JP2020033416A - Adhesive sheet, adhesive sheet with peel-off sheet, laminate, and laminate manufacturing method - Google Patents

Abstract

To provide an adhesive sheet that can demonstrate superior substrate adhesion and durability even under conditions of high temperature and high humidity.SOLUTION: This invention relates to an adhesive sheet which is formed from an adhesive composition containing an acryl copolymer, a polyfunctional monomer having two or more reactive double bonds in the molecule, a monofunctional monomer having one reactive double bond in the molecule, a hydrogen-withdrawing photopolymerization initiator and a self-cleavage photopolymerization initiator.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pressure-sensitive adhesive sheet, a pressure-sensitive adhesive sheet with a release sheet, a laminate, and a method for producing a laminate.

  Conventionally, input devices used in combination with a display device such as a liquid crystal display (LCD) or a display device such as a touch panel have been widely used. In the production of these display devices and input devices, transparent adhesive sheets are used for bonding optical members, and transparent adhesive sheets are also used for bonding display devices and input devices. .

  As a pressure-sensitive adhesive sheet for an optical member, a pressure-sensitive adhesive sheet using a solvent-type pressure-sensitive adhesive for a pressure-sensitive adhesive layer is widely used. The solvent-type pressure-sensitive adhesive generally contains an acrylic resin as a main component. Such an acrylic resin is obtained by performing a polymerization reaction in a solvent obtained by dissolving an acrylic monomer in a solvent by a technique called solution polymerization. In solution polymerization, as the polymerization proceeds, the molecular weight of the polymer increases and the viscosity of the reaction solution increases.Therefore, there are technical limitations in the synthesis of polymers having the molecular weight necessary to obtain the cohesive force required as an adhesive. is there. Therefore, in order to secure the necessary cohesive force of the pressure-sensitive adhesive, a crosslinking agent capable of reacting with an acrylic resin such as an isocyanate-based compound or an epoxide-based compound is blended into the pressure-sensitive adhesive composition. Such a cross-linking agent builds up a cross-linking network by reacting with the acrylic resin over time, and increases the cohesive force of the pressure-sensitive adhesive layer.

  In addition, as a method of forming a pressure-sensitive adhesive sheet for an optical member, a method is used in which polymerization is performed by heat (or active energy rays) and then polymerization is performed by two-stage polymerization in which polymerization is performed by active energy rays (or heat). There is. Since such a pressure-sensitive adhesive sheet is formed from, for example, a pressure-sensitive adhesive composition having both thermosetting properties and active energy ray-curing properties (hereinafter, sometimes referred to as “dual-curable pressure-sensitive adhesive composition”), It has thermosetting properties and active energy ray curability. For this reason, it is possible to perform temporary bonding by, for example, performing only thermal curing before bonding to the adherend, and then to further cure with active energy rays (referred to as post-curing or after-curing). Can be firmly bonded to the body.

For example, Patent Document 1 discloses a base polymer (A) containing a non-crosslinkable (meth) acrylate unit (a1) and an acrylic monomer unit (a2) having a crosslinkable functional group, and lauryl acrylate (b1). (B), a crosslinking agent (C) that reacts with the base polymer (A) by heat, and a polymerization initiator (D) that initiates a polymerization reaction of the monomer (B) by irradiation with active energy rays. ) And a solvent (E) are described. The pressure-sensitive adhesive sheet includes a pressure-sensitive adhesive layer obtained by half-curing a pressure-sensitive adhesive composition containing heat. Patent Document 2 discloses a pressure-sensitive adhesive sheet having at least one UV-curable pressure-sensitive adhesive layer. Here, the storage elastic modulus G ′ (1 Hz) at a measurement temperature of 20 ° C. and a frequency of 1 Hz after ultraviolet curing of the pressure-sensitive adhesive layer is 1 × 10 ⁴ to 1 × 10 ⁶ Pa.

JP-A-2006-084391 JP 2012-31059 A

However, when the present inventors examined the properties of the pressure-sensitive adhesive sheets described in Patent Literatures 1 and 2, there were cases where the substrate adhesion was insufficient, particularly under high-temperature and high-humidity conditions. It has been found that durability may not be sufficiently obtained.
Therefore, the present inventors have studied to solve such problems of the prior art with the aim of providing an adhesive sheet capable of exhibiting excellent substrate adhesion and durability even under high temperature and high humidity conditions. Advanced.

As a result of intensive studies to solve the above problems, an acrylic copolymer, a polyfunctional monomer having two or more reactive double bonds in the molecule, and one reactive double bond in the molecule By forming a pressure-sensitive adhesive sheet from a pressure-sensitive adhesive composition containing a monofunctional monomer having a hydrogen-abstraction type photopolymerization initiator and a self-cleaving type photopolymerization initiator, excellent substrate adhesion even under high temperature and high humidity conditions It has been found that a pressure-sensitive adhesive sheet capable of exhibiting properties and durability can be obtained.
Specifically, the present invention has the following configuration.

[1] Acrylic copolymer, polyfunctional monomer having two or more reactive double bonds in the molecule, monofunctional monomer having one reactive double bond in the molecule, hydrogen abstraction type photopolymerization An adhesive sheet formed from an adhesive composition containing an initiator and a self-cleaving photopolymerization initiator.
[2] The acrylic copolymer contains a unit derived from a (meth) acrylate containing at least one group selected from a carboxy group, a hydroxy group, an amino group, an amide group, an epoxy group and an isocyanate group. ] The pressure-sensitive adhesive sheet according to the above.
[3] The acrylic copolymer contains a unit derived from an alkoxyalkyl group-containing (meth) acrylate, a unit derived from a hydroxy group-containing (meth) acrylate, and a unit derived from methyl (meth) acrylate.
The content of the unit derived from the alkoxyalkyl group-containing (meth) acrylate is 50 to 90% by mass, and the content of the unit derived from the hydroxy group-containing (meth) acrylate is based on the total mass of the acrylic copolymer. The pressure-sensitive adhesive sheet according to [1] or [2], wherein the pressure-sensitive adhesive sheet has 5 to 35% by mass and a content of a unit derived from methyl (meth) acrylate is 5 to 15% by mass.
[4] The pressure-sensitive adhesive sheet according to any one of [1] to [3], wherein the content of the thermosetting crosslinking agent is 0.1% by mass or less based on the total weight of the pressure-sensitive adhesive sheet.
[5] The pressure-sensitive adhesive sheet according to any one of [1] to [4], wherein the pressure-sensitive adhesive sheet is a post-curable pressure-sensitive adhesive sheet, and has a gel fraction of 20% by mass or less before post-curing.
[6] The pressure-sensitive adhesive sheet according to any one of [1] to [5], wherein the monofunctional monomer is an alkyl (meth) acrylate.
[7] The pressure-sensitive adhesive sheet according to any one of [1] to [6], wherein a glass transition temperature (Tg) when the polyfunctional monomer is a homopolymer is less than 65 ° C.
[8] The pressure-sensitive adhesive sheet according to any one of [1] to [7], wherein the content of the polyfunctional monomer is 5 to 40 parts by mass with respect to 100 parts by mass of the acrylic copolymer.
[9] The pressure-sensitive adhesive sheet according to any one of [1] to [8], wherein the content of the monofunctional monomer is 1 to 20 parts by mass based on 100 parts by mass of the acrylic copolymer.
[10] A pressure-sensitive adhesive sheet with a release sheet, comprising a pair of release sheets having different release forces on both surfaces of the pressure-sensitive adhesive sheet according to any one of [1] to [9].
[11] An adhesive sheet cured by irradiating the adhesive sheet according to any one of [1] to [9] with an active energy ray, and an adherend on at least one surface side of the cured adhesive sheet. A laminate comprising:
[12] A method for producing a laminate, comprising a step of bonding the pressure-sensitive adhesive sheet according to any one of [1] to [9] to an adherend, and then irradiating an active energy ray to cure the pressure-sensitive adhesive sheet.

  ADVANTAGE OF THE INVENTION According to this invention, the adhesive sheet which can exhibit the outstanding base-material adhesiveness and durability under high temperature and high humidity conditions can be obtained.

