JP6729836B2 - Double-sided adhesive tape - Google Patents

Description

The present invention relates to a double-sided pressure-sensitive adhesive tape that can be used in the production scenes of various articles including electronic devices such as car navigation systems, personal computers, televisions, and smartphones.

The double-sided pressure-sensitive adhesive tape used for portable electronic devices such as smartphones is required to have shock resistance so that it does not peel off due to shock when the device is dropped. Therefore, the double-sided pressure-sensitive adhesive tape used for this purpose needs to have a shock absorbing layer.

In addition, portable electronic devices are required to have a waterproof function, and even double-sided adhesive tape used for fixing members has a high degree of compliance with steps on the housing joints and circuit boards to prevent water from entering. And high adhesive strength have been demanded. In addition, in recent years, from the viewpoint of designability, a curved surface or a panel having a complicated shape has been often used, and the double-sided adhesive tape has not only the unevenness and the high step, but also the ability to follow the curved surface and the complicated shape. It is desired (Patent Document 1).

On the other hand, in the process of assembling electronic devices that normally use double-sided adhesive tape with release paper on both sides, after peeling off one release paper from the double-sided adhesive tape, attach it to the housing and press and press in the direction perpendicular to the attachment surface. , Then, peel off the other release paper of the double-sided adhesive tape and stick the display, press the press in the direction perpendicular to the sticking surface in the same manner, but if the joint between the housing and the display is a three-dimensional curved surface, Since the force of pressurizing is vector-decomposed, it is not possible to apply a uniform force to all positions on the sticking surface, making it difficult to achieve perfect sticking. Therefore, the followability of the double-sided adhesive tape with respect to the three-dimensional curved surface is significantly reduced. If the double-sided adhesive tape does not completely follow the housing or display, a slight gap will be created there, and peeling will occur, and the gap will serve as a water immersion path, and there was a problem that the waterproof performance could not be secured. ..

Further, in the foam double-sided pressure-sensitive adhesive tape which has been used for waterproofing a portable electronic device having a conventional flat display, it is inevitable that relatively large bubbles called voids are mixed in due to its manufacturing method. In recent years, due to the expansion of the display section of portable electronic devices, the joint between the display and the case has become narrower, and when the tape width becomes smaller than the bubble diameter, there is a problem that it becomes a water entry path and loses waterproofness. ..

In addition to impact resistance and followability, it is also possible to create a double-sided adhesive tape that uses a flexible resin layer instead of a foam base material and laminates an adhesive layer with good followability It is also possible to achieve waterproofness at. However, since the pressure-sensitive adhesive laminate is easily torn during peeling and easily remains on the adherend, there is a problem in reworkability that it can be peeled off neatly when it is stuck in the assembly process of portable electronic devices. ..

Japanese Patent Laid-Open No. 2015-98554

The problem to be solved by the present invention is to properly follow various parts having a three-dimensional curved surface, especially parts for electronic devices, and to provide good impact resistance, waterproofness and reworkability even when narrow-width processing is performed. It is to provide a double-sided adhesive tape to be applied.

The inventors of the present invention have laminated a shock-absorbing pressure-sensitive adhesive layer on one or both sides of a substrate, and a pressure-sensitive adhesive layer having good followability on the outermost layers on the front and back sides, so that followability and impact resistance even in a narrow width. , And found a double-sided adhesive tape that is excellent in waterproofness and reworkability.

That is, the present invention is a double-sided pressure-sensitive adhesive tape having one or two or more pressure-sensitive adhesive layers on both sides of a substrate directly or via another layer, and the outermost pressure-sensitive adhesive layer among the pressure-sensitive adhesive layers ( The storage elastic modulus at 25° C. of 1) is 50 to 200 kPa, the glass transition temperature (Tg) of the pressure-sensitive adhesive layer (2) other than the outermost layer is 0° C. or less, and the thickness of the base material layer is 3 The present invention relates to a double-sided pressure-sensitive adhesive tape having a thickness of -30 μm.

INDUSTRIAL APPLICABILITY The double-sided pressure-sensitive adhesive tape of the present invention exhibits suitable adhesion to an adherend having a three-dimensional curved surface, can effectively prevent intrusion of water through the adhesion gap even with a narrow width, and has an excellent waterproof function. In addition, peeling does not occur even when the electronic device is dropped, and the tape can be easily disassembled without tearing when the electronic device is disassembled.
For this reason, the design is advanced and the waterproof performance and the impact resistance performance can be effectively imparted even to an electronic device or the like having a three-dimensional curved surface portion at the joint portion between the housing and the display.

It is a top view of the frame-shaped sample of the double-sided adhesive tape of this invention. FIG. 3 is a plan view (lattice portion is a curved surface shape) and a sectional view of an adherend A. FIG. It is a three-dimensional sectional view of the adherend A. FIG. 3 is a plan view (lattice part has a curved surface shape) and a cross-sectional view of an adherend B. FIG. It is explanatory drawing of the sample for impact resistance tests of the double-sided adhesive tape of this invention. It is a sample explanatory view for the impact resistance test of the double-sided adhesive tape of this invention. It is a sample explanatory view for the impact resistance test of the double-sided adhesive tape of this invention.

