KR101168416B1 - Optical Sheet and Back Light Unit using the same - Google Patents

Abstract

The present invention relates to an optical sheet to increase the light efficiency.

The optical sheet includes a transparent base film; A plurality of micro-lenses in the form of convex lenses formed on the base film and having a hole or a groove thereon, or a plurality of lenticular lenses in the form of convex lenses formed on the base film and the groove is formed on the base film.

Description

Optical Sheet and Back Light Unit using the same

1 is a cross-sectional view showing a conventional liquid crystal display device.

2 is a cross-sectional view showing the configuration of the optical sheets shown in FIG.

3 is a cross-sectional view showing a backlight unit according to the present invention.

4 and 5 are a plan view and a cross-sectional view showing a first embodiment of the optical sheet shown in FIG.

FIG. 6 is a view showing a light diffusion effect when light passes through the donut-shaped microlens shown in FIGS. 4 and 5.

7 is a view showing various shapes of a through hole or a groove formed in the donut-shaped micro lens.

8 and 9 are views showing the arrangement of a donut type micro lens.

10 and 11 are plan and cross-sectional views showing a second embodiment of the optical sheet shown in FIG.

12 is a simulation result diagram showing the light collecting and diffusing effects of the optical sheet according to the second and third embodiments of the present invention.

FIG. 13 is a simulation result view showing a light condensing effect of a convex lens in which grooves or holes are not formed. FIG.

14 and 15 are perspective views showing a third embodiment of the optical sheet shown in FIG.

16 shows several types of groove cross sections.

Description of the Related Art

11 LCD panel 12, 32 bottom cover

13: diffuser 14, 33: optical sheet

41, 51, 101: through hole, groove 42, 52, 102: micro lens

43, 53, 103: base film

The present invention relates to an optical sheet to increase the light efficiency. In addition, the present invention relates to a backlight unit to reduce the number of optical components required for the backlight unit by using the optical sheet.

In general, the liquid crystal display device has a trend that the application range is gradually widened due to the characteristics such as light weight, thin, low power consumption. According to this trend, the liquid crystal table market value is used for office automation equipment, audio / video equipment and the like. The liquid crystal display device displays a desired image on a screen by adjusting a transmission amount of light emitted from a backlight unit according to a signal applied to a plurality of control switches arranged in a matrix form.

Since the liquid crystal display device is not a self-luminous display device, a separate light source such as a backlight unit is required.

The backlight unit includes a direct type and an edge type according to the position of the light source. The edge type backlight unit installs a light source at one edge of the liquid crystal display device, and irradiates the liquid crystal display panel with light incident from the light source through the light guide plate and the plurality of optical sheets. In the direct type backlight, a plurality of light sources are disposed directly below the liquid crystal display, and light incident from the light sources is irradiated onto the liquid crystal display panel through the diffusion plate and the plurality of optical sheets.

Recently, the direct type backlight having higher luminance, light uniformity and color purity than the edge type has been used more mainly in LCD TVs.

Referring to FIG. 1, a conventional liquid crystal display device includes a liquid crystal display panel 11 for displaying an image and a backlight unit 10 for irradiating light onto the liquid crystal display panel 11.

In the liquid crystal display panel 11, a plurality of data lines and a plurality of scan lines are arranged to cross each other, and liquid crystal cells are arranged in an active matrix form between the upper and lower substrates. Further, pixel electrodes and a common electrode for applying an electric field to each of the liquid crystal cells are formed in the liquid crystal display panel. Thin film transistors (TFTs) for switching data voltages to be applied to the pixel electrodes are formed at intersections of the plurality of data lines and the plurality of scan lines. Gate drive integrated circuits and data drive integrated circuits are electrically connected to the liquid crystal display panel through a tape carrier package (TCP).

The backlight unit 10 includes a plurality of lamps 15, a bottom cover 12, a diffusion plate 13, and a plurality of optical sheets 14.

The lamps 15 emit light by an alternating current high voltage from an inverter (not shown) to generate light toward the diffusion plate 13.

The bottom cover 12 is manufactured in a container structure in which a plurality of lamps 15 are accommodated in an inner space, and reflecting plates are formed on the bottom and side surfaces of the inner space.

The diffusion plate 13 is assembled with the bottom cover 13. The diffuser plate 13 includes a plurality of beads and scatters the light incident through the lamps 15 using the beads to display the lamps 15 on the display surface of the liquid crystal display panel 11. ) And the luminance difference does not occur at the position between the lamps 15 and the position of the lamps 15. Since the diffuser plate 13 is manufactured in a structure in which beads are dispersed in a medium having the same refractive index, light cannot be collected.

The optical sheets 14 may include at least one diffusion sheet 14a and at least one prism sheet 14b as shown in FIG. 2 to uniform light incident from the diffusion plate 13 to the entire liquid crystal display panel 11. It serves to condense light and to condense the light traveling path in a direction perpendicular to the display surface to condense the light to the front of the display surface.

