Optical film and display device comprising same

Abstract

The present invention relates to an optical film. According to an embodiment of the present invention, the optical film includes an anisotropic diffusion layer. The film is capable of: improving the left-right viewing angle of a display device; even when manufactured in a large-area form, uniformly exhibiting the effect of improving the viewing angle; improving the viewing angle while enhancing the contrast ratio and minimizing color shift without compromising front brightness; and being widely used as an optical component of various display devices due to being suitable for mass production in a large-area form at a low cost.

Description

Optical film and display device including the same

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

[0002] For display devices, such as liquid crystal displays in which light from a backlight unit is used to create images through a liquid crystal panel, or self-emissive displays in which images are created by the operation of a display panel equipped with light sources like OLEDs or LEDs, brightness and contrast ratios decrease when viewed from the side compared to the front, and color tones also fluctuate; thus, variations and degradation of physical properties depending on the viewing angle are common.

[0003] To address this, various attempts have been made to increase brightness or contrast ratio from the sides. However, increasing side brightness or contrast ratio inevitably leads to a decrease in frontal brightness or contrast ratio. Therefore, it is necessary to increase side brightness or contrast ratio while minimizing the reduction in frontal brightness or contrast ratio.

[0004] Meanwhile, light diffusion is a method to enhance the viewing angle, and to this end, a method has been proposed to increase light diffusion through particles. However, spherical particles provided in optical films make it difficult to secure a sufficient viewing angle, or even if secured, may reduce brightness, and have almost no effect on improving contrast ratio.

[0005] As another example, there have been attempts to increase the viewing angle by providing an optical film with columnar or fibrous particles having an aspect ratio exceeding 1. However, it was not easy to align the long axis direction of each particle contained within the body of the film so that it faces a specific direction. Consequently, even if each particle can exhibit anisotropic diffusion, it is difficult to achieve anisotropic diffusion when considering the optical film as a whole, and ultimately, there is a problem in that it is difficult to secure a sufficient viewing angle. To solve this problem, the applicant extruded a different type of polymer to realize an optical film in which one polymer is long and aligned in a single axial direction, but there was a problem in that the brightness was significantly reduced and the achieved viewing angle was also insufficient.

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

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

[0008] To solve the above-mentioned problem, the present invention provides an optical film having an anisotropic diffusion layer comprising a matrix formed of a crystalline polyester resin and a plurality of dispersions, each comprising a first polymer dispersion formed of an amorphous modified polyester resin having an average aspect ratio of 3.0 or more and having the long axis direction arranged in one axis direction.

[0009] According to one embodiment of the present invention, the long axis direction of the inorganic particles in the first polymer dispersion may be arranged in the one axis direction or in a direction perpendicular to the one axis direction.

[0010] In addition, the above anisotropic diffusion layer can be formed through melt extrusion.

[0011] In addition, the crystalline polyester may be polyethylene terephthalate.

[0012] In addition, the above amorphous modified polyester may be a modified polyethylene terephthalate in which a portion of the ethylene glycol is substituted with 1,4-cyclohexanedimethanol.

[0013] In addition, the modified polyethylene terephthalate may contain 30 to 65 mol% of 1,4-cyclohexanedimethanol among the diol components.

[0014] In addition, the above inorganic particles and amorphous modified polyester resin may be included in a weight ratio of 1:3 to 10.

[0015] In addition, the above-mentioned inorganic particles may be contained in an amount of 0.5 to 10 weight percent based on the total weight of the anisotropic diffusion layer.

[0016] In addition, the above inorganic particles may have an average length of 3 to 15 μm and an average diameter of 0.5 to 2.0 μm.

[0017] In addition, the modified polyethylene terephthalate may contain 45 to 60 mol% of 1,4-cyclohexanedimethanol among the diol components.

[0018] In addition, the above anisotropic diffusion layer may have a thickness of 150㎛ or less.

[0019] In addition, it may further include a skin layer integrally formed on at least one surface of the anisotropic diffusion layer.

[0020] In addition, the present invention provides a polarizing plate disposed on a light-emitting surface of a liquid crystal display panel, wherein the polarizing plate comprises an absorption polarizing film and an optical film according to the present invention disposed on a light-emitting surface of the absorption polarizing film.

[0021]

[0022] In addition, the present invention provides a display device comprising a display panel and an optical film according to the present invention disposed on a light-emitting surface of the panel.

[0023] The optical film of the present invention can improve the left and right viewing angles of a display device and can uniformly exhibit the effect of improving the viewing angle even when manufactured over a large area. In addition, while improving the viewing angle, it can prevent a decrease in frontal brightness and contrast ratio and minimize color fluctuations. Furthermore, the dispersion is prevented from being visible, and side effects such as glare lines or light leakage can also be prevented. Moreover, since it is suitable for mass production over a large area at a low cost, it can be widely used as an optical component of various display devices.

[0024] FIG. 1 is a perspective view of an optical film according to one embodiment of the present invention,

[0025] FIGS. 2 and FIGS. 3 are schematic cross-sectional views along the Y-Y' and X-X' boundaries of the optical film according to FIG. 1.

[0026] FIG. 4 is a schematic diagram illustrating the long axis direction of inorganic particles provided in an optical film according to one embodiment of the present invention,

[0027] FIG. 5 is a schematic diagram illustrating alignment on a projection plane projected in the z-axis direction of inorganic particles dispersed in an optical film according to one embodiment of the present invention.

[0028] FIG. 6 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention, and

[0029] FIG. 7 is a cross-sectional schematic diagram of a liquid crystal display according to one embodiment of the present invention.

[0030] Hereinafter, embodiments of the present invention are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the invention. The present invention may be embodied in various different forms and is not limited to the embodiments described herein. In the drawings, parts unrelated to the explanation have been omitted to clearly explain the present invention, and the same reference numerals are assigned to identical or similar components throughout the specification. Furthermore, the present invention is not limited by the size or shape of a component shown in the drawings.

[0031]

[0032] Referring to FIGS. 1 to 4, 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).

[0033]

[0034] The above anisotropic diffusion layer (100) performs the function of anisotropically diffusing light that is incident on and transmitted through the optical film (200). To this end, the above anisotropic diffusion layer (100) includes a matrix (10) formed of a crystalline polyester resin and a first polymer dispersion (24) in which at least a portion of the matrix (10) has its respective major axis aligned in a certain axial direction. Specifically, when the thickness direction of the anisotropic diffusion layer (100) among the three mutually perpendicular axes is called the z-axis, light incident on a plane consisting of the remaining x-axis and y-axis can be diffused in a direction perpendicular to the major axis direction of the inorganic particle (22) provided in the first polymer dispersion (24), mainly depending on the major axis direction of the inorganic particle (22), and can be emitted to the opposite side facing the incident surface. For example, if the direction in which the major axis of the first polymer dispersion (24) is aligned is the x-axis and the major axis of the inorganic particle (22) inside the first polymer dispersion (24) is aligned in the x-axis direction, the incident light may have anisotropic diffusion properties that diffuse in the y-axis direction. Alternatively, as described later, if the stretching ratio is increased by TD through a variation of the stretching method, the major axis of the inorganic particle (22) placed inside the first polymer dispersion (24), which has a major axis in the x-axis direction, is aligned in the y-axis direction, and the incident light may have anisotropic diffusion properties that diffuse in the x-axis direction.

[0035]

[0036] The above matrix (10) is formed of a crystalline polyester resin as a body containing and supporting a dispersion (20) comprising a first polymer dispersion (24) in which inorganic particles (22) that exhibit anisotropic diffusion characteristics are disposed inside. Here, "crystalline" may refer to a conventional and inherent structural characteristic known to be possessed by the selected polyester resin, and includes the meaning of "semicrystalline" as expressed in the art. Furthermore, the above crystalline polyester resin may be used without limitation if it is a known crystalline polyester resin used as a conventional optical film. The above crystalline polyester resin may be, for example, one or more mixtures selected from the group consisting of polyethylene naphthalate (PEN), copolyethylene naphthalate (co-PEN), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), or two or more copolymers, and preferably may be polyethylene terephthalate, which may be advantageous in increasing the TD direction elongation in the biaxial stretching film-making process.

[0037]

[0038] Additionally, a plurality of dispersed bodies (20) dispersed within a matrix (10) formed of a crystalline polyester resin include a first polymer dispersed body (24), and the first polymer dispersed body (24) is formed of an amorphous modified polyester resin containing inorganic particles (22) having an aspect ratio of 3.0 or higher. The first polymer dispersed body (24) can be divided into a region that does not contain inorganic particles (22) and a region that contains inorganic particles (22) along the long axis direction. In this case, when viewed from the perspective of the inorganic particles (22) in the region containing inorganic particles (22), the amorphous modified polyester resin becomes a coating layer (21') surrounding the inorganic particles (22), and the coating layer (21') can structurally avoid the formation of an interface that comes into direct contact between the inorganic particles (22) and the matrix (10).

[0039]

[0040] Additionally, the coating layer (21') located between the inorganic particles (22) and the matrix (10) is formed of an amorphous modified polyester resin. When the long axis direction of the inorganic particles (22) within the first polymer dispersion (24) is aligned in a single axial direction called the MD direction, it may be advantageous to prevent interfacial separation between the side of the inorganic particles (22) that is the TD direction side and the matrix (10), and thus prevent the formation of voids, when the anisotropic diffusion layer (100) or optical film (200) is stretched in the TD direction perpendicular to this. Since the amorphous modified polyester resin has little or almost no limit on flexibility due to crystals formed during stretching, it is advantageous to exhibit high flexibility compared to the crystalline polyester resin forming the matrix (10), and through this, it can function as a buffer layer between the matrix (10) and the inorganic particles (22) to prevent the formation of voids.

[0041] In addition, when the anisotropic diffusion layer is melt-extruded in the MD direction during the manufacturing process and then stretched in the TD direction at a larger magnification, the long axis direction of the inorganic particles inside the first polymer dispersion, in which the long axis direction becomes the MD direction, rotates in the TD direction. The first polymer dispersion formed of an amorphous modified polyester surrounding the inorganic particles can be advantageous for improving and making uniform the alignment of inorganic particles by facilitating the rotation of the inorganic particles in the TD direction so that the TD direction becomes the long axis direction of the inorganic particles.

