KR102178180B1 - Adhesive composition, adhesive film, and article processing method - Google Patents

Abstract

Derived from an acrylic copolymer A containing a structural unit Ax derived from a (meth)acrylic acid alkyl ester having no hydroxyl group and a structural unit a derived from an acrylate monomer having a hydroxyl group, and a (meth)acrylate alkyl ester having no hydroxyl group Containing the structural unit Bx and the structural unit b derived from a methacrylate monomer having a hydroxyl group, an acrylic copolymer B having a weight average molecular weight smaller than the weight average molecular weight of the acrylic copolymer A, and an isocyanate compound, The sum of the hydroxyl value a of the acrylic copolymer A and the hydroxyl value b of the acrylic copolymer B is in the range of 40 mgKOH/g to 90 mgKOH/g, and the hydroxyl value of the hydroxyl value is 0.5 to 7.0. Adhesive composition in the range.

Description

Adhesive composition, adhesive film, and article processing method {Adhesive composition, adhesive film, and article processing method}

The present invention relates to an adhesive composition, an adhesive film, and a method of treating an article.

When processing or transporting articles such as metal plates, coated steel plates, synthetic resin plates, etc., in order to prevent the surface of the article from damage or dirt, an adhesive film is attached to protect it. The pressure-sensitive adhesive film used here generally has a pressure-sensitive adhesive layer for sticking to an article (hereinafter, also referred to as "adherent") on one side of a sheet-like base material.

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive film is required to have a degree of adhesion so that the pressure-sensitive adhesive film does not shift or fall off the surface of the adherend while the adherend surface needs to be protected. Furthermore, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film does not cause contamination of the adherend surface due to the remaining at least a portion of the pressure-sensitive adhesive layer or at least a part of the components constituting the pressure-sensitive adhesive layer when the pressure-sensitive adhesive film is peeled from the surface of the adherend, and is easy to leave It is required to have a peelability enough to be able to peel easily (hereinafter, also referred to as "easy peelability"). In addition, in the case of an article treatment method in which heat treatment is performed while the adhesive film is attached to the surface of the adherend, the adhesive layer of the adhesive film has good peelability such that it can be easily peeled off as described above even after heat treatment. It is required to have. Furthermore, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film is also required to have less a phenomenon called zipping, which occurs due to uneven adhesion between the pressure-sensitive adhesive layer and the surface of the adherend when the pressure-sensitive adhesive film is peeled from the surface of the adherend.

Japanese Laid-Open Patent Publication No. 2007-327036 discloses a pressure-sensitive adhesive composition containing an acrylic resin containing a hydroxyl group, an isocyanate crosslinking agent, and a low molecular weight non-reactive ester compound. It is described that the pressure-sensitive adhesive film having the pressure-sensitive adhesive layer formed of this pressure-sensitive adhesive composition on a base material has a small increase in the adhesive strength of the pressure-sensitive adhesive layer even after heat treatment, and thus it is difficult to contaminate the surface of the adherend after peeling.

Japanese Patent Laid-Open Publication No. 2003-205567 discloses a surface protective film having a high-density crosslinked adhesive layer as a surface protective film that is easily peeled even after heat treatment.

Japanese Laid-Open Patent Publication No. 2005-146151 discloses a surface protective sheet having a pressure-sensitive adhesive layer obtained by crosslinking a crosslinkable composition comprising two types of acrylic polymers having different glass transition temperatures and a crosslinking agent. It is described that the adherend protected by this surface protection sheet does not lift or peel between the pressure-sensitive adhesive layer and the adherend even when heat-treated, has good high-speed peelability at the time of peeling, and does not contaminate the adherend surface after peeling.

However, as described in Japanese Laid-Open Patent Publication No. 2007-327036, in the case of peeling the surface protective sheet after heat treatment, in the surface protective sheet having an adhesive layer formed of an adhesive composition containing a low molecular weight non-reactive ester compound, There are cases where surface contamination cannot be sufficiently suppressed.

As described in Japanese Patent Laid-Open No. 2003-205567, the crosslinking density of the pressure-sensitive adhesive layer is increased, or as described in Japanese Patent Laid-Open No. 2005-146151, the crosslinkable composition used for forming the pressure-sensitive adhesive layer has two different glass transition temperatures. In some cases, it is not sufficient after the heat treatment to achieve both the property that the surface protection sheet can be easily peeled off even when the resin is contained and the property that the surface of the adherend after peeling is less contaminated.

The present invention has been made in view of the above, and it is an object of the present invention to provide an adhesive composition and an adhesive film in which the peelability from the surface of an adherend is excellent even after heat treatment and contamination of the surface of an adherend after peeling is suppressed.

Furthermore, it is an object of the present invention to provide an article treatment method in which an adhesive film can be easily peeled off an adherend surface even after heat treatment, and contamination of an adherend surface after peeling is suppressed.

Specific means for achieving the above object are as follows.

<1> An acrylic copolymer A containing a structural unit Ax derived from a (meth)acrylate alkyl ester having no hydroxyl group, and a constitutional unit a derived from an acrylate monomer having a hydroxyl group, and (meth)acrylate alkyl having no hydroxyl group Containing the structural unit Bx derived from ester and the structural unit b derived from a methacrylate monomer having a hydroxyl group, an acrylic copolymer B having a weight average molecular weight smaller than the weight average molecular weight of the acrylic copolymer A, and an isocyanate compound And the sum of the hydroxyl value a of the acrylic copolymer A and the hydroxyl value b of the acrylic copolymer B is in the range of 40 mgKOH/g to 90 mgKOH/g, and the hydroxyl value of a is a ratio of the hydroxyl value to b (hydroxyl value The pressure-sensitive adhesive composition in which a/hydroxyl value b) is in the range of 0.5 to 7.0.

<2> The pressure-sensitive adhesive composition according to <1>, wherein the ratio of the weight average molecular weight of the acrylic copolymer B to the weight average molecular weight of the mixture of the acrylic copolymer A and the acrylic copolymer B is in the range of 0.1 to 0.5.

<3> The pressure-sensitive adhesive composition according to <1> or <2>, wherein the ratio of the hydroxyl value of a to b is in the range of 0.5 to 2.0.

<4> The pressure-sensitive adhesive composition according to any one of <1> to <3>, wherein the content of the structural unit a in the acrylic copolymer A is 30% by mass or less.

<5> The pressure-sensitive adhesive composition according to any one of <1> to <4>, wherein the content of the structural unit b in the acrylic copolymer B is 10% by mass or more.

<6> The pressure-sensitive adhesive composition according to any one of <1> to <5>, wherein the content of the isocyanate compound is 0.4 equivalent to 2.2 equivalents with respect to the amount of hydroxyl groups contained in the acrylic copolymer A and the acrylic copolymer B.

<7> The pressure-sensitive adhesive composition according to any one of <1> to <6>, wherein the acrylic copolymer A and the acrylic copolymer B each have a glass transition temperature (Tg) of -40°C or less.

<8> the weight average molecular weight of the acrylic copolymer A is in the range of 400,000 to 1.5 million, and the weight average molecular weight of the acrylic copolymer B is in the range of 100,000 to 500,000, in any one of <1> to <7> The adhesive composition described.

An adhesive film having a <9> base material and an adhesive layer derived from the pressure-sensitive adhesive composition according to any one of <1> to <8> provided on the base material.

An adhesive film attaching step of attaching the adhesive film according to <9> to the surface of a <10> article so that the adhesive layer and the surface are in contact with each other, a heat treatment step of heating the article to which the adhesive film is pasted in the attaching step, A method for treating an article comprising a peeling step of peeling the adhesive film from the surface of the article heated in the heat treatment step.

