JP2019094501A - Pressure sensitive adhesive sheet - Google Patents

Abstract

To provide a pressure sensitive adhesive sheet exhibiting a high peel strength to an adherend with a low polarity while excellent in flexibility.SOLUTION: A pressure sensitive adhesive sheet 1 includes: an adhesive layer (A) 12 forming an adhesive face 1A; and a viscoelastic layer (B) 14 supporting the adhesive layer (A). The viscoelastic layer (B) may include hollow particles or air bubbles. The adhesive layer (A) includes an acrylic polymer (a) as a base polymer. An acidic group-containing monomer is co-polymerized to the acrylic polymer (a). A copolymerization ratio of the acidic group-containing monomer is 5 wt.% or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an adhesive sheet.

  In general, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive, hereinafter the same) exhibits a soft solid (viscoelastic) state in a temperature range around room temperature, and has a property of easily adhering to an adherend by pressure. Taking advantage of such properties, pressure-sensitive adhesives are widely used in various industrial fields such as home appliances, automobiles, OA equipment, etc. as a bonding method with high workability and reliable adhesion. As a base polymer of an adhesive, the polymer which shows rubber elasticity at normal temperature can be employ | adopted preferably. Patent documents 1 and 2 are mentioned as a prior art literature about an adhesive. Patent Document 1 discloses a photocurable acrylic pressure-sensitive adhesive. Patent Document 2 relates to a pressure-sensitive adhesive sheet using a non-viscoelastic polyolefin-based foam substrate.

JP, 2011-84732, A JP, 2013-40329, A

  The pressure-sensitive adhesive is typically formed into a film and used in the form of a pressure-sensitive adhesive sheet containing the film-like pressure-sensitive adhesive (pressure-sensitive adhesive layer). The adhesive sheet is required to have various performances depending on the application. For example, it is useful to provide a pressure-sensitive adhesive sheet having high resistance to peeling from a low polarity adherend (peel strength) and excellent flexibility.

  Then, an object of the present invention is to provide a pressure sensitive adhesive sheet which exhibits high peeling strength to a low polarity adherend, and is excellent in flexibility.

  According to the present invention, there is provided a pressure-sensitive adhesive sheet comprising 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 the 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. And the copolymerization ratio of the acidic group containing monomer in the said acryl-type polymer (a) is 5 weight% or less.

  The pressure-sensitive adhesive sheet of the above-described constitution contains hollow particles or has a viscoelastic body layer (B) having air bubbles, and therefore, utilizing the mechanical properties of the viscoelastic body layer (B), the pressure-sensitive adhesive layer (A) The resistance to peeling of the adhesive surface (peel strength; for example, 90 degree peel strength measured according to the method described in the examples described later) is improved. Moreover, by providing the viscoelastic body layer (B), the pressure-sensitive adhesive sheet becomes excellent in flexibility, and effects such as improvement in surface followability can be expected. For example, the hollow particles can function as a filler of the viscoelastic layer (B) to increase the shear strength of the viscoelastic layer (B). An increase in shear strength of the viscoelastic layer (B) can advantageously contribute to improvement in peel strength. In addition, since the hollow particles have a small specific gravity, it is preferable that the viscoelastic layer (B) contains the hollow particles from the viewpoint of reducing the weight of the pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet provided with the viscoelastic body layer (B) having air bubbles has good followability to the surface shape and deformation of the adherend, and it is easy to maintain the adhesive surface in close contact with the adherend surface. This can advantageously contribute to the improvement of the peel strength for 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 the embodiment that “the visco-elastic body layer (B) contains hollow particles or has bubbles”, an embodiment in which the visco-elastic body layer (B) contains hollow particles and does not substantially have air bubbles; hollow particles And the embodiment having air bubbles substantially free of air bubbles; and the embodiment having hollow particles and having air bubbles. In addition, “an acrylic polymer having a copolymerization ratio of an acidic group-containing monomer of 5% by weight or less” is an acrylic polymer obtained by polymerizing a monomer material substantially free of an acidic group-containing monomer, and An acrylic polymer obtained by polymerizing a monomer material containing a group-containing monomer, wherein the ratio of the acid group-containing monomer in the monomer material is 5% by weight or less.

  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) of this configuration is preferable because it is easy to adjust the balance between flexibility and cohesion. In addition, when both the pressure-sensitive adhesive layer (A) and the visco-elastic body layer (B) contain an acrylic polymer, the adhesion (anchoring property) between the pressure-sensitive adhesive layer (A) and the visco-elastic body layer (B) is improved. When peeling off the pressure-sensitive adhesive sheet, an event of peeling (dropping) may be preferably suppressed between the pressure-sensitive adhesive layer (A) and the viscoelastic layer (B). By this, coexistence with the high peel strength and removability with respect to a low polarity adherend is preferably realized.

  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. By such a constitution, the cohesion of the visco-elastic layer (B) which does not constitute the adhesive surface is improved while maintaining the adhesiveness to the low polarity adherend, for example, the improvement of the shear strength and the retention strength I can expect it. In addition, 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 preferable embodiment of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive layer (A) is at least one selected from the group consisting of a rosin-based tackifying resin, a terpene-based tackifying resin, and a phenol-based tackifying resin. Contains a tackifier. By using the above-mentioned tackifier, the peel strength on the adhesive surface of the pressure-sensitive adhesive layer (A) is further improved. The content of the tackifier in the pressure-sensitive adhesive layer (A) is more preferably 10 to 50 parts by weight with respect to 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 It is above. By configuring in this manner, the action of the viscoelastic layer (B) (flexibility, peel strength, improvement of followability, etc.) can be exhibited better. In addition, the removability tends to be improved by limiting the thickness of the pressure-sensitive adhesive layer (A).

  In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive surface exhibits a 90-degree peel strength to polypropylene of a value of 30 N / 25 mm or more. The pressure-sensitive adhesive sheet exhibiting the above-mentioned adhesion to polypropylene, which is one of the representative examples of low polar materials, can exhibit higher peel strength to a low polar adherend.

It is a typical sectional view showing the composition of the pressure sensitive adhesive sheet concerning one embodiment. It is a schematic cross section which shows the structure of the adhesive sheet which concerns on other embodiment. It is a schematic cross section which shows the structure of the adhesive sheet which concerns on other embodiment.

Hereinafter, preferred embodiments of the present invention will be described. The matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be understood as the design matters of those skilled in the art based on the prior art in the relevant field. The present invention can be implemented based on the contents disclosed in the present specification and common technical knowledge in the field.
In the following drawings, the same reference numerals may be given to members / parts having the same function, and overlapping descriptions may be omitted or simplified. In addition, the embodiments described in the drawings are schematically illustrated to clearly explain the present invention, and do not accurately represent the size and scale of the pressure-sensitive adhesive sheet of the present invention actually provided as a product.

In the present specification, as described above, the term "adhesive" refers to a material which exhibits a soft solid (viscoelastic) state in a temperature range near room temperature and has a property of being easily adhered to an adherend by pressure. . The 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 art disclosed herein can also 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 is a main component (that is, the polymer component) of the polymers contained in the pressure-sensitive adhesive (typically, a polymer exhibiting rubber elasticity in a temperature range near room temperature). And the component with the largest blending ratio, typically accounting for more than 50% by weight).

<Basic composition of adhesive sheet>
The pressure-sensitive adhesive sheet disclosed herein comprises a pressure-sensitive adhesive layer (A) constituting a pressure-sensitive adhesive surface, and a viscoelastic body layer (B) supporting the pressure-sensitive adhesive layer (A). The pressure-sensitive adhesive layer (A) constitutes at least one surface (one side or both sides) of the pressure-sensitive adhesive sheet in a form supported by the viscoelastic body layer (B). The concept of the pressure-sensitive adhesive sheet herein includes those referred to as 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 roll form or in sheet form. Alternatively, it may be a pressure-sensitive adhesive sheet in a form further processed into various shapes.

Typical structural examples of the pressure-sensitive adhesive sheet disclosed herein are schematically shown in FIGS. 1 to 3.
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 body layer (B) 14 supporting the back surface thereof. The viscoelastic body 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 comprised by 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 adhesion to a low polarity adherend. Moreover, since the adhesive sheet 1 contains the viscoelastic body layer (B) 14, it can become the thing excellent in softness | flexibility. Taking advantage of such features, the pressure-sensitive adhesive sheet 1 adheres, for example, the first adhesive surface 1A to a low polarity adherend such as a polyolefin resin and the like, and adheres the second adhesive surface 1B to various adherends. It can be preferably used in an aspect. The pressure-sensitive adhesive sheet 1 is suitable, for example, as a double-sided pressure-sensitive adhesive sheet for firmly bonding various adherends to a low-polarity adherend.

  The pressure-sensitive adhesive sheet 2 shown in FIG. 2 comprises 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 body 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 layer (B) 24 There is. The second surface (second adhesive surface) 2B of the adhesive sheet 2 is composed of the surface 23A of the second adhesive layer (A) 23 supported by the second surface of the viscoelastic layer (B) 24. There is. In the pressure-sensitive adhesive sheet 2 having such a configuration, each of the first pressure-sensitive adhesive surface 2A and the second pressure-sensitive adhesive surface 2B can exhibit good adhesion to a low polarity adherend. Moreover, since the adhesive sheet 2 contains the viscoelastic body layer (B) 24, it can become the thing excellent in softness | 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 attached to an adherend of low polarity. 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 visco-elastic layer (B) 34 supporting the back surface, and a support base 36 further supporting the back surface. is there. The viscoelastic body layer (B) 34 is typically an adhesive layer. The adhesive sheet 3 is provided with the adhesive surface 3A comprised by the surface 32A of the adhesive layer (A) 32. As shown in FIG. The adhesive sheet 3 of such a configuration may be preferably used, for example, in a mode in which the 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 body layers (B) 14, 24 and 34 respectively contain air bubbles or hollow particles, and contain both air bubbles and hollow particles. It may be. As a preferable example from the viewpoint of weight reduction of the pressure-sensitive adhesive sheet, a structure in which the viscoelastic body layer (B) contains at least one of air bubbles and hollow particles, a structure in which the viscoelastic body layer (B) contains at least hollow particles, viscoelastic body A mode etc. in which layer (B) contains both air bubbles and hollow particles are mentioned.

