Adhesive film and surface protection film

Abstract

To provide an adhesive composition capable of aiming to combine excellent adhesive performance, anti-static performance, and anti-fouling performance, an adhesive film using the same, a surface protective film, and an optical film with an adhesive layer.SOLUTION: An adhesive composition containing an acrylic polymer, an antistatic agent, a crosslinking agent, and a polyether-modified siloxane compound, the acrylic polymer is an acrylic polymer of a copolymer obtained by co-polymerizing at least one of (meth)acrylic acid alkyl ester monomers and at least one of polyalkylene glycol mono (meth)acrylic acid ester monomers (D), and a polyether-modified siloxane compound purified to be odorless is a polyether-modified siloxane compound having an HLB value of 4 to 15 and a weight average molecular weight of 10,000 or less, from which propenyl etherified polyoxyalkylene as a byproduct and / or aldehyde condensate have been removed.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an adhesive composition containing an acrylic polymer and an antistatic agent, and to an adhesive film and a surface protective film using the same. More specifically, the present invention relates to an adhesive composition capable of achieving excellent adhesive performance, as well as antistatic and stain-resistant properties, and to providing an adhesive film and a surface protective film using the same. [Background technology]

[0002] Conventionally, in adhesive layers formed using adhesive compositions with antistatic properties, and in surface protective films using the same, there has been a trade-off between antistatic performance and stain resistance to the adherend, making it difficult to improve stain resistance while maintaining antistatic performance. Furthermore, in recent years, the variety of materials used for substrates to which surface protective films are laminated has increased. Additionally, the surface properties of these substrates vary widely due to various surface treatments applied to them. Therefore, it is becoming increasingly difficult to simultaneously satisfy both antistatic and stain-resistant properties for all substrates.

[0003] To solve these problems, for example, a surface protective film has been proposed that uses an adhesive composition for forming the adhesive layer of a surface protective film, which contains an acrylic copolymer obtained by copolymerizing specific monomers in a specific ratio, an antistatic agent, and a compound containing fluorine or silicon in its structure (Patent Document 1). Furthermore, it is stated that the compound containing fluorine or silicon in its structure is selected from among a polyether-modified polyorganosiloxane, a fluorine-containing alkyl group-containing fluorine-based surfactant, and an acrylic polymer containing fluorine or silicon in its structure. In addition, even when the substrate to which the surface protective film according to the invention described in Patent Document 1 is laminated is a functional layer formed by hard coating treatment using a fluorine-containing compound or a silicon-containing compound, or by low-reflection treatment or anti-fouling treatment using these compounds, the generation of static electricity itself when peeling the surface protective film from the substrate is suppressed, and the occurrence of contamination of the substrate due to peeling charge and damage to electronic circuits due to sparks caused by peeling charge can be suppressed.

[0004] Furthermore, it has been proposed to form the adhesive layer of the surface protective film using an adhesive composition containing a first (meth)acrylic copolymer containing a first structural unit having a specific structure having a carboxyl group and a second structural unit derived from a monomer having a hydroxyl group, a polyether-modified silicone having a hydroxyl group at the polyether end, and an alkali metal salt (Patent Document 2). The surface protective film according to the invention described in Patent Document 2 is said to be able to achieve a high level of both antistatic performance and low contamination of the adherend. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 5544800 [Patent Document 2] Patent No. 6058390 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, the surface protection film relating to the invention described in Patent Document 1 is used as a test method for contamination of the adherend, in which, "each of the previously obtained surface protection films was pressed and attached to the functional layer side surface of the above-mentioned AG polarizing plate and HC polarizing plate by pressing a 2kgf roller back and forth once. These samples were then left in an environment of 70°C for 3 days. After that, the samples were removed and left in 23°C and 50%RH for 24 hours, then the samples were peeled off the adherend, the degree of contamination was observed visually, and evaluated according to the following criteria." (Paragraph

[0049] of Cited Document 1). However, the surface protection film described in Patent Document 1 does not disclose or disclose anything regarding its stain resistance performance when stored under more severe test conditions, such as high temperature and high humidity (for example, in an atmosphere of 60°C and 90% RH humidity). Furthermore, while Reference 1 describes polyether-modified polyorganosiloxanes, it makes no mention of impurities contained in these compounds, nor does it offer any suggestions regarding the adverse effects of these impurities on the contamination of the substrate. Furthermore, the surface protection film described in Patent Document 1 uses an acrylic copolymer of an alkylene oxide group-containing (meth)acrylic acid ester as the base polymer of the adhesive. As a result, even if the required antistatic and adhesive properties can be obtained, it is difficult to obtain a film with an excellent balance of properties, including stain resistance. Furthermore, the surface protection film according to the invention described in Patent Document 2 achieves both antistatic performance and stain resistance by using a monomer component with a specific structure, such as a first structural unit containing a carboxyl group, as the (meth)acrylic copolymer of the adhesive composition that forms the adhesive layer. However, there was a problem in obtaining an adhesive layer with a sufficient balance of properties due to the poor compatibility between the polyether-modified silicone contained in the adhesive composition and the first (meth)acrylic copolymer, as well as the adhesive performance of the first (meth)acrylic copolymer itself. Furthermore, while Reference 2 describes polyether-modified polyorganosiloxanes, it makes no mention of the impurities contained in these compounds, nor does it offer any suggestions regarding their impact on the contamination of the substrate.

[0007] This invention has been made in view of the above circumstances, and aims to provide an adhesive composition that can achieve both excellent adhesive performance, antistatic performance, and stain resistance, as well as an adhesive film and a surface protective film using the same. [Means for solving the problem]

[0008] The inventors formed an adhesive layer using an adhesive composition containing an acrylic polymer copolymerized from polyalkylene glycol mono(meth)acrylic acid monomers, an antistatic agent, and a deodorized and purified polyether-modified siloxane compound as a polyether-modified siloxane compound. They found that this adhesive layer has excellent stain resistance to prevent contamination of the adherend surface, and that the addition of the deodorized and purified polyether-modified siloxane compound results in a layer free of impurities and exhibiting stable adhesive performance. In other words, we discovered that there is a difference in the performance of the adhesive layer, specifically in terms of antistatic properties and stain resistance, between purified polyether-modified siloxane compounds that do not contain impurities and polyether-modified siloxane compounds that contain impurities, and thus completed the present invention. The present invention is based on the technical concept of an adhesive composition containing an acrylic polymer copolymerized from polyalkylene glycol mono(meth)acrylic acid ester monomers, an antistatic agent, and an odorless, purified polyether-modified siloxane compound.

