WO2019131166A1

WO2019131166A1 - Pressure-sensitive adhesive tape and article

Info

Publication number: WO2019131166A1
Application number: PCT/JP2018/045831
Authority: WO
Inventors: 啓之中島; 佑輔高橋; 佳美杉浦; 岩崎　剛
Original assignee: Dic株式会社
Priority date: 2017-12-25
Filing date: 2018-12-13
Publication date: 2019-07-04

Abstract

The present invention addresses the problem of providing a pressure-sensitive adhesive tape which can maintain excellent adhesive strength over a long period of time even in cases where sweat, sebum, alcohols, and the like, adhere to the tape, and that exhibits excellent impact resistance. The present invention relates to a pressure-sensitive adhesive tape which has a thickness of 150 µm or more and which has a pressure-sensitive adhesive layer containing an acrylic pressure-sensitive adhesive that contains an acrylic copolymer which has a weight average molecular weight of 400,000 or more and which contains 5-30 mass% of a carboxyl group-containing monomer and 1.0 mass% or less of a hydroxyl group-containing monomer as constituent components.

Description

Adhesive tape and articles

The present invention relates to an adhesive tape that can be used, for example, in the manufacture of various products including electronic devices.

Adhesive tapes are widely used, for example, in the manufacture of various products including electronic devices and automobiles.

The pressure-sensitive adhesive tape is usually required to be able to maintain excellent adhesion over a long period of time regardless of the influence of water or heat. Above all, the adhesive tape used in the production scene of portable electronic devices with many opportunities for human touch and the fixation scene of automobile interior members, for example, can maintain excellent adhesion even when sweat or sebum adheres It is required that the so-called chemical resistance be excellent.

As a pressure-sensitive adhesive tape capable of maintaining excellent adhesion regardless of the influence of sweat, for example, 50 to 90% by mass of (meth) acrylic acid alkyl ester (A1) having an alkyl group having 4 to 12 carbon atoms, carboxyl Group-containing monomer (A2) 3 to 20% by mass, hydroxyl-containing monomer (A3) 3 to 20% by mass, and (meth) acrylic acid alkyl ester (A4) 3 to 15 having an alkyl group of 1 to 3 carbon atoms An acrylic copolymer (A) having a hydroxy group and a carboxy group, having a weight average molecular weight of 700,000 to 2,000,000 and a theoretical Tg of −40 ° C. or less, containing a mass% as a component, and a crosslinking agent (B) A pressure-sensitive adhesive tape obtained using a pressure-sensitive adhesive composition containing and is known (see, for example, Patent Document 1).

However, since the surface of portable electronic devices and automobile interiors frequently have contact opportunities with various substances such as sweat, sebum, alcohol, etc., the above-mentioned adhesive tape is used when such contact is repeated many times. However, this was not sufficient and could cause the adhesive strength to decrease with time.

International Publication 2014/002203 Pamphlet

The problem to be solved by the present invention is to provide a pressure-sensitive adhesive tape capable of maintaining excellent adhesion over a long period even when sweat, sebum, alcohol and the like adhere, and having excellent impact resistance. It is.

The present inventors select a carboxyl group-containing monomer and, if necessary, a hydroxyl group-containing monomer as constituent components, and set their contents as a specific range, and contain an acrylic copolymer having a weight average molecular weight of 400,000 or more. It has been found that the above-mentioned problems can be solved by using an acrylic pressure-sensitive adhesive and a pressure-sensitive adhesive tape having a specific thickness.

That is, the present invention comprises an acrylic copolymer containing 5 to 30% by mass of a carboxy group-containing monomer and 1.0% by mass or less of a hydroxyl group-containing monomer as a component and having an acrylic copolymer having a weight average molecular weight of 400,000 or more. The present invention relates to a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a pressure-sensitive adhesive and having a thickness of 150 μm or more.

The pressure-sensitive adhesive tape of the present invention has a good initial adhesive strength, for example, does not swell easily even when sweat, sebum, alcohol or the like adheres, maintains excellent adhesive strength over a long period of time, and has excellent resistance It has shockability.

In the pressure-sensitive adhesive tape according to the present invention, the pressure-sensitive adhesive layer comprises an acrylic copolymer having a weight average molecular weight of 400,000 or more and containing 5 to 30% by mass of a carboxyl group-containing monomer and 1.0% by mass or less of a hydroxyl group It contains an acrylic adhesive containing a polymer, and is characterized in that the thickness of the adhesive tape is 150 μm or more.

As an embodiment of the pressure-sensitive adhesive tape, for example, a pressure-sensitive adhesive tape having the pressure-sensitive adhesive layer directly or through another layer on one side or both sides of a substrate, a so-called substrateless pressure-sensitive adhesive tape constituted by the pressure-sensitive adhesive layer Can be mentioned. The pressure-sensitive adhesive layer may be a single layer or multiple layers of the same or different composition.

If the pressure-sensitive adhesive tape of the present invention is used to fix, for example, two or more adherends constituting an electronic device or the like, it is preferable to use the embodiment of the double-sided pressure-sensitive adhesive tape. Moreover, when using for a label etc., it is preferable to use in the embodiment of the single-sided adhesive tape which has the said adhesive layer directly or via another layer on the single side | surface of a base material.

Moreover, the adhesive tape of this invention may be stored etc. in the state on which the release film was laminated | stacked on the surface of the adhesive layer.

The adhesive tape of the present invention has a thickness of 150 μm or more in order to provide further excellent durability against sweat, sebum, alcohol and the like and to have excellent impact resistance. It is preferable to use one having a thickness in the range of 160 .mu.m to 500 .mu.m, more preferably one having a thickness in the range of 170 .mu.m to 400 .mu.m, still more preferably 180 .mu.m to 300 .mu.m. It is further preferred to use one having a diameter.

The pressure-sensitive adhesive layer constituting the above-mentioned pressure-sensitive adhesive tape has a further excellent durability against sweat, sebum, alcohol and the like and contributes 5 μm to 100 μm in thickness to contribute to thinning of electronic devices etc. It is preferred to use one having a thickness in the range, more preferably one having a thickness in the range of 10 μm to 80 μm, and still more preferably one having a thickness in the range from 15 μm to 70 μm. preferable.

As the pressure-sensitive adhesive layer, it is preferable to use one having a gel fraction of 40% by mass to 80% by mass, in order to develop further superior durability against sweat, sebum, alcohol and the like, 45 It is more preferable to use one having a gel fraction of mass% to 75 mass%.

