TW201915124A - Two-sided adhesive tape - Google Patents

Abstract

The problem to be solved by the present invention is to provide a two-sided adhesive tape that follows electronic equipment components having a three-dimensional curved surface well and imparts high waterproofness. The present invention provides a two-sided adhesive tape characterized in that the two-sided adhesive tape has a base material and an adhesive layer, the storage modulus of the adhesive layer at 25 DEG C is 50-200 kPa, the 25% compressive strength of the base material is 1-2000 kPa, and the two-sided adhesive tape is affixed to electronic equipment components having a three-dimensional curved surface.

Description

Double-sided adhesive tape

The present invention relates to a double-sided adhesive tape which can be used in a manufacturing place of various articles represented by, for example, electronic devices such as car navigation, personal computers, televisions, and smart phones.

In electronic devices centered on televisions or smart phones, waterproofing is progressing. Therefore, the double-sided adhesive tape used for fixing the member is required to have high followability to the step portion of the frame joint portion or the circuit board and the like, and high adhesion strength to prevent water immersion. In recent years, from the viewpoint of design, a curved surface or a panel having a complicated shape is often used, and it is further desired for the double-sided adhesive tape to follow not only the unevenness or the high step but also the performance of the curved surface or the complicated shape.

Further, in recent years, in order to achieve high definition of information display, the use of displays made of organic electroluminescence (EL) has progressed. The organic EL also has a bendable feature, so that a flat display to date can be curved. Along with the curved surface of such a display, there is a case where a three-dimensional curved surface is generated at a joint portion between the frame and the display.

Usually, in the assembly of an electronic device using a double-sided adhesive tape having a release paper on both sides, after peeling off the release paper of one side of the double-sided adhesive tape, it is attached to the frame and perpendicular to the attachment surface. Press and press on. Then, the release paper on the other side of the double-sided adhesive tape was peeled off and attached to the display, and similarly pressed and pressed in a direction perpendicular to the attachment surface.

However, when the joint portion between the frame and the display is a three-dimensional curved surface, the force of the pressing force is decomposed by the vector, so that it is impossible to apply the same force to all the positions of the attached surface, and it is difficult to achieve complete attachment. Therefore, for a three-dimensional surface, the followability of the double-sided adhesive tape is greatly reduced. In the case where the double-sided adhesive tape does not completely follow the frame or the display, a slight gap is generated there, and peeling occurs, and the gap becomes a water immersion path, whereby there is a problem that waterproof performance cannot be ensured.

Conventionally, a double-sided adhesive tape having a rubber-based foam sheet having a high elongation in a three-dimensional curved surface has been known as a base material (Patent Document 1). However, the base material is not versatile and cannot be used for various purposes. . [Prior Art Document] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 7-18229

[Problem to be Solved by the Invention] An object of the present invention is to provide a double-sided adhesive tape which is excellent in following various parts having a three-dimensional curved surface, particularly for electronic equipment, and which imparts high peeling resistance and water repellency. .

[Means for Solving the Problem] The present inventors discovered that by selecting an adhesive layer having a specific storage elastic modulus at 25 ° C corresponding to room temperature and selecting a substrate having a specific compressive strength and combining the above, A double-sided adhesive tape that satisfactorily follows a part having a three-dimensional curved surface, particularly a component for electronic equipment, and is excellent in peeling resistance and water repellency.

That is, the present invention relates to a double-sided adhesive tape characterized by having a substrate and an adhesive layer, and the adhesive layer has a storage elastic modulus at 25 ° C of 50 kPa to 200 kPa, and the substrate The 25% compressive strength is from 1 kPa to 2000 kPa, and the double-sided adhesive tape is attached to a three-dimensional curved surface.

[Effect of the Invention] The double-sided adhesive tape of the present invention exhibits appropriate adhesion to a adherend having a three-dimensional curved surface, can effectively prevent the intrusion of water from the gap, and has an excellent waterproof function. Therefore, in an electronic device or the like which has a high design progress and a three-dimensional curved surface portion at the joint portion between the casing and the display, the waterproof performance can be effectively imparted.

