Adhesive composition and adhesive film
Patent Information
- Authority / Receiving Office
- TW · TW
- Patent Type
- Patents
- Current Assignee / Owner
- FUJIMORI KOGYO CO LTD
- Filing Date
- 2020-09-30
- Publication Date
- 2026-08-01
Abstract
Description
Adhesive Composition and Adhesive Film The present invention relates to providing an adhesive composition and an adhesive film using the adhesive composition, and the adhesive composition can form an adhesive layer with a low water vapor transmission rate and excellent water vapor barrier properties. Hitherto, for specific drugs, organic EL (organic electroluminescence) displays, electronic papers, etc., in order to prevent the contents such as drugs and light-emitting elements from being adversely affected by moisture and oxygen in the atmosphere, a gas barrier film is used to seal the contents. In addition, in recent years, since the images of organic EL displays using self-emitting light-emitting elements are clearer than those of liquid crystal displays, they have gradually become popular as displays for televisions, smartphones, digital signage, etc. In particular, since the light-emitting elements of organic EL displays are formed of organic substances with low moisture resistance, they are extremely vulnerable to moisture in the atmosphere. Therefore, hitherto, a thin glass substrate having gas barrier properties and heat resistance has been used as the substrate and encapsulation member of the light-emitting element. However, in recent years, with the advancement of the flexibility of organic EL displays, a gas barrier film is used as a transparent substrate instead of the thin glass substrate. In addition, an adhesive layer having gas barrier properties is used to bond the gas barrier film. For example, Patent Document 1 discloses a gas barrier film that can be used for packaging applications of foods and drugs that require high gas barrier properties, or for electronic components such as solar cells, electronic papers, and organic EL displays. For a conventional gas barrier layer composed of a vapor deposition film formed by plasma CVD method mainly composed of silicon oxide, in order to obtain a water vapor transmission rate of 1×10 -3 g / (m 2 ‧day) or less, which is required for applications such as organic EL displays and electronic papers, it is necessary to thicken the vapor deposition film. However, since the formed gas barrier layer is a very dense and high-hardness layer, in the case of such a thick vapor deposition film, there is a problem that cracks are generated in the vapor deposition film when the gas barrier film is bent, and the gas barrier property decreases. Therefore, the gas barrier film of the invention of Patent Document 1 is a gas barrier film having a gas barrier layer composed of a vapor deposition film on at least one surface of a polymer film substrate, and the gas barrier layer is sequentially laminated with a first layer mainly composed of a compound containing at least one element belonging to Groups 3 to 14 of the periodic table of elements and a second layer mainly composed of a silicon compound from one side of the polymer film substrate. And by setting the thickness of each layer within a specific range, a gas barrier film with high gas barrier properties that is not easily reduced in gas barrier property even in a high-temperature environment or when bent can be obtained. In addition, Patent Document 2 discloses an adhesive composition applicable to the encapsulation of electronic devices such as display devices including organic EL elements, etc., and an adhesive sheet obtained from the composition. According to the adhesive composition of the invention of Patent Document 2, by using a polyisobutene resin and a polybutene resin having a specific molecular weight, the target adhesive properties can be exhibited, and at the same time, the water vapor transmission rate can be reduced, and the intrusion of moisture from the outside can be prevented. In addition, Patent Document 3 discloses an adhesive composition that does not turn white even under humid heat conditions and has excellent transparency and gas barrier properties. According to the adhesive composition of the invention of Patent Document 3, by forming an adhesive composition containing a tackifying resin, the gas barrier property can be significantly improved and the compatibility is good. [Prior Art Documents] [Patent Documents] [Patent Document 1]: Japanese Patent Application Laid-Open No. 2014-043096 [Patent Document 2]: Japanese Patent Application Laid-Open No. 2011-231313 [Patent Document 3]: Japanese Patent Application Laid-Open No. 2016-079256 [Technical Problem to be Solved by the Present Invention] However, the gas barrier film of the invention described in Patent Document 1 exhibits gas barrier properties by forming a vapor deposition film of a metal thin film layer on one surface of a substrate using a sputtering CVD apparatus. Therefore, a substrate having high rigidity such as a polyester film with a thickness of 188 μm needs to be used, and it cannot be applied to the case where a vapor deposition film is laminated on an adhesive layer having moderate flexibility to make it have gas barrier properties. In addition, in the adhesive composition of the invention described in Patent Document 2, since it contains a polybutene resin as an olefin resin, even if yellowing caused by deterioration due to ultraviolet rays is prevented by an antioxidant, there will still be inevitable discoloration due to potential changes over time. Therefore, there is a need for an adhesive composition that does not change color due to ultraviolet rays. In addition, in the adhesive sheet using the adhesive composition of the invention described in Patent Document 3, the water vapor transmission rate of the adhesive sheets of Examples 1 to 6 having an adhesive layer with a thickness of 100 μm is 70 to 110 g / (m 2 ‧day). However, since the adhesive layer with a thickness of 100 μm is a thick film, its scope of application is limited. Therefore, there is a need for an adhesive layer that has excellent water vapor barrier properties even if the adhesive layer is a thin film. And, as an optical adhesive film for various displays, high transparency is required to improve visibility. In view of the above problems, the present invention provides an adhesive composition and an adhesive film using the adhesive composition. Although the adhesive composition is an adhesive composition containing only acrylic monomers having a general structure, an adhesive layer with a low water vapor transmission rate and excellent water