Optical film, polarizing plate including the same, and optical display device including the same

Abstract

An optical film, a polarizing plate including the same, and an optical display device including the same are disclosed. The optical film includes, in the stated order, a third layer, a second primer layer, a first layer, a first primer layer, and a second layer, wherein each of the first primer layer and the second primer layer has a glass transition temperature (Tg) of 50 to 100℃, and is a (meth)acrylate-based primer layer.

Description

[0001] Cross-reference of related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2021-0188138, filed on December 27, 2021, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to an optical film, a polarizing plate including the optical film, and an optical display device including the polarizing plate. Background Technology

[0004] Organic light-emitting diode (OLED) displays can suffer from reduced visibility and contrast due to reflection of external light. To address this issue, a polarizing plate, including a polarizer and a retardation film, can be stacked on the light-emitting device panel. A retardation film is sandwiched between the polarizer and the light-emitting device panel. The retardation film typically consists of at least two retardation layers with different phase delays to achieve more thorough anti-reflection.

[0005] However, the at least two layers constituting the retardation film are formed of different materials. Therefore, it is necessary to ensure that the retardation film formed by bonding these layers together has good reliability and durability. In recent years, techniques have been developed in this field to reduce the thickness of the retardation film by applying a coating composition of a predetermined thickness to one surface of either layer, followed by drying the composition to form the retardation layer, rather than using an adhesive to bond the layers. Here, it is also necessary to ensure that the retardation film comprising at least two layers has good reliability and durability.

[0006] The background technology of the present invention is disclosed in Korean Patent Application Publication No. 10-2013-0103595 and other publications. Summary of the Invention

[0007] One aspect of the present invention is to provide an optical film that exhibits good properties in terms of durability, heat durability and damp heat reliability in hot water immersion tests.

[0008] Another aspect of the present invention is to provide an optical film with good interlayer peel strength and low haze.

[0009] Another aspect of the present invention is to provide a polarizing plate with good properties in terms of heat resistance, durability, and damp heat resistance reliability.

[0010] One aspect of the present invention relates to an optical film.

[0011] 1. The optical film comprises: a third layer, a second primer layer, a first layer, a first primer layer and a second layer stacked in the stated order, wherein each of the first primer layer and the second primer layer has a glass transition temperature (Tg) of 50°C to 100°C and is a (meth)acrylate-based primer layer.

[0012] 2. In 1, the first layer can be a hydrophobic delayed membrane.

[0013] 3. In 1 and 2, the hydrophobic delayed membrane may include at least one selected from cyclic olefin polymer (COP) membranes and cyclic olefin copolymer (COC) membranes.

[0014] 4. In 1 to 3, the second layer may have a non-liquid crystal layer with an in-plane retardation of 70 nm to 120 nm at a wavelength of 550 nm.

[0015] 5. In 1 to 4, the third layer can be a non-liquid crystal positive C delay layer.

[0016] 6. In 1 to 5, each of the second and third layers may contain at least one selected from polystyrene-based polymers and cellulose-based polymers.

[0017] 7. In 6, each of the polystyrene-based polymers and cellulose-based polymers may contain one or more halogens.

[0018] 8. In 6 and 7, halogens can be fluorine.

[0019] 9. In 1 to 8, the first layer may have a lower glass transition temperature and a higher Young's modulus than each of the second and third layers.

[0020] 10. In 1 to 9, the (meth)acrylate-based primer layer can be formed from a primer layer composition comprising a copolymer of monomer mixtures, the monomer mixtures comprising (meth)acrylate monomers having a glass transition temperature of 10°C to 100°C in a homopolymer phase.

[0021] 11. In 10, the (meth)acrylic acid monomer may contain alkyl-containing (meth)acrylates.

[0022] 12. In 10, the monomer mixture may also contain a peel strength enhancing compound.

[0023] 13. In 10 to 12, the peel strength enhancing compound may include at least one selected from methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, n-octyl methacrylate, lauryl methacrylate, stearyl methacrylate, butyl acetate, butyl formate, 2-methyl-2-cyclohexyl acrylate, 2-methyl-cyclohexyl acrylate, and isopropyl acetate.

[0024] 14. In 10 to 13, the peel strength enhancing compound may include at least one selected from butyl acetate, butyl formate, cyclohexyl 2-methyl-2-acrylate, 2-methyl-cyclohexyl 2-acrylate, and isopropyl acetate.

[0025] 15. In 10 to 14, the primer composition may further include at least one selected from peel strength enhancing compounds and curing agents.

[0026] 16. In 1 to 15, the haze of the optical film can be 0.3% or less than 0.3%, the peel strength between the first layer and the second layer can be 300gf / 25mm or greater than 300gf / 25mm, and the peel strength between the first layer and the third layer can be 300gf / 25mm or greater than 300gf / 25mm.

[0027] Another aspect of the present invention relates to a polarizing plate.

[0028] The polarizing plate includes: a polarizer; and an optical film according to the invention, disposed on at least one surface of the polarizer.

[0029] Another aspect of the present invention relates to an optical display device.

[0030] The optical display device includes a polarizing plate according to the present invention.

[0031] The present invention provides an optical film that exhibits good properties in terms of durability, heat resistance and damp heat reliability in hot water immersion tests.

[0032] This invention provides an optical film with good interlayer peel strength and low haze.

[0033] This invention provides a polarizing plate with good properties in terms of heat resistance, durability, and damp heat resistance reliability. Attached Figure Description

[0034] Figure 1This is a cross-sectional view of an optical film according to an embodiment of the present invention.

[0035] Figure 2 This is a cross-sectional view of a polarizing plate according to another embodiment of the present invention.

[0036] [Explanation of reference numerals in the attached figures]

[0037] 100: First layer

[0038] 150: First primer layer

[0039] 200: Second layer

[0040] 250: Second primer layer

[0041] 300: Third layer

[0042] 400: Polarizer

[0043] 500: Protective layer Detailed Implementation

[0044] In the following, embodiments of the invention will be described in detail with reference to the accompanying drawings to provide those skilled in the art with a full understanding of the invention. It should be understood that the invention can be implemented in various ways and is not limited to the following embodiments.

[0045] In the accompanying drawings, components irrelevant to the description have been omitted for clarity of the invention, and the same components will be indicated by the same reference numerals throughout the specification. Although the length, thickness, or width of various components may be exaggerated in the drawings for understanding, the invention is not limited thereto.

[0046] In this paper, "in-plane delay (Re)," "out-of-plane delay (Rth)," and "biaxiality (NZ)" are represented by equations A, B, and C, respectively:

[0047] [Equation A]

[0048] Re = (nx - ny)xd

[0049] [Equation B]

[0050] Rth=((nx+ny) / 2-nz)xd

[0051] [Equation C]

[0052] NZ = (nx - nz) / (nx - ny)

[0053] Where nx, ny, and nz are the refractive indices of the optical device in the slow axis direction, fast axis direction, and thickness direction of the optical device at the measurement wavelength, respectively, and d is the thickness of the optical device (unit: nm). In equations A to C, the measurement wavelength can be 450 nm, 550 nm, or 650 nm.

