KR20050097003A - Liquid crystal display device and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device of a transverse electric field system.

An object of the present invention is to provide a liquid crystal display device that can improve the light leakage generated by the protective layer of the polarizing plate without additionally using a compensation film.

The present invention, the first and second substrates facing each other; A liquid crystal layer filled between the first and second substrates; A first protective layer positioned below the first substrate and having a phase difference Rth = 50 to 200 nm in a direction perpendicular to a phase difference Re = 10 to 137 nm in a direction horizontal to the first substrate surface, and a lower portion of the first protective layer; A first polarizing plate comprising a first polarizing layer positioned at; And a second polarizing plate disposed on the second substrate, the second protective layer having the same phase difference (Re, Rth) as the first protective layer, and a second polarizing layer positioned on the second protective layer. A liquid crystal display device is provided.

The present invention has the effect of improving the viewing angle characteristic by improving the light leakage phenomenon in the diagonal direction by designing the phase difference (Re, Rth) value of the protective layer of the upper and lower polarizing plates differently from the prior art without using an additional compensation film. As a result, no additional compensation film is used, thereby reducing manufacturing costs.

Description

Liquid crystal display device and manufacturing method thereof

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device of a transverse electric field system.

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 vary according to the arrangement direction of the changed 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, a liquid crystal material is injected between the two substrates, and a voltage is applied to the two electrodes. By moving the liquid crystal molecules by an electric field, the device expresses an image by the transmittance of light that varies accordingly.

1 is a view schematically showing 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 excellent 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.

Although not shown, polarizers are positioned on the upper and lower portions of the upper and lower substrates 5 and 22, respectively. The polarizing plate transmits light having a polarization component coinciding with the transmission axis. The liquid crystal display is turned on / off due to the arrangement of the transmission axes of the two polarizing plates and the arrangement of the liquid crystals. In general, the transmission axes of the two polarizing plates are vertically arranged to implement an on / off state.

In general, a liquid crystal display device is driven by a vertical electric field method in which an liquid crystal layer is driven by an electric field perpendicular to the substrate surface to adjust an arrangement of liquid crystal molecules to display an image. However, when driving in the vertical electric field method, the viewing angle has a narrow problem, and thus, a transverse electric field method of controlling the arrangement of liquid crystal molecules using a transverse electric field parallel to the substrate surface is used.

2A and 2B are cross-sectional views illustrating an off / on state of a transverse electric field type liquid crystal display device, respectively.

As illustrated, in the transverse electric field type liquid crystal display device, the pixel electrode 40 and the common electrode 45 are formed on the first substrate 10, and the transverse electric field generated by the two electrodes 40 and 45 is provided. As a result, the liquid crystal molecules 52 change.

In the voltage-off state, as shown in FIG. 2A, no lateral electric field is formed between the two electrodes 40 and 45, so that no electric field is applied to the liquid crystal molecules 52. Therefore, the orientation change does not occur in the liquid crystal molecules 52.

On the other hand, in the voltage-on state, as shown in FIG. 2B, an electric field 56 is generated between the pixel electrode 40 and the common electrode 45. A vertical electric field is formed on the pixels and the common electrodes 40 and 45 so that the liquid crystal molecules 52a positioned therein have no change in the orientation direction, but the liquid crystal molecules 52b positioned between the common electrode 45 and the pixel electrode 40. Is arranged in parallel with the substrate by a horizontal (or lateral) electric field generated between the common electrode 45 and the pixel electrode 40.

As described above, the transverse electric field type liquid crystal display device is widely used because the liquid crystal molecules are driven by a transverse electric field generated between the pixel electrode and the common electrode.

3 is a cross-sectional view of a transverse electric field type liquid crystal display device having a compensation film. Here, the compensation film and the polarizing plate are shown separately for convenience of description.

As shown, the transverse electric field type liquid crystal display device includes a first and second substrates 110 and 130 facing each other, a liquid crystal layer 120 filled between the two substrates 110 and 130, and a first and a second liquid crystal display. First and second compensation films 140 and 150 formed on the lower and upper portions of the substrates 110 and 130, and first and second polarizing plates 160 and formed on the lower and upper portions of the first and second compensation films 140 and 150. 170).

