KR20070109125A - Diffusing plate, back light unit and liquid crystal display having the same - Google Patents

Abstract

A backlight unit and an LCD comprising the same are provided to widen the angles of lights emitted from LEDs(Light Emitting Diodes) using a light diffusing plate to make it unnecessary to increase the distance between the light diffusing plate and the LEDs to reduce the thickness of the backlight unit and form a wide white region. A plurality of LEDs(106) is disposed at the rear of an LCD panel(112) to supply lights to the LCD panel. A light diffusing plate(108) is disposed above the LEDs to increase the angles of the lights emitted from the LEDs. The light diffusing plate includes a light input surface and a light output surface facing the light input surface. The light input surface has a plurality of grooves arranged along the LEDs. In the light diffusing plate, the light inputted through the light input surface is diffused and outputted through the light output surface.

Description

Diffusion plate, backlight unit and liquid crystal display device having the same {DIFFUSING PLATE, BACK LIGHT UNIT AND LIQUID CRYSTAL DISPLAY HAVING THE SAME}

1A is a partial cross-sectional view of a conventional liquid crystal display device having a light emitting diode.

FIG. 1B is a plan view illustrating a state in which a light emitting diode is disposed in the backlight unit of FIG. 1A.

2 is a partial cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.

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

4 is a cross-sectional view showing a diffusion plate according to an embodiment of the present invention.

5 is a cross-sectional view showing a diffusion plate according to another embodiment of the present invention.

6 is a cross-sectional view showing a diffusion plate according to another embodiment of the present invention.

The present invention relates to a direct type backlight unit using a light emitting diode and a liquid crystal display device having the same. In addition, the present invention also relates to a diffuser plate having a new structure capable of forming a white region at a short distance from the light emitting diode as compared with the related art by enlarging the angle of light emitted from the light emitting diode.

In general, a liquid crystal display 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.

Liquid crystal display has been attracting attention as an alternative means to overcome the shortcomings of the CRT (Cathode Ray Tube), which has been widely used since it has the advantages of miniaturization, light weight, low power consumption, etc. Is installed in almost all information processing equipment.

Such liquid crystal displays generally apply a voltage to a liquid crystal having a specific molecular array and change it to another molecular array, and optical properties such as birefringence, photoreactivity, dichroism, and light scattering characteristics of the liquid crystal generated by the change of the molecular array. It is a display device that converts the change of the light into a visual change and uses modulation of light by liquid crystal.

A liquid crystal display device, which is a light-receiving element without a self-luminous source, requires a separate light source device capable of illuminating the entire screen of the device from the back side. Such an illumination device for a liquid crystal display device is commonly referred to as a backlight unit.

In the conventional backlight unit, an elongated cylindrical Cold Cathode Fluorescent Lamp (CCFL) is mainly used as a light source, and the backlight unit is an edge-light method according to the method in which the cold cathode fluorescent lamp is disposed. ) And direct lighting methods.

The edge-light method is a method in which a light emitting light source is disposed on a side of a light guide plate for guiding light generated from a light emitting light source, and is applied to a comparatively small liquid crystal display device such as a desktop computer or a laptop monitor. It is excellent in durability and advantageous in thinning the device. On the other hand, the direct method has been developed for use in medium and large display devices of 20 inches or more, and a method of directly illuminating the front of the liquid crystal panel by arranging a plurality of light sources under the liquid crystal panel.

The direct type is mainly used for a large screen liquid crystal display device requiring high luminance because the light utilization efficiency is higher than that of the edge-light type.

However, the liquid crystal display device adopting the direct method is used as a large monitor or a TV, which takes longer to use than a laptop computer and has a larger number of lamps. In the liquid crystal display of the lamp, the failure of the lamp and the lifetime of the lamp is more likely to appear that does not turn on.

On the other hand, in recent years, instead of the cold-cathode fluorescent lamp which was widely used as a light source, the light emitting diode (LED) is tending to be adopted. Light emitting diodes are more environmentally friendly than cold cathode fluorescent lamps, have excellent color reproducibility and contrast, and further have partial luminance control (adjusting the bright and dark areas).

FIG. 1A is a partial cross-sectional view of a conventional liquid crystal display device having a light emitting diode, and FIG. 1B is a plan view for explaining how the light emitting diode is disposed in the backlight unit of FIG. 1A.

