KR20240004226A - Laminated Optical Film - Google Patents

Abstract

The laminated optical film (X) of the present invention includes an optical film (10), an adhesive layer (20), and an optical film (30) in that order in the thickness direction (H). The adhesive layer 20 is bonded to the optical film 10 and is also bonded to the optical film 30. The optical film 30 has a boundary region 31 on the adhesive layer 20 side containing an adhesive raw material component derived from the adhesive layer 20 . The ratio of the thickness T2 of the adhesive raw material component-containing portion 40, which combines the adhesive layer 20 and the boundary region 31, to the thickness T1 of the adhesive layer 20 is 1.01 or more.

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 in a state in which it is bonded to another optical film, such as a protective film, through 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

As display panels become thinner, functional optical films are becoming thinner. The adhesive layer between optical films in a laminated optical film is also required to be thin. However, as the adhesive layer between optical films becomes thinner, the bonding strength between optical films tends to decrease. The low bonding force is undesirable from the viewpoint of bonding reliability between optical films. In a laminated optical film for a display panel that can be repeatedly bent (foldable), there is a strong requirement to secure bonding strength between optical films. In laminated optical films for foldable display panels used in high-temperature and high-humidity environments such as inside automobiles, excessive stress is generated in the optical film due to high temperature and high humidity, and the stress is concentrated at the adhesive interface, so delamination between optical films is likely to occur. Therefore, there is a particularly strong demand for securing adhesion between optical films by means of an adhesive layer.

The present invention provides a laminated optical film suitable for ensuring bonding strength between optical films even with a thin adhesive layer.

The present invention [1] is a laminated optical film comprising a first optical film, an adhesive layer, and a second optical film in that order in the thickness direction, wherein the adhesive layer is bonded to the first optical film and the second optical film. bonded to a film, wherein the second optical film has a boundary area containing an adhesive raw material component derived from the adhesive layer on the adhesive layer side, and the adhesive layer and the boundary area are combined for a thickness T1 of the adhesive layer. It includes a laminated optical film in which the ratio of the thickness T2 of the adhesive raw material component-containing portion is 1.01 or more.

The present invention [2] includes the laminated optical film according to [1] above, wherein the thickness T1 is 5 μm or less.

The present invention [3] includes the laminated optical film according to [1] or [2] above, wherein the 90° peel strength at 25°C of the second optical film with respect to the first optical film is 0.8 N/15 mm or more. .

The present invention [4] includes the laminated optical film according to any one of [1] to [3] above, wherein the first optical film is a polarizer film.

In the laminated optical film of the present invention, as described above, the second optical film has a boundary region containing the adhesive raw material component derived from the adhesive layer on the side of the adhesive layer that joins the first and second optical films. That is, the second optical film has a region (the boundary region) on the adhesive layer side into which the adhesive raw material component from the adhesive layer is penetrating. In the boundary area, the components of the second optical film and the adhesive raw material components are mixed. In the present laminated optical film, as described above, 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. That is, in the present laminated optical film, the thickness T2 of the portion (adhesive layer and boundary area) that contains the adhesive raw material component and participates in the adhesive function is greater than the adhesive layer thickness T1. These configurations regarding the boundary between the second optical film and the adhesive layer and its vicinity are suitable for realizing strong interaction between the second optical film and the adhesive layer and ensuring high bonding strength. And, securing the bonding force between the second optical film and the adhesive layer is helpful in securing the bonding force between the first and second optical films by the adhesive layer. Therefore, the present laminated optical film is suitable for ensuring bonding strength between optical films even with a thin adhesive layer. Securing bonding force between optical films is suitable for suppressing peeling between the optical films. In addition, this laminated optical film is suitable for securing bonding strength between optical films through a thin adhesive layer and suppressing peeling between optical films, even in a high temperature and high humidity environment.

