Decomposed optical thin films

Abstract

The objective of this invention is to provide a laminated optical film that maintains adhesion even with a thin adhesive layer between optical films. The solution is as follows: The laminated optical film X of this invention sequentially comprises an optical film 10, an adhesive layer 20, and an optical film 30 in the thickness direction H. The adhesive layer 20 is bonded to both the optical film 10 and the optical film 30. The optical film 30 has a boundary region 31 on the adhesive layer 20 side, and the boundary region 31 contains adhesive material components derived from the adhesive layer 20. The ratio of the thickness T2 of the adhesive material component-containing portion 40 to the thickness T1 of the adhesive layer 20 is 1.01 or more, and the adhesive material component-containing portion 40 is a portion formed by the merging of the adhesive layer 20 and the boundary region 31.

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, the thinning of functional optical films continues. Thin adhesive layers between the optical films in multilayered optical films are also required. However, the thinner the adhesive layer, the easier it is for the bonding strength between the optical films to decrease. From the perspective of bonding reliability, low bonding strength is undesirable. For multilayered optical films used in repeatedly bendable (foldable) display panels, ensuring bonding strength between optical films is crucial. For multilayered optical films used in foldable display panels operating in high-temperature and high-humidity environments such as automotive interiors, the high temperature and humidity generate excessive stress on the optical films, causing stress concentration at the bonding interface, which easily leads to peeling between the optical films. Therefore, it is particularly important to ensure bonding strength between the optical films using adhesive layers.

[0005] The present invention provides a laminated optical film that is suitable for ensuring bonding strength even when using a thin adhesive layer between optical films.

[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 second optical film has a boundary region on the side of the adhesive layer, the boundary region containing adhesive raw material components derived from the adhesive layer; and the ratio of the thickness T2 of the adhesive raw material component containing portion to the thickness T1 of the adhesive layer is 1.01 or more, the adhesive raw material component containing portion being a portion formed by the combination of the adhesive layer and the boundary region.

[0007] The present invention [2] includes a multilayer optical thin film as described in [1] above, wherein the aforementioned thickness T1 is less than 5µm.

[0008] The present invention [3] includes a laminated optical film as described in [1] or [2] above, wherein the second optical film has a 90° peel strength of 0.8 N / 15 mm or more against the first optical film at 25°.

[0009] The present invention [4] includes a multilayer optical thin film as described in any of [1] to [3] above, wherein the first optical thin film is a polarizing film.

[0010] Invention Effects In the laminated optical thin film of the present invention, as described above, the second optical thin film has a boundary region on the adhesive layer side where the first and second optical thin films are bonded, and this boundary region contains adhesive raw material components originating from the adhesive layer. That is, the second optical thin film has a region (the aforementioned boundary region) on the adhesive layer side infiltrated with adhesive raw material components from the adhesive layer. In the boundary region, the constituent components of the second optical thin film and the adhesive raw material components are mixed together. Moreover, in this laminated optical thin film, as described above, the ratio of the thickness T2 of the portion containing the adhesive raw material components to the thickness T1 of the adhesive layer is 1.01 or more. That is, in this laminated optical thin film, the thickness T2 of the portion containing the adhesive raw material components and participating in the bonding function (adhesive layer and boundary region) is greater than the thickness T1 of the adhesive layer. These configurations regarding the boundary between the second optical thin film and the adhesive layer and its vicinity enable a strong interaction between the second optical thin film and the adhesive layer, thus ensuring high bonding strength. Furthermore, ensuring the adhesion between the second optical film and the adhesive layer helps to ensure the adhesion between the first and second optical films using the adhesive layer. Therefore, this laminated optical film is suitable for ensuring adhesion between the optical films even using a thin adhesive layer. Ensuring the adhesion between the optical films is suitable for suppressing peeling between the optical films. Moreover, even in high temperature and high humidity environments, this laminated optical film can still ensure adhesion between the optical films using a thin adhesive layer, thus being suitable for suppressing peeling between the optical films. Simple Explanation of the Diagram

[0011] 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 laminated optical thin film shown in Figure 1. Figure 3 is a cross-sectional schematic diagram of another embodiment of the multilayer optical thin film of the present invention. The multilayer optical thin film of this embodiment has a second optical thin film, an adhesive layer, a first optical thin film, an adhesive layer, and a second optical thin film sequentially in the thickness direction. Implementation

[0012] 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 adhesive layer 20, and an optical film 30 (second optical film) sequentially in the thickness direction H. The adhesive layer 20 is bonded between the optical films 10 and 30. The multilayer optical film X has a sheet shape of a predetermined thickness and extends in a direction orthogonal to the thickness direction H (planar direction). The multilayer optical film X is a composite film incorporated into the multilayer structure of a display panel.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] Adhesive layer 20 is a cured form of the adhesive composition. Adhesive layer 20 is directly bonded to optical film 10 and optical film 30. The adhesive composition contains a curable resin. The specific composition of the adhesive composition is described below.

