KR20240070575A - Adhesive composition and laminate containing the same - Google Patents

Abstract

[Problem] The present invention provides an adhesive composition with high durability.
[Solution] The adhesive composition of the present invention is an adhesive composition containing a (meth)acrylic copolymer and a crosslinking agent, and the (meth)acrylic copolymer is an alkoxyalkyl (meth)acrylate of more than 50% by mass and less than 99.9% by mass. It is a copolymer of a monomer composition containing 0.1% by mass or more and 10% by mass or less of a hydroxyl group-containing monomer, and the weight average molecular weight of the (meth)acrylic copolymer is 1.65 million or more.

Description

Adhesive composition and laminate containing the same

The present invention relates to an adhesive composition and a laminate containing the same. In particular, the present invention relates to a highly durable adhesive composition and a laminate containing the same.

An image display device includes a plurality of transparent members such as optical films. Conventionally, adhesives have been used to laminate these transparent members.

In these applications, the adhesive is required to have adhesion and transparency, as well as to not foam or peel in a high-temperature environment.

Patent Document 1 discloses such an adhesive. This adhesive contains an acrylic polymer having a weight average molecular weight of 400,000 to 1.6 million, and the monomer component of this acrylic polymer substantially does not contain a carboxyl-containing monomer.

The adhesive disclosed in Patent Document 2 includes a copolymer of a composition containing a specific amount of an alkylene oxide chain-containing monomer, a hydroxyl group-containing monomer, an amide group or amino group-containing monomer, and a (meth)acrylic acid alkyl ester monomer. The weight average molecular weight of the copolymers specifically disclosed in Patent Document 2 is all 1 million or less.

The adhesive disclosed in Patent Document 3 includes a copolymer of a composition containing a specific amount of a polyoxyalkylene group- or alkoxyalkyl group-containing monomer, a hydroxyl group-containing monomer, a carboxyl group-containing monomer, and a (meth)acrylic acid alkyl ester monomer. The weight average molecular weight of the copolymers specifically disclosed in Patent Document 3 is all 1.2 million or less.

Japanese Patent Application Publication No. 2009-79203 International Publication No. 2014/168178 International Publication No. 2016/059979

The present invention provides a highly durable adhesive composition and a laminate containing the same.

The present inventors have discovered that the above problem can be solved by the present invention including the following aspects.

"Aspect 1"

An adhesive composition containing a (meth)acrylic copolymer and a crosslinking agent,

The (meth)acrylic copolymer is a copolymer of a monomer composition containing more than 50% by mass and less than 99.9% by mass of alkoxyalkyl (meth)acrylate and 0.1% by mass and less than 10% by mass of a hydroxyl group-containing monomer,

The weight average molecular weight of the (meth)acrylic copolymer is 1.65 million or more.

“Aspect 2”

In the adhesive composition according to aspect 1, the monomer composition comprises more than 80% by mass of alkoxyalkyl (meth)acrylate.

"Aspect 3"

In the adhesive composition according to Embodiment 1 or 2, the weight average molecular weight of the (meth)acrylic copolymer is 1.85 million or more and 2.5 million or less.

"Aspect 4"

In the pressure-sensitive adhesive composition according to any one of aspects 1 to 3, the monomer composition is substantially free of amide group-containing monomers or amino group-containing monomers.

"Aspect 5"

In the pressure-sensitive adhesive composition according to any one of aspects 1 to 4, the monomer composition is substantially free of carboxyl group-containing monomers.

"Aspect 6"

In the pressure-sensitive adhesive composition according to any one of Embodiments 1 to 5, the gel fraction of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition is 62% or more and 90% or less.

"Aspect 7"

In the pressure-sensitive adhesive composition according to any one of aspects 1 to 6, it further contains an antistatic agent containing a bis(trifluoromethanesulfonyl)imide anion.

"Aspect 8"

A laminate comprising a first member, a second member, and a pressure-sensitive adhesive layer for adhering them together, wherein the pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive composition according to any one of aspects 1 to 7.

1 is a cross-sectional view schematically showing an example of a laminate;
Figure 2 is a cross-sectional view schematically showing another example of a laminate.

“Adhesive composition”

The adhesive composition contains a (meth)acrylic copolymer and a crosslinking agent, and the (meth)acrylic copolymer contains more than 50% by mass and less than 99.9% by mass of alkoxyalkyl (meth)acrylate and 0.1% by mass and less than 10% by mass of hydroxyl group. It is a copolymer of a monomer composition containing monomers, and the weight average molecular weight of the (meth)acrylic copolymer is 1.65 million or more.

Conventionally, the heat resistance of the adhesive layer obtained from the adhesive composition has been considered to be sufficient at 80°C. This is because the heat resistance is considered sufficient considering normal use environments such as displays. However, the present inventors have found that the heat resistance may be insufficient under certain circumstances, and that if the heat resistance exceeds 100°C, foaming does not occur in the adhesive layer even under such circumstances, and the adhesive layer does not peel off from the adherend. Found it. In addition, in the past, when the weight average molecular weight of the copolymer contained in the adhesive composition was very high, it sometimes became difficult to apply the adhesive composition to the adhesive surface. However, it was found that this problem could be solved by changing the application method. there was.

