JP5556987B2 - Double-sided adhesive tape - Google Patents

Description

  The present invention relates to a double-sided pressure-sensitive adhesive tape having a foam base material as a core.

  In portable electronic devices such as electronic notebooks, mobile phones, PHS, cameras, music players, and televisions, double-sided adhesive tape is used to secure various members and modules, including bonding of the protective panel and casing of the information display unit. Has been. Various functions are required to secure a competitive advantage in the market, and one of them is required to provide a waterproof function.

For example, the pressure-sensitive adhesive tape used for fixing electronic parts has a maximum value of loss tangent (tan δ) in a temperature range of −40 to −15 ° C., and has a surface adhesive strength of 19 N / A double-sided pressure-sensitive adhesive sheet in which pressure-sensitive adhesive layers of cm ² or more are provided on both sides of a support is disclosed (see Patent Document 1). The double-sided pressure-sensitive adhesive sheet has a specific pressure-sensitive adhesive layer, has a good adhesive force, and has excellent impact resistance such that parts are not easily dropped due to an impact when the object falls. However, in the case of bonding between rigid bodies, such as bonding between a protective panel and a casing or bonding between a casing and a casing, the double-sided pressure-sensitive adhesive sheet makes it difficult to obtain complete adhesion at the bonding surface with the adherend. If there is a slight gap, water may have entered.

  As a double-sided adhesive tape with excellent adhesion, an acrylic resin having a foam as a base material and a temperature at which the maximum value of loss tangent (tan δ) is -25 ° C. or lower and a holding time in a holding test at 0 ° C. is 24 hours or longer. A double-sided adhesive tape having an adhesive layer is disclosed (see Patent Document 2). The double-sided adhesive tape is excellent in adhesion to adherends, and can be suitably joined between members when the members are adhered to each other. However, it is difficult to suppress a slight gap at the interface between the member and the adhesive layer simply by using a foam as a base material. If there is a gap or a float that allows water to enter even at a part of the interface, Since the intrusion path of water is enlarged, it is difficult to realize waterproofness. In particular, in portable electronic devices, it is difficult to provide sufficient waterproofness when narrow tape widths and thin tape thicknesses are required due to the demand for narrower frames and thinner thickness due to the recent increase in screen size. Met.

  In addition, for portable electronic devices, in order to improve the manufacturing yield, double-sided adhesive tape or parts that have failed to be joined are peeled off from the work in progress (rework), or the finished product is repaired, recycled, or reused. Cases and parts may be separated, disassembled, and disassembled. However, with double-sided adhesive tapes of conventional foam base materials, the foam base material is likely to remain on the surface of the part due to interlaminar failure and difficult to remove. The efficiency of the operation of re-attaching a new double-sided adhesive tape after removing the housing from the housing and parts, the yield of the housing and parts, products, and the recycling rate were reduced.

  However, the conventional foam base material has been required to have softness (compression strength) when compressed in the thickness direction, but there is a concept for strength (interlayer strength) when pulled in the thickness direction. There wasn't. Further, when the adhesive strength of the pressure-sensitive adhesive is simply lowered, the adhesion to the adherend is also lowered, so that it is difficult to impart sufficient waterproofness.

JP 2005-187513 A JP 2005-281360 A

  The problem to be solved by the present invention is to provide a double-sided pressure-sensitive adhesive tape excellent in adhesion and followability with an adherend, reworkability and removability.

  Moreover, in addition to the said subject, it is providing the waterproof double-sided adhesive tape which has the outstanding waterproof function and was suitable for the electronic device use.

  Furthermore, in addition to the said subject, it is providing the double-sided adhesive tape for waterproofing which has the outstanding impact resistance and was suitable for the portable electronic device use.

  As a result of diligent research, the present inventors have determined that both sides of a rigid body can be bonded together by using a foam base material having a specific flexibility and interlayer strength as a base material and an adhesive having a specific composition and blending. The present inventors have found that excellent adhesion between the adhesive tape and the adherend, rework suitability and removability can be realized, and that water immersion can be effectively prevented, and the above problems have been solved.

  That is, the present invention is a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both sides of a foam base material, wherein the foam base material has an interlayer strength of 12 N / cm or more and a 25% compressive strength of 30 to 170 kPa, Acrylic pressure-sensitive adhesive composition in which the pressure-sensitive adhesive layer contains an acrylic copolymer having (meth) acrylate having 4 to 12 carbon atoms and a vinyl monomer having a carboxyl group as monomer components, and a polymerized rosin ester-based tackifier resin The present invention provides a double-sided pressure-sensitive adhesive tape characterized by comprising a product.

  The double-sided pressure-sensitive adhesive tape of the present invention is less likely to cause interlaminar fracture of the foam base material, and can easily be peeled off without causing the adhesive to remain on the component surface even when interlaminar cracks occur. When removing double-sided adhesive tape or parts that have failed to be joined from hanging products (rework), or when separating or disassembling or disassembling the case or parts to repair, recycle, or reuse finished products such as portable electronic devices In addition, it is possible to improve the efficiency of removing a double-sided pressure-sensitive adhesive tape from a housing or part and then re-applying a new double-sided pressure-sensitive adhesive tape, the yield of the housing, parts, products, and the recycling rate.

  Furthermore, it exhibits suitable adhesion to the adherend, can effectively prevent water from entering from the adhesion gap, and has an excellent waterproof function. For this reason, the waterproof function can be effectively imparted even in a portable electronic device or the like in which the thickness is reduced, the volume limit in the housing is severe, and it is difficult to provide a separate water sealing means.

  The present invention is a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both surfaces of a foam base material, wherein the foam base material has an interlayer strength of 12 N / cm or more and a 25% compressive strength of 30 to 170 kPa. Acrylic pressure-sensitive adhesive composition in which the agent layer contains an acrylic copolymer having (meth) acrylate having 4 to 12 carbon atoms and a vinyl monomer having a carboxyl group as monomer components, and a polymerized rosin ester-based tackifier resin It is a double-sided adhesive tape characterized by comprising.

[Foam substrate]
The foam base material used in the present invention is a foam base material having an interlayer strength of 12 N / cm or more, preferably 15 to 40 N / cm, more preferably 18 to 35 N / cm. By using a foam having an interlayer strength within the above range, it is possible to impart ease of peeling of the double-sided pressure-sensitive adhesive tape even when an interlayer crack occurs in the flexible foam base material.

Interlaminar strength is measured for interlaminar strength by first affixing a 50 μm thick adhesive layer on both sides of the foam to be evaluated for interlaminar strength and then aging at 40 ° C. for 48 hours. Make double-sided adhesive tape.
Next, a double-sided adhesive tape sample having a width of 2 cm and a length of 10 cm (flow direction of the polyolefin-based foam) with the adhesive surface on one side lined with a 25 μm-thick polyester film was placed on a stainless steel plate (surface) at 23 ° C. and 50% RH. Is applied to the # 360 water-resistant abrasive paper with a hairline treatment) with a 2 kg roller reciprocating once, and left at 40 ° C. for 48 hours. After standing at 23 ° C. for 24 hours, the strength when the foam is torn in the direction of 90 ° at a tensile speed of 300 mm / min at 23 ° C. and 50% RH is measured.

  The foam base material used in the present invention is a foam base material having a 25% compressive strength of 30 to 170 kPa, preferably 40 to 150 kPa. By using a foam base material with a compressive strength of 25% within the above range, it has excellent adhesion to the adherend, and also preferably follows an adherend having an uneven shape or a rough surface. Excellent adhesion. In addition, since the foam base material of the compressive strength has an appropriate cushioning property, the pressure at the time of sticking tends to concentrate on the joint portion and easily push out the air present at the adhesion interface. Excellent adhesion without causing a gap for water to enter can be realized.

  For the 25% compressive strength, samples cut into 50 mm squares are overlapped until the thickness is about 10 mm. The sample is sandwiched with a plate having a larger area than the sample, and the sample is compressed by about 2.5 mm (25% of the original thickness) at 23 ° C. at a speed of 10 mm / min, stopped, and the strength after 20 seconds has passed. taking measurement.

