TW202100692A - Adhesive composition for protective film of acrylic substrate and protective film of acrylic substrate - Google Patents

Abstract

An adhesive composition for a protective film of an acrylic substrate, comprising: a (meth)acrylic copolymer that contains a structural unit derived from 4-hydroxybutyl acrylate in an amount of from 0.1% by mass to 9% by mass with respect all structural units thereof and a structural unit derived from a (meth)acrylic acid alkyl ester monomer in an amount of 50% by mass or more with respect to all structural units thereof; a trifunctional or higher-functional isocyanate crosslinking agent; an organopolysiloxane that has an oxyalkylene chain; and an ionic compound, wherein a bifunctional isocyanate crosslinking agent is not contained, or a proportion of a content of a bifunctional isocyanate crosslinking agent with respect to a content of the trifunctional or higher-functional isocyanate crosslinking agent exceeds 0% by mass but is less than 1% by mass, and a protective film of an acrylic substrate, are provided.

Description

Adhesive composition for acrylic base protective film and acrylic base protective film

The present invention relates to an adhesive composition for an acrylic base protective film and an acrylic base protective film.

In order to protect the surface of various substrates, protective films with adhesive layers are widely used. In particular, among various optical components represented by polarizing plates, protective films are often used. Regarding the adhesive composition used in the protective film, for example, considering the excellent transparency, some people choose an adhesive composition containing a (meth)acrylic copolymer.

For example, Japanese Patent Laid-Open No. 2015-28134 discloses an adhesive composition for acrylic film protection, which is characterized by containing 50 to 99.9% by weight of (methyl) having an alkyl group having 1 to 14 carbon atoms A (meth)acrylic polymer, a trifunctional isocyanate crosslinking agent, a bifunctional isocyanate crosslinking agent, an organopolysiloxane having an oxyalkylene chain, and an ionic compound having an acrylic monomer as a monomer component.

[The problem to be solved by the invention]

Generally speaking, the polarizing plate has a layer for protecting the polarizer. In the past, triacetyl cellulose (TAC) substrate has been used in the layer for protecting the polarizer. In recent years, the use of acrylic substrates instead of TAC substrates has gradually increased due to the excellent moisture permeability. However, if a protective film with an adhesive layer formed of an adhesive composition containing a (meth)acrylic copolymer is attached to the surface of an acrylic substrate, the adhesive force of the adhesive layer tends to change over time. Ascend after passing.

Since the protective film will eventually peel off from the adherend, the adhesive force of the adhesive layer should not increase over time. Therefore, the adhesive composition used for the protective film used to protect the surface of the acrylic substrate is required to form an adhesive layer whose adhesive force does not easily rise over time after the protective film is attached to the acrylic substrate .

In view of the above points, the adhesive composition described in Japanese Patent Application Publication No. 2015-28134 is considered to solve the problem of the increase in the adhesive force of the adhesive layer over time, and obtain an acrylic film with excellent releasability for protection purposes. Surface protection film. However, for the adhesive layer formed of the adhesive composition described in Japanese Patent Application Laid-Open No. 2015-28134, the increase in adhesive force over time cannot be said to be sufficiently suppressed, and there is still considerable room for improvement.

In addition, in general, an adhesive layer with a protective film is required to have an excellent appearance.

The problem to be solved by the present invention is to provide an adhesive for an acrylic substrate protective film that can sufficiently suppress the increase in adhesive force caused by the passage of time when attached to an acrylic substrate and form an adhesive layer with excellent appearance Composition and acrylic base protective film. [Means to solve the problem]

The specific methods used to solve the problem include the following aspects. <1> An adhesive composition for an acrylic base material protective film, containing: 0.1% to 9% by mass relative to all structural units containing structural units derived from 4-hydroxybutyl acrylate, and relative to all structural units It is a (meth)acrylic copolymer containing more than 50% by mass of the structural unit derived from an alkyl (meth)acrylate monomer, an isocyanate crosslinking agent with more than three functions, and an organopolysiloxane having an oxyalkylene chain , And ionic compounds, and do not contain a bifunctional isocyanate-based crosslinking agent or the content of a bifunctional isocyanate-based crosslinking agent relative to the content of the aforementioned trifunctional or higher isocyanate-based crosslinking agent is more than 0% by mass and less than 1% by mass. <2> The adhesive composition for an acrylic substrate protective film as in <1>, wherein the alkyl (meth)acrylate monomer contains n-butyl acrylate. <3> The adhesive composition for acrylic base protective film as in <1> or <2>, wherein the content of the structural unit derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer is, It is 0.5 mass%-3.5 mass% with respect to all the structural units of this (meth)acrylic-type copolymer. <4> The adhesive composition for an acrylic base protective film according to any one of <1> to <3>, wherein the (meth)acrylic copolymer contains a structural unit derived from a monomer having a carboxyl group. <5> An acrylic substrate protective film, comprising a substrate, and provided on the substrate and formed of the adhesive composition for an acrylic substrate protective film as in any one of <1> to <4> Adhesive layer. <6> The acrylic substrate protective film as in <5>, wherein the moisture permeability of the adhesive layer to the acrylic substrate does not reach 4.0 cm ² /sec. [Effects of Invention]

According to the present invention, it is possible to provide an adhesive composition for an acrylic substrate protective film that can sufficiently suppress the increase in adhesive force caused by the passage of time when attached to an acrylic substrate and form an adhesive layer with excellent appearance, And acrylic base protective film.

Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments at all, and can be implemented with appropriate changes within the scope of the purpose of the present invention.

The numerical range indicated by "~" in this manual represents the range that includes the numerical values before and after "~" as the minimum and maximum values. In the numerical ranges described stepwise in this specification, the upper limit or lower limit in a certain numerical range can be replaced with the upper limit or lower limit of the numerical range described in another step. In addition, in the numerical range described in this specification, the upper limit or the lower limit described in a certain numerical range can be replaced with the values shown in the examples. In this specification, a combination of two or more ideal aspects is a more ideal aspect. In this specification, the amount of each component, when there are multiple substances corresponding to each component, unless otherwise mentioned, it represents the total amount of multiple substances.

In this specification, the "(meth)acrylic copolymer" means that the content of structural units derived from a monomer having a (meth)acrylic acid group is all structural units (that is, (meth)acrylic copolymers). It is a copolymer of more than 50% by mass of all constituent units).

In this manual, "(meth)acrylate" is a term that includes both "acrylate" and "methacrylate", and "(meth)acrylate" includes "acrylate" and "methacrylic acid". The two terms of "ester", "(meth)acryl" is a term that includes both "acryl" and "methacryl".

In this manual, "positive" means normal, "different" means iso, "secondary" means secondary, and "tertiary" means tertiary.

In this specification, "adhesive composition" refers to a liquid or pasty substance before the end of the crosslinking reaction. In this specification, the "adhesive layer" refers to a film composed of substances in the adhesive composition after the crosslinking reaction is completed.

In this specification, "adhesive" refers to the object that touches the adhesive layer on the opposite side of the base material of the protective film when the protective film is used. In this specification, it refers to the acrylic base material. In addition, even when the adherend is a laminate of films or sheets of different materials (such as resin types), as long as the protective film is used, contact the adhesive on the opposite side of the base material of the protective film The object of the layer is an acrylic substrate, so it is defined as an acrylic substrate. In this manual, when simply referring to "substrate", it refers to the substrate of the protective film, which is different from the acrylic substrate of the adherend.

In this specification, "acrylic base" refers to a base containing (meth)acrylic resin. The "(meth)acrylic resin" refers to a polymer whose content of structural units derived from a monomer having a (meth)acrylic acid group is 50% by mass or more of all structural units. In addition, the content of the (meth)acrylic resin in the acrylic substrate is preferably 90% by mass or more, more preferably 95% by mass or more, and more preferably, relative to the total mass of the resin forming the acrylic substrate More than 96% by mass.

[Adhesive composition for acrylic base protective film] The adhesive composition for an acrylic base protective film of the present invention (hereinafter also referred to as "adhesive composition") contains: 0.1% to 9% by mass of acrylic acid-derived 4-hydroxybutane relative to all structural units The structural unit of the ester and the (meth)acrylic copolymer of the structural unit derived from the alkyl (meth)acrylate monomer at 50% by mass or more relative to all the structural units [hereinafter also referred to as "specific (meth)acrylic acid" Copolymers"], isocyanate crosslinking agents with more than trifunctional, organopolysiloxanes with oxyalkylene chains, and ionic compounds, and do not contain bifunctional isocyanate crosslinking agents or bifunctional isocyanate crosslinking The ratio of the content of the agent to the content of the aforementioned trifunctional or higher isocyanate-based crosslinking agent is more than 0% by mass and less than 1% by mass. According to the adhesive composition of the present invention, it is possible to sufficiently suppress the increase in adhesive force caused by the passage of time when it is attached to an acrylic substrate, and form an adhesive layer with excellent appearance. The reason why the adhesive composition of the present invention can achieve such an effect is not clear, but the inventors of the present application speculate as follows. However, the following speculation is not a limited interpretation of the adhesive composition of the present invention, but is explained as an example.

The adhesive composition of the present invention contains: a specific (meth)acrylic copolymer containing a structural unit derived from 4-hydroxybutyl acrylate in a specific range, an isocyanate-based crosslinking agent with three or more functions, and an oxyethylene oxide Chain organopolysiloxanes and ionic compounds are believed to be substantially free of bifunctional isocyanate-based crosslinking agents. The adhesive layer formed from the adhesive composition of the present invention has an appropriate crosslinking density and exhibits Acrylic substrates tend to have a moderately low moisture permeability rate. It is speculated that the adhesive composition of the present invention can therefore exhibit a suitable adhesive force as an acrylic substrate protective film, that is, the adhesive force to the extent that it can protect the surface of the acrylic substrate, and after being attached to the acrylic substrate , To form an adhesive layer that sufficiently suppresses the increase in adhesive force caused by the passage of time.

