Laminated optical film

Abstract

A multilayer optical film (X) according to the present invention is sequentially provided with an optical film (10), an adhesive layer (30) and an optical film (20) in the thickness direction (H). The adhesive layer (30) is bonded to the optical film (10), while also being bonded to the optical film (20). The adhesive layer (30) has an extended end part (30a). The extended end part (30a) extends outwardly beyond an edge (11) of the optical film (10) and an edge (21) of the optical film (20) in a plane direction that is perpendicular to the thickness direction (H).

Description

Technical Field

[0001] The present invention relates to a laminated optical film.

Background Art

[0002] A display panel has a laminated structure including, for example, a pixel panel, a touch panel, a surface protection cover, and the like. Various functional optical films having predetermined optical functions are also included in the laminated structure of the display panel. Examples of the functional optical film include a polarizer film and a retardation film. The functional optical film is incorporated into the laminated structure in a state joined to another optical film such as a protective film via an adhesive, that is, in the form of a laminated optical film. Such a laminated optical film is described in, for example, Patent Document 1 below.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As display panels become thinner, the optical films used are also becoming thinner. The thinner the optical film in a laminated optical film, the more susceptible the edges of the laminated optical film are to cracking and other damage from external forces. When cracks occur at the edges of a laminated optical film, these cracks grow, for example, extending into the interior region in the planar direction of the film. Cracks at the edges can lead to such large cracks, which is undesirable. Furthermore, in non-rectangular, irregularly shaped display panels, the display function is utilized up to the edge of the panel, so suppression of edge cracks is strongly required. In irregularly shaped display panels such as those in smartphones, conventionally, prolonged use of the device incorporating the panel has led to minute cracks at the edges of the panel around the irregular shape progressing inward, causing bright lines to appear on the device's display screen. Suppression of such defects is strongly required.

[0005] The present invention provides a laminated optical film suitable for suppressing damage to the edges of optical films. [Means for solving the problem]

[0006] The present invention [1] includes a laminated optical film comprising a first optical film, an adhesive layer, and a second optical film in order in the thickness direction, wherein the adhesive layer is bonded to the first optical film and to the second optical film, and the adhesive layer has an extended end, the extended end extending outward from the first edge of the first optical film and the second edge of the second optical film in a planar direction perpendicular to the thickness direction.

[0007] In this laminated optical film, as described above, the adhesive layer sandwiched between the first optical film and the second optical film has an extended end that extends outward beyond both optical films. In areas where such an extended end exists, when an external member approaches and collides with the laminated optical film, for example from the outward direction in the planar direction, the extended end that extends outward beyond both optical films receives the impact of the external member. This prevents further approach of the external member and prevents the external member from colliding with the first edge of the first optical film and the second edge of the second optical film. Alternatively, even if an external member collides with the first edge and / or the second edge, the impact force on these edges is mitigated. Such collision prevention and impact force mitigation are suitable for suppressing damage to the edges of the optical films in a laminated optical film. In addition, the presence of an extended end in the adhesive layer of this laminated optical film is suitable for suppressing the occurrence and growth of microcracks at the edges of the first and second optical films.

[0008] The present invention [2] includes the laminated optical film described in [1] above, wherein the first optical film is a polarizer film and the first edge is located outside the second edge in the planar direction.

[0009] Such a configuration is preferable in a laminated optical film for suppressing damage to the second edge of the second optical film.

[0010] The present invention [3] includes the laminated optical film described in [1] or [2] above, wherein the extension length of the extension end from the first edge in the planar direction is 0.01 μm or more and 5 μm or less.

[0011] Such a configuration is preferable for achieving both damage suppression and delamination suppression at the first edge of the first optical film.

[0012] The present invention [4] includes a laminated optical film according to any one of [1] to [3] above, wherein the extension length of the extension end from the second edge in the planar direction is 0.03 μm or more and 10 μm or less.

[0013] Such a configuration is preferable for achieving both damage suppression and delamination suppression at the second edge of the second optical film.

[0014] The present invention [5] includes a laminated optical film according to any one of [1] to [4] above, wherein the indentation modulus E1 of the adhesive layer at 25°C and the indentation modulus E2 of the adhesive layer at 80°C satisfy 0.05 ≤ E2 / E1 ≤ 0.25.

[0015] Such a configuration is preferable for forming the aforementioned extended edges when the laminated optical film is manufactured through a film shaping process in which the edges of the laminated optical film are heated. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic cross-sectional view of one embodiment of the laminated optical film of the present invention. [Figure 2] This is an enlarged cross-sectional view of the edge of the laminated optical film shown in Figure 1. [Figure 3] This represents one function of the extended end of the adhesive layer. [Modes for carrying out the invention]

[0017] As one embodiment of the laminated optical film of the present invention, the laminated optical film X comprises an optical film 10 (first optical film), an optical film 20 (second optical film), and an adhesive layer 30, as shown in Figure 1. The laminated optical film X has a sheet shape of a predetermined thickness and extends in a direction perpendicular to the thickness direction H (surface direction). Specifically, the laminated optical film X comprises the optical film 10, the adhesive layer 30, and the optical film 20 in order along the thickness direction H. The adhesive layer 30 joins the optical films 10 and 20. The laminated optical film X is also a composite film incorporated into the laminated structure of a display panel. The laminated optical film X may be in the form of a single sheet or a roll.

[0018] The optical film 10 is a functional optical film in this embodiment. Examples of the functional optical film include a polarizer film and a retardation film.