[0054] In this paper, "short wavelength dispersion" refers to Re(450) / Re(550), and "long wavelength dispersion" refers to Re(650) / Re(550), where Re(450), Re(550) and Re(650) refer to the in-plane retardation (Re) of a single retardation layer or a stack of retardation layers at wavelengths of 450 nm, 550 nm and 650 nm, respectively.

[0055] In this article, "+" indicates counterclockwise direction and "-" indicates clockwise direction.

[0056] In this document, "(meth)acryloyl" may mean acryloyl and / or methacryloyl.

[0057] In this paper, "modulus" refers to Young's modulus and indicates the degree of deformation of the target under pressure when measured by a tensile test at 25°C.

[0058] In this article, “X to Y” used to represent a specific numerical range means “greater than or equal to X and less than or equal to Y (X ≤ and ≤ Y)”.

[0059] The optical film according to the invention is an optical film laminate comprising a third layer, a second primer layer, a first layer, a first primer layer, and a second layer stacked sequentially in the stated order. The first layer and the third layer are tightly connected to each other through the second primer layer, and the first layer and the second layer are tightly connected to each other through the first primer layer.

[0060] Each of the first and second primer layers has a glass transition temperature of 50°C to 100°C and is a (meth)acrylate-based primer layer.

[0061] The optical film according to the invention has a haze of 0.3% or less and exhibits good properties in terms of durability, heat resistance, and damp heat resistance in hot water immersion tests. As described below, the optical film according to the invention is applied to a polarizing plate for anti-reflection purposes to provide an anti-reflective effect relative to external light. An optical film with a haze of 0.3% or less can further improve the above-mentioned effect. As described below, the optical film according to the invention requires tilt stretching or machine direction (MD) stretching during the formation of the second layer after the formation of the first primer layer. A first primer layer with a glass transition temperature within the above range can effectively form the first and second layers with the phase retardation according to the invention. In one embodiment, the haze of the optical film can be 0%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, or 0.3%, for example, 0% to 0.3%.

[0062] In the optical film according to the invention, each of the first and second primer layers has a glass transition temperature of 50°C to 100°C and is a (meth)acrylate-based primer layer. Thus, the optical film comprising the first, second, and third layers, each having the following glass transition temperatures and moduli, improves durability after immersion in hot water, heat resistance, and damp heat resistance. In one embodiment, the first layer has a lower glass transition temperature and a higher modulus than each of the second and third layers.

[0063] When applied to polarizing plates, the optical film according to the present invention can improve the heat resistance and damp heat resistance of the polarizing plate. Although not yet clearly understood, it is believed that this result is mainly achieved through the chemical and physical bonding between the phase-retarding resin and the primer layer, while improving reliability by ensuring good peel strength through the application of a primer layer with a relatively high glass transition temperature to suppress interlayer distortion at high temperatures. However, it should be understood that the invention is not limited thereto.

[0064] In one embodiment, the peel strength of the optical film between the first and second layers may be 300 gf / 25 mm or greater, for example, from 300 gf / 25 mm to 600 gf / 25 mm, and the peel strength between the first and third layers may be 300 gf / 25 mm or greater, for example, from 300 gf / 25 mm to 600 gf / 25 mm. Here, "peel strength" can be measured by the method described in the examples below.

[0065] In one embodiment, the first primer layer and the second primer layer may have the same glass transition temperature or different glass transition temperatures. Preferably, the first primer layer and the second primer layer have the same glass transition temperature, thereby easily achieving the effects of the present invention.

[0066] The following will refer to Figure 1 A detailed description of an optical film according to an embodiment of the present invention.

[0067] Reference Figure 1 The optical film includes a third layer 300, a second primer layer 250, a first layer 100, a first primer layer 150, and a second layer 200 stacked in the order stated.

[0068] The first layer 100 and the third layer 300 can be tightly connected to each other through the second primer layer 250, and the first layer 100 and the second layer 200 can be tightly connected to each other through the first primer layer 150.

[0069] In one embodiment, only a second primer layer may exist between the first layer and the third layer, and only a first primer layer may exist between the first layer and the second layer.

[0070] First layer

[0071] The first layer 100 may be a layer that does not substantially exhibit in-plane retardation. Preferably, the first layer is a retardation layer and has an in-plane retardation within a predetermined range, so that the optical film can provide anti-reflective properties.

[0072] In one embodiment, the first layer may have an in-plane retardation of 180 nm to 240 nm at a wavelength of 550 nm. Therefore, when combined with a second layer exhibiting in-plane retardation at a wavelength of 550 nm, the first layer can achieve a significant reduction in reflectivity on both the front and side surfaces, while simultaneously improving the ellipticity of the side surfaces. At a wavelength of 550 nm, the first layer may specifically have an in-plane retardation of 180 nm, 185 nm, 190 nm, 195 nm, 200 nm, 205 nm, 210 nm, 215 nm, 220 nm, 225 nm, 230 nm, 235 nm, or 240 nm, preferably an in-plane retardation of 180 nm to 235 nm.

[0073] The first layer 100 exhibits positive dispersion and may have a short-wavelength dispersion of 1 to 1.1 and a long-wavelength dispersion of 0.96 to 1. Within this range, when used in a polarizing plate, the optical film can reduce the reflectivity of the front and side surfaces while increasing the ellipticity. Preferably, the short-wavelength dispersion of the first layer is 1.03 to 1, and the long-wavelength dispersion is 0.98 to 1, specifically 0.99 to 1, and more specifically 0.995 to 1. In one embodiment, the first layer may have an in-plane retardation of 180 nm to 280 nm at a wavelength of 450 nm, preferably 185 nm to 260 nm, more preferably 190 nm to 250 nm, and an in-plane retardation of 175 nm to 270 nm at a wavelength of 650 nm, preferably 180 nm to 255 nm, more preferably 185 nm to 240 nm. Within this range, the first layer can achieve both short-wavelength dispersion and long-wavelength dispersion within the aforementioned range.

[0074] At a wavelength of 550 nm, the out-of-plane retardation of the first layer 100 can be from 80 nm to 250 nm, specifically 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, or 250 nm, preferably from 95 nm to 200 nm, and more preferably from 105 nm to 180 nm. Within this range, the first layer can improve lateral reflectivity.

[0075] At a wavelength of 550 nm, the biaxiality of the first layer can be 1 to 1.5, specifically 1, 1.1, 1.2, 1.3, 1.4, or 1.5, preferably 1 to 1.3, and more preferably 1.1 to 1.3. Within this range, the first layer can improve lateral reflectivity.

[0076] The thickness of the first layer 100 can be 70 μm or less, for example, greater than 0 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm or 70 μm, specifically from 20 μm to 70 μm, and more specifically from 20 μm to 50 μm. Within this range, the first layer can be used in optical films.

[0077] The first layer 100 may have a lower glass transition temperature than each of the second layer 200 and the third layer 300. The glass transition temperature of the first layer 100 may be from 100°C to 150°C, specifically 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, or 150°C, preferably from 120°C to 140°C. Within this range, the optical film can achieve the desired delay without cracking when stretched during the formation of the first and second layers.