<(meth)acrylic copolymer>

(Meth)acrylic copolymer has a weight average molecular weight (Mw) of 1.65 million or more. The weight average molecular weight may be 1.7 million or more, 1.8 million or more, 1.85 million or more, 1.9 million or more, 1.95 million or more, or 2 million or more, or 3 million or less, 2.8 million or less, 2.5 million or less, 2.2 million or less, or 2 million or less. It may be less than 10,000. For example, the weight average molecular weight may be 1.65 million to 3 million, or 1.85 million to 2.5 million. Within this range, very high heat resistance can be provided to the resulting adhesive layer without causing problems with applicability to the adhesive composition.

The polydispersity (Mw/Mn), expressed as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the (meth)acrylic copolymer, is 15.0 or less, 10.0 or less, 8.0 or less, 6.0 or less, or 5.0 or less. It can be 1.5 or higher, 2.0 or higher, 3.0 or higher, or 4.0 or higher. For example, the polydispersity of the (meth)acrylic copolymer may be 1.5 or more and 15.0 or less, or 2.0 or more and 8.0 or less.

The weight average molecular weight and number average molecular weight can be determined using GPC (gel permeation chromatography), and the weight average molecular weight (Mw) and number average molecular weight (Mn) can be obtained by conversion to standard polystyrene under the following conditions.

<GPC measurement conditions>

Measuring device: HLC-8120GPC (manufactured by TOSOH)

GPC column configuration: 5-unit column as follows (all manufactured by Tosoh)

(1) TSK-GEL HXL-H (guard column)

(2) TSK-GEL G7000HXL

(3) TSK-GEL GMHXL

(4) TSK-GEL GMHXL

(5) TSK-GEL G2500HXL

Sample concentration: diluted with tetrahydrofuran to 1.0 mg/cm ³

Mobile phase solvent: tetrahydrofuran

Flow rate: 1.0 cm ³ /min

Column temperature: 40℃

<(meth)acrylic copolymer-alkoxyalkyl (meth)acrylate>

The monomer composition to obtain the (meth)acrylic copolymer includes alkoxyalkyl (meth)acrylate. Alkoxyalkyl (meth)acrylate is a monomer in which at least one hydrogen atom of the alkyl group of the alkyl (meth)acrylate is replaced with an alkoxy group or a compound having an alkoxy group. For example, this monomer is represented by CH ₂ =CR ₁ -COO-R ₂ , where R ₁ is a hydrogen atom or a methyl group and R ₂ represents an alkyl or aralkyl group of a straight or branched chain having 14 or less carbon atoms. However, at least one of the hydrogen atoms constituting these groups is substituted with the group -O-(C _n H _2n O) _m -R ₃ , n represents an integer from 1 to 4, and m is 0 or an integer from 1 to 10. , and R ₃ constitutes a straight chain or branched chain alkyl group having 14 or less carbon atoms.

Specifically, alkoxyalkyl (meth)acrylates include methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, and 3-methoxypropyl (meth)acrylate. Latex, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, 4-ethoxybutyl (meth)acrylate, ethylcarbitol acrylate, 2-ethylhexyl-diglucol acrylate ester, methoxy-polyethylene glycol acrylate, etc., and among them, 2-methoxyethyl (meth)acrylate is especially mentioned.

Alkoxyalkyl (meth)acrylate is contained in the monomer composition in an amount exceeding 50% by mass and not exceeding 99.9% by mass. For example, the alkoxyalkyl (meth)acrylate is present in the monomer composition in an amount of 51% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, 95% by mass or more, Alternatively, it may be contained at 98 mass% or more, 99.5 mass% or less, 99.0 mass% or less, 98 mass% or less, 95 mass% or less, 90 mass% or less, or 80 mass% or less. For example, alkoxyalkyl (meth)acrylate may be included in the monomer composition in an amount of 70% by mass or more and 99.9% by mass or less, or 85% by mass or more and 99.9% by mass or less.

Compared to other monomers used in this field, when the content of alkoxyalkyl (meth)acrylate is in the high range as described above, the electrical resistance of the adhesive layer can be lowered. Usually, the electrical resistance of the adhesive layer is lowered by using an antistatic agent such as an ionic compound, but the electrical resistance can be further lowered by changing the composition of the (meth)acrylic copolymer.

<(meth)acrylic copolymer-hydroxyl group-containing monomer>

The monomer composition for obtaining a (meth)acrylic copolymer by polymerizing it includes a hydroxyl group-containing monomer. The hydroxyl group-containing monomer is not particularly limited as long as it is a monomer having a hydroxyl group and a polymerizable group, but examples of the polymerizable group include groups having a polymerizable double bond, such as a vinyl group and a (meth)acryloyl group.