As a pressure-sensitive adhesive used for the pressure-sensitive adhesive tape, an acrylic copolymer comprising a copolymer of (meth) acrylate, a carboxy group-containing monomer, and, if necessary, a hydroxyl group-containing monomer is used as a base polymer. A (meth) acrylic pressure-sensitive adhesive containing an additive such as a tackifier resin or a crosslinking agent can be used.

Examples of (meth) acrylates that can be used for the production of the acrylic copolymer include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate Meta) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) Examples thereof include (meth) acrylates in which an alkyl group such as acrylate has 1 to 12 carbon atoms, and one or more of these can be used. Among them, it is preferable to use a (meth) acrylate having 4 to 12 carbon atoms in the alkyl group, and to use a (meth) acrylate having a linear or branched structure having 4 to 8 carbon atoms preferable. In particular, the use of at least one of n-butyl acrylate and 2-ethylhexyl acrylate is preferable because adhesion to an adherend can be easily secured.

The content of the (meth) acrylate having 1 to 12 carbon atoms with respect to the total amount of the acrylic monomer used in producing the acrylic copolymer is preferably 80% by mass or more, and 80 to 98. The content is more preferably 5% by mass, further preferably 85 to 97.0% by mass.

Examples of carboxy group-containing monomers that can be used for producing the acrylic copolymer include acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth) acrylic acid dimer, crotonic acid, ethylene oxide-modified succinate acrylate, etc. Among them, it is preferable to use acrylic acid as a copolymerization component, in order to further enhance the durability to sweat, sebum, alcohol and the like.

The content of the carboxy group-containing monomer relative to the total amount of the acrylic monomer used in producing the acrylic copolymer is 5 to 30% by mass, but is preferably 5.5 to 20% by mass. Preferably, the content is 6 to 15% by mass, which is more preferable in order to exhibit further excellent durability to sweat, sebum, alcohol and the like.

Examples of hydroxyl group-containing monomers that can be used for producing the acrylic copolymer include, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxy Hydroxyl-containing (meth) acrylates such as hexyl (meth) acrylate can be used.

The content of the hydroxyl group-containing monomer with respect to the total amount of acrylic monomers that can be used when producing the acrylic copolymer is 1.0% by mass or less, but is 0.01 to 0.85% by mass. Is preferable, 0.02 to 0.7% by mass is preferable, 0.03 to 0.5% by mass is more preferable, and 0.04 to 0.3% by mass is more preferable. It is particularly preferable that the content is 0.05 to 0.2% by mass in order to exhibit further excellent durability to sweat, sebum, alcohol and the like.

The acrylic copolymer can be obtained by copolymerization by a known polymerization method such as solution polymerization method, bulk polymerization method, suspension polymerization method, emulsion polymerization method, etc. And bulk polymerization are preferred. The polymerization initiation method may be a peroxide type such as benzoyl peroxide or lauroyl peroxide, or a heat initiation method using an azo type thermal polymerization initiator such as azobis isobutyl nitrile, acetophenone type, benzoin ether type, benzyl A method by UV irradiation using a ketal type, acyl phosphine oxide type, benzoin type, benzophenone type photopolymerization initiator, or a method by electron beam irradiation can be arbitrarily selected.

The above-mentioned acrylic copolymer preferably has a weight-average molecular weight in terms of standard polystyrene equivalent determined by gel permeation chromatography (GPC) of 400,000 or more, and 45 to 1.1 million. It is more preferable that the molecular weight be in the range of 1 to 1,000,000 in order to further enhance the durability against sweat, sebum, alcohol and the like.

Here, the measurement of the molecular weight by the GPC method is a standard polystyrene conversion value measured using a Tosoh Corp. GPC apparatus (HLC-8329 GPC), and the measurement conditions are as follows.

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

As the pressure-sensitive adhesive that can be used in the present invention, those containing a tackifying resin can be used in order to obtain a pressure-sensitive adhesive sheet with even more excellent peel adhesion.

As the tackifying resin, for example, rosin-based tackifying resin, polymerized rosin-based tackifying resin, polymerized rosin ester-based tackifying resin, rosin phenol-based tackifying resin, stabilized rosin ester-based tackifying resin, disproportionated rosin ester Tackifier resin, hydrogenated rosin ester tackifier resin, terpene tackifier resin, terpene phenol tackifier resin, petroleum resin tackifier resin, (meth) acrylate resin tackifier resin, etc. can be used .

Further, as the pressure-sensitive adhesive, in order to form a pressure-sensitive adhesive layer having a further excellent cohesive force, it is preferable to use one containing a crosslinking agent.

As said crosslinking agent, 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. Among them, as the crosslinking agent, a crosslinking agent which is easy to use by mixing with the acrylic polymer (b1) prepared in advance or a solution thereof, and which can rapidly accelerate the crosslinking reaction can be used. Specifically, it is more preferable to use an isocyanate crosslinking agent or an epoxy crosslinking agent.

As the isocyanate type crosslinking agent, for example, tolylene diisocyanate, naphthylene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, trimethylolpropane modified tolylene diisocyanate, etc. can be used, and tolylene diisocyanate is used. It is preferable to use trimethylolpropane modified tolylene diisocyanate.

The cross-linking agent is more preferably selected and used such that the gel fraction relative to toluene of the pressure-sensitive adhesive layer is 40% by mass to 80% by mass, and the gel fraction is preferably 45% by mass to 75% by mass. It is more preferable to select and use it to obtain a pressure-sensitive adhesive tape having both of excellent durability and impact resistance against sweat, sebum, alcohol and the like.

In addition, the said gel fraction points out the value measured by the method shown below.
The adhesive coated on the release-treated surface of the release liner to a dry thickness of 50 μm is dried at 100 ° C. for 3 minutes, and then at 40 ° C. 2 The adhesive layer was formed by aging for days.

What cut the said adhesive layer into the square of length 50 mm and width 50 mm was made into the test piece.
After measuring the mass (G1) of the test piece, the test piece was immersed in toluene for 24 hours in an environment of 23 ° C.
The insoluble component to toluene was extracted by filtering the mixture of the said test piece and toluene using the 300 mesh metal-mesh after the said immersion. The mass (G2) of what dried the said insoluble component in 110 degreeC environment for 1 hour was measured.
The gel fraction was calculated based on the mass (G1), the mass (G2), and the following equation.
Gel fraction (mass%) = (G2 / G1) x 100

Examples of the adhesive include plasticizers, softeners, antioxidants, flame retardants, fibers and balloons made of glass and plastic, beads, fillers such as metals, metal oxides and metal nitrides, pigments, dyes, etc. What contains additives, such as a coloring agent, a leveling agent, a thickener, a water repellent, and an antifoamer, can be used.

