KR20080079466A - Optical sheet and display device having same - Google Patents

Abstract

An optical sheet and a display device having the same are provided to improve light diffusing and focusing effects by forming a hollow bead or a polygonal bead in the optical sheet. An optical sheet includes a base film(110) and a diffusion layer(120). The diffusion layer is formed on one surface of the base film. Hollow beads are contained in the diffusion layer. The hollow beads have spherical shapes. A size of the hollow bead lies between 5 and 30 um. The hollow bead is made of a material, which is selected from the group consisting of PMMA(PolyMethylMethAcrylate), PC(PolyCarbonate), MS(MethaStylene), and PS(PolyStylene). The diffusion layer contains hollow beads with different sizes. The diffusion layer includes a binder resin for fixing the hollow beads.

Description

Optical sheet and display device having the same {OPTICAL SHEET AND DISPLAY APPARATUS HAVING THE SAME}

1 is a perspective view showing an optical sheet according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the optical sheet shown in FIG. 1.

3 is a cross-sectional view showing an optical sheet according to another embodiment of the present invention.

4 is a perspective view showing the shapes of the bead shown in FIG.

5 is a cross-sectional view showing another embodiment of the bead shown in FIG.

6 is an exploded perspective view illustrating a display device according to an exemplary embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: optical sheet 110: base film

120: diffusion layer 122: hollow beads

124: binder resin 130: back coating layer

300: display device 400: light supply unit

410: lamp 420: reflective sheet

430 diffuser 500 display unit

510: display panel 520: driving circuit portion

The present invention relates to an optical sheet and a display device having the same, and more particularly, to an optical sheet and a display device having the same that can improve a diffusion function.

The liquid crystal display, which is one of display devices for displaying an image, is thinner and lighter than other display devices, has advantages of low driving voltage and low power consumption, and is widely used throughout the industry.

Since the liquid crystal display is a non-light emitting device in which a display panel for displaying an image does not emit light by itself, a separate backlight assembly for supplying light to the display panel is required.

The backlight assembly includes a lamp that substantially generates light, and an optical sheet such as a diffusion sheet, a prism sheet, and the like for improving the luminance characteristics of the light generated from the lamp.

In general, the diffusion sheet simply performs a diffusion function using sphere-shaped diffusion beads. Therefore, in order to improve the diffusion function, a large amount of diffusion beads are required and manufacturing costs are increased. On the other hand, when the amount of diffusion beads is reduced, the diffusion function is deteriorated.

Accordingly, the present invention has been made in view of such a problem, and the present invention provides an optical sheet capable of improving the diffusion function and reducing the manufacturing cost.

In addition, the present invention provides a display device having the above optical sheet.

An optical sheet according to an aspect of the present invention includes a base film and a diffusion layer formed on one surface of the base film and including hollow beads having an empty inside.

The hollow beads may have a substantially spherical shape. The hollow beads may have a size of about 5 μm to about 30 μm. The hollow beads may be formed of polymethyl methacrylate (PMMA), polycarbonate (PC), metastyrene (MS) or polystyrene (PS).

The diffusion layer may include the hollow beads of different sizes. The diffusion layer further includes a binder resin for fixing the hollow beads. The optical sheet may further include a back coating layer formed on the other surface of the base film.

The optical sheet according to another feature of the present invention is formed on one surface of the base film and the base film, and includes beads having a polyhedron shape having a plurality of planes.

The beads may have a substantially diamond shape in cross section. In addition, the beads may have a structure in which the inside is empty. The beads may have a size of about 5 μm to about 30 μm. The beads may be formed of polymethyl methacrylate (PMMA), polycarbonate (PC), metastyrene (MS) or polystyrene (PS).

The diffusion layer may include the beads of different sizes. The diffusion layer further includes a binder resin for fixing the beads. The optical sheet may further include a back coating layer formed on the other surface of the base film.

