JP6724956B2 - Adhesive sheet, adhesive sheet with release sheet, laminate and method for producing laminate - Google Patents

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.

BACKGROUND ART Conventionally, a display device such as a liquid crystal display (LCD) and an input device used in combination with a display device such as a touch panel have been widely used. In the manufacture of these display devices and input devices, transparent adhesive sheets are used for the purpose of 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 in a pressure-sensitive adhesive layer is widely used. Solvent-based pressure-sensitive adhesives generally contain acrylic resin as a main component. Such an acrylic resin can be obtained by a polymerization reaction in a solvent in which an acrylic monomer is dissolved by a method called solution polymerization. In solution polymerization, the molecular weight of the polymer increases as the polymerization proceeds, and the viscosity of the reaction solution increases.Therefore, there is a technical limit to the synthesis of a polymer having a molecular weight necessary to obtain the cohesive force required as an adhesive. is there. Therefore, in order to secure the cohesive force required for the pressure-sensitive adhesive, a cross-linking agent capable of reacting with an acrylic resin such as an isocyanate compound or an epoxide compound has been added to the pressure-sensitive adhesive composition. Such a cross-linking agent builds a cross-linking network by reacting with an acrylic resin over time, and enhances the cohesive force of the pressure-sensitive adhesive layer.

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

For example, in Patent Document 1, a base polymer (A) containing a non-crosslinkable (meth)acrylic acid ester unit (a1) and an acrylic monomer unit (a2) having a crosslinkable functional group, and lauryl acrylate (b1). Containing a monomer (B), a cross-linking 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 an active energy ray. ) And a solvent (E), the pressure-sensitive adhesive sheet containing the pressure-sensitive adhesive layer obtained by semi-curing by heating. Further, 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, 2016-084391, A JP2012-31059A

However, when the present inventors examined the characteristics of the pressure-sensitive adhesive sheets described in Patent Documents 1 and 2, the base material adhesion may be insufficient, and particularly under high temperature and high humidity conditions, the base material adhesion and It was found that the durability may not be sufficiently obtained.
Therefore, in order to solve the problems of the prior art, the present inventors have studied for the purpose of providing a pressure-sensitive adhesive sheet that can exhibit 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 was found that a pressure-sensitive adhesive sheet capable of exhibiting durability and durability can be obtained.
Specifically, the present invention has the following configurations.

[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 photopolymerization A pressure-sensitive adhesive sheet formed from a pressure-sensitive 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 [1 ] Adhesive sheet described in.
[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 units derived from the alkoxyalkyl group-containing (meth)acrylate is 50 to 90% by mass, and the content of the units 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], which has a content of 5 to 35 mass% and a content of units derived from methyl (meth)acrylate of 5 to 15 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 mass of the pressure-sensitive adhesive sheet.
[5] The pressure-sensitive adhesive sheet according to any one of [1] to [4], which is a pressure-sensitive adhesive sheet having a post-curing property and has a gel fraction before post-curing of 20% by mass or less.
[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], which has a glass transition temperature (Tg) of less than 65° C. when the polyfunctional monomer is a homopolymer.
[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 with respect to 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] A pressure-sensitive adhesive sheet obtained by curing the pressure-sensitive adhesive sheet according to any one of [1] to [9] by irradiating active energy rays, and an adherend on at least one surface side of the pressure-sensitive adhesive sheet after curing. And a laminated body including.
[12] A method for producing a laminate, which comprises a step of gluing the pressure-sensitive adhesive sheet according to any one of [1] to [9] on an adherend and then irradiating an active energy ray to cure the pressure-sensitive adhesive sheet.

According to the present invention, it is possible to obtain a pressure-sensitive adhesive sheet that can exhibit excellent substrate adhesion and durability even under high temperature and high humidity conditions.

FIG. 1 is a schematic view showing a cross section of a release sheet or an adhesive sheet having a base material. FIG. 2 is a schematic view showing a cross section of an example of the laminate of the present invention. FIG. 3 is a schematic view showing a cross section of another example of the laminated body of the present invention. FIG. 4 is a diagram illustrating a method of measuring the constant load peeling distance.

Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments or specific examples, but the present invention is not limited to such embodiments. In addition, in this specification, the numerical range represented using "-" means the range which includes the numerical value described before and after "-" as a lower limit and an upper limit.

In addition, in this specification, "(meth)acrylate" represents both an acrylate and a methacrylate, or either.
Further, in the present 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 the molecule, a monofunctional monomer having one reactive double bond in the molecule, and 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-mentioned constitution, it can exhibit excellent substrate adhesion. For example, excellent base material adhesion can be exhibited even under high temperature and high humidity conditions such as 85° C. and relative humidity of 85%. Further, the pressure-sensitive adhesive sheet of the present invention exhibits excellent durability even when left under a high temperature and high humidity condition 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 less than 25 mm, it can be determined that the adhesion of the base material is good. It is particularly preferable that the constant load peeling distance is less than 5 mm.

