TW201319209A - Double-sided pressure-sensitive adhesive tape - Google Patents

Abstract

A double-sided pressure-sensitive adhesive tape according to an embodiment contains a solvent-type acrylic copolymer, in which the total thickness of the tape is 150 mum or less and a mass increase after being dipped in artificial sebum under an atmosphere at 55 DEG C. for 3 days is 10% by mass or more and 150% by mass or less.

Description

Double-sided adhesive tape

The present invention relates to a double-sided adhesive tape. More specifically, the present invention relates to a double-sided adhesive tape for use in securing a member incorporated in a portable electronic device.

Portable mobile phones, PHS (Personal Handy-phone System), digital cameras, electronic notebooks, portable music players, handheld game consoles, smart phones, tablets, etc. In the machine, a double-sided display is used in the display panel disposed on the surface of the image display module and the subsequent fixing of various components or modules represented by a casing, a touch panel member, and an LCD (Liquid Crystal Display) member. Adhesive tape.

Mobile phones, PHSs, and smart phones have the following conditions: oil components such as sebum, cosmetics, hair styling agents, etc. are attached due to contact with the periphery of the ear or hair, and the joint portion of the panel and the casing is slowly used due to long-term use. Invade and invade to the double-sided adhesive tape. Moreover, in recent years, the portable electronic device that gives the touch panel function to the image display portion has increased, but the following problem has become a problem: sebum adhered from the finger intrudes into the inside of the member, and the double-sided adhesive tape for fixing the member is caused by sebum The adhesive properties are reduced and flaking, or the swell of the adhesive tape due to sebum.

In recent years, portable electronic devices have become thinner, and there has been a gradual demand for a thinner tape for a member to be used for a double-sided adhesive tape or a change in thickness direction of a touch panel member or the like. Especially for resistive touch panels In the fixation of ITO (Indium Tin Oxide) film/ITO glass, there is no significant change in the thickness direction.

Generally, an acrylic polymer of an acrylic type adhesive used for a double-sided adhesive tape has a property of absorbing sebum. When the amount of oil absorption is large, the thickness becomes thick due to swelling, and the thickness of the joined member changes, and the adhesive which expands from the thickness of the fixing to the image display region overflows, or in the fixed use of the resistive touch panel or the like. If the change in the thickness direction is uneven, a Newton's ring is generated and a defect occurs in the image display. Therefore, the change in the thickness direction is preferably small. If the thickness of the adhesive tape is thick, the amount of expansion caused by the oil is large, and the change in the thickness direction is increased.

Patent Document 1 discloses a measure for overflowing an adhesive agent caused by sebum in the width direction, but does not describe a change in the thickness direction.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-215355

Therefore, the problem to be solved by the present invention is to provide a double-sided adhesive tape which is less inflated by the intrusion of the oil component such as sebum, and has less expansion in the thickness direction, thereby utilizing When the components of the portable electronic device are fixed, even if they are used for a long period of time, they will not be caused by the invasion of the image display area of the adhesive tape due to the intrusion of oil components such as human sebum, or by the change in the thickness direction. The image of Newton's ring and other images shows the bad situation.

A certain aspect of the invention is a double-sided adhesive tape. The characteristics of the double-sided adhesive tape It is used in the fixed-use of components for portable electronic equipment, and it contains a solvent-based acrylic copolymer with a total thickness of 150 μm or less, and the mass increase after immersion in artificial sebum for 3 days in an environment of 55 ° C It is 10% by mass or more and 150% by mass or less.

In the double-sided adhesive tape of the above aspect, the solvent-type acrylic copolymer may have a weight average molecular weight of 400,000 or more and 700,000 or less. After being adhered to the transparent conductive film to be adhered, it was left in the state of 23 ° C and 50% RH for 72 hours without being immersed in artificial sebum, and then pulled at 300 mm/min in the 180° peeling direction. The peeling speed was peeled off, and the adhesive force (N/5 mm) at this time was set to A; after the transparent conductive film which was the adherend, the artificial sebum was wiped off after being immersed in artificial sebum at 55 ° C for 72 hours. , under conditions of 23 ° C, 50% RH for 1 hour, followed by peeling at a tensile speed of 300 mm / minute along the 180 ° peeling direction, the adhesion (N / 5 mm) at this time is set to B; At this time, B/A can also be 0.4 or more. Further, it can also be used for the subsequent adhesion of a transparent conductive film.

Furthermore, those who appropriately combine the above-described elements may also be included in the scope of the invention protected by the patent application of the present patent application.

The present invention is specifically described by the preferred embodiments, but the embodiments are intended to be illustrative only and not limiting.

Hereinafter, preferred embodiments of the present invention will be described. Furthermore, items other than the items specifically mentioned in the present specification and necessary for the implementation of the present invention can be understood as design items of the industry based on the prior art in the field. The present invention can be based on the content disclosed in the specification and the field Implemented with technical common sense.

The double-sided adhesive tape of the embodiment is used for component fixing of a portable electronic device. The double-sided adhesive tape contains a solvent-type acrylic copolymer as an adhesive composition, and has a total thickness of 150 μm or less, and the mass increase degree after immersion in artificial sebum for 3 days in an environment of 55 ° C is 10% by mass or more and 150% by mass. the following.

In the environment in which the double-sided adhesive tape of the present embodiment is immersed in artificial sebum for 3 days in an environment of 55 ° C, the mass increase degree (hereinafter, referred to as the oil absorption amount) is 10% by mass or more and 150% by mass or less. The oil absorption is preferably small, but the affinity between the acrylic adhesive and the oil is high, and it is difficult to prevent oil absorption. When the oil absorption amount is less than 10% by mass, the oil which cannot be absorbed by oil oozes out to the subsequent interface, whereby the adhesion of the double-sided adhesive tape is remarkably lowered. In particular, when the oil absorption amount is less than 0% by mass, the adhesive is eluted and the adhesive force is lowered, or the eluted adhesive overflows in the image display area. Further, when the eluted component is eluted in the electronic circuit, an adverse effect such as an increase in the resistance value occurs.