[0019] Examples of the polarizer film include a hydrophilic polymer film that has undergone a dyeing treatment with a dichroic substance and a subsequent stretching treatment. Examples of the dichroic substance include iodine and a dichroic dye. Examples of the hydrophilic polymer film include a polyvinyl alcohol (PVA) film, a partially formalized PVA film, and a partially saponified film of an ethylene-vinyl acetate copolymer. The polarizer film also includes a polyene-oriented film. Examples of the material of the polyene-oriented film include a dehydrated product of PVA and a dehydrochlorinated product of polyvinyl chloride. Since the polarizer film has excellent optical properties such as polarization characteristics, a PVA film that has undergone a dyeing treatment with iodine and a subsequent uniaxial stretching treatment is preferred.

[0020] From the perspective of thinning, the thickness of the optical film 10 as a polarizer film is preferably 15 μm or less, more preferably 12 μm or less, still more preferably 10 μm or less, and particularly preferably 8 μm or less. The thin polarizer film has excellent visibility because of less thickness unevenness, and also has excellent durability against thermal shock because of small dimensional changes due to temperature changes. From the perspective of strength, the thickness of the optical film 10 as a polarizer film is preferably 3 μm or more, more preferably 5 μm or more.

[0021] Examples of phase difference films include λ / 2 wavelength films, λ / 4 wavelength films, and viewing angle compensation films. Examples of materials for the phase difference film include polymer films that have been birefred by stretching. Examples of polymer films include cellulose films and polyester films. Examples of cellulose films include triacetylcellulose films. Examples of polyester films include polyethylene terephthalate films and polyethylene naphthalate films. The thickness of the optical film 10 as a phase difference film is, for example, 20 μm or more and, for example, 150 μm or less. Furthermore, a film comprising a substrate such as a cellulose film and an alignment layer of a liquid crystal compound such as a liquid crystal polymer on the substrate can also be preferably used as a phase difference film.

[0022] In this embodiment, the optical film 20 is a transparent protective film. The transparent protective film is, for example, a flexible transparent resin film. Examples of materials for the transparent protective film include polyolefins, polyesters, polyamides, polyimides, polyvinyl chloride, polyvinylidene chloride, cellulose, modified cellulose, polystyrene, and polycarbonate. Examples of polyolefins include cycloolefin polymers (COP), polyethylene, polypropylene, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, and ethylene-vinyl alcohol copolymers. Examples of polyesters include polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate. Examples of polyamides include polyamide 6, polyamide 6,6, and partially aromatic polyamides. An example of modified cellulose is triacetylcellulose. These materials may be used individually or in combination of two or more. From the viewpoint of cleanliness, polyolefins are preferably used as the material for the transparent protective film, and COP is more preferably used. The optical film 20 is preferably a uniaxially oriented film or a biaxially oriented film.

[0023] From the viewpoint of the strength of the laminated optical film X, the thickness of the optical film 20 is preferably 5 μm or more, more preferably 10 μm or more, still more preferably 20 μm or more. From the viewpoint of thinning the laminated optical film X, the thickness of the optical film 20 is preferably 100 μm or less, more preferably 70 μm or less, still more preferably 50 μm or less.

[0024] The adhesive layer 30 is a cured product of an adhesive composition. The adhesive layer 30 is directly joined to the optical film 10 and directly joined to the optical film 20. The adhesive composition contains a curable resin. The components of the adhesive composition are specifically as described below.

[0025] From the viewpoint of the bonding strength between the optical films 10 and 20, the thickness T1 of the adhesive layer 30 is preferably 0.1 μm or more, more preferably 0.4 μm or more, still more preferably 0.7 μm or more, particularly preferably 0.8 μm or more. From the viewpoint of thinning the laminated optical film X, the thickness T1 of the adhesive layer 30 is preferably 5 μm or less, more preferably 3 μm or less, still more preferably 1.5 μm or less, particularly preferably 1 μm or less.

[0026] The adhesive layer 30 has an extended end portion 30a at least a portion of its peripheral edge, as shown in Figure 2. The extended end portion 30a is the portion that extends outward (to the left in Figure 2) from the edge 11 (first edge) of the optical film 10 or the edge 21 (second edge) of the optical film 20 in a planar direction perpendicular to the thickness direction H. In the laminated optical film X, where such an extended end portion 30a exists, for example as shown in Figure 3, when an external member M approaches and collides with the laminated optical film X from the outside in the planar direction, the extended end portion 30a that extends outward from the optical films 10 and 20 receives the impact of the external member M. This prevents the external member M from approaching further, thus preventing the external member M from colliding with the edge 11 of the optical film 10 and the edge 21 of the optical film 20. Alternatively, even if the external member M collides with the edge 11 and / or edge 21, the impact force on these edges 11 and 21 is mitigated. Such collision prevention and collision force mitigation are suitable for suppressing damage to the edges of the optical films 10 and 20 in the laminated optical film X. In addition, having an extended edge 30a in the adhesive layer 30 of the laminated optical film X is suitable for suppressing the occurrence and growth of microcracks at the edges of the optical films 10 and 20.

[0027] When the optical film 10 is a polarizer film and the optical film 20 is a transparent protective film, the edge 11 is preferably located outward in the planar direction from the edge 21. Such a configuration is preferable in the laminated optical film X for suppressing damage to the edge 21 of the optical film 20.

[0028] The extension length L1 of the extension end 30a from the edge 11 in the planar direction is preferably 0.01 μm or more, more preferably 0.05 μm or more, even more preferably 0.1 μm, and particularly preferably 0.3 μm or more. Such a configuration is preferable for suppressing damage to the edge 11 of the optical film 10. Alternatively, the extension length L1 is preferably 8 μm or less, more preferably 5 μm or less, even more preferably 4 μm or less, even more preferably 3 μm, and particularly preferably 1 μm or less. Such a configuration is preferable for suppressing the occurrence of adhesive residue at the panel edge due to excessively extended adhesive during outer shape processing when the laminated optical film X is incorporated into a display panel such as a smartphone, and is preferable for suppressing display unevenness caused by such adhesive residue. Specifically, the extension length L1 is the distance in the planar direction between the edge 11 of the optical film 10 and the edge 31 of the adhesive layer 30.