FIG. 1 is a schematic diagram illustrating a cross section of a release sheet or a pressure-sensitive adhesive sheet having a substrate. FIG. 2 is a schematic diagram illustrating a cross section of an example of the laminate of the present invention. FIG. 3 is a schematic diagram illustrating a cross section of another example of the laminate of the present invention. FIG. 4 is a diagram illustrating a method of measuring a constant load peeling distance.

  Hereinafter, the present invention will be described in detail. The description of the components described below may be made based on representative embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit and an upper limit.

In addition, in this specification, "(meth) acrylate" represents both acrylate and methacrylate, or either one.
In this specification, “monomer” and “monomer” have the same meaning, and “polymer” and “polymer” have the same meaning.

<Adhesive sheet>
The pressure-sensitive adhesive sheet of the present invention includes an acrylic copolymer, a polyfunctional monomer having two or more reactive double bonds in a molecule, a monofunctional monomer having one reactive double bond in a molecule, hydrogen It is formed from a pressure-sensitive adhesive composition containing a pull-out type photopolymerization initiator and a self-cleaving type photopolymerization initiator.

  Since the pressure-sensitive adhesive sheet of the present invention has the above configuration, it can exhibit excellent substrate adhesion. For example, excellent substrate adhesion can be exhibited even under high temperature and high humidity conditions such as 85 ° C. and 85% relative humidity. Further, the pressure-sensitive adhesive sheet of the present invention exhibits excellent durability even when left under high temperature and high humidity conditions for a long time. In the present specification, the substrate adhesion can be evaluated, for example, by measuring the constant load peeling distance by the method described in the examples. When the constant load peeling distance is smaller than 25 mm, it can be determined that the substrate adhesion is good. It is particularly preferable that the constant load peeling distance is smaller than 5 mm.

  The pressure-sensitive adhesive sheet of the present invention preferably has post-curability (active energy ray curability), and the gel fraction of the pressure-sensitive adhesive sheet before irradiation with active energy rays (before post-curing) is 20% by mass or less. Preferably, it is 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less. The gel fraction of the pressure-sensitive adhesive sheet may be 0% by mass.

In the present specification, by irradiating the adhesive sheet with active energy rays under the following conditions, the gel fraction of the adhesive sheet has increased by 10% by mass or more, and the adhesive sheet has post-curability. I can say. When the pressure-sensitive adhesive sheet is post-cured by irradiating with an active energy ray, an optical transparent PET separator is attached to both surfaces of the pressure-sensitive adhesive sheet, and an active energy ray (high-pressure mercury lamp or metal halide lamp) is applied from the optical transparent PET separator side. Irradiation is performed so that the integrated light amount becomes 3000 mJ / cm ² .

  The gel fraction of the pressure-sensitive adhesive sheet after post-curing is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more.

The gel fraction of the pressure-sensitive adhesive sheet is a value measured by the following method. First, about 0.1 g of the adhesive sheet is collected in a sample bottle, 30 ml of ethyl acetate is added, and shaken for 24 hours. Thereafter, the contents of the sample bottle are filtered off with a 150-mesh stainless steel wire mesh, and the residue on the wire mesh is dried at 100 ° C. for 1 hour, and the dry mass (g) is measured. From the obtained dry mass, the gel fraction is determined by the following formula 1.
Gel fraction (% by mass) = (dry mass / collected mass of adhesive sheet) × 100 formula 1

The shear storage modulus at 23 ° C. and a frequency of 1 Hz of the pressure-sensitive adhesive sheet before post-curing is preferably 1.0 × 10 ⁴ Pa or more, more preferably 5.0 × 10 ⁴ Pa or more. Further, the shear storage modulus at 23 ° C. and a frequency of 1 Hz of the pressure-sensitive adhesive sheet is preferably 1.0 × 10 ⁶ Pa or less, more preferably 5.0 × 10 ⁵ Pa or less. The above-mentioned shear storage modulus is the shear storage modulus of the uncured pressure-sensitive adhesive sheet.

The pressure-sensitive adhesive sheet that was post-cured by irradiating the pressure-sensitive adhesive sheet with active energy rays so that the integrated light amount became 3000 mJ / cm ² had a shear storage modulus at 23 ° C. and a frequency of 1 Hz of 1.0 × 10 ⁶ Pa. It is preferably larger than 2.0 × 10 ⁶ Pa, more preferably 3.0 × 10 ⁶ Pa or more. The post-cured pressure-sensitive adhesive sheet preferably has a shear storage modulus at 23 ° C. and a frequency of 1 Hz of 5.0 × 10 ⁸ Pa or less.

  The shear storage modulus of the pressure-sensitive adhesive sheet can be measured using a dynamic viscoelasticity device. As the dynamic viscoelastic device, for example, Rheogel-E4000 (manufactured by UBM Corporation) can be mentioned. In the measurement, the shear storage modulus G 'of the pressure-sensitive adhesive layer in a temperature range from 0 ° C to 150 ° C is measured under the conditions of a solid shear mode, a frequency of 1 Hz, and a strain of 0.1%.

When the adhesive sheet is post-cured by irradiating the adhesive sheet with active energy rays so that the integrated light amount becomes 3000 mJ / cm ² , the elongation at break in the tensile test measurement at a tensile speed of 10 mm / min after the post-curing is 300%. It is preferably at least 400%, more preferably at least 400%, even more preferably at least 500%. Further, the elongation at break of the post-cured pressure-sensitive adhesive sheet in a tensile test measurement at a tensile speed of 10 mm / min is preferably 3000% or less, more preferably 2000% or less. Here, the breaking elongation is measured according to JIS K 7161-1. At that time, the tensile speed is 10 mm / min, and the measurement is performed at 23 ° C. and a relative humidity of 50%. Further, as a measurement sample, a pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) having a thickness of 25 μm, a width of 60 mm, and a length of 200 mm, which is rounded in the length direction and processed into a columnar shape having a cross-sectional area of 5 mm ² and a height of 60 mm, is used. This is pulled so that the distance between the chucks becomes 30 mm, and the elongation at break of the sample is defined as the elongation at break. As a measuring instrument, for example, an autograph AGS-X manufactured by Shimadzu Corporation can be used.

The probe tack value of the pressure-sensitive adhesive sheet measured at 23 ° C. under the following measurement conditions is preferably 1.0 N / 5 mmφ or more, and more preferably 1.5 N / 5 mmφ or more. Further, the probe tack value of the pressure-sensitive adhesive sheet measured at 23 ° C. under the following measurement conditions is preferably 20 N / 5 mmφ or less, more preferably 15 N / 5 mmφ or less. The probe tack value is the probe tack value of the uncured pressure-sensitive adhesive sheet.
(Measurement conditions of probe tack value)
Measuring equipment: NS probe tack tester (Nichiban Co., Ltd.)
Probe diameter: 5mmφ
Probe base material: stainless steel surface finish AA # 400 Polished mirror surface weight: 19.6 ± 0.2 g (made of brass)
Probe moving speed: 1.0 cm / sec Duel time: 1 sec

The probe tack value of the pressure-sensitive adhesive sheet post-cured by irradiating the pressure-sensitive adhesive sheet with active energy rays so that the integrated light amount becomes 3000 mJ / cm ² is preferably 1.0 N / 5 mmφ or less, and 0.5 N or less. / 5 mmφ or less, more preferably 0.1 N / 5 mmφ or less. The probe tack value of the post-cured adhesive sheet may be 0 N / 5 mmφ.

  The thickness of the pressure-sensitive adhesive sheet can be appropriately set according to the use, and is not particularly limited, but is preferably 5 to 500 μm, more preferably 10 to 300 μm, and particularly preferably 12 to 100 μm. By setting the thickness of the pressure-sensitive adhesive sheet within the above range, the substrate adhesion and the durability under high-temperature and high-humidity conditions can be more effectively increased. Further, since the sticking out and stickiness of the pressure-sensitive adhesive can be suppressed, workability can be improved. Further, by setting the thickness of the pressure-sensitive adhesive sheet within the above range, the production of the double-sided pressure-sensitive adhesive sheet becomes easy.

