Covered optical adhesive sheet

Abstract

An optical adhesive sheet (X), as a covered optical adhesive sheet according to the present invention, comprises an optical adhesive sheet (10), a transparent separation liner (20), and a surface protection film (30), in this order in the thickness direction (H). The optical adhesive sheet (10) has a first surface (11) and a second surface (12) on the reverse side from the first surface (11). The transparent separation liner (20) is disposed on the first surface (11). The surface protection film (30) has an adhesive surface (30a) and is affixed to the transparent separation liner (20) via the adhesive surface (30a). A first peeling force between the surface protection film (30) and the transparent separation liner (20) under the conditions of a peeling angle of 180° and a pulling speed of 300 mm / minute is smaller than a second peeling force between the transparent separation liner (20) and the optical adhesive sheet (10) under said conditions.

Description

Technical Field

[0001] The present invention relates to a covered optical adhesive sheet.

Background Art

[0002] An adhesive sheet having light transmissivity (optical adhesive sheet) is used in the manufacture of optical articles such as display panels. A display panel has a laminated structure including a pixel panel and a cover member. In the manufacturing process of a display panel, an optical adhesive sheet is used, for example, for joining elements included in the laminated structure on the light emitting side (image display side) of the pixel panel. Thus, an optical adhesive sheet is an adhesive sheet disposed at a location where light passes through in an optical article. Further, conventionally, an optical adhesive sheet has been manufactured in the form of an optical adhesive sheet with a release liner in which one or both sides of the sheet are covered with a release liner. Technologies related to such optical adhesive sheets are described, for example, in Patent Document 1 below.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the manufacturing process of an optical adhesive sheet, by irradiating an optical adhesive sheet with a release liner with light of a predetermined wavelength, the presence or absence of foreign matter inside and on the surface of the sheet is inspected. Further, in the manufacturing process of an optical article, after an optical adhesive sheet having one side covered with a release liner is bonded to a component of the optical article, by irradiating the optical adhesive sheet with a release liner with light of a predetermined wavelength, the presence or absence of foreign matter inside and on the surface of the sheet is inspected (foreign matter inspection of the optical adhesive sheet in the optical article manufacturing process).

[0005] Meanwhile, in the field of optoelectronics, various optical materials are becoming more sophisticated. For example, in the field of image display technology, display panels are becoming more pixel-rich. As optical materials become more sophisticated, a higher degree of cleanliness is required in the light-passing areas of those optical materials. Optical adhesive sheets are required to be supplied to the manufacturing process of optical materials with a high degree of cleanliness. The higher the required degree of cleanliness, the more precise the detection of minute foreign matter is required in foreign matter inspection (i.e., a more precise inspection is required).

[0006] However, with conventional optical adhesive sheets with release liners, environmental contaminants may adhere to the exposed surface of the release liner, and scratches may occur, between the time the optical adhesive sheet is manufactured and before it is supplied to the optical article manufacturing process (for example, during the transportation and handling of the sheet). In such cases, precise inspection of the optical adhesive sheet for foreign matter becomes difficult during the optical article manufacturing process. This is because it is impossible to distinguish between the aforementioned post-processing environmental contaminants and scratches on the release liner and foreign matter on the optical adhesive sheet itself. Such conventional optical adhesive sheets with release liners are not suitable for supplying optical adhesive sheets with a high degree of cleanliness to the optical article manufacturing process.

[0007] The present invention provides a covered optical adhesive sheet suitable for supplying highly clean optical adhesive sheets to the manufacturing process of optical articles. [Means for solving the problem]

[0008] The present invention [1] includes a covered optical adhesive sheet comprising, in order in the thickness direction, an optical adhesive sheet, a transparent release liner, and a surface protective film, wherein the optical adhesive sheet has a first surface and a second surface opposite to the first surface, the transparent release liner is placed on the first surface, the surface protective film has an adhesive surface and is attached to the transparent release liner on the adhesive surface, and the first peel force between the surface protective film and the transparent release liner at a peel angle of 180° and a tensile speed of 300 mm / min is less than the second peel force between the transparent release liner and the optical adhesive sheet at the same conditions.

[0009] As described above, the covered optical adhesive sheet comprises an optical adhesive sheet, a transparent release liner on the first surface of the sheet, and a surface protective film on the liner. This configuration is suitable for preventing the adhesion of environmental foreign matter to the transparent release liner and damage to the transparent release liner on the first surface side of the optical adhesive sheet, from the time the covered optical adhesive sheet is manufactured until it is supplied to the optical article manufacturing process, by using the surface protective film. Furthermore, in the covered optical adhesive sheet, as described above, the first peeling force between the surface protective film and the transparent release liner is smaller than the second peeling force between the transparent release liner and the optical adhesive sheet. This configuration is suitable for properly peeling the surface protective film from the transparent release liner while maintaining the state in which the transparent release liner is attached to the optical adhesive sheet on the optical article, after the optical adhesive sheet side of the covered optical adhesive sheet has been bonded to the components of the optical article (peeling process). After the peeling of the surface protective film, precise inspection of the optical adhesive sheet with the transparent release liner can be properly performed. Therefore, the covered optical adhesive sheet of the present invention is suitable for supplying highly clean optical adhesive sheets to the manufacturing process of optical articles.

[0010] The present invention [2] includes the covered optical adhesive sheet described in [1] above, wherein the surface protective film, after being laminated to the cycloolefin polymer film, has a peel force of 1.0 N / 50 mm or less on the cycloolefin polymer film under the conditions of a peel angle of 180° and a tensile speed of 300 mm / min.

[0011] This configuration is preferable for properly peeling off the surface protective film from the transparent release liner while maintaining the state in which the transparent release liner is attached to the optical adhesive sheet on the optical article after the optical adhesive sheet side of the covered optical adhesive sheet has been attached to the optical article.

[0012] The present invention [3] includes a covered optical adhesive sheet as described in [1] or [2] above, wherein the surface protective film has a third peel force with respect to the cycloolefin polymer film at a peel angle of 180° and a tensile speed of 300 mm / min after being laminated to the cycloolefin polymer film, and the surface protective film has a fourth peel force with respect to the cycloolefin polymer film at a peel angle of 180° and a tensile speed of 300 mm / min after two weeks at 50°C following lamination to the cycloolefin polymer film, and the ratio of the fourth peel force to the third peel force is 0.8 or more and 1.5 or less.

[0013] Such a configuration is preferable from the viewpoint of stabilizing the peeling force required to peel off the surface protective film during the peeling process.

[0014] The present invention [4] includes a covered optical adhesive sheet according to any one of [1] to [3] above, wherein the surface protective film has an adhesive layer forming the adhesive surface, and the adhesive layer has a gel fraction of 80% or more.

[0015] This configuration is preferable for achieving a peel force (slight tackiness) of approximately 1.0 N / 50 mm or less on the adhesive surface of the surface protective film.

[0016] The present invention [5] includes a covered optical adhesive sheet according to any one of [1] to [4] above, wherein the surface roughness Ra of the surface on the surface protective film side of the transparent release liner is 20 nm or less.

[0017] Such a configuration is preferable from the viewpoint of achieving both the slight tackiness of the surface protective film to the transparent release liner and the suppression of adhesive residue on the surface of the transparent release liner after the surface protective film has been removed.

[0018] The present invention [6] further comprises an additional transparent release liner and an additional surface protective film on the second surface side of the optical adhesive sheet, wherein the additional transparent release liner is disposed on the second surface of the optical adhesive sheet and the additional surface protective film has an adhesive surface and is attached to the additional transparent release liner on the adhesive surface.

[0019] Such covered optical adhesive sheets are suitable for preventing the adhesion of environmental contaminants to the transparent release liner and damage to the transparent release liner on the second side of the optical adhesive sheet, from the time the sheet is manufactured until it is supplied to the optical article manufacturing process, by using a surface protective film.

[0020] The present invention [7] includes the covered optical adhesive sheet described in [6] above, wherein the second peeling force is less than the fifth peeling force under the conditions between the additional transparent peeling liner and the optical adhesive sheet.

