JP6554834B2 - Adhesive sheet and electronic device - Google Patents

Description

  The present invention relates to an adhesive sheet that can be used when manufacturing an electronic device such as a portable electronic terminal.

  Adhesive sheets are used in the production scenes of various products including electronic devices and automobiles. For example, in the manufacturing scene of the electronic device, the adhesive sheet is used for fixing two or more casings constituting the electronic device, fixing a rechargeable battery, a circuit board, and the like.

  Examples of the pressure-sensitive adhesive sheet that can be used in the above-described scene include, for example, a polymer obtained by copolymerizing at least an alkyl acrylate ester, a hydroxyl group-containing monomer, vinyl acetate, and a carboxyl group-containing monomer, and the carboxyl group in the polymer. What is obtained using the pressure-sensitive adhesive composition is characterized in that the weight ratio of the group-containing monomer is 0.01 to 1.0 part by weight, contains a crosslinking agent, and has a ball tack of 12 to 30. (For example, refer to Patent Document 1).

  On the other hand, the use of electronic devices such as portable electronic terminals is diverse, and as the adhesive sheet, in addition to excellent peel adhesion, for example, when a portable electronic terminal is dropped, the impact Therefore, a level of impact resistance that does not cause peeling or the like is required.

  In particular, along with the increase in screen size and thinning of the portable electronic terminal, etc., the adhesive area of the pressure-sensitive adhesive sheet is small and the pressure-sensitive adhesive sheet is narrowed, so that both excellent impact resistance and peel adhesive strength are achieved. The pressure-sensitive adhesive sheet was not found.

JP 2011-168658 A

  The problem to be solved by the present invention is to provide a pressure-sensitive adhesive sheet having both excellent impact resistance and peel adhesive strength.

  The present inventors have found that a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a tensile strength obtained from a stress-strain curve (so-called S-S curve) having a predetermined value or more is excellent in excellent impact resistance and peel adhesive strength. I found it.

That is, the present invention is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer (A) having a tensile strength of 6 N / cm ² or more based on a strength-strain curve at a strain amount of 100% on one surface or both surfaces of a foam substrate. The foam base material has an average bubble diameter of 160 μm or less in the flow direction and the width direction, a ratio of [average bubble diameter in the flow direction / average bubble diameter in the thickness direction], and [width direction The pressure-sensitive adhesive sheet is characterized by being a foam substrate having a ratio of average bubble diameter / average bubble diameter in the thickness direction] of 6 or less and an interlayer strength of 10 N / cm or more.

  Since the pressure-sensitive adhesive sheet of the present invention can achieve both excellent impact resistance and peel adhesive strength, for example, fixing of two or more casings constituting an electronic device such as a portable electronic terminal, fixing of the casing and the lens member, It can be suitably used for fixing the casing to a rechargeable battery or the like.

The stress-strain curve of the adhesive layer which comprises the adhesive tape obtained in Example 9 is represented.

The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer (A) having a tensile strength of 6 N / cm ² or more based on a strength-strain curve at a strain amount of 100% on one surface or both surfaces of a foam substrate. The foam base material has an average bubble diameter in the flow direction and width direction of 160 μm or less, a ratio of [average bubble diameter in the flow direction / average bubble diameter in the thickness direction], and [width direction] The ratio of the average bubble diameter / average bubble diameter in the thickness direction] is 6 or less, and the foam base material has an interlayer strength of 10 N / cm or more.

As the pressure-sensitive adhesive layer (A) constituting the pressure-sensitive adhesive sheet of the present invention, one having a tensile strength based on a stress-strain curve at a strain amount of 100% is 6 N / cm ² or more.

  Here, the tensile strength was obtained by laminating a test piece made of an adhesive layer having a thickness of about 400 μm, a marked line interval of 2 cm, and a width of 1 cm obtained by laminating a 50 μm thick adhesive layer at a temperature of 23 ° C. and humidity. When the amount of strain is 100% in a stress-strain curve (so-called SS curve) measured by a tensile test at a tensile speed of 300 mm / min using a tensile tester in a measurement environment of 50%. Refers to the tensile strength of

Here, the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer having a tensile strength of less than 6 N / cm ² may not be able to achieve both excellent impact resistance and peel adhesive strength.

The tensile strength of the upper limit is not particularly limited, is preferably 30 N / cm ² or less, more preferably 25 N / cm ² or less, and more preferably 20 N / cm ² or less.

As the pressure-sensitive adhesive layer (A), a layer having a thickness of 1 μm to 150 μm is preferably used, and a layer having a thickness of 5 μm to 100 μm can be used to improve peel adhesion and impact resistance. It is further preferable in order to express the performance of the pressure-sensitive adhesive sheet including the balance in a balanced manner.
More preferred.

The pressure-sensitive adhesive layer (A) can be formed using various pressure-sensitive adhesives. Especially, as said adhesive layer (A), it is an adhesive layer formed using the adhesive containing an acrylic polymer (a1), tackifying resin (a2), and a crosslinking agent (a3), for example. It is preferable for forming a pressure-sensitive adhesive layer having a specific tensile strength.
Moreover, as said adhesive layer (A), it is preferable to use the thing whose tensile strength based on the stress-strain curve in the strain amount of 500% is 12 N / cm < ² > or more, and uses 13 N / cm < ² > or more. it is more preferable to, more preferably the use of 15N / cm ² or more of, more preferably the use of 17N / cm ² or more of, it is particularly preferred to use 19N / cm ² or more of . The upper limit of the tensile strength is preferably at 70N / cm ² or less, it is more preferable to use those 65N / cm ² or less. By using a pressure-sensitive adhesive layer having a tensile strength based on a stress-strain curve at a strain amount of 500% in the above range, adhesive properties such as impact strength and peel adhesive strength, push strength, static load holding force, etc. It is preferable for obtaining a pressure-sensitive adhesive sheet balanced in terms.

  As said acrylic polymer (a1) which may be contained in the said adhesive, the tensile strength of an adhesive layer (A) is set to a specific range, As a result, much more excellent impact resistance and peel adhesion In forming the pressure-sensitive adhesive layer, it is preferable to use one having an acid value in the range of 1 to 50, and more preferable to use one having an acid value in the range of 10 to 50. More preferably, those having an acid value in the range of 25-40 are used. The acid value is preferably an acid value derived exclusively from a carboxyl group. In addition, the said acid value points out mg of potassium hydroxide required in order to neutralize the acid group which exists in the said acrylic polymer (a1) solution.

  Moreover, as said acrylic polymer (a1), when forming the adhesive layer provided with much more excellent impact resistance and peel adhesive force, it is preferable to use what has an aliphatic cyclic structure.

  Examples of the aliphatic cyclic structure include a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a propylcyclohexyl group, a tricyclo [5,2,1,0,2,6] decyl group, and a bicyclo [ 4,3,0] -nonyl group, tricyclo [5,3,1,1] dodecyl group, propyltricyclo [5,3,1,1] dodecyl group, norbornene group, isobornyl group, dicyclopentanyl group, In order to obtain a pressure-sensitive adhesive sheet having both excellent peel strength and excellent push strength, cyclohexyl, norbornene, isobornyl, and adamantyl are among others. preferable.

  Moreover, as said acrylic polymer (a1), it is preferable to use what has a weight average molecular weight of 800,000 or more, in order to obtain the adhesive sheet which was further excellent in impact resistance and peel adhesive force, It is more preferable to use a material having a weight average molecular weight in the range of 800,000 to 3,000,000, and it is preferable to use a material having a weight average molecular weight in the range of 1,000,000 to 2,200,000. The strength is set to a specific range, and as a result, it is more preferable for obtaining a pressure-sensitive adhesive sheet that has both excellent impact resistance and peel adhesive strength. In addition, the said weight average molecular weight is a weight average molecular weight in standard polystyrene conversion measured with a gel permeation chromatograph (GPC).

  The molecular weight is measured by the GPC method using a Tosoh Corporation GPC apparatus (HLC-8329GPC) and converted to polystyrene.

Sample concentration: 0.5% by mass (tetrahydrofuran solution)
Sample injection volume: 100 μl
Eluent: Tetrahydrofuran Flow rate: 1.0 ml / min Measuring temperature: 40 ° C
This column: TSKgel GMHHR-H (20) 2 Guard column: TSKgel HXL-H
Detector: differential refractometer Standard polystyrene molecular weight: 10,000 to 20 million (manufactured by Tosoh Corporation)

  As said acrylic polymer (a1), it is preferable to use what has a glass transition temperature of -15 degrees C or less, and it is much more preferable to use what has a glass transition temperature of -45 degreeC--20 degreeC. It is more preferable for obtaining a pressure-sensitive adhesive sheet having both excellent impact resistance and peel adhesion. The glass transition temperature refers to a calculated value calculated by the FOX equation.