For example, the hydroxyl group-containing monomer may be a hydroxyalkyl (meth)acrylate represented by the formula CH ₂ =CR ₄ -COO-R ₅ -OH. Here, R ₄ is a hydrogen atom or a methyl group, and R ₅ is a straight chain or branched chain alkylene group. The number of carbon atoms of R ₅ may be 1 to 10, 2 to 5, or 2 to 4.

Specifically, hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate. late, 8-hydroxyoctyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, etc.

The hydroxyl group-containing monomer is contained in the monomer composition in an amount of 0.1% by mass or more and 10% by mass or less. For example, the hydroxyl group-containing monomer may be contained in the monomer composition in an amount of 0.3 mass% or more, 0.5 mass% or more, 0.8 mass% or more, or 1.0 mass% or more, and 8.0 mass% or less, 5.0 mass% or less, or 3.0 mass% or less. , may be contained in 2.0 mass% or less, or 1.5 mass% or less. For example, the hydroxyl group-containing monomer may be included in the monomer composition in an amount of 0.3 mass% or more and 5.0 mass% or less, or 0.5 mass% or more and 2.0 mass% or less. Hydroxyl groups derived from hydroxyl group-containing monomers can serve as crosslinking points, and within this range, the (meth)acrylic copolymer can be adjusted to an appropriate gel fraction.

<(meth)acrylic copolymer - other monomer components>

The monomer composition obtained by polymerizing the (meth)acrylic copolymer may contain monomers other than alkoxyalkyl (meth)acrylate and hydroxyl group-containing monomers within the range that can obtain the advantageous effects of the present invention.

For example, the monomer composition may contain an alkyl (meth)acrylate represented by the formula CH ₂ =CR ₆ -COO-R ₇ . Here, R ₆ is a hydrogen atom or a methyl group, and R ₇ is a straight chain or branched chain alkylene group. The number of carbon atoms of R ₇ may be in the range of 1 to 20, 1 to 10, or 2 to 8.

For example, alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, and n-butyl (meth)acrylate. , isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, 2-ethylhexyl ( Meth)acrylate, n-octyl(meth)acrylate, isooctyl(meth)acrylate, n-nonyl(meth)acrylate, isononyl(meth)acrylate, decyl(meth)acrylate, isodecyl(meth)acrylate ) Acrylate, undeca (meth)acrylate, lauryl (meth)acrylate, oleyl (meth)acrylate, n-stearyl (meth)acrylate, isostearyl (meth)acrylate, etc. there is.

For example, the alkyl (meth)acrylate may be contained in the monomer composition in an amount of 0% by mass or more, 5% by mass or more, 10% by mass or more, or 15% by mass or more, and less than 49% by weight, less than 48% by weight, or less than 40% by weight. It may be contained in % by weight or less, 30% by weight or less, 20% by weight or less, 10% by weight or less, or 5% by weight or less. For example, alkyl (meth)acrylate may be included in the monomer composition in an amount of 0 mass% to 48 mass% or 0 mass% to 10 mass%. According to the examination by the present inventors, it was found that when the content of alkyl (meth)acrylate is high, the electrical resistance of the obtained copolymer tends to increase. Additionally, it was found that when alkyl (meth)acrylate was included, the adhesiveness to glass tended to decrease. Accordingly, alkyl (meth)acrylate may not be substantially included in the monomer composition.

Other monomer compositions include, for example, (meth)acrylic acid esters having an aromatic ring group such as benzyl (meth)acrylate, 2-naphthylacrylate, and phenoxyethyl acrylate, styrene, α-methylstyrene, and o-methyl. Styrene-based monomers such as styrene and p-methylstyrene; Carboxylic acid vinyl esters such as vinyl acetate; It may contain a vinyl (meth)acryloyl group-containing macro monomer.

It is preferred that the monomer composition is substantially free of nitrogen-containing monomers, such as amide group-containing monomers or amino group-containing monomers. When a large amount of these monomers are included, the electrical resistance of the copolymer may increase. In addition, when a large amount of these monomers are included, it was found that when exposed to a high temperature environment for a long period of time, gelation of the adhesive layer progresses excessively, resulting in peeling, etc. between the adhesive layer and the bonded member.

In this specification, “substantially not included” means that the component may be contained as long as it does not impair the beneficial effects of the present invention. For example, if the component is not substantially included in the composition, it means that the component is less than 0.50 mass%, less than 0.30 mass%, less than 0.20 mass%, less than 0.10 mass%, or less than 0.05 mass% of the composition. There is.

An amide group-containing monomer is a compound that typically contains an amide group in its structure and also contains a polymerizable unsaturated double bond such as a (meth)acryloyl group or vinyl group. For example, examples of the amide group-containing monomer include acrylamide-based monomers such as (meth)acrylamide; N-acryloyl heterocyclic monomers such as N-(meth)acryloylpiperidine; and N-vinyl group-containing lactam monomers such as N-vinylpyrrolidone.

