KR20090069052A - Optical sheet - Google Patents

Abstract

An optical sheet is provided, which prevents the damage of the film and light loss due to scattering or the absorption by laminating a plurality of films. A prism layer(20) is formed in one side of the base layer(10). The diffusion layer(30) including a plurality of cylinder patterns is included on the other side of the base layer. The polyethylene terephthalate or polycarbonate is used as the base layer. The thickness of the base layer is 10~1000 micrometers. The refractive index of the base layer is 1.45~1.53. The prism layer includes the prism structure.

Description

Optical sheet

The present invention relates to an optical sheet 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.

In this way, a plurality of sheets or films, etc., are used in order to reach the maximum amount of light generated from the light source to the liquid crystal device. 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. However, in this case it may be advantageous in terms of cost or productivity, but there is a problem that the increase in brightness is far less than expected.

Accordingly, an aspect of the present invention is to provide an optical sheet capable of improving luminance while uniformly diffusing light emitted from a light guide plate.

In addition, the present invention is to provide an optical sheet that can prevent light loss, scattering or absorption of light generated by laminating a plurality of films, damage to the film, shorten the manufacturing process and reduce the cost. .

The present invention is a preferred embodiment, the base layer; A prism layer formed on one surface of the base layer; And a diffusion layer formed on the other side of the base layer and including a plurality of cylindrical patterns.

In the above embodiment, the cylindrical pattern of the diffusion layer may be 5 ~ 100㎛ diameter, 1 ~ 150㎛ height.

In the above embodiment, the diffusion layer may have a spacing between adjacent cylindrical patterns of 5 ~ 200㎛.

The present invention is another preferred embodiment, the optical sheet according to the embodiment; And a light diffusion member, at least one selected from the group consisting of a light diffusing member, a prism film, and a protective film, adjacent to one surface of the optical sheet.

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 sheet that can prevent light interference caused by laminating a plurality of films, loss of light such as scattering or absorption, and damage to the film.

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

1 is a longitudinal sectional view of an optical sheet according to a preferred embodiment of the present invention, Figure 2 is a rear view of an optical sheet according to a preferred embodiment of the present invention.

The optical sheet of the present invention forms a prism layer 20 on one surface of the substrate layer 10, and the other surface includes a diffusion layer 30 including a plurality of cylindrical patterns.

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 prism 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.

It is preferable that such a base material layer 10 has a refractive index of 1.45-1.53.

The prism layer 20 is formed on one surface or both surfaces of the substrate layer 10, and the prism layer 20 includes a prism structure, which is formed by molding with a thermosetting resin or an ultraviolet curable resin.

The thermosetting resin or the ultraviolet curable resin is a resin having a higher refractive index and a transparent resin than the resin used in the substrate layer 10. For example, unsaturated fatty acid esters, aromatic vinyl compounds, unsaturated fatty acids and derivatives thereof, unsaturated dibasic acids and derivatives thereof, Vinyl cyanide compounds such as methacrylonitrile and the like can be used.

The thickness of the prism layer 20, that is, the height of the prism structure is preferably 10 μm to 150 μm in terms of maximizing the luminance increase effect. The prism layer 20 preferably has a refractive index of 1.53 to 1.63 in terms of luminance improvement.

The optical sheet of the present invention includes a diffusion layer 30 formed on the other surface of the base layer 10, the diffusion layer 30 includes a plurality of cylindrical patterns. The cylindrical pattern has a diameter of 5 to 100 µm, a height of 1 to 150 µm, and a spacing between adjacent cylindrical patterns is 5 to 200 µm. This is to increase the light converging effect of the prism layer 20 while providing an appropriate light diffusion effect.

The method for forming the cylindrical pattern of the diffusion layer 30 is not particularly limited, and may be molded into a mold or may use lithography. Examples of the material that can form the cylindrical pattern of the diffusion layer 30 include an ultraviolet curable resin, and it is preferable to use a refractive index of 1.45 to 1.53 in consideration of light efficiency aspects such as diffusion.

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 on which the prism 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.

Although the light-diffusion particles vary depending on the thickness of the prism layer 20, 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 prism 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. Typical organic particles used are methyl methacrylate, acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, acrylamide, metyrolacrylamide, glycidyl methacrylate, ethyl acrylate. Of acrylic particles of isobutyl acrylate, normal butyl acrylate, 2-ethylhexyl acrylate homopolymer or copolymer and olefinic particles such as polyethylene, polystyrene and polypropylene, copolymer particles of acryl and olefinic copolymer and homopolymer After forming the particles, multi-layered multi-component particles made by covering the layers with other monomers are used. As 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 sheet 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 the function of light diffusion and brightness. .

In another aspect, the present invention can provide a backlight unit assembly including at least one selected from among a light diffusing member, a prism film, and a protective film formed adjacent to any one surface of the optical sheet described above, thereby providing more than the case of mounting only the optical composite film The brightness can be further improved.

Therefore, when the optical composite film of the present invention is applied to the backlight unit, it is possible to provide a backlight unit assembly having an appropriate brightness and viewing angle relative to the number of sheets to be mounted.

