JP2017132993A - Aqueous adhesive composition and utilization thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous adhesive composition capable of preventing metal corrosion at a high level, the aqueous adhesive composition not corroding a metal (such as silver) that has no direct contact with an adhesive sheet, in a state where the adhesive sheet and a metallic material coexist in a limited space such as inside electronic equipment.SOLUTION: An aqueous adhesive composition includes an acrylic polymer as a base polymer and a tackifying component. In the tackifying component, no CSis detected in gas chromatograph mass spectrometry carried out at a vaporization temperature of 250°C. The tackifying component is a tackifying resin emulsion including an antiseptic agent.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an aqueous pressure-sensitive adhesive (also referred to as pressure-sensitive adhesion; hereinafter the same) agent composition, and a pressure-sensitive adhesive sheet formed using the water-based pressure-sensitive adhesive composition. This application claims the benefit based on Malaysian application PI2016700346 filed on Jan. 29, 2016, the entire contents of which is incorporated herein by reference.

  An aqueous pressure-sensitive adhesive composition having an adhesive component in an aqueous medium (for example, an emulsion-type pressure-sensitive adhesive composition in which the adhesive component is dispersed in an aqueous medium) is a pressure-sensitive adhesive composition in which the adhesive component is dissolved in an organic solvent. Compared to (solvent-type pressure-sensitive adhesive composition), it is desirable from the viewpoint of environmental hygiene. For this reason, the adhesive sheet using an aqueous adhesive composition is utilized in various fields in a double-sided tape and other forms. As an example of this application field, there are various electronic devices such as home appliances and OA devices. Patent document 1 is mentioned as technical literature regarding an aqueous emulsion type pressure-sensitive adhesive.

US Patent Application Publication No. 2010/0255297

  By the way, the adhesive sheet formed from the aqueous adhesive composition may corrode a metal (for example, silver) that does not directly contact the adhesive sheet depending on the mode of use. For example, corrosion may occur in the non-contact metal material in a situation where the adhesive sheet and the metal material coexist in a limited space such as inside an electronic device. Such an event can be a cause of contact failure due to corrosion of a metal constituting a substrate or wiring of an electronic device. Further, in an electronic device having a display, a problem that the screen is discolored due to metal corrosion may occur. Therefore, when it is assumed that the adhesive sheet is used in the above-described applications, it is desirable that the pressure-sensitive adhesive sheet has a property that does not corrode metals.

  For example, Patent Document 1 proposes an adhesive sheet in which metal corrosion is suppressed by using a preservative that does not corrode a silver plate in a predetermined metal corrosion test. However, the pressure-sensitive adhesive sheet may be exposed to more severe conditions (specifically, high-temperature conditions) than assumed in Patent Document 1, and metal corrosion will only occur if the above-described metal corrosion test is satisfied. Suppression is not enough. Further, regarding the preservative to be considered for adoption, it is necessary to produce a pressure-sensitive adhesive containing the preservative each time and conduct a test, which is also inefficient. Further, the preservative is not only added to the pressure-sensitive adhesive composition, but may be preliminarily contained in the tackifier. In that case, even if the preservative added by the pressure-sensitive adhesive manufacturer is non-corrosive to metal, metal corrosion may occur depending on the type of preservative contained in the tackifier.

  As a result of intensive studies on the prevention of metal corrosion, the present inventors have found that even if the type of additives such as preservatives contained in the tackifier is unknown, it is better depending on whether or not a specific indicator substance is detected. The present inventors have found that metal corrosion prevention can be realized and have completed the present invention. That is, an object of the present invention is to provide an aqueous pressure-sensitive adhesive composition capable of highly suppressing metal corrosion in a composition containing a tackifier component. Another object of the present invention is to provide a pressure-sensitive adhesive sheet formed using such an aqueous pressure-sensitive adhesive composition.

According to the present invention, an aqueous pressure-sensitive adhesive composition comprising an acrylic polymer as a base polymer and a tackifier component is provided. The tackifying component is a tackifying component in which CS ₂ is not detected in gas chromatography mass spectrometry performed at a vaporization temperature of 250 ° C.

The present inventors investigated the causative substance of metal corrosion in the pressure-sensitive adhesive sheet, and found that the causative substance of metal corrosion exists among the additive components previously contained in the tackifier component. As a result of further investigation, a tackifying component that generates CS ₂ at a vaporization temperature (sample vaporization temperature) of 250 ° C. in gas chromatograph mass spectrometry was determined in a metal corrosion test carried out by the method described in the examples below. A relationship has been found that causes metal corrosion. Since CS ₂ itself does not corrode the metal even after being exposed to a metal (typically silver) for about one week, it is difficult to consider it as a causative substance of metal corrosion. Among the compounds in the tackifier component, it is speculated that a compound that decomposes at 250 ° C. to generate CS ₂ is a causative substance of metal corrosion. That is, by performing gas chromatography mass spectrometry on the tackifier component at a vaporization temperature of 250 ° C. and confirming whether CS ₂ is detected, the metal corrosion-causing substance in the tackifier component is specified. It was discovered that the metal corrosion caused by the causative substance could be predicted without any problem. Based on this discovery, according to the present invention, it is possible to highly suppress metal corrosion by using a tackifying component in which CS ₂ is not detected in gas chromatography mass spectrometry performed at a vaporization temperature of 250 ° C.

In a preferred embodiment of the technology disclosed herein, the tackifier component is a tackifier resin emulsion containing a preservative. Since the causative substance of metal corrosion is considered to be a preservative contained in the tackifier resin emulsion, a metal non-corrosive preservative is used as a tackifier component that does not generate CS ₂ at 250 ° C. in the above configuration. It is thought that. According to such a configuration, it is possible to preferably realize the effects of the technology disclosed herein while enjoying the advantage of good storage stability and easy production management.

  In a preferred aspect of the technology disclosed herein, the tackifier component includes a rosin-based tackifier resin. By using a rosin-based tackifying resin, excellent adhesive properties (for example, high peel strength) can be preferably obtained.

  In a preferred embodiment of the technology disclosed herein, the preservative is a compound having a heterocycle containing a sulfur atom (S) as a constituent atom. By using the preservative, it is possible to suppress metal corrosion at a higher level while enjoying the advantage of good storage stability and easy production management.

  Moreover, according to this invention, the adhesive sheet containing the adhesive layer formed from one of the aqueous adhesive compositions disclosed here is provided. Since the water-based pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains a tackifier component, the water-based pressure-sensitive adhesive composition can exhibit excellent pressure-sensitive adhesive properties, while being used in an environment where the metal material coexists, Corrosion can be suppressed at a higher level.

In the pressure-sensitive adhesive sheet according to a preferred embodiment, CS ₂ is not detected by gas chromatography mass spectrometry performed at a vaporization temperature of 250 ° C. When the pressure-sensitive adhesive sheet satisfying such properties is used in an environment in which it coexists with a metal material, the metal material is unlikely to corrode.

  The pressure-sensitive adhesive sheet according to a preferred embodiment has a 180-degree peel strength with respect to the stainless steel plate of 8 N / 20 mm or more. The pressure-sensitive adhesive sheet having the above-mentioned pressure-sensitive adhesive force is preferably used as a strong adhesive pressure-sensitive adhesive sheet for firmly fixing an article or member.

  A pressure-sensitive adhesive sheet according to a preferred embodiment includes a base material, a first pressure-sensitive adhesive layer disposed on one surface of the base material, and a second surface disposed on the other surface of the base material as the pressure-sensitive adhesive layer. And a pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet having such a structure generally has a large amount of pressure-sensitive adhesive contained in a unit weight of the pressure-sensitive adhesive sheet. Therefore, it is considered that the influence can be increased when a metal corrosion-causing substance is included. It is particularly meaningful to apply the technology disclosed herein to the pressure-sensitive adhesive sheet having the above-described configuration. Moreover, the double-sided pressure-sensitive adhesive sheet having the above configuration is preferably used for joining various articles and members.

  As described above, the pressure-sensitive adhesive sheet disclosed herein can highly suppress metal corrosion. Therefore, it is usually preferably used for an application arranged inside an electronic device in which a metal material may exist. Especially, it is used especially preferably as an adhesive sheet arrange | positioned in a non-contact state with a metal material in the internal space of an electronic device. For example, it can be preferably used as a pressure-sensitive adhesive sheet (typically a double-sided pressure-sensitive adhesive sheet) used for bonding in an internal space that coexists with a metal material such as a circuit board or wiring. Therefore, this invention provides the electronic device which has the junction location by the said adhesive sheet inside as another side surface.

Moreover, according to this specification, the manufacturing method of an adhesive sheet is provided. This production method includes: a step of mixing an acrylic polymer as a base polymer with a tackifying component to obtain an aqueous pressure-sensitive adhesive composition; and a step of forming a pressure-sensitive adhesive layer from the aqueous pressure-sensitive adhesive composition. Here, the tackifying component is a tackifying component in which CS ₂ is not detected in gas chromatography mass spectrometry performed at a vaporization temperature of 250 ° C. According to said manufacturing method, the adhesive sheet which can suppress metal corrosion highly is provided.

It is typical sectional drawing which shows the structure of the adhesive sheet which concerns on one Embodiment.

  Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention are based on the teachings on the implementation of the invention described in the present specification and the common general technical knowledge at the time of filing. Can be understood by those skilled in the art. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. Further, in the following drawings, members / parts having the same action may be described with the same reference numerals, and overlapping descriptions may be omitted or simplified. In addition, the embodiments described in the drawings are schematically illustrated in order to clearly explain the present invention, and do not necessarily accurately represent the size and scale of a product actually provided.

In this specification, the “pressure-sensitive adhesive” refers to a material that exhibits a soft solid (viscoelastic body) state in a temperature range near room temperature and adheres to an adherend by pressure. The adhesive here is generally defined as “CA Dahlquist,“ Adhesion: Fundamental and Practice ”, McLaren & Sons, (1966) P. 143”, and generally has a complex tensile modulus E ^* (1 Hz). It may be a material having a property satisfying <10 ⁷ dyne / cm ² (typically, a material having the above property at 25 ° C.). The pressure-sensitive adhesive in the technology disclosed herein can be grasped as a solid component (nonvolatile content) of the pressure-sensitive adhesive composition or a constituent component of the pressure-sensitive adhesive layer.

  In this specification, “(meth) acryloyl” means acryloyl and methacryloyl comprehensively. Similarly, “(meth) acrylate” means acrylate and methacrylate, and “(meth) acryl” generically means acrylic and methacryl.

