KR20090070287A - Color filter substrate of liquid crystal display device - Google Patents

Abstract

A color filter substrate for a liquid crystal display device improving the deterioration of the transmittance according to a rubbing defect is provided to minimize rubbing fault at a step height boundary face according to the first and second thicknesses. A substrate(105) is classified into a first unit and a second unit. An RGB(Red, Green and Blue) sub color filters are designed to the first and second thickness corresponding to first and second area. The step height boundary face according to first/second thicknesses is designed to the same direction as the rubbing direction. A common electrode is formed on RGB sub-color filters. An alignment layer is formed on the common electrode.

Description

Color Filter Substrate of Liquid Crystal Display Device

The present invention relates to a liquid crystal display device, and more particularly, to a color filter substrate for a liquid crystal display device capable of improving a decrease in transmittance due to poor rubbing.

In general, the driving principle of the liquid crystal display device uses the optical anisotropy and polarization property of the liquid crystal. The liquid crystal has a long and thin structure, and thus has a directivity in the arrangement of molecules. Can be controlled.

Accordingly, when the molecular arrangement direction of the liquid crystal is arbitrarily adjusted, the molecular arrangement of the liquid crystal is changed, and light is refracted in the molecular arrangement direction of the liquid crystal due to optical anisotropy to express image information.

Currently, active matrix LCDs (AM-LCDs) in which thin film transistors and pixel electrodes connected to the thin film transistors are arranged in a matrix manner are attracting the most attention because of their excellent resolution and video performance.

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

FIG. 1A is a plan view illustrating a unit pixel of a conventional array substrate for a liquid crystal display device, and FIG. 1B is a cross-sectional view taken along the line II ′ of FIG. 1A. The array substrate and the color filter substrate are opposed to each other. Indicates.

As shown in FIGS. 1A and 1B, the color filter substrate 5 and the array substrate 10 respectively divided into the display area AA and the non-display area NAA are opposed to each other, and the color filter substrate ( The liquid crystal layer 15 is interposed between the space between 5) and the array substrate 10.

On the upper surface of the transparent substrate 2 of the array substrate 10, a plurality of gate lines 20 in one direction and a plurality of data lines defining the pixel region P by perpendicularly crossing the gate lines 20 ( 30 and a plurality of thin film transistors T are formed at the intersection of the gate wiring 20 and the data wiring 30. The thin film transistor T includes a gate electrode 25, a semiconductor layer 42, and source and drain electrodes 32 and 34.

The semiconductor layer 42 includes an active layer 40 made of pure amorphous silicon and an ohmic contact layer 41 made of amorphous silicon containing impurities.

A passivation layer 55 is formed on the thin film transistor T, and the pixel electrode 70 in contact with the drain electrode 34 is exposed through the drain contact hole CH1 exposing a part of the drain electrode 34. It is comprised corresponding to the pixel area P. FIG. The lower alignment layer 19 is formed on the entire upper surface of the pixel electrode 70.

Meanwhile, a black matrix 12 for shielding light incident to the non-display area NAA and the black matrix 12 are sequentially disposed on the lower surface of the transparent substrate 1 of the color filter substrate 5. A color filter layer 14 including red, green, and blue sub color filters 14a, 14b, and 14c patterned to the same thickness, an overcoat layer 16 and a common electrode disposed under the color filter layer 14; 80 and the lower alignment layer 18 are sequentially disposed.

The liquid crystal display device having the above-described configuration is manufactured through a cell process step, and will be described in detail with reference to the accompanying drawings.

2 is a process flow diagram illustrating cell processing steps.

As shown, generally, the cell process step can be largely classified into seven steps.

First, the first step ST1 is to prepare an array substrate and a color filter substrate on which the array element and the color filter element are formed.

Next, the second step ST2 is an alignment layer forming and rubbing process, and the above step forms upper and lower alignment layers (18 and 19 of FIG. 2) on the array substrate and the color filter substrate using a polymer material such as polyimide. The rubbing process is a pretreatment step for uniformly aligning the liquid crystal molecules by giving a uniform pretilt angle.

