KR20080085658A - Multi-functional optic film - Google Patents

Abstract

A multi-functional optic film is provided to improve the efficiency of light incident to a prism layer by reducing a refractive index difference between resin and particles in forming a light diffusion layer to reduce internal reflection of the light. A multi-functional optic film includes a transparent base layer, a light diffusion layer, and a prism layer(30). The light diffusion layer is formed on one surface of the transparent base layer and includes binder resin and light diffusing particles. A refractive index difference between the binder resin and the light diffusing particles is less than 0.05. The prism layer is formed on the light diffusion layer. The multi-functional optic film further includes a protection layer. The protection layer is formed on the other surface of the transparent base layer and includes binder resin and particles.

Description

Multi-functional optic film

TECHNICAL FIELD This invention relates to the optical composite film used for a liquid crystal display.

As the industrial society develops into an advanced information age, the importance of the electronic display device as a medium for displaying and transmitting various information is increasing day by day. CRT (Cathode Ray Tube), which has been widely used in the past, has limitations due to large installation space, which makes it difficult to increase the size. Therefore, such as liquid crystal display (LCD), plasma display panel (PDP), field emission display (FED), and organic EL It is being replaced by various flat panel display devices. Among such flat panel display devices, in particular, in the case of liquid crystal display devices (LCDs), due to the advantages of thin, light, and low power consumption as a technology-intensive device in which liquid crystal and semiconductor technologies are combined, its structure and manufacturing technology have been researched and developed. In addition to the areas where liquid crystal displays have been widely used, such as notebook computers, desktop computer monitors, and portable personal communication devices (PDAs and mobile phones), large-sized technologies are gradually exceeding their limits. It has been applied as a new display device that can replace CRT, which is synonymous with display, as it has been applied to large-sized TVs.

In the liquid crystal display (LCD) device, since the liquid crystal itself cannot emit light, a separate light source is installed at the rear of the device to adjust the intensity of the passing light through the liquid crystal installed in each pixel to realize contrast. do. In more detail, the liquid crystal display device is a device for controlling the light transmittance by using the electrical properties of the liquid crystal material, the uniformity and the directionality is controlled by passing through various functional prism films or sheets by emitting light from the light source lamp on the back of the device Indirect light-emitting display device that implements an image by passing light through a color filter to realize red, blue, green (R, G, B) colors, and controlling the contrast of each pixel by an electric method As a light emitting device that provides a light source, it is an important component for determining image quality such as brightness and uniformity of a liquid crystal display device.

A backlight unit (BLU) is widely used as the light emitting device, and a general backlight unit is as shown in FIG. 1. That is, the backlight unit sequentially passes through the light guide plate 3, the diffusion sheet 4, and the prism sheet 5 by using light sources 1 such as a cold cathode fluorescent lamp (CCFL). To reach the liquid crystal panel 6. Here, the light guide plate 3 transmits the light emitted from the light source 1 to be distributed over the front surface of the liquid crystal panel 6 having a flat shape, and the diffusion sheet 4 may obtain uniform light intensity over the entire screen. In addition, the prism sheet 5 performs an optical path control function so that light beams in various directions passing through the diffusion sheet 4 are converted into a range of viewing angle θ suitable for the viewer to recognize the image. In addition, the lower portion of the light guide plate 5 is provided with a reflective sheet 2 for increasing the utilization efficiency of the light source by allowing the light that is not delivered to the liquid crystal panel 6 to be reflected back out of the path and used.

In order to effectively transmit the emitted light to the liquid crystal panel, a plurality of films having various functions are mounted. A Newton's Ring phenomenon caused by mounting a plurality of films or an air layer missing from the contact surface between the films is generated. It causes optical interference such as wet-out phenomenon, light is lost through scattering or absorption as it passes through a plurality of films, and the film is damaged due to physical contact between the films. There have been problems such as hikes.

In the conventional prism film, diffusion particles may be provided on the back surface of the substrate layer in addition to the substrate layer and the prism layer constituting the prism film. There was a problem that the loss of light still occurs because it must pass through the substrate layer until reaching.

On the other hand, Korean Patent Laid-Open Publication No. 2004-79028 includes a base film and a prism portion and an antireflection layer having a plurality of protrusions having a triangular cross-sectional shape, and a resin layer containing transparent beads includes a base film and a prism. A prism sheet is described which is located between the portions and / or between the base film and the antireflection layer.

