WO2016075753A1 - Adhesive tape having foamed resin base material, and method for producing same - Google Patents

Abstract

Disclosed are: an adhesive tape having a foamed resin base material that includes closed pores, and an adhesive layer provided on at least one surface of the foamed resin base material, wherein the average void size of the closed pores is 20-180 μm, the maximum void size is 300 μm or less, the dimensional change upon heating of the adhesive tape is within 100 ± 5% where the dimension before heating is 100%, and the rubber elastic elongation recovery rate of the adhesive tape is 85% or greater, the adhesive tape having particularly exceptional water resistance, anti-static properties, impact resistance, heat resistance, repair properties, and flexibility; and a method for producing the adhesive tape.

Description

Adhesive tape having foamed resin substrate and method for producing the same

The present invention is a pressure-sensitive adhesive tape having a foamed resin base material, which has sufficient properties even when thin and thin, and has particularly excellent waterproof properties, anti-static properties, impact resistance, heat resistance, repair properties and flexibility. The present invention relates to a pressure-sensitive adhesive tape and a method for producing the same.

In portable electronic devices such as smartphones and mobile phones, adhesive tape is used to bond the protective panel of the display to the housing and to fix other members and modules. And the waterproofness of this adhesive tape is important for the waterproofness of a portable electronic device. For example, Patent Documents 1 and 2 disclose waterproof adhesive tapes. Here, a flexible foam is used as the base material of the adhesive tape, and since it is thin and has good followability, it is suitable for use in portable electronic devices. Patent Document 3 discloses a double-sided pressure-sensitive adhesive tape using a laminate of a foam layer and a reinforcing layer (plastic film) as a base material. This adhesive tape is said to be excellent in removability.

In recent portable electronic devices, the display has become larger, the entire product has been slimmed down, and the design has been improved. Along with this, not only is the adhesive tape thin, but there is an increasing demand for a narrow tape width. For example, the width of the adhesive tape used for bonding the protective panel and the housing has been considerably reduced. In connection with this, the foamed resin base material which has the waterproof property which was excellent even if it was thin and thin is needed for the adhesive tape. Also, portable electronic devices with larger screens and slimming often do not have a space for grounding. Therefore, when a user who is charged with static electricity touches the portable electronic device, the static electricity passes through the adhesive tape. Built-in parts may be damaged and not work properly. Therefore, an adhesive tape is required to have a foamed resin base material having excellent anti-static properties even if it is thin and thin. Moreover, since a portable electronic device may be used or left at a high temperature or may receive an impact force, heat resistance and impact resistance are required. Furthermore, in order to easily peel off the adhesive tape without problems when re-attaching fixed parts or replacing parts during repair in the portable electronic device manufacturing process, the adhesive tape has excellent reworkability or high repairability. is necessary.

Japanese Patent No. 5370796 Japanese Patent No. 5477517 JP 2014-037543 A

An object of the present invention is to provide a pressure-sensitive adhesive tape having sufficient characteristics even when it is thin and thin, and having particularly excellent waterproof properties, anti-static properties, impact resistance, heat resistance, repair properties and flexibility, and a method for producing the same. It is to provide.

The present invention is an adhesive tape having a foamed resin base material containing closed cells and an adhesive layer provided on at least one side of the foamed resin base material, wherein the average void diameter of the closed cells is 20 to 180 μm, The maximum void diameter is 300 μm or less, the heating dimensional change rate of the adhesive tape is within 100% ± 5% when the dimension before heating is 100%, and the rubber elastic elongation recovery rate of the adhesive tape is 85% It is the adhesive tape which is the above.

Furthermore, the present invention is a method for producing the above-mentioned pressure-sensitive adhesive tape, comprising a step of obtaining a foamed resin base material by forming closed cells using thermally expandable microcapsules and / or already expanded hollow fillers. It is a manufacturing method of an adhesive tape.

The adhesive tape of the present invention controls the void diameter of closed cells of the foamed resin base material to a small size within a specific range, and thus has excellent waterproofness, electrostatic resistance and impact resistance in a narrow tape. Furthermore, since the heating dimensional change rate of the adhesive tape is low, it has excellent heat resistance, and since the rubber elastic elongation recovery rate is high, it has excellent repairability.

In the method for producing an adhesive tape of the present invention, closed cells are formed using thermally expandable microcapsules and / or pre-expanded hollow fillers. Therefore, the void diameter of closed cells in a substrate is set to a small size within a specific range of the present invention. Can be easily controlled.

It is an optical microscope photograph of one form of the closed cell in the adhesive tape of this invention. It is an optical micrograph of one form of the closed cell in the conventional adhesive tape. It is a schematic diagram for demonstrating the test method of the antistatic property of an Example. It is a schematic diagram for demonstrating the test method of the antistatic property of an Example.

<Foamed resin substrate>
The foamed resin base material in the present invention is a base material in which closed cells are formed by foaming the resin. The foamed resin base material containing closed cells is superior in water resistance and artificial sebum sweat oil resistance compared to the foamed resin base material containing open cells.

In the present invention, the average void diameter of closed cells in the foamed resin substrate is 20 to 180 μm, preferably 30 to 150 μm, more preferably 40 to 120 μm. Further, the maximum void diameter of the closed cells is 300 μm or less, preferably 250 μm or less, more preferably 200 μm or less. By controlling the void diameter to a small size within this specific range, even if the adhesive tape is thin and thin, excellent waterproofness, electrostatic resistance and impact resistance are exhibited.

Specifically, the measurement of the void diameter is performed by observing a number of closed cells in a 5 × 5 mm area of the foamed resin base material with an optical microscope using a transmission method, and measuring the average value and the maximum value of the void diameter. . FIG. 1 is an optical micrograph of one form of closed cells in the pressure-sensitive adhesive tape of the present invention. FIG. 2 is an optical micrograph of one form of closed cells in a conventional adhesive tape. As is apparent from these photographs, the size of the closed cells is greatly different.

When the average void diameter is as large as several hundred μm as shown in FIG. 2 (prior art), large foaming of 1 to 2 mm level may be partially formed. And the part will be in the penetration state, without maintaining the form of a closed cell. This penetrating state is a serious problem in terms of waterproofness, electrostatic resistance, etc., particularly when using a foamed resin base adhesive tape that has been processed to have a narrow width. Further, when using a film base material having no air bubbles, the base material has high rigidity, so that if there is a foreign substance (extra fine copper wire or the like) on the bonding surface, the stepped portion will float and the waterproofness will be impaired. On the other hand, when the void diameter is controlled to a small size within a specific range as in the present invention, these problems hardly occur, and excellent waterproofness can be maintained even when high water pressure is applied.

Electrostatic resistance is generally affected by the resin type of the foamed resin base material, but when the resin type is the same, the size of closed cells is considered to affect the antistatic characteristics. In fact, as shown in FIG. 2 (prior art), when the average void diameter is as large as several hundred μm, applying a static electricity of 15 kV in the width direction of the narrow-width processed adhesive tape will cause the foamed resin substrate to break down easily. In some cases, characteristics such as waterproofness may be impaired. On the other hand, even if the kind of resin is the same, if the void diameter is controlled to a small size within a specific range as shown in FIG. 1 (the present invention), the foamed resin base material is difficult to break. The reason why the antistatic property is improved is not necessarily clear, but there is a possibility that, for example, an increase in the number of resin films between bubbles is one of the factors. When the resin portion interposed between two bubbles is defined as a single “resin film”, the number of resin films increases when there are many small bubbles if the porosity is the same. Specifically, the number of resin films in the form of FIG. 1 (present invention) is about 10 times or more the number of sheets in FIG. 2 (prior art). In the present invention, it can be presumed that such an increase in the number of resin films has a favorable influence on the improvement of the antistatic property.

