KR100750928B1 - color filter panel for liquid crystal display - Google Patents

Abstract

Two insulating substrates face each other, and a lower wiring includes a gate wiring, a data wiring, a thin film transistor connected to these wirings to switch signals, and a pixel electrode connected to the thin film transistor. Red, green, and blue color filters corresponding to the pixel electrodes are formed on the upper substrate, and a black matrix is formed between the color filters. At this time, the blue color filter is formed of a resin larger than the color filter of the color having different light scattering properties. The color filter and black matrix are covered with a common electrode. Liquid crystal is injected between the two substrates. In this case, an example in which an image, which was white when viewed from the front, is shifted to yellow when viewed from the side, can be prevented.

Color filter, viewing angle, light scattering, resin

Description

Color filter substrate for liquid crystal display {color filter panel for liquid crystal display}

1 illustrates a V (voltage) -T (transmittance) curve for each color.

2 is a schematic cross-sectional view of a liquid crystal display device according to a first embodiment of the present invention;

3 is a view showing the luminance of blue according to the viewing angle in the liquid crystal display according to the prior art,

4 is a view showing luminance of red according to a viewing angle in the liquid crystal display according to the related art;

5 is a view illustrating luminance of green color according to a viewing angle in the liquid crystal display according to the related art;

6 is a view showing the luminance of red / blue luminance according to the viewing angle in the liquid crystal display according to the prior art,

7 is a view showing the luminance of the red / green luminance according to the viewing angle in the liquid crystal display according to the prior art,

8 is a view showing the luminance of red / blue luminance according to the viewing angle in the liquid crystal display according to the prior art,                 

9 is a cross-sectional view of a liquid crystal display according to a second exemplary embodiment of the present invention.

The present invention relates to a color filter substrate for a liquid crystal display device, and more particularly, to a color filter substrate for a liquid crystal display device for solving the side color coordinate shift problem.

The liquid crystal display is one of the most widely used flat panel display devices. The liquid crystal display includes two glass substrates on which electrodes are formed and a liquid crystal layer interposed therebetween. A display device for controlling the amount of light transmitted by rearranging them.

One substrate of such a liquid crystal display device generally includes a thin film transistor for switching a voltage applied to an electrode. In addition to the thin film transistor, the substrate includes a wiring including a gate line and a data line and a gate line receiving a signal from the outside. And gate pads and data pads respectively transferred to the data lines. A pixel electrode electrically connected to the thin film transistor is formed in the pixel region defined by the intersection of the gate line and the data line.

The other substrate facing the thin film transistor substrate is formed with a black matrix partitioning the pixel region, and each pixel region partitioned by the black matrix is formed with red, green, and blue color filters, and is disposed in a region other than the color filter. A black matrix is formed and a common electrode is formed on the color filter and the black matrix.

However, in such a liquid crystal display device, the color coordinates change according to the angle at which the liquid crystal display device is viewed, and when viewed from the side, the color coordinates are different from the front view. At this time, the change of color is mainly biased toward yellow or red color, so that the problem of visibility that the distinction of color as a whole becomes unclear occurs.

Next, with reference to FIG. 1, the cause which a color coordinate change generate | occur | produces is demonstrated.

Figure 1 shows the V (voltage) -T (transmittance) curve for each color.

가 커짐에 따라 더욱 심해진다. 한편, 측면에서 보는 빛이 통과한 액정층의 길이가 정면에서 보는 빛에 비하여 더 길기 때문에 빛이 느끼는

는 측면에서 보는 빛이 정면에서 보는 빛에 비하여 더 크다. 따라서 측면으로 갈수록 청색보다 녹색이나 적색의 빛의 양이 많아지게 되어 화상이 전체적으로 노란색 또는 붉은색에 가까워지는 것이다. 이는 액정의 유전율 이방성(birefringence)으로 인하여 나타나는 현상이다.As shown in FIG. 1, even when passing through the same liquid crystal layer, the shape of the VT curve varies because the degree of change in polarization varies depending on the wavelength of light. That is, the blue VT curve drops rapidly compared to the red or green VT curves. But the difference in shape of these VT curves

As it gets bigger, it gets worse. On the other hand, since the length of the liquid crystal layer through which the light viewed from the side passes is longer than the light seen from the front, the light is felt

The light seen from the side is larger than the light seen from the front. Therefore, the amount of light of green or red increases more toward blue, and the image becomes yellow or red as a whole. This is a phenomenon due to the dielectric anisotropy (birefringence) of the liquid crystal.

To solve this problem, the following method has been proposed.

가 낮으면 색좌표 이동이 상대적으로 약하게 발생하기 때문이다. 그러나, 이 방법에는 휘도도 함께 낮아지는 문제점이 있 다.first, Lowering

If is low, the color coordinate shift occurs relatively weakly. However, this method has a problem that the luminance is also lowered.