As for the foam base material used for this invention, the tensile elasticity modulus of a foam base material is 200 N / cm < ² > or more. The tensile strength per unit width is 10 N / cm or more, preferably 12.5 N / cm or more, more preferably 14 N / cm or more. Further, the cutting elongation is not particularly limited, but is 100 to 1000%, preferably 300 to 700%. With a foam base material having a tensile elastic modulus, tensile strength, and cut elongation within the above ranges, deterioration in workability, tearing, and deterioration in pasting workability of a double-sided pressure-sensitive adhesive tape can be suppressed even with a foamed flexible base material. Moreover, when peeling a double-sided adhesive tape, it is hard to generate | occur | produce the interlayer fracture of a foam, and even when an interlayer crack generate | occur | produces, the ease of peeling of a double-sided adhesive tape can be provided.

  In addition, the above-mentioned tensile elasticity modulus and the tensile strength per width are 23 degreeC and 50% RH, using a Tensilon tensile tester for the sample of a mark length 2cm (flow direction of a foam base material), and a width 1cm. It is the maximum strength measured under measurement conditions with a tensile speed of 300 mm / min.

The foam structure of the foam base material used in the present invention is preferably a closed cell structure because water can be effectively prevented from being cut from the cut surface of the foam base material. The shape of the bubbles that form the closed cell structure is not particularly limited, but the closed cells with a longer average cell size in the flow direction and / or width direction than the average cell size in the thickness direction of the foam are suitable for cushioning. This is preferable.
The expansion ratio of the foam base material is not particularly limited, but it is easy to realize both excellent adhesion to the adherend and ease of peeling by adjusting the interlayer strength, compressive strength, etc. within the above ranges. 12 times, preferably 2 to 8 times, more preferably 2.4 to 5 times.

  The average cell diameter in the thickness direction of the foam substrate is 1 to 200 μm, preferably 5 to 150 μm, more preferably 10 to 100 μm, although it depends on the thickness of the foam. The average cell diameter in the flow direction and the width direction of the foam substrate is preferably 1.2 to 700 μm, more preferably 10 to 500 μm, and still more preferably 100 to 400 μm. By setting the average cell diameter in this range, it is easy to maintain closed cells even when the width of the double-sided pressure-sensitive adhesive tape is narrowed, and the water immersion path from the cross section of the foam substrate can be suitably blocked.

  The ratio of the average bubble diameter is not particularly limited, but the ratio of the average bubble diameter in the flow direction of the foam substrate to the average bubble diameter in the thickness direction of the foam substrate (average bubble diameter in the flow direction / thickness direction). (Average bubble diameter) is preferably 1.2 to 15, more preferably 2 to 9. 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 15 is preferred, more preferably 2-11. Moreover, it is more preferable that the ratio range is in both the flow direction and the width direction. If the ratio is 1.2 or more, it is easy to ensure flexibility in the thickness direction, so that followability is improved. Further, when the ratio is 15 times or less, variations in flexibility and tensile strength in the flow direction and the width direction of the foam base material hardly occur.

  Furthermore, the ratio of the average cell diameter in the flow direction and the width direction is preferably 0.25 to 4 times, more preferably 0.33 to 3 times when the flow direction is 1. Within the above ratio range, variations in flexibility and tensile strength in the flow direction and width direction of the foam substrate are unlikely to occur.

  The average cell diameter in the width direction and the flow direction of the foam substrate is measured as follows. First, the foam base material is cut into 1 cm in both the width method and the flow direction. Next, after enlarging the central part of the cut surface of the foam base material 50 times with a scanning electron microscope (SEM), the cut surface of the foam base material is photographed over the entire length in the base material thickness direction. The cross section of the foam base material in the width direction or the flow direction is photographed so that it falls within the range. In the obtained photograph, all the bubble diameters existing on the cut surface having an actual length of 2 mm before expansion in the flow direction or the width direction are measured, and the average bubble diameter is calculated from the average value.

The average cell diameter in the thickness direction of the foam substrate is measured in the following manner. First, the thickness of the foam base material photographed with SEM is measured. Next, SEM photography is performed under the same conditions as the measurement of the average bubble diameter in the flow direction of the foam substrate. Next, in the obtained photograph, the number of bubbles in the thickness direction existing at an arbitrary position of the foam base material is visually counted, and the average cell diameter in the thickness direction is calculated from the following formula.
Average cell diameter in the thickness direction (μm) = thickness of the foam substrate (μm) / number of cells This is measured at three arbitrary locations, and the average value is taken as the average cell size in the thickness direction.

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

  Although the thickness of a foam base material should just be adjusted suitably with the aspect to be used, it is 50-1200 micrometers. In the case of fixing electronic device parts, particularly small and thin portable electronic devices, since a thin tape thickness is required, the substrate thickness is preferably 50 to 500 μm, and preferably 70 to 400 μm. preferable.

  Such a foam base material is obtained by supplying a polyolefin resin, a pyrolytic foaming agent and the like to an extruder, melt-kneading, and extruding a foamable polyolefin resin sheet formed by extruding into a sheet form from the extruder. Examples thereof include a crosslinked polyolefin resin foam obtained by foaming, stretching and thinning after crosslinking with a wire. As the polyolefin resin, conventionally known ones can be used, but those containing 40% by mass or more of a polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal are preferable. Further, after foaming the foam, the foamed sheet may be sliced in the thickness direction, and then stretched and covered with a hot roll.

  Additives to foam bases, if necessary, plasticizers, softeners, antioxidants, flame retardants, fillers such as glass and plastic fibers, balloons, beads, metal powders, pigments, dyes, etc. Known colorants, leveling agents, thickeners, water repellents, antifoaming agents, and the like can be optionally added to the resin.

  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.

[Adhesive layer]
The pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape of the present invention includes an acrylic copolymer having 4 to 12 carbon atoms (meth) acrylate and a vinyl monomer having a carboxyl group as monomer components, and a polymerized rosin. It consists of an acrylic adhesive composition containing ester-type tackifying resin.

  Examples of the (meth) acrylate having 4 to 12 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, n -Monomers such as octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and one or more of these are used. . Among these, (meth) acrylates having an alkyl group with 4 to 8 carbon atoms, particularly n-butyl acrylate, are preferable because they can easily ensure adhesion to the adherend and are excellent in cohesion and resistance to sebum. The content of n-butyl acrylate is preferably 60% by mass or more, and more preferably 90% by mass or more of all (meth) acrylates having 4 to 12 carbon atoms.

  The content of (meth) acrylate in the acrylic copolymer is preferably 80 to 98.5% by mass, and 90 to 98.5% by mass in the monomer component constituting the acrylic copolymer. It is more preferable.

  As the vinyl monomer having a carboxyl group, acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth) acrylic acid dimer, crotonic acid, ethylene oxide-modified succinic acid acrylate, etc. can be used. It is preferable to use it as a polymerization component.

  The content of the vinyl monomer having a carboxyl group in the acrylic copolymer is preferably 0.5 to 10.0% by mass in the monomer component constituting the acrylic copolymer, and 1.5 to 5.0% by mass. % Is more preferable.

  Furthermore, the acrylic copolymer used in the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape of the present invention contains a vinyl monomer having a tertiary amide skeleton in the molecule as a monomer component. Excellent strength and can suppress excessive improvement in adhesive strength. Resin such as polystyrene, ABS, acrylic, polycarbonate, polyamide polyester, polypropylene, polyurethane, phenolic resin, stainless steel, aluminum, etc., which are materials for casings and parts of electronic devices It is preferable in terms of both good adhesion, rework suitability and removability for metals such as galvanized steel sheets, glass and the like.

  As a vinyl monomer having a tertiary amide skeleton in the molecule, N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, N, N-dimethylacrylamide, etc. can be used, among which N-vinylpyrrolidone is a copolymer component. It is preferable to use as.