The double-sided adhesive tape of the present invention is a double-sided adhesive tape having a substrate and an adhesive layer, and the adhesive layer has a storage elastic modulus at 25 ° C of 50 kPa to 200 kPa, and the substrate The 25% compressive strength is from 1 kPa to 2000 kPa, and the double-sided adhesive tape is attached to a three-dimensional curved surface.

[Adhesive layer] The adhesive composition constituting the adhesive layer of the double-sided adhesive tape of the present invention may be any adhesive layer which has the above characteristics, and an adhesive used in a usual double-sided adhesive tape can be used. Composition. As the adhesive composition, an acrylic copolymer having a (meth) acrylate alone or a copolymer containing a (meth) acrylate and another monomer can be preferably used as a base polymer and as needed An acrylic pressure-sensitive adhesive composition obtained by applying an additive such as a resin or a crosslinking agent to the adhesive is prepared.

Examples of the (meth) acrylate monomer which can be used in the production of the acrylic copolymer include methyl (meth) acrylate, ethyl (meth) acrylate, and n-butyl (meth) acrylate. Ester, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, (A) As the cyclohexyl acrylate, 2-ethylhexyl methacrylate or the like, one type or two or more types of these may be used. Among them, a (meth) acrylate having an alkyl group having 1 to 12 carbon atoms is preferably used, and a (meth) acrylate having an alkyl group having 4 to 8 carbon atoms is preferably used, and n-butyl acrylate is used. It is preferred that either or both of the ester and the acrylate 2-ethylhexyl ester are easily adhered to the adherend and have excellent cohesive strength.

The (meth) acrylate monomer is preferably used in an amount of 60% by mass or more, and more preferably 80% by mass to 98.5% by mass, based on the total amount of the monomers used in the production of the acrylic copolymer. In the range of 90% by mass to 98.5% by mass, it is more preferable to use it in order to ensure adhesion to the adherend and to have excellent cohesive strength.

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 a mercapto group are particularly preferable. These other monomers may be used alone or in combination of two or more.

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. A hydroxyl group-containing (meth) acrylate such as 6-hydroxyhexyl acrylate.

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

As the vinyl monomer having a mercapto group, N-vinylpyrrolidone, N-vinyl caprolactam, acryloylmorpholine, acrylamide, N,N-dimethylpropene oxime can be used. Amines, etc.

Examples of the other highly polar vinyl monomer include vinyl acetate, ethylene oxide modified succinic acid acrylate, and 2-acrylamide-2-methylpropanesulfonic acid. a sulfonic acid group monomer or the like.

The content of the other monomer is preferably from 1% by mass to 20% by mass, more preferably from 2% by mass to 15% by mass, even more preferably from 2.5% by mass to 10% by mass, based on the monomer component constituting the acrylic copolymer. . It is more preferable because it is contained in this range, and it is easy to ensure adhesion with a to-be-adhered body, and it is excellent in cohesive force.

In the case of using the above-mentioned cross-linking agent as the above-mentioned adhesive, it is preferred to use the acrylic polymer having a functional group reactive with the functional group of the cross-linking agent as the acrylic polymer. Things. The functional group which the acrylic polymer can have is, for example, a hydroxyl group.

The hydroxyl group can be introduced into the acrylic polymer, for example, by using a vinyl monomer having a hydroxyl group as the monomer. In the case where an isocyanate crosslinking agent is used as the crosslinking agent, the vinyl monomer having a functional group reactive therewith is preferably a vinyl monomer having a hydroxyl group, particularly preferably (methyl). 4-hydroxybutyl acrylate, 6-hydroxyhexyl (meth) acrylate. The content of the vinyl monomer having a hydroxyl group reactive with the isocyanate crosslinking agent is preferably from 0.01% by mass to 1.0% by mass, more preferably from 0.03% by mass to 0.6% by mass, based on the monomer component constituting the acrylic copolymer. It is particularly preferably from 0.05% by mass to 0.3% by mass.