  The acrylic polymer (a1) is preferably contained in an amount of 5% by mass to 80% by mass and preferably 10% by mass to 50% by mass with respect to the total amount of the adhesive that can be used for forming the adhesive layer (A). It is more preferable to maintain good coating workability.

  As said acrylic polymer (a1), it is preferable to use what is obtained by superposing | polymerizing the vinyl monomer component containing a (meth) acryl monomer.

  The vinyl monomer component has a content of vinyl monomers other than (meth) acrylic monomers such as vinyl acetate and styrene for forming an adhesive layer having a predetermined tensile strength. It is preferably constituted by a mixture of (meth) acrylic monomers that is not more than mass%, preferably not more than 3 mass%, more preferably not more than 1 mass%.

As the vinyl monomer component, in forming an adhesive layer having a predetermined tensile strength, a vinyl monomer having a nitrogen atom such as N-vinyl-2-pyrrolidone, vinyl acetate, styrene, etc. The content of vinyl monomers other than (meth) acrylic monomers is 5% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less, based on the total amount of the vinyl monomer components. Some can be used.
The vinyl monomer component may be an alkyl having a homopolymer glass transition temperature of 100 ° C. or higher with respect to the total amount of the vinyl monomer component in forming an adhesive layer having a predetermined tensile strength. The total content of (meth) acrylate is preferably 1% by mass or less, more preferably 0.5% by mass or less, and 0.1% by mass or less. It is particularly preferred to use it. Specific examples of the alkyl (meth) acrylate having a glass transition temperature of 100 ° C. or higher include methyl methacrylate.

  As the vinyl monomer, for example, a vinyl monomer having a hydroxyl group, a vinyl monomer having an acid group, an alkyl (meth) acrylate, or the like can be used.

  Examples of the vinyl monomer having a hydroxyl group that can be used in producing the acrylic polymer (a1) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 3-hydroxypropyl (meth). Acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyhexyl (meth) acrylate, 6-hydroxyhexyl (meth) acryl, 8-hydroxyoctyl (meth) acrylate, 10-hydroxy (Meth) acrylic monomers having a hydroxyl group such as decyl (meth) acrylate and 12-hydroxylauryl (meth) acrylate can be used.

  Among these, as the vinyl monomer having a hydroxyl group, 4-hydroxybutyl (meth) acrylate is preferably used, and 4-hydroxybutyl acrylate is preferably used as 2-hydroxyethyl (meth) acrylate or the like. Compared to the case where it is used, it is more preferable for obtaining a pressure-sensitive adhesive sheet having both excellent impact resistance and peel adhesion.

  The vinyl monomer having a hydroxyl group is preferably used in a range of 0.01% by mass to 0.2% by mass with respect to the total amount of the vinyl monomer component, and 0.01% by mass or more and 0.1% by mass. It is more preferable to use in the range of less than mass%, and use in the range of 0.02 mass% to 0.08 mass% sets the tensile strength of the pressure-sensitive adhesive layer (A) to a specific range, and more It is more preferable for obtaining a pressure-sensitive adhesive sheet having both excellent impact resistance and peel adhesive strength.

  Examples of the vinyl monomer having an acid group that can be used for producing the acrylic polymer (a1) include acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, and (anhydrous). (Meth) acrylic monomers having carboxyl groups such as itaconic acid, (anhydrous) maleic acid, fumaric acid, crotonic acid, (meth) acrylamide propanesulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalene sulfone Vinyl monomers having a sulfonic acid group such as acid, sodium vinyl sulfonate, styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, 2- Hydroxyethyl acryloy Having a phosphoric acid group such as a phosphate (meth) can be used acrylic monomers and the like. Among them, it is preferable to use a (meth) acrylic monomer having a carboxyl group, and the use of acrylic acid or methacrylic acid provides a pressure-sensitive adhesive sheet that has more excellent impact resistance and peel adhesive strength. More preferable.

  The vinyl monomer having an acid group is not particularly limited as long as the acid value of the acrylic polymer (a1) is within a predetermined preferable range, but 1 mass with respect to the total amount of the vinyl monomer component. % To 30% by weight, more preferably 1% to 15% by weight, and more preferably 1% to 7% by weight. It is further preferable to obtain a pressure-sensitive adhesive sheet having both impact properties and peel adhesive strength.

  Further, when the acrylic polymer (a1) is produced, a vinyl monomer having an aliphatic cyclic structure is used as the vinyl monomer component in introducing the aliphatic cyclic structure into the acrylic polymer (a1). It is preferable to use a monomer.

  As the vinyl monomer having an aliphatic cyclic structure, cyclohexyl (meth) acrylate or the like is preferably used, and cyclohexyl acrylate is more preferably used.

The vinyl monomer having an aliphatic cyclic structure is more excellent in impact resistance when used in the range of 0.5 to 30% by mass with respect to the total amount of the vinyl monomer component. In addition, it is preferable to obtain a pressure-sensitive adhesive sheet having both peel adhesive strength and more preferably used in the range of 4% by mass to 25% by mass.

  As a vinyl monomer component that can be used for the production of the acrylic polymer (a1), other vinyl monomers can be used as required in addition to the above-described ones.

  Examples of the other vinyl monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, and isobutyl (meth) ) Acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) ) Acrylate, isodecyl (meth) acrylate, n-undecyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate and other alkyl (meth) acrylates It is possible to use.

  Among the above-mentioned other vinyl monomers, it is preferable to use alkyl (meth) acrylates having 4 to 12 carbon atoms in the alkyl group, and n-butyl acrylate and 2-ethylhexyl acrylate are used. It is preferable to obtain a pressure-sensitive adhesive sheet having both excellent impact resistance and peel adhesive strength.

  Among the alkyl (meth) acrylates usable as the other vinyl monomers, alkyl (meth) acrylates having an alkyl group having 4 to 12 carbon atoms are used for the production of the acrylic polymer (a1). It is preferably used in the range of 50% by mass to 8% by mass, more preferably in the range of 60% by mass to 98% by mass, and more preferably in the range of 70% by mass to 96% by mass with respect to the total amount of the vinyl monomer component. % Is preferably used in order to obtain a pressure-sensitive adhesive sheet having both excellent impact resistance and peel adhesion.

  Moreover, as another vinyl monomer which can be used for manufacture of the acrylic polymer (a1), for example, an acrylic monomer having an amide group, a (meth) acrylic monomer having an amino group, and an imide group are included. (Meth) acrylic monomers having a nitrogen atom such as (meth) acrylic monomers can be used.

  Examples of the (meth) acrylic monomer having an amide group include acrylamide, methacrylamide, diethylacrylamide, N-vinylpyrrolidone, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N, N-diethylacrylamide. N, N-diethylmethacrylamide, N, N′-methylenebisacrylamide, N, N-dimethylaminopropylacrylamide, N, N-dimethylaminopropylmethacrylamide, diacetoneacrylamide, acryloylmorpholine and the like can be used. .

  As the (meth) acrylic monomer having an amino group, for example, aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate or the like is used. be able to.

  As the (meth) acrylic monomer having an imide group, for example, cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, itaconimide and the like can be used.

  As the other vinyl monomers, in addition to the above, for example, cyano group-containing vinyl monomers such as acrylonitrile and methacrylonitrile, glycidyl such as glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, and allyl glycidyl ether Group-containing (meth) acrylic monomers, vinyl acetate, vinyl propionate, vinyl laurate, styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, other substituted styrenes, methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether, etc. You may use in the range which does not impair an effect.

  The acrylic polymer (a1) can be produced, for example, by supplying the vinyl monomer component and radically polymerizing them in the presence of an organic solvent. Specifically, the acrylic polymer (a1) is radically polymerized by mixing and stirring the vinyl monomer component, the polymerization initiator, and the organic solvent, preferably at a temperature of 40 ° C. to 90 ° C. Can be manufactured. The vinyl monomer component may be supplied all at once or dividedly supplied.

  Examples of the polymerization initiator include peroxides such as hydrogen peroxide, potassium persulfate, sodium persulfate, ammonium persulfate, benzoyl peroxide, cumene hydroxy peroxide, and 2,2′-azobis (2-methylbutyro Nitrile), 2,2′-azobis- (2-aminodipropane) dihydrochloride, 2,2′-azobis- (N, N′-dimethyleneisobutylamidine) dihydrochloride, 2,2′-azobis { An azo compound such as 2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide} or the like can be used. The amount of the polymerization initiator used is preferably in the range of 0.01% by mass to 5% by mass with respect to the total amount of the vinyl monomer component.

