WO2025052771A1 - Laminated optical film and image display device - Google Patents

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

The present invention relates to a laminated optical film in which at least an acrylic film and a first optical film are laminated via an adhesive layer. The laminated optical film can be used to form image display devices such as mobile phones, car navigation devices, computer monitors, and televisions.

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

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 concern that the adhesive strength between the acrylic film and other optical films will be insufficient when the film is made into a laminated optical film. In response to this, the following Patent Document 1 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, with the aim of providing a lightweight and thin optical film laminate in which 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 containing a polymerizable monomer that dissolves the (meth)acrylic resin layer and a polymerizable multifunctional acrylate compound.

JP 2014-232251 A

In recent years, one of the durability tests required for laminated optical films used in vehicle applications is a humidity durability test in which the film is exposed to an environment of 65°C and 95% humidity for 1000 hours. Here, the inventors of the present invention conducted a detailed study of the appearance of the laminated optical film after such a humidity durability test and found that bright spots caused by white hazy foreign matter appeared especially on the edges of the laminated optical film, resulting in a defective product 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 it was necessary to thoroughly study the problem in order to solve it.

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.

The above problems can be solved by the following configuration: That is, the present invention relates to a laminated optical film (1) 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 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 the elastic modulus of the adhesive layer being 1×10 ⁵ Pa or more and 3×10 ⁶ Pa or less.

In the above laminated optical film (1), it is preferable that the first optical film is a liquid crystal film or a retardation film (2).

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

Any of the laminated optical films (1) to (3) above is preferably a laminated optical film (4) in which a second optical film is further laminated via an adhesive layer on the surface of the first optical film opposite to the surface on which the acrylic film is laminated.

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

In any of the laminated optical films (1) to (5) above, 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. 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 A is preferably 4 parts by mass or more and 30 parts by mass or less. In the laminated optical film (6),

In any of the laminated optical films (1) to (6) above, 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 (7).

In any of the laminated optical films (1) to (7) above, the adhesive composition contains a polymerizable compound C, and 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. (8) is preferred.

Any of the laminated optical films (1) to (8) above, 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, the content of the polymerizable compound D is preferably 0 parts by mass or more and 95 parts by mass or less (9).

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

As mentioned above, there is concern that the adhesive strength of acrylic film may be insufficient when it is made into a laminated optical film because there are almost no functional groups on the film surface that can contribute to improving adhesive strength. Here, there is a method for increasing the adhesive strength between the acrylic film and the adhesive layer by applying an easy-adhesion adhesive containing a water-based urethane resin or the like to the acrylic film and forming 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 such a case, there is concern that the adhesive strength may be insufficient due to the low interaction between the acrylic film and the adhesive layer.

By the way, laminated optical films used for in-vehicle applications are required to have excellent appearance characteristics even after a humidity durability test in which the film is exposed to an environment of 65°C and 95% humidity for 1000 hours. Components that adversely affect appearance characteristics include oxalic acid bright spots that occur when oxalic acid present in the air forms a salt during heating and drying processes using ovens and heating devices, or during processes for modifying the film surface such as corona treatment, plasma treatment, and itro treatment. Conventionally, oxalic acid bright spots have been a problem in adhesive layers that contact polarizers containing metal components such as zinc that cause oxalic acid bright spots. However, as a result of the inventors' investigations, it has been found that even in adhesive layers that do not contact polarizers, specifically adhesive layers that directly contact acrylic films in this invention, the deterioration of appearance characteristics occurs due to oxalic acid bright spots that occur when oxalic acid is mixed in through water vapor or moisture in the air.

As described above, laminated optical films having acrylic films have a unique problem in that, due to the fact that there are almost no functional groups on the surface of the acrylic film that can contribute to adhesion, when the acrylic film is not treated with an easy-to-use adhesive containing an aqueous urethane resin or the like, that is, when the acrylic film is in direct contact with the adhesive layer, 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. However, in the laminated optical film of the present invention, the occurrence of bright spots due to foreign matter is suppressed even after a humid 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 possible.

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, and the adhesive layer is formed of a cured layer of an adhesive composition containing at least a polymerizable compound, and has a structure in which the acrylic film and the adhesive layer are in direct contact with each other. The adhesive composition is designed such that (i) the logPow representing the octanol/water partition coefficient based on the weighted average of the molar fraction of the polymerizable compound 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 3×10 ⁶ Pa or less. As described above, oxalic acid, which is a component that adversely affects the appearance characteristics, can be mixed into the adhesive layer from the atmosphere via water vapor or moisture in each manufacturing process, but in the present invention, since it has the above-mentioned configuration (i) in particular, the adhesive layer becomes sufficiently hydrophobic, and the mixing of oxalic acid into the adhesive layer can be suppressed, and the occurrence of oxalic acid bright spots that cause deterioration of the appearance characteristics can be suppressed. On the other hand, when the acrylic film and the 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, but the laminated optical film according to the present invention has the above-mentioned (ii) configuration, and the adhesive layer has a sufficiently low elasticity, which causes stress relaxation at the interface between the acrylic film and the adhesive layer, and the adhesion between the two is increased, thereby increasing the adhesive strength. As a result, in the laminated optical film according to the present invention, the occurrence of bright spots due to foreign matter is suppressed even after a humid durability test, and the laminated optical film has excellent appearance characteristics and excellent adhesive strength between the laminated optical films.

In particular, when the adhesive layer of the laminated optical film according to 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.

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

1 shows an example of a schematic cross-sectional view of a laminated optical film according to one embodiment of the present invention. In the laminated optical film 10 in this embodiment, an acrylic film 1 and a first optical film 2 are laminated via an adhesive layer 3, and no easy-adhesion 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 the laminated optical film 10 in this embodiment, 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 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 configuration will be described below.

<Acrylic film>
The acrylic film contains a (meth)acrylic resin. The (meth)acrylic resin film is obtained, for example, by extrusion molding a molding material containing a resin component mainly containing a (meth)acrylic resin.

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 a (meth)acrylic resin having a Tg (glass transition temperature) of 70°C or higher as a main component. The upper limit of the Tg of the (meth)acrylic resin is not particularly limited, but from the viewpoint of formability, etc., it is preferably 170°C or lower.