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, and from the viewpoint of water resistance of the adhesive, solution polymerization is preferred. Method or block polymerization. The initial method of polymerization may also be arbitrarily selected as follows: the use of heat of the azo-based thermal polymerization initiator such as peroxide, azobisisobutyronitrile or the like, such as benzamidine peroxide or oxidized laurel. Method, or using an acetophenone-based, benzoin ether-based, benzyl ketal-based, fluorenylphosphine oxide-based, benzoin-based, benzophenone-based photopolymerization initiator, starting method by ultraviolet irradiation, or using electrons The method of beam irradiation.

The molecular weight of the acrylic copolymer is preferably from 400,000 to 3,000,000 by weight-average molecular weight in terms of standard polystyrene measured by a gel permeation chromatograph (GPC), more preferably In order to use a weight average molecular weight of 600,000 to 2 million.

In addition, the weight average molecular weight is a value calculated by gel permeation chromatography (GPC method) and calculated by standard polystyrene conversion. Specifically, the weight average molecular weight can be measured by using a GPC apparatus (HLC-8320GPC) manufactured by Tosoh Corporation (TOSOH) Co., Ltd. under the following conditions.

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

In order to improve the adhesion to the adherend, it is preferred to use an adhesive-imparting resin in the acrylic adhesive composition used in the present invention. Examples of the adhesion-imparting resin include rosin-based, polymerized rosin-based, polymerized rosin-ester-based, rosin-phenol-based, stabilized rosin-ester, disproportionated rosin-ester, hydrogenated rosin-ester, terpene-based, terpene-phenol-based, and petroleum-based Resin type, (meth) acrylate type resin, etc. In the case of use in an emulsion type adhesive composition, it is preferred to use an emulsion type adhesion-imparting resin.

Among them, a disproportionated rosin ester-based adhesion-imparting resin, a polymerized rosin-based adhesion-imparting resin, a rosin-phenol-based adhesion-imparting resin, a hydrogenated rosin-based adhesion-imparting resin, a (meth)acrylate-based resin, and a terpene-phenol-based resin are preferable. , petroleum resin.

As the adhesion-imparting resin, it is preferred to use a softening point in the range of 30° C. to 180° C., and in the range of 70° C. to 140° C., it is easy to ensure adhesion to the adherend, and it is excellent in cohesive force. . When the (meth) acrylate adhesion-imparting resin is used, it is preferable to use a glass transition temperature of 30 ° C to 200 ° C as the (meth) acrylate adhesion-imparting resin, and more preferably 50 ° C to 50 ° C. 160 ° C.

The content ratio of the adhesion-imparting resin to 100 parts by mass of the acrylic copolymer is preferably 5 parts by mass to 50 parts by mass, more preferably 10 parts by mass to 40 parts by mass, based on the blending ratio of the acrylic copolymer and the tackifying resin. Share. By setting the ratio of both to this range, it is easy to ensure adhesion to the adherend.

In order to improve the cohesive force of the adhesive layer, it is preferred to crosslink the adhesive in the acrylic adhesive composition. 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 and which allows the crosslinking reaction to proceed is preferably an isocyanate crosslinking agent which is rich in reactivity with the (meth)acrylic copolymer and an epoxy system. Joint agent. Examples of the isocyanate crosslinking agent include toluene diisocyanate, anthranyl-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylene diisocyanate, and trimethylolpropane. Toluene diisocyanate and the like. Particularly preferred are trifunctional polyisocyanate compounds. Examples of the trifunctional isocyanate-based compound include toluene diisocyanate, a trimethylolpropane triadduct, and triphenylmethane isocyanate.

As an index of the degree of crosslinking, a value of a gel fraction for measuring an insoluble component after immersing the adhesive layer in toluene for 24 hours was used. The gel fraction is preferably from 25% by mass to 70% by mass, more preferably from 30% by mass to 60% by mass, even more preferably from 35% by mass to 55% by mass. When it is in the above range, it is easy to ensure adhesion to the adherend and it is excellent in cohesive force, which is preferable.

Further, the gel fraction was measured by the following contents. The adhesive was applied to a release liner of a release liner so as to have a thickness of 50 μm after drying, and dried in an environment of 100 ° C for 3 minutes, followed by an environment at 40 ° C. The aging was carried out for 2 days, whereby an adhesive layer was formed.