  As the pressure-sensitive adhesive that can be used in the present invention, it is preferable to use a pressure-sensitive adhesive sheet containing a tackifying resin (a2) in order to obtain a pressure-sensitive adhesive sheet that has both excellent impact resistance and peel adhesion. .

  Examples of the tackifying resin (a2) include a rosin-based tackifying resin, a polymerized rosin-based tackifying resin, a polymerized rosin ester-based tackifying resin, a rosin phenol-based tackifying resin, a stabilized rosin ester-based tackifying resin, Use of rosin ester-based tackifier resin, hydrogenated rosin ester-based tackifier resin, terpene-based tackifier resin, terpene phenol-based tackifier resin, petroleum resin-based tackifier resin, (meth) acrylate-based tackifier resin, etc. Can do.

  Among them, the tackifier resin (a2) is selected from the group consisting of a polymerized rosin ester tackifier resin, a disproportionated rosin ester tackifier resin, a petroleum tackifier resin, and a terpene phenol tackifier resin. It is preferable to use a combination of more than one species in order to obtain a pressure-sensitive adhesive sheet that is excellent in compatibility with the acrylic polymer (a1) and has both excellent impact resistance and peel adhesive strength. preferable.

  The softening point of the tackifying resin (a2) is preferably 100 ° C. or higher, and it is more preferable to use a resin having a temperature in the range of 120 ° C. to 170 ° C. It is more preferable for obtaining a pressure-sensitive adhesive sheet having a sufficient static load holding force.

  The tackifying resin (a2) is preferably used in an amount of 5 to 60 parts by mass, preferably 10 to 60 parts by mass with respect to 100 parts by mass of the acrylic polymer (a1). Preferably, it is more preferable to use in the range of 20 to 50 parts by mass in order to obtain a pressure-sensitive adhesive sheet that has both excellent impact resistance and peel adhesion.

  Moreover, as said adhesive, when forming the adhesive layer provided with the further outstanding cohesion force, it is preferable to use what contains a crosslinking agent (a3).

  As said crosslinking agent (a3), an isocyanate type crosslinking agent, an epoxy-type crosslinking agent, a metal chelate type crosslinking agent, an aziridine type crosslinking agent etc. can be used, for example. Especially, as said crosslinking agent, it is easy to mix and use the said acrylic polymer (a1) or its solution manufactured previously, and it is possible to use the crosslinking agent which can advance a crosslinking reaction rapidly. Specifically, it is more preferable to use an isocyanate crosslinking agent or an epoxy crosslinking agent.

  Examples of the isocyanate-based crosslinking agent include tolylene diisocyanate, naphthylene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, tolylene diisocyanate and their trimethylolpropane adducts, triphenylmethane isocyanate, and the like. Can be used. Especially, as said isocyanate type crosslinking agent, it is preferable to use tolylene diisocyanate, these trimethylol propane adducts, triphenylmethane isocyanate, etc.

  As an index of the degree of crosslinking of the pressure-sensitive adhesive layer (A) formed using the pressure-sensitive adhesive containing the cross-linking agent (a3), the insoluble content after the pressure-sensitive adhesive layer (A) was immersed in toluene for 24 hours was measured. The value of the gel fraction to do is mentioned. As said gel fraction, it is preferable that it is the range of 20 mass%-70 mass%, It is more preferable that it is the range of 30 mass%-60 mass%, It is the range of 35 mass%-55 mass% However, it is more preferable for imparting even more excellent impact resistance and peel adhesive strength.

  In addition, the said gel fraction can be measured by the method shown below.

  The pressure-sensitive adhesive is applied to one side of an arbitrary release liner so that the thickness after drying is 50 μm, dried at 100 ° C. for 3 minutes, and aged at 40 ° C. for 2 days to form a pressure-sensitive adhesive layer To do. A sample cut into a 50 mm square is used as a sample.

  Next, after measuring the mass (G1) of the sample, the sample is immersed in a toluene solution at 23 ° C. for 24 hours. The toluene-insoluble part of the sample after the immersion is separated by filtration through a 300 mesh wire net, and the mass (G2) of the residue after drying at 110 ° C. for 1 hour is measured, and the gel fraction is determined according to the following formula: .

    Gel fraction (mass%) = (G2 / G1) × 100

  As said adhesive, what contains the other component other than what was mentioned above as needed can be used.

  Examples of the other components include plasticizers, softeners, antioxidants, flame retardants, glass and plastic fibers, balloons and beads, fillers such as metals, metal oxides, and metal nitrides, pigments and dyes, and the like. Additives such as colorants, leveling agents, thickeners, water repellents and antifoaming agents can be used.

  In addition to the acrylic polymer (a1), the pressure-sensitive adhesive preferably contains a solvent as required in order to impart good coating workability. As said solvent, aqueous media, such as an organic solvent and water, etc. are mentioned, for example.

  Examples of the organic solvent include toluene, ethyl acetate, butyl acetate, methyl ethyl ketone, hexane, acetone, cyclohexanone, 3-pentanone, acetonitrile, propionitrile, isobutyronitrile, valeronitrile, dimethyl sulfoxide, dimethylformamide, and the like. be able to.

  The pressure-sensitive adhesive sheet of the present invention can be produced, for example, by applying the pressure-sensitive adhesive to one side or both sides of the specific foam base material using a roll coater, a die coater, or the like and drying. In addition, the pressure-sensitive adhesive sheet previously forms the pressure-sensitive adhesive layer (A) by applying the pressure-sensitive adhesive on the surface of the release liner in advance using a roll coater and the like, and then drying the pressure-sensitive adhesive layer (A). Can be produced by a transfer method in which is attached to one or both sides of a foam substrate.

  As the foam base material, for example, when it is used for fixing a component constituting a portable electronic terminal, etc., it expresses excellent impact resistance and the like, and the average cell diameter in the flow direction and the width direction is 160 μm or less. Yes, the ratio of [average bubble diameter in the flow direction / average bubble diameter in the thickness direction] and the ratio of [average bubble diameter in the width direction / average bubble diameter in the thickness direction] are 6 or less, and A foam base material having an interlayer strength of 10 N / cm or more is used. Moreover, the outstanding waterproof performance can be provided by using the said specific foam base material.

  The average cell diameter in the flow direction and the width direction of the foam substrate is the average cell size in the flow direction and the width direction in order to obtain a pressure-sensitive adhesive sheet having excellent peel adhesion and very excellent impact resistance. It is preferable to use a material having a diameter of 160 μm or less, more preferably a material having a diameter of 10 μm to 160 μm, still more preferably a material having a diameter of 30 μm to 150 μm, and a foam base material of 50 μm to 150 μm is used. It is particularly preferred.

  The average cell diameter in the thickness direction of the foam substrate is preferably in the range of 1 μm to 150 μm, more preferably in the range of 5 μm to 100 μm, although it depends on the thickness of the foam substrate. 10 μm to 60 μm More preferably, it is the range.

  The foam base material has a ratio of [average bubble diameter in the flow direction / average bubble diameter in the thickness direction] and [average bubble diameter in the width direction / average bubble diameter in the thickness direction] ratio. However, both are 6 or less, More preferably, it is 1.2-5.5, Furthermore, it is 1.2-4. By using a foam substrate having a ratio in the above range, it is easy to ensure flexibility in the thickness direction, so that the followability and cushioning properties of the resulting adhesive tape can be further improved to provide excellent waterproof properties And excellent impact resistance and peel adhesion can be imparted.

Moreover, as said foam base material, ratio of the average bubble diameter of the width direction with respect to the average bubble diameter of the flow direction of a foam base material (average bubble diameter of the width direction / average bubble diameter of the flow direction) is 0.25-0.25. 4 is preferable, 0.33 to 3 is more preferable, 0.6 to 1.5 is further preferable, and 0.7 to 1.3 is preferable. It is particularly preferable because it is possible to suppress variations in flexibility and tensile strength in the flow direction and width direction of the foam base material.
The average cell diameter in the width direction, the flow direction, and the thickness direction of the foam base material is a value measured in the following manner.
First, a foam base material is cut into a square having a width direction of 1 cm and a flow direction of 1 cm.
Next, after expanding the cut surface of the cut foam base material 200 times using a digital microscope (trade name “KH-7700”, manufactured by HiROX), the width direction and the flow direction of the foam base material The cut surface of was photographed.
Next, among the cut surfaces in the width direction of the foam base material, the bubble diameters of all the bubbles existing in an arbitrary range of thickness × width direction distance (2 mm) were measured, and the average value was calculated. . Moreover, what averaged ten average values calculated by performing the said measurement with respect to arbitrary 10 places of the said cut surface was made into the average bubble diameter of the width direction.
Moreover, the bubble diameter of all the bubbles which exist in the range of arbitrary thickness x flow direction distance (2 mm) among the cut surfaces of the flow direction of the said foam base material was measured, and the average value was computed. Moreover, what averaged ten average values calculated by performing the said measurement with respect to arbitrary 10 places of the said cut surface was made into the average bubble diameter of a flow direction.

