JP2020193338A - Double-sided adhesive tape and display device - Google Patents

Abstract

To provide a double-sided adhesive tape having both of followability to an adherend and conductivity, and a display device having the double-sided adhesive tape.SOLUTION: A double-sided adhesive tape has a foam substrate, an adhesive layer, and a conductive layer.SELECTED DRAWING: None

Description

The present invention relates to a double-sided adhesive tape and a display device having the double-sided adhesive tape.

In portable electronic devices equipped with image display devices or input devices (for example, mobile phones, personal digital assistants, etc.), double-sided adhesive tapes are used for assembly. Specifically, for example, a double-sided adhesive tape is used to bond a cover panel for protecting the surface of a portable electronic device to a touch panel module or a display panel module, or to bond a touch panel module and a display panel module. Has been done. Such a double-sided adhesive tape is used, for example, in the shape of a frame or the like so as to be arranged around the display screen (for example, Patent Documents 1 and 2). Double-sided adhesive tape is also used for fixing vehicle parts (for example, in-vehicle panels) to the vehicle body.

JP-A-2009-242541 JP-A-2009-258274

The double-sided adhesive tape used for fixing parts of portable electronic devices has high impact resistance and stress that not only has high adhesive strength but also does not cause cracking or interfacial peeling of the double-sided adhesive tape due to strong impact such as dropping. Flexibility, reworkability, etc. are required to alleviate the problem. As a double-sided adhesive tape having excellent impact resistance, for example, Patent Documents 1 and 2 have an acrylic pressure-sensitive adhesive layer laminated and integrated on at least one side of a base material layer, and the base material layer has a specific degree of cross-linking and a specific degree of cross-linking. A crosslinked polyolefin resin foam sheet having an aspect ratio of bubbles is disclosed.

In recent years, as a result of pursuing design and functionality, display devices such as television monitors have become narrower in frame. In the conventional manufacturing of display devices, the panel is fixed to the frame by fitting or screwing, but since it is difficult to fit or screw the panel in a narrow frame display device, the panel is fixed by adhesive tape. When an adhesive tape is used in the manufacture of a display device having a narrow frame, the adhesive tape is required to have the property of withstanding a large load, as well as the ease of sticking and the followability of stress relaxation. On the other hand, in recent years, a large amount of static electricity has been generated in panels due to the increase in size and power consumption of the panels. If static electricity accumulates on the panel, it causes display problems. Therefore, in a display device, a double-sided adhesive tape having conductivity that can fix the panel following the frame portion and at the same time release static electricity to the outside is required. ..

In view of the above situation, it is an object of the present invention to provide a double-sided adhesive tape having both followability and conductivity to an adherend and a display device having the double-sided adhesive tape.

The present invention is a double-sided adhesive tape having a foam base material, an adhesive layer, and a conductive layer.
The present invention will be described in detail below.

The double-sided adhesive tape of the present invention has a foam base material.
By using a foam base material as the base material of the double-sided adhesive tape, it exhibits high followability that follows the unevenness and curved surface of the adherend, and high impact resistance that is less likely to crack or peel due to impact such as dropping. be able to.

The foam base material is not particularly limited, and examples thereof include polyolefin foams and polyurethane foams. Examples of the polyolefin foam include polyethylene-based foams, polypropylene-based foams, ethylene-propylene-based foams, and the like. From the viewpoint of followability to the adherend, polyolefin foams and polyurethane foams are preferable, and polyurethane foams are more preferable.

The polyolefin resin constituting the polyolefin foam is not particularly limited, but a polyolefin resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst is preferable. Of these, a polyethylene resin obtained by using a metallocene compound is more preferable. Examples of the metallocene compound include Kaminsky catalysts and the like.

As the polyethylene resin obtained by using the metallocene compound, for example, a polyethylene resin obtained by copolymerizing ethylene with another α-olefin blended as needed using the metallocene compound or the like. Can be mentioned. Examples of the other α-olefin include propene, 1-butene, 1-pentene, 1-hexene and the like.

The polyethylene resin obtained by using the metallocene compound may be used in combination with other olefin resins. Examples of the other olefin resin include polyethylene, polypropylene, ethylene-propylene copolymer and the like.

Examples of the polyurethane resin constituting the polyurethane foam include a urethane resin composition containing a polyisocyanate and a polyol.
The polyisocyanate is not particularly limited, and examples thereof include aromatic polyisocyanates and aliphatic polyisocyanates used for general polyurethane foams. Specifically, for example, 4,4'-diphenylmethane diisocyanate (MDI), tolylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,5-naphthalenediisocyanis, paraphenylenediisocyanate, 2,2,4-trimethylhexamethylene diisocyanate. , 2,4,4-trimethylhexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, m-xylene diisocyanate, hexamethylene diisocyanate, hydrogenated MDI, isophorone diisocyanate and the like. Further, as the polyisocyanate, for example, a urethane prepolymer having an isocyanate group can be mentioned. These polyisocyanates may be used alone or in combination of two or more.

The above-mentioned polyol is not particularly limited, and examples thereof include polyols used for general polyurethane foams. Specific examples thereof include polyether polyols, polyester polyols, and polyether ester polyols. Examples of the polyol include short-chain diols such as trifunctional polyether polyol ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, glycerin, and trimethylolpropane. These polyols may be used alone or in combination of two or more.

The weight average molecular weight of the polyol is not particularly limited, but the preferred lower limit is 1000 and the preferred upper limit is 12000. When the weight average molecular weight of the polyol is in the above range, it is possible to prevent the base material from becoming too flexible and reducing its strength.

