KR100837305B1 - Optical sheet, backlight unit and liquid crystal display device using the same - Google Patents

Abstract

An optical sheet, a backlight unit and an LCD using the same are provided to reduce or remove moire and prevent a defect, occurring due to contact with the other optical member, from being visually detected in the outside. An LCD(Liquid Crystal Display) comprises an LC panel and a backlight unit. The backlight unit is disposed in the rear of the LC panel and lights the LC panel. The backlight unit comprises the following parts. One or more light sources provide light. An optical sheet(260A) is disposed to be adjacent to the light source. The optical sheet comprises the following parts. A structured surface includes plural hills(264a) and valleys(266a) and plural first beads(268a). A protection layer includes mother material made from resin and plural second beads distributed in the mother material. The structured surface is arranged along a length direction. The valleys and hills of the structured surface are formed in zigzags.

Description

Optical sheet, backlight unit and liquid crystal display using the same {OPTICAL SHEET, BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE USING THE SAME}

1 is a perspective view showing a conventional prism sheet.

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 plan view of the optical sheet shown in FIG. 4A.

5A is a perspective view illustrating an optical sheet according to another embodiment of the present invention.

FIG. 5B is a plan view of the optical sheet shown in FIG. 5A.

6A is a perspective view illustrating an optical sheet according to another embodiment of the present invention.

FIG. 6B is a plan view of the optical sheet shown in FIG. 6A.

7A is a perspective view illustrating an optical sheet according to another embodiment of the present invention.

FIG. 7B is a plan view of the optical sheet shown in FIG. 7A.

The present invention relates to an optical sheet, 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 called 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.

1 is a perspective view showing a conventional prism sheet.

Referring to FIG. 1, the prism sheet 100 includes a prism support 130 and a plurality of prism shapes 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, thereby increasing luminance in the effective viewing angle range.

However, since the prism-shaped portion 110 of the conventional prism sheet 100 has a flat side surface, the prism-shaped portion 110 refracts incident light in only one direction, which is not suitable for refracting light in two dimensions.

An object of the present invention is to provide an optical sheet having a structure capable of refracting light in two dimensions, a backlight unit and a liquid crystal display using the same.

Another object of the present invention is to provide an optical sheet, a backlight unit using the same, and a liquid crystal display device, in which defects caused by contact with other optical members, etc. are hardly detected visually from the outside.

Still another object of the present invention is to provide an optical sheet capable of simultaneously condensing and scattering light.

In order to achieve the above object, a 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 includes: a light source for providing light; And an optical sheet positioned adjacent the light source, the optical sheet comprising: a structured surface comprising a plurality of peaks and valleys and a plurality of first beads; And a protective layer comprising a base material made of a resin and a plurality of second beads disposed on the base material, wherein the structured face is arranged along a length direction, and the acid and valleys of the structured face are twisted from side to side. It is characterized by winding.

In one embodiment, a backlight unit includes: at least one light source for providing light; And an optical sheet positioned adjacent the light source, the optical sheet comprising: a structured surface comprising a plurality of peaks and valleys and a plurality of first beads; And a protective layer comprising a base material made of a resin and a plurality of second beads disposed on the base material, wherein the structured face is arranged along a length direction, and the acid and valleys of the structured face are twisted from side to side. It is characterized by winding.

An optical sheet according to an embodiment of the present invention comprises a structured surface comprising a plurality of peaks and valleys and a plurality of first beads; And a protective layer comprising a base material made of a resin and a plurality of second beads disposed on the base material, wherein the structured face is arranged along a length direction, and the acid and valleys of the structured face are twisted from side to side. It is characterized by winding.

The optical sheet, the backlight unit and the liquid crystal display using the same according to the present invention have an advantage of alleviating or removing the moiré phenomenon.

In addition, the optical sheet, the backlight unit, and the liquid crystal display using the same according to the present invention have an advantage that defects caused by contact with other optical members are difficult to be visually detected from the outside.