1 is a cross-sectional schematic diagram of one embodiment of the laminated optical film of the present invention.
FIG. 2 is a partially enlarged cross-sectional view of the laminated optical film shown in FIG. 1.
Figure 3 is a cross-sectional schematic diagram of another embodiment of the laminated optical film of the present invention. The laminated optical film of this embodiment includes a second optical film, an adhesive layer, a first optical film, an adhesive layer, and a second optical film in that order in the thickness direction.

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 (first optical film), an adhesive layer 20, and an optical film 30. (Second optical film) is provided in order in the thickness direction (H). The adhesive layer 20 bonds the optical films 10 and 30 together. 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 laminated optical film (X) is a composite film included in the laminated structure of the display panel.

In this embodiment, the optical film 10 is a functional optical film. 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 retardation films 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 adhesive layer 20 is a cured product of an adhesive composition. The adhesive layer 20 is directly bonded to the optical film 10 and also directly bonded to the optical film 30. The adhesive composition contains a curable resin. The components of the adhesive composition are specifically as described later.

The thickness T1 of the adhesive layer 20 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 the bonding force between the optical films 10 and 30. It is more than ㎛. From the viewpoint of reducing the thickness of the laminated optical film It is as follows. The thickness T1 of the adhesive layer 20 is the length in the thickness direction (H) of the area having the structure (formed from the constituents after curing) after curing of the adhesive composition. This length can be measured from images obtained through observation such as SEM observation. The thickness T1 of the adhesive layer 20 can be specifically measured by the method described later in Examples.

The first indentation elastic modulus of the adhesive layer 20 at 25°C measured by the nanoindentation method is preferably 0.01 GPa or more, more preferably 0.03 GPa or more, even more preferably 0.05 GPa or more, especially preferably is 0.07 GPa or more (the first indentation elastic modulus is the indentation elastic modulus under the first measurement conditions. The first measurement conditions are as described later with respect to the examples, and in the first measurement conditions, the measurement sample in the load application process The maximum indentation depth of the indenter is 200 nm). This configuration is desirable from the viewpoint of securing adhesion between the optical films 10 and 30. Additionally, the first indentation elastic modulus is preferably 5 GPa or less, more preferably 3 GPa or less, and even more preferably 1 GPa or less. This configuration is preferable for ensuring the flexibility of the adhesive layer 20 and, therefore, for ensuring the flexibility of the laminated optical film (X). Examples of methods for adjusting the press-fit elastic modulus of the adhesive layer 20 include adjusting the composition of the adhesive composition. Specifically, adjustment of the number of functional groups of the polymerizable compound described later in the adhesive composition forming the adhesive layer 20, that is, adjustment of the acrylic equivalent or epoxy equivalent of the polymerizable compound is a method of adjusting the indentation elastic modulus of the adhesive layer 20. It is effective as

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 second indentation elastic modulus of the adhesive layer 20 at 25°C 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 is 2GPa or more (the second indentation elastic modulus is the indentation elasticity modulus under the second measurement condition. The second measurement condition is as described later with respect to the examples, and in the second measurement condition, the The maximum indentation depth of the indenter is 50 nm). This configuration is desirable from the viewpoint of securing adhesion between the optical films 10 and 30. Additionally, the second indentation elastic modulus is preferably 7 GPa or less, more preferably 5 GPa or less, and even more preferably 3 GPa or less. This configuration is preferable for ensuring the flexibility of the adhesive layer 20 and, therefore, for ensuring the flexibility of the laminated optical film (X).

The optical film 30 is a transparent protective film in this embodiment. 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 triacetyl cellulose. 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.

The thickness of the optical film 30 is preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 20 μm or more from the viewpoint of the strength of the laminated optical film (X). From the viewpoint of thinning the laminated optical film (X), the thickness of the optical film 30 is preferably 100 μm or less, more preferably 70 μm or less, and still more preferably 50 μm or less.