1A and 1B, a conventional liquid crystal display device includes a liquid crystal panel 22 and a backlight unit 10 that illuminates the liquid crystal panel 22 from a rear surface of the liquid crystal panel 22.

In understanding and practicing the present invention, the specific structure of the liquid crystal panel 22 is not important. Therefore, the basic structure of the liquid crystal panel 22 will be described within the range necessary for understanding the present invention.

The liquid crystal panel 22 generally includes a pair of transparent substrates, a liquid crystal layer interposed between the transparent substrates, a color filter formed on each of the transparent substrates, a black matrix, a pixel electrode, a common electrode, and a TFT array.

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

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

The common electrode and the pixel electrode convert the arrangement of the molecules of the liquid crystal layer according to a predetermined voltage applied from the outside.

The liquid crystal layer is composed of a plurality of liquid crystal molecules, the liquid crystal molecules change the arrangement corresponding to the voltage difference generated between the pixel electrode and the common electrode, whereby the light provided from the backlight unit is the molecular arrangement of the liquid crystal layer The incident on the color filter corresponds to the change of.

The backlight unit 10 is disposed under the plurality of light emitting diodes 16 and the light emitting diodes 16 that emit light of any one color of red (R), green (G), or blue (B). A printed circuit board 14 for applying power to the diode, a bottom chassis 12 on which the printed circuit board 14 on which the light emitting diode 16 is mounted is mounted, and the plurality of light emitting diodes The diffuser plate 18 and the light, which serve to diffuse the light generated from the light source 16, are applied to the visible surface of the liquid crystal panel 22. At least one optical sheet 20 for uniformly delivering.

In addition, the liquid crystal panel 22 and the backlight unit 10 are supported by the guide panel 17 and fixed by the top case 19.

As described above, the light emitting diodes 16 generate light of red, green or blue color, and are sequentially arranged as shown in FIG. 1B, for example. The arrangement shown in FIG. 1B is presented by way of example only, and various arrangements are possible in addition to the manner shown to obtain white light.

On the other hand, white light is generated in a region in which light of red, green, and blue colors are mixed. Although the light emitting diode 160 is slightly different depending on its structure, a light emission angle ( θ ) of a limited range of about 120 ° is obtained. ), The white area where white light is actually expressed is limited to the area indicated by the hatched line in FIG. 1A.

Therefore, in order to obtain a wider white area, the distance between the light emitting diode 16 and the diffusion plate 18 is increased or a lens is formed on the light emitting diode 16 using a transparent resin such as polymethyl methacrylate. Attempts have been made in the past to attempt to enlarge the emission angle [ theta ] of light.

However, when the distance between the light emitting diode 16 and the diffuser plate 18 is increased, there is a problem that the device becomes thick. In addition, when the lens is formed on the upper portion of the light emitting diode 16, the light emission angle θ may be enlarged, but another problem that color reproducibility is lowered occurs.

Therefore, there is a need to develop a display device that can obtain a wider white area than conventionally, while maintaining the color reproducibility of the light emitting diode and thinning the device.

The present invention is to solve the problems of the prior art as described above, to provide a direct type backlight unit using a light emitting diode that can form a white region over a wide range of thin thickness and a liquid crystal display device having the same The purpose.

In addition, the present invention provides a diffuser plate provided in the direct type backlight unit having a structure capable of efficiently mixing the three colors of red, green, and blue light emitted from the light emitting diode to form a white region over a wide range. For other purposes.

In the first aspect of the present invention, the present invention provides a backlight unit for illuminating a liquid crystal panel. The backlight unit includes a plurality of light emitting diodes providing light for illuminating the liquid crystal panel from the rear of the liquid crystal panel, and a diffuser plate disposed above the light emitting diodes and enlarging an angle of light emitted from the light emitting diodes. do. In addition, the diffusion plate is a surface on which light emitted from the light emitting diode is input, and faces a light input surface and a light input surface having a plurality of grooves extending along a direction in which the light emitting diodes are arranged. It includes a light output surface structured so that light input through the input surface is scattered and output.

Here, the backlight unit according to the first aspect of the present invention may be disposed below the light emitting diode, and may further include a printed circuit board for applying power to the light emitting diode.

In addition, the backlight unit according to the first aspect of the present invention is disposed on an upper portion of the diffusion plate and receives light output from the diffusion plate on a visible surface of the liquid crystal panel. It may further include at least one or more optical sheets for uniformly delivering.

