KR100793091B1 - A brightness improving sheet and a backlight unit including the same - Google Patents

Abstract

A brightness improving sheet and a backlight unit including the same are provided to improve the brightness and enlarge the viewing angle by performing both concentration and diffusion of incident light using a diffusion unit formed of diffusion particles between prisms. A prism-shaped unit(310) includes a plurality of prisms arranged in parallel to each other on a base film(300). A diffusion unit(320) includes at least one diffusion particle(324) and a resin(322) and is formed between the prisms of the prism-shaped unit. The diffusion particle is a bead formed of polystyrene. The resin is an UV curable resin. A refractive index(n2) of the diffusion particle is substantially equal to a refractive index(n3) of the resin(n2 n3). A refractive index(n1) of the prism is larger than a refractive index(n3) of the resin(n1>n3).

Description

A brightness enhancement sheet and a backlight device including the same {A BRIGHTNESS IMPROVING SHEET AND A BACKLIGHT UNIT INCLUDING THE SAME}

1 is a cross-sectional view showing a backlight device of a conventional liquid crystal display device.

2 is a perspective view illustrating a liquid crystal display device using an edge-light backlight device according to an exemplary embodiment of the present invention.

3 is a cross-sectional view illustrating the liquid crystal display panel of FIG. 2.

4A and 4B are a perspective view and a cross-sectional view showing the structure of the brightness enhancement sheet used in the backlight device of FIG.

5A and 5B are cross-sectional views illustrating a manufacturing process of the brightness improving sheet of FIGS. 4A and 4B.

6 is a cross-sectional view illustrating a backlight device of a direct type according to another embodiment of the present invention.

The present invention relates to a brightness improving sheet and a backlight device including the same, and more particularly, to a brightness improving sheet capable of improving brightness and viewing angle.

In general, a liquid crystal display device (hereinafter referred to as an "LCD device") is an electronic device that transmits various electrical information generated by various devices to visual information by using a change in liquid crystal transmittance according to an applied voltage. Element.

Since the LCD element is a display element of various information and does not have its own light emitting source, a separate device is required to lightly illuminate the entire screen of the LCD element by placing a light source on the rear thereof, wherein the device providing the light is a backlight. Back Light Unit.

The backlight device is a direct method in which the lamp is positioned below the liquid crystal panel and the lamp is positioned on the side of the light guide plate according to a method of installing a light source, for example, a cold cathode fluorescent lamp (CCFL). There is an edge-light method.

1 is a cross-sectional view showing a backlight device of a conventional liquid crystal display device.

Referring to FIG. 1, the backlight device 100 is driven by an edge-light method and includes a light source unit 110, a light guide plate 120, a reflective sheet 130, and an optical film 140. .

The light source unit 110 includes one or more light sources 112 and a light source reflector plate 114.

The light source 112 generates light having a predetermined wavelength.

Light generated by the light source 112 is reflected by the light source reflecting plate 114 and the reflecting sheet 130, and then the reflected light is uniformly spread throughout the light guide plate 120 as shown in FIG. 1. .

The optical film 140 includes a diffusion sheet 142, a prism sheet 144, and a protective sheet 146.

Light uniformly diffused in the light guide plate 120 passes through the diffusion sheet 142. The diffusion sheet 142 diffuses or condenses the light passing through the light guide plate 120 to make the luminance uniform and widen the viewing angle.

The light passing through the diffusion sheet 142 is sharply reduced in brightness, the prism sheet 144 is used to prevent this. The prism sheet 144 refracts the light emitted from the diffusion sheet 142 so that the light incident at a low angle is concentrated toward the front, thereby increasing the luminance in the effective viewing angle range.

The protective sheet 146 is positioned on the prism sheet 144 to prevent scratches of the prism sheet 144 and to widen the viewing angle narrowed by the prism sheet 144.

On the other hand, since the optical film 140 is composed of a plurality of sheets, such as the diffusion sheet 142, the prism sheet 144 and the protective sheet 146, the thickness of the backlight device 100 was thick.