If the oil absorption amount is more than 150% by mass, when the double-sided adhesive tape is incorporated into the portable electronic device, the adhesive which is not completely limited to the allowable thickness overflows in the image display area, or the thickness is uneven. Generate a Newton ring. Further, when the oil absorption amount is more than 150% by mass, the adhesive of the double-sided adhesive tape is remarkably plasticized, and peeling occurs due to a decrease in adhesion or cohesive force.

The thickness of the double-sided adhesive tape is preferably changed to 20 μm or less. The portable electronic device is provided with a plurality of thickness directions in the structure, but in recent years, the thinning has been continuously developed, and the margin in the thickness direction is also reduced. If there is a variation in thickness greater than 20 μm, it is not limited to the thickness of the incorporation. Adhesive agent Newton rings occur as the display area overflows or due to uneven thickness.

If the total thickness of the double-sided adhesive tape is thicker than 150 μm, the amount of oil absorption is less than 20 μm even when immersed in sebum, resulting in a Newton ring or paste caused by a change in thickness direction. The agent oozes out. Therefore, the total thickness of the double-sided adhesive tape is preferably 150 μm or less, and more preferably 100 μm or less.

The oil absorption amount was determined based on the weight change before and after immersing the double-sided adhesive tape in the sebum, and was determined by the following procedure.

[Method of calculating oil absorption]

The double-sided adhesive tape was cut into a width of 50 mm and a length of 100 mm, and the weight (mass: Wa) of the sample after removing the double-sided release paper was measured, and the double-sided whole of the sample was immersed at 55 ° C. Immerse in artificial sebum for 3 days under the environment. After immersion for 3 days, the oil adhering to the surface of the double-sided adhesive tape was sufficiently sucked up using an oil absorbing film (for example, manufactured by Kanebo Cosmetics Co., Ltd.; Petit garden oil absorbing film N) until no discoloration of the oil absorbing film. The weight (mass: Wb) of the sample of the oil sucking the surface was measured in this manner. The actual oil absorption is calculated using the values and by the following formula.

Actual oil absorption (% by mass) = [(Wb-Wa)/Wa] × 100

Here, the artificial sebum refers to a user who is a substitute for sebum, and is not particularly limited as long as it has physical properties similar to sebum, and is preferably triolein or tripalmitoic acid. a mixture of a triglyceride such as glyceryl ester (Tripalmitin), an ester such as squalene or myristyl octadecyl ester, or a fatty acid such as oleic acid, and preferably 3 to 50% by mass of triglyceride as the mixing ratio. Squalene 5~20% by mass, ester 5~50 quality A mixture of 5% and 35% by mass of a fatty acid, and particularly preferably an artificial sebum having the following composition.

Artificial sebum: triglyceride triglyceride 33.3 mass%, oleic acid 20.0 mass%, squalene 13.3 mass%, nutmeg octadecyl ester 33.4% by mass

The double-sided adhesive tape of the embodiment contains a solvent-type acrylic copolymer as an adhesive composition. In the present specification, the "solvent-type acrylic copolymer" means an acrylic copolymer obtained by solution polymerization. The solvent-based acrylic copolymer is obtained by copolymerization using a known polymerization method by solution polymerization. Further, in the case of an acrylic copolymer obtained by a polymerization method other than solution polymerization, for example, an acrylic copolymer obtained by polymerization by emulsion polymerization, when immersed in artificial sebum, adhesion occurs. The layer will dissolve. Therefore, a solvent-type acrylic copolymer is suitable as an adhesive composition. When a solvent-based acrylic copolymer is used as the adhesive composition in place of, for example, a synthetic rubber-based or natural rubber-based adhesive composition, the adhesive layer is eluted when immersed in artificial sebum. Therefore, a solvent-type acrylic copolymer is suitable as an adhesive composition for the purpose of the present invention.

The monomer constituting the solvent-type acrylic copolymer is preferably selected such that the glass transition temperature of the solvent-type acrylic copolymer is from -56 ° C to -20 ° C. By adjusting the glass transition temperature of the solvent-type acrylic copolymer to within this range, it is possible to have the adhesiveness or stickiness as a basic adhesive property required for the double-sided adhesive tape, or to be used as an adherend. The foam is a fixed surface of the rough surface.

Here, the Tg (glass transition temperature) refers to the Tg of the homopolymer (Homopolymer) of each monomer constituting the monomer raw material and the mass fraction (copolymerization ratio) of the monomer and according to FOX (Fast Oxidation). System, rapid oxidation system) to find the value. The Tg of the homopolymer may be a value described in the "Adhesive Technology Manual" of Nikkan Kogyo Shimbun Co., Ltd., which is a known material, or the "Polymer Handbook" of Wiley-Interscience. For example, the Tg of the homopolymer in the art disclosed herein is set to: -70 ° C for 2-ethylhexyl acrylate, -54 ° C for butyl acrylate, and 8 ° C for methyl acrylate. Methyl methacrylate was used at 105 ° C, cyclohexyl methacrylate was used at 66 ° C, vinyl acetate was used at 32 ° C, acrylic acid was used at 106 ° C, and methacrylic acid was used at 228 ° C. Further, the Tg of the homopolymer of the monomer not described in the above-mentioned known materials is a value obtained by the following method. Specifically, the target monomer was subjected to solution polymerization to synthesize a homopolymer having an average polymerization ratio of 5 × 10 ⁴ to 10 × 10 ⁴ , and the obtained homopolymer solution was cast and dried on a release liner to prepare a test sample. For the test sample, the differential scanning calorimeter (DSC, Differential Scanning Calorimeter) and model "DSC6220" were used to change the temperature from -80 °C to 280 at a heating rate of 10 °C/min. Differential scanning calorimetry was performed at ° C using the initial endothermic onset temperature as the Tg of the homopolymer.

When the glass transition temperature of the solvent-type acrylic copolymer is less than -56 ° C, the cohesive force is insufficient, and a residue of the paste occurs when it is peeled off after a long time of bonding. Further, when the glass transition temperature of the solvent-based acrylic copolymer is higher than -20 ° C, the adhesion to the adherend is lowered, or the adhesion to the curved curved surface is lowered.

