KR20240004224A - Laminated Optical Film - Google Patents

Abstract

The laminated optical film (X) of the present invention includes an optical film (10), optical films (21, 22), and adhesive layers (31, 32). The adhesive layer 31 is bonded to the optical film 10 and is also bonded to the optical film 21 . The adhesive layer 32 is bonded to the optical film 10 and is also bonded to the optical film 22 . The indentation elastic modulus E1 of the adhesive layer 31 at 25°C and the indentation elasticity modulus E2 of the adhesive layer 32 at 25°C satisfy 0.3≤E2/E1<1.

Description

Laminated Optical Film

The present invention relates to laminated optical films.

The display panel has a laminated structure including, for example, a pixel panel, a touch panel, and a surface protective cover. The laminated structure of the display panel also includes various functional optical films that have certain optical functions. Examples of functional optical films include polarizer films and retardation films. The functional optical film is included in a laminated structure, for example, in a state in which another optical film such as a protective film is bonded to both sides of the film via an adhesive, that is, in the form of a laminated optical film. Such a laminated optical film is described, for example, in Patent Document 1 below.

Japanese Patent Publication No. 2019-147865

For example, the development of display panels that can be repeatedly bent (foldable) is in progress for smartphones and tablet terminals. In a foldable display panel, each element in the laminated structure is manufactured so that it can be repeatedly bent. Additionally, at bending points of the foldable display panel, tensile stress occurs in the optical film outside the bend in the laminated optical film. Conventionally, this tensile stress generates a photoelastic effect in the optical film outside the bend at the bending point, causing birefringence of light passing through the film. Birefringence of transmitted light is undesirable as it causes display unevenness in image display on the display panel. In particular, when the foldable display panel is repeatedly bent and used over a long period of time, display unevenness is likely to occur due to the birefringence due to the hardness of the adhesive layer disposed outside the bend.

The present invention provides a laminated optical film suitable for suppressing display unevenness when bending a foldable display panel.

The present invention [1] is a laminated optical film comprising a first optical film, a first adhesive layer, a second optical film, a second adhesive layer, and a third optical film in that order in the thickness direction, wherein the first An adhesive layer is bonded to the first optical film and also bonded to the second optical film, the second adhesive layer is bonded to the second optical film and also bonded to the third optical film, and the first adhesive layer It includes a laminated optical film in which the indentation elastic modulus E1 at 25°C and the indentation elasticity modulus E2 at 25°C of the second adhesive layer satisfy 0.3≤E2/E1<1.

The present invention [2] includes the laminated optical film according to [1] above, wherein the indentation elastic modulus E2 is 4 GPa or less.

The present invention [3] includes the laminated optical film according to [1] or [2] above, wherein the indentation elastic modulus E2 is 0.4 GPa or more.

The present invention [4] includes the laminated optical film according to any one of [1] to [3] above, wherein the indentation elastic modulus E1 is 0.5 GPa or more.

The present invention [5] includes the laminated optical film according to any one of [1] to [4] above, wherein the indentation elastic modulus E1 is 7 GPa or less.

The present invention [6] includes the laminated optical film according to any one of [1] to [5] above, wherein the second optical film is a polarizer film.

In the laminated optical film of the present invention, as described above, the indentation elastic modulus E1 of the first adhesive layer and the indentation elastic modulus E2 of the second adhesive layer satisfy 0.3≤E2/E1<1. The second adhesive layer has flexibility with a small indentation elastic modulus E2 such that the ratio (E2/E1) is less than 1. This second adhesive layer is suitable for relieving the tensile stress generated in the third optical film at the bent location when the laminated optical film is bent so that the third optical film is on the outside of the bend. At the bent portion of the third optical film, the above-described photoelastic effect is reduced by relaxation of the tensile stress, thereby suppressing display unevenness in image display on the display panel. Additionally, a second adhesive layer having an indentation elastic modulus E2 so large that the ratio (E2/E1) is 0.3 or more is suitable for ensuring bonding force between the second and third optical films at the bending point.

1 is a cross-sectional schematic diagram of one embodiment of the laminated optical film of the present invention.
FIG. 2 shows the laminated optical film shown in FIG. 1 in a bent state.

As shown in FIG. 1, the laminated optical film (X) as one embodiment of the laminated optical film of the present invention includes an optical film 10, optical films 21 and 22, and adhesive layers 31 and 32. Equipped with Specifically, the laminated optical film The adhesive layer 32 (second adhesive layer) and the optical film 22 (third optical film) are provided in that order in the thickness direction H. The laminated optical film (X) has a sheet shape with a predetermined thickness and extends in a direction (plane direction) perpendicular to the thickness direction (H). The adhesive layer 31 bonds the optical films 10 and 21 together. The adhesive layer 32 bonds the optical films 10 and 22 together. Additionally, the laminated optical film (X) is a composite film included in the laminated structure of the foldable display panel. The laminated optical film (X) is, for example, a laminated optical film disposed on the image display side surface of a display panel such as a foldable organic EL panel (OLED panel). In the foldable display panel, the laminated optical film (X) is bent so that the optical film 21 and adhesive layer 31 sides are inside, as shown in FIG. 2 . At the bent location B, the optical film 21 and the adhesive layer 31 are inside the bend (lower side in the figure) with respect to the optical film 10, and the optical film 22 and the adhesive layer 32 are inside the optical film 10. It is on the outside of the curve (upper side in the drawing) with respect to (10).

The optical film 10 is a functional optical film in this embodiment. Examples of functional optical films include polarizer films and retardation films.

Examples of the polarizer film include hydrophilic polymer films that have been dyed with a dichroic substance and subsequently subjected to stretching. 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 copolymer. As a polarizer film, a polyene orientation film is also listed. Examples of materials for the polyene orientation film include dehydrated PVA and dehydrochlorinated polyvinyl chloride. As a polarizer film, a PVA film that has been dyed with iodine and subsequently uniaxially stretched is preferred because it has excellent optical properties such as polarization properties.

From the viewpoint of thinning, the thickness of the optical film 10 as a polarizer film is preferably 15 μm or less, more preferably 12 μm or less, further preferably 10 μm or less, and particularly preferably 8 μm or less. A thin polarizer film has excellent visibility because there is little thickness unevenness, and also has excellent durability against thermal shock because dimensional changes due to temperature changes are small. The thickness of the optical film 10 as a polarizer film is preferably 3 μm or more, more preferably 5 μm or more from the viewpoint of strength.

