CN114981378A

CN114981378A - Adhesive tape

Info

Publication number: CN114981378A
Application number: CN202180008026.9A
Authority: CN
Inventors: 岩崎刚; 武井秀晃; 菊池洋匡; 北出祐也
Original assignee: DIC Corp
Current assignee: DIC Corp
Priority date: 2020-01-17
Filing date: 2021-01-07
Publication date: 2022-08-30
Also published as: JPWO2021145259A1; WO2021145259A1; JP7024928B2

Abstract

The present invention addresses the problem of providing an adhesive tape that can maintain excellent adhesion and impact resistance for a long period of time even when sweat, sebum, or the like adheres thereto. The present invention relates to an adhesive tape comprising a viscoelastic layer containing an acrylic adhesive and hollow particles or bubbles, wherein the acrylic adhesive comprises an acrylic copolymer and a crosslinking agent, the acrylic copolymer comprises (A) a carboxyl group-containing monomer, (B) a hydroxyl group-containing monomer, and (C) 1 or 2 or more members selected from the group consisting of alkyl (meth) acrylate monomers and alicyclic monomers other than (A) and (B) as constituent components, and the monomer (C) has an average carbon number of less than 4.

Description

Adhesive tape

Technical Field

The present invention relates to an adhesive (adhesive japanese original language "sticker") tape that can be used in manufacturing places of various products such as electronic devices.

Background

Adhesive tapes are widely used in manufacturing places of various products such as electronic devices and automobiles.

The pressure-sensitive adhesive tape is generally required to be able to maintain excellent adhesion for a long period of time without being affected by water, heat, or the like. Among them, an adhesive tape used in a manufacturing place of a portable electronic device and a fixing place of an automobile interior member, which are frequently touched by a person, is required to have excellent so-called oil resistance, which can maintain excellent adhesion even when sweat, sebum, or the like is adhered thereto.

As the pressure-sensitive adhesive tape having excellent chemical resistance, for example, a pressure-sensitive adhesive tape is known which is obtained by using a pressure-sensitive adhesive composition containing an acrylic copolymer (a) having a hydroxyl group and a carboxyl group, the acrylic copolymer (a) containing 50 to 90 mass% of an alkyl (meth) acrylate (a1) having an alkyl group having 4 to 12 carbon atoms, 3 to 20 mass% of a monomer (a2) having a carboxyl group, 3 to 20 mass% of a monomer (A3) having a hydroxyl group, and 3 to 15 mass% of an alkyl (meth) acrylate (a4) having an alkyl group having 1 to 3 carbon atoms as constituent components, and having a weight average molecular weight of 70 to 200 ten thousand and a theoretical Tg of-40 ℃ or less (see, for example, patent document 1.).

However, since there are frequent occasions where various substances such as sweat, sebum, alcohol, and the like come into contact with the surface of a portable electronic device or an automobile interior, the pressure-sensitive adhesive tape is insufficient when such contact is repeated a plurality of times, and the adhesive strength may decrease with time.

Further, impact resistance (adhesion reliability against impact generated when an object falls or collides) is required for a portable electronic device terminal, an automobile interior, and the like, but the above adhesive tape is insufficient and improvement of impact resistance is required.

In recent years, in image display modules, a frame width has been narrowed from the viewpoint of effective use of a screen and from the viewpoint of design, and accordingly, a width of an adhesive tape has also been narrowed (for example, 0.5 to 1.0 mm). Therefore, for example, in the technique described in patent document 1, the base material is easily elongated, and there is a possibility that defects may occur during processing, and if the bubbles become large, the bubble diameter becomes larger than the band width, and the waterproof performance may be lost. Since the adhesive tape having a narrow width has a small area to be attached, even a small amount of adhesive is easily affected by, for example, a decrease in adhesion force with time as compared with an adhesive tape having a wide width, and therefore, a higher oil resistance is required.

Documents of the prior art

Patent document

Patent document 1: international publication 2014/002203 pamphlet

Disclosure of Invention

Problems to be solved by the invention

An object of the present invention is to provide an adhesive tape that can maintain excellent adhesion and impact resistance for a long period of time even when sweat, sebum, or the like adheres thereto.

Means for solving the problems

The present inventors have found that the above-mentioned problems can be solved by a pressure-sensitive adhesive tape provided with a viscoelastic layer containing an acrylic pressure-sensitive adhesive containing an acrylic copolymer and a crosslinking agent, wherein the acrylic copolymer is obtained by selecting and combining 1 or 2 or more kinds of alkyl (meth) acrylate monomers and alicyclic monomers, excluding a carboxyl group-containing monomer and a hydroxyl group-containing monomer, each having a specific content of a carboxyl group-containing monomer, a specific content of a hydroxyl group-containing monomer, and an average carbon number of less than 4.

That is, the present invention relates to an adhesive tape including a viscoelastic layer containing hollow particles or bubbles and an acrylic adhesive containing an acrylic copolymer and a crosslinking agent, wherein the acrylic copolymer contains

(A) A carboxyl group-containing monomer;

(B) a hydroxyl-containing monomer; and

(C) 1 or 2 or more selected from the group consisting of alkyl (meth) acrylate monomers and alicyclic monomers other than (A) and (B)

As a constituent component of the above-mentioned thermoplastic resin composition,

the (C) monomer has an average number of carbon atoms of less than 4.

Effects of the invention

The pressure-sensitive adhesive tape of the present invention has good initial adhesion, is less likely to swell even when sweat, sebum, or the like adheres thereto, maintains excellent adhesion over a long period of time, and has excellent impact resistance.

Detailed Description

The adhesive tape of the present invention comprises a viscoelastic layer containing an acrylic adhesive and hollow particles or bubbles, wherein the acrylic adhesive comprises an acrylic copolymer and a crosslinking agent, and the acrylic copolymer comprises

(A) A carboxyl group-containing monomer;

(B) a hydroxyl-containing monomer; and

As the constituent components, a water-soluble polymer,

the average number of carbon atoms of the monomer (C) is less than 4 as calculated by the following formula.

An average carbon number [ { total (X) } + { total of the mole fraction (mol%) of the alkyl (meth) acrylate monomer with respect to the (C) and the product of the carbon number of the alkyl group contained in the alkyl (meth) acrylate monomer + { total (Y) }/100 } of the mole fraction (mol%) of the alicyclic monomer with respect to the (C) and the product of the carbon number of the alicyclic group contained in the alicyclic monomer (C) }/100 }

Examples of the pressure-sensitive adhesive tape include a so-called substrate-free pressure-sensitive adhesive tape comprising the viscoelastic layer, a pressure-sensitive adhesive tape comprising the pressure-sensitive adhesive layer on one or both sides of the viscoelastic layer directly or via another layer, and the like.

In the pressure-sensitive adhesive tape, the viscoelastic layer and the pressure-sensitive adhesive layer may be formed as separate layers or may be formed as a multilayer structure having 2 or more layers. In addition, a support base material and an adhesive layer may be disposed on one surface or both surfaces of the viscoelastic layer. In the case of producing a plurality of 2 or more layers, the resin composition, additives, and the like of the binder constituting each layer may be the same or different.

(viscoelastic layer)

As the acrylic adhesive used for the viscoelastic layer, a (meth) acrylic adhesive can be used which comprises, as a base polymer, an acrylic copolymer (C) comprising a carboxyl group-containing monomer (a), a hydroxyl group-containing monomer (B), and 1 or 2 or more kinds of copolymers as constituent components selected from the group consisting of alkyl (meth) acrylate monomers other than (a) and (B) and alicyclic monomers, and further comprises, if necessary, additives such as a tackifier resin and a crosslinking agent.

As the carboxyl group-containing monomer (a) that can be used for the production of the acrylic copolymer, acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth) acrylic acid dimer, crotonic acid, ethylene oxide-modified succinic acid acrylate, and the like can be used, and among these, acrylic acid is preferably used as a copolymerization component in view of exhibiting more excellent oil resistance against sweat, sebum, alcohol, and the like.

The content of the carboxyl group-containing monomer relative to the total amount of (a) to (C) used in the production of the acrylic copolymer and the total amount of other vinyl monomers except for (a) to (C) described later (hereinafter referred to as the total amount of acrylic monomers) is not particularly limited, but is preferably in the range of 2 to 30% by mass, more preferably in the range of 4.1 to 25% by mass, and particularly preferably in the range of 5.3 to 20% by mass from the viewpoint of exhibiting more excellent oil resistance and impact resistance to sweat, sebum, alcohol, and the like.