The monomer constituting the solvent-based acrylic copolymer preferably has a content of alkyl (meth)acrylate having a carbon number of 1 to 4 in an alkyl group of 80.0% by mass or more, and a radical polymerizable property having at least one carboxyl group. The content of the monomer is from 0.5 to 10.0% by mass, and the content of the other copolymerizable monomer is 19.5% by mass or less. When the content of the (meth)acrylic acid alkyl ester having 1 to 4 carbon atoms in the alkyl group constituting the solvent-based acrylic copolymer is 80.0% by mass or more, the oil absorption amount can be adjusted so as to be 10~ 150% by mass. Further, the monomer constituting the solvent-type acrylic copolymer is preferably a radical polymerization of at least one carboxyl group in which the content of the alkyl (meth)acrylate having a carbon number of 1 to 4 is 90.0% by mass or more. The content of the monomer is 0.5 to 10.0% by mass, and the content of the other copolymerizable monomer is 9.5 mass% or less. In the present specification, the term "(meth)acrylic acid" means "acrylic acid" and/or "methacrylic acid".

Examples of the alkyl (meth)acrylate having an alkyl group having 1 to 4 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, and isopropyl (meth)acrylate. A propyl acrylate, a n-butyl (meth) acrylate, an isobutyl (meth) acrylate, a tert-butyl (meth) acrylate, etc., may be used alone or in combination of two or more. use. More preferably, it is methyl acrylate, ethyl acrylate, n-butyl acrylate, and further preferably methyl acrylate or n-butyl acrylate.

The solvent-type acrylic copolymer preferably has a content of a radical polymerizable monomer having at least one carboxyl group as a functional group reactive with the crosslinking agent described below, and is 0.5 to 10.0% by mass.

Specific examples of the radical polymerizable monomer having at least one carboxyl group include (meth)acrylic acid, itaconic anhydride, itaconic acid, and butylene. Acid, maleic anhydride, maleic acid, 2-(methyl)propenyloxyethyl succinate, 2-propenyloxyethyl phthalate, hexahydrophthalic acid 2 - (meth) propylene methoxyethyl ester, etc., may be used alone or in combination of two or more. Preferred is acrylic acid.

The amount of the radically polymerizable monomer having at least one carboxyl group is preferably from 0.5 to 10.0% by mass based on 100% by mass of the total monomers. When the amount of the radically polymerizable monomer having at least one carboxyl group is 0.5% by mass or more, the monomer having a carboxyl group can sufficiently exhibit the function as a crosslinking point and suppress the adhesive in the obtained polymer. When the cohesive force of the layer is lowered, the residue of the paste is less likely to occur when peeling off after a long time of bonding. Further, there is a tendency that the stability of the solution as a water-dispersible pressure-sensitive adhesive is lowered. On the other hand, when the amount of the radically polymerizable monomer having at least one carboxyl group is 10.0% by mass or less, the glass transition temperature is not excessively increased, and the adhesion to the adherend can be suppressed from being lowered or bent. The fit of the surface is reduced.

As another monomer copolymerizable with the above-mentioned monomer constituting the solvent-type acrylic copolymer, a compound called a α, β-unsaturated compound which retains a polymerizable double bond in the molecule, may be mentioned as a copolymerization or adhesion. In terms of physical properties, an acrylic monomer is preferred.

For example, the following acrylic monomers are mentioned: 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, (A) Isodecyl acrylate, n-pentyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate Ester, octadecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, etc. Alkyl olefinates; cyclohexyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, phenyl (meth) acrylate, phenoxy (meth) acrylate (meth)acrylic acid cyclic esters such as ester; allyl (meth)acrylate, 1-methylallyl (meth)acrylate, 2-methylallyl (meth)acrylate, (methyl) ) 1-butenyl acrylate, 2-butenyl (meth) acrylate, 3-butenyl (meth) acrylate, 1,3-dimethyl-3-butenyl (meth) acrylate, ( 2-Chloropropyl methacrylate, 3-chloroallyl (meth)acrylate, o-allyl (meth)acrylate, 2-(allyloxy)ethyl (meth)acrylate , (meth)acrylic allyl niprate, citronellyl (meth) acrylate, geranyl (meth) acrylate, rose (meth) acrylate, cinnamyl (meth) acrylate, (methyl (meth)acrylates containing unsaturated groups such as vinyl acrylate; glycidyl (meth)acrylate, (3,4-epoxycyclohexyl)methyl (meth)acrylate, (meth)acrylic acid a (meth) acrylate containing a heterocyclic ring such as tetrahydrofurfuryl ester; N-methylamine (meth) acrylate Base ethyl ester, N-tributylaminoethyl (meth)acrylate, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl methacrylate, etc. Amino (meth) acrylates; 3-methacryloxypropyltrimethoxydecane, 3-methylpropenyloxypropyltriethoxydecane, 3-methylpropenyloxy Alkoxydecane, 3-methylpropenyloxypropylmethyldimethoxydecane, 3-methylpropenyloxypropylmethyldiethoxydecane, etc. Base (meth) acrylates; (meth)acrylic acid derivatives such as methoxyethyl (meth)acrylate and ethylene oxide adduct of (meth)acrylic acid; perfluoroethyl (meth)acrylate and (meth)acrylic acid Fluoropropyl ester, perfluorobutyl (meth)acrylate, perfluoroalkyl (meth)acrylate such as perfluorooctyl (meth)acrylate; trimethylolpropane trimethacrylate, pentaerythritol trimethyl Acrylate, 1,1,1-trimethylolethane diacrylate, 1,1,1-trimethylolethane triacrylate, 1,1,1-trimethylolpropane triacrylate Polyfunctional (meth) acrylates; perfluoromethyl (meth) acrylate, trifluoromethyl methyl (meth) acrylate, 2-trifluoromethyl ethyl (meth) acrylate, (methyl) Di-perfluoromethyl methyl acrylate, 2-perfluoroethyl ethyl (meth) acrylate, 2-perfluoromethyl-2-perfluoroethyl methyl (meth) acrylate, (meth) acrylate Trisperfluoromethyl methyl ester, 2-perfluoroethyl-2-perfluorobutyl ethyl (meth)acrylate, 2-perfluorohexylethyl (meth)acrylate, 2-(meth)acrylic acid Fluorinated ethyl ester, 2-(perfluorohexadecyl)ethyl (meth)acrylate, etc. Acrylates; but are not particularly limited to these. These may be used alone or in combination.