[0029] The extension length L2 of the extension end 30a from the edge 21 in the planar direction is preferably 0.03 μm or more, more preferably 0.1 μm or more, even more preferably 0.3 μm, and particularly preferably 0.5 μm or more. Such a configuration is preferable for suppressing damage to the edge 21 of the optical film 20. Alternatively, the extension length L2 is preferably 10 μm or less, more preferably 7 μm or less, even more preferably 5 μm, and particularly preferably 3 μm or less. Such a configuration is preferable for suppressing peeling from the adhesive layer 30 at the edge 21 of the optical film 20. Specifically, the extension length L2 is the distance in the planar direction between the edge 21 of the optical film 20 and the edge 31 of the adhesive layer 30.

[0030] The ratio of the extended length L2 to the extended length L1 (L2 / L1) is preferably 1.1 or more, more preferably 1.5 or more, even more preferably 2 or more, and particularly preferably 2.5 or more. The ratio (L2 / L1) is preferably 10 or less, more preferably 8 or less, even more preferably 7 or less, and particularly preferably 5 or less. These configurations are preferable for achieving both the aforementioned damage suppression and peeling suppression in the optical films 10 and 20.

[0031] The indentation modulus (E1) of the adhesive layer 30 at 25°C, measured by nanoindentation, is preferably 0.5 GPa or higher, more preferably 1 GPa or higher, even more preferably 1.5 GPa or higher, and particularly preferably 2 GPa or higher. Such a configuration is preferable from the viewpoint of ensuring bonding strength between the optical films 10 and 20. Such a configuration is also preferable for ensuring the aforementioned collision prevention and collision force mitigation functions of the extended end 30a, and helps to achieve both damage suppression and peel suppression in the optical films 10 and 20. The indentation modulus E1 is preferably 7 GPa or lower, more preferably 5 GPa or lower, and even more preferably 3 GPa or lower. Such a configuration is preferable for ensuring the flexibility of the adhesive layer 30 when the laminated optical film X is used in a display panel that can be repeatedly folded (foldable). As a method for adjusting the indentation modulus of the adhesive layer 30, for example, adjustment of the composition of the adhesive composition can be mentioned. Specifically, adjusting the number of functional groups of the polymerizable compound described later in the adhesive composition that forms the adhesive layer 30, that is, adjusting the acrylic equivalent and epoxy equivalent of the polymerizable compound, is an effective method for adjusting the indentation modulus of the adhesive layer 30.

[0032] Nanoindentation is a technique for measuring various physical properties of a sample on a nanometer scale. In this embodiment, the nanoindentation method is performed in accordance with ISO 14577. In the nanoindentation method, a process of pressing an indenter into the sample set on a stage (load application process) and a subsequent process of withdrawing the indenter from the sample (unloading process) are performed. During this series of processes, the load acting between the indenter and the sample and the relative displacement of the indenter with respect to the sample are measured (load-displacement measurement). This makes it possible to obtain a load-displacement curve. From this load-displacement curve, it is possible to determine various physical properties of the sample based on nanometer-scale measurements. For measuring the load-displacement of the cross-section of an adhesive layer using the nanoindentation method, for example, a nanoindenter (product name "Triboindenter", manufactured by Hysitron) can be used. Specifically, the examples will be described later.

[0033] The indentation modulus (E2) of the adhesive layer 30 at 80°C, measured by nanoindentation, is preferably 0.05 GPa or higher, more preferably 0.1 GPa or higher, even more preferably 0.2 GPa or higher, and particularly preferably 0.3 GPa or higher. This configuration is preferable for suppressing thermal shrinkage of the adhesive layer 30 during the film outline processing described later, when the edges of the laminated optical film X are heated, thereby forming the extended edges 30a described above. From the viewpoint of the processing resistance of the adhesive layer 30, the indentation modulus E2 is preferably 0.7 GPa or lower, more preferably 0.5 GPa or lower, and even more preferably 0.4 GPa or lower.

[0034] The indentation moduli E1 and E2 preferably satisfy the condition 0.05 ≤ E2 / E1 ≤ 0.25. Such a configuration is preferable for suppressing thermal shrinkage of the adhesive layer 30 and forming the extended end 30a described above during the film shaping process described later, in which the edges of the laminated optical film X are heated. The value of E2 / E1 is more preferably 0.1 or higher, even more preferably 0.12 or higher, and even more preferably 0.2 or lower, and even more preferably 0.18 or lower.

[0035] In the laminated optical film X, the 90° peel strength of optical film 20 relative to optical film 10 at 25°C is preferably 1 N / 15 mm or more, more preferably 1.2 N / 15 mm or more, and even more preferably 1.5 N / 15 mm or more. Such a configuration is preferable for achieving good bonding strength between optical films 10 and 20, and is particularly preferable for ensuring bonding strength between optical films 10 and 20 for foldable display panels. The 90° peel strength is, for example, 10 N / 15 mm or less. The 90° peel strength can be measured using, for example, a Tensilon universal tester (product name "RTC", manufactured by A&D Company, Limited). In this measurement, the measurement temperature is set to 25°C, the peel angle to 90°, and the peel speed to 1000 mm / min. As a method for adjusting the 90° peel strength, for example, adjustment of the composition of the adhesive composition can be mentioned. Specific methods for adjusting the 90° peel strength include adjusting the number of functional groups of the polymerizable compound described later in the adhesive composition, that is, adjusting the acrylic equivalent and epoxy equivalent of the polymerizable compound.

