JP6670958B2 - Adhesive sheet - Google Patents

Description

  The present invention relates to an adhesive sheet.

  Generally, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive; the same applies hereinafter) exhibits a state of a soft solid (viscoelastic body) in a temperature range around room temperature, and has a property of easily adhering to an adherend by pressure. Utilizing such properties, pressure-sensitive adhesives are widely used in various industrial fields such as home appliances, automobiles, OA equipment, and the like as joining means having good workability and high adhesion reliability. As the base polymer of the pressure-sensitive adhesive, a polymer exhibiting rubber elasticity at normal temperature can be preferably employed. Patent Documents 1 and 2 are known as prior art documents relating to an adhesive. Patent Document 1 discloses a photo-curable acrylic pressure-sensitive adhesive. Patent Document 2 relates to a pressure-sensitive adhesive sheet using a polyolefin-based foam base material that is a non-viscoelastic body.

JP 2011-84732 A JP 2013-40329 A

  The pressure-sensitive adhesive is typically formed in a film shape and used in the form of a pressure-sensitive adhesive sheet containing the film-shaped pressure-sensitive adhesive (pressure-sensitive adhesive layer). Various performances are required for the pressure-sensitive adhesive sheet depending on the application. For example, it would be useful if a pressure-sensitive adhesive sheet having high resistance to peeling from a low-polarity adherend (peel strength) and excellent flexibility was provided.

  Accordingly, an object of the present invention is to provide a pressure-sensitive adhesive sheet that exhibits high peel strength with respect to a low-polarity adherend and has excellent flexibility.

  According to the present invention, there is provided a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer (A) constituting a pressure-sensitive adhesive surface and a viscoelastic layer (B) supporting the pressure-sensitive adhesive layer (A). In this pressure-sensitive adhesive sheet, the viscoelastic layer (B) contains hollow particles or has air bubbles. The pressure-sensitive adhesive layer (A) contains an acrylic polymer (a) as a base polymer. The copolymerization ratio of the acidic group-containing monomer in the acrylic polymer (a) is 5% by weight or less.

  Since the pressure-sensitive adhesive sheet having the above configuration includes the viscoelastic body layer (B) containing hollow particles or having air bubbles, the pressure-sensitive adhesive layer (A) is utilized by utilizing the mechanical properties of the viscoelastic body layer (B). (Peel strength; for example, a 90-degree peel strength measured according to the method described in Examples described later) is improved. Further, by providing the viscoelastic layer (B), the pressure-sensitive adhesive sheet becomes excellent in flexibility, and an effect such as improvement in surface followability can be expected. For example, the hollow particles function as a filler for the viscoelastic body layer (B) and can increase the shear strength of the viscoelastic body layer (B). An increase in the shear strength of the viscoelastic layer (B) can advantageously contribute to an improvement in peel strength. Further, since the hollow particles have a small specific gravity, it is preferable that the viscoelastic layer (B) contains the hollow particles also from the viewpoint of reducing the weight of the pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet provided with the viscoelastic layer (B) having bubbles has good followability to the surface shape and deformation of the adherend, and easily maintains a state in which the pressure-sensitive adhesive surface is in close contact with the surface of the adherend. This can advantageously contribute to improving the peel strength of various adherends including low-polarity adherends. Furthermore, since the copolymerization ratio of the acidic group-containing monomer in the acrylic polymer (a) is suppressed to a predetermined value or less, the adhesion to the low-polarity adherend is further improved.

  In addition, "the viscoelastic body layer (B) contains hollow particles or has air bubbles" refers to an embodiment in which the viscoelastic body layer (B) contains hollow particles and has substantially no air bubbles; And an embodiment having bubbles, and an embodiment including hollow particles and having bubbles. The “acrylic polymer having a copolymerization ratio of the acidic group-containing monomer of 5% by weight or less” refers to an acrylic polymer obtained by polymerizing a monomer material substantially free of an acidic group-containing monomer, and an acidic polymer. An acrylic polymer obtained by polymerizing a monomer raw material containing a group-containing monomer and having a proportion of an acidic group-containing monomer of 5% by weight or less in the monomer raw material.

  In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the viscoelastic layer (B) contains an acrylic polymer (b) as a base polymer. The viscoelastic layer (B) having this configuration is preferable because the balance between flexibility and cohesiveness can be easily adjusted. Further, since both the pressure-sensitive adhesive layer (A) and the viscoelastic body layer (B) contain an acrylic polymer, the adhesion (anchoring property) between the pressure-sensitive adhesive layer (A) and the viscoelastic body layer (B) is improved. However, an event of peeling (anchor breakage) between the pressure-sensitive adhesive layer (A) and the viscoelastic body layer (B) when peeling the pressure-sensitive adhesive sheet can be preferably suppressed. Thereby, it is possible to preferably realize both high peel strength and re-peelability with respect to a low-polarity adherend.

  In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the acrylic polymer (b) is obtained by polymerizing a monomer material containing an acidic group-containing monomer. With such a configuration, the cohesiveness of the viscoelastic layer (B) that does not constitute the adhesive surface is improved while maintaining the adhesiveness to the low-polarity adherend, and for example, the shear strength and the holding power are improved. Can be expected. The ratio (ACb / ACa) of the copolymerization ratio ACb of the acidic group-containing monomer in the acrylic polymer (b) to the copolymerization ratio ACa of the acidic group-containing monomer in the acrylic polymer (a) is 2 or more. Is more preferred.

  In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive layer (A) is at least one kind selected from the group consisting of a rosin-based tackifying resin, a terpene-based tackifying resin, and a phenol-based tackifying resin. Contains tackifier. By using the above tackifier, the peel strength of the pressure-sensitive adhesive layer (A) on the pressure-sensitive adhesive surface is further improved. Further, the content of the tackifier in the pressure-sensitive adhesive layer (A) is more preferably 10 to 50 parts by weight based on 100 parts by weight of the base polymer.

In a preferred embodiment of the PSA sheet disclosed herein, the ratio of the thickness T _B of the pressure-sensitive adhesive layer wherein the viscoelastic layer to the thickness T _A of (A) (B) (T B / T A) is 12 That is all. With such a configuration, the action of the viscoelastic body layer (B) (improvement of flexibility, peel strength, followability, and the like) can be more sufficiently exhibited. In addition, since the thickness of the pressure-sensitive adhesive layer (A) is limited, the removability tends to be improved.

  In a preferred aspect of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive surface has a 90 ° peel strength with respect to polypropylene of 30 N / 25 mm or more. The pressure-sensitive adhesive sheet having the above-mentioned pressure-sensitive adhesive strength to polypropylene, which is a typical example of a low-polarity material, can exhibit a higher peel strength to a low-polarity adherend.

It is a schematic sectional view showing the composition of the pressure sensitive adhesive sheet concerning one embodiment. It is a typical sectional view showing the composition of the pressure sensitive adhesive sheet concerning other embodiments. It is a typical sectional view showing the composition of the pressure sensitive adhesive sheet concerning other embodiments.

Hereinafter, preferred embodiments of the present invention will be described. It should be noted that matters other than matters specifically mentioned in the present specification and necessary for carrying out the present invention can be grasped as design matters of those skilled in the art based on conventional techniques in the relevant field. The present invention can be implemented based on the contents disclosed in this specification and common technical knowledge in the field.
In the following drawings, members / parts having the same function will be denoted by the same reference numerals and described, and redundant description may be omitted or simplified. Further, the embodiments described in the drawings are schematically illustrated in order to clearly explain the present invention, and do not accurately represent the size or scale of the pressure-sensitive adhesive sheet of the present invention actually provided as a product.

In this specification, the term "pressure-sensitive adhesive" refers to a material which has a property of exhibiting a soft solid (viscoelastic body) state in a temperature range around room temperature and easily adhering to an adherend by pressure as described above. . The pressure-sensitive adhesive referred to here is generally a complex tensile modulus E ^* (1 Hz) as defined in "CA Dahlquist," Adhesion: Fundamental and Practice ", McLaren & Sons, (1966) P. 143. It is a material having a property satisfying <10 ⁷ dyne / cm ² (typically, a material having the above property at 25 ° C.). The pressure-sensitive adhesive in the technology disclosed herein can be understood as a solid content of the pressure-sensitive adhesive composition or a component of the pressure-sensitive adhesive layer.
Further, the “base polymer” of the pressure-sensitive adhesive refers to a main component of a polymer contained in the pressure-sensitive adhesive (typically, a polymer exhibiting rubber elasticity in a temperature range around room temperature) (that is, the polymer component). And the component having the largest blending ratio, typically a component occupying more than 50% by weight).

<Basic configuration of adhesive sheet>
The pressure-sensitive adhesive sheet disclosed herein includes a pressure-sensitive adhesive layer (A) constituting a pressure-sensitive adhesive surface, and a viscoelastic layer (B) supporting the pressure-sensitive adhesive layer (A). The pressure-sensitive adhesive layer (A) forms at least one surface (one or both surfaces) of the pressure-sensitive adhesive sheet in a form supported by the viscoelastic layer (B). The concept of the pressure-sensitive adhesive sheet referred to here includes what is called a pressure-sensitive adhesive tape, a pressure-sensitive adhesive label, a pressure-sensitive adhesive film and the like. The pressure-sensitive adhesive sheet provided by the present specification may be in the form of a roll or a sheet. Alternatively, the pressure-sensitive adhesive sheet may be a form processed into various shapes.

A typical configuration example of the pressure-sensitive adhesive sheet disclosed herein is schematically shown in FIGS.
The pressure-sensitive adhesive sheet 1 shown in FIG. 1 is a double-sided pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer (A) 12 and a viscoelastic layer (B) 14 supporting the back surface thereof. The viscoelastic layer (B) 14 is an adhesive layer. The first surface (first adhesive surface) 1A of the adhesive sheet 1 is constituted by the surface 12A of the adhesive layer (A) 12, and the second surface (second adhesive surface) 1B of the adhesive sheet 1 is a viscoelastic layer. (Adhesive layer) (B) It is constituted by the surface 14A of 14. In the pressure-sensitive adhesive sheet 1 having such a configuration, the first pressure-sensitive adhesive surface 1A can exhibit good adhesiveness to a low-polarity adherend. Further, since the pressure-sensitive adhesive sheet 1 includes the viscoelastic body layer (B) 14, it can be excellent in flexibility. Taking advantage of such features, the adhesive sheet 1 attaches the first adhesive surface 1A to a low-polarity adherend such as a polyolefin resin and adheres the second adhesive surface 1B to various adherends, for example. It can be preferably used in embodiments. The pressure-sensitive adhesive sheet 1 is suitable, for example, as a double-sided pressure-sensitive adhesive sheet for firmly joining various adherends to low-polarity adherends.

  The pressure-sensitive adhesive sheet 2 shown in FIG. 2 includes a first pressure-sensitive adhesive layer (A) 22 and a second pressure-sensitive adhesive layer (A) 23, and a viscoelastic body layer (B) 24 disposed therebetween. It is a double-sided adhesive sheet. The viscoelastic layer (B) 24 may be an adhesive layer or a non-adhesive layer. The first surface (first adhesive surface) 2A of the adhesive sheet 2 is constituted by the surface 22A of the first adhesive layer (A) 22 supported on the first surface of the viscoelastic body layer (B) 24. I have. The second surface (second adhesive surface) 2B of the adhesive sheet 2 is constituted by the surface 23A of the second adhesive layer (A) 23 supported on the second surface of the viscoelastic body layer (B) 24. I have. In the pressure-sensitive adhesive sheet 2 having such a configuration, both the first pressure-sensitive adhesive surface 2A and the second pressure-sensitive adhesive surface 2B can exhibit good adhesiveness to a low-polarity adherend. Further, since the pressure-sensitive adhesive sheet 2 includes the viscoelastic body layer (B) 24, it can be excellent in flexibility. Taking advantage of such features, the pressure-sensitive adhesive sheet 2 can be preferably used, for example, in a mode in which the first pressure-sensitive adhesive surface 2A and the second pressure-sensitive adhesive surface 2B are respectively adhered to low-polarity adherends. The pressure-sensitive adhesive sheet 2 is suitable, for example, as a double-sided pressure-sensitive adhesive sheet for firmly bonding low-polarity adherends to each other.

