WO2023074556A1

WO2023074556A1 - Optical pressure-sensitive adhesive sheet

Info

Publication number: WO2023074556A1
Application number: PCT/JP2022/039267
Authority: WO
Inventors: 大器下栗; 陽介清水; 裕貴小原; 新藤原
Original assignee: 日東電工株式会社
Priority date: 2021-10-27
Filing date: 2022-10-21
Publication date: 2023-05-04
Also published as: TW202328369A

Abstract

This pressure-sensitive adhesive sheet (10) is an optical pressure-sensitive adhesive sheet including a base polymer and having photocurability. The base polymer is a photopolymerization product. The pressure-sensitive adhesive sheet (10) has an adhesive force F1 in a given first peel test and has an adhesive force F2 in a given second peel test, the ratio of the adhesive force F2 to the adhesive force F1 being 0.4 or higher and the adhesive force F2 being 2-4.5 N/10 mm.

Description

optical adhesive sheet

The present invention relates to an optical adhesive sheet.

A display panel has a laminated structure including elements such as a pixel panel, a polarizing film and a cover glass. In the manufacturing process of the display panel, for example, an optically transparent adhesive sheet (optical adhesive sheet) is used for bonding elements included in the laminated structure. An optical pressure-sensitive adhesive sheet for use in display panels is described, for example, in Patent Document 1 below.

JP 2012-62345 A

The laminated structure of the display panel includes elements with surface steps. For example, a decorative or light-shielding printed layer is provided on the edge of the surface of the cover glass on the pixel panel side, and there is a step (printed step) between the surface of the cover glass and the surface of the printed layer. Therefore, an optical pressure-sensitive adhesive sheet for display panel applications is required to have reliability in bonding between adherends as well as softness to the extent that it can follow printing steps (step conformability). Insufficient step followability of the optical adhesive sheet is caused, for example, by air bubbles being formed along the printed layer between the optical adhesive sheet and the cover glass bonded to the surface of the cover glass with the printed layer. cause and is undesirable.

　The optical adhesive sheet is also required to have reworkability when laminating it to the adherend. Specifically, if there is a problem with the bonding of the optical adhesive sheet to the adherend (positional deviation of the optical adhesive sheet on the adherend, etc.), it is possible to perform bonding work with an alternative optical adhesive sheet. Therefore, the optical pressure-sensitive adhesive sheet is required to have light releasability for proper release from the adherend. Especially when the display panel contains expensive elements such as a polarizing film, there is a strong demand for reworkability of the optical pressure-sensitive adhesive sheet from the viewpoint of avoiding production loss due to lamination failure.

The present invention provides an optical pressure-sensitive adhesive sheet that is suitable for ensuring reworkability in bonding to an adherend and achieving both step followability and bonding reliability.

The present invention [1] is an optical pressure-sensitive adhesive sheet containing a base polymer and having photocurability, wherein the base polymer is a photopolymerized product, has adhesive strength F1 in the following first peel test, has an adhesive force F2 in the second peel test, the ratio of the adhesive force F2 to the adhesive force F1 is 0.4 or more, and the adhesive force F2 is 2 N / 10 mm or more and 4.5 N / 10 mm or less, Includes optical adhesive sheet.

First peel test:
First, the optical adhesive sheet is attached to an alkali glass plate produced by the float method to obtain a first laminate. Next, the first laminate is heat-treated under conditions of 50° C., 0.5 MPa, and 15 minutes. Next, the optical pressure-sensitive adhesive sheet is photo-cured by UV irradiation with an integrated light amount of 3000 mJ/cm ² . Next, the adhesive force F1 is measured by peeling the optical adhesive sheet from the alkali glass plate under the conditions of 23° C., 50% relative humidity, 180° peeling angle, and 300 mm/min tensile speed.

Second peel test:
First, the optical adhesive sheet is photo-cured by UV irradiation with an integrated light amount of 3000 mJ/cm ² . Next, the optical adhesive sheet is attached to an alkali glass plate produced by the float method to obtain a second laminate. Next, the second laminate is heat-treated under conditions of 50° C., 0.5 MPa, and 15 minutes. Next, the adhesive force F2 is measured by peeling the optical adhesive sheet from the alkali glass plate under the conditions of 23° C., 50% relative humidity, 180° peeling angle, and 300 mm/min tensile speed.

The present invention [2] has an adhesive strength B1 in the first tensile test below, an adhesive strength B2 in the second tensile test below, and the ratio of the adhesive strength B2 to the adhesive strength B1 is 0.8 The optical pressure-sensitive adhesive sheet according to [1] above is included.

First tensile test:
First, the first alkali glass plate and the second alkali glass plate are bonded in the thickness direction via the optical adhesive sheet to obtain a first bonded body. Next, the optical pressure-sensitive adhesive sheet is photo-cured by UV irradiation with an integrated light amount of 3000 mJ/cm ² . Next, the first joined body is heat-treated under conditions of 50° C., 0.5 MPa, and 15 minutes. Next, the first and second alkali glass plates in the first bonded body are pulled in opposite directions in the thickness direction under conditions of 25° C. and a tensile speed of 25 mm/min to measure the adhesive strength B1.

Second tensile test:
First, the optical adhesive sheet is attached to the first alkali glass plate to obtain a second joined body. Next, the optical pressure-sensitive adhesive sheet is photo-cured by UV irradiation with an integrated light amount of 3000 mJ/cm ² . Next, the second joined body is heat-treated under conditions of 50° C., 0.5 MPa, and 15 minutes. Next, the first alkali glass plate and the second alkali glass plate are bonded in the thickness direction via the optical adhesive sheet on the first alkali glass plate to obtain a third bonded body. Next, the first and second alkali glass plates in the third bonded body are pulled in the thickness direction opposite to each other under conditions of 25° C. and a tensile speed of 25 mm/min to measure the adhesive strength B2.

The present invention [3] includes the optical adhesive sheet according to [2] above, wherein the adhesive strength B2 is 4 MPa or more.

The present invention [4] is any one of [1] to [3] above, wherein the light transmittance at a wavelength of 420 nm is 85% or more and the light transmittance at a wavelength of 380 nm is 15% or less. The optical pressure-sensitive adhesive sheet described in .

The present invention [5] includes the optical pressure-sensitive adhesive sheet according to any one of [1] to [4] above, which has a haze of 1% or less.

The present invention [6] includes the optical adhesive sheet according to any one of [1] to [5] above, which further contains an ultraviolet absorber.

The present invention [7] further comprises a photopolymerization initiator, the photopolymerization initiator having a specific absorbance of 10 or more at a wavelength of 405 nm, and the ultraviolet absorber having a specific absorbance of 5 or less at a wavelength of 405 nm. The optical pressure-sensitive adhesive sheet described in [6] above is included.

The present invention [8] includes the optical adhesive sheet according to any one of [1] to [7] above, further comprising an antioxidant.

The present invention [9] includes the optical pressure-sensitive adhesive sheet according to any one of the above [1] to [8], which is substantially free of thermal polymerization initiator residue.

The optical adhesive sheet of the present invention has photocurability as described above. Such an optical pressure-sensitive adhesive sheet can be attached to the stepped surface of an adherend in a soft state before being photocured (it can be photocured after being attached). Such an optical pressure-sensitive adhesive sheet is suitable for realizing good step followability in bonding to an adherend having a stepped surface.

Further, as described above, the optical adhesive sheet of the present invention has an adhesive force F1 (adhesive force of the optical adhesive sheet photocured after lamination to the adherend) versus adhesive force F2 (sticking to the adherend after photocuring). The adhesive strength ratio of the combined optical adhesive sheets) is 0.4 or more, and the adhesive strength F2 is 2 N/10 mm or more. The optical pressure-sensitive adhesive sheet has such a large adhesive strength with respect to adherends bonded together after photocuring. Therefore, when the optical adhesive sheet is attached to the first adherend before photocuring and after photocuring, the second adherend is attached (that is, the first and second adherends are bonded via an optical adhesive sheet), it is suitable for achieving good bonding reliability.

In addition, as described above, the optical adhesive sheet of the present invention has an adhesive force F2 of 4.5 N/10 mm or less, which is not too large. Such an optical pressure-sensitive adhesive sheet is suitable for securing light releasability and achieving good reworkability in lamination to an adherend after photocuring.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram of one Embodiment of the optical adhesive sheet of this invention. An example of the manufacturing method of the optical adhesive sheet shown in FIG. 1 is represented. 2A represents the process of forming a coating film of the pressure-sensitive adhesive composition, FIG. 2B represents the process of forming the base pressure-sensitive adhesive sheet, FIG. 2C represents the process of peeling the light release liner, and FIG. Representing the step of applying the post-add component, FIG. 2E represents the step of laminating the light release liner to the sheet. An example of the usage method of the optical adhesive sheet shown in FIG. 1 is represented. FIG. 3A shows the step of laminating the optical adhesive sheet to the first adherend (lamination step), and FIG. 3B shows the step of photocuring the optical adhesive sheet on the first adherend (photocuring step). 3C shows a step (bonding step) of bonding the first adherend and the second adherend via the optical adhesive sheet on the first adherend. 1 shows the positional relationship between a glass plate and an adhesive sheet in a laminate used for evaluation of conformability to steps in Examples and Comparative Examples.

A pressure-sensitive adhesive sheet 10 as one embodiment of the optical pressure-sensitive adhesive sheet of the present invention, as shown in FIG. The adhesive sheet 10 has an adhesive surface 11 and an adhesive surface 12 opposite to the adhesive surface 11 . FIG. 1 exemplarily shows a state in which release

liners

21 and 22 are adhered to the

adhesive surfaces

11 and 12 of the adhesive sheet 10 . A release liner 21 is placed on the adhesive surface 11 . A release liner 22 is disposed on the adhesive surface 12 . Also, the adhesive sheet 10 is an optical adhesive sheet that is placed at a light passing portion of the display panel. Examples of display panels include liquid crystal panels and organic EL panels. A display panel has a laminated structure including elements such as, for example, a pixel panel, a polarizing film, a touch panel, and a cover glass. The pressure-sensitive adhesive sheet 10 is used, for example, for bonding elements included in a laminated structure in the manufacturing process of a display panel.

