KR101113782B1 - Photo compensation film for liquid crystal display device and liquid crystal display device including the same - Google Patents

Abstract

An object of the present invention, by using the A-plate and C-plate to improve the light leakage by increasing the manufacturing cost, increase the number of processes, and includes a polarizing plate for a liquid crystal display device that can improve the asymmetry of the light leakage It is to provide a liquid crystal display device.

The present invention, the first and second substrates facing each other; A liquid crystal layer filled between the first and second substrates; A first polarizing plate formed under the first substrate; A second polarizer formed on the second substrate; An A-plate having an abnormal refractive index parallel to the second substrate surface and a normal refractive index perpendicular to the abnormal refractive index; A liquid crystal display comprising a C-plate having an abnormal refractive index inclined at a b angle in a direction perpendicular to the second substrate surface and a normal refractive index perpendicular to the abnormal refractive index.

The present invention has the effect of improving the asymmetry of light leakage by using an A-plate and a tilted C-plate, and effectively improves light leakage by using only A-plates having a range of phase differences, The manufacturing cost and the number of processes can be reduced.

Description

Photo compensation film for liquid crystal display device and liquid crystal display device including the same}             

1 is a view showing a general liquid crystal display device.

2A and 2B are cross-sectional views showing the arrangement of liquid crystal molecules in a voltage off / on state in an IPS type liquid crystal display device, respectively.

3 is a view showing a transmission axis of a polarizing plate used in an IPS type liquid crystal display device.

Fig. 4 is a diagram showing a black state of an IPS type liquid crystal display device using polarizing plates orthogonal to each other.

FIG. 5 is a diagram showing a black state of an IPS type liquid crystal display using an A-plate and a C-plate. FIG.

Fig. 6 is a diagram showing the pretilt angle of the liquid crystal in the initial state of the IPS type liquid crystal display device.

7 is a cross-sectional view showing an IPS type liquid crystal display device including an inclined C-plate according to the first embodiment of the present invention.

8 is a plan view showing a substrate for an IPS type liquid crystal display device according to a first embodiment of the present invention;

9 illustrates the refractive index relationship of the A-plate according to the first embodiment of the present invention.

10 illustrates the refractive index relationship of a conventional C-plate.

FIG. 11 illustrates the refractive index relationship of an inclined C-plate according to the first embodiment of the present invention. FIG.

Fig. 12 is a diagram showing a black state of an IPS type liquid crystal display device using an inclined C-plate according to the first embodiment of the present invention.

Fig. 13 is a sectional view showing an IPS type liquid crystal display device including an A-plate according to a second embodiment of the present invention.

Fig. 14 is a diagram showing the phase difference and light leakage relationship between the A-plate and the C-plate in the diagonal direction with the polar angle of 70 degrees and the azimuth angle of 45 degrees;

Fig. 15 is a diagram showing a black state of an IPS type liquid crystal display device using an A-plate according to the second embodiment of the present invention.

16 and 17 illustrate an adhesion relationship between a polarizer and a substrate of an A-plate according to a second embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

ne`: anomaly index of inclined C-plate

no`: normal refractive index of inclined C-plate                 

b: tilt angle of inclined C-plate

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a photo compensation film used in a liquid crystal display device.

In general, a liquid crystal display device displays an image by using optical anisotropy and birefringence characteristics of liquid crystal molecules. When an electric field is applied, the arrangement of liquid crystals is changed and the characteristics of light transmission are also changed according to the arrangement direction of the liquid crystals. In the liquid crystal display, two substrates on which the field generating electrodes are formed are disposed so that the surfaces on which the two electrodes are formed face each other, the liquid crystal is injected between the two substrates, and an electric field generated by applying a voltage to the two electrodes. By moving the liquid crystal molecules by means of the device to express the image by the transmittance of light that varies accordingly.

1 is a schematic view of a general liquid crystal display device.