  The pressure-sensitive adhesive sheet 3 shown in FIG. 3 is a single-sided pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer (A) 32, a viscoelastic layer (B) 34 supporting the back surface thereof, and a support base material 36 supporting the back surface. is there. The viscoelastic layer (B) 34 is typically an adhesive layer. The pressure-sensitive adhesive sheet 3 has a pressure-sensitive adhesive surface 3A constituted by a surface 32A of the pressure-sensitive adhesive layer (A) 32. The pressure-sensitive adhesive sheet 3 having such a configuration can be preferably used, for example, in a mode in which the pressure-sensitive adhesive surface 3A is attached to a low-polarity adherend.

  In each of the pressure-sensitive adhesive sheets 1 to 3 shown in FIGS. 1 to 3, the viscoelastic material layers (B) 14, 24, and 34 each include air bubbles or hollow particles, and include both air bubbles and hollow particles. You may go out. Preferred examples from the viewpoint of reducing the weight of the pressure-sensitive adhesive sheet include a structure in which the viscoelastic layer (B) contains at least one of bubbles and hollow particles, a structure in which the viscoelastic layer (B) contains at least hollow particles, and a viscoelastic body. An embodiment in which the layer (B) contains both air bubbles and hollow particles is exemplified.

  The hollow particles and air bubbles contained in the viscoelastic layer (B) may reduce the smoothness of the surface of the viscoelastic layer (B) depending on the size and content. When the smoothness of the surface of the viscoelastic body layer (B) decreases, for example, when the viscoelastic body layer (B) is an adhesive layer and the surface is directly adhered to the adherend, the adhesion to the adherend is reduced. It may be insufficient and the peel strength tends to decrease. In the pressure-sensitive adhesive sheet disclosed herein, a pressure-sensitive adhesive layer (A) constituting a pressure-sensitive adhesive surface is disposed on the viscoelastic body layer (B). Therefore, the adhesion between the adherend and the adhesive surface is not easily affected by the surface smoothness of the viscoelastic layer (B). For this reason, the content ratio of hollow particles and air bubbles in the viscoelastic material layer (B) can be easily adjusted, and a pressure-sensitive adhesive sheet having more excellent performance balance can be suitably realized.

  In the pressure-sensitive adhesive sheets 1 to 3 illustrated in FIGS. 1 to 3, each layer illustrated in the drawings may have a single-layer structure, or may have a multilayer structure of two or more layers (that is, a structure including a plurality of layers). It may be. For example, each of the pressure-sensitive adhesive layers (A) 12, 22, 23, and 32 may be composed of a single-layered pressure-sensitive adhesive layer (A), or may be composed of a plurality of pressure-sensitive adhesive layers. Or a pressure-sensitive adhesive layer (A) disposed on both surfaces of a support substrate.

  Further, the pressure-sensitive adhesive sheets 1 to 3 illustrated in FIGS. 1 to 3 may further have a layer not shown in the drawings. For example, another layer may be arranged between any of the layers in FIGS. As an example of such a configuration, a configuration in which the second pressure-sensitive adhesive layer (A) is further disposed between the viscoelastic body layer (B) 34 and the support base material 36 in the structure illustrated in FIG. Can be The pressure-sensitive adhesive sheet disclosed herein is not exposed to the surface of the pressure-sensitive adhesive sheet, in addition to the pressure-sensitive adhesive layer (A) constituting the pressure-sensitive adhesive surface, as in the second pressure-sensitive adhesive layer (A), for example. (Which does not constitute a surface). The other layer may be a layer other than the pressure-sensitive adhesive layer. For example, it may be a plastic film, a primer layer, a primer layer, a release treatment layer, a coloring layer such as a printing layer, a metal deposition layer, an antistatic layer, a surface protection layer, and the like. Alternatively, the pressure-sensitive adhesive sheets 1 to 3 disclosed herein may not include a primer layer or a primer layer. The technology disclosed herein can be preferably implemented in a mode that does not include a primer layer between the surface of the adherend (not shown) and the adhesive surfaces 12A, 22A, 23A, and 32A. Also, for example, in the pressure-sensitive adhesive sheet, even in a mode in which there is no primer layer between the pressure-sensitive adhesive layer (A) and the viscoelastic material layer (B), the technique disclosed herein does not apply when the pressure-sensitive adhesive sheet is peeled off. This can be preferably performed without causing an anchor breaking event (an event of peeling between the pressure-sensitive adhesive layer (A) and the viscoelastic body layer (B)).

<Viscoelastic layer (B)>
[Base polymer (b)]
The composition of the viscoelastic body layer (B) is not particularly limited as long as it exhibits properties of the viscoelastic body in a temperature range around room temperature. The viscoelastic layer (B) is made of an acrylic viscoelastic, rubber viscoelastic, silicone viscoelastic, polyester viscoelastic, urethane viscoelastic, polyether viscoelastic, polyamide viscoelastic It may be a layer containing one or more selected from various viscoelastic bodies such as a body and a fluorine-based viscoelastic body. Here, the acryl-based viscoelastic body refers to an acryl-based polymer containing a base polymer (a main component of the polymer component, that is, a component having the largest blending ratio among the polymer components, typically more than 50% by weight. Viscoelastic body). The same applies to rubber-based and other viscoelastic materials. Here, the viscoelastic body referred to herein is a material having both viscous and elastic properties, that is, a material having a property that the phase of the complex elastic modulus is more than 0 and less than π / 2 (typically at 25 ° C. A material having the above properties). From the viewpoint of flexibility and the like, a material having a property satisfying the complex tensile modulus E ^* (1 Hz) <10 ⁷ dyne / cm ² (typically, a material having the above property at 25 ° C.) is preferable.

  The viscoelastic layer (B) may be an adhesive layer or a non-adhesive layer. Here, the “adhesive layer” refers to a SUS304 stainless steel plate as an adherend in accordance with JIS Z 0237 (2009), and a 2 kg roller is reciprocated once under a measurement environment of 23 ° C. to adhere to the adherend. A layer having a peel strength of 0.1 N / 20 mm or more when peeled in a 180 ° direction at a tensile speed of 300 mm / min after 30 minutes from the start. Also called an adhesive layer. The “non-adhesive layer” refers to a layer that does not correspond to the above-mentioned adhesive layer, and typically refers to a layer having the above-mentioned peel strength of less than 0.1 N / 20 mm. When a 2 kg roller is reciprocated one time in a measurement environment of 23 ° C. and pressed against a SUS304 stainless steel plate, a layer that does not stick to the stainless steel plate (a layer that does not substantially exhibit tackiness) is a non-adhesive layer referred to herein. Is a typical example included in the concept. Although not particularly limited, the technology disclosed herein includes a form including the viscoelastic layer (B) corresponding to the pressure-sensitive adhesive layer, that is, includes the pressure-sensitive adhesive layer (B) as the viscoelastic layer (B). It can be preferably implemented in the form of an adhesive sheet.

  In a preferred embodiment, the viscoelastic layer (B) may be a layer containing an acrylic polymer (b) as the base polymer (b), that is, an acrylic viscoelastic layer. The viscoelastic layer (B) having such a composition is preferable because the balance between flexibility and cohesiveness can be easily adjusted. Further, since both the pressure-sensitive adhesive layer (A) and the viscoelastic body layer (B) contain an acrylic polymer, the adhesion between the two layers is improved, and the phenomenon of anchor breakage when peeling off the pressure-sensitive adhesive sheet is preferably suppressed. obtain. The proportion of the acrylic polymer (b) in the viscoelastic layer (B) is not particularly limited, but is typically at least 50% by weight, preferably at least 70% by weight, more preferably at least 80% by weight. .

  As the acrylic polymer (b), for example, a polymer of a monomer raw material which contains an alkyl (meth) acrylate as a main monomer and may further contain a sub-monomer having copolymerizability with the main monomer is preferable. Here, the main monomer refers to a component that accounts for more than 50% by weight of all monomer components contained in the monomer raw material. Typically, the composition of the monomer component contained in the monomer raw material generally matches the composition of the monomer unit contained in the acrylic polymer (b).

As the alkyl (meth) acrylate, for example, a compound represented by the following formula (1) can be suitably used.
CH ₂ ＣC (R ¹ ) COOR ² (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. R ² is an alkyl group having 1 to 20 carbon atoms (hereinafter, such a range of the number of carbon atoms may be referred to as “C _1-20 ”). In light of the storage elastic modulus of the pressure-sensitive adhesive and the like, alkyl (meth) acrylate in which R ² is a C _1-14 alkyl group is preferable, and alkyl (meth) acrylate in which R ² is a C _1-10 alkyl group is more preferable. Alkyl (meth) acrylate in which R ² is a butyl group or a 2-ethylhexyl group is particularly preferred.

Examples of the alkyl (meth) acrylate in which R ² is a C _1-20 alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl (meth) acrylate. A) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (Meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate Rate, lauryl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, Eicosyl (meth) acrylate and the like. These alkyl (meth) acrylates can be used alone or in combination of two or more. Particularly preferred alkyl (meth) acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

  Although not particularly limited, the amount of the alkyl (meth) acrylate can be, for example, 60% by weight or more, and usually 70% by weight or more of all monomer components constituting the acrylic polymer (b). It is preferable that the content be 80% by weight or more. From the viewpoint of the cohesiveness of the viscoelastic layer (B), the amount of the alkyl (meth) acrylate is suitably 99.5% by weight or less, preferably 99% by weight or less, more preferably 95% by weight or less. is there.

Examples of the auxiliary monomer include a monomer having a functional group (hereinafter, also referred to as “functional group-containing monomer”). Such a functional group-containing monomer can be used for the purpose of introducing a crosslinking point into the acrylic polymer (b) to increase the cohesive force of the viscoelastic layer (B). As such a functional group-containing monomer,
For example, ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), crotonic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, citracone Carboxyl group-containing monomers such as ethylenically unsaturated dicarboxylic acids such as acids and metal salts thereof (eg, alkali metal salts);
An acid anhydride group-containing monomer such as an acid anhydride of the above-mentioned ethylenically unsaturated dicarboxylic acid such as maleic anhydride and itaconic anhydride;
For example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl Hydroxyalkyl (meth) acrylates such as (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, and (4-hydroxymethylcyclohexyl) methyl (meth) acrylate A) acrylates, N-methylol (meth) acrylamide, vinyl alcohol, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene Unsaturated alcohols such as recall monovinyl ether, hydroxyl group (hydroxyl group) containing monomer;
For example, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, N-methoxymethyl (meth) acrylamide, Amide group-containing monomers such as N-butoxymethyl (meth) acrylamide;
Cyano group-containing monomers such as acrylonitrile and methacrylonitrile;
For example, sulfonic acids such as styrenesulfonic acid, allylsulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, (meth) acrylamidopropanesulfonic acid, sulfopropyl (meth) acrylate, and (meth) acryloyloxynaphthalenesulfonic acid. Group-containing monomers;
A phosphoric acid group-containing monomer such as, for example, 2-hydroxyethylacryloyl phosphate;
Oxazoline group-containing monomers such as 2-vinyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline and 2-isopropenyl-2-oxazoline;
Aziridine group-containing monomers such as, for example, (meth) acryloylaziridine, 2-aziridinylethyl (meth) acrylate;
Amino group-containing monomers such as, for example, aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, t-butylaminoethyl (meth) acrylate;
For example, epoxy group (glycidyl group) -containing monomers such as glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, and allyl glycidyl ether;
For example, ketone group-containing monomers such as diacetone (meth) acrylamide, diacetone (meth) acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, and vinyl acetoacetate;
Isocyanate group-containing monomers such as 2- (meth) acryloyloxyethyl isocyanate;
For example, alkoxy group-containing monomers such as methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, and ethoxypropyl (meth) acrylate;
For example, 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 3- (meth) acryloxypropylmethyldimethoxysilane, 3- (meth) acryloxypropylmethyldiethoxysilane, etc. An alkoxysilyl group-containing monomer of
In addition, a macromonomer having a radically polymerizable vinyl group at the terminal of a monomer obtained by polymerizing a vinyl group may be used. These can be used alone or in combination of two or more.