  In this specification, “acrylic polymer” refers to a polymer containing more than 50% by weight of monomer units derived from acrylic monomers as monomer units constituting the polymer. The acrylic monomer refers to a monomer derived from a monomer having at least one (meth) acryloyl group in one molecule.

  In this specification, the “water dispersion type” means a form in which at least a part of the components are dispersed in water. For example, the “water-dispersed pressure-sensitive adhesive composition” means that the composition contains a pressure-sensitive adhesive composition and water and at least a part of the pressure-sensitive adhesive composition is dispersed in water. The water dispersion type includes a suspended state and an emulsified state.

<Water-based adhesive composition>
The pressure-sensitive adhesive composition disclosed herein is an aqueous pressure-sensitive adhesive composition in which a pressure-sensitive adhesive component is dissolved or dispersed in an aqueous medium. Here, the aqueous medium means that the solvent constituting the medium is water or a mixed solvent containing water as a main component (aqueous solvent). The concept of the aqueous pressure-sensitive adhesive composition includes what is generally called a water-dispersed (typically emulsion-type) pressure-sensitive adhesive and what is called a water-soluble pressure-sensitive adhesive. A typical example of the aqueous pressure-sensitive adhesive composition in the technology disclosed herein is an aqueous emulsion-type pressure-sensitive adhesive composition.

(Acrylic polymer)
The pressure-sensitive adhesive composition disclosed herein is an acrylic pressure-sensitive adhesive composition containing an acrylic polymer as a base polymer. Here, the “base polymer” refers to the main component of the polymer components contained in the pressure-sensitive adhesive composition (which may also be a pressure-sensitive adhesive). In the present specification, the “main component” refers to a component contained in an amount exceeding 50% by weight unless otherwise specified. In a preferred embodiment, the acrylic pressure-sensitive adhesive composition is an acrylic emulsion-type pressure-sensitive adhesive composition containing a water-dispersed acrylic polymer. The water-dispersed acrylic polymer has an emulsion form in which the acrylic polymer is dispersed in water. As such an acrylic polymer, an alkyl (meth) acrylate having a main constituent monomer component (a monomer main component, ie, a component occupying 50% by weight or more of the total amount of monomers constituting the acrylic polymer) is preferably employed. Can do.

  As the acrylic polymer, for example, a polymer of a monomer raw material (monomer component) that includes alkyl (meth) acrylate as a main monomer and can further include a submonomer copolymerizable with the main monomer is preferable. Here, the main monomer means a component occupying more than 50% by weight of the monomer composition in the monomer raw material.

As the alkyl (meth) acrylate, for example, a compound represented by the following formula (1) can be preferably used.
CH ₂ = C (R ¹ ) COOR ² (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. R ² is a chain alkyl group having 1 to 20 carbon atoms (hereinafter, such a range of the number of carbon atoms may be represented as “C _1-20 ”). From the viewpoint of the storage elastic modulus and the like of the pressure-sensitive adhesive, an alkyl (meth) acrylate in which R ² is a C _1-14 chain alkyl group is preferable, and R ² is an alkyl (meta) that is a C _1-10 chain alkyl group. ) Acrylate is more preferable, and alkyl (meth) acrylate in which R ² is a butyl group or a 2-ethylhexyl group is particularly preferable.

Examples of the alkyl (meth) acrylate in which R ² is a C _1-20 chain alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl. (Meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate , Octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) Acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, And eicosyl (meth) acrylate. These alkyl (meth) acrylates can be used alone or in combination of two or more. Preferred alkyl (meth) acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

In the technique disclosed herein, the monomer component is an alkyl (meth) acrylate (typically at least one of BA and 2EHA) in which R ^{2 in the} formula (1) is a C _4-10 chain alkyl group Among the alkyl (meth) acrylates contained in the monomer component, the total amount of alkyl (meth) acrylates in which R ^{2 in the} above formula (1) is a C _4-10 chain alkyl group (typically The total amount of BA and 2EHA) may preferably be carried out in an embodiment occupying 70% by weight or more (typically 80% by weight or more).

When the alkyl (meth) acrylate includes an alkyl (meth) acrylate (typically at least one of BA and 2EHA) in which R ^{2 in the} formula (1) is a C _4-10 chain alkyl group, The total amount of alkyl (meth) acrylate (alkyl (meth) acrylate in which R ^{2 in the} above formula (1) is a chain alkyl group of less than C ₄ or more than C ₁₀ ) is the monomer component constituting the acrylic polymer. It is preferably about 30% by weight or less (for example, 20% by weight or less, typically 15% by weight or less). Further, from the viewpoint of obtaining the effect of other alkyl (meth) acrylates, the total amount is approximately 1% by weight or more (for example, 5% by weight or more, typically 10% by weight or more) in the monomer component. preferable. Examples of the other alkyl (meth) acrylate, R ² in the formula (1) alkyl (meth) acrylates may be used preferably a chain alkyl group of C _1-3. Specific examples thereof include methyl acrylate (MA), methyl methacrylate (MMA), ethyl acrylate (EA) and the like. Of these, MA is more preferable.

A submonomer having copolymerizability with the main monomer, alkyl (meth) acrylate, can be useful for introducing a crosslinking point into the acrylic polymer or increasing the cohesive strength of the acrylic polymer. As the submonomer, for example, the following functional group-containing monomer components can be used singly or in combination of two or more.
Carboxyl group-containing monomers: ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), crotonic acid, etc .; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, citraconic acid and the anhydrides thereof (Maleic anhydride, itaconic anhydride, etc.).
Hydroxyl group-containing monomer: For example, hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate; Unsaturated alcohols such as vinyl alcohol and allyl alcohol.
Amide group-containing monomer: For example, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, N-methoxymethyl (Meth) acrylamide, N-butoxymethyl (meth) acrylamide.
Amino group-containing monomer: for example, aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate.
Monomers having an epoxy group: for example, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, allyl glycidyl ether.
Cyano group-containing monomer: for example, acrylonitrile, methacrylonitrile.
Keto group-containing monomers: for example, diacetone (meth) acrylamide, diacetone (meth) acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate.
Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinyl Pyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N- (meth) acryloylmorpholine.
Alkoxysilyl group-containing monomer: For example, 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 3- (meth) acryloxypropylmethyldimethoxysilane, 3- (meth) acryloxy Propylmethyldiethoxysilane.

  The said functional group containing monomer can be used individually by 1 type or in combination of 2 or more types. Among the functional group-containing monomers, a carboxyl group-containing monomer, a hydroxyl group-containing monomer, and a cyano group-containing monomer are preferable because introduction of a crosslinking point as described above and an improvement in cohesive force can be suitably realized. Monomers are more preferred. Of the carboxyl group-containing monomers, AA and MAA are preferred.

  In a preferred embodiment, AA and MAA are used in combination as the functional group-containing monomer. A pressure-sensitive adhesive composition containing an acrylic polymer having such a monomer composition (that is, a copolymer composition) can provide a pressure-sensitive adhesive sheet with higher performance (for example, more excellent repulsion resistance). The weight ratio of AA to MAA (AA / MAA) can be, for example, in the range of about 0.1 to 10, more preferably about 0.3 or more (typically 0.5 or more), Further, it is more preferably about 4 or less (typically 3 or less). When AA / MAA is within the above range, the effect of improving the repulsion resistance tends to be sufficiently obtained, and after production of the pressure-sensitive adhesive sheet, there is a tendency that the stability over time of the pressure-sensitive adhesive properties is excellent.

  The acrylic polymer is preferably copolymerized with an alkoxysilyl group-containing monomer. The alkoxysilyl group-containing monomer is typically an ethylenically unsaturated monomer having at least one (preferably two or more, for example, two or three) alkoxysilyl groups in one molecule, Specific examples are as described above. The said alkoxysilyl group containing monomer can be used individually by 1 type or in combination of 2 or more types. By copolymerizing the alkoxysilyl group-containing monomer, a crosslinked structure by silanol group condensation reaction (silanol condensation) can be introduced into the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition containing an acrylic polymer.

  When the functional group-containing monomer is copolymerized with the acrylic polymer, the ratio of the functional group-containing monomer in the total monomer components constituting the acrylic polymer is not particularly limited. Usually, from the viewpoint of achieving a good balance between cohesion and adhesiveness, the proportion of the functional group-containing monomer is about 0.1% by weight or more (eg, 0.5% by weight or more, typically 1% by weight or more). It is preferable to do. In consideration of the adhesive action due to alkyl (meth) acrylate, it is preferably about 40% by weight or less (for example, 30% by weight or less, typically 20% by weight or less). When a carboxyl group-containing monomer is copolymerized with the acrylic polymer, the proportion of the carboxyl group-containing monomer in the total monomer component is 0.1% by weight or more (for example, 0.5% from the viewpoint of aggregation properties, etc. % By weight or more, typically 1% by weight or more), and preferably 15% by weight or less (for example, 5% by weight or less, typically 3% by weight or less). When the alkoxysilyl group-containing monomer is copolymerized with the acrylic polymer, the proportion of the alkoxysilyl group-containing monomer in the total monomer component is 0.005% by weight or more of the total monomer component (for example, 0.8. 01% by weight or more) is appropriate, and it is appropriate that the content be about 0.1% by weight or less (eg, 0.03% by weight or less).

  For the purpose of increasing the cohesive strength of the acrylic polymer, other copolymer components other than the above-mentioned secondary monomer can be used. Examples of such copolymer components include vinyl ester monomers such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene, substituted styrene (α-methylstyrene, etc.), vinyltoluene; cyclohexyl (meth) acrylate, cyclopentyl ( Cycloalkyl (meth) acrylates such as meth) acrylate and isobornyl (meth) acrylate; aryl (meth) acrylate (eg phenyl (meth) acrylate), aryloxyalkyl (meth) acrylate (eg phenoxyethyl (meth) acrylate), aryl Aromatic ring-containing (meth) acrylates such as alkyl (meth) acrylates (eg benzyl (meth) acrylate); olefins such as ethylene, propylene, isoprene, butadiene and isobutylene Monomers; Chlorine-containing monomers such as vinyl chloride and vinylidene chloride; Isocyanate group-containing monomers such as 2- (meth) acryloyloxyethyl isocyanate; Alkoxy group-containing monomers such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate; And vinyl ether monomers such as vinyl ether and ethyl vinyl ether.

  Other examples of the copolymerizable component other than the above-mentioned submonomer include monomers having a plurality of functional groups in one molecule. Examples of such polyfunctional monomers include 1,6-hexanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) ) Acrylate, (poly) ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, Trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, glycerin di (meth) acrylate Over DOO, epoxy acrylate, polyester acrylate, urethane acrylate, divinylbenzene, butyl di (meth) acrylate, hexyl di (meth) acrylate, and the like.

