KR20090051408A - Condensing type optical film - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light converging optical film used in a liquid crystal display, and simultaneously provides a function of improving brightness while uniformly diffusing light emitted from a light guide plate, and thus, separately a light diffusing film and a prism. In addition to significantly shortening the manufacturing process as compared to the case of mounting a film, it is possible to reduce the cost, the present invention is the optical interference caused by laminating a plurality of films, the loss of light such as scattering or absorption, damage to the film It is possible to provide a thinner liquid crystal display while preventing the damage.

Description

Condensing type optical film {Condensing type optical film}

The present invention relates to a light collecting optical film used in a liquid crystal display.

A liquid crystal display used as an optical display element is an indirect light emission method of controlling the transmittance of an external light source to display an image, and a backlight unit, which is a light source device, is used as an important component for determining characteristics of a liquid crystal display.

The backlight unit uses a cold cathode fluorescent lamp having a reflector as a light source, and sequentially passes the light emitted from the light source through the light guide plate, the light diffusion film, the prism film, and the protective film to reach the liquid crystal panel.

The light emitted from the light source is distributed to the front surface of the flat liquid crystal panel through the light guide plate, and the light source passed through the light guide plate can obtain a uniform light intensity across the entire screen through the light diffusion film. A light path control function is performed such that light beams of various directions passing through the light diffusion film are converted into a range of a viewing angle suitable for an observer to recognize an image. In addition, the lower portion of the light guide plate is provided with a reflecting plate for increasing the utilization efficiency of the light source by being able to reflect back the light that is not delivered to the liquid crystal panel and out of the path.

Here, the prism film has a triangular array (array) structure having an inclined surface of 45 kHz to improve luminance in the front direction. Therefore, since the angles emitted from the same type of prism are the same for each array, even if there is a small crush on the corners of the triangle or minute scratches on the inclined surface, the defects may be caused by the difference in the light paths emitted between the damaged parts and the normal parts. Will be processed. Therefore, the inflow of fine foreign matter is not allowed in the production of the prism film, and even in the case of minute defects, the entire surface of the produced prism film may not be used. This leads to a decrease in productivity, which in turn is a burden of cost increase. In addition, several laminations are made by manpower when working on the backlight unit. Prismatic film also requires considerable attention when working by hand, and the back light unit is increased due to the increase in the TACT time required for assembling the backlight unit and the supply of manpower. This will lead to an increase in the supply cost.

In addition, the existing light diffusing film can be manufactured by using a film using a light diffusing member and an ultraviolet curing type imprinting method. There are limitations on the implementation of the diffusion film, and the refractive index of the binder polymer used for adhesion between the base film and the light diffusing member may also be changed in a limited range, thereby limiting the luminance improvement. And the light diffusing film (FIG. 3 and 4) manufactured by the UV-curable imprinting method can control the refractive index of the base layer 11 and the light collecting layer 12 and the size of the light collecting structure (8), but the light collecting structure (8) Due to the flat surface 9 between the two sides, the incident angle and the exit angle were the same, and thus the refractive angle was not refracted.

In order to reach the maximum amount of light generated from the light source to the liquid crystal device, a plurality of sheets or films are used in addition to the film. As a result of having a multi-layered material, the unit cost is increased, and light loss and scattering or absorption of light generated by stacking a plurality of films, and a problem of damage to the film are generated. It is occurring.

In recent years, attempts have been made to reduce the application of optical sheets or films used to simplify the production process. In the case of using a prism film adhered to a light diffusion plate or making a prism pattern on a light diffusion plate, There was. In this case, however, it may be advantageous in terms of cost and productivity, but there is a problem that the increase in brightness is far less than expected.

Therefore, the inventors have confirmed that the luminance can be sufficiently increased while minimizing the application of optical films to improve the luminance, and have completed the present invention.

Accordingly, an aspect of the present invention is to provide a light converging optical film capable of improving luminance while evenly spreading light emitted from a light guide plate.

In addition, the present invention provides a light converging optical film that can prevent light loss, scattering or absorption of light caused by laminating a plurality of films, damage to the film, and shorten the manufacturing process and reduce costs. I would like to.