[0021] Such a configuration is preferable when using a covered optical adhesive sheet in the manufacturing process of optical articles, as it allows for proper removal of the transparent release liner from the first surface of the optical adhesive sheet while maintaining the state in which the additional transparent release liner is attached to the second surface of the optical adhesive sheet.

[0022] The present invention [8] includes the covered optical adhesive sheet according to any one of [1] to [5] above, further comprising a polarizer film disposed on the second surface of the optical adhesive sheet.

[0023] According to such a configuration, a polarizer with an adhesive layer formed on the surface of the polarizer by an optical adhesive sheet can be supplied to the manufacturing process of an optical article in a state where the cleanliness of the optical adhesive sheet (adhesive layer) is high.

Brief Description of the Drawings

[0024] [Figure 1] It is a cross-sectional view of an embodiment of the covered optical adhesive sheet of the present invention. [Figure 2] It is a cross-sectional view of a modified example of the covered optical adhesive sheet of the present invention. In this modified example, a polarizer film is disposed on the second surface of the optical adhesive sheet.

Modes for Carrying Out the Invention

[0025] As an embodiment of the covered optical adhesive sheet of the present invention, an optical adhesive sheet X includes, as shown in FIG. 1, an optical adhesive sheet 10, transparent release liners 20 and 40, and surface protection films 30 and 50. Specifically, the optical adhesive sheet X includes, in the thickness direction H in order, a surface protection film 30, a transparent release liner 20, an optical adhesive sheet 10, a transparent release liner 40 (additional transparent release liner), and a surface protection film 50 (additional surface protection film). The optical adhesive sheet X has a sheet shape that spreads in a direction (plane direction) orthogonal to the thickness direction H. The optical adhesive sheet X has a first surface 11 (first adhesive surface) on one side in the thickness direction H and a second surface 12 (second adhesive surface) on the other side in the thickness direction H.

[0026] The optical adhesive sheet 10 is an optically transparent adhesive sheet. The optical adhesive sheet 10 is a transparent adhesive sheet placed at the light-passing portion of an optical article and is used as a component of the optical article. An example of an optical article is a display panel. A display panel has a laminated structure including a pixel panel and a cover member. In the manufacturing process of a display panel, predetermined elements placed on the image display side of the pixel panel are joined together, for example, via an optical adhesive sheet. Such display panels include panels for ultra-high-definition displays for VR (Virtual Reality) or AR (Augmented Reality) applications.

[0027] The transparent release liner 20 is placed on the first surface 11 of the optical adhesive sheet 10. The transparent release liner 20 protects the first surface 11 side of the optical adhesive sheet 10. The surface protection film 30 has an adhesive surface 30a and is attached to the transparent release liner 20 on the adhesive surface 30a. The surface protection film 30 protects the transparent release liner 20 and the optical adhesive sheet 10 on the first surface 11 side of the optical adhesive sheet 10.

[0028] In the optical adhesive sheet X, the first peeling force (the force required to peel the surface protective film 30 from the transparent peeling liner 20) between the surface protective film 30 and the transparent peeling liner 20 under the conditions of a peeling angle of 180° and a tensile speed of 300 mm / min is smaller than the second peeling force (the force required to peel the transparent peeling liner 20 from the optical adhesive sheet 10) between the transparent peeling liner 20 and the optical adhesive sheet 10 under the same conditions.

[0029] The first peeling force is preferably 0.01 N / 50 mm or more, more preferably 0.02 N / 50 mm or more, even more preferably 0.03 N / 50 mm or more, even more preferably 0.05 N / 50 mm or more, particularly preferably 0.1 N / 50 mm or more, and also preferably 0.95 N / 50 mm or less, more preferably 0.9 N / 50 mm or less, even more preferably 0.8 N / 50 mm or less, even more preferably 0.6 N / 50 mm or less, particularly preferably 0.5 N / 50 mm or less. This configuration regarding the first peeling force is preferable for achieving both good adhesion retention of the surface protective film 30 to the transparent release liner 20 and good peelability of the surface protective film 30 from the transparent release liner 20. High adhesion retention of the surface protective film 30 to the transparent release liner 20 helps suppress the incorporation of foreign matter between the transparent release liner 20 and the surface protective film 30.

[0030] The second peeling force is preferably 0.02 N / 50 mm or more, more preferably 0.03 N / 50 mm or more, even more preferably 0.05 N / 50 mm or more, even more preferably 0.1 N / 50 mm or more, particularly preferably 0.15 N / 50 mm or more, and also preferably 1.0 N / 50 mm or less, more preferably 0.95 N / 50 mm or less, even more preferably 0.9 N / 50 mm or less, even more preferably 0.8 N / 50 mm or less, particularly preferably 0.7 N / 50 mm or less. This configuration regarding the second peeling force is preferable for achieving both good adhesion retention of the transparent release liner 20 to the optical adhesive sheet 10 and good peelability of the transparent release liner 20 from the optical adhesive sheet 10. High adhesion retention of the transparent release liner 20 to the optical adhesive sheet 10 helps suppress the incorporation of foreign matter between the optical adhesive sheet 10 and the transparent release liner 20.

[0031] The transparent release liner 40 is placed on the second surface 12 of the optical adhesive sheet 10. The transparent release liner 40 protects the second surface 12 side of the optical adhesive sheet 10. The surface protection film 50 has an adhesive surface 50a and is attached to the transparent release liner 40 on the adhesive surface 50a. The surface protection film 50 protects the transparent release liner 40 and the optical adhesive sheet 10 on the second surface 12 side of the optical adhesive sheet 10.

[0032] In the optical adhesive sheet X, the force required to peel the transparent release liner 20 from the optical adhesive sheet 10 (second release force) and the force required to peel the transparent release liner 40 from the optical adhesive sheet 10 (fifth release force described below) may be the same or different. For example, the second release force is smaller than the fifth release force. In this case, the transparent release liner 20 is a light release liner with a relatively small release force, and the transparent release liner 40 is a heavy release liner with a relatively large release force.

[0033] The optical adhesive sheet X is used in the manufacturing process of optical articles. For example, after integrally peeling off the transparent release liner 20 and surface protective film 30 from the optical adhesive sheet 10 of the optical adhesive sheet X, the first surface 11 of the optical adhesive sheet 10 is bonded to a predetermined first member, and after integrally peeling off the transparent release liner 40 and surface protective film 50 from the optical adhesive sheet 10, the second surface 12 of the optical adhesive sheet 10 is bonded to a predetermined second member (the first member and the second member are each elements in the laminated structure of the optical article). In this way, the first member and the second member can be joined via the optical adhesive sheet 10.

[0034] As described above, the optical adhesive sheet X comprises an optical adhesive sheet 10, a transparent release liner 20 on the first surface 11 of the sheet, and a surface protection film 30 on the liner. This configuration is suitable for preventing environmental foreign matter from adhering to the transparent release liner 20 and for preventing damage to the transparent release liner 20 on the first surface 11 side of the optical adhesive sheet 10 from being supplied to the optical article manufacturing process after the optical adhesive sheet X is manufactured, by the surface protection film 30.

[0035] Furthermore, in the optical adhesive sheet X, as described above, the first peeling force between the surface protective film 30 and the transparent release liner 20 is smaller than the second peeling force between the transparent release liner 20 and the optical adhesive sheet 10. This configuration is suitable for properly peeling the surface protective film 30 from the transparent release liner 20 while maintaining the state in which the transparent release liner 20 is attached to the optical adhesive sheet 10. After the surface protective film 30 is peeled off, a precise inspection of the optical adhesive sheet 10 with the transparent release liner 20 attached can be properly performed in the inspection process.

[0036] Therefore, optical adhesive sheet X is suitable for supplying highly clean optical adhesive sheets to the manufacturing process of optical articles.

