Optical film and display device comprising same

Abstract

The present invention relates to an optical film, and more particularly, to an optical film capable of improving left and right viewing angles of a display device, maintaining uniform viewing angle improvements even when manufactured in a large-area format, and minimizing color variation as well as improving contrast ratio without degrading front luminance characteristics while improving the viewing angles.

Description

Optical film and display device including the same

[0001] The present invention relates to an optical film, and more specifically, to an optical film that improves the contrast ratio and viewing angle of a display device and minimizes color change.

[0002] Liquid crystal displays operate by light from a backlight unit being emitted through a liquid crystal panel. Therefore, while the contrast ratio (CR) is excellent on the front of the screen, it is generally poor on the sides compared to the front.

[0003] To address this, there are attempts to increase the contrast ratio from the sides by modifying the liquid crystal panel or liquid crystal structure. However, increasing the side contrast ratio inevitably leads to a decrease in the front contrast ratio. Therefore, it is necessary to increase the side contrast ratio while minimizing the reduction in the front contrast ratio.

[0004] Meanwhile, there is a method of diffusing light to improve the viewing angle, and for this purpose, a method has been proposed to enhance light diffusion by including inorganic particles, as an example. However, spherical inorganic particles provided in optical films make it difficult to secure a sufficient viewing angle, or even if secured, may reduce brightness, and have almost no effect on improving contrast ratio.

[0005] As another example, it has been studied that inorganic particles having an aspect ratio greater than 1 provided in an optical film can increase light diffusivity and simultaneously exhibit anisotropic diffusion characteristics compared to spherical inorganic particles. However, it is not easy to align the long axis direction of each of the numerous inorganic particles contained within the body of the film so that they face a specific direction. Furthermore, inorganic particles that are not uniformly aligned in a specific direction within the film may exhibit anisotropic diffusion, but when viewed as a whole optical film, it is difficult to exhibit anisotropic diffusion, and consequently, there is a problem in that it is difficult to secure a sufficient viewing angle.

[0006] The present invention was devised to solve the aforementioned problems and aims to provide an optical film capable of improving the left and right viewing angles of a display device and uniformly exhibiting a viewing angle improvement effect even when manufactured in a large area.

[0007] In addition, another objective of the present invention is to provide an optical film that improves the viewing angle while simultaneously improving the contrast ratio and minimizing color variation without degrading the frontal brightness characteristics.

[0008] To solve the above-mentioned problem, the present invention provides an optical film having an anisotropic diffusion layer comprising: a polymer matrix; a polymer dispersion and a non-polymer dispersion comprising inorganic particles having an average aspect ratio of 3.0 or higher, wherein the major axis direction of each of the polymer dispersion and the non-polymer dispersion is arranged in the x-axis direction among the mutually perpendicular x-axis, y-axis, and z-axis within the polymer matrix; wherein the inorganic particles have an average length of 3 to 15 μm and inorganic particles having a length of 2.5 μm or less account for 23% or less of the total inorganic particles.

[0009] According to one embodiment of the present invention, the inorganic particles may be located inside a polymer dispersion.

[0010] In addition, the above inorganic particles may have an average diameter of 0.5 to 2.0 μm.

[0011] In addition, the above inorganic particles have an average length of 3 to 15 μm, and inorganic particles with a length of 2.5 μm or less may be included in an amount of 17% or less of the total inorganic particles.

[0012] In addition, the above nonpolymer dispersion may be contained in an amount of 0.5 to 5 weight percent based on the total weight of the anisotropic diffusion layer.

[0013] In addition, the surface of the inorganic particle may be modified with one or more compounds among a compound represented by the following chemical formula 1 and a silane-based compound containing an epoxy group.

[0014] [Chemical Formula 1]

[0015]

[0016] In Chemical Formula 1, R1, R2 and R3 are each independently hydrogen, or a straight-chain or branched-chain alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms.

[0017] In addition, the polymer matrix and polymer dispersion may be included in a weight ratio of 6 to 9.8: 4 to 0.2.

[0018] In addition, when non-polymer dispersions dispersed within a polymer matrix are projected in the z-axis direction of the matrix, the number of non-polymer dispersions in which the angle between the x-axis direction and the major axis direction of the non-polymer dispersion is within ±5° on the projection plane, which is a plane formed by the x-axis and the y-axis, may be 75% or more of the total number of non-polymer dispersions.

[0019] In addition, the above anisotropic diffusion layer may have a thickness of 150㎛ or less.

[0020] In addition, it may further include a skin layer integrally formed on at least one surface of the anisotropic diffusion layer.

[0021]

[0022] In addition, the present invention provides a polarizing plate disposed on a light-emitting surface of a liquid crystal panel, wherein the polarizing plate comprises an absorption polarizing film and an optical film according to the present invention disposed on a light-emitting surface of the absorption polarizing film.

[0023]

[0024] In addition, the present invention provides a liquid crystal display device comprising a liquid crystal panel and a polarizing plate according to the present invention disposed on at least the light-emitting surface of the liquid crystal panel.

[0025]

[0026] In addition, a display device comprising a self-emissive display panel and an optical film according to the present invention disposed on at least the light-emitting surface of the self-emissive display panel is provided.

[0027] The optical film of the present invention can improve the left and right viewing angles of a display device and can uniformly exhibit the viewing angle improvement effect even when manufactured over a large area. Furthermore, while improving the viewing angle, it can minimize color fluctuations along with enhancing the contrast ratio without degrading frontal brightness characteristics. Moreover, the visibility of dispersed particles is prevented, and side effects such as glare lines and light leakage can also be prevented. In addition, as it is suitable for mass production over a large area, it can be widely used as an optical component in various display devices.

[0028] FIG. 1 is a perspective view of an optical film according to one embodiment of the present invention,

[0029] FIGS. 2 and 3 are schematic cross-sectional views along the Y-Y' and X-X' boundaries of the optical film according to FIG. 1.

[0030] FIG. 4 is a schematic diagram illustrating alignment on a projection plane projected in the z-axis direction of a non-polymer dispersion dispersed in an optical film according to one embodiment of the present invention.

[0031] FIG. 5 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention, and

[0032] FIG. 6 is a cross-sectional schematic diagram of a liquid crystal display according to one embodiment of the present invention.

[0033] Hereinafter, embodiments of the present invention are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the invention. The present invention may be embodied in various different forms and is not limited to the embodiments described herein. In the drawings, parts unrelated to the explanation have been omitted to clearly explain the present invention, and the same reference numerals are assigned to identical or similar components throughout the specification. Furthermore, it should be noted that the size and shape of a component shown in the drawings are examples and that the present invention is not limited by them.

[0034]

[0035] Referring to FIGS. 1 to 3, an optical film (200) according to one embodiment of the present invention includes an anisotropic diffusion layer (100) and may further include a skin layer (110) disposed on one or both sides of the anisotropic diffusion layer (100).

[0036]

[0037] The above anisotropic diffusion layer (100) performs the function of anisotropically diffusing light incident on an optical film (200). Specifically, when light is incident on a plane formed by the x-axis and y-axis, it can be diffused in the y-axis direction perpendicular to the x-axis, where the major axis direction of the disperser (20) is aligned, and emitted to the opposite side facing the incident surface. To this end, the above anisotropic diffusion layer (100) includes a polymer matrix (10) and a plurality of dispersers (20) in which each major axis is aligned in the x-axis direction within the polymer matrix (10).

[0038]

[0039] The above polymer matrix (10) is formed of a first polymer as a body containing and supporting a dispersion (20) that exhibits anisotropic diffusion characteristics, and the first polymer can be any known polymer used as a conventional optical film without limitation. The first polymer may be, for example, one or more mixtures or two or more copolymers selected from the group consisting of polyethylene naphthalate (PEN), copolyethylene naphthalate (co-PEN), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC), polycarbonate (PC) alloy, polystyrene (PS), polymethyl methacrylate (PMMA), 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), and cycloolefin polymers. Meanwhile, the above polycarbonate alloy may be a mixture in which a different known polyester resin is mixed with a polycarbonate main resin containing more than 50% by weight, and as an example, the different polyester resin may be polycyclohexylene dimethylene terephthalate.

[0040]

[0041] Additionally, the plurality of dispersed bodies (20) dispersed within the polymer matrix (10) described above include a polymer dispersed body (21) and a non-polymer dispersed body (22) containing inorganic particles. Each of the polymer dispersed body (21) and the non-polymer dispersed body (22) has a long shape in one direction, and the long axis direction of each of the polymer dispersed body (21) and the non-polymer dispersed body (22) is arranged in the x-axis direction among the mutually perpendicular x-axis, y-axis, and z-axis within the polymer matrix (10), thereby enabling anisotropic diffusion.

