JP2023095055A - Optical film with cover film - Google Patents

Abstract

To provide an optical film with a cover film appropriate for suppressing a laser output in laser processing.SOLUTION: An optical film X1 with a cover film includes an optical film 10, cover films 20, 30, and adhesive layers 40, 50. At least one of the optical film 10 and the cover film 20 has a Young's modulus of 2000 MPa or higher at 23°C, and optical transmittance of 10% or lower at wavelength 355 nm. At least one selected from a group consisting of the cover film 20, the adhesive layer 40, the optical film 10, and the adhesive layer 50 is a high transmission layer with an optical transmittance at wavelength 355 nm of 80% or higher. A ratio of thickness of at least one high transmission layer is less than 88%, with regard to a sum of thickness of the cover film 20, the adhesive layer 40, the optical film 10, and the adhesive layer 50.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to an optical film with a cover film.

A display panel has a laminated structure including elements such as, for example, a pixel panel, a touch panel, and a transparent cover film. An optical film having a predetermined optical function is provided in the laminated structure of the display panel. Examples of optical films include film-like polarizing plates and retardation films. The optical film is produced, for example, as an optical film with an adhesive layer in which an adhesive layer is provided on each of both surfaces of the optical film. Moreover, the optical film with a pressure-sensitive adhesive layer is manufactured as an optical film with a cover film in which the pressure-sensitive adhesive layer is covered with a cover film, for example. In the manufacturing process, conventionally, the outer shape of the optical film with a cover film is processed by punching. Such an optical film with a cover film is described, for example, in Patent Document 1 below.

JP 2018-111754 A

Development of foldable display panels for smartphones and tablet terminals is progressing. Specifically, the foldable display panel is repeatedly deformable between a bent shape and a flat non-bent shape. In such a foldable display panel, each element in the laminated structure is manufactured to be repeatedly foldable. The pressure-sensitive adhesive layer in the pressure-sensitive adhesive layer-attached optical film for foldable display panels is highly flexible so as to have sufficient conformability to the adherend when bent and excellent stress relaxation properties. Something is required.

However, the softer the pressure-sensitive adhesive layer, the more trouble occurs in the above-described punching process (the punching blade comes into contact with the soft pressure-sensitive adhesive layer) in the process of producing an optical film with a pressure-sensitive adhesive layer with a cover film. Cheap. Therefore, it is conceivable to process the outer shape of the optical film with a cover film by laser processing. However, conventional optical films with cover films require high laser power for proper laser processing.

The present invention provides an optical film with a cover film suitable for suppressing laser output in laser processing.

The present invention [1] provides a cover film-attached optical film comprising a first cover film, a first pressure-sensitive adhesive layer, an optical film, a second pressure-sensitive adhesive layer, and a second cover film in this order in the thickness direction. A film, wherein at least one of the first cover film and the optical film has a Young's modulus of 2000 MPa or more at 23° C. and a light transmittance of 10% or less at a wavelength of 355 nm; At least one selected from the group consisting of the cover film, the first pressure-sensitive adhesive layer, the optical film, and the second pressure-sensitive adhesive layer is a highly transmissive layer having a light transmittance of 80% or more at a wavelength of 355 nm, and The cover, wherein the ratio of the thickness of the at least one highly permeable layer to the total thickness of the first cover film, the first pressure-sensitive adhesive layer, the optical film and the second pressure-sensitive adhesive layer is less than 88%. Including optical film with film.

The present invention [2] is the cover film according to [1] above, wherein the first cover film has a Young's modulus of 2000 MPa or more at 23° C. and a light transmittance of 10% or less at a wavelength of 355 nm. Includes attached optical film.

The present invention [3] is the first cover film with the cover film according to [2] above, wherein the product of the Young's modulus (MPa) and the light transmittance (%) is 1×10 ⁵ or less. Includes optical film.

The present invention [4] resides in the above [1], wherein the first cover film and the optical film have a Young's modulus of 2000 MPa or more at 23° C. and a light transmittance of 10% or less at a wavelength of 355 nm. It includes an optical film with a cover film as described.

The present invention [5] is the above [4], wherein the product of the Young's modulus (MPa) and the light transmittance (%) is 1×10 ⁵ or less in each of the first cover film and the optical film. Including the optical film with a cover film described in .

The present invention [6] includes the optical film with a cover film according to any one of the above [1] to [5], which has a luminous transmittance Y of 60% or less.

In the present invention [7], after the second cover film is reattached to a polyimide film having a thickness of 25 μm, at a cut portion generated by laser cutting in the thickness direction from the polyimide film side, the thickness direction and Any one of the above [1] to [6], wherein the retraction length of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer from the edge of the optical film in the orthogonal plane direction is 10 μm or less. The optical film with the cover film described in 1 above is included.

The present invention [8] includes the optical film with a cover film according to any one of [1] to [7] above, wherein the optical film is a polarizing film.

In the optical film with a cover film of the present invention, as described above, at least one of the first cover film and the optical film has a Young's modulus of 2000 MPa or more at 23° C. and a light intensity of 10% or less at a wavelength of 355 nm. It has transmittance. In such a configuration, in the first cover film and/or the optical film, while ensuring the strength required for foldable display panel applications, the absorbability of the laser for processing is secured, and the outer shape of the optical film with the cover film is processed. It is suitable for reducing the energy of laser irradiation required for In the optical film with a cover film of the present invention, as described above, the high transmission layer (at a wavelength of 355 nm) with respect to the total thickness of the first cover film, the first adhesive layer, the optical film and the second adhesive layer light transmittance of 80% or more) is less than 88%. Such a configuration is suitable for ensuring the overall absorptivity of the processing laser of the optical film with the cover film, and is therefore suitable for reducing the laser irradiation energy required for contour processing of the same film. The optical film with a cover film as described above is suitable for suppressing laser output in laser processing.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram of 1st Embodiment of the optical film with a cover film of this invention. An example of the usage method of the optical film with a cover film shown in FIG. 1 is represented. FIG. 2A shows a first peeling step of peeling the second cover film, and FIG. 2B shows a first bonding step of bonding the optical film and the first adherend via the second pressure-sensitive adhesive layer. 2C represents a second peeling step of peeling the first cover film, and FIG. 2D represents a second bonding step of bonding the optical film and the second adherend via the first adhesive layer. It is a cross-sectional schematic diagram of 2nd Embodiment of the optical film with a cover film of this invention. An example of the usage method of the optical film with a cover film shown in FIG. 3 is represented. 4A shows a peeling step of peeling the second cover film, and FIG. 4B shows a bonding step of bonding the optical film and the first adherend via the second pressure-sensitive adhesive layer.

As shown in FIG. 1, the optical film X1 as the first embodiment of the optical film with a cover film of the present invention comprises an optical film 10, a cover film 20 (first cover film), and a cover film 30 (second cover film). cover film), an adhesive layer 40 (first adhesive layer), and an adhesive layer 50 (second adhesive layer). The optical film X1 has a sheet shape with a predetermined thickness and spreads in a direction perpendicular to the thickness direction H (surface direction). Specifically, the optical film X1 includes a cover film 20, an adhesive layer 40, an optical film 10, an adhesive layer 50, and a cover film 30 in order in the thickness direction H.

The optical film 10 is a functional optical film in this embodiment. Examples of functional optical films include film-like polarizing plates (polarizing films), retardation films, and combinations thereof. The optical film 10 has a first surface 11 and a second surface 12 opposite to the first surface 11 . The adhesive layer 40 is attached to the first surface 11 and has an adhesive surface 41 on the side opposite to the optical film 10 . The adhesive layer 50 adheres to the second surface 12 and has an adhesive surface 51 on the side opposite to the optical film 10 . The optical film 10 and the pressure-sensitive adhesive layers 40 and 50 form the pressure-sensitive adhesive layer-attached optical film Y1. The pressure-sensitive adhesive layer-attached optical film Y1 is, for example, an optical film to be incorporated into a laminate structure of a foldable display panel. The optical film X1 includes such an optical film Y1 with an adhesive layer and cover films 20 and 30. As shown in FIG. The cover film 20 is releasably arranged on the adhesive surface 41 of the optical film Y1 with an adhesive layer. The cover film 30 is releasably arranged on the adhesive surface 51 . The cover films 20, 30 have flexibility.

Such an optical film X1 is used as a supply material for the pressure-sensitive adhesive layer-attached optical film Y1 incorporated in the laminated structure of the foldable display panel in the process of manufacturing the same. In this embodiment, the cover film 20 is a release liner (heavy release liner) with a relatively large peel force, and the cover film 30 is a release liner (light release liner) with a relatively small peel force. The cover film 30 and the cover film 20 are peeled off from the adhesive layer-attached optical film Y1 in this order.

In the optical film X1, at least one of the optical film 10 and the cover film 20 has a Young's modulus of 2000 MPa or more at 23° C. and a light transmittance of 10% or less at a wavelength of 355 nm. Preferably, both the optical film 10 and the cover film 20 have a Young's modulus of 2000 MPa or more at 23° C. and a light transmittance of 10% or less at a wavelength of 355 nm.

The optical film 10 has a Young's modulus of 2000 MPa or more at 23° C. and a light transmittance (light transmittance T1) of 10% or less at a wavelength of 355 nm. In , it is suitable for securing the absorbability (laser absorbability) of the processing laser and reducing the laser irradiation energy required for the outer shape processing of the optical film X1. From the viewpoint of laser absorption of the optical film 10, the light transmittance T1 is preferably 8% or less, more preferably 6% or less, and even more preferably 5% or less. The light transmittance T1 is, for example, 0.1% or more. The method for measuring the light transmittance is as described below with respect to the examples. As a method for adjusting the light transmittance T1, for example, use of a member having a high ability to absorb light with a wavelength of 355 nm and blending of materials are exemplified.

The cover film 20 has a Young's modulus of 2000 MPa or more at 23° C. and a light transmittance (light transmittance T2) of 10% or less at a wavelength of 355 nm. , it is suitable for securing laser absorbency and reducing the energy of laser irradiation required for outer shape processing of the optical film X1. The light transmittance T2 is preferably 8% or less, more preferably 6% or less, even more preferably 4% or less, and particularly preferably 2% or less, from the viewpoint of the laser absorption of the cover film 20 . The light transmittance T2 is, for example, 0.1% or more. As a method for adjusting the light transmittance T2, for example, adjustment of the compounding amount of the ultraviolet absorber in the cover film 20 can be mentioned.

