KR20080094206A - Optical sheet and method for manufacturing the same, backlight unit and liquid crystal display device using the same - Google Patents

Abstract

An optical sheet, a manufacturing method using the same, a backlight unit using the same, and an LCD device are provided to perform simultaneously a light collecting function and a light scattering function by using a shape thereof. An LCD device includes an LCD panel and a backlight unit. The backlight unit is arranged at a backside of the LCD panel in order to illuminate the LCD panel. The backlight unit includes one or more light source for providing light and an optical sheet(260) positioned adjacently to the light source. The optical sheet includes a base film(262) for transmitting the light and a plurality of structures(264). The structures are arranged on one surface of the base film in order to disperse and condense the light. A sectional surface of each structure is a curved region protruded from a partial region of both sides of a triangle.

Description

TECHNICAL SHEET AND METHOD FOR MANUFACTURING THE SAME, BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE USING THE SAME}

1A is a perspective view showing a conventional prism sheet.

FIG. 1B is a cross-sectional view of the prism sheet shown in FIG. 1A.

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

FIG. 2B is a cross-sectional view illustrating an embodiment of the liquid crystal panel of FIG. 2A.

3 is a cross-sectional view of a liquid crystal display according to another exemplary embodiment of the present invention.

4A is a perspective view illustrating an optical sheet according to an embodiment of the present invention.

4B is a cross-sectional view of the optical sheet shown in FIG. 4A.

FIG. 5A is an enlarged cross-sectional view of a portion A of the optical sheet shown in FIG. 4B.

5B is a partial cross-sectional view of an optical sheet according to another embodiment of the present invention.

6A to 8B are views illustrating a manufacturing process of an optical sheet according to an embodiment of the present invention.

The present invention relates to an optical sheet and a method of manufacturing the same, a backlight unit and a liquid crystal display using the same.

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.

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.

The backlight unit includes a light source for emitting light, a light guide plate for guiding light emitted from the light source, and a plurality of optical members for converting a direction of light guided from the light guide plate. As part of the optical members, a prism sheet for collecting light is used.

1A is a perspective view showing a conventional prism sheet, and FIG. 1B is a cross-sectional view of the prism sheet shown in FIG. 1A.

1A and 1B, the prism sheet 100 includes a prism support 130 and a plurality of prism features 110 formed side by side over the entire surface on the prism support 130. The prism shape 110 has a side portion formed of the first face 112 and the second face 114, and forms a substantially isosceles triangle when viewed from the front. The first surface 112 and the second surface 114 generally form an angle of 90 °, but may be configured differently according to a selection.

A plurality of prismatic features 110 are formed in succession to the prism support 130 so that the valleys 118 and the peaks 116 are alternately formed. The prism sheet 100 configured as described above refracts the light incident on the prism support 130 while passing through the prism shape 110. As a result, light incident at a low angle is concentrated toward the front side along the first path L1, thereby increasing luminance in the effective viewing angle range.

However, after some light enters the first surface 112 or the second surface 114, it is totally constrained by the second path L2 and constrained to the inside. There was a problem.

In addition, since the first surface 112 and the second surface 114 are composed of flat surfaces, the light is refracted only in one dimension, which is advantageous for condensing, but there is a problem that it is not suitable for securing a wide effective viewing angle.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical sheet, a method of manufacturing the same, a backlight unit and a liquid crystal display device using the same, which can refract light two-dimensionally and improve light utilization efficiency.

In addition, the present invention provides an optical sheet and a manufacturing method thereof, a backlight unit and a liquid crystal display using the same, having a shape capable of simultaneously performing a function of condensing light and scattering light.

In order to achieve the above object, the liquid crystal display device according to an embodiment of the present invention, a liquid crystal panel; And a backlight unit disposed at a rear side of the liquid crystal panel to illuminate the liquid crystal panel, wherein the backlight unit comprises: one or more light sources for providing light; And an optical sheet positioned adjacent to the light source, the optical sheet comprising: a base film transmitting light; And a plurality of structures disposed on one surface of the base film and diffusing and condensing light, wherein a cross section of the structure has a shape in which a partial region of both hypotenuses of the triangle protrudes in a curve.

In one embodiment, a backlight unit includes: one or more light sources for providing light; And an optical sheet positioned adjacent to the light source, the optical sheet comprising: a base film transmitting light; And a plurality of structures disposed on one surface of the base film and diffusing and condensing light, wherein a cross section of the structure has a shape in which a partial region of both hypotenuses of the triangle protrudes in a curve.