In this regard, the adhesive composition described in Japanese Patent Application Laid-Open No. 2015-28134 uses a bifunctional isocyanate crosslinking agent and a trifunctional isocyanate crosslinking agent in combination with a (meth)acrylic polymer and a crosslinking agent. The density (the so-called crosslink density) of the crosslinked structure formed by the crosslinking reaction between the bifunctional isocyanate crosslinker and the trifunctional isocyanate crosslinker is not dense. Therefore, the adhesive layer formed of the adhesive composition described in Japanese Patent Application Laid-Open No. 2015-28134 has an excessively high moisture permeability rate for the acrylic substrate. If the moisture permeability of the adhesive layer to the acrylic substrate is too fast, it is thought that the moisture permeability and diffusion of the adhesive layer to the acrylic substrate due to the passage of time will change easily. Therefore, it can be assumed that Japanese Patent Publication 2015 The adhesive composition described in Bulletin -28134 cannot sufficiently suppress the increase in adhesive force caused by the passage of time.

In addition, it is estimated that the adhesive composition of the present invention contains the specific (meth)acrylic copolymer containing the structural unit derived from 4-hydroxybutyl acrylate in an amount in a specific range, and therefore it is not easy to apply the adhesive composition Produce coating lines and form an adhesive layer with excellent appearance.

Regarding this point, Japanese Patent Application Publication No. 2015-28134 does not mention the appearance of the adhesive layer at all.

If the moisture permeability of the adhesive layer to the acrylic base material is too fast, and the acrylic base material contains additives, the additives tend to be easily transferred to the adhesive layer. If the additives in the acrylic base material are transferred to the adhesive layer, it may sometimes cause problems such as the performance degradation of the acrylic base material and the adhesive force of the adhesive layer of the protective film. In contrast, the adhesive composition of the present invention, as described above, can form an adhesive layer with a moderately low moisture permeability rate to the acrylic substrate. For the adhesive layer with a moderately low moisture vapor transmission rate of the acrylic substrate, not only the adhesive force after being attached to the acrylic substrate is not easy to increase with time, but also the additives in the acrylic substrate are not easy to transfer. Therefore, it is inferred that the adhesive layer formed by the adhesive composition of the present invention is less likely to occur due to the transfer of the additives contained in the acrylic substrate to the adhesive layer, resulting in degradation of the performance of the acrylic substrate and the adhesive layer of the protective film. Problems such as decreased adhesion.

[Specific (meth)acrylic copolymer] The adhesive composition of the present invention contains: 0.1% to 9% by mass of structural units derived from 4-hydroxybutyl acrylate relative to all structural units, and 50% by mass or more relative to all structural units ( A (meth)acrylic copolymer [namely a specific (meth)acrylic copolymer] of the structural unit of an alkyl meth)acrylate monomer.

＜Constituted unit derived from 4-hydroxybutyl acrylate＞ The specific (meth)acrylic copolymer contains the structural unit derived from 4-hydroxybutyl acrylate at 0.1% by mass to 9% by mass with respect to all structural units. The constituent units derived from 4-hydroxybutyl acrylate contribute to the adjustment of the adhesive force and crosslinking density of the adhesive layer.

In this specification, "a structural unit derived from 4-hydroxybutyl acrylate" refers to a structural unit formed by addition polymerization of 4-hydroxybutyl acrylate.

The content rate of the structural unit derived from 4-hydroxybutyl acrylate in the specific (meth)acrylic copolymer (the so-called content ratio; the same below) is 0.1 relative to all the structural units of the specific (meth)acrylic copolymer Mass% to 9% by mass, more preferably 2% to 7% by mass, and still more preferably 2.5% to 3.5% by mass. The content rate of the structural unit derived from 4-hydroxybutyl acrylate in the specific (meth)acrylic copolymer is 0.1% by mass or more relative to the total structural unit of the specific (meth)acrylic copolymer, which means positively Contains the meaning of a structural unit derived from 4-hydroxybutyl acrylate. If the content of the structural unit derived from 4-hydroxybutyl acrylate in the specific (meth)acrylic copolymer is less than 9% by mass relative to all the structural units of the specific (meth)acrylic copolymer, there is coating The adhesive composition is not easy to produce coating lines, and it tends to form an adhesive layer with excellent appearance.

＜Constituted unit derived from alkyl (meth)acrylate monomer＞ The specific (meth)acrylic copolymer contains a structural unit derived from an alkyl (meth)acrylate monomer in an amount of 50% by mass or more with respect to all structural units. The structural unit derived from the alkyl (meth)acrylate monomer contributes to the adjustment of the adhesive force of the adhesive layer.

In this specification, "a structural unit derived from an alkyl (meth)acrylate monomer" refers to a structural unit formed by addition polymerization of an alkyl (meth)acrylate monomer.

The type of the alkyl (meth)acrylate monomer is not particularly limited. As far as the alkyl (meth)acrylate monomer is concerned, it is preferably an unsubstituted alkyl (meth)acrylate monomer. The alkyl group of the alkyl (meth)acrylate monomer may be linear, branched, or cyclic. In addition, the carbon number of the alkyl group is preferably 1-18, and more preferably 1-12, considering the adhesive force of the adhesive layer and the adhesiveness between the base material in the protective film and the adhesive layer.

As for the alkyl (meth)acrylate monomers, examples include: methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-butyl (meth)acrylate, tertiary butyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, N-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, stearyl (meth)acrylate, (meth) Lauryl acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, etc. Among them, for the alkyl (meth)acrylate monomer, for example, considering that it is easier to adjust the cohesive force and adhesion of the adhesive layer, it is preferably selected from n-butyl acrylate (n-BA) and acrylic acid 2 -At least one of the group consisting of ethylhexyl ester (2EHA). In addition, with regard to the alkyl (meth)acrylate monomer, for example, considering that the increase in the moisture transmission rate with respect to the acrylic base material can be suppressed more, it is preferable to include n-butyl acrylate (n-BA).

The specific (meth)acrylic copolymer may include only one type of structural unit derived from the alkyl (meth)acrylate monomer, or may include two or more types.

The content rate of the structural unit derived from the alkyl (meth)acrylate monomer in the specific (meth)acrylic copolymer is preferably 50% by mass or more with respect to all the structural units of the specific (meth)acrylic copolymer. It is 60% by mass or more, more preferably 70% by mass or more, and still more preferably 80% by mass or more. Here, the content rate of the structural unit derived from the alkyl (meth)acrylate monomer is 50% by mass or more with respect to all the structural units of the specific (meth)acrylic copolymer, which means that it contains alkyl (meth)acrylate The structural unit of the ester monomer is the meaning of the main component constituting the structural unit of the specific (meth)acrylic copolymer. The upper limit of the content rate of the structural unit derived from the alkyl (meth)acrylate monomer in the specific (meth)acrylic copolymer is not particularly limited, for example, relative to all the structural units of the specific (meth)acrylic copolymer It is preferably 99.9% by mass or less.

＜Constituted unit derived from monomer with hydroxyl group＞ The specific (meth)acrylic copolymer may also contain a structural unit derived from a monomer having a hydroxyl group (hereinafter also referred to as "another monomer having a hydroxyl group") other than 4-hydroxybutyl acrylate.

In this specification, "a structural unit derived from another monomer having a hydroxyl group" refers to a structural unit formed by addition polymerization of another monomer having a hydroxyl group.

The kind of other monomers having a hydroxyl group is not particularly limited. Specific examples of other monomers having a hydroxyl group include: 2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, ( 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylaurel (meth)acrylate Ester, 3-methyl-3-hydroxybutyl (meth)acrylate, 1,1-dimethyl-3-hydroxybutyl (meth)acrylate, 1,3-dimethyl-(meth)acrylate 3-hydroxybutyl ester, 2,2,4-trimethyl-3-hydroxypentyl (meth)acrylate, 2-ethyl-3-hydroxyhexyl (meth)acrylate, N-hydroxyethyl (meth) (Meth)acrylic acid hydroxyalkyl esters such as acrylamide, 1,4-cyclohexanedimethanol monoacrylate, caprolactone 2-acryloxy-ethyl ether, etc. Among them, in terms of other monomers having a hydroxyl group, for example, considering that the copolymerizability of the alkyl (meth)acrylate monomer is better, the hydroxyalkyl (meth)acrylate is preferable. For hydroxyalkyl (meth)acrylates, for example, considering that the reactivity with trifunctional or higher isocyanate crosslinking agents is better, it is preferably (methyl) having a hydroxyalkyl group with 1 to 5 carbon atoms The hydroxyalkyl acrylate is more preferably a hydroxyalkyl (meth)acrylate having a hydroxyalkyl group with a carbon number of 2 to 4, and more preferably 2-hydroxyethyl (meth)acrylate.

When it contains the structural unit derived from the other monomer which has a hydroxyl group, a specific (meth)acrylic-type copolymer may contain only 1 type of structural unit derived from the other monomer which has a hydroxyl group, and may contain 2 or more types.

In the case where the specific (meth)acrylic copolymer contains structural units derived from other monomers having hydroxyl groups, the content of structural units derived from other monomers having hydroxyl groups in the specific (meth)acrylic copolymers is not It is not particularly limited, and can be appropriately set in accordance with the content of the above-mentioned structural unit derived from 4-hydroxybutyl acrylate.

