Optical film and display comprising the same

Abstract

The present invention relates to an optical film, and more specifically, in the case of a display device, it can improve the left and right viewing angles, and can uniformly exhibit the viewing angle improvement effect when manufactured in a large area. Furthermore, while improving the viewing angle, it can increase the contrast without reducing the front brightness characteristics and minimize color variation.

Description

[Technical Field]

[0001] The present invention relates to an optical film and a display device comprising the same. [Previous Technology]

[0002] Liquid crystal display devices operate by emitting light through a liquid crystal panel from light emitted from a backlight unit. Therefore, the brightness and contrast ratio (CR) of the front side of the screen of a liquid crystal display device are excellent, but the brightness and contrast ratio of the sides are usually worse than those of the front side.

[0003] To solve this problem, attempts have been made to improve the contrast or brightness on the sides by changing the LCD panel or LCD structure. However, as the side contrast or brightness is increased, the front contrast or brightness inevitably decreases. Therefore, it is necessary to minimize the front contrast or brightness while improving the side contrast or brightness.

[0004] On the other hand, as a method to improve the viewing angle, there is a method for diffusing light. For this purpose, a method has been proposed, for example, to improve light diffusivity by including inorganic particles. However, the spherical inorganic particles included in the optical film are difficult to ensure a sufficient viewing angle, and even if they can be ensured, it may lead to a reduction in brightness and almost no improvement in contrast.

[0005] As another example, research has found that inorganic particles with an aspect ratio greater than 1 contained in optical films can exhibit anisotropic diffusion characteristics while improving light diffusion compared to spherical inorganic particles. However, it is not easy to align the long axis of each of the multiple inorganic particles contained in the film body in a certain direction. Furthermore, even if each inorganic particle can exhibit anisotropic diffusion characteristics, it is difficult to exhibit anisotropic diffusion characteristics from the perspective of the entire optical film, and ultimately there is a problem of not being able to ensure a sufficient viewing angle. [Summary of the Invention]

[0006] Problem to be solved by the invention The present invention is proposed to solve the above-mentioned problems, and its purpose is to provide an optical film that can improve the left and right viewing angles of a display device, and can uniformly exhibit the viewing angle improvement effect even when manufactured in a large area.

[0007] Furthermore, another object of the present invention is to provide an optical film that improves the viewing angle without reducing frontal brightness characteristics. Means for solving the problem

[0008] To solve the above-mentioned technical problems, the present invention provides an optical film having an anisotropic diffusion layer; the anisotropic diffusion layer includes: a matrix as a first polymer; and a dispersion, each of the dispersions being dispersed with its long axis oriented toward a certain axis direction within the matrix, the dispersion including a plurality of first dispersions as a second polymer and a plurality of second dispersions as inorganic particles. At a specified temperature, the difference in shear rate measured for the first polymer and the second polymer is less than 60 sec⁻¹.

[0009] According to one embodiment of the present invention, the difference in shear rate between the first polymer and the second polymer can be less than 45 sec-1.

[0010] In addition, at a specified temperature, the melt viscosity of the first polymer can be greater than that of the second polymer.

[0011] In addition, the anisotropic diffusion layer is formed by melt extrusion, and at least a portion of the surface of the second dispersion may be coated with the second polymer.

[0012] In addition, the first dispersion can be randomly dispersed within the cut surface of a matrix formed by two axes that are perpendicular to each other.

[0013] Alternatively, the matrix and the first dispersion may be contained in a weight ratio of 6 to 9: 4 to 1.

[0014] In addition, based on the total weight of the anisotropic diffusion layer, the content of the second dispersion can be 2 to 10% by weight.

[0015] In addition, the second dispersion may be rod-shaped with the length direction as the long axis direction, with an average length of 5~15μm and an average diameter of 0.5~2.0μm.

[0016] In addition, the thickness of the anisotropic diffusion layer can be less than 150 μm.

[0017] In addition, when the second dispersion dispersed in the matrix is ​​projected along the z-axis direction of the matrix, the number of the second dispersions whose angle between the x-axis direction and the major axis direction of the second dispersion is within ±5° on the projection plane which is a plane composed of the x-axis and the y-axis can account for more than 75% of the total number of the second dispersions.

[0018] In addition, the anisotropic diffusion rate can be 25% or more according to the following mathematical formula 1. [Mathematical Formula 1] Anisotropic diffusion rate (%) = [Luminance (nit) in the lateral (30°) direction relative to the principal surface] / [Luminance (nit) in the normal (90°) direction relative to the principal surface] × 100

[0019] Furthermore, the present invention provides a polarizing plate disposed on the light emitting surface of a liquid crystal panel, the polarizing plate comprising an absorptive polarizing film and an optical film according to the present invention disposed on the light emitting surface of the absorptive polarizing film.

[0020] Furthermore, the present invention provides a display device comprising a liquid crystal panel and a polarizing plate according to the present invention disposed at least on the light emitting surface of the liquid crystal panel.

[0021] Furthermore, the present invention provides a display device comprising a self-emissive display panel and an optical film according to the present invention disposed at least on the light-emitting surface of the self-emissive display panel. Effects of the Invention

[0022] 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 in a large area. Furthermore, it can improve the viewing angle while increasing contrast and minimizing color variation without reducing the front brightness characteristics. Moreover, by minimizing or preventing the formation of air voids, the reduction in front brightness and viewing angle improvement effect caused by voids can be prevented. At the same time, since it is suitable for large-area mass production, it can be widely used as an optical component in various display devices.

Implementation Method

[0028] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings to enable those skilled in the art to easily implement the invention. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. For clarity, parts irrelevant to the description have been omitted in the drawings, and the same or similar reference numerals are used throughout the specification. Furthermore, the dimensions or shapes of any configuration shown in the drawings should not be construed as limiting the present invention.

[0029] Referring to Figures 1 to 3, an optical film 200 of one embodiment of the present invention may include an anisotropic diffusion layer 100, and may further include a surface layer 110 disposed on one or both sides of the anisotropic diffusion layer 100.

[0030] The anisotropic diffusion layer 100 functions to anisotropically diffuse the light incident on the optical film 200. Specifically, when the light is incident on the plane formed by the x-axis and the y-axis, if the axis aligned with the long axis of the dispersion is taken as the x-axis, it diffuses along the y-axis direction perpendicular to the x-axis and exits from the opposite side to the incident surface.

[0031] In order to perform the optical function, the anisotropic diffusion layer 100 includes a substrate 10 and a plurality of dispersions 20 located within the substrate 10.