An optical sheet according to an embodiment of the present invention, the base film for transmitting light; And a plurality of structures disposed on one surface of the base film and diffusing and condensing light, wherein a cross section of the structure has a shape in which a partial region of both hypotenuses of the triangle protrudes in a curve.

According to one or more exemplary embodiments, a method of manufacturing an optical sheet includes: cutting a surface of a mold circle by a first depth into a prismatic bite; Cutting the surface of the mold circle into a round bite by a second depth; And processing the transparent resin with a mold manufactured by the cutting to manufacture an optical sheet, wherein the first depth is deeper than the second depth.

The optical sheet, the backlight unit and the liquid crystal display device using the same according to the present invention can be refracted in two dimensions, thereby improving the light utilization efficiency.

In addition, the optical sheet of the present invention has an advantage of being able to simultaneously perform a function of scattering light while performing a function of condensing light due to its shape.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2A is a cross-sectional view illustrating a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 2B is a cross-sectional view illustrating an embodiment of the liquid crystal panel of FIG. 2A.

2A and 2B, the liquid crystal display 200 according to an exemplary embodiment of the present invention displays a liquid crystal panel 210 and a liquid crystal panel 210 displaying an image according to a driving signal and a data signal applied from the outside. It is provided with a backlight unit 220 for illuminating the back.

The liquid crystal panel 210 includes a lower substrate 210a, an upper substrate 210b, a lower polarizing film 211a, an upper polarizing film 211b, a color filter 212, a black matrix 213, a common electrode 214, The TFT array 215 includes a pixel electrode 216 and a liquid crystal layer 217.

The color filter 212 includes color filters corresponding to red, green, and blue, and generates an image corresponding to red, green, or blue when light is applied.

The TFT array 215 switches the pixel electrode 216 as a switching element.

The common electrode 214 and the pixel electrode 216 convert the molecular arrangement of the liquid crystal layer 217 according to a predetermined voltage applied from the outside.

The liquid crystal layer 217 is composed of predetermined molecules, and the molecules are arranged in correspondence with the voltage difference applied between the pixel electrode 216 and the common electrode 214.

As a result, light provided from the backlight unit 220 below is incident on the color filter 212 corresponding to the molecular arrangement of the liquid crystal layer 217.

As already mentioned above, in understanding and implementing the present invention, the precise structural characteristics of the liquid crystal panel 210 are not important, and the idea of the present invention is not limited to any structure of liquid crystal panels commonly used in liquid crystal display devices. It can be widely applied. Therefore, the technical idea of the present invention will not be limitedly interpreted by the structure of the liquid crystal panel 210 mentioned above.

The backlight unit 220 according to an embodiment of the present invention includes a light source unit 230, a light guide plate 240, a reflective sheet 250, and an optical sheet 260, and optionally, further includes a protective sheet 280. do.

In the present embodiment, the light source 230 is driven by an edge-light method disposed on both side surfaces of the light guide plate 240. In another embodiment of the present invention, the light source unit 230 may be driven in an edge-light manner disposed only on one side of the light guide plate 240.

The light source unit 230 includes a light source 230a for generating light of a predetermined wavelength, for example, white light, and a light source reflector 230b disposed outside the light source 230a. The light source 230a of the present invention is not limited, and various light sources such as a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), or a light emitting diode (LED) may be used.

The light generated by the light source 230a is incident directly to the side surface of the light guide plate 240, that is, the light incident surface, or is reflected by the light source reflector 230b disposed outside the light source 230a and incident on the light incident surface.

The light source reflector 230b improves light efficiency by reflecting light generated from the light source 230a toward the light guide plate 240 to increase the amount of light incident on the light guide plate 240. To this end, the light source reflector 230b is made of a highly reflective material, and may coat silver (Ag) on its surface.

Since the light source unit 230 is located at the side of the backlight unit 220, the light generated by the light source unit 230 is concentrated at the edge of the light unit 230 without being uniformly transmitted over the entire surface of the backlight unit 220. Therefore, the light guide plate 240 is required to uniformly transmit the light to the entire surface of the visible surface of the liquid crystal panel 210. The light guide plate 240 is a direction substantially parallel to the viewing plane of the liquid crystal panel 210 disposed above the light incident through the light incident surface disposed on the side thereof, that is, substantially perpendicular to the light incident surface. It transmits in the direction of phosphorus, and mixes and equalizes light. To this end, the light guide plate 240 is designed such that a total total reflection occurs at or below a critical angle after light is incident on the light incident surface. The front surface of the light guide plate 240 is a light emitting surface for emitting light in the direction in which the liquid crystal panel 210 is disposed.