[0036] The ratio of the 90° peel strength (N / 15mm) to the indentation modulus E2 (GPa) is preferably 5 or more, more preferably 10 or more, even more preferably 15 or more, and also preferably 30 or less, more preferably 25 or less. Such a configuration is preferable from the viewpoint of the processing resistance of the adhesive layer 30.

[0037] The adhesive layer 30 is, for example, a cured product of an adhesive composition (active energy ray curable composition) containing an active energy ray curable resin. Examples of active energy ray curable compositions include electron beam curable compositions, ultraviolet light curable compositions, and visible light curable compositions. In this embodiment, the active energy ray curable composition is either a radical polymerization type composition or a cationic polymerization type composition, or both.

[0038] When an active energy ray-curable composition is a radical polymerization type composition, the composition contains a radical polymerizable compound as a monomer. A radical polymerizable compound is a compound having a radical polymerizable functional group. Examples of radical polymerizable functional groups include ethylenically unsaturated bond-containing groups. Examples of ethylenically unsaturated bond-containing groups include (meth)acryloyl groups, vinyl groups, and allyl groups. (Meth)acryloyl groups mean acryloyl groups and / or methacryloyl groups. From the viewpoint of the curability of the active energy ray-curable composition, it is preferable that the active energy ray-curable composition contains a radical polymerizable compound having a (meth)acryloyl group as a main component. The main component means the component that is most abundant by mass. The proportion of the (meth)acryloyl group-containing radical polymerizable compound in the active energy ray-curable composition is, for example, 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more. Examples of radical polymerizable compounds include monofunctional radical polymerizable compounds and bifunctional or polyfunctional radical polymerizable compounds.

[0039] Examples of monofunctional radical polymerizable compounds include (meth)acrylamide derivatives having a (meth)acrylamide group. Examples of (meth)acrylamide derivatives include N-alkyl group-containing (meth)acrylamide derivatives, N-hydroxyalkyl group-containing (meth)acrylamide derivatives, N-aminoalkyl group-containing (meth)acrylamide derivatives, N-alkoxy group-containing (meth)acrylamide derivatives, and N-mercaptoalkyl group-containing (meth)acrylamide derivatives. Examples of N-alkyl group-containing (meth)acrylamide derivatives include 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, with N,N-diethylacrylamide being preferred. Examples of N-hydroxyalkyl group-containing (meth)acrylamide derivatives include N-methylol(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, and N-methylol-N-propane(meth)acrylamide, with N-hydroxyethylacrylamide being preferred. (Meth)acrylamide derivatives may be used alone or in combination of two or more types.

[0040] Examples of monofunctional radical polymerizable compounds include (meth)acrylic acid derivatives having a (meth)acryloyloxy group. Examples of such (meth)acrylic acid derivatives include alkyl (meth)acrylates and (meth)acrylic acid derivatives other than alkyl (meth)acrylates. (Meth)acrylic acid derivatives may be used alone or in combination of two or more types.

[0041] Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, 2,2-dimethylbutyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, and n-octadecyl (meth)acrylate.

[0042] Examples of (meth)acrylic acid derivatives other than alkyl (meth)acrylates include cycloalkyl (meth)acrylates, aralkyl (meth)acrylates, hydroxyl group-containing (meth)acrylic acid derivatives, alkoxy group-containing (meth)acrylic acid derivatives, and phenoxy group-containing (meth)acrylic acid derivatives. Examples of cycloalkyl (meth)acrylates include cyclohexyl (meth)acrylate and cyclopentyl (meth)acrylate. Examples of aralkyl (meth)acrylates include benzyl (meth)acrylate and 3-phenoxybenzyl (meth)acrylate. Examples of hydroxyl group-containing (meth)acrylic acid derivatives include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, [4-(hydroxymethyl)cyclohexyl]methyl acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate. Examples of alkoxy group-containing (meth)acrylic acid derivatives include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, and 3-methoxybutyl (meth)acrylate. Examples of phenoxy group-containing (meth)acrylic acid derivatives include phenoxyethyl (meth)acrylate and phenoxydiethylene glycol (meth)acrylate. As a (meth)acrylic acid derivative other than alkyl (meth)acrylate, preferably at least one selected from the group consisting of 3-phenoxybenzyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, and phenoxydiethylene glycol acrylate is used.

[0043] Examples of monofunctional radical polymerizable compounds include carboxyl group-containing monomers. Examples of carboxyl group-containing monomers include (meth)acrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

[0044] Examples of monofunctional radical polymerizable compounds include lactam-based vinyl monomers. Examples of lactam-based vinyl monomers include N-vinyl-2-pyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone.

[0045] Examples of monofunctional radical polymerizable compounds include vinyl monomers having nitrogen-containing heterocycles. Examples of such monomers include vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, and vinylmorpholine.

[0046] Examples of polyfunctional radical polymerizable compounds include tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol diacrylate, 2-ethyl-2-butylpropanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, tricyclodecanedimethanol 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, and dipentaerythritol hexa(meth)acrylate, with tripropylene glycol diacrylate being preferred. Polyfunctional radical polymerizable compounds may be used alone or in combination of two or more types. The polyfunctional radical polymerizable compounds function as crosslinking agents.

[0047] When the active energy ray curable composition is an ultraviolet-curable composition or a visible light-curable composition, the active energy ray curable composition preferably contains a photopolymerization initiator. Examples of photopolymerization initiators include benzophenone compounds, benzoin ether compounds, and thioxanthone compounds. Examples of benzophenone compounds include benzyl, benzophenone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone. Examples of benzoin ether compounds include benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin butyl ether. Examples of thioxanthone compounds include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone.