[0042]

[0043] First, the polymer dispersion (21) is formed from a second polymer and may have a shape such as a long rod-shaped and / or fiber-shaped structure in one direction, thereby performing an anisotropic diffusion function that diffuses transmitted light in a direction perpendicular to the one direction. Specifically, in a cross-section perpendicular to the TD direction of the optical film, in other words, in a cross-section of the anisotropic diffusion layer (100) along the XX' boundary line shown in FIG. 3, the average aspect ratio, which is the ratio (a / b) between the average length of the major axis (a) of the polymer dispersion (21) and the average length of the minor axis (b) perpendicular to the major axis, may be greater than 100, or, as another example, greater than 1,000, greater than 10,000, or greater than 100,000. The average length of the minor axis (b) refers to the length of the largest line segment among the lengths of the line segments connecting the perimeter within the cross-section perpendicular to the major axis.

[0044] Additionally, the cross-sectional shape of the polymer dispersion (21) based on the cross-section plane, which is the yz plane of the anisotropic diffusion layer (100) corresponding to the cross-section along the YY' boundary line shown in FIG. 2, may be circular or elliptical. In this case, if the cross-sectional shape of the polymer dispersion (21) is elliptical, the average cross-sectional aspect ratio (c / d), which is the ratio of the average length of the major axis (c) to the average length of the minor axis (d) of the ellipse, may be greater than 1 and less than or equal to 350, but is not limited thereto. Here, the average length of the minor axis (d) refers to the average value of the length of the minor axis when the axis that perpendicularly bisects the major axis is called the minor axis. If the cross-sectional shape of the polymer dispersion (21) is elliptical, the average aspect ratio of the cross-section exceeds 350, which may indirectly imply that the alignment of multiple non-polymer dispersions (22) is reduced so that their major axis direction becomes the x-axis direction, or that fusion between the second polymers forming the polymer dispersion has occurred, and in this case, it may not be easy to achieve the desired effect of the present invention.

[0045]

[0046] Additionally, the second polymer forming the polymer dispersion (21) can be any known polymer used as a conventional optical film without limitation. For example, the second polymer may be one or more of polyethylene naphthalate (PEN), copolyethylene naphthalate (co-PEN), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC), polycarbonate (PC) alloy, polystyrene (PS), polymethyl methacrylate (PMMA), polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polyurethane (PU), polyimide (PI), polyvinyl chloride (PVC), styrene-acrylonitrile blend (SAN), ethylene vinyl acetate (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP), urea (UF), melanin (MF), unsaturated polyester (UP), and cycloolefin polymer, or two or more copolymers. Meanwhile, the above polycarbonate alloy may be a mixture in which a different known polyester resin is mixed with a polycarbonate main resin containing more than 50% by weight, and as an example, the different polyester resin may be polycyclohexylene dimethylene terephthalate.

[0047]

[0048] Additionally, the polymer dispersion (21) is contained in multiple quantities, and as an example, the polymer dispersion (21) has a unit area (1㎛). 2 It can contain 10 to 200 pieces.

[0049]

[0050] Additionally, a plurality of polymer dispersions (21) are arranged within the matrix (10) such that the x-axis direction is the major axis direction among the three mutually perpendicular x-axis, y-axis, and z-axis within the matrix (10). However, the arrangement such that the x-axis direction is the major axis direction of the polymer dispersion (21) does not mean that the major axis direction of all polymer dispersions (21) is arranged parallel to the x-axis, but rather means that the direction of the major axis that becomes the major axis direction of the polymer dispersion (21) is closer to the x-axis direction than to the y-axis and z-axis, and the angle formed between the major axis direction of the polymer dispersion (21) and the x-axis may be, for example, less than 10°, less than 5°, less than 3°, or, for another example, less than 1°.

[0051] Additionally, a plurality of polymer dispersions (21) may be randomly arranged based on a yz cross-section formed by the y-axis and z-axis of the matrix. Here, being randomly arranged means that the positions of the plurality of polymer dispersions (21) are randomly arranged in the yz cross-section regardless of the size and shape of the dispersion cross-section.

[0052]

[0053] Meanwhile, the polymer dispersion (21) can perform a guide function to align the long axis direction of the inorganic particles, which are provided as a non-polymer dispersion (22) described later, to the x-axis direction within the polymer matrix (10), in addition to the anisotropic diffusion function described above. Specifically, during the extrusion process in the manufacturing process, if the inorganic particles are extruded so that they are located inside the polymer dispersion (21), the inorganic particles cannot move toward the polymer matrix (10) and exhibit the effect of being trapped inside the polymer dispersion (21). In this case, during the subsequent extrusion process, the length of the polymer dispersion (21) gradually increases in the MD direction and the diameter decreases, and as a result, the long axis direction of the inorganic particles located inside the polymer dispersion (21) can be aligned in the MD direction. Accordingly, as the length of the polymer dispersion (21) increases through the extrusion and / or stretching process, the long axis direction of the inorganic particles can be aligned substantially parallel to the long axis direction of the polymer dispersion (21) in the MD direction, that is, in the x-axis direction of the polymer matrix (10), and the non-polymer dispersion (22) containing the inorganic particles can be located inside the polymer dispersion (21).

[0054]

[0055] Additionally, when the length of the polymer dispersion (21) increases during the process of the polymer dispersion (21) performing a guide function to align the long axis direction of the inorganic particles, the diameter of the region of the polymer dispersion (21) where the inorganic particles are not located becomes smaller than the diameter of the region of the polymer dispersion (21) where the inorganic particles are located. On the other hand, the region of the polymer dispersion (21) where the inorganic particles are located may have a diameter larger than the diameter of the inorganic particles due to the inorganic particles.

[0056]

[0057] Additionally, when looking at the region of the polymer dispersion (21) where the inorganic particles are located, the second polymer forming the polymer dispersion (21) can form a layer that covers the surface of the inorganic particles, specifically at least a portion of the lateral surface of the inorganic particles when viewed with respect to the long axis direction of the inorganic particles, and the layer formed by the second polymer can function as a buffer layer (23) that suppresses the generation of voids caused at the interface between the lateral surface of the inorganic particles and the polymer matrix (10). Specifically, the inorganic particles included in the first polymer forming the polymer matrix (10) and the non-polymer dispersion (21) have low compatibility due to being heterogeneous materials, and there is a risk of separation at the interface between the polymer matrix and the inorganic particles and the generation of voids when the anisotropic diffusion layer is stretched in the manufacturing process described later. In particular, voids formed on the side of the inorganic particle that becomes the TD direction side due to stretching in the TD direction may reduce the aspect ratio of the inorganic particle, thereby lowering anisotropic diffusivity, and increase the number of interfaces with different refractive indices, potentially lowering brightness. However, the second polymer forming the polymer dispersion (21) can form a buffer layer (23) that covers at least a portion of the side surface of the inorganic particle, thereby mitigating the difference in compatibility between the first polymer forming the polymer matrix (10) and the inorganic particle, and can minimize or prevent the formation of voids on the side of the inorganic particle. Here, the side of the inorganic particle refers to the outer surface defined as the right side or the left side when the two ends in the direction of the long axis of the inorganic particle are defined as the upper side and the lower side, or the front side and the rear side. Meanwhile, the number of sides and the specific shape of the inorganic particle can be defined according to the shape of the inorganic particle, so the present invention is not specifically limited thereto. For example, when assuming that an inorganic particle is a cylinder with the major axis direction being the height, the left and right sides that become the sides can be a single continuous curved surface.In addition, for example, if the above-mentioned inorganic particle is a polyhedron, the number of left and right faces may be two or more, the face directions may be the same or different from each other, and the shape of each face may be independently a flat or curved surface.

[0058]

[0059] Meanwhile, the function of the guide function and buffer layer of the polymer dispersion (21) described above may depend on the combination of physical properties between the second polymer forming the polymer dispersion (21) and the first polymer forming the polymer matrix (10).

[0060] Specifically, in order to perform a guide function, the melt viscosity of the first polymer at a predetermined temperature may be different from that of the second polymer. In addition, to facilitate the realization of the morphology of the polymer matrix (10) / polymer dispersion (21) determined by the formability and dispersibility of the polymer dispersion (21) formed by the second polymer within the polymer matrix (10) formed by the first polymer, and simultaneously to improve alignment such that the long axis direction of the inorganic particles is aligned with the x-axis direction of the polymer matrix (10), the melt viscosity of either the first polymer or the second polymer may preferably be 1.3 times or more than the melt viscosity of the other polymer, and as another example, may be 1.5 times or more, 1.8 times or more, 2 times or more, or 3 times or more, and as another example, may be 5 times or less, or 4 times or less. Meanwhile, regarding the relative melt viscosity between the first polymer and the second polymer, since the relationship between the relative melt viscosity of the two polymers varies by temperature even when assuming the same two polymers depending on the specific type of polymer, the present invention is not specifically limited thereto.