A test piece was prepared by cutting the adhesive layer in a square of 50 mm in length and 50 mm in width. After measuring the mass (G1, without release paper) of the test piece, the test piece was immersed in toluene for 24 hours in an environment of 23 °C. After the impregnation, the mixture of the test piece and toluene was filtered using a 300-mesh metal mesh, thereby extracting insoluble components in toluene. The mass (G2) obtained by drying the insoluble component in an environment of 110 ° C for 1 hour was measured. The gel fraction was calculated based on the mass (G1) and the mass (G2) and the following formula. Gel fraction (% by mass) = (G2/G1) × 100

As the acrylic pressure-sensitive adhesive composition, a plasticizer, a softener, an antioxidant, a fiber made of glass or plastic, a balloon, a bead, a metal powder, or the like may be optionally added to the acrylic adhesive composition. A known agent such as a coloring agent such as a filler, a pigment or a dye, a leveling agent, a thickener, a water repellent, and an antifoaming agent is used as an additive.

The adhesive layer used in the double-sided adhesive tape of the present invention preferably has a temperature at which the peak of the loss tangent (tan δ) at a frequency of 1 Hz is -40 ° C to 15 ° C, more preferably -20 ° C to 5 ° C. By setting the peak of the loss tangent of the adhesive layer to this range, it is easy to impart good adhesion to the adherend at normal temperature.

The loss tangent (tan δ) is a formula based on a storage elastic modulus (G'), a loss elastic modulus (G''), and a tan δ=G''/G' obtained by dynamic viscoelasticity measurement using temperature dispersion. Find out. The temperature indicating the peak of the loss tangent (tan δ) at a frequency of 1 Hz was obtained from the dynamic viscoelasticity measurement using temperature dispersion.

Further, the adhesive layer of the double-sided adhesive tape of the present invention has a storage elastic modulus at 25 ° C of 50 kPa to 200 kPa, preferably 52 kPa to 150 kPa, more preferably 55 kPa to 100 kPa, and still more preferably 60 kPa. 90 kPa. The reason for this is that when the storage elastic modulus of the adhesive layer is extremely high, the adhesion to the three-dimensional curved surface is lowered, and when the storage elastic modulus of the adhesive layer is extremely low, the peeling resistance is lowered due to a decrease in cohesive force. .

The dynamic viscoelastic property can be selected by appropriately selecting the kind or ratio of the monomer used in the copolymer constituting the adhesive, the kind of the polymerization initiator or the amount thereof, the kind or amount of the crosslinking agent or the adhesion imparting resin, The polymerization method is adjusted.

Furthermore, the dynamic viscoelastic property of the adhesive layer is defined by the loss tangent of the dynamic viscoelastic spectrum at a specific frequency and at a specific temperature, or the loss tangent and the storage elastic coefficient, and further by the dynamic viscosity at a specific frequency. The loss of the elastic spectrum is determined by the temperature of the peak of the tangent or the peak of the loss tangent. In the measurement of the dynamic viscoelasticity, a viscoelasticity tester (manufactured by TA Instruments Japan, trade name: ARES G2) was used, and a parallel disc of stainless steel having a diameter of 8 mm as a measuring portion of the test machine was used. The test piece (formed as an adhesive layer having a diameter of 8 mm and a thickness of about 2 mm) was sandwiched between the test pieces and the storage elastic modulus (G') and the loss elastic modulus (G' at -50 ° C to 150 ° C were measured at a frequency of 1 Hz. ').

The thickness of the adhesive layer of the double-sided adhesive tape of the present invention is preferably 10 μm in terms of the thickness of one side when it is easy to ensure adhesion to the adherend in the case of forming a thin tape. ～100 μm, more preferably 25 μm to 80 μm.

