KR20070012941A - Light-diffusion film - Google Patents

Abstract

A light-diffusion film is provided to improve the brightness by forming multi-diffusion layers including light-diffusion particles and making the light-diffusion particles different in diameter. A light-diffusion film includes a transparent base material layer(10), and multi-diffusion layers(20,30) formed on one side or both sides of the transparent base material layer. The multi-diffusion layers include a binder resin and light-diffusion particles(21,31), wherein the far the diffusion layer is from the transparent base material layer, the bigger the mean diameter of the light-diffusion particles is. A difference between the mean diameters of the light-diffusion particles is in a range from 3 to 30mum.

Description

Light-diffusion film

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the side sectional drawing of one form of the light-diffusion film which concerns on this invention.

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

10: transparent substrate layer 20: first diffusion layer

21 light diffusing particle 30 second diffusion layer

31: light diffusing particles 40: damage prevention layer

The present invention relates to a light diffusing film for a backlight unit of a liquid crystal display, and more particularly, to a multi-layered diffusion layer constituting the light diffusing film, characterized in that the average particle diameter of the light diffusing particles included in each layer is different from each other. It is related with the light-diffusion film made into.

Liquid crystal displays, which are recently used as major components in TVs, desktop computers, notebooks, mobile phones, etc., use a liquid crystal layer made of non-light-emitting materials. Therefore, a separate light source must be installed. The light is emitted through the diffuser plate, the light guide plate, the prism film, and the like, and is emitted to the front side. In this process, the intensity of the light from the initial light source is slightly canceled so that the brightness on the screen we see is only a few hundredth of the original light source. In order to solve this problem, attempts have been made to brighten the light source, reduce the thickness of each medium, or change the patterning of the light guide plate in various ways. However, these attempts are limited due to the productivity and workability of the users.

Recently, development of a high brightness light diffusing film has been attempted. For this purpose, the light transmittance and the light diffusivity must be high to increase the luminance. Japanese Patent Laid-Open No. 6-67003, Japanese Patent Laid-Open No. 7-174909, Japanese Patent Laid-Open No. 9-127314, and Korean Patent Publication Nos. 2003-0077472, 2003-0077469, 2003-0077468, and Republic of Korea 453336, 456805, and the like have proposed a light diffusing film in which one side of a transparent polymer resin film is coated with a solution in which inorganic particles or organic particles are dispersed in an organic solvent with a transparent binder resin as a light diffusing agent.

However, these conventional inventions are light-diffusion films coated with a non-uniform thickness on the binder resin irrespective of the size of the light-diffusion particles, and thus there is a problem that the uniformity of the brightness is lowered.

Accordingly, the present invention is to solve the above problems, it is possible to increase the brightness by configuring a diffusion layer including a light diffusing particles of a predetermined size in a multi-layer, the particle diameter of the light diffusing particles included in each layer are different from each other. The purpose is to provide a light diffusing film.

The present invention for achieving the above object is a transparent substrate layer; And it provides an optical dispersion film comprising a multi-layered diffusion layer formed on one side or both sides of the transparent base layer.

The multi-layered diffusion layer includes a binder resin and light-diffusing particles, and the average diffusion diameter of the light-diffusing particles included in the diffusion layer farther from the transparent base layer is larger.

The multilayer diffusion layer is characterized in that the difference in the average particle diameter of the light diffusing particles included in each layer is 3 ~ 30㎛.

The multi-layered diffusion layer is characterized by using at least one selected from a polyester resin, an acrylic resin, a cellulose acetate resin, a urethane resin, an epoxy resin, and a melamine resin as a binder resin.

The multilayer diffusion layer is light diffusing particles of at least one selected from acrylic, olefin and copolymers of acrylic and olefin or organic particles or multilayer oxide of silicon multi-layer particles, aluminum oxide, titanium oxide, zirconium oxide and magnesium fluoride. It is characterized by using at least one selected from inorganic particles.

The multi-layered diffusion layer is characterized in that the light-diffusing particles are contained 50 to 350 parts by weight based on 100 parts by weight of the binder resin.