A display device according to an aspect of the present invention includes a light supply unit for supplying light, an optical sheet disposed above the light supply unit, and a display panel disposed above the optical sheet to display an image. The optical sheet is formed on a base film and one surface of the base film, and includes a diffusion layer including hollow beads having hollow interiors or polyhedral beads having a plurality of planes.

According to such an optical sheet and a display device having the same, it is possible to improve the diffusion function or the light condensing function of the optical sheet and to reduce manufacturing costs.

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

1 is a perspective view showing an optical sheet according to an embodiment of the present invention, Figure 2 is a cross-sectional view of the optical sheet shown in FIG.

1 and 2, the optical sheet 100 according to an embodiment of the present invention includes a base film 110 and a diffusion layer 120 formed on one surface of the base film 110.

The base film 110 is formed of a transparent material to transmit light. For example, the base film 110 may be polyacrylate-based, polycarbonate-based, polysulfone-based, polystyrene-based, polyethylene-based, polyvinylchloride It may be formed of a single component or a copolymer or a combination thereof, such as a series, polyvinyl alcohol series, polyester (polyester) series. In particular, the base film 110 may be formed of polyethylene terephthalate (PET) material having excellent strength and heat resistance.

The diffusion layer 120 is formed on one surface of the base film 110. The diffusion layer 120 diffuses light passing through the optical sheet 100 to improve luminance uniformity. In addition, the diffusion layer 120 may prevent adhesion between other optical sheets and prevent quality defects such as moiré.

The diffusion layer 120 is formed to have a thickness of about 5 μm to about 100 μm. When the thickness of the diffusion layer 120 is 5 μm or less, the diffusion function may not be properly performed. When the thickness of the diffusion layer 120 is 100 μm or more, a thickness of the optical sheet 100 may be too thick. . Therefore, the diffusion layer 120 is preferably formed to a thickness of about 5㎛ ~ 100㎛ for thinning the product while performing the light diffusion function properly.

The diffusion layer 120 includes hollow beads 122 for diffusing light and a binder resin 124 for fixing the hollow beads 122.

The hollow beads 122 are distributed at high density on one surface of the base film 110. The hollow beads 122 have a substantially spherical shape and have a hollow structure to improve the light diffusing function. Such hollow beads 122 may be manufactured, for example, through a general blow molding method.

If the hollow beads 122 are too small or too large, the light diffusing function may be degraded. Therefore, the hollow beads 122 are preferably formed in a size of about 5㎛ ~ 30㎛. In particular, the hollow beads 122 exhibit the best light diffusing effect at a size of about 15 μm.

The hollow beads 122 are formed of a transparent organic polymer material. For example, the hollow beads 122 may be made of polymethyl methacrylate (PMMA), polycarbonate (PC), methylstyrene (MS), polystyrene (PS), etc., which have excellent optical properties. Can be formed.

The diffusion layer 120 may include hollow beads 122 having different particle sizes. As such, when hollow beads 122 having different particle sizes are used, the smaller sized hollow beads 122 may fill the space between the larger sized hollow beads 122 to further improve the light diffusion efficiency. Alternatively, the diffusion layer 120 may include hollow beads 122 of substantially the same size.

Meanwhile, in order to prevent scratches of the base film 110, the hollow beads 122 may be formed of a material having the same or smaller hardness as the base film 110.

As such, when the air layer having different refractive indices is formed inside the hollow bead 122, since a diffusion effect can be obtained in the outer surface and the inner surface of the hollow bead 122 contacting the air layer, a general spherical bead in which no air layer is formed is provided. Compared with these, the light diffusing effect can be improved. Accordingly, the same diffusion effect can be obtained even by using a smaller amount of hollow beads 122 than the general spherical beads, thereby reducing the manufacturing cost. In addition, since the hollow bead 122 having the air layer formed therein has a specific gravity lower than that of a general spherical bead, the specific gravity can be reduced to further reduce the amount of raw materials used.