[0061]

[0062] Additionally, to function as a buffer layer, the second polymer may comprise an amorphous resin and the first polymer may comprise a crystalline resin or a semicrystalline resin, and / or the second polymer may have a lower glass transition temperature than the first polymer. Specifically, the second polymer having a lower glass transition temperature than the first polymer under stretching temperature conditions may be softer than the first polymer, which may be advantageous for having relatively higher ductility or elasticity. And / or, if the second polymer comprises an amorphous resin, ductility limitation due to crystals occurs less frequently, making it advantageous for exhibiting higher ductility than the first polymer comprising a semicrystalline or crystalline resin. The physical properties of the second polymer compared to the first polymer can act as a buffer when stretched in the TD direction between the inorganic particles and the first polymer in a structure of inorganic particles, the second polymer (polymer dispersion (21)), and the first polymer (polymer matrix (10)) that are stacked in the TD direction, and this can be more advantageous in suppressing the occurrence of voids at the interface between heterogeneous materials. If the glass transition temperature or crystal structure between the first polymer and the second polymer does not satisfy the above-described conditions, the occurrence of voids on the side of the inorganic particles in the TD direction may be more frequent, and this may have the effect of relatively reducing the aspect ratio of the inorganic particles structurally, thereby reducing anisotropic diffusion. In addition, the difference in refractive index between the polymer matrix (10), the polymer dispersion (21), and / or the inorganic particles forming an interface with the formed voids increases, which may reduce brightness and / or cause the polymer dispersion (21), inorganic particles, and / or voids to be visible to the naked eye.

[0063] Meanwhile, it should be noted that when the combination of crystal structures between the first polymer and the second polymer is semicrystalline or crystalline and amorphous, the glass transition temperature between the first polymer and the second polymer does not necessarily have to be greater for the first polymer than for the second polymer. However, in this case, even if the glass transition temperature of the second polymer is greater, it is preferable that the glass transition temperature of the second polymer be 6°C or less greater than the glass transition temperature of the first polymer. If the glass transition temperature of the second polymer is more than 6°C higher than the glass transition temperature of the first polymer, it may be difficult to prevent the occurrence of voids on the side of the inorganic particle even if the crystal structure conditions of the first polymer and the second polymer described above are satisfied.

[0064]

[0065] Additionally, at a given temperature, the melt viscosity (Pa·S) of the first polymer and the melt viscosity (Pa·S) of the second polymer may each be independently 100 Pa·S or higher, more preferably 200 Pa·S or higher, and as another example, 2,000 Pa·S or lower. This facilitates the formation of a morphology in which the polymer dispersion (21), which is the second polymer, is formed and dispersed within the polymer matrix (10), which is the first polymer. It may also be advantageous to orient the long axis direction of the inorganic particles in the x-axis direction, which is the same direction as the long axis direction of the polymer dispersion (21), through a guide of the second polymer extending in a specific direction, specifically the x-axis. If the melt viscosity of either the first polymer or the second polymer is less than 100 Pa·S, it may be difficult to implement a morphology composed of a polymer matrix and a polymer dispersion. In addition, if the melt viscosity of one or more of the first polymer and the second polymer exceeds 2,000 Pa·S, the alignment and alignment uniformity of the inorganic particles may decrease, and the melt dispersion behavior between the two polymers may be difficult to occur, so the designed morphology may not be realized.

[0066]

[0067] Meanwhile, in the description of the melt viscosity described above, the predetermined temperature refers to any temperature between the temperature at which the first polymer and the second polymer begin to melt and the temperature at which they are completely melted. Specifically, it is a specific temperature within the temperature range between the spinodal and binodal of the first polymer and the second polymer exhibiting UCST behavior during melt blending, and as a specific example, it may be the melt processing temperature.

[0068]

[0069] Additionally, the first polymer and the second polymer forming the polymer matrix (10) and the polymer dispersion (21) of the anisotropic diffusion layer (100) may be contained in a weight ratio of 6 to 9.8: 4 to 0.2, as in other examples, a weight ratio of 8.0 to 9.8: 2 to 0.2, a weight ratio of 8.5 to 9.8: 1.5 to 0.2, or a weight ratio of 9.0 to 9.8: 1.0 to 0.2. If the second polymer is included in an amount less than 0.02 times the total weight of the first and second polymers, the number of polymer dispersions and cross-sectional diameters within the anisotropic diffusion layer are excessively reduced. Consequently, it may be difficult to exhibit sufficient anisotropic diffusion together with the non-polymer dispersions, and it may be difficult to act as a guide to align the long axis direction of the inorganic particles and as a buffer layer to suppress the occurrence of lateral voids in the inorganic particles. This may lead to a decrease in the alignment of the inorganic particles and an increase in the occurrence of lateral voids in the inorganic particles, which may result in a further decrease in anisotropic diffusion and brightness. Additionally, if the second polymer is included in an amount exceeding 0.4 times the total weight of the first and second polymers, the number of polymer dispersions and cross-sectional diameters may increase, which may make it difficult to achieve sufficient frontal brightness. Furthermore, the randomness of the alignment direction of the inorganic particles dispersed within the polymer dispersions increases, making it difficult to sufficiently improve the alignment of the inorganic particles despite guidance through the polymer dispersions.

[0070]

[0071] Meanwhile, although the above-described polymer matrix (10) and polymer dispersion (21) are described as being formed from a first polymer and a second polymer, it should be noted that the polymer matrix (10) and polymer dispersion (21) may additionally include, in addition to the first polymer and the second polymer, known additives such as heat stabilizers, antioxidants, and defoaming agents provided in conventional films or films for optical applications, as needed.

[0072]

[0073] Next, a nonpolymer dispersion (22) containing inorganic particles will be described.

[0074] The above-described nonpolymer dispersion (22) performs the function of exhibiting anisotropic diffusivity together with the above-described polymer dispersion (21). To this end, the above-described nonpolymer dispersion (22) includes inorganic particles, and the inorganic particles may have an average aspect ratio of 3.0 or higher, as another example, 3.5 or higher, 4.0 or higher, or 8.0 or higher, thereby enabling excellent anisotropic diffusivity. If the average aspect ratio of the inorganic particles is less than 3.0, it may be difficult to exhibit anisotropic diffusivity. However, as another example, the inorganic particles may have an average aspect ratio of 15.0 or lower, or 13.0 or lower. In order for the average aspect ratio of inorganic particles to exceed 15.0, inorganic particles with an aspect ratio much larger than 15.0 must be introduced to account for the possibility of inorganic particles breaking during the mixing process prior to melt extrusion. However, as the aspect ratio of the introduced inorganic particles increases, the degree of breaking during the mixing and melt extrusion processes becomes very irregular, making it difficult to exceed the average aspect ratio of 15.0. Furthermore, due to the irregular breaking, the number of inorganic particles with an aspect ratio of less than 3.0 may increase significantly, raising concerns that anisotropic diffusion may be greatly reduced. Here, the average aspect ratio (e / f) of the inorganic particles is the ratio of the average length in the major axis direction (e) to the average diameter (f) of the plane perpendicular to the major axis direction, and the diameter refers to the longest length among the line segments crossing the cross-section perpendicular to the major axis direction.

[0075]

[0076] In addition, the above-described inorganic particles may have the aspect ratio described above, while having an average length of 3 to 15 μm, which may be advantageous for exhibiting the desired anisotropic diffusivity.

[0077] In addition, the inorganic particles provided in the non-polymer dispersion (22) may include inorganic particles with a length of 2.5 μm or less in an amount of 23% or less, preferably 20% or less, and more preferably 17% or less of the total inorganic particles. Even when the inorganic particles satisfy an average aspect ratio of 3.0 or more and an average length of 3 to 15 μm, if inorganic particles with a length of 2.5 μm or less are included in an amount of 23% or less of the total inorganic particles, it may be advantageous to achieve high anisotropic diffusivity and brightness simultaneously. If inorganic particles with a length of 2.5 μm or less are included in an amount exceeding 23% of the total inorganic particles, anisotropic diffusivity may be reduced, and turbidity may increase, leading to a significant decrease in frontal brightness.

[0078]

[0079] Meanwhile, in order to control the proportion of particles having an insufficient length in the inorganic particle length distribution, the inorganic particles fed into the manufacturing process may undergo a screening process by filtering them before feeding to remove those that are shorter than (or less than) and / or longer than (or exceed) a specific length. Alternatively, during the melt extrusion process, a filtration unit within the equipment may be configured to remove inorganic particles shorter than a certain length, thereby controlling the extruded anisotropic diffusion layer so that inorganic particles shorter than a certain length are not included. Meanwhile, it should be noted that the method of controlling the exclusion of inorganic particles shorter than a certain length is not limited to this, and known means may be appropriately adopted or modified.

[0080]

[0081] In addition, the inorganic particles may have an average length of 3 to 15 μm and an average diameter of 0.5 to 2.0 μm, more preferably 0.5 to 1.5 μm, thereby enabling enhanced anisotropic diffusivity. If the average length and average diameter of the inorganic particles fall outside the aforementioned ranges, the improvement in anisotropic diffusivity may be minimal, and as the probability of the inorganic particles being recognized as foreign matter and filtered out increases during the melt extrusion process, there is a concern that the content of inorganic particles in the final product may be reduced compared to the input inorganic particles. Furthermore, if the average diameter of the inorganic particles exceeds 2.0 μm, they may be visible as foreign matter on the surface, and consequently, there is a concern that the visibility of the displayed image may be significantly reduced.