The diffusion layer in contact with the transparent substrate layer of the multilayer diffusion layer is characterized in that it comprises light diffusion particles having an average particle diameter of 2 ~ 30㎛.

Hereinafter, the present invention will be described in more detail.

The present invention is characterized in that it comprises a transparent base layer and a diffusion layer on one side or both sides of the transparent base layer in multiple layers.

As the transparent base layer, any transparent plastic support can be used, and polycarbonate, polypropylene, polyethylene terephthalate, polyethylene, epoxy, etc. are used, and mainly polyethylene terephthalate is used.

On the other hand, the transparent base layer should have high adhesion and light transmittance, and should have uniform flatness so that there is no variation in luminance. As for the thickness of a transparent base material layer, 50-250 micrometers is suitable, More preferably, 75-200 micrometers is suitable. If the thickness is 50 μm or less, the mechanical properties and the heat resistance of the film are insufficient, and if the thickness is 250 μm or more, the product becomes thick.

The diffusion layer includes a binder resin and light diffusing particles. As the binder resin, a resin having good adhesion to the transparent base layer and having good compatibility with the light diffusing particles included therein may be polyester resin, acrylic resin, cellulose acetate resin, urethane resin, epoxy resin, melamine resin Etc.

The light diffusing particles are dispersed in the binder resin to increase light transmittance and diffusion rate. Organic or inorganic particles may be used as the light diffusion particles, and organic particles are mainly used because the light diffusion properties of organic particles are superior to inorganic particles.

As organic particles, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate Acrylate, hydroxyethyl acrylate, acrylamide, metyrolacrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate, 2-ethylhexyl acrylate polymer or air thereof Acrylic polymer particles such as copolymers or terpolymers; Olefin polymer particles such as polyethylene and polypropylene; 1 type selected from the group consisting of acryl- and olefin-based copolymer particles, polystyrene-based polymer particles, and homopolymer-based particles, and then multi-layered multi-component particles made by covering them with other monomers on the layer and siloxane-based polymer particles. The above can be used.

The inorganic particles may be at least one selected from the group consisting of silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, and magnesium fluoride.

The diffusion layer as described above is formed in multiple layers on one or both surfaces of the transparent substrate layer. In this case, the light diffusing particles included in the diffusion layer are positioned farther from the transparent base layer as the average particle diameter is larger. When particles having a small average particle diameter are located far from the transparent substrate layer, the uniformity and smoothness of the surface of the substrate may be lowered, thereby lowering the brightness of light.

Each of the diffusion layers may be such that the light diffusing particles included have a particle size of a predetermined size. When light-diffusing particles having particle sizes of different sizes are mixed in the diffusion layer, uniformity and regularity of the particle surface smoothness are lowered, thereby causing a problem in that luminance is lowered. Therefore, if the diffusion layer having light diffusing particles having a predetermined particle diameter is configured in a multi-layer, and the particle diameters of the light diffusing particles of each layer are different from each other, the brightness of light can be increased while maintaining uniformity and regularity of particle surface smoothness.

At this time, it is preferable that the average particle diameter difference of each light-diffusion particle contained in the said multilayer diffusion layer is 3-30 micrometers. When the average particle diameter difference between particles is less than 3 μm, the light diffusion effect due to the particle size difference may be lowered. When the average particle size difference is larger than 30 μm, the distribution of small particles may be uneven and the surface uniformity may be reduced.

The light diffusing particles of the diffusing layer having the smallest particle diameter of the light diffusing particles included in the diffusing layer, that is, the light diffusing particles of the diffusing layer in contact with the transparent base layer, preferably have an average particle diameter of 2 to 30 μm. If it is less than 2㎛, it is difficult to expect the light diffusion effect by the particles, If it exceeds 30㎛, there is a fear of the light diffusion particles are separated, and the diffusion layer has to be laminated in multiple layers, so the thickness is too thick, easy to install on the product There is a problem that is not.