[0048] When the active energy ray curable composition is a visible light curable composition, a photopolymerization initiator that is highly sensitive to light of 380 nm or higher is preferably used. Examples of such photopolymerization initiators 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, and bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrole-1-yl)-phenyl)titanium.

[0049] Preferably, 2,4-diethylthioxanthone and / or 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one are used as photopolymerization initiators.

[0050] The content of the photopolymerization initiator in the active energy ray curable composition is preferably 0.1 parts by mass or more, more preferably 0.05 parts by mass or more, even more preferably 0.1 parts by mass or more, and preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the curable component (radical polymerizable compound).

[0051] When an active energy ray curable composition is a cationic polymerization type composition, the composition contains a cationic polymerizable compound as a monomer. A cationic polymerizable compound is a compound having a cationic polymerizable functional group, and includes monofunctional cationic polymerizable compounds having one cationic polymerizable functional group and polyfunctional cationic polymerizable compounds having two or more cationic polymerizable functional groups. Monofunctional cationic polymerizable compounds have relatively low liquid viscosity. By incorporating such a monofunctional cationic polymerizable compound into a resin composition, the viscosity of the resin composition can be reduced. Furthermore, monofunctional cationic polymerizable compounds often have functional groups that exhibit various functions. By incorporating such a monofunctional cationic polymerizable compound into a resin composition, various functions can be exhibited in the resin composition and / or in the cured product of the resin composition. On the other hand, curing a resin composition containing a polyfunctional cationic polymerizable compound yields a cured product having a three-dimensional crosslinked portion (the polyfunctional cationic polymerizable compound functions as a crosslinking agent). From this viewpoint, the use of polyfunctional cationic polymerizable compounds is preferred. When a monofunctional cationic polymerizable compound and a polyfunctional cationic polymerizable compound are used in combination, the amount of the polyfunctional cationic polymerizable compound per 100 parts by mass of the monofunctional cationic polymerizable compound is, for example, 10 parts by mass or more, and also, for example, 1000 parts by mass or less. Examples of cationic polymerizable functional groups include epoxy groups, oxetanyl groups, and vinyl ether groups. Examples of compounds having epoxy groups include aliphatic epoxy compounds, alicyclic epoxy compounds, and aromatic epoxy compounds. From the viewpoint of curability and adhesion of the cationic polymerized composition, alicyclic epoxy compounds are preferably used as the compounds having epoxy groups. Examples of alicyclic epoxy compounds include caprolactone-modified, trimethylcaprolactone-modified, and valerolactone-modified 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, or caprolactone-modified, trimethylcaprolactone-modified, and valerolactone-modified 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate.Examples of commercially available alicyclic epoxy compounds include Celoxide 2021, Celoxide 2021A, Celoxide 2021P, Celoxide 2081, Celoxide 2083, and Celoxide 2085 (all manufactured by Daicel Chemical Industries, Ltd.), as well as Cyracure UVR-6105, Cyracure UVR-6107, Cyracure 30, and R-6110 (all manufactured by Dow Chemical Japan). From the viewpoint of improving the curability and reducing the viscosity of cationic polymerization compositions, it is preferable to use compounds having an oxetanyl group and / or a vinyl ether group. Examples of compounds having an oxetanyl group include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl]benzene, 3-ethyl-3-(phenoxymethyl)oxetane, di[(3-ethyl-3-oxetanyl)methyl]ether, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, and phenol novolac oxetane. Examples of commercially available compounds having an oxetanyl group include Aronoxetane OXT-101, Aronoxetane OXT-121, Aronoxetane OXT-211, Aronoxetane OXT-221, and Aronoxetane OXT-212 (all manufactured by Toagosei Co., Ltd.). Examples of compounds having a vinyl ether group include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, triethylene glycol divinyl ether, cyclohexanedimethanol divinyl ether, cyclohexanedimethanol monovinyl ether, tricyclodecane vinyl ether, cyclohexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, and pentaerythritol-type tetravinyl ether.

[0052] When an active energy ray-curable composition is an ultraviolet-curable composition or a visible light-curable composition, the active energy ray-curable composition contains a photocationic polymerization initiator. The photocationic polymerization initiator generates a cationic species or Lewis acid upon irradiation with active energy rays (such as visible light, ultraviolet rays, X-rays, or electron beams), initiating the polymerization reaction of cationic polymerizable functional groups. Examples of photocationic polymerization initiators include photoacid generators and photobase generators, with photoacid generators being preferred. When the active energy ray-curable composition is a visible light-curable composition, it is particularly preferable to use a photocationic polymerization initiator that is highly sensitive to light of 380 nm or longer. Furthermore, when using a photocationic polymerization initiator, it is preferable to use in combination with a photosensitizer that exhibits maximum absorption for light with wavelengths longer than 380 nm. Since photocationic polymerization initiators are generally compounds that exhibit maximum absorption around 300 nm or shorter wavelengths, by using them in combination with photosensitizers that exhibit maximum absorption at wavelengths longer than 380 nm, it is possible to effectively utilize light at wavelengths longer than 380 nm to promote the generation of cationic species or Lewis acids from the photocationic polymerization initiator. Examples of photosensitizers include anthracene compounds, pyrene compounds, carbonyl compounds, organosulfur compounds, persulfides, redox compounds, azo compounds, diazo compounds, halogen compounds, and photoreducing dyes. These may be used alone or in combination of two or more. Anthracene compounds are particularly preferred due to their excellent photosensitizing effect. Examples of commercially available anthracene compounds as photosensitizers include Anthracure UVS-1331 and Anthracure UVS-1221 (manufactured by Kawasaki Chemical Co., Ltd.). The content of the photosensitizer in the composition is, for example, 0.1 to 5% by weight.

