WO2023074555A1

WO2023074555A1 - Photocurable adhesive sheet

Info

Publication number: WO2023074555A1
Application number: PCT/JP2022/039266
Authority: WO
Inventors: 陽介清水; 大器下栗; 裕貴小原; 崇弘野中
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: TW202336191A

Abstract

An adhesive sheet (S) according to the present invention is a photocurable adhesive sheet, wherein the ratio of a surface hardness H2 at 25°C, as measured by nano-indentation, at a location 100 μm away from a cut edge produced by laser cutting the photocurable adhesive sheet (S) to the inside of the photocurable adhesive sheet (S) in the planar direction, to a surface hardness H1 at 25°C, as measured by nano-indentation, is 1 to 1.5, inclusive.

Description

Photo-curable adhesive sheet

The present invention relates to a photocurable adhesive sheet.

A display panel has a laminated structure including elements such as a pixel panel, a polarizer 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.

Japanese Patent Application Laid-Open No. 2020-83996

A printed layer colored for decoration or light blocking is provided on the edge of the pixel panel side surface of the cover glass for smartphones and tablet terminals. The printed layer is provided, for example, over the entire periphery of the edge of the cover glass. This print layer has a predetermined thickness.
Therefore, on the pixel panel side of the cover glass, there is a step (printing step) between the surface of the cover glass and the surface of the printed layer. A pressure-sensitive adhesive sheet having a cover glass as an adherend is required to have not only reliability in bonding between adherends but also softness to the extent that it can follow printing steps (step conformability). Insufficient step followability of the adhesive sheet is the cause of the formation of air bubbles along the printed layer between the adhesive sheet and the cover glass, which is attached to the surface of the cover glass on the side of the pixel panel with the printed layer. and is not preferable.

Patent Document 1 describes a photocurable adhesive sheet (photocurable adhesive sheet). This pressure-sensitive adhesive sheet contains an acrylic base polymer having a cross-linked structure with a thermal cross-linking agent such as an isocyanate cross-linking agent, a photopolymerizable polyfunctional compound, and a photopolymerization initiator. According to Patent Document 1, this pressure-sensitive adhesive sheet has step absorbability in a soft state before photocuring, and has excellent adhesion durability after photocuring.

On the other hand, cutting by laser irradiation (laser cutting) is being considered as a method for highly accurate contour processing of adhesive sheets. However, in the conventional photocurable pressure-sensitive adhesive sheet, the vicinity of the cut portion (the edge of the pressure-sensitive adhesive sheet produced by cutting) becomes highly elastic due to laser cutting. It is presumed that this is because photocuring progresses in the vicinity of the cut portion of the adhesive sheet. Increasing the elasticity of the edge of the adhesive sheet is not preferable from the viewpoint of the above-described step conformability.

The present invention provides a photocurable adhesive sheet suitable for achieving both step followability and bonding reliability.

The present invention [1] is a photocurable pressure-sensitive adhesive sheet, the surface hardness H1 at 25 ° C. measured by the nanoindentation method is measured from the cut end surface of the photocurable pressure-sensitive adhesive sheet produced by laser cutting. A photocurable pressure-sensitive adhesive sheet having a surface hardness H2 ratio of 1 or more and 1.5 or less at 25° C. measured by a nanoindentation method at a site 100 μm away inward in the plane direction of .

The present invention [2] is described in the above [1], wherein the ratio of the surface hardness H3 of the cut end surface at 25° C. measured by a nanoindentation method to the surface hardness H1 is 1 or more and 4 or less. including a photocurable adhesive sheet.

The present invention [3] includes the photocurable pressure-sensitive adhesive sheet according to [1] or [2] above, which has an absorption wavelength with a light transmittance of 25% or less in the wavelength range of 200 nm to 400 nm.

The present invention [4] is any one of the above [1] to [3], which has a shear storage modulus of 210 kPa or more and 450 kPa or less at 25° C. after curing by light irradiation with an integrated irradiation light amount of 3000 mJ/cm ² . Including the photocurable pressure-sensitive adhesive sheet described in.

The present invention [5] is any one of the above [1] to [4], which has a gel fraction of 60% or more and 95% or less after curing by light irradiation with an integrated irradiation light amount of 3000 mJ/cm ² . including a photocurable adhesive sheet.

The photocurable adhesive sheet of the present invention has photocurability. In the case of a light-curable adhesive sheet, the adhesive sheet should be light-cured (highly elastic) after bonding, while ensuring the softness of the adhesive sheet when bonding between adherends using the same adhesive sheet (before light-curing). can be done. Further, in the photocurable pressure-sensitive adhesive sheet of the present invention, the ratio (H2/H1) of the surface hardness H2 of the predetermined portion after laser cutting to the surface hardness H1 is 1 or more and 1.5 or less as described above. Such a photocurable pressure-sensitive adhesive sheet is suitable for suppressing an increase in elastic modulus at the edges of the pressure-sensitive adhesive sheet formed by laser cutting and ensuring softness at the edges. The photocurable pressure-sensitive adhesive sheet as described above is suitable for achieving both conformability to a step on the surface of the adherend when the adherends are joined and bonding reliability after the adherends are joined.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram of one Embodiment of the photocurable adhesive sheet of this invention. It is a schematic diagram of a laser cutting test. FIG. 2A is a perspective view of the adhesive sheet during laser cutting, and FIG. 2B is a perspective view of the adhesive sheet after laser cutting. An example of the manufacturing method of the photocurable adhesive sheet shown in FIG. 1 is represented. 3A represents the process of forming a coating film of the pressure-sensitive adhesive composition, FIG. 3B represents the process of forming the base pressure-sensitive adhesive sheet, FIG. 3C represents the process of peeling the light release liner, and FIG. FIG. 3E represents the step of laminating a light release liner to the sheet, representing the step of applying the post-add component. An example of the usage method of the photocurable adhesive sheet shown in FIG. 1 is represented. FIG. 4A shows a step of preparing a photocurable adhesive sheet and two members (adherends), FIG. 4B shows a step of joining the members via the photocurable adhesive sheet, and FIG. It represents a step of photocuring a photocurable adhesive sheet between members.