  When the functional group-containing monomer as described above is used as the auxiliary monomer, the amount of the monomer may be appropriately selected so as to realize a desired cohesive force, and is not particularly limited. The amount of the functional group-containing monomer to be used can be, for example, 0.5% by weight or more of all monomer components constituting the acrylic polymer (b), and usually 1% by weight or more. It is preferably at least 3% by weight, more preferably at least 5% by weight. In addition, from the viewpoint of achieving a good balance between flexibility and cohesion, the amount of the functional group-containing monomer is appropriately set to 30% by weight or less of all the monomer components, and is preferably set to 25% by weight or less. More preferably, the content is 20% by weight or less.

  In a preferred embodiment, the acrylic polymer (b) disclosed herein is obtained by polymerizing a monomer material containing an acidic group-containing monomer. Thereby, the balance between the flexibility and the cohesiveness of the viscoelastic layer (B) can be preferably adjusted. The acidic group-containing monomer typically includes various carboxyl group-containing monomers, metal salts thereof (eg, alkali metal salts), and acid anhydride group-containing monomers. As specific examples of these acidic group-containing monomers, one or two or more of those exemplified above as the carboxyl group-containing monomer and its metal salt (for example, an alkali metal salt) and the acid anhydride group-containing monomer can be preferably used. . Among them, AA and MAA are more preferable.

  When an acidic group-containing monomer is used, its amount may be appropriately selected so as to achieve a desired cohesive force, and is not particularly limited. The amount of the acidic group-containing monomer used is suitably, for example, 1% by weight or more of all monomer components constituting the acrylic polymer (b), and is usually 3% by weight or more (for example, 5% by weight or more, typically It is preferably 8% by weight or more). From the viewpoint of achieving a good balance between flexibility and cohesion, the amount of the acidic group-containing monomer is 25% by weight or less (for example, 20% by weight or less, typically 15% by weight or less) of all monomer components. Is appropriate.

The monomer raw material may contain a sub-monomer other than the functional group-containing monomer described above for the purpose of adjusting the glass transition temperature (Tg), improving the cohesive force, and the like. Such secondary monomers include
For example, vinyl carboxylate esters such as vinyl acetate (VAc), vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl cyclohexanecarboxylate, and vinyl benzoate;
For example, aromatic vinyl compounds such as styrene, substituted styrene (such as α-methylstyrene), and vinyl toluene;
For example, aromatics such as aryl (meth) acrylates (eg, phenyl (meth) acrylate), aryloxyalkyl (meth) acrylates (eg, phenoxyethyl (meth) acrylate), arylalkyl (meth) acrylates (eg, benzyl (meth) acrylate) A (meth) acrylate containing a sex ring;
For example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N Monomers having a nitrogen atom-containing ring such as -vinyl oxazole, N-vinyl morpholine, N-vinyl caprolactam, N- (meth) acryloyl morpholine;
For example, olefin monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene;
Chlorine-containing monomers such as, for example, vinyl chloride and vinylidene chloride;
For example, vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether;
And the like. These can be used alone or in combination of two or more. The use amount of such a sub-monomer is not particularly limited as long as it is appropriately selected according to the purpose and application, but is preferably, for example, 10% by weight or less of all monomer components.

  The monomer raw material may contain a polyfunctional monomer as necessary for the purpose of crosslinking or the like. Examples of such polyfunctional monomers include 1,6-hexanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and polypropylene glycol di ( (Meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, Two or more polymerizable functional groups (typically, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, etc. (Meth) include monomers having an acryloyl group). These can be used alone or in combination of two or more. From the viewpoint of reactivity and the like, generally, a polyfunctional monomer having two or more (typically three or more) acryloyl groups in one molecule is preferable. When such a polyfunctional monomer is used, its amount is not particularly limited, but from the viewpoint of the flexibility of the viscoelastic layer (B), it is usually 2% by weight or less (more preferably 1% by weight) of all monomer components. % Or less).

  The monomer composition of the acrylic polymer (b) can be set so that the Tg of the acrylic polymer (b) is, for example, −70 ° C. or more and −10 ° C. or less. From the viewpoint of flexibility, the Tg of the acrylic polymer (b) is suitably −20 ° C. or lower, preferably −30 ° C. or lower, more preferably −40 ° C. or lower, and still more preferably −50 ° C. or lower. In addition, from the viewpoint of the cohesiveness of the viscoelastic layer (B), it is usually preferable that the Tg is -65 ° C or higher.

  Here, the Tg of the acrylic polymer (b) means the Tg of the homopolymer (homopolymer) of each monomer constituting the acrylic polymer (b) and the weight fraction of the monomer (copolymerization ratio based on weight). ) Means a value obtained from the Fox equation. Therefore, the Tg of the acrylic polymer (b) can be adjusted by appropriately changing the monomer composition (namely, the type and the amount ratio of the monomer used for the synthesis of the acrylic polymer (b)). As the Tg of the homopolymer, a value described in a known document is adopted.

In the technology disclosed herein, the following values are specifically used as the Tg of the homopolymer.
2-ethylhexyl acrylate -70 ° C
n-butyl acrylate -55 ° C
2-hydroxyethyl acrylate -15 ° C
Vinyl acetate 32 ° C
Acrylic acid 106 ° C
Methacrylic acid 228 ° C
For the Tg of the homopolymer other than those exemplified above, the values described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) are used.

If not described in the above “Polymer Handbook”, the value obtained by the following measurement method is used (see JP-A-2007-51271).
Specifically, 100 parts by weight of a monomer, 0.2 parts by weight of azobisisobutyronitrile and 200 parts by weight of ethyl acetate as a polymerization solvent were placed in a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser. It is charged and stirred for 1 hour while flowing nitrogen gas. After removing the oxygen in the polymerization system in this way, the temperature is raised to 63 ° C. and the reaction is performed for 10 hours. Next, the mixture is cooled to room temperature to obtain a homopolymer solution having a solid content of 33% by weight. The homopolymer solution is cast on a release liner and dried to prepare a test sample (sheet-like homopolymer) having a thickness of about 2 mm. This test sample was punched out into a disk shape having a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to a shear strain of a frequency of 1 Hz using a viscoelasticity tester (ARES, manufactured by Rheometrics), while being subjected to a temperature range of −70 to 150 ° C. The viscoelasticity is measured in a shearing mode at a temperature rising rate of 5 ° C./min, and the peak top temperature of tan δ is defined as Tg of the homopolymer.

  The acrylic polymer (b) can be adjusted by a known or commonly used polymerization method. Examples of the polymerization method include thermal polymerization such as solution polymerization, emulsion polymerization and bulk polymerization (typically performed in the presence of a thermal polymerization initiator); light such as ultraviolet (UV) light, β-ray, and γ. Active energy ray polymerization performed by irradiating an active energy ray such as radiation such as a ray; and the like can be appropriately employed. Examples of the active energy ray polymerization here include photopolymerization performed by irradiating light such as UV (typically performed in the presence of a photopolymerization initiator), α-ray, β-ray, and γ. Radiation polymerization performed by irradiating ionizing radiation such as a beam, a neutron beam and an electron beam. These polymerization methods can be used alone or in an appropriate combination of two or more.

In the polymerization, a known or commonly used polymerization initiator can be used depending on the polymerization method and the polymerization mode. As the polymerization initiator, one type can be used alone, or two or more types can be used in appropriate combination.
A photopolymerization initiator can be suitably used from the viewpoint that the polymerization time can be shortened. The photopolymerization initiator is not particularly limited, but, for example, a ketal-based photopolymerization initiator, an acetophenone-based photopolymerization initiator, a benzoin ether-based photopolymerization initiator, an acylphosphine oxide-based photopolymerization initiator, α- Ketol-based photopolymerization initiator, aromatic sulfonyl chloride-based photopolymerization initiator, photoactive oxime-based photopolymerization initiator, benzoin-based photopolymerization initiator, benzyl-based photopolymerization initiator, benzophenone-based photopolymerization initiator, thioxanthone-based light A polymerization initiator or the like can be used.

Specific examples of the ketal-based photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethan-1-one (for example, trade name “IRGACURE 651” manufactured by BASF).
Specific examples of the acetophenone-based photopolymerization initiator include 1-hydroxycyclohexyl-phenyl-ketone (for example, trade name “Irgacure 184” manufactured by BASF), 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one (for example, trade name “Irgacure 2959” manufactured by BASF), 2-hydroxy-2 -Methyl-1-phenyl-propan-1-one (for example, trade name "Darocur 1173" manufactured by BASF), methoxyacetophenone, and the like.
Specific examples of the benzoin ether-based photopolymerization initiator include benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, and benzoin isobutyl ether, and substituted benzoin ethers such as anisole methyl ether.
Specific examples of the acylphosphine oxide-based photopolymerization initiator include bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide (for example, trade name “Irgacure 819” manufactured by BASF) and bis (2,4,6). -Trimethylbenzoyl) -2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (for example, trade name “Lucillin TPO” manufactured by BASF), bis (2,6- Dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide.
Specific examples of the α-ketol-based photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1- [4- (2-hydroxyethyl) phenyl] -2-methylpropan-1-one, and the like. It is. Specific examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalenesulfonyl chloride. Specific examples of the photoactive oxime-based photopolymerization initiator include 1-phenyl-1,1-propanedione-2- (o-ethoxycarbonyl) -oxime and the like. Specific examples of the benzoin-based photopolymerization initiator include benzoin and the like. Specific examples of the benzyl-based photopolymerization initiator include benzyl and the like.
Specific examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3′-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexylphenyl ketone, and the like.
Specific examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, and isopropylthioxanthone , 2,4-diisopropylthioxanthone, dodecylthioxanthone and the like.

  The initiator for thermal polymerization is not particularly limited, but, for example, an azo-based polymerization initiator, a peroxide-based initiator, a redox-based initiator by a combination of a peroxide and a reducing agent, a substituted ethane-based initiator Initiators and the like can be used. More specifically, for example, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylpropionamidine) disulfate, 2,2′-azobis (2-amidinopropane) dihydrochloride 2,2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis (N, N'-dimethyleneisobutylamidine), 2,2 ' Azo-based initiators such as -azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate; persulfates such as potassium persulfate and ammonium persulfate; benzoyl peroxide, t-butyl hydroperoxide , Hydrogen peroxide and other peroxide initiators; for example, phenyl-substituted ethane and other substituted ethane initiators; for example, persulfate and sulfurous acid Combination of sodium hydrogen, redox initiators such as a combination of peroxide and sodium ascorbate; but the like, without limitation. In addition, thermal polymerization can be preferably performed at a temperature of, for example, about 20 to 100 ° C (typically, 40 to 80 ° C).

  The amount of the thermal polymerization initiator or the photopolymerization initiator to be used can be a usual amount according to the polymerization method, the polymerization mode, and the like, and is not particularly limited. For example, 0.001 to 5 parts by weight of initiator (typically 0.01 to 2 parts by weight, for example, 0.01 to 1 part by weight) can be used with respect to 100 parts by weight of the monomer raw material.

  As the composition for forming the viscoelastic body layer (B), a composition containing a partially polymerized polymer obtained by partially polymerizing a monomer component can be preferably used. Such a partially polymerized product typically exhibits a syrup (a viscous liquid) in which a polymer formed from a part of the monomer component and an unreacted monomer are mixed. Hereinafter, the partially polymerized product having such properties may be referred to as “monomer syrup” or simply “syrup”. The polymerization method for obtaining the above partially polymerized product is not particularly limited, and various polymerization methods as described above can be appropriately selected and used. From the viewpoint of efficiency and simplicity, a photopolymerization method can be preferably employed. According to photopolymerization, the polymerization conversion of the monomer mixture can be easily controlled by polymerization conditions such as the amount of light irradiation (light amount).

  The composition for forming the viscoelastic body layer (B) (the composition for forming a viscoelastic body layer) is an acrylic polymer (b) as a complete polymer of the monomer component (for example, the polymerization conversion of the monomer component). May contain 95% by weight or more of an acrylic polymer). For example, it may be in the form of a solvent type composition containing such an acrylic polymer (b) in an organic solvent, a water dispersion type composition in which the acrylic polymer (b) is dispersed in an aqueous solvent, and the like.