  In addition, the hollow particle and bubble contained in a viscoelastic body layer (B) may reduce the smoothness of the surface of a viscoelastic body layer (B) depending on the size and content. When the smoothness of the surface of the visco-elastic body layer (B) decreases, for example, when the visco-elastic body layer (B) is an adhesive layer and the surface is directly adhered to the adherend, adhesion to the adherend is It may become insufficient and the peel strength may tend to decrease. In the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive layer (A) constituting the 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, it is easy to adjust the content rate of a hollow particle and a bubble in a viscoelastic body layer (B), and the adhesive sheet which was more excellent in performance balance may be implement | achieved suitably.

  In the pressure-sensitive adhesive sheets 1 to 3 illustrated in FIGS. 1 to 3, each layer shown in the figure may have a single-layer structure or 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 formed of a single-layered pressure-sensitive adhesive layer (A), and a pressure-sensitive adhesive layer (A) comprising a plurality of pressure-sensitive adhesive layers The pressure-sensitive adhesive layer (A) may be disposed on both sides of the support substrate.

  Moreover, the adhesive sheets 1-3 illustrated by FIGS. 1-3 may further have a layer which is not shown by the figure. For example, another layer may be disposed between any of the layers in FIGS. As an example of such a configuration, a configuration in which a second pressure-sensitive adhesive layer (A) is further disposed between the viscoelastic body layer (B) 34 and the support base 36 in the structure shown in FIG. 3 is mentioned. Be The pressure-sensitive adhesive sheet disclosed herein is not exposed to the surface of the pressure-sensitive adhesive sheet other than the pressure-sensitive adhesive layer (A) constituting the pressure-sensitive adhesive surface as in the second pressure-sensitive adhesive layer (A), for example You may include the adhesive layer which does not comprise 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 peeling treatment layer, a colored layer such as a printing layer, a metal deposition layer, an antistatic layer, a surface protective layer and the like. Alternatively, the pressure-sensitive adhesive sheets 1 to 3 disclosed herein may not contain a primer layer or a primer layer. The technique disclosed herein can be preferably implemented in a mode that does not include a primer layer between the adherend surface (not shown) and the adhesive surfaces 12A, 22A, 23A, 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 body layer (B), the art disclosed herein is the case of peeling off the pressure-sensitive adhesive sheet. It is possible to preferably carry out without causing an anchorage failure event (a peeling event between the pressure-sensitive adhesive layer (A) and the viscoelastic layer (B)).

<Viscoelastic layer (B)>
[Base polymer (b)]
The composition of the viscoelastic layer (B) is not particularly limited as long as it exhibits the properties of the viscoelastic body in a temperature range around room temperature. The visco-elastic body layer (B) is an acrylic visco-elastic body, a rubber-based visco-elastic body, a silicone-based visco-elastic body, a polyester-based visco-elastic body, a urethane-based visco-elastic body, a polyether-based visco-elastic body, a polyamide-based visco-elastic body It may be a layer configured to contain one or more selected from various visco-elastic bodies such as a body and a fluorinated visco-elastic body. Here, the acrylic viscoelastic material means that the acrylic polymer is contained in the base polymer (the main component in the polymer component, that is, the component having the largest blending ratio among the polymer components, typically more than 50% by weight). Visco-elastic body). The same applies to rubber-based and other viscoelastic bodies. The visco-elastic body referred to here is a material having both viscosity and elasticity properties, that is, a material having a property in which the phase of the complex elastic modulus exceeds 0 and is less than π / 2 (typically at 25 ° C. A material having the above-mentioned properties). From the viewpoint of flexibility and the like, a material having a property satisfying the complex tensile elastic modulus E ^* (1 Hz) <10 ⁷ dyne / cm ² (typically, a material having the above-described 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 is crimped to the adherend by one reciprocation of a 2 kg roller under a measurement environment of 23 ° C. The layer has a peel strength of 0.1 N / 20 mm or more when peeled in the direction of 180 ° at a tensile speed of 300 mm / min after 30 minutes. It is also called a pressure-sensitive adhesive layer. Moreover, a "non-adhesion layer" means the layer which does not correspond to the said adhesion layer, and typically means the layer whose said peeling strength is less than 0.1 N / 20 mm. When a 2 kg roller is reciprocated once in a measurement environment of 23 ° C. and pressure-bonded to a SUS 304 stainless steel plate, a layer not adhering to the stainless steel plate (a layer showing substantially no adhesiveness) is the non-adhesive layer mentioned here It is a typical example included in the concept of Although not particularly limited, the technology disclosed herein includes a form including the viscoelastic layer (B) corresponding to the adhesive layer, that is, the pressure-sensitive adhesive layer (B) as the viscoelastic layer (B) It can be preferably carried out in the form of a pressure-sensitive adhesive sheet.

  In a preferred embodiment, the viscoelastic layer (B) may be a layer containing an acrylic polymer (b) as a base polymer (b), that is, an acrylic viscoelastic layer. The viscoelastic body layer (B) of such a composition is preferable because it is easy to control the balance between the flexibility and the cohesiveness. Further, when 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 50% by weight or more, preferably 70% by weight or more, and more preferably 80% by weight or more. .

  As the above-mentioned acrylic polymer (b), for example, a polymer of a monomer raw material which contains an alkyl (meth) acrylate as a main monomer and can further contain a submonomer having a 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 the monomer components contained in the above-mentioned monomer raw material. Typically, the composition of the monomer component contained in the above-mentioned monomer raw material substantially 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 = C (R ¹ ) COOR ² (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. Further, ^{R 2} is an alkyl group having 1 to 20 carbon atoms (hereinafter, such a range of the number of carbon atoms may be represented as _{"C 1-20".).} From the viewpoint of the storage elastic modulus of the pressure-sensitive adhesive, an alkyl (meth) acrylate in which R ² is a C _1-14 alkyl group is preferable, and an alkyl (meth) acrylate in which R ² is a C _1-10 alkyl group is more preferable Particularly preferred is an alkyl (meth) acrylate in which R ² is a butyl group or a 2-ethylhexyl group.

Examples of the alkyl (meth) acrylate wherein R ² is a C _1-20 alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate ) 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 , 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 can be mentioned. These alkyl (meth) acrylates can be used singly 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 of all monomer components constituting the acrylic polymer (b), usually 70% by weight or more Is more preferable, and 80% by weight or more is more preferable. 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, from the viewpoint of the cohesiveness of the viscoelastic layer (B), etc. is there.

Examples of the secondary monomer include monomers having a functional group (hereinafter also referred to as "functional group-containing monomers"). Such a functional group-containing monomer can be used for the purpose of introducing a crosslinking point into the acrylic polymer (b) and enhancing the cohesion of the viscoelastic layer (B). As such functional group containing monomers,
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, citraconic A carboxyl group-containing monomer such as an ethylenically unsaturated dicarboxylic acid such as an acid, and a metal salt thereof (eg, an alkali metal salt);
For example, an acid anhydride group-containing monomer such as an acid anhydride of the above-mentioned ethylenically unsaturated dicarboxylic acid such as maleic anhydride, itaconic anhydride and the like;
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-hydroxy lauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl (meth) acrylate ) 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;
For example, cyano group-containing monomers such as acrylonitrile and methacrylonitrile;
For example, sulfonic acids such as styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamido-2-methylpropane sulfonic acid, (meth) acrylamidopropane sulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalene sulfonic acid and the like Group-containing monomers;
Phosphoric acid group-containing monomers such as, for example, 2-hydroxyethyl acryloyl phosphate;
Oxazoline group-containing monomers such as, for example, 2-vinyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline;
Aziridine group-containing monomers such as, for example, (meth) acryloyl aziridine, 2-aziridinyl ethyl (meth) acrylate;
For example, amino group-containing monomers such as aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, etc.
For example, epoxy group (glycidyl group) -containing monomers such as glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, allyl glycidyl ether;
For example, a keto group-containing monomer such as diacetone (meth) acrylamide, diacetone (meth) acrylate, vinyl methyl ketone, vinyl ethyl ketone, allylacetoacetate, vinylacetoacetate;
For example, an isocyanate group-containing monomer 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;
Other examples include macromonomers having a radical polymerizable vinyl group at the terminal end of the monomer obtained by polymerizing a vinyl group. These can be used singly or in combination of two or more.

  When the functional group-containing monomer as described above is used as the sub-monomer, the amount thereof to be used may be appropriately selected so as to achieve a desired cohesive force, and is not particularly limited. The amount of the functional group-containing monomer used can be, for example, 0.5% by weight or more of all the monomer components constituting the acrylic polymer (b), and usually 1% by weight or more is suitable, The content is preferably 3% by weight or more, and more preferably 5% by weight or more. From the viewpoint of achieving both flexibility and cohesion in a well-balanced manner, the amount of the functional group-containing monomer is suitably 30% by weight or less of the total monomer components, and preferably 25% by weight or less, It is more preferable to make it 20 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. By this, the balance between the flexibility and the cohesiveness of the viscoelastic layer (B) can be preferably adjusted. As the above acidic group-containing monomer, typically, various carboxyl group-containing monomers and metal salts thereof (for example, alkali metal salts) and acid anhydride group-containing monomers can be mentioned. As specific examples of these acidic group-containing monomers, carboxyl group-containing monomers and metal salts thereof (eg, alkali metal salts), and one or more of those exemplified above as acid anhydride group-containing monomers can be preferably used. . Among them, AA and MAA are more preferable.

