KR100840572B1 - Lens sheet, backlight unit and liquid crystal display device using the same - Google Patents

Abstract

A lens sheet, a backlight unit and an LCD(Liquid Crystal Display) using the same are provided to reduce luminance smoothly, thereby maintaining uniformity of luminance and providing a large effective viewing angle. A backlight unit comprises at least one light source for providing light for illuminating an LC panel, and a lens sheet(260A) disposed adjacent to the light source. The lens sheet comprises the followings. A base sheet(262a) transmits the light. Plural structures(264a) are prolonged in one direction while being in contact with one side of the base sheet, and have a section shape of a convex semicircle. Plural diffusion particles(266a) diffuse light emitted through the structures. By adjusting a width of the structures according to a type and disposition state of the light source, a function of concentrating light in a specific direction is performed.

Description

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

1 is a cross-sectional view showing a conventional prism sheet.

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

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

4A to 6B are perspective views illustrating a lens sheet according to an embodiment of the present invention.

7 is a graph showing a luminance curve of light emitted through the lens sheet and the conventional prism sheet of the present invention.

The present invention relates to a lens 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. 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 cross-sectional view showing a conventional prism sheet.

Referring to FIG. 1, a plurality of prisms 120 are formed on one surface of the base film 110, and light incident on the base film 110 is emitted through the prism 120. Since the prism sheet 100 concentrates the light incident at a low angle toward the front side, the prism sheet 100 increases the luminance in the effective viewing angle range, but when the prism sheet 100 leaves the predetermined viewing angle range, the luminance sharply decreases.

In addition, when the prism sheet 100 is in contact with another optical sheet, the edge portion is likely to be structurally damaged, which may cause a decrease in reliability of the backlight unit or the liquid crystal display device employing the prism sheet 100. .

An object of the present invention is to provide a lens sheet capable of expanding a viewing angle while condensing light provided from a light source on a visible surface of a liquid crystal panel, a backlight unit using the same, and a liquid crystal display device.

Another object of the present invention is to provide a lens sheet, a backlight unit using the same, and a liquid crystal display device having the same structurally excellent wear resistance and improving reliability of a product.

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 comprises: at least one light source for providing light for illuminating the liquid crystal panel; And a lens sheet positioned adjacent to the light source, wherein the lens sheet comprises: a base sheet for transmitting the light; A plurality of structures disposed in contact with one surface of the base sheet and extending in one direction and having a convex semicircular cross-sectional shape; And a plurality of diffuse particles scattering light emitted through the structure.

In one embodiment, a backlight unit includes: at least one light source for providing light; And a lens sheet positioned adjacent to the light source, wherein the lens sheet comprises: a base sheet for transmitting the light; A plurality of structures disposed in contact with one surface of the base sheet and extending in one direction and having a convex semicircular cross-sectional shape; And a plurality of diffuse particles scattering light emitted through the structure.

Lens sheet according to an embodiment of the present invention, the base sheet for transmitting light; A plurality of structures disposed in contact with one surface of the base sheet and extending in one direction and having a convex semicircular cross-sectional shape; And a plurality of diffusing particles for scattering light emitted through the structure.

The lens sheet, the backlight unit, and the liquid crystal display using the same according to the present invention have the advantage of extending the viewing angle while condensing the light provided from the light source onto the visible surface of the liquid crystal panel.

In addition, the lens sheet according to the present invention is structurally excellent in wear resistance, there is an advantage that can improve the reliability of the backlight unit and the liquid crystal display device employing it.

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

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

2 and 3, 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 a lens sheet 260, and optionally, further includes a protective sheet 270. 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 exit 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 lens 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 lens sheet 260 will be described later.

The protective sheet 270 is positioned on the lens sheet 260 to prevent damage to the lens sheet 260.

In one embodiment of the present invention, a diffusion sheet (not shown) may be further disposed between the lens sheet 260 and the light guide plate 240.

The diffusion sheet functions to scatter light incident from the light guide plate to make the luminance uniform and to widen the viewing angle.

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 lens sheet of the present invention may be widely applied to any configuration commonly used in the liquid crystal display device.

4A to 6B are perspective views illustrating a lens sheet according to the present invention.

4A to 4C, the lens sheets 260A, 260B, and 260C of the present invention include a base sheet 262a, 262b, and 262c, a plurality of structures 264a, 264b, and 264c, and a plurality of diffused particles 266a, 266b and 266c).