[0018] From the viewpoint of the bonding strength between optical films 10 and 30, the thickness T1 of adhesive layer 20 is preferably 0.1µm or more, more preferably 0.4µm or more, more preferably 0.7µm or more, and especially preferably 0.8µm or more. From the viewpoint of thinning the laminated optical film X, the thickness T1 of adhesive layer 20 is preferably 5µm or less, more preferably 3µm or less, more preferably 1.5µm or less, and especially preferably 1µm or less. The thickness T1 of adhesive layer 20 is the length in the thickness direction H of the region having the cured structure of the adhesive composition (formed by the cured constituent components). This length can be measured in an image obtained by observation such as SEM. Specifically, the thickness T1 of adhesive layer 20 can be measured by the method described later with reference to the embodiments.

[0019] The first indentation modulus of the adhesive layer 20, measured by nanoindentation at 25°C, should preferably be 0.01 GPa or higher, more preferably 0.03 GPa or higher, more preferably 0.05 GPa or higher, and especially preferably 0.07 GPa or higher (the first indentation modulus is set as the indentation modulus under the first measurement condition; the first measurement condition is as described later with reference to the embodiment, in which the maximum indentation depth of the indenter on the test sample during the application of load is 200 nm). This configuration is preferred from the viewpoint of ensuring the bonding force between the optical films 10 and 30. Furthermore, the first indentation modulus should preferably be 5 GPa or lower, more preferably 3 GPa or lower, and more preferably 1 GPa or lower. This configuration is suitable for ensuring the flexibility of the adhesive layer 20, and therefore suitable for ensuring the flexibility of the laminated optical film X. The method for adjusting the indentation modulus of the adhesive layer 20 can be, for example, adjusting the composition of the adhesive composition. Specifically, the effective method for adjusting the indentation elastic modulus of the adhesive layer 20 is to adjust the functional group of the polymeric compound in the adhesive composition forming the adhesive layer 20, that is, to adjust the acrylonitrile equivalent or epoxy equivalent of the polymeric compound.

[0020] 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.

[0021] The second indentation modulus of the adhesive layer 20, measured by nanoindentation at 25°C, 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 (the second indentation modulus is set as the indentation modulus under the second measurement conditions; the second measurement conditions are as described later with reference to the embodiments, in which the maximum indentation depth of the indenter on the test sample during the application of load is 50 nm). This configuration is preferred from the viewpoint of ensuring the adhesion between the optical films 10 and 30. Furthermore, the second indentation modulus 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 20, and therefore suitable for ensuring the flexibility of the laminated optical film X.

[0022] In this embodiment, the optical film 30 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.

[0023] From the perspective of the strength of the multilayer optical film X, the thickness of the optical film 30 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 30 should preferably be 100µm or less, preferably 70µm or less, and even more preferably 50µm or less.

[0024] As shown in Figure 2, the optical thin film 30 has a boundary region 31 on the side of the adhesive layer 20 and a non-boundary region 32 on the opposite side of the adhesive layer 20. The boundary region 31 contains adhesive raw material components originating from the adhesive layer 20. The boundary region 31 contains a mixture of components of the optical thin film 30 and adhesive raw material components. For example, a method for detecting the adhesive raw material components can be time-of-flight secondary ion mass spectrometry (TOF-SIMS). On the other hand, the non-boundary region 32 does not contain adhesive raw material components originating from the adhesive layer 20. The non-boundary region 32 is composed of components of the optical thin film 30. In the optical thin film 30, the region where adhesive raw material components are detected at or above the detection limit value (positive and negative ion intensities of 0.1 counts / second) in the aforementioned detection method is the boundary region 31, while the region where adhesive raw material components are not detected at or above the aforementioned detection limit value is the non-boundary region 32. The ratio of the thickness of the boundary region 31 to the thickness of the non-boundary region 32 is, for example, more than 0.01%, preferably more than 0.05%, or, for example, less than 50%, preferably less than 20%.