Examples of the hydroxyl group-containing monomer (B) that can be used for the production of the acrylic copolymer include hydroxyl group-containing (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate.

The content of the hydroxyl group-containing monomer relative to the total amount of the acrylic monomers that can be used in the production of the acrylic copolymer is not particularly limited, but is preferably in the range of 0.01 to 1.0% by mass, more preferably in the range of 0.01 to 0.85% by mass, still more preferably in the range of 0.02 to 0.7% by mass, particularly preferably in the range of 0.03 to 0.5% by mass, even more preferably in the range of 0.04 to 0.3% by mass, and still even more preferably in the range of 0.05 to 0.2% by mass. When the amount is within the above range, the oil resistance is more excellent against sweat, sebum, and the like.

The alkyl (meth) acrylate monomer (C) is a (meth) acrylate having an alkyl group at the ester terminal. The alkyl group of the alkyl (meth) acrylate monomer may be a linear alkyl group or a branched alkyl group. Examples of the alkyl (meth) acrylate monomer include (meth) acrylates having an alkyl group having 1 to 18 carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and isostearyl (meth) acrylate, and 1 or 2 or more of them can be used, and preferably 2 or more of them are used. Among them, a (meth) acrylate monomer having an alkyl group with 1 to 12 carbon atoms is preferably used, and a (meth) acrylate monomer having 1 to 10 carbon atoms is more preferably used. In particular, the use of at least one (meth) acrylate monomer having 1 to 4 carbon atoms is preferable because the average carbon number of the alkyl group in the (meth) acrylate monomer can be easily adjusted to less than 4.

The alicyclic monomer of the above (C) has a polymerizable functional group having an unsaturated double bond such as a (meth) acryloyl group or a vinyl group, and has a group having an alicyclic structure. Here, the "alicyclic structure-containing group" refers to a substituent containing at least one alicyclic structure, and may be hereinafter referred to as an alicyclic group. Examples of the alicyclic group include a hydrocarbon group having an alicyclic structure and a hydrocarbyloxy group. Examples of the alicyclic monomer include isobornyl (meth) acrylate and cyclohexyl (meth) acrylate.

The above (C) is selected from the group consisting of alkyl (meth) acrylate monomers and alicyclic monomers, and 1 or 2 or more thereof have an average carbon number calculated from the following formula of less than 4, preferably in the range of 2.1 to 3.9, more preferably in the range of 2.5 to 3.8, more preferably in the range of 2.6 to 3.8, and particularly preferably in the range of 2.7 to 3.6. In particular, by using at least one of n-butyl acrylate, methyl acrylate, and ethyl acrylate in the above range, the adhesive composition has a good initial adhesive strength, is less likely to swell even when sweat, sebum, alcohol, or the like adheres thereto, and can maintain excellent adhesive strength and impact resistance for a long period of time.

The average number of carbon atoms was calculated as follows. The product of the number of carbon atoms of each alkyl group and the mole fraction (mol%) of the alkyl (meth) acrylate monomer in (C) is calculated for the alkyl (meth) acrylate monomer contained as (C). Similarly, the product of the number of carbon atoms of each alicyclic group and the mole fraction (mol%) of the alicyclic monomer in (C) is calculated for the alicyclic monomer contained as (C). The average number of carbon atoms is determined by dividing the total of the products calculated for each of the alkyl (meth) acrylate monomers and the alicyclic monomer contained in (C) by the total mole fraction (mol%) of 1 or 2 or more selected from the group consisting of the alkyl (meth) acrylate monomers and the alicyclic monomer in (C).

For example, in the case of using 2 kinds of alkyl (meth) acrylates and 1 kind of alicyclic monomers in combination, in the case of using an alkyl (meth) acrylate monomer containing an alkyl group having a carbon number a in a (mol%), an alkyl (meth) acrylate monomer containing an alkyl group having a carbon number B in B (mol%), and an alkyl (meth) acrylate monomer containing an alicyclic group having a carbon number C in C (mol%), the average carbon number is determined by (a × a + B × B + C × C)/(a + B + C), (where a + B + C is 100).

When the alicyclic monomer is not contained (the mole fraction of the alicyclic monomer is 0 mol%), the number of carbon atoms is determined by the following formula.

An average carbon number [ { the sum (X) }/100 of mole fraction (mol%) of the alkyl (meth) acrylate monomer with respect to the (C) and the product of the number of carbon atoms of the alkyl group contained in the alkyl (meth) acrylate monomer ]

For example, in the case of using 2 kinds of alkyl (meth) acrylates in combination, in the case of an alkyl (meth) acrylate monomer containing an alkyl group having a carbon number a in a (mol%) and an alkyl (meth) acrylate monomer containing an alkyl group having B in a (mol%) ratio, the average carbon number is determined by (a × a + B × B)/(a + B) (where a + B is 100).

The content of 1 or 2 or more selected from the group consisting of alkyl (meth) acrylate monomers and alicyclic monomers in the (C) is preferably 70% by mass or more, more preferably 79 to 98% by mass, and still more preferably 84 to 95.7% by mass, based on the total amount of acrylic monomers that can be used in the production of the acrylic copolymer.

In the production of the acrylic copolymer, other vinyl monomers than (a) to (C) may be used, and as the other vinyl monomer, a vinyl monomer having an amide group, a monomer having a sulfonic acid group, a vinyl ether monomer, a monomer having an alkoxy group, a macromonomer having a radical polymerizable vinyl group in the molecule, or the like may be used.

In the case of using the other vinyl monomer, the amount thereof may be appropriately selected so that the monomer is unlikely to swell even when sweat, sebum, alcohol, or the like adheres thereto, and excellent adhesion and impact resistance are achieved over a long period of time. The content of the other vinyl monomer is preferably 2 to 15% by mass, more preferably 2.5 to 10% by mass, based on the total amount of the acrylic monomer that can be used for producing the acrylic copolymer.

The acrylic copolymer can be obtained by copolymerization using a known polymerization method such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, and the like, and from the viewpoint of water resistance of the binder, the solution polymerization method and the bulk polymerization method are preferable, and from the viewpoint of safety, the solution polymerization method is preferable when n-butyl acrylate, methyl acrylate, or ethyl acrylate is used as a main component in the alkyl (meth) acrylate monomer and the alicyclic monomer of the above (C). The initiation method of polymerization may be any selected from a thermal initiation method using a peroxide-based thermal polymerization initiator such as benzoyl peroxide or lauroyl peroxide, an azo-based thermal polymerization initiator such as azobisisobutyronitrile, an ultraviolet irradiation initiation method using a photopolymerization initiator such as a acetophenone-based, benzoin ether-based, benzyl ketal-based, acylphosphine oxide-based, benzoin-based, or benzophenone-based photopolymerization initiator, and an electron beam irradiation initiation method.

The molecular weight of the acrylic copolymer is preferably 40 to 300 million in terms of a weight average molecular weight in terms of standard polystyrene as measured by Gel Permeation Chromatography (GPC), more preferably 50 to 200 million in terms of exhibiting more excellent oil resistance against sweat, sebum, alcohol, and the like.

The molecular weight was measured by GPC using a standard polystyrene conversion value measured by a GPC apparatus (HLC-8320GPC, manufactured by Tosoh corporation), and the measurement conditions were as follows.

Sample concentration: 1.0% by mass (THF solution)

Sample injection amount: 100 μ L

Eluent: THF (tetrahydrofuran)

Flow rate: 1.0 mL/min

Measuring temperature: 40 deg.C

Present column (present カラム): TSKgel GMHHR-H (S)2

Protection of the column: TSKguracoumm HHR (S)

A detector: differential refractometer

Molecular weight of standard polystyrene: 1 to 2000 thousands (made by Tosoh corporation)

The temperature at which the loss tangent (tan. delta.) of the viscoelastic layer of the adhesive tape of the present invention exhibits a peak at a frequency of 1Hz is preferably-40 ℃ to 5 ℃. By setting the peak value of the loss tangent of the pressure-sensitive adhesive layer in this range, good adhesion to an adherend at normal temperature can be easily provided. Further, from the viewpoint of improving impact resistance, it is more preferably from-35 ℃ to 3 ℃, and still more preferably from-25 ℃ to 0 ℃. When the viscoelastic layer is formed by mixing and laminating adhesive compositions having different compositions and has a plurality of loss tangent (tan δ) peaks, any one of the peaks may be within the above range, and the peak at the lowest temperature side is preferably within the above range, and more preferably all the peaks are within the above range.