[Substrate] The base material of the double-sided adhesive tape of the present invention has a 25% compression strength of 1 kPa to 2000 kPa, preferably 10 kPa to 1700 kPa, more preferably 20 kPa to 1500 kPa, and still more preferably 30 kPa to ～ 1400 kPa. By using a substrate having a 25% compressive strength in this range, it has excellent adhesion to the adherend, and is particularly suitable for following an adherend having a three-dimensional curved shape, a concave-convex shape, or a rough surface. Adhesiveness. In addition, since the base material of the compressive strength has moderate cushioning property, the pressure at the time of attaching concentrates on the joint portion, and it is easy to extrude the air existing in the subsequent interface, and thus, particularly, the rigid bodies having a three-dimensional curved shape are mutually In the joining, excellent adhesion without entering a gap such as water can be achieved.

Further, the type of the substrate is not particularly limited as long as it has the above-mentioned compressive strength, and for example, a polyethylene film, a polypropylene film, an ethylene-propylene copolymer film, or an ethylene-vinyl acetate copolymer film can be used. A polyolefin-based resin film, a polyurethane resin film, an acrylic resin film, a rubber-based film containing an elastomer, a polyethylene-based foam sheet, a polypropylene-based foam sheet, and an ethylene-propylene A polyolefin-based foam sheet such as a copolymer polymer foam sheet or an ethylene-vinyl acetate copolymer polymer foam sheet, a polyurethane foam sheet, an acrylic foam sheet, or the like . Among these substrates, from the viewpoint of dimensional stability or impact resistance when the double-sided adhesive tape is processed into a narrow sash shape, a polyurethane film or an acrylic resin is preferred. A resin film, a polyolefin foam sheet, a polyurethane foam sheet, or an acrylic foam sheet. Further, these substrates may be used alone or in combination of two or more.

Furthermore, the 25% compressive strength is to place a sample cut to 50 mm square on a water platform and compress the sample by 50% or more at a rate of 10 mm/min at 23 ° C and stop, and according to the obtained distance - The plot of compressive strength reads the intensity of the 25% compression time point.

[Double-sided adhesive tape for three-dimensional curved surface attachment] The double-sided adhesive tape of the present invention exhibits appropriate adhesion to a adherend having a three-dimensional curved surface by using the adhesive layer and the substrate, and particularly When the parts used for electrical equipment are fixed, it is possible to effectively prevent the intrusion of water or the like from the gap, and has an excellent waterproof function.

As an embodiment of the double-sided adhesive tape of the present invention, a configuration in which an adhesive layer is provided on both surfaces of a substrate is a basic configuration. The substrate and the adhesive layer may be directly laminated or may have other layers. These aspects may be appropriately selected depending on the intended use, and when a dimensional stability or a tensile strength is further imparted to the belt, a laminate layer such as a polyester film may be provided to impart concealability or light blocking property to the belt. In the case of a light shielding layer, a light reflection layer may be provided when light reflectivity is ensured. In the case where these other layers are provided, a water-repellent layer may be used as the other layer.

As the light-shielding layer, an ink-forming agent containing a coloring agent such as a pigment can be easily used, and a layer containing a black ink is preferably used because it is excellent in light-shielding property. As the reflective layer, a layer formed of a white ink can be easily used. The thickness of the layers is preferably from 2 μm to 20 μm, more preferably from 3 μm to 10 μm, more preferably from 4 μm to 6 μm. By setting the thickness to this range, it is difficult to cause curl of the substrate due to curing shrinkage of the ink, and the workability of the tape is good.

The double-sided adhesive tape of the present invention can be produced by a conventionally known method. For example, a direct printing method in which an acrylic adhesive composition is applied to a substrate directly or a surface of another layer laminated on a substrate is applied and dried; or an acrylic adhesive is applied to the release sheet. After the composition is dried and dried, it is applied to a transfer method of a substrate or other layer surface.

The thickness of the double-sided adhesive tape of the present invention may be appropriately adjusted according to the state of use, and is 70 μm to 1400 μm. In the case of fixed parts of electronic equipment, especially small and thin portable electronic devices, a thin strip thickness is required, so it is preferably 80 μm to 1000 μm, more preferably 100 μm to 500 μm. It is 200 μm to 400 μm. By setting the thickness of the tape to the thickness, it is easy to ensure adhesion to the adherend for a thin and small portable electronic device, and it is excellent in cohesive force and suitable for application, and a good waterproof function can be realized.