[0025] The thickness of the boundary region 31 is, for example, 0.01µm or more, preferably 0.05µm or more. The thickness of the boundary region 31 is, for example, 10µm or less, preferably 5µm or less. Methods for adjusting the thickness of the boundary region 31 include, for example, adjusting the composition of the adhesive. Another method for adjusting the thickness of the boundary region 31 is adjusting the time from the coating step to the curing step during the manufacturing process of the laminated optical film X. The longer this time, the thicker the boundary region 31 tends to be.

[0026] In the laminated optical film X, the boundary region 31 and the aforementioned adhesive layer 20 form an adhesive raw material component containing portion 40. To prevent insufficient adhesion when the boundary region 31 is too small (too thin), the ratio (T2 / T1) of the thickness T2 of the adhesive raw material component containing portion 40 to the thickness T1 of the adhesive layer 20 is 1.01 or more, preferably 1.05 or more, more preferably 1.1 or more, and more preferably 1.2 or more. From the viewpoint of balancing the adhesion between the adhesive layer 20 and the optical film 30 with the production stability of the laminated optical film X, the ratio (T2 / T1) is preferably 1.3 or less, more preferably 1.25 or less, and more preferably 1.2 or less. The aforementioned adhesion between the adhesive layer 20 and the optical film 30 can be ensured, for example, by ensuring the thickness of the adhesive layer 20, suppressing peeling caused by the load at the interface between the adhesive layer 20 and the optical film 30 when bending the laminated optical film X. The thickness T2 of the adhesive raw material component containing portion 40 is greater than the thickness of the adhesive layer 20, but less than the combined thickness of the adhesive layer 20 and the optical film 30. The thickness T2 of the adhesive raw material component containing portion 40 varies depending on the thickness and composition of the adhesive layer 20 and the material of the optical film 30, and is, for example, 0.101 µm or more, and, for example, 6.5 µm or less. The thickness T2 of the adhesive raw material component containing portion 40 and the thickness of the aforementioned boundary region 31 can be measured using the method described later in the embodiments.

[0027] As described above, the laminated optical thin film X has a boundary region 31 on the adhesive layer 20 side of the optical thin film 30. The boundary region 31 contains a mixture of components of the optical thin film 30 and adhesive raw material components. Furthermore, in the laminated optical thin film X, the ratio of the thickness T2 of the adhesive raw material component-containing portion 40 (adhesive layer 20, boundary region 31) to the thickness T1 of the adhesive layer 20 is at least 1.01, preferably at least 1.05, more preferably at least 1.1, and more preferably at least 1.2. That is, in the laminated optical thin film X, the thickness T2 of the portion containing the adhesive raw material component and participating in the bonding function (adhesive layer 20 and boundary region 31) is greater than the thickness T1 of the adhesive layer 20. These configurations regarding the boundary between the optical thin film 30 and the adhesive layer 20 and their vicinity enable a strong interaction between the optical thin film 30 and the adhesive layer 20, thus ensuring high adhesion. Furthermore, ensuring the bonding force between the optical film 30 and the adhesive layer 20 helps to ensure the bonding force between the optical films 10 and 30 using the adhesive layer 20. Therefore, the laminated optical film X is suitable for ensuring bonding force between the optical films 10 and 30 even using a thin adhesive layer 20. Ensuring the bonding force between the optical films 10 and 30 is suitable for suppressing peeling between the optical films 10 and 30. Moreover, even in high temperature and high humidity environments, the laminated optical film X can still ensure bonding force between the optical films 10 and 30 using a thin adhesive layer 20, and is suitable for suppressing peeling between the optical films 10 and 30. Specifically, as shown in the embodiments and comparative examples described later.

[0028] In the laminated optical film X, the 90° peel strength of the optical film 30 to the optical film 10 at 25°C is preferably 0.8 N / 15 mm or more, more preferably 1 N / 15 mm or more, more preferably 1.2 N / 15 mm or more, and especially preferably 1.5 N / 15 mm or more. This configuration is suitable for achieving good adhesion between the optical films 10 and 30, and is particularly suitable for ensuring adhesion between the optical films 10 and 30 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 by the method described later in the embodiments. Furthermore, the method for adjusting the 90° peel strength can be, for example, adjusting the aforementioned ratio (T2 / T1) or adjusting the composition of the adhesive composition.