Furthermore, when the void diameter is large as shown in FIG. 2 (prior art), the foamed resin base material is likely to be destructed by an impact at a low temperature. In addition, a film base material having no air bubbles or a double-sided pressure-sensitive adhesive tape having no base material is likely to peel off the adherend due to impact, and the display member such as glass may be destroyed. On the other hand, when the void diameter is controlled to a small size within a specific range as in the present invention, the impact absorbability is improved and sufficient impact resistance is exhibited even at low temperatures.

As described above, in the present invention, even if a high water pressure is applied, static electricity is applied, or an impact is applied, the bubbles in the foamed resin substrate are maintained in a closed cell state. Therefore, the foamed resin base material in the present invention is resistant to water resistance, artificial sebum sweat oil resistance, static electricity resistance and other characteristics, and is also a very excellent base material in terms of stability of each performance.

In the present invention, the resin constituting the foamed resin base material is not particularly limited. For example, it is preferable to appropriately select a base polymer and a crosslinking agent having water resistance and oil resistance from the viewpoint of waterproofness and resistance to artificial sebum sweat oil. Specific examples of base polymers include polyurethane resins, which are polymers of polyols and polyfunctional isocyanates; polyolefins such as polyethylene and polypropylene; styrene-butadiene-styrene-block copolymer, styrene-isobutylene-styrene-block copolymer Styrene block copolymer such as polymer; Ethylene copolymer such as ethylene-vinyl acetate, ethylene-ethyl acrylate, ethylene-methyl methacrylate; Acrylic block such as methyl methacrylate-butyl acrylate-methyl methacrylate Copolymerized polymers; acrylic acid ester copolymers obtained by copolymerizing 2-ethylhexyl acrylate, methyl acrylate and the like; halogenated polymers such as polyvinyl chloride; Of these, polyurethane resins are preferred from the viewpoints of antistatic properties, heat resistance, artificial sebum sweat oil resistance, flexibility, and impact resistance.

The polyurethane-based resin is generally a resin including a soft segment composed of a polyol monomer unit and a hard segment composed of a polyfunctional isocyanate compound or a low molecular glycol monomer unit.

The polyol used for the polyurethane-based resin is a compound having two or more hydroxyl groups. For example, the number of hydroxyl groups in the polyol is preferably close to 2 from the viewpoint of improving characteristics such as rubber elastic elongation recovery rate. Specifically, the number of hydroxyl groups in the polyol is preferably 2 to 3, and more preferably 2. As the polyol, for example, polyester polyol, polyether polyol, polycaprolactone polyol, polycarbonate polyol, or castor oil-based polyol can be used. Two or more polyols may be used in combination.

Polyester polyol is obtained, for example, by an esterification reaction between a polyol component and an acid component. Specific examples of the polyol component include ethylene glycol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl- 1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 2- Examples include methyl-1,8-octanediol, 1,8-decanediol, octadecanediol, glycerin, trimethylolpropane, pentaerythritol, hexanetriol, and polypropylene glycol. Specific examples of the acid component include succinic acid, methyl succinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, 1,12-dodecanedioic acid, 1,14-tetradecanedioic acid, dimer acid, 2-methyl-1 , 4-cyclohexanedicarboxylic acid, 2-ethyl-1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid Examples include acids and acid anhydrides thereof.

Polyether polyols start with, for example, water, low molecular weight polyols (eg propylene glycol, ethylene glycol, glycerin, trimethylolpropane, pentaerythritol), bisphenols (eg bisphenol A) or dihydroxybenzenes (eg catechol, resorcin, hydroquinone) As an agent, it can be obtained by addition polymerization of alkylene oxide such as ethylene oxide, propylene oxide, butylene oxide. Specific examples include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.
Specific examples of the polycaprolactone polyol include ring-opening polymers of cyclic ester monomers such as ε-caprolactone and σ-valerolactone.

Specific examples of the polycarbonate polyol include polycarbonate polyols obtained by polycondensation reaction of each of the above polyol components and phosgene; each of the above polyol components, dimethyl carbonate, diethyl carbonate, diprovir carbonate, diisopropyl carbonate, dibutyl carbonate, ethylbutyl carbonate, ethylene Polycarbonate polyol obtained by transesterification condensation with carbonic acid diesters such as carbonate, propylene carbonate, diphenyl carbonate and dibenzyl carbonate; copolymer polycarbonate polyol obtained by using two or more of each of the above polyol components; A polycarbonate polyol obtained by an esterification reaction with a carboxyl group-containing compound; each of the above polycarbonate polyols and a hydroxyl group-containing compound; Polycarbonate polyol obtained by etherification reaction; polycarbonate polyol obtained by transesterification of each of the above polycarbonate polyol and ester compound; polycarbonate polyol obtained by transesterification of each of the above polycarbonate polyol and hydroxyl group-containing compound; And polyester polycarbonate polyols obtained by polycondensation reaction of the above polycarbonate polyols and dicarboxylic acid compounds; copolymer polyether polycarbonate polyols obtained by copolymerization of the above polycarbonate polyols and alkylene oxides.

Castor oil-based polyol is obtained, for example, by reacting castor oil fatty acid with each of the above polyol components (for example, polypropylene glycol).

As the polyfunctional isocyanate compound used for the polyurethane resin, for example, a polyfunctional aliphatic isocyanate compound, a polyfunctional alicyclic isocyanate compound, or a polyfunctional aromatic isocyanate compound can be used. Trimethylolpropane adducts of these compounds, burettes reacted with water, and trimers having an isocyanurate ring can also be used. Two or more polyfunctional isocyanate compounds may be used in combination.

Specific examples of the polyfunctional aliphatic isocyanate compound include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4. 1,4-trimethylhexamethylene diisocyanate.

Specific examples of the polyfunctional alicyclic isocyanate compound include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, Examples include hydrogenated tolylene diisocyanate and hydrogenated tetramethylxylylene diisocyanate.

Specific examples of the polyfunctional aromatic diisocyanate compound include phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, Examples include 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, and xylylene diisocyanate.

The polyurethane-based resin is obtained by curing the composition containing the polyol and the polyfunctional isocyanate compound described above. In particular, from the viewpoint of characteristics such as a rubber elastic elongation recovery rate, a low crystalline linear polyester polyurethane resin is preferable, and a hexanediol copolyester polyurethane resin and a polytetramethylene glycol polyurethane resin are more preferable. Examples of commercially available polyurethane resins include the product name Samprene manufactured by Sanyo Kasei Kogyo Co., Ltd., the product name Desmocol manufactured by Sumika Bayer Urethane Co., Ltd., and the product name NIPPOLAN manufactured by Nippon Polyurethane Industry Co., Ltd. Specifically, according to JIS K 6253 “Rubber Hardness Standard”, the low crystallinity is obtained by preparing a resin test piece having a thickness of 6 mm and melting the test piece at 100 ° C. for 30 minutes, 23 ± 2 ° C., relative humidity This can be determined by measuring the time from when the resin is left in an environment of 50 ± 5% until the hardness of the resin reaches Shore A90. Specifically, a resin having a time period of 72 hours or longer until Shore A 90 is reached can be referred to as a low crystalline resin. For example, the product name Desmocol 500 manufactured by Sumika Bayer Urethane Co., Ltd. is a highly crystalline resin that takes about 5 minutes to reach Shore A90, and the product name Desmocol 540 is about 10 minutes. It is a medium crystalline resin for 48 hours. On the other hand, desmocol 406 is a low crystalline resin for 72 hours.

