Laminated optical film and image display device

Abstract

Provided is a laminated optical film including at least an acrylic film and a first optical film laminated to each other with an adhesive layer interposed therebetween, wherein the adhesive layer is made of a layer of a cured product formed from an adhesive composition including at least a polymerizable compound, the laminated optical film has a structure in which the acrylic film is in direct contact with the adhesive layer. The polymerizable compound contained in the adhesive composition has an octanol-water partition coefficient, log Pow, calculated as a weighted average of molar fractions, of 1.8-3.0. The adhesive layer has an elastic modulus of 1 × 105 Pa to 3 × 106 Pa inclusive.

Description

Laminated optical film and image display device

[0001] The present invention relates to a laminated optical film comprising at least an acrylic film and a first optical film laminated together via an adhesive layer, which can be used to form image displays such as mobile phones, car navigation devices, personal computer monitors, and televisions.

[0002] Image display devices such as mobile phones, car navigation devices, PC monitors, and televisions are equipped with laminated optical films in which multiple optical films are laminated via adhesive or pressure-sensitive adhesive layers. The optical films used are polarizers and transparent resin films such as acrylic films.

[0003] With regard to acrylic films, since there are almost no functional groups on the film surface that can contribute to improving adhesive strength, there is a concern that the adhesive strength between the acrylic film and other optical films may be insufficient when the film is formed into a laminated optical film. In response to this, Patent Document 1 below describes an optical film laminate in which a (meth)acrylic resin layer and a thermoplastic resin film such as a cycloolefin resin film are bonded together with sufficient adhesive strength using an active energy ray-curable adhesive, thereby achieving a lightweight and thin optical film laminate. The adhesive layer is formed using an active energy ray-curable adhesive containing 2 to 35 parts by weight of a polymerizable monomer that dissolves the (meth)acrylic resin layer and 30 to 60 parts by weight of a polymerizable multifunctional acrylate compound, relative to a total of 100 parts by weight of the active energy ray-curable compound, including a polymerizable monomer that dissolves the (meth)acrylic resin layer and a polymerizable multifunctional acrylate compound.

[0004] Japanese Patent Application Laid-Open No. 2014-232251

[0005] Recently, durability tests required for laminated optical films used in automotive applications include, for example, a humidity durability test in which the film is exposed to an environment of 65°C and 95% humidity for 1,000 hours. The present inventors conducted a detailed study of the appearance of the laminated optical film after such a humidity durability test and found that bright spots resulting from white, hazy foreign matter appear, particularly at the edges of the laminated optical film, resulting in product defects in terms of appearance characteristics. This phenomenon was observed for the first time after a durability test in a high-temperature, high-humidity environment, and further investigation was required to resolve the issue.

[0006] The present invention was developed in consideration of the above-mentioned circumstances, and aims to provide a laminated optical film that includes at least an acrylic film, in which the occurrence of bright spots caused by foreign matter is suppressed even after a humid durability test, and which has excellent appearance characteristics and excellent adhesive strength between laminated optical films.

[0007] The above-mentioned problems can be solved by the following configuration: That is, the present invention provides a laminated optical film in which at least an acrylic film and a first optical film are laminated via an adhesive layer, the adhesive layer being formed of a cured layer of an adhesive composition containing at least a polymerizable compound, the acrylic film and the adhesive layer having a structure in which they are in direct contact with each other, the log Pow representing an octanol / water partition coefficient calculated as a weighted average of the molar fractions of the polymerizable compounds contained in the adhesive composition being 1.8 or more and 3.0 or less, and the elastic modulus of the adhesive layer being 1×10 ５ Pa or more and 3 x 10 ６ The present invention relates to a laminated optical film (1) having a modulus of elasticity of 100 Pa or less.

[0008] In the laminated optical film (1), the first optical film is preferably a laminated optical film (2) in which the first optical film is a liquid crystal film or a retardation film.

[0009] In the laminated optical film (1) or (2), a laminated optical film (3) is preferred in which the thickness of the adhesive layer is 0.1 to 10 μm.

[0010] In any one of the laminated optical films (1) to (3), a laminated optical film (4) is preferred in which a second optical film is further laminated via a pressure-sensitive adhesive layer on the surface of the first optical film opposite to the surface on which the acrylic film is laminated.

[0011] In any one of the laminated optical films (1) to (4), a laminated optical film (5) is preferred in which the second optical film is a liquid crystal film or a retardation film.

[0012] In any one of the laminated optical films (1) to (5), the adhesive composition contains a polymerizable compound A, and the polymerizable compound A is a urethane (meth)acrylate having a molecular weight of 5,000 or more and having at least two polymerizable groups, and when the total amount of the polymerizable compounds contained in the adhesive composition is 100 parts by mass, a laminated optical film (6) is preferred in which the content of the polymerizable compound A is 4 parts by mass or more and 30 parts by mass or less.

[0013] In any one of the laminated optical films (1) to (6), the adhesive composition contains a polymerizable compound B, and the polymerizable compound B is a compound having at least two polymerizable groups. When the total amount of the polymerizable compounds contained in the adhesive composition is taken as 100 parts by mass, the content of the polymerizable compound B is preferably 0 parts by mass or more and 15 parts by mass or less.

[0014] In any one of the laminated optical films (1) to (7), the adhesive composition contains a polymerizable compound C, and the polymerizable compound C has a log Pow of 1.0 or more and 8.0 or less, which represents an octanol / water partition coefficient, and the content of the polymerizable compound C is 50 parts by mass or more and 95 parts by mass or less when the total amount of the polymerizable compounds contained in the adhesive composition is 100 parts by mass. (8)

[0015] In any one of the laminated optical films (1) to (8), the adhesive composition contains a polymerizable compound C, and the polymerizable compound D is a compound having a refractive index of 1.5 or more and 1.7 or less, and when the total amount of the polymerizable compounds contained in the adhesive composition is taken as 100 parts by mass, a laminated optical film (9) is preferred in which the content of the polymerizable compound D is 0 parts by mass or more and 95 parts by mass or less.

[0016] The present invention also relates to an image display device (10) comprising at least one of the laminated optical films (1) to (9).

[0017] As mentioned above, since there are almost no functional groups on the film surface that can contribute to improving adhesive strength, there is a concern that the adhesive strength will be insufficient when the acrylic film is used as a laminated optical film. Regarding acrylic films, there is a method of increasing the adhesive strength between the acrylic film and the adhesive layer by applying an easy-adhesion adhesive containing an aqueous urethane resin or the like to the acrylic film to form an easy-adhesion layer. However, due to process constraints, it may be necessary to manufacture a laminated optical film with a structure in which the acrylic film and the adhesive layer are in direct contact without forming an easy-adhesion layer on the acrylic film. In this case, there is a concern that the adhesive strength will be insufficient due to the low interaction between the acrylic film and the adhesive layer.

[0018] Incidentally, laminated optical films used in automotive applications, for example, are required to have excellent appearance characteristics even after a humidity durability test in which the films are exposed to an environment of 65°C and 95% humidity for 1,000 hours. Components that adversely affect appearance characteristics include oxalic acid bright spots, which are generated when oxalic acid present in the atmosphere forms a salt during heating or drying processes using ovens or heating devices, or during film surface modification processes such as corona treatment, plasma treatment, and Itro treatment. Conventionally, oxalic acid bright spots have been a problem in adhesive layers in contact with polarizers that contain metal components such as zinc, which cause oxalic acid bright spots. However, as a result of studies by the present inventors, it has been found that even in adhesive layers that do not contact polarizers, specifically adhesive layers in direct contact with acrylic films in this invention, deterioration of appearance characteristics occurs due to oxalic acid bright spots generated by the incorporation of oxalic acid via water vapor or moisture in the atmosphere.

[0019] As described above, laminated optical films including acrylic films have a unique problem in that, due to the absence of functional groups on the surface of the acrylic film that can contribute to adhesion, it is difficult to increase the adhesive strength between the acrylic film and the adhesive layer while suppressing the occurrence of oxalic acid bright spots when the acrylic film is not treated with an easy-to-use adhesive containing an aqueous urethane resin or the like, i.e., when the acrylic film and the adhesive layer are in direct contact with each other. However, in the laminated optical film according to the present invention, the occurrence of bright spots due to foreign matter is suppressed even after a humidity durability test, and the film has excellent appearance characteristics and excellent adhesive strength between the laminated optical films. The reason for this effect is unclear, but the following reasons are thought to be the cause.

[0020] The laminated optical film according to the present invention is a laminated optical film in which at least an acrylic film and a first optical film are laminated via an adhesive layer, the adhesive layer being formed of a cured layer of an adhesive composition containing at least a polymerizable compound, and the acrylic film and the adhesive layer are in direct contact with each other. The laminated optical film according to the present invention has a structure in which (i) the log Pow, which represents the octanol / water partition coefficient calculated by the weighted average of the molar fractions of the polymerizable compounds contained in the adhesive composition, is 1.8 or more and 3.0 or less, and (ii) the elastic modulus of the adhesive layer is 1×10 ５ Pa or more and 3 x 10 ６ The laminated optical film according to the present invention is designed to have a viscosity of 0.05 Pa or less. As described above, oxalic acid, a component that adversely affects appearance characteristics, can be mixed into the adhesive layer from the atmosphere via water vapor or moisture during each manufacturing process. However, in the present invention, the above-described configuration (i) is particularly provided, making the adhesive layer sufficiently hydrophobic, suppressing the incorporation of oxalic acid into the adhesive layer and suppressing the occurrence of oxalic acid bright spots that cause deterioration of appearance characteristics. On the other hand, when an acrylic film and an adhesive layer are in direct contact with each other, it is difficult to increase the adhesive strength between the acrylic film and the adhesive layer. However, since the laminated optical film according to the present invention has the above-described configuration (ii), the adhesive layer has a sufficiently low elasticity, which causes stress relaxation at the interface between the acrylic film and the adhesive layer, thereby increasing the adhesion between the two and increasing the adhesive strength. As a result, the laminated optical film according to the present invention suppresses the occurrence of bright spots due to foreign matter even after a humidity durability test, and exhibits excellent appearance characteristics and excellent adhesive strength between the laminated optical films.

[0021] In particular, when the adhesive layer of the laminated optical film of the present invention contains at least one of the specific polymerizable compounds A to D, the adhesion to the acrylic film or the effect of suppressing the generation and diffusion of oxalic acid bright spots is further improved.

[0022] 1 is an example of a cross-sectional schematic view of a laminated optical film according to one embodiment of the present invention.