An amino group-containing monomer is a compound that typically contains an amino group in its structure and also contains a polymerizable unsaturated double bond such as a (meth)acryloyl group or vinyl group. For example, examples of amino group-containing monomers include N,N-dimethylaminoethyl acrylate, N,N-dimethylaminoethyl methacrylate, and N,N-diethylaminoethyl methacrylate.

It is preferred that the monomer composition is substantially free of acidic group-containing monomers, such as carboxyl group-containing monomers. It was found that even when a large amount of this monomer is contained, when exposed to a high temperature environment for a long period of time, gelation of the adhesive layer progresses excessively, resulting in peeling, etc. between the adhesive layer and the bonded member.

<(meth)acrylic copolymer-polymerization initiator>

The monomer composition forming the (meth)acrylic copolymer may further include a polymerization initiator. As a polymerization initiator, it is possible to use organic peroxides, azo compounds, etc. that can normally be used in radical polymerization. Specifically, a polymerization initiator as described in Patent Document 3 can be used as a polymerization initiator.

Among the polymerization initiators, polymerization initiators in which a graft reaction is unlikely to occur during the polymerization reaction of the monomer component are preferable, and azo compounds are especially preferable. The polymerization initiator can be used in an amount of 0.01 to 2.0 parts by mass or 0.1 to 1.0 parts by mass based on a total of 100 parts by mass of monomer components.

<(meth)acrylic copolymer-solvent>

The monomer composition may include a solvent depending on the polymerization method. For example, when obtaining a copolymer by solution polymerization, an organic solvent capable of dissolving the monomer component can be used. Specifically, an organic solvent such as that described in Patent Document 3 can be used as the organic solvent. For example, it is preferable to use organic solvents that are difficult to cause chain transfer during the polymerization reaction, such as esters and ketones. In particular, in view of the solubility of the monomer component and the ease of the polymerization reaction, ethyl acetate and methyl Ethyl ketone, acetone, etc. can be used.

<(meth)acrylic copolymer-other ingredients>

The monomer composition may contain other components as long as they do not impair the beneficial effects of the present invention. For example, the monomer component may include a chain transfer agent as described in Patent Document 3, and may also include an emulsifier, dispersant, dispersion medium, etc. depending on the polymerization method.

<(Meth)acrylic copolymer-polymerization method>

The polymerization method of the (meth)acrylic copolymer is not particularly limited, and can be polymerized by known methods such as solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. When manufacturing an adhesive composition using a copolymer, it is preferable to obtain the copolymer by solution polymerization from the viewpoint that the processing process is relatively simple and can be performed in a short time.

<Cross-linking agent>

The adhesive composition may include a crosslinking agent. By containing a crosslinking agent, the gel fraction of the adhesive composition can be kept in an appropriate range. As a crosslinking agent, an isocyanate-based crosslinking agent known in the art can be used. For example, a crosslinking agent having two or more isocyanate groups or isocyanurate groups and a hydrocarbon group having 1 to 20 carbon atoms optionally containing an oxygen atom can be used. there is. Specifically, a crosslinking agent as described in Patent Document 3 can be used.

Additionally, an epoxy-based crosslinking agent can be used as a crosslinking agent. As an epoxy-based crosslinking agent, an epoxy compound having two or more epoxy groups per molecule can be used, specifically, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, and glycerin triglyceride. Diyl ether, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, N,N,N' ,N'-tetraglycidyl aminophenylmethane, triglycidyl isocyanurate, m-N,N-diglycidyl aminophenyl glycidyl ether, N,N-diglycidyl toluidine, N,N-di Glycidylaniline can be used.

Additionally, a metal chelate crosslinking agent can be used as a crosslinking agent. As a metal chelate crosslinking agent, compounds in which alkoxide, acetylacetone, ethyl acetoacetate, etc. are coordinated to polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium can be used. , specifically, aluminum isopropylate, aluminum sec-butylate, aluminum ethylacetoacetate/diisopropylate, aluminum trisethylacetoacetate, and aluminum trisacetylacetonate can be used.

The crosslinking agent may be contained in the adhesive composition at 0.05 parts by mass, 0.1 parts by mass, 0.2 parts by mass, 0.3 parts by mass, or 0.5 parts by mass, or 1.0 parts by mass, based on 100 parts by mass of (meth)acrylic copolymer. Hereinafter, it may be contained at 0.5 parts by mass or less, 0.3 parts by mass or less, or 0.2 parts by mass or less. For example, the crosslinking agent may be contained in an amount of 0.05 parts by mass or more and 1.0 parts by mass or less, or 0.1 parts by mass or more and 0.5 parts by mass or less, based on 100 parts by mass of the (meth)acrylic copolymer.

The adhesive composition has a gel fraction of 50% or more, 55% or more, 60% or more, 62% or more, 64% or more, 66% or more, or 68%, as measured by the method described in the Examples after the crosslinking agent crosslinks the copolymer. It may be % or more, 90% or less, 85% or less, 80% or less, 75% or less, or 70% or less. For example, the gel fraction of the adhesive composition may be 50% or more and 90% or less, or 62% or more and 90% or less.