Furthermore, in the present invention, it is preferable to use a crosslinking agent from the viewpoint of improving properties such as strength, heat resistance and rubber elasticity of the base polymer. As the crosslinking agent, for example, a metal chelate-based, metal alkoxide-based, epoxy-based, isocyanate-based, aziridine-based, polyfunctional acrylate, carbodiimide-based, oxazoline-based, or melamine-based crosslinking agent can be used. Among these, an isocyanate-based crosslinking agent is preferable from the viewpoints of reactivity, ease of synthesis, flexibility and impact resistance of the substrate itself, and adhesion to the pressure-sensitive adhesive layer. In particular, from the viewpoint of impact resistance, it is more preferable to use a polyurethane-based resin as a base polymer and to use this together with an isocyanate-based crosslinking agent.

Other components may be added to the resin composition for constituting the foamed resin base material. Specifically, for example, catalysts, other resin components, tackifiers, inorganic fillers, organic fillers, metal powders, pigments, foils, softeners, plasticizers, anti-aging agents, heat dissipation agents, conductive agents Antioxidants, ultraviolet absorbers, light stabilizers, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, lubricants, and solvents can be added. In particular, it is preferable to add a catalyst such as an organometallic compound or a tertiary amine compound for the curing reaction. Specific examples of organometallic compounds include iron compounds, tin compounds, titanium compounds, zirconium compounds, lead compounds, cobalt compounds, zinc compounds, and bismuth compounds. In particular, from the viewpoint of reaction rate and environmental load, iron-based compounds and bismuth-based compounds are preferable.

The method of forming closed cells in the resin described above is not particularly limited, but a method of forming using a foaming agent such as a thermally expandable microcapsule, an already expanded hollow filler, an inorganic foaming agent, an organic foaming agent, or the like. preferable. Among these, it is particularly preferable to use thermally expandable microcapsules and / or already expanded hollow fillers.

As described above, when the average void diameter is as large as several hundreds μm or partially as 1 to 2 mm as shown in FIG. 2 (prior art), a penetration state may be partially formed. In particular, the foamed resin-based adhesive tape processed with a narrow width is a big problem in properties such as waterproofness and electrostatic resistance. Therefore, in the prior art, an extremely large closed cell portion is removed by an optical detector. However, since the detection accuracy to be removed is not sufficient, problems such as a lack of reliability, a decrease in yield due to variations in manufacturing lots, and an increase in costs due to an increase in processing costs arise. On the other hand, if a foaming control system using thermally expandable microcapsules and / or already expanded hollow fillers is employed, the void diameter can be easily controlled to a small size within the specific range of the present invention.

The heat-expandable microcapsule is typically a microsphere comprising an outer shell mainly composed of a thermoplastic resin and a liquid low-boiling hydrocarbon contained in the outer shell. The boiling point of the liquid low boiling point hydrocarbon is not higher than the softening temperature of the thermoplastic resin constituting the outer shell. Closed cells can be formed by heating and foaming the resin containing the thermally expandable microcapsules. For example, the thermally expandable microcapsules are dispersed in a resin for constituting the base material, and thermally expand to such an extent that they do not rupture when the resin is thermoformed, and maintain the expanded shape after molding. Thereby, closed cells are formed in the resin. The average particle diameter of the thermally expandable microcapsule before expansion is preferably 5 to 50 μm, more preferably 10 to 30 μm, and the average particle diameter after expansion is preferably 30 to 150 μm, more preferably 40 to 120 μm. The thermal expansion start temperature of the thermally expandable microcapsule is preferably 100 to 170 ° C., the maximum foaming temperature is preferably 160 to 200 ° C., and the volume expansion coefficient is preferably about 50 to 100 times.

The thermoplastic resin constituting the outer shell of the thermally expandable microcapsule may be appropriately selected according to conditions such as the softening temperature and thermoforming temperature of the resin constituting the base material. Specific examples include homopolymers composed of monomers such as (meth) acrylonitrile, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate; and copolymers composed of two or more of these monomers. ; Inorganic particles such as titanium oxide, zinc oxide, alumina, silica, and calcium carbonate may be fixed to the surface of the outer shell using a binder resin. Further, the foaming characteristics (for example, the expansion coefficient) can be controlled by forming the outer shell mainly from acrylonitrile and silicon and adjusting the blending amount of silicon.

The liquid low-boiling hydrocarbons encapsulated in the thermally expandable microcapsules are preferably hydrocarbons that are vaporized when the resin constituting the substrate is thermoformed. Specific examples include low-boiling liquids such as normal butane, isobutane, normal pentane, isopentane, and petroleum ether.

Examples of commercially available thermal expandable microcapsules include Matsumoto Microspheres F-36D, F-36LVD, FN-80GSD, FN-100SD, FN-100MD, FN-100SSD, and FN manufactured by Matsumoto Yushi Seiyaku Co., Ltd. -105D, FN-180SSD, etc., trade names such as EXPANCEL 053-40, 909-80, 930-120, etc., and trade names Fine Cell Master MS401K, MS402K, MS405K, etc., manufactured by Dainichi Seika Kogyo.

The already expanded hollow filler is obtained by foaming a thermally expandable microcapsule alone. Only one of the thermally expandable microcapsule and the already expanded hollow filler may be used, or both may be used in combination.

Specific examples of the inorganic foaming agent include ammonium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, and sodium borohydride.

Specific examples of the organic foaming agent include chlorofluorinated alkanes such as trichloromonofluoromethane and dichloromonofluoromethane, azo compounds such as azobisisobutyronitrile, azodicarbonamide, barium azodicarboxylate, and paratoluene. Hydrazine compounds such as sulfonyl hydrazide, diphenyl sulfone-3,3′-disulfonyl hydrazide, 4,4′-oxybis (benzenesulfonyl hydrazide), allyl bis (sulfonyl hydrazide), ρ-toluylene sulfonyl semicarbazide, 4,4′- Semicarbazide compounds such as oxybis (benzenesulfonyl semicarbazide), triazole compounds such as 5-morpholyl-1,2,3,4-thiatriazole, N, N′-dinitrosopentamethylenetetramine, N, N′-dimethyl- N, N'-Gini N- nitroso compounds such as nitroso terephthalamide and the like.

The foamed resin base material used in the present invention is a base material in which closed cells are formed by foaming the resin. The expansion ratio is preferably 1.2 to 4 times, more preferably 2 to 3 times. The thickness of the foamed resin base material is preferably 0.05 to 1.0 mm, more preferably 0.08 to 0.3 mm.

The foamed resin base material may be subjected to a surface treatment for improving adhesion with the pressure-sensitive adhesive layer or other layers. Examples of the surface treatment include corona treatment, flame treatment, plasma treatment, hot air treatment, ozone / ultraviolet treatment, and application of an easy adhesion treatment agent. The degree of surface treatment can be determined by, for example, a wetting index with a wetting reagent. From the viewpoint of adhesion to the pressure-sensitive adhesive layer, the wetting index of the substrate surface after the surface treatment is preferably 36 mN / m or more, more preferably 40 mN / m, and particularly preferably 48 mN / m.