[0078] The first layer 100 may have a higher modulus than each of the second layer 200 and the third layer 300. The modulus of the first layer 100 may be from 1 GPa to 10 GPa, specifically 1 GPa, 2 GPa, 3 GPa, 4 GPa, 5 GPa, 6 GPa, 7 GPa, 8 GPa, 9 GPa or 10 GPa, for example, from 2 GPa to 5 GPa. Within this range, the reliability of the first layer can be further improved by bonding it with a primer layer according to the invention.

[0079] The first layer 100 is a non-liquid crystal film or a liquid crystal film. Preferably, the first layer 100 comprises a stretched non-liquid crystal film formed of an optically transparent resin. "Non-liquid crystal film" may mean a film that is not formed of at least one of liquid crystal monomers, liquid crystal oligomers, and liquid crystal polymers, or a film formed of a material that will not be converted into liquid crystal monomers, liquid crystal oligomers, or liquid crystal polymers by light irradiation.

[0080] For example, the first layer 100 may include at least one of the following: cellulose resins including triacetyl cellulose; polyester resins including polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate; cyclic olefin copolymer (COC) resins; cyclic olefin polymer (COP) resins; polycarbonate resins; polyethersulfone resins; polysulfone resins; polyamide resins; polyimide resins; polyolefin resins; polyarylate resins; polyvinyl alcohol resins; polyvinyl chloride resins; and polyvinylidene chloride resins. Preferably, the first layer 100 includes a cyclic olefin polymer (COP) film to ensure short-wavelength and long-wavelength dispersion within the aforementioned ranges. Cycloolefin polymer films can provide an advantageous effect of improving frontal reflectivity in polarizers according to the invention, and when applied to the first and second primer layers, they can ensure good peel strength.

[0081] The first layer 100 may be a hydrophobic film. For example, the hydrophobic film may include a cyclic olefin polymer (COP) film and / or a cyclic olefin copolymer (COC) film. In one embodiment, the first layer may include a film formed of a resin having a positive (+) intrinsic birefringence.

[0082] The first layer 100 can have the aforementioned delay by forming a first primer layer and a coating layer for the coating layer on an unstretched or partially stretched film for the first layer, and then simultaneously stretching the laminate of the unstretched or partially stretched film, the first primer layer, and the coating layer for the coating layer. Preferably, to ensure the effectiveness of the invention, the first layer is formed by a subsequent process. This will be described in more detail below.

[0083] Second floor

[0084] A second layer 200 is formed on the lower surface of the first primer layer 150. Although the second layer may be a layer that does not substantially exhibit in-plane retardation, preferably, the second layer 200 has an in-plane retardation of 70 nm to 120 nm at a wavelength of 550 nm to provide anti-reflective properties. Therefore, when combined with the first layer, the second layer 200 can achieve a significant reduction in reflectivity on both the front and side surfaces, while improving the ellipticity of the side surfaces. Specifically, at a wavelength of 550 nm, the in-plane retardation of the second layer 200 may be 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm, or 120 nm, preferably 80 nm to 115 nm, and more preferably 80 nm to 110 nm.

[0085] The second layer 200 exhibits positive dispersion and may have a short-wavelength dispersion of 1 to 1.15 and a long-wavelength dispersion of 0.94 to 1. Within this range, compared to the first layer, the second layer can improve the ellipticity at each wavelength by reducing wavelength dispersion, thereby improving reflectivity. Preferably, the second layer has a short-wavelength dispersion of 1 to 1.06 and a long-wavelength dispersion of 0.97 to 1. In one embodiment, the second layer may have an in-plane retardation of 80 nm to 120 nm at a wavelength of 450 nm, preferably 85 nm to 115 nm, more preferably 90 nm to 110 nm, and an in-plane retardation of 80 nm to 110 nm at a wavelength of 650 nm, preferably 85 nm to 105 nm. Within this range, the second layer can readily achieve short-wavelength and long-wavelength dispersions within the aforementioned ranges.

[0086] The out-of-plane retardation of the second layer 200 at a wavelength of 550 nm can be from -250 nm to -50 nm, specifically -250 nm, -240 nm, -230 nm, -220 nm, -210 nm, -200 nm, -190 nm, -180 nm, -170 nm, -160 nm, -150 nm, -140 nm, -130 nm, -120 nm, -110 nm, -100 nm, -90 nm, -80 nm, -70 nm, -60 nm, or -50 nm, preferably from -150 nm to -60 nm. Within this range, the second layer can improve lateral reflectivity by improving the ellipticity of the sides.

[0087] The biaxiality of the second layer 200 at a wavelength of 550 nm can be from -2 to -0.1, specifically -2, -1.9, -1.8, -1.7, -1.6, -1.5, -1.4, -1.3, -1.2, -1.1, -1.0, -0.9, -0.8, -0.7, -0.6, -0.5, -0.4, -0.3, -0.2, or -0.1, preferably from -1.5 to -0.1, and more preferably from -0.5 to -0.1. Within this range, the second layer can improve lateral reflectivity by improving the ellipticity of the sides.

[0088] The total light transmittance of the second layer can be 90% or greater than 90%, for example, 90% to 100%, and the haze of the second layer can be 2% or less than 2%, for example, 0% to 2%, or greater than 0.5% to 2%. Within this range, the second layer can be used in optical films.

[0089] The thickness of the second layer 200 can be greater than 0 μm to 10 μm, specifically greater than 0 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm, for example, 1 μm to 10 μm, preferably 2 μm to 8 μm. Within this range, the thickness of the optical film can be reduced.

[0090] The second layer 200 has a lower refractive index than the first layer, and may have a refractive index of 1 to 2, preferably 1.4 to 1.6, and more preferably 1.5 to 1.6. Within this range, the second layer can help reduce the haze of the optical film while improving its transparency by controlling its refractive index relative to the first layer.

[0091] The second layer 200 may have a higher glass transition temperature than the first layer. The glass transition temperature of the second layer may be between 200°C and 300°C, specifically 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, or 300°C, preferably between 220°C and 280°C, and more preferably between 240°C and 250°C. Within this range, the second layer ensures the reliability of the optical film under high temperature (humidity) conditions.

[0092] The modulus of the second layer 200 can be from 1 GPa to 10 GPa, specifically 1 GPa, 2 GPa, 3 GPa, 4 GPa, 5 GPa, 6 GPa, 7 GPa, 8 GPa, 9 GPa or 10 GPa, for example, from 2 GPa to 5 GPa. Within this range, the reliability of the second layer can be further improved by bonding it with the primer layer according to the invention.

[0093] The second layer 200 may be formed of a different material than the first layer and have a different birefringence than the first layer. The second layer may be formed of a material with a negative (-) intrinsic birefringence.