  The content of the vinyl monomer having a tertiary amide skeleton in the molecule of the acrylic copolymer is preferably 0.5 to 5.0% by mass in the monomer component constituting the acrylic copolymer. -3.0 mass% is more preferable.

  Moreover, when using an isocyanate type crosslinking agent as a crosslinking agent of the acrylic copolymer used for this invention, use of a hydroxyl-containing vinyl monomer is preferable as a vinyl monomer which has a functional group which reacts with this.

  Examples of the vinyl monomer having a hydroxyl group include hydroxyl groups such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate and the like. (Meth) acrylate can be used, and 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are particularly preferable. The content of the hydroxyl group-containing vinyl monomer that reacts with the isocyanate-based crosslinking agent is preferably 0.01 to 1.0% by mass of the monomer component constituting the acrylic copolymer, and is 0.03 to 0.3% by mass. % Is particularly preferred.

  Other vinyl monomers include vinyl acetate, sulfonic acid group-containing monomers such as 2-acrylamido-2-methylpropane sulfonic acid, (meth) acrylates having 1 to 3 carbon atoms, (meth) acrylates having 13 or more carbon atoms, isobornyl ( Known vinyl monomers such as (meth) acrylate and styrene are listed.

  The content of the other vinyl monomer is preferably 1.5 to 20% by mass, more preferably 1.5 to 10% by mass, in the monomer component constituting the acrylic copolymer. More preferably, it is 8 mass%. By containing in the said range, it is easy to adjust the cohesive force, holding force, and adhesiveness of an adhesive to a suitable range.

  The acrylic copolymer can be obtained by copolymerization by a known polymerization method such as a solution polymerization method, a cage polymerization method, a suspension polymerization method, or an emulsion polymerization method. A combination method or a bulk polymerization method is preferred. Polymerization can be initiated by peroxides such as benzoyl peroxide and lauroyl peroxide, thermal initiation using azo-based thermal polymerization initiators such as azobisisobutylnitrile, acetophenone-based, benzoin ether-based, benzyl A starting method by ultraviolet irradiation using a ketal-based, acylphosphine oxide-based, benzoin-based or benzophenone-based photopolymerization initiator, or a method by electron beam irradiation can be arbitrarily selected.

  As for the molecular weight of the acrylic copolymer, the weight average molecular weight in terms of standard polystyrene measured by gel permeation chromatography (GPC) is 400,000 to 1.6 million, preferably 600 to 1.2 million.

  In the acrylic pressure-sensitive adhesive composition used in the present invention, it is preferable to use a polymerized rosin ester-based tackifying resin in order to achieve both adhesion to the adherend, rework suitability and removability. The softening point of the polymerized rosin ester tackifying resin is 100 to 180 ° C, preferably 120 to 160 ° C.

  The compounding quantity of superposition | polymerization rosin ester type tackifying resin is 10-40 mass parts with respect to 100 mass parts of acrylic copolymers, Preferably it is 13-30 mass parts. In addition, 1 type (s) or 2 or more types may be used for superposition | polymerization rosin ester type tackifying resin.

  In addition, the acrylic pressure-sensitive adhesive composition used in the present invention contains 1 tackifying resin other than the polymerized rosin ester-based tackifying resin for the purpose of adjusting the adhesion with the adherend, the reworkability and the removability. More than one type can be used. Other tackifying resins include rosin, polymerized rosin, rosin phenol, stabilized rosin ester, disproportionated rosin ester, hydrogenated rosin ester, terpene, terpene phenol, petroleum resin, ( Examples thereof include (meth) acrylate resins. When used in an emulsion-type pressure-sensitive adhesive composition, it is preferable to use an emulsion-type tackifying resin.

  Of these, disproportionated rosin ester-based tackifier resin, rosin phenol-based tackifier resin, hydrogenated rosin ester-based tackifier resin, and (meth) acrylate-based resin are preferable, and disproportionated rosin having a softening point of 60 to 130 ° C. An ester tackifying resin is particularly preferred.

  The amount of the other tackifier resin used is preferably equal to or less than the amount of the polymerized rosin ester-based tackifier resin with respect to 100 parts by mass of the acrylic copolymer, more preferably 100 masses of the acrylic copolymer. The total amount of tackifying resin to part is 10 to 30 parts by mass. By setting the ratio between the two in this range, it becomes easy to ensure adhesion with the adherend.

  In the acrylic pressure-sensitive adhesive composition, it is preferable to crosslink the pressure-sensitive adhesive in order to increase the cohesive strength of the pressure-sensitive adhesive layer. Examples of such a crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, a metal chelate crosslinking agent, and an aziridine crosslinking agent. Among these, a crosslinking agent of a type that is added after the completion of polymerization and causes the crosslinking reaction to proceed is preferable, and an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent that are highly reactive with a (meth) acrylic copolymer are preferable. An isocyanate-based cross-linking agent is more preferable because adhesion to the substrate is improved.

  Examples of the isocyanate-based crosslinking agent include tolylene diisocyanate, naphthylene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and trimethylolpropane-modified tolylene diisocyanate. Particularly preferred are trifunctional polyisocyanate compounds. Examples of the trifunctional isocyanate compound include tolylene diisocyanate, trimethylolpropane adducts thereof, and triphenylmethane isocyanate.

  As an index of the degree of cross-linking, the value of the gel fraction for measuring the insoluble content after the pressure-sensitive adhesive layer is immersed in toluene for 24 hours is used. The gel fraction is preferably 25 to 70% by mass. More preferably in the range of 30 to 60% by mass, and still more preferably in the range of 33 to 55% by mass, both cohesion and adhesiveness are good.

The gel fraction is measured as follows. On the release sheet, the pressure-sensitive adhesive composition was applied so that the thickness after drying was 65 μm, dried at 100 ° C. for 5 minutes, and aged at 40 ° C. for 2 days. To do. Next, the weight (G1) of the sample before being immersed in toluene is measured in advance, and the toluene-insoluble matter of the sample after being immersed in a toluene solution at 23 ° C. for 24 hours is filtered by a 300-mesh wire mesh. The weight (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

  Additives include plasticizers, softeners, antioxidants, fillers such as glass and plastic fibers, balloons, beads, and metal powders, colorants such as pigments and dyes, leveling agents, and thickeners as necessary. Known agents such as an agent, a water repellent, and an antifoaming agent can be optionally added to the pressure-sensitive adhesive composition.

  The pressure-sensitive adhesive layer used for the double-sided pressure-sensitive adhesive tape of the present invention preferably has a temperature at which the maximum value of loss tangent (tan δ) at a frequency of 1 Hz is −30 ° C. to 10 ° C. In particular, in improving the drop impact resistance in a low temperature environment, it is more preferably −30 ° C. to 0 ° C., and further preferably −25 ° C. to −5 ° C.

  In the double-sided pressure-sensitive adhesive tape of the present invention, the temperature showing the maximum value of loss tangent (tan δ) at a frequency of 1 Hz is preferably −30 ° C. to 20 ° C., more preferably −30 ° C. to 10 ° C., and further preferably. Is −25 ° C. to 5 ° C. The maximum value of loss tangent (tan δ) at a frequency of 1 Hz is 1.0 or less, preferably 0.8 or less. By setting the temperature indicating the maximum value of the loss tangent of the pressure-sensitive adhesive layer or the maximum value of the loss tangent of the double-sided adhesive tape and the temperature indicating the maximum value within this range, good adhesion to the adherend at room temperature or It becomes easy to provide drop impact resistance in a low temperature environment of 0 ° C. or lower.

