JP2012172004A - Adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive sheet including at least three layers of (A) a substrate layer, (B1) a first adhesive layer and (B2) a second adhesive layer in this order and having strong interlayer adhesion.SOLUTION: This adhesive sheet is provided by including at least three layers of (A) the substrate layer, (B1) first adhesive layer and (B2) second adhesive layer in this order, wherein, (A) the substrate layer includes a thermoplastic resin, (B1) the first adhesive layer includes at least one selected from an α-olefin-based thermoplastic elastomer and a styrene-based thermoplastic elastomer, and (B2) the second adhesive layer includes an acrylic block copolymer including an acrylic acid ester block structure and a methacrylic acid ester block structure.

Description

  The present invention relates to an adhesive sheet. More specifically, the pressure-sensitive adhesive sheet is composed of at least three layers having a base material layer (A), a first pressure-sensitive adhesive layer (B1), and a second pressure-sensitive adhesive layer (B2) in this order. Related to high adhesive sheet.

  The acrylic polymer is excellent in light resistance and transparency, and functions suitable for various applications can be added by combining raw materials for synthesizing the acrylic polymer. For this reason, the acrylic polymer is preferably used as the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet.

  For example, block copolymer of acrylic ester, which is a soft segment, and methacrylic ester, which is a hard segment, are precisely polymerized by a living polymerization method, resulting in heat resistance, weather resistance, flexibility, transparency, and adhesiveness. A thermoplastic acrylic pressure-sensitive adhesive having excellent characteristics in various aspects has been proposed (see, for example, Patent Documents 1 to 3).

  Since the thermoplastic acrylic pressure-sensitive adhesive has thermoplasticity, a pressure-sensitive adhesive sheet can be produced by coextrusion molding using the thermoplastic acrylic pressure-sensitive adhesive. According to the co-extrusion molding, since the base material layer and the pressure-sensitive adhesive layer are extruded and laminated at the same time, the production in one step becomes possible. For this reason, the manufacturing cost can be reduced and the manufacturing process can be simplified. Moreover, in coextrusion molding, since a solvent such as an organic solvent is not used, there is an advantage that a drying step is unnecessary and the environmental load is low (for example, see Patent Documents 4 to 6).

  On the other hand, when an acrylic pressure-sensitive adhesive sheet is produced by coextrusion molding, since it is a one-step production, there arises a problem that the pretreatment on the surface of the material (base material sheet) constituting the base material layer cannot be performed. Generally, when a highly polar acrylic pressure-sensitive adhesive layer is provided on a base layer composed of a nonpolar material such as polyethylene or polypropylene, the electrostatic interaction is weak, and the base layer and the pressure-sensitive adhesive layer Since the adhesion is low, pretreatment such as corona treatment, plasma treatment, ultraviolet irradiation treatment, electron beam irradiation treatment, etc. is performed on the surface of the substrate sheet in advance to increase the adhesion between the substrate layer and the adhesive layer. Done. However, such pretreatment cannot be performed by coextrusion molding.

  In coextrusion molding, a method of providing an intermediate layer serving as an adhesive layer between the base material layer and the pressure-sensitive adhesive layer has been proposed in order to solve the above-described problems (see, for example, Patent Documents 5 to 6). ). However, when an ethylene-vinyl acetate copolymer is used for the intermediate layer (Patent Document 5), the electrostatic interaction with the acrylic pressure-sensitive adhesive is increased and the interlayer adhesion is improved to some extent. As a result, the required level of interlayer adhesion is not expected to improve. In addition, in the method (Patent Document 6) in which a modified olefin containing an epoxy group or a cyclic anhydride is used as the intermediate layer constituting resin and interlayer adhesion is obtained by ring opening of these functional groups, the reactivity of the intermediate layer constituting resin is high. Therefore, there is a high risk that the chemical properties of the acrylic pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer will change (especially, the thinner the pressure-sensitive adhesive layer).

  Further, when providing a pressure-sensitive adhesive sheet provided with a plurality of pressure-sensitive adhesive layers on a base material layer, when peeling off after being attached to an adherend, there is a tendency for adhesive residue to occur on the adherend. Such adhesive residue is likely to occur when the interlayer adhesion between the base material layer and the pressure-sensitive adhesive layer laminated adjacent thereto is low, or when the interlayer adhesion between a plurality of adjacent pressure-sensitive adhesive layers is low.

JP 2001-234146 A JP 2002-97238 A Japanese Patent Laid-Open No. 11-323072 JP 2009-125985 A JP 2009-241348 A JP 2009-249541 A

  This invention is made | formed in order to solve the said conventional subject, The place made into the objective is a base material layer (A), a 1st adhesive layer (B1), and a 2nd adhesive layer (B2). In this order, the pressure-sensitive adhesive sheet is composed of at least three layers and has high interlayer adhesion.

The pressure-sensitive adhesive sheet of the present invention is
A pressure-sensitive adhesive sheet consisting of at least three layers having a base material layer (A), a first pressure-sensitive adhesive layer (B1) and a second pressure-sensitive adhesive layer (B2) in this order,
The base material layer (A) contains a thermoplastic resin,
The first pressure-sensitive adhesive layer (B1) includes at least one selected from α-olefin-based thermoplastic elastomers and styrene-based thermoplastic elastomers,
The second pressure-sensitive adhesive layer (B2) includes an acrylic block copolymer including an acrylate block structure and a methacrylate block structure.

  In preferable embodiment, the said base material layer (A) contains polyolefin resin.

  In a preferred embodiment, the acrylic block copolymer has a weight average molecular weight of 30,000 to 300,000.

In a preferred embodiment, the pressure-sensitive adhesive sheet of the present invention is
A pressure-sensitive adhesive sheet that is a laminate including a laminated structure of a base material layer (A) / first pressure-sensitive adhesive layer (B1) / second pressure-sensitive adhesive layer (B2),
The laminate including the forming material (a) of the base material layer (A), the forming material (b1) of the first pressure-sensitive adhesive layer (B1), and the forming material (b2) of the second pressure-sensitive adhesive layer (B2) Are obtained by coextrusion molding of the forming materials.

  According to the present invention, the pressure-sensitive adhesive sheet is composed of at least three layers having a base material layer (A), a first pressure-sensitive adhesive layer (B1), and a second pressure-sensitive adhesive layer (B2) in this order, and has interlayer adhesion. Can provide a high pressure-sensitive adhesive sheet.

  According to the present invention, a pressure-sensitive adhesive sheet having high interlayer adhesion can be produced using co-extrusion, so that it can be produced in one process, and the production cost can be reduced and the production process can be simplified. Become.

  According to the present invention, a pressure-sensitive adhesive sheet having high interlayer adhesion can be produced using coextrusion, so that it is not necessary to use a solvent such as an organic solvent, a drying step is not required, and the environmental load is reduced. be able to.

It is a schematic sectional drawing of the adhesive sheet by preferable embodiment of this invention.

≪ << A. Adhesive sheet >>>>
The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet composed of at least three layers having a base material layer (A), a first pressure-sensitive adhesive layer (B1), and a second pressure-sensitive adhesive layer (B2) in this order. That is, the pressure-sensitive adhesive sheet of the present invention is a laminate including a laminated structure of a base material layer (A) / first pressure-sensitive adhesive layer (B1) / second pressure-sensitive adhesive layer (B2). Here, the expression “base material layer (A) / first pressure-sensitive adhesive layer (B1) / second pressure-sensitive adhesive layer (B2)” refers to the base material layer (A), the first pressure-sensitive adhesive layer (B1), and the first. 2 represents a structure in which the pressure-sensitive adhesive layer (B2) is directly laminated. The “first pressure-sensitive adhesive layer (B1) / second pressure-sensitive adhesive layer (B2)” to be laminated on the base material layer (A) may be present only on one side of the base material layer (A) or both sides. May be present on the side. When present on both sides, the pressure-sensitive adhesive sheet of the present invention comprises the second pressure-sensitive adhesive layer (B2) / first pressure-sensitive adhesive layer (B1) / base material layer (A) / first pressure-sensitive adhesive layer (B1) / second. It becomes an adhesive sheet which consists of at least 5 layers including the laminated structure of an adhesive layer (B2).

  The base material layer (A) may be a single layer or a laminate of two or more layers.

  The first pressure-sensitive adhesive layer (B1) may be a single layer or a laminate of two or more layers.

  The second pressure-sensitive adhesive layer (B2) may be a single layer or a laminate of two or more layers.

  The pressure-sensitive adhesive sheet of the present invention is a laminate that includes a laminated structure of the base material layer (A) / first pressure-sensitive adhesive layer (B1) / second pressure-sensitive adhesive layer (B2), and does not impair the effects of the present invention. Any suitable other layers may be included.