[0094] The second layer 200 is a non-liquid crystal retardation layer and may contain polystyrene-based polymers and / or cellulose-based polymers as major components. According to the invention, considering the aforementioned retardation and wavelength dispersion, while ensuring good peel strength relative to the first primer layer, the second layer is preferably formed of a composition containing halogen-containing polystyrene-based polymers and / or halogen-containing cellulose-based polymers. Preferably, the halogen is fluorine. In this document, "polymer" includes oligomers, polymers, or resins. In this document, "major component" refers to a component present in the second layer 200 in an amount of 95% by weight or greater than 95% by weight, specifically in an amount of 95% to 99% by weight.

[0095] Halogen-containing polystyrene polymers may include repeating units represented by Formula 1:

[0096] [Formula 1]

[0097]

[0098] in It is a connection site;

[0099] R 1 R 2 and R 3 Each is independently a hydrogen atom, an alkyl group, a substituted alkyl group, or a halogen;

[0100] R is independently an alkyl group, a substituted alkyl group, a halogen, a hydroxyl group, a carboxyl group, a nitro group, an alkoxy group, an amino group, a sulfonate group, a phosphate group, an acyl group, an acyloxy group, a phenyl group, an alkoxycarbonyl group, or a cyano group. 1 R 2 and R 3 At least one of them is a halogen and / or at least one R is a halogen; and n is an integer from 0 to 5.

[0101] In one embodiment, halogen represents fluorine (F), Cl, Br, or I, preferably F.

[0102] Halogenated polystyrene polymers can be formed, for example, by polymerizing a mixture containing, 1-(2,2-difluorovinyl)-2-fluorobenzene and / or 1',2',2'-trifluorostyrene. The mixture may also contain styrene.

[0103] Cellulose-based polymers may include at least one unit in which at least some of the hydroxyl groups [C2 hydroxyl, C3 hydroxyl, or C6 hydroxyl] of the sugar monomer constituting cellulose are replaced by acyl or ether groups. That is, cellulose-based polymers may include cellulose ester polymers and / or cellulose ether polymers.

[0104] For example, cellulose-based polymers may include cellulose ester polymers having units in which at least some of the hydroxyl groups [C2-hydroxyl, C3-hydroxyl, or C6-hydroxyl] of the sugar monomers constituting cellulose are substituted with acyl groups, as represented by Formula 2. Here, the acyl groups may be substituted or unsubstituted.

[0105] [Equation 2]

[0106]

[0107] Where n is 1 or an integer greater than 1.

[0108] Substituents for cellulose esters or acyl groups may include those selected from halogen atoms, nitro groups, alkyl groups (e.g., C1 to C2), and alkyl groups. 20 Alkyl), alkenyl (e.g., C2 to C3) 20 alkenyl), cycloalkyl (e.g., C3 to C4) 10 cycloalkyl), aryl (e.g., C6 to C6) 20 aryl), heteroaryl (e.g., C3 to C4), 10 aryl), alkoxy (e.g., C1 to C1) 20 The substituents may be the same as or different from each other.

[0109] In this paper, "acyl" can refer to the well-known RC (=O)-* (* is the linking site, R is C1 to C2). 20 Alkyl, C3 to C 20cycloalkyl, C6 to C 20 Aryl or C7 to C 20 Arylalkyl). The "acyl" group is coupled to the cellulose ring via ester bonding (through the oxygen atom) in cellulose.

[0110] Here, for convenience, "alkyl," "alkenyl," "cycloalkyl," "aryl," "heteroaryl," "alkoxy," and "acyl" refer to non-halogenated compounds. The second delayed layer composition may comprise a single cellulose ester polymer or a mixture including cellulose ester polymers.

[0111] Here, "halogen" means fluorine (F), Cl, Br or I, preferably F.

[0112] A "halogen-containing functional group" is an organic functional group containing at least one halogen atom, and may include aromatic, aliphatic, or alicyclic functional groups. For example, a halogen-containing functional group can represent halogen-substituted C1 to C2 atoms. 20 Alkyl groups, halogenated C2 to C3 groups 20 Alkenyl, halogenated C2 to C 20 Alkyne group, halogenated C3 to C 10 cycloalkyl, halogenated C1 to C 20 Alkoxy, halogenated acyl, halogenated C6 to C 20 Aryl or halogenated C7 to C 20 Arylalkyl groups, but not limited to them.

[0113] "Halogen-substituted acyl group" can be represented as R'-C(=O)-* (* is the linkage site, R' is the halogen-substituted C1 to C2 group). 20 Alkyl groups, halogenated C3 to C4 groups 20 cycloalkyl, halogenated C6 to C 20 aryl, or halogenated C7 to C 20 Arylalkyl). "Halogen-substituted acyl groups" can be coupled to the cellulose ring via ester bonding (through oxygen atoms) in cellulose.

[0114] Cellulose ester polymers can be prepared by typical methods known to those skilled in the art, or can be obtained from commercially available products. For example, cellulose ester polymers having acyl groups as substituents can be prepared by reacting trifluoroacetic acid or trifluoroacetic anhydride with a sugar monomer or polymer of a sugar monomer constituting cellulose represented by Formula 2, by reacting trifluoroacetic acid or trifluoroacetic anhydride with it followed by further reacting it with an acylating agent (e.g., a carboxylic anhydride or carboxylic acid), or by reacting both an acylating agent and trifluoroacetic acid or trifluoroacetic anhydride with it.

[0115] The second retardation layer composition may also contain typical additives known to those skilled in the art. These additives may include, but are not limited to, wavelength dispersion modifiers (e.g., compounds containing aromatic fused rings, including 2-naphthylbenzoate, anthracene, phenanthrene, 2,6-naphthyldicarboxylate, etc.), pigments, antioxidants, antistatic agents, and heat stabilizers.

[0116] The second layer 200 is a stretched coating layer. This will be described in detail in the method for forming the optical film.

[0117] Third layer

[0118] The third layer 300 can further improve the lateral reflectivity. Although the third layer 300 can be a layer that does not substantially exhibit in-plane retardation, the third layer can include a positive (+)C layer that satisfies the following relationship: nz>nx≒ny (nx, ny, and nz are the refractive indices of the third layer in the slow axis, fast axis, and thickness direction, respectively, at a wavelength of 550 nm).

[0119] In one embodiment, the out-of-plane retardation of the third layer at a wavelength of 550 nm can be -300 nm to 0 nm, for example -200 nm to -10 nm. The in-plane retardation of the third layer at a wavelength of 550 nm can be 0 nm to 10 nm, for example 0 nm to 5 nm. Within this range, the third layer can achieve the aforementioned effect of reducing frontal reflectivity.

[0120] The third layer 300 may have a higher glass transition temperature than the first layer. The glass transition temperature of the third layer 300 may be between 200°C and 300°C, preferably between 220°C and 280°C, and more preferably between 240°C and 250°C. Within this range, the third layer will not deform at high temperatures, thus providing an advantageous effect in terms of peel strength reliability at high temperatures.

[0121] The modulus of the third layer 300 can be from 1 GPa to 10 GPa, for example, from 2 GPa to 5 GPa. Within this range, the reliability of the third layer can be further improved by combining it with the primer layer according to the invention.