The binder resin 124 fixes the hollow beads 122 to one surface of the base film 110. For example, the binder resin 124 is formed of a thermosetting resin or an ultraviolet curable resin cured by heat or ultraviolet rays.

The diffusion layer 120 may be formed by mixing the hollow beads 122 and the binder resin 124 and applying it to one surface of the base film 110, and then curing the binder resin 124. At this time, in order to make the optical properties of the optical sheet 100 excellent, it is preferable to uniformly disperse the binder resin 124 and the hollow beads 122 so that the hollow beads 122 are distributed at the highest density.

When the haze of the diffusion layer 120 is 10% or less, the moiré concealment effect of the optical sheet 100 is lowered. When the haze of the diffusion layer 120 is 90% or more, the transmittance may be lowered to decrease luminance. Therefore, the diffusion layer 120 preferably has a haze of about 10% to about 90%.

The optical sheet 100 may further include a back coating layer 130 formed on the other surface of the base film 110. The back coating layer 130 is formed on the base film 110 in order to prevent contact with other optical members such as a light guide plate or a diffusion plate and to prevent quality defects such as moiré.

The back coating layer 130 may include beads 132 and a binder resin 134 for fixing the beads 132.

The beads 132 are preferably distributed at least at a density low enough to prevent adhesion in order to prevent scratches caused by friction with other optical members such as a light guide plate or a diffusion plate. Thus, the beads 132 are distributed at significantly less density than the hollow beads 122.

Beads 132 may be formed of transparent spherical particles. Beads 132 are formed to have a diameter of, for example, about 1 μm to about 10 μm, which is smaller than the hollow beads 122. When the diameter of the beads 132 is 1 μm or less, workability and processability may be inferior in manufacturing process, or poor adhesion to other optical members may occur. When the diameter of the beads 132 is 10 μm or more, visual This may cause visual defects or cause scratches. Therefore, the beads 132 are preferably formed with a diameter of about 1㎛ to about 10㎛.

In addition, the beads 132 may be formed of a material having a hardness less than that of the other optical members, in order to prevent scratches with other optical members. For example, the beads 132 are formed of polymethyl methacrylate (PMMA) or polycarbonate (PC) material.

The binder resin 134 fixes the beads 132 to the other surface of the base film 110. For example, the binder resin 134 is formed of a thermosetting resin or an ultraviolet curable resin cured by heat or ultraviolet rays.

3 is a cross-sectional view showing an optical sheet according to another embodiment of the present invention. In FIG. 3, except for the beads included in the diffusion layer, the same reference numerals are used for the same components, and the detailed description thereof will be omitted.

Referring to FIG. 3, the optical sheet 200 according to another embodiment of the present invention includes a diffusion layer 220 formed on one surface of the base film 110, and the diffusion layer 220 includes beads 222 and beads. A binder resin 224 to fix the 222.

Beads 222 are formed into a polyhedron shape with multiple planes. The beads 222 of this type may be formed of, for example, beads 222 having an angular shape while being manufactured in a circle or ellipse form, and then shaking in a predetermined frame. In addition, the polyhedral beads 222 may be manufactured by various methods that can give a predetermined crystal form. In particular, the beads 222 are preferably formed to have a substantially diamond cross section in order to increase the light collection efficiency.

If the sizes of the beads 222 are too small or too large, the light diffusion and condensing functions may be degraded. Therefore, the beads 222 are preferably formed in a size of about 5㎛ ~ 30㎛.

Beads 222 are formed of a transparent organic polymer material. For example, the beads 222 are formed of polymethyl methacrylate (PMMA), polycarbonate (PC), methyl styrene (MS), polystyrene (PS), or the like having excellent optical properties. Can be.

The diffusion layer 220 may include beads 222 having different particle sizes. As such, when beads 222 having different particle sizes are used, the smaller beads 222 may fill the space between the larger beads 222 to increase the distribution density of the beads 222. Alternatively, the diffusion layer 220 may include beads 222 of substantially the same size.

