Optical film and display device including same

Abstract

The present invention relates to an optical film and, more specifically, to an optical film that can improve the left-right viewing angle of a display device, can uniformly exhibit the viewing angle improvement effect even when manufactured with a large area, and while improving the viewing angle, can improve the contrast ratio and minimize color variation without degrading front luminance characteristics.

Description

Optical film and display device including the same

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

[0002] Liquid crystal displays (LCDs) operate by emitting light from a backlight unit through a liquid crystal panel. Therefore, while the front of an LCD screen typically boasts excellent brightness and contrast ratio (CR), the side views typically exhibit poorer brightness and contrast ratios compared to the front.

[0003] To address this, attempts have been made to modify the liquid crystal panel or liquid crystal structure to increase side contrast and brightness. However, increasing side contrast and brightness inevitably reduces front contrast and brightness. Therefore, it is necessary to increase side contrast and brightness while minimizing the decrease in front contrast and brightness.

[0004] Meanwhile, methods for increasing the viewing angle include diffusing light. For example, a method has been proposed to enhance light diffusion by incorporating inorganic particles. However, spherical inorganic particles incorporated into optical films can make it difficult to secure a sufficient viewing angle. Even if they do, they can reduce brightness and have little effect in improving contrast ratio.

[0005] As another example, it has been studied that inorganic particles having an aspect ratio exceeding 1 contained in an optical film can exhibit anisotropic diffusion characteristics while increasing light diffusion properties compared to spherical inorganic particles, but it is not easy to align the long axis direction of each of the numerous inorganic particles contained inside the body of the film so that it faces a certain direction, and inorganic particles that are not uniformly aligned in a certain direction inside the film have difficulty exhibiting anisotropic diffusion properties when viewed as a whole in the optical film, even if each of them can exhibit anisotropic diffusion properties, and ultimately, there is a problem that it is difficult to secure a sufficient viewing angle.

[0006] The present invention has been devised to solve the above-described problem, 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 on a large area.

[0007] In addition, another object of the present invention is to provide an optical film that improves the viewing angle while not lowering the frontal luminance characteristics.

[0008] In order to solve the above-described problem, the present invention provides an optical film comprising an anisotropic diffusion layer including a matrix which is a first polymer, and a dispersion including a plurality of first dispersions which are second polymers and a plurality of second dispersions which are inorganic particles, each of which is dispersed such that its major axis direction is in the x-axis direction within the matrix, and wherein one of the first polymer and the second polymer has a melt viscosity measured at a predetermined temperature that is at least twice the melt viscosity of the other polymer measured at the same temperature.

[0009] According to one embodiment of the present invention, the melting viscosity of the first polymer and the second polymer may each independently be 100 to 2000 Pa·S.

[0010] Additionally, the melting viscosity of the first polymer may be more than twice that of the second polymer.

[0011] In addition, the above-mentioned diffusion layer may be formed through melt extrusion, and at least a portion of the surface of the second dispersion may be coated with a second polymer.

[0012] Additionally, the first dispersion can be randomly distributed within the cross-section of the matrix formed by the y-axis and the z-axis which are mutually perpendicular to the x-axis.

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

[0014] Additionally, the second dispersion may be contained in an amount of 2 to 10 wt% based on the total weight of the anisotropic diffusion layer.

[0015] In addition, the second dispersed body is a rod-shaped body whose length direction is the long axis direction, and may have an average length of 5 to 30 ㎛ and an average diameter of 0.5 to 2.0 ㎛.

[0016] Additionally, the toughness of the first polymer may be greater than the toughness of the second polymer.

[0017] Additionally, the anisotropic diffusion layer may have a thickness of 150 μm or less.

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

[0019] Additionally, the anisotropic diffusivity according to the following mathematical formula 1 may be 25% or more.

[0020] [Mathematical Formula 1]

[0021]

[0022]

[0023] In addition, the present invention provides a polarizing plate disposed on a light emitting surface of a liquid crystal panel, wherein the polarizing plate includes an absorbing polarizing film and an optical film according to the present invention disposed on the light emitting surface of the absorbing polarizing film.

[0024]

[0025] In addition, the present invention provides a display device including a liquid crystal panel and a polarizing plate according to the present invention arranged on at least a light emitting surface of the liquid crystal panel.

[0026]

[0027] In addition, the present invention provides a display device including a self-luminous display panel and an optical film according to the present invention disposed on at least a light-emitting surface of the self-luminous display panel.

[0028] The optical film of the present invention can improve the left-right viewing angle of a display device, and can uniformly exhibit the viewing angle improvement effect even when manufactured on a large area. Furthermore, while improving the viewing angle, it can simultaneously enhance contrast ratio without compromising frontal luminance characteristics and minimize color variation. Furthermore, it prevents the visibility of dispersions, and adverse effects such as streaking and light leakage can also be prevented. Furthermore, because it is suitable for mass production on a large area, it can be widely used as an optical component in various display devices.

[0029] Figure 1 is a perspective view of an optical film according to one embodiment of the present invention;

[0030] Figures 2 and 3 are cross-sectional schematic diagrams along the Y-Y' and X-X' boundaries of the optical film according to Figure 1.

[0031] FIG. 4 is a schematic diagram illustrating the alignment of a second dispersion dispersed in an optical film according to one embodiment of the present invention on a projection plane projected in the z-axis direction.

[0032] Figure 5 is a cross-sectional schematic diagram of a polarizing plate according to one embodiment of the present invention, and

[0033] Figure 6 is a cross-sectional schematic diagram of a liquid crystal display according to one embodiment of the present invention.

[0034] Hereinafter, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily practice the present invention. The present invention can be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, parts irrelevant to the description are omitted for clarity of description, and the same reference numerals are assigned to identical or similar components throughout the specification. Furthermore, the present invention is not limited by the size or shape of a single component shown in the drawings.

[0035]

[0036] 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).

[0037]

[0038] The above anisotropic diffusion layer (100) performs the function of anisotropically diffusing light incident on the optical film (200), and specifically, when light is incident on a plane formed by the x-axis and the y-axis, the light is diffused in the y-axis direction perpendicular to the x-axis where the long axis direction of the dispersion body is aligned, and can be emitted to the opposite surface opposite to the incident surface. The above anisotropic diffusion layer (100) includes a matrix (10) and a plurality of dispersion bodies (20) positioned within the matrix (10).