  The composition for forming the viscoelastic layer (B) may include a crosslinking agent. As the cross-linking agent, a known or common cross-linking agent in the field of an acrylic pressure-sensitive adhesive can be used. For example, epoxy crosslinking agents, isocyanate crosslinking agents, silicone crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, silane crosslinking agents, alkyl etherified melamine crosslinking agents, metal chelate crosslinking agents, and the like. it can. Alternatively, the composition may be substantially free of such a crosslinking agent.

[Filling material]
The viscoelastic layer (B) may contain a filler. By including a filler in the viscoelastic layer (B), the shear strength of the viscoelastic layer (B) can be increased. Thereby, the resistance (peeling strength) against peeling the pressure-sensitive adhesive sheet from the adherend can be improved. Further, by using the filler, excessive deformation of the viscoelastic body layer (B) can be suppressed, and the balance between flexibility and cohesiveness of the entire pressure-sensitive adhesive sheet can be suitably adjusted.

Various particulate substances can be used as the filler. Constituent materials of such particulate matter include, for example, metals such as copper, nickel, aluminum, chromium, iron and stainless steel; metal oxides such as alumina and zirconia; carbides such as silicon carbide, boron carbide and nitrogen carbide; aluminum nitride; Nitrides such as silicon nitride and boron nitride; inorganic materials such as calcium carbide, calcium carbonate, aluminum hydroxide, glass and silica; polystyrene, acrylic resin (for example, polymethyl methacrylate), phenol resin, benzoguanamine resin, urea resin, and silicone resin , Polyester, polyurethane, polyethylene, polypropylene, polyamide (for example, nylon, etc.), polyimide, polymer such as vinylidene chloride; and the like. Alternatively, natural raw material particles such as volcanic shirasu and sand may be used. These can be used alone or in combination of two or more.
The outer shape and particle shape of the particulate matter are not particularly limited. The outer shape of the particulate matter may be, for example, spherical, flake-like, irregular, or the like. Further, the particle structure of the particulate matter may be, for example, a dense structure, a porous structure, a hollow structure, or the like.

  The technology disclosed herein can be preferably implemented in a mode in which the viscoelastic layer (B) contains a particulate material having a hollow structure (hereinafter, also referred to as “hollow particles”) as the filler. From the viewpoint of photocurability (polymerization reactivity) of the composition for forming a viscoelastic layer, hollow particles made of an inorganic material can be preferably used. Examples of such hollow particles include glass balloons such as hollow glass balloons; metal oxide hollow balloons such as hollow alumina balloons; and porcelain hollow balloons such as hollow ceramic balloons.

  As the hollow glass balloon, for example, trade names “Glass Micro Balloon”, “Fuji Balloon H-40” and “Fuji Balloon H-35” manufactured by Fuji Silysia Chemical Ltd., and “Celstar Z-20” manufactured by Tokai Kogyo Co., Ltd. , "Celstar Z-27", "Celstar CZ-31T", "Celstar Z-36", "Celstar Z-39", "Celstar Z-39", "Celstar T-36", "Celstar PZ-6000", Product name “Cyrax Fine Balloon” manufactured by Fine Balloon Co., Ltd. Product name “Q-CEL (trademark) 5020”, “Q-CEL (trademark) 7014” manufactured by Potters Barottini Co., Ltd. ) 110P8 "," Sphericel (TM) 25P45 "," Sphericel (TM) 34P30 "," Commercial products such as Sphericel (trademark) 60P18, trade names “Super Balloon BA-15” and “Super Balloon 732C” manufactured by Showa Chemical Industry Co., Ltd. can be used.

The average particle size of the hollow particles used is not particularly limited. For example, it can be selected from the range of 1 μm to 500 μm, preferably 5 μm to 400 μm, more preferably 10 μm to 300 μm, and still more preferably 10 μm to 200 μm (for example, 10 to 150 μm). Usually, the average particle diameter of the hollow particles is suitably not more than 50% of the thickness of the viscoelastic layer (B), preferably not more than 30% (for example, not more than 10%).
While the specific gravity of the hollow particles is not particularly limited, in view of the uniform dispersibility and mechanical strength, etc., for example 0.1~1.8g / cm ^3, preferably 0.1 to 1.5 g / cm ^3, more preferably Can be selected from the range of 0.1 to 0.5 g / cm ³ (for example, 0.2 to 0.5 g / cm ³ ).
The amount of the hollow particles used is not particularly limited, and can be, for example, about 1 to 70% by volume of the total volume of the viscoelastic layer (B), and usually about 5 to 50% by volume. Yes, it is preferably about 10 to 40% by volume. From the viewpoint of improving the peeling force, the amount of the hollow particles used is preferably 15% by volume or more (for example, 20% by volume or more, typically 30% by volume or more) of the total volume of the viscoelastic layer (B).

[Bubbles]
The viscoelastic layer (B) may have bubbles. By including bubbles in the viscoelastic body layer (B), the cushioning property of the pressure-sensitive adhesive sheet is improved, and the flexibility can be increased. When the flexibility of the pressure-sensitive adhesive sheet is increased, irregularities and steps on the surface of the adherend are easily absorbed by deformation of the pressure-sensitive adhesive sheet, so that the pressure-sensitive adhesive surface can be more closely adhered to the surface of the adherend. Good adhesion of the pressure-sensitive adhesive surface to the adherend surface can advantageously contribute to improvement in peel strength on low-polarity surfaces and other various surfaces. Further, the improvement in the flexibility of the pressure-sensitive adhesive sheet can also contribute to a reduction in the resilience of the pressure-sensitive adhesive sheet. Thereby, when the adhesive sheet is attached along the surface of the adherend having a curved surface or a step, or when the adherend to which the adhesive sheet is attached is deformed, the adhesive sheet is repelled by its own repulsion. An event of peeling (lifting) from the surface of the adherend can be effectively suppressed.
The viscoelastic layer (B) may contain both the above-mentioned filler (for example, hollow particles) and bubbles. The pressure-sensitive adhesive sheet containing such a viscoelastic layer (B) is preferable because it tends to be excellent in balance between flexibility and cohesion.

  The cells contained in the viscoelastic layer (B) may be closed cells, open cells, or a mixture of these cells. From the viewpoint of cushioning property, the viscoelastic body layer (B) having a structure containing many closed cells is more preferable. In the case of closed cells, the gas components contained in the bubbles (gas components forming the bubbles, hereinafter sometimes referred to as “bubble forming gas”) are not particularly limited, and are inert gases such as nitrogen, carbon dioxide, and argon. In addition, various gas components such as air may be used. When performing a polymerization reaction or the like in a state where the bubble forming gas is contained, it is preferable to use a gas that does not inhibit the reaction. From such a viewpoint and cost viewpoint, nitrogen can be suitably used as the bubble forming gas.

The shape of the bubble is typically, but not limited to, generally spherical. The average diameter of the bubbles (average bubble diameter) is not particularly limited, and can be selected, for example, from the range of 1 μm to 1000 μm, preferably 10 μm to 500 μm, and more preferably 30 μm to 300 μm. Usually, the average cell diameter is suitably not more than 50% of the thickness of the viscoelastic material layer (B), and preferably not more than 30% (for example, not more than 10%).
The average bubble diameter can be typically determined by scanning electron microscope (SEM), preferably for 10 or more bubbles, and arithmetically averaging the results of measuring the diameters of those bubbles. At this time, for the non-spherical bubbles, the average pore diameter is determined by converting the bubbles into spherical bubbles having the same volume.

  When the viscoelastic body layer (B) has air bubbles, the volume ratio (bubble content) of the air bubbles in the viscoelastic body layer (B) is not particularly limited, and the desired cushioning property and flexibility can be achieved. Can be set as appropriate. For example, it can be about 3 to 70% by volume with respect to the volume of the viscoelastic layer (B) (refers to an apparent volume, which can be calculated from the thickness and area of the viscoelastic layer (B)). Usually, it is suitable to be about 5 to 50% by volume, preferably about 8 to 40% by volume. From the viewpoint of improving the peeling force, the volume ratio of the bubbles in the viscoelastic layer (B) is preferably less than 30% by volume (for example, less than 20% by volume, typically 15% by volume or less).

In the technology disclosed herein, the method for forming the viscoelastic body layer having bubbles (bubble-containing viscoelastic body layer) is not particularly limited, and a known method can be appropriately employed. For example, (1) a viscoelastic material layer-forming composition (preferably, a composition that forms a viscoelastic material by being cured by an active energy ray such as UV) in which a bubble-forming gas is mixed in advance is cured. A method for forming a bubble-containing viscoelastic body layer, (2) a method for forming a bubble-containing viscoelastic body layer by forming bubbles from a foaming agent using a composition for forming a viscoelastic body layer containing a foaming agent, Etc. can be appropriately adopted. The foaming agent used is not particularly limited, and can be appropriately selected from known foaming agents. For example, a foaming agent such as heat-expandable microspheres can be preferably used.
In the formation of the bubble-containing viscoelastic body layer by the method (1), the method for preparing the viscoelastic body layer-forming composition mixed with the bubble-forming gas is not particularly limited, and a known bubble mixing method is used. be able to. For example, as an example of an air bubble mixing device, a stator having a large number of fine teeth on a disk having a through hole in the center portion, and a rotor facing the stator and having fine teeth similar to the stator on the disk And the like. A composition for forming a viscoelastic material layer (composition precursor for forming a viscoelastic material layer) before mixing of bubbles is introduced between the teeth on the stator and the teeth on the rotor in such a bubble mixing apparatus, and the rotor is rotated. While rotating at a high speed, a gas component (bubble forming gas) for forming bubbles is introduced into the viscoelastic material layer forming composition precursor through the through holes. As a result, a composition for forming a viscoelastic body layer in which bubbles are finely dispersed and mixed is obtained.
The composition containing the bubble-forming gas as described above is applied on a predetermined surface and cured, whereby the bubble-containing viscoelastic layer can be formed. As a curing method, a method of heating, a method of irradiating with an active energy ray (for example, UV), or the like can be preferably adopted. Forming a bubble-containing viscoelastic body layer suitably by curing the composition for forming a viscoelastic body layer mixed with a bubble forming gas by heating or irradiating with active energy rays while holding the bubbles stably. can do.

A surfactant may be added to the composition for forming a viscoelastic body layer from the viewpoints of mixing of the bubble forming gas and stability of the bubbles. Examples of such a surfactant include an ionic surfactant, a hydrocarbon-based surfactant, a silicone-based surfactant, and a fluorine-based surfactant. Among them, fluorine surfactants are preferred, and fluorine surfactants having an oxyalkylene group (typically, an oxyalkylene group having 2 to 3 carbon atoms) and a fluorinated hydrocarbon group in the molecule are particularly preferred. One type of fluorine-based surfactant may be used alone, or two or more types may be used in combination. As a commercially available fluorine-based surfactant that can be preferably used, a trade name “Surflon S-393” manufactured by AGC Seimi Chemical Co., Ltd. is exemplified.
The amount of the surfactant to be used is not particularly limited. For example, it may be about 0.01 to 3 parts by weight based on the solid content based on 100 parts by weight of the acrylic polymer contained in the viscoelastic layer (B). it can.

[Other ingredients]
The viscoelastic material layer (B) is a tackifying component such as an acrylic oligomer, a plasticizer, a softener, a coloring agent (pigment, dye, etc.), an antioxidant, and a leveling as long as the effects of the present invention are not significantly impaired. Known additives such as agents, stabilizers and preservatives may be contained as necessary. For example, when the viscoelastic material layer forming composition is cured by a photopolymerization method to form the viscoelastic material layer (B), the viscoelastic material layer (B) is colored so that the photopolymerization is not hindered. (Color pigment) can be used as a coloring agent. When black is desired as the coloring of the viscoelastic layer (B), for example, carbon black can be preferably used as a coloring agent. The amount of carbon black used is, for example, 0.15 parts by weight or less (for example, 0.001 parts by weight) with respect to 100 parts by weight of the target viscoelastic layer (B) in consideration of the degree of coloring, photopolymerization reactivity, and the like. To 0.15 parts by weight), preferably from 0.01 to 0.1 parts by weight. In addition, the viscoelastic layer (B) may be substantially free of tackifier (for example, acrylic oligomer). Such a composition can be preferably employed, for example, in the non-adhesive viscoelastic layer (B).