As shown in FIG. 2 , the optical film 30 has a border region 31 on the adhesive layer 20 side and a non-boundary region 32 on the opposite side to the adhesive layer 20. The border area 31 contains adhesive raw material components derived from the adhesive layer 20. In the boundary area 31, the components of the optical film 30 and the adhesive raw material components are mixed. Examples of methods for detecting adhesive raw material components include time-of-flight secondary ion mass spectrometry (TOF-SIMS). On the other hand, the non-boundary area 32 does not contain adhesive raw material components derived from the adhesive layer 20. The non-boundary area 32 is made of components of the optical film 30. In the optical film 30, the area where adhesive raw material components exceeding the detection limit value (positive/negative secondary ion intensity 0.1 counts/sec) in the above detection method are detected is the border area 31, and the area where the adhesive raw material component is detected is the detection limit value or more. The area in which adhesive raw material components are not detected is the non-boundary area 32. The ratio of the thickness of the border region 31 to the thickness of the non-boundary region 32 is, for example, 0.01% or more, preferably 0.05% or more, and is for example 50% or less, preferably 20% or less. am.

The thickness of the border area 31 is, for example, 0.01 μm or more, and is preferably 0.05 μm or more. The thickness of the border area 31 is, for example, 10 μm or less, and is preferably 5 μm or less. Examples of methods for adjusting the thickness of the boundary region 31 include adjusting the composition of the adhesive composition. As a method of adjusting the thickness of the boundary region 31, adjustment of the time from the later application process to the curing process in the manufacturing process of the laminated optical film (X) is listed. The longer the time, the thicker the border area 31 tends to be.

In the laminated optical film (X), the boundary region 31 and the above-described adhesive layer 20 form the adhesive raw material component-containing portion 40. 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 to prevent insufficient adhesion when the boundary area 31 is too small (too thin). , is 1.01 or more, preferably 1.05 or more, more preferably 1.1 or more, and even more preferably 1.2 or more. The ratio (T2/T1) is preferably 1.3 or less, more preferably 1.25 or less, from the viewpoint of both adhesion between the adhesive layer 20 and the optical film 30 and production stability of the laminated optical film (X). Preferably it is 1.2 or less. The adhesion between the adhesive layer 20 and the optical film 30 ensures, for example, the thickness of the adhesive layer 20, and when bending the laminated optical film (X), the adhesive layer 20 and the optical film ( This can be ensured by suppressing the occurrence of peeling due to the load at the interface of 30). The thickness T2 of the adhesive raw material component-containing portion 40 is larger than the thickness of the adhesive layer 20 and smaller than the total thickness of the adhesive layer 20 and the optical film 30. The thickness T2 of the adhesive raw material component containing portion 40 is, for example, 0.101 μm or more, for example, 6.5 μm or less, depending on the thickness and composition of the adhesive layer 20 and the material of the optical film 30. The thickness T2 of the adhesive raw material component-containing portion 40 and the thickness of the boundary region 31 described above can be measured by the method described later in the Examples.

In the laminated optical film (X), as described above, the optical film 30 has a boundary region 31 on the adhesive layer 20 side of the film. In the boundary area 31, the components of the optical film 30 and the adhesive raw material components are mixed. And, in the laminated optical film , preferably 1.05 or more, more preferably 1.1 or more, and even more preferably 1.2 or more. That is, in the laminated optical film These configurations regarding the boundary between the optical film 30 and the adhesive layer 20 and its vicinity are suitable for realizing strong interaction between the optical film 30 and the adhesive layer 20 and ensuring high bonding strength. In addition, securing the bonding force between the optical film 30 and the adhesive layer 20 is helpful in securing the bonding force between the optical films 10 and 30 by the adhesive layer 20. Therefore, the laminated optical film (X) is suitable for ensuring bonding force between the optical films (10, 30) by the thin adhesive layer (20). Securing the bonding force between the optical films 10 and 30 is suitable for suppressing peeling between the optical films 10 and 30. In addition, this laminated optical film ( Suitable. Specifically, it is as shown in the later examples and comparative examples.