Examples of the retardation film include λ/2 wavelength film, λ/4 wavelength film, and viewing angle compensation film. As a material for the retardation film, for example, a polymer film birefringent through stretching treatment is listed. Examples of polymer films include cellulose films and polyester films. Examples of the cellulose film include triacetylcellulose film. Examples of the polyester film include polyethylene terephthalate film and polyethylene naphthalate film. The thickness of the optical film 10 as a retardation film is, for example, 20 μm or more, for example, 150 μm or less. Additionally, as a retardation film, a film comprising a substrate such as a cellulose film and an alignment layer of a liquid crystal compound such as a liquid crystal polymer on the substrate can also be preferably used.

The optical films 21 and 22 are each transparent protective film. The transparent protective film is, for example, a flexible transparent resin film. Examples of materials for the transparent protective film include polyolefin, polyester, polyamide, polyimide, polyvinyl chloride, polyvinylidene chloride, cellulose, modified cellulose, polystyrene, and polycarbonate. Examples of polyolefins include cycloolefin polymer (COP), polyethylene, polypropylene, ethylene/propylene copolymer, ethylene/vinyl acetate copolymer, and ethylene/vinyl alcohol copolymer. Examples of polyester include polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate. Examples of polyamides include polyamide 6, polyamide 6,6, and partially aromatic polyamide. Examples of modified cellulose include triacetylcellulose. These materials may be used individually, or two or more types may be used together. As a material for the transparent protective film, from the viewpoint of cleanliness, polyolefin is preferably used, and COP is more preferably used. In addition, the material of the optical film 21 and the material of the optical film 22 may be the same or different.

From the viewpoint of the strength of the laminated optical film From the viewpoint of reducing the thickness of the laminated optical film The thickness of the optical film 21 and the thickness of the optical film 22 may be the same or different.

The adhesive layer 31 is a cured product of the first adhesive composition. The adhesive layer 31 is directly bonded to the optical film 10 and also directly bonded to the optical film 21. The first adhesive composition contains a curable resin. The components of the first adhesive composition are specifically as described below.

The thickness T1 of the adhesive layer 31 is preferably 0.1 μm or more, more preferably 0.4 μm or more, further preferably 0.7 μm or more, especially preferably, from the viewpoint of bonding force between the optical films 10 and 21. It is 0.8㎛ or more. From the viewpoint of reducing the thickness of the laminated optical film It is as follows.

The indentation elastic modulus E1 at 25°C of the adhesive layer 31 measured by the nanoindentation method is preferably 0.5 GPa or more, more preferably 1 GPa or more, further preferably 1.5 GPa or more, especially preferably 2 GPa. That's it. This configuration is preferable for ensuring bonding force between the optical films 10 and 21 at the bending point B when the laminated optical film X is bent so that the optical film 21 side is inside. The indentation elastic modulus E1 is preferably 7 GPa or less, more preferably 6 GPa or less, and even more preferably 5.2 GPa or less. This configuration is desirable for relieving the compressive stress acting on the adhesive layer 31 at the bending point B. At the bending point B, the relaxation of the compressive stress of the adhesive layer 31 is helpful in suppressing peeling between the optical films 10 and 21. In addition, the above-mentioned configuration regarding the upper limit of the indentation elastic modulus E1 ensures low elasticity in the adhesive layer 31 (adhesive layer inside the bend) at the bending point B, so that it has an elasticity with respect to the optical films 10 and 21. This is desirable for obtaining sufficient adhesion, and is therefore suitable for suppressing buckling of the optical film 10 at the bending point B. As a method of adjusting the indentation elastic modulus E1 of the adhesive layer 31, for example, adjustment of the composition of the first adhesive composition is listed. Specifically, adjustment of the number of functional groups of the polymerizable compound described later in the first adhesive composition, that is, adjustment of the acrylic equivalent or epoxy equivalent of the polymerizable compound, is effective as a method of adjusting the indentation elastic modulus E1 of the adhesive layer 31.

Nanoindentation is a technology that measures all physical properties of a sample on a nanometer scale. In this embodiment, the nanoindentation method is performed based on ISO14577. In the nanoindentation method, a process of indenting an indenter into a sample set on a stage (load application process) and later a process of pulling the indenter from the sample (unloading process) are performed. Among the series of processes, the indenter -The load acting between the samples and the relative displacement of the indenter with respect to the sample are measured (load-displacement measurement). By this, it is possible to obtain a load-displacement curve. From this load-displacement curve, it is possible to obtain, for the measurement sample, all physical properties based on nanometer scale measurements. For load-displacement measurement of the cross section of the adhesive layer by the nanoindentation method, for example, a nano indenter (trade name "Triboindenter", manufactured by Hysitron) can be used. Specifically, examples will be described later.

The adhesive layer 32 is a cured product of the second adhesive composition. The adhesive layer 32 is directly bonded to the optical film 10 and is also directly bonded to the optical film 22. The second adhesive composition contains a curable resin. The components of the second adhesive composition are specifically as described below.

The thickness T2 of the adhesive layer 32 is preferably 0.1 μm or more, more preferably 0.4 μm or more, further preferably 0.7 μm or more, particularly preferably 0.8 from the viewpoint of bonding strength between the optical films 10 and 22. It is more than ㎛. From the viewpoint of reducing the thickness of the laminated optical film It is as follows. The thickness T2 of the adhesive layer 32 and the thickness T1 of the adhesive layer 31 described above may be the same or different. Additionally, the ratio (T2/T1) of thickness T2 to thickness T1 is, for example, 0.5 or more, and is, for example, 2 or less.

The indentation elastic modulus E2 at 25°C measured by the nanoindentation method of the adhesive layer 32 is within a limit smaller than the indentation elastic modulus E1, and is preferably 0.4 GPa or more, more preferably 0.8 GPa or more, even more preferably is 1.2 GPa or more, particularly preferably 1.8 GPa or more. The indentation elastic modulus E2 is within the limit of being smaller than the indentation elastic modulus E1, and is preferably 4 GPa or less, more preferably 3 GPa or less, and even more preferably 2.5 GPa or less. These configurations are desirable for ensuring adhesion between the optical films 10 and 22. As a method of adjusting the indentation elastic modulus E2 of the adhesive layer 32, for example, adjustment of the composition of the second adhesive composition is listed. Specifically, adjustment of the number of functional groups of the polymerizable compound described later in the second adhesive composition, that is, adjustment of the acrylic equivalent or epoxy equivalent of the polymerizable compound, is effective as a method of adjusting the indentation elastic modulus E2 of the adhesive layer 32.

