WO2023074558A1

WO2023074558A1 - Optical adhesive sheet

Info

Publication number: WO2023074558A1
Application number: PCT/JP2022/039269
Authority: WO
Inventors: 駿溝端; 大器下栗; 裕貴小原
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: TW202334359A

Abstract

This adhesive sheet (10) contains a base polymer as a photopolymer and is photocurable. This adhesive sheet (10) has a gel fraction of at least 75% by mass after curing by a photocuring process under the condition of an irradiation integrated light quantity of 3000 mJ/cm². The adhesive sheet (10) has an adhesive strength of 2.5 N/10 mm or higher in a peeling test for peeling the adhesive sheet (10) from an alkaline glass plate under the condition of 85°C, a peeling angle of 180°, and a tensile speed of 300 mm/minute, the peeling test being performed after: performing a photocuring process having a condition in which the irradiation integrated light quantity is 3000 mJ/cm² with respect to the adhesive sheet (10); bonding the adhesive sheet (10) to the alkaline glass sheet, which is fabricated by a float method; and heating and pressurizing the adhesive sheet (10) which is on the alkaline glass sheet, under the condition of 50°C, 0.5 MPa and for 15 minutes.

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, a transparent adhesive sheet (optical adhesive sheet) is used for bonding elements included in the laminated structure. A pressure-sensitive adhesive sheet for use in display panels is described, for example, in Patent Document 1 below.

JP 2012-62345 A

The optical adhesive sheet of Patent Document 1 is produced as follows. First, after preparing a reaction solution containing monomer components for forming an acrylic base polymer, a thermal polymerization initiator, and a solvent, the acrylic base polymer is formed by solution polymerization in the reaction solution. Next, a solvent is added to the reaction solution to prepare a polymer solution having an adjusted polymer concentration. Next, a thermal cross-linking agent is added to the polymer solution to prepare an adhesive composition (solvent type adhesive composition). Next, the pressure-sensitive adhesive composition is applied onto the substrate to form a coating film. Next, the coating film on the substrate is dried by heating to form an adhesive layer (drying step). Next, by aging treatment, the cross-linking reaction of the base polymer by the thermal cross-linking agent proceeds in the pressure-sensitive adhesive layer. As described above, the optical adhesive sheet is formed on the substrate. Thus, Patent Document 1 describes an optical pressure-sensitive adhesive sheet formed from a solvent-based pressure-sensitive adhesive composition.

However, in the drying process, a relatively large amount of solvent in the coating volatilizes out of the coating. An optical pressure-sensitive adhesive sheet including such steps in the manufacturing process is not preferable from the viewpoint of reducing the environmental load.

On the other hand, 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. For example, the polarizing film-side surface of a pixel panel with a polarizing film is provided with a predetermined resin layer along a part of the peripheral edge of the polarizing film on the pixel panel, and the surface of the polarizing film edge and the resin layer surface are provided. There is a step (resin step). Such a pixel panel with a polarizing film and the above-described cover glass are joined via an optical adhesive sheet in the manufacturing process of the display panel. Therefore, an optical pressure-sensitive adhesive sheet for display panels is required to have a degree of softness (step conformability) that can follow printing steps. Insufficient step followability of the optical adhesive sheet is due to the fact that an adherend with a surface step (e.g., a cover glass with a printed step and a pixel panel with a polarizing film with a resin step) has an optical surface with a step. When the pressure-sensitive adhesive sheets are stuck together, it causes air bubbles to be formed along the steps, which is not preferable.

In addition, the laminated structure of the display panel includes elements with high surface smoothness, such as cover glass and polarizing film. Therefore, optical adhesive sheets for display panels are required to have high adhesiveness.

The present invention provides an optical pressure-sensitive adhesive sheet that is suitable for reducing environmental impact and suitable for use in display panels.

The present invention [1] is an optical pressure-sensitive adhesive sheet that contains a base polymer as a photopolymer and has photocurability, and has a photocuring treatment of 75% by mass after curing by a photocuring treatment under the condition of an integrated irradiation light amount of 3000 mJ/cm ² . Photocuring treatment of the optical pressure-sensitive adhesive sheet under the conditions described above, bonding the optical pressure-sensitive adhesive sheet to an alkali glass plate prepared by a float method, and then performing a heat treatment at 50°C. , under the conditions of 0.5 MPa and 15 minutes, the optical adhesive sheet on the alkali glass plate is subjected to heat and pressure treatment, and then the alkali glass is peeled off under the conditions of 85° C., a peeling angle of 180°, and a tensile speed of 300 mm/min. It includes an optical adhesive sheet having an adhesive strength of 2.5 N/10 mm or more in a peel test for peeling the optical adhesive sheet from a plate.