<Adhesive layer>
An adhesive layer is a layer which consists of an adhesive composition, and is provided in the at least single side | surface of a foamed resin base material. The pressure-sensitive adhesive composition is not particularly limited as long as it contains a pressure-sensitive adhesive that does not impair the effects of the present invention. For example, an emulsion-based adhesive, a solvent-based adhesive, an oligomer-based adhesive, a solid adhesive, and a hot-melt adhesive can be used.

Examples of the type of pressure-sensitive adhesive include acrylic pressure-sensitive adhesive, rubber-based pressure-sensitive adhesive (natural rubber-based pressure-sensitive adhesive or synthetic rubber-based pressure-sensitive adhesive), silicone-based pressure-sensitive adhesive, polyester-based pressure-sensitive adhesive, urethane-based pressure-sensitive adhesive, and polyamide-based pressure-sensitive adhesive. Agents, epoxy adhesives, vinyl alkyl ether adhesives, and fluorine adhesives. Two or more pressure-sensitive adhesives may be used in combination. In particular, an acrylic pressure-sensitive adhesive is preferable from the viewpoint of properties such as heat resistance, cold resistance, water resistance, and resistance to artificial sebum sweat oil. The acrylic pressure-sensitive adhesive is generally a composition containing as a main component a compound obtained by curing an acrylic copolymer [(meth) acrylic acid ester copolymer etc.] as a base polymer with a crosslinking agent. Specifically, for example, the pressure-sensitive adhesive described in International Publication No. 2014/002203 can be suitably used.

The acrylic copolymer used for the acrylic pressure-sensitive adhesive is typically a (meth) acrylic acid ester copolymer having a hydroxyl group and a carboxyl group. In particular, (meth) acrylic acid ester copolymer obtained by copolymerizing at least four components of long chain (meth) acrylic acid alkyl ester, carboxyl group-containing monomer, hydroxyl group-containing monomer and short chain (meth) acrylic acid alkyl ester Coalescence is preferred.

The long-chain (meth) acrylic acid alkyl ester is preferably a (meth) acrylic acid alkyl ester having an alkyl group having 4 to 12 carbon atoms. Specific examples thereof include butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, and lauryl (meth) acrylate. Can be mentioned. Specific examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, 2-stroxy-1-butene, 2-strol-1-oxypentene, 2-strol ruboxy. Examples include -1-hexene and 2-stroxyl-heptene. When an appropriate amount of the carboxyl group-containing monomer is used, properties such as waterproofness and load resistance are improved. Specific examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. The short chain (meth) acrylic acid alkyl ester is a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 3 carbon atoms. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, propyl ( (Meth) acrylate. Of these, methyl acrylate is preferable.

The content of the long chain (meth) acrylic acid alkyl ester unit is preferably 50 to 90% by mass, more preferably 50%, in 100% by mass of the constituent component (monomer unit) of the (meth) acrylic acid ester copolymer. ~ 80% by mass. The content of the carboxyl group-containing monomer unit is preferably 3 to 20% by mass, more preferably 3 to 12% by mass. The content of the hydroxyl group-containing monomer unit is preferably 3 to 20% by mass, more preferably 3 to 18% by mass. The content of the short-chain (meth) acrylic acid alkyl ester unit is preferably 3 to 15% by mass, more preferably 3 to 12% by mass. Furthermore, the total content of the carboxyl group-containing monomer unit and the hydroxyl group-containing monomer unit is preferably 13% by mass or more. Moreover, within the range which does not impair the effect of this invention, monomer units other than these four components may be included.

The acrylic copolymer can be obtained by copolymerizing a plurality of monomers. The polymerization method is not particularly limited, but radical solution polymerization is preferable from the viewpoint of easy polymer design. Alternatively, an acrylic syrup composed of an acrylic copolymer and its monomer may be prepared first, and this acrylic syrup may be blended with a crosslinking agent and an additional photopolymerization initiator for polymerization.

The weight average molecular weight of the acrylic copolymer is preferably 700,000 to 2,000,000, more preferably 700 to 1,500,000. The lower limit of these ranges is significant in terms of load resistance and workability. Moreover, an upper limit has significance in the point of the applicability | paintability of an adhesive composition. This weight average molecular weight is a value measured by the GPC method.

The theoretical Tg of the acrylic copolymer is preferably −40 ° C. or lower, more preferably −50 ° C. to −75 ° C. This theoretical Tg is a value calculated by the FOX equation.
The main resin component of the acrylic pressure-sensitive adhesive is an acrylic copolymer, but other types of resin components can be used in combination as long as the characteristics are not impaired.

The crosslinking agent used for the acrylic pressure-sensitive adhesive is a compound that reacts with the acrylic copolymer to form a crosslinked structure, and typically reacts with a carboxyl group and / or a hydroxyl group of the acrylic copolymer. The resulting compound. In particular, from the viewpoint of properties such as waterproofness, load resistance, processability, impact resistance, artificial sebum resistance, and artificial sweat oil resistance, an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent are preferable. These may be used in combination. The blending amount of the crosslinking agent is preferably 0.001 to 1 part by mass with respect to 100 parts by mass of the acrylic copolymer.

Specific examples of the isocyanate crosslinking agent include tolylene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and modified prepolymers thereof. Two or more of these may be used in combination. The amount of the isocyanate-based crosslinking agent is preferably 0.02 to 1 part by mass, more preferably 0.05 to 0.2 part by mass with respect to 100 parts by mass of the acrylic copolymer.

Specific examples of the epoxy crosslinking agent include epoxy groups such as N, N, N ′, N′-tetraglycidyl-m-xylylenediamine and 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane. The compound which has 2 or more is mentioned. Two or more of these may be used in combination. The blending amount of the epoxy crosslinking agent is preferably 0.001 to 0.5 parts by mass, more preferably 0.001 to 0.1 parts by mass with respect to 100 parts by mass of the acrylic copolymer.

For example, a tackifier, a plasticizer, a filler, and a colorant can be added to the adhesive. Specific examples of the tackifier include rosin resins (rosin ester, polymerized rosin, disproportionated rosin ester, etc.), terpene phenol resins, terpene resins, petroleum resins, and styrene resins. A specific example of the filler is silicon oxide. Specific examples of the colorant include carbon black, titanium oxide, aniline black, acetylene black, and ketjen black. Further, for example, carbon black, carbon nanotube, or black inorganic filler may be added as the light-shielding filler.

The pressure-sensitive adhesive layer can be formed by, for example, applying a pressure-sensitive adhesive on a base material and causing a crosslinking reaction by heating or ultraviolet irradiation. Further, for example, the pressure-sensitive adhesive can be applied on a release paper or other film, and a pressure-sensitive adhesive layer can be formed by crosslinking reaction by heating or ultraviolet irradiation, and this pressure-sensitive adhesive layer can be bonded to one side or both sides of the substrate. . For the application of the adhesive, for example, a coating device such as a roll coater, a die coater, or a lip coater can be used. When heating after application, the solvent in the pressure-sensitive adhesive composition can be removed together with the crosslinking reaction by heating. The thickness of the pressure-sensitive adhesive layer is preferably 5 to 100 μm, more preferably 10 to 80 μm.

