TWI424042B - Double-sided adhesive tape - Google Patents

Description

Double-sided adhesive tape

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

In portable electronic devices such as electronic notebooks, mobile phones, PHS, cameras, music players, and televisions, the combination of the protective panel and the housing of the information display unit is used, and the use of various components and modules is double. Adhesive tape. In order to ensure the superiority of competition in the market, and to pursue a variety of functions, one of them pursues the function of imparting water resistance.

As an adhesive tape for fixing a member for an electronic device, the following technique has been disclosed: for example, a maximum value of loss tangent (tan δ) in a temperature range of -40 to -15 ° C, and a surface stickiness for a specific adherend A double-sided adhesive sheet in which the adhesive layer having a strength of 19 N/cm ² or more is provided on both surfaces of the support (refer to Patent Document 1). The double-sided adhesive sheet has a good adhesive force by having a specific adhesive layer, and has excellent impact resistance such that the member is not easily peeled off due to an impact when the object is dropped. However, if the bonding of the protective panel and the casing, and the bonding of the casing and the casing, in the joining of the rigid bodies, it is difficult to obtain the complete bonding surface with the adherend due to the double-sided adhesive sheet. The adhesion is such that when there is a small gap, water immersion occurs.

As a double-sided adhesive tape which is excellent in adhesiveness, the double-sided adhesive tape which has a temperature which shows the maximum value of the loss tangent (tan δ) is -25 degrees C or less, using the foam as a base material. The acrylic pressure-sensitive adhesive layer having a holding time in a holding test at 0 ° C for 24 hours or more (refer to Patent Document 2). In the double-sided adhesive tape, the adhesion to the adherend is excellent, and even when the members are bonded to each other, the members can be appropriately joined. However, if the foam is used alone as a substrate, it is difficult to suppress a minute gap at the interface between the member and the adhesive layer, even if a part of the interface has a void or float which can be immersed in water, Water leakage is difficult to achieve because the water intrusion path is enlarged from there. In particular, in the case of portable electronic devices, it is difficult to give adequate use in the case of narrow tape width and thin tape thickness, in accordance with the requirements for narrow frame and further thinness associated with the large-screening in recent years. Waterproof.

In addition, in the case of a portable electronic device or the like, in order to improve the yield during manufacturing, the double-sided adhesive tape, members, and the like which are unsuccessfully joined to the unfinished product may be peeled off (reprocessed). In order to repair, regenerate, and reuse the finished product, the casing and the member are separated, decomposed, and disintegrated. However, in the case of the double-sided adhesive tape of the conventional foam substrate, the foam substrate is liable to occur between the layers. Damage, easy to remain on the surface of the member, and difficult to remove, thus reducing the efficiency of re-attaching the new double-sided adhesive tape after removing the double-sided adhesive tape from the casing and the member, the yield of the casing, the member, and the product, And recovery rate.

However, in the conventional foam base material, although the softness (compressive strength) at the time of compression in the thickness direction is pursued, there is no concept of strength (interlayer strength) when it is stretched in the thickness direction. Further, when the adhesive force of the adhesive is lowered individually, the adhesion to the adherend is also lowered, so that it is difficult to impart sufficient water repellency.

Patent Document 1: JP-A-2005-187513

Patent Document 2: JP-A-2005-281360

An object of the present invention is to provide a double-sided adhesive tape which is excellent in adhesion to a adherend and adherence, and which is excellent in rework suitability and re-peelability.

Further, in addition to the above-mentioned problems, a double-sided adhesive tape having an excellent waterproof function and being a waterproof double-sided adhesive tape suitable for use in electronic equipment is also provided.

Further, in addition to the above problems, there is also provided a double-sided adhesive tape which has excellent impact resistance and is a double-sided adhesive tape for waterproofing applications for portable electronic equipment.

As a result of intensive studies, the inventors have found that by using a foam substrate having specific flexibility and interlayer strength as a substrate and an adhesive having a specific composition, even when the rigid bodies are bonded to each other, In this case, the above-mentioned problem can be solved by achieving excellent adhesion between the double-sided adhesive tape and the adherend, reworkability and removability, and further preventing immersion of water.

That is, the present invention provides a double-sided adhesive tape which is a double-sided adhesive tape having an adhesive layer on both surfaces of a foam base material, wherein the foam base material has an interlayer strength of 12 N/cm or more, 25 The % compression strength is 30 to 170 kPa, and the adhesive layer is composed of an acrylic pressure-sensitive adhesive composition containing an acrylic copolymer and a rosin ester-based adhesion-imparting resin. The acrylic copolymer contains a (meth) acrylate having 4 to 12 carbon atoms and a vinyl monomer having a carboxyl group as a monomer component.

In the double-sided adhesive tape of the present invention, since interlayer damage of the foam substrate is less likely to occur, and even in the case where interlayer cracks occur, the adhesive does not remain on the surface of the member and is easily peeled off, so that it is portable. When manufacturing an electronic device or the like, peeling (reprocessing) a double-sided adhesive tape or member that has not been successfully bonded to an unfinished product, and repairing or regenerating a finished product such as a portable electronic device Separation of the casing and the member by reuse, ‧ disintegration and ‧ disassembly, the efficiency of the housing, the member, and the efficiency of reattaching the new double-sided adhesive tape after removing the double-sided adhesive tape from the casing and the member Product yield and recovery.

Further, the double-sided adhesive tape of the present invention exhibits an appropriate adhesion to the adherend, can effectively prevent the intrusion of water from the adhesion gap, and has an excellent waterproof function. Therefore, the thinning is improved, the volume restriction in the casing is strict, and the portable electronic device or the like which is difficult to separately provide the water sealing means can also effectively impart a waterproof function.

The present invention relates to a double-sided adhesive tape having a double-sided adhesive tape having adhesive layers on both sides of a foam substrate, wherein the foam substrate has an interlayer strength of 12 N/cm or more and 25%. The adhesive strength is 30 to 170 kPa, and the adhesive layer is composed of an acrylic pressure-sensitive adhesive composition containing an acrylic copolymer and a polymerized rosin ester-based adhesion-imparting resin, and the acrylic copolymer is A (meth) acrylate having 4 to 12 carbon atoms and a vinyl monomer having a carboxyl group are contained as a monomer component.

[Foam substrate]

The foam substrate used in the present invention is a foam substrate 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 this range, even when a soft foam substrate is caused to have interlayer cracks of the substrate, the peeling property of the double-sided adhesive tape can be imparted.

Here, in terms of the interlayer strength, first, each of the adhesive layers having a thickness of 50 μm is bonded to both surfaces of the foam to which the interlayer strength is to be evaluated, and then cured at 40° C. for 48 hours to form an interlayer. Double-sided adhesive tape for strength measurement.

Next, on a stainless steel plate (the surface was treated with a #360 water-resistant abrasive paper with a hairline treatment) under a condition of 23 ° C and ‧50% RH, the adhesive on one side was applied. A double-sided adhesive tape sample of 2 cm wide and 10 cm long (flow direction of polyolefin-based foam) lining a polyester film having a thickness of 25 μm on the surface was subjected to one back pressure bonding, and placed at 40 ° C. 48 hours. After standing at 23 ° C for 24 hours, the strength at the time of tearing the foam in the direction of 90 degrees at a tensile speed of 300 mm/min in an environment of ‧50% RH at 23 ° C was measured.

The foam substrate used in the present invention is a foam substrate having a 25% compression strength of 30 to 170 kPa, preferably 40 to 150 kPa. By using a foam base material having a compression strength of 25% in this range, it has excellent adhesion to the adherend, and particularly to an adherend having a concave-convex shape or a rough surface, it is also excellently followed. The adhesion. Further, in the foam base material having such a compressive strength, since the cushioning property is moderate, the pressure at the time of attachment concentrates on the joint portion, and the air existing in the adhesive interface is easily squeezed, so that the rigid bodies are mutually In terms of joining, it is also possible to achieve excellent adhesion of voids which do not cause water to enter.