vapor barrier properties can be obtained. [Technical Means for Solving the Technical Problem] Regarding an adhesive composition with low moisture permeability, generally, the water vapor transmission rate measured for an adhesive layer with a thickness of 100 μm obtained from an acrylic polymer shows a high value of 300 g / (m 2 ‧day) or more. In addition, since the thinner the thickness of the adhesive layer, the lower the water vapor barrier property, if the adhesive layer is made into a thin film, the value of the water vapor transmission rate will show a higher value. The adhesive composition of the present invention that solves the above technical problems is characterized in that the water vapor transmission rate when the thickness of the adhesive layer is 25 μm is 100 g / (m 2 ‧day) or less, and an adhesive layer with excellent water vapor barrier property can be obtained. The inventive concept of the present invention is to use an adhesive composition containing at least the following components and crosslink the adhesive composition to form an adhesive layer: in the case of not containing nitrogen-containing vinyl monomers such as carboxyl group-containing vinyl monomers and amino group-containing vinyl monomers, an acrylic polymer copolymerized from at least one or more of (A-1) (meth)acrylic acid alkyl esters with an alkyl group having 14 or more and 20 or less carbon atoms and (B) at least one or more of (meth)acrylic acid esters containing a hydroxyl group, and a polyfunctional isocyanate compound as (C) a crosslinking agent. As a result, it was found that although it is an adhesive composition containing only acrylic monomers with a general structure, an adhesive layer with an unprecedentedly low moisture permeability can be obtained, and thus the present invention was completed. In order to solve the above technical problems, the present invention provides an adhesive composition, which is characterized in that it contains an acrylic polymer copolymerized only from (meth)acrylic acid esters as monomer components and (C) a crosslinking agent. For the water vapor transmission rate of the adhesive layer formed by crosslinking the adhesive composition with a thickness of 25 μm, when measured by the infrared detection sensor method according to JIS K7129, the water vapor transmission rate is 100 g / (m 2 ‧day) or less. Preferably, the acrylic polymer contained in the adhesive composition is an acrylic polymer having a weight average molecular weight of 50,000 to 1,500,000 obtained by copolymerizing the following components in the absence of a carboxyl group-containing vinyl monomer and a nitrogen-containing vinyl monomer: at least one of (A-1) alkyl (meth)acrylates having 14 or more and 20 or less carbon atoms in the alkyl group in a total amount of 100 parts by weight, or (A-2) at least one of alkyl (meth)acrylates having 14 or more and 20 or less carbon atoms in the alkyl group in a total amount of 85 to 100 parts by weight and at least one of compounds selected from the group consisting of alkyl (meth)acrylates having 1 or more and 13 or less carbon atoms in the alkyl group, (meth)acrylates containing an alicyclic hydrocarbon group, and (meth)acrylates containing an aromatic ring structure in a total amount of 15 to 0.0 parts by weight, and at least one of (B) hydroxy group-containing (meth)acrylates in a total amount of 0.1 to 5.0 parts by weight; the adhesive composition contains a polyfunctional isocyanate compound having three or more functional groups as the (C) crosslinking agent in a proportion of 0.01 to 2.0 parts by weight relative to 100 parts by weight of the acrylic polymer. Preferably, the SP value of the acrylic polymer is 9.0 (cal / cm 3 ) 0.5 or less. Preferably, for an adhesive film formed by laminating an adhesive layer with a thickness of 25 μm on one surface of a polyester film substrate with a thickness of 50 μm, when the adhesive layer is crosslinked by the adhesive composition and the adhesive force of the adhesive layer is measured according to JIS Z0237, the adhesive force of the adhesive layer to a high-density polyethylene resin is 10 N / 25 mm or more. Preferably, the acrylic polymer contains at least one of alkyl (meth)acrylates having 14 or more and 20 or less carbon atoms in the alkyl group in a proportion of 80 parts by weight or more relative to 100 parts by weight of the acrylic polymer. Preferably, the (B) hydroxy group-containing (meth)acrylate is at least one selected from the group consisting of 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate. Preferably, when the thickness of the adhesive layer crosslinked by the adhesive composition is 25 μm, the total light transmittance is 90% or more and the haze value is 1.0% or less. In addition, the present invention provides an adhesive film formed by forming an adhesive layer on at least one surface of a substrate, and the adhesive layer is crosslinked from the adhesive composition. [Effect of the Invention] Although the adhesive composition of the present invention is an adhesive composition containing only acrylic monomers having a general structure, an adhesive layer with a low water vapor transmission rate and excellent water vapor barrier properties can be obtained. Hereinafter, the present invention will be described by preferred embodiments. The adhesive composition of the present embodiment is characterized by containing an acrylic polymer obtained by copolymerizing only (meth)acrylate as a monomer component and a (C) crosslinking agent. For the water vapor transmission rate of the adhesive layer formed by crosslinking the adhesive composition when the thickness of the adhesive layer is made 25 μm, when measured by the infrared sensing method according to JIS K7129, the water vapor transmission rate is 100 g / (m 2 ‧day) or less. The acrylic polymer functions as a main component of the adhesive composition. As the monomer component constituting the acrylic polymer, (meth)acrylate is preferably used. (Meth)acrylate may be one or more of acrylate, one or more of methacrylate, or a mixture of one or more of acrylate and one or more of methacrylate. In addition, since the adhesive composition of the present invention is an adhesive composition containing only acrylic monomers having a general structure, the acrylic polymer preferably does not contain copolymerizable monomer components other than (meth)acrylate, such as amide monomers such as (meth)acrylamide, nitrile monomers such as (meth)acrylonitrile, olefin monomers such as styrene, and vinyl esters such as vinyl acetate. Further, when the adherend of the adhesive layer is a metal surface