<Adhesive tape>
The pressure-sensitive adhesive tape of the present invention has the above-described foamed resin base material containing closed cells and a pressure-sensitive adhesive layer provided on at least one surface of the foamed resin base material. A single-sided adhesive tape having an adhesive layer provided on only one side of the substrate may be used, but a double-sided adhesive tape provided on both sides is particularly preferred.

As the base material of the adhesive tape, it is preferable to use the above-described foamed resin base material containing closed cells alone. However, for example, a laminate obtained by laminating another base material or another layer on the foamed resin base material can be used as the base material within a range not impairing the effects of the present invention.

The antistatic property according to IEC6100 of the adhesive tape is preferably 15 kV or more, more preferably 18 kV or more. As explained above, the antistatic properties are generally considered to be affected by the type of resin, but if the resin type is the same, the void diameter of the closed cell of the foamed resin substrate should be controlled to a small size within a specific range. It is estimated that the anti-static property is improved. Although the value of the above-mentioned antistatic property is a measured value with respect to the adhesive tape, it is preferable that the measured value is the same even when measured with respect to the foamed resin base material alone. Specifically, the anti-static property based on IEC6100 is the voltage value when a constant voltage in the width direction of the adhesive tape is sparked by 100 shots with an electrostatic gun as described in the examples described later. Means.

The heating dimensional change rate of the adhesive tape is 100% ± 5% or less, preferably ± 1% or less, assuming that the dimension before heating is 100%. This heating dimensional change rate (heat resistance) is important in applications of products that may be used or left at high temperatures. For example, portable information terminals such as a car navigation system used in the vicinity of a front panel or a dashboard of an automobile may have a temperature exceeding 80 ° C. in summer. In this case, the base material of the adhesive tape that fixes the information display unit of the car navigation and the housing may shrink and peel off due to distortion. And in the product use with the high request | requirement of narrowing of adhesive tapes, such as the recent information portable terminal, such peeling at high temperature tends to arise. On the other hand, even if it is an adhesive tape that has been processed to be narrow, if it exhibits the above-mentioned rate of change in heating dimensions, peeling will occur even if it is used or left under high temperature and subjected to vibration over a long period of time. It becomes difficult. From the viewpoint of such a heating dimensional change rate (heat resistance), it is preferable to use a polyurethane resin for the foamed resin base material rather than the polyolefin resin. Specifically, the heating dimensional change rate means the dimensional change rate after heating the adhesive tape at 90 ° C. for 2 hours and allowing it to stand at room temperature for 1 hour or longer as described in Examples below.

The rubber elastic elongation recovery rate (2 times and 4 times) of the adhesive tape is 85% or more, preferably 90% or more. This rubber elastic elongation recovery rate is important in applications of products that require reworkability, repairability (elongation peelability) and flexibility. Specifically, as described in the examples to be described later, the repair property is a state in which two hard surfaces are bonded to each other with a double-sided adhesive tape, and one end of the adhesive tape is pulled and stretched to easily peel off without any problem. It means the performance that enables. For example, when one component of an information portable terminal such as a smartphone or a mobile phone breaks down, the adhesive tape that has been fixed between the components can be easily removed in order to replace the component, and a residue such as an adhesive is left at the separation location. It is desirable not to remain. However, if the adhesive tape does not have an appropriate elasticity, even if one end of the adhesive tape is pulled, the adhesive layer does not extend sufficiently, resulting in insufficient decrease in adhesive strength, and the adhesive tape is cut off halfway. On the other hand, even if the pressure-sensitive adhesive tape has been processed to be narrow, the pressure-sensitive adhesive can be obtained by pulling one end of the pressure-sensitive adhesive tape as long as the pressure-sensitive adhesive tape has a recovery rate and a high degree of flexibility. The layer is also continuously stretched uniformly and the adhesive strength is moderately reduced. As a result, the layer can be easily peeled off without any problem. Furthermore, the high degree of flexibility enables to cope with unevenness, steps, and distortion on the surface of the adherend, and contributes to improvement in properties such as adhesion, waterproofness, and impact resistance. Specifically, as described in the examples described later, this rubber elastic elongation recovery rate is the elongation at the time when 10 seconds have elapsed after the tape length was pulled to double or quadruple and the tensile force was released. The percentage of recovery per hit.

The compressive deformation rate in the thickness direction of the adhesive tape is preferably 3.0% or more, more preferably 5.0% or more. This compressive deformation rate is important in applications of products in which there are irregularities and steps on the adherend surface, and the member itself may be distorted. For example, when an information display member of an information portable terminal such as a smartphone or a mobile phone is bonded to the housing, the adherend surface of each member is not necessarily a flat surface, and usually has unevenness and steps. In addition, each member itself may be distorted during use. Therefore, if the adhesive tape cannot absorb these distortions, peeling will occur. On the other hand, even if the pressure-sensitive adhesive tape is processed with a narrow width, if it is a pressure-sensitive adhesive tape having such flexibility and stress relaxation as to exhibit the above-described compression deformation rate, peeling is unlikely to occur. Specifically, the compression deformation rate is based on the thickness when the dial gauge load is 20 kPa according to the thickness test method of JIS Z 0237: 2000, as described in Examples below. This is the rate of change in thickness when the load is increased to 100 kPa.

The interlayer strength of the entire pressure-sensitive adhesive tape having the foamed resin base material is preferably 10 N / 10 mm or more, more preferably 15 N / 10 mm or more. This interlaminar strength (90-degree peel adhesion) is important in the use of products that require reworkability. Specifically, the reworkability means a performance that allows easy peeling without any problem when peeling the adhesive tape in a bonded state, as described in Examples below. For example, it may be necessary to peel off the adhesive tape once bonded in the manufacturing process of an information portable terminal such as a smart phone or a mobile phone and start the process again (rework). At that time, it is desirable that the adhesive tape can be easily peeled off and that a residue such as an adhesive does not remain at the peeled portion. However, if the interlaminar strength of the foamed resin base material is low, the base material itself is destroyed when the adhesive tape is peeled, or the adhesiveness between the adhesive layer and the foamed base material (depending on the strength of the adhesive strength of the adhesive layer) When the adhesive strength is weak, delamination between the pressure-sensitive adhesive layer and the substrate occurs, and it becomes difficult to remove the residue by adhering to the adherend. On the other hand, if it is an adhesive tape comprised with the said foaming resin base material which has said interlayer intensity | strength, even in such a case, it will be hard to produce a destruction from the conventional foaming resin base material. Specifically, the interlayer strength is 90 ° peel adhesive strength in accordance with JISＪZ 0237 “Testing method of adhesive tape / adhesive sheet” as described in the examples described later.

The tensile strength in the longitudinal direction and the transverse direction of the adhesive tape is preferably 6.0 N / 10 mm or more. The tensile strength is preferably 110% or more when the tensile strength of the foamed resin base material alone is 100%. Furthermore, when one of the tensile strengths in the longitudinal direction and the transverse direction is 100%, the other tensile strength is within 100% ± 15%. The elongation at break in the longitudinal and lateral directions of the adhesive tape is preferably 300% or more. Further, when one of the elongation at break in the longitudinal direction and the transverse direction is defined as 100%, the tensile strength of the other is within 100% ± 15%. Particularly, the aspect ratio of tensile strength and elongation is small, which is important in the use of products that require an adhesive tape formed into a frame shape by punching. For example, an adhesive tape that fixes an information display unit and a housing of an information portable terminal such as a smartphone or a mobile phone is often punched into a substantially rectangular frame shape. In this case, if the tensile strength and the aspect ratio of elongation are large, variations in physical properties occur. On the other hand, if the pressure-sensitive adhesive tape has a small aspect ratio, variations in physical properties are unlikely to occur regardless of the direction of punching. Specifically, the tensile strength and elongation are the strength and elongation at break when a specific size adhesive tape is subjected to a tensile test, as described in Examples below.