The present invention [2] includes the optical adhesive sheet according to [1] above, further including a photopolymerizable polyfunctional compound and a photopolymerization initiator.

The present invention [3] includes the optical pressure-sensitive adhesive sheet according to [1] or [2] above, wherein the base polymer has a weight average molecular weight of 800,000 or more.

In the present invention [4], the optical pressure-sensitive adhesive sheet after curing by photocuring treatment under the conditions of an integrated irradiation light amount of 3000 mJ/cm ² is stretched up to 6 times its length under the conditions of 23° C. and a tensile speed of 200 mm/min. The optical pressure-sensitive adhesive sheet according to any one of [1] to [3] above, wherein the optical pressure-sensitive adhesive sheet has a residual stress of 55 N/m ² or less after 5 minutes.

The present invention [5] comprises a photocuring treatment of the optical adhesive sheet under the condition of an integrated irradiation light amount of 3000 mJ/cm ² , and subsequent lamination of the optical adhesive sheet to an alkali glass plate produced by a float method. , followed by heat and pressure treatment of the optical adhesive sheet on the alkali glass plate under the conditions of 50°C, 0.5 MPa and 15 minutes, 23°C, peel angle 90° and tensile load 2.5N. The optic according to any one of [1] to [4] above, wherein the peel speed is 35 μm/sec or less in a constant load peel test in which the optical adhesive sheet is peeled from the alkali glass plate under the condition of /10 mm. Includes adhesive sheet.

In the optical adhesive sheet of the present invention, the base polymer is a photopolymer as described above. Such a pressure-sensitive adhesive sheet is suitable for production from a solvent-free pressure-sensitive adhesive composition. In addition, the solvent-free PSA composition does not require a drying step for volatilizing and removing the solvent from the coating film of the composition in the process of producing a PSA sheet from the composition, thus reducing the environmental load. Suitable.

In addition, 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 photocuring. Then, the optical pressure-sensitive adhesive sheet can be photo-cured after being attached to an adherend so as to have high elasticity. Such an optical pressure-sensitive adhesive sheet is suitable for realizing good step followability in bonding to an adherend having a stepped surface. Therefore, the optical pressure-sensitive adhesive sheet of the present invention is suitable for bonding elements including elements having surface steps (such as cover glass) in the manufacturing process of display panels.

In addition, as described above, the optical pressure-sensitive adhesive sheet of the present invention, after photocuring under predetermined conditions, is applied to an alkali glass plate prepared by the float method at a high temperature (85°C) of 2.5 N/ It has an adhesive strength of 10 mm or more. Alkali glass plates produced by the float method have high surface smoothness, so that adhesives are difficult to stick to them, but the optical pressure-sensitive adhesive sheet of the present invention has excellent adhesiveness to the glass plates. Such an optical pressure-sensitive adhesive sheet is suitable for bonding adherends with high surface smoothness such as cover glasses and polarizing films in display panels. Therefore, the optical pressure-sensitive adhesive sheet of the present invention is suitable for use in display panels.

In addition, the optical pressure-sensitive adhesive sheet of the present invention has a gel fraction of 75% by mass or more after photocuring under predetermined conditions, as described above. The optical pressure-sensitive adhesive sheet with a high gel fraction in this way can be used to protect the adherend after curing (high elasticity) of the pressure-sensitive adhesive sheet. It is also less likely to be peeled off from the adherend. Such an optical pressure-sensitive adhesive sheet capable of increasing the gel fraction can be laminated to a first adherend having a surface step (bonding the same pressure-sensitive adhesive sheet in a soft state before photocuring), and the same pressure-sensitive adhesive sheet and the bonding of the first adherend and the second adherend via the adhesive sheet to ensure good bonding reliability between the first and second adherends. Therefore, the optical pressure-sensitive adhesive sheet of the present invention is suitable for use in display panels.

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 step followability (before photocuring) in Examples and Comparative Examples.