In addition to the above components, the adhesive composition may contain components selected from antistatic agents, ultraviolet absorbers, antioxidants, tackifying resins, plasticizers, anti-foaming agents, fillers, stabilizers, softeners, and wettability regulators to the extent that they do not impair the effect of the present invention. It may be possible.

<Silane coupling agent>

The adhesive composition may include a silane coupling agent. An adhesive composition containing a silane coupling agent can maintain good adhesion between the adherend and the adhesive layer.

As the silane coupling agent, silane coupling agents known in the art can be used, for example, silicon compounds containing a polymerizable unsaturated group such as vinyltrimethoxysilane; Silicon compounds having an epoxy structure such as 3-glycidoxypropyltrimethoxysilane; Amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane; 3-chloropropyltrimethoxysilane; Oligomeric type silane coupling agents can be mentioned. Among these, a silane coupling agent having a functional group that reacts with a functional group contained in the (meth)acrylic copolymer or its monomer component is particularly preferable because it is difficult to cause peeling in a high-humidity heat environment.

The silane coupling agent may be contained in the adhesive composition in an amount of 0.05 parts by mass or more, 0.1 parts by mass or more, 0.2 parts by mass or more, 0.3 parts by mass, or 0.5 parts by mass or more, based on 100 parts by mass of (meth)acrylic copolymer. It may be contained in 0.5 parts by mass or less, 0.3 parts by mass or less, or 0.2 parts by mass or less. For example, the silane coupling agent may be contained in an amount of 0.05 to 1.0 parts by mass, or 0.1 to 0.5 parts by mass, based on 100 parts by mass of the (meth)acrylic copolymer.

<Antistatic agent>

The adhesive composition may include an antistatic agent made of an ionic compound. The pressure-sensitive adhesive composition containing an antistatic agent can realize high antistatic performance by coordinating the oxygen atom of the alkoxyalkyl group of the (meth)acrylic copolymer to an ionic group contained in the antistatic agent.

Examples of antistatic agents include ionic compounds that are liquid or solid at 25°C and contain anions and cations. Specifically, alkali metal salts, ionic liquids, surfactants, etc. as described in Patent Document 3 can be mentioned.

Cations constituting the ionic compound include inorganic cations and organic cations. Examples of inorganic cations include Li ⁺ , Na ⁺ , and K ⁺ . Examples of organic cations include pyridinium cation, piperidinium cation, pyrrolidinium cation, pyrroline cation, pyrrole cation, imidazolium cation, tetrahydropyrimidinium cation, dihydropyrimidinium cation, and pyrazolium cation. , pyrazolinium cation, tetraalkylammonium cation, trialkylsulfonium cation, tetraalkylphosphonium cation, and derivatives thereof.

The anion constituting the ionic compound is not particularly limited as long as it can form an ionic compound by ionic bonding with the cation. For example, F ^- , Cl ^- , Br ^- , I ^- , AlCl ₄ ^- , Al ₂ Cl ₇ ^- , BF ₄ ^- , PF ₆ ^- , SCN ^- , ClO ₄ ^- , NO ₃ ^- , CH ₃ COO ^- , CF ₃ COO ^- , CH ₃ SO ₃ ^- , CF ₃ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , (CF ₃ SO ₂ ) ₃ C ^- , AsF ₆ ^- , SbF ₆ ^- , NbF ₆ ^- , TaF ₆ ^- , F(HF) _n ^- , (CN) ₂ N ^- , C ₄ F ₉ SO ₃ ^- , (C ₂ F ₅ SO ₂ ) ₂ N ^- , C ₃ F ₇ COO ^- , and (CF ₃ SO ₂ )(CF ₃ CO)N ^- .

Among these, the anionic portion containing a fluorine atom is preferably used because an ionic compound with good ion dissociation properties can be obtained. Moreover, among the anions containing a fluorine atom, the fluorine-containing imide anion is preferable, and among them, the bis(trifluoromethanesulfonyl)imide anion and the bis(fluorosulfonyl)imide anion are preferable. In particular, bis(trifluoromethanesulfonyl)imide anion is preferable because it can provide excellent antistatic properties by adding a relatively small amount and maintains adhesive properties, which is advantageous for durability in humidified or heated environments.

Ionic compounds specifically include lithium bis(trifluoromethanesulfonyl)imide, lithium bis(difluorosulfonyl)imide, lithium tris(trifluoromethanesulfonyl)methane, and potassium bis(trifluoro)imide. Methanesulfonyl)imide, potassium bis(difluorosulfonyl)imide, 1-ethylpyridinium hexafluorophosphate, 1-butyl-4-methylpyridinium hexafluorophosphate, 1-hexyl-4-methyl Pyridinium hexafluorophosphate, 1-octyl-4-methylpyridinium hexafluorophosphate, 1-octyl-4-methylpyridinium bis(fluorosulfonyl)imide, 1-octyl-4-methylpyridinium bis (trifluoromethanesulfonyl)imide, (N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium tetrafluoroborate, butyltrimethylammonium bis(trifluoromethanesulfonyl) Imide, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide, 1-octylpyridinium bis(trifluoromethanesulfonyl) imide and 1-octyl-3-methylpyridinium bis(trifluorosulfonyl)imide.

