KR20110059983A - Liquid crystal display evice - Google Patents

Abstract

PURPOSE: A liquid crystal display device is provided to implement narrow viewing angle and to insert a compensating film of a polarizer in the upper side of a liquid crystal panel. CONSTITUTION: Adhesion layers(111,112) are composed in the upper and lower part of a liquid crystal cell. First and second compensating films are attached to the upper side of the liquid crystal cell and compensate the liquid crystal direction of the liquid crystal cell. The first and second compensating films project the light on the upper side of the liquid crystal cell.

Description

Liquid Crystal Display Device

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having a narrow viewing angle.

Generally, the driving principle of a liquid crystal display device utilizes the optical anisotropy and polarization properties of a liquid crystal. Since the liquid crystal is thin and long in structure, the liquid crystal has directivity in the arrangement of the molecules, and the direction of the molecular arrangement can be controlled by artificially applying an electric field to the liquid crystal.

Therefore, when the molecular alignment direction of the liquid crystal is arbitrarily adjusted, the molecular arrangement of the liquid crystal is changed, and light is refracted in the molecular alignment direction of the liquid crystal by optical anisotropy, so that image information can be expressed.

In addition, the liquid crystal display includes a color filter substrate having a common electrode, an array substrate having pixel electrodes, and a liquid crystal filled between the two substrates. By driving the liquid crystal, it has excellent characteristics such as transmittance and aperture ratio, but has a disadvantage of poor viewing angle characteristics.

On the other hand, the liquid crystal cell of the liquid crystal display device is TN (Twisted Nematic) and IPS (In-Plane Switching), which can be applied to any of the transmissive and reflective types by displaying ON and OFF due to the difference in the alignment state of the liquid crystal components. Display modes such as OCB (0ptically Compensatory Bend), VA (Vertically Aligned), and ECB (Electrically Controduced Birefringence) have been proposed.

However, recently, when working with security-critical documents, the screen can be recognized at the front viewing angle, and the wide viewing angle mode and the narrow viewing angle mode can be selectively driven so that the screen is not transmitted to the viewers positioned at the left and right viewing angles, especially the side seats. There is a way to do it.

In particular, products such as ATMs, mobile applications, and notebooks require narrow viewing angles on the left and right or top and bottom portions to protect privacy in public places, and the car navigation system displays screens on the front glass. The upper and lower narrow viewing angles are required to prevent reflection.

1 is a schematic configuration diagram for implementing a narrow viewing angle in a liquid crystal display according to the prior art.

As shown in FIG. 1, the liquid crystal display according to the related art includes a fluorescent lamp 1, a light guide plate 2, a reflecting plate 3, a diffusion sheet 4, a first and a second prism sheet 5, 6. And a LCF (Light Control Film) 7, a liquid crystal panel 8, and upper and lower polarizing plates 9 and 10.

First, when the voltage is applied to the fluorescent lamp 1, residual electrons existing in the fluorescent lamp 1 move to the anode, and the moving residual electrons collide with argon (Ar) to excite argon to proliferate cations, The multiplying cations collide with the cathode to release secondary electrons.

When the discharged secondary electrons flow through the tube to initiate discharge, the flow of electrons by the discharge collides with, and ionizes, mercury vapor to emit ultraviolet rays and visible light, and the emitted ultraviolet rays excite the phosphor coated on the inner wall of the lamp to display visible light. It emits light and emits light.

Subsequently, the light guide plate 2 is a wave guide for injecting the light emitted from the fluorescent lamp 1 into the surface to emit a surface light source to the top, and has excellent light transmittance. PMMA (Poly Methyl Meth Acrylate) ) Is used.

Factors related to light incidence efficiency of the light guide plate 2 include light guide plate thickness versus lamp diameter, the distance between the light guide plate and the lamp, the shape of the lamp reflector, and the like. In general, the fluorescent lamp 1 is thicker than the center of the light guide plate 2. By inclining in the direction, light incidence efficiency is increased.

The light guide plate 2 of the backlight unit for an LCD includes a printing light guide plate, a V-cut light guide plate, and a scattering light guide plate.

Subsequently, the reflector 3 is installed at the rear end of the light guide plate 2 so that the light emitted from the fluorescent lamp 1 is incident into the light guide plate 2.