In the optical film X1, at least one selected from the group consisting of the cover film 20, the adhesive layer 40, the optical film, and the adhesive layer 50 is a highly transmissive layer having a light transmittance of 80% or more at a wavelength of 355 nm. . Then, the thickness of the high transmission layer with respect to the total thickness of the cover film 20, the adhesive layer 40, the optical film, and the adhesive layer 50 (when there are multiple high transmission layers, the thickness of all the high transmission layers total) is less than 88%. Such a configuration is suitable for ensuring the overall laser absorptivity of the optical film X1. The ratio R1 is preferably 85% or less, more preferably 82% or less, even more preferably 80% or less, and particularly preferably 78% or less, from the viewpoint of ensuring the overall laser absorbency of the optical film X1. The ratio R1 is, for example, 10% or more.

The optical film X1 as described above is suitable for suppressing the laser output during outer shape processing by laser processing, as shown in Examples and Comparative Examples below.

It is preferable that the optical film 10 has a Young's modulus (Young's modulus E1) of 2000 MPa or more at 23° C. in order to secure the strength required for foldable display panel applications. From the viewpoint of ensuring the strength of the optical film 10, the Young's modulus E1 is preferably 2500 MPa or more, more preferably 2800 MPa or more, and still more preferably 3000 MPa or more. Young's modulus E1 is preferably 10000 MPa or less, more preferably 7000 MPa or less, even more preferably 5000 MPa or less, still more preferably 4000 MPa or less, from the viewpoint of ensuring the flexibility required for foldable display panel applications in the optical film 10. It is preferably 3500 MPa or less. A method for measuring the Young's modulus is as described below with respect to Examples.

In the optical film 10, the product (E1×T1) of the Young's modulus E1 (MPa) and the above-mentioned light transmittance T1 (%) is determined from the viewpoint of ease of processing the optical film 10 with a laser (laser processability). , preferably 1×10 ⁵ or less, more preferably 0.7×10 ⁵ or less, still more preferably 0.4×10 ⁵ or less, still more preferably 0.3×10 ⁵ or less, particularly preferably 0.25×10 ⁵ or less. The product (E1×T1) is, for example, 0.01×10 ⁵ or more.

It is preferable for the cover film 20 to have a Young's modulus (Young's modulus E2) of 2000 MPa or more at 23° C. in order to secure the protective function of the pressure-sensitive adhesive layer-attached optical film Y1 by the cover film 20 . Young's modulus E2 is preferably 3000 MPa or more, more preferably 4000 MPa or more, and still more preferably 5000 MPa or more from the viewpoint of ensuring the protection function of the cover film 20 . Young's modulus E2 is preferably 10000 MPa or less, more preferably 8000 MPa or less, even more preferably 6000 MPa or less, and particularly preferably 5500 MPa or less, from the viewpoint of ensuring the flexibility of the cover film 20 .

In the cover film 20, the product (E2×T2) of the Young's modulus E2 (MPa) and the light transmittance T2 (%) described above is preferably 1×10 ⁵ or less from the viewpoint of the laser processability of the cover film 20. It is more preferably 0.7×10 ⁵ or less, still more preferably 0.4×10 ⁵ or less, still more preferably 0.3×10 ⁵ or less, and particularly preferably 0.25×10 ⁵ or less. The product (E2×T2) is, for example, 0.01×10 ⁵ or more.

The luminous transmittance Y of the optical film X1 is preferably 60% or less, more preferably 50% or less, and still more preferably 45% or less from the viewpoint of ensuring a good appearance by reducing light reflection in the display panel. . From the viewpoint of suppressing reduction in the light extraction efficiency of the display panel, it is preferably 20% or more, more preferably 30% or more, and even more preferably 40% or more. A method for measuring the luminous transmittance Y is as described later with respect to Examples.

In the optical film X1, after the cover film 30 is replaced with a polyimide film having a thickness of 25 μm, a cut portion produced by laser cutting in the thickness direction H from the polyimide film side is cut in a plane direction orthogonal to the thickness direction H. , the retraction length of the adhesive layer 40 from the edge 10a of the optical film 10 (the distance between the edge 10a and the edge 40a of the adhesive layer 40 in the plane direction) is the adhesive layer-attached optical film Y1 is preferably 10 μm or less, more preferably 7 μm or less, even more preferably 5 μm or less, and even more preferably 3 μm or less, from the viewpoint of suppressing interference with the image display area of the display panel after it is incorporated into the laminated structure of the display panel. , particularly preferably 1 μm or less, very preferably 0 μm.

In the optical film X1, after the cover film 30 is replaced with a polyimide film having a thickness of 25 μm, the edge of the optical film 10 in the plane direction is cut by laser cutting in the thickness direction H from the polyimide film side. The retraction length of the adhesive layer 50 from the edge 10a (the distance between the edge 10a and the edge 50a of the adhesive layer 50 in the plane direction) is the distance between the adhesive layer-attached optical film Y1 and the laminated structure of the display panel. From the viewpoint of suppressing interference with the image display area of the panel after being incorporated in the panel, it is preferably 10 μm or less, more preferably 7 μm or less, even more preferably 5 μm or less, even more preferably 3 μm or less, and particularly preferably 1 μm or less. Very preferably it is 0 μm.

In the optical film X1, the optical film 10 is preferably a polarizing film. A polarizing film includes, for example, a polarizing film including a polarizer and a transparent protective film attached to one or both sides of the polarizer. Polarizers include, for example, uniaxially stretched hydrophilic polymer films to which a dichroic substance is adsorbed, and oriented polyene films. Hydrophilic polymer films include, for example, polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films. Dichroic substances include, for example, iodine and dichroic dyes. Examples of oriented polyene films include dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride.

A thin polarizer having a thickness of 10 μm or less may be used as the polarizer. Examples of thin polarizers include polarizers described in JP-A-51-069644, JP-A-2000-338329, WO2010/100917, Japanese Patent No. 4691205, and Japanese Patent No. 4751481. .

As the transparent protective film, a film excellent in transparency, mechanical strength, thermal stability, water barrier property and optical isotropy is preferred. Materials for such transparent protective films include, for example, cellulose resins, cyclic polyolefin resins, acrylic resins, phenylmaleimide resins, and polycarbonate resins.

Examples of the cover film 20 include a flexible plastic film. Examples of the plastic film include polyethylene terephthalate film, polyethylene film, polypropylene film, and polyester film. The surface of the cover film 20 on the pressure-sensitive adhesive layer 40 side is preferably subjected to release treatment. Examples of the release treatment include silicone release treatment and fluorine release treatment (the same applies to the release treatment described below).

Examples of the cover film 30 include the plastic films described above with respect to the cover film 20 . The surface of the cover film 30 on the pressure-sensitive adhesive layer 50 side is preferably subjected to release treatment.

The adhesive layer 40 is a pressure sensitive adhesive layer formed from the first adhesive composition. The adhesive layer 40 has transparency (visible light transmittance). The first PSA composition contains at least a base polymer.

The base polymer is an adhesive component that develops adhesiveness in the adhesive layer 40 . Base polymers include, for example, acrylic polymers, silicone polymers, polyester polymers, polyurethane polymers, polyamide polymers, polyvinyl ether polymers, vinyl acetate/vinyl chloride copolymers, modified polyolefin polymers, epoxy polymers, fluoropolymers, and rubber polymers. The base polymer may be used alone or in combination of two or more. From the viewpoint of ensuring good transparency and adhesiveness in the adhesive layer 40, an acrylic polymer is preferably used as the base polymer.

The acrylic polymer is a copolymer of monomer components containing 50% by mass or more of (meth)acrylic acid alkyl ester. "(Meth)acrylic acid" means acrylic acid and/or methacrylic acid.

As the (meth)acrylic acid alkyl ester, a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms is preferably used. The (meth)acrylic acid alkyl ester may have a linear or branched alkyl group, or may have a cyclic alkyl group such as an alicyclic alkyl group.

Examples of (meth)acrylic acid alkyl esters having a linear or branched alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and isobutyl (meth)acrylate. , s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, (meth)acrylate Heptyl acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, (meth) ) isodecyl acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate (that is, lauryl acrylate), isotridecyl (meth) acrylate, tetradecyl (meth) acrylate, isotetradecyl (meth) acrylate, (meth) Pentadecyl acrylate, cetyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, and nonadecyl (meth)acrylate.

Examples of (meth)acrylic acid alkyl esters having an alicyclic alkyl group include (meth)acrylic acid cycloalkyl esters, (meth)acrylic acid esters having a bicyclic aliphatic hydrocarbon ring, and tricyclic (Meth)acrylic acid esters having the above aliphatic hydrocarbon ring can be mentioned. Cycloalkyl (meth)acrylates include, for example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate. Examples of (meth)acrylic acid esters having a bicyclic aliphatic hydrocarbon ring include isobornyl (meth)acrylate. (Meth)acrylic esters having a tricyclic or higher aliphatic hydrocarbon ring include, for example, dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, tricyclopentanyl (meth)acrylate , 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate.

As the (meth)acrylic acid alkyl ester, an acrylate alkyl ester having an alkyl group having 3 to 15 carbon atoms is preferably used, and more preferably n-butyl acrylate, 2-ethylhexyl acrylate, and acrylic acid. At least one selected from the group consisting of dodecyl is used.

The ratio of the (meth)acrylic acid alkyl ester in the monomer component is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably, from the viewpoint of appropriately expressing basic properties such as adhesiveness in the adhesive layer 40. is 70% by mass or more. The same ratio is, for example, 99% by mass or less.

The monomer component may also contain a copolymerizable monomer copolymerizable with the (meth)acrylic acid alkyl ester. Examples of copolymerizable monomers include monomers having a polar group. Polar group-containing monomers include, for example, nitrogen atom-containing ring-containing monomers, hydroxy group-containing monomers, and carboxy group-containing monomers. The polar group-containing monomer is useful for modifying the acrylic polymer, such as introducing cross-linking points into the acrylic polymer and securing the cohesive strength of the acrylic polymer.

