KR102385160B1 - Reflective polarizing film, light source assembly comprising the same, and display comprising the same - Google Patents

Abstract

The present invention relates to a reflective polarizing film, and more particularly, to a reflective polarizing film having an improved viewing angle, which can realize a display with minimized bright lines, and minimized display of internal foreign objects, and a light source assembly and liquid crystal display including the same It's about the device.

Description

Reflective polarizing film, light source assembly comprising the same, and liquid crystal display device

The present invention relates to a reflective polarizing film, and more particularly, to a reflective polarizing film having an improved viewing angle, which can realize a display with minimized bright lines, and minimized display of internal foreign objects, and a light source assembly and liquid crystal display including the same It's about the device.

In flat panel display technology, liquid crystal display (LCD), projection display and plasma display (PDP), which have already secured a market in the TV field, are the mainstream, and field emission display (FED) and electroluminescence display (ELD) are related technologies. It is expected to occupy the field according to each characteristic along with the improvement of Liquid crystal displays are currently being used in laptops, personal computer monitors, liquid crystal TVs, automobiles, aircraft, etc., occupying about 80% of the flat panel market.

A conventional liquid crystal display arranges a liquid crystal and an electrode matrix between a pair of light absorbing optical films. In a liquid crystal display, a liquid crystal part has an optical state that is changed accordingly by moving the liquid crystal part by an electric field generated by applying a voltage to two electrodes. In this process, 'pixels' carrying information are displayed using polarization in a specific direction. For this reason, liquid crystal displays include a front optical film and a rear optical film that induce polarization.

The optical film used in such a liquid crystal display does not necessarily have high utilization efficiency of light emitted from the backlight. This is because 50% or more of the light emitted from the backlight is absorbed by the back side optical film (absorption type polarizing film). Therefore, in order to increase the efficiency of use of backlight light in the liquid crystal display, a reflective polarizer is provided between the optical cavity and the liquid crystal assembly.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the optical principle of a reflection type polarizer. Specifically, P-polarized light from the optical cavity toward the liquid crystal assembly passes through the reflective polarizer to be transmitted to the liquid crystal assembly, and S-polarized light is reflected from the reflective polarizer to the optical cavity, and then the polarization direction of the light on the diffuse reflection surface of the optical cavity is By repeating the cycle of being reflected in a randomized state and then transferred back to the reflective polarizer, eventually S-polarized light is converted into P-polarized light that can pass through the polarizer of the liquid crystal assembly so that it is transmitted to the liquid crystal assembly after passing through the reflection polarizer. will be.

In the case of a reflective polarizer that expresses the above function, for example, a multilayer reflective polarizer in which a flat optical layer having an optically anisotropic refractive index and a flat optical layer having an optically isotropic refractive index are alternately stacked, a spiral cholesteric liquid crystal in a specific direction A cholesteric liquid crystal type reflective polarizer containing There are island-in-the-sea yarn dispersion type reflection polarizers, wire-grid type reflection polarizers, and the like.

As an example of the polymer dispersed reflective polarizer, a reflective polarizer dispersed in a dispersion capable of achieving the function of a reflective polarizer by arranging a birefringent polymer elongated in the longitudinal direction inside a substrate has been proposed. Specifically, FIG. 2 is a perspective view of the reflective polarizer 20 including a rod-shaped polymer, in which the birefringent polymer 22 extending in the longitudinal direction is arranged inside the substrate 21 in one direction. Through this, the light modulation effect is induced by the birefringent interface between the substrate 21 and the birefringent polymer 22 to perform the function of the reflective polarizer. However, the polymer dispersed reflective polarizer having such a structure has a problem in that it is difficult to reflect light in the entire wavelength region of visible light, so that the light modulation efficiency is too low. In addition, there was a problem in that light leakage or bright lines were observed due to the spacing between the rod-shaped polymers. In addition, there is still a problem of color change in appearance caused by the non-uniformity of the light transmitted through the reflective polarizer in the entire visible light region.

On the other hand, a characteristic that has recently emerged as an important characteristic of a display is the viewing angle, which means that the brightness and contrast ratio do not change significantly even when the display is not observed from the front. However, the conventional reflective polarizer has only a function of transmitting/reflecting light according to polarization and does not have a function to diffuse the light emitted from the reflective polarizer, so the viewing angle is not good. Although it is common to provide a diffusion plate in a light source assembly such as a backlight unit, there is a light loss due to an air layer between the diffusion sheet or the diffusion plate and the reflective polarizer, and there is a problem in that it is difficult to obtain a desired level of viewing angle.

Accordingly, there is an urgent need to develop a reflective polarizing film capable of achieving high luminance while improving the viewing angle.

Laid-open Patent Publication No. 10-2016-0150388

The present invention has been devised to solve the above problems, has an improved viewing angle, can implement a display with minimized bright lines, and has a reflective polarizing film in which defects such as internal foreign objects are not visually identified on the display or minimized , An object of the present invention is to provide a light source assembly and a liquid crystal display including the same.

In order to solve the above problems, the present invention provides a reflective polarizing layer that transmits a first polarized light among incident light and reflects a second polarized light; and a light diffusion layer disposed adjacent to each of the light incident surface and the light exit surface of the reflective polarizing layer, wherein, when the normal direction of the plane of the reflective polarizing layer is defined as a viewing angle of 0°, relative optics for the first polarization The gain provides a reflective polarizing film having a maximum value at viewing angles in excess of 60°.

According to an embodiment of the present invention, the reflective polarizing layer may include a substrate and a core layer including a plurality of dispersions dispersedly included in the substrate, and having different refractive indices in at least one axial direction from the substrate. there is.

In addition, the reflective polarizing layer may further include a skin layer integrally formed on at least one surface of the core layer.

In addition, the dispersion may be randomly dispersed inside the substrate.

In addition, the light diffusion layer may include a first light diffusion layer disposed adjacent to the light incidence surface including the first diffusion particles and a second light diffusion layer disposed adjacent to the light exit surface including the second diffusion particles. can

In addition, the weight ratio of the first diffusion particles and the second diffusion particles may be 1: 3.5 to 20.

In addition, the first diffusion particles and the second diffusion particles each independently may have an average particle diameter of 3 ~ 15㎛.

In addition, in the first diffusion particle, the particles belonging to ± 5% of the average particle diameter of the first diffusion particle are 65 to 80% by volume of the total volume of the first diffusion particle, and the second diffusion particle is the average particle diameter of the second diffusion particle Particles in the range of ± 5% may be 65 to 80% by volume of the total volume of the second diffusion particles.

In addition, the first diffusion particles may be included in an amount of 3 to 15% by weight based on the total weight of the first light diffusion layer, and the second diffusion particles may be included in an amount of 20 to 50% by weight relative to the total weight of the second light diffusion layer.

In addition, the relative optical gain with respect to the first polarization may have a maximum value at a viewing angle of greater than 60° and less than or equal to 75°.

In addition, the light diffusion layer may have a thickness of 2 to 15 μm.

In addition, the present invention provides a light source assembly including the reflective polarizing film according to the present invention.

In addition, the present invention provides a liquid crystal display including the light source assembly according to the present invention.

The reflective polarizing film according to the present invention has an improved viewing angle and can realize a display in which the bright line phenomenon is minimized. In addition, defects such as the appearance of internal foreign objects are not visually discernable on the display or have a minimized quality. Accordingly, it can be widely applied as an optical component of a light source assembly, which is a component of a liquid crystal display.