The light guide plate 240 according to the exemplary embodiment of the present invention may be made of a transparent acrylic resin such as polymethylmethacrylate.

The reflective sheet 250 is disposed on the bottom surface of the light guide plate 240 and serves to reflect light exiting to the bottom surface of the light guide plate 240 to re-inject into the light guide plate 240. Reflective sheet 250 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 250 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.

The light emitted from the light guide plate 240 is effectively incident on the visible surface of the liquid crystal panel 210 to improve luminance, and the light incident on the liquid crystal panel 210 is uniformly uniform so that the entire surface of the visible surface has a uniform luminance distribution. To this end, the backlight unit 220 includes one or more optical members.

The optical sheet 260 modulates light incident at a low angle from the light guide plate 240 into light in a direction perpendicular to the visible surface of the liquid crystal panel 210 to condense the light onto the liquid crystal panel 210 to form a wide effective viewing angle range. The detailed structure of the optical sheet 260 will be described later.

The protective sheet 280 is positioned on the optical sheet 260 to prevent damage to the optical sheet 260. The protective sheet 280 prevents defects caused by the optical sheet 260 in direct contact with the liquid crystal panel 210, for example, scratches, and spreads the viewing angle narrowed by the optical sheet 260 in a predetermined range. Can be performed.

The protective sheet 280 includes a diffusion layer featuring low haze and high transmittance, and optimally diffuses the strong light emitted from the optical sheet 260 to the liquid crystal panel 210.

In understanding and practicing the present invention, the precise structural and material properties of the protective sheet 280 are not critical, and the spirit of the present invention may be applied to the protective sheet 280 using any structure and material commonly used in the backlight unit. It can be widely applied.

In addition, in the case of the backlight unit 220 employing the optical sheet 260 of the present invention, since the optical sheet 260 of the present invention may perform some functions of the protective sheet 280, that is, the diffusion function, The backlight unit 220 may be configured without the sheet 280.

3 is a cross-sectional view of a liquid crystal display according to another exemplary embodiment of the present invention.

Referring to FIG. 3, the present invention shows a liquid crystal display device 300 employing a direct type backlight unit 320.

Hereinafter, a description will be focused on the difference from the above-described edge-light backlight unit 220, and the same reference numerals will be omitted for the same or similar components, and detailed descriptions thereof will be omitted.

The light source 330 emits light of a predetermined wavelength for illuminating the liquid crystal panel 210. The light source 330 of the present invention is not limited, and various light sources such as a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), or a light emitting diode (LED) may be used.

The optical plate 340 has a predetermined pattern formed therein to remove radiation of light generated from the light source 330. The optical plate 340 may be formed of, for example, polymethyl methacrylate (PMMA).

The frame 350 provides a space for accommodating the light source 330, and optionally, a reflective sheet 360 may be further disposed thereon.

The reflective sheet 360 reflects light emitted from the light source 330 to the bottom in the direction of the liquid crystal panel 210, thereby improving light utilization efficiency.

In one embodiment of the present invention, the reflective sheet 360 is coated with silver (Ag) on a sheet made of SUS, Brass, aluminum, PET, and the like, even if the heat is generated fine titanium coating to prevent deformation due to endothermic long time Can be produced. In addition, in another embodiment of the present invention, the reflective sheet 360 may be manufactured by dispersing bubbles for scattering light on a sheet made of synthetic resin such as PET.

As described above, as the backlight unit 220 for illuminating the liquid crystal panel 210 from the rear side, the light generated from the light source 230a is applied to the liquid crystal panel 210 through one or both sides of the light guide plate 240. The technical concept of the present invention may be applied to the backlight unit 220 of the direct type as well as the backlight unit 220 of the edge-light type.

In the understanding and implementation of the present invention, the configuration of the liquid crystal display device is not limited to that shown in the drawings, and the optical sheet of the present invention may be widely applied to any configuration commonly used in the liquid crystal display device.

4A is a perspective view illustrating an optical sheet according to an embodiment of the present invention, and FIG. 4B is a cross-sectional view of the optical sheet illustrated in FIG. 4A.

