JP5928808B2 - Double-sided adhesive tape, electromagnetic shielding material and heat conduction material - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive tape used for fixing a magnetic sheet or a heat conductive sheet used in an electronic device, a magnetic sheet composite product and a heat conductive sheet composite product obtained by bonding these tapes. More specifically, the present invention relates to an adhesive tape excellent in reworkability, a magnetic sheet composite product, and a heat conductive sheet composite product.

  Conventionally, magnetic sheets are used for electronic devices in order to absorb electromagnetic waves radiated from the electronic devices or the like, or to absorb electromagnetic waves that enter the electronic device or the like. Particularly in recent years, a magnetic sheet has been reflected when there is a conductive member such as a metal in the vicinity of the antenna coil, for example, on the back side, in an RFID (Radio Frequency Identification) tag that uses an antenna coil to communicate with electromagnetic waves. Transmission and reception are difficult because of electromagnetic interference. Therefore, a method of suppressing reflection of electromagnetic waves by placing a magnetic sheet having a high magnetic permeability between the antenna coil of the RFID tag and the conductive member has attracted attention. For these magnetic sheets, a thin and high permeability ferrite sintered body is used. Moreover, in order to dissipate the heat generated from the electronic device, a heat conductive sheet is used. These magnetic sheets and heat conductive sheets are used as a composite product by fixing one side with a single-sided adhesive tape and the other side with a double-sided adhesive tape. (Patent Documents 1 and 2)

  Magnetic sheet composites and heat conductive sheet composites are required to be re-applied (reworkability) at the time of application.

  In recent years, as electronic devices become lighter and thinner, pressure-sensitive adhesive tapes for fixing them have been required to be thinner. In Patent Document 3, the tape thickness is 25 μm or less, the tack of the adhesive layer on the low adhesive strength side is the ball number 3 or higher, the adhesive strength on the low adhesive strength side is 0.05 to 10 N / 20 mm, and high An adhesive tape having an adhesive force on the adhesive side of 2 to 30 N / 20 mm is disclosed.

  Even if fixed with the above thin tape, the magnetic sheet and the heat conductive sheet are very fragile, and there is a problem that the magnetic sheet composite product and the heat conductive sheet composite product are broken and cannot be reworked when reattached.

JP 2005-15293 A JP 2008-80672 A JP 2007-169327 A

  The problem to be solved by the present invention is to provide a thin adhesive tape having excellent reworkability even when fixed to a magnetic sheet or a heat conductive sheet. Another object of the present invention is to provide a magnetic sheet composite product and a heat conductive sheet composite product that are thin but have excellent reworkability.

  As a result of intensive studies to achieve the above object, the present inventors have found that the object of the present invention can be achieved with a base material having a specific thickness and a pressure-sensitive adhesive tape having a specific thickness and adhesive force. It came to complete.

  That is, the present invention is a double-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on both surfaces of the substrate, the adhesive strength of each surface being different, the thickness of the substrate is 3 to 6 μm, the total thickness is 5 to 20 μm, Among the pressure-sensitive adhesive layers on each surface, the thickness of the pressure-sensitive adhesive layer on the low adhesive strength side is 0.1 to 7 μm, and the adhesive strength on the low adhesive strength side (temperature 23 ° C., relative humidity 50% RH) A SUS304 steel plate is crimped by a single reciprocation using a 2 kg roller and left in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH for 1 hour, and then in a 180 ° direction at a peeling speed of 300 mm / min. The adhesive force when peeled off) is 0.05 to 0.2 N / 20 mm, and is to provide a double-sided pressure-sensitive adhesive tape used for fixing a magnetic sheet or a heat conductive sheet.

  The adhesive tape of the present invention has a total thickness of 20 μm or less, and is excellent in reworkability even when used as a magnetic sheet or a heat conductive sheet composite.

  The pressure-sensitive adhesive tape of the present invention is a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both sides of a base material and having different adhesive strengths on each side, and the base material has a thickness of 3 to 6 μm and a total thickness of 5 to 20 μm. Yes, among the pressure-sensitive adhesive layers on each surface, the thickness of the pressure-sensitive adhesive layer on the low adhesive force side is 0.1 to 7 μm, and the adhesive force on the low adhesive force side is 0.05 to 0.2 N / 20 mm. It is a double-sided adhesive tape used for fixing a magnetic sheet or a heat conductive sheet.

(Adhesive strength)
The adhesive force is an adhesive force measured according to JIS Z0237, and is bonded to a SUS304 steel plate in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH using a 2 kg roller with one reciprocation. It is the adhesive strength when the film is left in an environment of 23 ° C. and a relative humidity of 50% RH for 1 hour and then peeled in the 180 ° direction at a peeling speed of 300 mm / min. The adhesive strength on the low adhesive strength side is more preferably 0.07 to 0.18 N / 20 mm, and most preferably 0.09 to 0.13 N / 20 mm. By being in the said range, the rework property and restickability as a composite product can be highly compatible.