A pressure-sensitive adhesive sheet 10 as an embodiment of the present invention has a sheet shape with a predetermined thickness and spreads in a direction perpendicular to the thickness direction H (plane direction), 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 base polymer as a photopolymer, further contains a photopolymerizable polyfunctional compound and a photopolymerization initiator in this embodiment, and has photocurability. The term “photocurability” refers to the property of becoming highly elastic when irradiated with active energy rays such as ultraviolet rays. The adhesive sheet 10 has a gel fraction of 75% by mass or more after curing by photocuring treatment under the condition of an integrated irradiation light amount of 3000 mJ/cm ² , and an adhesiveness of 2.5 N/10 mm or more in the following peel test. has a force F. The method for measuring the gel fraction is as described below with regard to the examples. The adhesive force F is the adhesive force that the adhesive sheet 10 attached to the alkali glass plate after photocuring has to the glass plate. The strength of the adhesive strength of the adhesive sheet to the alkali glass plate is an index of the strength of the adhesive strength of the adhesive sheet to the polarizing film, for example.

In the peeling test, the adhesive sheet 10 was subjected to a photocuring treatment under the condition of an integrated irradiation light amount of 3000 mJ/cm ² , and then the adhesive sheet 10 was attached to an alkali glass plate prepared by the float method, and then heated at 50°C. , under the conditions of 0.5 MPa and 15 minutes, heat and pressurize the adhesive sheet 10 on the alkali glass plate, and then adhere from the alkali glass plate under the conditions of 85 ° C., peel angle of 180 ° and tensile speed of 300 mm / min. The sheet 10 is peeled off and the adhesive force F is measured. The peel test is more specifically as described below with respect to the Examples.

The base polymer of the adhesive sheet 10 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 PSA composition does not require a drying step for volatilizing and removing the solvent from the coating film of the composition in the process of producing a PSA sheet from the composition, thus reducing the environmental load. Suitable.

In addition, the adhesive sheet 10 has photocurability as described above. Such an adhesive sheet 10 can be attached to the stepped surface of an adherend in a soft state before photocuring. Then, the pressure-sensitive adhesive sheet 10 can be photo-cured after being attached to an adherend so as to have high elasticity. Such a pressure-sensitive adhesive sheet 10 is suitable for realizing good step followability in bonding to an adherend having a stepped surface. Therefore, the pressure-sensitive adhesive sheet 10 is suitable for bonding elements including elements having surface steps (such as cover glass) in the manufacturing process of the display panel.

In addition, as described above, after photocuring under predetermined conditions, the pressure-sensitive adhesive sheet 10 has a tensile strength of 2.5 N/10 mm or more at a high temperature (85° C.) with respect to an alkali glass plate produced by the float method. It has adhesive force F. Alkaline glass plates produced by the float method have high surface smoothness, so adhesives are difficult to stick to them, but the adhesive sheet 10 has excellent adhesiveness to the same glass plates. Such adhesive sheet 10 is suitable for bonding adherends with high surface smoothness such as glass substrates and polarizing films in display panels. Therefore, the adhesive sheet 10 is suitable for use in display panels.

In addition, the adhesive sheet 10 has a gel fraction of 75% by mass or more after photocuring under predetermined conditions, as described above. The pressure-sensitive adhesive sheet 10 having a high gel fraction in this way can be used even from an adherend adhered before curing (high elasticity) of the pressure-sensitive adhesive sheet 10 . It is also less likely to be peeled off from the adherend. The adhesive sheet 10 capable of achieving such a high gel fraction can be laminated to a first adherend having a surface step (bonding the adhesive sheet 10 in a soft state before photocuring), and and the bonding of the first and second adherends via the adhesive sheet 10 after curing to ensure good bonding reliability between the first and second adherends. Suitable for Therefore, the adhesive sheet 10 is suitable for use in display panels.

As described above, the pressure-sensitive adhesive sheet 10 is suitable for reducing environmental loads and is suitable for use in display panels.

The adhesive force F is preferably 2.7 N/10 mm or more, more preferably 2.9 N/10 mm or more, and still more preferably 3.1 N/10 mm or more, from the viewpoint of good bondability to adherends with high surface smoothness. is. The adhesive force F is, for example, 4 N/10 mm or less, 7 N/10 mm or less, or 10 N/10 mm or less. Methods for adjusting the adhesive force F include, for example, selection of the type of base polymer in the adhesive sheet 10, adjustment of the molecular weight, and adjustment of the compounding amount. Selecting the type of base polymer involves adjusting the composition of the monomers forming the base polymer. Methods for adjusting the adhesive force F 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.