  FIG. 1 is a schematic cross-sectional view of an adhesive sheet according to a preferred embodiment of the present invention. The pressure-sensitive adhesive sheet 100 includes a base material layer (A) 1, a first pressure-sensitive adhesive layer (B 1) 21, and a second pressure-sensitive adhesive layer (B 2) 22. In the case of storage, the pressure-sensitive adhesive sheet shown in FIG. 1 is preferably wound into a roll so that the base material layer (A) 1 is on the outside.

  The thickness of the pressure-sensitive adhesive sheet of the present invention can be set to any appropriate thickness depending on the application. Preferably they are 10 micrometers-500 micrometers, More preferably, they are 10 micrometers-300 micrometers, More preferably, they are 10 micrometers-200 micrometers.

  In the pressure-sensitive adhesive sheet of the present invention, the laminate including the laminated structure of the base material layer (A) / first pressure-sensitive adhesive layer (B1) / second pressure-sensitive adhesive layer (B2) is preferably formed integrally by coextrusion molding. It has been done. That is, in the pressure-sensitive adhesive sheet of the present invention, preferably, the laminated surface of the base material layer (A) / first pressure-sensitive adhesive layer (B1) or the first pressure-sensitive adhesive layer (B1) / second pressure-sensitive adhesive layer (B2). The laminated surface is not subjected to pretreatment such as corona treatment, plasma treatment, ultraviolet ray irradiation treatment, and electron beam irradiation treatment.

  The pressure-sensitive adhesive sheet of the present invention is peeled when the first pressure-sensitive adhesive layer (B1) is peeled from the base material layer (A) under the conditions of a measurement temperature of 23 ° C., a tensile speed of 0.3 m / min, and a peeling angle of 180 degrees. The force is preferably 2.0 N / 20 mm or more, more preferably 2.5 N / 20 mm or more, still more preferably 3.0 N / 20 mm or more, and particularly preferably 3.5 N / 20 mm or more. When such a peeling force is within the above range, it is possible to form a clean peeling surface free from adhesive residue when peeling from an adherend (for example, an optical component). In addition, specific operation at the time of measuring the said peeling force can be performed according to description of the Example mentioned later, for example.

  The pressure-sensitive adhesive sheet of the present invention peels the second pressure-sensitive adhesive layer (B2) from the first pressure-sensitive adhesive layer (B1) under the conditions of a measurement temperature of 23 ° C., a tensile speed of 0.3 m / min, and a peeling angle of 180 degrees. Is preferably 2.0 N / 20 mm or more, more preferably 2.5 N / 20 mm or more, still more preferably 3.0 N / 20 mm or more, and particularly preferably 3.5 N / 20 mm or more. is there. When such a peeling force is within the above range, it is possible to form a clean peeling surface free from adhesive residue when peeling from an adherend (for example, an optical component). In addition, specific operation at the time of measuring the said peeling force can be performed according to description of the Example mentioned later, for example.

  The pressure-sensitive adhesive sheet of the present invention is peeled when the first pressure-sensitive adhesive layer (B1) is peeled from the base material layer (A) under the conditions of a measurement temperature of 23 ° C., a tensile speed of 0.3 m / min, and a peeling angle of 180 degrees. The force is preferably 2.0 N / 20 mm or more, and the peeling force when peeling the second pressure-sensitive adhesive layer (B2) from the first pressure-sensitive adhesive layer (B1) is preferably 2.0 N / 20 mm or more. As a result, the interlayer adhesion between the base material layer (A) and the first pressure-sensitive adhesive layer (B1) is enhanced, and the interlayer adhesion between the first pressure-sensitive adhesive layer (B1) and the second pressure-sensitive adhesive layer (B2). When it peels after sticking to a to-be-adhered body, it becomes possible to form the beautiful peeling surface without an adhesive residue.

  The pressure-sensitive adhesive sheet of the present invention preferably has an adhesive force to the stainless steel plate (SUS plate) of the second pressure-sensitive adhesive layer (B2) under the conditions of a measurement temperature of 23 ° C., a tensile speed of 0.3 m / min, and a peeling angle of 180 degrees. Is 1.0 N / 20 mm or more, more preferably 1.2 N / 20 mm or more, still more preferably 1.4 N / 20 mm or more, particularly preferably 1.6 N / 20 mm or more, and most preferably 1. .8N / 20 mm or more. However, the preferable adhesive force range of the pressure-sensitive adhesive sheet of the present invention may vary depending on the use mode. For example, when using the adhesive sheet of this invention for bonding of an optical member, the said adhesive force becomes like this. Preferably it is 1.0 N / 20mm or more, More preferably, it is 2.5-50.0 N / 20mm. Moreover, when using the adhesive sheet of this invention as a protective film, the said adhesive force becomes like this. Preferably it is 0.01-10.0 N / 20mm. In addition, the measurement of the said adhesive force can be performed based on the measuring method of the adhesive force described in the Example mentioned later based on JIS-Z-0237 (2000).

<< A-1. Base material layer (A) >>
Arbitrary appropriate thickness can be employ | adopted for the thickness of a base material layer (A) according to a use. The thickness of the base material layer (A) is preferably 10 μm to 300 μm, more preferably 20 μm to 250 μm, and further preferably 30 to 200 μm.

  The base material layer (A) may be a single layer or a laminate of two or more layers. When a base material layer (A) is a laminated body of 2 or more layers, Preferably it is 2-5 layers, More preferably, it is 2-3 layers. When the base material layer (A) is only one layer, coextrusion molding at the time of producing the pressure-sensitive adhesive sheet can be facilitated. When the base material layer (A) is a laminate of two or more layers, the function can be divided by each layer. For example, when the base material layer (A) is a laminate of two layers, an easy rewinding layer from the roll body is adopted as the first base material layer, and the adhesive layer is adhered to the adhesive layer as the second base material layer. A layer with good properties can be employed.

  The base material layer (A) contains a thermoplastic resin. Any appropriate thermoplastic resin can be selected as the thermoplastic resin. The content ratio of the thermoplastic resin in the base material layer (A) is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, still more preferably 90 to 100% by weight, and particularly preferably. Is from 95 to 100% by weight, most preferably substantially 100% by weight.

  The base material layer (A) preferably contains a polyolefin resin. Any appropriate polyolefin-based resin can be adopted as the polyolefin-based resin as long as the sheet can be formed by melt extrusion.

  Examples of polyolefin resins include α-olefin homopolymers, copolymers of two or more α-olefins, block polypropylene, random polypropylene, one or more α-olefins and other vinyl monomers. A polymer etc. are mentioned. Examples of the form of the copolymer include a block form and a random form.

  Preferred examples of the polyolefin resin include α-olefin homopolymers, copolymers of two or more α-olefins, block polypropylene, and random polypropylene. More specifically, the polyolefin resin is more preferably polyethylene (PE), homopolypropylene (PP), block polypropylene, or random polypropylene.

  The α-olefin is preferably an α-olefin having 2 to 12 carbon atoms. Examples of such α-olefins include ethylene, propylene, 1-butene, 4-methyl-1-pentene and the like.

  Examples of the α-olefin homopolymer include polyethylene (PE), homopolypropylene (PP), poly (1-butene), poly (4-methyl-1-pentene), and the like.

  Examples of polyethylene (PE) include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene, and high density polyethylene (HDPE).

  The structure of homopolypropylene may be any of isotactic, atactic and syndiotactic.

  Examples of the copolymer of two or more kinds of α-olefins include, for example, an ethylene / propylene copolymer, an ethylene / 1-butene copolymer, an ethylene / propylene / 1-butene copolymer, and an ethylene / carbon atom number of 5 to 5. 12 α-olefin copolymers, propylene / α-olefin copolymers having 5 to 12 carbon atoms, and the like.

  Examples of the copolymer of one or more α-olefins and other vinyl monomers include, for example, ethylene / vinyl acetate copolymer, ethylene / acrylic acid alkyl ester copolymer, and ethylene / methacrylic acid alkyl ester copolymer. And an ethylene-nonconjugated diene copolymer.

  In the base material layer (A), the polyolefin-based resin may contain only one kind or two or more kinds. Examples of the form containing two or more types include blending and copolymerization.

  A commercially available product may be used as the polyolefin resin.

  The base material layer (A) can contain any appropriate additive as required. Examples of additives that can be contained in the base material layer (A) include ultraviolet absorbers, heat-resistant stabilizers, fillers, lubricants, colorants (dyes, etc.), antioxidants, anti-spot agents, and anti-blocking agents. , Foaming agents, polyethyleneimine and the like. The kind, number, and amount of the additive contained in the base material layer (A) can be appropriately set depending on the purpose.