As the pressure-sensitive adhesive, it is preferable to use one containing a solvent in order to maintain good coating workability and the like. As the solvent, for example, toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, hexane and the like can be used. Moreover, when setting it as a water-based adhesive composition, the aqueous solvent which has water or water as a main can be used.

The pressure-sensitive adhesive tape of the present invention includes, for example, a pressure-sensitive adhesive tape comprising the pressure-sensitive adhesive layer on one side or both sides of a non-woven fabric substrate, a foam substrate or a resin film substrate; A materialless adhesive tape can be mentioned.

The pressure-sensitive adhesive tape of the present invention can be produced, for example, by applying the pressure-sensitive adhesive to one side or both sides of the substrate using a knife coater, a roll coater, a die coater or the like and drying. The pressure-sensitive adhesive tape is formed by applying the pressure-sensitive adhesive to the surface of the release liner in advance using a knife coater, a roll coater, a die coater or the like and drying to form a pressure-sensitive adhesive layer, and then the pressure-sensitive adhesive layer Can be produced by a transfer method in which one side or both sides of a substrate is bonded.

The substrate-less pressure-sensitive adhesive sheet can be manufactured by applying the pressure-sensitive adhesive to the surface of the release liner in advance using a knife coater, a roll coater, a die coater, or the like and drying it.
As a base material which comprises the said adhesive sheet, a resin base material, a foam base material, a nonwoven fabric base material, cloth, paper etc. can be used, for example. Among them, a foam substrate is preferably used as the substrate.

As the foam base material, for example, one having a 25% compressive strength of preferably 20 kPa or more is preferably used, and one having 30 kPa to 1000 kPa is more preferably used, and one having 120 to 700 kPa is used. It is more preferable to use one having a pressure of 200 to 600 kPa, in order to develop a suitable adhesive force to an adherend having a concavo-convex shape and a rough surface.

The 25% compressive strength was measured according to JIS K 6767. The samples cut into 25 corners are overlaid to a thickness of about 10 mm. The sample is sandwiched by a stainless steel plate having a larger area than the sample, and the strength when the sample is compressed about 2.5 mm (25% of the original thickness) at a speed of 10 mm / min at 23 ° C. is measured.

The foam base material has an interlaminar strength of 4 N / cm or more, preferably 6 N / cm to 150 N / cm, more preferably 10 N / cm to 100 N / cm, more preferably 20 N / cm to 60 N / cm. Body substrates can be used.

By using the foam having the interlayer strength in the above range, it is possible to realize good followability to the adherend and excellent impact resistance. Furthermore, in order to improve the yield at the time of manufacturing of portable electronic devices, when peeling off the adhesive sheet or parts from the work-in-progress (rework), or separating the casings or parts for repairing or reusing the finished product, Even when interlayer cracking of the substrate occurs in disassembling and disassembling, the adhesive tape can be easily peeled off.
As the foam base material, for example, one having a 25% compressive strength of preferably 20 kPa or more is preferably used, and one having 30 kPa to 1000 kPa is more preferably used, and one having 120 to 700 kPa is used. It is more preferable to use one having a pressure of 200 to 600 kPa, in order to develop a suitable adhesive force to an adherend having a concavo-convex shape and a rough surface.

By using the foam having the interlayer strength in the above range, it is possible to realize good followability to the adherend and excellent impact resistance. Furthermore, in order to improve the yield at the time of manufacturing portable electronic devices, when peeling off the adhesive tape or parts from the work-in-progress (rework), or separating the case or parts in order to repair or reclaim the finished product, Even when interlayer cracking of the substrate occurs in disassembling and disassembling, the adhesive tape can be easily peeled off.

The interlayer strength is measured by the following method. The adhesive layer of 50 μm thick (not peeled off from the adherend and the foam substrate at the time of the following high-speed peeling test) was bonded one by one on both sides of the foam substrate to evaluate the interlayer strength. Thereafter, it is aged at 40 ° C. for 48 hours to prepare a double-sided pressure-sensitive adhesive tape for interlayer strength measurement. Next, a double-sided adhesive tape with a width of 1 cm and a length of 15 cm (flow direction and width direction of the foam substrate) with the adhesive surface on one side backed by a 25 μm thick polyester film is thickened at 23 ° C and 50% RH. The polyester film is 50 μm in size, 3 cm in width, and 20 cm in length, and is pressure-bonded by one reciprocation of a 2 kg roller and allowed to stand at 60 ° C. for 48 hours. After standing for 24 hours at 23 ° C., fix the side bonded to the 50 μm thick polyester film under 23 ° C. 50% RH to the mounting jig of the high-speed peel tester, and pull the 25 μm thick polyester film at a tensile speed of 15 m Measure the maximum strength when tearing the foam by pulling in the direction of 90 degrees in 1 / min.

The tensile elastic modulus in the flow direction and the width direction of the foam substrate is not particularly limited, but is preferably 200 N / cm ² or more, more preferably 300 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 ~ 800N / cm ^2, and more preferably 600 ~ 700N / cm ^2. At this time, the tensile modulus in the high direction is preferably 700 to 1800 N / cm ² , and more preferably 800 to 1600 N / cm ² . The tensile elongation at the time of cutting in the tensile test is not particularly limited, but preferably 200 to 1500%, more preferably 400 to 1000%, and still more preferably 450 to 800%. is there. With the foam base having the above range of tensile elastic modulus and tensile elongation, it is possible to suppress the deterioration of the processability of the pressure-sensitive adhesive tape and the lowering of the attachment workability even if it is a flexible base having a foam. In addition, when the pressure-sensitive adhesive tape is peeled off, interlayer breakage or chipping of the foam is less likely to occur, and even when an interlayer crack occurs, the pressure-sensitive adhesive tape can be easily peeled off.

In addition, the tensile elasticity modulus of the flow direction of the above-mentioned foam base material and the width direction was measured according to JISK6767. It is the maximum strength of a sample with a length of 2 cm and a width of 1 cm measured using a Tensilon tensile tester under an environment of 23 ° C. and 50% RH under a measurement condition of a tensile speed of 300 mm / min.

The cell structure of the foam substrate is preferably a closed cell structure, as it can effectively prevent water immersion from the cut surface of the foam substrate. The shape of the cells forming the closed cell structure is appropriately followed by setting the shape of the closed cell to be a shape in which the average cell diameter in the flow direction, width direction, or both is longer than the average cell diameter in the thickness direction of the foam. It is preferable because it has sex and cushioning properties.