A pressure-sensitive adhesive sheet S as an embodiment of the photocurable pressure-sensitive adhesive sheet of the present invention, as shown in FIG. . FIG. 1 exemplarily shows a state in which release liners L1 and L2 are attached to both sides of an adhesive sheet S. As shown in FIG. The release liner L1 is arranged on one surface of the adhesive sheet S in the thickness direction D. As shown in FIG. The release liner L2 is arranged on the other side of the adhesive sheet S in the thickness direction D. As shown in FIG. The release liners L1 and L2 are peeled off from the adhesive sheet S when the adhesive sheet S is used. Also, the adhesive sheet S is a transparent adhesive sheet (optical adhesive sheet) that is arranged at a light passage portion of the display panel. Examples of display panels include liquid crystal panels and organic EL panels. A display panel has, for example, a laminated structure including elements such as a pixel panel, a film-like polarizing plate (polarizing film), a touch panel, and a cover glass. The pressure-sensitive adhesive sheet S is used, for example, in the process of manufacturing display panels to bond elements included in a laminated structure.

The adhesive sheet S is a sheet-like pressure-sensitive adhesive. The adhesive sheet S contains a base polymer, further contains a photopolymerizable polyfunctional compound and a photopolymerization initiator in this embodiment, and has photocurability. The adhesive sheet S may contain a monofunctional monomer as a polymerizable component in addition to the photopolymerizable polyfunctional compound.

The adhesive sheet S has a surface hardness H1 at 25° C. measured by a nanoindentation method, from a cut end surface Z2 produced by cutting (laser cutting) of the adhesive sheet S with a laser R (schematically shown in FIG. 2A). The ratio (H2/H1) of the surface hardness H2 at 25° C. measured by the nanoindentation method of the site Z1 (schematically shown in FIG. 2B) 100 μm away in the surface direction of the pressure-sensitive adhesive sheet S is 1 or more. 1.5 or less. In laser cutting, a picosecond laser with a wavelength of 355 nm is irradiated to the adhesive sheet S under the conditions of a frequency of 50 kHz, a pulse width of 0.2 μm, and an output of 0.19 W, and the scanning speed of the laser irradiation point is 10 mm / sec, and the line to be cut is cut. It is assumed that the number of scanning times of laser irradiation along is 18. Further, the surface hardness H1 is the surface hardness measured before the adhesive sheet S is laser-cut, or the surface hardness of a portion 5000 μm or more away from the laser-cut end face when the adhesive sheet S is laser-cut. be.

The ratio (H2/H1) represents the degree of variation in softness of the adhesive sheet S in the vicinity of the laser cutting location. The ratio (H2/H1) is preferably 1.4 or less, more preferably 1.3 or less, still more preferably 1.2 or less, and particularly preferably 1.1 or less. Methods for adjusting the ratio (H2/H1) include, for example, selecting the types of the photopolymerizable polyfunctional compound and the photopolymerization initiator in the pressure-sensitive adhesive sheet S and adjusting the blending amounts. Methods for adjusting the ratio (H2/H1) include selection of the type of ultraviolet absorber in the adhesive sheet S and adjustment of the blending amount.

In addition, the nanoindentation method is a technique for measuring the physical properties of samples on a nanometer scale. In this embodiment, the nanoindentation method is performed in compliance with ISO14577. In the nanoindentation method, a process of pushing an indenter into a sample set on a stage (loading process) and then a process of withdrawing the indenter from the sample (unloading process) are performed. The load acting between the indenter and the sample and the relative displacement of the indenter with respect to the sample are measured (load-displacement measurement). This makes it possible to obtain a load-displacement curve. From this load-displacement curve, physical properties such as hardness and elastic modulus based on nanometer scale measurement can be obtained for the measurement sample. For the load-displacement measurement of the sample surface by the nanoindentation method, for example, a nanoindenter (product name “Triboindenter”, manufactured by Hysitron) can be used. In the measurement, the measurement mode was single indentation measurement, the measurement temperature was 25 ° C., and the indenter used was a Berkovich (triangular pyramid) type diamond indenter (diameter 20 μm). The depth (maximum displacement hmax) is 4 μm, the pressing speed of the indenter is 1000 nm/sec, and the withdrawal speed of the indenter from the measurement sample during the unloading process is 1000 nm/sec. Based on the load-displacement curve obtained by this measurement, the maximum load Pmax (the load acting on the indenter at the maximum displacement hmax) and the projected contact area Ap (the projected area of the contact area between the indenter and the sample at the maximum load) can be obtained. Then, the surface hardness (=Pmax/Ap) of the sample surface can be calculated from the maximum load Pmax and the contact projected area Ap.

The adhesive sheet S has photocurability as described above. In the photocurable adhesive sheet S, the adhesive sheet S (before photocuring) is used to secure the softness of the adhesive sheet S when bonding the adherends, while the adhesive sheet S is photocured (highly elasticized) after bonding. ). In addition, as described above, the pressure-sensitive adhesive sheet S has a ratio (H2/H1) of the surface hardness H2 of the predetermined portion after laser cutting to the surface hardness H1 of 1.5 or less, preferably 1.4 or less. It is more preferably 1.3 or less, still more preferably 1.2 or less, and particularly preferably 1.1 or less. Such an adhesive sheet S is suitable for suppressing an increase in elastic modulus at the edges of the adhesive sheet formed by laser cutting and ensuring softness at the edges. The pressure-sensitive adhesive sheet S as described above is suitable for achieving both conformability to a step on the surface of the adherend when the adherends are joined together and joint reliability after the adherends are joined.

The adhesive sheet S preferably has a ratio (H3/H1) of the surface hardness H3 of the cut end surface Z2 at 25°C measured by the nanoindentation method to the surface hardness H1 of 1 or more and 4 or less. The ratio (H3/H1) represents the degree of variation in softness of the laser-cut end surface Z2 of the adhesive sheet S. FIG. The ratio (H3/H1) is more preferably 3.7 or less, still more preferably 3.5 or less, even more preferably 3.3 or less, and particularly preferably 3.1 or less. Such a configuration is preferable for ensuring step followability at the laser-cut edge of the adhesive sheet S after laser cutting.

The adhesive sheet S has an absorption wavelength λ with a light transmittance of 25% or less in the wavelength range of 200 nm to 400 nm, and the light transmittance of the absorption wavelength λ is more preferably 20%, more preferably 15%. 10% or less is particularly preferable. Such a configuration is preferable in order to secure ultraviolet absorbability and realize good laser processability in the pressure-sensitive adhesive sheet S when an ultraviolet laser is used in laser cutting.