On the other hand, in the backlight unit according to the first aspect of the present invention, the diffusion plate is preferably made of polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyethylene naphthalate or polyimide.

The light output surface of the diffusion plate may include a plurality of convex portions arranged regularly or irregularly.

In a second aspect of the present invention, the present invention provides a backlight unit for illuminating a liquid crystal panel. The backlight unit may include a plurality of light emitting diodes providing light for illuminating the liquid crystal panel from a rear side of the liquid crystal panel and a diffusion plate disposed above the light emitting diodes and expanding an angle of light emitted from the light emitting diodes. Include. The diffusion plate is a layer through which light emitted from the light emitting diode is input, and is disposed on the first diffusion layer and the first diffusion layer having a plurality of grooves formed on a bottom thereof and extending along a direction in which the light emitting diodes are arranged. And a second diffusion layer made of a base material made of a resin that can transmit light and a plurality of beads arranged to be dispersed in the base material and capable of scattering light input to the base material.

Here, the backlight unit according to the second aspect of the present invention may be disposed below the light emitting diode, and may further include a printed circuit board for applying power to the light emitting diode.

In addition, the backlight unit according to the second aspect of the present invention is disposed on an upper portion of the diffusion plate and receives light output from the diffusion plate on a visible surface of the liquid crystal panel. It may further include at least one or more optical sheets for uniformly delivering.

On the other hand, in the backlight unit according to the second aspect of the present invention, the first diffusion layer of the diffusion plate is preferably made of polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyethylene naphthalate or polyimide.

In this case, the beads of the second diffusion layer may be arranged regularly, and at least some of the beads of the second diffusion layer may have different sizes.

In the third aspect of the present invention, the present invention relates to a liquid crystal panel and a liquid crystal panel that display an image by controlling the amount of light transmitted to be changed by changing the arrangement of liquid crystal molecules of the liquid crystal layer according to an electrical signal applied from the outside. Provided is a liquid crystal display including a backlight unit for providing light input to the liquid crystal panel from the rear. The backlight unit may include a plurality of light emitting diodes providing light for illuminating the liquid crystal panel from a rear side of the liquid crystal panel, and a surface into which light emitted from the light emitting diodes is input, and extends along a direction in which the light emitting diodes are arranged. A diffusion plate including a light input surface having a plurality of grooves formed therein and a light output surface facing the light input surface and configured to scatter and output light input through the light input surface; Take the visible side of the liquid crystal panel At least one or more optical sheets for uniform delivery.

On the other hand, in the liquid crystal display device according to the third aspect of the present invention, the diffusion plate is preferably made of polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyethylene naphthalate or polyimide.

In addition, the light output surface of the diffusion plate may include a plurality of convex portions arranged regularly or irregularly.

In the fourth aspect of the present invention, the present invention provides a liquid crystal panel for controlling an amount of light transmitted and displaying an image by changing an arrangement of liquid crystal molecules in a liquid crystal layer according to an electrical signal applied from the outside, and a rear of the liquid crystal panel. The present invention provides a liquid crystal display including a backlight unit for providing light input to the liquid crystal panel. Here, the backlight unit is a plurality of light emitting diodes for providing light for illuminating the liquid crystal panel from the rear of the liquid crystal panel, and a layer into which light emitted from the light emitting diodes is input, and the direction in which the light emitting diodes are arranged on a bottom surface thereof It is disposed on the first diffusion layer and the first diffusion layer formed with a plurality of grooves extending along, the base material made of a resin that can transmit light and is dispersed in the base material and can scatter the light input to the base material A diffusion plate including a second diffusion layer made up of a plurality of beads, and receiving light from the diffusion plate on a visible surface of the At least one or more optical sheets for uniform delivery.

In the liquid crystal display according to the fourth aspect of the present invention, the first diffusion layer of the diffusion plate may be made of polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyethylene naphthalate or polyimide.

Meanwhile, in the liquid crystal display according to the fourth aspect of the present invention, the beads of the second diffusion layer of the diffusion plate may be arranged regularly, and at least some of the beads of the second diffusion layer may have different sizes. Can be.

In the fifth aspect of the present invention, the present invention provides a light input surface, which is opposed to the light input surface and the light input surface having a plurality of grooves extending along one direction, and is input through the light input surface. Provided is a diffuser plate comprising a light output surface structured such that the light is scattered and output.