As the surfactant, any of nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants can be used. Additionally, as other antistatic agents, conductive polymers, conductive carbon, ammonium chloride, aluminum chloride, copper chloride, iron chloride, ammonium sulfate, etc. can be used.

The antistatic agent may be contained in the adhesive composition in an amount of 0.1 parts by mass or more, 0.3 parts by mass or more, 0.5 parts by mass or more, 1.0 parts by mass, or 2.0 parts by mass or more, based on 100 parts by mass of (meth)acrylic copolymer. parts by mass or less, 5.0 parts by mass or less, 3.0 parts by mass or less, or 2.0 parts by mass or less. For example, the antistatic agent may be contained in an amount of 0.1 to 10 parts by mass, or 0.5 to 5.0 parts by mass, based on 100 parts by mass of the (meth)acrylic copolymer.

<Solvent>

The adhesive composition may contain a solvent to adjust applicability. The type of solvent may be the same as the above polymerization solvent for polymerizing (meth)acrylic copolymer.

The solid content concentration of the adhesive composition can be adjusted by containing a solvent. The solids concentration of the adhesive composition may be 10 mass% or more, 12 mass% or more, 14 mass% or more, or 16 mass% or more, and may be 30 mass% or less, 25 mass% or less, 20 mass% or less, or 18 mass% or less. there is. For example, the solid content concentration of the adhesive composition may be 10 mass% or more and 30 mass% or less, or 12 mass% or more and 20 mass% or less.

《Laminate》

The laminate includes a first member, a second member, and an adhesive layer that adheres them, and the adhesive layer is formed from the adhesive composition described above. The adhesive layer can be obtained, for example, by drying and/or crosslinking the adhesive composition.

The adhesive layer is formed by applying an adhesive composition to the first member and/or second member as an adherend, or to the surface of a release film (separator), and drying it at, for example, 50°C to 150°C depending on the type of solvent. After this, it can be formed by attaching a release film to the side of the adhesive layer that is not in contact with other layers. In addition, after forming the pressure-sensitive adhesive layer, the gel fraction of the pressure-sensitive adhesive composition can be adjusted to the above-mentioned range by curing the pressure-sensitive adhesive layer in an environment of 23° C. to 50° C. for, for example, 3 to 10 days to promote crosslinking.

Application methods of the adhesive composition include known methods, such as spin coat method, knife coat method, roll coat method, bar coat method, blade coat method, die coat method, and gravure coat method, especially the blade coat method. can be mentioned.

The thickness of the adhesive layer may be 5 μm or more, 7 μm or more, 10 μm or more, or 15 μm or more, or 50 μm or less, 30 μm or less, 20 μm or less, or 15 μm or less. For example, the thickness of the adhesive layer may be 5 μm or more and 50 μm or less, or 10 μm or more and 30 μm or less.

The first and second members that are adherends are not particularly limited, but examples include optical members, such as glass substrates, polarizing plates, and optical films such as retardation films. As a polarizing plate and an optical film, specifically, those described in Patent Document 3 can be used. It is preferable that the (meth)acrylic copolymer contained in the adhesive layer contains a large amount of alkoxyalkyl (meth)acrylate as a monomer component because the adhesiveness of the adhesive layer to the glass substrate increases.

1 is a cross-sectional view schematically showing an example of a laminate.

As shown in FIG. 1, the laminate 100 includes a glass substrate 10 as a first member, a polarizing film 30 as a second member, and an adhesive layer 20 that adheres them. The polarizing film 30 includes a polycycloolefin-based film 32, a polyvinyl alcohol film 34 on the polycycloolefin-based film 32, and a TAC film 36 on the polyvinyl alcohol film 34. do. The glass substrate 10 and the polycycloolefin-based film 32 are adhered to each other using an adhesive layer 20.

Figure 2 is a cross-sectional view schematically showing another example of a laminate.

As shown in FIG. 2, the laminate 200 includes a glass substrate 10 as a first member, a polycycloolefin-based film (retardation film) 32 as a second member, and a polarizing film 130 as a third member. and includes adhesive layers 20 and 22 that adhere them. More specifically, the polycycloolefin-based film 32 and the polarizing film 130 are adhered to each other using an adhesive layer 20. In addition, the glass substrate 10 and the polycycloolefin-based film 32 are adhered to each other using an adhesive layer 22. The polarizing film 130 includes a layer 38 that is a polycycloolefin-based film (second polycycloolefin-based film) or a TAC film, a polyvinyl alcohol film 34 on the layer 38, and a polyvinyl alcohol film 34 ) Includes the TAC film 36 above. The polycycloolefin-based film (first polycycloolefin-based film) 32 and the layer (second polycycloolefin-based film) 38 are adhered with an adhesive layer 20.