  Examples of the ultraviolet absorber include benzotriazole compounds, benzophenone compounds, benzoate compounds, and the like. Any appropriate content can be adopted as the content of the ultraviolet absorber as long as it does not bleed out during molding. Typically, it is 0.01 to 5 weight% with respect to the thermoplastic resin in a base material layer (A).

  Examples of the heat resistance stabilizer include hindered amine compounds, phosphorus compounds, and cyanoacrylate compounds. Any appropriate content can be adopted as the content of the heat-resistant stabilizer as long as it does not bleed out during molding. Typically, it is 0.01 to 5 weight% with respect to the thermoplastic resin in a base material layer (A).

  Examples of the filler include inorganic fillers such as talc, titanium oxide, calcium oxide, magnesium oxide, zinc oxide, titanium oxide, calcium carbonate, silica, clay, mica, barium sulfate, whisker, and magnesium hydroxide. The average particle diameter of the filler is preferably 0.1 μm to 10 μm. The content of the filler is preferably 1 to 200% by weight with respect to the thermoplastic resin in the base material layer (A).

<< A-2. First pressure-sensitive adhesive layer (B1) >>
Arbitrary appropriate thickness can be employ | adopted for the thickness of a 1st adhesive layer (B1) according to a use. The thickness of the first pressure-sensitive adhesive layer (B1) is preferably 1 μm to 100 μm, more preferably 2 μm to 75 μm, still more preferably 3 μm to 50 μm.

  The first pressure-sensitive adhesive layer (B1) may be a single layer or a laminate of two or more layers. When a 1st adhesive layer (B1) is a laminated body of 2 or more layers, Preferably it is 2-5 layers, More preferably, it is 2-3 layers. When the first pressure-sensitive adhesive layer (B1) is only one layer, coextrusion molding at the time of producing the pressure-sensitive adhesive sheet can be facilitated. When the first pressure-sensitive adhesive layer (B1) is a laminate of two or more layers, the function can be divided by each layer. For example, when the first pressure-sensitive adhesive layer (B1) is a laminate of two layers, a layer having good adhesion to the base material layer is adopted as one first pressure-sensitive adhesive layer, and the first pressure-sensitive adhesive layer is the first pressure-sensitive adhesive layer. A layer having good adhesion to the two pressure-sensitive adhesive layers can be employed.

  The first pressure-sensitive adhesive layer (B1) includes at least one selected from α-olefin-based thermoplastic elastomers and styrene-based thermoplastic elastomers. Any appropriate α-olefin-based thermoplastic elastomer can be selected as the α-olefin-based thermoplastic elastomer. Any appropriate styrenic thermoplastic elastomer can be selected as the styrenic thermoplastic elastomer. The content ratio of at least one selected from α-olefin thermoplastic elastomer and styrene thermoplastic elastomer in the first pressure-sensitive adhesive layer (B1) is preferably 40 to 100% by weight, more preferably 50 to 50%. It is 100% by weight, more preferably 60 to 100% by weight.

  As the α-olefin-based thermoplastic elastomer, any appropriate α-olefin-based elastomer can be adopted as long as the film can be formed by melt extrusion. The α-olefin elastomer refers to an elastomer obtained using a monomer component containing at least one α-olefin. Such an α-olefin-based elastomer is preferably an amorphous propylene- (1-butene) copolymer. As used herein, “amorphous” refers to a property that does not have a clear melting point, such as crystalline. Only 1 type may be sufficient as an alpha olefin type thermoplastic elastomer, and 2 or more types may be sufficient as it.

  The amorphous propylene- (1-butene) copolymer can be preferably obtained by copolymerizing propylene and 1-butene using a metallocene catalyst. The amorphous propylene- (1-butene) copolymer obtained by copolymerization using a metallocene catalyst exhibits a narrow molecular weight distribution (for example, 2 or less). If an amorphous propylene- (1-butene) copolymer having such a narrow molecular weight distribution is used, bleeding of low molecular weight components can be prevented.

  The content ratio of the structural unit derived from propylene in the amorphous propylene- (1-butene) copolymer is preferably 80 to 99 mol%, more preferably 85 to 99 mol%, and still more preferably 90 to 99 mol%. 99 mol%. If the content ratio of the structural unit derived from propylene in the amorphous propylene- (1-butene) copolymer is in such a range, the first pressure-sensitive adhesive layer (B1) excellent in balance between toughness and flexibility is obtained. And the effects of the present invention can be expressed more effectively.

  The content ratio of the structural unit derived from 1-butene in the amorphous propylene- (1-butene) copolymer is preferably 1 to 15 mol%, more preferably 1 to 10 mol%. If the content ratio of the structural unit derived from 1-butene in the amorphous propylene- (1-butene) copolymer is in such a range, the first pressure-sensitive adhesive layer (B1) excellent in balance between toughness and flexibility ) And the effects of the present invention can be expressed more effectively.

  Any appropriate copolymer structure can be adopted as the copolymer structure of the amorphous propylene- (1-butene) copolymer. Examples of such a copolymer structure include a block copolymer and a random copolymer.

  The weight average molecular weight (Mw) of the amorphous propylene- (1-butene) copolymer is preferably 200000 or more, more preferably 200000-500000, and further preferably 200000-300000. When the weight average molecular weight (Mw) of the amorphous propylene- (1-butene) copolymer is in such a range, the first pressure-sensitive adhesive layer (B1) having an appropriate adhesive force can be obtained, The effects of the invention can be expressed more effectively.

  When the first pressure-sensitive adhesive layer (B1) contains an amorphous propylene- (1-butene) copolymer, the first pressure-sensitive adhesive layer (B1) is used to adjust the pressure-sensitive adhesive strength of the first pressure-sensitive adhesive layer (B1). ) May further contain a crystalline polypropylene resin. When the first pressure-sensitive adhesive layer (B1) contains a crystalline polypropylene resin, the pressure-sensitive adhesive force of the first pressure-sensitive adhesive layer (B1) can be appropriately reduced and the storage elastic modulus can be increased. When the first pressure-sensitive adhesive layer (B1) further contains a crystalline polypropylene resin, the content of the crystalline polypropylene resin in the first pressure-sensitive adhesive layer (B1) depends on the desired adhesive strength and storage elastic modulus. And can be set to any appropriate content ratio. The content ratio of such a crystalline polypropylene resin is preferably 0 to 50 weights with respect to the total weight of the amorphous propylene- (1-butene) copolymer and the crystalline polypropylene resin. %, More preferably 0 to 40% by weight, still more preferably 0 to 30% by weight.

  Any appropriate styrenic thermoplastic elastomer can be adopted as the styrenic thermoplastic elastomer as long as the film can be formed by melt extrusion. The styrenic thermoplastic elastomer refers to an elastomer obtained using a monomer component containing at least one styrene monomer. Only one type of styrene thermoplastic elastomer may be used, or two or more types may be used.

  Examples of the styrenic thermoplastic elastomer include styrene-based AB diblock copolymers such as styrene-ethylene-butylene copolymer (SEB); styrene-butadiene-styrene copolymer (SBS), and hydrogenated product of SBS. (Styrene-ethylene-butylene-styrene copolymer (SEBS)), styrene-isoprene-styrene copolymer (SIS), hydrogenated product of SIS (styrene-ethylene-propylene-styrene copolymer (SEPS)), styrene -Styrenic ABA type triblock copolymer such as isobutylene-styrene copolymer (SIBS); Styrene type ABAB type tetrablock copolymer such as styrene-butadiene-styrene-butadiene (SBSB); Styrene-butadiene-styrene- Butadiene-styrene (SBSBS), etc. Styrene ABABA-type pentablock copolymers; styrene multi-block copolymers having these more AB repeat units; styrenic block copolymer, and the like. Moreover, the hydrogenation thing which hydrogenated the ethylenic double bond of styrene random copolymers, such as a styrene-butadiene rubber (SBR), is also mentioned.

  The content of the styrene block structure in the styrenic block copolymer is preferably 5 to 40% by weight, more preferably 7 to 30% by weight, and further preferably 9 to 20% by weight. When the content of the styrene block structure is less than 5% by weight, adhesive residue due to insufficient cohesive force of the first pressure-sensitive adhesive layer (B1) is likely to occur. When there is more content rate of a styrene block structure than 40 weight%, there exists a possibility that a 1st adhesive layer (B1) may become hard and cannot acquire favorable adhesiveness with respect to a rough surface.

  When the styrenic block copolymer has an ethylene-butylene block structure, the content ratio of the structural unit derived from butylene in the ethylene-butylene block structure is preferably 50% by weight or more, more preferably 60% by weight or more, and still more preferably. Is 70% by weight or more, particularly preferably 70 to 90% by weight. When the content ratio of the structural unit derived from butylene is in such a range, the first pressure-sensitive adhesive layer (B1) that is excellent in wettability and adhesiveness and can adhere well to a rough surface can be obtained.