The isocyanate index of the polyisocyanate in the urethane resin composition is not particularly limited, but a preferable lower limit is 70 and a preferable upper limit is 120.
The isocyanate index is an index relating to the isocyanate equivalent in the reaction between isocyanate and an active hydrogen-containing compound. When the isocyanate index is less than 100, it means that the reactive group such as a hydroxyl group is more than the isocyanate group, and when the isocyanate index is more than 100, it means that the isocyanate group is more than the reactive group such as the hydroxyl group.
When the isocyanate index is 70 or more, the cross-linking with the polyisocyanate is sufficient, and the foam base material can have appropriate flexibility. When the isocyanate index is 120 or less, it is possible to prevent the foam base material from being cured due to excessive cross-linking by the polyisocyanate. Further, when the isocyanate index is within the above range, the flexibility of the foam base material is enhanced, and the followability and stress relaxation property of the obtained double-sided adhesive tape to the adherend can be enhanced.

The urethane resin composition may contain a catalyst, if necessary.
Examples of the catalyst include organic tin compounds such as stanas octoate, dibutyltin diacetate and dibutyltin dilaurate, organic zinc compounds such as zinc octylate, organic nickel compounds such as nickel acetylacetoate and nickel diacetylacetoate, and iron acetyl. Organic iron compounds such as acetoate, alkoxides of alkali metals or alkaline earth metals such as sodium acetate, metal catalysts such as phenoxide, triethylamine, triethylenediamine, N-methylmorpholine dimethylaminomethylphenol, imidazole, 1,8-diazabicyclo [ 5.4.0] Examples thereof include tertiary amine-based catalysts such as undecene and organic acid salts. Of these, organic tin compounds are preferable. These catalysts may be used alone or in combination of two or more.
The amount of the catalyst added is not particularly limited, but the preferable lower limit is 0.05 parts by weight, the preferable upper limit is 5.0 parts by weight, and the more preferable upper limit is 4.0 parts by weight with respect to 100 parts by weight of the polyol.

The foam base material is preferably crosslinked. Impact resistance can be enhanced by cross-linking the foam base material.
The method of cross-linking the foam base material is not particularly limited, and for example, a method of irradiating the foam base material with ionizing radiation such as electron beam, α ray, β ray, and γ ray, and the foam base material. Examples thereof include a method of decomposing a premixed organic peroxide by heating.

The method for producing the foam base material is not particularly limited, but for example, a foamable resin composition containing a base material resin and a foaming agent is prepared, and the foamable resin composition is extruded into a sheet using an extruder. A method in which a foaming agent is foamed during processing and the obtained foam base material is crosslinked, if necessary, is preferable.

The foam base material preferably has a density of 30 kg / m ³ or more and 700 kg / m ³ or less.
When the density of the foam base material is within the above range, both the flexibility and the strength of the obtained double-sided adhesive tape can be achieved. From the viewpoint of further achieving both the flexibility and strength of the obtained double-sided adhesive tape, the density of the foam base material is more preferably 40 kg / m ³ or more, further preferably 50 kg / m ³ or more, and 600 kg. / more preferably ^{m 3} or less, further preferably 500 kg / ^{m 3} or less.
More specifically, when the foam substrate is a polyolefin foam (especially polyethylene based foam) is preferably the density of the foam substrate is 30kg / m ³ or more, 50 kg / m ³ The above is more preferable, 500 kg / m ³ or less is preferable, 300 kg / m ³ or less is more preferable, and 90 kg / m ³ or less is further preferable.
When the foam base material is a polyurethane foam, the density of the foam base material is preferably 200 kg / m ³ or more, more preferably 250 kg / m ³ or more, and 300 kg / m. It is more preferably ³ or more, preferably 600 kg / m ³ or less, more preferably 550 kg / m ³ or less, and further preferably 500 kg / m ³ or less.
The density can be measured using an electronic hydrometer (for example, "ED120T" manufactured by Mirage Co., Ltd.) in accordance with JIS K 6401 (when polyurethane is used) and JIS K 6767 (when polyethylene is used).

The lower limit of the thickness of the foam base material is not particularly limited, but a preferable lower limit is 30 μm, a more preferable lower limit is 50 μm, a further preferable lower limit is 70 μm, a further preferable lower limit is 100 μm, a particularly preferable lower limit is 150 μm, and a particularly preferable lower limit is 150 μm. It is 200 μm. When the thickness of the foam base material is at least the above lower limit, the impact resistance of the obtained double-sided adhesive tape can be further improved. The upper limit of the thickness of the foam base material is not particularly limited, but it can be obtained when the preferable upper limit is 800 μm, the more preferable upper limit is 750 μm, the further preferable upper limit is 700 μm, and the thickness of the foam base material is not more than the above upper limit. It is possible to further improve the followability of the double-sided adhesive tape to the adherend.

The double-sided adhesive tape of the present invention has an adhesive layer.
The pressure-sensitive adhesive layer constitutes the outermost surface of the double-sided pressure-sensitive adhesive tape. The double-sided adhesive tape of the present invention may have an aspect in which the pressure-sensitive adhesive layer constituting the outermost surface thereof is covered with a protective release film. When the double-sided adhesive tape of the present invention has a release film, when the double-sided adhesive tape is used for adhesive fixing, the release film is peeled off and used.
The pressure-sensitive adhesive layer constituting each outermost surface may be composed of the same pressure-sensitive adhesive or different pressure-sensitive adhesives.

The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited, but an acrylic pressure-sensitive adhesive is preferable because the adhesive strength can be easily adjusted and it can be applied to various adherends. Of these, an acrylic copolymer obtained by copolymerizing a monomer mixture containing butyl acrylate and 2-ethylhexyl acrylate is more preferable.
The preferred lower limit of the content of butyl acrylate in the total monomer mixture is 40% by weight, and the preferred upper limit is 80% by weight. When the content of butyl acrylate is within this range, both high adhesive strength and cohesive strength can be achieved at the same time.
The preferred lower limit of the content of 2-ethylhexyl acrylate in the total monomer mixture is 10% by weight, and the preferred upper limit is 40% by weight. When the content of 2-ethylhexyl acrylate is within this range, both high adhesive strength and cohesive strength can be achieved at the same time.