~Concentration of structural units derived from monomers with hydroxyl groups~ The content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth)acrylic copolymer is preferably 0.5% by mass to 9% by mass relative to all the structural units of the specific (meth)acrylic copolymer. It is more preferably 0.5% by mass to 7% by mass, still more preferably 0.5% by mass to 3.5% by mass, and particularly preferably 2.5% by mass to 3.5% by mass. Here, "the content rate of the structural unit derived from the monomer having a hydroxyl group in the specific (meth)acrylic copolymer", the specific (meth)acrylic copolymer contains the structural unit derived from other monomers having a hydroxyl group In the case of, it means the total content of the structural unit derived from 4-hydroxybutyl acrylate and the structural unit derived from other monomers having a hydroxyl group. The content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth)acrylic copolymer can be formed if it is 0.5% by mass or more with respect to all the structural units of the specific (meth)acrylic copolymer More fully suppress the tendency of the adhesive layer to increase the moisture permeability of the acrylic base material. The content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth)acrylic copolymer is 9% by mass or less relative to all the structural units of the specific (meth)acrylic copolymer. The tendency of the adhesive layer with better appearance.

＜Constituted unit derived from monomer having carboxyl group＞ The specific (meth)acrylic copolymer may also contain a structural unit derived from a monomer having a carboxyl group. The structural unit derived from a monomer having a carboxyl group is useful for adjusting the density of the crosslinked structure formed by the crosslinking reaction between a specific (meth)acrylic copolymer and a trifunctional or higher isocyanate crosslinking agent (the so-called crosslinking Link density) has contributed.

In this specification, "a structural unit derived from a monomer having a carboxyl group" refers to a structural unit formed by addition polymerization of a monomer having a carboxyl group.

The type of the monomer having a carboxyl group is not particularly limited. Specific examples of monomers having carboxyl groups include: acrylic acid (AA), methacrylic acid (MAA), crotonic acid, maleic anhydride, fumaric acid, itaconic acid, glutaconic acid, citraconic acid , Ω-carboxy-polycaprolactone mono(meth)acrylate (e.g. ω-carboxy-polycaprolactone (n≒2) monoacrylate), succinate (e.g. 2-propenyloxyethyl succinate) )Wait. Among these, for the monomer having a carboxyl group, for example, considering the viewpoint that the increase in the moisture permeability to the acrylic base material can be more sufficiently suppressed, acrylic acid (AA) is preferable.

When it contains the structural unit derived from the monomer which has a carboxyl group, a specific (meth)acrylic-type copolymer may contain only 1 type of structural unit derived from the monomer which has a carboxyl group, and may contain 2 or more types.

When the specific (meth)acrylic copolymer contains the structural unit derived from the monomer having a carboxyl group, the content of the structural unit derived from the monomer having the carboxyl group in the specific (meth)acrylic copolymer is relative to The total constituent units of the specific (meth)acrylic copolymer are preferably 0.1% by mass to 5.0% by mass, more preferably 0.3% by mass to 1.0% by mass. The content of the structural unit derived from the monomer having a carboxyl group in the specific (meth)acrylic copolymer is 0.1% by mass or more relative to the total structural unit of the specific (meth)acrylic copolymer. More fully suppresses the tendency of the adhesive layer to increase the moisture vapor transmission rate of the acrylic base material. The content of the structural unit derived from the monomer having a carboxyl group in the specific (meth)acrylic copolymer can be formed if it is 5.0% by mass or less with respect to all the structural units of the specific (meth)acrylic copolymer The tendency of the adhesive layer with better appearance.

＜Other components＞ Within the range where the effects of the present invention can be exerted, the specific (meth)acrylic copolymer may also contain structural units other than the above-mentioned structural units, that is, in addition to the necessary structural units that are derived from 4-hydroxybutyl acrylate Units and structural units derived from alkyl (meth)acrylate monomers, as well as arbitrary structural units, namely structural units derived from other monomers having hydroxyl groups and structural units other than structural units derived from monomers having carboxyl groups (the so-called Other building blocks).

The monomer constituting the other structural unit is not particularly limited as long as it can be copolymerized with the monomer constituting the aforementioned structural unit. As for the monomers constituting other structural units, for example, benzyl (meth)acrylate and phenoxyethyl (meth)acrylate are represented by (meth)acrylates having a cyclic group, and (Meth) methoxy ethyl acrylate, and (meth) ethoxy ethyl acrylate represented by alkoxy alkyl (meth) acrylate, styrene, α-methyl styrene, tertiary butyl Aromatic monoethylene represented by methyl styrene, p-chlorostyrene, chloromethyl styrene, and vinyl toluene, nitrile ethylene represented by acrylonitrile and methacrylonitrile, and vinyl formate and vinyl acetate Ester, vinyl propionate, and vinyl versatate are representative vinyl esters. In addition, various derivatives of these monomers can be cited.

＜＜Weight average molecular weight of specific (meth)acrylic copolymer＞＞ The weight average molecular weight (Mw) of the specific (meth)acrylic copolymer is preferably 300,000 to 1.5 million, more preferably 300,000 to 1 million, and even more preferably 350,000 to 550,000. If the weight average molecular weight (Mw) of the specific (meth)acrylic copolymer is 300,000 or more, there is a tendency that an adhesive layer can be formed that more sufficiently suppresses the increase in the moisture permeability of the acrylic substrate. If the weight average molecular weight (Mw) of the specific (meth)acrylic copolymer is 1.5 million or less, there is a tendency to form an adhesive layer with a more excellent appearance.

The weight average molecular weight (Mw) of the specific (meth)acrylic copolymer is a value measured by the following method. Specifically, the measurement is performed according to the following (1) ~ (3). (1) Apply a solution of a specific (meth)acrylic copolymer to release paper and dry at 100°C for 1 minute to obtain a film of specific (meth)acrylic copolymer. (2) Using the film-like specific (meth)acrylic copolymer obtained in (1) above and tetrahydrofuran, a sample solution having a solid content concentration of 0.2% by mass is obtained. (3) Using Gel Permeation Chromatography (GPC), under the following conditions, the weight average molecular weight (Mw) of the specific (meth)acrylic copolymer is measured using standard polystyrene conversion values.

~Conditions~ Measuring device: High-speed GPC [Model: HLC-8220　GPC, manufactured by Tosoh Corporation] Detector: Differential refractometer (RI) [embedded in HLC-8220, manufactured by Tosoh Co., Ltd.] String: Connect 4 TSK-GEL　GMHXL in series [Tosoh Corporation] Column temperature: 40℃ Eluent: Tetrahydrofuran Sample concentration: 0.2% by mass Injection volume: 100μL Flow rate: 0.6mL/min

＜＜Concentration of specific (meth)acrylic copolymer＞＞ The content of the specific (meth)acrylic copolymer in the adhesive composition of the present invention is not particularly limited. For example, the content of the specific (meth)acrylic copolymer in the adhesive composition is preferably 80% by mass to 99% by mass relative to the total solid content in the adhesive composition , More preferably 90% to 98% by mass, and more preferably 95% to 97% by mass. If the content of the specific (meth)acrylic copolymer in the adhesive composition of the present invention is 80% by mass or more with respect to the total solid content in the adhesive composition, it is shown that acrylic acid can be protected better It is the tendency of the degree of adhesion of the surface of the substrate. If the content of the specific (meth)acrylic copolymer in the adhesive composition of the present invention is 99% by mass or less with respect to the total solid content in the adhesive composition, the formation of the It is the tendency of the adhesive layer to increase the moisture permeability of the substrate. In this specification, "the amount of total solids in the adhesive composition" means the total mass of the adhesive composition when the adhesive composition does not contain solvents and other volatile components. In the case of other volatile components, it refers to the mass of the residue obtained by removing the solvent and other volatile components from the adhesive composition.

[Method for manufacturing specific (meth)acrylic copolymer] The production method of the specific (meth)acrylic copolymer is not particularly limited. The specific (meth)acrylic copolymer can be produced by polymerizing the above-mentioned monomer by a known polymerization method represented by, for example, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, and a bulk polymerization method.

The weight average molecular weight (Mw) of a specific (meth)acrylic copolymer can be prepared by adjusting the polymerization temperature, polymerization time, the amount of organic solvent used, the type of polymerization initiator, and the amount of polymerization initiator used. To achieve the desired value.

Regarding the polymerization method, considering that the processing steps are relatively simple and can be performed in a short time when preparing the adhesive composition of the present invention after manufacture, the solution polymerization method is preferable. In the solution polymerization method, generally speaking, a predetermined organic solvent, monomer, polymerization initiator, and chain transfer agent used as needed are added to the polymerization tank in a nitrogen stream and/or at the reflux temperature of the organic solvent , Heating and reacting for several hours while stirring. At this time, at least a part of an organic solvent, a monomer, a polymerization initiator, and/or a chain transfer agent may be gradually added.

Examples of organic solvents used in the polymerization reaction include aromatic hydrocarbon compounds, aliphatic or alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds, and alcohol compounds. As for the organic solvent used in the polymerization reaction, more specifically, it can be, for example, benzene, toluene, ethylbenzene, n-propylbenzene, tertiary butylbenzene, o-xylene, m-xylene, p-xylene, four Aromatic hydrocarbon compounds represented by hydrogenated naphthalene, decalin, and aromatic naphtha, n-hexane, n-heptane, n-octane, isooctane, n-decane, dipentene, mineral spirits (mineral spirit), solvent naphtha, and aliphatic or alicyclic hydrocarbon compounds represented by turpentine, ethyl acetate, n-butyl acetate, n-pentyl acetate, 2-hydroxyethyl acetate, acetic acid 2 -Butoxyethyl, 3-methoxybutyl acetate, and methyl benzoate as representative ester compounds, acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexane Ketones and ketone compounds represented by methylcyclohexanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, Glycol ether compounds represented by diethylene glycol monobutyl ether, and methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, secondary butanol, and tertiary butanol are Representative alcohol compounds. During the polymerization reaction, only one type of these organic solvents may be used, or two or more types may be mixed and used.

