KR20220148282A - adhesive tape - Google Patents

Abstract

20 parts by mass or more and less than 40 parts by mass of (meth)acrylic acid alkoxyalkyl ester, 10 parts by mass or more and less than 25 parts by mass of a carboxylic acid group-containing (meth)acrylic monomer, an alkyl group having 1 to 3 carbon atoms, a cyclohexyl group or isobor 5 parts by mass or more and less than 20 parts by mass of (meth)acrylic acid alkylester having a nyl group, and 30 parts by mass or more and less than 50 parts by mass of (meth)acrylic acid alkylester having an alkyl group having 4 to 12 carbon atoms (sum of each of the above monomers) 100 parts by mass), a crosslinked structure is formed using one or both of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent, and an acrylic copolymer having a weight average molecular weight of 200,000 or more and less than 450,000 is used as an adhesive Disclosed is an adhesive tape. This adhesive tape has high durability with respect to oils and fats components such as sebum, sweat, food, and cosmetics, and has moderate adhesive strength when attached to an adherend.

Description

adhesive tape

The present invention relates to an adhesive tape having high durability against oils and fats components such as sebum, sweat, food, and cosmetics, and having adequate adhesive strength when attached to an adherend.

Recently, small portable electronic devices, such as smartphones and tablet PCs, are rapidly spreading. In many of these, the display panel and the housing are joined by an acrylic adhesive or a double-sided adhesive tape. In addition, most mobile electronic devices are equipped with a touch panel, so that they are operated by touching them with a human finger or touching a person's face when making a call.

When the touch panel comes into contact with a person's hand or face, oils such as sebum and support are attached to the touch panel. Since this fat and oil contains components, such as oleic acid, and the SP value (solubility parameter) of fats and oils is close to an industrial organic solvent, a general acrylic resin is melt|dissolved.

Since general industrial organic solvents have a low boiling point and vaporize in a short time, it is difficult to damage the adhesive or adhesive. On the other hand, oils and fats such as oleic acid have a high boiling point and do not vaporize under living conditions and remain in electronic devices. do.

Small mobile electronic devices such as smartphones take a long time to hold and use by hand, and may touch your face during a call. Therefore, oils and fats such as sebum, sweat, food, and cosmetics tend to adhere to small portable electronic devices, and when these oils and fats reach an adhesive or an adhesive tape, there is a fear that the adhesive force may decrease. In addition, when the adhesive layer of an adhesive tape is softened due to holding|maintenance, the adhesive may peel off from the side surface of an adhesive tape, and the design and function inside an apparatus may be impaired. Moreover, the pressure to the outside may be applied by swelling of an adhesive layer, and the screen display of an electronic device may not be performed normally.

In addition, with the narrowing and thinning of internal components accompanying the screen enlargement of small portable electronic devices such as smartphones, and the practical use of small wearable devices, the adhesive tape used inside these electronic devices has also become narrower and smaller. There exists, and it is thought that the above problems are becoming more easy to generate|occur|produce.

Patent Document 1 discloses a double-sided adhesive tape used for fixing parts of portable electronic devices, wherein the adhesive does not soften or swell even when an oily component such as sebum penetrates, and the adhesive does not protrude. . However, the invention of patent document 1 is not examined about the fall of the adhesive force directly connected with floatation and peeling of the adhesive agent or adhesive tape which generate|occur|produce inside an electronic device. Moreover, when the durability of an oil and fat component is improved, the adhesive force at the time of affixing an adhesive tape to a to-be-adhered body falls, and there exists a subject that the improvement of durability and maintenance of adhesive force are not compatible.

Patent Document 1: Japanese Patent Application Laid-Open No. 2009-215355

Accordingly, an object of the present invention is to provide an adhesive tape having high durability against oils and fats components such as sebum, sweat, food, and cosmetics, and having adequate adhesive strength when attached to an adherend.

The adhesive tape of this invention, as a monomer composition, 20 mass parts or more and less than 40 mass parts of (meth)acrylic acid alkoxyalkyl ester, 10 mass parts or more and less than 25 mass parts of a carboxylic acid group containing (meth)acrylic monomer, following 5 parts by mass or more and less than 20 parts by mass of the (meth)acrylic acid alkylester represented by Formula 1, and 30 parts by mass or more and less than 50 parts by mass of the (meth)acrylic acid alkylester represented by the following Formula 2 (each of the above monomers) of 100 parts by mass), a crosslinked structure is formed by using one or both of a bifunctional or more isocyanate group-containing compound and a bifunctional or more functional glycidyl group-containing compound as a crosslinking agent, and the weight average molecular weight is It is an adhesive tape in which the adhesive composition containing the said acrylic copolymer of 200,000 or more and less than 450,000 was used as an adhesive.