The double-sided adhesive tape of the present invention exhibits appropriate adhesion to the adherend, and can effectively prevent the intrusion of water from the gap, and has an excellent waterproof function. Therefore, in the portable electronic device in which the thinning progresses and the volume restriction in the casing is strict and it is difficult to separately provide the water seal member, the waterproof function can be effectively imparted. As a specific use aspect, for example, in a portable electronic device such as an electronic notebook, a mobile phone, a smart phone, a tablet terminal, a PHS, a camera, a music player, etc., a protective panel suitable for the information display part and Bonding of the frame, bonding of the frames, fitting of the frame to a tablet such as a tenkey or a touch panel, bonding of the frame to the decorative sheet, and various other components or modules Fixed etc. [Examples]

Hereinafter, the examples will be specifically described, but the present invention is not limited to the examples.

(Preparation of Adhesive A) 95.9 parts by mass of n-butyl acrylate, 4 parts by mass of acrylic acid, 0.1 parts by mass of 2-hydroxyethyl acrylate, and acetic acid were placed in a reaction vessel including a stirrer, a reflux cooling tube, a nitrogen gas introduction tube, and a thermometer. 200 parts by mass of ethyl ester was heated to 72 ° C while blowing nitrogen gas under stirring.

To the mixture, 2 parts by mass of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate (solid content: 0.1% by mass) was added and maintained at 72 ° C under stirring (hold After 4 hours, it was kept at 75 ° C for 5 hours. Filtration was carried out using a 200-mesh metal net to obtain an acrylic polymer solution A (nonvolatile content: 33.3% by mass) having a weight average molecular weight of 1.04 million.

Next, the acrylic polymer A and the polymerized rosin ester-based adhesion-providing resin D-125 (manufactured by Arakawa Chemical Industries Co., Ltd.) 10 parts by mass and disproportionated rosin ester-based adhesion-imparting resin A-100 (Arakawa Chemical Industry Co., Ltd.) After the mixture was stirred and mixed with 10 parts by mass, ethyl acetate was added, whereby an adhesive solution A having a solid content of 38% was obtained.

Burnoc D-40 as a crosslinking agent (manufactured by Dixon (DIC), a trimethylolpropane adduct of toluene diisocyanate, isocyanate, 100 parts by mass of the adhesive solution A The base content was 7% by mass, and the nonvolatile content was 40% by mass. 1.2 parts by mass, and the mixture was stirred and mixed so as to be uniform, and then filtered using a 100-mesh metal net to obtain the adhesive A.

(Preparation of Adhesive B) 60.94 parts by mass of n-butyl acrylate, 35 parts by mass of 2-ethylhexyl acrylate, 4 parts by mass of acrylic acid, and acrylic acid were placed in a reaction vessel including a stirrer, a reflux cooling tube, a nitrogen gas introduction tube, and a thermometer. 0.06 parts by mass of 4-hydroxybutyl ester and 200 parts by mass of ethyl acetate were heated to 72 ° C while blowing nitrogen gas under stirring.

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

5 parts by mass of the acrylic polymer B and the polymerized rosin ester-based adhesive resin D-125 (manufactured by Arakawa Chemical Co., Ltd.) and disproportionated rosin ester-based adhesion-providing resin A-100 (manufactured by Arakawa Chemical Industries Co., Ltd.) After 10 parts by mass of the mixture was stirred and stirred, ethyl acetate was added, whereby an adhesive solution B having a solid content of 31% was obtained.

Addition of Burnock D-40 as a crosslinking agent to the adhesive solution B 100 parts by mass (manufactured by Dixon (DIC) Co., Ltd., trimethylolpropane adduct of toluene diisocyanate, isocyanate The base content was 7% by mass, and the nonvolatile content was 40% by mass. 2.4 parts by mass, and the mixture was stirred and mixed so as to be uniform, and then filtered using a 100-mesh metal net to obtain the adhesive B.