[0039]

[0040] The above matrix (10) is a body containing and supporting a dispersion (20) exhibiting anisotropic diffusion characteristics, and is formed of a first polymer. The first polymer can be used without limitation as a known polymer used as a typical optical film. The first polymer is, for example, one selected from the group consisting of 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 (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 polymers, or a mixture of two or more, or a copolymer of two or more. Can be.

[0041]

[0042] In addition, the dispersion (20) dispersed within the above-described matrix (10) is described. The dispersion (20) includes a plurality of first dispersions (21) which are second polymers and a plurality of second dispersions (22) which are inorganic particles. Each of the first dispersions (21) and the second dispersions (22) has an elongated shape in one direction, and the longitudinal direction of each of the first dispersions (21) and the second dispersions (22) is arranged in the x-axis direction among the x-axis, y-axis, and z-axis which are mutually perpendicular to each other within the matrix (10), thereby exhibiting anisotropic diffusion properties.

[0043]

[0044] First, the first dispersion (21) is formed of the second polymer and may have a shape such as a long rod or fiber in one direction. Accordingly, the average aspect ratio, which is the ratio (a / b) between the average length (a) of the major axis in the longitudinal direction of the first dispersion (21) and the average length (b) of the minor axis perpendicular to the major axis in the cross-section perpendicular to the TD direction of the optical film, may be greater than 100, or, for example, greater than 1,000, greater than 10,000, or greater than 100,000. The average length (b) of the minor axis refers to the diameter of the circle when the cross-section is a circle, and refers to the length of the longest line segment among two line segments connecting the circumference when the cross-section is not a circle. In addition, the cross-sectional shape of the first dispersion (21) based on the cross-section plane, which is the yz plane of the anisotropic diffusion layer (100), may be circular or elliptical. At this time, when the cross-sectional shape of the first dispersion body (21) is elliptical, the cross-sectional average aspect ratio (c / d), which is the ratio of the major axis length (c) and minor axis length (d) of the ellipse, may be greater than 1 and less than or equal to 350. The minor axis length (d) refers to 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 first dispersion body (21) is elliptical and the cross-sectional average aspect ratio exceeds 350, this may indirectly mean that the alignment of the major axis directions of a plurality of second dispersion bodies (22) to be in the x-axis direction is reduced, or that fusion has occurred between the second polymers forming the first dispersion body, and in this case, it may not be easy to achieve the effect intended by the present invention.

[0045]

[0046] In addition, the second polymer forming the first dispersion (21) can be used without limitation as a known polymer used as a conventional optical film. For example, the second polymer may be one or a mixture of two or more, or a copolymer of two or more, of 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 (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.

[0047]

[0048] In addition, the first dispersion (21) is contained in a plurality of pieces in the matrix (10), and for example, the first dispersion (21) has a unit area (1 μm) in the yz cross-section of the matrix (10). 2 ) can contain 10 to 200 units.

[0049]

[0050] In addition, a plurality of first dispersion bodies (21) are arranged in the matrix (10) such that the x-axis direction among the three mutually perpendicular x-axis, y-axis, and z-axis in the matrix (10) becomes the long-axis direction. However, the arrangement here such that the x-axis direction becomes the long-axis direction of the first dispersion bodies (21) does not mean that the long-axis direction of all the first dispersion bodies (21) is arranged to be parallel to the x-axis, but means that the direction of the main axis that becomes the long-axis direction of the first dispersion bodies (21) is closer to the x-axis direction than the y-axis or z-axis, and the angle formed between the long-axis direction of each first dispersion body (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] In addition, a plurality of first dispersion bodies (21) can be randomly arranged based on the 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 first dispersion bodies (21) are randomly arranged in the yz cross-section regardless of the cross-sectional size and shape of the dispersion bodies.

[0052]

[0053] In addition, the first polymer forming the above-described matrix (10) and the second polymer forming the first dispersion (21) may satisfy that the melt viscosity of one of the two polymers measured at a predetermined temperature is at least twice the melt viscosity of the other polymer, preferably at least three times, for example, at most five times, and preferably at most four times. There are several types of known polymers known to form optical films, but depending on the combination of the polymer forming the matrix and the polymer forming the dispersion among several known polymers, the formation of the first dispersion (21) in the matrix (10) may not be proper, or even if formed, dispersion may be difficult, making it difficult to realize the morphology of the intended anisotropic diffusion layer (100). In addition, the longitudinal alignment of the second dispersion (22) contained in the anisotropic diffusion layer (100) may vary greatly depending on how the first polymer and the second polymer are combined. That is, even if a combination of a first polymer and a second polymer enables the formation and dispersion of a first dispersion (21) in the matrix (10) described above and the longitudinal direction of the first dispersion (21) is aligned with the x-axis direction of the matrix (10), there is a concern that the longitudinal direction of the second dispersion (22) may not be aligned with the x-axis direction of the matrix (10).

[0054] The inventor of the present invention has found, through continuous research on this point, that the morphology implementation of the matrix (10) / first dispersion (21) determined by the formability and dispersibility of the first dispersion (21) formed of the second polymer within the matrix (10) formed of the first polymer can be smoothly achieved, and at the same time, the alignment in which the long axis direction of the second dispersion (22) is aligned in the x-axis direction of the matrix (10) and the alignment uniformity among a plurality of second dispersions (22) can be improved, that is, when the melt viscosity of the first polymer and the second polymer at a predetermined temperature satisfies that the melt viscosity of one of the two polymers is at least twice that of the other polymer, the morphology implementation of the first dispersion (21) within the matrix (10) and the alignment and alignment uniformity of the second dispersion (22) can be improved. Here, the predetermined temperature means any temperature between the temperature at which the first polymer and the second polymer begin to melt and the temperature range at which they are completely melted. Specifically, the predetermined temperature may be a specific temperature within a temperature range between spinodal and binodal in the first polymer and the second polymer, which exhibit UCST (upper critical solution temperature) behavior during melt blending. If the melt viscosity of either polymer at the predetermined temperature between the first polymer and the second polymer is less than twice that of the other polymer, the morphology of the first dispersion and the dispersion of the formed first dispersion may not be smooth, and there is a concern that the alignment and alignment uniformity of the second dispersion may deteriorate.