The indentation elastic modulus E1 of the adhesive layer 31 at 25°C and the indentation elasticity modulus E2 of the adhesive layer 32 at 25°C satisfy 0.3≤E2/E1<1.

The adhesive layer 32 has flexibility such that the ratio (E2/E1) is less than 1 and the indentation elastic modulus E2 is small. This adhesive layer 32 is suitable for relieving the tensile stress generated in the optical film 22 at the bent location B when the laminated optical film X is bent so that the optical film 22 is on the outside of the bend. . At the bent portion of the optical film 22, the photoelastic effect is reduced by relaxation of the tensile stress, and display unevenness in image display on the display panel is suppressed. From this point of view, the ratio (E2/E1) is preferably 0.97 or less, more preferably 0.8 or less.

In addition, the adhesive layer 32 having a press-fit elastic modulus E2 such that the ratio (E2/E1) is 0.3 or more is suitable for securing the bonding force between the optical films 10 and 22 at the bending point B. In addition, the adhesive layer 31 having a small indentation elastic modulus E1 such that the ratio (E2/E1) is 0.3 or more has low elasticity in the adhesive layer 31 (adhesive layer inside the bend) at the bending point B. This is desirable to ensure sufficient adhesion to the optical films 10 and 21, and is therefore suitable for suppressing buckling of the optical film 10 at the bending point B. From these viewpoints, the ratio (E2/E1) is preferably 0.5 or more, more preferably 0.6 or more.

As a method of adjusting the ratio (E2/E1), adjustment of the indentation elastic modulus E1 and adjustment of the indentation elasticity modulus E2 are listed.

In the laminated optical film More preferably, it is 1.2N/15mm or more, and particularly preferably, is 1.5N/15mm or more. This configuration is desirable for ensuring good bonding strength between the optical films 10 and 21, and in particular, when the laminated optical film , it is desirable to secure it. Additionally, the 90° peel strength F1 is, for example, 10 N/15 mm or less. The 90° peel strength F1 can be measured by the method described later in Examples. The peeling strength of the optical film 21 with respect to the optical film 10 is the force required to peel the optical film 21 from the optical film 10, and the peeling involves the optical film 10 and the adhesive layer ( 31) This includes interfacial peeling, peeling due to cohesive failure of the adhesive layer 31, interfacial peeling between the adhesive layer 31 and the optical film 21, and peeling due to a combination thereof. Additionally, as a method for adjusting the 90° peel strength F1, for example, adjusting the composition of the first adhesive composition is listed. Specific examples of the method for adjusting the 90° peel strength F1 include adjusting the number of functional groups of the polymerizable compound described later in the first adhesive composition, that is, adjusting the acrylic equivalent or epoxy equivalent of the polymerizable compound.

In the laminated optical film More preferably, it is 1.2N/15mm or more, and particularly preferably, is 1.5N/15mm or more. This configuration is desirable for ensuring good bonding strength between the optical films 10 and 22, and in particular, when the laminated optical film , it is desirable to secure it. In addition, the 90° peel strength F2 is, for example, 10 N/15 mm or less. The 90° peel strength F2 can be measured by the method described later in Examples. The peeling strength of the optical film 22 with respect to the optical film 10 is the force required to peel the optical film 22 from the optical film 10, and the peeling involves the optical film 10 and the adhesive layer ( 32) This includes interfacial peeling, peeling due to cohesive failure of the adhesive layer 32, interfacial peeling between the adhesive layer 32 and the optical film 22, and peeling due to a combination thereof. Additionally, as a method for adjusting the 90° peel strength F2, for example, adjustment of the composition of the second adhesive composition is listed. Specific examples of the method for adjusting the 90° peel strength F2 include adjusting the number of functional groups of the polymerizable compound described later in the second adhesive composition, that is, adjusting the acrylic equivalent or epoxy equivalent of the polymerizable compound.

The adhesive layer 31 is, for example, a cured product of the first adhesive composition (first active energy ray-curable composition) containing an active energy ray-curable resin. Examples of the first active energy ray curable composition include electron beam curable composition, ultraviolet ray curable composition, and visible ray curable composition. In addition, in this embodiment, the first active energy ray-curable composition is one or both of a radical polymerization type composition and a cation polymerization type composition.

When the first active energy ray-curable composition is a radically polymerizable composition, the composition contains a radically polymerizable compound as a monomer. A radically polymerizable compound is a compound having a radically polymerizable functional group. Examples of radically polymerizable functional groups include ethylenically unsaturated bond-containing groups. Examples of ethylenically unsaturated bond-containing groups include (meth)acryloyl group, vinyl group, and allyl group. (meth)acryloyl group means acryloyl group and/or methacryloyl group. From the viewpoint of curability of the first active energy ray-curable composition, the first active energy ray-curable composition preferably contains a radically polymerizable compound having a (meth)acryloyl group as a main component. The main component refers to the component that is most abundant in terms of mass ratio. The proportion of the (meth)acryloyl group-containing radically polymerizable compound in the first active energy ray-curable composition is, for example, 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more. am. Additionally, examples of the radically polymerizable compounds include monofunctional radically polymerizable compounds and bifunctional or more polyfunctional radically polymerizable compounds.

Examples of monofunctional radically polymerizable compounds include (meth)acrylamide derivatives having a (meth)acrylamide group. As (meth)acrylamide derivatives, (meth)acrylamide derivatives containing an N-alkyl group, (meth)acrylamide derivatives containing an N-hydroxyalkyl group, (meth)acrylamide derivatives containing an N-aminoalkyl group, (meth)acrylamide derivatives containing an N-alkoxy group ( Meth)acrylamide derivatives, and N-mercaptoalkyl group-containing (meth)acrylamide derivatives are listed. Examples of N-alkyl group-containing (meth)acrylamide derivatives include N-methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, and N- Isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, and N-hexyl(meth)acrylamide are listed, and N,N-diethylacrylamide is preferably used. Examples of N-hydroxyalkyl group-containing (meth)acrylamide derivatives include N-methylol (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, and N-methylol-N-propane (meth)acrylamide. ) Acrylamides are listed, and N-hydroxyethyl acrylamide is preferably used. The (meth)acrylamide derivative may be used individually, or two or more types may be used together.

