KR20090071714A - Optical sheet - Google Patents

Abstract

An optical sheet is provided to prevent damage of a film and loss of the light, a light interference phenomenon due to laminate of a plurality of films by forming a structural layer including a plurality of prism patterns and a cylindrical pattern. An optical sheet includes a structural layer(20) and a base material layer(10). The structural layer is formed on one side or both sides of the base material layer. The structural layer comprises a plurality of prism patterns(21) and a plurality of cylinder patterns(22) The prism pattern and cylinder pattern are by turns repetitively molded. The prism pattern is molded with thermoset and UV resin.

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. 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.

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; And a structural layer formed on one or both surfaces of the base layer, wherein the structural layer includes a plurality of prism patterns and a plurality of cylindrical patterns.

In the above embodiment, the structural layer may be formed by alternately repeating the prism pattern and the cylindrical pattern.

In the above embodiment, the cylindrical pattern of the structural layer may be 40 ~ 70 ㎛ in diameter, 20 ~ 35 ㎛ in height.

In the above embodiment, the structure layer may have a spacing between adjacent cylindrical patterns of 5 ~ 70㎛.

In the above embodiment, the prism pattern of the structural layer may be a pitch of 40 ~ 70㎛, 20㎛ ~ 35㎛ height.

The present invention is another preferred embodiment, the optical sheet; 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 perspective view of an optical sheet according to a preferred embodiment of the present invention.

The optical sheet of the present invention includes a structural layer 20 on one or both surfaces of the base layer 10, the structural layer 20 includes a plurality of prismatic patterns 21 and a plurality of cylindrical patterns 22. do.

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.

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

The structural layer 20 includes a plurality of prismatic patterns 21 and a plurality of cylindrical patterns 22, and the prism pattern 21 and the cylindrical patterns 22 are alternately repeatedly formed.

The prism pattern 21 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 base 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, etc. can be used.

The thickness of the structural layer 20, that is, the height of the prism pattern 21 is preferably 20 μm to 35 μm in terms of maximizing the luminance increase effect. Moreover, it is preferable that the pitch of the prism pattern 21 is 40 micrometers-70 micrometers.

The cylindrical pattern 22 preferably has a diameter of 30 to 50 µm, a height of 10 to 30 µm, and an interval between adjacent cylindrical patterns 22 of 30 to 60 µm. This is to provide an appropriate light diffusion effect and at the same time increase the light condensing effect of the structural layer 20.

The method of forming the cylindrical pattern 22 is not particularly limited, and may be molded into a mold or may use lithography. For example, after the prism pattern 21 is formed, the cylindrical pattern 22 may be formed by a lithography method using a photoresist. ) Can be formed. Examples of the material capable of forming the cylindrical pattern 22 include an ultraviolet curable resin, and the like, and a refractive index of 1.45 to 1.53 is preferably used in consideration of light efficiency such as diffusivity and the difference in refractive index with the light collecting layer. .

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 diffusion particles may be coated on one surface of the base layer 10 on which the structure 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 structural layer 20, but the average particle diameter is appropriately 0.1 ~ 200㎛, preferably 0.1 ~ 100㎛. If the average particle diameter of the light diffusing particles exceeds 200㎛ can be separated from the structural 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>

The acrylic UV curable resin composition (refractive index: 1.52) was coated on a frame in which a prism pattern was carved by a common known method, and as a base layer, a super-transparent polyethylene terephthalate film T600 (Mitsubishi Corp.) having a thickness of 125 µm (refractive index: 1.49) In the state in which one side of the contact with the coating surface coated on the stamping frame, by irradiating UV light toward the base layer photocuring the composition coated on the frame, the coating layer adhered to the base layer cured from the stamping frame I was. The height of the prism pattern was 25 micrometers.

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

A 30 μm thick dry film photoresist was bonded to the prism film structure obtained above at a speed of 2 m / min under a temperature of 110 ^° C. and a pressure of 4 kg _f . It was. Therefore, the height of the cylindrical pattern is 30㎛ determined by the above dry film. After exposure, a cylindrical pattern (refractive index: 1.512) was formed on the prism pattern as shown in FIG. 2 using 30 ^° C. and 1% developer.

<Example 2>

Under the same conditions as in Example 1, a 20 µm dry film photoresist was used to expose and develop a cylindrical pattern mask having a diameter of 40 µm and a spacing of 5 µm to form a cylindrical pattern having a height of 20 µm on the prism valleys.

<Example 3>

Under the same conditions as in Example 1, using a 25 μm dry film photoresist, a cylindrical pattern mask having a diameter of 60 μm and an interval of 20 μm was exposed and developed to form a cylindrical pattern having a height of 25 μm on the prism valleys.

<Example 4>

Under the same conditions as in Example 1, using a 35 μm dry film photoresist, a cylindrical pattern mask having a diameter of 70 μm and a spacing of 5 μm was exposed and developed to form a cylindrical pattern having a height of 35 μm on the prism valleys.

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 / ㎡)>

Laminating and fixing the optical sheet of the Example and Comparative Example prepared above to the back light unit for 17-inch liquid crystal display panel (Model name: LM170E01, manufactured by Heesung Electronics Korea), but in the case of Comparative Example 1 light diffusion film (KOLON, LD602) and It was mounted between the 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 4502 2.9 Example 2 4416 3.4 Example 3 4466 3.3 Example 4 4358 3.9 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 perspective 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: substrate layer 20: structure layer

21: prism pattern 22: cylinder pattern

Claims (6)

Base layer; And It includes a structural layer formed on one side or both sides of the base layer, The structural layer comprises a plurality of prismatic patterns and a plurality of cylindrical patterns. The method of claim 1, The structural layer is an optical sheet, characterized in that the prism pattern and the cylindrical pattern is formed alternately repeated. The method of claim 1, The cylindrical pattern of a structural layer is 40-70 micrometers in diameter, and an optical sheet characterized by having a height of 20-35 micrometers. The method of claim 1, The structural layer is an optical sheet, characterized in that the interval between adjacent cylindrical patterns is 5 ~ 70㎛. The method of claim 1, The prism pattern of a structural layer is 40 micrometers-70 micrometers in pitch, and 20 micrometers-35 micrometers in height, The optical sheet characterized by the above-mentioned. An optical sheet of any one of claims 1 to 5; 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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