In the pressure-sensitive adhesive sheet 10, the weight average molecular weight (Mw) of the base polymer is preferably 800,000 or more, more preferably 850,000 or more, and still more preferably 900,000, from the viewpoint of ensuring the reliability of bonding between adherends by the pressure-sensitive adhesive sheet 10. That's it. The weight average molecular weight of the base polymer is preferably 1,500,000 or less, more preferably 1,200,000 or less, and still more preferably 1,000,000 or less, from the viewpoint of ensuring the reliability of bonding between adherends by the adhesive sheet 10 . The weight average molecular weight is calculated by measuring with gel permeation chromatography (GPC) and converting to polystyrene.

The gel fraction of the adhesive sheet 10 after photocuring is preferably 76% or more, more preferably 77% or more, and still more preferably 78% or more, from the viewpoint of ensuring the flexibility of the adhesive sheet 10 after curing. . The gel fraction of the adhesive sheet 10 after photocuring is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less, from the viewpoint of ensuring flexibility of the adhesive sheet 10 after curing. Methods for adjusting the gel fraction after photocuring of the adhesive sheet 10 include, for example, selection of the type of base polymer in the adhesive sheet 10, adjustment of the molecular weight, and adjustment of the compounding amount. Methods for adjusting the gel fraction after photocuring include selection of the type of photopolymerizable polyfunctional compound in the pressure-sensitive adhesive sheet 10, adjustment of the molecular weight, and adjustment of the compounding amount. Moreover, the method for measuring the gel fraction is as described later with regard to the examples.

The gel fraction of the pressure-sensitive adhesive sheet 10 (before photocuring) is preferably 20% or more, more preferably 25% or more, and still more preferably 30% or more, from the viewpoint of ensuring handleability of the pressure-sensitive adhesive sheet 10. It is preferably 65% or less, more preferably 60% or less, still more preferably 55% or less. Methods for adjusting the gel fraction of the adhesive sheet 10 before photocuring include, for example, selection of the type of base polymer in the adhesive sheet 10, adjustment of the molecular weight, and adjustment of the compounding amount.

The pressure-sensitive adhesive sheet 10 is cured by photocuring treatment under the conditions of 3000 mJ/cm ² of cumulative irradiation light intensity, and then stretched to 6 times its length under the conditions of 23° C. and tensile speed of 200 mm/min. However, it is preferably 55 N/m ² or less, more preferably 50 N/m ² or less, still more preferably 40 N/m ² or less. The residual stress S is preferably 10 N/m ² or more, more preferably 20 N/m ² or more, still more preferably 30 N/m ² or more. These configurations regarding the residual stress S are preferable for ensuring the followability of the pressure-sensitive adhesive sheet 10 after photocuring. Methods for adjusting the residual stress S include, for example, adjusting the monomer composition of the base polymer in the adhesive sheet 10, adjusting the molecular weight, adjusting the blending amount, and adjusting the degree of cross-linking. The method for measuring the residual stress S is specifically as described later with regard to Examples.

The adhesive sheet 10 preferably has a peel speed of 35 µm/sec or less, more preferably 30 µm/sec or less, and preferably 25 µm/sec or less in the constant load peel test described below. The peeling speed is, for example, 0.1 μm/second or more, 0.5 μm/second or more, or 1 μm/second or more.
Such a configuration regarding the peeling speed ensures the reliability of bonding of the adhesive sheet 10 to the adherend when the adhesive sheet 10 after photocuring is adhered to the stepped portion of the surface of an adherend having a stepped surface. preferred.

In the constant load peeling test, the adhesive sheet 10 was subjected to a photocuring treatment under the condition of an integrated irradiation light amount of 3000 mJ/cm ² , then the adhesive sheet 10 was attached to an alkali glass plate produced by the float method, and then, After heat and pressure treatment of the adhesive sheet 10 on the alkali glass plate under the conditions of 50°C, 0.5 MPa and 15 minutes, alkaline The optical adhesive sheet is peeled off from the glass plate and the peeling speed is measured. The constant load peel test is more specifically described below with respect to the Examples. Methods for adjusting the peeling speed include, for example, selection of the type of the first photopolymerizable polyfunctional compound described later in the adhesive sheet 10, adjustment of the molecular weight, and adjustment of the blending amount. Methods for adjusting the peeling speed include adjustment of the monomer composition of the base polymer in the pressure-sensitive adhesive sheet 10, adjustment of the molecular weight, adjustment of the compounding amount, and adjustment of the degree of cross-linking.