[0122] The third layer 300 is a non-liquid crystal delay layer and may be formed of the same material as the second layer. The third layer may comprise a polystyrene-based polymer and / or a cellulose-based polymer having repeating units of Formula 1 or Formula 2 to ensure good peel strength relative to the second primer layer. For example, the third layer may be formed of a composition comprising a halogenated polystyrene-based polymer and / or a halogenated cellulose-based polymer. Preferably, the halogen is fluorine.

[0123] In one embodiment, a fluorinated polystyrene polymer can be prepared by polymerizing a mixture comprising 1-(2,2-difluorovinyl)-2-fluorobenzene and / or 1',2',2'-trifluorostyrene. The mixture may also contain styrene.

[0124] The thickness of the third layer 300 can be greater than 0 μm to 10 μm, for example greater than 1 μm to 5 μm, preferably greater than 1 μm to 2 μm. Within this range, the thickness of the optical film can be reduced.

[0125] The third layer 300 is an unstretched coating layer. This will be described in detail in the method for forming the optical film.

[0126] First primer layer and second primer layer

[0127] Each of the first primer layer 150 and the second primer layer 250 has a glass transition temperature of 50°C to 100°C and is a (meth)acrylate-based primer layer.

[0128] According to the present invention, a first primer layer disposed between the first and second layers and a second primer layer disposed between the first and third layers have specific glass transition temperatures and are formed of specific materials. Therefore, the optical film achieves delay in the separation of each of the first and second layers, prevents separation between the first and second layers during high-temperature stretching, and prevents delamination by reducing stress variations between the first, second, and third layers, thereby ensuring high reliability. The first, second, and third layers each have glass transition temperatures and moduli within the aforementioned ranges when evaluating durability through hot water immersion tests, heat resistance, and damp heat resistance. Furthermore, polarizing plates employing the optical film exhibit excellent heat resistance and damp heat resistance, and do not suffer from primer layer breakage due to embrittlement of the primer layer in either the optical film or the polarizing plate.

[0129] If the glass transition temperature of either the first or second primer layer is less than 50°C, the reliability and durability of the optical film and polarizer may deteriorate. If the glass transition temperature of either the first or second primer layer is greater than 100°C, there may be issues with primer layer breakage due to embrittlement. When the primer layer other than the (meth)acrylate resin has a glass transition temperature between 50°C and 100°C, there may be issues with poor durability, heat resistance, and damp heat resistance, or deterioration in the reliability of the polarizer.

[0130] Specifically, the glass transition temperature of each of the first primer layer and the second primer layer is 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, preferably 60°C to 100°C.

[0131] The first primer layer 150 and the second primer layer 250 may have the same glass transition temperature or different glass transition temperatures. Preferably, the difference in glass transition temperature between the first primer layer and the second primer layer may be in the range of 0°C to 10°C, specifically 0°C, 1°C, 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C, or 10°C, more preferably 0°C to 5°C. Within this range, good processability can be utilized to manufacture polarizing plates.

[0132] In one embodiment, each of the first primer layer 150 and the second primer layer 250 may have a lower modulus than each of the first, second, and third layers. Therefore, the optical film or polarizing plate can help improve durability, heat durability, and damp heat durability during immersion testing in hot water. In one embodiment, the modulus of each of the first primer layer 150 and the second primer layer 250 may be from 0.1 GPa to 5 GPa, preferably from 0.1 GPa to 3 GPa.

[0133] Each of the first primer layer 150 and the second primer layer 250 may be formed from a (meth)acrylate-based primer composition. The glass transition temperature of each of the first primer layer 150 and the second primer layer 250 may be achieved by adjusting the type and / or content of monomers in the (meth)acrylate-based copolymer and their weight-average molecular weight in the primer composition.

[0134] The primer composition may contain a (meth)acrylate copolymer as a major component and may achieve a glass transition temperature of 50°C to 100°C after curing. Here, "major component" means a component present in each of the first primer layer 150 and the second primer layer 250 in an amount of 95% by weight or greater than 95% by weight, specifically from 95% by weight to 99% by weight.

[0135] (Meth)acrylate copolymers can be copolymers comprising a mixture of monomers containing (meth)acrylic acid monomers, wherein the (meth)acrylic acid monomers have a glass transition temperature in the homopolymer phase of 10°C to 100°C, preferably 50°C to 80°C, and more preferably 60°C to 70°C. Within this range, the glass transition temperature of the primer layer can be readily achieved. Here, the "glass transition temperature in the homopolymer phase" can be measured by typical methods known to those skilled in the art, or can be obtained by referring to commercially available catalogues.

[0136] (Meth)acrylic acid monomers may include at least one selected from methyl methacrylate, butyl acrylate, hydroxyethyl methacrylate, cyclohexyl methacrylate, and 2-ethylhexyl acrylate. For example, (meth)acrylic acid monomers may be alkyl-containing (meth)acrylates, such as those containing C1 to C2. 10 Alkyl (meth)acrylates can improve the adhesion between the first and second layers, which each exhibit hydrophobic properties.

[0137] In addition to monomers having a glass transition temperature of 10°C to 100°C in the homopolymer phase, the monomer mixture may also contain peel strength enhancing compounds that can improve the peel strength of the interlayer.

[0138] Modified (meth)acrylate copolymers can be prepared by polymerization of peel strength enhancing compounds with monomers having a glass transition temperature of 10°C to 100°C in the homopolymer phase, or by modification of the side chains of homopolymers of monomers having a glass transition temperature of 10°C to 100°C, thereby improving the interlayer peel strength of each primer layer. When the peel strength enhancing compound is polymerized with monomers having a glass transition temperature of 10°C to 100°C in the homopolymer phase, the modified (meth)acrylate copolymer can be a random copolymer, block copolymer, alternating copolymer, or graft copolymer of monomers having a glass transition temperature of 10°C to 100°C in the homopolymer phase and the peel strength enhancing compound, preferably a block copolymer.

[0139] Peel strength enhancing compounds may include (meth)acrylate compounds and / or ester compounds.

[0140] (Meth)acrylate compounds may include at least one selected from the group consisting of alkyl (meth)acrylates, cycloalkyl (meth)acrylates, and non-cycloalkyl (meth)acrylates. Here, "alkyl" may be C1 to C2. 10 Alkyl groups, "cycloalkyl groups" can be C3 to C4. 10 Cycloalkyl, and "non-cycloalkyl" can be C5 to C6. 20 Non-cycloalkyl. For example, (meth)acrylate compounds may include (meth)acrylic acid with C1 to C2 atoms. 20 At least one monoester compound of a monool, such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, n-octyl methacrylate, lauryl methacrylate, and stearyl methacrylate, but not limited thereto.

[0141] The ester compound may be selected from formate ester compounds, acetate ester compounds, or (meth)acrylate ester compounds (e.g., butyl acetate, butyl formate, cyclohexyl 2-methyl-2-acrylate, 2-methyl-cyclohexyl 2-acrylate, and isopropyl acetate) to improve peel strength.