The pressure-sensitive adhesive sheet of the present invention preferably has a post-curability (curing ability with active energy rays), 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. It is preferable that the amount is 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 3% by mass or less. The gel fraction of the adhesive sheet may be 0% by mass.

In the present specification, by irradiating the pressure-sensitive adhesive sheet with an active energy ray under the following conditions, the gel fraction of the pressure-sensitive adhesive sheet is increased by 10% by mass or more, and the pressure-sensitive adhesive sheet has post-curability. I can say. When the pressure-sensitive adhesive sheet is post-cured by irradiating with active energy rays, 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 further 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 the mixture is shaken for 24 hours. Then, the contents of this sample bottle are filtered by a 150-mesh stainless steel wire net, and the residue on the wire net is dried at 100° C. for 1 hour to measure the dry mass (g). From the obtained dry mass, the gel fraction is calculated by the following formula 1.
Gel fraction (mass %)=(dry mass/adhesive sheet collection mass)×100...Equation 1

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

Further, the shear storage elastic modulus at 23° C. and a frequency of 1 Hz 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 1.0×10 ⁶ Pa. It is preferably larger, more preferably 2.0×10 ⁶ Pa or more, further preferably 3.0×10 ⁶ Pa or more. The shear storage elastic modulus of the post-cured pressure-sensitive adhesive sheet at 23° C. and a frequency of 1 Hz is preferably 5.0×10 ⁸ Pa or less.

The shear storage elastic modulus of the pressure-sensitive adhesive sheet can be measured using a dynamic viscoelastic device. Examples of the dynamic viscoelastic device include Rheogel-E4000 (manufactured by UBM Co., Ltd.). At the time of measurement, the shear storage elastic modulus G′ of the pressure-sensitive adhesive layer in the temperature region from 0° C. to 150° C. is measured under the conditions of individual shear mode, frequency 1 Hz, and strain 0.1%.

When the adhesive sheet is post-cured by irradiating the adhesive sheet with active energy rays so that the accumulated light amount becomes 3000 mJ/cm ² , the adhesive sheet after post-curing has a breaking elongation of 300% in a tensile test measurement at a pulling speed of 10 mm/min. It is preferably at least above, more preferably at least 400%, further preferably at least 500%. The breaking elongation of the pressure-sensitive adhesive sheet after post-curing in a tensile test measurement at a pulling speed of 10 mm/min is preferably 3000% or less, and more preferably 2000% or less. Here, the breaking elongation is measured according to JIS K7161-1. At that time, the tensile speed is 10 mm/min, and the measurement is performed at 23° C. and a relative humidity of 50%. As the measurement sample, an adhesive sheet (adhesive layer) having a thickness of 25 μm, a width of 60 mm and a length of 200 mm is rolled 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. This is pulled so that the distance between chucks is 30 mm, and the elongation at which the sample breaks is defined as the breaking elongation. As the measuring device, for example, 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. Moreover, 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, and more preferably 15 N/5 mmφ or less. The probe tack value is the probe tack value of the uncured adhesive sheet.
(Probe tack value measurement conditions)
Measuring equipment: NS probe tack tester (manufactured by Nichiban Co., Ltd.)
Probe diameter: 5mmφ
Probe base material: Stainless steel surface finish AA#400 Mirror surface weight by polishing: 19.6±0.2g (made of brass)
Probe moving speed: 1.0 cm/sec Duel time: 1 sec

Further, 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 quantity becomes 3000 mJ/cm ² , is preferably 1.0 N/5 mmφ or less, and 0.5 N or less. /5 mmφ or less is more preferable, and 0.1 N/5 mmφ or less is further preferable. The probe tack value of the post-cured pressure-sensitive adhesive sheet may be 0 N/5 mmφ.

The thickness of the pressure-sensitive adhesive sheet can be appropriately set depending on the application 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, it is possible to more effectively enhance the substrate adhesion and durability under high temperature and high humidity conditions. Further, since the sticking out and stickiness of the adhesive can be suppressed, the workability can be improved. Furthermore, when the thickness of the pressure-sensitive adhesive sheet is within the above range, the double-sided pressure-sensitive adhesive sheet can be easily manufactured.

The pressure-sensitive adhesive sheet of the present invention may be a single-layer pressure-sensitive adhesive sheet composed only of 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. The double-sided pressure-sensitive adhesive sheet may be a single-layer pressure-sensitive adhesive sheet composed of a pressure-sensitive adhesive layer, a multi-layer pressure-sensitive adhesive sheet in which a plurality of pressure-sensitive adhesive layers are laminated, or a multi-layer pressure-sensitive adhesive in which another pressure-sensitive adhesive layer is laminated between pressure-sensitive adhesive layers. Sheet, multi-layered pressure-sensitive adhesive sheet in which a support is laminated between pressure-sensitive adhesive layers, and a multi-layered pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is laminated on one side of a support and another pressure-sensitive adhesive layer is laminated on the other side Are listed. 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, like the transparent substrate, can be used. Since such a double-sided PSA sheet is excellent in transparency as a whole PSA sheet, it can be suitably used for bonding optical members to each other.