The adhesive sheet 10 has a transmittance R1 of 85% or more at a wavelength of 420 nm and a 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 transmittance R1 is preferably 87% or higher, more preferably 89% or higher, and even more preferably 90% or higher. The transmittance R1 is, for example, 99% or less. From the viewpoint of protective function, the 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%. Below, more preferably 8% or less, more preferably 7% or less, more preferably 6% or less, more preferably 5% or less. The transmittance R2 is, for example, 0.1% or more. The method for measuring the light transmittance at a wavelength of 380 nm and the light transmittance at a wavelength of 420 nm is specifically described below with respect to the examples.

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 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, Di(meth)acryloyl isocyanurate and ethoxylated bisphenol A diacrylate (BPAEODE).

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. The first photopolymerizable polyfunctional compound may be used alone, or two or more of them may be used in combination. The first photopolymerizable polyfunctional compound is preferably at least selected from the group consisting of ethoxylated bisphenol A diacrylate (BPAEODE), trimethylolpropane triacrylate (TMPTA), and dipentaerythritol hexaacrylate (DPHA). one is used.

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 still more preferably 3.5 parts by mass or more per 100 parts by mass of the base polymer. and preferably 8 parts by mass or less, more preferably 7 parts by mass or less, and even 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-based antioxidants include, for example, pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (product name "Irganox 1010", manufactured by BASF), and , octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (product name “Irganox 1076”, 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 system containing the 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 pressure-sensitive adhesive sheet 10 formed from a solvent-free pressure-sensitive adhesive composition is suitable for reducing environmental loads. Also, 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. The member 33 may have the above-described resin level difference on the surface (one surface in the thickness direction H) on the adhesive sheet 10 side. 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, after photocuring under predetermined conditions, the adhesive sheet 10 has an adhesive force F of 2.5 N/10 mm or more at high temperature (85° C.) to an alkali glass plate produced by the float method. have Such adhesive sheet 10 is suitable for bonding adherends with high surface smoothness such as glass substrates and polarizing films in display panels. Therefore, the adhesive sheet 10 is suitable for use in display panels.

The adhesive sheet 10 has a gel fraction of 75% by mass or more after photocuring under predetermined conditions, as described above. The adhesive sheet 10 having a high gel fraction in this way is less likely to be peeled off from the adherend bonded before the adhesive sheet 10 is cured and from the adherend bonded after the adhesive sheet 10 is cured. The adhesive sheet 10 capable of achieving such a high gel fraction is laminated to a cover glass 31 (first adherend) having a surface step (FIG. 3A), and the adhesive sheet 10 is photocured (FIG. 3B). and the bonding of the cover glass 31 and the member 33 (second adherend) via the cured adhesive sheet 10 to ensure good bonding reliability between the first and second adherends. Suitable. Therefore, the adhesive sheet 10 is suitable for use in display panels.

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 mass of the monomer mixture, the first photopolymerization initiator (product name "Omnirad 184", 1-hydroxycyclohexylphenyl ketone, manufactured by BASF) 0.031 parts by weight, the second photopolymerization initiator (product name "Omnirad 651", 2,2-dimethoxy-1,2-diphenylethan-1-one, manufactured by BASF) and 0.031 parts by mass were added, and then the mixture was irradiated with ultraviolet rays 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 “Omnirad819”, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, manufactured by BASF) 0.4 parts by mass, and an antioxidant (product name “Irganox 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 Kogyo 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 (wavelength: 320 nm to 400 nm, manufactured by Toshiba) was used as the light source, the illuminance was set at 6.5 mW/cm ² , and the integrated irradiation 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, 4.0 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 Photopolymerization initiator (product name "Omnirad 819", manufactured by BASF) 0.3 parts by weight, ultraviolet absorber (product name "Tinosorb S", manufactured by BASF) 7.0 parts by weight, ethyl acetate 88.7 parts by weight 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 amount of the post-addition component solution. The units for the amounts shown in Table 1 are relative "parts by weight".

<Production of photocurable optical 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 the coating treatment and the drying treatment, the post-addition components (polyfunctional acrylate monomer, third photopolymerization initiator, ultraviolet absorber) were permeated into the base adhesive sheet, and the solvent was 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, 4 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) (TMPTA in Example 1) 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, 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 was laminated onto the adhesive sheet on the first release liner. rice field.

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

[Examples 2 to 5]
PSA sheets with double-sided release liners of Examples 2 to 5 were prepared in the same manner as the PSA sheet with double-sided release liners of Example 1, except that the composition of the post-additive component solution was changed to the composition shown in Table 1. . In Examples 3 to 5, in the preparation of the post-additive component solution, in addition to TMPTA, ethoxylated bisphenol A diacrylate (BPAEODE) (product name “ABE-300”, Shin-Nakamura Chemical Co., Ltd.) was used as the first photopolymerizable polyfunctional compound. Kogyosha) was used.