(In Formula 1, R ¹ represents CH ₂ =CH- or CH ₂ =C(CH ₃ )-, and R ² represents an alkyl group having 1 to 3 carbon atoms, a cyclohexyl group, or an isobornyl group.)

(In Formula 2, R ³ represents CH ₂ =CH- or CH ₂ =C(CH ₃ )-, and R ⁴ represents an alkyl group having 4 to 12 carbon atoms.)

In the pressure-sensitive adhesive tape according to the present invention, the pressure-sensitive adhesive composition may further include a tackifying resin.

In the adhesive tape according to the present invention, the adhesive composition may further include a silane coupling agent.

In the adhesive tape according to the present invention, the pressure-sensitive adhesive composition may further include an antioxidant.

The adhesive tape which concerns on this invention can further have a base material, and can form an adhesive layer on the single side|surface or both surfaces of the said base material using an adhesive composition.

The adhesive tape according to the present invention has high durability against oils and fats components such as sebum, sweat, food, and cosmetics, and specifically has oil resistance capable of maintaining a constant adhesive force even when oils and fats are attached. Moreover, the adhesive tape which concerns on this invention has moderate adhesive force when affixing to a to-be-adhered body, and is excellent in adhesive force holding|maintenance performance when an oil-fat component adheres. Accordingly, the adhesive tape according to the present invention can be suitably used for, for example, bonding of a display panel and a housing of a small portable electronic device such as a smartphone or fixing parts inside the housing.

<Acrylic copolymer>

The acrylic copolymer according to the present invention has, as a monomer composition, a (meth)acrylic acid alkoxyalkyl ester, a carboxylic acid group-containing (meth)acrylic monomer, a (meth)acrylic acid alkylester represented by the formula (1), and the formula (2) A crosslinked structure is formed by containing the (meth)acrylic acid alkyl ester that appears, and using a bifunctional or higher isocyanate group-containing compound or a bifunctional or higher functional glycidyl group-containing compound as a crosslinking agent, and has a weight average molecular weight of 200,000 or more and less than 450,000 to be.

As (meth)acrylic acid alkoxyalkyl ester, for example, (meth)acrylic acid methoxyethyl, (meth)acrylic acid methoxypropyl, (meth)acrylate methoxybutyl, (meth)acrylic acid ethoxyethyl, (meth)acrylic acid Toxypropyl, (meth)acrylic acid ethoxybutyl, etc. can be used. In consideration of the stability of the polymerization reaction and the ease of availability, it is preferable to use methoxyethyl (meth)acrylate.

(meth)acrylic acid alkoxyalkyl ester, carboxylic acid group-containing (meth)acrylic monomer, (meth)acrylic acid alkyl ester represented by the above formula (1), and (meth)acrylic acid alkyl ester represented by the above formula (2) (hereinafter, “4 above”) Content of (meth)acrylic-acid alkoxyalkyl ester with respect to a total of 100 mass parts of a kind of monomer" is 20 mass parts or more and less than 40 mass parts. When this content is less than 20 parts by mass, the amount of monomer units with high SP values in the acrylic copolymer of the present invention decreases, so that the durability to the oil and fat components decreases, and when oil and fat components such as sebum, sweat, food, and cosmetics adhere to it. Adhesive force is remarkably reduced, and it is not possible to maintain the adhesive force required for applications such as fixing parts inside electronic devices. Moreover, since the initial stage adhesive force of an adhesive falls that this content is 40 mass parts or more, workability|operativity falls at the time of a component fixing operation inside an electronic device, etc. It is more preferable that this content is 25 mass parts or more and less than 40 mass parts.

Examples of the carboxylic acid group-containing (meth)acrylic monomer include (meth)acrylic acid, (meth)acrylic acid β-carboxyethyl, itaconic acid, crotonic acid, maleic acid, fumaric acid, citraconic acid, grataconic acid, 2- Acryloyloxyethyl succinic acid, 2-acryloyloxyethyl phthalic acid, etc. can be used. Among these, it is preferable to use (meth)acrylic acid when the crosslinking density of the adhesive obtained and the ease of acquisition are considered.

Content of the carboxylic acid group containing (meth)acryl monomer with respect to a total of 100 mass parts of said 4 types of monomers is 10 mass parts or more and less than 25 mass parts. When this content is less than 10 parts by mass, the crosslinking density of the pressure-sensitive adhesive decreases, and the pressure-sensitive adhesive swells with oils and fats such as sebum, sweat, food, and cosmetics. Moreover, since the initial stage adhesive force of an adhesive falls that this content is 25 mass parts or more, workability|operativity falls at the time of a component fixing operation inside an electronic device, etc. As for this content, it is more preferable that they are 10 mass parts or more and 23 mass parts or less.

As the (meth)acrylic acid alkylester represented by the above formula (1), for example, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, (meth)acrylic acid cyclohexyl, (meth)acrylic acid isobornyl, etc. can be used. . Considering availability, it is preferable to use methyl acrylate.