The monomer mixture may contain other copolymerizable monomers other than butyl acrylate and 2-ethylhexyl acrylate, if necessary.
As the other copolymerizable monomer, for example, the number of carbon atoms of an alkyl group such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and isopropyl (meth) acrylate. (Meta) acrylic acid alkyl ester having 13 to 18 carbon atoms, (meth) acrylic acid alkylalkyl, such as (meth) acrylic acid alkyl ester, tridecyl methacrylate, stearyl (meth) acrylic acid, etc. , Glycerindimethacrylate, glycidyl (meth) acrylate, 2-methacryloyloxyethyl isocyanate, (meth) acrylic acid, itaconic acid, maleic anhydride, crotonic acid, maleic acid, fumaric acid and other functional monomers.

In order to copolymerize the monomer mixture to obtain the acrylic copolymer, the monomer mixture may be subjected to a radical reaction in the presence of a polymerization initiator. The polymerization initiator is not particularly limited, and examples thereof include organic peroxides and azo compounds. Examples of the organic peroxide include 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5. -Dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxy Examples thereof include isobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate and t-butylperoxylaurate. Examples of the azo compound include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. These polymerization initiators may be used alone or in combination of two or more.

A conventionally known method is used as a method for radically reacting the above-mentioned monomer mixture, that is, as a polymerization method, for example, solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, massive polymerization, living radical polymerization and the like. Can be mentioned.

The weight average molecular weight (Mw) of the acrylic copolymer has a preferable lower limit of 400,000 and a preferable upper limit of 1 million. When the weight average molecular weight is in the above range, the cohesive force of the acrylic pressure-sensitive adhesive layer is enhanced, and the adhesive strength of the double-sided pressure-sensitive adhesive tape is further improved. The more preferable lower limit of the weight average molecular weight is 500,000, and the more preferable upper limit is 700,000.
In order to adjust the weight average molecular weight within the above range, the polymerization conditions such as the polymerization initiator and the polymerization temperature may be adjusted.
The weight average molecular weight (Mw) is a standard polystyrene-equivalent weight average molecular weight by GPC (Gel Permeation Chromatography: Gel Permeation Chromatography).

The pressure-sensitive adhesive layer may contain a pressure-imparting resin.
Examples of the tackifier resin include rosin ester resin, hydrogenated rosin resin, terpene resin, terpene phenol resin, kumaron inden resin, alicyclic saturated hydrocarbon resin, C5 petroleum resin, and C9 resin. Examples thereof include petroleum resins and C5-C9 copolymerized petroleum resins. These tackifier resins may be used alone or in combination of two or more.

The content of the tackifier resin is not particularly limited, but the preferable lower limit is 10 parts by weight and the preferable upper limit is 60 parts by weight with respect to 100 parts by weight of the acrylic copolymer. When the content of the tackifier resin is within this range, high adhesive strength can be exhibited.

A cross-linking agent may be added to the pressure-sensitive adhesive layer for the purpose of improving the cohesive force.
The above-mentioned cross-linking agent is not particularly limited, and examples thereof include isocyanate-based cross-linking agents, aziridine-based cross-linking agents, epoxy-based cross-linking agents, and metal chelate-type cross-linking agents. Of these, isocyanate-based cross-linking agents are preferable.
The preferable lower limit of the amount of the cross-linking agent added to 100 parts by weight of the acrylic copolymer is 0.01 parts by weight, the preferable upper limit is 10 parts by weight, the more preferable lower limit is 0.1 parts by weight, and the more preferable upper limit is 3. It is a part by weight.

The pressure-sensitive adhesive layer preferably has conductivity.
Since the pressure-sensitive adhesive layer has conductivity, static electricity generated on the surface of the device is accumulated in the conductive layer of the tape, and the static electricity can be gradually released to the outside through the pressure-sensitive adhesive. Examples of the method for imparting conductivity to the pressure-sensitive adhesive layer include a method using a conductive filler. It should be noted that the above-mentioned conductivity can be exhibited at least as long as the pressure-sensitive adhesive layer on the side of the above-mentioned foam layer on which the conductive layer described later is formed has.

The material of the conductive filler is not particularly limited, and examples thereof include conductive metals such as copper, nickel, silver, and nickel, carbon black, and the like. Of these, nickel and silver are preferable because of their high conductivity.

The shape of the conductive filler is not particularly limited, and examples thereof include a spherical shape, a particle shape, a needle shape, a plate shape, a flaky shape, a rod shape, and an amorphous shape. Among these shapes, a spherical shape is preferable because it has excellent dispersibility.

The average particle size of the conductive filler is not particularly limited, but the preferable lower limit is 0.1 μm and the preferable upper limit is 30 μm. When the average particle size of the conductive filler is 0.1 μm or more, the adhesive applicability, workability, and the like can be improved. When the average particle size of the conductive filler is 30 μm or less, the surface of the pressure-sensitive adhesive layer is less likely to be roughened, and the adhesion to the adherend is improved, so that the load bearing capacity can be improved. The more preferable lower limit of the average particle size of the conductive filler is 0.2 μm, and the more preferable upper limit is 25 μm.

The preferable lower limit of the content of the conductive filler in the pressure-sensitive adhesive layer is 0.1% by volume, and the preferable upper limit is 10% by volume. When the content of the conductive filler is 0.1% by volume or more, sufficient conductivity can be obtained, and when it is 10% by volume or less, the adhesion to the adherend is less likely to decrease. , Constant load peelability can be improved. The more preferable lower limit of the content of the conductive filler is 1% by volume, and the more preferable upper limit is 5% by volume.