The loss tangent (tan δ) at a frequency of 1Hz is determined from the formula tan δ ═ G "/G 'based on the storage elastic modulus (G') and the loss elastic modulus (G") obtained in the dynamic viscoelasticity measurement based on the temperature dispersion. In the measurement of dynamic viscoelasticity, a specimen formed into an adhesive layer having a thickness of about 2mm was sandwiched between parallel disks made of stainless steel having a diameter of 8mm as a measurement portion of a viscoelasticity tester (TA Instruments Japan, trade name: ARES G2), and a storage elastic modulus (G ') and a loss elastic modulus (G') at-60 ℃ to 150 ℃ were measured at a frequency of 1 Hz.

The viscoelastic layer contains hollow particles or bubbles. The viscoelastic layer is a pressure-sensitive adhesive tape having both excellent oil resistance and impact resistance against sweat, sebum, alcohol, and the like, which is obtained by applying the acrylic copolymer to the viscoelastic layer and forming a hollow structure by containing hollow particles or bubbles. In order to form the hollow structure, a form containing hollow particles is preferable from the viewpoint of oil resistance and impact resistance, and hollow particles made of glass or thermoplastic resin are particularly preferably used. The hollow particles are preferably heat-expandable microcapsules made of a thermoplastic resin as a shell and containing a heat-expanding agent such as a saturated hydrocarbon having 4 to 7 carbon atoms such as heptane, hexane, isobutane as an inner shell, and the like. The thermally expandable microcapsules can be used after being appropriately expanded by heating, and it is preferable to use thermally expandable microcapsules expanded in advance from the viewpoint of thickness accuracy of the viscoelastic base material and easiness of production.

Among the hollow particles made of a thermoplastic resin, a thermoplastic resin obtained by polymerizing a vinyl monomer having a homopolymer glass transition temperature of 80 ℃ or higher, preferably 100 ℃ or higher is preferable as the thermoplastic resin constituting the outer shell, and a thermoplastic resin mainly composed of acrylonitrile, methacrylonitrile, and methyl methacrylate is more preferable from the viewpoint of exhibiting more excellent oil resistance and impact resistance against sweat, sebum, alcohol, and the like.

The average particle diameter of the hollow particles is preferably not more than the thickness of the viscoelastic layer, and is preferably not more than 90%, more preferably 20 to 50% of the thickness of the viscoelastic layer. Within the above range, it is preferably not more than 150 μm, more preferably 10 to 90 μm, and particularly preferably 20 to 60 μm, since sufficient impact resistance can be obtained without impairing initial adhesion. The average particle diameter of the hollow particles is, for example, a 50% average particle diameter by using a laser scattering particle size distribution measuring apparatus.

The true specific gravity of the hollow particles is not particularly limited, but is from 0.01 to 0.50g/cm in consideration of the mechanical strength, uniform dispersibility, etc. of the hollow particles ³ Preferably 0.01 to 0.30g/cm ³ More preferably 0.02 to 0.20g/cm ³ Is selected from the range of (1).

The amount of the hollow particles in the viscoelastic layer is preferably 5 to 60 vol%, more preferably 15 to 45 vol%, based on the total amount of the binder used in the viscoelastic layer. When the content is within this range, sufficient impact resistance can be obtained, and the viscoelastic layer has high tensile strength, so that excellent punching workability can be obtained. As a method of dispersing the empty particles, any stirring machine such as a mixer or a dissolver may be used as long as the effect of the present invention is not impaired.

The apparent density of the viscoelastic layer is not particularly limited, and is 0.50 to 1.1g/cm from the viewpoint of easily achieving both impact resistance and excellent adhesion to an adherend ³ Preferably 0.60 to 1.0g/cm ³ More preferably 0.7 to 1.0g/cm ³ . The apparent density was measured in accordance with JISK 6767. A viscoelastic layer (thickness measured) cut into a 4cm × 5cm rectangular shape was prepared to be about 15cm ³ On the left and right sides, the mass was measured to obtain the apparent density.

As the acrylic adhesive that can be used in the present invention, an acrylic adhesive containing a tackifier resin can be used in order to obtain an adhesive sheet having more excellent adhesiveness.

Examples of the tackifier resin include rosin-based tackifier resins, polymerized rosin-based tackifier resins, rosin phenol-based tackifier resins, stabilized rosin-based tackifier resins, disproportionated rosin-based tackifier resins, hydrogenated rosin-based tackifier resins, terpene phenol-based tackifier resins, petroleum resin-based tackifier resins, and (meth) acrylate resin-based tackifier resins. The softening point of the tackifier resin is not particularly limited, and is 30 to 180 ℃, preferably 40 to 140 ℃.

The content of the tackifier resin is not particularly limited as long as the temperature at which the loss tangent (tan δ) of the viscoelastic layer at a frequency of 1Hz is at a peak is in the range of-40 to 5 ℃, and is preferably 35 parts by mass or less, and more preferably 25 parts by mass or less, from the viewpoint that the oil resistance to sweat, sebum, and the like is more excellent when 50 parts by mass or less is contained per 100 parts by mass of the resin solid content in the acrylic adhesive. In addition, the above-mentioned tackifier resins may be used in combination of 2 or more.

In addition, the viscoelastic layer is crosslinked with a crosslinking agent to have a more excellent cohesive force. As an index of the degree of crosslinking of the pressure-sensitive adhesive layer, a value obtained by measuring the gel fraction of insoluble components after the pressure-sensitive adhesive layer was immersed in toluene for 24 hours was used. When the gel fraction is in the range of preferably 20 to 90% by mass, more preferably 30 to 80% by mass, and still more preferably 30 to 70% by mass, both of the cohesiveness and adhesiveness are good.

For the measurement of gel fraction, a binder containing the above acrylic binder and a crosslinking agent was applied, dried at 90 ℃ for 3 minutes, aged at 40 ℃ for 2 days, and the resultant was cut into 50mm squares to obtain samples. Then, the mass of the sample was measured (G1), and the sample was immersed in a toluene solution at 23 ℃ for 24 hours. The toluene-insoluble matter of the impregnated sample was separated by filtration through a 200-mesh wire gauze, and the mass of the residue after drying at 110 ℃ for 1 hour was measured (G2), and the gel fraction was calculated according to the following formula.

Gel fraction (% by mass) of (G2-G3)/(G1-G3) × 100

-G3: mass of hollow particles present in the sample

As the crosslinking agent, a conventionally known or customary crosslinking agent in the field of acrylic adhesives can be used. For example, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, metal chelate-based crosslinking agents, aziridine-based crosslinking agents, oxazoline-based crosslinking agents, and the like can be used. Among them, a crosslinking agent which can be easily mixed with the acrylic copolymer or its solution prepared in advance and can rapidly perform a crosslinking reaction is preferably used, and specifically, an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent are more preferably used. One kind of the crosslinking agent may be used or two or more kinds may be used in combination.

Examples of the isocyanate-based crosslinking agent include tolylene diisocyanate, naphthalene-1, 5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, trimethylolpropane-modified tolylene diisocyanate, and the like, and tolylene diisocyanate and trimethylolpropane-modified tolylene diisocyanate are preferably used. The epoxy crosslinking agent is preferably 1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N ', N' -tetrakis (oxiranylmethyl) -1, 3-xylylenediamine, or the like.

The amount of the crosslinking agent used is not particularly limited as long as the gel fraction can be adjusted, but is preferably 0.001 to 5.0 parts by mass per 100 parts by mass of the resin solid content in the acrylic pressure-sensitive adhesive, and more preferably 0.01 to 4.3 parts by mass in terms of exhibiting more excellent oil resistance against sweat, sebum, and the like.

The acrylic pressure-sensitive adhesive is preferably a coating liquid containing a solvent in terms of maintaining its good coating workability. Examples of the solvent include toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, and hexane. In view of the solvent resistance of the thermoplastic resin hollow particles, the proportion of ethyl acetate in the entire solvent component is preferably 70% by mass or more, and more preferably 90% by mass or more. When the coating liquid is prepared using a solvent, the solid content concentration (acrylic resin) is not particularly limited, but is preferably 10 to 80% by mass.

The viscoelastic layer may be colored in order to impart design properties, light-shielding properties, concealing properties, light-reflecting properties, and light resistance to the pressure-sensitive adhesive tape. The coloring agent may be used singly or in combination of 2 or more.

