Decomposed optical thin films

Abstract

The present invention provides a laminated optical thin film suitable for suppressing damage to the ends of the optical thin film. The solution is as follows: The laminated optical thin film X of the present invention sequentially comprises an optical thin film 10, an adhesive layer 30, and an optical thin film 20 in the thickness direction H. The adhesive layer 30 is bonded to the optical thin film 10 and also to the optical thin film 20. The adhesive layer 30 has an extended end 30a. In a plane direction orthogonal to the thickness direction H, the extended end 30a extends further outward than the end edge 11 of the optical thin film 10 and the end edge 21 of the optical thin film 20.

Description

Technical Field

[0001] This invention relates to a multilayer optical thin film. Prior Technology

[0002] The display panel has a multilayer structure, including, for example, a pixel panel, a touch panel, and a surface protective cover. The multilayer structure of the display panel also includes various functional optical films having predetermined optical functions. Examples of functional optical films include polarizing films and retardation films. The functional optical films are, for example, assembled into the multilayer structure in a state where they are bonded to other optical films such as protective films through an adhesive, i.e., in the form of multilayer optical films. Such multilayer optical films are described, for example, in Patent Document 1 below. Previous technical documents Patent documents

[0003] Patent Document 1: Japanese Patent Application Publication No. 2019-147865 Summary of the Invention

[0004] The problem the invention aims to solve As display panels become thinner, optical films continue to be made thinner. The thinner the laminated optical film, the more susceptible it is to cracks and other damage at its edges due to external forces. If a crack occurs at the edge of the laminated optical film, it can extend and grow towards the inner region of the film's surface. Cracks at the edge can cause larger cracks, which is undesirable. Furthermore, the display function of non-rectangular irregularly shaped display panels utilizes the panel's edge, thus there is a strong demand to suppress edge cracks. In the case of irregularly shaped display panels such as smartphones, due to long-term use of devices incorporating such panels, tiny cracks at the panel edges around the irregular shape can propagate inwards, easily causing bright lines on the displayed image. Therefore, there is a strong demand to suppress this defect.

[0005] The present invention provides a laminated optical thin film suitable for suppressing damage at the ends of the optical thin film.

[0006] The means to solve the problem The present invention [1] includes a laminated optical film having a first optical film, an adhesive layer and a second optical film sequentially provided 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, which extends further outward than the first edge of the first optical film and the second edge of the second optical film in a plane direction orthogonal to the thickness direction.

[0007] In this laminated optical film, as described above, the adhesive layer sandwiched between the first and second optical films has an extended end that extends further outward than the two optical films. Where this extended end exists, for example, when an external member approaches from the surface and impacts the laminated optical film, the extended end that extends further outward than the two optical films will withstand the impact of the external member. This prevents further approach of the external member and prevents impact on the first edge of the first optical film and the second edge of the second optical film. Alternatively, even if the external member impacts the first edge and / or the second edge, the impact force on these ends can be mitigated. This prevention of impact and mitigation of impact force is suitable for suppressing damage to the ends of the optical films in the laminated optical film. Furthermore, the fact that the adhesive layer of this laminated optical film has an extended end is suitable for suppressing the occurrence and growth of microcracks at the ends of the first and second optical films.

[0008] The present invention [2] includes a multilayer optical thin film as described in [1] above, wherein the first optical thin film is a polarizing film, and in the aforementioned surface direction, the first end edge is located further outward than the second end edge.

[0009] The configuration is suitable for suppressing damage to the second edge of the second optical film in a multilayer optical film.

[0010] The present invention [3] includes a stacked optical film as described in [1] or [2] above, wherein the aforementioned extended end has an extension length of 0.01µm or more and 5µm or less measured from the aforementioned first end edge in the aforementioned surface direction.

[0011] The configuration is suitable for both suppressing damage and suppressing peeling at the first edge of the first optical film.

[0012] The present invention [4] includes a multilayer optical thin film as described in any of [1] to [3] above, wherein the length of the aforementioned extended end, measured from the aforementioned second end edge in the aforementioned planar direction, is 0.03µm or more and 10µm or less.

[0013] The configuration is suitable for both suppressing damage and suppressing peeling at the second edge of the second optical film.

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

[0015] The aforementioned extended end is suitable for forming during the fabrication of a multilayer optical film by processing the film shape, which involves heating at the end of the multilayer optical film. Simple Explanation of the Diagram

[0016] Figure 1 is a cross-sectional schematic diagram of one embodiment of the stacked optical thin film of the present invention. Figure 2 is a partially enlarged cross-sectional view of the end of the laminated optical thin film shown in Figure 1. Figure 3 shows a function of the extended end of the adhesive layer. Implementation

[0017] As one embodiment of the multilayer optical film of the present invention, the multilayer optical film X, as shown in FIG1, comprises an optical film 10 (first optical film), an optical film 20 (second optical film), and an adhesive layer 30. The multilayer optical film X has a sheet shape of predetermined thickness and extends in a direction orthogonal to the thickness direction H (planar direction). Specifically, the multilayer optical film X comprises the optical film 10, the adhesive layer 30, and the optical film 20 sequentially in the thickness direction H. The adhesive layer 30 is used to bond the optical films 10 and 20. Furthermore, the multilayer optical film X is a composite film incorporated into the multilayer structure of a display panel. The multilayer optical film X can be in sheet form or in roll form.