The storage elastic modulus (G ′) at a frequency of 1 Hz of the pressure-sensitive adhesive layer used in the double-sided pressure-sensitive adhesive tape of the present invention is not particularly defined as long as the loss tangent (tan δ) is satisfied, but the storage elasticity at 20 ° C. When the rate (G ′) is 2.6 × 10 ⁵ Pa or more, preferably 3.0 × 10 ⁵ Pa or more, an increase in internal pressure accompanying an increase in device temperature in an electronic device having high airtightness, or a water depth of 1 m It becomes easy to impart resistance (airtightness) when a force equal to or higher than the water pressure (0.11 MPa) is applied from the direction in which the component fixed with the double-sided pressure-sensitive adhesive tape is peeled off.

  The loss tangent (tan δ) is obtained from the equation of tan δ = G ″ / G ′ from the storage elastic modulus (G ′) and loss elastic modulus (G ″) obtained by dynamic viscoelasticity measurement by temperature dispersion. From the dynamic viscoelasticity measurement by temperature dispersion, the maximum value of the loss tangent (tan δ) at a certain frequency and the temperature indicating the maximum value are obtained.

  Dynamic viscoelastic properties are the types and ratios of monomers used in the acrylic copolymer constituting the pressure-sensitive adhesive, types and amounts of polymerization initiators, crosslinking agents, and polymerized rosin ester-based tackifying resins. It can adjust by selecting suitably the kind, usage-amount, polymerization method, etc. of these.

  The dynamic viscoelastic properties of the pressure-sensitive adhesive layer are defined by the loss tangent of the dynamic viscoelastic spectrum or the loss tangent and the storage elastic modulus at a specific frequency and a specific temperature. It is defined by the temperature indicating the maximum value of the loss tangent of the viscoelastic spectrum or the maximum value of the loss tangent. In the measurement of dynamic viscoelasticity, using a viscoelasticity testing machine (Rheometrics, trade name: Ares 2KSTD), a test piece is sandwiched between parallel disks which are measuring parts of the testing machine, and the frequency is 1 Hz. The storage elastic modulus (G ′) and loss elastic modulus (G ″) from −50 ° C. to 150 ° C. are measured. The test piece is formed by forming an adhesive layer or a double-sided adhesive tape to a thickness of about 2 mm, Measure between them.

  The thickness of the pressure-sensitive adhesive layer used in the present invention is 10 to 100 μm in terms of the thickness of one side because it is easy to ensure adhesion with the adherend, rework suitability and removability even when a thin tape is used. Preferably, it is 30-80 micrometers.

  Although it does not specifically limit as a release sheet used for this invention, At least one surface of base materials, such as synthetic resin films, such as polyethylene, a polypropylene, and a polyester film, paper, a nonwoven fabric, cloth, a foam sheet, metal foil, and these laminated bodies In addition, examples in which a release treatment such as a silicone treatment, a long-chain alkyl treatment, a fluorine treatment or the like for improving the peelability from the adhesive are given.

  Among these, a polyethylene-laminated paper and a release sheet in which a silicone release treatment is performed on one side of a polyester film are preferable.

[Double-sided adhesive tape]
The double-sided pressure-sensitive adhesive tape of the present invention exhibits suitable adhesion to the adherend by using the foam base material and the pressure-sensitive adhesive layer, and is less likely to cause interlaminar fracture of the foam base material. If adhesive occurs, the adhesive can be easily peeled off without remaining on the surface of the part, so the double-sided adhesive tape or parts that have failed to be joined can be removed (rework) from the work-in-progress when manufacturing portable electronic devices, etc. When separating, disassembling, or disassembling the housing or parts for repairing, recycling, or reusing finished products such as electronic devices, remove the double-sided adhesive tape from the housing or parts, and then reapply a new double-sided adhesive tape. Efficiency, component yield, and recycling rate can be improved. Furthermore, in fixing components of an electronic device having a waterproof function, it is possible to effectively prevent water from entering from the close contact gap and to have an excellent waterproof function.

  As an embodiment of the double-sided pressure-sensitive adhesive tape of the present invention, a basic structure is a structure in which a foam base material is used as a core and an adhesive layer is provided on both surfaces of the base material. The substrate and the pressure-sensitive adhesive layer may be directly laminated or may have other layers. These modes may be appropriately selected depending on the intended use. When further imparting dimensional stability and tensile strength to the tape, a laminate layer such as a polyester film is used. When providing the tape with a light shielding property, a light shielding layer is provided. When ensuring light reflectivity, a light reflection layer may be provided. When these other layers are provided, a waterproof layer is used as the other layers.

  As the laminate layer, various resin films including a polyester film can be used. As these thickness, 1-16 micrometers is preferable from the surface of the followable | trackability of a foam base material, and 3-12 micrometers is more preferable.

  As the light shielding layer, those formed from an ink containing a colorant such as a pigment are easily used, and a layer made of black ink is preferably used because of its excellent light shielding properties. As the reflective layer, a layer formed from white ink can be easily used. The thickness of these layers is preferably 2 to 20 μm, and more preferably 4 to 6 μm. By setting the thickness within the range, curling of the substrate due to curing shrinkage of the ink hardly occurs, and the workability of the tape is improved.

  The double-sided pressure-sensitive adhesive tape of the present invention can be produced by a known and usual method. For example, a direct copy method in which an acrylic pressure-sensitive adhesive composition is applied and dried directly on a foam base material or on the surface of another layer laminated on the foam base material, or an acrylic pressure-sensitive adhesive on a release sheet An example is a transfer method in which the composition is applied and dried, and then bonded to the surface of the foam substrate or other layer. The transfer method is preferably a transfer method in which an acrylic pressure-sensitive adhesive composition is applied to a release sheet and dried, and then bonded to the surface of a foam substrate or another layer.

  The thickness of the double-sided pressure-sensitive adhesive tape of the present invention may be appropriately adjusted depending on the mode of use, but is 70 to 1400 μm. In the case of fixing electronic parts, particularly small and thin portable electronic devices, since a thin tape thickness is required, the thickness is preferably 100 to 600 μm, and particularly preferably 120 μm to 500 μm. By setting the tape thickness to the thickness, it can be suitably applied to thin and small portable electronic devices, and a good waterproof function can be realized.

In the double-sided pressure-sensitive adhesive tape of the present invention, the surface adhesive strength 1 measured under the following measurement conditions is preferably 100 N / 4 cm ² or more, and more preferably 130 N / 4 cm ² or more.

The measurement conditions for the surface adhesion strength 1 are as follows.
1) At 23 ° C., two double-sided adhesive tapes having a width of 5 mm and a length of 4 cm are applied in parallel to an acrylic plate having a thickness of 2 mm and a size of 5 cm.
2) Next, a 2 mm thick, 10 × 15 cm rectangular smooth ABS plate with a 1 cm diameter hole in the center, and the acrylic plate with the double-sided adhesive tape created in 1) was placed between the center of the acrylic plate and the ABS. Affixed so that the centers of the plates coincide, press once with a 2 kg roller, and leave at 23 ° C. for 1 hour to obtain a test piece.
3) The acrylic plate is pushed at 10 mm / min with a tensile tester equipped with a stainless steel probe having a diameter of 8 mm through the hole of the ABS plate from the ABS side of the test piece, and the strength at which the acrylic plate is peeled is measured.

  In the double-sided pressure-sensitive adhesive tape of the present invention, the surface adhesive strength 2 measured under the following measurement conditions is preferably 250 mJ or more, and more preferably 350 mJ or more.

The measurement conditions of the surface adhesive strength 2 are as follows.
1) After cutting a double-sided adhesive tape into a 2 cm square, it is attached to an acrylic plate having a thickness of 2 mm and a 2 cm square.
2) Acrylic plate with double-sided adhesive tape, 2cm thick and 4cm square polyamide plate (40% by mass glass fiber added) with a 1cm diameter hole in the center, and the center of the acrylic plate and the center of the polyamide plate Are attached so that the two coincide with each other, press once with a 2 kg roller, and then left at 23 ° C. for 24 hours to obtain a test piece.
3) A test piece is placed on a stainless steel pedestal having an outer diameter of 4 cm square, a length of 3 cm, and a thickness of 5 mm with the polyamide side facing up.
4) A brass cone having a weight of 100 g and having a protrusion having a diameter of 5 mm and a length of 1 cm at the tip is continuously dropped at intervals of 10 cm to 10 cm (three times per step) on the acrylic plate through a hole on the polyamide side. Measure the height when the tape is peeled or broken.
5) The fall energy mJ (= 9.8 × height (m) × 100 g) is calculated from the measurement result.