[0037] The surface protection film 30, after being laminated to the cycloolefin polymer (COP) film, preferably has a third peel force of 1.0 / 50 mm or less when peeled at a peel angle of 180° and a tensile speed of 300 mm / min. Specifically, the third peel force is the force required to peel the surface protection film 30 from the COP film under the above conditions. The third peel force is more preferably 0.95 N / 50 mm or less, even more preferably 0.9 N / 50 mm or less, even more preferably 0.8 N / 50 mm or less, even more preferably 0.6 N / 50 mm or less, and particularly preferably 0.5 N / 50 mm or less. This configuration is preferable for properly peeling the surface protection film 30 from the transparent release liner 20 while maintaining the state in which the transparent release liner 20 is attached to the optical adhesive sheet 10. Furthermore, the third peeling force is preferably 0.02 N / 50 mm or more, more preferably 0.03 N / 50 mm or more, even more preferably 0.05 N / 50 mm or more, even more preferably 0.1 N / 50 mm or more, and particularly preferably 0.15 N / 50 mm or more. Such a configuration is preferable for ensuring the adhesion of the surface protective film 30 to the transparent peeling liner 20, for example, during the transport process of the optical adhesive sheet X.

[0038] The surface protective film 30 has a fourth peel force when peeled from the cycloolefin polymer film at a peel angle of 180° and a tensile speed of 300 mm / min, after two weeks at 50°C following lamination to the cycloolefin polymer film. The ratio of the fourth peel force to the third peel force is preferably 0.8 or higher, more preferably 0.9 or higher, and preferably 1.5 or lower, more preferably 1.3 or lower (the fourth peel force is the force required to peel the surface protective film 30 from the COP film under the above conditions after two weeks at 50°C following lamination). Such a configuration is preferable from the viewpoint of stabilizing the peel force required to peel the surface protective film 30. Furthermore, the fourth peeling force is preferably 0.02 N / 50 mm or more, more preferably 0.03 N / 50 mm or more, even more preferably 0.05 N / 50 mm or more, even more preferably 0.1 N / 50 mm or more, particularly preferably 0.15 N / 50 mm or less, and also preferably 0.95 N / 50 mm or less, more preferably 0.9 N / 50 mm or less, even more preferably 0.8 N / 50 mm or less, even more preferably 0.6 N / 50 mm or less, particularly preferably 0.5 N / 50 mm or less.

[0039] The surface protection film 30 preferably has an adhesive layer forming an adhesive surface 30a, and the adhesive layer has a gel fraction of 80% or more. The gel fraction is more preferably 85% or more, and even more preferably 90% or more. Such a configuration is preferable for achieving a peel force (slight tackiness) of about 1.0 N / 50 mm or less on the adhesive surface of the surface protection film. The gel fraction is, for example, 95% or less. The gel fraction can be measured by the method described later with respect to the examples.

[0040] The surface roughness Ra (arithmetic mean surface roughness according to JIS B 0601-2001) of the surface of the transparent peel-off liner 20 on the side of the surface protective film 30 is preferably 20 nm or less, more preferably 17 nm or less, even more preferably 15 nm or less, especially preferably 12 nm or less, even more preferably 10 nm or less, even more preferably 8 nm or less, particularly preferably 6 nm or less, and extremely preferably 5 nm or less. Such a configuration is preferable from the viewpoint of achieving both the slight tackiness of the surface protective film 30 to the transparent peel-off liner 20 and the suppression of adhesive residue on the surface of the transparent peel-off liner 20 after peeling off the surface protective film 30. The surface roughness Ra is, for example, 0.1 nm or more.

[0041] The surface roughness Rz (maximum height according to JIS B 0601-2001) of the surface of the transparent release liner 20 on the side of the surface protection film 30 is preferably 600 nm or less, more preferably 400 nm or less, even more preferably 300 nm or less, especially preferably 200 nm or less, even more preferably 100 nm or less, even more preferably 80 nm or less, particularly preferably 60 nm or less, and extremely preferably 50 nm or less. Such a configuration is preferable from the viewpoint of achieving both the slight tackiness of the surface protection film 30 to the transparent release liner 20 and the suppression of adhesive residue on the surface of the transparent release liner 20 after the surface protection film 30 has been peeled off. The surface roughness Rz is, for example, 1 nm or more.

[0042] As described above, the optical adhesive sheet X is provided with a transparent release liner 40 on the second surface 12 side of the optical adhesive sheet 10, and a surface protection film 50 on the liner. This configuration is suitable for preventing environmental foreign matter from adhering to the transparent release liner 40 and for preventing damage to the transparent release liner 40 on the second surface 12 side of the optical adhesive sheet 10, from the time the optical adhesive sheet X is manufactured until it is supplied to the optical article manufacturing process, by the surface protection film 50.

[0043] In the optical adhesive sheet X, the second peeling force between the transparent release liner 20 and the optical adhesive sheet 10 is preferably smaller than the fifth peeling force (the force required to peel the transparent release liner 40 from the optical adhesive sheet 10) between the transparent release liner 40 and the optical adhesive sheet 10 under conditions of a peeling angle of 180° and a tensile speed of 300 mm / min. This configuration is preferable when using the optical adhesive sheet X in the manufacturing process of optical articles, as it allows for the proper peeling of the transparent release liner 20 from the first surface 11 of the optical adhesive sheet 10 while maintaining the state in which the transparent release liner 40 is adhered to the second surface 12 of the optical adhesive sheet 10. The fifth peeling force is preferably 0.03 N / 50 mm or more, more preferably 0.05 N / 50 mm or more, even more preferably 0.08 N / 50 mm or more, even more preferably 0.12 N / 50 mm or more, particularly preferably 0.18 N / 50 mm or more, and also preferably 2.0 N / 50 mm or less, more preferably 1.5 N / 50 mm or less, even more preferably 1.2 N / 50 mm or less, particularly preferably 1.0 N / 50 mm or less.

[0044] The optical adhesive sheet 10 is a transparent adhesive sheet. The optical adhesive sheet 10 is a pressure-sensitive adhesive layer formed from an adhesive composition (first adhesive composition). The first adhesive composition contains a base polymer.

[0045] The base polymer is an adhesive component that provides tackiness in the optical adhesive sheet 10. The base polymer exhibits rubber elasticity at room temperature. Examples of base polymers include acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluoropolymers. From the viewpoint of ensuring good transparency and tackiness in the optical adhesive sheet 10, an acrylic base polymer is preferably used as the base polymer.

[0046] The acrylic-based polymer (first acrylic-based polymer) is a copolymer of a monomer component (first monomer component) containing 50% by mass or more of alkyl (meth)acrylate. "(meth)acrylic acid" means acrylic acid and / or methacrylic acid.

[0047] (Meth)acrylate alkyl esters include (meth)acrylate alkyl esters in which the alkyl group has 1 to 20 carbon atoms, i.e., (meth)acrylate C 1-20 Alkyl esters are preferably used. Alkyl (meth)acrylate esters may have linear or branched alkyl groups, or cyclic alkyl groups such as alicyclic alkyl groups.

[0048] Examples of alkyl (meth)acrylate esters having linear or branched alkyl groups include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, and methacrylic acid Examples include isooctyl, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, isotridecyl (meth)acrylate, tetradecyl (meth)acrylate, isotetradecyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, and nonadecyl (meth)acrylate.

[0049] Examples of alkyl (meth)acrylates having an alicyclic alkyl group include cycloalkyl (meth)acrylates, (meth)acrylates having a bicyclic aliphatic hydrocarbon ring, and (meth)acrylates having three or more aliphatic hydrocarbon rings. Examples of cycloalkyl (meth)acrylates include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate. An example of a (meth)acrylate ester having a bicyclic aliphatic hydrocarbon ring is isobornyl (meth)acrylate. Examples of (meth)acrylic acid esters having three or more aliphatic hydrocarbon rings include 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.

[0050] The amount of alkyl (meth)acrylate per 100 parts by mass of the total first monomer components is, for example, 60 parts by mass or more, and also, for example, 100 parts by mass or less.

[0051] The first acrylic-based polymer preferably contains a polar group-containing monomer in addition to the above-mentioned alkyl (meth)acrylate as the first monomer component. Examples of polar group-containing monomers include hydroxyl group-containing monomers, carboxyl group-containing monomers, and nitrogen-containing monomers. The inclusion of a polar group-containing monomer in the first monomer component tends to increase the cohesive strength of the polymer and improve adhesion retention at high temperatures. Furthermore, when a crosslinked structure is introduced into the first acrylic-based polymer using a crosslinking agent such as an isocyanate crosslinking agent or an epoxy crosslinking agent, hydroxyl groups and carboxyl groups serve as introduction points for the crosslinked structure.