The shear storage modulus G at 25° C. after curing by light irradiation with an integrated light quantity of 3000 mJ/cm ² is preferably 210 kPa or more and 450 kPa or less. The shear storage modulus G is more preferably 250 kPa or more, more preferably 270 kPa or more, more preferably 290 kPa or more, more preferably 300 kPa or more, more preferably 310 kPa or more, more preferably 320 kPa or more, and more preferably It is 440 kPa or less, more preferably 430 kPa or less, more preferably 420 kPa or less, more preferably 410 kPa or less, more preferably 400 kPa or less. Such a configuration is suitable for suppressing the formation of air bubbles between the adherend and the adhesive sheet S in a state where the adhesive sheet S after photocuring is attached to the adherend. Methods for adjusting the shear storage modulus G include, for example, selection of the type of base polymer in the adhesive sheet S, adjustment of the molecular weight, and adjustment of the compounding amount. Methods for adjusting the shear storage modulus G include selection of the type of photopolymerizable polyfunctional compound in the adhesive sheet S, adjustment of the molecular weight, and adjustment of the compounding amount. Moreover, the method for measuring the shear storage elastic modulus G is as described later with regard to Examples.

The loss tangent tan δ of the pressure-sensitive adhesive sheet S after curing by light irradiation with an integrated irradiation light amount of 3000 mJ/cm ² preferably has a peak top of 1.5 or more within the range of -40°C to 5°C. The peak top value is more preferably 2 or more, still more preferably 2.5 or more, and particularly preferably 3 or more. Such a configuration is preferable from the viewpoint of low-temperature adhesion reliability of the pressure-sensitive adhesive sheet S. Methods for adjusting the peak top value include, for example, adjusting the composition ratio of the high Tg monomer in the base polymer and adjusting the amount of the high Tg additive added to the pressure-sensitive adhesive sheet S. A method for measuring the loss tangent tan δ is as described later with regard to Examples.

The gel fraction of the pressure-sensitive adhesive sheet S after curing by light irradiation with an integrated irradiation light amount of 3000 mJ/cm ² is preferably 60% or more and 95% or less. The gel fraction is more preferably 65% or more, still more preferably 68% or more, particularly preferably 70% or more, more preferably 92% or less, still more preferably 90% or less, and even more preferably 88%. % or less, particularly preferably 86% or less. Such a configuration is suitable for suppressing the formation of air bubbles between the adherend and the adhesive sheet S in a state where the adhesive sheet S after photocuring is attached to the adherend. Methods for adjusting the gel fraction after photocuring include, for example, selection of the type of base polymer in the adhesive sheet S, 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 S, 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 adhesive sheet S (before photocuring) is preferably 20% or more and 65% or less. The gel fraction is more preferably 25% or more, still more preferably 30% or more, particularly preferably 35% or more, and more preferably 60% or less, more preferably 58% or less, and more preferably 56%. Below, more preferably 54% or less, more preferably 52% or less, more preferably 50% or less, more preferably 48% or less, more preferably 46% or less. Such a configuration is preferable for suppressing glue dripping during processing of the adhesive sheet S, and also preferable for suppressing deformation of the adhesive sheet S during storage. Methods for adjusting the gel fraction before photocuring include, for example, selection of the type of base polymer in the adhesive sheet S, adjustment of the molecular weight, and adjustment of the compounding amount.

The adhesive sheet S contains a base polymer, a photopolymerizable polyfunctional compound (first photopolymerizable polyfunctional compound), and a photopolymerization initiator, and has photocurability. The term “photocurability” refers to the property that the adhesive sheet becomes highly elastic due to the progress of the polymerization reaction of the photopolymerizable polyfunctional compound upon irradiation with active energy rays such as ultraviolet rays.

The base polymer is an adhesive component that makes the adhesive sheet S exhibit adhesiveness. The base polymer may be a first type base polymer (first base polymer) described below or a second type base polymer (second base polymer) described below.

The first base polymer is a base polymer as a photopolymer. 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 pressure-sensitive adhesive sheet S whose base polymer is a photopolymer (first base polymer) 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. From the viewpoint of reducing environmental load, the base polymer is preferably the first base polymer.

The first 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 first base polymer is, for example, a partial polymer obtained by photopolymerization of a monofunctional monomer (a mixture of a polymerized product of a monofunctional monomer and an unreacted monofunctional monomer) and a photopolymerization of a second photopolymerizable polyfunctional compound. It is a polymer obtained by 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 first 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 first 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 first base polymer is preferably an acrylic polymer (first 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 first 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 S. , more preferably 70% by mass or more, particularly preferably 75% 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 the above monofunctional monomer. Examples of copolymerizable monomers include monomers having a polar group. 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.

From the viewpoint of securing the cohesive force of the adhesive sheet S, 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. 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 the compatibility between the various additive components in the adhesive sheet S and the acrylic polymer). 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 S and ensuring the adhesion of the adhesive sheet S to the adherend. It is at least 5% by mass, more preferably at least 5% by mass. The same ratio is preferably 20% by mass or less, more preferably 10% by mass or less, from the viewpoints of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of acid corrosion of the adherend.

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

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

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

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

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

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

Examples of trifunctional (meth)acrylates include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and tris(acryloyloxyethyl) isocyanurate.

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

The molecular weight of the polyfunctional monomer is preferably 5000 or less, more preferably 3000 or less, still more preferably 2000 or less, particularly preferably 1000 or less, and preferably 200 or more. Such a configuration is preferable from the viewpoint of appropriately adjusting the viscoelasticity (for example, shear storage modulus and loss tangent) of the first 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 first 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 pressure-sensitive adhesive sheet S before photocuring, and therefore preferable for ensuring the handleability of the pressure-sensitive adhesive sheet S. 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 secure a high degree of softness in the pressure-sensitive adhesive sheet S before photocuring and to realize good step conformability.

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.

The second base polymer is a base polymer that is not a photopolymer. Such base polymers include, for example, acrylic polymers, silicone polymers, polyester polymers, polyurethane polymers, polyamide polymers, polyvinyl ether polymers, vinyl acetate/vinyl chloride copolymers, modified polyolefin polymers, epoxy polymers, fluoropolymers, and rubber polymers. mentioned. The second base polymer may be used alone, or two or more of them may be used in combination. From the viewpoint of ensuring good transparency and adhesiveness in the adhesive sheet S, an acrylic polymer (second acrylic polymer) is preferably used as the second base polymer.