[Thickness of viscoelastic layer (B)]
The thickness of the viscoelastic layer (B) is not particularly limited, but is preferably about 100 μm or more. The viscoelastic body layer (B) is excellent in flexibility since it is a viscoelastic body. Therefore, by supporting the pressure-sensitive adhesive layer (A) with the viscoelastic body layer (B), the surface (adhesive surface) of the pressure-sensitive adhesive layer (A) can be suitably brought into close contact with the adherend. In light of this flexibility, the thickness of the viscoelastic layer (B) is preferably equal to or greater than 200 μm, and more preferably equal to or greater than 300 μm (eg, equal to or greater than 350 μm). From the viewpoint of obtaining higher flexibility, the thickness of the viscoelastic body layer (B) can be 500 μm or more, and may be 700 μm or more. The technology disclosed herein can be preferably implemented even in a mode in which the thickness of the viscoelastic layer (B) is 1 mm or more. The upper limit of the thickness of the viscoelastic layer (B) is not particularly limited, and may be, for example, about 10 mm or less. The thickness of the viscoelastic body layer (B) is usually 5 mm or less, and preferably 3 mm or less (for example, 2 mm or less), from the viewpoints of easy formation and cohesiveness of the viscoelastic body layer (B).

<Adhesive layer (A)>
[Base polymer (a)]
The pressure-sensitive adhesive layer (A) is a layer containing an acrylic polymer (a) as the base polymer (a). As the acrylic polymer (a), for example, a polymer of a monomer raw material which contains an alkyl (meth) acrylate as a main monomer and may further contain a sub-monomer having copolymerizability with the main monomer is preferable. As the constituent monomer component of the acrylic polymer (a), one or more of alkyl (meth) acrylate as a main monomer and various auxiliary monomers exemplified as monomers that can be used in the acrylic polymer (b) Can be used.

In a preferred embodiment, the main monomer is one type of an alkyl (meth) acrylate in which R ² is C _1-14 (for example, C _1-10 , typically C _4-8 ) in the above formula (1). Alternatively, two or more kinds are used. Among them, BA or 2EHA is more preferable, and BA is particularly preferable from the viewpoint of adhesiveness and removability.

  Although not particularly limited, the amount of the alkyl (meth) acrylate as a main monomer is, for example, 60% by weight or more (for example, 80% by weight or more, typically 80% by weight or more of all monomer components constituting the acrylic polymer (a)). Is preferably 90% by weight or more). From the viewpoint of the cohesiveness of the pressure-sensitive adhesive layer (A), the amount of the alkyl (meth) acrylate is suitably 100% by weight or less (for example, 99.5% by weight or less, typically 99% by weight or less).

  The copolymerization ratio of the acidic group-containing monomer in the acrylic polymer (a) disclosed herein is 5% by weight or less. In other words, the acrylic polymer (a) is obtained by polymerizing a monomer material containing no acidic group-containing monomer or containing 5% by weight or less. Thereby, the adhesiveness of the pressure-sensitive adhesive layer (A) to the low-polarity adherend is improved. The proportion of the acidic group-containing monomer in the constituent monomer component (monomer raw material) of the acrylic polymer (a) is preferably 4% by weight or less (for example, 3% by weight or less). The constituent monomer component may not substantially contain an acidic group-containing monomer.

  The acidic group-containing monomer typically includes various carboxyl group-containing monomers, metal salts thereof (eg, alkali metal salts), and acid anhydride group-containing monomers. Examples of these acidic group-containing monomers include one or more of the carboxyl group-containing monomers and metal salts thereof (for example, alkali metal salts) and acid anhydride group-containing monomers that can be used in the acrylic polymer (b). It can be preferably used. Among them, AA and MAA are more preferable.

  In a preferred embodiment, the ratio (ACb / ACa) of the copolymerization ratio ACb of the acidic group-containing monomer in the acrylic polymer (b) to the copolymerization ratio ACa of the acidic group-containing monomer in the acrylic polymer (a) is greater than 1. Thereby, the amount of the acidic group-containing monomer used in the pressure-sensitive adhesive layer (A) is limited, and the viscoelastic material layer (B) which does not constitute a pressure-sensitive adhesive surface while maintaining good adhesion to a low-polarity adherend. ) Tends to be improved, for example, the shear strength and the holding power are further improved. The ratio (ACb / ACa) is more preferably 2 or more (for example, 2.5 or more, typically 3 or more). Although the upper limit of the ratio (ACb / ACa) is not particularly limited, it is appropriate to set it to about 10 or less (eg, 5 or less).

  In the synthesis of the acrylic polymer (a), various kinds of sub-monomers (functional group-containing monomers, sub-monomers other than functional group-containing monomers, and polyfunctional monomers exemplified in the above-mentioned acrylic polymer (b) are included. When a group-containing monomer is used, the amount of use is not particularly limited, and may be appropriately selected so as to adjust Tg or to achieve a desired cohesive force. The amount of the functional group-containing monomer other than the acidic group-containing monomer is, for example, 0.01% by weight or more (for example, 0.1% by weight or more, typically 1% by weight) of all monomer components constituting the acrylic polymer (a). % By weight or more). From the viewpoint of achieving a good balance between flexibility and cohesion, the amount of the functional group-containing monomer is 30% by weight or less (for example, 25% by weight or less, typically 20% by weight or less) of all monomer components. It is appropriate to do so.

  Although not particularly limited, as the acrylic polymer (a), a polymer obtained by copolymerizing a hydroxyl group-containing monomer can be preferably used. As the hydroxyl group-containing monomer, one or more of the hydroxyl group-containing monomers exemplified as the constituent monomer of the acrylic polymer (b) can be preferably used. Among them, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, etc. Hydroxyalkyl (meth) acrylate is more preferred.

  Such a hydroxyl group-containing monomer is preferably used in a range of about 0.001% by weight or more and 10% by weight or less based on the total amount of monomer components used for synthesizing the acrylic polymer (a). Thereby, the pressure-sensitive adhesive layer (A) in which the above-mentioned adhesive force and cohesive force are balanced at a higher level can be realized. By setting the amount of the hydroxyl group-containing monomer to be about 0.01% by weight to 5% by weight (for example, 0.05% by weight to 2% by weight), better results can be achieved.

  Further, the acrylic polymer (a) may include vinyl esters (for example, VAc) as a constituent monomer component. In that case, the content is suitably about 0.1 to 20% by weight (typically 0.5 to 15% by weight) of the total amount of the above monomer components.

  The copolymer composition of the acrylic polymer (a) is suitably designed so that the Tg of the polymer is −15 ° C. or less (typically −70 ° C. or more and −15 ° C. or less). Is -25 ° C or lower (for example, -60 ° C to -25 ° C), more preferably -40 ° C or lower (for example, -60 ° C to -40 ° C). It is preferable that the Tg of the acrylic polymer (a) be equal to or less than the above upper limit from the viewpoint of adhesive properties (for example, impact resistance). The Tg of the acrylic polymer (a) is determined by the same method as the Tg of the acrylic polymer (b) described above.

  The acrylic polymer (a) can be adjusted by a known or commonly used polymerization method. Examples of the polymerization method include thermal polymerization such as solution polymerization, emulsion polymerization and bulk polymerization (typically performed in the presence of a thermal polymerization initiator); light such as UV, β-ray, γ-ray, and the like. Active energy ray polymerization performed by irradiating active energy rays such as radiation; and the like can be appropriately adopted. For example, a solution polymerization method can be preferably used. As a monomer supply method for performing the solution polymerization, a batch supply method, a continuous supply (dropping) method, a divided supply (dropping) method, or the like, in which all the monomer raw materials are supplied at one time, can be appropriately adopted. The polymerization temperature can be appropriately selected depending on the type of the monomer and the solvent to be used, the type of the polymerization initiator, and the like. For example, the polymerization temperature is about 20 ° C to 170 ° C (typically 40 ° C to 140 ° C). it can.

  The solvent (polymerization solvent) used for the solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds such as toluene (typically aromatic hydrocarbons); aliphatic or alicyclic hydrocarbons such as ethyl acetate; halogenated alkanes such as 1,2-dichloroethane; (E.g., monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; More than one kind of mixed solvent can be used.

  The initiator used for the polymerization can be appropriately selected from conventionally known polymerization initiators according to the type of the polymerization method. For example, one or more polymerization initiators exemplified as the initiator for thermal polymerization that can be used for the polymerization of the acrylic polymer (b) can be preferably used. Among them, azo initiators such as 2,2'-azobisisobutyronitrile are more preferable. The amount of the polymerization initiator used may be a usual amount, for example, about 0.005 to 1 part by weight (typically 0.01 to 1 part by weight) based on 100 parts by weight of all the monomer components. You can choose from a range.

The weight average molecular weight (Mw) of the acrylic polymer (a) disclosed herein is not particularly limited, and may be, for example, in a range of 10 × 10 ⁴ or more and 500 × 10 ⁴ or less. From the viewpoint of balancing the cohesive force and the adhesive force at a high level, the acrylic polymer (a) has a Mw of 10 × 10 ^{4 to} 150 × 10 ⁴ (for example, 20 × 10 ⁴ to 75 × 10 ⁴ , typically It is preferably in the range of 35 × 10 ^{4 to} 65 × 10 ⁴ ). Here, Mw refers to a value in terms of standard polystyrene obtained by gel permeation chromatography (GPC). As the GPC device, for example, a model name “HLC-8320GPC” (column: TSKgelGMH-H (S), manufactured by Tosoh Corporation) may be used. The same applies to the embodiments described later.

  In a preferred embodiment, the degree of dispersion (Mw / Mn) of the acrylic polymer (a) is 3 to 10. When the degree of dispersion is equal to or more than a predetermined value, a predetermined amount of a low molecular weight component is present, and the initial peel strength tends to be improved. Further, the anchoring property to the viscoelastic body layer (B) is improved, and good removability tends to be obtained. When the degree of dispersion is 10 or less, the heat resistance and removability of the pressure-sensitive adhesive sheet tend to be improved. More preferably, the degree of dispersion is 4 to 8 (for example, 5 to 7). The degree of dispersion can be adjusted by selecting a polymerization initiator (for example, selection based on a 10-hour half-life temperature), polymerization conditions, aging conditions, and the like. The degree of dispersion can be determined by GPC using the same method as for Mw. The same applies to the embodiments described later.

In a preferred embodiment, the ratio of the component having a molecular weight of 10 × 10 ⁴ or less in the acrylic polymer (a) is about 10 to 30% by weight. Thereby, the initial peel strength and the anchoring property to the viscoelastic body layer (B) tend to be improved, and the heat resistance and the removability of the pressure-sensitive adhesive sheet tend to be improved. The proportion of the component having a molecular weight of 10 × 10 ⁴ or less is more preferably 15 to 30% by weight (for example, 20 to 30% by weight). The proportion of the component having a molecular weight of 10 × 10 ⁴ or less can be adjusted by selecting a polymerization initiator (for example, selection based on a 10-hour half-life temperature), polymerization conditions, aging conditions, and the like. The proportion of the component having a molecular weight of 10 × 10 ⁴ or less can be determined by GPC. The same applies to the embodiments described later.

[Tackifier]
In a preferred embodiment, the pressure-sensitive adhesive layer (A) contains a tackifier. The tackifier is not particularly limited, for example, rosin-based tackifier resin, terpene-based tackifier resin, hydrocarbon-based tackifier resin, phenol-based tackifier resin, epoxy-based tackifier resin, polyamide-based tackifier resin, Various tackifying resins such as an elastomer-based tackifying resin and a ketone-based tackifying resin can be used. Such tackifying resins can be used alone or in combination of two or more. Among them, rosin-based tackifying resins, terpene-based tackifying resins, hydrocarbon-based tackifying resins, and phenol-based tackifying resins are preferred, and rosin-based tackifying resins, terpene-based tackifying resins, and phenol-based tackifying resins are more preferred. .