The adhesive sheet 10 is a sheet-like pressure-sensitive adhesive. The adhesive sheet 10 contains a photopolymer as a base polymer, further contains a photopolymerizable polyfunctional compound and a photopolymerization initiator in this embodiment, and has photocurability. In addition, the adhesive sheet 10 has an adhesive force F1 in the first peel test below, has an adhesive force F2 in the second peel test below, and the ratio of the adhesive force F2 to the adhesive force F1 (F2/F1) is It is 0.4 or more, and the adhesive force F2 is 2 N/10 mm or more and 4.5 N/10 mm or less. The adhesive force F1 is the adhesive force that the adhesive sheet 10 attached to the alkali glass plate before photocuring has to the glass plate after photocuring on the alkali glass plate. The adhesive force F2 is the adhesive force that the adhesive sheet 10 attached to the alkali glass plate after photocuring has with respect to the glass plate. The magnitude of the adhesive force of the adhesive sheet to the alkali glass is an index of the magnitude of the adhesive force of the adhesive sheet to the polarizing film.

First peel test:
First, the adhesive sheet 10 is attached to an alkali glass plate produced by the float method to obtain a first laminate. Next, the first laminate is heat-treated under conditions of 50° C., 0.5 MPa, and 15 minutes. Next, the pressure-sensitive adhesive sheet 10 is photo-cured by UV irradiation with an integrated light amount of 3000 mJ/cm ² . Next, the adhesive force F1 is measured by peeling the adhesive sheet 10 from the alkali glass plate under the conditions of 23° C., 50% relative humidity, 180° peeling angle, and 300 mm/min tensile speed. The first peel test is more specifically as described below with respect to the examples.

Second peel test:
First, the adhesive sheet 10 is photo-cured by UV irradiation with an integrated light amount of 3000 mJ/cm ² . Next, the adhesive sheet 10 is attached to the alkali glass plate produced by the float method to obtain a second laminate. Next, the second laminate is heat-treated under conditions of 50° C., 0.5 MPa, and 15 minutes. Next, the adhesive force F2 is measured by peeling the adhesive sheet 10 from the alkali glass plate under the conditions of 23° C., 50% relative humidity, 180° peeling angle, and 300 mm/min tensile speed. The second peel test is more specifically as described below with respect to the Examples.

The adhesive sheet 10 has photocurability as described above. Such a pressure-sensitive adhesive sheet 10 can be attached to the stepped surface of an adherend in a soft state before being photocured (it can be photocured after being attached). Such a pressure-sensitive adhesive sheet 10 is suitable for realizing good step followability in bonding to an adherend having a stepped surface.

In addition, as described above, the adhesive sheet 10 has an adhesive force F1 (adhesive force of the adhesive sheet 10 photocured after being attached to the adherend) versus an adhesive force F2 (the adhesive force applied to the adherend after being photocured). The adhesive strength of the adhesive sheet 10) is 0.4 or more, and the adhesive strength F2 is 2 N/10 mm or more. The pressure-sensitive adhesive sheet 10 has such a large adhesive force to adherends bonded together after photocuring. Therefore, the pressure-sensitive adhesive sheet 10 achieves good bonding reliability when it is attached to the first adherend before photocuring and when the second adherend is attached after photocuring. Suitable for

In addition, as described above, the adhesive sheet 10 has an adhesive force F2 of 4.5 N/10 mm or less, which is not too large. Such a pressure-sensitive adhesive sheet 10 is suitable for securing light releasability and realizing good reworkability in lamination to an adherend after photocuring.

As described above, the pressure-sensitive adhesive sheet 10 is suitable for ensuring reworkability in bonding to an adherend and achieving both step followability and bonding reliability. Additionally, in the adhesive sheet 10, the base polymer is a photopolymer as described above. Such a pressure-sensitive adhesive sheet 10 is suitable for production from a solvent-free pressure-sensitive adhesive composition. In addition, the solvent-free adhesive composition does not require a drying step for volatilizing and removing the solvent from the coating film of the composition in the process of manufacturing the adhesive sheet 10 from the composition, thus reducing the environmental load. Suitable for

The adhesive force F1 is preferably 4 N/10 mm from the viewpoint of ensuring temporary fixability when the adhesive sheet 10 before photocuring is attached to an adherend and ensuring the adhesive force after photocuring of the adhesive sheet 10. Above, more preferably 5 N/10 mm or more, still more preferably 5.5 N/10 mm or more, particularly preferably 6 N/10 mm or more. The adhesive force F1 is, for example, 15 N/10 mm or less, 7.5 N/10 mm or less, or 6.3 N/10 mm or less. Methods for adjusting the adhesive force F1 include, for example, selection of the type of base polymer in the adhesive sheet 10, adjustment of the molecular weight, and adjustment of the blending amount. Selecting the type of base polymer involves adjusting the composition of the monomers forming the base polymer. Methods for adjusting the adhesive force F1 include selection of the types of components other than the base polymer in the adhesive sheet 10 and adjustment of the compounding amounts of the components. Such components include photopolymerizable polyfunctional compounds, photopolymerization initiators, silane coupling agents, and oligomers. The adhesive force adjusting method as described above also applies to the adhesive force F2, which will be described later.

The ratio (F2/F1) of the adhesive force F2 to the adhesive force F1 is determined from the viewpoint of the above-described bonding reliability of the adhesive sheet 10 and the temporary fixability when the adhesive sheet 10 and the adherend after photocuring are bonded together. is preferably 0.5 or more, more preferably 0.56 or more, and still more preferably 0.58 or more, from the viewpoint of ensuring . The ratio (F2/F1) is preferably 0.75 or less, more preferably 0.75 or less, more preferably 0.75 or less, from the viewpoint of securing light releasability in laminating the pressure-sensitive adhesive sheet 10 to an adherend and realizing good reworkability. 7 or less, more preferably 0.65 or less, particularly preferably 0.62 or less.

The adhesive force F2 is preferably 2.5 N from the viewpoint of the above-described bonding reliability of the pressure-sensitive adhesive sheet 10 and from the viewpoint of ensuring temporary fixability when bonding the pressure-sensitive adhesive sheet 10 and the adherend after photocuring. /10 mm or more, more preferably 3 N/10 mm or more, still more preferably 3.3 N/10 mm or more. The adhesive force F2 is preferably 4.2 N/10 mm or less, more preferably 4 N/10 mm, from the viewpoint of ensuring light releasability in laminating the adhesive sheet 10 to the adherend and realizing good reworkability. Below, more preferably 3.8 N/10 mm or less, particularly preferably 3.6 N/10 mm or less.

The adhesive sheet 10 has adhesive strength B1 in the first tensile test below, and adhesive strength B2 in the second tensile test below. The ratio (B2/B1) of the adhesive strength B2 to the adhesive strength B1 is preferably 0.8 or more, more preferably 0.9 or more, and still more preferably 0.93 from the viewpoint of the bonding reliability of the adhesive sheet 10. That's it. The ratio (B2/B1) is preferably 1 or less, more preferably 0.96 or less, from the viewpoint of ensuring light releasability in laminating the adhesive sheet 10 to the adherend and realizing good reworkability. is. The strength of adhesion of the pressure-sensitive adhesive sheet to alkali glass is an index of the strength of adhesion of the pressure-sensitive adhesive sheet to the polarizing film.

First tensile test:
First, the first alkali glass plate and the second alkali glass plate are joined together in the thickness direction via the adhesive sheet 10 to obtain a first joined body. Next, the pressure-sensitive adhesive sheet 10 is photo-cured by UV irradiation with an integrated light amount of 3000 mJ/cm ² . Next, the first joined body is heat-treated under conditions of 50° C., 0.5 MPa, and 15 minutes. Next, the first and second alkali glass plates in the first joined body are pulled in the thickness direction opposite to each other under conditions of 25° C. and a tensile speed of 25 mm/min to measure the adhesive strength B1. The first tensile test is more specifically as described below with respect to the examples.

Second tensile test:
First, the adhesive sheet 10 is attached to the first alkali glass plate to obtain the second joined body. Next, the pressure-sensitive adhesive sheet 10 is photo-cured by UV irradiation with an integrated light amount of 3000 mJ/cm ² . Next, the second joined body is heat-treated under conditions of 50° C., 0.5 MPa, and 15 minutes. Next, the first alkali glass plate and the second alkali glass plate are joined in the thickness direction via the adhesive sheet 10 on the first alkali glass plate to obtain a third joined body. Next, the first and second alkali glass plates in the third bonded body are pulled in the thickness direction opposite to each other under conditions of 25° C. and a tensile speed of 25 mm/min to measure the adhesive strength B2. The second tensile test is more specifically as described below with respect to the examples.

The adhesive strength B1 is preferably 4.2 MPa or more, more preferably 4.4 MPa or more, and even more preferably 4.6 MPa from the viewpoint of ensuring the above-described temporary fixability in the adhesive sheet 10 and ensuring the adhesive strength after photocuring. That's it. The adhesive strength B1 is, for example, 10 MPa or less, 7 MPa or less, or 5 MPa or less. Methods for adjusting the adhesive strength B1 include, for example, selection of the type of base polymer in the adhesive sheet 10, adjustment of the molecular weight, and adjustment of the blending amount. Selecting the type of base polymer involves adjusting the composition of the monomers forming the base polymer. Methods for adjusting the adhesive strength B1 include selection of the types of components other than the base polymer in the pressure-sensitive adhesive sheet 10 and adjustment of the compounding amounts of the components. Such components include photopolymerizable polyfunctional compounds, photopolymerization initiators, silane coupling agents, and oligomers. The adhesive strength adjusting method as described above also applies to the adhesive strength B2, which will be described later.

From the viewpoint of the bonding reliability of the adhesive sheet 10, the adhesive strength B2 is preferably 4 MPa or higher, more preferably 4.2 MPa or higher, and even more preferably 4.4 MPa or higher. The adhesive strength B2 is, for example, 10 MPa or less, 7 MPa or less, or 5 MPa or less.

The adhesive sheet 10 has a light transmittance R1 of 85% or more at a wavelength of 420 nm and a light transmittance R2 of 15% or less at a wavelength of 380 nm. Such a configuration is preferable for securing the transparency required for display panel applications in the pressure-sensitive adhesive sheet 10 and securing the protective function of the display panel by blocking ultraviolet rays. From the viewpoint of transparency, the light transmittance R1 is preferably 87% or higher, more preferably 89% or higher, and even more preferably 90% or higher. The light transmittance R1 is, for example, 99% or less. From the viewpoint of protective function, the light transmittance R2 is preferably 14% or less, more preferably 13% or less, more preferably 12% or less, more preferably 11% or less, more preferably 10% or less, more preferably 9 % or less, more preferably 8% or less, more preferably 7% or less, more preferably 6% or less, more preferably 5% or less. The light transmittance R2 is, for example, 0.1% or more.