Examples of monofunctional radically polymerizable compounds include (meth)acrylic acid derivatives having a (meth)acryloyloxy group. Examples of the (meth)acrylic acid derivatives include (meth)acrylic acid alkyl esters and (meth)acrylic acid derivatives other than (meth)acrylic acid alkyl esters. (meth)acrylic acid derivatives may be used individually, or two or more types may be used together.

Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, and n-butyl (meth)acrylate. Acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, 2,2-dimethylbutyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate and n-octadecyl (meth)acrylate are listed.

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

Monofunctional radically polymerizable compounds also include carboxyl group-containing monomers. Examples of carboxyl group-containing monomers include (meth)acrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

As monofunctional radically polymerizable compounds, lactam-based vinyl monomers are also listed. Examples of lactam-based vinyl monomers include N-vinyl-2-pyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone.

Examples of monofunctional radically polymerizable compounds include vinyl monomers having a nitrogen-containing heterocycle. Examples of the monomers include vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, acryloylmorpholine, and vinylmorpholine. do.

Examples of polyfunctional radically polymerizable compounds include tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and 1,9-nonanedi. Old-(meth)acrylate, 1,10-decanediol diacrylate, 2-ethyl-2-butylpropanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, tricyclodecane dimethanol di( Meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, dioxane glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol Tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate are used, preferably tripropylene glycol diacrylate and hydroxypivalic acid neopentyl glycol acrylic acid adduct. These are listed. As the polyfunctional radically polymerizable compound, at least one selected from the group consisting of tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, and hydroxypivalic acid neopentyl glycol acrylic acid adduct is preferably used. . The polyfunctional radically polymerizable compound may be used individually, or two or more types may be used together. The polyfunctional radically polymerizable compound functions as a crosslinking agent.

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

When the first active energy ray-curable composition is a visible light-curable composition, a photopolymerization initiator that is highly sensitive to light of 380 nm or more is preferably used. Such photopolymerization initiators include, for example, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholy) Nophenyl)-butanone-1,2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2,4 ,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and bis(η5-2,4-cyclopentadien-1-yl)-bis( 2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium is listed.

As a photopolymerization initiator, 2,4-diethylthioxanthone and/or 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one is preferably used.

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

When the first active energy ray-curable composition is a cationically polymerizable composition, the composition contains a cationically polymerizable compound as a monomer. Cationically polymerizable compounds are compounds having a cationically polymerizable functional group, and include monofunctional cationically polymerizable compounds having one cationically polymerizable functional group, and polyfunctional cationically polymerizable compounds having two or more cationically polymerizable functional groups. Monofunctional cationic polymerizable compounds have relatively low liquid viscosity. By blending such a monofunctional cationically polymerizable compound into the resin composition, the viscosity of the resin composition is reduced. In addition, monofunctional cationic polymerizable compounds often have functional groups that express various functions. By blending such a monofunctional cationically polymerizable compound into a resin composition, various functions are expressed in the resin composition and/or a cured product of the resin composition. On the other hand, by curing a resin composition containing a polyfunctional cationically polymerizable compound, a cured product having a three-dimensional crosslinked portion is obtained (the polyfunctional cationically polymerizable compound functions as a crosslinking agent). From this point of view, the use of polyfunctional cationically polymerizable compounds is desirable. When using a monofunctional cationic polymerizable compound and a polyfunctional cationic polymerizable compound together, the amount of the polyfunctional cationic polymerizable compound relative to 100 parts by mass of the monofunctional cationic polymerizable compound is, for example, 10 parts by mass or more. For example, it is 1000 parts by mass or less. Examples of cationically polymerizable functional groups include epoxy group, oxetanyl group, and vinyl ether group. Examples of compounds having an epoxy group include aliphatic epoxy compounds, alicyclic epoxy compounds, and aromatic epoxy compounds. As the compound having an epoxy group, an alicyclic epoxy compound is preferably used from the viewpoint of curability and adhesiveness of the cationically polymerizable composition. Examples of the alicyclic epoxy compound include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate or 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate. Caprolactone denatures, trimethylcaprolactone denatures, and valerolactone denatures are listed. Examples of commercially available alicyclic epoxy compounds include Celoxide 2021, Celoxide 2021A, Celoxide 2021P, Celoxide 2081, Celoxide 2083, and Celoxide 2085 (manufactured by Daicel Chemical Industries, Ltd.). , Cyracure UVR-6105, Cyracure UVR-6107, Cyracure 30, and R-6110 (manufactured by Dow Chemical Japan) are also listed. From the viewpoint of improving the curability and lowering the viscosity of the cationically polymerizable composition, it is preferable to use a compound having an oxetanyl group and/or a compound having a vinyl ether group. Examples of compounds having an oxetanyl group include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl]benzene, and 3-ethyl- 3-(phenoxymethyl)oxetane, di[(3-ethyl-3-oxetanyl)methyl]ether, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, and phenolnovolaxoxetane. These are listed. Commercially available compounds having an oxetanyl group include, for example, Aaronoxetane OXT-101, Aaronoxetane OXT-121, Aaronoxetane OXT-211, Aaronoxetane OXT-221, and Aaronoxetane OXT-212 (above , manufactured by Toagosei Co., Ltd.) are listed. Examples of compounds having a vinyl ether group include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, triethylene glycol divinyl ether, and cyclohexanedi. Methanol divinyl ether, cyclohexanedimethanol monovinyl ether, tricyclodecane vinyl ether, cyclohexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, and pentaerythritol type tetravinyl ether are listed.

When the first active energy ray curable composition is an ultraviolet ray curable composition or a visible ray curable composition, the first active energy ray curable composition contains a photo cationic polymerization initiator. The photo cationic polymerization initiator is irradiated with active energy rays (visible rays, ultraviolet rays, As photocationic polymerization initiators, photoacid generators and photobase generators are listed, and photoacid generators are preferably used. When the first active energy ray-curable composition is a visible ray-curable composition, it is preferable to use a photo cationic polymerization initiator that is particularly sensitive to light of 380 nm or more. Additionally, when using a photo cationic polymerization initiator, it is preferable to use together a photosensitizer that exhibits maximum absorption for light with a wavelength longer than 380 nm. Since the photo cationic polymerization initiator is generally a compound that shows maximum absorption in the vicinity of 300 nm or shorter wavelength region, it can be used in combination with a photosensitizer that shows maximum absorption in light with a wavelength longer than 380 nm. When used effectively, it can promote the generation of cationic species or Lewis acids from the photocationic polymerization initiator. Examples of photosensitizers include anthracene compounds, pyrene compounds, carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo compounds, diazo compounds, halogen compounds, and photoreducible dyes. These may be used individually, or two or more types may be used together. In particular, anthracene compounds are preferable because they have excellent light sensitization effects. Commercially available anthracene compounds as photosensitizers include, for example, Anthracure UVS-1331 and Anthracene UVS-1221 (manufactured by Kawasaki Kasei Chemicals Ltd.). The content of the photosensitizer in the composition is, for example, 0.1 to 5% by weight.