[0042] If the first polymer dispersion (24) is formed of a crystalline polyester resin, it is difficult to avoid the formation of voids on the side of inorganic particles whose long axis is aligned in the MD direction when the anisotropic diffusion layer or optical film is stretched in the TD direction at a stretching ratio smaller than that in the MD direction, so there is a high risk of voids being formed at the interface between the matrix (10) and the first polymer dispersion (24), and / or at the interface between the polyester resin portion forming the first polymer dispersion (24) and the side of the inorganic particle (22). In addition, if the first polymer dispersion (24) is formed of a crystalline polyester resin, it is not easy to rotate the long axis of the inorganic particles in the TD direction when the anisotropic diffusion layer or optical film is stretched in the TD direction at a stretching ratio larger than that in the MD direction, and as a result, the ratio of inorganic particles whose long axis is aligned in the TD direction is greatly reduced, and as the alignment uniformity is also reduced, there is a high risk that the anisotropic diffusion property will be greatly reduced.

[0043] Meanwhile, the side of the inorganic particle (22) here refers to an outer surface defined as the right side or left side when the two ends of the long axis direction (l) of the inorganic particle (22) are defined as the upper surface and the lower surface, or the front and the rear surface. Meanwhile, the number of sides and the specific shape of the inorganic particle (22) can be defined according to the shape of the inorganic particle (22), so the present invention is not specifically limited thereto. For example, assuming the inorganic particle (22) is a cylinder with the long axis direction (l) as the height, the left side and the right side that become the sides may be a single continuous curved surface. Also, for example, if the inorganic particle (22) is a polyhedron, the number of left side and right side may be two or more, the surface directions between them may be the same or different, and the shape of each surface may be independently a flat surface or a curved surface.

[0044]

[0045] In addition, the first polymer dispersion (24) has a different crystal structure from the matrix (10), but both are formed from polyester resins, which is advantageous for making the difference in refractive index at the interface between the matrix (10) and the first polymer dispersion (24) small in at least two of the three mutually perpendicular axial directions. For example, between the amorphous modified polyester resin in the first polymer dispersion (24) and the matrix (10), the difference in refractive index can be independently implemented to be less than 0.1 in at least two of the three mutually perpendicular axial directions, for example, in the direction excluding the direction with a large stretching ratio during biaxial stretching in the process. Through this, it is advantageous to improve light transmission, particularly positive transmission, at the interface between the polymer portion of the first polymer dispersion (24) and the matrix (10), thereby enabling anisotropic diffusion without lowering the frontal brightness.

[0046]

[0047] The amorphous modified polyester resin forming the first polymer dispersion (24) can be used without limitation as long as it is a resin that has an amorphous nature and can be conventionally referred to as polyester. However, preferably, it may be a modified polyethylene terephthalate in which a portion of the ethylene glycol, which is a diol component, is substituted with 1,4-cyclohexanedimethanol, and through this, there is an advantage of suppressing interfacial delamination and / or peeling caused in the biaxial stretching film-making process due to incompatibility between the inorganic particles and the polymer matrix due to heterogeneous materials. In addition, the modified polyethylene terephthalate may have a portion of the ethylene glycol substituted with 1,4-cyclohexanedimethanol to a level that allows it to have an amorphous nature, and more preferably, the 1,4-cyclohexanedimethanol among the diol components may be provided in an amount of 30 to 65 mol%, and even more preferably 45 to 60 mol%. If 1,4-cyclohexanedimethanol is contained in an amount of less than 30 mol% of the diol component, compatibility with the crystalline polyester forming the matrix increases during the melt extrusion process, whereas, conversely, compatibility with inorganic particles decreases, making it difficult to prevent delamination or peeling at the interface between the inorganic particles and the polymer matrix, and there is a risk that the alignment of the inorganic particles along the long axis may decrease. In addition, if the above 1,4-cyclohexanedimethanol exceeds 65 mol%, crystallinity is exhibited, which may reduce or make it difficult to obtain the advantages associated with the use of the amorphous polyester resin described above, and the difference in refractive index with the matrix increases, which may significantly reduce the desired anisotropic diffusivity.

[0048]

[0049] Meanwhile, it should be noted that the above-mentioned amorphous modified polyethylene terephthalate may be modified with a known polyvalent aromatic carboxylic acid such as isophthalic acid or a known polyvalent aliphatic carboxylic acid such as adipic acid, for example, in an amount of 10 mol% or less of the acidic component, or 5 mol% or less of the acidic component, to the extent that the acidic component is not modified or does not hinder the achievement of the purpose of the present invention.

[0050] In addition, the modified polyethylene terephthalate may be formed by reacting an acid component, which is a polycarboxylic acid component including terephthalate as a monomer forming it, with a diol component including ethylene glycol and 1,4-cyclohexanedimethanol in a molar ratio of 1:1.0 to 1.2. In addition, the modified polyethylene terephthalate may, for example, have a weight-average molecular weight of 18,000 to 28,000.

[0051]

[0052] Additionally, the glass transition temperature of the crystalline polyester resin forming the matrix (10) may be greater than the glass transition temperature of the amorphous modified polyester resin forming the first polymer dispersion (24), and this may be advantageous for the amorphous modified polyester resin to function as a buffer layer at the process temperature of the stretching process. However, the relationship between the glass transition temperatures of the two resins is not limited to this, and for example, even if the glass transition temperature of the amorphous modified polyester resin is greater than that of the crystalline polyester resin, it may be sufficient to function as a buffer layer. However, even in this case, it is preferable that the glass transition temperature of the amorphous modified polyester resin be greater than the glass transition temperature of the crystalline polyester resin by 6°C or less, and if the glass transition temperature of the amorphous modified polyester resin is higher than the glass transition temperature of the crystalline polyester resin by more than 6°C, it may be difficult to prevent the occurrence of voids on the side of the inorganic particle (22).

[0053]

[0054] Meanwhile, the amorphous modified polyester resin forming the first polymer dispersion (24) can perform a guide function to align the long axis direction of the inorganic particles (22) located inside so that it becomes the x-axis direction or y-axis direction within the matrix (10). Specifically, when the inorganic particles (22) are extruded to be located inside the first polymer dispersion (24) during the extrusion process in the manufacturing process, the inorganic particles (22) cannot move toward the matrix (10) due to the difference in melt viscosity between the crystalline polyester resin forming the matrix (10) and the amorphous modified polyester resin forming the first polymer dispersion (24), and instead exhibit the effect of being trapped inside the first polymer dispersion (24). In this case, during the continuous extrusion process, the length of the first polymer dispersion (24) gradually increases in the x-axis direction, which is the MD direction, and the diameter decreases, and as a result, the long axis direction of the inorganic particles (22) located inside the first polymer dispersion (24) can be aligned in the MD direction. In addition, through a subsequent stretching process, when the MD direction is stretched at a greater magnification than the TD direction, the first polymer dispersion (24) is further extended in the MD direction, and as a result, the long axis direction of the inorganic particles (22) can be aligned in the MD direction, or in other words, in the x-axis direction of the matrix (10), substantially parallel to the long axis direction of the first polymer dispersion (24), and the inorganic particles (22) can be located inside the first polymer dispersion (24). Alternatively, through a subsequent stretching process, the TD direction is stretched at a greater magnification than the MD direction, causing the first polymer dispersion (24) to be stretched in the TD direction, and the long axis direction of the inorganic particles (22) is rotated from the MD direction to the TD direction. Ideally, the TD direction, or in other words, the y-axis direction of the matrix (10), can be aligned substantially perpendicular to the long axis direction of the first polymer dispersion (24), and the inorganic particles (22) can be located inside the first polymer dispersion (24).

[0055]

[0056] Meanwhile, as the first polymer dispersion (24) performs a guide function to align the long axis direction of the inorganic particle (22), if the length of the first polymer dispersion (24) becomes longer, the diameter of the portion of the first polymer dispersion (24) where the inorganic particle (22) is not located becomes smaller than the diameter of the portion of the first polymer dispersion (24) where the inorganic particle (22) is located. On the other hand, the portion of the first polymer dispersion (24) where the inorganic particle (22) is located has a diameter larger than the diameter of the inorganic particle (22) due to the inorganic particle (22), and may be larger than the diameter of the portion of the first polymer dispersion (24) where the inorganic particle (22) is not located, and this result can serve as indirect evidence proving that it was manufactured by melt extrusion.

[0057]

[0058] Meanwhile, the guide function of the first polymer dispersion (24) described above and the function as a buffer layer of the coating layer (21') which surrounds the inorganic particles at the portion where the inorganic particles (22) are located can be expressed dependently according to the combination of physical properties between the amorphous modified polyester resin forming the first polymer dispersion (24) (and the second polymer dispersion (21)) and the crystalline polyester resin forming the matrix (10).

[0059] Specifically, in order to perform a guide function, the melt viscosity of the crystalline polyester resin at a predetermined temperature may be different from that of the amorphous modified polyester resin. In addition, in order to facilitate the realization of the morphology of the matrix (10) / first polymer dispersion (24) determined by the formability and dispersibility of the first polymer dispersion (24) formed of the amorphous modified polyester resin within the matrix (10) formed of the crystalline polyester resin, and at the same time improve the alignment such that the long axis direction of the inorganic particles (22) is aligned in the x-axis direction or y-axis direction of the matrix (10), the melt viscosity of either the crystalline polyester resin or the amorphous modified polyester resin may preferably be 1.3 times or more than the melt viscosity of the other polymer, and as another example, may be 1.5 times or more, 1.8 times or more, 2 times or more, or 3 times or more, and as another example, may be 5 times or less, or 4 times or less. Meanwhile, regarding the relative melt viscosity between crystalline polyester resin and amorphous modified polyester resin, since the relationship between the relative melt viscosities of the two polymers varies by temperature even when assuming the same two polymers depending on the specific type of polymer, the present invention is not particularly limited thereto.