[Comparative Examples 1 to 3]
PSA sheets with double-sided release liners of Comparative Examples 1 to 3 were prepared in the same manner as the PSA sheet with double-sided release liners of Example 1, except for the following. The composition of the post-addition component solution was changed to that shown in Table 1. In the ultraviolet irradiation step for preparing the base adhesive sheet, ultraviolet irradiation (first irradiation) with a black light was followed by ultraviolet irradiation (second irradiation) with an ultraviolet LED light (wavelength: 365 nm, manufactured by Quark Technology). In the second irradiation, the illuminance was set to 90 mW/cm ² and the irradiation integrated light amount was set to 1800 mJ/cm ² . Through such an ultraviolet irradiation step, a base polymer P2 having a weight average molecular weight (Mw) smaller than that of the base polymer P1 was formed.

<Weight average molecular weight>
Each weight average molecular weight (Mw) of the above base polymers P1 and P2 was obtained. Specifically, the Mw of the base polymer was measured by gel permeation chromatography (GPC) under the following measurement conditions and calculated as a polystyrene equivalent value. In the measurement, a GPC measurement device (product name “Alliance”, manufactured by Waters) was used. A sample solution was prepared as follows. First, using a base polymer as a sample, a tetrahydrofuran (THF) solution (containing 10 mM phosphoric acid) having a sample concentration of 0.15% by mass was prepared, and then the THF solution was allowed to stand for 20 hours. Next, the THF solution was filtered with a membrane filter having an average pore size of 0.45 μm, and the filtrate was obtained as a sample solution for molecular weight measurement.

[GPC measurement conditions]
Column: G7000H _XL (upstream side), GMH _XL and GMH _XL (downstream side), each Tosoh column temperature: 40°C
Eluent: tetrahydrofuran solution containing phosphoric acid (phosphoric acid concentration 10 mM)
Flow rate: 0.8 mL/min Sample injection volume: 100 μL
Standard sample: polystyrene (PS)
Detector: differential refractometer (RI)

<Gel fraction>
The gel fraction after photocuring was measured for each of the optical adhesive sheets of Examples 1-5 and Comparative Examples 1-3. Specifically, it is as follows.

First, the optical adhesive sheet between the release liners was irradiated with ultraviolet rays through the release liners. 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, about 1 g of adhesive sample was taken from the optical adhesive sheet. Next, the mass (W ₁ ) of the adhesive sample was measured. Next, the adhesive sample was immersed in 40 g of ethyl acetate in a container for 7 days. Next, all components insoluble in ethyl acetate (insoluble portion) were collected. The undissolved portion was then dried (removal of ethyl acetate) at 130° C. for 2 hours. Next, the mass (W ₂ ) of the undissolved portion was measured. Then, the gel fraction of the optical adhesive sheet after photocuring was calculated based on the following formula. The values are shown in Table 2.

Gel fraction (% by mass) = ( _W2 / _W1 ) x 100

<Transmittance>
The transmittance of each of the optical adhesive sheets of Examples 1-5 and Comparative Examples 1-3 was measured as follows. First, a sample for transmittance measurement was produced. Specifically, after peeling off one release liner from the optical adhesive sheet, the exposed surface of the optical adhesive sheet was attached to non-alkali glass (manufactured by Matsunami Glass Co., Ltd.), and the release liner was peeled off from the optical 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 optical 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 optical adhesive sheet.

<Adhesive force>
For each optical adhesive sheet in Examples 1-5 and Comparative Examples 1-3, the adhesive force was measured by the following peel test.

First, a test piece was produced for each optical adhesive sheet. In the preparation of the test piece, first, the third release liner is peeled off from the optical adhesive sheet, and a PET film (thickness 50 μm) is attached to the exposed surface of the optical adhesive sheet exposed by this, and the laminated film (first release liner/optical adhesive sheet/PET film). Next, a test piece (width 10 mm×length 100 mm) was cut out from the laminated film. Next, the optical adhesive sheet in the test piece was irradiated with ultraviolet rays from the first release liner 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, under an environment of 23° C. and a relative humidity of 50%, the first release liner was peeled off from the optical adhesive sheet of the test piece, and the exposed surface of the optical adhesive sheet thus exposed was covered with alkali glass prepared by the float method. A first laminated body (alkali glass plate/optical adhesive sheet/PET film) was obtained by laminating to the air surface of a plate (Soita 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 first 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 first laminate was allowed to stand in an environment of 23° C. and 50% relative humidity for 30 minutes.

