KR20140002390A - Liquid crystal display device - Google Patents

Abstract

A liquid crystal display device of the present invention adopts a luminance enhanced film to enhance luminance, and improves Newton's ring and spectrum mura with three optical sheets, by performing haze processing on the rear side of an upper prism sheet and meanwhile forming an up and down step in a prism pattern. The liquid crystal display device includes: a liquid crystal panel which has a liquid crystal layer formed between a color filter substrate and an array substrate and outputs an image; an upper and a lower polarization plate attached to the outside of the liquid crystal panel; a luminance enhancement film attached to the lower side of the lower polarization plate; a light emitting diode (LED) array which is installed on the lower part of one side of the liquid crystal panel and supplies light for the liquid crystal panel; a light waveguide plate installed along the light emission direction of the LED array; and an optical sheet which is arranged between the luminance enhanced film and the light waveguide plate, and comprises an upper prism sheet, a lower prism sheet and a lower diffusion sheet. The upper prism sheet comprises a haze layer which is haze-processed on the rear side, and the up and down step is formed on the prism pattern.

Description

[0001] LIQUID CRYSTAL DISPLAY DEVICE [0002]

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device to which a brightness enhancement film is applied.

2. Description of the Related Art In general, a liquid crystal display device is a display device which can display a desired image by individually supplying data signals according to image information to pixels arranged in a matrix form and adjusting light transmittance of the pixels.

Accordingly, a liquid crystal display device includes a liquid crystal panel in which pixels are arranged in a matrix form, and a driver for driving the pixels.

The liquid crystal panel is a liquid crystal layer formed in a color filter substrate and an array substrate and a cell gap between the color filter substrate and the array substrate, which are bonded to face each other to maintain a uniform cell gap. It consists of.

At this time, a common electrode and a pixel electrode are formed on the liquid crystal panel in which the color filter substrate and the array substrate are bonded together to apply an electric field to the liquid crystal layer.

Therefore, when the voltage of the data signal applied to the pixel electrode is controlled while the voltage is applied to the common electrode, the liquid crystal of the liquid crystal layer is rotated by dielectric anisotropy according to the electric field between the common electrode and the pixel electrode And a character or an image is displayed by transmitting or blocking light for each pixel.

In this case, since the liquid crystal display device is a light-receiving device that can not emit light itself but displays an image by adjusting the transmittance of light coming from the outside, a separate device for irradiating light to the liquid crystal panel, that is, a backlight unit Is required.

Hereinafter, a general liquid crystal display device will be described in detail with reference to the drawings.

1 is an exploded perspective view schematically showing a structure of a general liquid crystal display device.

As shown in the figure, a typical liquid crystal display device includes a liquid crystal panel 10 in which pixels are arranged in a matrix form to output an image, drivers 15 and 16 for driving the pixels, And a panel guide 45 for receiving and fixing the liquid crystal panel 10 and the backlight unit.

In this case, although not shown, the liquid crystal panel 10 includes a color filter substrate and an array substrate bonded together to maintain a uniform cell gap facing each other, and a liquid crystal layer formed in a cell gap between the color filter substrate and the array substrate. .

A common electrode and a pixel electrode are formed on the liquid crystal panel 10 to which the color filter substrate and the array substrate are attached to each other. An electric field is applied to the liquid crystal layer. Data applied to the pixel electrode When the voltage of the signal is controlled, the liquid crystal of the liquid crystal layer rotates by dielectric anisotropy according to an electric field between the common electrode and the pixel electrode to transmit or block light for each pixel to display characters or images.

In order to control the voltage of the data signal applied to the pixel electrode on a pixel-by-pixel basis, a switching element such as a thin film transistor (TFT) is individually provided in the pixels.

The upper and lower polarizers (not shown) are attached to the outside of the liquid crystal panel 10, respectively, and the lower polarizer polarizes the light transmitted through the backlight unit. The upper polarizer is disposed on the liquid crystal panel 10 Polarized light.

A light emitting diode (LED) assembly 30 for generating light is provided on one side of a light guide plate 42. The backlight unit 30 includes a light guide plate 42, A reflection plate 41 is provided.

