TW201623508A - Adhesive tape having foamed-resin base and process for producing the same - Google Patents

Abstract

An adhesive tape having a foamed-resin base comprising closed-cells, and an adhesive layer provided on at least one surface of the foamed-resin base, wherein the average void diameter of the closed-cells is 20 to 180 [mu]m, the maximum void diameter of the closed-cells is 300 [mu]m or less, the dimensional change rate by heating of the adhesive tape is within 100% ± 5% based on 100% of the dimension before heating, the rubber-elastic elongation recovery rate of the adhesive tape is 85% or more, especially, said adhesive tape has excellent, waterproofness, antistatic property, impact resistance, heat resistance, repairability and flexibility; and a process for producing the same.

Description

Adhesive tape with foamed resin substrate and method of manufacturing same

The present invention relates to an adhesive tape which has a foamed resin substrate and which is thin and thin but has sufficient characteristics, particularly excellent water resistance, electrostatic resistance and impact resistance. Properties, heat resistance, repairability and softness.

In a portable electronic device such as a smart phone or a mobile phone, an adhesive tape is used to bond the protective panel of the display to the casing or to fix other components and modules. Moreover, the waterproofness of the adhesive tape is important for the waterproofness of the portable electronic device. For example, in Patent Documents 1 and 2, a water-repellent adhesive tape is disclosed. Here, the use of a soft foam as a base material of an adhesive tape is suitable for use in a portable electronic device because it is thin and has good followability. Further, Patent Document 3 discloses a double-sided adhesive tape using a laminate of a foam layer and a reinforcing layer (plastic film) as a base material. This adhesive tape is excellent in removability.

In the portable electronic devices of recent years, the large screen of the display, the reduction of the overall product, and the improvement of design have been continuously developed. Along with this, not only is the requirement for making the adhesive tape thinner, but the requirement for thinning the bandwidth is also more intense. For example, the narrowing of the adhesive tape used to protect the panel and the casing has been considerably developed. Along with this, it is necessary for the adhesive tape to be a thinner and thinner foamed resin substrate having excellent water repellency. Moreover, the portable type that has been enlarged and reduced in size In the case where the grounding space is not available in the child machine, when the user with static electricity touches the portable electronic device, the static electricity is damaged by the adhesive tape and the normal operation cannot be performed. Therefore, it is necessary for the adhesive tape to be a thinner and thinner foamed resin substrate having excellent electrostatic resistance. Further, the portable electronic device is required to be used or placed at a high temperature or subjected to an impact force, so that heat resistance and impact resistance are required. Further, when the fixed component is reattached in the manufacturing process of the portable electronic device or the component is exchanged during the repair, the adhesive tape has excellent secondary workability in order to easily peel off the adhesive tape without problems. Or higher repairability becomes a must.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent No. 5370796

Patent Document 2: Japanese Patent No. 5477517

Patent Document 3: Japanese Patent Laid-Open Publication No. 2014-037543

An object of the present invention is to provide an adhesive tape which is thin and thin but has sufficient characteristics, particularly excellent in water repellency, electrostatic resistance, impact resistance, heat resistance and repairability. And softness.

The present invention relates to an adhesive tape comprising a foamed resin substrate comprising independent bubbles and an adhesive layer disposed on at least one side of the foamed resin substrate, and the average void diameter of the independent bubbles is 20~. 180μm, the maximum gap diameter is 300μm Hereinafter, the heating dimensional change rate of the adhesive tape is 100% ± 5% when the size before heating is 100%, and the rubber elastic elongation recovery rate of the adhesive tape is 85% or more.

Further, the present invention relates to a method of producing an adhesive tape, which is a method for producing the above adhesive tape, and has a foamed resin substrate obtained by forming a closed cell by using a heat-expandable microcapsule and/or an expanded hollow filler. step.

Since the adhesive tape of the present invention controls the void diameter of the closed cells of the foamed resin substrate to a small size in a specific range, it has excellent water repellency, electrostatic resistance, and impact resistance in the case of a narrow web. Further, since the adhesive tape has a low rate of change in heating dimensionality, it has excellent heat resistance, and has excellent repairability because of high rubber elastic elongation recovery rate.

Since the method for producing an adhesive tape of the present invention forms closed cells by using heat-expandable microcapsules and/or expanded hollow filler, the void diameter of the closed cells in the substrate can be easily controlled to a smaller size within a specific range of the present invention. .

1‧‧‧Double adhesive tape

2‧‧‧ HV electrode

3‧‧‧Touch pattern analog electrode

4‧‧‧TEG substrate

5‧‧‧Insulating sheet

6‧‧‧SUS platform

7‧‧‧Acrylic board

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an optical micrograph of one of the forms of individual bubbles in the adhesive tape of the present invention.

Figure 2 is an optical micrograph of one of the forms of closed cells in a conventional adhesive tape.

Fig. 3 is a schematic view showing a test method for the electrostatic resistance of the embodiment.

Fig. 4 is a schematic view showing a test method for the electrostatic resistance of the embodiment.

<Foamed resin substrate>

The foamed resin substrate in the present invention is a substrate in which independent bubbles are formed inside by foaming the resin. The foamed resin substrate containing the closed cells is superior in water repellency and artificial sebum resistance to the foamed resin substrate containing the continuous cells.

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

Specifically, the measurement of the void diameter is carried out by observing a plurality of independent bubbles in a 5 × 5 mm area of the foamed resin substrate by an optical microscope using a transmission method, and measuring the average value of the void diameter and Maximum value. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an optical micrograph of one of the forms of individual bubbles in the adhesive tape of the present invention. Figure 2 is an optical micrograph of one of the forms of closed cells in a conventional adhesive tape. According to these photos, it can be seen that the size of the independent bubbles of the two is very different.

When the average void diameter is as large as several hundred μm as shown in Fig. 2 (a conventional technique), there is a case where a large bubble of a size of 1 to 2 mm is locally formed. Moreover, this portion cannot maintain the form of the closed cells, but becomes a through state. This through state is a problem mainly in terms of water repellency, antistatic property, and the like in the case of using a narrow-processed foamed resin substrate adhesive tape. Further, in the case of using a film substrate having no bubble at all, the rigidity of the substrate is high. Therefore, if foreign matter (such as a very thin copper wire) is present on the surface, the ridge is generated in the step portion to impair the water repellency. On the other hand, if it is as in the present invention When the void diameter is controlled to a small size in a specific range, it is difficult to cause such a problem, and even if a high water pressure is applied, excellent water repellency can be maintained.