The haze of the adhesive sheet 10 is preferably 1% or less, more preferably 0.8% or less, even more preferably 0.6% or less, and particularly preferably 0.4% or less. Such a configuration is preferable for suppressing light scattering in the pressure-sensitive adhesive sheet 10 and ensuring the transparency required for display panel applications. The haze of the adhesive sheet 10 is, for example, 0.01% or more. Haze can be measured using a haze meter in accordance with JIS K7136 (2000). Examples of the haze meter include "NDH2000" manufactured by Nippon Denshoku Industries Co., Ltd. and "HM-150N" manufactured by Murakami Color Research Laboratory.

The adhesive sheet 10 contains a base polymer (photopolymerized product), a photopolymerizable polyfunctional compound (first photopolymerizable polyfunctional compound), and a photopolymerization initiator, and has photocurability. The adhesive sheet 10 may contain a monofunctional monomer as a polymerizable component in addition to the photopolymerizable polyfunctional compound. A photopolymer is a polymer produced by photopolymerization. Photopolymerization is a polymerization method in which the polymerization reaction of polymerizable components proceeds by irradiation with active energy rays such as ultraviolet rays. The term “photocurability” refers to the property of becoming highly elastic when irradiated with active energy rays such as ultraviolet rays.

The base polymer is a polymer obtained by photopolymerization of polymerizable components including a monofunctional monomer and a photopolymerizable polyfunctional compound (second photopolymerizable polyfunctional compound). The base polymer is, for example, a partial polymer obtained by photopolymerization of a monofunctional monomer (a mixture of a polymerized monofunctional monomer and an unreacted monofunctional monomer) and a second photopolymerizable polyfunctional compound obtained by photopolymerization. It is a polymer. A monofunctional monomer may be used independently and two or more types may be used together. The second photopolymerizable polyfunctional compound may be used alone, or two or more of them may be used in combination.

Such a base polymer includes a photopolymerized polymer (first photopolymerized polymer) having a photocrosslinked structure. The photocrosslinked structure is a structure in which a linear structure of units derived from a monofunctional monomer is crosslinked by a unit derived from the second photopolymerizable polyfunctional compound. The base polymer may contain a photopolymerized polymer (second photopolymerized polymer) that does not have such a photocrosslinked structure. The second photopolymer polymer is a polymer of monofunctional monomers. Also, the base polymer is preferably an acrylic polymer. The acrylic polymer is a copolymer of polymerizable components containing 50% by mass or more of (meth)acrylic acid ester. "(Meth)acrylic" means acrylic and/or methacrylic.

A monofunctional (meth)acrylic acid ester is preferably used as the monofunctional monomer. As the monofunctional (meth)acrylic acid ester, an alkyl (meth)acrylic acid ester is preferably used, and an alkyl (meth)acrylic acid ester having an alkyl group having 1 to 20 carbon atoms is more preferably used. be done. 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.

Linear or branched (meth)acrylic acid alkyl esters include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-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, (meth)acrylic acid Heptyl, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, (meth)acrylic Isodecyl Acid, Undecyl (Meth)acrylate, Dodecyl (Meth)acrylate, Isotridecyl (Meth)acrylate, Tetradecyl (Meth)acrylate, Isotetradecyl (Meth)acrylate, Pentadecyl (Meth)acrylate, (Meth)acrylate cetyl 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, for example, (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 rings 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 acid 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 monofunctional monomer in the polymerizable component forming the base polymer is preferably 50% by mass or more, more preferably 60% by mass or more, from the viewpoint of appropriately expressing basic properties such as adhesiveness in the adhesive sheet 10. Preferably, it is 70% by mass or more. The same ratio is, for example, 99% by mass or less.

The polymerizable component may contain, as a monofunctional monomer, a copolymerizable monomer that can be copolymerized with a monofunctional (meth)acrylic acid ester. Examples of copolymerizable monomers include polar group-containing monomers. Polar group-containing monomers include, for example, hydroxyl group-containing monomers, carboxy group-containing monomers, and monomers having a nitrogen atom-containing ring. A polar group-containing monomer is useful for modifying the acrylic polymer, such as ensuring the cohesive strength of the acrylic polymer.

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, and 12-hydroxylauryl (meth)acrylate mentioned. As the hydroxy group-containing monomer, preferably at least one selected from the group consisting of 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate is used.

The proportion of the hydroxy group-containing monomer in the polymerizable component is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, from the viewpoint of ensuring the cohesive force of the adhesive sheet 10 . The same ratio is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 20% 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 sheet 10). is 15% by mass or less.

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 polymerizable component is preferably 1% by mass or more, more preferably 3% by mass, from the viewpoint of ensuring the cohesive force of the adhesive sheet 10 and ensuring the adhesion of the adhesive sheet 10 to the adherend. It is at least 5% by mass, more preferably at least 5% by mass. The same ratio is preferably 20% by mass or less, more preferably 10% 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.

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, N-vinylisothiazole, and acryloylmorpholine. The monomer having a nitrogen atom-containing ring is preferably at least one selected from the group consisting of N-vinyl-2-pyrrolidone and acryloylmorpholine.

The ratio of the monomer having a nitrogen atom-containing ring in the polymerizable component is preferably 1% by mass or more, more preferably 1% by mass or more, from the viewpoint of ensuring the cohesive force of the adhesive sheet and ensuring the adhesion of the adhesive sheet to the adherend. is 3% by mass or more, more preferably 5% by mass or more. The same ratio is preferably 30% by mass or less 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 various additive components and the acrylic polymer in the pressure-sensitive adhesive sheet). More preferably, it is 20% by mass or less.

Examples of the second photopolymerizable polyfunctional compound include polyfunctional monomers and polyfunctional oligomers, preferably polyfunctional oligomers.

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

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

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.

Examples of trifunctional (meth)acrylates include 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.

The molecular weight of the polyfunctional monomer is preferably 5000 or less, more preferably 3000 or less, still more preferably 2000 or less, particularly preferably 1000 or less, and preferably 200 or more. Such a configuration is preferable from the viewpoint of appropriately adjusting the viscoelasticity (for example, shear storage modulus and loss tangent) of the base polymer.

Examples of polyfunctional oligomers include urethane acrylate oligomers (oligomers having a urethane skeleton and two or more acryloyl groups), epoxy acrylate oligomers (oligomers having an epoxy skeleton and two or more acryloyl groups), and silicone acrylate oligomers ( oligomers having a siloxane skeleton and two or more acryloyl groups). A urethane acrylate oligomer is preferably used as the polyfunctional oligomer. Commercially available urethane acrylate oligomers include, for example, Artresin UN-333, UN-350, UN-353, UN-5500, and UN-5590 manufactured by Negami Kogyo Co., Ltd.

The weight average molecular weight (Mw) of the polyfunctional oligomer is preferably 20,000 or less, more preferably 15,000 or less, and preferably 5,000 or more. Such a configuration is preferable from the viewpoint of appropriately adjusting the viscoelasticity (for example, shear storage modulus and loss tangent) of the base polymer. The weight average molecular weight is calculated by measuring with gel permeation chromatography (GPC) and converting to polystyrene.

The proportion of the second photopolymerizable polyfunctional compound in the polymerizable component is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more. Such a configuration is preferable for maintaining the sheet shape of the adhesive sheet 10 before photocuring, and therefore preferable for ensuring handleability of the adhesive sheet 10 . The proportion of the second photopolymerizable polyfunctional compound in the polymerizable component is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less. Such a configuration is preferable in order to ensure a high level of softness in the pressure-sensitive adhesive sheet 10 before photocuring, and to achieve good conformability to unevenness.

The polymerizable 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.

Examples of the first photopolymerizable polyfunctional compound include polyfunctional monomers and polyfunctional oligomers, and polyfunctional monomers are preferably used. Examples of polyfunctional monomers include the polyfunctional monomers described above for the second photopolymerizable polyfunctional compound. Examples of polyfunctional oligomers include the polyfunctional oligomers described above with respect to the second photopolymerizable polyfunctional compound. As the polyfunctional monomer, trifunctional (meth)acrylate is preferably used, more preferably trimethylolpropane tri(meth)acrylate, and still more preferably trimethylolpropane triacrylate (TMPTA).

The content of the first photopolymerizable polyfunctional compound in the adhesive sheet 10 is preferably 2.5 parts by mass or more, more preferably 3 parts by mass or more, and preferably 8 parts by mass per 100 parts by mass of the base polymer. Below, more preferably 7 parts by mass or less, still more preferably 6 parts by mass or less. Such a configuration is suitable for ensuring good bonding reliability in the adhesive sheet 10 after photocuring.

Examples of photopolymerization initiators include radical photopolymerization initiators, cationic photopolymerization initiators, and anionic photopolymerization initiators.

Examples of radical photopolymerization initiators include acylphosphine oxide photopolymerization initiators, benzoin ether photopolymerization initiators, acetophenone photopolymerization initiators, α-ketol photopolymerization initiators, and aromatic sulfonyl chloride photopolymerization initiators. Polymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators are listed. be done.

Examples of acylphosphine oxide photopolymerization initiators include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-di-n-butoxyphenyl Included are phosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide. Examples of benzoin ether-based photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and 2,2-dimethoxy-1,2-diphenylethan-1-one. mentioned. Acetophenone-based photopolymerization initiators include, for example, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenylketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl ) dichloroacetophenone. Examples of α-ketol photopolymerization initiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. . Examples of aromatic sulfonyl chloride photopolymerization initiators include 2-naphthalenesulfonyl chloride. Examples of photoactive oxime-based photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Examples of benzoin-based photopolymerization initiators include benzoin. Examples of benzyl-based photopolymerization initiators include benzyl. Benzophenone photoinitiators include, for example, benzophenone, benzoylbenzoic acid, 3,3′-dimethyl-4-methoxybenzophenone, and polyvinylbenzophenone. Examples of ketal photopolymerization initiators include benzyl dimethyl ketal. Thioxanthone photoinitiators include, for example, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone.