Any appropriate (meth)acrylic resin may 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 (MS resins, etc.), and polymers having alicyclic hydrocarbon groups (for example, methyl methacrylate-cyclohexyl methacrylate copolymers, methyl methacrylate-norbornyl (meth)acrylate copolymers, etc.). Preferred are poly(meth)acrylic acid C1-6 alkyls 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).

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.

Examples of (meth)acrylic resins having a glutaric anhydride structure include (meth)acrylic resins having a glutaric anhydride structure described in JP-A-2006-283013, JP-A-2006-335902, JP-A-2006-274118, etc.

Examples of (meth)acrylic resins having a lactone ring structure include (meth)acrylic resins having a lactone ring structure described in JP-A-2000-230016, JP-A-2001-151814, JP-A-2002-120326, JP-A-2002-254544, JP-A-2005-146084, etc.

Examples of (meth)acrylic resins having a glutarimide structure include (meth)acrylic resins having a glutarimide structure described in JP-A-2006-309033, JP-A-2006-317560, JP-A-2006-328329, JP-A-2006-328334, JP-A-2006-337491, JP-A-2006-337492, JP-A-2006-337493, JP-A-2006-337569, JP-A-2007-009182, etc.

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 inherent high heat resistance and high transparency of the (meth)acrylic resin may not be fully reflected.

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 inherent high heat resistance and high transparency of the (meth)acrylic resin may not be fully reflected.

The (meth)acrylic resin film may contain other thermoplastic resins in addition to the above (meth)acrylic resins. Examples of other thermoplastic resins include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymers, and poly(4-methyl-1-pentene); halogenated vinyl polymers such as vinyl chloride, vinylidene chloride, and chlorinated vinyl resins; acrylic polymers such as polymethyl methacrylate; styrene polymers such as polystyrene, styrene-methyl methacrylate copolymers, styrene-acrylonitrile copolymers, and acrylonitrile-butadiene-styrene block copolymers; 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; polyether sulfone; polyoxybenzylene; polyamide imide; polybutadiene rubber, and rubber-like polymers such as ABS resins and ASA resins blended with acrylic rubber.

The content of other thermoplastic resins 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.

The (meth)acrylic resin film may contain additives. Examples of additives include hindered phenol, phosphorus, and sulfur antioxidants; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fibers and carbon fibers; 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.

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.

The method for producing the (meth)acrylic resin film is not particularly limited, but for example, the (meth)acrylic resin can be thoroughly mixed with other polymers, additives, etc. by any suitable mixing method to form a thermoplastic resin composition in advance, which can then be molded into a film. Alternatively, the (meth)acrylic resin and other polymers, additives, etc. can each be made into separate solutions, which are then mixed together to form a uniform mixture, which can then be molded into a film.

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, such as an extruder such as a single screw extruder or a twin screw extruder, or a pressure kneader.

The above-mentioned film forming method may be, for example, any suitable film forming method such as solution casting, melt extrusion, calendaring, compression molding, etc. Among these film forming methods, the solution casting and melt extrusion methods are preferred.

Solvents used in the above solution casting method (solution casting method) include, for example, 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.

Equipment for carrying out the above-mentioned solution casting method (solution casting method) includes, for example, a drum-type casting machine, a band-type casting machine, a spin coater, etc.

Examples of the melt extrusion method include the T-die method and the inflation method. The molding temperature is preferably 150 to 350°C, more preferably 200 to 300°C.

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 film extruded into a film shape is wound up to obtain a rolled film. At this time, it is possible to perform uniaxial stretching by appropriately adjusting the temperature of the winding roll and applying stretching in the extrusion direction. It is also possible to perform simultaneous biaxial stretching, sequential biaxial stretching, etc. by stretching the film in a direction perpendicular to the extrusion direction.

The (meth)acrylic resin film may be either an unstretched film or a stretched film. If it is a stretched film, it may be either a uniaxially stretched film or a biaxially stretched film. If it is a biaxially stretched film, it may be either a simultaneous biaxially stretched film or a sequential biaxially stretched film. When biaxially stretched, the mechanical strength is improved, and the film performance is improved. By mixing the (meth)acrylic resin film with other thermoplastic resins, the increase in phase difference can be suppressed even when stretched, and optical isotropy can be maintained.

The stretching temperature is preferably close to 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, and stable stretching may not be possible.

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

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 will take 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.

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

The thickness of the (meth)acrylic resin film is preferably 20 to 60 μm, and more preferably 20 to 30 μm. If the thickness is less than 20 μm, not only will the strength decrease, but there is also a risk of significant shrinkage when the laminated optical film is subjected to a durability test. If the thickness exceeds 60 μm, there is a risk of reduced transparency.

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, a surface modification treatment may be performed on the surface of the acrylic film that is in contact with the adhesive layer. Examples of the surface modification treatment include corona treatment, plasma treatment, and itro treatment, and corona treatment is particularly preferable.

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

The retardation film may be any of the following formulas (1) to (3):
0.70<Re[450]/Re[550]<0.97...(1)
1.5×10-3<Δn<6×10-3...(2)
1.13<NZ<1.50...(3)
(wherein Re[450] and Re[550] are in-plane retardation values of the retardation film measured with light having wavelengths of 450 nm and 550 nm at 23° C., respectively; Δn is in-plane birefringence, which is nx-ny, where nx and ny are the refractive indices in the slow axis direction and 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.) A reverse wavelength dispersion type retardation film that satisfies the above may be used.

<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 a water-based urethane resin or the like is provided between the acrylic film and the adhesive layer.

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

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 means that the substance is lipophilic, that is, hydrophobic. The logPow value can be measured (using the flask shaking 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.