[0018] In this embodiment, the optical thin film 10 is a functional optical thin film. Examples of functional optical thin films include polarizing films and phase difference films.

[0019] Examples of polarizing films include hydrophilic polymer films that have undergone dyeing with dichroic substances and subsequent stretching treatment. Examples of dichroic substances include iodine and dichroic dyes. Examples of hydrophilic polymer films include polyvinyl alcohol (PVA) films, partially formalized PVA films, and partially saponified films of ethylene-vinyl acetate copolymers. Another example of a polarizing film is a polyene-oriented film. Examples of materials for polyene-oriented films include dehydrated PVA and dehydrochlorinated polyvinyl chloride. Considering the excellent optical properties such as polarization characteristics, a PVA film that has undergone dyeing with iodine and subsequent uniaxial stretching treatment is preferable for polarizing films.

[0020] From the perspective of thinning, the thickness of the optical thin film 10, which serves as a polarizing element thin film, should preferably be 15µm or less, more preferably 12µm or less, even more preferably 10µm or less, and especially preferably 8µm or less. Thin polarizing thin films have excellent visibility due to their smaller thickness variations, and their dimensional changes due to temperature variations are small, resulting in excellent thermal shock resistance. From the perspective of strength, the thickness of the optical thin film 10, which serves as a polarizing element thin film, should preferably be 3µm or more, and more preferably 5µm or more.

[0021] Examples of phase retardation films include, for example, λ / 2 wavelength films, λ / 4 wavelength films, and viewing angle compensation films. Materials for phase retardation films include, for example, polymer films that have undergone birefringence through a stretching process. Examples of polymer films include cellulose films and polyester films. Examples of cellulose films include, for example, cellulose triacetate films. Examples of polyester films include, for example, polyethylene terephthalate films and polyethylene naphthalate films. The thickness of the optical film 10, as a phase retardation film, is, for example, 20 µm or more, and for example, 150 µm or less. Furthermore, phase retardation films can also be suitable films comprising a substrate such as a cellulose film and an alignment layer of a liquid crystal compound such as a liquid crystal polymer on that substrate.

[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, polyvinyl chloride, cellulose, modified cellulose, polystyrene, and polycarbonate. Examples of polyolefins include cyclic olefin 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 some aromatic polyamides. Examples of modified cellulose include cellulose triacetate. These materials can be used alone or in combination of two or more. From a cleanliness perspective, polyolefins are preferable for the transparent protective film, and COPs are more suitable. Furthermore, the optical thin film 20 is preferably a uniaxially stretched thin film or a biaxially stretched thin film.

[0023] From the perspective of the strength of the multilayer optical film X, the thickness of the optical film 20 should preferably be 5µm or more, preferably 10µm or more, and even more preferably 20µm or more. From the perspective of the thinning of the multilayer optical film X, the thickness of the optical film 20 should preferably be 100µm or less, preferably 70µm or less, and even more preferably 50µm or less.

[0024] Adhesive layer 30 is a cured form of the adhesive composition. Adhesive layer 30 is directly bonded to optical film 10 and optical film 20. The adhesive composition contains a curable resin. The specific composition of the adhesive composition is described below.

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

[0026] As shown in Figure 2, the adhesive layer 30 has an extended end portion 30a at at least a portion of its peripheral edge. In a plane direction orthogonal to the thickness direction H, the extended end portion 30a extends further outward (to the left in Figure 2) than the edge 11 (first edge) of the optical film 10 or the edge 21 (second edge) of the optical film 20. In the laminated optical film X, where the extended end portion 30a is present, for example, as shown in Figure 3, when an external member M approaches from the outside in the plane direction and impacts the laminated optical film X, the extended end portion 30a, which extends further outward than the optical films 10 and 20, will withstand the impact of the external member M. This prevents the external member M from approaching further and prevents the external member M from impacting the edge 11 of the optical film 10 and the edge 21 of the optical film 20. Alternatively, even if the external member M impacts the edge 11 and / or the edge 21, the impact force on these edges 11 and 21 can be mitigated. The impact prevention and impact force mitigation are suitable for suppressing end damage of optical films 10 and 20 in the laminated optical film X. Furthermore, the adhesive layer 30 of the laminated optical film X having an extended end 30a is suitable for suppressing the occurrence and growth of microcracks at the ends of optical films 10 and 20.

[0027] When optical thin film 10 is a polarizing film and optical thin film 20 is a transparent protective film, edge 11 is preferably located further outward in the planar direction than edge 21. This configuration is suitable for suppressing damage to edge 21 of optical thin film 20 in the laminated optical thin film X.

[0028] The extension length L1 of the extended end 30a, measured from the end edge 11 in the planar direction, is preferably 0.01µm or more, more preferably 0.05µm or more, more preferably 0.1µm, and especially preferably 0.3µm or more. This configuration is suitable for suppressing damage to the end edge 11 of the optical film 10. Furthermore, the extension length L1 is preferably 8µm or less, more preferably 5µm or less, more preferably 4µm or less, even more preferably 3µm, and especially preferably 1µm or less. This configuration is suitable for suppressing the formation of adhesive residue at the panel end caused by excessively extended adhesive during the shaping process when the laminated optical film X is assembled into a display panel such as a smartphone, and is also suitable for suppressing display unevenness caused by such adhesive residue. Specifically, the extension length L1 is the distance in the planar direction between the end edge 11 of the optical film 10 and the end edge 31 of the adhesive layer 30.