(Preparation of Adhesive C) 80.94 parts by mass of n-butyl acrylate, 5 parts by mass of 2-ethylhexyl acrylate, and 10 parts by mass of cyclohexyl acrylate were placed in a reaction vessel including a stirrer, a reflux cooling tube, a nitrogen introduction tube, and a thermometer. The mixture was subjected to 4 parts by mass of acrylic acid, 0.06 parts by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate, and the temperature was raised to 72 ° C while blowing nitrogen gas under stirring.

To the mixture, 2 parts by mass of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate (solid content: 0.1% by mass) was added, and the mixture was kept at 72 ° C for 4 hours while stirring. After that, it was kept at 75 ° C for 5 hours. This was filtered with a 200-mesh metal net to obtain an acrylic polymer solution C (nonvolatile content: 33.3% by mass) having a weight average molecular weight of 1,200,000.

Next, the acrylic polymer C and the polymerized rosin ester-based adhesion-providing resin D-125 (manufactured by Arakawa Chemical Industries Co., Ltd.) 5 parts by mass and disproportionated rosin ester-based adhesion-imparting resin A-100 (Arakawa Chemical Industry Co., Ltd.) After the mixture was stirred and mixed with 15 parts by mass, ethyl acetate was added, whereby an adhesive solution C having a solid content of 31% was obtained.

Addition of Burnock D-40 as a crosslinking agent to the adhesive solution C 100 (manufactured by Dixon (DIC), trimethylolpropane adduct of toluene diisocyanate, isocyanate The base content was 7% by mass, and the nonvolatile content was 40% by mass. 1.0 part by mass, and the mixture was stirred and mixed so as to be uniform, and then filtered using a 100-mesh metal net to obtain an adhesive C.

(Preparation of Adhesive E) Barnock D-40 (Diane Aisheng (DIC)) was added as a crosslinking agent to 100 parts by mass of the acrylic polymer solution A (nonvolatile content: 3.33 mass%). Manufactured, a trimethylolpropane adduct of toluene diisocyanate, an isocyanate group content of 7 mass%, a nonvolatile content of 40 mass%) of 1.2 parts by mass, stirred and mixed so as to be uniform, and then a 100 mesh metal mesh was used. Filtration was carried out, whereby Adhesive E was obtained.

(Example 1) The adhesive was applied to the surface of a release paper (manufactured by a chemical processing paper) of a fluorenone treatment using a bar coater so that the thickness of the dried adhesive layer was 25 μm. A, and dried at 80 ° C for 3 minutes, thereby preparing an adhesive layer A.

Similarly, the adhesive C was formed into a layer of the adhesive C in a thickness of 50 μm after drying on the surface of the release paper (manufactured by the chemical processing paper) which was treated with fluorenone, and The work was repeated three times, and three sheets of the adhesive C layer were laminated to form an acrylic substrate A having a thickness of 150 μm (25% compressive strength: 1360 kPa).

Next, the adhesive A layer was attached to both surfaces of an acrylic substrate A having a thickness of 150 μm, and cured in an environment of 40 ° C for 48 hours to prepare a double-sided adhesive tape having a thickness of 200 μm.

(Example 2 - Example 8) The thickness of the adhesive A layer was changed to the value shown in Table 1, and the base material of Table 1 was used instead of the acrylic base material A, and the use and examples were used. 1 The same method is used to make a double-sided adhesive tape.

(Example 9) A double-sided adhesive tape was produced in the same manner as in Example 8 except that the adhesive B was used instead of the adhesive A.

(Example 10) A double-sided adhesive tape was produced in the same manner as in Example 4 except that the adhesive C was used instead of the adhesive A.

(Example 11) A double-sided adhesive tape was produced in the same manner as in Example 8 except that the adhesive C was used instead of the adhesive A.

(Comparative Example 1) In place of the adhesive A, the adhesive D (Burnock D-40) was added as a crosslinking agent to 100 parts by mass of SK-Dyne 2094 (manufactured by K.K.). Manufactured by Aisheng (DIC), a trimethylolpropane adduct of toluene diisocyanate, an isocyanate group content of 7 mass%, a nonvolatile content of 40% by mass) of 1.2 parts by mass, and stirred in a uniform manner A double-sided adhesive tape was produced in the same manner as in Example 8 except that the mixture was filtered by a 100-mesh metal mesh.