[0082]

[0083] In addition, the non-polymer dispersion (22) can be used without limitation in the case of known inorganic particles employed in the optical film. For example, the inorganic particles may contain one or more selected from the group consisting of titanium oxide, zinc oxide, magnesium oxide, strontium carbonate, calcium carbonate, magnesium carbonate, cobalt carbonate, manganese carbonate, calcium silicate, calcium sulfate, aluminum hydroxide, imagolite, silicon carbide, and silicon oxide, and may be calcium carbonate.

[0084]

[0085] Additionally, as the non-polymer dispersion (22), inorganic particles may be contained in an amount of 0.5 to 10 weight% based on the total weight of the anisotropic diffusion layer (100), or, as another example, 0.5 to 5 weight%, 0.5 to 3 weight%, or 0.5 to 1.5 weight%, thereby maximizing anisotropic diffusion while minimizing the loss of frontal light transmittance. If the inorganic particles are contained in an amount less than 0.5 weight% based on the total weight of the anisotropic diffusion layer, it may be difficult to achieve sufficient anisotropic diffusion, and if they are contained in an amount exceeding 10 weight%, the turbidity increases, which lowers the frontal light transmittance, and thus there is a concern that the brightness of the final product may be lowered. Meanwhile, depending on the shape of the inorganic particles, if both ends in the long axis direction are pointed like needles, a void may be formed extending from both ends of the inorganic particles outward in the long axis direction due to stress at the ends during extrusion and / or stretching. In this case, the non-polymer dispersion can form a single dispersion in the order of a void, an inorganic particle, and a void at the other end along the long axis direction. Since the void at the first end and the void at the other end are located at the ends of the inorganic particle along the long axis direction, this results in a greater aspect ratio of the non-polymer dispersion (22), thereby achieving greater anisotropic diffusion. However, voids formed to extend outward from the ends of the inorganic particle along the long axis direction increase anisotropic diffusion but, conversely, may reduce frontal brightness. Accordingly, when voids formed to extend outward from the ends of the inorganic particle along the long axis direction are provided, the inorganic particle may be included in an amount of 5% or less by weight, or, as another example, 3% or less by weight, or 1.5% or less based on the total weight of the anisotropic diffusion layer (100). By reducing the total volume of voids contained within the anisotropic diffusion layer (100), the reduction in brightness can be minimized.

[0086]

[0087] Additionally, referring to FIG. 4, according to one embodiment of the present invention, when non-polymer dispersions (22) dispersed within a matrix (10) are projected in the z-axis direction of the matrix, the number of non-polymer dispersions (22) in which the angle (θ) between the x-axis direction and the major axis direction (ℓ1, ℓ2) of the non-polymer dispersions (22) is within ±5° on a projection plane (S), which is a plane formed by the x-axis and y-axis, may be 75% or more of the total number of non-polymer dispersions (22), and more preferably 80% or more, which may be advantageous for achieving the desired anisotropic diffusion. If the number of non-polymer dispersions (22) in which the angle (θ) formed by the x-axis direction and the major axis direction (ℓ1, ℓ2) of the non-polymer dispersion (22) on the projection plane (S) is within ±5° is less than 75% of the total number of non-polymer dispersions (22), it may be insufficient to achieve sufficient anisotropic diffusion.

[0088]

[0089] Additionally, according to one embodiment of the present invention, the surface of the inorganic particle may be modified to suppress and prevent the occurrence of voids at the interface between the non-polymer dispersion (21) and / or the polymer matrix (10). The modification of the inorganic particle may be performed without limitation using a known compound that improves compatibility with the first polymer and / or the second polymer, and preferably, it may be modified with a compound represented by the following chemical formula 1 or a silane-based compound. Specifically, the inorganic particle has poor compatibility with the first polymer forming the polymer matrix (10) and / or the second polymer forming the polymer dispersion (21) due to being of a different material, and there is a risk that voids may exist at the interface between the polymer matrix (10) and / or the polymer dispersion (21) and the inorganic particle during the process of stretching the extruded A-sheet film. In addition, if the inorganic particles have hygroscopic properties, they can generate alkali hydroxides with a pH of 9 or higher through hygroscopic absorption. The generated alkali hydroxides promote high-temperature hydrolysis of the first or second polymer, causing gas, and in this process, there is a risk of voids forming at the interface between the side of the inorganic particles and the polymer dispersion (21) or the polymer matrix (10).

[0090] However, when the surface of an inorganic particle is modified with a specific compound, for example, a compound represented by Chemical Formula 1 below or a silane-based compound, it may be advantageous to increase compatibility at the interface between the first polymer and / or the second polymer and the inorganic particle. In particular, in the case of the compound represented by Chemical Formula 1, it reacts with moisture absorbed before the inorganic particle, thereby reducing the moisture absorption of the inorganic particle. This can prevent high-temperature hydrolysis of the first or second polymer caused by the products resulting from the moisture absorption of the inorganic particle, as well as the release of gas and the formation of voids on the side of the inorganic particle. Furthermore, the compound represented by Chemical Formula 1 reacts with the absorbed moisture to produce phosphoric acid and alcohols (R1OH, R2OH, and / or R3OH). Since the generated phosphoric acid is weakly acidic, it can lower the high pH of the alkali hydroxide produced by the reaction due to the moisture absorption of the inorganic particle, which may be even more advantageous for preventing high-temperature hydrolysis of the first or second polymer. Furthermore, the generated alcohols (R1OH, R2OH, and / or R3OH) do not induce yellowing in the optical film and do not react with inorganic particles, thereby preventing the formation of additional lateral voids on the inorganic particles due to the generated product. In other words, if a compound used for surface modification (e.g., a fatty acid) reacts with moisture to generate moisture again, the generated moisture is absorbed by the inorganic particles; consequently, considering the shape of the inorganic particles, there is a risk of generating lateral voids through the mechanism described above. Additionally, the generated moisture can cause yellowing, which may degrade the appearance quality and the color reproduction of the display.

[0091] [Chemical Formula 1]

[0092]

[0093] In Chemical Formula 1, R1, R2, and R3 may each independently be hydrogen, a straight-chain or branched-chain alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, and more preferably, R1, R2, and R3 may each independently be a straight-chain or branched-chain alkyl group having 1 to 5 carbon atoms or an aryl group having 6 to 10 carbon atoms. If the number of carbon atoms exceeds 10, the surface of the inorganic particle may not be easily modified with the material represented by Chemical Formula 1.

[0094]

[0095] In addition, the above-mentioned silane compounds may be used without limitation in the case of compounds that enhance compatibility between inorganic particles and polymer compounds; however, as examples thereof, vinyltrichlorosilane, trimethoxyvinylsilane, triethoxyvinylsilane, vinyltris(methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-(2-aminoethyl-3-aminopropyl)trimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-(methacryloxypropyl)methyldimethoxysilane, 3-(methacryloxypropyl)trimethoxysilane, 3-(methacryloxypropyl)methyldiethoxysilane, 3-(methacryloxypropyl)triethoxysilane, N-β-(amino It may include one or more selected from the group consisting of ethyl)-γ-aminopropylmethyldimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, (3-chloropropyl)trimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT), and bis[(triethoxysilyl)propyl]disulfide, and more preferably, it may be an epoxy-silane, which is a silane compound containing an epoxy group, or a vinyl-silane, which is a silane compound containing a vinyl group, and even more preferably, it may be an epoxy-silane.

[0096]

[0097] In addition, the above-described anisotropic diffusion layer (100) may have a thickness of 150 μm or less, preferably 100 μm or less, more preferably 80 μm or less, and even more preferably 60 μm or less. If the thickness of the matrix exceeds 150 μm, it may be difficult to sufficiently express brightness and anisotropic diffusion properties, and if it is less than 60 μm, there is a concern that the frontal transmittance may be significantly reduced due to increased turbidity caused by an increase in the content of a non-polymer dispersion composed of inorganic particles.

[0098]

[0099] Additionally, the optical film (200) may further include a skin layer (110) disposed on at least one surface of the anisotropic diffusion layer (100). The skin layer (110) serves to supplement mechanical strength and protect the anisotropic diffusion layer (100) from external factors. Furthermore, preferably, the skin layer (110) may be formed integrally by co-extruding together with the anisotropic diffusion layer without a separate adhesive layer. As a result, not only can the degradation of optical properties caused by the adhesive layer be prevented, but it is also advantageous for realizing a thinner optical film.

[0100] In addition, the skin layer (110) included in one embodiment of the present invention may be stretched in at least one axial direction after a stretching process is performed following co-extrusion with the anisotropic diffusion layer (100). Through this, the surface hardness is improved compared to the unstretched skin layer, thereby improving scratch resistance and heat resistance.