The LED assembly 30 includes an LED array 31 and an LED housing 32 to which an LED printed circuit board (PCB) (not shown) for driving the LED array 31 is attached. Lt; / RTI >

The light emitted from the LED array 31 is incident on a side surface of the light guide plate 42 of transparent material and the reflection plate 41 disposed on the back surface of the light guide plate 42 is transmitted to the back surface of the light guide plate 42 The light is reflected toward the optical sheets 43 on the upper surface of the light guide plate 42 to reduce light loss and improve the uniformity.

The liquid crystal panel 10 composed of the color filter substrate and the array substrate is mounted on the upper part of the backlight unit thus configured through the panel guide 45. The liquid crystal panel 10, the panel guide 45, are connected to each other by a cover bottom 50 and a top case top 60 through a screw to constitute a liquid crystal display device.

Currently, three optical sheets are used for display devices of notebooks or mobile devices, but four optical sheets are required when a brightness enhancing film such as Advanced Polarizing Collimation Film (APCF) is applied to improve brightness. It is an obstacle to saving and slimming of a display device. This is because when using only three optical sheets as in the past, such defects as Newton's ring and spectrum mura cannot be solved.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a liquid crystal display device in which a Newton's ring and a spectrum mura are improved using only three optical sheets when a brightness enhancement film is applied. .

Other objects and features of the present invention will be described in the following description of the invention and claims.

In order to achieve the above object, the liquid crystal display device of the present invention comprises a liquid crystal panel formed between the color filter substrate and the array substrate to output an image; Upper and lower polarizers attached to an outer side of the liquid crystal panel; A brightness enhancing film attached to a lower side of the lower polarizer; An array of light emitting diodes (LEDs) disposed under one side of the liquid crystal panel to supply light to the liquid crystal panel; A light guide plate provided in an output direction of the LED array; And an optical sheet disposed between the brightness enhancement film and the light guide plate, the optical sheet including an upper prism sheet, a lower prism sheet, and a lower diffusion sheet, wherein the upper prism sheet includes a haze layer having a haze treatment on a rear surface thereof. On the other hand, it is characterized in that the upper and lower steps are formed in the prism pattern.

In this case, the brightness enhancement film is characterized in that it comprises an Advanced Polarizing Collimation Film (APCF).

The brightness enhancing film is characterized by having a multilayer structure in which the first thermoplastic resin and the second thermoplastic resin are alternately laminated.

The base film of the upper prism sheet is characterized in that the orientation angle by stretching is 0 °.

At this time, the haze of the haze layer is characterized in that it has 20 to 25%.

In this case, the haze layer is formed on the lower side of the base film of the upper prism sheet through bead coating or matte treatment.

The prism pattern of the upper prism sheet is characterized in that it has a vertical step of ± 2㎛ on the top.

At this time, the prism pattern of the upper prism sheet is characterized in that it has a refractive index of 1.54 ~ 1.56.

At this time, the prism pattern of the upper prism sheet has a pitch of 48 ~ 52㎛, its vertex is characterized in that it has an angle of 88 ~ 92 °.

As described above, the liquid crystal display according to the present invention has three optical films even when a brightness enhancement film is applied by hazeing the back surface of the upper prism sheet and forming a vertical step on the prism pattern. The sheet alone can improve Newton rings and spectral murah. Accordingly, the thickness of the backlight unit can be reduced, contributing to the slimming of the display device, and reducing the cost by reducing the number of optical sheets.