[0032] The substrate 10 is a body comprising and supporting the dispersion 20 exhibiting anisotropic diffusion characteristics, and is formed of a first polymer. The first polymer can be used without limitation in the case of conventional polymers commonly used as optical films. As an example, the first polymer may be selected from polyethylene naphthalate (PEN), copolyethylene 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 copolymer (ABS), polyurethane (PU), polyimide (PI), polyvinyl chloride (PVC), and styrene-acrylonitrile copolymer (styrene). It may be one or a mixture of two or more of the following: acrylonitrile (SAN), ethylene vinyl acetate (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP), urea-formaldehyde resin (UF), melamine resin (MF), unsaturated polyester (UP), and cycloolefin polymers (COP), or it may be a copolymer of two or more of these.

[0033] Furthermore, the dispersion 20 dispersed within the matrix 10 includes a plurality of first dispersions 21 as the second polymer and a plurality of second dispersions 22 as inorganic particles. The first dispersions 21 and the second dispersions 22 are each elongated in a certain direction, and the long axis of each of the first dispersions 21 and the second dispersions 22 is arranged along a certain axis within the matrix 10 (for example, the x-axis direction among the mutually perpendicular x-axis, y-axis and z-axis), thereby exhibiting anisotropic diffusion characteristics.

[0034] First, the first dispersion 21 is formed from the second polymer and may have a shape such as a long rod or fiber along one direction. Based on this, in a cross section perpendicular to the transverse direction (TD) of the optical film (for example, as a cut surface of the xz plane of the anisotropic diffusion layer 100), the ratio (a / b) between the average length of the long axis (a) of the first dispersion 21 and the average length of the short axis (b) perpendicular to the long axis (i.e., the average aspect ratio) may be greater than 100, or, for another example, greater than 1000, or greater than 10000, or greater than 100000. The average length (b) of the short axis refers to the length of the longest line segment among the line segments connecting the perimeter of the cross section perpendicular to the long axis.

[0035] Furthermore, the cross-sectional shape of the first dispersion 21, based on the cut surface along the yz plane of the anisotropic diffusion layer 100, can be circular or elliptical. In this case, when the cross-sectional shape of the first dispersion 21 is elliptical, the ratio between the average length (c) of the major axis and the average length (d) of the minor axis (i.e., the average aspect ratio (c / d)) can be greater than 1 and less than or equal to 350. The average length (d) of the minor axis refers to the average length of the minor axis when the axis perpendicularly bisects the major axis is defined as the minor axis. If the cross-sectional shape of the first dispersion 21 is elliptical and the average aspect ratio is greater than 350, it may mean that the alignment of the plurality of second dispersions 22 aligned with their major axis directions toward the x-axis direction is reduced, or indirectly, it may mean that the second polymers forming the first dispersion have fused together. In this case, the intended effects of the present invention may not be easily achieved.

[0036] Furthermore, if the second polymer forming the first dispersion 21 is a conventional polymer commonly used as an optical film, it can be used without limitation. As an example, the second polymer can be polyethylene naphthalate (PEN), copolyethylene 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 copolymer (ABS), polyurethane (PU), polyimide (PI), polyvinyl chloride (PVC), or styrene-acrylonitrile copolymer (styrene). A mixture of one or more of the following, or a copolymer of two or more: acrylonitrile (SAN), ethylene vinyl acetate (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP), urea-formaldehyde resin (UF), melamine resin (MF), unsaturated polyester (UP), and cycloolefin polymers (COP).

[0037] In addition, the matrix 10 contains a plurality of first dispersions 21. For example, in the yz cut plane of the matrix 10, each unit area (1μm 2) may contain 10 to 200 first dispersions 21.

[0038] Furthermore, the plurality of first dispersions 21 are arranged within the matrix 10 with the x-axis direction (i.e., x-axis, y-axis, and z-axis) being the major axis direction among the three mutually perpendicular axes (i.e., x-axis, y-axis, and z-axis) within the matrix 10. However, the arrangement with the x-axis direction as the major axis direction of the first dispersions 21 does not mean that the major axis direction of all the first dispersions 21 is parallel to the x-axis. Rather, it means that the direction of the major axis direction of the first dispersions 21 is closer to the x-axis direction than the y-axis and z-axis. For example, the angle formed between the major axis direction of each first dispersion 21 and the x-axis may be less than 10°, less than 5°, less than 3°, or less than 1°.

[0039] Furthermore, based on the yz cutting plane formed by the y-axis and z-axis of the matrix, a plurality of first dispersions 21 can be randomly arranged. Here, "random arrangement" means that the positions of the plurality of first dispersions 21 are randomly arranged on the yz cutting plane, and are independent of the size and shape of the dispersion cross-section.

[0040] Furthermore, the difference in shear rate between the first polymer forming the matrix 10 and the second polymer forming the first dispersion 21, measured at a predetermined temperature, is 60 sec⁻¹ or less, preferably 45 sec⁻¹ or less. Alternatively, it can be 30 sec⁻¹ or less, 20 sec⁻¹ or less, 10 sec⁻¹ or less, or 5 sec⁻¹ or less. This facilitates the achievement of the objectives of the present invention. That is, there are many known polymer types where one of the two polymers forming the optical film forms the matrix and the other forms the dispersion. When, among the known polymers, the difference in shear rate between the polymer forming the matrix and the polymer forming the dispersion exceeds 60 sec⁻¹ at a predetermined temperature, the formation of the first dispersion 21 within the matrix 10 may not be normal, or even if it is formed, its dispersibility may be hindered, making it difficult to achieve the desired anisotropic diffusion layer 100 morphology.

[0041] The shear rate measurement of the polymer is performed on a polymer at a specified temperature according to the following Formula 1, wherein the specified temperature refers to any temperature between the temperature at which the first polymer and the second polymer begin to melt and the temperature range from their fully molten state. Specifically, the specified temperature is a specific temperature within the temperature range between the spinodal and binodal lines of the first and second polymers that exhibit upper critical solution temperature (UCST) behavior during melt blending; for example, it may be the melt processing temperature. [Formula 1]

[0042] At this time, in Formula 1, Q represents the amount of the first or second polymer ejected from the extruder (cm3 / sec), W represents the width of the die outlet opening (cm), and H represents the die lip gap (cm).

[0043] Furthermore, the shear rates of the first polymer and the second polymer can each be independently 5 to 80 sec⁻¹, which is beneficial for achieving the objectives of the present invention. When the two polymers are not the same, it is substantially difficult to satisfy a shear rate of 5 sec⁻¹ or less. In addition, if the shear rate is greater than 80 sec⁻¹, it may be difficult to achieve a morphological structure in which the first dispersion of the second polymer is dispersed within the matrix of the first polymer through the first polymer and the second polymer.

[0044] According to one embodiment of the present invention, at a specified temperature, the melt viscosity of the first polymer can be greater than that of the second polymer. Therefore, during the stretching process, particularly during stretching along the TD direction, the second polymer can act as a buffer between the matrix 10 and the second dispersion 22, which is composed of inorganic particles. This is more conducive to preventing the formation of voids at the interface between heterogeneous materials. When the melt viscosity of the first polymer is equal to or less than that of the second polymer, voids may be generated more frequently, and the refractive index difference between the formed voids and the matrix 10, the first dispersion 21, and / or the second dispersion 22 forming the interface increases, thereby posing a risk of reduced anisotropy.