When manufacturing specific (meth)acrylic copolymers, it is advisable to use organic solvents such as aromatic hydrocarbon compounds, ester compounds, ketone compounds, and alcohol compounds that are not prone to chain transfer during polymerization reactions, especially considering specific (meth)acrylic copolymers Toluene, ethyl acetate, acetone, methyl ethyl ketone, tertiary butanol, etc. are suitable from the viewpoints of the solubility of the substance and the ease of the polymerization reaction.

As for the polymerization initiator, organic peroxides, azo compounds, etc. used in ordinary solution polymerization methods can be cited. For organic peroxides, for example: tertiary butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene peroxide, benzyl peroxide, laurel peroxide, peroxide Hexane, diisopropyl peroxydiacetate, di-2-ethylhexyl peroxydiacetate, tert-butyl peroxypivalate, 2,2-bis(4,4) -Di(tertiary butyl)cyclohexyl peroxide)propane, 2,2-bis(4,4-bis(tertiary pentyl)cyclohexyl peroxide)propane, 2,2-bis(4,4-di (Tertiary octyl) cyclohexyl peroxide) propane, 2,2-bis(4,4-diα-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-bis(tri (Tertiary butyl)peroxycyclohexyl)butane, and 2,2-bis(4,4-di(tertiary octyl)peroxycyclohexyl)butane. For azo compounds, for example, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (ABVN), 2 ,2'-Azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-Azobis(1-cyanocyclohexane)(1,1'-Azobis( cyclohexane-1-carbonitrile), and 2,2'-azobis(isobutyric acid) dimethyl ester. During the polymerization reaction, only one type of these polymerization initiators may be used, or two or more types may be mixed and used.

When manufacturing a specific (meth)acrylic copolymer, it is preferable to use a polymerization initiator that does not cause a graft reaction during the polymerization reaction, and it is particularly suitable to use an azobis-based polymerization initiator.

The amount of the polymerization initiator used is not particularly limited, and can be appropriately set according to the molecular weight of the specific (meth)acrylic copolymer for the purpose.

When manufacturing a specific (meth)acrylic copolymer, you may use a chain transfer agent as needed in the range which does not impair the objective and effect of this invention. For chain transfer agents, for example, cyanoacetic acid, cyanoacetic acid alkyl ester compounds with carbon numbers 1 to 8, bromoacetic acid, bromoacetic acid alkyl ester compounds with carbon numbers 1 to 8, and α-methylstyrene Aromatic compounds represented by anthracene, phenanthrene, quince, and 9-phenyl sulfide, p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and p-nitro Aromatic nitro compounds represented by toluene, benzoquinone derivatives represented by benzoquinone and 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives represented by tributylborane, Represented by carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and 3-chloro-1-propene Halogenated hydrocarbon compounds, aldehyde compounds represented by chloral and furfural, alkyl mercaptan compounds with carbon number 1 to 18, aromatic mercaptan compounds represented by thiophenol and toluene mercaptan, thioacetic acid, thioacetic acid Alkyl ester compounds with 1 to 10 carbons, hydroxyalkyl mercaptan compounds with 1 to 12 carbons, and terpenes represented by pinene and terpinene.

When manufacturing a specific (meth)acrylic copolymer, when a chain transfer agent is used, the amount of chain transfer agent used is not particularly limited, and can be set appropriately according to the molecular weight of the specific (meth)acrylic copolymer for the purpose .

The polymerization temperature is not particularly limited, and can be appropriately set according to the molecular weight of the specific (meth)acrylic copolymer for the purpose.

[Isocyanate crosslinking agent with more than trifunctional] The adhesive composition of the present invention contains a trifunctional or higher isocyanate crosslinking agent. In this specification, the "isocyanate-based crosslinking agent with three or more functions" refers to a compound having three or more isocyanate groups in the molecule.

There are no particular limitations on the type of isocyanate-based crosslinking agent having three or more functions. As far as the isocyanate crosslinking agent is trifunctional or higher, it can be an addition-formed trifunctional isocyanate compound or an isocyanate trimer type isocyanate compound or biuret type trifunctional isocyanate compound. The above isocyanate compound. Specific examples of isocyanate-based crosslinking agents with more than three functions include: isocyanate trimer of hexamethylene diisocyanate (HMDI), trimethylolpropane/toluene diisocyanate (TDI) 3 weight body Adduct, trimethylolpropane/hexamethylene diisocyanate (HMDI) 3-weight adduct, hexamethylene diisocyanate (HMDI) biuret modification, hexamethylene diisocyanate (HMDI) Uroformate modified body, etc.

As for the isocyanate-based crosslinking agent having a trifunctional or higher level, a commercially available product can be used. Examples of commercially available products of isocyanate-based crosslinking agents with more than three functions include: "TAKENATE (registered trademark) D-102", "TAKENATE (registered trademark) D-103", "TAKENATE (registered trademark) D-103H", "TAKENATE (registered trademark) D-103M2", "TAKENATE (registered trademark) P49-75S", "TAKENATE (registered trademark) D-110N", "TAKENATE (registered trademark) D-120N", " TAKENATE (registered trademark) D-140N", "TAKENATE (registered trademark) D-160N", "TAKENATE (registered trademark) D-127N", "TAKENATE (registered trademark) D-170N", "TAKENATE (registered trademark) D -170HN", "TAKENATE (registered trademark) D-172N", "TAKENATE (registered trademark) D-177N", "TAKENATE (registered trademark) D-165N", and "TAKENATE (registered trademark) NP1100" (above is Mitsui Chemical Corporation), "Desmodur (registered trademark) L-75", "Desmodur (registered trademark) UL57SP", "Desmodur (registered trademark) N-3600", "Desmodur (registered trademark) N-3900", " "Desmodur (registered trademark) Z4470BA", "Sumidur (registered trademark) N-3300", and "Desmodur (registered trademark) N-3200" (above manufactured by Sumika Covestro Urethane Co., Ltd.), "Coronate (registered trademark) "HL", "Coronate (registered trademark) HX", "Coronate (registered trademark) L", and "Coronate (registered trademark) HK" [the above are Tosoh (stock) system], and "Duranate (registered trademark) TPA- 100", "Duranate (registered trademark) TKA-100", "Duranate (registered trademark) TSA-100", "Duranate (registered trademark) TSS-100", "Duranate (registered trademark) TLA-100", "Duranate ( Registered trademark) TSE-100" and "Duranate (registered trademark) 24A-100" [above are manufactured by Asahi Kasei Co., Ltd.].

The adhesive composition of the present invention may contain only one type of trifunctional or more isocyanate-based crosslinking agent, or may contain two or more types.

The content of the trifunctional or higher isocyanate crosslinking agent in the adhesive composition of the present invention is not particularly limited. For example, it is preferably 1.0 to 10.0 parts by mass relative to 100 parts by mass of the specific (meth)acrylic copolymer. It is more preferably 2.0 parts by mass to 5.0 parts by mass. If the content of the trifunctional or higher isocyanate-based crosslinking agent in the adhesive composition of the present invention is 1.0 parts by mass or more relative to 100 parts by mass of the specific (meth)acrylic copolymer, the formation of The tendency of the adhesive layer to increase the moisture permeability of acrylic substrates. If the content of the trifunctional or higher isocyanate crosslinking agent in the adhesive composition of the present invention is 10.0 parts by mass or less relative to 100 parts by mass of the specific (meth)acrylic copolymer, it appears that it can be better protected The degree of adhesion tendency of the acrylic substrate surface.

[2-functional isocyanate-based crosslinking agent] The adhesive composition of the present invention does not contain a bifunctional isocyanate-based crosslinking agent or the ratio of the content of the bifunctional isocyanate-based crosslinking agent to the content of the aforementioned trifunctional or higher isocyanate-based crosslinking agent is more than 0% by mass and does not reach 1% by mass. If the adhesive composition of the present invention contains a trifunctional or more isocyanate-based crosslinking agent, and does not contain a bifunctional isocyanate-based crosslinking agent; or it contains a trifunctional or more isocyanate-based crosslinking agent and is crosslinked by a bifunctional isocyanate-based crosslinking agent The ratio of the content of the agent to the content of the aforementioned trifunctional or higher isocyanate-based crosslinking agent is more than 0% by mass and less than 1% by mass, then the specific (meth)acrylic copolymer and the isocyanate-based crosslinking agent The density of the cross-linked structure formed by the cross-linking reaction is appropriate, and the moisture permeability rate of the acrylic base material is moderately low. Therefore, it exhibits adhesion to the extent that it can protect the surface of the acrylic substrate, and after being attached to the acrylic substrate, there is a tendency to form an adhesive layer that suppresses the increase in adhesion caused by the passage of time.

In this specification, "bifunctional isocyanate-based crosslinking agent" refers to a compound having two isocyanate groups in the molecule.

The adhesive composition of the present invention uses the above-mentioned commercially available product as a trifunctional or higher isocyanate crosslinking agent, and therefore unavoidably contains a bifunctional isocyanate crosslinking agent that may be contained in a certain proportion as an impurity in the commercial product Except in the case, it is preferable not to contain a bifunctional isocyanate-based crosslinking agent. In the adhesive composition of the present invention, the ratio of the content of the bifunctional isocyanate crosslinking agent to the content of the trifunctional or higher isocyanate crosslinking agent is preferably 0.7% by mass or less, more preferably 0.5% by mass or less, and more It is preferably 0.3% by mass or less, and particularly preferably 0% by mass, that is, the adhesive composition of the present invention does not contain a bifunctional isocyanate-based crosslinking agent.