The average cell diameter in the flow direction and width direction of the foam substrate is 1.2 to 700 μm, preferably 10 to 500 μm, more preferably 30 to 300 μm, and still more preferably 50 to 200 μm. By setting the average cell diameter in the flow direction and width direction to the above range, the number of closed cells per unit width increases even when the width of the adhesive tape is narrowed, so the water immersion path from the cross section of the foam substrate is preferable. Can block it.

The average cell diameter in the thickness direction of the foam substrate is, depending on the thickness of the foam substrate, 1 to 150 μm, preferably 5 to 100 μm, and more preferably 10 to 60 μm.

The ratio of the average cell diameter in the flow direction of the foam substrate to the average cell diameter in the thickness direction of the foam substrate of the foam substrate (average cell diameter in the flow direction / average cell diameter in the thickness direction), And the ratio of the average cell diameter in the width direction of the foam substrate to the average cell diameter in the thickness direction of the foam substrate (average cell diameter in the width direction / average cell diameter in the thickness direction) is 1.2 to It is 15 or less, more preferably 1.2 to 10, and even more preferably 2 to 8. When the ratio is 1.2 or more, the flexibility in the thickness direction can be easily ensured, and the followability is improved. In addition, when the ratio is 15 times or less, the durability against foam interlayer breakage at the time of drop impact is dramatically improved. Moreover, the variation in the flexibility and the tensile strength of the flow direction and the width direction of the foam base is unlikely to occur. The pressure-sensitive adhesive tape using the foam substrate having the ratio of the average cell diameter has suitable followability and cushioning property in the thickness direction, so the pressure at the time of sticking is concentrated at the bonding portion and exists at the bonding interface Since it is easy to push out the air to be bonded, it is possible to realize excellent adhesion that does not cause a gap into which water enters even in bonding rigid bodies.

Further, the ratio of the average cell diameter in the flow direction and the width direction is not particularly limited, but when the flow direction is 1, it is preferably 0.25 to 4 times, more preferably 0.33 to 3 times, still more preferably 0. It is 6 to 1.5 times, particularly preferably 0.7 to 1.3 times. Within the above ratio range, variations in flexibility and tensile strength in the flow direction and width direction of the foam substrate are less likely to occur.

The average cell diameter in the width direction, flow direction, and thickness direction of the foam substrate is measured in the following manner. First, the foam substrate is cut into about 1 cm in both the width direction and the flow direction. Next, the foam digital microscope the cut surface of a substrate (trade name "KH-7700", manufactured by HiROX Co.) After enlarged 200 times, the imaging width direction or flow direction of the switching section of the foam substrate did. In the obtained enlarged image, all the bubble diameters of the bubbles existing in the cut surface of 2 mm for the actual length before enlargement in the flow direction or width direction are measured, and the average bubble diameter is calculated from the average value. The average cell diameter was determined from the results of measurement at 10 arbitrary locations.

Although the apparent density of the foam substrate is not particularly limited, it is easy to achieve both the impact resistance and the excellent adhesion with the adherend by adjusting the interlayer strength, the compressive strength, the average cell diameter and the like within the above range. From 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 , particularly preferably 0.3 to 0.6 g It is ³ cm ³ . In addition, apparent density was measured according to JISK6767. A foam substrate cut into a 4 cm × 5 cm rectangle is prepared for about 15 cm ³ minutes, and its mass is measured to determine an apparent density.

The interlayer strength, compressive strength, tensile modulus and the like of the foam substrate can be appropriately adjusted depending on the material of the substrate to be 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 interlayer strength, 25% compressive strength, tensile modulus and the like, but polyethylene, polypropylene, ethylene-propylene copolymer, ethylene- Polyolefin based foams made of vinyl acetate copolymer, polyurethane based foams, rubber based foams made of acrylic rubber and other elastomers, etc. can be used. A polyolefin-based foam can be preferably used because it is easy to produce a thin closed-cell foam base excellent in buffer absorption and the like.

Among polyolefin-based foams using a polyolefin-based resin, it is preferable to use a polyethylene-based resin because it can be easily produced with a uniform thickness and can easily impart suitable flexibility. In particular, the content of the polyethylene resin in the polyolefin resin 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. Is particularly preferred.

Moreover, as a polyethylene-based resin used for the said polyolefin-type foam, when the polyethylene-based resin obtained using the metallocene compound containing the transition metal of a tetravalent as a polymerization catalyst has narrow molecular weight distribution and it is a copolymer, Since the copolymer component is introduced at almost the same ratio to any molecular weight component, the polyolefin foam can be uniformly crosslinked. For this reason, since the foamed sheet is uniformly crosslinked, it is easy to stretch the foamed sheet uniformly as necessary, and it is preferable because the thickness of the obtained polyolefin resin foam is easily uniformed as a whole.

Further, the polyolefin resin constituting the polyolefin foam may contain a polyolefin resin other than the polyethylene resin obtained by using the metallocene compound containing a tetravalent transition metal as a polymerization catalyst. . As such polyolefin resin, polyethylene resin other than the above, a polypropylene resin, etc. are mentioned. The polyolefin resins may be used alone or in combination of two or more.

As such polyethylene-based resin, for example, linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-α-olefin copolymer containing 50% by weight or more of ethylene, ethylene 50 The ethylene-vinyl acetate copolymer etc. which contain weight% or more are mentioned, These may be used independently and 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, 1-octene and the like It can be mentioned.

The polypropylene-based resin is not particularly limited, and examples thereof include polypropylene and a propylene-α-olefin copolymer containing 50% by weight or more of propylene, and two types of these may be used alone. 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, 1-octene and the like It can be mentioned.

The polyolefin-based foam may be crosslinked, but in the case of foaming the foamable polyolefin-based resin sheet with a thermal decomposition-type foaming agent, it is preferable to be crosslinked.

Next, a method for producing a polyolefin resin foam will be described. The method for producing a 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-based resin composition containing a thermal decomposition-type foaming agent and a foaming aid, and a coloring agent for coloring the foam to black or white, etc. is supplied to an extruder and melt-kneaded, and the sheet is formed from the extruder Manufacturing a foamable polyolefin-based resin sheet by extruding into a sheet, crosslinking the foamable polyolefin-based resin sheet, foaming the foamable polyolefin-based resin sheet, and melting or obtaining the obtained foam sheet A process to soften and stretch the foamed sheet by stretching it in either or both of the flow direction and the 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.

Then, as a method of crosslinking the polyolefin resin foam base material, for example, a method of irradiating a foamable polyolefin resin sheet with ionizing radiation, and blending an organic peroxide in advance to the foamable polyolefin resin composition There is a method of heating the obtained expandable polyolefin resin sheet to decompose the organic peroxide, and the like, 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 base material falls within the above-mentioned preferable range, but a range of 5 to 200 kGy is preferable. In addition, it is preferable to irradiate both sides of the foamable polyolefin-based resin sheet, since irradiation of ionizing radiation is easy to obtain a uniform foaming state, and it is more preferable to make the irradiation dose to both sides the same.