[0045] Furthermore, in order to more smoothly achieve the morphological structure of matrix 10 / first dispersion 21 determined by the formation and dispersibility of the first dispersion 21 formed by the second polymer within the matrix 10 formed by the first polymer, while further improving the alignment of the long axis direction of the second dispersion 22 along the x-axis direction of the matrix 10 and the alignment uniformity among the plurality of second dispersions 22, the melt viscosity of the first polymer measured at a specified temperature can be more than twice the melt viscosity of the second polymer, more preferably more than three times, and as another example, less than five times, preferably less than four times. Here, the specified temperature refers to any temperature between the temperature at which the first polymer and the second polymer begin to melt and the temperature range of the fully melted state. Specifically, it is a specific temperature within the temperature range between the spinodal and binodal lines in the first polymer and the second polymer exhibiting UCST behavior during melt blending. As a specific example, it can be the melt processing temperature. If the melt viscosity of the first polymer is less than twice the melt viscosity of the second polymer, it may lead to poor formation of the morphology and structure of the first dispersion and poor dispersion of the already formed first dispersion, and there is a risk of reduced alignment or alignment uniformity of the second dispersion.

[0046] Furthermore, at a specified temperature, the melt viscosity (Pa·s) of the first polymer and the melt viscosity (Pa·s) of the second polymer can each independently be 100 Pa·s or more, more preferably 200 Pa·s or more, and as another example, can be 2000 Pa·s or less. This makes it easier to form a morphological structure in which the first dispersion 21 of the second polymer is formed and dispersed within the matrix 10 of the first polymer. Furthermore, by guiding the second polymer extending in a specific direction (specifically, along the x-axis), it is advantageous to orient the long axis of the second dispersion 22 along the x-axis direction, which is the same as the long axis of the first dispersion 21. If the melt viscosity of one or more of the first polymer and the second polymer is less than 100 Pa·s, even if the difference in shear rate measured at the same temperature between the first polymer and the second polymer satisfies 60 sec⁻¹ or less, it may be difficult to achieve the target morphological structure composed of the matrix and the first dispersion. Furthermore, when the melt viscosity of one or more of the first and second polymers is greater than 2000, it may lead to a decrease in the alignment and alignment uniformity of the second dispersion, and it may be difficult for the two polymers to undergo melt dispersion behavior, thus making it impossible to achieve the designed morphological structure.

[0047] Furthermore, the first polymer and the second polymer forming the anisotropic diffusion layer 100 can be contained in a weight ratio of 6 to 9:4 to 1, more preferably 7 to 9:3 to 1. When the weight ratio of the second polymer is less than 1 / 10 compared to the total weight of the first polymer and the second polymer, the number and cross-sectional diameter of the first dispersion in the anisotropic diffusion layer are excessively reduced. As a result, it may be difficult for the first dispersion to express sufficient anisotropic diffusion characteristics together with the second dispersion, and it may be difficult to play a guiding role in aligning the long axis direction of the second dispersion, thereby reducing the alignment of the second dispersion and potentially further reducing the anisotropic diffusion characteristics. In addition, when the weight ratio of the second polymer is greater than 4 / 10 compared to the total weight of the first polymer and the second polymer, the number and cross-sectional diameter of the first dispersion may increase. As a result, it may be difficult to achieve sufficient frontal brightness, and the randomness of the alignment direction of the second dispersion dispersed in the first dispersion increases. Therefore, even after stretching, it may be difficult to sufficiently improve the alignment of the second dispersion.

[0048] Next, the second dispersion 22, which is an inorganic particle, will be described.

[0049] The second dispersion 22 has the function of expressing anisotropic diffusion characteristics together with the first dispersion 21 described above. For this purpose, the shape of the second dispersion 22 can be rod-shaped. Preferably, the average aspect ratio can be 4 or more, more preferably 8 or more, thereby exhibiting excellent anisotropic diffusion characteristics. If the average aspect ratio is less than 4, there may be a risk that it is difficult to express anisotropic characteristics or that the diffusion characteristics expressed are insufficient. However, as another example, the average aspect ratio of the second dispersion 22 can be 15 or less. In order to make the average aspect ratio of the second dispersion exceed 15, considering that the second dispersion may break during the mixing process before melt extrusion, the average aspect ratio of the second dispersion fed into the extruder needs to be much greater than 15. However, as the aspect ratio of the fed inorganic particles increases, the degree of breakage during the mixing and melt extrusion process is very irregular. Therefore, it is difficult for the average aspect ratio to exceed 15, and due to irregular breakage, the number of second dispersions with an aspect ratio of less than 5 may increase, thereby posing a risk of reduced anisotropic diffusion. The average aspect ratio (e / f) of the second dispersion refers to the ratio of the average length (e) of the second dispersion along its major axis to the average diameter (f) of the surface perpendicular to the major axis. Here, the diameter of the second dispersion refers to the length of the longest line segment that traverses the surface perpendicular to the major axis.

[0050] Furthermore, the second dispersion 22 can be rod-shaped with its long axis having the aforementioned aspect ratio. Specifically, its average length can be 5-30 μm, more preferably 5-15 μm, and its average diameter can be 0.5-2.0 μm, more preferably 0.5-1.5 μm, thereby exhibiting enhanced anisotropic diffusion characteristics. When the average length and average diameter of the second dispersion exceed the aforementioned ranges, the improvement in anisotropic diffusion characteristics is not significant, and as the probability of the second dispersion being identified as a foreign object in the melt extrusion process increases, there is a risk that the content of the second dispersion in the final product is lower than the amount of the second dispersion added. In addition, when the average diameter of the second dispersion exceeds 2.0 μm, it may be visually identified as an external foreign object, thereby greatly reducing the visibility of the displayed image.

[0051] Furthermore, the second dispersion 22 can be used without limitation in the case of conventional inorganic particles used in optical films. As an example, the inorganic particles may comprise one or more selected from the group consisting of titanium dioxide (TiO₂), zinc oxide (ZnO), magnesium oxide (MgO), strontium carbonate (SrCO₃), calcium carbonate (CaCO₃), magnesium carbonate (MgCO₃), cobalt carbonate (CoCO₃), manganese carbonate (MnCO₃), calcium silicate (CaSiO₃), calcium sulfate (CaSO₄), aluminum hydroxide oxide (Al(OH)₂O), imogolite, silicon carbide (SiC), and silicon dioxide (SiO₂). As an example, it may be calcium carbonate.