1 is an exploded perspective view schematically showing a structure of a general liquid crystal display device.
2 is a schematic cross-sectional view of a structure of a liquid crystal display according to a first exemplary embodiment of the present invention.
FIG. 3 is an exemplary view schematically showing a principle of improving luminance in the liquid crystal display device to which the luminance improving film shown in FIG. 2 is applied.
4 is a cross-sectional view schematically illustrating a structure of a brightness enhancement film in a liquid crystal display device to which the brightness enhancement film shown in FIG. 2 is applied.
5A and 5B are photographs showing, for example, the external appearance of a liquid crystal panel in which a Newton ring and a spectral mura phenomenon have occurred.
6 is a schematic cross-sectional view of a structure of a liquid crystal display according to a second exemplary embodiment of the present invention.
7A and 7B are cross-sectional views schematically illustrating a structure of an upper prism sheet in the liquid crystal display according to the second embodiment of the present invention shown in FIG.
8 is a perspective view schematically illustrating a structure of an upper prism sheet in the liquid crystal display according to the second exemplary embodiment of the present invention shown in FIG. 6.
9A to 9D are photographs showing the appearance state of the liquid crystal panel according to the degree of haze when the haze treatment is applied to the rear surface of the upper prism sheet.
FIG. 10 is a photograph showing, for example, an external appearance of a liquid crystal panel in which a Newton ring and a spectral mura phenomenon are improved in the liquid crystal display according to the second exemplary embodiment of the present invention. FIG.

Hereinafter, preferred embodiments of the liquid crystal display according to the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

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

As shown in the figure, the liquid crystal display according to the first exemplary embodiment of the present invention includes a liquid crystal panel 110 in which pixels are arranged in a matrix form to output an image, and installed on a rear surface of the liquid crystal panel 110. The backlight unit emits light over the entire surface of the 110 and a panel guide (not shown) for accommodating and fixing the liquid crystal panel 110 and the backlight unit.

At this time, although not shown in detail, the liquid crystal panel 110 is composed of a color filter substrate and an array substrate and a liquid crystal layer formed in the cell gap between the color filter substrate and the array substrate facing each other to maintain a uniform cell gap. do.

The color filter substrate distinguishes between a color filter composed of a plurality of sub-color filters that implements red, green, and blue colors, and light that passes through the liquid crystal layer and distinguishes between the sub-color filters. A black matrix for blocking the black matrix and a transparent common electrode for applying a voltage to the liquid crystal layer.

The array substrate includes a plurality of gate lines and data lines arranged vertically and horizontally to define a plurality of pixel regions, a thin film transistor serving as a switching element formed in a crossing region between the gate lines and the data lines, and a pixel electrode formed on the pixel region consist of. In this case, in the case of an in-plane switching (IPS) type liquid crystal display, a common electrode is formed on the array substrate instead of the color filter substrate.

Upper and lower polarizers 111 and 101 are attached to the outside of the liquid crystal panel 110 configured as described above, and the lower polarizer 101 polarizes light passing through the backlight unit and the upper polarizer 111. ) Polarizes the light passing through the liquid crystal panel 110.

At this time, the lower polarizing plate 101 of the present invention is attached to the lower brightness enhancement film 170 such as APCF (Advanced Polarizing Collimation Film) is characterized in that it can improve the efficiency of light incident from the backlight unit .

In detail, the backlight unit includes a reflector plate 141 disposed on a cover bottom (not shown), and an array of light emitting diodes (LEDs) for generating light on at least one side of the reflector plate 141. The light guide plate 142 which emits light generated by the LED array in the direction of the liquid crystal panel 110 is installed in the light emitting direction of the LED array.

In this case, although not shown, the LED assembly may include a plurality of LED arrays and an LED housing to which an LED printed circuit board (PCB) for driving the LED array is attached.

The light emitted from the LED array is incident on the side of the light guide plate 142 of a transparent material, and the reflective plate 141 disposed on the rear surface of the light guide plate 142 transmits light transmitted to the rear surface of the light guide plate 142. Reflecting toward the optical sheets 143 on the upper surface reduces the loss of light and improves the uniformity.

In this case, the optical sheets 143 according to the first embodiment of the present invention are applied to the upper and lower diffusion sheets 143d and 143a and the upper and lower prism sheets 143c and 143b by applying the brightness enhancing film 170 described above. 4 sheets in total) and a protective sheet may be added.

The lower diffusion sheet 143a disperses the light incident from the light guide plate 142 to prevent the light from being partially concentrated to prevent staining of an image displayed on the liquid crystal panel 110, and to enter the light from the light guide plate 142. Refract the angle of light vertically.

The upper and lower prism sheets 143c and 143b collect light incident from the lower diffusion sheet 143a to be uniformly distributed on the entire surface of the liquid crystal panel 110.