The transmission axes of the first and second polarizers 160 and 170 are disposed perpendicular to each other. The first and second polarizers 160 and 170 are respectively disposed on upper and lower polarizing layers 162 and 172 and polarizing layers 162 and 172 to protect the polarizing layers 162 and 172. 171, 173). However, the protective layers 161, 163, 171, and 173 protecting the polarization layers 162 and 172 function as optical films having negative uniaxial properties, that is, negative C-plates. In particular, the protective layers 161 and 173 positioned on the inner surfaces of the first and second polarizing plates 160 and 170 have optical characteristics. Here, all of the protective layers 161, 163, 171, and 173 have a phase difference Re = 4 nm in a direction horizontal to the substrate plane and a phase difference Rth = 40 nm in a direction perpendicular to the substrate plane.

4 is a diagram illustrating a light leakage phenomenon when no compensation film is used, and a protective layer having the same phase difference (Rth) value located on the inner surface of the first and second polarizers (see 160 and 170 of FIG. 3). Due to the optical characteristics of 161, 173 of 3), light leakage mainly occurs in A1 and A2 which are diagonal directions (45 degrees) of the transmission axes of the first and second polarizing plates.

FIG. 5 is a diagram illustrating viewing angle characteristics in a black state of a liquid crystal display when no compensation film is used, and a lot of light leakage occurs in diagonal directions A1 and A2 compared to other directions. Here, the light leakage increases from blue to red.

In order to improve the generation of light leakage according to the optical characteristics of the protective layers 161 and 173 disposed on the inner surfaces of the first and second polarizers 160 and 170, the upper and lower portions of the first and second polarizers 160 and 170 may be formed. The first and second compensation films 140 and 150 are positioned to compensate for the phase differences Re and Rth of the protective layers 161 and 173 located on the inner surfaces of the first and second polarizers 160 and 170.

6 is a view illustrating improvement of a viewing angle of a liquid crystal display when a compensation film is used.

As shown, the light leakage generated by the protective layer of the polarizing plate is improved by compensating for the phase difference Rth using a compensation film. In particular, the light leakage that occurred most at the viewing angle of 70 degrees (based on the axis perpendicular to the substrate) is significantly improved by the compensation film.

By the way, in order to improve the light leakage generated by the protective layer of the polarizing plate, by using an additional compensation film, the manufacturing cost increases, and the manufacturing process increases.

An object of the present invention for solving the above problems is to provide a liquid crystal display device that can improve the light leakage caused by the protective layer of the polarizing plate without additionally using a compensation film.

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 protective layer positioned below the first substrate and having a phase difference Rth = 50 to 200 nm in a direction perpendicular to a phase difference Re = 10 to 137 nm in a direction horizontal to the first substrate surface, and a lower portion of the first protective layer; A first polarizing plate comprising a first polarizing layer positioned at; And a second polarizing plate disposed on the second substrate, the second protective layer having the same phase difference (Re, Rth) as the first protective layer, and a second polarizing layer positioned on the second protective layer. A liquid crystal display device is provided.

Here, the first and second protective layers may have Re = 62 nm and Rth = 130 nm, respectively.

The first polarizing plate may further include a third protective layer positioned below the first polarizing layer, and the second polarizing plate may further include a third protective layer positioned above the second polarizing layer.

The display device may further include an adhesive layer attaching each of the first and second polarizing plates to the first and second substrates.

In addition, the first substrate may have a pixel electrode and a common electrode forming a transverse electric field.

In another aspect, the present invention, the first protective layer having a phase difference Rth = 50 to 200 nm in the direction perpendicular to the phase difference Re = 10 to 137 nm in a direction horizontal to the first substrate surface below the first substrate; Forming a first polarizing plate including a first polarizing layer disposed below the first protective layer; Forming a second polarizing plate on the second substrate, the second protective layer having the same phase difference Re and Rth as the first protective layer, and a second polarizing layer positioned on the second protective layer. Wow; Bonding the first and second substrates together; It provides a method for manufacturing a liquid crystal display device comprising the step of filling a liquid crystal layer between the first and second substrates.

Here, the first and second protective layers may have Re = 62 nm and Rth = 130 nm, respectively.

The method may further include forming a third passivation layer under the first polarization layer, and further comprising forming a fourth passivation layer on the second polarization layer.

The method may further include attaching each of the first and second polarizers to the first and second substrates.

The method may further include forming a pixel electrode and a common electrode forming a transverse electric field on the first substrate.

In the present invention, the phase difference (Re, Rth) values of the protective layers of the upper and lower polarizers are designed differently from the prior art without using an additional compensation film. Therefore, it is possible to improve the viewing angle characteristic by improving the light leakage phenomenon in the diagonal direction.

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

7 is a cross-sectional view illustrating a liquid crystal display device according to an embodiment of the present invention, and FIG. 8 is a plan view showing an array substrate for a liquid crystal display device according to an embodiment of the present invention.

