KR20100007847A - In-plane switching liquid crystal display - Google Patents

Abstract

PURPOSE: A horizontal field-type LCD(Liquid Crystal Display) device is provided to apply upper/lower polarizing plates for the reduction of phase delay in a thickness direction, thereby reducing yellowing in a black status. CONSTITUTION: A lower polarizing plate(12) is arranged under a first substrate(1). A first polarizing film(12b) is arranged between a first supporter(12a) and a second supporter(12c). An upper polarizing plate(22) is arranged on a second substrate(2). A second polarizing film(22b) is arranged between a third supporter(22a) and a fourth supporter(22c). Phase delay in a thickness direction is Rth. The Rth of the third supporter and the second supporter is 0nm to 29nm. The first to fourth supporters is TAC(Triacetyl cellulous).

Description

Horizontal Electric Field Liquid Crystal Display {IN-PLANE SWITCHING LIQUID CRYSTAL DISPLAY}

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device using a horizontal electric field.

The liquid crystal display is composed of upper and lower display panels on which electrodes are formed and liquid crystal materials injected therebetween. Such a liquid crystal display device displays an image by applying an electric field to the liquid crystal material injected between two display panels using an electrode, and adjusting the intensity of the electric field to adjust the amount of light passing through the display panel.

Among liquid crystal display devices, a liquid crystal display device using a horizontal electric field forms a lower display panel by forming both a common electrode and a pixel electrode on a substrate on which a thin film transistor is formed, and a horizontal electric field formed between them (a horizontal electric field relative to the display panel). By changing the orientation of the liquid crystal using the to adjust the amount of light passing through the upper and lower display panels and to display an image.

However, such a horizontal field type liquid crystal display has a problem in that a yellow shift phenomenon occurs severely in terms of displaying black (black state). This is a leak of green and red light on the side, which worsens the visibility on the side and lowers the contrast ratio, which greatly deteriorates the display quality.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and improves the image quality of the liquid crystal display by eliminating yellowing on the side of the liquid crystal display.

In the horizontal field type liquid crystal display according to the present invention for achieving the above object, a common electrode and a common electrode formed on the inner surface side of any one of the first and second substrates, the first substrate and the second substrate are formed. A pixel electrode formed on an inner surface side of the same substrate as the substrate in which the substrate is located, a liquid crystal layer injected between the first and second substrates, and disposed below the first substrate, and having a first polarization between the first and second supports A lower polarizing plate on which a film is disposed, an upper polarizing plate disposed on a second substrate, and having a second polarizing film disposed between the third support and the fourth support, wherein the phase delay in the thickness direction is Rth, Rth of the second and third supports is 0 nm to 29 nm, and the first to fourth supports are TAC (Triacetyl cellulous).

Or a common electrode formed on the inner surface side of any one of the first and second substrates, the first substrate and the second substrate, and a pixel electrode formed on the inner surface side of the same substrate as the substrate on which the common electrode is formed; A liquid crystal layer injected between the first and second substrates, disposed under the first substrate, disposed on the lower polarizing plate, the second substrate, on which the first polarizing film is disposed between the first and second supports, An upper polarizing plate having a second polarizing film disposed between the third support and the fourth support, wherein the phase delay in the thickness direction is referred to as Rth, and the angles formed by the long axes of the liquid crystals lying obliquely with the first and second substrates are respectively set. When referred to as the first inclination angle and the second inclination angle, the Rth of the second support and the third support is 50nm to 70nm, the first inclination angle and the second inclination angle is greater than 2 ° and less than 5 °, the first to fourth support Triacetyl cel lulous).

The first polarizing plate and the second polarizing plate may be optical recycling films.

The delay axis of the second support and the third support may be parallel to the initial alignment direction of the liquid crystal included in the liquid crystal layer.

The delay axes of the second support and the third support may be parallel to the absorption axes of the lower and upper polarizers, respectively.

The pixel electrode and the common electrode may be formed in a band shape and at least part of the pixel electrode may be refracted.

The pixel electrode and the common electrode are alternately disposed, and when the regions are divided based on a line connecting the refracted portions, portions of the pixel electrode and portions of the common electrode included in the same region are mutually different. Can be side by side.

The pretilt angles of the first alignment layer and the second alignment layer respectively formed on the inside of the first substrate and the second substrate may be greater than 2 ° and less than or equal to 5 °.