4A and 4B, the optical sheet 260 of the present invention is disposed on one surface of the base film 262 and the base film 262 that transmit light, and the plurality of structures 264 for diffusing and condensing light. ).

The base film 262 supports the structure 264 disposed thereon and is made of a resin through which light provided by the light sources 230a and 330 can pass.

The thickness of the base film 262 is not limited, and those skilled in the art will be able to select an appropriate range of values in consideration of the environment in which the optical sheet 260 of the present invention is used. For example, when the optical sheet 260 of the present invention is used as a prism sheet of a mobile phone terminal, the thickness of the base film 262 has a value between 30 μm and 60 μm. Preferably, the thickness of the base film 262 has a value between 45 μm and 55 μm. In addition, when the optical sheet 260 of the present invention is used as a prism sheet of a TV / monitor, the thickness of the base film 262 has a value between 100 µm and 300 µm. Preferably, the thickness of the base film 262 has a value between 120 μm and 260 μm.

On the other hand, the base film 262 is manufactured in the form of a sheet, and has a good transmittance and a balance of mechanical properties (particularly impact resistance), heat resistance and electrical properties, for example, without limitation, polymethyl methacrylate It is preferable to use a material such as (Polymethyl Methacrylate; PMMA), Polyethylene Terephthalate (PET), Polycarbonate (PC) or Polyester.

The cross section of the structure 264 has a shape in which some areas of both hypotenuses of the triangle protrude in a curved shape, and due to its structural characteristics, light can be diffused and collected. That is, as shown in FIG. 4B, the optical sheet of the present invention has a function of condensing light when light transmitted through the base film 262 follows the first path H1 and the third path H3. Perform.

In addition, due to the convex shape, the light that the conventional prism sheet is restrained internally by total reflection can be discharged and diffused to the outside along the second path H2. Accordingly, light can be emitted two-dimensionally, and light utilization efficiency can be improved.

The structure 264 may be made of a thermoplastic resin such as polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polycarbonate (PC), or polyester.

FIG. 5A is an enlarged cross-sectional view of part A of the optical sheet shown in FIG. 4B, and FIG. 5B is a partial cross-sectional view of an optical sheet according to another embodiment of the present invention.

5A and 5B, the cross-sections of the structures 264a and 264b have a shape in which a portion of the triangular hypotenuses 266a, 268a, 266b and 268b protrudes in a curved line as described above.

The inner angles α1 and α2 of the triangles are factors that determine the degree of light condensation. Generally, the more the angles α1 and α2 are formed at an acute angle, the better the light condensation is. In the present invention, the sizes of the cabinets α1 and α2 are not particularly limited and may be configured at angles between 60 ° and 150 °.

The sizes of the first base angles β1 and β2 and the second base angles γ1 and γ2 adjust the shape of the triangle, and the first base angle β1 and the second base angle γ1 of the structure 264a shown in FIG. 5A. The size is the same. Accordingly, the cross section of the structure 264a has a shape in which a part of the two oblique sides 266a and 268a of the isosceles triangle protrude in a curved shape, and is symmetric about one axis X1.

Meanwhile, the sizes of the first base angle β2 and the second base angle γ2 of the structure 264b illustrated in FIG. 5B are different. Accordingly, the cross section of the structure 264b is different in size from the shape protruding in a curve from the two oblique sides 266b and 268b of the triangle, and is asymmetric.

Since the structure 264a illustrated in FIG. 5A has a symmetrical shape with respect to one axis X1, the structure 264a may have uniform luminance characteristics as compared with the structure 264b illustrated in FIG. 5B.

6A to 8B are views illustrating a manufacturing process of an optical sheet according to an embodiment of the present invention.

6A and 6B, mold prototypes 600a and 600b are provided for manufacturing the optical sheet 260 of the present invention. The mold prototypes 600a and 600b are in a state before the mold is processed and may be a metal cylinder or a metal plate. The material constituting the metal cylinder and the metal plate is not particularly limited, and may be made of copper (Cu) or nickel (Ni).

Subsequently, the prismatic bite 710 and round 720 bite, as shown in FIGS. 7A and 7B, cut the surfaces of mold circles 600a and 600b. Here, the prismatic bite 710 is defined as a bite having a triangular cross section of the cutting area, and the round bite 720 is defined as a bite having an arch of a cross section of the cutting area.

On the other hand, in order to constitute a shape characteristic such as the optical sheet 260 of the present invention, the triangular width w1 of the prismatic bite 710 is larger than the arcuate width w2 of the round bite 720. It is desirable to be wide.