The bifunctional isocyanate-based crosslinking agent includes aliphatic polyisocyanate compounds such as trimethylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate (HMDI), and pentamethylene diisocyanate (PDI) , Isophorone diisocyanate (IPDI), hydrogenated xylylene isocyanate, hydrogenated diphenylmethane diisocyanate, 1,4-cyclohexane diisocyanate and other alicyclic polyisocyanate compounds, xylylene isocyanate (XDI ), diphenylmethane diisocyanate, triphenylmethane triisocyanate, toluene diisocyanate (TDI) and other aromatic polyisocyanate compounds.

[Organic polysiloxane with oxyalkylene chain] The adhesive composition of the present invention contains an organopolysiloxane having an oxyalkylene chain (hereinafter also referred to as "specific organopolysiloxane"). Specific organopolysiloxanes can act as additives for ionic compounds mentioned later. If a specific organopolysiloxane is used in combination with an ionic compound, the ions caused by the ionic compound will easily move, which can effectively suppress charging when the protective film is peeled from the acrylic substrate.

The specific organopolysiloxane is not particularly limited, and any known organopolysiloxane having an oxyalkylene chain can be used. Regarding the specific organopolysiloxane, for example, a siloxane-containing site (i.e., a so-called siloxane site) can be used as the main chain, and an oxygen extension chain is bonded to the end of the main chain.

As for the specific organopolysiloxane, for example, the specific organopolysiloxane represented by the following formula (1) is preferably a specific organopolysiloxane having an oxygen extension chain bonded to the end of the main chain.

[化1]

In the formula (1), R ¹ and/or R ² represent an oxyalkylene chain having 1 to 6 carbon atoms. The alkylene group in the oxyalkylene chain may be straight or branched. The terminal of the oxyalkylene chain may be an alkoxy group or a hydroxyl group. In addition, either R ¹ or R ² may be a hydroxyl group, an alkyl group, or an alkoxy group, or a functional group in which a part of the alkyl group and the alkoxy group is substituted with a heteroatom. N represents an integer from 1 to 300.

In formula (1), R ¹ and/or R ² preferably represent an oxyalkylene chain containing a hydrocarbon group with 1 to 6 carbon atoms. As for the oxyethylene chain, oxymethylene, oxyethylene, oxyethylene, oxyethylene, etc. can be mentioned. Among these, as far as the oxyethylene chain is concerned, it is preferably oxyethylene or oxyethylene. When R ¹ and R ^{2 both} represent an oxyalkylene chain, R ¹ and R ² may be the same or different.

The hydrocarbon group of the oxyalkylene chain may be straight or branched.

For the purpose of protecting the surface of the adhesive layer, when the release film is attached to the surface of the adhesive layer, if it is an organopolysiloxane with a hydroxyl group at the end of the oxyextension chain, interaction between the release films will occur. When the peeling film is peeled from the surface of the adhesive layer, the adhesive force (the so-called peel force) increases. Considering this point of view, the terminal of the oxyalkylene chain may be an alkoxy group or a hydroxyl group, but it is preferably an alkoxy group.

n represents an integer from 1 to 300, preferably an integer from 10 to 200, and more preferably an integer from 20 to 150. If n is an integer of 1 to 300, for example, the compatibility with a specific (meth)acrylic copolymer tends to become good.

The compound represented by formula (1) may further have reactive substituents such as (meth)acryloyl group, allyl group, and hydroxyl group in the molecule.

Examples of commercially available products of the compound represented by formula (1) include "X-22-4952", "X-22-4272", "X-22-6266", Shin-Etsu Chemical Co., Ltd. "KF-6004" and "KF-889", "BY16-201" and "SF8427" of Dow Corning Toray Co., Ltd., and "IM22" (above) of wacker asahikasei silicone co., Ltd. (shares) Is the product name).

The above-mentioned organopolysiloxane can suitably use a well-known organopolysiloxane having a polyoxyalkylene chain. Regarding specific organopolysiloxanes, in addition to organosiloxanes bonded with oxyalkylene chains to the main chain, they can also be used for side chains with oxyalkylene chains. Compared with the main chain, a more ideal aspect is that the side chain is bonded with an oxyalkylene chain.

Regarding the specific organopolysiloxane having an oxyalkylene chain bonded to the side chain, for example, it is preferably a specific organopolysiloxane having an oxyalkylene chain bonded to the side chain represented by the following formula (2). [化2]

In formula (2), R ³ represents a monovalent organic group, R ⁴ , R ⁵ , and R ⁶ each independently represent an alkylene group, and R ⁷ represents a hydrogen atom or a monovalent organic group. m and n each independently represent an integer from 0 to 1000. However, m and n will not be 0 at the same time. a and b each independently represent an integer of 0-100. However, a and b will not be 0 at the same time.

In formula (2), the monovalent organic group represented by R ³ includes alkyl groups such as methyl, ethyl, and propyl, aryl groups such as phenyl and tolyl, benzyl, phenethyl, etc. Aralkyl etc. These groups may have substituents such as a hydroxyl group.

In the formula (2), the alkylene group represented by R ⁴ , R ⁵ , and R ⁶ is preferably an alkylene group having 1 to 8 carbon atoms. As for the alkylene group having 1 to 8 carbon atoms, a methylene group, an ethylene group, and a propylene group can be mentioned. R ⁵ and R ^{6 are} preferably different alkylene groups. The alkylene groups represented by R ⁴ , R ⁵ , and R ⁶ may be the same or different. Either R ⁵ or R ⁶ is preferably ethylene or propylene.

Examples of the monovalent organic group represented by R ⁷ include alkyl groups such as methyl, ethyl, and propyl groups, and acyl groups such as acetyl groups and propyl groups. These groups may have substituents such as a hydroxyl group.

The compound represented by formula (2) may further have reactive substituents such as (meth)acryloyl group, allyl group, and hydroxyl group in the molecule.

Examples of commercially available products of the compound represented by formula (2) include: "KF-351A", "KF-352A", "KF-353", and "KF-354L" of Shin-Etsu Chemical Co., Ltd. , "KF-355A", "KF-615A", "KF-945", "KF-640", "KF-642", "KF-643", "KF-6022", "X-22-6191" , "X-22-4515", "KF-6011", "KF-6012", "KF-6015", "KF-6017", and "X-22-2516", Dow Corning Toray Co., Ltd. "SF8428", "FZ-2162", "SH3749", "FZ-77", "L-7001", "FZ-2104", "FZ-2110", "L-7002", "FZ-2122" ”, “FZ-2164”, “FZ-2203”, “FZ-7001”, “SH-3773M”, “SH8400”, “SH8700”, “SF8410”, and “SF8422”, manufactured by Momentive Performance Materials "TSF-4440", "TSF-4441", "TSF-4445", "TSF-4446", "TSF-4450", "TSF-4452", and "TSF-4460", and manufactured by BYK-Chemie Japan "BYK-307", "BYK-333", "BYK-377", "BYK-UV3500", and "BYK-UV3570" (the above are product names).

For specific organopolysiloxanes, for example, considering the contamination of the adherend, the value of Hydrophilic-Lipophilic Balance (Hydrophilic-Lipophilic Balance: also referred to as "HLB" hereinafter) should be 1-16. More preferably, it is 3~14.

The adhesive composition of the present invention may contain only one specific organopolysiloxane, or may contain two or more types.

The content of the specific organopolysiloxane in the adhesive composition of the present invention is not particularly limited. For example, considering the antistatic property, it is preferably 0.01 parts by mass relative to 100 parts by mass of the specific (meth)acrylic copolymer ~5 parts by mass, more preferably 0.03 parts by mass to 3 parts by mass, and still more preferably 0.05 parts by mass to 1 part by mass.

[Ionic compound] The adhesive composition of the present invention contains an ionic compound. Ionic compounds can function as antistatic agents.

The ionic compound is not particularly limited. Examples of ionic compounds include alkali metal salts and organic salts. Regarding ionic compounds, for example, considering the viewpoint that ion dissociation is high and exhibits excellent antistatic properties even in a small amount, it is preferably at least one selected from the group consisting of alkali metal salts and organic salts.

As far as the alkali metal salt is concerned, it only needs to be a metal salt in which alkali metal ions such as lithium ion (Li ⁺ ), sodium ion (Na ⁺ ), potassium ion (K ⁺ ), rubidium ion (Rb ⁺ ) become cations, and There is no particular limitation. For specific examples of alkali metal salts, for example, refer to the description in paragraph [0044] of JP 2015-28134 A.

Alkali metal salts such should be selected from the group consisting of by Li ^+, Na ^+, and K ⁺ in the group consisting of at least one cation selected from the group consisting of ^{Cl -, Br -, I -} , BF 4 -, PF 6 -, _{^{SCN -, ClO 4 -, CF}} 3 SO 3 -, (FSO 2) 2 N -, (CF 3 SO 2) 2 N -, (C 2 F 5 SO 2) 2 N -, and (CF ₃ SO _{2) 3} C ^- A metal salt composed of at least one anion in the group consisting of ₃ C. Among them, as for the alkali metal salt, considering the antistatic property, it is suitable for example: LiBr, LiI, LiBF ₄ , LiPF ₆ , LiSCN, LiClO ₄ , LiCF ₃ SO ₃ (the so-called LiTFS), Li(FSO ₂ ) ₂ N, Li(CF ₃ SO ₂ ) ₂ N, Li(C ₂ F ₅ SO ₂ ) ₂ N, Li(CF ₃ SO ₂ ) ₃ C and other lithium salts, more preferably selected from LiClO ₄ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, Li(C ₂ F ₅ SO ₂ ) ₂ N, and Li(CF ₃ SO ₂ ) ₃ C constitute at least one kind of lithium salt.