The present invention is a substrate layer as a preferred embodiment; And a light collecting layer formed on one surface of the base layer, the light collecting layer filled with a plurality of light collecting structures having a polygonal bottom surface.

In the above embodiment, the light collecting structure may have a semi-circular or semi-elliptical longitudinal section.

In the above embodiment, the light collecting layer may have a refractive index difference of 0.02 or more from the base layer.

In the above embodiment, the light collecting structure may have a diagonal length of 10 to 200 μm when the bottom surface is a polygon instead of a triangle.

In the above embodiment, the light collecting structure may have a length of one side of 10 ~ 200㎛ when the bottom surface is a triangle.

As described above, the present invention can simultaneously provide a function of improving the brightness while evenly spreading the light emitted from the light guide plate, which significantly shortens the manufacturing process as compared with the case of separately mounting a light diffusing film and a prism film. In addition to reducing the cost, it is possible to provide a thinner liquid crystal display.

In addition, the present invention can provide an optical film that can prevent the loss of light, such as light interference phenomenon, scattering or absorption caused by laminating a plurality of films, damage to the film.

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

5 is a plan view of an optical film constructed in accordance with one preferred embodiment of the present invention, FIG. 6 is a cross-sectional view taken along line AA of FIG. 5, FIG. 7 is a plan view of an optical film constructed in accordance with another preferred embodiment of the present invention, and FIG. BB cross section.

In the optical film of the present invention, the light collecting layer 20 is formed on one surface or both surfaces of the substrate layer 10.

The substrate layer 10 may be used without limitation as long as it is a transparent support. For example, polyethylene terephthalate, polycarbonate, polypropylene, polyethylene, polystyrene or polyepoxy may be used, and among these, polyethylene terephthalate or polycarbonate. Is preferred. The base layer 10 has a high light transmittance and should not affect the light collecting layer 20.

It is preferable that the thickness of the said base material layer 10 is 10-1000 micrometers, More preferably, it is 30-400 micrometers. If the thickness of the base layer 10 is less than 10㎛ there is a problem that the mechanical strength and thermal stability is weak, when the thickness of more than 1000㎛ there is a problem that the flexibility of the film is lowered and the loss of transmitted light may occur.

A light collecting layer 20 is formed on one or both surfaces of the base layer 10, and the light collecting layer 20 includes light collecting structures 21, 22, and 23, and one or both surfaces of the base layer 10. It is formed by molding into a thermosetting resin or an ultraviolet curable resin.

The resin for forming the light collecting structures 21, 22, and 23 uses a thermosetting resin or an ultraviolet curable resin as a resin having a higher refractive index and a transparent resin than the resin used for the base layer 10. For example, unsaturated fatty acid esters, aromatic vinyl compounds, unsaturated fatty acids and derivatives thereof, unsaturated dibasic acids and derivatives thereof, vinylcyanide compounds such as methacrylonitrile, and the like can be used.

The light converging structures 21, 22, and 23 have a bottom surface contacting the substrate layer 10 and a vertical cross section having a semicircular shape or a semi-elliptic shape, preferably a hexagonal shape or a mixture of octagonal and rectangular shapes. The light collecting structures 21, 22, and 23 are densely located on the entire surface of the base layer 10 so as to cover the base layer 10 to form the light collecting layer 20. As a result, the flat surface between the structure and the structure is minimized, and thus the incident angle and the exit angle are the same, thereby minimizing the amount of light that cannot be refracted, thereby effectively increasing the luminance. In addition, the cross section is semi-circular or semi-elliptical in shape to effectively diffuse light.

The light converging structure does not specifically limit the size of the bottom polygon, but if the base is a non-triangular polygon, the diagonal length may be 10 to 200 μm, and if the bottom is a triangle, the length of one side is 10 to 200 μm. It may be.

In addition, the refractive index of the light collecting layer 20 is preferably higher than the refractive index of the base layer 10 by 0.02 or more. When the refractive index of the light collecting layer 20 is lower than the base layer 10, the back surface of the base layer 10 This is because a part of the light incident from the front side may be totally reflected at the surface of the light collecting layer 20 in contact with the base layer 10 and may not be incident into the light collecting structures 21, 22, and 23. In addition, the greater the difference in refractive index between the incident medium and the exiting medium, the more the path of the emitted light is bent. Thus, the higher the refractive index, the higher the brightness in the front direction. It is preferable that the refractive index of the light collecting layer 20 for effectively increasing the brightness while diffusing light is 0.02 or more than the refractive index of the base layer 10 in consideration of the refractive index of air, which is the incident medium, being 1.

