KR20030058515A - High aperture ratio lcd device removed black matrix - Google Patents

Abstract

PURPOSE: A high aperture ratio liquid crystal display without a black matrix is provided to prevent color mix between adjacent pixel areas without forming the black matrix, thereby preventing an aperture ratio from decreasing due to the black matrix. CONSTITUTION: A plurality of gate bus lines and data bus lines(2) are crossly arranged on a first glass substrate(1) of a lower substrate(10). Thin film transistors are formed at cross points. A pixel electrode(6) formed of an ITO(Indium Tin Oxide) material is formed in each pixel area and extended to the upper parts of the gate bus lines and the data bus lines. R, G, and B color filters(14) are formed on a second glass substrate(11) of an upper substrate(20), corresponding to the pixel areas. An overcoat layer(16) is formed on a front surface of the second glass substrate, having concave patterns at surface parts corresponding to boundary parts between the pixel areas. A relative electrode(18) formed of the ITO material is formed on the overcoat layer. A liquid crystal layer(30) is interposed between the lower substrate and the upper substrate.

Description

HIGH APERTURE RATIO LCD DEVICE REMOVED BLACK MATRIX}

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 in which a black matrix is removed to obtain a high opening ratio.

As is well known, liquid crystal displays have been developed in place of the CRT (Cathod-ray tube). In particular, the thin film transistor liquid crystal display device has been in the spotlight in the information display of a portable terminal device, the screen display of a notebook PC, the monitor of a laptop computer, etc., and thus, the utilization of the thin film transistor as a display device that can replace the CRT has been very high. .

In such a liquid crystal display device, in order to obtain a high quality display screen, the improvement of the aperture ratio indicating the actual light transmission ratio with respect to the pixel electrode area is a priority, and as one technique for improving the aperture ratio, the area of the pixel electrode is conventionally increased. Top Indium Tin Oxide (ITO) structure has been proposed.

The top ITO structure is a structure in which the pixel electrode is disposed up to an upper portion of the data line by interposing an organic insulating film having a low dielectric constant between the pixel electrode and the data bus line. Not only can the aperture ratio be improved, but the additional effect of process simplification can also be obtained.

1 is a cross-sectional view schematically illustrating a liquid crystal display device having a top ITO structure formed according to the prior art, which will be described below.

The lower substrate 10 and the upper substrate 20 are spaced apart from each other, and the liquid crystal layer 30 is interposed between the substrates 10 and 20.

Here, a plurality of gate bus lines (not shown) and data bus lines 2 are vertically intersected on the lower substrate 10, and thin film transistors (not shown) are formed at each intersection as switching elements. In each pixel region partitioned by the gate bus line and the data bus line 2, a pixel electrode 6 made of ITO extends to the upper portion of the gate bus line and the data bus line 2 through the organic insulating film 4. It is arranged to extend.

In the upper substrate 20, a black matrix 12 is formed at a portion corresponding to the gate bus line and the data bus line 2 and corresponds to a thin film transistor, and a pixel correspondence region partitioned by the black matrix 12. An R, G, and B color filter 14 is formed, and an overcoat film 16 for planarization is applied on the black matrix 12 and the color filter 14, and on the overcoat film 16 with ITO. A counter electrode 18 is formed.

Unexplained reference numeral 1 denotes a first glass substrate and 11 denotes a second glass substrate.

However, the conventional high aperture liquid crystal display device as described above has the following problems. As is well known, the black matrix serves to block light leakage while preventing color mixing between the color filters, and in consideration of occurrence of misalignment when the lower substrate and the upper substrate are bonded, It is designed to be wider than it is wide. At this time, since the black matrix is designed to extend by a predetermined value toward the opening area in consideration of misalignment, the opening rate is substantially reduced, and thus a high opening rate cannot be secured.

On the other hand, in consideration of the aperture ratio, the black matrix may be omitted. In this case, color mixing may occur at the end of the pixel, resulting in deterioration of screen quality and productivity of the liquid crystal display device. It is difficult.

Accordingly, an object of the present invention is to provide a liquid crystal display device capable of preventing a decrease in aperture ratio due to a black matrix, which is devised to solve the above problems.

1 is a cross-sectional view schematically showing a high aperture liquid crystal display device having a top ITO structure formed according to the prior art;

2 is a cross-sectional view of a liquid crystal display without a black matrix according to an embodiment of the present invention.

3 is a cross-sectional view of a liquid crystal display device without a black matrix according to another embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

1: first glass substrate 2: data bus line

4 organic insulating film 6 pixel electrode

10: lower substrate 11: second glass substrate

12: black matrix 14: color filter

16: overcoat film 18: counter electrode

20: upper substrate 30: liquid crystal layer

A: concave lens B: convex lens

In the liquid crystal display device of the present invention for achieving the above object, several gate bus lines and data bus lines are arranged on the first glass substrate, the thin film transistor is formed at the intersections of the lines, A lower substrate having a pixel electrode made of ITO formed in each pixel region defined by lines to extend to an upper portion of the gate bus line and the data bus line through an organic insulating film; A color filter of R, G, and B is formed on the second glass substrate to face the lower substrate, and corresponds to the boundary between the pixel regions on the front surface of the second glass substrate including the color filter. An upper substrate having a concave or convex pattern formed on a surface portion thereof, the upper substrate having a counter electrode made of ITO formed along the surface thereof; And a liquid crystal layer interposed between the lower substrate and the upper substrate.