[0060]

[0061] In addition, at a given temperature, the melt viscosity (Pa˙S) of the crystalline polyester resin and the melt viscosity (Pa˙S) of the amorphous modified polyester resin may each be independently 100 Pa˙S or more, more preferably 200 Pa˙S or more, and as another example, 2,000 Pa˙S or less, thereby making it easy to implement a morphology in which the first polymer dispersion (24), which is an amorphous modified polyester resin, is formed and dispersed within the matrix (10), which is a crystalline polyester resin, and the long axis direction of the inorganic particles (22) located inside can be oriented in the x-axis direction, which is the same direction as the long axis direction of the first polymer dispersion (24), through a guide of the amorphous modified polyester resin extending in one axial direction, specifically the x-axis. Alternatively, since the first polymer dispersion (24), which is an amorphous modified polyester resin, can be easily extended in the y-axis direction, it may be advantageous to orient the long axis direction of the inorganic particles (22) located inside in the y-axis direction perpendicular to the long axis direction of the first polymer dispersion. If the melt viscosity of one or more of the crystalline polyester resin and the amorphous modified polyester resin is less than 100 Pa·S, it may be difficult to implement the morphology composed of the matrix (10) and the first polymer dispersion (24). In addition, if the melt viscosity of one or more of the crystalline polyester resin and the amorphous modified polyester resin exceeds 2,000 Pa·S, the alignment and alignment uniformity of the inorganic particles (22) 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.

[0062]

[0063] Meanwhile, regarding the description of melt viscosity described above, the specified temperature refers to any temperature between the temperature at which the crystalline polyester resin and the amorphous modified polyester resin begin to melt and the temperature at which they are completely melted. Specifically, it is a specific temperature within the temperature range between the spinodal and binodal of the crystalline polyester resin and the amorphous modified polyester resin that exhibit UCST behavior during melt blending, and as a specific example, it may be the melt processing temperature.

[0064]

[0065] Additionally, the content of the amorphous polyester resin contained in the anisotropic diffusion layer (100) can affect the alignment of the inorganic particles (22) and the function as a buffer layer, as well as the brightness characteristics. Preferably, the inorganic particles (22) and the amorphous modified polyester resin can be provided in a weight ratio of 1:3 to 10, and more preferably in a weight ratio of 1:3 to 7. This allows for increased alignment of the inorganic particles (22) and the function as a buffer layer while minimizing the reduction in frontal brightness. If the amorphous modified polyester resin is contained in an amount less than 3 times the weight of the inorganic particles, it may be difficult to act as a guide to align the long axis direction of the inorganic particles and as a buffer layer to suppress the occurrence of voids on the side of the inorganic particles. Consequently, the alignment of the inorganic particles may be reduced, and the occurrence of voids on the side of the inorganic particles may increase, which may lead to a decrease in anisotropic diffusion and brightness. In addition, if the amorphous modified polyester resin exceeds 10 times the weight of the inorganic particles, the improvement in anisotropic diffusion is minimal and, conversely, the brightness is reduced, making it difficult to achieve sufficient frontal brightness. Furthermore, as the diameter of the first polymer dispersion increases and the guide role of aligning the long axis direction of the inorganic particles becomes minimal, there is a concern that the randomness of the alignment direction of the inorganic particles increases and the anisotropic diffusion decreases.

[0066]

[0067] Meanwhile, the dispersion (20) further includes a second polymer dispersion (21) formed from the same resin as the amorphous modified polyester resin that forms the first polymer dispersion (24), which is aligned in a axial direction substantially identical to the axial direction in which the long axis of the first polymer dispersion (24) is aligned. The second polymer dispersion (21) is formed by the fact that the portion of the amorphous modified polyester resin that does not contain inorganic particles (22) forms a single dispersion during the process of extruding after feeding it into an extruder so that inorganic particles (22) are located inside the amorphous modified polyester resin, and is structurally aligned in a axial direction substantially identical to the first polymer dispersion (24), thereby performing the function of improving anisotropic diffusion.

[0068]

[0069] In addition, the first polymer dispersion (24) and the second polymer dispersion (21) may have an average aspect ratio of more than 100, which may be advantageous for aligning the long axis of the inorganic particles (22) in one axis direction and preventing void formation.

[0070] Specifically, to explain using an example of an optical film stretched at a higher stretching ratio in the MD direction than in the TD direction, the average aspect ratio (a / b), which is the ratio between the average length of the major axis (a) of the first polymer dispersion (24) and the second polymer dispersion (21) and the average length of the minor axis (b) perpendicular to the major axis in the cross-section perpendicular to the TD direction (e.g., the x-axis direction) of the optical film, in other words, the average aspect ratio, may be greater than 100, or, for other examples, greater than 1,000, greater than 10,000, or greater than 100,000. The average length of the minor axis (b) refers to the length of the largest line segment among the lengths of the line segments connecting the perimeter within the cross-section perpendicular to the major axis. Additionally, the average length of the minor axis (b) in the first polymer dispersion (24) refers to the length in the part where the inorganic particle (22) is not located.

[0071] Additionally, the cross-sectional shape of the first polymer dispersion (24) and the cross-sectional shape of the second polymer dispersion (21) in the portion where the inorganic particle (22) is not located, based on the cross-section of the anisotropic diffusion layer (100) corresponding to the YY' boundary line shown in FIG. 2, may be circular or elliptical. In this case, if the cross-sectional shape is elliptical, the average aspect ratio (c / d), which is the ratio of the average length of the major axis (c) and the average length of the minor axis (d) of the ellipse, may be greater than 1 and less than or equal to 350, but is not limited thereto. Here, the average length of the minor axis (d) refers to the average value of the length of the minor axis when the axis that perpendicularly bisects the major axis is called the minor axis.

[0072]

[0073] Additionally, each of the first polymer dispersion (24) and the second polymer dispersion (21) described above is arranged within the matrix (10) such that, when the thickness direction of the optical film (200) or the anisotropic diffusion layer (100) is denoted as the z-axis among the three mutually perpendicular x-axis, y-axis, and z-axis within the matrix (10), at least a portion of them have the x-axis direction as the major axis direction. Furthermore, the arrangement of the major axis direction of one dispersion (20) to be the x-axis direction does not mean that the major axis direction of the polymer dispersion is arranged to be completely parallel to the x-axis, but rather means that the major axis direction of the polymer dispersion is closer to the x-axis direction than to the y-axis and z-axis. For example, the angle formed by the major axis direction of each of the first polymer dispersion (24) and the second polymer dispersion (21) with the x-axis direction may be, for example, less than 10°, less than 5°, less than 3°, or for another example, less than 1°.

[0074]

[0075] Additionally, a plurality of dispersed bodies (20) may be randomly arranged in a yz cross-section formed by the y-axis and z-axis of the optical film (200) or the anisotropic diffusion layer (100). Here, being randomly arranged means that the positions of the plurality of dispersed bodies (20) are randomly arranged in the yz cross-section regardless of the size and shape of the dispersed body cross-section.

[0076]

[0077] Additionally, the first polymer dispersion (24) and the second polymer dispersion (21) are, for example, a unit area (1 μm) within the yz cross-section of the matrix (10). 2 It can contain 10 to 200 pieces per )

[0078]

[0079] Next, the inorganic particles (22) located inside the first polymer dispersion (24) will be described in detail.

[0080] The first polymer dispersion (24) contains inorganic particles (22) having an average aspect ratio of 3.0 or higher. The inorganic particles (22) inside the first polymer dispersion (24) exhibit excellent anisotropic diffusivity through structural anisotropy. Additionally, in the case of an embodiment where the long axis direction of the inorganic particles (22) is the x-axis direction, the structural anisotropy and alignment characteristics of the first polymer dispersion (24), in which the long axes are aligned in the same direction, may be advantageous for further improving anisotropic diffusivity. If the average aspect ratio of the inorganic particles is less than 3.0, it may be difficult to achieve the desired anisotropic diffusivity. In addition, if the inorganic particles (22) are not located inside the first polymer dispersion (24) but are dispersed while in direct contact with the surface of the polymer matrix within the matrix (10), the alignment of the inorganic particles (22) along the long axis is significantly reduced, and as a result, it may be difficult to achieve anisotropic diffusion. Also, even if the polymer matrix has an amorphous structure and thus has good elongation characteristics and flexibility due to stretching, etc., the inorganic particles placed without the polymer dispersion or outside the polymer dispersion may find it difficult to achieve alignment along the desired x-axis or y-axis within the matrix. Furthermore, due to the difference in compatibility caused by the different materials between the inorganic particles (22) and the matrix (10), voids may occur at the interface between the inorganic particles (22) and the matrix (10), and as a result, there is a concern that the brightness may be significantly reduced.

[0081]

[0082] Additionally, the inorganic particles (22) may preferably have an average aspect ratio of 3.5 or more, 4.0 or more, or 8.0 or more. However, as another example, the inorganic particles (22) may have an average aspect ratio of 15.0 or less. In order for the average aspect ratio of the inorganic particles (22) to exceed 15.0, inorganic particles with an aspect ratio much larger than 15.0 must be introduced, taking into account the situation where the inorganic particles may break during the mixing process before melt extrusion. However, the larger the aspect ratio of the inorganic particles introduced, the more irregular the degree of breaking during the mixing and melt extrusion processes becomes, making it difficult to exceed an average aspect ratio of 15.0. Furthermore, due to the irregular breaking, the number of inorganic particles with an aspect ratio of less than 3.0 may increase significantly, which may instead cause a significant decrease in anisotropic diffusion. Here, the average aspect ratio (e / f) of the inorganic particle is the ratio of the average length (e) to the length in the major axis direction (l) and the average diameter (f) of the cross-section in the minor axis direction (l') perpendicular to the major axis direction (l), where the diameter of the cross-section refers to the longest length of the line segment crossing the cross-section.

[0083]

[0084] Additionally, the inorganic particles (22) have the aspect ratio described above, specifically having an average length of 3 to 30 μm, more preferably 3 to 15 μm, and an average diameter of 0.5 to 2.0 μm, more preferably 0.5 to 1.5 μm, which may be advantageous for exhibiting increased anisotropic diffusion. If the average length and average diameter of the inorganic particles deviate from the range described above, the improvement in anisotropic diffusion may be minimal, and as the probability of the inorganic particles being recognized as foreign matter and filtered out during the melt extrusion process increases, there is a concern that the content of inorganic particles contained in the final product may be low compared to the inorganic particles introduced. Furthermore, if the average diameter of the inorganic particles exceeds 2.0 μm, they may be visible as foreign matter on the exterior, and consequently, there is a concern that the visibility of the displayed image may be reduced.