The double-sided pressure-sensitive adhesive tape of the present invention is a double-sided pressure-sensitive adhesive tape having one or more pressure-sensitive adhesive layers on both sides of the substrate directly or via another layer, and the pressure-sensitive adhesive layer is the outermost layer. The storage layer at 25° C. has a storage elastic modulus of 50 to 200 kPa, the adhesive layer (2) other than the outermost layer has a glass transition temperature (Tg) of 0° C. or less, and the thickness of the base material layer. The double-sided pressure-sensitive adhesive tape has a thickness of 3 to 30 μm.

[Adhesive layer]
The outermost pressure-sensitive adhesive layer (1) of the double-sided pressure-sensitive adhesive tape of the present invention has a storage elastic modulus at 25°C of 50 to 200 kPa, preferably 52 to 150 kPa, more preferably 55 to 100 kPa, and 60 to 90 kPa. More preferable. By selecting the above range for the storage elastic modulus at 25° C., suitable followability for a three-dimensional curved surface and no adhesive remaining on the adherend when the double-sided adhesive tape is peeled off by hand, and good reworkability can be obtained. realizable.

The pressure-sensitive adhesive layer (2) other than the outermost surface has a glass transition temperature (Tg) of 0° C. or lower, preferably −40 to 0° C., more preferably −30 to −5° C., and −20 to −10° C. Particularly preferred. By setting the glass transition temperature (Tg) of the adhesive layer other than the outermost surface within the above range, when an electronic device or the like joined with the double-sided adhesive tape is dropped, it is possible to appropriately absorb impact and prevent peeling. You can

Moreover, the thickness of each pressure-sensitive adhesive layer is preferably 1 to 100 μm, more preferably 5 to 90 μm, and further preferably 20 to 80 μm. This is because by setting the thickness of the pressure-sensitive adhesive layer within this range, suitable pressure-sensitive adhesive strength is exhibited.

(Adhesive composition)
The pressure-sensitive adhesive composition that constitutes the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape of the present invention may be any pressure-sensitive adhesive composition that can be used for ordinary double-sided pressure-sensitive adhesive tapes as long as it can form a pressure-sensitive adhesive layer having the above-mentioned properties. As the pressure-sensitive adhesive composition, an acrylic copolymer consisting of (meth)acrylate alone or a copolymer of (meth)acrylate and another monomer is used as a base polymer, and if necessary, a tackifying resin or a cross-linking resin is used. An acrylic pressure-sensitive adhesive composition containing an additive such as an agent can be preferably used.

Examples of the (meth)acrylate monomer that can be used in the production of the acrylic copolymer include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and t-. Butyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl methacrylate, and the like, and one or more of them are listed. Used. Among them, it is preferable to use a (meth)acrylate having an alkyl group having 1 to 12 carbon atoms, and it is more preferable to use a (meth)acrylate having an alkyl group having 4 to 8 carbon atoms. It is preferable to use either one or both of -butyl acrylate and 2-ethylhexyl acrylate because the adhesion to the adherend is easily secured and the cohesive force is excellent.

The (meth)acrylate monomer is preferably used in an amount of 60% by mass or more, and in the range of 80% by mass to 98.5% by mass, based on the total amount of the monomers used for producing the acrylic copolymer. Is more preferable, and it is more preferable to use it in the range of 90% by mass to 98.5% by mass because it is easy to secure the adhesiveness to the adherend and the cohesive force is excellent.

As the other monomer, a highly polar vinyl monomer is preferably used, and a vinyl monomer having a hydroxyl group, a vinyl monomer having a carboxyl group, and a vinyl monomer having an amide group are particularly preferable. These other monomers can be used alone or in combination of two or more.

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, and 6-hydroxyhexyl (meth)acrylate. (Meth)acrylate can be used.

As the vinyl monomer having a carboxyl group, acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth)acrylic acid dimer, crotonic acid and the like can be used, and among them, acrylic acid is preferably used.

As the vinyl monomer having an amide group, N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylamide, N,N-dimethylacrylamide and the like can be used.

Other high polar vinyl monomers include, in addition to those mentioned above, vinyl acetate, ethylene oxide-modified succinic acid acrylate, sulfonic acid group-containing monomers such as 2-acrylamido-2-methylpropanesulfonic acid, and the like.

The content of the other monomer is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and more preferably 2.5 to 10% by mass in the monomer component constituting the acrylic copolymer. % Is more preferable. It is more preferable that the content is within the above range because the adhesion to the adherend is easily secured and the cohesive force is excellent.

When the adhesive containing a crosslinking agent described below is used, it is preferable to use an acrylic polymer having a functional group that reacts with a functional group of the crosslinking agent as the acrylic polymer. Examples of the functional group that the acrylic polymer may have include a hydroxyl group.