1 is a schematic diagram illustrating the principle of a reflective polarizing film;
2A and 2B are cross-sectional views of a reflective polarizing film according to various embodiments of the present invention;
3 is a perspective view of a reflective polarizing layer included in an embodiment of the present invention;
4 is a cross-sectional view of a reflective polarizing layer included in an embodiment of the present invention;
5 is a cross-sectional view of a dispersion provided in a reflective polarizing film according to an embodiment of the present invention;
6 is a cross-sectional view of a coat-hanger die, which is a kind of a flow control unit used in a manufacturing process of a reflective polarizing film according to an embodiment of the present invention;
7 is a side view of FIG. 6 ;
8 is a cross-sectional view of a liquid crystal display according to an embodiment of the present invention;
9 is an exploded perspective view of a liquid crystal display device according to an embodiment of the present invention;
10 is a schematic diagram of a manufacturing process of a plate-shaped polymer dispersed reflective polarizing layer according to an embodiment of the present invention;
11 is an exploded perspective view of a sea-island-type extrusion nozzle according to an embodiment of the present invention;
12 is a cross-sectional view of a plate-shaped polymer dispersed reflective polarizing layer manufactured according to an embodiment of the present invention;
13 is a cross-sectional SEM photograph of a core layer of a reflective polarizing film according to an embodiment of the present invention;
14 is an exploded perspective view of a slit-type extrusion nozzle for manufacturing a multi-layered reflective polarizing layer according to a comparative example of the present invention;
15 is an exploded perspective view of a slit-type extrusion nozzle for manufacturing a multi-layered reflective polarizing layer according to a comparative example of the present invention;
16 is a cross-sectional view of a multi-layered reflective polarizing layer prepared according to a comparative example of the present invention, and
17 is a graph of relative optical gain for each viewing angle of a reflective polarizing film according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and the same reference numerals are added to the same or similar elements throughout the specification.

Referring to FIG. 2A , a reflective polarizing film 1000 according to an embodiment of the present invention includes light diffusion layers 210 and 220 disposed adjacent to a light incident surface and a light exit surface of the reflective polarizing layer 100 , respectively.

The reflective polarization layer 100 is a polarizing film having a transmission axis in a first direction and a reflection axis in a second direction perpendicular to the first direction. The polarized light is transmitted and the second polarized light is reflected. For example, the first polarized light may be P-polarized light, and the reflected second polarized light may be S-polarized light.

The reflective polarizing layer 100 may be a known polarizing film exhibiting such polarization characteristics, or may be a reflective polarizing film. The reflective polarizing film is, for example, a multilayer reflective polarizing film in which a flat optical layer having an optically anisotropic refractive index and a flat optical layer having an optically isotropic refractive index are alternately laminated, a cholesteric liquid crystal containing a spiral cholesteric liquid crystal in a specific direction A steric liquid crystal type reflective polarizing film, a polymer dispersed reflective polarizing film including a discontinuous phase having an optically anisotropic or optically isotropic refractive index inside a continuous phase having an optically isotropic or optically anisotropic refractive index, including a birefringent sea-island yarn inside an isotropic substrate There are islands-in-the-sea yarn dispersion type reflective polarizing film and wire-grid type reflective polarizing film.

However, the multilayer type reflective polarizing film is not easy to manufacture, has a high production cost, and may include a layer capable of reducing or changing optical properties such as an adhesive layer. In addition, since the cholesteric liquid crystal type reflective polarizing film needs to further include a separate retardation film that transforms circularly polarized light into linearly polarized light, it may not be good for a thin display. In addition, the island-in-the-sea yarn dispersion type reflective polarizing film has a remarkable problem of light leakage and visible bright lines. Furthermore, the wire-grid type reflective polarizing film may have a resolution problem of grid spacing.

Preferably, the reflective polarizing layer 100 may be a polymer dispersed reflective polarizing film, specifically dispersed in the substrate 111 as shown in FIG. 3 , and at least one of the substrate 111 and at least one A core layer 110 including a dispersion 112 having a different refractive index in the axial direction may be provided, and at least one surface of the core layer 110 has a skin layer ( 121 and 122) may be further provided.

A birefringent interface may be formed between the substrate 111 and the dispersion 112 included in the substrate. Specifically, the size of the substantial match or mismatch of refractive indices along the X, Y, and Z axes spatially between the substrate 111 and the dispersion 112 affects the degree of scattering of light rays polarized along the axes. In general, the scattering power varies in proportion to the square of the refractive index mismatch. Thus, the greater the degree of discrepancy in the refractive index along a particular axis, the stronger the scattered rays of light polarized along that axis. Conversely, if the discrepancy along a particular axis is small, light rays polarized along that axis are scattered to a lesser extent. If the refractive index of the substrate along some axis substantially coincides with that of the dispersion, incident light polarized with an electric field parallel to that axis will pass through the dispersion without being scattered, regardless of the size, shape, and density of portions of the dispersion. something to do. Also, when the refractive indices along its axes are substantially coincident, light rays pass through the object substantially unscattered. More specifically, the first polarized light (P-polarized light) is transmitted without being affected by the birefringent interface formed at the boundary between the substrate 111 and the dispersion 112, but the second polarized light (S-polarized light) is the substrate 111 and Modulation of light occurs under the influence of the birefringent interface formed at the boundary between the dispersions 112 . Through this, the P-polarized light is transmitted, and the S-polarized light causes light modulation such as light scattering and reflection, and eventually the separation of the polarized light occurs.

Therefore, since the substrate 111 and the dispersion 112 must form a birefringent interface to induce a light modulation effect, when the substrate 111 is optically isotropic, the dispersion 112 may have birefringence and Conversely, when the substrate 111 has optical birefringence, the dispersion 112 may have optical isotropy. Specifically, the refractive index of the dispersion 112 in the x-axis direction is n _X1 , the refractive index in the y-axis direction is n _Y1 , and the refractive index in the z-axis direction is n _Z1 , and the refractive index of the substrate 111 is n _X2 , n _Y2 and n _Z2 , in-plane birefringence between n _X1 and n _Y1 may occur. More preferably, at least one of the X, Y, and Z-axis refractive indices of the substrate 111 and the dispersion 112 may be different, and more preferably, when the extension axis is the X-axis, the Y-axis and the Z-axis direction are different. The difference in refractive index may be 0.05 or less, and the difference in refractive index in the X-axis direction may be 0.1 or more. On the other hand, in general, if the difference in refractive index is 0.05 or less, it is interpreted as matching.

The substrate 111 may be used without limitation if it is a material used in a conventional polymer dispersed reflective polarizing film, preferably polyethylene naphthalate (PEN), co-polyethylene naphthalate (co-PEN), polyethylene tere. Phthalate (PET), polycarbonate (PC), polycarbonate (PC) alloy, polystyrene (PS), heat-resistant polystyrene (PS), polymethyl methacrylate (PMMA), polybutylene terephthalate (PBT), polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polyurethane (PU), polyimide (PI), polyvinyl chloride (PVC), styrene-acrylonitrile mixture (SAN), ethylene vinyl acetate (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP), urea (UF), melanin (MF), unsaturated polyester (UP), silicone (SI) and cycloolefin polymers. It can be used and, for example, may be a polycarbonate (PC) alloy.

The dispersion 120 may be used without limitation if it is a material of a dispersion typically used in a polymer dispersed reflective polarizing film, preferably polyethylene naphthalate (PEN), co-polyethylene naphthalate (co-PEN), Polyethylene terephthalate (PET), polycarbonate (PC), polycarbonate (PC) alloy, polystyrene (PS), heat-resistant polystyrene (PS), polymethyl methacrylate (PMMA), polybutylene terephthalate (PBT), Polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polyurethane (PU), polyimide (PI), polyvinyl chloride (PVC), styrene-acrylonitrile mixture (SAN), ethylene Vinyl acetate (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP), urea (UF), melanin (MF), unsaturated polyester (UP), silicone (SI) and cycloolefin The polymer may be used alone or in combination, and for example, it may be PEN.

In addition, as shown in FIGS. 3 and 4 , the plurality of dispersions 121 , 122 , and 123 dispersed in the substrate 110 have an aspect ratio of 1/10 to 1/2 in order to express more improved viewing angle characteristics, and the average length of the long axis. may be 0.7 to 1.5 μm. The aspect ratio means the ratio (b/a) of the length of the minor axis (b) to the length of the major axis (a) based on the vertical section in the longitudinal direction of the dispersion as shown in FIG. 5 . Desired optical properties can be achieved by satisfying the aspect ratio of the dispersion to 1/10 to 1/2. If the aspect ratio is less than 1/10, the viewing angle having the maximum value of the relative optical gain may be reduced, and due to this The viewing angle characteristic may be deteriorated. In addition, when the aspect ratio exceeds 1/2, the viewing angle may be widened, but as the overall luminance is significantly lowered, there is no meaning to have a wide viewing angle, and it may be difficult to commercialize as a product.