This is to adjust the surface roughness in order to obtain a light diffusion effect, the adhesion between the prism portion and the bead layer is reduced due to the uneven transparent bead layer may cause damage to the roll because it is not adhered to the base film when the prism portion coating Desorption of the prism part easily occurs, which may cause a failure rate when mounted on the backlight. In addition, a high refractive resin should be used for efficient light condensation. However, when the light is diffused in the light diffusion layer and collected in the prism layer and partially totally reflected and recycled, the recycling efficiency is inferior due to the large refractive index difference between the two materials.

An object of the present invention is to provide an optical composite film that can easily form a prism layer on a light diffusion layer and can prevent light loss due to superposition of particles.

In addition, the present invention is to provide an optical composite film that can increase the efficiency of light incident on the prism layer by reducing the amount of internal reflection of the light by reducing the difference in refractive index between the resin and particles when forming the light diffusion layer.

In addition, the present invention is to provide an optical composite film that can prevent the light loss by reducing the total reflection of the light by adjusting the difference between the refractive index of the prism layer and the binder resin refractive index of the diffusion layer.

In addition, the present invention is to provide an optical composite film having a wide viewing angle as compared to using a conventional light diffusing film and a prism film laminated.

In another aspect, the present invention is to provide an optical composite film that can reduce the contact with the upper panel to prevent loss of brightness or damage to the prism layer.

In one embodiment of the present invention; A light diffusion layer formed on one surface of the transparent substrate layer and including a binder resin and light diffusing particles, wherein a difference in refractive index between the light diffusing particles and the binder resin is 0.05 or less; And a prism layer formed on the light diffusion layer.

Another embodiment of the present invention provides an optical composite film further comprising a damage preventing layer formed on the other side of the transparent substrate layer and including a binder resin and particles.

In the optical composite film according to the embodiment of the present invention, the light diffusing layer may have a cross-sectional structure in which the light diffusing particles are dispersed in a single layer.

In the optical composite film according to the embodiment of the present invention, the light diffusing layer may include 10 to 300 parts by weight of light diffusing particles having a size of 1 to 50 ㎛ with respect to 100 parts by weight of the binder resin solid content.

In the optical composite film according to the embodiment of the present invention, the prism layer may have a refractive index of 0.01 to 0.2 higher than that of the binder resin in the light diffusion layer.

In the optical composite film according to the embodiment of the present invention, the prism layer has a three-dimensional columnar structure having a semi-circular shape or a semi-elliptic shape, and a three-dimensional structure selected from a columnar structure having a triangular or polygonal cross section, a cone, and a polyhedron pyramid. The structure may be arranged so that the surface is structured.

In the optical composite film according to the embodiment of the present invention, the prism layer is selected from a column-like structure having a semi-circular shape or a semi-elliptic shape, and a column-shaped structure having a cross section of a triangle or a polygon, a cone and a polyhedron pyramid. A plurality of three-dimensional structures are arranged to the surface of the structure, three-dimensional structure having the same width and different height at least two types of three-dimensional structure may be repeated regularly or irregularly.

In the optical composite film according to the embodiment of the present invention, the prism layer is selected from a column-like structure having a semi-circular shape or a semi-elliptic shape, and a column-shaped structure having a cross section of a triangle or a polygon, a cone and a polyhedron pyramid. A plurality of three-dimensional structure is arranged to the surface of the structure, three-dimensional structure having the same height and at least two different three-dimensional structure of different widths may be repeated regularly or irregularly.

In the optical composite film according to the embodiment of the present invention, the prism layer has a plurality of three-dimensional structures selected from columnar three-dimensional structures whose cross sections are semicircular or semi-elliptic, and columnar three-dimensional structures whose cross sections are triangular or polygonal. The surface is structured, and may not be straight when the arrangement of each three-dimensional structure is based on a plane.

In the optical composite film according to the embodiment of the present invention, the prism layer has a plurality of three-dimensional structures selected from conical and polyhedral pyramids arranged on its surface, and three-dimensional structures of the same shape and specification are continuously formed adjacent to each other. The virtual lines connecting the vertices of the individual three-dimensional structures with respect to the plane may be arranged in a non-linear arrangement.