As shown in the drawing, a general color liquid crystal display device 11 has a common color deposited on the black matrix 6 and the color filter layer 8 formed between the color filter layer 8 and the color filter layer 8 of red, green, and blue. The upper substrate 5 on which the electrode 18 is formed, and the pixel region P are defined, and the pixel electrode P and the switching element T are formed in the pixel region P, and the peripheral region of the pixel region P is formed. The lower substrate 22 includes an array wiring, and the liquid crystal 14 is filled between the upper substrate 5 and the lower substrate 22.

The lower substrate 22 is also called an array substrate, and the thin film transistor T, which is a switching element, is positioned in a matrix type, and the gate wiring 13 passing through the plurality of thin film transistors TFT is crossed. And data wiring 15 is formed. In this case, the pixel region P is a region defined by the intersection of the gate wiring 13 and the data wiring 15. A transparent pixel electrode 17 is formed on the pixel region P as described above.

The pixel electrode 17 uses a transparent conductive metal having relatively high light transmittance, such as indium-tin-oxide (ITO). A storage capacitor C _ST connected in parallel with the pixel electrode 17 is formed on the gate wiring 13, and a portion of the gate wiring 13 is used as the first electrode of the storage capacitor C _ST . As the second electrode, an island-shaped source / drain metal layer 30 formed of the same material as the source and drain electrodes is used.

In this case, the source / drain metal layer 30 is configured to be in contact with the pixel electrode 17 to receive a signal of the pixel electrode.

The liquid crystal display device is driven by applying an electric field to the liquid crystal using the voltage difference between the common electrode and the pixel electrode to display an image, wherein the common electrode and the pixel electrode are formed on the same substrate to form a horizontal electric field in the liquid crystal layer. In-plane switching mode (hereinafter referred to as IPS type) liquid crystal displays are widely used because of their excellent viewing angle characteristics.

2A and 2B are cross-sectional views showing the arrangement of liquid crystal molecules in a voltage off / on state in an IPS type liquid crystal display device, respectively.

In the voltage-off state, as shown in FIG. 1A, since no electric field is formed in the liquid crystal molecules 50, the liquid crystal molecules 50 are maintained in the initial arrangement state.

In the voltage-on state, as shown in FIG. 1B, since a vertical electric field is formed on the common electrode 38 and the pixel electrode 40, the liquid crystal molecules 50a positioned therein have no change in the arrangement direction, but the common electrode ( The liquid crystal molecules 50b positioned between the 38 and the pixel electrode 40 are arranged in parallel with the substrates 10 and 60 by a horizontal electric field generated between the common electrode 38 and the pixel electrode 40. Will have

In the IPS type liquid crystal display device driven as described above, first and second polarizers 70 and 80 are positioned below the first substrate 10 and the second substrate 60, respectively.

3 is a diagram showing a transmission axis of a polarizing plate used in an IPS type liquid crystal display device.

As shown, the transmission axes of the first and second polarizing plates (see 70 and 80 of FIG. 2A) are perpendicular to each other. The IPS type liquid crystal display implements black in a voltage off state when operating in a normally black mode. That is, light of a component coinciding with the transmission axis of the first polarizing plate among the light incident on the first polarizing plate passes, but since the transmission axis of the second polarizing plate is perpendicular to the transmission axis of the first polarizing plate, it passes through the first polarizing plate. The light does not pass through the second polarizing plate to realize a black state.

By the way, the transmission axes of the first and second polarizing plates are orthogonal to the front of the IPS type liquid crystal display device in the H direction perpendicular to the polarizing plate surface, but the first and second in the A direction inclined by an α degree in the H direction. The transmission axis of the polarizing plate does not appear to be orthogonal. Therefore, in the A direction, the first and second transmission axes do not appear orthogonal to each other, and light leakage occurs. In particular, such light leakage occurs severely in the direction rotated by an azimuthal angle in the transmission axis of the first polarizing plate, that is, in the direction between the transmission axes of the first and second polarizing plates which are orthogonal to each other.

FIG. 4 is a diagram showing a black state of an IPS type liquid crystal display device using polarizing plates orthogonal to each other. Here, light leakage increases from a dark color to a light color.

As shown, light leakage occurs in a diagonal direction with a polar angle of about 70 degrees and an azimuthal angle of 45 degrees. In particular, the asymmetry of the light leakage occurs in the right portion is more severe than the left portion. In order to improve the light leakage, the A-plate and C-plate, which are optical compensation films, are stacked and used.