In addition, in the plurality of dispersions 121 , 122 , and 123 , the average length of the long axis a may be 0.7 to 1.5 μm. If the average length of the long axis a is less than 0.7 μm, the dispersion distributed inside the substrate 110 . The separation distance between (121, 122, 123) increases, and the light incident on the rear surface of the reflective polarizing film cannot be light-modulated and can pass through the upper surface of the reflective polarizing film as it is. In this case, the opportunity to reuse the second polarization (S-polarized light) is eliminated Accordingly, the light use efficiency may decrease, and ultimately, it may not be possible to achieve high luminance. In addition, if the average length of the major axis (a) exceeds 1.5㎛, the number of dispersions (121,122,123) that can be provided in the substrate 110 of a limited thickness is significantly reduced, and the length of the minor axis is difficult to control. Therefore, the polarization degree of the emitted light is lowered, the bright line visibility is increased, and it may be difficult to achieve the transmittance of the first polarized light and the reflectance of the second polarized light to the desired level in all wavelength bands of visible light, and in some wavelength bands, the desired level of Optical properties may not be achieved. In addition, there is a problem that the viewing angle may be significantly narrowed.

In addition, according to a preferred embodiment of the present invention, in order to significantly reduce light leakage and bright line visibility, improve viewing angle, and express excellent polarization characteristics in the entire wavelength range of visible light, the average length of the major axis of the plurality of dispersions is 0.7 ~ At the same time satisfying 1.5㎛, the dispersion coefficient for the major axis length according to Equation 1 below may be 60 to 92%.

[Equation 1]

The dispersion coefficient (%) for the major axis length according to Equation 1 indicates the degree of spread of each dispersion for each major axis length in the major axis length distribution diagram for a plurality of dispersions. The smaller the dispersion coefficient, the smaller the major axis length of each dispersion. converges to the average length of the major axis, and the larger the dispersion coefficient, the larger the length of the major axis of each dispersion does not converge to the mean length of the major axis, but spreads widely. If the dispersion coefficient of the long axis length of the dispersion provided in the reflective polarizing film is less than 60%, there is a fear that the polarization characteristics may be deteriorated in any wavelength band of the visible light wavelength range. The polarization characteristic deteriorated in any wavelength band of the visible light wavelength band eventually causes non-uniformity of light transmittance for each wavelength, which may cause the appearance to be rainbow-colored or to show a specific color. In addition, it may be difficult to express an excellent viewing angle due to a decrease in light diffusion characteristics, and the maximum value of the relative optical gain may appear at a viewing angle of 60° or less.

In addition, if the dispersion coefficient of the major axis length of the dispersion exceeds 92%, the distribution of the major axis length is diversified, and this makes it easy to adjust the minor axis length of each dispersion to achieve uniformity of light transmittance for each wavelength in the entire visible light region The following may be advantageous, but in some cases, there is a concern that light leakage and bright lines may become noticeable.

On the other hand, in order to improve the viewing angle and to prevent light leakage and bright lines more significantly, the ratio of the long axis length of the dispersion D ₅₀ to the long axis length of the dispersion D ₁₀ in the distribution of the cumulative number by the major axis length of the dispersion is 1.6 ~ It could be 2.4.

The meaning of D _X is the long axis length of the dispersion corresponding to X% of the total number of dispersions when the cumulative number distribution curve for each major axis length is drawn in the order from the shortest major axis length to the longest axis length based on the major axis length of the dispersion. it means. For example, when the total number of dispersions is 10 and the major axis lengths of each dispersion are 0.5 μm, 0.6 μm, 0.6 μm, 0.7 μm, 0.7 μm, 0.7 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm , D ₂₀ is the major axis length of the dispersion corresponding to 20% of the 10 dispersions, 0.6 μm, and D ₅₀ is the long axis length of the dispersion corresponding to 50% of the 10 dispersions, which is 0.7 μm. . If the ratio of the long axis length of the D ₅₀ dispersion to the long axis length of the D ₁₀ dispersion (D ₅₀ /D ₁₀ ) is less than 1.6, there is a concern that light leakage and bright lines are noticeable or the viewing angle characteristics may deteriorate due to a decrease in the light diffusion function there is In addition, when D ₅₀ /D ₁₀ exceeds 2.4, the desired level of optical properties may not be expressed, and light leakage and bright lines may become noticeable, or there is a risk that the quality of the exterior color may occur.

More preferably, D ₅₀ is 0.5 to 0.9 μm, and D ₁₀ may be 0.3 μm or more, thereby further preventing light leakage, bright lines, appearance color quality problems, and achieving desired optical properties such as excellent viewing angle. can be beneficial to

In addition, the plurality of dispersions (112a, 112b, 112c) may be elongated and/or arranged so that the major axis direction is substantially parallel to any one axis direction of the reflective polarizing layer, and more preferably, to light irradiated from an external light source. It is effective to maximize the light modulation effect if the dispersions are stretched or arranged in parallel in the vertical direction.

In addition, the plurality of dispersions 112a, 112b, and 112c may be randomly dispersed inside the substrate 111, through which the viewing angle characteristics are strengthened through light diffusion, and at the boundary between the randomly dispersed dispersion and the substrate. It may be more advantageous to express the light modulation effect of

Meanwhile, the reflective polarizing layer 100 included in the exemplary embodiment of the present invention may further include skin layers 121 and 122 provided on at least one surface of the core layer 110 . The skin layers 121 and 112 are to supplement the mechanical strength of the core layer 100 . At this time, a separate adhesive layer may be further provided between the core layer 100 and the skin layers 121 and 122 , but preferably, the skin layers 121 and 122 are co-extruded together with the core layer 100 without a separate adhesive layer. It may be integrally formed. As a result, it is possible to not only prevent deterioration of optical properties due to the adhesive layer, but also to add more layers to a limited thickness, thereby remarkably improving the optical properties. Furthermore, unlike the case of post-adhesion with the unstretched skin layer after stretching the conventional core layer, the skin layers 121 and 122 included in the embodiment of the present invention are co-extruded together with the core layer 100 and then the stretching process is performed. Therefore, the skin layers 121 and 122 may also be stretched in at least one axial direction. Through this, the surface hardness is improved compared to the unstretched skin layer, so that scratch resistance can be improved and heat resistance can be improved.

The skin layers 121 and 122 may be made of a material of a skin layer commonly used to perform a supporting function of the reflective polarizing film, preferably polyethylene naphthalate (PEN), co-polyethylene naphthalate (co-PEN), polyethylene Terephthalate (PET), polycarbonate (PC), polycarbonate (PC) alloy, polystyrene (PS), heat-resistant polystyrene (PS), polymethyl methacrylate (PMMA), polybutylene terephthalate (PBT), poly Propylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polyurethane (PU), polyimide (PI), polyvinyl chloride (PVC), styrene-acrylonitrile mixture (SAN), ethylene acetic acid Vinyl (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP), urea (UF), melanin (MF), unsaturated polyester (UP), silicone (SI) and cycloolefin polymers may be used alone or in combination, and more preferably, the same material as that of the above-described base material 111 may be used.

In the aforementioned reflective polarizing layer 100 , the thickness of the substrate 111 may be 20 to 180 μm, and the thickness of the skin layers 121 and 122 may be 50 to 500 μm, but is not limited thereto. In addition, the number of the total dispersion 112 may be 25,000,000 to 80,000,000 when the thickness of the substrate 111 is 120 μm based on 32 inches, but is not limited thereto.

Next, the light diffusion layers 210 and 220 will be described.

The light diffusion layers 210 and 220 are disposed adjacent to the light incident surface and the light exit surface of the above-described reflective polarizing layer 100, respectively, and may be disposed so that their surfaces directly contact each other or may be disposed through another optical layer. However, when additional layers of different materials are provided, in order to minimize light loss due to an optical interface that is generated, it may be disposed so that the surfaces directly contact each other without intervening additional layers.

The light diffusion layers 210 and 220 may be known optical layers having a light diffusion function, and for example, light diffusion particles 212 may be dispersed in the matrix 211 as shown in FIG. 1 .

Specifically, the light diffusion layers 210 and 22 may be formed by applying a diffusion coating composition to both surfaces of the reflective polarizing layer and then solidifying. For example, the diffusion coating composition may include a binder component, light diffusion particles and a solvent.