In the liquid crystal display device using the horizontal electric field according to the present invention, the yellowing phenomenon in the black state can be reduced and the side contrast ratio can be improved by applying the upper and lower polarizing plates to reduce the phase delay in the thickness direction. This is directly related to the enlargement of the viewing angle and the improvement of the color characteristics.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

A liquid crystal display and a liquid crystal display according to an exemplary embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view of a liquid crystal display device according to a first embodiment of the present invention, FIG. 2 is a layout view of a thin film transistor substrate for a liquid crystal display device according to an embodiment of the present invention, and FIGS. 3A and 3B are embodiments of the present invention. In the liquid crystal display device according to the example, it is a conceptual diagram showing the arrangement of the rubbing direction and the delay axis of the second support and the third support.

The liquid crystal display according to the first exemplary embodiment of the present invention is a liquid crystal material that is injected and sealed between the thin film transistor display panel 1 and the color filter display panel 2 facing each other, and the two display panels 1 and 2. A second liquid crystal layer 3, the first and second polarizing films 12b and 22b and the first and second polarizing films 12b and 22b respectively disposed on the outer surface side of the two display panels 1 and 2, respectively. It comprises one to fourth support (12a, 12c, 22a, 22c).

As shown in FIG. 2, the thin film transistor array panel 1 includes a gate line 121, a data line 171, a thin film transistor, a pixel electrode 190, a common electrode line 131, and a common electrode 133a, 133b, and 133c. ) Is formed. The gate line 121 and the data line 171 cross each other to define a pixel area in a matrix shape, and a thin film transistor as a switching element, a pixel electrode 190, and a common electrode 133a, 133b, and 133c are formed in each pixel area. It is.

The thin film transistor may include a gate electrode that is a part of the gate line 121, a gate insulating film (not shown) covering the gate line 121, a semiconductor layer 154 formed on the gate insulating film on the gate electrode, and a data line 171. Source electrode 173 extending to the top of the semiconductor layer 154, the opposite electrode of the source electrode 173, a drain formed on the semiconductor layer 154 and connected to the pixel electrode 190 And a protective film (not shown) that covers and protects the electrode 175 and the semiconductor layer 154.

On the other hand, the data line 171 is not formed in a straight line but is periodically refracted at a predetermined angle. The refraction period of the data line 171 in the first embodiment of the present invention is twice per pixel area.

The pixel electrode 190 and the common electrodes 133a, 133b, and 133c are all formed in a band shape, are alternately disposed, and are refracted in the same pattern as the data line 171. Therefore, when the regions are divided based on the lines connecting the refraction units, the pixel electrodes 190 and the common electrodes 133a, 133b, and 133c positioned in the same region are parallel to each other.

The data line 171, the pixel electrode 190, and the common electrodes 133a, 133b, and 133c may be formed in a straight line.

When a potential difference is applied between the pixel electrode 190 and the common electrodes 133a, 133b, and 133c, a horizontal electric field is formed with respect to the display panels 1 and 2, and the alignment of the liquid crystal is caused by the electric field.

The color filter display panel 2 is provided with a black matrix, a color filter, and the like. The black matrix defines a pixel area in a matrix shape, and red, green, and blue color filters are repeatedly formed in each pixel area. In this case, the color filter may be formed on the thin film transistor array panel 1 without being formed on the color filter display panel 2.

The liquid crystal molecules of the liquid crystal layer 3 are oriented so that their long axes point in a direction orthogonal to the gate line 121 (arrow direction in FIG. 2), which is an alignment film (not shown) formed on the two display panels 1 and 2. Not rubbing) in the direction of the arrow of FIG. 2.

 The first polarizing film 12b and the second polarizing film 22b may be formed by combining a polarizing film and an optical recycling film. As the photorecycling film, DBEF-D film, Bepol or Nipocs is used. Absorption sides (or transmission axes) of the two polarizing films 12b and 22b are arranged to be perpendicular to each other when viewed from the front. Any one of the absorption axes of the two polarizing films 12b and 22b may be aligned with the long axis direction of the liquid crystal. It is arranged to be side by side.

It is preferable to use TAC (Triacetyl cellulous) as the material of the first to fourth supports.

Thin films such as the lower polarizer 12 and the upper polarizer 22 act as a phase delay to solve the problem of securing a viewing angle or inverting the color tone, and a value representing the degree of phase delay of the thin film is expressed by the following equation. Is shown.

Here, Ro is a phase delay in the horizontal direction of the thin film, d is the thickness of the thin film, Nx is the refractive index in the major axis direction of the molecules constituting the thin film, and Ny is the refractive index in the axial direction of the molecules constituting the thin film.

Rth is a phase delay in the thickness direction of the thin film, and Nz is a refractive index in the vertical direction of the molecules constituting the thin film.