 Here, the diffusion plate may be made of polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyethylene naphthalate or polyimide.

In addition, the light output surface may include a plurality of convex portions arranged regularly or irregularly.

In the sixth aspect of the present invention, the present invention is a layer into which light is input, and is disposed on the first diffusion layer and the first diffusion layer having a plurality of grooves extending in one direction on a bottom thereof, and light is transmitted therethrough. Provided is a diffusion plate comprising a base material made of a resin and a second diffusion layer made up of a plurality of beads which are dispersed and disposed on the base material and can scatter light input to the base material.

Here, the first diffusion layer of the diffusion plate is preferably made of polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyethylene naphthalate or polyimide.

In addition, the beads of the second diffusion layer may be arranged regularly, and at least some of the beads of the second diffusion layer may be different in size.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

2 is a partial cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention. 3 is a cross-sectional view illustrating an example of the liquid crystal panel of FIG. 2, and FIG. 4 is a cross-sectional view illustrating a diffusion plate according to an embodiment of the present invention.

2 to 4, the liquid crystal display according to the exemplary embodiment of the present invention illuminates the liquid crystal panel 112 and the liquid crystal panel 112 displaying an image according to a driving signal and a data signal applied from the outside. In order to include a backlight unit 100 disposed on the rear of the liquid crystal panel.

In understanding and implementing the present invention, the precise structural characteristics of the liquid crystal panel 112 are not important, and the spirit of the present invention may be widely applied to any structure of the liquid crystal panel commonly used in the liquid crystal display device. Therefore, the structure of the liquid crystal panel 112 described below is merely provided as an example for understanding the present invention.

The liquid crystal panel 112 includes an upper substrate 113a and a lower substrate 113b, a color filter 116, a black matrix 115, a pixel electrode 120, a common electrode 116, a liquid crystal layer 121, and a TFT array. 119, and a pair of polarizing films 113a and 113b are disposed on both surfaces of the liquid crystal panel 112.

The color filter 116 includes color filters corresponding to red (R), green (G), and blue (B). When the light is applied, the color filter 116 generates an image corresponding to the color of red, green, or blue.

The TFT array 119 switches the pixel electrode 120 as a switching element.

The common electrode 116 and the pixel electrode 120 convert the arrangement of the molecules of the liquid crystal layer 121 according to a predetermined voltage applied from the outside.

The liquid crystal layer 121 is composed of a plurality of liquid crystal molecules, and the liquid crystal molecules change an arrangement in correspondence to a voltage difference generated between the pixel electrode 120 and the common electrode 116, whereby the backlight unit ( Light provided from 100 is incident on the color filter 116 in response to a change in the molecular arrangement of the liquid crystal layer 121.

The backlight unit 100 is positioned at the rear of the liquid crystal panel 112 and provides light, for example, white light, to the liquid crystal panel 112.

The backlight unit 100 includes a plurality of light emitting diodes 106 generating red, green, or blue light, a printed circuit board 104 disposed below the plurality of light emitting diodes 106, and a bottom on which the printed circuit boards are installed. And a diffuser plate 108 and an optical sheet 110 for diffusing or condensing the light generated from the plurality of light emitting diodes 106 and transmitting the light to the liquid crystal panel 112, wherein the light source is a liquid crystal panel 112. It is driven in a direct manner arranged at the bottom of the).

In addition, as shown in FIG. 2, the liquid crystal panel 112 is disposed on the upper portion of the backlight unit 100, and the liquid crystal panel 112 and the backlight unit 100 are supported by the guide panel 107. 109 is fixed.

The light emitting diodes 102 generate red, green, and blue light, and are sequentially arranged in one direction on the printed circuit board 104.

The printed circuit board 104 supports the plurality of light emitting diodes 106 and controls the light emission of the plurality of light emitting diodes 106 by a circuit configured therein. In the printed circuit board 104, a metal core printed circuit board (MCPCB), which is a printed circuit board for a light emitting diode array, is preferably used.

The backlight unit 100 according to the exemplary embodiment includes a diffusion plate 108 and an optical sheet 110 disposed between the plurality of light emitting diodes 106 and the liquid crystal panel 112. They uniformly mix the red, green and blue light emitted from the plurality of light emitting diodes 106 and convert it into white light. In addition, the light is effectively incident on the visible surface of the liquid crystal panel 112 to improve the brightness, and the light is uniform so that the entire surface of the liquid crystal panel 112 visible surface has a uniform luminance distribution.