The organic salt contains an organic cation and its counter ion. The organic salt includes, for example, an ionic solid having a melting point of 30°C or higher and an ionic liquid having a melting point of less than 30°C. The organic salt may be any one of an ionic solid with a melting point of 30°C or higher or an ionic liquid with a melting point of less than 30°C. For example, considering that it is less likely to transfer to the adherend, the organic salt should preferably be an ionic solid with a melting point of 30°C or higher.

Organic cations include imidazole cations, pyridine cations, alkylpyridinium cations, ammonium cations with organic groups as substituents, phosphonium cations with organic groups as substituents, phosphonium cations with organic groups as substituents, etc. . Among them, in terms of organic cations, for example, considering antistatic properties, pyridine cations or imidazole cations are preferable. Moreover, regarding organic cations, for example, the cation components described in paragraphs [0047] to [0062] of JP 2015-28134 A can also be preferably used. Among them, in terms of organic cations, for example, considering antistatic properties, pyridine cations or imidazole cations are preferable.

The anion part that becomes the opposite ion of the organic cation is not particularly limited, and may be either an inorganic anion or an organic anion. An anionic portion of the cationic organic counterions, e.g. consider the viewpoint of antistatic property, the fluorine-containing anion is suitably fluoro atoms, more suitably from a hexafluorophosphate anion (PF ₆ ^-). In addition, as for the anion part that becomes the counter ion of the organic cation, for example, the anion component described in paragraphs [0063] to [0066] of JP 2015-28134 A can also be preferably used.

Examples of organic salts include pyridine salts, imidazole salts, alkyl ammonium salts, alkyl pyrrolidinium salts, and alkyl phosphonium salts. Among them, the organic salt is preferably a pyridine salt or an imidazole salt, and more preferably a salt of a pyridine cation, an imidazole cation, and a fluorine-containing anion.

The adhesive composition of the present invention may contain only one type of ionic compound, or may contain two or more types.

The content of the ionic compound in the adhesive composition of the present invention is not particularly limited. For example, relative to 100 parts by mass of the specific (meth)acrylic copolymer, it is preferably 1 part by mass or less, more preferably 0.05 parts by mass to 0.5 parts by mass. Parts by mass, more preferably 0.1 parts by mass to 0.3 parts by mass. If the content of the ionic compound in the adhesive composition of the present invention is 1 part by mass or less with respect to 100 parts by mass of the specific (meth)acrylic copolymer, the tendency to transfer to the adherend can be more suppressed.

[Organic solvents] The adhesive composition of the present invention may also contain an organic solvent. The organic solvent contributes to improving the coatability of the adhesive composition. The organic solvent may be, for example, the same as the organic solvent used in the polymerization reaction of the above-mentioned specific (meth)acrylic copolymer.

When the adhesive composition of the present invention contains an organic solvent, it may contain only one organic solvent, or two or more kinds.

When the adhesive composition of the present invention contains an organic solvent, the content of the organic solvent is not particularly limited, and can be appropriately set according to the purpose.

[Other ingredients] The adhesive composition of the present invention may contain components other than the above-mentioned components (that is, so-called other components) as needed, within a range that does not impair the effects of the present invention. As for other components, examples include polymers other than specific (meth)acrylic copolymers, crosslinking agents other than isocyanate crosslinking agents, crosslinking catalysts, tackifiers, antioxidants, colorants (such as Dyes and pigments), light stabilizers (such as ultraviolet absorbers), etc.

~Moisture permeability rate for acrylic base material~ For the adhesive layer formed by the adhesive composition of the present invention, the moisture permeability rate for the acrylic base material is preferably less than 4.0cm ² /sec, more preferably 3.0cm ² /sec or less. If the moisture permeability of the adhesive layer to the acrylic base material is too fast, the additives sometimes contained in the acrylic base material tend to be easily transferred to the adhesive layer. If the additives are transferred to the adhesive layer, problems such as degradation of the performance of the acrylic base material and reduction of the adhesive force of the adhesive layer of the protective film may sometimes occur. On the other hand, if the moisture permeability of the adhesive layer to the acrylic base material does not reach 4.0 cm ² /sec, the additives contained in the acrylic base material are not easily transferred. Therefore, it is caused by the transfer of the additives contained in the acrylic base material to the adhesive The performance of the acrylic base material is reduced due to the layer, and the adhesive force of the adhesive layer of the protective film is reduced. The adhesive layer formed from the adhesive composition of the present invention is not particularly limited to the lower limit of the moisture vapor transmission rate of the acrylic substrate, for example, it is preferably 1.0 cm ² /sec or more, more preferably 2.0 cm ² /sec or more.

[use] The adhesive composition of the present invention can be ideally used as a film for protecting the surface of an acrylic substrate (ie, an acrylic substrate protective film). The adhesive composition of the present invention can form an adhesive layer with excellent durability against acrylic substrates and excellent appearance, so it is suitable for the application of attaching a protective film to acrylic substrates.

In addition, the adhesive composition of the present invention can form an adhesive layer exhibiting a moderately low moisture permeability rate with respect to acrylic substrates, so it is particularly suitable for attaching protective films to acrylic substrates containing various additives The purpose. By using the protective film of the adhesive composition of the present invention, even if the acrylic substrate of the adherend contains additives, the additives are not easily transferred to the adhesive layer, so the adhesive force is not easily reduced and the performance of the acrylic substrate Reduce and other issues.

Examples of additives that may be contained in acrylic base materials include: ultraviolet absorbers, antioxidants, heat stabilizers, processing aids, plasticizers, impact resistance agents, phase difference reducing agents, and refractive index modifiers. , Matting agent, antibacterial agent, antifungal agent, bubble inhibitor, coloring agent, lubricant, etc.

[Acrylic base protective film] The acrylic substrate protective film of the present invention (hereinafter also referred to as "protective film") includes a substrate and an adhesive layer formed on the substrate and formed of the adhesive composition of the present invention. That is, in the protective film of the present invention, the substrate and the adhesive layer formed of the adhesive composition of the present invention are laminated. Since the protective film of the present invention has an adhesive layer formed from the adhesive composition of the present invention, after being attached to an acrylic substrate, the adhesive force of the adhesive layer is not easy to increase with time. In addition, the protective film of the present invention has an adhesive layer formed from the adhesive composition of the present invention, and has no appearance defects such as coating lines on the adhesive layer and has an excellent appearance. In addition, the adhesive layer provided in the protective film of the present invention is formed of the adhesive composition of the present invention, and has a moderately low moisture permeability rate for the acrylic substrate, so it is one of the acrylic substrates of the adherend Additives are not easily transferred to the adhesive layer. Therefore, with the protective film of the present invention, it is not easy to cause problems caused by the transfer of the additives in the acrylic base material to the adhesive layer, the adhesive force of the adhesive layer is reduced, and the performance of the acrylic base material is reduced.

The protective film of the present invention can be ideally used for various members having acrylic base materials. The various components with acrylic base material include: polarizing plates, dice sheets, lens sheets, anti-reflection films, light diffusion films, optical compensation films, near-infrared absorption films, conductive films and other optical components, various covers Covers, various terminal boards, printed wiring boards, various nameplates, etc.

The substrate in the protective film of the present invention is not particularly limited as long as the adhesive layer can be formed on the substrate. As for the substrate, for example, it contains: polyester resin, acetate resin (for example, triacetyl cellulose resin), polyether cellulose resin, polycarbonate resin, polyamide resin, poly Films of resins such as imide resins, polyolefin resins, vinyl chloride resins, ABS resins, and fluorine resins. For example, considering the viewpoint of inspection and management of optical components performed by fluoroscopy, as far as the base material is concerned, it is preferable to contain selected from: polyester resin, acetate resin, polyether turpentine resin, and polycarbonate resin , A film of at least one type of resin from the group consisting of polyamide resin, polyimide resin, and polyolefin resin. Also, for example, considering the surface protection performance, a film containing polyester resin is preferable, and a film containing polyethylene terephthalate (PET) is particularly preferable considering practicality.

Moreover, as for the substrate, as long as the performance of the protective film of the present invention can be obtained, a film containing acrylic resin can also be used. For example, surface treatment such as corona discharge treatment is applied to the surface of the acrylic substrate, and the adhesion between the acrylic substrate and the adhesive layer is improved, so that a film containing acrylic resin can be used as the substrate.

The substrate may also contain various additives such as plasticizers, colorants (such as dyes and pigments), heat stabilizers, light stabilizers, antistatic agents, and flame retardants. In addition, a pattern may be applied to a part or the whole of the base material.

The thickness of the substrate is generally 500 μm or less, preferably 300 μm or less, and more preferably 200 μm or less. The lower limit of the thickness of the substrate, for example, considering the strength of the protective film, is preferably 5 μm or more, more preferably 10 μm or more.

One or both sides of the substrate can also be provided with an antistatic layer. In addition, the surface of the substrate on the side where the adhesive layer is provided may be subjected to surface treatments such as corona discharge treatment and plasma discharge treatment from the viewpoint of improving the adhesion between the substrate and the adhesive layer.

The method of forming the adhesive layer is not particularly limited, and a commonly used method can be used. As for the method of forming the adhesive layer on the substrate, for example, the following method can be used. The adhesive composition of the present invention is coated on a substrate in its original state or in a state obtained by diluting with a solvent as needed to form a coating film on the substrate. Then, after drying the formed coating film and removing the solvent, the adhesive layer is formed on the substrate by aging. In addition, the exposed surface of the adhesive layer can also be protected by a release film. The release film is not particularly limited as long as it can be easily released from the surface of the adhesive layer. Examples include paper and resin film obtained by surface treatment with a release agent applied to one or both sides. Wait. As the resin film, for example, a polyester film represented by a polyethylene terephthalate (PET) film can be mentioned. As the release agent, fluorine-based resin, paraffin wax, silicone resin, long-chain alkyl compound, etc. can be mentioned. The peeling film protects the surface of the adhesive layer before actually using it on the protective film, and peels off during use.