The pressure-sensitive adhesive layer preferably has a shear storage elastic modulus of 1.0 × 10 ⁴ Pa or more and 8.0 × 10 ⁴ Pa or less at 10 Hz and 80 ° C.
When the shear storage elastic modulus of the pressure-sensitive adhesive layer at 10 Hz and 80 ° C. is within the above range, high holding characteristics at high temperatures can be exhibited. The storage elastic modulus of the pressure-sensitive adhesive layer at 10 Hz and 80 ° C. is more preferably 2 × 10 ⁴ Pa or more, further preferably 3.5 × 10 ⁴ Pa or more, and 7 × 10 ⁴ Pa or less. It is more preferable, and it is further preferable that it is 6 × 10 ⁴ Pa or less.
The storage elastic modulus of the pressure-sensitive adhesive layer at 10 Hz and 80 ° C. was determined by using a viscoelastic spectrometer (for example, DVA-200 manufactured by IT Measurement Control Co., Ltd.) at 10 ° C./min in a constant-velocity heating shear mode. It can be obtained as the storage elastic modulus at 80 ° C. when the dynamic viscoelasticity spectrum at −40 ° C. to 140 ° C. is measured under the condition of 10 Hz.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, but the preferable lower limit of the thickness of the pressure-sensitive adhesive layer on one side is 10 μm, and the preferable upper limit is 100 μm. When the thickness of the pressure-sensitive adhesive layer is within the above range, a double-sided pressure-sensitive adhesive tape having both higher holding characteristics can be obtained.

The double-sided adhesive tape of the present invention has a conductive layer.
The conductive layer is formed between the pressure-sensitive adhesive layer and the foam base material, and by having the conductive layer, static electricity generated from the adherend can be easily released to the outside. The conductive layer can exert its effect if at least one layer is formed, but it may be formed on both sides of the foam base material. Further, another layer may be provided between the conductive layer and the pressure-sensitive adhesive layer or between the conductive layer and the foam base material.

The conductive layer preferably contains a metal or a conductive polymer. The conductivity can be improved by containing a metal or a conductive polymer in the conductive layer.
Examples of the metal include aluminum, copper, silver, nickel and the like. Of these, aluminum, copper, and nickel are preferable from the viewpoint of cost, conductivity, and corrosion resistance.

Examples of the conductive polymer include aliphatic polyacetylene, aromatic polyparaphenylene, polyphenylene vinylene, heterocyclic polypyrrole, polythiophene, heteropolyaniline, polyphenylene sulfide, and polyphenylene sulfide. Of these, conductive polymers containing aromatic rings and heterocycles are preferable because they are excellent in conductive performance due to the stability of the conjugated system due to the double bond, and aromatic polyparaphenylene, heterocyclic polypyrrole, polythiophene, and heteropolyaniline are particularly preferable.

When the conductive layer contains a conductive polymer, the conductive layer preferably contains a binder resin.
By containing the binder resin, the conductive layer and the foam base material or another layer can be reliably adhered to each other. Examples of the binder resin include acrylic / methacrylic-modified silicone, compounds containing a silanol skeleton, an ester skeleton, or a styrene skeleton.

The concentration of the conductive polymer in the conductive layer is preferably 5% by weight at the lower limit and 80% by weight at the upper limit. When the content of the conductive polymer is within this range, a double-sided adhesive tape having an excellent balance between conductive performance and adhesion to an adherend can be obtained. A more preferable concentration of the conductive polymer is 10% by weight at the lower limit and 50% by weight at the upper limit.

The surface resistance value of the conductive layer is preferably 2000 mΩ / □ or less.
When the surface resistance value of the conductive layer is within the above range, the conductivity of the double-sided adhesive tape is improved, and the static electricity generated from the adherend can be more reliably released to the outside. From the viewpoint of further improving the conductivity of the double-sided adhesive tape, the surface resistance value of the conductive layer is more preferably 1000 mΩ / □ or less, further preferably 500 mΩ / □ or less, still more preferably 200 mΩ / □ or less, and particularly preferably 100 mΩ. / □ or less. The lower limit of the tape conductivity is not particularly limited, and the lower the limit, the better, but it is, for example, 1 mΩ. The tape conductivity can be measured by the method described in Examples.

The thickness of the conductive layer is preferably 100 nm or more.
When the thickness of the conductive layer is within the above range, a double-sided adhesive tape having more excellent conductivity can be obtained. From the viewpoint of further enhancing the conductivity, the thickness of the conductive layer is more preferably 10 nm or more, and further preferably 50 nm or more. The upper limit of the thickness of the conductive layer is not particularly limited, but it is preferably 18 μm or less from the viewpoint of followability to the adherend and handleability.

When the conductive layer contains a metal, the thickness of the conductive layer is preferably 2 μm or more, more preferably 5 μm or more, still more preferably 9 μm or more, and has a followability to the adherend, from the viewpoint of improving reworkability. From the viewpoint, it is preferably 35 μm or less, more preferably 30 μm or less, still more preferably 25 μm or less.

The method for forming the conductive layer is not particularly limited, and examples thereof include a method for forming a metal film by vapor deposition, sputtering, etc., a method for applying and drying a solution containing a conductive polymer, a method for laminating metal foils, and the like. Be done.

The double-sided adhesive tape of the present invention preferably has a resin film. By having the resin film, the obtained adhesive tape is less likely to be torn, and the reworkability can be improved.

The double-sided adhesive tape of the present invention preferably has a composite conductive layer including a conductive layer and a resin film.
In the present specification, the composite conductive layer refers to a laminated body having a structure in which the conductive layer is directly laminated on the resin film. By having the composite conductive layer, the obtained adhesive tape is less likely to be torn, and the reworkability can be improved. Further, when forming the conductive layer, methods such as vapor deposition on the resin film, sputtering, and bonding of metal foils can be used, so that the conductive layer can be made thinner. Therefore, it is possible to further improve the followability to the adherend while ensuring the conductivity of the obtained double-sided adhesive tape.