The binder component is a component that forms the matrix of the coating layer, and may be used without limitation if it is a binder commonly used in the field of optical films, preferably an acrylic binder, a urethane-based binder, a urethane-acrylic copolymer binder, an ester-based binder, At least one selected from the group consisting of an ether-based binder, an imide-based binder, an amide-based binder, and an epoxy-based binder may be used. More preferably, the binder component may use a urethane-based binder.

Next, the light-diffusing particles may be used without limitation in the case of diffusion particles typically provided in the diffusion film, for example, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, and normal butyl. Methyl methacrylate, acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, acrylamide, methylol acrylamide, glycidyl methacrylate, ethyl acrylate, At least one selected from the group consisting of isobutyl acrylate, normal butyl acrylate, 2-ethylhexyl acrylate, polyethylene, acrylic, polystyrene and polypropylene may be used, and more preferably, acrylic bead particles.

On the other hand, the light diffusion layers 210 and 220 include a first light diffusion layer 220 disposed adjacent to the light incident surface of the reflective polarizing layer 100 and a second light diffusion layer 210 disposed adjacent to the light exit surface, and , the content of the diffusion particles provided in the first light diffusion layer 220 and the second light diffusion layer 210 may be different, preferably, the first diffusion particles and the second light provided in the first light diffusion layer 220 The weight ratio of the second diffusion particles provided in the diffusion layer 210 may be 1: 3.5 to 20, more preferably 4.7 to 20. If the weight of the second diffusion particle is less than 3.5 times the weight of the first diffusion particle, the luminance characteristic increases at the normal viewing angle of the emitted light, but the moire phenomenon occurs due to the absence of hiding power for defects and the second light diffusion layer There may be a risk of quality deterioration. In addition, when it exceeds 20 times, the quality such as improvement of hiding power and reduction of the moire phenomenon may be increased, but the luminance characteristic may be deteriorated at the viewing angle in the normal direction, and the reflective polarization function may also be deteriorated.

In addition, the first diffusion particles and the second diffusion particles may each independently have an average particle diameter of 3 to 20 μm. If the average particle diameter of the first and second diffusion particles is less than 3 μm, coating stains may occur, and if the average particle diameter exceeds 20 μm, poor leveling may occur.

In addition, according to a preferred embodiment of the present invention, in the first diffused particles, the particles belonging to ± 5% of the average particle diameter of the first diffused particles are 65 to 80% by volume of the total volume of the first diffused particles, and the second As for the diffusion particles, 65 to 80 vol% of the second diffusion particles are in the range of ± 5% of the average particle diameter of the second diffusion particles. It can be more uniformly dispersed in the second light diffusion layer, and there is an advantage in that the uniformity of optical properties is improved. If the volume of particles falling within the range of ± 5% of the average particle diameter of each diffusing particle out of the total volume of each diffusing particle is less than 65%, the uniformity of the optical properties is lowered, and the dark part (staining) phenomenon in the emitted light due to the decrease in particle dispersibility This can happen. In addition, if the volume of such particles exceeds 80%, the uniformity of the optical properties may be improved, but there is a concern that the surface durability may be relatively reduced.

In addition, the first diffusion particles may be included in an amount of 3 to 15% by weight based on the total weight of the first light-diffusion layer, and the second diffusion particles may be included in an amount of 20-50% by weight relative to the total weight of the second light-diffusion layer, and this It can be more advantageous in achieving the desired optical properties through It may be more useful, and may be even more useful when the optical film is an optical film having a structured surface such as a prism or a lenticular. If the amount of the first diffusion particles is less than 3% by weight relative to the total weight of the first light diffusion layer, scratch resistance is significantly reduced, and in particular, when assembled with a light source assembly, a prism film that can be assembled under the first light diffusion layer and When in contact with the same light collecting film, scratches may be remarkably generated on the surface of the first light diffusion layer due to the peak of the acid shape of the prism film, and the generated scratches may be identified as defects on the display panel. In addition, when the first diffusion particles are provided in excess of 15% by weight relative to the total weight of the first light diffusion layer, in particular, when assembled as a light source assembly, the light collecting film such as a prism film that can be assembled under the first light diffusion layer Conversely, there is a concern that damage may be caused to make it impossible to maintain an acid-shaped peak, thereby degrading the function of the optical film. In addition, if the amount of the second diffusion particles is less than 20% by weight relative to the total weight of the second light diffusion layer, defects due to the reflective polarizing film or the first light diffusion layer may be identified through the display panel, and the moire phenomenon may significantly occur there is In addition, if the second diffusion particles are provided in excess of 50% by weight, damage to the optical film that can be disposed on the second light diffusion layer may be damaged, thereby reducing the function of the optical film, and lowering the mechanical strength of the light diffusion layer There is a possibility that cracks and peeling may occur.

In addition, the solvent does not have a problem in dissolving the binder component in consideration of the type of the selected binder component, does not affect the dispersibility of light-diffusing particles, etc., and can be used without limitation in the case of a solvent that does not affect the reflective polarizing layer. . For example, the solvent may be propylene glycol monoethyl ether (PGME). This PGME expresses high leveling properties without any additives, improves the dispersibility of the light-diffusing particles, and at the same time, a polycarbonate-based component preferred as a component of the substrate 110 or skin layer 121 and 122 of the reflective polarizing layer 100 and There are several advantages such as not causing coating stains due to excellent compatibility.

The content of the solvent and the binder component in the diffusion coating composition may include 20 to 300 parts by weight of the solvent based on 100 parts by weight of the binder component, but is not limited thereto, and may be appropriately changed in consideration of the required viscosity according to the coating method.

The diffusion coating composition, in addition to the above-mentioned components, light stabilizer, ultraviolet absorber, antistatic agent, lubricant, leveling agent, antifoaming agent, polymerization accelerator, antioxidant, flame retardant, infrared absorber, surfactant, surface modifier, etc. at least one additive such as suitably It can be included, and specific types for each component can be selected from known ones.

The thickness of the light diffusion layers 210 and 220 may be 2 to 15 μm, but is not limited thereto. In addition, the thickness of each of the first light diffusion layer 220 and the second light diffusion layer 210 may be different from each other.

On the other hand, the light diffusion layers 210 and 220 may have a structured surface with irregularities on the outer surface A as shown in FIG. 2A, and the irregularities are formed by protruding light diffusion particles, or a matrix is formed to have an irregular surface. and can be implemented. Alternatively, as shown in FIG. 2B , the light diffusion layers 210 ′ and 220 ′ may have a flat outer surface and include light diffusion particles therein.

As the above-described reflective polarizing films 1000 and 1000 ′ have improved viewing angles, when the normal direction of the plane of the reflective polarizing layer 100 is defined as a viewing angle of 0°, the relative optical gain for the first polarization exceeds 60° It can have a maximum value at the viewing angle.

The relative optical gain is the result of calculating the luminance for each viewing angle measured at the top of the panel, respectively, with and without the reflective polarizing film between the light source having a predetermined amount of light and the panel through the following equation, and the relative optical gain is 1 The larger the value exceeds, the greater the degree of increase in luminance at the corresponding viewing angle through the reflective polarizing film. When the relative optical gain is 1, it means that there is no change in luminance at the corresponding viewing angle. means that the luminance has decreased through As the reflective polarizing film according to the present invention has a maximum value at a viewing angle exceeding 60°, the relative optical gain defined as above can display an image with high luminance from the side of the display (see Table 1 and FIG. 17) Also, preferably, the relative optical gain may have a maximum value at a viewing angle of greater than 60° and less than or equal to 75°. If the relative optical gain has a maximum value at a viewing angle of 60˚ or less, an improved viewing angle cannot be obtained at the desired level. As it decreases, it may be difficult to commercialize it as a product.

The above-described reflective polarizing film 1000 according to the present invention may be manufactured through a manufacturing method described later, but is not limited thereto.

The manufacturing method of the reflective polarizing film 1000 according to an embodiment of the present invention includes the steps of manufacturing a reflective polarizing layer and forming a light diffusion layer adjacent to the light incident surface and light exit surface of the manufactured reflective polarizing layer through the steps of can be performed.

The reflective polarizing layer 100 may be implemented through a manufacturing method to be described later. However, the manufacturing method to be described later is only an example and is not limited thereto.