[0101] The skin layer (110) may be a material of a skin layer commonly used to perform a supporting function of an optical film (200), and preferably, any one of polyethylene naphthalate (PEN), copolyethylene naphthalate (co-PEN), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC), polycarbonate (PC) alloy, polystyrene (PS), polymethyl methacrylate (PMMA), polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polyurethane (PU), polyimide (PI), polyvinyl chloride (PVC), styrene-acrylonitrile blend (SAN), ethylene vinyl acetate (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP), urea (UF), melanin (MF), unsaturated polyester (UP), and cycloolefin polymer, either alone or in combination of two or more It can be used in combination, and more preferably, a material identical to the components of the matrix (10) described above can be used.

[0102] In addition, the thickness of the skin layer (110) may be 5 to 30 μm, more preferably 10 to 15 μm, and through this, there is an advantage of minimizing the reduction in brightness through the skin layer (110) and minimizing the change in the wavelength of polarized light caused by a phase difference due to birefringence.

[0103]

[0104] Additionally, the optical film (200) is placed on the upper part of the LCD panel, and when mounting an upper polarizer equipped with a conventional upper TAC film, the front brightness (N) is set as the blank value. When the upper TAC film of the upper polarizer is changed to an optical film (200) of the same thickness and mounted, it can be implemented to have high anisotropic diffusion properties without significantly reducing the ratio of front brightness (M). In other words, since the anisotropic diffusion properties imparted to the optical film inevitably cause a reduction in front brightness to varying degrees, it is important to exhibit anisotropic diffusion properties while ensuring that the front brightness exhibited when mounted on a commercial TV is at a level sufficient for the product to function adequately. Even if the anisotropic diffusion properties are excellent, it is difficult to commercialize the product if it causes a significant reduction in front brightness. Accordingly, an optical film (200) according to one embodiment of the present invention satisfies a frontal luminance ratio of 80% or more according to the following mathematical formula 1, as in other examples, 81% or more, 82% or more, 83% or more, 85% or more, 86% or more, or 87% or more, while simultaneously having an anisotropic diffusivity of 20% or more according to the following mathematical formula 2, as in other examples, 22% or more, 24% or more, 25% or more, or 26% or more, or as in other examples, 30% or less. If the frontal luminance ratio relative to Blank is less than 80%, the luminance decrease is significant, so even if the anisotropic diffusivity is high, the value as a product that can be mounted on a light source such as a TV may decrease. Furthermore, even if a desirable frontal luminance ratio relative to Blank is achieved, if the anisotropic diffusivity is less than 20%, it may not be desirable in terms of achieving the purpose of the present invention, such as improving the viewing angle when adopted in a display. Meanwhile, it should be noted that although an anisotropic diffusion of more than 30% may be numerically judged to have an excellent viewing angle, an optical film implemented with an anisotropic diffusion of more than 30% is not desirable because it may fail to meet optical physical properties as a product that can be mounted on a light source, such as having high haze and / or low brightness.

[0105] [Mathematical Formula 1]

[0106]

[0107] In mathematical formula 1, N is the frontal luminance (nit) measured after mounting an upper polarizer, which has a conventional TAC film on its upper surface, onto a predetermined panel, and M is the frontal luminance (nit) measured by the same method after mounting an upper polarizer, which has the same configuration as the upper polarizer but has the same thickness as the upper TAC film, onto the same panel, having an optical film to be measured instead of the upper TAC film.

[0108]

[0109] [Mathematical Formula 2]

[0110]

[0111] Meanwhile, the normal and lateral luminance for the main surface measured in mathematical formulas 1 and 2 may be measured by luminance measurement methods known in the art, and the present invention does not specifically limit the specific method when the normal and lateral directions are measured by the same measurement method.

[0112]

[0113] The optical film (200) described above, in particular an anisotropic diffusion layer, can be manufactured through melt extrusion among various methods for manufacturing films. Specifically, it can be manufactured by (1) a step of manufacturing an unoriented film by extruding and solidifying a first polymer to form a polymer matrix (10), a second polymer to form a polymer dispersion (21) among the dispersions (20), and inorganic particles to form a non-polymer dispersion (22) through an extrusion unit, and (2) a step of stretching the unoriented film.

[0114]

[0115] First, as step (1), a step of manufacturing an unoriented film by extruding and solidifying through an extrusion unit is performed.

[0116] (1) The step may be performed using a conventional apparatus and method for manufacturing an unoriented film, specifically 1-1) a step of supplying a first polymer to form a polymer matrix (10), a second polymer to form a polymer dispersion (21) among the dispersions (20), and inorganic particles to form a non-polymer dispersion (22) to an extrusion section. At this time, each of the supplied components may be supplied to a single extrusion section after being mixed, or each component may be supplied individually to independent extrusion sections.

[0117] In addition, the inorganic particles forming the nonpolymer dispersion (22) may be used with their lengths controlled to a predetermined length range prior to mixing so that they can have an appropriate length distribution within the final anisotropic diffusion layer. This prevents an increase in the number of inorganic particles with lengths that are too small, such as 2.5 μm or less, due to breakage during the melt extrusion process, and is advantageous for designing to have a desired length range.

[0118] Preferably, in order to increase the orientation in which the long axis direction of the inorganic particles within the anisotropic diffusion layer (100) is aligned with the x-axis direction within the polymer matrix (10), the inorganic particles may be in a composite chip state mixed with the second polymer before being fed into the extrusion section, and by feeding them into the extrusion section in the composite chip state, the orientation guide of the inorganic particles through the second polymer can be induced. In addition, when supplying the first polymer chip and the composite chip to a single extrusion section, a sufficient stirring process may be performed before supplying them to the extrusion section to induce uniform dispersion, and through this, it may be advantageous to uniformly disperse the dispersed bodies (20) within the anisotropic diffusion layer (100) and to uniformly implement the size in the z-axis direction within the cross-section of the polymer dispersed body (21) in the yz-cross plane of the polymer matrix (10).

[0119] Meanwhile, regarding the dispersion and orientation guide of inorganic particles through the second polymer in the composite chip state, the inorganic particles in the composite chip can be trapped in the second polymer by blocking them from moving toward the first polymer by moving away from the interface between the second polymer and the first polymer due to the difference in melt viscosity between the second polymer and the first polymer in the molten state. Through this, the dispersibility of the inorganic particles within the polymer matrix (10) can be increased, thereby preventing secondary aggregation among the inorganic particles. Additionally, the second polymer within the molten first polymer is separated to form a plurality of polymer dispersions (21), and at least one inorganic particle is disposed in at least some of these polymer dispersions. Each polymer dispersion (21) is extended in the x-axis direction which is the MD direction within the first polymer in a molten state after extrusion. During the process of the polymer dispersion (21) being extended, the inorganic particle trapped within the polymer dispersion (21) is oriented along the polymer dispersion (21) which is extended in length and has a reduced diameter. Therefore, the inorganic particle can be oriented and aligned in the x-axis direction which is the MD direction, in the same direction as the orientation and alignment of the polymer dispersion (21). The polymer dispersion (21) (or the second polymer) acts as a guide for the inorganic particle, and the alignment and alignment uniformity of the inorganic particle can be increased despite the fact that the anisotropic diffusion layer (100) is realized by melt extrusion.

[0120]

[0121] However, even if the second polymer and the inorganic particles are mixed in a composite chip state and fed into the extrusion section together with the first polymer, the long axis direction of the inorganic particles cannot always be easily aligned in the x-axis direction. That is, as described above, when the melt viscosity of either the second polymer or the first polymer is greater than the melt viscosity of the other polymer, for example, 1.3 times or more, or 1.5 times or more, the inorganic particles in the molten second polymer can have excellent dispersibility within the first polymer and the long axis direction can be easily aligned in the x-axis direction, which is the MD direction in which the second polymer is extruded, and through the stretching process described later, the long axis direction of the inorganic particles can be aligned so that it is closer to the direction in which the polymer dispersion (21), which is the second polymer, is oriented, and the alignment direction of each inorganic particle can be aligned more uniformly. Even if the inorganic particles are introduced in the form of a composite chip mixed with a first polymer forming a polymer matrix rather than a second polymer, or are introduced alone into the extrusion section together with the first polymer and the second polymer without forming a composite chip with the second polymer, and the melt viscosity conditions between the first polymer and the second polymer or the melt viscosity conditions of the preferred polymers are satisfied, and / or the stretching process described below is performed, it may be difficult to achieve dispersibility, orientation, and orientation uniformity of the inorganic particles.

[0122]

[0123] Meanwhile, as described above, the inorganic particles trapped within the polymer dispersion dispersed inside the first polymer that is melted after extrusion are aligned so that the long axis direction becomes the x-axis direction as the polymer dispersion (21) is extended in the MD direction, which is the x-axis direction. Subsequently, in the stretching process described later, as the length of the polymer dispersion (21) becomes longer and the diameter becomes relatively smaller, the diameter of the polymer dispersion (21) in the part where the inorganic particles are not located may become smaller than the diameter of the inorganic particles. Meanwhile, the fact that inorganic particles are located inside the polymer dispersion (21), or that there is a difference in diameter between the part containing inorganic particles and the part not containing inorganic particles in a single continuous polymer dispersion (21), may be a technical feature that indirectly proves that it is a melt-extruded film.