The antistatic property is generally affected by the type of the resin of the foamed resin substrate. When the type of the resin is the same, it is considered that the size of the closed cells also affects the electrostatic resistance. In fact, when the average void diameter is as large as several hundred μm as in the prior art (as in the prior art), if 15 kV of static electricity is applied in the width direction of the narrow-width processed adhesive tape, there is a foamed resin substrate. It is prone to damage, and it is detrimental to characteristics such as water repellency. On the other hand, even if the types of the resins are the same, if the void diameter is controlled to a small size within a specific range as in the case of the present invention (1), the foamed resin substrate is less likely to be broken. Although the reason why the antistatic property is improved is not clear, for example, an increase in the number of the resin film between the bubbles and the bubbles may be one of the causes. In the case where the resin portion interposed between the two bubbles is defined as a "resin film", if the same void ratio is present, the number of resin films in which a plurality of smaller bubbles are present is large. Specifically, the number of sheets of the resin film in the form of Fig. 1 (invention) is about 10 times or more the number of sheets of Fig. 2 (conventional technique). In the present invention, it is presumed that the increase in the number of such resin films has a better influence on the improvement of the antistatic property.

Further, when the void diameter is large as shown in FIG. 2 (conventional technique), interlayer damage of the foamed resin substrate is likely to occur due to the impact at low temperature. Further, the film substrate having no bubble at all or the double-sided adhesive tape having no substrate may be easily peeled off by the adherend due to impact, and the display member such as glass may be broken. 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 a low temperature.

As described above, in the present invention, even if a high water pressure is applied, even if static electricity is applied, even if an impact is applied, the bubbles in the foamed resin substrate are maintained independently. The state of the bubble. Therefore, the foamed resin substrate of the present invention is a substrate which is excellent in water repellency, artificial sebum resistance, electrostatic resistance, and other characteristics, and is excellent in stability of each property.

In the present invention, the resin constituting the foamed resin substrate is not particularly limited. For example, from the viewpoint of water repellency or artificial sebum resistance, it is preferred to appropriately select a base polymer having a water resistance or oil resistance and a crosslinking agent. Specific examples of the base polymer include a polyurethane resin which is a polymer of a polyhydric alcohol and a polyfunctional isocyanate; a polyolefin such as polyethylene or polypropylene; and styrene-butadiene-styrene. a styrene block copolymer such as a block copolymer or a styrene-isobutylene-styrene-block copolymer; ethylene copolymerization such as ethylene-vinyl acetate, ethylene-ethyl acrylate or ethylene-methyl methacrylate Acrylic block copolymer such as methyl methacrylate-butyl acrylate-methyl methacrylate; acrylate copolymer obtained by copolymerizing 2-ethylhexyl acrylate or methyl acrylate; polychlorinated A halogenated polymer such as ethylene. Among them, in view of electrostatic resistance, heat resistance, artificial sebum resistance, flexibility, and impact resistance, a polyurethane resin is preferred.

The polyurethane resin is generally a resin comprising a soft segment comprising a polyol monomer unit; and a hard segment comprising a polyfunctional isocyanate compound or a low molecular weight diol monomer unit.

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

The polyester polyol is obtained, for example, by an esterification reaction of a polyol component and an acid component. Specific examples of the polyol component include ethylene glycol, diethylene glycol, 1,3-butylene glycol, 1,4-butanediol, neopentyl glycol, and 3-methyl-1,5- Pentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, 1,6-hexane Alcohol, 1,8-octanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,8-nonanediol, octadecanediol, glycerin, trishydroxyl Propane, pentaerythritol, hexanetriol, polypropylene glycol. Specific examples of the acid component include succinic acid, methyl succinic acid, adipic acid, pimelic acid, sebacic acid, sebacic acid, 1,12-dodecanedioic acid, 1,14-fourteen. Alkanoic acid, dimer acid, 2-methyl-1,4-cyclohexanedicarboxylic acid, 2-ethyl-1,4-cyclohexanedicarboxylic acid, p-nonanoic acid, m-decanoic acid, o-quinone Acid, 1,4-naphthalene dicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and such anhydrides.

Polyether polyols are, for example, water, low molecular polyols (for example propylene glycol, ethylene glycol, glycerol, trimethylolpropane, pentaerythritol), bisphenols (for example bisphenol A) or dihydroxybenzene (for example catechol) And resorcinol and hydroquinone are used as a starting agent, and are obtained by addition polymerization of an alkylene oxide such as ethylene oxide, propylene oxide or butylene oxide. Specific examples thereof include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Specific examples of the polycaprolactone polyol include a ring-opening polymer of a cyclic ester monomer such as ε-caprolactone or σ-valerolactone.

Specific examples of the polycarbonate polyol include a polycarbonate polyol obtained by subjecting each of the above polyol components to carbon trichloride to undergo polycondensation reaction; and each of the above polyol components, and dimethyl carbonate and carbonic acid Ethyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, butyl carbonate, ethylene carbonate, propylene carbonate, diphenyl carbonate, dibenzyl carbonate, etc. a polycarbonate polyol obtained by transesterification condensation; a copolymerized polycarbonate polyol obtained by using two or more of the above polyol components in combination; and each of the above polycarbonate polyols and a carboxyl group-containing compound a polycarbonate polyol obtained by an esterification reaction; a polycarbonate polyol obtained by subjecting each of the above polycarbonate polyols to a hydroxyl group-containing compound by etherification reaction; and performing the above respective polycarbonate polyols and ester compounds a polycarbonate polyol obtained by a transesterification reaction; a polycarbonate polyol obtained by subjecting each of the above polycarbonate polyols to a transesterification reaction with a hydroxyl group-containing compound; and each of the above polycarbonate polyols and dicarboxylic acids A polyester-based polycarbonate polyol obtained by subjecting a compound to a polycondensation reaction; a copolymerized polyether-based polycarbonate polyol obtained by copolymerizing each of the above polycarbonate polyols with an alkylene oxide.

The castor oil-based polyol is obtained, for example, by reacting a 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. Further, a trimethylolpropane adduct of the compounds, a biuret formed by reacting with water, and a trimer having an isocyanurate ring may also be used. Two or more kinds of polyfunctional isocyanate compounds may also be used in combination.

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

Specific examples of the polyfunctional alicyclic isocyanate compound include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, and isophorone. Diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated dimethyl dimethyl diisocyanate, hydrogenated toluene diisocyanate, hydrogenated tetramethyl phthalate Diisocyanate.

Specific examples of the polyfunctional aromatic diisocyanate compound include phenyl diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, and 2,2'-diphenylmethane diisocyanate. 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene Isocyanate, phenyldimethyl diisocyanate.

The polyurethane resin is obtained by curing a composition containing the above-described polyol and a polyfunctional isocyanate compound. In particular, from the viewpoint of properties such as rubber elastic elongation recovery ratio, a linear polyester polyester resin having a low crystallinity is preferred, and a hexylene glycol copolyester polyurethane is more preferred. Resin, polytetramethylene glycol based polyurethane resin. The commercial product of the polyurethane resin is, for example, Sanprene manufactured by Sanyo Chemical Industries Co., Ltd., trade name Desmocoll manufactured by Sumika Bayer Urethane Co., Ltd., and NIPPOLLAN manufactured by Nippon Polyurethane Industry Co., Ltd., and the like. Specifically, the low crystallinity can be determined by the following procedure: a resin test piece having a film thickness of 6 mm is produced in accordance with JIS K 6253 "Rubber hardness specification", and the test piece is melted at 100 ° C for 30 minutes, and placed in 23 After an environment of ±2 ° C and a relative humidity of 50 ± 5%, the time until the hardness of the resin became A90 was measured. Specifically, a resin which is 72 hours or longer in the case of the Shore A90 can be referred to as a low crystallinity resin. For example, the product name Desmocoll 500 manufactured by Sumika Bayer Urethane Co., Ltd. is a highly crystalline resin having a time of about 5 minutes from the A90, and the product name Desmocoll 540 is a highly crystalline resin of about 10 minutes. The product name is Desmocoll 176. Crystalline resin in the hour. On the other hand, Desmocoll 406 is a 72 hour low crystalline resin.