  The foam base material has an interlayer strength of 20 N / cm or more, preferably 20 N / cm to 150 N / cm, more preferably 25 N / cm to 100 N / cm, more preferably 25 N / cm to 60 N / cm. Use body substrate. By using a foam base material having an interlayer strength in the above range, a pressure-sensitive adhesive sheet having excellent impact resistance and good followability to an adherend can be obtained. In addition, in order to improve the yield when manufacturing portable electronic devices, the adhesive sheet or parts are peeled off from the work-in-progress (rework), or the case or parts are used to repair, recycle or reuse the finished product. Even when separation, decomposition, and disassembly cause an interlaminar crack of the substrate, it is possible to impart ease of peeling of the adhesive sheet.

  The interlayer strength can be measured by the following method. A pressure-sensitive adhesive layer having a thickness of 50 μm (which does not peel off from the adherend and the foam substrate during the following high-speed peel test) was bonded to both surfaces of the foam base material for evaluating the interlayer strength one by one. Thereafter, aging is carried out at 40 ° C. for 48 hours to prepare a double-sided pressure-sensitive adhesive sheet for measuring interlayer strength. Next, a double-sided pressure-sensitive adhesive sheet having a width of 1 cm and a length of 15 cm (in the flow direction and width direction of the foam base material) lined with a polyester film having a thickness of 25 μm on one side is thickened at 23 ° C. and 50% RH. A polyester film having a thickness of 50 μm, a width of 3 cm, and a length of 20 cm is pressure-applied with one reciprocation of a 2 kg roller and allowed to stand at 60 ° C. for 48 hours. After standing at 23 ° C. for 24 hours, the side bonded to the 50 μm-thick polyester film at 23 ° C. and 50% RH is fixed to a mounting jig of a high-speed peel tester, and the 25 μm-thick polyester film is pulled at a speed of 15 m. The maximum strength is measured when the foam is torn in the direction of 90 degrees per minute.

  As said foam base material, it is preferable to use the thing whose 25% compressive strength is 80 kPa or more, for example, It is more preferable to use what is 80 kPa-1000 kPa, Use 120-700 kPa thing is used. It is more preferable to use a material having a viscosity of 200 to 600 kPa in order to develop a suitable adhesive force to an adherend having an uneven shape or a rough surface.

  The 25% compressive strength was measured according to JISK6767. The samples cut into 25 corners are overlapped to a thickness of about 10 mm. The sample is sandwiched with a stainless plate having a larger area than the sample, and the strength is measured when the sample is compressed by approximately 2.5 mm (25% of the original thickness) at a rate of 10 mm / min at 23 ° C.

The tensile elastic modulus in the flow direction and the width direction of the foam base material is not particularly limited, but is preferably 500 N / cm ² or more, more preferably 600 to 1800 N / cm ² . Also preferably the tensile modulus of the flow direction and the ones of the widthwise tensile low elasticity modulus direction is 500~1400N / cm ^2, more preferably 600~1200N / cm ^2. Preferably high direction tensile modulus when this is 700~1800N / cm ^2, more preferably 800~1600N / cm ^2. Further, the tensile elongation at the time of cutting in the tensile test is not particularly limited, but the tensile elongation in the flow direction is preferably 200 to 1500%, more preferably 400 to 1000%, still more preferably 620 to 950%, Particularly preferably, it is 450 to 800%. With a foam base material having a tensile elastic modulus and tensile elongation within the above range, deterioration of workability of the pressure-sensitive adhesive sheet and reduction in workability of sticking can be suppressed even with a foamed flexible base material. Moreover, when peeling an adhesive sheet, it is hard to generate | occur | produce the interlayer destruction of a foam base material, and a tear, and even when an interlayer crack generate | occur | produces, the ease of peeling of an adhesive sheet can be provided.

  The tensile elastic modulus in the flow direction and the width direction of the foam base material was measured according to JISK6767. This is the maximum strength of a sample with a marked line length of 2 cm and a width of 1 cm measured using a Tensilon tensile tester under the measurement conditions of a tensile speed of 300 mm / min in an environment of 23 ° C. and 50% RH.

  The cell structure of the foam base material is preferable because it is possible to effectively prevent water from entering from the cut surface of the foam base material by adopting a closed cell structure. The shape of the bubbles forming the closed cell structure is moderate by making the closed cell in the shape where the average cell diameter in the flow direction and / or the width direction is longer than the average cell diameter in the thickness direction of the foam substrate. It is preferable because it has excellent followability and cushioning properties.

The apparent density of the foam substrate is not particularly limited, but it is easy to achieve both impact resistance and excellent adhesion to the adherend by adjusting the interlayer strength, compressive strength, average cell diameter, etc. to the above ranges. 0.08 to 0.7 g / cm ³ , preferably 0.1 to 0.65 g / cm ³ , more preferably 0.2 to 0.65 g / cm ³ , and particularly preferably 0.3 to 0.6. It is. The apparent density was measured according to JISK6767. A foam base material cut into a 4 cm × 5 cm rectangle is prepared for about 15 cm ³ minutes, and its mass is measured to determine the apparent density.

  The interlaminar strength, compressive strength, tensile elastic modulus, and the like of the foam base material can be appropriately adjusted depending on the material used and the foam structure. The type of the foam substrate used in the present invention is not particularly limited as long as it has the above-mentioned interlayer strength, 25% compressive strength, tensile elastic modulus, etc., but polyethylene, polypropylene, ethylene-propylene copolymer, ethylene- Polyolefin foam made of vinyl acetate copolymer, polyurethane foam, rubber foam made of acrylic rubber, other elastomers, etc. can be used. Since it is easy to produce a foam substrate having a thin closed-cell structure excellent in buffer absorbability and the like, a polyolefin-based foam can be preferably used.

  Among the polyolefin-based foams, it is preferable to use a polyethylene-based resin because it is easy to produce with a uniform thickness and easily imparts suitable flexibility. In particular, the content of the polyethylene resin in the polyolefin tree is preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, and 100% by mass. It is particularly preferred.

  As the polyethylene resin, a polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst has a narrow molecular weight distribution, and in the case of a copolymer, any molecular weight component is a copolymer component. Are introduced at substantially equal ratios, the polyolefin foam can be uniformly crosslinked. For this reason, since the foamed sheet is uniformly cross-linked, the foamed sheet can be easily stretched uniformly as necessary, and the thickness of the resulting polyolefin-based resin foam is easily uniformed, which is preferable.

  The polyolefin resin may contain a polyolefin resin other than a polyethylene resin obtained using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst. Examples of such polyolefin resins include polyethylene resins and polypropylene resins other than those described above. In addition, polyolefin resin may be used independently or 2 or more types may be used together.

  Examples of such polyethylene resins include linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, an ethylene-α-olefin copolymer containing 50% by weight or more of ethylene, and 50% of ethylene. The ethylene-vinyl acetate copolymer etc. which contain weight% or more are mentioned, These may be used independently or 2 or more types may be used together. Examples of the α-olefin constituting the ethylene-α-olefin copolymer include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene. Can be mentioned.

  In addition, the polypropylene resin is not particularly limited, and examples thereof include polypropylene and a propylene-α-olefin copolymer containing 50% by weight or more of propylene. The above may be used in combination. Examples of the α-olefin constituting the propylene-α-olefin copolymer include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene. Can be mentioned.

  The step of crosslinking the expandable polyolefin resin sheet is preferably crosslinked when the expandable polyolefin resin sheet is foamed with a pyrolytic foaming agent, for example.

  Next, a method for producing a polyolefin resin foam will be described. The method for producing the polyolefin resin foam is not particularly limited. For example, a polyolefin resin containing 40% by weight or more of a polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, and A foamable polyolefin resin composition containing a heat decomposable foaming agent, a foaming aid, and a colorant for coloring the foam in black or white is supplied to an extruder and melt-kneaded. A step of producing a foamable polyolefin resin sheet by extruding the foamed polyolefin resin sheet, a step of crosslinking the foamable polyolefin resin sheet, a step of foaming the foamable polyolefin resin sheet, and melting or A process to stretch the foamed sheet by softening and stretching in either or both of the flow direction or width direction And a method of containing. In addition, the process of extending | stretching a foam sheet should just be performed as needed, and may be performed in multiple times.