The multi-layered diffusion layer is such that 50 to 350 parts by weight of light-diffusing particles included in each layer are included with respect to 100 parts by weight of the binder resin of each layer. If it contains less than 50 parts by weight, light diffusion efficiency is lowered, and if it contains more than 350 parts by weight, turbidity occurs, making it difficult to use.

A curing agent may be further included to increase heat resistance, abrasion resistance, and adhesion of the diffusion layer. The curing agent should have good light transmittance and good adhesion to the transparent base layer, and for example, aliphatic isocyanate is used.

There is no particular limitation on the method of forming the diffusion layer having the above-described configuration on the transparent base layer, and may be applied by a comma knife or gravure. At this time, the thickness of the diffusion layer is suitable 5 ~ 50㎛, if less than 5㎛ it is difficult to distribute the light diffusing particles to have a light diffusion characteristics, if the thickness exceeds 50㎛ it is difficult to mount on the product.

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

1 is a cross-sectional side view of a form of a light diffusing film according to the present invention, in which a first diffusion layer 20 including light diffusing particles 21 and 31 having a constant particle size on one surface of a transparent base layer 10 is shown. ) And the second diffusion layer 30 are sequentially stacked. The second diffusion layer 30, which is a diffusion layer located far from the transparent substrate layer 10, may have light diffusing particles 31 having a larger particle diameter than the first diffusion layer 20, which is a diffusion layer contacting the transparent substrate layer 10. It is included.

In the present invention, when the diffusion layer is provided only on one surface of the transparent base layer 10, the damage prevention layer 40 may be selectively provided on the back surface.

Hereinafter, examples of the present invention will be described in more detail, but the scope of the present invention is not limited to these examples.

<Example 1>

A first diffusion layer is applied to one side of a 100 μm ultra-transparent polyethylene terephthalate film (FCTT, Kolon) using gravure to have a dry thickness of 8 μm. The first diffusion layer is prepared by mixing 100 parts by weight of acrylic resin (Aekyung Chemical, 52-666), 100 parts by weight of methyl ethyl ketone, and 100 parts by weight of toluene with a binder resin, 120 parts by weight of polymethyl methacrylate particles (manufactured by Soken, MX500) particles having an average particle diameter of 5 μm as the diffusion particles are mixed and dispersed by a mill, and then applied. Coating using gravure and hot air drying at 100 ℃ 30 seconds to form a coating layer. The second diffusion layer was mixed with 120 parts by weight of polymethyl methacrylate particles (manufactured by Soken, MX1000) having an average particle diameter of 10 μm with light diffusing particles based on 100 parts by weight of the binder resin of the first diffusion layer. Coating is carried out so that it may become micrometer. After the coating, hot air was dried at 100 ° C. for 30 seconds to prepare a light diffusing film having a coating layer.

<Example 2>

In Example 1, the light diffusion film was manufactured in the same manner except that the particle diameter of the light diffusion particles of the second diffusion layer was 20 μm (manufactured by Soken, MX2000) and the drying thickness of the second diffusion layer was 25 μm.

<Example 3>

In Example 1, the particle size of the light diffusion particles of the first diffusion layer is 10 μm (manufactured by Soken, MX1000), the dry thickness of the first diffusion layer is 15 μm, and the particle diameter of the light diffusion particles of the second diffusion layer is 20 μm (Soken manufacture, MX2000), except that the drying thickness of the second diffusion layer is 25㎛ all were made the light-diffusion film.

Comparative Example 1

In Example 1, the particle diameter of the light diffusion particles of the first diffusion layer is 1.5 μm (manufactured by Soken, MX150), the dry thickness of the first diffusion layer is 2 μm, and the particle diameter of the light diffusion particles of the second diffusion layer is 20 μm (Soken manufacture, MX2000) and the light-diffusion film were manufactured in the same manner except that the dry thickness of the 2nd diffusion layer was 25 micrometers.

Comparative Example 2

In Example 1, the dry thickness of the first diffusion layer is 10 μm, the average particle diameter of the light-converted particles of the second diffusion layer is 60 μm, polymethyl methacrylate particles (Soken, MR-60G), and the dry thickness of the second diffusion layer. A light diffusing film was prepared in the same manner except that the thickness was 70 μm.