  When the acidic group-containing monomer is used, the amount thereof to be used 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, for example, suitably 1% by weight or more of all the monomer components constituting the acrylic polymer (b), and usually 3% by weight or more (eg 5% by weight or more, typical) It is preferable to set it as 8 weight% or more). Also, from the viewpoint of achieving both flexibility and cohesion in a well-balanced manner, 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 above-mentioned monomer raw material may also contain sub-monomers other than the functional group-containing monomer described above for the purpose of adjusting the glass transition temperature (Tg), improving cohesion, etc. As such secondary monomers,
For example, carboxylic acid vinyl esters such as vinyl acetate (VAc), vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl cyclohexanecarboxylate, vinyl benzoate and the like;
For example, aromatic vinyl compounds such as styrene, substituted styrene (α-methylstyrene and the like), vinyl toluene and the like;
For example, aromatics such as aryl (meth) acrylate (eg phenyl (meth) acrylate), aryloxyalkyl (meth) acrylate (eg phenoxyethyl (meth) acrylate), arylalkyl (meth) acrylate (eg benzyl (meth) acrylate) Ring-containing (meth) acrylates;
For example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N -A monomer having a nitrogen atom-containing ring, such as vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N- (meth) acryloylmorpholine, etc .;
For example, olefin monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene;
For example, chlorine-containing monomers such as vinyl chloride and vinylidene chloride;
For example, vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether;
Etc. These can be used singly or in combination of two or more. The amount of such sub-monomers used is not particularly limited as long as it is appropriately selected according to the purpose and application, but for example, it is preferably 10 wt% or less of the total monomer components.

  The monomer raw material may optionally contain a polyfunctional monomer for the purpose of crosslinking and the like. As such polyfunctional monomers, for example, 1,6-hexanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di ( Meta) 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 in one molecule (typically, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, etc.) (Meth) include monomers having an acryloyl group). These can be used singly or in combination of two or more. From the viewpoint of reactivity, etc., usually, polyfunctional monomers having two or more (typically three or more) acryloyl groups in one molecule are preferable. When such a polyfunctional monomer is used, the amount thereof to be used is not particularly limited, but from the viewpoint of flexibility of the viscoelastic layer (B), usually 2% by weight or less of the total monomer components (more preferably 1 weight) % Or less) is appropriate.

  The monomer composition of the acrylic polymer (b) may be set such 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 less, preferably -30 ° C or less, more preferably -40 ° C or less, and still more preferably -50 ° C or less. Moreover, it is preferable that said Tg is -65 degreeC or more normally from a cohesive viewpoint of a viscoelastic body layer (B).

  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 (the copolymerization ratio based on weight) The value obtained from the equation of Fox based on Therefore, the Tg of the acrylic polymer (b) can be adjusted by appropriately changing the monomer composition (that is, the type and ratio of the monomers used for the synthesis of the acrylic polymer (b)). As the Tg of the homopolymer, the value described in the known data 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
As for the Tg of homopolymers other than those exemplified above, the numerical values described in “Polymer Handbook” (Third Edition, John Wiley & Sons, Inc., 1989) are used.

When it is not described in the above-mentioned "Polymer Handbook", a value obtained by the following measurement method is used (refer to 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 are added to a reactor equipped with a thermometer, a stirrer, a nitrogen introducing pipe and a reflux condenser. Charge and stir for 1 hour while flowing nitrogen gas. After oxygen in the polymerization system is removed in this manner, the temperature is raised to 63 ° C. and reaction is carried out for 10 hours. Then, it is cooled to room temperature to obtain a homopolymer solution having a solid concentration of 33% by weight. The homopolymer solution is cast coated on a release liner and dried to prepare a test sample (sheet-like homopolymer) having a thickness of about 2 mm. This test sample is punched out into a disk shape of 7.9 mm in diameter, sandwiched by parallel plates, and subjected to shear strain at a frequency of 1 Hz using a viscoelasticity tester (ARES, manufactured by Rheometrics), temperature range -70 to 150 ° C The visco-elasticity is measured by shear mode at a heating rate of 5 ° C./min, and the peak top temperature of tan δ is taken as the Tg of the homopolymer.

  The acrylic polymer (b) can be prepared by a known or conventional polymerization method. As a polymerization method, for example, thermal polymerization such as solution polymerization, emulsion polymerization, bulk polymerization and the like (typically performed in the presence of a thermal polymerization initiator); light such as ultraviolet light (UV), β ray, γ, γ An active energy ray polymerization to be performed by irradiating an active energy ray such as radiation such as a line can be appropriately adopted. Examples of active energy ray polymerization as used herein include photopolymerization (typically performed in the presence of a photopolymerization initiator) and irradiation with light such as UV, α rays, β rays, and γ Radiation polymerization performed by irradiating ionizing radiation such as radiation, neutron beam, and electron beam. These polymerization methods can be used singly or in appropriate combination of two or more.

In polymerization, a known or conventional polymerization initiator may be used depending on the polymerization method, polymerization mode and the like. The polymerization initiators can be used singly or in appropriate combination of two or more.
A photoinitiator can be used suitably from the advantage etc. which can shorten superposition | polymerization time. The photopolymerization initiator is not particularly limited. For example, ketal photopolymerization initiator, acetophenone photopolymerization initiator, benzoin ether photopolymerization initiator, acyl phosphine oxide photopolymerization initiator, α- Ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, photoactive oxime photopolymerization initiator, benzoin photopolymerization initiator, benzyl photopolymerization initiator, benzophenone photopolymerization initiator, thioxanthone photo light A polymerization initiator or the like can be used.

Specific examples of the ketal photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethane-1-one (for example, trade name “IRGACURE 651” manufactured by BASF Corp.) and the like.
Specific examples of the acetophenone photopolymerization initiator include 1-hydroxycyclohexyl-phenyl-ketone (for example, trade name “IRGACURE 184” manufactured by BASF Corp.), 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one (eg, trade name “IRGACURE 2959” manufactured by BASF Corp.), 2-hydroxy-2 -Methyl-1-phenyl-propan-1-one (eg, trade name “Darocure 1173” manufactured by BASF Corp.), methoxyacetophenone and the like are included.
Specific examples of the benzoin ether 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 acyl phosphine oxide photopolymerization initiator include bis (2,4,6-trimethyl benzoyl) phenyl phosphine oxide (for example, trade name “IRGACURE 819” manufactured by BASF Corp.), bis (2,4,6) -Trimethylbenzoyl) -2,4-di-n-butoxyphenyl phosphine oxide, 2,4,6-trimethyl benzoyl diphenyl phosphine oxide (for example, trade name "Lucillin TPO" manufactured by BASF Corp.), bis (2,6-) Dimethoxybenzoyl) -2,4,4-trimethylpentyl phosphine oxide and the like are included.
Specific examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1- [4- (2-hydroxyethyl) phenyl] -2-methylpropan-1-one and the like Be 2-naphthalene sulfonyl chloride etc. are contained in the example of an aromatic sulfonyl chloride type photoinitiator. 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 photopolymerization initiator include benzoin and the like. Specific examples of the benzyl-based photopolymerization initiator include benzyl and the like.
Specific examples of benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinyl benzophenone, α-hydroxycyclohexyl phenyl ketone and the like.
Specific examples of thioxanthone photopolymerization initiators include thioxanthone, 2-chlorothioxanthone, 2-methyl thioxanthone, 2,4-dimethyl thioxanthone, isopropyl thioxanthone, 2,4-dichloro thioxanthone, 2,4-diethyl thioxanthone, isopropyl thioxanthone 2,4-diisopropylthioxanthone, dodecyl thioxanthone and the like.

  The initiator for thermal polymerization is not particularly limited. For example, azo type polymerization initiator, peroxide type initiator, redox type initiator by combination of peroxide and reducing agent, substituted ethane type An initiator etc. 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'-dimethylene isobutylamidine), 2,2 ' -Azo initiators such as azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate; persulfates such as potassium persulfate, ammonium persulfate; benzoyl peroxide, t-butyl hydroperoxide Peroxide initiators such as hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; persulfates and sulfites Combination of sodium hydrogen, redox initiators such as a combination of peroxide and sodium ascorbate; but the like, without limitation. Thermal polymerization can be preferably carried out, for example, at a temperature of about 20 to 100 ° C. (typically, 40 to 80 ° C.).

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

  As a composition for forming a viscoelastic body layer (B), the thing containing the partial polymer which polymerized a part of monomer component can be used preferably. Such a partially polymerized product typically exhibits a syrupy form (viscous liquid) in which a polymer formed from a part of the monomer components and an unreacted monomer are mixed. Hereinafter, such partially polymerized product of this nature may be referred to as "monomer syrup" or simply "syrup". The polymerization method in particular in obtaining the said partially polymerized material is not restrict | limited, The various polymerization methods as mentioned above can be selected suitably, and can be used. From the viewpoint of efficiency and simplicity, the photopolymerization method can be preferably employed. According to the photopolymerization, the polymerization conversion ratio of the above-mentioned monomer mixture can be easily controlled by the polymerization conditions such as the irradiation amount (light amount) of light.