[0052] Furthermore, based on the total weight of the anisotropic diffusion layer 100, it may contain 2 to 10% by weight of the second dispersion 22. If less than 2% by weight of the second dispersion is contained based on the total weight of the anisotropic diffusion layer, it may be difficult to achieve sufficient anisotropic diffusion characteristics, while if more than 10% by weight is contained, the turbidity will increase, which may lead to a potential decrease in the front light transmittance.

[0053] Referring to Figure 4, according to one embodiment of the present invention, when the second dispersion 22 dispersed within the matrix 10 is projected along the z-axis direction of the matrix, the number of the second dispersion 22 whose angle θ formed by the x-axis direction and the major axis directions ℓ1 and ℓ2 of the second dispersion 22 is within ±5° on the plane formed by the x-axis and y-axis (i.e., the projection plane S) can be 75% or more of the total number of the second dispersion 22, more preferably 80% or more, thereby facilitating the realization of anisotropic diffusion characteristics. If the number of the second dispersion 22 whose angle θ formed by the x-axis direction and the major axis directions ℓ1 and ℓ2 of the second dispersion 22 is within ±5° on the projection plane S is less than 75% of the total number of the second dispersion 22, it may be insufficient to achieve sufficient anisotropic diffusion characteristics.

[0054] Furthermore, the thickness of the anisotropic diffusion layer 100 can be 150 μm or less, preferably 100 μm or less, or 80 μm or less, or 60 μm or less. As another example, it can be 35 μm or more, or 10 μm or more. If the thickness of the anisotropic diffusion layer is greater than 150 μm, it may be difficult to fully exhibit brightness and anisotropic diffusion characteristics. If it is less than 35 μm, it is difficult to exert anisotropic diffusion characteristics, and the surface quality of the anisotropic diffusion layer decreases because it is a second dispersion of inorganic particles.

[0055] Furthermore, the optical film 200 may further include a surface layer 110 disposed on at least one surface of the anisotropic diffusion layer 100. The surface layer 110 serves to supplement mechanical strength and provide protection against external factors. Preferably, the surface layer 110 can be co-extruded integrally with the optical layer without the need for an additional adhesive layer. As a result, not only can the degradation of optical performance due to adhesive layers be prevented, but it is also advantageous to achieve thinner optical films.

[0056] Furthermore, according to an embodiment of the present invention, the surface layer 110 is subjected to a stretching process after being co-extruded simultaneously with the anisotropic diffusion layer 100, thus allowing it to be stretched along at least one axial direction. This increases the surface hardness compared to an unstretched surface layer, thereby improving scratch resistance and heat resistance.

[0057] The surface layer 110 can be a surface material commonly used to perform the supporting function of the optical film 200. Preferably, it can be used alone or in combination with polyethylene naphthalate (PEN), copolyethylene 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), or acrylonitrile butadiene-styrene copolymer. The following materials may be used: styrene (ABS), polyurethane (PU), polyimide (PI), polyvinyl chloride (PVC), styrene-acrylonitrile copolymer (SAN), ethylene vinyl acetate copolymer (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy resin (EP), urea-formaldehyde resin (UF), melamine resin (MF), unsaturated polyester (UP), silicon (SI), and cycloolefin polymer (COP). More preferably, materials with the same composition as the matrix 10 described above may be used.

[0058] Furthermore, the thickness of the surface layer 110 can be 5~30μm, more preferably 10~15μm, thereby having the following advantages: the decrease in brightness caused by the surface layer 110 can be minimized, and the phase difference caused by birefringence can be minimized and the change in polarized light wavelength can be minimized.

[0059] Furthermore, according to the following mathematical formula 1, the anisotropic diffusion characteristic of the optical film 200 can be 25% or more, more preferably 26.1% or more, even more preferably 27% or more, and as another example, it can be 30% or less. If the anisotropic diffusion characteristic is 25% or less, it may not be preferred in terms of achieving the objectives of the present invention, such as improving the viewing angle, when applied to a display. [Mathematical Formula 1] Anisotropic diffusion rate (%) = [luminance (nit) in the side (30°) direction relative to the main surface] / [luminance (nit) in the normal (90°) direction relative to the main surface] × 100

[0060] On the other hand, the brightness of the normal direction and the lateral direction on the principal surface measured in mathematical formula 1 can be measured using brightness measurement methods known in the art, and the present invention does not particularly limit the specific method when the normal direction and the lateral direction are measured using the same specific method.

[0061] The optical film 200 described above, in particular, the anisotropic diffusion layer can be manufactured by melt extrusion in various film manufacturing methods. Specifically, in step (1), the first polymer used to form the matrix 10, the second polymer used to form the first dispersion 21 in the dispersion 20, and the inorganic particles used as the second dispersion 22 are extruded through an extrusion section and solidified to manufacture a film before stretching; and in step (2), the film before stretching is stretched.

[0062] First, step (1) is performed, that is, extrusion and curing are carried out through the extrusion section to produce a pre-stretch film.

[0063] Step (1) can generally be performed using an apparatus and method for manufacturing a pre-stretch film. Specifically, step 1-1) can be performed, that is, supplying the first polymer for forming the matrix 10, the second polymer for forming the first dispersion 21 in the dispersion 20, and the inorganic particles as the second dispersion 22 to the extrusion section. At this time, the supplied components can be supplied to a single extrusion section after mixing, or each component can be supplied to an independent extrusion section separately.

[0064] Preferably, in order to improve and homogenize the orientation of the inorganic particles within the anisotropic diffusion layer 100, the inorganic particles may be in a composite core state mixed with the second polymer before being fed into the extrusion section. By feeding them into the extrusion section in the composite core state, the orientation of the inorganic particles can be induced by the second polymer. Furthermore, when the first polymer wafer and the composite core are supplied to a single extrusion section, a thorough stirring process can be performed before supplying them to the extrusion section in order to induce uniform dispersion. This facilitates the uniform dispersion of the dispersion 20 within the anisotropic diffusion layer 100 and also facilitates the uniform realization of the size of the first dispersion 21 along the z-axis in the cross-section of the substrate 10 in the yz-cut plane.

[0065] On the other hand, in the composite core state, the dispersion and orientation induction of inorganic particles through the second polymer are specifically explained as follows: Under the action of the melt viscosity difference between the molten second polymer and the first polymer, the inorganic particles in the composite core are prevented from detaching from the interface between the second polymer and the first polymer and moving towards the first polymer side. This confines the inorganic particles within the second polymer, thereby improving the dispersibility of the inorganic particles in the matrix and preventing secondary aggregation. Furthermore, the second polymer within the molten first polymer separates and forms a plurality of first dispersions. Each first dispersion extends elongated along the x-axis direction, which is the MD direction, within the molten first polymer after extrusion. During the extension of the first dispersion, the inorganic particles confined within the first dispersion are oriented along the extended first dispersion. Therefore, it can serve as a guide to orient and align the inorganic particles in the same manner as the orientation and alignment direction of the first dispersion along the x-axis direction toward the MD direction. Even after melt extrusion, the alignment and alignment uniformity of the inorganic particles can be improved.