[0052] Examples of monomers containing a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate.

[0053] Examples of carboxyl group-containing monomers include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid.

[0054] Examples of nitrogen-containing monomers include nitrogen-containing vinyl monomers and cyanoacrylate monomers. Examples of nitrogen-containing vinyl monomers include N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, and N-vinylcaprolactam. Examples of cyanoacrylate monomers include acrylonitrile and methacrylonitrile.

[0055] From the viewpoint of ensuring good adhesive strength in the optical adhesive sheet 10, the amount of polar group-containing monomer relative to 100 parts by mass of the total first monomer components is, for example, 5 parts by mass or more, and also, for example, 25 parts by mass or less.

[0056] Methods for introducing a crosslinked structure into a base polymer include, for example, a method in which a base polymer having a functional group that can react with a crosslinking agent is polymerized, and then the crosslinking agent is added to react the base polymer with the crosslinking agent (first method); and a method in which a branched structure (crosslinked structure) is introduced into the polymer chain by including a polyfunctional compound in the polymerization component of the base polymer (second method). Multiple types of crosslinked structures may be introduced into the base polymer by using a combination of these methods.

[0057] In the first method, a crosslinking agent is added to the polymerized base polymer, and a crosslinked structure is introduced into the base polymer by heating as needed. Examples of crosslinking agents include compounds that react with functional groups (e.g., hydroxyl groups and carboxyl groups) contained in the base polymer. Examples of crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, carbodiimide crosslinking agents, and metal chelate crosslinking agents.

[0058] In the first method, isocyanate crosslinking agents and epoxy crosslinking agents are preferred as crosslinking agents because they have high reactivity with the functional groups (e.g., hydroxyl groups and carboxyl groups) of the base polymer and facilitate the introduction of a crosslinked structure. These crosslinking agents react with the functional groups (e.g., hydroxyl groups and carboxyl groups) introduced into the base polymer to form a crosslinked structure. In acid-free adhesives where the base polymer does not contain carboxyl groups, it is preferable to use an isocyanate crosslinking agent to form a crosslinked structure by the reaction of the isocyanate crosslinking agent with the hydroxyl groups in the base polymer.

[0059] In the second method described above, the first monomer component constituting the first acrylic base polymer and the entire amount of the polyfunctional compound for introducing the crosslinking structure may be reacted (polymerized) at once, or polymerized in multiple steps. In the multi-step polymerization method, for example, first, the monofunctional monomer constituting the base polymer is polymerized (prepolymerization) to prepare a partially polymerized product (prepolymer composition). Next, a polyfunctional compound such as a polyfunctional (meth)acrylate is added to the prepolymer composition to polymerize the prepolymer composition and the polyfunctional monomer (main polymerization). The prepolymer composition is a partially polymerized product containing polymers with a low degree of polymerization and unreacted monomers.

[0060] Examples of polyfunctional compounds used to introduce crosslinked structures include compounds containing two or more polymerizable functional groups (ethylenically unsaturated groups) having unsaturated double bonds in one molecule. As polyfunctional compounds, polyfunctional (meth)acrylates are preferred because they readily copolymerize with the first monomer component of the first acrylic-based polymer. When introducing branched (crosslinked) structures by active energy ray polymerization (photopolymerization), polyfunctional acrylates are preferred.

[0061] Examples of polyfunctional (meth)acrylates include polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, bisphenol A ethylene oxide modified di(meth)acrylate, bisphenol A propylene oxide modified di(meth)acrylate, alkanediol di(meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, ethoxylated isocyanuric acid tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol Examples include di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropanetetra(meth)acrylate, ethoxylated pentaerythritoltetra(meth)acrylate, pentaerythritoltetra(meth)acrylate, dipentaerythritol poly(meth)acrylate, dipentaerythritol hexa(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerin di(meth)acrylate, epoxy(meth)acrylate, butadiene(meth)acrylate, and isoprene(meth)acrylate.

[0062] Examples of polymerization methods for the first acrylic-based polymer include solution polymerization, active energy ray polymerization, bulk polymerization, and emulsion polymerization. Solution polymerization and active energy ray polymerization (e.g., UV polymerization) are preferred in terms of transparency, water resistance, and cost of the adhesive. Examples of solvents for solution polymerization include ethyl acetate and toluene.

[0063] When preparing the first acrylic-based polymer, a polymerization initiator may be used depending on the type of polymerization reaction. Examples of polymerization initiators include photopolymerization initiators and thermal polymerization initiators. Examples of photopolymerization initiators include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, and acylphosphine oxide-based photopolymerization initiators. Examples of thermal polymerization initiators include azo-based initiators, peroxide-based initiators, and redox-based initiators combining peroxides and reducing agents (for example, a combination of persulfate and sodium bisulfite, and a combination of peroxide and sodium ascorbate).

[0064] In polymerization, chain transfer agents and polymerization inhibitors (polymerization retarders) may be used, for example, from the viewpoint of molecular weight adjustment. Examples of chain transfer agents include thiols such as α-thioglycerol, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol, and α-methylstyrene dimers.

[0065] The first adhesive composition preferably contains 50% by mass or more of the first acrylic base polymer (or prepolymer composition) relative to the total amount of nonvolatile matter, more preferably 70% by mass, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0066] The first adhesive composition may contain other components besides those listed above. Examples of other components include silane coupling agents, tackifiers, plasticizers, softeners, degradation inhibitors, fillers, colorants, UV absorbers, antioxidants, surfactants, and antistatic agents.

[0067] From the viewpoint of ensuring sufficient adhesion to the adherend, the thickness of the optical adhesive sheet 10 is preferably 5 μm or more, more preferably 10 μm or more. From the viewpoint of handling the optical adhesive sheet 10, the thickness of the optical adhesive sheet 10 is preferably 300 μm or less, more preferably 200 μm or less.

[0068] The haze of the optical adhesive sheet 10 is preferably 3% or less, more preferably 2% or less. The haze of the optical adhesive sheet 10 can be measured using a haze meter in accordance with JIS K7136 (2000). Examples of haze meters include the "NDH2000" manufactured by Nippon Denshoku Industries Co., Ltd. and the "HM-150" manufactured by Murakami Color Technology Laboratory Co., Ltd.

[0069] The transmittance of light emitted from a white LED light source in the optical adhesive sheet 10 is, for example, 50% or more, preferably 80% or more, and more preferably 90% or more. Such a configuration is preferable from the viewpoint of appropriately performing foreign object inspection using a white LED light source. Furthermore, the infrared transmittance in the optical adhesive sheet 10 is, for example, 50% or more, preferably 80% or more, and more preferably 90% or more. Such a configuration is preferable from the viewpoint of appropriately performing foreign object inspection using infrared light.

[0070] The transparent peel-off liner 20 is a flexible, transparent resin film. Examples of materials for the resin film include polyolefins, polyesters, polyamides, polyimides, polyvinyl chloride, polyvinylidene chloride, cellulose, modified cellulose, polystyrene, and polycarbonate. Examples of polyolefins include polyethylene, polypropylene, cycloolefin polymer (COP), poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-vinyl alcohol copolymer. Examples of polyesters include polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate. Examples of polyamides include polyamide 6, polyamide 6,6, and partially aromatic polyamides. Examples of modified cellulose include triacetylcellulose (TAC). These resin materials may be used individually or in combination of two or more. For the transparent peel-off liner 20, materials with high cleanliness suitable for optical applications are preferred. From the viewpoint of obtaining a transparent peelable liner 20 with high cleanliness, polyolefin is preferably used as the material for the transparent peelable liner 20, and COP is more preferably used.

[0071] Furthermore, the resin material preferably contains no filler or substantially no filler. On the other hand, if the resin material contains a filler, the filler is preferably a nanofiller (a nanofiller refers to particles with a maximum length of 100 nm or less). These configurations are preferable from the viewpoint of obtaining a transparent peel-off liner 20 with a high degree of cleanliness.