[0009] The adhesive composition containing a copolymerized acrylic polymer containing a polyalkylene glycol mono(meth)acrylate monomer, an antistatic agent, and a deodorized and purified polyether-modified siloxane compound, and an adhesive film and a surface protection film using the same can achieve both antistatic performance and stain resistance performance while having excellent adhesion performance. The adhesive composition according to the present invention, and an adhesive film and a surface protection film using the same solve the problems of the prior art.

[0010] In order to solve the above problems, the present invention provides an adhesive composition containing an acrylic polymer, an antistatic agent, a crosslinking agent, and a polyether-modified siloxane compound, wherein the acrylic polymer is a copolymerized acrylic polymer obtained by copolymerizing at least one or more (meth)acrylic acid alkyl ester monomers and at least one or more (D) polyalkylene glycol mono(meth)acrylate monomers, the polyether-modified siloxane compound is a deodorized and purified polyether-modified siloxane compound, and the adhesive composition is characterized in that the deodorized and purified polyether-modified siloxane compound is contained in a proportion of 0.01 to 1.0 parts by weight based on 100 parts by weight of the acrylic polymer.

[0011] The deodorized and purified polyether-modified siloxane compound is preferably a polyether-modified siloxane compound having an HLB value of 4 to 15 and a weight average molecular weight of 10,000 or less from which by-products such as propenyl etherified polyoxyalkylene and / or aldehyde condensates have been removed.

[0012] The acrylic polymer is a copolymer obtained by copolymerizing (A) at least one (meth)acrylic acid ester monomer having an alkyl group with 1 to 18 carbon atoms in a total amount of 100 parts by weight, (B) at least one copolymerizable monomer containing a hydroxyl group in a total amount of 0.1 to 10 parts by weight, (C) at least one copolymerizable monomer containing a carboxyl group in a total amount of 0.01 to 0.5 parts by weight, and (D) at least one polyalkylene glycol mono(meth)acrylate ester monomer in a total amount of 1 to 30 parts by weight, and having an acid value of 0.1 to 1.0 and a weight average molecular weight of more than 300,000 and less than or equal to 1,000,000. Among the total 100 parts by weight of at least one (meth)acrylic acid ester monomer having an alkyl group with 1 to 18 carbon atoms in (A), it contains 2-ethylhexyl acrylate at a ratio of 60 parts by weight or more. The glass transition temperature of the acrylic polymer is 0°C or lower. The crosslinking agent is (E) a polyfunctional isocyanate compound. The antistatic agent is an ionic compound having a melting point of 25 to 50°C. It is preferable that the adhesive composition further contains (F) a crosslinking retarder and (G) a crosslinking catalyst other than a tin compound as a crosslinking catalyst.

[0013] The antistatic agent is an ionic compound, and the cation of the ionic compound is selected from the group consisting of pyridinium, imidazolium, phosphonium, sulfonium, pyrrolidinium, guanidinium, ammonium, isouronium, thiouronium, piperidinium, pyrazolium, methylium, lithium, and morpholinium. It is preferable that the ionic compound is contained as an essential component at a ratio of 0.01 to 10 parts by weight with respect to 100 parts by weight of the acrylic polymer.

[0014] The surface resistivity of the adhesive layer obtained by crosslinking the adhesive composition is 1.0×10 Preferably, the adhesive band voltage of the adhesive layer is within the range of +0.3 to -0.3 kV with respect to a low refractive index layer formed on the surface of a substrate using a composition for forming a low refractive index layer containing a fluorine compound, and the adhesive strength of the crosslinked adhesive layer with respect to a polarizing plate on which the low refractive index layer is applied is 0.04 to 0.2 N / 25 mm at a low peeling speed of 0.3 m / min, and the adhesive strength at a high peeling speed of 30 m / min is 2.0 N / 25 mm or less. Preferably, after bonding the crosslinked adhesive layer with respect to a polarizing plate on which the low refractive index layer is applied, it is left in an atmosphere of 60°C and 90% RH for 2 days, and after 1 day has elapsed since removal from the atmosphere, the adhesive layer is peeled off the polarizing plate without contamination.

[0015] The copolymerizable monomer containing a hydroxyl group (B) is at least one selected from the group of compounds consisting of 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, N-hydroxy(meth)acrylamide, N-hydroxymethyl (meth)acrylamide, and N-hydroxyethyl (meth)acrylamide, and the copolymerizable monomer containing a carboxyl group (C) is (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, and 2-(meth)acryloyloxyethyl phthalic acid. The (D) polyalkylene glycol mono(meth)acrylic acid monomer is preferably at least one selected from the group of compounds consisting of sucrose acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl maleic acid, carboxypolycaprolactone mono(meth)acrylate, and 2-(meth)acryloyloxyethyl tetrahydrophthalic acid, and the (D) polyalkylene glycol mono(meth)acrylic acid ester monomer is preferably at least one selected from polyalkylene glycol mono(meth)acrylate, methoxypolyalkylene glycol (meth)acrylate, and ethoxypolyalkylene glycol (meth)acrylate, wherein the average number of repeating alkylene oxides constituting the polyalkylene glycol chain is 3 to 14, the diester content in the monomer is 0.1% or less, and the water content is 0.1% or less.