  The pressure-sensitive adhesive sheet of the present invention may be a single-layer pressure-sensitive adhesive sheet composed of only a pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet may be a single-sided pressure-sensitive adhesive sheet having a substrate (preferably a transparent substrate) on one side or a double-sided pressure-sensitive adhesive sheet. As a double-sided pressure-sensitive adhesive sheet, a single-layer pressure-sensitive adhesive sheet composed of a pressure-sensitive adhesive layer, a multilayer pressure-sensitive adhesive sheet in which a plurality of pressure-sensitive adhesive layers are laminated, a multilayer pressure-sensitive adhesive in which another pressure-sensitive adhesive layer is laminated between the pressure-sensitive adhesive layers Sheet, a multi-layer pressure-sensitive adhesive sheet in which a support is laminated between pressure-sensitive adhesive layers, a multi-layer pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is laminated on one side of the support and another pressure-sensitive adhesive layer is laminated on the other side Is mentioned. When the double-sided pressure-sensitive adhesive sheet has a support, it is preferable to use a transparent support as the support. As the support, a general film used in the optical field as well as the transparent substrate can be used. Such a double-sided pressure-sensitive adhesive sheet has excellent transparency as a whole pressure-sensitive adhesive sheet, and thus can be suitably used for bonding optical members.

  When the pressure-sensitive adhesive sheet of the present invention is a single-sided pressure-sensitive adhesive sheet, the pressure-sensitive adhesive sheet 11 may have a configuration in which a transparent substrate 12a is provided on one side, as shown in FIG. In this case, it is preferable that the other surface of the adhesive sheet 11 is covered with the release sheet 12b. When an adhesive sheet is used, the release sheet 12b is peeled off and bonded so that the adhesive sheet 11 is in close contact with a desired adherend, and then cured (post-cured) by irradiating active energy rays or the like. Is preferred. As the transparent substrate, a general film used in the optical field such as a polyethylene terephthalate film, an acrylic film, a polycarbonate film, a triacetyl cellulose film, and a cycloolefin polymer film can be used. Further, an easy-adhesion layer may be provided on the pressure-sensitive adhesive sheet side of these transparent substrates. Further, a functional layer such as a hard coat layer, an antireflection layer, an antifouling layer, and an ultraviolet absorbing layer may be provided on the surface of the transparent substrate opposite to the adhesive sheet.

  The present invention may be related to a pressure-sensitive adhesive sheet with a release sheet provided with release sheets on both surfaces of the pressure-sensitive adhesive sheet. When release sheets are provided on both surfaces of the pressure-sensitive adhesive sheet of the present invention, it is preferable to have release sheets 12a and 12b on both surfaces of the pressure-sensitive adhesive sheet 11, as shown in FIG.

As the release sheet, a release laminate sheet having a release sheet substrate and a release agent layer provided on one surface of the release sheet substrate, or a polyolefin film such as a polyethylene film or a polypropylene film as a low polarity substrate Is mentioned.
Papers and polymer films are used as the release sheet base material in the release laminate sheet. As the release agent constituting the release agent layer, for example, a general-purpose addition-type or condensation-type silicone release agent or a compound having a long-chain alkyl group is used. In particular, an addition type silicone release agent having high reactivity is preferably used.
Specific examples of the silicone release agent include BY24-4527 and SD-7220 manufactured by Dow Corning Toray Silicone Co., Ltd., and KS-3600, KS-774, and X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd. Is mentioned. Further, the silicone-based release agent may contain a silicone resin which is an organosilicon compound having SiO ₂ units and (CH ₃ ) ₃ SiO _1/2 units or CH ₂ ＣＨCH (CH ₃ ) SiO _1/2 units. preferable. Specific examples of the silicone resin include BY24-843, SD-7292, SHR-1404 manufactured by Dow Corning Toray Silicone Co., Ltd., and KS-3800, X92-183 manufactured by Shin-Etsu Chemical Co., Ltd.
A commercially available product may be used as the peelable laminated sheet. For example, a heavy separator film that is a release-treated polyethylene terephthalate film manufactured by Teijin Dupont Film Co., Ltd., and a light separator film that is a release-treated polyethylene terephthalate film manufactured by Teijin Dupont Film Co., Ltd. may be mentioned. it can.

  When the pressure-sensitive adhesive sheet of the present invention is a double-sided pressure-sensitive adhesive sheet, the pressure-sensitive adhesive sheet preferably has a pair of release sheets having different peeling forces. That is, the release sheet preferably has different release properties between the release sheet 12a and the release sheet 12b in order to facilitate release. If the releasability from one side is different from the releasability from the other, it becomes easy to peel off only the release sheet having the higher releasability first. In this case, the releasability of the release sheet 12a and the release sheet 12b may be adjusted according to the bonding method and the bonding order.

  Further, the present invention may relate to a pressure-sensitive adhesive sheet with a transparent film provided with a transparent film on at least one surface of the pressure-sensitive adhesive sheet. In this case, the transparent film is preferably at least one selected from a polyethylene terephthalate film, an acrylic film, a polycarbonate film, a triacetyl cellulose film, and a cycloolefin polymer film. The adhesive sheet with a transparent film may be a sheet in which a transparent film / an adhesive sheet / a release sheet is laminated in this order.

<Acrylic copolymer>
The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive sheet contains an acrylic copolymer. The acrylic copolymer is not particularly limited as long as it has an acrylic monomer unit, but it is preferable that the acrylic copolymer has a degree of transparency that does not reduce the visibility of the display device. For example, it is preferable that the acrylic copolymer contains a unit derived from a (meth) acrylate having a crosslinkable functional group. In the present specification and claims, "unit" is a repeating unit (monomer unit) constituting a polymer.

The crosslinkable functional group is preferably at least one selected from a carboxy group, a hydroxy group, an amino group, an amide group, an epoxy group and an isocyanate group, and is selected from a carboxy group, a hydroxy group, an amino group and an epoxy group. More preferably, it is at least one kind.
Examples of the carboxy group-containing monomer unit include acrylic acid and methacrylic acid.
The hydroxy group-containing monomer unit is a repeating unit derived from the hydroxy group-containing monomer. Examples of the hydroxy group-containing monomer include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxypropyl (meth) acrylate; (Meth) acrylic acid [(mono, di or poly) alkylene glycol] such as (meth) acrylic acid mono (diethylene glycol), and (meth) acrylic acid lactone such as (meth) acrylic acid monocaprolactone.
Examples of the amino group-containing monomer unit include a repeating unit derived from an amino group-containing monomer such as (meth) acrylamide and allylamine.
Examples of the epoxy group-containing monomer unit include a repeating unit derived from a glycidyl group-containing monomer such as glycidyl (meth) acrylate.

  The acrylic copolymer preferably further contains a non-crosslinkable (meth) acrylate unit. The non-crosslinkable (meth) acrylate unit is preferably a repeating unit derived from an alkyl (meth) acrylate. Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylate. Isobutyl acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, ( Isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-undecyl (meth) acrylate, (meth) N-dodecyl acrylate, stearyl (meth) acrylate, methoxyethyl (meth) acrylate, ) Ethoxyethyl acrylate, cyclohexyl (meth) acrylate include benzyl (meth) acrylate and the like. One of these may be used alone, or two or more thereof may be used in combination.

  Among them, the acrylic copolymer preferably contains a unit derived from an alkoxyalkyl group-containing (meth) acrylate, a unit derived from a hydroxy group-containing (meth) acrylate, and a unit derived from methyl (meth) acrylate.

<Alkoxyalkyl group-containing (meth) acrylate>
The alkoxyalkyl group-containing (meth) acrylate is an alkoxyalkyl (meth) acrylate. As the alkoxyalkyl (meth) acrylate, for example, an alkoxyalkyl (meth) acrylate in which the alkoxy group has 1 to 12 carbon atoms and the alkylene group bonded to the alkoxy group has 1 to 18 carbon atoms is preferable. The alkoxy group preferably has 1 to 8 carbon atoms, more preferably has 1 to 4 carbon atoms, and particularly preferably has 1 or 2 carbon atoms. The alkylene group bonded to the alkoxy group preferably has 1 to 12 carbon atoms, more preferably 1 to 8, more preferably 1 to 4, and particularly preferably 1 to 3. preferable.

  Examples of such alkoxyalkyl (meth) acrylates include 2-methoxymethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxymethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, Examples thereof include 3-methoxypropyl (meth) acrylate, 3-ethoxypropyl (meth) acrylate, 4-methoxybutyl (meth) acrylate, and 4-ethoxybutyl (meth) acrylate. Among these, 2-methoxyethyl (meth) acrylate is particularly preferred. By using 2-methoxyethyl (meth) acrylate as the alkoxyalkyl (meth) acrylate, the pressure-sensitive adhesive sheet can increase the wettability to the substrate while suppressing stickiness.