The hydroxyl group can be introduced into the acrylic polymer by using, for example, a vinyl monomer having a hydroxyl group as the monomer. When an isocyanate cross-linking agent is used as the cross-linking agent, a vinyl monomer having a hydroxyl group is preferable as the vinyl monomer having a functional group that reacts with the cross-linking agent, and 4-hydroxybutyl (meth)acrylate or 6-hydroxyhexyl (meth) is used. Acrylate is especially preferred. The content of the vinyl monomer having a hydroxyl group that reacts with the isocyanate cross-linking agent is preferably 0.01 to 1.0 mass% of the monomer component constituting the acrylic copolymer, and 0.03 to 0.6. Mass% is more preferable, and 0.05 mass%-0.3 mass% is especially preferable.

Acrylic copolymer can be obtained by copolymerization by a known polymerization method such as a solution polymerization method, a hull-shaped polymerization method, a suspension polymerization method, an emulsion polymerization method, but from the viewpoint of the water resistance of the pressure-sensitive adhesive. A solution polymerization method and a bulk polymerization method are preferable. The method for initiating the polymerization is also a peroxide-based method such as benzoyl peroxide or lauroyl peroxide, or a heat-based method using an azo-based thermal polymerization initiator such as azobisisobutylnitrile, acetophenone-based, benzoin ether-based, benzyl. An initiation 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.

The acrylic copolymer preferably has a molecular weight of 400,000 to 3,000,000 in terms of standard polystyrene measured by gel permeation chromatograph (GPC) and a weight average molecular weight of 600,000 to 2,000,000. It is more preferable to use one having an average molecular weight.

The weight average molecular weight refers to a value measured by gel permeation chromatography (GPC method) and converted to standard polystyrene. Specifically, the weight average molecular weight can be measured under the following conditions using a GPC device (HLC-8320GPC) manufactured by Tosoh Corporation.

Sample concentration: 1.0 mass% (tetrahydrofuran solution)
Sample injection volume: 100 μL
Eluent: Tetrahydrofuran Flow rate: 0.8 mL/min Measurement temperature: 40°C
This column: TSKgel GMHHR-H(S) x 2 Guard column: TSKguradcolumn HHR(S)
Detector: Differential refractometer Weight average molecular weight of standard polystyrene: 10,000 to 20 million (manufactured by Tosoh Corporation)

In the acrylic pressure-sensitive adhesive composition used in the present invention, it is preferable to use a tackifying resin in order to improve the adhesion to the adherend. As the tackifying resin, rosin-based, polymerized rosin-based, polymerized rosin ester-based, rosin phenol-based, stabilized rosin ester-based, disproportionated rosin ester-based, hydrogenated rosin ester-based, terpene-based, terpene phenol-based, petroleum resin Examples thereof include resins and (meth)acrylate resins. When used in an emulsion type pressure-sensitive adhesive composition, it is preferable to use an emulsion type tackifying resin.

Among them, disproportionated rosin ester-based tackifier resin, polymerized rosin ester-based tackifier resin, rosin phenol-based tackifier resin, hydrogenated rosin ester-based tackifier resin, (meth)acrylate-based resin, terpene phenol-based resin, petroleum Resins are preferred.

As the tackifying resin, it is preferable to use one having a softening point in the range of 30° C. to 180° C., and one having a softening point in the range of 70° C. to 140° C. ensures the adhesion to the adherend. It is more preferable because it is easy and has excellent cohesive force. When the (meth)acrylate tackifying resin is used, the (meth)acrylate tackifying resin preferably has a glass transition temperature of 30° C. to 200° C., and 50° C. to 160° C. Is more preferable.

Regarding the compounding ratio when the acrylic copolymer and the tackifying resin are used, the content of the tackifying resin is preferably 5 to 50 parts by mass, and 10 to 40 parts by mass based on 100 parts by mass of the acrylic copolymer. More preferably, it is parts by mass. By setting the ratio of the both to be within the range, it becomes easy to secure the adhesion to the adherend.

In the acrylic pressure-sensitive adhesive composition, it is preferable to crosslink the pressure-sensitive adhesive in order to increase the cohesive force of the pressure-sensitive adhesive layer. Examples of such a crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, a metal chelate-based crosslinking agent, and an aziridine-based crosslinking agent. Among them, a crosslinking agent of a type that is added after completion of the polymerization to promote a crosslinking reaction is preferable, and an isocyanate crosslinking agent and an epoxy crosslinking agent that are highly reactive with a (meth)acrylic copolymer are preferable. Examples of the isocyanate cross-linking agent include tolylene diisocyanate, naphthylene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and trimethylolpropane-modified tolylene diisocyanate. Particularly preferred is a trifunctional polyisocyanate compound. Examples of the trifunctional isocyanate compound include tolylene diisocyanate, trimethylolpropane 3-adducts thereof, and triphenylmethane isocyanate.

As an index of the degree of crosslinking, a gel fraction value 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 30 to 60% by mass, still more preferably 35 to 55% by mass. Within the above range, the adhesion to the adherend is easily secured and the cohesive force is excellent, which is preferable.