Cationic photopolymerization initiators (photoacid generators) include, for example, onium compounds that generate acid when irradiated with ultraviolet rays. The onium compound is provided, for example, in the form of an onium salt of an onium cation and an anion. Onium cations include, for example, sulfonium and iodonium. Examples of anions include Cl ⁻ , Br ⁻ , I ⁻ , ZnCl ₃ ⁻ , HSO ₃ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CH ₃ SO ₃ ⁻ , CF ₃ SO ₃ ⁻ , C ₄ F ₉ HSO ₃ ⁻ , (C ₆ F ₅ ) ₄ B ⁻ , and (C ₄ H ₉ ) ₄ B ⁻ . Commercially available cationic photopolymerization initiators include, for example, San-Apro CPI-100, CPI-100P, CPI-101A, CPI-200K, CPI-210S, IK-1, IK-2, CPI-310B, and CPI-410S. Examples of commercially available cationic photopolymerization initiators include SP-056, SP-066, SP-130, SP-140, SP-150, SP-170, SP-171, and SP-172 manufactured by ADEKA. is also mentioned.

Examples of anionic photopolymerization initiators (photobase generators) include α-aminoacetophenone compounds, oxime ester compounds, and compounds having biguanide-type cations. Biguanide-type cations include, for example, alkylbiguanidiniums, cycloalkylbiguanidiniums, and cycloalkyl-alkylbiguanidiniums. Examples of anions that form pairs with biguanide cations include borate anions. Examples of commercially available anionic photopolymerization initiators include WPBG-018 (9-anthramethyl N,N'-diethylcarbamate) and WPBG-027 ((E)-1-[3-( 2-hydroxyphenyl)-2-propenoyl]piperidine), WPBG-082 (Guanidium 2-(3-benzoylphenyl)propionate), WPBG-140 (1-(anthraquinon-2-yl)ethylimidazole carboxylate), WPBG- 266 (1,2-diisopropyl-3-[bis(dimethylamino)methylene]guanidinium 2-(3-benzoylphenyl)propionate), WPBG-300 (1,2-dicyclohexyl-4,4,5,5-tetramethyl biguanidinium n-butyltriphenylborate) and WPBG-345 (1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidium tetrakis(3-fluorophenyl)borate).

The content of the photopolymerization initiator in the adhesive sheet 10 is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, and still more preferably 0.03 parts by mass or more per 100 parts by mass of the base polymer. It is preferably 0.05 parts by mass or more, more preferably 0.07 parts by mass or more, even more preferably 0.1 parts by mass or more, and particularly preferably 0.2 parts by mass or more. Such a configuration is preferable for forming a crosslinked network with a sufficient crosslink density in the adhesive sheet 10 by a photopolymerization reaction when the adhesive sheet 10 is irradiated with light, thereby significantly changing the viscoelasticity of the adhesive sheet 10. . The content of the photopolymerization initiator in the adhesive sheet 10 is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less per 100 parts by mass of the base polymer. Such a configuration is preferable for suppressing excessive generation of the polymerization initiator when the adhesive sheet 10 is irradiated with light and for forming a long-distance and continuous crosslinked network by photopolymerization reaction.

The adhesive sheet 10 may contain other components. Other components include, for example, oligomers, ultraviolet absorbers, antioxidants, silane coupling agents, rust inhibitors, rework improvers, isocyanate cross-linking agents, and metal deactivators.

When the base polymer is an acrylic polymer, an acrylic oligomer is preferably used as the oligomer. The acrylic oligomer is a copolymer of monomer components containing 50% by mass or more of (meth)acrylic acid ester, and has a weight average molecular weight of, for example, 1,000 or more and 30,000 or less.

The acrylic oligomer is preferably a (meth)acrylic acid alkyl ester having a chain alkyl group (chain alkyl (meth)acrylate) and a (meth)acrylic acid alkyl ester having an alicyclic alkyl group (alicyclic alkyl It is a polymer of monomer components containing (meth)acrylate). Specific examples of these (meth)acrylic acid alkyl esters include, for example, the (meth)acrylic acid alkyl esters described above as the polymerizable 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 mass or more, more preferably 20% by mass or more, and still more preferably 30% by mass or more. The same ratio is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. The proportion of chain alkyl (meth)acrylate in the monomer component of the acrylic oligomer is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. The same ratio is preferably 10% by mass or more, more preferably 20% by mass or more, and still more preferably 30% by mass or more.

The acrylic oligomer is obtained by polymerizing the monomer component of the acrylic oligomer. Polymerization methods include, for example, solution polymerization, bulk polymerization, and emulsion polymerization. Acrylic oligomers are preferably formed by solution polymerization. Solvents in solution polymerization include, for example, toluene and ethyl acetate. In the polymerization of the acrylic oligomer, a thermal polymerization initiator may be used, and a chain transfer agent may be used for the purpose of adjusting the molecular weight. Further, in the present embodiment, after the acrylic oligomer is formed, the low-molecular-weight components and the solvent are volatilized and removed from the reaction system such as the reaction solution by heating. Low-molecular-weight components include, for example, unreacted monomers, chain transfer agents, thermal polymerization initiators, and decomposition products (residues) thereof.

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.

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 weight average molecular weight of the oligomer is preferably 1,000 or more, more preferably 1,500 or more, and even 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 oligomer is preferable for securing the adhesive strength of the pressure-sensitive adhesive sheet 10 .

In order to sufficiently increase the adhesive strength of the adhesive sheet 10, the content of the oligomer in the adhesive sheet 10 is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, per 100 parts by mass of the base polymer. More preferably, it is 1 part by mass or more. From the viewpoint of ensuring the transparency of the adhesive sheet 10, the content of the oligomer in the adhesive sheet 10 is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 5 parts by mass per 100 parts by mass of the base polymer. parts or less, more preferably 4 parts by mass or less, and particularly preferably 3 parts by mass or less.

Examples of ultraviolet absorbers include triazine-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, and cyanoacrylate-based ultraviolet absorbers. As the ultraviolet absorber, a triazine-based ultraviolet absorber and a benzotriazole-based ultraviolet absorber are preferable because they have high absorbability of ultraviolet rays in the wavelength range of 320 to 370 nm and are excellent in compatibility with acrylic polymers. The ultraviolet absorbers may be used alone, or two or more of them may be used in combination.

Examples of commercially available triazine-based UV absorbers include bisethylhexyloxyphenolmethoxyphenyltriazine (product name “Tinosorb S”, manufactured by BASF), 2-(4,6-bis(2,4-dimethylphenyl)-1, Reaction product of 3,5-triazin-2-yl)-5-hydroxyphenyl and [(alkyloxy)methyl]oxirane (product name "TINUVIN 400", manufactured by BASF), 2-(2,4-dihydroxyphenyl) A reaction product of -4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine and (2-ethylhexyl)-glycidate (product name "TINUVIN 405", manufactured by BASF), ( 2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine (product name “TINUVIN 460”, manufactured by BASF), 2-(4 ,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol (product name “TINUVIN 577”, manufactured by BASF), 2-(2-hydroxy-4-[1 -octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine (product name "TINUVIN 479", manufactured by BASF), and 2-(4,6-diphenyl- 1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]-phenol (“ADK STAB LA-46”, manufactured by ADEKA).

Examples of commercially available benzotriazole-based UV absorbers include 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3 -tetramethylbutyl)phenol (product name "TINUVIN 928", manufactured by BASF), 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole (product name "TINUVIN PS", manufactured by BASF), 2-( 2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (product name “TINUVIN 900”, manufactured by BASF), 2-(2H-benzotriazol-2-yl)- 6-dodecyl-4-methylphenol (product name “TINUVIN571”, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-p-cresol (product name “TINUVIN P”, manufactured by BASF), 2-(2H- benzotriazol-2-yl)-4-6-bis(1-methyl-1-phenylethyl)phenol (product name "TINUVIN 234", manufactured by BASF), 2-[5-chloro(2H)-benzotriazole-2- yl]-4-methyl-6-(tert-butyl)phenol (product name “TINUVIN 326”, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol ( Product name “TINUVIN 328”, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (Product name “TINUVIN 329”, manufactured by BASF), and 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimidomethyl)-5-methylphenyl]benzotriazole (product name “Sumisorb 250”, manufactured by Sumitomo Chemical).

In the adhesive sheet 10, the specific absorbance (first specific absorbance) at a wavelength of 405 nm of the photopolymerization initiator is preferably 10 or more, more preferably 15 or more, and the specific absorbance at a wavelength of 405 nm of the ultraviolet absorber. (Second specific absorbance) is preferably 5 or less, more preferably 3 or less. Such a configuration is preferable from the viewpoint of achieving both an ultraviolet blocking function for device protection and photocurability in the pressure-sensitive adhesive sheet 10 . Among the above photopolymerization initiators, for example, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide have a first specific absorbance of 15 or more. Among the above UV absorbers, for example, bisethylhexyloxyphenolmethoxyphenyltriazine and 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1, 1,3,3-Tetramethylbutyl)phenol has a second specific absorbance of 3 or less.

The content of the ultraviolet absorber in the adhesive sheet 10 is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 3 parts by mass or less per 100 parts by mass of the base polymer. Preferably, it is 2 parts by mass or less. Such a configuration is preferable from the viewpoint of achieving both an ultraviolet blocking function for device protection and photocurability in the pressure-sensitive adhesive sheet 10 .

Examples of antioxidants include phenol antioxidants, phosphorus antioxidants, sulfur antioxidants, and amine antioxidants. The antioxidants may be used alone, or two or more of them may be used in combination.

As the antioxidant, a phenolic antioxidant is preferably used, and a hindered phenolic antioxidant is more preferably used. Hindered phenol antioxidants include, for example, pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (product name "Irganox 1010", manufactured by BASF), octadecyl -3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (product name “Irganox 1076”, manufactured by BASF), 4,6-bis(dodecylthiomethyl)-o-cresol (product name “Irga Nox 1726", manufactured by BASF), triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate] (product name "Irganox 245", manufactured by BASF), bis(2, 2,6,6-tetramethyl-4-piperidyl) sebacate (product name “TINUVIN770”, manufactured by BASF), and dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidine ethanol (product name "TINUVIN622", manufactured by BASF).

The content of the antioxidant in the adhesive sheet 10 is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 3 parts by mass or less, or more, per 100 parts by mass of the base polymer. Preferably, it is 2 parts by mass or less. Such a configuration is preferable from the viewpoint of achieving both suppression of oxidative deterioration of the pressure-sensitive adhesive sheet 10 and photocurability.

