JP6705542B1 - Adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive sheet exhibiting excellent adhesion to various adherends having different polarities and suppressing yellowing. A (meth)acrylic polymer A having a (meth)acrylic monomer unit having a hydroxyl group and a (meth)acrylic monomer unit having a ring structure and having a weight average molecular weight of more than 10,000, and a weight average molecular weight. Of (meth)acryl having a hydroxyl group of 3000 to 10000 and a glass transition temperature of 20 to 120° C., which is a (meth)acrylic polymer having a hydroxyl group. The content of the monomer unit is 20% by mass or more based on the total mass of the (meth)acrylic polymer A, and the (meth)acrylic monomer unit having a ring structure does not have a nitrogen atom as a ring-constituting atom, The content of the (meth)acrylic polymer B is 1 part by mass or more based on 100 parts by mass of the (meth)acrylic polymer A, which is an adhesive sheet. [Selection diagram] None

Description

The present invention relates to an adhesive sheet.

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 these display devices and input devices, a transparent adhesive sheet is used for the purpose of bonding optical members, and a transparent adhesive sheet is also used for bonding the display device and the input device.

For example, Patent Documents 1 to 5 disclose pressure-sensitive adhesive sheets for bonding optical members. Here, an acrylic copolymer is obtained by polymerizing various monomers, and an acrylic pressure-sensitive adhesive sheet is formed from a pressure-sensitive adhesive composition containing such an acrylic copolymer. Such a pressure-sensitive adhesive sheet may be a double-sided pressure-sensitive adhesive sheet, and for example, it may be used for bonding a transparent resin layer and a glass layer (for example, Patent Document 4). Further, it has been studied to use an adhesive sheet having after-curing property in order to bond it to an adherend having irregularities (for example, Patent Document 5).

JP 2012-2333060A International Publication No. 2010/147047 JP, 2016-186618, A JP, 2018-001615, A International Publication No. 2015/080120

A pressure-sensitive adhesive sheet that is attached to an optical member is required to have high transparency and adhesiveness. In recent years, an optical member to which an adhesive sheet is attached may be used in a severe environment such as a high temperature or high humidity environment, and it is required to exhibit high transparency and adhesion even under such a condition. There is.

Moreover, the sticking target of the pressure-sensitive adhesive sheet is diverse, and may be stuck to various adherends having different polarities such as a resin layer and a glass layer. Therefore, the pressure-sensitive adhesive sheet is required to exhibit excellent adhesion regardless of the type of adherend.

Therefore, in order to solve the problems of the prior art, the present inventors provide a pressure-sensitive adhesive sheet that exhibits excellent adhesion to various adherends having different polarities and that suppresses yellowing. Therefore, we proceeded with the study.

As a result of intensive studies to solve the above problems, the present inventors have shown excellent adhesion to various adherends by blending different acrylic polymers in the pressure-sensitive adhesive sheet, It has also been found that an adhesive sheet in which yellowing is suppressed can be obtained.
Specifically, the present invention has the following configurations.

[1] A (meth)acrylic polymer A having a (meth)acrylic monomer unit having a hydroxyl group and a (meth)acrylic monomer unit having a ring structure, and having a weight average molecular weight of more than 10,000.
A pressure-sensitive adhesive sheet comprising a (meth)acrylic polymer B having a weight average molecular weight of 3,000 to 10,000 and a glass transition temperature of 20 to 120° C.,
The content of the (meth)acrylic monomer unit having a hydroxyl group in the (meth)acrylic polymer A is 20% by mass or more based on the total mass of the (meth)acrylic polymer A and has a ring structure (meth). The acrylic monomer unit does not have a nitrogen atom as a ring-constituting atom,
The content of the (meth)acrylic polymer B is 1 part by mass or more based on 100 parts by mass of the (meth)acrylic polymer A, which is an adhesive sheet.
[2] The content of the (meth)acrylic monomer unit having a ring structure in the (meth)acrylic polymer A is 5% by mass or more based on the total mass of the (meth)acrylic polymer A, [1] Adhesive sheet.
[3] The (meth)acrylic polymer B is the pressure-sensitive adhesive sheet according to [1] or [2], which contains a monomer unit having an alicyclic ring.
[4] The pressure-sensitive adhesive sheet according to any one of [1] to [3], wherein the (meth)acrylic polymer B contains a monomer unit having an alicyclic ring, and the alicyclic ring has 6 or more carbon atoms.
[5] The (meth)acrylic polymer B is the pressure-sensitive adhesive sheet according to any one of [1] to [4], which has substantially no functional group.
[6] The pressure-sensitive adhesive sheet according to any one of [1] to [5], further including at least one selected from a polyfunctional monomer and a crosslinking agent.
[7] Adhesion according to any one of [1] to [6], further comprising a photopolymerization initiator, wherein the photopolymerization initiator is an acetophenone photopolymerization initiator or an acylphosphine oxide photopolymerization initiator. Sheet.

ADVANTAGE OF THE INVENTION According to this invention, the adhesive sheet which showed the outstanding adhesiveness with respect to various to-be-adhered materials from which polarity differs, and suppressed yellowing can be obtained.

FIG. 1 is a schematic view showing a cross section of an adhesive sheet having a release sheet.

Hereinafter, the present invention will be described in detail. The description of the constituent requirements 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)acryl" represents both acryl and methacryl, 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 present invention has a (meth)acrylic monomer unit having a hydroxyl group and a (meth)acrylic monomer unit having a ring structure, and a (meth)acrylic polymer A having a weight average molecular weight of more than 10,000, and a weight average molecular weight. Of (meth)acrylic polymer B having a glass transition temperature of 20 to 120° C. and a glass transition temperature of 3000 to 10000. Here, the content of the (meth)acrylic monomer unit having a hydroxyl group in the (meth)acrylic polymer A is 20% by mass or more based on the total mass of the (meth)acrylic polymer A, and has a ring structure. The (meth)acrylic monomer unit does not have a nitrogen atom as a ring-constituting atom. Moreover, the content of the (meth)acrylic polymer B is 1 part by mass or more based on 100 parts by mass of the (meth)acrylic polymer A.