  The adhesive strength on the high adhesive strength side is not particularly limited, but is preferably 2.5 to 15 N / 20 mm. More preferably, it is 3-12N / 20mm, Most preferably, it is 4-10N / 20mm. By being in the above range, it is easy to achieve both reworkability and restickability as a composite product.

(Ball tack measurement method)
Ball tack is measured according to JIS Z0237. The ball tack is not particularly limited, but if the ball tack measured in accordance with the tilting ball tack test method defined in JIS Z 0237 is less than the ball number 3, the air release property at the time of sticking Excellent.

(Composition of adhesive tape)
The structure of the pressure-sensitive adhesive tape of the present invention is a re-peelable double-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer having a low adhesive force on one surface of a substrate and a pressure-sensitive adhesive layer having a high adhesive force on the other surface. Each pressure-sensitive adhesive layer is preferably protected with a release liner.

(Adhesive tape thickness)
The thickness of the adhesive tape is 5 to 20 μm. The thickness does not include a release liner. A preferable range of the thickness is 7 to 15 μm, and more preferably 8 to 12 μm.

(Base material)
The thickness of the base material is 3 to 12 μm, preferably 3 to 6 μm, more preferably 3.5 to 5 μm, so that the composite product can be suitably used even when laminated with a magnetic sheet or a heat conductive sheet. Reworkability can be realized. Although it does not specifically limit as a kind of base material, A polyester film, a polyimide film, a polyamide film, a polyolefin film, a nylon film, a peak film, etc. are mentioned. Among these, a polyester film is preferable, and a polyethylene terephthalate film is particularly preferable from the viewpoint of cost and strength. The tensile strength of the substrate is preferably 7N to 20N / 10 mm. More preferably, it is 9-15N / 10mm. The F5 value is preferably 80 MPa to 150 MPa, more preferably 100 MPa to 130 MPa. When it is within the above range, the reworkability as a composite product is improved. The tensile strength and F5 value are values measured according to JIS C2151.

(Adhesive)
As the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer used in the re-peelable double-sided pressure-sensitive adhesive tape of the present invention, known acrylic, silicone-based or rubber-based pressure-sensitive resins can be used. As the rubber-based adhesive, block copolymer systems such as styrene-isoprene-styrene, synthetic rubber-based adhesives such as polybutadiene and polybutylene, natural rubber, and the like can be used. When natural rubber is used, it is preferable not to contain sulfur. If it contains sulfur, it may cause contact failure. In addition, as the silicone-based pressure-sensitive adhesive, a peroxide crosslinking type or an addition condensation type may be used alone or as a mixture. Furthermore, it can also be used by mixing with an acrylic or rubber adhesive, or an adhesive having a silicone component pendant on the polymer main chain or side chain of the acrylic adhesive may be used. The pressure-sensitive adhesive used for the low-adhesive strength side and the high-adhesive strength-side pressure-sensitive adhesive layer can be appropriately selected from these pressure-sensitive adhesives, but it is easy to adjust and handle the adhesive strength. It is preferable to use an acrylic pressure-sensitive adhesive using an acrylic copolymer on both the high adhesive strength sides.

  When an acrylic pressure-sensitive adhesive is used as the pressure-sensitive adhesive used on the low adhesive force side, an acrylic copolymer obtained by reacting a radical polymerizable monomer containing an acrylate ester having an alkyl side chain having 1 to 14 carbon atoms as a monomer component is used. It is preferable to use a polymer. Examples of the acrylate ester having an alkyl side chain having 1 to 14 carbon atoms include (Group 1) methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sce-butyl acrylate, and t-butyl. Acrylate, n-hexyl acrylate, cyclohexyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, isodecyl acrylate, lauryl acrylate methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n- Butyl methacrylate, sce-butyl methacrylate, t-butyl methacrylate, n-hexyl methacrylate, B hexyl methacrylate, n- octyl methacrylate, isooctyl methacrylate, 2-ethylhexyl methacrylate, isononyl methacrylate, isodecyl methacrylate, lauryl methacrylate and the like. Among them, the use of a methacrylic acid alkyl ester having an alkyl side chain having 4 to 9 carbon atoms or an acrylic acid alkyl ester having an alkyl side chain having 4 to 9 carbon atoms reduces the adhesive force on the low adhesive force side to 0. It is preferable because it can be easily controlled in the range of 0.05 to 0.2 N / 20 mm.

  As the monomer component, it is preferable to add an acrylic ester having a polar group such as a hydroxyl group, a carboxyl group or an amino group in the side chain, or other vinyl monomers.