FIG. 5 is a diagram illustrating a black state of an IPS type liquid crystal display using an A-plate and a C-plate.

As shown, the light leakage in the diagonal direction is improved compared to FIG. 4 by using the A-plate and the C-plate.

However, even when the A-plate and the C-plate are used, the asymmetry of the light leakage, in which the light leakage is more severe than the left portion, is not improved. Asymmetry of light leakage causes reagent angle asymmetry, resulting in a narrowing of the overall viewing angle.                         

This asymmetry of light leakage is because, as shown in FIG. 6, the liquid crystal 50 initially has a pretilt angle γ of about 1 to 2 degrees with the surfaces of the substrates 10 and 60.

In addition, by using two polarizing films having different optical properties such as A-plate and C-plate to improve light leakage, manufacturing cost increases and the number of processes increases.

An object of the present invention to solve the problems described above is to use the A-plate and C-plate to improve the light leakage, which increases the manufacturing cost, increases the number of processes, can improve the asymmetry of the light leakage A polarizing plate for a liquid crystal display device and a liquid crystal display device including the same are provided.

In order to achieve the object as described above, the present invention, the first and second substrates facing each other; A liquid crystal layer filled between the first and second substrates; A first polarizing plate formed under the first substrate; A second polarizer formed on the second substrate; An A-plate having an abnormal refractive index parallel to the surface of the second substrate and a normal refractive index perpendicular to the abnormal refractive index; Has an abnormal refractive index inclined at an angle b in a direction perpendicular to the second substrate surface and a normal refractive index perpendicular to the abnormal refractive index, wherein b includes a C-plate having a range of 0 ° <b ≦ 5 ° The first substrate provides a liquid crystal display having a pixel electrode and a common electrode forming a transverse electric field in the liquid crystal layer.
In this case, the A-plate and the C-plate is located between the first substrate and the first polarizing plate, the selected between the second substrate and the second polarizing plate, the A-plate is the top and bottom of the C-plate Located in the selected one of the.
The transmission axes of the first and second polarizing plates are perpendicular to each other.
In addition, the present invention and the first and second substrates facing each other; A liquid crystal layer filled between the first and second substrates; A first polarizing plate formed under the first substrate; A second polarizer formed on the second substrate; Wherein the phase difference R includes an A-plate having an ideal refractive index parallel to the surface of the second substrate and a normal refractive index perpendicular to the abnormal refractive index, and having a range of 0 <R ≤ 100 nm, wherein the first substrate is the liquid crystal A liquid crystal display device having a pixel electrode and a common electrode forming a transverse electric field in a layer is provided.
Here, the A-plate is positioned between the first substrate and the first polarizing plate, and between the second substrate and the second polarizing plate, and the A-plate is applied to the selected one of the first and second substrates. .
The transmission axes of the first and second polarizing plates are perpendicular to each other.
In addition, the present invention is an optical compensation film for a liquid crystal display device to compensate for the phase change of the light passing through the liquid crystal, an A-plate having an abnormal refractive index parallel to the plane of the optical compensation film and a normal refractive index perpendicular to the abnormal refractive index Wow; Has an abnormal refractive index inclined at an angle b in a direction perpendicular to the plane of the optical compensation film and a normal refractive index perpendicular to the abnormal refractive index, wherein b includes a C-plate having a range of 0 ° <b ≦ 5 ° The liquid crystal provides an optical compensation film for a liquid crystal display device that is driven by a transverse electric field, and is an optical compensation film for a liquid crystal display device that compensates for a phase change of light passing through the liquid crystal, the ideal being parallel to the surface of the optical compensation film. It has a refractive index and a normal refractive index perpendicular to the abnormal refractive index, the phase difference R comprises an A-plate having a range of 0 <R ≤ 100 nm, wherein the liquid crystal is provided with an optical compensation film for a liquid crystal display device driven by a transverse electric field do.

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Hereinafter, embodiments of the present invention will be described with reference to the drawings.