The log Pow of the main polymerizable compounds is shown below. Hydroxyethylacrylamide (trade name "HEAA", Kohjin Co., Ltd., Log Pow; -0.56), diethylacrylamide (trade name "DEAA", KJ Chemicals Co., Ltd., Log Pow; 1.69), unsaturated fatty acid hydroxyalkyl ester modified ε-caprolactone (trade name "Placcel FA1DDM", Daicel Co., Ltd., Log Pow; 1.06), N-vinylformamide (trade name "Beamset 770", Arakawa Chemical Co., Ltd., Log Pow; -0.25), acryloylmorpholine (trade name "ACMO", Kohjin Co., Ltd., Log Pow; -0.20), γ-butyrolactone acrylate (trade name "GBLA", manufactured by Osaka Organic Chemical Industry Co., Ltd., Log Pow; 0.19), acrylic acid dimer (trade name "β-CEA", manufactured by Daicel Corporation, Log Pow; 0.2), N-vinylpyrrolidone (trade name "NVP", manufactured by Nippon Shokubai Co., Ltd., Log Pow; 0.24), acetoacetoxyethyl methacrylate (trade name "AAEM", manufactured by Nippon Synthetic Chemical Industry Co., Ltd., Log Pow; 0.27), 2-hydroxyethyl acrylate (trade name "HEA", manufactured by Osaka Organic Chemical Industry Co., Ltd., Log Pow; 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 Kohjin 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, Log Pow; 0.69), Polyethylene glycol diacrylate (trade name "Light Acrylate 3EG-A", manufactured by Kyoeisha Chemical Co., Ltd., Log Pow; 0.72), PEG400# diacrylate (trade name "Light Acrylate 9EG-A", manufactured by Kyoeisha Chemical Co., Ltd., Log Pow; -0.1), polypropylene glycol diacrylate (trade name "Aronix M-220", manufactured by Toagosei Co., Ltd., Log Pow; 1.68), dicyclopentenyl acrylate (trade name "Fancryl FA-511AS", manufactured by Hitachi Chemical Co., Ltd., Log Pow; 2.26), butyl acrylate (trade name "A 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 neopentyl 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 "Arono Xetan OXT-212" manufactured by Toagosei Co., Ltd., Log Pow; 4.24), bisphenol-A diglycidyl ether (trade name "JER828" manufactured by Mitsubishi Chemical Co., Ltd., 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", Examples include bisphenol A PO3 mol modified diacrylate (product name "FA-P323A", Hitachi Chemical Co., Ltd., Log Pow; 6.26), bisphenol A PO4 mol modified diacrylate (product name "FA-P324A", Hitachi Chemical Co., Ltd., Log Pow; 6.43), lauryl acrylate (product name "Light Acrylate L-A", Kyoeisha Chemical Co., Ltd., Log Pow; 6), isostearyl acrylate (product name "ISTA", Osaka Organic Chemical Industry Co., Ltd., Log Pow; 7.46).

The adhesive layer will be described in detail below. The adhesive layer is formed from a cured layer of an adhesive composition containing at least a polymerizable compound, and is preferably formed from a cured layer of an active energy ray curable adhesive composition, such as an electron beam curable, ultraviolet ray curable, or visible light curable adhesive composition. 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, from the viewpoint of improving the appearance characteristics and adhesive strength of the laminated optical film. Active energy ray curable adhesive compositions can be divided into radical polymerization curable adhesive compositions and cationic polymerization 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.

The polymerizable compound constituting the radical polymerization curing adhesive composition includes a radical polymerizable compound. The radical polymerizable compound includes a compound having a radical 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. As these radical polymerizable compounds, for example, a compound having a (meth)acryloyl group is suitable. In the present invention, (meth)acryloyl means an acryloyl group and/or a methacryloyl group, and "(meth)" has the same meaning below.

Examples of monofunctional radically polymerizable compounds include (meth)acrylamide derivatives having a (meth)acrylamide group. (Meth)acrylamide derivatives are preferred because they ensure adhesion to polarizers and various transparent protective films, and because they have a fast 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 heterocyclic ring-containing (meth)acrylamide derivatives in which the nitrogen atom of the (meth)acrylamide group forms a heterocyclic ring include N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, and N-acryloylpyrrolidine.

Among the above (meth)acrylamide derivatives, N-hydroxyalkyl group-containing (meth)acrylamide derivatives are preferred from the viewpoint of adhesion to polarizers and various transparent protective films, and examples of monofunctional radical polymerizable compounds 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.

The (meth)acrylic acid derivatives include, for example, 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. Polycyclic (meth)acrylates such as diethyl (meth)acrylate and dicyclopentanyl (meth)acrylate; alkoxy or phenoxy group-containing (meth)acrylates such as 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; and the like.

Furthermore, 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-trifluoroethylethyl (meth)acrylate, and 2,2,2-trifluoroethylethyl (meth)acrylate; (meth)acrylates containing halogens 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, and Examples of such acrylates include oxetane group-containing (meth)acrylates such as 3-ethyl-oxetanylmethyl (meth)acrylate, 3-butyl-oxetanylmethyl (meth)acrylate, and 3-hexyl-oxetanylmethyl (meth)acrylate; (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.

In addition, examples of monofunctional radically polymerizable compounds 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.

Examples of monofunctional radically polymerizable compounds include lactam-based vinyl monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone; and vinyl monomers having nitrogen-containing heterocycles such as vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, and vinylmorpholine.

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 radical 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 radical polymerizable compound having an active methylene group is preferably an acetoacetoxyalkyl (meth)acrylate.

In the present invention, it is preferable that the adhesive composition contains a polymerizable compound B. The polymerizable compound B has a logPow, 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, product name: MEDOL-10, manufacturer: Osaka Organic Chemical Industry Co., Ltd. (logPow: 1.6), benzyl acrylate, product name: Viscoat #160, manufacturer: Osaka Organic Chemical Industry Co., Ltd. (logPow: 2.46), phenoxyethyl acrylate, product name: Viscoat #192HP, manufacturer: Osaka Organic Chemical Industry Co., Ltd. (logPow: 2.52), cyclohexyl Lauryl acrylate, trade name: Viscoat #155, manufacturer: Osaka Organic Chemical Industry Co., Ltd. (logPow: 2.46), lauryl acrylate, trade name: LA, manufacturer: Osaka Organic Chemical Industry Co., Ltd. (logPow: 6), phenoxydiethylene glycol acrylate, trade name: P2H-A, manufacturer: Kyoeisha Chemical Co., Ltd. (logPow: 2.15), phenoxybenzyl acrylate, trade name: POB-A, manufacturer: Kyoeisha Chemical Co., Ltd. (logPow: 3.91). The adhesive composition used in the present invention 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, which is preferable.