  Examples of the monomer containing a hydroxyl group include (Group 2) 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, hydroxypropyl (meth) acrylate, caprolactone modified (meta ) Acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol (meth) acrylate and the like. Preferred examples include 4-hydroxybutyl (meth) acrylate and 6-hydroxyhexyl (meth) acrylate. Among these, when 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are used, the adhesive force on the low adhesive force side can be easily controlled in the range of 0.05 to 0.2 N / 20 mm.

  In addition, as a monomer having a polar group other than a hydroxyl group, (Group 3) monomers having a carboxyl group such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, acrylic acid dimer, ethylene oxide-modified succinic acid acrylate, Monomers having an amide group such as N-vinyl-2-pyrrolidone, n-vinylcaprolactam, acryloylmorpholine, acrylamide, N, N-dimethylacrylamide, 2- (perhydrophthalimido-N-yl) ethyl acrylate, acrylonitrile, maleic anhydride Examples thereof include acid and itaconic anhydride. Among them, it is preferable to use a carboxyl group-containing monomer, and particularly when acrylic acid or methacrylic acid is used, the adhesive force on the low adhesive force side can be easily controlled in the range of 0.05 to 0.2 N / 20 mm.

  As the pressure-sensitive adhesive used for the low adhesive strength surface, the adhesive strength on the low adhesive strength side is controlled in the range of 0.05 to 0.2 N / 20 mm by using (Group 1), (Group 2) and (Group 3). It is preferable because it is easy to do. In the monomer component constituting the acrylic copolymer of the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer on the low adhesive strength side, the content of (Group 1) is preferably 70% by mass or more, more preferably 70 to 99% by mass. %, And most preferably 80 to 99% by mass. In the monomer component constituting the acrylic copolymer, the content of (Group 2) is preferably 0.001 to 10% by mass, more preferably 0.01 to 7% by mass, and most preferably 0.8. It is 05-5 mass%. In the monomer component constituting the acrylic copolymer, the content of (Group 3) is preferably 0.1 to 3% by mass, and more preferably 0.5 to 2% by mass.

  When an acrylic pressure-sensitive adhesive is used as the pressure-sensitive adhesive used on the high adhesive force side, an acrylic system reacted with a radical polymerizable monomer containing an acrylate ester having an alkyl side chain having 1 to 14 carbon atoms as a monomer component It is preferable to use a copolymer. As the acrylate ester having an alkyl side chain having 1 to 14 carbon atoms, for example, the acrylate ester exemplified as the above (Group 1) can be used, and among them, at least one of n-butyl acrylate and 2-ethylhexyl acrylate is used. It is preferable to do.

  In addition, in the acrylic pressure-sensitive adhesive used on the high adhesive side, as a monomer component used in the acrylic copolymer, an acrylic ester having a polar group such as a hydroxyl group, a carboxyl group or an amino group in the side chain or other It is preferable to add a vinyl monomer. In particular, in the pressure-sensitive adhesive layer on the high adhesive strength side, it is preferable to use the polar group-containing monomer exemplified as the above (Group 3) because it is easy to realize suitable adhesiveness. In particular, it is preferable to use a carboxyl group-containing monomer, and acrylic acid or methacrylic acid is particularly preferable.

  As the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer on the high adhesion side, it is preferable to use the above (Group 1) and (Group 3) because the adhesion force on the high adhesion side can be easily controlled. In the monomer component constituting the acrylic copolymer of the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer on the high adhesive force side, the content of (Group 1) is preferably 70% by mass or more, more preferably 70 to 99% by mass. %, And most preferably 80 to 99% by mass. In the monomer component constituting the acrylic copolymer, the content of (Group 3) is preferably 0.1 to 5% by mass, more preferably 1 to 3% by mass.

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

  In order to increase the cohesive strength of the pressure-sensitive adhesive layer, it is also preferable to add a crosslinking agent to the pressure-sensitive adhesive. Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, a chelate crosslinking agent, and a photocurable crosslinking agent. As the addition amount of the cross-linking agent, the pressure-sensitive adhesive on the low adhesive strength side is preferably adjusted to an amount such that the gel fraction is 70 to 99% by mass, and most preferably 80 to 95% by mass. . On the other hand, the pressure-sensitive adhesive on the high adhesive strength side is preferably adjusted to a gel fraction of 10 to 50% by mass, and most preferably 15 to 40% by mass. The gel fraction is obtained by immersing the composition of the pressure-sensitive adhesive layer after curing in toluene, measuring the mass after drying of the unnecessary portion remaining after standing for 24 hours, and expressing it as a percentage of the original weight.

  Various additives such as tackifier resins, antioxidants, ultraviolet absorbers, fillers, pigments, thickeners and the like may be added to the pressure-sensitive adhesive as long as the performance is not impaired. In particular, the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer on the high adhesive strength side is preferable because it contains a tackifier resin and a suitable adhesive force can be easily obtained.