&Lt; Embodiment 1 >

FIG. 7 is a cross-sectional view of an IPS type liquid crystal display including an inclined C-plate according to a first embodiment of the present invention. 8 is a plan view showing a substrate for an IPS type liquid crystal display device according to a first embodiment of the present invention.

As shown in FIG. 7, the liquid crystal display according to the first embodiment of the present invention is filled between the first and second substrates 110 and 160 facing each other and the first and second substrates 110 and 160. The liquid crystal layer 150, the first and second polarizers 170 and 180 positioned on the lower portion of the first substrate 110 and the second substrate 160, respectively, the second substrate 160 and the second polarizer 180. A-plate 120 and C-plate 130 positioned between the ()).

As shown in FIG. 8, the first substrate 110 is an array substrate, and gate wirings and data wirings GL and DL are formed to define the pixels P at right angles to each other. The thin film transistor T connected to the GL and DL is formed at a portion where the gate line and the data line GL and DL cross each other. The thin film transistor T is connected to the pixel electrode PE, and the common electrode CE is connected to the common line CL. When the thin film transistor T is turned on, the pixel electrode PE and the common electrode CE formed in parallel with each other form a transverse electric field.

As illustrated in FIG. 7, a first alignment layer 115 is formed on the first substrate 110 to align the liquid crystals 150.

The second substrate 160 is a color filter substrate, and a second alignment layer 165 is formed below the second substrate 160 to align the liquid crystal 150. Meanwhile, a color filter layer (not shown) is formed between the second substrate 160 and the second alignment layer 165.

The liquid crystal layer 150 is filled between the first and second substrates 110 and 160 to be aligned in the alignment direction of the first and second alignment layers 115 and 165, and the pixel electrode (see PE in FIG. 8) and the common electrode. It is driven by the transverse electric field generated between (see CE of FIG. 8). The liquid crystal 150 has a pretilt angle inclined by about 1 to 2 degrees due to the characteristics of the alignment layer.

The transmission axes of the first and second polarizing plates 170 and 180 are perpendicular to each other. When operating in the normally black mode, the light passing through the first polarizing plate 170 has a component that matches the transmission axis of the first polarizing plate 170, and such light causes the second polarizing plate 180. It will not pass and will implement a black state.

The A-plate 120 and the inclined C-plate 130 are compensation films, which are located between the second substrate 160 and the second polarizing film 180 and change in phase of light passing through the liquid crystal layer 150. To compensate.

The A-plate 120 is positioned below the inclined C-plate 130, on the contrary, the A-plate 120 may be positioned above the inclined C-plate 130.

In addition, the A-plate 120 and the C-plate 130 may be positioned between the first substrate 110 and the first polarizer 170.

9 is a diagram showing the refractive index relationship of the A-plate according to the first embodiment of the present invention. Where x and y are axes parallel to the A-plate plane and z is an axis perpendicular to the A-plate plane.

The refractive index of the A-plate (see 120 in FIG. 7) has a relationship of nx> ny = nz. That is, the A-plate is a uniaxial optical compensation film having a relationship of extraordinary refractive index ne = nx and normal refractive index no = ny = nz.

FIG. 10 is a diagram illustrating a refractive index relationship of a conventional C-plate, and FIG. 11 is a diagram illustrating a refractive index relationship of an inclined C-plate according to a first embodiment of the present invention. Where x and y are axes parallel to the C-plate plane and z is an axis perpendicular to the C-plate plane.

As shown in FIG. 10, the refractive index of the conventional C-plate has a relationship of nz> nx = ny. That is, the C-plate is a uniaxial optical compensation film having a relationship of extraordinary refractive index ne = nz and normal refractive index no = nx = ny.

On the other hand, as shown in FIG. 11, the refractive index of the inclined C-plate (see 130 in FIG. 7) is inclined by b degrees on the plate surface of the abnormal refractive index ne` and the normal refractive index no`. The normal refractive index no` of the inclined C-plate is the same as the normal refractive index no of the conventional C-plate. The abnormal refractive index ne` of the inclined C-plate is different from the conventional refractive index ne` of the conventional C-plate, and the abnormal refractive index ne` of the inclined C-plate is

), w = (ne/no)²-1ne` = ne / (

), w = (ne / no) ² -1

It has a value according to the relation of.