As such, when the shape of the bead 222 is formed into a polyhedral shape having a plurality of planes, the bead 222 serves as a prism, and condensing function is enhanced as compared with a general spherical diffusion bead. As a result, the luminance gain corresponding to the interruption degree of the general diffusion sheet and prism sheet can be obtained. Therefore, at least one prism sheet of two or more prism sheets used can be removed, thereby reducing the cost of the product.

FIG. 4 is a perspective view illustrating shapes of the beads illustrated in FIG. 3, and FIG. 5 is a cross-sectional view illustrating another embodiment of the beads illustrated in FIG. 3.

Referring to Figure 4, the polyhedral beads 222 are a cuboid shown in (a), a tetrahedron shown in (b), a parallelepiped shown in (C), a cuboid shown in (d), (e) It has various forms of polyhedrons, such as the tetrahedron shown in ()), the cube shown in (f), the octahedron shown in (g), the dodecahedron shown in (h), and the icosahedron shown in (i). Can be.

Meanwhile, the polyhedral beads 226 according to another embodiment may have a structure in which the inside thereof is empty, as shown in FIG. 5. As such, when the air layers having different refractive indices are formed inside the polyhedral beads 226 having a plurality of planes, the light condensing function may be enhanced while having a certain diffusion effect. In this case, the shapes of the beads 226 having an empty inside may also have various polyhedral shapes as shown in FIG. 4.

6 is an exploded perspective view illustrating a display device according to an exemplary embodiment of the present invention.

Referring to FIG. 6, the display device 300 according to the exemplary embodiment includes a light supply unit 400, an optical sheet 100, and a display unit 500.

The light supply unit 400 is disposed under the display unit 500 to supply light. The light supply unit 400 may include lamps 410 for generating light, a reflective sheet 420 disposed under the lamps 410, and a diffuser plate 430 disposed over the lamps 410. have.

A plurality of lamps 410 are disposed below the diffuser plate 430 and generate light in response to a driving power applied from an external inverter (not shown). The lamp 410 is made of, for example, a cold cylindrical fluorescent lamp (CCFL) having an elongated cylindrical shape. Alternatively, the lamp 410 may have a curved shape in the form of a "U". In addition, the lamp 410 may be formed of an external electrode fluorescent lamp (EEFL) in which electrodes are formed on outer surfaces of both ends or one end. Meanwhile, the light supply unit 400 may use light emitting diodes (LEDs) as a light source instead of the lamp 410.

The reflective sheet 420 is disposed under the lamps 410, and reflects light from the lamps 410 toward the diffuser plate 430 to improve light utilization efficiency.

The diffuser plate 430 diffuses light from the lamps 410 to improve luminance uniformity. The diffusion plate 430 is made of a transparent material for transmitting light, and may include a diffusion material therein for light diffusion. The diffusion plate 430 is formed of, for example, polymethyl methacrylate (PMMA) material.

Meanwhile, as illustrated in FIG. 4, the light supply unit 400 may have a direct structure in which the lamps 410 are disposed below the diffuser plate 430. Alternatively, the lamp may be disposed on the side of the light guide plate. It may have an edge structure.

The optical sheet 100 is disposed above the diffuser plate 430. If the light supply unit 400 has an edge structure, the optical sheet 100 is disposed above the light guide plate. Since the optical sheet 100 may have the same configuration as shown in FIGS. 2 to 5, detailed description thereof will be omitted.

Although not shown, other optical sheets such as a prism sheet, a reflective polarizing sheet, and a protective sheet may be further disposed on the optical sheet 100.

The display unit 500 includes a display panel 510 disposed on the optical sheet 100 to substantially display an image, and a driving circuit unit 50 to drive the display panel 50.

The display panel 50 includes a first substrate 512, a second substrate 514 coupled to the first substrate 512, and a liquid crystal layer interposed between the first substrate 512 and the second substrate 514. 516 may be included.