[0072] From the viewpoint of ensuring the strength of the transparent release liner 20, the thickness of the transparent release liner 20 is preferably 5 μm or more, more preferably 10 μm or more, and more preferably 20 μm or more. Furthermore, from the viewpoint of ensuring appropriate flexibility in the transparent release liner 20, the thickness of the transparent release liner 20 is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less.

[0073] The haze of the transparent peel-off liner 20 is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less. The haze of the transparent peel-off liner 20 can be measured using a haze meter in accordance with JIS K7136 (2000).

[0074] The transmittance of light emitted from a white LED light source in the transparent peel-off liner 20 is, for example, 50% or more, preferably 80% or more, and more preferably 90% or more. Such a configuration is preferable from the viewpoint of appropriately performing foreign object inspection using a white LED light source. Furthermore, the infrared transmittance in the transparent peel-off liner 20 is, for example, 50% or more, preferably 80% or more, and more preferably 90% or more. Such a configuration is preferable from the viewpoint of appropriately performing foreign object inspection using infrared rays.

[0075] In this embodiment, the surface protection film 30 comprises a base film 31 and an adhesive layer 32 on the base film 31. In the surface protection film 30, the adhesive layer 32 forms an adhesive surface 30a.

[0076] The base film 31 is a flexible transparent resin film. Examples of materials for the resin film include the material used for the resin film of the transparent release liner 20. The thickness of the base film 31 is preferably 5 μm or more, more preferably 10 μm or more, and more preferably 20 μm or more, from the viewpoint of ensuring the strength of the surface protection film 30. Furthermore, from the viewpoint of ensuring appropriate flexibility in the surface protection film 30, the thickness of the surface protection film 30 is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less.

[0077] The adhesive layer 32 is a pressure-sensitive adhesive layer formed from an adhesive composition (second adhesive composition). The second adhesive composition contains a base polymer. Examples of the base polymer include the base polymer described above for the first adhesive composition. From the viewpoint of ensuring good transparency and tackiness in the adhesive layer 32, an acrylic base polymer (second acrylic base polymer) is preferably used as the base polymer of the second adhesive composition. Examples of monomer components that form the second acrylic base polymer (second monomer component) include the monomer component described above as the first monomer component that forms the first acrylic base polymer in the optical adhesive sheet 10.

[0078] The second monomer component preferably includes an alkyl (meth)acrylate having an alkyl group having 3 to 10 carbon atoms, and more preferably includes at least one selected from the group consisting of butyl acrylate and 2-ethylhexyl acrylate. The amount of alkyl (meth)acrylate having an alkyl group having 3 to 10 carbon atoms, relative to 100 parts by mass of the total second monomer component, is preferably 80 parts by mass or more, more preferably 90 parts by mass or more, even more preferably 93 parts by mass or more, and also, for example, 100 parts by mass or less, preferably 99 parts by mass or less, and more preferably 98 parts by mass or less.

[0079] The second monomer component preferably comprises at least one selected from the group consisting of hydroxyl group-containing monomers and carboxyl group-containing monomers, and more preferably comprises at least one selected from the group consisting of acrylic acid and 2-hydroxyethyl acrylate. The amount of polar group-containing monomer per 100 parts by mass of the total second monomer component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and also preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less.

[0080] The thickness of the adhesive layer 32 is preferably 1 μm or more, more preferably 3 μm or more, even more preferably 5 μm or more, and also preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less.

[0081] The transparent release liner 40 is a flexible transparent resin film. The material, thickness, haze, and transmittance of the transparent release liner 40 are the same as those described above for the transparent release liner 20.

[0082] The transparent release liner 40 preferably has a release layer on the optical adhesive sheet 10 side. The release layer is a layer that ensures the release of the transparent release liner 40 from the surface of the optical adhesive sheet 10. Examples of materials for the release layer include silicone resin, long-chain alkyl resin, and fatty acid amide resin. These resins may contain fluorine atoms in their polymer side chains. For example, the silicone resin may be a fluorinated silicone resin containing fluorine atoms in its side chains. When the transparent release liner 40 has a release layer on the optical adhesive sheet 10 side, methods for adjusting the peeling force between such a transparent release liner 40 and the optical adhesive sheet 10 include, for example, selecting the type of release layer material and adjusting the concentration of the release layer material.

[0083] In this embodiment, the surface protection film 50 comprises a base film 51 and an adhesive layer 52 on the base film 51. In the surface protection film 50, the adhesive layer 52 forms an adhesive surface 50a.

[0084] The base film 51 is a flexible transparent resin film. Examples of materials for the resin film include the material used for the resin film of the transparent release liner 20. The thickness of the base film 51 is preferably 5 μm or more, more preferably 10 μm or more, and more preferably 20 μm or more, from the viewpoint of ensuring the strength of the surface protection film 50. Furthermore, from the viewpoint of ensuring appropriate flexibility in the surface protection film 50, the thickness of the surface protection film 50 is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less.

[0085] The adhesive layer 52 is a pressure-sensitive adhesive layer formed from an adhesive composition (third adhesive composition). The third adhesive composition contains a base polymer. Examples of the base polymer include the base polymer described above for the first adhesive composition. From the viewpoint of ensuring good transparency and tackiness in the adhesive layer 52, an acrylic base polymer (third acrylic base polymer) is preferably used as the base polymer of the third adhesive composition. Examples of monomer components that form the third acrylic base polymer (third monomer component) include the monomer component described above as the first monomer component that forms the first acrylic base polymer in the optical adhesive sheet 10.

[0086] The third monomer component preferably includes an alkyl (meth)acrylate having an alkyl group having 3 to 10 carbon atoms, and more preferably includes at least one selected from the group consisting of butyl acrylate and 2-ethylhexyl acrylate. The amount of alkyl (meth)acrylate having an alkyl group having 3 to 10 carbon atoms, relative to 100 parts by mass of the total third monomer component, is preferably 80 parts by mass or more, more preferably 90 parts by mass or more, even more preferably 93 parts by mass or more, and also, for example, 100 parts by mass or less, preferably 99 parts by mass or less, and more preferably 98 parts by mass or less.

[0087] The third monomer component preferably comprises at least one selected from the group consisting of hydroxyl group-containing monomers and carboxyl group-containing monomers, and more preferably comprises at least one selected from the group consisting of acrylic acid and 2-hydroxyethyl acrylate. The amount of polar group-containing monomer per 100 parts by mass of the total third monomer component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and also preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less.

[0088] The thickness of the adhesive layer 52 is preferably 1 μm or more, more preferably 3 μm or more, even more preferably 5 μm or more, and also preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less.

[0089] The optical adhesive sheet X can be manufactured, for example, by preparing an optical adhesive sheet 10 with transparent release liners 20 and 40, and surface protective films 30 and 50, and then laminating them together. The optical adhesive sheet X is preferably manufactured in a cleanroom. The higher the air cleanliness of the manufacturing line for the optical adhesive sheet X (for example, the air cleanliness of the cleanroom), the less environmental foreign matter and the smaller the size of the environmental foreign matter on the inside and surface of the manufactured optical adhesive sheet X. The air cleanliness of the manufacturing line is preferably Class 3 or lower, more preferably Class 2 or lower, and even more preferably Class 1 according to the ISO 14644-1 standard.

[0090] The method for manufacturing the optical adhesive sheet 10 with transparent release liners 20 and 40 is as follows, for example.

[0091] First, the first adhesive composition described above is applied to the transparent release liner 20 to form a coating film, and then the coating film is dried. Examples of application methods for the first 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 (the same applies to the application methods of the adhesive composition described later). If the first adhesive composition contains a crosslinking agent, the crosslinking reaction proceeds simultaneously with the drying described above or by subsequent aging. The aging conditions are set appropriately depending on the type of crosslinking agent. In addition, before or after aging, a transparent release liner 40 is further laminated on top of the optical adhesive sheet 10 on the transparent release liner 20.