[0055]

[0056] In addition, preferably, the melt viscosity of the first polymer forming the matrix (10) among the first polymer and the second polymer may be at least twice that of the second polymer, and through this, the second polymer may act as a buffer between the matrix (10) and the second dispersion (22), which is an inorganic particle, during the stretching process, particularly during stretching in the TD direction, and this may be more advantageous in preventing voids from occurring at the interface between different materials. If the melt viscosity of the second polymer is at least twice that of the first polymer, voids may occur more frequently, and there is a concern that the difference in refractive index between the formed void and the matrix (10), the first dispersion (21), and / or the second dispersion (22) forming the interface may increase, thereby lowering anisotropy.

[0057]

[0058] In addition, 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 independently be 100 Pa˙S or more, more preferably 200 Pa˙S or more, and as another example, 2,000 Pa˙S or less, through which a morphology may be easily formed and dispersed in the matrix (10) of the first polymer, and it may be advantageous to orient the major axis direction of the second dispersion (22) in the x-axis direction, which is the same direction as the major axis direction of the first dispersion (21), through the guide of the second polymer extending in a specific direction, specifically, in the x-axis. If the melt viscosity of either of the first polymer and the second polymer is less than 100 Pa˙S, it may be difficult to realize the desired morphology composed of the matrix and the dispersion. In addition, if the melt viscosity of either the first polymer or the second polymer exceeds 2,000 Pa˙S, the alignment and alignment uniformity of the second dispersion may decrease, and it may be difficult for melt dispersion behavior between the two polymers to occur, so the designed morphology may not be implemented.

[0059]

[0060] In addition, the toughness of the first polymer may be greater than the toughness of the second polymer, thereby enabling stretching in the TD direction as well as the MD direction, and by stretching in the TD direction, the shape of the first dispersion (21) can be implemented as a lens shape in the matrix yz cross-section, which is advantageous for further improving the anisotropic diffusion property. If the toughness of the first polymer is less than the toughness of the second polymer, stretching in the TD direction is impossible and stretching can only be done in the MD direction, which may make it difficult to achieve improved anisotropic diffusion property. Here, the toughness is a toughness of the material against destruction, and is a value measured as the energy per volume applied until the film is broken using a tensile strength tester for a specimen formed into a film. In addition to cases where the stress until the film is broken is large, a material with a large amount of deformation until the film is broken and a large amount of absorbed energy can be considered a material with strong toughness.

[0061]

[0062] In addition, the first polymer and the second polymer forming the matrix (10) and the first dispersion (21) of the anisotropic diffusion layer (100) may be contained in a weight ratio of 6 to 9: 4 to 1, more preferably 7 to 9: 3 to 1. If the second polymer is contained in a weight ratio of less than 1 / 10 of 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 may be excessively reduced, and as a result, it may be difficult to exhibit sufficient anisotropic diffusion properties together with the second dispersion, and it may be difficult to serve as a guide for aligning the long axis direction of the second dispersion, so the alignment properties of the second dispersion may be reduced, and there is a concern that the anisotropic diffusion properties may be further reduced. In addition, if the second polymer is included in a weight ratio exceeding 4 / 10 of the total weight of the first polymer and the second polymer, the number and cross-sectional diameter of the first dispersion may increase, which may make it difficult to achieve sufficient frontal brightness, and the randomness of the alignment direction of the second dispersion dispersed in the first dispersion may increase, making it difficult to sufficiently improve the alignment of the second dispersion despite stretching.

[0063]

[0064] Next, the second dispersed particle (22) will be described.

[0065] The above second dispersion body (22) performs the function of expressing anisotropic diffusion properties together with the above-described first dispersion body (21). For this purpose, the second dispersion body (22) may have a rod-shaped shape, and preferably, the average aspect ratio may be 4 or more, more preferably, 8 or more, through which excellent anisotropic diffusion properties may be expressed. If the average aspect ratio is less than 4, there is a concern that the anisotropic diffusion properties may be difficult to express or insufficient. However, as another example, the second dispersion body (22) may have an average aspect ratio of 15 or less. In order for the average aspect ratio of the second dispersion to exceed 15, the average aspect ratio of the second dispersion fed into the extruder must be much larger than 15, considering that the second dispersion may be broken during the mixing process before melt extrusion. However, the larger the aspect ratio of the inorganic particles fed, the more irregular the degree of breaking during the mixing and melt extrusion processes. Therefore, it is difficult for the average aspect ratio to exceed 15. Due to the irregular breaking, the number of second dispersions having an aspect ratio of less than 5 may increase, which may reduce anisotropic diffusion. Here, the average aspect ratio of the second dispersion is the ratio (e / f) between the average length (e) of the second dispersion in the major axis direction and the average diameter (f) of the cross-section perpendicular to the major axis direction, and here, the diameter of any one second dispersion means the longest length among the line segments crossing the cross-section perpendicular to the major axis direction.

[0066] In addition, the second dispersion (22) may be a rod-shaped body with the longitudinal direction as the long axis having the above-described aspect ratio, and specifically, the average length may be 5 to 30 ㎛, more preferably 5 to 15 ㎛, and the average diameter may be 0.5 to 2.0 ㎛, more preferably 0.5 to 1.5 ㎛, through which improved anisotropic diffusion properties may be exhibited. If the average length and average diameter of the second dispersion are outside the above-described range, the improvement in anisotropic diffusion properties may be minimal, and since the probability that the second dispersion will be recognized as a foreign substance in the melt extrusion process and filtered out increases, there is a concern that the content of the second dispersion contained in the final product may be low compared to the second dispersion that was introduced. In addition, if the average diameter exceeds 2.0 ㎛, it may be recognized as a foreign substance by the naked eye, which may significantly reduce the visibility of the image being implemented.

[0067] In addition, the second dispersion (22) can be used without limitation as long as it is a known inorganic particle employed in an optical film. For example, the inorganic particle may contain at least one 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, imogolite, silicon carbide, and silicon oxide, and an example thereof may be calcium carbonate.