  The content of the unit derived from the alkoxyalkyl group-containing (meth) acrylate is preferably 50% by mass or more, more preferably 55% by mass or more, based on the total mass of the acrylic copolymer. More preferably, it is not less than mass%. The content of the unit derived from the alkoxyalkyl group-containing (meth) acrylate is preferably 90% by mass or less based on the total mass of the acrylic copolymer. By setting the content of the unit derived from the alkoxyalkyl group-containing (meth) acrylate within the above range, the pressure-sensitive adhesive sheet can easily adhere to the base material, while the post-cured pressure-sensitive adhesive sheet has high hardness. , High temperature durability and workability can be further improved.

<Hydroxy group-containing (meth) acrylate>
Examples of the hydroxy group-containing (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 3-chloro-2-hydroxypropyl (meth). Examples thereof include acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, and polyalkylene glycol mono (meth) acrylate. Above all, at least one selected from 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate is preferably used.

  The content of the unit derived from the hydroxy group-containing (meth) acrylate is preferably 5% by mass or more, more preferably 7% by mass or more, based on the total mass of the acrylic copolymer. Further, the content of the unit derived from the hydroxy group-containing (meth) acrylate is preferably 35% by mass or less, more preferably 30% by mass or less, based on the total mass of the acrylic copolymer. By setting the content of the unit derived from the hydroxy group-containing (meth) acrylate within the above range, the adhesion to the adherend can be further improved.

<Alkyl (meth) acrylate>
The acrylic copolymer contains a unit derived from methyl (meth) acrylate. The content of the unit derived from methyl (meth) acrylate is preferably at least 5% by mass, more preferably at least 7% by mass, based on the total mass of the acrylic copolymer. Further, the content of the unit derived from methyl (meth) acrylate is preferably 15% by mass or less, more preferably 10% by mass or less, based on the total mass of the acrylic copolymer.

  The acrylic copolymer may contain a unit derived from an alkyl (meth) acrylate in addition to a unit derived from a methyl (meth) acrylate. Examples of the alkyl (meth) acrylate include ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, and cetyl ( Examples include alkyl (meth) acrylates such as (meth) acrylate, stearyl (meth) acrylate, and behenyl (meth) acrylate. The content of the unit derived from the alkyl (meth) acrylate other than methyl (meth) acrylate is preferably 1% by mass or more, and more preferably 3% by mass or more based on the total mass of the acrylic copolymer. More preferred. Further, the content of units derived from alkyl (meth) acrylate other than methyl (meth) acrylate is preferably 50% by mass or less based on the total mass of the acrylic copolymer. By setting the content of the unit derived from an alkyl (meth) acrylate other than methyl (meth) acrylate within the above range, it is possible to increase the adhesion to the substrate while suppressing stickiness (tackiness).

<Other monomers>
It is preferable that the acrylic copolymer further contains a unit derived from a nitrogen-containing monomer. The unit derived from the nitrogen-containing monomer may be a unit derived from the above-mentioned (meth) acrylate having a crosslinkable functional group.

  The nitrogen-containing monomer is a monomer containing a nitrogen element in one molecule. Examples of the nitrogen-containing monomer include, for example, dimethylacrylamide, diethylacrylamide, acryloylmorpholine, hydroxyethylacrylamide, methylolacrylamide, methoxymethylacrylamide, ethoxymethylacrylamide, dimethylaminoethylacrylamide, N-vinylcaprolactam, N-vinyl-2-vinyl Examples include pyrrolidone, dimethylaminoethyl (meth) acrylate, N-vinylformamide, (meth) acrylonitrile, vinylpyrrolidone, and vinylpyridine. Among them, the nitrogen-containing monomer is preferably at least one selected from an acrylamide derivative, an amino group-containing monomer, and a nitrogen-containing heterocycle-containing monomer, and more preferably an acrylamide derivative. The acrylamide derivative is more preferably at least one selected from dimethylacrylamide, diethylacrylamide and acryloylmorpholine, and particularly preferably dimethylacrylamide. The acrylic copolymer contains a unit derived from a nitrogen-containing monomer as described above, so that the pressure-sensitive adhesive sheet easily adheres to the base material, while the post-cured pressure-sensitive adhesive sheet has a high hardness. , High temperature durability and workability can be further improved.

  The content of the unit derived from the nitrogen-containing monomer is preferably at least 1% by mass, more preferably at least 3% by mass, based on the total mass of the acrylic copolymer. The content of the unit derived from the nitrogen-containing monomer is preferably 20% by mass or less based on the total mass of the acrylic copolymer.

  The acrylic copolymer may have other monomer units in addition to the above-mentioned monomer units, if necessary. The other monomer may be any copolymerizable with the above-mentioned acrylic monomer, and examples thereof include vinyl acetate, styrene, and vinyl chloride. The content of the other monomer units in the acrylic copolymer is preferably 20% by mass or less, more preferably 15% by mass or less.

<Weight average molecular weight of acrylic copolymer>
The weight average molecular weight of the acrylic copolymer is preferably 100,000 to 2,000,000, and more preferably 200,000 to 1.5,000,000. When the weight average molecular weight is within the above range, the pressure-sensitive adhesive sheet tends to have high hardness when post-cured, and is excellent in workability. The weight average molecular weight is a value measured by size exclusion chromatography (SEC) and determined based on polystyrene. As the acrylic copolymer, a commercially available product may be used, or a product synthesized by a known method may be used.

<Polyfunctional monomer>
The pressure-sensitive adhesive composition contains a polyfunctional monomer having two or more reactive double bonds in the molecule. The polyfunctional monomer has two or more reactive double bonds. Among them, the polyfunctional monomer preferably has two or more and less than five reactive double bonds. It is more preferable to have at least four.

  Examples of the polyfunctional monomer include ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, and 1,3-butylene glycol (meth) acrylate. 4-butylene glycol, 1,9-nonanediol di (meth) acrylate, 1,6-hexanediol diacrylate, polybutylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, di (meth) acrylate ) Tetraethylene glycol acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, tetra (meth) acryl Polyvalent alcohols such as pentaerythritol acid (Meth) acrylic acid esters of Le, and vinyl methacrylate.

  Commercial products can be used as the polyfunctional monomer. Examples of commercially available products include trimethylolpropane propylene oxide-modified triacrylate (Toagosei Co., Ltd., Aronix M-321), a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (Toagosei Co., Ltd., Alonix M-405), manufactured by Toagosei Co., Ltd., and a bifunctional monomer M240 (polyethylene glycol diacrylate).

  The glass transition temperature (Tg) when the polyfunctional monomer is a homopolymer is preferably lower than 65 ° C, more preferably lower than 60 ° C. The glass transition temperature (Tg) when the polyfunctional monomer is a homopolymer is preferably −35 ° C. or higher. By setting the glass transition temperature (Tg) when the polyfunctional monomer is a homopolymer within the above range, curling of the pressure-sensitive adhesive sheet is suppressed even when the pressure-sensitive adhesive sheet is placed under high-temperature conditions. be able to. Examples of the polyfunctional monomer having a glass transition temperature (Tg) within the above range when the polyfunctional monomer is a homopolymer include, for example, trimethylolpropane propylene oxide-modified triacrylate (manufactured by Toagosei Co., Ltd. Alonix M-321) and a bifunctional monomer M240 (polyethylene glycol diacrylate) manufactured by Toagosei Co., Ltd.

  The content of the polyfunctional monomer is preferably 5 to 40 parts by mass, more preferably 5 to 30 parts by mass, based on 100 parts by mass of the acrylic copolymer. One of the above polyfunctional monomers may be used alone, or two or more may be used in combination. When two or more are used in combination, the total mass is preferably within the above range. By setting the content of the polyfunctional monomer in the above range, the hardness of the post-cured pressure-sensitive adhesive sheet can be more effectively increased, and the workability of the pressure-sensitive adhesive sheet can be improved.

<Monofunctional monomer>
The pressure-sensitive adhesive composition contains a monofunctional monomer having one reactive double bond in the molecule.