In addition, the protective sheet protects the optical sheets 143 which are sensitive to dust and scratches, and serves to prevent the flow of the optical sheets 143 when carrying the backlight unit.

Although not shown, the liquid crystal panel 110 including the color filter substrate and the array substrate is seated on the upper portion of the backlight unit configured as described above through the panel guide, and the liquid crystal panel 110 and the panel guide and the backlight unit are screwed. Through a plurality of fastening means such as) is coupled to each other by the bottom of the cover bottom and the top of the upper to form a liquid crystal display device.

FIG. 3 is an exemplary view schematically illustrating a principle of improving luminance in the liquid crystal display device to which the luminance enhancing film shown in FIG. 2 is applied.

In addition, FIG. 4 is a cross-sectional view schematically showing the structure of the brightness enhancement film in the liquid crystal display device to which the brightness enhancement film shown in FIG. 2 is applied.

Referring to the drawings, the liquid crystal panel 110 according to the present invention is characterized in that it further comprises a brightness enhancement film 170 on the lower side of the lower polarizing plate (101).

The lower polarizer 101 separates the incident light into two orthogonal polarization components in the same manner as the upper polarizer 111 by the optical means for converting natural light or polarization into linearly polarized light, and transmits one polarization component to the other. Has the function of absorbing, reflecting and / or scattering polarization components.

The thickness of the lower polarizing plate 101 is not particularly limited, and includes a general concept of a thin film, a film, and a sheet.

The lower polarizing plate 101 may be a layer (polarizer) having a polarization function of a single layer, or may be a laminate composed of a plurality of layers. When the said polarizing plate is a laminated body, as a structure, it is (a) laminated body containing polarizer 101a and protective layers 101b and 101c, for example, (b) polarizer, protective layer, and surface treatment layer containing The laminated body, the laminated body containing (c) two or more polarizers, etc. are mentioned.

Arbitrary suitable things may be employ | adopted as the said polarizer 101a, For example, it has a polyvinyl alcohol (PVA) type resin containing iodine as a main component. The polarizer 101a can be obtained by stretching a polymer film containing iodine-containing PVA resin as a main component, and the PVA resin is obtained by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester monomer. You can get it.

The protective layers 101b and 101c are disposed on both sides of the polarizer 101a, and serve to prevent the polarizer 101a from contracting or expanding or to prevent deterioration by ultraviolet rays.

In addition, a first adhesive layer 180a may be disposed between the liquid crystal panel 110 and the lower polarizing plate 101 for practical use, and may be disposed between the lower polarizing plate 101 and the brightness enhancement film 170. The second adhesive layer 180b may be disposed on the second adhesive layer 180b.

The brightness enhancement film 170 separates the incident light into two orthogonal polarization components, transmits one polarization component, reflects the other polarization component, and recycles the light to recover light from the final liquid crystal display device. Has the function to improve the efficiency.

In the case of a general polarizer, P-polarized light is transmitted through the liquid crystal panel, but S-polarized light is absorbed. However, when the brightness enhancement film 170 is used, the P-polarized light is transmitted to the liquid crystal panel 110, and the S-polarized light is reflected toward the backlight unit 140 to be unpolarized by diffusion or scattering to be recycled. Will be.

The brightness enhancing film 170 has a multi-layered structure in which several hundreds or more of the first thermoplastic resin 170a and the second thermoplastic resin 170b are alternately stacked. As the first thermoplastic resin 170a, polyethylene terephthalate ( Polyethylene Terephthalate (PET) resin, Polytrimethylene Terephthalate (PTT) resin, Polybutylene Terephthalate (PBT) resin, Polyethylene Naphthalate (PEN) resin, Polybutyl Or butyl naphthalate (PBN) -based resins, or mixtures thereof. In addition, the second thermoplastic resin 170b may include a polystyrene resin, a polymethyl methacrylate (PMMA) resin, a polystyrene glycidyl methacrylate resin, a coPEN, or a mixture thereof. can do.