[0023] FIG. 1 shows an example of a cross-sectional schematic diagram of a laminated optical film according to one embodiment of the present invention. In this embodiment, a laminated optical film 10 includes an acrylic film 1 and a first optical film 2 laminated together via an adhesive layer 3. No adhesive layer or the like is interposed between the acrylic film 1 and the adhesive layer 3, and the acrylic film 1 and the adhesive layer 3 are in direct contact with each other. Details of the acrylic film 1, the first optical film 2, and the adhesive layer 3 will be described separately. In this embodiment, the laminated optical film 10 further includes a triacetyl cellulose film 6, which is a transparent protective film, laminated via an aqueous adhesive layer 7 on the surface of the acrylic film 1 opposite to the surface on which the first optical film 2 is laminated. Furthermore, a second optical film 4 is laminated via an adhesive layer 5 on the surface of the first optical film 2 opposite to the surface on which the acrylic film 1 is laminated. Details of the adhesive layer 5 and the second optical film 4 will be described separately. In this embodiment, the surface of the second optical film 4 opposite to the surface on which the first optical film 2 is laminated is attached to an image display device (not shown in FIG. 1 ) via an adhesive layer 8. Each component will be described below.

[0024] <Acrylic Film> The acrylic film contains a (meth)acrylic resin. The (meth)acrylic resin film can be obtained, for example, by extrusion molding a molding material containing a resin component mainly containing a (meth)acrylic resin.

[0025] The (meth)acrylic resin preferably has a Tg (glass transition temperature) of 70° C. or higher, more preferably 110° C. or higher, even more preferably 115° C. or higher, and particularly preferably 120° C. or higher. The (meth)acrylic resin film can have excellent durability by containing, as a main component, a (meth)acrylic resin having a Tg (glass transition temperature) of 70° C. or higher. The upper limit of the Tg of the (meth)acrylic resin is not particularly limited, but is preferably 170° C. or lower from the viewpoint of formability, etc.

[0026] Any appropriate (meth)acrylic resin can be used as the (meth)acrylic resin. Examples include poly(meth)acrylic acid esters such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymers, methyl methacrylate-(meth)acrylic acid ester copolymers, methyl methacrylate-acrylic acid ester-(meth)acrylic acid copolymers, methyl (meth)acrylate-styrene copolymers (such as MS resins), and polymers having alicyclic hydrocarbon groups (such as methyl methacrylate-cyclohexyl methacrylate copolymers and methyl methacrylate-norbornyl (meth)acrylate copolymers). Preferred are poly(C1-6 alkyl(meth)acrylates) such as polymethyl (meth)acrylate. More preferred are methyl methacrylate resins containing methyl methacrylate as the main component (50 to 100% by weight, preferably 70 to 100% by weight).

[0027] In the present invention, the (meth)acrylic resin is preferably a (meth)acrylic resin having a glutaric anhydride structure, a (meth)acrylic resin having a lactone ring structure, or a (meth)acrylic resin having a glutarimide structure, because they have high heat resistance, high transparency, and high mechanical strength.

[0028] Examples of the (meth)acrylic resin having a glutaric anhydride structure include (meth)acrylic resins having a glutaric anhydride structure described in JP-A Nos. 2006-283013, 2006-335902, and 2006-274118.

[0029] Examples of the (meth)acrylic resin having a lactone ring structure include (meth)acrylic resins having a lactone ring structure described in JP-A Nos. 2000-230016, 2001-151814, 2002-120326, 2002-254544, and 2005-146084.

[0030] Examples of the (meth)acrylic resin having a glutarimide structure include (meth)acrylic resins having a glutarimide structure described in JP-A Nos. 2006-309033, 2006-317560, 2006-328329, 2006-328334, 2006-337491, 2006-337492, 2006-337493, 2006-337569, and 2007-009182.

[0031] The content of the (meth)acrylic resin in the (meth)acrylic resin film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, even more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. If the content of the (meth)acrylic resin in the (meth)acrylic resin film is less than 50% by weight, the high heat resistance and high transparency inherent to the (meth)acrylic resin may not be fully exhibited.

[0032] The content of the (meth)acrylic resin in the molding material used to mold the (meth)acrylic resin film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, even more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. If the content of the (meth)acrylic resin in the molding material used to mold the (meth)acrylic resin film is less than 50% by weight, the high heat resistance and high transparency inherent to the (meth)acrylic resin may not be fully exhibited.

[0033] The (meth)acrylic resin film may contain other thermoplastic resins in addition to the (meth)acrylic resins. Examples of other thermoplastic resins include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, and poly(4-methyl-1-pentene); halogenated vinyl polymers such as vinyl chloride, vinylidene chloride, and chlorinated vinyl resin; acrylic polymers such as polymethyl methacrylate; styrene polymers such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, and acrylonitrile-butadiene-styrene block copolymer; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyamides such as nylon 6, nylon 66, and nylon 610; polyacetal; polycarbonate; polyphenylene oxide; polyphenylene sulfide; polyether ether ketone; polysulfone; polyethersulfone; polyoxybenzylene; polyamide imide; and rubbery polymers such as ABS resins and ASA resins blended with polybutadiene rubber or acrylic rubber.

[0034] The content of the other thermoplastic resin in the (meth)acrylic resin film is preferably 0 to 50% by weight, more preferably 0 to 40% by weight, even more preferably 0 to 30% by weight, and particularly preferably 0 to 20% by weight.

[0035] The (meth)acrylic resin film may contain additives. Examples of the additives include hindered phenol-based, phosphorus-based, and sulfur-based antioxidants; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fiber and carbon fiber; ultraviolet absorbers such as phenyl salicylate, (2,2'-hydroxy-5-methylphenyl)benzotriazole, and 2-hydroxybenzophenone; near-infrared absorbers; flame retardants such as tris(dibromopropyl)phosphate, triallyl phosphate, and antimony oxide; antistatic agents such as anionic, cationic, and nonionic surfactants; colorants such as inorganic pigments, organic pigments, and dyes; organic and inorganic fillers; resin modifiers; organic and inorganic fillers; plasticizers; lubricants; antistatic agents; flame retardants; and retardation reducers.

[0036] The content of the additive in the (meth)acrylic resin film is preferably 0 to 5% by weight, more preferably 0 to 2% by weight, and even more preferably 0 to 0.5% by weight.

[0037] The method for producing a (meth)acrylic resin film is not particularly limited, but for example, a (meth)acrylic resin and other polymers, additives, etc. may be thoroughly mixed by any appropriate mixing method to form a thermoplastic resin composition in advance, which may then be molded into a film. Alternatively, a (meth)acrylic resin and other polymers, additives, etc. may be prepared as separate solutions, which may then be mixed to form a uniform mixture, which may then be molded into a film.

[0038] To produce the thermoplastic resin composition, the film raw materials are preblended in any suitable mixer such as an omnimixer, and then the resulting mixture is extrusion-kneaded. In this case, the mixer used for extrusion-kneading is not particularly limited, and any suitable mixer can be used, for example, an extruder such as a single-screw extruder or a twin-screw extruder, or a pressure kneader.

[0039] Examples of the film forming method include any appropriate film forming method such as solution casting (solution flow casting), melt extrusion, calendaring, compression molding, etc. Among these film forming methods, solution casting (solution flow casting) and melt extrusion are preferred.

[0040] Examples of solvents used in the solution casting method (solution flow casting method) include aromatic hydrocarbons such as benzene, toluene, xylene, etc.; aliphatic hydrocarbons such as cyclohexane, decalin, etc.; esters such as ethyl acetate, butyl acetate, etc.; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.; alcohols such as methanol, ethanol, isopropanol, butanol, isobutanol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, etc.; ethers such as tetrahydrofuran, dioxane, etc.; halogenated hydrocarbons such as dichloromethane, chloroform, carbon tetrachloride, etc.; dimethylformamide; dimethyl sulfoxide, etc. These solvents may be used alone or in combination of two or more.

[0041] Examples of devices for carrying out the solution casting method include a drum-type casting machine, a band-type casting machine, and a spin coater.

[0042] Examples of the melt extrusion method include a T-die method, an inflation method, etc. The molding temperature is preferably 150 to 350°C, more preferably 200 to 300°C.

[0043] When forming a film using the T-die method, a T-die is attached to the tip of a known single-screw extruder or twin-screw extruder, and the extruded film is wound up to obtain a roll of film. In this case, uniaxial stretching can be performed by appropriately adjusting the temperature of the winding roll and stretching in the extrusion direction. Furthermore, simultaneous biaxial stretching, sequential biaxial stretching, etc. can also be performed by stretching the film in a direction perpendicular to the extrusion direction.

[0044] The (meth)acrylic resin film may be either an unstretched film or a stretched film. When it is a stretched film, it may be either a uniaxially stretched film or a biaxially stretched film. When it is a biaxially stretched film, it may be either a simultaneous biaxially stretched film or a sequential biaxially stretched film. When it is biaxially stretched, the mechanical strength is improved and the film performance is improved. When the (meth)acrylic resin film is mixed with another thermoplastic resin, an increase in retardation can be suppressed even when stretched, and optical isotropy can be maintained.

[0045] The stretching temperature is preferably near the glass transition temperature of the thermoplastic resin composition that is the raw material for the film, and specifically, is preferably within the range of (glass transition temperature - 30°C) to (glass transition temperature + 100°C), and more preferably (glass transition temperature - 20°C) to (glass transition temperature + 80°C). If the stretching temperature is below (glass transition temperature - 30°C), a sufficient stretch ratio may not be obtained. Conversely, if the stretching temperature exceeds (glass transition temperature + 100°C), flow of the resin composition may occur, making stable stretching impossible.

[0046] The stretching ratio defined by the area ratio is preferably 1.1 to 25 times, more preferably 1.3 to 10 times. If the stretching ratio is less than 1.1 times, there is a risk that the stretching will not lead to an improvement in toughness. If the stretching ratio exceeds 25 times, there is a risk that the effect of increasing the stretching ratio will not be achieved.

[0047] The stretching speed in one direction is preferably 10 to 20,000% / min, more preferably 100 to 10,000% / min. If the stretching speed is less than 10% / min, it takes a long time to achieve a sufficient stretch ratio, which may increase production costs. If the stretching speed exceeds 20,000% / min, the stretched film may break.

[0048] The (meth)acrylic resin film may be subjected to heat treatment (annealing) or the like after stretching in order to stabilize its optical isotropy and mechanical properties. Any appropriate conditions may be adopted as the heat treatment conditions.

[0049] The thickness of the (meth)acrylic resin film is preferably 20 to 60 μm, more preferably 20 to 30 μm. If the thickness is less than 20 μm, not only will the strength decrease, but crimping may become significant when a durability test of the laminated optical film is performed. If the thickness exceeds 60 μm, transparency may decrease.

[0050] The laminated optical film according to the present invention has a structure in which an acrylic film and a first optical film are laminated via an adhesive layer, and the acrylic film and the adhesive layer are in direct contact with each other. In other words, the acrylic film does not have an easy-adhesion layer. However, the surface of the acrylic film that contacts the adhesive layer may be subjected to a surface modification treatment. Examples of the surface modification treatment include corona treatment, plasma treatment, and Itro treatment, with corona treatment being particularly preferred.

