JP2016117806A - Adhesive tape, method for producing the same, article and portable electronic terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive tape having excellent impact resistance without causing peeling or the like due to shocks such as falling even when it is thinner than conventional one.SOLUTION: There is provided an adhesive tape which has a structure in which an adhesive layer (B) is laminated directly or via other layer on at least one surface of a substrate layer (A) having a storage elastic modulus (E') measured at a temperature of -10°C and a frequency of 1.0 Hz of 1×10Pa or less and can be suitably used in producing an electronic device, for example a portable electronic terminal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pressure-sensitive adhesive tape that can be used for bonding various adherends.

  Adhesive tapes are widely used, for example, in scenes such as fixing parts constituting electronic equipment. Specifically, the adhesive tape is fixed to a protective panel and a casing of an image display unit constituting a small electronic device such as a portable electronic terminal, a camera, a personal computer, an exterior component or a battery to the small electronic device. Used for fixing rigid parts.

  As the pressure-sensitive adhesive tape, a double-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on both surfaces of a flexible foam base material is known as a thin film having excellent followability to an adherend and impact resistance. For example, see Patent Document 1.)

  However, the adhesive tape using the conventional foam base material is inevitably caused by the thickness of the foam base material, while further thinning of the adhesive tape is required with the thinning of portable electronic terminals and the like. Since the film tends to be thick, it may not be able to sufficiently meet the market demand for thinning.

  On the other hand, the adhesive tape is required to have excellent impact resistance at a level that can prevent a component from being lost due to the impact even when, for example, a portable electronic terminal is dropped.

  However, since the coexistence of the thinning of the adhesive tape and the excellent impact resistance is contradictory in a certain aspect, the adhesive strength is reduced when the thickness of the adhesive layer is thinned in order to achieve the thinning. It tends to cause a drop, and as a result, it may cause peeling or the like due to impact.

  As described above, the actual situation is that a thin adhesive tape having excellent impact resistance has not yet been found.

JP 2013-53177 A

  The problem to be solved by the present invention is to provide a pressure-sensitive adhesive tape that is thin and has excellent impact resistance.

The present inventors have at least a base material layer (A) having a thickness of 250 μm or less and a storage elastic modulus (E ′ ₋₁₀ ) measured at a temperature of −10 ° C. and a frequency of 1.0 Hz of 1 × 10 ⁸ Pa or less. The said subject was solved by the adhesive tape characterized by having the structure by which the adhesive layer (B) was laminated | stacked on one side directly or through another layer.

  The pressure-sensitive adhesive tape of the present invention can be used for adhesion of two or more adherends, and is less likely to cause peeling due to impact even if it is thinner than conventional ones.

It is the conceptual diagram which looked at the test piece for an impact resistance test from the upper surface. It is the conceptual diagram which looked at the test piece for an impact resistance test from the cross-sectional direction. It is the conceptual diagram which looked at the state which attached the test piece for impact resistance tests to the jig | tool for drop tests from the cross-sectional direction.

The pressure-sensitive adhesive tape of the present invention has a storage elastic modulus (E ′ ₋₁₀ ) measured at a temperature of −10 ° C. and a frequency of 1.0 Hz of 1 × 10 ⁸ Pa or less and a thickness of 250 μm or less of the base material layer (A). It has a configuration in which the pressure-sensitive adhesive layer (B) is laminated on at least one surface directly or via another layer.

  As 1st embodiment of the adhesive tape of this invention, the single-sided adhesive tape by which the adhesive layer (B) was laminated | stacked on the one surface side of the said base material layer (A), for example, or the said base material layer (A ), And a double-sided pressure-sensitive adhesive tape in which the pressure-sensitive adhesive layer (B) is laminated. The pressure-sensitive adhesive layer (B) may be directly laminated on the surface of the base material layer (A), or may be laminated via another layer such as a foam base material layer. The double-sided pressure-sensitive adhesive tape may have a pressure-sensitive adhesive layer having the same pressure-sensitive adhesive force on each surface of the base material layer (A), or may have pressure-sensitive adhesive layers having different pressure-sensitive adhesive forces. May be.

[Base material layer (A)]
The pressure-sensitive adhesive tape of the present invention has a base material layer (A) having a storage elastic modulus (E ′ ₋₁₀ ) measured at a temperature of −10 ° C. and a frequency of 1.0 Hz of 6 × 10 ⁸ Pa or less as a so-called core. use. By using the specific substrate layer (A) as a substrate, a pressure-sensitive adhesive tape excellent in impact resistance can be obtained even if it is thin.

As said base material layer (A), the storage elastic modulus (E'- ₁₀ ) measured by the dynamic viscoelastic spectrum of temperature-10 degreeC and frequency 1.0Hz is 4 * 10 < ⁷ > Pa-6 * 10 < ⁸ > Pa. It is preferable to use those in the range of 4 × 10 ⁷ Pa to 1 × 10 ⁸ Pa in order to obtain an adhesive tape excellent in impact resistance even if it is thin. preferable.