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

[0030] The ratio of the extension length L2 to the extension length L1 (L2 / L1) is preferably 1.1 or more, more preferably 1.5 or more, more preferably 2 or more, and especially preferably 2.5 or more. The ratio (L2 / L1) is preferably 10 or less, more preferably 8 or less, more preferably 7 or less, and especially preferably 5 or less. This configuration is suitable for achieving both the above-mentioned suppression of damage and suppression of peeling of the optical films 10 and 20.

[0031] The indentation modulus (indentation modulus E1) of the adhesive layer 30 at 25°C, measured using nanoindentation, is preferably 0.5 GPa or higher, more preferably 1 GPa or higher, more preferably 1.5 GPa or higher, and especially preferably 2 GPa or higher. This configuration is preferable from the viewpoint of ensuring the bonding strength between the optical films 10 and 20. Furthermore, this configuration is suitable for ensuring the aforementioned impact prevention and impact force mitigation functions of the extended end 30a, and also helps to balance the aforementioned damage suppression and peeling suppression of the optical films 10 and 20. The indentation modulus E1 is preferably 7 GPa or lower, more preferably 5 GPa or lower, and more preferably 3 GPa or lower. This configuration is suitable for ensuring the flexibility of the adhesive layer 30 when the laminated optical film X is used in a repeatedly bendable (foldable) display panel. The method for adjusting the indentation modulus of the adhesive layer 30 can be, for example, by adjusting the composition of the adhesive components. Specifically, the effective method for adjusting the indentation elastic modulus of the adhesive layer 30 is to adjust the functional group of the polymeric compound in the adhesive composition forming the adhesive layer 30, that is, to adjust the acrylonitrile equivalent or epoxy equivalent of the polymeric compound.

[0032] Nanoindentation is a method for determining the properties of a sample at the nanoscale. In this embodiment, nanoindentation is performed according to ISO 14577. Nanoindentation involves pressing an indenter into the sample mounted on a platform (load application process) and then pulling the indenter out of the sample (unloading process), measuring the load acting between the indenter and the sample and the relative displacement of the indenter relative to the sample during this series of processes (load-displacement measurement). This yields a load-displacement curve. From this load-displacement curve, the properties of the sample can be determined based on nanoscale measurements. Load-displacement measurements of the adhesive layer cross-section using nanoindentation can be performed, for example, using a nanoindenter (trade name "Triboindenter," manufactured by Hysitron). Specifically, as described later with reference to the embodiments.

[0033] The indentation modulus (indentation modulus E2) of the adhesive layer 30 at 80°C, as 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 suitable for suppressing thermal shrinkage of the adhesive layer 30 during the processing of the film shape where the end of the laminated optical film X will heat up, thereby forming the aforementioned extended end 30a. From the viewpoint of the processing toughness 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 elastic moduli E1 and E2 should preferably satisfy 0.05 ≤ E2 / E1 ≤ 0.25. This configuration is suitable for suppressing thermal shrinkage of the adhesive layer 30 during the processing of the film shape at the end of the laminated optical film X, where the film will heat up, thereby forming the aforementioned extended end 30a. The value of E2 / E1 is preferably 0.1 or higher, more preferably 0.12 or higher, and preferably 0.2 or lower, more preferably 0.18 or lower.

[0035] In the laminated optical thin film X, the 90° peel strength of the optical thin film 20 against the optical thin 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. This configuration is suitable for achieving good adhesion between the optical thin films 10 and 20, and is particularly suitable for ensuring adhesion between the optical thin films 10 and 20 used in foldable display panels. The 90° peel strength is, for example, 10 N / 15 mm or less. The 90° peel strength can be measured, for example, using a TENSILON universal testing machine (product name "RTC", manufactured by A&D Company, Limited). In this measurement, the measurement temperature is set to 25°C, the peel angle is set to 90°, and the peel speed is set to 1000 mm / min. Furthermore, the 90° peel strength can be adjusted, for example, by adjusting the composition of the adhesive. Specifically, methods for adjusting the 90° peel strength include, for example, adjusting the number of functional groups of the polymeric compound in the adhesive composition, i.e., adjusting the acrylonitrile equivalent or epoxy equivalent of the polymeric 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, more preferably 15 or more, and preferably 30 or less, more preferably 25 or less. This configuration is preferred from the viewpoint of the processing toughness of the adhesive layer 30.

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

[0038] When a hardening composition of an active energy line is a free radical polymer type composition, the composition contains a free radical polymerizable compound as a monomer. A free radical polymerizable compound is a compound having a free radical polymerizable functional group. Examples of free radical polymerizable functional groups include those containing vinyl unsaturated bonds. Examples of groups containing vinyl unsaturated bonds include (meth)acryl, vinyl, and allyl. (Meth)acryl refers to acrylonitrile and / or methacryl. From the viewpoint of the hardening properties of the active energy line hardening composition, it is preferable that the active energy line hardening composition contains a free radical polymerizable compound having a (meth)acryl group as the main component. The main component refers to the component with the highest mass percentage. The proportion of the free radical polymerizable compound containing a (meth)acryl group in the active energy line hardening composition is, for example, 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more. Furthermore, examples of free radical polymers include monofunctional free radical polymers and polyfunctional free radical polymers with two or more functions.