(Comparative Example 2) A double-sided adhesive tape was produced in the same manner as in Example 8 except that the adhesive E was used instead of the adhesive A.

(Comparative Example 3) A double-sided film was produced in the same manner as in Example 3 except that the thickness of the adhesive A was changed to the value described in Table 1, and a PET film having a thickness of 125 μm was used instead of the substrate B. Adhesive tape.

(Exfoliation resistance test) The double-sided adhesive tapes produced in the examples and the comparative examples were processed into a window frame shape having an outer diameter of 14 mm × 14 mm and a width of 2 mm. Attached to a 30 mm × 60 mm stainless steel plate with a hole of 10 mm in diameter at a temperature of 23 ° C and a relative humidity of 50 % RH, and adhered to a thickness of 2 mm, 17 mm on the other adhesive surface. See the square acrylic plate (Mitsubishi Rayon) Acrylite MR200 "trade name", hue: transparent), after pressing for 10 seconds at 10 N/cm ² , it will stand for 24 hours. The original is set as a test piece.

Next, the stainless steel plate side of the test piece was set to the upper surface in an environment of a temperature of 23 ° C and a relative humidity of 50% RH, and a portion of 5 mm from one end of the long side was fixed. Then, 100 g of a stainless steel probe of 8 mm in diameter was passed through the hole from the upper surface, contacted with an acrylic plate to apply a load, and left for 24 hours. Further, after 24 hours, it was confirmed whether or not the double-sided adhesive tape was peeled off from the stainless steel plate or the acrylic plate, and the peeling resistance was evaluated.

○: no peeling ×: there is peeling off

(Waterproof test) As shown in Fig. 1, the double-sided adhesive tapes produced in the examples and the comparative examples were made into the following frame-like samples: the curvature of the outer diameter of the outer diameter of 136 mm × 66 mm, the width of 2 mm, and the four corners. 4 mm, the inner diameter of the four corners has a curvature of 2 mm, and a triangular-shaped slit is provided at four corners with a minimum width portion of the belt from the outer side of the frame of 1 mm. After being attached to the acrylic adherend A shown in FIG. 2 and FIG. 3, it is attached to the acrylic adherend B shown in FIG. 4, and pressed at a pressure of 20 N/cm ² for 10 seconds. The test piece was set to stand still for 24 hours.

The test piece was allowed to stand in a water depth of 1 m (according to IPX7 of JIS C0920) for 30 minutes, and it was evaluated whether or not there was water immersion in the frame of the double-sided adhesive tape.

○: no water immersion ×: water immersion

[Table 1]

[Table 2]

[table 3]

[Table 4]

no

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a plan view showing a frame-like sample of a double-sided adhesive tape of the present invention. 2 is a plan view of the adherend A (the lattice portion is a curved shape) and a cross-sectional view. 3 is a perspective cross-sectional view of the adherend A. 4 is a plan view of the adherend B (the lattice portion is a curved shape) and a cross-sectional view.

Claims (5)

A double-sided adhesive tape characterized by having a substrate and an adhesive layer, and the adhesive layer has a storage elastic modulus at 25 ° C of 50 kPa to 200 kPa, and the substrate has a 25% compressive strength of 1 kPa to 2000 kPa, and the double-sided adhesive tape is attached to a three-dimensional curved surface. The double-sided adhesive tape according to the first aspect of the invention, wherein the adhesive layer contains an acrylic copolymer and an adhesive-imparting resin, and the adhesive-imparting resin is contained in an amount of 100 parts by mass based on the acrylic copolymer. The content is from 5 parts by mass to 40 parts by mass. The double-sided adhesive tape according to claim 1 or 2, which is used for bonding a rigid body having a three-dimensional curved surface to each other. The double-sided adhesive tape according to claim 1 or 2, wherein the adhesive tape has a thickness of 70 μm to 1400 μm. The double-sided adhesive tape according to claim 1 or 2, which is used for fixing a part of an electronic device and imparts waterproof performance to the electronic device at the fixing portion.