Moreover, as said base material layer (A), the storage elastic modulus (E'- ₂₀ ) measured by the dynamic-viscoelastic spectrum of temperature-20 degreeC and frequency 1.0Hz is 5 * 10 < ⁸ > Pa or less. It is preferable to use one having a range of 5 × 10 ⁷ Pa to 3 × 10 ⁸ Pa in order to obtain a pressure-sensitive adhesive tape excellent in impact resistance even if it is thin.

Moreover, as said base material layer (A), the storage elastic modulus ( _E'-30 ) measured by the dynamic viscoelastic spectrum of temperature-30 degreeC and frequency 1.0Hz is 1 * 10 < ⁹ > Pa or less. It is preferable to use it, and it is more preferable to use the thing of the range of 1 * 10 < ⁸ > Pa-3 * 10 < ⁹ > Pa in order to obtain the adhesive tape excellent in impact resistance even if it is thin.

The storage elastic modulus (E ′ ₋₁₀ ), the storage elastic modulus (E ′ ₋₂₀ ) and the storage elastic modulus (E ′ ₋₃₀ ) are composed of a rectangular base material layer having a thickness of 100 μm, a width of 5 mm and a length of 25 mm. A test piece was prepared, and the dynamic viscoelasticity of the test piece was measured under the conditions of measurement temperature range: −30 ° C. to 100 ° C. and frequency: 1 Hz (sine wave) using RSA3 manufactured by TA Instruments. The spectrum was measured.

Moreover, as said base material layer (A), when obtaining the adhesive tape with the adhesive force of the level which can join 2 or more to-be-adhered bodies favorably in a normal state, temperature 23 degreeC and frequency 1.0Hz It is preferable to use one having a storage elastic modulus (E ′ ₂₃ ) measured by a dynamic viscoelastic spectrum of 1.0 × 10 ³ Pa to 5.0 × 10 ⁸ Pa. 1 × 10 ⁶ Pa to 1 It is more preferable to use what is * 10 < ⁸ > Pa, and it is still more preferable to use what is 5.0 * 10 < ⁶ > Pa-5 * 10 < ⁷ > Pa.

  As the base material layer (A), one having a thickness of 200 μm or less is used. The thickness is preferably 10 μm to 200 μm, more preferably 10 μm to 150 μm, and even more preferably 40 μm to 130 μm. In addition, the thickness of the said base material layer (A) is an average value of the value obtained by measuring the thickness of five places selected at random among the said base material layers (A). By using the base material layer (A) having a thickness in the above range, it is easy to form the base material layer (A), and it is possible to obtain a pressure-sensitive adhesive tape that is further excellent in impact resistance.

  Moreover, as said base material layer (A), in order to obtain the adhesive tape provided with the further outstanding impact resistance, it may be foamed, but the thickness reduction of the adhesive tape and the excellent impact resistance In order to achieve both of these, non-foaming is preferable.

As the base material layer (A), any layer can be used as long as it has the specific storage elastic modulus (E ′ ₋₁₀ ). Among them, a layer containing a thermoplastic resin is preferably used. It is more preferable to use a polyurethane-based substrate in order to obtain a pressure-sensitive adhesive tape having even better impact resistance even if it is thin.

As the polyurethane-based substrate, it is preferable to use a material obtained by using a polyurethane-based resin in order to obtain a pressure-sensitive adhesive tape having even better impact resistance even if it is thin.

  As the polyurethane resin, for example, a resin obtained by reacting polyisocyanate and polyol can be used.

  As said polyurethane-type resin, it is preferable to use what has an isocyanate group. Specifically, as the polyurethane-based resin, it is possible to further soften the base material layer (A) by using a polyurethane resin having an isocyanate group equivalent of 1000 to 1600. Even if it exists, since the adhesive tape provided with the further outstanding impact resistance can be obtained, it is preferable. The isocyanate group equivalent represents the molecular weight of the polyurethane resin per mole of isocyanate group.

  Examples of the polyisocyanate include tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, partially carbodiimidized diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, tolylene diisocyanate, naphthalene diisocyanate, phenylene diisocyanate, hexamethylene diisocyanate. , Isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, cyclohexane diisocyanate and other aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates and the like can be used alone or in combination of two or more. Among these, as the polyisocyanate, it is possible to further soften the base material layer (A) by using 4,4′-diphenylmethane diisocyanate. This is preferable because an adhesive tape having impact resistance can be obtained.

  As said polyol, polyether polyol, polyester polyol, and another polyol can be used individually or in combination of 2 or more types, for example.

Among them, as the polyol, it is possible to form a base material layer (A) having a storage elastic modulus (E ′ ₋₁₀ ) in the predetermined range by using a combination of a polyether polyol and a polyester polyol, Even if it is thin, it is preferable for obtaining a pressure-sensitive adhesive tape that is further excellent in impact resistance.

  The mass ratio of the polyether polyol and the polyester polyol [polyether polyol / polyester polyol] is preferably in the range of 15/85 to 85/15, more preferably in the range of 30/70 to 60/40. The base layer (A) can be made more flexible by using in a range of 40/60 to 60/40, and as a result, even with a thin shape, it has even better impact resistance. Since an adhesive tape can be obtained, it is preferable.