The inclined C-plate is inclined at an angle b of abnormal refractive index ne` and normal refractive index no` by the conventional refractive index, thereby compensating for the phase change caused by the liquid crystal having a pretilt angle of about 1-2 degrees with the substrate surface. Will be. Therefore, it is possible to effectively improve the asymmetry of the light leakage by the liquid crystal having a pretilt angle.

The inclined angle b of the inclined C-plate has a range of approximately 0 ° <b ≦ 10 ° in consideration of the phase difference of the liquid crystal and the phase difference of the A-plate.

FIG. 12 is a diagram showing a black state of an IPS type liquid crystal display using an inclined C-plate according to the first embodiment of the present invention.

As shown, the light leakage of the right part and the left part is symmetrical compared to FIGS. 4 and 5. Therefore, the conventional light leakage asymmetry is improved, thereby widening the viewing angle.

In the first embodiment of the present invention, by using the inclined C-plate, it is possible to effectively improve the asymmetry of light leakage due to the pretilt angle of the liquid crystal.

&Lt; Embodiment 2 >

The second embodiment of the present invention uses only A-plates as light compensation films.

In the second embodiment of the present invention, description of the same or corresponding matters as the first embodiment of the present invention will be omitted.

FIG. 13 is a cross-sectional view of an IPS type liquid crystal display device including an A-plate according to a second embodiment of the present invention.

As shown in FIG. 13, the liquid crystal display according to the second embodiment of the present invention is filled between the first and second substrates 210 and 260 facing each other and the first and second substrates 210 and 260. The liquid crystal layer 250, the first and second polarizers 270 and 280 positioned below the first substrate 210 and the second substrate 260, respectively, and the second substrate 260 and the second polarizer 280. It is configured to include an A-plate 220 positioned between). Meanwhile, the first alignment layer 215 is positioned on the first substrate 210, and the second alignment layer 265 is positioned below the second substrate 260.

As shown in FIG. 9, in the A-plate, the abnormal refractive index ne has a larger value than the normal refractive index no, and the A-plate having the thickness d has a positive retardation, R = (ne−). no) * d,                     

In the second embodiment of the present invention, the phase difference R of the A-plate is approximately in the range of 0 <R ≦ 100 nm.

FIG. 14 is a diagram showing the phase difference and the light leakage relationship between the A-plate and the C-plate in a diagonal direction with a polar angle of 70 degrees and an azimuthal angle of 45 degrees.

As shown, the light leakage is lowest when the phase difference of the C-plate is approximately 45 nm and the phase difference of the A-plate is approximately 90 nm.

On the other hand, when the C-plate has a phase difference of 0 nm, i.e., only the A-plate having a phase difference in the range of approximately 0 < R &lt; 100 nm without using the C-plate, Compared to the case where no A-plate and C-plate are used at all, light leakage is improved.

FIG. 15 illustrates a black state of an IPS type liquid crystal display using an A-plate according to a second embodiment of the present invention. Here, the A-plate has a phase difference of approximately 45 nm.

As shown, it can be seen that the light leakage is reduced compared to FIG. 4 in which the A-plate and the C-plate are not used at all.

Therefore, only A-plates having a phase difference in the range of approximately 0 < R &lt; 100 nm can be used to improve light leakage that occurs when no A-plate and no C-plate are used at all.

A-plate having the above optical properties may be manufactured in the form of a film, or directly applied to the substrate surface.                     

16 and 17 are diagrams illustrating an attachment relationship between a polarizer and a substrate of an A-plate according to a second embodiment of the present invention.

As shown in FIG. 16, when the A-plate 220 is manufactured in the form of a film, the second substrate 260 and the second substrate are formed by the first and second adhesive layers 291 and 292 respectively positioned at the lower and upper portions thereof. 2 is attached to the polarizing plate 280. Here, the A-plate 220 is manufactured integrally with the second polarizing plate 280 and then attached to the second substrate 260.