The resin film is not particularly limited, and examples thereof include a polyethylene terephthalate film, a polyimide film, a polyurethane film, and a (meth) acrylic film. Of these, polyethylene terephthalate film and (meth) acrylic film are preferable because they can improve cost and reworkability.

The thickness of the resin film is not particularly limited, but is preferably 20 μm or more, more preferably 30 μm or more, preferably 80 μm or less, and more preferably 60 μm or less. When the thickness of the resin film is within the above range, the reworkability and the followability to the adherend can be further improved.

The conductive layer (including the conductive layer constituting the composite conductive layer) is preferably in contact with the pressure-sensitive adhesive layer constituting the outermost surface. In this case, it suffices to be in contact with at least one adhesive layer (which constitutes the outermost surface). By doing so, the conductivity of the double-sided adhesive tape can be increased.

The conductive layer or the composite conductive layer preferably has a tensile breaking strength of 2.5 N or more. When the tensile breaking strength of the conductive layer or the composite conductive layer is within the above range, reworkability can be imparted to the obtained double-sided adhesive tape. The tensile breaking strength is more preferably 10 N or more, further preferably 20 N or more, and even more preferably 40 N or more. The upper limit of the tensile breaking strength is not particularly limited, but is preferably 150 N or less from the viewpoint of handleability and followability to the adherend. The tensile breaking strength can be measured by a method according to JIS K 7161.
The tensile breaking strength of the conductive layer or the composite conductive layer includes the resin film when the conductive layer is laminated on the resin film, that is, when the double-sided adhesive tape of the present invention has the composite conductive layer. It means the tensile breaking strength of the composite conductive layer. Further, when the tensile breaking strength is 2.5 N or more, sufficient reworkability is exhibited when low-speed peeling is performed manually, but when the tensile breaking strength is 30 N or more, a high speed using a machine is exhibited. Sufficient reworkability can be exhibited even when peeling is performed.

The double-sided adhesive tape of the present invention preferably has a 25% compression strength of 1200 kPa or less.
By setting the 25% compression strength of the double-sided adhesive tape within the above range, it is possible to improve the followability to the adherend. From the viewpoint of further improving the followability to the adherend, the 25% compression strength is more preferably 150 kPa or less, further preferably 100 kPa or less, and particularly preferably 50 kPa or less. The lower limit of the 25% compression strength is not particularly limited, but is preferably 3 kPa, more preferably 5 kPa, from the viewpoint of balance with impact resistance.
The 25% compression strength can be measured according to JIS K 6767. Specifically, a laminated body having a thickness of 5 mm was prepared by stacking double-sided adhesive tapes cut to 20 mm × 20 mm, left at room temperature for 1 hour, and then at room temperature, 10 mm / min in the thickness direction of the laminated body. It can be compressed to 50% of the original thickness at a high speed, and the 25% compression strength can be calculated from the obtained SS curve.

The double-sided adhesive tape of the present invention preferably has a total thickness of 3 mm or less.
When the layer thickness of the double-sided adhesive tape is within the above range, the double-sided adhesive tape of the present invention can be used for fixing parts of a thin electronic device. The total thickness of the double-sided adhesive tape is more preferably 2 mm or less, and further preferably 1 mm or less. The total thickness of the double-sided adhesive tape is not particularly limited, but is preferably 0.3 mm or more, and more preferably 0.5 mm or more, from the viewpoint of the balance between the strength of the double-sided adhesive tape and the followability to the adherend. preferable. The total thickness of the double-sided adhesive tape means a thickness that does not include the thickness of the release film when the double-sided tape has the release film.

Examples of the method for producing the double-sided adhesive tape of the present invention include the following methods.
First, a pressure-sensitive adhesive solution containing the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer and, if necessary, an additive is applied on the release-treated surface of the release film and dried to form the pressure-sensitive adhesive layer and the release film. Obtain a laminated film. Next, a pair of laminated films is produced in the same manner. On the other hand, a conductive layer is formed on the surface of the foam base material by a method of laminating a metal foil on the foam base material or a method of laminating a composite conductive layer (the resin film in which the conductive layer is formed by vapor deposition, sputtering, etc.). To do. Then, the pressure-sensitive adhesive layers of a pair of laminated films (release film and pressure-sensitive adhesive layer) are laminated on both sides of the foam base material so as to face the foam base material to prepare a laminated body. Then, by pressurizing this laminated body with a rubber roller or the like, both sides have adhesive layers on the outermost surfaces on both sides of the foam base material, and the surface of the adhesive layer is covered with a protective release film. Get adhesive tape.

The use of the double-sided adhesive tape of the present invention is not particularly limited, but it can be particularly preferably used for fixing a component that generates static electricity such as a liquid crystal panel or an organic EL panel to a frame when manufacturing a display device. In particular, since the double-sided adhesive tape of the present invention can exhibit conductivity in the direction perpendicular to the double-sided adhesive tape (thickness direction), joining of parts requiring conductivity in a direction substantially perpendicular to the double-sided adhesive tape. Can be used advantageously for.
A display device having the double-sided adhesive tape of the present invention is also one of the present inventions.

According to the present invention, it is possible to provide a double-sided adhesive tape having both followability to an adherend and conductivity, and a display device having the double-sided adhesive tape.