The first active energy ray-curable composition may contain an oligomer. Oligomers include acrylic oligomers, fluorine oligomers, and silicone oligomers, and acrylic oligomers are preferably used. The incorporation of oligomers into the first active energy ray-curable composition helps suppress shrinkage during curing of the composition. Suppression of curing shrinkage of the first active energy ray-curable composition is desirable to reduce the interfacial stress between the formed adhesive layer 31 and the optical films 10 and 21. Suppression of interfacial stress helps ensure bonding strength between the optical films 10 and 21.

Examples of (meth)acrylic monomers forming acrylic oligomers include (meth)acrylic acid alkyl esters having 1 to 20 carbon atoms, cycloalkyl (meth)acrylates, aralkyl (meth)acrylates, and polycyclic (meth)acrylates. , hydroxyl group-containing (meth)acrylic acid ester, and halogen-containing (meth)acrylic acid ester. Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, and 2-methyl-2-nitropropyl. (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, S-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, t-pentyl (meth)acrylate, 3-pentyl (meth)acrylate, 2,2-dimethylbutyl (meth)acrylate, n-hexyl (meth)acrylate, cetyl (meth)acrylate, n-octyl ( Meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, and N-octadecyl (meth)acrylate. Examples of cycloalkyl (meth)acrylate include cyclohexyl (meth)acrylate and cyclopentyl (meth)acrylate. Examples of aralkyl (meth)acrylate include benzyl (meth)acrylate. Polycyclic (meth)acrylates include, for example, 2-isobornyl (meth)acrylate, 2-norbornylmethyl (meth)acrylate, and 5-norbornen-2-yl-methyl (meth)acrylate. nitrate, and 3-methyl-2-norbornylmethyl(meth)acrylate. Examples of hydroxyl group-containing (meth)acrylic acid esters include hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2,3-dihydroxypropylmethyl-butyl (meth)methacrylate. are listed. Halogen-containing (meth)acrylic acid esters include, for example, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,2-trifluoroethyl ethyl (meth)acrylate, and tetrafluoropropyl. (meth)acrylate, hexafluoro propyl (meth)acrylate, octafluoropentyl (meth)acrylate, and heptadecafluorodecyl (meth)acrylate are listed. These (meth)acrylates may be used individually, or two or more types may be used together.

The weight average molecular weight (Mw) of the acrylic oligomer is preferably 15,000 or less, more preferably 10,000 or less, and even more preferably 5,000 or less. The Mw of the acrylic oligomer is preferably 500 or more, more preferably 1000 or more, and still more preferably 1500 or more.

The content of acrylic oligomer in the first active energy ray-curable composition is preferably 2% by mass or more, more preferably 4% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less. am.

The first active energy ray curable composition may contain other components. Other ingredients include silane coupling agents, leveling agents, surfactants, plasticizers, and ultraviolet absorbers. The mixing amount of the other components is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, further preferably 3 parts by mass or less, and for example, 0.01 parts by mass or more, based on 100 parts by mass of the curable component. am.

The viscosity of the first active energy ray-curable composition at 25°C is preferably 3 mPa·s or more, more preferably 5 mPa·s or more, and still more preferably 10 mPa·s from the viewpoint of coatability in the later application process. or more, and is preferably 100 mPa·s or less, more preferably 50 mPa·s or less, and even more preferably 30 mPa·s or less. The viscosity of the composition is a value measured with an E-type viscometer (corn plate type viscometer).

The adhesive layer 32 is, for example, a cured product (active energy ray curable composition) of the second adhesive composition containing an active energy ray curable resin. Examples of the second active energy ray curable composition include electron beam curable composition, ultraviolet ray curable composition, and visible ray curable composition. Among these, the second active energy ray curable composition and the first active energy ray curable composition may be the same type of composition or may be different types of compositions. In addition, the second active energy ray curable composition is a radical polymerization type composition in this embodiment.

As the component contained in the second active energy ray-curable composition, the component described above as the component contained in the first active energy ray-curable composition can be used. The content range of the components of the second active energy ray-curable composition is as described above as the range of the component content of the first active energy ray-curable composition. The composition of the second active energy ray curable composition and the composition of the first active energy ray curable composition may be the same or different.

The laminated optical film (X) can be manufactured as follows, for example.

First, the first active energy ray-curable composition is applied to one side (the surface to be bonded) of the optical film 21 to form a first coating film of the composition (first application step). Additionally, a second active energy ray-curable composition is applied to one side (the surface to be bonded) of the optical film 22 to form a second coating film of the same composition (second application process). Before each application process, the surface to be bonded to the optical film may be subjected to surface modification treatment. Surface modification treatments include corona treatment, plasma treatment, excimer treatment, and frame treatment. Examples of coating methods in this process include reverse coater, gravure coater, variverse coater, roll coater, die coater, bar coater, and rod coater.

Next, the optical film 21 is bonded to one side of the optical film 10 through the first coating film, and the optical film 22 is bonded to the other side of the optical film 10 through the second coating film. Join together. For bonding, for example, a roll laminator that performs both bonding simultaneously can be used.

Next, active energy rays are irradiated to the first coating film and the second coating film, the first coating film is cured to form the adhesive layer 31, and the second coating film is cured to form the adhesive layer 32 (adhesive Layers 31 and 32 are not pressure-sensitive adhesive layers). From this, the optical films 10 and 21 are bonded through the adhesive layer 31, and the optical films 10 and 22 are bonded through the adhesive layer 32.

In this process, from the viewpoint of suppressing deterioration of the optical film 10 as a functional optical film, the active energy ray for curing the first coating film is preferably irradiated from the optical film 21 side, and the active energy ray for curing the first coating film is preferably irradiated from the optical film 22 side. Active energy rays for curing the second coating film are irradiated from . As active energy rays, electron beams, ultraviolet rays, and visible rays can be used. Examples of the electron beam irradiation means include electron beam accelerators. Light sources of ultraviolet rays and visible rays include, for example, LED lights, gallium-filled metal halide lamps, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon lamps, halogen lamps, and gallium lamps. In this process, a wavelength cut filter for cutting a part of the wavelength range in the ultraviolet rays and/or visible rays emitted from the light source may be used as needed.