Examples of silane coupling agents include silane coupling agents containing epoxy groups. Epoxy group-containing silane coupling agents include, for example, 3-glycidoxydialkyldialkoxysilanes and 3-glycidoxyalkyltrialkoxysilanes. 3-glycidoxydialkyldialkoxysilanes include, for example, 3-glycidoxypropylmethyldimethoxysilane and 3-glycidoxypropylmethyldiethoxysilane. 3-glycidoxyalkyltrialkoxysilanes include, for example, 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane. As the silane coupling agent, 3-glycidoxyalkyltrialkoxysilane is preferably used, and 3-glycidoxypropyltrimethoxysilane is more preferably used. Silane coupling agents may be used alone, or two or more of them may be used in combination. The content of the silane coupling agent in the adhesive sheet 10 is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and preferably 5 parts by mass or less, per 100 parts by mass of the base polymer. More preferably, it is 3 parts by mass or less.

The adhesive sheet 10 does not substantially contain any residue of the thermal polymerization initiator. The residue of the thermal polymerization initiator includes decomposition products of the thermal polymerization initiator. The proportion of the residue of the thermal polymerization initiator in the adhesive sheet 10 is preferably 0.005% by mass or less, more preferably 0.001% by mass or less, and particularly preferably 0%.

The thickness of the adhesive sheet 10 is preferably 10 μm or more, more preferably 15 μm or more, from the viewpoint of ensuring sufficient adhesion to the adherend. From the standpoint of handleability and laser processability of the adhesive sheet 10, the thickness of the adhesive sheet 10 is preferably 500 μm or less, more preferably 400 μm or less, more preferably 300 μm or less, more preferably 250 μm or less, more preferably 200 μm or less. , more preferably 150 μm or less, more preferably 135 μm or less, more preferably 100 μm or less, more preferably 75 μm or less, more preferably 50 μm or less.

The total light transmittance of the adhesive sheet 10 is preferably 90% or higher, more preferably 92% or higher. Such a configuration is preferable for ensuring the transparency required for the pressure-sensitive adhesive sheet 10 for display panel applications. The total light transmittance of the adhesive sheet 10 is, for example, 100% or less. The total light transmittance can be measured according to JIS K 7375 (2008).

The adhesive sheet 10 can be manufactured, for example, as follows.

First, a prepolymer composition is prepared (prepolymer composition preparation step). Specifically, first, a mixture (liquid) containing the above-described monofunctional monomer for forming the base polymer and a photopolymerization initiator is prepared. This mixture is solvent-free. Next, by irradiating the mixture with ultraviolet rays, part of the monofunctional monomers in the mixture is photopolymerized to obtain a prepolymer composition (solvent-free prepolymer composition). Light sources for ultraviolet irradiation include, for example, ultraviolet LED lights, black lights, high-pressure mercury lamps, and metal halide lamps. Moreover, in the ultraviolet irradiation, a wavelength cut filter for cutting a part of the wavelength region of the light emitted from the light source may be used as necessary. In the ultraviolet irradiation, the illuminance is, for example, 5 to 200 mW/cm ² m, and the irradiation integrated light amount is, for example, 100 to 5000 mJ/cm ² . UV irradiation is preferably continued until the composition has a viscosity of about 15 to 25 Pa·s. This viscosity is a value measured with a Brookfield viscometer under the conditions of rotor No. 5, rotor speed of 10 rpm, and temperature of 30°C. The prepolymer composition contains a photopolymerized product of a monofunctional monomer (second photopolymerized polymer) and a monofunctional monomer that has not undergone polymerization reaction (residual monomer). Also, the prepolymer composition is solvent-free.

Next, a second photopolymerizable polyfunctional compound, a photopolymerization initiator, and optionally other components are added to the prepolymer composition to prepare an adhesive composition (adhesive composition preparation process). Other ingredients include, for example, antioxidants and silane coupling agents. Since the adhesive composition does not contain a solvent, it is a solvent-free adhesive composition.

Next, as shown in FIG. 2A, a coating film 10A is formed between the release liners 21, 22' (coating film forming step). Specifically, the coating film 10A is formed by coating the adhesive composition on the release liner 21, and then the coating film 10A on the release liner 21 is laminated with the release liner 22'.

The release liners 21, 22' are each, for example, a flexible plastic film. Examples of such plastic films include polyester films such as polyethylene terephthalate films, polyethylene films, and polypropylene films. The thickness of the release liner is, for example, 3 μm or more and, for example, 200 μm or less. The surface of the release liner is preferably release treated.

Examples of methods for applying the 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, and lip coating. , and die coats.

Next, as shown in FIG. 2B, the coating film 10A between the release liners 21 and 22' is irradiated with ultraviolet rays for photocuring to form the base adhesive sheet 10B (base adhesive sheet forming step). When irradiated with ultraviolet rays, the photopolymerization reaction proceeds in the reaction system containing the above-described residual monomer and the second photopolymerizable polyfunctional compound in the coating film, forming the first photopolymerizable polymer having a photocrosslinked structure.

Next, as shown in FIG. 2C, the release liner 22' is peeled off from the base adhesive sheet 10B (peeling step).

Next, as shown in FIG. 2D, the post-additive component is supplied to the base adhesive sheet 10B (post-additive component supply step). For example, a post-additive component solution (not shown) containing a post-additive component and a solvent is applied to the exposed surface of the base adhesive sheet 10B. The post-addition component contains the first photopolymerizable polyfunctional compound and a photopolymerization initiator, and may contain additives such as ultraviolet absorbers and antioxidants. Next, while permeating the post-addition component from the surface of the base pressure-sensitive adhesive sheet 10B into the base pressure-sensitive adhesive sheet 10B, the solvent is vaporized by heating as necessary. Before this step, the base polymer already has a crosslinked structure to form the base adhesive sheet 10B. Therefore, the vaporization of the solvent in this step does not easily form the surface of the citrus peel on the base adhesive sheet 10B (it is not substantially formed). Also, the photocurable adhesive sheet 10 is formed by the base adhesive sheet 10B and the post-addition component. The amount of the first photopolymerizable polyfunctional compound added in this step is preferably 2.5 parts by mass or more per 100 parts by mass of the prepolymer composition and the second photopolymerizable polyfunctional compound. It is more preferably 3 parts by mass or more, still more preferably 3.5 parts by mass or more, and is preferably 8 parts by mass or less, more preferably 7 parts by mass or less, and still more preferably 6 parts by mass or less. Such a configuration is suitable for ensuring good bonding reliability in the adhesive sheet 10 after photocuring.

Next, as shown in FIG. 2E, the release liner 22 is attached to the adhesive sheet 10 (attaching step). Release liners 22 include, for example, the plastic films described above for release liners 21, 22'.

As described above, the adhesive sheet 10 whose adhesive surface is covered and protected by the

release liners

21 and 22 can be manufactured. The

release liners

21 and 22 are peeled off from the adhesive sheet 10 when the adhesive sheet 10 is used.

3A to 3C show an example of how to use the adhesive sheet 10. FIG. The method of using the adhesive sheet 10 is a method of bonding adherends using the adhesive sheet 10 . The method includes a lamination step (FIG. 3A), a photocuring step (FIG. 3B), and a bonding step (FIG. 3C).

First, in the bonding step, as shown in FIG. 3A, the adhesive sheet 10 is bonded to the cover glass 31 (first adherend). The cover glass 31 has a first surface 31a and a second surface 31b opposite to the first surface 31a. A printing layer 32 for decoration or light shielding is formed on the edge of the first surface 31a. The printed layer 32 is provided, for example, over the entire periphery of the edge of the cover glass 31 . The cover glass 31 has a step (printing step) between the first surface 31 a and the surface of the printed layer 32 . That is, the cover glass 31 is a stepped adherend having a stepped surface. Specifically, in this step, the adhesive sheet 10 before photocuring is adhered to a region including the printed layer 32 on the surface 31 a of the cover glass 31 . FIG. 3A exemplarily shows a case where the adhesive sheet 10 before photocuring is attached to the entire surface 31a of the cover glass 31. FIG.

Next, in the photo-curing step, as shown in FIG. 3B, the adhesive sheet 10 on the cover glass 31 is photo-cured by ultraviolet irradiation. Due to the ultraviolet irradiation, the photopolymerization reaction of the first photopolymerizable polyfunctional compound proceeds in the adhesive sheet 10 to form a photopolymerized product of the first photopolymerizable polyfunctional compound. Since the photopolymerization reaction proceeds around the base polymer (the first photopolymerization polymer and the second photopolymerization polymer having a photocrosslinking structure), the photopolymerization product of the first photopolymerizable polyfunctional compound interacts with the base polymer. It is formed while forming an interstitial polymer network (IPN). Thereby, the pressure-sensitive adhesive sheet 10 becomes highly elastic. Light sources for ultraviolet irradiation include, for example, ultraviolet LED lights, black lights, high-pressure mercury lamps, and metal halide lamps. Moreover, in ultraviolet irradiation, a wavelength cut filter may be used to cut a part of the wavelength region of the light emitted from the light source. In the ultraviolet irradiation, the irradiation integrated light amount is, for example, 50 to 10000 mJ/cm ² .

Next, in the bonding step, as shown in FIG. 3C, the cover glass 31 and the member 33 are bonded via the photo-cured adhesive sheet 10 on the cover glass 31 . The member 33 is, for example, a pixel panel for a display panel, a polarizing film, or a touch panel. As a result, a joined body W (cover glass 31/adhesive sheet 10/member 33) is obtained.

The adhesive sheet 10 has photocurability as described above. In the bonding step (FIG. 3A), such adhesive sheet 10 can be bonded to the stepped surface of the adherend (surface 31a of cover glass 31) in a soft state before photocuring. Therefore, the pressure-sensitive adhesive sheet 10 is suitable for realizing good step followability.

As described above, the adhesive sheet 10 has an adhesive force F1 (adhesive force of the adhesive sheet 10 photocured after being attached to the adherend) and an adhesive force F2 (the adhesive sheet attached to the adherend after photocuring). 10) is 0.4 or more, and the adhesive force F2 is 2 N/10 mm or more. The pressure-sensitive adhesive sheet 10 has such a large adhesive force to adherends bonded together after photocuring. Therefore, the adhesive sheet 10 is suitable for achieving good bonding reliability between adherends after the bonding step (FIG. 3C).

As described above, the adhesive sheet 10 has an adhesive force F2 of 4.5 N/10 mm or less, which is not too large. Such a pressure-sensitive adhesive sheet 10 is suitable for securing light releasability and achieving good reworkability in the bonding step (FIG. 3C) after photocuring.