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 realizing good bonding strength between the optical films 10 and 30, and is particularly desirable for ensuring good bonding strength between the optical films 10 and 30 for the foldable display panel. 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 Examples. In addition, as a method of adjusting the 90° peel strength, for example, adjustment of the ratio (T2/T1) and adjustment of the composition of the adhesive composition are listed.

The ratio of the 90° peel strength (N/15 mm) to the above-mentioned first indentation elastic modulus (GPa) is preferably 5 or more, more preferably 10 or more, further preferably 15 or more, and also preferably 30. or less, more preferably 25 or less. This configuration is preferable in that it suppresses peeling between the optical films 10 and 30 when repeatedly bending the laminated optical film (X) (especially the thin laminated optical film (X)).

The ratio of the 90° peel strength (N/15 mm) to the above-mentioned second indentation elastic modulus (GPa) is preferably 0.2 or more, more preferably 0.3 or more, further preferably 0.4 or more, and further preferably 5 or less. , more preferably 3 or less, even more preferably 2 or less. This configuration is preferable in that it suppresses peeling between the optical films 10 and 30 when repeatedly bending the laminated optical film (X) (especially the thin laminated optical film (X)).

The adhesive layer 20 is, for example, a cured product of an adhesive composition containing an active energy ray-curable resin (active energy ray-curable composition). Examples of the active energy ray curable composition include electron beam curable composition, ultraviolet ray curable composition, and visible ray curable composition. In the present embodiment, the active energy ray-curable composition is one or both of a radical polymerization type composition and a cation polymerization type composition.

The radically polymerizable 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 active energy ray-curable composition, it is preferable that the active energy ray-curable composition 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 active energy ray-curable composition is, for example, 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more. 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. The (meth)acrylic acid derivative 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. Rate, 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-hydroxybutyl. (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 selected from the group consisting of 3-phenoxybenzyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, and phenoxydiethylene glycol acrylate. At least one selected 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 monomer include vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, and vinylmorpholine.

Examples of the polyfunctional radically polymerizable compound include tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and 1,9-no. Nandiol di(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, penta Erythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate are used, and tripropylene glycol diacrylate 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 active energy ray-curable composition is an ultraviolet ray-curable composition or a visible ray-curable composition, the active energy ray-curable composition 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. , 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone.

When the active energy ray-curable composition is a visible ray-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 active energy ray-curable composition is preferably 0.1 part by mass or more, more preferably 0.05 part by mass or more, and still more preferably 0.1 part by mass, based on 100 parts by mass of the curable component (radically polymerizable compound). parts 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 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 denatured products, trimethylcaprolactone denatured products, and valerolactone denatured products 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.). , Also listed are Cyracure UVR-6105, Cyracure UVR-6107, Cyracure 30, and R-6110 (manufactured by Dow Chemical Japan Limited). 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 active energy ray curable composition is an ultraviolet ray curable composition or a visible ray curable composition, the 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 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 effectively absorb light with a wavelength longer than 380 nm by using it together with a photosensitizer that shows maximum absorption in light with a wavelength longer than 380 nm. When used, the generation of cationic species or Lewis acids from a photocationic polymerization initiator can be promoted. Examples of the photosensitizer 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 preferred 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 active energy ray-curable composition may contain an oligomer. As oligomers, acrylic oligomers, fluorine oligomers, and silicone oligomers are listed, and acrylic oligomers are preferably used. The addition of oligomers to the active energy ray-curable composition helps adjust the viscosity of the composition and also helps suppress shrinkage during curing of the composition. Suppression of curing shrinkage of the active energy ray-curable composition is desirable for reducing the interfacial stress between the formed adhesive layer 20 and the optical films 10 and 30. Suppression of interfacial stress helps secure adhesion between the optical films 10 and 30.

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. esters, hydroxyl group-containing (meth)acrylic acid esters, and halogen-containing (meth)acrylic acid esters are listed. 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-nitro. Propyl (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-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, hexafluoropropyl (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 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. .