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

  The composition for forming the viscoelastic body layer (B) may contain a crosslinking agent. As the crosslinking agent, crosslinking agents known or commonly used in the field of acrylic pressure-sensitive adhesives can be used. For example, epoxy type crosslinking agents, isocyanate type crosslinking agents, silicone type crosslinking agents, oxazoline type crosslinking agents, aziridine type crosslinking agents, silane type crosslinking agents, alkyl etherified melamine type crosslinking agents, metal chelate type crosslinking agents, etc. it can. Alternatively, the composition may be substantially free of such a crosslinking agent.

[Filling material]
The viscoelastic body 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. By this, the resistance (peeling strength) with respect to peeling off an adhesive sheet from a to-be-adhered body can be improved. Moreover, excessive deformation of the viscoelastic layer (B) can be suppressed by the use of the filler, and the balance between the flexibility and the cohesion as the whole pressure-sensitive adhesive sheet can be suitably adjusted.

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

  The art disclosed herein can be preferably practiced in a mode in which the viscoelastic body layer (B) includes 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; hollow balloons made of metal oxide such as hollow alumina balloons; and hollow balloons made of porcelain such as hollow ceramic balloons.

  As a hollow glass balloon, for example, trade name "Glass micro balloon" manufactured by Fuji Silysia Chemical, "Fuji balloon H-40", "Fuji balloon H-35", trade name "Celstar Z-20" manufactured by Tokai Industry Co., Ltd. "Cellster Z-27", "Cellster CZ-31T", "Cellster Z-36", "Cellster Z-39", "Cellster Z-39", "Cellster T-36", "Cellster PZ-6000", Trade name "Cylux Fineballoon" manufactured by Fineballoon Co., "Q-CEL (trademark) 5020" manufactured by Potters Barrotini, "Q-CEL (trademark) 7014", trade name "Sphericel (trademark) 110P8 "," Sphericel (TM) 25 P 45 "," Sphericel (TM) 34 P 30 "," Commercial products such as Sphericel (trademark) 60P18, trade names "Super Balloon BA-15" and "Super Balloon 732C" manufactured by Showa Kagaku Kogyo 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). The average particle size of the hollow particles is usually 50% or less of the thickness of the viscoelastic layer (B), and preferably 30% or less (e.g. 10% or less).
The specific gravity of the hollow particles is not particularly limited, but is, for example, 0.1 to 1.8 g / cm ³ , preferably 0.1 to 1.5 g / cm ³ , more preferably, in consideration of uniform dispersibility, mechanical strength, etc. 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 use amount of the hollow particles is not particularly limited, and can be, for example, about 1 to 70% by volume of the whole volume of the viscoelastic layer (B), and usually about 5 to 50% by volume is appropriate. And preferably about 10 to 40% by volume. From the viewpoint of improving the peeling force, the amount of use of the hollow particles 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 body layer (B) may have air bubbles. By including air bubbles in the viscoelastic layer (B), the cushioning properties of the pressure-sensitive adhesive sheet can be improved, and the flexibility can be enhanced. When the flexibility of the pressure-sensitive adhesive sheet becomes high, deformation of the pressure-sensitive adhesive sheet makes it easy to absorb bumps and bumps on the surface of the adherend, whereby the pressure-sensitive adhesive surface can be more closely adhered to the surface of the adherend. Good adhesion of the adhesive surface to the adherend surface can advantageously contribute to the improvement of peel strength to a low polarity surface and other various surfaces. Moreover, the improvement of the softness | flexibility of an adhesive sheet can also contribute to the reduction of the repulsive force of an adhesive sheet. Thus, when the pressure-sensitive adhesive sheet is attached along the surface of an adherend having a curved surface or a step, or when the adherend to which the pressure-sensitive adhesive sheet is attached is deformed, etc. An event of peeling off (lifting) from the surface of the adherend can be effectively suppressed.
The visco-elastic body layer (B) may contain both the filler (for example, hollow particles) as described above and air bubbles. An adhesive sheet containing such a viscoelastic body layer (B) is preferable because it tends to be excellent in the balance between the flexibility and the cohesion.

  The cells contained in the viscoelastic layer (B) may be closed cells or open cells, or may be mixed. From the viewpoint of cushioning properties, a viscoelastic body layer (B) having a configuration containing a large number of closed cells is more preferable. In the case of a closed cell, the gas component contained in the cell (a gas component forming a cell, hereinafter sometimes referred to as a "bubble forming gas") is not particularly limited, and an inert gas such as nitrogen, carbon dioxide or argon Besides, it may be various gas components such as air. When a polymerization reaction or the like is performed in a state where the bubble-forming gas is contained as the bubble-forming gas, it is preferable to use a gas that does not inhibit the reaction. From this point of view, cost, etc., nitrogen can be suitably employed as the bubble-forming gas.

The shape of the air bubble is typically, but not limited to, generally spherical. The average diameter (average cell diameter) of the cells is not particularly limited, and can be selected, for example, in the range of 1 μm to 1000 μm, preferably 10 μm to 500 μm, and more preferably 30 μm to 300 μm. The average cell diameter is usually 50% or less of the thickness of the viscoelastic layer (B), and preferably 30% or less (e.g. 10% or less).
In addition, the said average bubble diameter can be typically calculated | required by carrying out the arithmetic mean of the result of having measured the diameter of the bubble about 10 or more bubbles preferably with a scanning electron microscope (SEM). At this time, with regard to the non-spherical bubbles, the average pore diameter is determined by converting them into spherical bubbles having the same volume.

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

In the art disclosed herein, the method for forming the viscoelastic body layer having bubbles (bubble-containing viscoelastic layer) is not particularly limited, and a known method can be appropriately adopted. For example, (1) a composition for forming a visco-elastic body layer (preferably a composition of the type that cures with active energy rays such as UV to form a visco-elastic body) in which a bubble-forming gas is mixed beforehand Method for forming bubble-containing viscoelastic body layer, (2) Method for forming bubble-containing viscoelastic body layer by forming cells from the foaming agent using a composition for forming a viscoelastic body layer containing a foaming agent Etc. can be adopted appropriately. The foaming agent to be used is not particularly limited, and can be appropriately selected from known foaming agents. For example, a foaming agent such as thermally expandable microspheres can be preferably used.
In the formation of the bubble-containing viscoelastic material layer according to the method (1), the method for preparing the composition for forming a viscoelastic material layer 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 a bubble mixing apparatus, a stator having a large number of fine teeth on a disk having a through hole at the center, 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 visco-elastic body layer (composition precursor for forming a visco-elastic body layer) before mixing in air 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 While rotating at high speed, a gas component (bubble forming gas) for forming a bubble is introduced into the composition precursor for forming a viscoelastic layer through the through hole. Thereby, the composition for viscoelastic body layer formation with which air bubbles were disperse | distributed finely and mixed is obtained.
A bubble-containing visco-elastic layer can be formed by applying and curing the composition containing the bubble-forming gas on a predetermined surface. As a curing method, a method of heating, a method of irradiating active energy rays (for example, UV), and the like can be preferably employed. The composition for forming a visco-elastic body layer in which a bubble-forming gas is mixed is subjected to heating, active energy ray irradiation, etc. to be cured in a state where bubbles are stably held, thereby suitably forming a bubble-containing visco-elastic body layer. can do.

A surfactant may be added to the composition for forming a viscoelastic layer from the viewpoint of the mixing property of the bubble forming gas and the stability of the bubbles. Examples of such surfactants include ionic surfactants, hydrocarbon surfactants, silicone surfactants, fluoro surfactants and the like. Among them, fluorine surfactants are preferable, 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 preferable. The fluorine-based surfactants can be used singly or in combination of two or more. As a commercial item of the fluorochemical surfactant which can be preferably used, the brand name "Surflon S-393" by AGC Seimi Chemical Co., Ltd. is exemplified.
The amount of the surfactant used is not particularly limited, and may be, for example, about 0.01 to 3 parts by weight on a solids basis with respect to 100 parts by weight of the acrylic polymer contained in the viscoelastic layer (B). it can.

[Other ingredients]
The viscoelastic layer (B) is a tackifier component such as an acrylic oligomer, a plasticizer, a softener, a colorant (pigment, dye, etc.), an antioxidant, a leveling agent, to the extent that the effects of the present invention are not significantly impaired. If necessary, known additives such as agents, stabilizers and preservatives may be contained. For example, when the composition for forming a visco-elastic body layer is cured by photopolymerization to form a visco-elastic body layer (B), the degree to which photopolymerization is not inhibited in order to color the visco-elastic body layer (B) Pigments (colored pigments) can be used as colorants. When black is desired as coloring of a viscoelastic body layer (B), carbon black can be preferably used as a coloring agent, for example. The amount of carbon black used is, for example, 0.15 parts by weight or less (for example, 0.001 parts by weight or less with respect to 100 parts by weight of the target viscoelastic body layer (B), in consideration of the degree of coloring, photopolymerization reactivity, etc. It is desirable to select from the range of -0.15 parts by weight, preferably 0.01-0.1 parts by weight. Moreover, the viscoelastic body layer (B) may be a thing which does not contain a tackifying component (for example, acryl-type oligomer) substantially. Such a composition can be preferably adopted, for example, in the non-adhesive viscoelastic layer (B).

[Thickness of Visco-Elastic Layer (B)]
The thickness of the visco-elastic body layer (B) is not particularly limited, but is suitably about 100 μm or more. The viscoelastic body layer (B) is excellent in flexibility because it is a viscoelastic body. Therefore, by supporting the pressure-sensitive adhesive layer (A) with the viscoelastic body layer (B), the surface (pressure-sensitive adhesive surface) of the pressure-sensitive adhesive layer (A) can be suitably adhered to the adherend. From the viewpoint of this flexibility, the thickness of the viscoelastic layer (B) is preferably 200 μm or more, and more preferably 300 μm or more (for example, 350 μm or more). From the viewpoint of obtaining higher flexibility, the thickness of the viscoelastic layer (B) can be 500 μm or more, and may be 700 μm or more. The technique disclosed herein can be preferably implemented even in an embodiment 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 can be, for example, about 10 mm or less. The thickness of the viscoelastic layer (B) is usually 5 mm or less, preferably 3 mm or less (e.g., 2 mm or less), from the viewpoint of ease of formation and cohesion of the viscoelastic layer (B).