Here, in terms of 25% compressive strength, a sample cut into a 50 mm square was laminated to a thickness of about 10 mm. The sample was sandwiched by a plate having an area larger than the sample, and the sample was compressed to about 2.5 mm (amount of 25% of the original thickness) at a rate of 10 mm/min at 23 ° C, and then stopped, and the strength after 20 seconds passed was measured.

In the foam base material used in the present invention, the foam base material has a tensile elastic modulus of 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, and more preferably 14 N/cm or more. Further, the cutting elongation is not particularly limited, but is preferably from 100 to 1,000%, preferably from 300 to 700%. By using a foam base material having a tensile modulus, a tensile strength, and a cutting elongation in this range, it is possible to suppress deterioration of workability of the double-sided adhesive tape even in a foamed soft base material. , broken, attached workability is reduced. Further, when the double-sided adhesive tape is peeled off, it is difficult to cause interlayer damage of the foam, and even when interlayer cracks are generated, the peeling property of the double-sided adhesive tape can be imparted.

Here, the tensile modulus of the tensile modulus and the unit width are as follows: using a Tensilon tensile tester at a tensile temperature of 300 mm/min under the condition of 23 ° C ‧50% RH The maximum strength obtained by measuring the sample having a length of 2 cm (flow direction of the foam substrate) and a width of 1 cm.

By making the foamed structure of the foam base material used in the present invention into a closed cell structure, it is possible to effectively prevent water immersion from the cut surface of the foam substrate, which is preferable. The shape of the bubble forming the closed cell structure is not particularly limited, but the shape of the flow direction, the width direction, or the average bubble diameter of the two directions is longer than the average cell diameter in the thickness direction of the foam. The closed cells are preferred because of their moderate cushioning properties.

Although the expansion ratio of the foam base material is not particularly limited, it is easy to adjust the interlayer strength, the compressive strength, and the like to the above range, and it is easy to achieve both excellent adhesion to the adherend and easiness of peeling. It is 2 to 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 preferably from 1 to 200 μm, preferably from 5 to 150 μm, more preferably from 10 to 100 μm, depending on the thickness of the foam. The average cell diameter in the flow direction and the width direction of the foam substrate is preferably from 1.2 to 700 μm, more preferably from 10 to 500 μm, most preferably from 100 to 400 μm. By setting the average cell diameter to this range, even when the width of the double-sided adhesive tape is narrow, it is easy to maintain the closed cells, and the water immersion path from the cross section of the foam substrate can be appropriately blocked.

The ratio of the average cell diameter is not particularly limited, but 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 (average cell diameter in the flow direction / thickness direction) The average cell diameter) is preferably from 1.2 to 15, more preferably from 2 to 9. Further, 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 preferably 1.2 to 15, more preferably 2 to 11. Further, it is preferable that both the flow direction and the width direction are the above ratio ranges. When the ratio is 1.2 or more, since the flexibility in the thickness direction is easily ensured, the followability is improved. On the other hand, when it is 15 times or less, the flexibility of the flow direction and the width direction of the foam base material or the unevenness of the tensile strength are less likely to occur.

Further, when the flow direction is 1, 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 it is the above ratio range, the softness of the foam base material and the width direction or the unevenness of the tensile strength are less likely to occur.

The average cell diameter in the width direction and the flow direction of the foam substrate was measured in accordance with the following procedure. First, the foam base material was cut into 1 cm in both the width direction and the flow direction. Next, the central portion of the cut surface of the cut foam substrate is magnified 50 times by a scanning electron microscope (SEM), and then the cross section of the foam substrate in the width direction or the flow direction is photographed. The cut surface of the foam substrate is accommodated in the photograph for the entire length of the substrate in the thickness direction. In the obtained photograph, all the bubble diameters existing in the cut surface of the 2 mm portion in the flow direction or the width direction before the enlargement were measured, and the average bubble diameter was calculated from the average value.

The average cell diameter in the thickness direction of the foam substrate was measured in accordance with the following procedure. First, the thickness of the foam substrate photographed by the SEM was measured. Next, SEM photographing was carried out 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 in an arbitrary portion of the foam base material was counted by visual observation, and the average bubble diameter in the thickness direction was calculated by the following formula.

Average bubble diameter in the thickness direction (μm) = thickness of the foam substrate (μm) / number of bubbles

The measurement was carried out at any three places, and the average value thereof was defined as the average cell diameter in the thickness direction.

The interlayer strength, the compressive strength, the tensile elastic modulus, and the like of the foam base material can be appropriately adjusted by the raw material of the substrate to be 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 is a foam base material having the above-mentioned interlayer strength, compressive strength, tensile modulus, and the like, and polyethylene, polypropylene, or the like can be used. a polyolefin-based foam composed of an ethylene-propylene copolymer, an ethylene-vinyl acetate copolymer, or the like, a polyurethane foam, a rubber-based foam composed of an acrylic rubber, another elastomer, or the like. Since it is easy to prepare a foam base material having a thin closed cell structure excellent in followability to irregularities on the surface of the adherend, cushion absorption, and the like, a polyolefin foam can be preferably used.

The thickness of the foam base material may be appropriately adjusted according to the use form, and is 50 to 1200 μm. In the case of fixing the components of the electronic device, particularly in the case of a small, thin portable electronic device, since the thickness of the tape is sought, the thickness of the substrate is preferably 50 to 500 μm, more preferably 70 to 400 μm.

The foamed base material is a crosslinked polyolefin-based resin foam obtained by supplying a polyolefin-based resin and a thermally decomposable foaming agent to an extruder for melt-kneading. The foamable polyolefin-based resin sheet is extruded into a sheet shape from an extruder, and after being crosslinked by an electron beam, it is obtained by foaming, stretching, and flaking. A polyolefin-based resin which is conventionally known can be used as the polyolefin-based resin, and a polyolefin-based resin containing 40% by mass or more of a polyethylene-based resin obtained by using a metal aromatic compound containing a tetravalent transition metal is preferable. . In addition, after foaming the foam, the foamed sheet is sliced in the thickness direction, and then stretched and skinned by a heat roll.

In the foam substrate, any of the following known additives may be added to the resin as needed: a plasticizer, a softener, an antioxidant, a flame retardant, a fiber made of glass or plastic, a hollow sphere, and a bead. ‧ Fillers such as metal powders, colorants such as pigments and dyes, leveling agents, tackifiers, water repellents, defoamers, etc.

In order to improve the adhesion to the adhesive layer or other layers, the foam substrate may be subjected to corona treatment, flame treatment, plasma treatment, hot air treatment, ozone, ultraviolet treatment, and easy adhesion treatment. Surface treatment such as coating. In terms of surface treatment, by making the wetting index based on the wetting agent 36 mN/m or more, preferably 40 mN/m or more, further preferably 48 mN/m or more, good adhesion to the adhesive can be obtained. Sex.

[Adhesive layer]

The adhesive composition constituting the adhesive layer of the double-sided adhesive tape of the present invention is characterized in that it is composed of an acrylic pressure-sensitive adhesive composition containing an acrylic copolymer and a polymerized rosin ester-based adhesive. The resin is provided, and the acrylic copolymer contains a (meth) acrylate having 4 to 12 carbon atoms and a vinyl monomer having a carboxyl group as a monomer component.

Examples of the (meth) acrylate having 4 to 12 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and (methyl). ) isobutyl acrylate, tert-butyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, cyclohexyl (meth)acrylate A monomer such as 2-ethylhexyl (meth)acrylate may be used alone or in combination of two or more kinds thereof. Among them, a (meth) acrylate having an alkyl group having 4 to 8 carbon atoms, particularly n-butyl acrylate, is excellent in adhesion to a adherend, and is excellent in cohesive force and sebum resistance. Therefore, it is better. The content of n-butyl acrylate is preferably 60% by mass or more, and more preferably 90% by mass or more, based on the total of (meth) acrylate having 4 to 12 carbon atoms.

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

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, or the like can be used. It is preferred to use acrylic acid as a copolymerization component.