The first to fourth supports 12a, 12c, 22a, and 22c, which are thin films forming the lower polarizing plate 12 and the upper polarizing plate 22, are thin films in which Ro is 0 and only Rth is present. Among them, only Rth of the second support 12c and the third support 22a contributes to the characteristics of the liquid crystal display. In practice, it is difficult to produce the first to fourth supports such that Ro is 0 nm, so it is preferable to prepare the first to fourth supports so that Ro is in the range of 0 nm to 5 nm. It is the same below.

In general, the Rth of the thin film serves to compensate the inclined liquid crystal from the side. However, in the horizontal field liquid crystal display device of the present invention, since the liquid crystal is not inclined, the Rth of the thin film affects the side surface. That is, when the phase retardation of the thin film is larger than the phase retardation of the liquid crystal, yellowing occurs in the black state. Therefore, in the horizontal field liquid crystal display device, minimizing Rth of the second support and the third support suppresses yellowing in the black state.

In order to prove this, we used the TEG polarizer which is used as a thin film in the notebook to see how the yellowing of the side in the black state occurred, and the TAC between the second and third supports and the two display panels of the liquid crystal display was applied. Note how the yellowing of the side occurs in the black state if you place more chapters.

3 shows a CIE coordinate system.

In this case, the SEG polarizer is a general polarizer, and Rth is about 50 to 60 nm, and the TEG polarizer has a smaller Rth. In FIG. 3, region A represents a yellowing phenomenon in the black state when one more TAC is placed on the SEG polarizing plate, and region B represents the yellowing phenomenon in the black state when only SEG is used. And C region shows yellowing phenomenon in the black state when only TEG is used.

As shown in FIG. 3, when one more TAC is placed on the SEG polarizer, the yellowing phenomenon is much more severe, and when the TEG having a small Rth is used, the yellowing phenomenon is much less.

Therefore, when the thin film having a smaller Rth than the TEG polarizer is used, yellowing of the side in the black state is much less.

Therefore, in the horizontal field liquid crystal display device of the present invention, it is preferable that Ro of the second support and the third support is 0 nm, and Rth is 0 nm to 50 nm.

A liquid crystal display according to a second embodiment of the present invention is shown in FIG. Here, the same reference numerals as in the above-described drawings indicate the same members having the same function.

As shown in FIG. 4, the liquid crystal display according to the second exemplary embodiment of the present invention is injected between the thin film transistor array panel 1 and the color filter panel 2 facing each other and the two display panels 1 and 2. A liquid crystal layer 3 made of a sealed liquid crystal material, first and second polarizing films 12b and 22b disposed on outer surfaces of the two display panels 1 and 2, and first and second polarizing films 12b, And first to fourth supports 12a, 12c, 22a, and 22c, which are supports of 22b).

As shown in FIG. 2, the thin film transistor array panel 1 includes a gate line 121, a data line 171, a thin film transistor, a pixel electrode 190, a common electrode line 131, and a common electrode 133a, 133b, and 133c. ) Is formed. The gate line 121 and the data line 171 cross each other to define a pixel area in a matrix shape, and a thin film transistor as a switching element, a pixel electrode 190, and a common electrode 133a, 133b, and 133c are formed in each pixel area. It is.

When a potential difference is applied between the pixel electrode 190 and the common electrodes 133a, 133b, and 133c, a horizontal electric field is formed with respect to the display panels 1 and 2, and the alignment of the liquid crystal is caused by the electric field.

The color filter display panel 2 is provided with a black matrix, a color filter, and the like. The black matrix defines a pixel area in a matrix shape, and red, green, and blue color filters are repeatedly formed in each pixel area. In this case, the color filter may be formed on the thin film transistor array panel 1 without being formed on the color filter display panel 2.

The liquid crystal molecules of the liquid crystal layer 3 are oriented so that their long axes point in a direction orthogonal to the gate line 121 (arrow direction in FIG. 2), which is an alignment film (not shown) formed on the two display panels 1 and 2. Not rubbing) in the direction of the arrow of FIG. 2.

 The first polarizing film 12b and the second polarizing film 22b may be formed by combining a polarizing film and an optical recycling film. As the photorecycling film, DBEF-D film, Bepol or Nipocs is used. The absorption sides (or transmission axes) of the two polarizing films 12b and 22b are arranged to be perpendicular to each other when viewed from the front, and any one of the absorption axes of the two polarizing films 12b and 22b is parallel to the long axis direction of the liquid crystal. It is arranged to be.