As the organic peroxide, for example, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, 2,2-bis t-Butyl peroxy) octane, n-butyl-4,4-bis (t-butyl peroxy) valerate, di-t-butyl peroxide, t-butyl cumyl 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, cumylperoxy neodecanate, t-butylperoxybenzoate, 2,5-dimethyl-2,5-di ( These include nzoylperoxy) hexane, t-butylperoxyisopropyl carbonate, t-butyl peroxyallyl carbonate and the like, which may be used alone or in combination of two or more.

The amount of the organic peroxide added is preferably 0.01 parts by mass to 5 parts by mass, and more preferably 0.1 parts by mass to 3 parts by mass with respect to 100 parts by mass of the polyolefin resin.

The addition amount of the thermal decomposition type foaming agent in the foamable polyolefin resin composition may be appropriately determined according to the expansion ratio of the polyolefin resin foam base, but 1 mass per 100 mass parts of the polyolefin resin A part to 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 foamable 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 with a salt bath, a method with an oil bath, etc. May be used in combination. Among them, a method of heating with hot air or a method of heating with infrared rays is preferable because the appearance of the surface of the polyolefin resin foam substrate is small on the front and back sides.

And, the stretching of the foam substrate may be carried out after the foamable polyolefin resin sheet is foamed to obtain the foam substrate, or the foamable polyolefin resin sheet may be foamed. . In addition, after extending a foam base after foaming a foamable polyolefin resin sheet and obtaining a foam base, the molten state at the time of foaming is maintained without cooling the foam base. Subsequently, the foam substrate may be stretched, or after the foam substrate is cooled, the foam sheet may be heated again to be in a molten or softened state, and then the foam substrate may be stretched.

Here, the molten state of the foam base refers to a state in which the foam base is heated to the melting point or more of the polyolefin resin constituting the foam base. The softening of the foam base refers to a state in which the foam base is heated to a temperature above the softening point of the polyolefin resin constituting the foam base and below the melting point. By stretching the foam substrate, the cells of the foam substrate can be stretched and deformed in a predetermined direction to produce a polyolefin foam in which the aspect ratio of the cells is in a predetermined range.

Furthermore, in the stretching direction of the foam base, the elongated foamable polyolefin resin sheet is stretched in the flow direction or the width direction, or in the flow direction and the width direction. When the foam substrate is stretched in the flow direction and the width direction, the foam substrate may be simultaneously stretched in the flow direction and the width direction, or may be separately stretched in each direction. .

As a method of stretching the foam base in the flow direction, for example, a longer foamed sheet after foaming than a speed (supplying speed) at which a long foamable polyolefin resin sheet is supplied to the foaming step. A method of stretching the foam substrate in the flow direction by increasing the winding speed (winding speed) while cooling, foaming than the speed of supplying the obtained foam substrate to the drawing step (feed rate) Examples include a method of stretching the foam substrate in the flow direction by increasing the winding speed of the body substrate (winding speed).

In the former method, since the foamable polyolefin resin sheet expands in the flow direction by its own foaming, when stretching the foam substrate in the flow direction, the foam polyolefin resin sheet is foamed. In consideration of the expansion in the flow direction, it is necessary to adjust the feeding 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 in the width direction, both ends in the width direction of the foam base are gripped by a pair of gripping members, and the pair of gripping members are gradually moved in a direction away from each other The method of extending | stretching a foam base material to the width direction by making it carry out is preferable. In addition, since the foamable polyolefin resin sheet expands in the width direction by its own foaming, when the foam base is stretched in the width direction, the expansion in the width direction due to the foam of the foamable polyolefin resin sheet In consideration of the amount, it is necessary to adjust so that the foam substrate is stretched in the width direction more than the amount of expansion.

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

The stretching ratio in the width direction of the polyolefin foam substrate is preferably 1.2 times to 4.5 times, and more preferably 1.5 times to 3.5 times.

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

When the light-shielding property, the hiding property, and the light resistance are imparted to the pressure-sensitive adhesive tape, the foam base is colored black. As black colorants, 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 oxide Black pigments, anthraquinone organic black pigments, and the like can be used. Among them, carbon black is preferable from the viewpoints of cost, availability, insulation, heat resistance to withstand the temperature of the step of extruding the foamable polyolefin resin composition and the heating and foaming step.

When a design, light reflectivity, etc. are imparted to the adhesive tape, the foam base is colored white. As white colorants, titanium oxide, zinc oxide, aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, calcium oxide, tin oxide, barium oxide, cesium oxide, yttrium 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 oxide, talc, silica, alumina, clay, kaolin, phosphoric acid Inorganic white colorants such as titanium, mica, gypsum, white carbon, diatomaceous earth, bentonite, lithopone, zeolite, sericite, etc., silicone resin particles, acrylic resin particles, urethane resin particles, melamine resin particles, etc. And the like can be used white colorant. Among them, aluminum oxide and zinc oxide are preferable from the viewpoints of cost, availability, color tone, heat resistance to withstand the temperature of the step of extruding the foamable polyolefin resin composition and the heating and foaming step.

In the foamable polyolefin resin composition, if necessary, a plasticizer, an antioxidant, a foaming aid such as zinc oxide, and a cell nucleus adjusting material, as long as the physical properties of the polyolefin resin foam base are not impaired. , Thermal stabilizers, flame retardants such as aluminum hydroxide and magnesium hydroxide, antistatic agents, hollow balloons or beads made of glass or plastic, fillers such as metal powder or metal compound, conductive fillers, thermally conductive fillers And the like may be optionally contained in the resin. The polyolefin-based resin foam substrate used in the pressure-sensitive adhesive sheet of the present invention is preferably 0.1% by mass to 10% by mass, with respect to the polyolefin-based resin, in order to maintain appropriate followability and cushioning properties. % To 7% by mass is preferable.

When the coloring agent, the heat decomposable foaming agent, the foaming auxiliary agent, etc. are blended in the foamable polyolefin resin composition, they are supplied to the extruder from the viewpoint of preventing color unevenness, partial excessive foaming and insufficient foaming. It is preferable to make a masterbatch in advance with a thermoplastic resin having high compatibility with the foamable polyolefin resin composition and the foamable polyolefin resin composition in advance.