  Examples of the polyether polyol include one kind of polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, glycerin, polytetramethylene ether glycol, trimethylolpropane, glucose, sorbitol, and shoelace. Or what can be obtained by making 2 or more types react with 1 type, or 2 or more types, such as a propylene oxide, ethylene oxide, an oxide, a styrene oxide, can be used. Specifically, polyethylene glycol, polypropylene glycol, polyoxytetramethylene glycol or the like can be used as the polyether polyol.

Among these, as the polyether polyol, use of polypropylene glycol or polyoxytetramethylene glycol forms the base material layer (A) having the storage elastic modulus (E ′ ₋₁₀ ) in the predetermined range. Even if it is thin, it is more preferable for obtaining a pressure-sensitive adhesive tape that is further excellent in impact resistance.

  The polyoxytetramethylene glycol is preferably used in a range of 20% by mass or more with respect to the total amount of the polyether polyol, and may be used in a range of 50% by mass to 100% by mass, even if it is thin. It is more preferable for obtaining a pressure-sensitive adhesive tape having further excellent impact resistance.

  Moreover, as said polyester polyol, what is obtained by making polycarboxylic acid and a polyol react can be used.

  Examples of the polycarboxylic acid include aliphatic polycarboxylic acids such as succinic acid, maleic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid, and aromatics such as o-phthalic acid. A group polycarboxylic acid or the like can be used.

  Examples of polyols that can be used in the production of the polyester polyol include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,2 -Dimethyl-1,3-propanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, diethylene glycol, triethylene glycol, dipropylene glycol, cyclohexane-1,4 -Diol, cyclohexane-1,4-dimethanol and the like can be used.

Moreover, as a polyol which can be used for manufacture of the said polyester polyol, using the polyol which alkylene oxide added to the bisphenol compound, the base material layer ( _E'-10 ) provided with the storage elastic modulus ( _E'-10 ) of the said predetermined range. A) can be formed, and even if it is thin, it is more preferable for obtaining a pressure-sensitive adhesive tape that is further excellent in impact resistance.

  Examples of the bisphenol compound include bisphenol A. Examples of the alkylene oxide include ethylene oxide and propylene oxide. The alkylene oxide is preferably added in an amount of 1 mol to 10 mol, and more preferably 2 mol to 8 mol, with respect to 1 mol of the bisphenol compound.

  As said base material layer (A), what contains an additive as needed other than resin, such as the said polyurethane-type resin, can be used.

  The base material layer (A) is, for example, coated on the surface of the release sheet with a composition (a) containing a resin such as the polyurethane-based resin and, if necessary, the above-mentioned additive or solvent, and the like. Can be manufactured.

  Examples of the composition (a) include a composition containing the resin or the like and an organic solvent, a composition containing the resin or the like and an aqueous medium, a solventless composition that substantially does not contain the solvent, or the like. Can be used. Especially, it is preferable to use the solvent-free composition as the composition (a) because the tensile strength is high and the adhesive tape of the present invention is not easily broken when it is cut.

  As the solventless composition, a solventless polyurethane resin composition can be used as long as the polyurethane resin is used as the resin, and a thermoplastic, so-called polyurethane hot melt composition can be used. Things can be used.

The polyurethane hot melt composition contains a moisture curable polyurethane hot melt in which an isocyanate group which the polyurethane resin may have can react with moisture (humidity) in the atmosphere to form a crosslinked structure. Compositions can be used.
As a method of forming the base material layer (A) using the moisture-curable polyurethane hot melt-containing composition, for example, a step of applying the composition to the surface of a release film by a roll coating method, the coating The method which has the process of carrying out a moisture hardening reaction by making it harden | cure for about 72 hours in _ temperature 23 degreeC and relative humidity 50% environment is mentioned.

[Adhesive layer (B)]
Next, the adhesive layer (B) which comprises the adhesive tape of this invention is demonstrated.

  The pressure-sensitive adhesive layer (B) is a layer that adheres to the adherend. In the double-sided pressure-sensitive adhesive tape which is one embodiment of the present invention, the pressure-sensitive adhesive layers (B) provided on both surfaces of the base material layer (A) may each have a pressure-sensitive adhesive layer having the same adhesive force. It may have a pressure-sensitive adhesive layer having different adhesive strength.

  The pressure-sensitive adhesive layer (B) can be formed using various pressure-sensitive adhesives.

  Examples of the pressure-sensitive adhesive include natural rubber-based pressure-sensitive adhesives, synthetic rubber-based pressure-sensitive adhesives, acrylic pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, and vinyl ether-based pressure-sensitive adhesives. As the form of the pressure-sensitive adhesive, a solvent-based pressure-sensitive adhesive, an emulsion-type pressure-sensitive adhesive, a water-based pressure-sensitive adhesive such as a water-soluble pressure-sensitive adhesive, a hot-melt pressure-sensitive adhesive, a UV curable pressure-sensitive adhesive, and an EB-curable pressure-sensitive adhesive. An adhesive etc. are mentioned.

  Especially, as said adhesive, it is preferable to use the acrylic adhesive which contains an acrylic polymer and contains tackifying resin, a crosslinking agent, etc. as needed.

  As the acrylic polymer, it is preferable to use a polymer obtained by polymerizing a vinyl monomer component containing a vinyl monomer.