In the optical composite film according to the embodiment of the present invention, the damage prevention layer may be one containing the same or different particles of the light diffusion layer.

According to the present invention, while simultaneously providing a function to improve the brightness while evenly spreading the light emitted from the light guide plate or the diffusion plate, it is easy to form a prism layer on the light diffusion layer and can reduce the loss of light amount.

In addition, in consideration of light diffusing and condensing function, a part of the optical film that has been conventionally used, for example, a protective film, may be omitted, thereby preventing light loss such as light interference, scattering or absorption, and damage to the film. The optical composite film which can be provided can be provided.

In addition, by adjusting the shape of the surface of the prism layer, by reducing the contact with the panel, it is possible to prevent the luminance damage due to the prism layer damage.

The present invention will be described in more detail as follows.

The optical composite film of the present invention has a structure in which a light diffusing layer is formed on one surface of a transparent base layer, and a prism layer is formed on the light diffusing layer.

First, as the transparent base layer, a polyethylene terephthalate film, a polycarbonate film, a polypropylene film, a polyethylene film, a polystyrene film, or a polyepoxy film may be used, and mainly a polyethylene terephthalate film and a polycarbonate film are used. The transparent substrate layer may have a thickness of 10 μm to 1000 μm, particularly 15 μm to 400 μm in terms of mechanical strength, thermal stability, and flexibility, and may prevent loss of transmitted light.

The light diffusing layer formed on one surface of the transparent base layer is formed by dispersing the light diffusing particles in the binder resin, in the present invention, by adjusting the difference in the refractive index of the binder resin and the light diffusing particles to 0.05 or less as the difference in the refractive index between the two materials By reducing the internal reflection of the light generated thereby to increase the efficiency of the light incident on the prism layer.

In this case, as the binder resin, a resin having good adhesion with the transparent base layer and having good compatibility with the light diffusing particles dispersed therein, that is, the light diffusing particles are uniformly dispersed in the resin and is not easily separated or precipitated. As such resin, For example, unsaturated polyester, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylic acid, hydroxy Ethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, acrylamide, methrol acrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate, 2-ethyl Acrylic resins, such as a homopolymer of hexyl acrylate, these copolymers, or a terpolymer, a urethane resin, an epoxy resin, a melamine resin, etc. are mentioned.

The light diffusing particles may be used in an amount of 10 to 300 parts by weight based on 100 parts by weight of the binder resin, and when the particle size is 1 to 50 µm, the light diffusing particles may be dispersed in a single layer in the light diffusion layer, and the light diffusion effect It is appropriate to expect and can prevent the clouding phenomenon and the detachment of particles due to excessive usage.

When the light diffusing particles included in the light diffusing layer are dispersed in a single layer, it is easy to form a prism layer on the light diffusing layer, and the light loss due to the overlapping of particles may be prevented.

As the light diffusing particles, 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 The multi-layered multicomponent particles formed by forming the particles and then covering the layers with other types of monomers may be used. Examples of the inorganic particles may include silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, magnesium fluoride, and the like. 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.

A prism layer is formed on one surface of the light diffusion layer.

Usually, as the material constituting the prism layer, a polymer resin including an ultraviolet curable resin or a thermosetting resin is used, and a resin composition capable of forming a crosslinking bond having excellent transparency and suitable for maintaining the shape of an optical structure can be used. For example, it is possible to use an epoxy resin-ruic acid-based, polyethylol-based, unsaturated polyester-styrene, acrylic or methacrylic acid ester, and the like. Preference is given to using. Such resin types include oligomers such as polyurethane acrylics or methacrylates, epoxy acrylics or methacrylates, polyester acrylics or methacrylates, and are alone or diluted with acrylic or methacrylate monomers having a polyfunctional or monofunctional group. Can be used.

In the present invention, the prism layer has a columnar three-dimensional structure whose cross section is semi-circular or semi-elliptic, and a plurality of three-dimensional structures selected from the column-shaped three-dimensional structure, the cone and the polyhedron whose cross section is triangular or polygonal, and the surface thereof is structured. It may have been. At this time, the shape is not limited.