[0124] In addition, the second polymer, as a buffer layer (23) coated on the surface of the inorganic particle, can function as a buffer to buffer void formation that may occur at the interface between the first polymer forming the polymer matrix and the inorganic particle, and thus can be useful for reducing voids formed toward the long axis reference side of the inorganic particle within the implemented anisotropic diffusion layer (100). Furthermore, the skin layer (110) and the anisotropic diffusion layer (100) can be formed integrally without including an adhesive or adhesive layer between them, and this technical feature may also be a feature that indirectly proves that it is a melt-extruded film.

[0125]

[0126] In addition, the extrusion unit described above may be a known extruder, and may further include a heating means to convert the supplied polymer components in a solid state into a liquid state. In addition, the size control of the polymer dispersion (21) described above and the uniform dispersion of the polymer dispersion (21) and inorganic particles can be achieved primarily through process control of step (1). Specifically, the size of the polymer dispersion or the dispersion of the polymer dispersion and the non-polymer dispersion can be controlled by changing whether sufficient stirring is performed before feeding the composite chip and the first polymer chip into the extrusion unit, the discharge amount during extrusion, the rotational speed of the extruder involved in shear stress, and the type of extruder (single, coaxial twin, etc.).

[0127]

[0128] In addition, a skin layer forming component may be introduced into the extrusion unit so that a skin layer (110) disposed on at least one surface of the anisotropic diffusion layer (100) in step (1) is extruded together. For example, the skin layer may be extruded to the upper and / or lower portions of the anisotropic diffusion layer (100) through separate extrusion units to form the skin layer (110), or if a single extrusion unit is used, the melt forming the anisotropic diffusion layer (100) may be flowed to the central region through different flow paths arranged in the thickness direction, and the melt forming the skin layer may be flowed to the upper and lower regions respectively, and then discharged through a T-DIE, thereby forming a three-layer optical film in a single extrusion unit. Whether a single extrusion unit or multiple extrusion units are used, the skin layer that is co-extruded together with the anisotropic diffusion layer has the advantage of being able to form the skin layer within the process of forming the anisotropic diffusion layer without a separate adhesive. Meanwhile, for example, it may be desirable to use a material for the skin layer that is identical to or highly compatible with the first polymer used as the polymer matrix. Additionally, it is desirable to design the thickness of the skin layer to an appropriate thickness to prevent a reduction in brightness due to total internal reflection.

[0129]

[0130] Next, as step 1-2), a step of inducing spreading in a flow control unit is performed so that the dispersed particles (20) contained within the polymer matrix (10) can be arranged randomly. The flow control unit may use a known flow control unit, and as an example, a coat-hanger die may be used. By inducing spreading through the flow control unit in step (2), it is possible to secondarily further control the size of the polymer dispersed particles (21) or the dispersibility of the polymer dispersed particles (21) and the non-polymer dispersed particles (22).

[0131]

[0132] Next, as step 1-3) of the present invention, a cooling and smoothing step can be performed. As a step of cooling and smoothing the film conveyed from the flow control unit, the film can be cooled and solidified under conditions used in the manufacture of conventional optical films, and then a smoothing step can be adopted and modified. For example, the cooling and smoothing process can be performed in a casting roll. Preferably, one side of the sheet conveyed through the flow control unit is cooled by contacting it with the main cooling roll, and at this time, the temperature of the main cooling roll can be cooled at 40°C or lower, more preferably at 35°C or lower, or as another example, at 20°C or lower. If the temperature of the main cooling roll exceeds 40°C, there is a risk that haze will increase significantly due to the formation of spheroids caused by the crystallization of the first polymer of the polymer matrix or the second polymer of the polymer dispersion, and size differences are likely to be induced between polymer dispersions (21) placed in different regions in the thickness direction of the anisotropic diffusion layer (100). This can occur through bonding between polymer dispersions (21) dispersed in a molten state, which may cause the size of the solidified polymer dispersion to increase, or the polymer dispersion in the bonded mass may spread out in the left-right direction, that is, in the y-axis direction of the polymer matrix, thereby making the thickness thinner. In addition, the proportion of the polymer matrix modified into a third substance by chemical reaction at the interface between the polymer dispersion (21) and the polymer matrix (10) may increase, thereby significantly increasing the area percentage of the polymer dispersion. Furthermore, more preferably, the opposite side that does not come into contact with the cooling roll is cooled together through an auxiliary cooling means, and the auxiliary cooling means may be, for example, cooling air, and more preferably, the temperature of the cooling air may be 30°C or lower, and more preferably 20°C or lower.

[0133]

[0134] Next, as step (2) of the present invention, a step of stretching the cooled and smoothed unoriented film may be performed. The stretching may be performed by employing and modifying the apparatus and process conditions used for optical films, but preferably, in order to more uniformly align the long axis direction of the inorganic particles in the x-axis direction within the polymer matrix (10) and to secure the shape stability, mechanical properties, and thickness uniformity of the film, the unoriented film may be stretched 2 to 6 times in the x-axis direction which is the MD direction and stretched 2 to 6 times in the y-axis direction which is the TD direction, and more preferably, it may be stretched 2.5 to 4.5 times in the MD direction and 2.5 to 4.5 times in the TD direction. If the above conditions are not satisfied even when uniaxial stretching is performed only in the x-axis direction or biaxial stretching is performed, it may be difficult to secure the shape stability, etc., that is basically required for the film, the alignment and alignment uniformity of the inorganic particles may be reduced, and there is a risk of causing voids on the side relative to the long axis direction of the inorganic particles. In addition, the stretching temperature may be performed at a temperature 10 to 20°C higher than the larger of the glass transition temperatures of the first polymer and the second polymer, respectively. If the stretching is performed at a temperature less than 10°C higher than the larger of the glass transition temperatures of the first polymer and the second polymer, stretching may not occur or may cause fracture. Furthermore, if stretching is performed at a temperature exceeding 20°C higher than the larger of the glass transition temperatures of the first polymer and the second polymer, or if the residence time is excessively long even at an appropriate temperature, the uniformity of stretching may be reduced, and there is a risk that the alignment uniformity of the non-polymer dispersion may also be reduced.

[0135]

[0136] In addition, a step of heat-setting the stretched optical film can be performed. The heat-setting can be performed using a conventional method, and preferably, it can be performed using an IR heater at 180 to 200°C for 0.1 to 3 minutes.

[0137]

[0138] Referring to FIGS. 5 and 6, an optical film (200) according to one embodiment of the present invention, manufactured through the above-described manufacturing method, can be implemented as a polarizing plate (4000). Specifically, the polarizing plate (4000) is suitable as an upper polarizing plate placed on the light-emitting surface of a liquid crystal panel (5000). Specifically, the polarizing plate (4000) includes an absorption polarizing film (2000) and an optical film (200) placed on the light-emitting surface of the absorption polarizing film (2000). When placed on the light-emitting surface of the absorption polarizer (2100) of the upper polarizing plate, there is an advantage that the contrast ratio improvement effect due to internal light is significant, the viewing angle is increased, and excellent brightness characteristics can be achieved.

[0139] The above absorption polarizing film (2000) is a polarizer having an optical function such as transmitting the first polarization (or the second polarization) and absorbing the second polarization (or the first polarization) among the first polarization and the second polarization having mutually orthogonal planes of vibration, and is equipped with a known absorption polarizer (2100) having such optical function. As an example, the absorption polarizer (2100) may be a substrate film such as polyvinyl alcohol that is dyed with an iodine-based component or a dichroic dye. In addition, the iodine-based component, which is one of the dyes dyed on the substrate, may be an iodine-based compound such as iodine and / or potassium iodide. In addition, the above-mentioned dichroic dye can be used without limitation in the case of known dichroic dyes that have high absorbance over a wide range of wavelengths in the direction of the long axis of the molecule and extremely low absorbance in the direction of the short axis, have good affinity for the film that serves as the substrate, can dye even in crystalline regions, are easy to align together when the substrate is stretched, have vivid colors, and have high visual contrast. Therefore, the present invention is not specifically limited to such dyes and a detailed description is omitted.

[0140] In addition, the thickness of the absorption polarizer (2100) may be, for example, 10 to 200 μm, but is not limited thereto and can be changed according to the purpose.