When applying the brightness enhancing film to the lower side of the lower polarizing plate, as described above, in order to prevent the Newton ring and the spectral mura phenomenon, the lower diffusion sheet, the upper and lower prism sheets as well as the upper diffusion sheet are added as the optical sheet. Four sheets are needed. This is because the existing lower diffusion sheet and the three optical sheets of the upper and lower prism sheets alone cannot solve the Newton ring and spectral murah phenomenon.

5A and 5B are photographs showing, for example, a front of screen (FOS) state of a liquid crystal panel in which a Newton ring and a spectral mura phenomenon occur.

At this time, the appearance state may be represented by a relative level of 1 to 5 levels, and the 2 to 5 levels indicate a defective state in which the display quality is degraded due to the occurrence of a Newton ring or spectrum mura.

Referring to the drawings, in the liquid crystal display device to which the brightness enhancement film is applied, it can be seen that when only the existing three optical sheets are used, the Newton ring, which is similar to the oil strip, and the spectral mura, which are spectral phenomena, are generated. FOS measurement level 5).

For reference, a Newton ring is a contact point when a flat or convex surface with a large radius of curvature (a few m or more) is placed on a flat glass, and light is emitted almost vertically from above to observe reflected light or transmitted light. A number of concentric circles appearing around. This is the interference pattern of light caused by the thin air layer between the convex surface of the flat glass and the flat convex lens. It is colored in normal light, but becomes dark when illuminated with monochromatic light. The pattern is visible, but the contrast is completely opposite in the transmitted light. Also, if the glass is a perfect plane, the pattern is also a perfect concentric circle.

As described above, the Newton ring is a ring-type pattern generated by constructive interference caused by a difference in path when light due to some reflections proceeds to different paths by a medium, and light emitted through an optical sheet is a medium such as a polarizing plate or glass. Part of the reflection is reflected back to the optical sheet is divided into two, and then proceeds to different paths, and when they meet again, various interferences occur due to the difference in the paths. In this case, when two light rays that are separated and then meet again have the same phase, constructive interference occurs, and when they have different phases, destructive interference occurs.

The spectral mura is iridescent with the difference in the angle of refraction for each wavelength at the boundary of the prism. In the condensing area, the light is scattered but the amount is small, so it is recognized as white, but the side lobe In the region, as the optical path becomes longer due to total internal reflection inside the prism sheet, the spectral angle becomes larger and is recognized as an iridescent band.

On the other hand, in the liquid crystal display device to which the brightness enhancement film is applied, when applying a total of four optical sheets, the above-described Newton ring and spectrum mura phenomenon can be solved, but active in slimming the display device which reduces the thickness of the backlight unit. Will not respond. That is, in order to reduce the thickness of the liquid crystal display device, the thickness of the backlight unit should be reduced. In order to reduce the thickness of the backlight unit, the number of optical sheets as well as the thickness of the light guide plate and the LED should be reduced.

Accordingly, in the second embodiment of the present invention, the haze treatment is performed on the rear surface of the upper prism sheet, and the upper and lower steps are formed on the prism pattern to improve the Newton ring and the spectral murah with only three optical sheets even when the brightness enhancement film is applied. This will be described in detail with reference to the drawings.

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

In this case, the liquid crystal display device according to the second embodiment of the present invention is substantially the same as the liquid crystal display device according to the first embodiment of the present invention except for the structure of the optical sheet.

That is, as shown in the figure, the liquid crystal display device according to the second embodiment of the present invention is arranged on the liquid crystal panel 210, the rear panel of the liquid crystal panel 210, the pixels are arranged in a matrix form to output an image The backlight unit emits light over the entire surface of the liquid crystal panel 210 and a panel guide (not shown) for accommodating and fixing the liquid crystal panel 210 and the backlight unit.

At this time, although not shown in detail, the liquid crystal panel 210 is composed of a color filter substrate and an array substrate and a liquid crystal layer formed in the cell gap between the color filter substrate and the array substrate facing each other to maintain a uniform cell gap. do.

The color filter substrate may include a color matrix composed of a plurality of sub-color filters for realizing red, green, and blue colors, a black matrix for distinguishing between the sub-color filters and blocking light passing through the liquid crystal layer, and the liquid crystal layer. It consists of a transparent common electrode that applies a voltage to it.