Examples of monomers having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl -3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N -vinylthiazole, and N-vinylisothiazole. N-vinyl-2-pyrrolidone is preferably used as the monomer having a nitrogen atom-containing ring.

The ratio of the monomer having a nitrogen atom-containing ring in the monomer component is preferably 0.1 mass from the viewpoint of ensuring the cohesive force of the adhesive layer 40 and ensuring the adhesive strength of the adhesive layer 40 to the adherend. % or more, more preferably 0.3 mass % or more, and still more preferably 0.55 mass % or more. The same ratio is preferably 30% by mass from the viewpoint of adjusting the glass transition temperature of the acrylic polymer and adjusting the polarity of the acrylic polymer (related to compatibility between the various additive components in the adhesive layer 40 and the acrylic polymer). Below, more preferably 20% by mass or less.

Examples of hydroxy group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, ( 4-hydroxybutyl meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. As the hydroxy group-containing monomer, 4-hydroxybutyl (meth)acrylate is preferably used, and 4-hydroxybutyl acrylate is more preferably used.

The ratio of the hydroxy group-containing monomer in the monomer component is preferably 0.1% by mass or more, more preferably 0.5, from the viewpoint of introducing a crosslinked structure into the acrylic polymer and ensuring cohesive strength in the pressure-sensitive adhesive layer 40. It is at least 0.8% by mass, more preferably at least 0.8% by mass. The same ratio is preferably 20% by mass or less, more preferably 10% by mass or less, from the viewpoint of adjusting the polarity of the acrylic polymer (related to compatibility between various additive components and the acrylic polymer in the adhesive layer 40). .

Carboxy group-containing monomers include, for example, acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

The ratio of the carboxyl group-containing monomer in the monomer component is preferable from the viewpoint of introducing a crosslinked structure into the acrylic polymer, ensuring cohesive force in the adhesive layer 40, and ensuring adhesion to the adherend in the adhesive layer 40. is 0.1% by mass or more, more preferably 0.5% by mass or more, and still more preferably 0.8% by mass or more. The same ratio is preferably 30% by mass or less, more preferably 20% by mass or less, from the viewpoints of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of acid corrosion of the adherend.

In order to prevent metal elements such as electrodes in a foldable display panel from being corroded by acid components, the adhesive layer 40 preferably has a low acid content. Moreover, when the adhesive layer 40 is used for bonding a polarizing film, the acid content of the adhesive layer 40 is preferably small in order to suppress polyene formation of the polyvinyl alcohol polarizer due to the acid component. The content of organic acid monomers (for example, (meth)acrylic acid and carboxyl group-containing monomers) in such an acid-free pressure-sensitive adhesive layer 40 is preferably 100 ppm or less, more preferably 70 ppm or less, and even more preferably 50 ppm or less. be. The organic acid monomer content of the adhesive layer 40 is obtained by quantifying the acid monomer extracted into water by immersing the adhesive layer 40 in pure water and heating at 100° C. for 45 minutes by ion chromatography. is required by

From the viewpoint of acid-free, it is preferable that the base polymer in the pressure-sensitive adhesive layer 40 does not substantially contain organic acid monomers as monomer components. From the viewpoint of acid-free, the ratio of the organic acid monomer in the monomer component is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and still more preferably 0.05% by mass. is 0.

The monomer component may contain other copolymerizable monomers. Other copolymerizable monomers include, for example, acid anhydride monomers, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, alkoxy group-containing monomers, and aromatic vinyl compounds. be done. These other copolymerizable monomers may be used alone, or two or more of them may be used in combination.

The base polymer has a crosslinked structure in this embodiment. As a method of introducing a crosslinked structure into the base polymer, the base polymer having a functional group capable of reacting with the crosslinker and the crosslinker are blended in the first adhesive composition, and the base polymer and the crosslinker are combined into the adhesive layer 40. A base in which a polyfunctional monomer is included in the monomer components forming the base polymer and a branched structure (crosslinked structure) is introduced into the polymer chain by polymerization of the monomer components. A method of forming a polymer (second method) is included. These methods may be used in combination.

Examples of the cross-linking agent used in the first method include compounds that react with functional groups (hydroxy groups, carboxy groups, etc.) contained in the base polymer. Such crosslinkers include, for example, isocyanate crosslinkers, peroxide crosslinkers, epoxy crosslinkers, oxazoline crosslinkers, aziridine crosslinkers, carbodiimide crosslinkers, and metal chelate crosslinkers. The cross-linking agents may be used alone, or two or more of them may be used in combination. As the cross-linking agent, an isocyanate cross-linking agent, a peroxide cross-linking agent, and an epoxy cross-linking agent are preferably used because they are highly reactive with the hydroxy groups and carboxy groups in the base polymer and facilitate the introduction of a cross-linked structure. be done.

Examples of isocyanate cross-linking agents include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, isocyanates, and polymethylene polyphenyl isocyanates. The isocyanate cross-linking agent also includes derivatives of these isocyanates. Examples of the isocyanate derivative include isocyanurate-modified products and polyol-modified products. Commercially available isocyanate cross-linking agents include, for example, Coronate L (trimethylolpropane adduct of tolylene diisocyanate, manufactured by Tosoh), Coronate HL (trimethylolpropane adduct of hexamethylene diisocyanate, manufactured by Tosoh), Coronate HX (hexa isocyanurate of methylene diisocyanate, manufactured by Tosoh), and Takenate D110N (trimethylolpropane adduct of xylylene diisocyanate, manufactured by Mitsui Chemicals).

Peroxide crosslinking agents include dibenzoyl peroxide, di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, t- butyl peroxyneodecanoate, t-hexyl peroxypivalate, and t-butyl peroxypivalate.

Examples of epoxy cross-linking agents include bisphenol A, epichlorohydrin type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether. , diglycidylaniline, diamine glycidylamine, N,N,N',N'-tetraglycidyl-m-xylylenediamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

An isocyanate cross-linking agent (especially a bifunctional isocyanate cross-linking agent) and a peroxide cross-linking agent are preferable from the viewpoint of ensuring appropriate flexibility (thus flexibility) of the pressure-sensitive adhesive layer 40 . An isocyanate cross-linking agent (especially a trifunctional isocyanate cross-linking agent) is preferable from the viewpoint of ensuring the durability of the pressure-sensitive adhesive layer 40 . In the base polymer, difunctional isocyanate and peroxide crosslinkers form softer two-dimensional crosslinks, while trifunctional isocyanate crosslinkers form stronger three-dimensional crosslinks. From the viewpoint of achieving both durability and flexibility of the pressure-sensitive adhesive layer 40, it is preferable to use a trifunctional isocyanate cross-linking agent together with a peroxide cross-linking agent and/or a bifunctional isocyanate cross-linking agent.

From the viewpoint of ensuring the cohesive force of the pressure-sensitive adhesive layer 40, the amount of the cross-linking agent is, for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more, more preferably 0.05 parts by mass or more with respect to 100 parts by mass of the base polymer. is 0.07 parts by mass or more. From the viewpoint of ensuring good tackiness in the pressure-sensitive adhesive layer 40, the amount of the cross-linking agent blended with respect to 100 parts by mass of the base polymer is, for example, 10 parts by mass or less, preferably 5 parts by mass or less, and more preferably 3 parts by mass or less. is.

In the second method, the monomer components (including the polyfunctional monomer for introducing the crosslinked structure and other monomers) may be polymerized at once or in multiple stages. In the multi-stage polymerization method, first, a monofunctional monomer for forming the base polymer is polymerized (prepolymerization), thereby containing a partially polymerized product (a mixture of a polymerized product with a low degree of polymerization and an unreacted monomer). A prepolymer composition is prepared. Next, after adding a polyfunctional monomer to the prepolymer composition, the partial polymer and the polyfunctional monomer are polymerized (main polymerization).

Examples of polyfunctional monomers include polyfunctional (meth)acrylates containing two or more ethylenically unsaturated double bonds in one molecule. As the polyfunctional monomer, a polyfunctional acrylate is preferable from the viewpoint that a crosslinked structure can be introduced by active energy ray polymerization (photopolymerization).

Polyfunctional (meth)acrylates include bifunctional (meth)acrylates, trifunctional (meth)acrylates, and tetrafunctional or higher polyfunctional (meth)acrylates.

Examples of bifunctional (meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol dimethacrylate, 1,6-hexanediol di (meth)acrylate, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, neopentyl glycol di(meth)acrylate, stearic acid-modified pentaerythritol di(meth)acrylate, dicyclopentenyl diacrylate, Examples include di(meth)acryloyl isocyanurate and alkylene oxide-modified bisphenol di(meth)acrylate.

Trifunctional (meth)acrylates include, for example, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and tris(acryloyloxyethyl)isocyanurate.

Tetrafunctional or higher polyfunctional (meth)acrylates include, for example, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, and alkyl-modified dipentaerythritol pentaacrylate. , and dipentaerythritol hexa(meth)acrylate.

Acrylic polymers can be formed by polymerizing the monomer components described above. Polymerization methods include, for example, solution polymerization, bulk polymerization, and emulsion polymerization. Solution polymerization is preferred from the viewpoints of transparency, water resistance, and cost of the pressure-sensitive adhesive layer 40 . Ethyl acetate and toluene, for example, are used as solvents for solution polymerization. Moreover, as a polymerization initiator, for example, a thermal polymerization initiator and a photopolymerization initiator are used. The amount of the polymerization initiator to be used is, for example, 0.05 parts by mass or more and, for example, 1 part by mass or less with respect to 100 parts by mass of the monomer component.

Thermal polymerization initiators include, for example, azo polymerization initiators and peroxide polymerization initiators. Examples of azo polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionate)dimethyl, 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2- imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, and 2,2'-azobis(N,N'-dimethyleneisobutyramidine) dihydrochloride mentioned. Peroxide polymerization initiators include, for example, dibenzoyl peroxide, t-butyl permaleate, and lauroyl peroxide.

Examples of photopolymerization initiators include benzoin ether photopolymerization initiators, acetophenone photopolymerization initiators, α-ketol photopolymerization initiators, aromatic sulfonyl chloride photopolymerization initiators, photoactive oxime photopolymerization initiators, and benzoin photopolymerization initiators. Initiators include benzyl photoinitiators, benzophenone photoinitiators, ketal photoinitiators, thioxanthone photoinitiators, and acylphosphine oxide photoinitiators.