[0039] Monofunctional free radical polymerizable compounds include, for example, (meth)acrylamide derivatives containing a (meth)acrylamide group. Examples of (meth)acrylamide derivatives include: (meth)acrylamide derivatives containing N-alkyl groups, (meth)acrylamide derivatives containing N-hydroxyalkyl groups, (meth)acrylamide derivatives containing N-aminealkyl groups, (meth)acrylamide derivatives containing N-alkoxy groups, and (meth)acrylamide derivatives containing N-mercaptoalkyl groups. Examples of (meth)acrylamide derivatives containing N-alkyl groups 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; N,N-diethylacrylamide is preferred. Examples of N-hydroxyalkyl (meth)acrylamide derivatives include: N-hydroxymethyl (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, and N-hydroxymethyl-N-propane (meth)acrylamide. N-hydroxyethylacrylamide is preferred. (Methacrylamide)acrylamide derivatives may be used alone or in combination of two or more.

[0040] Examples of monofunctional free radical polymerizable compounds include (meth)acrylic acid derivatives having a (meth)acryloxy group. Examples of such (meth)acrylic acid derivatives include alkyl (meth)acrylates and other (meth)acrylic acid derivatives. (Methacryl)acrylic acid derivatives can be used alone or in combination of two or more.

[0041] Examples of alkyl methacrylates include: methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, 2,2-dimethylbutyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, 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-containing (meth)acrylic acid derivatives, alkoxy-containing (meth)acrylic acid derivatives, and phenoxy-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-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]methacrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate. Examples of alkoxy-containing (meth)acrylate derivatives include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, and 3-methoxybutyl (meth)acrylate. Examples of phenoxy-containing (meth)acrylate derivatives include phenoxyethyl (meth)acrylate and phenoxydiethylene glycol (meth)acrylate. (Meth)acrylate derivatives other than alkyl (meth)acrylates may preferably be selected from at least one of the group consisting of 3-phenoxybenzyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, and phenoxydiethylene glycol acrylate.

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

[0044] Monofunctional free radical polymerizable compounds also include lactone-based vinyl monomers. Examples of lactone-based vinyl monomers include N-vinyl-2-pyrrolidone, N-vinyl-ε-caprolactone, and methylvinylpyrrolidone.

[0045] Monofunctional free radical polymerizable compounds may also include vinyl monomers having nitrogen-containing heterocycles. Examples of such monomers include: vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperidine, vinylpyridine, vinylpyrrole, vinylimidazolium, vinylpyrazole, and vinylmorpholin.

[0046] Polyfunctional radical polymerizable compounds may 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, neopentyl glycol di(meth)acrylate, tricyclodecanediethanol di(meth)acrylate, cyclic trimethylolpropane acetal (meth)acrylate, dialkyldiol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, neopentyltetrol tri(meth)acrylate, neopentyltetrol tetra(meth)acrylate, dinepentyltetrol penta(meth)acrylate, and dinepentyltetrol hexa(meth)acrylate. Tripropylene glycol diacrylate is also suitable. Polyfunctional radical polymerizable compounds may be used alone or in combination of two or more. Multifunctional free radical polymerizable compounds can function as crosslinking agents.

[0047] When the active energy line curing composition is an ultraviolet-curing composition or a visible light-curing composition, it should preferably contain a photopolymerization initiator. Examples of photopolymerization initiators include diphenyl ketone compounds, benzoin ether compounds, and 9-oxosulfuron. Compounds. Examples of diphenyl ketone compounds include benzyl, diphenyl ketone, benzoic acid, and 3,3'-dimethyl-4-methoxydiphenyl ketone. Examples of benzoin ether compounds include benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether. 9-Oxysulfuron Examples of compounds include: 9-oxosulfuron 2-Chloro-9-oxysulfur 2-Methyl-9-oxosulfur 2,4-Dimethyl-9-oxosulfur Isopropyl 9-oxosulfur 2,4-Dichloro-9-oxosulfur 2,4-Diethyl-9-oxosulfur 2,4-Diisopropyl-9-oxosulfur and dodecyl 9-oxosulfur .

[0048] When the active energy line curing composition is a visible light curing composition, a photopolymerization initiator with high sensitivity to light above 380 nm should be used. Examples of such photopolymerization initiators include: 2-methyl-1-(4-methylthiophenyl)-2-morphofolinylprop-1-one, 2-benzyl-2-dimethylamino-1-(4-morphofolinylphenyl)-but-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morphofolinyl)phenyl]-1-butanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and bis(n5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrole-1-yl)-phenyl)titanium.

[0049] 2,4-Diethyl-9-oxosulfuron is a suitable photopolymerization initiator. And / or 2-methyl-1-(4-methylthiophenyl)-2-morphofolinylprop-1-one.

[0050] Relative to 100 parts by mass of the curing component (free radical polymerizable compound), the content of the photopolymerization initiator in the active energy line curing composition should preferably be 0.1 parts by mass or more, more preferably 0.05 parts by mass or more, 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 more preferably 5 parts by mass or less.