The foam substrate has surface treatment such as corona treatment, flame treatment, plasma treatment, hot air treatment, ozone / ultraviolet treatment, and application of an easy-adhesion treatment agent in order to improve adhesion with the pressure-sensitive adhesive layer and other layers. It may be done. When the surface treatment is performed by setting the wetting index by the wetting reagent to 36 mN / m or more, preferably 40 mN / m, and more preferably 48 mN / m, good adhesion to the pressure-sensitive adhesive can be obtained. The foam substrate having improved adhesion may be bonded to the pressure-sensitive adhesive layer in a continuous process, or may be wound up once. In the case of temporarily winding the foam substrate, the foam substrate is wound together with a paper such as paper, a film of polyethylene, polypropylene, polyester, etc. in order to prevent the blocking phenomenon of the foam substrates with increased adhesion. Preferably, a polypropylene film or a polyester film having a thickness of 25 μm or less is preferable.

Moreover, as a resin base material which can be used for the said base material, plastic films, such as a polyester film, a polyethylene film, a polypropylene film, a polyvinyl chloride film, etc. can be used, for example. As the resin base material, in order to improve the anchoring properties of the pressure-sensitive adhesive layer, those to which a corona treatment, an anchor coat treatment and the like have been applied can be used.

It is preferable to use a substrate having a thickness of 1 μm to 400 μm as the substrate. When a resin substrate is used as the substrate, it is preferable to use one having a thickness of 1 μm to 150 μm as the resin substrate, and use one having a thickness of 1 μm to 100 μm. It is more preferable to exert the effect of imparting excellent processability of the tape and excellent followability to the adherend. When the foam base is used as the base, the foam base preferably has a thickness of 50 μm to 400 μm, preferably 50 μm to 300 μm. It is more preferable to use the above to impart excellent processability of the tape and excellent followability to the adherend.

As a method for producing the pressure-sensitive adhesive tape of the present invention, for example, in the case of a pressure-sensitive adhesive tape having a substrate (core), the pressure-sensitive adhesive composition is coated on one side or both sides of the substrate and dried. The pressure-sensitive adhesive layer is formed by applying a pressure-sensitive adhesive composition to the surface of a method (direct method) or a release liner and drying or the like, and then transferring the pressure-sensitive adhesive layer to one side or both sides of the substrate Manufacturing method (transfer method).

Moreover, as a manufacturing method of the said substrate-less adhesive tape, the method of forming an adhesive layer, for example by coating an adhesive composition on the surface of a release liner, and drying is mentioned.
Examples of the method for applying the pressure-sensitive adhesive composition to the substrate or release liner include a method using an applicator, a roll coater, a gravure coater, a reverse coater, a spray coater, an air knife coater, a die coater, etc. Be

Examples of the method of drying the pressure-sensitive adhesive composition include a method of drying at 50 ° C. to 140 ° C. for 30 seconds to 10 minutes. After the drying, aging may be further performed in the range of 30 ° C. to 50 ° C. in order to accelerate the curing reaction.

As described above, the pressure-sensitive adhesive tape according to the present invention has good initial adhesion by combining the pressure-sensitive adhesive layer (A) and the base material layer (B), and in the case where sweat, sebum, alcohol or the like is attached. Even if it does, it is what can maintain the outstanding adhesion over a long period, without causing the fall of adhesion.

Therefore, the pressure-sensitive adhesive composition of the present invention is a double-sided tape used for bonding of a casing constituting an electronic device such as a portable electronic terminal or a tablet personal computer, a label for providing design on the surface of the casing, a waterproof tape And medical adhesive tapes can be suitably used.

Hereinafter, the present invention will be described in more detail using examples.

Adjustment Example 1
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen introducing pipe, and a thermometer, 89.94 parts by mass of n-butyl acrylate, 10 parts by mass of acrylic acid, 0.06 parts by mass of 4-hydroxybutyl acrylate, and ethyl acetate 200 parts by mass was charged, and after stirring for 4 hours at 72 ° C., it was held for 5 hours at 75 ° C.

Next, 2 parts by mass (solid content: 0.1% by mass) of a solution of 2,2′-azobis (2-methylbutyronitrile) previously dissolved in ethyl acetate is added to the mixture in the above mixture, and the mixture is 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 a solution of an acrylic copolymer (A-1) having a weight average molecular weight of 590,000.

An adduct of tolylene diisocyanate and trimethylolpropane so that the above-mentioned acrylic copolymer (A-1) has a gel fraction of 54% ("Barnock D-40" manufactured by DIC Corporation, hereinafter, "D-40") ) Was added to give a pressure-sensitive adhesive composition (P-1).

Adjustment Example 2
A pressure-sensitive adhesive composition (P-2) was obtained by adding D-40 to the acrylic copolymer (A-1) so that the gel fraction was 71%.

Adjustment Example 3
An acrylic copolymer (A-2) solution having a weight average molecular weight of 920,000 was obtained in the same manner as in Preparation Example 1 except that 92.94 parts by mass of n-butyl acrylate and 7 parts by mass of acrylic acid were changed. . A pressure-sensitive adhesive composition (P-3) was obtained by adding D-40 to the acrylic copolymer (A-2) so that the gel fraction was 56%.

Adjustment Example 4
Acrylic having a weight average molecular weight of 700,000 in the same manner as in Preparation Example 1 except that 89.9 parts by mass of n-butyl acrylate, 10 parts by mass of acrylic acid, and 0.1 parts by mass of 4-hydroxybutyl acrylate are changed. A copolymer (A-3) solution was obtained. A pressure-sensitive adhesive composition (P-4) was obtained by adding D-40 to the acrylic copolymer (A-3) so that the gel fraction was 60%.

Adjustment Example 5
A pressure-sensitive adhesive composition (P-5) was obtained by adding D-40 to the acrylic copolymer (A-3) so that the gel fraction was 75%.

Adjustment Example 6
An acrylic copolymer (A-4) solution having a weight average molecular weight of 750,000 was obtained in the same manner as in Preparation Example 1 except that 90 parts by mass of n-butyl acrylate and 10 parts by mass of acrylic acid were changed. A pressure-sensitive adhesive composition (P-6) was obtained by adding D-40 to the acrylic copolymer (A-4) so that the gel fraction was 52%.

Example 1
The pressure-sensitive adhesive composition (P-1) obtained in Preparation Example 1 was applied to the release-treated surface of a release liner (polyethylene terephthalate film having a thickness of 75 μm, which has been subjected to release treatment on one side). Of 25 .mu.m and drying at 100.degree. C. for 3 minutes, two pressure-sensitive adhesive layers with a thickness of 25 .mu.m were produced.