When light-shielding properties, concealing properties, and light resistance are imparted to the pressure-sensitive adhesive tape, the viscoelastic layer is colored black. As the black colorant, carbon black, graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine black, activated carbon, ferrite, magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complex, composite oxide-based black pigment, anthraquinone-based organic black pigment, and the like can be used. Among them, carbon black is preferable from the viewpoint of cost, availability, and insulation properties.

When design properties, light reflectivity, and the like are imparted to the pressure-sensitive adhesive tape, the viscoelastic layer is colored white. Examples of the white colorant include inorganic white colorants such as titanium oxide, zinc oxide, aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, calcium oxide, tin oxide, barium oxide, cesium oxide, yttrium oxide, magnesium carbonate, calcium carbonate, barium carbonate, zinc carbonate, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, zinc hydroxide, aluminum silicate, calcium silicate, barium sulfate, calcium sulfate, barium stearate, zinc white, talc, silica, aluminum oxide, clay, kaolin, titanium phosphate, mica, gypsum, white carbon, diatomaceous earth, bentonite, lithopone, zeolite, sericite, and organic white colorants such as silicone resin particles, acrylic resin particles, urethane resin particles, and melamine resin particles. Among them, alumina, zinc oxide, and calcium carbonate are preferable from the viewpoint of cost, availability, and color tone.

The viscoelastic layer may optionally contain known additives such as a plasticizer, an antioxidant, a leveling agent, a flame retardant such as aluminum hydroxide or magnesium hydroxide, an antistatic agent, a filler such as glass particles or fibers, plastic particles or fibers, a metal powder or a metal compound, an electrically conductive filler, and a thermally conductive filler. In order to maintain appropriate conformability and cushioning properties, the total amount of the additives is preferably in the range of 0.1 to 10 mass%, more preferably in the range of 1 to 7 mass%, relative to 100 parts by mass of the resin solid content in the acrylic adhesive constituting the viscoelastic layer, as the viscoelastic layer used in the adhesive sheet of the present invention.

The thickness of the viscoelastic layer constituting the pressure-sensitive adhesive tape of the present invention is preferably 20 μm to 500 μm, more preferably 25 μm to 400 μm, and still more preferably 30 μm to 300 μm, in terms of having more excellent oil resistance against sweat, sebum, and the like and contributing to thinning of electronic devices and the like. By setting the thickness of the viscoelastic layer to the above range, an adherend having an uneven shape, a 3D shape, and a rough surface can exhibit appropriate adhesive strength and impact resistance.

The viscoelastic layer is preferably a multilayer (preferably 2 or 3 layers) viscoelastic layer. In particular, when a viscoelastic layer having a thickness of 90 μm or more is produced from the coating liquid of the acrylic pressure-sensitive adhesive, it is preferable to produce a pressure-sensitive adhesive sheet having a thickness of less than 90 μm by laminating them in order to prevent appearance defects due to foaming of a solvent generated during drying. When a plurality of viscoelastic layers are laminated as described above, an adhesive tape having impact resistance can be easily obtained. This is considered to be because, when the viscoelastic layer is formed into a multilayer body, the hollow particles in the viscoelastic layer are easily uniformly dispersed.

The viscoelastic layer in the present invention is a viscoelastic layer having the above-described viscoelastic properties and the like, and thus can be used as a layer having adhesive properties of maintaining excellent adhesion even when sweat, sebum, or the like adheres thereto while maintaining the properties as a base material in a conventional adhesive tape.

(adhesive layer)

As the acrylic adhesive used in the adhesive layer, a (meth) acrylic adhesive can be used which is composed of, as a base polymer, an acrylic copolymer (C) composed of a copolymer containing, as constituent components, 1 or 2 or more selected from the group consisting of alkyl (meth) acrylate monomers other than (a) and (B) and alicyclic monomers, and further contains, as necessary, additives such as a tackifier resin and a crosslinking agent.

As the carboxyl group-containing monomer (a) that can be used for the production of the acrylic copolymer, acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth) acrylic acid dimer, crotonic acid, ethylene oxide-modified succinic acid acrylate, and the like can be used, and among these, acrylic acid is particularly preferably used as a copolymerization component in view of exhibiting more excellent oil resistance and impact resistance against sweat, sebum, alcohol, and the like.

The content of the carboxyl group-containing monomer is not particularly limited, but is preferably in the range of 2 to 30% by mass, more preferably in the range of 4.1 to 25% by mass, and particularly preferably in the range of 5.3 to 20% by mass from the viewpoint of exhibiting more excellent oil resistance and impact resistance against sweat, sebum, alcohol, and the like, relative to the total amount of (a) to (C) used in the production of the acrylic copolymer and the total amount of other vinyl monomers except for (a) to (C) (hereinafter referred to as the total amount of acrylic monomers).

The content of the hydroxyl group-containing monomer is not particularly limited, but is preferably in the range of 0.01 to 1.0% by mass, more preferably in the range of 0.01 to 0.85% by mass, even more preferably in the range of 0.02 to 0.7% by mass, even more preferably in the range of 0.03 to 0.5% by mass, even more preferably in the range of 0.04 to 0.3% by mass, and even more preferably in the range of 0.05 to 0.2% by mass, based on the total amount of the acrylic monomers that can be used in the production of the acrylic copolymer. When the amount is within the above range, the oil resistance is more excellent against sweat, sebum, and the like.

The alkyl (meth) acrylate monomer (C) is a (meth) acrylate having an alkyl group at the ester terminal. The alkyl group of the alkyl (meth) acrylate monomer may be a linear alkyl group or a branched alkyl group. Examples of the alkyl (meth) acrylate monomer include (meth) acrylates having an alkyl group of 1 to 18 carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and isostearyl (meth) acrylate, and 1 or 2 or more, preferably 2 or more of them can be used. Among them, a (meth) acrylate monomer having an alkyl group with 1 to 12 carbon atoms is preferably used, and a (meth) acrylate monomer having 1 to 10 carbon atoms is more preferably used. In particular, the use of at least one (meth) acrylate monomer having 1 to 4 carbon atoms is preferable because the average carbon number of the alkyl group in the (meth) acrylate monomer can be easily adjusted to less than 4.

The average carbon number of 1 or 2 or more selected from the group consisting of alkyl (meth) acrylate monomers and alicyclic monomers in the above (C) is less than 4, preferably in the range of 2.1 to 3.9, more preferably in the range of 2.5 to 3.8, more preferably in the range of 2.6 to 3.8, and particularly preferably in the range of 2.7 to 3.6. In particular, by using n-butyl acrylate and at least one of methyl acrylate and ethyl acrylate within the above range, excellent initial adhesion is obtained, and the adhesive composition is less likely to swell even when sweat, sebum, alcohol, or the like adheres thereto, and can maintain excellent adhesion and impact resistance over a long period of time.

The average number of carbon atoms of 1 or 2 or more selected from the group consisting of alkyl (meth) acrylate monomers and alicyclic monomers is calculated as follows. The product of the number of carbon atoms of each alkyl group and the mole fraction (mol%) of the alkyl (meth) acrylate monomer in (C) is calculated for the alkyl (meth) acrylate monomer contained as (C). Similarly, the product of the number of carbon atoms of each alicyclic group and the mole fraction (mol%) of the alicyclic monomer in (C) is calculated for the alicyclic monomer contained as (C). The average number of carbon atoms is determined by dividing the total of the products calculated for each of the alkyl (meth) acrylate monomers and the alicyclic monomer contained in (C) by the total mole fraction (mol%) of 1 or 2 or more selected from the group consisting of the alkyl (meth) acrylate monomers and the alicyclic monomer in (C).

For example, in the case of using 2 kinds of alkyl (meth) acrylates and 1 kind of alicyclic monomers in combination, in the case of using an alkyl (meth) acrylate monomer containing an alkyl group having a carbon number a in a (mol%), an alkyl (meth) acrylate monomer containing an alkyl group having a carbon number B in B (mol%), and an alkyl (meth) acrylate monomer containing an alicyclic group having a carbon number C in C (mol%), the average carbon number is determined by (a × a + B × B + C × C)/(a + B + C) (where a + B + C is 100).

An average carbon number [ { total (X) }/100 of a product of a mole fraction (mol%) of the alkyl (meth) acrylate monomer with respect to the (C) and a carbon number of an alkyl group contained in the alkyl (meth) acrylate monomer ]

In the production of the acrylic copolymer, other vinyl monomers than (a) to (C) may be used, and as the other vinyl monomers, a vinyl monomer having an amide group, a monomer having a sulfonic acid group, a vinyl ether monomer, a monomer having an alkoxy group, a macromonomer having a radical polymerizable vinyl group in the molecule, or the like may be used.