  Specific examples of the rosin-based tackifying resin include unmodified rosins (raw rosins) such as gum rosin, wood rosin and tall oil rosin; modified rosins obtained by modifying these unmodified rosins by hydrogenation, disproportionation, polymerization and the like ( Hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosins, etc. The same applies hereinafter.); Various other rosin derivatives; Examples of the rosin derivative include rosins such as unmodified rosin esterified with alcohols (ie, rosin esterified product) and modified rosin esterified with alcohols (ie, modified rosin esterified product). Esters: Unmodified rosin, modified rosin, and unsaturated fatty acid-modified rosins modified with unsaturated fatty acids; rosin esters, modified with unsaturated fatty acids, unsaturated fatty acid modified rosins; Unmodified rosin, modified rosin, unsaturated Rosin alcohols obtained by reducing carboxyl groups in fatty acid-modified rosins or unsaturated fatty acid-modified rosin esters; metal salts of rosins (particularly, rosin esters) such as unmodified rosin, modified rosin, and various rosin derivatives; (Unmodified rosin, modified rosin, various rosin derivatives, etc.) Rosin phenol resins obtained by thermal polymerization by adding Nord acid catalyst; and the like. When an acrylic polymer is used as the base polymer, it is preferable to use a rosin-based tackifying resin. From the viewpoint of improving the adhesive properties such as repulsion resistance and adhesive strength, one of the above-mentioned rosin-based tackifying resins may be selected and used, and may differ in kind, characteristics (for example, softening point) and the like. Two or more kinds may be used in combination.

  Examples of terpene-based tackifying resins include terpene resins such as α-pinene polymer, β-pinene polymer, and dipentene polymer; and modification of these terpene resins (phenol modification, aromatic modification, hydrogenation modification, hydrocarbon Modified terpene resin). Examples of the modified terpene resin include a terpene phenol resin, a styrene-modified terpene resin, an aromatic-modified terpene resin, a hydrogenated terpene resin, and the like. When an acrylic polymer is used as the base polymer, it is preferable to use a terpene-based tackifying resin (for example, a terpene phenol resin). From the viewpoint of improving adhesive properties such as repulsion resistance and adhesive strength, one of the above-mentioned terpene-based tackifying resins (for example, terpene phenol resin) may be selected and used, and the type and properties (for example, (Softening point) and the like.

  Examples of the hydrocarbon-based tackifying resin include aliphatic hydrocarbon resins, aromatic hydrocarbon resins (eg, xylene resin), aliphatic cyclic hydrocarbon resins, and aliphatic / aromatic petroleum resins (styrene- Olefin-based copolymers), aliphatic / alicyclic-based petroleum resins, hydrogenated hydrocarbon resins, coumarone-based resins, and coumarone-indene-based resins.

  Examples of the phenolic tackifier resin include, for example, condensates of various phenols such as phenol, m-cresol, 3,5-xylenol, p-alkylphenol, resorcin, and formaldehyde (for example, alkylphenol resin, xylene formaldehyde resin). Resins, etc.), resols obtained by the addition reaction of the above-mentioned phenols and formaldehyde with an alkali catalyst, novolaks obtained by the condensation reaction of the above-mentioned phenols and formaldehyde with an acid catalyst, and rosins (unmodified rosin and modified rosin) Rosin derivatives) obtained by subjecting phenol to an acid catalyzed to various rosin derivatives and subjecting to thermal polymerization.

  In the technology disclosed herein, a tackifier resin having a softening point (softening temperature) of about 60 ° C. or more (preferably about 80 ° C. or more, typically 100 ° C. or more) can be preferably used. According to the tackifier resin having the softening point, a higher-performance (for example, higher adhesiveness) pressure-sensitive adhesive sheet can be realized. The upper limit of the softening point of the tackifier resin is not particularly limited, and may be about 180 ° C or less (for example, about 140 ° C or less). When two or more tackifier resins are used, each tackifier resin preferably has the above softening point. Here, the softening point of the tackifier resin is defined as a value measured by a softening point test method (ring and ball method) specified in either JIS K 5902: 2006 or JIS K 2207: 2006.

  The amount of the tackifier used is not particularly limited, and can be appropriately set according to the desired tackiness performance (adhesive strength and the like). For example, based on 100 parts by weight of the acrylic polymer (a) on a solid content basis, about 5 to 80 parts by weight (more preferably 10 to 60 parts by weight, further preferably 20 to 50 parts by weight) of the tackifier resin is used. It is preferred to use them in proportions.

[Other ingredients]
In the pressure-sensitive adhesive composition (A) used for forming the pressure-sensitive adhesive layer (A), a crosslinking agent may be used as necessary. The type of the crosslinking agent is not particularly limited, and can be appropriately selected from conventionally known crosslinking agents. As such a crosslinking agent, one or more of various crosslinking agents exemplified in the viscoelastic layer (B) can be used. Of these, use of an isocyanate-based crosslinking agent and / or an epoxy-based crosslinking agent is preferred from the viewpoint of improving cohesive strength. The amount of the crosslinking agent is not particularly limited, and is, for example, about 10 parts by weight or less (for example, about 0.005 to 10 parts by weight, preferably about 0.01 to 5 parts by weight) with respect to 100 parts by weight of the acrylic polymer (a). Part) can be selected from the range.

  The pressure-sensitive adhesive composition (A) may contain a leveling agent, a crosslinking assistant, a plasticizer, a softener, a filler, a coloring agent (eg, a pigment and a dye), an antistatic agent, an antioxidant, and an ultraviolet absorber, if necessary. It may contain various additives commonly used in the field of pressure-sensitive adhesive compositions, such as agents, antioxidants, and light stabilizers. As for such various additives, conventionally known ones can be used in a conventional manner, and do not particularly characterize the present invention, and thus detailed description thereof will be omitted.

  The pressure-sensitive adhesive layer (A) disclosed herein comprises a water-based pressure-sensitive adhesive composition, a solvent-based pressure-sensitive adhesive composition, a hot-melt-type pressure-sensitive adhesive composition, and an active-energy-ray-curable pressure-sensitive adhesive composition. Can be The water-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition in the form of a pressure-sensitive adhesive (pressure-sensitive adhesive layer-forming component) in a solvent containing water as a main component (water-based solvent), and is typically dispersed in water. And a so-called pressure-sensitive adhesive composition (a composition in which at least a part of the pressure-sensitive adhesive is dispersed in water). Further, the solvent-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition in a form containing a pressure-sensitive adhesive in an organic solvent. The technique disclosed herein is preferably implemented in a mode including a pressure-sensitive adhesive layer (A) formed from a solvent-type pressure-sensitive adhesive composition, from the viewpoint of appropriately realizing pressure-sensitive adhesive properties.

  The method for forming the pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer (A) and the viscoelastic material layer (B) is not particularly limited. For example, an adhesive layer (A) is formed on a surface having good releasability (a release surface, for example, the surface of a release liner), and the adhesive layer (A) is attached to the surface of the viscoelastic body layer (B) ( Transfer) can be preferably employed. Further, the pressure-sensitive adhesive composition (A) for forming the pressure-sensitive adhesive layer (A) is applied to the surface of the viscoelastic layer (B) and cured (for example, dried) to form the viscoelastic layer (B). Pressure-sensitive adhesive layer (A) may be formed on the surface. Alternatively, the composition (B) for forming the viscoelastic layer (B) is applied to the surface of the pressure-sensitive adhesive layer (A) and cured (for example, UV-cured), so that the pressure-sensitive adhesive layer (A) is cured. The viscoelastic material layer (B) may be formed on the surface. For the purpose of improving the adhesion between the pressure-sensitive adhesive layer (A) and the viscoelastic material layer (B), for example, before laminating the pressure-sensitive adhesive layer (A) and the viscoelastic material layer (B), The surface of the pressure-sensitive adhesive layer (A) of B) or the surface of the pressure-sensitive adhesive layer (B) of the pressure-sensitive adhesive layer (B) on the side of the pressure-sensitive adhesive layer (B) may be subjected to a surface treatment (adhesion improving treatment) such as a corona discharge treatment. It is not necessary.

[Thickness of adhesive layer (A)]
In the technology disclosed herein, the thickness of the pressure-sensitive adhesive layer (A) constituting the pressure-sensitive adhesive surface is not particularly limited, and can be approximately 1 μm or more. From the viewpoint of peel strength, the thickness of the pressure-sensitive adhesive layer (A) is suitably 5 μm or more (for example, 10 μm or more, typically 20 μm or more). In addition, from the viewpoint of the cohesiveness and the like, the thickness is usually appropriately 200 μm or less, and preferably 150 μm or less (for example, 100 μm or less, typically 80 μm or less). Since the pressure-sensitive adhesive sheet disclosed herein includes the viscoelastic layer (B), even if the pressure-sensitive adhesive layer (A) has a small thickness, it effectively absorbs irregularities and steps on the surface of the adherend, Good adhesion to the surface of the adherend can be achieved. This can achieve high peel strength. From such a viewpoint, the thickness of the pressure-sensitive adhesive layer (A) may be 60 μm or less (for example, 40 μm or less).

In one preferred embodiment, the ratio of the thickness _{T B} of the viscoelastic material layer to the thickness _{T A} of the pressure-sensitive adhesive layer _{(A) (B) (T} B / T A) is greater than 1. Thereby, the action of the viscoelastic body layer (B) (flexibility, improvement in peel strength based on flexibility, improvement in followability, and the like) can be more sufficiently exhibited. In addition, since the thickness of the pressure-sensitive adhesive layer (A) is limited, the removability tends to be improved. The ratio (T _B / T _A ) is more preferably 10 or more (for example, 12 or more, typically 15 or more), and even 20 or more (for example, 30 or more, typically 40 or more). Good. The upper limit of the ratio (T _B / T _A ) is not particularly limited, but may be about 100 or less (for example, 50 or less).

<Supporting substrate>
The pressure-sensitive adhesive sheet disclosed herein may include a support substrate, for example, as in the single-sided pressure-sensitive adhesive sheet 3 shown in FIG. As the supporting substrate, for example, a plastic film such as a polypropylene film, an ethylene-propylene copolymer film, a polyester film, or a polyvinyl chloride film; a foam sheet made of a foam such as a polyurethane foam, a polyethylene foam, or a polychloroprene foam; Woven and non-woven fabrics (Japanese paper, fine paper) made of various fibrous substances (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, and semi-synthetic fibers such as acetate, etc.) alone or as a blend. And metal foils such as aluminum foil and copper foil; and the like can be appropriately selected and used according to the use of the pressure-sensitive adhesive sheet. As the plastic film (typically, a non-porous plastic film, which is a concept distinguished from a woven fabric or a nonwoven fabric), any of a non-stretched film and a stretched (uniaxially stretched or biaxially stretched) film is used. Can also be used.

  The thickness of the supporting substrate can be appropriately selected according to the purpose, but is generally about 2 μm to 500 μm, and usually about 10 μm to 200 μm can be preferably used. When the supporting base material is a foam sheet, the upper limit of the thickness of the supporting base material can be, for example, about 10 cm, and is usually about 5 cm (for example, about 2 cm).

  The surface of the supporting base material on the side where the pressure-sensitive adhesive layer is provided may be subjected to a surface treatment such as corona discharge treatment or formation of a primer layer, which enhances the non-peeling property (anchor property) of the surface. Further, on the surface of the support base opposite to the side on which the pressure-sensitive adhesive layer is provided, a treatment for enhancing the releasability of the surface (formation of a release treatment layer, lamination of a low-adhesion material such as a polyolefin film, etc.) Etc.), a process for improving the non-peeling property or printability of the surface (corona discharge treatment or the like), a process for enhancing the decorative property of the surface (for example, printing, metal deposition), or the like. Good.

<Release liner>
The pressure-sensitive adhesive sheet disclosed herein may be in a form in which the pressure-sensitive adhesive surface is protected by a release liner before use (that is, before sticking to an adherend). As the release liner, a conventional release paper or the like can be used and is not particularly limited. For example, a release liner having a release treatment layer on the surface of a substrate such as a plastic film or paper, or a release liner made of a low-adhesion material such as a fluoropolymer (such as polytetrafluoroethylene) or a polyolefin resin (such as polyethylene or polypropylene). Etc. can be used. The release treatment layer may be formed, for example, by subjecting the base material to a surface treatment with a release treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.
In addition, for example, in a single-sided pressure-sensitive adhesive sheet such as the pressure-sensitive adhesive sheet 3 shown in FIG. 3, the surface 36A of the support base material 36 is a release surface. May be in a protected form by contacting the surface 36A. Thus, the pressure-sensitive adhesive sheet in a form in which the supporting substrate also functions as a release liner may be used.