[0051] <First Optical Film> The laminated optical film according to the present invention comprises at least an acrylic film and a first optical film laminated together via an adhesive layer. The first optical film is preferably a liquid crystal film or a retardation film. Examples of liquid crystal films include oriented films of liquid crystal polymers and films in which an oriented layer of a liquid crystal polymer is supported by the film. Examples of retardation films include retardation films having a front retardation of 40 nm or more and / or a thickness retardation of 80 nm or more. The front retardation is typically controlled to a range of 40 to 200 nm, and the thickness retardation is typically controlled to a range of 80 to 300 nm. Examples of retardation films include birefringent films obtained by uniaxially or biaxially stretching a polymer material, oriented films of liquid crystal polymers, and films in which an oriented layer of a liquid crystal polymer is supported by the film. The thicknesses of the liquid crystal film and the retardation film are not particularly limited, but are generally about 1 to 150 μm.

[0052] As the retardation film, a reverse wavelength dispersion type retardation film that satisfies the following formulas (1) to (3) may be used: 0.70<Re

[450] / Re

[550] <0.97 (1) 1.5×10-3<Δn<6×10-3 (2) 1.13<NZ<1.50 (3) (where Re

[450] and Re

[550] are in-plane retardation values ​​of the retardation film measured at 23° C. with light of wavelengths of 450 nm and 550 nm, respectively; Δn is in-plane birefringence, which is nx-ny, where nx and ny are refractive indices in the slow axis direction and the fast axis direction of the retardation film, respectively; and NZ is the ratio of nx-nz, which is the thickness direction birefringence, to nx-ny, which is the in-plane birefringence, where nz is the refractive index in the thickness direction of the retardation film).

[0053] <Adhesive Layer> The laminated optical film according to the present invention has at least an acrylic film and a first optical film laminated together via an adhesive layer. The acrylic film and the adhesive layer are in direct contact with each other. In other words, no easy-adhesion layer containing an aqueous urethane resin or the like is provided between the acrylic film and the adhesive layer.

[0054] In the laminated optical film according to the present invention, the adhesive layer has the following characteristics: (i) the log Pow, which represents the octanol / water partition coefficient, calculated by the weighted average of the molar fractions of the polymerizable compounds contained in the adhesive composition, is 1.8 or more and 3.0 or less; (ii) the elastic modulus of the adhesive layer is 1×10 ５ Pa or more and 3 x 10 ６ With regard to (i) above, log Pow is more preferably 2.0 or more and 2.8 or less.

[0055] The octanol / water partition coefficient (logPow) is an index that indicates the lipophilicity of a substance, and refers to the logarithm of the octanol / water partition coefficient. A high logPow indicates lipophilicity, that is, hydrophobicity. The logPow value can be measured (using the flask immersion method described in JIS-Z-7260), but it can also be calculated. In this specification, the logPow value calculated using ChemDraw Ultra by CambridgeSoft is used.

[0056] The log Pow of major polymerizable compounds is shown below. Hydroxyethyl acrylamide (trade name "HEAA", manufactured by Kojin Co., Ltd., Log Pow; -0.56), diethyl acrylamide (trade name "DEAA", manufactured by KJ Chemicals, Log Pow; 1.69), unsaturated fatty acid hydroxyalkyl ester-modified ε-caprolactone (trade name "Placcel FA1DDM", manufactured by Daicel Corporation, Log Pow; 1.06), N-vinylformamide (trade name "Beamset 770", manufactured by Arakawa Chemical Industries, Ltd., Log Pow; -0.25), acryloyl morpholine (trade name "ACMO", manufactured by Kojin Co., Ltd., Log Pow; LogPow; -0.20), γ-butyrolactone acrylate (trade name "GBLA", manufactured by Osaka Organic Chemical Industry Ltd., LogPow; 0.19), acrylic acid dimer (trade name "β-CEA", manufactured by Daicel Corporation, LogPow; 0.2), N-vinylpyrrolidone (trade name "NVP", manufactured by Nippon Shokubai Co., Ltd., LogPow; 0.24), acetoacetoxyethyl methacrylate (trade name "AAEM", manufactured by Nippon Synthetic Chemical Industry Co., Ltd., LogPow; 0.27), 2-hydroxyethyl acrylate (trade name "HEA", manufactured by Osaka Organic Chemical Industry Ltd., LogPow; 0 28), glycidyl methacrylate (trade name "Light Ester G", manufactured by Kyoeisha Chemical Co., Ltd., Log Pow; 0.57), dimethylacrylamide (trade name "DMAA", manufactured by Kojinsha Co., Ltd., Log Pow; 0.58), tetrahydrofurfuryl alcohol acrylic acid polymer ester (trade name "Viscoat #150D", manufactured by Osaka Organic Chemical Industry Co., Ltd., Log Pow; 0.60), 4-hydroxybutyl acrylate (trade name "4-HBA", manufactured by Osaka Organic Chemical Industry Co., Ltd., Log Pow; 0.68), acrylic acid (trade name "Acrylic Acid", manufactured by Mitsubishi Chemical Corporation , LogPow; 0.69), triethylene glycol diacrylate (trade name "Light Acrylate 3EG-A", Kyoeisha Chemical Co., Ltd., LogPow; 0.72), PEG400# diacrylate (trade name "Light Acrylate 9EG-A", Kyoeisha Chemical Co., Ltd., LogPow; -0.1), polypropylene glycol diacrylate (trade name "Aronix M-220", Toagosei Co., Ltd., LogPow; 1.68), dicyclopentenyl acrylate (trade name "Fancryl FA-511AS", Hitachi Chemical Co., Ltd., LogPow;2.26), butyl acrylate (trade name "Butyl Acrylate", manufactured by Mitsubishi Chemical Corporation, Log Pow; 2.35), 1,6-hexanediol diacrylate (trade name "Light Acrylate 1.6HX-A", manufactured by Kyoeisha Chemical Co., Ltd., Log Pow; 2.43), dicyclopentanyl acrylate (trade name "Fancryl FA-513AS", manufactured by Hitachi Chemical Co., Ltd., Log Pow; 2.58), dimethylol-tricyclodecane diacrylate (trade name "Light Acrylate DCP-A", manufactured by Kyoeisha Chemical Co., Ltd., Log Pow; 3.05), isobornyl acrylate (trade name "Light Acrylate IB-XA", manufactured by Kyoeisha Chemical Co., Ltd., Log Pow; 3.27), hydroxypivalic acid neo Pentyl glycol acrylic acid adduct (trade name "Light Acrylate HPP-A", manufactured by Kyoeisha Chemical Co., Ltd., Log Pow; 3.35), 1,9-nonanediol diacrylate (trade name "Light Acrylate 1,9ND-A", manufactured by Kyoeisha Chemical Co., Ltd., Log Pow; 3.68), o-phenylphenol EO-modified acrylate (trade name "Fancryl FA-301A", manufactured by Hitachi Chemical Co., Ltd., Log Pow; 3.98), 2-ethylhexyl oxetane (trade name "Aron Oxetane OXT-212", manufactured by Toagosei Co., Ltd., Log Pow; 4.24), bisphenol-A diglycidyl ether (trade name "JER828", manufactured by Mitsubishi Chemical Corporation, Log Pow; 4.76), bisphenol A EO 6 mol modified diacrylate (trade name "FA-326A", manufactured by Hitachi Chemical Co., Ltd., Log Pow; 4.84), bisphenol A EO 4 mol modified diacrylate (trade name "FA-324A", manufactured by Hitachi Chemical Co., Ltd., Log Pow; 5.15), bisphenol A PO 2 mol modified diacrylate (trade name "FA-P320A", manufactured by Hitachi Chemical Co., Ltd., Log Pow; 6.10), bisphenol A PO 3 mol modified diacrylate (trade name "FA-P323A", manufactured by Hitachi Chemical Co., Ltd., Log Pow; 6.26), bisphenol A Examples of such a diacrylate include PO4 mol-modified diacrylate (trade name "FA-P324A", manufactured by Hitachi Chemical Co., Ltd., Log Pow: 6.43), lauryl acrylate (trade name "Light Acrylate LA", manufactured by Kyoeisha Chemical Co., Ltd., Log Pow: 6), and isostearyl acrylate (trade name "ISTA", manufactured by Osaka Organic Chemical Industry Co., Ltd., Log Pow: 7.46).

[0057] The adhesive layer will be described in detail below. The adhesive layer is formed from a cured product layer of an adhesive composition containing at least a polymerizable compound, and is preferably formed from a cured product layer of an active energy ray-curable adhesive composition, such as an electron beam-curable, ultraviolet-curable, or visible light-curable adhesive composition. From the viewpoint of improving the appearance characteristics and adhesive strength of the laminated optical film, the thickness of the adhesive layer after drying is preferably 0.1 μm to 10 μm, and more preferably 0.1 μm to 5 μm. Active energy ray-curable adhesive compositions can be divided into radical polymerization-curable adhesive compositions and cationically polymerizable adhesive compositions. In the present invention, active energy rays in the wavelength range of 10 nm to less than 380 nm are referred to as ultraviolet rays, and active energy rays in the wavelength range of 380 nm to 800 nm are referred to as visible light.

[0058] Examples of polymerizable compounds constituting the radical polymerization curable adhesive composition include radical polymerizable compounds. Examples of radical polymerizable compounds include compounds having a radically polymerizable functional group of a carbon-carbon double bond, such as a (meth)acryloyl group or a vinyl group. These monomer components can be either monofunctional radical polymerizable compounds or polyfunctional radical polymerizable compounds having two or more polymerizable functional groups. These radical polymerizable compounds can be used alone or in combination of two or more. Suitable examples of these radical polymerizable compounds include compounds having a (meth)acryloyl group. In the present invention, (meth)acryloyl refers to an acryloyl group and / or a methacryloyl group, and "(meth)" has the same meaning hereinafter.

[0059] Examples of the monofunctional radically polymerizable compound include (meth)acrylamide derivatives having a (meth)acrylamide group. (Meth)acrylamide derivatives are preferred in terms of ensuring adhesion to polarizers and various transparent protective films, as well as in terms of high polymerization rate and excellent productivity. Specific examples of the (meth)acrylamide derivative include N-alkyl group-containing (meth)acrylamide derivatives such as N-methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, and N-hexyl(meth)acrylamide; N-hydroxyalkyl group-containing (meth)acrylamide derivatives such as N-methylol(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, and N-methylol-N-propane(meth)acrylamide; N-aminoalkyl group-containing (meth)acrylamide derivatives such as aminomethyl(meth)acrylamide and aminoethyl(meth)acrylamide; N-alkoxy group-containing (meth)acrylamide derivatives such as N-methoxymethylacrylamide and N-ethoxymethylacrylamide; and N-mercaptoalkyl group-containing (meth)acrylamide derivatives such as mercaptomethyl(meth)acrylamide and mercaptoethyl(meth)acrylamide. Examples of heterocycle-containing (meth)acrylamide derivatives in which the nitrogen atom of the (meth)acrylamide group forms a heterocycle include N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, and N-acryloylpyrrolidine.