  Examples of the (meth) acrylic monomer that can be used for the production of the acrylic polymer include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t- Carbon such as butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate A (meth) acrylate having an alkyl group having 1 to 12 atoms can be used.

  Among these, as the (meth) acrylic monomer, it is preferable to use a (meth) acrylate having an alkyl group having 4 to 12 carbon atoms, and having an alkyl group having 4 to 8 carbon atoms. It is more preferable to use (meth) acrylate, and the use of any one of n-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl (meth) acrylate or a combination thereof further improves impact resistance and peel adhesion. It is preferable for obtaining a pressure-sensitive adhesive sheet that satisfies both of the above.

  The (meth) acrylate having an alkyl group having 1 to 12 carbon atoms is preferably used in an amount of 60% by mass or more, based on the total amount of monomers used for the production of the acrylic polymer. It is more preferable to use in the range of 98.5% by mass, and to use in the range of 90% by mass to 98.5% by mass provides a pressure-sensitive adhesive sheet that has both excellent impact resistance and peel adhesive strength. In addition, it is preferable.

  Moreover, when manufacturing the said acrylic polymer, a highly polar vinyl monomer can be used as a monomer. As the highly polar vinyl monomer, a vinyl monomer having a hydroxyl group, a vinyl monomer having a carboxyl group, a vinyl monomer having an amide group, or the like can be used alone or in combination.

  Examples of the monomer having a hydroxyl group include a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate. (Meth) acrylates can be used.

  As the vinyl monomer having a carboxyl group, for example, acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth) acrylic acid dimer, crotonic acid, ethylene oxide-modified oxalic acid acrylate, etc. can be used. Of these, acrylic acid is preferably used.

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

  As the high-polarity vinyl monomer, vinyl acetate, ethylene oxide-modified succinic acid acrylate, 2-acrylamido-2-methylpropane sulfonic acid and the like can be used in addition to those described above.

  The high-polarity vinyl monomer is preferably used in a range of 1.5% by mass to 20% by mass with respect to the total amount of monomers used for the production of the acrylic polymer. It is more preferable to use in the range of 10 to 10% by mass, and it is more preferable to use in the range of 2 to 8% by mass in order to achieve both excellent adhesive force and excellent followability.

  When using the thing containing the crosslinking agent mentioned later as the said adhesive, it is preferable to use the acrylic polymer which has a functional group which reacts with the functional group which the said crosslinking agent has as said acrylic polymer. Examples of the functional group that the acrylic polymer may have include a hydroxyl group.

  The hydroxyl group can be introduced into the acrylic polymer, for example, by using a vinyl monomer having a hydroxyl group as the monomer.

  The vinyl monomer having a hydroxyl group is preferably used in the range of 0.01% by mass to 1.0% by mass with respect to the total amount of monomers used for the production of the acrylic polymer. It is more preferable to use in the range of mass% to 0.3 mass%.

  The acrylic polymer can be produced by polymerizing the monomer by a method such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, etc., and adopting a solution polymerization method Is preferable for improving the production efficiency of the acrylic polymer.

  Examples of the solution polymerization method include a method of radical polymerization by mixing and stirring the monomer, a polymerization initiator, and an organic solvent, preferably at a temperature of 40 ° C. to 90 ° C.

  Examples of the polymerization initiator include peroxides such as benzoyl peroxide and lauryl peroxide, azo thermal polymerization initiators such as azobisisobutylnitrile, acetophenone photopolymerization initiators, benzoin ether photopolymerization initiators, benzyl A ketal photopolymerization initiator, an acyl phosphine oxide photopolymerization initiator, a benzoin photopolymerization initiator, a benzophenone photopolymerization initiator, or the like can be used.

  The acrylic polymer obtained by the above method may be in a state of being dissolved or dispersed in an organic solvent as long as it is produced by a solution polymerization method, for example.

  As said acrylic polymer, it is preferable to use what has a weight average molecular weight of 400,000-3 million, and it is more preferable to use what has a weight average molecular weight of 700,000-2,500,000.

  The weight average molecular weight is a value measured by gel permeation chromatography (GPC method) and calculated in terms of standard polystyrene. Specifically, the weight average molecular weight can be measured under the following conditions using a GPC apparatus (HLC-8329GPC) manufactured by Tosoh Corporation.

Sample concentration: 0.5% by mass (tetrahydrofuran solution)
Sample injection volume: 100 μl
Eluent: Tetrahydrofuran Flow rate: 1.0 ml / min Measuring temperature: 40 ° C
This column: TSKgel GMHHR-H (20) 2 Guard column: TSKgel HXL-H
Detector: Differential refractometer Weight average molecular weight of standard polystyrene: 10,000 to 20 million (manufactured by Tosoh Corporation)

  As the pressure-sensitive adhesive that can be used for forming the pressure-sensitive adhesive layer (B), it is preferable to use a pressure-sensitive adhesive-containing material in order to obtain a pressure-sensitive adhesive tape excellent in impact resistance.