According to the present invention, even after heat treatment, it is possible to provide an adhesive composition and an adhesive film in which the peelability from the surface of the adherend is excellent and contamination of the surface of the adherend after peeling is suppressed.

Furthermore, according to the present invention, the adhesive film can be easily peeled from the adherend surface even after heat treatment, and there is provided an article treatment method in which contamination of the adherend surface after peeling is suppressed.

In the present specification, the term "process" is included in the term as long as the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes as well as independent processes.

In the present specification, the numerical range indicated by using "~" represents a range including the numerical values described before and after "~" as a minimum value and a maximum value, respectively.

The amount of each component in the composition means the total amount of the plurality of substances present in the composition, unless otherwise specified, when a plurality of substances corresponding to each component are present in the composition.

The term "(meth)acrylic acid alkylester" is meant to include both "acrylic acid alkylester" and "methacrylic acid alkylester". Similarly, the term "(meth)acrylate" means to include both "acrylate" and "methacrylate", and the term "(meth)acrylamide" refers to both "acrylamide" and "methacrylamide". It means to include everything.

In the acrylic copolymer, that a certain structural unit is "the main component" means that the content rate based on the mass of the structural unit is the largest among all the structural units of the acrylic copolymer. In certain embodiments of the present invention, the content of the structural unit that is the main component of the acrylic copolymer is 50% by mass or more.

<Adhesive composition>

The pressure-sensitive adhesive composition of the present invention comprises an acrylic copolymer A comprising a structural unit Ax derived from a (meth)acrylate alkyl ester having no hydroxyl group and a constitutional unit a derived from an acrylate monomer having a hydroxyl group, and an acrylic copolymer A having no hydroxyl group (meta ) A structural unit Bx derived from an acrylic acid alkyl ester and a structural unit b derived from a methacrylate monomer having a hydroxyl group, an acrylic copolymer B having a lower weight average molecular weight than the acrylic copolymer A, and an isocyanate compound, The sum of the hydroxyl value a of the acrylic copolymer A and the hydroxyl value b of the acrylic copolymer B is 40 mgKOH/g to 90 mgKOH/g, and the ratio of the hydroxyl value of a to b (hydroxyl value a/hydroxyl value b) is 0.5 ~7.0. By satisfying the above requirements, the pressure-sensitive adhesive composition of the present invention is excellent in peelability from the adherend after heat treatment, and contamination of the adherend is suppressed.

The present inventors think as follows about the reason why the pressure-sensitive adhesive composition of the present invention has excellent peelability from the adherend after heat treatment and suppresses contamination of the adherend. That is, the pressure-sensitive adhesive composition of the present invention contains two types of acrylic copolymers having different crosslinking reactivity, an acrylic copolymer A and an acrylic copolymer B. For this reason, when the pressure-sensitive adhesive composition is crosslinked, a portion having a high crosslinking density derived from the constitutional unit a in the acrylic copolymer A and a portion having a low crosslinking density derived from the constitutional unit b in the acrylic copolymer B are generated. Since the part with high crosslink density and the part with low crosslink density are entangled with each other in the crosslinked adhesive composition, the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition has adequate adhesive strength and is difficult to deteriorate during heat treatment. It is thought that the peelability is excellent and contamination of the adherend is suppressed.

In the pressure-sensitive adhesive composition of the present invention, the sum of the hydroxyl value a of the acrylic copolymer A and the hydroxyl value b of the acrylic copolymer B is 40 mgKOH/g to 90 mgKOH/g. When the sum of the hydroxyl value a and the hydroxyl value b is less than 40 mgKOH/g, the crosslinking reaction becomes insufficient, and the increase in the adhesive strength of the pressure-sensitive adhesive composition cannot be sufficiently suppressed, and the fouling property may deteriorate. When the sum of the hydroxyl value a and the hydroxyl value b exceeds 90 mgKOH/g, the crosslinking reaction proceeds excessively and the necessary adhesive strength may not be maintained. In addition, the viscosity of the pressure-sensitive adhesive composition is liable to rise and the storage properties may deteriorate.

The sum of the hydroxyl value a of the acrylic copolymer A and the hydroxyl value b of the acrylic copolymer B is preferably 45 mgKOH/g or more, more preferably 52 mgKOH/g or more, and even more preferably 56 mgKOH/g or more. In addition, the sum of the hydroxyl value a of the acrylic copolymer A and the hydroxyl value b of the acrylic copolymer B is preferably 74 mgKOH/g or less, more preferably 70 mgKOH/g or less, more preferably 65 mgKOH/g or less, and 61 mgKOH/ More preferably less than g.

In the pressure-sensitive adhesive composition of the present invention, the hydroxyl value of the acrylic copolymer A is a ratio of the hydroxyl value of the acrylic copolymer B to b (hydroxyl value a/hydroxyl value b) of 0.5 to 7.0. When the value of the hydroxyl value a/hydroxyl value b is less than 0.5, the ratio of the portion with the low crosslink density to the portion with a high crosslink density is too large, and the fouling property may deteriorate. When the value of the hydroxyl value a/hydroxyl value b exceeds 7.0, the ratio of the portion with the low crosslink density to the portion with a high crosslink density is too small, and the adhesive strength increases after the heat treatment and the peelability may deteriorate.

The ratio of the hydroxyl value of the acrylic copolymer A to the hydroxyl value of the acrylic copolymer B of a (hydroxyl value a/hydroxyl value b) is preferably 0.6 or more, more preferably 0.7 or more, and even more preferably 0.8 or more. In addition, the ratio of the hydroxyl value of the acrylic copolymer A to the hydroxyl value of the acrylic copolymer B of a (hydroxyl value a/hydroxyl value b) is preferably 2.0 or less, more preferably 1.7 or less, and more preferably 1.4 or less. And more preferably 1.0 or less.

If the hydroxyl value of the acrylic copolymer A is a ratio of the hydroxyl value of the acrylic copolymer B to b (hydroxyl value a/hydroxyl value b) of 2.0 or less, zipping occurring during peeling is suppressed.

When the ratio is 2.0 or less, the portion having a high crosslinking density derived from the constitutional unit a in the acrylic copolymer A and the portion having a low crosslinking density derived from the constitutional unit b in the acrylic copolymer B are more evenly dispersed in the pressure-sensitive adhesive composition. Is done. Therefore, since the difference in strength and weakness depending on the location of the pressure-sensitive adhesive layer in the adhesive force of the pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition to the adherend is small, it is considered that the jipped generated during peeling is suppressed.

In the present invention, the hydroxyl value a of the acrylic copolymer A and the hydroxyl value b of the acrylic copolymer B are obtained by the following calculation formulas, respectively.

Hydroxyl value a(mgKOH/g)={(A1/100)÷B1}×C1×1000

A1 = content of the monomer having a hydroxyl group used in the acrylic copolymer A in all monomers used in the acrylic copolymer A and the acrylic copolymer B (% by mass)

B1 = molecular weight of the monomer having a hydroxyl group used in the acrylic copolymer A

Molecular weight of C1=KOH

Hydroxyl value b(mgKOH/g)={(A2/100)÷B2}×C2×1000

A2 = content of the monomer having a hydroxyl group used in the acrylic copolymer B in the total monomers used in the acrylic copolymer A and the acrylic copolymer B (% by mass)

B2 = molecular weight of the monomer having a hydroxyl group used in the acrylic copolymer B

Molecular weight of C2=KOH

When at least one of the acrylic copolymer A and the acrylic copolymer B is a mixture of two or more copolymers, or when there are two or more monomers having a hydroxyl group used in at least one of the acrylic copolymer A and the acrylic copolymer B, respectively For the acrylic copolymer or monomer of, the hydroxyl value is calculated according to the above formula, and the obtained values are summed to obtain a hydroxyl value a or a hydroxyl value b.