[0029] The ratio of the 90° peel strength (N / 15mm) to the first indentation modulus (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 advantageous in that, when the laminated optical film X (especially a thin laminated optical film X) is repeatedly bent, peeling between the optical films 10 and 30 can be suppressed.

[0030] The ratio of the 90° peel strength (N / 15mm) to the second indentation modulus (GPa) is preferably 0.2 or more, more preferably 0.3 or more, more preferably 0.4 or more, and preferably 5 or less, more preferably 3 or less, and more preferably 2 or less. This configuration is advantageous in that, when the laminated optical film X (especially a thin laminated optical film X) is repeatedly bent, peeling between the optical films 10 and 30 can be suppressed.

[0031] The adhesive layer 20 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. In this embodiment, the active energy line curing composition is either a free radical polymeric composition or a cationic polymeric composition, or both.

[0032] Free radical polymerizable compositions contain free radical polymerizable compounds as monomers. Free radical polymerizable compounds are compounds possessing free radical polymerizable functional groups. 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 curing properties of active energy line hardening compositions, active energy line hardening compositions preferably contain a free radical polymerizable compound possessing a (meth)acryl group as the main component. The main component refers to the component with the highest mass percentage. The proportion of free radical polymerizable compounds containing (meth)acryl groups in active energy line hardening compositions 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] Monofunctional free radical polymerizable compounds also include lactamine-based vinyl monomers. Examples of lactamine-based vinyl monomers include N-vinyl-2-pyrrolidone, N-vinyl-ε-caprolactone, and methylvinylpyrrolidone.

[0039] Monofunctional free radical polymerizable compounds may also include vinyl monomers having nitrogen-containing heterocycles. Examples of such monomers include: vinylpyridine, vinylpiperidinone, vinylpyrimidine, vinylpiperidine, vinylpyridine, vinylpyrrole, vinylimidazolium, vinylpyrazole, and vinylmorphofolin.

[0040] 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.

[0041] When the active energy line curing composition is an ultraviolet-curing composition or a visible light-curing composition, it contains 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-oxosulfuron and dodecyl 9-oxosulfur .

[0042] When the active energy line-curing composition is a visible light-curing composition, a photopolymerization initiator with high sensitivity to light above 380nm should be used. Examples of photopolymerization initiators include: 2-methyl-1-(4-methylthiophenyl)-2-mofolinylprop-1-one, 2-benzyl-2-dimethylamino-1-(4-mofolinylphenyl)-but-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-mofolinyl)phenyl]-1-butanone, 2,4,6-trimethylbenzoyl-diphenyl-phosphine 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.

[0043] The photopolymerization initiator should preferably be 2,4-diethyl-9-oxosulfuron. And / or 2-methyl-1-(4-methylthiophenyl)-2-methylfolinylprop-1-one.

[0044] For every 100 parts by weight of the hardening component (free radical polymerizable compound), the content of the photopolymerization initiator in the active energy line hardening component should preferably be 0.1 parts by weight or more, preferably 0.05 parts by weight or more, even more preferably 0.1 parts by weight or more, and preferably less than 20 parts by weight, preferably less than 10 parts by weight, even more preferably less than 5 parts by weight.

[0045] 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.

[0046] 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.

[0047] 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 adjust its viscosity and 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 20 and the optical films 10 and 30. Suppression of interfacial stress helps ensure adhesion between the optical films 10 and 30.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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).

[0053] The laminated optical thin film X can be manufactured, for example, in the following manner.

[0054] 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 30) 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.

[0055] Next, one optical film (optical film 30 or optical film 10) is laminated to one of the optical films over the component coating. The lamination can be performed using, for example, a roll laminator.

[0056] In terms of forming a boundary region 31 of sufficient thickness, the active energy line curing composition preferably contains a monomer with an SP value close to that of the resin in the optical film 30. When the active energy line curing composition contains the aforementioned monomer, during the coating and curing process of the active energy line curing composition, the monomer will dissolve into the surface of the optical film 30 before contacting it, thus easily forming the boundary region 31.

