KR100701898B1 - Optical Sheet And Back Light Unit Using The Same - Google Patents

Abstract

The present invention relates to an optical sheet and a backlight unit using the same.

The optical sheet has a plurality of holes in the optical sheet disposed below the liquid crystal display panel for guiding light emitted from the outside toward the liquid crystal display panel.

Description

Optical sheet and back light unit using the same             

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

FIG. 2 is a cross-sectional view illustrating a cross section taken along the line II-II ′ of FIG. 1.

3 is a diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

4 is a cross-sectional view taken along the line IV-IV ′ of FIG. 3.

FIG. 5 is a detailed view of a part of the optical sheet shown in FIG. 4.

6 is a view showing an optical path of the optical sheet shown in FIG.

<Description of Symbols for Main Parts of Drawings>

2, 102: liquid crystal display panels 8, 18, 108, 118: polarizing sheet

10, 110: optical sheet 12, 112: diffuser plate

14, 114: reflector 34, 134: case

36, 136: lamp 120: hall

The present invention relates to an optical sheet and a backlight unit using the same, and more particularly, to an optical sheet capable of realizing high luminance and a backlight unit using the same.

In general, liquid crystal displays (hereinafter referred to as "LCDs") have tended to be increasingly wider in application due to features such as light weight, thinness, and low power consumption. According to this trend, LCDs are used for office automation equipment, audio / video equipment, and the like. On the other hand, the LCD is controlled to display the desired image on the screen by adjusting the transmission amount of the light beam according to the image signal applied to the plurality of control switches arranged in a matrix form.

Since the LCD is not a self-luminous display device, a light source such as a back light is required. Such LCD backlight has a direct type and an edge type. In the edge type system, a lamp is installed outside the flat plate, and light is incident from the lamp onto the entire surface of the liquid crystal display panel using a transparent light guide plate. The direct type places several lamps in the plane. A diffusion plate is provided between the lamp and the liquid crystal display panel to maintain a constant space between the liquid crystal display panel and the lamp. On the other hand, according to the type of lamp, the cold cathode tube ("CCFL") method of supplying power by inserting electrodes at both ends of the glass tube of the lamp, and the metal tube of both ends of the glass tube of the lamp There is an external electrode fluorescent lamp ("EEFL") that supplies power to the surrounding electrode.

1 and 2 show a conventional LCD.

1 and 2, a conventional LCD includes a liquid crystal display panel 2 for displaying an image and a backlight unit for irradiating uniform light onto the liquid crystal display panel 2.

In the liquid crystal display panel 2, liquid crystal cells are arranged in an active matrix between upper and lower substrates, and pixel electrodes and a common electrode for applying an electric field to each of the liquid crystal cells are provided. Each of these pixel electrodes is connected to a thin film transistor used as a switch element. The pixel electrode drives the liquid crystal cell along with the common electrode according to the data signal supplied through the thin film transistor to display an image corresponding to the video signal.

The backlight unit includes a case 34, a reflecting plate 14 stacked on the front of the case 34, a plurality of lamps 36 positioned on the reflecting plate 14, and a plurality of lamps 36. The diffuser plate 12 and the optical sheet 10 which are arrange | positioned are provided.

The case 34 converts a path of light generated from the lamps 36 by reflecting visible light traveling toward the side and the back of the plurality of lamps 36 toward the front side, that is, the diffuser plate 12.

The reflective plate 14 is disposed between the upper surface of the case 34 and the plurality of lamps 36 to reflect the light generated from the lamps 36 and to be irradiated toward the liquid crystal display panel 2 to improve the efficiency of the light. .

Each of the plurality of lamps 36 includes a glass tube, inert gases inside the glass tube, and a cathode and an anode portion made of metal covering both ends of the glass tube. These multiple lamps 36 are arranged side by side on the case 34.

The diffusion plate 12 allows the light emitted from the plurality of lamps 36 to propagate to the liquid crystal display panel and to be incident at a wide range of angles.

The optical sheets 10 may improve the front brightness of the liquid crystal display and reduce power consumption by narrowing the viewing angle of the light emitted from the diffuser plate 12.