  The amount of the copolymerization component other than the submonomer is not particularly limited as long as it is appropriately selected depending on the purpose and application, but is preferably 10% by weight or less of the monomer composition of the acrylic polymer, for example.

  The acrylic polymer in the technology disclosed herein is designed so that the glass transition temperature (Tg) of the polymer is −25 ° C. or lower (typically −75 ° C. or higher and −25 ° C. or lower). Is appropriate. The Tg of the acrylic polymer is preferably −40 ° C. or lower (for example, −70 ° C. or higher and −40 ° C. or lower), more preferably −50 ° C. or lower (typically −70 ° C. or higher and −50 ° C. or lower). Setting the Tg of the acrylic polymer to be equal to or lower than the above-described upper limit is preferable from the viewpoint of improving the adhesive strength. The Tg of the acrylic polymer can be adjusted according to the type of monomer used in the synthesis of the polymer and the usage ratio.

Here, the Tg of the acrylic polymer refers to a Tg determined by the Fox formula based on the composition of the monomer component used for the synthesis of the polymer. The formula of Fox is a relational expression between Tg of a copolymer and glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below.
1 / Tg = Σ (Wi / Tgi)
In the above Fox equation, Tg is the glass transition temperature (unit: K) of the copolymer, Wi is the weight fraction of monomer i in the copolymer (copolymerization ratio on a weight basis), and Tgi is the monomer i. Represents the glass transition temperature (unit: K) of the homopolymer.

As the glass transition temperature of the homopolymer used for the calculation of Tg, the values described in known materials are used. For example, for the monomers listed below, the following values are used as the glass transition temperature of the homopolymer of the monomer.
2-Ethylhexyl acrylate -70 ° C
n-Butyl acrylate -55 ° C
Methyl methacrylate 105 ° C
Methyl acrylate 8 ℃
Vinyl acetate 32 ° C
Acrylic acid 106 ℃
Methacrylic acid 228 ° C

  Regarding the glass transition temperature of homopolymers of monomers other than those exemplified above, the values described in “Polymer Handbook” (3rd edition, John Wiley & Sons, Inc., 1989) are used. When multiple types of values are described in this document, the highest value is adopted.

  For monomers whose homopolymer glass transition temperature is not described in the Polymer Handbook, values obtained by the following measurement method are used (see Japanese Patent Application Publication No. 2007-51271). Specifically, a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux condenser is charged with 100 parts by weight of monomer, 0.2 part by weight of azobisisobutyronitrile and 200 parts by weight of ethyl acetate as a polymerization solvent. Stir for 1 hour while flowing nitrogen gas. After removing oxygen in the polymerization system in this way, the temperature is raised to 63 ° C. and the reaction is carried out for 10 hours. Next, the mixture is cooled to room temperature to obtain a homopolymer solution having a solid concentration of 33% by weight. Next, this homopolymer solution is cast-coated on a release liner and dried to prepare a test sample (sheet-like homopolymer) having a thickness of about 2 mm. This test sample was punched into a disk shape having a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to shear strain at a frequency of 1 Hz using a viscoelasticity tester (ARES, manufactured by Rheometrics), in a temperature range of −70 to 150 ° C. The viscoelasticity is measured by the shear mode at a heating rate of 5 ° C./min, and the peak top temperature of tan δ is defined as Tg of the homopolymer.

  The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as synthetic methods for acrylic polymers, such as solution polymerization method, emulsion polymerization method, bulk polymerization method, suspension polymerization method, photopolymerization method, etc. Can be adopted as appropriate. As a polymerization method that can be preferably employed, an emulsion polymerization method is exemplified. The mode of emulsion polymerization is not particularly limited, and can be carried out by appropriately adopting various monomer supply methods, polymerization conditions, materials used and the like similar to those of conventionally known general emulsion polymerization. For example, as a monomer supply method, a batch charging method in which all monomer raw materials are supplied at once, a continuous supply (dropping) method, a divided supply (dropping) method, or the like can be appropriately employed. The monomer raw material may be added dropwise in the form of an aqueous emulsion. The polymerization temperature can be, for example, about 20 ° C. or more (usually 40 ° C. or more), and is suitably about 100 ° C. or less (usually 80 ° C. or less).

  The initiator used for the polymerization can be appropriately selected from conventionally known polymerization initiators according to the type of the polymerization method. For example, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylpropionamidine) disulfate, 2,2′-azobis (2-methylpropionamidine) dihydrochloride, 2, 2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate, 2,2′-azobis (N, N Azo initiators such as' -dimethyleneisobutylamidine), 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride; for example, persulfate such as potassium persulfate and ammonium persulfate Salt initiators; for example, peroxide-based initiators such as benzoyl peroxide, t-butyl hydroperoxide and hydrogen peroxide; for example, substituted ethane initiators such as phenyl-substituted ethane; For example, carbonyl initiators such as aromatic carbonyl compounds; for example, redox initiators such as a combination of persulfate and sodium bisulfite, a combination of peroxide and sodium ascorbate; It is not limited to. Such a polymerization initiator can be used individually by 1 type or in combination of 2 or more types.

  The usage-amount of a polymerization initiator should just be a normal usage-amount, and is not specifically limited. For example, it is selected from a range of about 0.005 parts by weight (preferably 0.01 parts by weight or more) and about 1 part by weight or less (preferably 0.8 parts by weight or less) with respect to 100 parts by weight of all monomer components. be able to.

  The emulsifier used for emulsion polymerization is not particularly limited. For example, sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium polyoxyethylene lauryl sulfate, sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkyl phenyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene Anionic emulsifiers such as sodium alkylsulfosuccinate; nonionic emulsifiers such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene polyoxypropylene block polymer, and the like. Further, a radical polymerizable (reactive) emulsifier in which a radical polymerizable functional group (reactive group) such as a propenyl group or an allyl ether group is introduced into these anionic emulsifiers and nonionic emulsifiers may be used. Moreover, from the viewpoint of storage stability of the pressure-sensitive adhesive composition, an embodiment in which only an emulsifier having no radical polymerizable functional group is used as the emulsifier can be preferably employed. These emulsifiers can be used alone or in combination of two or more. The amount of the emulsifier used is, for example, about 0.2 parts by weight (preferably 0.5 parts by weight) or more, for example, 10 parts by weight or less (preferably 5 parts by weight or less) with respect to 100 parts by weight of the total amount of monomer components. Can be about.

  In the polymerization, a chain transfer agent (which can also be grasped as a molecular weight regulator or a polymerization degree regulator) can be used as necessary. Examples of the chain transfer agent include mercaptans such as dodecyl mercaptan (dodecanethiol), lauryl mercaptan, glycidyl mercaptan, 2-mercaptoethanol, mercaptoacetic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. Other examples include α-methylstyrene dimer. Such chain transfer agents can be used alone or in combination of two or more.

  In addition, the said chain transfer agent may become a generation | occurrence | production factor of the metal corrosive gas which contains sulfur as a structural atom depending on the kind and usage mode (usage etc.). The technique disclosed here can be preferably implemented in an embodiment in which no chain transfer agent is used in the polymerization. This can prevent the corrosion of the metal due to the chain transfer agent.

  In another preferred embodiment of the technology disclosed herein, a chain transfer agent comprising a compound not containing sulfur as a constituent atom is used in the polymerization. Typically, only compounds that do not contain sulfur as a constituent atom are used as chain transfer agents (in other words, compounds that contain sulfur as a constituent atom are not substantially used). According to such an aspect, the sulfur-containing metal corrosive gas is not generated due to the chain transfer agent, so that corrosion of the metal due to the chain transfer agent can be prevented in advance. Specific examples of the chain transfer agent comprising a compound not containing sulfur as a constituent atom include anilines such as N, N-dimethylaniline and N, N-diethylaniline; terpenoids such as α-pinene and terpinolene; α-methyl Styrenes such as styrene and α-methylstyrene dimer; compounds having a benzylidenyl group such as dibenzylideneacetone, cinnamyl alcohol, cinnamylaldehyde; hydroquinones such as hydroquinone and naphthohydroquinone; quinones such as benzoquinone and naphthoquinone; Olefins such as 3-dimethyl-2-butene and 1,5-cyclooctadiene; alcohols such as phenol, benzyl alcohol and allyl alcohol; benzyl hydrogens such as diphenylbenzene and triphenylbenzene;

  In another preferred embodiment of the technology disclosed herein, a chain transfer agent that contains sulfur as a constituent atom but hardly generates the sulfur-containing metal corrosive gas in the polymerization is used. As such a chain transfer agent, a mercaptan having only one hydrogen atom (H) bonded to a carbon atom (C) to which a mercapto group (-SH) is bonded (for example, a mercapto group is bonded to a secondary carbon atom). Mercaptans, that is, secondary mercaptans), mercaptans in which no hydrogen atom is bonded to the carbon atom (for example, mercaptans in which a mercapto group is bonded to a tertiary carbon atom, that is, tertiary mercaptan), and the carbon atom is resonant. Examples include mercaptans having a structure (such as aromatic mercaptans). It is preferred that substantially no mercaptan having a primary mercapto group is used.

  Specific examples of the tertiary mercaptan include tertiary butyl mercaptan, tertiary octyl mercaptan, tertiary nonyl mercaptan, tertiary lauryl mercaptan, tertiary tetradecyl mercaptan, tertiary hexadecyl mercaptan, and the like. A tertiary alkyl mercaptan having 4 or more carbon atoms can be preferably used. From the viewpoint of reducing the odor of the pressure-sensitive adhesive composition and the pressure-sensitive adhesive sheet, it is advantageous to select a tertiary alkyl mercaptan having 6 or more carbon atoms (more preferably 8 or more). The upper limit of the number of carbon atoms is not particularly limited, but is typically 20 or less. For example, tertiary lauryl mercaptan can be preferably used.

  The aromatic mercaptan may be a compound having a bond between a structural part having aromaticity (typically an aromatic ring) and a mercapto group in at least a part of the skeleton, an isomer thereof, or a derivative having a mercapto group. . Specific examples of the aromatic mercaptan include phenyl mercaptan, 4-tolyl mercaptan, 4-methoxyphenyl mercaptan, 4-fluorobenzenethiol, 2,4-dimethylbenzenethiol, 4-aminobenzenethiol, 4-fluorobenzenethiol, 4 -Chlorobenzene thiol, 4-bromobenzene thiol, 4-iodobenzene thiol, 4-t-butylphenyl mercaptan, 1-naphthyl mercaptan, 1-azulene thiol, 1-anthracene thiol, 4,4'thiobenzene thiol, etc. It is done. An aromatic mercaptan having about 6 to 20 carbon atoms is preferred. For example, phenyl mercaptan can be preferably used.