[0016] The adhesive composition contains (F) a crosslinking retarder and (G) a crosslinking catalyst other than a tin compound, wherein the (F) crosslinking retarder is a ketoenol tautomer compound and is contained in a ratio of 0.1 to 300 parts by weight of the (F) crosslinking retarder per 100 parts by weight of the acrylic polymer, and the (G) crosslinking catalyst is at least one metal chelate compound selected from the group consisting of aluminum chelate compounds, titanium chelate compounds, and iron chelate compounds and is contained in a ratio of 0.001 to 0.5 parts by weight of the (G) crosslinking catalyst per 100 parts by weight of the acrylic polymer, and preferably the (F) / (G) weight ratio is 80 to 1000.

[0017] Furthermore, the present invention provides an adhesive film characterized in that an adhesive layer, formed by crosslinking the above-mentioned adhesive composition, is laminated on one side of a resin film.

[0018] Furthermore, the present invention provides a surface protection film using the above-described adhesive film.

[0019] Furthermore, the present invention provides a surface protective film for polarizing plates that uses the above-described adhesive film.

[0020] Furthermore, the present invention provides an optical film with an adhesive layer, wherein an adhesive layer formed by crosslinking the above-mentioned adhesive composition is laminated on at least one surface of the optical film.

[0021] Furthermore, the present invention provides an adhesive film in which one side of the resin film, the side opposite to the side on which the adhesive layer is formed, is treated with an antistatic treatment and an antifouling treatment. [Effects of the Invention]

[0022] The surface protective film of the present invention can be applied to the surface of an optical film on which the adherend is selected from the group of substrates consisting of triacetylcellulose (TAC), polyethylene terephthalate (PET), and polymethyl methacrylate (PMMA). The surface protective film of the present invention has excellent adhesive properties, stain resistance, and peel-resistant properties for these substrates. Furthermore, even when a stain-resistant layer containing a fluorine compound or a low refractive index layer is formed on the surface of the adherend, the surface protective film of the present invention has excellent adhesive performance, stain resistance, and excellent peel-resistant properties. According to the present invention, it is possible to provide an adhesive composition that achieves excellent adhesive performance, as well as antistatic and stain-resistant properties, and an adhesive film and surface protective film using the same. For this reason, the present invention has great industrial value. The reason why an adhesive layer formed using the adhesive composition of the present invention, which contains an acrylic polymer copolymerized with polyalkylene glycol mono(meth)acrylic acid ester monomers, an antistatic agent, and an odorless and purified polyether-modified siloxane compound, can achieve excellent adhesive performance, as well as simultaneous antistatic and stain-resistant properties, is not clear. Possible reasons include, for example, that the odorless and purified polyether-modified siloxane compound results in a state where the by-products contained in the polyether-modified siloxane compound are extremely low, improving compatibility with the acrylic polymer and thus improving dispersibility to prevent bleed-out of the polyether-modified siloxane compound. [Modes for carrying out the invention]

[0023] The present invention will be described below based on preferred embodiments. The adhesive composition of the present invention is an acrylic polymer mainly composed of an alkyl (meth)acrylate ester and containing at least one polyalkylene glycol mono(meth)acrylate monomer, an antistatic agent, a crosslinking agent, and a polyether-modified siloxane compound, wherein the polyether-modified siloxane compound is an odorless and purified polyether-modified siloxane compound, and is contained in a ratio of 0.01 to 1.0 parts by weight per 100 parts by weight of the acrylic polymer.

[0024] The acrylic polymer used in the adhesive composition of this embodiment is the main polymer of the adhesive composition and is an acrylic polymer with a glass transition temperature of 0°C or lower. Furthermore, among alkyl (meth)acrylate esters, copolymers mainly composed of (meth)acrylate ester monomers in which the alkyl group has C1 to C18 carbon atoms are preferred. Here, the proportion of the main component is preferably 50 parts by weight or more, more preferably 80 parts by weight or more, and particularly preferably 90 parts by weight or more, based on 100 parts by weight of the total acrylic polymer.

[0025] (A) Examples of (meth)acrylic acid ester monomers with C1 to C18 in the alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl ( Examples include meth)acrylate, isononyl(meth)acrylate, decyl(meth)acrylate, undecyl(meth)acrylate, dodecyl(meth)acrylate, tridecyl(meth)acrylate, tetradecyl(meth)acrylate, pentadecyl(meth)acrylate, hexadecyl(meth)acrylate, heptadecyl(meth)acrylate, octadecyl(meth)acrylate, cyclopentyl(meth)acrylate, and cyclohexyl(meth)acrylate. The alkyl group of the alkyl(meth)acrylate monomer may be linear, branched, or cyclic. The acrylic polymer used in the adhesive composition of this embodiment preferably contains 2-ethylhexyl acrylate in an amount of 60 parts by weight or more, more preferably 70 parts by weight or more, and particularly preferably 80 parts by weight or more, of a total of 100 parts by weight of at least one (meth)acrylic acid ester monomer having C1 to C18 C1 alkyl groups.

[0026] The acrylic polymer used in the adhesive composition of this embodiment contains at least one of (D) polyalkylene glycol mono(meth)acrylic acid monomers. (D) polyalkylene glycol mono(meth)acrylic acid monomer is a mono(meth)acrylic acid monomer having a polyalkylene glycol chain. Since the (meth)acrylic acid ester group is a polymerizable group, it can be copolymerized with the acrylic polymer. Of the multiple ends included in the polyalkylene glycol chain, the ends that do not have a (meth)acrylic acid ester group may be hydroxyl groups (-OH), or converted to alkyl ethers (-OR), etc.

[0027] The polyalkylene glycol constituting the polyalkylene glycol chain can be any glycol compound having one or more alkylene groups, such as polyethylene glycol, polypropylene glycol, polybutylene glycol, polyethylene glycol-polypropylene glycol, polyethylene glycol-polybutylene glycol, polypropylene glycol-polybutylene glycol, and polyethylene glycol-polypropylene glycol-polybutylene glycol.