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

Further, in the acrylic copolymer used in the adhesive composition constituting the adhesive layer of the double-sided adhesive tape of the present invention, it is preferred to use a vinyl monomer having a tertiary amine skeleton in the molecule as a monomer. The reason for the composition is that it is excellent in cohesive force and can suppress an excessive increase in the adhesive force. Therefore, polystyrene, ABS, acrylic, polycarbonate, polyamide polyester, and poly are used as materials for housings and members of electronic equipment. Resins such as propylene, polyurethane, and phenol resins, metals such as stainless steel, aluminum, and galvanized steel sheets, and glass, etc., can achieve both good adhesion, reworkability, and removability.

As the vinyl monomer having a tertiary amine skeleton in the molecule, N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, N,N-dimethylacrylamide, or the like can be used. Among them, N-vinylpyrrolidone is preferably used as a copolymerization component.

The content of the vinyl monomer having a tertiary amine skeleton in the molecule in the acrylic copolymer is preferably from 0.5 to 5.0% by mass, more preferably from 1.5 to 3.0% by mass, based on the monomer component constituting the acrylic copolymer.

Further, when an isocyanate crosslinking agent is used as a crosslinking agent of the acrylic copolymer used in the present invention, it is preferred to use a hydroxyl group-containing vinyl monomer as the vinyl monomer having a functional group reactive therewith.

As the vinyl monomer having a hydroxyl group, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, (methyl) can be used. Acrylic 6. A hydroxyl group-containing (meth) acrylate such as hydroxyhexyl ester, particularly preferably 2-hydroxyethyl (meth)acrylate or 4-hydroxybutyl (meth)acrylate. The content of the hydroxyl group-containing vinyl monomer to be reacted with the isocyanate crosslinking agent is preferably from 0.01 to 1.0% by mass, particularly preferably from 0.03 to 0.3% by mass, based on the monomer component constituting the acrylic copolymer.

Examples of the other vinyl monomer include a sulfonic acid group-containing monomer such as vinyl acetate or 2-propenylamine-2-methylpropanesulfonic acid; and a (meth)acrylic acid having 1 to 3 carbon atoms. A known vinyl monomer such as an ester or a (meth) acrylate having 13 or more carbon atoms, isobornyl (meth)acrylate or styrene.

The content of the other vinyl monomer is preferably from 1.5 to 20% by mass, more preferably from 1.5 to 10% by mass, even more preferably from 2 to 8% by mass, based on the monomer component constituting the acrylic copolymer. By being contained in this range, the cohesive force, the holding power, and the adhesiveness of the adhesive can be easily adjusted to an appropriate range.

The acrylic copolymer can be obtained by copolymerization by a known polymerization method such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method, or an emulsion polymerization method. However, from the viewpoint of water resistance of the adhesive, a solution polymerization method or a bulk is preferred. Polymerization method. The method for initiating the polymerization may be arbitrarily selected as follows: a thermal initiation method using an azo-based thermal polymerization initiator such as a peroxide system such as benzamidine peroxide or ruthenium laurate or a azobisisobutyronitrile; An ultraviolet irradiation initiation method using an acetophenone-based, benzoin-ether-based, benzoin-ketal-based, fluorenylphosphine oxide-based, benzoin-based, or benzophenone-based photopolymerization initiator; Radiation method.

The molecular weight of the acrylic copolymer is from 40 to 1.6 million, preferably from 60 to 1.2 million, in terms of standard polystyrene, as measured by a gel permeation chromatography (GPC).

In the acrylic pressure-sensitive adhesive composition used in the present invention, in order to achieve compatibility with the adherend, reworkability, and removability, it is preferred to use a polymerized rosin ester-based adhesion-imparting resin. The softening point of the polymerized rosin ester-based adhesion-imparting resin is from 100 to 180 ° C, preferably from 120 to 160 ° C.

The amount of the polymerized rosin ester-based adhesion-imparting resin is from 10 to 40 parts by mass, preferably from 13 to 30 parts by mass, per 100 parts by mass of the acrylic copolymer. In addition, one type or two or more types of the polymerizable rosin ester type adhesion-imparting resin can be used.

Further, in the acrylic pressure-sensitive adhesive composition used in the present invention, one type other than the polymerized rosin ester-based adhesion-imparting resin can be used for the purpose of adjusting the adhesion to the adherend, the reworkability, and the re-peelability. The above adhesion imparts a resin. Examples of the other adhesion-imparting resin include rosin-based, polymerized rosin-based, rosin-phenol-based, stabilized rosin-ester-based, disproportionated rosin-ester-based, hydrogenated rosin-ester-based, terpene-based, terpene-phenolic, and petroleum-based resin resins. , (meth) acrylate resin, and the like. When it is used for an emulsion type adhesive composition, it is preferable to use an emulsion type adhesion-imparting resin.

Among them, a disproportionated rosin ester-based adhesion-imparting resin, a rosin-phenol-based adhesion-imparting resin, a hydrogenated rosin-based adhesion-imparting resin, and a (meth)acrylate-based resin are preferable, and a disproportionation having a softening point of 60 to 130 ° C is particularly preferable. The rosin ester is adhered to the resin.

In the case of using the other adhesive-bonding resin, the amount of the polymerized rosin ester-based adhesion-imparting resin is preferably equal to or less than 100 parts by mass of the acrylic copolymer, and more preferably 100 parts by mass of the acrylic copolymer. The total amount of the resin to be imparted is 10 to 30 parts by mass. By setting the ratio of both sides to this range, it is easy to ensure adhesion to the adherend.

In the acrylic pressure-sensitive adhesive composition, in order to improve the cohesive force of the pressure-sensitive adhesive layer, it is preferred to crosslink the pressure-sensitive adhesive. 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 them, a crosslinking agent of a type which is added after the completion of the polymerization to carry out a crosslinking reaction is preferred; an isocyanate crosslinking agent and an epoxy crosslinking agent which are rich in reactivity with the (meth)acrylic copolymer are preferred. The isocyanate crosslinking agent is more preferable from the viewpoint of improving the adhesion to the foam substrate.

Examples of the isocyanate crosslinking agent include toluene diisocyanate, naphthalene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylene diisocyanate, and trimethylolpropane. Toluene diisocyanate and the like. Particularly preferred is a trifunctional polyisocyanate compound. Examples of the trifunctional isocyanate compound include tolylene diisocyanate, a trimethylolpropane adduct thereof, and triphenylmethane isocyanate.

As an index of the degree of crosslinking, the value of the gel fraction of the insoluble portion after the adhesive layer was immersed in toluene for 24 hours was used. The gel fraction is preferably from 25 to 70% by mass. More preferably, it is 30 to 60% by mass, and most preferably 33 to 55% by mass. When it is in this range, both aggregability and adhesion are good.

Further, the measurement of the gel fraction is based on the following. On the release sheet, the adhesive composition was applied to a thickness of 65 μm after drying, and dried at 100 ° C for 5 minutes, aged at 40 ° C for 2 days, and cut into 50 mm squares to prepare a sample. Next, the weight (G1) of the sample before the toluene immersion was measured in advance, and the toluene-insoluble portion of the sample immersed in the toluene solution at 23 ° C for 24 hours was filtered with a 300-mesh metal mesh to separate and measure. The weight (G2) of the residue after drying at 110 ° C for 1 hour was determined by the following formula.

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

As an additive, if necessary, it can be arbitrarily added to the adhesive composition: a plasticizer, a softener, an antioxidant, a glass, a plastic fiber, a hollow microsphere, a bead, a metal powder, a filler, a pigment, a dye, and the like. A known additive such as a leveling agent, a tackifier, a water repellent, and an antifoaming agent.

In the adhesive layer used for the double-sided adhesive tape of the present invention, the temperature at which the maximum value of the loss tangent (tan δ) is displayed at a frequency of 1 Hz is preferably -30 ° C to 10 ° C. In particular, when it is desired to improve the drop impact resistance in a low temperature environment, it is more preferably from -30 ° C to 0 ° C, most preferably from -25 ° C to -5 ° C.