[0057] In the manufacturing process of the laminated optical thin film X, an active energy line is then irradiated onto the composition coating between optical thin films 10 and 30, causing the coating (an active energy line-cured composition) to harden (curing step). This forms an adhesive layer 20 between the optical thin films 10 and 30, and the optical thin films 10 and 30 are bonded through the adhesive layer 20 (the adhesive layer 20 is not a pressure-sensitive adhesive layer). 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 sources of ultraviolet and visible light 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 may also be used as needed to block a portion of the wavelength range of ultraviolet and / or visible light emitted from the light source.

[0058] As shown in Figure 3, the stacked optical film X can also have an optical film 30 bonded to both sides of the optical film 10 in the thickness direction H via an adhesive layer 20. The stacked optical film X (stacked optical film X') shown in Figure 3 sequentially comprises an optical film 30, an adhesive layer 20, an optical film 10, an adhesive layer 20, and an optical film 30 in the thickness direction H. The compositions of the active energy line curing components forming the two adhesive layers 20 can be the same or different. The materials of the two optical films 30 can be the same or different. The stacked optical film X' can be manufactured, for example, by further bonding the optical film 30 to the stacked optical film X of Figure 1 via the adhesive layer 20.

[0059] In the laminated optical thin film X', at least one optical thin film 30 has the aforementioned boundary region 31, and preferably two optical thin films 30 have the boundary region 31. In the laminated optical thin film X', taking each adhesive raw material component containing portion 40 formed by the boundary region 31 of each adhesive layer 20 and optical thin film 30 in contact with the adhesive layer 20 as an example, the ratio (T2 / T1) of the thickness T2 of the adhesive raw material component containing portion 40 to the thickness T1 of the adhesive layer 20 is 1.01 or more, preferably 1.05 or more, more preferably 1.1 or more, and more preferably 1.2 or more.

[0060] 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".

[0061] [Example 1] Mix the following components at 25°C for 1 hour according to the mixing amounts shown in Table 1 (mixing amounts based on solid content) to prepare the adhesive composition (preparation step). The mixing amounts shown in Table 1 are in relative "parts by mass".

[0062] LIGHT ACRYLATE POB-A (monomer): 3-phenoxybenzyl acrylate, manufactured by Kyoei Chemical Co., Ltd. LIGHT ACRYLATE P2H-A (monomer): Phenoxy diethylene glycol acrylate, manufactured by Kyoei Chemical Co., Ltd. ARONIX M-5700 (monomer): 2-hydroxy-3-phenoxypropyl acrylate, manufactured by Dong-A Synthetic Co., Ltd. ARONIX M-220 (monomer): Tripropylene glycol diacrylate, manufactured by Dong-A Synthetic Co., Ltd. HEAA (monomer): Hydroxyethyl acrylamide, manufactured by KJ Chemicals Corporation DEAA (monomer): Diethylacrylamide, manufactured by KJ Chemicals Corporation OMINIRAD907 (photopolymerization initiator): 2-Methyl-1-(4-methylthiophenyl)-2-morphofolinylprop-1-one, manufactured by IGM Resins. KAYACURE DETX-S (Photopolymerization Initiator): 2,4-Diethyl-9-oxosulfur Nippon Kayaku Co., Ltd. ARUFON 1190 (acrylic oligomer): viscosity 6000 mPa·s (25℃), Mw 1700, Tg -50℃, manufactured by Dong-A Synthetic Co., Ltd. BYK-UV3505 (Leveling Agent): Acrylic-modified polydimethylsiloxane, manufactured by BYK Corporation.

[0063] Then, in a roll-to-roll manner, while the long strip of transparent protective film is moved at a predetermined production line speed, the coating, lamination, and curing steps are performed sequentially. In the coating step, an adhesive composition is applied to a 23µm thick strip of COP film (brand name "ZeonorFilm ZF14", manufactured by ZEON Corporation, Japan), forming an adhesive coating film with a thickness of 0.9µm. 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). In the subsequent lamination step, a polarizing film (5µm thick) is laminated to the transparent protective film through the adhesive coating film. In the subsequent curing step, the adhesive coating film between the films is cured by irradiating it with ultraviolet light through the transparent protective film. Ultraviolet irradiation is performed using a gallium lamp. In this way, a multilayer optical film is obtained by bonding a transparent protective film and a polarizing film.

[0064] 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.