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

In one preferred embodiment, one of alkyl (meth) acrylates in which R ² is C _1-14 (eg, C _1-10 , typically C _4-8 ) in the above formula (1) as the main monomer. Or 2 or more types 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 the main monomer is, for example, 60% by weight or more (eg, 80% by weight or more, typically) 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 (eg 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 acid group-containing monomer or in a proportion of 5% by weight or less. Thereby, the adhesion 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 (eg, 3% by weight or less). The constituent monomer component may be substantially free of the acid group-containing monomer.

  As the above acidic group-containing monomer, typically, various carboxyl group-containing monomers and metal salts thereof (for example, alkali metal salts) and acid anhydride group-containing monomers can be mentioned. Examples of these acidic group-containing monomers include carboxyl group-containing monomers that can be used for the acrylic polymer (b) and metal salts thereof (eg, alkali metal salts), and one or more of the acid anhydride group-containing monomers exemplified above. It can be used preferably. 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 while maintaining good adhesion to the low-polar adherend, a viscoelastic body layer (B C), and, for example, tends to further improve shear strength and holding power. The ratio (ACb / ACa) is more preferably 2 or more (e.g., 2.5 or more, typically 3 or more). The upper limit of the above ratio (ACb / ACa) is not particularly limited, but is preferably about 10 or less (for example, 5 or less).

  In the synthesis of the acrylic polymer (a), various secondary monomers (functional group-containing monomers, secondary monomers other than functional group-containing monomers, and polyfunctional monomers) exemplified in the above-mentioned acrylic polymer (b) are included, however, they are acidic. In the case of using a group-containing monomer), the amount thereof to be used may be suitably selected so as to achieve adjustment of Tg and desired cohesion, and is not particularly limited. The amount of the functional group-containing monomer other than the acidic group-containing monomer is, for example, 0.01% by weight or more (eg, 0.1% by weight or more, typically 1%) of all monomer components constituting the acrylic polymer (a). % Or more). From the viewpoint of achieving both flexibility and cohesion in a well-balanced manner, 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.

  Although not particularly limited, as the acrylic polymer (a), those obtained by copolymerizing a hydroxyl group-containing monomer can be preferably used. As a hydroxyl group containing monomer, 1 type (s) or 2 or more types of a hydroxyl group containing monomer illustrated as a constituent monomer of the said acryl-type polymer (b) can be used preferably. Among them, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, etc. More preferred is hydroxyalkyl (meth) acrylate.

  Such a hydroxyl group-containing monomer is preferably used in a range of about 0.001% by weight to 10% by weight based on the total amount of the monomer components used for the synthesis of the acrylic polymer (a). By this, the adhesive layer (A) which balanced the said adhesive force and cohesion by a higher level can be implement | achieved. By setting the amount of the hydroxyl group-containing monomer to about 0.01 wt% to 5 wt% (eg, 0.05 wt% to 2 wt%), better results can be achieved.

  The acrylic polymer (a) may also contain a vinyl ester (for example, VAc) as its constituent monomer component. In that case, the content thereof is suitably, for example, about 0.1 to 20% by weight (typically 0.5 to 15% by weight) based on the total amount of the above-mentioned monomer components.

  The copolymerization composition of the acrylic polymer (a) is suitably designed such that the Tg of the polymer is -15 ° C or less (typically -70 ° C or more and -15 ° C or less), and preferably Is −25 ° C. or less (eg, −60 ° C. or more and −25 ° C. or less), more preferably −40 ° C. or less (eg, −60 ° C. or more and −40 ° C. or less). It is preferable from the viewpoint of adhesive properties (for example, impact resistance etc.) to make the Tg of the acrylic polymer (a) not more than the above-mentioned upper limit value. The Tg of the acrylic polymer (a) is determined from the same method as the Tg of the above-mentioned acrylic polymer (b).

  The acrylic polymer (a) can be prepared by a known or conventional polymerization method. As a polymerization method, for example, thermal polymerization such as solution polymerization, emulsion polymerization, bulk polymerization and the like (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 to be performed by irradiation with an active energy ray such as radiation can be appropriately adopted. For example, solution polymerization can be preferably used. As a monomer supply method at the time of performing solution polymerization, a batch preparation method of supplying all the monomer raw materials at one time, a continuous supply (dropping) method, a divided supply (dropping) method or the like can be appropriately adopted. The polymerization temperature can be appropriately selected according to the type of monomer and solvent used, the type of polymerization initiator, etc., and may be, for example, about 20 ° C. to 170 ° C. (typically 40 ° C. to 140 ° C.) it can.

  The solvent (polymerization solvent) used for 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; isopropyl alcohol etc. A lower alcohol (for example, a monohydric alcohol having 1 to 4 carbon atoms); an ether such as tert-butyl methyl ether; a ketone such as methyl ethyl ketone; Mixed solvents of more than species can be used.

  The initiator used for polymerization can be suitably selected from conventionally known polymerization initiators according to the type of polymerization method. For example, one or more of the polymerization initiators exemplified as the initiator for thermal polymerization which 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 normal amount, for example, about 0.005 to 1 part by weight (typically 0.01 to 1 part by weight) with respect to 100 parts by weight of all the monomer components. It can be selected from the range.

The weight average molecular weight (Mw) of the acrylic polymer (a) disclosed herein is not particularly limited, and may be, for example, in the range of 10 × 10 ⁴ or more and 500 × 10 ⁴ or less. Mw of the acrylic polymer (a) is 10 × 10 ^{4 to} 150 × 10 ⁴ (eg, 20 × 10 ⁴ to 75 × 10 ⁴ , typically) from the viewpoint of balancing the cohesion and adhesion at a high level. It is preferable to be 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 a GPC apparatus, model name "HLC-8320GPC" (column: TSKgelGMH-H (S), Tosoh Corp. make) may be used, for example. The same applies to the examples 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 low molecular weight component is present, and the initial peel strength tends to be improved. Moreover, the anchorability to a viscoelastic body layer (B) improves, and there exists a tendency for favorable removability to be obtained. By setting the degree of dispersion to 10 or less, the heat resistance and removability of the pressure-sensitive adhesive sheet tend to be improved. The dispersion degree is more preferably 4 to 8 (e.g. 5 to 7). The degree of dispersion can be adjusted by selection of 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 a method similar to the above-mentioned Mw. The same applies to the examples described later.

In a preferred embodiment, the proportion of components 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 anchorability to the viscoelastic layer (B) tend to be improved, and the heat resistance and 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 (eg, 20 to 30% by weight). The proportion of the component having a molecular weight of 10 × 10 ⁴ or less can be adjusted by the selection of a polymerization initiator (for example, selection based on a 10-hour half-life temperature), polymerization conditions, aging conditions and the like. The ratio of the component having a molecular weight of 10 × 10 ⁴ or less can be determined by GPC. The same applies to the examples described later.

[Tackifier]
In a preferred embodiment, the pressure-sensitive adhesive layer (A) contains a tackifier. The tackifier is not particularly limited, and, 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 elastomeric tackifying resin and a ketone tacking resin can be used. Such tackifying resins can be used singly 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 preferable, and rosin-based tackifying resins, terpene-based tackifying resins, and phenol-based tackifying resins are more preferable. .

  Specific examples of the rosin-based tackifying resin include unmodified rosin (raw rosin) such as gum rosin, wood rosin and tall oil rosin; modified rosin obtained by modifying these unmodified rosins by hydrogenation, disproportionation, polymerization, etc. Hydrogenated rosins, disproportionated rosins, polymerized rosins, other chemically modified rosins, etc. The same applies hereinafter); various other rosin derivatives; Examples of the above-mentioned rosin derivatives include rosins such as those obtained by esterifying unmodified rosins with alcohols (that is, esterified products of rosin), those obtained by esterifying modified rosins with alcohols (that is, esterified products of modified rosin) Esters; Unmodified rosin or unsaturated fatty acid modified rosin obtained by modifying modified rosin with unsaturated fatty acid; Unsaturated fatty acid modified rosin ester obtained by modifying rosin ester with unsaturated fatty acid; unmodified rosin, modified rosin, unsaturated Rosin alcohols obtained by reducing the carboxyl group of fatty acid-modified rosins or unsaturated fatty acid-modified rosin esters; Metal salts of rosins (especially rosin esters) such as unmodified rosins, modified rosins, 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 adhesion properties such as repulsion resistance and adhesion, an appropriate one may be selected and used from the above-mentioned rosin-based tackifying resins, and the type, characteristics (eg, softening point), etc. are different. Two or three or more may be used in combination.

  Examples of terpene-based tackifying resins include terpene resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers; these terpene resins are modified (phenol modification, aromatic modification, hydrogenation modification, hydrocarbon Modified terpene resin; and the like. Examples of the modified terpene resin include terpene phenol resin, styrene modified terpene resin, aromatic modified terpene resin, hydrogenated terpene resin and the like. When using an acryl-type polymer as a base polymer, it is preferable to use terpene-type tackifying resin (for example, terpene phenol resin). From the viewpoint of improving adhesion characteristics such as repulsion resistance and adhesion, an appropriate one may be selected and used from the above-mentioned terpene-based tackifying resins (for example, terpene phenol resin), and the type and characteristics (for example, Two or more different types such as softening point) may be used in combination.