  The pressure-sensitive adhesive is prepared by dissolving the acrylic copolymer, additives, and other additives as required in an organic solvent. The organic solvent is not particularly limited as long as the above-described blending components are dissolved, but a known and commonly used organic solvent such as ethyl acetate, toluene, xylene, methanol, isopropyl alcohol is used alone or in combination. be able to.

(Release liner)
In the pressure-sensitive adhesive tape of the present invention, a release liner may be provided on the surface of each pressure-sensitive adhesive layer in order to protect the pressure-sensitive adhesive layer. A known release liner may be appropriately selected and used as the release liner. A resin film that has been subjected to a release treatment is preferred because of its excellent smoothness. Of these, a polyester film having excellent heat resistance is preferably subjected to a release treatment. In addition, the total thickness of the colored adhesive tape as used in the field of this invention means the thickness of the adhesive tape itself which does not contain the said release liner.

  The surface of these release liners is preferably provided with a release treatment layer in order to impart easy peelability. The release treatment layer can be formed of various release treatment agents used for release liners for double-sided pressure-sensitive adhesive tapes. Examples of such release treatment agents include silicone-based, fluorine-based, and long-chain alkyl-based agents. A release treatment agent or the like can be preferably used. The release treatment layer may be formed on the above resin film by lamination or coating.

  The release force of the release liner may be appropriately adjusted according to the use mode and the like, but the release force for the pressure-sensitive adhesive layer is 0.01 to 2 N / 20 mm, preferably 0.05 to 0.15 N / 20 mm. When peeling the release liner, it is preferable because deformation of the double-sided pressure-sensitive adhesive tape is easily suppressed. The peeling force can be measured by peeling a release liner or a 50 μm thick PET-backed pressure-sensitive adhesive layer in a 180 ° direction at a speed of 0.3 to 10 m / min.

  The double-sided pressure-sensitive adhesive tape of the present invention has a magnetic sheet or a heat conductive sheet that is easily cracked or peeled off due to the above-described structure, because it is extremely thin with a thickness of 20 μm or less and can suitably fix components and has excellent reworkability. Can be suitably used for the purpose of fixing these sheets. In particular, it can be preferably used for fixing a ferrite sheet that is liable to be cracked or a graphite sheet that is liable to be broken in layers.

(Magnetic sheet)
Magnetic sheets are used for EMI countermeasures such as electronic devices, for RFID, for NFC, and for wireless charging. Examples of the magnetic sheet include a sintered body of magnetic powder and a mixture of magnetic powder in an elastomer. Among them, a sintered body of magnetic powder, especially a ferrite sintered body is useful for these applications because of cost and performance. These magnetic sheets are used by being fixed to an electronic device or an electronic component with an adhesive tape. However, these magnetic powder sintered bodies are very fragile and difficult to rework when they are misaligned. Therefore, when the re-peelable pressure-sensitive adhesive tape of the present invention is used, the reworkability is greatly improved. In addition, the magnetic sheet divided into small pieces having a piece of 1 to 10 mm exhibits a further exceptional reworkability improving effect. Examples of commercially available magnetic sheets include TDK IBF10 and IBF20 and MARUWA FSF series.

(Thermal conductive sheet)
The thermally conductive sheet is used for the purpose of radiating heat from a heating element such as a CPU or LED. As a kind of heat conductive sheet, a film, a graphite sheet, etc. which mix | blended the heat conductive filler with the elastomer are mentioned. Among these, graphite sheets having extremely high thermal conductivity are useful for eliminating heat spots in electronic equipment. Among them, an artificial graphite sheet made from a polyimide film or the like is particularly useful. These heat conductive sheets are used by being fixed to an electronic device or an electronic component with an adhesive tape. Since these heat conductive sheets are very fragile and difficult to rework at the time of misalignment or the like, the reworkable pressure-sensitive adhesive tape of the present invention exhibits a remarkable reworkability improving effect. Examples of the commercially available graphite sheet include PGS graphite sheet EYG type manufactured by Panasonic Corporation, Graffiti manufactured by Kaneka Corporation, SS400 manufactured by Graphtec Corporation, and the like.

  Examples of the present invention will be described below in more detail.

[Adjustment of acrylic adhesive]
(Acrylic adhesive (A))
In a reaction vessel equipped with a condenser, stirrer, thermometer, and dropping funnel, 90 parts of 2-ethylhexyl acrylate, 3 parts of 4-hydroxybutyl acrylate, 6 parts of 2-methoxyethyl acrylate, 1 part of acrylic acid and 2 as a polymerization initiator , 2'-azobisisobutylnitrile dissolved in 100 parts of ethyl acetate, purged with nitrogen, polymerized at 80 ° C for 8 hours, and made of an acrylic copolymer having a weight average molecular weight of 900,000. (A) was obtained.