However, such a backlight unit 10 requires a large number of optical components such as a diffuser plate 12 and a plurality of optical sheets 14 for light uniformity and a light collecting effect. There are many causes and high manufacturing costs. In addition, the conventional backlight unit 10 has a problem of low light efficiency.

Accordingly, it is an object of the present invention to provide an optical sheet having a brightness enhancement effect and a diffusion effect by increasing light efficiency.

Another object of the present invention relates to a backlight unit to reduce the number of optical components required for the backlight unit by using the optical sheet.

In order to achieve the above object, the optical sheet according to an embodiment of the present invention is a transparent base film; It is provided with a plurality of micro lenses of the convex lens shape formed on the base film and having a hole or a groove on the top.

The micro lens is disposed in the matrix form, honeycomb form or delta form on the base film.

Optical sheet according to another embodiment of the present invention is a transparent base film; A plurality of lenticular lenses of the convex lens shape is formed on the base film and the groove is formed on the base film.

The lenticular lens is disposed in the form of a mesh or stripe on the base film.

The backlight unit according to the present invention includes a light source; The optical sheet is provided. The optical sheet increases the efficiency and brightness of light incident from the light source.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. 3 to 16.

Referring to FIG. 3, the backlight unit according to the exemplary embodiment of the present invention has a bottom cover 32 in which the light sources 31 are accommodated, and a hole (or a hole) in each of the lenses for directing the light from the light sources 31. Perforated) or grooves, and one or more optical sheets stacked on the optical sheet 33, for example, a reflective polarizing film 34.

The light sources 31 include a plurality of lamps, a plurality of light emitting diodes, or surface light emitters to generate light.

The bottom cover 32 includes a bottom surface and a side surface and a reflecting plate is attached thereto.

The optical sheet 33 includes a micro-lens array (MLA) in which circular or oval micro-lenses are arranged in a matrix or honeycomb form, or a strip of lenticular lenses having grooves. Or a lenticular lens array arranged in a mesh form to collect and diffuse incident light from each lens to increase the efficiency of light passing through the optical sheet 33 and to diffuse the light at the same time. Increase the uniformity of light. Detailed description of the optical sheet 33 will be described later.

The reflective polarizing film 34 selectively emits only light of a specific polarization component from the light from the composite lens sheet 33 and reflects light of a different polarization component to increase the polarization efficiency of light incident on the liquid crystal display panel. Do it. The reflective polarizing film 34 may be selected as a commercially available dual brightness enhancement film (DBEF), and any other known polarization selection film may be implemented.

On the other hand, the optical sheet 33 and the reflective polarizing film 34 may be manufactured separately and independently assembled to the liquid crystal display module, or may be integrated into one piece and assembled to the liquid crystal display module. In addition, the optical sheet 33 may be composed of two or more sheets.

4 to 9 are diagrams showing the optical sheet 33 according to the first embodiment of the present invention.

4 and 5, the optical sheet 33 according to the first embodiment of the present invention includes a plurality of donut micro lenses 42 each having a through hole 41.

Each of the plurality of donut-shaped micro lenses 42 is formed on the base film 43, and a hole 41 is formed in each of the lenses 42. Therefore, the surface of the base film 43 is exposed through the through hole 41 of the donut-shaped micro lens 42.

The base film 43 on which the donut-type microlenses 42 are formed is polyethylene terephthalate (hereinafter referred to as "PET"), and each of the microlenses has ultraviolet curable resin having a refractive index of about 1.4 to 1.7 (or UV resin). The manufacturing method of the optical sheet 33 is a process of coating the UV resin on the base film 43, UV resin coating process followed by a roll coating method (Roll Coating) intaglio patterns corresponding to each of the lenses having a hole The microlenses are irradiated with ultraviolet rays (UV) to the formed microlenses following the lens forming process and the lens forming process, which are formed by extrusion molding the formed molds to form microlenses with holes formed on the base film 43, respectively. A curing process for curing, and a process for separating the mold from the cured micro lenses following the curing process. Here, the mold is manufactured by processing a plurality of desired lens shapes by processing a metal plate using a drill tip of the desired lens shape. The lens surface of the mold thus produced is subjected to surface etching for a short time to smooth it. Another way to make a mold is by laser processing.

The donut-type micro lenses 42 collect incident light through the convex surface around the through hole 41 as shown in FIG. 6 to increase the luminance of the light transmitted through the optical sheet 33 and at the same time, incident light through the through hole 41. Diffuses to increase the light diffusion and uniformity. Adjacent toroidal micro lenses 42 are arranged without any gap as shown in FIG. 6.

The micro lenses 42 are shaped into a circular shape as shown in FIG. 4 or an elliptical shape as shown in FIGS. 5 and 7 when viewed from above, and the shape of the through hole 41 is a circular shape as shown in FIG. 4 or an elliptical shape as shown in FIGS. 5 and 7.

These donut micro lenses 42 are arranged in a matrix form as shown in FIG. 8 on the base film 43, or in a honeycomb or delta form as shown in FIG.