The 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. .

The viscosity of the 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 or more from the viewpoint of coatability in the later application process. , and is also 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 laminated optical film (X) can be manufactured, for example, as follows.

First, an active energy ray-curable composition is applied to one side (the surface to be bonded) of one optical film (optical film 10 or optical film 30) to form a coating film of the composition (application process). Before this 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 other optical film (optical film 30 or optical film 10) is bonded to one optical film via the composition coating film. For example, a roll laminator can be used for joining.

In order to form the boundary region 31 with sufficient thickness, it is preferable that the active energy ray-curable composition contains a monomer having a SP value close to the SP value of the resin in the optical film 30. When the active energy ray-curable composition contains such a monomer, in the process of application and curing of the active energy ray-curable composition, the monomer in contact with the surface of the optical film 30 is compatible with the surface, and the boundary region 31 ) becomes easier to form.

In the manufacturing process of the laminated optical film . As a result, the adhesive layer 20 is formed between the optical films 10 and 30, and the optical films 10 and 30 are bonded via the adhesive layer 20 (the adhesive layer 20 is a pressure-sensitive adhesive layer). not this). In this process, it is preferable to irradiate active energy rays from the optical film 30 side from the viewpoint of suppressing deterioration of the optical film 10 as a functional optical film. 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 partial wavelength range in the ultraviolet rays and/or visible rays emitted from the light source may be used as needed.

As shown in FIG. 3 , the laminated optical film The laminated optical film (X) (laminated optical film ( (30) are provided in order in the thickness direction (H). The compositions of the active energy ray-curable compositions forming the two adhesive layers 20 may be the same or different. Materials of the two optical films 30 may be the same or different. For example, the laminated optical film (X)' is formed by attaching an additional optical film 30 to the laminated optical film It can be manufactured by joining.

In the laminated optical film (X)', at least one optical film 30 has the boundary region 31 described above, and preferably, the two optical films 30 have the boundary region 31. In the laminated optical film ( , 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, even more preferably is 1.2 or more.

Example

The present invention will be described in detail below by giving examples. The present invention is not limited to the examples. In addition, specific values such as the mixing amount (content), physical property values, and parameters described below are described in the above-mentioned "Specific Details for Carrying Out the Invention". The corresponding mixing amount (content), physical property values, and parameters are described below. 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 following components were mixed in the mixing amounts (mixing amounts in solid content) shown in Table 1 at 25°C for 1 hour to prepare an adhesive composition (preparation step). The unit of the mixing 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 polydimethyl siloxane with an acrylic group, manufactured by BYK

Then, the application process, bonding process, and curing process were performed sequentially while running the long transparent protective film at a predetermined line speed in a roll-to-roll method. In the application process, the adhesive composition was applied onto a 23-μm-thick long COP film (product name “Zeonor Film ZF14”, manufactured by Zeon Corporation) as a transparent protective film to form an adhesive film with a thickness of 0.9 μm. For coating, an MCD coater manufactured by FUJI MACHINERY Co., Ltd. (cell shape: honeycomb, number of gravure rolls 1000 pieces/inch, rotation speed 140%/line speed) was used. Next, in the bonding process, a polarizer film (5 μm thick) was bonded to the transparent protective film through an adhesive coating film on the film. In the subsequent curing process, the adhesive coating film between the films was cured by irradiating ultraviolet rays to the adhesive coating film through a transparent protective film. A gallium lamp was used for ultraviolet irradiation. As a result, a transparent protective film and a polarizer film were bonded 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 polarizer film (5 μm thick), an adhesive layer, and a transparent protective film (23 μm thick) in this order in the thickness direction.

[Example 2]

The laminated optical film of Example 2 was produced in the same manner as the laminated optical film of Example 1 except for the following. The above line speed was increased to a certain degree, and the time from the application process to the curing process was shortened. In the application process, the thickness of the coating film formed on the transparent protective film (COP film) was set to 2.6 μm.