Further, in the double-sided adhesive tape of the present invention, the temperature at which the maximum value of the loss tangent (tan δ) is displayed at a frequency of 1 Hz is preferably -30 ° C to 20 ° C, more preferably -30 ° C to 10 ° C, preferably. It is -25 ° C ~ 5 ° C. Further, the maximum value of the loss tangent (tan δ) at a frequency of 1 Hz is 1.0 or less, preferably 0.8 or less. By setting the maximum value of the tangent to the display loss of the adhesive layer or the maximum value of the loss tangent of the double-sided adhesive tape and the temperature indicating the maximum value, it is possible to easily impart good adhesion to the adherend at normal temperature. Adhesion resistance and drop resistance in a low temperature environment below 0 °C.

Here, the storage elastic modulus (G') of the adhesive layer used in the double-sided adhesive tape of the present invention at a frequency of 1 Hz is not particularly specified as long as the above-described loss tangent (tan δ) range is satisfied, but when When the storage elastic modulus (G') at 20 ° C is 2.6 × 10 ⁵ Pa or more, preferably 3.0 × 10 ⁵ Pa or more, the tolerance (airtightness) can be easily imparted in the following cases: airtightness A high electronic device may be caused by an increase in the internal pressure accompanying an increase in the temperature of the machine; and a force of a water pressure (0.11 MPa) or more having a water depth of 1 m may be applied to the member fixed by the double-sided adhesive tape from the press-peeling direction.

Loss tangent (tan δ), from the storage elastic modulus (G') obtained by dynamic dispersion measurement based on temperature dispersion, and the loss elastic modulus (G"), according to the formula of tan δ = G" / G' Out. According to the dynamic viscoelasticity measurement based on temperature dispersion, the maximum value of the loss tangent (tan δ) at a certain frequency and the temperature at which the maximum value is displayed can be obtained.

The dynamic viscoelastic property can be selected by appropriately selecting the kind and ratio of the monomer used in the acrylic copolymer constituting the adhesive, the kind of the polymerization initiator and the amount thereof, the crosslinking agent, and the polymerized rosin ester-based adhesion. The type and amount of the resin to be adhered to the resin, the polymerization method, and the like are adjusted.

Here, in terms of the dynamic viscoelastic property of the above-mentioned adhesive layer, it is specified according to the loss tangent of the dynamic viscoelastic spectrum at a specific frequency, a specific temperature, or the loss tangent and the storage elastic modulus, and further, according to a specific frequency The dynamic viscoelastic spectrum is defined by the temperature of the loss tangent maximum, or the maximum value of the loss tangent. In the measurement of dynamic viscoelasticity, a viscoelasticity tester (trade name: Ares2KSTD, manufactured by Rheometric Co., Ltd.) was used, and a test piece was sandwiched between parallel disks as a measuring unit of the test machine, and the measurement was performed at a frequency of 1 Hz from -50. Storage elastic modulus (G') and loss elastic modulus (G") from °C to 150 ° C. For the test piece, the adhesive layer or double-sided adhesive tape is formed to a thickness of about 2 mm, sandwiched between parallel disks Between the measurements.

The thickness of the adhesive layer used in the present invention is simple from the viewpoint of ensuring adhesion to the adherend, reworkability, and removability even when a thin adhesive tape is formed. The thickness is preferably from 10 to 100 μm, more preferably from 30 to 80 μm.

The release sheet used in the present invention is not particularly limited, but may be, for example, a synthetic resin film such as polyethylene, polypropylene or polyester film, paper, non-woven fabric, cloth, foamed sheet or metal poise, and their laminates. A release sheet which is subjected to a release treatment such as an organic lanthanum treatment, a long-chain alkyl group treatment, or a fluorine-based treatment for improving the releasability from the adhesive is applied to at least one surface of the substrate such as a body.

Among them, a release sheet which is subjected to an organic bismuth release treatment on a single side of a paper in which polyethylene is laminated and a polyester film is preferably used.

[double-sided adhesive tape]

In the double-sided adhesive tape of the present invention, by using the above-mentioned foam substrate and the adhesive layer, proper adhesion to the adherend is exhibited, and interlayer damage of the foam substrate is less likely to occur, and Even in the case where interlaminar cracks are generated, the adhesive does not remain on the surface of the member and is easily peeled off. Therefore, in the manufacture of a portable electronic device or the like, the double-sided adhesive tape which is unsuccessfully joined to the unfinished product When the member or the like is peeled off (reworked), and when the casing or the member is separated, detached, and disassembled in order to repair, regenerate, or reuse the finished product such as a portable electronic device, the improvement can be improved. The efficiency of the work of re-attaching the new double-sided adhesive tape after the double-sided adhesive tape is removed from the casing and the member, the yield of the member and the like, and the recovery rate. Further, in terms of fixing the members of the electronic device having the waterproof function, the intrusion of water from the adhesion gap can be effectively prevented, and the waterproof function is excellent.

As an embodiment of the double-sided adhesive tape of the present invention, the basic structure is such that a foam base material is used as a center core, and an adhesive layer is provided on both surfaces of the base material. The substrate and the adhesive layer may be directly laminated or may have other layers. These forms may be appropriately selected depending on the intended use, and when the tape is further provided with dimensional stability and tensile strength, a laminate layer such as a polyester film may be provided; and when the tape is provided with light blocking properties, shading may be provided. Layer; when ensuring light reflectivity, a light reflecting layer may be provided. In the case where these other layers are provided, a water-repellent layer is used as the other layer.

As the laminate layer, a film made of various resins typified by a polyester film can be used. The thickness of the foamed substrate is preferably from 1 to 16 μm, more preferably from 3 to 12 μm, from the viewpoint of followability of the foam substrate.

As the light-shielding layer, a light-shielding layer formed of an ink having a coloring agent such as a pigment can be easily used, and a layer formed of a black ink can be preferably used because it has excellent light-shielding properties. As the reflective layer, a layer formed of a white ink can be easily used. The thickness of these layers is preferably 2 to 20 μm, more preferably 4 to 6 μm. When the thickness is within this range, curling of the substrate due to curing shrinkage of the ink is less likely to occur, and the workability of the tape is good.

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

The thickness of the double-sided adhesive tape of the present invention may be appropriately adjusted depending on the form of use, and is 70 to 1400 μm. In the case of fixing a member of an electronic device, particularly in the case of a small-sized and thin portable electronic device, since a thin tape thickness is required, it is preferably 100 to 600 μm, particularly preferably 120 μm to 500 μm. By making the thickness of the tape to this thickness, it is also suitable for a thin type ‧ small portable electronic machine, and a good waterproof function can be achieved.

In the double-sided adhesive tape of the present invention, the surface adhesive strength 1 measured by 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 of the above-mentioned surface bonding strength 1 are as follows.

1) Two sheets of a double-sided adhesive tape having a width of 5 mm and a length of 4 cm were attached in parallel to a 5 cm square acrylic plate having a thickness of 2 mm at 23 °C.

2) Next, the acrylic plate with the double-sided adhesive tape made of 1) is attached to the center of the acrylic plate in such a manner that the center of the acrylic plate is aligned with the center of the ABS plate, and the thickness of the hole having a diameter of 1 cm is 2 mm at the center portion. A 10×15 cm rectangular smooth ABS plate was pressed one by one with a 2 kg roller, and then left at 23° C. for 1 hour to serve as a test piece.

3) From the ABS side of the test piece, the acrylic plate was pressed at 10 mm/min by a tensile tester equipped with a stainless steel probe having a diameter of 8 mm, and the strength of the peeled acrylic plate was measured.

Further, in the double-sided adhesive tape of the present invention, the surface adhesive strength 2 measured according to the following measurement conditions is preferably 250 mJ or more, and more preferably 350 mJ or more.

The measurement conditions of the above-mentioned surface bonding strength 2 are as follows.