In the case of using the other vinyl monomer, the amount thereof may be appropriately selected so that the monomer is unlikely to swell even when sweat, sebum, alcohol, or the like adheres thereto, and excellent adhesion and impact resistance are achieved over a long period of time. The content of the other vinyl monomer is preferably 2 to 15% by mass, more preferably 2.5 to 10% by mass, based on the total amount of the acrylic monomers that can be used in the production of the acrylic copolymer.

The acrylic copolymer can be obtained by copolymerization using a known polymerization method such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, and the like, and the solution polymerization method and the bulk polymerization method are preferable from the viewpoint of water resistance of the binder, and the solution polymerization method is preferable from the viewpoint of safety when n-butyl acrylate, methyl acrylate, or ethyl acrylate is used as a main component in the alkyl (meth) acrylate monomer of the above (C). The initiation method of polymerization may be any selected from a thermal initiation method using a peroxide-based thermal polymerization initiator such as benzoyl peroxide or lauroyl peroxide, an azo-based thermal polymerization initiator such as azobisisobutyronitrile, an ultraviolet irradiation initiation method using a photopolymerization initiator such as a acetophenone-based, benzoin ether-based, benzyl ketal-based, acylphosphine oxide-based, benzoin-based, or benzophenone-based photopolymerization initiator, and an electron beam irradiation initiation method.

The temperature at which the loss tangent (tan. delta.) at a frequency of 1Hz of the adhesive used in the adhesive layer of the adhesive tape of the present invention shows a peak is preferably-40 ℃ to 5 ℃. By setting the peak value of the loss tangent of the pressure-sensitive adhesive layer in this range, good adhesion to an adherend at normal temperature can be easily provided. Further, from the viewpoint of improving impact resistance, it is more preferably from-35 ℃ to 3 ℃, and still more preferably from-25 ℃ to 0 ℃. When the viscoelastic layer is formed by mixing and laminating adhesive compositions having different compositions and has a plurality of loss tangent (tan δ) peaks, any one of the peaks may be within the above range, and the peak at the lowest temperature side is preferably within the above range, and more preferably all the peaks are within the above range.

The adhesive layer may be introduced into the hollow structure so as to contain hollow particles or air bubbles, as in the case of the viscoelastic layer. When the embodiment of the double-sided pressure-sensitive adhesive tape having the pressure-sensitive adhesive layer on both sides of the viscoelastic layer is used for fixing 2 or more adherends constituting an electronic device or the like, the hollow structure may be introduced into the pressure-sensitive adhesive layer on both sides, or the hollow structure may be introduced into the pressure-sensitive adhesive layer on the side to be attached to the first adherend, or the hollow structure may not be introduced into the pressure-sensitive adhesive layer on the side to be attached to 2 or more adherends.

From the viewpoint of chemical resistance and impact resistance, the hollow structure is preferably introduced in a form containing hollow particles, and particularly, hollow particles made of glass or hollow particles made of thermoplastic resin are preferably used. The hollow particles are preferably heat-expandable microcapsules made of a thermoplastic resin as a shell and containing a heat-expanding agent such as a saturated hydrocarbon having 4 to 7 carbon atoms such as heptane, hexane, isobutane as an interior of the shell, and the like. The thermally expandable microcapsules can be used after being appropriately expanded by heating, and it is preferable to use thermally expandable microcapsules expanded in advance from the viewpoint of thickness accuracy of the viscoelastic base material and easiness of production.

The average particle diameter of the hollow particles is preferably not more than the thickness of the pressure-sensitive adhesive layer, and is preferably 90% or less, more preferably 50% or less, and still more preferably 20 to 40% with respect to the thickness of the pressure-sensitive adhesive layer. Within the above range, it is preferably 100 μm or less, preferably 10 to 80 μm, and 20 to 60 μm, since sufficient impact resistance can be obtained without impairing initial adhesion. The average particle diameter of the hollow particles is, for example, a 50% average particle diameter by using a laser scattering particle size distribution measuring apparatus.

The amount of the hollow particles in the viscoelastic layer is preferably 5 to 60 vol%, more preferably 15 to 45 vol%, based on the total amount of the binder used in the viscoelastic layer. When the content is within this range, sufficient impact resistance can be obtained, and the viscoelastic layer has high tensile strength, so that excellent punching workability can be obtained. As a method of dispersing the hollow particles, any stirring machine such as a mixer or a dissolver may be used as long as the effect of the present invention is not impaired.

The apparent density of the pressure-sensitive adhesive layer is not particularly limited, and is 0.50 to 1.1g/cm from the viewpoint of easily achieving both impact resistance and excellent adhesion to an adherend ³ Preferably 0.60 to 1.0g/cm ³ More preferably 0.7 to 1.0g/cm ³ . The apparent density was measured in accordance with JISK 6767. An adhesive layer (thickness measured) cut into a 4cm × 5cm rectangular shape was prepared to be about 15cm ³ On the left and right sides, the mass was measured to obtain the apparent density.

Examples of the tackifier resin include rosin-based tackifier resins, polymerized rosin ester-based tackifier resins, rosin phenol-based tackifier resins, stabilized rosin ester-based tackifier resins, disproportionated rosin ester-based tackifier resins, hydrogenated rosin ester-based tackifier resins, terpene phenol-based tackifier resins, petroleum resin-based tackifier resins, and (meth) acrylate resin-based tackifier resins. The softening point of the tackifier resin is not particularly limited, and is 30 to 180 ℃, preferably 40 to 140 ℃.

The content of the tackifier resin is not particularly limited as long as the temperature at which the loss tangent (tan δ) at a frequency of 1Hz shows a peak is in the range of-40 to 5 ℃, but is preferably 35 parts by mass or less, and more preferably 25 parts by mass or less, from the viewpoint that the oil resistance is more excellent against sweat, sebum, and the like when 50 parts by mass or less is contained with respect to 100 parts by mass of the resin solid content in the acrylic adhesive. In addition, the above-mentioned tackifier resins may be used in combination of 2 or more.

In addition, the pressure-sensitive adhesive layer is crosslinked with a crosslinking agent in order to have a more excellent cohesive force. As an index of the degree of crosslinking of the pressure-sensitive adhesive layer, a value obtained by measuring the gel fraction of insoluble components after the pressure-sensitive adhesive layer was immersed in toluene for 24 hours was used. When the gel fraction is in the range of preferably 20 to 90% by mass, more preferably 30 to 80% by mass, and still more preferably 30 to 70% by mass, both of the cohesiveness and the adhesiveness are good.

For the measurement of gel fraction, a binder containing the above binder composition and a crosslinking agent was applied, dried at 90 ℃ for 3 minutes, aged at 40 ℃ for 2 days, and the resultant was cut into 50mm squares to obtain samples. Then, the mass of the sample was measured (G1), and the sample was immersed in a toluene solution at 23 ℃ for 24 hours. The toluene-insoluble matter of the impregnated sample was separated by filtration through a 200-mesh wire gauze, and the mass of the residue after drying at 110 ℃ for 1 hour was measured (G2), and the gel fraction was calculated according to the following formula.

Gel fraction (% by mass) of (G2-G3)/(G1-G3) × 100

-G3: mass of hollow particles present in the sample

As the crosslinking agent, a conventionally known or customary crosslinking agent in the field of acrylic adhesives can be used. For example, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, metal chelate-based crosslinking agents, aziridine-based crosslinking agents, oxazoline-based crosslinking agents, and the like can be used. Among these, a crosslinking agent which can be easily mixed with the acrylic copolymer or a solution thereof prepared in advance and can rapidly perform a crosslinking reaction is preferably used, and specifically, an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent are more preferably used. One kind of the crosslinking agent may be used or two or more kinds may be used in combination.

As the acrylic pressure-sensitive adhesive, a solvent-containing acrylic pressure-sensitive adhesive is preferably used in view of maintaining its good coating workability. Examples of the solvent include toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, and hexane. In view of the solvent resistance of the thermoplastic resin hollow particles, the proportion of ethyl acetate in the entire solvent component is preferably 70% by mass or more, and more preferably 90% by mass or more.

The acrylic pressure-sensitive adhesive may be colored in order to impart design properties, light-shielding properties, concealing properties, light-reflecting properties, and light resistance to the pressure-sensitive adhesive tape. The coloring agents may be used singly or in combination of 2 or more.