As for other methods of forming the adhesive layer on the substrate, for example, the following methods can be used. The adhesive composition of the present invention, in its original state or in a state obtained by diluting with a solvent as required, is applied to a release film such as a paper or resin film obtained by applying a release agent to the surface treatment. A coating film is formed on it. Then, the formed coating film is dried and the solvent is removed. Then, the surface of the release film on which the adhesive layer is formed is brought into contact with the substrate and pressed, and the adhesive layer is transferred to the substrate to form an adhesive layer on the substrate. Then, it is matured.

The method for coating the adhesive composition on the substrate or the release film is not particularly limited, and examples include: gravure roll coater, reverse roll coater, and roll coater Known methods such as (kiss-roll coater), dipping roll coater, knife coater, spray coater, coating bar, coater, etc. The coating amount of the adhesive composition on the substrate or the release film can be appropriately set according to the thickness of the formed adhesive layer.

The thickness of the adhesive layer can be appropriately set according to the adhesive force required by the protective film, the type (such as material and shape) of the adherend, and the surface roughness of the adherend. The thickness of the adhesive layer is generally in the range of 1 μm or more and 100 μm or less, preferably in the range of 5 μm or more and 50 μm or less, and more preferably in the range of 10 μm or more and 30 μm or less.

The method of drying the coating film formed on the substrate or the release film is not particularly limited, and examples include methods such as natural drying, heat drying, hot air drying, and vacuum drying. The drying temperature and drying time of the coating film are not particularly limited, and can be appropriately set according to the thickness of the coating film, the amount of organic solvent in the coating film, and the like.

The maturation is performed for 1 to 10 days in an environment of 23° C. and 50% RH, for example. By aging, the cross-linking reaction of the adhesive composition is completed to form an adhesive layer. [Example]

Hereinafter, the present invention will be explained more specifically by using examples. The present invention is not limited by the following embodiments as long as it does not exceed the gist.

[Production of (meth)acrylic copolymer] [Manufacturing Example 1] 171.0 parts by mass of ethyl acetate and 249.0 parts by mass of tertiary butanol were put into a reaction vessel equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a reflux cooler. In addition, 577.8 parts by mass of n-butyl acrylate (n-BA; alkyl acrylate monomer), 18.0 parts by mass of 4-hydroxybutyl acrylate (4HBA), and 4.2 parts by mass of acrylic acid (AA; monomer having a carboxyl group) were placed Put it into another container, mix and make a monomer mixture. Add 20.0% by mass of the monomer mixture to the above-mentioned reaction vessel. Then, after replacing the air in the reaction vessel with nitrogen, 0.08 parts by mass of 2,2'-azobisisobutyronitrile [AIBN; polymerization initiator] was added, and the reaction vessel was stirred while stirring under a nitrogen atmosphere. The temperature of the contents was raised to 85°C, and the initial reaction started. In the reaction vessel after the initial reaction was almost completed, it took about 2 hours to gradually add the remaining 80.0% by mass of the monomer mixture, 88.0 mass parts of ethyl acetate and 0.80 mass parts of AIBN, while keeping the contents of the reaction vessel The reaction was carried out, and after the addition was completed, the reaction was continued for 2 hours to obtain the reactant (A). Thereafter, a solution prepared by dissolving 0.60 parts by mass of tert-butyl peroxypivalate (polymerization initiator) in 132.0 parts by mass of ethyl acetate was added dropwise to the reaction vessel over 1 hour In the inner reactant (A), after the dropping is finished, react for another 1.5 hours to obtain reactant (B). The reactant (B) obtained was diluted with ethyl acetate so that the solid content became 45% by mass to obtain a solution of a (meth)acrylic copolymer. In addition, the "solid content" of the solution of the (meth)acrylic copolymer refers to the remaining components obtained by removing volatile components such as solvent from the solution of the (meth)acrylic copolymer.

[Manufacturing Examples 2~7] In Production Examples 2 to 7, except that the monomer composition of the (meth)acrylic copolymer in Production Example 1 was changed to the monomer composition shown in Table 1, and the amount of organic solvent used and the polymerization initiator were adjusted Use at least one of the amounts of the (meth)acrylic copolymer to change the weight average molecular weight (Mw) of the (meth)acrylic copolymer to the weight average molecular weight (Mw) shown in Table 1, and perform the same operation as in Production Example 1 to obtain (Meth) acrylic copolymer solution.

The monomer composition (unit: mass %) and weight average molecular weight [Mw, unit: 10,000 (indicated as "×10 ⁴ ")] of the (meth)acrylic copolymer are shown in Table 1. The weight average molecular weight (Mw) of the (meth)acrylic copolymer is measured by the same method as the weight average molecular weight (Mw) of the above-mentioned specific (meth)acrylic copolymer.

Among the (meth)acrylic copolymers prepared in manufacturing examples 1 to 7, the (meth)acrylic copolymers prepared in manufacturing examples 1 to 6 correspond to the specific (meth)acrylic copolymers in the present invention Acrylic copolymer.

[Table 1] (Meth) acrylic copolymer Monomer composition (mass%) Mw [x10 ⁴ ] n-BA 2EHA 4HBA 2HEA AA Manufacturing example 1 96.3 - 3.0 - 0.7 43.5 Manufacturing example 2 96.2 - 0.1 3.0 0.7 43.0 Manufacturing example 3 90.3 - 9.0 - 0.7 51.0 Manufacturing example 4 60.0 36.3 3.0 - 0.7 45.2 Manufacturing example 5 - 96.3 3.0 - 0.7 50.0 Manufacturing example 6 97.0 - 3.0 - - 42.0 Manufacturing example 7 88.3 - 11.0 - 0.7 52.0

The details of each monomer described in Table 1 are as follows. "N-BA": n-butyl acrylate (alkyl acrylate monomer) "2EHA": 2-ethylhexyl acrylate (alkyl acrylate monomer) "4HBA": 4-hydroxybutyl acrylate "2HEA": 2-hydroxyethyl acrylate (other monomers with hydroxyl groups) "AA": acrylic acid (monomer with carboxyl group)

In Table 1, "-" means that the monomer in this column is not used. In Table 1, "weight average molecular weight (Mw)" is abbreviated as "Mw".

[Preparation of adhesive composition] [Example 1] 222.2 parts by mass of the (meth)acrylic copolymer solution prepared in Manufacturing Example 1 (100 parts by mass in solid content) was used as an ionic compound LiTFS [lithium trifluoromethanesulfonate [Li(CF ₃ SO ₃ )], manufactured by Morita Chemical Industry Co., Ltd.] 0.25 parts by mass, added to a four-necked flask equipped with a stirring blade, a thermometer, a cooler, and a dropping funnel , Keep the liquid temperature in the flask around 25°C while stirring for 4 hours. Then, add Sumidur (registered trademark) N-3300 [trade name, 4-fold dilution of isocyanate trimer (trifunctional isocyanate compound) of hexamethylene diisocyanate (HMDI), Sumika Covestro Urethane Co., Ltd.] 14.0 parts by mass (solid content 3.50 parts by mass) as a trifunctional or higher isocyanate crosslinking agent, and SH-3773M [trade name, manufactured by Dow Corning Toray Co., Ltd.] 0.30 parts by mass as a specific organic poly Silicone, fully agitated to obtain the adhesive composition.

[Examples 2 to 6 and Comparative Examples 1 to 3] In Examples 2 to 6 and Comparative Examples 1 to 3, except that the composition of the adhesive composition was changed to the composition shown in Table 1, the same operation as in Example 1 was performed to obtain an adhesive composition.

[Table 2]

In Table 2, "-" means that the ingredient is not included. The details of the bifunctional isocyanate-based crosslinking agent described in Table 2 are as follows. "TAKENATE600" [Trade name: TAKENATE (registered trademark) 600, Chemical name: 1,3-bis(isocyanatomethyl)cyclohexane, hydrogenated xylylene isocyanate, manufactured by Mitsui Chemicals Co., Ltd.] The details of the crosslinking catalyst described in Table 2 are as follows. "DOTDL": [Trade name: ADK STAB (registered trademark) OT-1, Chemical name: Dioctyltin dilaurate, manufactured by ADEKA (stock)]

[Production of protective film for evaluation] Polyethylene terephthalate (PET) film as a substrate [trade name: TEIJIN (registered trademark) Tetoron (registered trademark) film, model: G2, thickness: 38μm, TEIJIN On FILM SOLUTIONS (manufactured by stock), the adhesive composition is applied so that the coating amount after drying becomes 15 g/m ^{2 to} form a coating film. Then, the formed coating film was dried at 100°C for 60 seconds using a hot-air circulation dryer to form an adhesive film on the PET film. Then, the exposed surface of the adhesive film formed on the PET film and the release film obtained by surface treatment with a silicone resin release agent [trade name: FILMBYNA (registered trademark) 100E-0010N023, thickness: 100μm , Fujimori Kogyo Co., Ltd.] The surface treatment surface is laminated and made into a laminate. After the laminate is crimped and bonded by a pair of pressure rollers, it is aged for 7 days under an ambient temperature of 23°C and 50%RH and undergoes a crosslinking reaction to obtain a substrate/adhesive layer/release film Protective film for evaluation of laminated structure.