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

Other components may be added to the resin composition constituting the foamed resin substrate. Specifically, for example, a catalyst, other resin component, an adhesion-imparting agent, an inorganic filler, an organic filler, a metal powder, a pigment, a foil, a softener, a plasticizer, an anti-aging agent, a heat sink, and a conductive agent may be added. Agents, antioxidants, UV absorbers, light stabilizers, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, slip agents, solvents. In particular, in order to harden the reaction, it is preferred to add a catalyst such as an organometallic compound or a tertiary amine compound. Specific examples of the organometallic compound include an iron compound, a tin compound, a titanium compound, a zirconium compound, a lead compound, a cobalt compound, a zinc compound, and an anthraquinone compound. In particular, from the viewpoint of the reaction rate and the environmental load, an iron compound or a lanthanoid compound is preferred.

The method for forming the closed cells in the resin described above is not particularly limited, and a method of forming a foaming agent such as a thermally expandable microcapsule, an expanded hollow filler, an inorganic foaming agent or an organic foaming agent is preferred. . Among them, it is particularly preferable to use a heat-expandable microcapsule and/or an expanded hollow filler.

As described above, in the case where the average void diameter is as large as several hundred μm or locally as large as 1 to 2 mm as in the conventional technique of FIG. 2, there is a local shape. In the case of the through state, especially in the narrow-processed foamed resin substrate adhesive tape, it has a large problem in terms of water repellency or electrostatic resistance. Therefore, in the prior art, the operation of removing the extremely large independent bubble portion is performed by an optical detector. However, the detection accuracy of the removal is not sufficient, and thus there is a problem that the yield is deteriorated due to lack of reliability or variations in manufacturing lots, and the cost is increased due to an increase in processing cost. On the other hand, if a foaming control method using a heat-expandable microcapsule and/or an expanded hollow filler is employed, the void diameter can be easily controlled to a small size within a specific range of the present invention.

The heat-expandable microcapsules are representative, and are mainly microspheres including a shell of a thermoplastic resin and a liquid low-boiling hydrocarbon contained in the shell. The boiling point of the liquid low-boiling hydrocarbon is below the softening temperature of the thermoplastic resin constituting the outer shell. The closed cells can be formed by heating and foaming the resin containing the heat-expandable microcapsules. For example, the heat-expandable microcapsules are dispersed in a resin constituting a substrate, and the resin is thermally expanded to a degree that does not break when thermoformed, and is maintained in an expanded shape after molding. Thereby, independent bubbles are formed in the resin. The average particle diameter of the heat-expandable microcapsules before expansion is preferably from 5 to 50 μm, more preferably from 10 to 30 μm, and the average particle diameter after expansion is preferably from 30 to 150 μm, more preferably from 40 to 120 μm. The thermal expansion initiation temperature of the heat-expandable microcapsules is preferably from 100 to 170 ° C, the maximum expansion temperature is preferably from 160 to 200 ° C, and the volume expansion ratio is preferably from about 50 to 100 times.

The thermoplastic resin constituting the outer shell of the heat-expandable microcapsules may be appropriately selected depending on conditions such as the softening temperature or the hot forming temperature of the resin constituting the substrate. Specific examples include homopolymers of monomers such as (meth)acrylonitrile, methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate; and two kinds thereof. A copolymer of the above monomers. Binder resin can also be used to make titanium oxide and oxygen Inorganic fine particles such as zinc, alumina, ceria, and calcium carbonate are fixed on the surface of the outer casing. Further, it is also possible to mainly form an outer shell of acrylonitrile and hydrazine, and to control foaming characteristics (for example, expansion ratio) by adjusting the amount of hydrazine.

The liquid low-boiling hydrocarbon contained in the heat-expandable microcapsule is preferably a hydrocarbon which is vaporized at the time of thermoforming of the resin constituting the substrate. Specific examples thereof include low boiling point liquids such as n-butane, isobutane, n-pentane, isopentane, and petroleum ether.

As a commercially available product of the heat-expandable microcapsules, for example, Matsumoto Microsphere F-36D, F-36LVD, FN-80GSD, FN-100SD, FN-100MD, FN-100SSD, FN-105D, manufactured by Matsumoto Oil & Fats Pharmaceutical Co., Ltd. FN-180SSD, etc., trade names of Expancel 053-40, 909-80, 930-120, etc. manufactured by EXPANCEL, and trade names such as FINECELL MASTER MS401K, MS402K, MS405K, etc. manufactured by Daisei Seiki Co., Ltd.

The expanded hollow filler is obtained by foaming the heat-expandable microcapsules alone. Further, only one of the heat-expandable microcapsules and the expanded hollow filler may be used, or both may be used in combination.

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

Specific examples of the organic foaming agent include chlorofluoroalkanes such as trichloromonofluoromethane and dichloromonofluoromethane; azobisisobutyronitrile, azobiscarboxyguanamine, and bisazodicarboxylate; An azo compound; p-toluenesulfonate, diphenylindole-3,3'-disulfonium, 4,4'-oxybis(phenylsulfonate), allyl bis(sulfonate) An isosine compound; an ureidourea compound such as ρ-methylphenylsulfonyl urea, 4,4'-oxybis(phenylsulfonylaminourea); Triazole compound such as phenyl-1,2,3,4-thiatriazole; N,N'-dinitrosopentamethylenetetramine, N,N'-dimethyl-N,N'- An N-nitroso compound such as dinitroso-p-xylyleneamine.

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

The foamed resin substrate may also be subjected to a surface treatment for improving the adhesion to the adhesive layer or other layers. As the surface treatment, for example, corona treatment, flame treatment, plasma treatment, hot air treatment, ozone. UV treatment, easy to apply the coating agent. The degree of surface treatment can be judged, for example, based on the moisture permeability index obtained by using a moisture permeable reagent. The moisture permeability index of the surface of the substrate after the surface treatment is preferably 36 mN/m or more, more preferably 40 mN/m, and particularly preferably 48 mN/m, in terms of adhesion to the adhesive layer.