Next, the adhesive layer of 25 μm in thickness was attached to both sides of a polyethylene foam of 100 μm in thickness under a 23 ° C. environment, and laminated with a linear pressure of 5 kg / cm from the upper surface of the release liner. .
Thereafter, the mixture was aged at 40 ° C. for 48 hours to obtain a 150 μm-thick double-sided pressure-sensitive adhesive tape (T-1).

Example 2
A 150 μm-thick double-sided pressure-sensitive adhesive tape (T-2) was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive composition (P-2) was used instead of the pressure-sensitive adhesive composition (P-1). .

[Example 3]
A 150 μm-thick double-sided pressure-sensitive adhesive tape (T-3) was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive composition (P-3) was used instead of the pressure-sensitive adhesive composition (P-1). .

Example 4
A 150 μm-thick double-sided pressure-sensitive adhesive tape (T-4) was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive composition (P-4) was used instead of the pressure-sensitive adhesive composition (P-1). .

[Example 5]
A 150 μm-thick double-sided pressure-sensitive adhesive tape (T-5) was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive composition (P-5) was used instead of the pressure-sensitive adhesive composition (P-1). .

[Example 6]
The pressure-sensitive adhesive composition (P-1) obtained in Preparation Example 1 was applied to the release-treated surface of a release liner (polyethylene terephthalate film having a thickness of 75 μm, which has been subjected to release treatment on one side). 200 μm double-sided pressure-sensitive adhesive tape in the same manner as in Example 1 except that two 50 μm-thick adhesive layers are prepared by coating so as to be 50 μm and drying at 100 ° C. for 3 minutes I got (T-6).

[Example 7]
The pressure-sensitive adhesive composition (P-3) obtained in Preparation Example 3 was applied to the release-treated surface of a release liner (a polyethylene terephthalate film having a thickness of 75 μm and subjected to release treatment on one side). 200 μm double-sided pressure-sensitive adhesive tape in the same manner as in Example 1 except that two 50 μm-thick adhesive layers are prepared by coating so as to be 50 μm and drying at 100 ° C. for 3 minutes I got (T-7).

[Example 8]
The pressure-sensitive adhesive composition (P-4) obtained in Preparation Example 4 was applied to the release-treated surface of a release liner (a polyethylene terephthalate film having a thickness of 75 μm and subjected to release treatment on one side). 200 μm double-sided pressure-sensitive adhesive tape in the same manner as in Example 1 except that two 50 μm-thick adhesive layers are prepared by coating so as to be 50 μm and drying at 100 ° C. for 3 minutes I got (T-8).

[Example 9]
A 150 μm-thick double-sided pressure-sensitive adhesive tape (T-9) was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive composition (P-6) was used instead of the pressure-sensitive adhesive composition (P-1). .

[Comparative adjustment example 1]
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen introduction tube, and a thermometer, 95.94 parts by mass of n-butyl acrylate, 4 parts by mass of acrylic acid, 0.06 parts by mass of 4-hydroxybutyl acrylate, and ethyl acetate 200 parts by mass was charged, and after stirring for 4 hours at 72 ° C., it was held for 5 hours at 75 ° C.

Next, 2 parts by mass (solid content: 0.1% by mass) of a solution of 2,2′-azobis (2-methylbutyronitrile) previously dissolved in ethyl acetate is added to the mixture in the above mixture, and the mixture is 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 copolymer (B-1) solution having a weight-average molecular weight of 950,000.
D-40 was blended to the acrylic copolymer (B-1) so that the gel fraction was 65%, to obtain a pressure-sensitive adhesive composition (Q-1).

"Comparative adjustment example 2"
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen introducing pipe, and a thermometer, 64.94 parts by mass of n-butyl acrylate, 35 parts by mass of acrylic acid, 0.06 parts by mass of 4-hydroxybutyl acrylate, and ethyl acetate 200 parts by mass was charged, and after stirring for 4 hours at 72 ° C., it was held for 5 hours at 75 ° C.

Next, 2 parts by mass (solid content: 0.1% by mass) of a solution of 2,2′-azobis (2-methylbutyronitrile) previously dissolved in ethyl acetate is added to the mixture in the above mixture, and the mixture is 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 a solution of an acrylic polymer (B-2) having a weight average molecular weight of 700,000.
D-40 was blended to the acrylic copolymer (B-2) so that the gel fraction was 60%, to obtain a pressure-sensitive adhesive composition (Q-2).

[Comparative adjustment example 3]
88 parts by mass of n-butyl acrylate, 10 parts by mass of acrylic acid, 2 parts by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate in a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen introducing pipe, and a thermometer The mixture was charged, held at 72 ° C. for 4 hours under stirring, and then held at 75 ° C. for 5 hours.

Next, 2 parts by mass (solid content: 0.1% by mass) of a solution of 2,2′-azobis (2-methylbutyronitrile) previously dissolved in ethyl acetate is added to the mixture in the above mixture, and the mixture is 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-3) solution having a weight average molecular weight of 700,000.
D-40 was blended with the acrylic copolymer (B-3) so that the gel fraction was 78%, to obtain a pressure-sensitive adhesive composition (Q-3).

[Comparative adjustment example 4]
89.9 parts by mass of n-butyl acrylate, 10 parts by mass of acrylic acid, 0.1 parts by mass of 4-hydroxybutyl acrylate, and ethyl acetate in a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen introducing pipe, and a thermometer 200 parts by mass was charged, and after stirring for 4 hours at 72 ° C., it was held for 5 hours at 75 ° C.

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

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-4) solution having a weight-average molecular weight of 350,000.
D-40 was blended with the acrylic copolymer (B-4) so that the gel fraction was 64%, to obtain a pressure-sensitive adhesive composition (Q-4).

Comparative Example 1
The pressure-sensitive adhesive composition (Q-1) obtained in Comparative Preparation Example 1 was applied to the release-treated surface of a release liner (polyethylene terephthalate film having a thickness of 75 μm, which has been subjected to release treatment on one side). By coating so as to be 25 μm and drying at 100 ° C. for 3 minutes, two pressure-sensitive adhesive layers with a thickness of 25 μm were produced.

Next, the adhesive layer of 25 μm in thickness was attached to both sides of a polyethylene foam of 100 μm in thickness under a 23 ° C. environment, and laminated with a linear pressure of 5 kg / cm from the upper surface of the release liner. .
Thereafter, the mixture was aged at 40 ° C. for 48 hours to obtain a 150 μm-thick double-sided pressure-sensitive adhesive tape (U-1).