(Acrylic copolymer A)

The pressure-sensitive adhesive composition of the present invention contains at least one type of acrylic copolymer A comprising a structural unit Ax derived from a (meth)acrylate alkyl ester having no hydroxyl group and a structural unit a derived from an acrylate monomer having a hydroxyl group. . In the present specification, the "constituent unit derived from an acrylate monomer having a hydroxyl group" refers to a repeating unit formed by addition polymerization of an acrylate monomer having a hydroxyl group.

It is preferable that the content rate of the structural unit a contained in the acrylic copolymer A is 7 mass% or more with respect to the total structural units of the acrylic copolymer A (that is, relative to the mass of the acrylic copolymer A). When the content of the structural unit a contained in the acrylic copolymer A is 7% by mass or more, the crosslinking reaction proceeds sufficiently, and in the crosslinked pressure-sensitive adhesive composition, a portion with high crosslinking density derived from the structural unit a and low adhesiveness tends to be sufficiently formed. have. It is more preferable that it is 9 mass% or more, and, as for the content rate of the structural unit a contained in the acrylic copolymer A, it is still more preferable that it is 11 mass% or more.

It is preferable that the content rate of the structural unit a contained in the acrylic copolymer A is 30 mass% or less with respect to the total structural units of the acrylic copolymer A (that is, relative to the mass of the acrylic copolymer A). If the content of the structural unit a contained in the acrylic copolymer A is 30% by mass or less, excessive progression of the crosslinking reaction is suppressed, and in the crosslinked pressure-sensitive adhesive composition, a portion of the crosslinked pressure-sensitive adhesive composition with high crosslink density and low adhesiveness derived from the structural unit a is appropriately formed. There is a tendency. Moreover, it can effectively suppress that the viscosity rises during storage of an adhesive composition. The content rate of the structural unit a contained in the acrylic copolymer A is more preferably 25% by mass or less, still more preferably 20% by mass or less, and even more preferably 18% by mass or less.

The structure of the acrylate monomer having a hydroxyl group used to form the acrylic copolymer A is not particularly limited. For example, an alkyl acrylate having a hydroxyl group and a polyalkylene glycol acrylate having a hydroxyl group may be mentioned.

The alkyl moiety of the alkyl acrylate having a hydroxyl group may be linear, branched, or cyclic. It is preferable that the number of carbon atoms in the alkyl moiety of the alkyl acrylate having a hydroxyl group is in the range of 1 to 12. When the number of carbon atoms in the alkyl moiety is within the above range, it is advantageous in terms of adhesiveness and adhesiveness to the base material when used as an adhesive film. The number of carbon atoms in the alkyl moiety of the alkyl acrylate having a hydroxyl group is more preferably 2 to 6, and still more preferably 2 to 4.

Examples of the alkylene glycol constituting the polyalkylene glycol moiety of the polyalkylene glycol acrylate having a hydroxyl group include ethylene glycol, propylene glycol, a combination of ethylene glycol and propylene glycol.

As an acrylate monomer having a hydroxyl group, specifically, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 6-hydroxyhexyl acrylate, 10-hydroxydecyl acrylate, 12-hydroxylauryl acrylate, 3-methyl-3-hydroxybutyl acrylate, 1,1-dimethyl-3-butyl acrylate, 1,3-dimethyl-3-hydroxy Roxybutyl acrylate, 2,2,4-trimethyl-3-hydroxypentyl acrylate, 2-ethyl-3-hydroxyhexyl acrylate, glycerin monoacrylate, polypropylene glycol monoacrylate, polyethylene glycol monoacrylate , Poly(ethylene glycol-propylene glycol) monoacrylate, and the like. The acrylate monomers having a hydroxyl group may be used singly or in combination of two or more.

From the viewpoint of obtaining adequate adhesion to the adherend and good releasability, the acrylate monomer having a hydroxyl group is preferably an alkyl acrylate having a hydroxyl group, and 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, 6- It is more preferable to contain at least one selected from the group consisting of hydroxyhexyl acrylate, 10-hydroxydecyl acrylate, and 12-hydroxylauryl acrylate, and 2-hydroxyethyl acrylate, 4-hydroxy It is more preferable to contain at least one selected from the group consisting of oxybutyl acrylate and 6-hydroxyhexyl acrylate.

As the alkyl acrylate having a hydroxyl group, at least one of 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate is particularly preferable. These are particularly good in compatibility and copolymerization with other monomers when synthesizing the acrylic copolymer A, and particularly good in crosslinking reaction with the crosslinking agent when a crosslinking agent is used in combination.

The acrylic copolymer A preferably contains a structural unit Ax derived from an alkyl (meth)acrylate having no hydroxyl group as a main component.

The ratio of the structural unit Ax to all the structural units of the acrylic copolymer A is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more.

The alkyl moiety of the (meth)acrylate alkyl ester having no hydroxyl group may be linear or branched, and the number of carbon atoms is preferably in the range of 1 to 18. When the number of carbon atoms in the alkyl moiety is within the above range, it is advantageous in terms of adhesion and adhesion to the base material when used as an adhesive film. It is more preferable that the number of carbon atoms in the alkyl moiety is in the range of 1 to 12. It is preferable that the alkyl moiety of the (meth)acrylic acid alkyl ester which does not have a hydroxyl group is unsubstituted.

As a (meth)acrylic acid alkyl ester having no hydroxyl group, specifically methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, s-butyl (meth) )Acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, i-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, i-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, and the like. The (meth)acrylic acid alkyl ester having no hydroxyl group may be used alone or in combination of two or more.

(Meth) acrylate alkyl ester that does not have a hydroxyl group from the viewpoint of expressing an appropriate adhesion to the adherend is composed of 2-ethylhexyl (meth) acrylate, n-butyl (meth) acrylate and lauryl (meth) acrylate. It is preferable to include at least one selected from the group.

Acrylic copolymer A is a structural unit y derived from a monomer having a hydroxyl group other than the structural unit a in addition to the structural unit a derived from an acrylate monomer having a hydroxyl group, for example, a structural unit derived from a methacrylate monomer having a hydroxyl group It may contain, etc. As a methacrylate monomer having a hydroxyl group, the specific example described in the item of the acrylic copolymer B mentioned later is mentioned.

When the acrylic copolymer A contains the structural unit y, the content rate of the structural unit y relative to the total mass of the structural units in the acrylic copolymer A is preferably 7% by mass or less. By setting the content rate of the structural unit y to 7 mass% or less with respect to the total mass of the structural units in the acrylic copolymer A, contamination to the adherend can be suppressed. The content rate of the structural unit y relative to the total mass of the structural units in the acrylic copolymer A is more preferably 5% by mass or less, and still more preferably 3% by mass or less.

In addition to the structural unit Ax derived from the (meth)acrylic acid alkyl ester having no hydroxyl group, the constitutional unit a derived from the acrylate monomer having a hydroxyl group, and the constitutional unit y contained as desired, other than these as necessary. Constituent unit c derived from another monomer of may be included. When the acrylic copolymer A contains the structural unit c, the number of monomers used for formation of the structural unit c may be one or two or more.

As a monomer used for formation of a structural unit c, a monomer other than the (meth)acrylate alkyl ester which does not have a hydroxyl group, a monomer which has a functional group other than a hydroxyl group, etc. are mentioned.