The gel fraction is measured as follows. The release-treated surface of the release liner was coated with the pressure-sensitive adhesive so that the thickness after drying was 50 μm, and dried in an environment of 100° C. for 3 minutes, and then in an environment of 40° C. The pressure-sensitive adhesive layer was formed by aging for a day.
A test piece was obtained by cutting the pressure-sensitive adhesive layer into a square having a length of 50 mm and a width of 50 mm.
After measuring the mass (G1, not including the release liner) of the test piece, the test piece was immersed in toluene for 24 hours in an environment of 23°C.
After the immersion, the mixture of the test piece and toluene was filtered using a 300-mesh wire net to extract an insoluble component in toluene. The mass (G2) of the insoluble component dried in an environment of 110° C. for 1 hour was measured.
The gel fraction was calculated based on the mass (G1), the mass (G2) and the following formula.

Gel fraction (mass %)=(G2/G1)×100
As the acrylic pressure-sensitive adhesive composition, as an additive, if necessary, a plasticizer, a softening agent, an antioxidant, a filler such as glass or plastic fibers, balloons, beads, metal powder, or a pigment/dye. Known agents such as colorants, leveling agents, thickeners, water repellents, defoamers, etc. can be optionally added to the acrylic pressure-sensitive adhesive composition.

The pressure-sensitive adhesive layer used in the double-sided pressure-sensitive adhesive tape of the present invention preferably has a temperature showing a peak value of loss tangent (tan δ) at a frequency of 1 Hz of −40° C. to 15° C., more preferably −20° C. to 5° C. .. By setting the peak value of the loss tangent of the pressure-sensitive adhesive layer within the above range, it becomes easy to give good adhesion to the adherend at room temperature.

The loss tangent (tan δ) is calculated from the storage elastic modulus (G′) and the loss elastic modulus (G″) obtained by the dynamic viscoelasticity measurement by temperature dispersion from the equation tan δ=G″/G′. To be From the dynamic viscoelasticity measurement by temperature dispersion, the temperature showing the peak value of the loss tangent (tan δ) at a frequency of 1 Hz can be obtained.

The 25°C storage elastic modulus of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape of the present invention is 50 to 200 kPa, preferably 52 to 150 kPa, more preferably 55 to 100 kPa, and further preferably 60 to 90 kPa. This is because when the storage elastic modulus of the adhesive layer is extremely high, the adhesiveness to the three-dimensional curved surface decreases, and when the storage elastic modulus of the adhesive layer is extremely low, the cohesive force decreases and peeling resistance increases. This is because

The dynamic viscoelastic properties include the types and ratios of monomers used in the copolymer constituting the pressure-sensitive adhesive, the types and amounts of polymerization initiators, the types and amounts of cross-linking agents and tackifying resins, polymerization methods, etc. It can be adjusted by selecting appropriately.

The above-mentioned 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, and further, at a specific frequency. It is defined by the temperature at which the loss tangent peak of the viscoelastic spectrum is shown, or the peak value of the loss tangent. In the measurement of dynamic viscoelasticity, a viscoelasticity tester (manufactured by TA Instruments Japan Co., trade name: ARES G2) was used, and the measuring unit of the tester was made of stainless steel and had a diameter of 8 mm. A test piece (a pressure-sensitive adhesive layer formed to have a diameter of 8 mm and a thickness of about 2 mm) is sandwiched between disks, and the storage elastic modulus (G') and loss elastic modulus (G'' from -50°C to 150°C at a frequency of 1 Hz). ) Is measured.

The thickness of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape of the present invention is preferably 10 to 100 μm in terms of the thickness on one side, because adhesion to the adherend is easily secured even when a thin tape is used, and preferably 25 to 80 μm. Is more preferable.

[Base material]
The base material of the double-sided pressure-sensitive adhesive tape of the present invention has a thickness of 3 to 30 μm, preferably 4 to 20 μm, and more preferably 5 to 15 μm. By using a base material having a thickness within the above range, excellent adhesion can be realized even when joining rigid bodies having a three-dimensional curved surface shape without causing a gap into which water or the like enters.

The breaking strength of the base material is preferably 4 to 85 N/10 mm, more preferably 7 to 80 N/10 mm, and further preferably 8 to 35 N/10 mm. At this time, the breaking strength is the maximum value of the tensile strength obtained by conducting a tensile test on a substrate having a width of 10 mm at 300 m/min. When a base material having a breaking strength within the above range is selected, the base material will not be torn when the double-sided pressure-sensitive adhesive tape is manually peeled off. Furthermore, since the base material has a certain degree of rigidity, the repulsion of the base material is small, and the base material suitably follows even an adherend having a three-dimensional curved surface shape, an uneven shape, or a rough surface, and has excellent adhesion.

Further, the type of the substrate is not particularly limited, for example, a polyolefin resin film such as a polyethylene film, a polypropylene film, an ethylene-propylene copolymer polymer film, an ethylene-vinyl acetate copolymer polymer film, a polyurethane resin film, an acrylic resin. Polyolefin foam sheets such as films, rubber films made of elastomers, polyethylene foam sheets, polypropylene foam sheets, ethylene-propylene copolymer polymer foam sheets, ethylene-vinyl acetate copolymer polymer foam sheets, etc. A polyurethane foam sheet, an acrylic foam sheet or the like can be used. Among these substrates, polyester films, polyurethane resin films, acrylic resin films, polyolefin foams from the viewpoints of dimensional stability and impact resistance when double-sided adhesive tapes are processed into narrow window frame shapes. Sheets, polyurethane foam sheets, and acrylic foam sheets are preferred. Further, these base materials may be used alone or as a laminate of two or more kinds.