[0068] In addition, the second dispersion (22) may be contained in an amount of 2 to 10 wt% based on the total weight of the anisotropic diffusion layer (100). If the second dispersion is contained in an amount less than 2 wt% based on the total weight of the anisotropic diffusion layer, it may be difficult to achieve sufficient anisotropic diffusion, and if it is contained in an amount exceeding 10 wt%, there is a concern that turbidity may increase, thereby lowering the frontal light transmittance.

[0069]

[0070] Referring to FIG. 4, according to one embodiment of the present invention, when the second dispersion (22) dispersed in the matrix (10) is projected in the z-axis direction of the matrix, the number of second dispersions (22) in which the angle (θ) formed by the x-axis direction and the long axis direction (ℓ1, ℓ2) of the second dispersion (22) is within ±5° on the projection plane (S), which is a plane formed by the x-axis and the y-axis, may be 75% or more of the total number of second dispersions (22), and more preferably 80% or more, and thereby may be advantageous in achieving the desired anisotropic diffusion property. If the number of second dispersers (22) in which the angle (θ) formed by the x-axis direction and the long axis direction (ℓ1, ℓ2) of the second disperser (22) on the projection surface (S) is within ±5° is less than 75% of the total number of second dispersers (22), it may be insufficient to achieve sufficient anisotropic diffusion.

[0071]

[0072] 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 turbidity may increase due to the increase in the content of the second dispersion composed of inorganic particles, resulting in a significant decrease in frontal transmittance.

[0073]

[0074] In addition, 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 against external factors. In addition, preferably, the skin layer (110) may be formed integrally with the optical layer by co-extrusion without a separate adhesive layer. As a result, not only can the deterioration of optical properties due to the adhesive layer be prevented, but it is also advantageous in realizing a thinner optical film.

[0075] In addition, the skin layer (110) included in one embodiment of the present invention may be stretched in at least one axial direction since it is co-extruded simultaneously with the anisotropic diffusion layer (100) and then subjected to a stretching process. Through this, the surface hardness is improved compared to the unstretched skin layer, thereby improving scratch resistance and heat resistance.

[0076] The above skin layer (110) may be a material of a skin layer commonly used to perform the support function of the optical film (200), and preferably, polyethylene naphthalate (PEN), co-polyethylene naphthalate (co-PEN), polyethylene terephthalate (PET), polycarbonate (PC), polycarbonate (PC) alloy, polystyrene (PS), heat-resistant polystyrene (PS), polymethyl methacrylate (PMMA), polybutylene terephthalate (PBT), polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polyurethane (PU), polyimide (PI), polyvinyl chloride (PVC), styrene acrylonitrile blend (SAN), ethylene vinyl acetate (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP), urea (UF), melanin (MF), unsaturated polyester (UP), silicone (SI), and Cycloolefin polymers can be used alone or in combination, and more preferably, the same material as the component of the matrix (10) described above can be used.

[0077] In addition, the thickness of the skin layer (110) may be 5 to 30 μm, more preferably 10 to 15 μm, thereby minimizing a decrease in brightness through the skin layer (110) and minimizing a change in the wavelength of polarized light due to a phase difference caused by birefringence.

[0078]

[0079] In addition, the optical film (200) may have an anisotropic diffusivity of 25% or more according to the following mathematical formula 1, more preferably 26.3% or more, even more preferably 27% or more, and as another example, 30% or less. If the anisotropic diffusivity is 25% or less, it may not be preferable in terms of achieving the purpose of the present invention, such as improving the viewing angle when employed in a display.

[0080] [Mathematical Formula 1]

[0081]

[0082] Meanwhile, the normal and lateral luminance for the main surface measured in mathematical expression 1 can be measured by a luminance measurement method known in the art, and the present invention is not particularly limited to a specific method when the normal and lateral directions are measured by the same specific method.

[0083]

[0084] The optical film (200) described above, particularly the anisotropic diffusion layer, can be manufactured through melt extrusion, one of several methods for manufacturing films. Specifically, it can be manufactured through (1) a step of extruding and solidifying a first polymer for forming a matrix (10), a second polymer for forming a first dispersion (21) among dispersions (20), and inorganic particles as the second dispersion (22) through an extrusion unit to manufacture a film before stretching, and (2) a step of stretching the film before stretching.

[0085]

[0086] First, as step (1), a step of manufacturing a pre-stretching film by extruding and solidifying through an extrusion unit is performed.

[0087] (1) The step may be performed by a device and method for manufacturing a film before stretching, and specifically, 1-1) a step of supplying a first polymer for forming a matrix (10), a second polymer for forming a first dispersion (21) among dispersions (20), and inorganic particles as the second dispersion (22) to an extrusion unit may be performed. At this time, each of the supplied components may be mixed and then supplied to a single extrusion unit, or each component may be individually supplied to independent extrusion units.

[0088] In order to make the orientation of the inorganic particles in the anisotropic diffusion layer (100) preferably high and uniform, the inorganic particles may be in a composite chip state mixed with the second polymer before being fed into the extrusion unit, and by being fed into the extrusion unit in the composite chip state, the orientation guide of the inorganic particles through the second polymer can be induced. In addition, when the first polymer chip and the composite chip are supplied to a single extrusion unit, a sufficient stirring process may be performed before being supplied to the extrusion unit in order to induce uniform dispersion, and through this, it may be advantageous to uniformly disperse the dispersions (20) in the anisotropic diffusion layer (100) while uniformly implementing the size in the z-axis direction within the cross-section of the first dispersion (21) in the yz cross-section of the matrix.

[0089] Meanwhile, in a composite chip state, the dispersion and orientation induction of inorganic particles through the second polymer are specifically explained. Inorganic particles in the composite chip can be confined within the second polymer by preventing them from moving toward the first polymer beyond 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 a molten state, thereby increasing the dispersibility of the inorganic particles within the matrix and preventing secondary aggregation. In addition, the second polymer in the molten first polymer is separated to form a plurality of first dispersions, and each of the first dispersions is elongated in the x-axis direction, which becomes the MD direction, within the first polymer in a molten state after extrusion, and inorganic particles trapped in the first dispersion are oriented along the elongated first dispersion during the process of the first dispersion being elongated, so that the inorganic particles serve as a guide to orient and align them in the x-axis direction, which becomes the MD direction, in the same direction as the orientation and alignment of the first dispersion, and the alignment and uniformity of the inorganic particles can be improved despite being melt-extruded.