[Evaluation] 1. Appearance The protective film for evaluation prepared in the above was cut into a size of 25 mm×150 mm, and a protective film sheet for appearance evaluation was prepared. The protective film sheet for durability evaluation obtained from the preparation peels off the release film to expose the surface of the adhesive layer. In addition, the surface of the exposed adhesive layer was visually observed, and the appearance of the adhesive layer was evaluated according to the following evaluation criteria. The results are shown in Table 3. If the evaluation result is "A", it is judged to be an adhesive layer with excellent appearance.

-Evaluation criteria- A: No coating lines are confirmed on the surface of the adhesive layer. B: Coating lines are confirmed on the surface of the adhesive layer.

2. Adhesion The protective film for evaluation prepared above was cut into a size of 25 mm×150 mm, and two protective film sheets for adhesive force evaluation were prepared. The protective film sheet for adhesion evaluation obtained from the preparation peels off the release film, and separates the surface of the adhesive layer exposed by the peeling with another acrylic resin plate [trade name: Acrylite (registered trademark) L001, Mitsubishi Chemical (Strand) laminated surface, using a desktop laminator for crimping, to make test pieces A-1 and A-2.

(1) Initial adhesion Place the test piece A-1 in an environment with an ambient temperature of 23°C and 50%RH for 30 minutes. Regarding the test piece A-1 after being placed, the single-tube column material tester (model: STA-1225) manufactured by A&D Company, Limited was used as the measuring device, and the measurement was performed at an ambient temperature of 23°C and 50%RH. Under the condition of a peeling speed of 0.3m/min, the adhesive force when the protective film sheet (adhesive layer/substrate) for adhesion evaluation is peeled from the acrylic resin board at 180° along the long side (150mm) direction (unit: N/25mm) ). The results are shown in Table 3.

(2) Adhesion over time Carry out an accelerated test to evaluate the adhesive force over time. The test piece A-2 was placed in a dryer at 60°C for 1 week. Regarding the placed test piece A-2, after taking it out of the dryer, place it in an ambient temperature of 23℃ and 50%RH for 24 hours, and use the single-tube column material testing machine manufactured by A&D Company, Limited (model: STA -1225) As a measuring device, measure the protective film sheet (adhesive layer/base) from the acrylic resin board under the conditions of a peeling speed of 0.3m/min under an ambient temperature of 23℃ and 50%RH. (Unit: N/25mm) when peeling 180° along the long side (150mm) direction. The results are shown in Table 3.

(3) The rate of increase in adhesion over time Based on the value of the adhesive force measured in the above "(1) Initial adhesive force" and the value of the adhesive force measured in the above "(2) Adhesive force over time", calculate the time elapsed The rate of increase in adhesion. Specifically, after dividing the value of "adhesion over time" by the value of "initial adhesion", by rounding the third digit below the decimal point, the rate of increase in adhesion over time is obtained . In addition, the durability of the adhesive layer was evaluated according to the following evaluation criteria. The results are shown in Table 3. If the evaluation result is "A" or "B", it is judged that the adhesive layer has sufficiently suppressed the increase in the adhesive force with the passage of time.

-Evaluation criteria- A: The increase rate of the adhesive force over time is 1.00 or less. B: The increase rate of the adhesive force over time exceeds 1.00 and does not reach 1.40. C: The increase rate of the adhesive force over time is 1.40 or more.

3. Moisture permeability rate The evaluation test of the moisture permeability rate of the adhesive layer with respect to the acrylic base material is based on the "1st moisture permeability rate measurement" described in the paragraph [0060] of JP 2012-224805 A "Method. Specifically, follow the steps (1) to (5) below. (1) The protective film for evaluation prepared as described above was cut into a size of 25 mm×150 mm, and a protective film sheet for evaluation of moisture permeability rate was prepared. (2) In an environment with an ambient temperature of 23°C and 50%RH, peel off the protective film sheet for evaluating the moisture vapor transmission rate obtained from the release film so that the short side ends of the adhesive layer surface exposed by the peeling When the part is in contact with the acrylic resin plate [trade name: Acrylite (registered trademark) L001, manufactured by Mitsubishi Chemical Co., Ltd.], the inclination angle of the protective film sheet (adhesive layer/substrate) for evaluating the moisture permeability rate is The range of 20°~30°. (3) Release the protective film sheet (adhesive layer/substrate) for evaluation of the moisture vapor transmission rate from the hand, make it adhere to the acrylic resin board only by its own weight, and record it away from the hand at 0.2 second intervals with a digital camera The moisture permeability of the adhesive layer of the protective film sheet for the subsequent evaluation of the moisture permeability rate spread to the acrylic resin board. The recording performed by the digital camera starts when the protective film sheet for evaluating the moisture permeability rate is removed from the hand. (4) In the above (2), let the surface of the adhesive layer other than the part that first touched the acrylic resin board come into contact with the acrylic resin board as the starting point. The situation of wet diffusion was analyzed using ImageJ. [Image processing software, developer: National Institute of Health (NIH)]. (5) Based on the analysis results, use the following formula to obtain the moisture permeability rate. The second digit below the decimal point of the calculated value is rounded off. Moisture permeability rate (unit: cm ² /sec) = [moisture permeability area (unit: cm ² ) after 0.2 seconds from the starting point-moisture permeability area of the starting point (unit: cm ² )]/0.2 (unit :second)

The above evaluation test was independently performed 3 times, and the values of the moisture vapor transmission rate obtained by the evaluation test for the 3 times were arithmetic averaged, and the second digit below the decimal point was rounded off. Based on the obtained value, the following evaluation criteria were followed to evaluate the moisture permeability of the adhesive layer to the acrylic resin board. The results are shown in Table 3. If the evaluation result is "A" or "B", it is judged to be an adhesive layer exhibiting a suitably low moisture permeability rate for the acrylic resin board.

-Evaluation Criteria- A: The moisture permeability rate is 3.0 cm ² /sec or less. B: The moisture permeability rate exceeds 3.0 cm ² /sec and does not reach 4.0 cm ² /sec. C: The moisture permeability rate is 4.0 cm ² /sec or more.

[table 3]

As shown in Table 3, it contains: 0.1 to 9% by mass relative to all structural units derived from 4-hydroxybutyl acrylate and 50 mass% or more relative to all structural units derived from (methyl) (Meth)acrylic copolymers [that is, specific (meth)acrylic copolymers] as the constituent units of alkyl acrylate monomers, isocyanate crosslinking agents with more than trifunctional, and organopolysiloxanes with oxyalkylene chains Alkyl (ie, specific organopolysiloxane), and ionic compounds, and does not contain bifunctional isocyanate-based crosslinking agent or bifunctional isocyanate-based crosslinking agent content relative to the content of isocyanate-based crosslinking agent more than trifunctional It was confirmed that the adhesive layer formed from the adhesive composition of Examples 1 to 6 with a ratio of more than 0% by mass and less than 1% by mass was able to sufficiently suppress the increase in the adhesive force over time. In addition, the adhesive layers formed from the adhesive compositions of Examples 1 to 6 were all confirmed to have excellent appearance. Furthermore, it was confirmed that the adhesive layer formed of the adhesive composition of Examples 1 to 6 has a moderately low moisture permeability rate for the acrylic resin board.

On the other hand, the adhesive layer formed by the adhesive composition of Comparative Example 1 containing a bifunctional isocyanate-based crosslinking agent instead of a trifunctional or more isocyanate-based crosslinking agent was confirmed to be unable to sufficiently suppress the lapse of time. The increase in adhesion. In addition, it was confirmed that the adhesive layer formed of the adhesive composition of Comparative Example 1 had an excessively high moisture permeability rate for the acrylic resin board. Adhesive layer formed by the adhesive composition of Comparative Example 2 whose content of bifunctional isocyanate-based crosslinking agent to content of trifunctional or higher isocyanate-based crosslinking agent is 57.1% by mass and 1% by mass or more , It was confirmed that the increase in adhesion over time was not sufficiently suppressed. In addition, it was confirmed that the adhesive layer formed of the adhesive composition of Comparative Example 2 had an excessively high moisture permeability rate for the acrylic resin board. The adhesive of Comparative Example 3 in which the content of the constituent units derived from 4-hydroxybutyl acrylate in the (meth)acrylic copolymer is more than 9% by mass relative to all the constituent units of the (meth)acrylic copolymer The adhesive layer formed by the composition had poor appearance.

Claims (6)

An adhesive composition for acrylic substrate protective film, containing: Containing 0.1% to 9% by mass of structural units derived from 4-hydroxybutyl acrylate relative to all structural units, and a composition derived from alkyl (meth)acrylate monomers of 50% by mass or more relative to all structural units Unit of (meth)acrylic copolymer, Isocyanate crosslinking agent with more than 3 functions, Organopolysiloxane with oxyalkylene chain, And ionic compounds, And the ratio of the content of the bifunctional isocyanate-based crosslinking agent or the content of the bifunctional isocyanate-based crosslinking agent to the content of the trifunctional or higher isocyanate-based crosslinking agent is more than 0% by mass and less than 1% by mass. The adhesive composition for an acrylic substrate protective film according to claim 1, wherein the alkyl (meth)acrylate monomer contains n-butyl acrylate. The adhesive composition for an acrylic substrate protective film of claim 1 or 2, wherein the content of the structural unit derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer is relative to the (former) The total structural unit of the base) acrylic copolymer is 0.5% by mass to 3.5% by mass. The adhesive composition for an acrylic base protective film according to claim 1 or 2, wherein the (meth)acrylic copolymer contains a structural unit derived from a monomer having a carboxyl group. An acrylic substrate protective film is provided with a substrate and an adhesive layer provided on the substrate and formed of the adhesive composition for an acrylic substrate protective film according to any one of claims 1 to 4. The acrylic substrate protective film of claim 5, wherein the moisture permeability of the adhesive layer to the acrylic substrate does not reach 4.0 cm ² /sec.