However, when the optical composite film of the present invention is used in the backlight unit, the diffusion and condensing effects may be simultaneously performed, and thus the use of a separate protective film may be omitted. In this case, the panel and the prism layer may come into contact with each other. Damage to the structured surface of the can be a concern.

In consideration of this point, the prism layer has a columnar three-dimensional structure of semi-circular or semi-elliptic cross section, and a three-dimensional structure selected from columnar three-dimensional structures, cones and polyhedrons whose cross section is triangular or polygonal, and the surface thereof is arranged. With this structured, the three-dimensional structure may be one in which at least two types of three-dimensional structures having the same width and different heights are regularly or irregularly repeated.

In this case, when the panels are stacked on the composite film, the contact area with the upper panel may be reduced, thereby reducing the possibility of defects caused by the increase of the contact area .

An example thereof is illustrated in FIG. 2, which is an optical composite film having a prism layer 30 in which a plurality of columnar three-dimensional structures having a triangular cross section are arranged and whose surface is structured. 30 shows an example in which two kinds of three-dimensional structures 30a and 30b have the same width a and different height b.

In such a case, the structured surface of the prism layer that is in contact when the panel is stacked on top reduces the number of contact surfaces, thereby reducing the number of cases of damage.

In FIG. 2, only the case where the cross-section is a triangular three-dimensional structure, and when the two kinds are regularly repeated, the shape of the cross-section may be a semi-circle, semi-ellipse, polygon, etc., the width Of course, multiple species of different heights can coexist and the arrangement can be repeated regularly or irregularly.

On the other hand, as another example of the surface structure of the prism layer that can achieve the same purpose, among the three-dimensional columnar structure having a semi-circular or semi-elliptic cross section and the columnar structure, cone and polyhedron pyramid whose cross section is triangular or polygonal The selected three-dimensional structure is arranged in a plurality and the surface is structured, the three-dimensional structure may have the same height and at least two types of three-dimensional structure having a different width is repeated regularly or irregularly.

An example thereof is illustrated in FIG. 3.

3 is an optical composite film having a prism layer 40 having a plurality of columnar three-dimensional structures having a triangular cross section and structured on the surface thereof, wherein the prism layer 40 has the same width a. The height b shows an example in which the other two types of three-dimensional structures 40a and 40b are regularly repeated.

In FIG. 3, only the case where the cross-section is a triangular columnar structure having a triangular shape, and the type of two kinds is regularly repeated, the shape of the cross section may be a semi-circle, a semi-ellipse, a polygon, or the like, and the height thereof. Of course, multiple species of different widths may coexist and the arrangement may be repeated regularly or irregularly.

As another example of the prism layer, a plurality of three-dimensional structures selected from columnar three-dimensional structures having semi-circular or semi-elliptic cross-sections and columnar three-dimensional structures having triangular or polygonal cross-sections are arranged and the surfaces thereof are structured. The arrangement of each solid structure may be non-linear when based on a plane.

An example thereof is illustrated in FIG. 4, which shows a prism layer 50 arranged in a zigzag form when a three-dimensional structure having a triangular cross section is viewed in plan view.

In FIG. 4, only the case of the columnar three-dimensional structure 50a having a triangular cross section and a case arranged in a zigzag form, the cross section may have a semi-circular shape, a semi-elliptic shape, a polygonal shape, or the like, and is not zigzag-shaped. Of course, the arrangement may be non-linear, such as in the form of an S-shape.

As another example of the prism layer, a plurality of three-dimensional structures selected from cones and polyhedron pyramids are arranged and the surfaces thereof are structured, and three-dimensional structures of the same shape and specification are successively formed adjacent to each other, but each of them is based on a plane. The imaginary line connecting the vertices of the three-dimensional structure may have a non-linear arrangement.

An example thereof is illustrated in FIG. 5. FIG. 5 illustrates a case in which a triangular pyramid-shaped three-dimensional structure 60a is formed adjacent to each other and an imaginary line between vertices of each triangular pyramid is arranged to have a zigzag shape.

In FIG. 5, only the case where the shape of the three-dimensional structure is a triangular pyramid and a case arranged in a zigzag form may be a cone, a polygonal pyramid, or the like, and the arrangement may be non-linear in an S-shape, not a zigzag form.