[0060] Among the (meth)acrylamide derivatives, N-hydroxyalkyl group-containing (meth)acrylamide derivatives are preferred from the viewpoint of adhesion to polarizers and various transparent protective films. Furthermore, examples of the monofunctional radical polymerizable compound include various (meth)acrylic acid derivatives having a (meth)acryloyloxy group. Specific examples include (meth)acrylic acid (C1-20) alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, 2-methyl-2-nitropropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, t-pentyl (meth)acrylate, 3-pentyl (meth)acrylate, 2,2-dimethylbutyl (meth)acrylate, n-hexyl (meth)acrylate, cetyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, and n-octadecyl (meth)acrylate.

[0061] Examples of the (meth)acrylic acid derivatives include cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate and cyclopentyl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate; 2-isobornyl (meth)acrylate, 2-norbornylmethyl (meth)acrylate, 5-norbornen-2-yl-methyl (meth)acrylate, 3-methyl-2-norbornylmethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxy (meth)acrylate, and the like. Examples of the alkoxy group- or phenoxy group-containing (meth)acrylates include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-methoxymethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethyl carbitol (meth)acrylate, phenoxyethyl (meth)acrylate, and alkylphenoxy polyethylene glycol (meth)acrylate.

[0062] In addition, examples of the (meth)acrylic acid derivatives include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate. hydroxyl group-containing (meth)acrylates such as [4-(hydroxymethyl)cyclohexyl]methyl acrylate, cyclohexanedimethanol mono(meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate; epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate glycidyl ether; 2,2,2-trifluoroethyl (meth)acrylate, 2,2,2-trifluoroethyl ethyl (meth)acrylate; (meth)acrylates containing halogen, such as tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropentyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth)acrylate; alkylaminoalkyl (meth)acrylates such as dimethylaminoethyl (meth)acrylate; 3-oxetanylmethyl (meth)acrylate, 3-methyl-oxetanylmethyl (meth)acrylate; acrylate, 3-ethyl-oxetanylmethyl (meth)acrylate, 3-butyl-oxetanylmethyl (meth)acrylate, 3-hexyl-oxetanylmethyl (meth)acrylate, and other oxetane group-containing (meth)acrylates; (meth)acrylates having a heterocycle such as tetrahydrofurfuryl (meth)acrylate and butyrolactone (meth)acrylate; hydroxypivalic acid neopentyl glycol (meth)acrylic acid adduct; and p-phenylphenol (meth)acrylate.

[0063] Furthermore, examples of the monofunctional radically polymerizable compound include carboxyl group-containing monomers such as (meth)acrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

[0064] Examples of the monofunctional radically polymerizable compound include lactam vinyl monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone; and vinyl monomers having a nitrogen-containing heterocycle such as vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, and vinylmorpholine.

[0065] Furthermore, as the monofunctional radical polymerizable compound, a radical polymerizable compound having an active methylene group can be used. The radical polymerizable compound having an active methylene group is a compound having an active double bond group such as a (meth)acrylic group at the end or in the molecule, and also having an active methylene group. Examples of the active methylene group include an acetoacetyl group, an alkoxymalonyl group, and a cyanoacetyl group. It is preferable that the active methylene group is an acetoacetyl group. Specific examples of radically polymerizable compounds having an active methylene group include acetoacetoxyalkyl (meth)acrylates such as 2-acetoacetoxyethyl (meth)acrylate, 2-acetoacetoxypropyl (meth)acrylate, and 2-acetoacetoxy-1-methylethyl (meth)acrylate; 2-ethoxymalonyloxyethyl (meth)acrylate, 2-cyanoacetoxyethyl (meth)acrylate, N-(2-cyanoacetoxyethyl)acrylamide, N-(2-propionylacetoxybutyl)acrylamide, N-(4-acetoacetoxymethylbenzyl)acrylamide, and N-(2-acetoacetylaminoethyl)acrylamide. The radically polymerizable compound having an active methylene group is preferably an acetoacetoxyalkyl (meth)acrylate.

[0066] In the present invention, the adhesive composition preferably contains a polymerizable compound B. The polymerizable compound B has a log Pow, which represents the octanol / water partition coefficient, of 1.0 or more and 8.0 or less, and when the total amount of the polymerizable compounds contained in the adhesive composition is taken as 100 parts by mass, the content of the polymerizable compound B is preferably 50 parts by mass or more and 90 parts by mass or less, and more preferably 65 parts by mass or more and 90 parts by mass or less. Among the monofunctional radically polymerizable compounds, the following can be exemplified as the polymerizable compound B. (2-Methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate, trade name: MEDOL-10, manufacturer: Osaka Organic Chemical Industry Ltd. (log Pow: 1.6), benzyl acrylate, trade name: Viscoat #160, manufacturer: Osaka Organic Chemical Industry Ltd. (log Pow: 2.46), phenoxyethyl acrylate, trade name: Viscoat #192HP, manufacturer: Osaka Organic Chemical Industry Ltd. (log Pow: 2.52), cyclohexyl Examples of the adhesive composition used in the present invention include: methyl acrylate, trade name: Viscoat #155, manufacturer: Osaka Organic Chemical Industry Co., Ltd. (log Pow: 2.46); lauryl acrylate, trade name: LA, manufacturer: Osaka Organic Chemical Industry Co., Ltd. (log Pow: 6); phenoxydiethylene glycol acrylate, trade name: P2H-A, manufacturer: Kyoeisha Chemical Co., Ltd. (log Pow: 2.15); and phenoxybenzyl acrylate, trade name: POB-A, manufacturer: Kyoeisha Chemical Co., Ltd. (log Pow: 3.91). The adhesive composition used in the present invention preferably contains polymerizable compound B, which makes the adhesive layer sufficiently hydrophobic, suppresses the incorporation of oxalic acid into the adhesive layer, and suppresses the occurrence of oxalic acid bright spots that cause deterioration of appearance characteristics.

[0067] Examples of polyfunctional radically polymerizable compounds having two or more polymerizable functional groups include tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol diacrylate, 2-ethyl-2-butylpropanediol di(meth)acrylate, bisphenol A di(meth)acrylate, bisphenol A ethylene oxide adduct di(meth)acrylate, bisphenol A propylene oxide adduct di(meth)acrylate, bisphenol A diglycidyl ether di(meth)acrylate, and neopentyl glycol. di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, dioxane glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, EO-modified diglycerin tetra(meth)acrylate, and other esters of (meth)acrylic acid with polyhydric alcohols; and 9,9-bis[4-(2-(meth)acryloyloxyethoxy)phenyl]fluorene. Specific examples include Aronix M-220 (manufactured by Toagosei Co., Ltd.), Light Acrylate 1,9ND-A (manufactured by Kyoeisha Chemical Co., Ltd.), Light Acrylate DGE-4A (manufactured by Kyoeisha Chemical Co., Ltd.), Light Acrylate DCP-A (manufactured by Kyoeisha Chemical Co., Ltd.), SR-531 (manufactured by Sartomer Co., Ltd.), CD-536 (manufactured by Sartomer Co., Ltd.), etc. Furthermore, various epoxy (meth)acrylates, urethane (meth)acrylates, polyester (meth)acrylates, various (meth)acrylate monomers, etc. may also be used as necessary.

[0068] In the present invention, the adhesive composition preferably contains a polymerizable compound A. The polymerizable compound A is a urethane (meth)acrylate having a molecular weight of 5,000 or more and having at least two polymerizable groups. When the total amount of polymerizable compounds contained in the adhesive composition is 100 parts by mass, the content of the polymerizable compound A is preferably 4 parts by mass or more and 30 parts by mass or less, and more preferably 10 parts by mass or more and 20 parts by mass or less. Examples of the polymerizable compound A include "UV3000B" (log Pow: 12.8) manufactured by Mitsubishi Chemical Corporation, "EBECRYL4491" manufactured by Daicel Allnex Corporation, "EBECRYL8413" manufactured by Daicel Allnex Corporation, and "CN8888NS" manufactured by Sartomer Corporation. By including the polymerizable compound A in the adhesive composition used in the present invention, the elastic modulus of the adhesive is reduced, enabling adhesion through stress relaxation.

[0069] In the present invention, the adhesive composition preferably contains a polymerizable compound C. The polymerizable compound C is a compound having at least two polymerizable groups, and when the total amount of polymerizable compounds contained in the adhesive composition is 100 parts by mass, the content of the polymerizable compound C is preferably 0 parts by mass or more and 15 parts by mass or less, and more preferably 1 part by mass or more and 10 parts by mass or less. Examples of the polymerizable compound C include the above-mentioned polyfunctional radically polymerizable compounds. By containing the polymerizable compound C in the adhesive composition used in the present invention, it is possible to achieve an elastic modulus that satisfies both adhesion to acrylic films and oxalic acid bright spots.

[0070] In the present invention, the adhesive composition serving as a raw material for the adhesive layer of the laminated optical film can contain, in addition to a radically polymerizable compound, an acrylic oligomer obtained by polymerizing a (meth)acrylic monomer. By including an acrylic oligomer in the adhesive composition, cure shrinkage when the composition is irradiated with active energy rays and cured can be reduced, and interfacial stress between the adhesive layer and an adherend such as a polarizer or an optical film can be reduced. As a result, a decrease in adhesion between the adhesive layer and the adherend can be suppressed.

[0071] Considering workability and uniformity during application, it is preferable that the active energy ray-curable adhesive has a low viscosity, and therefore it is preferable that the acrylic oligomer obtained by polymerizing a (meth)acrylic monomer also has a low viscosity. As an acrylic oligomer that has a low viscosity and can prevent cure shrinkage of the adhesive layer, one having a weight average molecular weight (Mw) of preferably 15,000 or less, more preferably 10,000 or less, and particularly preferably 5,000 or less. On the other hand, in order to sufficiently suppress cure shrinkage of the cured product layer (adhesive layer), the weight average molecular weight (Mw) of the acrylic oligomer is preferably 500 or more, more preferably 1,000 or more, and particularly preferably 1,500 or more. Specific examples of the (meth)acrylic monomer constituting the acrylic oligomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, 2-methyl-2-nitropropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, t-pentyl (meth)acrylate, 3-pentyl (meth)acrylate, 2,(Meth)acrylic acid (C1-20) alkyl esters such as 2-dimethylbutyl (meth)acrylate, n-hexyl (meth)acrylate, cetyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, and N-octadecyl (meth)acrylate; further, for example, cycloalkyl (meth)acrylates (for example, cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, etc.), aralkyl (meth)acrylates (for example, benzyl (meth)acrylate, etc.), polycyclic (meth)acrylates (for example, 2-isobornyl (meth)acrylate, 2-norbornylmethyl (meth)acrylate, 5-norbornen-2-yl-methyl (meth)acrylate, 3-methyl-2-norbornylmethyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, and 4-methyl-2-propylpentyl (meth)acrylate; (meth)acrylate, etc.), hydroxyl group-containing (meth)acrylic acid esters (for example, hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2,3-dihydroxypropylmethyl-butyl (meth)methacrylate, etc.), alkoxy group- or phenoxy group-containing (meth)acrylic acid esters (2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-methoxymethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethyl carbitol (meth)acrylate, phenoxyethyl (meth)acrylate, etc.), epoxy group-containing (meth)acrylic acid esters (for example, glycidyl (meth)acrylate, etc.), halogen-containing (meth)acrylic acid esters (for example, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,Examples of the acrylic oligomer (E) include 2-trifluoroethylethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropentyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, etc., and alkylaminoalkyl (meth)acrylates (for example, dimethylaminoethyl (meth)acrylate, etc.). These (meth)acrylates can be used alone or in combination of two or more. Specific examples of the acrylic oligomer (E) include "ARUFON" manufactured by Toagosei Co., Ltd., "Actflow" manufactured by Soken Chemical & Engineering Co., Ltd., and "JONCRYL" manufactured by BASF Japan Ltd.