As monomers other than the (meth)acrylic acid alkyl ester having no hydroxyl group, specifically, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, phenoxyethyl (meth)acrylate, etc. (Meth)acrylic acid ester monomer having a cyclic group, (meth)acrylic acid alkoxyalkyl ester monomer such as methoxyethyl (meth)acrylate, styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, Aromatic monovinyl monomers such as vinyltoluene, vinyl cyanide monomers such as acrylonitrile and methacrylonitrile, vinyl ester monomers such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate, and various derivatives of these monomers. I can.

Specific examples of the monomer having a functional group other than a hydroxyl group include a monomer having a carboxyl group, a monomer having a glycidyl group, a monomer having an amide group or N-substituted amide group, and a monomer having a tertiary amino group.

As a monomer having a carboxy group, specifically acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, citraconic acid, cinnamonic acid, succinic acid monohydroxyethyl (meth)acrylate, maleic acid monohydroxy Ethyl (meth)acrylate, fumaric acid monohydroxyethyl (meth)acrylate, phthalic acid monohydroxyethyl (meth)acrylate, 1,2-dicarboxycyclohexane monohydroxyethyl (meth)acrylate, (meth) Acrylic acid dimers, ω-carboxy-polycaprolactone mono (meth)acrylate, and the like.

As a monomer having a glycidyl group, specifically, glycidyl (meth)acrylate, 3,4-epoxycyclohexyl methyl (meth)acrylate, glycidyl vinyl ether, 3,4-epoxycyclohexyl vinyl ether, glycidyl Cidyl (meth) allyl ether, 3,4-epoxycyclohexyl (meth) allyl ether, etc. are mentioned.

As a monomer having an amide group or an N-substituted amide group, specifically acrylamide, methacrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-methoxy methyl (meth) acrylamide, N-ethoxy methyl (meth)acrylamide, N-propoxy methyl (meth)acrylamide, N-butoxy methyl (meth)acrylamide, N-tert-butylacrylamide, N-octylacrylamide, diacetoneacrylamide And amides.

Specific examples of the monomer having a tertiary amino group include dimethylamino ethyl (meth)acrylate, diethylamino ethyl (meth)acrylate, and dimethylamino propyl (meth)acrylamide.

When the acrylic copolymer A contains the structural unit c, the content rate of the structural unit c is preferably 10% by mass or less, and more preferably 5% by mass or less with respect to the total mass of the structural units in the acrylic copolymer A.

The weight average molecular weight (Mw) of the acrylic copolymer A is preferably in the range of 400,000 to 1.5 million, more preferably in the range of 500,000 to 1.3 million, and even more preferably in the range of 600,000 to 1.2 million. If the Mw of the acrylic copolymer A is 400,000 or more, contamination to the adherend can be more suppressed. In addition, when the Mw of the acrylic copolymer A is 1.5 million or less, the adhesive strength upon re-peeling is not too large, so that the adhesive film can be more easily peeled off.

The dispersibility (Mw/Mn) expressed as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic copolymer A is not particularly limited, but from the viewpoint of adhesion and contamination suppression of the adherend of 1 to 30 It is preferably within the range.

The weight average molecular weight (Mw) and number average molecular weight (Mn) of the acrylic copolymer A are values measured by the following method. Specifically, it is measured according to the following (1) to (3).

(1) The solution of acrylic copolymer A is applied on a release paper and dried at 100°C for 2 minutes to obtain a film-shaped acrylic copolymer A.

(2) Using the film-like acrylic copolymer A and tetrahydrofuran obtained in the above (1), a sample solution having a solid content concentration of 0.2% by mass is obtained.

(3) The weight average molecular weight (Mw) and number average molecular weight (Mn) of the acrylic copolymer A are measured as standard polystyrene conversion values using gel permeation chromatography (GPC) under the following conditions.

-Condition-

·GPC: HLC-8220 GPC [made by Tosoh Corporation]

·Column: Use 4 TSK-GEL GMHXL

Mobile phase solvent: tetrahydrofuran

Flow rate: 0.6 mL/min

·Column temperature: 40℃

It is preferable that the glass transition temperature (Tg) of the acrylic copolymer A is -40°C or less. When the Tg of the acrylic copolymer A is -40°C or less, the flowability of the pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition is excellent and the adherence to the adherend is good. The Tg of the acrylic copolymer A is more preferably -60°C or less, and even more preferably -70°C or less.

The Tg of the acrylic copolymer A is a value obtained by converting the absolute temperature (K) obtained by calculation from the following Equation 1 into degrees Celsius (°C).

1/Tg=w1/Tg1+w2/Tg2+... +w(k-1)/Tg(k-1)+wk/Tgk… (Equation 1)

In Equation 1, Tg1, Tg2, ... , Tg(k-1), and Tgk represent the glass transition temperature (K) of the homopolymer of each monomer constituting the acrylic copolymer A, respectively. w1, w2,… , w(k-1), wk denote the mass fraction of each monomer constituting the acrylic copolymer A, and w1+w2+... +w(k-1)+wk=1.

The content rate of the acrylic copolymer A in the pressure-sensitive adhesive composition is preferably in the range of 40% by mass to 90% by mass, and 45% by mass to 85% by mass with respect to the total mass of the pressure-sensitive adhesive composition from the viewpoint of adhesion and suppression of contamination to an adherend. It is more preferable that it is a range of, and it is still more preferable that it is a range of 45 mass%-80 mass %.

(Acrylic copolymer B)

The pressure-sensitive adhesive composition of the present invention contains at least one type of acrylic copolymer B comprising a structural unit Bx derived from a (meth)acrylate alkyl ester having no hydroxyl group and a structural unit b derived from a methacrylate monomer having a hydroxyl group. do. In the present specification, the "constituent unit derived from a methacrylate monomer having a hydroxyl group" means a repeating unit formed by addition polymerization of a methacrylate monomer having a hydroxyl group.

The content rate of the structural unit b contained in the acrylic copolymer B is preferably 10% by mass or more with respect to the total structural units of the acrylic copolymer B (that is, relative to the mass of the acrylic copolymer B). When the content rate of the structural unit b contained in the acrylic copolymer B is 10% by mass or more, there is a tendency that excessive increase in adhesive force after heat treatment can be suppressed. It is more preferable that it is 14 mass% or more, and, as for the content rate of the structural unit b contained in the acrylic copolymer B, it is still more preferable that it is 17 mass% or more.

It is preferable that the content rate of the structural unit b contained in the acrylic copolymer B is 25 mass% or less with respect to all the structural units of the acrylic copolymer B. When the content rate of the structural unit b contained in the acrylic copolymer B is 25% by mass or less, contamination of the adherend tends to be suppressed. It is more preferable that it is 22 mass% or less, and, as for the content rate of the structural unit b contained in the acrylic copolymer B, it is still more preferable that it is 20 mass% or less.

The structure of the methacrylate monomer having a hydroxyl group used to form the acrylic copolymer B is not particularly limited. For example, an alkyl methacrylate having a hydroxyl group, a polyalkylene glycol methacrylate having a hydroxyl group, and the like can be mentioned.

The alkyl moiety of the alkyl methacrylate having a hydroxyl group may be linear, branched, or cyclic. It is preferable that the number of carbon atoms of the alkyl moiety of the alkyl methacrylate having a hydroxyl group is in the range of 1 to 12. When the number of carbon atoms in the alkyl moiety is within the above range, it is advantageous in terms of adhesion and adhesion to the base material when used as an adhesive film. The number of carbon atoms in the alkyl moiety of the alkyl methacrylate having a hydroxyl group is more preferably 2 to 6, and still more preferably 2 to 4.