In polymerization, a chain transfer agent and/or a polymerization inhibitor (polymerization retarder) may be used for the purpose of molecular weight adjustment and the like. Chain transfer agents include α-thioglycerol, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol, and α-methylstyrene. Dimers are included.

The molecular weight of the base polymer can be adjusted by adjusting the type and/or amount of polymerization initiator. For example, in radical polymerization, the larger the amount of the polymerization initiator, the higher the radical concentration in the reaction system, the higher the density of reaction initiation points, and the smaller the molecular weight of the base polymer formed. On the other hand, the smaller the amount of the polymerization initiator, the lower the density of the reaction initiation points, the easier it is for the polymer chain to extend, and the greater the molecular weight of the base polymer formed.

The weight-average molecular weight of the acrylic polymer is preferably 100,000 or more, more preferably 300,000 or more, and still more preferably 500,000 or more, from the viewpoint of securing the cohesive force in the pressure-sensitive adhesive layer 40 . The weight-average molecular weight is preferably 5 million or less, more preferably 3 million or less, still more preferably 2 million or less. The weight average molecular weight of the acrylic polymer is calculated by measuring by gel permeation chromatography (GPC) and converting to polystyrene.

The glass transition temperature (Tg) of the base polymer is preferably 0°C or lower, more preferably -10°C or lower, and even more preferably -20°C or lower. The glass transition temperature is, for example, −80° C. or higher.

As the glass transition temperature (Tg) of the base polymer, the glass transition temperature (theoretical value) obtained based on the following Fox formula can be used. The Fox equation is a relational expression between the glass transition temperature Tg of a polymer and the glass transition temperature Tgi of a homopolymer of monomers constituting the polymer. In the Fox formula below, Tg represents the glass transition temperature (° C.) of the polymer, Wi represents the weight fraction of the monomer i constituting the polymer, and Tgi represents the glass transition of the homopolymer formed from the monomer i. Indicates temperature (°C). Literature values can be used for the glass transition temperature of homopolymers. For example, in "Polymer Handbook" (4th edition, John Wiley & Sons, Inc., 1999) and "New Polymer Bunko 7: Introduction to Synthetic Resins for Paints" (Kyozo Kitaoka, Kobunshi Publications, 1995), , which lists the glass transition temperatures of various homopolymers. On the other hand, the glass transition temperature of a homopolymer of a monomer can also be determined by the method specifically described in JP-A-2007-51271.

Fox's formula 1/(273+Tg)=Σ[Wi/(273+Tgi)]

The first PSA composition may contain one or more oligomers in addition to the base polymer. When an acrylic polymer is used as the base polymer, preferably an acrylic oligomer is used as the oligomer. The acrylic oligomer is a copolymer of monomer components containing 50% by mass or more of (meth)acrylic acid alkyl ester, and has a weight average molecular weight of, for example, 1,000 or more and 30,000 or less.

The glass transition temperature of the acrylic oligomer is preferably 60° C. or higher, more preferably 80° C. or higher, still more preferably 100° C. or higher, and particularly preferably 110° C. or higher. The glass transition temperature of the acrylic oligomer is, for example, 200° C. or lower, preferably 180° C. or lower, more preferably 160° C. or lower. The combined use of a low-Tg acrylic polymer (base polymer) introduced with a crosslinked structure and a high-Tg acrylic oligomer can increase the adhesive strength of the pressure-sensitive adhesive layer 40, especially at high temperatures. The glass transition temperature of the acrylic oligomer is calculated by the above Fox formula.

The acrylic oligomer having a glass transition temperature of 60° C. or higher is preferably a (meth)acrylic acid alkyl ester having a chain alkyl group (chain alkyl (meth)acrylate) and a (meth)acrylic acid having an alicyclic alkyl group. It is a polymer of a monomer component containing an acid alkyl ester (alicyclic alkyl (meth)acrylate). Specific examples of these (meth)acrylic acid alkyl esters include, for example, the (meth)acrylic acid alkyl esters described above as the monomer component of the acrylic polymer.

As the chain alkyl (meth)acrylate, methyl methacrylate is preferable because it has a high glass transition temperature and excellent compatibility with the base polymer. Preferred alicyclic alkyl (meth)acrylates are dicyclopentanyl acrylate, dicyclopentanyl methacrylate, cyclohexyl acrylate and cyclohexyl methacrylate. That is, the acrylic oligomer is a monomer component containing methyl methacrylate and at least one selected from the group consisting of dicyclopentanyl acrylate, dicyclopentanyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate. A coalescence is preferred.

The proportion of the alicyclic alkyl (meth)acrylate in the monomer component of the acrylic oligomer is preferably 10% by weight or more, more preferably 20% by weight or more, and still more preferably 30% by weight or more. The same ratio is preferably 90% by weight or less, more preferably 80% by weight or less, and even more preferably 70% by weight or less. The proportion of chain alkyl (meth)acrylate in the monomer component of the acrylic oligomer is preferably 90% by weight or less, more preferably 80% by weight or less, and even more preferably 70% by weight or less. The ratio is preferably 10% by weight or more, more preferably 20% by weight or more, and still more preferably 30% by weight or more.

The weight average molecular weight of the acrylic oligomer is preferably 1,000 or more, more preferably 1,500 or more, and still more preferably 2,000 or more. The molecular weight is preferably 30,000 or less, more preferably 10,000 or less, still more preferably 8,000 or less. Such a molecular weight range of the acrylic oligomer is preferable for ensuring the adhesive strength and adhesive holding power of the pressure-sensitive adhesive layer 40 .

Acrylic oligomers are obtained by polymerizing the monomer components of the acrylic oligomers. Polymerization methods include, for example, solution polymerization, active energy ray polymerization (eg, UV polymerization), bulk polymerization, and emulsion polymerization. In the polymerization of the acrylic oligomer, a polymerization initiator may be used, and a chain transfer agent may be used for the purpose of adjusting the molecular weight.

The content of the acrylic oligomer in the pressure-sensitive adhesive layer 40 is preferably 0.5 parts by mass or more, more preferably 0.5 parts by mass or more with respect to 100 parts by mass of the base polymer, in order to sufficiently increase the adhesive strength of the pressure-sensitive adhesive layer 40 . It is 8 parts by mass or more, more preferably 1 part by mass or more. On the other hand, from the viewpoint of ensuring the transparency of the adhesive layer 40, the content of the acrylic oligomer in the adhesive layer 40 is preferably 5 parts by mass or less, more preferably 4 parts by mass with respect to 100 parts by mass of the base polymer. 3 parts by mass or less, more preferably 3 parts by mass or less. In the pressure-sensitive adhesive layer 40, when the content of the acrylic oligomer is too large, the haze tends to increase and the transparency tends to decrease due to the decrease in compatibility of the acrylic oligomer.

The first PSA composition may contain a silane coupling agent. The content of the silane coupling agent in the first pressure-sensitive adhesive composition is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, relative to 100 parts by mass of the base polymer. The content is preferably 5 parts by mass or less, more preferably 3 parts by mass or less.

The first pressure-sensitive adhesive composition may contain other components as necessary. Other ingredients include, for example, tackifiers, plasticizers, softeners, antidegradants, fillers, colorants, UV absorbers, antioxidants, surfactants, and antistatic agents.

The haze of the adhesive layer 40 is preferably 3% or less, more preferably 2% or less, and more preferably 1% or less. The haze of the adhesive layer 40 can be measured using a haze meter according to JIS K7136 (2000). Examples of the haze meter include "NDH2000" manufactured by Nippon Denshoku Industries Co., Ltd. and "HM-150 type" manufactured by Murakami Color Research Laboratory.

The total light transmittance of the adhesive layer 40 is preferably 60% or higher, more preferably 80% or higher, and even more preferably 85% or higher. The total light transmittance of the adhesive layer 40 is, for example, 100% or less. The total light transmittance of the adhesive layer 40 can be measured according to JIS K 7375 (2008).

The adhesive layer 50 is a pressure sensitive adhesive layer formed from the second adhesive composition. The adhesive layer 50 has transparency. The second PSA composition contains at least a base polymer. Examples of the base polymer contained in the second pressure-sensitive adhesive composition include the base polymers described above with respect to the first pressure-sensitive adhesive composition. The base polymer in the first PSA composition and the base polymer in the second PSA composition may be the same or different. The second PSA composition may contain components other than the base polymer. Examples of the components contained in the second pressure-sensitive adhesive composition include the components other than the base polymer described above for the first pressure-sensitive adhesive composition. The composition of the first pressure-sensitive adhesive composition and the composition of the second pressure-sensitive adhesive composition may be the same or different.

The haze of the adhesive layer 50 is preferably 3% or less, more preferably 2% or less, and more preferably 1% or less. The haze of the adhesive layer 50 can be measured using a haze meter according to JIS K7136 (2000).

The total light transmittance of the adhesive layer 50 is preferably 60% or higher, more preferably 80% or higher, and even more preferably 85% or higher. The total light transmittance of the adhesive layer 50 is, for example, 100% or less. The total light transmittance of the adhesive layer 50 can be measured according to JIS K 7375 (2008).

The optical film X1 can be manufactured, for example, as follows.

First, the optical film 10, the adhesive layer 40 with the cover film 20, and the adhesive layer 50 with the cover film 30 are prepared (preparation step).

The pressure-sensitive adhesive layer 40 with the cover film 20 can be formed by applying the first pressure-sensitive adhesive composition (varnish) on the cover film 20 to form a coating film, and then drying the coating film. Examples of the method of applying the first pressure-sensitive adhesive composition include roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, Lip coating and die coating can be mentioned (the same applies to other methods of applying other pressure-sensitive adhesive compositions described below). Another release liner may be laminated on the adhesive layer 40 on the cover film 20 . This release liner is peeled off before bonding the optical film 10 and the adhesive layer 40 together.

The pressure-sensitive adhesive layer 50 with the cover film 30 can be formed by applying the second pressure-sensitive adhesive composition (varnish) on the cover film 30 to form a coating film, and then drying the coating film. Another release liner may be laminated on the adhesive layer 50 on the cover film 30 . This release liner is peeled off before bonding the optical film 10 and the adhesive layer 50 together.