  Monofunctional monomers include, for example, isobornyl acrylate, isostearyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, benzyl methacrylate, N-acryloyloxyethyl hexahydrophthalimide, acrylamide, N, N-dimethylacrylamide, N , N-diethylacrylamide, acryloylmorpholine, vinylpyrrolidone, and the like. Above all, the monofunctional monomer is preferably an alkyl (meth) acrylate, preferably at least one selected from isobornyl acrylate and isostearyl acrylate, and more preferably isobornyl acrylate. preferable. Examples of commercially available monofunctional monomers include IBXA manufactured by Osaka Organic Chemical Industry Co., Ltd., and ISTA manufactured by Osaka Organic Chemical Industry Co., Ltd.

  The glass transition temperature (Tg) of the homopolymer when a monofunctional monomer is polymerized is preferably −20 ° C. or higher, more preferably 0 ° C. or higher, even more preferably 50 ° C. or higher, The temperature is more preferably 55 ° C or higher, and particularly preferably 60 ° C or higher. The glass transition temperature (Tg) of the homopolymer obtained by polymerizing the monofunctional monomer is preferably 180 ° C. or lower, more preferably 150 ° C. or lower.

  The content of the monofunctional monomer is preferably from 1 to 20 parts by mass, more preferably from 2 to 20 parts by mass, based on 100 parts by mass of the acrylic copolymer. One of the above monofunctional monomers may be used alone, or two or more may be used in combination. When two or more are used in combination, the total mass is preferably in the above range.

  Further, the total content of the monofunctional monomer and the polyfunctional monomer is preferably 6 to 50 parts by mass, more preferably 10 to 45 parts by mass with respect to 100 parts by mass of the acrylic copolymer. And more preferably 15 to 40 parts by mass. By setting the total content of the monofunctional monomer and the polyfunctional monomer within the above range, it is possible to obtain a pressure-sensitive adhesive sheet having excellent workability, in which the end face is not sticky after post-curing.

<Hydrogen abstraction type photopolymerization initiator>
The pressure-sensitive adhesive composition contains a hydrogen abstraction type photopolymerization initiator. The hydrogen abstraction type photopolymerization initiator is for initiating the polymerization reaction of the above-mentioned acrylic copolymer or acrylic monomer by irradiation with active energy rays. The hydrogen abstraction type photopolymerization initiator is a photopolymerization initiator that forms an exciplex with the photoexcited initiator and the hydrogen donor in the system, and promotes polymerization by transferring hydrogen of the hydrogen donor.

  Examples of the hydrogen abstraction type photopolymerization initiator include, for example, benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, 3,3′-dimethyl-4-methoxybenzophenone, 2,4,6-trimethyl Benzophenone, 4-methylbenzophenone, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, camphorquinone, dibenzosuberone, 2-ethylanthraquinone, 3 , 3 ', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone, benzyl, 9,10-phenanthrenequinone and the like. Above all, the hydrogen abstraction type photopolymerization initiator is preferably a benzophenone-based photopolymerization initiator. Examples of the benzophenone-based photopolymerization initiator include benzophenone, 4-methylbenzophenone and 2,4,6-trimethyl. Benzophenone and the like can be mentioned.

  The content of the hydrogen-abstraction-type photopolymerization initiator in the pressure-sensitive adhesive composition is preferably at least 0.1 part by mass, and more preferably at least 0.3 part by mass with respect to 100 parts by mass of the acrylic copolymer. Is more preferred. Further, the content of the hydrogen abstraction type photopolymerization initiator is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, based on 100 parts by mass of the acrylic copolymer. By setting the content of the hydrogen-abstraction-type photopolymerization initiator within the above range, yellowing of the pressure-sensitive adhesive sheet can be suppressed while sufficiently increasing the hardness when the pressure-sensitive adhesive sheet is post-cured.

  Commercial products can be used as the hydrogen abstraction type photopolymerization initiator. Examples of commercially available products include Speed Cure MBP and Speed Cure TZT manufactured by LAMBSON.

<Self-cleavable photopolymerization initiator>
The pressure-sensitive adhesive composition contains a self-cleavable photopolymerization initiator. The self-cleaving photopolymerization initiator starts the polymerization reaction of the above-mentioned acrylic copolymer or acrylic monomer by irradiation with active energy rays. In the present invention, by using a self-cleaving type photopolymerization initiator and a hydrogen abstraction type photopolymerization initiator in combination, the pressure-sensitive adhesive sheet can exhibit higher hardness when it is post-cured, and has excellent substrate adhesion and durability. Can be increased. Also, by using a self-cleaving photopolymerization initiator and a hydrogen abstraction photopolymerization initiator together, a polymer composed of a polyfunctional monomer or a monofunctional monomer polymerized by the self-cleaving photoinitiator and an acrylic The copolymer and the copolymer can be bonded by a chemical bond using a hydrogen abstraction initiator, and as a result, the curl resistance of the pressure-sensitive adhesive sheet can be improved.

Examples of the self-cleavable photopolymerization initiator include, for example, acetophenone-based initiator, benzoin ether-based initiator, benzophenone-based initiator, hydroxyalkylphenone-based initiator, thioxanthone-based initiator, amine-based initiator, and acylphosphine oxide-based initiator. Agents and the like.
Specific examples of the acetophenone-based initiator include diethoxyacetophenone and benzyldimethyl ketal.
Specific examples of the benzoin ether-based initiator include benzoin and benzoin methyl ether.
Specific examples of the benzophenone-based initiator include benzophenone and methyl o-benzoylbenzoate.
Specific examples of the hydroxyalkylphenone-based initiator include 1-hydroxy-cyclohexyl-phenyl-ketone (manufactured by BASF Japan Ltd., commercially available as IRGACURE 184).
Specific examples of the thioxanthone-based initiator include 2-isopropylthioxanthone and 2,4-dimethylthioxanthone.
Specific examples of the amine initiator include triethanolamine and ethyl 4-dimethylbenzoate.
Specific examples of the acylphosphine oxide-based initiator include phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide (manufactured by BASF Japan Ltd., commercially available as IRGACURE819).

  The content of the self-cleavable photopolymerization initiator in the pressure-sensitive adhesive composition is preferably at least 0.1 part by mass, and more preferably at least 0.3 part by mass with respect to 100 parts by mass of the acrylic copolymer. Is more preferable, and it is further preferable that the amount is 0.5 parts by mass or more. The content of the self-cleaving photopolymerization initiator is preferably 5.0 parts by mass or less based on 100 parts by mass of the acrylic copolymer. By setting the content of the self-cleaving photopolymerization initiator within the above range, the hardness when the pressure-sensitive adhesive sheet is post-cured can be sufficiently increased.

<Thermosetting crosslinking agent>
In the pressure-sensitive adhesive sheet of the present invention, the content of the thermosetting crosslinking agent is preferably 0.1% by mass or less based on the total weight of the pressure-sensitive adhesive sheet. This means that the pressure-sensitive adhesive sheet contains substantially no thermosetting crosslinking agent. That is, in the pressure-sensitive adhesive sheet, the content of the thermosetting crosslinking agent is more preferably 0% by mass based on the total mass of the pressure-sensitive adhesive sheet. Examples of the thermosetting crosslinking agent include known crosslinking agents such as isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, and butylated melamine compounds.

  In the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive sheet contains the acrylic monomer as described above, and further, since the pressure-sensitive adhesive sheet does not substantially contain a thermosetting crosslinker, the pressure-sensitive adhesive sheet does not need to be provided with an aging step. Necessary adhesive properties and the like can be exhibited. In addition, the pressure-sensitive adhesive sheet can exhibit excellent workability. Specifically, stickiness of the end surface of the pressure-sensitive adhesive sheet is suppressed, and for example, adhesion of the pressure-sensitive adhesive to the punching blade during punching, deformation of the pressure-sensitive adhesive sheet, and the like can be prevented. Furthermore, since the pressure-sensitive adhesive sheet does not substantially contain a thermosetting crosslinking agent, the pressure-sensitive adhesive sheet can easily exhibit excellent substrate adhesion and durability even under high temperature and high humidity conditions.