The diffusion sheet 4 is installed on the light guide plate 2 to obtain uniform luminance according to a viewing angle. The diffusion sheet 4 may be formed of PET or PC (poly carbonate) resin. In the upper portion of the diffusion sheet 4 has a particle coating layer to serve as a diffusion.

Subsequently, the first and second prism sheets 5 and 6 are used to increase the front luminance of the light that is transmitted through the diffusion sheet 4 and reflected thereon. Only light of a certain angle is transmitted, and light incident at the remaining angles causes total internal reflection to return back to the bottom of the first prism sheet 5. As described above, the returning light is reflected by the reflecting plate 4 attached to the lower part of the light guide plate 2.

The liquid crystal panel 8 receives light incident through the lower first and second prism sheets 5 and 6 to display an image, and the upper and lower polarizers 9 and 10 are formed of the liquid crystal panel 8. It is attached to the upper and lower portions and serves to pass light in a specific direction, respectively.

The LCF 7 is configured between the backlight unit and the liquid crystal panel 8 to adjust the left and right or the upper and lower portions at a narrow viewing angle when an image is displayed through the liquid crystal panel 8.

Table 1 below shows the transmission characteristics of the LCF.

division Spec. Measure 0 ° transmittance 70% 60% 15 ° transmittance 35% 30% Cut off angle  30 °  35 °

As shown in Table 1, it can be seen that the result of measuring the transmittance is lower than the spec, and the cut off angle is also wider than the spec.

However, the liquid crystal display according to the prior art, which uses LCF to implement the narrow viewing angle as described above, has the following problems.

First, the front luminance decreases by about 30% due to the LCF formed between the backlight unit and the liquid crystal panel.

Second, a wave pattern appears on the screen displayed on the liquid crystal panel by the LCF.

Third, the overall manufacturing cost rises by applying LCF.

An object of the present invention is to provide a liquid crystal display device which implements a narrow viewing angle by inserting a compensation film between a liquid crystal panel and a polarizing plate formed on upper and lower portions of the liquid crystal panel.

The liquid crystal display device according to the present invention for achieving the above object is a liquid crystal cell of the liquid crystal cell is attached to the upper and lower surfaces of the liquid crystal cell by a liquid crystal cell, an adhesive layer formed on the upper and lower parts of the liquid crystal cell, and the adhesive layer The first and second compensation films for compensating the direction to realize the narrow viewing angle and the first and second compensation films attached to the upper and lower surfaces of the liquid crystal cell are transmitted through the polarized light in a predetermined direction. It is characterized by comprising a first polarizing plate and a second polarizing plate.

The liquid crystal display device according to the present invention has the following effects.

That is, by inserting a compensation film between the liquid crystal panel and the polarizing plates formed on the upper and lower parts of the liquid crystal panel to implement a narrow viewing angle, it is possible to reduce the front luminance and prevent the occurrence of wave patterns and to reduce the manufacturing cost.

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

2 is a view schematically showing a liquid crystal display according to the present invention.

In the liquid crystal display according to the present invention, as shown in FIG. 2, the liquid crystal cell 110 in the VA or OCB mode and the first and second adhesive layers (PSA) formed at upper and lower portions of the liquid crystal cell 110 are provided. Sensitive Adhesives (111, 112) and the first and second adhesive layers (111, 112) are attached to the upper and lower surfaces of the liquid crystal cell (110) to compensate for the liquid crystal direction of the liquid crystal cell (110) to achieve a narrow viewing angle The first and second compensation films 120 and 130 and the first and second compensation films 120 and 130 attached to the upper and lower surfaces of the liquid crystal cell 110 transmit light polarized in a predetermined direction among incident light. It is comprised including the 1st, 2nd polarizing plates 140 and 150. FIG.

Here, the first and second compensation films 120 and 130 are biaxial films, and the narrow viewing angle is realized by compensating the liquid crystal direction at −90 ° or 90 ° according to the rubbing direction of the liquid crystal cell 110. Do it.

The first and second polarizers 140 and 150 may be polarized films 141 and 151 such as polyvinyl alcohol (PVA) films that transmit light polarized in a predetermined direction among incident light, and at least one surface of the polarizers 141 and 151. And a protective / supporting layer 142, 152, such as a TriAcetyl Cellulose (TAC) layer, which protects and supports the polarizing plates 141 and 151.