[0066] However, even when the second polymer and inorganic particles are fed into the extrusion section together with the first polymer in a mixed composite core state, it is not always easy to align them in such a way that the long axis of the inorganic particles is aligned with the x-axis direction. That is, as mentioned above, the melt viscosity of either the second polymer or the first polymer can be more than twice the melt viscosity of the other polymer. Preferably, when the melt viscosity of the second polymer is less than that of the first polymer, the inorganic particles in the molten second polymer can be more easily aligned along the MD direction (i.e., the x-axis direction) as the direction in which the second polymer is extruded, while improving the dispersibility within the first polymer. Through the stretching process described later, the long axis of the inorganic particles is aligned closer to the orientation direction of the first dispersion of the second polymer, which is beneficial for achieving further uniform alignment of the alignment directions of each inorganic particle. If inorganic particles are fed into the extrusion section in a composite core state mixed with the first polymer forming the matrix (instead of the second polymer), or separately mixed and stirred with the first and second polymers without forming a composite core with the second polymer, even if the melt viscosity conditions between the first and second polymers or the melt viscosity conditions of the preferred polymers are met and / or the stretching process described later is performed, it is difficult to achieve the dispersibility, orientation and orientation uniformity of the second dispersion of inorganic particles, or the degree of achievement may be insufficient.

[0067] On the other hand, as mentioned above, for the inorganic particles confined within the first dispersion dispersed inside the first polymer after extrusion and melting, their long axis direction is adjusted in the x-axis direction as the first dispersion extends long along the x-axis direction toward the MD direction. Subsequently, in the stretching process described later, as the length of the first dispersion further increases and its diameter relatively decreases, the diameter of the first dispersion becomes smaller than the diameter of the second dispersion, which is the inorganic particle. This ultimately causes part and / or all of the first dispersion encapsulating the inorganic particle to peel off from the inorganic particle. Therefore, the first dispersion 21 breaks along its length at the portion where the inorganic particle is disposed, and at least a portion of the inorganic particle may be located outside the first dispersion 21. Based on the morphological changes that occur during the process as described above, the surface of the second dispersion 22, which is the inorganic particle, may be partially or entirely coated with the second polymer derived from the first dispersion 21. The coating of the second dispersion 22 with the second polymer can serve as a technical feature that indirectly proves that it is a melt-extruded film. Furthermore, the second polymer coated on the surface of the second dispersion 22 can act as a buffer, cushioning the formation of voids that may occur at the interface between the first polymer forming the matrix and the inorganic particles that form the second dispersion, thereby helping to reduce voids within the achieved anisotropic diffusion layer. Moreover, the absence of an adhesive or bonding layer between the surface layer and the anisotropic diffusion layer, allowing for integral molding, is another technical feature that indirectly proves it is a melt-extruded film.

[0068] Furthermore, the extrusion section described above can be a conventional extruder, which may further include a heating unit for converting the supplied solid polymer components into a liquid phase, etc. In addition, the size adjustment of the first dispersion and the uniform dispersion of the first dispersion and the second dispersion can first be achieved through the process adjustment in step (1). Specifically, the size of the first dispersion or the dispersion of the first dispersion and the second dispersion can be adjusted by: whether sufficient stirring is performed before feeding the composite core and the first polymer wafer into the extrusion section, or by changing the discharge volume during extrusion, the extruder speed of the shear stress, or the type of extruder (single screw, co-rotating twin screw, etc.).

[0069] Furthermore, in step (1), the components forming the surface layer can be fed into the extrusion section, so that the surface layer 110 disposed on at least one surface of the anisotropic diffusion layer 100 is extruded together. For example, the surface layer can be extruded to the upper and / or lower part of the anisotropic diffusion layer 100 through separate extrusion sections to achieve the surface layer 110, or when using one extrusion section, the melt forming the anisotropic diffusion layer 100 is flowed to the central region through different channels arranged along the thickness direction, and the melt forming the surface layer flows to the upper region and the lower region respectively, and is then ejected through a T-die (T-DIE), thereby achieving a three-layer optical film in one extrusion section. Whether using one extrusion section or multiple extrusion sections, the surface layer co-extruded together with the anisotropic diffusion layer has the advantage of forming the surface layer in the process of forming the anisotropic diffusion layer without the need for a separate binder. On the other hand, preferably, the material of the surface layer can be the same as the first polymer used as the matrix, or a highly compatible material can be used. In addition, to prevent a decrease in brightness due to total internal reflection, it is preferable to design the surface layer to be of an appropriate thickness.

[0070] Next, as in steps 1-2), the flow control unit induces expansion, allowing the dispersions 20 contained within the matrix 10 to be randomly arranged. The flow control unit can be a conventional flow control unit; for example, a coat-hanger die can be used. Through the flow control unit-induced expansion in step (2), the size of the first dispersion 21 or the dispersibility of the first dispersion 21 and the second dispersion 22 can be adjusted secondary.

[0071] Next, as steps 1-3 of the present invention, a cooling and smoothing step can be performed. This step involves cooling and smoothing the film transferred from the flow control unit. The film is cooled and cured under conditions typically used for manufacturing optical films. This can be performed by adopting and modifying the smoothing step. For example, the cooling and smoothing process can be performed on a casting roller. Preferably, one surface of the sheet transferred via the flow control unit contacts the main cooling roller for cooling. At this time, the temperature of the main cooling roller can be controlled below 40°C, more preferably below 35°C, and as another example, below 20°C for cooling. If the temperature of the main cooling roller exceeds 40°C, crystallization of the first polymer of the matrix or the second polymer of the first dispersion leads to the formation of spherulites, which poses a risk of significantly increased haze and easily causes size differences between the first dispersions 21 arranged in different regions along the thickness direction of the anisotropic diffusion layer 100. This is due to the bonding between the first dispersions dispersed in a molten state, which leads to an increase in the size of the solidified first dispersions, or the first dispersions that have formed clumps diffuse laterally (i.e., along the y-axis of the matrix), potentially resulting in a thinner thickness. Furthermore, at the interface between the first dispersion and the matrix, the proportion of the matrix that is converted into a third substance due to a chemical reaction increases, potentially leading to a significant increase in the area percentage of the first dispersion. More preferably, the opposite side, which is not in contact with the cooling roller, is simultaneously cooled by an auxiliary cooling unit. For example, the auxiliary cooling unit can be a cooling airflow; more preferably, the temperature of the cooling airflow can be below 30°C; and even more preferably, it can be below 20°C.