SUMMARY OF THE INVENTION An object of the present invention is to provide a brightness enhancing sheet capable of improving both brightness and viewing angle by performing both a light converging function and a diffusing function of an incident light using a diffusion part formed of diffusion particles between prisms, and a backlight device including the same. will be.

In addition, an object of the present invention is to configure the optical film with a brightness enhancement sheet having a light condensing and diffusing function may not use a diffusion sheet or a protective sheet, to provide a backlight device that can reduce the thickness and manufacturing cost of the optical film It is.

In order to achieve the above object, a backlight device according to an embodiment of the present invention is a light source for emitting light of a predetermined wavelength, a light guide plate for uniformly transmitting the light generated by the light source and the light emitted through the light guide plate And a brightness improving sheet for collecting and diffusing the light.

In addition, the backlight device according to another embodiment of the present invention includes a light source for emitting light of a predetermined wavelength, a transparent plate for passing the light emitted from the light source and a brightness enhancement sheet for condensing and diffusing the light emitted from the transparent plate do.

The brightness enhancing sheet includes a base film, a prism shape formed of a plurality of prisms arranged side by side on the base film, and a plurality of diffusion particles and a resin, and a diffusion part formed between the prisms of the prism shape. It features.

The brightness improving sheet and the backlight device including the same may improve brightness and viewing angle by performing both a light converging function and a light diffusing function by using a diffusion part formed of diffusion particles between prisms.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the brightness enhancement sheet and a backlight device including the same according to the present invention.

FIG. 2 is a perspective view illustrating a liquid crystal display device using an edge-light backlight device according to an exemplary embodiment of the present invention, and FIG. 3 is a cross-sectional view of the liquid crystal display panel of FIG. 2.

Referring to FIGS. 2 and 3, a liquid crystal display device (hereinafter referred to as an LCD device) 200 may include a liquid crystal panel 210 displaying an image according to a driving signal and a data signal applied from the outside. The backlight device 220 is disposed on the rear surface of the liquid crystal panel 210 to illuminate the liquid crystal panel 210.

In understanding and practicing the invention, the precise structural characteristics of the liquid crystal panel 210 are not important, and the idea of the present invention can be applied to a wide range of liquid crystal panels commonly used in LCD devices. Therefore, the structure of the liquid crystal panel 210 described below is merely provided as an example for understanding the present invention.

The liquid crystal panel 210 includes an upper substrate 211b and a lower substrate 211a, a color filter 212, a black matrix 217, a pixel electrode 214, a common electrode 215, a liquid crystal layer 216, and a TFT array. 213, and a pair of polarizing films 218a and 218b are disposed on both surfaces of the liquid crystal panel 210.

The color filter 212 includes color filters corresponding to red (R), green (G), and blue (B). When light is applied, the color filter 212 generates an image corresponding to the color of red, green, or blue.

The TFT array 213 switches the pixel electrode 214 as a switching element.

The common electrode 215 and the pixel electrode 214 convert an array of molecules of the liquid crystal layer 216 according to a predetermined voltage applied from the outside.

The liquid crystal layer 216 is composed of a plurality of liquid crystal molecules, and the liquid crystal molecules change an arrangement in accordance with a voltage difference generated between the pixel electrode 214 and the common electrode 215, whereby the backlight device ( Light provided from 220 is incident on the color filter 212 in response to a change in the molecular arrangement of the liquid crystal layer 216.

The backlight device 220 is located at the rear of the liquid crystal panel 210 and provides light, for example, white light, to the liquid crystal panel 210.

The backlight device 220 may include a direct light source in which a lamp is positioned below the liquid crystal panel and a lamp of the light guide plate according to a method of installing a light source, for example, a cold cathode fluorescent lamp (CCFL). There is an edge-light method located on the side.