In addition, the optical sheet of the present invention has the advantage of being able to perform the function of scattering light due to the bead, while performing the function of focusing 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 directly incident 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 serves to prevent defects caused by the optical sheet 260 in direct contact with the liquid crystal panel 210, for example, scratches, and to spread the viewing angle narrowed by the optical sheet 260 in a predetermined range. Can be done.

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, the 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 plan view of the optical sheet illustrated in FIG. 4A. 5A is a perspective view showing an optical sheet according to another embodiment of the present invention, and FIG. 5B is a plan view of the optical sheet shown in FIG. 5A.

4A and 5A, the optical sheets 260A and 260B of the present invention include a structured face and first beads 268a and 268b. In the case of the optical sheet 260B shown in FIG. 5A, a protective layer 270b is further included as compared with the optical sheet 260A shown in FIG. 4A.

The optical sheets 260A and 260B transmit light and form a surface on which the plurality of mountains 264a and 264b and the valleys 266a and 266b are structured. Here, the mountains 264a and 264b and the valleys 266a and 266b of the structured face are formed tortuous to the left and right.

That is, as shown in FIGS. 4B and 5B, the peaks 264a and 264b and the valleys 266a and 266b of the optical sheets 260A and 260B are periodically formed to the left and right, respectively.

The method for manufacturing the above-described optical sheets 260A and 260B is not particularly limited, and for example, the surfaces of the optical sheets 260A and 260B may be processed and acidified while periodically reciprocating the mold (not shown). 264a and 264b and the valleys 266a and 266b may be formed to be meandered from side to side.

When the peaks 264a and 264b and the valleys 266a and 266b of the optical sheets 260A and 260B are twisted from side to side, a curved surface is formed, so that light emitted through the optical sheets 260A and 260B is two-dimensional. Can be deflected by

The optical sheets 260A and 260B have a good transmittance and have a balance of mechanical properties (particularly impact resistance), heat resistance and electrical properties, such as, but not limited to, polymethyl methacrylate (PMMA), It is preferable to use a material such as polyethylene terephthalate (PET) or polycarbonate (PC).

The first beads 268a and 268b are located on the structured side, scattering light emitted through the optical sheets 260A and 260B. The first beads 268a and 268b may be made of a transparent resin or a material having a certain turbidity.

In addition, the sizes of the first beads 268a and 268b may be variously selected according to the use environment of the optical sheets 260A and 260B, and a first bead of uniform size or a first bead of uneven size may be used. .

The protective layer 270b improves heat resistance of the optical sheet 260B, and diffuses light propagating from the light guide plate 240 or the optical plate 340 disposed under the optical sheet 260B to make the light uniform.

In detail, the protective layer 270b includes a resin base material 272b and a plurality of second beads 274b dispersed in the base material 272b.

The resin used for the base material 272b is transparent, and an acrylic resin excellent in heat resistance and mechanical properties can be used. Preferably, the acrylic resin is polyacrylate or polymethyl methacrylate (PMMA).

The second bead 274b may be manufactured using the same type or different types of resin as the base material 272b, and preferably includes 25 wt% to 35 wt% with respect to the base material 272b. The weight ratio of the second bead 274b to 272b) is 30 wt%.

The size of the second bead 274b may be appropriately selected according to the thickness of the optical sheet 260B, and may be configured to have a size of 2 μm to 10 μm.

In one embodiment of the present invention, the size of the second bead 274b is substantially the same, and the distribution in the base material 272b is regular. When the second bead 274b having substantially the same size is regularly distributed in the base material 272b, the haze effect is reduced but the brightness is increased.

Meanwhile, in another embodiment of the present invention, the second beads 274b of various sizes may be irregularly distributed on the base material 272b. In this case, since the haze effect increases, the effect of preventing defects such as scratches caused by physical contact or the like from being projected onto the liquid crystal panel 210 as it is becomes larger.

In addition, the protective layer 270b prevents the optical sheet 260B from being deformed by heat generated from the light sources 230a and 330. That is, wrinkles do not occur in the optical sheet 260B due to the heat resistant base material 272b, and even when the optical sheet 260B is deformed at a high temperature, the restoring force of returning to the shape of the optical sheet 260B in the original state again at room temperature is obtained. good.