[0072] The amount of acrylic oligomer blended is usually preferably 15 parts by weight or less per 100 parts by weight of the total amount of monomer components in the adhesive composition. If the content of acrylic oligomer in the composition is too high, the viscosity of the composition increases, which is undesirable because it results in poor surface smoothness after coating and poor appearance. On the other hand, in order to sufficiently suppress cure shrinkage of the adhesive layer, it is preferable that the composition contain 3 parts by weight or more of acrylic oligomer.

[0073] When a radical polymerizable compound is used, the photopolymerization initiator is appropriately selected depending on the active energy ray. When curing with ultraviolet light or visible light, a photopolymerization initiator that is cleaved by ultraviolet light or visible light is used. Examples of the photopolymerization initiator include benzophenone-based compounds such as benzil, benzophenone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone; aromatic ketone compounds such as 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, and α-hydroxycyclohexylphenyl ketone; acetophenone-based compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, and 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropane-1; benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin methyl ether. aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; photoactive oxime compounds such as 1-phenone-1,1-propanedione-2-(o-ethoxycarbonyl)oxime; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone; camphorquinone; halogenated ketones; acylphosphinoxides; and acylphosphonates.

[0074] The amount of the photopolymerization initiator is 20% by weight or less, preferably 0.01 to 20% by weight, more preferably 0.05 to 10% by weight, and even more preferably 0.1 to 5% by weight, based on the total amount of the active energy ray-curable adhesive composition being 100% by weight.

[0075] Furthermore, when the curable adhesive for laminated optical films of the present invention is used as a visible light curable type containing a radically polymerizable compound as a curable component, it is preferable to use a photopolymerization initiator that is particularly sensitive to light of 380 nm or more. Photopolymerization initiators that are highly sensitive to light of 380 nm or more will be described later.

[0076] It is also preferable to add a polymerization initiation aid as needed. Examples of the polymerization initiation aid include triethylamine, diethylamine, N-methyldiethanolamine, ethanolamine, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, and isoamyl 4-dimethylaminobenzoate, with ethyl 4-dimethylaminobenzoate being particularly preferred. When a polymerization initiation aid is used, the amount added is usually 0 to 5 parts by weight, preferably 0 to 4 parts by weight, and most preferably 0 to 3 parts by weight, relative to 100 parts by weight of the total amount of the curable components.

[0077] Furthermore, a known photopolymerization initiator can be used in combination as needed. Because a transparent protective film having UV absorption ability does not transmit light of 380 nm or shorter, it is preferable to use a photopolymerization initiator that is highly sensitive to light of 380 nm or longer. Specific examples include 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium, and the like.

[0078] In particular, as the photopolymerization initiator, in addition to the photopolymerization initiator of general formula (1), a compound represented by the following general formula (2):

[0079] (In the formula, R ３ , R４ and R ５ -H, -CH ３ , -CH ２ CH ３ , -iPr or Cl, R ３ , R ４ and R ５ As the compound represented by general formula (2), commercially available products such as 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (trade name: Omnirad 819, manufacturer: IGM Resins B.V.) and 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (trade name: Omnirad 907, manufacturer: IGM Resins B.V.) can be suitably used. In addition, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 (trade name: Omnirad369, manufacturer: IGM Resins B.V.) and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone (trade name: Omnirad379, manufacturer: IGM Resins B.V.) are preferred due to their high sensitivity.

[0080] In the present invention, among the above photopolymerization initiators, it is preferable to use a hydroxyl group-containing photopolymerization initiator. When the active energy ray-curable adhesive composition contains a hydroxyl group-containing photopolymerization initiator as a polymerization initiator, the solubility in the adhesive layer on the polarizer side where the concentration of component A is high is increased, and the curability of the adhesive layer is improved. Examples of photopolymerization initiators having a hydroxyl group include 2-methyl-2-hydroxypropiophenone (trade name "DAROCUR1173", manufactured by BASF), 1-hydroxycyclohexyl phenyl ketone (trade name "IRGACURE184", manufactured by BASF), 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one (trade name "IRGACURE2959", manufactured by BASF), and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one (trade name "IRGACURE127", manufactured by BASF). 1-Hydroxycyclohexyl phenyl ketone is particularly preferred because of its excellent solubility in adhesive layers having a high concentration of component A.

[0081] In the present invention, a cationically polymerizable adhesive composition may be used as the adhesive composition serving as the raw material for the adhesive layer of the laminated optical film. The cationically polymerizable compounds used in the cationically polymerizable adhesive composition are classified into monofunctional cationically polymerizable compounds having one cationically polymerizable functional group in the molecule and polyfunctional cationically polymerizable compounds having two or more cationically polymerizable functional groups in the molecule. Monofunctional cationically polymerizable compounds have relatively low liquid viscosity, and their inclusion in a resin composition can reduce the liquid viscosity of the resin composition. Furthermore, monofunctional cationically polymerizable compounds often have functional groups that impart various functions. Their inclusion in a cationically polymerizable adhesive composition can impart various functions to the cationically polymerizable adhesive composition and / or the cured product of the cationically polymerizable adhesive composition. Polyfunctional cationically polymerizable compounds are preferably included in the cationically polymerizable adhesive composition because they can three-dimensionally crosslink the cured product of the cationically polymerizable adhesive composition. The ratio of the monofunctional cationically polymerizable compound to the polyfunctional cationically polymerizable compound is preferably in the range of 10 to 1,000 parts by weight per 100 parts by weight of the monofunctional cationically polymerizable compound. Examples of the cationically polymerizable functional group include an epoxy group, an oxetanyl group, and a vinyl ether group. Examples of compounds having an epoxy group include an aliphatic epoxy compound, an alicyclic epoxy compound, and an aromatic epoxy compound. The cationically polymerizable adhesive composition of the present invention particularly preferably contains an alicyclic epoxy compound because of its excellent curability and adhesive properties. Examples of the alicyclic epoxy compound include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, caprolactone-modified products, trimethylcaprolactone-modified products, and valerolactone-modified products of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and specific examples thereof include Celloxide 2021, Celloxide 2021A, Celloxide 2021P, Celloxide 2081, Celloxide 2083, and Celloxide 2085 (all manufactured by Daicel Chemical Industries, Ltd.), and Cyracure UVR-6105, Cyracure UVR-6107, Cyracure 30, and R-6110 (all manufactured by Dow Chemical Japan Ltd.).Compounds having an oxetanyl group are preferably contained because they have the effect of improving the curing properties of the cationically polymerizable adhesive composition and reducing the liquid viscosity of the composition. Examples of compounds having an oxetanyl group include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl]benzene, 3-ethyl-3-(phenoxymethyl)oxetane, di[(3-ethyl-3-oxetanyl)methyl]ether, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, and phenol novolac oxetane. Commercially available compounds include Aronoxetane OXT-101, Aronoxetane OXT-121, Aronoxetane OXT-211, Aronoxetane OXT-221, and Aronoxetane OXT-212 (all manufactured by Toagosei Co., Ltd.). Compounds having a vinyl ether group are preferably contained because they have the effect of improving the curing properties of the cationically polymerizable adhesive composition and reducing the liquid viscosity of the composition. Examples of compounds having a vinyl ether group include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, triethylene glycol divinyl ether, cyclohexanedimethanol divinyl ether, cyclohexanedimethanol monovinyl ether, tricyclodecane vinyl ether, cyclohexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, and pentaerythritol tetravinyl ether.

[0082] The cationically polymerizable adhesive composition contains at least one compound selected from the group consisting of the epoxy group-containing compound, the oxetanyl group-containing compound, and the vinyl ether group-containing compound described above as a curable component. Since these compounds all cure by cationic polymerization, a photocationic polymerization initiator is incorporated into the composition. This photocationic polymerization initiator generates cationic species or a Lewis acid upon irradiation with active energy rays such as visible light, ultraviolet light, X-rays, or electron beams, thereby initiating the polymerization reaction of the epoxy group or the oxetanyl group. The photoacid generator described below is preferably used as the photocationic polymerization initiator. Furthermore, when the cationically polymerizable adhesive composition is used as a visible light-curable composition, it is preferable to use a photocationic polymerization initiator that is highly sensitive to light of 380 nm or longer. However, since photocationic polymerization initiators generally exhibit a maximum absorption in the wavelength range around 300 nm or shorter, incorporating a photosensitizer that exhibits a maximum absorption in the longer wavelength range, specifically, light of wavelengths longer than 380 nm, can be used to stimulate the generation of cationic species or acid from the photocationic polymerization initiator. Examples of photosensitizers include anthracene compounds, pyrene compounds, carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreducible dyes, and two or more of these may be used in combination. Anthracene compounds are particularly preferred because of their excellent photosensitizing effect, and specific examples include Anthracure UVS-1331 and Anthracure UVS-1221 (manufactured by Kawasaki Chemical Industries, Ltd.). The content of the photosensitizer is preferably 0.1% by weight to 5% by weight, and more preferably 0.5% by weight to 3% by weight.

[0083] In the laminated optical film 10 shown in FIG. 1 , a triacetyl cellulose film 6, which is a transparent protective film, is laminated via a water-based adhesive layer 7 on the surface of the acrylic film 1 opposite to the surface on which the first optical film 2 is laminated, and a second optical film 4 is further laminated via a pressure-sensitive adhesive layer 5 on the surface of the first optical film 2 opposite to the surface on which the acrylic film 1 is laminated.

[0084] <Adhesive Layer> The adhesive for forming the adhesive layer is not particularly limited, and can be appropriately selected and used, for example, those having a base polymer such as an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based polymer, a rubber-based polymer, etc. In particular, those having excellent optical transparency, exhibiting adhesive properties such as appropriate wettability, cohesion, and adhesiveness, and having excellent weather resistance, heat resistance, etc., such as acrylic adhesives, can be preferably used.