[0072] Next, as step (2) of the present invention, a stretching step of the cooled and smoothed anisotropic diffusion layer can be performed. The stretching can be performed by adopting and changing the apparatus and process conditions used in the optical film, but preferably, in order to make the long axis direction of the second dispersion 22 more easily and uniformly aligned with the x-axis direction of the substrate 10, the stretching can be performed 2 to 6 times along the x-axis direction which is the MD direction, and the stretching can be performed 2 to 6 times along the y-axis direction which is the TD direction. If uniaxial stretching is performed only along the x-axis direction, or if the above conditions are not met even in the case of biaxial stretching, it may be difficult to improve the alignment and alignment uniformity of the long axis direction of the second dispersion toward the x-axis direction of the substrate. In addition, the stretching temperature can be performed at a temperature 10 to 20°C higher than the higher glass transition temperature of the first polymer and the second polymer. If the stretching is performed at a temperature within 10°C higher than the higher glass transition temperature of the first polymer and the second polymer, it may become a cause of failure to stretch or breakage. Furthermore, if stretching is performed at a temperature 20°C higher than the glass transition temperature of the first and second polymers, or if the holding time is too long even at an appropriate temperature, there is a risk that the stretching uniformity may decrease, which in turn may reduce the alignment uniformity of the second dispersion.

[0073] In addition, a heat-fixing step can be performed on the stretched optical film. The heat-fixing can be performed by a general method, preferably by using an infrared (IR) heater at 180~200°C for 0.1~3 minutes.

[0074] Referring to Figures 5 and 6, the optical film 200 of one embodiment of the present invention manufactured by the above-described manufacturing method can be realized as a polarizing plate 4000. Specifically, the polarizing plate 4000 is suitable as an upper polarizing plate disposed on the upper part of the light emitting surface of the liquid crystal panel 5000. Specifically, the polarizing plate 4000 includes an absorptive polarizing film 2000 and an optical film 200 disposed on the light emitting surface of the absorptive polarizing film 2000. When disposed on the light emitting surface of the polarizing device 2100 of the upper polarizing plate, it has the following advantages: the contrast improvement effect due to internal light is significant, the viewing angle can be increased, and excellent brightness characteristics can be achieved.

[0075] The absorptive polarizing film 2000 is a polarizing device that transmits first polarized light (or second polarized light) and absorbs second polarized light (or first polarized light) in a first polarized light and a second polarized light having mutually orthogonal vibrational planes, and has a conventional polarizing layer 2100 having such optical function. As an example of the polarizing layer 2100, it can be formed by dyeing a substrate film such as polyvinyl alcohol with an iodine-based component or a dichroic dye. In addition, the iodine-based component, which is one of the dyes used to dye the substrate, can be an iodine-based compound such as iodine and / or potassium iodide. Furthermore, conventional dichroic dyes that meet the following conditions can be used without limitation, so the present invention does not make any particular limitation in this regard, and the specific description is omitted. The conditions are: high absorbance in a wide wavelength range in the long axis direction of the molecule, and extremely low absorbance in the short axis direction, while having good affinity for the film as the substrate; dyeability in crystalline regions; easy synchronous orientation when the substrate is stretched; and bright color and high visual contrast.

[0076] As an example, the thickness of the polarizing layer 2100 is 10~200μm, but it is not limited to this and can be changed according to the purpose.

[0077] Furthermore, the absorptive polarizing film 2000 may have a protective film 2210 disposed on one or both surfaces to support and protect the polarizing layer 2100. The protective film 2210 can be used without limitation as a protective film for general absorptive polarizing films, and is preferably made of polymers with excellent transparency, mechanical strength, thermal stability, or moisture resistance. For example, the protective film 2210 may be made of acetate-based resins such as triacetyl cellulose (TAC), polyester-based resins, polyethersulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, acrylic-based resins, and polynorbornene-based resins. As an example, considering optical properties, the protective film can be a triacetyl cellulose (TAC) film. Alternatively, considering heat resistance and moisture resistance, a polyester-based film can be used; as a specific example, it can be a polyethylene terephthalate (PET) film. The in-plane phase difference of the PET film can be greater than 8000 nm, or in the range of 10000~15000 nm. Furthermore, the thickness of the protective film 2210 can be 50~150 μm, but is not limited thereto. Furthermore, referring to Figure 6, the protective film (TAC film) typically disposed on the upper part of the polarizing layer 2100 is not provided; the optical film 200 according to an embodiment of the present invention has the advantage of omitting and replacing the upper TAC film disposed on the upper part of the polarizing layer 2100.

[0078] Furthermore, a separate adhesive layer (not shown in the figure) can be inserted at the interface between the aforementioned absorptive polarizing device 2000 and the optical film 200 to achieve integrated bonding. This adhesive layer, used for adhesion between the optical films, can be achieved by using a conventional adhesive component that does not degrade optical properties. For example, an adhesive component containing a vinyl alcohol-based polymer can be used alone, or an adhesive component can be formed by combining an adhesive component with at least one water-soluble crosslinking agent selected from vinyl alcohol-based polymers such as boric acid, borax, glutaraldehyde, melamine, and oxalic acid. Furthermore, the adhesive can be combined with other additives or acid catalysts.

[0079] Furthermore, the polarizing plate 4000 may further have a functional layer 3000 disposed on the optical film 200. The functional layer 3000 may be a primer layer, a hard coating layer, an anti-fingerprint layer, an anti-reflective layer, an anti-glare layer, a low-reflection layer, or an ultra-low-reflection layer, etc. Moreover, the functional layer 3000 may also achieve composite functions through multi-layer stacking. Since the thickness of the functional layer 3000 can be appropriately varied depending on the type of functional layer and the number of stacked layers, the present invention is not particularly limited in this regard.

[0080] Furthermore, as shown in Figure 6, the polarizing plate 4000 according to an embodiment of the present invention can be implemented as a liquid crystal display device 8000, which is opposite to the backlight unit 7000 arranged below the liquid crystal panel 5000 and arranged above the liquid crystal panel 5000, that is, on the light emitting surface of the polarizing plate 4000 arranged adjacent to the visual recognition side of the liquid crystal display device 8000.

[0081] Specifically, the liquid crystal display device 8000 can be arranged and implemented in the following order: backlight unit 7000, absorptive polarizing film 2000 as lower polarizing plate, liquid crystal panel 5000, color conversion layer 5300, and polarizing plate 4000 of one embodiment of the present invention as upper polarizing plate.

[0082] The backlight unit 7000 can be used in a general LCD display. For example, it can be composed of a light source, a reflective film, a light guide plate, a light diffusion film, a light collecting film, a reflective polarizing film, and other conventional structures.

[0083] Furthermore, the liquid crystal panel 5000 may include a liquid crystal layer 5100 and support plates 5210 and 5220 supporting the upper and lower parts of the liquid crystal layer 5100, and may further include conventional configurations such as electrode lines. In addition, the liquid crystal panel 5000 may employ vertical alignment (VA) mode, in-plane switching (IPS) mode, patterned vertical alignment (PVA) mode, or super-patterned vertical alignment (S-PVA) mode, but is not limited to these.