The thickness of the light collecting layer 20, that is, the height of the light collecting structure is preferably 10 μm to 150 μm in terms of maximizing the luminance increase effect.

The optical film of the present invention may further include light diffusing particles (not shown).

The light diffusing particles may include 1 to 500 parts by weight based on 100 parts by weight of the binder resin. When the light diffusing particles are used in less than 1 part by weight, it is difficult to expect the light diffusion effect. When the light diffusing particles is more than 500 parts by weight, cloudiness and separation of particles may occur, resulting in low light diffusion efficiency.

In addition, the light diffusing particles may be coated on one surface of the base layer 10 in which the light collecting layer 20 is not formed. The coating method is not particularly limited as long as it is a known coating method such as gravure coating and can be used.

The light diffusing particles vary depending on the thickness of the light collecting layer 20, but the average particle diameter is suitably 0.1 to 200 mu m, and preferably 0.1 to 100 mu m. If the average particle diameter of the light diffusing particles exceeds 200㎛ can be separated from the light collecting layer 20, if less than 0.1㎛ it is because it is difficult to expect the light diffusion effect.

As the light diffusion particles, a plurality of organic particles or inorganic particles may be used. Representative organic particles are methyl methacrylate, acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, acrylamide, metyrolacrylamide, glycidyl methacrylate, ethyl acryl Acryl-based particles of acrylate, isobutyl acrylate, normal butyl acrylate, 2-ethylhexyl acrylate homopolymer or copolymer and olefinic particles such as polyethylene, polystyrene, polypropylene, copolymer particles and homopolymers of acryl and olefinic After the particles are formed, the multi-layered multicomponent particles made by covering the layer with other monomers are used. As the inorganic particles, silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, magnesium fluoride and the like are used. The organic and inorganic particles are merely exemplary and are not limited to the particles of the organic or inorganic materials listed above, and may be replaced by other known materials as long as the main object of the present invention can be achieved. Obviously, such material change is also within the scope of the technical idea of the present invention.

By manufacturing the optical film as described above, the amount of light loss is greatly reduced compared to the conventional, and the manufacturing process and cost is reduced because the separately manufactured films are manufactured at once to provide a function of light diffusion and brightness increase. .

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to the following Examples.

<Example 1>

As a base layer, a 125 μm ultra-transparent polyethylene terephthalate film T600 (Mitsubishi Corporation) (refractive index: 1.49) was used, and an acrylic ultraviolet curable resin composition (refractive index: 1.52) was arranged in a light-converging structure having a hexagonal bottom surface and a semicircular cross section. A light collecting type optical film having a light collecting layer (refractive index: 1.53) of a light collecting structure having a diagonal length of 50 μm and a height of 25 μm was formed by inserting into a roller frame having a shape and molding the substrate layer.

<Example 2>

In Example 1, a light collecting optical film was manufactured in the same manner as in FIG. 7 except that the light collecting structure had a shape in which an underside was arranged adjacent to an octagon and a rectangle. The diagonal length of the octagon was 50 μm, and the length of one side of the rectangle was 25 μm. The height of the octagonal structure was 25 μm and the height of the rectangular structure was 12.5 μm.

<Example 3>

As the base layer, a 125 μm ultra-transparent polyethylene terephthalate film T600 (Mitsubishi Corporation) (refractive index: 1.49) was used, and an acrylic ultraviolet curable resin composition (refractive index: 1.48) was arranged at the bottom of a hexagon and a semicircular cross-section of a light converging structure. A light collecting type optical film having a light collecting layer (refractive index: 1.49) of a light collecting structure having a diagonal length of 50 μm and a height of 25 μm was formed by inserting into a roller frame having a shape and molding the substrate layer.