With the above structure, the pressure-sensitive adhesive sheet of the present invention can exhibit excellent adhesion to various adherends having different polarities. Specifically, the pressure-sensitive adhesive sheet of the present invention exhibits excellent adhesion to both adherends having different polarities such as a resin plate and a glass plate. Further, such adhesiveness is exhibited even when left in a moist heat environment for a long time.

In the present specification, the adhesiveness of the pressure-sensitive adhesive sheet can be evaluated by measuring the wet heat constant load. When measuring the constant heat and humidity load, first, a polyester film is attached to one surface of the adhesive sheet, and then a polycarbonate sheet or a glass plate is attached to the other surface of the adhesive sheet. After that, it is treated in an autoclave at a temperature of 30° C. and a pressure of 0.5 MPa for 30 minutes, and then allowed to stand for 1 day under atmospheric pressure and room temperature. Then, the pressure-sensitive adhesive sheet attached to each adherend is left to stand for 30 minutes inside a thermo-hygrostat adjusted to a temperature of 85° C. and a relative humidity of 85%. And measure the time until the adhesive sheet is peeled from the adherend surface and the weight falls. At this time, when the time taken for the pressure-sensitive adhesive sheet to be peeled from the surface of the adherend and the weight to fall is 15 minutes or more, it can be evaluated that the adhesion to each adherend is good.

Furthermore, since the pressure-sensitive adhesive sheet of the present invention has the above-mentioned constitution, yellowing is suppressed. Therefore, the highly transparent pressure-sensitive adhesive sheet is maintained even after being bonded to the optical member. Yellowing of the pressure-sensitive adhesive sheet can be evaluated by measuring the chromaticity b ^* value in the L ^* a ^* b ^* color space. The b ^* value of the pressure-sensitive adhesive sheet is preferably less than 3, and more preferably less than 2. Furthermore, in the pressure-sensitive adhesive sheet of the present invention, yellowing is suppressed even after being subjected to a weather resistance test. For example, even when the pressure-sensitive adhesive sheet is irradiated with light rays for 300 hours under the conditions of a relative humidity of 50% with a xenon weather meter, a black panel temperature of 63° C., and an illuminance of 180 W/cm ² , the b ^* value of the pressure-sensitive adhesive sheet is It is preferably less than 3, and more preferably less than 2. The b ^* value of the pressure-sensitive adhesive sheet can be measured, for example, using a colorimeter, Color Coat i, manufactured by Suga Test Instruments. In this specification, evaluation before b * b * value after weathering test is increased relative to the value, if the b ^* value after the test is less than 3, the yellowing suppressing effect is obtained Can be evaluated.

The pressure-sensitive adhesive sheet of the present invention is preferably a pressure-sensitive adhesive sheet composed of only a pressure-sensitive adhesive layer, and is preferably 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. A sheet is included. The pressure-sensitive adhesive sheet of the present invention may be a multi-layer pressure-sensitive adhesive sheet in which a support is laminated between pressure-sensitive adhesive layers. 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.

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, the pressure-sensitive adhesive sheet 10 with a release sheet may have release sheets 12a and 12b on both surfaces of the pressure-sensitive adhesive layer 11, as shown in FIG. preferable.

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 polar base material. Can be 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 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, and KS-3600, KS-774 and X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd. Is mentioned. Further, the silicone release agent may contain a silicone resin which is an organic silicon compound having an SiO ₂ unit and a (CH ₃ ) ₃ SiO _1/2 unit or a CH ₂ ═CH(CH ₃ ) SiO _1/2 unit. preferable. Specific examples of the silicone resin include BY24-843, SD-7292, and SHR-1404 manufactured by Toray Dow Corning Silicone Co., Ltd., and KS-3800 and 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 A71 which is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Films Co., Ltd., and a light separator film A38ST which is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Films Co., Ltd. are exemplified. be able to.

The pressure-sensitive adhesive sheet with a release sheet preferably has a pair of release sheets having different release forces on both surfaces of the pressure-sensitive adhesive sheet. That is, it is preferable that the release sheet has different release properties from 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 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 1000 μm, more preferably 8 to 500 μm, and particularly preferably 10 to 300 μm. By setting the thickness of the pressure-sensitive adhesive sheet within the above range, it is possible to suppress sticking out and stickiness of the pressure-sensitive adhesive while maintaining the pressure-sensitive adhesive performance, so that the processability can be improved. Furthermore, when the thickness of the pressure-sensitive adhesive layer is within the above range, the double-sided pressure-sensitive adhesive sheet can be easily manufactured.

<(Meth)acrylic polymer A>
The pressure-sensitive adhesive sheet contains a (meth)acrylic monomer unit having a hydroxyl group and a (meth)acrylic monomer unit having a ring structure, and contains a (meth)acrylic polymer A having a weight average molecular weight of more than 10,000. The content of the (meth)acrylic monomer unit having a hydroxyl group in the (meth)acrylic polymer A is 20% by mass or more based on the total mass of the (meth)acrylic polymer A. The (meth)acrylic monomer unit having a ring structure in the (meth)acrylic polymer A does not have a nitrogen atom as a ring-constituting atom.

Examples of the (meth)acrylic monomer having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth). ) Acrylate, 4-hydroxyoxy(meth)acrylate, 6-hydroxyhexyl(meth)acrylate, 8-hydroxyoctyl(meth)acrylate, polyalkylene glycol mono(meth)acrylate and the like. Among them, at least one selected from 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate is preferably used.