The laminated optical film of Example 2 includes a polarizer film (5 μm thick), an adhesive layer, and a transparent protective film (23 μm thick) in this order in the thickness direction.

[Example 3]

The laminated optical film of Example 3 was produced in the same manner as the laminated optical film of Example 1 except for the following. The above line speed was lowered to a certain extent, and the time from the application process to the curing process was lengthened. In the application process, the thickness of the coating film formed on the transparent protective film (COP film) was set to 1.2 μm.

The laminated optical film of Example 3 includes a polarizer film (5 μm thick), an adhesive layer, and a transparent protective film (23 μm thick) in this order in the thickness direction.

[Comparative Example 1]

A laminated optical film of Comparative Example 1 was produced in the same manner as in Example 1 except for the following (line speed between the application process and the curing process is the same as in Example 1).

In the preparation process, an adhesive composition with the composition (components, compounding amounts) shown in Table 1 was prepared. Among the monomers, instead of "Light Acrylate POB-A" and "Light Acrylate P2H-A", Kyoeisha Chemical Co., Ltd. 36 parts by mass of “Light Acrylate 1.9ND-A” (1,9-nonanediol diacrylate) manufactured by Kyoeisha Chemical Co., Ltd. and “Light Acrylate HPP-A” (Neohydroxypivalic acid) manufactured by Kyoeisha Chemical Co., Ltd. pentyl glycol acrylic acid adduct) 12.5 parts by mass were used.

In the application process, the thickness of the coating film formed on the transparent protective film (COP film) was set to 0.93 μm.

The laminated optical film of Comparative Example 1 includes a polarizer film (5 μm thick), an adhesive layer, and a transparent protective film (23 μm thick) in this order in the thickness direction.

<Thickness of adhesive layer>

The thickness T1 of the 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. Next, conductive treatment to a thickness of 5 nm or less was performed on the cut surface of the laminated optical film on which the cut surface was formed. 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 measure the thickness of the adhesive layer. 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 adhesive layer is shown in Table 1.

<Thickness of the part containing adhesive raw material ingredients>

The thickness T2 of the adhesive raw material component-containing portion in each laminated optical film of Examples 1 to 3 and Comparative Example 1 was measured as follows. First, the transparent protective film of the film piece cut out from the laminated optical film was thinned by cutting to a predetermined depth from the surface side of the transparent protective film using a microtome. In this way, a measurement sample was obtained. Next, the measurement sample was analyzed from the transparent protective film side by time-of-flight secondary ion mass spectrometry (TOF-SIMS). For the analysis, a time-of-flight secondary ion mass spectrometer (product name “TRIFT-V nanoTOF, ULVAC-PHI, manufactured by INCORPORATED) was used. In this analysis, irradiation with the ion beam for etching and subsequent irradiation with the ion beam for measurement (primary ion beam) were alternately repeated. In the ion beam irradiation for etching, Ar gas cluster ions (cluster size (median value) is 2500) are used, the acceleration voltage is 20 kV, the ion beam current value is 10 nA, and the irradiation range is 1000 ㎛ × 1000 ㎛. And the investigation time was set to 5 seconds. In the ion beam irradiation for measurement, the double charge ion (Bi ₃ ⁺⁺ ) of the bismuth cluster is used as the irradiation primary ion, the acceleration voltage is set to 30 kV, and the irradiation range is 200 ㎛ × the center of the etching ion beam irradiation area. It was set at 200 μm, and a neutralizing gun was used to correct charging of the sample during analysis. Additionally, this analysis was conducted at room temperature. Through this analysis, a depth profile (depth profile) of the mass spectrum of secondary ion (positive ion, negative ion) intensity was obtained. The secondary ion intensity was converted to the value when the value of C ₃ H ₅ ⁺ was set as the standard value of 1 for positive ions, and the value of C ₂ H ⁻ was set as the standard value of 1 for negative ions. Next, based on the acquired depth direction profile, the area (boundary area) in the transparent protective film where adhesive raw material components exceeding the detection limit (positive/negative secondary ion intensity 0.1 counts/sec) was detected was specified. Then, the thickness T2 of the adhesive raw material component-containing portion was determined from the thickness of this boundary region and the above-mentioned thickness T1 of the adhesive layer. The thickness T2 (μm) is shown in Table 1. Additionally, the ratio of thickness T2 to thickness T1 is also shown in Table 1.