Next, the first surface 11 of the optical film 10 and the pressure-sensitive adhesive layer 40 side of the pressure-sensitive adhesive layer 40 with the cover film 20 are pasted together (first pasting step). Next, the second surface 12 of the optical film 10 and the pressure-sensitive adhesive layer 50 side of the pressure-sensitive adhesive layer 50 with the cover film 30 are pasted together (second pasting step). Preferably, the first surface 11 and the second surface 12 of the optical film 10, the exposed surface of the pressure-sensitive adhesive layer 40 with the cover film 20, and the exposed surface of the pressure-sensitive adhesive layer 50 with the cover film 30 are preferably attached before the bonding. is plasma treated.

As described above, the above optical film X1 (optical film with cover film) can be manufactured. The optical film X1 is suitable for suppressing the laser output as described above when the outer shape is processed by laser processing. Laser cutting is preferable as an outer shape processing method because the outer shape can be processed with high precision.

Lasers for laser processing include, for example, gas lasers, solid-state lasers, and semiconductor lasers. Gas lasers include, for example, excimer lasers and CO ₂ lasers (numbers in parentheses represent laser wavelengths; the same applies hereinafter for lasers). Excimer lasers include, for example, _F2 excimer laser (157 nm), ArF excimer laser (193 nm), KrF excimer laser (248 nm), and XeCl excimer laser (308 nm). Examples of solid-state lasers include Nd:YAG laser (1064 nm), second harmonic of Nd:YAG laser (532 nm), third harmonic of Nd:YAG laser (355 nm), and fourth harmonic of Nd:YAG laser. waves (266 nm). Examples of semiconductor lasers include semiconductor lasers with a wavelength of 405 nm. In laser processing, the pulse width of the irradiation laser is, for example, 0.5 to 50 μs, the pulse frequency is, for example, 1 to 200 kHz, and the laser output is, for example, 2 to 250W.

2A to 2D show an example of how to use the optical film X1.

In this method, first, as shown in FIG. 2A, the cover film 30 is peeled off from the adhesive layer 50 of the optical film X1. Thereby, the adhesive surface 51 of the adhesive layer 50 is exposed.

Next, as shown in FIG. 2B, the optical film 10 and the first member M1 (first adherend) are joined with the adhesive layer 50 interposed therebetween. The first member M1 is, for example, one element in the laminated structure of the flexible display panel. Examples of such elements include a pixel panel, a touch panel, and a transparent cover film (the same applies to the second member M2 described later). In the present embodiment, the laminated body obtained in this joining step is contour-processed by laser processing. Preferably, the laminate shown in FIG. 2B is laser-cut in the thickness direction H by irradiating the first member M1 side of the laminate shown in FIG. 2B with a laser in the thickness direction H. Lasers for laser processing include, for example, gas lasers, solid-state lasers, and semiconductor lasers, and specific examples are as described above. The optical film X1 is suitable for suppressing the laser output as described above in the laser processing after the cover film 30 is peeled off.

Next, as shown in FIG. 2C, the cover film 20 is peeled off from the adhesive layer 40. Then, as shown in FIG. Thereby, the adhesive surface 41 of the adhesive layer 40 is exposed.

Next, as shown in FIG. 2D, the optical film 10 and the second member M2 (second adherend) are joined with the adhesive layer 40 interposed therebetween.

For example, the optical film X1 is used as described above in the process of manufacturing a flexible panel.

Optical film X2 as a second embodiment of the optical film with a cover film of the present invention, as shown in FIG. cover film), an adhesive layer 40 (first adhesive layer), and an adhesive layer 50 (second adhesive layer). The optical film X2 has a sheet shape with a predetermined thickness and spreads in a direction perpendicular to the thickness direction H (surface direction). Specifically, the optical film X2 includes a cover film 60, an adhesive layer 40, an optical film 10, an adhesive layer 50, and a cover film 30 in order in the thickness direction H.

The optical film X2 is different from the optical film X1 in that the optical film Y1 with an adhesive layer and the cover film 60 with an adhesive layer 40 are provided instead of the optical film Y1 with an adhesive layer and the cover films 20 and 30 . The pressure-sensitive adhesive layer-attached optical film Y2 is the same as the pressure-sensitive adhesive layer-attached optical film Y1 except that the pressure-sensitive adhesive layer 40 is not provided. The cover film 60 with the adhesive layer 40 includes the cover film 60 and the adhesive layer 40 on one surface of the cover film 60 in the thickness direction H. The cover film 60 is a flexible, transparent surface protection film. The adhesive layer 40 is in contact with the first surface 11 of the optical film 10 of the optical film Y2 with an adhesive layer. The cover film 60 with the adhesive layer 40 is a surface protective film with an adhesive layer that is releasably arranged on the first surface 11 of the optical film Y2 with the adhesive layer. Other configurations of the optical film X2 are the same as those of the optical film X1.

Such an optical film X2 is used as a supply material for the pressure-sensitive adhesive layer-attached optical film Y2 incorporated in the laminated structure of the foldable display panel in the manufacturing process of the same panel. The cover film 30 is peeled off from the pressure-sensitive adhesive layer-attached optical film Y2 at a predetermined timing during the manufacturing process of the foldable display panel. The cover film 60 with the adhesive layer 40 may not be peeled off from the optical film Y2 with the adhesive layer.

Examples of the cover film 60 (surface protection film) include a plastic film having both flexibility and transparency. Examples of the plastic film include polyethylene terephthalate film, polyethylene film, polypropylene film, and polyester film.

In the optical film X2, at least one of the optical film 10 and the cover film 60 has a Young's modulus of 2000 MPa or more at 23° C. and a light transmittance of 10% or less at a wavelength of 355 nm. Preferably, both the optical film 10 and the cover film 60 have a Young's modulus of 2000 MPa or more at 23° C. and a light transmittance of 10% or less at a wavelength of 355 nm.

The hard cover film 60 in the optical film X2 has a Young's modulus of 2000 MPa or more at 23° C. and a light transmittance (light transmittance T3) of 10% or less at a wavelength of 355 nm. , it is suitable for securing laser absorbency and reducing the energy of laser irradiation required for outer shape processing of the optical film X2. The light transmittance T2 is preferably 8% or less, more preferably 6% or less, even more preferably 4% or less, and particularly preferably 2% or less, from the viewpoint of the laser absorption of the cover film 60 . The light transmittance T3 is, for example, 0.1% or more. As a method for adjusting the light transmittance T3, for example, adjustment of the blending amount of the ultraviolet absorber in the cover film 60 can be mentioned.

In the cover film 60, the product (E3×T3) of the Young's modulus E3 (MPa) and the light transmittance T3 (%) described above is preferably 1×10 ⁵ or less from the viewpoint of the laser processability of the cover film 60. It is more preferably 0.7×10 ⁵ or less, still more preferably 0.4×10 ⁵ or less, still more preferably 0.3×10 ⁵ or less, and particularly preferably 0.25×10 ⁵ or less. The product (E3×T3) is, for example, 0.01×10 ⁵ or more.

In the optical film X2, at least one selected from the group consisting of the cover film 60, the adhesive layer 40, the optical film, and the adhesive layer 50 is a highly transmissive layer having a light transmittance of 80% or more at a wavelength of 355 nm. . Then, the thickness of the high transmission layer with respect to the total thickness of the cover film 60, the adhesive layer 40, the optical film and the adhesive layer 50 (if there are multiple high transmission layers, the thickness of all the high transmission layers total) is less than 88%. Such a configuration is suitable for ensuring the overall laser absorptivity of the optical film X2. The ratio R2 is preferably 85% or less, more preferably 82% or less, even more preferably 80% or less, and particularly preferably 78% or less, from the viewpoint of ensuring the overall laser absorbency of the optical film X2. The ratio R2 is, for example, 10% or more.

The optical film 10, the cover film 30 and the adhesive layers 40 and 50 in the optical film X2 are the same as the optical film 10, the cover film 30 and the adhesive layers 40 and 50 in the optical film X2.

The optical film X2 as described above is suitable for suppressing the laser output during outer shape processing by laser processing, as shown in Examples and Comparative Examples below.

It is preferable that the optical film 10 has a Young's modulus (Young's modulus E1) of 2000 MPa or more at 23° C. in order to secure the strength required for foldable display panel applications. From the viewpoint of ensuring the strength of the optical film 10, the Young's modulus E1 is preferably 2500 MPa or more, more preferably 2800 MPa or more, and still more preferably 3000 MPa or more. Young's modulus E1 is preferably 10000 MPa or less, more preferably 7000 MPa or less, even more preferably 5000 MPa or less, still more preferably 4000 MPa or less, from the viewpoint of ensuring the flexibility required for foldable display panel applications in the optical film 10. It is preferably 3500 MPa or less. A method for measuring the Young's modulus is as described below with respect to Examples.

In the optical film 10, the product (E1×T1) of the Young's modulus E1 (MPa) and the above-mentioned light transmittance T1 (%) is determined from the viewpoint of ease of processing the optical film 10 with a laser (laser processability). , preferably 1×10 ⁵ or less, more preferably 0.7×10 ⁵ or less, still more preferably 0.4×10 ⁵ or less, still more preferably 0.3×10 ⁵ or less, particularly preferably 0.25×10 ⁵ or less. The product (E1×T1) is, for example, 0.01×10 ⁵ or more.

It is preferable for the cover film 60 to have a Young's modulus (Young's modulus E2) of 2000 MPa or more at 23° C. in order to secure the protective function of the pressure-sensitive adhesive layer-attached optical film Y1 by the cover film 60 . Young's modulus E2 is preferably 3000 MPa or more, more preferably 4000 MPa or more, and still more preferably 5000 MPa or more from the viewpoint of ensuring the protection function of the cover film 60 . Young's modulus E2 is preferably 10000 MPa or less, more preferably 8000 MPa or less, even more preferably 6000 MPa or less, and particularly preferably 5500 MPa or less, from the viewpoint of ensuring flexibility of the cover film 60 .

In the cover film 60, the product (E2×T2) of the Young's modulus E2 (MPa) and the light transmittance T2 (%) described above is preferably 1×10 ⁵ or less from the viewpoint of the laser processability of the cover film 60. It is more preferably 0.7×10 ⁵ or less, still more preferably 0.4×10 ⁵ or less, still more preferably 0.3×10 ⁵ or less, and particularly preferably 0.25×10 ⁵ or less. The product (E2×T2) is, for example, 0.01×10 ⁵ or more.