A (meth)acrylic acid alkyl ester is preferably used as the (meth)acrylic acid ester of the second acrylic polymer. (Meth)acrylic acid alkyl esters include, for example, the (meth)acrylic acid alkyl esters described above with respect to the first acrylic polymer. The (meth)acrylic acid esters may be used alone, or two or more of them may be used in combination. As the (meth)acrylic acid alkyl ester of the second acrylic polymer, an acrylate alkyl ester having an alkyl group having 3 to 15 carbon atoms is preferably used, more preferably n-butyl acrylate, 2- At least one selected from the group consisting of ethylhexyl and dodecyl acrylate is used.

As the copolymerizable monomer to be copolymerized with the (meth)acrylic acid alkyl ester of the second acrylic polymer, for example, the copolymerizable monomers described above for the first acrylic polymer may be used. The copolymerizable monomers may be used alone, or two or more of them may be used in combination. As the copolymerizable monomer, preferably at least one selected from the group consisting of hydroxyl group-containing monomers and nitrogen atom-containing ring-containing monomers is used. The hydroxy group-containing monomer is preferably 4-hydroxybutyl acrylate. 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 space between the second base polymers is crosslinked by a thermal crosslinking agent in this embodiment. Examples of thermal cross-linking agents include compounds that react with functional groups contained in the second base polymer. Such crosslinkers include, for example, isocyanate crosslinkers, peroxide crosslinkers, epoxy crosslinkers, oxazoline crosslinkers, aziridine crosslinkers, carbodiimide crosslinkers, and metal chelate crosslinkers. The cross-linking agents may be used alone, or two or more of them may be used in combination.

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

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

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

From the viewpoint of ensuring the cohesive strength of the pressure-sensitive adhesive sheet S, the amount of the thermal cross-linking agent is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass, with respect to 100 parts by mass of the second base polymer. Above, more preferably 0.1 parts by mass or more. From the viewpoint of ensuring good tackiness in the pressure-sensitive adhesive sheet S, the amount of the thermal cross-linking agent blended with respect to 100 parts by mass of the base polymer is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 1 part by mass. It is below the department.

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

The content of the first photopolymerizable polyfunctional compound in the adhesive sheet S is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and still more preferably 1 part by mass or more per 100 parts by mass of the base polymer. and preferably 20 parts by mass or less, more preferably 17 parts by mass or less, and even more preferably 15 parts by mass or less. Such a configuration is suitable for ensuring good bonding reliability in the adhesive sheet S 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 specific absorbance (first specific absorbance) of the photopolymerization initiator at a wavelength of 405 nm is preferably 10 or more, more preferably 15 or more, still more preferably 20 or more, still more preferably 30 or more, still more preferably 40 or more, and especially is preferably 45 or more, particularly preferably 50 or more. Such a configuration is preferable from the viewpoint of ensuring the photocurability of the adhesive sheet S. 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. The specific absorbance can be determined by the method described below with respect to the examples.

The content of the photopolymerization initiator in the adhesive sheet S 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 S by a photopolymerization reaction when the adhesive sheet S is irradiated with light, and for significantly changing the viscoelasticity of the adhesive sheet S. . The content of the photopolymerization initiator in the adhesive sheet S 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 S is irradiated with light and for forming a long-distance and continuous crosslinked network by photopolymerization reaction.

The adhesive sheet S preferably contains an ultraviolet absorber. 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 S, 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 compatibility between the UV cut function for device protection and the photocurability in the pressure-sensitive adhesive sheet S. 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 S 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 compatibility between the UV cut function for device protection and the photocurability in the pressure-sensitive adhesive sheet S.

The adhesive sheet S 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 ensuring the adhesive strength of the pressure-sensitive adhesive sheet S.

In order to sufficiently increase the adhesive strength of the adhesive sheet S, the content of the oligomer in the adhesive sheet S 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 S, the content of the oligomer in the adhesive sheet S 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 antioxidants include phenol antioxidants, phosphorus antioxidants, sulfur antioxidants, and amine antioxidants. The antioxidants may be used alone, or two or more of them may be used in combination.

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

The content of the antioxidant in the pressure-sensitive adhesive sheet S 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 adhesive sheet S 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 S 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.

When the base polymer is the first base polymer, the adhesive sheet S 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 S 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 S 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 S, the thickness of the adhesive sheet S 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 S 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 S for use in display panels. The total light transmittance of the adhesive sheet S is, for example, 100% or less. The total light transmittance can be measured according to JIS K 7375 (2008).

The adhesive sheet S containing the first base polymer as the base polymer can be produced, 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 first 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 , and the integrated irradiation 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. 3A, a coating film 10 is formed between the release liners L1 and L2' (coating film forming step). Specifically, after coating the adhesive composition on the release liner L1 to form the coating film 10, the release liner L2' is adhered onto the coating film 10 on the release liner L1.

The release liners L1 and L2' 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. 3B, the coating film 10 between the release liners L1 and L2' is irradiated with ultraviolet rays for photocuring to form a base adhesive sheet 10A (base adhesive sheet forming step). When irradiated with ultraviolet light, the photopolymerization reaction proceeds in the reaction system containing the above-described residual monomer and the second photopolymerizable polyfunctional compound in the coating film, and the first photopolymerization polymer having a photocrosslinking structure undergoes the second photopolymerization. Formed around a polymer. As a result, the base adhesive sheet 10A containing the first base polymer of the first photopolymerization polymer and the second photopolymerization polymer is formed. The polymerization rate of the polymerizable component in the base adhesive sheet 10A is preferably 90% or higher, more preferably 95% or higher, even more preferably 97% or higher, particularly preferably 99% or higher. Such a configuration is preferable for suppressing the odor of the pressure-sensitive adhesive sheet S. The same polymerization rate is, for example, 100%.

Next, as shown in FIG. 3C, the release liner L2' is peeled off from the base adhesive sheet 10A (peeling step).

Next, as shown in FIG. 3D, the post-additive component is supplied to the base adhesive sheet 10A (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 10A. 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 10A into the base pressure-sensitive adhesive sheet 10A, the solvent is vaporized by heating as necessary. Prior to this step, the first base polymer already has a crosslinked structure to form the base PSA sheet 10A. Therefore, the vaporization of the solvent in this step does not easily form the citrus skin surface on the base adhesive sheet 10A (it is not substantially formed). A photocurable adhesive sheet S is formed by the base adhesive sheet 10A and the post-addition component. The amount of the first photopolymerizable polyfunctional compound added in this step is preferably 0.5 parts by mass or more per 100 parts by mass of the prepolymer composition and the second photopolymerizable polyfunctional compound. It is more preferably 0.8 parts by mass or more, still more preferably 1 part by mass or more, and is preferably 20 parts by mass or less, more preferably 17 parts by mass or less, and still more preferably 15 parts by mass or less. Such a configuration is suitable for ensuring good bonding reliability in the adhesive sheet S after photocuring.