Examples of the alkylene glycol constituting the polyalkylene glycol moiety of the polyalkylene glycol methacrylate having a hydroxyl group include ethylene glycol, propylene glycol, a combination of ethylene glycol and propylene glycol.

As a methacrylate monomer having a hydroxyl group, specifically 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxy Hexyl methacrylate, 10-hydroxydecyl methacrylate, 12-hydroxylauryl methacrylate, 3-methyl-3-hydroxybutyl methacrylate, 1,1-dimethyl-3-butyl methacrylate, 1,3-dimethyl-3-hydroxybutyl methacrylate, 2,2,4-trimethyl-3-hydroxypentyl methacrylate, 2-ethyl-3-hydroxyhexyl methacrylate, glycerin monomethacrylate , Polypropylene glycol monomethacrylate, polyethylene glycol monomethacrylate, and poly(ethylene glycol-propylene glycol) monomethacrylate. The methacrylate monomer having a hydroxyl group may be used alone or in combination of two or more.

The methacrylate monomer having a hydroxyl group is preferably an alkyl methacrylate having a hydroxyl group, and 2-hydroxyethyl methacrylate and 4-hydroxybutyl methacrylate are obtained from the viewpoint of obtaining adequate adhesion to the adherend and good peelability. Rate, 6-hydroxyhexyl methacrylate, 10-hydroxydecyl methacrylate, and more preferably at least one selected from the group consisting of 12-hydroxylauryl methacrylate, and 2-hydroxy It is more preferable to contain at least one selected from the group consisting of ethyl methacrylate, 4-hydroxybutyl methacrylate, and 6-hydroxyhexyl methacrylate.

The acrylic copolymer B preferably contains a structural unit Bx derived from an alkyl (meth)acrylate having no hydroxyl group as a main component.

The ratio of the structural unit Bx to all the structural units of the acrylic copolymer B is preferably 50% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more.

Specific examples and preferred examples of the (meth)acrylate alkyl ester having no hydroxyl group include the specific examples and preferred examples described in the section of the acrylic copolymer A described above.

The acrylic copolymer B is a structural unit z derived from a monomer having a hydroxyl group other than the structural unit b in addition to the structural unit b derived from a methacrylate monomer having a hydroxyl group, for example, a structural unit derived from an acrylate monomer having a hydroxyl group May be included. As an acrylate monomer having a hydroxyl group, the specific example described in the item of the above-mentioned acrylic copolymer A is mentioned.

When the acrylic copolymer B contains the structural unit z, the content ratio of the structural unit z to all the structural units of the acrylic copolymer B is preferably 7% by mass or less. By making the content of the structural unit z relative to all the structural units of the acrylic copolymer B to be 7% by mass or less, excessive progression of the crosslinking reaction can be suppressed and zipping can be suppressed. It is more preferable that it is 5 mass% or less, and, as for the content rate of the structural unit z with respect to all structural units of the acrylic copolymer B, it is still more preferable that it is 3 mass% or less.

The acrylic copolymer B is, if necessary, in addition to the structural unit Bx derived from the (meth)acrylic acid alkyl ester having no hydroxyl group, the structural unit b derived from the methacrylate monomer having a hydroxyl group, and the structural unit z contained as desired. Constituent units d derived from other monomers may be included. When the acrylic copolymer B contains the structural unit d, the number of monomers used to form the structural unit d may be one or two or more. When the acrylic copolymer B contains the constituent unit d, specific examples and preferred examples of the monomers used for the formation of the constituent unit d are specific examples of the monomer used for the formation of the constituent unit c described in the section of the acrylic copolymer A And preferable examples are mentioned.

When the acrylic copolymer B contains the structural unit d, the content rate of the structural unit d is preferably 10% by mass or less, and more preferably 5% by mass or less with respect to the total mass of the structural units in the acrylic copolymer B.

The weight average molecular weight (Mw) of the acrylic copolymer B is smaller than the weight average molecular weight of the acrylic copolymer A. When the weight average molecular weight (Mw) of the acrylic copolymer B is less than the weight average molecular weight of the acrylic copolymer A, it is easy to secure the wettability of the pressure-sensitive adhesive composition.

The weight average molecular weight (Mw) of the acrylic copolymer B is preferably in the range of 100,000 to 500,000, more preferably in the range of 150,000 to 450,000, and even more preferably in the range of 200,000 to 400,000.

If the Mw of the acrylic copolymer B is 100,000 or more, contamination of the adherend due to the formation of the acrylic copolymer B having a low molecular weight can be more suppressed. In addition, when the Mw of the acrylic copolymer B is 500,000 or less, the adhesive strength at the time of re-peeling is not too large, and the adhesive film can be more easily peeled off.

The dispersibility (Mw/Mn) expressed as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic copolymer B is not particularly limited, but from the viewpoint of adhesion and contamination suppression to the adherend It is preferably within the range.

The weight average molecular weight (Mw) and number average molecular weight (Mn) of the acrylic copolymer B can be measured by the method described in the section of the acrylic copolymer A described above.

The glass transition temperature (Tg) of the acrylic copolymer B is preferably -40°C or less. When the Tg of the acrylic copolymer B is -40°C or less, the flowability of the pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition is excellent and the adherence to the adherend is good. The Tg of the acrylic copolymer B is more preferably -45°C or less, and still more preferably -50°C or less. The Tg of the acrylic copolymer B can be determined by the calculation formula described in the section of the acrylic copolymer A described above.

The content rate of the acrylic copolymer B in the pressure-sensitive adhesive composition is preferably in the range of 10% by mass to 60% by mass, and 15% by mass to 55% by mass with respect to the total mass of the pressure-sensitive adhesive composition from the viewpoint of adhesion and suppression of contamination to an adherend. It is more preferable that it is a range of, and it is still more preferable that it is a range of 20 mass%-55 mass %.

In the pressure-sensitive adhesive composition of the present invention, the content ratio (A/B) of the (meth)acrylic copolymer A to the acrylic copolymer B is preferably in the range of 90/10 to 40/60 on a mass basis. When the content ratio of the acrylic copolymer A exceeds 90% by mass, the easy peelability after heat treatment may deteriorate. In addition, when the content ratio of the acrylic copolymer B exceeds 60% by mass, the easy peelability after heat treatment may deteriorate.

In the pressure-sensitive adhesive composition of the present invention, the content ratio (A/B) of the acrylic copolymer A to the acrylic copolymer B is preferably in the range of 85/15 to 45/55 based on the mass, and 85/15 to 55/45 The range of is more preferable.

In the pressure-sensitive adhesive composition of the present invention, the ratio of the weight average molecular weight of the acrylic copolymer B to the weight average molecular weight of the mixture of the acrylic copolymer A and the acrylic copolymer B is preferably in the range of 0.1 to 0.5. If the ratio is less than 0.1, contamination may deteriorate. In addition, when the ratio exceeds 0.5, the adhesive strength increases after heat treatment and the peelability may deteriorate.

The weight average molecular weight of the mixture of the acrylic copolymer A and the acrylic copolymer B means a weighted square average value calculated by the following formula (2).

[AMw×AMw×A+BMw×BMw×B]/[AMw×A+BMw×B]… (Equation 2)

In Equation 2,

AMw represents the weight average molecular weight of the acrylic copolymer A,

BMw represents the weight average molecular weight of the acrylic copolymer B,

A and B represent the mass of the acrylic copolymer A and the mass of the acrylic copolymer B contained in the pressure-sensitive adhesive composition, respectively.