　Examples of polyfunctional radically polymerizable compounds having two or more polymerizable functional groups include, for example, 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, neopentyl glycol diglycidyl ether di(meth)acrylate, bisphenol A ... Examples of the ester compound of (meth)acrylic acid with a polyhydric alcohol include esters of (meth)acrylic acid with a polyhydric alcohol, such as dipentaerythritol 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, and EO-modified diglycerin tetra(meth)acrylate; 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. In addition, various epoxy (meth)acrylates, urethane (meth)acrylates, polyester (meth)acrylates, various (meth)acrylate monomers, etc. may be used as necessary.

In the present invention, it is preferable that the adhesive composition contains a polymerizable compound A. The polymerizable compound A is a urethane (meth)acrylate having a molecular weight of 5000 or more and having at least two polymerizable groups. When the total amount of the 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" (logPow: 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 containing the polymerizable compound A in the adhesive composition used in the present invention, the elastic modulus of the adhesive is reduced, and adhesion by stress relaxation is possible.

In the present invention, it is preferable that the adhesive composition contains a polymerizable compound C. The polymerizable compound C 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 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 radical polymerizable compounds. By containing the polymerizable compound C, the adhesive composition used in the present invention can have an elastic modulus that satisfies both adhesion to acrylic films and oxalic acid bright spots.

In the present invention, the adhesive composition that is the raw material for the adhesive layer of the laminated optical film can contain, in addition to the radically polymerizable compound, an acrylic oligomer obtained by polymerizing a (meth)acrylic monomer. By containing an acrylic oligomer in the adhesive composition, it is possible to reduce the cure shrinkage that occurs when the composition is irradiated with active energy rays and cured, and to reduce the interfacial stress between the adhesive layer and the adherend, such as a polarizer or an optical film. As a result, it is possible to suppress a decrease in adhesion between the adhesive layer and the adherend.

When 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 the adhesive layer from shrinking on curing, it is preferable that it has a weight average molecular weight (Mw) of 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 the shrinkage of the cured layer (adhesive layer) on curing, it is preferable that the weight average molecular weight (Mw) of the acrylic oligomer is 500 or more, more preferably 1,000 or more, and particularly preferably 1,500 or more. Specific examples of (meth)acrylic monomers constituting acrylic oligomers 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, 2,2-dimethylbutyl (meth)acrylate, n-hexyl (meth)acrylate, cetyl (meth)acrylate, (meth)acrylic acid (C1-20) alkyl esters such as (meth)acrylic acid (C1-20) alkyl esters, such as 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-norbornene-2-methyl-3-phenylenediamine (meth)acrylate, etc.), -yl-methyl (meth)acrylate, 3-methyl-2-norbornylmethyl (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, phenoxy group oxyethyl (meth)acrylate, etc.), epoxy group-containing (meth)acrylic acid esters (e.g., glycidyl (meth)acrylate, etc.), halogen-containing (meth)acrylic acid esters (e.g., 2,2,2-trifluoroethyl (meth)acrylate, 2,2,2-trifluoroethylethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropentyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, etc.), alkylaminoalkyl (meth)acrylates (e.g., dimethylaminoethyl (meth)acrylate, etc.). These (meth)acrylates can be used alone or in combination of two or more kinds. 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.

The amount of acrylic oligomer is 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 will increase, leading to poor surface smoothness after application and poor appearance, which is not preferred. On the other hand, in order to sufficiently suppress cure shrinkage of the adhesive layer, it is preferred that the composition contains 3 parts by weight or more of acrylic oligomer.

When a radical polymerizable compound is used, the photopolymerization initiator is appropriately selected depending on the active energy ray. When curing with ultraviolet or visible light, a photopolymerization initiator that is cleaved by ultraviolet 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-hydroxycyclohexylphenylketone; 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. These include benzoin ether compounds such as benzoin butyl ether and anisoin methyl ether; aromatic ketal compounds such as benzil dimethyl ketal; 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.

The amount of the photopolymerization initiator is 20% by weight or less when the total amount of the active energy ray-curable adhesive composition is taken as 100% by weight. The amount of the photopolymerization initiator is 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.

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 highly 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.

It is also preferable to add a polymerization initiator aid as necessary. Examples of polymerization initiator aids 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 preferable. When a polymerization initiator 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, per 100 parts by weight of the total amount of the curable components.

If necessary, a known photopolymerization initiator can be used in combination. Since a transparent protective film with UV absorption ability does not transmit light of 380 nm or less, it is preferable to use a photopolymerization initiator that is highly sensitive to light of 380 nm or more. Specifically, 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-cyclopentadiene-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium, and the like.

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

（式中、Ｒ^３、Ｒ^４およびＲ^５は－Ｈ、－ＣＨ_３、－ＣＨ_２ＣＨ_３、－ｉＰｒまたはＣｌを示し、Ｒ^３、Ｒ^４およびＲ^５は同一または異なっても良い）を使用することが好ましい。一般式（２）で表される化合物としては、市販品でもある２，４，６－トリメチルベンゾイル－ジフェニル－フォスフィンオキサイド（商品名：Ｏｍｎｉｒａｄ８１９　メーカー：ＩＧＭ　Ｒｅｓｉｎｓ　Ｂ．Ｖ．）、２－メチル－１－（４－メチルチオフェニル）－２－モルフォリノプロパン－１－オン（商品名：Ｏｍｎｉｒａｄ９０７　メーカー：ＩＧＭ　Ｒｅｓｉｎｓ　Ｂ．Ｖ．）が好適に使用可能である。その他、２－ベンジル－２－ジメチルアミノ－１－（４－モルフォリノフェニル）－ブタノン－１（商品名：Ｏｍｎｉｒａｄ３６９　メーカー：ＩＧＭ　Ｒｅｓｉｎｓ　Ｂ．Ｖ．）、２－（ジメチルアミノ）－２－［（４－メチルフェニル）メチル］－１－［４－（４－モルホリニル）フェニル］－１－ブタノン（商品名：Ｏｍｎｉｒａｄ３７９　メーカー：ＩＧＭ　Ｒｅｓｉｎｓ　Ｂ．Ｖ．）が感度が高いため好ましい。

(wherein R ³ , R ⁴ and R ⁵ represent -H, -CH ₃ , -CH ₂ CH ₃ , -iPr or Cl, and R ³ , R ⁴ and R ⁵ may be the same or different.) As the compound represented by the general formula (2), commercially available products such as 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (product name: Omnirad 819, manufacturer: IGM Resins B.V.) and 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (product 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.