[0084] Furthermore, according to an embodiment of the present invention, an optical film 200 is disposed on the light emitting surface of a self-emissive display panel, thereby enabling the realization of a self-emissive display device. The self-emissive display panel may be a panel used in conventional self-emissive displays such as plasma display panels (PDPs) and OLED panels; the present invention does not impose any particular limitation on this.

[0085] On the other hand, although the application of the optical film has been described in this invention using liquid crystal display devices or self-emissive display devices as examples, it is not limited thereto and can be widely applied to various conventional 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. Specific embodiments

[0086] The present invention will be further described in detail through the following embodiments, but the following embodiments do not limit the scope of the present invention and should be interpreted as helping to understand the present invention. <Embodiment 1>

[0087] As the first polymer to realize the matrix, polyethylene terephthalate (PET) was prepared. As the second polymer to realize the first dispersion, polyethylene terephthalate-1,4-cyclohexylene dimethylene terephthalate (PCTG) was prepared by polymerization of terephthalate and glycol components (ethylene glycol and cyclohexanediethanol mixed in a 1:2 molar ratio) in a 1:1 molar ratio. As the inorganic particles for the second dispersion, calcium carbonate with an average length of 25 μm and an average diameter of 1.4 μm was prepared. The prepared second polymer and inorganic particles were mixed and fed into an extruder to produce a composite core in which inorganic particles are dispersed in the second polymer. Subsequently, the obtained composite core was mixed with the first polymer and fed into the first extrusion section. At the time of feeding, the first polymer and the second polymer were mixed at a weight ratio of 8:2. The content of inorganic particles in the total weight of the mixture fed into the first extrusion section was 5.0% by weight. Furthermore, to create the surface layer, the first polymer is fed into the second extrusion section, and the second extrusion section is manufactured using a flow path device, so that the surface layer is disposed on the upper and lower parts of the substrate with the same thickness. On the other hand, the prepared first polymer and the second polymer, in the extrusion section described later, have melt viscosities of 180 Pa·s and 100 Pa·s, respectively, at an extrusion temperature of 260°C, and shear rates of 120 sec⁻¹ and 110 sec⁻¹, respectively.

[0088] At this time, the extrusion temperature of the first extrusion section is set to 260°C. The polymer flow is corrected by confirming with a capillary rheometer to achieve a melt viscosity ratio of 3.2 between the two components. The polymer flows through a channel equipped with a Filtration Mixer to induce the first dispersion formed by the second polymer to disperse within the matrix formed by the first polymer. Subsequently, the first polymer flow forming the surface layer is adhered to the two surfaces of the matrix. The polymer is then induced to expand in a coat-hanger die used to correct the flow rate and pressure gradient, thereby inducing the first dispersion to disperse randomly. Specifically, the die inlet width is 200 mm, the thickness is 10 mm, the die outlet width is 1260 mm, the thickness is 0.75 mm, and the flow rate is 1.0 m / min. Afterward, a cooling and smoothing process on the casting roller is performed, followed by a 5x stretch along the MD direction and then a 4x stretch along the TD direction. Subsequently, an anisotropic diffusion layer optical film with randomly dispersed first dispersions as shown in Table 1 was manufactured. The film underwent heat setting at 180°C for 2 minutes in a heating chamber, resulting in an anisotropic diffusion layer optical film as shown in Table 1 below: the substrate thickness is 60 μm, and two surface layers with a thickness of 30.25 μm are respectively disposed on the two surfaces of the main surface of the substrate, with a total thickness of 125 μm. As shown in Figure 2, the long axes of the first and second dispersions are aligned along the x-axis of the substrate. The average aspect ratio of the first dispersion along the x-axis of the substrate is greater than 100, and the average aspect ratio of the second dispersion is 4.3. The average aspect ratio on the yz-section plane of the substrate is 200. <Examples 2-5>

[0089] The optical film shown in Table 1 was manufactured by changing the type / content of the first polymer and the second polymer, the content of the second dispersion, and / or the type of polymer in which inorganic particles are dispersed in the composite core, as shown in Table 1 below, in the same manner as in Example 1.

[0090] In this case, in Examples 2-4 and Example 6, the extrusion temperature of the extrusion section was changed to 280°C. In Table 1, the melt viscosity of the first polymer and the second polymer are the melt viscosities at 280°C. On the other hand, as the second polymer, a PC alloy composed of 38% by weight of PCTG, 60% by weight of polycarbonate, and 2% by weight of phosphate-containing heat stabilizer from Example 1 was used. <Comparative Example 1>

[0091] The optical film shown in Table 1 below was manufactured by changing the type of the second polymer, as shown in Table 1 below, in the same manner as in Example 2. <Comparative Example 2>

[0092] The process was carried out and manufactured in the same manner as in Example 1. As shown in Table 1 below, the ratio of the first polymer and the second polymer was changed without including the second dispersion as inorganic particles, and the stretching along the TD direction was omitted during stretching, thereby producing the optical film shown in Table 1 below. <Comparative Example 3>

[0093] The process was carried out and manufactured in the same manner as in Example 1, as shown in Table 1 below, without the second polymer, and the stretching along the TD direction was omitted during stretching, thereby producing the optical film shown in Table 1 below. <Experimental Example>

[0094] The optical films according to the Examples and Comparative Examples were evaluated for the following physical properties, and the results are shown in Table 1. 1. Alignment evaluation of the second dispersion

[0095] As shown in Figure 4, the angle formed by the long axis of the second dispersion and the x-axis of the matrix was measured. Specifically, after peeling off the surface layer of the optical film, the surface was treated with plasma at 500W for 10 minutes, and then the specimen was photographed using a scanning electron microscope (SEM). The ratio of the number of second dispersions within ±5° was calculated in the photographs, using the x-axis as a reference. 2. Evaluation of the size of the second dispersion

[0096] The anisotropic diffusion layer of the optical film was dissolved in hexafluoroisopropanol (HFIP) solvent, filtered through a 5-micron nitrocellulose (CN) filter membrane, and then the length and diameter of the obtained sample were measured using a scanning electron microscope. The average length, average diameter, and average aspect ratio were calculated accordingly. 3. Evaluation of Anisotropic Diffusion Characteristics

[0097] A hard coating and a low refractive index coating were applied to one surface of the optical film. The prepared optical film was bonded to the upper surface of the absorptive polarizing device and a triacetate cellulose (TAC) film was placed on the lower surface of the absorptive polarizing device to manufacture a polarizing plate. The polarizing plate was then used as the object to replace the upper polarizing plate of the liquid crystal panel of a commercially available LCD, and the brightness in the front (90° relative to the normal direction of the main surface of the optical film) and side (30° relative to the main surface of the optical film) directions was measured.