[0085] The exposed surface of the pressure-sensitive adhesive layer is covered with a temporary separator to prevent contamination until the product is put into practical use. This prevents contact with the pressure-sensitive adhesive layer during normal handling. As the separator, apart from the thickness requirements mentioned above, any suitable conventional separator can be used, such as a suitable thin sheet such as a plastic film, rubber sheet, paper, cloth, nonwoven fabric, net, foam sheet, metal foil, or a laminate thereof, optionally coated with a suitable release agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide-based release agent.

[0086] <Second Optical Film> In the present invention, the second optical film is preferably a liquid crystal film or a retardation film. As the liquid crystal film and the retardation film, the same films as those exemplified for the first optical film can be suitably used.

[0087] The laminated optical film according to the present invention may include the following optical films in addition to the acrylic film, the first optical film, and the second optical film.

[0088] The laminated optical film according to the present invention may include a polarizer as another optical film. Polyvinyl alcohol or a derivative thereof is used as the material for the polyvinyl alcohol-based film used in the polarizer. Examples of polyvinyl alcohol derivatives include polyvinyl formal, polyvinyl acetal, and the like, as well as derivatives modified with olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, their alkyl esters, and acrylamide. Polyvinyl alcohols with a degree of polymerization of about 1,000 to 10,000 and a degree of saponification of about 80 to 100 mol% are generally used.

[0089] The polyvinyl alcohol film may contain additives such as a plasticizer. Examples of the plasticizer include polyols and condensates thereof, such as glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of the plasticizer used is not particularly limited, but is preferably 20% by weight or less of the polyvinyl alcohol film.

[0090] In producing a polarizer, the polyvinyl alcohol-based film is subjected to a dyeing step in which it is dyed with iodine and a stretching step in which it is stretched in at least one direction. Generally, a method is employed in which the polyvinyl alcohol-based film is subjected to a series of steps including swelling, dyeing, crosslinking, stretching, water washing, and drying.

[0091] The swelling step is carried out, for example, by immersing the polyvinyl alcohol film in a swelling bath (water bath). This treatment cleans the surface of the polyvinyl alcohol film of dirt and antiblocking agents, and also swells the polyvinyl alcohol film, thereby preventing unevenness such as uneven dyeing. Glycerin, potassium iodide, etc. may be added to the swelling bath as appropriate. The temperature of the swelling bath is usually about 20 to 60°C, and the immersion time in the swelling bath is usually about 0.1 to 10 minutes.

[0092] The dyeing process is carried out, for example, by immersing the polyvinyl alcohol film in an iodine solution. The iodine solution is usually an aqueous iodine solution containing iodine and potassium iodide as a solubilizing agent. The iodine concentration is usually about 0.01 to 1 wt %, preferably 0.02 to 0.5 wt %. The potassium iodide concentration is usually about 0.01 to 10 wt %, preferably 0.02 to 8 wt %.

[0093] In the iodine dyeing step, the temperature of the iodine solution is usually about 20 to 50°C, preferably 25 to 40°C. The immersion time is usually about 10 to 300 seconds, preferably 20 to 240 seconds. In the iodine dyeing treatment, it is preferable to adjust conditions such as the concentration of the iodine solution, the immersion temperature of the polyvinyl alcohol film in the iodine solution, and the immersion time so that the iodine content and potassium content in the polyvinyl alcohol film fall within the above-mentioned ranges.

[0094] The crosslinking step is carried out, for example, by immersing an iodine-dyed polyvinyl alcohol film in a treatment bath containing a crosslinking agent. Any appropriate crosslinking agent can be used. Specific examples of crosslinking agents include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. These agents can be used alone or in combination. Water is typically used as the solvent for the crosslinking bath solution, but an appropriate amount of an organic solvent compatible with water may also be added. The crosslinking agent is typically used in a ratio of 1 to 10 parts by weight per 100 parts by weight of the solvent. It is desirable that the crosslinking bath solution further contains an auxiliary agent such as iodide. The concentration of the auxiliary agent is preferably 0.05 to 15% by weight, more preferably 0.5 to 8% by weight. The temperature of the crosslinking bath is typically about 20 to 70°C, preferably 40 to 60°C. The immersion time in the crosslinking bath is typically about 1 second to 15 minutes, preferably 5 seconds to 10 minutes.

[0095] The stretching step is a step in which a polyvinyl alcohol-based film is stretched in at least one direction. Generally, the polyvinyl alcohol-based film is uniaxially stretched in the conveying direction (longitudinal direction). The stretching method is not particularly limited, and either wet stretching or dry stretching can be employed. When wet stretching is employed, the polyvinyl alcohol-based film is stretched to a predetermined stretch ratio in a treatment bath. A solution prepared by adding compounds necessary for various treatments to a solvent such as water or an organic solvent (e.g., ethanol) is preferably used as the solution for the stretching bath. Examples of dry stretching methods include roll-to-roll stretching, heated roll stretching, and compression stretching. In the production of a polarizer, the stretching step may be performed at any stage. Specifically, the stretching step may be performed simultaneously with swelling, dyeing, or crosslinking, or may be performed before or after each of these steps. Furthermore, the stretching step may be performed in multiple stages. The cumulative stretch ratio of the polyvinyl alcohol-based film is usually 5 times or more, preferably about 5 to 7 times.

[0096] In the present invention, the polarizer preferably contains a metal component capable of becoming a divalent metal cation in water, more preferably magnesium, calcium, copper, or zinc, and particularly preferably zinc. When the polarizer contains zinc, the decrease in transmittance and deterioration in hue of the laminated optical film after a heating test tend to be suppressed. When the polarizer contains zinc, the zinc content in the polarizer is preferably 0.002 to 2 wt %, more preferably 0.01 to 1 wt %.

[0097] In the present invention, the polarizer preferably contains sulfate ions. When the polarizer contains sulfate ions, a decrease in the transmittance of the laminated optical film after a heating test tends to be suppressed. When the polarizer contains sulfate ions, the content of sulfate ions in the polarizer is preferably 0.02 to 0.45 wt %, more preferably 0.05 to 0.35 wt %, and even more preferably 0.1 to 0.25 wt %. The content of sulfate ions in the polarizer is calculated from the sulfur atom content.

[0098] In order to incorporate zinc into the polarizer, it is preferable to carry out a zinc impregnation treatment in the manufacturing process of the polarizer. In order to incorporate sulfate ions into the polarizer, it is preferable to carry out a sulfate ion treatment in the manufacturing process of the polarizer.

[0099] Zinc impregnation treatment is carried out, for example, by immersing a polyvinyl alcohol film in a zinc salt solution. Suitable zinc salts include inorganic salt compounds such as zinc halides (e.g., zinc chloride and zinc iodide), zinc sulfate, and zinc acetate in aqueous solutions. Various zinc complex compounds may also be used for zinc impregnation treatment. Furthermore, it is preferable to use an aqueous solution of potassium ions and iodine ions (e.g., potassium iodide) as the zinc salt solution, as this facilitates impregnation with zinc ions. The potassium iodide concentration in the zinc salt solution is preferably about 0.5 to 10 wt %, more preferably 1 to 8 wt %.

[0100] The sulfate ion treatment is carried out, for example, by immersing the polyvinyl alcohol film in an aqueous solution containing a metal sulfate. The metal sulfate is preferably one that easily separates into sulfate ions and metal ions in the treatment solution and that is easily introduced into the polyvinyl alcohol film in the ionic state. Examples of metals that form metal sulfates include alkali metals such as sodium and potassium; alkaline earth metals such as magnesium and calcium; and transition metals such as cobalt, nickel, zinc, chromium, aluminum, copper, manganese, and iron.

[0101] In the production of a polarizer, the zinc impregnation treatment and sulfate ion treatment may be performed at any stage. That is, the zinc impregnation treatment and sulfate ion treatment may be performed before or after the dyeing step. The zinc impregnation treatment and sulfate ion treatment may be performed simultaneously. In the present invention, it is preferable to use zinc sulfate as the zinc salt and the metal sulfate salt, and to simultaneously perform the zinc impregnation treatment and the sulfate ion treatment by immersing the polyvinyl alcohol film in a treatment bath containing zinc sulfate. Alternatively, the zinc salt and the metal sulfate salt may be present in a dyeing solution, and the zinc impregnation treatment and / or sulfate ion treatment may be performed simultaneously with the dyeing step. The zinc impregnation treatment and sulfate ion treatment may be performed simultaneously with the stretching step.

[0102] In the zinc impregnation treatment and sulfate ion treatment, the zinc content and sulfate ion content in the polarizer are adjusted by adjusting conditions such as the concentration of the zinc salt solution and the metal sulfate salt solution, the immersion temperature of the polyvinyl alcohol film in the treatment bath, and the immersion time. In the zinc impregnation treatment and sulfate ion treatment, the temperature of the zinc salt solution and the metal sulfate salt solution is typically about 15 to 85°C, preferably 25 to 70°C. The immersion time is typically about 1 to 120 seconds, preferably 3 to 90 seconds. The concentrations of the zinc salt solution and the metal sulfate salt solution vary depending on the type of zinc salt and metal sulfate salt, but are typically about 0.5 to 20 wt %, preferably 1 to 10 wt %, and more preferably 2 to 7 wt %. By setting the zinc salt concentration and the metal sulfate concentration within the above ranges, the zinc content and sulfate ion content in the polarizer can be adjusted to fall within the above-mentioned preferred ranges.

[0103] The polyvinyl alcohol film (stretched film) that has been subjected to the above-mentioned treatments is subjected to a water washing step and a drying step according to a conventional method.

[0104] The water washing step is usually carried out by immersing the polyvinyl alcohol film in a water washing bath. The water washing bath may be pure water or an aqueous solution of iodide (e.g., potassium iodide, sodium iodide, etc.). The concentration of the aqueous iodide solution is preferably 0.1 to 10% by weight. An auxiliary agent such as zinc sulfate or zinc chloride may be added to the aqueous iodide solution.

[0105] The water washing temperature is usually in the range of 5 to 50°C, preferably 10 to 45°C, and more preferably 15 to 40°C. The immersion time is usually about 10 to 300 seconds, and preferably 20 to 240 seconds. The water washing step may be carried out only once, or may be carried out multiple times as necessary. When the water washing step is carried out multiple times, the type and concentration of additives contained in the water washing bath used for each treatment are appropriately adjusted.

[0106] The drying process of the polyvinyl alcohol-based film is carried out by any appropriate method (for example, natural drying, air drying, or heat drying). The thickness of the polarizer after the drying process is preferably 3 to 20 μm.

[0107] In the present invention, the obtained polarizer may be subjected to a surface modification treatment. Examples of the surface modification treatment include corona treatment, plasma treatment, and Itro treatment, with corona treatment being particularly preferred. Corona treatment generates reactive functional groups such as carbonyl groups and amino groups on the polarizer surface, improving adhesion to the durability-improving layer. In addition, the ashing effect removes foreign matter from the surface and reduces surface irregularities, allowing the production of a laminated optical film with excellent appearance characteristics.

