liquid crystal layer 25 from an unillustrated backlight, light leaks through the interface (X-X 'line of FIG. 1 (b)). This happens.

In order to prevent light leakage at the boundary of the domain as described above, as shown in FIGS. 1A and 1B, a black matrix is formed along the boundary of the domain on the second substrate 2. It forms (11) to prevent light leakage, which is an important factor in lowering the aperture ratio. Furthermore, since the storage capacitor metal layer 13 covers not only the gate wiring 7 but also a part of the pixel region, the aperture ratio is further lowered.

The present invention is to solve the above problems, the pixel has a plurality of domains, by forming an opaque metal layer on the boundary portion of the domain to prevent light leakage to the boundary portion of the domain, the image quality is further improved liquid crystal display device The purpose is to provide.

Another object of the present invention is to provide a liquid crystal display device having an improved aperture ratio by using an opaque metal layer formed at a boundary portion of a domain as an electrode for storage capacitance.

In order to achieve the above object, the liquid crystal display device according to the present invention includes a gate wiring and a data wiring arranged vertically and horizontally on the first substrate and the second substrate, the first substrate to define a pixel region, and the gate. A thin film transistor disposed at the intersection of the wiring and the data wiring, a first alignment film applied over the entire substrate and divided into a plurality of regions having different orientation directions, and formed in a boundary region between the domains on the substrate; A black matrix formed on the metal layer, the second substrate to prevent light leakage near the gate wiring, the data wiring, and the thin film transistor; a color filter layer formed on the black matrix and the second substrate; A counter electrode stacked on the filter layer, a second alignment film stacked over the entire second substrate and having a plurality of orientation directions determined, and the first group described above And a liquid crystal layer formed between the plate and the second substrate. The metal layer is an opaque metal formed at the same time as the gate wiring and serves as a black matrix which prevents light leakage to the boundary between domains in the pixel, and also functions as an electrode for storage capacitance to stabilize the signal voltage applied to the pixel. .

Fig. 1A is a plan view of a conventional liquid crystal display element.

(B) is sectional drawing A-A 'of FIG. 1 (a).

2A is a plan view of a liquid crystal display device according to the present invention.

(B) is sectional drawing along the line B-B 'of FIG.

Explanation of symbols on the main parts of the drawing

101: first substrate 102: second substrate

103: source / drain electrode 105: gate electrode

107: gate wiring 109: data wiring

110: semiconductor layer 111: black matrix

115: gate insulating film 117: first alignment film

118: second alignment layer 121: pixel electrode

122: counter electrode 123: color filter layer

125: liquid crystal layer 126: liquid crystal molecules

130: metal layer

The biggest feature of the present invention is to form an opaque metal layer at the boundary of the domain in the pixel divided into a plurality of domains to prevent the light from leaking to the boundary of the domain while the metal layer is used as a capacitance accumulation electrode. It acts as a black matrix.

As shown in FIG. 2, a gate wiring 107 and a metal layer 130 are formed on the first substrate 101, and a gate insulating film 115 is formed thereon. The metal layer 130 serves as a black matrix that prevents light from leaking to the boundary portion of the domain (X-X 'line of FIG. 2B) during the domain division and as the storage capacitor electrode. At the same time, a metal such as Ta, Al, or Al alloy is stacked by etching and then etched, and the gate insulating film 115 is formed by laminating SiNx or SiOx by plasma CVD (Plasma Chemical Vapor Deposition). In addition, in order to improve insulation of the gate wiring 107, the gate wiring 107 may be anodized to form an anodized film. On the gate insulating film 115, a metal such as Ti, Cr, Al, or Al alloy is stacked and etched by a sputtering method to form a data wiring 109. The TFT is disposed at the intersection of the gate wiring 107 and the data wiring 109. The gate electrode 105 is formed at the same time as the gate wiring 107 and the metal layer 130, and the source / drain electrode 103 is disposed. Is formed simultaneously with the data wiring 109. Formed on the gate electrode 105 and source / drain electrodes 103, between, the lamination of the amorphous silicon, and although the etching of the semiconductor layer 110, the active layer (active layer) is formed by, the drawings do not show the semiconductive layer 110, n ⁺ Amorphous silicon is laminated to form an ohmic contact layer. In the pixel region, a transparent metal such as indium tin oxide (ITO) is laminated and etched by a sputtering method to form a pixel electrode 121, on which a first alignment layer 117 is applied and oriented in different directions, respectively. A plurality of domains in which different orientation directions are determined are formed.

There are two methods for the alignment treatment of the alignment film 117 as follows. The first method is to form an alignment layer 117 by applying an organic material such as polyimide, and then rubbing to determine the alignment direction. However, the rubbing alignment method generates dust or charge on the substrate. In particular, since the rubbing treatment must be performed several times in order to make a multi-domain as in the present invention, the alignment layer is formed by generating more dust or charge on the substrate. It is an important cause of breakage.