After that, a tensile test was performed by peeling the test piece from the alkali glass plate under the conditions of 85°C, 50% relative humidity, 180° peeling angle, and 300 mm/min tensile speed to measure the peel strength. For this measurement, a tensile tester (product name “Tensile Compression Tester TCM-1kNB”, manufactured by Minebea Co., Ltd.) was used. The measured peel strength is shown in Table 2 as an adhesive force F (N/10 mm) after photocuring to an alkali glass plate produced by the float method.

<Residual stress>
The optical adhesive sheets of Examples 1 to 5 and Comparative Examples 1 to 3 were examined for residual stress during elongation (during strain). Specifically, it is as follows.

First, a sheet piece (first release liner/optical adhesive sheet/third release liner) with a width of 10 mm and a length of 60 mm was cut out from the optical adhesive sheet with double-sided release liner. Next, the first and third release liners were peeled off from the optical adhesive sheet of the sheet piece to obtain a test piece (optical adhesive sheet piece). Next, the test piece was pulled in the longitudinal direction by a tensile tester (product name "Autograph AGS-J", manufactured by Shimadzu Corporation), and the residual stress generated in the test piece was measured at a strain value of 600% (6 times the length). bottom. In this test, the initial chuck-to-chuck distance is 100 mm, and the temperature condition is 23°C. In this test, while measuring the stress generated in the test piece, the test piece was stretched at a tensile speed of 200 mm/min up to 6 times its length (distance between chucks: 600 mm), and then the length was maintained. Table 2 shows the value of the residual stress S after 5 minutes from the time when the test piece was stretched to 6 times its length.

<Constant load peeling test>
For each optical adhesive sheet in Examples 1 to 5 and Comparative Examples 1 to 3, the peel speed was measured in the following constant load peel test.

First, a test piece was produced for each optical adhesive sheet. In the preparation of the test piece, first, the third release liner is peeled off from the optical adhesive sheet, and a PET film (thickness 50 μm) is attached to the exposed surface of the optical adhesive sheet exposed by this, and the laminated film (first release liner/optical adhesive sheet/PET film). Next, a test piece (width 10 mm×length 100 mm) was cut out from the laminated film. Next, the optical adhesive sheet in the test piece was irradiated with ultraviolet rays from the first release liner 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, under an environment of 23° C. and a relative humidity of 50%, the first release liner was peeled off from the optical adhesive sheet of the test piece, and the exposed surface of the optical adhesive sheet thus exposed was covered with alkali glass prepared by the float method. A second laminate (alkali glass plate/optical adhesive sheet/PET film) was obtained by laminating on the air side of a plate (Soita Glass, manufactured by Matsunami Glass Industry). Next, the second 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 second laminate was allowed to stand in an environment of 23° C. and 50% relative humidity for 30 minutes.

After that, a tensile test was performed by peeling the test piece from the alkali glass plate under the conditions of 23° C., 50% relative humidity, 90° peel angle, and 2.5 N/10 mm (constant) tensile load to measure the peel speed. . For this measurement, a tensile tester (product name “Tensile Compression Tester TCM-1kNB”, manufactured by Minebea Co., Ltd.) was used. Table 2 shows the measured peel rates (μm/sec).

<Followability of unevenness before photocuring>
The step conformability of each of the optical adhesive sheets of Examples 1 to 5 and Comparative Examples 1 to 3 before photocuring was examined as follows.

First, a sample sheet (length 75 mm x width 45 mm) was cut out from the optical adhesive sheet with a double-sided release liner. Next, the third release liner was peeled off from the optical adhesive sheet of the sample sheet, and the exposed surface of the optical adhesive sheet thus exposed was attached to the center of a PET film (length 100 mm x 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 was peeled off from the optical adhesive sheet on the PET film, and the exposed surface of the optical adhesive sheet thus exposed was applied to a glass plate with a printed layer (length 100 mm x width 50 mm, thickness 500 µm). They were bonded together by vacuum pressure bonding (surface pressure: 0.3 MPa, pressure: 100 Pa) to obtain a first joined body. FIG. 4 shows the positional relationship between the glass plate 41 and the optical adhesive sheet 42 in this first bonded 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 optical 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 periphery 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 optical adhesive sheet 42 within a range of 2.5 mm outward from the inner edge of the same layer.