Another method is to adjust the cell gap by varying the thickness of the red, green, and blue color filters, in which spacers formed between the two substrates are moved inside the cell to maintain the cell gap of the two substrates. There is a problem that a defect occurs and the cell gap is uneven.

An object of the present invention is to improve side visibility of a liquid crystal display.

In order to achieve such a problem, in the present invention, the blue color filter is formed of a larger resin than the light scattering characteristic green or red color filter.

According to the present invention, red, green, and blue color filters are formed on an insulating substrate, and a black matrix is formed between the color filters on the substrate. The color filter and black matrix are covered with a common electrode. Here, it is preferable that a blue color filter consists of resin with a larger light scattering characteristic than a red and green color filter.

In this case, the common electrode may be patterned to have a plurality of openings.

In the present invention, blue light from the front side is diffused to the side by a blue color filter made of a resin having a large light scattering property, thereby improving color coordinate movement at the side.

Next, a color filter substrate for a liquid crystal display device according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the same.

First, the structure of the liquid crystal display according to the first exemplary embodiment of the present invention will be described in detail with reference to FIG. 2.

2 is a schematic cross-sectional view of a liquid crystal display according to a first exemplary embodiment of the present invention.

In the liquid crystal display according to the first exemplary embodiment, the lower substrate 10 and the upper substrate 100 face each other, and a liquid crystal material 70 is injected between the two substrates 10 and 100. Polarizers 11 and 101 are attached to the outer side of the lower substrate 10 and the upper substrate 100, respectively. A plurality of gate wires (not shown) and data wires (not shown) are formed on the lower substrate 10, and the thin film transistors 20 connected to the wires to receive signals are formed. In addition, a pixel electrode 30 connected to the thin film transistor 20 and made of a transparent conductive material is formed on the lower substrate 10. The black matrix 40 partitioning the pixel region is formed in the upper substrate 100, and the red, green, and blue color filters 51, 52, and 53 are repeatedly formed in the pixel region. At this time, the blue color filter 52 has greater light scattering characteristics than the red color filter 51 or the green color filter 53. In order to make the light scattering characteristic of the blue color filter 52 larger than that of the red or green color filter 53, scattering particles may be added to the resin forming the blue color filter. The common electrode 60 is formed on the color filter 50 and the black matrix 40.                     

In such a liquid crystal display, an electric field is formed between the two substrates 10 and 100 by the voltage applied to the pixel electrode 30 and the common electrode 60, and the liquid crystal orientation is changed by the electric field, and thus the light transmittance is changed. The image is displayed differently.

As described above, when the light scattering characteristics of the blue color filter 52 are larger than those of the red or green color filters 51 and 52, the amount of blue light directed to the side by scattering increases, so that the image becomes red or no as it goes to the side. It is possible to prevent the phenomenon that the color of the color shifts. Next, the reason why the blue color filter is formed of a resin having high light scattering characteristics will be described in more detail with reference to FIGS. 3 to 8.

3 to 5 are views showing luminance of blue, red, and green according to a viewing angle, respectively, in the liquid crystal display according to the related art, and circular figures respectively positioned at upper sides show luminances by colors and correspondingly, In the graph located at, the horizontal axis represents the viewing angle and the vertical axis represents the luminance. 6 to 8 are views showing red luminance / blue luminance, red luminance / green luminance, and red luminance / blue luminance according to a viewing angle in the liquid crystal display according to the related art.

3 to 5, the luminance of each color is the highest at the front (0 °) and lower toward the side (± 80 °), the luminance at the front is low in the order of green, red, blue.

As described above, after measuring the luminance for each color, the ratios of the luminance of the two colors are respectively calculated and shown in FIGS. 6 to 8.                     

First, as shown in FIG. 6, when looking at the luminance of red / blue, the luminance value of the luminance of red / blue is about 3 at the front side (0 °), and the ratio increases toward the side to about 4 at ± 80 °. Represents a value. This means that the blue luminance is reduced by about 25% based on the red luminance. That is, it can be seen that the blue ratio at the side is lower than the blue ratio at the front.

On the other hand, when looking at the red luminance / green luminance as shown in Figure 7, it can be seen that the red luminance / green luminance values in the front and side does not change significantly at about 0.35. This means that the luminance of red and green has almost no difference in front and side.

As shown in FIG. 8, when the luminance of green / blue is measured, the luminance value of green / blue is about 8 at the front (0 °), and the ratio increases toward the side, and is about 12 at ± 80 °. Indicates a value. This means that the blue luminance is significantly lowered based on the green luminance. That is, it can be seen that the blue ratio at the side is lower than the blue ratio at the front.