It is preferable to use TAC (Triacetyl cellulous) as the material of the first to fourth supports.

In general, the Rth of the thin film serves to compensate the inclined liquid crystal from the side. However, in the horizontal field liquid crystal display, since the liquid crystal is not inclined, the Rth of the thin film affects the side surface. That is, when the phase retardation of the thin film is larger than the phase retardation of the liquid crystal, yellowing occurs in the black state.

Therefore, when the liquid crystal is tilted in the horizontal field liquid crystal display to compensate for the Rth of the TAC used in the current general polarizer, the side yellowing phenomenon in the black state is improved. At present, the pretilt angle of the alignment layer is set to about 1 ° to 2 ° in a horizontal field liquid crystal display, and the side of the black state caused by the Rth of the TAC is left using an alignment layer having a slightly higher pretilt angle. Solve the yellowing problem.

Accordingly, the phase delay in the horizontal direction is referred to as Ro and the phase delay in the thickness direction is referred to as Rth, and the first and second inclination angles θ1 and the second inclination angle θ2 are respectively formed by angles formed by the long axes of the liquid crystals lying down obliquely. When I say

It is preferable that Ro of a 2nd support body and a 3rd support body is 0 nm, Rth is 50 nm-70 nm, and a 1st inclination angle and a 2nd inclination angle are 2 degrees-5 degrees.

Here, since it is difficult to manufacture the 1st-4th support body so that Ro may be 0 nm, it is preferable to manufacture the 1st-4th support body so that Ro exists in 0 nm-5 nm range.

For this purpose, it is preferable to form the pretilt angles of the first alignment layer and the second alignment layer which are formed inside the first display panel and the second display panel, respectively, from 2 ° to 5 °.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

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

2 is a layout view of a thin film transistor substrate for a liquid crystal display according to a first embodiment of the present invention;

3 is a CIE coordinate system showing a yellowing phenomenon in a black state,

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

<Description of the symbols for the main parts of the drawings>

1: first display panel 2: second display panel

12a: first support 12c: second support

12: lower polarizer 22: upper polarizer

22a: third support 22c: fourth support

Claims (8)

First and second substrates, A common electrode formed on an inner surface side of any one of the first substrate and the second substrate, A pixel electrode formed on an inner surface side of the same substrate as the substrate on which the common electrode is formed; A liquid crystal layer injected between the first and second substrates, A lower polarizer disposed under the first substrate and having a first polarizing film disposed between the first and second supports, An upper polarizer disposed on the second substrate and having a second polarizing film disposed between the third and fourth supports; Including, When the phase delay in the thickness direction is referred to as Rth, Rth of the second support and the third support is 0nm to 29nm, And the first to fourth supports are triacetyl cellulous (TAC). First and second substrates, A common electrode formed on an inner surface side of any one of the first substrate and the second substrate, A pixel electrode formed on an inner surface side of the same substrate as the substrate on which the common electrode is formed; A liquid crystal layer injected between the first and second substrates, A lower polarizer disposed under the first substrate and having a first polarizing film disposed between the first and second supports, An upper polarizer disposed on the second substrate and having a second polarizing film disposed between the third and fourth supports; Including, When the phase delay in the thickness direction is referred to as Rth, and the angle formed between the first and second substrates and the long axis of the liquid crystal lying obliquely is called the first inclination angle and the second inclination angle, respectively, Rth of the second support and the third support is 50nm to 70nm, the first inclination angle and the second inclination angle is more than 2 ° and less than 5 °, And the first to fourth supports are triacetyl cellulous (TAC). The method of claim 1 or 2, And the first polarizing plate and the second polarizing plate are optical recycling films. In claim 3, The delay axis of the second support and the third support is a horizontal field type liquid crystal display device parallel to the initial alignment direction of the liquid crystal contained in the liquid crystal layer. In claim 3, The horizontal axis type liquid crystal display device of which the retardation axes of the second and third supports are parallel to the absorption axes of the lower and upper polarizers, respectively. In claim 3, And the pixel electrode and the common electrode are formed in a band shape, and at least part of the pixel electrode and the common electrode are refracted. In claim 6, The pixel electrode and the common electrode are alternately disposed, and when the regions are divided based on a line connecting the refracted portions, portions of the pixel electrode and portions of the common electrode included in the same region are mutually different. Side by side horizontal field type liquid crystal display. In claim 2, A horizontal electric field liquid crystal display device, wherein the pretilt angles of the first alignment layer and the second alignment layer formed inside the first substrate and the second substrate, respectively, exceed 2 ° and 5 °.

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