[0090]

[0091] However, even if the composite chip containing the second polymer and the inorganic particles is injected into the extrusion section together with the first polymer, it is not always easy to align the major axis direction of the inorganic particles in the x-axis direction. That is, as described above, when the melt viscosity of either the second polymer or the first polymer is more than twice that of the other polymer, and preferably, when the melt viscosity of the second polymer is lower than that of the first polymer, the inorganic particles in the molten second polymer can be more easily aligned in the major axis direction in the x-axis direction, which is the MD direction in which the second polymer is extruded, while increasing the dispersibility thereof in the first polymer. In addition, through the stretching process described below, the major axis direction of the inorganic particles is aligned closer to the orientation direction of the first dispersion, which is the second polymer, and it may be advantageous to align the alignment directions of the respective inorganic particles more uniformly. If the inorganic particles are introduced in the form of a composite chip mixed with the first polymer forming a matrix other than the second polymer, or if they are introduced into the mixing, stirring and extrusion section alone together with the first polymer and the second polymer without forming a composite chip, and the melt viscosity conditions between the first polymer and the second polymer or the melt viscosity conditions of the desired polymers are satisfied and / or the stretching process described below is performed, it may be difficult to achieve the dispersibility, orientation and orientation uniformity of the second dispersion which is the inorganic particles or the degree of achievement may not be sufficient.

[0092]

[0093] Meanwhile, as described above, the inorganic particles trapped in the first dispersion dispersed inside the first polymer melted after extrusion are aligned in a direction such that the longitudinal direction becomes the x-axis direction as the first dispersion is elongated in the x-axis direction, which is the MD direction. Then, in the stretching process described later, as the length of the first dispersion becomes longer and the diameter becomes relatively smaller, the diameter of the first dispersion becomes smaller than the diameter of the second dispersion, which is the inorganic particle, and ultimately, the first dispersion surrounding the inorganic particles is peeled off from the inorganic particles, so that the first dispersion (21) is cut in the longitudinal direction at the portion where the inorganic particles are arranged, and the inorganic particles can be located outside the first dispersion (21). Depending on the morphological change that occurs during this process, a part or all of the surface of the second dispersion (22), which is an inorganic particle, may be coated with a second polymer derived from the first dispersion (21), and the coating of the second polymer on the surface of the second dispersion (22) may be a technical feature that indirectly proves that it is a melt-extruded film. In addition, the second polymer coated on the surface of the second dispersion (22) may function as a buffer that buffers the formation of voids that may occur at the interface between the first polymer forming the matrix and the inorganic particles, which are the second dispersion, and thus may be useful in reducing voids in the implemented anisotropic diffusion layer. Furthermore, the skin layer and the anisotropic diffusion layer may be formed integrally without an adhesive or bonding layer being included between them, and this technical feature may also be a feature that indirectly proves that it is a melt-extruded film.

[0094]

[0095] In addition, the extrusion unit described above may be a known extruder, and may further include a heating means, etc. to convert the supplied polymer components in a solid phase into a liquid phase. In addition, the size control of the first dispersion described above and the uniform dispersibility of the first dispersion and the second dispersion can be primarily achieved through the process control of step (1), and specifically, the size of the first dispersion or the dispersibility of the first dispersion and the second 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, or by changing the extruder rotation speed and the type of extruder (single, coaxial twin, etc.) involved in the extrusion output and shear stress.

[0096]

[0097] In addition, in step (1), the skin layer forming component may be fed into the extrusion unit so that the skin layer (110) disposed on at least one side of the anisotropic diffusion layer (100) is extruded together. For example, the skin layer may be extruded through separate, different extrusion units to the upper and / or lower portions of the anisotropic diffusion layer (100) to implement the skin layer (110), or when one extrusion unit is used, the melt forming the anisotropic diffusion layer (100) may be flowed to the central region through different 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 the T-DIE, thereby implementing a three-layer optical film in one extrusion unit. Regardless of whether one extrusion unit or multiple extrusion units are used, the skin layer co-extruded 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, 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 matrix. Furthermore, it is desirable to design the skin layer to an appropriate thickness to prevent luminance reduction due to total reflection.

[0098]

[0099] Next, in step 1-2), a step of inducing spreading in a flow control unit is performed so that the dispersions (20) included within the matrix (10) can be randomly arranged. The flow control unit can utilize a known flow control unit, and for example, a coat-hanger die can be used. Through the induction of spreading through the flow control unit in step (2), it is possible to secondarily further control the size of the first dispersion (21) or the dispersibility of the first dispersion (21) and the second dispersion (22).

[0100]

[0101] Next, a cooling and smoothing step can be performed as step 1-3) of the present invention. The step of cooling and smoothing the film conveyed from the flow control unit can be performed by cooling and solidifying under conditions used in the production of a conventional optical film, and then adopting and modifying the smoothing step. For example, the cooling and smoothing process can be performed on a casting roll. Preferably, one side of the sheet conveyed through the flow control unit is cooled by contacting the main cooling roll. At this time, the temperature of the main cooling roll can be 40°C or lower, more preferably 35°C or lower, and as another example, 20°C or lower. If the temperature of the main cooling roll exceeds 40°C, there is a concern that the haze may significantly increase due to the formation of spherulites due to the crystallization of the first polymer of the matrix or the second polymer of the first dispersion, and a size difference is likely to be induced between the first dispersions (21) arranged in different regions in the thickness direction of the anisotropic diffusion layer (100). This occurs due to the bonding between the first dispersions dispersed in a molten state, which may cause the size of the solidified first dispersion to increase, or the first dispersion of the bonded lumps to spread in the left-right direction, that is, in the y-axis direction of the matrix, thereby reducing the thickness. In addition, the ratio of the matrix modified into a third material by a chemical reaction at the interface between the first dispersion and the matrix may increase, thereby significantly increasing the area percentage of the first dispersion. In addition, it is more preferable to cool the opposite side that does not contact the cooling roll 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.