<Peel strength>

The peeling strength between the transparent protective film and the polarizer film in each laminated optical film of Examples 1 to 3 and Comparative Example 1 was examined. First, a 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 polarizer film side of the sample film was bonded to a glass plate through a strong adhesive. Next, the 90° peel strength (N/15 mm) of the 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 measurement temperature was 25°C, the peeling angle was 90°, and the peeling speed was 1000 mm/min. The measured 90° peel strength is shown in Table 1 as peel strength F ₁ .

<Indentation elastic modulus>

The elastic modulus of the adhesive layer in each laminated optical film of Examples 1 to 3 and Comparative Example 1 was investigated 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 nano indenter (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 JIS Z 2255:2003, and the load -Displacement curve was 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 set to 25°C. (Maximum displacement hmax) was set to 200 nm, the indentation speed was set to 10 nm/sec, and the pulling speed of the indenter from the measurement sample during the unloading process was set to 10 nm/sec (first measurement condition). 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 of the adhesive layer (=(π ^1/2 D)/(2S ^1/2 )) was calculated. The value is shown in Table 1 as the indentation elastic modulus M ₁ (GPa) (the indentation elastic modulus M ₁ is the above-mentioned first indentation elastic modulus). Additionally, the ratio of peel strength F ₁ to indentation elastic modulus M ₁ (F ₁ /M ₁ ) is also shown in Table 1.

Meanwhile, load-displacement measurement using a nano indenter was performed under the same measurement conditions (second measurement conditions) as the first measurement conditions, except that the maximum indentation depth was changed from 200 nm to 50 nm. Then, the obtained measurement data was processed with "TI950 Triboindenter" dedicated analysis software (Ver. 9.4.0.1), and the indentation elastic modulus of the adhesive layer was calculated. The value is shown in Table 1 as the indentation elastic modulus M ₂ (GPa) (the indentation elastic modulus M ₂ is the above-mentioned second indentation elastic modulus). Additionally, the ratio of the peel strength F ₁ to the indentation elastic modulus M ₂ (F ₁ /M ₂ ) is also shown in Table 1.

<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 produced. Specifically, first, the exposed surface of the polarizer film of the laminated optical film and the adhesive surface of the adhesive layer with a single-sided release liner were bonded. In this bonding, the surface of the polarizer film in the laminated optical film and the surface of the adhesive layer were pressed together by reciprocating a 2 kg roller once in an environment of 23°C (later bonding was also performed under the same conditions. ). Next, after peeling the release liner from the adhesive layer, a polyethylene terephthalate (PET) film (product name “Diafoil”, thickness 125 μm, manufactured by Mitsubishi Chemical Corporation) was bonded to the exposed surface of the adhesive sheet. . As a result, a multilayer film was obtained. The adhesive layer with the single-sided release liner was produced as follows.