1) After cutting the double-sided adhesive tape into 2 cm square, it was attached to an acrylic plate having a thickness of 2 mm and 2 cm square.

2) The acrylic plate with the double-sided adhesive tape attached to the center portion of the acrylic plate and the central portion of the polyimide plate is attached to a 4 cm square having a thickness of 1 cm in the center portion and having a thickness of 2 cm. On a polyamide plate (40% by mass of glass fiber was added), one back pressure was applied to a 2 kg roller, and then left at 23 ° C for 24 hours to obtain a test piece.

3) The test piece was placed on a stainless steel pedestal having a height of 3 cm and a thickness of 5 mm, which was 4 cm square, and the polyamine side was turned upward.

4) The copper cone having a weight of 5 mm and a length of 1 cm at the front end of the polyacetamide side was made to have an aluminum foil having a diameter of 5 mm and a length of 1 cm, and the cone was continuously dropped at intervals of 10 cm from the height of 10 cm (3 times per stage). Measurement: The height at which the tape was peeled off or damaged was confirmed on the test piece.

5) Calculated based on the measurement results: drop energy mJ (= 9.8 × height (m) × 100 g).

With the double-sided adhesive tape of the present invention, even a thin tape thickness exhibits good adhesion and followability with the adherend, and reworkability and re-peelability. Therefore, in order to improve the yield at the time of manufacture of an electronic device, etc., the double-sided adhesive tape, a member, etc. which are unsuccessfully joined to an unfinished product are peeled (reprocessed), or in order to repair a finished product. It is also possible to separate the casing and the member by recycling or recycling, and to disassemble and disintegrate the body. It is also easy to remove the double-sided adhesive tape, thereby improving the efficiency of re-cooperation, the yield and recovery rate of components and products. . As a specific use form, it can be suitably used in the electronic device such as an electronic notebook, a mobile phone, a PHS, a camera, a music player, a television, etc., and the protective panel of the information display part is attached to the casing, and the casings are mutually The combination of the housing, the sheet-shaped numeric key, the input device such as a touch panel, the bonding of the casing and the decorative sheet, and the fixing of various other members and modules.

Further, in the double-sided adhesive tape of the present invention, even a thin tape thickness exhibits an appropriate adhesion to the adherend, and can effectively prevent water from entering from the adhesion gap, and has excellent waterproof function. . Therefore, it is possible to effectively impart a waterproof function to a portable electronic device in which the thickness is increased, the volume restriction in the casing is strict, and it is difficult to separately provide a water sealing means. As a specific use form, it can be suitably used for: in a portable electronic device such as an electronic notebook, a mobile phone, a PHS, a camera, a music player, a television, etc., the protective panel of the information display part is attached to the casing, and the casing is The bodies are bonded to each other, and the housing is bonded to an input device such as a sheet-like numeric key or a touch panel, a combination of a casing and a decorative sheet, and fixing of various other members and modules. In addition, it is possible to separate the casing and the member, and to disassemble and disintegrate the casing and the member while effectively providing the waterproof function to the portion using the conventional water sealing means such as a rubber seal, a gasket, or a sealant. Repair, regenerate, and reuse the finished product.

Example

(Modulation of Adhesive Solution A)

In a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel, and a nitrogen inlet, 93.54 parts by mass of butyl acrylate, 3 parts by mass of vinyl acetate, 2.2 parts by mass of acrylic acid, and N-vinyl-2-pyrrolidone 1.2 parts by mass, 0.06 parts by mass of 4-hydroxybutyl acrylate, 0.1 parts by mass of 2,2'-azobisisobutyronitrile as a polymerization initiator, dissolved in a solvent composed of 100 parts by mass of ethyl acetate, The mixture was polymerized at 60 ° C for 12 hours to obtain an acrylic copolymer having a weight average molecular weight of 700,000 (in terms of polystyrene). Then, 15 parts by mass of PENSELD 135 (pentaerythritol ester of polymerized rosin, softening point 135 ° C) manufactured by Arakawa Chemical Co., Ltd., and SUPER ESTERA 100 (a glyceride of disproportionated rosin, softening point 100) manufactured by Arakawa Chemical Co., Ltd. were added to 100 parts by mass of the acrylic copolymer. °C) 12 parts by mass, ethyl acetate was added, and uniformly mixed to obtain an adhesive solution A having a nonvolatile content of 40%.

(Modulation of Adhesive Solution B)

In a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel, and a nitrogen inlet, 74.9 parts by mass of butyl acrylate, 20 parts by mass of 2-ethylhexyl acrylate, 2 parts by mass of acrylic acid, and vinyl acetate 3 were used. 0.1 parts by mass, 0.1 parts by mass of 4-hydroxybutyl acrylate, and 0.1 parts by mass of 2,2'-azobisisobutyronitrile as a polymerization initiator, dissolved in a solvent composed of 100 parts by mass of ethyl acetate, at 70 The polymerization was carried out for 12 hours at ° C to obtain an acrylic copolymer having a weight average molecular weight of 500,000 (in terms of polystyrene). Then, 25 parts by mass of PENSEL D135 manufactured by Arakawa Chemical Co., Ltd. was added to 100 parts by mass of the acrylic copolymer, and ethyl acetate was added thereto, and uniformly mixed to obtain an adhesive solution B having a nonvolatile content of 50%.

[Example 1]

(modulation of double-sided adhesive tape)

To 1.100 parts by mass of the above-mentioned 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 added, and after stirring for 15 minutes, the peeling treatment was performed. The PET film having a thickness of 75 μm was applied, and the thickness after drying was 35 μm, and dried at 80 ° C for 3 minutes to form an adhesive layer.

Next, in 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 electric power) On both sides of the haze-treated wetting index of 52 mN/m), after laminating one of the aforementioned adhesive sheets, lamination was carried out using a roller having a linear pressure of 5 kg/cm. Thereafter, it was aged at 40 ° C for 48 hours to obtain a double-sided adhesive sheet having a thickness of 200 μm.

[Examples 2 to 5]

The foam base material described in Table 1 was used instead of the white polyolefin-based foam, and the thickness after drying of the pressure-sensitive adhesive was changed to the thickness shown in Table 1, and the same method as in Example 1 was obtained. Double-sided adhesive tape.

[Embodiment 6]

The same method as in Example 1 was carried out 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 in an amount of 100 parts by mass based on 100 parts by mass of the adhesive solution A. To get a double-sided adhesive tape.

[Examples 7, 8]

2.0 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 above-mentioned adhesive solution B, and the mixture was stirred for 15 minutes, and then subjected to a peeling treatment. The PET film having a thickness of 75 μm was applied, and the thickness after drying was set to the thickness 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 as in Example 1 except that the adhesive layer was used.

[Embodiment 9]

Replacement of white polyolefin-based foam in black ethylene-vinyl acetate foam (thickness: 800 μm, expansion ratio of 8 times, 25% compressive strength: 34 kPa, tensile strength: 24.8 N/cm, surface electricity) On both sides of the haze treatment with a wetting index of 52 mN/m), 2.0 parts by mass of "Coronate L-45" manufactured by Nippon Polyurethane Co., Ltd. (isocyanate-based crosslinking agent, solid content 45%) was added to 100 parts by mass of the adhesive solution B. After stirring for 15 minutes, the film was coated on a PET film having a thickness of 75 μm which was subjected to the release treatment, and dried to a thickness of 50 μm, and dried at 80° C. for 3 minutes to form an adhesive layer. A double-sided adhesive tape was obtained by the same method as in Example 8 except that the adhesive layer was used.