Next, as shown in FIG. 3E, a release liner L2 is adhered to the adhesive sheet S (lamination step). Release liner L2 includes, for example, the plastic films described above for release liners L1 and L2'.

After that, the adhesive sheet S is contour-processed by laser cutting (laser processing step). Specifically, the pressure-sensitive adhesive sheet S with a double-sided release liner is cut by irradiating a laser in the thickness direction D and scanning the laser-irradiated portion along the planned cutting line. Laser cutting is preferable as an outer shape processing method because the outer shape can be processed with high precision. Lasers for laser cutting include, for example, gas lasers, solid-state lasers, and semiconductor lasers. Gas lasers include, for example, excimer lasers and CO ₂ lasers (10.6 μm) (numbers in parentheses represent laser wavelengths; the same applies hereinafter in this paragraph). Excimer lasers include, for example, _F2 excimer laser (157 nm), ArF excimer laser (193 nm), KrF excimer laser (248 nm), and XeCl excimer laser (308 nm). Examples of solid-state lasers include Nd:YAG laser (1064 nm), second harmonic of Nd:YAG laser (532 nm), third harmonic of Nd:YAG laser (355 nm), and fourth harmonic of Nd:YAG laser. waves (266 nm). Examples of semiconductor lasers include a semiconductor laser with a wavelength of 405 nm, a semiconductor laser with a wavelength of 650 nm, a semiconductor laser with a wavelength of 780 nm, a semiconductor laser with a wavelength of 808 nm, and a semiconductor laser with a wavelength of 940 nm. As the laser, an ultraviolet laser having a wavelength in the ultraviolet region is preferable from the viewpoint of workability.

The output of the laser is preferably 0.01 W or more, more preferably 0.03 W or more, and still more preferably 0, from the viewpoint of realizing cutting with fewer laser scanning times and cutting with a shorter laser irradiation time. 0.05 W or more, more preferably 0.07 W or more, and particularly preferably 0.1 W or more. The output of the laser is preferably 100 W or less, more preferably 50 W or less, and still more preferably 10 W, from the viewpoint of suppressing carbonization of the edges of the adhesive sheet due to laser cutting and suppressing excessive melt generation due to laser cutting. Below, it is particularly preferably 5 W or less, still more preferably 1 W or less, still more preferably 0.7 W or less, particularly preferably 0.5 W or less, and extremely preferably 0.3 W or less. From the viewpoint of processing time, the scanning speed of the laser is preferably 1 mm/sec or more, more preferably 5 mm/sec or more. From the viewpoint of processing accuracy, the laser scanning speed is preferably 1000 mm/sec or less, more preferably 500 mm/sec or less, even more preferably 300 mm/sec or less, and particularly preferably 100 mm/sec or less. From the viewpoint of avoiding a decrease in processing accuracy due to repeated laser scanning, the number of laser scans is preferably 100 or less, more preferably 50 or less, still more preferably 30 or less, still more preferably 20 or less, and still more preferably 10. 5 or less is particularly preferable.

As described above, the adhesive sheet S (including the first base polymer) whose adhesive surface is covered and protected by the release liners L1 and L2 can be manufactured.

The adhesive sheet S containing the second base polymer as the base polymer can be produced, for example, as follows.

First, after a reaction solution containing monomer components for forming the second base polymer, a thermal polymerization initiator, and a solvent is prepared, the second 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, a photopolymerizable polyfunctional compound and a photopolymerization initiator are added to the polymer solution to prepare an adhesive composition (solvent type adhesive composition). Next, the pressure-sensitive adhesive composition is applied onto the release liner L1 to form a coating film. Next, the coating film on the release liner L1 is dried by heating to form an adhesive layer. Next, a release liner L2 is laminated on the adhesive layer on the release liner L1. Next, by aging treatment, the adhesive sheet S is formed by the crosslinking reaction of the second base polymer by the thermal crosslinking agent in the adhesive layer. Next, the adhesive sheet S is contoured by laser cutting. Specifically, it is the same as the laser processing step described above. As described above, the adhesive sheet S (including the second base polymer) whose adhesive surface is covered and protected by the release liners L1 and L2 can be produced.

4A to 4C show an example of how to use the adhesive sheet S.

In this method, first, as shown in FIG. 4A, a member 21, a cover glass 22, and an adhesive sheet S are prepared. The member 21 is, for example, a pixel panel for a display panel, a film-like polarizing plate (polarizing film), or a touch panel. The cover glass 22 has a first surface 22a on the member 21 side and a second surface 22b opposite to the first surface 22a. A printing layer 23 for decoration or light shielding is formed on the edge of the first surface 22a. The printed layer 23 is provided, for example, over the entire periphery of the edge of the cover glass 22 . On the member 21 side of the cover glass 22 , there is a step (printing step) between the first surface 22 a and the surface of the printing layer 23 .

Next, as shown in FIG. 4B, one side in the thickness direction D of the member 21 and the other side in the thickness direction D of the cover glass 22 are joined via the adhesive sheet S (joining step).

Next, as shown in FIG. 4C, the adhesive sheet S is photo-cured between members by ultraviolet irradiation (photo-curing step). The ultraviolet irradiation causes the photopolymerization reaction of the first photopolymerizable polyfunctional compound to proceed in the adhesive sheet S, forming a photopolymerized product of the first photopolymerizable polyfunctional compound. Since the photopolymerization reaction proceeds around the base polymer having a crosslinked structure, the photopolymerized product of the first photopolymerizable polyfunctional compound is formed while forming an interpenetrating polymer network (IPN) with the base polymer. be done. As a result, the adhesive sheet S becomes highly elastic, and the bonding strength between the member 21 and the cover glass 22 increases. 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 .