[0051] When the active energy line curing composition is a cationic polymer composition, the composition contains a cationic polymeric compound as a monomer. The cationic polymeric compound is a compound having a cationic polymeric functional group, including monofunctional cationic polymeric compounds having one cationic polymeric functional group and polyfunctional cationic polymeric compounds having two or more cationic polymeric functional groups. Monofunctional cationic polymeric compounds have relatively low liquid viscosity. By incorporating the monofunctional cationic polymeric compound into the resin composition, the viscosity of the resin composition can be reduced. Furthermore, monofunctional cationic polymeric compounds mostly possess functional groups capable of exhibiting various functions. By incorporating the monofunctional cationic polymeric compound into the resin composition, the resin composition and / or the cured resin composition can exhibit various functions. On the other hand, by curing a resin composition incorporating a polyfunctional cationic polymeric compound, a cured product with a 3D cross-linked portion can be obtained (the polyfunctional cationic polymeric compound functions as a cross-linking agent). From this perspective, it is preferable to utilize polyfunctional cationic polymeric compounds. When using both monofunctional cationic polymeric compounds and polyfunctional cationic polymeric compounds, the amount of the polyfunctional cationic polymeric compound is, for example, 10 parts by mass or more, and for example, 1000 parts by mass or less, relative to 100 parts by mass of the monofunctional cationic polymeric compound. Examples of cationic polymeric functional groups include epoxy groups, oxetyl groups, and vinyl ether groups. Examples of compounds containing epoxy groups include aliphatic epoxy compounds, alicyclic epoxy compounds, and aromatic epoxy compounds. From the viewpoint of the curability and adhesion of cationic polymeric compositions, alicyclic epoxy compounds are preferable to be used as epoxy groups. Examples of alicyclic epoxy compounds include: 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, or caprolactone-modified, trimethylcaprolactone-modified, and valproicone-modified versions of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate. Commercially available alicyclic epoxy compounds include, for example, CELLOXIDE 2021, CELLOXIDE 2021A, CELLOXIDE 2021P, CELLOXIDE 2081, CELLOXIDE 2083, and CELLOXIDE 2085 (all manufactured by DAICL Chemical Co., Ltd.), and Cyracure UVR-6105, Cyracure UVR-6107, Cyracure 30, and R-6110 (all manufactured by DOW CHEMICAL Japan Co., Ltd.). From the perspective of improved curability and reduced viscosity of cationic polymeric compositions, compounds containing oxetane groups and / or compounds containing vinyl ether groups are preferable.Examples of compounds containing oxetane include: 3-ethyl-3-hydroxymethyloxetane, 1,4-bis[(3-ethyl-3-oxetane)methoxymethyl]benzene, 3-ethyl-3-(phenoxymethyl)oxetane, di[(3-ethyl-3-oxetane)methyl] ether, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, and phenolic varnish oxetane. Commercially available examples of compounds containing oxetane include: ARON OXETANE OXT-101, ARON OXETANE OXT-121, ARON OXETANE OXT-211, ARON OXETANE OXT-221, and ARON OXETANE OXT-212 (all manufactured by Toa Synthetic Co., Ltd.). Compounds containing a vinyl ether group include, for example: 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, triethylene glycol divinyl ether, cyclohexanediethanol divinyl ether, cyclohexanediethanol monovinyl ether, tricyclodecane vinyl ether, cyclohexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, and neopentyl tetravinyl ether.

[0052] When the active energy line curing composition is an ultraviolet-curing composition or a visible light-curing composition, it contains a photocationic polymerization initiator. When irradiated by active energy lines (visible light, ultraviolet light, X-rays, electron beams, etc.), the photocationic polymerization initiator generates cationic species or Lewis acids, initiating the polymerization reaction of cationic polymerizable functional groups. Examples of photocationic polymerization initiators include photoacid generators and photobase generators; photoacid generators are preferred. When the active energy line curing composition is a visible light-curing composition, it is particularly advisable to use a photocationic polymerization initiator with high sensitivity to light above 380 nm. Furthermore, when using a photocationic polymerization initiator, it is advisable to also use a photosensitizer that exhibits maximum absorption to light with wavelengths longer than 380 nm. Photocationic polymerization initiators are generally compounds that exhibit maximum absorption in the wavelength region around 300 nm or shorter. Therefore, by using them in conjunction with photosensitizers that exhibit maximum absorption in wavelengths longer than 380 nm, the generation of cationic species or Lewis acids from the photocationic polymerization initiator can be effectively promoted using light with wavelengths longer than 380 nm. Examples of photosensitizers include anthracene compounds, pyrene compounds, carbonyl compounds, organosulfur compounds, persulfides, redox compounds, azo compounds, diazo compounds, halogen compounds, and photoreducing pigments. These can be used alone or in combination of two or more. Anthracene compounds are particularly ideal due to their excellent photosensitizing effect. 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] Active energy line curable compositions may also contain oligomers. Examples of oligomers include acrylic oligomers, fluoro oligomers, and polysiloxane oligomers; acrylic oligomers are preferred. The blending of oligomers into the active energy line curable composition helps suppress shrinkage during curing. Suppression of curing shrinkage in the active energy line curable composition appropriately reduces the interfacial stress between the formed adhesive layer 30 and the optical films 10 and 20. Suppression of interfacial stress helps ensure adhesion between the optical films 10 and 20.