The adhesive layers 20 and 22 in FIGS. 1 and 2 are formed on the surface of the adherend. As a method of forming the adhesive composition on the surface of the adherend, for example, the adhesive composition is applied to the surface of a release film (separator) with good smoothness, the coating film is dried, and then the coating film is applied to a specific resin film. One example is a transfer method that involves transferring onto the surface of .

The laminate can be used, for example, in an image display device, especially a liquid crystal display device. More specifically, the laminate can be used, for example, in an image display device for a touch panel. In this case, the glass substrate included in the laminate may be a glass substrate for a liquid crystal display device.

The image display device may be, for example, a TFT (thin film transistor) liquid crystal display device used in liquid crystal TVs, computer monitors, mobile phones, tablets, etc.

The present invention is explained in more detail in the following examples, but the present invention is not limited thereto.

Example

《Manufacturing example》

<Example 1>

99 parts by mass of 2-methoxyethyl acrylate, 1 part by mass of 4-hydroxybutylacrylate, and 100 parts by mass of ethyl acetate were added to a flask equipped with a stirring device, a nitrogen gas introduction pipe, a thermometer, and a reflux cooling pipe. Afterwards, the contents were heated to 65°C while introducing nitrogen gas into the flask. Next, 0.05 parts by mass of 2,2'-azobis-i-butyronitrile (AIBN) was added under stirring into a flask sufficiently substituted with nitrogen gas. The reaction was performed for 6 hours while maintaining the temperature of the contents in the flask at 65°C.

After 6 hours, 300 parts by mass of ethyl acetate was additionally added to the reaction mixture to obtain a solution containing a (meth)acrylic copolymer. The Mw measured by GPC for the obtained (meth)acrylic copolymer was 1.9 million.

An isocyanate-based crosslinking agent (TD-75, manufactured by Soken Chemical Co., Ltd.) and an antistatic agent (Py- PF6 (1-butyl-4-methylpyridinium hexafluorophosphate)) was blended. Additionally, 0.2 parts by mass of a silane coupling agent (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) was further added to each composition and mixed well to obtain an adhesive composition. Here, solid content refers to all components excluding the organic solvent from the adhesive composition.

<Examples 2 to 13, Comparative Examples 1 to 3>

The adhesive compositions of Examples 2 to 13 and Comparative Examples 1 to 3 were obtained in the same manner as in Example 1 except that the components used were changed as shown in Table 1.

In addition, for the (meth)acrylic copolymer prepared in Example 8, ethyl acetate added at the beginning of polymerization was 90 parts by mass, and for the (meth)acrylic copolymer prepared in Example 9, ethyl acetate added at the beginning of polymerization was 90 parts by mass. 110 parts by mass, 80 parts by mass of ethyl acetate added at the beginning of polymerization for the (meth)acrylic copolymer prepared in Example 10, and 80 parts by mass of acetic acid added at the beginning of polymerization for the (meth)acrylic copolymer prepared in Example 11. The Mw of the (meth)acrylic copolymer was adjusted by setting ethyl to 70 parts by mass, and ethyl acetate added at the beginning of polymerization to the (meth)acrylic copolymer produced in Comparative Example 3 to 120 parts by mass.

<Polarizing film with adhesive layer>

The adhesive composition obtained in the examples and comparative examples was applied onto the peeled PET film using a doctor blade at a liquid temperature of 25°C so that the film thickness after drying was 25 μm. After that, it was dried at 90°C for 3 minutes to obtain a PET film with an adhesive layer. PET film with an adhesive layer and a polarizing plate (COP film 40 μm/polarizing film 20 μm/TAC film 40 μm) were bonded together so that the adhesive layer of the PET film with an adhesive layer and the COP film surface of the polarizing plate were in contact. And it was left still for 3 days under conditions of 50°C, and a polarizing plate with an adhesive layer was obtained.

<Adhesive sheet>

The adhesive composition obtained in the examples and comparative examples was applied onto the peeled PET film using a doctor blade at a liquid temperature of 25°C so that the film thickness after drying was 25 μm. After that, it was dried at 90°C for 3 minutes to obtain a PET film with an adhesive layer. The PET film with an adhesive layer and the peeled PET film were bonded together so that the adhesive layer of the PET film with an adhesive layer and the peeling treated surface of the PET film were in contact. Then, it was left to stand for 3 days under conditions of 50°C to obtain an adhesive sheet.

"Test Methods"

<Surface resistivity>

After peeling the PET film from the polarizing plate with the adhesive layer, use a resistivity meter (Hiresta UX MCP-HT800, manufactured by Nitto Seiko Analytech) to measure 23°C/50°C at an applied voltage of 1000V in accordance with JIS-K-6911. The surface resistivity of the adhesive layer was measured under %RH environment.