The second method is a photo-alignment method in which an alignment layer is formed by applying a photoreactive material such as a polyvinylcinnamate (PVCN) -based material or a polysiloxane-based material, and then irradiating the alignment layer with light such as ultraviolet rays to determine the alignment direction. Directionality is imparted to the polymer of the alignment film by light irradiation, whereby a director of liquid crystal molecules is arranged in an arbitrary direction. Such an alignment method is very useful because no dust or charge is generated in the alignment layer during the alignment treatment. Particularly, in the case where a step occurs in the alignment layer as in the present invention, when the alignment treatment is performed by the optical alignment method described above, the alignment is performed near the step. An area whose direction is not determined does not occur, and the image quality is further improved.

The black matrix 111 and the color filter layer 123 are formed on the second substrate 102. The black matrix 111 is to prevent light leakage near the gate wiring 107, near the data wiring 109, and near the TFT. The black matrix 111 is formed by stacking and etching an opaque metal such as Cr or Cr0 by a sputtering method. R, G, and B are repeated in each pixel. An overcoat layer may be formed on the color filter layer 123 to improve flatness, and the counter electrode 122 and the second alignment layer 118 are formed thereon. Like the pixel electrode 121, the counter electrode 122 uses a transparent metal such as ITO, and the second alignment layer 118 also uses a polyimide or photoreactive material such as the first alignment layer 117.

Although not shown in the drawing, a spacer is formed between the two substrates 101 and 102 to maintain a uniform gap between the substrates 101 and 102, and then a liquid crystal is injected in a vacuum state so that the liquid crystal layer 125 ) Is formed, and then the liquid crystal display device is completed through an encapsulation process.

In the liquid crystal display device having the above structure, each pixel is divided into four domains to improve the viewing angle characteristic. The orientation directions of the respective domains are oriented in opposite directions to the adjacent domains, or the orientation directions of the entire domains are oriented in different directions. Therefore, when light is incident from the backlight (not shown), the area passing through the liquid crystal layer 125 without being affected by the liquid crystal molecules 126 at the boundary portion (X-X 'line) of the domain. Although the presence of the foreground occurs on the screen, in the present invention, since the opaque metal layer 130 formed in the pixel region covers the region, the occurrence of the foreground is prevented. In addition, since the metal layer 130 serves as an electrode for the storage capacitor, the aperture ratio is much improved compared to the conventional liquid crystal display device in which the storage capacitor is formed on the gate wiring.

Although only the four-domain liquid crystal display device has been described herein, the present invention is not limited to the above-described four-domain liquid crystal device, but can of course be applied to all multi-domain liquid crystal display devices having two or more domains.

Since the opaque metal layer is formed in the boundary region between the domains of the pixels as described above, the present invention prevents light from leaking to the boundary of the domains so that the foreground is generated on the screen. Moreover, the aperture ratio is further improved because the metal layer serves as the storage capacitor electrode.

Claims (15)

A first substrate; A pixel region formed on the substrate and divided into a plurality of domains; An opaque metal layer formed at a boundary of the domain of the pixel region; A second substrate; A liquid crystal display device comprising a liquid crystal layer formed between the first substrate and the second substrate. The method of claim 1, Gate and data lines arranged vertically and horizontally on the first substrate to define pixel regions; A switching element arranged at an intersection point of the gate line and the data line; An alignment film applied over the entire first substrate; The liquid crystal display device further comprises a color filter layer formed on the second substrate. The liquid crystal display device according to claim 2, wherein the gate wiring and the metal layer are made of the same metal. 4. The liquid crystal display device according to claim 3, wherein the gate wiring and the metal layer are formed at the same time. The liquid crystal display device according to claim 2, wherein the alignment film is polyimide. The liquid crystal display device according to claim 2, wherein the alignment layer is a photoreactive material. 7. The liquid crystal display device according to claim 6, wherein the photoreactive material is a polyvinylcinnamate (PVCN) material. 7. The liquid crystal display device according to claim 6, wherein the photoreactive material is a polysiloxane material. A first substrate; A plurality of gate wirings and data wirings arranged vertically and horizontally on the first substrate to define pixel regions; A plurality of switching elements arranged at intersections of the gate wirings and data wirings; A pixel electrode formed in the pixel region; An alignment film coated over the entire first substrate and having a plurality of regions having different alignment directions; An opaque metal layer formed at a boundary of each region of the alignment layer to prevent light leakage through the boundary and to stabilize a voltage applied to the pixel electrode; A second substrate; A color filter layer formed on the second substrate; A counter electrode formed on the color filter layer; A liquid crystal display device comprising a liquid crystal layer formed between the first substrate and the second substrate. The liquid crystal display device according to claim 9, wherein the metal layer is the same metal as the gate wiring. The liquid crystal display device according to claim 10, wherein the gate wiring and the metal layer are simultaneously formed. 10. The liquid crystal display device according to claim 9, wherein the alignment film is polyimide. 10. The liquid crystal display device according to claim 9, wherein the alignment layer is a photoreactive material. The liquid crystal display device of claim 13, wherein the photoreactive material is a polyvinylcinnamate (PVCN) -based material. The liquid crystal display device according to claim 13, wherein the photoreactive material is a polysiloxane material.