As shown, the transverse electric field type liquid crystal display device according to an exemplary embodiment of the present invention includes a liquid crystal layer filled between the first and second substrates 200 and 300 facing each other and the first and second substrates 200 and 300. 250. The first and second polarizers 400 and 500 are positioned below the first substrate 200 and the upper portion of the second substrate 300, respectively.

As shown in FIG. 5, the first substrate 200 is an array substrate, and the pixel electrode 250 and the common electrode 260 are formed to form a transverse electric field to drive the liquid crystal layer (see 250 of FIG. 4). do.

The first substrate 200 is connected to the thin film transistor T formed at a portion where the gate and the data lines 210 and 220 are perpendicular to each other, and the gate and the data lines 210 and 220 intersect with the thin film transistor T. The common electrode 260 spaced in parallel with the pixel electrode 250 and the pixel electrode 250 is formed. The thin film transistor T includes a source electrode 221 connected to the data line 220, a drain electrode 223 spaced apart from the source electrode 221 by a predetermined distance, and a gate electrode 211. The pixel electrode 250 is connected to the drain electrode 223, and the common electrode 260 is spaced apart in parallel with the pixel electrode 250 to form a transverse electric field.

The second substrate 300 is a color filter substrate, although not shown, a color filter layer is formed. The black matrix is formed corresponding to the metal pattern of the first substrate 200.

First and second polarizers 400 and 500 are positioned below the first substrate 200 and above the second substrate 300, respectively.

The transmission axes of the first and second polarizers 400 and 500 are disposed perpendicular to each other to represent black and white states depending on whether the polarization passes.

The first polarizing plate 400 includes a first polarizing layer 420 and first and second protective layers 410 and 430 positioned at upper and lower portions of the first polarizing layer 420, respectively. The first polarization layer 420 has a transmission axis formed in one direction, and incident light becomes polarized light parallel to the transmission axis.

The first and second protective layers 410 and 430 serve to protect and support the first polarization layer 420 from the outside.

In particular, the first protective layer 410 is positioned above the first polarization layer 420 to perform an optical function. That is, the first protective layer 410 may function as a negative C-plate having optically negative uniaxial properties.

9 is a diagram illustrating a refractive index relationship of a first passivation layer, wherein the first passivation layer 410 has a phase difference Re = (nx-ny) × d> 0 in a direction horizontal to the substrate plane and a direction perpendicular to the substrate plane. Has a value of the phase difference Rth = (nx-nz) x d> 0 (d is the film thickness).

In an embodiment of the present invention, the first protective layer 410 has a phase difference value of, for example, Re = 10 to 137 nm Rth = 50 to 200 nm.

On the other hand, the second protective layer 430 is located below the first polarization layer 420, and does not perform an optical function.

The second polarizing plate 500 is composed of a second polarizing layer 520 and third and fourth protective layers 510 and 530 which are positioned on the upper and lower portions of the second polarizing layer 520, respectively. The transmission axis of the second polarization layer 520 is perpendicular to the transmission axis of the first polarization layer 420.

Like the first and second protective layers 410 and 430, the third and fourth protective layers 510 and 530 serve to protect and support the second polarization layer 520 from the outside.

In particular, the fourth protective layer 530 is positioned under the second polarizing layer 520 to perform an optical function. That is, the fourth protective layer 530, like the first protective layer 410, functions as a negative C-plate having an optically negative uniaxial property.

In the embodiment of the present invention, like the first passivation layer 410, the fourth passivation layer 530 has a retardation value of Re = 10 to 137 nm Rth = 50 to 200 nm.

On the other hand, the third protective layer 510 is positioned on the second polarization layer 520 and does not have an optical function.

The first and second polarization layers may be made of a material such as polyvinyl alcohol (PVA), and the first, second, third and fourth protective layers may be tri-acetate cellulose (TAC), poly carbonate (PC), arton, liquid crystal. It can be made of such materials.

As described above, the present invention is configured by differently designing the phase difference (Re, Rth) value of the first protective layer positioned on the first polarization layer and the fourth protective layer disposed on the lower portion of the second polarization layer. .

FIG. 10 is a diagram illustrating an improvement degree of light leakage according to design values of phase differences Re and Rth of the first and second passivation layers according to an exemplary embodiment of the present invention. Here, A component and C component represent Re and Rth, respectively.

As shown, the first protective layer and the fourth protective layer can most effectively improve light leakage when they have a phase difference value of (Re, Rth) = (62, 130) nm.

Although not shown, the first and second polarizing plates are attached to the first and second substrates by an adhesive layer.