  And, as a method of crosslinking the polyolefin resin foam, for example, a method of irradiating the foamable polyolefin resin sheet with ionizing radiation, an organic peroxide is blended in advance in the foamable polyolefin resin composition, Examples include a method of heating the obtained expandable polyolefin resin sheet to decompose the organic peroxide, and these methods may be used in combination.

  Examples of ionizing radiation include electron beams, α rays, β rays, and γ rays. The dose of ionizing radiation is appropriately adjusted so that the gel fraction of the polyolefin resin foam is within the above-mentioned preferable range, but a range of 5 to 200 kGy is preferable. Further, the irradiation with ionizing radiation forms a uniform cross-linked structure, and as a result, in order to form a relatively uniform foamed structure, it is preferable to irradiate from both sides of the foamable polyolefin resin sheet. Are preferably the same.

  Examples of the organic peroxide include 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, 2,2-bis ( t-butylperoxy) octane, n-butyl-4,4-bis (t-butylperoxy) valerate, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α, α ′ -Bis (t-butylperoxy-m-isopropyl) benzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butyl) Peroxy) hexyne-3, benzoyl peroxide, cumyl peroxyneodecanate, t-butyl peroxybenzoate, 2,5-dimethyl-2,5-di (ben (Zoylperoxy) hexane, t-butylperoxyisopropyl carbonate, t-butylperoxyallyl carbonate and the like may be mentioned, and these may be used alone or in combination of two or more.

  0.01 mass part-5 mass parts are preferable with respect to 100 mass parts of polyolefin resin, and, as for the addition amount of an organic peroxide, 0.1 mass part-3 mass parts are more preferable.

  The amount of the thermally decomposable foaming agent added in the foamable polyolefin resin composition may be appropriately determined according to the expansion ratio of the polyolefin resin foam, but from 1 part by mass to 100 parts by mass of the polyolefin resin. 40 parts by mass is preferable, and 1 part by mass to 30 parts by mass is more preferable.

  Further, the method for foaming the expandable polyolefin resin sheet is not particularly limited, and examples thereof include a method of heating with hot air, a method of heating with infrared rays, a method using a salt bath, and a method using an oil bath. May be used in combination. Of these, the method of heating with hot air or the method of heating with infrared rays is preferable because the appearance of the surface of the polyolefin resin foam has little difference between the front and back surfaces.

  The foam may be stretched after the foamable polyolefin resin sheet is foamed to obtain a foam substrate, or may be performed while foaming the foamable polyolefin resin sheet. In addition, after foaming the foamable polyolefin resin sheet to obtain a foam base material, when the foam base material is stretched, the molten state at the time of foaming is maintained without cooling the foam base material. Subsequently, the foam base material may be stretched, or after the foam base material is cooled, the foam base material may be stretched again by heating the foam sheet to a molten or softened state.

  Here, the molten state of the foam base material means a state in which the foam base material is heated to a temperature equal to or higher than the melting point of the polyolefin resin constituting the foam base material. The softening of the foam base material means a state in which the foam base material is heated to a temperature not lower than the melting point and lower than the melting point of the polyolefin resin constituting the foam base material. By stretching the foam base material, the foam of the foam base material can be produced by stretching the foam base material in a predetermined direction and deforming the foam base material so that the aspect ratio of the foam is within a predetermined range.

  Furthermore, in the extending | stretching direction of a foam base material, it extends | stretches toward the flow direction or the width direction of a elongate foamable polyolefin resin sheet, or toward a flow direction and the width direction. When the foam base material is stretched in the flow direction and the width direction, the foam base material may be stretched simultaneously in the flow direction and the width direction, or may be stretched separately one by one. .

  As a method of stretching the foam base material in the flow direction, for example, a long foam sheet after foaming is used rather than a speed (supply speed) at which a long foamable polyolefin resin sheet is supplied to the foaming process. A method of stretching the foam base material in the flow direction by increasing the winding speed (winding speed) while cooling, foaming rather than the speed (supply speed) of supplying the obtained foam base material to the stretching process Examples include a method of stretching the foam base material in the flow direction by increasing the speed of winding the body base material (winding speed).

  In the former method, the foamable polyolefin resin sheet expands in the flow direction by its own foaming. Therefore, when the foam base material is stretched in the flow direction, the foamable polyolefin resin sheet is foamed. In consideration of the amount of expansion in the flow direction, it is necessary to adjust the supply speed and the winding speed of the foam base so that the foam base is stretched in the flow direction more than the expansion.

  Further, as a method of stretching the foam base material in the width direction, both ends of the foam base material in the width direction are gripped by a pair of gripping members, and the pair of gripping members are gradually moved away from each other. A method of stretching the foam base material in the width direction is preferable. In addition, since the foamable polyolefin resin sheet expands in the width direction by its own foaming, when the foam base material is stretched in the width direction, expansion in the width direction due to foaming of the foamable polyolefin resin sheet. In consideration of the amount, it is necessary to adjust so that the foam base material is stretched in the width direction more than the expansion amount.

  Here, the draw ratio in the flow direction of the polyolefin-based foam is preferably 1.1 to 2.0 times, and more preferably 1.2 to 1.5 times.

  Moreover, 1.2 times-4.5 times are preferable and, as for the draw ratio in the width direction of a polyolefin-type foam base material, 1.5 times-3.5 times are more preferable.

  The foam base material may be colored in order to develop design properties, light shielding properties, concealing properties, light reflectivity, and light resistance in the pressure-sensitive adhesive sheet. The colorants can be used alone or in combination of two or more.

  When the light-shielding property, concealing property, and light resistance are imparted to the pressure-sensitive adhesive sheet, the foam base material is colored black. Black colorants include carbon black, graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine black, activated carbon, ferrite, magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complex, complex oxidation Physical black pigments and anthraquinone organic black pigments can be used. Of these, carbon black is preferred from the viewpoint of cost, availability, insulation, and heat resistance that can withstand the temperatures of the process of extruding the foamable polyolefin resin composition and the heating foaming process.

  When imparting design properties, light reflectivity, or the like to the pressure-sensitive adhesive sheet, the foam substrate is colored white. White colorants include titanium oxide, zinc oxide, aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, calcium oxide, tin oxide, barium oxide, cesium oxide, yttrium oxide, magnesium carbonate, calcium carbonate, barium carbonate, zinc carbonate , Aluminum hydroxide, magnesium hydroxide, calcium hydroxide, zinc hydroxide, aluminum silicate, calcium silicate, barium sulfate, calcium sulfate, barium stearate, zinc white, talc, silica, alumina, clay, kaolin, phosphoric acid Organic white colorants such as titanium, mica, gypsum, white carbon, diatomaceous earth, bentonite, lithopone, zeolite, sericite, etc., and organics such as silicone resin particles, acrylic resin particles, urethane resin particles, melamine resin particles And the like can be used white colorant. Of these, aluminum oxide and zinc oxide are preferable from the viewpoint of cost, availability, color tone, and heat resistance that can withstand the temperature of the step of extruding the foamable polyolefin resin composition and the heating and foaming step.

  In addition, the foamable polyolefin-based resin composition includes a foaming aid such as a plasticizer, an antioxidant, and zinc oxide, and a cell core modifier as long as the physical properties of the polyolefin-based resin foam substrate are not impaired. , Heat stabilizers, flame retardants such as aluminum hydroxide and magnesium hydroxide, antistatic agents, glass and plastic hollow balloon beads, metal powder, fillers such as metal compounds, conductive fillers, thermal conductive fillers A known material such as may be optionally contained in the resin. The polyolefin resin foam base material used in the pressure-sensitive adhesive sheet of the present invention is preferably 0.1% by mass to 10% by mass, preferably 1% by mass, based on the polyolefin resin, in order to maintain appropriate followability and cushioning properties. % To 7% by mass is preferable.

  In addition, when blending the colorant, the thermally decomposable foaming agent, the foaming aid, and the like into the foamable polyolefin resin composition, it is supplied to the extruder from the viewpoint of preventing color unevenness, partial excessive foaming, and insufficient foaming. It is preferable to prepare a masterbatch with a thermoplastic resin having high compatibility with the expandable polyolefin resin composition or the expandable polyolefin resin composition in advance.

  In order to improve the adhesion of the foam substrate to the pressure-sensitive adhesive layer and other layers, surface treatment such as corona treatment, flame treatment, plasma treatment, hot air treatment, ozone / ultraviolet treatment, easy-adhesive treatment agent application, etc. May have been made. In the surface treatment, when the wetting index by the wetting reagent is 36 mN / m or more, preferably 40 mN / m, more preferably 48 mN / m, good adhesion to the adhesive can be obtained. The foam base material having improved adhesion may be bonded to the pressure-sensitive adhesive layer in a continuous process. In addition, the foam base material with improved adhesion may be temporarily wound and stored, and then bonded to the pressure-sensitive adhesive layer in a separate process at a later date. When winding up the foam base material, the foam base material should be wound with paper such as paper, polyethylene, polypropylene, polyester film, etc. in order to prevent the blocking phenomenon between the foam base materials with improved adhesion. It is preferable to take a polypropylene film or a polyester film having a thickness of 25 μm or less.