The adhesive sheet S has photocurability as described above. In the photocurable adhesive sheet S, the adhesive sheet S (before photocuring) ensures the softness of the adhesive sheet S when the adherends are joined together (FIG. 4B). S can be photocured (high elasticity) (FIG. 4C). In addition, as described above, the pressure-sensitive adhesive sheet S has a ratio (H2/H1) of the surface hardness H2 of the predetermined portion after laser cutting to the surface hardness H1 of 1.5 or less, preferably 1.4 or less. It is more preferably 1.3 or less, still more preferably 1.2 or less, and particularly preferably 1.1 or less. Such an adhesive sheet S is suitable for suppressing an increase in elastic modulus at the edges of the adhesive sheet formed by laser cutting and ensuring softness at the edges. The pressure-sensitive adhesive sheet S as described above is suitable for achieving both conformability to a step on the surface of the adherend when the adherends are joined together and joint reliability after the adherends are joined.

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

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

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

<Preparation of adhesive composition>
Next, 100 parts by mass of the prepolymer composition, 3 parts by mass of the above acrylic oligomer, and 0.6 mass of urethane acrylate oligomer (product name "UN-350", manufactured by Negami Kogyo Co., Ltd.) as the second photopolymerizable polyfunctional compound part, a third photopolymerization initiator (product name “Irgacure 819”, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, manufactured by BASF) 0.4 parts by mass, and an antioxidant (product name “Irga Nox 1010", manufactured by BASF) 0.5 parts by mass, a rust inhibitor (product name "BT-120", manufactured by Johoku Chemical Industry Co., Ltd.) 0.2 parts by mass, and a silane coupling agent (product name "KBM-403", Shin-Etsu Chemical Co., Ltd.) was mixed with 0.3 parts by mass to obtain an adhesive composition C1.

<Preparation of base adhesive sheet>
Next, the pressure-sensitive adhesive composition C1 was 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. formed. Next, the release-treated surface of the second release liner (product name: "Diafoil MRE", thickness: 75 μm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side was laminated onto the coating film on the first release liner. rice field. Next, the coating film between the release liners was irradiated with ultraviolet rays from the second release liner side, and the coating film was photocured to form a pressure-sensitive adhesive layer with a thickness of 100 μm (ultraviolet irradiation step). In the ultraviolet irradiation, a black light (manufactured by Toshiba) was used as a light source, the illuminance was set at 6.5 mW/cm ² , and the irradiation integrated light amount was set at 1500 mJ/cm ² . In the ultraviolet irradiation step, the photopolymerization reaction proceeds in the system containing the residual monomer and the second photopolymerizable polyfunctional compound in the coating film to form a photopolymerization polymer P1b having a photocrosslinking structure. 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, 28.9 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 1.3 parts by mass of a photopolymerization initiator (product name “Irgacure 819”, manufactured by BASF), 9.5 parts by mass of an ultraviolet absorber (product name “Tinosorb S”, manufactured by BASF), and 71.1 parts by mass of ethyl acetate as a solvent were mixed together to prepare a post-addition component solution (everything other than the solvent in the solution is a post-addition component). Table 1 shows the composition of the post-addition component solution. In Table 1, the unit of the blending amount of each component is relative "parts by mass".

<Preparation of photocurable adhesive sheet>
Next, after peeling off the second release liner from the double-sided release liner-attached base PSA sheet, the post additive component solution was applied to a thickness of 20 μm on the exposed surface of the base PSA sheet thus exposed (coating treatment). . A bar coater RDS No. 10 manufactured by RD SPECIALTIES was used for coating. Next, it was dried in a dryer at 110° C. for 60 seconds. By coating treatment and drying treatment, the post-addition component (polyfunctional acrylate monomer as the first photopolymerizable polyfunctional compound, the third photopolymerization initiator, the ultraviolet absorber) is permeated into the base adhesive sheet, and the solvent is removed. vaporized. The base pressure-sensitive adhesive sheet changed into a photocurable pressure-sensitive adhesive sheet due to the permeation of the post-addition component. In this example, 5 parts by mass of the first photopolymerizable polyfunctional compound per 100 parts by mass of the prepolymer composition and the second photopolymerizable polyfunctional compound (i.e., 100 parts by mass of the base polymer) was added to the base adhesive sheet (the number of parts by mass of the first photopolymerizable polyfunctional compound per 100 parts by mass of the base polymer is shown in Table 2). Next, on the photocurable adhesive sheet on the first release liner, the release-treated surface of a third release liner (product name: "DIAFOIL MRE", thickness: 75 µm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side. pasted together.

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

[Examples 2 to 6]
Photocurable pressure-sensitive adhesive sheets with double-sided release liner of Examples 2 to 6 were prepared in the same manner as the photocurable pressure-sensitive adhesive sheet with double-sided release liner of Example 1, except that the composition of the post-additive component solution was changed to the composition shown in Table 1. An adhesive sheet was produced.

[Example 7]
First, 64.5 parts by mass of n-butyl acrylate (BA) and 6.0 parts by mass of cyclohexyl acrylate (CHA) were mixed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube. , N-vinyl-2-pyrrolidone (NVP) 9.6 parts by mass, 4-hydroxybutyl acrylate (4HBA) 14.9 parts by mass, isostearyl acrylate 5.0 parts by mass, and a thermal polymerization initiator 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a, 0.065 parts by mass of α-thioglycerol as a chain transfer agent, and 233 parts by mass of ethyl acetate as a polymerization solvent in nitrogen The mixture was reacted at 56° C. for 5 hours and then at 70° C. for 3 hours (polymerization reaction) while stirring under an atmosphere. Thus, a polymer solution containing an acrylic polymer was obtained.

Next, in the polymer solution, per 100 parts by mass of the acrylic polymer, 0.1 parts by mass of an isocyanate cross-linking agent (product name "Takenate D110N", trimethylolpropane adduct of xylylene diisocyanate, manufactured by Mitsui Chemicals) and a polyfunctional acrylate monomer 4.7 parts by mass of dipentaerythritol hexaacrylate (DPHA), 5 parts by mass of the acrylic oligomer, the first photopolymerization initiator (product name "Irgacure 184", manufactured by BASF) 0.2 parts by mass, and a silane cup A ring agent (product name “KBM-403”, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.3 parts by mass and an ultraviolet absorber (product name “Chinosorb S”, manufactured by BASF) 0.7 parts by mass are mixed to form an adhesive composition. C2 was obtained.

Next, the pressure-sensitive adhesive composition C2 was 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. formed. Next, the coating film on the first release liner was dried by heating at 100° C. for 3 minutes to form a pressure-sensitive adhesive layer with a thickness of 100 μm. Next, the release-treated surface of a second release liner (product name: "Diafoil MRE", thickness: 75 μm, manufactured by Mitsubishi Chemical Corporation) whose one side was release-treated was attached to the pressure-sensitive adhesive layer on the first release liner. . After that, aging treatment was performed at 25° C. for 3 days, and the cross-linking reaction of the acrylic polymer with the isocyanate cross-linking agent was allowed to proceed in the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer thus formed contains, as a base polymer P2, an acrylic polymer having a thermally crosslinked structure with an isocyanate crosslinking agent.