such as indium tin oxide (ITO), the acrylic polymer preferably does not contain (meth)acrylate monomers containing a carboxyl group, and compounds such as (meth)acrylic acid and (meth)acrylate that cause corrosion of the metal surface, which will be described in detail later. Examples of (meth)acrylate, which is the main component of the monomer component, include at least one of (A-1) (meth)acrylic acid alkyl esters having 14 or more and 20 or less carbon atoms in the alkyl group, or (A-2) at least one of (meth)acrylic acid alkyl esters having 14 or more and 20 or less carbon atoms in the alkyl group and at least one selected from the group consisting of (meth)acrylic acid alkyl esters having 1 or more and 13 or less carbon atoms in the alkyl group, (meth)acrylic acid esters containing an alicyclic hydrocarbon group, and (meth)acrylic acid esters containing an aromatic ring structure. As specific examples of the (meth)acrylic acid alkyl ester having 14 or more and 20 or less carbon atoms in the alkyl group common to (A-1) and (A-2), examples include those selected from: (meth)acrylic acid tetradecyl ester, isomyristyl (meth)acrylate, myristyl (meth)acrylate, isomyristyl (meth)acrylate, etc., (meth)acrylic acid alkyl esters having 14 carbon atoms in the alkyl group; (meth)acrylic acid pentadecyl ester, isopentadecyl (meth)acrylate, etc., (meth)acrylic acid alkyl esters having 15 carbon atoms in the alkyl group; (meth)acrylic acid hexadecyl ester, isohexadecyl (meth)acrylate, cetyl (meth)acrylate, isocetyl (meth)acrylate, etc., (meth)acrylic acid alkyl esters having 16 carbon atoms in the alkyl group; (meth)acrylic acid heptadecyl ester, isoheptadecyl (meth)acrylate, etc., (meth)acrylic acid alkyl esters having 17 carbon atoms in the alkyl group; (meth)acrylic acid octadecyl ester, isooctadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, etc., (meth)acrylic acid alkyl esters having 18 carbon atoms in the alkyl group; (meth)acrylic acid nonadecyl ester, isononadecyl (meth)acrylate, etc., (meth)acrylic acid alkyl esters having 19 carbon atoms in the alkyl group; (meth)acrylic acid eicosyl ester, isoeicosyl (meth)acrylate, etc., (meth)acrylic acid alkyl esters having 20 carbon atoms in the alkyl group, and at least one or more selected from the group consisting of them. As the (meth)acrylic acid alkyl ester having 1 or more and 13 or less carbon atoms in the alkyl group in (A-2), examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, secondary butyl (meth)acrylate, tertiary butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, isohexyl (meth)acrylate, heptyl (meth)acrylate, isoheptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, isoundecyl (meth)acrylate, dodecyl (meth)acrylate, isododecyl (meth)acrylate, tridecyl (meth)acrylate, isotridecyl (meth)acrylate, etc. Specific examples of the (meth)acrylate of the alicyclic hydrocarbon group in the above (A-2) include at least one selected from the group consisting of (meth)acrylates of monocyclic alicyclic hydrocarbon groups such as cyclopentyl (meth)acrylate and cyclohexyl (meth)acrylate; (meth)acrylates of polycyclic alicyclic hydrocarbon groups such as isobornyl (meth)acrylate, bicycloheptyl (meth)acrylate, dicyclooctyl (meth)acrylate, dimethylbicycloheptyl (meth)acrylate, dicyclopentyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenoxyethyl (meth)acrylate. Specific examples of the (meth)acrylate of the aromatic ring structure in the above (A-2) include at least one selected from the group consisting of benzyl (meth)acrylate, naphthyl (meth)acrylate, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxybutyl (meth)acrylate, phenoxyethoxyethyl (meth)acrylate, 2-(1-naphthyloxy)ethyl (meth)acrylate, 2-(2-naphthyloxy)ethyl (meth)acrylate, 6-(1-naphthyloxy)hexyl (meth)acrylate, 6-(2-naphthyloxy)hexyl (meth)acrylate, 8-(1-naphthyloxy)octyl (meth)acrylate, and 8-(2-naphthyloxy)octyl (meth)acrylate. The (meth)acrylate of the aromatic ring structure is preferably a (meth)acrylate that does not contain a hydroxyl group, a carboxyl group, or a nitrogen atom. For example, it includes (meth)acrylates containing an aromatic hydrocarbon group, (meth)acrylic alkyl esters containing an aromatic hydrocarbon group, and (meth)acrylic alkyl esters containing an aromatic ether group. The (A-1) may be composed of two or more of (meth)acrylic acid alkyl esters having 14 or more and 20 or less carbon atoms in the alkyl group in a total amount of 100 parts by weight. In addition, the total amount of 100 parts by weight of the (A-2) may be composed of at least one or more of (meth)acrylic acid alkyl esters having 14 or more and 20 or less carbon atoms in the alkyl group in a total amount of 85 to 100 parts by weight, and at least one or more selected from the group consisting of (meth)acrylic acid alkyl esters having 1 or more and 13 or less carbon atoms in the alkyl group, (meth)acrylic acid esters containing an alicyclic hydrocarbon group, and (meth)acrylic acid esters containing an aromatic ring structure in a total amount of 15 to 0.0 parts by weight. In addition, in order to reduce the water vapor transmission rate of the adhesive layer, in 100 parts by weight of the total amount of the (A-2), it is preferably contained in a specific proportion range: at least one or more of (meth)acrylic acid alkyl esters having 14 or more and 20 or less carbon atoms in the alkyl group in a total amount of 85 to 100 parts by weight, and at least one specific (meth)acrylic acid ester selected from the group consisting of (meth)acrylic acid alkyl esters having 1 or more and 13 or less carbon atoms in the alkyl group, (meth)acrylic acid esters containing an alicyclic hydrocarbon group, and (meth)acrylic acid esters containing an aromatic ring structure. For example, relative to 100 parts by weight of the acrylic polymer, it is preferably contained in a proportion of 80 parts by weight or more, more preferably in a proportion of 85 parts by weight or more, and particularly preferably in a proportion of 90 parts by weight or more of one or more of (meth)acrylic acid alkyl esters having 14 or more and 20 or less carbon atoms in the alkyl group. In addition, relative to 100 parts by weight of the acrylic polymer, it is preferably contained in a proportion of 20 parts by weight or less, more preferably in a proportion of 15 parts by weight or less, and particularly preferably in a proportion of 10 parts by weight or less of at least one selected from (meth)acrylic acid alkyl esters having 1 or more and 13 or less carbon atoms in the alkyl group, (meth)acrylic acid esters containing an alicyclic hydrocarbon group, or (meth)acrylic