<Solvent>
The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive sheet may include a solvent. In this case, the solvent is used for improving the coating suitability of the pressure-sensitive adhesive composition. Examples of the solvent include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; halogenated hydrocarbons such as dichloromethane, trichloroethane, trichloroethylene, tetrachloroethylene, and dichloropropane; methanol, ethanol, Alcohols such as propanol, isopropyl alcohol, butanol, isobutyl alcohol and diacetone alcohol; ethers such as diethyl ether, diisopropyl ether, dioxane and tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone and cyclohexanone; methyl acetate Esters such as ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, ethyl butyrate; Chi glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, polyols and derivatives thereof such as propylene glycol monomethyl ether acetate.

The content of the solvent in the pressure-sensitive adhesive composition is not particularly limited, but is preferably 25 to 500 parts by mass, more preferably 30 to 400 parts by mass, per 100 parts by mass of the acrylic copolymer.
Further, the content of the solvent is preferably from 10 to 90% by mass, more preferably from 20 to 80% by mass, based on the total mass of the pressure-sensitive adhesive composition. One type of solvent may be used alone, or two or more types may be used in combination. When two or more types are used in combination, the total mass is preferably within the above range. A part of the solvent in the pressure-sensitive adhesive composition may remain on the pressure-sensitive adhesive sheet.

<Other components>
The pressure-sensitive adhesive sheet may contain other components other than the above as long as the effects of the present invention are not impaired. As other components, components known as additives for adhesives can be exemplified. For example, a plasticizer, an antioxidant, a metal corrosion inhibitor, a tackifier, a silane coupling agent, an ultraviolet absorber, a light stabilizer such as a hindered amine compound or the like can be selected as necessary. Further, a dye or a pigment may be added for the purpose of coloring.
Examples of the plasticizer include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, and benzoate. Examples include carboxylic acid vinyl esters such as vinyl acid and styrene.
Examples of the antioxidant include a phenolic antioxidant, an amine antioxidant, a lactone antioxidant, a phosphorus antioxidant, and a sulfur antioxidant. One of these antioxidants may be used alone, or two or more thereof may be used in combination.
As the metal corrosion inhibitor, a benzotriazole-based resin can be mentioned as a preferred example in view of the compatibility and the high effect of the pressure-sensitive adhesive.
Examples of the tackifier include a rosin resin, a terpene resin, a terpene phenol resin, a coumarone indene resin, a styrene resin, a xylene resin, a phenol resin, and a petroleum resin.
Examples of the silane coupling agent include a mercaptoalkoxysilane compound (for example, a mercapto group-substituted alkoxy oligomer and the like).
Examples of the ultraviolet absorber include a benzotriazole-based compound and a benzophenone-based compound. However, when ultraviolet rays are used as the active energy rays at the time of post-curing, it is preferable to add them within a range that does not inhibit the polymerization reaction.

<Production method of adhesive sheet>
The method for producing a pressure-sensitive adhesive sheet of the present invention preferably includes a step of applying a pressure-sensitive adhesive composition on a release sheet to form a coating film. The application of the pressure-sensitive adhesive composition can be performed using a known coating device. Examples of the coating device include a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a microgravure coater, a rod blade coater, a lip coater, a die coater, a curtain coater, and the like.

  The method for producing the pressure-sensitive adhesive sheet preferably includes a step of heating the coating film. In this case, a known heating device such as a heating furnace or an infrared lamp can be used for heating the coating film formed by applying the pressure-sensitive adhesive composition.

  As described above, it is preferable that the pressure-sensitive adhesive composition has substantially no thermosetting crosslinking agent. In such a case, it is not necessary to perform an aging treatment in which the pressure-sensitive adhesive sheet is allowed to stand at a constant temperature for a certain period of time after coating. Therefore, it is possible to provide a pressure-sensitive adhesive sheet capable of exhibiting necessary pressure-sensitive adhesive properties without providing an aging step, and it is possible to suppress the production cost of the pressure-sensitive adhesive sheet.

<How to use the adhesive sheet>
In the method of using the pressure-sensitive adhesive sheet of the present invention, it is preferable that the pressure-sensitive adhesive sheet of the pressure-sensitive adhesive sheet is brought into contact with the surface of the adherend. In particular, when the pressure-sensitive adhesive sheet is in an uncured state, it is preferable that the pressure-sensitive adhesive sheet is bonded to an adherend, and the pressure-sensitive adhesive sheet is cured by, for example, irradiating active energy rays.

<Applications of adhesive sheet>
The pressure-sensitive adhesive sheet of the present invention is preferably used for optical members that require durability even under high-temperature and high-humidity conditions, particularly for applications that require a punching process or a cutting process after forming a laminate having a complicated shape.

<Laminate>
The present invention also relates to a laminate including the above-mentioned pressure-sensitive adhesive sheet cured by irradiating the pressure-sensitive adhesive sheet with an active energy ray, and an adherend on at least one surface side of the cured pressure-sensitive adhesive sheet. Here, the adherend is more preferably a substrate and an optical member, and particularly preferably a TAC film, a polycarbonate substrate, a polarizing plate, a transparent film, a transparent resin, or glass.

  FIG. 2 is a schematic diagram illustrating a cross section of an example of the laminate of the present invention. FIG. 2 is a cross-sectional view illustrating an example of a configuration of a laminate 20 in which the pressure-sensitive adhesive sheet 21 of the present invention is bonded to a base material 22 and an optical member 24. As shown in FIG. 2, the pressure-sensitive adhesive sheet 21 of the present invention is preferably used for bonding to a substrate 22, and may be used for bonding the substrate 22 to another optical member 24. preferable. Note that the pressure-sensitive adhesive sheet 21 of the present invention may be used for bonding to a polarizing plate.

Examples of the optical member included in the laminate include various components in optical products such as a touch panel and an image display device, and a scattering prevention film bonded to the outermost cover lens. As a constituent member of the touch panel, for example, an ITO film in which an ITO film is provided on a transparent resin film, an ITO glass in which an ITO film is provided on a surface of a glass plate, a transparent conductive film in which a conductive polymer is coated on a transparent resin film, Hard coat films, fingerprint resistant films and the like can be mentioned. The constituent members of the image display device include, for example, an antireflection film, an alignment film, a polarizing film, a retardation film, and a brightness enhancement film used for a liquid crystal display device.
Examples of materials used for these members include glass, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polyethylene naphthalate, cycloolefin polymers, triacetyl cellulose, polyimide, and cellulose acylate.

  When the pressure-sensitive adhesive sheet of the present invention is a double-sided pressure-sensitive adhesive sheet, it can be used for bonding two adherends. In this case, the pressure-sensitive adhesive sheet of the present invention is used for bonding the transparent optical films inside the touch panel, bonding the transparent optical film and the glass, bonding the transparent optical film of the touch panel to the liquid crystal panel, and covering the cover glass. It is used for laminating a transparent optical film with a cover glass, and laminating a cover glass and a transparent optical film, and is useful when any member is a resin plate such as a polycarbonate substrate. As the transparent optical film, general films used in the optical field such as a polyethylene terephthalate film, an acrylic film, a polycarbonate film, a triacetyl cellulose film, and a cycloolefin polymer film can be used. Further, a hard coat layer may be provided on the transparent optical film or the polycarbonate substrate.

  FIG. 3 is a schematic diagram illustrating a cross section of another example of the laminate of the present invention. As shown in FIG. 3, the adherend may have step portions (27a, 27b, 27c, 27d). In FIG. 3, the substrate has a step (27a, 27b), and the optical member has a step (27c, 27d). The thickness of the steps (27a, 27b, 27c, 27d) is usually 5 to 60 μm. As described above, the pressure-sensitive adhesive sheet 21 of the present invention can be bonded to a member having a step, and can follow irregularities generated from the step.

<Production method of laminate>
The present invention also relates to a method for producing a laminate including a step of curing the pressure-sensitive adhesive sheet by irradiating an active energy ray after bonding the pressure-sensitive adhesive sheet to an adherend. The method for producing a laminate preferably includes a step of bonding the above-described pressure-sensitive adhesive sheet of the pressure-sensitive adhesive sheet to an adherend in an uncured state, and then irradiating active energy rays to cure the pressure-sensitive adhesive sheet. Before the irradiation with the active energy ray, the pressure-sensitive adhesive sheet is in an uncured state, so that the initial adhesiveness to the substrate is improved. As described above, after the pressure-sensitive adhesive sheet is bonded to the adherend, the pressure-sensitive adhesive sheet is post-cured with active energy rays, whereby the cohesive force of the pressure-sensitive adhesive sheet is increased, and the adhesiveness to the adherend is improved. Further, the post-cured pressure-sensitive adhesive sheet can prevent the substrate from being deformed or distorted.