  Examples of the tackifying resin include a rosin tackifying resin, a polymerized rosin tackifying resin, a polymerized rosin ester tackifying resin, a rosin phenol tackifying resin, a stabilized rosin ester tackifying resin, and a disproportionated rosin ester. -Based tackifier resins, hydrogenated rosin ester-based tackifier resins, terpene-based tackifier resins, terpene phenol-based tackifier resins, petroleum resin-based tackifier resins, (meth) acrylate resin-based tackifier resins, and the like. . When using an emulsion-type pressure-sensitive adhesive as the pressure-sensitive adhesive, it is preferable to use an emulsion-type tackifying resin as the tackifying resin.

  Examples of the tackifying resin include disproportionated rosin ester tackifying resin, polymerized rosin ester tackifying resin, rosin phenol tackifying resin, hydrogenated rosin ester tackifying resin, (meth) acrylate, among others. It is preferable to use one or a combination of two or more of resins, terpene phenol resins, and petroleum resins.

  As the tackifier resin, those having a softening point in the range of 30 ° C. to 180 ° C. are preferable, and those having a softening point in the range of 70 ° C. to 140 ° C. are used. ) Is more preferable for achieving both excellent adhesive strength and excellent followability. When the (meth) acrylate tackifying resin is used, it is preferable to use a (meth) acrylate tackifying resin having a glass transition temperature of 30 ° C. to 200 ° C., and a resin having a temperature of 50 ° C. to 160 ° C. It is more preferable.

  The tackifying resin is preferably used in the range of 5 to 65 parts by mass, more preferably in the range of 8 to 55 parts by mass with respect to 100 parts by mass of the acrylic polymer. It is more preferable for obtaining a pressure-sensitive adhesive tape excellent in impact resistance.

  As the pressure-sensitive adhesive used for forming the pressure-sensitive adhesive layer (B), it is preferable to use a cross-linking agent in order to obtain a pressure-sensitive adhesive tape having further excellent impact resistance.

  As said crosslinking agent, an isocyanate type crosslinking agent, an epoxy-type crosslinking agent, a metal chelate type crosslinking agent, an aziridine type crosslinking agent etc. can be used, for example. Especially, as said crosslinking agent, it is preferable to use any one or both of the isocyanate type crosslinking agent and epoxy-type crosslinking agent which are rich in the reactivity with an acrylic polymer, and using an isocyanate type crosslinking agent is preferable. More preferred.

  Examples of the isocyanate-based crosslinking agent include tolylene diisocyanate, naphthylene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, trimethylolpropane-modified tolylene diisocyanate, and the like. It is preferable to use trimethylolpropane-modified tolylene diisocyanate.

  The crosslinking agent is preferably selected and used in such an amount that the gel fraction with respect to toluene of the pressure-sensitive adhesive layer (B) is 70% by mass or less. It is more preferable to use it, and it is more preferable to select and use an amount with which the gel fraction is 25% by mass to 55% by mass in order to obtain a pressure-sensitive adhesive tape having further excellent impact resistance.

  In addition, the said gel fraction points out the value measured by the method shown below.

  The pressure-sensitive adhesive coated on the release treatment surface of the release liner so that the thickness after drying is 50 μm is dried for 3 minutes in an environment of 100 ° C., and then 2 in an environment of 40 ° C. The pressure-sensitive adhesive layer was formed by aging for a day.

  A test piece was prepared by cutting the pressure-sensitive adhesive layer into a square of 50 mm length and 50 mm width.

  After measuring the mass (G1) of the test piece, the test piece was immersed in toluene for 24 hours in an environment of 23 ° C.

  After the immersion, the mixture of the test piece and toluene was filtered using a 300 mesh wire net to extract insoluble components in toluene. The mass (G2) of the insoluble component dried at 110 ° C. for 1 hour was measured.

  The gel fraction was calculated based on the mass (G1), the mass (G2), and the following formula.

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

  Examples of the pressure-sensitive adhesive include plasticizers, softeners, antioxidants, flame retardants, glass and plastic fibers and balloons, beads, metals, metal oxides, metal nitride fillers, pigments, dyes, and the like. What contains additives, such as a coloring agent, a leveling agent, a thickener, a water repellent, an antifoamer, can be used.

  As the pressure-sensitive adhesive, it is preferable to use a pressure-sensitive adhesive containing a solvent for maintaining good coating workability. Examples of the solvent include toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, hexane, and the like. Moreover, when setting it as an aqueous adhesive composition, water or the aqueous solvent which has water as a main can be used.

  If the pressure-sensitive adhesive tape of the present invention is, for example, the pressure-sensitive adhesive tape of the first embodiment, the step of forming the pressure-sensitive adhesive layer (B) by coating the pressure-sensitive adhesive on the surface of the release sheet and drying, It can manufacture by passing the process of transferring the said adhesive layer (B) to one or both surfaces of the base material layer (A) previously manufactured by the said method. Moreover, the said adhesive tape can also be manufactured by forming an adhesive layer (B) by coating and drying the said adhesive directly on the single side | surface or both surfaces of the said base material layer (A) manufactured previously. it can.

  When using an adhesive containing an acrylic polymer and a crosslinking agent as an adhesive forming the adhesive layer (B), the adhesive was applied to the surface of the base material layer (A) and dried. Preferably, the substrate layer (A) and the pressure-sensitive adhesive layer (B) are allowed to age for about 2 to 7 days in an environment of preferably 20 ° C. to 50 ° C., more preferably 23 ° C. to 45 ° C. It is preferable for obtaining a pressure-sensitive adhesive tape that is firmly bonded.