  The first pressure-sensitive adhesive layer (B1) can contain any appropriate other component as necessary. Other components include, for example, a tackifier; a softener; an anti-aging agent; an olefin resin; a silicone resin; a liquid acrylic copolymer; a polyethyleneimine; a fatty acid amide; a phosphate ester; and a hindered amine light stabilizer; UV absorbers; heat-resistant stabilizers; fillers or pigments such as calcium oxide, magnesium oxide, silica, zinc oxide, and titanium oxide; other additives; The kind, number, and amount of other components that can be contained in the first pressure-sensitive adhesive layer (B1) can be appropriately set depending on the purpose. The amount of the other component is preferably 5% by weight or less, more preferably 1% by weight or less, based on the entire first pressure-sensitive adhesive layer (B1).

  The tackifier is effective for improving the adhesive strength. Moreover, since the tackifier is compatible with both the first pressure-sensitive adhesive layer (B1) and the second pressure-sensitive adhesive layer (B2), it can function as a compatibilizing agent. When the first pressure-sensitive adhesive layer (B1) contains a tackifier, the content ratio of the tackifier in the first pressure-sensitive adhesive layer (B1) considers prevention of occurrence of adhesive residue due to a decrease in cohesive force, Any appropriate content ratio can be set. The content ratio of the tackifier in the first pressure-sensitive adhesive layer (B1) is preferably 1 to 60% by weight, more preferably 3 to 50% by weight with respect to the resin component of the first pressure-sensitive adhesive layer (B1). %, More preferably 4 to 45% by weight, and particularly preferably 5 to 40% by weight.

  Examples of tackifiers include hydrocarbon tackifiers, terpene tackifiers, rosin tackifiers, phenol tackifiers, epoxy tackifiers, polyamide tackifiers, and elastomer tackifiers. And ketone-based tackifiers. Only 1 type may be sufficient as the tackifier in a 1st adhesive layer (B1), and 2 or more types may be sufficient as it.

  Examples of the hydrocarbon tackifier include aliphatic hydrocarbon resins, aromatic hydrocarbon resins (for example, xylene resins), aliphatic cyclic hydrocarbon resins, aliphatic / aromatic petroleum resins (for example, Styrene-olefin copolymers, aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, coumarone-indene resins, and the like.

  Examples of the terpene tackifier include terpene resins such as α-pinene polymers and β-pinene polymers; modified terpenes obtained by modifying terpene resins (eg, phenol modification, aromatic modification, hydrogenation modification, etc.) Resin (for example, terpene-phenol resin, styrene-modified terpene resin, hydrogenated terpene resin, etc.);

  Examples of rosin-based tackifiers include unmodified rosins such as gum rosin and wood rosin (raw rosin); modified rosins modified by hydrogenation, disproportionation, polymerization, etc. (for example, hydrogenated rosin, non-modified rosin) Averaged rosin, polymerized rosin, other chemically modified rosins, etc.); other various rosin derivatives: and the like.

  Examples of the phenol tackifier include resol type or novolac type alkylphenols.

  The tackifier may be commercially available as a blend with an olefin resin or a thermoplastic elastomer.

  The softening agent is effective for improving the adhesive strength. When the first pressure-sensitive adhesive layer (B1) contains a softening agent, any appropriate amount can be adopted as the content ratio of the softening agent in the first pressure-sensitive adhesive layer (B1). If the content of the softening agent in the first pressure-sensitive adhesive layer (B1) becomes too large, the amount of adhesive residue at the time of high temperature or outdoor exposure tends to increase, so softening in the first pressure-sensitive adhesive layer (B1) The content ratio of the agent is preferably 40% by weight or less, more preferably 20% by weight or less, and still more preferably 10% by weight or less.

  Examples of the softening agent include low molecular weight diene polymers, polyisobutylene, hydrogenated polyisoprene, hydrogenated polybutadiene, and derivatives thereof. Examples of the derivative include those having an OH group or a COOH group at one or both ends. Specific examples include hydrogenated polybutadiene diol, hydrogenated polybutadiene monool, hydrogenated polyisoprene diol, and hydrogenated polyisoprene monool. In order to further suppress the improvement in adhesive strength, hydrogenated products of diene polymers such as hydrogenated polybutadiene and hydrogenated polyisoprene, olefinic softeners, and the like are preferable. Specific examples include “Kuraprene LIR-200” manufactured by Kuraray Co., Ltd. Only 1 type may be sufficient as the softener in a 1st adhesive layer (B1), and 2 or more types may be sufficient as it.

  The molecular weight of the softener can be set to any suitable amount. If the molecular weight of the softener becomes too small, it may cause contamination by bleeding from the first pressure-sensitive adhesive layer (B1). On the other hand, if the molecular weight of the softener becomes too large, the effect of improving the adhesive strength is poor. Therefore, the number average molecular weight of the softening agent is preferably 5,000 to 100,000, more preferably 10,000 to 50,000.

<< A-3. Second pressure-sensitive adhesive layer (B2) >>
The thickness of a 2nd adhesive layer (B2) can be set to arbitrary appropriate thickness according to a use. The thickness of the second pressure-sensitive adhesive layer (B2) is preferably 1 μm to 100 μm, more preferably 2 μm to 75 μm, and still more preferably 3 μm to 50 μm. The second pressure-sensitive adhesive layer (B2) may be protected by temporarily attaching a separator or the like until practical use, if necessary.

  Any appropriate pressure-sensitive adhesive can be adopted as the pressure-sensitive adhesive contained in the second pressure-sensitive adhesive layer (B2) as long as the effects of the present invention are not impaired. The pressure-sensitive adhesive constituting the second pressure-sensitive adhesive layer (B2) may be only one type or two or more types.

  The pressure-sensitive adhesive contained in the second pressure-sensitive adhesive layer (B2) is preferably an acrylic type containing an acrylate block structure (referred to as “Ac block”) and a methacrylate block structure (referred to as “MAc block”). A block copolymer is mentioned. More preferably, the second pressure-sensitive adhesive layer (B2) contains 50% by weight or more of such an acrylic block copolymer, more preferably 70% by weight or more, and particularly preferably 90% by weight or more. The second pressure-sensitive adhesive layer (B2) may contain only one kind of such an acrylic block copolymer, or may contain two or more kinds.

  The acrylic block copolymer preferably has a block structure in which Ac blocks and MAc blocks are alternately arranged. Further, the total number of blocks of the Ac block and the MAc block is preferably 3 or more, and more preferably 3 to 5.

  The Ac block preferably has a block structure derived from a monomer mainly composed of an acrylate ester. Specifically, the content of the acrylate ester in the monomer for constituting the Ac block is preferably 50% by weight or more, more preferably 70% by weight or more, still more preferably 90% by weight or more, Particularly preferred is 95% by weight or more, and most preferred is substantially 100% by weight.

  The acrylic ester in the monomer for constituting the Ac block may be only one kind or two or more kinds.

  When the monomer for constituting the Ac block includes a monomer (another monomer) other than the acrylate ester, any appropriate monomer can be adopted as the other monomer.

  Examples of the acrylic acid ester in the monomer for constituting the Ac block include an aliphatic hydrocarbon ester of acrylic acid, an alicyclic hydrocarbon ester of acrylic acid, an aromatic hydrocarbon ester of acrylic acid, and an ether bond. Examples include esters of alcohol and acrylic acid, acrylic esters having a hydroxyl group, acrylic esters having an amino group, acrylic esters having an alkoxysilyl group, and alkylene oxide adducts of acrylic acid.

  Examples of the aliphatic hydrocarbon ester of acrylic acid include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, Examples thereof include n-heptyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, isononyl acrylate, decyl acrylate, dodecyl acrylate, stearyl acrylate and the like.

  Examples of the alicyclic hydrocarbon ester of acrylic acid include cyclohexyl acrylate and isobornyl acrylate.

  Examples of the aromatic hydrocarbon ester of acrylic acid include phenyl acrylate, benzyl acrylate, toluyl acrylate, and the like.

  Examples of the ester of an alcohol containing an ether bond and acrylic acid include alkoxyalkyl acrylates such as 2-methoxyethyl acrylate and 2-methoxybutyl acrylate; epoxy group-containing acrylates such as glycidyl acrylate and methyl glycidyl acrylate; .

  Examples of the acrylic acid ester having a hydroxyl group include hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, and 4-hydroxybutyl acrylate.

  Examples of the acrylic acid ester having an amino group include 2-aminoethyl acrylate, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminopropyl acrylate, and the like.