Meanwhile, according to one embodiment of the present invention, the prism layer may have a refractive index of about 0.01 to 0.2 higher than that of the binder resin forming the light diffusing layer, thereby reducing light loss by reducing total reflection.

In general, the higher the refractive index of the prism layer, the narrower the angle at which light is emitted relative to the front surface, so that the front brightness can be improved.

Meanwhile, a damage prevention layer may be further formed on the other side of the transparent base layer, that is, the back of the light diffusion layer. The damage prevention layer is formed by dispersing particles in a binder resin, and has good adhesion with the transparent base layer and is compatible with dispersed particles. A resin having good properties, that is, particles are uniformly dispersed in the resin and used to separate or hardly precipitate, and a specific example thereof may be the same as the binder resin of the light diffusion layer. The particles included in the damage prevention layer may use organic particles or inorganic particles. For example, the light diffusing particles included in the light diffusing layer may be the same as or different from the particles of the light diffusing layer.

The damage preventing layer is advantageous in that it contains 0.01 to 30 parts by weight of particles with respect to 100 parts by weight of the binder resin, which is advantageous for the expression of the damage prevention effect, and in the case of organic particles, may be light diffused to weaken the front luminance. In this case, the use of excess may be disadvantageous because light may be reflected or absorbed at the surface of the particle to reduce the light utilization efficiency by weakening the front brightness.

The damage prevention layer is brought into contact with the opposing surface or other laminated optical film in the processing apparatus during the loading or storage of the optical film or the process of assembling the optical film with other parts by the protrusion of the surface formed by the particles dispersed in the binder resin. By reducing the area, it protects the surface from damage that may occur during separation, movement or assembly into sheets.

By manufacturing the optical composite film as described above, the light is first diffused while passing through the particles of the damage prevention layer and then passed through the transparent substrate layer and evenly diffused by the light diffusing particles of the light diffusion layer passes through the prism layer. By reducing the internal reflection of light by reducing the difference in refractive index between the binder resin and the light diffusing particles in the light diffusing layer, the efficiency of light can be increased more, and the amount of light loss is greatly reduced, and the light diffusion function and brightness In order to provide a function of increasing the manufacturing process and the cost of the film separately manufactured and laminated separately to reduce the manufacturing process and cost, it is advantageous to reduce the number of films in the optical sheet assembly for the backlight.

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>

100 parts by weight of methyl ethyl ketone and 100 parts by weight of toluene were measured and diluted to 100 parts by weight of acrylic resin 52-666 (Aekyung Chemical Co., Ltd.) to prepare a binder resin having a refractive index of 1.5, and a spherical polymethyl having a refractive index of 1.50 having an average particle diameter of 1.50 μm. Methacrylate particles MH20F (Kolon Co., Ltd.) 130 parts by weight of the binder resin was mixed and dispersed by a mill.

Using a gravure coater on one side of the 125 μm ultra-transparent polyethylene terephthalate film FHSS (Kolon Co., Ltd.), which is a transparent base layer, it is cured at 120 ° C. for 60 seconds after coating to form a light diffusion layer having a thickness of 23 μm after drying. I was. At this time, the particles of the light diffusion layer was coated with a single layer.

Meanwhile, 200 parts by weight of methyl ethyl ketone and 150 parts by weight of toluene were added to 100 parts by weight of acrylic resin 52-666 (Aekyung Chemical Co., Ltd.) on the back of the transparent substrate layer to prepare a binder resin, and then spherical polymethyl having an average particle diameter of 11.5 μm. The methacrylate particles MH10F (Kolon Co., Ltd.) was mixed with 20 parts by weight of the binder resin, dispersed in a mill, and cured at 120 ° C. for 60 seconds to form a damage prevention layer so that the thickness was 1 to 3 μm after drying.

On one surface of the cured light diffusion layer, a photosensitive composition obtained by mixing 80 parts by weight of high refractive acrylate, 15 parts by weight of 2-phenylethyl methacrylate, 3 parts by weight of 1,6-hexanediol acrylate, and 2 parts by weight of a BAPO-based photoinitiator After coating, ultraviolet rays (Fusion, 300 Watt / inch ² ) were irradiated from the transparent substrate layer to form a linear triangular prism (50 m wide and 25 m tall isosceles triangle triangular shape). The refractive index of the prism layer was set to 1.53.