Examples of the active energy ray include an ultraviolet ray, an electron beam, a visible ray, an X-ray, and an ion beam, and can be appropriately selected depending on the polymerization initiator contained in the pressure-sensitive adhesive sheet. Above all, from the viewpoint of versatility, ultraviolet rays or electron beams are preferable, and ultraviolet rays are particularly preferable.
As the ultraviolet light source, for example, a high-pressure mercury lamp, a low-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a carbon arc, a xenon arc, and an electrodeless ultraviolet lamp can be used.
As the electron beam, for example, electron beams emitted from various types of electron beam accelerators such as Cockloft-Wald type, Bande-Crafts type, Resonant transformer type, Insulated core transformer type, Linear type, Dynamitron type and High frequency type are used. it can.
Radiation output of the UV, integrated light quantity is preferably to be a 100~10000mJ / cm ^2, and more preferably made to be 500~5000mJ / cm ^2.

  Hereinafter, features of the present invention will be described more specifically with reference to examples and comparative examples. Materials, usage amounts, ratios, processing contents, processing procedures, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples described below.

[Example 1]
<Synthesis of acrylic copolymer (A-1)>
Acrylic copolymer (A-1) was prepared by solution polymerization in ethyl acetate. 2-methoxyethyl acrylate monomer (MEA), 2-hydroxyethyl acrylate monomer (2HEA), methyl methacrylate (MMA), dimethyl acrylamide (DMAA) and butyl acrylate (BA) in a mass ratio of 70: 10: 10: 5: 5. And AIBN (azobisisobutyronitrile) was dissolved in the solution as a radical polymerization initiator. The solution was heated to 60 ° C. for random copolymerization to obtain an acrylic copolymer solution (A-1) having a solid content of 35% by mass and a solution viscosity at 23 ° C. of 2000 mPa · s.

  15 parts by mass of trimethylolpropane propylene oxide-modified triacrylate (manufactured by Toagosei Co., Ltd., trifunctional monomer M321, Tg = 50 ° C.) as a polyfunctional monomer with respect to 100 parts by mass of the acrylic copolymer solution (A-1) Parts, 15 parts by mass of isobornyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., IBXA, Tg = 97 ° C.) as a monofunctional monomer, and 1-hydroxy-cyclohexyl-phenyl-ketone as a self-cleavable photopolymerization initiator ( 0.7 parts by mass of BASF Japan Ltd., IRGACURE 184) and 0.5 parts by mass of 4-methylbenzophenone (manufactured by LAMBSON: 4MBP) as a hydrogen abstraction type photopolymerization initiator are added, and the solid content concentration is 40 parts by mass. % As a solvent to obtain a pressure-sensitive adhesive composition.

The pressure-sensitive adhesive composition was applied onto a first release sheet (a heavy separator film, a polyethylene terephthalate film manufactured by Teijin Dupont Co., Ltd., which was subjected to a release treatment). The coating was performed using a doctor blade YD type manufactured by Yoshimitsu Seiki Co., Ltd. so that the thickness after drying was 25 μm. Thereafter, the resultant was dried at 100 ° C. for 3 minutes using a hot air drier to remove the solvent, thereby forming an adhesive sheet.
A second release sheet (light separator film, manufactured by Teijin Dupont Film Co., Ltd.), which has been subjected to a release treatment having a higher releasability than the first release sheet, is attached to one side of the adhesive sheet, and the adhesive with the release sheet is attached. An adhesive sheet of Example 1 which was a sheet was obtained.

[Example 2]
Example 2 Example 2 was repeated in the same manner as in Example 1 except that isostearyl acrylate (ISTA, Tg = -18 ° C, manufactured by Osaka Organic Chemical Industry Co., Ltd.) was used instead of isobornyl acrylate as the monofunctional monomer. Was obtained.

[Example 3]
An adhesive sheet of Example 3 was obtained in the same manner as in Example 1 except that the polyfunctional monomer was changed to polyethylene glycol diacrylate (Toagosei Co., Ltd., trifunctional monomer M240, Tg = 50 ° C.).

[Example 4]
A pressure-sensitive adhesive sheet of Example 4 was obtained in the same manner as in Example 1, except that the polyfunctional monomer was changed to bisphenol A ethylene oxide-modified diacrylate (manufactured by Toagosei Co., Ltd., Aronix M211B, Tg = 75 ° C.). Was.

[Comparative Example 1]
A pressure-sensitive adhesive sheet of Comparative Example 1 was obtained in the same manner as in Example 1, except that no hydrogen-pulling photopolymerization initiator was blended.

[Comparative Example 2]
Without mixing a polyfunctional monomer, a monofunctional monomer and a self-cleavable photopolymerization initiator, 0.2 parts by mass of a xylylene diisocyanate compound (Takenate D-110N, manufactured by Mitsui Chemicals, Inc.) as a crosslinking agent. A pressure-sensitive adhesive sheet of Comparative Example 2 was obtained in the same manner as in Example 1 except for blending.

[Comparative Example 3]
A xylylene diisocyanate compound (Takenate D- manufactured by Mitsui Chemicals, Inc.) was used as a crosslinking agent without blending a polyfunctional monomer, a monofunctional monomer, a self-cleavable photopolymerization initiator and a hydrogen abstraction type photopolymerization initiator. 110N) was obtained in the same manner as in Example 1 except that 0.2 parts by mass of the adhesive sheet of Comparative Example 3 was obtained.

[Measurement and evaluation]
<Shear storage modulus G '>
Eight pressure-sensitive adhesive sheets (one sheet 25 μm) were overlapped so that the pressure-sensitive adhesive layer had a thickness of 200 μm, to prepare a measurement sample.
Eight adhesive sheets (25 μm per sheet) are stacked so that the thickness of the adhesive layer becomes 200 μm, and ultraviolet light is applied from the first release sheet side which is a heavy separator film so that the integrated light amount becomes 3000 mJ / cm ^2. Irradiation was performed to prepare a measurement sample after post-curing.
With respect to the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of each measurement sample, using a dynamic viscoelasticity device Rheogel-E4000 (manufactured by UBM Co., Ltd.) under the conditions of solid shear mode, frequency of 1 Hz, and strain of 0.1%, 0 ° C. The shear storage modulus G ′ of the pressure-sensitive adhesive layer in a temperature range of up to 150 ° C. was measured. The shear storage modulus G ′ of the pressure-sensitive adhesive layer at 23 ° C. is shown in Table 1 below.

<Elongation at break>
The elongation at break was measured according to JIS K 7161-1. At that time, the tensile speed was 10 mm / min, and the measurement was performed in an environment of 23 ° C. and a relative humidity of 50%. As a measurement sample, a pressure-sensitive adhesive sheet having a thickness of 25 μm, a width of 60 mm, and a length of 200 mm was rounded in the length direction and processed into a columnar shape having a cross-sectional area of 5 mm ² and a height of 60 mm. The sample was set and pulled so that the distance between the chucks was 30 mm, and the elongation at break of the sample was defined as the elongation at break. In addition, an autograph AGS-X manufactured by Shimadzu Corporation was used as a measuring instrument.