(Acrylic adhesive (B))
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 76.8 parts of n-butyl acrylate, 20 parts of 2-ethylhexyl acrylate, 3.0 parts of acrylic acid, 0.2 part of β-hydroxyethyl acrylate Then, 0.2 part of 2,2′-azobisisobutylnitrile as a polymerization initiator is dissolved in 100 parts of ethyl acetate, and after substitution with nitrogen, polymerization is carried out at 80 ° C. for 8 hours to obtain an acrylic copolymer having a weight average molecular weight of 800,000. A resin solution of the combined (B) was obtained. Next, 30 parts of rosin-based tackifier resin (D-135, manufactured by Arakawa Chemical Co., Ltd.) is blended with the acrylic copolymer (B), and the acrylic resin is mixed so that the solid content of the mixed solution becomes 40% with ethyl acetate. The pressure-sensitive adhesive (B) was adjusted.

(Acrylic adhesive (C))
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 99.0 parts of n-butyl acrylate, 1.0 part of acrylic acid, and 2,2′-azobisisobutylnitrile 0.2 as a polymerization initiator Were dissolved in 100 parts of ethyl acetate, purged with nitrogen, and polymerized at 80 ° C. for 8 hours to obtain an acrylic pressure-sensitive adhesive (C) comprising an acrylic copolymer having a weight average molecular weight of 700,000.

(Acrylic adhesive (D))
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 98.0 parts of 2-ethylhexyl acrylate, 2.0 parts of acrylic acid, and 2,2′-azobisisobutylnitrile 0.2 as a polymerization initiator. Were dissolved in 100 parts of ethyl acetate, purged with nitrogen, and then polymerized at 80 ° C. for 8 hours to obtain an acrylic pressure-sensitive adhesive (D) comprising an acrylic copolymer having a weight average molecular weight of 500,000.

(Acrylic adhesive (E))
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 68.0 parts of n-butyl acrylate, 29.0 parts of 2-ethylhexyl acrylate, 3.0 parts of acrylic acid, and 2,2 as a polymerization initiator Dissolve 0.2 parts of '-azobisisobutylnitrile in 100 parts of ethyl acetate, and after purging with nitrogen, polymerize at 80 ° C for 8 hours to obtain a resin solution of an acrylic copolymer (E) having a weight average molecular weight of 500,000. Obtained. 20 parts of polymerized rosin-based tackifier resin (Pencel D125 manufactured by Arakawa Chemical Co., Ltd.) is blended with 100 parts by weight of the acrylic copolymer (E), and acrylic is mixed so that the solid content of the mixed solution becomes 40% with ethyl acetate. System adhesive (E) was prepared.

(Acrylic adhesive (F))
In a reaction vessel equipped with a condenser, stirrer, thermometer, and dropping funnel, 93 parts 2-ethylhexyl acrylate, 4 parts β-hydroxyethyl acrylate, 1 part acrylic acid, 2 parts vinyl acetate, 2,2 ′ as a polymerization initiator -Acrylic pressure-sensitive adhesive (F) comprising 0.2 part of azobisisobutylnitrile dissolved in 100 parts of ethyl acetate, polymerized at 80 ° C. for 8 hours after substitution with nitrogen, and an acrylic copolymer having a weight average molecular weight of 800,000 )

(Acrylic adhesive (G))
In a reaction vessel equipped with a condenser, stirrer, thermometer, and dropping funnel, 93.4 parts of n-butyl acrylate, 3.5 parts of acrylic acid, 0.1 part of β-hydroxyethyl acrylate, 3 parts of vinyl acetate, polymerization As an initiator, 0.2 part of 2,2′-azobisisobutylnitrile is dissolved in 100 parts of ethyl acetate, substituted with nitrogen, polymerized at 80 ° C. for 8 hours, and an acrylic copolymer having a weight average molecular weight of 600,000 ( A resin solution B) was obtained. Next, 20 parts of rosin-based tackifier resin (D-135, manufactured by Arakawa Chemical Co., Ltd.) is blended with the acrylic copolymer (B), and the acrylic liquid is mixed so that the solid content of the mixed solution becomes 40% with ethyl acetate. The pressure-sensitive adhesive (G) was adjusted.

Example 1
To 100 parts of the acrylic pressure-sensitive adhesive (A), 2 parts of an isocyanate-based cross-linking agent (manufactured by DIC, trade name: NC40) was blended, and the solid content of the mixed liquid was adjusted to 15% with ethyl acetate. Then, it was coated on a 75 μm-thick polyester film subjected to a release treatment so that the thickness after drying was 3 μm, and dried at 100 ° C. for 2 minutes to prepare a pressure-sensitive adhesive layer on the low adhesive strength side. . It was transferred to a polyester film “4AF53” (3.5 μm) manufactured by Toray and laminated at a pressure of 4 kgf / cm to obtain a single-sided adhesive tape. Next, 100 parts of the acrylic pressure-sensitive adhesive (B) was mixed with 1 part of an isocyanate-based crosslinking agent (trade name: NC40, manufactured by DIC), and adjusted with ethyl acetate so that the solid content was 15%. Then, it was coated on a 75 μm-thick polyester film subjected to a release treatment so that the thickness after drying was 3.5 μm, and dried at 100 ° C. for 2 minutes to form a pressure-sensitive adhesive layer on the high adhesive strength side. Created. Next, the pressure-sensitive adhesive layer on the high adhesion side was transferred to the polyester film surface of the single-sided pressure-sensitive adhesive tape and laminated at a pressure of 4 kgf / cm to obtain a double-sided pressure-sensitive adhesive tape of Example 1. In addition, the obtained double-sided adhesive tape was used for the test after aging at 40 degreeC for 2 days.