acid esters containing an aromatic ring structure. In addition, in order to suppress the influence of ultraviolet rays and the like, as the (meth)acrylic acid ester containing an alicyclic hydrocarbon group and the (meth)acrylic acid ester containing an aromatic ring structure, a compound having no olefinic double bond in the side chain portion of the acrylic polymer is preferably selected. However, the reason why the adhesive layer obtained using the adhesive composition of the present invention has excellent gas barrier properties is not yet clear, but it is speculated as follows. That is, it is speculated that by containing a (meth)acrylate having a long-chain alkyl group with 14 or more and 20 or less carbon atoms in the alkyl group in an amount of 80 parts by weight or more based on 100 parts by weight of the acrylic polymer, the hydrophilicity of the acrylic polymer is suppressed, the hydrophobicity is enhanced, the moisture invading the adhesive layer is not easily absorbed by the adhesive layer, and it is not easily permeated through the adhesive layer, and the water vapor transmission rate of the adhesive layer is reduced. Therefore, it is considered that if the number of carbon atoms of the long-chain alkyl group is further increased to more than 20 to make the molecular structure of the (meth)acrylate longer and larger, the hydrophobicity of the acrylic polymer is further enhanced. However, at this time, since the viscosity of the adhesive composition dissolving the acrylic polymer increases, there will be a problem that it is difficult to coat the substrate and stack the adhesive layer. Therefore, for the adhesive composition of the present embodiment, it is preferable to contain at least one or more of (meth)acrylic acid alkyl esters having 14 or more and 20 or less carbon atoms in the alkyl group in an amount of 80 to 100 parts by weight in total based on 100 parts by weight of the acrylic polymer, since a practical adhesive composition for solving the technical problems of the present invention can be obtained thereby. Specific examples of the (B) hydroxyl group-containing (meth)acrylate include at least one or more of 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2,3-dihydroxypropyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, and other polyalkylene glycol mono(meth)acrylates. Relative to 100 parts by weight in total of the said (A-1) or (A-2), the hydroxyl group-containing (meth)acrylate (B) is preferably contained in a proportion of 0.1 to 5.0 parts by weight, more preferably in a proportion of 0.6 to 5.0 parts by weight, and particularly preferably in a proportion of 1.2 to 5.0 parts by weight. Further, the hydroxyl group-containing (meth)acrylate (B) is preferably a hydroxyl group-substituted (meth)acrylic acid alkyl ester in which the alkyl group has 2 or more to 8 or less carbon atoms, and preferably at least one selected from the group consisting of 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate. Furthermore, the hydroxyl group-containing (meth)acrylate (B) is more preferably a hydroxyl group-substituted (meth)acrylic acid alkyl ester in which the alkyl group has 4 or more to 8 or less carbon atoms, and is particularly preferably at least one selected from the group consisting of 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, because when it is at least one selected from the group consisting of these compounds, the cohesion of the adhesive layer can be increased, and thus the adhesive force can be increased. The acrylic polymer is preferably an acrylic polymer copolymerized in the absence of a carboxyl group-containing vinyl monomer. Examples of the carboxyl group-containing vinyl monomer include carboxyl group-containing monomers without an ester group such as (meth)acrylic acid, itaconic acid, crotonic acid, maleic acid, and fumaric acid; (meth)acrylic acid carboxyethyl ester, (meth)acrylic acid carboxypentyl ester, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl maleic acid, carboxyl group-containing polycaprolactone mono(meth)acrylate, 2-(meth)acryloyloxyethyl tetrahydrophthalic acid, etc. (meth)acrylate monomers having a carboxyl group, but are not limited thereto. The acrylic polymer is preferably an acrylic polymer copolymerized in the absence of a nitrogen-containing vinyl monomer. Examples of the nitrogen-containing vinyl monomer include cyclic (meth)acrylamides such as N-(meth)acryloylmorpholine, N-(meth)acryloylpyrrolidine, and N-(meth)acryloylpiperidine; N-vinyl cyclic monomers such as N-vinylpyrrolidone; non-cyclic (meth)acrylamides such as (meth)acrylamide, N-alkyl (meth)acrylamide, and N,N-dialkyl (meth)acrylamide; (meth)acrylic acid esters containing a substituted amino group such as N,N-dialkylaminoalkyl (meth)acrylate; (meth)acrylamides containing a substituted amino group such as N,N-dialkylaminoalkyl (meth)acrylamide; nitrile group-containing vinyl monomers such as (meth)acrylonitrile; isocyanate group-containing vinyl monomers; quaternary ammonium group-containing vinyl monomers such as (meth)acryloyloxyalkyltrimethylammonium salt, etc., but are not limited thereto. In addition, the adhesive sheet of the invention described in Patent Document 3 above requires copolymerization of an amide group-containing monomer with an acrylic polymer, but the adhesive composition of the present embodiment does not require an amide group-containing monomer as an essential component. Therefore, according to the present embodiment, even an adhesive composition containing an acrylic polymer obtained by copolymerizing only (meth)acrylate as a monomer component can obtain an adhesive layer with a low water vapor transmission rate and excellent water vapor barrier properties. The polymerization method of the copolymer used as the acrylic polymer is not particularly limited, and suitable and well-known polymerization methods such as solution polymerization and emulsion polymerization can be used. The acrylic polymer is preferably an acrylic polymer having a weight average molecular weight of 50,000 to 1,500,000, more preferably an acrylic polymer having a weight average molecular weight of 150,000 to 1,500,000, and particularly preferably an acrylic polymer having a weight average molecular weight of 300,000 to 1,500,000. The acrylic polymer is preferably an acrylic polymer having an acid value of 0. The acrylic polymer is preferably an acrylic polymer copolymerized in the absence of not only carboxyl group-containing vinyl monomers but also acidic monomers such as sulfonic acid group-containing vinyl monomers and phosphonic acid group-containing vinyl monomers. Since acidic groups such as