Referring back to FIG. 2, the backlight device 220 is driven by an edge-light method, and includes a light source unit 222, a light guide plate 224, a reflective sheet 226, and an optical film 228. ).

The light source unit 222 is positioned at the side of the backlight device 220 and includes a light source 222a and a light source reflector 222b.

The light source 222a is formed of a plurality of cold cathode fluorescent lamps (CCFLs) as an aggregate. The CCFL is a lamp that provides very bright white light.

In addition to the CCFL, the light source 222a may be a light emitting diode (LED) or an external electrode fluorescent lamp (EEFL).

The LED can be composed of red, green and blue or a single color of white light. In the case of the backlight device 220 using the LED as a light source, it is possible to maintain the uniformity of the light while miniaturizing the backlight device 220 and improving the light efficiency.

The EEFL has a higher luminance than the CCFL and is advantageous in that the electrode is external to operate in parallel. In particular, the EEFL can reduce the number of inverters required by the conventional light source, thereby reducing the cost of components and the weight of the LCD module.

The light source reflector 222b mounts the light source 222a and is intended to improve light efficiency by allowing light from the light source 222a to enter the side of the light guide plate 224. To this end, the light source reflector 222b is made of a highly reflective material, and may coat silver (Ag) on its surface.

The reflective sheet 226 is disposed under the light guide plate 224 to reflect light from the light source 222a to the front surface of the light guide plate 224. Reflective sheet 226 according to an embodiment of the present invention is coated on a silver (silver) on a sheet made of SUS, Brass, aluminum, PET, etc., even if the heat is generated fine titanium coating to prevent deformation due to endothermic long time Can be produced. In addition, the reflective sheet 226 according to another embodiment of the present invention may be manufactured by dispersing bubbles for scattering light on a sheet of synthetic resin such as PET.

The light guide plate 224 is designed such that continuous total reflection occurs below a critical angle after light is incident on the side surface. Since the light source 222a is located at the side of the backlight device 220, the light generated from the light source 222a is concentrated at the edge of the backlight device 220 without being uniformly transmitted. Accordingly, the light guide plate 224 is required to uniformly transmit light to the front surface. The light guide plate 224 is generally made of a transparent acrylic resin such as polymethyl methacrylate (hereinafter referred to as "PMMA"). The PMMA is characterized by high strength, low cracking, low deformation, and high visible light transmittance.

In addition, the light guide plate 224 propagates light toward the liquid crystal panel 210.

The optical film 228 may include a brightness enhancing sheet 228a, and may further include a protective sheet 228b.

Light emitted from the light guide plate 224 toward the liquid crystal panel 210 passes through the brightness enhancement sheet 228a. The brightness enhancement sheet 228a not only collects and diffuses light incident from the light guide plate 224, It prevents partial compaction and makes luminance uniform.

Accordingly, the light passing through the brightness improving sheet 228a mostly proceeds perpendicularly to the plane of the liquid crystal panel 210 to have a uniform brightness distribution. The detailed structure of the brightness improving sheet 228a is mentioned later.

The protective sheet 228b is positioned on the brightness improving sheet 228a to prevent scratches of the brightness improving sheet 228a, and serves to widen the viewing angle narrowed by the brightness improving sheet 228a.

Meanwhile, in the present embodiment, the optical film 228 is made of the brightness improving sheet 228a and the protective sheet 228b. However, the optical film 228 may be configured to include a diffusion sheet instead of the protective sheet 228b.

As such, the optical film may include a diffusion sheet (not shown) and a brightness enhancement sheet 228a.

In this case, light emitted from the light guide plate 224 toward the liquid crystal panel 210 passes through the diffusion sheet, which diffuses the light incident from the light guide plate 224 to prevent the light from being partially concentrated. Make luminance uniform.

The light passing through the diffusion sheet is rapidly lowered in brightness, and the brightness enhancement sheet 228a compensates for the light.

Hereinafter, the structure of the brightness improving sheet 228a is explained in full detail.