<Example 2>

An optical composite film was manufactured in the same manner as in Example 1, except that the refractive index of 1.52 was used instead of the spherical polymethylmethacrylate particles having a refractive index of 1.50 having a particle diameter of 20 μm when the light diffusing layer was formed.

<Example 3>

An optical composite film was manufactured in the same manner as in Example 1, except that the refractive index of 1.54 was used instead of the spherical polymethylmethacrylate particles having a refractive index of 1.50 having a particle diameter of 20 μm when the light diffusing layer was formed.

<Example 4>

An optical composite film was manufactured in the same manner as in Example 1, except that the prism layer was formed to have a refractive index of 1.6.

<Example 5>

An optical composite film was manufactured in the same manner as in Example 1, except that 5 µm in particle size was used instead of spherical polymethylmethacrylate particles having a refractive index of 1.50 in particle size of 20 µm when the light diffusing layer was formed.

<Example 6>

The optical composite film was manufactured in the same manner as in Example 1, except that the shape of the prism layer was 50 μm in width and 25 μm in height as shown in FIG. 2 (50a in FIG. 2) and 50 in width. An optical composite film was prepared in which a second pitch (30b in FIG. 2) having a thickness of 23 μm and alternately repeated with each other was repeated.

<Example 7>

An optical composite film was manufactured in the same manner as in Example 1 except that the shape of the prism layer was 50 μm in width and 25 μm in height as shown in FIG. A second composite (30b in FIG. 2) having a height of 25 μm and a height of 25 μm was alternately repeated to prepare an optical composite film.

<Example 8>

An optical composite film was manufactured in the same manner as in Example 1, except that the prism layer had a planar shape in which a pitch of 50 μm in width and 25 μm in height was arranged in a zigzag form as shown in FIG. 4. The composite film for was prepared.

Comparative Example

(1) 100 parts by weight of methyl ethyl ketone and 100 parts by weight of toluene were added to 100 parts by weight of acrylic resin 52-666 (Aekyung Chemical Co., Ltd.), followed by dilution. 130 parts by weight of the acrylic resin is mixed and dispersed by a mill, and then coated with a light diffusing layer so as to have a thickness of 20 μm after drying using gravure on one side of a 125 μm ultra-transparent polyethylene terephthalate film (FHSS, Kolon). A film was prepared.

(2) Separately, 80 parts by weight of high refractive acrylate, 15 parts by weight of 2-phenylethyl methacrylate, 1,6-hexanediol acrylate on the back surface of the ultra-transparent polyethylene terephthalate film (FHSS, Kolon) plastic substrate An optical film was prepared by coating a photosensitive composition including 3 parts by weight and 2 parts by weight of a BAPO-based photoinitiator, and irradiating ultraviolet (Fusion, 300 Watt / inch ² ) from the transparent substrate layer to form a linear triangular prism.

The optical film in which the linear triangular prism was formed was laminated on the optical film to which the light-diffusion layer obtained as described above was applied.

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

<Luminance evaluation (Cd / ㎡)>

The optical films of Examples and Comparative Examples prepared above were laminated or fixed to a 24-inch liquid crystal display panel backlight unit, and an arbitrary 13 was used by using a luminance meter (model name: BM-7, Japan TOPCON). The luminance of the spot was measured and its average value was obtained.

<Viewing angle>

Fixing the optical films of Examples and Comparative Examples prepared above to the backlight unit for a 24-inch liquid crystal display panel, and using a luminance meter (model name: BM-7, Japan TOPCON Co., Ltd.), the brightness of the left and right angles of 80 degrees and 10 degrees each It measured at intervals and the angle which shows 1/2 luminance of the maximum luminance was calculated | required.

<Optical Interference Measurement>

Two optical films of each of the above examples or comparative examples were placed between a plurality of glass plates, and pressure was applied to the glass plates to observe Newton's Ring due to excessive adhesion occurring in the film. Relative evaluation as follows.