The array substrate includes a plurality of gate lines and data lines arranged vertically and horizontally to define a plurality of pixel regions, a thin film transistor serving as a switching element formed in a crossing region between the gate lines and the data lines, and a pixel electrode formed on the pixel region consist of. At this time, in the case of the transverse electric field type liquid crystal display device, a common electrode is formed on the array substrate instead of the color filter substrate.

Upper and lower polarizers 211 and 201 are attached to the outside of the liquid crystal panel 210 configured as described above, and the lower polarizer 201 polarizes light passing through the backlight unit, and the upper polarizer 211. ) Polarizes the light passing through the liquid crystal panel 210.

At this time, the lower polarizing plate 201 of the present invention is characterized in that the brightness enhancement film 270 such as APCF is attached to the lower side to improve the efficiency of the light incident from the backlight unit.

In detail, the backlight unit is provided with a reflector plate 241 on a cover bottom (not shown), and an LED array (not shown) for generating light on at least one side of the reflector plate 241 is provided. The light guide plate 242 is provided in the light emitting direction of the LED array to emit light generated in the LED array toward the liquid crystal panel 210.

At this time, although not shown, the LED assembly may be composed of a plurality of LED array and the LED housing to which the LED printed circuit board for driving the LED array is attached.

The light emitted from the LED array is incident on the side of the light guide plate 242 of a transparent material, and the reflective plate 241 disposed on the rear surface of the light guide plate 242 transmits light transmitted to the rear surface of the light guide plate 242. Reflecting toward the optical sheets 243 on the upper surface reduces the loss of light and improves the uniformity.

At this time, the optical sheet 243 according to the second embodiment of the present invention is different from the case of the first embodiment of the present invention described above, the total of the lower diffusion sheet 243a and the upper and lower prism sheets 243c and 243b. It includes three sheets, and a protective sheet can be added.

The lower diffusion sheet 243a disperses the light incident from the light guide plate 242, thereby preventing the light from being partially concentrated and causing stains on an image displayed on the liquid crystal panel 210, and entering the light from the light guide plate 242. Refract the angle of light vertically.

The upper and lower prism sheets 243c and 243b collect light incident from the lower diffusion sheet 243a to be uniformly distributed on the entire surface of the liquid crystal panel 210.

In addition, the protective sheet protects the optical sheets 243 which are sensitive to dust and scratches, and serves to prevent the flow of the optical sheets 243 when carrying the backlight unit.

Although not shown, the liquid crystal panel 210 formed of the color filter substrate and the array substrate is seated on the upper portion of the backlight unit configured as described above through the panel guide, and the liquid crystal panel 210 and the panel guide and the backlight unit are made of screws. A plurality of fastening means are coupled to each other by a lower cover bottom and an upper case top to form a liquid crystal display.

As described above, the liquid crystal panel 210 according to the present invention is further provided with a brightness enhancement film 270 under the lower polarizer 201.

The lower polarizing plate 201 is the same as the upper polarizing plate 211, and separates the incident light into two orthogonal polarization components by the optical means for converting the natural light or polarization into linearly polarized light, and transmits one polarization component and the other Has the function of absorbing, reflecting and / or scattering polarization components.

The thickness of the lower polarizer 201 is not particularly limited, and includes a general concept of a thin film, a film, and a sheet.

Although not shown in detail, the lower polarizing plate 201 may be a layer (polarizer) having a polarization function of a single layer, or may be a laminate composed of a plurality of layers. When the said polarizing plate is a laminated body, as a structure, it is (a) laminated body containing a polarizer and a protective layer, (b) laminated body containing a polarizer, a protective layer, and a surface treatment layer, and (c) two layers, for example. The laminated body containing the above polarizer etc. are mentioned.

Any appropriate one can be adopted as the polarizer, and is based on, for example, a polyvinyl alcohol (PVA) -based resin containing iodine. The polarizer can be obtained by stretching a polymer film containing iodine-containing PVA resin as a main component, and the PVA resin can be obtained by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester monomer.