<Adhesion to alkali-free glass>

A test piece was produced by cutting a polarizing plate with an adhesive layer to a width of 25 mm. The peel-treated PET film was peeled from the test piece, and the exposed adhesive layer was attached to an alkali-free glass plate. Afterwards, they were kept in an autoclave adjusted to 50°C/5atm for 20 minutes and compressed. After compression, it was left to stand for 1 hour in an environment of 23°C/50%RH, and the end of the test piece was pulled at a speed of 300 mm/min with the polarizing plate with the adhesive layer at an angle of 180° with respect to the glass plate to measure the adhesive force.

<Gel fraction>

Approximately 0.1 g of adhesive was collected from the adhesive sheet into a sample bottle. 30 mL of ethyl acetate was added to the sample bottle and shaken for 4 hours. The contents of this sample bottle were filtered through a 200 mesh stainless steel wire mesh, and the residue on the wire mesh was dried at 90°C for 2 hours and the dry weight was measured. The gel fraction of the adhesive was calculated using the following equation.

Gel fraction (%) = (dry weight/adhesive collected weight) × 100 (%)

<Gel fraction after heat resistance>

The adhesive sheet was left for 500 hours under conditions of a temperature of 105°C. After that, it was left for 1 hour in an environment of 23°C/50%RH. Approximately 0.1 g of adhesive was collected in a sample bottle, 30 mL of ethyl acetate was added, and the sample was shaken for 4 hours. The contents of this sample bottle were filtered through a 200 mesh stainless steel wire mesh, and the residue on the wire mesh was dried at 90°C for 2 hours and the dry weight was measured. The gel fraction of the adhesive was calculated using the following equation.

Gel fraction (%) = (dry weight/adhesive collected weight) × 100 (%)

<105℃ dry heat resistance>

A test piece was produced by cutting a polarizing plate with an adhesive layer into a size of 160 mm (MD direction) x 90 mm (TD direction). After peeling the PET film from the test piece, the polarizing plate with the adhesive layer was attached to one side of a liquid crystal panel having an alkali-free glass plate with a thickness of 2 mm as a glass substrate using a laminator roll so that the adhesive layer and the alkali-free glass plate were in contact. The obtained laminate was kept in an autoclave adjusted to 50°C/5 atm for 20 minutes to produce a test plate. The test panel was left for 500 hours under conditions of a temperature of 105°C, and external defects such as foaming from the adhesive layer of the test panel, cracks in the test panel, and peeling of the adhesive layer were visually observed and evaluated according to the following criteria.

○: No appearance defects

△: Some cosmetic defects are observed, but there are no problems in actual use.

×: Appearance defects

"result"

The results are shown in Table 1 below.

As can be seen from Table 1, the (meth)acrylic copolymer was made from a monomer containing alkoxyalkyl (meth)acrylate, and when the weight average molecular weight was sufficiently high, it was found that heat resistance and durability were good. .

Additionally, when the monomer component includes acrylamide, an amide group-containing monomer, or dimethylaminoethyl methacrylate, an amino group-containing monomer, there is no practical problem, but heat resistance deteriorates. This is thought to be because the gel fraction after heat resistance became too high and the flexibility of the adhesive layer was lost.

In addition, it was found that when butyl acrylate, an alkyl (meth)acrylate, was included in the monomer component, the surface resistance increased. Additionally, it was found that the adhesion to glass also decreased.

In addition, in Examples 1 to 3, the results of Examples 14 to 19 performed by changing the antistatic agent are shown in Table 2 below.

10 Glass substrate
20, 22 Adhesive layer
30, 130 polarizing film
32 Retardation film (polycycloolefin-based film)
34 Polyvinyl alcohol (PVA) film
36 TAC Film
38 Polycycloolefin-based film or TAC film
100, 200 laminate

Claims (8)

An adhesive composition containing a (meth)acrylic copolymer and a crosslinking agent,
The (meth)acrylic copolymer is a copolymer of a monomer composition containing more than 50% by mass and less than 99.9% by mass of alkoxyalkyl (meth)acrylate and 0.1% by mass and less than 10% by mass of a hydroxyl group-containing monomer,
An adhesive composition in which the weight average molecular weight of the (meth)acrylic copolymer is 1.65 million or more. According to paragraph 1,
The monomer composition is an adhesive composition containing more than 80% by mass of alkoxyalkyl (meth)acrylate. According to paragraph 1,
An adhesive composition wherein the (meth)acrylic copolymer has a weight average molecular weight of 1.85 million to 2.5 million. According to paragraph 1,
The monomer composition is an adhesive composition that substantially does not contain an amide group-containing monomer or an amino group-containing monomer. According to paragraph 1,
The monomer composition is an adhesive composition that substantially does not contain a carboxyl group-containing monomer. According to paragraph 1,
A pressure-sensitive adhesive composition wherein the gel fraction of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition is 62% or more and 90% or less. According to paragraph 1,
An adhesive composition further containing an antistatic agent containing a bis(trifluoromethanesulfonyl)imide anion. A laminate comprising a first member, a second member, and an adhesive layer for adhering them, wherein the adhesive layer is formed from the adhesive composition according to any one of claims 1 to 7.