[0092] When the first adhesive composition is a photopolymerizable composition containing a prepolymer composition and a polyfunctional compound, etc., the first adhesive composition is applied to the transparent release liner 20 to form a coating film, and then photocuring is performed by irradiating the coating film with active light. When performing photocuring, it is preferable to laminate the transparent release liner 40 on the coating film and irradiate the coating film with active light while sandwiched between the two release liners to prevent polymerization inhibition by oxygen.

[0093] The active light is selected depending on the type of monomer component, polymerizable component (e.g., polyfunctional (meth)acrylate), and photopolymerization initiator. Generally, ultraviolet and / or short-wavelength visible light are used. The integrated light intensity of the irradiation is, for example, 100 to 5000 mJ / cm². 2 To that extent, a light source capable of emitting light in the wavelength range to which the photopolymerization initiator contained in the adhesive composition is sensitive is used as the light source for light irradiation. Examples of light sources include LED light sources, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, and xenon lamps.

[0094] In this manner, an optical adhesive sheet 10 with transparent release liners 20 and 40 can be manufactured.

[0095] The surface protective film 30 can be manufactured, for example, by applying the above-described second adhesive composition onto a base film 31 to form a coating film, and then drying the coating film to form an adhesive layer 32.

[0096] The surface protective film 50 can be manufactured, for example, by applying the above-described third adhesive composition onto a base film 51 to form a coating film, and then drying the coating film to form an adhesive layer 52.

[0097] Then, the surface protective film 30 is bonded to the transparent release liner 20 side of the optical adhesive sheet 10 with transparent release liners 20 and 40 using the adhesive layer 32, and the surface protective film 50 is bonded to the transparent release liner 40 side using the adhesive layer 52. This results in an optical adhesive sheet X.

[0098] As shown in Figure 2, the optical adhesive sheet X may include a polarizer film 60 instead of a transparent release liner 40 and a surface protection film 50. The optical adhesive sheet X shown in Figure 2 comprises a surface protection film 30, a transparent release liner 20, an optical adhesive sheet 10, and a polarizer film 60 in order in the thickness direction H. The optical adhesive sheet 10 is bonded to the polarizer film 60. With such an optical adhesive sheet X, a polarizer film with an adhesive layer formed on the surface of the polarizer film 60 by the optical adhesive sheet 10 can be supplied to the optical article manufacturing process with a high degree of cleanliness of the optical adhesive sheet 10 (adhesive layer). [Examples]

[0099] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Furthermore, the specific numerical values ​​such as the amounts (content), physical properties, and parameters described below can be substituted with the upper limits (numerical values ​​defined as "less than or equal to" or "less than") or lower limits (numerical values ​​defined as "greater than or equal to" or "greater than") of the corresponding amounts (content), physical properties, and parameters described in the "Modes for Carrying Out the Invention" above.

[0100] [Preparation of surface protective film SPV1] <Preparation of the first acrylic polymer> In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, a mixture containing 96.2 parts by mass of 2-ethylhexyl acrylate (2EHA), 3.8 parts by mass of 2-hydroxyethyl acrylate (HEA), 0.2 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 stirred at 65°C for 6 hours under a nitrogen atmosphere (polymerization reaction). This yielded a first polymer solution containing a first acrylic polymer (solid content concentration 40% by mass). The weight-average molecular weight of the first acrylic polymer was 540,000.

[0101] <Preparation of adhesive composition> Ethyl acetate was added to the first polymer solution to adjust the solid content concentration to 20% by mass. Then, 3 parts by mass of a crosslinking agent (product name "Coronate HX", isocyanurate of hexamethylene diisocyanate, manufactured by Tosoh Corporation) and 0.03 parts by mass of dibutyltin dilaurate as a crosslinking catalyst were added to the polymer solution per 100 parts by mass of the first acrylic polymer and mixed to obtain the first adhesive composition.

[0102] <Formation of the adhesive layer> After corona-treating one side of a polyethylene terephthalate (PET) film (product name "Diafoil T100C-38", thickness 38 μm, manufactured by Mitsubishi Chemical Corporation), a first adhesive composition was applied to the corona-treated side of the PET film to form a coating. Next, the coating on the PET film was dried by heating at 130°C for 2 minutes to form a first adhesive layer with a thickness of 23 μm.

[0103] The surface protection film SPV1 was prepared as described above. The surface protection film SPV1 has a laminated structure of a PET film and a first adhesive layer (thickness 23 μm, first acrylic polymer), and has an adhesive surface on one side.

[0104] [Preparation of surface protective film SPV2] Surface protective film SPV2 was prepared in the same manner as surface protective film SPV1, except for the following: In the preparation of the adhesive composition, the amount of dibutyltin dilaurate was set to 0.04 parts by mass. In the formation of the adhesive layer, the thickness of the adhesive layer formed on the PET film was set to 10 μm.

[0105] The surface protection film SPV2 has a laminated structure consisting of a PET film and a second adhesive layer (10 μm thick, first acrylic polymer), and has an adhesive surface on one side.

[0106] [Preparation of surface protective film SPV3] <Preparation of the second acrylic polymer> In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, a mixture containing 95 parts by mass of butyl acrylate (BA), 5 parts by mass of acrylic acid (AA), 0.2 parts by mass of AIBN as a thermal polymerization initiator, and 186 parts by mass of ethyl acetate as a solvent was stirred at 63°C for 10 hours under a nitrogen atmosphere (polymerization reaction). This yielded a second polymer solution containing the second acrylic polymer (solid content concentration 35% by mass). The weight-average molecular weight of the second acrylic polymer was 500,000.

[0107] <Preparation of adhesive composition> Ethyl acetate was added to the second polymer solution to adjust the solid content concentration to 20% by mass. Then, 5 parts by mass of a crosslinking agent (product name "Tetrad C", 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, manufactured by Mitsubishi Gas Chemical Co., Ltd.) was added to the polymer solution per 100 parts by mass of the second acrylic polymer and mixed to obtain the second adhesive composition.

[0108] <Formation of the adhesive layer> After corona-treating one side of a PET film (product name "Diafoil T100C-38", thickness 38 μm, manufactured by Mitsubishi Chemical Corporation), a second adhesive composition was applied to the corona-treated side of the PET film to form a coating. Next, the coating on the PET film was dried by heating at 130°C for 2 minutes to form a third adhesive layer with a thickness of 5 μm.

[0109] The surface protection film SPV3 was prepared as described above. The surface protection film SPV3 has a laminated structure of a PET film and a third adhesive layer (thickness 5 μm, second acrylic polymer), and has an adhesive surface on one side.

[0110] [Example 1] A covered optical adhesive sheet was fabricated in a cleanroom using the following method.

[0111] First, a cycloolefin polymer (COP) film (product name "Zeonor Film ZF16", thickness 50 μm, manufactured by Nippon Zeon) was prepared as the base film for the first transparent release liner. Next, the adhesive side of the surface protection film SPV3 was bonded to one side of this COP film. Then, a first silicone-based release layer was formed on the other side of the COP film. Specifically, a release agent solution was prepared by diluting a mixture of 30 parts by mass of addition-type silicone composition (product name "LTC761", manufactured by Toray Dow Corning), 0.9 parts by mass of silicone dispersion (product name "BY 24-850", manufactured by Toray Dow Corning), and 2 parts by mass of platinum catalyst for silicone curing (product name "SRX 212", manufactured by Toray Dow Corning) with a mixed solvent of toluene and hexane (volume ratio of toluene to hexane is 1:1). Next, this solution was applied to the other side of the COP film and heated and dried in a hot air dryer at 130°C for 1 minute. This yielded a first transparent release liner with a surface protective film SPV3.

[0112] On the other hand, a cycloolefin polymer (COP) film (product name "Zeonor Film ZF16", thickness 50 μm, manufactured by Nippon Zeon) was prepared as the base film for the second transparent release liner. Next, the adhesive side of the surface protection film SPV1 was bonded to one side of this COP film. Then, a second silicone-based release layer was formed on the other side of the COP film. This resulted in obtaining a second transparent release liner with the surface protection film SPV1. The second silicone-based release layer has a different composition and thickness from the first silicone-based release layer of the first transparent release liner, and has a higher peeling force than the first silicone-based release layer.