<Adhesive layer>

The adhesive layer is a layer comprising an adhesive composition disposed on at least one side of the foamed resin substrate. The adhesive composition is not particularly limited as long as it is a composition containing an adhesive which does not impair the effects of the present invention. For example, a latex-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 the adhesive include an acrylic adhesive, a rubber adhesive (a natural rubber adhesive or a synthetic rubber adhesive), a polyoxygen adhesive, a polyester adhesive, and a urethane. An ester-based adhesive, a polyamide-based adhesive, an epoxy-based adhesive, a vinyl alkyl ether-based adhesive, or a fluorine-based adhesive. It is also possible to use two or more types of adhesives together. In particular, an acrylic adhesive is preferred from the viewpoints of heat resistance, cold resistance, water resistance, and artificial sebum resistance. Acrylic adhesive In general, a composition containing a compound obtained by curing an acrylic copolymer [(meth)acrylate copolymer or the like) as a base polymer by a crosslinking agent as a main component is used. Specifically, for example, an adhesive described in International Publication No. 2014/002203 can be preferably used.

The acrylic copolymer used for the acrylic adhesive is typically a (meth) acrylate copolymer having a hydroxyl group and a carboxyl group. More preferably, it is obtained by copolymerizing at least four components of a long chain alkyl (meth) acrylate, a carboxyl group-containing monomer, a hydroxyl group-containing monomer, and a short-chain alkyl (meth) acrylate ( Methyl) acrylate copolymer.

As the long-chain alkyl (meth)acrylate, an alkyl (meth)acrylate having an alkyl group having 4 to 12 carbon atoms is preferred. Specific examples thereof include butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, and (meth)acrylic acid. Isooctyl ester, isodecyl (meth)acrylate, lauryl (meth)acrylate. Specific examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, 2-carboxy-1-butene, and 2-carboxy-1- Pentene, 2-carboxy-1-hexene, 2-carboxy-1-heptene. When a monomer containing a carboxyl group is used in an appropriate amount, characteristics such as water repellency and load-bearing 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 alkyl (meth)acrylate is an alkyl (meth)acrylate having an alkyl group having 1 to 3 carbon atoms, specifically, methyl (meth)acrylate or ethyl (meth)acrylate Ester, propyl (meth)acrylate. Among them, methyl acrylate is preferred.

In 100% by mass of the constituent component (monomer unit) of the (meth) acrylate copolymer, the content of the long-chain alkyl (meth) acrylate unit is preferably 50 to 90% by mass. %, more preferably 50 to 80% by mass. The content of the carboxyl group-containing monomer unit is preferably from 3 to 20% by mass, more preferably from 3 to 12% by mass. The content of the monomer unit having a hydroxyl group is preferably from 3 to 20% by mass, more preferably from 3 to 18% by mass. The content of the short-chain alkyl (meth) acrylate unit is preferably from 3 to 15% by mass, more preferably from 3 to 12% by mass. Further, the total content of the carboxyl group-containing monomer unit and the hydroxyl group-containing monomer unit is preferably 13% by mass or more. Further, a monomer unit other than the above four components may be included in the range which does not impair the effects of the present invention.

The acrylic copolymerization system is obtained by copolymerizing a plurality of monomers. The polymerization method is not particularly limited, and in terms of ease of polymer design, radical solution polymerization is preferred. Further, first, an acrylic slurry containing an acrylic copolymer and a monomer thereof may be prepared, and a crosslinking agent and an additional photopolymerization initiator may be added to the acrylic slurry to polymerize the same.

The weight average molecular weight of the acrylic copolymer is preferably from 700,000 to 2,000,000, more preferably from 70 to 1.5 million. The lower limits of these ranges are meaningful in terms of load resistance and processability. Further, the upper limit is meaningful in terms of the coatability of the adhesive composition. The weight average molecular weight is a value obtained by a gel permeation chromatography (GPC) method.

The theoretical Tg of the acrylic copolymer is preferably -40 ° C or lower, more preferably -50 ° C to -75 ° C. The theoretical Tg is a value calculated using the FOX equation. The main resin component of the acrylic adhesive is an acrylic copolymer, and other types of resin components can be used in combination with the properties of the acrylic adhesive.

The crosslinking agent used for the acrylic pressure-sensitive adhesive is a compound which reacts with the acrylic copolymer to form a crosslinked structure, and is typically a compound which can react with a carboxyl group and/or a hydroxyl group of the acrylic copolymer. Especially waterproof and resistant From the viewpoints of characteristics such as gravity, workability, impact resistance, artificial sebum resistance, and artificial sweat resistance, an isocyanate crosslinking agent or an epoxy crosslinking agent is preferred. These can also be used together. The amount of the crosslinking agent to be added is preferably 0.001 to 1 part by mass based on 100 parts by mass of the acrylic copolymer.

Specific examples of the isocyanate crosslinking agent include toluene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and the modified prepolymer. These may also be used in combination of two or more types. 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, per 100 parts by mass of the acrylic copolymer.

Specific examples of the epoxy-based crosslinking agent include N, N, N', N'-tetraglycidyl-m-xylylenediamine, and 1,3-bis(N,N'-diglycidylamine). A compound having two or more epoxy groups such as methyl)cyclohexane. These may also be used in combination of two or more types. The amount of the epoxy-based crosslinking agent is preferably 0.001 to 0.5 parts by mass, more preferably 0.001 to 0.1 parts by mass, per 100 parts by mass of the acrylic copolymer.

For example, an adhesive-imparting agent, a plasticizer, a filler, and a colorant may be added to the adhesive. Specific examples of the adhesion-imparting agent include rosin-based resins (rosin ester-based, polymerized rosin-based, disproportionated rosin-ester-based, etc.), anthracene-based resin, terpene-based resin, petroleum-based resin, and styrene-based resin. Specific examples of the filler include cerium oxide. Specific examples of the colorant include carbon black, titanium oxide, nigrosine, acetylene black, and ketjen black. Further, for example, carbon black, a carbon nanotube, or a black inorganic filler may be added as a light-shielding filler.

The adhesive layer can be formed, for example, by applying an adhesive to a substrate and subjecting it to crosslinking reaction by heating or ultraviolet irradiation. Further, for example, an adhesive may be applied to the release paper or other film, and the adhesive may be crosslinked by heating or ultraviolet irradiation to form an adhesive. The layer is adhered to one 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. In the case of heating after coating, the solvent in the adhesive composition can also be removed while the crosslinking reaction is carried out by heating. The thickness of the adhesive layer is preferably from 5 to 100 μm, more preferably from 10 to 80 μm.

<adhesive tape>

The adhesive tape of the present invention has the above-described foamed resin substrate containing closed cells and an adhesive layer provided on at least one side of the foamed resin substrate. It may be a single-sided adhesive tape provided with an adhesive layer on only one side of the substrate, but it is preferably a double-sided adhesive tape provided on both sides.

As the substrate of the adhesive tape, it is preferred to use the foamed resin substrate containing the closed cells described above separately. However, it is also possible to use, for example, a laminate having a base material or another laminated layer on a foamed resin substrate as a substrate, without departing from the effects of the present invention.