The diffusion plate 108 according to an embodiment of the present invention receives the red, green, and blue color light generated from the plurality of light emitting diodes 106 and mixes them into white light, and converts the light into a wide range of gradients. The light is diffused to be incident on the optical sheet 110 disposed thereon.

The diffusion plate 108 includes a light input surface 140 through which light emitted from the plurality of light emitting diodes 106 is input, and a light output surface 130 facing the light input surface and outputting the input light. .

Here, the light input surface 130 is formed with a plurality of grooves 142 extending along the direction in which the plurality of light emitting diodes 106 are arranged, the groove 142 is a plurality of light emission as shown in FIG. The light incident from the diode 106 serves to enlarge the angular range. As a result, an area in which the three colors of red, green, and blue are mixed, that is, the white area can be greatly expanded.

In one embodiment of the present invention, the plurality of grooves 142 are formed in one direction along a direction in which a plurality of light emitting diodes 106 generating red, green, and blue light are sequentially arranged.

In another embodiment of the present invention, the plurality of grooves 142 may be formed along a direction in which the plurality of light emitting diodes 106 are sequentially arranged, or may be formed in a direction orthogonal thereto.

The light output surface 130 is structured so that light input through the light input surface 140 is scattered and output. That is, as illustrated, a plurality of convex portions 132 that may scatter light input through the light input surface 140 may be disposed over the entire light output surface 130. As a result, the light emitted through the light output surface 130 may have a slope of a wide distribution. The plurality of convex portions 132 may be regularly arranged on the light output surface 130 in the same shape and size, or may be irregularly arranged on the light output surface 130 in different sizes and shapes.

The diffusion plate 108 having the above structure may be manufactured by injection molding using a thermoplastic material known in the art.

The diffusion plate 108 is preferably made of a thermoplastic material having excellent light transmittance and excellent thermal and mechanical stability. Preferably, the diffuser plate 108 is comprised of polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyethylene naphthalate or polyimide.

Hereinafter, another embodiment of the diffusion plate of the present invention will be described with reference to the drawings.

5 is a cross-sectional view showing a diffusion plate according to another embodiment of the present invention, Figure 6 is a cross-sectional view showing a diffusion plate according to another embodiment of the present invention.

First, referring to FIG. 5, in another embodiment of the present invention, the diffusion plate 208 includes a first diffusion layer 240 and a second diffusion layer 230 disposed on the first diffusion layer.

The first diffusion layer 240 is a layer through which light emitted from a plurality of light emitting diodes (106 in FIG. 2) disposed under the first diffusion layer 240 is formed. It includes a plurality of grooves (241).

The groove 241 formed on the bottom of the first diffusion layer 240 serves to enlarge the angular range of light incident from the bottom as shown. As a result, a region where three colors of red, green, and blue incident from the bottom are mixed, that is, the white region can be greatly expanded.

The plurality of grooves 241 may have various arrangements according to the arrangement of the light emitting diodes disposed at the bottom thereof. For example, in the present embodiment, the plurality of grooves 241 are formed in one direction along a direction in which a plurality of light emitting diodes generating red, green, and blue light are sequentially arranged. However, in another embodiment of the present invention, the plurality of grooves 241 may be formed along the direction in which the plurality of light emitting diodes are sequentially arranged, and may also be formed in the direction orthogonal thereto.

The first diffusion layer 240 having the above structure may be manufactured by injection molding using a thermoplastic material known in the art.

The first diffusion layer 240 is basically composed of a thermoplastic material having excellent light transmittance and excellent thermal and mechanical stability. Preferably, the first diffusion layer 240 is composed of polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyethylene naphthalate or polyimide.

The second diffusion layer 230 is disposed above the first diffusion layer 240, and includes a base material 231 made of a resin that can transmit light and a plurality of beads 232 dispersed and disposed in the base material.

Here, the plurality of beads 232 serves as a kind of diffuser for scattering the input light to output the light with a wide range of inclination, the base material 231 is a bead (top) on the first diffusion layer 240 232).

The second diffusion layer 240 may be obtained by applying a mixture prepared by dispersing a plurality of beads 232 in a liquid resin to the upper portion of the first diffusion layer 240 and curing it. The liquid resin applied to the upper portion of the first diffusion layer 240 is cured to form the base material 231.