The protective layer is disposed on both sides of the polarizer, and serves to prevent the polarizer from contracting or expanding or to prevent degradation by ultraviolet rays.

And, in practice, a first adhesive layer (not shown) may be disposed between the liquid crystal panel 210 and the lower polarizing plate 201, and the lower polarizing plate 201 and the brightness enhancing film 270 may be disposed. A second adhesive layer (not shown) for attaching both may be disposed therebetween.

As described above, the brightness enhancement film 270 has a multilayer structure in which several hundreds or more layers of a first thermoplastic resin and a second thermoplastic resin are alternately stacked. As the first thermoplastic resin, polyethylene terephthalate (PET) is used. ) Resin, Polytrimethylene Terephthalate (PTT) Resin, Polybutylene Terephthalate (PBT) Resin, Polyethylene Naphthalate (PEN) Resin, Polybutylene Naphthalate (PTT) Resin Polybutylene Naphthalate (PBN) -based resin, or a mixture thereof. In addition, the second thermoplastic resin may include a polystyrene resin, a polymethyl methacrylate (PMMA) resin, a polystyrene glycidyl methacrylate resin, a coPEN, or a mixture thereof. have.

When the brightness enhancement film 270 is applied to the lower side of the lower polarizing plate 201, the lower diffusion sheet 243a and the upper and lower prism sheets are used as optical sheets to prevent the Newton ring and the spectral mura phenomenon as described above. 243c, 243b) as well as the top diffusion sheet should be added.

 However, in the second embodiment of the present invention, even when the luminance enhancement film 270 is applied by applying a haze treatment to the rear surface of the upper prism sheet 243c and forming a vertical step in the prism pattern, the three optical sheets 243 are applied. ) Can be used to improve the Newton ring and spectrum mura.

7A and 7B are cross-sectional views schematically illustrating a structure of an upper prism sheet in the liquid crystal display according to the second exemplary embodiment of the present invention shown in FIG. 6. In this case, FIG. 7B schematically illustrates a cross section of the upper prism sheet illustrated in FIG. 7A cut from the front to the rear with respect to one prism pattern.

8 is a perspective view schematically illustrating a structure of an upper prism sheet in the liquid crystal display according to the second exemplary embodiment of the present invention shown in FIG. 6.

First, in the case where the brightness enhancement film is applied to the lower side of the lower polarizing plate, the orientation angle due to the stretching of the base film 243c-1 of the upper prism sheet to improve the Newton ring and spectral mura defects generated when the upper diffusion sheet is deleted. Keep in the horizontal direction.

Because, the level difference of the Newton ring occurs according to the orientation angle of the base film 243c-1 of the upper prism sheet. When the orientation angles are -30 °, 30 ° and 0 °, the FOS measurement results are 5 levels, respectively. This is because they were measured at level 5 and level 3.

In this case, as described above, the appearance state may be represented by a relative level of 1 to 5 levels, and the 2 to 5 levels indicate a defective state in which a display quality is degraded due to the occurrence of a Newton ring or a spectrum mura.

As such, the base film 243c-1 of the upper prism sheet is further improved to further improve the Newton ring and the spectral mura defect while maintaining the orientation angle due to the stretching of the base film 243c-1 of the upper prism sheet at 0 °. The haze layer 243c-2 is formed on the lower side through a bead coating or a matte treatment.

For reference, FIGS. 9A to 9D are photographs showing the appearance state of the liquid crystal panel according to the degree of haze when the haze treatment is applied to the back surface of the upper prism sheet.

9A to 9D show the appearance state of the liquid crystal panel when the haze is treated by 3%, 13%, 20% and 30%, respectively.

Referring to the drawings, when the haze treatment 3 ~ 11%, 13 ~ 18%, 20 ~ 25% and 28 ~ 31% FOS measurement results were measured at 5 levels, 4 levels, 2 levels and 1.5 levels, respectively.

In addition, when the haze was treated with 3 to 11%, 13 to 18%, 20 to 25%, and 28 to 31%, the luminance result was 103.0% and 101.2, respectively, when using 4 optical sheets as 100%. %, 97.7% and 93.3%.