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 having a high concentration of component A on the polarizer side is increased, and the curability of the adhesive layer is increased. 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). In particular, 1-hydroxycyclohexyl phenyl ketone is more preferable because it has excellent solubility in the adhesive layer having a high concentration of component A.

In the present invention, a cationic polymerizable adhesive composition may be used as an adhesive composition that is a raw material for the adhesive layer provided in the laminated optical film. The cationic polymerizable compounds used in the cationic polymerizable adhesive composition are classified into monofunctional cationic polymerizable compounds having one cationic polymerizable functional group in the molecule and polyfunctional cationic polymerizable compounds having two or more cationic polymerizable functional groups in the molecule. Since the liquid viscosity of the monofunctional cationic polymerizable compound is relatively low, the liquid viscosity of the resin composition can be reduced by including it in the resin composition. In addition, the monofunctional cationic polymerizable compound often has a functional group that exhibits various functions, and by including it in the cationic polymerizable adhesive composition, various functions can be exhibited in the cationic polymerizable adhesive composition and/or the cured product of the cationic polymerizable adhesive composition. The polyfunctional cationic polymerizable compound can three-dimensionally crosslink the cured product of the cationic polymerizable adhesive composition, so it is preferable to include it in the cationic polymerizable adhesive composition. The ratio of the monofunctional cationic polymerizable compound to the polyfunctional cationic polymerizable compound is preferably in the range of 10 parts by weight to 1000 parts by weight of the polyfunctional cationic polymerizable compound mixed with 100 parts by weight of the monofunctional cationic polymerizable compound. Examples of the cationic 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 cationic polymerizable adhesive composition of the present invention is particularly preferably one that contains an alicyclic epoxy compound because of its excellent curability and adhesiveness. 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 specifically, CELLOXIDE 2021, CELLOXIDE 2021A, CELLOXIDE 2021P, CELLOXIDE 2081, CELLOXIDE 2083, CELLOXIDE 2085 (all manufactured by Daicel Chemical Industries, Ltd.), Cyracure UVR-61 No. 05, Cyracure UVR-6107, Cyracure 30, R-6110 (all manufactured by Dow Chemical Japan, Ltd.). Compounds having an oxetanyl group are preferably contained since 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-ox Examples of such compounds include 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, phenol novolak oxetane, and the like. ARON OXETANE OXT-101, ARON OXETANE OXT-121, ARON OXETANE OXT-211, ARON OXETANE OXT-221, ARON OXETANE OXT-212 (all manufactured by Toagosei Co., Ltd.) and the like are commercially available. Compounds having a vinyl ether group are preferably contained since 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 ether group include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, triethylene glycol divinyl ether, cyclohexane dimethanol divinyl ether, cyclohexane dimethanol monovinyl ether, tricyclodecane vinyl ether, cyclohexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, and pentaerythritol tetravinyl ether.

The cationic polymerizable adhesive composition contains at least one compound selected from the compounds having an epoxy group, the compounds having an oxetanyl group, and the compounds having a vinyl ether group described above as a curable component, and since all of these are cured by cationic polymerization, a photocationic polymerization initiator is blended. This photocationic polymerization initiator generates cationic species or Lewis acid by irradiation with active energy rays such as visible light, ultraviolet light, X-rays, and electron beams, and initiates the polymerization reaction of the epoxy group or the oxetanyl group. As the photocationic polymerization initiator, a photoacid generator described below is preferably used. In addition, when the cationic 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 more, but since photocationic polymerization initiators are generally compounds that show maximum absorption in the vicinity of 300 nm or shorter wavelength range, by blending a photosensitizer that shows maximum absorption in the longer wavelength range, specifically, light of wavelengths longer than 380 nm, it is possible to promote the generation of cationic species or acid from the photocationic polymerization initiator by responding to light of wavelengths in this vicinity. Examples of photosensitizers include anthracene compounds, pyrene compounds, carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, photoreducible dyes, etc., 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% to 5% by weight, and more preferably 0.5% to 3% by weight.

The laminated optical film 10 shown in FIG. 1 further comprises a triacetyl cellulose film 6, which is a transparent protective film, 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 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.

<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, cohesiveness, and adhesiveness, and having excellent weather resistance, heat resistance, etc., such as acrylic adhesives, can be preferably used.

　A separator is temporarily attached to cover the exposed surface of the adhesive layer to prevent contamination until it is put to practical use. This prevents contact with the adhesive layer during normal handling. As a separator, apart from the thickness conditions mentioned above, any suitable thin material such as a plastic film, rubber sheet, paper, cloth, nonwoven fabric, net, foam sheet, metal foil, or laminates thereof, coated as necessary with a suitable release agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide release agent, may be used in accordance with conventional methods.

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

The laminated optical film according to the present invention may include the optical films shown below in addition to the acrylic film, the first optical film, and the second optical film.

The laminated optical film according to the present invention may include a polarizer as another optical film. As the material for the polyvinyl alcohol-based film applied to the polarizer, polyvinyl alcohol or a derivative thereof is used. Examples of polyvinyl alcohol derivatives include polyvinyl formal, polyvinyl acetal, etc., as well as those modified with olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, their alkyl esters, acrylamide, etc. Polyvinyl alcohols with a degree of polymerization of about 1000 to 10000 and a degree of saponification of about 80 to 100 mol % are generally used.