When the pressure-sensitive adhesive sheet of the present invention is a single-sided pressure-sensitive adhesive sheet, as shown in FIG. 1, the pressure-sensitive adhesive sheet 11 may be provided with a transparent substrate 12a on one surface thereof. In this case, the other surface of the adhesive sheet 11 is preferably covered with the release sheet 12b. When an adhesive sheet is used, the release sheet 12b is peeled off, and the adhesive sheet 11 is adhered to a desired adherend so that the adhesive sheet 11 is in close contact, and then cured (post-cured) by irradiating with active energy rays. It is preferable. 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, a cycloolefin polymer film can be used. Further, an easy-adhesion layer may be provided on the 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 relate to a pressure-sensitive adhesive sheet with a release sheet, which comprises release sheets on both surfaces of the pressure-sensitive adhesive sheet. When a release sheet is 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 peelable laminated sheet having a release sheet base material and a release agent layer provided on one surface of the release sheet base material, or a polyolefin film such as a polyethylene film or a polypropylene film as a low polarity base material. Are listed.
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 type release agent or a long chain alkyl group-containing compound is used. In particular, an addition type silicone release agent having high reactivity is preferably used.
Specific examples of the silicone-based release agent include BY24-4527 and SD-7220 manufactured by Toray Dow Corning Silicone Co., Ltd., KS-3600, KS-774 and X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd. Are listed. Further, the silicone 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 ═CH(CH ₃ )SiO _1/2 units. preferable. Specific examples of the silicone resin include BY24-843, SD-7292, SHR-1404 manufactured by Toray Dow Corning 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 which is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Films Co., Ltd. and a light separator film which is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Films 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, it is preferable to have a pair of release sheets having different peeling forces. That is, it is preferable that the release sheet has different releasability between the release sheet 12a and the release sheet 12b in order to facilitate the release. When the releasability from one side and the releasability from the other are different, it becomes easier to first release only the release sheet having the higher releasability. In that case, the releasability of the release sheet 12a and the release sheet 12b may be adjusted according to the attaching method and the attaching order.

The present invention may also be directed to a pressure-sensitive adhesive sheet with a transparent film, which comprises 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 polyethylene terephthalate film, acrylic film, polycarbonate film, triacetyl cellulose film and cycloolefin polymer film. The transparent film-attached pressure-sensitive adhesive sheet may be a sheet in which a transparent film/pressure-sensitive adhesive sheet/release sheet are 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 it has transparency to such an extent that the visibility of the display device is not deteriorated. For example, the acrylic copolymer preferably contains a unit derived from a (meth)acrylate having a crosslinkable functional group. In addition, in the present specification and claims, the “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; Examples thereof include (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 repeating units derived from amino group-containing monomers 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.

It is preferable that the acrylic copolymer further contains a non-crosslinkable (meth)acrylic acid ester unit. The non-crosslinkable (meth)acrylic acid ester unit is preferably a repeating unit derived from a (meth)acrylic acid alkyl ester. 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). 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) Examples thereof include n-dodecyl acrylate, stearyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, and benzyl (meth)acrylate. These may be used alone or in combination of two or more.

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 a 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 1 to 4 carbon atoms, and particularly preferably 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 carbon atoms, still more preferably 1 to 4 carbon atoms, and particularly preferably 1 to 3 carbon atoms. preferable.

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

The content of units derived from the alkoxyalkyl group-containing (meth)acrylate is preferably 50% by mass or more, more preferably 55% by mass or more, and 60% by mass based on the total mass of the acrylic copolymer. More preferably, it is at least mass %. The content of the units 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 be easily adhered to the base material, while the pressure-sensitive adhesive sheet after post-curing has high hardness. The high temperature durability and processability 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. Among them, at least one selected from 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate is preferably used.

The content of the units derived from the hydroxy group-containing (meth)acrylate is preferably 5% by mass or more, and more preferably 7% by mass or more, based on the total mass of the acrylic copolymer. The content of units derived from the hydroxy group-containing (meth)acrylate is preferably 35% by mass or less, and 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 enhanced.

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

The acrylic copolymer may contain units derived from alkyl(meth)acrylate in addition to units derived from methyl(meth)acrylate. Examples of alkyl (meth)acrylates include ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, cetyl ( Examples thereof include alkyl (meth)acrylates such as (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate. The content of units derived from an alkyl (meth)acrylate other than methyl (meth)acrylate is preferably 1% by mass or more, and preferably 3% by mass or more, based on the total mass of the acrylic copolymer. More preferable. 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, the stickiness (tackiness) can be suppressed and the adhesion to the substrate can be enhanced.