First, the base component, the dispersion component, and the skin layer component are supplied to the extrusion unit. The base component and the dispersion component may be individually supplied to independent extruding parts, and in this case, the extruding part may be composed of two or more. In addition, it is also included in the present invention to supply one extruder including a separate supply path and a distribution port so that the polymers do not mix. The extruder may be an extruder, which may further include a heating means to convert the supplied polymers in a solid phase into a liquid phase.

The viscosity is designed so that there is a difference in polymer flowability so that the dispersion component can be arranged inside the base component, and preferably, the base component has better flowability than the dispersion component. Then, as the base material and the dispersion component pass through the mixing zone and the mesh filter zone, the dispersion components are randomly arranged in the base material through a difference in viscosity.

Thereafter, at least one surface of the prepared core layer is laminated with the skin layer component transferred from the extrusion unit. Preferably, the skin layer component may be laminated on both sides of the core layer. When the skin layer is laminated on both sides, the material and thickness of the skin layer may be the same or different from each other.

Next, spreading is induced in the flow control unit so that the dispersion components included in the substrate can be randomly arranged. Specifically, FIG. 8 is a cross-sectional view of a coat-hanger die, which is a type of a preferred flow control unit that can be applied to the present invention, and FIG. 9 is a side view of FIG. The size and arrangement of the cross-sectional area of the component can be adjusted randomly. Specifically, since the substrate on which the skin layer transferred through the flow path in FIG. 8 is laminated spreads left and right in the coat-hanger die, the dispersion component included therein also spreads widely left and right.

According to a preferred embodiment of the present invention, the steps of cooling and smoothing the reflective polarizing layer transferred from the flow control unit to which the spreading is induced, stretching the reflective polarizing film that has undergone the smoothing step; and heat-setting the stretched reflective polarizing layer.

First, the step of cooling and smoothing the reflective polarizing layer transferred from the flow control unit adopts or appropriately changes the method and conditions used in the manufacture of the conventional reflective polarizing layer, solidifies it after cooling, and then smoothes it through a casting roll process, etc. can do.

Thereafter, a process of stretching the reflective polarizing layer that has undergone the smoothing step is performed. The stretching may be performed through a conventional reflective polarizing layer stretching process, and through this, a difference in refractive index between the base component and the dispersion component may be caused to cause a light modulation phenomenon at the interface, and the spreading-induced dispersion component is stretched This further reduces the aspect ratio. For this purpose, preferably, the stretching process may perform uniaxial stretching or biaxial stretching, more preferably uniaxial stretching, and still more preferably uniaxial stretching in the MD direction. In addition, uniaxial stretching may be performed in the longitudinal direction of the dispersion. In addition, the draw ratio may be 3 to 12 times. On the other hand, a method of changing an isotropic material to birefringence is commonly known and, for example, when stretching under an appropriate temperature condition, the dispersed polymer molecules may be oriented to exhibit birefringence.

Next, a final reflective polarization layer may be manufactured through a step of heat-setting the stretched reflective polarization layer. The heat setting may be performed by appropriately adopting and changing the conditions of a known method, and preferably may be performed through an IR heater at 180 to 200° C. for 0.1 to 3 minutes.

Next, the light diffusion layers 211 and 212 may be formed by applying a light diffusion coating composition to the upper and lower portions of the skin layers 121 and 122 of the prepared reflective polarizing layer 100 . The light-diffusion coating composition may include a binder component, light-diffusing particles and a solvent as described above, and preferably may not include an antifoaming agent and/or a dispersing agent. Anti-foaming agent refers to a drug used to remove harmful air bubbles. The defoaming action has a foaming action and an antifoaming action, and the foaming action can remove the generated air bubbles, but cannot prevent the foaming, and the defoaming action can prevent the foaming, but it cannot remove the generated air bubbles. It says impossible action. Commonly used antifoaming agents include octyl alcohol, cyclohexanol, and nonionic surfactants. The dispersing agent refers to a component added to disperse solid fine particles in a liquid and to make a stable solution. Commonly used dispersants include alkylalkoxysilane, siloxane, silane, and polycarboxylic acid. Meanwhile, according to another preferred embodiment of the present invention, the diffusion coating composition may not contain both an antifoaming agent and a dispersing agent, thereby reducing production costs, simplifying the manufacturing process, and adding an antifoaming agent and/or a dispersing agent. When compared to the diffusion coating composition containing, it is possible to express the effect at a level with no significant difference.

The light-diffusion coating composition can be carried out by a conventional coating method, for example, gravure coating, bar coating, comma coating, etc., and more preferably, microgravure coating can be used.

After the light-diffusion coating composition is treated on the reflective polarizing layer, drying at 70 to 90° C. for 0.5 to 2 minutes may be further performed. The drying step serves to facilitate volatilization of the solvent. If the temperature of the drying step is less than 70° C. and/or the drying time is less than 0.5 minutes, the diffusion coating layer may be peeled off from the skin layer because the solvent is not volatilized well, and there may be a problem of coating mura (staining). , when the temperature exceeds 90° C. and/or the drying time exceeds 2 minutes, the diffusion coating layer and the skin layer are overdried, so that the diffusion coating layer may be peeled off from the skin layer.

Thereafter, a step of irradiating the dried diffusion coating layer with ultraviolet (UV) light at 70 to 90 Kw for 5 to 15 seconds may be performed. In the step of irradiating the ultraviolet rays, the diffusion coating layer is cured to prevent the diffusion coating layer and the skin layer from being peeled off. If the intensity of ultraviolet (UV) is less than 70Kw and/or the curing time is less than 5 seconds, since the diffusion coating layer is not cured well, a problem may occur in which the diffusion coating layer and the skin layer are peeled off, and if it exceeds 90Kw and/or the curing time is less than 5 seconds If this time exceeds 15 seconds, the diffusion coating layer and the skin layer may be peeled off because the diffusion coating layer is excessively hardened.

The reflective polarizing film according to an embodiment of the present invention manufactured by the above-described manufacturing method is employed in a light source assembly or a liquid crystal display including the same, and can be used to improve light efficiency. The light source assembly is classified into a direct light source assembly in which the lamp is located at the bottom, an edge type light source assembly in which the lamp is located at the side, and the reflective polarizing film according to embodiments of the present invention can be employed in any type of light source assembly. . Also, it is applicable to a backlight assembly disposed below the liquid crystal panel or a front light assembly disposed above the liquid crystal panel. Hereinafter, as an example of various application examples, a case in which the reflective polarizing film is applied to a liquid crystal display device including an edge-type light source assembly will be exemplified.

8 is a cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention, wherein the liquid crystal display 2700 includes a backlight unit 2400 and a liquid crystal panel assembly 2500 .

The backlight unit 2400 includes a reflective polarizing film 2111 that modulates the optical characteristics of the emitted light. may vary according to the present invention is not particularly limited.

However, according to a preferred embodiment of the present invention, as shown in FIG. 8 , a light source 2410 , a light guide plate 2415 for guiding light emitted from the light source 2410 , and a reflective film 2320 disposed below the light guide plate 2415 . ), and a reflective polarizer 2111 disposed above the light guide plate 2415 .

In this case, the light sources 2410 are disposed on both sides of the light guide plate 2415 . The light source 2410 may be, for example, a Light Emitting Diode (LED), a Cold Cathode Fluorescent Lamp (CCFL), a Hot Cathode Fluorescent Lamp (HCFL), or an External Electrode Fluorescent Lamp (EEFL). In another embodiment, the light source 2410 may be disposed on only one side of the light guide plate 2415 .

The light guide plate 2415 moves the light emitted from the light source 2410 through total internal reflection and emits it upward through a scattering pattern formed on the lower surface of the light guide plate 2415 . A reflective film 2420 is disposed under the light guide plate 2415 to reflect light emitted downward from the light guide plate 2415 upward.

A reflective polarizing film 2111 is disposed on the light guide plate 2415 . Since the reflective polarizing film 2111 has been described in detail above, a redundant description thereof will be omitted. Other optical sheets may be further disposed above or below the reflective polarizing film 2111 . For example, an optical film capable of controlling the direction of light, such as condensing light or diffusing light, or a retardation film and/or protective film for changing the phase of light may be further installed. In this case, the optical film for controlling the direction of the light will be effective when the reflective polarizing film does not separately have a structured surface layer as described above.