(Example 2)
A double-sided pressure-sensitive adhesive tape of Example 2 was obtained in the same manner as in Example 1 except that the amount of the isocyanate-based crosslinking agent blended in 100 parts of the acrylic pressure-sensitive adhesive (A) was changed from 2 parts to 0.5 parts.

(Example 3)
Toray polyester film “4AF53” (3.5 μm) is used instead of Toray polyester film “4AF53” (4.5 μm), and the adhesive layer thickness on the high adhesive side is set to 2.5 μm instead of 3.5 μm. A double-sided pressure-sensitive adhesive tape of Example 3 was obtained in the same manner as Example 1 except that.

Example 4
Instead of the Toray polyester film “4AF53” (3.5 μm), the Toray polyester film “5AF53” (4.5 μm) is used, and the amount of the isocyanate-based crosslinking agent blended in 100 parts of the acrylic pressure-sensitive adhesive (A) is 2 The adhesive layer thickness on the low adhesive strength side was changed to 4 μm instead of 3 μm, and the adhesive layer thickness on the high adhesive strength side was changed to 2.5 μm instead of 3.5 μm. Obtained the double-sided pressure-sensitive adhesive tape of Example 4 in the same manner as in Example 1.

(Example 5)
Change the amount of isocyanate cross-linking agent blended in 100 parts of acrylic adhesive (A) from 2 parts to 3 parts. Adhesive layer thickness on the low adhesive side is 2 μm instead of 3 μm, adhesive on the high adhesive side A double-sided pressure-sensitive adhesive tape of Example 5 was obtained in the same manner as in Example 1 except that the thickness of the agent layer was changed to 4.5 μm instead of 3.5 μm.

(Example 6)
A double-sided pressure-sensitive adhesive tape of Example 6 was obtained in the same manner as in Example 1 except that the acrylic pressure-sensitive adhesive (F) was used instead of the acrylic pressure-sensitive adhesive (A).

(Example 7)
A double-sided pressure-sensitive adhesive tape of Example 7 was obtained in the same manner as in Example 1 except that the acrylic pressure-sensitive adhesive (G) was used instead of the acrylic pressure-sensitive adhesive (B).

(Comparative Example 1)
The double-sided pressure-sensitive adhesive tape of Comparative Example 1 was used in the same manner as in Example 1 except that Mitsubishi polyester film “K100-2.0W” (2 μm) was used instead of Toray polyester film “4AF53” (3.5 μm). Obtained.

(Comparative Example 2)
Mitsubishi polyester film “K100-2.0W” (2 μm) is used instead of Toray polyester film “4AF53” (3.5 μm), and the adhesive layer thickness on the high adhesion side is 5 μm instead of 3.5 μm. A double-sided pressure-sensitive adhesive tape of Comparative Example 2 was obtained in the same manner as in Example 1 except that.

(Comparative Example 3)
Example 1 except that the amount of the isocyanate-based crosslinking agent blended in the acrylic pressure-sensitive adhesive (A) was changed from 2 parts to 0.1 part and the pressure-sensitive adhesive layer thickness on the low adhesive strength side was changed from 3.5 μm to 8 μm. In the same manner, a double-sided pressure-sensitive adhesive tape of Comparative Example 3 was obtained.

(Comparative Example 4)
Comparative Example 4 was used in the same manner as in Example 1 except that the acrylic pressure-sensitive adhesive (C) was used instead of the acrylic pressure-sensitive adhesive (A), and the amount of the isocyanate-based crosslinking agent was changed from 2 parts to 2.8 parts. A double-sided adhesive tape was obtained.

(Comparative Example 5)
Toray polyester film “4AF53” (3.5 μm) is used instead of Toray polyester film “S10 # 9” (9 μm), acrylic adhesive (A) is used instead of acrylic adhesive (C), A double-sided pressure-sensitive adhesive tape of Comparative Example 5 was obtained in the same manner as in Example 1 except that the amount of the isocyanate-based crosslinking agent was changed from 2 parts to 2.8 parts.