The polyvinyl alcohol film may contain additives such as plasticizers. Examples of plasticizers include polyols and their condensates, such as glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. There are no particular restrictions on the amount of plasticizer used, but it is preferable for it to be 20% by weight or less in the polyvinyl alcohol film.

In manufacturing a polarizer, a dyeing process in which the polyvinyl alcohol-based film is dyed with iodine and a stretching process in which the polyvinyl alcohol-based film is stretched in at least one direction are carried out. In general, a method is adopted in which the polyvinyl alcohol-based film is subjected to a series of processes including swelling, dyeing, crosslinking, stretching, washing with water, and drying.

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 anti-blocking agents, and also swells the polyvinyl alcohol film, 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.

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 dissolution aid. The iodine concentration is usually about 0.01 to 1% by weight, and preferably 0.02 to 0.5% by weight. The potassium iodide concentration is usually about 0.01 to 10% by weight, and preferably 0.02 to 8% by weight.

In the iodine dyeing process, 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 process, 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 are within the above ranges.

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

The stretching process is a process in which a polyvinyl alcohol-based film is stretched in at least one direction. In general, the polyvinyl alcohol-based film is uniaxially stretched in the conveying direction (longitudinal direction). There are no particular limitations on the stretching method, and either a wet stretching method or a dry stretching method can be used. When a wet stretching method is used, the polyvinyl alcohol-based film is stretched to a predetermined ratio in a treatment bath. As a solution for the stretching bath, a solution in which compounds necessary for various treatments are added to a solvent such as water or an organic solvent (e.g., ethanol) is preferably used. Examples of dry stretching methods include a roll-to-roll stretching method, a heated roll stretching method, and a compression stretching method. In the manufacture of a polarizer, the stretching process may be performed at any stage. Specifically, it may be performed simultaneously with swelling, dyeing, and crosslinking, or it may be performed before or after each of these steps. In addition, the stretching may be performed in multiple stages. The cumulative stretching ratio of the polyvinyl alcohol-based film is usually 5 times or more, and preferably about 5 to 7 times.

In the present invention, the polarizer preferably contains a metal component that can become a divalent metal cation in water, more preferably contains magnesium, calcium, copper or zinc, and particularly preferably contains zinc. When the polarizer contains zinc, there is a tendency for the decrease in transmittance and deterioration in hue of the laminated optical film after a heating test 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 %.

In the present invention, it is preferable that the polarizer contains sulfate ions. When the polarizer contains sulfate ions, the decrease in the transmittance of the laminated optical film after the 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% by weight, more preferably 0.05 to 0.35% by weight, and even more preferably 0.1 to 0.25% by weight. The content of sulfate ions in the polarizer is calculated from the sulfur atom content.

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

The zinc impregnation process 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, such as zinc chloride and zinc iodide, zinc sulfate, and zinc acetate in aqueous solutions. Various zinc complex compounds may also be used for the zinc impregnation process. It is preferable to use an aqueous solution of potassium ions and iodine ions, such as potassium iodide, as the zinc salt solution, as this makes it easier to impregnate the zinc ions. The concentration of potassium iodide in the zinc salt solution is preferably about 0.5 to 10% by weight, and more preferably 1 to 8% by weight.

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 is easily separated into sulfate ions and metal ions in the treatment solution and that is easily introduced in the ionic state into the polyvinyl alcohol film. For example, types of metals that form metal sulfate 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.

In the manufacture of a polarizer, the zinc impregnation and sulfate ion treatment may be performed at any stage. That is, the zinc impregnation and sulfate ion treatment may be performed before or after the dyeing process. The zinc impregnation 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 perform the zinc impregnation and sulfate ion treatment simultaneously by immersing the polyvinyl alcohol film in a treatment bath containing zinc sulfate. In addition, the zinc salt and the metal sulfate salt may be present in the dyeing solution, and the zinc impregnation and/or sulfate ion treatment may be performed simultaneously with the dyeing process. The zinc impregnation and sulfate ion treatment may be performed simultaneously with the stretching.

In the zinc impregnation treatment and sulfate ion treatment, the zinc content and sulfate ion content in the polarizer are adjusted by adjusting the conditions such as the concentration of the zinc salt solution and the metal sulfate 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 solution is usually about 15 to 85°C, preferably 25 to 70°C. The immersion time is usually about 1 to 120 seconds, preferably 3 to 90 seconds. The concentration of the zinc salt solution and the metal sulfate solution varies depending on the type of zinc salt and metal sulfate, but is usually about 0.5 to 20% by weight, preferably 1 to 10% by weight, and more preferably 2 to 7% by weight. By setting the zinc salt concentration and the metal sulfate concentration in the corresponding ranges, the zinc content and sulfate ion content in the polarizer can be set within the above-mentioned preferred ranges.

The polyvinyl alcohol film (stretched film) that has been subjected to the above treatments is subjected to a water washing process and a drying process according to the usual method.

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 such as zinc sulfate or zinc chloride may be added to the aqueous iodide solution.

The 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 washing process may be carried out only once, or may be carried out multiple times as necessary. When the washing process is carried out multiple times, the type and concentration of additives contained in the washing bath used for each treatment are appropriately adjusted.

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

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, and corona treatment is particularly preferable. 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, making it possible to produce a laminated optical film with excellent appearance characteristics.

The laminated optical film according to the present invention may be provided with a transparent protective film as another optical film. As a material constituting the transparent protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture blocking property, isotropy, etc. is used. 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, colorants, etc. 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 of the thermoplastic resin may not be fully exhibited.

Furthermore, as a material for forming the transparent protective film, one having excellent transparency, mechanical strength, thermal stability, moisture blocking properties, isotropy, etc. is preferred, and one having a moisture permeability of 150 g/ ^m2 /24 h or less is more preferred, one having a moisture permeability of 140 g/ ^m2 /24 h or less is particularly preferred, and one having a moisture permeability of 120 g/ ^m2 /24 h or less is even more preferred.

The transparent protective film may be provided with functional layers such as a hard coat layer, an anti-reflection layer, an anti-sticking layer, a diffusion layer, or an anti-glare layer. The above-mentioned functional layers such as the hard coat layer, the anti-reflection layer, the anti-sticking layer, the diffusion layer, and the anti-glare layer may be provided on the transparent protective film itself, or may be provided separately from the transparent protective film.