Base sheets 262a, 262b, and 262c have good transmittance and are materials that have a good balance of mechanical properties (especially impact resistance), heat resistance and electrical properties, such as, but not limited to, polymethyl methacrylate, methyl polyacrylate (methyl), polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polystyrene, polyester acrylate or unsaturated polyester Preference is given to using the substance.

There is no limitation on the thickness of the base sheets 262a, 262b and 262c, and those skilled in the art will be able to select an appropriate range of values in consideration of the environment in which the lens sheets 260A, 260B and 260C of the present invention are used. Could be.

In one embodiment of the present invention, the thickness of the base sheets 262a, 262b and 262c has a value between 30 μm and 130 μm. Preferably, the thicknesses of the base sheets 262a, 262b and 262c have a value between 50 μm and 130 μm.

The plurality of structures 264a, 264b, and 264c have convex shapes, are disposed adjacent to one surface of the base sheets 262a, 262b, and 262c, and extend along one direction. The structures 264a, 264b, and 264c refract light transmitted from the light guide plate 240 to condense light toward the liquid crystal panel 210.

In one embodiment of the present invention, the lens sheets 260A, 260B, and 260C of the present invention are made of the same material and the base sheets 262a, 262b, and 262c and the structures 264a, 264b, and 264c are integrally formed. .

In another embodiment of the present invention, the base sheets 262a, 262b and 262c and the structures 264a, 264b and 264c of the present invention are made of different materials. In this case, the base sheets 262a, 262b, and 262c are formed first, and then the lens sheets 260A, 260B, and the method are bonded to the structures 264a, 264b, and 264c on one surface of the base sheets 262a, 262b, and 262c. 260C) can be configured.

Diffusion particles 266a, 266b, and 266c are attached to the outer surface of the structures 264a, 264b, and 264c to scatter light emitted through the structures 264a, 264b, and 264c. Diffusion particles 266a, 266b, and 266c may be composed of a transparent resin or a material having a certain turbidity.

In addition, the size of the diffusion particles (266a, 266b and 266c) can be selected in various ways depending on the environment of use of the lens sheet (260A, 260B and 260C), the diffusion particles of a uniform size or diffusion particles of non-uniform size can be used. have.

The width L1 of each structure 264a disposed on one surface of the base sheet 262a in the lens sheet 260A of FIG. 4A is constant, and one surface of the base sheet 262b in the lens sheet 260B of FIG. 4B. The widths L2, L3, L4, L5, and L6 of the structure 264b disposed at are randomly changed.

In addition, in the lens sheet 260C of FIG. 4C, the widths L7 and L8 of the structure 264c disposed on one surface of the base sheet 262c periodically change. In the lens sheet 260C of FIG. 4C, two widths L7 and L8 are periodically formed, but three or more widths may be formed periodically.

Assuming the heights of the structures 264a, 264b, and 264c are constant, the larger the width of the structures 264a, 264b, and 264c, the smaller the curvature of the structures 264a, 264b, and 264c, so that the effect of refracting light Decreases.

Accordingly, the width of the structures 264a, 264b, and 264c may be adjusted according to the type and the arrangement of the light sources 230a to perform light condensing in a specific direction.

5A to 5C, the lens sheets 260D, 260E, and 260F of the present invention may include a base sheet 262d, 262e, and 262f, a plurality of structures 264d, 264e, and 264f, and a plurality of diffused particles 266d, 266e and 266f).

Since the base sheets 262d, 262e and 262f and the diffusion particles 266d, 266e and 266f are the same as or similar to those described above, detailed description thereof will be omitted below.

The height H1 of each structure 264d in the lens sheet 260D of FIG. 5A is constant, and the heights H2, H3, H4, H5 and H6 of the structure 264e in the lens sheet 260E of FIG. 5B. Changes randomly.

In addition, in the lens sheet 260F of FIG. 5C, the heights H7 and H8 of the structure 264f periodically change. In the lens sheet 260F of FIG. 5C, two heights H7 and H8 are periodically formed, but three or more heights may be formed periodically.

The width L of each of the structures 264d, 264e, and 264f of the lens sheets 260D, 260E, and 260F shown in FIGS. 5A through 5C is constant or randomly changed as described with reference to FIGS. 4A through 4C. Or may change periodically.

On the other hand, when the heights of the structures 264e and 264f are differently configured, such as the lens sheets 260E and 260F shown in Figs. 5B and 5C, the physical contact with other optical sheets is higher than the case where the height of the structures is constant. Since the amount can be reduced, the moire phenomenon can be alleviated.