Comparative Example 3

A single diffusion layer is applied to one side of a 125 μm ultra-transparent polyethylene terephthalate film (Mitsubishi, T600) using gravure to have a dry thickness of 20 μm. The diffusion layer was diluted by adding 100 parts by weight of methyl ethyl ketone and 100 parts by weight of toluene to 100 parts by weight of an acrylic resin (52-666, manufactured by Aekyung Chemical Co., Ltd.). 120 micrometers of polymethyl methacrylate (KOLON, PBX010) particle | grains of micrometers are mixed, it disperse | distributes with a mill, and apply | coats. Coating using gravure and hot air drying at 100 ℃ for 30 seconds to prepare a light diffusion film having a coating layer.

<Comparative Example 4>

A light diffusing film was prepared in the same manner as in Comparative Example 3 except that the light diffusing particles of the diffusion layer were polymethyl methacrylate (manufactured by Soken, MX2000) having an average particle diameter of 20 μm.

After cutting the light diffusing film manufactured according to the above embodiment and the comparative example to be mounted on the backlight unit, the brightness of the diffusion sheet alone on the backlight unit light guide plate and finally the diffusion type dual luminance improvement film (3M, Dual Brightness) The Enhancement Film, Vikuiti ^TM DBEF-D440) was mounted and averaged by measuring nine luminances with a TOPCON BM7 luminance meter, shown in Table 1 below.

Particle Size of the First Diffusion Layer (µm) Particle Size of the Second Diffusion Layer (µm) Luminance (㏅ / ㎡) Example 1 5 10 3170 Example 2 5 20 3250 Example 3 10 20 3227 Comparative Example 1 1.5 20 3130 Comparative Example 2 5 60 3007 Comparative Example 3 10 - 3105 Comparative Example 4 20 - 3130

As a result of the experiment, in the case of the embodiment according to the present invention, the luminance was excellent, but the particle size of the light diffusion particles of the first diffusion layer is too small, the particle size of the light diffusion particles of the second diffusion layer is too large, or the comparative example composed of a single diffusion layer It can be seen that the luminance is low compared with the present invention.

As described above, the present invention can increase the luminance of the light-diffusion film by forming a diffusion layer including light-diffusion particles having a predetermined size in a multi-layer and varying the particle diameters of the light-diffusion particles included in each layer.

Claims (7)

Transparent substrate layer; And Optical diffusion film, characterized in that it comprises a multi-layered diffusion layer formed on one side or both sides of the transparent base layer. The method of claim 1, The multi-layered diffusion layer includes a binder resin and light-diffusion particles, and the light-diffusion film is characterized in that the average particle diameter of the light-diffusion particles is larger as the diffusion layer is farther from the transparent substrate layer. The method according to claim 1 or 2, The multi-layer diffusion layer is a light diffusion film, characterized in that the difference in the average particle diameter of the light diffusion particles contained in each layer is 3 ~ 30㎛. The method of claim 1, The multilayer diffusion layer is an optical acid film using at least one selected from a polyester resin, an acrylic resin, a cellulose acetate resin, a urethane resin, an epoxy resin, and a melamine resin as a binder resin. The method according to claim 1 or 2, The multilayer diffusion layer is light diffusing particles of at least one selected from acrylic, olefin and copolymers of acrylic and olefin or organic particles or multilayer oxide of silicon multi-layer particles, aluminum oxide, titanium oxide, zirconium oxide and magnesium fluoride. Light-diffusion film, characterized in that used at least one selected from inorganic particles. The method according to claim 1 or 2, The multi-diffusion layer is a light diffusion film, characterized in that the light diffusion particles are contained 50 to 350 parts by weight based on 100 parts by weight of the binder resin. The method according to claim 1 or 2, The diffusion layer in contact with the transparent substrate layer of the multi-layer diffusion layer is an optical dispersion film, characterized in that it comprises light diffusion particles having an average particle diameter of 2 ~ 30㎛.

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