10 to 12 show an optical sheet 33 according to a second embodiment of the present invention.

10 to 12, the optical sheet 33 according to the second embodiment of the present invention includes a plurality of donut type micro lenses 52 each having a groove 51.

Each of the plurality of donut-shaped micro lenses 52 is formed on the base film 53, and each of the lenses 52 is recessed with a groove 51. The groove 51 forms a concave lens surface between the convex lenses. Since the groove 51 is formed only to a partial depth of the convex lens 52, the surface of the base film 53 is not exposed through the groove 41.

The material and manufacturing method of such donut micro lenses 52 are made of the same material as the first embodiment, and the manufacturing method is substantially the same as that of the first embodiment except that only the intaglio pattern of the mold is different.

The donut type micro lenses 52 collect incident light through the convex surface around the groove 51 to increase the luminance of the light transmitted through the optical sheet 33 and form concave lenses as shown in FIGS. 11 to 12. The incident light is diffused through the groove 51 to increase the diffusivity and uniformity of the light. On the other hand, the convex lens in which no groove or through-hole is formed has only a light collecting effect and little diffusion effect as shown in FIG.

The adjacent donut micro lenses 42 are arranged without any gap, and are arranged in a matrix form as shown in FIG. 8 on the base film 53, or in a honeycomb or delta form as shown in FIG.

In addition, the micro lenses 52 are shaped into a circle or oval when viewed from above, and the shape of the groove 51 is also shaped into a circle or oval.

14 to 16, the optical sheet 33 according to the third exemplary embodiment of the present invention includes lenticular lenses 102 having grooves 101 formed therein.

The plurality of lenticular lenses 102 are formed of a convex lens disposed on the base film in a stripe shape as shown in FIG. 14 or disposed on the base film in a mesh shape as shown in FIG. Grooves 101 which are recessed in the grooves are formed in the grooves.

In the case where the lenticular lenses 102 are arranged in a mesh form, the spacing between neighboring lenticular lenses 102 should be disposed within one lens width. If the distance between the neighboring lenticular lenses 102 is too large, there may be too much light passing directly through the base film without passing through the lenses 12 from the lower light source, so that a bright line may be seen in front of the optical sheet 33. Because.

The manufacturing method of the optical sheet 33 is substantially the same as the manufacturing method of the optical sheet 33 in which the microlenses are formed. However, in the manufacturing of the mold, the microlenses processed each lens with a drill tip, but the lenticular lenses 102 were scraped with the drill tip to process a single lenticular lens to manufacture a mold capable of making multiple lenses. There is a difference.

This lenticular lens 102 has the same cross-sectional shape as the micro lens of the second embodiment and can be described with reference to FIG. 12.

The lenticular lens 102 diffuses the light from the lamp 31, and the groove 101 serves to diffuse the light with the concave lens effect. In other words, the groove of the lenticular lens 102 improves the light diffusion efficiency by the concave lens effect, and the convex lens collects the incident light.

16 is a cross-sectional view of the groove 101 formed in the lenticular lens 102, the groove 101 is concave in various shapes at the top of the lens 102 in the shape of a hemispherical, elliptical, polygonal shape Can be formed.

Accordingly, the optical sheet according to the present invention may increase light efficiency and brightness by using a donut-type micro lens or a lenticular lens having grooves formed therein. The backlight unit according to the present invention can minimize the manufacturing tolerances and defects by reducing the number of diffuser plates and the number of optical sheets required compared to the prior art by using the optical sheet can not only reduce the manufacturing cost, but also irradiate the liquid crystal display panel The efficiency and brightness of the light can be increased.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the 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 (6)

A transparent base film; Is formed on the base film, provided with a plurality of micro lenses of the convex lens form, The plurality of micro lenses, Forming a through-hole through the center, the optical sheet, characterized in that to expose the base film through the through, diffuse the incident light through the through. The method of claim 1, The micro lens, Optical sheet, characterized in that arranged on the base film in the form of a matrix, honeycomb form or delta. A transparent base film; Is formed on the base film, and provided with a plurality of lenticular lenses in the form of convex lenses, The plurality of lenticular lenses, And forming a groove recessed to a depth of the convex lens so as not to expose the base film, and diffusing incident light using the groove as the recess lens. The method of claim 3, wherein The lenticular lens is Optical sheet, characterized in that arranged on the base film in the form of a mesh or stripe. A light source; A transparent base film irradiated with light from the light source, an optical sheet formed on the base film, the optical sheet including a plurality of micro lenses in the form of a convex lens, The plurality of micro lenses, And forming a through hole in the center, exposing the base film through the through hole, and diffusing the light through the through hole. A light source; A transparent base film irradiated with light from the light source, an optical sheet formed on the base film, the optical sheet including a plurality of lenticular lenses in the form of convex lenses, The plurality of lenticular lenses, And forming a recess recessed to a part depth of the convex lens so as not to expose the base film, and diffusing the light using the recess as a recess lens.

Images