  The thickness of the pressure-sensitive adhesive layer (B) formed by the above method is preferably 5 μm to 100 μm in order to achieve both excellent adhesion to the adherend and foam and excellent followability. More preferably, it is 10 micrometers-80 micrometers, and it is especially preferable that it is 15 micrometers-80 micrometers.

  As the pressure-sensitive adhesive tape of the present invention obtained by the above method or the like, it is preferable to use a tape having a thickness of 300 μm or less because it easily contributes to thinning of a small electronic device. It is more preferable to use one having a thickness of 50 μm to 180 μm.

  Moreover, as an adhesive tape of this invention, what has another layer other than the said base material layer (A) and an adhesive layer (B) as needed can be used.

  Examples of the other layers include a laminated layer such as a polyester film, a light-shielding layer, a light reflection layer, a metal layer, and other heat conductive layers, for example, for imparting dimensional stability and good tensile strength and reworkability of the pressure-sensitive adhesive sheet. Is mentioned.

  As an adhesive tape of this invention, the peeling sheet may be laminated | stacked on the surface of the adhesive layer (B).

  As the release sheet, for example, a film obtained by using a synthetic resin such as polyethylene, polypropylene, polyester, paper, non-woven fabric, cloth, foamed sheet, metal substrate, and at least one side of a laminate thereof is treated with silicone. In addition, those subjected to a peeling treatment such as a long-chain alkyl treatment or a fluorine treatment can be used.

  The pressure-sensitive adhesive tape of the present invention can be used, for example, for fixing a member whose width of the narrowest portion of the pressure-sensitive adhesive tape is limited to 5 mm or less due to restrictions such as an application site and a shape. In that case, as the adhesive tape, it is preferable to use a tape cut to a width of 5 mm or less, more preferably a tape cut to a width of 0.1 mm to 3 mm, and a cut to 0.1 mm to 1 mm. It is further preferable to use those prepared.

  The narrow member is often used as a member in industrial applications such as electronic terminals such as mobile phones, automobiles, building materials, OA, and home appliance industries.

  Specific examples of the member include two or more casings and lens members that constitute an electronic terminal.

  As the pressure-sensitive adhesive tape, it is preferable to use one cut into a frame shape or the like, for example, when fixing two or more casings constituting the information display device such as a display, and the casing and the lens member. can do.

  An article such as an electronic terminal to which two or more cases and lens members are fixed using the pressure-sensitive adhesive sheet of the present invention is not easily disassembled by an impact such as dropping, and has an excellent waterproof property.

  Hereinafter, the present invention will be described with reference to examples.

[Production Example 1]
Obtained by reacting 54 parts by mass of a polyoxytetramethylene glycol having a number average molecular weight of 2000 in a 1 liter four-necked flask and a polyol obtained by adding 6 mol of propylene oxide to bisphenol A, sebacic acid and isophthalic acid. 18 parts by mass of a polyester polyol (PES1) having a number average molecular weight of 2000, 14 parts by mass of a polyester polyol (PES2) having a number average molecular weight of 1000 obtained by reacting 1,4-butanediol and adipic acid, and diethylene glycol 14 parts by mass of a polyester polyol having a number average molecular weight of 1000 obtained by reacting with o-phthalic acid was mixed and heated under reduced pressure at 100 ° C. to dehydrate until the water content became 0.03% by mass.

  Next, after cooling the inside of the four-necked flask to 70 ° C., 25.0 parts by mass of 4,4′-diphenylmethane diisocyanate was added to the flask, and 0.01 mass of di-n-butyltin dilaurate was added as a catalyst. After the addition, the mixture was heated to 110 ° C. and reacted for 3.0 hours until the isocyanate group content became constant, whereby a moisture-curable polyurethane hot melt containing a polyurethane having an isocyanate group (isocyanate group equivalent 1034) A composition (A-1) was obtained.

  Next, the moisture curable polyurethane hot melt composition (A-1) was applied to the release-treated surface of the release sheet so that the thickness after curing was 100 μm. The base material layer (A-1) was produced by curing for 72 hours in an environment of humidity 50% RH.

[Production Example 2]
Polyurethane having an isocyanate group in the same manner as in Production Example 1 except that the amount of polyoxytetramethylene glycol used is changed from 54 parts by mass to 32 parts by mass and that 22 parts by mass of polyoxypropylene glycol is newly used. A moisture-curable polyurethane hot melt composition (A-2) containing (isocyanate group equivalent 1034) was obtained.

  Next, the moisture curable polyurethane hot melt composition (A-2) was applied to the release-treated surface of the release sheet so that the thickness after curing was 100 μm. A base material layer (A-2) was produced by curing for 72 hours in an environment of 50% RH.

[Production Example 3]
Moisture containing polyurethane having an isocyanate group (isocyanate group equivalent 1034) in the same manner as in Production Example 1 except that 54 parts by mass of polyoxypropylene glycol is used instead of 54 parts by mass of polyoxytetramethylene glycol. A curable polyurethane hot melt composition (A-3) was obtained.