  The double-sided pressure-sensitive adhesive tape of the present invention exhibits good adhesiveness and followability with an adherend, rework suitability and removability even with a thin tape thickness. For this reason, in order to improve the yield when manufacturing electronic devices, the double-sided adhesive tape or parts that have failed to be joined are peeled off from the work in progress (rework), or the finished product is repaired, recycled, or reused. In the case of separating, disassembling and dismantling the body and parts, the double-sided adhesive tape can be easily removed, so that the re-working efficiency, the yield of parts and products, and the recycling rate are improved. Specifically, in electronic notebooks, mobile phones, PHS, cameras, music players, televisions, and other electronic devices, the protection panel of the information display unit and the casing are bonded together, the casings are bonded together, It can be suitably used for laminating a body and an input device such as a sheet-like numeric keypad or a touch panel, laminating a housing and a decorative sheet, and fixing various other members and modules.

  In addition, the double-sided pressure-sensitive adhesive tape of the present invention exhibits suitable adhesion to an adherend even when the tape thickness is thin, can effectively prevent water from entering from the adhesion gap, and has an excellent waterproof function. . For this reason, the waterproof function can be effectively imparted even in a portable electronic device or the like in which the thickness is reduced, the volume limit in the housing is severe, and it is difficult to provide a separate water sealing means. As a specific usage mode, in a portable electronic device such as an electronic notebook, a mobile phone, a PHS, a camera, a music player, and a television, the bonding between the protective panel of the information display unit and the casing, the bonding between the casings, It can be suitably used for bonding of a housing and an input device such as a sheet-like numeric keypad or a touch panel, bonding of the housing and a decorative sheet, and fixing of various other members and modules. In addition, it can effectively provide a waterproof function even in parts where conventional water-sealing means such as rubber packing, gaskets, sealants, etc. are used, and the case and parts to repair, recycle and reuse the finished product Can be easily separated, disassembled and disassembled.

(Adjustment of adhesive solution A)
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 93.54 parts by mass of butyl acrylate, 3 parts by mass of vinyl acetate, 2.2 parts by mass of acrylic acid, N-vinyl-2 A solvent comprising 100 parts by mass of ethyl acetate and 1.2 parts by mass of pyrrolidone, 0.06 parts by mass of 4-hydroxybutyl acrylate, 0.1 part by mass of 2,2′-azobisisobutyronitrile as a polymerization initiator And polymerized at 60 ° C. for 12 hours to obtain an acrylic copolymer having a weight average molecular weight of 700,000 (polystyrene conversion). Next, 15 parts by mass of Pencel D135 (polymerized rosin pentaerythritol ester, softening point 135 ° C.) by Arakawa Chemical Co., Ltd. and super ester A100 (disproportionated rosin by Arakawa Chemical Co., Ltd.) with respect to 100 parts by mass of the acrylic copolymer. Of glycerin ester, softening point 100 ° C.) was added, and ethyl acetate was added and mixed uniformly to obtain a pressure-sensitive adhesive solution A having a nonvolatile content of 40%.

(Adjustment of adhesive solution B)
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 74.9 parts by mass of butyl acrylate, 20 parts by mass of 2-ethylhexyl acrylate, 2 parts by mass of acrylic acid, 3 parts by mass of vinyl acetate , 0.1 part by mass of 4-hydroxybutyl acrylate and 0.1 part by mass of 2,2′-azobisisobutyronitrile as a polymerization initiator were dissolved in a solvent consisting of 100 parts by mass of ethyl acetate, and Polymerization was performed for 12 hours to obtain an acrylic copolymer having a weight average molecular weight of 500,000 (polystyrene conversion). Next, 25 parts by mass of Pencel D135 manufactured by Arakawa Chemical Co., Ltd. was added to 100 parts by mass of the acrylic copolymer, and ethyl acetate was added and mixed uniformly to obtain an adhesive solution B having a nonvolatile content of 50%.

[Example 1]
(Adjustment of double-sided adhesive tape)
1.100 parts by mass of the above-mentioned pressure-sensitive adhesive solution A, 1.24 parts by mass of “Coronate L-45” (isocyanate-based crosslinking agent, solid content 45%) manufactured by Nippon Polyurethane Co., Ltd. was stirred for 15 minutes, and then peeled to a thickness of 75 μm. On the PET film, it was coated so that the thickness after drying was 35 μm, and dried at 80 ° C. for 3 minutes to form an adhesive layer.

Next, a white polyolefin-based foam (thickness: 130 μm, expansion ratio 2.5 times, 25% compression strength: 130 kPa, tensile elastic modulus: 1140 N / cm ² , tensile strength 14.8 N / cm, surface is corona treated. The pressure-sensitive adhesive sheets were bonded to both surfaces of a wetting index of 52 mN / m, and then laminated with a roll having a linear pressure of 5 kg / cm. Thereafter, aging was performed at 40 ° C. for 48 hours to obtain a double-sided adhesive sheet having a thickness of 200 μm.

[Examples 2 to 5]
The same method as in Example 1 except that the foam base material described in Table 1 was used instead of the white polyolefin-based foam, and the thickness after drying of the adhesive was changed to the thickness shown in Table 1. A double-sided adhesive tape was obtained.

[Example 6]
The same method as in Example 1 except that 0.8 parts by mass of “Coronate L-45” (isocyanate-based crosslinking agent, solid content 45%) manufactured by Nippon Polyurethane Co., Ltd. was added to 100 parts by mass of the adhesive solution A. A double-sided adhesive tape was obtained.

[Examples 7 and 8]
To 100 parts by mass of the pressure-sensitive adhesive solution B, 2.0 parts by mass of “Coronate L-45” (isocyanate-based crosslinking agent, solid content 45%) manufactured by Nippon Polyurethane Co., Ltd. was added and stirred for 15 minutes. Example 1 except that a PET film was coated on the PET film so that the thickness after drying was as shown in Table 1, and dried at 80 ° C. for 3 minutes to form an adhesive layer. A double-sided adhesive tape was obtained by the same method.

[Example 9]
Black ethylene-vinyl acetate foam instead of white polyolefin foam (thickness: 800 μm, expansion ratio 8 times, 25% compression strength: 34 kPa, tensile strength: 24.8 N / cm, surface wetting index by corona treatment 52 parts by weight of the adhesive solution B was added to 2.0 parts by mass of “Coronate L-45” (isocyanate-based crosslinking agent, solid content 45%) manufactured by Nippon Polyurethane Co., Ltd. for 15 minutes. After stirring, this was carried out except that a 75 μm-thick PET film with a thickness of 50 μm after drying was applied and dried at 80 ° C. for 3 minutes to form an adhesive layer. A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 8.

[Example 10]
(Adjustment of adhesive solution F)
In a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel and a nitrogen gas inlet, 85.9 parts by weight of butyl acrylate, 4 parts by weight of acrylic acid, 10 parts by weight of methyl methacrylate, 4-hydroxybutyl acrylate 0.1 part by mass, 0.1 part by mass of 2,2′-azobisisobutyronitrile as a polymerization initiator was dissolved in a solvent consisting of 100 parts by mass of ethyl acetate, and polymerized at 60 ° C. for 12 hours. An acrylic copolymer having a weight average molecular weight of 700,000 (polystyrene conversion) was obtained. Next, acrylic resin (weight average) consisting of 10 parts by weight of Pencel D160 (pentaerythritol ester of polymerized rosin), 97 parts by weight of cyclohexyl methacrylate, and 3 parts by weight of acrylic acid based on 100 parts by weight of the acrylic copolymer. 10 parts by mass) (molecular weight: 6000, glass transition temperature: 66 ° C.) were added, and ethyl acetate was added and mixed uniformly to obtain an adhesive solution F having a nonvolatile content of 30%.