The third step ST3 is a cell gap forming process, which uniformly secures cell gaps of the array and the color filter substrate. In this case, the liquid crystal display is an electro-optic device that drives voltage by applying a voltage to the injected liquid crystal molecules with a predetermined gap between the array substrate and the color filter substrate, and thus transmits light through the portion if the cell gap of both substrates is not constant. Is difficult to achieve uniform brightness.

Therefore, in the above step, it is important to uniformly secure the cell gap of both substrates by uniformly spraying spacers on the front surface of the liquid crystal panel to be driven.

The fourth step ST4 is a bonding process. The above step is a process of bonding both substrates while maintaining a constant cell gap in a seal pattern made of a thermosetting resin or an ultraviolet curable resin.

The fifth step (ST5) is a cell cutting process, and the above step is a process of cutting and separating each substrate in cell units after the seal pattern curing process. It can be divided into a scribing process to form a brake process and cutting by applying a force.

The sixth step ST6 is a liquid crystal injection process, and the above step is a liquid crystal injection into both substrates. In this case, when minute air bubbles in the liquid crystal are injected into the cell, bubbles may be formed due to the combination of liquid crystal molecules with time, and thus defects may be caused. It is preferable to proceed by dividing.

Finally, the seventh step ST7 is a polarizing plate attaching process, and the above step is a process of attaching upper and lower polarizing plates (not shown) to both sides of the cell after inspecting by applying optical and electrical signals to the cells into which the liquid crystal is injected. Finally, the cell process step is completed.

However, if the thicknesses of the red, green, and blue sub-color filters are the same in the above-described configuration, it is not a problem in the front viewing angle, but may cause a problem in that the color reproducibility falls due to color inversion in the left and right viewing angles.

As part of improving the problem, efforts are being made to improve the color reproducibility by improving the contrast ratio by improving the transmittance through designing different thicknesses of the red, green, and blue sub color filters.

3A is a plan view illustrating a color filter substrate for a liquid crystal display device capable of improving color reproducibility, and FIG. 3B is a cross-sectional view taken along line III-III ′ of FIG. 3A, and will be described in detail with reference to the drawing.

As shown in FIGS. 3A and 3B, on the color filter substrate 5 divided into the first and second regions A1 and A2, the black matrix 12 and the black matrix 12 are bordered on each other. The green and blue sub color filters 14a, 14b and 14c are sequentially formed. The red, green, and blue sub color filters 14a, 14b, and 14c are formed to have first and second thicknesses t1 and t2 corresponding to the first and second regions A1 and A2, respectively.

That is, the red, green, and blue subcolor filters 14a, 14b, and 14c corresponding to the first area A1 have red, green, and blue subcolors corresponding to the first thickness t1 and the second area A2. The filters 14a, 14b, 14c are each formed with a second thickness t2. The first and second thicknesses t1 and t2 may have different thicknesses, that is, the first thickness t1 may be thicker or thinner than the second thickness t2.

Such a configuration has the red, green, and blue sub color filters 14a, 14b, and 14c designed to have different thicknesses corresponding to the first and second regions A1 and A2, in particular, the thinly formed red, green, and blue subs. There is an advantage that the color reproducibility may be improved due to the improvement of the luminous properties by improving the transmittance in the portions corresponding to the color filters 14a, 14b, and 14c.

The overcoat layer (not shown), the common electrode 80, and the upper alignment layer 18 are sequentially formed on the color filter substrate 5. The exposed upper alignment layer 18 of the color filter substrate 5 is bonded to the array substrate (not shown) after the rubbing process using the rubbing cloth.

This rubbing process determines the alignment direction of the liquid crystal molecules by aligning the polymer chains on the surface of the upper alignment layer 18 in a constant direction by rubbing the surface of the upper alignment layer 18 with a rubbing cloth at a uniform pressure and time.