carboxyl groups have high hydrophilicity, if an acidic monomer is copolymerized with the acrylic polymer, the water vapor transmission rate may increase and the water vapor barrier property may decrease. In addition, when the adherend is a metal surface such as indium tin oxide (ITO), the adhesive layer containing an acrylic polymer copolymerized with a carboxyl group-containing vinyl monomer will corrode the metal surface, resulting in a change in the resistance value of the transparent conductive film. Therefore, the acrylic polymer is preferably an acrylic polymer copolymerized in the absence of a carboxyl group-containing vinyl monomer as a compound that causes corrosion of the metal surface. As the (C) crosslinking agent, examples thereof include diisocyanate compounds such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, and xylylene diisocyanate, or at least one or more of polyisocyanate compounds such as biuret-modified products, isocyanurate-modified products, and adducts with polyhydric alcohols having a valence of 3 or more such as trimethylolpropane or glycerol. Even in the case of an acrylic polymer copolymerized without a carboxyl group-containing vinyl monomer, the polyisocyanate compound can react with the (B) hydroxyl group-containing (meth)acrylate to crosslink the adhesive composition. The adhesive composition preferably contains a polyisocyanate compound having a functionality of 3 or more as the (C) crosslinking agent in a proportion of 0.01 to 2.0 parts by weight based on 100 parts by weight of the acrylic polymer. When the polyisocyanate compound has a functionality of 3 or more, a higher density crosslinking can be formed compared to the bifunctional case. When the amount of the (C) crosslinking agent used is excessive, gaps are generated between the polymer chains of the acrylic polymer, and there is a possibility that the water vapor transmission rate increases and the water vapor barrier property decreases. In the adhesive composition, as optional components, known additives such as silane coupling agents, antioxidants, antistatic agents, surfactants, curing accelerators, plasticizers, fillers, crosslinking catalysts, crosslinking retardants, curing retardants, processing aids, and anti-aging agents can be appropriately added. These components can be used alone or in combination of two or more. In addition, the adhesive sheet of the above Patent Document 3 contains a tackifying resin such as terpene phenol resin as an essential component, but the adhesive composition of the present embodiment does not contain a tackifying resin as an essential component. Therefore, according to the present embodiment, even if the adhesive composition contains only the acrylic polymer as a resin component and the adhesive composition contains only acrylic monomers having a general structure, an adhesive layer having a low water vapor transmission rate and excellent water vapor barrier property can be obtained. Therefore, the adhesive composition of the present embodiment can produce a high-quality adhesive layer that can be bonded to high-quality optical components. The adhesive layer of the present embodiment can be obtained by applying the adhesive composition to a substrate or a release film and then crosslinking the adhesive composition. The gel fraction of the crosslinked adhesive layer is preferably 40 to 85%, 60 to 90%, or 95 to 100% depending on the situation. In order to promote the reaction of the (C) crosslinking agent, it is preferable to store the adhesive layer under specified temperature conditions to carry out curing. The thickness of the adhesive layer can be appropriately set according to the use, etc., and examples thereof include a thickness of 1 to 50 μm and a thickness of 1 to 25 μm. Regarding the adhesive composition, when the thickness of the adhesive layer formed by crosslinking the adhesive composition is made 25 μm, the water vapor transmission rate of the adhesive layer, when measured by the infrared sensing method based on JIS K7129, is preferably 100 g / (m 2 ‧day) or less, more preferably 90 g / (m 2 ‧day) or less, in an atmosphere of 32 °C × 90% RH. Details of the method for measuring the water vapor transmission rate are described in Method B of JIS K7129 "Plastics - Films and Sheets - Calculation of Water Vapor Transmission Rate (Instrumental Measurement Method)" revised in 2008, or JIS K7129-2 "Plastics - Films and Sheets - Calculation of Water Vapor Transmission Rate - Part 2: Infrared Sensing Method" established in 2019. The SP value (solubility parameter) of the acrylic polymer is preferably 9.0 (cal / cm 3 ) 0.5 or less. In addition, the SP value of the polymer used in the adhesive composition in this embodiment is a value calculated using the Fedors formula, which is a standard for judging the compatibility of mixed polymers. According to the Fedors formula, using the cohesive energy ΔE i (cal / mol) and molar volume ΔV i (cm 3 / mol) values provided by each structural unit such as atoms, atomic groups, and functional groups of the constituent molecules, the SP value is calculated by the following formula. In addition, the 0.5 power (or 1 / 2 power) has the same meaning as the square root. SP=(ΣΔE i / ΣΔV i ) 0.5 In the Fedors formula, the subscript i represents the serial number assigned to each structural unit, and Σ represents the sum with respect to the subscript i. When there are multiple identical structural units in the molecule, the number corresponding to the subscript i is denoted as n i , and Σ(n i ×ΔE i ) can be used instead of ΣΔE i , and Σ(n i ×ΔV i ) instead of ΣΔV i When it is difficult to represent the existence ratio of each structural unit as an integer ratio, as n i , a non-integer ratio (such as a mole fraction) can be used. For the adhesive composition, in an adhesive film formed by laminating an adhesive layer with a thickness of 25 μm on one surface of a polyester film substrate with a thickness of 50 μm, and the adhesive layer is crosslinked from the adhesive composition, when measuring the adhesive force of the adhesive layer according to JIS Z0237, the adhesive force of the adhesive layer to a high-density polyethylene resin is preferably 10 N / 25 mm or more. Examples of the adherend used in the adhesive force test include polyethylene resins such as high-density polyethylene. Since the SP value of polyethylene is about 7.7 to 8.4, if the SP value of the acrylic polymer is greater than 9.0, the adhesive force to the adherend polyethylene resin will decrease. When the adhesive layer is used for bonding optical components such as optical films and optical glass, in order