It is a schematic diagram explaining the measuring method of a tape conductivity.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Preparation of adhesive (a))
A reactor equipped with a thermometer, a stirrer, and a cooling tube contains 50 parts by weight of butyl acrylate, 47 parts by weight of 2-ethylhexyl acrylate, 3 parts by weight of acrylic acid, 0.1 part by weight of 2-hydroxyethyl acrylate, and 80 parts by weight of ethyl acetate. The portion was added and replaced with nitrogen. Then, 0.1 part by weight of azobisisobutyronitrile was added as a polymerization initiator, and the mixture was polymerized at 60 ° C. for 8 hours to obtain a solution of an acrylic copolymer. The weight average molecular weight of the obtained acrylic copolymer was measured by the GPC method and found to be 1.4 million.
With respect to 100 parts by weight of the solid content of the acrylic copolymer contained in the obtained solution of the acrylic copolymer, 15 parts by weight of the polymerized rosin ester, 125 parts by weight of ethyl acetate (manufactured by Fuji Chemical Co., Ltd.), and isocyanate-based cross-linking. 1.5 parts by weight of the agent was added and stirred to obtain the pressure-sensitive adhesive (a). The measuring instruments and measuring conditions for the polymerized rosin ester, the isocyanate-based cross-linking agent, and the GPC were as follows.
Polymerized rosin ester: D-135, softening point 135 ° C, isocyanate-based cross-linking agent manufactured by Arakawa Chemical Industries, Ltd .: Coronate L45, manufactured by Tosoh Co., Ltd. <GPC measuring equipment and measuring conditions>
Gel permeation chromatograph: e2695 Separations Module (manufactured by Waters)
Detector: Differential refractometer (2414, manufactured by Waters)
Column: GPC KF-806L (manufactured by Showa Denko KK)
Standard sample: STANDRAD SM-105, manufactured by Showa Denko Co., Ltd. Sample flow rate: 1 mL / min
Column temperature: 40 ° C

(Preparation of adhesive (b))
With respect to 100 parts by weight of the solid content of the acrylic copolymer obtained by the pressure-sensitive adhesive (a), 15 parts by weight of the polymerized rosin ester, 125 parts by weight of ethyl acetate (manufactured by Fuji Chemical Co., Ltd.), and Ni 255 (manufactured by Fukuda Metal Co., Ltd.) ) To 22 parts by weight and 1.5 parts by weight of the isocyanate-based cross-linking agent were added and stirred to obtain a pressure-sensitive adhesive (b). As the polymerized rosin ester and the isocyanate-based cross-linking agent, the same ones as the pressure-sensitive adhesive (a) were used.

(Example 1)
(1) Preparation of foam base material (PE) 100 parts by weight of linear low-density polyethylene resin, 3 parts by weight of azodicarbonamide as a pyrolysis foaming agent, 1 part by weight of zinc oxide as a decomposition temperature adjuster, and antioxidant As an agent, 0.5 parts by weight of 2,6-di-t-butyl-p-cresol was supplied to a uniaxial extruder, melt-kneaded at 130 ° C., and extruded as a raw fabric sheet having a thickness of 800 μm.

Next, the raw sheet is crosslinked by irradiating both sides with an electron beam having an accelerating voltage of 150 kV for 8.8 Mrad, and then continuously sent into a foaming furnace held at 250 ° C. by hot air and an infrared heater to heat the sheet. And foamed to obtain a foamed sheet. Next, the polyolefin foam base material (foam base material (PE), represented as PE in the table) having a thickness of 700 μm was obtained by stretching to MD and TD at 110 ° C. so that the total thickness was 700 μm. It was.
The density of the obtained foam base material was measured by a method conforming to JIS K-6767 using an electronic hydrometer (trade name "ED120T") manufactured by Mirage.

(2) Preparation of Double-sided Adhesive Tape A conductive layer was obtained by forming an Al layer (layer b) having a thickness of 0.1 μm on one side of a polyethylene terephthalate (PET) film (layer a) having a thickness of 50 μm by a vapor deposition machine. The pressure-sensitive adhesive (a) is applied on the surface of the conductive layer on the layer a side and dried at 100 ° C. for 5 minutes to form a pressure-sensitive adhesive layer having a thickness of 30 μm, which is used as a foam base material (PE). By laminating, a conductive layer with a PET film was formed on one side of the foam base material. Next, a release paper having a thickness of 50 μm was prepared, the pressure-sensitive adhesive (a) was applied to the release-treated surface of the release paper, and the product was dried at 100 ° C. for 5 minutes to obtain a pressure-sensitive adhesive layer A having a thickness of 30 μm. Next, another pressure-sensitive adhesive layer was formed by the same operation to obtain a pressure-sensitive adhesive layer B having a thickness of 30 μm and made of the pressure-sensitive adhesive (b). After that, the surface of the foam base material (PE) on which the conductive layer was formed and the pressure-sensitive adhesive layer B were bonded together, and the opposite surface and the pressure-sensitive adhesive layer A were bonded together. As a result, a double-sided adhesive tape (total thickness 840 μm excluding the paper pattern) covered with the paper pattern was obtained.

(Examples 2 and 3, Comparative Examples 1 and 3)
By adjusting the foaming and stretching conditions, the density of the foam base material is as shown in Tables 1 and 3, and the type of adhesive used for the adhesive layers A and B and the type and thickness of the metal of the layer b A double-sided adhesive tape was obtained in the same manner as in Example 1 except that Tables 1 and 3 were used.

(Example 4)
A conductive layer was obtained by forming an Al layer (layer b) having a thickness of 0.1 μm on one surface of a PET film (layer a) having a thickness of 50 μm by magnetron sputtering. Next, the pressure-sensitive adhesive (a) is applied onto the surface of the conductive layer on the layer a side and dried at 100 ° C. for 5 minutes to form a pressure-sensitive adhesive layer having a thickness of 30 μm, which is then used as a foam base material (PE). ) To form a conductive layer on one side of the foam base material. A double-sided adhesive tape (total thickness 840 μm excluding the paper pattern) was obtained in the same manner as in Example 1 except for the above points.