4A and 4B are a perspective view and a cross-sectional view showing the structure of the brightness enhancement sheet used in the backlight device of FIG.

4A and 4B, the brightness enhancing sheet 228a includes a prism shape 310 and a diffusion 320 formed on the base film 300.

The prism shape 310 includes a plurality of prisms formed side by side over the entire surface of the base film 300. The prism is approximately triangular in shape. The shape of the prism is composed of an equilateral triangle, an isosceles triangle, an isosceles triangle, and the like, and the vertex angle of the prism generally forms an angle of 90 °, but may be configured differently according to a selection.

For example, the prism may be formed in a triangular shape having a base of about 60 μm and a height of about 30 μm, as shown in FIG. 4B.

The prism shape portion 310 is formed with a plurality of prisms in series to alternately form valleys and peaks. The prism-shaped portion 310 configured as described above refracts light incident through the base film 300. As a result, light incident at a low angle is concentrated toward the front, thereby increasing luminance in the effective viewing angle range.

The diffuser 320 is formed between the prisms of the prism shape 310.

In addition, since the diffusion part 320 fills between the prisms using the resin 322 including the plurality of diffusion particles 324, the upper surface of the brightness improving sheet 228a is generally flat.

The light collected by the prism shape 310 is scattered by the diffuser particles 324 while passing through the diffuser 320 to diffuse the light toward the entire surface of the brightness improving sheet 228a. This prevents the light from partially condensing, makes the luminance uniform, and improves the viewing angle.

For example, the diffusion particles 324 are composed of beads having a diameter of about 3 μm, and made of polystyrene.

The polystyrene is a transparent resin, which is the most easily processed among plastics, and has a high refractive index of about 1.55.

As such, when the diffusion particles 324 are formed of the polystyrene, the diffusion particles 324 may be processed to a size of 3 μm.

Resin 322 uses UV curable resin, for example.

In addition, in the diffusion part 320 of the present invention, the refractive index n2 of the diffusion particles 324 and the refractive index n3 of the resin 322 are substantially the same (n2 ≒ n3). As the refractive index n2 of the diffusion particles 324 and the refractive index n3 of the resin 322 are similar, the light may pass through the diffusion portion 320 without loss of light.

Preferably, the difference between the refractive index n2 of the diffusion particles 324 and the refractive index n3 of the resin 322 is 0.1 or less (| n2-n3 | ≤0.1).

In addition, the refractive index n1 of the prism is larger than the refractive index n3 of the resin 322 (n1> n3).

This is because when the light emitted from the prism shape portion 310 is incident on the diffusion portion 320, the refractive index n3 of the resin 322 is smaller than the prism refractive index n1 of the prism shape portion 310. This is because light may be refracted toward the front of 228a).

As described above, the difference between the refractive index n2 of the diffusion particle 324 and the refractive index n3 of the resin 322 is smaller than the difference between the refractive index n3 of the resin 322 and the refractive index n1 of the prism (| n2). -n3 | <| n3-n1 |).

The larger the number of diffusion particles 324 per unit volume, the better the diffusion effect.

Hereinafter, the manufacturing method of the brightness improving sheet 228a is explained in full detail.

5A and 5B are cross-sectional views illustrating a manufacturing process of the brightness improving sheet of FIGS. 4A and 4B.

First, as illustrated in FIG. 5A, a resin 322 including diffusion particles 324 is coated on a base film 300 on which a prism shape portion 310 is formed.

Subsequently, the resin 322 including the diffused particles 324 is pressed with a roller to fill the resin 322 including the diffused particles 324 between the prisms of the prism shape 310, and the surface thereof. Planarize.

Subsequently, the resin 322 including the diffusion particles 324 is cured. When the resin 322 is a UV curable resin, ultraviolet rays are irradiated for a predetermined time to cure the resin 322.

As a result, the brightness enhancing sheet 228a as shown in FIG. 5B is formed.

Hereinafter, the light emission operation of the LCD element 200 will be described in detail.