The loss factor (tan δ) of the adhesive tape at −20 ° C. is preferably 0.20 or more, more preferably 0.3 or more. The storage elastic modulus at 85 ° C. is preferably 2.0 × 10 ⁵ Pa or more, more preferably 2.5 × 10 ⁵ Pa or more, and the loss coefficient (tan δ) at 85 ° C. is preferably 0.20 or more. More preferably, it is 0.3 or more. This storage modulus and loss factor are important in product applications where a narrow adhesive tape is required. For example, information mobile terminals such as smartphones and mobile phones have been developed to increase the screen size of information display units (displays, etc.), to make the entire product slimmer, and to improve the design. It is becoming. In this case, if the storage elastic modulus and loss factor are low, there may be a problem in adhesion. On the other hand, if the pressure-sensitive adhesive tape has the above storage elastic modulus and loss factor, even a narrow-width processed pressure-sensitive adhesive tape is less likely to cause an adhesive problem. Specifically, the storage elastic modulus and loss factor were measured and calculated at a frequency of 1 Hz with an adhesive tape having a thickness of 0.2 mm sandwiched between parallel plates of a viscoelasticity tester as described in Examples below. Value.

Each of the above characteristics is manifested mainly by appropriately adjusting various conditions such as the type of resin of the foamed resin base material, the size of closed cells, and the type of adhesive layer. Specific examples of the foamed resin base material and the pressure-sensitive adhesive layer are as described above.

The width of the adhesive tape is not limited. However, the excellent characteristics obtained in the present invention are particularly useful in a narrow adhesive tape, and the width is preferably 0.5 to 5.0 mm, more preferably 0.7 to 3.0 mm. The thickness of the adhesive tape is preferably 0.08 to 0.5 mm, more preferably 0.1 to 0.4 mm. When punching (narrow processing) to produce a narrow adhesive tape, design the product so that the total thickness of the adhesive layer does not become much larger than the thickness of the base material, and to the punching blade It is preferable to prevent the adhesive from sticking or protruding.

Hereinafter, the present invention will be described in more detail with reference to examples. In the following description, “part” means “part by mass”.

<Preparation of acrylic pressure-sensitive adhesive composition>
Mix 75 parts of 2-ethylhexyl acrylate, 10 parts of methyl acrylate, 10 parts of acrylic acid and 5 parts of 2-hydroxyethyl acrylate in a reactor equipped with a stirrer, thermometer, reflux condenser and nitrogen gas inlet tube. Then, ethyl acetate, n-dodecanethiol as a chain transfer agent, and 0.1 part of lauryl peroxide as a radical polymerization initiator were charged. Nitrogen gas was sealed in the reactor, and the polymerization reaction was carried out at 68 ° C. for 3 hours and then at 78 ° C. for 3 hours under a nitrogen gas stream while stirring.

Then, it was cooled to room temperature and ethyl acetate was added. As a result, an acrylic copolymer having a solid content concentration of 30%, a theoretical Tg of 64.8, and a weight average molecular weight of 1.1 million was obtained. Next, 0.07 part of an isocyanate-based crosslinking agent (trade name Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) and an appropriate amount of an organic solvent are added to 100 parts of this acrylic copolymer, and the mixture is stirred with a stirrer until uniform. An acrylic pressure-sensitive adhesive composition was obtained.

<Preparation of polyurethane resin composition>
An appropriate amount of organic hot metal was added to powdery components such as a foaming agent and a colorant, and the mixture was dispersed with a stirrer. Next, a polyurethane resin solution and a crosslinking agent were added, and the mixture was stirred with a stirrer until uniform dispersion was obtained to obtain a polyurethane resin composition. The amounts (parts) of each component are shown in Tables 1 and 2.

<Examples 1-8 and Comparative Examples 1-2>
The polyurethane resin composition was applied to one side of a release paper having a silicone release agent formed on both sides, and dried at 70 ° C. for 2 minutes + 90 ° C. for 2 minutes to remove the solvent. Subsequently, it was made to foam by heating at 130 degreeC for 2 minutes, and this was wound up. Further, aging was performed at 40 ° C. for 3 days to complete the curing reaction, and a foamed resin base material (thickness: 0.10 mm) was obtained.

The above-mentioned acrylic pressure-sensitive adhesive composition was applied to a release paper subjected to a double-sided silicone release treatment and dried to form a pressure-sensitive adhesive layer. And this adhesive layer was bonded together, performing a corona discharge process to a foamed resin base material. Furthermore, the pressure-sensitive adhesive layer was bonded to the opposite surface of the foamed resin substrate by the same method. Thereafter, aging was carried out at 40 ° C. for 3 days to complete the curing reaction of the pressure-sensitive adhesive layer, and a double-sided pressure-sensitive adhesive tape having a thickness of about 0.20 mm (the thickness of each pressure-sensitive adhesive layer was about 50 μm) was obtained.

<Comparative Example 3>
Double-sided pressure-sensitive adhesive tape having a thickness of about 0.20 mm in the same manner as in Example 1 except that a polyethylene (PE) -based foam (manufactured by Sekisui Chemical Co., Ltd., trade name Bollala XL-H black # 1001) was used as the base material. (The thickness of each surface pressure-sensitive adhesive layer was about 50 μm).

<Comparative example 4>
A double-sided adhesive tape having a thickness of about 0.20 mm (each side adhesive) except that a polyethylene terephthalate (PET) film (trade name Lumirror S-10, manufactured by Toray Industries, Inc.) was used as the substrate. A layer thickness of about 75 μm) was produced.

<Comparative Example 5>
A baseless double-sided tape having a thickness of 0.20 mm without a base material was produced by applying the acrylic pressure-sensitive adhesive composition of Example 1 to a release paper to a thickness of 0.2 mm.

<Test method>
The following tests were performed on the double-sided pressure-sensitive adhesive tapes obtained in the examples and comparative examples. The results are shown in Tables 1 to 3.

[Void diameter]
A number of closed cells in a 5 × 5 mm area of the foamed resin substrate were observed with an optical microscope based on the transmission method, and the average value and the maximum value of the void diameter were measured.