In addition, the light source 2410 , the light guide plate 2415 , the reflective film 2420 , and the reflective polarizing film 2111 may be accommodated by the bottom chassis 2440 .

The liquid crystal panel assembly 2500 includes a first display panel 2511 , a second display panel 2512 , and a liquid crystal layer (not shown) interposed therebetween. It may further include a polarizing plate (not shown) respectively attached to the surface.

The liquid crystal display 2700 may further include a top chassis 2600 that covers the edges of the liquid crystal panel assembly 2500 and surrounds sides of the liquid crystal panel assembly 2500 and the backlight unit 2400 .

On the other hand, specifically, FIG. 9 is an example of a liquid crystal display device employing a reflective polarizing film according to a preferred embodiment of the present invention, wherein a reflective plate 3280 is inserted on a frame 3270 , and an upper surface of the reflective plate 3280 . A cold cathode fluorescent lamp 3290 is located in the An optical film 3320 is positioned on the upper surface of the cold cathode fluorescent lamp 3290, and the optical film 3320 is laminated in the order of a diffusion plate 3321, a reflective polarizing film 3322, and an absorption polarizing film 3323. However, the components included in the optical film and the stacking order between each component may vary depending on the purpose, some components may be omitted or provided in plurality, and other types of optics for controlling light not listed above A film may be further provided. Meanwhile, the liquid crystal display panel 3310 may be positioned on the upper surface of the optical film 3320 by being inserted into the mold frame 3300 .

Looking at the path of the light, the light irradiated from the cold cathode fluorescent lamp 3290 reaches the diffusion plate 3321 of the optical film 3320 . The light transmitted through the diffusion plate 3321 passes through the reflective polarizing film 3322 in order to propagate the light in a vertical direction with respect to the optical film 3320, and light modulation occurs. Specifically, the P-polarized light transmits the reflective polarizer without loss, but in the case of the S-polarized light, light modulation (reflection, scattering, refraction, etc.) occurs and is again reflected by the reflecting plate 3280, which is the back side of the cold cathode fluorescent lamp 3290, and its After the property of light is randomly changed to P-polarized light or S-polarized light, it passes through the reflective polarizing film 3322 again. Thereafter, after passing through the absorption polarizing film 3323 , the liquid crystal display panel 3310 is reached. Meanwhile, the cold cathode fluorescent lamp 3290 may be replaced with an LED.

Meanwhile, in the present invention, the use of the reflective polarizing film has been mainly described for liquid crystal displays, but is not limited thereto, and can be widely used in flat panel display technologies such as projection displays, plasma displays, field emission displays and electroluminescence displays, but is not limited thereto. , glass windows, and work lighting requiring polarization can be widely applied.

The present invention will be described in more detail through the following examples, but the following examples are not intended to limit the scope of the present invention, which should be construed to aid understanding of the present invention.

<Example 1>

Polyethylene naphthalate (PEN) having a refractive index of 1.65 as a dispersion component, and polycyclohexylene dimethylene terephthalate (poly cyclohexylene) polymerized in a molar ratio of 1:2 with terephthalate, ethyl glycol, and cyclohexanedimethanol as a base component A polycarbonate alloy having a refractive index of 1.58 including 38 wt% of dimethylene terephthalate (PCTG), 60 wt% of polycarbonate, and 2 wt% of a heat stabilizer containing phosphate was added to the first and second extrusion sections, respectively. As a skin layer component, a raw material including the same component as the base component was added to the third extrusion unit.

The extrusion temperature of the base component and the dispersion component was set to 245 ° C., the Cap.Rheometer was checked, the polymer flow was corrected through IV adjustment, and the dispersion was induced to be randomly dispersed inside the substrate by passing through the channel to which the Filteration Mixer was applied, and then the substrate layer The skin layer component was laminated on both sides of the component. Then, the polymer was induced to spread in the coat hanger dies of FIGS. 6 and 7 to correct the flow rate and pressure gradient. Specifically, the width of the die inlet was 200 mm, the thickness was 10 mm, the width of the die outlet was 1,260 mm, the thickness was 2.5 mm, and the flow rate was 1.0 m/min. After that, a smoothing process was performed on a cooling and casting roll, and stretching was performed 6 times in the MD direction. Then, heat setting is performed at 180° C. for 2 minutes through a heater chamber, and the dispersion having the cross-sectional structure as shown in FIG. 3 is randomly dispersed with a thickness of 80 μm (total thickness including the 60 μm skin layer on both sides is 200 μm). A reflective polarizing layer was prepared (see FIG. 13). The refractive index of the dispersion component of the prepared reflective polarizing layer was (n _x : 1.88, n _y : 1.58, n _z : 1.58) and the refractive index of the base component was 1.58, and the plurality of dispersions were subjected to the conditions shown in Table 1 below. Satisfied.

A urethane acrylate compound having a weight average molecular weight of 2000 and 6 functional groups based on 100 parts by weight of propylene glycol monomethyl ether (PGME) as a first diffusion coating composition on the lower skin layer, which is the light incident surface of the prepared reflective polarizing layer (Miwon) Sangsa, Miramer PU620) 65 parts by weight, an average particle diameter of 5 μm, and 5 parts by weight of a first diffusion particle made of polybutyl methacrylate, in which particles falling within ± 5% of the average particle diameter account for 70% by volume of the total volume , 10 parts by weight of a photoinitiator (Chibage, Igacure-184) was mixed and stirred for 15 minutes at 1500 rpm in a stirrer to coat the first diffusion coating composition using a micro gravure roll of 150 mesh and dried at 80 ° C. for 1 minute A first light-diffusion layer having a thickness of 2.5 μm was prepared by curing it by irradiating it with an ultraviolet intensity of 80 kW for 10 seconds.

In addition, as a second diffusion coating composition on the upper skin layer, which is the light emitting surface of the reflective polarizing layer, a weight average molecular weight of 2000 with respect to 100 parts by weight of propylene glycol monomethyl ether (PGME), a urethane acrylate compound having 6 functional groups (Miwon) Sangsa, Miramer PU620) 65 parts by weight, the average particle diameter is 5 μm, and the particles belonging to ± 5% of the average particle diameter account for 70% by volume of the total volume 25 parts by weight of the second diffusion particles made of polybutyl methacrylate The second diffusion coating composition, prepared by mixing and stirring at 1500 rpm in a stirrer for 15 minutes, is coated using a 150 mesh micro gravure roll, dried at 80° C. for 1 minute, and irradiated for 10 seconds with an ultraviolet ray intensity of 80 kW for 10 seconds to cure and have a thickness of 2.5 μm A second light-diffusing layer was prepared to prepare a reflective polarizing film as shown in Table 1 below.

<Examples 2 to 11>

It was prepared in the same manner as in Example 1, except that the content of the first diffusion particles/second diffusion particles provided in the first light diffusion layer and/or the second light diffusion layer was changed as shown in Table 1 or Table 2 below. A reflective polarizing film as shown in 1 or Table 2 was prepared.