Referring to FIGS. 2 and 3 again, the backlight device 220 provides the planar light, which is white light, to the liquid crystal panel 210.

Subsequently, the TFT array 213 switches the pixel electrode 214.

Subsequently, a predetermined voltage difference is applied between the pixel electrode 214 and the common electrode 215, and as a result, the liquid crystal layer 216 is arranged corresponding to the red color filter, the green color filter, and the blue color filter, respectively.

In this case, the light provided from the backlight device 220 passes through the liquid crystal layer 216, and the light amount is adjusted, and the light with the adjusted light amount is provided to the color filter 212.

As a result, the color filter 212 implements an image with a predetermined gray scale.

In detail, the red color filter, the green color filter, and the blue color filter form one pixel, and the pixels implement a predetermined image by a combination of light passing through the red color filter, the green color filter, and the blue color filter. do.

Meanwhile, the light may be provided to the liquid crystal panel 210 using the backlight device of the direct type in addition to the above-described edge-light backlight device 220.

6 is a cross-sectional view illustrating a backlight device of a direct type according to another embodiment of the present invention.

Referring to FIG. 6, the backlight device 420 is driven in a direct light method and includes a light source 422, a transparent plate 424, a reflective sheet 426, and an optical film 428. do.

The light source 422 is formed by a plurality of cold cathode fluorescent lamps (CCFL). The CCFL is a lamp that provides very bright white light.

In addition to the CCFL, the light source 422 may include a light emitting diode (LED) or an external electrode fluorescent lamp (EEFL).

The LED can be composed of red, green and blue or a single color of white light. In the case of the backlight device 420 using the LED as a light source, it is possible to maintain the uniformity of the light while miniaturizing the backlight device 420 and improving the light efficiency.

The EEFL has a higher luminance than the CCFL and is advantageous in that the electrode is external to operate in parallel. In particular, the EEFL can reduce the number of inverters required by the conventional light source, thereby reducing the cost of components and the weight of the LCD module.

The reflective sheet 426 is positioned under the light source 422 to reflect light from the light source 422 to the front surface of the transparent plate 424. Reflective sheet 426 according to an embodiment of the present invention is coated on a silver (silver) on a sheet made of SUS, Brass, aluminum, PET, etc., even if the heat is generated fine titanium coating to prevent deformation due to endothermic long time Can be produced. In addition, the reflective sheet 426 according to another embodiment of the present invention may be manufactured by dispersing bubbles for scattering light on a sheet made of synthetic resin such as PET.

On the other hand, the light source 422 is mounted by placing a light source reflector (not shown) below the light source 422 instead of the reflective sheet 426, and the light emitted from the light source 422 is incident on the brightness enhancement sheet 428a to emit light. It can also be configured to improve the efficiency. The light source reflector is made of a highly reflective material, and may be coated with silver (Ag) on the surface.

The transparent plate 424 passes light incident from the light source 422. The transparent plate 424 may be a transparent acrylic plate, and it is preferable to use polymethyl methacrylate (PMMA) as the transparent acrylic plate.

Unlike the edge-lighting method of the backlight device 420 of the direct method, since the plurality of light sources 422 are positioned under the liquid crystal panel 210, the bright lines generated from the light source 422 are disposed on the upper part of the liquid crystal panel 210. It appears in a pattern. The transparent plate 424 has a pattern, and serves to pass light while removing bright lines generated from the light source 422. However, of course, the backlight device 420 according to the present invention may use a transparent plate on which a pattern is not formed.

The optical film 428 may include a brightness enhancing sheet 428a and optionally further include a protective sheet 428b.

Light emitted from the transparent plate 424 toward the liquid crystal panel 210 passes through the brightness enhancement sheet 428a. The brightness enhancement sheet 428a not only collects and disperses the light incident from the transparent plate 424. It prevents the light from partially condensing and makes the luminance uniform.