Further, other monomers such as a vinyl monomer copolymerizable with the acrylic monomer may also be used.

For example: styrene, α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 1-butylstyrene, chlorostyrene, styrene An aromatic vinyl monomer such as a sulfonic acid or a sodium salt thereof; a trioxane such as a vinyl trimethoxy decane or a vinyl triethoxy decane; a vinyl-based monomer such as a methoxyalkyl group; a vinyl-based monomer containing fluorene such as γ-(methacryloxypropyl)trimethoxynonane; and a nitrile group such as acrylonitrile or methacrylonitrile; Vinyl monomers; vinyl monomers containing amidino group such as acrylamide or methacrylamide; vinyl acetate, vinyl propionate, vinyl pivalate, vinyl benzoate, A vinyl ester such as vinyl cinnamate; a fluorine-containing monomer such as perfluoroethylene, perfluoropropene or vinylidene fluoride; but it is not particularly limited thereto. One of these may be used alone or in combination of two or more. Preferred is vinyl acetate.

Further, in terms of an increase in oil absorption, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, The alkyl (meth)acrylate having an alkyl group having 8 or more carbon atoms such as an alkyl (meth)acrylate is preferably contained in an amount of 10% by mass or less, and more preferably is not contained.

As the initiator for the above polymerization method, for example, 2,2'-azobisisobutyronitrile and 2,2-azobis(4-methoxy-2,4-dimethylvaleronitrile can be cited. ), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-dimethylbutyronitrile), 1,1'-azobis(cyclo) Hexane-1-carbonitrile), 2,2'-azo (2,4,4-trimethylpentane), dimethyl 2,2'-azobis(2-methylpropionate) Azo system, benzamidine peroxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, tert-butyl peroxybenzoate, dicumyl peroxide, 1,1- Bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxide) ring An oil-soluble initiator such as a peroxide such as dodecane may be used alone or in combination of two or more. The amount of the initiator to be used may be an amount generally used in the above polymerization method, and is, for example, 0.01 to 1.0% by mass based on 100% by mass of the monomer.

Further, in order to impart a suitable molecular weight to the obtained polymer, a chain transfer agent may be used in the above polymerization. As the chain transfer agent, a conventional chain transfer agent may be mentioned, for example, lauryl mercaptan, glycidyl mercaptan, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1 - Propanol, an α-methylstyrene dimer, etc., may be used alone or in combination of two or more. The amount of the chain transfer agent to be used may be an amount generally used in the above polymerization method, and is, for example, about 0.01 to 15% by mass based on 100% by mass of the monomer.

The weight average molecular weight of the solvent-type acrylic copolymer is preferably in the range of 400,000 to 700,000. When the weight average molecular weight of the solvent-type acrylic copolymer is 400,000 or more, the cohesive force of the pressure-sensitive adhesive layer is likely to be lowered, and the residue of the paste is less likely to occur when peeling is performed after bonding for a long period of time. When the weight average molecular weight of the solvent-type acrylic copolymer is 700,000 or less, the cohesive force of the adhesive layer does not become excessively high, and the decrease in the adhesion to the adherend or the decrease in the adhesion to the curved curved surface can be suppressed. The weight average molecular weight of the solvent-type acrylic copolymer is more preferably from 400,000 to 650,000, and still more preferably from 400,000 to 600,000.

In addition, the weight average molecular weight as described in the present specification means that it is obtained by extraction by tetrahydrofuran (hereinafter, also referred to as THF) by measurement by GPC (Gel Permeation Chromatography). The polystyrene-equivalent weight average molecular weight obtained by obtaining a soluble portion (also referred to as a weight average molecular weight of the sol portion) of the non-volatile portion of the acrylic copolymer.

Further, the adhesive composition contained in the double-sided adhesive tape preferably has a gel fraction of 20 to 90%. When the gel fraction of the adhesive composition is 20% or more, the cohesive force is further improved, and when immersed in artificial sebum, the elution can be further suppressed. Further, when the gel fraction of the adhesive composition is 90% or less, the adhesion to the adherend can be improved and the adhesion to the curved curved surface can be further improved. The gel fraction of the adhesive composition is more preferably from 20% to 70%, further preferably from 20% to 60%.

In addition, the gel fraction referred to in the present specification refers to a mass ratio of an insoluble portion remaining by leaving a nonvolatile portion of the water-dispersible pressure-sensitive adhesive composition after extraction with ethyl acetate, and is calculated by the following method.

Approximately 0.1 g of the adhesive applied to the release liner and dried was coated on a Teflon (registered trademark) sheet having a diameter of 0.2 μm (trade name "NTF1122", manufactured by Nitto Denko Corporation), using a kite line. Bundle and place in a 50 ml container filled with ethyl acetate at a ratio and allow to stand at room temperature for 1 week. Thereafter, the Teflon sheet was taken out from the container, and the mass of the sample which was removed by drying in a dryer at 130 ° C for 2 hours to remove ethyl acetate was measured, and the gel fraction was calculated according to the following formula.

Gel fraction (%) = {(Teflon + kite line after drying + mass of gel) - (initial quality of Teflon + kite line)} / {(Initial Teflon + Kite Line + Adhesive Quality) - (Initial Teflon + Kite Line Quality)} × 100

The method of increasing the gel fraction of the adhesive composition is not particularly limited, and for example, a crosslinking agent may be added to the above polymer. The crosslinking agent is not particularly limited, and may be a conventionally known one, and examples thereof include an epoxy-based or isocyanate-based compound such as polyethylene glycol diglycidyl ether. An oxazoline type, an aziridine type, a hydrophilically treated carbodiimide type, an active methylol group, a reactive alkoxymethyl group, a metal chelate compound, a decane coupling agent, or the like. These crosslinking agents may be used singly or in combination of two or more. The crosslinking agent is usually used in an amount of 0.001 to 10 parts by mass, preferably 0.001 to 5 parts by mass, based on 100 parts by mass of the polymer.