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>

After coating the acrylic UV curable resin composition on a transparent polyethylene terephthalate film (T600 (Mitsubishi Co., Ltd.), 125 μm (refractive index: 1.49), exposure was carried out using a cylindrical pattern mask so as to have a cylindrical interval of 5 μm, a diameter of 5 μm, and a height of 1 μm. After exposure, the height cylindrical pattern (refractive index: 1.515) was formed using the developing solution of 30 ^degreeC and 1%, and it is a conventionally well-known method using the acrylic ultraviolet curable resin composition (refractive index: 1.52) on the opposite surface. The prism structure is coated on the frame, and the other surface of the transparent polyethylene terephthalate film is contacted with the coating surface coated on the relief frame, and irradiated with UV rays toward the base layer to form a composition coated on the frame. The photo-cured and adhered and cured coating layer on the substrate layer was separated from the stamp frame.

At this time, the ultraviolet system was equipped with a Type-D blub to the electrodeless ultraviolet irradiation device (600W / inch) of the United States Fusion Corporation irradiated 900mJ / ㎠.

<Example 2>

In Example 1, a 20 μm thick dry film photoresist was bonded to a transparent polyethylene terephthalate film at a temperature of 110 ^° C. and a pressure of 4 kg _f at a rate of 2 m per minute, and a cylindrical interval of 50 μm, a diameter of 30 μm, and a height of 20 μm. Exposure was performed using the pattern mask. After exposure, the columnar pattern was formed using the developing solution of 30 ^degreeC and 1%. Thereafter, a prism layer was formed on the opposite side in the same manner as in Example 1.

<Example 3>

In Example 1, a 100 μm thick dry film photoresist was bonded to the transparent polyethylene terephthalate film at a temperature of 110 ^° C. and a pressure of 4 kg _f at a rate of 2 m per minute, and the cylindrical spacing was 100 μm, diameter 50 μm, height 100 μm. Exposure was performed using the cylinder pattern mask. After exposure, the columnar pattern was formed using the developing solution of 30 ^degreeC and 1%. Thereafter, a prism layer was formed on the opposite side in the same manner as in Example 1.

<Example 4>

A 150 μm thick dry film photoresist was bonded to the transparent polyethylene terephthalate film in Example 1 at a temperature of 110 ^° C. and a pressure of 4 kg _f at a rate of 2 m per minute, and a cylinder interval of 200 μm, diameter of 100 μm, height of 150 μm Exposure was performed using the pattern mask. After exposure, the columnar pattern was formed using the developing solution of 30 ^degreeC and 1%. Thereafter, a prism layer was formed on the opposite side in the same manner as in Example 1.

Comparative Example 1

Of the non-cylindrical pattern state prism sheet 213 LC (Kolon社, EverRay ^®) was prepared.

Comparative Example 2

Three sheets of light-diffusion films (KOLON, LD602) were prepared.

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 / ㎡)>

Fix the optical sheet of Example and Comparative Example prepared above to the backlight unit for 17-inch liquid crystal display panel (Model name: LM170E01, manufactured by Heesung Electronics, Korea), but in the case of Comparative Example 1, a light diffusion film (KOLON, LD602) and a protective film (KOLON, LD143). The brightness | luminance of 13 arbitrary points was measured using the luminance meter (model name: BM-7, TOPCON, Japan), and the average value was calculated | required.

Concealment

The luminance was measured using a luminance meter (model name: BM-7, TOPCON, Japan) while scanning the sheet in 2 mm units after mounting the sheet as in the luminance evaluation on the BLU. The results are shown in FIG. 3. In the graph, the x-axis is a distance (mm) and the y-axis is an arbitrary luminance value (Cd / m ² ). The lower the hiding value calculated by Equation 1 below, the better the hiding property.

<Equation 1>

Where A is the maximum luminance value and C is the difference between the maximum and minimum luminance values.

division Luminance (Cd / ㎡) Concealability (%) Example 1 4122 4.3 Example 2 4472 3.1 Example 3 4314 3.4 Example 4 4258 3.8 Comparative Example 1 4436 4.6 Comparative Example 2 3726 4.4

As a result of the physical property evaluation, it was found that the optical sheet according to the embodiment of the present invention had better brightness and better concealment than the case of Comparative Example 1 without the cylindrical pattern. In addition, it was possible to provide the same level of brightness and excellent concealment as in the case of Comparative Example 2 having a light diffusing film and a prism film separately.

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 longitudinal sectional view of an optical sheet according to a preferred embodiment of the present invention;

2 is a rear view of an optical sheet according to a preferred embodiment of the present invention;

3 is a graph illustrating the concealment measurement principle.

* Description of the main parts of the drawings

10: base material layer

20: prism layer

30: diffusion layer

Claims (4)

Base layer; A prism layer formed on one surface of the base layer; And It is formed on the other side of the base layer, the optical sheet comprising a diffusion layer comprising a plurality of cylindrical patterns. The method of claim 1, The cylindrical pattern of the diffusion layer is an optical sheet, characterized in that the diameter is 5 ~ 100㎛, the height is 1 ~ 150㎛. The method of claim 1, The diffusion layer is an optical sheet, characterized in that the spacing between adjacent cylindrical patterns is 5 ~ 200㎛. An optical sheet of any one of claims 1 to 3; And A backlight unit assembly adjacent to one surface of the optical sheet and including at least one selected from a light diffusing member, a prism film, and a protective film.

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