[0142] Other monomers used in the monomer mixture may include at least one compound selected from, for example, having polymerizable unsaturated bonds, other than hydroxyl-containing monomers and (meth)acrylate monomers: amide-containing monomers, such as (meth)acrylamide; carboxyl-containing monomers, such as maleic acid; epoxy-containing monomers, such as (meth)acryloyl glycidyl; acrylonitrile, styrene, vinyl acetate, vinyl chloride, etc.

[0143] The content of the peel strength enhancing compound relative to 100 parts by weight of the monomer mixture can be from 1 part by weight to 10 parts by weight, for example, from 5 parts by weight to 10 parts by weight. Within this range, the peel strength enhancing compound can improve the interlayer peel strength by increasing the interlayer adhesion without affecting the glass transition temperature of the primer layer.

[0144] Each of the (meth)acrylic acid copolymers and modified (meth)acrylic acid copolymers can be prepared by typical polymerization methods well known to those skilled in the art.

[0145] The primer composition may also contain at least one selected from peel strength enhancing compounds and curing agents.

[0146] The peel strength enhancing compound may include the peel strength enhancing compound described above. The content of the peel strength enhancing compound may optionally be from 0 to 10 parts by weight, for example, more than 0 to 5 parts by weight, relative to 100 parts by weight of the (meth)acrylate copolymer or modified (meth)acrylate copolymer. Within this range, the peel strength enhancing compound can improve the interlayer peel strength by increasing the interlayer adhesion without affecting the glass transition temperature of the primer layer.

[0147] Curing agents can further improve the peel strength of the primer layer by curing (meth)acrylate copolymers or modified (meth)acrylate copolymers. The curing agent can be appropriately selected based on the types of monomers contained in each of the (meth)acrylate copolymers or modified (meth)acrylate copolymers. For example, the curing agent may include an isocyanate curing agent as a thermosetting agent. Isocyanate curing agents may include hexamethylene diisocyanate and / or octamethylene diisocyanate.

[0148] The curing agent content relative to 100 parts by weight of the (meth)acrylate copolymer or modified (meth)acrylate copolymer may optionally be from 0 parts by weight to 10 parts by weight, specifically 0 parts by weight, 0.1 parts by weight, 0.5 parts by weight, 1 part by weight, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 4.5 parts by weight, 5 parts by weight, 5.5 parts by weight, 6 parts by weight, 6.5 parts by weight, 7 parts by weight, 7.5 parts by weight, 8 parts by weight, 8.5 parts by weight, 9 parts by weight, 9.5 parts by weight, or 10 parts by weight, for example, greater than 0 parts by weight to 5 parts by weight, specifically greater than 0.1 parts by weight to 3 parts by weight. Within this range, the curing agent can improve interlayer peel strength by increasing interlayer adhesion without affecting the glass transition temperature of the primer layer.

[0149] The primer composition may also contain a solvent. Organic solvents can provide poor properties in terms of haze and compatibility due to residual organic solvents, either by melting the first and second layers or by melting the first primer layer, but aqueous solvents do not suffer from these problems. Aqueous solvents may be water, including, but are not limited to, ultrapure water. Aqueous solvents may be present in the composition in balance. According to the invention, the primer composition contains an aqueous solvent and increases the peel strength between the first and second layers without increasing haze by improving the compatibility between the first and second layers.

[0150] The primer composition may also contain typical additives known to those skilled in the art.

[0151] Each of the primer layers can be formed by applying a primer layer composition to a predetermined thickness on a first layer and then performing light curing and / or heat curing.

[0152] The first primer layer 150 and the second primer layer 250 may have the same thickness or different thicknesses, and their thicknesses may be greater than 0 nm to 1,000 nm, specifically 1 nm, 5 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm or 1,000 nm, for example 100 nm to 500 nm, preferably 200 nm to 400 nm. Within this range, the optical film can further improve the interlayer reliability.

[0153] Next, a method for manufacturing an optical film according to one embodiment will be described.

[0154] The optical film according to the invention can be manufactured by forming a first primer layer on an unstretched or partially stretched film for a first layer, applying a second layer composition on the first primer layer to form a coating for the second layer, stretching the film, the first primer layer and the coating for the second layer as a whole, forming a second primer layer on the upper surface of the film, and then applying a third layer composition on the upper surface of the second primer layer to form a coating for the third layer.

[0155] The stretching can preferably be performed at 110°C to 150°C by stretching the film, the first primer layer, and the coating for the second layer as a whole to 1.1 to 1.8 times (preferably 1.1 to 1.5 times, more preferably 1.1 to 1.3 times) their initial length. The stretching can be performed by uniaxial or biaxial stretching of the film, the first primer layer, and the coating for the second layer as a whole in the machine direction (MD) or tilt direction of the film.

[0156] Stretching can be performed by dry stretching or wet stretching. Preferably, dry stretching is performed to reduce changes in the properties of the base film and the coating layer.

[0157] polarizing plate

[0158] The polarizing plate according to the invention includes a polarizer and an optical film according to the invention located on at least one surface of the polarizer.

[0159] Next, we will refer to Figure 2 A polarizing plate according to an embodiment of the present invention is described.

[0160] Reference Figure 2 The polarizing plate includes a protective layer 500, a polarizer 400, and an optical film, the optical film including a third layer 300, a second primer layer 250, a first layer 100, a first primer layer 150, and a second layer 200 stacked sequentially from the polarizer 400 in the stated order.

[0161] The third layer 300, the second primer layer 250, the first layer 100, the first primer layer 150, and the second layer 200 are substantially the same as the layers of the aforementioned optical film.

[0162] The polarizer 400 can convert natural light or polarized light into linearly polarized light by linearly polarizing light in a specific direction. The thickness of the polarizer can be from 2 μm to 30 μm, specifically from 4 μm to 25 μm. Within this range, the polarizer can be used in polarizing plates.

[0163] The polarizer 400 can be made of a polymer film mainly composed of polyvinyl alcohol resin.

[0164] The protective layer 500 is used to protect the polarizer from the influence of the external environment, while improving the mechanical strength of the polarizing plate.

[0165] The protective layer 500 may include an optically transparent protective coating layer and / or an optically transparent protective film. The protective coating layer may include a coating layer formed from a composition containing a photochemically curable compound. The protective film is an optically transparent film and may include a film formed from at least one of, for example: cellulose resins including triacetyl cellulose (TAC); polyester resins including polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, etc.; cyclic olefin polymer resins; polycarbonate resins; polyethersulfone resins; polysulfone resins; polyamide resins; polyimide resins; polyolefin resins; polyarylate resins; polyvinyl alcohol resins; polyvinyl chloride resins; and polyvinylidene chloride resins. Specifically, the protective film may be a TAC film or a PET film. The thickness of the protective layer may be from 0.1 μm to 100 μm, specifically from 5 μm to 70 μm, and more specifically from 15 μm to 45 μm. Within this scope, protective films can be used in polarizing plates. The protective layer can be omitted from the polarizing plate as long as it provides its inherent function. Although Figure 2 Not shown, but specifically, the protective layer can be bonded to the polarizer via an adhesive layer. The adhesive layer can be formed of a photocurable adhesive and / or a water-based adhesive, but is not limited thereto.