to reduce the reflection of light at the interface between the adhesive layer and the optical component, it is desirable that the refractive index difference is as small as possible. Therefore, the refractive index of the adhesive layer is preferably 1.47 to 1.50. The refractive index of the adhesive layer can be adjusted by the addition ratio of monomer components such as (meth)acrylate containing an aromatic ring structure. The acrylic polymer can set the refractive index of the adhesive layer to a value of 1.47 to 1.50 by containing 3 to 30 parts by weight of a (meth)acrylate monomer containing an aromatic ring structure in 100 parts by weight in total of the (A-2). When the adhesive layer is used for display devices such as organic EL displays, liquid crystal displays, and electronic papers, an adhesive layer with excellent transparency is preferred. Specifically, for the adhesive composition, the total light transmittance of the adhesive layer crosslinked from the adhesive composition, when the thickness is 25 μm, is preferably 90% or more, more preferably 92% or more, and particularly preferably 94% or more. In addition, for the adhesive composition, the haze value of the adhesive layer crosslinked from the adhesive composition, when the thickness is 25 μm, is preferably 1.0% or less, more preferably 0.8% or less, and particularly preferably 0.6% or less. According to the adhesive composition of the present embodiment, even without adding additives such as fillers, an adhesive layer with low water vapor transmission rate and excellent water vapor barrier property can be obtained. Therefore, an adhesive layer with suppressed light diffusion and the like caused by additives, high total light transmittance, low haze value, and excellent transparency can be obtained. The adhesive film of the present embodiment is formed by forming an adhesive layer on at least one surface of a substrate, and the adhesive layer is crosslinked from the adhesive composition. As the substrate film used when forming the adhesive layer, or the release film (separator film) for protecting the adhesive surface, a resin film such as a polyester film can be used. For the substrate film, on the surface of the resin film opposite to the side where the adhesive layer is formed, anti-fouling treatment based on silicone-based, fluorine-based release agents or coating agents, silica fine particles, etc., or antistatic treatment based on coating or kneading of antistatic agents, etc. can be carried out. For the release film, release treatment can be carried out on the surface on the side that is adhered to the adhesive surface of the adhesive layer using silicone-based, fluorine-based release agents, etc. By laminating the two surfaces of the adhesive layer with the surface of the release film on which the release treatment has been carried out, a structure of "release film / adhesive layer / release film" can be formed. At this time, the peeling forces required to peel the release film from the two surfaces of the adhesive layer can be the same or different from each other. By peeling off at least one release film from the adhesive film, the adhesive surface of the adhesive layer is exposed, and it can be laminated with an optical component such as an optical film. Examples of the optical film include a polarizing film, a retardation film, an antireflection film, an antiglare film, an ultraviolet absorption film, an infrared absorption film, an optical compensation film, a brightness enhancement film, and a substrate film for a light-emitting element in an organic EL display. The optical film can be various optical films for organic EL displays, various optical films for liquid crystal displays, various optical films for touch panels, and various optical films for electronic paper. The optical film laminated with the adhesive layer or the adhesive film of the present embodiment can be applied to, for example, organic EL displays, liquid crystal displays, touch panels, electronic paper, etc. Therefore, the adhesive composition of the present invention and the adhesive film using the adhesive composition have great industrial utilization value. [Examples] Hereinafter, the present invention will be specifically described by way of examples. <Preparation of Acrylic Polymer and Adhesive Composition> [Example 1] Nitrogen was introduced into a reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, and the air in the reaction apparatus was replaced with nitrogen. Then, tetradecyl methacrylate in a proportion of 95 parts by weight, benzyl acrylate in a proportion of 5 parts by weight, and 8-hydroxyoctyl acrylate in a proportion of 3.0 parts by weight were added to the reaction apparatus together with a solvent (ethyl acetate). Then, after dropping azobisisobutyronitrile as a polymerization initiator over 2 hours, the polymerization reaction was continued to obtain a solution of the acrylic polymer of Example 1. To the acrylic polymer solution of Example 1, CORONATE (registered trademark) L as a crosslinking agent was added in a proportion of 0.4 parts by weight, and stirring and mixing were carried out to obtain the adhesive composition of Example 1. [Examples 2 to 6 and Comparative Examples 1 to 7] Except for using the monomer components described in Group (A) and Group (B) of Table 1, respectively, in the same manner as the acrylic polymer solution of Example 1 above, acrylic polymer solutions of Examples 2 to 6 and Comparative Examples 1 to 7 were obtained. In addition, except for using the crosslinking agent described in Group (C) of Table 1, in the same manner as the adhesive composition of Example 1 above, adhesive compositions of Examples 2 to 6 and Comparative Examples 1 to 7 were obtained. [Table 1] In Examples 1, 3, 4, 6 and Comparative Examples 4 to 7 in Table 1, the monomer in Group (A) contains at least one or more of (meth)acrylic acid alkyl esters in which the number of carbon atoms of the alkyl group (A-2) is C14 or more and C20 or less and at least one or more of the compounds selected from the group consisting of (meth)acrylic acid alkyl esters in which the number of carbon atoms of the alkyl group is C1 or more and C13 or less, (meth)acrylic acid esters containing an alicyclic hydrocarbon group, and (meth)acrylic acid esters containing an aromatic ring structure. In addition, in Examples 2 and 5, the monomer in Group (A) is at least one or more of (meth)acrylic acid alkyl esters in which the number of carbon atoms of the alkyl group (A-1) is C14 or more and C20 or less. In addition, in Examples 1 to 7 and Comparative Examples 4 to 7, relative to 100 parts by weight of