[Embodiment 10]

(Modulation of Adhesive Solution F)

In a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel, and a nitrogen inlet, 85.9 parts by mass of butyl acrylate, 4 parts by mass of acrylic acid, 10 parts by mass of methyl methacrylate, and 4-hydroxybutyl acrylate were used. 0.1 parts by mass of 0.1 parts by mass of 2,2'-azobisisobutyronitrile as a polymerization initiator, dissolved in a solvent composed of 100 parts by mass of ethyl acetate, and polymerized at 60 ° C for 12 hours to obtain a weight average An acrylic copolymer having a molecular weight of 700,000 (in terms of polystyrene). Then, 10 parts by mass of PENSEL D160 (pentaerythritol ester of polymerized rosin) manufactured by Arakawa Chemical Co., Ltd., acrylic resin composed of 97 parts by mass of cyclohexyl methacrylate and 3 parts by mass of acrylic acid were added to 100 parts by mass of the acrylic copolymer. (weight average molecular weight: 6000, glass transition temperature: 66 ° C) 10 parts by mass, ethyl acetate was added, and uniformly mixed to obtain an adhesive solution F having a nonvolatile content of 30%.

(modulation of double-sided adhesive tape)

0.9 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 above-mentioned adhesive solution F, and after stirring for 15 minutes, the peeling treatment was performed. The PET film having a thickness of 75 μm was coated on the film to have a thickness of 35 μm after drying, and dried at 80 ° C for 3 minutes to form an adhesive layer. A double-sided adhesive tape was obtained by the same method as in Example 1 except that the adhesive layer was used.

[Example 11]

(Modulation of Adhesive Solution G)

71.9 parts by mass of butyl acrylate, 20 parts by mass of 2-ethylhexyl acrylate, 5 parts by mass of acrylic acid, and methyl acrylate 3 in a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel, and a nitrogen inlet. 0.1 parts by mass of 2-hydroxyethyl acrylate, 0.1 parts by mass of 2,2'-azobisisobutyronitrile as a polymerization initiator, dissolved in a solvent composed of 100 parts by mass of ethyl acetate, at 70 parts by mass The polymerization was carried out for 12 hours at ° C to obtain an acrylic copolymer having a weight average molecular weight of 600,000 (in terms of polystyrene). Then, 20 parts by mass of PENSEL D135 (pentaerythritol ester of polymerized rosin) manufactured by Arakawa Chemical Co., Ltd., and 10 parts by mass of T160 (terpene phenol) manufactured by YASUHARA CHEMICAL Co., Ltd. were added to 100 parts by mass of the acrylic copolymer, and ethyl acetate was added thereto to be uniform. The mixture was mixed to obtain an adhesive solution G having a nonvolatile content of 45%.

(modulation 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 above-mentioned adhesive solution G, and the thickness of the peeling treatment was performed after stirring for 15 minutes. The 75 μm PET film was coated, dried to a thickness of 35 μm, and dried at 80 ° C for 3 minutes to form an adhesive layer. Except for this, a double-sided adhesive tape was obtained by the same method as in Example 1.

[Comparative Examples 1, 2]

A double-sided adhesive tape was obtained in the same manner as in Example 1 except that the foam base material described in Table 2 was used instead of the white polyolefin foam.

[Comparative Example 3]

A non-woven fabric (weight per unit area: 17 g/m ² , tensile strength: 16.0 N/cm) was used instead of the white polyolefin-based foam, and an adhesive having a thickness of 70 μm after drying was used, and Example 1 was used. The same method is used to obtain a double-sided adhesive sheet.

[Comparative Example 4]

In addition to using polyethylene terephthalate (PET) film (thickness: 100μm, tensile strength: 210N/cm, surface corona treatment with a wetting index of 52mN/m) instead of white polyolefin hair A double-sided adhesive sheet was obtained by the same method as in Example 1 except that the thickness of the foam was dried after the adhesive was dried.

[Comparative Example 5]

(Modulation of Adhesive Solution C)

In a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel, and a nitrogen inlet, 93.54 parts by mass of butyl acrylate, 3 parts by mass of vinyl acetate, 2.2 parts by mass of acrylic acid, and N-vinyl-2-pyrrolidone 1.2 parts by mass, acrylic acid 4. 0.06 parts by mass of hydroxybutyl ester and 0.1 parts by mass of 2,2'-azobisisobutyronitrile as a polymerization initiator, dissolved in a solvent composed 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 (in terms of polystyrene) was obtained. Then, 25 parts by mass of Arakawa Chemical SUPER ESTER A 100 was added as an adhesion-imparting resin to 100 parts by mass of the acrylic copolymer, and ethyl acetate was added thereto to uniformly mix to obtain an adhesive solution C having a nonvolatile content of 40%. .

(modulation of double-sided adhesive tape)

1.0 part 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 above-mentioned adhesive solution C, and the mixture was stirred for 15 minutes, and then subjected to a peeling treatment. The PET film having a thickness of 75 μm was coated on the film to have a thickness of 35 μm after drying, and dried at 80 ° C for 3 minutes to form an adhesive layer. Except for this, a double-sided adhesive tape was obtained by the same method as in Example 1.

[Comparative Example 6]

(Modulation of Adhesive Solution D)

In a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel, and a nitrogen gas inlet, 97.9 parts by mass of butyl acrylate, 2.0 parts by mass of acrylic acid, and 0.1 part by mass of 4-hydroxybutyl acrylate were used as a polymerization initiator. 0.1 parts by mass of 2,2'-azobisisobutyronitrile, dissolved in a solvent composed of 100 parts by mass of ethyl acetate, and polymerized at 70 ° C for 12 hours to obtain a weight average molecular weight of 800,000 (in terms of polystyrene) Conversion) of acrylic copolymer. Next, ethyl acetate was added and uniformly mixed to obtain an adhesive solution D having a nonvolatile content of 30%.

(modulation of double-sided adhesive tape)

2.5 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 D, and the thickness of the peeling treatment was performed after stirring for 15 minutes. The 75 μm PET film was coated, dried to a thickness of 50 μm, and dried at 80 ° C for 3 minutes to form an adhesive layer. Except for this, a double-sided adhesive tape was obtained by the same method as in Example 1.

[Comparative Example 7]

(Modulation of Adhesive Solution E)

98 parts by mass of 2-ethylhexyl acrylate, 1 part by mass of acrylic acid, and 1 part by mass of 4-hydroxybutyl acrylate were used as a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel, and a nitrogen inlet. 0.1 parts by mass of 2,2'-azobisisobutyronitrile of a polymerization initiator was dissolved in a solvent composed of 100 parts by mass of ethyl acetate, and polymerized at 70 ° C for 12 hours to obtain a weight average molecular weight of 800,000 ( Acrylic copolymer in terms of polystyrene. Ethyl acetate was added and uniformly mixed to obtain an adhesive solution E having a nonvolatile content of 30%.

(modulation of double-sided adhesive tape)

1.8 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 E, and the thickness of the peeling treatment was performed after stirring for 15 minutes. The 75 μm PET film was coated, dried to a thickness of 50 μm, and dried at 80 ° C for 3 minutes to form an adhesive layer. Except for this, a double-sided adhesive tape was obtained by the same method as in Example 1.

The foam substrate used in the above examples and comparative examples, and the double-sided adhesive tapes obtained in the above examples and comparative examples were evaluated as follows. The results obtained are shown in Tables 1-3.

[Thickness of foam substrate and double-sided adhesive tape]

The measurement was carried out by a DIAL THICKNESS GAUGES G type manufactured by Ozaki. In the case of a double-sided adhesive tape, the measurement was performed after peeling off the release film.

[Interlayer strength of foam substrate]

1.1 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 C, and the thickness of the peeling treatment was performed after stirring for 15 minutes. The 75 μm PET film was coated, dried to a thickness of 50 μm, and dried at 80 ° C for 3 minutes to form an adhesive layer. Next, each of the above-mentioned adhesive layers was bonded to both surfaces of the foam to which the interlayer strength was to be evaluated, and then laminated by a roll having a linear pressure of 5 kgf/cm. Thereafter, the film was aged at 40 ° C for 48 hours to prepare a double-sided adhesive tape for measuring the interlayer strength.