In the above adhesive composition, an adhesion-imparting agent can also be formulated. As the adhesion-imparting agent, for example, one or two or more kinds of various adhesion-imparting resins selected from the group consisting of a rosin-based resin, a rosin-based resin, a petroleum-based resin, a terpene-based resin, a phenol-based resin, and a ketone-based resin can be used. The amount of the adhesion-imparting agent added is from 10 to 50% by mass, preferably from 15 to 40% by mass, based on 100% by mass of the solvent-based acrylic copolymer.

Next, a more specific aspect of the double-sided adhesive tape of the embodiment will be described.

The first aspect of the double-sided adhesive tape has a multilayer structure in which an adhesive layer formed of the above-described adhesive composition is laminated on both surfaces of a non-releasable sheet-like substrate (adhesive layer/non-releasable sheet) Substrate/adhesive layer). Further, a release sheet-like substrate is laminated on the adhesive surface of each of the adhesive layers for the double-sided adhesive tape before use.

The second aspect of the double-sided adhesive tape has a single-layer structure of a so-called coreless material including only an adhesive layer. A peelable sheet-like substrate is laminated on each of the adhesive faces of the adhesive layer for the double-sided adhesive tape before use.

Examples of the non-releasable sheet-like substrate include a polyolefin resin such as polyethylene, a polyester resin such as polyethylene terephthalate, a vinyl acetate resin, a polyimide resin, and a fluorine system. Resin, plastic film including plastic such as eucalyptus; paper such as kraft paper, Japanese paper; rubber sheet including natural rubber, butyl rubber, etc.; foaming of polyurethane, polychloroprene rubber, etc. A foamed sheet; a metal foil such as an aluminum foil or a copper foil; a composite of the above. Further, these may be subjected to a surface treatment such as corona treatment on one side or both sides.

The release sheet-form substrate is also referred to as a separator. Examples of such a release sheet-like substrate include a film of cellophane, kraft paper, Clay Coated Paper, and laminated polyethylene. Paper, a paper coated with a resin such as polyvinyl alcohol or an acrylate copolymer, or a fluororesin or a enamel resin as a release agent on a synthetic resin film such as polyester or polypropylene, but there is no particular limited.

Further, in the case where a peelable sheet-like substrate is laminated on the adhesive layer of the double-sided adhesive tape, in order to improve the workability, it is preferable to select the peeling force of the peelable sheet-like base material which is laminated on both sides. Respective release sheet substrates. For example, the peeling sheet-like base material which is bonded to the surface of the double-sided adhesive tape first has a peeling force which is smaller than the peeling force of the peelable sheet-like base material on the surface side which is subsequently bonded. The material is improved in workability.

The double-sided adhesive tape of the embodiment can be obtained by various methods.

For example, it can be obtained by coating an adhesive solution on one side of a non-releasable sheet-like substrate and drying it, and superposing a peelable sheet-like substrate on the surface of the formed adhesive layer; or a release sheet. One side of a substrate The cloth adhesive solution is dried and a non-releasable sheet-like substrate is superposed on the surface of the formed adhesive layer.

The coating device used when applying the pressure-sensitive adhesive to various sheet-like substrates is not particularly limited, and examples of the coating device that is generally used include a roll blade coater and a die coater. , roll coater, bar coater, gravure roll coater, reverse roll coater, dip coating, knife coater, and the like.

Further, the drying conditions may be such that the solvent or the residual monomer of the adhesive solution is dried and removed during drying, and the functional group of the solvent-type acrylic copolymer reacts with the crosslinking agent to form a crosslink. structure. The drying conditions are, for example, preferably 60 to 120 ° C for about 1 to 5 minutes, but are not limited thereto. After drying, the adhesive layer may be immersed in a state in which the adhesive layer is sandwiched between the sheet-like substrates, and the crosslinking reaction may be carried out.

Further, the double-sided adhesive tape of the embodiment may be provided in a roll shape, may be provided in a single piece state, or may be further processed into various shapes.

The double-sided adhesive tape of the embodiment is preferably placed in a state of not immersed in artificial sebum at 23 ° C and 50% RH for 72 hours after being adhered to the transparent conductive film as the adherend, and thereafter. Peeling at a tensile speed of 300 mm/min in a 180° peeling direction, and setting the adhesion force (N/5 mm) at this time to A; and after adhering to the transparent conductive film as the adherend, at 55 ° C After immersing in artificial sebum for 72 hours, the artificial sebum was wiped off, and it was allowed to stand at 23 ° C and 50% RH for 1 hour, and then peeled off at a stretching speed of 300 mm/min in the 180° peeling direction. The adhesive force (N/5 mm) is set to B; at this time, B/A is 0.4 or more. If B/A is 0.4 As described above, even if the oil component such as sebum enters, sufficient adhesion can be maintained.

In the double-sided adhesive tape of the embodiment, the change in the expansion or thickness direction caused by the intrusion of the oil component such as sebum is greatly improved as compared with the conventional double-sided adhesive tape. Therefore, it can be particularly preferably used for the subsequent adhesion of a transparent conductive film such as a touch panel. The double-sided adhesive tape of the embodiment is used for a transparent conductive film such as a touch panel, whereby the change in the thickness direction of the transparent conductive film can be reduced and the transparent conductive film can be suppressed even after long-term use. The accuracy of touch detection is reduced.

[Examples]

Hereinafter, an embodiment and the like which specifically show the configuration and effects of the present embodiment will be described, but the present invention is not limited to these. In the description of the examples and the like, in the case of "parts" and "%", "parts by mass" and "mass%" are respectively indicated unless otherwise specified.

(acrylic copolymer I)

2.9 parts by mass of acrylic acid, 5 parts by mass of vinyl acetate, 92 parts by mass of butyl acrylate, 0.1 parts by mass of hydroxyethyl acrylate, and a reaction vessel having a stirrer, a reflux condenser, a thermometer, a drip device, and a nitrogen introduction tube; 30 parts by mass of ethyl acetate and 120 parts by mass of toluene as a polymerization solvent were stirred for 2 hours while introducing nitrogen gas.