[0085]

[0086] In addition, according to one embodiment of the present invention, the inorganic particles (22) may have an average length of 3 to 15 μm, and may include inorganic particles with a length of 2.5 μm or less in an amount of 23% or less, preferably 20% or less, more preferably 17% or less of the total inorganic particles. Even when the inorganic particles (22) satisfy an average aspect ratio of 3.0 or more and have an average length of 3 to 15 μm, if inorganic particles with a length of 2.5 μm or less are included in an amount of 23% or less of the total inorganic particles, it may be advantageous to achieve high anisotropic diffusivity and brightness simultaneously. If inorganic particles with a length of 2.5 μm or less are included in an amount exceeding 23% of the total inorganic particles, anisotropic diffusivity may be reduced, and there is a risk that frontal brightness may decrease due to increased turbidity.

[0087]

[0088] Meanwhile, in order to exclude inorganic particles having a length that is too short in the inorganic particle length distribution from the first polymer dispersion (24), the inorganic particles introduced into the manufacturing process may undergo a filtering process to remove those with a length shorter than a certain length before introduction. Additionally, in the melt extrusion process, a filter unit within the equipment may be configured to remove inorganic particles of a length shorter than a certain length, thereby controlling the extrusion so that inorganic particles of a length shorter than a certain length are not included in the anisotropic diffusion layer. Meanwhile, it should be noted that the method of controlling the exclusion of inorganic particles of a length shorter than a certain length is not limited to this, and known means may be appropriately adopted or modified.

[0089]

[0090] Additionally, it is preferable that the inorganic particles (22) be positioned within the first polymer dispersion (24) and aligned such that their long axis direction is aligned with one axis, for example, the x-axis direction or the y-axis direction, so as to exhibit anisotropic diffusion. The alignment of the long axis of the inorganic particles (22) with one axis direction does not mean that the long axis direction of the inorganic particles (22) is arranged to be completely parallel to the x-axis or y-axis direction, but rather means that the long axis direction of the inorganic particles (22) is closer to the x-axis or y-axis direction compared to the other axis. Additionally, regarding the fact that the long axis direction of the inorganic particle (22) is closer to the x-axis or y-axis direction compared to other axes, if we explain based on the embodiment in FIG. 5 where the long axis direction of the inorganic particle (22) is aligned with the x-axis direction, it means that the angle (θ) formed by the x-axis direction of the polymer matrix and the long axis direction (ℓ1, ℓ2) of the inorganic particle (22) on the observation surface (S) falls within an angle range of ±15°, and the angle (θ) can be more preferably within ±10°, and more preferably within ±5°. Additionally, at least some of the major axis directions of the multiple inorganic particles (22) may be aligned in the x-axis or y-axis direction, and the ratio of inorganic particles in which the major axis direction forms an angle (θ) with the x-axis or y-axis direction within ±15° may be 65% or more of the total inorganic particles, more preferably 70% or more, 75% or more, 80% or more, or 85% or more, and this may be advantageous for achieving sufficient anisotropic diffusion in the y-axis or x-axis direction.

[0091] At this time, among the plurality of inorganic particles (22), the ratio of inorganic particles whose major axis direction forms an angle (θ) with the x-axis or y-axis direction within ±15° can be evaluated and calculated by the following method. Specifically, for an optical film specimen with a width and height of 10 cm × 10 cm, five arbitrary points are designated, and the surface of the specimen is observed using an optical microscope equipped with a polarizing filter, with a magnification of 500x in transmission / reflection mode, while adjusting the focus in the direction of the specimen thickness to observe the inorganic particles. To quantify the inorganic particles that fall within the angle range, photographs taken of the inorganic particle observation areas that are in focus are analyzed using the observation surface (S). The total number of inorganic particles observed at the five derived points and the number of inorganic particles whose major axis direction forms an angle (θ) with the x-axis or y-axis direction within ±15° can be counted and calculated as a percentage. At this time, the specimen may be analyzed in the form of an optical film having a skin layer, etc., in addition to the anisotropic diffusion layer, or the anisotropic diffusion layer with the skin layer removed may be analyzed to make observation easier, and the present invention is not particularly limited thereto. If the number of inorganic particles in which the angle (θ) formed by the x-axis or y-axis direction and the major axis direction (ℓ1, ℓ2) of the inorganic particle (22) is within ±15° is less than 65% of the total inorganic particles, it may be insufficient to achieve sufficient anisotropic diffusion.

[0092]

[0093] In addition, the inorganic particles (22) are provided in an amount of 0.5 to 10.0 weight%, more preferably 0.5 to 5.0 weight%, based on the total weight of the anisotropic diffusion layer (100), which may be advantageous for exhibiting anisotropic diffusion at a desired level. If the inorganic particles are provided in an amount of less than 0.5 weight% based on the total weight of the anisotropic diffusion layer, it may be difficult to exhibit anisotropic diffusion, and if the amount exceeds 10 weight%, the turbidity may increase, potentially lowering the frontal light transmittance.

[0094]

[0095] Additionally, the inorganic particles (22) may be used without limitation as known inorganic particles used in optical films. For example, the inorganic particles may contain one or more selected from the group consisting of titanium oxide, zinc oxide, magnesium oxide, strontium carbonate, calcium carbonate, magnesium carbonate, cobalt carbonate, manganese carbonate, calcium silicate, calcium sulfate, aluminum hydroxide, imagolite, silicon carbide, barium sulfate, and silicon oxide, and for example, may contain one or more of calcium carbonate and barium sulfate.

[0096]

[0097] Additionally, when the inorganic particle (22) has the aspect ratio described above, there are no specific limitations on its shape. For example, the inorganic particle (22) may be needle-shaped in the case of calcium carbonate and plate-shaped in the case of barium sulfate.

[0098]

[0099] Meanwhile, as described above, due to the low compatibility between the inorganic particles (22) and the matrix (10) materials, there is a risk that voids may occur at the interface between the matrix (10) and the inorganic particles (22) during the stretching process. In addition, if the inorganic particles (22) have hygroscopic properties, they may generate alkali hydroxides with a pH of 9 or higher through hygroscopic absorption. The generated alkali hydroxides promote high-temperature hydrolysis of crystalline polyester resin or amorphous modified polyester resin, thereby inducing gas, and in this process, there is a risk of voids occurring at the interface between the side of the inorganic particles (22) and the first polymer dispersion.

[0100] According to one embodiment of the present invention, a modified layer (23) formed on the surface of an inorganic particle (22) may be provided with one or more compounds including a compound represented by Formula 1 and a silane compound containing an epoxy group, and more preferably, a modified layer formed with a compound represented by Formula 1 and a silane compound containing an epoxy group may be provided, and through this, it is advantageous to prevent voids formed on the side due to external force from the stretching process and high-temperature hydrolysis of the resin when the long axis direction of the inorganic particle (22) is referenced as up and down.

[0101] For example, the alkoxy group in the compound represented by Chemical Formula 1 reacts with moisture absorbed before the inorganic particles, thereby minimizing or preventing the hydrolysis of the polyester resin caused by the dissociation of moisture by the absorbed inorganic particles at high temperatures. In addition, the phosphate group in the compound represented by Chemical Formula 1 is configured so that the surface of the surface-treated inorganic particles becomes a weak acid with a pH of 5 or lower. This allows for the neutralization of the alkaline hydroxide produced even if the inorganic particles absorb moisture and thereby generate an alkaline hydroxide with a pH of 9 or higher, thereby suppressing the hydrolysis and yellowing of the polyester resin and preventing gas release due to hydrolysis and the formation of voids on the side of the inorganic particles. Specifically, the compound represented by Chemical Formula 1 produces phosphoric acid and alcohols (R1OH, R2OH, and / or R3OH) by reacting with alkoxy groups within the compound after moisture absorbed by inorganic particles dissociates at high temperatures. The generated phosphoric acid is weakly acidic and can lower the high pH of alkaline hydroxides produced by the reaction between inorganic particles and moisture. Furthermore, the conversion of moisture into alcohols exerts a moisture removal effect, which can be more advantageous in preventing high-temperature hydrolysis and void formation in polyester resins forming a matrix / first polymer dispersion. Additionally, the generated alcohols (R1OH, R2OH, and / or R3OH) do not induce yellowing in the optical film, do not react with inorganic particles, and can easily vaporize even at low temperatures, thereby preventing the formation of additional voids on the sides of the inorganic particles due to the product. In other words, if a compound used for surface modification (e.g., a fatty acid) reacts with moisture to generate moisture again, the generated moisture is eventually absorbed by the inorganic particles. Consequently, there is a risk of voids forming on the inorganic particles through the mechanism described above, and the generated moisture can cause yellowing, which may degrade the appearance quality of the optical film and the color reproduction of the display.

[0102] [Chemical Formula 1]

[0103]

[0104] R1, R2, and R3 may each independently be hydrogen, or a straight-chain or branched-chain alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, and more preferably, R1, R2, and R3 may each independently be a straight-chain or branched-chain alkyl group having 1 to 5 carbon atoms, or an aryl group having 6 to 10 carbon atoms. If the number of carbon atoms exceeds 10, the surface of the inorganic particle may not be easily modified with a material represented by Formula 1.

[0105]

[0106] Additionally, the above silane-based compound may be used without limitation in the case of a compound that increases compatibility between the inorganic particle (22) and the polyester resin forming the matrix / first polymer dispersion, but as an example thereof, vinyltrichlorosilane, trimethoxyvinylsilane, triethoxyvinylsilane, vinyltris(methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-(2-aminoethyl-3-aminopropyl)trimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-(methacryloxypropyl)methyldimethoxysilane, 3-(methacryloxypropyl)trimethoxysilane, 3-(methacryloxypropyl)methyldiethoxysilane, It may include one or more selected from the group consisting of 3-(methacryloxypropyl)triethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, (3-chloropropyl)trimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT), and bis[(triethoxysilyl)propyl]disulfide, and the like; more preferably, it may include epoxy-silane, which is a silane compound containing an epoxy group, or vinyl-silane, which is a silane compound containing a vinyl group. It can be, more preferably, an epoxy-silane, and through this, the binder properties with the polyester resin are improved, which can be advantageous for achieving the objectives of the present invention, such as preventing or minimizing the occurrence of voids during stretching.

[0107]

[0108] Additionally, the dispersion (20) may further include a second polymer dispersion (21) in which the long axis direction is aligned with the one axis direction, for example, the x-axis direction. The second polymer dispersion (21) is formed from an amorphous modified polyester resin and may have a shape such as a long rod-shaped and / or fiber-shaped structure in one direction, thereby performing an anisotropic diffusion function that diffuses transmitted light in a direction perpendicular to the one direction.