  It is preferable to use a foam substrate having a thickness of 1500 μm or less as the foam substrate, more preferably a thickness of 1200 μm or less, and use of a thickness of 500 μm or less is excellent. It is more preferable for imparting excellent workability of the tape and excellent followability to the adherend. The lower limit of the thickness is preferably 50 μm.

  Moreover, the said adhesive sheet may have another layer as needed other than the said foam base material and an adhesive layer.

  Examples of the other layers include a laminate layer such as a polyester film, a light shielding layer, a light reflection layer, a metal layer, and the like in order to provide, for example, dimensional stability of the pressure-sensitive adhesive sheet and good tensile strength and reworkability. Can be mentioned.

  The pressure-sensitive adhesive sheet of the present invention has even more excellent impact resistance and peel adhesive strength. The pressure-sensitive adhesive sheet of the present invention has excellent impact resistance and peel adhesive strength. Therefore, the pressure-sensitive adhesive sheet of the present invention has a width of the narrowest portion of the pressure-sensitive adhesive sheet of 5 mm or less, preferably 0.1 mm to 3 mm, more preferably 0.5 mm to 2.5 mm, for example, due to restrictions such as the application site and shape. It can be used for fixing a restricted member.

  The narrow member is often used as a member in industrial applications such as portable electronic devices such as mobile phones, automobiles, building materials, OA, and home appliance industries.

  Specific examples of the member include two or more casings and lens members that constitute an electronic terminal.

  An article such as an electronic device in which two or more cases and lens members are fixed using the pressure-sensitive adhesive sheet of the present invention does not easily fall off due to an impact such as dropping, and has excellent waterproof properties.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.

[Preparation Example 1] Method for Producing Acrylic Polymer (A-1) In a reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet tube, and thermometer, 80.94 parts by mass of n-butyl acrylate, 2-ethylhexyl acrylate 5 Mass parts, 10 parts by mass of cyclohexyl acrylate, 4 parts by mass of acrylic acid, 0.06 parts by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate were charged, and the temperature was raised to 72 ° C. while blowing nitrogen under stirring. .

  Next, 2 parts by mass of a 2,2′-azobis (2-methylbutyronitrile) solution previously dissolved in ethyl acetate (solid content: 0.1% by mass) was added to the mixture, and the mixture was stirred at 72 ° C. After holding for 4 hours, it was held at 75 ° C. for 5 hours.

  Next, the mixture was diluted with 98 parts by mass of ethyl acetate and filtered through a 200 mesh wire mesh to obtain an acrylic polymer (A-1) solution (nonvolatile content: 40% by mass) having a weight average molecular weight of 1,600,000.

In addition, the said weight average molecular weight is a weight average molecular weight in standard polystyrene conversion measured by a gel permeation chromatograph (GPC), and was measured with the following method.
The measurement of the molecular weight by GPC method is a standard polystyrene conversion value measured using a GPC apparatus (HLC-8329GPC) manufactured by Tosoh Corporation.

Sample concentration: 0.5% by mass (tetrahydrofuran solution)
Sample injection volume: 100 μl
Eluent: THF (tetrahydrofuran)
Flow rate: 1.0 ml / min Measurement temperature: 40 ° C
This column: TSKgel GMHHR-H (20) 2 Guard column: TSKgel HXL-H
Detector: differential refractometer Standard polystyrene molecular weight: 10,000 to 20 million (manufactured by Tosoh Corporation)

[Preparation Example 2] Production method of acrylic polymer (A-2) The amount of 4-hydroxybutyl acrylate used was changed from 0.06 parts by mass to 0.02 parts by mass, and the amount of n-butyl acrylate used The acrylic polymer (A-2) solution (non-volatile content: 40% by mass) having a weight average molecular weight of 1,640,000 was prepared in the same manner as in Preparation Example 1, except that 80.94 parts by mass was changed from 80.94 parts by mass to 80.98 parts by mass. Obtained.

[Preparation Example 3] Production method of acrylic polymer (A-3) The amount of 4-hydroxybutyl acrylate used was changed from 0.06 parts by weight to 0.1 parts by weight, and the amount of n-butyl acrylate used. The acrylic polymer (A-3) solution having a weight average molecular weight of 16.2 million (nonvolatile content: 40% by mass) was prepared in the same manner as in Preparation Example 1 except that 80.94 parts by mass was changed from 80.94 parts by mass to 80.9 parts by mass. Obtained.

[Preparation Example 4] Production method of acrylic polymer (A-4) Preparation example, except that the cyclohexyl acrylate is not used and the amount of 2-ethylhexyl acrylate is changed from 5 parts by mass to 15 parts by mass 1 was used to obtain an acrylic polymer (A-4) solution (nonvolatile content: 40% by mass) having a weight average molecular weight of 1.32 million.

[Preparation Example 5] Method for Producing Acrylic Polymer (A-5) The amount of acrylic acid used is changed from 4 parts by mass to 2 parts by mass, and the amount of n-butyl acrylate used is from 80.94 parts by mass. An acrylic polymer (A-5) solution having a weight average molecular weight of 1,640,000 (nonvolatile content: 40 mass) in the same manner as in Preparation Example 1 except that the content is changed to 97.94 parts by mass and 2-ethylhexyl acrylate is not used. %).

[Preparation Example 6] Method for Producing Acrylic Polymer (A-6) The amount of acrylic acid used is changed from 4 parts by mass to 6 parts by mass, and the amount of n-butyl acrylate used is from 80.94 parts by mass. An acrylic polymer (A-6) solution having a weight average molecular weight of 1,640,000 (nonvolatile content: 40 mass) in the same manner as in Preparation Example 1 except that the content is changed to 93.94 parts by mass and 2-ethylhexyl acrylate is not used. %).

[Preparation Example 7] Production method of acrylic polymer (A-7) The amount of 2,2′-azobis (2-methylbutyronitrile) solution used is from 2 parts by mass (solid content: 0.1% by mass) to 1 mass. An acrylic polymer (A-7) solution (non-volatile content 40% by mass) having a weight average molecular weight of 1.780,000 was obtained in the same manner as in Preparation Example 1, except that the content was changed to parts (solid content 0.05% by mass). .

[Preparation Example 8] Production method of acrylic polymer (A-8) The amount of 2,2′-azobis (2-methylbutyronitrile) solution used is from 2 parts by mass (solid content: 0.1% by mass) to 10 masses. An acrylic polymer (A-8) solution (nonvolatile content 40% by mass) having a weight average molecular weight of 810,000 was obtained in the same manner as in Preparation Example 1, except that the content was changed to parts (solid content 0.5% by mass). .

[Comparative Preparation Example 1] Production method of acrylic polymer (B-1) In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube and a thermometer, 95.9 parts by mass of n-butyl acrylate and 4 parts by mass of acrylic acid Part, 0.1 part by mass of 2-hydroxyethyl acrylate, and 200 parts by mass of ethyl acetate were added and the temperature was raised to 72 ° C. while blowing nitrogen under stirring.

  Next, 2 parts by mass of a 2,2′-azobis (2-methylbutyronitrile) solution previously dissolved in ethyl acetate (solid content: 0.1% by mass) was added to the mixture, and the mixture was stirred at 72 ° C. After holding for 4 hours, it was held at 75 ° C. for 5 hours.

  Next, the mixture was diluted with 98 parts by mass of ethyl acetate and filtered through a 200 mesh wire mesh to obtain an acrylic polymer (B-1) solution (nonvolatile content: 40% by mass) having a weight average molecular weight of 1,860,000.

[Comparative Preparation Example 2] Production method of acrylic polymer (B-2) In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet, and a thermometer, 63.9 parts by mass of n-butyl acrylate, 2-ethylhexyl acrylate 32 parts by mass, 4 parts by mass of acrylic acid, 0.1 part by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate were charged, and the temperature was raised to 72 ° C. while blowing nitrogen under stirring.

  Next, 2 parts by mass of a 2,2′-azobis (2-methylbutyronitrile) solution previously dissolved in ethyl acetate (solid content: 0.1% by mass) was added to the mixture, and the mixture was stirred at 72 ° C. After holding for 4 hours, it was held at 75 ° C. for 5 hours.

  Next, the mixture was diluted with 98 parts by mass of ethyl acetate and filtered through a 200 mesh wire mesh to obtain an acrylic polymer (B-2) solution (nonvolatile content: 40% by mass) having a weight average molecular weight of 750,000.