[0053] The active energy ray curable composition may contain oligomers. Examples of oligomers include acrylic oligomers, fluorine oligomers, and silicone oligomers, with acrylic oligomers being preferred. The incorporation of oligomers into the active energy ray curable composition helps suppress shrinkage during curing. Suppressing curing shrinkage of the active energy ray curable composition is preferable for reducing interfacial stress between the formed adhesive layer 30 and the optical films 10, 20. Suppressing interfacial stress helps ensure bonding strength between the optical films 10, 20.

[0054] Examples of (meth)acrylic monomers that form acrylic oligomers include alkyl (meth)acrylates having 1 to 20 carbon atoms, cycloalkyl (meth)acrylates, aralkyl (meth)acrylates, polycyclic (meth)acrylates, hydroxyl group-containing (meth)acrylates, and halogen-containing (meth)acrylates. Examples of alkyl (meth)acrylates 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, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, and N-octadecyl (meth)acrylate. Examples of cycloalkyl (meth)acrylates include cyclohexyl (meth)acrylate and cyclopentyl (meth)acrylate. Examples of aralkyl (meth)acrylates include benzyl (meth)acrylate. Examples of polycyclic (meth)acrylates include 2-isobornyl (meth)acrylate, 2-norbornylmethyl (meth)acrylate, 5-norbornen-2-ylmethyl (meth)acrylate, and 3-methyl-2-norbornylmethyl (meth)acrylate. Examples of hydroxyl-containing (meth)acrylic acid esters include hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2,3-dihydroxypropylmethyl-butyl (meth)methacrylate.Examples of halogen-containing (meth)acrylic acid esters include 2,2,2-trifluoroethyl (meth)acrylate, 2,2,2-trifluoroethylethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropentyl (meth)acrylate, and heptadecafluorodecyl (meth)acrylate. These (meth)acrylates may be used individually or in combination of two or more types.

[0055] The weight-average molecular weight (Mw) of the acrylic oligomer is preferably 15,000 or less, more preferably 10,000 or less, and even more preferably 5,000 or less. The Mw of the acrylic oligomer is preferably 500 or more, more preferably 1,000 or more, and even more preferably 1,500 or more.

[0056] The acrylic oligomer content in the active energy ray curable composition is preferably 2% by mass or more, more preferably 4% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less.

[0057] The active energy ray curable composition may contain other components. Examples of other components include silane coupling agents, leveling agents, surfactants, plasticizers, and ultraviolet absorbers. The amount of these other components is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less, and also, for example, 0.01 parts by mass or more, per 100 parts by mass of the curable component.

[0058] The viscosity of the active energy ray-curable composition at 25°C is preferably 3 mPa·s or higher, more preferably 5 mPa·s or higher, even more preferably 10 mPa·s or higher, and also preferably 100 mPa·s or lower, more preferably 50 mPa·s or lower, and even more preferably 30 mPa·s or lower, from the viewpoint of coatability in the coating process described later. The viscosity of the composition is measured using an E-type viscometer (cone plate viscometer).

[0059] The laminated optical film X can be manufactured, for example, as follows:

[0060] First, an active energy ray curable composition is applied to one side (the side to be joined) of one of the optical films (optical film 10 or optical film 20) to form a coating of the composition (coating step). Before this coating step, the side to be joined of the optical film may be subjected to a surface modification treatment. Examples of surface modification treatments include corona treatment, plasma treatment, excimer treatment, and flame treatment. Examples of coating methods in this step include a reverse coater, gravure coater, bar reverse coater, roll coater, die coater, bar coater, and rod coater.

[0061] Next, one optical film is laminated to the other optical film (optical film 20 or optical film 10) via the composition coating. For lamination, for example, a roll laminator can be used.

[0062] Next, the composition coating film between the optical films 10 and 20 is irradiated with active energy rays to cure the coating film (active energy ray curable composition) and form an adhesive layer 30 (the adhesive layer 30 is not a pressure-sensitive adhesive layer). Thus, the optical films 10 and 20 are joined via the adhesive layer 30 to obtain the raw material film for the laminated optical film X. In this process, from the viewpoint of suppressing the degradation of the optical film 10 as a functional optical film, it is preferable to irradiate the optical film 30 side with active energy rays. As the active energy rays, electron beams, ultraviolet rays, and visible light can be used. As an electron beam irradiation means, for example, an electron beam accelerator can be used. As a light source for ultraviolet rays and visible light, for example, LED lights, gallium-filled metal halide lamps, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon lamps, halogen lamps, and gallium lamps can be used. In this process, a wavelength cut filter may be used as needed to cut out some wavelength ranges in the ultraviolet rays and / or visible light emitted from the light source.

[0063] Next, at least a portion of the peripheral edge of the raw material film is shaped (shape-shaping process). For example, one end in the longitudinal direction of a roll of raw material film is trimmed. For example, a roll of raw material film is cut into sheets. Methods for these shape-shaping processes include, for example, laser processing by CO2 laser irradiation, cutting with a punching blade, and end milling. At the shape-shaping points of the raw material film, relatively large thermal shrinkage occurs in the optical films 10 and 20, forming an extended end 30a. Specifically, the edges of the optical films 10 and 20 shrink so that the edges 11 and 21 of the optical films 10 and 20 recede inward in the planar direction from the edge 31 of the adhesive layer 30, forming an extended end 30a. The length by which the edges of the optical films 10 and 20 shrink, i.e., the extension lengths L1 and L2 of the extended end 30a, can be adjusted by adjusting the material (dimensional shrinkage rate) and thickness of the optical films 10 and 20, as well as the processing conditions. One example of a processing condition is the adjustment of the stretching ratio.