The antistatic property of the adhesive tape according to IEC6100 is preferably 15 kV or more, more preferably 18 kV or more. As described above, it is considered that the antistatic property is generally affected by the kind of the resin, but when the types of the resins are the same, it is presumed that the void diameter of the closed cells of the foamed resin substrate is controlled to a small size of a specific range. It can improve the antistatic properties. The value of the above-mentioned antistatic property is a value obtained by measuring the adhesive tape, and it is of course preferable to use the same measurement value even when the foamed resin substrate is separately measured. The antistatic property according to IEC6100 specifically means a value obtained by using an electrostatic gun to emit a fixed voltage for 100 times in the width direction of the adhesive tape as described in the following embodiments. .

The heating dimensional change rate of the adhesive tape is 100% ± 5% or less, preferably ± 1% or less, in the case where the size before heating is set to 100%. This heating dimensional change rate (heat resistance) is important in the use of a product which is used or placed at a high temperature. For example, information carrying terminals such as car navigation used in front of a car or around a dashboard may exist in summer when the temperature exceeds 80 °C. In this case, the base material of the adhesive tape that fixes the information display portion of the car navigation and the casing is shrunk, and peeling occurs due to deformation. Further, in the case of a product having a high requirement for narrowing the adhesive tape, such as a recent information carrying terminal, peeling at such a high temperature is liable to occur. On the other hand, even if it is a narrow-processed adhesive tape, as long as the said heating-size change rate is shown, it is hard to generate|occur|produce the peeling, even if it is used or it is high- From the viewpoint of such a heating dimensional change rate (heat resistance), it is preferred to use a polyurethane resin for the foamed resin substrate as compared with the polyolefin resin. The heating dimensional change rate specifically means the change rate of the size after the adhesive tape is heated at 90 ° C for 2 hours and left at room temperature for 1 hour or more as described in the following examples.

The rubber elastic elongation recovery rate (2 times and 4 times) of the adhesive tape is 85% or more, preferably 90% or more. The rubber elastic elongation recovery ratio is important in applications requiring secondary workability, repairability (elongation peelability), and flexibility. The term "repairability" specifically means a property in which one end of the adhesive tape is stretched while the faces of the two hard bodies are adhered to each other by a double-sided adhesive tape as described in the following examples. The adhesive tape is elongated and can be peeled off without problems and simply. For example, when a component of a information carrying terminal such as a smart phone or a mobile phone fails, it is desirable to easily peel off the adhesive tape that fixes the parts in order to exchange parts, and no adhesive remains in the peeling portion. Residue. However, if the adhesive tape does not have moderate elasticity, the adhesive layer will not stretch sufficiently even if one end of the adhesive tape is stretched. Long, the adhesion is not fully reduced, and the adhesive tape will be broken in the middle. On the other hand, even if it is an adhesive tape which has been processed in a narrow width, as long as it is an adhesive tape which exhibits the recovery rate of the rubber elastic elongation recovery rate and a high degree of flexibility, by stretching one end of an adhesive tape, On the other hand, the adhesive layer is continuously and uniformly elongated, and the adhesive force is moderately lowered, and as a result, peeling can be performed without any problem. Further, the high degree of softness performance satisfies the unevenness, step, and deformation of the surface of the adherend, and contributes to improvement in characteristics such as adhesion, water repellency, and impact resistance. Specifically, the rubber elastic elongation recovery ratio is a ratio such that the length of the adhesive tape is doubled or four times as described in the following examples, and the tensile force is released for 10 seconds. The ratio of the amount of recovery at the time relative to the amount of elongation.

The compression set ratio in the thickness direction of the adhesive tape is preferably 3.0% or more, more preferably 5.0% or more. This compression deformation ratio is important in the use of a product in which the unevenness or step is present on the adhesion surface or the deformation of the member itself occurs. For example, when the information display member of the information carrying terminal such as a smart phone or a mobile phone is attached to the casing, the contact faces of the members are not necessarily flat, and there are usually irregularities or steps. Moreover, there is a case where the respective members themselves are deformed at the time of use. Therefore, if the adhesive tape cannot absorb the deformation, peeling occurs. On the other hand, even in the case of an adhesive tape which has been subjected to narrow processing, it is difficult to cause peeling even in the above case as long as it is an adhesive tape which exhibits the flexibility or stress relaxation property as described above. Specifically, the compression deformation ratio is as follows. As described in the following examples, according to the test method of the thickness of JIS Z 0237:2000, the thickness of the disk gauge is 20 kPa as a reference, and the load is increased. The ratio of the thickness change to 100 kPa.

The interlayer strength of the entire adhesive tape having a foamed resin substrate is preferably 10 N/10 mm or more, and more preferably 15 N/10 mm or more. The strength of the layer (90 degree peeling Adhesion is important in the use of products requiring secondary processing. Specifically, the secondary workability means a property in which the peeling property can be easily performed without any problem when the adhesive tape in the adhesive state is peeled off as described in the following examples. For example, in the manufacturing steps of a information carrying terminal such as a smart phone or a mobile phone, it is necessary to peel off the adhesive tape and re-perform the step (for secondary processing). At this time, it is desirable that the adhesive tape can be easily peeled off, and no residue such as an adhesive remains at the peeled portion. However, if the interlayer strength of the foamed resin substrate is low, it depends on the strength of the adhesive force of the adhesive layer, but the substrate itself is broken when the adhesive tape is peeled off, or if the adhesive layer and the foamed substrate are The adhesion (follow strength) is weak, which causes peeling between the layers between the adhesive layer and the substrate, and the residue adheres to the adherend and is difficult to remove. On the other hand, in the case of the adhesive tape including the foamed resin substrate having the above interlayer strength, even in the above case, the foamed resin substrate is less likely to be broken. Specifically, the interlaminar strength is a 90-degree peeling adhesive force obtained in accordance with JIS Z 0237 "Adhesive tape. Adhesive sheet test method" as described in the following examples.

The tensile strength in the longitudinal direction and the transverse direction of the adhesive tape is preferably 6.0 N/10 mm or more. Moreover, when the tensile strength of the foamed resin substrate alone is 100%, the tensile strength is preferably 110% or more. Further, when one of the tensile strengths in the longitudinal direction and the transverse direction is set to 100%, the other elongation is 100% ± 15% or less. The elongation in the longitudinal direction and the transverse direction of the adhesive tape is preferably 300% or more. Further, when one of the elongation at the time of breaking in the longitudinal direction and the transverse direction is 100%, the other elongation is 100% ± 15% or less. In particular, the case where the tensile strength and the elongation are relatively small in the aspect ratio is important in the use of a product which is required to be formed into a frame-shaped adhesive tape by punching. For example, in an adhesive tape in which the information display portion of the information carrying terminal such as a smart phone or a mobile phone is fixed to the casing, the punching process is substantially a square edge. There are more frames. In this case, if the tensile strength and the elongation are relatively large, the physical properties will vary. On the other hand, in the case of the above-mentioned adhesive tape which is relatively small in the vertical and horizontal directions, it is difficult to cause a variation in physical properties regardless of the direction in which the punching is performed. The tensile strength and the elongation are specifically the strength and elongation at the time of breaking when the tensile test of the adhesive tape of a specific size is carried out as described in the following examples.