<Other monomers>
The acrylic copolymer preferably further contains units 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 dimethylacrylamide, diethylacrylamide, acryloylmorpholine, hydroxyethylacrylamide, methylolacrylamide, methoxymethylacrylamide, ethoxymethylacrylamide, dimethylaminoethylacrylamide, N-vinylcaprolactam, N-vinyl-2-. Pyrrolidone, dimethylaminoethyl (meth)acrylate, N-vinylformamide, (meth)acrylonitrile, vinylpyrrolidone, vinylpyridine and the like can be mentioned. Among them, the nitrogen-containing monomer is preferably at least one selected from acrylamide derivatives, amino group-containing monomers and nitrogen-containing heterocycle-containing monomers, and more preferably acrylamide derivatives. The acrylamide derivative is more preferably at least one selected from dimethylacrylamide, diethylacrylamide and acryloylmorpholine, and particularly preferably dimethylacrylamide. Acrylic copolymer, by containing a unit derived from the nitrogen-containing monomer as described above, the pressure-sensitive adhesive sheet, it becomes easy to adhere to the substrate, while the post-curing pressure-sensitive adhesive sheet becomes high hardness. The high temperature durability and processability can be further improved.

The content of the units derived from the nitrogen-containing monomer is preferably 1% by mass or more, and more preferably 3% by mass or more, based on the total mass of the acrylic copolymer. The content of the units 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. Any other monomer may be used as long as it can be copolymerized with the above-mentioned acrylic monomer, and examples thereof include vinyl acetate, styrene, and vinyl chloride. The content of the other monomer unit in the acrylic copolymer is preferably 20% by mass or less, and 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, more preferably 200,000 to 1,500,000. 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 processability. The weight average molecular weight is a value measured by size exclusion chromatography (SEC) and determined on a polystyrene basis. As the acrylic copolymer, a commercially available one may be used, or one 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, and among them, the polyfunctional monomer preferably has two or more and less than five reactive double bonds, and preferably two. It is more preferable that the number is less than four.

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

A commercial item can be used as a 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., Aronix M-405), a bifunctional monomer M240 (polyethylene glycol diacrylate) manufactured by Toagosei Co., Ltd., and the like.

The glass transition temperature (Tg) when the polyfunctional monomer is a homopolymer is preferably less than 65°C, more preferably less than 60°C. Further, 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) in the above range when the polyfunctional monomer is a homopolymer include, for example, trimethylolpropane propylene oxide-modified triacrylate (manufactured by Toagosei Co., Ltd., Aronix M-321) and a bifunctional monomer M240 (polyethylene glycol diacrylate) manufactured by Toagosei Co., Ltd. can be mentioned.

The content of the polyfunctional monomer is preferably 5 to 40 parts by mass, and more preferably 5 to 30 parts by mass with respect to 100 parts by mass of the acrylic copolymer. The polyfunctional monomers may be used alone or in combination of two or more, and 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 within the above range, the hardness of the pressure-sensitive adhesive sheet after post-curing can be more effectively increased, and the workability of the pressure-sensitive adhesive sheet can be increased.

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

Examples of the monofunctional monomer include 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. Among them, 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, ISTA manufactured by Osaka Organic Chemical Industry, and the like.

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, further preferably 50° C. or higher, It is more preferably 55° C. or higher, particularly preferably 60° C. or higher. Further, the glass transition temperature (Tg) of the homopolymer obtained by polymerizing the monofunctional monomer is preferably 180° C. or lower, and more preferably 150° C. or lower.

The content of the monofunctional monomer is preferably 1 to 20 parts by mass, and more preferably 2 to 20 parts by mass with respect to 100 parts by mass of the acrylic copolymer. The above monofunctional monomers may be used alone or in combination of two or more, and when two or more are used in combination, the total mass is preferably within the above range.

Further, the total content of the monofunctional monomer and the polyfunctional monomer is preferably 6 to 50 parts by mass, and more preferably 10 to 45 parts by mass with respect to 100 parts by mass of the acrylic copolymer. It is more preferably from 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 which is excellent in processability because the stickiness of the end surface is suppressed 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 starts 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 promotes the polymerization by forming an exciplex between the photoexcited initiator and the hydrogen donor in the system and transferring the hydrogen of the hydrogen donor.

Examples of the hydrogen abstraction type photopolymerization initiator include 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. Among them, the hydrogen abstraction type photopolymerization initiator is preferably a benzophenone type photopolymerization initiator, and examples of the benzophenone type photopolymerization initiator include benzophenone, 4-methylbenzophenone and 2,4,6-trimethyl. Examples thereof include benzophenone.