The laminated optical film (X) can be manufactured as described above, for example.

(Example)

The present invention will be described in detail below by way of examples. The present invention is not limited to the examples. In addition, the specific values of the mixing amount (content), physical property values, and parameters described below are the corresponding mixing amounts (content), physical property values, and parameters described in the above-mentioned "Specific Details for Carrying out the Invention." It can be replaced with an upper limit (a numerical value defined as “less than” or “less than”) or a lower limit (a numerical value defined as “more than” or “exceeds”).

[Example 1]

The first adhesive composition for the first adhesive layer was prepared by mixing the following components in the mixing amount (mixing amount in solid content) shown in Table 1 at 25°C for 1 hour (first preparation step). Additionally, the second adhesive composition for the second adhesive layer was prepared by mixing the following components in the mixing amount (mixing amount in solid content) shown in Table 1 at 25°C for 1 hour (second preparation step). The unit of the compounding amount shown in Table 1 is a relative "part by mass."

Light Acrylate POB-A (monomer): 3-phenoxybenzyl acrylate, Kyoeisha Chemical Co., Ltd. produce

Light Acrylate P2H-A (monomer): Phenoxydiethylene glycol acrylate, Kyoeisha Chemical Co., Ltd. produce

Aronics M-5700 (monomer): 2-hydroxy-3-phenoxypropyl acrylate, Toagosei Co., Ltd. produce

Aronics M-220 (monomer): Tripropylene glycol diacrylate, Toagosei Co., Ltd. produce

HEAA (monomer): Hydroxyethylacrylamide, manufactured by KJ Chemicals Corporation

DEAA (monomer): diethyl acrylamide, manufactured by KJ Chemicals Corporation

OMINIRAD907 (photopolymerization initiator): 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, manufactured by IGM Resins.

KAYACURE DETX-S (photopolymerization initiator): 2,4-diethylthioxanthone, Nippon Kayaku Co., Ltd. produce

Arupon 1190 (acrylic oligomer): Viscosity 6000 mPa·s (25°C), Mw 1700, Tg-50°C, Toagosei Co., Ltd. produce

BYK-UV3505 (leveling agent): modified polydimethylsiloxane with an acrylic group, manufactured by BYK

Next, the application process was performed. Specifically, it is as follows. The first adhesive composition was applied onto a COP film (product name “Zeonor Film ZF14”, manufactured by Zeon Corporation) with a thickness of 23 μm as the first transparent protective film, and a first adhesive coating film with a thickness of 1 μm was formed. Meanwhile, the second adhesive composition was applied onto a 23-μm-thick COP film (product name “Zeonor Film ZF14”, manufactured by Zeon Corporation) as the second transparent protective film to form a second adhesive coating film with a thickness of 1 μm. For each coating, an MCD coater (manufactured by FUJI MACHINERY Co., Ltd., honeycomb cell shape, number of gravure rolls 1000 pieces/inch, rotation speed 140%/unit line speed) was used.

Next, the first transparent protective film with the first adhesive coating film, the polarizer film, and the second transparent protective film with the second adhesive coating film were bonded together (joining process). Specifically, the first adhesive film side of the first transparent protective film is bonded to one side of the polarizer film by a roll laminator, while the second adhesive film side of the second transparent protective film is bonded to the other side of the polarizer film. I ordered it.

Next, while irradiating ultraviolet rays to the first adhesive coating film from the first transparent protective film side, the adhesive coating film between the films was cured by irradiating ultraviolet rays to the second adhesive coating film from the second transparent protective film side (curing process). . For ultraviolet irradiation, an ultraviolet irradiation device (product name “Light HAMMER10”, valve: V valve, manufactured by Fusion UV Systems, Inc.) equipped with a gallium-encapsulated metal halide lamp as a light source was used. In ultraviolet irradiation, the peak irradiance was 1600 mW/cm ² and the accumulated irradiation amount was 1000 mJ/cm ² (wavelength 380 to 440 nm) (the illuminance was measured using the “Sola-Check system” manufactured by Solatell). As a result, the first transparent protective film and the polarizer film were bonded together with the first adhesive layer, and the second transparent protective film and the polarizer film were bonded together with the second adhesive layer to obtain a laminated optical film.

As described above, the laminated optical film of Example 1 was produced. The laminated optical film of Example 1 includes a first transparent protective film (thickness 23 μm), a first adhesive layer, a polarizer film (5 μm thick), a second adhesive layer, and a second transparent protective film (thickness 23 μm). ) are provided in this order in the thickness direction.

Example 1 first adhesive layer second adhesive layer monomer Light Acrylate POB-A 45 45 Light Acrylate P2H-A 25 25 Aronix M-5700 10 10 Aronix M-220 15 5 HEAA 5 5 DEAA 5 5 Light polymerization initiator OMINIRAD 907 3 3 KAYACURE DETX-S 3 3 oligomer Arupone 1190 5 5 leveling agent BYK-UV 3505 0.5 0.5

[Example 2]

Except for the following, the same as the laminated optical film of Example 1, the laminated optical film of Example 2 (1st transparent protective film/1st adhesive layer/polarizer film/2nd adhesive layer/2nd transparent protective film) produced.

In the first preparation process, “Light Acrylate POB-A”, “Light Acrylate P2H-A”, and “Aronics M-220” were not used, but were manufactured by Kyoeisha Chemical Co., Ltd. 40 parts by mass of “Light Acrylate 1.9ND-A” (1,9-nonanediol diacrylate) produced by Kyoeisha Chemical Co., Ltd. Using 9 parts by mass of the produced “light acrylate HPP-A” (hydroxypivalic acid neopentyl glycol acrylic acid adduct), the mixing amount of “Aronix M-5700” was 22 parts by mass, and the mixing amount of “HEAA” was 12.5. In parts by mass, the mixing amount of “DEAA” was 6 parts by mass, the mixing amount of “HEAA” was 12.5 parts by mass, and the mixing amount of “Arupon 1190” was 10 parts by mass. In addition, in the application process, the thickness of the first adhesive layer coating film formed on the first transparent protective film was set to 1.1 μm, and the thickness of the second adhesive layer coating film formed on the second transparent protective film was set to 1.2 μm. .

[Example 3]

Except for the following, the same as the laminated optical film of Example 1, the laminated optical film of Example 3 (1st transparent protective film/1st adhesive layer/polarizer film/2nd adhesive layer/2nd transparent protective film) produced.