[0108] The laminated optical film according to the present invention may include a transparent protective film as another optical film. Examples of materials that can be used to form the transparent protective film include thermoplastic resins that are excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, and isotropy. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene-based resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The transparent protective film may contain one or more suitable additives. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, coloring inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and colorants. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, even more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. If the content of the thermoplastic resin in the transparent protective film is 50% by weight or less, the inherent high transparency and other properties of the thermoplastic resin may not be fully exhibited.

[0109] The material for forming the transparent protective film is preferably one that is excellent in transparency, mechanical strength, thermal stability, moisture blocking property, isotropy, etc., and in particular, a moisture permeability of 150 g / m ２ / 24h or less is more preferable, and 140g / m ２ / 24h or less is particularly preferred, and 120g / m ２ / 24 hours or less is even more preferable.

[0110] The transparent protective film may be provided with a functional layer such as a hard coat layer, an anti-reflection layer, an anti-sticking layer, a diffusion layer, an anti-glare layer, etc. The functional layer such as the hard coat layer, the anti-reflection layer, the anti-sticking layer, the diffusion layer, or the anti-glare layer may be provided on the transparent protective film itself, or may be provided separately from the transparent protective film.

[0111] The thickness of the transparent protective film can be determined as appropriate, but is generally about 1 to 500 μm, preferably 1 to 300 μm, more preferably 5 to 200 μm, further preferably 10 to 200 μm, and more preferably 20 to 80 μm, from the viewpoints of workability such as strength and handleability, thinness, etc.

[0112] The laminated optical film according to the present invention can be produced, for example, by the following production method: A method for producing a laminated optical film in which at least an acrylic film and a first optical film are laminated via an adhesive layer, the adhesive layer being formed of a cured layer of an adhesive composition containing at least a polymerizable compound, the method comprising: a coating step of applying the adhesive composition to at least one of the acrylic film and the first optical film; a laminating step of bonding the acrylic film and the first optical film so that the acrylic film and the adhesive layer are in direct contact with each other; and a bonding step of irradiating the acrylic film surface side or the first optical film surface side with active energy rays to cure at least the adhesive composition, thereby bonding the acrylic film and the first optical film via the adhesive layer formed. Each step will be described below.

[0113] (Coating Process) The method for applying the adhesive composition to at least one of the acrylic film and the first optical film is appropriately selected depending on the viscosity of the composition and the desired thickness, and examples thereof include a reverse coater, a gravure coater (direct, reverse, or offset), a bar reverse coater, a roll coater, a die coater, a bar coater, and a rod coater. The viscosity of the adhesion-promoting composition and the adhesive composition is preferably 0.1 to 200 mPa·s, more preferably 1 to 100 mPa·s, and most preferably 5 to 50 mPa·s. A high viscosity of the composition is undesirable because it results in poor surface smoothness after application and poor appearance. For this reason, each composition can be heated or cooled to adjust the viscosity to a preferred range before application.

[0114] (Laminating step) The acrylic film and the first optical film are laminated together so that the acrylic film and the adhesive layer are in direct contact with each other. When the adhesive composition is applied to the acrylic film in the coating step, the acrylic film is directly coated with the adhesive composition and then laminated to the first optical film without coating the acrylic film with an easy-adhesive containing an aqueous urethane resin or the like. Also, when the adhesive composition is applied to the first optical film in the coating step, the adhesive composition-coated surface of the first optical film is directly laminated to the acrylic film without using an easy-adhesive or the like. When the acrylic film and the first optical film are laminated together via the adhesive composition, they are laminated using a roll laminator or the like.

[0115] (Bonding Step) The acrylic film and the first optical film are bonded together via an adhesive layer formed by curing at least the adhesive composition by irradiating the adhesive composition with active energy rays from the acrylic film side or the first optical film side. The irradiation direction of the active energy rays (electron beams, ultraviolet rays, visible light, etc.) can be any appropriate direction.

[0116] When irradiating with electron beams, any suitable irradiation conditions can be adopted as long as they are sufficient to at least cure the adhesive composition. For example, the acceleration voltage for electron beam irradiation is preferably 5 kV to 300 kV, more preferably 10 kV to 250 kV. If the acceleration voltage is less than 5 kV, the electron beam may not reach the adhesive, resulting in insufficient curing. If the acceleration voltage is greater than 300 kV, the penetration force through the sample may be too strong, potentially damaging the first optical film and the second optical film. The irradiation dose is 5 to 100 kGy, more preferably 10 to 75 kGy. If the irradiation dose is less than 5 kGy, the adhesive may not be cured sufficiently. If the irradiation dose is greater than 100 kGy, the first optical film and the second optical film may be damaged, resulting in a decrease in mechanical strength and yellowing, making it impossible to obtain the desired optical properties.

[0117] Electron beam irradiation is usually performed in an inert gas atmosphere, but may be performed in the atmosphere or with a small amount of oxygen introduced, if necessary. Depending on the materials of the first and second optical films, by appropriately introducing oxygen, oxygen inhibition is intentionally caused on the first and second optical film surfaces that are first hit by the electron beam, thereby preventing damage to the first and second optical films and allowing the electron beam to be efficiently irradiated only on the adhesive.

[0118] When producing the laminated optical film according to the present invention, it is preferable to use active energy rays that include visible light in the wavelength range of 380 nm to 450 nm, and particularly active energy rays that have the highest exposure dose of visible light in the wavelength range of 380 nm to 450 nm. When using ultraviolet light and visible light, if a second optical film with ultraviolet absorption ability, such as an ultraviolet-opaque transparent protective film, is used, light with a wavelength shorter than approximately 380 nm is absorbed, and light with a wavelength shorter than 380 nm does not reach the adhesive composition and does not contribute to the polymerization reaction. Furthermore, light with a wavelength shorter than 380 nm absorbed by the first optical film and the second optical film is converted into heat, which generates heat in the first optical film and the second optical film, causing defects such as curling and wrinkling in the laminated optical film. Therefore, when ultraviolet rays and visible light are used in the present invention, it is preferable to use an active energy ray generator that does not emit light with a wavelength shorter than 380 nm. More specifically, the ratio of the integrated illuminance in the wavelength range of 380 to 440 nm to the integrated illuminance in the wavelength range of 250 to 370 nm is preferably 100:0 to 100:50, more preferably 100:0 to 100:40. When producing the laminated optical film according to the present invention, the active energy ray is preferably a gallium-encapsulated metal halide lamp or an LED light source that emits light in the wavelength range of 380 to 440 nm. Alternatively, light sources containing ultraviolet and visible light, such as low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, incandescent lamps, xenon lamps, halogen lamps, carbon arc lamps, metal halide lamps, fluorescent lamps, tungsten lamps, gallium lamps, excimer lasers, or sunlight, can be used. A bandpass filter can also be used to block ultraviolet rays with a wavelength shorter than 380 nm. In order to prevent curling of the laminated optical film while improving the adhesive performance of the adhesive layer between the first optical film and the second optical film, it is preferable to use active energy rays obtained by using a gallium-encapsulated metal halide lamp and passing through a bandpass filter capable of blocking light with wavelengths shorter than 380 nm, or active energy rays with a wavelength of 405 nm obtained by using an LED light source.

[0119] When the laminated optical film according to the present invention is produced on a continuous line, the line speed depends on the curing time of the adhesive composition, but is preferably 1 to 500 m / min, more preferably 5 to 300 m / min, and even more preferably 10 to 100 m / min. If the line speed is too slow, productivity will be poor, or the damage to the first optical film or the second optical film will be too great, making it impossible to produce a laminated optical film that can withstand durability tests and the like. If the line speed is too high, the adhesive composition will not cure sufficiently, and the desired adhesiveness may not be obtained.

[0120] (Laminated Optical Film) The laminated optical film according to the present invention can be preferably used for forming various image display devices such as liquid crystal display devices. The formation of a liquid crystal display device can be carried out in a conventional manner. That is, a liquid crystal display device is generally formed by appropriately assembling a liquid crystal cell, a polarizing film or an optical film, and, if necessary, components such as an illumination system, and incorporating a drive circuit, but in the present invention, there are no particular limitations except for the use of the laminated optical film according to the present invention, and the method can be carried out in a conventional manner. Regarding the liquid crystal cell, any type, such as a TN type, an STN type, or a π type, can be used.

[0121] Appropriate liquid crystal display devices can be formed, such as those in which an optical laminate is disposed on one or both sides of a liquid crystal cell, or those in which a backlight or reflector is used in the illumination system. In such cases, the optical laminate according to the present invention can be disposed on one or both sides of the liquid crystal cell. When optical laminates are disposed on both sides, they may be the same or different. Furthermore, when forming a liquid crystal display device, appropriate components such as a diffuser, anti-glare layer, anti-reflection film, protective plate, prism array, lens array sheet, light diffuser, backlight, etc. can be disposed in one or more layers at appropriate positions.

[0122] Examples of the present invention will be described below, but the embodiments of the present invention are not limited to these.

[0123] (Method for measuring storage modulus of adhesive layer) The storage modulus of the adhesive layer was measured using a dynamic viscoelasticity measuring device Dva225 manufactured by IT Measurement Control Co., Ltd. under the following measurement conditions: Sample size: width 50 mm, length 30 mm, clamp distance 20 mm, measurement mode: tension, frequency: 1 Hz, heating rate: 5°C / min. Dynamic viscoelasticity was measured, and the measured value of the storage modulus at 25°C was recorded.

[0124] <Acrylic Film> As the acrylic film, a product name "RX420" manufactured by Nippon Shokubai Co., Ltd. was used.

[0125] <Liquid Crystal Film> The following λ / 2 retardation film was obtained as a liquid crystal film based on the following photopolymerizable liquid crystal composition.

[0126] <Photopolymerizable Liquid Crystal Composition> A photopolymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (BASF's "Paliocolor LC242") was dissolved in cyclopentanone to prepare a solution with a solids concentration of 30% by weight. A surfactant (BYK-360, BYK-Chemie) and a photopolymerization initiator (IGM Resins' "Omnirad 907") were added to this solution to prepare a liquid crystal composition solution. The amounts of the leveling agent and polymerization initiator added were 0.01 parts by weight and 3 parts by weight, respectively, relative to 100 parts by weight of the photopolymerizable liquid crystal compound.

[0127] <λ / 2 Retardation Film> A biaxially stretched norbornene film (Zeon Corporation's "ZEONORFILM", thickness: 33 μm, front retardation: 135 nm) was used as a substrate. The liquid crystal composition was applied to the substrate using a bar coater so that the phase difference was λ / 2, and the liquid crystal was aligned by heating at 100° C. for 3 minutes. After cooling to room temperature, the film was irradiated with an integrated light intensity of 400 mJ / cm under a nitrogen atmosphere. ２ The laminate was then photocured by irradiating it with ultraviolet light of 1000 kJ / cm 2 , to obtain a laminate provided with a homogeneously aligned liquid crystal layer.