[Double-sided adhesive tape]
The double-sided pressure-sensitive adhesive tape of the present invention shows suitable adhesion to an adherend having a three-dimensional curved surface by using the pressure-sensitive adhesive layer and the base material, and particularly when used for fixing parts of electric equipment. Has an excellent waterproof function, which can effectively prevent intrusion of water and the like from the close contact gap.

The double-sided pressure-sensitive adhesive tape of the present invention basically has a constitution in which a pressure-sensitive adhesive layer is provided on both surfaces of a base material. The base material and the pressure-sensitive adhesive layer may be laminated directly or via another layer. Specifically, the adhesive layer (1)-adhesive layer (2)-base material-adhesive layer (2)-adhesive layer (1) may have a five-layer structure, or the adhesive layer (1)- The four-layer structure of the pressure-sensitive adhesive layer (2)-base material-pressure-sensitive adhesive layer (1) may be used. Further, the pressure-sensitive adhesive having a storage elastic modulus at 25° C. of 50 to 200 kPa and a glass transition temperature (Tg) of 0° C. or less is used in both the pressure-sensitive adhesive layer (1) and the pressure-sensitive adhesive layer (2). Applicable to That is, the pressure-sensitive adhesive layer (1) and the pressure-sensitive adhesive layer (2) can be laminated with the same pressure-sensitive adhesive layer.

These modes may be appropriately selected depending on the intended use. When imparting dimensional stability and tensile strength to the tape, a laminate layer such as a polyester film is used, and when imparting concealing property or light shielding property to the tape. The light-shielding layer may be provided with a light-reflecting layer when ensuring light reflectivity. When these other layers are provided, a waterproof layer may be used as the other layer.

As the light-shielding layer, a layer formed of an ink containing a colorant such as a pigment is simply used, and a layer made of black ink is preferably used because it has excellent light-shielding properties. As the reflective layer, a layer formed of white ink can be easily used. The thickness of these layers is preferably 2 to 20 μm, more preferably 3 to 10 μm, and most preferably 4 to 6 μm. When the thickness is within the above range, curling of the substrate due to curing shrinkage of the ink is unlikely to occur, and the workability of the tape becomes good.

The double-sided pressure-sensitive adhesive tape of the present invention can be produced by a known and commonly used method. For example, a direct copying method in which an acrylic pressure-sensitive adhesive composition is applied and dried directly on the base material or on the surface of another layer laminated on the base material, or an acrylic pressure-sensitive adhesive composition is applied to a release sheet. Then, a transfer method in which the substrate is dried and then attached to the surface of the substrate or another layer is mentioned.

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 device parts, particularly in the case of small and thin portable electronic devices, a thin tape thickness is required, and therefore the thickness is preferably 80 to 1000 μm, more preferably 100 to 500 μm, and more preferably 200 μm to Particularly preferably, it is 400 μm. By setting the tape thickness to the above thickness, it is easy to secure the adhesion to the adherend even for thin and small portable electronic devices, and it has excellent cohesive force, so it can be suitably applied and has a good waterproof function. realizable.

INDUSTRIAL APPLICABILITY The double-sided pressure-sensitive adhesive tape of the present invention exhibits suitable adhesion to an adherend, can effectively prevent water from entering through the adhesion gap, and has an excellent waterproof function. For this reason, it is possible to effectively provide the waterproof function even in a portable electronic device or the like, which is becoming thinner and the volume limitation in the housing is severe and it is difficult to provide a separate water sealing means. As a specific usage mode, for example, in a portable electronic device such as an electronic notebook, a mobile phone, a smartphone, a tablet type terminal, a PHS, a camera, a music player, the protection panel of the information display unit is attached to the casing, and the casing is used. It can be suitably used for sticking bodies to each other, sticking a housing to an input device such as a ten-key pad or a touch panel, sticking a housing to a decorative sheet, and fixing other various members and modules.

Examples will be specifically described below, but the present invention is not limited to these examples.

(Adjustment of adhesive A)
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen introduction tube, and a thermometer, 95.9 parts by mass of n-butyl acrylate, 4 parts by mass of acrylic acid, 0.1 part by mass of 2-hydroxyethyl acrylate, and ethyl acetate. 200 parts by mass were charged, and the temperature was raised to 72° C. with stirring while blowing nitrogen.

To the above mixture, 2 parts by mass of a 2,2′-azobis(2-methylbutyronitrile) solution (solid content: 0.1% by mass) previously dissolved in ethyl acetate was added, and the mixture was stirred and held at 72° C. for 4 hours. After that, it was held at 75° C. for 5 hours. By filtering through a 200-mesh wire mesh, an acrylic polymer solution A (nonvolatile content: 33.3 mass%) having a weight average molecular weight of 1.04 million was obtained.