Meanwhile, in the VA mode liquid crystal display device, the rubbing directions of the first and second compensation films 120 and 130 and the liquid crystal cell 110 are the same, and in the OCB mode liquid crystal display device, the first and second compensation films 120 and 130 are used. ) And the rubbing direction of the liquid crystal cell 110 are orthogonal and the liquid crystal cell 110 is the same as the up and down rubbing direction.

3 is a block diagram illustrating a liquid crystal display in more detail to implement a narrow viewing angle in the liquid crystal display of FIG. 2.

As shown in FIG. 2, the liquid crystal display according to the present invention includes a liquid crystal panel 100 for displaying an image and a backlight unit 200 for irradiating light formed on the rear surface of the liquid crystal panel 100. It is.

Herein, the liquid crystal panel 100 includes a first substrate 161 and a second substrate 162 disposed at regular intervals, and a liquid crystal layer formed between the first substrate 161 and the second substrate 162. 163, a first polarizing plate 140 formed under the first substrate 161, and an axis in a direction perpendicular to the first polarizing plate 140 on the second substrate 162. A first polarizer formed between the second polarizer 150, the first substrate 161 and the second substrate 162, and the first polarizer 140 and the second polarizer 150 to compensate for the narrow viewing angle. 2 is composed of a compensation film (120,130).

The first and second polarizers 140 and 150 are responsible for extending the viewing angle of the image displayed by the liquid crystal cell matrix.

Here, the first substrate 161 is a TFT array substrate, a plurality of gate lines arranged in one direction at a predetermined interval, a plurality of data lines arranged at regular intervals in a direction perpendicular to the respective gate lines, A plurality of pixel electrodes formed in a matrix form in each pixel region defined by crossing each of the gate lines and the data lines, and a plurality of pixels which are switched by signals of the gate lines to transfer signals of the data lines to the pixel electrodes Thin film transistors are formed.

The second substrate 162 is a color filter substrate, and includes a black matrix layer for blocking light in portions other than the pixel region, an R, G, and B color filter layers for expressing color colors, and an image. The common electrode is formed.

In the IPS mode, the common electrode is formed on the first substrate 161.

The backlight unit 200 includes at least one light source 201 that emits light, and is configured on one side of the light source 201 to receive light emitted from the light source 201 through an incident surface to receive light. A light guide plate 202 emitted from the light guide plate, a reflector plate 203 disposed on a rear surface of the light guide plate 202, and reflecting light incident to itself through the rear surface of the light guide plate 202 toward the light guide plate 202; A diffusion sheet 204 disposed on the light guide plate 202 to diffuse light through the light guide plate 202 and first and second prism sheets 205 and 206 for condensing light through the diffusion sheet 204. It is configured to include.

The light source 201 includes one of red, green, and blue light emitting diodes, a plurality of white light emitting diodes, an EEFL, and a CCFL fluorescent lamp.

The light guide plate 202 may use a prism light guide plate having an inclined back surface and a prism-shaped exit surface having hills and valleys formed in a linear or circular shape. That is, the exit surface of the light guide plate 202 is formed with a plurality of prisms formed in a linear or circular shape having a peak and a valley. Therefore, both the x component and the y component of light incident on the light guide plate 202 having a linear or circular prism can be incident in the z direction, that is, in the vertical direction of the liquid crystal display panel.

By using the first and second prism sheets 205 and 206, the amount of light lost can be reduced.

The diffusion sheet 204 allows the light incident at an angle from the surface of the reflecting plate 203 to proceed vertically toward the liquid crystal panel 100.

Although the liquid crystal display according to the present invention has been described using the VA mode or the OCB mode as an example, the present invention is not limited thereto, and when the LCD is implemented in a display mode such as TN, IPS, or ECB, the narrow viewing angle may be implemented.

4A and 4B illustrate transmission of light in VA mode before and after applying the liquid crystal display according to the present invention.

That is, FIG. 4A is a liquid crystal display device in VA mode before the compensation film is applied, and FIG. 4B is a liquid crystal display device in VA mode after the compensation film is applied.

Before applying the compensation film, as shown in Figure 4a it can be seen that Δnd difference in the front and side light transmitted from the side due to λ / 4 or less.

On the other hand, when the compensation film is applied as shown in FIG. 4B, the difference between the front and side Δnd is approximately λ / 2, and the light transmitted from the side is significantly reduced, thereby realizing the narrow viewing angle.

5 is a view comparing the TN before and the OCB optical structure after applying the compensation film in the liquid crystal display according to the present invention.