[0109]

[0110] In addition, the above-described anisotropic diffusion layer (100) may have a thickness of 150 μm or less, preferably 100 μm or less, 80 μm or less, or 60 μm, and as another example, 10 μm or more, or 35 μm or more. If the thickness of the anisotropic diffusion layer exceeds 150 μm, it may be difficult to sufficiently express brightness and anisotropic diffusion properties, and if it is less than 10 μm, it may be difficult to express anisotropic diffusion properties, and the surface quality of the anisotropic diffusion layer may be degraded due to the non-polymer dispersion.

[0111]

[0112] Additionally, the optical film (200) may further include a skin layer (110) disposed on at least one surface of the anisotropic diffusion layer (100). The skin layer (110) serves to supplement mechanical strength and protect against external factors. Additionally, preferably, the skin layer (110) may be formed integrally by co-extruding with the optical layer without a separate adhesive layer. As a result, not only can the degradation of optical properties caused by the adhesive layer be prevented, but it is also advantageous for realizing a thinner optical film.

[0113] In addition, the skin layer (110) included in one embodiment of the present invention may be stretched in at least one axial direction after a stretching process is performed following co-extrusion with the anisotropic diffusion layer (100). Through this, the surface hardness is improved compared to the unstretched skin layer, thereby improving scratch resistance and heat resistance.

[0114] The skin layer (110) may be a material of a skin layer commonly used to perform a supporting function of an optical film (200), and preferably may use polyethylene naphthalate (PEN), copolyethylene naphthalate (co-PEN), polyethylene terephthalate (PET), polycarbonate (PC), polycarbonate (PC) alloy, polystyrene (PS), polymethyl methacrylate (PMMA), polybutylene terephthalate (PBT), polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polyurethane (PU), polyimide (PI), polyvinyl chloride (PVC), styrene acrylonitrile mixture (SAN), ethylene vinyl acetate (EVA), polyamide (PA), polyacetal (POM), phenol, epoxy (EP), urea (UF), melamine (MF), unsaturated polyester, silicone, and cycloolefin polymers alone or in combination, and more preferably The same material as the crystalline polyester resin forming the matrix (10) described above can be used.

[0115]

[0116] In addition, the thickness of the skin layer (110) may be 5 to 30 μm, more preferably 10 to 15 μm, and through this, there is an advantage of minimizing the reduction in brightness through the skin layer (110) and minimizing the change in the wavelength of polarized light caused by a phase difference due to birefringence.

[0117]

[0118] Additionally, the optical film (200) is placed on the upper part of the LCD panel, and when mounting an upper polarizer equipped with a conventional upper TAC film, the front brightness (N) is set as the blank value. When the upper TAC film of the upper polarizer is changed to an optical film (200) of the same thickness and mounted, it can be implemented to have high anisotropic diffusion properties without significantly reducing the ratio of front brightness (M). In other words, since the anisotropic diffusion properties imparted to the optical film inevitably cause a reduction in front brightness to varying degrees, it is important to exhibit anisotropic diffusion properties while ensuring that the front brightness exhibited when mounted on a commercial TV is at a level sufficient for the product to function adequately. Even if the anisotropic diffusion properties are excellent, it is difficult to commercialize the product if it causes a significant reduction in front brightness. Accordingly, an optical film (200) according to one embodiment of the present invention satisfies a frontal luminance ratio of 79% or more according to the following mathematical formula 1, as in other examples 80% or more, 81% or more, 82% or more, 83% or more, 85% or more, 86% or more, or 87% or more, while simultaneously having an anisotropic diffusivity of 20% or more according to the following mathematical formula 2, as in other examples 22% or more, 24% or more, 25% or more, or 26% or more, or as in other examples 30% or less. If the frontal luminance ratio relative to Blank is less than 79%, the luminance decrease is significant, so even if the anisotropic diffusivity is high, the value as a product that can be mounted on a light source such as a TV may decrease. Furthermore, even if a desirable frontal luminance ratio relative to Blank is achieved, if the anisotropic diffusivity is less than 20%, it may not be desirable in terms of achieving the purpose of the present invention, such as improving the viewing angle when adopted in a display. Meanwhile, it should be noted that although an anisotropic diffusion of more than 30% may be numerically judged to have an excellent viewing angle, an optical film implemented with an anisotropic diffusion of more than 30% is not desirable because it may fail to meet optical physical properties as a product that can be mounted on a light source, such as having high haze and / or low brightness.

[0119] [Mathematical Formula 1]

[0120]

[0121] In mathematical formula 1, N is the frontal luminance (nit) measured after mounting an upper polarizer, which has a conventional TAC film on its upper surface, onto a predetermined panel, and M is the frontal luminance (nit) measured by the same method after mounting an upper polarizer, which has the same configuration as the upper polarizer but has the same thickness as the upper TAC film, onto the same panel, having an optical film to be measured instead of the upper TAC film.

[0122]

[0123] [Mathematical Formula 2]

[0124]

[0125] Meanwhile, the normal and lateral luminance for the main surface measured in mathematical formulas 1 and 2 may be measured by luminance measurement methods known in the art, and the present invention does not specifically limit the specific method when the normal and lateral directions are measured by the same measurement method.

[0126]

[0127] The above-described optical film (200), particularly the anisotropic diffusion layer (100), can be manufactured through melt extrusion among various methods of manufacturing films. Specifically, it can be manufactured by (1) a step of manufacturing an unoriented film by extruding and solidifying a crystalline polyester resin to form a matrix (10), an amorphous modified polyester resin to form a dispersion (20), and inorganic particles (22) through an extrusion unit, and (2) a step of stretching the unoriented film.

[0128]

[0129] First, the step of manufacturing an unoriented film as step (1) is described.

[0130] (1) Step (1) may be performed using a conventional apparatus and method for manufacturing an unoriented film, specifically 1-1) a step of supplying a crystalline polyester resin to form a matrix (10), an amorphous modified polyester resin to form a dispersion (20), and inorganic particles (22) to an extrusion section. At this time, each of the supplied components may be supplied to a single extrusion section after being mixed, or each component may be supplied individually to independent extrusion sections.

[0131] In order to increase the orientation in which the long axis direction of the inorganic particles (22) in the anisotropic diffusion layer (100) is preferably aligned in the x-axis direction or y-axis direction within the matrix (10) and to prevent the formation of voids that may occur on the side of the inorganic particles (22), the inorganic particles (22) may be placed inside the first polymer dispersion (24) before being introduced into the extrusion section in the form of composite chips mixed with an amorphous modified polyester resin. In addition, when supplying the crystalline polyester resin and the composite chip to a single extrusion section, a sufficient stirring process may be performed before supplying to the extrusion section to induce uniform dispersion, and through this, the dispersions (20) within the anisotropic diffusion layer (100) may be uniformly dispersed, and it may be advantageous to uniformly achieve the size in the z-axis direction within the cross section of the second polymer dispersion (21) and the portion where the inorganic particle (22) is not located in the first polymer dispersion (24) in the yz cross section of the matrix (10).

[0132] Meanwhile, regarding the dispersion and orientation guide of inorganic particles (22) through the amorphous modified polyester resin in the composite chip state, the inorganic particles (22) in the composite chip can be trapped in the amorphous modified polyester resin by blocking them from moving toward the crystalline polyester resin by moving away from the interface between the amorphous modified polyester resin and the crystalline polyester resin due to the difference in melt viscosity between the molten amorphous modified polyester resin and the crystalline polyester resin, thereby increasing the dispersibility of the inorganic particles (22) within the matrix (10) and preventing secondary aggregation among the inorganic particles (22). Additionally, the amorphous modified polyester resin within the molten crystalline polyester resin is separated to form a plurality of first polymer dispersions (24), and at least one inorganic particle (22) is disposed in each of these first polymer dispersions (24). Each first polymer dispersion (24) is extended in the x-axis direction which is the MD direction within the molten crystalline polyester resin after extrusion. As the first polymer dispersion (24) is extended, the inorganic particle (22) trapped within the first polymer dispersion (24), which gradually increases in length and decreases in diameter, is oriented in the long axis direction along the length direction of the first polymer dispersion (24). Therefore, the inorganic particle (22) can be primarily oriented and aligned in the x-axis direction which is the MD direction, in the same direction as the orientation and alignment of the first polymer dispersion (24). Ultimately, the first polymer dispersion (24) (or amorphous modified polyester resin) serves as a guide for the inorganic particles (22), and even though the anisotropic diffusion layer (100) is formed by melt extrusion, the alignment and alignment uniformity of the inorganic particles (22) can be improved.

[0133]

[0134] However, even if the amorphous modified polyester resin and inorganic particles (22) are mixed and fed into the extrusion section together with the crystalline polyester resin in the form of a composite chip, the long axis direction of the inorganic particles (22) can not always be easily aligned in the x-axis direction. That is, as described above, when the melt viscosity of one polymer among the amorphous modified polyester resin and the crystalline polyester resin is greater than the melt viscosity of the other polymer, for example, 1.3 times or more, or 1.5 times or more, the inorganic particles (22) in the molten amorphous modified polyester resin can have excellent dispersibility in the crystalline polyester resin and the long axis can be generally uniformly aligned in the x-axis direction, which is the MD direction in which the amorphous modified polyester resin is extruded. In addition, in the subsequent stretching process, the long axis of the inorganic particles (22) is secondarily aligned in the direction with the higher stretching ratio between MD or TD, so the inorganic particles (22) are aligned closer to the x-axis or y-axis direction, which is the orientation axis of the polymer matrix (10), and at the same time, the alignment direction of each inorganic particle can be aligned more uniformly. If the inorganic particles (22) are introduced in the form of composite chips mixed with a crystalline polyester resin forming a matrix (10) rather than an amorphous modified polyester resin, or are introduced into the extrusion section alone without forming composite chips with the amorphous modified polyester resin and the crystalline polyester resin and the amorphous modified polyester resin, and the melt viscosity conditions between the crystalline polyester resin and the amorphous modified polyester resin or the melt viscosity conditions of the preferred polymers are satisfied, and / or the stretching process described later is performed, it may be difficult to achieve the dispersibility, orientation, and orientation uniformity of the inorganic particles (22).