Content of the (meth)acrylic-acid alkylester represented by the said General formula (1) with respect to a total of 100 mass parts of said 4 types of monomers is 5 mass parts or more and less than 20 mass parts. If this content is less than 5 mass parts, the repulsion resistance of an adhesive will decrease, and the adhesive force required for uses, such as component fixation inside an electronic device, cannot be satisfied. Moreover, when this content is 20 mass parts or more, the initial stage adhesive force of an adhesive falls, and workability|operativity falls in the case of a component fixing operation inside an electronic device, etc. As for this content, it is more preferable that they are 5 mass parts or more and 15 mass parts or less.

Examples of the (meth)acrylic acid alkyl ester represented by the above formula (2) include butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, iso (meth)acrylate Hexyl, (meth) acrylate octyl, (meth) acrylate isooctyl, (meth) acrylic acid-2-ethylhexyl, (meth) acrylate nonyl, (meth) acrylate isononyl, (meth) acrylate decyl, (meth) acrylate iso Decyl, (meth)acrylic acid dodecyl, (meth)acrylic acid isododecyl, etc. can be used. In order to maintain the tack as an adhesive of the acrylic copolymer, it is preferable to use (meth)acrylic acid-2-ethylhexyl or the like having a low Tg (glass transition point).

Content of the (meth)acrylic-acid alkylester represented by the said Formula (2) with respect to a total of 100 mass parts of said 4 types of monomers is 30 mass parts or more and less than 50 mass parts. Since the initial stage adhesive force of an adhesive falls that this content is less than 30 mass parts, workability|operativity falls in the case of the component fixing operation|work inside an electronic device, etc. When this content is 50 parts by mass or more, the durability to the fat and oil components decreases, and when oil and fat components such as sebum, sweat, food, and cosmetics adhere to it, the adhesive force is significantly lowered, which is necessary for applications such as fixing parts inside electronic devices. Cannot maintain adhesion. As for this content, it is more preferable that they are 30 mass parts or more and 45 mass parts or less.

As a compound containing a bifunctional or more functional isocyanate group (hereinafter also referred to as "isocyanate-based crosslinking agent"), for example, tolylene diisocyanate, xylene diisocyanate, chlorphenylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone di Isocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, etc. can be used.

Examples of the bifunctional or higher glycidyl group-containing compound (hereinafter also referred to as "epoxy crosslinking agent") include 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N' ,N'-tetraglycidyl-m-xylenediamine, N,N,N',N'-tetraglycidylaminophenylmethane, triglycidylisocyanurate, m-N,N-diglycidylaminophenyl Glycidyl ether, N,N-diglycidyltoluidine, N,N-diglycidylaniline, pentaerythritol polyglycidyl ether, 1,6-hexanediol diglycidyl ether, etc. can be used.

The addition amount of the bifunctional or more than bifunctional isocyanate group containing compound and the bifunctional or more than bifunctional glycidyl group containing compound used as a crosslinking agent is not specifically limited. The amount of the crosslinking agent may be adjusted so that the degree of swelling of the pressure-sensitive adhesive composition is suitable for the environment of use of the pressure-sensitive adhesive tape according to the present invention.

The acrylic copolymer according to the present invention can be produced by polymerizing these monomers in various polymerization methods such as solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization. For example, an acrylic copolymer can be obtained by dissolving these monomers and a polymerization initiator in a solvent such as ethyl acetate in a reaction vessel, and stirring at a constant temperature for a certain period of time.

In addition, the acrylic copolymer having a crosslinked structure can be produced by adding a crosslinking agent alone or together with a polymerization initiator to the acrylic copolymer and stirring.

The weight average molecular weight of the acrylic copolymer according to the present invention is 200,000 or more and less than 450,000. When this weight average molecular weight is less than 200,000, the cohesive force required for an adhesive is not acquired, but it becomes a cause which produces the honeycomb of an adhesive when an adhesive tape is affixed to a to-be-adhered body. In addition, when this weight average molecular weight is 450,000 or more, the followability|trackability with respect to the to-be-adhered body of an adhesive tape falls, and the adhesive force required for component fixing etc. inside an electronic device cannot be acquired. As for this weight average molecular weight, it is more preferable that they are 250,000 or more and less than 450,000.

Arbitrary components, such as tackifying resin, a silane coupling agent, and antioxidant, can be added to the acrylic copolymer which concerns on this invention as needed.

Examples of the tackifying resin include rosin ester resins (rosin esters, disproportionated rosin esters, hydrogenated rosin esters, etc.), terpene resins (terpene resins, aromatic modified terpene resins, hydrogenated terpene resins, terpene phenols, etc.) , petroleum resins (aliphatic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins, aliphatic petroleum resins, etc.), pure monomer resins (coumarone indene resins, styrene resins, etc.), condensed resins (phenolic resins, etc.) resin, xylene resin, etc.) can be used. By adding tackifying resin, the hardness of an adhesive falls and the initial stage adhesive force with respect to a to-be-adhered body improves.