  The total thickness (excluding the thickness of the release liner) of the pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer (A) and the viscoelastic material layer (B) is suitably more than 100 μm, preferably more than 200 μm ( For example, it is preferably more than 350 μm, typically more than 500 μm). The technology disclosed herein can be preferably implemented even in a mode in which the total thickness of the pressure-sensitive adhesive sheet exceeds 1 mm. The upper limit of the total thickness of the pressure-sensitive adhesive layer is not particularly limited, and can be, for example, about 15 mm or less, usually about 10 mm or less is appropriate, preferably 7 mm or less, more preferably 5 mm or less (eg, 3 mm or less).

<Characteristics of adhesive sheet>
It is preferable that the pressure-sensitive adhesive sheet disclosed herein (specifically, the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer (A)) exhibits a peel strength of 90 ° relative to polypropylene (90 ° peel strength relative to PP) of 30 N / 25 mm or more. The pressure-sensitive adhesive sheet having the above peel strength can be firmly adhered to an adherend (particularly, a low-polarity adherend such as PP). The 90 degree peel strength with respect to PP is more preferably 32 N / 25 mm or more (for example, 35 N / 25 mm or more, typically 40 N / 25 mm or more), and more preferably 45 N / 25 mm or more (for example, 50 N / 25 mm or more). More preferred. The 90 degree peel strength with respect to PP is measured by the method described in Examples described later.

  The pressure-sensitive adhesive sheet disclosed herein preferably exhibits a 90-degree peel strength (vs. 90-degree peel strength with respect to ABS) of 40 N / 25 mm or more with respect to an acrylonitrile-butadiene-styrene copolymer (ABS) plate. The pressure-sensitive adhesive sheet having the above peel strength can be firmly bonded to various adherends (for example, adherends made of resin such as ABS). The 90-degree peel strength with respect to ABS is more preferably 42 N / 25 mm or more (for example, 45 N / 25 mm or more, typically 50 N / 25 mm or more), and more preferably 55 N / 25 mm or more (for example, 60 N / 25 mm or more). More preferred. The 90-degree peel strength with respect to ABS is measured by a method described in Examples described later.

  In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the delamination strength between the pressure-sensitive adhesive layer (A) and the viscoelastic material layer (B) is 30 N / 25 mm or more. When the delamination strength shows a value equal to or higher than a predetermined value, for example, when an adhesive sheet firmly adhered to an adherend is removed, occurrence of anchor breakage is suppressed or prevented, and excellent removability is preferably realized. Is done. The delamination strength is more preferably 40 N / 25 mm or more (for example, 50 N / 25 mm or more, typically 60 N / 25 mm or more). The following values are employed as the delamination strength. That is, when the peel strength is measured by performing a 90-degree peel strength with respect to PP or a 90-degree peel strength with respect to ABS described in Examples described later, the peeling mode is determined to be interface destruction (adhesive surface of the pressure-sensitive adhesive layer (A)). Delamination form at the interface between the pressure-sensitive adhesive layer and the adherend), the interlayer peel strength between the pressure-sensitive adhesive layer (A) and the viscoelastic body layer (B) is at least equal to or higher than the peel strength measured above. Therefore, the measured peel strength (90-degree peel strength relative to PP or 90-degree peel strength relative to ABS) can be adopted as the delamination strength (90-degree delamination strength) [N / 25 mm]. .

<Application>
The pressure-sensitive adhesive sheet disclosed herein can be preferably used in a mode in which a pressure-sensitive adhesive surface composed of a pressure-sensitive adhesive layer (A) is attached to various adherends. Although not particularly limited, preferred adherends of the pressure-sensitive adhesive sheet disclosed herein include, for example, polyolefin resins such as polyethylene resins and polypropylene resins, ABS resins, impact-resistant polystyrene (HIPS) resins, and polycarbonate (PC). A resin-made adherend such as a resin or a polymer blend of PC and ABS (PC / ABS) resin may be used.
Further, the pressure-sensitive adhesive sheet disclosed herein has high flexibility (is easily deformed) by including the viscoelastic layer (B). Irregularities or manufacturing errors of the members can be absorbed by deformation of the adhesive, and a good joining state between the two members can be realized. Therefore, the pressure-sensitive adhesive sheet is useful for joining between members in various OA devices, home appliances, automobiles, and the like (for example, for fixing various components in such products).

  Hereinafter, some examples of the present invention will be described, but the present invention is not intended to be limited to those shown in the examples. In the following description, “parts” and “%” are based on weight unless otherwise specified.

(Preparation of pressure-sensitive adhesive layer (A1))
In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel, 100 parts of n-butyl acrylate (BA), 8 parts of vinyl acetate (VAc), and 3 parts of acrylic acid (AA) 0.1 parts of 2-hydroxyethyl acrylate (HEA), 0.2 parts of 2,2′-azobisisobutyronitrile (AIBN) as a polymerization initiator, and 5 parts of toluene and ethyl acetate as a polymerization solvent. A mixed solvent mixed at a weight ratio of 5 was charged, the mixture was refluxed with nitrogen for 1 hour at room temperature, and then a solution polymerization reaction was performed at about 58 ° C. for 6 hours. Next, a ripening reaction was performed at 65 ° C. for 2 hours and at 72 ° C. for 2 hours. Thereafter, the mixture was allowed to cool to obtain a solution of the acrylic polymer (a1). Mw of this acrylic polymer (a1) was about 60 × 10 ⁴ . Mw / Mn was 5.0, and the ratio of the polymer having a molecular weight of 100,000 or less was about 20%.
In the solution of the acrylic polymer (a1) obtained above, 100 parts of the acrylic polymer (a1) and 10 parts of a rosin phenol resin (trade name “Tamanol 803”, manufactured by Arakawa Chemical Industry Co., Ltd.) as a tackifier resin. And 10 parts of hydrogenated rosin glycerin ester (trade name "Ester Gum H" manufactured by Arakawa Chemical Co., Ltd.) and 15 parts of polymerized rosin pentaerythritol ester (trade name "Pencel D125" manufactured by Arakawa Chemical Co., Ltd.) Then, 2 parts of an isocyanate-based crosslinking agent (trade name “Coronate L”, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added as a crosslinking agent to prepare a pressure-sensitive adhesive composition (A1).
A sheet-like release liner was prepared in which a polyethylene layer having a thickness of 25 μm was laminated on one side of high-quality paper, and a release treatment with a silicone-based release agent was performed thereon. The pressure-sensitive adhesive composition (A1) was applied to the release surface of the release liner, and dried at 120 ° C. for 3 minutes to form a pressure-sensitive adhesive layer (A1). As the pressure-sensitive adhesive layer (A1), two types of pressure-sensitive adhesive layers having different thicknesses (thickness: 25 μm, 50 μm) were prepared.

(Preparation of pressure-sensitive adhesive layer (A2))
A reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel was charged with 95 parts of BA, 5 parts of AA, and toluene as a polymerization solvent. The temperature was raised to ° C, 0.2 parts of AIBN was added as a polymerization initiator, and a polymerization reaction was carried out at about 63 ° C for 7 hours to obtain a solution of an acrylic polymer (a2). Mw of this acrylic polymer (a2) was about 50 × 10 ⁴ .
In the solution of the acrylic polymer (a2) obtained above, 100 parts of the acrylic polymer (a2), and 20 parts of a rosin phenol resin (trade name “Tamanol 803”, manufactured by Arakawa Chemical Industries) as a tackifier resin. And 30 parts of a xylene formaldehyde-based tackifying resin having a hydroxyl group (trade name “Nicanol H-80”, manufactured by Mitsubishi Gas Chemical Company, Inc.), and a hydroxy compound containing a nitrogen atom as a hydroxy compound (trade name “EDP- 300 "(manufactured by Asahi Denka) and 4 parts of an isocyanate-based cross-linking agent (trade name" Coronate L ", manufactured by Nippon Polyurethane Industry Co., Ltd.) as a cross-linking agent to prepare an adhesive composition (A2). did.
A sheet-like release liner was prepared in which a polyethylene layer having a thickness of 25 μm was laminated on one side of high-quality paper, and a release treatment with a silicone-based release agent was performed thereon. The pressure-sensitive adhesive composition (A2) was applied to the release surface of the release liner and dried at 110 ° C. for 3 minutes to form a 25 μm-thick pressure-sensitive adhesive layer (A2).

(Preparation of pressure-sensitive adhesive layer (A3))
A monomer mixture consisting of 94 parts of 2-ethylhexyl acrylate (2EHA) and 6 parts of AA was mixed with 2,2-dimethoxy-1,2-diphenylethan-1-one (trade name "IRGACURE 651" manufactured by BASF) as a photopolymerization initiator. )) And 0.05 part of 1-hydroxycyclohexyl-phenyl-ketone (manufactured by BASF, trade name "Irgacure 184") in a four-necked flask, and irradiated with UV under a nitrogen atmosphere. A syrup containing a partially polymerized product was obtained by photopolymerization.
In addition, an acrylic oligomer was prepared. Specifically, 4 parts of thioglycolic acid as a chain transfer agent and toluene as a solvent were mixed with 60 parts of cyclohexyl methacrylate and 40 parts of isobutyl methacrylate, and dissolved oxygen was removed by blowing nitrogen gas. Next, this mixture was heated to 90 ° C., and 0.005 parts of trade name “Perhexyl O” (manufactured by NOF Corporation) as a polymerization initiator and 0.01 g of trade name “Perhexyl D” (manufactured by NOF Corporation) After stirring at 90 ° C. for 1 hour, the temperature was raised to 150 ° C. over 1 hour, followed by stirring at 150 ° C. for 60 minutes. Next, the temperature was raised to 170 ° C. over 1 hour, and the mixture was stirred at 170 ° C. for 60 minutes. Thereafter, the pressure was reduced at 170 ° C., and the mixture was stirred for 1 hour to remove the residual monomer, thereby obtaining an acrylic oligomer having Mw of 3,700.
A pressure-sensitive adhesive composition (A3) was prepared by adding and mixing 0.08 part of 2-isocyanatoethyl acrylate and 20 parts of the acrylic oligomer to 100 parts of the syrup obtained above.
Two 38 μm-thick PET films each having a release surface treated with a silicone-based release agent were prepared. The pressure-sensitive adhesive composition (A3) obtained above was applied to the release surface of the first PET film using a roll coater. Next, a second PET film was bonded to the outer surface of the composition (A3) so that the peeled surfaces of the PET film overlapped with each other. Next, UV irradiation was performed from both sides with a black light lamp having an illuminance of 5 mW / cm ² for 3 minutes. Thus, a pressure-sensitive adhesive layer (A3) having a thickness of 70 μm was formed.

(Preparation of viscoelastic layer (B1))
To a monomer mixture composed of 85 parts of 2EHA and 15 parts of AA, 0.05 parts of 2,2-dimethoxy-1,2-diphenylethan-1-one (trade name “Irgacure 651”, manufactured by BASF) and 1 part as a photopolymerization initiator. After blending 0.05 part of -hydroxycyclohexyl-phenyl-ketone (trade name "Irgacure 184" manufactured by BASF), UV irradiation was performed until the viscosity became about 15 Pa · s, and a part of the monomer mixture was removed. A polymerized monomer syrup (b1) (partially polymerized product) was produced. The viscosity was measured using a BH viscometer, using a rotor No. 5. The measurement was performed under the conditions of a rotation speed of 10 rpm and a measurement temperature of 30 ° C.
For 100 parts of this monomer syrup (b1), 0.15 part of dipentaerythritol hexaacrylate (DPHA) and a hollow glass balloon (average particle diameter 40 μm, trade name “Fuji Balloon H-40”, trade name of Fuji Silysia Chemical Ltd.) (B1) was added to obtain a composition (B1) for forming a viscoelastic body layer.
Two 38 μm-thick PET films each having a release surface treated with a silicone-based release agent were prepared. To 100 parts of the composition for forming a viscoelastic layer (B1), 0.03 part of “Irgacure 651” was added, and this was applied to the peeled surface of the first PET film, and two sheets were further placed thereon. The PET film was covered with the peeled surface of the eye and irradiated with UV light having an illuminance of 5 mW / cm ² from both sides for 3 minutes to be cured. For UV irradiation, "Black Light" manufactured by Toshiba Corporation was used. The UV was measured using an industrial UV checker having a peak sensitivity wavelength of about 350 nm (manufactured by Topcon Corporation, trade name “UVR-T1”, light receiving unit model UD-T36). Thus, a viscoelastic layer (B1) having a thickness of 800 μm was formed.