[0064] For example, a laminated optical film X can be manufactured in the manner described above. [Examples]

[0065] The present invention will be specifically described below with reference to examples. The present invention is not limited to these examples. Furthermore, the specific numerical values ​​such as the amounts (content), physical properties, and parameters described below can be substituted with the upper limits (numerical values ​​defined as "less than or equal to" or "less than") or lower limits (numerical values ​​defined as "greater than or equal to" or "greater than") of the corresponding amounts (content), physical properties, and parameters described in the "Modes for Carrying Out the Invention" above.

[0066] [Example 1] The following components were mixed at 25°C for 1 hour to prepare the adhesive composition (preparation step).

[0067] 45 parts by mass of 3-phenoxybenzyl acrylate (product name "Light Acrylate POB-A", monomer, manufactured by Kyoeisha Chemical Co., Ltd.) 25 parts by mass of phenoxydiethylene glycol acrylate (product name "Light Acrylate P2H-A", monomer, manufactured by Kyoeisha Chemical Co., Ltd.) 15 parts by mass of tripropylene glycol diacrylate (product name "Aronix M-220", monomer, manufactured by Toagosei Co., Ltd.) 10 parts by mass of 2-hydroxy-3-phenoxypropyl acrylate (product name "Aronix M-5700", monomer, manufactured by Toagosei Co., Ltd.) 5 parts by mass of hydroxyethyl acrylamide (product name "HEAA", monomer, manufactured by KJ Chemicals Co., Ltd.) 5 parts by mass of diethylacrylamide (product name "DEAA", monomer, manufactured by KJ Chemicals Co., Ltd.) 3 parts by mass of 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (product name "OMINIRAD907", photopolymerization initiator, manufactured by IGM Resins) 3 parts by mass of 2,4-diethylthioxanthone (product name "KAYACURE DETX-S", photopolymerization initiator, manufactured by Nippon Kayaku Co., Ltd.) 5 parts by mass of acrylic oligomer (product name "Alphon 1190", viscosity 6000 mPa·s (25℃), Mw 1700, Tg -50℃, manufactured by Toagosei Co., Ltd.) 0.5 parts by mass of modified polydimethylsiloxane having an acrylic group (product name "BYK-UV3505", leveling agent, manufactured by BYK).

[0068] Next, an adhesive composition was applied to a 23 μm thick COP film (product name "Zeonor Film ZF14", manufactured by Zeon Corporation) to form a 1 μm thick adhesive coating. An MCD coater (manufactured by Fuji Machinery Co., Ltd.) (cell shape: honeycomb, gravure roll line count: 1000 lines / inch, rotation speed: 140% / line speed) was used for coating. Next, a polarizer film was bonded to the transparent protective film via the adhesive coating on the film. Finally, the adhesive coating between the films was cured by irradiating the adhesive coating from the transparent protective film side with ultraviolet light. For ultraviolet irradiation, an ultraviolet irradiation device (product name "Light HAMMER10", bulb: V-bulb, manufactured by Fusion UV Systems, Inc.) equipped with a gallium-filled metal halide lamp was used as the light source. The peak illuminance during ultraviolet irradiation was 1600 mW / cm². 2 The cumulative irradiation dose is 1000 mJ / cm². 2 The wavelength was set to 380-440 nm (illuminance was measured using Solatell's "Sola-Check system"). This allowed for the bonding of a transparent conductive film and a polarizer film to obtain a laminated optical film.

[0069] Next, the laminated optical film was shaped (shape-forming process). Specifically, the laminated optical film was cut in the thickness direction by irradiation with a CO2 laser to obtain a laminated optical film with a predetermined planar shape. For CO2 laser irradiation, the wavelength was 9.4 μm, the output was 48 W, and the scanning speed was 500 mm / second. Next, the laminated optical film was left at room temperature for 24 hours.

[0070] As described above, the laminated optical film of Example 1 was fabricated. The laminated optical film of Example 1 comprises a polarizer film (thickness 5 μm), an adhesive layer, and a transparent protective film (thickness 23 μm) in this order in the thickness direction.

[0071] [Example 2] The laminated optical film of Example 2 (polarizer film / adhesive layer / transparent protective film) was prepared in the same manner as the laminated optical film of Example 1, except as follows: In the preparation process, the amount of "Arronix M-220" added was changed from 15 parts by mass to 5 parts by mass, and the thickness of the adhesive layer coating formed on the transparent protective film was set to 1 μm.

[0072] [Example 3] The laminated optical film of Example 3 (polarizer film / second adhesive layer / transparent protective film) was prepared in the same manner as the laminated optical film of Example 1, except for the following:

[0073] In the preparation process, the amount of "Light Acrylate POB-A" was 43 parts by mass, the amount of "Light Acrylate P2H-A" was 29 parts by mass, and the amount of "Aronics M-220" was 3 parts by mass. In the coating process, the thickness of the adhesive layer coating film formed on the transparent protective film was 1 μm.