As the silane coupling agent, for example, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3- Glycidoxypropyltriethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, etc. can be used. A silane coupling agent may use 2 or more types together. By using a silane coupling agent, the repulsion resistance of an adhesive can be improved, and the heat-and-moisture load resistance which falls with narrowing and microprocessing of an adhesive tape can be improved.

As an antioxidant, a hindered phenol type antioxidant etc. can be used, for example. By adding antioxidant, the repulsion resistance of an adhesive can be improved, and the heat-and-moisture load resistance which falls with narrowing and microprocessing of an adhesive tape can be improved.

<Adhesive tape>

The adhesive tape which concerns on this invention is an adhesive tape in which the adhesive composition containing the above-mentioned acrylic copolymer (and optional component as needed) was used as an adhesive. "Adhesive tape in which an adhesive composition is used as an adhesive" means, for example, an adhesive tape (so-called baseless type adhesive tape) in which the adhesive composition is formed into a sheet, or one side of a substrate using the adhesive composition Or it is the adhesive tape which formed the adhesive layer on both surfaces.

The baseless type adhesive tape can be formed, for example, by coating the acrylic copolymer on a support such as a release paper and drying it thereafter. On the other hand, in the adhesive tape having a substrate, the adhesive layer may be formed by coating the acrylic copolymer on the substrate and then drying, or after forming the adhesive layer by applying the acrylic copolymer on a support such as a release paper, this The adhesive layer can be bonded to one or both sides of the substrate. A single layer may be sufficient as the adhesive layer of a baseless type adhesive tape and the adhesive tape which has a base material, and what consists of a laminated body of several layers may be sufficient as it.

The thickness of the adhesive layer in the adhesive tape which has a base material becomes like this. Preferably it is 1-200 micrometers, More preferably, it is 5-100 micrometers. The thickness of the adhesive tape of a baseless type becomes like this. Preferably it is 1-200 micrometers, More preferably, it is 5-100 micrometers.

A method of applying the acrylic copolymer on a substrate or a support such as a release paper is not particularly limited, and a known method may be used. As the specific example, the method using a roll coater, a die coater, a lip coater, a dip roll coater, a bar coater, a knife coater, a spray roll coater, etc. is mentioned.

When an adhesive tape has a base material, the base material is not specifically limited, What is necessary is just to use a well-known base material. Specific examples of the substrate include fiber-based substrates such as paper, cloth, non-woven fabric, and nets, olefin-based resins, polyester-based resins, polyvinyl chloride-based resins, vinyl acetate-based resins, polyamide-based resins, polyimide-based resins, and polyethers Resin base materials (resin film or resin sheet), such as ether ketone (PEEK) and polyphenylene sulfide (PPS), a rubber sheet, foam seat|seet (foam base material), metal foil, and a metal plate are mentioned. Moreover, these laminates may be used, for example, a laminate of a resin substrate and a substrate other than a resin, or a laminate of resin substrates. The substrate may be either a single layer or a multilayer. Various treatments, such as a back surface treatment, an antistatic treatment, an undercoating process, may be given to the surface on which the adhesive layer of a base material is provided as needed. The thickness of the substrate is preferably 5 to 500 μm, more preferably 10 to 200 μm.

The adhesive tape can be protected with a release paper or other film. The release paper or other film is not particularly limited, and a known one may be used as needed.

Example

Hereinafter, the present invention will be described in more detail by way of Examples and Comparative Examples.

(weight average molecular weight)

The weight average molecular weight (Mw) of the acrylic copolymer is a value obtained by measuring the molecular weight of the acrylic copolymer in terms of standard polystyrene by the GPC method with the following measuring apparatus and conditions.

・Apparatus: LC-2000 series (manufactured by Nippon Spectroscopy Co., Ltd.)

·Column: Shodex KF-806M×2ea, Shodex KF-802M×1ea

·Eluent: tetrahydrofuran (THF)

・Flow rate: 1.0 mL/min

・Column temperature: 40℃

・Injection amount: 100 μL

・Detector: Refractometer (RI)

(Initial Adhesion)

In case of using substrate A: A sample of 10 mm wide double-sided adhesive tape backed by a polyester film with a thickness of 25 μm is pressure-attached to a SUS304 plate polished with No. The adhesive force (N/10 mm width) after peeling off 180 degree|times was measured by the method of JIS Z0237:2000 described.