Next, the acrylic polymer A is polymerized rosin ester-based tackifying resin D-125 (manufactured by Arakawa Chemical Industry Co., Ltd.) and 10 parts by mass of disproportionated rosin ester-based tackifying resin A-100 (manufactured by Arakawa Chemical Industry Co., Ltd.). ) 10 parts by mass were mixed and stirred, and then ethyl acetate was added to obtain an adhesive solution A having a solid content of 38%.

Vernock D-40 (manufactured by DIC Corporation, trimethylolpropane adduct of tolylene diisocyanate, isocyanate group content 7% by mass, nonvolatile content 40% by mass) as a cross-linking agent with respect to 100 parts by mass of the adhesive solution A. After adding 2 parts by mass and stirring and mixing so as to be uniform, an adhesive A was obtained by filtering with a 100 mesh wire mesh.

(Adjustment of adhesive B)
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen introduction tube, and a thermometer, 60.94 parts by mass of n-butyl acrylate, 35 parts by mass of 2-ethylhexyl acrylate, 4 parts by mass of acrylic acid, 0.4 parts of 4-hydroxybutyl acrylate. 06 parts by mass and 200 parts by mass of ethyl acetate were charged, and the temperature was raised to 72° C. while blowing nitrogen while stirring.

To the above mixture, 2 parts by mass of a 2,2′-azobis(2-methylbutyronitrile) solution (solid content: 0.1% by mass) previously dissolved in ethyl acetate was added, and the mixture was stirred and held at 72° C. for 4 hours. After that, it was held at 75° C. for 5 hours. This was filtered through a 200-mesh wire net to obtain an acrylic polymer solution B (nonvolatile content: 33.3 mass%) having a weight average molecular weight of 900,000.

The acrylic polymer B is polymerized rosin ester-based tackifying resin D-125 (manufactured by Arakawa Chemical Industry Co., Ltd.) 5 parts by mass and disproportionated rosin ester-based tackifying resin A-100 (manufactured by Arakawa Chemical Industry Co., Ltd.) 10 masses. After mixing and stirring the parts, ethyl acetate was added to obtain an adhesive solution B having a solid content of 31%.

1. Vernock D-40 (manufactured by DIC Corporation, trimethylolpropane adduct of tolylene diisocyanate, isocyanate group content 7% by mass, nonvolatile content 40% by mass) as a cross-linking agent relative to 100 parts by mass of the adhesive solution B. After adding 4 parts by mass and stirring and mixing so as to be uniform, an adhesive B was obtained by filtering with a 100-mesh wire net.

(Adjustment of adhesive C)
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen introduction tube, and a thermometer, 80.94 parts by mass of n-butyl acrylate, 5 parts by mass of 2-ethylhexyl acrylate, 10 parts by mass of cyclohexyl acrylate, 4 parts by mass of acrylic acid, 4 -Hydroxybutyl acrylate (0.06 parts by mass) and ethyl acetate (200 parts by mass) were charged, and the temperature was raised to 72°C while blowing nitrogen while stirring.

To the above mixture, 2 parts by mass of a 2,2′-azobis(2-methylbutyronitrile) solution (solid content: 0.1% by mass) previously dissolved in ethyl acetate was added, and the mixture was stirred and held at 72° C. for 4 hours. After that, it was held at 75° C. for 5 hours. By filtering this through a 200-mesh wire net, an acrylic polymer solution C (nonvolatile content: 33.3% by mass) having a weight average molecular weight of 1.2 million was obtained.

Next, the acrylic polymer C was polymerized rosin ester-based tackifying resin D-125 (manufactured by Arakawa Chemical Industry Co., Ltd.) and 5 parts by mass of disproportionated rosin ester-based tackifying resin A-100 (manufactured by Arakawa Chemical Industry Co., Ltd.). ) 15 parts by mass were mixed and stirred, and then ethyl acetate was added to obtain an adhesive solution C having a solid content of 31%.

Vernock D-40 (manufactured by DIC Corporation, trimethylolpropane adduct of tolylene diisocyanate, isocyanate group content 7% by mass, nonvolatile content 40% by mass) as a crosslinking agent, relative to 100 parts by mass of the pressure-sensitive adhesive solution C. The adhesive C was obtained by adding 0 parts by mass, stirring and mixing so as to be uniform, and then filtering with a 100-mesh wire net.

(Adjustment of adhesive D)
Vernock D-40 (manufactured by DIC Corporation, trimethylolpropane adduct of tolylene diisocyanate, isocyanate group content 7% by mass, nonvolatile content 40% by mass) relative to 100 parts by mass of SK Dyne 2094 (manufactured by Soken Kagaku) %) 1.2 parts by mass was added, and the mixture was stirred and mixed so as to be uniform and then filtered through a 100-mesh wire net to obtain an adhesive D.

(Adjustment of adhesive E)
Vernock D-40 (manufactured by DIC Corporation, trimethylolpropane adduct of tolylene diisocyanate) as a cross-linking agent, and an isocyanate group content of 7 with respect to 100 parts by mass of the acrylic polymer solution A (nonvolatile content: 33.3% by mass). % By mass and 40% by mass of non-volatile content), 1.2 parts by mass were added, and the mixture was stirred and mixed so as to be uniform, and then filtered through a 100-mesh wire net to obtain an adhesive E.