[0065] [Example 2] Except for the following, the multilayer optical film of Example 2 was produced in the same manner as the multilayer optical film of Example 1. The speed of the above production line was increased by a predetermined amount, and the time from the coating step to the curing step was shortened. The coating thickness to be formed on the transparent protective film (COP film) in the coating step was set to 2.6µm.

[0066] The multilayer optical film of Example 2 has a polarizing film (thickness 5µm), an adhesive layer and a transparent protective film (thickness 23µm) sequentially in the thickness direction.

[0067] [Example 3] Except for the following, the multilayer optical film of Example 3 was produced in the same manner as the multilayer optical film of Example 1. The speed of the above production line was reduced by a predetermined degree, and the time from the coating step to the curing step was increased. The coating thickness to be formed on the transparent protective film (COP film) in the coating step was set to 1.2µm.

[0068] The multilayer optical film of Example 3 has a polarizing film (thickness 5µm), an adhesive layer and a transparent protective film (thickness 23µm) sequentially in the thickness direction.

[0069] [Comparative Example 1] Except for the following, the composite optical film of Comparative Example 1 was produced in the same manner as the composite optical film of Example 1 (the production line speed between the coating step and the curing step was the same as that of Example 1).

[0070] In the preparation step, the adhesive composition (components, blending amounts) shown in Table 1 was prepared. In the monomers, 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" (neopentyl 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".

[0071] The coating thickness to be formed on the transparent protective film (COP film) in the coating step is set to 0.93µm.

[0072] The composite optical film of Comparative Example 1 has a polarizing film (thickness 5µm), an adhesive layer and a transparent protective film (thickness 23µm) sequentially in the thickness direction.

[0073] <Adhesive layer thickness> The thickness T1 of the adhesive layer in each of the stacked optical films of Examples 1-3 and Comparative Example 1 was measured as follows. First, a 5mm × 10mm film sheet (stacked optical film) was cut from the stacked optical film. Next, the stacked optical film was cut using a freeze-cutting method. Specifically, after cooling the stacked 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 a stacked optical film with a cut surface, and then a conductive treatment of less than 5nm thickness was performed on the cut surface. This yielded a sample for observation. Next, the thickness of the adhesive layer was measured by SEM observation of the sample for observation. Specifically, a scanning electron microscope (product name "REGULUS8220", manufactured by HITACHI Corporation) was used to observe and capture secondary electron images of the cut surface of the sample for observation, and the thickness of the adhesive layer was measured. In this observation, the accelerating voltage was set to 3.0 kV, the current to 10 µA, the working distance to 8 mm, the magnification to 100,000 times, and the detection mode to Upper+Lower mode. The adhesive layer thickness T1 (µm) is shown in Table 1.

[0074] <Thickness of adhesive raw material components> The thickness T2 of the adhesive raw material content in each laminated optical film of Examples 1-3 and Comparative Example 1 was measured as follows. First, using a slicing machine, the transparent protective film of the film sheet cut from the laminated optical film was removed from the surface side of the transparent protective film to a predetermined depth to thin it. This yielded the test sample. Next, the test sample was analyzed from the transparent protective film side using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The analysis was performed using a time-of-flight secondary ion mass spectrometer (TRIFT-V nanoTOF, manufactured by ULVAC-PHI). In this analysis, the etching ion beam and the subsequent measurement ion beam (primary ion beam) were alternately irradiated. For the etching ion beam, Ar gas cluster ions (cluster size (central value) 2500) were used, with an accelerating voltage of 20 kV, an ion beam current of 10 nA, an irradiation range of 1000 µm × 1000 µm, and an irradiation time of 5 seconds. For the measurement ion beam, bismuth cluster double-charged ions (Bi33) were used. (++) As the irradiation of ions, the accelerating voltage was set to 30 kV, and the irradiation range was set to the central part of the irradiation area of ​​the etching ion beam, 200 µm × 200 µm. A neutralization gun was used to correct the charge of the sample in the analysis. Furthermore, this analysis was performed at room temperature. Through this analysis, depth profiles of the mass spectra of secondary ion (positive and negative) intensities were obtained. Regarding the secondary ion intensities, for positive ions, the values ​​are converted to a baseline of C3H5+, and for negative ions, the values ​​are converted to a baseline of C2H5+. - The value is the value when the baseline value is 1. Next, based on the obtained depth direction profile, the region (boundary region) where the adhesive raw material component in the transparent protective film is detected to be above the detection limit value (positive and negative ion intensity 0.1 counts / second) is identified. Then, the thickness T2 of the adhesive raw material component containing the portion is calculated from the thickness of this boundary region and the aforementioned thickness T1 of the adhesive layer. Its thickness T2 (µm) is shown in Table 1. Also, the ratio of thickness T2 to thickness T1 is shown in Table 1.