(Adjustment of double-sided adhesive tape)
To 100 parts by mass of the pressure-sensitive adhesive solution F, 0.9 part by mass of “Coronate L-45” (isocyanate-based crosslinking agent, solid content 45%) manufactured by Nippon Polyurethane Co., Ltd. was stirred for 15 minutes, and then peeled to a thickness of 75 μm. A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the film was coated on the PET film so that the thickness after drying was 35 μm and dried at 80 ° C. for 3 minutes to form an adhesive layer. .

[Example 11]
(Adjustment of adhesive solution G)
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 71.9 parts by mass of butyl acrylate, 20 parts by mass of 2-ethylhexyl acrylate, 5 parts by mass of acrylic acid, 3 parts by mass of methyl acrylate , 0.1 part by mass of 2-hydroxyethyl acrylate and 0.1 part by mass of 2,2′-azobisisobutyronitrile as a polymerization initiator were dissolved in a solvent consisting of 100 parts by mass of ethyl acetate at 70 ° C. Polymerization was performed for 12 hours to obtain an acrylic copolymer having a weight average molecular weight of 600,000 (polystyrene conversion). Next, Arakawa Chemical Co., Ltd. Pencel D135 (polymeric rosin pentaerythritol ester) 20 parts by mass, Yashara Chemical Co., Ltd. T160 (terpene phenol) 10 parts by mass are added to 100 parts by mass of the acrylic copolymer, and ethyl acetate is added. To obtain a pressure-sensitive adhesive solution G having a nonvolatile content of 45%.

(Adjustment of double-sided adhesive tape)
1.2 parts by mass of “Coronate L-45” (isocyanate-based crosslinking agent, solid content 45%) manufactured by Nippon Polyurethane Co., Ltd. was added to 100 parts by mass of the pressure-sensitive adhesive solution G and stirred for 15 minutes. A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the film was coated on the PET film so that the thickness after drying was 35 μm and dried at 80 ° C. for 3 minutes to form an adhesive layer. .

[Comparative Examples 1 and 2]
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the foam base material shown in Table 2 was used instead of the white polyolefin-based foam.

[Comparative Example 3]
Implemented except that a non-woven fabric (basis weight: 17 g / m ² , tensile strength: 16.0 N / cm) was used instead of the white polyolefin-based foam, and the pressure-sensitive adhesive after drying had a thickness of 70 μm. A double-sided PSA sheet was obtained in the same manner as in Example 1.

[Comparative Example 4]
A film made of polyethylene terephthalate (PET) (thickness: 100 μm, tensile strength: 210 N / cm, surface wetted by corona treatment to 52 mN / m) was used in place of the white polyolefin foam, and the adhesive was dried. A double-sided pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the thickness described in the table was used.

[Comparative Example 5]
(Adjustment of adhesive solution C)
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 93.54 parts by mass of butyl acrylate, 3 parts by mass of vinyl acetate, 2.2 parts by mass of acrylic acid, N-vinyl-2 A solvent comprising 100 parts by mass of ethyl acetate and 1.2 parts by mass of pyrrolidone, 0.06 parts by mass of 4-hydroxybutyl acrylate, 0.1 part by mass of 2,2′-azobisisobutyronitrile as a polymerization initiator And polymerized at 60 ° C. for 12 hours to obtain an acrylic copolymer having a weight average molecular weight of 700,000 (polystyrene conversion). Next, 25 parts by mass of Arakawa Chemical Superester A100 as a tackifier resin is added to 100 parts by mass of the acrylic copolymer, and ethyl acetate is added and mixed uniformly to obtain an adhesive solution C having a nonvolatile content of 40%. Obtained.

(Adjustment of double-sided adhesive tape)
To 100 parts by mass of the pressure-sensitive adhesive solution C, 1.0 part by mass of “Coronate L-45” (isocyanate-based cross-linking agent, solid content 45%) manufactured by Nippon Polyurethane Co., Ltd. was stirred for 15 minutes, and then peeled to a thickness of 75 μm. A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the film was coated on the PET film so that the thickness after drying was 35 μm and dried at 80 ° C. for 3 minutes to form an adhesive layer. .

[Comparative Example 6]
(Adjustment of adhesive solution D)
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 97.9 parts by mass of butyl acrylate, 2.0 parts by mass of acrylic acid, 0.1 part by mass of 4-hydroxybutyl acrylate, As a polymerization initiator, 0.1 part by mass of 2,2′-azobisisobutyronitrile is dissolved in a solvent composed of 100 parts by mass of ethyl acetate, polymerized at 70 ° C. for 12 hours, and the weight average molecular weight is 800,000. An acrylic copolymer (polystyrene conversion) was obtained. Next, ethyl acetate was added and mixed uniformly to obtain a pressure-sensitive adhesive solution D having a nonvolatile content of 30%.

(Adjustment of double-sided adhesive tape)
With respect to 100 parts by mass of the adhesive solution D, 2.5 parts by mass of “Coronate L-45” (isocyanate-based crosslinking agent, solid content 45%) manufactured by Nippon Polyurethane Co., Ltd. was added and stirred for 15 minutes. A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1, except that the film was coated on a PET film so that the thickness after drying was 50 μm, and dried at 80 ° C. for 3 minutes to form an adhesive layer. .

[Comparative Example 7]
(Adjustment of adhesive solution E)
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 98 parts by mass of 2-ethylhexyl acrylate, 1 part by mass of acrylic acid, 1 part by mass of 4-hydroxybutyl acrylate, polymerization initiator 0.1 part by mass of 2,2′-azobisisobutyronitrile is dissolved in a solvent consisting of 100 parts by mass of ethyl acetate, polymerized at 70 ° C. for 12 hours, and the weight average molecular weight is 800,000 (polystyrene conversion). An acrylic copolymer was obtained. Ethyl acetate was added and mixed uniformly to obtain an adhesive solution E having a nonvolatile content of 30%.

(Adjustment of double-sided adhesive tape)
With respect to 100 parts by mass of the pressure-sensitive adhesive solution E, 1.8 parts by mass of “Coronate L-45” (isocyanate-based crosslinking agent, solid content 45%) manufactured by Nippon Polyurethane Co., Ltd. was stirred for 15 minutes, and then the peel-treated 75 μm thick. A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1, except that the film was coated on a PET film so that the thickness after drying was 50 μm, and dried at 80 ° C. for 3 minutes to form an adhesive layer. .

  The following evaluation was performed about the foam base material used by the said Example and comparative example, and the double-sided adhesive tape obtained by the said Example and comparative example. The obtained results are shown in Tables 1-3.

[Foam substrate and double-sided adhesive tape thickness]
It was measured with a dial series gauge G type manufactured by Ozaki Seisakusho. In the case of a double-sided pressure-sensitive adhesive tape, measurement was performed after the release film was peeled off.

[Interlayer strength of foam substrate]
1.1 parts by mass of “Coronate L-45” (isocyanate-based cross-linking agent, solid content 45%) manufactured by Nippon Polyurethane Co., Ltd. was added to 100 parts by mass of the pressure-sensitive adhesive solution C and stirred for 15 minutes. It coated so that the thickness after drying might be set to 50 micrometers on a PET film, and it dried at 80 degreeC for 3 minute (s), and formed the adhesive layer. Next, after sticking the said adhesive layer one sheet | seat on both surfaces of the foam which evaluates interlayer intensity | strength, it laminated | stacked with the roll of linear pressure 5kgf / cm. Thereafter, aging is performed at 40 ° C. for 48 hours to prepare a double-sided pressure-sensitive adhesive tape for measuring interlayer strength.
Next, a double-sided pressure-sensitive adhesive tape sample having a width of 2 cm and a length of 10 cm (in the flow direction of the foam base material) lined with a 25 μm-thick polyethylene terephthalate film on one side of the adhesive surface was placed on a stainless steel plate at 23 ° C. and 50% RH. Apply pressure with one reciprocation of 2kg roller and leave at 40 ° C for 48 hours. After standing at 23 ° C. for 24 hours, the strength when the foam was torn in the 90 ° direction at 23 ° C. and 50% RH at a tensile speed of 300 mm / min (broken substrate) was measured. Unit: N / cm.