[0141] Additionally, the absorption polarizing film (2000) may be provided with a protective film (2210) on one or both sides to support and protect the absorption polarizer (2100). The protective film (2210) may be used without limitation as a protective film used in conventional absorption polarizing films, and a polymer with excellent transparency, mechanical strength, thermal stability, or moisture barrier properties may be preferably employed. As an example, the protective film (2210) may use an acetate resin such as triacetylcellulose (TAC), a polyester resin, a polyethersulfone resin, a polycarbonate resin, a polyamide resin, a polyimide resin, a polyolefin resin, an acrylic resin, a polynorbornene resin, etc. As an example, the protective film may use a triacetylcellulose (TAC) film considering optical properties. Alternatively, in terms of heat resistance and moisture resistance, it may be a polyester-based film, specifically as an example, a polyethylene terephthalate film. The polyethylene terephthalate film may have a phase difference within the plane of 8,000 nm or more, or 10,000 to 15,000 nm. In addition, the protective film (2210) may have a thickness of 50 to 150 μm, but is not limited thereto. Also, referring to FIG. 6, a protective film such as a TAC film that is typically placed on top of the absorption polarizer (2100) is not provided, and the optical film (200) according to one embodiment of the present invention has the advantage of being able to omit and replace the upper TAC film placed on top of the absorption polarizer (2100).

[0142]

[0143] In addition, the above-described absorption polarizing film (2000) and the optical film (200) may be integrally bonded by interposing a separate adhesive layer (not shown) at the interface between them. The adhesive layer is used for bonding between optical films and can be implemented using a known adhesive component that does not degrade optical properties. For example, it may be formed as an adhesive in which the adhesive component is used alone, or in combination with at least one water-soluble crosslinking agent of the vinyl alcohol-based polymer, such as boric acid, borax, glutaraldehyde, melamine, or oxalic acid. Additionally, the adhesive may be combined with other additives or catalysts such as acids.

[0144]

[0145] Additionally, the polarizing plate (4000) may further include a functional layer (1500) on the optical film (200). The functional layer (1500) may be a primer layer, a hard coating layer, an anti-fingerprint layer, an anti-reflection layer, an anti-glare layer, a low-reflection layer, an ultra-low-reflection layer, etc. Additionally, the functional layer (1500) may be implemented by stacking multiple layers to exhibit a composite function. Since the thickness of the functional layer (1500) can be appropriately changed considering the type of functional layer provided and the number of layers, the present invention is not specifically limited thereto.

[0146]

[0147] In addition, as illustrated in FIG. 6, a polarizing plate (4000) according to one embodiment of the present invention can be implemented as a liquid crystal display device (8000) that is positioned on the light-emitting surface of the polarizing plate (4000) positioned above the liquid crystal panel (5000), that is, adjacent to the viewing side of the liquid crystal display device (8000), opposite to a backlight unit (7000) positioned below the liquid crystal panel (5000).

[0148] Specifically, the liquid crystal display device (8000) can be implemented by arranging in the order of a backlight unit (7000), an absorption polarizing film (2000) as a lower polarizing plate, a liquid crystal panel (5000), a color conversion layer (5300), and a polarizing plate (4000) according to one embodiment of the present invention as an upper polarizing plate.

[0149] The above backlight unit (7000) may be used in a conventional LCD display and may be composed of known components such as a light source, a reflective film, a light guide plate, a light diffusion film, a light collecting film, and a reflective polarizing film.

[0150] Additionally, the liquid crystal panel (5000) includes a liquid crystal layer (5100) and a support plate (5210, 5220) that supports the upper and lower portions of the liquid crystal layer (5100), and may further include known configurations such as electrode lines. Additionally, the liquid crystal panel (5000) may adopt a VA (vertical alignment) mode, an IPS mode, a PVA (patterned vertical alignment) mode, or an S-PVA (super-patterned vertical alignment) mode, but is not limited thereto.

[0151]

[0152] In addition, an optical film (200) according to one embodiment of the present invention may be disposed on the light-emitting surface of a self-emissive display panel to implement a self-emissive display device. The self-emissive display panel may be a panel employed in known self-emissive displays, such as a plasma display panel (PDP) or an OLED panel, and the present invention is not particularly limited thereto.

[0153]

[0154] Meanwhile, although the applications of the optical film in this invention have been described using liquid crystal display devices or self-emissive display devices as examples, they are not limited thereto and can be widely used in various known display technologies such as projection displays and field emission displays. Furthermore, in addition to display technologies, it can be widely applied to various light sources such as glass windows and work lighting requiring polarization.

[0155] The present invention will be explained more specifically through the following examples, but the following examples are not intended to limit the scope of the invention and should be interpreted as being for the purpose of aiding understanding of the invention.

[0156]

[0157] <Example 1>

[0158] Polyethylene terephthalate (PET) was prepared as a first polymer to form a polymer matrix, and polycyclohexylene dimethylene terephthalate (PCTG) was prepared as a second polymer to form a polymer dispersion by polymerizing terephthalate and a diol component mixed with ethyl glycol and cyclohexanedimethanol in a 1:1 molar ratio in a 1:1 molar ratio. Calcium carbonate powder was prepared by treating calcium carbonate powder, which had an average length of 25 μm and an average diameter of 1.3 μm with a length of 5 μm or less and was filtered in advance, with a solution containing an epoxy-silane compound to form an epoxy-silane compound modified layer on the surface of the calcium carbonate. Inorganic particles were mixed with the prepared second polymer and fed into an extruder to manufacture a composite chip in which inorganic particles were dispersed in the second polymer. Subsequently, the manufactured composite chip and the first polymer were mixed and fed into the first extrusion unit, wherein the weight ratio of the first polymer to the second polymer was 9.5:0.5, and the content of inorganic particles in the total weight of the mixture fed into the first extrusion unit was 2.0 wt%. In addition, to manufacture a skin layer, the first polymer was fed into the second extrusion unit, and the second extrusion unit was manufactured using a flow path so that the skin layer was placed on the upper and lower surfaces of the polymer matrix with the same thickness. Meanwhile, the prepared first polymer was a semicrystalline resin with a glass transition temperature of 78°C, and the second polymer was an amorphous resin with a glass transition temperature of 82°C, and at an extrusion temperature of 260°C in the extrusion unit described later, the melt viscosities were 180 Pa·S and 100 Pa·S, respectively.

[0159] At this time, the extrusion temperature of the first extrusion section was set to 260°C, and the polymer flow was corrected by checking the Cap.Rheometer. The polymer dispersion formed by the second polymer was induced to be dispersed within the polymer matrix formed by the first polymer by passing through a flow path to which a filtration mixer was applied, and subsequently, the first polymer flow forming a skin layer on both sides of the polymer matrix was laminated. Afterwards, spreading was induced in a coat hanger die that corrects the flow velocity and pressure gradient to induce random dispersion of the polymer dispersion. Specifically, the width of the die inlet was 200 mm and the thickness was 10 mm, the width of the die outlet was 1,260 mm and the thickness was 0.75 mm, and the flow velocity was 1.0 m / min. Subsequently, a cooling and smoothing process was performed in a casting roll, and the material was stretched 4.0 times in the MD direction and then stretched 3.0 times in the TD direction. Subsequently, heat setting was performed through a heater chamber at 180°C for 2 minutes to align the major axis directions of the polymer dispersion and inorganic particles, respectively, with the x-axis direction of the polymer matrix as shown in FIGS. 2 and 3. An anisotropic diffusion layer with a thickness of 60 μm was randomly dispersed on the polymer matrix in which the polymer dispersion, with inorganic particles located inside, was positioned at the yz cross-section of the polymer matrix, and skin layers with a thickness of 10 μm were provided on both sides of the anisotropic diffusion layer, thereby producing an optical film as shown in Table 1 below with a total thickness of 80 μm. In this case, the average aspect ratio of the polymer dispersion in the anisotropic diffusion layer produced exceeded 100. Additionally, no voids were formed on the lateral side perpendicular to the major axis direction of the inorganic particles.

[0160]

[0161] <Examples 2 ~ 7>

[0162] An optical film as shown in Table 1 was prepared by carrying out the same procedure as in Example 1, but with the content of inorganic particles and / or the average length, average diameter, and average aspect ratio of the inorganic particles changed as shown in Table 1 below.

[0163]

[0164] <Comparative Example 1>

[0165] An optical film as shown in Table 1 was manufactured by carrying out the same procedure as in Example 1, but with the content of inorganic particles, average length of inorganic particles, average diameter, and average aspect ratio changed as shown in Table 1 below.

[0166]

[0167] <Comparative Example 2>

[0168] An optical film as shown in Table 1 was manufactured by carrying out the same procedure as in Example 1, but without introducing the second polymer-containing composite chip into the first extrusion section, and by introducing the composite chip, in which inorganic particles are combined with the first polymer as shown in Table 1 below, into the first extrusion section alone.

[0169]

[0170] <Experimental Example>

[0171] The following physical properties were evaluated for optical films according to the examples and comparative examples, and the results are shown in Table 1 below.

[0172]

[0173] 1. Evaluation of the alignment of inorganic particles as a non-polymer dispersion

[0174] As shown in Fig. 4, the angle formed by the major axis direction of the nonpolymer dispersion and the x-axis direction of the polymer matrix was measured. Specifically, the skin layer of the optical film was peeled off, and after treating the surface with plasma at 500W for 10 minutes, the specimen was photographed using a scanning electron microscope (SEM). The ratio of the number of nonpolymer dispersions within a range of ±5° relative to the x-axis direction in the photograph was calculated.