The content of the (meth)acrylic monomer unit having a hydroxyl group in the (meth)acrylic polymer A may be 20 mass% or more based on the total mass of the (meth)acrylic polymer A, and is 25 mass% or more. Preferably. The content of the (meth)acrylic monomer unit having a hydroxyl group in the (meth)acrylic polymer A is preferably 50% by mass or less. By making the content of the (meth)acrylic monomer unit having a hydroxyl group within the above range, it is possible to impart hydrophilicity, and thereby, the adhesiveness between the pressure-sensitive adhesive sheet and the adherend and the moist-heat-whitening resistance are more effective. Can be increased to

The (meth)acrylic monomer having a ring structure is preferably a (meth)acrylic monomer having an alicyclic ring or an aromatic ring. Examples of the alicyclic ring include cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, cyclododecane, norbornene, norbornadiene, dicyclopentadiene, isobornyl, tetrahydrofuran and tetrahydropyran. Be done. The alicyclic ring may have a spiro structure. Examples of the aromatic ring include benzene, naphthalene, anthracene, pyridine, furan, benzofuran, pyrrole, thiophene, imidazole and oxazole. Among them, the ring structure is particularly preferably at least one selected from cyclohexane, benzene, dicyclopentadiene and isobornyl. The ring structure described above may further have a substituent. Examples of the substituent include a halogen atom, halogenated alkyl group, alkyl group, alkenyl group, acyl group, hydroxy group, hydroxyalkyl group, alkoxy group, aryl group, heteroaryl group, alicyclic group, cyano group, epoxy group. , An oxetanyl group, a mercapto group, an amino group, a (meth)acryloyl group, and the like, which can be substituted. However, the ring structure does not have a nitrogen atom as a ring-constituting atom.

Examples of the (meth)acrylic monomer having a ring structure include cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, and phenoxyethyl (meth). Acrylate, 3 phenoxybenzyl (meth)acrylate, O-phenylphenoxyethyl (meth)acrylate and the like can be preferably used.

The content of the (meth)acrylic monomer unit having a ring structure in the (meth)acrylic polymer A is preferably 1% by mass or more based on the total mass of the (meth)acrylic polymer A, and 3% by mass. The above content is more preferable, the content is more preferably 5 mass% or more, still more preferably 9 mass% or more. The content of the (meth)acrylic monomer unit having a ring structure in the (meth)acrylic polymer A is preferably 30% by mass or less. By setting the content of the (meth)acrylic monomer unit having a ring structure within the above range, the compatibility of the (meth)acrylic polymer A and the (meth)acrylic polymer B can be increased, and thus the adhesiveness The adhesion between the sheet and the adherend can be enhanced more effectively.

The (meth)acrylic polymer A may contain an alkyl(meth)acrylate unit in addition to the (meth)acrylic monomer unit having a hydroxyl group and the (meth)acrylic monomer unit having a ring structure. Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl ( Examples thereof include alkyl (meth)acrylates such as (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate. The content of the alkyl (meth)acrylate unit is preferably 30% by mass or more, and more preferably 40% by mass or more, based on the total mass of the (meth)acrylic polymer A. Further, the content of the alkyl (meth)acrylate unit is preferably 80% by mass or less, and more preferably 75% by mass or less, based on the total mass of the (meth)acrylic polymer A. By setting the content of the alkyl (meth)acrylate unit within the above range, the adhesion to the adherend can be increased.

The (meth)acrylic polymer A has a (meth)acrylic monomer unit having a hydroxyl group and a (meth)acrylic monomer unit having a crosslinkable functional group, in addition to the (meth)acrylic monomer unit having a ring structure. May be. Examples of the crosslinkable functional group of the (meth)acrylic monomer having a crosslinkable functional group include a carboxy group, an amide group, an amino group, a thiol group, an isocyanate group, an epoxy group, and a silanol group. The content of the (meth)acrylic monomer unit having a crosslinkable functional group in the (meth)acrylic polymer A is preferably 10% by mass or less, and more preferably 5% by mass or less.

The (meth)acrylic polymer A may have other monomer units, if necessary. Any other monomer may be used as long as it can be copolymerized with the above-mentioned monomer components, and examples thereof include (meth)acrylonitrile, vinyl acetate, vinyl chloride, and ethyl vinyl ether. The content of the other monomer unit in the (meth)acrylic polymer A is preferably 10% by mass or less, and more preferably 5% by mass or less.

The weight average molecular weight of the (meth)acrylic polymer A may be greater than 10,000, preferably 100,000 or more, and more preferably 200,000 or more. The weight average molecular weight of the (meth)acrylic polymer A is preferably 2,000,000 or less, more preferably 1,500,000 or less, and further preferably 1,000,000 or less. The weight average molecular weight of the (meth)acrylic polymer A is a value obtained by measuring by gel permeation chromatography (GPC) and converting it using a calibration curve prepared using standard polystyrene having a known molecular weight. is there. As the (meth)acrylic polymer A, a commercially available one may be used, or one synthesized by a known method may be used.

<(Meth)acrylic polymer B>
The pressure-sensitive adhesive sheet contains the (meth)acrylic polymer B having a weight average molecular weight of 3,000 to 10,000 and a glass transition temperature of 20 to 120°C. The (meth)acrylic polymer B is a lower molecular weight component than the (meth)acrylic polymer A, and has a function as an acrylic tackifier. The (meth)acrylic polymer B preferably has substantially no functional group, and in this case, the (meth)acrylic polymer B has a crosslinked structure with the (meth)acrylic polymer A described above. Do not form.

Since the pressure-sensitive adhesive sheet of the present invention contains the (meth)acrylic polymer B in addition to the (meth)acrylic polymer A, the pressure-sensitive adhesive sheet has excellent adhesion to various adherends having different polarities. Show. Furthermore, since the pressure-sensitive adhesive sheet of the present invention uses the (meth)acrylic polymer A that does not contain a nitrogen atom as a ring-constituting atom, it has excellent yellowing resistance. As described above, in the present invention, by containing a (meth)acrylic polymer having a predetermined structure and a different (meth)acrylic polymer, the adhesiveness and yellowing resistance of the pressure-sensitive adhesive sheet can be increased at a high level. It became possible to be compatible.