When light-shielding properties, concealing properties, and light resistance are imparted to the pressure-sensitive adhesive tape, the pressure-sensitive adhesive layer is colored black. As the black colorant, carbon black, graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine black, activated carbon, ferrite, magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complex, composite oxide-based black pigment, anthraquinone-based organic black pigment, and the like can be used. Among them, carbon black is preferred from the viewpoint of cost, availability, insulation properties, and heat resistance to withstand the temperature of the step of extruding the foamable polyolefin resin composition and the heating foaming step.

When design properties, light reflectivity, and the like are imparted to the pressure-sensitive adhesive tape, the pressure-sensitive adhesive layer is colored white. Examples of the white colorant include inorganic white colorants such as titanium oxide, zinc oxide, aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, calcium oxide, tin oxide, barium oxide, cesium oxide, yttrium oxide, magnesium carbonate, calcium carbonate, barium carbonate, zinc carbonate, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, zinc hydroxide, aluminum silicate, calcium silicate, barium sulfate, calcium sulfate, barium stearate, zinc white, talc, silica, aluminum oxide, clay, kaolin, titanium phosphate, mica, gypsum, white carbon, diatomaceous earth, bentonite, lithopone, zeolite, sericite, and organic white colorants such as silicone resin particles, acrylic resin particles, urethane resin particles, and melamine resin particles. Among them, alumina, zinc oxide, and calcium carbonate are preferable from the viewpoint of cost, availability, and color tone.

The pressure-sensitive adhesive layer may optionally contain known additives such as a plasticizer, an antioxidant, a leveling agent, a flame retardant such as aluminum hydroxide or magnesium hydroxide, an antistatic agent, a filler such as glass particles or fibers, plastic particles or fibers, metal powder or metal compounds, an electrically conductive filler, and a thermally conductive filler, as required. In order to maintain appropriate conformability and cushioning properties, the total amount of the additives is preferably 0.1 to 10 mass%, preferably 1 to 7 mass%, based on 100 parts by mass of the resin solid content in the acrylic adhesive constituting the adhesive layer. The average particle size of the additive is preferably not more than the thickness of the pressure-sensitive adhesive layer, preferably not more than 90%, more preferably not more than 50%, and 20 to 40% of the thickness of the pressure-sensitive adhesive layer, because it has little influence on the initial adhesion of the pressure-sensitive adhesive tape.

The pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive tape of the present invention is preferably a pressure-sensitive adhesive layer having a thickness in the range of 1 to 200 μm, more preferably a pressure-sensitive adhesive layer having a thickness in the range of 10 to 140 μm, and still more preferably a pressure-sensitive adhesive layer having a thickness in the range of 10 to 100 μm, in terms of having more excellent oil resistance against sweat, sebum, and the like and contributing to thinning of electronic devices and the like.

(adhesive tape)

The adhesive tape of the invention may comprise a support substrate. Examples of the supporting substrate include resin substrates, foam substrates, nonwoven fabric substrates, fabrics, paper, and metal foils. Among them, a resin base material is preferably used.

Examples of the resin substrate include films and sheets obtained by using polyesters such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, polyolefins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymers, poly (meth) acrylates such as polymethyl methacrylate having a loss tangent (tan δ) at a frequency of 1Hz of 50 ℃ or higher, polyurethanes, polyamides, and polyimides.

The thickness of the supporting substrate can be suitably selected according to the purpose, and it is preferable to use 1 to 500. mu.m, and a supporting substrate of 2 to 200 μm is particularly preferable.

In order to improve the adhesion to the pressure-sensitive adhesive layer and the viscoelastic layer, the support base material may be subjected to surface treatment such as corona treatment, flame treatment, plasma treatment, hot air treatment, ozone/ultraviolet treatment, or application of an easy-adhesion treatment agent. The surface treatment can provide good adhesion by setting the wetting index with the wetting agent to 36mN/m or more, preferably 40mN/m, and more preferably 48 mN/m. The support base material may be subjected to a treatment (mixing of a pigment, printing, vapor deposition of a metal, or the like) for improving design properties, concealing properties, and light shielding properties.

Examples of the method for producing the adhesive tape of the present invention include: a method in which the adhesive composition for the viscoelastic layer is applied to the surface of a release liner in advance and dried to form the viscoelastic layer, and the adhesive composition is applied to one surface or both surfaces of the viscoelastic layer and dried, thereby producing the viscoelastic layer (direct method); alternatively, the adhesive layer is formed by applying an adhesive composition to the surface of the release liner and drying the adhesive composition, and then the adhesive layer is transferred to one surface or both surfaces of the viscoelastic layer, thereby producing the viscoelastic composite material (transfer method).

The adhesive tape of the present invention can be stored in a sheet form or a roll form in a state where a release film is laminated on the surface of the adhesive layer.

The thickness of the pressure-sensitive adhesive tape of the present invention is not particularly limited, and in view of having more excellent oil resistance against sweat, sebum, and the like and having excellent impact resistance, a pressure-sensitive adhesive tape having a thickness of 40 μm or more is preferably used, a pressure-sensitive adhesive tape having a thickness in the range of 80 μm to 900 μm is more preferably used, a pressure-sensitive adhesive tape having a thickness in the range of 90 μm to 500 μm is further preferably used, and a pressure-sensitive adhesive tape having a thickness in the range of 100 μm to 400 μm is further preferably used.

The adhesive tape of the present invention has good initial adhesion, is less likely to swell even when sweat, sebum, or the like adheres thereto, maintains excellent adhesion for a long period of time, and has excellent impact resistance and repellency, and therefore, the adhesive tape can be suitably used in various fields such as double-sided tapes used for bonding housings of electronic devices such as portable electronic terminals and tablet computers, labels for imparting design properties to the surfaces of the housings, waterproof tapes, and adhesive tapes for medical devices.

Examples

The present invention will be described in more detail below with reference to examples.

[ adjustment example 1]

77.4 parts by mass of n-butyl acrylate, 7.5 parts by mass of acrylic acid, 15 parts by mass of methyl acrylate, 0.1 part by mass of 4-hydroxybutyl acrylate and 200 parts by mass of ethyl acetate were put into a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen introduction tube and a thermometer, and nitrogen bubbling was performed at normal temperature for 1 hour under stirring to obtain a mixture.

Subsequently, 2 parts by mass (solid content: 1.0% by mass) of a2, 2' -azobis (2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the upper mixture, and the mixture was kept at 72 ℃ for 4 hours under stirring and then at 75 ℃ for 5 hours. '

Then, the mixture was diluted with ethyl acetate and filtered through a 200-mesh wire gauze, thereby obtaining an acrylic copolymer (a-1) solution (solid content concentration 26 mass%) having a weight average molecular weight of 88 ten thousand and an average carbon number of saturated hydrocarbon groups contained in the alkyl acrylate monomer of 3.3.

To 100 parts by mass of the acrylic copolymer (A-1) solution were added hollow particles made of a thermoplastic resin (Matsumoto Microsphere FN-80SDE, available from Songban oil & fat pharmaceuticals Co., Ltd., acrylonitrile copolymer, having an average particle diameter of 30 μm and a density of 0.025g/cm ³ )0.16 part by mass was uniformly dispersed, and then 0.8 part by mass of Burnock D-40 (an adduct of toluene diisocyanate and trimethylolpropane, manufactured by DIC Co., Ltd., nonvolatile matter content: 40% by mass, hereinafter referred to as D-40) was added as a crosslinking agent to obtain an adhesive composition (P-1).

[ adjustment example 2]

An adhesive composition (P-2) was obtained by adding 0.05 part by mass of thermoplastic resin hollow beads (Matsumoto Microsphere FN-80SDE) to 100 parts by mass of the acrylic copolymer (A-1) solution, uniformly dispersing the mixture, and then adding 0.8 part by mass of D-40.

[ adjustment example 3]

To 100 parts by mass of the acrylic copolymer (A-1) solution, 0.64 parts by mass of thermoplastic resin hollow particles (Matsumoto Microsphere FN-80SDE) were added and uniformly dispersed, and then 0.8 parts by mass of D-40 was added to obtain an adhesive composition (P-3).

[ adjustment example 4]

To 100 parts by mass of the acrylic copolymer (A-1) solution, 0.67 parts by mass of thermoplastic resin hollow particles (Matsumoto Microsphere FN-80SDE) were added and uniformly dispersed, and then 0.8 parts by mass of D-40 was added to obtain an adhesive composition (P-4).