[0175]

[0176] 2. Evaluation of inorganic particle size as a non-polymer dispersion

[0177] After selecting five random points on a specimen measuring 5 cm × 5 cm in width and height, the surface of the specimen was observed and images were captured using an OLYMPUS MX50LT-1273MU optical microscope equipped with a polarizing filter (the magnification of the objective lens was adjusted to 10x, 20x, or 50x, and the magnification of the eyepiece lens was 10x). Then, the length and diameter of the inorganic particles were measured using Image-J, an open program available on the internet, for the five images. Using the inorganic particles measured from the five images as a sample, the average length in the major axis direction (e), the average diameter in the minor axis direction (f), and the average aspect ratio (e / f) of the inorganic particles were calculated.

[0178]

[0179] 3. Observation of void formation

[0180] Void analysis of the optical film was performed using an Olympus optical microscope (model name: MX50LT-1273MU) at a magnification of 500x in transmission / reflection mode, using a polarizing filter to adjust the focus on particles with height differences in the film thickness direction, and measuring the length of inorganic particles using a program linked to the microscope. The occurrence of voids was observed, and if voids were present, the location of the voids relative to the long axis of the inorganic particles (end or side in the long axis direction of the inorganic particles) was observed. If voids were formed, they were marked with ○, and if not formed, they were marked with ×.

[0181]

[0182] 4. Observation of Optical Properties

[0183] Optical characteristics were evaluated using an upper polarizer to which the optical films according to the examples and comparative examples were applied, replacing the upper TAC film of the LCD upper polarizer in the Samsung Electronics Q80A LCD TV, a high-end model on the market. At this time, an upper polarizer to which a conventional upper TAC film of the same thickness as the optical film was applied was used as a control group, and the frontal luminance ratio of each of the examples and comparative examples relative to the control group was defined as the frontal luminance ratio relative to the blank.

[0184] Specifically, a hard coating and a low-refractive index coating were applied to one side of the optical film. The prepared optical film was laminated to the upper surface of an absorption polarizer corresponding to the upper polarizer of the LCD, and a polarizer was manufactured with a TAC (triacetate cellulose) film on the lower surface of the absorption polarizer. After applying the manufactured polarizer as the upper polarizer of the LCD panel of a commercially available Samsung Electronics Q80A LCD TV, the brightness was measured in the front (normal direction, 90° to the main surface of the optical film) and side (30° to the main surface of the optical film) directions.

[0185] In addition, the upper polarizer of the LCD panel of the same LCD TV was fitted with an upper polarizer to which a conventional upper TAC was applied, and the frontal luminance (N) was measured in the same way, and the measured luminance was used as the blank value for the frontal luminance.

[0186] In addition, using the measured values, the frontal luminance ratio relative to Blank was calculated via Equation 1 below, and the anisotropic diffusivity was calculated via Equation 2.

[0187] [Mathematical Formula 1]

[0188]

[0189] In mathematical formula 1, M is the frontal luminance (nit) measured by applying an upper polarizer with an optical film according to an example or comparative example, and N is the frontal luminance (nit) measured by applying an upper polarizer that is a control group.

[0190]

[0191] [Mathematical Formula 2]

[0192]

[0193]

[0194] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Comparative Example 1 Comparative Example 2 Polymer Matrix First Polymer (A) Type / Melting Viscosity (Pa·S) PET / 180 PET / 185 PET / 182 PET / 180 PET / 181 PET / 178 PET / 180 PET / 180 PET / 180 Polymer Dispersion Second Polymer (B) Type / Melting Viscosity (Pa·S) PCTG / 100 PCTG / 102 PCTG / 100 PCTG / 102 PCTG / 101 PCTG / 100 PCTG / 100 PCTG / 100 Non-polymer Dispersion Inorganic Particle Content (Weight%) 1.4 1.4 1.4 2.0 0.7 2.0 2.0 2.0 5.0 Inorganic Particles Average Length (e) / Average Diameter (f) / Average Aspect Ratio (e / f) 5.6 / 1.3 / 4.3 6.1 / 1.2 / 5.1 5.5 / 1.2 / 4.6 4.1 / 1.2 / 3.4 7.9 / 1.1 / 7.2 12.5 / 1.2 / 10.4 13.1 / 1.2 / 10.9 10.8 / 1.1 / 9.8 5.5 / 1.3 / 4.2 Proportion of Length 2.5 µm or Less (%) 9.5 7.5 4.9 6.2 9.9 16.3 19.2 32.6 15.3 Presence / Absence of Lateral Voids × × × × × × × ○ Anisotropic Diffusion Layer A:B Weight ratio 9.5:0.5 9.5:0.5 9.5:0.5 9.3:0.7 9.5:0.5 9.3:0.7 9.3:0.7 9.3:0.7 - Crystalline phase (A / B) Semicrystalline / Amorphous semicrystalline / Amorphous semicrystalline / Amorphous semicrystalline / Amorphous semicrystalline / Amorphous semicrystalline / Amorphous semicrystalline / Amorphous semicrystalline / Amorphous semicrystalline / Amorphous - Process composite chip Second polymer / Inorganic particle Second polymer / Inorganic particle Second polymer / Inorganic particle Second polymer / Inorganic particle Second polymer / Inorganic particle Second polymer / Inorganic particle Second polymer / Inorganic particle Second polymer / Inorganic particle First polymer / Inorganic particle Anisotropic diffusion layer Non-polymer dispersion aligned within ±5° in the x-axis direction Quantity Ratio (%) 87 89 87 88 89 88 88 655 Optical Characteristics Front-to-Blank Luminance Ratio (%) 85.7 86.7 87.5 81.7 88.1 84.7 80.1 69.3 58.4 Anisotropic Diffusivity (%) 26.4 26.9 27.4 27.2 25.7 26.3 25.3 35.2 38.5

[0195] As can be seen from Table 1, compared to Comparative Example 2, in which only a non-polymer dispersion is dispersed within a polymer matrix without a polymer dispersion, the examples demonstrate excellent alignment in the x-axis direction of the inorganic particles, which are the non-polymer dispersion, and excellent anisotropic diffusion, while simultaneously achieving a sufficiently high frontal luminance ratio.

[0196] In addition, compared to Comparative Example 1, in which the proportion of inorganic particles with a size of 2.5 μm or less exceeds 23%, it can be confirmed that the embodiments achieve excellent anisotropic diffusion and a sufficiently high frontal luminance ratio.

[0197]

[0198] Although an embodiment of the present invention has been described above, the concept of the present invention is not limited to the embodiments presented in this specification. Those skilled in the art who understand the concept of the present invention may easily propose other embodiments within the scope of the same concept by adding, changing, deleting, or adding components, and such embodiments shall also be considered to fall within the scope of the concept of the present invention.

Claims

1. Polymer matrix; and An optical film comprising a polymer dispersion and a non-polymer dispersion including inorganic particles having an average aspect ratio of 3.0 or higher, wherein a plurality of dispersions are arranged in the x-axis direction among the x-axis, y-axis, and z-axis mutually perpendicular within the polymer matrix, and wherein the inorganic particles have an average length of 3 to 15 μm and inorganic particles having a length of 2.5 μm or less constitute 23% or less of the total inorganic particles.

2. In Paragraph 1, The above-mentioned inorganic particles are optical films located inside a polymer dispersion.

3. In Paragraph 1, The above inorganic particles are an optical film having an average diameter of 0.5 to 2.0 μm.

4. In Paragraph 1, The above-mentioned inorganic particles have an average length of 3 to 15 μm, and the optical film contains inorganic particles with a length of 2.5 μm or less in an amount of 17% or less of the total inorganic particles.

5. In Paragraph 1, An optical film containing the above-mentioned nonpolymer dispersion in an amount of 0.5 to 5 weight percent based on the total weight of the anisotropic diffusion layer.

6. In Paragraph 1, The above-mentioned inorganic particles are an optical film whose surface is modified with one or more compounds selected from a compound represented by the following chemical formula 1 and a silane-based compound containing an epoxy group: [Chemical Formula 1] In Chemical Formula 1, R1, R2, and R3 are each independently hydrogen, or a straight-chain or branched-chain alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms.

7. In Paragraph 1, An optical film comprising the above polymer matrix and polymer dispersion in a weight ratio of 6 to 9.8: 4 to 0.

2.

8. In Paragraph 1, The above anisotropic diffusion layer is an optical film formed through melt extrusion.

9. A polarizing plate disposed on the light-emitting surface of a liquid crystal panel, wherein the polarizing plate Absorbing polarizing film; and A polarizing plate comprising an optical film according to any one of claims 1 to 8 disposed on the light emission surface of the absorption polarizing film.

10. Liquid crystal panel; and A liquid crystal display device comprising: at least a polarizing plate according to claim 9 disposed on the light-emitting surface of the liquid crystal panel.

11. Self-emissive display panel; and A display device comprising at least one optical film according to any one of claims 1 to 8 disposed on the light-emitting surface of the self-emissive display panel.

Images