(Examples 5, 7, 11, 12)
By adjusting the foaming and stretching conditions, the density and thickness of the foam base material can be set as shown in Tables 1 and 2, the type of adhesive used for the adhesive layers A and B, the type of metal of layer b, and the type. A double-sided adhesive tape was obtained in the same manner as in Example 2 except that the thickness and the resin film used for the layer a were as shown in Tables 1 and 2. The resin film used is as follows.
Ac sheet: Acrylic triblock copolymer, LA2250, manufactured by Kuraray

(Example 6)
As the composite conductive layer, a PET with a Cu foil made of a Cu foil (conductive layer; layer b) having a thickness of 9 μm and a PET film (layer a) having a thickness of 50 μm was prepared. The pressure-sensitive adhesive (a) was applied to one side of the Cu foil and dried at 100 ° C. for 5 minutes to form a pressure-sensitive adhesive layer having a thickness of 30 μm, and a foam base material (PE) was bonded thereto. Next, a release paper having a thickness of 50 μm was prepared, the pressure-sensitive adhesive (a) was applied to the release-treated surface of the release paper, and the product was dried at 100 ° C. for 5 minutes to obtain a pressure-sensitive adhesive layer A having a thickness of 30 μm. Next, a pressure-sensitive adhesive layer B having a thickness of 30 μm made of the thick pressure-sensitive adhesive (b) was obtained by the same operation as that of the pressure-sensitive adhesive layer A except that the pressure-sensitive adhesive (b) was used. Then, the surface on which the composite conductive layer of the foam base material on which the conductive layer was formed and the pressure-sensitive adhesive layer B were bonded, and the opposite surface and the pressure-sensitive adhesive A were bonded together. As a result, a double-sided adhesive tape covered with a paper pattern having a total thickness of 799 μm was obtained.

(Examples 8 to 10 and 16)
A double-sided adhesive tape was obtained in the same manner as in Example 6 except that the type and thickness of the metal foil used for the layer b were as shown in Tables 1 and 2 without using the resin film (layer a).

(Comparative Examples 4 and 5)
A double-sided adhesive tape was obtained in the same manner as in Example 6 except that the pressure-sensitive adhesive layers A and B were bonded to both sides of the Al foil or Cu foil without using the foam base material and the resin film.

(Example 13)
(1) Preparation of foam base material (PU) 0.7 parts by weight of amine catalyst in 92 parts by weight of polypropylene glycol (weight average molecular weight 1000) and 8 parts by weight of 1,5-pentanediol (molecular weight 1000), defoaming agent 1 part by weight and 0.05 part by weight of a defoaming agent were added, and the mixture was stirred. The dinuclear monomeric MDI was adjusted and charged there so as to have an isocyanate index of 100. Then, it was mixed and stirred with nitrogen gas so as to be 400 kg / m ³ , and a solution containing fine bubbles was obtained.
Next, a conductive layer was obtained by forming an Al layer (layer b) having a thickness of 0.1 μm on one side of a polyethylene terephthalate (PET) film (layer a) having a thickness of 50 μm by a vapor deposition machine.
A polyurethane foam having a thickness of 750 μm is applied onto the surface of the layer a of the conductive layer obtained by obtaining the solution containing the fine bubbles to a predetermined thickness using an applicator, and the foam raw material is reacted. A base material (foam base material (PU), represented by PU in the table) was formed. The density of the obtained polyurethane foam was measured by a method conforming to JIS K 6401 using an electronic hydrometer (trade name "ED120T") manufactured by Mirage. The details of the raw materials are as follows.
Amine catalyst: Dowco LV33, Sankyo Air Products defoamer: SZ5740M, Toray Dow Corning defoamer: SILBK9210, BIC Chemie

(2) Preparation of Double-sided Adhesive Tape An adhesive with a thickness of 30 μm is prepared by preparing a release paper with a thickness of 50 μm, applying the adhesive (a) to the release-treated surface of the release paper, and drying at 100 ° C. for 5 minutes. Layer A was obtained. Next, a pressure-sensitive adhesive layer B having a thickness of 30 μm made of the thick pressure-sensitive adhesive (b) was obtained by the same operation as that of the pressure-sensitive adhesive layer A except that the pressure-sensitive adhesive (b) was used. After that, the surface of the foam base material (PU) on which the conductive layer was formed on the conductive layer side and the pressure-sensitive adhesive layer B were bonded together, and the opposite surface and the pressure-sensitive adhesive A were bonded together. As a result, a double-sided adhesive tape covered with a paper pattern having a total thickness of 860 μm was obtained.

(Examples 14 and 15, Comparative Example 2)
By adjusting the foaming conditions, the density of the foam base material is as shown in Tables 2 and 3, and the type of adhesive used for the adhesive layers A and B and the type and thickness of the metal of the layer b are shown in Table 2. A double-sided adhesive tape was obtained in the same manner as in Example 16 except as described in 3.

<Measurement of physical properties>
(1) Measurement of Shear Storage Elastic Modulus of Adhesive Layer A measurement sample consisting of only an adhesive layer having a thickness of 30 μm using the adhesive (a) and the adhesive (b) was prepared by the above method. For the obtained measurement sample, a viscoelastic spectrometer (DVA-200, manufactured by IT Measurement Control Co., Ltd.) was used to move at -40 ° C to 140 ° C under the condition of 10 ° C / min and 10 Hz in the constant speed temperature rise shear mode. The storage elastic modulus at 80 ° C. when the viscoelastic spectrum was measured was measured. As a result, the shear storage elastic modulus of the pressure-sensitive adhesive layer using the pressure-sensitive adhesive (a) was 4.6 × 10 ⁴ Pa, and the shear storage elastic modulus of the pressure-sensitive adhesive layer using the pressure-sensitive adhesive (b) was 7.0. It was × 10 ⁴ Pa.

(2) Measurement of tensile breaking strength and breaking elongation of the conductive layer and the composite conductive layer The tensile breaking strength and breaking elongation of the conductive layer and the composite conductive layer were measured by a method according to JIS K 7161.
First, by forming the layer b on the layer a by the above method, a measurement sample composed of only the composite conductive layer was prepared. When there was no layer a, only the layer b was used as it was as the conductive layer. The obtained measurement sample was punched into a dumbbell shape having a width of 10 mm using a punching blade "Tensile No. 1 type dumbbell shape" manufactured by Polymer Instruments. The tensile strength and elongation at break of the conductive layer are measured by measuring the punched measurement sample using "Autograph AGS-X" manufactured by Shimadzu Corporation under the conditions of a chuck interval of 85 mm and a tensile speed of 100 mm / min. did.