  The amount of chain transfer agent used is about 0.001 part by weight or more (typically about 0.005 part by weight or more, for example, about 0.001 part by weight or more) with respect to 100 parts by weight of the monomer component. For example, it can be about 5 parts by weight or less (typically about 2 parts by weight or less, for example, about 1 part by weight or less). By setting the amount of the chain transfer agent used within an appropriate range, a desired polymerization rate can be obtained.

  According to the emulsion polymerization, a polymerization liquid (acrylic polymer emulsion) in the form of an emulsion in which an acrylic polymer is dispersed in water can be prepared. The aqueous pressure-sensitive adhesive composition disclosed herein can be preferably produced using the above polymerization solution or a solution obtained by subjecting the polymerization solution to an appropriate post-treatment. Alternatively, an acrylic polymer emulsion may be prepared by synthesizing an acrylic polymer using a polymerization method other than the emulsion polymerization method (for example, solution polymerization, photopolymerization, bulk polymerization, etc.) and dispersing the polymer in water. Good.

The weight average molecular weight of the acrylic polymer (Mw) may be particularly limited without, for example, ¹⁰ × 10 ⁴ ~500 × 10 4 range. Here, the Mw of the acrylic polymer refers to the Mw of the toluene-soluble component (sol component) of the acrylic polymer. The Mw of the acrylic polymer refers to a standard polystyrene equivalent value based on GPC (gel permeation chromatography). From the viewpoint of improving the adhesive properties, the Mw of the acrylic polymer is preferably 150 × 10 ⁴ or less, more preferably 100 × 10 ⁴ or less. Further, from the viewpoint of cohesiveness and the like, the Mw of the acrylic polymer is preferably 20 × 10 ⁴ or more, more preferably 30 × 10 ⁴ or more (for example, 40 × 10 ⁴ or more).

(Tackifier component)
The aqueous pressure-sensitive adhesive composition disclosed herein includes a tackifier component. Thereby, the adhesive sheet which shows the outstanding adhesion characteristic (for example, adhesive force, repulsion resistance) is obtained. Further, CS ₂ is not detected in the above-mentioned tackifying component by gas chromatography mass spectrometry (GC-mass) performed at a vaporization temperature of 250 ° C. By using a tackifying component that satisfies such characteristics, metal corrosion can be highly suppressed. Such a tackifier component is typically determined to be acceptable in a metal corrosion test (tackifier component) described later. In the present specification, “tackifying component” is defined as containing at least a tackifier (typically a tackifying resin) and further containing additives such as preservatives and emulsifiers as optional components. . The GC-mass can be carried out by employing known or conventional methods and conditions except that the vaporization conditions (conditions for vaporizing the sample) are set to 250 ° C. for 10 minutes. As a measuring device, a commercially available device (for example, heating furnace type pyrolyzer (DSP: Double Shot Pyrolysis), model “PY-2020iD”, manufactured by Frontier Laboratories, and GC-mass, model “7890A / 5975C”, Agilent Technologies) may be used. The sample amount is preferably in the range of 0.5 mg to 2.0 mg. Specifically, it is carried out by the method described in Examples described later.

  The tackifying component according to a preferred embodiment is a tackifying resin emulsion. That is, the aqueous pressure-sensitive adhesive composition disclosed herein may contain a tackifying component in the form of an emulsion in which a tackifying resin is dispersed in water. For example, an adhesive composition containing these components in a desired ratio can be easily prepared by mixing an aqueous emulsion of an acrylic polymer and an emulsion of the tackifying resin. As the tackifier resin emulsion, it is preferable to use one that does not substantially contain at least an aromatic hydrocarbon solvent (more preferably, substantially does not contain an aromatic hydrocarbon solvent or other organic solvent). This can provide an adhesive sheet with a lower total amount of volatile organic compounds (TVOC).

  Examples of the tackifier resin include rosin tackifier resins (including rosin derivative tackifier resins), petroleum tackifier resins, terpene tackifier resins, phenol tackifier resins, ketone tackifier resins, and the like. Can be mentioned. These can be used alone or in combination of two or more.

Examples of the rosin-based tackifying resin include, in addition to rosins such as gum rosin, wood rosin, tall oil rosin, stabilized rosin (for example, stabilized rosin obtained by disproportionating or hydrogenating the rosin), polymerized rosin (for example, Rosin multimers, typically dimers), modified rosins (eg, unsaturated acid-modified rosin modified with an unsaturated acid such as maleic acid, fumaric acid, (meth) acrylic acid, etc.) Can be mentioned.
Examples of the rosin derivative tackifier resin include esterified products of the rosin resin (for example, rosin esters such as stabilized rosin ester and polymerized rosin ester), phenol-modified products of the rosin resin (phenol-modified rosin), and The esterified product (phenol-modified rosin ester) and the like can be mentioned.
Examples of the petroleum-based tackifier resins include aliphatic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins, alicyclic petroleum resins, and hydrides thereof.
Examples of the terpene-based tackifier resin include α-pinene resins, β-pinene resins, aromatic modified terpene resins, terpene phenol resins, and the like.
Examples of the ketone-based tackifying resin include ketone-based resins obtained by condensation of ketones (for example, aliphatic ketones such as methyl ethyl ketone, methyl isobutyl ketone, and acetophenone; alicyclic ketones such as cyclohexanone and methylcyclohexanone) and formaldehyde. And the like.

  As the tackifier resin in the technology disclosed herein, a rosin-based tackifier resin can be preferably employed. Preferable examples include stabilized rosin esters and polymerized rosin esters.

  The softening point of the tackifying resin to be used is not particularly limited. From the viewpoint of compatibility with the acrylic polymer, cohesive force, and the like, a tackifying resin having a softening point of 80 ° C. or higher (typically 90 ° C. or higher, for example, 100 ° C. or higher) can be preferably used. Further, by selecting a tackifying resin having a softening point of 160 ° C. or lower (more preferably 145 ° C. or lower, for example, 135 ° C. or lower), there is a tendency that the adhesive strength and repulsion resistance are effectively improved. .

  In addition, the softening point of the tackifier resin here is defined as a value measured based on a softening point test method (ring ball method) defined in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible, and is carefully filled so that no bubbles are formed in the ring placed on a flat metal plate. After cooling, cut off the raised part from the plane including the top of the ring with a slightly heated sword. Next, a supporter (ring stand) is put in a glass container (heating bath) having a diameter of 85 mm or more and a height of 127 mm or more, and glycerin is poured until the depth becomes 90 mm or more. Next, the steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in glycerin so as not to contact each other, and the temperature of glycerin is maintained at 20 ° C. plus or minus 5 ° C. for 15 minutes. . Next, a steel ball is placed on the center of the surface of the sample in the ring, and this is placed in a fixed position on the support. Next, the distance from the upper end of the ring to the glycerin surface is maintained at 50 mm, a thermometer is placed, the center of the mercury bulb of the thermometer is set to the same height as the center of the ring, and the container is heated. The flame of the Bunsen burner used for heating is placed between the center and the edge of the bottom of the container so that the heating is even. It should be noted that the rate at which the bath temperature rises after reaching 40 ° C. after heating has started must be 5.0 plus or minus 0.5 ° C. per minute. The temperature at the time when the sample gradually softens and flows down from the ring and finally comes into contact with the bottom plate is read and used as the softening point. Two or more softening points are measured simultaneously, and the average value is adopted.

  The tackifier component according to a preferred embodiment is a tackifier resin emulsion containing a preservative. By adding a preservative to the tackifier component, the storage stability is improved. However, metal corrosion may occur depending on the type of preservative. For example, a compound having a thiocyanate skeleton or a compound having a thioacetal skeleton (methylenedithioisocyanate, 2- (thiocyanomethylthio) benzothiazole, etc.) is likely to cause metal corrosion. Moreover, when the preservative is previously blended with the tackifier component, it may not be easy to determine whether it is a metal corrosive preservative. According to the technique disclosed here, the presence or absence of a metal corrosive substance derived from the tackifier component can be confirmed without specifying the type and amount of the preservative that can be included as an additive in the tackifier component.

  As a preservative that can be included in the tackifier component, it is preferable to select a material that emits very little volatile metal corrosive substances. It is preferable to use a preservative (a sulfur-free preservative) that does not contain a sulfur atom (S) as a constituent atom. Or even if it is a preservative containing a sulfur atom, it is preferable to use the compound which has a heterocyclic ring containing a sulfur atom (S) as a structural atom. By using the preservative having the above structure, metal corrosion can be highly suppressed. Specific examples of preservatives that can be preferably used in the technology disclosed herein include thiazoline preservatives (2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazoline-3- ON, etc.), benzoisothiazole preservatives (1,2-benzisothiazol-3 (2H) -one, 3-methoxy-1,2-benzisothiazole, etc.), benzodithiol preservatives (3H-1, 2-benzodithiol-3-one, etc.), cyanoacetamide preservatives (for example, halocyanoacetamides such as 2,2-dibromo-2-cyanoacetamide), phenolic and phenylester preservatives (pentachlorophenyl laurate) , 2,4,6-tribromophenol, etc.). Conversely, as a preservative for the tackifier component disclosed herein, a compound having a thiocyanate skeleton that diffuses a metal corrosive gas or a compound having a thioacetal skeleton (methylenedithioisocyanate, 2- (thiocyanomethylthio) benzothiazole Etc.) is preferably avoided.

The amount of the preservative used in the tackifier component is not particularly limited as long as the desired antiseptic performance is imparted depending on the application and usage. For example, the preservative can be used in an amount of about 1 × 10 ⁻⁷ parts by weight (that is, 0.1 ppm on a weight basis) or more, typically about 0.1 ppm to 1000 ppm based on 1 part by weight of the tackifier component. . Usually, it is appropriate that the preservative is used in an amount of 1 × 10 ⁻⁶ parts by weight (that is, 1 ppm by weight) or more, typically about 1 ppm to 500 ppm with respect to 1 part by weight of the tackifier component. By making the usage-amount of a preservative into said range, antiseptic property can be provided to a tackifying component, obtaining favorable adhesive performance.