In addition, in the above-described bonding method, after the adhesive sheet 10 is photocured (highly elasticized) in the photocuring step (Fig. 3B), the adherend bonding step (Fig. 3C) is performed. Such a method is more suitable for suppressing edge waviness at the ends of the joined body W than the method in which the photocurable adhesive sheet is photocured after the bonding process between the adherends. In a joined body such as the joined body W, the edge waveness means that there is a difference between the adherends due to the difference in tendency and degree of deformation (expansion, contraction, warp, etc.) at various parts of the edges of the adherend. It means that the thickness of the edge of the adhesive sheet varies depending on the position.

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 properties, 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 acrylic oligomer>
First, 60 parts by mass of dicyclopentanyl methacrylate (DCPMA), 40 parts by mass of methyl methacrylate (MMA), and a chain A mixture containing 3.5 parts by mass of α-thioglycerol as a transfer agent and 100 parts by mass of toluene as a polymerization solvent was stirred at 70° C. for 1 hour under a nitrogen atmosphere. Next, 0.2 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 then heated at 70° C. for 2 hours under a nitrogen atmosphere. , and then reacted at 80° C. for 2 hours (polymerization reaction). Next, by heating the reaction solution at 130° C., the toluene, the chain transfer agent and the unreacted monomer were volatilized and removed. As a result, an acrylic oligomer (solid form) was obtained. The weight average molecular weight of this acrylic oligomer was 5,100.

<Preparation of prepolymer composition>
In a flask, 71 parts by mass of n-butyl acrylate (BA), 13 parts by mass of N-vinyl-2-pyrrolidone (NVP), 13 parts by mass of 4-hydroxybutyl acrylate (4HBA), and acryloylmorpholine ( ACMO) 3 parts by weight of the monomer mixture, the first photopolymerization initiator (product name "Irgacure 184", 1-hydroxy-cyclohexyl-phenyl-ketone, manufactured by BASF) 0.031 parts by weight, the second photopolymerization After adding 0.031 parts by mass of an initiator (product name “Irgacure 651”, 2,2-dimethoxy-1,2-diphenylethan-1-one, manufactured by BASF), the mixture was exposed to ultraviolet light under a nitrogen atmosphere. A part of the monomer components in the mixture was polymerized to obtain a prepolymer composition. UV irradiation was continued until the viscosity of the composition reached about 20 Pa·s. This viscosity is a value measured with a Brookfield viscometer under the conditions of rotor No. 5, rotor speed of 10 rpm, and temperature of 30°C. The resulting prepolymer composition contains a photopolymer (photopolymer P1a) and a monomer component (residual monomer) that has not undergone a polymerization reaction.

<Preparation of adhesive composition>
Next, 100 parts by mass of the prepolymer composition, 3 parts by mass of the above acrylic oligomer, and 0.6 mass of urethane acrylate oligomer (product name "UN-350", manufactured by Negami Kogyo Co., Ltd.) as the second photopolymerizable polyfunctional compound part, a third photopolymerization initiator (product name “Irgacure 819”, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, manufactured by BASF) 0.4 parts by mass, and an antioxidant (product name “Irga Nox 1010", manufactured by BASF) 0.5 parts by mass, a rust inhibitor (product name "BT-120", manufactured by Johoku Chemical Industry Co., Ltd.) 0.2 parts by mass, and a silane coupling agent (product name "KBM-403", Shin-Etsu Chemical Co., Ltd.) was mixed with 0.3 parts by mass to obtain an adhesive composition.

<Preparation of base adhesive sheet>
Next, a pressure-sensitive adhesive composition is applied onto the release-treated surface of the first release liner (product name: "Diafoil MRF", thickness: 75 μm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side to form a coating film. bottom. Next, the release-treated surface of the second release liner (product name: "Diafoil MRE", thickness: 75 μm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side was laminated onto the coating film on the first release liner. rice field. Next, the coating film between the release liners was irradiated with ultraviolet rays from the second release liner side, and the coating film was photocured to form a pressure-sensitive adhesive layer with a thickness of 100 μm (ultraviolet irradiation step). In the ultraviolet irradiation, a black light (manufactured by Toshiba) was used as a light source, the illuminance was set at 6.5 mW/cm ² , and the irradiation integrated light amount was set at 1500 mJ/cm ² . In the ultraviolet irradiation step, the photopolymerization reaction proceeds in the system containing the residual monomer and the second photopolymerizable polyfunctional compound (urethane acrylate oligomer) in the coating film, and the photopolymerization polymer P1b having a photocrosslinking structure is formed. It is formed. Moreover, since the photopolymerization reaction proceeds around the photopolymerization polymer P1a, the photopolymerization polymer P1b is formed around the photopolymerization polymer P1a. The adhesive layer formed in this step contains the photopolymerization polymer P1a and the photopolymerization polymer P1b as the base polymer P1. As described above, a base PSA sheet with a double-sided release liner (first release liner/base PSA sheet (thickness: 100 μm)/second release liner) was produced.

[Example 1]
<Preparation of post-addition component solution>
First, 17.4 parts by mass of a polyfunctional acrylate monomer (product name “Viscoat #295”, trimethylolpropane triacrylate (TMPTA), manufactured by Osaka Organic Chemical Industry Co., Ltd.) as a first photopolymerizable polyfunctional compound, and a third 0.8 parts by mass of a photopolymerization initiator (product name “Irgacure 819”, manufactured by BASF), 7 parts by mass of an ultraviolet absorber (product name “Tinosorb S”, manufactured by BASF), and 82.6 parts by mass of ethyl acetate as a solvent were mixed to prepare a post-addition component solution (anything other than the solvent in the solution is a post-addition component). Table 1 shows the composition of the post-addition component solution. In Table 1, the unit of the blending amount of each component is relative "parts by mass".

<Preparation of photocurable adhesive sheet>
Next, after peeling off the second release liner from the double-sided release liner-attached base PSA sheet, the post additive component solution was applied to a thickness of 20 μm on the exposed surface of the base PSA sheet thus exposed (coating treatment). . A bar coater RDS No. 10 manufactured by RD SPECIALTIES was used for coating. Next, it was dried in a dryer at 110° C. for 60 seconds. By coating treatment and drying treatment, the post-addition component (polyfunctional acrylate monomer as the first photopolymerizable polyfunctional compound, the third photopolymerization initiator, the ultraviolet absorber) is permeated into the base adhesive sheet, and the solvent is removed. vaporized. The base pressure-sensitive adhesive sheet changed into a photocurable pressure-sensitive adhesive sheet due to the permeation of the post-addition component. In this example, 3 parts by mass of the first photopolymerizable polyfunctional compound per 100 parts by mass of the prepolymer composition and the second photopolymerizable polyfunctional compound (i.e., 100 parts by mass of the base polymer) was added to the base adhesive sheet (the number of parts by mass of the first photopolymerizable polyfunctional compound per 100 parts by mass of the base polymer is shown in Table 2). Next, on the photocurable adhesive sheet on the first release liner, the release-treated surface of a third release liner (product name: "DIAFOIL MRE", thickness: 75 µm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side. pasted together.

As described above, the pressure-sensitive adhesive sheet with double-sided release liner of Example 1 (first release liner/photocurable pressure-sensitive adhesive sheet (thickness: 100 μm)/third release liner) was produced.

[Examples 2 and 3 and Comparative Examples 1 to 3]
Each double-sided release liner of Examples 2 and 3 and Comparative Examples 1-3 was prepared in the same manner as the adhesive sheet with a double-sided release liner of Example 1, except that the composition of the post additive component solution was changed to that shown in Table 1. A pressure-sensitive adhesive sheet was produced.

<Specific absorbance>
The specific absorbance at a wavelength of 405 nm was examined for the third photopolymerization initiator (product name: "Irgacure 819", manufactured by BASF) and the ultraviolet absorber (product name: "Tinosorb S", manufactured by BASF). Specifically, first, an ethyl acetate solution of a sample (third photopolymerization initiator or ultraviolet absorber) having a predetermined concentration was prepared as a sample solution. Next, the absorption spectrum of the sample solution was measured with a spectrophotometer (product name “U4100”, manufactured by Hitachi High-Technologies Corporation). In this measurement, the temperature condition was 23° C., the measurement cell length was 10 mm, and the measurement range wavelength was 300 to 500 nm. Then, in the spectrophotometer, the absorbance (vertical axis) of the measured absorption spectrum was converted to specific absorbance (the specific absorbance is the absorbance when the sample concentration is 1 mg/mL and the measurement cell length is 1 cm). . The specific absorbance of the third photopolymerization initiator (product name “Irgacure 819”) at a wavelength of 405 nm was 18.2 (cm ⁻¹ ). The specific absorbance at a wavelength of 405 nm of the ultraviolet absorber (product name “Tinosorb S”) was 3.4 (cm ⁻¹ ). That is, the specific absorbance at a wavelength of 405 nm of the third photopolymerization initiator was 10 (cm ⁻¹ ) or more, and the specific absorbance at a wavelength of 405 nm of the ultraviolet absorber was 5 (cm ⁻¹ ) or less.

<Transmittance>
The transmittance of each pressure-sensitive adhesive sheet of Examples 1-3 and Comparative Examples 1-3 was measured as follows. First, a sample for transmittance measurement was produced. Specifically, after removing one release liner from the adhesive sheet, the exposed surface of the adhesive sheet was attached to non-alkali glass (manufactured by Matsunami Glass Co., Ltd.), and the release liner was removed from the adhesive sheet on the glass. A sample for measurement was thus obtained. Next, using a spectrophotometer (product name “U4100”, manufactured by Hitachi High-Technologies Corporation), the transmittance of the pressure-sensitive adhesive sheet in the sample was measured. In addition, in this measurement, the measurement result obtained by measuring only the alkali-free glass under the same conditions was used as a baseline. Table 1 shows the transmittance at a wavelength of 380 nm and the transmittance at a wavelength of 420 nm measured for the adhesive sheet.

<Haze>
The haze of each pressure-sensitive adhesive sheet of Examples 1-3 and Comparative Examples 1-3 was measured as follows. First, a sample for haze measurement was prepared in the same manner as the above sample for transmittance measurement. Next, the haze of the sample was measured according to JIS K7136 (2000) using a haze meter "HM-150N" manufactured by Murakami Color Research Laboratory. Table 1 shows the measurement results.