The (meth)acrylic polymer B preferably contains a monomer unit having an alicyclic ring. Further, when the (meth)acrylic polymer B contains a monomer unit having an alicyclic ring, it is preferable that the alicyclic ring has 6 or more carbon atoms. Examples of the alicyclic group having 6 or more carbon atoms include cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, cyclododecane, norbornene, norbornadiene, dicyclopentadiene and isobornyl. The alicyclic ring may have a spiro structure. Moreover, the alicyclic ring described above may further have a substituent. Examples of the substituent include a halogen atom, halogenated alkyl group, alkyl group, alkenyl group, acyl group, hydroxy group, hydroxyalkyl group, alkoxy group, aryl group, heteroaryl group, alicyclic group, cyano group, epoxy group. , An oxetanyl group, a mercapto group, an amino group, a (meth)acryloyl group, and the like, which can be substituted.

As the monomer having an alicyclic ring, for example, isobornyl (meth)acrylate, diciplopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate and the like can be preferably used.

When the (meth)acrylic polymer B contains a monomer unit having a ring structure, the content of the monomer unit having a ring structure is 10% by mass or more based on the total mass of the (meth)acrylic polymer B. It is preferable that the content is 20% by mass or more. Moreover, the content of the monomer unit having a ring structure is preferably 60% by mass or less, and more preferably 50% by mass or less, based on the total mass of the (meth)acrylic polymer B. By setting the content of the monomer unit having a ring structure within the above range, the compatibility between the acrylic polymer A and the acrylic polymer B can be enhanced, and the adhesiveness between the pressure-sensitive adhesive sheet and the adherend can be enhanced.

The (meth)acrylic polymer B may further contain an alkyl(meth)acrylate unit in addition to the monomer unit having a ring structure. Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl ( Examples thereof include alkyl (meth)acrylates such as (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate. Among them, the (meth)acrylic polymer B preferably contains methyl (meth)acrylate. The content of the alkyl (meth)acrylate unit is preferably 40% by mass or more, and more preferably 50% by mass or more, based on the total mass of the (meth)acrylic polymer B. In addition, the content of the alkyl (meth)acrylate unit is preferably 95% by mass or less, and more preferably 90% by mass or less, based on the total mass of the (meth)acrylic polymer B. By setting the content of the alkyl (meth)acrylate unit within the above range, the compatibility between the acrylic polymer A and the acrylic polymer B can be increased, and the adhesiveness between the pressure-sensitive adhesive sheet and the adherend can be increased.

The (meth)acrylic polymer B may have other monomer units, if necessary. Any other monomer may be used as long as it can be copolymerized with the above-mentioned monomer components, and examples thereof include (meth)acrylonitrile, vinyl acetate, vinyl chloride, and ethyl vinyl ether. The content of the other monomer unit in the (meth)acrylic polymer B is preferably 10% by mass or less, and more preferably 5% by mass or less.

The weight average molecular weight of the (meth)acrylic polymer B may be 3000 or more, preferably 3200 or more, and more preferably 3500 or more. The weight average molecular weight of the (meth)acrylic polymer B may be 10,000 or less, more preferably 8,000 or less, and further preferably 6000 or less. The weight average molecular weight of the (meth)acrylic polymer B is a value measured by gel permeation chromatography (GPC) and converted by using a calibration curve prepared using standard polystyrene having a known molecular weight. As the (meth)acrylic polymer B, a commercially available one may be used, or one synthesized by a known method may be used.

The glass transition temperature of the (meth)acrylic polymer B may be 20° C. or higher, preferably 30° C. or higher, and more preferably 40° C. or higher. The glass transition temperature of the (meth)acrylic polymer B may be 120°C or lower, preferably 100°C or lower, and more preferably 80°C or lower. By setting the glass transition temperature of the (meth)acrylic polymer B within the above range, the adhesiveness of the pressure-sensitive adhesive sheet to the adherend can be more effectively enhanced.

The content of the (meth)acrylic polymer B in the pressure-sensitive adhesive sheet may be 1 part by mass or more based on 100 parts by mass of the (meth)acrylic polymer A, and is preferably 1.5 parts by mass or more. It is more preferable that the amount is at least parts by mass. Further, the content of the (meth)acrylic polymer B in the pressure-sensitive adhesive sheet is preferably 20 parts by mass or less based on 100 parts by mass of the (meth)acrylic polymer A. By setting the content of the (meth)acrylic polymer B within the above range, the adhesiveness of the pressure-sensitive adhesive sheet to the adherend can be more effectively enhanced.

<Polyfunctional monomer>
The pressure-sensitive adhesive sheet of the present invention may contain 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 or more and less than four. It is more preferable to have one.

Examples of the polyfunctional monomer include, as bifunctional monomers, polyethylene glycol diacrylate, polypropylene diacrylate, alkyl diacrylate, polytetramethylene glycol diacrylate, polypropylene glycol diacrylate, dioxane diacrylate, tricyclodecanol diacrylate, and fullerene. Mention may be made of orange acrylate. Further, as trifunctional or higher functional monomers, alkoxylated trimethylolpropane triacrylate, alkoxylated glycerin triacrylate, caprolactone-modified isocyanurate triacrylate, pentaerythritol acrylate, alkoxylated pentaerythritol acrylate, (alkoxylated) pentaerythritol acrylate, Examples thereof include (alkoxylated) ditrimethylolpropane acrylate, (alkoxylated) dipentaerythritol acrylate, (ethoxylated) polyglycerin acrylate, and the like.

The polyfunctional monomer is preferably a polyfunctional monomer having an alkylene glycol group in one molecule. In this case, the number of alkylene glycol groups in one molecule is preferably 1-20.