[Rubber elastic recovery rate]
A double-sided pressure-sensitive adhesive tape was cut into a width of 10 mm and a length of 150 to 200 mm, and its adhesiveness was deactivated with calcium carbonate was used as a test piece. One end of the test piece was fixed to a tensile tester with a chuck interval set to 100 mm, and both sides with a length of 100 mm for the tape test were marked with magic. Pulling at a speed of 1500 mm / min and releasing the one chuck when the length is doubled (extended portion 100 mm) or quadrupled (extended portion 300 mm), the total length of the marked part after 10 seconds (Full length at the time of recovery) was measured. Then, the ratio of the recovery amount (the total length at the extension-the total length at the recovery) to the extension was determined, and this was used as the rubber elastic extension / recovery rate. The specific calculation method is as follows.
Double elongation recovery rate (%) = (200-total length at recovery) ÷ 100 x 100
4-fold elongation recovery rate (%) = (400-total length at recovery) / 300 x 100

[Heating dimensional change rate]
A double-sided adhesive tape was cut into a size of 100 × 100 mm, and the test piece was prepared by deactivating the adhesiveness with calcium carbonate. The test piece was suspended in a dryer at 90 ° C. for 2 hours and then allowed to stand at room temperature for 1 hour or more to measure dimensions. A specific method for calculating the heating dimensional change rate is as follows.
Heating dimensional change rate (%) = [(Dimension after heating)-(Dimension before heating)] ÷ (Dimension before heating) x 100

[Narrow width workability]
While maintaining the state that the double-sided adhesive tape is shredded into 10 pieces having a width of 5 mm and a length of 125 mm (that is, each of the shredded adhesive tapes maintains the adjacent state at the time of shredding), 65 ° C., It was left for 1 day in an atmosphere of 80% RH. Then, the release paper was peeled in the direction of 180 degrees for each one, the adhesion with the adjacent portion was visually confirmed, and the narrow width workability was evaluated according to the following criteria.
“◯”: There was almost no adhesion with the adjacent part, and it was able to peel without peeling off the adjacent part.
"X": There was remarkable adhesion in the adjacent part, and the adjacent part was peeled off at the same time.

[Reworkability]
One side of the double-sided adhesive tape is lined with aluminum foil (0.08 mm thick) as a test piece, and in accordance with JIS Z 0237 “Adhesive tape / adhesive sheet test method”, 30 minutes after tape application to a stainless steel plate A 90-degree peel test was performed and evaluated according to the following criteria.
“◯”: There was no interlaminar fracture or adhesive residue on the substrate.
“× (a)”: The interlayer of the base material was broken during peeling.
“× (b)”: Adhesive residue was observed on the stainless steel plate after peeling.

[Load resistance]
The double-sided adhesive tape was cut into a size of 25 × 25 mm, and one release paper was peeled off. A double-sided adhesive tape was bonded to the test hook plate, and then the other release paper was peeled off and bonded to a polycarbonate plate. A load of 700 gf was applied to the hook and held at 85 ° C. for 60 minutes, and load resistance was evaluated according to the following criteria.
“O”: The hook did not fall for 60 minutes.
"X": The hook fell within 60 minutes.

[Shock resistance]
Double-sided adhesive tape is cut into a frame with a width of 0.8 mm and a size of 50 x 45 mm, one release paper is peeled off and bonded to a 2 mm thick glass plate, and the other release paper is peeled off to release a 3 mm thick polycarbonate. Laminated to the board. Then, using an autoclave, pressure treatment was performed at 23 ° C. and 0.5 MPa for 1 hour. Further, using a SUS plate, the whole weight was adjusted to 250 g, and placed in an environment of −20 ° C. for 1 hour or longer. Then, from 1.5m height, pass the test plate vertically through the cylinder and drop it on the concrete floor until the glass plate peels or breaks (A) or until the interlaminar fracture of the substrate occurs ( The number of drops in B) was measured.

[Waterproof]
Double-sided adhesive tape is cut into a frame with a width of 0.8 mm and a size of 40 x 50 mm, one release paper is peeled off and bonded to a 2 mm thick glass plate, and the other release paper is peeled off to remove a 2 mm thick glass. The plates were bonded together. The sample was subjected to a pressure treatment (0.5 MPa) for 1 hour at 23 ° C. using an autoclave. After that, it was submerged in accordance with the IPX7 test method of the waterproof standard IEC “International Electrotechnical Commission” 60529: 2001 [equivalent standard: JIS C 0920: 2003 “Special Protection for Electrical Equipment (IP Code)”] and waterproofed. Sex was evaluated. Further, another sample is subjected to a pressure treatment at 23 ° C. for 1 hour using an autoclave, and then, in water of 0.1 MPa, 0.25 MPa, and 0.5 MPa based on the waterproof standard IPX8 test method. Each was submerged and evaluated for waterproofness. This evaluation was performed according to a level of grade that the waterproof property satisfies the condition defined in the protection class IPX8 or the waterproof property does not satisfy the condition defined in IPX7.

Also, the same test was performed except that the width of the double-sided adhesive tape was changed to 2 mm, and one ultrafine copper wire having a diameter of 0.04 mm was inserted and bonded to one joining surface. This evaluation is an evaluation of waterproofness in a state where foreign matter (extra fine copper wire) exists on the joint surface.

[Artificial sebum / artificial liver oil resistance]
Double-sided adhesive tape is cut into a frame with a width of 0.8 mm and a size of 40 x 50 mm, one release paper is peeled off and bonded to a 2 mm thick glass plate, and the other release paper is peeled off to remove a 2 mm thick glass. The plates were bonded together. And the pressurization process for 1 hour was performed at 23 degreeC and 0.5 Mpa using the autoclave. This sample was immersed in artificial sebum (33.3% triolein, 20.0% oleic acid, 13.3% squalene, 33.4% myristyl octadodecylate) or artificial sweat oil for 1 hour. This sample was taken out and allowed to stand in an atmosphere of 85 ° C. and 85% RH for 72 hours, and then left in a normal atmosphere for 240 hours. The sample was visually observed, and artificial sebum resistance and artificial liver oil resistance were evaluated according to the following criteria.
“O”: No tape peeling.
“×”: The tape is peeled off.

[Static resistance]
A double-sided adhesive tape having a width of 0.7 mm was used as a test piece, and the double-sided adhesive tape 1 was disposed between the HV electrode 2 and the Touch pattern simulation electrode 3 as shown in FIG. The electrodes 2 and 3 are wired on the TEG substrate 4, and the TEG substrate 4 is placed on the SUS table 6 via the insulating sheet 5. The Touch pattern simulation electrode 3 is grounded to the SUS table 5. Furthermore, as shown in FIG. 4, the acrylic board 7 was covered on the test surface. Then, according to IEC61000-4-2, 100 voltage shots were applied to the HV electrode 2 using an electrostatic gun, and the voltage value when sparking toward the Touch pattern simulation electrode 3 was measured.

[Repairability]
A double-sided adhesive tape having a width of 10 mm was bonded between two polycarbonate plates (50 × 50 mm) so that one end portion was longer than the glass plate by about 10 mm. After 30 minutes, one end of the tape was stretched to test whether the tape could be peeled off and evaluated according to the following criteria.
“◯”: Elongation and peeling were possible.
“Δ”: When the elongation rate was slowed, elongation peeling was possible.
“×”: The tape was cut.

[Tensile strength and elongation (tape / base material) and aspect ratio]
Each of the foamed resin base material and the double-sided pressure-sensitive adhesive tape was cut into a width of 10 mm and a length of 200 mm, fixed to a tensile tester with a chuck interval set to 100 mm, pulled at a speed of 300 mm / min, and the strength at break (N / 10 mm) and elongation (%). Further, regarding the double-sided adhesive tape, the transverse direction is cut out to have a length of 200 mm, and the strength and elongation are measured under the same conditions. The aspect ratio of each measured value [(lateral tensile strength and elongation / longitudinal tensile Strength and elongation) × 100]%.