The loss coefficient (tan δ) of the adhesive tape at -20 ° C is preferably 0.20 or more, more preferably 0.3 or more. In addition, the storage at 85 ℃ elastic modulus is preferably not less than 2.0 × 10 ⁵ Pa, more preferably not less than 2.5 × 10 ⁵ Pa, the loss factor (tan [delta]) at the 85 ℃ is preferably 0.20 or more, more preferably 0.3 or more . The storage elastic modulus and loss factor are important in the use of articles requiring a narrow strip of adhesive tape. For example, a information carrying terminal such as a smart phone or a mobile phone is required to have a large screen of the information display unit (display), a reduction in the overall size of the product, and an improvement in design, so that a narrow adhesive tape is required. In this case, if the storage elastic modulus or the loss coefficient is low, there is a problem that the adhesion is problematic. On the other hand, in the case of the adhesive tape having the above-described storage elastic modulus and loss coefficient, even if it is a narrow-width processed adhesive tape, it is difficult to cause a problem of adhesion. Specifically, the storage elastic modulus and the loss coefficient are as described in the following examples, and an adhesive tape having a thickness of 0.2 mm is interposed between the parallel disks of the viscoelasticity testing machine, and the value is measured and calculated at a frequency of 1 Hz. .

Each of the above characteristics is mainly exhibited by appropriately adjusting the conditions of the type of the resin of the foamed resin substrate, the size of the closed cells, and the type of the adhesive layer. Specific examples of the foamed resin substrate and the adhesive layer are as described above.

The width of the adhesive tape is not limited. However, the width is preferably from 0.5 to 5.0 mm, more preferably from 0.7 to 3.0 mm, from the viewpoint that the properties obtained in the present invention are excellent, particularly in a narrow-width adhesive tape. Also, the thickness of the adhesive tape is preferably 0.08 ~0.5mm, more preferably 0.1~0.4mm. In the case of punching (narrow processing) for producing a narrow-sized adhesive tape, it is preferable to carry out product design in such a manner that the total thickness of the adhesive layer is not larger than the thickness of the substrate, and the adhesion is prevented. The agent adheres or spills to the punching knife.

[Examples]

Hereinafter, the present invention will be described in detail by way of examples. In the following description, "parts" means "parts by mass".

<Preparation of Acrylic Adhesive Composition>

In a reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube, 75 parts of 2-ethylhexyl acrylate, 10 parts of methyl acrylate, 10 parts of acrylic acid, and 5 parts of 2-hydroxyethyl acrylate were mixed. Further, ethyl acetate, n-dodecyl mercaptan as a chain transfer agent, and 0.1 part of a peroxidic lauryl group as a radical polymerization initiator were added. Nitrogen gas was sealed in the reaction apparatus, and polymerization was carried out at 68 ° C for 3 hours while stirring under a nitrogen gas stream, followed by polymerization at 78 ° C for 3 hours.

Thereafter, it was cooled to room temperature and ethyl acetate was added. Thereby, an acrylic copolymer having a solid content concentration of 30%, a theoretical Tg-64.8, and a weight average molecular weight of 1.1 million was obtained. Then, 0.07 parts of an isocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name Coronate L) and an appropriate amount of an organic solvent were added to 100 parts of the acrylic copolymer, and the mixture was stirred until uniformized by a stirrer to obtain an acrylic resin. Adhesive composition.

<Preparation of Polyurethane Resin Composition>

Adding an appropriate amount of an organic solvent to a powdery component such as a foaming agent or a coloring agent, and utilizing Disperse the mixer. Then, the polyurethane solution and the crosslinking agent were added, and the mixture was stirred until uniformly dispersed by a stirrer to obtain a polyurethane resin composition. The amounts (parts) of each component are shown in Tables 1 and 2.

<Examples 1 to 8 and Comparative Examples 1 to 2>

The polyurethane resin composition was applied to one side of a release paper having a polyoxymethylene mold release agent formed on both sides, and dried at 70 ° C for 2 minutes + 90 ° C for 2 minutes to remove the solvent. . Then, it was foamed by heating at 130 ° C for 2 minutes, and it was taken up. Further, the mixture was aged at 40 ° C for 3 days to complete the hardening reaction, and a foamed resin substrate (thickness 0.10 mm) was obtained.

The acrylic adhesive composition was applied onto a double-sided release paper subjected to polyoxynitridation treatment and dried to form an adhesive layer. Then, the foamed resin substrate is subjected to a corona discharge treatment, and the adhesive layer is bonded to the surface. Further, the adhesive layer was bonded to the opposite side of the foamed resin substrate by the same method. Thereafter, the mixture was aged at 40 ° C for 3 days to complete the hardening reaction of the adhesive layer to obtain a double-sided adhesive tape having a thickness of about 0.20 mm (the thickness of each adhesive layer was about 50 μm).

<Comparative Example 3>

A double-sided adhesive having a thickness of about 0.20 mm was produced in the same manner as in Example 1 except that a polyethylene (PE) foam (manufactured by Sekisui Chemical Co., Ltd., trade name: VOLARA XL-H black #1001) was used as the substrate. The tape (the thickness of each adhesive layer is about 50 μm).

<Comparative Example 4>

A double-sided thickness of about 0.20 mm was produced in the same manner as in Example 1 except that a polyethylene terephthalate (PET) film (trade name: Lumirror S-10, manufactured by Toray Industries, Inc.) was used as the substrate. Adhesive tape (the thickness of each adhesive layer is about 75 μm).

<Comparative Example 5>

The acrylic pressure-sensitive adhesive composition of Example 1 was applied to a release paper so as to have a thickness of 0.2 mm to produce a baseless double-sided tape having a substrate-free thickness of 0.20 mm.

<Test method>

The following tests were carried out on the double-sided adhesive tapes obtained in the examples and comparative examples. The results are shown in Tables 1 to 3.

[Void diameter]

The average value and the maximum value of the void diameter were measured by observing a plurality of independent bubbles in a 5 × 5 mm area of the foamed resin substrate by an optical microscope of a transmission method.

[Rubber elastic elongation recovery rate]

The double-sided adhesive tape was cut into a width of 10 mm and a length of 150 to 200 mm, and the adhesion was inactivated by calcium carbonate, and the resultant was used as a test piece. One end of the test piece was fixed to a tensile tester which set the collet interval to 100 mm, and marked ink was marked on both sides with a test length of 100 mm. Stretching at a speed of 1500 mm/min, when the length is 2 times (100 mm elongation) or 4 times (300 mm elongation) Open a collet and measure the total length of the marked portion (the total length at the time of recovery) after 10 seconds. Then, the ratio of the recovery amount (the total length at the time of elongation - the total length at the time of recovery) to the elongation amount was determined, and this was taken as the rubber elastic elongation recovery ratio. The specific calculation method is as follows.