Newton's Ring: Not Occurred ← ◎-○-△-× → Occurred

Luminance (Cd / ㎡) Viewing angle (°) Optical interference Example 1 11615 ± 55 ^o ○ Example 2 11590 ± 55 ^o ○ Example 3 11576 ± 55 ^o ○ Example 4 12100 ± 55 ^o ○ Example 5 10750 ± 55 ^o ○ Example 6 11345 ± 54 ^o ◎ Example 7 11320 ± 54 ^o ◎ Example 8 11410 ± 54 ^o ◎ Comparative Example 1 12480 ± 45 ^o △

As a result of the physical property evaluation, as shown in Examples 1 to 8, when the difference between the refractive index of the resin and the refractive index of the light diffusing layer is less than 0.05, it can be seen that the brightness is high even in the composite film. In particular, when the light diffusing particles are dispersed in a single layer as in Examples 1 to 8, and the refractive index of the prism layer is higher than that of the binder resin of the light diffusing layer, the difference was higher than about 0.01 to 0.2.

In addition, the composite film according to Examples 1 to 8 was able to obtain a wider viewing angle than when the diffusion film and the prism film has a laminated structure.

On the other hand, when the pattern of the prism layer is non-linear as in Examples 6 to 8, it was confirmed that the optical interference phenomenon is reduced compared to the optical composite film of Example 1, whereby the linear pattern when the display panel is stacked thereon It can be seen that it is more advantageous for the optical interference and the reduction of the contact surface with the laminated panel.

1 is a schematic view showing a conventional backlight unit.

Figure 2 is a cross-sectional view showing an optical composite film of the present invention.

Figure 3 is another cross-sectional view showing an optical composite film of the present invention.

Figure 4 is a sectional view and a perspective view of the optical composite film of the present invention.

5 is a cross-sectional view and a perspective view of the optical composite film of the present invention.

Claims (11)

Transparent substrate layer; A light diffusion layer formed on one surface of the transparent substrate layer and including a binder resin and light diffusing particles, wherein a difference in refractive index between the light diffusing particles and the binder resin is 0.05 or less; And Optical composite film comprising a prism layer formed on the light diffusion layer. The optical composite film of claim 1, further comprising a damage preventing layer formed on the other side of the transparent substrate layer and comprising a binder resin and particles. The optical composite film according to claim 1, wherein the light diffusing layer has a cross-sectional structure in which light diffusing particles are dispersed in a single layer. The optical composite film according to claim 1 or 3, wherein the light diffusing layer comprises light diffusing particles having a size of 1 to 50 µm in an amount of 10 to 300 parts by weight based on 100 parts by weight of the binder resin solid content. The optical composite film according to claim 1, wherein the prism layer has a refractive index of 0.01 to 0.2 higher than that of the binder resin in the light diffusion layer. The method of claim 1, wherein the prism layer has a column-shaped three-dimensional structure of semi-circular or semi-elliptic cross-section and a column-shaped three-dimensional structure of conical and polyhedral pyramids having a triangular or polygonal cross-section, and Optical composite film, characterized in that the surface is structured. The method of claim 1, wherein the prism layer has a column-shaped three-dimensional structure of semi-circular or semi-elliptic cross-section and a column-shaped three-dimensional structure of conical and polyhedral pyramids having a triangular or polygonal cross-section, and Surface is structured, three-dimensional structure having the same width, at least two types of three-dimensional structure of different height is repeated or irregularly optical film, characterized in that repeated. The method of claim 1, wherein the prism layer has a column-shaped three-dimensional structure of semi-circular or semi-elliptic cross-section and a column-shaped three-dimensional structure of conical and polyhedral pyramids having a triangular or polygonal cross-section, and Surface is structured, three-dimensional structure having the same height and at least two types of three-dimensional structure different from each other in the optical composite film, characterized in that repeated regularly or irregularly. The method of claim 1, wherein the prism layer is formed of a column-like three-dimensional structure of semi-circular or semi-elliptic cross-section and a column-like three-dimensional structure of the triangular or polygonal cross-section of the prism layer is a surface structured , The optical composite film, characterized in that the array of each three-dimensional structure is not linear when based on the plane. The method of claim 1, wherein the prism layer has a plurality of three-dimensional structure selected from conical and polyhedral pyramid arranged and the surface is structured, the three-dimensional structure of the same shape and specification are continuously formed adjacent to each other, but based on the plane An optical composite film, wherein the virtual lines connecting the vertices of individual three-dimensional structures have an array that is not linear. The optical composite film of claim 2, wherein the damage prevention layer comprises particles that are the same as or different from the particles of the light diffusion layer.

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