[0028] (D) The polyalkylene glycol mono(meth)acrylic acid monomer preferably has an average repeating number of alkylene oxides constituting the polyalkylene glycol chain of 3 to 14. "Average repeating number of alkylene oxides" refers to the average number of repeating alkylene oxide units in the "polyalkylene glycol chain" portion included in the molecular structure of (D) polyalkylene glycol mono(meth)acrylic acid monomer. Furthermore, it is preferable that the diester content in (D) polyalkylene glycol mono(meth)acrylic acid monomer is 0.1% or less and the moisture content is 0.1% or less. "Diester content in monomer" refers to the content (weight %) of polyalkylene glycol di(meth)acrylic acid ester contained in (D) polyalkylene glycol mono(meth)acrylic acid monomer.

[0029] (D) The polyalkylene glycol mono(meth)acrylic acid ester monomer can be at least one selected from polyalkylene glycol mono(meth)acrylate, methoxypolyalkylene glycol (meth)acrylate, and ethoxypolyalkylene glycol (meth)acrylate. Here, polyalkylene glycol mono(meth)acrylate is a compound having a hydroxyl group at the other end as described above. Methoxypolyalkylene glycol (meth)acrylate and ethoxypolyalkylene glycol (meth)acrylate are compounds in which the other ends as described above have been converted to methyl ether and ethyl ether, respectively. The acrylic polymer used in the adhesive composition of this embodiment preferably contains (A) at least one (meth)acrylic acid ester monomer having C1 to C18 alkyl groups in a total of 100 parts by weight, and (D) at least one polyalkylene glycol mono(meth)acrylic acid ester monomer in a total of 1 to 30 parts by weight.

[0030] In the acrylic polymer used in the adhesive composition of this embodiment, monomers copolymerized with (A) (meth)acrylic acid ester monomers having C1 to C18 C1 alkyl groups and (D) polyalkylene glycol mono(meth)acrylic acid ester monomers include (B) copolymerizable monomers containing hydroxyl groups and (C) copolymerizable monomers containing carboxyl groups.

[0031] (B) Examples of copolymerizable monomers containing a hydroxyl group include at least one selected from the group of compounds consisting of 8-hydroxyoctyl(meth)acrylate, 6-hydroxyhexyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate, N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, and N-hydroxyethyl(meth)acrylamide. The acrylic polymer used in the adhesive composition of this embodiment preferably contains (A) at least one (meth)acrylic acid ester monomer having C1 to C18 alkyl groups in a total of 100 parts by weight, and (B) at least one copolymerizable monomer containing a hydroxyl group in a total of 0.1 to 10 parts by weight, more preferably 1.0 to 6.0 parts by weight, even more preferably 2.0 to 5.0 parts by weight, and particularly preferably 2.5 to 4.5 parts by weight.

[0032] (C) Examples of copolymerizable monomers containing a carboxyl group include at least one selected from the group of compounds consisting of (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl maleic acid, carboxypolycaprolactone mono(meth)acrylate, and 2-(meth)acryloyloxyethyl tetrahydrophthalic acid. The acrylic polymer used in the adhesive composition of this embodiment preferably contains (A) at least one (meth)acrylic acid ester monomer having C1 to C18 alkyl groups in a total of 100 parts by weight, and (C) at least one copolymerizable monomer containing a carboxyl group in a total of 0.01 to 0.5 parts by weight, more preferably 0.01 to 0.4 parts by weight, and particularly preferably 0.01 to 0.3 parts by weight.

[0033] The acrylic polymer used in the adhesive composition of this embodiment is preferably a copolymer having an acid value of 0.1 to 1.0 and a weight average molecular weight of more than 300,000 and not more than 1,000,000. More preferably, Mw is not more than 850,000, and even more preferably not more than 700,000. This can contribute to improving the stain resistance performance. Here, the "acid value" is one of the indexes representing the acid content, and is represented by the number of mg of potassium hydroxide required to neutralize 1 g of the polymer containing a carboxyl group.

[0034] The production method of the acrylic polymer used in the adhesive composition of this embodiment is not particularly limited, and known polymerization methods such as solution polymerization method and emulsion polymerization method can be appropriately used. The monomers used in the production of the acrylic polymer preferably contain at least one or more of the above (A) to (D). Within the range that does not impair the effects of the present invention, it is possible to copolymerize other monomers.

[0035] The adhesive composition according to this embodiment contains an antistatic agent. The antistatic agent of this embodiment is preferably an ionic compound, and particularly preferably an ionic compound that is solid at a temperature of 25 ° C and has a melting point of 25 to 50 ° C. Such an ionic compound has a low melting point and a long-chain alkyl group, so it is presumed to have a high affinity with the acrylic polymer. It is preferable that at least one or more of the ionic compounds are contained as essential components in a proportion of 0.01 to 10 parts by weight based on 100 parts by weight of the acrylic polymer.

[0036] As the anion of the ionic compound, phosphate hexafluoride (PF6 - ), thiocyanate (SCN - ), perchlorate (ClO4 - ), inorganic anions such as tetrafluoroborate (BF4 - ), carboxylate (RCOO - ), sulfonate (RSO3 - ), alkoxide or phenoxide salt (RO - ), organic imide salt (R2N - ), methide salt (R3C- ), organic borate salt (R4B - Examples include organic anions such as ). The R in each general formula of an organic anion is an organic group which may have fluorine substitution. Examples of organic groups include at least one of alkyl groups, alkoxy groups, aromatic groups (aryl groups, aralkyl groups, etc.), aliphatic or aromatic carbonyl groups, aliphatic or aromatic sulfonyl groups, etc. Some or all of the hydrogen atoms in these organic groups may be substituted with fluorine atoms.

[0037] The cation of the aforementioned ionic compound may be one selected from the group consisting of pyridinium, imidazolium, phosphonium, sulfonium, pyrrolidinium, guanidinium, ammonium, isouronium, thiouronium, piperidinium, pyrazolium, methylium, lithium, and morpholinium. When the anion and / or cation of an ionic compound contains organic groups such as alkyl groups, a compound with a melting point of 25 to 50°C can be obtained by selecting the chain length of the alkyl group, the position and number of substituents, etc.