[0098] Furthermore, based on the measured brightness in the front and side directions, the anisotropic diffusion characteristics were calculated according to Formula 1, which corresponds to the percentage of side direction brightness relative to the front direction brightness. [Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Comparative Example 1 Comparative Example 2 Comparative Example 3 matrix First polymer (A) type / melt viscosity (Pa·s) / shear rate (sec) -1 ) PET / 180 / 120 PET / 165 / 125 PEN / 1600 / 20 PET / 168 / 118 PC alloy / 500 / 60 PET / 220 / 152 PET / 245 / 165 PET / 180 / 145 PEN / 1600 / 120 PEN / 1600 / 120 First dispersion Second polymer (B) type / melt viscosity (Pa·s) / shear rate (sec) -1 ) PCTG / 100 / 110 PET / 120 / 105 PC alloy / 530 / 40 PET / 115 / 105 PEN / 1400 / 35 PCTG / 105 / 108 PET / 120 / 107 PET / 170 / 80 PC alloy / 600 / 40 Not included Average aspect ratio 200:1 185:1 170:1 180:1 160:1 190:1 185:1 185:1 300:1 - Second dispersion Types of Inorganic Particles Calcium carbonate Calcium carbonate Calcium carbonate Calcium carbonate Calcium carbonate Calcium carbonate Calcium carbonate Calcium carbonate Not included Calcium carbonate Inorganic particle content (by weight %) 2.0 2.4 4.3 3.6 2.8 2.4 2.2 4.7 3.6 5.0 Average length (e) / Average diameter of minor axis (f) / Average aspect ratio (e / f) 5.6 1.3 4.3 5.5 1.3 4.2 5.4 1.2 4.5 5.7 1.2 4.8 5.6 1.1 4.4 5.7 1.3 4.2 5.8 1.2 4.6 5.5 1.2 4.6 5.7 1.2 4.8 5.5 1.3 3.9 process Composite core Second polymer / inorganic particles Second polymer / inorganic particles Second polymer / inorganic particles Second polymer / inorganic particles Second polymer / inorganic particles Second polymer / inorganic particles Second polymer / inorganic particles Second polymer / inorganic particles Second polymer / inorganic particles First polymer / inorganic particles Anisotropic diffusion layer A:B content ratio 8:2 8:2 9:1 7:3 8:2 8:2 8:2 9:1 6:4 - The shear rate difference between A and B (sec) -1 ) 10 20 20 13 25 44 58 65 80 - Relationship between the melt viscosities of A and B A > B A > B A > B A > B B > A A > B A > B A > B A > B - The melt viscosity ratio of A to B 3.0 4.1 3.0 2.8 2.8 2.1 2.0 1.0 2.6 - The percentage of second dispersions aligned within ±5° of the x-axis direction. 88 86 78 75 83 86 83 52 - 34 gap No occurrence No occurrence No occurrence No occurrence occur No occurrence No occurrence No occurrence No occurrence occur brightness front 752nit 751nit 748nit 747nit 545nit 742nit 736 nits 729nit 756 nits 734nit Side view (30°) 206 nits 196nit 187nit 190nit 230nit 204nit 195nit 155nit 170nit 110 nits Anisotropic diffusion characteristics (%) 27.4 26.1 25.0 25.4 42.2 27.5 26.5 21.2 22.5 15.0

[0099] As can be seen from Table 1, the anisotropic diffusion films of most embodiments have superior anisotropic diffusion characteristics compared to the anisotropic diffusion films of Comparative Examples 1 to 3, and no voids were found.

[0100] Although some embodiments of the present invention have been described above, the ideas of the present invention are not limited to the embodiments presented in this specification. Those skilled in the art who understand the spirit of the present invention can easily propose other embodiments by adding, modifying, deleting, or supplementing the same ideas, but these are also considered to fall within the scope of the present invention. [Simplified Explanation of the Diagram]

[0023] Figure 1 is a perspective view of an optical film according to an embodiment of the present invention.

[0024] Figures 2 and 3 are schematic cross-sectional views along the Y-Y' and X-X' boundary lines of the optical film in Figure 1.

[0025] Figure 4 is a schematic diagram illustrating the alignment of a second dispersion dispersed within an optical film onto a projection plane projected along the z-axis direction, according to an embodiment of the present invention.

[0026] Figure 5 is a cross-sectional schematic diagram of a polarizing plate according to an embodiment of the present invention.

[0027] Figure 6 is a cross-sectional schematic diagram of a liquid crystal display according to an embodiment of the present invention. [Biomaterial Storage]

[0102] Domestic Storage Information (Please note in order of storage institution, date, and number) None

[0103] Overseas Deposit Information (Please note in the order of deposit country, institution, date, and number) None

Claims

1. An optical film, wherein the optical film has an anisotropic diffusion layer; the anisotropic diffusion layer comprises: As a matrix of the first polymer and a dispersion, each of the dispersions is dispersed in a manner with its long axis oriented toward a certain axial direction within the matrix, the dispersions including a plurality of first dispersions as a second polymer and a plurality of second dispersions as inorganic particles; at a specified temperature, the difference in shear rate measured for the first polymer and the second polymer is less than 45 sec⁻¹.

2. The optical film of claim 1, wherein at a specified temperature, the melt viscosity of the first polymer is greater than the melt viscosity of the second polymer.

3. The optical film of claim 1, wherein the anisotropic diffusion layer is formed by melt extrusion, and at least a portion of the surface of the second dispersion is coated with the second polymer.

4. The optical film of claim 1, wherein the first dispersion is randomly dispersed within a cut surface of a matrix formed by two axes, each perpendicular to the first axis.

5. The optical film of claim 1, wherein the matrix and the first dispersion are contained in a weight ratio of 6 to 9: 4 to 1.

6. The optical film of claim 1, wherein the content of the second dispersion is 2 to 10% by weight based on the total weight of the anisotropic diffusion layer.

7. The optical film of claim 1, wherein the second dispersion is rod-shaped with its length direction as its long axis, having an average length of 5 to 15 μm and an average diameter of 0.5 to 2.0 μm.

8. The optical film of claim 1, wherein the thickness of the anisotropic diffusion layer is 150 μm or less.

9. A polarizing plate disposed on the light emitting surface of a liquid crystal panel, comprising: Absorption polarizing film; And an optical film as described in any one of claims 1 to 8, disposed on the light emitting surface of the absorptive polarizing film.

10. A liquid crystal display device, comprising: LCD panel; And the polarizing plate as claimed in claim 9, is disposed at least on the light emitting surface of the liquid crystal panel.

11. A display device, comprising: Self-illuminating display panel; And an optical film as described in any one of claims 1 to 8, at least disposed on the light-emitting surface of the self-emissive display panel.

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