<Adhesive force>
For each adhesive sheet in Examples 1 to 3 and Comparative Examples 1 to 3, the adhesive force F1 was measured by the following first peel test, and the adhesive force F2 was measured by the following second peel test.

[First peel test]
First, a test piece was produced for each adhesive sheet. In preparing the test piece, first, the third release liner was peeled off from the adhesive sheet, and a PET film (thickness of 50 μm) was attached to the exposed surface of the adhesive sheet exposed by this, and the laminated film (first release liner/ Adhesive sheet/PET film) was obtained. Next, a test piece (width 10 mm×length 100 mm) was cut out from the laminated film. Next, under an environment of 23° C. and a relative humidity of 50%, the first release liner was peeled off from the adhesive sheet of the test piece, and the exposed surface of the adhesive sheet thus exposed was placed on an alkali glass plate ( A laminated body (first laminated body: alkali glass plate/adhesive sheet/PET film) was obtained by bonding to the air side of soda plate glass, manufactured by Matsunami Glass Industry). The air surface is the exposed surface of the alkali glass plate (the surface opposite to the surface in contact with the molten metal) when the alkali glass plate flows over the molten metal in the manufacturing process of the alkali glass plate. In the bonding, the test piece was press-bonded to the alkali glass plate by reciprocating a 2-kg roller once (the same applies to the bonding described below). Next, the laminate was autoclaved (heated). In the autoclave treatment, the temperature was 50° C., the pressure was 0.5 MPa, and the treatment time was 15 minutes. Next, the adhesive sheet in the laminate was irradiated with ultraviolet rays from the alkali glass plate side (photocuring treatment). In the ultraviolet irradiation, a metal halide lamp was used as a light source, the illuminance was set to 300 mW/cm ² , and the irradiation integrated light amount was set to 3000 mJ/cm ² . Next, the laminate was allowed to stand for 30 minutes in an environment of 23° C. and 50% relative humidity. Next, under an environment of 23° C. and a relative humidity of 50%, a test was conducted in which the test piece was peeled from the alkali glass plate to measure the peel strength. For this measurement, a tensile tester (product name “Tension Compression Tester TCM-1kNB”, manufactured by Minebea Co., Ltd.) was used. In this measurement, the peel angle of the test piece to the adherend was set at 180°, the tensile speed of the test piece was set at 300 mm/min, and the peel length was set at 50 mm (measurement conditions of the peel test). The measured peel strength is shown in Table 2 as adhesive force F1 (N/10 mm) to an alkali glass plate produced by the float method.

[Second peel test]
First, a test piece was produced for each adhesive sheet. In preparing the test piece, first, the third release liner was peeled off from the adhesive sheet, and a PET film (thickness of 50 μm) was attached to the exposed surface of the adhesive sheet exposed by this, and the laminated film (first release liner/ Adhesive sheet/PET film) was obtained. Next, a test piece (width 10 mm×length 100 mm) was cut out from the laminated film. Next, the pressure-sensitive adhesive sheet in the test piece was irradiated with ultraviolet rays from the side of the first release liner (photocuring treatment). In the ultraviolet irradiation, a metal halide lamp was used as a light source, the illuminance was set to 300 mW/cm ² , and the irradiation integrated light amount was set to 3000 mJ/cm ² . Next, under an environment of 23° C. and a relative humidity of 50%, the first release liner was peeled off from the adhesive sheet of the test piece, and the exposed surface of the adhesive sheet thus exposed was placed on an alkali glass plate ( A laminated body (second laminated body: alkali glass plate/adhesive sheet/PET film) was obtained. Next, the laminate was autoclaved (heated and pressurized). In the autoclave treatment, the temperature was 50° C., the pressure was 0.5 MPa, and the treatment time was 15 minutes. Next, the laminate was allowed to stand for 30 minutes in an environment of 23° C. and 50% relative humidity. Next, under an environment of 23° C. and a relative humidity of 50%, a test was conducted in which the test piece was peeled from the alkali glass plate to measure the peel strength. The measured peel strength is shown in Table 2 as adhesive force F2 (N/10 mm) to an alkali glass plate produced by the float method. Table 2 also shows the ratio of the adhesive force F2 to the adhesive force F1.

<Adhesion strength>
For each pressure-sensitive adhesive sheet in Examples 1 to 3 and Comparative Examples 1 to 3, the adhesive strength B1 was measured by the following first tensile test, and the adhesive strength B2 was measured by the following second tensile test.

[First tensile test]
First, a measurement sample was prepared for each adhesive sheet. In preparing the measurement sample, first, the first release liner of the adhesive sheet piece (10 mm × 10 mm) cut out from the adhesive sheet with double-sided release liner was peeled off, and the exposed surface thus exposed was placed on one alkali glass plate ( first alkali glass plate). Next, the third release liner was peeled off from the adhesive sheet piece on the alkali glass plate, and the exposed surface thus exposed was adhered to the other alkali glass plate (second alkali glass plate) to join the glass plates together. . As a result, a first joined body was obtained in which the first alkali glass plate and the second alkali glass plate were joined in the thickness direction via the adhesive sheet piece. Next, the adhesive sheet between the glass plates was photocured by ultraviolet irradiation. In the ultraviolet irradiation, a metal halide lamp was used as a light source, the illuminance was set to 300 mW/cm ² , and the irradiation integrated light amount was set to 3000 mJ/cm ² . Next, the first joined body was heat-treated under the conditions of a temperature of 50° C., a pressure of 0.5 MPa, and 15 minutes, and the adhesive sheet pieces were pressure-bonded to both glass plates. As described above, measurement samples (first alkali glass plate/adhesive sheet piece/second alkali glass plate) were prepared.

Next, a test was conducted in which the two metal-supported alkali glass plates in the measurement sample were pulled in opposite directions in the thickness direction, and the force required to separate the glass plates was measured. For this measurement, a tensile tester (product name “Autograph AG-50NX plus”, manufactured by Shimadzu Corporation) was used. In this measurement, the measurement temperature was 25° C., the relative humidity was 55%, and the tensile speed was 25 mm/min. Table 2 shows the maximum value of the measured force as the adhesive strength B1 (MPa).

[Second tensile test]
First, a measurement sample was prepared for each adhesive sheet. In preparing the measurement sample, first, the first release liner of the adhesive sheet piece (10 mm × 10 mm) cut out from the adhesive sheet with double-sided release liner was peeled off, and the exposed surface thus exposed was placed on one alkali glass plate ( 3rd alkaline glass plate). Next, the adhesive sheet on the alkali glass plate was photocured by ultraviolet irradiation. In the ultraviolet irradiation, a metal halide lamp was used as a light source, the illuminance was set to 300 mW/cm ² , and the irradiation integrated light amount was set to 3000 mJ/cm ² . Next, the third release liner was peeled off from the adhesive sheet piece on the alkali glass plate, and the exposed surface thus exposed was adhered to the other alkali glass plate (the fourth alkali glass plate) to join the glass plates together. . As a result, a second joined body was obtained in which the third alkali glass plate and the fourth alkali glass plate were joined in the thickness direction via the adhesive sheet piece. Next, the second joined body was heat-treated under the conditions of a temperature of 50° C., a pressure of 0.5 MPa, and 15 minutes, and the adhesive sheet pieces were pressure-bonded to both glass plates. As described above, measurement samples (third alkali glass plate/adhesive sheet piece/fourth alkali glass plate) were prepared.

Next, a test was conducted in which the two metal-supported glass plates in the measurement sample were pulled in opposite directions in the thickness direction, and the force required to separate the glass plates was measured. The measurement method and conditions are the same as those described above for the first tensile test. Table 2 shows the measured adhesive strength B2 (MPa). Table 2 also shows the ratio (B2/B1) of the adhesive strength B2 to the adhesive strength B1 described above.

〈Followability over bumps〉
The level difference followability of each adhesive sheet of Examples 1 to 3 and Comparative Examples 1 to 3 was examined as follows.

First, a sample sheet (length 75 mm x width 45 mm) was cut out from an adhesive sheet with a double-sided release liner. Next, the third release liner was peeled off from the pressure-sensitive adhesive sheet of the sample sheet, and the exposed surface of the pressure-sensitive adhesive sheet thus exposed was adhered to the center of a PET film (length 100 mm×width 50 mm, thickness 125 μm). In the bonding, a roll laminator was used, the pressure between rolls was set to 0.2 MPa, and the feed rate was set to 100 mm/min (the same applies to bonding described later). Next, the first release liner is peeled off from the adhesive sheet on the PET film, and the exposed surface of the adhesive sheet thus exposed is vacuum pressure bonded to a glass plate with a printed layer (length 100 mm x width 50 mm, thickness 500 μm). (surface pressure: 0.3 MPa, pressure: 100 Pa) to obtain a joined body. FIG. 4 shows the positional relationship between the glass plate 41 and the adhesive sheet 42 in this joined body. A printing layer 43 (thickness: 45 μm, black ink layer) is formed on one side of the glass plate 41 in the thickness direction along the entire periphery of the edge of the glass plate 41 . The printed layer 43 is formed in a range of 15 mm inward from each end of the glass plate 41 in the length direction L1, and is formed in a range of 5 mm inward from each end of the glass plate 41 in the width direction L2. (In FIG. 4, the printed layer is represented by hatching). The adhesive sheet 42 is attached to the center of one side of the glass plate 41 in the thickness direction, and is in contact with the printed layer 43 over the entire circumference of the edge of the sheet. That is, the printed layer 43 on the glass plate 41 is sandwiched between the glass plate 41 and the adhesive sheet 42 within a range of 2.5 mm outward from the inner edge of the same layer.

Next, the joined body was autoclaved for 30 minutes under conditions of 50°C and 0.5 MPa. After that, the vicinity of the inner edge of the printed layer in the joined body was observed. Specifically, using a digital microscope, the inside of the inner edge of the printed layer (the area where the adhesive sheet should be brought into close contact with the glass plate) was observed from the PET film side of the joined body at an observation magnification of 20. Then, with respect to the conformability of the pressure-sensitive adhesive sheet to unevenness, a case where no air bubbles were observed in the observation range was evaluated as "excellent", and a case where air bubbles were observed was evaluated as "poor". Table 2 shows the results.

<Joining reliability>
The bonding reliability of each adhesive sheet of Examples 1-3 and Comparative Examples 1-3 was examined as follows.