6A and 6B, the lens sheets 260G and 260H of the present invention include base sheets 262g and 262h, a plurality of structures 264g and 264h, and a plurality of diffuse particles 266g and 266h.

Further, in the lens sheet 260G of FIG. 6A, the diffusion particles 266g are randomly attached to the outer surface of the structure 264g, and in the lens sheet 260H of FIG. 6B, the diffusion particles 266h are formed of the structure 264h. It is attached to the outer surface in a periodic pattern.

When the diffusion particles 266g are randomly attached to the outer surface of the structure 264g, the scattering effect of light through the entire lens sheet 260G may be increased as compared with the case where the diffusion particles 266g are attached in a periodic pattern.

According to the type and arrangement of the light source 230a, when the light emitted through the lens sheet 260H concentrates in a specific region, the diffusion particles 266h are attached to the region in a periodic pattern, thereby the lens sheet 260H. The brightness of the light emitted through the whole can be adjusted to be uniform. On the other hand, the periodic pattern is not limited to the pattern shown in Fig. 6B.

4A to 6B, the number of structures 264 of the lens sheet 260 of the present invention is illustrated as five for convenience of description, but the number of structures 264 is not limited to a constant.

7 is a graph showing a luminance curve of light emitted through the lens sheet and the conventional prism sheet of the present invention. Here, A represents the luminance curve of the lens sheet 260 of the present invention, B represents the luminance curve of the conventional prism sheet 100. In addition, the X axis represents an angle with respect to the normal direction of the lens sheet 260 and the prism sheet 100, and the Y axis represents an intensity of luminance.

Referring to FIG. 7, the lens sheet 260 of the present invention has a lower luminance than the conventional prism sheet 100 within a predetermined angle range.

However, when the conventional prism sheet 100 deviates from a certain angle, the brightness decreases sharply, whereas the lens sheet 260 of the present invention decreases the brightness gradually. Accordingly, the lens sheet 260 of the present invention can provide a wide effective viewing angle while maintaining uniformity of luminance.

Preferred embodiments of the present invention described above are 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, changes and Additions should be considered to be within the scope of the following claims.

The lens sheet, the backlight unit, and the liquid crystal display using the same according to the present invention have the advantage of extending the viewing angle while condensing the light provided from the light source onto the visible surface of the liquid crystal panel.

In addition, the lens sheet according to the present invention is structurally excellent in wear resistance, there is an advantage that can improve the reliability of the backlight unit and the liquid crystal display device employing it.

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, At least one light source for providing light for illuminating the liquid crystal panel; And Including a lens sheet positioned adjacent to the light source, The lens sheet, A base sheet for transmitting the light; A plurality of structures disposed in contact with one surface of the base sheet and extending in one direction and having a convex semicircular cross-sectional shape; And And a plurality of diffused particles for scattering light emitted through the structure. The liquid crystal display of claim 1, wherein the width of the structure is constant, randomly changed, or periodically changed. The liquid crystal display device according to claim 1 or 2, wherein the height of the structure is constant, randomly changed, or periodically changed. The liquid crystal display device of claim 1, wherein the diffusion particles are attached to the outer surface of the structure in a periodic pattern or randomly attached. At least one light source for providing light; And Including a lens sheet positioned adjacent to the light source, The lens sheet, A base sheet for transmitting the light; A plurality of structures disposed in contact with one surface of the base sheet and extending in one direction and having a convex semicircular cross-sectional shape; And The backlight unit, characterized in that it comprises a plurality of diffuse particles for scattering the light emitted through the structure. The backlight unit of claim 5, wherein the width of the structure is constant, randomly changed, or periodically changed. 7. The backlight unit of claim 5 or 6, wherein the height of the structure is constant, randomly changed, or periodically changed. The backlight unit of claim 5, wherein the diffusion particles are attached to the outer surface of the structure in a periodic pattern or randomly attached. A base sheet for transmitting light; A plurality of structures disposed in contact with one surface of the base sheet and extending in one direction and having a convex semicircular cross-sectional shape; And Lens sheet, characterized in that it comprises a plurality of diffuse particles for scattering the light emitted through the structure. 10. The lens sheet of claim 9, wherein the width of the structure is constant, randomly changed, or periodically varied. The lens sheet according to claim 9 or 10, wherein the height of the structure is constant, randomly changed, or periodically changed. The lens sheet of claim 9, wherein the diffusion particles are attached to the outer surface of the structure in a periodic pattern or randomly attached.

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