[0054] Examples of (meth)acrylic acid monomers that form acrylic acid oligomers include: alkyl (meth)acrylic acid esters with 1 to 20 carbon atoms, cycloalkyl (meth)acrylic acid esters, aralkyl (meth)acrylic acid esters, polycyclic (meth)acrylic acid esters, hydroxyl-containing (meth)acrylic acid esters, and halogen-containing (meth)acrylic acid esters. Examples of alkyl methacrylates include: methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, 2-methyl-2-nitropropyl (meth)acrylate, n-butyl methacrylate, isobutyl methacrylate, S-butyl methacrylate, tributyl methacrylate, n-pentyl methacrylate, tripentyl methacrylate, 3-pentyl methacrylate, 2,2-dimethylbutyl (meth)acrylate, n-hexyl methacrylate, cetyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, 4-methyl-2-propylpentyl (meth)acrylate, and N-octadecyl (meth)acrylate. Examples of cycloalkyl methacrylates include cyclohexyl methacrylate and cyclopentyl methacrylate. Examples of aralkyl methacrylates include benzyl methacrylate. Examples of polycyclic (meth)acrylates include 2-isocamphene (meth)acrylate, 2-norcamphenylmethyl (meth)acrylate, 5-norcamphen-2-yl-methyl (meth)acrylate, and 3-methyl-2-norcamphenylmethyl (meth)acrylate. Examples of hydroxyl-containing (meth)acrylates include hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2,3-dihydroxypropylmethyl-butyl (meth)methacrylate. Examples of halogen-containing (meth)acrylates 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 can be used alone or in combination of two or more.

[0055] The weight average molecular weight (Mw) of acrylic oligomers should preferably be below 15,000, more preferably below 10,000, and even more preferably below 5,000. The Mw of acrylic oligomers should preferably be above 500, more preferably above 1,000, and even more preferably above 1,500.

[0056] The content of acrylic oligomer in the active energy line hardening type composition should preferably be 2% by mass or more, more preferably 4% by mass or more, and preferably less than 20% by mass, more preferably less than 15% by mass.

[0057] The active energy line hardening composition may also contain other components. Other components may include silane coupling agents, leveling agents, surfactants, plasticizers, and ultraviolet absorbers. The amount of these other components should preferably be less than 10 parts by mass relative to 100 parts by mass of the hardening component, more preferably less than 5 parts by mass, and even more preferably less than 3 parts by mass, and for example, more than 0.01 parts by mass.

[0058] From the perspective of coatability in the coating step described later, the viscosity of the active energy linear hardening composition at 25°C should preferably be 3 mPa·s or higher, more preferably 5 mPa·s or higher, more preferably 10 mPa·s or higher, and preferably 100 mPa·s or lower, more preferably 50 mPa·s or lower, and more preferably 30 mPa·s or lower. The viscosity of the composition is measured using an E-type viscometer (cone-plate viscometer).

[0059] The laminated optical thin film X can be manufactured, for example, in the following manner.

[0060] First, an active energy line-curing composition is coated onto one side (the pre-bonding surface) of one of the optical films (optical film 10 or optical film 20) to form a coating of the composition (coating step). Prior to this coating step, the pre-bonding surface of the optical film may also undergo surface modification treatment. Surface modification treatments may include corona treatment, plasma treatment, excimer laser treatment, and flame treatment. The coating method in this step may include, for example, a reverse coating machine, a gravure coating machine, a bar reverse coating machine, a roll coating machine, a die coating machine, a bar coating machine, and a rod coating machine.

[0061] Next, one optical film (optical film 20 or optical film 10) is laminated to one optical film over the composition coating. The lamination can be performed using, for example, a roll laminator.

[0062] Next, an active energy line is irradiated onto the composition coating between optical thin films 10 and 20, causing the coating (an active energy line-cured composition) to harden and form an adhesive layer 30 (the adhesive layer 30 is not a pressure-sensitive adhesive layer). In this way, optical thin films 10 and 20 are bonded together through the adhesive layer 30, thus obtaining the raw material film of the laminated optical thin film X. From the viewpoint of suppressing the degradation of the optical thin film 10 as a functional optical thin film, it is preferable to irradiate the active energy line from the optical thin film 30 side in this step. The active energy line can be an electron beam, ultraviolet light, or visible light. An electron beam irradiation mechanism can be, for example, an electron beam accelerator. Examples of ultraviolet and visible light sources include: 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. In this step, a wavelength cutoff filter can also be used as needed to cut off a portion of the wavelength region of ultraviolet and / or visible light emitted from the light source.

[0063] Next, at least a portion of the periphery of the raw material film is shaped (shape forming step). For example, one end of the long side of the rolled raw material film is trimmed. For example, the rolled raw material film is cut into a single sheet. Such shape forming methods include, for example, laser processing using CO2 laser irradiation, cutting using a punch, and end milling. The shape forming area of ​​the raw material film will undergo significant thermal shrinkage at the optical films 10 and 20 to form an extended end 30a. Specifically, the ends of the optical films 10 and 20 will shrink so that the end edges 11 and 21 of the optical films 10 and 20 at the ends of the raw material film recede inward in the surface direction from the end edge 31 of the adhesive layer 30, thus forming the extended end 30a. The length of the shrinkage at the ends of the optical films 10 and 20, that is, the extension length 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. Processing conditions can include, for example, adjusting the elongation ratio.

[0064] For example, a multilayer optical thin film X can be manufactured using the above method.

[0065] Example The following examples illustrate the present invention. The present invention is not limited to the examples. Furthermore, the specific values ​​of blending amount (content), physical property value, parameters, etc., described below can be replaced by the upper limit (values ​​defined as "below" or "less than") or lower limit (values ​​defined as "above" or "greater than") of the blending amount (content), physical property value, parameters, etc., corresponding to those described in the above "Forms for Implementing the Invention".

[0066] [Example 1] Mix the following ingredients at 25°C for 1 hour to prepare the adhesive composition (preparation step).