The prismatic bite 710 and the round bite 720 may be made of carbon steel, high speed steel, cemented carbide, or ceramics in consideration of durability and hardness of the mold prototypes 600a and 600b.

8A and 8B are enlarged views of a part of a mold prototype under cutting.

8A and 8B, the mold circle 600 is cut by the first depth D1 by the prismatic bite 710. The surface of the mold circle 600 is cut corresponding to the shape of the prism bite 710 to form a groove 810 having a first width w1.

Subsequently, the surface of the mold circle 600 cut by the first depth D1 by the prismatic bite 710 is cut into the round bite 720 by the second depth D2. Here, the second depth D2 is shallower than the first depth D1, and the second width w2 additionally cut by the round bite 720 is narrower than the first width w1. Accordingly, the groove 820 of a specific shape is formed in an intaglio pattern, thereby completing the mold.

In the manufacturing process of the mold, the cutting process is performed by the prism-type bite 710, and then the cutting process by the round-type bite 720 has been described, but the spirit of the present invention is not limited thereto. After cutting the first depth D2 to 720, the first depth D1 may be cut to the prismatic bite 710.

Further, the prismatic bite 710 and the round bite 720 perform the cutting process independently of each other, or in consideration of the depth cut by the prismatic bite 710 and the round bite 720, After adjustment, the prismatic bite 710 and the round bite 720 can be combined with a fastening means (not shown) to configure the surface of the mold prototype 600 continuously.

Subsequently, in the mold manufactured by the above process, a transparent resin such as polymethyl methacrylate (PMMA), polyethylene tere via a stamping, extrusion, injection or casting method, which is a technique well known in the art. A thermoplastic resin such as phthalate (Polyethylen Terephthalate (PET), polycarbonate (PC) or polyester) is processed to manufacture the optical sheet 260 of the present invention.

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

The optical sheet, the backlight unit, and the liquid crystal display device using the same according to the present invention can refract light in two dimensions, thereby improving the light utilization efficiency.

In addition, the optical sheet of the present invention has an advantage of being able to simultaneously perform a function of scattering light while performing a function of condensing light due to its shape.

Claims (13)

Liquid crystal panels; And Is disposed on the rear of the liquid crystal panel and includes a backlight unit for illuminating the liquid crystal panel, The backlight unit, One or more light sources for providing light; And An optical sheet positioned adjacent to the light source, The optical sheet, A base film that transmits light; And Is disposed on one surface of the base film, including a plurality of structures for diffusing and condensing light, The cross-section of the structure is a liquid crystal display device, characterized in that the protruding curved portion of the partial region of the triangle. The liquid crystal display device according to claim 1, wherein the shape of the cross section of the structure is symmetric about one axis. The liquid crystal display device according to claim 1, wherein the cross section of the structure has an asymmetric shape. One or more light sources for providing light; And Including an optical sheet positioned adjacent to the light source, The optical sheet, A base film that transmits light; And Is disposed on one surface of the base film, including a plurality of structures for diffusing and condensing light, The cross-section of the structure is a backlight unit, characterized in that the protruding curved portion of the partial region of the triangle. The backlight unit of claim 4, wherein the cross-sectional shape of the structure is symmetric about one axis. The backlight unit of claim 4, wherein a cross section of the structure has an asymmetrical shape. A base film that transmits light; And Is disposed on one surface of the base film, including a plurality of structures for diffusing and condensing light, The cross section of the structure is an optical sheet, characterized in that the partial protruding portion of the triangular hypotenuse is curved. The optical sheet according to claim 7, wherein the shape of the cross section of the structure is symmetric about one axis. 8. An optical sheet according to claim 7, wherein the cross section of the structure is asymmetrical. Cutting the surface of the mold circle into a prismatic bite by a first depth; Cutting the surface of the mold circle into a round bite by a second depth; And Processing the transparent resin into a mold prepared by the cutting, comprising the steps of manufacturing an optical sheet, And said first depth is deep compared to said second depth. The method of manufacturing an optical sheet according to claim 10, wherein the width of the prismatic bite is wider than the width of the round bite. The manufacturing method of the optical sheet according to claim 10, wherein the mold prototype is a metal cylinder or a metal plate. The manufacturing method of the optical sheet according to claim 10, wherein the prismatic bite and the round bite are joined by a fastening means to continuously cut the surface of the mold circle.

Images