  Next, the moisture-curable polyurethane hot melt composition (A-3) was applied to the release-treated surface of the release sheet so that the thickness after curing was 100 μm, and the temperature was 23 ° C. and relative A base material layer (A-3) was produced by curing for 72 hours in an environment of 50% RH.

[Production Example 4]
Instead of 54 parts by mass of polyoxytetramethylene glycol, 34 parts by mass of polyoxypropylene glycol is used, the amount of PES1 used is changed from 18 parts by mass to 26 parts by mass, and the amount of PES2 used is changed from 14 parts by mass. A moisture-curable polyurethane hot melt containing a polyurethane having an isocyanate group in the same manner as in Production Example 1 except that the amount is changed to 20 parts by mass and the amount of PES3 used is changed from 14 parts by mass to 20 parts by mass. A composition (A-4) was obtained.

  Next, the moisture-curable polyurethane hot melt composition (A-4) was applied to the release-treated surface of the release sheet so that the thickness after curing was 100 μm, and the temperature was 23 ° C. and the relative The base material layer (A-4) was produced by curing for 72 hours in an environment with a humidity of 50% RH.

[Preparation Example 1]
In addition to the above, in a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer, 80.94 parts by mass of n-butyl acrylate, 5 parts by mass of 2-ethylhexyl acrylate, 10 parts by mass of cyclohexyl acrylate, acrylic acid 4 parts by mass, 0.06 part by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate were charged, and the temperature was raised to 72 ° C. while blowing nitrogen under stirring.

  Next, 2 parts by mass of a 2,2′-azobis (2-methylbutyronitrile) solution previously dissolved in ethyl acetate (solid content: 0.1% by mass) was added to the mixture, and the mixture was stirred at 72 ° C. After holding for 4 hours, it was held at 75 ° C. for 5 hours.

  Next, the mixture was diluted with 98 parts by mass of ethyl acetate and filtered through a 200 mesh wire netting to obtain an acrylic polymer (B-1) solution (nonvolatile content: 40% by mass) having a weight average molecular weight of 1,600,000.

In addition, the said weight average molecular weight is a weight average molecular weight in standard polystyrene conversion measured by a gel permeation chromatograph (GPC), and was measured with the following method.
The measurement of the molecular weight by GPC method is a standard polystyrene conversion value measured using a GPC apparatus (HLC-8329GPC) manufactured by Tosoh Corporation.

Sample concentration: 0.5% by mass (tetrahydrofuran solution)
Sample injection volume: 100 μl
Eluent: THF (tetrahydrofuran)
Flow rate: 1.0 ml / min Measurement temperature: 40 ° C
This column: TSKgel GMHHR-H (20) 2 Guard column: TSKgel HXL-H
Detector: differential refractometer Standard polystyrene molecular weight: 10,000 to 20 million (manufactured by Tosoh Corporation)
In a container, 5 parts by mass of D-125 (manufactured by Arakawa Chemical Co., Ltd.), which is a polymerized rosin ester-based tackifier resin, and petroleum-based tackifier resin with respect to 100 parts by mass of the acrylic polymer (B-1). After mixing and stirring 10 parts by mass of FTR6125 (Mitsui Chemicals Co., Ltd.), ethyl acetate was added to obtain an adhesive solution having a solid content of 31% by mass.

  Next, Vernock D-40 (manufactured by DIC Corporation, trimethylolpropane adduct of tolylene diisocyanate, isocyanate group content 7% by mass, nonvolatile content 40% by mass with respect to 100 parts by mass of the pressure-sensitive adhesive solution. ) After adding 1.4 parts by mass, stirring and mixing so as to be uniform, the mixture was filtered through a 100 mesh wire net to obtain an adhesive (B-1).

[Example 1]
The pressure-sensitive adhesive (B-1) is coated on the release-treated surface of the release sheet so that the thickness of the pressure-sensitive adhesive layer after drying is 25 μm, and is dried at 80 ° C. for 3 minutes. Two pieces of (B-1) were produced.

  Next, the pressure-sensitive adhesive layer (B-1) is attached to each side of the base material layer (A-1) one by one, and the surface is reciprocated once using a roll with a linear pressure of 5 kg / cm. They were laminated by. Next, the laminated product was aged in an environment of 40 ° C. for 48 hours to obtain a double-sided pressure-sensitive adhesive tape having a thickness of 150 μm.

[Example 2]
A double-sided pressure-sensitive adhesive tape was produced in the same manner as in Example 1 except that the base material layer (A-2) was used instead of the base material layer (A-1).

[Example 3]
A double-sided pressure-sensitive adhesive tape was produced in the same manner as in Example 1 except that the base material layer (A-3) was used instead of the base material layer (A-1).

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

[Comparative Example 2]
Instead of the base material layer (A-1), a black polyolefin-based foam (thickness: 300 μm, apparent density 0.20 g / cm 3, 25% compressive strength: 90 kPa, tensile modulus in flow direction: 530 N / cm 2, width A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that a base material layer having a tensile elastic modulus in the direction: 340 N / cm 2 and interlayer strength: 22.0 N / cm was used.