[0075] <Peel strength> The peel strength between the transparent protective film and the polarizing film in each of the laminated optical films of Examples 1-3 and Comparative Example 1 was investigated. First, a sample film with dimensions of 200 mm on the first side and 15 mm on the second side was cut from the laminated optical film. The first side extends along the extension direction of the polarizing film. The second side extends along a direction orthogonal to the aforementioned extension direction. Next, the polarizing film side of the sample film was adhered to a glass plate using a strong adhesive. Then, the 90° peel strength (N / 15 mm) of the transparent protective film peeling from the polarizing film was measured using a TENSILON universal testing machine (product name "RTC", manufactured by A&D Company, Limited). In this measurement, the measurement temperature was set to 25°C, the peel angle to 90°, and the peel speed to 1000 mm / min. The measured 90° peel strength is shown as peel strength F1 in Table 1.

[0076] <Indentation modulus> The elastic modulus of the adhesive layer in each laminated optical film of Examples 1-3 and Comparative Example 1 was investigated using nanoindentation. Specifically, a 5mm × 10mm film sheet (laminated optical film) was first cut from the laminated optical film. Next, the laminated optical film was cut using a 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 a sample for testing. Then, using a nanoindentation testing machine (product name "TI950 Triboindenter", manufactured by Hysitron Corporation), load-displacement measurements were performed on the exposed surface of the adhesive layer in the sample according to JIS Z 2255:2003 to obtain load-displacement curves. 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 200 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 (first measurement condition). Then, the obtained measurement data were 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 projected 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 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 in Table 1 as the indentation modulus M1 (GPa) (the indentation modulus M1 is the first indentation modulus mentioned above). Also, the ratio of peel strength F1 to indentation modulus M1 (F1 / M1) is shown in Table 1.

[0077] On the other hand, except that the maximum indentation depth was changed from 200 nm to 50 nm, load-displacement measurements were performed using a nano-indenter under the same measurement conditions as the first measurement condition (the second measurement condition). Then, the measurement data was processed using the dedicated analysis software (Ver. 9.4.0.1) of the "TI950 Triboindenter" to calculate the indentation elastic modulus of the adhesive layer. This value is shown in Table 1 as the indentation elastic modulus M2 (GPa) (the indentation elastic modulus M2 is the second indentation elastic modulus mentioned above). Furthermore, the ratio of peel strength F1 to indentation elastic modulus M2 (F1 / M2) is also shown in Table 1.

[0078] High Temperature and High Humidity Flexural Test High temperature and high humidity flexural tests were conducted on each of the laminated optical films of Examples 1-3 and Comparative Example 1 in the following manner.

[0079] First, evaluation samples were prepared. Specifically, the exposed surface of the polarizing film of the multilayer optical film was first bonded to the adhesive surface of an adhesive layer with a release liner attached to one side. This bonding was performed at 23°C by pressing the surface of the polarizing film of the multilayer optical film and the surface of the adhesive layer together by pressing a 2kg roller back and forth once (the bonding described below was also performed under the same conditions). Next, after peeling off the release liner from the adhesive layer, the exposed adhesive sheet surface was obtained, and a polyethylene terephthalate (PET) film (brand name "DIAFOIL", thickness 125µm, manufactured by Mitsubishi Chemical Co.) was bonded to this exposed surface. This yielded a multilayer film. The adhesive layer with a release liner attached to one side was prepared as follows.