As such, the luminance of blue is significantly lower than the luminance of red and green toward the side, and the screen looks yellow or red on the side.

To solve this problem, a method of diffusing the blue light of the front side to the side is used. That is, by using a blue color filter using a blue resin having a large light scattering property used in a reflective liquid crystal display device, blue light at the front side is diffused to the side. Resin with such large light scattering characteristics can be obtained by adding light scattering particle | grains to general resin for color filters. In this case, the remaining green and red color filters may be used resins.

Here, the liquid crystal display of the twisted nematic (TN) mode is taken as an example, but the patterned vertical alignment (PVA) having the pixel electrode 30 and the common electrode 60 having a plurality of openings and the common electrode 60 to secure a wide viewing angle is provided. The present invention can also be applied to a liquid crystal display device in mode.

Next, a second embodiment of the present invention will be described with reference to FIG.

A gate line (not shown) formed in the horizontal direction is formed on the lower substrate 10, and a gate electrode 21 is connected to the gate line. A gate insulating film 22 is formed on the gate line and the gate electrode 21, a semiconductor layer 23 made of amorphous silicon is formed on the gate insulating film 22, and a gate electrode 21 is formed on the semiconductor layer 23. The contact layers 24 and 25 which are isolate | separated to both sides are formed. The source electrode 26 and the drain electrode 27 are formed on the contact layers 24 and 25, and the double source electrode 26 is connected to the data line 28 formed in the vertical direction. The passivation layer 29 is formed on the source and drain electrodes 26 and 27 and the data line 28, and the pixel electrode 30 is formed on the passivation layer 28. At this time, the protective film 29 may be formed of an inorganic insulating material such as silicon nitride, or may be formed of an organic insulating material such as various resins. When the passivation layer 29 is formed of an organic insulating material, the pixel electrode 30 may be formed on the surface of the flat passivation layer 29, so that uniformity of the cell gap may be easily secured, and between the data line 28 and the pixel electrode 30. Since the signal interference is small, the pixel electrode 30 may be formed to overlap the data line 28, thereby maximizing the aperture ratio. On the other hand, an opening 31 is formed in the pixel electrode 30 as a domain dividing means to secure a wide viewing angle.

The gate line transfers the scan signal to the gate electrode 21, and the data line 28 transfers the image signal to the source electrode 26. Channels are formed or disappeared in the semiconductor layer in accordance with the scan signal to transfer or block the image signal from the source electrode 26 to the drain electrode 27. The drain electrode 27 is connected to the pixel electrode 30 so that the image signal is transmitted to the pixel electrode 30 through the drain electrode 27.

The transparent upper substrate 100 has a black matrix 40 made of an opaque conductive material composed of a double layer of chromium and chromium oxide. In this case, the black matrix 40 may be formed of an organic material. Red, green, and blue color filters 51, 52, and 53 are formed in the pixel region partitioned by the black matrix 40, and an overcoat film 70 is formed on the color filters 51, 52, and 53, respectively. It is. At this time, the blue color filter 52 has greater light scattering characteristics than the red color filter 51 or the green color filter 53. In order to enlarge the light scattering characteristic of the blue color filter 52 compared with the red or green color filter 53, scattering particle | grains can be added to resin which comprises a blue color filter. A common electrode 60 made of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO) is formed on the overcoat layer 70. In this case, an opening 61 is formed in the common electrode 60 to form a fringe field together with the opening 31 of the pixel electrode 30 to secure a wide viewing angle.

The liquid crystal material 200 is injected between the upper substrate 100 and the lower substrate 10. The liquid crystal molecules of the liquid crystal material 200 are vertically aligned with respect to the two substrates 10 and 100, and preferably have negative dielectric anisotropy.

An upper polarizer 101 and a lower polarizer 11 are attached to the upper substrate 100 and the lower substrate 10, respectively.

As described above, in the present invention, the color coordinate shift in the side surface can be improved by forming a blue color filter using a resin having a larger light scattering property than other color filters.

Claims (4)

A black matrix formed on the insulating substrate and partitioning the pixel region; Red, green, and blue color filters formed in the pixel region; A common electrode formed on the color filter and the black matrix Including; The blue color filter is a color filter substrate for a liquid crystal display device made of a resin having greater light scattering characteristics than the red and green color filters. In claim 1, The common electrode is a color filter substrate for a liquid crystal display device is patterned to have a plurality of openings. The method of claim 1 or 2, A color filter substrate for a liquid crystal display device wherein light scattering particles are added to the resin forming the blue color filter; The method of claim 1 or 2, And an overcoat film disposed between the color filter and the common electrode and covering the color filter.

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