(Comparative Example 6)
100 parts of acrylic pressure-sensitive adhesive (D) 1 part of an isocyanate-based crosslinking agent (trade name: Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.), 0.15 of an epoxy-based crosslinking agent (trade name: Tetrad C, manufactured by Mitsubishi Gas Chemical Company) The mixture was mixed with ethyl acetate so that the solid content of the mixed solution was 15%. Then, it was coated on a 75 μm-thick polyester film subjected to a release treatment so that the thickness after drying was 4 μm, and dried at 100 ° C. for 1 minute to prepare a pressure-sensitive adhesive layer on the low adhesive strength side. . It was transferred to a polyester film “K100-2.0W” (2 μm) manufactured by Mitsubishi Resin and laminated at a pressure of 4 kgf / cm to obtain a single-sided adhesive tape. Next, 100 parts of the acrylic pressure-sensitive adhesive (E) is mixed with 1 part of an isocyanate-based crosslinking agent (trade name: Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) so that the solid content of the mixed solution becomes 15% with ethyl acetate. It was adjusted. Then, it was coated on a 75 μm-thick polyester film subjected to a release treatment so that the thickness after drying was 4 μm, and dried at 100 ° C. for 1 minute to prepare a pressure-sensitive adhesive layer on the high adhesion side. . Next, the pressure-sensitive adhesive layer on the high adhesive force side was transferred to the polyester film surface of the single-sided pressure-sensitive adhesive tape and laminated at a pressure of 4 kgf / cm to obtain a double-sided pressure-sensitive adhesive tape of Comparative Example 6. The obtained re-peelable double-sided pressure-sensitive adhesive tape was used for a test after aging at 40 ° C. for 2 days.

(Comparative Example 7)
The amount of the isocyanate-based crosslinking agent to be blended with the acrylic pressure-sensitive adhesive (A) is changed from 2 parts to 4 parts, and further, 0.2 part of an epoxy-based crosslinking agent (trade name: Tetrad C, manufactured by Mitsubishi Gas Chemical Company) is blended. Obtained a double-sided pressure-sensitive adhesive tape of Comparative Example 7 in the same manner as in Example 1.

[Evaluation]
About the adhesive tape which concerns on an Example and a comparative example, adhesive force, tape thickness, retention strength, ball tack, gel fraction, rework property as a composite article, rework property of a tape simple substance, and restickability as a composite article were evaluated.

(Adhesive strength)
The adhesive tape is lined with a polyester film 25 μm (Unitika S25) and cut into a width of 20 mm. In accordance with JIS-Z0237, using a Tensilon tensile tester, peel adhesive strength (peeling angle: 180 °, tensile speed: 300 mm / min, measurement atmosphere: 23 ° C., 50% RH, adherend: stainless steel plate, pasting time : 1 hour). The adhesive strength was measured on both the low adhesive strength side and the high adhesive strength side.

(Tape thickness)
The thickness was measured with a Nikon thickness gauge “DIGIMICRO MFC-101”.

(Holding power)
The adhesive tape is lined with 50 μm aluminum foil and cut into a width of 20 mm. According to JIS-Z0237, a load of 0.1 kg was applied at 100 ° C. and the measurement was performed. The holding force was measured on the low adhesion side.

(Ball tack)
It measured according to JIS-Z0237.

(Gel fraction)
On the release sheet, the pressure-sensitive adhesive composition was coated so that the thickness after drying was 20 μm, dried at 100 ° C. for 3 minutes, and aged at 40 ° C. for 2 days. To do. Next, the weight (G1) of the sample before being immersed in toluene is measured in advance, and the toluene-insoluble matter of the sample after being immersed in a toluene solution at 23 ° C. for 24 hours is filtered by a 300-mesh wire mesh. And the weight (G2) of the residue after drying at 110 degreeC for 1 hour was measured, and the gel fraction was calculated | required according to the following formula | equation.
Gel fraction (mass%) = (G2 / G1) × 100

(Tape rework)
The pressure-sensitive adhesive side of the pressure-sensitive adhesive tape is attached to an aluminum plate and left at 23 ° C. and 50% RH for 24 hours. This was peeled off at a speed of about 1 m / min in the 90 ° direction to evaluate whether or not the adhesive tape could be peeled without breaking. Evaluation was carried out at n10 and judged as follows.
A: All 10 pieces were removed without breaking.
○: 8 or more and less than 10 were peeled without breaking.
X: Seven or less pieces were removed without breaking.

(Making ferrite sintered plate)
100 parts by weight of Ni-Zn-Cu ferrite FRX-952 (trade name, manufactured by Toda Kogyo Co., Ltd.) as magnetic powder, 2 ml of butylphthalylbutyl glycolate, 12 parts by weight of butyral resin and 100 ml of toluene as a solvent are mixed and dissolved in a ball mill. Distributed. After defoaming under reduced pressure with an oil rotary vacuum pump, the resulting mixture was applied to a 100 μm thick polyethylene terephthalate (PET) film with a doctor blade to a certain thickness and dried with hot air at 100 ° C. for 30 minutes. A green sheet having a thickness of 100 μm was obtained.