In the pressure-sensitive adhesive composition of the present invention, the content rate of the structural unit a in the total mass of the acrylic copolymer A and the acrylic copolymer B is in the range of 4% by mass to 12% by mass, and the content rate of the constituent unit b is 4% by mass to 12% by mass It is preferably in the range of %. Thereby, the adhesive film can be easily peeled off even after heat treatment, and contamination to an adherend can also be effectively suppressed.

In the pressure-sensitive adhesive composition of the present invention, the content rate of the structural unit a in the total mass of the acrylic copolymer A and the acrylic copolymer B is in the range of 5 mass% to 10 mass%, and the content rate of the structural unit b is 6 mass% to 11 It is more preferable that it is a range of mass %, and it is especially preferable that the content rate of structural unit a is 6 mass%-8 mass %, and it is still more preferable that the content rate of said structural unit b is 8 mass%-10 mass %.

(Polymerization method of acrylic copolymer)

The polymerization method of the acrylic copolymer A and the acrylic copolymer B (hereinafter, collectively referred to as acrylic copolymer) used in the pressure-sensitive adhesive composition of the present invention is not particularly limited. As the polymerization method, known methods such as solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization can be applied. Among them, a method by solution polymerization is preferable in that a treatment process is relatively simple and can be performed in a short time in producing a pressure-sensitive adhesive composition by mixing a copolymer obtained by polymerization.

Solution polymerization is generally carried out by putting a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent used as necessary in a polymerization tank, and reacting with heating for several hours while stirring in a nitrogen stream or at the reflux temperature of the organic solvent. In this case, at least a part of an organic solvent, a monomer, a polymerization initiator and/or a chain transfer agent may be added in order.

As an organic solvent used in the polymerization reaction, for example, benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, aromatic naphtha, etc. Aromatic hydrocarbons, n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, aliphatic or alicyclic hydrocarbons such as terepine oil, ethyl acetate, n acetic acid -Esters such as butyl, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate, acetone, methyl ethyl ketone, methyl-i-butyl ketone, iso Ketones such as poron, cyclohexanone, methylcyclohexanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono Glycol ethers such as butyl ether, alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, t-butyl alcohol, etc. I can. These organic solvents may be used alone or in combination of two or more.

In the case of polymerization of the acrylic copolymer among organic solvents, it is preferable to use an organic solvent that is difficult to cause chain transfer during polymerization reactions such as esters and ketones. In particular, ethyl acetate, methyl ethyl ketone, acetone, and the like are preferable from the viewpoints of the solubility of the acrylic copolymer and the ease of polymerization reaction.

As the polymerization initiator, it is possible to use an organic peroxide, an azo compound, etc., which are usually used in solution polymerization.

Examples of organic peroxides include t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propylperoxy dicarbonate, di-2-ethyl Hexylperoxy dicarbonate, t-butylperoxypivalate, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t- Amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl) Propane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)butane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane, etc. are mentioned. .

As an azo compound, for example, 2,2'-azobis-i-butylnitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 2,2'-azobis-4-methoxy-2 , 4-dimethylvaleronitrile, etc. are mentioned.

Among the polymerization initiators, in polymerization of the acrylic copolymer, the use of a polymerization initiator that does not cause a graft reaction during the polymerization reaction is preferred, and an azobis-based polymerization initiator is particularly preferred. In this case, the amount of the polymerization initiator used is preferably in the range of 0.01 parts by mass to 2 parts by mass, and more preferably in the range of 0.1 parts by mass to 1 part by mass with respect to 100 parts by mass of the total amount of the monomers constituting the acrylic copolymer.

In the production of the acrylic copolymer, it is possible to use a chain transfer agent if necessary so long as the object and effect of the present invention are not impaired.

As a chain transfer agent, cyanoacetic acid; C1-C8 alkyl esters of cyanoacetic acid; Bromoacetic acid; C1-C8 alkyl esters of bromoacetic acid; aromatic compounds such as α-methylstyrene, anthracene, phenanthrene, fluorene, and 9-phenylfluorene; aromatic nitro compounds such as p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and p-nitrotoluene; Benzoquinone derivatives such as benzoquinone and 2,3,5,6-tetramethyl-p-benzoquinone; Borane derivatives such as tributylborane; Halogenation of carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, 3-chloro-1-propene, etc. Hydrocarbons; Aldehydes such as chloral and furaldehyde; Alkyl mercaptans having 1 to 18 carbon atoms; Aromatic mercaptans such as thiophenol and toluene mercaptan; Mercaptoacetic acid and C1-C10 alkyl esters of mercaptoacetic acid; Hydroxyalkyl mercaptans having 1 to 12 carbon atoms; Terpenes such as pinene and terpinolene; And the like.

The amount of the chain transfer agent used can be, for example, in the range of 0.005 parts by mass to 10.0 parts by mass per 100 parts by mass of the total amount of the monomers constituting the acrylic copolymer.

The polymerization temperature during the polymerization reaction is preferably in the range of about 30°C to 180°C, more preferably in the range of 50°C to 150°C. In particular, the polymerization temperature in the case of producing an acrylic copolymer is more preferably in the range of 50°C to 90°C, and still more preferably in the range of 50°C to 80°C.

(Isocyanate compound)

The pressure-sensitive adhesive composition of the present invention contains an isocyanate compound. The content of the isocyanate compound can be, for example, in the range of 0.4 equivalents to 2.2 equivalents with respect to the total amount of hydroxyl groups included in the acrylic copolymer A and the hydroxyl groups included in the acrylic copolymer B. In other words, the isocyanate compound in an amount in the range of 0.4 equivalents to 2.2 equivalents per 1 equivalent of the hydroxyl groups included in the acrylic copolymer A and the hydroxyl groups included in the acrylic copolymer B is contained. I can. By containing the isocyanate compound in an amount within the above range, an increase in adhesive strength after heat treatment can be further suppressed, and contamination to an adherend can be further suppressed.

Examples of the isocyanate compound include aromatic polyisocyanate compounds such as xylylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, and tolylene diisocyanate; Chain or cyclic aliphatic polyisocyanate compounds such as hexamethylene diisocyanate (HMDI), isophorone diisocyanate, and hydrogenated products of the above aromatic polyisocyanate compounds; Biuret, dimer, trimer, or pentamer of these polyisocyanate compounds; Adducts of these polyisocyanate compounds and polyol compounds, such as trimethylolpropane, etc. are mentioned. These isocyanate compounds may be used alone or in combination of two or more.

As the isocyanate compound, among others, in the case of being used for applications in which the transparency of the pressure-sensitive adhesive composition is important, from the group consisting of a chain or cyclic aliphatic polyisocyanate compound and a chain or cyclic aliphatic polyisocyanate compound, a biuret, dimer, trimer and adduct body At least one selected is preferred, and at least one selected from the group consisting of an isocyanate compound having an isocyanurate structure, which is a trimer of hexamethylene diisocyanate, an adduct body of hexamethylene diisocyanate, and a biuret body of hexamethylene diisocyanate. More preferable. Since these isocyanate compounds do not have a structure derived from an aromatic ring, the pressure-sensitive adhesive layer after heat treatment is hardly yellowed, and an adhesive film having more excellent transparency can be obtained.

As for the isocyanate compound, a commercial item can be used. As a commercial item, for example, "Colonate HX", "Colonate HL-S", "Colonate L", "Colonate 2031", "Colonate 2030", "Colonate 2234", "Colonate 2785", " Aquanate 200", "Aquanate 210" (or higher, manufactured by Nippon Polyurethane Co., Ltd.), "Smidule N3300", "Death Module N3400", "Semidule N-75" (above, Sumitomo Bayer Urethane Corporation product), 「 Duranate E-405-80T”, “Duranate 24A-100”, “Duranate TSE-100” (above, manufactured by Asahi Chemical Industries, Ltd.), “Takenate D-110N”, “Takenate D-120N”, Commercially available products such as "Takenate M-631N" and "MT-Olester NP1200" (above, manufactured by Mitsui Takeda Chemical Co., Ltd.) can be suitably used.