In the first preparation process, “Light Acrylate POB-A”, “Aronix M-220”, “Aronix M-5700”, “DEAA”, and “Arupon 1190” were not used, but Kyoeisha Chemical Co. , Ltd. 27 parts by mass of "Light Acrylate 1.9ND-A" (1,9-nonanediol diacrylate) manufactured by KJ Chemicals Corporation and 59 parts by mass of "ACMO-LI" (acryloylmorpholine) manufactured by KJ Chemicals Corporation were used, The mixing amount of “Light Acrylate P2H-A” was 10 parts by mass, and the mixing amount of “HEAA” was 3 parts by mass. In the second preparation process, the mixing amount of “Light Acrylate POB-A” is 43 parts by mass, the mixing amount of “Light Acrylate P2H-A” is 29 parts by mass, and the mixing amount of “Aronix M-220” is 3 parts by mass. As a result, the mixing amount of “Aronix M-5700” was set to 10 parts by mass. In addition, in the application process, the thickness of the first adhesive layer coating film formed on the first transparent protective film was set to 1.2 μm, and the thickness of the second adhesive layer coating film formed on the second transparent protective film was set to 0.9 μm. .

[Comparative Example 1]

Except for the following, it was the same as the laminated optical film of Example 1, and the laminated optical film of Comparative Example 1 (1st transparent protective film/1st adhesive layer/polarizer film/2nd adhesive layer/2nd transparent protective film) produced.

In the first preparation step, the same composition as the second adhesive composition in Example 1 was prepared. In the second preparation process, Kyoeisha Chemical Co. , Ltd. 23 parts by mass of "Light Acrylate 1.9ND-A" (1,9-nonanediol diacrylate) manufactured by KJ Chemicals Corporation and 60 parts by mass of "ACMO-LI" (acryloylmorpholine) manufactured by KJ Chemicals Corporation were used, The mixing amount of “Light Acrylate P2H-A” was 13 parts by mass, and the mixing amount of “HEAA” was 3 parts by mass. In addition, in the application process, the thickness of the first adhesive layer coating film formed on the first transparent protective film was set to 1.0 μm, and the thickness of the second adhesive layer coating film formed on the second transparent protective film was set to 1.2 μm. .

<Thickness of adhesive layer>

The thickness T of each adhesive layer in each laminated optical film of Examples 1 to 3 and Comparative Example 1 was measured as follows. First, a 5 mm x 10 mm film piece (laminated optical film) was cut from the laminated optical film. Next, the laminated optical film was cut by the cryomicrotome method. Specifically, the laminated optical film was cooled to -30°C, cut with a hard knife in the thickness direction of the film, and then returned to room temperature. The cut surface of the laminated optical film on which the cut surface was formed was subjected to conductive treatment to a thickness of 5 nm or less. As a result, a sample for observation was obtained. Next, the thickness of the adhesive layer was measured by SEM observation of the observation sample. Specifically, a scanning electron microscope (product name "REGULUS8220", manufactured by HITACHI) was used to observe and image the secondary electron image of the cut surface in the observation sample, and the thickness of each adhesive layer was measured. In this observation, the acceleration voltage was set to 3.0 kV, the current amount was set to 10 μA, the walking distance was set to 8 mm, the magnification was set to 100,000 times, and the detection mode was set to Upper+Lower mode. The thickness T1 (μm) of the first adhesive layer and the thickness T2 (μm) of the second adhesive layer are shown in Table 2. The ratio of thickness T2 to thickness T1 (T2/T1) is also shown in Table 2.

<Peel strength>

The 90° peeling strength between the first transparent protective film and the polarizer film in each of the laminated optical films of Examples 1 to 3 and Comparative Example 1 was measured as follows (first measurement). First, a first sample film with a size of 200 mm on the first side and 15 mm on the second side was cut from the laminated optical film. The first side is a side extending in the stretching direction of the polarizer film. The second side is a side extending in a direction perpendicular to the stretching direction. Next, the second transparent protective film side of the first sample film was bonded to a glass plate through a strong adhesive. Next, the 90° peel strength (N/15 mm) of the first transparent protective film from the polarizer film was measured using a Tensilon universal testing machine (product name “RTC”, manufactured by A&D Company, Limited). In this measurement, the ten A glass plate and the first transparent film of the first sample film on the glass plate are held in a first chuck equipped with the Ceylon universal testing machine, and the first transparent film of the first sample film is held in a second chuck equipped with the same testing machine. The protective film was held. In addition, in this measurement, the measurement temperature was 25°C, the peeling angle was 90°, and the peeling speed was 1000 mm/min. Table 2 shows the 90° peel strength F1 (N/15 mm) in the peel test for peeling the first transparent protective film from the polarizer film.

In addition, the 90° peeling strength between the second transparent protective film and the polarizer film in each of the laminated optical films of Examples 1 to 3 and Comparative Example 1 was measured as follows (second measurement). First, a second sample film identical to the first sample film was cut from the laminated optical film. Next, the first transparent protective film side of the second sample film was bonded to a glass plate through a strong adhesive. Next, the 90° peel strength (N/15 mm) of the second transparent protective film from the polarizer film was measured using a Tensilon universal tester (product name “RTC”, manufactured by A&D Company, Limited). In this measurement, the glass plate and the second sample film on the glass plate are held from the glass plate to the polarizer film by the first chuck provided by the Tensilon universal testing machine, and the second sample is held by the second chuck provided by the same testing machine. The second transparent protective film of the film was held. The measurement conditions in the second measurement are the same as the above-mentioned measurement conditions in the first measurement. Table 2 shows the 90° peel strength F2 (N/15 mm) in the peel test for peeling the second transparent protective film from the polarizer film.