[0038] The adhesive composition according to this embodiment further contains a crosslinking agent. The crosslinking agent is preferably an isocyanate compound with three or more (E) functions. Examples of such isocyanate compounds include biuret-modified and isocyanurate-modified diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate, as well as adducts with trivalent or higher polyols such as trimethylolpropane and glycerin. The composition preferably contains at least one isocyanate compound with three or more (E) functions in a total of 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, and particularly preferably 1 to 3 parts by weight, per 100 parts by weight of the acrylic polymer.

[0039] The adhesive composition according to this embodiment may contain (F) a crosslinking retarder. The (F) crosslinking retarder is preferably a ketoenol tautomer compound, and specific examples include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate, and β-diketones such as acetylacetone, 2,4-hexanedione, and benzoylacetone. In adhesive compositions using a polyisocyanate compound as a crosslinking agent, these can block the isocyanate group of the crosslinking agent, thereby suppressing excessive viscosity increase and gelation of the adhesive composition after the addition of the crosslinking agent, and extending the pot life of the adhesive composition. It is preferable that the (F) crosslinking retarder is contained in a ratio of 0.1 to 300 parts by weight per 100 parts by weight of the acrylic polymer.

[0040] The adhesive composition according to this embodiment may contain a crosslinking catalyst other than a tin compound as (G) the crosslinking catalyst. Examples of crosslinking catalysts other than tin compounds include amine compounds such as tertiary amines and metal chelate compounds other than tin chelates. Examples of tertiary amines include trialkylamines, N,N,N',N'-tetraalkyldiamines, N,N-dialkylamino alcohols, triethylenediamines, morpholine derivatives, and piperazine derivatives. (G) Preferably, the crosslinking catalyst is at least one metal chelate compound selected from the group consisting of aluminum chelate compounds, titanium chelate compounds, and iron chelate compounds. Specific examples of metal chelate compounds include tris(2,4-pentanedionato)iron(III), iron trisacetylacetonate, titanium trisacetylacetonate, aluminum trisacetylacetonate, tris(2,4-hexanedionato)iron(III), tris(2,4-hexanedionato)titanium, tris(2,4-hexanedionato)aluminum, etc. It is preferable that the acrylic polymer contains (G) a crosslinking catalyst in an amount of 0.001 to 0.5 parts by weight per 100 parts by weight.

[0041] (F) The crosslinking retarder has the opposite effect of (G) the crosslinking catalyst in that it has the effect of suppressing crosslinking. Therefore, it is preferable to set the ratio of (F) the crosslinking retarder to (G) the crosslinking catalyst appropriately. In order to extend the pot life of the adhesive composition and improve storage stability, the weight ratio of (F) / (G) is preferably 80 to 1000, more preferably 80 to 700, and particularly preferably 80 to 300. Here, the weight ratio of (F) / (G) is the quotient obtained by dividing the weight of (F) by the weight of (G).

[0042] The adhesive composition according to this embodiment contains a deodorized and purified polyether-modified siloxane compound as the polyether-modified siloxane compound. Preferably, the deodorized and purified polyether-modified siloxane compound is contained in a ratio of 0.01 to 1.0 parts by weight, and more preferably in a ratio of 0.01 to 0.8 parts by weight, per 100 parts by weight of the acrylic polymer. By incorporating a deodorized and purified polyether-modified siloxane compound into the adhesive composition, the tackiness and stain resistance of the adhesive layer can be improved. Furthermore, the adhesive layer formed using the adhesive composition containing the odorless and purified polyether-modified siloxane compound according to this embodiment has excellent stain resistance that prevents contamination of the adherend surface.

[0043] Polyether-modified siloxane compounds are siloxane compounds having a polyether group, and have the usual siloxane unit [-SiR 1 In addition to 2-O-, there are siloxane units having a polyether group [-SiR 1 (R 2 O(R 3 O) n R 4 It has )-O-]. Here, R 1 R is one or more alkyl or aryl groups, 2 and R 3 R is one or more alkylene groups, 4This represents one or more alkyl groups or acyl groups (terminal groups). Examples of polyether groups include polyoxyethylene groups [(C2H4O)] n ] and polyoxypropylene group [(C3H6O) n Examples of polyoxyalkylene groups include ]. In a siloxane unit having a polyether group, the terminal end of the polyether group is an OH group (R in the above general formula). 4 =H) is acceptable.

[0044] Polyether-modified siloxane compounds can be obtained, for example, by grafting an organic compound having unsaturated bonds and polyoxyalkylene groups onto a polyorganosiloxane main chain having silicon hydride groups via a hydrosilylation reaction. Specifically, examples include dimethylsiloxane-methyl(polyoxyethylene)siloxane copolymers, dimethylsiloxane-methyl(polyoxyethylene)siloxane-methyl(polyoxypropylene)siloxane copolymers, and dimethylsiloxane-methyl(polyoxypropylene)siloxane polymers.

[0045] This invention is characterized by the use of an odorless, purified polyether-modified siloxane compound from which by-products have been removed. This by-product may, for example, be generated when an allyl ether-modified polyoxyalkylene is used as an organic compound having an unsaturated bond and a polyoxyalkylene group in a hydrosilylation reaction, due to isomerization of the allyl group, resulting in the formation of propenyl ether-modified polyoxyalkylene. Furthermore, hydrolysis of the propenyl ether group may produce propionaldehyde or its condensates (such as acetals). Therefore, it is preferable that the odorless and purified polyether-modified siloxane compound is a polyether-modified siloxane compound from which the by-products propenyl ether-modified polyoxyalkylene and / or aldehyde condensates have been removed. These by-products can be removed by acid decomposition, hydrogenation, etc. By using an odorless and purified polyether-modified siloxane compound from which the above by-products have been removed, the stain resistance can be improved. The adhesive composition according to this embodiment does not contain an odorless and purified polyether-modified siloxane compound, and thus can be an adhesive composition that does not contain the above by-products.