  Examples of the acrylic acid ester having an alkoxysilyl group include 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, 3-acryloxypropylmethyldimethoxysilane, and 3-acryloxypropylmethyldiethoxysilane. Is mentioned.

Examples of the alkylene oxide adduct of acrylic acid include an ethylene oxide adduct represented by CH ₂ ═CHCOO (CH ₂ CH ₂ O) _n H (n is, for example, 1 to 10).

  The acrylic ester in the monomer for constituting the Ac block is preferably an aliphatic hydrocarbon ester of acrylic acid. The acrylic ester in the monomer for constituting the Ac block is more preferably an alkyl acrylate having an alkyl group having 1 to 20 carbon atoms, and still more preferably having 1 to 14 carbon atoms. Acrylic acid alkyl ester having an alkyl group. As the acrylic acid ester in the monomer for constituting the Ac block, methyl acrylate, n-butyl acrylate, tert-butyl acrylate, and 2-ethylhexyl acrylate are particularly preferable.

  The MAc block is preferably a block structure derived from a monomer mainly composed of a methacrylic ester. Specifically, the content of the methacrylic acid ester in the monomer for constituting the MAc block is preferably 50% by weight or more, more preferably 70% by weight or more, still more preferably 90% by weight or more, Particularly preferred is 95% by weight or more, and most preferred is substantially 100% by weight.

  The methacrylic acid ester in the monomer for constituting the MAc block may be only one kind or two or more kinds.

  When the monomer for constituting the MAc block contains a monomer other than the methacrylic acid ester (other monomer), any appropriate monomer can be adopted as the other monomer.

  Examples of the methacrylic acid ester in the monomer constituting the MAc block include, for example, an aliphatic hydrocarbon ester of methacrylic acid, an alicyclic hydrocarbon ester of methacrylic acid, an aromatic hydrocarbon ester of methacrylic acid, and an ether bond. Examples include esters of alcohol and methacrylic acid, methacrylates having a hydroxyl group, methacrylates having an amino group, methacrylates having an alkoxysilyl group, and alkylene oxide adducts of methacrylic acid.

  Examples of the aliphatic hydrocarbon ester of methacrylic acid include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, There may be mentioned n-heptyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, isononyl methacrylate, decyl methacrylate, dodecyl methacrylate, stearyl methacrylate and the like.

  Examples of alicyclic hydrocarbon esters of methacrylic acid include cyclohexyl methacrylate and isobornyl methacrylate.

  Examples of the aromatic hydrocarbon ester of methacrylic acid include phenyl methacrylate, benzyl methacrylate, toluyl methacrylate and the like.

  Examples of the ester of alcohol containing an ether bond and methacrylic acid include alkoxyalkyl methacrylates such as 2-methoxyethyl methacrylate and 2-methoxybutyl methacrylate; epoxy group-containing methacrylates such as glycidyl methacrylate and methyl glycidyl methacrylate; .

  Examples of the methacrylic acid ester having a hydroxyl group include hydroxyalkyl methacrylates such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, and 4-hydroxybutyl methacrylate.

  Examples of the methacrylic acid ester having an amino group include 2-aminoethyl methacrylate, N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminopropyl methacrylate and the like.

  Examples of the methacrylic acid ester having an alkoxysilyl group include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, and 3-methacryloxypropylmethyldiethoxysilane. Is mentioned.

Examples of the alkylene oxide adduct of methacrylic acid include an ethylene oxide adduct represented by CH ₂ ═C (CH ₃ ) COO (CH ₂ CH ₂ O) _n H (n is, for example, 1 to 10). Can be mentioned.

  The methacrylic acid ester in the monomer for constituting the MAc block is preferably an aliphatic hydrocarbon ester of methacrylic acid. The methacrylic acid ester in the monomer for constituting the MAc block is more preferably a methacrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms, more preferably 1 to 14 carbon atoms. It is a methacrylic acid alkyl ester having an alkyl group. As the methacrylic acid ester in the monomer for constituting the MAc block, methyl methacrylate and ethyl methacrylate are particularly preferable.

  As an acrylic block copolymer, the Ac block and the MAc block are composed of a polymer having a hard structure excellent in cohesion and elasticity such as AB type, ABA type, ABAB type, and ABABA type. The segment) and the B block (soft segment) made of a polymer having a soft structure excellent in viscosity preferably have a block structure in which they are alternately arranged. The second pressure-sensitive adhesive layer (B2) containing the acrylic block copolymer having such a structure as a main component can be a pressure-sensitive adhesive layer in which cohesive force, elasticity and viscosity are highly compatible. Moreover, the 2nd adhesive layer (B2) which contains the acrylic block copolymer of such a structure as a main component can become the thing excellent in extrusion moldability. The acrylic block copolymer preferably has a block structure (ABA type, ABABA type, etc.) in which A blocks (hard segments) are arranged at both ends of the molecule. The acrylic block copolymer having such a block structure can be excellent in balance between cohesiveness and thermoplasticity.

  When the acrylic block copolymer has two or more A blocks (hard segments), the monomer composition, molecular weight (degree of polymerization), structure, etc. of these A blocks may be the same or different from each other. Also good.

  When the acrylic block copolymer has two or more B blocks (soft segments), the monomer composition, molecular weight (degree of polymerization), structure, etc. of these B blocks may be the same or different from each other. Also good.

  As the A block (hard segment), a MAc block can be preferably used.

  As the B block (soft segment), an Ac block can be preferably used.

  A preferred form of the block structure of the acrylic block copolymer is, for example, a triblock structure of MAc block / Ac block / MAc block (ABA type) structure. A more preferable form of the block structure of the acrylic block copolymer is one in which the two MAc blocks have a structure derived from substantially the same monomer in the above triblock structure.

  The ratio of Ac block to MAc block contained in the acrylic block copolymer is a weight ratio, and the weight ratio of Ac block / MAc block is preferably 96/4 to 10/90, more preferably 93 / It is 7-20 / 80, More preferably, it is 90 / 10-30 / 70, Most preferably, it is 80 / 20-50 / 50. If the proportion of the Ac block is too large, the cohesive force and elasticity may be insufficient. If the proportion of the MAc block is too large, the adhesive strength may be insufficient.

  The weight average molecular weight of the acrylic block copolymer is preferably 30000 to 300000, more preferably 35000 to 250,000, still more preferably 40000 to 200000, and particularly preferably 50000 to 150,000. When the weight average molecular weight of the acrylic block copolymer is less than 30000, there is a possibility that the adhesive properties and cohesiveness are likely to be lowered. If the weight average molecular weight of the acrylic block copolymer exceeds 300,000, the acrylic block copolymer may have insufficient thermoplasticity, and it may be difficult to form the second pressure-sensitive adhesive layer (B2) by coextrusion molding. There is.

  The weight average molecular weight of the acrylic block copolymer can be determined by performing gel permeation chromatography (GPC) measurement on a sample prepared by dissolving the acrylic block copolymer in an appropriate solvent such as tetrahydrofuran. The value in terms of polystyrene. Specifically, the weight average molecular weight of the acrylic block copolymer can be determined by performing GPC measurement under the conditions described in the examples described later.

  The glass transition temperature (Tg) of the Ac block is preferably −80 to −10 ° C., more preferably −75 to −20 ° C., and further preferably −75 to −50 ° C.

  The glass transition temperature (Tg) of the MAc block is preferably 40 to 240 ° C, more preferably 60 to 230 ° C, and further preferably 80 to 230 ° C.

  Here, the glass transition temperature (Tg) of the Ac block or the MAc block is the fox based on the Tg of the homopolymer of each monomer constituting the block and the content ratio (weight fraction) of the monomer. A value obtained from the formula (FOX). As the Tg of the homopolymer, for example, the values described in “Adhesion Technology Handbook” of Nikkan Kogyo Shimbun and “Polymer Handbook” of Wiley-Interscience can be adopted. For example, Tg of 2-ethylhexyl acrylate can be -70 ° C, Tg of n-butyl acrylate can be -54 ° C, and Tg of methyl methacrylate can be 105 ° C.

  Arbitrary appropriate other monomers other than acrylic acid ester and methacrylic acid ester may be copolymerized with the acrylic block copolymer. Examples of such other monomers include cyano group-containing vinyl compounds such as acrylonitrile and methacrylonitrile; vinyl esters such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene and α-methylstyrene; N— Vinyl group-containing heterocyclic compounds such as vinyl pyrrolidone; Amide group-containing vinyl compounds such as acrylamide and methacrylamide; Unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid or salts thereof (sodium salt, potassium salt, etc.); maleic acid, Unsaturated dicarboxylic acids such as fumaric acid or salts thereof (sodium salt, potassium salt, etc.); unsaturated dicarboxylic acid anhydrides such as maleic anhydride; methyl 2- (trifluoromethyl) (meth) acrylate, methyl 2- (par Fluoroethyl) (meth) acrylate, ethyl 2- (trifluoromethyl) (meth) acrylate, ethyl 2- (perfluoroethyl) (meth) acrylate, ethyl 2- (perfluorohexyl) (meth) acrylate, ethyl 2- (perfluorodecyl) (meth) acrylate And fluorinated alkyl (meth) acrylates such as ethyl 2- (perfluorohexadecyl) (meth) acrylate and ethyl 2- (perfluorobutyl) (meth) acrylate. Such other monomers may be only one kind or two or more kinds.