[Tensile modulus, tensile strength]
When measuring the foam substrate or double-sided adhesive sheet (peeling the release film) processed into a test piece with a marked line interval of 2 cm (foam substrate flow direction) and a width of 1 cm until it is cut at a tensile speed of 300 mm / min. The maximum intensity of was measured.

[Average cell diameter in the flow direction and width direction of the foam substrate]
The foam base material was cut to 1 cm in both the width method and the flow direction, and the cut surface central portion of the cut foam base material was magnified 50 times with a scanning electron microscope (SEM) (S-2380N, manufactured by Hitachi, Ltd.). Then, the cross section of the width direction of a foam base material or the flow direction was photographed so that the cut surface of a foam base material might fit in a photograph over the full length of the base material thickness direction. In the obtained photograph, all the bubble diameters existing on the cut surface having an actual length of 2 mm before expansion in the flow direction or the width direction were measured, and the average bubble diameter was calculated from the average value.

[Average cell diameter in the thickness direction of the foam substrate]
The thickness of the foam base material photographed with SEM was measured, and SEM photography was performed under the same conditions as the measurement of the average cell diameter in the flow direction of the foam base material. In the obtained photograph, the number of bubbles in the thickness direction present at an arbitrary location on the foam substrate was visually counted, and the average cell diameter in the thickness direction was calculated from the following formula.
Average cell diameter in the thickness direction (μm) = thickness of the foam substrate (μm) / number of cells This was measured at three arbitrary locations, and the average value was taken as the average cell size in the thickness direction.

[Surface bond strength 1]
1) Two double-sided adhesive tapes 5 mm wide and 4 cm long parallel to an acrylic plate (Mitsubishi Rayon Co., Ltd. Acrylite MR200 “trade name”, hue: transparent) at 23 ° C. and 2 mm thick Affix it.
2) Next, a 2 mm thick, 10 x 15 cm rectangular ABS plate (made by Takiron, hue: natural, no wrinkles) with a 1 cm diameter hole in the center is attached with double-sided adhesive tape made in 1) The acrylic plate is attached so that the center of the acrylic plate and the center of the ABS plate coincide with each other, pressed once with a 2 kg roller, and then left at 23 ° C. for 1 hour to obtain a test piece.
3) Through the hole of the ABS plate 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, and the strength at which the acrylic plate was peeled was measured.

[Surface bond strength 2]
1) After cutting a double-sided adhesive tape into a 2 cm square, it is attached to an acrylic plate having a thickness of 2 mm and a 2 cm square.
2) An acrylic plate with a double-sided adhesive sheet was added to a 2 mm thick, 4 cm square polyamide plate (Mitsubishi Engineering Plastics Co., Ltd. Reny “trade name”, 40 wt% glass fiber added) with a 1 cm diameter hole in the center. Attaching so that the center part of the acrylic plate and the center part of the polyamide plate coincide with each other, and pressurizing and reciprocating once with a 2 kg roller, the test piece is left at 23 ° C. for 24 hours.
3) A test piece is placed on a stainless steel pedestal having an outer diameter of 4 cm square, a length of 3 cm, and a thickness of 5 mm with the polyamide side facing up.
4) A brass cone having a weight of 100 g and having a protrusion having a diameter of 5 mm and a length of 1 cm at the tip is continuously dropped at intervals of 10 cm to 10 cm (three times per step) on the acrylic plate through a hole on the polyamide side. Measure the height when the tape is peeled or broken. In addition, when there was no peeling or breakage of the tape on the test piece after the test having a height of 70 cm, the test was ended there, and “686 <” was set.
5) The drop energy mJ (= 9.8 × height (m) × 100 g) was calculated from the measurement result.

[Rework suitability]
1) A double-sided pressure-sensitive adhesive tape was used to prepare a frame-shaped sample having an outer diameter of 65 mm × 43 mm and a width of 2 mm, and an acrylic plate (Mitsubishi Rayon Co., Ltd. Acrylite MR200 “trade name”, hue: transparent) The same shall apply hereinafter. Next, affixed to an ABS plate with a thickness of 2 mm and an outer diameter of 90 mm × 50 mm (made by Takiron Co., Ltd., hue: natural, no wrinkles, the same applies hereinafter), pressurized once with a 2 kg roller, and left at 23 ° C. for 24 hours. Use a test piece.
2) The state of the tape when the test piece is peeled off at 23 ° C. in the vertical direction is evaluated.
3) Next, the ease with which the double-sided pressure-sensitive adhesive tape remaining on the ABS or acrylic plate was peeled off by hand in the direction of a peeling angle of about 135 degrees was evaluated.
(Double-circle): It was able to peel off without the interlaminar crack of a base material, or a residue.
○: The foam substrate was cracked between the layers, but when the remaining double-sided adhesive tape was pulled by hand, it was peeled off without any residue.
X: The glue remained on the adherend. Alternatively, the foam substrate was cracked between the layers, and the remaining double-sided pressure-sensitive adhesive tape could not be peeled off by pulling by hand.

[Removability]
1) A frame-shaped sample having an outer diameter of 65 mm × 43 mm and a width of 2 mm is prepared using a double-sided adhesive tape, and is attached to an acrylic plate having a thickness of 2 mm and an outer diameter of 65 mm × 45 mm. Next, it is attached to an ABS plate having a thickness of 2 mm and an outer shape of 90 mm × 50 mm, pressed once with a 2 kg roller, and then left at 23 ° C. for 24 hours.
2) Next, after being left in an environment of 60 ° C. and 90% RH for 7 days, the test piece is placed in an environment of 23 ° C. and 50% RH.
3) Evaluate the state of the tape when the test piece is peeled off at 23 ° C. in the vertical direction.
4) Next, the ease of peeling when the double-sided pressure-sensitive adhesive tape remaining on the ABS or acrylic plate was peeled in the direction of a peeling angle of 135 degrees was evaluated.
(Double-circle): There was no interlayer crack of a foam base material, and it was able to peel off without remaining residue after that.
○: The foam substrate was cracked between the layers, but when the remaining double-sided adhesive tape was pulled, it was peeled off without any residue.
×: Residue remaining on the adherend. Alternatively, the foam substrate was cracked between the layers, and the remaining double-sided pressure-sensitive adhesive tape could not be peeled off by pulling by hand.

[Followability test]
1) A double-sided pressure-sensitive adhesive tape is cut to a width of 1 cm and a length of 5 cm, and is attached to the central portion in the width direction of an acrylic plate having a thickness of 2 mm, a width of 2 cm and a length of 5 cm to produce an acrylic plate with a double-sided pressure-sensitive adhesive tape. (FIG. 1).
2) Next, two polyethylene terephthalate-based adhesive tapes having a thickness of 20 μm, a width of 5 mm and a length of 2 cm are placed in the center of another acrylic sheet having a thickness of 2 mm and a width of 2 cm × 5 cm. Acrylic plates with steps are created by applying them in parallel at intervals (FIG. 2).
3) Place an acrylic plate with a double-sided adhesive tape on the pressure-sensitive adhesive tape portion of the stepped acrylic plate at 23 ° C., and then pressurize and reciprocate with a 2 kg roller from the end (FIG. 3).
4) From the side of the stepped acrylic plate, the follow-up state of the double-sided adhesive tape near the step is visually evaluated.
○: The double-sided adhesive tape is in close contact with the stepped acrylic plate.
X: The double-sided adhesive tape does not adhere to the stepped acrylic plate near the step.