  Examples of hydrocarbon tackifying resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins (for example, xylene resin etc.), aliphatic cyclic hydrocarbon resins, aliphatic and aromatic petroleum resins (styrene- Various hydrocarbon-based resins such as olefin-based copolymers, aliphatic / alicyclic-based petroleum resins, hydrogenated hydrocarbon resins, coumarone-based resins, coumarone-indene-based resins, etc. may be mentioned.

  Examples of phenol-based tackifying resins include condensation products of various phenols such as phenol, m-cresol, 3,5-xylenol, p-alkylphenol, resorcin and formaldehyde (eg, alkylphenol-based resin, xylene formaldehyde based resin) Resins, etc.) Resol obtained by addition reaction of the above-mentioned phenols and formaldehyde with an alkali catalyst, and novolac obtained by condensation reaction of the above-mentioned phenols and formaldehyde with an acid catalyst, as well as rosins (unmodified rosins and modified rosins And rosin-modified phenol resins obtained by adding phenol to various rosin derivatives etc. by an acid catalyst and thermally polymerizing them.

  In the art 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. With the tackifying resin having the above-mentioned softening point, a higher performance (for example, highly adhesive) adhesive sheet can be realized. The upper limit of the softening point of the tackifying resin is not particularly limited, and can be about 180 ° C. or less (eg, about 140 ° C. or less). When using 2 or more types of tackifying resin, it is preferable that each tackifying resin has the said softening point. In addition, the softening point of tackifying resin here is defined as a value measured by the softening point test method (ring and ball method) prescribed in any of JIS K 5902: 2006 and JIS K 2207: 2006.

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

[Other ingredients]
In the pressure-sensitive adhesive composition (A) used to form 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, 1 type, or 2 or more types of various crosslinking agents illustrated in the viscoelastic body layer (B) can be used. Among them, the use of an isocyanate-based crosslinking agent and / or an epoxy-based crosslinking agent is preferable from the viewpoint of improving the cohesive force. The use amount of the crosslinking agent is not particularly limited, and for example, about 10 parts by weight or less (eg, about 0.005 to 10 parts by weight, preferably about 0.01 to 5 parts by weight, based on 100 parts by weight of the acrylic polymer (a)) Can be selected from the range of

  The above-mentioned pressure-sensitive adhesive composition (A) contains, if necessary, a leveling agent, a crosslinking aid, a plasticizer, a softener, a filler, a coloring agent (pigment, dye, etc.), an antistatic agent, an antiaging agent, and an ultraviolet absorbing agent. It may contain various additives commonly used in the field of the pressure-sensitive adhesive composition, such as agents, antioxidants, light stabilizers and the like. With respect to such various additives, conventionally known ones can be used by a conventional method, and since they do not particularly characterize the present invention, detailed description will be omitted.

  The pressure-sensitive adhesive layer (A) disclosed herein is a pressure-sensitive adhesive layer formed from an aqueous pressure-sensitive adhesive composition, a solvent-type pressure-sensitive adhesive composition, a hot melt-type pressure-sensitive adhesive composition, and an active energy ray-curable pressure-sensitive adhesive composition. It can be. The water-based pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition in a form containing a pressure-sensitive adhesive (pressure-sensitive adhesive layer-forming component) in a water-based solvent (water-based solvent). And pressure-sensitive adhesive compositions (compositions in which at least a portion of the pressure-sensitive adhesive is dispersed in water) and the like are included. Moreover, a solvent type adhesive composition means the thing of the adhesive composition of the form which contains an adhesive in an organic solvent. The technology disclosed herein is preferably carried out in a mode including the pressure-sensitive adhesive layer (A) formed of a solvent-based pressure-sensitive adhesive composition, from the viewpoint of suitably achieving the adhesive property.

  The method of forming the adhesive sheet containing an adhesive layer (A) and a viscoelastic body layer (B) is not specifically limited. For example, a pressure-sensitive adhesive layer (A) is formed on a surface having good releasability (a peeling surface, for example, the surface of a release liner), and the pressure-sensitive adhesive layer (A) is bonded to the surface of a viscoelastic body layer (B) The method of transferring) can be preferably employed. In addition, the pressure-sensitive adhesive composition (A) for forming the pressure-sensitive adhesive layer (A) is applied to the surface of the viscoelastic body layer (B) and cured (for example, dried) to form a viscoelastic body layer (B) The pressure-sensitive adhesive layer (A) may be formed on the surface of Alternatively, the composition (B) for forming the viscoelastic body layer (B) is applied to the surface of the pressure-sensitive adhesive layer (A) and cured (for example, UV curing) on the pressure-sensitive adhesive layer (A) The viscoelastic body layer (B) may be formed on For example, before laminating the pressure-sensitive adhesive layer (A) and the viscoelastic body layer (B) for the purpose of improving the adhesion between the pressure-sensitive adhesive layer (A) and the viscoelastic body layer (B), for example, The surface of the pressure-sensitive adhesive layer (A) of B) or the surface of the viscoelastic layer (B) of the pressure-sensitive adhesive layer (A) may be subjected to surface treatment such as corona discharge treatment (adhesion improvement treatment). It does not have to be.

[Thickness of adhesive layer (A)]
In the art disclosed herein, the thickness of the pressure-sensitive adhesive layer (A) constituting the pressure-sensitive adhesive surface is not particularly limited, and can be about 1 μm or more. From the viewpoint of peel strength, the thickness of the pressure-sensitive adhesive layer (A) is preferably 5 μm or more (eg, 10 μm or more, typically 20 μm or more). The thickness is usually 200 μm or less, preferably 150 μm or less (eg, 100 μm or less, typically 80 μm or less), from the viewpoint of cohesiveness and the like. The pressure-sensitive adhesive sheet disclosed herein effectively absorbs bumps and bumps on the surface of the adherend even if the thickness of the pressure-sensitive adhesive layer (A) is thin, since the pressure-sensitive adhesive sheet includes the viscoelastic layer (B). It can be well adhered to the adherend surface. 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 layer (B) (flexibility, improvement in peel strength based on the flexibility, improvement in followability, etc.) can be exhibited better. In addition, the removability tends to be improved by limiting the thickness of the pressure-sensitive adhesive layer (A). The above ratio (T _B / T _A ) is more preferably 10 or more (eg 12 or more, typically 15 or more), and even 20 or more (eg 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 (e.g., 50 or less).

<Supporting substrate>
The pressure-sensitive adhesive sheet disclosed herein may include a supporting substrate, such as the single-sided pressure-sensitive adhesive sheet 3 shown in FIG. Examples of the supporting substrate include plastic films such as polypropylene film, ethylene-propylene copolymer film, polyester film, polyvinyl chloride film and the like; foam sheets made of foam such as polyurethane foam, polyethylene foam and polychloroprene foam; Woven and non-woven fabrics (Japanese paper, high-quality paper) by single or mixed spinning of various fibrous materials (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, semi-synthetic fibers such as acetate, etc.) Etc.); aluminum foil, metal foil such as copper foil; etc. can be appropriately selected and used according to the application of the pressure-sensitive adhesive sheet. As the above-mentioned plastic film (typically, a non-porous plastic film and a concept to be distinguished from woven fabric and non-woven fabric), any of non-oriented film and stretched (uniaxially stretched or biaxial stretched) film Are also available.

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

  The surface of the supporting substrate on which the pressure-sensitive adhesive layer is provided may be subjected to surface treatment such as corona discharge treatment or formation of a primer layer to enhance the non-peelability (anchorability) of the surface. In addition, on the surface of the supporting substrate opposite to the side on which the pressure-sensitive adhesive layer is provided, treatment to enhance the releasability of the surface (formation of a release-treated layer or lamination of a low adhesion material such as a polyolefin film) Etc.) treatment to enhance the non-peelability and printability of the surface (eg, corona discharge treatment), and treatment to enhance the decorativeness of the surface (eg, printing, deposition of metal) Good.

<Peeling liner>
The pressure-sensitive adhesive sheet disclosed herein can be in a form in which the pressure-sensitive adhesive surface is protected by a release liner before its use (that is, before application to an adherend). As a release liner, a conventional release paper etc. can be used, It does not specifically limit. For example, a release liner having a release treatment layer on the surface of a substrate such as a plastic film or paper, a release liner made of a low adhesive material such as a fluorine-based polymer (polytetrafluoroethylene etc.) or a polyolefin resin (polyethylene, polypropylene etc.) Etc. can be used. The release treatment layer may be formed, for example, by surface treating the base material with a release treatment agent such as silicone, long-chain alkyl, fluorine, or molybdenum sulfide.
For example, in the single-sided adhesive sheet such as the adhesive sheet 3 shown in FIG. 3, the surface 36 A of the support base 36 is a peeling surface, and the adhesive face 3 A is a support base 36 by winding the adhesive sheet 3. It may be in the form of being in contact with and protected by the surface 36A. Thus, the pressure-sensitive adhesive sheet may be one in which the supporting substrate also functions as a release liner.

  The total thickness of the pressure-sensitive adhesive sheet (not including the thickness of the release liner) containing the pressure-sensitive adhesive layer (A) and the viscoelastic layer (B) is suitably more than 100 μm, preferably more than 200 μm For example, it is preferable to be more than 350 μm, typically more than 500 μm). The technology disclosed herein can be preferably practiced 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 may be, for example, about 15 mm or less, and usually about 10 mm or less is suitable, preferably 7 mm or less, and more preferably 5 mm or less (eg 3 mm or less).