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

A commercially available product 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-cleaving photopolymerization initiator>
The pressure-sensitive adhesive composition contains a self-cleaving photopolymerization initiator. The self-cleavage type 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, it is possible to exhibit higher hardness when the pressure-sensitive adhesive sheet is post-cured, and the substrate adhesion and durability are improved. Can be increased. In addition, by using a self-cleaving photopolymerization initiator and a hydrogen abstraction type photopolymerization initiator together, a polyfunctional monomer polymerized by the self-cleaving photoinitiator, a polymer composed of a monofunctional monomer and an acrylic The copolymer can be bonded to the copolymer by a chemical bond with a hydrogen abstraction type initiator, and as a result, the curl resistance of the pressure-sensitive adhesive sheet can be improved.

Examples of the self-cleaving type photopolymerization initiator include acetophenone type initiators, benzoin ether type initiators, benzophenone type initiators, hydroxyalkylphenone type initiators, thioxanthone type initiators, amine type initiators, acylphosphine oxide type initiators. Agents and the like.
Specific examples of the acetophenone-based initiator include diethoxyacetophenone and benzyl dimethyl 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 initiator include 1-hydroxy-cyclohexyl-phenyl-ketone (manufactured by BASF Japan Ltd., commercially available as IRGACURE184).
Specific examples of the thioxanthone initiator include 2-isopropylthioxanthone and 2,4-dimethylthioxanthone.
Specific examples of the amine-based 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-cleaving photopolymerization initiator in the pressure-sensitive adhesive composition is preferably 0.1 parts by mass or more, and 0.3 parts by mass or more based on 100 parts by mass of the acrylic copolymer. Is more preferable and 0.5 mass part or more is still more preferable. 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, it is possible to sufficiently increase the hardness when the adhesive sheet is post-cured.

<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 mass 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 mass% with respect to 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 the pressure-sensitive adhesive sheet does not substantially contain a thermosetting crosslinking agent, so that the pressure-sensitive adhesive sheet does not need to be provided with an aging step. It can exhibit necessary adhesive properties and the like. In addition, the pressure-sensitive adhesive sheet can exhibit excellent processability. Specifically, the stickiness of the end face of the pressure-sensitive adhesive sheet can be suppressed, and, for example, the adhesion of the pressure-sensitive adhesive to the punching blade during the punching process and the accompanying deformation of the pressure-sensitive adhesive sheet can be prevented. Furthermore, since the pressure-sensitive adhesive sheet contains substantially no 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 contain 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, diacetone alcohol; ethers such as diethyl ether, diisopropyl ether, dioxane, tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone; methyl acetate , Ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, ethyl butyrate, etc.; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene Examples thereof include polyols such as glycol monomethyl ether acetate and derivatives thereof.

The content of the solvent in the pressure-sensitive adhesive composition is not particularly limited, but is preferably 25 to 500 parts by mass, and more preferably 30 to 400 parts by mass with respect to 100 parts by mass of the acrylic copolymer.
Further, the content of the solvent is preferably 10 to 90% by mass, and more preferably 20 to 80% by mass, based on the total mass of the pressure-sensitive adhesive composition. As the solvent, one type 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. In addition, a part of the solvent in the pressure-sensitive adhesive composition may remain in the pressure-sensitive adhesive sheet.

<Other ingredients>
The pressure-sensitive adhesive sheet may contain components other than the above components as long as the effects of the present invention are not impaired. Examples of other components include components known as additives for pressure-sensitive adhesives. For example, a plasticizer, an antioxidant, a metal corrosion inhibitor, a tackifier, a silane coupling agent, an ultraviolet absorber, and a light stabilizer such as a hindered amine compound 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 benzoic acid. Examples thereof include carboxylic acid vinyl esters such as vinyl acid salt and styrene.
Examples of the antioxidant include a phenol-based antioxidant, an amine-based antioxidant, a lactone-based antioxidant, a phosphorus-based antioxidant, a sulfur-based antioxidant and the like. These antioxidants may be used alone or in combination of two or more.
As the metal corrosion inhibitor, a benzotriazole resin can be mentioned as a preferable example because of the compatibility of the pressure-sensitive adhesive and the high effect.
Examples of the tackifier include rosin resin, terpene resin, terpene phenol resin, coumarone indene resin, styrene resin, xylene resin, phenol resin, petroleum resin and the like.
Examples of the silane coupling agent include a mercaptoalkoxysilane compound (eg, a mercapto group-substituted alkoxy oligomer).
Examples of the ultraviolet absorber include benzotriazole compounds and benzophenone compounds. However, when ultraviolet rays are used as the active energy rays at the time of post-curing, it is preferable to add them in a range that does not hinder 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 coating of the pressure-sensitive adhesive composition can be carried out 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 micro gravure coater, a rod blade coater, a lip coater, a die coater, and a curtain coater.

The pressure-sensitive adhesive sheet manufacturing method 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 to heat the coating film formed by applying the pressure-sensitive adhesive composition.