[0102]

[0103] Next, as step (2) of the present invention, a step of stretching the cooled and smoothed anisotropic diffusion layer can be performed. The stretching can be performed by employing and modifying the device and process conditions employed in the optical film, but preferably, in order for the major axis direction of the second dispersion (22) to be more easily and uniformly aligned in the x-axis direction of the matrix (10), the stretching may be performed 2 to 6 times in the x-axis direction, which is the MD direction, and 2 to 6 times in the y-axis direction, which is the TD direction. If the major axis direction of the second dispersion is uniaxially stretched only in the x-axis direction or biaxially stretched, if the above conditions are not satisfied, it may be difficult to improve the alignment and alignment uniformity of the major axis direction of the second dispersion in the x-axis direction of the matrix. In addition, the stretching temperature may be performed at a temperature that is 10 to 20°C higher than the larger glass transition temperature among the glass transition temperatures of the first polymer and the second polymer, respectively. If the temperature during stretching is lower than the larger glass transition temperature of the first polymer and the second polymer by 10℃, stretching may not occur or may cause breakage. In addition, if stretching is performed at a temperature higher than the larger glass transition temperature of the first polymer and the second polymer by 20℃, or if the residence time is excessively long even at an appropriate temperature, stretching uniformity may deteriorate, and there is a concern that the alignment uniformity of the second dispersion may also deteriorate.

[0104]

[0105] Additionally, the stretched optical film can undergo a heat-setting step. 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.

[0106]

[0107] Referring to FIGS. 5 and 6, an optical film (200) according to an 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 arranged on the light exit surface of a liquid crystal panel (5000). Specifically, the polarizing plate (4000) includes an absorbing polarizing film (2000) and an optical film (200) arranged on the light exit surface of the absorbing polarizing film (2000), and when arranged on the light exit surface of the absorbing polarizer (2100) of the upper polarizing plate, there is an advantage in that the contrast ratio is significantly improved by internal light, the viewing angle is increased, and excellent brightness characteristics can be achieved.

[0108] The above-mentioned absorption polarizing film (2000) is a polarizer that transmits the first polarization (or the second polarization) and absorbs the second polarization (or the first polarization) among the first and second polarizations having mutually orthogonal vibration planes, and has a known polarizing layer (2100) having such an optical function. The polarizing layer (2100) may be, for example, a base film such as polyvinyl alcohol dyed with an iodine-based component or a dichroic dye. In addition, the iodine-based component, which is one of the dyes dyed to the base film, may be an iodine-based compound such as iodine and / or potassium iodide. In addition, the above dichroic dye has a large absorbance in a wide range of wavelengths in the long-axis direction of the molecule, and has an extremely small absorbance in the short-axis direction, but has good affinity for the film to be used as a substrate, can dye even the crystal region, is easy to orient together with the substrate when it is stretched, and is known to have a vivid color and a large visual contrast. Therefore, the present invention is not particularly limited thereto, and a specific description thereof is omitted.

[0109] The above polarizing layer (2100) may have a thickness of, for example, 10 to 200 μm, but is not limited thereto and may be changed according to the purpose.

[0110] In addition, the above-described absorption polarizing film (2000) may have a protective film (2210) on one or both sides to support and protect the polarizing layer (2100). The protective film (2210) may be any protective film used in a typical absorption polarizing film without limitation, and a polymer having excellent transparency, mechanical strength, thermal stability, or moisture shielding properties may be preferably employed. The protective film (2210) may be, for example, an acetate-based resin such as triacetyl cellulose (TAC), a polyester-based resin, a polyethersulfone-based resin, a polycarbonate-based resin, a polyamide-based resin, a polyimide-based resin, a polyolefin-based resin, an acrylic resin, a polynorbornene-based resin, or the like. For example, the protective film may be a triacetyl cellulose (TAC) film in consideration of optical properties. Or, in terms of heat resistance and moisture resistance, it may be a polyester film, specifically, a polyethylene terephthalate film. The polyethylene terephthalate film may have an in-plane retardation 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. In addition, referring to FIG. 6, a protective film such as a TAC film that is typically disposed on top of the polarizing layer (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 disposed on top of the polarizing layer (2100).

[0111]

[0112] In addition, the interface between the above-described absorption polarizer (2000) and the optical film (200) may be integrally bonded by interposing a separate adhesive layer (not shown). The adhesive layer is used for attachment between optical films and may be implemented using a known adhesive component that does not deteriorate optical properties. For example, it may be formed as an adhesive using only an adhesive component including a vinyl alcohol-based polymer or a combination of the adhesive component and at least one water-soluble crosslinking agent of a vinyl alcohol-based polymer, such as boric acid, borax, glutaraldehyde, melamine, or oxalic acid. In addition, the adhesive may be mixed with other additives or a catalyst such as an acid.

[0113]

[0114] In addition, the polarizing plate (4000) may further include a functional layer (3000) on the optical film (200). The functional layer (3000) 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. In addition, the functional layer (3000) may be implemented by laminating multiple layers to exhibit a complex function. The thickness of the functional layer (3000) may be appropriately changed in consideration of the type of functional layer provided and the number of laminations, and therefore the present invention is not particularly limited thereto.

[0115]

[0116] In addition, as illustrated in FIG. 6, a polarizing plate (4000) according to an embodiment of the present invention may be implemented as a liquid crystal display (8000) that is disposed on the light-emitting surface of the polarizing plate (4000) that is disposed above the liquid crystal panel (5000), i.e., adjacent to the viewing side of the liquid crystal display (8000), facing the backlight unit (7000) disposed below the liquid crystal panel (5000).

[0117] Specifically, the liquid crystal display (8000) can be implemented by arranging in the following order: 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 an embodiment of the present invention as an upper polarizing plate.

[0118] The above backlight unit (7000) may be employed in a typical 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, for example.

[0119] In addition, the liquid crystal panel (5000) includes a liquid crystal layer (5100) and a support plate (5210, 5220) supporting the upper and lower portions of the liquid crystal layer (5100), and may further include known configurations such as electrode lines. In addition, the liquid crystal panel (5000) may employ, but is not limited to, a VA (vertical alignment) mode, an IPS mode, a PVA (patterned vertical alignment) mode, or an S-PVA (super-patterned vertical alignment) mode.