[0135]

[0136] Meanwhile, as described above, the inorganic particles (22) trapped within the first polymer dispersion (24) dispersed within the molten crystalline polyester resin after extrusion are first aligned such that the long axis direction becomes the MD direction as the first polymer dispersion (24) is extended in the MD direction. Subsequently, in the stretching process, which is a second alignment described later, if the MD direction is stretched at a higher stretching ratio, the first polymer dispersion (24) becomes longer and its diameter becomes relatively smaller, allowing the inorganic particles (22) to be secondarily aligned more uniformly in the MD direction. In addition, in this case, the diameter of the first polymer dispersion (24) in the part where the inorganic particles (22) are not located may be smaller than the diameter of the inorganic particles (22). Alternatively, if the TD direction is stretched at a higher stretching ratio, the inorganic particles (22) rotate in the TD direction, and as a result, the diameter of the first polymer dispersion (24) where the inorganic particles (22) are located may increase in the TD direction, and the diameter of the remaining part of the first polymer dispersion (24) may be relatively smaller compared to the part where the inorganic particles (22) are located. Meanwhile, the feature that the inorganic particles (22) are located inside the first polymer dispersion (24), or that the diameter of a single continuous first polymer dispersion (24) differs between the part containing the inorganic particles (22) and the part not containing them, may be a technical feature that indirectly proves that the anisotropic diffusion layer or optical film is a melt-extruded film.

[0137]

[0138] In addition, the extrusion unit described above may be a known extruder, and may further include a heating means to convert the supplied polymer components in a solid state into a liquid state. In addition, the size control and uniform dispersion of the dispersion (20) can be achieved primarily through process control of step (1), and specifically, the size or dispersion of the dispersion can be controlled by changing whether sufficient stirring is performed before feeding the composite chip and crystalline polyester resin chip into the extrusion unit, the discharge amount during extrusion, the rotational speed of the extruder involved in shear stress, and the type of extruder (single, coaxial twin, etc.).

[0139]

[0140] In addition, a skin layer forming component may be introduced into the extrusion unit so that a skin layer (110) disposed on at least one surface of the anisotropic diffusion layer (100) in step (1) is extruded together. For example, the skin layer may be extruded to the upper and / or lower portions of the anisotropic diffusion layer (100) through separate extrusion units to form the skin layer (110), or if a single extrusion unit is used, the melt forming the anisotropic diffusion layer (100) may be flowed to the central region through different flow paths arranged in the thickness direction, and the melt forming the skin layer may be flowed to the upper and lower regions respectively, and then discharged through a T-DIE, thereby forming a three-layer optical film in a single extrusion unit. Whether a single extrusion unit or multiple extrusion units are used, the skin layer that is co-extruded together with the anisotropic diffusion layer has the advantage of being able to form the skin layer within the process of forming the anisotropic diffusion layer without a separate adhesive. Meanwhile, it may be preferable to use a material for the skin layer that is identical to or highly compatible with the crystalline polyester resin used as the matrix (10), for example. Additionally, it is desirable to design the thickness of the skin layer to an appropriate thickness to prevent a decrease in brightness due to total reflection. Meanwhile, the skin layer (110) and the anisotropic diffusion layer (100) may be formed integrally without including an adhesive or adhesive layer between them, and this technical feature may also be a feature that indirectly proves that it is a melt-extruded film.

[0141]

[0142] Next, as step 1-2), a step of inducing spreading in a flow control unit is performed so that the dispersed bodies (20) contained within the matrix (10) can be arranged randomly. The flow control unit may use a known flow control unit, and as an example, a coat-hanger die may be used. By inducing spreading through the flow control unit in step (2), it is possible to secondarily further control the size of the first polymer dispersed body (24) or the dispersibility of the second polymer dispersed body (21) and the first polymer dispersed body (24).

[0143]

[0144] Next, as step 1-3) of the present invention, a cooling and smoothing step can be performed. As a step of cooling and smoothing the film conveyed from the flow control unit, the film can be cooled and solidified under conditions used in the manufacture of conventional optical films, and then a smoothing step can be adopted and modified. For example, the cooling and smoothing process can be performed on a casting roll. Preferably, one side of the sheet conveyed through the flow control unit is cooled by contacting it with the main cooling roll, and at this time, the temperature of the main cooling roll can be 40°C or lower, more preferably 35°C or lower, or as another example, 20°C or lower. If the temperature of the main cooling roll exceeds 40°C, there is a risk that haze will increase significantly due to the formation of spheroids caused by crystallization resulting from the slow cooling of the crystalline polyester resin forming the matrix, and size differences are likely to be induced between the first polymer dispersions (24) placed in different regions in the thickness direction of the anisotropic diffusion layer (100). This can occur through bonding between the first polymer dispersions (24) dispersed in a molten state, which may cause the size of the solidified polymer dispersion to increase, or the polymer dispersions in the bonded mass may spread out in the left-right direction, that is, in the y-axis direction of the matrix, thereby making the thickness thinner. In addition, the ratio of the matrix modified into a third substance by a chemical reaction at the interface between the first polymer dispersion (24) and the matrix (10) may increase, and the area percentage of the first polymer dispersion (24) may increase significantly. Furthermore, more preferably, the opposite side that does not come into contact with the cooling roll is cooled together through an auxiliary cooling means, and the auxiliary cooling means may be, for example, cooling air, and more preferably, the temperature of the cooling air may be 30°C or lower, more preferably 20°C or lower.

[0145]

[0146] Next, as step (2) of the present invention, a step of stretching the cooled and smoothed unoriented film can be performed.

[0147] The above stretching can be performed by employing and modifying the apparatus and process conditions used for optical films, but preferably, in order to more uniformly align the long axis direction of the inorganic particles (22) in the x-axis direction or y-axis direction within the matrix (10) while exhibiting anisotropic diffusivity, and to secure the shape stability, mechanical properties, and thickness uniformity of the film, the unstretched film can be biaxially stretched in the MD direction and the TD direction, and the stretching ratio in either the MD direction or the TD direction can be greater.

[0148] Specifically, the unoriented film can be biaxially stretched 1 to 6 times in the MD direction and 2.0 to 6.0 times in the TD direction, and more preferably 1.0 to 2.0 times in the MD direction, as in another example 1.0 to 1.5 times and 4.0 to 6.0 times in the TD direction, as in another example 4.0 to 5.0 times, but the stretching ratio in the TD direction is set to be greater than that in the MD direction to further improve the realization of a wide optical film, processability and film formationability, and prevent voids formed to extend in the long axis direction from both ends of the inorganic particles (22), thereby preventing a decrease in brightness.

[0149] Alternatively, the above stretching process may be set to stretch 4.5 to 6.0 times in the MD direction and 2.5 to 3.5 times in the TD direction, or, as another example, 2.5 to 3.0 times, with the stretching ratio in the MD direction being greater than in the TD direction, thereby forming voids extending in the long axis direction from both ends of the inorganic particles in the long axis direction, so as to produce an effect similar to having a dispersion having a larger aspect ratio with the inorganic particles and voids as outlines, and further enhancing the alignment of the inorganic particles in the long axis direction to achieve large anisotropic diffusion.

[0150] If the above conditions are not satisfied even when the film is uniaxially stretched only in the MD or TD direction, or when it is biaxially stretched, it may be difficult to secure the shape stability and anisotropic diffusivity fundamentally required of the film, the alignment and alignment uniformity of inorganic particles may be reduced, and there is a risk of reduced brightness due to the induction of voids on the side relative to the long axis of the inorganic particles.

[0151]

[0152] In addition, the stretching temperature may be performed at a temperature 10 to 20°C higher than the larger glass transition temperature between the glass transition temperatures of the crystalline polyester resin and the amorphous modified polyester resin, respectively. If the stretching temperature is performed at a temperature less than 10°C higher than the glass transition temperature between the crystalline polyester resin and the amorphous modified polyester resin, stretching may not occur or may cause fracture. Furthermore, if the stretching temperature is performed at a temperature exceeding 20°C higher than the glass transition temperature between the crystalline polyester resin and the amorphous modified polyester resin, or if the residence time is excessively long even at an appropriate temperature, the uniformity of stretching may be reduced, and there is a risk that the alignment uniformity of inorganic particles may also be reduced.

[0153]

[0154] In addition, a step of heat-setting the stretched optical film can be performed. The heat-setting can be performed by a conventional method, and preferably, it can be performed using an IR heater at 180 to 200°C for 0.1 to 3 minutes.

[0155]

[0156] Referring to FIGS. 6 and 7, an optical film (200) according to one embodiment of the present invention, manufactured through the above-described manufacturing method, can be implemented as a polarizing plate (4000). Specifically, the polarizing plate (4000) is suitable as an upper polarizing plate placed on the light-emitting surface of a liquid crystal panel (5000). Specifically, the polarizing plate (4000) includes an absorption polarizing film (2000) and an optical film (200) placed on the light-emitting surface of the absorption polarizing film (2000). When placed on the light-emitting surface of the absorption polarizer (2100) of the upper polarizing plate, there is an advantage that the contrast ratio improvement effect due to internal light is significant, the viewing angle is increased, and excellent brightness characteristics can be achieved.

[0157] The above absorption polarizing film (2000) is a polarizer having an optical function such as transmitting the first polarization (or the second polarization) and absorbing the second polarization (or the first polarization) among the first polarization and the second polarization having mutually orthogonal planes of vibration, and is equipped with a known absorption polarizer (2100) having such optical function. As an example, the absorption polarizer (2100) may be a substrate film such as polyvinyl alcohol that is dyed with an iodine-based component or a dichroic dye. In addition, the iodine-based component, which is one of the dyes dyed on the substrate, may be an iodine-based compound such as iodine and / or potassium iodide. In addition, the above-mentioned dichroic dye can be used without limitation in the case of known dichroic dyes that have high absorbance over a wide range of wavelengths in the direction of the long axis of the molecule and extremely low absorbance in the direction of the short axis, have good affinity for the film that serves as the substrate, can dye even in crystalline regions, are easy to align together when the substrate is stretched, have vivid colors, and have high visual contrast. Therefore, the present invention is not specifically limited to such dyes and a detailed description is omitted.

[0158] In addition, the thickness of the absorption polarizer (2100) may be, for example, 10 to 200 μm, but is not limited thereto and can be changed according to the purpose.