[0166] Optical display devices

[0167] The optical display device according to the present invention may include the optical film or polarizing plate according to the present invention. The optical display device may include organic light emitting diode (OLED) displays and liquid crystal displays.

[0168] In one embodiment, the OLED display device may include: an OLED panel comprising a flexible substrate; and a polarizing plate according to the invention stacked on the OLED panel.

[0169] In another embodiment, the OLED display device may include: an OLED panel comprising a non-flexible substrate; and a polarizing plate according to the invention stacked on the OLED panel.

[0170] The invention will now be described in more detail with reference to examples. However, it should be noted that these examples are for illustrative purposes only and should not be construed as limiting the invention in any way.

[0171] Example 1

[0172] (Meth)acrylic acid copolymers were prepared by polymerizing a monomer mixture containing only methyl methacrylate (glass transition temperature in the homopolymer phase: 60°C). Each of the first and second primer layer compositions was prepared by mixing 100 parts by weight of the (meth)acrylic acid copolymer with 1 part by weight of hexamethylene diisocyanate (HDI) as a curing agent.

[0173] A first primer layer is formed by depositing a first primer layer composition to a predetermined thickness on the lower surface of a cyclic olefin polymer (COP) membrane (ZD membrane, Zeon Co., Ltd.) (the membrane being stretched at an angle of 45° relative to the machine direction), followed by drying and curing.

[0174] A coating for the second layer is formed by depositing a second layer composition [containing a fluorinated polystyrene polymer, VM500, Eastman] on the lower surface of the first primer layer and then drying it.

[0175] A first primer layer (thickness: 200 nm) and a second layer (positive dispersion, thickness: 5 μm) were sequentially formed on the lower surface of the first layer (positive dispersion, thickness: 40 μm) by tilting and stretching the laminate of the COP film, the first primer layer, and the coating layer to 1.3 times its initial length at 0° relative to the machine direction of the COP film at 130°.

[0176] A second primer layer was formed by depositing a second primer layer composition on the upper surface of a first layer, followed by drying and curing. A third layer composition [containing a fluorinated polystyrene polymer, VM500, EASTMAN] was deposited onto the upper surface of the second primer layer and dried thereon to prepare a mixture in which the third layer (+C, Rth at 550 nm: -60 nm, positive dispersion, thickness: 2 μm, Tg: 240 to 250 °C, modulus: 2 GPa), the second primer layer (thickness: 200 nm, modulus: 0.5 GPa), and the first layer (550 nm) were deposited onto the upper surface of the second primer layer and dried thereon. The optical films are stacked in the order stated: Re: 225nm, NZ: 1.16, positive dispersion, thickness: 40μm, Tg: 120℃ to 140℃, modulus: 3GPa), first primer layer (thickness: 200nm, modulus: 0.5GPa) and second layer (Re: 110nm, NZ: -0.30, positive dispersion, thickness: 5μm, Tg: 240℃ to 250℃, modulus: 2GPa) at 550nm.

[0177] A polarizer (thickness: 13 μm, transmittance: 44%) was prepared by stretching a polyvinyl alcohol film to three times its initial length at 60 °C, dyeing the polyvinyl alcohol film with iodine, and then stretching the dyed polyvinyl alcohol film to 2.5 times its initial length in a boric acid aqueous solution at 40 °C.

[0178] A polarizing plate was prepared by bonding the prepared optical film to the lower surface of the polarizer, while simultaneously bonding a triacetyl cellulose film to the upper surface of the polarizer using a photocurable adhesive.

[0179] Example 2

[0180] The optical film and polarizing plate were prepared in the same manner as in Example 1, except that a composition containing a cellulose ester polymer (VM512, EASTMAN) was used instead of a composition containing a fluorinated polystyrene polymer as the second layer composition.

[0181] Example 3

[0182] A modified (meth)acrylic acid copolymer (a block copolymer of methyl methacrylate and cyclohexyl 2-methyl-2-acrylate) was prepared by polymerizing 100 parts by weight of a monomer mixture (containing 90 parts by weight of methyl methacrylate (glass transition temperature in the homopolymer phase: 60°C) and 10 parts by weight of 2-methyl-2-acrylate). Each of the first and second primer layer compositions was prepared by mixing 100 parts by weight of the (meth)acrylic acid copolymer with 1 part by weight of hexamethylene diisocyanate as a curing agent. Optical films and polarizing plates were prepared in the same manner as in Example 1, except that the prepared first and second primer layer compositions were used.

[0183] Example 4

[0184] A modified (meth)acrylic acid copolymer (a block copolymer of methyl methacrylate and butyl acetate) was prepared by polymerizing 100 parts by weight of a monomer mixture (containing 95 parts by weight of methyl methacrylate (glass transition temperature in the homopolymer phase: 60°C) and 5 parts by weight of butyl acetate). Each of the first and second primer layer compositions was prepared by mixing 100 parts by weight of the (meth)acrylic acid copolymer with 1 part by weight of hexamethylene diisocyanate as a curing agent. Optical films and polarizing plates were prepared in the same manner as in Example 1, except that the prepared first and second primer layer compositions were used.

[0185] Example 5

[0186] A modified (meth)acrylic acid copolymer was prepared by polymerizing 100 parts by weight of a monomer mixture comprising 90 parts by weight of methyl methacrylate (glass transition temperature in the homopolymer phase: 60°C) and 10 parts by weight of butyl formate. Each of the first and second primer layer compositions was prepared by mixing 100 parts by weight of the (meth)acrylic acid copolymer (a block copolymer of methyl methacrylate and butyl formate) with 1 part by weight of hexamethylene diisocyanate as a curing agent. Optical films and polarizing plates were prepared in the same manner as in Example 1, except that the prepared first and second primer layer compositions were used.

[0187] Example 6

[0188] Except for changing the polymerization time and temperature in the preparation of the (meth)acrylic acid copolymer, the optical film and polarizing plate were prepared in the same manner as in Example 1.

[0189] Comparative Examples 1 to 8

[0190] Except for changes to the first and second primer compositions as listed in Table 1, the optical film and polarizing plate were prepared in the same manner as in Example 1.

[0191] Table 1

[0192]

[0193] *In Table 1, Comparative Example 1 is Paraloid B-44 (Dow Inc.).

[0194] The following properties of the optical films and polarizing plates prepared in the examples and comparative examples were evaluated, and the results are shown in Table 2.

[0195] (1) Glass transition temperature of primer layer (unit: °C): The glass transition temperature Tg of the first primer layer (which was formed in the same manner as the second primer layer) formed in the same manner as each of the examples and comparative examples was measured by differential scanning calorimetry (DSC).

[0196] (2) Haze (unit: %) and transmittance (unit: %) of optical film: The haze and transmittance of optical film were measured at wavelengths from 380 nm to 780 nm using a haze meter (Nippon Denshoku Co., Ltd.).