[0120]

[0121] In addition, an optical film (200) according to one embodiment of the present invention may be placed on the light-emitting surface of a self-luminous display panel to implement a self-luminous display device. The self-luminous display panel may be a panel employed in a known self-luminous display, such as a plasma display panel (PDP) or an OLED panel, and the present invention is not particularly limited thereto.

[0122]

[0123] Meanwhile, while the present invention has been described using liquid crystal displays and self-luminous displays as examples of applications for optical films, the present invention is not limited thereto and can be widely used in various known display technologies such as projection displays and field emission displays. In addition to display technologies, the present invention can be widely applied to various light sources such as glass windows and task lighting requiring polarization.

[0124] The present invention will be described in more detail through the following examples, but the following examples do not limit the scope of the present invention, and should be interpreted as helping to understand the present invention.

[0125]

[0126] <Example 1>

[0127] As a first polymer for implementing a matrix, polyethylene naphthalate (PEN) was prepared, and as a second polymer for implementing a first dispersion, a polycarbonate alloy containing 38 wt% polycyclohexylene dimethylene terephthalate (PCTG) polymerized with a 1:2 molar ratio of terephthalate, ethyl glycol, and cyclohexanedimethanol, 60 wt% polycarbonate, and 2 wt% of a heat stabilizer containing phosphate was prepared, and calcium carbonate having an average length of 25 μm and an average diameter of 1.3 μm was prepared as inorganic particles that serve as a second dispersion. The inorganic particles were mixed with the prepared second polymer and fed into an extruder to manufacture a composite chip in which the inorganic particles were dispersed in the second polymer. After that, the manufactured composite chip and the first polymer were mixed and fed into the first extrusion unit. The weight ratio of the first polymer and the second polymer was 8:2 at the time of feeding, and the content of the inorganic particles among the total weight of the mixture fed into the first extrusion unit was 5.0 wt%. In addition, in order to produce a skin layer, the first polymer was fed into the second extrusion unit. The second extrusion unit was manufactured using a flow path so that the skin layer was arranged on the upper and lower parts of the matrix with the same thickness. Meanwhile, the prepared first polymer and second polymer had melt viscosities of 1600 Pa·S and 500 Pa·S, respectively, at an extrusion temperature of 260°C in the extrusion unit described below.

[0128] At this time, the extrusion temperature of the first extrusion part was set to 260℃, and the polymer flow was corrected so that the melt viscosity ratio of the two components was 3.2 by checking with a Cap.Rheometer, and the first dispersion formed from the second polymer was dispersed inside the matrix formed from the first polymer by passing through a path applied with a Filteration Mixer, and then the first polymer flow forming a skin layer on both sides of the matrix was combined. After that, the polymer was spread in a coat hanger die that corrects the flow rate and pressure gradient to induce random dispersion of the first dispersion. Specifically, the die inlet had a width of 200 mm and a thickness of 10 mm, the die outlet had a width of 1,260 mm and a thickness of 0.75 mm, and the flow rate was 1.0 m / min. After that, a smoothing process was performed on a cooling and casting roll, and the stretching was performed 5 times in the MD direction and 4 times in the TD direction. Then, heat fixation was performed through a heater chamber at 180°C for 2 minutes to manufacture an optical film having a matrix thickness of 60 μm, a skin layer having a thickness of 30.25 μm on both sides of the main surface of the matrix, a total thickness of 125 μm, and a longitudinal direction of each of the first dispersion and the second dispersion as in FIG. 2 aligned in the x-axis direction of the matrix, an average aspect ratio of the first dispersion in the x-axis direction of the matrix exceeding 100, an average length of the second dispersion of 5.6 μm, an average diameter of 1.3 μm, an average aspect ratio of 4.3, and an anisotropic diffusion layer in which the first dispersion having an average aspect ratio of 200 is randomly dispersed on the yz cross-section of the matrix, as shown in Table 1 below.

[0129]

[0130] <Examples 2 to 5>

[0131] An optical film was manufactured in the same manner as in Example 1, but the types / contents 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 chip were changed as shown in Table 1 below, thereby manufacturing an optical film as shown in Table 1 below.

[0132] At this time, in Examples 2 to 4 and Example 6, the extrusion temperature in the extrusion section was changed to 280°C, and the melting viscosity of the first polymer and the second polymer in Table 1 is the melting viscosity at 280°C.

[0133]

[0134] <Comparative Example 1>

[0135] An optical film was manufactured in the same manner as Example 2, but the type of the second polymer was changed as shown in Table 1 below, thereby manufacturing an optical film as shown in Table 1 below.

[0136]

[0137] Comparative Example 2

[0138] The same process as Example 1 was performed to manufacture the film, but the ratio of the first polymer and the second polymer was changed without including the second dispersion, which is an inorganic particle, as shown in Table 1 below, and stretching in the TD direction was omitted during stretching, thereby manufacturing an optical film as shown in Table 1 below.

[0139]

[0140] <Comparative Example 3>

[0141] An optical film was manufactured in the same manner as in Example 1, but the second polymer was not included and stretching in the TD direction was omitted during stretching, as shown in Table 1 below, to manufacture the optical film as shown in Table 1 below.

[0142]

[0143] <Experimental Example>

[0144] The following physical properties were evaluated for optical films according to examples and comparative examples, and the results are shown in Table 1 below.

[0145]

[0146] 1. Evaluation of the alignment of the second dispersion

[0147] As shown in Fig. 4, the angle formed by the longitudinal direction of the second dispersion and the x-axis direction of the matrix was measured. Specifically, the skin layer of the optical film was peeled off, the surface was treated with plasma at 500 W for 10 minutes, and the specimen was photographed using a scanning electron microscope (SEM). In the photographed image, the ratio of the number of second dispersions within a range of ±5° with respect to the x-axis direction was calculated.

[0148]

[0149] 2. Size evaluation of the second dispersed body

[0150] After filtering the sample obtained by dissolving the anisotropic diffusion layer of the optical film in HFIP solvent using a 5-micron CN filter, the length and diameter were measured using SEM, and the average length, average diameter, and average aspect ratio were calculated from this.

[0151]

[0152] 3. Evaluation of heterogeneous diffusion

[0153] Hard coating and low-refractive coating were applied to one side of an optical film. The prepared optical film was laminated to the upper side of an absorption polarizer, and a polarizing plate equipped with a TAC (triacetate cellulose) film on the lower side of the absorption polarizer was manufactured. The manufactured polarizing plate was replaced with the upper polarizing plate of a commercially available LCD liquid crystal panel, and the luminance was measured in the front (90° normal to the principal plane of the optical film) and side (30° normal to the principal plane of the optical film) directions.