After removing oxygen in the polymerization system in this manner, 0.2 part by mass of AIBN (2,2'-azobisisobutyronitrile) was added, and the temperature was raised to 60 ° C to carry out a polymerization reaction for 6 hours. The obtained polymer had a solid content of 40.0% and a weight average molecular weight of 500,000.

(acrylic copolymer II)

5 parts by mass of acrylic acid, 95 parts by mass of butyl acrylate, and 150 parts by mass of toluene as a polymerization solvent were placed in a reaction vessel having a stirrer, a reflux condenser, a thermometer, a drip device, and a nitrogen gas introduction tube, and nitrogen gas was introduced while stirring. hour.

After the oxygen in the polymerization system was removed in this manner, 0.2 part by mass of benzoyl peroxide was added, and the temperature was raised to 60 ° C to carry out a polymerization reaction for 6 hours. The obtained polymer had a solid content of 40.0% and a weight average molecular weight of 600,000.

(acrylic copolymer III)

3 parts by mass of acrylic acid, 70 parts by mass of butyl acrylate, 27 parts by mass of 2-ethylhexyl acrylate, and 4-hydroxybutyl acrylate were placed in a reaction vessel having a stirrer, a reflux condenser, a thermometer, a dropping device, and a nitrogen introduction tube. 0.05 parts by mass of the base ester and 135 parts by mass of toluene as a polymerization solvent were stirred while introducing nitrogen gas for 2 hours.

After removing oxygen in the polymerization system in this manner, 0.1 part by mass of AIBN (2,2'-azobisisobutyronitrile) was added, and the temperature was raised to 60 ° C to carry out a polymerization reaction for 6 hours. The obtained polymer had a solid content of 42.5% and a weight average molecular weight of 400,000.

(acrylic copolymer IV)

10 parts by mass of acrylic acid, 90 parts by mass of 2-ethylhexyl acrylate, and 190 parts by mass of ethyl acetate as a polymerization solvent are placed in a reaction vessel having a stirrer, a reflux condenser, a thermometer, a drip device, and a nitrogen introduction tube. The mixture was stirred for 2 hours while introducing nitrogen gas.

After removing oxygen in the polymerization system in this way, adding benzamidine peroxide 0.6 parts by mass, and the temperature was raised to 60 ° C to carry out a polymerization reaction for 6 hours. The obtained polymer had a solid content of 34.4% and a weight average molecular weight of 1.2 million.

(acrylic copolymer V)

Distilled water and emulsifier (trade name "Latemul E-118B", manufactured by Kao Corporation; hereinafter, simply referred to as "emulsifier") in a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a drip device, and a nitrogen inlet tube 0.1 part by mass, and nitrogen gas was introduced while stirring at 60 ° C for 1 hour or more while introducing nitrogen gas. 2-2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate (trade name "VA-057" and manufactured by Wako Pure Chemical Industries, Ltd.) was added to the reaction vessel. The mass fraction is used as a polymerization initiator. This was maintained at 60 ° C, and it took 4 hours to slowly dropwise add a monomer emulsion to carry out an emulsion polymerization reaction. As the monomer emulsion, 85 parts by mass of 2-ethylhexyl acrylate, 13 parts by mass of methyl acrylate, 1.25 parts by mass of acrylic acid, 0.75 parts by mass of methacrylic acid, and 3-methylpropenyloxypropyltrimethoxy were used. 0.020 parts by mass of a decane (trade name "KBM-503", manufactured by Shin-Etsu Chemical Co., Ltd.), 0.02 parts by mass of dodecanethiol, and 1.9 parts by mass of an emulsifier were added to distilled water to be emulsified. After the monomer emulsion was added dropwise, the mixture was further kept at 60 ° C for 3 hours to stop the heating. Then, 0.75 parts by mass of a 10% aqueous hydrogen peroxide solution was added per 100 parts by mass of the monomer, and after 5 minutes, 0.5 part by mass of ascorbic acid was added per 100 parts by mass of the monomer. After cooling to room temperature, 10% aqueous ammonia was added to adjust the liquidity to pH 7.2, and an acrylic polymer emulsion having a solid content of 57% was obtained. The weight fraction of the sol portion was 530,000.

(Rubber adhesive I)

The SIS block copolymer (trade name "JSR SIS5505P", manufactured by JSR Shell Elastomer Co., Ltd., was used in a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a drip device, and a nitrogen gas introduction tube at 60 ° C, and the solid content was 100%) 100 g, petroleum resin (trade name "Quintone C200S", manufactured by Japan ZEON Co., Ltd., solid content: 100%) 90 g, terpene resin (trade name "YS resin TO-L", manufactured by Yasuhara Chemical Co., Ltd., solid type The composition was 100%) 10 g and 300 g of toluene were stirred for 5 hours to prepare an adhesive solution having a solid content of 40%.

(Example 1)

Acrylic copolymer I 100 g, rosin resin (trade name "Pensel D-125", manufactured by Arakawa Chemical Co., Ltd., solid content: 100%) 4 g, rosin resin (trade name "Super Ester A-100" Arakawa Chemical Industry Co., Ltd. Manufactured, solid content: 100%) 4 g, rosin resin (trade name "Forarin 8020F", manufactured by Eastman Chemical Co., Ltd., solid content: 100%) 2 g, indophenol resin (trade name "Tamanol 803L" manufactured by Arakawa Chemical Industry Co., Ltd. The solid content is 100%) 6 g, and the mixture is sufficiently stirred until the resin is dissolved. To the adjustment adhesive solution, 1.1 g of an aromatic polyisocyanate (trade name "Coronate L", manufactured by Nippon Polyurethane Co., Ltd., solid content: 75%) was added as a crosslinking agent and sufficiently stirred. The solvent-based adhesive solution (adhesive 1) was applied to a treated surface of a PET separator (trade name "Diafoil MRF38", manufactured by Mitsubishi Plastics Co., Ltd., thickness: 38 μm) to a dry coating thickness of 34 μm. Coating, drying at 100 ° C for 2 minutes and laminating a film substrate including polyester on the adhesive layer (trade name "Lumirror #12S10", manufactured by Toray, thickness Step 12 is obtained for 12 μm).