The content of the isocyanate compound in the pressure-sensitive adhesive composition of the present invention is more preferably 0.6 equivalents to 1.8 equivalents, and particularly 0.7 equivalents to 1.3 equivalents with respect to the total amount of the hydroxyl groups in the acrylic copolymer A and the hydroxyl groups in the acrylic copolymer B. It is more preferable to be. That is, it is more preferable that the isocyanate group contained in the isocyanate compound is in the range of 0.6 equivalents to 1.8 equivalents with respect to 1 equivalent of the total hydroxyl groups included in the acrylic copolymer A and the hydroxyl groups included in the acrylic copolymer B, In particular, it is more preferable that it is an amount in the range of 0.7 equivalents to 1.3 equivalents.

(Other ingredients)

In addition to the acrylic copolymer A, the acrylic copolymer B, and the isocyanate compound, the pressure-sensitive adhesive composition of the present invention may contain various additives, solvents, weather stabilizers, tackifiers, plasticizers, softeners, dyes, in amounts within a range that does not impair the effects of the pressure-sensitive adhesive composition. It may contain pigments, inorganic fillers, and polymers other than the acrylic copolymer A and the acrylic copolymer B. When the pressure-sensitive adhesive composition contains these components, the content can be appropriately set.

<Adhesive film>

The adhesive film of the present invention is provided with a base material and an adhesive layer provided on the base material and derived from the adhesive composition of the present invention. In the adhesive film of the present invention, the adhesive layer is constituted as a layer derived from the adhesive composition of the present invention, so that it is excellent in low staining property to an adherend in addition to adhesiveness. Accordingly, the productivity of the optical member can be improved and the yield can be improved.

The base material constituting the pressure-sensitive adhesive film of the present invention can be selected from any material as long as the pressure-sensitive adhesive layer can be formed thereon.

The base material is, for example, polyester resin, acetate resin, polyethersulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin from the viewpoint of inspection and management of optical members by perspective. And a sheet or film made of an acrylic resin or the like. Among them, a base material of a polyester resin is preferred from the viewpoint of surface protection performance, and a base material of a polyethylene terephthalate resin is particularly preferred from the viewpoint of practicality.

The thickness of the base material can be selected depending on the application and is not particularly limited, but is generally 500 μm or less. Among these, the preferable thickness is in the range of 5 µm to 300 µm, and about 10 µm to 200 µm can be illustrated as a more preferable range.

The method of forming the pressure-sensitive adhesive layer provided on the base material is not particularly limited, and can be performed by a method commonly used. For example, the pressure-sensitive adhesive composition of the present invention may be applied directly to a base material, which is a base film, as it is or diluted with a solvent, if necessary, and dried to remove the solvent.

As another method, first, the pressure-sensitive adhesive composition of the present invention is applied onto a release sheet such as paper or polyester film subjected to a release treatment with a silicone resin, etc., followed by heat drying to form a pressure-sensitive adhesive layer, and then the pressure-sensitive adhesive layer of the release sheet is The formed surface may be brought into contact with the base material and pressurized, and the pressure-sensitive adhesive layer may be transferred to the base material side.

A release film may be laminated as needed on the surface of the pressure-sensitive adhesive layer on the base material thus produced.

It is preferable that the pressure-sensitive adhesive layer is in a state in which the acrylic copolymer A and the acrylic copolymer B are crosslinked by an isocyanate compound contained in the pressure-sensitive adhesive composition. This makes it possible to achieve both the adhesiveness of the pressure-sensitive adhesive layer and the low-staining property to the adherend. The conditions for crosslinking the acrylic copolymer A and the acrylic copolymer B with an isocyanate compound are not particularly limited. For example, it can crosslink by heating an adhesive film.

The pressure-sensitive adhesive layer has sufficient adhesion to adherends such as optical members (the adhesive strength is sufficiently large when peeling off at a low speed), and can be easily peeled when peeling off at a medium speed (the adhesive strength when peeling off at a medium speed is not increased) It is desirable.

Furthermore, the pressure-sensitive adhesive layer has sufficient fluidity and has good conformability that allows the pressure-sensitive adhesive to sufficiently wet the adherend surface not only when used for an adherend with a smooth surface, but also when used for an adherend having minute irregularities on the surface ( In the case of cutting, it is preferable that the cutting end is not raised.

That is, the adhesive force of the 180 degree peel at 23° C. to the adherend of the pressure-sensitive adhesive layer preferably has an adhesive force (peel force) of 0.6 N/25 mm or less at a peel rate of 10 m/min (medium speed peeling). It is more preferable that it is 0.3N/25mm or less.

It can be easily peeled off because the adhesive force at the time of medium speed peeling is 0.6N/25mm or less. Particularly, the peelability in a wide width becomes good.

The thickness of the pressure-sensitive adhesive layer formed on the base material can be appropriately set according to the adhesive force required for the protective film or the surface roughness of the adherend. In general, it is in the range of 1 μm to 100 μm, preferably in the range of 5 μm to 50 μm, and more preferably in the range of 15 μm to 30 μm.

Examples of the use of the pressure-sensitive adhesive film of the present invention include a surface protective film for an optical member subjected to heat treatment such as hard coat PET, a surface protective film and a reinforcing film used in the manufacturing process of an electronic member such as a flexible printed circuit board. That is, the adhesive film of the present invention can be used as a heat-resistant adhesive film that protects or reinforces the surface in a heat treatment step and can be easily peeled off without contamination after the heat treatment step.

Among them, since the pressure-sensitive adhesive composition of the present invention has high transparency, the pressure-sensitive adhesive film provided with the pressure-sensitive adhesive layer derived from the pressure-sensitive adhesive composition of the present invention can be subjected to inspection steps such as appearance inspection while being adhered to the adherend. For this reason, it is suitable for use as a surface protective film for optical members such as hard coat PET.

Further, the surface protective film of the optical member is laminated on the surface of the optical member to protect the surface of the optical member from being contaminated or damaged. The optical member is subjected to heat treatment such as a high temperature dry printing process and an etching process while the surface protection film is laminated on the optical member. After that, peeling is removed from the optical member in a step where the surface protection is not required.

Example

Hereinafter, the present invention will be described in more detail by examples, but the present invention is not limited to the following examples unless it goes beyond the gist. In addition, unless otherwise specified, "parts" and "%" are based on mass.

-Preparation of acrylic copolymer A and acrylic copolymer B-

(Production Example A1)

100 parts of ethyl acetate, 66.3 parts of 2-ethylhexyl acrylate (2EHA) as an acrylic acid alkyl ester having no hydroxyl group, and 4-hydroxyl as an acrylate monomer having a hydroxyl group in a reactor equipped with a thermometer, agitator, reflux condenser and sequential dropping device. 5.7 parts of hydroxybutyl acrylate (4HBA) was added and the temperature in the reaction vessel was raised until reflux occurred while stirring. After 10 minutes from the start of reflux, a solution in which azobisisobutyronitrile (AIBN) was dissolved in ethyl acetate as a polymerization initiator was added dropwise, and the reaction was completed over an additional 120 minutes after the dropwise addition was completed. After completion of the reaction, it was diluted with ethyl acetate so that the solid content was 35% by mass to obtain a solution of the acrylic copolymer A1.