  Other monomers may be included, for example, to adjust the characteristics (such as adhesive characteristics and extrusion moldability) of the second pressure-sensitive adhesive layer (B2). Other structural parts derived from monomers can be introduced into the Ac block or MAc block in the form of a random copolymer, block copolymer, graft copolymer or the like.

  In the monomer for constituting the acrylic block copolymer, the content of other monomers is preferably 20% by weight or less, more preferably 10% by weight in the monomer for constituting the acrylic block copolymer. % Or less, more preferably 5% by weight or less, and particularly preferably substantially 0% by weight. In the monomer for constituting the acrylic block copolymer, if the content of the other monomer is too large, the transparency of the second pressure-sensitive adhesive layer (B2) may be impaired.

  In particular, the acrylic block copolymer preferably does not substantially contain an acid group-containing monomer as another monomer in the monomer constituting the acrylic block copolymer. The second pressure-sensitive adhesive layer (B2) containing such an acrylic block copolymer can have a lower property of corroding the adherend. For example, in a pressure-sensitive adhesive sheet for use in bonding an adherend having a transparent electrode such as ITO (Indium Tin Oxide) (for example, a component of a touch panel), the adherend corrosivity of the pressure-sensitive adhesive layer is low. Especially preferred. In addition, an acrylic block copolymer composed of a monomer that does not substantially contain an acidic group-containing monomer as a monomer is preferable in that it can avoid the melt viscosity of the pressure-sensitive adhesive layer from becoming too high.

  The acrylic block copolymer can be produced by any appropriate method. As a manufacturing method of an acryl-type block copolymer, the manufacturing method using a living polymerization method etc. are mentioned, for example. According to the living polymerization method, the acrylic block copolymer has excellent thermoplasticity and good extrudability by maintaining the original transparency and weather resistance of the acrylic block copolymer, and by excellent structural control unique to the living polymerization method. Copolymers can be produced. In addition, the living polymerization method can control the molecular weight distribution of the acrylic block copolymer narrowly, thereby suppressing a decrease in cohesiveness due to the presence of low molecular weight components (for example, adhesive residue at the time of peeling). Thus, a pressure-sensitive adhesive sheet having excellent peelability can be provided.

  The acrylic block copolymer can also be obtained as a commercial product. Examples of the acrylic block copolymer available as a commercial product include a trade name “LA polymer” series (for example, LA2140e, LA2250, etc.) manufactured by Kuraray Co., Ltd.

  The second pressure-sensitive adhesive layer (B2) can contain an optional component other than the acrylic block copolymer for the purpose of controlling the adhesive properties. Examples of such an optional component include polymers other than acrylic block copolymers and called oligomers (having a weight average molecular weight of, for example, 500 to 5000). Examples of such oligomers include random copolymers of monomers mainly composed of acrylic monomers (such as acrylic acid esters and methacrylic acid esters), and have no block structure, olefinic resins, silicones. System polymers and the like. Moreover, in order not to impair the transparency of a 2nd adhesive layer (B2), it is preferable to select the polymer excellent in compatibility with an acryl-type block copolymer for such arbitrary components. There may be only one optional component, or two or more optional components.

  The content of the optional component is preferably 50 parts by weight or less, more preferably 10 parts by weight or less, still more preferably 5 parts by weight or less, with respect to 100 parts by weight of the acrylic block copolymer. Preferably it is substantially 0 part by weight.

  The second pressure-sensitive adhesive layer (B2) can contain any appropriate other component as necessary. Examples of other components include tackifiers, fillers, colorants (dyes, etc.), antioxidants, metal chelate compounds, cross-linking agents (eg, polyfunctional isocyanates, polyfunctional amines, polyfunctional alcohols, etc.) Is mentioned. The kind, number, and amount of other components that can be contained in the second pressure-sensitive adhesive layer (B2) can be appropriately set depending on the purpose. From the viewpoint of taking advantage of the transparency of the acrylic block copolymer, the amount of other components is preferably 5% by weight or less, more preferably 1% by weight based on the entire second pressure-sensitive adhesive layer (B2). % Or less.

  The tackifier is effective for improving the adhesive strength. Moreover, since the tackifier is compatible with both the first pressure-sensitive adhesive layer (B1) and the second pressure-sensitive adhesive layer (B2), it can function as a compatibilizing agent. When the second pressure-sensitive adhesive layer (B2) contains a tackifier, the content ratio of the tackifier in the second pressure-sensitive adhesive layer (B2) takes into consideration prevention of occurrence of adhesive residue due to a decrease in cohesive force, Any appropriate content ratio can be set. The content ratio of the tackifier in the second pressure-sensitive adhesive layer (B2) is preferably 1 to 60% by weight, more preferably 3 to 50% by weight with respect to the resin component of the second pressure-sensitive adhesive layer (B2). %, More preferably 4 to 45% by weight, and particularly preferably 5 to 40% by weight.

  Examples of tackifiers include hydrocarbon tackifiers, terpene tackifiers, rosin tackifiers, phenol tackifiers, epoxy tackifiers, polyamide tackifiers, and elastomer tackifiers. And ketone-based tackifiers. Only 1 type may be sufficient as the tackifier in a 1st adhesive layer (B1), and 2 or more types may be sufficient as it.

  Examples of the hydrocarbon tackifier include aliphatic hydrocarbon resins, aromatic hydrocarbon resins (for example, xylene resins), aliphatic cyclic hydrocarbon resins, aliphatic / aromatic petroleum resins (for example, Styrene-olefin copolymers, aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, coumarone-indene resins, and the like.

  Examples of the terpene tackifier include terpene resins such as α-pinene polymers and β-pinene polymers; modified terpenes obtained by modifying terpene resins (eg, phenol modification, aromatic modification, hydrogenation modification, etc.) Resin (for example, terpene-phenol resin, styrene-modified terpene resin, hydrogenated terpene resin, etc.);

  Examples of rosin-based tackifiers include unmodified rosins such as gum rosin and wood rosin (raw rosin); modified rosins modified by hydrogenation, disproportionation, polymerization, etc. (for example, hydrogenated rosin, non-modified rosin) Averaged rosin, polymerized rosin, other chemically modified rosins, etc.); other various rosin derivatives: and the like.

  Examples of the phenol tackifier include resol type or novolac type alkylphenols.

  The tackifier may be commercially available as a blend with an olefin resin or a thermoplastic elastomer.

  Examples of the filler include inorganic fillers such as talc, titanium oxide, calcium oxide, magnesium oxide, zinc oxide, titanium oxide, calcium carbonate, silica, clay, mica, barium sulfate, whisker, and magnesium hydroxide. The average particle diameter of the filler is preferably 0.1 μm to 10 μm.

≪≪B. Manufacturing method of adhesive sheet >>>>
The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet that is a laminate including a laminated structure of a base material layer (A) / first pressure-sensitive adhesive layer (B1) / second pressure-sensitive adhesive layer (B2), and the base material layer A forming material for the laminate comprising the forming material (a) of (A), the forming material (b1) of the first pressure-sensitive adhesive layer (B1), and the forming material (b2) of the second pressure-sensitive adhesive layer (B2). It is obtained by coextrusion molding and integration.

  The method of coextrusion molding can be performed according to an inflation method, a T-die method, or the like, using an extruder and a co-extrusion die for each layer forming material. By this coextrusion molding, the layers derived from the respective forming materials are integrated into a laminate.