Then, the above-mentioned adhesive was applied to a treated surface of a PET separator (trade name "#75 Serapiru MDA(S)", manufactured by Toray Membrane Processing Co., Ltd., thickness: 75 μm) so that the dry coating film thickness was 34 μm. 1. Drying at 100 ° C for 2 minutes, and bonding the adhesive layer to the PET substrate surface of the above step 1 to make a double-sided adhesive tape having a total thickness of 80 μm. The obtained double-sided adhesive tape was evaluated in an environment of 50 ° C for 24 hours.

(Example 2)

An acrylic polyisocyanate (trade name "Coronate L", manufactured by Nippon Polyurethane Co., Ltd., solid content of 75%) 1.0 g of an adhesive is added to the acrylic copolymer I 100 g to form a film substrate as a substrate. (The product name "Lumirror #5AF53", manufactured by Toray Co., Ltd., thickness: 5 μm) was applied so that the thickness of the dried coating film on both sides was 27.5 μm, and the total thickness was made in the same manner as in Example 1. 60 μm double-sided adhesive tape.

(Example 3)

An adhesive of 0.5 g of an aromatic polyisocyanate (trade name "Coronate L", manufactured by Nippon Polyurethane Co., Ltd., solid content: 75%) was added to 100 g of the acrylic copolymer II, and Example 2 was used. A double-sided adhesive tape having a total thickness of 60 μm was produced in the same manner.

(Example 4)

For the acrylic copolymer II 100 g, a nonylphenol resin (trade name "YS Polystar S-145", manufactured by Yasuhara Chemical Co., Ltd., 100% solid content) was added, and 8 g of aromatic polyisocyanate (trade name "Coronate" was used. A double-sided adhesive tape having a total thickness of 60 μm was produced in the same manner as in Example 2 except that an adhesive of 7 g of a solid content of 75% was produced by Nippon Polyurethane Industries Co., Ltd.

(Example 5)

For the acrylic copolymer II 100 g, an indophenol resin (trade name "YS Polystar S-145", manufactured by Yasuhara Chemical Co., Ltd., 100% solid content) was used, and an epoxy crosslinking agent (trade name " A double-sided adhesive tape having a total thickness of 60 μm was produced in the same manner as in Example 2 except that TETRAD-C, manufactured by Mitsubishi Gas Chemical Co., Ltd., having a solid content of 100% by weight of 0.02 g.

(Comparative Example 1)

Used in the acrylic copolymer III 100 g, rosin resin (trade name "Pensel D-125", manufactured by Arakawa Chemical Industries Co., Ltd., solid content 100%), 4 g, indophenol resin (trade name "YS Polystar S-" 145", manufactured by Yasuhara Chemical Co., Ltd., having a solid content of 100%) 12.8 g, an aromatic polyisocyanate (trade name "Coronate L", manufactured by Nippon Polyurethane Industry Co., Ltd., solid content of 75%) 1.1 g of adhesive, used A film substrate (trade name "Lumirror #25S105", manufactured by Toray Co., Ltd., thickness: 25 μm) was used as a substrate, and the thickness of the dried coating film on both sides was 27.5 μm, and the examples were the same as in the examples. 1 A double-sided adhesive tape having a total thickness of 80 μm was produced in the same manner.

(Comparative Example 2)

Used in the addition of aromatic polyisocyanate to the acrylic copolymer IV 100 g (trade name "Coronate L", manufactured by Nippon Polyurethane Industry Co., Ltd., solid A double-sided adhesive tape having a total thickness of 60 μm was produced in the same manner as in Example 2 except that the amount of the composition was 75% by weight of 0.5 g.

(Comparative Example 3)

The total thickness was changed in the same manner as in Example 2 except that the amount of the aromatic polyisocyanate (trade name "Coronate L", manufactured by Nippon Polyurethane Co., Ltd., solid content of 75%) was changed to 0.4 g. 60 μm double-sided adhesive tape.

(Comparative Example 4)

An acrylic resin (trade name "YS Polystar S-145", manufactured by Yasuhara Chemical Co., Ltd., 100% solid content) was added to the acrylic copolymer IV 100 g, and an aromatic polyisocyanate (trade name "Coronate L" was used. A double-sided adhesive tape having a total thickness of 60 μm was produced in the same manner as in Example 2 except that an adhesive of 7 g of a solid content of 75% was produced by Nippon Polyurethane Industries Co., Ltd.

(Comparative Example 5)

An adhesive of 1.1 g of an aromatic polyisocyanate (trade name "Coronate L", manufactured by Nippon Polyurethane Co., Ltd., solid content: 75%) was added to the acrylic copolymer V 100 g, and Example 2 was used. A double-sided adhesive tape having a total thickness of 60 μm was produced in the same manner.

(Comparative Example 6)

A film substrate (trade name "Lumirror #25S105", manufactured by Toray Co., Ltd., thickness: 25 μm) was used as a substrate, and the thickness of the dried coating film on both sides was 67.5 μm, and the same was carried out. In the same manner as in Example 1, a double-sided adhesive tape having a total thickness of 160 μm was produced.

(Comparative Example 7)

A double-sided adhesive tape having a total thickness of 60 μm was produced in the same manner as in Example 2 except that the rubber-based adhesive I was used as the adhesive.

(Comparative Example 8)

As an adhesive, a water-dispersible rosin resin (trade name "KE-802", manufactured by Arakawa Chemical Industries Co., Ltd., solid content: 50.1%) was added to the acrylic adhesive IVI 100 g to 34.2 g, and the viscosity was 10 Pa. A double-sided adhesive tape having a total thickness of 60 μm was produced in the same manner as in Example 2 except that the adhesive of polyacrylic acid as a tackifier was adjusted in the manner of s.

The double-sided adhesive tape obtained above was supplied to the following evaluation test. The results obtained are shown in Tables 1 and 2.