  The tackifying resin emulsion may be prepared using an emulsifier as necessary. As the emulsifier, one or two or more of the same emulsifiers that can be used for preparing the acrylic polymer emulsion can be selected and used. Usually, the use of an anionic emulsifier or a nonionic emulsifier is preferred. The emulsifier used for preparing the acrylic polymer emulsion and the emulsifier used for preparing the tackifying resin emulsion may be the same or different. For example, an embodiment using an anionic emulsifier for the preparation of any emulsion, an embodiment using a nonionic emulsifier for all, an embodiment using an anionic emulsifier for one, and a nonionic emulsifier for the other can be preferably employed. The amount of the emulsifier used is not particularly limited as long as the amount of the tackifier resin can be adjusted to an emulsion form. For example, 0.2 parts by weight or more (preferably with respect to 100 parts by weight of the tackifier resin (solid content basis)) Can be about 0.5 parts by weight or more, and about 10 parts by weight or less (preferably 5 parts by weight or less).

  The amount of the tackifier component (based on solid content) is usually suitably 1 part by weight or more with respect to 100 parts by weight of the acrylic polymer, preferably from the viewpoint of suitably exhibiting the effect of use. It is 3 parts by weight or more (for example, 5 parts by weight or more), more preferably 12 parts by weight or more, still more preferably 16 parts by weight or more, and particularly preferably 22 parts by weight or more (for example, 25 parts by weight or more). From the viewpoint of cohesive strength and the like, the amount of tackifier used is usually 90 parts by weight or less, preferably 70 parts by weight or less, more preferably 100 parts by weight or less based on 100 parts by weight of the acrylic polymer. Is 55 parts by weight or less, more preferably 50 parts by weight or less (for example, 40 parts by weight or less, typically 35 parts by weight or less).

(Crosslinking agent)
The aqueous pressure-sensitive adhesive composition (preferably water-dispersed pressure-sensitive adhesive composition) used for forming the pressure-sensitive adhesive layer preferably contains a crosslinking agent as an optional component. The pressure-sensitive adhesive layer in the technology disclosed herein contains the crosslinking agent in a form after the crosslinking reaction, a form before the crosslinking reaction, a partially crosslinked reaction, an intermediate or composite form thereof, and the like. obtain. The crosslinking agent is typically contained in the pressure-sensitive adhesive layer exclusively in the form after the crosslinking reaction.

  The type of the crosslinking agent is not particularly limited. For example, an isocyanate crosslinking agent, an epoxy crosslinking agent, an oxazoline crosslinking agent, an aziridine crosslinking agent, a melamine crosslinking agent, a peroxide crosslinking agent, a urea crosslinking agent, a metal An alkoxide crosslinking agent, a metal chelate crosslinking agent, a metal salt crosslinking agent, a carbodiimide crosslinking agent, a hydrazine crosslinking agent, an amine crosslinking agent and the like can be appropriately selected and used. As the crosslinking agent used here, both oil-soluble and water-soluble can be used. A crosslinking agent can be used individually or in combination of 2 or more types. The amount of the cross-linking agent used is not particularly limited. For example, it is appropriate that the amount is about 10 parts by weight or less (for example, about 0.005 to 10 parts by weight), preferably about 5 parts per 100 parts by weight of the acrylic polymer. It is below the weight part (0.01-5 weight part).

(Preservative)
It is preferable that a preservative is added to the aqueous pressure-sensitive adhesive composition. As the preservative that can be contained in the aqueous pressure-sensitive adhesive composition, it is preferable to use a preservative that does not easily cause metal corrosion, similar to that contained in the tackifier component. Therefore, when the aqueous pressure-sensitive adhesive composition disclosed herein contains a preservative, the preservative should be used by selecting an appropriate one from those exemplified as preservatives that can be included in the tackifier component. Can do.

The amount of the preservative used in the aqueous pressure-sensitive adhesive composition is not particularly limited as long as the desired preservative performance is imparted depending on the use and usage of the pressure-sensitive adhesive composition. For example, the amount of the preservative used per 1 part by weight of the aqueous pressure-sensitive adhesive composition should be about 1 × 10 ⁻⁷ parts by weight (that is, 0.1 ppm on a weight basis), typically about 0.1 ppm to 1000 ppm. Can do. Usually, it is appropriate that the preservative is used in an amount of 1 × 10 ⁻⁶ parts by weight (that is, 1 ppm by weight) or more, typically about 1 ppm to 500 ppm with respect to 1 part by weight of the aqueous pressure-sensitive adhesive composition. . By making the usage-amount of an antiseptic into said range, antiseptic property can be provided to an aqueous adhesive composition, obtaining favorable adhesive performance.

(Other additive components)
In addition, the aqueous pressure-sensitive adhesive composition disclosed herein preferably contains a silicon compound (typically a silane coupling agent) from the viewpoint of light release from the release liner. Examples of silicon compounds include alkyl alkoxysilane compounds, vinyl group-containing silane compounds, epoxy group-containing silane compounds, styryl group-containing silane compounds, (meth) acryloyl group-containing silane compounds, amino group-containing silane compounds, ureido group-containing silane compounds, and mercapto. 1 type (s) or 2 or more types, such as a group containing silane compound, an isocyanate group containing silane compound, a silyl group containing sulfide, can be used. Of these, alkylalkoxysilane compounds are preferred. The molecular weight of the silicon compound is suitably about 100 or more (for example, 200 or more), and can be about 500 or less (for example, 350 or less).

  As the alkylalkoxysilane compound, any of alkyltrialkoxysilane, dialkyldialkoxysilane, trialkylmonoalkoxysilane, tetraalkoxysilane, and phenylalkoxysilane can be used. The alkyl includes chain and cyclic. Specific examples of the compound include methyltrimethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, n-hexyltrimethoxysilane, and n-octyltrimethoxysilane. N-decyltrimethoxysilane, hexadecyltrimethoxysilane, methyltriethoxysilane, dimethoxydimethylsilane, diethoxydimethylsilane, cyclohexylmethyldimethoxysilane, methoxytrimethylsilane, octadecyldimethylmethoxysilane, phenyltrimethoxysilane, phenyltriethoxy Examples include silane, dimethoxydiphenylsilane, diphenylethoxymethylsilane, dimethoxymethylphenylsilane, and the like. Of these, alkyltrialkoxysilane is preferable.

  The content of the silicon compound is 0.005 parts by weight or more (for example, 0.01 parts by weight or more, typically 0.03 parts by weight with respect to 100 parts by weight of the acrylic polymer) from the viewpoint of sufficiently exhibiting the addition effect. Part or more). From the viewpoint of storage stability, the content of the silicon compound is less than 1.0 part by weight (for example, 0.5 part by weight or less, typically 0.3 part by weight or less) with respect to 100 parts by weight of the acrylic polymer. ) Is preferable.

  The pressure-sensitive adhesive composition disclosed herein may contain an acid or a base (such as aqueous ammonia) used for the purpose of pH adjustment or the like, if necessary. Other optional components that can be incorporated into the composition include viscosity modifiers (thickeners, etc.), leveling agents, crosslinking aids, release modifiers, plasticizers, softeners, fillers, colorants (pigments, dyes). Etc.), antistatic agents, anti-aging agents, ultraviolet absorbers, antioxidants, light stabilizers and the like. About such various additives, conventionally well-known things can be used by a conventional method, and since it does not characterize this invention in particular, detailed description is abbreviate | omitted.

<Adhesive sheet>
(Structural example of adhesive sheet)
The pressure-sensitive adhesive sheet disclosed herein includes a pressure-sensitive adhesive layer formed using the above-mentioned aqueous pressure-sensitive adhesive composition. It may be a pressure-sensitive adhesive sheet with a base material having such a pressure-sensitive adhesive layer on one side or both sides of a base material (support), and the pressure-sensitive adhesive layer may be grasped as a release liner (a base material having a release surface). It may be a substrate-less pressure-sensitive adhesive sheet such as a form held in (). The concept of the pressure-sensitive adhesive sheet herein may include what are called pressure-sensitive adhesive tapes, pressure-sensitive adhesive labels, pressure-sensitive adhesive films and the like. The pressure-sensitive adhesive layer is typically formed continuously, but is not limited to such a form. For example, the pressure-sensitive adhesive layer is formed in a regular or random pattern such as a dot shape or a stripe shape. It may be. In addition, the pressure-sensitive adhesive sheet may be in a roll shape or a single wafer shape. Or the adhesive sheet of the form processed into various shapes may be sufficient.

  The pressure-sensitive adhesive sheet disclosed herein can be, for example, in the form of a double-sided pressure-sensitive adhesive sheet having a cross-sectional structure schematically shown in FIG. The pressure-sensitive adhesive sheet 1 includes a base material 15 and a first pressure-sensitive adhesive layer 11 and a second pressure-sensitive adhesive layer 12 that are respectively supported on both surfaces of the base material 15. More specifically, the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12 are provided on the first surface 15A and the second surface 15B (both non-peelable) of the base material 15, respectively. As shown in FIG. 1, the double-sided pressure-sensitive adhesive sheet 1 before use (before being attached to an adherend) is wound in a spiral shape with the front surface 21A and the back surface 21B overlapped with a release liner 21 which is a release surface. It can be in the form of In the double-sided pressure-sensitive adhesive sheet 1 having such a configuration, the surface (second pressure-sensitive adhesive surface 12A) of the second pressure-sensitive adhesive layer 12 is peeled off by the front surface 21A of the release liner 21, and the surface of the first pressure-sensitive adhesive layer 11 (first pressure-sensitive adhesive surface 11A) is peeled off. The liner 21 is protected by the back surface 21B. Alternatively, the first adhesive surface 11A and the second adhesive surface 12A may be protected by two independent release liners.

(Characteristics of adhesive sheet)
In the pressure-sensitive adhesive sheet according to a preferred embodiment, CS ₂ is not detected by gas chromatography mass spectrometry performed at a vaporization temperature of 250 ° C. The pressure-sensitive adhesive sheet satisfying this characteristic is unlikely to cause corrosion of the metal material when used in an environment where the metal material coexists. The gas chromatograph mass spectrometry can be carried out by employing known or conventional methods and conditions except that the vaporization condition is set at 250 ° C. for 10 minutes. As a measuring apparatus, a commercially available apparatus (for example, heating furnace type pyrolyzer (DSP), model “PY-2020iD”, manufactured by Frontier Laboratories, and GC-mass, model “7890A / 5975C”, manufactured by Agilent Technologies). ). The sample amount is preferably in the range of 0.5 mg to 2.0 mg. Specifically, it is carried out by the method described in Examples described later.