As described above, a pressure-sensitive adhesive sheet with a double-sided release liner (first release liner/adhesive sheet (thickness: 100 μm)/second release liner) of Example 7 was produced.

[Comparative Example 1]
The pressure-sensitive adhesive sheet with a double-sided release liner of Comparative Example 1 was prepared in the same manner as the pressure-sensitive adhesive sheet with a double-sided release liner of Example 7, except that the ultraviolet absorber (product name "Tinosorb S") was not used in the preparation of the pressure-sensitive adhesive composition C2. A sheet was produced.

[Comparative Example 2]
<Preparation of adhesive composition>
First, 100 parts by mass of the prepolymer composition, 0.4 parts by mass of a third photopolymerization initiator (product name "Irgacure 819", manufactured by BASF), 5.8 parts by mass of the acrylic oligomer, and a urethane acrylate oligomer ( Product name "UN-350", manufactured by Neagari Kogyo Co., Ltd.) 1.1 parts by mass, antioxidant (product name "Irganox 1010", manufactured by BASF) 0.5 parts by mass, rust inhibitor (product name "BT-120" , Johoku Chemical Co., Ltd.) 0.2 parts by mass, a silane coupling agent (product name “KBM-403”, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.3 parts by mass, and a polyfunctional acrylate monomer (product name “Viscoat #295” , Osaka Organic Chemical Industry Co., Ltd.) and 0.7 parts by mass of an ultraviolet absorber (product name: "Tinosorb S", manufactured by BASF) were mixed to obtain an adhesive composition C3.

<Preparation of adhesive sheet>
Next, the pressure-sensitive adhesive composition C3 was applied onto the release-treated surface of the first release liner (product name “Diafoil MRF”, thickness 38 μm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side to form a coating film. formed. Next, the release-treated surface of a second release liner (product name: "Diafoil MRE", thickness: 38 µm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side was laminated onto the coating film on the first release liner. rice field. Next, the coating film between the release liners was irradiated with ultraviolet rays from the second release liner side, and the coating film was photocured to form a pressure-sensitive adhesive layer with a thickness of 100 μm (ultraviolet irradiation step). In the ultraviolet irradiation, a black light (manufactured by Toshiba) was used as a light source, the illuminance was set to 5 mW/cm ² , and the irradiation integrated light amount was set to 1500 mJ/cm ² . In the ultraviolet irradiation step, a photopolymerization reaction proceeds around the photopolymerization polymer P1a in the coating film to form a photopolymerization polymer P2b having a photocrosslinking structure. The pressure-sensitive adhesive layer formed in this step contains the photopolymerization polymer P1a and the photopolymerization polymer P2b as the base polymer P3.

As described above, a pressure-sensitive adhesive sheet with a double-sided release liner (first release liner/adhesive sheet (thickness: 100 μm)/second release liner) of Comparative Example 2 was produced.

<Specific absorbance>
The specific absorbance at a wavelength of 405 nm was examined for the third photopolymerization initiator (product name: "Irgacure 819", manufactured by BASF) and the ultraviolet absorber (product name: "Tinosorb S", manufactured by BASF). Specifically, first, an ethyl acetate solution of a sample (third photopolymerization initiator or ultraviolet absorber) having a predetermined concentration was prepared as a sample solution. Next, the absorption spectrum of the sample solution was measured with a spectrophotometer (product name “U4100”, manufactured by Hitachi High-Technologies Corporation). In this measurement, the temperature condition was 23° C., the measurement cell length was 10 mm, and the measurement range wavelength was 300 to 500 nm. Then, in the spectrophotometer, the absorbance (vertical axis) of the measured absorption spectrum was converted to specific absorbance (the specific absorbance is the absorbance when the sample concentration is 1 mg/mL and the measurement cell length is 1 cm). . The specific absorbance E1 of the third photopolymerization initiator (product name “Irgacure 819”) at a wavelength of 405 nm was 18.2 (cm ⁻¹ ). The specific absorbance E1 of the ultraviolet absorber (product name “Tinosorb S”) at a wavelength of 405 nm was 3.4 (cm ⁻¹ ).

<Gel fraction>
For each adhesive sheet of Examples 1 to 7 and Comparative Example 1, the gel fraction after photocuring was measured. Specifically, it is as follows.

First, the 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 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 recovered. 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 adhesive sheet after photocuring was calculated based on the following formula. The values are shown in Table 2.

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

For the pressure-sensitive adhesive sheet of Comparative Example 2, the gel fraction was measured in the same manner as the above gel fraction measurement, except that the ultraviolet irradiation was not performed. The values are shown in Table 2.

<Light transmittance>
The light transmittance of each pressure-sensitive adhesive sheet of Examples 1 to 7 and Comparative Examples 1 and 2 was measured using a spectrophotometer (product name: "U4100", manufactured by Hitachi High-Technologies Corporation). In this measurement, after cutting out a sample piece (first release liner/adhesive layer/third or second release liner) from the adhesive sheet, the release liners were peeled off from both sides of the adhesive layer, and the adhesive layer did not deform. The pressure-sensitive adhesive layer was fixed to a measuring jig of a spectrophotometer as shown. Further, in this measurement, the temperature condition was set to 23° C., and the measurement range wavelength was set to 300 to 800 nm. Table 2 shows the measured light transmittance (%) at a wavelength of 380 nm.

<Shear storage modulus>
Dynamic viscoelasticity was measured for each adhesive sheet of Examples 1 to 7 and Comparative Example 1 (after photocuring).

A required number of measurement samples were prepared for each adhesive sheet. Specifically, first, the 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, 20 adhesive sheet pieces cut out from the adhesive sheet were pasted together to prepare a sample sheet having a thickness of about 2 mm. Next, this sheet was punched out to obtain cylindrical pellets (diameter 7.9 mm) as samples for measurement.