Next, the first 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 first joined body was observed. Specifically, using a digital microscope, the inside of the inner edge of the printed layer (the area where the optical adhesive sheet should be brought into close contact with the glass plate) was observed from the PET film side of the first joined body at an observation magnification of 20. Then, the conformability of the optical adhesive sheet to steps was evaluated as "excellent" when no air bubbles were observed in the observation range, and as "bad" when air bubbles were observed. Table 2 shows the results.

<Followability of unevenness after photocuring>
The step followability after photocuring of the optical adhesive sheets of Examples 1 to 5 and Comparative Examples 1 to 3 was examined as follows.

First, a sample sheet of a predetermined size was cut out from the optical pressure-sensitive adhesive sheet with a double-sided release liner. Next, the third release liner was peeled off from the optical adhesive sheet of the sample sheet, and the exposed surface of the optical adhesive sheet thus exposed was attached to a glass plate. The optical adhesive sheet on the glass plate was irradiated with ultraviolet rays from the side of the first release liner to photocure the optical adhesive sheet. 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 .

On the other hand, after laminating a predetermined polarizing film on one side of a PET film (thickness 75 μm), a polyimide (PI) tape (thickness 50 μm) were laminated together. As a result, a PET film with a polarizing film having surface steps (simulated resin steps) formed by the PI tape was obtained.

Next, after peeling off the first release liner from the optical adhesive sheet on the glass plate, the optical adhesive sheet was attached to the polarizing film side of the PET film with the polarizing film to obtain a second joined body. Specifically, the optical pressure-sensitive adhesive sheet and the PET film with the polarizing film were bonded together in such a manner that the end portions of the PI tape and the end portions of the optical pressure-sensitive adhesive sheet overlapped each other by 180 μm. A vacuum bonding apparatus was used for this bonding. The bonding pressure was 0.1 MPa. After this bonding, the second joined body was autoclaved for 5 minutes under heating and pressurizing conditions of 40° C. and 0.4 MPa.

Next, an optical microscope was used to observe the edge of the PI tape in the second bonded body, and it was confirmed that no air bubbles were generated. The second bonded body was then subjected to a high temperature humidification test for 100 hours. In this test, the heating temperature was 85° C. and the relative humidity was 85%. After the hot humidification test, the PI tape edge on the second joint was observed with an optical microscope. Then, the followability of the optical pressure-sensitive adhesive sheet after photocuring was evaluated as "excellent" when no air bubbles were observed in the observation range, and as "bad" when air bubbles were observed. Table 2 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 optical 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 as a photopolymer and having photocurability,
Having a gel fraction of 75% by mass or more after curing by photocuring treatment under the condition of an integrated irradiation light amount of 3000 mJ/cm 2 ,
Photocuring treatment of the optical adhesive sheet under the conditions described above, then bonding the optical adhesive sheet to an alkali glass plate prepared by the float method, and then conditions of 50° C., 0.5 MPa, and 15 minutes. After the heat and pressure treatment of the optical adhesive sheet on the alkali glass plate in , the optical adhesive sheet is peeled from the alkali glass plate under the conditions of 85° C., a peeling angle of 180°, and a tensile speed of 300 mm/min. An optical adhesive sheet having an adhesive strength of 2.5 N/10 mm or more in a peel test.
The optical adhesive sheet according to claim 1, further comprising a photopolymerizable polyfunctional compound and a photopolymerization initiator.
The optical pressure-sensitive adhesive sheet according to claim 1, wherein the base polymer has a weight average molecular weight of 800,000 or more.
The optical pressure-sensitive adhesive sheet after curing by photocuring treatment under the conditions of an integrated irradiation light amount of 3000 mJ/cm 2 was stretched to 6 times its length under the conditions of 23 ° C. and a tensile speed of 200 mm / min. The optical pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive sheet has a residual stress of 55 N/m 2 or less.
Photocuring treatment of the optical adhesive sheet under conditions of an integrated irradiation light amount of 3000 mJ/cm 2 , lamination of the optical adhesive sheet to an alkali glass plate prepared by the float method, and then 50° C. After heating and pressurizing the optical adhesive sheet on the alkali glass plate under conditions of 0.5 MPa and 15 minutes, the alkali The optical pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the peel speed is 35 µm/sec or less in a constant-load peel test for peeling the optical pressure-sensitive adhesive sheet from a glass plate.