[Measurement method of storage modulus of base material layer]
The storage elastic modulus at −10 ° C., −20 ° C. and −30 ° C. of the base material layer was measured by the following method. A test piece was prepared by cutting the 100 μm-thick base material layer produced by the above method into a rectangle having a width of 5 mm and a length of 25 mm. The dynamic viscoelastic spectrum of the test piece was measured using RSA3 manufactured by TA Instruments, under the conditions of measurement temperature range: −30 ° C. to 100 ° C., frequency: 1 Hz (sine wave). It was measured.

[Impact resistance evaluation method]
By cutting the double-sided adhesive tape in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH, two adhesive tapes having a width of 5 mm and a length of 400 mm were produced.

  Next, the two adhesive tapes are placed on one side of an acrylic plate (Mitsubishi Rayon Co., Ltd. Acrylite MR200 “trademark”, hue: transparent) having a thickness of 2 mm, a width of 50 mm, and a length of 50 mm. Attached so that a space of 45 mm could be taken (see FIG. 1).

  Next, an acrylonitrile butadiene styrene plate (ABS plate, thickness 2 mm, width 100 mm and length 150 mm) was placed on the surface of the adhesive tape, and the surface was reciprocated once with a 5 kg roller, then at 23 ° C. and relative The test piece was obtained by leaving still for 24 hours in the environment of humidity 50% RH (FIG. 2).

  Next, a U-shaped measuring table (made of aluminum with a thickness of 5 mm) having a length of 150 mm, a width of 100 mm, and a height of 45 mm was installed on the base of a DuPont impact tester (manufactured by Tester Sangyo Co., Ltd.) Above, the said test piece was installed so that the acrylic board which comprises it might face down.

  Next, a stainless steel hitting core having a diameter of 25 mm and a mass of 300 g was dropped from the ABS plate side five times from a position having a height of 10 cm.

  The above test was repeated while increasing the drop height by 10 cm, and the impact resistance of the adhesive tape was determined based on the drop height (cm) when peeling of the adhesive tape or separation of the acrylic plate was confirmed. evaluated.

  A: The drop height was 70 cm or more.

  ○: The drop height was 60 cm or more and less than 70 cm.

  Δ: The drop height was 40 cm or more and less than 60 cm.

  X: The drop height was less than 40 cm.

[Evaluation of thinness]
Even if the total thickness of the adhesive tape is 200 μm or less, it was evaluated as “◎” if it had excellent impact resistance, and if the total thickness was 200 μm or less, the impact resistance was significantly reduced. What caused was evaluated as “x”, and when the total thickness exceeded 200 μm, those having good impact resistance were evaluated as “x”.

DESCRIPTION OF SYMBOLS 1 Adhesive tape 2 Acrylic board 3 ABS board 4 U-shaped measuring stand 5 Strike core

Claims (11)

The storage elastic modulus (E ′ ₋₁₀ ) measured at a temperature of −10 ° C. and a frequency of 1.0 Hz is 6 × 10 ⁸ Pa or less, and at least one side of the base material layer (A) having a thickness of 250 μm or less, directly or other A pressure-sensitive adhesive tape having a structure in which the pressure-sensitive adhesive layer (B) is laminated via the layer. 2. The pressure-sensitive adhesive tape according to claim 1, wherein the base material layer (A) has a storage elastic modulus (E ′ ₋₂₀ ) measured at a temperature of −20 ° C. and a frequency of 1.0 Hz of 5 × 10 ⁸ Pa or less. The pressure-sensitive adhesive tape according to claim 2, wherein the base material layer (A) has a storage elastic modulus ( _E'-30 ) measured at a temperature of -30 ° C and a frequency of 1.0 Hz of 1 x 10 ⁹ Pa or less. The pressure-sensitive adhesive tape according to any one of claims 1 to 3, wherein the substrate layer (A) is a polyurethane-based substrate. The pressure-sensitive adhesive tape according to any one of claims 1 to 4, wherein the polyurethane-based substrate is obtained using a moisture-curable polyurethane hot melt-containing composition. The pressure-sensitive adhesive tape according to claim 5, wherein the moisture-curable polyurethane hot melt is obtained by reacting a polyol containing a polyether polyol with a polyisocyanate. The pressure-sensitive adhesive tape according to claim 6, wherein the polyether polyol contains polyoxytetramethylene glycol. The pressure-sensitive adhesive tape according to claim 7, wherein the amount of the polyoxytetramethylene glycol used is 20% by mass or more based on the total amount of the polyol. A storage elastic modulus (E ′ ₋₁₀ ) measured at a temperature of −10 ° C. and a frequency of 1.0 Hz by applying the moisture-curable polyurethane hot melt-containing composition to the surface of the release liner and reacting with the surface is 6 ×. A step [1] of producing a polyurethane-based substrate having a pressure of 10 ⁸ Pa or less, a step [2] of forming a pressure-sensitive adhesive layer by applying a pressure-sensitive adhesive to the surface of a release liner different from the above, and A method for producing a pressure-sensitive adhesive tape, comprising a step [3] of transferring the pressure-sensitive adhesive layer to at least one surface of the polyurethane-based substrate. An article having a configuration in which two or more adherends are bonded by the pressure-sensitive adhesive tape according to any one of claims 1 to 8. A portable electronic terminal having a configuration in which two or more cases, or a case and a lens member are bonded by the adhesive tape according to any one of claims 1 to 8.

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