(Adjustment of adhesive F)
Vernock D-40 (manufactured by DIC Corporation, trimethylolpropane adduct of tolylene diisocyanate, isocyanate group content 7% by mass, nonvolatile content 40% by mass) relative to 100 parts by mass of SK Dyne 1502C (manufactured by Soken Chemical Industry Co., Ltd.) %) 1.5 parts by mass was added, and the mixture was stirred and mixed so as to be uniform and then filtered through a 100-mesh wire net to obtain an adhesive F.

(Example 1)
The pressure-sensitive adhesive A was applied to the surface of a silicone-treated release liner (manufactured by Sumika Kogyo Co., Ltd.) using a bar coater so that the thickness of the pressure-sensitive adhesive layer after drying would be 62 μm. A pressure-sensitive adhesive layer (1) was prepared by drying at 80° C. for 3 minutes.
Similarly, a pressure-sensitive adhesive layer (2) was formed on the surface of a silicone-treated release liner (manufactured by Sumika Paper Co., Ltd.) so that the thickness of the pressure-sensitive adhesive B after drying was 60 μm. ..

Next, the pressure-sensitive adhesive layer (2) was attached to both sides of a polyester film substrate having a thickness of 6 μm, and the pressure-sensitive adhesive layer (1) was attached to both sides of the polyester film substrate so that the environment was 40° C. A double-sided pressure-sensitive adhesive tape having a thickness of 250 μm was prepared by aging it for 48 hours.

(Example 2)
A double-sided pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 except that a polyester film base material having a thickness of 12 μm was used instead of the polyester film base material having a thickness of 6 μm.

(Example 3)
A double-sided pressure-sensitive adhesive tape was produced in the same manner as in Example 1 except that the pressure-sensitive adhesive C was used instead of the pressure-sensitive adhesive B in the pressure-sensitive adhesive layer (2).

(Example 4)
A double-sided pressure-sensitive adhesive tape was prepared in the same manner as in Example 2 except that the pressure-sensitive adhesive C was used instead of the pressure-sensitive adhesive B in the pressure-sensitive adhesive layer (2).

(Example 5)
In the same manner as in Example 1 except that the pressure-sensitive adhesive B was used in place of the pressure-sensitive adhesive A in the pressure-sensitive adhesive layer (1) and the pressure-sensitive adhesive A was used in place of the pressure-sensitive adhesive B in the pressure-sensitive adhesive layer 2. A double-sided adhesive tape was made.

(Example 6)
A double-sided pressure-sensitive adhesive tape was prepared in the same manner as in Example 5 except that the pressure-sensitive adhesive C was used instead of the pressure-sensitive adhesive A in the pressure-sensitive adhesive layer (2).

(Example 7)
A double-sided pressure-sensitive adhesive tape was produced in the same manner as in Example 5 except that the pressure-sensitive adhesive C was used instead of the pressure-sensitive adhesive B in the pressure-sensitive adhesive layer (1).

(Example 8)
A double-sided pressure-sensitive adhesive tape was prepared in the same manner as in Example 5 except that the pressure-sensitive adhesive B was used instead of the pressure-sensitive adhesive A in the pressure-sensitive adhesive layer (2).

(Example 9)
The pressure-sensitive adhesive A was applied to the surface of a silicone-treated release liner (produced by Sumika Paper Co., Ltd.) using a bar coater so that the thickness of the pressure-sensitive adhesive layer after drying was 77 μm. A pressure-sensitive adhesive layer (1) was prepared by drying at 80° C. for 3 minutes.
Similarly, a pressure-sensitive adhesive layer (2) was formed on the surface of a silicone-treated release liner (manufactured by Sumika Kogyo Co., Ltd.) so that the thickness of the pressure-sensitive adhesive B after drying was 90 μm. ..

Next, the pressure-sensitive adhesive layer (2) was attached to one side of a polyester film substrate having a thickness of 6 μm, and the pressure-sensitive adhesive layer (1) was attached to both sides of the polyester film substrate so that the environment was 40° C. A double-sided pressure-sensitive adhesive tape having a thickness of 250 μm was prepared by aging it for 48 hours.

(Comparative Example 1)
A double-sided pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 except that a polyester film base material having a thickness of 2 μm was used instead of the polyester film base material having a thickness of 6 μm.

(Comparative example 2)
A double-sided pressure-sensitive adhesive tape was produced in the same manner as in Example 1 except that a 38 μm-thick polyester film base was used instead of the 6 μm-thick polyester film base.

(Comparative example 3)
A double-sided pressure-sensitive adhesive tape was prepared in the same manner as in Example 5 except that the pressure-sensitive adhesive D was used instead of the pressure-sensitive adhesive B in the pressure-sensitive adhesive layer (1).

(Comparative Example 4)
A double-sided pressure-sensitive adhesive tape was produced in the same manner as in Example 5 except that the pressure-sensitive adhesive E was used instead of the pressure-sensitive adhesive B in the pressure-sensitive adhesive layer (1).