  The pressure-sensitive adhesive sheet disclosed herein is typically composed of 5 g of the pressure-sensitive adhesive sheet and a silver plate (for example, silver having a purity exceeding 99.95% and having a size of 1 mm × 10 mm × 10 mm in a container having a volume of 100 mL. In a metal corrosion test in which an LED (light emitting diode) bar having a silver plate is used so as not to contact each other and the container is sealed and held at 100 ° C. for 80 hours, the silver plate is not corroded. Can be a thing. The weight of the pressure-sensitive adhesive sheet 5g used in the above test is the total weight including the pressure-sensitive adhesive layer and the base material (not including the release liner). Moreover, about the adhesive sheet without a base material, it is set as the weight of adhesive layer itself. Specifically, the metal corrosivity test is performed by the method described in Examples described later.

  The pressure-sensitive adhesive sheet disclosed here (typically, a double-sided pressure-sensitive adhesive sheet) preferably has a 180 ° peel strength (vs. SUS plate peel strength) of 8 N / 20 mm or more with respect to the stainless steel plate. The pressure-sensitive adhesive sheet exhibiting such characteristics is preferably used as a strong adhesive pressure-sensitive adhesive sheet for firmly fixing an article or member. The SUS plate peel strength is more preferably 9 N / 20 mm or more, and further preferably 9.5 N / 20 mm or more (for example, 10 N / 20 mm or more, further 10.5 N / 20 mm or more). When the pressure-sensitive adhesive sheet disclosed herein is a double-sided pressure-sensitive adhesive sheet, it is preferable that both adhesive surfaces exhibit the above-described peel strength. The SUS plate peel strength is measured by the method described in Examples described later.

  The pressure-sensitive adhesive sheet disclosed here (typically, a double-sided pressure-sensitive adhesive sheet) preferably has a floating height at the end of a test piece of 5 mm or less in a foam repulsion resistance test described later. The floating height is preferably 2 mm or less, more preferably 1 mm or less.

  The pressure-sensitive adhesive sheet disclosed here (typically a pressure-sensitive adhesive sheet with a substrate) preferably has a retention time of 1 hour or longer in a SUS creep test described later. When the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet, it is preferable that the above-mentioned holding time is 1 hour or longer for both pressure-sensitive adhesive surfaces. The pressure-sensitive adhesive sheet according to a more preferable embodiment has a displacement distance of 1 mm or less (more preferably 3 mm or less, particularly preferably 2 mm or less) after 1 hour in a SUS creep test to be described later. When the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet, it is preferable that the displacement distance after 1 hour is within the above range for both pressure-sensitive adhesive surfaces.

  The pressure-sensitive adhesive sheet disclosed herein is preferably excellent in the above adhesive residue preventing property and tearing preventing property and excellent in recyclability. From the standpoint of preventing tearing, the tensile strength of the pressure-sensitive adhesive sheet measured with respect to the first direction of the pressure-sensitive adhesive sheet (for example, the longitudinal direction in the case of a long pressure-sensitive adhesive sheet) and the second direction perpendicular thereto However, it is preferably about 6 N / 10 mm or more (more preferably 12 N / 10 mm or more). When the pressure-sensitive adhesive sheet disclosed herein is a double-sided pressure-sensitive adhesive sheet comprising a nonwoven fabric substrate, the flow direction of the nonwoven fabric (typically, the longitudinal direction of the long pressure-sensitive adhesive sheet: MD direction) and the width direction (TD direction) It is appropriate that at least one (typically both) of the tensile strength of the pressure-sensitive adhesive sheet measured with respect to the above is about 6 N / 10 mm or more, and about 8 N / 10 mm or more (more preferably 12 N / 10 mm). Or more). The pressure-sensitive adhesive sheet having the above-described tensile strength is obtained by using a base material having a high tensile strength, impregnating the base material (typically non-woven fabric) with an adhesive by a direct method, and pressing a laminate of the base material and the adhesive layer. Etc. The tensile strength of the pressure-sensitive adhesive sheet and the substrate is measured according to the “tensile strength” measurement method described in JIS Z0237: 2009.

  In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive sheet is generated from 1 g of the pressure-sensitive adhesive sheet (including the base material and the pressure-sensitive adhesive layer but not including the release liner) when heated at 80 ° C. for 30 minutes. The total amount of volatile organic compounds (TVOC) is 1000 μg (hereinafter also referred to as “1000 μg / g” or the like). The pressure-sensitive adhesive sheet that satisfies such characteristics can be preferably used for applications that are highly demanded to reduce VOCs, such as home appliances and OA equipment used indoors, automobiles that constitute closed rooms, and the like. A pressure-sensitive adhesive sheet having a TVOC of 500 μg / g or less is more preferable, and it is further preferably 300 μg / g or less. In addition, TVOC of an adhesive sheet can be measured with the following method.

[TVOC measurement]
A pressure-sensitive adhesive sheet cut into a predetermined size (here, an area of about 5 cm ² ) with the pressure-sensitive adhesive layer exposed is used as a sample piece, and the sample piece is placed in a 20 mL vial and sealed. Next, the vial is heated at 80 ° C. for 30 minutes, and 1.0 mL (sample gas) of the heated state is injected into a gas chromatograph (GC) measurement device using a headspace autosampler (HSS). Based on the obtained gas chromatogram, the amount of gas generated from the sample piece is determined as an n-decane equivalent amount. The n-decane conversion amount is obtained by applying a calibration curve of n-decane prepared in advance, assuming that the detection intensity of the generated gas obtained by GC-mass is the detection intensity of n-decane.

  The total thickness of the pressure-sensitive adhesive sheet disclosed herein is not particularly limited. The total thickness of the pressure-sensitive adhesive sheet can be, for example, 1 mm or less (for example, 500 μm or less). Here, the total thickness of the pressure-sensitive adhesive sheet refers to the total thickness of the base material and the pressure-sensitive adhesive layer. In a preferred embodiment, the total thickness may be 300 μm or less (more preferably 200 μm or less). The lower limit of the total thickness of the pressure-sensitive adhesive sheet can be, for example, 30 μm or more, and is usually 50 μm or more, preferably 70 μm or more, more preferably 100 μm or more (for example, 120 μm or more).

<Adhesive layer>
The pressure-sensitive adhesive layer in the technique disclosed herein can be suitably formed by applying the above-described aqueous pressure-sensitive adhesive composition on a predetermined surface and drying or curing it. A conventional coater (for example, a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater, etc.) is used for applying the adhesive composition (typically coating). be able to. The thickness of the pressure-sensitive adhesive layer is not particularly limited, and is usually suitably about 2 μm or more, preferably about 5 μm or more, more preferably 10 μm or more, more preferably 20 μm or more (typically 30 μm or more, for example, 50 μm or more). In addition, the thickness of the pressure-sensitive adhesive layer is usually appropriately about 200 μm or less, preferably about 120 μm or less (for example, 100 μm or less, typically 80 μm or less).

<Base material>
In the pressure-sensitive adhesive sheet disclosed herein, examples of the base material for supporting (lining) the pressure-sensitive adhesive layer include films made of polyolefin (polyethylene, polypropylene, ethylene-propylene copolymer, etc.) and films made of polyester (polyethylene terephthalate, etc.). , Vinyl chloride resin film, vinyl acetate resin film, polyimide resin film, polyamide resin film, fluorine resin film, and other plastic films such as cellophane; Japanese paper, kraft paper, glassine paper, Papers such as high-quality paper, synthetic paper, top coat paper, etc .; woven fabrics and nonwoven fabrics made of various fibrous materials alone or blended; rubber sheets made of natural rubber, butyl rubber, etc .; foamed polyurethane, foamed poly Foam sheets made of foam such as chloroprene rubber; Miniumu foil, a metal foil such as copper foil; and the like can be used; these complexes. The plastic films may be a non-stretch type or a stretch type (uniaxial stretch type or biaxial stretch type). The substrate may have a single layer form or may have a laminated form.

  A non-woven fabric substrate is used as the substrate according to a preferred embodiment. For example, non-woven fabric composed of natural fibers such as wood pulp, cotton, hemp (eg Manila hemp); chemicals such as polyester fiber, rayon, vinylon, acetate fiber, polyvinyl alcohol (PVA) fiber, polyamide fiber, polyolefin fiber, polyurethane fiber Any of non-woven fabric composed of fibers (synthetic fibers); non-woven fabric composed of two or more kinds of fibers having different materials can be used. Especially, the nonwoven fabric base material comprised from hemp (for example, Manila hemp) is preferable. In that case, the amount of hemp contained in the nonwoven fabric is preferably 90% by weight or more, more preferably 95% by weight or more. Particularly preferably, a nonwoven fabric substantially consisting only of hemp is used.

When using a nonwoven fabric as a base material, it is preferable to use a nonwoven fabric having a basis weight of about 10 g / m ² or more (for example, 13 g / m ² or more) and about 25 g / m ² or less (for example, 22 g / m ² or less). Can do. Further, non-woven fabric of the bulk density (which can be calculated by dividing the thickness of the basis weight.) Is preferably in the range of approximately ^{0.25g / cm 3 ~0.50g / cm 3} . A non-woven fabric having a tensile strength in the flow direction (MD) and a width direction (TD) of about 8 N / 15 mm or more is preferred, and at least an MD tensile strength of 12 N / 15 mm or more (for example, 18 N / 15 mm or more, or even 24 N / 15 mm or more) ) Is more preferable, and a nonwoven fabric having both MD and TD tensile strengths of approximately 12 N / 15 mm or more (for example, 16 N / 15 mm or more) is more preferable. A nonwoven fabric satisfying such tensile strength is suitable for constituting a pressure-sensitive adhesive sheet having excellent tensile strength.

  Further, in the production stage of the nonwoven fabric, a polymer such as viscose, starch, cationic polymer (for example, polyamide, amine, epichlorohydrin) may be used for the purpose of improving the strength (for example, tensile strength) of the nonwoven fabric. . Such a polymer (which can be grasped as a non-woven fabric strength improver) may be added at the non-woven paper making stage (fiber accumulation stage), or may be applied or impregnated after paper making. A nonwoven fabric using such a strength improver is suitable for constituting an adhesive sheet excellent in tensile strength. Therefore, for example, in a double-sided pressure-sensitive adhesive sheet that is used by being attached to a recycling part, it is particularly effective to use a non-woven fabric using the above strength improver.