Next, the adhesive side of one side was lined with a 2 cm wide and 10 cm long (flow direction of the foam substrate) of a polyethylene terephthalate film having a thickness of 25 μm, at 23 ° C. In a ‧50% RH environment, one back and forth pressure was applied to the stainless steel plate with a 2 kg roller and placed at 40 ° C for 48 hours. After standing at 23 ° C for 24 hours, the strength at which the foam was torn (damaged to the substrate) at a tensile speed of 300 mm/min at a tensile speed of 300 mm/min in an environment of 23 ° C ‧50% RH was measured. (N/cm).

[Tensile modulus, tensile strength]

The foam substrate or the double-sided adhesive sheet (peeling off the release film) of the test piece having a line spacing of 2 cm (flow direction of the foam substrate) and a width of 1 cm was processed at a stretching speed of 300 mm/min. The film was stretched to cut off, and the maximum strength in the measurement was measured.

[Average bubble diameter in the flow direction and width direction of the foam substrate]

The foam substrate was cut into 1 cm in the width direction and the flow direction, and the central portion of the cut surface of the cut foam substrate was cut by a scanning electron microscope (SEM) (S-2380N, manufactured by Hitachi, Ltd.). After magnifying 50 times, the cross section in the width direction or the flow direction of the foam base material was photographed, and the cut surface of the foam base material was accommodated in the photograph for the entire length in the thickness direction of the base material. In the obtained photograph, all the bubble diameters existing in the cut surface of the 2 mm portion in the flow direction or the width direction before the enlargement were measured, and the average bubble diameter was calculated from the average value.

[Average bubble diameter in the thickness direction of the foam substrate]

The thickness of the foam base material photographed by SEM was measured, and SEM photographing was performed under the same conditions as the measurement of the average bubble diameter in the flow direction of the foam base material. In the obtained photograph, the number of bubbles in the thickness direction existing in an arbitrary place of the foam base material was counted by visual observation, and the average bubble diameter in the thickness direction was calculated from the following formula.

Average bubble diameter in the thickness direction (μm) = thickness of the foam substrate (μm) / number of bubbles

It was measured at arbitrary three places, and the average value was made into the average bubble diameter in the thickness direction.

[surface bonding strength 1]

1) Two sheets of double-sided adhesive tape having a width of 5 mm and a length of 4 cm were attached in parallel to an acrylic plate having a thickness of 2 mm and a thickness of 5 cm at 23 ° C (ACRYLITE MR200 (trade name) manufactured by Mitsubishi Rayon Co., Ltd., hue: Transparent).

2) Next, an acrylic plate with a double-sided adhesive tape made of 1) was attached to a rectangular ABS plate having a thickness of 1 cm in the center and having a diameter of 1 cm and a thickness of 10 × 15 cm (Takiron, hue: Natural color, no wrinkles), the center of the acrylic plate was aligned with the center of the ABS plate, and one back pressure was applied with a 2 kg roller, and then left at 23 ° C for 1 hour to serve as a test piece.

3) From the ABS side of the test piece, the acrylic plate was pressed at 10 mm/min by a tensile tester equipped with a stainless steel probe having a diameter of 8 mm, and the strength of the peeled acrylic plate was measured.

[surface bonding strength 2]

1) After the double-sided adhesive tape was cut into 2 cm squares, it was attached to an acrylic plate having a thickness of 2 mm and a size of 2 cm square.

2) Attach an acrylic plate with a double-sided adhesive sheet to a polyamine plate with a diameter of 1 cm at the center and a thickness of 2 mm and 4 cm square (Reny (trade name) manufactured by Mitsubishi Engineering Plastics Co., Ltd.) 40% by weight of glass fiber was added, the center portion of the acrylic plate was aligned with the center portion of the polyamide plate, and one back pressure was applied with a 2 kg roller, and then left at 23 ° C for 24 hours to obtain a test piece.

3) The test piece was placed on a stainless steel pedestal having a shape of 4 cm square, a height of 3 cm, and a thickness of 5 mm with the polyamine side facing up.

4) The copper cone having a weight of 5 mm and a length of 1 cm at a tip end of the polyacrylamide side was continuously dropped from 10 cm at intervals of 10 cm (three times per stage) toward the acrylic plate, and it was measured: The height at which the tape is peeled off or damaged can be confirmed on the test piece. Here, when the test piece after the test of the height of 70 cm was not peeled off or damaged, the test was terminated, and it was called "686<".

5) The drop energy mJ (= 9.8 × height (m) × 100 g) was calculated from the measurement results.

[Reprocessing suitability]

1) A double-sided adhesive tape is formed into a frame-like sample having a shape of 65 mm × 43 mm and a width of 2 mm, and attached to an acrylic plate having a thickness of 2 mm and a shape of 65 mm × 45 mm (Mitsubishi Laiyang Co., Ltd. ACRYLITE MR200 (trade name), hue : Transparent, the same below). Next, it was attached to an ABS board (manufactured by Takiron Co., Ltd., hue: natural color, no wrinkles, the same below) having a thickness of 2 mm and a shape of 90 mm × 50 mm, and was subjected to one back and forth press with a 2 kg roller, and then placed at 23 ° C. 24 hours as a test piece.

2) For the test piece, the acrylic plate was peeled off in the vertical direction at 23 ° C, and the state of the tape at this time was evaluated.

3) Next, the double-sided adhesive tape remaining on the ABS or the acrylic plate was peeled off by a hand at a peeling angle of about 135 degrees, and the ease of peeling at this time was evaluated.

◎: There was no interlaminar crack in the substrate and it was peeled off without a paste residue.

○: Although the foam base material is broken between the layers, when the double-sided adhesive tape remaining by hand is used, it can be peeled off without any residue.

×: The paste remains on the adherend. Or the foam substrate is ruptured between the layers, and then the double-sided adhesive tape remaining by hand is used and cannot be peeled off.

[re-peelability]

1) A double-sided adhesive tape was formed into a frame-like sample having a shape of 65 mm × 43 mm and a width of 2 mm, and attached to an acrylic plate having a thickness of 2 mm and an outer shape of 65 mm × 45 mm. Next, the ABS plate having a thickness of 2 mm and an outer shape of 90 mm × 50 mm was attached, and the mixture was pressurized one by one with a 2 kg roller, and then left at 23 ° C for 24 hours.

2) Next, it was left to stand in an environment of ‧90% RH at 60 ° C for 7 days, and then placed in an environment of 23 ° C and ‧50% RH as a test piece.

3) For the test piece, the acrylic plate was peeled off in the vertical direction at 23 ° C, and the state of the tape at this time was evaluated.

4) Next, the double-sided adhesive tape remaining on the ABS or acrylic plate was peeled off by a hand at a peeling angle of about 135 degrees, and the ease of peeling at this time was evaluated.

◎: Interlaminar cracks of the non-foamed substrate were removed, and then peeled off without a paste residue.

○: Although the foam base material is broken between the layers, when the double-sided adhesive tape remaining by hand is used, it can be peeled off without any residue.

×: The paste remains on the adherend. Alternatively, the foam substrate may be ruptured between the layers, and thereafter, the double-sided adhesive tape remaining by hand may not be peeled off.

[following test]

1) The double-sided adhesive tape was cut into a width of 1 cm and a length of 5 cm, and attached to a central portion in the width direction of an acrylic plate having a thickness of 2 mm and a width of 2 cm × a length of 5 cm to prepare an acrylic plate with a double-sided adhesive tape. (figure 1).

2) Next, two adhesive tapes of a polyethylene terephthalate substrate having a thickness of 20 μm and a width of 5 mm and a length of 2 cm were attached in parallel to another width of 2 mm in the width direction at intervals of 1 cm. At the center of the 2 cm × 5 cm acrylic plate, an acrylic plate with a height difference was formed (Fig. 2).

3) After the adhesive sheet with the double-sided adhesive tape was placed on the adhesive tape portion of the acrylic sheet with the height difference at 23 ° C, one back pressure was applied from the end with a 2 kg roller (Fig. 3).

4) From the side of the acrylic plate with the height difference, the following state of the double-sided adhesive tape in the vicinity of the height difference was evaluated by visual observation.