[Waterproof test 1]
1) A double-sided adhesive tape is used to create a frame-shaped sample with an outer diameter of 65 mm x 45 mm and a width of 2 mm, and affixed to an acrylic plate with a thickness of 2 mm and an outer diameter of 65 mm x 45 mm. After sticking and pressurizing once with a 2 kg roller, the test piece is left at 23 ° C. for 24 hours.
2) The test piece was immersed in a 5% by mass surfactant solution (produced by diluting P & G Joy with tap water) at 23 ° C. for 10 minutes, taken out and left for 10 minutes for 30 cycles. The presence or absence of water in the frame when immersed was evaluated.
○: No flooding ×: Flooding

[Waterproof test 2]
1) A double-sided adhesive tape is used to create a frame-shaped sample with an outer diameter of 65 mm x 45 mm and a width of 2 mm, and affixed to an acrylic plate with a thickness of 2 mm and an outer diameter of 65 mm x 45 mm. Affixed to the center (FIG. 4). After one reciprocating pressurization with a 2 kg roller, the test piece is left at 23 ° C. for 24 hours.
2) On a pedestal of a DuPont impact tester (manufactured by Tester Sangyo Co., Ltd.) at 23 ° C., a U-shaped measuring table (made of aluminum having a thickness of 5 mm) having a length of 150 mm, a width of 100 mm, and a height of 45 mm. Then, the test piece was placed thereon with the acrylic plate facing downward (FIG. 5). A stainless steel strike core having a diameter of 25 mm and a mass of 300 g is dropped from a position of 30 cm from the ABS plate side, and an impact is applied to the central portion of the ABS plate 5 times at 10 second intervals (FIG. 6). In addition, when the impact was given and the acrylic board fell off, the test was complete | finished there.
3) The impacted test piece was immersed for 10 minutes in a 5% by weight surfactant solution (produced by diluting P &G's Joy with tap water) at 23 ° C. and then removed and left for 10 minutes for 30 cycles. The presence or absence of water immersion in the frame when immersed in the solution was evaluated.
(Double-circle): There was no water immersion and the external appearance of the foam did not change.
○: No water immersion, but a slight tear was confirmed in a part of the foam layer.
X: The acrylic board dropped out at the stage of water immersion or drop impact.

[Airtightness test]
1) Create a frame-like sample with an outer diameter of 5 cm x 4 cm and a width of 2 mm using a double-sided adhesive tape, and apply it to a perforated acrylic board having a thickness of 2 mm, an outer diameter of 5 cm x 5 cm, and a hole with a diameter of 3 mm in the center. Affixed to the central part of a rectangular acrylic plate of 3 mm and 7 cm × 5 cm in outer shape (FIG. 7). After one reciprocating pressurization with a 2 kg roller, the test piece is left at 23 ° C. for 24 hours.
2) At 23 ° C., a pressure of 0.02 MPa is applied with nitrogen gas from a perforated acrylic plate (FIG. 8).
3) The time until nitrogen leaked from the window frame-shaped tape portion was measured.

  As in Examples 1 to 9, it was clear that the double-sided pressure-sensitive adhesive tape of the present invention achieved both excellent adhesion to the adherend, rework suitability and removability. Moreover, the double-sided pressure-sensitive adhesive tapes of Examples 10 to 11 had suitable airtightness as well as excellent adhesion and reworkability. On the other hand, since the double-sided pressure-sensitive adhesive tape of Comparative Example 1 has low interlaminar strength and tensile strength of the foam substrate, the double-sided pressure-sensitive adhesive tape is difficult to peel off during rework or re-peeling in practical use. Moreover, since the double-sided pressure-sensitive adhesive tapes of Comparative Examples 2 to 4 were all poor in followability, water was confirmed in the waterproof test, and the waterproof property could not be realized. In Comparative Example 5, the double-sided pressure-sensitive adhesive tape was difficult to peel off during rework and re-peeling. In Comparative Examples 6 and 7, the adhesive strength was low, and waterproofness could not be realized.

It is a conceptual diagram which shows the acrylic board with a double-sided adhesive tape for a follow-up test. It is a conceptual diagram which shows the acrylic board with a level | step difference for a follow-up test. It is the conceptual diagram which looked at the state which bonded together the acrylic board with a double-sided adhesive tape of a followability test, and the acrylic board with a level | step difference from the cross-sectional direction. It is a conceptual diagram which shows the test piece for the waterproof test 2. FIG. Concept viewed from the bottom side of the measurement table 6 with the test piece for the measurement table waterproof test 2 placed on the U-shaped measurement table 6 (made of aluminum having a thickness of 5 mm) with the acrylic plate facing downward. FIG. It is a conceptual diagram which shows operation which gives a drop impact. It is a conceptual diagram which shows the test piece of an airtightness test. It is a conceptual diagram which shows operation which applies a pressure to a test piece.

DESCRIPTION OF SYMBOLS 1 Double-sided adhesive tape 2 Acrylic board 3 Adhesive tape for level | step difference 4 The place which evaluates followability 5 ABS board 6 The place which hits an impact core 7 The impact core for a drop impact 8 U-shaped measuring stand 9 Perforated acrylic board 10 Thickness 3mm Acrylic plate 11 Nitrogen introduction tube 12 Nitrogen

Claims (14)

A double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both sides of a foam base material having a thickness of 50 to 500 μm , wherein the foam base material has an interlayer strength of 12 N / cm or more and a 25% compressive strength of 30 to 170 kPa, The pressure-sensitive adhesive layer contains an acrylic copolymer having, as monomer components, a (meth) acrylate having 4 to 12 carbon atoms and a carboxyl group, and a polymerized rosin ester-based tackifier resin. A double-sided pressure-sensitive adhesive tape comprising the composition. ^2. The double-sided pressure-sensitive adhesive tape according to claim 1, wherein the foam base material has a tensile elastic modulus of 200 N / cm ² or more and a tensile strength per unit width of 10 N / cm or more. The double-sided pressure-sensitive adhesive tape according to claim 1 or 2, wherein an average cell diameter in the thickness direction of the foam substrate is 1 to 200 µm, and an average cell size in the flow direction and the width direction is 1.2 to 700 µm. The ratio of the average bubble diameter in the flow direction to the average bubble diameter in the thickness direction of the foam substrate is 1.2 to 15, and the ratio of the average bubble diameter in the width direction to the average bubble diameter in the thickness direction is 1. It is 2-15, The double-sided adhesive tape in any one of Claims 1-3. The double-sided pressure-sensitive adhesive tape according to claim 1, wherein the foam base material is a polyolefin-based foam base material. The double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 5, comprising 10 to 40 parts by mass of the polymerized rosin ester-based tackifier resin with respect to 100 parts by mass of the acrylic copolymer. Furthermore, the double-sided adhesive tape in any one of Claims 1-6 containing disproportionated rosin ester type tackifying resin. The double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 7 , wherein the acrylic copolymer contains a vinyl monomer having a tertiary amide skeleton in a molecule as a monomer component. Thickness is 100-600 micrometers, The double-sided adhesive tape in any one of Claims 1-8. The double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 9 , wherein the double-sided pressure-sensitive adhesive tape is used for fixing parts of an electronic device that can be recycled or reused. The foam substrate is foamed body made of closed cell double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 10 for use in the component fixing of an electronic device having a waterproof function. The double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 11, which is used for fixing a component constituting a portable electronic device. Double-sided pressure-sensitive adhesive tape according to any one of the pressure-sensitive adhesive layer according to claim 1 to 12 temperature is -30～10 ° C. showing the maximum of loss tangent in a dynamic viscoelasticity spectrum at frequency 1Hz of. The temperature showing a maximum of loss tangent in a dynamic viscoelasticity spectrum of the double-sided adhesive tape of the frequency 1Hz is -30~20 ℃, claim 1-13 maximal value of the loss tangent is 1.0 or less The double-sided adhesive tape in any one of.

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