  For the above-mentioned base material, a filler (inorganic filler, organic filler, etc.), anti-aging agent, antioxidant, ultraviolet absorber, antistatic agent, lubricant, plasticizer, colorant (pigment, Various additives such as dyes) may be blended. The surface of the substrate (particularly the surface on which the pressure-sensitive adhesive layer is provided) may be subjected to known or conventional surface treatments such as corona discharge treatment, plasma treatment, and application of a primer. Such a surface treatment can be, for example, a treatment for enhancing the substrate anchoring property of the pressure-sensitive adhesive layer.

  The thickness of the substrate can be appropriately selected depending on the purpose, but is approximately 10 μm or more, usually 20 μm or more, preferably 30 μm or more (typically 40 μm or more, for example, 50 μm or more). By increasing the thickness of the base material, the strength of the base material and the pressure-sensitive adhesive sheet is increased, and the handleability (workability) during production or use tends to be improved. The thickness is about 800 μm or less, usually 450 μm or less, preferably 300 μm or less (typically 150 μm or less, for example, 100 μm or less). By limiting the thickness of the base material, the followability to the surface shape (step difference, etc.) of the adherend tends to be improved.

<Release liner>
The release liner that protects or supports the pressure-sensitive adhesive layer (may have both protective and support functions) is not particularly limited in material and configuration, and an appropriate one selected from known release liners is used. be able to. For example, a release liner having a configuration in which a release treatment is performed on at least one surface of the substrate (typically, a release treatment layer with a release treatment agent is provided) can be suitably used. As a base material (exfoliation processing object) constituting this type of release liner, the same base materials (various plastic films, papers, cloths, rubber sheets, etc.) as described above as the base material constituting the pressure-sensitive adhesive sheet, Foam sheets, metal foils, composites thereof and the like can be appropriately selected and used. As the release treatment agent for forming the release treatment layer, a known or commonly used release treatment agent (for example, release treatment agents such as silicone-based, fluorine-based, and long-chain alkyl-based) can be used. Fluorine polymers (eg, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, chlorofluoroethylene-vinylidene fluoride copolymer, etc.) Alternatively, a low-adhesive base material made of a low-polar polymer (for example, an olefin resin such as polyethylene or polypropylene) may be used as a release liner without subjecting the surface of the base material to a release treatment. Or you may use what gave the peeling process to the surface of this low adhesive base material as a peeling liner.

  The thickness of the base material and the release treatment layer constituting the release liner is not particularly limited and can be appropriately selected depending on the purpose and the like. The total thickness of the release liner (in the case of a release liner having a release treatment layer on the substrate surface, the total thickness including the substrate and the release treatment layer) is, for example, about 15 μm or more (typically about 15 μm to 500 μm). It is preferable that it is about 25 micrometers-500 micrometers.

<Method for producing double-sided PSA sheet with substrate>
In the production of the double-sided pressure-sensitive adhesive sheet with a substrate, the method of providing the pressure-sensitive adhesive layer on one surface and the other surface of the substrate is not particularly limited. Usually, (1) an aqueous pressure-sensitive adhesive composition is applied (typically applied) to a release liner and dried to form a pressure-sensitive adhesive layer on the release liner, and the pressure-sensitive adhesive layer is attached to a substrate. A method of transferring (lamination) together (hereinafter also referred to as “transfer method”); and (2) a method of applying (typically applying) an aqueous pressure-sensitive adhesive composition directly to a substrate and drying (hereinafter, referred to as “transfer method”). , “Direct coating method” or “direct method”), it is preferable to apply any one method selected from the above-mentioned one surface and the other surface. For example, a double-sided PSA sheet may be manufactured by applying a transfer method to both sides of the substrate (transfer-transfer method), or one side of the substrate (typically, the PSA layer is first provided. A double-sided PSA sheet may be manufactured by applying a transfer method to the surface) and applying a direct coating method to the other surface (transfer-direct method). The above transfer-direct method is preferably employed from the viewpoint that a double-sided pressure-sensitive adhesive sheet (for example, a pressure-sensitive adhesive sheet having a high tensile strength) suitable for applications (for example, fixing of parts for recycling) can be easily obtained. be able to. In the production of the double-sided PSA sheet by this transfer-direct method, the viscosity of the PSA composition used for the direct method may be lower than the viscosity of the PSA composition used for the transfer method. By this, the impregnation property to the base material of the adhesive layer and the adhesive property can be realized at a higher level.

<Application>
According to the pressure-sensitive adhesive sheet disclosed herein, it is possible to reliably prevent or suppress metal corrosion and defects associated therewith (contact failure, deterioration in appearance quality, etc.). Therefore, the pressure-sensitive adhesive sheet, for example, in a housing of a television (liquid crystal television, plasma television, cathode-ray tube television, etc.), computer (display, main body, etc.), audio equipment, other home appliances, OA equipment, etc. It can be preferably used for purposes such as bonding, surface protection, information display, sealing or filling of holes and gaps, buffering of vibration and impact, and the like. In particular, adhesives used in environments where the temperature inside the housing is likely to rise due to the use of electronic equipment, and therefore metal corrosive gas derived from preservatives or metal corrosion is likely to be accelerated (such as inside LCD television housings). It is suitable as a sheet. According to the pressure-sensitive adhesive sheet disclosed herein, even in such a use mode, high metal corrosion resistance can be exhibited.

  Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to the specific examples. In the following description, “parts” and “%” are based on weight unless otherwise specified. Each characteristic in the following description was measured or evaluated as follows.

[Metal corrosion test (tackifying component)]
Prepare a measurement sample consisting of 5 g of tackifying component and a silver plate (silver purity> 99.95%, size 1 mm × 10 mm × 10 mm), and use a metal corrosion tester to measure the metal corrosivity of the tackifying component. evaluated. That is, the tackifying component and the silver plate were put in a transparent glass screw tube bottle having a volume of 50 mL washed with ethanol so as not to be in direct contact, and sealed. This was held at 80 ° C. for 48 hours. The silver plate after the test (after 48 hours) is compared with the unused silver plate (before the test) to visually check for the occurrence of corrosion (determined by the appearance change such as loss of metallic luster and coloring). The metal corrosivity was evaluated. Specifically, when corrosion was found, the metal corrosivity was “failed”, and when corrosion was not found, the metal corrosivity was “passed”.

[Metal corrosion test (adhesive sheet)]
Prepare 5 g of the adhesive sheet with the release liner peeled off and an LED bar having a silver plate (silver purity> 99.95%, size 1 mm × 10 mm × 10 mm), and use a metal corrosive tester to make the metal of the adhesive sheet Corrosivity was evaluated. That is, the pressure-sensitive adhesive sheet and the LED bar were put in a transparent glass bottle having a volume of 100 mL washed with ethanol so as not to be in direct contact, and sealed. This was kept at 100 ° C. for 80 hours. The silver plate after the test (after the elapse of 80 hours) is compared with the unused silver plate (before the test) to visually check for the occurrence of corrosion (determined by appearance change such as loss of metallic luster and coloring). The metal corrosivity was evaluated. Specifically, when corrosion was not observed, metal corrosiveness “◯” was evaluated, and when corrosion was observed, metal corrosiveness “x” was evaluated.

[CS ₂ (250 ° C) detection]
The adhesive sheet was evaluated by the following DSP (Double Shot Pyrolysis) and GC-mass to determine whether CS ₂ was detected at a vaporization temperature of 250 ° C.
[DSP]
As a DSP measuring apparatus, a model “PY-2020iD” manufactured by Frontier Laboratories was used under the following conditions.
(conditions)
Sample amount: 1mg
Vaporization conditions: 250 ° C. for 10 minutes [GC-mass]
As the GC-mass measuring apparatus, model “7890A / 5975C” manufactured by Agilent Technologies was used under the following conditions.
(conditions)
Column: HP-5MS UI 30m × 0.25mmid × 0.25μm filmickness
Column temperature: The temperature was raised from 40 ° C. to 300 ° C. at a rate of 20 ° C./min and held.
Column pressure: 24.3 kPa (constant flow mode)
Carrier gas: He (3.0 mL / min)
Inlet: Split (split ratio 10: 1)
Inlet temperature: 250 ° C
Detector: MS / FPD
Detector temperature: 250 ° C

[Release strength against SUS plate]
The peel strength against the SUS plate of the pressure-sensitive adhesive sheet was measured as follows. That is, the release liner covering one side of the pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet) was peeled off and attached to a polyethylene terephthalate (PET) film having a thickness of 25 μm and backed. The backing adhesive sheet was cut into a size of 20 mm in width and 100 mm in length to produce a sample piece. In an environment of 23 ° C. and 50% RH, the test piece was pressed against a stainless steel plate (SUS304BA plate) as an adherend by reciprocating a 2 kg roller. After leaving this in an environment of 23 ° C. and 50% RH for 30 minutes, according to JIS Z0237, a 180 ° peel strength [N / 20 mm] is measured using a tensile tester at a tensile speed of 300 mm / min. did. The measurement was performed three times (that is, N = 3), and the average value thereof was defined as the peel strength against the SUS plate of the pressure-sensitive adhesive sheet. In addition, when measuring by a single-sided adhesive sheet, the backing by a film is unnecessary.

[Form rebound resistance test]
The release liner covering the second pressure-sensitive adhesive layer of the double-sided PSA sheet is peeled off and bonded to a 10 mm thick urethane foam (trade name “SC Foam” available from INOAC) with a hand roller, which is 10 mm wide and long. A sample piece was prepared by cutting to 50 mm. The release liner is peeled off from the first pressure-sensitive adhesive layer (transfer surface) of the sample piece, and the sample piece is placed on one side of an ABS (acrylonitrile-butadiene-styrene copolymer) plate having a thickness of 2 mm, and the width is 10 mm. A 2 kg roller was reciprocated once for pressure bonding so as to obtain a bonding area of 10 mm. Next, the remaining part (width 10 mm, length 40 mm) of the sample piece was bent and bonded to the other surface of the ABS plate by approximately 180 °. This is left for 24 hours in an environment of 23 ° C., and further left for 2 hours in an environment of 70 ° C., and then a sample piece is formed from the one side of the ABS plate (the side where the adhesive area is 10 mm wide and 10 mm long). The height (mm) at which the end of the surface was raised was measured, and the floating height of 2 mm or less was judged as good (◯), and the height exceeding 2 mm was judged as defective (×).