First, in a reaction vessel equipped with a reflux cooling tube, a nitrogen introduction tube, a thermometer, and a stirrer, 100 parts by mass of n-butyl acrylate, 3 parts by mass of acrylic acid, 0.1 part by mass of 2-hydroxyethyl acrylate, and a thermal polymerization initiator. A mixture containing 0.3 parts by mass of 2,2'-azobisisobutyronitrile as a solvent and ethyl acetate as a solvent was stirred at 55°C for 8 hours in a nitrogen atmosphere (polymerization reaction). As a result, a polymer solution containing an acrylic base polymer was obtained. The weight average molecular weight of the acrylic base polymer in this polymer solution was about 2.2 million. Next, for the polymer solution, per 100 parts by mass of acrylic base polymer, 0.5 parts by mass of a crosslinking agent (product name "Coronate L", manufactured by Nippon Polyurethane Industry Co., Ltd.), and a silane coupling agent (product name "KMB-403", 0.075 parts by mass of γ-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) was added and mixed to prepare an adhesive solution. Next, the adhesive solution was applied on the peel-treated surface of the release liner to form a coating film (20 μm thick). This release liner is a polyethylene terephthalate film (thickness 38 μm) that has been subjected to a predetermined release treatment. Next, the coating film on the release liner was dried to form an adhesive layer.

In producing the sample for evaluation, the sample for evaluation was cut out from the multilayer film prepared as described above. 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 end 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 fixed). It is in a state where it is not ready). 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 flexed 200,000 times at a bending speed of 60 rpm between a bent form in which the surface on the polarizer film side is inside and a non-bent form. It was repeatedly deformed (bended). Specifically, the bending form in this test is a form in which the axial direction of the bending moment acting on the sample and the absorption axial 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°. Regarding the ability to suppress peeling between films (transparent protective film, polarizer film) in this bending test, a case where no peeling occurs between films up to 200,000 bending counts is evaluated as "excellent", and a bending count of 80,000 or more is 20. Cases where delamination occurred at less than 10,000 times were evaluated as “good,” and cases where delamination occurred at less than 80,000 bending times were evaluated as “bad.” The evaluation results are shown in Table 1.

Example 1 Example 2 Example 3 Comparative Example 1 monomer Light Acrylate POB-A 45 45 45 - Light Acrylate P2H-A 25 25 25 - Light Acrylate 1.9ND-A - - - 36 Light Acrylate HPP-A - - - 12.5 Aronix M-5700 10 10 10 22 Aronix M-220 5 5 5 - HEAA 5 5 5 12.5 DEAA 5 5 5 6 photopolymerization initiator OMINIRAD 907 3 3 3 3 KAYACURE DETX-S 3 3 3 3 oligomer Arupone 1190 5 5 5 10 leveling agent BYK-UV 3505 0.5 0.5 0.5 0.5 Thickness of adhesive layer T1 (㎛) 0.81 2.52 1.2 0.93 Thickness T2 (㎛) of the part containing adhesive raw material ingredients 0.9 2.57 1.50 0.93 T2/T1 1.11 1.02 1.25 1.00 Peel strength F _One (N/15mm) 1.0 0.9 2.5 0.6 Indentation modulus M _One (GPa) 0.057 0.057 0.057 0.09 Indentation modulus M ₂ (GPa) 2.34 2.34 2.34 3.21 F _One /M _One 18 18 18 6.7 F _One /M ₂ 0.43 0.43 0.43 0.19 High temperature and humidity bending test Great 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 (first optical film)
20 adhesive layer
30 Optical film (second optical film)
31 border area
40 Adhesive raw material ingredient content
H Thickness direction

Claims (4)

A laminated optical film comprising a first optical film, an adhesive layer, and a second optical film in that order in the thickness direction,
The adhesive layer is bonded to the first optical film and also bonded to the second optical film,
The second optical film has a border region on the adhesive layer side containing an adhesive raw material component derived from the adhesive layer,
A laminated optical film, wherein the ratio of the thickness T2 of the adhesive raw material component-containing portion combining the adhesive layer and the boundary region to the thickness T1 of the adhesive layer is 1.01 or more. According to claim 1,
A laminated optical film wherein the thickness T1 is 5 μm or less. According to claim 1,
A laminated optical film, wherein the 90° peel strength at 25° C. of the second optical film with respect to the first optical film is 0.8 N/15 mm or more. The method according to any one of claims 1 to 3,
A laminated optical film, wherein the first optical film is a polarizer film.