[0074] [Comparative Example 1] A laminated optical film (polarizer film / adhesive layer / transparent protective film) for Comparative Example 1 was prepared in the same manner as the laminated optical film for Example 1, except for the following:

[0075] In the preparation process, instead of "Light Acrylate POB-A" and "Light Acrylate P2H-A", 36 parts by mass of "Light Acrylate 1.9ND-A" (1,9-nonanediol diacrylate) manufactured by Kyoeisha Chemical Co., Ltd. and 12.5 parts by mass of "Light Acrylate HPP-A" (hydroxypivalate neopentyl glycol acrylic acid adduct) manufactured by Kyoeisha Chemical Co., Ltd. were used, "Aronics M-220" was not used, the amount of "Aronics M-5700" was set to 22 parts by mass, the amount of "HEAA" was set to 12.5 parts by mass, the amount of "DEAA" was set to 6 parts by mass, the amount of "HEAA" was set to 12.5 parts by mass, and the amount of "Alphon 1190" was set to 10 parts by mass.

[0076] <Observation of the edges> The longitudinal cross-sectional shape of the edges of each laminated optical film in Examples 1-3 and Comparative Example 1 was investigated. First, a section arbitrarily selected from the peripheral edge of the laminated optical film was cut in the thickness direction to form a longitudinal cross-section for observation. Next, this longitudinal cross-section was observed and photographed using an optical microscope. It was confirmed that in each observed cross-section, the adhesive layer had a portion (extended end) that extended outward from the edge of the polarizer film (first edge) and the edge of the transparent protective film (second edge) in the film plane direction. In addition, the extension length L1 of the extended end from the first edge in the plane direction and the extension length L2 of the extended end from the second edge in the plane direction were measured in each observed cross-section. The results are shown in Table 1.

[0077] Furthermore, regarding the suppression of damage to the laminated optical film, the evaluation was based on the following criteria: "Good" was evaluated if no damage (cracks, chips, etc.) occurred in both the polarizer film and the transparent protective film in the observed cross-section described above, and "Poor" was evaluated if damage occurred in at least one of the polarizer film and the transparent protective film. The results are shown in Table 1.

[0078] <Indentation modulus> The indentation modulus of the adhesive layer in each of the laminated optical films in Examples 1-3 and Comparative Example 1 was measured by nanoindentation (first modulus measurement). Specifically, first, a 5mm x 10mm film piece (laminated optical film) was cut from the laminated optical film. Next, the laminated optical film was cut using the cryomicrotome method. Specifically, the laminated optical film was cooled to -30°C, cut in the thickness direction of the film with a hard knife, and then returned to room temperature. This obtained a sample for measurement. Next, using a nanoindenter (product name "TI950 Triboindenter", manufactured by Hysitron), load-displacement measurements were performed on the exposed surface of the adhesive layer in the measurement sample in accordance with JIS Z 2255:2003, and a load-displacement curve was obtained. In this measurement, the measurement mode was single-indentation measurement, the measurement temperature was 25°C, the indenter used was a Berkovich (triangular pyramidal) type diamond indenter, the maximum indentation depth (maximum displacement hmax) of the indenter into the sample during the load application process was 50 nm, the indentation speed of the indenter was 10 nm / second, and the withdrawal speed of the indenter from the sample during the unloading process was 10 nm / second. The obtained measurement data was processed using the dedicated analysis software (Ver. 9.4.0.1) of "TI950 Triboindenter". Specifically, based on the obtained load (f)-displacement (h) curve, the maximum load fmax (load acting on the indenter at maximum displacement hmax), the contact projection area S (projected area of ​​the contact region between the indenter and the sample at maximum load), and the slope D of the tangent to the load-displacement curve at the start of the unloading process were obtained. Then, from the slope D and the contact projection area S, the indentation modulus of the adhesive layer (=(π)) was calculated. 1 / 2 D) / (2S 1 / 2 The indentation modulus E1 (GPa) was calculated. This value is shown in Table 1.

[0079] Furthermore, the indentation modulus at 80°C of the adhesive layer in each laminated optical film of Examples 1-3 and Comparative Example 1 was measured in the same manner as the first modulus measurement, except that the measurement temperature was changed from 25°C to 80°C (second modulus measurement). The values ​​are shown in Table 1 as the indentation modulus E2 (GPa). The ratio of the indentation modulus E2 at 80°C to the indentation modulus E1 at 25°C (E2 / E1) is also shown in Table 1.

[0080] [Table 1] [Industrial applicability]

[0081] The laminated optical film of the present invention can be used, for example, as an element included in the laminated structure of a display panel, such as a foldable display panel. [Explanation of Symbols]

[0082] X Laminated Optical Film H thickness direction 10 Optical film (first optical film) 11 Edge (First Edge) 20 Optical film (second optical film) 21 Edge (Second Edge) 30 Adhesive layer 30a Extension end 31 Edge

Claims

1. A laminated optical film comprising a first optical film, an adhesive layer, and a second optical film in order in the thickness direction, The adhesive layer is bonded to the first optical film and to the second optical film. The adhesive layer has an extended end, and the extended end extends outward in a planar direction perpendicular to the thickness direction, beyond the first edge of the first optical film and the second edge of the second optical film. A laminated optical film in which, in the aforementioned planar direction, the first edge is located outside the second edge.

2. The laminated optical film according to claim 1, wherein the first optical film is a polarizer film.

3. The laminated optical film according to claim 1, wherein the extension length of the extension end from the first edge in the plane direction is 0.01 μm or more and 5 μm or less.

4. The laminated optical film according to claim 1, wherein the extension length of the extension end from the second edge in the plane direction is 0.03 μm or more and 10 μm or less.

5. The indentation modulus E1 of the adhesive layer at 25°C and the indentation modulus E2 of the adhesive layer at 80°C satisfy 0.05 ≤ E2 / E1 ≤ 0.

25. The laminated optical film according to any one of claims 1 to 4, wherein the indentation modulus E1 and the indentation modulus E2 are the indentation modulus of the adhesive layer when the maximum indentation depth of a triangular pyramidal diamond indenter into the adhesive layer is 50 nm.

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