In case of using base B: A sample of a 10 mm wide double-sided adhesive tape backed by a 50 μm thick polyester film on a SUS 304 plate polished with No. 280 water resistant abrasive paper was pressure-attached by a 2.0 kg roller in one reciprocation, and 20 minutes elapsed after the pressure was applied. The adhesive force (N/10 mm width) after peeling off 180 degree|times was measured by the method of JIS Z0237:2000 described.

(Adhesive strength over time)

In case of using substrate A: A sample of 10 mm wide double-sided adhesive tape backed by a 25 μm thick polyester film on a SUS 304 plate polished with No. 280 waterproof abrasive paper was pressure-attached with one reciprocating 2.0 kg roller, and 72 hours after pressure application 180° drawing and peeling adhesive force (N/10 mm width) was measured by the method described in JIS Z0237:2000.

In case of using base B: A sample of 10 mm wide double-sided adhesive tape backed by a 50 μm thick polyester film on a SUS304 plate polished with No. 280 water-resistant abrasive paper was pressure-attached with a 2.0 kg roller 2.5 reciprocations, and 72 hours after pressure attachment. 180° drawing and peeling adhesive force (N/10 mm width) was measured by the method described in JIS Z0237:2000.

(Adhesiveness after promotion: Na)

In case of using substrate A: A sample of 10 mm wide double-sided adhesive tape backed by a 25 μm thick polyester film was applied to a SUS 304 plate polished with No. 280 water-resistant abrasive paper by pressure and attached with one reciprocation of a 2.0 kg roller, temperature 65±5°C and humidity It was left to stand in the atmosphere of 90±10% for 72 hours. Thereafter, it was left to stand for 2 hours in an atmosphere with a temperature of 23±5°C and a humidity of 50±5%. The 180° pull-out peel adhesive force (N/10 mm width) of this sample was measured by the method described in JIS Z0237:2000.

In case of using substrate B: A sample of 10 mm wide double-sided adhesive tape backed by a 50 μm thick SUS film was pressed and attached to a SUS 304 plate polished with No. It was left to stand in the atmosphere of +/-10% for 72 hours. Thereafter, it was left to stand for 2 hours in an atmosphere with a temperature of 23±5°C and a humidity of 50±5%. The 180° pull-out peel adhesive force (N/10 mm width) of this sample was measured by the method described in JIS Z0237:2000.

(Adhesiveness after oleic acid immersion: Nb)

In case of using base A: A sample of double-sided adhesive tape with a width of 10 mm backed with a polyester film having a thickness of 25 μm was applied to a SUS 304 plate polished with No. This sample was immersed in oleic acid and left to stand for 72 hours in an atmosphere of a temperature of 65±5° C. and a humidity of 90±10%. After that, the sample was taken out from the container, the oleic acid was wiped off using pure water, and the water droplets were wiped off, and then left to stand for 2 hours in an atmosphere with a temperature of 23±5° C. and a humidity of 50±5%. The 180° pull-out peel adhesive force (N/10 mm width) of this sample was measured by the method described in JIS Z0237:2000.

In case of using base B: A sample of double-sided adhesive tape with a width of 10 mm supported by a SUS film having a thickness of 50 μm was applied to a SUS 304 plate polished with No. This sample was immersed in oleic acid and left to stand for 72 hours in an atmosphere with a temperature of 60±5° C. and a humidity of 90±10%. After that, the sample was taken out from the container, the oleic acid was wiped off using pure water, and the water droplets were wiped off, and then left to stand for 2 hours in an atmosphere with a temperature of 23±5° C. and a humidity of 50±5%. The 180° pull-out peel adhesive force (N/10 mm width) of this sample was measured by the method described in JIS Z0237:2000.

(Adhesiveness retention rate after oleic acid immersion: X)

It calculated|required by the following formula.

X=100×Nb/Na

(Destroy Mode)

For the sample after the measurement of the adhesive force (Na) after promotion and the sample after the measurement of the adhesive force (Nb) after immersion in oleic acid (Nb), the site in which the fracture occurred was observed. Cohesive failure (“agglomeration” in Tables 2 to 4) when the adhesive is fractured, interfacial fracture when fracture occurs between the pressure-sensitive adhesive and the adherend, and substrate destruction when fracture occurs in the substrate ( It was set as "remark" of Tables 2-4).

[Example 1]

(Preparation of acrylic copolymer)

In a reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen introduction tube, the monomer constituting the copolymer in parts by mass shown in Table 1, ethyl acetate, 0.03 parts by mass of n-dodecanthiol as a chain transfer agent, and a radical polymerization initiator Ra After adding 0.05 mass parts of uryl peroxide and sealing nitrogen gas, it was made to react under nitrogen gas stream for 3 hours at 67 degreeC, stirring. Then, it was made to react at 82 degreeC for 3 hours. After completion of the reaction, the mixture was cooled to room temperature, and ethyl acetate was added. Thus, a copolymer having a solid content concentration of 30% was obtained. The weight average molecular weight of the acrylic copolymer prepared in Example 1 was 420,000.