[ adjustment example 5]

An adhesive composition (P-5) was obtained by mixing and uniformly dispersing 100 parts by mass of the acrylic copolymer (A-1) solution with 1.38 parts by mass of thermoplastic resin hollow beads (Matsumoto microspheres FN-80SDE), and then mixing 0.8 part by mass of D-40.

[ adjustment example 6]

An adhesive composition (P-6) was obtained by adding 0.19 part by mass of hollow particles made of a thermoplastic resin (Expancel 920DE40D30, manufactured by Japan Fillite Co., Ltd., acrylonitrile copolymer, average particle diameter 45 μm, density 0.03g/cm3) to 100 parts by mass of the acrylic copolymer (A-1) solution, uniformly dispersing the mixture, and then adding 0.8 part by mass of D-40.

[ adjustment example 7]

An adhesive composition (P-7) was obtained by adding 1.30 parts by mass of Glass hollow beads (Glass Bubbles K-15, 3M, average particle size 60 μ M, density 0.15g/cm3) to 100 parts by mass of the acrylic copolymer (A-1) solution and uniformly dispersing them, and then adding 0.8 part by mass of D-40.

[ adjustment example 8]

An acrylic copolymer (A-2) solution having an average molecular weight of 75 ten thousand and an average carbon number of a saturated hydrocarbon group contained in an alkyl acrylate monomer of 3.3 (solid content concentration: 26%) was obtained in the same manner as in preparation example 1, except that n-butyl acrylate was changed to 74.9 parts by mass, acrylic acid was changed to 10 parts by mass, methyl acrylate was changed to 15 parts by mass, and 4-hydroxybutyl acrylate was changed to 0.1 part by mass. To 100 parts by mass of the acrylic copolymer (A-2) solution, 0.16 parts by mass of thermoplastic resin hollow particles (Matsumoto Microsphere FN-80SDE, manufactured by Songbo oil & fat pharmaceuticals Co., Ltd.) were added and uniformly dispersed, and then 0.8 part by mass of D-40 was added to obtain an adhesive composition (P-8).

[ adjustment example 9]

An acrylic copolymer (A-3) solution having a weight-average molecular weight of 70 ten thousand and an average carbon number of saturated hydrocarbon groups contained in an alkyl acrylate monomer of 2.6 was obtained in the same manner as in preparation example 1, except that n-butyl acrylate was changed to 59.9 parts by mass, acrylic acid was changed to 10 parts by mass, methyl acrylate was changed to 30 parts by mass, and 4-hydroxybutyl acrylate was changed to 0.1 part by mass. To 100 parts by mass of the acrylic copolymer (A-2) solution, 0.16 parts by mass of thermoplastic resin hollow particles (Matsumoto Microsphere FN-80SDE, manufactured by Songbo oil & fat pharmaceuticals Co., Ltd.) were added and uniformly dispersed, and then 0.8 parts by mass of D-40 was added to obtain an adhesive composition (P-9).

[ adjustment example 10]

An acrylic copolymer (A-3) solution having a weight-average molecular weight of 71 ten thousand and an average carbon number of saturated hydrocarbon groups contained in an alkyl acrylate monomer of 2.6 was obtained in the same manner as in preparation example 1, except that n-butyl acrylate was changed to 59.9 parts by mass, acrylic acid was changed to 5 parts by mass, methyl acrylate was changed to 35 parts by mass, and 4-hydroxybutyl acrylate was changed to 0.1 part by mass. To 100 parts by mass of the acrylic copolymer (A-2) solution, 0.16 part by mass of thermoplastic resin hollow particles (Matsumoto Microsphere FN-80SDE, manufactured by Songbo oil and fat pharmaceuticals Co., Ltd.) were uniformly dispersed, and then 0.8 part by mass of D-40 was added to obtain a pressure-sensitive adhesive composition (P-9).

[ example 1]

The pressure-sensitive adhesive composition (P-1) obtained in preparation example 1 was applied to a release-treated surface of a release liner (a polyethylene terephthalate film having a thickness of 75 μm and a release-treated surface on one side thereof) so that the thickness thereof after drying became 66 μm, and dried at 90 ℃ for 3 minutes to prepare 1 viscoelastic layer. In the same manner, 2 viscoelastic layers were prepared, and the adhesive composition (P-1) was applied and dried to a thickness of 67 μm after drying. Next, after the exposed surfaces of 2 viscoelastic layers were laminated, the layers were laminated from the upper surface of the release liner by a roller with a linear pressure of 5 kg/cm. After lamination, another viscoelastic layer was laminated on the surface exposed by peeling off one release liner, and then lamination was performed at room temperature from the upper surface of the release liner with a roller having a linear pressure of 5 kg/cm. The adhesive tape (T-1) was aged at 40 ℃ for 48 hours to obtain an adhesive tape having a thickness of 200 μm.

[ examples 2 to 10]

Adhesive tapes (T-2 to T-10) having a thickness of 200 μm were obtained in the same manner as in example 1, except that the adhesive compositions (P-2 to P-10) obtained in preparation examples 2 to 10 were used.

Comparative adjustment example 1

To 100 parts by mass of the acrylic copolymer (A-1) solution, 0.8 part by mass of D-40 was added to obtain an adhesive composition (Q-1).

Comparative adjustment example 2

An acrylic copolymer (B-1) solution having a weight-average molecular weight of 106 million and an average carbon number of a saturated hydrocarbon group contained in an alkyl acrylate monomer of 4.4 (solid content concentration: 26%) was obtained in the same manner as in preparation example 1, except that 79.9 parts by mass of n-butyl acrylate, 6 parts by mass of 2-ethylhexyl acrylate, 10 parts by mass of cyclohexyl acrylate, 4 parts by mass of acrylic acid, and 0.1 part by mass of 4-hydroxybutyl acrylate were used.

A pressure-sensitive adhesive composition (Q-2) was obtained by uniformly mixing 1.3 parts by mass of a polymerized rosin ester "HARITACK PCJ" manufactured by Harima Chemicals Group and 3.9 parts by mass of an aromatic hydrocarbon resin "FTR 6125" manufactured by Mitsui Chemicals, Inc. with 100 parts by mass of the acrylic polymer (B-1) solution, mixing 0.16 part by mass of a hollow pellet (Matsumoto Microsphere FN-80SDE) made of a thermoplastic resin, uniformly dispersing the mixture, and mixing 1.3 parts by mass of D-40.

Comparative adjustment example 3

An acrylic copolymer (B-2) solution (solid content concentration: 26%) having a weight average molecular weight of 71 ten thousand and an average carbon number of saturated hydrocarbon groups contained in an alkyl acrylate monomer of 4.0 was obtained in the same manner as in preparation example 1, except that 89.9 parts by mass of n-butyl acrylate, 10 parts by mass of acrylic acid and 0.1 part by mass of 4-hydroxybutyl acrylate were used.

An adhesive composition (Q-3) was obtained by mixing 0.16 part by mass of thermoplastic resin hollow particles (Matsumoto Microsphere FN-80SDE) with 100 parts by mass of the acrylic polymer (B-2) solution, uniformly dispersing the mixture, and then mixing 0.6 part by mass of D-40.

Comparative adjustment example 4 "

An acrylic copolymer (B-3) solution having a weight-average molecular weight of 87 ten thousand and an average carbon number of saturated hydrocarbon groups of an alkyl acrylate monomer of 6.5 (solid content concentration 26%) was obtained in the same manner as in preparation example 1, except that the amount of 2-ethylhexyl acrylate was changed to 75 parts by mass, 10 parts by mass, and 5.0 parts by mass of methyl acrylate.

To the acrylic copolymer (B-3) solution, 0.16 parts by mass of thermoplastic resin hollow beads (Matsumoto Microsphere FN-80SDE) was added per 100 parts by mass of the resin solid content, and uniformly dispersed, and then 0.1 part by mass of D-40 was added to obtain an adhesive composition (Q-4).

Comparative example 1

A double-sided pressure-sensitive adhesive tape (U-1) having a thickness of 200 μm was obtained in the same manner as in example 1, except that the pressure-sensitive adhesive composition (Q-1) was used in place of the pressure-sensitive adhesive composition (P-1).

Comparative example 2

A double-sided pressure-sensitive adhesive tape (U-2) having a thickness of 200 μm was obtained in the same manner as in example 1, except that the pressure-sensitive adhesive composition (Q-2) was used in place of the pressure-sensitive adhesive composition (P-1).