Here, the concave or convex pattern of the overcoat layer is selected according to the refractive indices of the liquid crystal and the overcoat film material. When the refractive index of the liquid crystal is larger than that of the overcoat film material, the concave pattern is reversed. If it is smaller than the refractive index of the film material, a convex pattern is provided.

According to the present invention, the black matrix can be omitted by providing the concave or convex pattern in the overcoat film portion corresponding to the boundary portion of the pixel, thereby improving the aperture ratio.

(Example)

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention, wherein the same parts as in FIG. 1 are designated by the same reference numerals.

As illustrated, the liquid crystal display of the present invention has a structure in which the lower substrate 10 and the upper substrate 20 are bonded to each other under the liquid crystal layer 30. In the lower substrate 10, several gate bus lines (not shown) and data bus lines 2 are arranged on the first glass substrate 1 in the same manner as the conventional one, and at the intersections of the lines, A thin film transistor (not shown) is formed, and in each pixel region defined by the lines, a pixel electrode made of ITO material extends to an upper portion of the gate bus line and the data bus line 2 through an organic insulating film 4. (6) has a formed structure.

On the other hand, the upper substrate 20 has a structure without a black matrix as compared with the conventional one, and in particular, a concave lens in a counter electrode portion corresponding to a region where the black matrix is removed, that is, a boundary between pixel regions. (A) is provided.

In detail, the upper substrate 20 includes R, G, and B color filters 14 formed on the second glass substrate 11 to correspond to the pixel region, and the second glass substrate including the color filter 14. An overcoat film 16 having a concave pattern is formed on the front surface of the surface 11 corresponding to the boundary between the pixel regions, and the counter electrode 18 of ITO material is formed on the overcoat film 16 along the surface thereof. In this case, as the ITO is deposited on the concave pattern of the overcoat layer 16, a concave lens A is formed in this portion.

The overcoat layer 16 is preferably formed of a photosensitive resin film, and the following process is performed to form a concave pattern on the photosensitive resin film.

First, in a state in which color filters of R, G, and B are formed on the second glass substrate, for example, a photosensitive resin film such as acrylic, BCB, and polyimide is coated using a spin coater. Then, the soft-baking process for the coated photosensitive resin film is performed to remove the solvent component, and the region where the concave pattern is to be formed is chrome-treated or an exposure process using an chromium-free exposure mask and UV. Do this. Subsequently, development of the exposed photosensitive resin film is performed using an alkaline solution such as TetraMethyl Ammonium Hydroxide (TMAH) to form a concave pattern on the surface of the photosensitive resin film.

At this time, during the exposure, light is irradiated to a portion of the photosensitive resin film, that is, a boundary between pixels, to form a concave pattern according to the type of the photosensitive resin film, that is, a negative type or a positive type, or vice versa. The irradiation method is used, and the exposure amount is appropriately adjusted.

Then, a hard bake process is performed on the hot plate to complete formation of an overcoat film having a concave pattern on the surface. In this case, the hard bake process is performed at a higher temperature than the soft bake process, and the substrate is heated at a high temperature of 200 ° C. or higher in consideration of the curvature of the pattern, thereby stabilizing subsequent processes.

In such a structure, the concave lens A functions to collect light spreading from the end of the pixel region to a point, thereby preventing color mixing between the pixels. Therefore, color mixing between adjacent pixel regions can be prevented without the formation of the black matrix, and therefore, the reduction of the aperture ratio due to the black matrix can be prevented, so that a liquid crystal display device having a high aperture ratio can be realized.

On the other hand, as a substitute for the black matrix, in addition to the above-mentioned concave lens A, as shown in FIG. 3, a convex lens B can be provided.

Here, the concave lens A or the convex lens B is selected according to the refractive index of the liquid crystal and the overcoat film material, that is, the refractive index of the resin film. For example, when the refractive index of the liquid crystal is larger than that of the resin film, the concave lens A or the convex lens B is concave in the overcoat film. By forming a pattern to form a concave lens (A), on the contrary, when the refractive index of the liquid crystal is smaller than that of the resin film, a convex pattern is formed on the surface of the overcoat film to make the convex lens (B).

As described above, according to the present invention, by forming a concave or convex lens in the black matrix forming region, color mixing between adjacent pixel regions can be prevented without forming the black matrix, and thus, the formation of the black matrix can be omitted. As a result, it is possible to prevent the reduction of the aperture ratio due to the black matrix, and thus to provide a liquid crystal display device having a high opening ratio.

In addition, this invention can be implemented in various changes within the range which does not deviate from the summary.

Claims (4)

Several gate bus lines and data bus lines are intersected on the first glass substrate, and thin film transistors are formed at the intersections of the lines, and in each pixel region defined by the lines, the organic insulating film is interposed therebetween. A lower substrate on which a pixel electrode made of ITO is formed to extend to an upper portion of the gate bus line and the data bus line; A color filter of R, G, and B is formed on the second glass substrate to face the lower substrate, and corresponds to the boundary between the pixel regions on the front surface of the second glass substrate including the color filter. An upper substrate having a concave or convex pattern formed on a surface portion thereof, the upper substrate having a counter electrode made of ITO formed along the surface thereof; And And a liquid crystal layer interposed between the lower substrate and the upper substrate. The method of claim 1, wherein the concave or convex pattern of the overcoat layer A liquid crystal display device, characterized in that selected according to the refractive index of the liquid crystal and the overcoat material. The liquid crystal display device according to claim 2, wherein the concave pattern is selected if the refractive index of the liquid crystal is larger than that of the overcoat material. The liquid crystal display device according to claim 2, wherein the convex pattern is selected if the refractive index of the liquid crystal is smaller than the refractive index of the overcoat material.