As described above, the pressure-sensitive adhesive composition preferably 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 for a certain period of time after the coating. Therefore, it is possible to provide a pressure-sensitive adhesive sheet that can exhibit the necessary pressure-sensitive adhesive properties and the like without providing an aging step, and it is possible to suppress the manufacturing 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 to bring the pressure-sensitive adhesive sheet of the pressure-sensitive adhesive sheet into contact with the surface of the adherend. In particular, it is preferable to bond the pressure-sensitive adhesive sheet to an adherend when the pressure-sensitive adhesive sheet is in an uncured state, and to cure the pressure-sensitive adhesive sheet by, for example, irradiating with active energy rays.

<Use 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 complicated punching or cutting after forming a laminated body.

<Laminate>
The present invention also relates to a laminate including a pressure-sensitive adhesive sheet that is cured by irradiating the above-mentioned pressure-sensitive adhesive sheet with an active energy ray, and an adherend on at least one surface side of the pressure-sensitive adhesive sheet after curing. 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 view showing a cross section of an example of the laminate of the present invention. FIG. 2 is a cross-sectional view showing an example of the configuration of the laminate 20 in which the pressure-sensitive adhesive sheet 21 of the present invention is attached to the base material 22 and the optical member 24. As shown in FIG. 2, the pressure-sensitive adhesive sheet 21 of the present invention is preferably used for bonding to the base material 22, and is used for bonding the base material 22 and the other optical member 24. preferable. The pressure-sensitive adhesive sheet 21 of the present invention may be used for bonding with a polarizing plate.

Examples of the optical member included in the laminated body include various constituent members in optical products such as a touch panel and an image display device, and an anti-scattering film attached to the cover lens of the outermost layer. As a component of the touch panel, for example, an ITO film provided with an ITO film on a transparent resin film, an ITO glass provided with an ITO film on the surface of a glass plate, a transparent conductive film obtained by coating a conductive polymer on a transparent resin film, A hard coat film, a fingerprint resistant film and the like can be mentioned. Examples of constituent members of the image display device include an antireflection film, an alignment film, a polarizing film, a retardation film, and a brightness enhancement film used in a liquid crystal display device.
Examples of materials used for these members include glass, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polyethylene naphthalate, cycloolefin polymer, 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 a laminate of transparent optical films in a touch panel, a transparent optical film and a glass, a transparent optical film of a touch panel and a liquid crystal panel, a cover glass. And a transparent optical film, or 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, 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. A hard coat layer may be provided on the transparent optical film or the polycarbonate substrate.

FIG. 3 is a schematic view showing a cross section of another example of the laminated body of the present invention. As shown in FIG. 3, the adherend may have stepped portions (27a, 27b, 27c, 27d). In FIG. 3, the base material has step portions (27a, 27b), and the optical member has step portions (27c, 27d). The thickness of the step portions (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 attached to a member having a step portion, and can follow the unevenness generated from the step portion.

<Method of manufacturing laminated body>
The present invention also relates to a method for producing a laminated body, which comprises the step of irradiating an active energy ray to cure the pressure-sensitive adhesive sheet after the pressure-sensitive adhesive sheet is attached to an adherend. It is preferable that the method for producing a laminate includes a step of bonding the pressure-sensitive adhesive sheet of the pressure-sensitive adhesive sheet described above to an adherend in an uncured state, and then irradiating with active energy rays to cure the pressure-sensitive adhesive sheet. Prior to irradiation with active energy rays, the pressure-sensitive adhesive sheet of the pressure-sensitive adhesive sheet is in an uncured state, so that the initial adhesiveness to the substrate becomes good. In this way, after the pressure-sensitive adhesive sheet is attached 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 base material from being deformed or distorted.

Examples of active energy rays include ultraviolet rays, electron rays, visible rays, X-rays, and ion rays, which can be appropriately selected according to the polymerization initiator contained in the pressure-sensitive adhesive sheet. Among them, ultraviolet rays or electron beams are preferable, and ultraviolet rays are particularly preferable, from the viewpoint of versatility.
As the ultraviolet light source, for example, a high pressure mercury lamp, a low pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide lamp, a carbon arc, a xenon arc, an electrodeless ultraviolet lamp, or the like can be used.
As the electron beam, for example, an electron beam emitted from each type of electron beam accelerator such as Cockloft-Walt type, Bande-Craft type, resonance transformer type, insulating core transformer type, linear type, dynamitron type, high frequency type, etc. is 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.

The features of the present invention will be described more specifically below with reference to Examples and Comparative Examples. The 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 limitedly interpreted by the following specific examples.

[Example 1]
<Synthesis of acrylic copolymer (A-1)>
The 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. 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 concentration of 35 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). Part, 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-cleaving photopolymerization initiator). BASF Japan Ltd., IRGACURE 184) 0.7 parts by mass, 4-methylbenzophenone as a hydrogen abstraction type photopolymerization initiator (LAMBSON: 4MBP) 0.5 parts by mass was added, and the solid content concentration was 40 parts by mass. Ethyl acetate was added as a solvent to obtain a pressure-sensitive adhesive composition.