[0046] The HLB value of the polyether-modified siloxane compound is preferably in the range of 4 to 15. The HLB value is the hydrophilic-lipophilic balance (hydrophilic-lipophilic ratio) as defined in, for example, JIS K3211 (Surfactant Terminology). Furthermore, the molecular weight of the polyether-modified siloxane compound is preferably 10,000 or less, for example, as the weight-average molecular weight (Mw). From the viewpoint of compatibility with acrylic polymers, a lower HLB value and lower molecular weight result in better compatibility. However, if the polyether-modified siloxane compound has a low molecular weight, excellent antistatic performance can be obtained even if the HLB value is relatively high and the compatibility with the polymer is somewhat low.

[0047] The adhesive composition of this embodiment is not limited to the additives described above, but may also contain known additives such as surfactants, curing accelerators, plasticizers, fillers, curing retarders, processing aids, anti-aging agents, and antioxidants as appropriate. These can be used individually or in combination of two or more.

[0048] The adhesive composition of this embodiment is suitable as an adhesive composition for a surface protective film to be bonded to a surface substrate (for example, a protective layer for the polarizer) of a polarizing plate. Here, the protective layer for the polarizer of the polarizing plate can be selected from the group consisting of TAC-based film, PMMA-based film, and PET-based film. Here, TAC is an abbreviation for triacetylcellulose, PMMA is an abbreviation for polymethyl methacrylate, and PET is an abbreviation for polyethylene terephthalate. Furthermore, the surface treatment applied to the protective layer of the polarizer of the polarizing plate may be one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment. Here, AG stands for Anti-Glare, LR stands for Low Reflection, and AR stands for Anti-Reflection.

[0049] The adhesive composition of this embodiment has a surface resistivity of 1.0 × 10⁻⁶ of the adhesive layer formed by crosslinking it. +12 It is preferable that the value is Ω / □ or less, and 5.0 × 10 +11 It is more preferable that the ratio is less than or equal to Ω / □, and 1.0 × 10 +11 It is particularly preferable that the surface resistivity is Ω / □ or less. If the surface resistivity is high, the adhesive layer will not be able to dissipate the static electricity generated when peeling it from the adherend. Therefore, by making the surface resistivity sufficiently low, the peel voltage generated by the static electricity generated when peeling the adhesive layer from the adherend can be reduced, and the impact on the adherend can be suppressed.

[0050] In this embodiment, the adhesive composition is crosslinked to form an adhesive layer, and it is preferable that the peel band voltage of the adhesive layer relative to a low refractive index layer formed using a composition for forming a low refractive index layer containing a fluorine compound is in the range of +0.3 to -0.3 kV. Examples of fluorine compounds used in the composition for forming a low refractive index layer include fluorine-containing copolymers which are polymers of one or more polymers of fluorinated olefins, fluorinated vinyl ethers, fluorinated alkyl (meth)acrylates, etc., and condensates such as fluorinated alkyl group-containing silane compounds. In addition to fluorinated monomers, the fluorine-containing copolymer may also contain copolymers of unfluorinated monomers such as olefins, vinyl ethers, and (meth)acrylates. The low refractive index layer may be combined with a high refractive index layer to form an anti-reflective layer. Examples of substrates on which the low refractive index layer is formed include at least one selected from triacetylcellulose (TAC), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), etc. It is preferable that the peel band voltage of the adhesive layer relative to a low refractive index layer using PMMA as the substrate is in the range of +0.3 to -0.3 kV.

[0051] In this embodiment, it is preferable that the adhesive composition, when crosslinked to form an adhesive layer, is attached to an adherend, left in an atmosphere of 60°C and 90% RH for 2 days (48 hours), and then peeled off the adherend after 1 day has elapsed since removal from the atmosphere, does not cause contamination. Examples of adherends include surface substrates such as PMMA substrates and TAC substrates, or a low refractive index layer formed on the surface thereof using a composition for forming a low refractive index layer containing a fluorine compound, or a polarizing plate having such a surface substrate or low refractive index layer.

[0052] The adhesive composition of this embodiment preferably has an adhesive strength of 0.04 to 0.2 N / 25 mm at a low peeling speed of 0.3 m / min and an adhesive strength of 2.0 N / 25 mm or less at a high peeling speed of 30 m / min, and more preferably 0.2 to 1.6 N / 25 mm at the latter. This provides performance in which the adhesive strength does not change much with the peeling speed, and enables rapid peeling even at high peeling speeds. Furthermore, when peeling the surface protective film from the adherend for reapplication, it does not require excessive force and is easy to peel off from the adherend. Examples of adherends include surface substrates such as PMMA substrates and TAC substrates, or low refractive index layers formed on their surfaces using a composition for forming low refractive index layers containing fluorine compounds, or polarizing plates having these surface substrates or low refractive index layers, such as polarizing plates with low reflectivity (LR) surface treatment or polarizing plates with AG-LR treatment.

[0053] The gel fraction of the adhesive layer formed by crosslinking the adhesive composition of this embodiment is preferably 95-100%, and more preferably 97-100%. This high gel fraction of the adhesive layer prevents excessive adhesion at low peeling speeds. Furthermore, the elution of unpolymerized monomers or oligomers from the copolymer contained in the adhesive composition is reduced, improving durability at high temperatures and humidity, and contributing to suppressing contamination of the adherend.

[0054] The adhesive film of this embodiment is formed by creating an adhesive layer on one or both sides of a resin film, which is formed by crosslinking the adhesive composition of this embodiment. The surface protection film of this embodiment is a surface protection film in which the adhesive layer is formed on one side of a resin film. The adhesive composition of this embodiment has excellent antistatic properties, a good balance of adhesive strength at both low and high peeling speeds, and excellent stain resistance. For these reasons, it can be suitably used as a surface protection film for polarizing plates.