[0113] Next, in a cleanroom, an adhesive composition having UV curing properties was applied to the release layer side of the first transparent release liner to form a coating film (thickness 50 μm). Then, the release layer side of the second transparent release liner was bonded to the exposed surface of the coating film to obtain a laminate. UV light was irradiated onto this laminate from the second transparent release liner side to photocur the adhesive composition coating film and form an adhesive layer. The UV light source had an irradiation intensity of 5 mW / cm² at the irradiation surface directly below the lamp. 2 A black light was used, positioned to achieve the desired result (the same method was used for ultraviolet irradiation, as described later).

[0114] As described above, the covered optical adhesive sheet of Example 1 was prepared. The covered optical adhesive sheet of Example 1 comprises, in the thickness direction, a surface protective film SPV3, a first transparent release liner (light release liner), an optical adhesive sheet, a second transparent release liner (heavy release liner), and a surface protective film SPV1.

[0115] [Example 2] The covered optical adhesive sheet of Example 2 was prepared in the same manner as the covered optical adhesive sheet of Example 1, except that the surface protective film SPV2 was used instead of the surface protective film SPV1.

[0116] The covered optical adhesive sheet of Example 2 comprises, in the thickness direction, a surface protective film SPV3, a first transparent release liner (light release liner), an optical adhesive sheet, a second transparent release liner (heavy release liner), and a surface protective film SPV2, in that order.

[0117] [Example 3] A covered optical adhesive sheet was fabricated in a cleanroom using the following method.

[0118] First, a first transparent release liner with a surface protection film SPV3 was prepared in the same manner as the first transparent release liner with a surface protection film SPV3 in the covered optical adhesive sheet of Example 1.

[0119] On the other hand, a UV-curable adhesive composition was applied to the release layer side of a predetermined first release liner having a release layer on one side to form a coating film (thickness 50 μm). Next, the release layer side of a predetermined second release liner having a release layer on one side was bonded to the exposed surface of the coating film to obtain a laminate. UV light was irradiated onto this laminate from the second release liner side to photo-cur the adhesive composition coating film and form an adhesive layer. Next, the second release liner was peeled off the adhesive layer, and a polarizer film (thickness 34 μm) was bonded to the exposed adhesive layer. Next, the first release liner was peeled off the adhesive layer with the polarizer film, and the release layer side of a first transparent release liner with a surface protection film SPV3 was bonded to the exposed adhesive layer.

[0120] As described above, the covered optical adhesive sheet of Example 3 was prepared. The covered optical adhesive sheet of Example 3 comprises, in the thickness direction, a surface protective film SPV3, a first transparent release liner, an optical adhesive sheet, and a polarizer film.

[0121] [Example 4] A covered optical adhesive sheet was fabricated in a cleanroom using the following method.

[0122] First, a COP film (product name "Zeonor Film ZF16", thickness 50 μm, manufactured by Nippon Zeon Co., Ltd.) was prepared as the base film for the first transparent release liner. Next, the adhesive side of a surface protection film SPV4 (product name "PEARL PREMIUM", Tredegger Co., Ltd.), which has an adhesive side on one side, was bonded to one side of the COP film. Then, a first silicone-based release layer was formed on the other side of the COP film (the method for forming the first silicone-based release layer was the same as described above for Example 1). This resulted in obtaining a first transparent release liner with the surface protection film SPV4 attached.

[0123] Then, the covered optical adhesive sheet of Example 4 was prepared in the same manner as the covered optical adhesive sheet of Example 3, except that the first transparent release liner with surface protection film SPV4 was used instead of the first transparent release liner with surface protection film SPV3. The covered optical adhesive sheet of Example 4 comprises, in the thickness direction, a surface protection film SPV4, a first transparent release liner, an optical adhesive sheet, and a polarizer film.

[0124] [Comparative Example 1] A covered optical adhesive sheet was fabricated in a cleanroom using the following method.

[0125] First, two first transparent release liners with the surface protective film SPV1 described above were prepared for Example 1. Next, in a cleanroom, an adhesive composition having UV curing properties was applied to the release layer side of one of the first transparent release liners to form a coating film (thickness 50 μm). Then, the release layer side of the other first transparent release liner was bonded to the exposed surface of the coating film to obtain a laminate. UV light was irradiated onto this laminate from the other first transparent release liner side to photocur the adhesive composition coating film and form an adhesive layer.

[0126] As described above, a covered optical adhesive sheet of Comparative Example 1 was prepared. The covered optical adhesive sheet of Comparative Example 1 comprises, in the thickness direction, a surface protective film SPV1, a first transparent release liner, an optical adhesive sheet, a first transparent release liner, and the surface protective film SPV1 in that order.

[0127] <Peel strength between the transparent release liner and the surface protective film> The peeling force required to peel the surface protective films SPV1 to SPV4 from the aforementioned COP film (product name "Zeonor Film ZF16", thickness 50 μm, manufactured by Nippon Zeon) used as a transparent peeling liner was measured (first measurement).

[0128] In preparing the test specimens for measurement, first, the adhesive side of the surface protection film was bonded to the COP film. This bonding was performed by pressing the surface protection film against the COP film using a 2kg hand roller in a 23°C environment. Next, the strong adhesive layer side of a PET substrate, which has a strong adhesive layer formed on one side, was bonded to the COP film to obtain a laminate. Then, a test specimen (50mm wide x 100mm long) was cut from this laminate (PET substrate / strong adhesive layer / COP film / surface protection film). The test specimens for measurement were prepared in the manner described above.

[0129] Next, after allowing the test specimens to stand at 23°C for 1 hour, a peel test was performed to peel the surface protective film from the COP film on the test specimens, and the peel force was measured. A tensile testing machine (product name "Autograph AG-50NX plus", manufactured by Shimadzu Corporation) was used for this measurement. In this measurement, the measurement temperature was set to 23°C, the peel angle to 180°, the tensile speed to 300 mm / min, and the peel length to 50 mm. The measured peel force is shown in Table 1 as peel force f1 (N / 50 mm). Peel force f1 corresponds to the third peel force in this invention.

[0130] Furthermore, the peeling force f1 for peeling the surface protection film SPV3 from the COP film is shown in Table 2 as the peeling force F1 in Examples 1, 2, and 3. The peeling force F1 is the force required to peel the first surface protection film from the first transparent release liner, and corresponds to the first peeling force in the present invention (the same applies to the peeling force F1 described later). The peeling force f1 for peeling the surface protection film SPV2 from the COP film is shown in Table 2 as the peeling force F3 in Example 2. The peeling force f1 for peeling the surface protection film SPV4 from the COP film is shown in Table 2 as the peeling force F1 in Example 4. The peeling force f1 for peeling the surface protection film SPV1 from the COP film is shown in Table 2 as the peeling force F1 in Comparative Example 1. The peeling force f1 for peeling the surface protection film SPV1 from the COP film is shown in Table 2 as the peeling force F3 in Example 1 and Comparative Example 1. The peeling force F3 is the force required to peel the second surface protective film from the second transparent peeling liner (the same applies to the peeling force F3 described later).

[0131] On the other hand, the peeling forces required to peel the surface protective films SPV1 to SPV4 from the COP film (product name "Zeonor Film ZF16", thickness 50 μm, manufactured by Nippon Zeon) were measured in the same manner as in the first measurement, except for the following: The prepared test specimens were stored at 50°C for two weeks, and then stored at 23°C and 50% relative humidity for one day, and the peeling forces were measured for the test specimens after such storage. The measurement conditions were the same as in the first measurement described above. The measured peeling forces are shown in Table 1 as peeling force f1' (N / 50 mm). Peeling force f1' corresponds to the fourth peeling force in this invention. The ratio of peeling force f1' to peeling force f1 (f1' / f1) is also shown in Table 1.

[0132] Furthermore, the peeling force f1' for peeling the surface protective film SPV3 from the COP film is shown in Table 2 as the peeling force F1' in Examples 1, 2, and 3. The peeling force F1' is the peeling force for peeling the first surface protective film from the first transparent release liner after the above-mentioned heat storage (the same applies to the peeling force F1' described later). The peeling force f1' for peeling the surface protective film SPV4 from the COP film is shown in Table 2 as the peeling force F1' in Example 4. The peeling force f1' for peeling the surface protective film SPV1 from the COP film is shown in Table 2 as the peeling force F1' in Comparative Example 1.