[adhesion]

The release liner of one side of the double-sided adhesive tape (38 μm PET spacer side) was peeled off and attached to a 25 μm thick polyethylene terephthalate (PET) film for support. The supported double-sided adhesive tape was cut into a size of 5 mm in width and 100 mm in length to prepare a sample piece. The release liner was peeled off from the other side of the sample piece, and the sample piece was pressure-bonded to the adherend so that the 2 k g roller was reciprocated once. The adherend was an ITO-treated surface of an ITO film (trade name "V270L-TFMP", manufactured by Nitto Denko Corporation) at 140 ° C for 9 hours.

When not immersed in artificial sebum, after 72 hours from the attachment, the tensile tester was used at a tensile speed of 300 mm at a temperature of 23 ° C and a relative humidity of 50%. Minute, the angle of stretching is 180° The adhesion force A (N/5 mm) was measured under the conditions.

In the case of immersion in artificial sebum, the attached sample piece was immersed in artificial sebum and allowed to stand at 55 ° C for 72 hours. The artificial sebum adhered to the surface of the sample piece after the passage was sufficiently wiped off, and left at a temperature of 23 ° C and a relative humidity of 50% for 1 hour, and then subjected to a tensile tester at a tensile speed of 300 mm. The adhesion force B (N/5 mm) was measured under the conditions of a stretching angle of 180°.

[oil absorption]

The measurement was carried out by the method described in the above [Oil absorption amount calculation method]. Further, as the artificial sebum, the following components were used.

Artificial sebum: triglyceride triglyceride 33.3 mass%, oleic acid 20.0 mass%, squalene 13.3 mass%, nutmeg octadecyl ester 33.4% by mass

[thickness]

The thickness of the sample before and after the impregnation of the sample was measured using a 1/1000 dial gauge.

The oil absorption amounts of Comparative Examples 7 and 8 were eluted by the sebum-impregnated adhesive layer and were significantly plasticized, so that the artificial sebum could not be wiped off, and thus the measurement could not be performed.

The oil absorption amount of the double-sided adhesive tape of each of the examples shown in Table 1 was in the range of 10% by mass or more and 150% by mass or less, and the change in thickness was less than 20 μm. Further, it has been confirmed that the adhesive force B/adhesion force A of the double-sided adhesive tape of each of the examples is 0.4 or more, and the decrease in the adhesive force can be suppressed. As described above, it has been confirmed that even if the double-sided adhesive tape of each embodiment is immersed in oil, dimensional change or adhesive force change in the thickness direction is small.

On the other hand, the double-sided adhesive tapes of Comparative Examples 1, 2, 4, and 5 shown in Table 2 had an oil absorption amount of more than 150% by mass, and the thickness variation was also greatly increased from 20 μm. Further, in the double-sided adhesive tapes of Comparative Examples 1, 2, 4, and 5, the adhesive force B/adhesive force A was less than 0.4, and the decrease in the adhesive force was remarkable. Further, it was confirmed that the double-sided adhesive tapes of Comparative Examples 3, 7, and 8 were eluted by artificial sebum to dissolve the adhesive layer. It has been confirmed that the double-sided adhesive tape of Comparative Example 6 has a small oil absorption amount, but since the belt thickness is thick, the change in the thickness direction is larger than 20 μm.

The present invention is not limited to the above-described embodiments, and various modifications such as design changes may be made based on the knowledge of those skilled in the art, and embodiments in which such modifications are applied may be included in the scope of the present invention.

The present invention described above is organized into the following items.

(Item 1)

A double-sided adhesive tape characterized in that it is used for component fixing of a portable electronic device, and contains a solvent-type acrylic copolymer having a total thickness of 150 μm or less and an artificial sebum at 55 ° C. The mass increase after 3 days of immersion is 10 The mass% is 150% by mass or more.

(Project 2)

The double-sided adhesive tape of item 1, wherein the solvent-type acrylic copolymer has a weight average molecular weight of from 400,000 to 700,000.

(Item 3)

The double-sided adhesive tape of item 1 or 2, wherein, after being adhered to the transparent conductive film as the adherend, it is allowed to stand under conditions of 23 ° C and 50% RH for 72 hours without being immersed in the artificial sebum. Thereafter, the peeling was performed at a stretching speed of 300 mm/min along the 180° peeling direction, and the adhesive force (N/5 mm) at this time was set to A,

After adhering to the transparent conductive film as the adherend, the artificial sebum was wiped off in artificial sebum at 55 ° C for 72 hours, and then peeled off at 23 ° C, 50% RH for 1 hour, and then peeled off at 180 °. The direction was peeled at a tensile speed of 300 mm/min, and when the adhesive force (N/5 mm) at this time was B, B/A was 0.4 or more.

(Item 4)

A double-sided adhesive tape according to any one of items 1 to 3, which is used for a transparent conductive film.

Claims (5)

A double-sided adhesive tape characterized in that it is used for fixing components of a portable electronic device, and contains a solvent-based acrylic copolymer having a total thickness of 150 μm or less and an artificial sebum at 55 ° C. The mass increase degree after 3 days of immersion in the middle is 10% by mass or more and 150% by mass or less. The double-sided adhesive tape of claim 1, wherein the solvent-type acrylic copolymer has a weight average molecular weight of from 400,000 to 700,000. The double-sided adhesive tape of claim 1 or 2, wherein, after the transparent conductive film as the adherend, is immersed in the artificial sebum at a temperature of 23 ° C and 50% RH for 72 hours. Then, it was peeled off at a stretching speed of 300 mm/min along the 180° peeling direction, and the adhesive force (N/5 mm) at this time was set to A, followed by the transparent conductive film as the adherend, After immersing in artificial sebum at 55 ° C for 72 hours, the artificial sebum was wiped off, and it was allowed to stand at 23 ° C and 50% RH for 1 hour, and then peeled off at a stretching speed of 300 mm / minute in the 180 ° peeling direction. When the adhesive force (N/5 mm) at this time is B, B/A is 0.4 or more. A double-sided adhesive tape as claimed in claim 1 or 2, which is used for the subsequent adhesion of a transparent conductive film. A double-sided adhesive tape as claimed in claim 3, which is used for the subsequent adhesion of a transparent conductive film.