<Example 4>

As a substrate layer, a 125 μm ultra-transparent polyethylene terephthalate film T600 (Mitsubishi Corporation) (refractive index: 1.49) was used, and an acrylic ultraviolet curable resin composition (refractive index: 1.49) was arranged in a light-condensing structure having a hexagonal bottom surface and a semicircular cross section. A light collecting type optical film having a light collecting layer (refractive index: 1.50) made of a light collecting structure having a diagonal length of 50 µm and a height of 25 µm was formed by inserting into a roller frame having a shape and forming the substrate layer.

Comparative Example 1

On one surface of the same substrate layer used in Example 1 to form a coating layer (refractive index: 1.49) in which a mono-layer arrangement of particles of polymethyl methacrylate having an average particle diameter of 50㎛ in the gravure coating method was prepared.

Comparative Example 2

A light converging optical film was manufactured in the same manner except that a bottom surface of the same base layer used in Example 1 was formed with a circular spherical shape having an average particle diameter of 50 μm and a hemispherical shape having a height of 25 μm.

Comparative Example 3

A light converging optical film was manufactured in the same manner as in Comparative Example 2, except that the spacing between the hemispherical light collecting structure and the light collecting structure was constantly arranged at 5 μm.

<Comparative Example 4>

In Example 1, a prism film was manufactured in the same manner except that a light collecting layer (refractive index 1.53) having a pitch interval of 50 μm and a height of 25 μm having a triangular array structure was formed on one surface of the base layer.

Comparative Example 5

The prism film manufactured in 4 was laminated | stacked on the light-diffusion film manufactured by the comparative example 1 in comparison.

The physical property evaluation of the said Example and the comparative example was performed as mentioned later, The evaluation result is as Table 1 below.

<Luminance evaluation (Cd / ㎡)>

Two prism films of Examples and Comparative Examples prepared above were laminated and fixed in a backlight unit for a 17-inch liquid crystal display panel (Model name: LM170E01, manufactured by Heesung Electronics, Korea), and a luminance meter (Model name: BM-7, Japan) Using TOPCON Co., Ltd., measure the luminance at any of 13 points and calculate the average value.

division Luminance (cd / ㎡) Backlight unit with light guide plate only 1624 Example 1 2586 Example 2 2579 Example 3 2521 Example 4 2549 Comparative Example 1 2389 Comparative Example 2 2402 Comparative Example 3 2348 Comparative Example 4 2302 Comparative Example 5 2623

As a result of evaluating the physical properties, the embodiments having the light collecting layer of the present invention had better brightness than the case of having the light collecting layer other than the present invention, including the conventional prism structure. The brightness | luminance equivalent to the case where it was provided was provided.

Therefore, the luminance can be increased by increasing the utilization efficiency of the light source while minimizing the light loss. Thus, even if the light diffusing film and the prism film are not used separately as in the related art, the luminance can be equal to or higher than that of the conventional light source. Problems can be prevented.

1 is a cross-sectional view of a backlight unit of a general liquid crystal display device;

2 is a cross-sectional view of a conventional prism film,

3 is a plan view of a light diffusing film manufactured by a conventional ultraviolet curing type imprinting method,

4 is a cross-sectional view of FIG.

5 is a plan view of an optical film constructed in accordance with a preferred embodiment of the present invention;

6 is a cross-sectional view taken along line A-A of FIG.

7 is a plan view of an optical film constructed according to another preferred embodiment of the present invention;

FIG. 8 is a cross-sectional view taken along line B-B in FIG. 7.

* Description of the main parts of the drawings

10: base material layer

20: light collecting layer

21, 22, 23: light collecting structure

Claims (5)

Base layer; And A light converging optical film formed on one surface of the base layer and including a light collecting layer filled with a plurality of light collecting structures having a polygonal bottom surface. The method of claim 1, The light converging structure is a light converging optical film, characterized in that the longitudinal section is semi-circular or semi-elliptic. The method of claim 1, The light collecting layer is a light collecting type optical film, wherein the refractive index difference from the base layer is 0.02 or more. The method of claim 1, The light converging structure is a light converging optical film, characterized in that the diagonal length is 10 ~ 200㎛ when the bottom surface is a polygon rather than a triangle. The method of claim 1, The light converging structure is a light converging optical film, characterized in that the length of one side is 10 ~ 200㎛ when the base is a triangle.

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