2 times elongation recovery rate (%) = (200 - total length at recovery) ÷ 100 × 100

4 times elongation recovery rate (%) = (400 - total length at recovery) ÷ 300 × 100

[heating dimensional change rate]

The double-sided adhesive tape was cut into 100 × 100 mm, and the adhesion was inactivated by calcium carbonate, and the resultant was used as a test piece. The test piece was suspended in a dryer at 90 ° C for 2 hours, and then left at room temperature for 1 hour or more, and the size was measured. The specific calculation method of the heating dimensional change rate is as follows.

Heating dimensional change rate (%) = [(heated size) - (pre-heating size)] ÷ (pre-heating size) × 100

[Narrow processing]

The double-sided adhesive tape is cut into 10 pieces with a width of 5 mm and a length of 125 mm, and the state is maintained (that is, the adjacent adhesive state of the finely-cut adhesive tape is maintained at the time of fine break), at 65 ° C, 80%. Placed in an atmosphere of relative humidity (RH, Relative Humidity) for 1 day. Then, for each one, the release paper was peeled off together with the release paper in the direction of 180 degrees, and the adhesion to the adjacent portion was visually confirmed, and the narrow workability was evaluated by the following criteria.

"○": There is almost no adhesion to the adjacent portion, and peeling can be performed without peeling off the adjacent portion.

"X": There is a significant adhesion to the adjacent portion, and the adjacent portion is simultaneously peeled off.

[Secondary processing property]

The aluminum foil (0.08 mm thick) on one side of the double-sided adhesive tape was used as a test piece, and the adhesive tape was attached to the stainless steel according to JIS Z 0237 "Adhesive tape. Adhesive sheet test method". The 90 degree peel test after 30 minutes of the board was evaluated by the following criteria.

"○": no interlayer damage or paste residue.

"×(a)": Destruction occurs between the layers of the substrate at the time of peeling.

"×(b)": After peeling off, the paste remains on the stainless steel plate.

[Loadworthiness]

The double-sided adhesive tape was cut into a size of 25 × 25 mm, and a release paper was peeled off. The double-sided adhesive tape was attached to the test hook plate (HOOK BOARD), and then another release paper was peeled off and attached to the polycarbonate plate. Then, a load of 700 gf was applied to the hook, and the temperature was maintained at 85 ° C for 60 minutes, and the load-bearing resistance was evaluated by the following criteria.

"○": The hook did not fall for 60 minutes.

"X": The hook falls within 60 minutes.

[impact resistance]

Cut the double-sided adhesive tape into a frame shape of 50×45 mm with a width of 0.8 mm, peel off a release paper, attach it to a 2 mm thick glass plate, and peel off another release paper, and attach it to a 3 mm thick polycarbonate. board. Then, using an autoclave, pressurization was performed at 23 ° C and 0.5 MPa for 1 hour. Furthermore, using the SUS board, the overall weight is adjusted. It is 250 g and is allowed to stand at -20 ° C for 1 hour or more. Then, from the height of 1.5 m, one side of the test plate is passed through the tube in a vertical direction to the concrete floor, and measured until the glass plate is peeled or broken (A), or until the interlayer damage of the substrate is generated (B) The number of falls.

[waterproof]

The double-sided adhesive tape was cut into a frame shape of 40×50 mm with a width of 0.8 mm, a release paper was peeled off, bonded to a glass plate of 2 mm thick, and another release paper was peeled off, and bonded to a glass plate of 2 mm thickness. Then, the sample was subjected to a pressure treatment (0.5 MPa) at 23 ° C for 1 hour using an autoclave. Then, based on the waterproof specification IEC "International Electrical Standards Conference" 60529:2001 [equivalent: JIS C 0920:2003 "Degrees of protection provided by enclosures (IP code)" The test method of IPX7, the sample was not used in water, and the water repellency was evaluated. Further, an autoclave was used for the other samples, and the pressure treatment was performed at 23 ° C for 1 hour. Thereafter, the other samples were submerged in water of 0.1 MPa, 0.25 MPa, and 0.5 MPa, respectively, based on the test method of IPX8 of the above-mentioned waterproof specification. And evaluate the waterproofness. This evaluation is carried out in the following stages, that is, the water repellency is water resistance which satisfies the conditions specified in the protection level IPX8 and does not satisfy the conditions specified in IPX7.

Further, 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 into one joint surface, and the same test was carried out. This evaluation is an evaluation of the water repellency in a state where foreign matter (very fine copper wire) is present on the joint surface.

[Resistant to artificial sebum. Artificial sweaty]

The double-sided adhesive tape was cut into a frame shape of 40×50 mm with a width of 0.8 mm, a release paper was peeled off, bonded to a glass plate of 2 mm thick, and another release paper was peeled off, and bonded to a glass plate of 2 mm thickness. Then, using an autoclave, pressurization was performed at 23 ° C and 0.5 MPa for 1 hour. The sample was immersed in artificial sebum (33.3% triolein, 20.0% oleic acid, 13.3% squalene, 33.4% crotonyl myristate) or artificial sweat for 1 hour. The sample was taken out, allowed to stand in an environment of 85 ° C and 85% RH for 72 hours, and then left in a usual environment for 240 hours. The sample was visually observed and the artificial sebum was resistant to the following criteria. Artificial sweating was evaluated.

"○": Stripping without a belt.

"X": There is a stripping of the belt.

[Antistatic properties]

A double-sided adhesive tape having a width of 0.7 mm was used as a test piece. As shown in FIG. 3, a double-sided adhesive tape 1 was disposed between the high voltage (HV) electrode 2 and the touch pattern analog electrode 3. The electrodes 2 and 3 are wired on a test element group (TEG) substrate 4, and the TEG substrate 4 is placed on the SUS platform 6 via the insulating sheet 5. The touch pattern analog electrode 3 is grounded to the SUS platform 6. Further, as shown in FIG. 4, the acrylic plate 7 was covered on the test surface. Then, according to IEC61000-4-2, a certain fixed voltage is emitted to the HV electrode 2 100 times using an electrostatic gun, and the voltage value when the spark is applied to the touch pattern analog electrode 3 is measured.

[repairability]

A double-sided adhesive tape having a width of 10 mm was attached between the two polycarbonate sheets (50 × 50 mm) so that one end portion became about 10 mm longer than the polycarbonate sheet. About 30 points Whether or not the one end portion was stretched after the clock was peeled off and the test was carried out, and the evaluation was performed using the following criteria.

"○": extensible peeling.

"△": When the elongation rate is slowed down, the peeling can be extended.

"X": A break in the belt is produced.