The thickness of the transparent protective film can be determined as appropriate, but is generally about 1 to 500 μm in terms of strength, ease of handling, thinness, etc., with 1 to 300 μm being preferred, and 5 to 200 μm being more preferred. Furthermore, 10 to 200 μm is more preferred, and 20 to 80 μm is more preferred.

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, comprising the steps of:
the adhesive layer is formed of a cured layer of an adhesive composition containing at least a polymerizable compound,
a coating step of coating the adhesive composition on at least one of the acrylic film and the first optical film;
A method for producing a laminated optical film, comprising: a lamination step of laminating the acrylic film and the first optical film together so that the acrylic film and the adhesive layer are in direct contact with each other; and an adhesion step of adhering the acrylic film and the first optical film via an adhesive layer formed by irradiating an active energy ray from the acrylic film surface side or the first optical film surface side to cure at least the adhesive composition. Each step will be described below.

(Coating process)
The method of 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. If the viscosity of the composition is high, the surface smoothness after application is poor, which is not preferable because it causes poor appearance. For this reason, each composition can be heated or cooled to adjust the viscosity to a preferred range and then applied.

(Lamination process)
The acrylic film and the first optical film are bonded together so that the acrylic film and the adhesive layer are in direct contact with each other. In the coating process, when the adhesive composition is applied to the acrylic film, the adhesive composition is directly applied to the acrylic film and then the first optical film is bonded to the acrylic film without applying an easy-to-adhesive containing an aqueous urethane resin or the like to the acrylic film. In the coating process, even when the adhesive composition is applied to the first optical film, the adhesive composition-coated surface of the first optical film and the acrylic film are directly bonded together without using an easy-to-adhesive or the like. When the acrylic film and the first optical film are bonded together via the adhesive composition, they are bonded together using a roll laminator or the like.

(Bonding process)
The acrylic film and the first optical film are bonded 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.

When irradiating with electron beams, any suitable irradiation conditions can be adopted as long as they are conditions that can at least cure the adhesive composition. For example, the acceleration voltage of the 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, and if the acceleration voltage exceeds 300 kV, the penetration force through the sample may be too strong, resulting in damage to 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, and if it exceeds 100 kGy, the first optical film and the second optical film may be damaged, resulting in a decrease in mechanical strength and yellowing, and the specified optical characteristics may not be obtained.

Electron beam irradiation is usually performed in an inert gas, but may be performed in air or with a small amount of oxygen introduced if necessary. Depending on the materials of the first and second optical films, appropriate oxygen introduction can be used to intentionally cause oxygen inhibition on the first and second optical film surfaces that are first hit by the electron beam, preventing damage to the first and second optical films and allowing the electron beam to be efficiently irradiated only to the adhesive.

When manufacturing the laminated optical film of 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 in particular active energy rays that have the greatest irradiation amount of visible light in the wavelength range of 380 nm to 450 nm. When using ultraviolet rays and visible light, if a second optical film with ultraviolet absorption ability is used, such as an ultraviolet-opaque transparent protective film, 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, and the first optical film and the second optical film themselves generate heat, causing defects such as curling and wrinkling of the laminated optical film. Therefore, when ultraviolet rays and visible light are employed in the present invention, it is preferable to use a device that does not emit light with a wavelength shorter than 380 nm as an active energy ray generator, and 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, a light source containing ultraviolet rays and visible light such as a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, an incandescent lamp, a xenon lamp, a halogen lamp, a carbon arc lamp, a metal halide lamp, a fluorescent lamp, a tungsten lamp, a gallium lamp, an excimer laser, or sunlight can be used, and a bandpass filter can 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 a gallium-encapsulated metal halide lamp and active energy rays obtained 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 using an LED light source.

When the laminated optical film of the present invention is manufactured 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 adhesion may not be obtained.

(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 the liquid crystal display device can be carried out in accordance with the conventional method. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, a polarizing film or an optical film, and an optional lighting system, and incorporating a driving circuit, but in the present invention, there is no particular limitation except that the laminated optical film according to the present invention is used, and the method can be carried out in accordance with the conventional method. As for the liquid crystal cell, any type such as a TN type, STN type, or π type can be used.

It is possible to form suitable liquid crystal display devices, 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 lighting system. In such cases, the optical laminate according to the present invention can be disposed on one or both sides of a 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, suitable components such as a diffuser plate, anti-glare layer, anti-reflection film, protective plate, prism array, lens array sheet, light diffuser plate, backlight, etc. can be disposed in suitable positions in one or more layers.

The following are examples of the present invention, but the present invention is not limited to these.

(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 20mm,
Measurement mode: tension, frequency: 1Hz,
Heating rate: 5° C./min. Dynamic viscoelasticity was measured, and the measured value at 25° C. was taken as the storage modulus.

<Acrylic film>
The acrylic film used was "RX420" manufactured by Nippon Shokubai Co., Ltd.

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

<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 solid concentration of 30% by weight. A surfactant (BYK-360 manufactured by BYK-Chemie) and a photopolymerization initiator (IGM Resins'"Omnirad907") were added to this solution to prepare a liquid crystal composition solution. The amounts of the leveling agent and the 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.

<λ/2 Phase Difference Film>
A biaxially stretched norbornene-based film (ZEON Corporation's "ZEONORFILM", thickness: 33 μm, front retardation: 135 nm) was used as a substrate, and the above liquid crystal composition was applied onto the substrate with 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 substrate was irradiated with ultraviolet light with an integrated light quantity of 400 mJ/cm ² in a nitrogen atmosphere for photocuring, to obtain a laminate provided with a homogeneously aligned liquid crystal layer.