[0067] 45 parts by weight of 3-phenoxybenzyl acrylate (brand name "LIGHT ACRYLATE POB-A", monomer, manufactured by Kyoei Chemical Co., Ltd.) 25 parts by weight of phenoxy diethylene glycol acrylate (brand name "LIGHT ACRYLATE P2H-A", monomer, manufactured by Kyoei Chemical Co., Ltd.) 15 parts by weight of tripropylene glycol diacrylate (brand name "ARONIX M-220", monomer, manufactured by Toa Synthetic Co., Ltd.) 10 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate (brand name "ARONIX M-5700", monomer, manufactured by Toa Synthetic Co., Ltd.) 5 parts by weight of hydroxyethyl acrylamide (product name "HEAA", monomer, manufactured by KJ Chemicals Corporation) 5 parts by weight of diethylacrylamide (product name "DEAA", monomer, manufactured by KJ Chemicals Corporation) 3 parts by weight of 2-methyl-1-(4-methylthiophenyl)-2-morphofolinylprop-1-one (brand name "OMINIRAD907", photopolymerization initiator, manufactured by IGM Resins) 3 parts by mass of 2,4-diethyl-9-oxosulfur (Product name "KAYACURE DETX-S", photopolymerization initiator, manufactured by Nippon Kayaku Co., Ltd.) 5 parts by weight of acrylic oligomer (brand name "ARUFON 1190", viscosity 6000 mPa·s (25℃), Mw 1700, Tg -50℃, manufactured by Toa Synthetic Co., Ltd.) 0.5 parts by weight of acrylonitrile-modified polydimethylsiloxane (brand name "BYK-UV3505", leveling agent, manufactured by BYK Corporation)

[0068] Next, an adhesive composition is coated onto a 23µm thick COP film (brand name "ZeonorFilm ZF14", manufactured by ZEON Corporation, Japan) serving as a transparent protective film, forming an adhesive coating film with a thickness of 1µm. Coating is performed using an MCD coating machine (manufactured by Fuji Machinery Co., Ltd.) (groove shape: honeycomb, gravure roller line count 1000 lines / inch, rotation speed 140% / line speed). Next, a polarizing film is bonded to the transparent protective film through the adhesive coating film. Then, the adhesive coating film is cured by irradiating it with ultraviolet light from the transparent protective film side. For ultraviolet irradiation, an ultraviolet irradiation device equipped with a gallium-filled metal halide lamp (brand name "Light HAMMER10", bulb: V bulb, manufactured by Fusion UV Systems, Inc.) is used as the light source. Under ultraviolet irradiation, the peak illuminance was 1600 mW / cm², and the cumulative irradiance was set to 1000 mJ / cm² (wavelength 380~440 nm) (illuminance was measured using the "Sola-Check system" manufactured by Solatell). Based on this, a multilayer optical film was obtained by bonding a transparent conductive film and a polarizing film.

[0069] Next, the stacked optical film undergoes shape processing (shape processing step). Specifically, the stacked optical film is cut along its thickness direction by irradiation with a CO2 laser to obtain a stacked optical film with a predetermined top view shape. During CO2 laser irradiation, the wavelength is set to 9.4µm, the output is set to 48W, and the scanning speed is set to 500mm / second. The stacked optical film is then placed at room temperature for 24 hours.

[0070] Following the above method, the multilayer optical film of Example 1 was fabricated. The multilayer optical film of Example 1 has a polarizing film (thickness 5µm), an adhesive layer and a transparent protective film (thickness 23µm) sequentially formed in the thickness direction.

[0071] [Example 2] Except for the following, the multilayer optical film (polarizing film / adhesive layer / transparent protective film) of Example 2 was fabricated in the same manner as the multilayer optical film of Example 1. In the modulation step, the amount of "ARONIX M-220" was set to 5 parts by mass instead of 15 parts by mass, and the thickness of the adhesive layer coating formed on the transparent protective film was set to 1µm.

[0072] [Example 3] Except for the following, the multilayer optical film (polarizing film / second adhesive layer / transparent protective film) of Example 3 was produced in the same manner as the multilayer optical film of Example 1.

[0073] In the preparation step, the blending amount of "LIGHT ACRYLATE POB-A" is set to 43 parts by mass, the blending amount of "LIGHT ACRYLATE P2H-A" is set to 29 parts by mass, and the blending amount of "ARONIX M-220" is set to 3 parts by mass. In the coating step, the thickness of the adhesive layer coating to be formed on the transparent protective film is set to 1µm.

[0074] [Comparative Example 1] Except for the following, the composite optical film (polarizing film / adhesive layer / transparent protective film) of Comparative Example 1 was produced in the same manner as the composite optical film of Example 1.

[0075] In the preparation step, 36 parts by weight of "LIGHT ACRYLATE 1.9ND-A" (1,9-nonanediol diacrylate) manufactured by Kyoei Chemical Co., Ltd. and 12.5 parts by weight of "LIGHT ACRYLATE HPP-A" (hydroxytrimethylacetic acid neopentyl glycol acrylate adduct) manufactured by Kyoei Chemical Co., Ltd. were used to replace "LIGHT ACRYLATE POB-A" and "LIGHT ACRYLATE P2H-A". "ARONIX M-220" was not used. The blending amount of "ARONIX M-5700" was set to 22 parts by weight, the blending amount of "HEAA" was set to 12.5 parts by weight, the blending amount of "DEAA" was set to 6 parts by weight, the blending amount of "HEAA" was set to 12.5 parts by weight, and the blending amount of "ARUFON 1190" was set to 10 parts by weight.