the acrylic polymer, the total amount of at least one or more of (meth)acrylic acid alkyl esters in which the number of carbon atoms of the alkyl group is C14 or more and C20 or less is 80 parts by weight or more. In addition, in Comparative Examples 1 to 3, relative to 100 parts by weight of the acrylic polymer, the total amount of at least one or more of (meth)acrylic acid alkyl esters in which the number of carbon atoms of the alkyl group is C14 or more and C20 or less is less than 80 parts by weight. In Table 1, the numerical value of the parts by weight obtained when the total amount of the monomers in Group (A) is set to 100 parts by weight is shown after the abbreviated symbol corresponding to the compound name. And in Group (B) and Group (C), the numerical value of the parts by weight obtained when the acrylic polymer is set to 100 parts by weight is shown in parentheses (). In addition, the abbreviated symbols corresponding to the compound names used in Table 1 are as follows. In addition, in Table 1, in Group (A), regarding the (meth)acrylic acid alkyl esters with the number of carbon atoms of the alkyl group being C14 or more and C20 or less, tetradecyl methacrylate is represented as "TDMA", tetradecyl acrylate is represented as "TDA", pentadecyl acrylate is represented as "PDA", hexadecyl methacrylate is represented as "HDMA", and isostearyl acrylate is represented as "ISTA". In addition, in Group (A), regarding the (meth)acrylic acid esters containing an alicyclic hydrocarbon group and the (meth)acrylic acid esters containing an aromatic ring structure, benzyl acrylate is represented as "BZA", and isobornyl acrylate is represented as "IBOA". In addition, in Group (A), regarding the (meth)acrylic acid alkyl esters with the number of carbon atoms of the alkyl group being C1 or more and C13 or less and the nitrogen-containing vinyl monomers, 2-ethylhexyl acrylate is represented as "2EHA", n-butyl acrylate is represented as "BA", methyl acrylate is represented as "MA", and N,N-dimethylacrylamide is represented as "DMAA". In addition, in Table 1, regarding Group (B), 8-hydroxyoctyl acrylate is represented as "8HOA", 6-hydroxyhexyl acrylate is represented as "6HHA", 4-hydroxybutyl acrylate is represented as "4HBA", 2-hydroxyethyl acrylate is represented as "HEA", and acrylic acid is represented as "AAc". In addition, in Table 1, regarding Group (C), CORONATE (registered trademark) L (trade name of TOSOH CORPORATION: TMP adduct of TDI) is represented as "L", CORONATE (registered trademark) HX (trade name of TOSOH CORPORATION: isocyanurate of HDI) is represented as "HX", CORONATE (registered trademark) HL (trade name of TOSOH CORPORATION: HDI adduct) is represented as "HL", and TAKENATE (registered trademark) D-110N (trade name of Mitsui Chemicals, Inc.: XDI adduct) is represented as "D-110N". Here, "TDI" refers to toluene diisocyanate, "TMP" refers to trimethylolpropane, "HDI" refers to hexamethylene diisocyanate, and "XDI" refers to xylylene diisocyanate. <Manufacture of Adhesive Layer and Adhesive Film> The adhesive compositions of Examples 1 to 6 and Comparative Examples 1 to 7 were respectively coated on the surface of a release film (a polyethylene terephthalate (PET) film coated with a silicone resin). After coating, drying was carried out at 90°C to remove the solvent, and then curing was carried out for 7 days in an atmosphere of 23°C and 50% RH. Thus, the adhesive films of Examples 1 to 6 and Comparative Examples 1 to 7 were obtained, and these adhesive films had an adhesive layer with a thickness of 25 μm crosslinked from the adhesive composition on one surface of the release film. <Test Methods and Evaluation> The release film (PET film coated with silicone resin) was peeled off from the adhesive films of Examples 1 to 6 and Comparative Examples 1 to 7, thereby exposing the adhesive layer. <Method for Measuring Water Vapor Transmission Rate> Regarding the water vapor transmission rate of the adhesive layer with a thickness of 25 μm, g / (m 2 ‧day), using the MOCON (registered trademark) water vapor transmission rate tester PERMATRAN-W (registered trademark) 3 / 34G of Hitachi High-Tech Science Corporation., by the infrared sensing method according to Method B of JIS K7129, based on the amount of water vapor (g) transmitted within 24 hours in an atmosphere of 32 °C × 90% RH, the value per 1 m 2 area was calculated and measured. When the measured value was 900 g / (m 2 ‧day) or more, since it reached the measurement upper limit value of the tester, the measured value was not specified and was expressed as "900 g / (m 2 ‧day) or more". <Method for Measuring Adhesion> On one surface of a polyester film substrate with a thickness of 50 μm, an adhesive layer with a thickness of 25 μm was transferred to obtain an adhesive film (optical film with an adhesive layer) as a specimen. The obtained adhesive film was adhered to the surface of a high-density polyethylene resin with a thickness of 2 mm by a pressure roller, and after heat pressing treatment under the conditions of 50 °C, 0.5 MPa × 20 minutes, it was returned to an atmosphere of 23 °C × 50% RH and left for 1 hour. As a method for measuring the adhesion when peeling the adhesive film from the surface of the high-density polyethylene resin, according to JIS Z0237 (Adhesive Tape - Test Methods for Adhesive Sheets), using a tensile testing machine, the peel strength of the adhesive film was measured, and the peel strength when peeling at a speed of 300 mm / min in the 180° direction was taken as the adhesion (N / 25 mm) of the adhesive layer of the adhesive film. <Method for Measuring Total Light Transmittance> For the adhesive layer with a thickness of 25 μm, according to JIS K7361-1 (Plastics - Test Methods for Total Light Transmittance of Transparent Materials - Part 1: Single Beam Method), using a HAZE METER (product name: NDH4000) manufactured by NIPPON DENSHOKU INDUSTRIES Co., LTD, the total light transmittance (%) of the adhesive layer was measured. <Measurement of haze value>Regarding the adhesive layer with a thickness of 25 μm, in accordance with JIS K7136 (Method for calculating haze of plastic - transparent materials), using a HAZE METER (product name: NDH4000) manufactured by NIPPON DENSHOKU INDUSTRIES Co., LTD, the haze value (%) of the adhesive layer was measured. The measurement results for the evaluation of the adhesive layer are shown in Table 2. And in Table 2, the weight - average molecular weight and SP value of the acrylic polymer are shown in the columns of "polymer molecular weight" and "polymer SP value", respectively. [Table 2] According to the test results in Table 