Comparative Example 2
A 150 μm-thick double-sided pressure-sensitive adhesive tape (U-2) was obtained in the same manner as in Comparative Example 1 except that the pressure-sensitive adhesive composition (Q-2) was used instead of the pressure-sensitive adhesive composition (Q-1). .

Comparative Example 3
A 150 μm-thick double-sided pressure-sensitive adhesive tape (U-3) was obtained in the same manner as in Comparative Example 1 except that the pressure-sensitive adhesive composition (Q-3) was used instead of the pressure-sensitive adhesive composition (Q-1). .

Comparative Example 4
The pressure-sensitive adhesive composition (P-2) is used instead of the pressure-sensitive adhesive composition (Q-1), and then 10 μm thick on both sides of a polyethylene foam 100 μm thick under a 23 ° C. environment. A double-sided pressure-sensitive adhesive tape (U-4) having a thickness of 120 μm was obtained in the same manner as in Comparative Example 1 except that the pressure-sensitive adhesive layer was attached.

Comparative Example 6
A 150 μm-thick double-sided pressure-sensitive adhesive tape (U-5) was obtained in the same manner as in Comparative Example 1 except that the pressure-sensitive adhesive composition (Q-4) was used instead of the pressure-sensitive adhesive composition (Q-1). .

[Method of measuring adhesion]
The release liner on one side of the double-sided pressure-sensitive adhesive tape obtained in Examples and Comparative Examples was peeled off, backed with a 50 μm thick SUS foil, and cut into a 5 mm width to obtain a test piece.

The release liner on the other side of the test piece is peeled off and attached to the surface of a stainless steel (SUS) plate (adhesion area 5 mm × 80 mm), and then the upper surface is attached by pressing the 2 kg roll twice. I got a thing.

The patch was allowed to stand under an atmosphere of 23 ° C. and 50% RH for 24 hours, and then left under an atmosphere of 60 ° C. and 90% RH for 3 days. Thereafter, it was left at 23 ° C. and 50% RH for 24 hours.
Next, 180-degree peel strength (N / 5 mm) was measured under an atmosphere of 23 ° C. and 50% RH.

[Method of measuring gel fraction of adhesive layer]
The pressure-sensitive adhesive layer is coated on one side of an optional 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. Were cut into 50 mm squares and used as samples.

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 filtration 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 determined according to the following equation The
Gel fraction (mass%) = (G2 / G1) x 100

[Method for evaluating oleic acid resistance]
The patch obtained in the above [Method of measuring adhesion] is left in an atmosphere of 23 ° C. and 50% RH for 24 hours, and then immersed in an oleic acid solution having a concentration of 99% by mass, 60 ° C. and 90% It was left for 3 days under an atmosphere of RH.
Thereafter, the patch was removed from the solution, washed, and left at 23 ° C. and 50% RH for 24 hours.
Next, the 180 degree peel strength of the test piece constituting the patch was measured under an atmosphere of 23 ° C. and 50% RH.

[Method of evaluating water resistance]
The patch obtained in the above [Determination method of adhesive strength] is left in an atmosphere of 23 ° C. and 50% RH for 24 hours, and then immersed in ion exchange water, under an atmosphere of 60 ° C. and 90% RH It was left for 3 days.

Thereafter, the patch was removed from the solution, washed, and left at 23 ° C. and 50% RH for 24 hours.
Next, the 180 degree peel strength of the test piece constituting the patch was measured under an atmosphere of 23 ° C. and 50% RH.

[Evaluation method of impact resistance]
A 2 mm thick, 50 mm square acrylic board (Mitsubishi Rayon Co., Ltd. Acrilite MR 200 "trade name", hue: transparent) in an environment of temperature 23 ° C and relative humidity 50% RH, with a width of 5 mm and a length of 40 mm Two cut adhesive sheets were stuck in parallel at intervals of 40 mm.

Next, a 2 mm thick, 100 × 150 mm rectangular ABS plate (Tough Ace R EAR 003 manufactured by Sumitomo Bakelite Co., Ltd., hue: natural, no embossing), the acrylic plate attached with the adhesive sheet is used as the acrylic plate. Affixing the sample so that the center and the center of the ABS plate coincide, pressing one reciprocation with a 2 kg roller, and leaving it for 1 hour in an environment of temperature 23 ° C. and relative humidity 50% RH was used as a test piece .

Next, install a U-shaped measurement stand (made of aluminum 5 mm thick) with a length of 150 mm, a width of 100 mm, and a height of 45 mm on the base of Dupont impact tester (manufactured by Tester Sangyo Co., Ltd.) On top of the above, the test piece was placed with the acrylic plate constituting it facing downward.

Next, after dropping a stainless steel hammer core 25 mm in diameter and 300 g in weight from the position of 10 cm from the ABS plate side five times from the position of 10 cm in height, the presence or absence of peeling of the adhesive sheet of the test piece or substrate breakage is evaluated. did. When there is no peeling, 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 after dropping five times and breakage of the substrate is confirmed. After that, if there is no peeling or substrate breakage, the drop height is increased by 10 cm and the same test is repeated, and finally the falling height when peeling of the adhesive sheet of the test piece or substrate breakage is recognized (Cm) was measured.

:: The drop height was 90 cm or more.
:: The drop height was 80 cm or more and less than 90 cm.
B: The drop height was 70 cm or more and less than 80 cm.
X: The drop height was less than 70 cm.

Claims

An adhesive comprising an acrylic pressure-sensitive adhesive comprising an acrylic copolymer containing 5 to 30% by mass of a carboxy group-containing monomer and 1.0% by mass or less of a hydroxyl group-containing monomer as a component and having a weight average molecular weight of 400,000 or more. The adhesive tape which has an agent layer and whose thickness of an adhesive tape is 150 micrometers or more.
The pressure-sensitive adhesive tape according to claim 1, wherein the thickness of the pressure-sensitive adhesive layer is 5 μm to 100 μm.
3. The pressure-sensitive adhesive tape according to claim 1, further comprising a pressure-sensitive adhesive layer containing 0.01 to 1.0% by mass of the hydroxyl group-containing monomer as a component.
The pressure-sensitive adhesive tape according to any one of claims 1 to 3, wherein the gel fraction of the pressure-sensitive adhesive layer is 40 to 80% or less.
The pressure-sensitive adhesive tape according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive layer is provided on one side or both sides of the substrate directly or through another layer.
The pressure-sensitive adhesive tape according to any one of claims 1 to 5, wherein the substrate is a foam substrate.
The 180 ° peel strength after leaving in an atmosphere of 60 ° C. and 90% RH for 3 days while being immersed in an oleic acid solution having a concentration of 99% by mass is 4N / 5 mm or more. The adhesive tape as described in a term.