Meanwhile, as shown in FIG. 17, the A-plate 220 is coated on the second substrate 260 and formed by the third adhesive layer 293 disposed on the A-plate 220. 2 is attached to the polarizing plate 280.

In the second embodiment of the present invention, by using only A-plates having a phase difference in the range of approximately 0 < R ≤ 100 nm, light leakage generated when no A-plate and C-plate are used at all can be improved. Therefore, by using two polarizing films having different optical properties such as A-plate and C-plate to improve light leakage, it is possible to improve the manufacturing cost and increase the number of processes. In particular, when the A-plate is coated and formed on the substrate surface, the A-plate can be manufactured in the liquid crystal cell manufacturing process, thereby eliminating the process of attaching the A-plate to the substrate and reducing the manufacturing cost.

Embodiment of the present invention as described above is an example of the present invention, various modifications thereof are possible. It is apparent to those skilled in the art that such modifications fall within the scope of the present invention, within the scope included in the spirit of the present invention. The scope of the present invention will be embodied through the claims.

The present invention has the effect of improving the asymmetry of light leakage by using an A-plate and a tilted C-plate.

In addition, by using only the A-plate having a range of phase difference, there is an effect to effectively improve the light leakage, and to reduce the manufacturing cost and the number of processes.

Claims (11)

First and second substrates facing each other; A liquid crystal layer filled between the first and second substrates; A first polarizing plate formed under the first substrate; A second polarizer formed on the second substrate; An A-plate having an abnormal refractive index parallel to the surface of the second substrate and a normal refractive index perpendicular to the abnormal refractive index; C-plate having an abnormal refractive index inclined at an angle b in a direction perpendicular to the second substrate surface and a normal refractive index perpendicular to the abnormal refractive index, wherein b has a range of 0 ° <b ≦ 5 ° Wherein the first substrate has a pixel electrode and a common electrode forming a transverse electric field in the liquid crystal layer. delete The method of claim 1, And the A-plate and the C-plate are positioned at a selected one between the first substrate and the first polarizing plate and between the second substrate and the second polarizing plate. The method of claim 3, wherein The A-plate is a liquid crystal display device positioned on the selected one of the top and bottom of the C-plate. Claim 5 was abandoned upon payment of a set-up fee. The method of claim 1, The transmission axes of the first and second polarizers are perpendicular to each other. First and second substrates facing each other; A liquid crystal layer filled between the first and second substrates; A first polarizing plate formed under the first substrate; A second polarizer formed on the second substrate; An A-plate having an abnormal refractive index parallel to the surface of the second substrate and a normal refractive index perpendicular to the abnormal refractive index, and the phase difference R is in a range of 0 <R ≤ 100 nm Wherein the first substrate has a pixel electrode and a common electrode forming a transverse electric field in the liquid crystal layer. The method of claim 6, And the A-plate is positioned between one of the first substrate and the first polarizing plate, and one of the second substrate and the second polarizing plate. The method of claim 6, And the A-plate is coated on one selected from the first and second substrates. Claim 9 has been abandoned due to the setting registration fee. The method of claim 6, The transmission axes of the first and second polarizers are perpendicular to each other. An optical compensation film for a liquid crystal display device that compensates for a phase change of light passing through a liquid crystal. An A-plate having an abnormal refractive index parallel to the plane of the optical compensation film and a normal refractive index perpendicular to the abnormal refractive index; Has an abnormal refractive index inclined at an angle b in a direction perpendicular to the plane of the optical compensation film and a normal refractive index perpendicular to the abnormal refractive index, wherein b is a C-plate having a range of 0 ° <b ≦ 5 ° It includes, The liquid crystal is an optical compensation film for a liquid crystal display device driven by a transverse electric field. An optical compensation film for a liquid crystal display device that compensates for a phase change of light passing through a liquid crystal. A-plate having an ideal refractive index parallel to the surface of the optical compensation film and a normal refractive index perpendicular to the abnormal refractive index, and the phase difference R is in a range of 0 <R ≤ 100 nm. It includes, The liquid crystal is an optical compensation film for a liquid crystal display device driven by a transverse electric field.

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