Examples of such polyfunctional monomers include polyethylene glycol diacrylate, trimethylolpropane propylene oxide-modified triacrylate, and the like.

A commercial item can be used as a polyfunctional monomer. Examples of commercially available products include Shin-Nakamura Chemical Co., Ltd., bifunctional monomer A-400 (polyethylene glycol #400 diacrylate), trifunctional monomer A-TMPT ((alkoxylated) totimethylol propane acrylate), Toagosei Co., Ltd. The bifunctional monomer M240 (polyethylene glycol diacrylate), the tetrafunctional monomer M-408 (ditrimethylolpropane tetraacrylate), etc. are mentioned.

In the pressure-sensitive adhesive sheet, the polyfunctional monomer forms a crosslinked structure with the above-mentioned (meth)acrylic polymer. The content of the polyfunctional monomer in the pressure-sensitive adhesive composition described below is preferably 0.01 to 10% by mass, and more preferably 0.05 to 5% by mass, based on the total mass of the pressure-sensitive adhesive composition. Is more preferable. By setting the content of the polyfunctional monomer within the above range, the hardness of the pressure-sensitive adhesive sheet can be increased, and the durability and workability of the pressure-sensitive adhesive sheet can be increased.

<Crosslinking agent>
The pressure-sensitive adhesive sheet of the present invention may contain a crosslinking agent. The cross-linking agent can be appropriately selected in consideration of the reactivity with the cross-linkable functional group of the (meth)acrylic polymer. For example, it can be selected from known crosslinking agents such as an isocyanate compound, an epoxy compound, an oxazoline compound, an aziridine compound, a metal chelate compound and a butylated melamine compound. Among these, the crosslinking agent preferably contains at least one selected from an isocyanate compound, an epoxy compound and a metal chelate compound.

Examples of the isocyanate compound include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and the like. Examples of commercially available products include tolylene diisocyanate compound (Toronoh Co., Ltd., Coronate L), xylylene diisocyanate compound (Mitsui Chemicals, Inc., Takenate D-110N) and the like. Examples of the epoxy compound include TETRAD-C (manufactured by Mitsubishi Gas Chemical Company), TETRAD-X manufactured by Mitsubishi Gas Chemical Company), and the like. Examples of the metal chelate compound include aluminum chelate A (manufactured by Kawaken Fine Chemicals Co., Ltd.) and the like.

The cross-linking agent forms a cross-linking structure with the above-mentioned (meth)acrylic polymer in the pressure-sensitive adhesive sheet. However, some of the crosslinking agents are detected without forming a crosslinked structure. The content of the crosslinking agent in the pressure-sensitive adhesive composition described below is preferably 0.01 to 10% by mass, and 0.05 to 5% by mass, based on the total mass of the pressure-sensitive adhesive composition. Is more preferable. By setting the content of the crosslinking agent within the above range, the hardness of the pressure-sensitive adhesive sheet can be increased, and the durability and workability of the pressure-sensitive adhesive sheet can be increased.

<Photopolymerization initiator>
The pressure-sensitive adhesive sheet of the present invention may contain a photopolymerization initiator. The photopolymerization initiator starts polymerization of the polyfunctional monomer by irradiation with active energy rays. Here, the “active energy ray” means an electromagnetic wave or a charged particle beam having an energy quantum, and examples thereof include ultraviolet rays, electron rays, visible rays, X rays, and ion rays. Among them, ultraviolet rays or electron beams are preferable, and ultraviolet rays are particularly preferable, from the viewpoint of versatility.

The photopolymerization initiator is not particularly limited, but for example, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone, 1-[4 -(2-hydroxyethoxyl)-phenyl]-2-hydroxy-methylpropanone, 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methyl- Acetophenone-based photopolymerization initiators such as 1-propanone and acylphosphine oxide-based photopolymerization initiators such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2,4,6-trimethylbenzoyl)phenylphosphine oxide In addition to the agents, intramolecular hydrogen abstraction type photopolymerization initiators such as methyl benzoylformate and 4-methylbenzophenone, oil-soluble polymerization initiators such as oxime ester photopolymerization initiators and cationic photopolymerization initiators can be mentioned. Among them, the photopolymerization initiator is preferably an acetophenone photopolymerization initiator or an acylphosphine oxide photopolymerization initiator.

A commercially available product of such an acetophenone-based photopolymerization initiator is EsacureOne (oligo(2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenylpropanone], manufactured by IGM RESINS BV. Photoinitiator), Omnirad651 (2,2-dimethoxy-2-phenylacetophenone, manufactured by IGM RESINS BV), Omnirad184 (1-hydroxycyclohexyl phenyl ketone, manufactured by IGM RESINS BV), Omnirad1173 (2). -Hydroxy-2-methyl-1-phenylpropanone, manufactured by IGM RESINS BV, etc. Further, as a commercially available acylphosphine oxide photopolymerization initiator, Omnirad 819 (bis(2 , 4,6-Trimethylbenzoyl)phenylphosphine oxide manufactured by IGM RESINS BV), Omnirad TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide manufactured by IGM RESINS BV), and the like. Be done.

The content of the photopolymerization initiator in the pressure-sensitive adhesive composition is preferably 0.01 to 10% by mass, and preferably 0.1 to 5% by mass, based on the total mass of the pressure-sensitive adhesive composition. More preferable. By setting the content of the photopolymerization initiator within the above range, the hardness of the pressure-sensitive adhesive sheet can be increased, and the durability and workability of the pressure-sensitive adhesive sheet can be increased.

<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 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.