[0154] In addition, the anisotropic diffusivity was calculated according to mathematical formula 1, which corresponds to the percentage of lateral luminance to frontal luminance through the measured frontal and side luminance.

[0155]

[0156] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Matrix First polymer type / melt viscosity (Pa·S) PEN / 1600 PET / 650 PET / 550 PET / 550 PET / 650 PET / 550 PEN / 1600 PEN / 1600 First dispersion system Second polymer type / melt viscosity (Pa·S) PC alloy / 500 PET / 215 PET / 250 PET / 250 PET / 180 PET / 325 PC alloy / 500 Excluding Average aspect ratio 200:1 185:1 170:1 180:1 185:1 185:1 300:1 - Second dispersion system Inorganic particles TypeCalcium carbonateCalcium carbonateCalcium carbonateCalcium carbonateCalcium carbonateCalcium carbonateCalcium carbonateInorganic particle content (wt%)5.04.84.34.64.84.74.65.0Average length (e) / Average diameter (f) / Average aspect ratio (e / f)5.61.34.35.51.34.25.41.24.55.71.24.85.51.34.25.51.24.65.71.24.8-Polymer ratioContent ratio of first polymer and second polymer8:27:37:36:47:39:16:4-Melt viscosity of first polymer and second polymer 3.23.02.22.23.61.73.2-Process composite chip 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 Number ratio of second dispersion aligned within ±5° in the x-axis direction (%) 858878756152-34 Luminance Front 743nit 752nit 758nit 748nit 734nit 726nit 767nit 734nit Side (30°) 196nit 206nit 192nit 187nit 157nit 155nit 170nit 110nit Anisotropic diffusivity (%) 26.5 27.4 25.3 25.0 21.4 21.4 22.115.0

[0157] As can be seen from Table 1, Example 1, which includes both the first dispersion and the second dispersion in the matrix and has their major axis aligned in the x-axis direction of the matrix, has a synergistic effect in anisotropic diffusion, compared to Comparative Example 2, which does not contain the second dispersion, which is an inorganic particle, and Comparative Example 3, in which only the second dispersion is dispersed in the matrix without the first dispersion.

[0158]

[0159] In addition, with regard to the alignment of the second dispersion, which is an inorganic particle, as can be seen in Comparative Example 3, even when the first polymer and the inorganic particles are mixed and melt-extruded and stretched in the MD direction, the alignment degree in the longitudinal direction of the second dispersion, which is an inorganic particle, is very low without the first dispersion. In addition, in Comparative Example 3, it can be seen that the alignment degree in the longitudinal direction of the second dispersion, which is an inorganic particle, is low, and at the same time, the brightness in the front and side views is also lowered due to scattering caused by the inorganic particles.

[0160]

[0161] In addition, in the case of Comparative Example 1, where the melting viscosity ratio between the first polymer and the second polymer is less than 2.0, it can be seen that the alignment of the second dispersion is greatly reduced and the anisotropic diffusion is also greatly reduced compared to Examples 3 and 4.

[0162]

[0163] Furthermore, in the case of Example 5, where the melting viscosity of the second polymer was excessively low, it was found that the alignment of the second dispersion was lowered compared to Example 2, and thus the anisotropic diffusion was lowered and the frontal brightness was also reduced.

[0164]

[0165] Although one embodiment of the present invention has been described above, the spirit of the present invention is not limited to the embodiment presented in this specification, and a person skilled in the art who understands the spirit of the present invention will be able to easily propose other embodiments by adding, changing, deleting, or adding components within the scope of the same spirit, but this will also be considered to fall within the spirit of the present invention.

Claims

1. A first polymer matrix; and An anisotropic diffusion layer comprising a dispersion comprising a plurality of first dispersions which are second polymers and a plurality of second dispersions which are inorganic particles, each of which is dispersed such that the longitudinal direction thereof is the x-axis direction within the matrix; An optical film wherein one of the first polymer and the second polymer has a melt viscosity measured at a predetermined temperature that is at least twice the melt viscosity of the other polymer measured at the same temperature.

2. In paragraph 1, An optical film in which the melting viscosity of the first polymer and the second polymer is independently 100 to 2000 Pa·S.

3. In paragraph 1, An optical film in which the melting viscosity of the first polymer is at least twice that of the second polymer.

4. In paragraph 1, An optical film characterized in that the above-mentioned diffusion layer is formed through melt extrusion, and at least a portion of the surface of the second dispersion body is coated with a second polymer.

5. In paragraph 1, An optical film in which the first dispersion is randomly dispersed within a cross-section of a matrix consisting of a y-axis and a z-axis that are mutually perpendicular to the x-axis.

6. In paragraph 1, An optical film in which the above matrix and the first dispersed body are included in a weight ratio of 6 to 9:4 to 1.

7. In paragraph 1, An optical film in which the second dispersion is contained in an amount of 2 to 10 wt% based on the total weight of the anisotropic diffusion layer.

8. In paragraph 1, The above second dispersion is an optical film in the form of a rod whose length direction is the long axis direction, has an average length of 5 to 30 ㎛, and an average diameter of 0.5 to 2.0 ㎛.

9. In paragraph 1, An optical film characterized in that the toughness of the first polymer is greater than the toughness of the second polymer.

10. In paragraph 1, The above-mentioned anisotropic diffusion layer is an optical film having a thickness of 150㎛ or less.

11. A polarizing plate placed on the light emitting surface of the liquid crystal panel, wherein the polarizing plate is Absorption polarizing film; and A polarizing plate comprising an optical film according to any one of claims 1 to 10, which is disposed on the light emission surface of the above-mentioned absorption polarizing film.

12. Liquid crystal panel; and A liquid crystal display device comprising a polarizing plate according to claim 11, which is arranged at least on the light-emitting surface of the liquid crystal panel.

13. Self-luminous display panel; and A display device comprising an optical film according to any one of claims 1 to 10, which is arranged on at least a light-emitting surface of the self-luminous display panel.

Images