Conventional liquid crystal display devices having such a structure have a lot of problems in achieving high luminance due to poor light transmittance of the polarizing plates 8 and 18 and the liquid crystal. Accordingly, there is an urgent need for an optical member capable of scattering light generated from the lamps 36 to increase diffusibility, and increase light condensation to improve overall light efficiency.

Accordingly, it is an object of the present invention to provide an optical sheet capable of achieving high luminance and a backlight unit using the same.

In order to achieve the above object, the optical sheet according to the embodiment of the present invention, in the optical sheet disposed below the liquid crystal display panel, has a plurality of holes for guiding light emitted from the outside toward the liquid crystal display panel.
The hole has an incident side of the light formed in at least one of a circle, an ellipse, and a polygonal shape.
The hole has a ratio of the size of the incident side and the size of the exit side 1: 1 to 5: 1.
The backlight unit according to the exemplary embodiment of the present invention includes an optical sheet in which a plurality of holes are formed to guide light from light sources toward the liquid crystal display panel.

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Other objects and features of the present invention in addition to the above object will be apparent from the description of the embodiments with reference to the accompanying drawings.

3 and 4 illustrate a liquid crystal display according to an exemplary embodiment of the present invention.

3 and 4, a liquid crystal display according to an exemplary embodiment includes a liquid crystal display panel 102 and a backlight unit for irradiating light onto the liquid crystal display panel 102.

In the liquid crystal display panel 102, liquid crystal cells are arranged in an active matrix between upper and lower glass substrates, and thin film transistors for switching video signals are provided in each of the liquid crystal cells. It is installed. The liquid crystal display panel 102 may display an image corresponding to the video signal by changing the refractive index of each of the liquid crystal cells according to the video signal. A tape carrier package (not shown) in which a driver integrated circuit for applying a driving signal to a thin film transistor is mounted on the lower substrate of the liquid crystal display panel 102 is attached. In addition, polarizing sheets 108 and 118 are provided on the front and rear surfaces of the liquid crystal display panel 102, respectively. Here, the polarizing sheets 108 and 118 function to improve the viewing angle of the image displayed by the liquid crystal cells.

The backlight unit receives power from an external power source, a plurality of lamps 136 for irradiating light to the liquid crystal display panel 102, a case 134 for storing the plurality of lamps 136, a lamp 136 and A reflection plate 114 disposed between the case 134 to prevent leakage of light generated from the lamp 136 and reflecting the light, a diffuser plate 112 to diffuse the light generated from the lamp 136, and a diffusion plate. One or more optical sheets 110 are disposed on the upper side of the display panel, and the one or more optical sheets 110 improve light efficiency while advancing the light generated from the lamp 136 toward the liquid crystal display panel 102.

Each of the lamps 136 includes a glass tube, inert gases inside the glass tube, and a cathode and an anode installed at both ends of the glass tube. Inert gas is filled in the glass tube, and phosphor is coated on the inner wall of the glass tube. Each of the plurality of lamps 136, when the AC voltage from the inverter is applied to the high voltage electrode and the low pressure electrode, the electrons are released from the low pressure electrode collides with the inert gas inside the glass tube to increase the amount of electrons exponentially. . These exponentially increased electrons cause electric current to flow inside the glass tube, and the electrons emit ultraviolet rays as the inert gas is excited by the electrons. Ultraviolet rays emitted in this manner collide with the luminescent phosphor applied to the inner wall of the glass tube to emit visible light.

The case 134 housing the plurality of lamps 136 is generated in the lamps 136 by reflecting visible light traveling toward the side and the back of the plurality of lamps 136 toward the front, that is, the diffuser plate 112. The path of the light to be converted. In this case 134, a plurality of lamps 136 are arranged at regular intervals.

The reflective plate 114 is disposed between the upper surface of the case 134 and the plurality of lamps 136 to convert the path of the light emitted from the lamps 136 in the opposite direction of the liquid crystal display panel 102 to convert the liquid crystal. Irradiation toward the display panel 102 improves the efficiency of light.