(Comparative example 5)
A double-sided pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 except that the pressure-sensitive adhesive F was used instead of the pressure-sensitive adhesive B in the pressure-sensitive adhesive layer (2).

(Comparative example 6)
The surface of a silicone-treated release liner (manufactured by Sumika Paper Co., Ltd.) was coated with the pressure-sensitive adhesive A using a bar coater so that the thickness of the pressure-sensitive adhesive layer after drying was 25 μm. An adhesive A layer was prepared by drying at 80° C. for 3 minutes.
Next, the above-mentioned pressure-sensitive adhesive A layer was attached to both sides of the polyolefin foam base material A having a thickness of 200 μm and aged at 40° C. for 48 hours to prepare a double-sided pressure-sensitive adhesive tape having a thickness of 250 μm.

(Follow-up/Waterproof test)
The double-sided pressure-sensitive adhesive tapes produced in Examples and Comparative Examples were cut to have an outer diameter of 136 mm×66 mm, a width of 0.5 mm, and a curvature of 4 mm at the outer diameters of the four corners, to prepare a frame-shaped sample as shown in FIG. After being adhered to the acrylic adherend A shown in FIGS. 2 and 3, it was adhered to the acrylic adherend B shown in FIG. 4, pressurized at a pressure of 20 N/cm ² for 10 seconds, and then allowed to stand for 24 hours. What was done was made into the test piece. However, the portions of the adherend A and the adherend B to which the frame-shaped sample is attached have a three-dimensional curved surface shape.

After allowing the test piece to stand at a water depth of 1 m for 30 minutes (in conformity with IPX7 of JIS C0920), the presence or absence of water immersion in the frame of the frame-shaped double-sided adhesive tape was evaluated.
◯: No water infiltration, good followability to three-dimensional curved surface ×: Poor water, poor followability to three-dimensional curved surface

(Rework test)
The sample used in the waterproof test is disassembled and the double-sided adhesive tape is peeled off by hand. At that time, it was confirmed whether or not the tape was torn and adhesive was left on the adherend.
○: Tear, no adhesive residue ×: Tear or adhesive residue

(Impact resistance test)
The double-sided pressure-sensitive adhesive tapes produced in Examples and Comparative Examples were cut into two pressure-sensitive adhesive tapes having a width of 5 mm and a length of 400 mm.
Next, under an environment of a temperature of 23° C. and a relative humidity of 50% RH, an acrylic plate having a thickness of 2 mm, a width of 50 mm and a length of 50 mm and having a smooth surface (Acrylite MR200 “trademark” of Mitsubishi Rayon Co., Ltd., hue: transparent) was used. The two adhesive tapes were attached to one surface so that a space of 45 mm could be provided in the width direction (FIG. 5).

Next, an acrylonitrile butadiene styrene plate (ABS plate, thickness 2 mm, width 100 mm and length 150 mm) was placed on the surface of the pressure-sensitive adhesive tape, and the surface was reciprocated once with a 5 kg roller, then at 23° C. and relative temperature. A test piece was obtained by allowing it to stand for 24 hours in an environment with a humidity of 50% RH (Fig. 6).
Next, on a pedestal of a DuPont type impact tester (manufactured by Tester Sangyo Co., Ltd.), 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 is installed. The test piece was placed on the top of the test piece so that the acrylic plate forming the test piece faced downward (FIG. 7).
Next, a stainless steel hammer having a diameter of 25 mm and a mass of 300 g was dropped 5 times from the position of 10 cm in height from the ABS plate side.

The above test is repeated while increasing the drop height by 10 cm, and the impact resistance of the adhesive tape is determined based on the drop height (cm) when peeling of the adhesive tape or separation of the acrylic plate is confirmed. evaluated.
◯: The above-mentioned drop height was 70 cm or more.
X: The above-mentioned drop height was less than 70 cm.

1 Double-sided adhesive tape 2 Acrylic plate 3 ABS plate 4 U-shaped measuring table 5 Hammer

Claims (6)

A double-sided pressure-sensitive adhesive tape having one or two or more pressure-sensitive adhesive layers on both sides of a base material directly or through another layer,
Two or more layers of the pressure-sensitive adhesive layer are provided on at least one surface of the base material,
Out of the pressure-sensitive adhesive layers, the outermost pressure-sensitive adhesive layer (1) has a storage elastic modulus at 25° C. of 50 to 200 kPa, and the pressure-sensitive adhesive layers (2) other than the outermost layer have a glass transition temperature (Tg) of 0. Below ℃,
A double-sided pressure-sensitive adhesive tape, wherein the base material has a thickness of 3 to 30 μm. The double-sided pressure-sensitive adhesive tape according to claim 1, wherein the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive composition containing an acrylic copolymer. The double-sided pressure-sensitive adhesive tape according to claim 2 weight-average molecular weight of the acrylic copolymer is from 400000 to 3000000. The double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer has a gel fraction of 25 to 70% by mass. The double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 4, which is attached to a three-dimensional curved surface. Used for component fixing of the electronic device, the double-sided adhesive tape according to claim 1 for imparting water resistance to a fixed portion of the electronic device.

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