(Preparation of viscoelastic layer (B2))
A monomer syrup (b2) was prepared in the same manner as in the monomer syrup (b1) except that a monomer mixture consisting of 90 parts of 2EHA and 10 parts of AA was used.
To 100 parts of this monomer syrup (b2), 0.15 part of DPHA as a crosslinking agent and 12.5 parts of a hollow glass balloon (average particle diameter 40 μm, trade name “Fuji Balloon H-40”, manufactured by Fuji Silysia Chemical Ltd.) are added. Thus, a composition (B2) for forming a viscoelastic body layer was obtained. A viscoelastic body layer (B2) was prepared in the same manner as the viscoelastic body layer (B1) except that the composition for forming a viscoelastic body layer (B2) was used. As the viscoelastic body layer (B2), three kinds of viscoelastic body layers having different thicknesses (thickness: 400 μm, 800 μm, and 1200 μm) were prepared.

(Preparation of viscoelastic layer (B3))
For 100 parts of the monomer syrup (b2), 0.08 part of 1,6-hexanediol diacrylate (HDDA) as a crosslinking agent and a hollow glass balloon (average particle diameter 40 μm, trade name “Fuji Balloon H-40”, Fuji Silysia) 12.5 parts was added to perform defoaming treatment. After the defoaming treatment, 0.7 part of a fluorine-based surfactant was added to obtain a precursor of the composition for forming a viscoelastic body layer. The precursor was stirred with a nitrogen gas introduced from a through-hole of the apparatus using a bubble mixing apparatus to obtain a viscoelastic material layer forming composition (B3) in which bubbles were dispersed and mixed. A viscoelastic body layer (B3) was prepared in the same manner as the viscoelastic body layer (B1) except that the composition for forming a viscoelastic body layer (B3) was used. The proportion of bubbles in the viscoelastic layer (B3) was about 10% by volume.

(Preparation of viscoelastic layer (B4))
A viscoelastic material layer forming composition (B4) was prepared in the same manner as the viscoelastic material layer forming composition (B3) except that the composition was mixed so that the ratio of the bubbles was changed. A viscoelastic body layer (B4) was prepared in the same manner as the viscoelastic body layer (B1) except that the composition for forming a viscoelastic body layer (B4) was used. The proportion of bubbles in the viscoelastic layer (B4) was about 20% by volume.

(Preparation of viscoelastic layer (B5))
To 100 parts of the monomer syrup (b2), 0.08 parts of HDDA was added as a crosslinking agent, and then 0.5 parts of hollow glass microspheres (trade name "Celstar Z-27", manufactured by Tokai Kogyo Co., Ltd.) were added. Thereafter, 0.5 part of a fluorine-based surfactant was added to obtain a precursor of the composition for forming a viscoelastic body layer. The ratio of hollow glass microspheres to the precursor of the composition for forming a viscoelastic layer was about 1.5% by volume.
By stirring the precursor of the composition for forming a viscoelastic body layer obtained above with a nitrogen gas introduced from a through hole of the apparatus using a bubble mixing apparatus, a viscoelastic body layer in which bubbles are dispersed and mixed is provided. A forming composition (B5) was obtained. In the composition (B5) for forming a viscoelastic body layer, bubbles are mixed so as to be about 20% by volume based on the total volume of the composition (B5).
Two PET films having a thickness of 38 μm, one surface of which is a release surface treated with a silicone-based release agent, were prepared. The viscoelastic material layer obtained above was placed on the release surface of the first PET film. The forming composition (B5) was applied using a roll coater. Next, a second PET film was bonded to the outer surface of the composition (B5) so that the peeled surfaces of the PET film overlapped with each other. Next, UV irradiation was performed from both sides with a black light lamp having an illuminance of 5 mW / cm ² for 3 minutes. Thus, a 730 μm thick viscoelastic layer (B5) was formed.

<Example 1>
The PET film covering one surface of the viscoelastic body layer (B1) was peeled off, and the pressure-sensitive adhesive layer (A1) was bonded thereto using a laminator (200 mm / min, 0.2 MPa). Thus, the pressure-sensitive adhesive sheet according to Example 1 including the viscoelastic material layer (B1) having a thickness of 800 μm and the pressure-sensitive adhesive layer (A1) having a thickness of 25 μm held on one surface thereof was obtained.

<Examples 2 to 10>
The pressure-sensitive adhesive sheets according to Examples 2 to 10 were prepared in the same manner as in Example 1 except that the type and thickness of the pressure-sensitive adhesive layer (A) and the type and thickness of the viscoelastic body layer (B) were changed to those shown in Table 1. Obtained.

<Examples 11 and 12>
As the pressure-sensitive adhesive sheets according to Examples 11 and 12, a pressure-sensitive adhesive layer (A1) and a pressure-sensitive adhesive layer (A2) each having a thickness of 25 μm were used as they were.

<Examples 13 to 18>
As the pressure-sensitive adhesive sheets according to these examples, the viscoelastic material layers (B1) to (B4) having the thicknesses shown in Table 1 were used as they were.

[Measurement of 90-degree peel strength against ABS]
One side of the pressure-sensitive adhesive sheet according to each example was attached to and backed by an alumite-treated aluminum foil having a thickness of 130 μm. The backed pressure-sensitive adhesive sheet was cut into a width of 25 mm and a length of 70 mm to obtain a test piece. For Examples 1 to 10, 13 to 18, the surface of the viscoelastic layer was adhered to the aluminum foil, and for Examples 11 and 12, the surface of the pressure-sensitive adhesive layer was adhered to the aluminum foil.
The surface of an acrylonitrile butadiene styrene copolymer plate (ABS plate) as an adherend was washed with isopropyl alcohol (IPA). The adhesive surface of each test piece was pressed against the ABS plate by reciprocating a 5 kg roller two times. After the pressure bonding, aging was performed for 20 minutes in an atmosphere of 23 ° C. and 50% RH. In Examples 1 to 12, the surface (adhesive surface) of the pressure-sensitive adhesive layer was adhered to the adherend, and in Examples 13 to 18, the surface of the viscoelastic material layer was adhered to the adherend. After aging, using a tensile tester (manufactured by Shimadzu Corporation, device name "Tensilon"), the adherend (at a tensile speed of 300 mm / min and a peeling angle of 90 degrees under an atmosphere of 23 ° C. and 50% RH) was used. The test piece was peeled from the ABS plate, and the peel strength [N / 25 mm] at that time was measured. Table 1 shows the obtained results.

[Measurement of peel strength with respect to PP 90 degrees]
One side of the pressure-sensitive adhesive sheet according to each example was attached to and backed by an alumite-treated aluminum foil having a thickness of 130 μm. The backed pressure-sensitive adhesive sheet was cut into a width of 25 mm and a length of 70 mm to obtain a test piece. For Examples 1 to 10, 13 to 18, the surface of the viscoelastic layer was adhered to the aluminum foil, and for Examples 11 and 12, the surface of the pressure-sensitive adhesive layer was adhered to the aluminum foil.
The surface of a polypropylene plate (PP plate) as an adherend was washed with IPA. The adhesive surface of each test piece was pressed on the PP plate by reciprocating a 5 kg roller two times. After the pressure bonding, aging was performed for 20 minutes in an atmosphere of 23 ° C. and 50% RH. In Examples 1 to 12, the surface (adhesive surface) of the pressure-sensitive adhesive layer was adhered to the adherend, and in Examples 13 to 18, the surface of the viscoelastic material layer was adhered to the adherend. After aging, using a tensile tester (manufactured by Shimadzu Corporation, device name "Tensilon"), the adherend (at a tensile speed of 300 mm / min and a peeling angle of 90 degrees under an atmosphere of 23 ° C. and 50% RH) was used. The test piece was peeled from the PP plate), and the peel strength [N / 25 mm] at that time was measured. Table 1 shows the obtained results.

  As shown in Table 1, the viscoelastic body layer (B) is arranged, and the copolymerization ratio of the acidic group-containing monomer in the acrylic polymer (a) of the pressure-sensitive adhesive layer (A) is suppressed to a predetermined value or less. The pressure-sensitive adhesive sheets according to Examples 1 to 9 showed a high value of 90 ° peel strength with respect to the PP plate of 30 N / 25 mm or more. Specifically, in the pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer (A1) and any one of the viscoelastic material layers (B1) to (B4), the pressure-sensitive adhesive sheet is peeled at 90 degrees relative to PP as compared with Example 11 including only the pressure-sensitive adhesive layer (A1). The strength increased to about 1.1 times or more (about 1.1 to 1.8 times). It is inferred that the same tendency is observed in the comparison between Examples 8 and 9 and Example 12. In the pressure-sensitive adhesive sheet according to Example 10 in which the copolymerization ratio of the acidic group-containing monomer in the acrylic polymer (a) of the pressure-sensitive adhesive layer (A) exceeds 5% by weight, the 90-degree peel strength with respect to PP showed a low value. In the evaluation of the viscoelastic material layer (B) alone (Examples 13 to 18), the peel strength at 90 ° to PP showed a low value. This result suggests that the surface smoothness of the viscoelastic layer (B) is lower than that of the pressure-sensitive adhesive layer (A). In Examples 1 to 9, the peeling form in the evaluation of the 90-degree peeling strength was all interface destruction (peeling off at the interface between the adhesive surface of the adhesive layer (A) and the adherend). From these results, the low-polarity adherend can be obtained by combining the pressure-sensitive adhesive layer (A) and the viscoelastic material layer (B) and suppressing the amount of the acidic group-containing monomer used in the pressure-sensitive adhesive layer (A). It can be seen that a pressure-sensitive adhesive sheet exhibiting high peel strength is realized. Since this pressure-sensitive adhesive sheet includes the viscoelastic body layer (B), it is also excellent in flexibility.

  As described above, the specific examples of the present invention have been described in detail. However, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples illustrated above.

1,2,3 adhesive sheet 12,22,23,32 adhesive layer (A)
14, 24, 34 Viscoelastic layer (B)
36 Supporting substrate

Claims (5)

An adhesive layer (A) constituting an adhesive surface;
A viscoelastic layer (B) supporting the pressure-sensitive adhesive layer (A),
The viscoelastic layer (B) contains hollow particles or has air bubbles,
The pressure-sensitive adhesive layer (A) contains an acrylic polymer (a) as a base polymer,
Wherein the acrylic polymer (a) are copolymerized acidic group-containing monomer, the copolymerization ratio of the acidic group-containing monomer is 5% by weight or less,
The viscoelastic layer (B) contains an acrylic polymer (b),
An acidic group-containing monomer is copolymerized in the acrylic polymer (b), and the copolymerization ratio of the acidic group-containing monomer is 10% by weight or less,
The ratio (ACb / ACa) of the copolymerization ratio ACb of the acidic group-containing monomer in the acrylic polymer (b) to the copolymerization ratio ACa of the acidic group-containing monomer in the acrylic polymer (a) is 10 or less,
The pressure-sensitive adhesive sheet , wherein the pressure-sensitive adhesive layer (A) is a pressure-sensitive adhesive layer formed from a water-based pressure-sensitive adhesive composition, a solvent-based pressure-sensitive adhesive composition, or a hot-melt-type pressure-sensitive adhesive composition . The pressure-sensitive adhesive sheet according to claim 1, wherein the acrylic polymer (b) is a polymer of a monomer material containing an alkyl (meth) acrylate and a functional group-containing monomer. The pressure-sensitive adhesive sheet according to claim 1, wherein the ratio (ACb / ACa) is 2 or more. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the ratio (ACb / ACa) is 2.5 or more. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein a copolymerization ratio of the acidic group-containing monomer in the acrylic polymer (b) is 1% by weight or more.

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