Accordingly, most of the light passing through the brightness enhancing sheet 428a proceeds perpendicularly to the plane of the liquid crystal panel 210 to have a uniform brightness distribution. Since the detailed structure of the brightness improving sheet 428a is the same as that mentioned above, description is abbreviate | omitted below.

The protective sheet 428b is positioned on the brightness improving sheet 428a to prevent scratches of the brightness improving sheet 428a, and also serves to widen the viewing angle narrowed by the brightness improving sheet 428a.

Meanwhile, in the present exemplary embodiment, the optical film 428 is made of the luminance improving sheet 428a and the protective sheet 428b. However, the optical film 428 may be configured to include a diffusion sheet instead of the protective sheet 428b.

As such, the optical film may include a diffusion sheet (not shown) and a brightness enhancement sheet 428a.

In this case, the light emitted from the transparent plate 424 toward the liquid crystal panel 210 passes through the diffusion sheet, which diffuses the light incident from the transparent plate 424 to partially condense the light. Prevent and make the luminance uniform.

The light passing through the diffusion sheet is suddenly lowered in brightness, and the brightness enhancement sheet 428a compensates for the light.

Preferred embodiments of the present invention described above are disclosed for purposes of illustration, and those skilled in the art having various ordinary knowledge of the present invention may make various modifications, changes, and additions within the spirit and scope of the present invention. Additions should be considered to be within the scope of the following claims.

As described above, the brightness enhancing sheet and the backlight device including the same improve the brightness and the viewing angle by performing both the light condensing and the diffusing functions of the incident light by using the diffuser formed of the diffuser particles between the prisms. The advantage is that you can.

In addition, the backlight device according to the present invention may not use a diffusion sheet or a protective sheet by configuring an optical film as a brightness enhancement sheet having a light condensing and diffusing function, and may reduce the thickness and manufacturing cost of the optical film. have.

Claims (11)

Base film; A prism shape formed of a plurality of prisms arranged side by side on the base film; And And at least one diffuser particle and a resin, said diffuser formed between said prisms of said prism shape. The method of claim 1, The diffusion particle is a brightness improving sheet, characterized in that the beads made of polystyrene. The method of claim 1, Said resin is UV curable resin, The brightness improving sheet characterized by the above-mentioned. The method of claim 1, And a refractive index (n2) of the diffusion particles and a refractive index (n3) of the resin are substantially the same (n2? N3). The method of claim 1, The difference between the refractive index (n2) of the diffusion particles and the refractive index (n3) of the resin is 0.1 or less (| n2-n3 | ≤0.1) characterized in that the brightness enhancement sheet. The method of claim 1, The difference between the refractive index n2 of the diffusion particle and the refractive index n3 of the resin is smaller than the difference between the refractive index n3 of the resin and the refractive index n1 of the prism (| n2-n3 | <| n3-n1 |) A brightness enhancing sheet characterized by the above. The method of claim 1, And a refractive index (n1) of the prism is larger than the refractive index (n3) of the resin (n1> n3). A light source emitting light of a predetermined wavelength; A light guide plate uniformly transmitting the light generated from the light source; And Including a brightness enhancement sheet for condensing and diffusing light emitted through the light guide plate, the brightness enhancement sheet, Base film; A prism shape formed of a plurality of prisms arranged side by side on the base film; And And at least one diffuser particle and a resin, and comprising a diffuser formed between the prisms of the prism shape. The method of claim 8, The diffusion particles are beads made of polystyrene, and the resin is a UV curable resin. A light source emitting light of a predetermined wavelength; A transparent plate through which light emitted from the light source passes; And A brightness enhancement sheet for condensing and diffusing light emitted from the transparent plate, wherein the brightness enhancement sheet, Base film; A prism shape formed of a plurality of prisms arranged side by side on the base film; And And at least one diffuser particle and a resin, and comprising a diffuser formed between the prisms of the prism shape. The method of claim 10, The diffusion particles are beads made of polystyrene, and the resin is a UV curable resin.

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