11 is a view illustrating viewing angle characteristics in a black state of a liquid crystal display according to an exemplary embodiment of the present invention. Here, the light leakage increases from blue to red.

Compared with FIG. 5, it can be seen that light leakage in the diagonal directions A1 and A2 in the black state is improved compared to the conventional art. In addition, as compared with the prior art, the contour lines are generally formed to be smooth, so that the light leakage is improved in the entire viewing angle.

As described above, the present invention can improve the viewing angle characteristic by improving the light leakage phenomenon in the diagonal direction by designing a phase difference (Re, Rth) value of the protective layer of the upper and lower polarizing plates differently from the prior art without using an additional compensation film. Will be. In addition, it is possible to reduce the manufacturing cost by using no additional compensation film.

As described above, the present invention design a phase difference (Re, Rth) value of the protective layer of the upper and lower polarizers differently from the prior art without using an additional compensation film to improve the light leakage phenomenon in the diagonal direction to improve the viewing angle characteristics. It can be effective. In addition, since the compensation film is not additionally used, there is an effect of reducing the manufacturing cost.

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

2A and 2B are cross-sectional views showing an off / on state of a transverse electric field type liquid crystal display device, respectively.

3 is a cross-sectional view showing a transverse electric field type liquid crystal display device having a compensation film.

4 is a view showing a light leakage phenomenon when not using a compensation film.

FIG. 5 illustrates viewing angle characteristics in a black state of a liquid crystal display when no compensation film is used. FIG.

6 is a view illustrating improvement of a viewing angle of a liquid crystal display when a compensation film is used.

7 is a cross-sectional view showing a liquid crystal display device according to an embodiment of the present invention.

8 is a plan view showing an array substrate for a liquid crystal display device according to an embodiment of the present invention.

9 illustrates a refractive index relationship of a first protective layer.

10 is a view showing the degree of improvement of the light leakage according to the design value of the phase difference (Re, Rth) of the first, second protective layer in accordance with an embodiment of the present invention.

11 is a view showing viewing angle characteristics in a black state of a liquid crystal display according to an exemplary embodiment of the present invention.

<Brief description of the main parts of the drawing>

200: first substrate 250: liquid crystal layer

300: second substrate 400: first polarizing plate

410: first protective layer 420: first polarizing layer

430: second protective layer 500: second polarizing plate

510: third protective layer 520: second polarizing layer

530: fourth protective layer

Claims (10)

First and second substrates facing each other; A liquid crystal layer filled between the first and second substrates; A first protective layer positioned below the first substrate and having a phase difference Rth = 50 to 200 nm in a direction perpendicular to a phase difference Re = 10 to 137 nm in a direction horizontal to the first substrate surface, and a lower portion of the first protective layer; A first polarizing plate comprising a first polarizing layer positioned at; A second polarizing plate disposed on the second substrate and having a second protective layer having the same retardation (Re, Rth) as the first protective layer, and a second polarizing layer positioned on the second protective layer; Liquid crystal display comprising a. The method of claim 1, And the first and second protective layers have Re = 62 nm and Rth = 130 nm, respectively. The method of claim 1, The first polarizing plate further includes a third protective layer positioned below the first polarizing layer, and the second polarizing plate further includes a fourth protective layer positioned above the second polarizing layer. The method of claim 1, And an adhesive layer for attaching the first and second polarizing plates to the first and second substrates, respectively. The method of claim 1, The first substrate has a pixel electrode and a common electrode forming a transverse electric field. Under the first substrate, the first protective layer having a phase difference Re = 10 to 137 nm in a direction horizontal to the first substrate surface and a phase difference Rth = 50 to 200 nm in a direction perpendicular to the first substrate, and a lower portion of the first protective layer. Forming a first polarizing plate comprising a first polarizing layer positioned thereon; Forming a second polarizing plate on the second substrate, the second protective layer having the same phase difference Re and Rth as the first protective layer, and a second polarizing layer positioned on the second protective layer. Wow; Bonding the first and second substrates together; Filling a liquid crystal layer between the first and second substrates Liquid crystal display device manufacturing method comprising a. The method of claim 6, Wherein the first and second protective layers have Re = 62 nm and Rth = 130 nm, respectively. The method of claim 6, And forming a third passivation layer under the first polarization layer, and further comprising forming a fourth passivation layer on the second polarization layer. The method of claim 6, And attaching each of the first and second polarizers to the first and second substrates. The method of claim 6, And forming a common electrode and a pixel electrode for forming a transverse electric field on the first substrate.