[0159] Additionally, the absorption polarizing film (2000) may be provided with a protective film (2210) on one or both sides to support and protect the absorption polarizer (2100). The protective film (2210) may be used without limitation as a protective film used in conventional absorption polarizing films, and a polymer with excellent transparency, mechanical strength, thermal stability, or moisture barrier properties may be preferably employed. As an example, the protective film (2210) may use an acetate resin such as triacetylcellulose (TAC), a polyester resin, a polyethersulfone resin, a polycarbonate resin, a polyamide resin, a polyimide resin, a polyolefin resin, an acrylic resin, a polynorbornene resin, etc. As an example, the protective film may use a triacetylcellulose (TAC) film considering optical properties. Alternatively, in terms of heat resistance and moisture resistance, it may be a polyester-based film, specifically as an example, a polyethylene terephthalate film. The polyethylene terephthalate film may have a phase difference within the plane of 8,000 nm or more, or 10,000 to 15,000 nm. In addition, the protective film (2210) may have a thickness of 50 to 150 μm, but is not limited thereto. Also, referring to FIG. 6, a protective film such as a TAC film that is typically placed on top of the absorption polarizer (2100) is not provided, and the optical film (200) according to one embodiment of the present invention has the advantage of being able to omit and replace the upper TAC film placed on top of the absorption polarizer (2100).

[0160]

[0161] In addition, the above-described absorption polarizing film (2000) and the optical film (200) may be integrally bonded by interposing a separate adhesive layer (not shown) at the interface between them. The adhesive layer is used for bonding between optical films and can be implemented using a known adhesive component that does not degrade optical properties. For example, it may be formed as an adhesive in which the adhesive component is used alone, or in combination with at least one water-soluble crosslinking agent of the vinyl alcohol-based polymer, such as boric acid, borax, glutaraldehyde, melamine, or oxalic acid. Additionally, the adhesive may be combined with other additives or catalysts such as acids.

[0162]

[0163] Additionally, 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. Additionally, the functional layer (3000) may be implemented by stacking multiple layers to exhibit a composite function. Since the thickness of the functional layer (3000) can be appropriately changed considering the type of functional layer provided and the number of layers, the present invention is not specifically limited thereto.

[0164]

[0165] In addition, as illustrated in FIG. 7, a polarizing plate (4000) according to one embodiment of the present invention can be implemented as a liquid crystal display device (8000) that is positioned on the light-emitting surface of the polarizing plate (4000) positioned above the liquid crystal panel (5000), that is, adjacent to the viewing side of the liquid crystal display device (8000), opposite to a backlight unit (7000) positioned below the liquid crystal panel (5000).

[0166] Specifically, the liquid crystal display device (8000) can be implemented by arranging in the order of a backlight unit (7000), an absorption polarizing film (2000) as a lower polarizing plate, a liquid crystal panel (5000), a color conversion layer (5300), and a polarizing plate (4000) according to one embodiment of the present invention as an upper polarizing plate.

[0167] The above backlight unit (7000) may be used in a conventional LCD display and may be composed of known components such as a light source, a reflective film, a light guide plate, a light diffusion film, a light collecting film, and a reflective polarizing film.

[0168] Additionally, the liquid crystal panel (5000) includes a liquid crystal layer (5100) and a support plate (5210, 5220) that supports the upper and lower portions of the liquid crystal layer (5100), and may further include known configurations such as electrode lines. Additionally, the liquid crystal panel (5000) may adopt a VA (vertical alignment) mode, an IPS mode, a PVA (patterned vertical alignment) mode, or an S-PVA (super-patterned vertical alignment) mode, but is not limited thereto.

[0169]

[0170] In addition, an optical film (200) according to one embodiment of the present invention may be disposed on the light-emitting surface of a self-emissive display panel to implement a self-emissive display device. The self-emissive display panel may be a panel employed in known self-emissive displays, such as a plasma display panel (PDP) or an OLED panel, and the present invention is not particularly limited thereto.

[0171]

[0172] Meanwhile, although the applications of the optical film in this invention have been described using liquid crystal display devices or self-emissive display devices as examples, they are not limited thereto and can be widely used in various known display technologies such as projection displays and field emission displays. Furthermore, in addition to display technologies, it can be widely applied to various light sources such as glass windows and work lighting requiring polarization.

[0173]

[0174] The present invention will be explained more specifically through the following examples, but the following examples are not intended to limit the scope of the invention and should be interpreted as being for the purpose of aiding understanding of the invention.

[0175]

[0176] <Example 1>

[0177] Polyethylene terephthalate (PET) was prepared as a crystalline polyester resin forming a matrix, and polycyclohexylene dimethylene terephthalate (PCTG) was prepared by polymerizing an acidic component, which is terephthalate, and a diol component composed of ethyl glycol and 1,4-cyclohexanedimethanol, in which 1,4-cyclohexanedimethanol is 55 mol%, in a 1:1 molar ratio as an amorphous modified polyester resin forming a first polymer dispersion. Calcium carbonate powder was prepared by surface treating the calcium carbonate powder, which was filtered beforehand as an inorganic particle with an average length of 25 μm and an average diameter of 1.3 μm with a length of 5 μm or less, with a compound represented by the following chemical formula 1-1, and then treating it with a solution containing an epoxy-silane compound to form an epoxy-silane compound modified layer on the surface of the calcium carbonate. Inorganic particles were mixed with the prepared amorphous modified polyester resin in a weight ratio of 4:1 and fed into an extruder to produce a composite chip in which inorganic particles were dispersed in the amorphous modified polyester resin. Subsequently, the produced composite chip and crystalline polyester resin were mixed and fed into the first extrusion section, with the amount fed being adjusted so that the content of inorganic particles was 1.4% by weight of the total weight of the mixture fed into the first extrusion section. In addition, to produce a skin layer, PET, which is a crystalline polyester resin, was fed into the second extrusion section, and the second extrusion section was manufactured using a flow path so that the skin layer was placed on the upper and lower parts of the matrix with the same thickness. Meanwhile, the prepared crystalline polyester resin PET is a (semi)crystalline resin with a glass transition temperature of 78°C, and the amorphous modified polyester resin has a glass transition temperature of 82°C and a weight-average molecular weight of 21,000, and the melt viscosity at an extrusion temperature of 260°C in the extrusion section described later was 180 Pa·S and 100 Pa·S, respectively.

[0178] At this time, the extrusion temperature of the first extrusion section was set to 260°C, and the polymer flow was corrected by checking the Cap.Rheometer. The first polymer dispersion, formed from an amorphous modified polyester resin, was induced to be dispersed within a matrix formed from a crystalline polyester resin by passing through a flow path to which a filtration mixer was applied. Subsequently, the crystalline polyester resin flow was laminated to form a skin layer on both sides of the matrix. Afterward, spreading was induced in a coat hanger die that corrects the flow velocity and pressure gradient to induce the first polymer dispersion to be randomly dispersed. Specifically, the width of the die inlet was 200 mm and the thickness was 10 mm, the width of the die outlet was 1,260 mm and the thickness was 0.75 mm, and the flow velocity was 1.0 m / min. Afterward, a cooling and smoothing process was performed in a casting roll, and the material was stretched 4.0 times in the MD direction and then stretched 3.0 times in the TD direction. Subsequently, heat setting was performed through a heater chamber at 180°C for 2 minutes to produce an optical film as shown in Table 1 below, having a total thickness of 80 μm, wherein the major axis directions of the first polymer dispersion, the inorganic particles located inside it, and the second polymer dispersion were each aligned in the x-axis direction of the matrix as illustrated in FIGS. 2 and 3, and the first polymer dispersion and the second polymer dispersion, each having inorganic particles inside it, were randomly dispersed on the matrix, and the optical film had a total thickness of 80 μm, with skin layers having a thickness of 10 μm on both sides of the anisotropic diffusion layer, and as shown in FIGS. 3. At this time, the average aspect ratio of the first polymer dispersion and the second polymer dispersion in the anisotropic diffusion layer produced exceeded 100. In addition, the average aspect ratio of the inorganic particles was 4.3, and the average length was 5.6 μm, with inorganic particles having a length of 2.5 μm or less accounting for 9.5% of the total inorganic particles. In addition, no voids were formed on the lateral side perpendicular to the long axis direction of the inorganic particles. Also, the average aspect ratio of the first polymer dispersion and the second polymer dispersion in the manufactured anisotropic diffusion layer exceeded 100.

[0179]

[0180] <Examples 2 ~ 4>

[0181] An optical film as shown in Table 1 was prepared by carrying out the same procedure as in Example 1, but with the content of inorganic particles and / or the average length, average diameter, and average aspect ratio of the inorganic particles changed as shown in Table 1 below.

[0182]

[0183] <Comparative Example 1>

[0184] The optical film as shown in Table 1 was manufactured by carrying out the same procedure as in Example 1, but without feeding the composite chip containing the amorphous modified polyester resin into the first extrusion section, and instead feeding the composite chip in which inorganic particles were composited with the crystalline polyester resin as shown in Table 1 into the first extrusion section alone.

[0185]

[0186] <Comparative Example 2>

[0187] An optical film as shown in Table 1 was manufactured by carrying out the same procedure as in Example 4, but the amorphous modified polyester resin was changed to crystalline PET as shown in Table 1 below, and the TD direction stretching ratio was changed to 2 times.

[0188]

[0189] <Experimental Example 1>

[0190] The following physical properties were evaluated for optical films according to the examples and comparative examples, and the results are shown in Table 1 below.

[0191]

[0192] 1. Observation of the alignment, size, and presence of voids in inorganic particles

[0193] After selecting five arbitrary points on a specimen measuring 10 cm × 10 cm in width and length, the surface of the specimen was observed and images were captured using an OLYMPUS MX50LT-1273MU optical microscope equipped with a polarizing filter (the magnification of the objective lens was adjusted to 10x, 20x, or 50x, and the magnification of the eyepiece lens was 10x). Then, the length and diameter of the inorganic particles were measured using Image-J, an open program available on the internet, for the images of the five points. Using the inorganic particles measured through the five images as a sample, the average length in the major axis direction (e), the average diameter in the minor axis direction (f), and the average aspect ratio (e / f) of the inorganic particles were calculated.

[0194] In addition, for the void analysis of the optical film, five arbitrary points were designated on a specimen measuring 10 cm by 10 cm, and the surface of the specimen was observed by five experts using an OLYMPUS MX50LT-1273MU optical microscope equipped with a polarizing filter. The microscope was set to a magnification of 500x and used in transmission / reflection mode, with the focus adjusted in the direction of the specimen thickness to determine whether voids occurred relative to the long axis direction of the inorganic particles. As a result of the observation, Comparative Examples 1 and 2, in which voids occurred on almost all of the observed sides of the inorganic particles, were assigned a score of 5, and cases where no voids occurred or hardly any occurred were assigned a score of 0. The level of void occurrence was then relatively evaluated from 0 to 5, and the average value for the five experts was calculated.