<Example 12>

It was prepared in the same manner as in Example 1, but by changing the reflective polarizing layer as follows. Specifically, PEN having a refractive index of 1.65 as the plate-shaped polymer dispersion component (hereinafter the first component), and terephthalate, ethyl glycol, and cyclohexanedimethanol as a base component (hereinafter the second component) are polymerized in a molar ratio of 1:2. A polycarbonate alloy having a refractive index of 1.58 including 38 wt% of poly cyclohexylene dimethylene terephthalate (PCTG), 60 wt% of polycarbonate, and 2 wt% of a heat stabilizer containing phosphate as a polycarbonate alloy and skin layer component The same components as the components were introduced into the first extruding unit 220, the second extruding unit 221, and the third extruding unit 222 of FIG. 10, respectively. The extrusion temperature of the first component and the second component was set to 295°C, the Cap.Rheometer was checked, and the polymer flow was corrected through IV adjustment, and the skin layer was extruded at a temperature level of 280°C. The first component was transferred to the first pressurizing means 230 (Kawasaki Gear Pump), and the second component was also transferred to the second pressurizing means 231 (Kawasaki Gear Pump). The discharge amount of the first pressing means is 8.9 kg/h in order, respectively, and the discharge amount of the second pressing means is 8.9 kg/h. Thereafter, a sea-island type composite was prepared using a sea-island type extrusion nozzle as shown in FIG. 11 . Specifically, the number of island component layers of the fourth spinneret distribution plate T4 among the island-in-the-island extrusion slits was 400, the diameter of the nozzle hole of the island component supply path was 0.17 mm, and the number of island component supply paths was 25000, respectively. The diameter of the discharge port of the 6th nozzle distribution plate was 15 mm×15 mm. In the feed block having a three-layer structure, the skin layer component flowed through the flow path from the third extrusion unit to form skin layers on the upper and lower surfaces of the sea-island composite flow (core layer polymer). The spread of the core layer polymer with the skin layer was induced in the coat hanger dies of FIGS. 6 and 7 in which the flow velocity and pressure gradient were corrected so that the aspect ratio of the sea-island composite flow was 1/30295. Specifically, the width of the die inlet was 200 mm, the thickness was 20 mm, the width of the die outlet was 960 mm, the thickness was 2.4 mm, and the flow rate was 1 m/min. After that, a smoothing process was performed on the cooling and casting rolls, and stretching was performed 6 times in the MD direction. As a result, the major axis length of the longitudinal section of the first component did not change, but the minor axis length decreased. Thereafter, heat setting was performed through an IR heater at 180° C. for 2 minutes to prepare a reflective polarizing layer in which the polymer as shown in FIG. 12 was dispersed. The refractive index of the dispersion component of the prepared reflective polarizing layer was (n _x : 1.88, n _y : 1.58, n _z : 1.58), the refractive index of the base component was 1.58, the aspect ratio of the polymer was approximately 1/180000, and the number of layers was 400 It was a layer, and the short axis length (thickness direction) was 84 nm, the major axis length 15.5 mm, and the average optical thickness was 138 nm. In this case, the thickness of the prepared reflective polarizing layer core layer was 59 μm, and the total thickness of the skin layer was 170.5 μm.

A reflective polarizing film as shown in Table 2 was prepared by forming a light diffusion layer in the same manner as in Example 1 above and below the skin layer of the prepared reflective polarizing layer.

<Comparative Example 1>

It was prepared in the same manner as in Example 1, but by changing the reflective polarizing layer as follows. Specifically, PEN having a refractive index of 1.65 as a first component and polycyclohexylene dimethylene terephthalate (poly cyclohexylene dimethylene terephthalate, PCTG) of 38% by weight, polycarbonate 60% by weight, and a heat stabilizer containing phosphate 2% by weight of a polycarbonate alloy having a refractive index of 1.58 and a skin layer component. It was put into the extruding part and the third extruding part. The extrusion temperature of the first component and the second component was set to 295, and the I.V. The polymer flow was corrected through adjustment, and the skin layer was extruded at a temperature level of 280.

Four composite streams having different average optical thicknesses were prepared using four slit-type extrusion nozzles of FIGS. 14 and 15 . Specifically, the first component transferred from the first extrusion part was distributed to four slit-type extrusion nozzles, and the second component transferred from the second extrusion part was transferred to four slit-type extrusion nozzles. One slit-type extrusion nozzle is composed of 300 layers, the thickness of the slit of the first slit-type extrusion nozzle on the bottom of the fifth nozzle distribution plate of FIG. 15 is 0.26 mm, and the slit thickness of the second slit-type extrusion nozzle is 0.21 mm , the slit thickness of the third slit-type extrusion nozzle was 0.17 mm, the slit thickness of the fourth slit-type extrusion nozzle was 0.30 mm, and the diameter of the discharge port of the sixth slit-type extrusion nozzle was 15 mm 15 mm. The four multi-layer composite flow discharged through the four slit-type extrusion nozzles and the skin layer component transferred through a separate flow path were laminated in a collection block to form a single core layer and a skin layer integrally formed on both sides of the core layer. . The core layer polymer on which the skin layer was formed was induced to spread in the coat hanger dies of FIGS. 6 and 7 for correcting the flow rate and pressure gradient. Specifically, the width of the die inlet was 200 mm, the thickness was 20 mm, the width of the die outlet was 960 mm, the thickness was 2.4 mm, and the flow rate was 1 m/min. After that, a smoothing process was performed on a cooling and casting roll, and stretching was performed 6 times in the MD direction. Then, heat setting was performed through an IR heater at 180° C. for 2 minutes to prepare a multilayer reflective polarizer as shown in FIG. 16 . The refractive index of the first component of the prepared reflective polarizer was (nx:1.88, ny:1.64, nz:1.64) and the refractive index of the second component was 1.58. Group A had 300 layers (150 repeating units), the thickness of the repeating unit was 168nm, the average optical thickness was 275.5nm, and the optical thickness deviation was around 20%. Group B had 300 layers (150 repeating units), the thickness of the repeating unit was 138 nm, the average optical thickness was 226.3 nm, and the optical thickness deviation was around 20%. Group C had 300 layers (150 repeating units), the thickness of the repeating unit was 110nm, the average optical thickness was 180.4nm, and the optical thickness deviation was around 20%. Group D had 300 layers (150 repeating units), the thickness of the repeating unit was 200nm, the average optical thickness was 328nm, and the optical thickness deviation was around 20%. The thickness of the core layer of the prepared multilayer reflective polarizer was 92.4 μm, the thickness of the skin layer was 60 μm, and the total thickness was 212.4 μm.

<Comparative Examples 2-3>

A reflective polarizing film as shown in Table 3 was implemented without forming the first light-diffusion layer and/or the second light-diffusion layer, except that it was prepared in the same manner as in Example 1.

<Experimental Example 1>

The following physical properties were evaluated for the reflective polarizing films prepared in Examples and Comparative Examples, and the results are shown in Tables 1 to 3.

1. Relative luminance

In order to measure the luminance of the reflective polarizing film, it was carried out as follows. After manufacturing a test display in which a panel was assembled on a 32" edge-type backlight unit provided sequentially with a reflective film, a light guide plate, a diffuser plate, and a reflective polarizing film, 9 points on the panel were measured using Topcon's BM-7 measuring instrument. The luminance was measured and an average value was indicated.

Relative luminance shows relative luminance values of other Examples and Comparative Examples when the luminance of the reflective polarizing film of Example 1 is 100 (standard).

2. Evaluation of relative optical gain according to viewing angle

The average value (a) was calculated by measuring the luminance of 9 points on the panel at different viewing angles using a BM-7 measuring instrument of Topcon Corporation in the display manufactured for the measurement of relative luminance. At this time, the viewing angle was based on the normal direction to the panel as the viewing angle 0˚, and the viewing angle was changed to (left) -90˚ ~ (right) +90˚.

On the other hand, after removing the reflective polarizing film from the same assembly device, the luminance of 9 points on the panel was measured in the same way at different viewing angles to calculate the average value (b), and the relative optical gain according to the viewing angle was calculated by the following formula . At this time, the results according to Example 1 are shown in FIG. 17, and in the table, relative values of luminance of the remaining Examples and Comparative Examples based on the value of Example 1 as 100 with respect to the average luminance at a viewing angle of ±80° (%) , represents the viewing angle at which the calculated relative optical gain has the maximum value. In addition, the calculated minimum value of relative optical gain is also shown.

[Equation] Relative optical gain at viewing angle X˚ = luminance at viewing angle X˚ (a) / luminance at viewing angle X˚ (b)

3. Moire phenomenon

On the display manufactured for measuring relative luminance, when the moire phenomenon is not observed by visually observing the panel, 0, when the moire phenomenon appears, the degree of the moire phenomenon shown in Comparative Example 4 is 5 based on the degree of relative 1 ~ It was rated as 5.

4. Concealment

In the display manufactured for measuring relative luminance, the appearance of the panel was visually observed to evaluate whether various defects such as foreign objects, bedrock, and bright lines were observed. For reliability of evaluation, after manufacturing 10 displays for each Example and Comparative Example, the observation of defects was evaluated. As a result of observation, the case in which no defect occurred was evaluated as 0, and when the defect occurred, the degree of occurrence in Comparative Example 3 was set as 5, and a rating of 1 to 5 was relatively evaluated depending on the degree of occurrence.