As the liquid resin, an acrylic resin having excellent heat resistance and mechanical properties can be used. Preferably, the acrylic resin is polyacrylate or polymethyl methacrylate. Also preferably, the liquid resin is a UV curable resin.

The beads 232 may be manufactured using the same type or different types of resins as the base material 231, and preferably include 25 wt% to 35 wt% with respect to the base material 231, most preferably for the base material. The weight ratio of the beads is 30wt%.

In this embodiment, the size and distribution of the beads 232 are random. When the beads 232 of various sizes are irregularly distributed in the base material 231, the haze effect may increase, and thus uniformity of light may be improved.

Hereinafter, a diffusion plate according to another embodiment of the present invention will be described with reference to the drawings. However, the portions corresponding to each other will not be repeatedly described in detail.

Referring to FIG. 6, in another embodiment of the present invention, the diffusion plate 308 includes a first diffusion layer 340 and a second diffusion layer 330 disposed on the first diffusion layer.

 The first diffusion layer 340 is a layer through which light emitted from a plurality of light emitting diodes (106 of FIG. 2) disposed below the input layer, and extends along a direction in which a plurality of light emitting diodes 106 are arranged on a bottom surface thereof. It includes a plurality of grooves 341. The first diffusion layer 340 corresponds to the first diffusion layer 240 of the diffusion plate 208 described above with reference to FIG. 5.

The second diffusion layer 330 is disposed on the first diffusion layer 340, and includes a base material 331 made of a resin that can transmit light and a plurality of beads 332 dispersed and disposed in the base material. The second diffusion layer 330 corresponds to the second diffusion layer 230 of the diffusion plate 208 shown in FIG. 5, but is characterized in that the beads 332 are regularly distributed in the second diffusion layer 330. have.

When the same size beads 332 are regularly distributed, the haze effect is somewhat reduced compared to the case of irregular distribution, but the luminance can be increased relatively.

Referring back to FIG. 2, at least one optical sheet 110 which concentrates or diffuses light on the diffusion plate 108 to improve light utilization efficiency and provides uniform light to the liquid crystal panel 112. It may be provided.

However, in understanding and practicing the present invention, the exact structural and material properties of the optical sheet 110 are not critical, and the optical sheet 110 using any structure and material conventionally used in a backlight unit may be used. Ideas can be applied broadly. For example, at least one prism sheet having a plurality of microprism arrays generally provided in a conventional backlight may be provided on the diffusion plate 108. In addition, a protective sheet may be provided that is disposed on top of the prism sheet to protect the prism array of the prism sheet and to enlarge the viewing angle reduced by the prism sheet again.

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

According to the present invention, since the angle of light emitted from the light emitting diode is increased by the diffusion plate, it is not necessary to increase the distance between the light emitting diode and the diffusion plate. Accordingly, there is an advantage in that a direct backlight unit using a light emitting diode and a liquid crystal display device having the same may be obtained using a light emitting diode capable of forming a white region over a wide range while having a small thickness of the device.

Claims (25)