(Preparation of adhesive)

With respect to 100 mass parts of solid content of this copolymer, 1.8 mass parts of isocyanate type crosslinking agents (crosslinking agent A) (The Tosoh Corporation make, brand name L-45E) were added as a crosslinking agent, and the adhesive was prepared.

(Manufacture of double-sided adhesive tape)

A separately prepared primer was applied to both surfaces of a 12 µm-thick polyethylene terephthalate film (base A) subjected to double-sided corona discharge treatment and dried at 120° C. to form an undercoat layer on the substrate A. On the undercoat layer on the 1st surface side of the base material A, the prepared adhesive was apply|coated to the whole surface, it heat-dried at 100 degreeC, and the 19-micrometer-thick adhesive layer was formed. Further, a silicone-treated release paper was bonded onto the pressure-sensitive adhesive layer. Then, on the primer layer on the 2nd surface side, the adhesive prepared similarly was apply|coated and dried, the release paper was bonded together, and it cured at 40 degreeC for 3 days. Thereby, the double-sided adhesive tape with a total thickness of 50 micrometers was obtained.

[Example 2]

Preparation of the adhesive WHEREIN: Except having changed the crosslinking agent into the epoxy-type crosslinking agent (crosslinking agent B) (trade name E-5CM), it carried out similarly to Example 1, and produced the double-sided adhesive tape.

[Example 3]

Production of the double-sided adhesive tape WHEREIN: The adhesive prepared similarly to Example 1 was apply|coated smoothly on the silicone-treated release paper, and it heat-dried at 90 degreeC, and formed the 50-micrometer-thick adhesive layer. Then, the pressure-sensitive adhesive on the release paper is bonded to both sides of the base material (substrate B) having a thickness of 100 µm made of a polyethylene (PE)-based foam that has been corona-discharged on both sides, cured at 40 ° C for 3 days, and then both surfaces with a total thickness of 200 µm An adhesive tape was obtained.

[Example 4]

Preparation of the adhesive WHEREIN: 8 mass parts of Arakawa Chemical Industry Co., Ltd. D-6011 (brand name) made into a 50% dilution liquid with ethyl acetate as a tackifying resin was made into a 5% dilution liquid with ethyl acetate as a silane coupling agent as 8 mass parts. 2 parts by mass of KBM-403 (trade name) manufactured by Shin-Etsu Chemical Industries, Ltd. and 0.2 parts by mass of Irganox (registered trademark) 1010 manufactured by BASF Japan Co., Ltd. as an antioxidant were added in the same manner as in Example 3, and both surfaces An adhesive tape was produced.

[Comparative Example 1]

(Preparation of acrylic copolymer)

In the same manner as in Example 1, except that 50 parts by mass of methoxyethyl acrylate, 10 parts by mass of acrylic acid, and 40 parts by mass of 2-ethylhexyl acrylate without using methyl acrylate, and the addition amount of the crosslinking agent was changed to 1.2 parts by mass, , a copolymer having a solid content concentration of 30% was obtained. The weight average molecular weight of the acrylic copolymer prepared in Comparative Example 1 was 750,000.

(Preparation of adhesive)

With respect to 100 parts by mass of the solid content of the copolymer, 1.2 parts by mass of an isocyanate-based crosslinking agent (crosslinking agent A) (manufactured by Tosoh Corporation, trade name L-45E) as a crosslinking agent, and 50% dilution with ethyl acetate as a tackifying resin, Arakawa Chemical Industry Co., Ltd. 8 parts by mass of D-6011 (trade name) manufactured by K.K., 2 parts by mass of KBM-403 (trade name) manufactured by Shin-Etsu Chemical Co., Ltd. (trade name) obtained by diluting 5% with ethyl acetate as a silane coupling agent, as an antioxidant, BASF Japan 0.2 mass parts of Irganox (trademark) 1010 made by a corporation|Co., Ltd.|KK was added, and the adhesive was prepared.

(Manufacture of double-sided adhesive tape)

Except having used this adhesive, it carried out similarly to Example 1, and obtained the double-sided adhesive tape.

[Comparative Example 2]

In the production of the acrylic copolymer, without using methyl acrylate, 86 parts by mass of methoxyethyl acrylate, 10 parts by mass of acrylic acid, and 4 parts by mass of 2-ethylhexyl acrylate, except that the amount of the crosslinking agent was changed to 1.2 parts by mass. It carried out similarly to Example 1, and produced the double-sided adhesive tape. The weight average molecular weight of the acrylic copolymer prepared in Comparative Example 2 was 1.05 million.