<Gel fraction>
The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were cut so as to have a size of 100 mm × 60 mm to prepare measurement samples before curing.
The pressure-sensitive adhesive sheet is cut so as to have a size of 100 mm × 60 mm, and ultraviolet rays are irradiated from the first release sheet side, which is a heavy separator film, so that the integrated light amount becomes 3000 mJ / cm ² , thereby preparing a post-curing measurement sample. did.
About 0.1 g of the pressure-sensitive adhesive sheet of each measurement sample was collected in a sample bottle, and 30 ml of ethyl acetate was added and shaken for 24 hours. Thereafter, the contents of this sample bottle were filtered off with a 150-mesh stainless steel wire mesh, the residue on the wire mesh was dried at 100 ° C. for 1 hour, and the dry mass (g) was measured. The gel fraction was determined from the obtained dry mass according to the following formula 1.
Gel fraction (% by mass) = (dry mass / collected mass of adhesive sheet) × 100 formula 1

<Probe tack value>
The second release sheet, which was a light separator film of the pressure-sensitive adhesive sheet, was peeled off and adhered to a PET film to prepare an uncured measurement sample.
The second release sheet, which was a light separator film of another pressure-sensitive adhesive sheet, was peeled off and adhered to a PET film. Next, ultraviolet rays were irradiated from the side of the first release sheet, which is a heavy separator film, so that the integrated amount of light became 3000 mJ / cm ² , to prepare a post-curing measurement sample.
Each measurement sample was cut into a size of 3 cm × 3 cm, and measured with a probe tack tester under the following conditions. The measurement temperature was 23 ° C.
Measuring equipment: NS probe tack tester (Nichiban Co., Ltd.)
Probe diameter: 5mmφ
Probe base material: stainless steel surface finish AA # 400 polished mirror surface weight: 19.6 g (made of brass)
Probe moving speed: 1.0 cm / sec Duel time: 1 sec

<Substrate adhesion>
The light release separator as the second release sheet was peeled off, and instead of the peeled separator, a triacetylcellulose film (Fujitack TD60UL, thickness 60 μm, manufactured by FUJIFILM Corporation) was attached using a hand roller to prepare a laminated film. . This laminated film was cut into a size having a width of 25 mm and a length of 100 mm, and the first release sheet was peeled off. Next, the 25 mm wide and 75 mm long region of the exposed adhesive surface having a width of 25 mm and a length of 100 mm was coated on the hard coat side of the adherend (polycarbonate plate with hard coat layer: Iupilon MR58, thickness 1 mm, manufactured by Mitsubishi Gas Chemical Company, Inc.). Was attached using a 2 kg pressure roller. In this state, after being held in an autoclave under the conditions of 40 ° C. and 5 atm for 30 minutes to adhere to the PC plate, ultraviolet light is irradiated from the triacetyl cellulose film side so that the integrated light amount becomes 3000 mJ / cm ² , Test pieces were prepared.
The test piece was left for 24 hours in an environment of 85 ° C. and a relative humidity of 85%, and then was composed of an adhesive sheet 1 and a triacetyl cellulose film 30 in an environment of 85 ° C. and a relative humidity of 85% as shown in FIG. A 100 g weight 34 is hung at a longitudinal end of the non-bonded region (width 25 mm, length 25 mm) of the laminated film, and a load of 100 g is applied in a direction at 90 ° to the plane of the adherend 32. It was left for 5 minutes in the state. During that time, the length L (mm) of the portion where the laminated film was peeled was measured and evaluated according to the following criteria.
◎: L <5 mm
：: 5 mm ≦ L <25 mm
Δ: 25 mm ≦ L <50 mm
×: 50 mm ≦ L

<Curl resistance>
The second release sheet as a light separator film was peeled off, and a triacetyl cellulose film (Fujitack TD60UL, thickness 60 μm, manufactured by FUJIFILM Corporation) was bonded.
Next, the first release sheet, which was a heavy separator film, was peeled off and attached to a PC board. The sample having the structure of PET / adhesive layer / PC was subjected to an autoclave treatment (40 ° C., 0.5 MPa, 30 min), and then irradiated with ultraviolet light from the PET film side so that the integrated light amount became 3000 mJ / cm ^2, and 100 mm × A test sample having a size of 200 mm was obtained. A test sample having a size of 100 mm × 200 mm was prepared in the same manner as in the evaluation of outgas resistance, except that a TAC film using a triacetyl cellulose film (Fujifilm TD60UL, thickness 60 μm) instead of a PET film was used. did. Next, the test sample was placed in a dry environment at 105 ° C. for 30 min 30 minutes, and then taken out in an environment at 23 ° C. and a relative humidity of 50%. Within 5 minutes after being taken out of the environment at 23 ° C. and a relative humidity of 50%, the sample is placed in such a manner that the four sides float on a horizontal surface by curling, and then the height of the test sample floating from the horizontal surface on each side. The height was measured, and the average value of the heights of the four sides was obtained, and evaluated according to the following criteria.
◎: Average height of four sides is 5 mm or less ：: Average height of four sides is greater than 5 mm and 10 mm or less Δ: Average height of four sides is greater than 10 mm and 15 mm or less X: Average height of four sides Is larger than 15mm

<Durability>
The second release sheet, which was a light separator film, was peeled off and bonded to a triacetyl cellulose film (Fujitack TD60UL, thickness 60 μm, manufactured by FUJIFILM Corporation).
Next, the first release sheet, which is a heavy separator film, was peeled off and adhered to a PC plate (a polycarbonate plate with a hard coat layer: Iupilon MR58, thickness 1 mm, manufactured by Mitsubishi Gas Chemical Company, Inc.). The sample having the structure of triacetylcellulose film / adhesive layer / PC was subjected to autoclave treatment (40 ° C., 0.5 MPa, 30 min), and then the ultraviolet light was applied from the triacetylcellulose film side to 3000 mJ / cm ^2. Irradiation was performed to obtain a test sample having a size of 100 mm x 200 mm. Next, the test sample was placed in an environment of 85 ° C. and a relative humidity of 85%, and after 240 hours, the presence or absence of floating and peeling was observed.
：: no lifting and / or peeling of 1.0 mm or more is observed ×: floating and / or peeling of 1.0 mm or more is observed

  From Table 1 above, the pressure-sensitive adhesive sheets of the examples were excellent in substrate adhesion and durability. Further, the pressure-sensitive adhesive sheets of Examples 1 to 3 were also excellent in curl resistance.

Reference Signs List 1 adhesive sheet with release sheet 11 adhesive sheet 12a transparent base material or release sheet 12b release sheet 20 laminate 21 adhesive sheet 22 base material 24 optical member 27a, 27b, 27c, 27d step 30 triacetyl cellulose film 32 adherend 34 Weight L Constant load peeling distance

Claims (12)

  Acrylic copolymer, polyfunctional monomer having two or more reactive double bonds in the molecule, monofunctional monomer having one reactive double bond in the molecule, hydrogen abstraction type photopolymerization initiator and An adhesive sheet formed from an adhesive composition containing a self-cleaving photopolymerization initiator.   2. The acrylic copolymer according to claim 1, wherein the acrylic copolymer includes a unit derived from a (meth) acrylate containing at least one group selected from a carboxy group, a hydroxy group, an amino group, an amide group, an epoxy group, and an isocyanate group. The pressure-sensitive adhesive sheet according to the above. The acrylic copolymer contains a unit derived from an alkoxyalkyl group-containing (meth) acrylate, a unit derived from a hydroxy group-containing (meth) acrylate, and a unit derived from methyl (meth) acrylate.
The content of the unit derived from the alkoxyalkyl group-containing (meth) acrylate is 50 to 90% by mass relative to the total mass of the acrylic copolymer, and the content of the unit derived from the hydroxy group-containing (meth) acrylate is The pressure-sensitive adhesive sheet according to claim 1, wherein the content is 5 to 35% by mass, and the content of the unit derived from the methyl (meth) acrylate is 5 to 15% by mass.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the content of the thermosetting crosslinking agent is 0.1% by mass or less based on the total weight of the pressure-sensitive adhesive sheet.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive sheet is a post-curable pressure-sensitive adhesive sheet, and has a gel fraction of 20% by mass or less before post-curing.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the monofunctional monomer is an alkyl (meth) acrylate.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein a glass transition temperature (Tg) when the polyfunctional monomer is a homopolymer is less than 65 ° C.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the content of the polyfunctional monomer is 5 to 40 parts by mass with respect to 100 parts by mass of the acrylic copolymer.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 8, wherein the content of the monofunctional monomer is 1 to 20 parts by mass with respect to 100 parts by mass of the acrylic copolymer.   A pressure-sensitive adhesive sheet with a release sheet, comprising a pair of release sheets having different release forces on both surfaces of the pressure-sensitive adhesive sheet according to claim 1.   A pressure-sensitive adhesive sheet cured by irradiating the pressure-sensitive adhesive sheet according to any one of claims 1 to 9 with an active energy ray, and an adherend on at least one surface side of the cured pressure-sensitive adhesive sheet. Laminate.   A method for producing a laminate, comprising: a step of bonding the pressure-sensitive adhesive sheet according to any one of claims 1 to 9 to an adherend, and then irradiating an active energy ray to cure the pressure-sensitive adhesive sheet.

Images