<Preparation of Polarizing Film>
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 stretched 2.2 times in the conveying direction while swelling by immersing in a swelling bath (water bath) at 30° C. between rolls with different peripheral speed ratios (swelling step), and then stretched 3.3 times in the conveying direction based on the original polyvinyl alcohol film (polyvinyl alcohol film not stretched at all in the conveying direction) while dyeing by immersing in a dyeing bath (iodine aqueous solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with respect to 100 parts by weight of water) at 30° C. for 30 seconds while adjusting the iodine concentration so that the polarizing film has a predetermined transmittance (dyeing step). Next, the dyed polyvinyl alcohol film was immersed in a crosslinking bath (aqueous solution with a boric acid concentration of 3.5 wt%, a potassium iodide concentration of 3.0 wt%, and a zinc sulfate concentration of 3.6 wt%) at 40° C. for 28 seconds to be stretched to 3.6 times the original polyvinyl alcohol film in the conveying direction (crosslinking step). Further, the obtained polyvinyl alcohol film was immersed in a stretching bath (aqueous solution with a boric acid concentration of 4.8 wt%, a potassium iodide concentration of 5.0 wt%, and a zinc sulfate concentration of 5.0 wt%) at 64° C. for 60 seconds to be stretched to 6.0 times the original polyvinyl alcohol film in the conveying direction (stretching step), and then immersed in a washing bath (potassium iodide concentration of 2.3 wt%) at 29° C. for 10 seconds (washing step). The washed polyvinyl alcohol film was dried at 40° C. for 30 seconds to prepare a polarizing film. The polarizing film had a thickness of 18 μm.

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

<Active energy rays>
Visible light (gallium-filled metal halide lamp) was used as the active energy ray. Irradiation device: Light HAMMER10 manufactured by Fusion UV Systems, Inc. Bulb: V bulb Peak illuminance: 1600 mW/cm ² , cumulative irradiation amount: 1000 mJ/cm ² (wavelength: 380 to 440 nm). The illuminance of visible light was measured using a Sola-Check system manufactured by Solatell.

Examples 1 to 4 and Comparative Examples 1 to 2
The adhesive composition adjusted to the blending amount shown in Table 1 was applied to the acrylic film surface of the polarizing film and the homogeneously oriented liquid crystal layer surface of the liquid crystal film (a laminate of a biaxially stretched norbornene-based film and a homogeneously oriented 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%/to line speed) on the polarizing film 1 so that the adhesive layer had a thickness of 2 μm, and then laminated with a roll machine. Thereafter, the adhesive composition was cured by irradiating the above-mentioned 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.

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

(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 alkali-free glass having a thickness of 0.7 mm through a pressure-sensitive adhesive layer (thickness 20 μm). After placing the sample in an environment of 85 ° C.-85% humidity, a humidity durability test was performed in which the sample was exposed for 500 hours. Using a differential interference microscope, a 2 mm × 3 mm range with the most oxalic acid bright spots was trimmed from within a range of 5 mm from the end face of the sample at a magnification of 5 times, an exposure time of 760 μs, and a gain of 1 time, and counting was performed using ImageJ ver. 1.8.0. The number of bright spots was less than 15, "◯", the number of bright spots was 15 to 30, and the number of bright spots was more than 30, "×". The results are shown in Table 1.

(Initial peel strength (initial adhesive strength))
The obtained laminated optical film was cut into a size of 200 mm x 15 mm, and the laminated optical film was attached to a glass plate. Then, a cutter knife was used to make a cut between the acrylic film and the first optical film, and the acrylic film and the first optical film were peeled off in a 90-degree direction at a peeling speed of 10,000 mm/min using a Tensilon, 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, it was marked as "◎", when the peel strength was 1 to 1.5 N, it was marked as "◯", when the peel strength was 0.5 N or more and less than 1 N, it was marked as "△", and when the peel strength was less than 0.5 N, it was marked as "×". The results are shown in Table 1.

(Peel strength under humid conditions (adhesive strength under humid conditions))
The obtained laminated optical film was left in an oven at a temperature of 20° C. and a humidity of 98% for 240 hours, and then the laminated optical film was cut into a size of 200 mm×15 mm, and the laminated optical film was attached to a glass plate. Then, a cut 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 off in a 90-degree direction with 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, it was marked as “◎”, when the peel strength was 1 to 1.5 N, it was marked as “◯”, when the peel strength was 0.5 N or more and less than 1 N, it was marked as “△”, and when the peel strength was less than 0.5 N, it was marked as “×”. The results are shown in Table 1.

In Table 1, "average logPow" refers to "logPow, which represents the octanol/water partition coefficient based on the weighted average of the molar fractions of the monomer components contained in the adhesive composition."

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

Claims (10)

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 is formed of a cured layer of an adhesive composition containing at least a polymerizable compound,
The acrylic film and the adhesive layer have a structure in which they are in direct contact with each other,
the adhesive composition has a logPow, which represents an octanol/water partition coefficient calculated by a weighted average of the mole fractions of the polymerizable compounds contained therein, of 1.8 or more and 3.0 or less;
A laminated optical film, wherein the adhesive layer has an elastic modulus of 1×10 ⁵ Pa or more and 3×10 ⁶ Pa or less. The laminated optical film according to claim 1, wherein the first optical film is a liquid crystal film or a retardation film. The laminated optical film according to claim 1 or 2, wherein the thickness of the adhesive layer is 0.1 to 10 μm. The 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. The laminated optical film according to claim 4, wherein the second optical film is a liquid crystal film or a retardation film. The adhesive composition contains a polymerizable compound A,
The polymerizable compound A is a urethane (meth)acrylate having a molecular weight of 5000 or more and having at least two polymerizable groups,
The laminated optical film according to any one of claims 1 to 5, wherein 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. The adhesive composition contains a polymerizable compound B,
The polymerizable compound B is a compound having at least two polymerizable groups,
The laminated optical film according to any one of claims 1 to 6, wherein the content of the polymerizable compound B is 0 parts by mass or more and 15 parts by mass or less when the total amount of the polymerizable compounds contained in the adhesive composition is 100 parts by mass. The adhesive composition contains a polymerizable compound C,
The polymerizable compound C has a log Pow, which represents an octanol/water partition coefficient, of 1.0 or more and 8.0 or less,
The laminated optical film according to any one of claims 1 to 7, wherein 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. 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,
The laminated optical film according to any one of claims 1 to 8, wherein the content of the polymerizable compound D is 0 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. An image display device comprising at least one laminated optical film according to claim 1.

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