In Tables 1 to 4, the content of diffusion particles in each light diffusion layer is the content of diffusion particles relative to 100 parts by weight of the binder component in each composition for forming a diffusion layer.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 first diffusion layer first diffuse particle Content ¹⁾ (parts by weight) 5.5 5.5 5.5 5.5 5.5 5.5 Average particle diameter (㎛) 5 5 5 5 5 5 Particles belonging to the average particle diameter ±5% (volume %) 70 70 70 70 70 70 Weight % in the first diffusion layer 6.83 6.83 6.83 6.83 6.83 6.83 reflective polarizing layer type Polymer Random Dispersion Polymer Random Dispersion Polymer Random Dispersion Polymer Random Dispersion Polymer Random Dispersion Polymer Random Dispersion dispersion average aspect ratio 1/5.3 1/5.3 1/5.3 1/5.3 1/5.3 1/5.3 Average long axis length (㎛) 1.03 1.03 1.03 1.03 1.03 1.03 Dispersion coefficient for major axis length (%) 70.41 70.41 70.41 70.41 70.41 70.41 D50/D10 1.88 1.88 1.88 1.88 1.88 1.88 D10 (μm) 0.43 0.43 0.43 0.43 0.43 0.43 D50(㎛) 0.81 0.81 0.81 0.81 0.81 0.81 second diffusion layer 2nd diffuse particle Content (parts by weight) 26.4 18.15 19.25 22 24.75 55 Average particle diameter (㎛) 5 5 5 5 5 5 Average particle diameter ±5% 70 70 70 70 70 70 Weight % in the second diffusion layer 26.04 19.48 20.42 22.68 24.81 42.31 1st diffused particle: 2nd diffused particle weight ratio 1:4.8 1:3.3 1:3.5 1:4 1:4.5 1:10 Properties Relative luminance (%) 100 102.8 102.5 102.0 101.4 96.7 Relative luminance (%) at ±80˚ viewing angle 100 96.1 98.5 98.7 99.9 97.5 The viewing angle at which the relative optical gain has the maximum value (˚) -63 -58.3 -60.4 -62.2 -63.1 -68.8 moire phenomenon 0 One 0 0 0 0 hiding power 0 One 0 0 0 0

Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 first light diffusion layer first diffuse particle Content ¹⁾ (parts by weight) 3 3 3 2 15 5.5 Average particle diameter (㎛) 5 5 5 5 5 5 Particles belonging to ±5% of average particle diameter (volume %) 70 70 70 70 70 70 Weight % in the first light diffusion layer 3.8 3.8 3.8 2.6 16.7 6.83 reflective polarizing layer type Polymer Random Dispersion Polymer Random Dispersion Polymer Random Dispersion Polymer Random Dispersion Polymer Random Dispersion polymer dispersion type dispersion average aspect ratio 1/5.3 1/5.3 1/5.3 1/5.3 1/5.3 1/180000 Average long axis length (㎛) 1.03 1.03 1.03 1.03 1.03 15500 Dispersion coefficient for major axis length (%) 70.41 70.41 70.41 70.41 70.41 0 D50/D10 1.88 1.88 1.88 1.88 1.88 - D10 (μm) 0.43 0.43 0.43 0.43 0.43 D50(㎛) 0.81 0.81 0.81 0.81 0.81 second light diffusion layer 2nd diffuse particle Content (parts by weight) 45 57 63 38 72 26.4 Average particle diameter (㎛) 5 5 5 5 5 5 Average particle diameter ±5% 70 70 70 70 70 70 Weight % in the second light diffusion layer 37.5 43.2 45.7 33.6 49.0 26.04 Weight ratio of first diffused particle: second diffused particle 1:15 1:19 1:21 1:19 1:4.8 1:4.8 Properties Relative luminance (%) 97.2 96.8 96.1 98.4 91.1 98.5 Relative luminance (%) at ±80˚ viewing angle 97.6 96.2 93.0 98.9 86.4 90.9 The viewing angle at which the relative optical gain has the maximum value (˚) -66.1 -67.9 -70.4 -64.6 -76.5 +60.5 moire phenomenon 0 0 0 0 0 0 hiding power 0 0 0 2 0 4

Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 first light diffusion layer first diffuse particle Content ¹⁾ (parts by weight) 5.5 5.5 not included not included Average particle diameter (㎛) 5 5 Particles belonging to ±5% of average particle diameter (volume %) 70 70 Weight % in the first light diffusion layer 6.83 6.83 reflective polarizing layer type multi-layered Polymer Random Dispersion Polymer Random Dispersion Polymer Random Dispersion dispersion average aspect ratio - 1/5.3 1/5.3 1/5.3 Average long axis length (㎛) 1.03 1.03 1.03 Dispersion coefficient for major axis length (%) 70.41 70.41 70.41 D50/D10 1.88 1.88 1.88 D10 (μm) 0.43 0.43 0.43 D50(㎛) 0.81 0.81 0.81 second light diffusion layer 2nd diffuse particle Content (parts by weight) 26.4 not included 26.4 not included Average particle diameter (㎛) 5 5 Average particle diameter ±5% 70 70 Weight % in the second light diffusion layer 26.04 26.04 1st diffused particle: 2nd diffused particle weight ratio 1:4.8 - - - Properties Relative luminance (%) 104.8 104.7 103.5 105.1 Relative luminance (%) at ±80˚ viewing angle 35.7 84.0 93.6 75.8 The viewing angle at which the relative optical gain has the maximum value (˚) +37.8 +51.0 +54.3 +50.6 moire phenomenon 0 5 0 5 hiding power 0 5 0 5

In Tables 1 to 4, the content of diffusion particles in each light diffusion layer is the content of diffusion particles relative to 100 parts by weight of the binder component in each composition for forming a diffusion layer.

As can be seen from Tables 1 to 4, the reflective polarizing film according to Comparative Example 1 is superior to the Example in relative luminance, but it can be confirmed that the relative luminance at a ±80° viewing angle is significantly lower than in Examples. In addition, in the case of Comparative Examples 2 to 4 having a light diffusion layer on only one surface or no light diffusion layer on both surfaces, it can be seen that the viewing angle is significantly lowered compared to Example 1.

100: reflective polarizing layer 110: core layer
121,122: skin layer 210,220: light diffusion layer
1000: reflective polarizing film

Claims (13)

a reflective polarization layer that transmits a first polarized light among the incident light and reflects a second polarized light; and
A first light diffusion layer disposed adjacent to the light incident surface of the reflective polarizing layer and including first diffusion particles, and a second light diffusion layer disposed adjacent to the light exit surface of the reflective polarizing layer and including second diffusion particles Including; a light diffusion layer having a
The reflective polarizing layer includes a substrate and a core layer including a plurality of dispersions included in the substrate, and when the longitudinal direction of the dispersion among mutually orthogonal x, y, and z axes is the x-axis, the reflective polarizing layer In the yz section of the plurality of dispersions are randomly dispersed inside the substrate,
The weight ratio of the first diffusing particles and the second diffusing particles is 1: 3.5 to 20, the first diffusing particles are included in an amount of 3 to 15 wt % based on the total weight of the first light diffusing layer, and the second diffusing particles are the It is included in an amount of 20 to 50% by weight based on the total weight of the second light diffusion layer,
When the normal direction of the plane of the reflective polarizing layer is defined as a viewing angle of 0°, the relative optical gain for the first polarization has a maximum value at a viewing angle exceeding 60°. delete According to claim 1,
The reflective polarizing film further includes a skin layer integrally formed on at least one surface of the core layer. delete delete delete According to claim 1,
The first diffusion particles and the second diffusion particles each independently have an average particle diameter of 3 ~ 15㎛ reflective polarizing film. 8. The method of claim 7,
In the first diffusion particles, the particles belonging to the range of ± 5% of the average particle diameter of the first diffusion particles are 65 to 80% by volume of the total volume of the first diffusion particles,
The second diffusing particle is a reflective polarizing film in which the particles belonging to ± 5% of the average particle diameter of the second diffusing particle are 65 to 80 volume % of the total volume of the second diffusing particle. delete According to claim 1,
The relative optical gain with respect to the first polarization film has a maximum value at a viewing angle of more than 60˚ to 75˚ or less. According to claim 1,
The light diffusion layer is a reflective polarizing film having a thickness of 2 ~ 15㎛. A light source assembly comprising the reflective polarizing film according to any one of claims 1, 3, 7, 8, 10 and 11. A liquid crystal display device comprising the light source assembly according to claim 12 .

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