  In the manufacturing method of the adhesive sheet of this invention, you may irradiate ionizing radiation to the laminated body obtained by integrating by said coextrusion molding. Specifically, for example, the obtained laminate may be irradiated with ionizing radiation before being wound in a roll shape or in a state of being rewound again after being wound in a roll shape. Irradiation with ionizing radiation is preferably performed in an inert gas atmosphere such as nitrogen. Examples of the ionizing radiation include X-rays, γ-rays, ultraviolet rays, visible rays, and electron beams. An electron beam is preferable as the ionizing radiation because of the high generation rate of the reactive species upon irradiation and the deep penetration of the irradiation target. As the electron beam source, various electron beam accelerators such as a Cockloft Walton type, a bandegraft type, a resonant transformer type, an insulating core transformer type, a linear type, a dynamitron type, and a high frequency type can be used. The ionizing radiation may be irradiated from one side of the laminate or from both sides. In terms of simplification of the process, the ionizing radiation is preferably irradiated by ionizing radiation by guiding the laminate to an ionizing radiation irradiating apparatus before winding it into a roll. The irradiation dose of ionizing radiation is preferably 10 to 500 kGy, more preferably 10 to 400 kGy, and still more preferably 10 to 300 kGy, from the viewpoint of improving interlayer adhesion and maintaining the physical properties of the pressure-sensitive adhesive sheet. The acceleration voltage of the ionizing radiation can be appropriately selected according to the type of resin used for the adhesive sheet and the thickness of the adhesive sheet. The acceleration voltage of ionizing radiation is usually preferably in the range of 50 to 300 kV. The ionizing radiation may be irradiated once or a plurality of times (preferably twice).

  The pressure-sensitive adhesive sheet of the present invention can be appropriately stretched uniaxially in the longitudinal direction (extrusion direction) or in the width direction (direction orthogonal to the extrusion direction) or biaxially in the longitudinal direction and the width direction. The stretching ratio in the longitudinal direction when stretching is, for example, preferably 1.01 to 10 times, more preferably 1.01 to 5 times, and further preferably 1.01 to 3 times. The draw ratio in the width direction is, for example, preferably 1.01 to 8 times, more preferably 1.01 to 4 times, and still more preferably 1.01 to 2.5 times. Stretching may be performed in one stage per axis, or may be performed in two or more stages depending on the intended use of the pressure-sensitive adhesive sheet. The stretching temperature at the time of stretching is preferably in the range of (Tg−20 ° C.) to (Tg + 50 ° C.) with respect to the glass transition temperature (Tg) of the polymer constituting the base layer (A) from the viewpoint of stretchability and the like. .

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples at all. In addition, the test and evaluation method in an Example etc. are as follows. Moreover, a part means a weight part.

(1) Measurement of weight average molecular weight GPC measurement was performed under the following conditions.
Measuring device: Model “HLC-8120GPC” manufactured by Tosoh Corporation
Column: TSKgel SuperHZM-H / HZ4000 + HZ3000 + HZ2000 manufactured by Tosoh Corporation was used in series.
Column size: each 6.0 mm inner diameter x 15.0 cm length
Column temperature: 40 ° C
Flow rate: 0.6 mL / min Eluent: Tetrahydrofuran Sample injection volume: 20 μL
Detector: RI (differential refractometer)
Standard sample: Polystyrene

(2) Measurement of peeling force An acrylic pressure-sensitive adhesive sheet (manufactured by Nitto Denko Corporation, trade name “No. 31B”) is attached to the pressure-sensitive adhesive layer side of the pressure-sensitive adhesive sheet, and then a strip test having a length of 100 mm and a width of 20 mm. A piece was cut out. After the test piece is lined on a SUS plate, when the adhesive layer of the pressure-sensitive adhesive sheet is from the end of the test piece to the position of 30 mm in the longitudinal direction or when the base material adhesion is good and it is difficult to peel off the pressure-sensitive adhesive layer In addition, only the acrylic pressure-sensitive adhesive sheet (No. 31B) was peeled (the peel interface when the pressure-sensitive adhesive layer was peeled off was the base layer (A) / first pressure-sensitive adhesive layer (B1) layer, or 1 adhesive layer (B1) / second adhesive layer (B2), and when the adhesive layer cannot be peeled, the peeling interface is the second adhesive layer (B2) / acrylic adhesive sheet (No. 31B) Between the layers). The partially peeled test piece was gripped with a chuck of a tensile tester, peeled in the direction of 180 ° at a pulling speed of 300 mm / min, and the peeling force required for the peeling was measured. If the measured peel force is, for example, 2.0 N / 20 mm or more, the peel force when peeling the adhesive layer laminated adjacently from the base material layer is 2.0 N / 20 mm or more, And the peeling force at the time of peeling several adjacent adhesive layers is 2.0 N / 20mm or more.

(3) Measurement of adhesive strength A strip-shaped test piece having a length of 100 mm and a width of 20 mm was cut out from the adhesive sheet, and the adhesive strength was measured according to JIS-Z-0237 (2000). Specifically, a SUS430BA plate was used as the adherend, and the surface was washed with toluene. The pressure-sensitive adhesive layer surface of the test piece is bonded to the surface of the adherend by reciprocating a 2 kg roller once, and after 30 minutes, the test piece is peeled in the direction of 180 ° at a pulling speed of 300 mm / min to measure the adhesive force. did.

[Production Example 1]
<Manufacture of acrylic block copolymer Ac1>
After replacing the inside of a 2 L (liter) reaction vessel equipped with a nitrogen introduction tube, a thermometer, and a stirrer with nitrogen gas, 800 mL of toluene, N, N, N ′, N ″, N ″ -pentamethyldiethylenetriamine 2.5 mL, 34 mL of 0.6 mol / L toluene solution of isobutylbis (2,6-di-t-butyl-4-methylphenoxy) aluminum, and 3.5 mL of 1.3 mol / L toluene solution of sec-butyllithium Was charged. To this, 27 mL of methyl methacrylate (MMA) was added and reacted at room temperature for 3 hours. Next, the reaction solution was cooled to −15 ° C., and 160 mL of n-butyl acrylate (BA) was added dropwise over 7 hours. Subsequently, 27 mL of MMA was added, and the reaction solution was returned to room temperature and stirred for 10 hours. The reaction solution was poured into a large amount of methanol, and the deposited precipitate was recovered to obtain an acrylic block copolymer having a triblock structure of polyMMA-polyBA-polyMMA. Mw (weight average molecular weight) of the obtained acrylic block copolymer is 8.0 × 10 ⁴ , and the mass ratio of the polyMMA block (total mass of the two blocks) to the polyBA block is 25/75. there were. Hereinafter, this acrylic block copolymer is referred to as “Ac1”.

[Production Example 2]
<Manufacture of acrylic block copolymer Ac2>
After replacing the inside of a reaction vessel having a capacity of 2 L equipped with a nitrogen introduction tube, a thermometer, and a stirrer with nitrogen gas, 800 mL of toluene, 2.5 mL of N, N, N ′, N ″, N ″ -pentamethyldiethylenetriamine , 34 mL of a 0.6 mol / L toluene solution of isobutylbis (2,6-di-t-butyl-4-methylphenoxy) aluminum and 3.5 mL of a 1.3 mol / L toluene solution of sec-butyllithium were charged. . MMA27mL was added here and it was made to react at room temperature for 3 hours. Next, the reaction solution was cooled to −15 ° C., and 225 mL of 2-ethylhexyl acrylate (2EHA) was added dropwise over 7 hours. Subsequently, 27 mL of MMA was added, and the reaction solution was returned to room temperature and stirred for 10 hours. This reaction solution was poured into a large amount of methanol, and the deposited precipitate was recovered to obtain an acrylic block copolymer having a triblock structure of polyMMA-poly2EHA-polyMMA. Mw of the obtained acrylic block copolymer was 8.5 × 10 ⁴ , and the mass ratio of the polyMMA block (total mass of two blocks) to the poly-2EHA block was 25/75. Hereinafter, this acrylic block copolymer is referred to as “Ac2”.

[Example 1]
Low density polyethylene (LDPE) (trade name “Petrocene 190” manufactured by Tosoh Corporation) as a base material layer forming material and α-olefin-based pressure sensitive adhesive (AO) as a first pressure sensitive adhesive layer forming material (Sumitomo Chemical Co., Ltd.) Manufactured, trade name “Tufselen H5002”) and acrylic block copolymer as a second pressure-sensitive adhesive layer forming material (trade name “LA polymer LA2140e”, Mw = 8.0 × 10 ⁴ ) (hereinafter referred to as “Kuraray”) The acrylic block copolymer is referred to as “Ac3”) into an extruder, and melt extrusion is performed from a T die to obtain a base material layer (thickness 50 μm) / first pressure-sensitive adhesive layer (thickness 10 μm) / After forming into the sheet | seat shape with which the 2nd adhesive layer (10 micrometers in thickness) overlapped, it wound up in roll shape and obtained the adhesive sheet (1).
The evaluation results for the pressure-sensitive adhesive sheet (1) are shown in Table 1.

[Example 2]
The pressure-sensitive adhesive sheet (2) was obtained in the same manner as in Example 1 except that Ac1 (acrylic block copolymer having a polyMMA-polyBA-polyMMA triblock structure) was used as the second pressure-sensitive adhesive layer forming material. Obtained.
The evaluation results for the pressure-sensitive adhesive sheet (2) are shown in Table 1.