A backlight unit for illuminating a liquid crystal panel, A plurality of light emitting diodes providing light for illuminating the liquid crystal panel from the rear of the liquid crystal panel; And It is disposed on the light emitting diode, and includes a diffusion plate for expanding the angle of light emitted from the light emitting diode, The diffusion plate includes a light input surface on which light emitted from the light emitting diode is input, the light input surface having a plurality of grooves extending along a direction in which the light emitting diodes are arranged; And And a light output surface facing the light input surface and configured to scatter and output light input through the light input surface. The backlight unit of claim 1, further comprising a printed circuit board disposed under the light emitting diode and configured to apply power to the light emitting diode. The liquid crystal display device of claim 1, wherein the light is emitted from the diffuser plate and is disposed on a visible surface of the liquid crystal panel. A backlight unit further comprising at least one optical sheet for uniformly delivering. The backlight unit of claim 1, wherein the diffusion plate is made of polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, or polyimide. The backlight unit of claim 1, wherein the light output surface comprises a plurality of convex portions arranged regularly or irregularly. A backlight unit for illuminating a liquid crystal panel, A plurality of light emitting diodes providing light for illuminating the liquid crystal panel from the rear of the liquid crystal panel; And It is disposed on the light emitting diode, and includes a diffusion plate for expanding the angle of light emitted from the light emitting diode, The diffusion plate, A first diffusion layer in which light emitted from the light emitting diode is input, the first diffusion layer having a plurality of grooves formed on a bottom thereof extending in a direction in which the light emitting diodes are arranged; And A base material disposed on the first diffusion layer and made of a resin that can transmit light; And a second diffusion layer disposed on the base material, the second diffusion layer comprising a plurality of beads capable of scattering light input to the base material. The backlight unit of claim 6, further comprising a printed circuit board disposed under the light emitting diode and configured to apply power to the light emitting diode. The liquid crystal display of claim 6, wherein the light is disposed on the diffuser plate and receives light output from the diffuser plate. A backlight unit further comprising at least one optical sheet for uniformly delivering. The backlight unit of claim 6, wherein the first diffusion layer of the diffusion plate is made of polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, or polyimide. The backlight unit of claim 6, wherein the beads of the second diffusion layer are arranged regularly. The backlight unit of claim 6, wherein at least some of the beads of the second diffusion layer have different sizes. A liquid crystal panel which displays an image by controlling an amount of light transmitted through changing an arrangement of liquid crystal molecules of a liquid crystal layer according to an electrical signal applied from the outside; And It includes a backlight unit for providing light input to the liquid crystal panel from the rear of the liquid crystal panel, The backlight unit, A plurality of light emitting diodes providing light for illuminating the liquid crystal panel from the rear of the liquid crystal panel; A light input surface on which light emitted from the light emitting diode is input, the light input surface having a plurality of grooves extending along a direction in which the light emitting diodes are arranged; And A diffuser plate facing the light input surface, the diffuser plate comprising a light output surface structured to scatter and output light input through the light input surface; And The light of the diffusion plate is input to the visible surface of the liquid crystal panel. Liquid crystal display comprising at least one optical sheet for uniformly transmitting. The liquid crystal display of claim 12, wherein the diffusion plate is made of polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, or polyimide. 13. The liquid crystal display device according to claim 12, wherein the light output surface includes a plurality of convex portions arranged regularly or irregularly. A liquid crystal panel which displays an image by controlling an amount of light transmitted through changing an arrangement of liquid crystal molecules of a liquid crystal layer according to an electrical signal applied from the outside; And A backlight unit for providing light input to the liquid crystal panel from the rear of the liquid crystal panel, The backlight unit, A plurality of light emitting diodes providing light for illuminating the liquid crystal panel from the rear of the liquid crystal panel; A first diffusion layer in which light emitted from the light emitting diode is input, the first diffusion layer having a plurality of grooves formed on a bottom thereof extending in a direction in which the light emitting diodes are arranged; And A base material disposed on the first diffusion layer and made of a resin that can transmit light; And a second diffusion layer disposed on the base material, the second diffusion layer including a plurality of beads capable of scattering light input to the base material. And The light of the diffusion plate is input to the visible surface of the liquid crystal panel. Liquid crystal display comprising at least one optical sheet for uniformly transmitting. The liquid crystal display of claim 15, wherein the first diffusion layer of the diffusion plate is made of polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, or polyimide. The liquid crystal display of claim 15, wherein the beads of the second diffusion layer are arranged regularly. The liquid crystal display of claim 15, wherein at least some of the beads of the second diffusion layer have different sizes. A light input surface, the light input surface having a plurality of grooves extending in one direction; And And a light output surface facing the light input surface and configured to scatter and output light input through the light input surface. 20. The diffusion plate of claim 19 wherein the diffusion plate is comprised of polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyethylene naphthalate or polyimide. 20. The diffuser plate of claim 19 wherein the light output surface includes a plurality of convex portions arranged regularly or irregularly. A light input layer, comprising: a first diffusion layer having a plurality of grooves extending in one direction on a bottom thereof; And A base material disposed on the first diffusion layer and made of a resin that can transmit light; And a second diffusion layer disposed on the base material and formed of a plurality of beads capable of scattering light input to the base material. 23. The diffusion plate of claim 22 wherein the first diffusion layer of the diffusion plate consists of polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyethylene naphthalate or polyimide. 23. The diffuser plate of claim 22 wherein the beads of the second diffusion layer are arranged regularly. 23. The diffuser plate of claim 22 wherein at least some of the beads of the second diffusion layer are different in size.

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