[0197] (3) Peel strength between layers (unit: gf / 25mm): Each of the optical films was cut into samples of 25mm × 100mm in size, and then laminated onto an alkali-free glass plate using a pressure-sensitive adhesive, so that the second layer was attached to the glass plate. Next, the samples were compressed in an autoclave (at 50°C and 5 atm) for 20 minutes and placed under constant temperature and humidity conditions (23°C, 50% RH) for 4 hours. Subsequently, the peel strength was measured using a peel strength tester (Texture analyzer, Stable Micro-System Inc., UK (GB)) at 25°C under peel rate of 300mm / min and peel angle of 180°. With the first layer (i.e., COP film) fixed to the peel strength tester by the clamps of the peel strength tester, the peel strength of the interlayer primer between the first and second layers was measured while the sample was pulled from the second layer at a 180° angle with a constant force.

[0198] (4) Cross-cut between layers: Adhesion was evaluated using a cross-cut method. Each component of the optical film was cut into 10mm × 10mm (length × width) square samples. Then, 10 longitudinal lines and 10 transverse lines were drawn on the samples, and the samples were cut along these lines to the depth of the first layer to divide the samples into a total of 100 pieces. Adhesive tape (General Consumables, Nichiban Co., Ltd.) was applied to the second layer, and the number of pieces remaining on the second layer was counted when the tape was peeled off. The more pieces remaining on the second layer, the better the peel strength. Retaining 100 blocks on the second layer is rated 5B, retaining 80 to less than 100 blocks on the second layer is rated 4B, retaining 60 to less than 80 blocks on the second layer is rated 3B, retaining 40 to less than 60 blocks on the second layer is rated 2B, and retaining less than 40 blocks on the second layer is rated 1B.

[0199] (5) Durability under immersion in hot water: Each of the optical films was cut into a 10mm × 10mm (length × width) square sample, which was then immersed in water at 85°C for 1 hour. After that, the separation between the first and second layers and between the first and third layers was evaluated. No separation was rated as "○", and even slight separation was rated as "x".

[0200] (6) Reliability of the optical film: Each optical film was cut into a 10mm × 10mm (length × width) square sample and then placed at 85°C for 500 hours (heat resistance) or at 85°C and 85% RH for 500 hours (damp heat resistance). Afterwards, bulging, delamination, appearance deformation, and bubble formation at the end portions were visually evaluated. The absence of such phenomena was rated as "○", while the presence of such phenomena was rated as "x".

[0201] (7) Reliability of polarizing plates: Each polarizing plate was cut into a 10mm × 10mm (length × width) square sample and then placed at 85°C for 500 hours (heat resistance) or at 85°C and 85% RH for 500 hours (damp heat resistance). Afterwards, bulging, delamination, appearance deformation, and bubble formation at the ends were visually evaluated. The absence of such phenomena was rated as "○", while the presence of such phenomena was rated as "x".

[0202] Table 2

[0203]

[0204] As shown in Table 2, the optical film according to the present invention exhibits low haze and good interlayer peel strength, while providing good adhesion between the primer layer and the delay layer by providing good cross-cut evaluation results. The optical film according to the present invention exhibits good properties in terms of durability, heat durability, and damp heat durability during hot water immersion tests. Furthermore, polarizing plates including the optical film according to the present invention exhibit good properties in both heat durability and damp heat durability.

[0205] Conversely, the optical films of Comparative Examples 1 to 6, which were prepared without using a (meth)acrylate primer layer as the first and second primer layers, failed to achieve all the effects of the present invention. The optical films of Comparative Examples 7 and 8, prepared using a (meth)acrylate primer layer whose glass transition temperature is outside the range of the present invention, also failed to achieve all the effects of the present invention.

[0206] It should be understood that those skilled in the art can make various modifications, alterations, changes, and equivalent embodiments without departing from the spirit and scope of the invention.

Claims

1. An optical film, comprising: The third layer, the second primer layer, the first layer, the first primer layer and the second layer are stacked in the order stated, wherein each of the first primer layer and the second primer layer has a glass transition temperature of 50°C to 100°C, and each of the first primer layer and the second primer layer is a (meth)acrylate primer layer. The first layer has a lower glass transition temperature and a higher Young's modulus than each of the second and third layers; the Young's modulus of the first, second, and third layers are 1 GPa to 10 GPa, respectively; the glass transition temperature of the first layer is 100°C to 150°C; and the glass transition temperatures of the second and third layers are 200°C to 300°C, respectively. The (meth)acrylate-based primer layer is formed by a primer layer composition comprising a copolymer of monomer mixtures, wherein the monomer mixtures contain (meth)acrylate monomers having a glass transition temperature of 10°C to 100°C in a homopolymer phase. The copolymer of the (meth)acrylic acid monomer is a component present in the primer composition in an amount of 95% to 99% by weight.

2. The optical film according to claim 1, wherein the first layer is a hydrophobic retardation film.

3. The optical film according to claim 2, wherein the hydrophobic retardation film comprises at least one selected from cyclic olefin polymer films and cyclic olefin copolymer films.

4. The optical film according to claim 1, wherein the second layer is a non-liquid crystal layer having an in-plane retardation of 70 nm to 120 nm at a wavelength of 550 nm.

5. The optical film according to claim 1, wherein the third layer is a non-liquid crystal positive C delay layer.

6. The optical film of claim 1, wherein each of the second layer and the third layer comprises at least one selected from polystyrene-based polymers and cellulose-based polymers.

7. The optical film of claim 6, wherein each of the polystyrene polymer and the cellulose polymer comprises one or more halogens.

8. The optical film according to claim 7, wherein the halogen is fluorine.

9. The optical film according to claim 1, wherein the (meth)acrylic monomer comprises an alkyl-containing (meth)acrylic ester.

10. The optical film of claim 1, wherein the monomer mixture further comprises a peel strength enhancing compound.

11. The optical film according to claim 10, wherein the peel strength enhancing compound comprises at least one selected from methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, n-octyl methacrylate, lauryl methacrylate, stearyl methacrylate, butyl acetate, butyl formate, 2-methyl-2-cyclohexyl acrylate, 2-methyl-cyclohexyl acrylate, and isopropyl acetate.

12. The optical film of claim 11, wherein the peel strength enhancing compound comprises at least one selected from butyl acetate, butyl formate, cyclohexyl 2-methyl-2-acrylate, 2-methyl-cyclohexyl 2-acrylate, and isopropyl acetate.

13. The optical film of claim 1, wherein the primer composition further comprises at least one selected from peel strength enhancing compounds and curing agents.

14. The optical film according to claim 1, wherein the haze of the optical film is 0.3% or less than 0.3%, the peel strength between the first layer and the second layer is 300 gf / 25 mm or greater than 300 gf / 25 mm, and the peel strength between the first layer and the third layer is 300 gf / 25 mm or greater than 300 gf / 25 mm.

15. A polarizing plate, comprising: polarizer; And an optical film according to any one of claims 1 to 14, formed on at least one surface of the polarizer.

16. An optical display device comprising a polarizing plate according to claim 15.

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