The diffusion plate 112 allows the light emitted from the plurality of lamps 136 to propagate to the liquid crystal display panel 102, and allows incident light from a wide range of angles. The diffuser plate 112 has a plurality of beads formed therein to diffuse light generated from the lamps 136, thereby extending the emission range of the light emitted from the surface of the diffuser plate 112. The diffusion plate 112 may be formed of at least one of optical resins such as high purity acrylic resin PMMA (polymethylmethacrylate), polycarbonate, and methyl methacrylate-styrene copolymer (MS resin).

At least one optical sheet 110 is disposed between the liquid crystal display panel 102 and the diffusion plate 112 so that light incident to the liquid crystal display panel 102 is converted by converting a path of the light emitted from the diffusion plate 112. The luminance of the front surface of the liquid crystal display panel 102 is improved by adjusting the liquid crystal display panel 102 to be directly oriented. This optical sheet 110 will be described in detail with reference to FIG. 5.

Referring to FIG. 5, an optical sheet 110 according to an exemplary embodiment of the present invention has an arrangement of a plurality of holes 120 from the front surface of the optical sheet 110 to the back surface. The incident side shape of the hole 120 is formed of any one of a circle or an ellipse and a polygon, and the exit side shape of the hole 120 is formed of any one of a circle or an ellipse and a polygon having an incident side size or less. Therefore, the vertical cut surface of the hole 120 is formed in a trapezoidal shape. Here, the size ratio of the incidence side and the exit side of the hole 120 is formed in the range of 1: 1 to 5: 1 in consideration of the thickness and firmness of the optical sheet and the light transmittance. The optical path of the optical sheet 110 will be described in detail with reference to FIG. 6. Referring to FIG. 6, first, light “1” directly directed to the hole 120 is transmitted without loss as much as the size of the exit side of the hole 120 and is incident on the liquid crystal display panel 102.

"2" light is incident on the optical sheet 110 having a predetermined refractive index without passing through the hole 120 and then incident on the liquid crystal display panel 102.

After the light “③” enters the inside of the hole 120, the light passes through the hole 120 and is totally reflected at the front surface of the optical sheet 110. Such "C" light is recycled by the diffuser plate 112, the reflector plate 114, and the like disposed under the optical sheet 110.

After the "4" light and the "5" light are incident on the optical sheet 110 having a predetermined refractive index, the light is totally reflected at a predetermined angle at the outer wall of the hole 120 and is emitted to the front surface of the optical sheet 110.

The optical sheet 110 according to the embodiment of the present invention having such a structure can increase the light efficiency by transmitting the light emitted to the exit side of the hole 120 without loss. In addition, since the surface of the optical sheet 110 has a flat shape as a whole, it is possible to minimize damage due to external force acting from the outside. As such, the optical sheet 110 having the holes 120 may be configured in a plurality of layers.

As described above, the optical sheet according to the embodiment of the present invention can not only improve the efficiency of the light irradiated from the lamp to achieve high brightness of the liquid crystal display device, but also minimize damage caused by the external force of the optical sheet. Having a structure makes it possible to reduce the occurrence of defective products.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (7)

In the optical sheet disposed below the liquid crystal display panel, And a plurality of holes for guiding light emitted from the outside toward the liquid crystal display panel. The method of claim 1, The hole is The incident side of the light is formed in at least one of a circle, ellipse, polygonal form, The light exit side of the light sheet is characterized in that formed in at least one of the form of a circle, an ellipse, a polygon less than the size of the incident side. The method of claim 1, The hole is An optical sheet, characterized in that the ratio of the size of the incident side and the size of the exit side is 1: 1 to 5: 1. In the backlight unit for irradiating light to the liquid crystal display panel including a plurality of light sources, And an optical sheet on which a plurality of holes are formed to guide the light from the light sources toward the liquid crystal display panel. The method of claim 4, wherein And a diffuser plate disposed between the light sources and the optical sheet to diffuse light from the light sources. The method of claim 4, wherein The hole is The incident side of the light is formed in at least one of a circle, ellipse, polygonal form, And a light emitting side of the light is formed of at least one of a circle, an ellipse, and a polygonal shape having a size smaller than that of the light incident side. The method of claim 4, wherein The hole is A backlight unit, characterized in that the ratio of the size of the incident side and the size of the exit side is 1: 1 to 5: 1.

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