The luminous transmittance Y of the optical film X2 is preferably 60% or less, more preferably 50% or less, and still more preferably 45% or less from the viewpoint of ensuring a good appearance by reducing light reflection in the display panel. . From the viewpoint of suppressing reduction in the light extraction efficiency of the display panel, it is preferably 20% or more, more preferably 30% or more, and even more preferably 40% or more.

In the optical film X2, after the cover film 30 is replaced with a polyimide film having a thickness of 25 μm, a cut portion produced by laser cutting in the thickness direction H from the polyimide film side is cut in a plane direction perpendicular to the thickness direction H. , the retraction length of the adhesive layer 40 from the edge 10a of the optical film 10 (the distance between the edge 10a and the edge 40a of the adhesive layer 40 in the plane direction) is the adhesive layer-attached optical film Y1 is preferably 10 μm or less, more preferably 7 μm or less, even more preferably 5 μm or less, and even more preferably 3 μm or less, from the viewpoint of suppressing interference with the image display area of the display panel after it is incorporated into the laminated structure of the display panel. , particularly preferably 1 μm or less, very preferably 0 μm.

In the optical film X2, the edge of the optical film 10 in the plane direction at the cut point generated by laser cutting in the thickness direction H from the polyimide film side after the cover film 30 is replaced with a 25 μm thick polyimide film. The retraction length of the adhesive layer 50 from the edge 10a (the distance between the edge 10a and the edge 50a of the adhesive layer 50 in the plane direction) is the distance between the adhesive layer-attached optical film Y1 and the laminated structure of the display panel. From the viewpoint of suppressing interference with the image display area of the panel after being incorporated in the panel, it is preferably 10 μm or less, more preferably 7 μm or less, even more preferably 5 μm or less, even more preferably 3 μm or less, and particularly preferably 1 μm or less. Very preferably it is 0 μm.

The optical film X2 can be produced, for example, as follows.

First, the optical film 10, the adhesive layer 50 with the cover film 30, and the cover film 60 with the adhesive layer 40 are prepared (preparation step). The method for forming the pressure-sensitive adhesive layer 50 with the cover film 30 is as described above for the first embodiment.

In forming the cover film 60 with the pressure-sensitive adhesive layer 40, first, the surface of the cover film 60 is plasma-treated. Next, a predetermined adhesive composition (varnish) is applied to the plasma-treated surface of the cover film 60 to form a coating film, and then the coating film is dried. Thereby, the cover film 60 with the adhesive layer 40 is obtained. Another release liner may be laminated on the adhesive layer 40 on the cover film 60 . This release liner is peeled off before bonding the optical film 10 and the adhesive layer 40 together.

Next, the second surface 12 of the optical film 10 and the pressure-sensitive adhesive layer 50 side of the pressure-sensitive adhesive layer 50 with the cover film 30 are pasted together (first pasting step). Preferably, prior to this lamination, the second surface 12 of the optical film 10 and the exposed surface of the adhesive layer 50 with the cover film 30 are plasma treated.

Next, the first surface 11 of the optical film 10 and the pressure-sensitive adhesive layer 40 side of the cover film 60 with the pressure-sensitive adhesive layer 40 are pasted together (second pasting step).

As described above, the above optical film X2 (optical film with cover film) can be produced. The optical film X2 is suitable for suppressing the laser output as described above when the outer shape is processed by laser processing.

4A and 4B show an example of how to use the optical film X2.

In this method, first, as shown in FIG. 4A, the cover film 30 is peeled off from the adhesive layer 50 of the optical film X2. Thereby, the adhesive surface 51 of the adhesive layer 50 is exposed.

Next, as shown in FIG. 4B, the optical film 10 and the first member M1 (first adherend) are joined with the adhesive layer 50 interposed therebetween. The first member M1 is, for example, one element in the laminated structure of the flexible panel. Such elements include, for example, pixel panels and touch panels. In the present embodiment, the laminated body obtained in this joining step is contour-processed by laser processing. Preferably, the laminate shown in FIG. 4B is laser-cut in the thickness direction H by irradiating the first member M1 side of the laminate shown in FIG. 4B with a laser in the thickness direction H. Lasers for laser processing include, for example, gas lasers, solid-state lasers, and semiconductor lasers, and specific examples are as described above. The optical film X2 is suitable for suppressing the laser output as described above in the laser processing after the cover film 30 is peeled off.

For example, the optical film X2 is used as described above in the process of manufacturing a flexible panel.

EXAMPLES The present invention will be specifically described below with reference to examples. However, the invention is not limited to the examples. In addition, the specific numerical values such as the compounding amount (content), physical property values, parameters, etc. described below are the corresponding compounding amounts ( content), physical property values, parameters, etc., upper limits (values defined as “less than” or “less than”) or lower limits (values defined as “greater than” or “greater than”).

<Preparation of first acrylic base polymer>
64 parts by mass of 2-ethylhexyl acrylate (2EHA), 30 parts by mass of n-butyl acrylate (BA), and lauryl acrylate (LA) 4 parts by mass, 4-hydroxybutyl acrylate (4HBA) 1 part by mass, N-vinyl-2-pyrrolidone (NVP) 1 part by mass, and 2,2'-azobis as a thermal polymerization initiator A mixture containing 0.3 parts by mass of isobutyronitrile (AIBN) and ethyl acetate as a solvent was stirred at 56° C. for 6 hours under a nitrogen atmosphere (polymerization reaction). This gave a first polymer solution containing the first acrylic base polymer. The weight average molecular weight of the first acrylic base polymer in this polymer solution was about 2 million.

<Preparation of second acrylic base polymer>
First, 96.2 parts by mass of 2-ethylhexyl acrylate (2EHA) and 3.2 parts by mass of 2-hydroxyethyl acrylate (HEA) were mixed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube. A mixture containing 8 parts by mass, 0.3 parts by mass of 2,2′-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator, and 150 parts by mass of ethyl acetate as a solvent was heated at 65° C. The mixture was stirred for hours under a nitrogen atmosphere (polymerization reaction). This gave a second polymer solution containing a second acrylic base polymer. The weight average molecular weight of the second acrylic base polymer in this polymer solution was about 540,000.

<Preparation of acrylic oligomer>
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, 95 parts by mass of cyclohexyl methacrylate (CHMA), 5 parts by mass of acrylic acid (AA), and an α- A mixture containing 10 parts by mass of methylstyrene dimer and toluene as a solvent was stirred at room temperature for 1 hour under a nitrogen atmosphere. After that, 10 parts by mass of 2,2′-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator is added to the mixture to prepare a reaction solution, which is reacted at 85° C. for 5 hours under a nitrogen atmosphere. (formation of acrylic oligomers). As a result, an oligomer solution containing an acrylic oligomer (solid concentration: 50% by mass) was obtained. The acrylic oligomer had a weight average molecular weight of 4,000. Moreover, the glass transition temperature (Tg) of the acrylic oligomer was 84°C.

<Preparation of adhesive composition C1>
In the first polymer solution, 1.5 parts by mass of an acrylic oligomer and a first cross-linking agent (product name "Niper BMT-40SV", dibenzoyl peroxide, Japan) are added to 100 parts by mass of the first acrylic base polymer in the polymer solution. Fats and oils) 0.26 parts by mass, the second cross-linking agent (product name “Coronate L”, trimethylolpropane adduct of tolylene diisocyanate, manufactured by Tosoh) 0.02 parts by mass, and a silane coupling agent (product name “KBM- 403", manufactured by Shin-Etsu Chemical Co., Ltd.) was added and mixed to prepare an adhesive composition C1.

<Preparation of adhesive composition C2>
A pressure-sensitive adhesive composition C2 was prepared in the same manner as the pressure-sensitive adhesive composition C1, except that 0.04 parts by mass of an ultraviolet absorber (product name "Tinosorb S", manufactured by BASF) was further added.

<Preparation of adhesive composition C3>
A pressure-sensitive adhesive composition C3 was prepared in the same manner as the pressure-sensitive adhesive composition C1, except that 0.175 parts by mass of an ultraviolet absorber (product name "Tinosorb S", manufactured by BASF) was further added.

<Production of first adhesive sheet>
The pressure-sensitive adhesive composition C1 was applied onto the release-treated surface of the release liner L1, one surface of which was silicone release-treated, to form a coating film. The release liner L1 is a polyethylene terephthalate (PET) film (product name “DIAFOIL MRV75T500 (SJUV04T-CT)”, thickness 75 μm, manufactured by Mitsubishi Chemical Co., Ltd.) with one side subjected to silicone release treatment, and a predetermined ultraviolet absorber is added. It is Next, the release-treated surface of release liner L2 having one surface subjected to silicone release treatment was attached to the coating film on release liner L1. The release liner L2 is a PET film (product name “DIAFOIL MHE50”, thickness 50 μm, manufactured by Mitsubishi Chemical Co., Ltd.) one side of which is subjected to silicone release treatment. Next, the coating film sandwiched between the release liner L1 and the release liner L2 is dried by heating at 100° C. for 1 minute and then at 150° C. for 3 minutes to form a transparent pressure-sensitive adhesive layer having a thickness of 50 μm. A first pressure-sensitive adhesive sheet consisting of C1' was formed. As described above, a first adhesive sheet with release liners L1 and L2 (release liner L1/adhesive layer C1′ (thickness: 50 μm)/release liner L2) was produced.

A first PSA sheet with release liners L3 and L2 (release liner L3/adhesive A layer C1′ (50 μm thick)/release liner L2) was produced. The release liner L3 is a PET film (product name “DIAFOIL MRV75”, thickness 75 μm, manufactured by Mitsubishi Chemical Co., Ltd.) one side of which is subjected to silicone release treatment, and no ultraviolet absorber is added.

A first PSA sheet with first release liners L4 and L2 (release liner L4 /Adhesive layer C1′ (thickness: 50 μm)/Release liner L2) was prepared. The release liner L4 is a PET film (product name: "DIAFOIL MRV125", thickness: 125 µm, manufactured by Mitsubishi Chemical Co., Ltd.) one side of which is subjected to silicone release treatment, and no ultraviolet absorber is added.