  Using a blade having a tip having a triangular (V-shaped) cross-sectional shape of the blade, a groove having a depth of 40 μm is formed on the surface of the obtained laminated green sheet having a thickness of 100 μm in a lattice shape with a width of 3 mm. did. Next, the temperature was raised from room temperature to 500 ° C. at a temperature rising rate of 0.5 ° C./min, held at 500 ° C. for 6 hours for degreasing, then heated to 900 ° C. and sintered for 2 hours. The obtained sintered ferrite plate has a thickness of about 80 μm, the grooves are grid-shaped V-shaped grooves with a width of 2.6 mm, the groove opening width is about 110 μm, and the groove depth is about 40 μm. there were.

(Making magnetic sheet composite product)
A 10 μm polyester substrate single-sided adhesive tape “IL-10BMF made by DIC” (PET thickness 4.5 μm) is bonded to the surface of the ferrite sintered plate having an opening, and the examples and comparative examples are peeled off on the opposite surface. The adhesive surface on the high adhesive side of the double-sided adhesive tape was attached. Further, using a small-diameter roller, the ferrite sintered plate was divided into free-form small pieces.

(Reworkability as a composite product)
The magnetic sheet composite product punched into 50 mm × 50 mm is attached to an aluminum plate and left at 23 ° C. and 50% RH for 24 hours. It was peeled off at a speed of about 1 m / min in the 90 ° direction to evaluate whether the magnetic sheet composite could be peeled without breaking. Evaluation was carried out at n10 and judged as follows.
A: All 10 pieces were removed without breaking.
○: 8 or more and less than 10 were peeled without breaking.
X: Seven or less pieces were removed without breaking.

(Re-pasteability as a composite product)
The magnetic sheet composite product that was evaluated as ◎ and ◯ in the above test was attached to an aluminum plate, and after 1 hour, the magnetic sheet composite product was left to face down to evaluate whether or not it dropped. Evaluation was carried out at n5 and judged as follows.
A: All 5 pieces did not fall.
○: 4 pieces did not fall.
X: Two or more drops.

  As is clear from the above table, the double-sided pressure-sensitive adhesive tape of the present invention can suitably fix a magnetic sheet that is easily cracked and has suitable reworkability and re-stickability even when combined with a magnetic sheet. It was. The obtained magnetic sheet composite product had good magnetic properties and flexibility. On the other hand, when the double-sided pressure-sensitive adhesive tapes of Comparative Examples 1 to 7 were combined with a magnetic sheet, good reworkability was not obtained.

Claims (6)

A double-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on both sides of the base material and having different adhesive strength on each side,
The thickness of the substrate is 3 to 12 μm, the total thickness is 5 to 20 μm,
Among the pressure-sensitive adhesive layers on each surface, the thickness of the pressure-sensitive adhesive layer on the low adhesive force side is 0.1 to 7 μm,
Adhesive strength on the low-adhesion side (temperature 23 ° C., relative humidity 50% RH) SUS304 steel plate with a 2 kg roller, with one round reciprocation, temperature 23 ° C., relative humidity 50% RH The adhesive force when peeled in the 180 ° direction at a peeling speed of 300 mm / min after standing for 1 hour in the environment is 0.05 to 0.2 N / 20 mm,
A double-sided pressure-sensitive adhesive tape used for fixing a magnetic sheet or a heat conductive sheet. Among the pressure-sensitive adhesive layers on each surface, the thickness of the pressure-sensitive adhesive layer on the high adhesive force side is 0.1 to 7 μm,
Adhesive strength on the high adhesive strength side (temperature 23 ° C., relative humidity 65% RH) SUS304 steel plate is crimped with a 2 kg roller with one reciprocation, temperature 23 ° C., relative humidity 50% RH 2. The double-sided pressure-sensitive adhesive tape according to claim 1, wherein the adhesive force when peeled in a 180 ° direction at a peeling speed of 300 mm / min after standing for 1 hour in the environment is 2.5 to 15 N / 20 mm.   The double-sided pressure-sensitive adhesive tape according to claim 1 or 2, wherein a ball tack measured according to an inclined ball tack test method defined in JIS Z 0237 of the pressure-sensitive adhesive layer on the low adhesion side is less than a ball number 3. .   The double-sided pressure-sensitive adhesive tape according to claim 1, wherein the magnetic sheet or the heat conductive sheet is a ferrite sheet or a graphite sheet.   The electromagnetic wave shielding material by which the double-sided adhesive tape in any one of Claims 1-4 was laminated | stacked on the at least one surface of the magnetic sheet.   The heat conductive material by which the double-sided adhesive tape in any one of Claims 1-4 was laminated | stacked on the at least one surface of the heat conductive sheet.