The above-mentioned pressure-sensitive adhesive composition was applied onto a first release sheet (heavy separator film, Teijin DuPont Films Co., Ltd., release-treated polyethylene terephthalate film). 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. Then, it was dried at 100° C. for 3 minutes with a hot air dryer to remove the solvent and form an adhesive sheet.
A second release sheet (light separator film, manufactured by Teijin DuPont Films Co., Ltd.), which has been subjected to a release treatment having a higher releasability than the first release sheet, is attached to one surface of this pressure-sensitive adhesive sheet, and an adhesive sheet with a release sheet is attached. A pressure-sensitive adhesive sheet of Example 1 which is a sheet was obtained.

[Example 2]
Example 2 was repeated in the same manner as in Example 1 except that isostearyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., ISTA, Tg=-18° C.) was used instead of isobornyl acrylate as the monofunctional monomer. The adhesive sheet of 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]
An 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 (Aronix M211B, manufactured by Toagosei Co., Ltd., Tg=75° C.). It 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 the hydrogen abstraction type photopolymerization initiator was not added.

[Comparative example 2]
0.2 parts by mass of a xylylene diisocyanate compound (Takenate D-110N manufactured by Mitsui Chemicals, Inc.) as a cross-linking agent without blending a polyfunctional monomer, a monofunctional monomer and a self-cleaving photopolymerization initiator. A pressure-sensitive adhesive sheet of Comparative Example 2 was obtained in the same manner as in Example 1 except that it was compounded.

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

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

<Break elongation>
The breaking elongation 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 the measurement sample, an adhesive sheet having a thickness of 25 μm, a width of 60 mm and a length of 200 mm was rolled 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 chucks was 30 mm, and the elongation at break of the sample was defined as the elongation at break. In addition, as a measuring instrument, an autograph AGS-X manufactured by Shimadzu Corporation was used.

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

<Probe tack value>
The second release sheet, which is a light separator film of the pressure-sensitive adhesive sheet, was peeled off and attached to a PET film to prepare an uncured measurement sample.
The second release sheet, which is a light separator film of another pressure-sensitive adhesive sheet, was peeled off and attached to a PET film. Next, ultraviolet rays were radiated from the side of the first release sheet, which was a heavy separator film, so that the integrated light amount was 3000 mJ/cm ^2, and a post-curing measurement sample was prepared.
Each measurement sample was cut into 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 (manufactured by Nichiban Co., Ltd.)
Probe diameter: 5mmφ
Probe base material: Stainless steel surface finish AA#400 Mirror surface weight by polishing: 19.6 g (made of brass)
Probe moving speed: 1.0 cm/sec Duel time: 1 sec

<Substrate adhesion>
The light release separator which is the second release sheet was peeled off, and instead of the peeled off separator, a triacetyl cellulose film (Fuji Film Co., Fujitac TD60UL thickness 60 μm) was laminated 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. Then, the exposed area of 25 mm in width and 100 mm in length of the adhesive surface is covered with a region of 25 mm in width and 75 mm in length on the hard coat surface side of the adherend (polycarbonate plate with hard coat layer: Mitsubishi Gas Chemical Co., Inc., Iupilon MR58 thickness 1 mm) Was attached using a 2 kg pressure roller. In this state, it was kept in an autoclave under the conditions of 40° C. and 5 atm for 30 minutes and brought into close contact with the PC plate, and then irradiated with ultraviolet rays from the triacetyl cellulose film side so that the integrated light amount was 3000 mJ/cm ² , A test piece was prepared.
After leaving this test piece for 24 hours in an environment of 85° C. and a relative humidity of 85%, it is composed of the pressure-sensitive adhesive sheet 1 and the 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 the lengthwise 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 the direction of 90° with respect to the plane of the adherend 32. It was left standing for 5 minutes. During that time, the length L (mm) of the portion where the laminated film was peeled off was measured and evaluated according to the following criteria.
⊚: L<5 mm
○: 5 mm≦L<25 mm
Δ: 25 mm≦L<50 mm
X: 50 mm ≤ L

<Curl resistance>
The second release sheet, which is a light separator film, was peeled off, and a triacetyl cellulose film (Fujitac TD60UL, thickness 60 μm, manufactured by FUJIFILM Corporation) was attached.
Next, the first release sheet, which is a heavy separator film, was peeled off and attached to a PC board. A sample having a composition of PET/adhesive layer/PC was autoclaved (40° C., 0.5 MPa, 30 min), and then ultraviolet rays were irradiated from the PET film side so that the integrated light amount was 3000 mJ/cm ^2, and 100 mm× A test sample with 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 the evaluation of the outgas resistance except that a TAC film using a triacetyl cellulose film (manufactured by FUJIFILM Corporation, Fujitac TD60UL thickness 60 μm) was used instead of the PET film. did. Then, the test sample was placed in a dry environment at 105° C. for 30 minutes for 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 in an environment of 23°C and 50% relative humidity, the sample was placed on a horizontal surface so that four sides float due to curls, 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 calculated and evaluated according to the following criteria.
◎: Average height of 4 sides is 5 mm or less ○: Average height of 4 sides is greater than 5 mm and 10 mm or less △: Average height of 4 sides is greater than 10 mm and 15 mm or less X: Average height of 4 sides Is larger than 15 mm