[0080] First, in a reaction vessel equipped with a reflux cooling pipe, a nitrogen inlet pipe, a thermometer, and a stirrer, a mixture containing 100 parts by weight of n-butyl acrylate, 3 parts by weight of acrylic acid, 0.1 parts by weight of 2-hydroxyethyl acrylate, 0.3 parts by weight of 2,2'-azobisisobutyronitrile (2,2'-azobisisobutyronitrile) as a thermal polymerization initiator, and ethyl acetate as a solvent was stirred at 55°C under nitrogen atmosphere for 8 hours (polymerization reaction). This yielded a polymer solution containing an acrylic base polymer. The weight average molecular weight of the acrylic base polymer in this polymer solution was approximately 2.2 million. Next, for every 100 parts by weight of the acrylic base polymer, 0.5 parts by weight of a crosslinking agent (product name "CORONATE L", manufactured by Polyurethane Japan) and 0.075 parts by weight of a silane coupling agent (product name "KMB-403", γ-epoxypropoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Industry) were added and mixed to prepare an adhesive solution. Next, an adhesive solution is applied to the peel-off surface of the release liner to form a coating (20µm thick). The release liner is a polyethylene terephthalate film (38µm thick) that has undergone a predetermined peel-off treatment. The coating on the release liner is then dried to form an adhesive layer.

[0081] When preparing the evaluation specimen, the evaluation specimen is then cut from the multilayer film prepared in the manner described above. Specifically, a rectangular specimen of 25 mm × 100 mm is cut from the multilayer film in such a way that the absorption axis direction of the polarizing film in the specimen to be cut is parallel to the long side direction.

[0082] Next, a flexural test was performed on the specimen using a planar unloaded U-shaped stretching tester (manufactured by YUASA SYSTEM). In this test, flexural fixtures were installed at both ends of the specimen along its long side, within a range of 20 mm from the edge of the specimen, and the specimen was then fixed in the tester (the central 60 mm area along the long side of the specimen was unfixed). Furthermore, in this test, the specimen was repeatedly deformed (flexed) 200,000 times in a constant temperature and humidity chamber at a temperature of 60°C and a relative humidity of 90%, with a flexural speed of 60 rpm, alternating between a flexed and non-flexed state on the inner side of the polarizer film. Specifically, the flexural state in this test refers to a state where the axis of the bending moment acting on the specimen is orthogonal to the absorption axis of the polarizer film. In this flexural state, the bending radius of the specimen was set to 3 mm, and the bending angle was set to 180°. Then, regarding the peeling inhibition between films (transparent protective film, polarizing film) in the flexural test, the situation where no peeling occurred between films after 200,000 flexes was evaluated as "excellent", the situation where peeling occurred after 80,000 to 200,000 flexes was evaluated as "good", and the situation where peeling occurred after less than 80,000 flexes was evaluated as "poor". The evaluation results are shown in Table 1.

[0083] [Table 1]

[0084] X,X': Stacked optical thin films 10: Optical Thin Films (First Optical Thin Film) 20: Adhesive layer 30: Optical Thin Film (Second Optical Thin Film) 31: Boundary Area 32: Non-boundary area 40: Adhesive raw material components contain part H: Thickness direction T1: Thickness of the adhesive layer T2: Thickness of the adhesive raw material component

Claims

1. A laminated optical thin film, comprising, sequentially in a thickness direction, a first optical thin film, an adhesive layer, and a second optical thin film; wherein the adhesive layer is bonded to both the first and second optical thin films; the second optical thin film has a boundary region on the side of the adhesive layer, the boundary region containing adhesive raw material components derived from the adhesive layer; the ratio of the thickness T2 of the adhesive raw material containing portion to the thickness T1 of the adhesive layer is [formula missing]. 1.01 or higher, the adhesive raw material composition includes a portion that is formed by the combination of the aforementioned adhesive layer and the aforementioned boundary region; and the aforementioned second optical film has a 90° peel strength of 0.8 N / 15 mm or higher against the aforementioned first optical film at 25°.

2. A laminated optical thin film, comprising a first optical thin film, an adhesive layer, and a second optical thin film sequentially in the thickness direction; wherein the adhesive layer is a cured product of an active energy line curing composition; wherein the adhesive layer is bonded to the first optical thin film and to the second optical thin film; wherein the second optical thin film has a boundary region on the side of the adhesive layer, the boundary region containing an adhesive raw material component derived from the adhesive layer; and wherein the ratio of the thickness T2 of the adhesive raw material component portion to the thickness T1 of the adhesive layer is 1.01 or more and 1.3 or less, the adhesive raw material component portion being a portion formed by the merging of the adhesive layer and the boundary region.

3. The laminated optical thin film as claimed in claim 1 or 2, wherein the aforementioned thickness T1 is less than 5µm.

4. The laminated optical film as claimed in claim 1 or 2, wherein the aforementioned first optical film is a polarizing film.

Images