[Comparative Example 3]

In the production of the acrylic copolymer, a double-sided adhesive tape was prepared in the same manner as in Comparative Example 2, except that the amount of n-dodecanthiol as a chain transfer agent was changed to 0.06 parts by mass and the amount of the crosslinking agent A was changed to 2.4 parts by mass. The weight average molecular weight of the acrylic copolymer prepared in Comparative Example 3 was 340,000.

[Comparative Example 4]

In the production of the acrylic copolymer, the double-sided adhesive tape was prepared in the same manner as in Comparative Example 2, except that 86 parts by mass of acrylic acid-2-(ethoxyethoxy)ethyl (EOEOEA) was used without using methoxyethyl acrylate. made. The weight average molecular weight of the acrylic copolymer prepared in Comparative Example 4 could not be measured.

[Comparative Example 5]

In the manufacture of a double-sided adhesive tape, the pressure-sensitive adhesive prepared in the same manner as in Comparative Example 1 was applied to a silicone-treated release paper in a smooth entire surface, and dried by heating at 90° C. to form an adhesive layer having a thickness of 50 µm. Then, the pressure-sensitive adhesive on the release paper is bonded to both sides of the base material (substrate B) having a thickness of 100 µm made of a polyethylene (PE)-based foam that has been corona-discharged on both sides, cured at 40 ° C for 3 days, and then both surfaces with a total thickness of 200 µm An adhesive tape was obtained.

[Comparative Example 6]

In the production of the double-sided adhesive tape, the pressure-sensitive adhesive prepared in the same manner as in Comparative Example 2 was applied to the silicone-treated release paper in a smooth entire surface, and dried by heating at 90° C. to form an adhesive layer having a thickness of 50 µm. Then, the pressure-sensitive adhesive on the release paper is bonded to both sides of the base material (substrate B) having a thickness of 100 µm made of a polyethylene (PE)-based foam that has been corona-discharged on both sides, cured at 40 ° C for 3 days, and then both surfaces with a total thickness of 200 µm An adhesive tape was obtained.

[Comparative Example 7]

Production of the double-sided adhesive tape WHEREIN: The adhesive prepared similarly to the comparative example 3 was apply|coated smoothly on the silicone-treated release paper, and it heat-dried at 90 degreeC, and formed the 50-micrometer-thick adhesive layer. Then, the pressure-sensitive adhesive on the release paper is bonded to both sides of the base material (substrate B) having a thickness of 100 µm made of a polyethylene (PE)-based foam that has been corona-discharged on both sides, cured at 40 ° C for 3 days, and then both surfaces with a total thickness of 200 µm An adhesive tape was obtained.

[Comparative Example 8]

Preparation of the acrylic copolymer WHEREIN: Except having used 10 mass parts of acrylic acid 4-hydroxybutyl instead of 10 mass parts of acrylic acid, it carried out similarly to the comparative example 2, and produced the double-sided adhesive tape. The weight average molecular weight of the acrylic copolymer prepared in Comparative Example 8 was 730,000.

Table 1 shows the base material used when forming the compounding of Examples 1 - Example 4 and Comparative Examples 1 - Comparative Example 8, the weight average molecular weight of an acrylic copolymer, and a double-sided adhesive tape. In addition, the initial adhesive force, the adhesive force over time, the adhesive force after promotion Na, the adhesive force Nb after immersion in oleic acid, the adhesive force retention X after immersion in oleic acid, and the failure mode measured for each double-sided adhesive tape are shown in Tables 2 to 4.

The abbreviations used in Table 1 are as follows.

AME = methoxyethyl acrylate

EOEOEA = Acrylic acid-2-(2-ethoxyethoxy)ethyl

AA = acrylic acid

4-HBA=acrylic acid-4-hydroxybutyl

MA = methyl acrylate

2-EHA = Acrylic acid-2-ethylhexyl

As shown in Tables 2-4, the double-sided adhesive tape of Examples 1-4 had high initial stage adhesive force and aging adhesive force, and was maintaining moderate adhesive force also after immersion in oleic acid. Therefore, it can be seen that these double-sided adhesive tapes are adhesive tapes having high durability against oils and fats such as sebum, sweat, food, and cosmetics, and having adequate adhesive strength when attached to an adherend. In addition, comparing Example 3 and Example 4, the numerical value of the initial adhesive force was smaller in Example 4 to which the tackifying resin was added, but Example 3 was an interfacial failure, whereas Example 4 was a substrate failure. Therefore, it is thought that the fall of adhesive force has not generate|occur|produced.

On the other hand, the monomer composition of the acrylic copolymer used in Comparative Examples 1 to 4 and 8 (the thickness of each pressure-sensitive adhesive layer of 19 μm, the substrate A) was used in Examples 1 and 2 (the thickness of each pressure-sensitive adhesive layer of 19 μm, the substrate A). It is different from the monomer composition of the acrylic copolymer. In addition, the weight average molecular weight of the acrylic copolymer used in Comparative Examples 1, 2, 4 and 8 is larger than the weight average molecular weight of the acrylic copolymer used in Examples 1 and 2.