[0195] In addition, for the analysis of the alignment direction of inorganic particles, the specimen, equipment, and method used for void analysis were used to adjust the focus in the thickness direction of the specimen at each point, and the parts of the inorganic particles that were in focus during observation were photographed to quantify the inorganic particles that fall within the angle range. Subsequently, through the analysis of the captured photographs, the total number of inorganic particles observed at five points and the inorganic particles whose angle (θ) formed between the x-axis direction and the major axis direction (ℓ1, ℓ2) of the inorganic particles (22) was within ±15° were counted, as shown in FIG. 6, and the percentage of the number of inorganic particles whose angle (θ) formed between the x-axis direction and the major axis direction of the inorganic particles (22) was within ±15° was calculated.

[0196]

[0197] 2. Evaluation of Optical Characteristics

[0198] Optical characteristics were evaluated using an upper polarizer to which the optical films according to the examples and comparative examples were applied, replacing the upper TAC film of the LCD upper polarizer in the Samsung Electronics Q80A LCD TV, a high-end model on the market. At this time, an upper polarizer to which a conventional upper TAC film of the same thickness as the optical film was applied was used as a control group, and the frontal luminance ratio of each of the examples and comparative examples relative to the control group was defined as the frontal luminance ratio relative to the blank.

[0199] Specifically, a hard coating and a low-refractive index coating were applied to one side of the optical film. The prepared optical film was laminated to the upper surface of an absorption polarizer corresponding to the upper polarizer of the LCD, and a polarizer was manufactured with a TAC (triacetate cellulose) film on the lower surface of the absorption polarizer. After applying the manufactured polarizer as the upper polarizer of the LCD panel of a commercially available Samsung Electronics Q80A LCD TV, the brightness was measured in the front (normal direction, 90° to the main surface of the optical film) and side (30° to the main surface of the optical film) directions.

[0200] In addition, the upper polarizer of the LCD panel of the same LCD TV was fitted with an upper polarizer to which a conventional upper TAC was applied, and the frontal luminance (N) was measured in the same way, and the measured luminance was used as the blank value of the frontal luminance.

[0201] In addition, using the measured values, the frontal luminance ratio relative to Blank was calculated via Equation 1 below, and the anisotropic diffusivity was calculated via Equation 2.

[0202] [Mathematical Formula 1]

[0203]

[0204] In mathematical formula 1, M is the frontal luminance (nit) measured by applying an upper polarizer with an optical film according to an example or comparative example, and N is the frontal luminance (nit) measured by applying an upper polarizer that is a control group.

[0205]

[0206] [Mathematical Formula 2]

[0207]

[0208]

[0209] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Polymer Matrix Crystalline Polyester Resin (A) Type / Melting Viscosity (Pa·S) PET / 180 PET / 180 PET / 180 PET / 180 PET / 180 PET / 180 Dispersed Polyester Resin (B) Type / Melting Viscosity (Pa·S) PCTG (Amorphous) / 100 PCTG (Amorphous) / 100 PCTG (Amorphous) / 100 PCTG (Amorphous) / 102 Non-containing PET (Crystalline) / 200 Inorganic Particle (C) Content (Weight%) 1.4 1.4 2.0 2.0 5.0 2.0 Inorganic Particle Average length (e) / Average diameter (f) / Average aspect ratio (e / f) 5.6 / 1.3 / 4.3 5.5 / 1.2 / 4.6 10.4 / 1.2 / 8.7 4.1 / 1.2 / 3.4 5.5 / 1.3 / 4.2 4.1 / 1.2 / 3.4 Ratio of inorganic particles with a length of 2.5 µm or less (%) 9.5 4.9 19.2 6.2 15.3 6.2 C : B weight ratio 1:4 1:41:41:4 1:4 Process composite chip B + inorganic particle B + inorganic particle B + inorganic particle B + inorganic particle A + inorganic particle B + inorganic particle Direction with high extension magnification MD (x-axis) MD (x-axis) MD (x-axis) MD (x-axis) MD (x-axis) MD (x-axis) Anisotropic diffusion layer Non-polymer dispersion aligned within ±15° in the x-axis direction Quantity Ratio (%) 87 87 88 87 55 54 Degree of Side Void Formation (0 ~ 5 points) 00 0 0 55 Optical Characteristics Front Luminance Ratio Compared to Blank (%) 85.7 87.1 80.9 81.1 58.4 59.1 Anisotropic Diffusivity (%) 26.4 26.9 27.9 28.9 49.6 51.2

[0210] As can be seen from Table 1, the optical film according to the embodiment, in which a first polymer dispersion formed of an amorphous modified polyester resin and having inorganic particles is dispersed within a matrix formed of a crystalline polyester resin, can be seen to have excellent alignment of inorganic particles in the x-axis direction and excellent anisotropic diffusion, and at the same time achieve a sufficiently high frontal luminance ratio, compared to Comparative Example 1, in which inorganic particles are dispersed within a matrix without guidance of the first polymer dispersion through the amorphous modified polyester resin.

[0211] Meanwhile, the optical film of Comparative Example 2, in which the polymer forming the first polymer dispersion was changed to a crystalline polyester resin, showed significant side voids when the long axis direction of the inorganic particles was referenced vertically even after being stretched twice in the TD direction, and as a result, it was confirmed that the brightness and anisotropic diffusivity were significantly reduced compared to the optical film of Example 4.

[0212]

[0213] <Examples 5 ~ 8>

[0214] An optical film as shown in Table 2 was prepared by carrying out the same procedure as in Example 2, but with the mol% of 1,4-cyclohexanedimethanol among the diol components in the amorphous modified polyester resin changed as shown in Table 2 below.

[0215]

[0216] <Experimental Example 2>

[0217] The following physical properties were evaluated for Examples 2 and 5 to 8, and the results are shown in Table 2.

[0218]

[0219] 1. PCTG weight-average molecular weight

[0220] The molecular weight and molecular weight distribution of the polymer used in the present invention were measured using Gel Permeation Chromatography (GPC).

[0221] The analysis was performed using THF as the mobile phase at a flow rate of 1.0 mL / min, and a Shodex KF-804L column was used. A Refractive Index (RI) detector was used, and measurements were taken at 40°C. A calibration curve was constructed using monodisperse polystyrene (PS) as the standard.

[0222]

[0223] 2. Degree of lateral void formation

[0224] The evaluation was performed in the same manner as the method of Experimental Example 1.

[0225]

[0226] 3. Evaluation of Optical Characteristics

[0227] The evaluation was performed in the same manner as the method of Experimental Example 1.

[0228]

[0229] Example 2 Example 5 Example 6 Example 7 Example 8 Crystalline Polyester Resin (A) Type / Melting Viscosity (Pa·S) PET / 180 PET / 180 PET / 180 PET / 180 PET / 180 Modified Polyester (PCTG) CHDM Molar % in Diol Component 55 46 59 64 33 Crystalline Structure Amorphous Amorphous Amorphous Amorphous Amorphous Melting Viscosity (Pa·S) 100 105 98 95 132 Weight Average Molecular Weight 21,000 21,400 21,800 22,400 21,200 Inorganic Particle Content (Weight%) 1.4 1.4 1.4 1.4 1.4 Degree of Lateral Void Formation (0 ~ 5 points) 000 12 Optical Properties Blank Contrast Frontal Luminance Ratio (%) 87.1 85.4 84.1 83.4 79.2 Anisotropic Diffusivity (%) 26.9 26.1 25.9 27.9 29.5

[0230] As can be seen from Table 2, Examples 2, 5 to 8 simultaneously satisfy the frontal luminance ratio relative to Blank and anisotropic diffusivity.

[0231]

[0232] Although an embodiment of the present invention has been described above, the concept of the present invention is not limited to the embodiments presented in this specification. Those skilled in the art who understand the concept of the present invention may easily propose other embodiments within the scope of the same concept by adding, changing, deleting, or adding components, and such embodiments shall also be considered to fall within the scope of the concept of the present invention.

Claims

A matrix formed of crystalline polyester resin; and An optical film having an anisotropic diffusion layer comprising a plurality of dispersions, each having a first polymer dispersion formed of an amorphous modified polyester resin containing inorganic particles having an average aspect ratio of 3.0 or higher and arranged in a certain axial direction. In paragraph 1, An optical film in which the long axis direction of the inorganic particles within the first polymer dispersion is arranged in the one axis direction or in a direction perpendicular to the one axis direction. In paragraph 1, The above anisotropic diffusion layer is an optical film formed through melt extrusion. In paragraph 1, The above crystalline polyester is an optical film that is polyethylene terephthalate. In paragraph 1, The above-mentioned amorphous modified polyester is an optical film in which a portion of the ethylene glycol is replaced with 1,4-cyclohexanedimethanol, which is a modified polyethylene terephthalate. In paragraph 5, The above modified polyethylene terephthalate is an optical film comprising 30 to 65 mol% of 1,4-cyclohexanedimethanol among the diol components. In paragraph 1, An optical film comprising the above-mentioned inorganic particles and amorphous modified polyester resin in a weight ratio of 1:3 to 10. In paragraph 1, An optical film containing the above-mentioned inorganic particles in an amount of 0.5 to 10 weight percent based on the total weight of the anisotropic diffusion layer. In paragraph 1, The above-mentioned inorganic particles are an optical film having an average length of 3 to 15 μm and an average diameter of 0.5 to 2.0 μm. In paragraph 5, The above modified polyethylene terephthalate is an optical film comprising 45 to 60 mol% of the above 1,4-cyclohexanedimethanol among the diol components. In paragraph 1, An optical film comprising a second polymer dispersion formed of the amorphous modified polyester resin, wherein the dispersion is aligned in the axial direction. A polarizing plate disposed on the light-emitting surface of a liquid crystal display panel, wherein the polarizing plate is Absorbing polarizing film; and A polarizing plate comprising an optical film according to any one of claims 1 to 11 disposed on the light emission surface of the absorption polarizing film. Display panel; and A display device comprising an optical film according to any one of claims 1 to 11 disposed on the light emission surface of the above panel.

Images