The first substrate 512 includes, for example, a TFT substrate on which a thin film transistor (hereinafter, referred to as TFT), which is a switching element, is formed in a matrix form. Data lines and gate lines may be connected to source and gate terminals of the TFTs, and pixel electrodes made of a transparent conductive material may be connected to drain terminals.

The second substrate 514 includes, for example, a color filter substrate in which an RGB color filter for realizing color is formed in a thin film form. A common electrode made of a transparent conductive material may be formed on the second substrate 514. Meanwhile, the color filter may be formed on the first substrate 512.

In the display panel 510, when a gate signal is applied to a gate terminal of the TFT and the TFT is turned on, a data signal is applied to the pixel electrode, and an electric field is formed between the pixel electrode and the common electrode. Due to the electric field, the arrangement of liquid crystal molecules of the liquid crystal layer 516 disposed between the lower substrate 512 and the upper substrate 514 is changed, and the transmittance of light is changed according to the arrangement of the liquid crystal molecules to obtain an image having a desired gray scale. Will be displayed.

The driving circuit unit 520 may include a data printed circuit board 522 for supplying a data driving signal to the display panel 510, a gate printed circuit board 524 for supplying a gate driving signal to the display panel 510, and a data printed circuit board. The data driving circuit film 526 connecting the 522 to the display panel 510 and the gate driving circuit film 528 connecting the gate printed circuit board 524 to the display panel 510 may be included. The data driving circuit film 526 and the gate driving circuit film 528 may be formed of a tape carrier package (TCP) or a chip on film (COF) including a driving chip. Meanwhile, the gate printed circuit board 524 may be removed by forming separate signal wires on the display panel 510 and the gate driving circuit film 528.

According to such an optical sheet and a display device having the same, by using the beads used in the optical sheet as hollow beads or polyhedral beads with empty interiors, the light diffusing function or the light condensing function can be improved and manufacturing cost can be reduced. Can be.

In the detailed description of the present invention described above with reference to the preferred embodiments of the present invention, those skilled in the art or those skilled in the art having ordinary skill in the art will be described in the claims to be described later It will be understood that various modifications and variations can be made in the present invention without departing from the scope of the present invention.

Claims (16)

Base film; And An optical sheet including a diffusion layer formed on one surface of the base film, the hollow layer including hollow beads. The optical sheet of claim 1, wherein the hollow beads have a substantially spherical shape. The optical sheet of claim 2, wherein the hollow beads have a size of about 5 μm to about 30 μm. The optical sheet of claim 2, wherein the hollow beads are formed of any one selected from polymethyl methacrylate (PMMA), polycarbonate (PC), metastyrene (MS), and polystyrene (PS). The optical sheet of claim 2, wherein the diffusion layer comprises hollow beads of different sizes. The optical sheet of claim 2, wherein the diffusion layer further comprises a binder resin for fixing the hollow beads. The optical sheet of claim 6, further comprising a back coating layer formed on the other surface of the base film. Base film; And An optical sheet formed on one surface of the base film, and comprising a diffusion layer comprising a plurality of polyhedral beads having a plurality of planes. The optical sheet of claim 8, wherein the beads have a substantially diamond shape in cross section. The optical sheet of claim 8, wherein the beads have a size of about 5 μm to about 30 μm. The optical sheet of claim 8, wherein the beads are formed of any one selected from polymethyl methacrylate (PMMA), polycarbonate (PC), metastyrene (MS), and polystyrene (PS). The optical sheet of claim 8, wherein the diffusion layer comprises the beads of different sizes. The optical sheet of claim 8, wherein the beads have a hollow structure. The optical sheet of claim 8, wherein the diffusion layer further comprises a binder resin for fixing the beads. The optical sheet according to claim 13, further comprising a back coating layer formed on the other surface of the base film. A light supply unit for supplying light; An optical sheet disposed on an upper portion of the light supply unit, the optical sheet including a base film and a diffusion layer formed on one surface of the base film and including hollow beads or polyhedral beads having a plurality of planes; And And a display panel disposed on the optical sheet to display an image.

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