[0055] For the base film of the adhesive layer and the release film (separator) that protects the adhesive surface, resin films such as polyester film can be used. One side of the resin film, opposite to the side on which the adhesive layer is formed, may be treated with an antistatic and antifouling treatment. Examples of antistatic treatment include applying or kneading an antistatic agent. Examples of antifouling treatment include treatment with silicone-based or fluorine-based release agents or coatings, or silica fine particles. The release film may be treated with a release agent on the side that comes into contact with the adhesive surface of the adhesive layer, such as a silicone-based, fluorine-based, or long-chain alkyl-based release agent.

[0056] Furthermore, an optical film with an adhesive layer can be obtained by laminating an adhesive layer, in which the adhesive composition of this embodiment is crosslinked, onto at least one surface of an optical film. Examples of optical films include polarizing films, phase difference films, anti-reflective films, anti-glare films, ultraviolet absorbing films, infrared absorbing films, optical compensation films, and brightness-enhancing films. Examples of devices to which optical components are applied include liquid crystal panels, organic EL panels, and touch panels. In the case of optical surface protection films and adhesive films, such as surface protection films for polarizing plates, it is preferable that the base film and adhesive layer have sufficient transparency. [Examples]

[0057] The present invention will be specifically described below with reference to examples.

[0058] <Manufacturing of acrylic polymers> [Example 1] Nitrogen gas was introduced into a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube to replace the air in the reactor with nitrogen gas. Then, 100 parts by weight of 2-ethylhexyl acrylate, 4.0 parts by weight of 8-hydroxyoctyl acrylate, 0.1 parts by weight of acrylic acid, and 10 parts by weight of polypropylene glycol monoacrylate (average repeat number of alkylene oxides n=12) were added to the reactor along with a solvent (ethyl acetate). Subsequently, 0.1 parts by weight of azobisisobutyronitrile was added dropwise over 2 hours as a polymerization initiator, and the reaction was carried out at 65°C for 6 hours to obtain the acrylic polymer used in Example 1. [Examples 2-6 and Comparative Examples 1-3] Except for using monomer compositions as shown in (A) to (D) of Table 1, the acrylic polymer solutions used in Examples 2 to 6 and Comparative Examples 1 to 3 were obtained in the same manner as the acrylic polymer solution used in Example 1 above. The weight-average molecular weight (Mw) of the acrylic polymers in Examples 1-6 and Comparative Examples 1-3 is shown in Table 2.

[0059] <Manufacturing of adhesive compositions and surface protective films> [Example 1] To the acrylic polymer solution of Example 1 prepared as described above, 2.0 parts by weight of a crosslinking agent (Coronate HX), 9.0 parts by weight of a crosslinking retarder (acetylacetone), 0.1 parts by weight of a crosslinking catalyst (titanium trisacetylacetonate), 0.9 parts by weight of an antistatic agent (4-methyl-1-octylpyridinium hexafluoride phosphate), and 0.05 parts by weight of an odorless purified polyether-modified siloxane compound (KF-6017P (odorless type), HLB value = 5) were added and stirred to obtain the adhesive composition of Example 1. This adhesive composition was applied onto a release film (silicone resin-coated PET film), and the solvent was removed by drying at 90°C to obtain an adhesive layer with a thickness of 20 μm. Subsequently, an adhesive layer with a release film was transferred to the side of the base film (a PET film with antistatic and antifouling treatment on one side) opposite to the side with the antistatic and antifouling treatment, thereby obtaining the surface protection film of Example 1 having a laminated structure of "base film / adhesive layer / release film". [Examples 2-6 and Comparative Examples 1-3] Except for the additive compositions being as described in (E) to (I) of Table 1, surface protective films for Examples 2 to 6 and Comparative Examples 1 to 3 were obtained in the same manner as the surface protective film for Example 1 described above.

[0060] [Table 1]

[0061] [Table 2]

[0062] In Table 1, the parts by weight of each component was calculated assuming the sum of (A) was 100 parts by weight. In addition, in columns (E) to (I), the parts by weight of each component, calculated assuming 100 parts by weight of acrylic polymer, are shown in parentheses ( ). Table 3 shows the compound names of the abbreviated symbols used for each component in Table 1. Note that Coronate® HX, HL, and L are trade names of Tosoh Corporation, and Takenate® D-140N is a trade name of Mitsui Chemicals, Inc. In Table 3, column (D), n represents the average number of repeats of the alkylene oxide. D-1 to D-6 have a diester content of 0.1% or less and a water content of 0.1% or less in the monomer. D-7 has a diester content of 0.3% and a water content of 0.6%. Table 3 shows that H-1 to H-5 are ionic compounds (solid at room temperature) with melting points of 25 to 50°C, while H-6 is an ionic compound (solid at room temperature) with a melting point exceeding 50°C. Column (I) in Table 3 lists both the HLB value and the product name. Products I-1 and I-3 to I-6 are from Shin-Etsu Chemical Co., Ltd., and I-2 is from Toray Dow Corning Co., Ltd. The weight-average molecular weight (Mw) of I-1 to I-4 is all 10,000 or less, while the Mw of I-5 was 20,000 and the Mw of I-6 was 30,000.

[0063] [Table 3]

[0064] <Test Methods and Evaluation> The surface protective films in Examples 1-6 and Comparative Examples 1-3 were each aged for 7 days in an atmosphere of 23°C and 50% RH, and then evaluated using the following test methods.

[0065] <Method for testing adhesive strength> The surface protection film, with the release film removed to expose the adhesive layer, was bonded to the surface of a polarizing plate via the adhesive layer. After being left for one day, it was autoclaved at 50°C, 5 atmospheres for 20 minutes, and then left at room temperature for another 12 hours. This was used as the sample for measuring adhesive strength. The obtained sample was peeled off in a 180° direction using a tensile testing machine at a low speed (0.3 m / min) or high speed (30 m / min), and the peel strength was measured and defined as the adhesive strength.