In general, as shown in FIG. 4, the red, green, and blue sub color filters designed to the first and second thicknesses t1 and t2 do not consider the rubbing direction R (14a, 14b, 14c). The rubbing process will proceed. In general, the rubbing direction R is a diagonal direction forming an oblique line with the gate wiring 20 (FIG. 1).

However, when the rubbing direction R and the direction of the stepped boundary F according to the first and second thicknesses t1 and t2 are different, the liquid crystal molecules corresponding to the stepped boundary F are not uniformly aligned. The generation of the foreground line does not cause a problem that the transmittance is lowered. As a result, the contrast ratio in the entire liquid crystal panel area is reduced.

The present invention has been made to solve the above-described problem, and an object thereof is to improve rubbing defects at a stepped interface due to different thicknesses of red, green, and blue sub-color filters.

A color filter substrate for a liquid crystal display according to the present invention for achieving the above object includes a substrate divided into a first region and a second region; A black matrix on the substrate; Red, designed to have different first and second thicknesses corresponding to the first and second regions, respectively, with the black matrix as a boundary, and the stepped interface according to the first and second thicknesses being designed in the same direction as the rubbing direction, Green and blue sub color filters; A common electrode on the red, green, and blue sub color filters; And an alignment layer on the common electrode.

In this case, the rubbing direction is a diagonal direction forming an oblique line with the gate wiring, and the red, green, and blue sub color filters designed separately to correspond to the first and second regions are designed as a quadrangle including a trapezoid. .

The first thickness is thicker or thinner than the second thickness, and an overcoat layer is further configured between the red, green, and blue sub color filters and the common electrode.

In the present invention, first, by designing the stepped interface of the red, green, and blue sub color filters designed to the first and second thicknesses corresponding to the first and second areas in the same direction as the rubbing direction, The rubbing defect can be improved.

Second, there is an advantage that can improve the contrast ratio by improving the transmittance at the stepped interface.

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The present invention provides a red, green, and blue sub color filter designed to have a first thickness and a second thickness corresponding to a first region and a second region. It is characterized by the design.

Hereinafter, a liquid crystal display according to the present invention will be described with reference to the accompanying drawings.

5 is a plan view illustrating a color filter substrate for a liquid crystal display according to the present invention.

As shown, on the color filter substrate 105 divided into the first and second regions A1 and A2, the red, green, and blue sub color filters are surrounded by the black matrix 112 and the black matrix 112. 114a, 114b, 114c are formed sequentially. The red, green, and blue sub color filters 114a, 114b, and 114c are formed to have first and second thicknesses t1 and t2 corresponding to the first and second regions A1 and A2, respectively.

That is, the red, green, and blue sub colors corresponding to the first area A1 are red, green, and blue sub colors corresponding to the first thickness t1 and the second area A2. The filters 114a, 114b, 114c are each formed with a second thickness t2. At this time, the present invention is characterized in that the stepped interface (F) according to the first and second thickness (t1, t2) is designed in the same oblique direction as the rubbing direction (F). The first and second thicknesses t1 and t2 may have different thicknesses, that is, the first thickness t1 may be thicker or thinner than the second thickness t2.

In this case, in the present invention, the stepped interface F according to the first and second thicknesses t1 and t2 may be designed in each of the first and second regions A1 and A2 so as to be designed in the same direction as the rubbing direction R. FIG. Correspondingly designed red, green, and blue sub-color filters 114a, 114b, and 114c are designed as quadrangular trapezoidal shapes, but according to the rubbing direction R, the first and second thicknesses t1 and t2. The pattern shapes of the red, green, and blue sub color filters 114a, 114b, and 114c designed by) may vary. In general, the rubbing direction R is a diagonal direction forming an oblique line with the gate line (not shown).

Although not shown in detail in the drawings, an overcoat layer (not shown), a common electrode (not shown), and an upper alignment layer (not shown) are sequentially formed on the color filter substrate 105 having the above-described configuration. After performing a rubbing process using the rubbing cloth on the exposed upper alignment layer of the color filter substrate 105, a process of opposing and bonding the array substrate (not shown) is performed.