[Tensile strength and elongation (belt/substrate) and its aspect ratio]

The foamed resin substrate and the double-sided adhesive tape were each cut into a width of 10 mm and a length of 200 mm, and fixed to a tensile tester which set the gap between the chucks to 100 mm, and stretched at a speed of 300 mm/min to measure the breakage. Strength (N/10mm) and elongation (%). Further, the double-sided adhesive tape was cut so that the lateral length became 200 mm, and the strength and elongation were measured under the same conditions, and the aspect ratio of each measured value was calculated [(transverse strength and elongation in the transverse direction/longitudinal direction) 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 of the case where the load of the dial gauge is small (20 kPa) and the case of the larger case (100 kPa) is measured. . Then, the compression set ratio was obtained by a calculation formula of a compression deformation ratio (%) = [(thickness at 100 kPa pressure) - (thickness at 20 kPa pressure)] ÷ (thickness at a pressure of 20 kPa) × 100.

[Storage modulus and loss factor]

For the dynamic viscoelasticity measurement, a double-sided adhesive tape having a thickness of about 0.2 mm was inserted into the parallel disk of the measuring portion of the testing machine using a viscoelasticity tester at a frequency. The storage elastic modulus (G') and the loss elastic modulus (G") from -50 ° C to 150 ° C were measured at 1 Hz. Further, the loss coefficient was obtained by a calculation formula of loss coefficient (tan δ) = G" / G'.

[UE1]: Linear polyester-based urethane elastomer having low crystallinity (manufactured by Nippon Polyurethane Industry, trade name NIPPOLLAN 2304)

[UE2]: Linear polyester urethane elastomer of low crystallinity (manufactured by Sumika Bayer Urethane, trade name Desmocoll 406)

[UE3]: Linear polyester-based urethane elastomer with low crystallinity (manufactured by Sanyo Chemical Industries, Ltd., trade name Sanprene LQ-540)

[UE4]: Linear polyester-based urethane elastomer with low crystallinity (Sanyo Chemical Manufactured by an industrial company, trade name Sanprene IB-129)

[UE5]: a linear crystalline polyester urethane elastomer (manufactured by Sumika Bayer Urethane, trade name Desmocoll 176)

[UE6]: Highly crystalline linear polyester urethane elastomer (manufactured by Sumika Bayer Urethane, trade name Desmocoll 500)

"SIBS": Synthetic rubber containing styrene-isobutylene-styrene copolymer (manufactured by Kaneka Co., Ltd., trade name SIBSTAR)

[CR]: Isocyanate crosslinking agent (manufactured by Nippon Polyurethane Industry, trade name Coronate L)

[FA1]: Thermal expansion type foaming agent (manufactured by Matsumoto Oil & Fats Pharmaceutical Co., Ltd., trade name FN100SSD)

[FA2]: Intumescent foaming agent (manufactured by Japan Fillite Co., Ltd., trade name 920DE40d30)

[CB]: Carbon black (manufactured by Electric Chemical Industry Co., Ltd., trade name DENKA BLACK HS100)

<evaluation>

According to the results shown in Tables 1 to 3, it is understood that the adhesive tapes of Examples 1 to 8 are excellent in various characteristics. Further, the adhesive tapes of Examples 4 and 5 were inferior in repairability (elongation peeling property). However, in the adhesive tapes of Examples 4 and 5, since the tensile strength was low, the tape was broken at the time of elongation peeling. Further, the adhesive tapes of Examples 4 and 5 were excellent in other characteristics such as electrostatic resistance.

On the other hand, in the adhesive tapes of Comparative Examples 1 and 2, since the elastic elastic elongation recovery rate was too low, even if the tensile strength of the adhesive tape was sufficient, it was produced at the time of elongation peeling. The belt is broken. Comparative Examples 1 and 2 are different from Examples 4 and 5 in this respect.

The adhesive tape of Comparative Example 3 is an example of a PE-based foamed resin substrate having a large void diameter using bubbles, and has poor characteristics such as electrostatic resistance. The adhesive tape of Comparative Example 4 is an example in which a bubble-free PET film is used as a substrate, and characteristics such as impact resistance are inferior. The adhesive tape of Comparative Example 5 is an example of a substrate-free double-sided double-sided tape, and has poor impact resistance and the like.

(industrial availability)

For example, since the adhesive tape of the present invention has excellent water repellency, even if the machine is not in the water or a high water pressure is applied, it is difficult for the water to be immersed inside, and the malfunction of the machine can be reduced. Moreover, since it has excellent antistatic property, even if a user with static electricity touches the machine, it is difficult for static electricity to pass through the adhesive tape, and it is difficult to damage the built-in parts. Moreover, since it has excellent heat resistance and impact resistance, it is difficult to cause problems even if the machine is used or placed at a high temperature or subjected to an impact force. Moreover, since it has excellent repairability (elongation peeling property), the parts exchange work at the time of machine repair becomes easy. Therefore, the adhesive tape of the present invention is particularly composed of a smart phone, a mobile phone, an electronic notepad, a personal handy-phone system (PHS), a personal computer (PC), a digital camera, and music. It is very useful for the subsequent or fixed use of components of portable information terminal devices such as players, portable televisions, notebook computers, and game machines. In particular, a thinner and thinner adhesive tape is required for the protective panel of the information display unit (display, etc.) of a smart phone or a mobile phone, and the rear of the frame, or the fixing of the module (battery, etc.) of the device. It can be preferably used in its use.

Claims (10)

An adhesive tape comprising a foamed resin substrate comprising independent cells and an adhesive layer disposed on at least one side of the foamed resin substrate, wherein the independent cells have an average void diameter of 20 to 180 μm and a maximum gap When the diameter is 300 μm or less, the heating dimensional change rate of the adhesive tape is 100% ± 5% when the size before heating is 100%, and the rubber elastic elongation recovery rate of the adhesive tape is 85% or more. The adhesive tape of claim 1, wherein the foamed resin substrate comprises a polyurethane resin as a base polymer. The adhesive tape of claim 2, wherein the polyurethane resin is a low crystalline linear polyester urethane resin. The adhesive tape of claim 1, which is a double-sided adhesive tape provided with an adhesive layer on both sides of the foamed resin substrate. The adhesive tape of claim 1, wherein the tensile strength in the longitudinal direction and the transverse direction is 6.0 N/10 mm or more, and the tensile strength is 110% in the case where the tensile strength of the foamed resin substrate alone is 100%. In the case where one of the tensile strengths in the longitudinal direction and the transverse direction is 100%, the other tensile strength is 100% ± 15%, and the elongation in the longitudinal direction and the transverse direction is 300% or more. When one of the elongation at the time of breaking in the longitudinal direction and the transverse direction is set to 100%, the other elongation is within 100% ± 15%. The adhesive tape of claim 1, wherein the electrostatic resistance according to IEC6100 is 15 kV or more. The adhesive tape of claim 1, wherein the compression deformation ratio in the thickness direction is 3.0% or more. The adhesive tape of 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. The adhesive tape of claim 1 is used to form or fix a component of the portable information terminal machine. A method for producing an adhesive tape, which is a method for producing the adhesive tape of claim 1, and has a step of obtaining a foamed resin substrate by forming a closed cell by using a heat-expandable microcapsule and/or an expanded hollow filler.