[0076] <Observation of the End> The longitudinal cross-sectional shape of the ends of each laminated optical film of Examples 1-3 and Comparative Example 1 was investigated. First, a longitudinal cross-section for observation was formed by cutting along the thickness direction at an arbitrarily selected point from the periphery of the laminated optical film. Next, the longitudinal cross-section was observed and photographed using an optical microscope. Then, in each observation cross-section, a portion (extended end) of the adhesive layer extending further outward in the film surface direction than the end edge (first end edge) of the polarizing film and the end edge (second end edge) of the transparent protective film was identified. Furthermore, the extension length L1 of the extended end in the surface direction from the first end edge and the extension length L2 of the extended end in the surface direction from the second end edge were measured in each observation cross-section. The results are shown in Table 1.

[0077] Furthermore, regarding the suppression of damage to the multilayer optical thin film, the following criteria were used for evaluation: a condition in which neither the polarizing film nor the transparent protective film showed any damage (cracks, notches, etc.) in the observed cross-section was evaluated as "good," and a condition in which at least one of the polarizing film or the transparent protective film showed damage was evaluated as "poor." The results are shown in Table 1.

[0078] <Indentation modulus> The indentation elastic modulus (first elastic modulus) of the adhesive layer in each laminated optical film of Examples 1-3 and Comparative Example 1 was determined by nanoindentation. Specifically, a 5mm × 10mm film sheet (laminated optical film) was first cut from the laminated optical film. Then, the laminated optical film was cut using the freeze-cutting method. Specifically, after cooling the laminated optical film to -30°C, it was cut along the thickness direction of the film with a hard cutter, and then restored to room temperature. This yielded the test sample. Next, using a nanoindentation testing machine (product name "TI950 Triboindenter", manufactured by Hysitron Corporation), the exposed surface of the adhesive layer in the test sample was subjected to load-displacement measurement according to JIS Z 2255:2003 to obtain the load-displacement curve. In this measurement, the measurement mode was set to single indentation measurement, the measurement temperature was set to 25℃, and a Berkovich (triangular pyramidal) diamond indenter was used. During load application, the maximum indentation depth (maximum displacement hmax) of the indenter on the test sample was set to 50 nm, the indentation speed was set to 10 nm / s, and the pull-out speed of the indenter from the test sample during unloading was set to 10 nm / s. The measurement data were then processed using the dedicated analysis software (Ver. 9.4.0.1) of the "TI950 Triboindenter". Specifically, based on the obtained load (f)-displacement (h) curve, the following were obtained: maximum load fmax (the load acting on the indenter with the maximum displacement hmax), contact projection area S (the projected area of ​​the contact region between the indenter and the sample at maximum load), and the slope D of the tangent line of the load-displacement curve at the start of unloading. Then, the indentation elastic modulus of the adhesive layer (=(π 1 / 2D) / (2S 1 / 2)) is calculated from the slope D and the contact projected area S. This value is shown as the indentation elastic modulus E1 (GPa) in Table 1.

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

[0080] [Table 1]

[0081] X: Multilayer optical thin film 10: Optical Thin Films (First Optical Thin Film) 11: The edge (first edge) of the optical thin film 10 20: Optical Thin Film (Second Optical Thin Film) 21: The second edge of the optical thin film 20 30: Adhesive layer 30a: Extended end 31: End edge of the adhesive layer L1, L2: Extension length H: Thickness direction M: External components

Claims

1. A laminated optical thin film, comprising, in a thickness direction, a first optical thin film, an adhesive layer, and a second optical thin film sequentially thereon; the adhesive layer is bonded to the first optical thin film and to the second optical thin film; the adhesive layer has an extended end, which extends further outward than a first edge of the first optical thin film and a second edge of the second optical thin film in a plane direction orthogonal to the thickness direction; wherein the first optical thin film is a polarizing film, and in the plane direction, the first edge is located further outward than the second edge.

2. A laminated optical thin film comprising, in a thickness direction, a first optical thin film, an adhesive layer, and a second optical thin film sequentially thereon; wherein the adhesive layer is bonded to the first optical thin film and to the second optical thin film; wherein the adhesive layer has an extended end, which extends outwardly beyond a first edge of the first optical thin film and a second edge of the second optical thin film in a plane direction orthogonal to the thickness direction; wherein the extension length of the extended end, measured from the first edge in the plane direction, is 0.01µm or more and 5µm or less.

3. A laminated optical thin film, comprising a first optical thin film, an adhesive layer, and a second optical thin film sequentially in a thickness direction; wherein the adhesive layer is bonded to the first optical thin film and to the second optical thin film; wherein the adhesive layer has an extended end, which extends outward beyond a first edge of the first optical thin film and a second edge of the second optical thin film in a plane direction orthogonal to the thickness direction; wherein the extension length of the extended end, measured from the second edge in the plane direction, is 0.03µm or more and 10µm or less.

4. A laminated optical thin film, comprising, in a thickness direction, a first optical thin film, an adhesive layer, and a second optical thin film sequentially thereon; the adhesive layer is bonded to the first optical thin film and to the second optical thin film; the adhesive layer has an extended end, which extends further outward than a first edge of the first optical thin film and a second edge of the second optical thin film in a plane direction orthogonal to the thickness direction; 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.

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