In this case, if the haze is maintained at 28 to 31%, the appearance is improved, but as the brightness decreases relatively, the haze is maintained at 20 to 25%, and the upper and lower step d is ± 2 on the prism pattern (243c-3). It is formed in a micrometer.

As the upper and lower steps d are alternately formed on the prism pattern 243c-3, the wave-shaped haze may be added.

In this case, the prism pattern 243c-3 of the upper prism sheet may have a refractive index of 1.54 to 1.56, preferably 1.55.

The prism pattern 243c-3 of the upper prism sheet may have a pitch of 48 to 52 μm, and its vertex angle may have an angle of 88 to 92 °.

For reference, FIG. 10 illustrates the improvement of the Newton ring and the spectral mular phenomenon when the haze treatment is performed on the rear surface of the upper prism sheet and the upper and lower steps are formed on the prism pattern in the liquid crystal display according to the second embodiment of the present invention. It is the photograph which shows the external appearance state of the liquid crystal panel made up, for example.

Referring to the drawings, in the second embodiment of the present invention, even if the brightness enhancement film is applied, the FOS measurement results are measured at one level, which is equivalent to the case of using only four conventional optical sheets, thereby improving the Newton ring and the spectral murah. You can see that.

In addition, the luminance result is measured at 96.6% when using 4 optical sheets as a 100%, it can be seen that a good level.

As described above, the liquid crystal display according to the present invention is capable of improving the Newton ring and the spectral mula using only three optical sheets even when a brightness enhancement film is applied by performing a haze treatment on the rear surface of the upper prism sheet and forming a vertical step on the prism pattern. It becomes possible. Accordingly, the thickness of the backlight unit can be reduced, contributing to the slimming of the display device, and the cost can be reduced by reducing the number of optical sheets.

While a great many are described in the foregoing description, it should be construed as an example of preferred embodiments rather than limiting the scope of the invention. Therefore, the invention should not be construed as limited to the embodiments described, but should be determined by equivalents to the appended claims and the claims.

101,201, 111,211: polarizer 110,210: liquid crystal panel
141,241: reflector 142,242: light guide plate
143,243: Optical sheet 143a, 243a, 143d: Diffusion sheet
143b, 243b, 143c, 243c: Prism Sheet
170270: brightness enhancement film 243c-1: base film
243c-2: haze layer 243c-3: prism pattern

Claims (9)

A liquid crystal panel formed between the color filter substrate and the array substrate to output an image;
Upper and lower polarizers attached to an outer side of the liquid crystal panel;
A brightness enhancing film attached to a lower side of the lower polarizer;
An array of light emitting diodes (LEDs) disposed under one side of the liquid crystal panel to supply light to the liquid crystal panel;
A light guide plate provided in an output direction of the LED array; And
Is disposed between the brightness enhancement film and the light guide plate, and comprises an optical sheet consisting of an upper prism sheet, a lower prism sheet and a lower diffusion sheet,
The upper prism sheet is provided with a haze layer having a haze treatment on a rear surface thereof, and an upper and lower steps are formed on the prism pattern. The liquid crystal display of claim 1, wherein the brightness enhancing film comprises an Advanced Polarizing Collimation Film (APCF). The liquid crystal display device of claim 1, wherein the brightness enhancing film has a multilayer structure in which a first thermoplastic resin and a second thermoplastic resin are alternately stacked. The liquid crystal display device according to claim 1, wherein the base film of the upper prism sheet has an orientation angle of 0 ° due to stretching. 5. The liquid crystal display device according to claim 4, wherein the haze of the haze layer has 20 to 25%. The liquid crystal display of claim 5, wherein the haze layer is formed by bead coating or matting under the base film of the upper prism sheet. 6. The liquid crystal display of claim 5, wherein the prism pattern of the upper prism sheet has an upper and lower step of ± 2 mu m on the upper side. The liquid crystal display of claim 7, wherein the prism pattern of the upper prism sheet has a refractive index of 1.54 to 1.56. The liquid crystal display of claim 8, wherein the prism pattern of the upper prism sheet has a pitch of 48 to 52 μm, and a vertex of the upper prism sheet has an angle of 88 to 92 degrees.

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