[Example 1]
In a container, with respect to 100 parts by mass of the acrylic polymer (A-1), 15 parts by mass of polymerized rosin ester-based tackifier resin D-125 (Arakawa Chemical Industries, Ltd.) and disproportionated rosin ester-based tackifier resin After mixing and stirring 10 parts by mass of A-125 (manufactured by Arakawa Chemical Industries, Ltd.), ethyl acetate was added to obtain an adhesive solution having a solid content of 31% by mass.

  Next, Vernock D-40 (manufactured by DIC Corporation, trimethylolpropane adduct of tolylene diisocyanate, isocyanate group content 7% by mass, nonvolatile content 40% by mass with respect to 100 parts by mass of the pressure-sensitive adhesive solution. ) After adding 1.4 parts by mass, stirring and mixing so as to be uniform, an adhesive (p-1) was obtained by filtering through a 100 mesh wire net.

  Next, the pressure-sensitive adhesive is coated on the surface of the release liner using a bar coater so that the thickness of the pressure-sensitive adhesive layer after drying is 65 μm, and dried at 80 ° C. for 3 minutes. A layer was made.

Next, the pressure-sensitive adhesive layer was made into a polyolefin foam substrate having a thickness of 170 μm (average bubble diameter in the flow direction of 97 μm, average bubble diameter in the width direction of 130 μm, average bubble diameter in the thickness direction of 39 μm, [average in the flow direction Bubble diameter / average bubble diameter in thickness direction = 2.5, ratio of [average bubble diameter in width direction / average bubble diameter in thickness direction] = 3.3, interlayer strength 29.4 N / cm, apparent density 0 .42 g / cm ³ , 25% compressive strength 391 kPa, surface adjusted to a wetting index of 54 mN / m by corona treatment), and cured for 48 hours in an environment of 40 ° C. (P− 1) was produced. In addition, the tensile strength measured by the method mentioned later of the adhesive layer which the said adhesive sheet (P-1) has was 11.3 N / cm < ² >.

[Example 2]
Instead of the acrylic polymer (A-1) solution, the acrylic polymer (A-2) solution is used, and the compounding amount of Bernock D-40 is changed from 1.4 parts by mass to 1.6 parts by mass. Except for this, a pressure-sensitive adhesive (p-2) and a pressure-sensitive adhesive sheet (P-2) were obtained in the same manner as in Example 1.

[Example 3]
Instead of the acrylic polymer (A-1) solution, the acrylic polymer (A-3) solution is used, and the compounding amount of Bernock D-40 is changed from 1.4 parts by mass to 1.2 parts by mass. Except for this, a pressure-sensitive adhesive (p-3) and a pressure-sensitive adhesive sheet (P-3) were obtained in the same manner as in Example 1.

[Example 4]
Instead of the acrylic polymer (A-1) solution, the pressure-sensitive adhesive (p-4) and pressure-sensitive adhesive sheet (P-4) and pressure-sensitive adhesive sheet (P-4) were prepared in the same manner as in Example 1 except that the acrylic polymer (A-4) solution was used. P-4) was obtained.

[Example 5]
Instead of the acrylic polymer (A-1) solution, the pressure-sensitive adhesive (p-5) and pressure-sensitive adhesive sheet (P-5) and pressure-sensitive adhesive sheet (P-5) were used in the same manner as in Example 1 except that the acrylic polymer (A-5) solution was used. P-5) was obtained.

[Example 6]
Instead of the acrylic polymer (A-1) solution, the pressure-sensitive adhesive (p-6) and pressure-sensitive adhesive sheet (p-6) and pressure-sensitive adhesive sheet (P-6) were used in the same manner as in Example 1 except that the acrylic polymer (A-6) solution was used. P-6) was obtained.

[Example 7]
A pressure-sensitive adhesive (p-7) and a pressure-sensitive adhesive sheet (p-7) and pressure-sensitive adhesive sheet (p-7) were prepared in the same manner as in Example 1 except that the acrylic polymer (A-7) solution was used instead of the acrylic polymer (A-1) solution. P-7) was obtained.

[Example 8]
Instead of the acrylic polymer (A-1) solution, the pressure-sensitive adhesive (p-8) and pressure-sensitive adhesive sheet (p-8) and pressure-sensitive adhesive sheet (P-8) were prepared in the same manner as in Example 1 except that the acrylic polymer (A-8) solution was used. P-8) was obtained.

[Example 9]
As the tackifier resin, 10 parts by mass of the polymerized rosin ester tackifier resin D-125 (Arakawa Chemical Industries, Ltd.) and disproportionated rosin ester tackifier resin A-125 (Arakawa Chemical Industries, Ltd.) 5 A pressure-sensitive adhesive (p-9) and pressure-sensitive adhesive sheet (P-9) in the same manner as in Example 1 except that 15 parts by weight of petroleum-based tackifying resin FTR6125 (Mitsui Chemicals, Inc.) are used. Got.

[Example 10]
Instead of the polyolefin foam substrate having a thickness of 170 μm, a polyolefin foam substrate having a thickness of 200 μm (average bubble diameter in the flow direction is 117 μm, average bubble diameter in the width direction is 159 μm, average bubble diameter in the thickness direction is 43 μm) [Average bubble diameter in the flow direction / average bubble diameter in the thickness direction] = 2.7, ratio of [average bubble diameter in the width direction / average bubble diameter in the thickness direction] = 3.7, interlayer strength 24.5 N / cm, apparent density 0.40 g / cm ³ , 25% compression strength 360 kPa, surface adjusted to a wetting index of 54 mN / m by corona treatment), and the thickness of the pressure-sensitive adhesive layer after drying is from 65 μm A pressure-sensitive adhesive sheet (P-10) was obtained in the same manner as in Example 1 except that the thickness was changed to 50 μm.

[Example 11]
Instead of the polyolefin foam substrate having a thickness of 170 μm, a polyolefin foam substrate having a thickness of 150 μm (average cell diameter in the flow direction is 150 μm, average cell diameter in the width direction is 121 μm, and average cell diameter in the thickness direction is 32 μm. [Average bubble diameter in flow direction / average bubble diameter in thickness direction] = 4.7, ratio of [average bubble diameter in width direction / average bubble diameter in thickness direction] = 3.8, interlayer strength 26.9 N / cm, apparent density 0.51 g / cm ³ , 25% compression strength 521 kPa, surface adjusted to a wetting index of 54 mN / m by corona treatment), and the thickness of the pressure-sensitive adhesive layer after drying is from 65 μm A pressure-sensitive adhesive sheet (P-11) was obtained in the same manner as in Example 1 except that the thickness was changed to 75 μm.

[Comparative Example 1]
Other than using the acrylic polymer (B-1) solution instead of the acrylic polymer (A-1) solution and changing the amount of Vernock D-40 from 1.4 parts by mass to 1.2 parts by mass Obtained the adhesive (q-1) and the adhesive sheet (Q-1) by the same method as Example 1.

[Comparative Example 2]
Other than using the acrylic polymer (B-2) solution instead of the acrylic polymer (A-1) solution and changing the amount of Vernock D-40 from 1.4 parts by mass to 1.6 parts by mass Obtained the adhesive (q-2) and the adhesive sheet (Q-2) by the same method as Example 1.

[Comparative Example 3]
Instead of the polyolefin foam substrate having a thickness of 170 μm, a polyolefin foam substrate having a thickness of 200 μm (average bubble diameter in the flow direction of 173 μm, average bubble diameter in the width direction of 210 μm, average bubble diameter in the thickness direction of 42 μm) [Average bubble diameter in flow direction / average bubble diameter in thickness direction] = 4.1, ratio of [average bubble diameter in width direction / average bubble diameter in thickness direction] = 5.0, interlayer strength 12.9 N / cm, apparent density 0.20 g / cm ³ , 25% compression strength 52 kPa, surface adjusted to a wetting index of 54 mN / m by corona treatment), and the thickness of the pressure-sensitive adhesive layer after drying is from 65 μm A pressure-sensitive adhesive sheet (Q-3) was obtained in the same manner as in Example 1 except that the thickness was changed to 50 μm.

[Measurement Method of Tensile Strength Based on Stress-Strain Curve at 100% and 500% Strain]
The pressure-sensitive adhesive is applied to one side of an arbitrary release liner so that the thickness after drying is 50 μm, dried at 80 ° C. for 3 minutes, and aged at 40 ° C. for 48 hours to form a pressure-sensitive adhesive layer. did. Next, this pressure-sensitive adhesive layer was laminated to a thickness of about 400 μm to prepare a test piece having a marked line interval of 2 cm and a width of 1 cm.