First, the same joined body as that used for the evaluation of step followability was prepared. The joined body was then autoclaved for 30 minutes at 50° C. and 0.5 MPa. Next, the adhesive sheet in the joined body was irradiated with ultraviolet rays from the glass plate side to photocure the adhesive sheet. In the ultraviolet irradiation, a metal halide lamp was used as a light source, the illuminance was set at 300 mW/cm ² , and the irradiation integrated light amount was set at 3000 mJ/cm ² . Next, the joined body was allowed to stand under conditions of 23° C. and 50% relative humidity for 24 hours. The conjugate was then stored at 85° C. for 500 hours. After that, the adhesive sheet in the joined body was observed with a magnifying glass along the edges. Then, regarding the bonding reliability of the adhesive sheet, a case where no peeling or foaming at the edge of the adhesive sheet occurred was evaluated as "excellent", and peeling or foaming at the edge of the adhesive sheet was 1 mm from the inner end of the printing step. If it occurs in an area of less than 1 mm, it is evaluated as "good", and if peeling or foaming at the edge of the adhesive sheet occurs in an area 1 mm or more inside (viewable area side) from the inner edge of the printing step, it is "bad". and evaluated. Table 2 shows the results.

<Reworkability>
The reworkability of each pressure-sensitive adhesive sheet in Examples 1-3 and Comparative Examples 1-3 was examined as follows.

First, a test piece was prepared for each adhesive sheet. In preparing the test piece, first, the third release liner was peeled off from the pressure-sensitive adhesive sheet, and a PET film (thickness: 25 µm) was adhered to the exposed surface of the pressure-sensitive adhesive layer thus exposed to obtain a laminate. Next, a test piece (width 25 mm×length 100 mm) was cut out from this laminate. The first release liner was then peeled from the adhesive layer of the test piece and the exposed surface was plasma treated. On the other hand, a polyimide film (product name “GV200D”, thickness 80 μm, manufactured by SKC Kolon PI) as an adherend was also plasma-treated. In each plasma treatment, a plasma irradiation apparatus (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. Then, the exposed surface of the pressure-sensitive adhesive layer of the test piece and the plasma-treated surface of the polyimide film were bonded together. In this bonding, the test piece was press-bonded to the adherend by reciprocating a 2-kg roller one time in an environment of 25°C. Next, after standing at 25° C. for 2 minutes, the end of the test piece on the adherend was pulled by hand to peel the test piece from the adherend (peeling work). The angle formed by the adherend and the adhesive surface of the test piece during peeling was about 180 degrees. Then, regarding the reworkability of the adhesive sheet, it was evaluated as "good" when the test piece could be properly peeled off without causing adhesive residue on the adherend by the peeling work, and when adhesive residue was generated after peeling. Or, when the test piece was broken during the peeling operation, it was evaluated as "poor". As described above, the reworkability of the pressure-sensitive adhesive sheet on the adherend was evaluated. Table 1 shows the evaluation results.

<Drop impact resistance>
The drop impact resistance of each pressure-sensitive adhesive sheet of Examples 1-3 and Comparative Examples 1-3 was examined as follows.

First, a bonded body for evaluation was produced. Specifically, first, a rectangular sample sheet (length 75 mm×width 45 mm) was cut out from a pressure-sensitive adhesive sheet with a double-sided release liner. Next, the third release liner was peeled off from the adhesive sheet on the sample sheet, and the exposed surface of the adhesive sheet thus exposed was placed in the center of a rectangular first glass plate (length 100 mm x width 75 mm, thickness 500 µm) on four sides. pasted along. In the lamination, a roll laminator was used, the pressure between rolls was 0.2 MPa, and the feed rate was 100 mm/min. Next, the adhesive sheet on the first glass plate was photocured by ultraviolet irradiation. In the ultraviolet irradiation, a metal halide lamp was used as a light source, the illuminance was set to 300 mW/cm ² , and the irradiation integrated light amount was set to 3000 mJ/cm ² . Next, the first release liner was peeled off from the adhesive sheet on the first glass plate, and the exposed surface of the adhesive sheet thus exposed was placed on a rectangular second glass plate (length 100 mm x width 50 mm, thickness 500 μm in thickness) along four sides by vacuum pressure bonding (surface pressure: 0.3 MPa, pressure: 100 Pa) to obtain a joined body. A printed layer (thickness: 30 μm, black ink layer) is formed on one side in the thickness direction of the second glass plate over the entire periphery of the edge of the second glass plate. The printed layer is formed in a range of 15 mm inward from each end of the second glass plate in the length direction, and formed in a range of 5 mm inward from each end of the second glass plate in the width direction. there is The adhesive sheet is attached to the center of one side in the thickness direction of the second glass plate, and is in contact with the printed layer along the entire periphery of the edge of the sheet. That is, the printed layer on the second glass plate is sandwiched between the second glass plate and the adhesive sheet within a range of 2.5 mm outward from the inner edge of the same layer. Such a joined body was then heat-treated (autoclave) under the conditions of 50° C., 0.5 MPa and 30 minutes.

A drop impact resistance test was carried out as follows using the bonded body produced as described above. First, the joined body was placed on a predetermined support base. Specifically, the joined body was placed on the support stand so that the first glass plate in the joined body was positioned on the upper side and both widthwise ends of the first glass plate were supported by the support stand from below. (The lower second glass plate is not in contact with the support). Next, the joined body on the support was fixed to the support with an adhesive tape. Next, the support base and the assembly were held in an environment of -5°C for 24 hours. Next, within 40 seconds after the support table and the joined body were returned to the room temperature environment, a metal ball was dropped toward the joined body on the support stand, and the metal ball collided with the first glass plate of the joined body. let me The mass of the metal ball is 15g, and the drop height of the metal ball is 300mm. Also, the drop position of the metal ball onto the joined body is a position separated from the printed layer by 10 mm in each of the length direction and the width direction. Two tests (tests on different samples) were performed for each adhesive sheet (n=2). Then, regarding the drop impact resistance of the adhesive sheet, the case where the peeling between the first and second glass plates did not occur in any test was evaluated as "excellent", and the case where it occurred only in one test was evaluated as "excellent". It was evaluated as "good", and when it occurred in any test, it was evaluated as "bad". Table 1 shows the results.

The optical pressure-sensitive adhesive sheet of the present invention is used, for example, in the manufacturing process of display panels to bond elements included in the laminated structure of the same panels.

10 adhesive sheet (optical adhesive sheet)

H thickness direction

21, 22 release liner 31 cover glass 32 printed layer 33 member

Claims

An optical pressure-sensitive adhesive sheet containing a base polymer and having photocurability,
The base polymer is a photopolymer,
Having an adhesive force F1 in the first peel test below,
Having an adhesive force F2 in the following second peel test,
The ratio of the adhesive force F2 to the adhesive force F1 is 0.4 or more,
The optical adhesive sheet, wherein the adhesive force F2 is 2 N/10 mm or more and 4.5 N/10 mm or less.
First peel test:
First, the optical adhesive sheet is attached to an alkali glass plate produced by the float method to obtain a first laminate. Next, the first laminate is heat-treated under conditions of 50° C., 0.5 MPa, and 15 minutes. Next, the optical pressure-sensitive adhesive sheet is photo-cured by UV irradiation with an integrated light amount of 3000 mJ/cm 2 . Next, the adhesive force F1 is measured by peeling the optical adhesive sheet from the alkali glass plate under the conditions of 23° C., 50% relative humidity, 180° peeling angle, and 300 mm/min tensile speed.
Second peel test:
First, the optical adhesive sheet is photo-cured by UV irradiation with an integrated light amount of 3000 mJ/cm 2 . Next, the optical adhesive sheet is attached to an alkali glass plate produced by the float method to obtain a second laminate. Next, the second laminate is heat-treated under conditions of 50° C., 0.5 MPa, and 15 minutes. Next, the adhesive force F2 is measured by peeling the optical adhesive sheet from the alkali glass plate under the conditions of 23° C., 50% relative humidity, 180° peeling angle, and 300 mm/min tensile speed.
Having an adhesive strength B1 in the first tensile test below,
Having an adhesive strength B2 in the second tensile test below,
2. The optical pressure-sensitive adhesive sheet according to claim 1, wherein the ratio of said adhesive strength B2 to said adhesive strength B1 is 0.8 or more.
First tensile test:
First, the first alkali glass plate and the second alkali glass plate are bonded in the thickness direction via the optical adhesive sheet to obtain a first bonded body. Next, the optical pressure-sensitive adhesive sheet is photo-cured by UV irradiation with an integrated light amount of 3000 mJ/cm 2 . Next, the first joined body is heat-treated under conditions of 50° C., 0.5 MPa, and 15 minutes. Next, the first and second alkali glass plates in the first bonded body are pulled in opposite directions in the thickness direction under conditions of 25° C. and a tensile speed of 25 mm/min to measure the adhesive strength B1.
Second tensile test:
First, the optical adhesive sheet is attached to the first alkali glass plate to obtain a second joined body. Next, the optical pressure-sensitive adhesive sheet is photo-cured by UV irradiation with an integrated light amount of 3000 mJ/cm 2 . Next, the second joined body is heat-treated under conditions of 50° C., 0.5 MPa, and 15 minutes. Next, the first alkali glass plate and the second alkali glass plate are bonded in the thickness direction via the optical adhesive sheet on the first alkali glass plate to obtain a third bonded body. Next, the first and second alkali glass plates in the third bonded body are pulled in the thickness direction opposite to each other under conditions of 25° C. and a tensile speed of 25 mm/min to measure the adhesive strength B2.
The optical pressure-sensitive adhesive sheet according to claim 2, wherein the adhesive strength B2 is 4 MPa or more.
The optical adhesive sheet according to any one of claims 1 to 3, which has a light transmittance of 85% or more at a wavelength of 420 nm and a light transmittance of 15% or less at a wavelength of 380 nm.
The optical pressure-sensitive adhesive sheet according to any one of claims 1 to 3, which has a haze of 1% or less.
The optical adhesive sheet according to any one of claims 1 to 3, further comprising an ultraviolet absorber.
7. The optical system according to claim 6, further comprising a photopolymerization initiator, wherein the photopolymerization initiator has a specific absorbance of 10 or more at a wavelength of 405 nm, and the ultraviolet absorber has a specific absorbance of 5 or less at a wavelength of 405 nm. adhesive sheet.
The optical adhesive sheet according to any one of claims 1 to 3, further comprising an antioxidant.
The optical pressure-sensitive adhesive sheet according to any one of claims 1 to 3, which does not substantially contain a residue of a thermal polymerization initiator.