The rubbing process determines the alignment direction of the liquid crystal molecules by rubbing the surface of the upper alignment layer with a rubbing cloth at a uniform pressure and time to align the polymer chains on the surface of the upper alignment layer in a predetermined direction.

In this case, as shown in FIG. 6, when the stepped radial interface F according to the first and second thicknesses t1 and t2 is designed in the same direction as the rubbing direction R, the stepped boundary surface F during the rubbing process The rubbing cloth has an advantage that can proceed smoothly along the valley (not shown) generated by the). Through this, rubbing defects at the stepped interface F can be minimized.

Therefore, in the present invention, the line inclination angle of the entire area of the color filter substrate can be secured uniformly, and thus the contrast ratio is improved.

7A and 7B are diagrams illustrating simulation results according to the related art and the present invention, which will be described with reference to the drawings.

As shown in FIGS. 7A and 7B, a foreground line in which the liquid crystal LC is irregularly oriented due to rubbing defects is generated in the stepped boundary F of the first and second regions. The generation of this foreground line acts as a factor to lower the transmittance.

Meanwhile, in the present invention, the transmittance at the stepped boundary F can be improved by the uniform alignment of the liquid crystal LC corresponding to the stepped boundary F of the first and second regions.

Figure 7c is a view comparing the transmittance according to the prior art and the present invention, will be described in detail with reference to this.

As shown, the relationship between voltage V and transmittance T according to the prior art and the present invention is shown. In this case, it can be seen that the transmittance T in the present invention is generally improved over the conventional transmittance T regardless of the voltage V. FIG.

Therefore, in the present invention, the contrast ratio is improved by improving the transmittance at the stepped interface between the first and second regions.

However, the present invention is not limited to the above embodiments, and it will be apparent that various changes and modifications can be made without departing from the spirit and the spirit of the present invention.

1A is a plan view illustrating a unit pixel of a conventional array substrate for a liquid crystal display device.

1B is a cross-sectional view taken along the line II ′ of FIG. 1A;

2 is a process flow diagram illustrating cell processing steps.

3A is a plan view illustrating a color filter substrate for a liquid crystal display device capable of improving color reproducibility.

3B is a cross-sectional view taken along the line III-III ′ of FIG. 3A;

4 is a view for explaining a stepped boundary surface and rubbing direction according to the prior art.

5 is a plan view showing a color filter substrate for a liquid crystal display device according to the present invention;

6 is a view for explaining the stepped boundary and the rubbing direction according to the present invention.

7A and 7B are diagrams showing simulation results according to the prior art and the present invention, respectively.

Figure 7c is a view comparing the transmittance according to the prior art and the present invention.

* Explanation of symbols for the main parts of the drawings *

105: substrate 112: black matrix

114a, 1114b, 114c: Red, Green, Blue Sub Color Filter

t1, t2: 1st and 2nd thickness R: rubbing direction

F: stepped boundary surface A1, A2: first and second regions

Claims (5)

A substrate divided into a first region and a second region; A black matrix on the substrate; Red, designed to have different first and second thicknesses corresponding to the first and second regions, respectively, with the black matrix as a boundary, and the stepped interface according to the first and second thicknesses being designed in the same direction as the rubbing direction, Green and blue sub color filters; A common electrode on the red, green, and blue sub color filters; Alignment layer on the common electrode Color filter substrate for a liquid crystal display device comprising a. The method of claim 1, And the rubbing direction is a diagonal direction forming an oblique line with the gate line. The method of claim 1, The red, green, and blue sub-color filters designed to be separated from each other corresponding to the first and second regions are designed in a quadrangular shape including a trapezoid. The method of claim 1, And the first thickness is thicker or thinner than the second thickness. The method of claim 1, An overcoat layer is further formed between the red, green, and blue sub color filters and the common electrode.

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