[Compression deformation rate]
According to the thickness test method of JIS Z 0237: 2000 “Adhesive tape / adhesive sheet test method”, the thickness of the double-sided adhesive tape was measured when the dial gauge load was small (20 kPa) and large (100 kPa). Then, the compression deformation rate (%) = [(thickness at a pressure of 100 kPa) − (thickness at a pressure of 20 kPa)] ÷ (thickness at a pressure of 20 kPa) × 100.

[Storage modulus and loss factor]
Using a viscoelasticity tester for dynamic viscoelasticity measurement, a double-sided adhesive tape with a thickness of about 0.2 mm is sandwiched between the parallel plates of the measurement unit of the tester, and the frequency is 1 Hz and -50 ° C to 150 ° C. The storage elastic modulus (G ′) and loss elastic modulus (G ″) up to 0 ° C. were measured. Furthermore, the loss coefficient was obtained by the calculation formula of loss coefficient (tan δ) = G ″ / G ′.

[UE1]: Low crystalline linear polyester urethane elastomer (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name NIPPOLAN 2304)
[UE2]: Low crystalline linear polyester urethane elastomer (manufactured by Sumika Bayer Urethane Co., Ltd., trade name Desmocol 406)
[UE3]: Low crystalline linear polyester urethane elastomer (manufactured by Sanyo Chemical Industries, trade name Samprene LQ-540)
[UE4]: Low crystalline linear polyester urethane elastomer (manufactured by Sanyo Chemical Industries, trade name Samprene IB-129)
[UE5]: Medium crystalline linear polyester urethane elastomer (manufactured by Sumika Bayer Urethane Co., Ltd., trade name Desmocol 176)
[UE6]: Highly crystalline linear polyester urethane elastomer (manufactured by Sumika Bayer Urethane Co., Ltd., trade name Desmocol 500)
"SIBS": Synthetic rubber made of styrene-isobutylene-styrene copolymer (manufactured by Kaneka Corporation, trade name: Shibster)
[CR]: Isocyanate-based crosslinking agent (trade name Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.)
[FA1]: Thermal expansion type foaming agent (Matsumoto Yushi Seiyaku Co., Ltd., trade name FN100SSD)
[FA2]: Expanded foaming agent (manufactured by Nippon Philite Co., Ltd., trade name: 920DE40d30)
[CB]: Carbon black (trade name Denka Black HS100, manufactured by Denki Kagaku Kogyo Co., Ltd.)

<Evaluation>
As is clear from the results shown in Tables 1 to 3, the adhesive tapes of Examples 1 to 8 were excellent in each characteristic. In addition, the adhesive tape of Example 4 and 5 was inferior in repair property (elongation peelability). However, since the adhesive tapes of Examples 4 and 5 have low tensile strength, the tape breaks during elongation peeling. The adhesive tapes of Examples 4 and 5 were excellent with respect to other characteristics such as antistatic characteristics.

On the other hand, the adhesive tapes of Comparative Examples 1 and 2 had a rubber elastic elongation recovery rate that was too low, so that even if the adhesive tape had sufficient tensile strength, the tape was broken during elongation peeling. In this respect, Comparative Examples 1 and 2 are significantly different from Examples 4 and 5.

The pressure-sensitive adhesive tape of Comparative Example 3 is an example using a PE-based foamed resin base material in which the bubble void diameter is too large, and was inferior in properties such as anti-static properties. The pressure-sensitive adhesive tape of Comparative Example 4 is an example in which a PET film having no air bubbles is used as a base material, and properties such as impact resistance are inferior. The pressure-sensitive adhesive tape of Comparative Example 5 is an example of a baseless double-sided tape without a substrate, and has poor properties such as impact resistance.

For example, since the adhesive tape of the present invention has an excellent waterproof property, even if the device is submerged or a high water pressure is applied, it is difficult for water to enter the inside, and the occurrence of device failure can be reduced. In addition, since it has excellent anti-static properties, even if a user charged with static electricity touches the device, it is difficult for the static electricity to pass through the adhesive tape, and the built-in components are not easily damaged. In addition, since it has excellent heat resistance and impact resistance, problems do not easily occur even if the device is used or left under high temperature or receives impact force. In addition, since it has excellent repairability (extension peelability), it is easy to replace parts when repairing the equipment. Therefore, the adhesive tape of the present invention is a member constituting a portable information terminal device such as a smartphone, a mobile phone, an electronic notebook, a PHS, a tablet PC, a digital camera, a music player, a portable TV, a notebook computer, and a game machine. Very useful in adhesive or fastening applications. In particular, applications that require thin and thin adhesive tapes, such as bonding of protective panels and housings of information display sections (displays, etc.) of devices such as smartphones and mobile phones, or fixing of modules (batteries, etc.) of such devices Can be preferably used.

DESCRIPTION OF SYMBOLS 1 Double-sided adhesive tape 2 HV electrode 3 Touch pattern simulation electrode 4 TEG board 5 Insulation sheet 6 SUS table 7 Acrylic board

Claims (10)

1. An adhesive tape having a foamed resin substrate containing closed cells and an adhesive layer provided on at least one side of the foamed resin substrate, wherein the average void diameter of the closed cells is 20 to 180 μm and the maximum void diameter is The pressure-sensitive adhesive tape is 300 μm or less, the heating dimensional change rate of the pressure-sensitive adhesive tape is 100% ± 5% or less when the dimension before heating is 100%, and the rubber elastic elongation recovery rate of the pressure-sensitive adhesive tape is 85% or more. tape.
2. The pressure-sensitive adhesive tape according to claim 1, wherein the foamed resin base material contains a polyurethane-based resin as a base polymer.
3. The pressure-sensitive adhesive tape according to claim 2, wherein the polyurethane resin is a low crystalline linear polyester polyurethane resin.
4. 2. The pressure-sensitive adhesive tape according to claim 1, wherein the pressure-sensitive adhesive tape is a double-sided pressure-sensitive adhesive tape provided with a pressure-sensitive adhesive layer on both sides of the foamed resin base material.
5. The tensile strength in the machine direction and the transverse direction is 6.0 N / 10 mm or more, and the tensile strength is 110% or more when the tensile strength of the foamed resin substrate alone is 100%. When one of the strengths is 100%, the tensile strength of the other is within 100% ± 15%, the elongation at break in the machine direction and the transverse direction is 300% or more, and at the time of break in the machine direction and the transverse direction 2. The pressure-sensitive adhesive tape according to claim 1, wherein when one of the elongations is 100%, the other has a tensile strength of 100% ± 15%.
6. 2. The pressure-sensitive adhesive tape according to claim 1, wherein the antistatic property conforming to IEC6100 is 15 kV or more.
7. The pressure-sensitive adhesive tape according to claim 1, wherein the compressive deformation rate in the thickness direction is 3.0% or more.
8. 2. The pressure-sensitive adhesive tape according to claim 1, wherein the loss coefficient at −20 ° C. is 0.20 or more, the storage elastic modulus at 85 ° C. is 2.0 × 10 ⁵ Pa or more, and the loss coefficient at 85 ° C. is 0.20 or more. .
9. The pressure-sensitive adhesive tape according to claim 1, which is used for bonding or fixing a member constituting a portable information terminal device.
10. It is a method for manufacturing the adhesive tape of Claim 1, Comprising: The adhesive tape which has the process of obtaining a foamed resin base material by forming a closed cell using a thermally expansible microcapsule and / or an already-expanded hollow filler. Manufacturing method.
    

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