<Characteristics of adhesive sheet>
The pressure-sensitive adhesive sheet disclosed herein (specifically, the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer (A)) preferably exhibits a 90 ° peel strength to polypropylene (30 ° peel strength to PP) of 30 N / 25 mm or more. The pressure-sensitive adhesive sheet exhibiting the peel strength can be firmly adhered to an adherend (particularly, a low-polar adherend such as PP). The above-mentioned PP 90 degree peel strength 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 45 N / 25 mm or more (for example 50 N / 25 mm or more) More preferable. The anti-PP 90 degree peel strength is measured by the method described in the examples below.

  The pressure-sensitive adhesive sheet disclosed herein preferably exhibits 90 ° peel strength of 40 N / 25 mm or more (against ABS 90 ° peel strength) to an acrylonitrile butadiene styrene copolymer (ABS) plate. The pressure-sensitive adhesive sheet exhibiting the peeling strength can be firmly adhered to various adherends (for example, resin adherends such as ABS). The above-mentioned ABS 90 degree peel strength to the above ABS is more preferably 42 N / 25 mm or more (eg 45 N / 25 mm or more, typically 50 N / 25 mm or more), 55 N / 25 mm or more (eg 60 N / 25 mm or more) More preferable. The anti-ABS 90 degree peel strength is measured by the method described in the examples below.

  In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the interlayer peel strength between the pressure-sensitive adhesive layer (A) and the viscoelastic layer (B) is 30 N / 25 mm or more. When the delamination strength shows a predetermined value or more, for example, in the case of removing the pressure-sensitive adhesive sheet firmly adhered to the adherend, occurrence of anchor breakage is suppressed or prevented, and excellent removability is preferably realized. Be done. The interlayer peel strength is more preferably 40 N / 25 mm or more (e.g., 50 N / 25 mm or more, typically 60 N / 25 mm or more). The following values are adopted as the above-mentioned delamination strength. That is, when the above-mentioned peel strength is measured by carrying out the anti-PP 90 degree peel strength or the anti-90 ABS peel strength described in the examples described later, the peel form is interfacial failure (adhesive surface of the pressure-sensitive adhesive layer (A) Between the pressure-sensitive adhesive layer (A) and the visco-elastic layer (B) is at least equal to or greater than the peel strength measured above. It can be recognized that the above-mentioned peel strength (against PP 90 degree peel strength or ABS 90 degree peel strength) can be adopted as delamination strength (90 degree delamination strength) [N / 25 mm] .

<Use>
The pressure-sensitive adhesive sheet disclosed herein can be preferably used in a mode in which the pressure-sensitive adhesive surface formed of the 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 resin and polypropylene resin, ABS resin, high impact polystyrene (HIPS) resin, polycarbonate (PC) An adherend made of resin such as resin, polymer blend of PC and ABS (PC / ABS) resin, etc. may be mentioned.
In addition, the pressure-sensitive adhesive sheet disclosed herein has high flexibility (is easily deformed) by including the viscoelastic body layer (B), and therefore, a step or a step that may exist on the surface of the members in bonding between such members. Irregularities or manufacturing errors of members can be absorbed by deformation of the adhesive, and a good bonding state between both members can be realized. Therefore, the pressure-sensitive adhesive sheet is useful, for example, for bonding between members in various OA devices, home appliances, automobiles and the like (for example, fixing applications of various parts in such products).

  The following examples illustrate some of the embodiments of the present invention, but are not intended to limit the present invention to those shown. In the following description, "parts" and "%" are on a weight basis unless otherwise noted.

(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, toluene and ethyl acetate as a polymerization solvent 5: The mixed solvent mixed at a weight ratio of 5 was charged, nitrogen reflux was performed at room temperature for 1 hour, and then a solution polymerization reaction was performed at about 58 ° C. for 6 hours. Then, the aging reaction was performed at 65 ° C. for 2 hours and at 72 ° C. for 2 hours. Thereafter, the resultant was allowed to cool to obtain a solution of an acrylic polymer (a1). The Mw of this acrylic polymer (a1) was about 60 × 10 ⁴ . Mw / Mn was 5.0, and the polymer ratio with a molecular weight of 100,000 or less was about 20%.
As a tackifying resin, 10 parts of rosin phenol resin (trade name "Tamanor 803", Arakawa Chemical Industries Co., Ltd.) as a tackifying resin is added to the solution of the acrylic polymer (a1) obtained above with 100 parts of the acrylic polymer (a1) 10 parts of hydrogenated rosin glycerin ester (trade name "ester gum H", manufactured by Arakawa Chemical Industries, Ltd.) and 15 parts of polymerized rosin pentaerythritol ester (trade name "Pencel D125, manufactured by Arakawa Chemical Industries, Ltd.) Then, 2 parts of an isocyanate-based crosslinking agent (trade name "CORONATE L", manufactured by Nippon Polyurethane Industry Co., Ltd.) as a crosslinking agent was added to prepare a pressure-sensitive adhesive composition (A1).
A 25 μm-thick polyethylene layer was laminated on one side of a high-quality paper, and a sheet-like release liner was prepared on which a release treatment with a silicone release agent was performed. The above-mentioned 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 a pressure-sensitive adhesive layer (A1), two types (thickness: 25 μm, 50 μm) of pressure-sensitive adhesive layers having different thicknesses were prepared.

(Preparation of pressure-sensitive adhesive layer (A2))
In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel, 95 parts of BA, 5 parts of AA, and toluene as a polymerization solvent are charged, and nitrogen reflux is performed at room temperature for 1 hour. 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). The Mw of this acrylic polymer (a2) was about 50 × 10 ⁴ .
As a tackifying resin, 20 parts of a rosin phenol resin (trade name "Tamanor 803, manufactured by Arakawa Chemical Industries, Ltd.) as a tackifying resin in a solution of the acrylic polymer (a2) obtained above is added to 100 parts of the acrylic polymer (a2) And 30 parts of a xylene formaldehyde-based tackifying resin (trade name "Nicanol H-80", manufactured by Mitsubishi Gas Chemical Company, Inc.) having a hydroxyl group, and further containing a nitrogen atom as a hydroxy compound (trade name "EDP- An adhesive composition (A2) was prepared by adding 0.05 parts of 300 ′ ′ (manufactured by Asahi Denka Co., Ltd.) and 4 parts of an isocyanate-based crosslinking agent (trade name “Coronate L”, manufactured by Nippon Polyurethane Industry Co., Ltd.) as a crosslinking agent. did.
A 25 μm-thick polyethylene layer was laminated on one side of a high-quality paper, and a sheet-like release liner was prepared on which a release treatment with a silicone release agent was performed. 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 added to 2,2-dimethoxy-1,2-diphenylethan-1-one (manufactured by BASF, trade name “IRGACURE 651” as a photopolymerization initiator. ) And 0.05 parts of 1-hydroxycyclohexyl-phenyl-ketone (manufactured by BASF, trade name “IRGACURE 184”), and charged in a four-necked flask with UV irradiation under a nitrogen atmosphere By photopolymerization, a syrup containing a partially polymerized product was obtained.
Also, 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 nitrogen gas was blown to remove dissolved oxygen. Then, the mixture is heated to 90 ° C., and 0.005 part of a trade name “Perhexyl O” (manufactured by NOF Corporation) as a polymerization initiator and a trade name “Perhexyl D” (manufactured by NOF Corporation) 0.01 The reaction mixture was stirred at 90 ° C. for 1 hour, heated to 150 ° C. over 1 hour, and stirred at 150 ° C. for 60 minutes. Then, 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 under the condition of 170 ° C., and stirring was performed for 1 hour to remove the residual monomer, thereby obtaining an acrylic oligomer having a Mw of 3700.
A pressure-sensitive adhesive composition (A3) was prepared by adding and mixing 0.08 parts of 2-isocyanatoethyl acrylate and 20 parts of the above-mentioned acrylic oligomer to 100 parts of the syrup obtained above.
Two PET films with a thickness of 38 μm, one surface of which was a release surface treated with a silicone release treatment agent, were prepared. The pressure-sensitive adhesive composition (A3) obtained above was applied to the release surface of the first PET film with a roll coater. Next, a second PET film was attached to the outer surface of the composition (A3) applied so that the peeling surface of the PET film overlapped. Next, UV irradiation was performed from both sides with a black light lamp with an illuminance of 5 mW / cm ² for 3 minutes. Thus, a 70 μm thick adhesive layer (A3) was formed.

(Preparation of Viscoelastic Layer (B1))
2 parts of a monomer mixture consisting of 85 parts of EHA and 15 parts of AA and 0.05 parts of 2,2-dimethoxy-1,2-diphenylethan-1-one (manufactured by BASF, trade name “IRGACURE 651”) as a photopolymerization initiator -After blending 0.05 parts of hydroxycyclohexyl-phenyl-ketone (manufactured by BASF, trade name "IRGACURE 184"), UV is irradiated until the viscosity becomes about 15 Pa · s, and a part of the above-mentioned monomer mixture is A polymerized monomer syrup (b1) (partially polymerized product) was produced. The viscosity was measured using a BH viscometer, using rotor no. It measured on the conditions of 5 and rotational speed 10rpm and the measurement temperature of 30 degreeC.
To 100 parts of this monomer syrup (b1), 0.15 parts of dipentaerythritol hexaacrylate (DPHA) as a cross-linking agent and a hollow glass balloon (average particle diameter 40 μm, trade name “Fuji Balloon H-40”, Fuji Silysia Chemical Ltd. 15 parts were added to obtain a composition for forming a viscoelastic layer (B1).
Two PET films with a thickness of 38 μm, one surface of which was a release surface treated with a silicone release treatment agent, were prepared. To 100 parts of the composition for forming a viscoelastic body layer (B1), 0.03 parts of “IRGACURE 651” is added, this is applied to the peeling surface of the first PET film, and 2 sheets are placed on it The peeling surface of the eye PET film was covered, and UV with an illumination intensity of 5 mW / cm ² was irradiated from both sides for 3 minutes to be cured. For the UV irradiation, a trade name "Blacklight" manufactured by Toshiba Corporation was used. The measurement of UV was performed using an industrial UV checker with peak sensitivity wavelength of about 350 nm (trade name "UVR-T1" manufactured by Topcon Corporation, 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 the above 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) were added 0.15 parts of DPHA 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.”) as a crosslinking agent Thus, a composition (B2) for forming a viscoelastic layer was obtained. A viscoelastic body layer (B2) was produced in the same manner as the above-mentioned viscoelastic body layer (B1) except that the composition (B2) for forming a viscoelastic body layer was used. As a visco-elastic body layer (B2), the visco-elastic body layer of three types (Thickness: 400 micrometers, 800 micrometers, and 1200 micrometers) from which thickness differs is prepared.