[0066] <Test method for surface resistivity> After aging the surface protective film, and before laminating it to the polarizing plate, the release film was peeled off to expose the adhesive layer, and the surface resistivity of the adhesive layer was measured using a resistivity meter, Hi-Resta UP-HT450 (manufactured by Mitsubishi Chemical Analytec).

[0067] <Test method for stripping voltage> The surface protection film, with its adhesive layer exposed after peeling off the release film, was laminated to the surface of the polarizing plate. The adherend surface of the polarizing plate has a low refractive index layer formed using a composition for forming a low refractive index layer containing a fluorine compound with polymethyl methacrylate (PMMA) as the base material. Furthermore, when the surface protection film was peeled off 180° from this adherend surface at a tensile speed of 30 m / min, the voltage (band voltage) generated by the charge on the adherend was measured using high-precision electrostatic sensors SK-035 and SK-200 (manufactured by Keyence Corporation), and the maximum measured value was defined as the peel band voltage.

[0068] <Test method for stain resistance> A polarizing plate with a low-reflection (LR) surface treatment was bonded to one side of a glass plate using a laminating machine via an adhesive layer (double-sided adhesive tape). Subsequently, a surface protection film was bonded to the surface of the polarizing plate using the laminating machine. After bonding to the substrate, the substrate was left for 2 days (48 hours) in an atmosphere of 60°C and 90% RH humidity. After removing the substrate from the atmosphere, the surface protection film was peeled off, and the contamination status of the polarizing plate surface was visually observed. The criteria for judging the contamination resistance performance were as follows: "○" for no contamination on the surface of the polarizing plate, "△" for slight contamination, and "×" for contamination.

[0069] <Test method for odorlessness> In the stain resistance test, when the surface protective film was peeled off the substrate, the odor of the adhesive layer of the peeled surface protective film and the surface of the polarizing plate was smelled and the degree of odor was evaluated. When peeled off, "○" was used to indicate no particular odor, "△" to indicate a slight odor, and "×" to indicate a strong odor. Furthermore, the amount of impurities contained in the polyether-modified siloxane compound, such as the by-product propenyl etherified polyoxyalkylene and aldehyde condensates, is so extremely small that it cannot be detected by instrumental analysis. Therefore, an odorless test was adopted as a method to determine whether the polyether-modified siloxane compound was purified and deodorized.

[0070] Table 4 shows the evaluation results of various tests for the surface protection films of Examples 1-6 and Comparative Examples 1-3. "Surface resistivity" is calculated as "m × 10 +n This was expressed using the formula "mE+n" (where m is an arbitrary real number and n is a positive integer). The "Stain Resistance Performance" column shows the material (PMMA) and surface treatment (AG-LR) of the surface substrate of the polarizing plate used in the performance tests of the surface protection films in Examples 1-6 and Comparative Examples 1-3.

[0071] [Table 4]

[0072] The surface protective films in Examples 1 to 6 exhibited excellent adhesive performance, with an adhesive strength of 0.04 to 0.2 N / 25 mm at a low peeling speed of 0.3 m / min to the polarizing plate (the adherend), and an adhesive strength of 2.0 N / 25 mm or less at a high peeling speed of 30 m / min. Furthermore, the surface protective films in Examples 1 to 6 have an adhesive layer surface resistivity of 1.0 × 10⁻⁶. +12 The coefficient of friction was Ω / □ or less, and the peel voltage of the adhesive layer on the substrate of the low refractive index layer formed using a composition for forming a low refractive index layer containing a fluorine compound was within the range of +0.3 to -0.3 kV, indicating excellent antistatic performance. Furthermore, the surface protective films of Examples 1 to 6 were left in an atmosphere of 60°C and 90% RH for 2 days after being bonded to the substrate, and then peeled off the substrate 1 day after being removed from the atmosphere. The films showed no contamination and exhibited excellent stain resistance. In other words, the evaluation results shown in Table 4 demonstrate that the surface protective films of Examples 1 to 6 can solve the problems of the present invention.

[0073] In the surface protection films of Comparative Examples 1 to 3, the antistatic performance and stain resistance to the above-mentioned substrates were poor, possibly because the adhesive composition contained polyether-modified siloxane compounds that had not been deodorized or purified. In particular, although Example 1 and Comparative Example 1 had the same composition ratio of acrylic polymers, there was a difference in stain resistance between Example 1, which contained deodorized or purified polyether-modified siloxane compounds, and Comparative Example 1, which contained polyether-modified siloxane compounds that had not been deodorized or purified. Furthermore, in the surface protection film of Comparative Example 3, the adhesive strength at both the low peeling speed of 0.3 m / min and the high peeling speed of 30 m / min was too high, indicating that the adhesive performance of the adhesive layer was also poor. Thus, the surface protective films in Comparative Examples 1 to 3 failed to solve the problems of the present invention.

Claims

1. This adhesive film has an adhesive layer laminated on one side of a resin film, the adhesive layer being formed by crosslinking an adhesive composition containing an acrylic polymer, an antistatic agent, a crosslinking agent, and a polyether-modified siloxane compound. The acrylic polymer is an acrylic polymer that is a copolymer obtained by copolymerizing at least one (meth)acrylate alkyl ester monomer and at least one (D) polyalkylene glycol mono(meth)acrylate monomer. The polyether-modified siloxane compound is an odorless and purified polyether-modified siloxane compound, and the odorless and purified polyether-modified siloxane compound is a polyether-modified siloxane compound with an HLB value of 4 to 15 and a weight-average molecular weight of 10,000 or less, from which the by-product propenyl etherified polyoxyalkylene and / or aldehyde condensate has been removed. An adhesive film characterized by containing 0.01 to 0.8 parts by weight of the odorless and purified polyether-modified siloxane compound per 100 parts by weight of the acrylic polymer.

2. A surface protective film using the adhesive film described in claim 1.

3. A surface protective film for a polarizing plate, using the adhesive film described in claim 1.

4. The adhesive film according to claim 1, wherein one side of the resin film, opposite to the side on which the adhesive layer is formed, is treated with an antistatic treatment and an antifouling treatment.

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