(3) Measurement of 25% Compression Strength The 25% compression strength of the obtained double-sided adhesive tape was calculated in accordance with JIS K 6767. The results are shown in Tables 1-3. For those with a 25% compression strength of 2000 kPa or more, N.I. D. And said.

(4) Measurement of Surface Resistance Value A foam base material on which a conductive layer (or composite conductive layer) was formed was prepared by the above method and used as a measurement sample. For the obtained measurement sample, the surface resistance value of the surface of the base material on the conductive layer side was measured by a method according to JIS K 7194. High Restor-UX (manufactured by Mitsubishi Chemical Analytical Co., Ltd.) was used for the measurement, and the surface of the obtained foam substrate on the conductive layer (or composite conductive layer) side was arranged in a straight line at equal intervals, and the probe spacing was 5 mm. The surface resistance values at 9 points were measured with the probe of No. 1 and the average value was obtained as the surface resistance value.

<Evaluation>
The double-sided adhesive tapes obtained in Examples and Comparative Examples were evaluated as follows. The results are shown in Tables 1-3.

(1) Measurement of Tape Conductivity FIG. 1 shows a schematic diagram illustrating a method for measuring tape conductivity. First, the obtained double-sided adhesive tape 1 was cut into 25 mm × 75 mm. Next, two 25 mm × 75 mm × 0.5 mm copper plates 2 processed into the shape shown in the figure were prepared and installed so as to have an interval of 25 mm. Next, the pressure-sensitive adhesive layer B of the cut double-sided adhesive tape was attached to the copper plate so that the sticking areas were 25 mm × 25 mm, respectively (that is, the conductive layer of the double-sided adhesive tape was a foam of the double-sided adhesive tape. Located between the substrate and the copper plate). After the double-sided adhesive tape 1 is attached to the copper plate 2, a weight 3 having the same bottom area (25 mm × 25 mm) as the attached portion and weighing 500 g is placed directly above the portion bonded to the copper plate of the double-sided adhesive tape. I put each one. Then, using a resistance meter RM3545 (manufactured by HIOKI), the resistance value 1 minute after pasting was read. The tape conductivity was evaluated as "⊚" when the resistance value was less than 1000 mΩ, "◯" when it was 1000 mΩ or more and less than 50,000 mΩ, and "x" when it was unmeasurable (OL).

(2) Evaluation of followability Place the obtained double-sided adhesive tape with the adhesive layer A side facing down so as to straddle the steps of a plate having a step of 380 μm in height, and place a 2 kg roller on the double-sided adhesive tape. It was pasted together by making one round trip. The step portion was observed with a 3D measurement microscope AR-3000 (manufactured by KEYENCE), and the length of the air portion remaining because the double-sided adhesive tape could not follow was measured. When the length of the remaining air part is less than 400 μm in the horizontal direction of the plate from the start point of the step, it is “◎”, when it is 400 μm or more and less than 1000 μm, it is “○”, and when it is 1000 μm or more and less than 2000 μm. The followability of the double-sided adhesive tape was evaluated with "Δ" and 2000 μm or more as “x”.

(3) Evaluation of Reworkability One side of the obtained double-sided adhesive tape on the conductive layer side was placed on a glass plate and reciprocated once with a 2 kg roller to bond them. Then, the double-sided adhesive tape was peeled off. At the time of peeling, if the base material can be peeled off without tearing even when it is peeled off at a high speed of 15000 mm / min using a peeling tester, "◎" indicates that the base material is torn off at high speed peeling. When the base material was peeled off by hand, the reworkability was evaluated as "○" when the base material could be peeled off without tearing, and "Δ" when the base material was peeled off by hand.

According to the present invention, it is possible to provide a double-sided adhesive tape having both followability to an adherend and conductivity, and a display device having the double-sided adhesive tape.

1 Double-sided adhesive tape 2 Copper plate 3 Weight (500g)

Claims (14)

A double-sided adhesive tape having a foam base material, an adhesive layer, and a conductive layer. The double-sided adhesive tape according to claim 1, wherein the foam base material is a polyurethane foam. The double-sided adhesive tape according to claim 1, wherein the density of the foam base material is 50 kg / m ³ or more and 90 kg / m ³ or less. The double-sided adhesive tape according to claim 1, 2 or 3, which has a composite conductive layer including a conductive layer and a resin film. The double-sided adhesive tape according to claim 4, wherein the resin film is a (meth) acrylic film. The double-sided adhesive tape according to claim 1, 2, 3, 4 or 5, wherein the conductive layer or the composite conductive layer has a tensile breaking strength of 2.5 N or more. The double-sided adhesive tape according to claim 1, 2, 3, 4, 5 or 6, wherein the conductive layer contains a metal or a conductive polymer. The double-sided adhesive tape according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the conductive layer has a thickness of 100 nm or more. The double-sided adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein the 25% compression strength is 1200 kPa or less. Claims 1, 2, 3, 4, 5, 6, 7, the shear storage elastic modulus of the pressure-sensitive adhesive layer at 10 Hz and 80 ° C. is 1.0 × 10 ⁴ Pa or more and 8.0 × 10 ⁴ Pa or less. The double-sided adhesive tape according to 8 or 9. The double-sided adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, wherein the pressure-sensitive adhesive layer has conductivity. The double-sided adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11, wherein the surface resistance value of the conductive layer is 2000 mΩ / □ or less. The double-sided adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, wherein the total thickness is 3 mm or less. A display device having the double-sided adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or 13.

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