In addition, the protective layer 270b also serves to prevent scratches on the optical sheet 260B due to external impact or other physical force.

6A is a perspective view illustrating an optical sheet according to another exemplary embodiment of the present invention, and FIG. 6B is a plan view of the optical sheet illustrated in FIG. 6A. 7A is a perspective view showing an optical sheet according to another embodiment of the present invention, and FIG. 7B is a plan view of the optical sheet shown in FIG. 7A.

6A and 7A, the optical sheets 460A and 460B of the present invention comprise structured faces and first beads 468a and 468b. In the case of the optical sheet 460B shown in FIG. 7A, a protective layer 470b is further included as compared with the optical sheet 460A shown in FIG. 6A.

The optical sheets 460A and 460B transmit light and form a surface on which the plurality of mountains 464a and 464b and the valleys 466a and 466b are structured. Here, the ridges 464a and 464b and the valleys 466a and 466b of the structured side are meandered from side to side.

That is, as shown in FIGS. 6B and 7B, the peaks 464a and 464b and the valleys 466a and 466b of the optical sheets 460A and 460B are each formed randomly to the left and right.

The method for manufacturing the above-described optical sheets 460A and 460B is not particularly limited. For example, the surfaces of the optical sheets 460A and 460B may be processed by randomly reciprocating a mold (not shown). The 464a and 464b and the valleys 466a and 466b may be meandered from side to side.

In the case of the optical sheets 460A and 460B shown in Figs. 6A to 7B, since the peaks 464a and 464b and the valleys 466a and 466b have a randomly twisted shape from side to side, the other optical members It is difficult to visually detect a defect caused by contact with the outside, and it is possible to alleviate the moiré phenomenon that a certain pattern is reflected on the liquid crystal panel 210.

The protective layer 470b improves heat resistance of the optical sheet 460B, and diffuses light propagating from the light guide plate 240 or the optical plate 340 disposed under the optical sheet 460B to make the light uniform.

In one embodiment of the present invention, the protective layer 470b includes a resin-based base material 472b and a plurality of second beads 474b dispersed in the base material 472b. Details of the base material 472b and the second bead 474b are as described above.

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 using the same according to the present invention have an advantage of alleviating or removing the moiré phenomenon.

In addition, the optical sheet, the backlight unit, and the liquid crystal display using the same according to the present invention have an advantage that defects caused by contact with other optical members are difficult to be visually detected from the outside.

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

Claims (12)

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 light source for providing light; And Including an optical sheet positioned adjacent to the light source, The optical sheet, A structured face comprising a plurality of hills and valleys and a plurality of first beads; And A protective layer comprising a base material made of a resin and a plurality of second beads disposed dispersed in the base material, And the structured surface is arranged along a length direction, and the peaks and valleys of the structured surface are twisted from side to side. delete The liquid crystal display device of claim 1, wherein the plurality of second beads have a size of about 2 μm to about 10 μm. The liquid crystal display device of claim 1, wherein the peaks and valleys are twisted randomly or periodically from side to side. A backlight unit for illuminating a liquid crystal panel, One light source for providing light; And Including an optical sheet positioned adjacent to the light source, The optical sheet, A structured face comprising a plurality of hills and valleys and a plurality of first beads; And A protective layer comprising a base material made of a resin and a plurality of second beads disposed dispersed in the base material, And the structured surface is arranged along a length direction, and the hills and valleys of the structured surface are twisted from side to side. delete The backlight unit of claim 5, wherein the plurality of second beads have a size of about 2 μm to about 10 μm. 6. The backlight unit of claim 5, wherein the hills and valleys are respectively meandered randomly or periodically. A structured face comprising a plurality of hills and valleys and a plurality of first beads; And A protective layer comprising a base material made of a resin and a plurality of second beads disposed dispersed in the base material, The structured face is arranged along a length direction, and the peaks and valleys of the structured face are meandering from side to side. delete The optical sheet of claim 9, wherein the plurality of second beads have a size of about 2 μm to about 10 μm. 10. The optical sheet according to claim 9, wherein the peaks and valleys are respectively meandered randomly or periodically to the left and right.

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