A second pressure-sensitive adhesive sheet with release liners L1 and L2 was prepared in the same manner as the first pressure-sensitive adhesive sheet with release liners L1 and L2, except that the release liner L4 was used instead of the release liner L1 and the thickness of the pressure-sensitive adhesive composition C1′ was set to 250 μm. A first adhesive sheet with release liners L4 and L2 (release liner L4/adhesive layer C1' (thickness: 250 μm)/release liner L2) was prepared.

A first PSA sheet with release liners L5 and L2 (release liner L5/adhesive A layer C1′ (50 μm thick)/release liner L2) was produced. The release liner L5 is a PET film (product name: "DIAFOIL MRV50", thickness: 50 µm, manufactured by Mitsubishi Chemical Co., Ltd.) one side of which is subjected to silicone release treatment, and no ultraviolet absorber is added.

<Preparation of the second adhesive sheet>
The pressure-sensitive adhesive composition C2 was applied to the release-treated surface of the release liner L3 to form a coating film. Next, the release-treated surface of the release liner L2 was attached to the coating film on the release liner L3. Next, the coating film sandwiched between the release liner L3 and the release liner L2 is dried by heating at 100° C. for 1 minute and then at 150° C. for 3 minutes to form a transparent pressure-sensitive adhesive layer having a thickness of 50 μm. A second pressure-sensitive adhesive sheet consisting of C2' was formed. As described above, a second adhesive sheet with release liners L3 and L2 (release liner L3/adhesive layer C2' (thickness: 50 μm)/release liner L2) was produced.

<Preparation of the third adhesive sheet>
The pressure-sensitive adhesive composition C3 was applied to the release-treated surface of the release liner L1 to form a coating film. Next, the release-treated surface of the release liner L2 was attached to the coating film on the release liner L1. Next, the coating film sandwiched between the release liner L1 and the release liner L2 is dried by heating at 100° C. for 1 minute and then at 150° C. for 3 minutes to form a transparent pressure-sensitive adhesive layer having a thickness of 50 μm. A third pressure-sensitive adhesive sheet consisting of C3' was formed. As described above, a third adhesive sheet with release liners L1 and L2 (release liner L1/adhesive layer C3' (thickness: 50 μm)/release liner L2) was produced.

On the other hand, the third PSA sheet with release liners L3 and L2 (release liner L3/ A pressure-sensitive adhesive layer C3′ (thickness: 50 μm)/release liner L2) was prepared.

[Example 1]
First, the release liner L2 was peeled off from the first pressure-sensitive adhesive sheet with release liners L1 and L2, and the exposed surface was plasma-treated. On the other hand, both surfaces (first surface and second surface) of the polarizing film having a thickness of 31 μm were also plasma-treated. In each plasma treatment, a plasma irradiation device (product name “AP-TO5”, manufactured by Sekisui Kogyo Co., Ltd.) was used, the voltage was 160 V, the frequency was 10 kHz, and the treatment speed was 5000 mm / min (also in the plasma treatment described later similar). Then, the exposed surface of the first adhesive sheet and the first surface of the polarizing film were bonded together. In this bonding, the first pressure-sensitive adhesive sheet with the release liner L1 and the polarizing film were pressure-bonded by reciprocating a 2-kg roller once in an environment of 25°C.

Next, the release liner L2 was peeled off from the first pressure-sensitive adhesive sheet with release liners L5 and L2, and the exposed surface thereby exposed was plasma-treated. Then, the exposed surface of the first pressure-sensitive adhesive sheet and the second surface of the polarizing film were bonded together. In this bonding, the first pressure-sensitive adhesive sheet with the release liner L5 and the polarizing film were pressure-bonded by reciprocating a 2-kg roller once in an environment of 25°C.

As described above, an optical film with a cover film of Example 1 was produced. This optical film with a cover film includes a release liner L1 (thickness: 75 μm) as the first cover film, a first adhesive sheet (thickness: 50 μm) as the first adhesive layer, and a polarizing film (thickness: 31 μm thick), a first adhesive sheet (50 μm thick) as a second adhesive layer, and a release liner L5 (50 μm thick) as a second cover film are provided in this order in the thickness direction. The first pressure-sensitive adhesive layer, the polarizing film and the second pressure-sensitive adhesive layer form a double-sided pressure-sensitive adhesive layer-attached polarizing film (the same applies to Examples 2 to 5 and Comparative Examples 1 and 2 below).

[Example 2]
The cover film of Example 2 was prepared in the same manner as the optical film with the cover film of Example 1, except that the third pressure-sensitive adhesive sheet with release liners L1 and L2 was used instead of the first pressure-sensitive adhesive sheet with release liners L1 and L2. A coated optical film was produced. The optical film with a cover film of Example 2 includes a release liner L1 (thickness: 75 μm) as the first cover film, a third adhesive sheet (thickness: 50 μm) as the first adhesive layer, and a polarizing film as the optical film. A film (thickness 31 μm), a first adhesive sheet (thickness 50 μm) as a second adhesive layer, and a release liner L5 (thickness 50 μm) as a second cover film are provided in order in the thickness direction.

[Example 3]
The cover film of Example 3 was prepared in the same manner as the optical film with the cover film of Example 1, except that the first pressure-sensitive adhesive sheet with release liners L3 and L2 was used instead of the first pressure-sensitive adhesive sheet with release liners L1 and L2. A coated optical film was produced. The optical film with a cover film of Example 3 includes a release liner L3 (thickness: 75 μm) as the first cover film, a first adhesive sheet (thickness: 50 μm) as the first adhesive layer, and a polarizing film as the optical film. A film (thickness 31 μm), a first adhesive sheet (thickness 50 μm) as a second adhesive layer, and a release liner L5 (thickness 50 μm) as a second cover film are provided in order in the thickness direction.

[Example 4]
The cover film of Example 4 was prepared in the same manner as the optical film with the cover film of Example 1, except that the second pressure-sensitive adhesive sheet with release liners L3 and L2 was used instead of the first pressure-sensitive adhesive sheet with release liners L1 and L2. A coated optical film was produced. The optical film with a cover film of Example 4 includes a release liner L3 (thickness: 75 μm) as the first cover film, a second adhesive sheet (thickness: 50 μm) as the first adhesive layer, and a polarizing film as the optical film. A film (thickness 31 μm), a first adhesive sheet (thickness 50 μm) as a second adhesive layer, and a release liner L5 (thickness 50 μm) as a second cover film are provided in order in the thickness direction.

[Example 5]
The cover film of Example 5 was prepared in the same manner as the optical film with the cover film of Example 1, except that the third pressure-sensitive adhesive sheet with release liners L3 and L2 was used instead of the first pressure-sensitive adhesive sheet with release liners L1 and L2. A coated optical film was produced. The optical film with a cover film of Example 5 includes a release liner L3 (thickness: 75 μm) as the first cover film, a third adhesive sheet (thickness: 50 μm) as the first adhesive layer, and a polarizing film as the optical film. A film (thickness 31 μm), a first adhesive sheet (thickness 50 μm) as a second adhesive layer, and a release liner L5 (thickness 50 μm) as a second cover film are provided in order in the thickness direction.

[Comparative Example 1]
Comparative Example 1 was prepared in the same manner as the optical film with a cover film of Example 1, except that the first pressure-sensitive adhesive sheet with release liners L4 and L2 was used instead of the first pressure-sensitive adhesive sheet with release liners L1 and L2. An optical film with a cover film was produced. The optical film with a cover film of Comparative Example 1 includes a release liner L4 (thickness: 125 μm) as the first cover film, a first adhesive sheet (thickness: 50 μm) as the first adhesive layer, and a polarizing film as the optical film. A film (thickness 31 μm), a first adhesive sheet (thickness 50 μm) as a second adhesive layer, and a release liner L5 (thickness 50 μm) as a second cover film are provided in order in the thickness direction.

[Comparative Example 2]
Comparative Example 2 was prepared in the same manner as the optical film with a cover film of Example 1, except that the first pressure-sensitive adhesive sheet with release liners L4 and L2 was used instead of the first pressure-sensitive adhesive sheet with release liners L1 and L2. An optical film with a cover film was produced. The optical film with a cover film of Comparative Example 2 includes a release liner L4 (thickness: 125 μm) as the first cover film, a first adhesive sheet (thickness: 250 μm) as the first adhesive layer, and a polarizing film as the optical film. A film (thickness 31 μm), a first adhesive sheet (thickness 50 μm) as a second adhesive layer, and a release liner L5 (thickness 50 μm) as a second cover film are provided in order in the thickness direction.

[Example 6]
Example 6 was prepared in the same manner as the optical film with a cover film of Example 1, except that a base film (product name “Lumirror S10”, PET film, thickness 0 μm, manufactured by Toray Industries, Inc.) was used instead of the polarizing film. An optical film with a cover film was produced. The optical film with a cover film of Example 6 includes a release liner L1 (thickness: 75 µm) as the first cover film, a first adhesive sheet (thickness: 50 µm) as the first adhesive layer, and a base film as the optical film. A material film (thickness 50 μm), a first adhesive sheet (thickness 50 μm) as a second adhesive layer, and a release liner L5 (thickness 50 μm) as a second cover film are provided in order in the thickness direction. The first pressure-sensitive adhesive layer, the substrate film and the second pressure-sensitive adhesive layer form a double-sided pressure-sensitive adhesive sheet having a core substrate (the same applies to Comparative Example 3 below).

[Comparative Example 3]
The first pressure-sensitive adhesive sheet with release liners L4 and L2 was used instead of the first pressure-sensitive adhesive sheet with release liners L1 and L2, and the base film (product name: Lumirror S10, PET film , a thickness of 50 μm, manufactured by Toray Industries, Inc.) was used in the same manner as the optical film with a cover film of Example 1, to prepare an optical film with a cover film of Comparative Example 3. The optical film with a cover film of Comparative Example 3 includes a release liner L4 (thickness: 125 μm) as the first cover film, a first adhesive sheet (thickness: 50 μm) as the first adhesive layer, and a base film as the optical film. A material film (thickness 50 μm), a first adhesive sheet (thickness 50 μm) as a second adhesive layer, and a release liner L5 (thickness 50 μm) as a second cover film are provided in order in the thickness direction.