(Preparation of Viscoelastic Layer (B3))
To 100 parts of monomer syrup (b2), 0.08 parts of 1,6-hexanediol diacrylate (HDDA) as a cross-linking agent and a hollow glass balloon (average particle size 40 μm, trade name “Fuji Balloon H-40”, Fuji Silysia A degassing treatment was carried out by adding 12.5 parts of Chem. After the defoaming treatment, 0.7 part of a fluorine-based surfactant was added to obtain a precursor of a composition for forming a viscoelastic body layer. The precursor was stirred with a nitrogen gas introduced from the through holes of the device using a bubble mixing device to obtain a composition (B3) for forming a viscoelastic body layer in which the bubbles were dispersed and mixed. A viscoelastic body layer (B3) was produced in the same manner as the above-mentioned viscoelastic body layer (B1) except that this composition for forming a viscoelastic body layer (B3) was used. The proportion of air bubbles in the viscoelastic layer (B3) was about 10% by volume.

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

(Preparation of Viscoelastic Layer (B5))
After adding 0.08 parts of HDDA as a crosslinking agent to 100 parts of monomer syrup (b2), 0.5 parts of hollow glass microspheres (trade name "Celster Z-27", manufactured by Tokai Kogyo Co., Ltd.) were further added. Thereafter, 0.5 part of a fluorine-based surfactant was added to obtain a precursor of a composition for forming a viscoelastic body layer. The proportion of hollow glass microspheres in the precursor of the composition for forming a viscoelastic layer was about 1.5% by volume.
A viscoelastic body layer in which air bubbles are dispersed and mixed 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 an air bubble mixing device. The composition for formation (B5) was obtained. In the composition for forming a viscoelastic body layer (B5), the air bubbles are mixed so as to be about 20% by volume with respect to the total volume of the composition (B5).
Two 38 μm-thick PET films, one of which is a release surface treated with a silicone release treatment agent, are prepared, and the viscoelastic layer obtained above is formed on the release surface of the first PET film. The composition for formation (B5) was applied by a roll coater. Next, a second PET film was attached to the outer surface of the coated composition (B5) such that the release surface of the PET film overlapped. Next, UV irradiation was performed from both sides with a black light lamp with an illuminance of 5 mW / cm ² for 3 minutes. Thus, a 730 μm thick viscoelastic body layer (B5) was formed.

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

<Examples 2 to 10>
The pressure-sensitive adhesive sheets according to Examples 2 to 10 are the same as Example 1 except that the type and thickness of the pressure-sensitive adhesive layer (A) and the type and thickness of the viscoelastic layer (B) are changed to the contents 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 13-18>
As an adhesive sheet which concerns on these examples, viscoelastic body layer (B1)-(B4) of the thickness shown in Table 1 was used as it was, respectively.

[Abs 90 degree peel strength measurement]
One side of the pressure-sensitive adhesive sheet according to each example was attached and backed to a 130 μm-thick aluminum foil subjected to anodizing treatment. The backed adhesive sheet was cut into a width of 25 mm and a length of 70 mm as a test piece. The surfaces of the viscoelastic layer in Examples 1 to 10 and 13 to 18 and the surface of the pressure-sensitive adhesive layer in Examples 11 and 12 were attached to the above aluminum foil.
The surface of an acrylonitrile butadiene styrene copolymer board (ABS board) as an adherend was washed with isopropyl alcohol (IPA). The pressure-sensitive adhesive surface of each test piece was crimped to the ABS plate by reciprocating a 5-kg roller twice. After pressure bonding, it was aged for 20 minutes under an atmosphere of 23 ° C. and 50% RH. The surface (adhesive surface) of the pressure-sensitive adhesive layer was adhered to the adherend in Examples 1 to 12 and the surface of the viscoelastic layer in Examples 13 to 18. After aging, using a tensile tester (manufactured by Shimadzu Corporation, device name "Tensilon"), adherend under conditions of a tensile speed of 300 mm / min and a peeling angle of 90 degrees under an atmosphere of 23 ° C and 50% RH. The test piece was peeled off from the ABS plate, and the peel strength [N / 25 mm] at that time was measured. The obtained results are shown in Table 1.

[To PP 90 degree peel strength measurement]
One side of the pressure-sensitive adhesive sheet according to each example was attached and backed to a 130 μm-thick aluminum foil subjected to anodizing treatment. The backed adhesive sheet was cut into a width of 25 mm and a length of 70 mm as a test piece. The surfaces of the viscoelastic layer in Examples 1 to 10 and 13 to 18 and the surface of the pressure-sensitive adhesive layer in Examples 11 and 12 were attached to the above aluminum foil.
The surface of a polypropylene plate (PP plate) as an adherend was washed with IPA. The pressure-sensitive adhesive surface of each test piece was crimped to this PP plate by moving a 5-kg roller twice. After pressure bonding, it was aged for 20 minutes under an atmosphere of 23 ° C. and 50% RH. The surface (adhesive surface) of the pressure-sensitive adhesive layer was adhered to the adherend in Examples 1 to 12 and the surface of the viscoelastic layer in Examples 13 to 18. After aging, using a tensile tester (manufactured by Shimadzu Corporation, device name "Tensilon"), adherend under conditions of a tensile speed of 300 mm / min and a peeling angle of 90 degrees under an atmosphere of 23 ° C and 50% RH. The test piece was peeled from the PP plate), and the peel strength [N / 25 mm] at that time was measured. The obtained results are shown in Table 1.

  As shown in Table 1, the viscoelastic layer (B) is disposed, 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 level or less. The pressure-sensitive adhesive sheets according to Examples 1 to 9 exhibited high values of 90 N peel strength with respect to a PP plate of 30 N / 25 mm or more. Specifically, in the pressure-sensitive adhesive sheet provided with the pressure-sensitive adhesive layer (A1) and any one of the viscoelastic layers (B1) to (B4), the peeling with respect to PP 90 degrees compared to Example 11 of only the pressure-sensitive adhesive layer (A1) The strength increased to about 1.1 times or more (about 1.1 to 1.8 times). The same tendency is assumed in the comparison of Examples 8 and 9 with 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 peel strength against PP 90 degrees showed a low value. Further, in the evaluation of the visco-elastic body layer (B) alone (Examples 13 to 18), the peel strength against PP 90 degrees 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, all of the peeling modes in the evaluation of the above-mentioned 90 degree peeling strength were interfacial failure (peeling at the interface between the adhesive surface of the pressure-sensitive adhesive layer (A) and the adherend). From these results, a low polarity adherend is obtained by combining the pressure-sensitive adhesive layer (A) and the viscoelastic body 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. The pressure-sensitive adhesive sheet is also excellent in flexibility because it includes the viscoelastic layer (B).

  As mentioned above, although the specific example of this invention was described in detail, these are only an illustration and do not limit a claim. The art set forth in the claims includes various variations and modifications of the specific examples illustrated above.

1,2,3 Pressure-sensitive adhesive sheet 12, 22, 22, 23, 32 Pressure-sensitive adhesive layer (A)
14, 24, 34 Viscoelastic layer (B)
36 Support base material

Claims (8)

An adhesive layer (A) constituting an adhesive surface,
And visco-elastic layer (B) supporting the pressure-sensitive adhesive layer (A),
The viscoelastic layer (B) contains hollow particles or has bubbles.
The pressure-sensitive adhesive layer (A) contains an acrylic polymer (a) as a base polymer,
The adhesive sheet whose copolymerization ratio of the acidic group containing monomer in the said acryl-type polymer (a) is 5 weight% or less.   The pressure-sensitive adhesive sheet according to claim 1, wherein the viscoelastic body layer (B) contains an acrylic polymer (b) as a base polymer.   The pressure-sensitive adhesive sheet according to claim 2, wherein the acrylic polymer (b) is obtained by polymerizing a monomer raw material containing an acidic group-containing monomer.   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. The adhesive sheet as described in 3.   The pressure-sensitive adhesive layer (A) contains at least one tackifier selected from the group consisting of a rosin-based tackifying resin, a terpene-based tackifying resin, and a phenol-based tackifying resin. The pressure-sensitive adhesive sheet as described in 1 or 2.   The adhesive sheet according to claim 5, wherein the content of the tackifier in the adhesive layer (A) is 10 to 50 parts by weight with respect to 100 parts by weight of the base polymer. The ratio (T _B / T _A ) of the thickness T _B of the visco-elastic body layer (B) to the thickness T _A of the pressure-sensitive adhesive layer (A) is 12 or more. The adhesive sheet as described in a term.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the pressure-sensitive adhesive surface exhibits a 90-degree peel strength to polypropylene of 30 N / 25 mm or more.

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