2, for the adhesive films of Examples 1 - 6 of the present invention, when measuring the water vapor transmission rate of the adhesive layer with a thickness of 25 μm using the infrared sensing method in accordance with JIS K7129, the water vapor transmission rate is 100 g / (m 2 ‧day) or less in an atmosphere of 32 °C × 90% RH, and the water vapor barrier property of the adhesive layer is excellent. In addition, for the adhesive films of Examples 1 - 6 of the present invention, an adhesive film was prepared by laminating an adhesive layer with a thickness of 25 μm on one surface of a polyester film substrate with a thickness of 50 μm, and when measuring the adhesive force of the adhesive layer in accordance with JIS Z0237, the adhesive force of the adhesive layer to the high - density polyethylene resin is 10 N / 25 mm or more, and the adhesive force of the adhesive layer is excellent. In addition, for the adhesive films of Examples 1 - 6 of the present invention, the total light transmittance of the adhesive layer with a thickness of 25 μm is 90% or more, and the haze value is 1.0% or less, and the transparency of the adhesive layer is excellent. That is, the adhesive films according to Examples 1 - 6 of the present invention can solve the technical problems of the present invention. In addition, for the adhesive films of Comparative Examples 1 - 3 of the present invention, since the acrylic polymer has (meth)acrylic acid alkyl esters with 8 or 4 carbon atoms in the alkyl group as the main component, the water vapor transmission rate is high and the water vapor barrier property is poor. In addition, the adhesive force of the adhesive films of Comparative Examples 1 - 3 of the present invention to the high - density polyethylene resin is low. In addition, for the adhesive films of Comparative Examples 4 and 6 of the present invention, since the acrylic polymer does not contain a hydroxyl - containing (meth)acrylate but contains a carboxyl - containing vinyl monomer, the water vapor transmission rate is high and the water vapor barrier property is poor. In addition, the adhesive force of the adhesive films of Comparative Examples 4 and 6 of the present invention to the high - density polyethylene resin is low. In addition, for the adhesive films of Comparative Examples 5 and 7 of the present invention, it is considered that due to the excessive content of the cross-linking agent for cross-linking the acrylic polymer, the distribution of the cross-linking points of the acrylic polymer is uneven, and there are较多 gaps in the network structure of the acrylic polymer, resulting in a high water vapor transmission rate and poor water vapor barrier property of the adhesive layer. Moreover, the adhesion to the high-density polyethylene resin is low. In addition, for the adhesive films of Comparative Examples 5 and 7 of the present invention, it is considered that due to the uneven distribution of the cross-linking points of the acrylic polymer, the haze value of the adhesive layer is high and the total light transmittance is low. Additionally, for the adhesive film of Comparative Example 5 of the present invention, although the acrylic polymer of Comparative Example 5 of the present invention is the same as the acrylic polymer of Example 1 of the present invention in terms of monomer composition, weight average molecular weight, and SP value, and is also a polymer cross-linked using an isocyanate compound having a trifunctional or higher functionality as a cross-linking agent, for the adhesive films of Example 1 and Comparative Example 5, only the content of the cross-linking agent is different, and thus there are significant differences in the measurement results of the two. None None None.
Claims
1. An adhesive composition comprising an acrylic polymer and a (C) crosslinking agent, said acrylic polymer being copolymerized from (meth)acrylate as a monomer component only, said acrylic polymer being an acrylic polymer with a weight average molecular weight of 50,000 to 1,500,000 copolymerized from the following components: The total amount is 100 parts by weight of at least two of the following (A-1) alkyl esters with a carbon number of C14 to C20, or at least one of the following (A-2) alkyl esters with a carbon number of C14 to C20, comprising at least 85 parts by weight and less than 100 parts by weight, and at least one of the following compounds selected from the group consisting of alkyl esters with a carbon number of C1 to C13, alkyl esters containing alicyclic hydrocarbon groups, and alkyl esters containing aromatic rings, comprising more than 0 parts by weight and less than 15 parts by weight, and at least one of the following (B) hydroxyl-containing alkyl esters; the solubility parameter of the acrylic polymer is 9.0 (cal / cm3) to 0.5 or less, wherein, When the thickness of the adhesive layer formed by crosslinking the adhesive composition is 25 μm, the water vapor transmission rate of the adhesive layer is measured using infrared sensing according to JIS K7129, and the water vapor transmission rate is less than 100 g / (m2‧day) in an atmosphere of 32°C × 90%RH. In this case, an adhesive layer with a thickness of 25 μm is laminated on one side of a polyester film substrate with a thickness of 50 μm, the adhesive layer is formed by crosslinking the adhesive composition, and the adhesion of the adhesive layer to high-density polyethylene resin is measured according to JIS Z0237, and the adhesion of the adhesive layer to high-density polyethylene resin is 10 N / 25 mm or more.
2. The adhesive composition as claimed in claim 1, wherein, The adhesive composition contains, at a ratio of 0.01 to 2.0 parts by weight of an isocyanate compound with a higher degree of trifunctionality as the crosslinking agent (C), relative to 100 parts by weight of the acrylic polymer.
3. The adhesive composition as claimed in claim 1 or 2, wherein, Relative to 100 parts by weight of the acrylic polymer, the acrylic polymer contains at least one of (meth)acrylate alkyl esters with a carbon number of C14 to C20 or more in a total proportion of 80 parts by weight or more.
4. The adhesive composition as claimed in claim 1 or 2, wherein, The (B) hydroxyl-containing (meth)acrylate is at least one selected from the group consisting of 8-hydroxyoctyl methacrylate, 6-hydroxyhexyl methacrylate, 4-hydroxybutyl methacrylate, 2-hydroxypropyl methacrylate, and 2-hydroxyethyl methacrylate.
5. An adhesive film formed by forming an adhesive layer on at least one surface of a substrate, said adhesive layer being crosslinked from an adhesive composition as described in any one of claims 1 to 4.