[Example 7]
<Preparation of cover film with adhesive layer>
First, in the second polymer solution, 5 parts by mass of a fourth cross-linking agent (product name “Coronate HX”, isocyanurate of hexamethylene diisocyanate, manufactured by Tosoh) per 100 parts by mass of the second acrylic base polymer in the polymer solution, 0.03 parts by mass of dibutyltin dilaurate as a cross-linking catalyst was added and mixed to prepare adhesive composition C4.

Next, the pressure-sensitive adhesive composition C4 was applied onto the corona-treated surface of a surface protective film (product name “T100C-38”, polyester film, thickness 38 μm, manufactured by Mitsubishi Chemical Co., Ltd.) one side of which had been corona-treated. formed. Next, the release-treated surface of the release liner L4 was adhered to the coating film on the surface protective film. The release liner L4 is a polyester film (thickness 25 μm) with one side subjected to silicone release treatment. Next, the coating film sandwiched between both films was dried by heating at 130° C. for 2 minutes to form a transparent pressure-sensitive adhesive layer C4′ with a thickness of 10 μm. After that, the release liner L4 was peeled off from the pressure-sensitive adhesive layer C4'. As described above, a surface protective film with an adhesive layer (cover film with an adhesive layer) was produced.

<Production of optical film with cover film>
First, the release liner L2 was peeled off from the first pressure-sensitive adhesive sheet with release liners L5 and L2, and the exposed surface thereby exposed was plasma-treated. On the other hand, both surfaces (first surface and second surface) of the polarizing film having a thickness of 31 μm were also plasma-treated. Then, the exposed surface of the first adhesive sheet and the second surface of the polarizing film were bonded together. In this bonding, the first pressure-sensitive adhesive sheet with the release liner L5 and the polarizing film were pressure-bonded by reciprocating a 2-kg roller once in an environment of 25°C.

Next, the pressure-sensitive adhesive layer side of the surface protective film with the pressure-sensitive adhesive layer and the first surface of the polarizing film were bonded together. In this bonding, the pressure-sensitive adhesive layer-attached surface protective film and the polarizing film were pressure-bonded by reciprocating a 2-kg roller once in an environment of 25°C.

As described above, an optical film with a cover film of Example 7 was produced. This optical film with a cover film includes a surface protective film (thickness 38 μm) with an adhesive layer (thickness 10 μm) as the first cover film with the first adhesive layer and a polarizing film (thickness 31 μm) as the optical film. , a first adhesive sheet (50 μm thick) as a second adhesive layer, and a release liner L5 (50 μm thick) as a second cover film are provided in this order in the thickness direction. The polarizing film and the second adhesive layer form a polarizing film with a single-sided adhesive layer.

<Light transmittance>
For each film and each adhesive layer used in Examples 1 to 7 and Comparative Examples 1 to 3, a spectrophotometer (product name "U-4100", manufactured by Hitachi High-Technologies Corporation) was used to measure the light transmittance T at a wavelength of 355 nm. It was measured. The measurement temperature was 23°C. In measuring the light transmittance of the pressure-sensitive adhesive layer, a measurement sample obtained by bonding the pressure-sensitive adhesive layer to a glass plate was used, and the transmittance obtained by measuring only the glass plate under the same conditions was used as the baseline. Tables 1 and 2 show the measurement results. In addition, in the total thickness of the first cover film, the first adhesive layer, the optical film and the second adhesive layer (shown in Tables 1 and 2), the high transmission layer (light transmittance at a wavelength of 355 nm is 80% The thickness ratio R (%) of the above layers) and the thickness ratio R′ (%) of the low-transmission layer (the layer having a light transmittance of less than 80% at a wavelength of 355 nm) are also shown in Table 1. .

<Luminous transmittance Y>
The optical films with cover films of Examples 1 to 7 and Comparative Examples 1 to 3 were measured for luminous transmittance Y using a spectrophotometer (product name: "U-4100", manufactured by Hitachi High-Technologies Corporation). Specifically, the transmission spectrum of visible light (280 nm to 780 nm) of the optical film with the cover film was measured with a spectrophotometer, and the luminous transmittance Y (%) was calculated from the obtained transmission spectrum. Tables 1 and 2 show the measurement results.

<Young's modulus>
The Young's modulus at 23° C. was examined for each film and each pressure-sensitive adhesive layer used in Examples 1-7 and Comparative Examples 1-3. Specifically, it is as follows.

First, a test piece (width 10 mm×predetermined length) was cut out from a measurement object (film, adhesive layer). Next, the test piece was subjected to a tensile test using a tensile tester (product name "Autograph AGS-J", manufactured by Shimadzu Corporation) in an environment of 23 ° C. and a relative humidity of 50%. Stress was measured. In this tensile test, the initial distance between chucks was 10 mm, and the tensile speed was 200 mm/min. Then, from the tensile stress σ ₁ at a tensile deformation (ε ₁ ) of 0.05% (= 0.0005) and the tensile stress σ ₂ at a tensile deformation (ε ₂ ) of 0.25% (= 0.0025) , Young's modulus E was determined based on the following formula. Tables 1 and 2 show the determined Young's modulus E (MPa). Tables 1 and 2 also show the product of Young's modulus E (MPa) and light transmittance T (%) for each film and each pressure-sensitive adhesive layer.

E = (σ ₂ - σ ₁ )/(ε ₂ - ε ₁ )

<Laser processing>
The optical films with cover films of Examples 1 to 7 and Comparative Examples 1 to 3 were examined for laser processability. Specifically, it is as follows.

First, after peeling off the second cover film from the second pressure-sensitive adhesive layer in the optical film with the cover film, the exposed surface of the second pressure-sensitive adhesive layer thus exposed was covered with a 25 μm thick polyimide (PI) film (product name: Upilex). ”, manufactured by Ube Industries, Ltd.) to obtain a laminate. Next, using a picosecond laser processing device (maximum laser output 4 W) equipped with a Coherent oscillator, the laminate is cut while irradiating a laser from the PI film side in the thickness direction of the laminate. The cutting process of scanning the laser irradiation site along the planned line was performed (tried) multiple times. In each cutting process, a picosecond laser with a wavelength of 355 nm is used, the laser frequency is 50 kHz, the pulse width is 0.2 μm, and the laser attenuator (attenuator) of the device is set to a predetermined output to set the laser output to a predetermined value. value, the scanning speed was set to 10 mm/sec, and the number of laser irradiation scans along the planned cutting line was set to 3. Among the multiple trials of the cutting process, in the first trial, the laser attenuator (LA) output is set to 100%, and the LA output is successively decreased for each trial until the laminate is cut at a predetermined LA output. repeated. Tables 1 and 2 show the maximum LA output (%) that could cut the laminate. In addition, the ratio of the laser output at the maximum LA output to the maximum laser output (4 W) is shown in Tables 1 and 2 as cutting laser output (%) (the smaller the cutting laser output, the easier it is to cut. ).

<Retraction length of adhesive layer>
Regarding the optical films with cover films (first cover film/first pressure-sensitive adhesive layer/optical film/second pressure-sensitive adhesive layer/PI film) of Examples 1 to 7 and Comparative Examples 1 to 3 after the laser processing described above, The retraction length of the first pressure-sensitive adhesive layer and the retraction length of the second pressure-sensitive adhesive layer from the edge of the optical film were examined as follows.

First, the first cover film was peeled off from the first adhesive layer. Next, a predetermined portion selected from the outer peripheral edge of the optical film with the double-sided pressure-sensitive adhesive layer on the PI film was observed with an optical microscope. Specifically, the optical film with double-sided pressure-sensitive adhesive layers was observed and photographed with an optical microscope from the side opposite to the PI film in the thickness direction of the optical film with double-sided pressure-sensitive adhesive layers. Then, in the photographed image, the retraction length d1 of the edge of the first adhesive layer in the plane direction from the edge of the optical film and the length of the second adhesive layer in the plane direction from the edge of the optical film The withdrawal length d2 of the edge was measured. Tables 1 and 2 show the measurement results.

X1, X2 optical film (optical film with cover film)
Y1, Y2 Optical film H with adhesive layer Thickness direction 10 Optical film 11 First surface 12 Second surface 20, 60 Cover film (first cover film)
30 cover film (second cover film)
40 adhesive layer (first adhesive layer)
41, 51 Adhesive surface 50 Adhesive layer (second adhesive layer)

Claims (8)

An optical film with a cover film, comprising a first cover film, a first pressure-sensitive adhesive layer, an optical film, a second pressure-sensitive adhesive layer, and a second cover film in this order in the thickness direction,
at least one of the first cover film and the optical film has a Young's modulus of 2000 MPa or more at 23° C. and a light transmittance of 10% or less at a wavelength of 355 nm;
At least one selected from the group consisting of the first cover film, the first pressure-sensitive adhesive layer, the optical film and the second pressure-sensitive adhesive layer is a high transmission layer having a light transmittance of 80% or more at a wavelength of 355 nm. and the ratio of the thickness of the at least one highly permeable layer to the total thickness of the first cover film, the first pressure-sensitive adhesive layer, the optical film and the second pressure-sensitive adhesive layer is less than 88%. An optical film with a cover film. The optical film with a cover film according to claim 1, wherein the first cover film has a Young's modulus of 2000 MPa or more at 23°C and a light transmittance of 10% or less at a wavelength of 355 nm. 3. The optical film with a cover film according to claim 2, wherein the first cover film has a product of Young's modulus (MPa) and light transmittance (%) of 1*10 ^{<5 >} or less. 2. The optical film with cover film according to claim 1, wherein said first cover film and said optical film have a Young's modulus of 2000 MPa or more at 23[deg.] C. and a light transmittance of 10% or less at a wavelength of 355 nm. 5. The optical film with a cover film according to claim 4, wherein the product of the Young's modulus (MPa) and the light transmittance (%) is 1×10 ⁵ or less in each of the first cover film and the optical film. . The optical film with a cover film according to any one of claims 1 to 5, wherein the luminous transmittance Y is 60% or less. After the second cover film is reattached to a polyimide film having a thickness of 25 μm, at the cutting point caused by laser cutting in the thickness direction from the polyimide film side, the The optical film with a cover film according to any one of claims 1 to 6, wherein the retraction length of the first adhesive layer and the second adhesive layer from the edge of the optical film is 10 µm or less. The optical film with a cover film according to any one of claims 1 to 7, wherein the optical film is a polarizing film.

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