  From the stress-strain curve (so-called SS curve) measured at a tensile speed of 300 mm / min using a tensile tester in a measurement environment at a temperature of 23 ° C. and a humidity of 50%, the amount of strain was measured. Tensile strength was determined at 100% and 500%.

[Measurement method of gel fraction]
The gel fraction described in the table was measured by the method shown below.

  The pressure-sensitive adhesive composition is coated on one side of an arbitrary release liner so that the thickness after drying is 50 μm, dried at 80 ° C. for 3 minutes, and aged at 40 ° C. for 2 days. Form. A sample cut into a 50 mm square was used as a sample.

  Next, after measuring the mass (G1) of the sample, the sample is immersed in a toluene solution at 23 ° C. for 24 hours. The toluene-insoluble matter of the sample after the immersion is separated by filtering through a 300 mesh wire mesh, and the mass (G2) of the residue after drying at 110 ° C. for 1 hour is measured, and the gel fraction is obtained according to the following formula. It was.

    Gel fraction (mass%) = (G2 / G1) × 100

[Measurement method of 180 ° peel adhesive strength]
Under an environment of a temperature of 23 ° C. and a relative humidity of 50% RH, one side of the pressure-sensitive adhesive sheets prepared in Examples and Comparative Examples was lined with a polyethylene terephthalate film having a thickness of 25 μm, and then cut into a length of 120 mm and a width of 20 mm. Next, the other pressure-sensitive adhesive surface is affixed to a stainless steel plate, and the upper surface of the pressure-sensitive adhesive sheet is reciprocated once using a 2 kg roller, and then they are placed in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH for 1 hour. By allowing to stand, a test piece 1 in which the pressure-sensitive adhesive sheet and the stainless steel plate were pressure-bonded was produced.

  Next, using a Tensilon peel tester, the strength when the pressure-sensitive adhesive sheet was peeled off in the 180 ° direction under the condition of a tensile speed of 300 mm / min was measured with the stainless steel plate constituting the test piece fixed.

[Impact resistance evaluation method]
The pressure-sensitive adhesive sheet was cut under an environment of a temperature of 23 ° C. and a relative humidity of 50% RH to prepare two pressure-sensitive adhesive sheets having an outer diameter of 2 mm × 20 mm. Next, in the vicinity of the short side end of one side of a rectangular acrylic plate (Mitsubishi Rayon Co., Ltd. Acrylite MR200 “trademark”, hue: transparent) having a thickness of 2 mm, a width of 25 mm, and a length of 50 mm, the rectangular adhesive Two sheets were stuck in parallel at a position where the interval in the width direction was 45 mm. Affixed to.

  Next, an acrylic plate having a thickness of 2 mm, a width of 25 mm, and a length of 50 mm different from the above is pasted on the adhesive surface of the adhesive sheet, and the upper surface of the adhesive sheet is reciprocated once using a 2 kg roller, Test pieces 2 were prepared by allowing them to stand in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH for 24 hours.

  The test piece 2 was affixed to a stainless steel drop measuring jig (total weight 300 g) with a metal weight using a double-sided adhesive sheet having a width of 25 mm and a length of 50 mm. The patch obtained above was dropped 5 times from a height of 10 cm onto a concrete surface with the test piece 2 facing downward in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH. The presence or absence of peeling or substrate destruction was evaluated. When there is no peeling or the like, the drop height is increased by 10 cm from the previous time, and the presence or absence of peeling of the pressure-sensitive adhesive sheet of the test piece or substrate destruction after dropping five times is confirmed. Thereafter, when there is no peeling or base material destruction, the drop height is increased by 10 cm and the test is repeated in the same manner. Finally, the drop height when peeling of the adhesive sheet of the test piece or base material destruction is observed. The thickness (cm) was measured.

[Evaluation method of static load holding force]
In an atmosphere of a temperature of 23 ° C. and a relative humidity of 50% RH, one adhesive layer of a frame-like pressure-sensitive adhesive sheet having an outer shape of 14 mm × 14 mm and a pressure-sensitive adhesive sheet width of 2 mm is applied to an acrylic plate (Mitsubishi). It was affixed to Rayon Co., Ltd. Acrylite MR200 “trademark”, hue: transparent.

Next, an acrylic plate with an adhesive sheet is attached to a rectangular stainless steel plate having a diameter of 8 mm in the center and a thickness of 2 mm and an outer shape of 65 mm × 30 mm, and then the hole is closed, and then 50 N / cm ² The test piece was pressed for 10 seconds.

  In an atmosphere of a temperature of 40 ° C. and a relative humidity of 50% RH, the test piece was leveled with the acrylic plate side down, and then both ends on the short side of the stainless steel plate were fixed. Next, a weight of 400 g was attached to the center of the acrylic plate, and the acrylic plate was left in a state of being loaded downward.

  The time (minutes) until the distance between the acrylic plate to which the weight was attached and the stainless steel plate was 0.2 mm apart from before the start of the test was measured. In addition, even if 24 hours passed from the start of the test, the increase in the distance between the acrylic plate and the stainless steel plate was less than 0.2 mm, which was described as “1440 minutes or more” in the table described later.

[Push strength]
A rectangular acrylic plate (Mitsubishi Rayon Co., Ltd. Acrylite MR200 “trademark”, hue: transparent) having a thickness of 2 mm and an outer shape of 65 mm × 45 mm in an atmosphere of a temperature of 23 ° C. and a relative humidity of 50% RH. A frame-shaped pressure-sensitive adhesive sheet having a rectangular width of 2 mm and a width of the pressure-sensitive adhesive sheet was pasted.

  Next, affix the adhesive sheet to a rectangular ABS plate (Sumitomo Bakelite Co., Ltd. Toughace REAR003, hue: natural, no wrinkles) with a 10 mm diameter hole in the center and a thickness of 2 mm, 100 × 150 mm The acrylic plate was pasted so that the center of the acrylic plate coincided with the center of the ABS plate, pressed once with a 2 kg roller, and then allowed to stand at 23 ° C. for 1 hour as a test piece. .

  From the ABS side of the test piece, the acrylic plate was pushed at 10 mm / min with a tensile tester equipped with a 8 mm diameter stainless steel probe through a hole in the ABS plate, and the strength at which the acrylic plate was peeled was measured.

Claims (11)

On one or both sides of the foam substrate, the strength of the distortion amount 100% - based tensile strength strain curve is a pressure-sensitive adhesive sheet having 6N / cm ² or more 30 N / cm ² or less is the pressure-sensitive adhesive layer (A) ,
The foam base material has an average bubble diameter in the flow direction and width direction of 160 μm or less, a ratio of [average bubble diameter in the flow direction / average bubble diameter in the thickness direction], and [average bubble in the width direction]. The pressure-sensitive adhesive sheet is a foam substrate having a ratio of diameter / average cell diameter in the thickness direction] of 6 or less and an interlayer strength of 10 N / cm or more.   The pressure-sensitive adhesive sheet according to claim 1, wherein the foam substrate has a thickness of 1500 μm or less.   The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the foam substrate has a 25% compressive strength of 80 kPa or more. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive layer (A) has a thickness in the range of 1 µm to 100 µm.   The said adhesive layer (A) is formed using the adhesive containing an acrylic polymer (a1), tackifying resin (a2), and a crosslinking agent (a3), Either of Claims 1-4 Item 1. The pressure-sensitive adhesive sheet according to item 1. The pressure-sensitive adhesive sheet according to claim 5, wherein the acrylic polymer (a1) is an acrylic polymer having an aliphatic cyclic structure. The pressure-sensitive adhesive sheet according to claim 5 or 6, wherein the acrylic polymer (a1) has a weight average molecular weight of 800,000 or more. The acrylic polymer (a1) is obtained by polymerizing a vinyl monomer component,
An alkyl (meth) having a total content of vinyl monomers other than the (meth) acrylic monomer of 5% by mass or less and a glass transition temperature of the homopolymer of 100 ° C. or higher with respect to the total amount of the vinyl monomer component. The pressure-sensitive adhesive sheet according to any one of claims 5 to 7, wherein the total content of acrylate is 1% by mass or less. The tackifier resin (a2) contains two or more selected from the group consisting of a polymerized rosin ester tackifier resin, a disproportionated rosin ester tackifier resin, a petroleum tackifier resin, and a terpene phenol tackifier resin. The pressure-sensitive adhesive sheet according to any one of claims 5 to 8. The pressure-sensitive adhesive sheet according to any one of claims 1 to 9, which is used for fixing a casing or a lens constituting an electronic device. The electronic device obtained by fixing two or more components which comprise an electronic device using the adhesive sheet of any one of Claims 1-10.

Images