[0133] <Gel fraction of the adhesive layer of the surface protective film> The gel fraction of each adhesive layer in surface protective films SPV1 to SPV3 was measured. Specifically, the results are as follows:

[0134] First, an adhesive sample of approximately 0.1 g (mass: W1 mg) was taken from the adhesive layer of the surface protective film. Next, the adhesive sample was wrapped in a drawstring-like shape with a porous membrane made of tetrafluoroethylene resin with an average pore size of 0.2 μm (mass: W2 mg), and the opening was tied with kite string (mass: W3 mg) to obtain a package. As the porous membrane made of tetrafluoroethylene resin, a porous membrane manufactured by Nitto Denko Corporation (product name "Nitoflon NTF1122") was used. Next, the package containing the adhesive sample was placed in a 50 mL container, and the container was filled with ethyl acetate (one container was used for each package). After standing at 23°C for 7 days, the package was removed from the container and dried at 130°C for 2 hours. After that, the mass of the package (W4 mg) was measured. Then, the gel fraction of the adhesive layer was calculated by substituting the values ​​of W1 to W4 into the following formula. The values ​​are shown in Table 1.

[0135] Gel fraction (%) = [(W4 - W2 - W3) / W1] × 100

[0136] <Peeling force between optical adhesive sheet and transparent release liner> In each of the covered optical adhesive sheets in Examples 1 to 4, the peeling force required to peel the first transparent release liner from the optical adhesive sheet was measured. Specifically, first, test specimens for measurement were prepared. In preparing the test specimens, a sheet piece (50 mm wide x 100 mm long) was first cut from the covered optical adhesive sheet. Next, the surface protective film was peeled off both sides of the sheet piece. This obtained a test specimen for measurement. Next, after the test specimen was left to stand at 23°C for 60 minutes, a peel test was performed to peel the first transparent release liner from the optical adhesive sheet on the test specimen, and the peeling force was measured (second measurement). A tensile testing machine (product name "Autograph AG-50NX plus", manufactured by Shimadzu Corporation) was used for this measurement. In this measurement, the measurement temperature was set to 23°C, the peeling angle to 180°, the tensile speed to 300 mm / min, and the peeling length to 50 mm. The measured peeling forces are shown in Table 2 as the peeling force F2 (N / 50 mm) for Examples 1 to 4. The peeling force F2 is the force required to peel the first transparent release liner from the optical adhesive sheet (i.e., the second peeling force) (the same applies to the peeling force F2 described later).

[0137] On the other hand, in each of the covered optical adhesive sheets in Examples 1 and 2, the peeling force required to peel the second transparent release liner from the optical adhesive sheet was measured. Specifically, first, test specimens for measurement were prepared. In preparing the test specimens, the first transparent release liner was peeled off the covered optical adhesive sheet together with the surface protective film on it. Next, a PET substrate was bonded to the exposed surface of the optical adhesive sheet that was exposed by this peeling to obtain a laminate. In this bonding process, the PET substrate was pressed against the optical adhesive sheet by running a 2 kg hand roller back and forth once in an environment of 23°C. Next, a test specimen (width 50 mm × length 100 mm) was cut out from this laminate. This obtained a test specimen for measurement. Next, after the test specimen was left to stand at 23°C for 60 minutes, a peel test was performed to peel the second transparent release liner from the optical adhesive sheet on the test specimen, and the peeling force was measured. Specifically, the procedure was the same as for the second measurement. The measured peeling force is shown in Table 2 as the peeling force F4 (N / 50 mm) in Examples 1 and 2. The peeling force F4 corresponds to the fifth peeling force in this invention.

[0138] On the other hand, in the covered optical adhesive sheet of Comparative Example 1, the peeling force required to peel one of the first transparent release liners from the optical adhesive sheet was measured. Specifically, first, a test specimen for measurement was prepared. In preparing the test specimen, a sheet piece (width 50 mm × length 100 mm) was first cut from the covered optical adhesive sheet. Next, the surface protective film was peeled off both sides of the sheet piece. This obtained a test specimen for measurement. Next, after the test specimen was left to stand at 23°C for 60 minutes, a peel test was performed to peel one of the first transparent release liners from the optical adhesive sheet, and the peeling force was measured. Specifically, the procedure was the same as for the second measurement. The measured peeling forces are shown in Table 2 as peeling forces F2 and F4 (N / 50 mm) in Comparative Example 1.

[0139] <Evaluation of the peelability of surface protective films> In the covered optical adhesive sheets of Examples 1-4 and Comparative Example 1, the peelability of each surface protective film from the transparent release liner was investigated.

[0140] Specifically, first, one of the surface protective films, which was the subject of evaluation in the covered optical adhesive sheet, was manually peeled off from the transparent release liner to which it was in contact. The peelability of the surface protective film was evaluated as "good" if the surface protective film could be peeled off while the transparent release liner remained on the optical adhesive sheet, and as "poor" if the transparent release liner to which the surface protective film was in contact with was peeled off from the optical adhesive sheet together with the surface protective film. The evaluation results are shown in Table 2.

[0141] [Table 1]

[0142] [Table 2] [Industrial applicability]

[0143] The covered optical adhesive sheet of the present invention can be used, for example, as a supply material for optical adhesive sheets in the manufacturing process of display panels. [Explanation of Symbols]

[0144] X Optical adhesive sheet (covered optical adhesive sheet) H thickness direction 10 Optical adhesive sheets 11 Page 1 12 Side 2 20,40 Transparent peel-off liner 30,50 Surface protective film 30a, 50a Adhesive surface 60 Polarizer Film

Claims

1. The optical adhesive sheet, the transparent release liner, and the surface protective film are arranged in order in the thickness direction. The optical adhesive sheet has a first surface and a second surface opposite to the first surface. The transparent release liner is placed on the first surface, The surface protective film has an adhesive surface and is attached to the transparent release liner by the adhesive surface. The first peeling force between the surface protective film and the transparent release liner, under the conditions of a peeling angle of 180° and a tensile speed of 300 mm / min, is smaller than the second peeling force between the transparent release liner and the optical adhesive sheet under the same conditions. After the surface protective film is laminated to the cycloolefin polymer film, a third peel force is applied to the cycloolefin polymer film under the conditions of a peel angle of 180° and a tensile speed of 300 mm / min. The surface protective film, after being laminated to the cycloolefin polymer film and after two weeks at 50°C, has a fourth peel force relative to the cycloolefin polymer film under the conditions of a peel angle of 180° and a tensile speed of 300 mm / min. A covered optical adhesive sheet in which the ratio of the fourth peeling force to the third peeling force is 0.8 or more and 1.5 or less.

2. The covered optical adhesive sheet according to claim 1, wherein the surface protective film, after being laminated to the cycloolefin polymer film, has a peel force of 1.0 N / 50 mm or less on the cycloolefin polymer film under the conditions of a peel angle of 180° and a tensile speed of 300 mm / min.

3. The covered optical adhesive sheet according to claim 1, wherein the surface protective film has an adhesive layer that forms the adhesive surface, and the adhesive layer has a gel fraction of 80% or more.

4. The covered optical adhesive sheet according to claim 1, wherein the surface roughness Ra of the surface on the surface protective film side of the transparent release liner is 20 nm or less.

5. The optical adhesive sheet further comprises an additional transparent release liner and an additional surface protective film on the second surface side, The additional transparent release liner is placed on the second surface of the optical adhesive sheet, The covered optical adhesive sheet according to any one of claims 1 to 4, wherein the additional surface protective film has an adhesive surface and is attached to the additional transparent release liner by the adhesive surface.

6. The covered optical adhesive sheet according to claim 5, wherein the second peeling force is smaller than the fifth peeling force between the additional transparent peeling liner and the optical adhesive sheet under the conditions described above.

7. The covered optical adhesive sheet according to any one of claims 1 to 4, further comprising a polarizer film disposed on the second surface of the optical adhesive sheet.

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