<Indentation elastic modulus>

The indentation elastic modulus of the first adhesive layer in each laminated optical film of Examples 1 to 3 and Comparative Example 1 was measured by the nanoindentation method. Specifically, first, a film piece (laminated optical film) with a size of 5 mm x 10 mm was cut from the laminated optical film. Next, the laminated optical film was cut by the cryomicrotome method. Specifically, the laminated optical film was cooled to -30°C, cut with a hard knife in the thickness direction of the film, and then returned to room temperature. As a result, a sample for measurement was obtained. Next, using a nanoindenter (product name “TI950 Triboindenter”, manufactured by Hysitron), load-displacement measurement was performed on the exposed surface of the adhesive layer in the measurement sample in accordance with JISZ 2255:2003, and load-displacement measurement was performed based on JISZ 2255:2003. Displacement curves were obtained. In this measurement, the measurement mode is single indentation measurement, the measurement temperature is 25°C, the indenter used is a Berkovich (triangular pyramid) type diamond indenter, and the maximum indentation depth of the indenter to the measurement sample during the load application process is (Maximum displacement hmax) was set to 50 nm, the press-in speed of the indenter was set to 10 nm/sec, and the pull-out speed of the indenter from the measurement sample in the unloading process was set to 10 nm/sec. Then, the obtained measurement data was processed using “TI950 Triboindenter” dedicated analysis software (Ver. 9.4.0.1). Specifically, based on the obtained load (f)-displacement (h) curve, the maximum load fmax (load acting on the indenter at the maximum displacement hmax) and the contact projection area S (contact between the indenter and the sample at the maximum load) The projected area of the area) and the slope D of the tangent line of the load-displacement curve at the start of the unloading process were obtained. And from the slope D and the contact projection area S, the indentation elastic modulus (=(π ^1/2 D)/(2S ^1/2 )) of the first adhesive layer was calculated. The value is shown in Table 2 as the indentation elastic modulus E1 (GPa).

In addition, the indentation elastic modulus of the second adhesive layer in each of the laminated optical films of Examples 1 to 3 and Comparative Example 1 was measured in the same manner as the above-described indentation elastic modulus E1 of the first adhesive layer. The value is shown in Table 2 as the indentation elastic modulus E2 (GPa). The ratio of the indentation elastic modulus E2 to the indentation elastic modulus E1 (E2/E1) is also shown in Table 2.

<Display unevenness>

When each of the laminated optical films of Examples 1 to 3 and Comparative Example 1 was mounted on a display panel, the presence or absence of display unevenness when the display panel was bent was investigated. As the display panel, an organic EL panel (OLED panel) taken from a commercially available foldable smartphone was used. The laminated optical film was placed on the image display side surface of the display panel. Specifically, the second transparent protective film side of the laminated optical film was bonded to the image display side surface of the display panel through an adhesive. Then, with the display panel displaying an image, the display panel was bent at 90°, and the image of the bent location was visually observed. Cases where display unevenness (change in color tone) was not observed in the image of the bent location were evaluated as “good”, and cases where display unevenness was confirmed were evaluated as “poor.” The results are shown in Table 2.

<High temperature and high humidity bending test>

For each laminated optical film of Examples 1 to 3 and Comparative Example 1, a high-temperature, high-humidity bending test was performed as follows.

First, a sample for evaluation was cut from the laminated optical film. Specifically, a rectangular sample of 25 mm x 100 mm was cut out from the laminated film so that the absorption axis direction of the polarizer film was parallel to the long side direction in the cut sample. Next, a bending test was performed on the sample using a planar unloaded U-shaped stretching tester (manufactured by YUASA SYSTEM Co., Ltd.). In this test, a bending jig was attached to each of the ends of the sample in the long side direction in a range of 20 mm from the edge of the sample, and the sample was fixed to the tester (the center 60 mm area in the long side direction of the sample was It is in an unfixed state). In addition, in this test, in a constant temperature and humidity chamber under the conditions of a temperature of 60°C and a relative humidity of 90%, the sample was subjected to bending at a bending speed of 60 rpm between a bent form in which the surface on the first transparent protective film side was inside and a non-bent form. It was repeatedly deformed (bended) 80,000 times. The bending form in this test is, specifically, a form in which the axial direction of the bending moment acting on the sample and the absorption axis direction of the polarizer film are orthogonal. In the above bending form, the bending radius of the sample was set to 3 mm, and the bending angle was set to 180°. In this bending test, regarding the ability to suppress peeling between the films (the first transparent protective film, the polarizer film, and the second transparent protective film), a case where no peeling between the films occurred up to 80,000 bending cycles was evaluated as “good.” And, cases where peeling occurred at less than 80,000 bends were evaluated as “bad.” The evaluation results are shown in Table 1.

Example 1 Example 2 Example 3 Comparative Example 1 1st
adhesive layer 2nd
adhesive layer 1st
adhesive layer 2nd
adhesive layer 1st
adhesive layer 2nd
adhesive layer 1st
adhesive layer 2nd
adhesive layer Thickness of adhesive layer (㎛) (T1)
1.23 (T2)
0.81 (T1)
1.1 (T2)
1.2 (T1)
1.2 (T2)
0.9 (T1)
1.0 (T2)
1.2 T2/T1 0.66 1.1 0.75 1.2 90° peeling
robbery
(N/15mm) (F1)
1.0 (F2)
1.0 (F1)
1.4 (F2)
1.0 (F1)
1.0 (F2)
1.4 (F1)
1.3 (F2)
1.0 Indentation modulus (GPA) (E1)
2.41 (E2)
2.34 (E1)
3.21 (E2)
2.34 (E1)
6.12 (E2)
2.01 (E1)
2.34 (E2)
5.08 E2/E1 0.97 0.73 0.33 2.17 Evaluation of display unevenness Good Good Good error Evaluation of delamination inhibition Good Good Good error

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

X Laminated Optical Film
10 Optical film (second optical film)
21 Optical film (first optical film)
22 Optical film (3rd optical film)
31 Adhesive layer (first adhesive layer)
32 Adhesive layer (second adhesive layer)
H Thickness direction
B bending point

Claims (6)

A laminated optical film comprising a first optical film, a first adhesive layer, a second optical film, a second adhesive layer, and a third optical film in that order in the thickness direction,
The first adhesive layer is bonded to the first optical film and also bonded to the second optical film,
the second adhesive layer is bonded to the second optical film and also bonded to the third optical film,
A laminated optical film wherein the indentation elastic modulus E1 of the first adhesive layer at 25°C and the indentation elasticity modulus E2 of the second adhesive layer at 25°C satisfy 0.3≤E2/E1<1. According to claim 1,
A laminated optical film wherein the indentation elastic modulus E2 is 4 GPa or less. According to claim 1,
A laminated optical film wherein the indentation elastic modulus E2 is 0.4 GPa or more. According to claim 1,
A laminated optical film wherein the indentation elastic modulus E1 is 0.5 GPa or more. According to claim 1,
A laminated optical film wherein the indentation elastic modulus E1 is 7 GPa or less. The method according to any one of claims 1 to 5,
A laminated optical film, wherein the second optical film is a polarizer film.