○: The double-sided adhesive tape is adhered to the acrylic plate with the height difference.

×: The double-sided adhesive tape is not adhered to the acrylic plate with the height difference in the vicinity of the height difference.

[Water resistance test 1]

1) The double-sided adhesive tape was formed into a frame-like sample having a shape of 65 mm × 45 mm and a width of 2 mm, attached to an acrylic plate having a thickness of 2 mm and a shape of 65 mm × 45 mm, and then attached to an ABS plate having a thickness of 2 mm and a shape of 65 mm × 45 mm. After one back pressure was applied with a 2 kg roller, it was allowed to stand at 23 ° C for 24 hours to serve as a test piece.

2) The test piece was immersed for 10 minutes in a 5 mass% surfactant solution (made by tapping a JOY manufactured by P & G Co., Ltd.) at 23 ° C, and then taken out for 30 minutes for 30 minutes, and then evaluated for re-impregnation. Whether there is water immersion in the frame at the time of solution.

○: no water immersion

×: There is water immersion

[Water resistance test 2]

1) A double-sided adhesive tape was formed into a frame-like sample having a shape of 65 mm × 45 mm and a width of 2 mm, attached to an acrylic plate having a thickness of 2 mm and a shape of 65 mm × 45 mm, and attached to an ABS plate having a thickness of 2 mm and a shape of 150 mm × 100 mm. Central Department (Figure 4). After one back pressure was applied with a 2 kg roller, it was allowed to stand at 23 ° C for 24 hours as a test piece.

2) U at a pedestal of DuPont-type impact tester (manufactured by TESTER Industries Co., Ltd.) at a height of 150 mm, a width of 100 mm, and a height of 45 mm at 23 ° C A font measuring table (aluminum material having a thickness of 5 mm) was placed thereon with a test piece and the acrylic plate facing downward (Fig. 5). From the side of the ABS plate, a stainless steel core having a diameter of 25 mm and a mass of 300 g was dropped from a height of 30 cm, and impact on the central portion of the ABS plate was applied five times at intervals of 10 seconds (Fig. 6). Here, when an impact was applied and the acrylic sheet fell off, the test was terminated.

3) The test piece subjected to the impact was immersed for 10 minutes at a temperature of 23 ° C in a 5 mass % surfactant solution (manufactured by tapping a JOY manufactured by P & G Co., Ltd.), and then taken out for 30 minutes for 30 minutes. The presence or absence of water immersion in the frame was evaluated when immersed in the solution again.

◎: There was no water immersion, and the appearance of the foam did not change.

○: Although there was no water immersion, it was confirmed that a part of the foam layer had a slight laceration.

×: There is water immersion, or the acrylic plate peels off at the stage of falling impact.

[Air tightness test]

1) A double-sided adhesive tape was formed into a frame-like sample having a shape of 5 cm × 4 cm and a width of 2 mm, and attached to a thickness of 2 mm and an outer shape of 5 cm × 5 cm, and an open-cell acrylic plate having a hole having a diameter of 3 mm at the center, and attached to the thickness The central portion of a rectangular acrylic plate having a diameter of 3 mm and a shape of 7 cm × 5 cm (Fig. 7). After one back pressure was applied with a 2 kg roller, it was allowed to stand at 23 ° C for 24 hours as a test piece.

2) At 23 ° C, a pressure of 0.02 MPa was applied from the open-cell acrylic plate with nitrogen (Fig. 8).

3) Determine the time until nitrogen leaks from the sash-like tape portion.

As is apparent from the above-described Examples 1 to 9, the double-sided adhesive tape of the present invention has excellent adhesion to the adherend, reworkability, and removability. Further, the double-sided adhesive tapes of Examples 10 to 11 have excellent airtightness and excellent workability while being excellent in adhesion and reworkability. On the other hand, in the double-sided adhesive tape of Comparative Example 1, since the interlayer strength and the tensile strength of the foam base material are low, it is difficult to peel off the double-sided adhesive tape at the time of reworking or re-peeling in practical use. . Further, in the double-sided adhesive tapes of Comparative Examples 2 to 4, since the followability was poor, it was confirmed that water immersion was observed in the water repellency test, and it was difficult to achieve water repellency. In Comparative Example 5, it was difficult to peel off the double-sided adhesive tape during reworking and re-peeling. In the case of Comparative Examples 6 and 7, the adhesion was low, and it was difficult to achieve water repellency.

1. . . Double-sided adhesive tape

2. . . Acrylic board

3. . . Adhesive tape for height difference

4. . . Evaluation of follow-up

5. . . ABS board

6. . . Where the core hits

7. . . Falling impact

8. . . U-shaped measuring bench

9. . . Open cell acrylic plate

10. . . 3mm thick acrylic plate

11. . . Nitrogen introduction tube

12. . . Nitrogen

Fig. 1 is a conceptual view showing an acrylic plate with a double-sided adhesive tape for the following test.

Fig. 2 is a conceptual view showing an acrylic plate with a height difference for the following test.

Fig. 3 is a conceptual view for observing the state of adhesion of an acrylic plate with a double-sided adhesive tape and an acrylic plate with a height difference in the following direction from the cross-sectional direction.

Fig. 4 is a conceptual diagram showing a test piece for the water repellency test 2.

Figure 5 shows the test piece for the test stand waterproof test 2 loaded on the U with the acrylic plate facing downward. In the state of the font measuring table 6 (aluminum material having a thickness of 5 mm), a conceptual view is observed from the bottom surface side of the measuring table 6.

Fig. 6 is a conceptual diagram showing an operation of applying a drop impact.

Fig. 7 is a conceptual diagram showing a test piece of the airtightness test.

Fig. 8 is a conceptual diagram showing an operation of applying pressure to a test piece.

1. . . Double-sided adhesive tape

2. . . Acrylic board

Claims (11)

A double-sided adhesive tape having an adhesive layer 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. The adhesive layer is composed of an acrylic pressure-sensitive adhesive composition containing an acrylic copolymer and a polymerized rosin ester-based adhesion-imparting resin, and the acrylic copolymer contains 4 carbon atoms. The (meth) acrylate of ～12 and the vinyl monomer having a carboxyl group are used as a monomer component. The double-sided adhesive tape according to the first aspect of the invention, 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 adhesive tape according to claim 1 or 2, wherein the foam substrate has an average cell diameter in the thickness direction of from 1 to 200 μm, and an average cell diameter in the flow direction and the width direction of from 1.2 to 700 μm. The double-sided adhesive tape of claim 3, wherein a ratio of an average bubble diameter in a flow direction of the foam substrate to an average bubble diameter in a thickness direction is 1.2 to 15, and an average bubble diameter in a width direction is relative to The ratio of the average cell diameter in the thickness direction is 1.2 to 15. A double-sided adhesive tape according to claim 1 or 2, wherein the foam substrate is a polyolefin-based foam substrate. The double-sided adhesive tape according to the first or second aspect of the invention, wherein the polymerized rosin ester-based adhesion-imparting resin is contained in an amount of 10 to 40 parts by mass based on 100 parts by mass of the acrylic copolymer. The double-sided adhesive tape according to claim 1 or 2, wherein the acrylic copolymer contains a vinyl monomer having a tertiary amine skeleton in the molecule as a monomer component. A double-sided adhesive tape according to claim 1 or 2, which is used for fixing a member of an electronic machine that can be regenerated or reused. A double-sided adhesive tape according to claim 1 or 2, which is used for fixing a member of an electronic machine having a waterproof function, which is a foam formed of closed cells. The double-sided adhesive tape of claim 1 or 2, wherein the adhesive layer exhibits a maximum value of loss tangent in the dynamic viscoelastic spectrum at a frequency of 1 Hz of -30 to 10 °C. For example, in the double-sided adhesive tape of claim 1, wherein the double-sided adhesive tape exhibits a maximum value of the loss tangent in the dynamic viscoelastic spectrum at a frequency of 1 Hz, the temperature is -30 to 20 ° C, and the maximum value of the loss tangent It is 1.0 or less.