Comparative example 3

A double-sided pressure-sensitive adhesive tape (U-3) having a thickness of 200 μm was obtained in the same manner as in example 1, except that the pressure-sensitive adhesive composition (Q-3) was used in place of the pressure-sensitive adhesive composition (P-1).

Comparative example 4

A double-sided pressure-sensitive adhesive tape (U-4) having a thickness of 200 μm was obtained in the same manner as in example 1, except that the pressure-sensitive adhesive composition (Q-4) was used in place of the pressure-sensitive adhesive composition (P-1).

Comparative example 5

In a polyolefin foam (thickness 170 μm, density 0.54 g/cm) ³ 25% compressive strength: 600kPa, manufactured by Water chemical industries, Ltd., the surface is set as wetting index 54mN/m), 1 dried adhesive layer made of adhesive composition (Q-1) with thickness of 15 μm is laminated on each of both sides by corona treatment, and then lamination is performed from the upper surface of the release liner at room temperature by a roller with line pressure of 5 kg/cm. This was aged at 40 ℃ for 48 hours to obtain a double-sided adhesive tape (U-5) having a foam base with a thickness of 200. mu.m.

[ example 11]

The pressure-sensitive adhesive composition (P-1) obtained in preparation example 1 was applied to the release-treated surface of a release liner (polyethylene terephthalate film having a thickness of 75 μm and a release treatment on one surface side) so that the dried thickness became 100 μm, and dried at 90 ℃ for 3 minutes to prepare 1 viscoelastic layer. In the same manner, 2 adhesive layers were prepared, and the adhesive composition (Q-1) was applied and dried to a thickness of 50 μm after drying. Subsequently, after laminating the viscoelastic layer and 1 sheet of the adhesive layer, lamination was performed from the upper surface of the release liner by a roller having a linear pressure of 5 kg/cm. After lamination, another 1 pressure-sensitive adhesive layer was laminated on the exposed surface of the release liner on the side of the viscoelastic layer, and then lamination was performed at room temperature from the upper surface of the release liner with a roller having a linear pressure of 5 kg/cm. The adhesive tape (T-11) was aged at 40 ℃ for 48 hours to obtain an adhesive tape having a thickness of 200 μm.

[ example 12]

An adhesive tape (T-12) having a thickness of 200 μm was obtained in the same manner as in example 10, except that the thickness of the viscoelastic layer was 60 μm and the thickness of the adhesive layer was 70 μm.

[ method for measuring pressing Strength ]

The double-sided adhesive tapes obtained in examples and comparative examples were cut into a sash shape having an outer dimension of 14mm square and a width of 1mm, the release liner on one surface side of the double-sided adhesive tape was peeled off in an atmosphere of 23 ℃ and 50% RH, and 1 sheet of the adhesive tape was attached to a soda-lime glass plate (color tone: colorless transparency) having a thickness of 3mm and 20mm square so that the center of the sash-shaped processed product overlapped with the center of the glass plate.

The release liner on the other surface side of the test piece was peeled off, and the resulting sheet was bonded to the surface of a 2mm thick polycarbonate plate (makrolon, color tone: transparent, manufactured by Bayer corporation) having a hole of 10mm diameter at the center (bonding area: 0.52 cm) ² ) From a glass plate at 50N/cm ² Pressure-bonding for 10 seconds, thereby obtaining a sticker.

The above-mentioned sticker was left to stand at 23 ℃ under an atmosphere of 50% RH for 24 hours, and then left to stand at 60 ℃ under an atmosphere of 90% RH for 24 hours. Then, the mixture was left at 23 ℃ and 50% RH for 24 hours.

Next, the glass plate was pressed from the hole of the polycarbonate plate of the above-mentioned adherend at a speed of 5mm/min by using a SUS probe having a diameter of 7mm, and the peel strength of the glass plate was measured (G1).

[ method for evaluating oil resistance ]

After the patch obtained in the above [ method for measuring pressing strength ] was left to stand in an atmosphere of 23 ℃ and 50% RH for 24 hours, about 10mg of oleic acid (purity 99%) was dropped from the hole of the polycarbonate plate: squalene-1: 1 (mass ratio) was left to stand at 60 ℃ for 24 hours in an atmosphere of 90% RH. Then, the mixture was left at 23 ℃ and 50% RH for 24 hours.

Next, the glass plate was pressed from the hole of the polycarbonate plate of the above-mentioned adherend at a speed of 5mm/min by a probe having a diameter of 7mm, and the peel strength of the glass plate was measured (G2).

The adhesion retention was calculated from the above-mentioned press strengths (G1) and (G2), and the oil resistance was evaluated.

Adhesion retention (%) (G2/G1) × 100

[ method for evaluating impact resistance ]

The patch obtained in the above [ method for measuring pressing strength ] was left to stand at 23 ℃ and 50% RH for 24 hours, and then set on a pedestal of a dupont impact TESTER (manufactured by TESTER SANGYO corporation) so that the glass plate of the test piece faces downward.

Next, an impact core made of stainless steel having a diameter of 9.5mm and a mass of 200g was dropped 3 times from the polycarbonate plate side from a position having a height of 10cm, and then the test piece was evaluated for the presence or absence of peeling of the adhesive tape and breakage of the base material. In the case of no peeling, the falling height was 10cm higher than the previous one, and it was confirmed that there was no peeling of the adhesive tape or substrate breakage in the test piece after 3 times of falling. Thereafter, when the test piece was not peeled off and the substrate was broken, the test was repeated by increasing the drop height by 10cm each time, and the drop height (cm) at which the peeling of the pressure-sensitive adhesive tape and the breakage of the substrate were finally confirmed was measured.

The above results are shown in the following table. In the table, the average carbon number is the average carbon number of the saturated hydrocarbon group of the alkyl (meth) acrylate monomer used.

[ Table 1]

[ Table 2]

[ Table 3]

[ Table 4]

From the above results, it is clear that examples 1 to 12, which are the present invention, have excellent properties in all of the adhesion (pressing strength), oil resistance (adhesion maintaining rate) and impact resistance. In particular, even a narrow tape having a width of 1mm is excellent in oil resistance. On the other hand, in comparative examples 1 to 5, it was found that any one or more of the above characteristics were inferior.

Claims

1. An adhesive tape comprising a viscoelastic layer containing an acrylic adhesive and hollow particles or bubbles, wherein the acrylic adhesive contains an acrylic copolymer and a crosslinking agent,

the acrylic copolymer comprises

(A) A carboxyl group-containing monomer;

(B) a hydroxyl-containing monomer; and

As the constituent components, a water-soluble polymer,

the average number of carbon atoms of the monomer (C) is less than 4,

an average carbon number [ { a total (X) } of a product of a mole fraction (mol%) of the alkyl (meth) acrylate monomer with respect to the (C) and a carbon number of an alkyl group contained in the alkyl (meth) acrylate monomer + { a total (Y) }/100] of a product of a mole fraction (mol%) of the alicyclic monomer with respect to the (C) and a carbon number of an alicyclic group contained in the alicyclic monomer.

2. The adhesive tape according to claim 1,

the adhesive tape has an adhesive layer on at least one surface of the viscoelastic layer directly or via another layer,

the adhesive layer contains an acrylic adhesive comprising an acrylic copolymer and a crosslinking agent, the acrylic copolymer comprising

(A) A carboxyl group-containing monomer;

(B) a hydroxyl-containing monomer; and

As the constituent components, a water-soluble polymer,

the average number of carbon atoms of the monomer (C) is less than 4,

3. The adhesive tape according to claim 1 or 2,

the viscoelastic layer comprises 5 to 60 volume% of the hollow particles in the viscoelastic layer.

4. The adhesive tape according to any one of claims 1 to 3,

the hollow particles are heat-expandable microcapsules each having a thermoplastic resin shell and containing a heat-expanding agent in the shell.

5. The adhesive tape according to any one of claims 1 to 4,

the temperature at which the loss tangent tan delta of the viscoelastic layer and/or the adhesive layer shows a peak at a frequency of 1Hz is-40 ℃ to 5 ℃.

6. The adhesive tape according to any one of claims 1 to 5,

the weight average molecular weight of the acrylic copolymer is 40 to 300 ten thousand.

7. The adhesive tape according to any one of claims 1 to 6,

the thickness of the viscoelastic layer is 20 to 500 [ mu ] m.

8. The adhesive tape according to any one of claims 1 to 7,

the thickness of the adhesive layer is 1-200 μm.