Example 3
A pressure-sensitive adhesive sheet (3) was prepared in the same manner as in Example 1 except that Ac2 (acrylic block copolymer having a triblock structure of polyMMA-poly2EHA-polyMMA) was used as the second pressure-sensitive adhesive layer forming material. Obtained.
The evaluation results for the pressure-sensitive adhesive sheet (3) are shown in Table 1.

Example 4
A pressure-sensitive adhesive sheet (4) was obtained in the same manner as in Example 1 except that polystyrene-polyisobutylene-polystyrene block copolymer (SIBS) (trade name “SIBSTAR 072T”) manufactured by Kaneka Corporation was used as the first pressure-sensitive adhesive layer forming material. )
The evaluation results for the pressure-sensitive adhesive sheet (4) are shown in Table 1.

Example 5
As a first pressure-sensitive adhesive layer forming material, 100 parts by weight of styrene-ethylene-butylene-styrene block copolymer (SEBS) (manufactured by JSR, trade name “Dynalon 8600P”), and a terpene-phenol copolymer weight which is a tackifier A pressure-sensitive adhesive sheet (5) was obtained in the same manner as in Example 1 except that a mixture (hereinafter referred to as SEBS (20)) with 20 parts by weight (trade name “YS Polystar TH130” manufactured by Yasuhara Chemical Co., Ltd.) was used.
The evaluation results for the pressure-sensitive adhesive sheet (5) are shown in Table 1.

Example 6
As the first pressure-sensitive adhesive layer forming material, 100 parts by weight of SEBS (manufactured by JSR, trade name “Dynalon 8600P”) and a terpene-phenol copolymer as a tackifier (trade name “YS Polystar TH130”, manufactured by Yashara Chemical Co., Ltd.) ) A pressure-sensitive adhesive sheet (6) was obtained in the same manner as in Example 1 except that a mixture with 38 parts by weight (hereinafter referred to as SEBS (38)) was used.
The evaluation results for the pressure-sensitive adhesive sheet (6) are shown in Table 1.

Example 7
As a second pressure-sensitive adhesive layer forming material, a mixture of 100 parts by weight of Ac3 and 38 parts by weight of a terpene-phenol copolymer (manufactured by Yasuhara Chemical Co., Ltd., trade name “YS Polyster TH130”) as a tackifier (hereinafter referred to as AC3). A pressure-sensitive adhesive sheet (7) was obtained in the same manner as in Example 1 except that (38)) was used.
The evaluation results for the pressure-sensitive adhesive sheet (7) are shown in Table 1.

Example 8
A pressure-sensitive adhesive sheet (8) was obtained in the same manner as in Example 1 except that SEBS (38) was used as the first pressure-sensitive adhesive layer forming material and AC3 (38) was used as the second pressure-sensitive adhesive layer forming material.
The evaluation results for the pressure-sensitive adhesive sheet (8) are shown in Table 1.

[Comparative Example 1]
A pressure-sensitive adhesive sheet (C1) was obtained in the same manner as in Example 1 except that LDPE (trade name “Petrocene 190” manufactured by Tosoh Corporation) was used instead of the first pressure-sensitive adhesive layer-forming material. .
The evaluation results for the pressure-sensitive adhesive sheet (C1) are shown in Table 2.

[Comparative Example 2]
In the same manner as in Example 1, except that high-density polyethylene (HDPE) (manufactured by Nippon Polyethylene Co., Ltd., trade name “NOVATEC HJ580”) was used as the intermediate layer forming material instead of the first adhesive layer forming material, C2) was obtained.
The evaluation results for the pressure-sensitive adhesive sheet (C2) are shown in Table 2.

[Comparative Example 3]
In the same manner as in Example 1, except that random-type polypropylene (r-PP) (manufactured by Sumitomo Chemical Co., Ltd., trade name “Nobrene S131”) was used as the intermediate layer forming material instead of the first pressure sensitive adhesive layer forming material, A sheet (C3) was obtained.
The evaluation results for the pressure-sensitive adhesive sheet (C3) are shown in Table 2.

[Comparative Example 4]
Example 1 was used except that an ethylene-vinyl acetate copolymer (EVA) (trade name “Ultrasen 752”, manufactured by Tosoh Corporation) was used as an intermediate layer forming material instead of the first adhesive layer forming material. The pressure-sensitive adhesive sheet (C4) was obtained.
The evaluation results for the pressure-sensitive adhesive sheet (C4) are shown in Table 2.

[Comparative Example 5]
Example 1 was used except that an ethylene-methyl methacrylate copolymer (EMMA) (manufactured by Sumitomo Chemical Co., Ltd., trade name “ACRIFTH WH302”) was used as an intermediate layer forming material instead of the first adhesive layer forming material. The pressure-sensitive adhesive sheet (C5) was obtained.
The evaluation results for the pressure-sensitive adhesive sheet (C5) are shown in Table 2.

[Comparative Example 6]
Example except that acrylic random copolymer (copolymer having 95% by weight of BA and 5% by weight of acrylic acid (AA) as a constituent monomer (weight average molecular weight: 500,000)) was used as the second pressure-sensitive adhesive layer forming material. In the same manner as in Example 1, an attempt was made to form a sheet shape in which the base material layer / first pressure-sensitive adhesive layer / second pressure-sensitive adhesive layer overlapped, but the second pressure-sensitive adhesive layer forming material does not plasticize even when heated. The pressure-sensitive adhesive sheet could not be obtained because it could not be discharged from the extruder.

[Comparative Example 7]
As a second pressure-sensitive adhesive layer forming material, a cross-linked acrylic random copolymer (a copolymer containing 95% by weight of BA and 5% by weight of AA (weight average molecular weight: 500,000)) is used as an isocyanate cross-linking agent (manufactured by Nippon Polyurethane Co., Ltd.). , Trade name “Coronate L”) A sheet in which the base material layer / first pressure-sensitive adhesive layer / second pressure-sensitive adhesive layer overlapped in the same manner as in Example 1 except that 2% by weight of the crosslinked pressure-sensitive adhesive was used. An attempt was made to form the shape, but the second pressure-sensitive adhesive layer-forming material was not plasticized even when heated, so that it could not be discharged from the extruder and a pressure-sensitive adhesive sheet could not be obtained.

  As shown in Examples 1 to 8 in Table 1, it can be confirmed that the pressure-sensitive adhesive sheet of the present invention can express good interlayer adhesion and can express good adhesive force.

  The pressure-sensitive adhesive sheet obtained in the present invention is preferably used in an optical member that requires visibility. Moreover, it is suitable for the bonding use of optical components, such as a polarizing plate for liquid crystal display panels, a wavelength plate, a phase difference plate, an optical compensation film, a brightness enhancement film, a light diffusion sheet, and a reflection sheet. In particular, the pressure-sensitive adhesive sheet obtained in the present invention preferably exhibits high adhesive force due to electrostatic action on an acrylic adherend, and is therefore suitable for use in bonding optical parts using acrylic resin. It is. Moreover, since the adhesive sheet obtained by this invention preferably shows low adhesive force with respect to nonpolar resins, such as an olefin, it is suitable for the surface protection use as which light peeling is calculated | required.

100 pressure-sensitive adhesive sheet 1 base material layer 21 first pressure-sensitive adhesive layer 22 second pressure-sensitive adhesive layer

Claims (4)

A pressure-sensitive adhesive sheet consisting of at least three layers having a base material layer (A), a first pressure-sensitive adhesive layer (B1) and a second pressure-sensitive adhesive layer (B2) in this order,
The base material layer (A) contains a thermoplastic resin,
The first pressure-sensitive adhesive layer (B1) includes at least one selected from α-olefin-based thermoplastic elastomers and styrene-based thermoplastic elastomers,
The second pressure-sensitive adhesive layer (B2) includes an acrylic block copolymer including an acrylate block structure and a methacrylate block structure.
Adhesive sheet.   The pressure sensitive adhesive sheet according to claim 1 in which said base material layer (A) contains polyolefin system resin.   The pressure sensitive adhesive sheet according to claim 1 or 2 whose weight average molecular weights of said acrylic block copolymer are 30000-300000. A pressure-sensitive adhesive sheet that is a laminate including a laminated structure of a base material layer (A) / first pressure-sensitive adhesive layer (B1) / second pressure-sensitive adhesive layer (B2),
The laminate including the forming material (a) of the base material layer (A), the forming material (b1) of the first pressure-sensitive adhesive layer (B1), and the forming material (b2) of the second pressure-sensitive adhesive layer (B2) Obtained by co-extrusion of the forming material of
The pressure-sensitive adhesive sheet according to any one of claims 1 to 3.

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