As a result, the double-sided adhesive tapes of Comparative Examples 1 and 8 were compared with the double-sided adhesive tapes of Examples 1 and 2, the initial adhesive strength, the adhesive strength over time, the adhesive strength after promotion Na, the adhesive strength Nb after immersion in oleic acid, and the adhesive strength retention X after immersion in oleic acid was inferior

Compared with the double-sided adhesive tapes of Examples 1 and 2, the double-sided adhesive tape of Comparative Example 2 was inferior in initial adhesive force, adhesive force with time, and adhesive force Na after promotion.

Comparative Example 3 is an example in which the weight average molecular weight of the acrylic polymer is lowered than in Comparative Example 2. As a result, in Comparative Example 3, several items were improved compared to Comparative Example 2. However, compared with Examples 1 and 2, the initial adhesive force, the aging adhesive force, and the adhesive force Na after promotion were inferior.

Compared with the double-sided adhesive tapes of Examples 1 and 2, the double-sided adhesive tape of Comparative Example 4 was inferior to the adhesive strength over time, the adhesive strength Na after promotion, the adhesive strength Nb after oleic acid immersion, and the adhesive strength retention rate X after oleic acid immersion.

The double-sided adhesive tapes of Comparative Examples 5 to 7 (the thickness of each pressure-sensitive adhesive layer of 50 µm, the base material B) have a monomer composition of the acrylic copolymer in Examples 3 and 4 (the thickness of each pressure-sensitive adhesive layer of 50 µm, the base material B). It is different from the monomer composition of the acrylic copolymer. In addition, the weight average molecular weight of the acrylic copolymer used in Comparative Examples 5 and 6 is larger than the weight average molecular weight of the acrylic copolymer used in Examples 3 and 4.

As a result, compared with the double-sided adhesive tapes of Examples 3 and 4, the double-sided adhesive tape of Comparative Example 5 had lower initial adhesive strength, adhesive strength Nb after immersion in oleic acid, and adhesive strength retention X after immersion in oleic acid. In addition, the failure modes (Na) and (Nb) were both cohesive failure, and the cohesive force of the adhesive layer was inferior.

The double-sided adhesive tape of Comparative Example 6 was inferior in initial adhesive strength compared to the double-sided adhesive tapes of Examples 3 and 4. In addition, the failure modes (Na) and (Nb) were both cohesive failure, and the cohesive force of the pressure-sensitive adhesive layer was inferior.

Comparative Example 7 is an example of applying the adhesive of Comparative Example 3 to the base B. As a result, in Comparative Example 7, several items were improved compared to Comparative Example 6. However, the initial adhesive force was inferior to Examples 3 and 4.

The adhesive tape which concerns on this invention can be used suitably for uses, such as bonding of the display panel of small portable electronic devices, such as a smart phone, and a casing, and fixing of components inside a casing, for example.

Claims (5)

A monomer composition comprising:
(meth)acrylic acid alkoxyalkyl ester 20 parts by mass or more and less than 40 parts by mass;
10 parts by mass or more and less than 25 parts by mass of a carboxylic acid group-containing (meth)acrylic monomer;
5 mass parts or more and less than 20 mass parts of (meth)acrylic acid alkylester represented by following formula 1, and,
An acrylic copolymer containing 30 parts by mass or more and less than 50 parts by mass of (meth)acrylic acid alkylester represented by the following formula 2 (the sum of the above monomers is 100 parts by mass),
A crosslinked structure is formed by using one or both of a bifunctional or higher functional isocyanate group-containing compound and a bifunctional or higher functional glycidyl group-containing compound as a crosslinking agent,
An adhesive tape in which a pressure-sensitive adhesive composition containing the acrylic copolymer having a weight average molecular weight of 200,000 or more and less than 450,000 is used as the pressure-sensitive adhesive.

(In Formula 1, R ¹ represents CH ₂ =CH- or CH ₂ =C(CH ₃ )-, and R ² represents an alkyl group having 1 to 3 carbon atoms, a cyclohexyl group, or an isobornyl group.)

(In Formula 2, R ³ represents CH ₂ =CH- or CH ₂ =C(CH ₃ )-, and R ⁴ represents an alkyl group having 4 to 12 carbon atoms.) According to claim 1,
The adhesive tape in which the said adhesive composition further contains a tackifying resin. According to claim 1,
An adhesive tape wherein the pressure-sensitive adhesive composition further comprises a silane coupling agent. According to claim 1,
An adhesive tape wherein the pressure-sensitive adhesive composition further comprises an antioxidant. According to claim 1,
The adhesive tape further has a substrate, and an adhesive layer is formed on one or both sides of the substrate by using the pressure-sensitive adhesive composition.