As the plasticizer, for example, a non-functional acrylic polymer may be used. As the non-functional group acrylic polymer, a polymer composed only of an acrylic monomer unit having no functional group other than an acrylate group, or an acrylic monomer unit having no functional group other than an acrylate group and having no functional group A polymer composed of a non-acrylic monomer unit can be mentioned. Since the non-functional acrylic polymer does not crosslink, it is possible to enhance the step followability when it is attached to an adherend without affecting the adhesiveness.
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 silane coupling agent include mercaptoalkoxysilane compounds (eg, mercapto group-substituted alkoxy oligomers) and (meth)acryloxypropylmethoxysilane.
Examples of the ultraviolet absorber include benzotriazole compounds, benzophenone compounds, and triazine compounds.

<Adhesive composition>
The pressure-sensitive adhesive sheet of the present invention is preferably a sheet including a pressure-sensitive adhesive layer obtained by curing a pressure-sensitive adhesive composition (coating liquid). The pressure-sensitive adhesive composition contains at least (meth)acrylic polymer A and (meth)acrylic polymer B. Further, the pressure-sensitive adhesive composition may contain the above-mentioned polyfunctional monomer, crosslinking agent, photopolymerization initiator, and other components.

The pressure-sensitive adhesive composition may contain an acrylic syrup A containing a (meth)acrylic polymer A. Here, the acrylic syrup A contains at least a (meth)acrylic polymer A and a monomer constituting the (meth)acrylic polymer A. Therefore, the pressure-sensitive adhesive composition may contain, in addition to the (meth)acrylic polymer A, a monomer constituting the (meth)acrylic polymer A. In addition, when the acrylic syrup A contains the monomer which comprises the (meth)acrylic polymer A, these monomers superpose|polymerize in the process of manufacturing an adhesive sheet, and form the (meth)acrylic polymer A.

Further, the pressure-sensitive adhesive composition may contain a solvent. In this case, the solvent is used to improve 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 and other esters; 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.

<Production method of adhesive sheet>
The method for producing a pressure-sensitive adhesive sheet of the present invention preferably includes the steps of applying a pressure-sensitive adhesive composition on a release sheet to form a coating film, and irradiating the coating film with active energy rays. When the pressure-sensitive adhesive composition contains a solvent, it is also preferable to include a heating step. In the heating step, the pressure-sensitive adhesive layer may be formed by heating the coating film while removing the solvent.

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.

In the step of irradiating an active energy ray to the coating, the irradiation is preferably the integrated light quantity irradiated with active energy rays so that 100~10000mJ / cm ^2, an active energy ray such that 500~5000mJ / cm ² More preferably. In the step of irradiating the coating film with the active energy ray, the active energy ray may be irradiated in two steps. For example, the irradiation intensity in the second step can be increased as compared with the first step. By performing such two-step irradiation, it becomes easy to adjust the molecular weight of the polymer contained in the obtained pressure-sensitive adhesive sheet, and it is possible to suppress heat shrinkage of the separator and the like.

<Use of adhesive sheet>
The pressure-sensitive adhesive sheet of the present invention is preferably for bonding optical members. Examples of the optical member include respective constituent members in optical products such as a touch panel and an image display device. 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, Examples include hard coat films and anti-fingerprint films. Examples of components 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. Further, the pressure-sensitive adhesive sheet of the present invention may be used for bonding modules such as a liquid crystal module and a touch panel module.
Examples of materials used for these members include glass, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polyethylene naphthalate, cycloolefin polymer, triacetyl cellulose, polyimide, and cellulose acylate.

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)
(Preparation of syrup A containing a (meth)acrylic polymer)
To a 2 L flask equipped with a stirrer, a nitrogen introduction tube, a cooling tube, and a thermometer, butyl acrylate 450 g, acrylate 4 hydroxylbutyl 360 g, cyclohexyl acrylate 100 g, isobutyl methacrylate 90 g, and n-dodecyl mercaptan 0.4 g were charged, After substituting nitrogen for 60 minutes at a nitrogen flow rate of 300 ml/min, the nitrogen flow rate was reduced to 100 ml/min, and the temperature was raised to 60° C. in a water bath and heated. Next, 0.15 g of AIBN was added, the reaction was performed for 30 minutes while controlling the heat generation, and then the mixture was cooled to synthesize a (meth)acrylic polymer. Then, the above-mentioned acrylic monomer was charged into the flask at a ratio of 45:36:10:9 to obtain an acrylic syrup A having a solid content concentration of 30% by mass.

(Molecular weight measurement of (meth)acrylic polymer A)
100 g of acrylic syrup A. IGM RESINS B. V. 0.5 g of a photoinitiator (EsacureOne) manufactured by the same company was added, and the mixture was stirred and defoamed, and coated on a 50 μm polyester film coated with a silicone release agent so that the thickness would be 100 μm. A 50 μm polyester film coated with a silicone release agent was overlaid. Then, it was irradiated with a chemical lamp at a light intensity of 7 mW/cm ² for 2 minutes to obtain a layer composed of the (meth)acrylic polymer A. As a result of GPC measurement of this layer collected and dissolved in ethyl acetate, the weight average molecular weight of the (meth)acrylic polymer A was 400,000.

(Synthesis of (meth)acrylic polymer B)
300 g of methyl methacrylate, 200 g of dicyclopentanyl methacrylate, 35 g of n-dodecyl mercaptan, 300 g of ethyl acetate, 200 g of methyl ethyl ketone were charged into a 2 L flask equipped with a stirrer, a nitrogen introducing tube, a cooling tube, and a thermometer, and a nitrogen flow rate of 300 ml/ After replacing the atmosphere with nitrogen for 60 minutes, the nitrogen flow rate was reduced to 100 ml/min, and the temperature was raised to 70° C. in a water bath and heated. Next, 0.4 g of AIBN was added, and after reacting for 3 hours while controlling heat generation, 0.6 g of AIBN was further added and reacted for 4 hours. In this way, a resin solution B containing the (meth)acrylic polymer B was obtained. As a result of GPC measurement of the resin solution B, the weight average molecular weight of the (meth)acrylic polymer B was 3,600.