[Vs. SUS creep test]
The release liner covering one surface of the pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet) was peeled off and attached to a PET film having a thickness of 25 μm and backed. The backing adhesive sheet was cut into a size of 10 mm in width and 100 mm in length to produce a sample piece. The release liner was peeled off from the other surface of the sample piece, and the sample piece was pressure-bonded to a bakelite plate as an adherend by reciprocating a 2 kg roller once with a bonding area of 10 mm width and 20 mm length. After the sample piece attached to the adherend in this manner is suspended in an environment of 40 ° C. and left for 30 minutes, a load of 500 g is applied to the free end of the sample piece, according to JIS Z0237, The deviation distance (mm) of the sample piece after being left for 1 hour in an environment of 40 ° C. with the load applied was measured. In addition, when measuring by a single-sided adhesive sheet, the backing by a film is unnecessary.

<Evaluation of tackifier component>
For the tackifier components listed in Table 1, a metal corrosion test was performed. The results are shown in Table 1. Tackifying components A to E are all tackifying resin emulsions manufactured by Arakawa Chemical Industries, Ltd., A is the trade name “Superester 730-55” (made in Taiwan), and B is “Superester E-865NT”. It is. Tackifying component C is a modification of the preservative species of tackifying component A.
In addition, although the present inventors examined metal corrosiveness also about the chain transfer agent contained in an adhesive, an emulsifier, a thickener, and a silicon compound, the metal corrosion causative substance is not contained in these. I have confirmed that. It was speculated that the metal corrosion-causing substance in the pressure-sensitive adhesive was in an additive (typically preservative) in the tackifier component, and the above examination was performed.

  Next, GC-mass was performed on tackifying components A and C, and additives (preservatives) and sulfur-containing gases were examined. Moreover, tackifying components F and G in which the preservative species of the tackifying component A were changed were prepared and similarly analyzed by GC-mass, and a metal corrosion test was also conducted. The results are shown in Table 2. In the table, “-” means that the corresponding component was not detected.

As shown in Tables 1 and 2, it was not possible to identify which compound was the causative substance of metal corrosion from the type of preservative detected in the tackifier component. For example, although the tackifying component G contains a thiazoline-based, benzoisothiazole-based, or benzodithiol-based compound, the metal corrosion test was a result (that is, no metal corrosion). However, what should be noted is the presence or absence of CS ₂ detection. CS ₂ is undetected tackifying component C, while G was both pass the test of corrosive behavior of metals, CS ₂ is detected tackifying component A, F is a failure that the test of corrosive behavior of metals there were. Regarding the above study, CS ₂ itself does not corrode metal even if exposed to a silver plate for about one week. From the above results, the compound that decomposes at 250 ° C. to generate CS ₂ is a causative substance of metal corrosion. It is assumed that there is. This means that even if the type of preservative that causes metal corrosion cannot be specified, whether or not the tackifier component and, by extension, the adhesive sheet is corrosive, is determined by the presence or absence of CS ₂ detection. It suggests that you can. Based on this knowledge, the type of tackifier component was changed, and the following examination was conducted on the metal corrosion prevention property of the pressure-sensitive adhesive sheet.

<Example 1 to Example 9>
Monomer component consisting of 85 parts of 2EHA, 13 parts of MA, 1 part of AA, 1 part of MAA and 3-methacryloxypropyltrimethoxysilane (trade name “KBM-503”, manufactured by Shin-Etsu Chemical Co., Ltd.) and 100 parts of the monomer component An aqueous emulsion of a monomer mixture by mixing 0.048 parts of a solid lauryl mercaptan (chain transfer agent) and 2.0 parts of an emulsifier in 100 parts of ion-exchanged water and emulsifying the mixture. (Monomer emulsion) was prepared. As the emulsifier, sodium polyoxyethylene alkyl ether sulfate (trade name “Latemul E-118B”, manufactured by Kao Corporation) was used.
The monomer emulsion was placed in a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer, and a stirring device, and stirred at room temperature for 1 hour or more while introducing nitrogen gas. Next, the temperature of the system was raised to 60 ° C., and 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate (polymerization initiator) (trade name “VA- 057 ", manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the monomer emulsion was allowed to react for 6 hours while maintaining the system at 60 ° C. After cooling the system to room temperature, the pH was adjusted to 7.5 by adding 10% aqueous ammonium to obtain an aqueous dispersion of an acrylic polymer.

30 parts of tackifier component per 100 parts of the acrylic polymer (base polymer) and 0.067 parts of silicon compound (n-decyltrimethoxysilane, product) The name "Z-6210 SILANE" (Toray Dow Corning) was added. Furthermore, pH and viscosity were adjusted using 10% aqueous ammonia as a pH adjuster and polyacrylic acid (an aqueous solution having a nonvolatile content of 36%) as a thickener. As the tackifier component according to each example, those shown in Table 3 were used. Thus, the water-dispersed acrylic pressure-sensitive adhesive composition according to each example was obtained.
The tackifier component H has the same composition as the tackifier component A except that it does not contain a preservative. The tackifier component I is a tackifier resin emulsion (product name “Superester E-200NT”, terpene phenol, softening point 150 ° C.) manufactured by Arakawa Chemical Industries, Ltd., and the tackifier component J is a sticker manufactured by Harima Kasei Co., Ltd. It is an imparted resin emulsion (product name “SK915”, polymerized rosin ester, softening point 110 ° C.).

A double-sided PSA sheet was prepared by the following procedure using the PSA composition according to each example. That is, two release liners having both surfaces treated with a silicone release agent were prepared. Among them, the pressure-sensitive adhesive composition is applied to one surface (first release surface) of the first release liner, and dried at 100 ° C. for 2 minutes to form a pressure-sensitive adhesive layer having a thickness of about 40 μm on the one surface. Formed. By sticking this release liner with a pressure-sensitive adhesive layer to one surface (first surface) of the nonwoven fabric, a first pressure-sensitive adhesive layer by a transfer method was provided on the first surface.
Next, an adhesive composition having an amount of 40 μm in dry film thickness is directly applied to the other surface (second surface) of the nonwoven fabric, dried at 100 ° C. for 2 minutes, and then directly applied to the second surface. A second pressure-sensitive adhesive layer was formed. The other surface (second release surface) of the second release liner was laminated on the second pressure-sensitive adhesive layer. A laminate having the structure of “release liner (first sheet) / first pressure-sensitive adhesive layer / nonwoven fabric / second pressure-sensitive adhesive layer / release liner (second sheet)” is formed with a pressure of 0.3 MPa and a speed of 0.5 m / After passing once through a laminator having a roll temperature of 80 ° C. under the conditions of minutes (press treatment), it was kept in an oven at 50 ° C. for 3 days for curing. Thus, the double-sided adhesive sheet (total thickness of 130 micrometers) which concerns on each example was obtained.
As the nonwoven fabric, a nonwoven fabric having a basis weight of 18.0 g / m ² , a thickness of 60 μm, a bulk density of 0.30 g / cm ³ , a tensile strength MD of 26.0 N / 15 mm, and a TD of 19.0 N / 15 mm was used.

  Table 3 shows the evaluation results of the obtained pressure-sensitive adhesive sheet. In Table 3, “-” represents unconfirmed and unmeasured.

As shown in Table 3, the pressure-sensitive adhesive sheets according to Examples 2 and 6 using tackifying components C and G in which CS ₂ is not detected by GC-mass (vaporization temperature 250 ° C.) are silver in a metal corrosion evaluation test. The plate was not corroded. Since the pressure-sensitive adhesive sheets according to Examples 3, 4 and 7 also did not corrode the silver plate in the metal corrosivity evaluation test, the tackifier components D, E and H used in these examples were also the above-mentioned GC-mass. It is presumed that CS ₂ is a component that is not detected. In addition, these pressure-sensitive adhesive sheets all exhibited excellent pressure-sensitive adhesive properties (vs. SUS plate peel strength, foam repulsion resistance, SUS creep resistance). Incidentally, every PSA sheet of Example 6 was subjected to GC-mass at the vaporization temperature of 250 ° C., CS ₂ was not detected.
On the other hand, the pressure-sensitive adhesive sheets according to Examples 1 and 5 using the tackifier components A and F in which CS ₂ was detected by the GC-mass caused metal corrosion in the metal corrosivity evaluation test. Since the adhesive sheets according to Examples 8 and 9 also corroded the silver plate in the metal corrosivity evaluation test, CS ₂ was also detected by the above GC-mass in the tackifier components I and J used in those examples. It is presumed to be a component.
From the above results, the pressure-sensitive adhesive sheet in which metal corrosion is highly suppressed can be obtained by using an aqueous pressure-sensitive adhesive composition containing a tackifying component in which CS ₂ is not detected in gas chromatography mass spectrometry performed at a vaporization temperature of 250 ° C. It turns out that it is obtained.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

DESCRIPTION OF SYMBOLS 1 Adhesive sheet 11 1st adhesive layer 11A 1st adhesive surface 12 2nd adhesive layer 12A 2nd adhesive surface 15 Base material (support body)
21 Release liner

Claims (10)

An aqueous pressure-sensitive adhesive composition comprising an acrylic polymer as a base polymer and a tackifying component,
The tackifier component is an aqueous pressure-sensitive adhesive composition that is a tackifier component in which CS ₂ is not detected in gas chromatography mass spectrometry performed at a vaporization temperature of 250 ° C.   The aqueous pressure-sensitive adhesive composition according to claim 1, wherein the tackifying component is a tackifying resin emulsion containing a preservative.   The aqueous pressure-sensitive adhesive composition according to claim 2, wherein the tackifying component comprises a rosin-based tackifying resin.   The aqueous pressure-sensitive adhesive composition according to claim 2 or 3, wherein the preservative is a compound having a heterocycle containing a sulfur atom (S) as a constituent atom.   The adhesive sheet containing the adhesive layer formed from the aqueous adhesive composition as described in any one of Claims 1-4. The pressure-sensitive adhesive sheet according to claim 5, wherein CS ₂ is not detected by gas chromatography mass spectrometry performed at a vaporization temperature of 250 ° C.   The pressure-sensitive adhesive sheet according to claim 5 or 6, wherein the 180-degree peel strength with respect to the stainless steel plate is 8 N / 20 mm or more.   Double-sided adhesive comprising a base material, a first pressure-sensitive adhesive layer disposed on one surface of the base material, and a second pressure-sensitive adhesive layer disposed on the other surface of the base material as the pressure-sensitive adhesive layer The pressure-sensitive adhesive sheet according to any one of claims 5 to 7, wherein the pressure-sensitive adhesive sheet is configured as a conductive pressure-sensitive adhesive sheet.   The pressure-sensitive adhesive sheet according to any one of claims 5 to 8, which is disposed inside an electronic device.   The pressure-sensitive adhesive sheet according to any one of claims 5 to 8, which is disposed in a non-contact state with a metal material in an internal space of the electronic device.

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