As shown in FIG. 5, when the general TN structure without the compensation film is compared with the OCB structure with the compensation film, the front contrast ratio may be improved when the compensation film is applied, thereby implementing a narrow viewing angle.

6A and 6B illustrate optical structures according to incident angles of light before and after applying a compensation film in a liquid crystal display according to the present invention.

That is, Figure 6a before applying the compensation film, Figure 6b is to implement a narrow viewing angle by rotating the rubbing direction of the liquid crystal cell 90 ° by applying an optical film.

 6A and 6B, when the retardation film is applied to be perpendicular to the cell rubbing direction for the narrow viewing angle, the rubbing direction of each retardation film is set up and down parallel to be reversely compensated. As a result, the narrow viewing angle can be realized by differentizing the left and right asymmetric Δnd.

7A and 7B illustrate a VA and OCB mode structure for implementing a narrow viewing angle in a liquid crystal display according to the present invention.

As shown in FIG. 7A, in the VA mode liquid crystal display, the rubbing directions of the compensation film and the liquid crystal cell are the same at 270 °.

In addition, as shown in FIG. 7B, in the OCB mode liquid crystal display, the rubbing direction of the compensation film is -90 ° or 90 °, while the rubbing directions of the liquid crystal cells are orthogonal to each other at 0 ° or 180 °, and the liquid crystal cells are vertically rubbing. Same as the direction.

On the other hand, the present invention described above is not limited to the above-described embodiment and the accompanying drawings, it is possible that various substitutions, modifications and changes within the scope without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill in Esau.

1 is a schematic configuration diagram for implementing a narrow viewing angle in a liquid crystal display according to the prior art

2 is a view schematically showing a liquid crystal display according to the present invention.

FIG. 3 is a block diagram illustrating a liquid crystal display in more detail to implement a narrow viewing angle in the liquid crystal display of FIG. 2.

4A and 4B illustrate light transmission in VA mode before and after applying a liquid crystal display according to the present invention.

5 is a view comparing the TN before and after applying the compensation film in the liquid crystal display according to the present invention the OCB optical structure

6A and 6B illustrate optical structures according to incident angles of light before and after applying a compensation film in a liquid crystal display according to the present invention.

7A and 7B illustrate a VA and OCB mode structure for implementing a narrow viewing angle in a liquid crystal display according to the present invention.

Explanation of symbols for the main parts of the drawings

100: liquid crystal panel 110: liquid crystal cell

120,130: compensation film 140,150: polarizer

200: backlight unit

Claims (5)

A liquid crystal cell, An adhesive layer formed on upper and lower portions of the liquid crystal cell; First and second compensation films attached to upper and lower surfaces of the liquid crystal cell by the adhesive layer to compensate the liquid crystal direction of the liquid crystal cell to realize a narrow viewing angle; And a first polarizing plate and a second polarizing plate configured to transmit light polarized in a predetermined direction among light incident on the first and second compensation films attached to upper and lower surfaces of the liquid crystal cell. . The liquid crystal display of claim 1, wherein the liquid crystal cell is in VA or OCB mode. The liquid crystal display of claim 1, wherein the first and second compensation films are biaxial films. The liquid crystal display device of claim 1, wherein the first and second compensation films compensate the liquid crystal direction at −90 ° or 90 ° depending on the rubbing direction of the liquid crystal cell. A liquid crystal display device comprising a liquid crystal panel displaying an image and a backlight unit configured to irradiate light on a rear surface of the liquid crystal panel, The liquid crystal panel may include a first substrate and a second substrate corresponding to each other at regular intervals, a liquid crystal layer formed between the first substrate and the second substrate, a first polarizing plate disposed under the first substrate, A second polarizing plate configured on the second substrate, and first and second compensation films configured between the first and second substrates, the first polarizing plate, and the second polarizing plate to compensate for the narrow viewing angle. Composed, The backlight unit may include at least one light source for emitting light, a light guide plate configured to be disposed at one side of the light source, and receiving light emitted from the light source through an incident surface to emit light as a surface light source, and disposed on a rear surface of the light guide plate. A reflection plate for reflecting light incident to the light through the rear surface of the light guide plate toward the light guide plate, a diffusion sheet disposed on the light guide plate to diffuse light through the light guide plate, and light for condensing light through the diffusion sheet. And a first prism sheet and a second prism sheet.

Images