<Durability>
The second release sheet, which is a light separator film, was peeled off and attached to a triacetyl cellulose film (Fujitac TD60UL, thickness 60 μm, manufactured by FUJIFILM Corporation).
Next, the first release sheet, which is a heavy separator film, was peeled off and attached to a PC plate (polycarbonate plate with a hard coat layer: Mitsubishi Gas Chemical Co., Inc., Iupilon MR58 thickness 1 mm). The sample of the composition of triacetyl cellulose film/adhesive layer/PC is autoclaved (40° C., 0.5 MPa, 30 min), and then the integrated amount of ultraviolet rays from the side of the triacetyl cellulose film becomes 3000 mJ/cm ^2. Irradiation was performed to obtain a test sample having a size of 100 mm×200 mm. Then, the test sample was placed in an environment of 85° C. and a relative humidity of 85%, and the presence or absence of occurrence of floating and peeling after 240 hours was observed.
◯: Floating and peeling of 1.0 mm or more are not observed. X: Floating and/or peeling of 1.0 mm or more are observed.

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

1 Adhesive Sheet with Release Sheet 11 Adhesive Sheet 12a Transparent Substrate or Release Sheet 12b Release Sheet 20 Laminate 21 Adhesive Sheet 22 Substrate 24 Optical Member 27a, 27b, 27c, 27d Stepped Part 30 Triacetyl Cellulose Film 32 Adherent 34 Weight L Constant load separation distance

Claims (6)

Acrylic copolymer, polyfunctional monomer having two or more reactive double bonds in molecule, monofunctional monomer having one reactive double bond in molecule, hydrogen abstraction type photopolymerization initiator, and A pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition containing a self-cleaving photopolymerization initiator ,
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 mass% with respect to the total weight of the acrylic copolymer, and the content of the unit derived from the hydroxy group-containing (meth)acrylate is The content is 5 to 35% by mass, the content of the unit derived from the methyl (meth)acrylate is 5 to 15% by mass,
Examples of the polyfunctional monomer include ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylic acid, and di(meth)acrylic acid 1,4-. Butylene glycol, 1,9-nonanediol di(meth)acrylic acid, 1,6-hexanediol diacrylic acid, polybutylene glycol di(meth)acrylic acid, neopentyl glycol di(meth)acrylic acid, di(meth)acrylic Acid tetraethylene glycol, di(meth)acrylic acid tripropylene glycol, di(meth)acrylic acid polypropylene glycol, tri(meth)acrylic acid trimethylolpropane, tri(meth)acrylic acid pentaerythritol, tetra(meth)acrylic acid penta At least one selected from the group consisting of erythritol and vinyl methacrylate,
Examples of the monofunctional monomer include isobornyl acrylate, isostearyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, benzyl methacrylate, N-acryloyloxyethylhexahydrophthalimide, acrylamide, N,N-dimethylacrylamide, N,N. -At least one selected from the group consisting of diethylacrylamide, acryloylmorpholine and vinylpyrrolidone,
Based on 100 parts by mass of the acrylic copolymer, the content of the polyfunctional monomer is 5 to 40 parts by mass, the content of the monofunctional monomer is 1 to 20 parts by mass,
The pressure-sensitive adhesive sheet is a pressure-sensitive adhesive sheet containing substantially no thermosetting crosslinking agent. The pressure-sensitive adhesive sheet according to claim 1 , wherein the pressure-sensitive adhesive sheet is a post-curable pressure-sensitive adhesive sheet, and the gel fraction before post-curing is 20% by mass or less. The pressure-sensitive adhesive sheet according to claim 1 or 2 , which has a glass transition temperature (Tg) of less than 65°C when the polyfunctional monomer is a homopolymer. Release-sheet laminated adhesive sheet release force to both surfaces of the adhesive sheet comprises a different pair release sheet together according to any one of claims 1-3. Comprising a pressure-sensitive adhesive sheet was cured by irradiating an active energy ray to the pressure-sensitive adhesive sheet according to any one of claims 1 to 3 and, and the adherend on at least one surface side of the adhesive sheet after curing Laminate. After pasting the pressure-sensitive adhesive sheet according to an adherend to any one of claims 1 to 3 method for producing a laminate comprising the step of curing the adhesive sheet by irradiation with active energy rays.

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