(Preparation of adhesive sheet)
The resin solution B was poured into a metal vat, dried at a dryer temperature of 120° C. for 2 hours, and the solvent-removed product was dissolved in 10 g of 100 g of acrylic syrup A, and then IGM RESINS B. V. 0.5 g of a photoinitiator (EsacureOne) manufactured by the same company and 0.4 g of a polyfunctional monomer (A-400) manufactured by Shin-Nakamura Chemical Co., Ltd. were added and stirred and defoamed to prepare an adhesive composition. The coating liquid is applied on a 50 μm polyester film coated with a silicone release agent so that the adhesive layer has a thickness of 100 μm, and a 50 μm polyester film coated with a silicone release agent is further laid on it. It was After that, the pressure-sensitive adhesive sheet of Example 1 was obtained by irradiating with a chemical lamp at a light intensity of 7 mW/cm ² for 2 minutes and then irradiating with a high-pressure mercury lamp so that the integrated light amount was 1500 mJ/cm ² .

(Example 2)
The composition of the monomers in (Preparation of syrup A containing (meth)acrylic polymer) was changed to be as shown in Table 1. The amount of n-dodecyl mercaptan added in (Synthesis of (meth)acrylic polymer B) was changed to 30 g to obtain a polymer B having a weight average molecular weight of 4,900. Furthermore, the mixing amount of the (meth)acrylic polymer B with respect to the acrylic syrup A was changed to the ratio shown in Table 1, and the addition amount was set to 5 g. Except for the above matters, a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 1.

(Example 3)
The composition of the monomer in (Preparation of syrup A containing (meth)acrylic polymer) was changed to be as shown in Table 1, and the composition of the monomer in (Synthesis of (meth)acrylic polymer B) was as shown in Table 1. A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 1 except that the following changes were made.

(Example 4)
The composition of the monomers in (Preparation of syrup A containing (meth)acrylic polymer) was changed to be as shown in Table 1, and the addition amount of (meth)acrylic polymer B to acrylic syrup A was changed to 5 g. In the same manner as in Example 1, a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained.

(Example 5)
The composition of the monomers in (Preparation of syrup A containing (meth)acrylic polymer) was changed to be as shown in Table 1. The composition of the monomer in (Synthesis of (meth)acrylic polymer B) was changed as shown in Table 1. Further, the amount of the (meth)acrylic polymer B added to the acrylic syrup A was changed to 5 g. Except for the above matters, a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 1.

(Example 6)
To a 2 L flask equipped with a stirrer, a nitrogen introducing tube, a cooling tube, and a thermometer, 310 g of butyl acrylate, 145 g of 4-hydroxylbutyl acrylate, 45 g of cyclohexyl acrylate, 500 g of ethyl acetate, 0.4 g of n-dodecyl mercaptan were charged, and nitrogen was added. After substituting nitrogen for 60 minutes at a flow rate of 300 ml/min, the nitrogen flow rate was reduced to 100 ml/min, and the temperature was raised to 70° C. in a water bath and heated. Next, 0.25 g of AIBN was added and reacted for 2 hours while controlling heat generation, then 0.5 g of AIBN was additionally added and reacted at 75° C. for 5 hours. Then, 200 g of ethyl acetate was added and cooled to obtain a (meth)acrylic polymer A solution having a solid content concentration of 40% by mass. As a result of GPC measurement, the weight average molecular weight of the (meth)acrylic polymer A was 400,000.
To 100 g of the resulting acrylic polymer A solution, 4 g of the (meth)acrylic polymer B used in Example 1 was added, and 0.67 g of Tosoh Coronate L-75 as a cross-linking agent was added and mixed with stirring. It was an adhesive composition.
By applying the above-mentioned pressure-sensitive adhesive composition onto a 50 μm polyester film coated with a silicone release agent so that the thickness of the pressure-sensitive adhesive sheet layer after drying will be 100 μm, and drying in a dryer at 90° C. for 3 minutes. The adhesive sheet of Example 6 was obtained.

(Comparative Example 1)
Same as Example 1 except that the composition of the monomers in (Preparation of syrup A containing (meth)acrylic polymer) was changed as shown in Table 1 and that (meth)acrylic polymer B was not added. Then, an adhesive composition and an adhesive sheet were obtained.

(Comparative example 2)
Except that the composition of the monomers in (Preparation of syrup A containing (meth)acrylic polymer) was changed as shown in Table 1 and the addition amount of the polyfunctional monomer (A-400) was 0.3 g, A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 1.

(Comparative example 3)
(Preparation of syrup A containing (meth)acrylic polymer) The composition of the monomers was changed to be as shown in Table 1, except that the addition amount of the polyfunctional monomer (A-400) was 0.3 g. A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 1.

(Comparative example 4)
Except that the composition of the monomers in (Preparation of syrup A containing (meth)acrylic polymer) was changed as shown in Table 1 and the addition amount of the polyfunctional monomer (A-400) was 0.3 g, A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 1.

(Comparative example 5)
The composition of the monomers in (Preparation of syrup A containing (meth)acrylic polymer) was changed to be as shown in Table 1. Further, the composition of the (meth)acrylic polymer B was changed as shown in Table 1 and the amount of n-dodecyl mercaptan was changed to 1 g to obtain a polymer B having a weight average molecular weight of 14,000. Except for the above matters, a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 1.

(Comparative example 6)
The composition of the monomers in (Preparation of syrup A containing (meth)acrylic polymer) was changed to be as shown in Table 1, and hydrogenated terpene phenol resin (UH-115 average molecular weight manufactured by Yasuhara Chemical Co., Ltd.) was used instead of polymer B. A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 1 except that 700, glass transition temperature 113°C) was added.