[0128] A polyvinyl alcohol film having an average degree of polymerization of 2,400, a degree of saponification of 99.9 mol%, and a thickness of 45 μm was prepared. The polyvinyl alcohol film was immersed in a swelling bath (water bath) at 30° C. for 30 seconds between rolls with different peripheral speed ratios, and stretched 2.2 times in the conveyance direction while swelling (swelling step). Subsequently, the film was immersed in a dye bath at 30° C. (iodine aqueous solution obtained by blending iodine and potassium iodide at a weight ratio of 1:7 with 100 parts by weight of water) at 30° C. for 30 seconds while adjusting the iodine concentration so that the polarizing film had a predetermined transmittance. The film was then stretched 3.3 times in the conveyance direction relative to the original polyvinyl alcohol film (a polyvinyl alcohol film that was not stretched in the conveyance direction) (dyeing step). The dyed polyvinyl alcohol film was then immersed in a 40°C crosslinking bath (aqueous solution containing 3.5 wt% boric acid, 3.0 wt% potassium iodide, and 3.6 wt% zinc sulfate) for 28 seconds and stretched in the conveying direction to 3.6 times the original polyvinyl alcohol film (crosslinking step). The resulting polyvinyl alcohol film was then immersed in a 64°C stretching bath (aqueous solution containing 4.8 wt% boric acid, 5.0 wt% potassium iodide, and 5.0 wt% zinc sulfate) for 60 seconds and stretched in the conveying direction to 6.0 times the original polyvinyl alcohol film (stretching step). The resulting polyvinyl alcohol film was then immersed in a 29°C washing bath (containing 2.3 wt% potassium iodide) for 10 seconds (washing step). The washed polyvinyl alcohol film was dried at 40°C for 30 seconds to produce a polarizing film. The polarizing film had a thickness of 18 μm.

[0129] <Preparation of Polarizing Film> An aqueous solution containing an acetoacetyl group-containing polyvinyl alcohol resin (average degree of polymerization: 1,200, degree of saponification: 98.5 mol%, degree of acetoacetylation: 5 mol%) and methylol melamine in a weight ratio of 3:1 was used as the adhesive. Using this adhesive, a 39 μm-thick triacetyl cellulose film (manufactured by Konica Minolta, product name "KC4UY") having a hard coat layer was bonded as a transparent protective film to one side of the polarizing film obtained above via an aqueous adhesive layer 7, and a 30 μm-thick acrylic film (RX420) was bonded to the other side via an aqueous adhesive layer 3 using a roll laminator. This was then subsequently heated and dried in an oven (temperature: 60°C, time: 4 minutes) to prepare polarizing film 1.

[0130] <Active energy rays> Visible light (gallium-filled metal halide lamp) was used as the active energy rays. Irradiation device: Light HAMMER10 manufactured by Fusion UV Systems, Inc. Bulb: V bulb Peak irradiance: 1600 mW / cm ２ , cumulative irradiation dose 1000 mJ / cm ２ The illuminance of visible light was measured using a Sola-Check system manufactured by Solatell.

[0131] Examples 1 to 4 and Comparative Examples 1 and 2: An adhesive composition prepared in the formulation amounts shown in Table 1 was applied to the acrylic film surface of polarizing film 1 and the homogeneously aligned liquid crystal layer surface of a liquid crystal film (a laminate of a biaxially stretched norbornene-based film and a homogeneously aligned liquid crystal layer) using an MCD coater (manufactured by Fuji Machine Co., Ltd.) (cell shape: honeycomb, gravure roll line count: 700 rolls / inch, rotation speed 140% / relative to line speed) so that the adhesive layer was 2 μm thick, and the films were then laminated using a roller. The adhesive composition was then cured by irradiating it with visible light from the biaxially stretched norbornene-based film side using an active energy ray irradiation device, and the biaxially stretched norbornene-based film was peeled off to obtain a laminated optical film.

[0132] The materials constituting the adhesive composition are as follows: Polymerizable compound A: (trade name "UV3000B", manufactured by Mitsubishi Chemical Corporation) (log Pow; 12.7) Polymerizable compound B: (triisopropyl glycol diacrylate) trade name "Aronix M-220", manufactured by Toagosei Co., Ltd., log Pow; 1.68) Polymerizable compound C: (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate) (trade name "MEDOL-10", manufactured by Osaka Organic Chemical Industry Ltd.) (log Pow; 1.51) Polymerizable compound D: lauryl acrylate (trade name "Light Acrylate L-A", manufactured by Kyoeisha Chemical Co., Ltd., log Pow; 6) Polymerizable compound E: (phenoxydiethylene glycol acrylate) (trade name "Light Acrylate P2H-A", manufactured by Kyoeisha Chemical Co., Ltd.) (log Pow; 2.15) (refractive index; 1.517) Polymerizable compound F: (3-phenoxybenzyl acrylate) (trade name "Light Acrylate POB-A", manufactured by Kyoeisha Chemical Co., Ltd.) (log Pow; 3.91) (refractive index; 1.566) Initiator 1 (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide): (trade name: Omnirad 819, manufacturer: IGM Resins B.V.)

[0133] (Appearance Evaluation (Evaluation of the Presence or Absence of Oxalic Acid Bright Spots)) A sample for evaluating humidity durability test was prepared by bonding the manufactured laminated optical film to one side of a 0.7 mm thick alkali-free glass sheet via a pressure-sensitive adhesive layer (20 μm thick). A humidity durability test was conducted by placing the sample in an environment of 85°C and 85% humidity and exposing it for 500 hours. Using a differential interference microscope with a magnification of 5x, an exposure time of 760 μs, and a gain of 1x, a 2 mm x 3 mm area with the most oxalic acid bright spots was trimmed from within 5 mm of the sample edge, and counted using ImageJ ver. 1.8.0. Fewer than 15 bright spots were evaluated as "Good," 15 to 30 bright spots were evaluated as "Good," and more than 30 bright spots were evaluated as "Poor." The results are shown in Table 1.

[0134] (Initial Peel Strength (Initial Adhesion Strength)) The obtained laminated optical film was cut into a size of 200 mm x 15 mm, and the laminated optical film was bonded to a glass plate. Then, an incision was made between the acrylic film and the first optical film with a cutter knife, and the acrylic film and the first optical film were peeled in a 90-degree direction using a Tensilon at a peeling speed of 10,000 mm / min, and the peel strength (N / 15 mm) was measured. When the acrylic film or the first optical film broke or the peel strength exceeded 1.5 N, the result was evaluated as "◎", when the peel strength was 1 to 1.5 N, the result was evaluated as "◯", when the peel strength was 0.5 N or more but less than 1 N, the result was evaluated as "△", and when the peel strength was less than 0.5 N, the result was evaluated as "×". The results are shown in Table 1.

[0135] (Humidified Peel Strength (Humidified Adhesion Strength)) The obtained laminated optical film was left in an oven at a temperature of 20°C and a humidity of 98% for 240 hours, after which the laminated optical film was cut into a size of 200 mm x 15 mm, and the laminated optical film was bonded to a glass plate. An incision was made between the acrylic film and the first optical film with a cutter knife, and the acrylic film and the first optical film were peeled at a 90-degree angle using a Tensilon at a peeling speed of 10,000 mm / min, and the peel strength (N / 15 mm) was measured. Cases in which the acrylic film or the first optical film broke or the peel strength exceeded 1.5 N were evaluated as "◎", cases in which the peel strength was 1 to 1.5 N were evaluated as "◯", cases in which the peel strength was 0.5 N or more but less than 1 N were evaluated as "△", and cases in which the peel strength was less than 0.5 N were evaluated as "×". The results are shown in Table 1.

[0136]

[0137] In Table 1, "average log Pow" refers to "log Pow representing the octanol / water partition coefficient based on the weighted average of the molar fractions of the monomer components contained in the adhesive composition."

[0138] The results in Table 1 show that the laminated optical films of Examples 1 to 4 suppress the occurrence of bright spots due to foreign matter even after the humid durability test, have excellent appearance characteristics, and have excellent adhesive strength between the laminated optical films.

Claims

1. A laminated optical film in which at least an acrylic film and a first optical film are laminated via an adhesive layer, the adhesive layer being formed of a cured layer of an adhesive composition containing at least a polymerizable compound, the acrylic film and the adhesive layer having a structure in which they are in direct contact with each other, a log Pow representing an octanol / water partition coefficient based on a weighted average of the molar fraction of the polymerizable compound contained in the adhesive composition being 1.8 or more and 3.0 or less, and an elastic modulus of the adhesive layer being 1×10 ５ Pa or more and 3×10 ６ The laminated optical film has a modulus of elasticity of 1.0 Pa or less.

2. The laminated optical film according to claim 1, wherein the first optical film is a liquid crystal film or a retardation film.

3. The laminated optical film according to claim 1 or 2, wherein the thickness of the adhesive layer is 0.1 to 10 μm.

4. A laminated optical film according to any one of claims 1 to 3, further comprising a second optical film laminated via an adhesive layer on the surface of the first optical film opposite to the surface on which the acrylic film is laminated.

5. The laminated optical film according to claim 4, wherein the second optical film is a liquid crystal film or a retardation film.

6. A laminated optical film according to any one of claims 1 to 5, wherein the adhesive composition contains a polymerizable compound A, the polymerizable compound A being a urethane (meth)acrylate having a molecular weight of 5,000 or more and having at least two polymerizable groups, and the content of the polymerizable compound A is 4 parts by mass or more and 30 parts by mass or less when the total amount of the polymerizable compounds contained in the adhesive composition is 100 parts by mass.

7. A laminated optical film according to any one of claims 1 to 6, wherein the adhesive composition contains a polymerizable compound B, the polymerizable compound B is a compound having at least two polymerizable groups, and when the total amount of the polymerizable compounds contained in the adhesive composition is taken as 100 parts by mass, the content of the polymerizable compound B is 0 parts by mass or more and 15 parts by mass or less.

8. A laminated optical film according to any one of claims 1 to 7, wherein the adhesive composition contains a polymerizable compound C, the polymerizable compound C has a logPow of 1.0 or more and 8.0 or less, which represents an octanol / water partition coefficient, and the content of the polymerizable compound C is 50 parts by mass or more and 95 parts by mass or less, when the total amount of the polymerizable compounds contained in the adhesive composition is taken as 100 parts by mass.

9. A laminated optical film according to any one of claims 1 to 8, wherein the adhesive composition contains a polymerizable compound D, the polymerizable compound D is a compound having a refractive index of 1.5 or more and 1.7 or less, and when the total amount of the polymerizable compounds contained in the adhesive composition is taken as 100 parts by mass, the content of the polymerizable compound D is 0 parts by mass or more and 95 parts by mass or less.

10. An image display device comprising at least one laminated optical film according to claim 1.

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