Then, the measurement sample was fixed to a parallel plate jig with a diameter of 7.9 mm using a dynamic viscoelasticity measuring device (product name “Advanced Rheometric Expansion System (ARES)”, manufactured by Rheometric Scientific) and then moved. A viscoelasticity measurement was performed. In this measurement, the measurement mode was the shear mode, the measurement temperature range was −50° C. to 150° C., the temperature increase rate was 5° C./min, and the frequency was 1 Hz. From the measurement results, the shear storage modulus G (kPa) at 25°C was read. The values are shown in Table 2. Moreover, the shear loss elastic modulus and the loss tangent (=shear loss elastic modulus/shear storage elastic modulus) can also be read from the measurement results.

For the pressure-sensitive adhesive sheet of Comparative Example 2, the shear storage modulus (kPa) was measured in the same manner as the above shear storage modulus measurement, except that the measurement sample was not irradiated with ultraviolet rays. The values are shown in Table 2.

<surface hardness>
The pressure-sensitive adhesive sheets of Examples 1 to 7 and Comparative Examples 1 and 2 were subjected to load-displacement measurement by the nanoindentation method (first measurement). In preparing a sample for the first measurement, first, a 20 mm×20 mm sheet piece (first release liner/adhesive sheet/third or second release liner) was cut out from the adhesive sheet. Next, after peeling off the third or second release liner from the adhesive sheet of the sheet piece, the exposed surface exposed by this is attached to a polarizing film (thickness 100 μm) to form a laminate (polarizing film/adhesive sheet/first release liner). Release liner) was obtained. Next, this laminate was autoclaved under conditions of 50° C., 0.5 MPa, and 15 minutes. Next, after peeling the first release liner from the adhesive sheet of the sheet piece, the exposed surface of the adhesive sheet exposed by this is subjected to ISO 14577 using a nanoindenter (product name "Triboindenter", manufactured by Hysitron). A load-displacement measurement was performed and a load-displacement curve was obtained. The measurement site is a site distant from the edge of the adhesive sheet by 5000 μm or more. In this measurement, the measurement mode was single indentation measurement, the measurement temperature was 25°C, and the indenter used was a Berkovich (triangular pyramid) type diamond indenter (diameter 20 μm). The depth (maximum displacement hmax) was 4 μm, the indentation speed was 1000 nm/sec, and the indenter withdrawal speed was 1000 nm/sec during the unloading process. Based on the obtained load-displacement curve, the maximum load Pmax (the load acting on the indenter at the maximum displacement hmax) and the projected contact area Ap (the projected area of the contact area between the indenter and the sample at the maximum load) Obtained. Then, the surface hardness (=Pmax/Ap) of the pressure-sensitive adhesive sheet was calculated from the maximum load Pmax and the projected contact area Ap. The calculated surface hardness is shown in Table 2 as surface hardness H1 (kPa).

On the other hand, for each adhesive sheet of Examples 1 to 7 and Comparative Examples 1 and 2, load-displacement measurement was performed by the nanoindentation method after laser cutting (second measurement). In preparing the sample for the second measurement, first, a 20 mm×20 mm sheet piece (first release liner/adhesive sheet/third or second release liner) was cut out from the adhesive sheet. Next, after peeling off the third or second release liner from the adhesive sheet of the sheet piece, the exposed surface exposed by this is attached to a polarizing film (thickness 100 μm) to form a laminate (polarizing film/adhesive sheet/first release liner). A release liner) was obtained. Next, this laminate was autoclaved under conditions of 50° C., 0.5 MPa, and 15 minutes. Next, the laminate was laser-cut in the thickness direction (cutting step). Specifically, the laminate was irradiated with a laser from the side of the first release liner along a planned cutting line (indicated by a dashed line in FIG. 2A). In this step, the laminate is irradiated with a picosecond laser with a wavelength of 355 nm under the conditions of a frequency of 50 kHz, a pulse width of 0.2 μm, and an output of 0.19 W, the scanning speed is 10 mm / sec, and the laser is irradiated along the line to be cut. was scanned 18 times.

Then, after peeling the first release liner from the laminate after the cutting step, a site Z1 (schematically illustrated in FIG. 2B ) was subjected to load-displacement measurement using a nanoindenter (product name “Triboindenter”, manufactured by Hysitron) to obtain a load-displacement curve. The measurement conditions for this measurement are the same as those for the first measurement. Based on the maximum load Pmax and the projected contact area Ap obtained from the obtained load-displacement curve, the surface hardness (=Pmax/Ap) of the portion Z1 of the adhesive sheet was calculated. The calculated surface hardness is shown in Table 2 as surface hardness H2 (kPa).

In addition, load-displacement measurement was performed using a nanoindenter (product name “Triboindenter”, manufactured by Hysitron) on the cut end surface Z2 (schematically shown in FIG. 2B) of the adhesive sheet in the measurement sample, and the load-displacement curve was obtained. got The measurement conditions for this measurement are the same as those for the first measurement. Then, the surface hardness (=Pmax/Ap) of the cut end surface Z2 of the adhesive sheet was calculated based on the maximum load Pmax and the projected contact area Ap obtained from the obtained load-displacement curve. The calculated surface hardness is shown in Table 2 as surface hardness H3 (kPa).

The photocurable 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 panels.

S adhesive sheet (photocurable adhesive sheet)
D thickness direction L1, L2 release liner 21 member 22 cover glass 23 printed layer

Claims

A photocurable adhesive sheet,
With respect to the surface hardness H1 at 25 ° C. measured by the nanoindentation method, a portion 100 μm away from the cut end surface of the photocurable adhesive sheet produced by laser cutting in the surface direction of the adhesive sheet, by the nanoindentation method. A photocurable pressure-sensitive adhesive sheet having a measured surface hardness H2 ratio at 25°C of 1 or more and 1.5 or less.
The photocurable pressure-sensitive adhesive sheet according to claim 1, wherein the ratio of the surface hardness H3 of the cut end surface at 25°C measured by a nanoindentation method to the surface hardness H1 is 1 or more and 4 or less.
The photocurable pressure-sensitive adhesive sheet according to claim 1, which has an absorption wavelength with a light transmittance of 25% or less within a wavelength range of 200 nm to 400 nm.
2. The photocurable pressure-sensitive adhesive sheet according to claim 1, which has a shear storage elastic modulus of 210 kPa or more and 450 kPa or less at 25° C. after curing by light irradiation with an integrated irradiation light amount of 3000 mJ/cm 2 .
The photocurable pressure-sensitive adhesive sheet according to any one of claims 1 to 4, which has a gel fraction of 60% or more and 95% or less after curing by light irradiation with an integrated irradiation light amount of 3000 mJ/ cm2 .