(Measurement)
(Measurement of glass transition temperature of (meth)acrylic polymer B)
For measuring the glass transition temperature of the (meth)acrylic polymer B, a DSC6200 manufactured by Seiko Instruments Inc. was used. The reference is 10 mg of alumina, and about 10 mg of the solvent-removed product of the resin solution B is put in a sample aluminum pan having a diameter of 5 mm, and the temperature is raised from 0°C to 150°C at a temperature rising rate of 10°C/min in an environment of a nitrogen flow rate of 50 ml/min. The temperature was raised. At that time, the inflection point at which the specific heat changes was read as the glass transition temperature of the (meth)acrylic polymer B.

(Evaluation)
(Moist heat constant load)
The separators on one surface of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were removed, and the pressure-sensitive adhesive sheets were attached to a 100 μm polyester film (A4300 manufactured by Toyobo) that had been subjected to an easy-adhesion treatment. Next, the portion to be adhered to the adherend was cut to have a width of 25 mm and a length of 75 mm. This sample was placed on a float glass having a thickness of 1 mm, a width of 115 mm, and a length of 250 mm, or a polycarbonate having a thickness of 1 mm, a width of 115 mm, and a length of 250 mm (Panlite 1151 made by Teijin Ltd.) at a distance of 20 mm or more from the end of the adherend, and a total length of 75 mm After adhering 50 mm of the above to the adherend, it was reciprocated twice with a 2 kg roller and pressure-bonded. After that, it was treated in an autoclave at a temperature of 30° C. and a pressure of 0.5 MPa for 30 minutes, and then allowed to stand for one day under atmospheric pressure and room temperature. Then, the sample containing each adherend was left to stand for 30 minutes inside a thermo-hygrostat adjusted to a temperature of 85° C. and a relative humidity of 85%. At that time, the adherends were placed so that they were on top. Then, a weight of 100 g was hooked on an end portion of the sample, which is an unbonded portion, having a length of 25 mm, the time until the adhesive sheet was peeled from the adherend surface and the weight fell, was measured and evaluated according to the following criteria.
◯: Time required for peeling the adhesive sheet from the adherend surface and dropping the weight is 15 minutes or more. X: Time required for peeling the adhesive sheet from the adherend surface and dropping the weight is less than 15 minutes.

(Yellowing)
After sticking glass (made by Matsunami) having a width of 52 mm, a length of 76 mm, and a thickness of 1 mm on both sides of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, the temperature was 30° C. in an environment of 0.5 MPa in an autoclave. It was treated for 30 minutes, and allowed to stand for 1 day under atmospheric pressure and room temperature environment. Then, a sample including each adherend was placed on a xenon weather meter SX75 manufactured by Suga Test Instruments Co., Ltd., and a light beam was irradiated for 300 hours under the conditions of a relative humidity of 50%, a black panel temperature of 63° C. and an illuminance of 180 W/cm ² , and then a suga test. The b* value of chromaticity was measured with a device colorimeter, Color Cute i, and evaluated according to the following criteria.
◯: The b* value after the weather resistance test increased with respect to the b* value before evaluation, and the b* value was less than 2. Δ: The b* value after the weather resistance test increased with respect to the b* value before evaluation. However, the b* value is 2 or more and less than 3, and the b* value after the weathering test is increased with respect to the b* value before the evaluation, and the b* value is 3 or more.

<Alkyl (meth)acrylate>
BA: butyl acrylate 2EHA: 2-ethylhexyl acrylate iBMA: isobutyl methacrylate MMA: methyl methacrylate <(meth)acrylic monomer having a hydroxyl group>
4HBA: 4-hydroxylbutyl acrylate <monomer having ring structure>
CHA: cyclohexyl acrylate CHMA: cyclohexyl methacrylate DCPA: dicyclopentanyl acrylate PO-A: phenylnoxyethyl acrylate NVP: n-vinylpyrrolidone DCPMA: dicyclopentanyl methacrylate IBXMA: isobornyl methacrylate St: styrene

The pressure-sensitive adhesive sheets obtained in the examples showed excellent adhesion to any adherend and had low yellowing. In Comparative Examples 1 to 3, it was shown that the adhesion to polycarbonate or glass was poor, and excellent adhesion could not be obtained depending on the type of adherend. Further, in Comparative Example 4, the adhesive sheet was yellowed.

10 Adhesive Sheet with Release Sheet 11 Adhesive Layer 12a Release Sheet 12b Release Sheet

Claims (4)

A (meth)acrylic polymer A having a (meth)acrylic monomer unit having a hydroxyl group and a (meth)acrylic monomer unit having a ring structure and having a weight average molecular weight of more than 10,000.
A pressure-sensitive adhesive sheet comprising a (meth)acrylic polymer B having a weight average molecular weight of 3,000 to 10,000 and a glass transition temperature of 20 to 120° C.,
The content of the (meth)acrylic monomer unit having a hydroxyl group in the (meth)acrylic polymer A is 20 mass% or more based on the total mass of the (meth)acrylic polymer A, and the ring structure is The (meth)acrylic monomer unit having does not have a nitrogen atom as a ring-constituting atom,
The (meth)acrylic polymer B contains a monomer unit having an alicyclic ring, and the alicyclic ring has 6 or more carbon atoms,
The (meth)acrylic polymer B has substantially no functional group,
The content of the (meth)acrylic polymer B is 1 part by mass or more based on 100 parts by mass of the (meth)acrylic polymer A, which is an adhesive sheet. The content of the (meth)acrylic monomer unit having the ring structure in the (meth)acrylic polymer A is 5% by mass or more based on the total mass of the (meth)acrylic polymer A. Adhesive sheet. Further comprising at least one selected from the polyfunctional monomer and the crosslinking agent, the adhesive sheet according to claim 1 or 2. Further comprising a photopolymerization initiator, the photopolymerization initiator, acetophenone-based photopolymerization initiator or acylphosphine oxide-based photopolymerization initiator, the pressure-sensitive adhesive sheet according to any one of claims 1-3.