Table 1 shows the content (mass%), weight average molecular weight (Mw), and Tg values of 2EHA and 4HBA of the obtained acrylic copolymer A1. The weight average molecular weight (Mw, unit: only) and the Tg value were measured by the method previously described.

In addition, the "solid content" is the amount of residue obtained by removing volatile components such as a solvent from the solution of the acrylic copolymer A1.

(Production Examples A2 to A26)

In Preparation Example A1, the composition of the acrylate monomer having 2EHA and a hydroxyl group as an alkyl acrylate ester having no hydroxyl group was changed as shown in Table 1, and the molecular weight was adjusted as shown in Table 1 below by adjusting the amount of solvent or initiator. Solutions of acrylic copolymers A2 to A26 were obtained by the same method as in Production Example A1 except having adjusted. In the acrylic copolymer A17, 2-hydroxyethyl acrylate (2HEA) was used as an acrylate monomer having a hydroxyl group. Table 1 shows the composition (mass%), weight average molecular weight (Mw, unit: only), and Tg values of the obtained acrylic copolymers A2 to A26.

(Production Examples B1-B26)

In Preparation Example A1, 2-hydroxyethyl methacrylate (2HEMA) or 4-hydroxybutyl methacrylate (4HBMA) was used as a methacrylate monomer having a hydroxyl group instead of an acrylate monomer having a hydroxyl group, and the composition is shown in Table 1 A solution of acrylic copolymers B1 to B26 was obtained by the same method as in Production Example A1 except that the molecular weight was adjusted as shown in Table 1 below by changing the amount as shown in Table 1 below by adjusting the amount of the solvent and the amount of initiator. Table 1 shows the composition (mass%), weight average molecular weight (Mw, unit: only), and Tg values of the obtained acrylic copolymers B1 to B26.

(Example 1)

-Preparation of adhesive composition-

A solution of 60 parts by mass of the solution (solid content: 35 parts by mass) of the acrylic copolymer A1 obtained in Preparation Example A1 as the acrylic copolymer A, and a solution (solid content: 35 parts by mass) of the acrylic copolymer B1 obtained in Preparation Example B1 as the acrylic copolymer B ) 40 parts by mass and 5.5 parts by mass of an isocyanate compound (manufactured by Sumidal N3300 Sumica Bayer Urethane Co., Ltd.) (included in the isocyanate compound with respect to 1 equivalent of the total hydroxyl group of the hydroxyl groups contained in the acrylic copolymer A1 and the hydroxyl groups contained in the acrylic copolymer B1) The resulting isocyanate group was 1.00 equivalent) and 2.1 parts by mass of a crosslinking catalyst (Adecastab OT-1, manufactured by ADEKA Co., Ltd., active ingredient: 100 parts by mass) diluted 300 times with acetylacetone and sufficiently stirred to obtain a pressure-sensitive adhesive composition. . Using the obtained pressure-sensitive adhesive composition, a test pressure-sensitive adhesive film was produced according to the following method for producing a test pressure-sensitive adhesive film, and various tests were performed.

-Production of test adhesive film-

Using the pressure-sensitive adhesive composition obtained above, a test pressure-sensitive adhesive film was produced as follows.

Apply adhesive composition on polyethylene terephthalate (PET) film (Tetoron film HPE 50㎛, manufactured by Teijin DuPont Film Co., Ltd.) so that the coating volume after drying is 20g/m2, and dry it at 100℃ for 60 seconds with a hot air circulation dryer To form an adhesive layer. Thereafter, a PET film was placed on the release film surface-protected with a silicone release agent so that the pressure-sensitive adhesive layer was in contact with each other, followed by pressing and bonding with a pressure nip roll. Then, curing was performed for 2 days in an environment of 23°C and 50% RH to obtain an adhesive film for testing.

-Measurement and evaluation-

[One. Initial adhesion]

The release film was peeled from the obtained adhesive film piece by cutting the adhesive film for test prepared above into a size of 25 mm x 150 mm.

Using a double-sided tape (NITTO No.5000N, manufactured by Nitto Electric Co., Ltd.) as an adherend, a polyimide film (Kapton Film 100H, manufactured by Toray DuPont Corporation) is attached to the SUS plate in advance, and adhered to the polyimide film. A test sample was prepared by attaching a film and pressing a 2 kg rubber roll by reciprocating one. This test sample was allowed to stand for 1 hour in an environment at 23°C and 50% RH. Thereafter, the adhesive force at 180° peeling when the adhesive film was peeled in the direction of the long side (150 mm) was measured under conditions of a peel rate of 10 m/min (medium speed peeling). Table 3 shows the measurement results.

[2. Adhesion after heat treatment]

The release film was peeled from the adhesive film piece obtained by cutting the test adhesive film prepared above into a size of 25 mm × 150 mm, attached to a polyimide film (Kapton Film 100H, manufactured by Toray DuPont), and a 2 kg rubber roll was reciprocated. Pressed.

This test sample was left to stand in an environment at 23°C and 50% RH for 1 hour, then subjected to heat treatment for 1 hour in an environment at 150°C, and then left to stand in an environment at 23°C and 50% RH for 1 hour. Thereafter, the adhesive force at 180° peeling when the adhesive film was peeled in the direction of the long side (150 mm) was measured under conditions of a peel rate of 10 m/min (medium speed peeling). Table 3 shows the measurement results.

In addition, the "evaluation" column of "adhesion" in Table 3 was described according to the following criteria.

A: When the adhesion after heat treatment is more than 0.05 N/25 mm and not more than 0.3 N/25 mm (workability is very good).

B: When the adhesive force after heat treatment is more than 0.01N/25mm and not more than 0.05N/25mm or more than 0.3N/25mm and less than 0.45N/25mm (workability is good).

C: After heat treatment, the adhesive strength is more than 0.45 N/25 mm and 0.6 N/25 mm or less (workability is poor, but within the allowable range).

D: After heat treatment, the adhesive strength is more than 0.6 N/25 mm or less than 0.01 N/25 mm (defective).

[3. Pollution (water contact angle after peeling)]

2 μL of pure water was added dropwise onto the surface of the polyimide film after peeling the test protective film, which was used to measure the adhesive force after the heat treatment in the above 2, and 30 seconds after the dropping, a contact angle measuring device (Contact angle meter CA-D, Kyowa Interface Science Co., Ltd.) was used to measure the contact angle (θ1) of water. The absolute value (Δθ=|θ1-θ0|) of the difference between the obtained value and the water contact angle (θ0=64°) of the polyimide film to which the test protective film was not attached was used as an index of contamination. Table 3 shows the results.

In addition, the "evaluation" column of "contamination" in Table 3 was described according to the following criteria.

A: When Δθ is 2.0 or less (pollution property is low and very good).

B: When Δθ is more than 2.0 and not more than 4.5 (pollution property is low and good).

C: When Δθ is more than 4.5 and not more than 7.0 (pollution property is low, but within the allowable range).

D: When Δθ exceeds 7.0 (contamination is high and poor).

[4. Zipping]

If the difference in strength and weakness of the adhesive force of the adhesive film is large, zipping (crunchy sound) occurs when peeling from the adherend. The occurrence of zipping can cause contamination or wrinkles in places with high adhesion. In the evaluation of the zipping, the ratio (maximum adhesive force/minimum adhesive force) to the minimum value of the maximum value of the adhesive force of the adhesive film measured in the measurement of the adhesive force after the heat treatment in the above 2 was calculated and shown in Table 3.

In addition, the "evaluation" column of "ziping" in Table 3 was described according to the following criteria.

A: When the value of the ratio of the maximum value of the adhesive force to the minimum value is 1.0 or less (the occurrence of zipping is sufficiently suppressed and very good).

B: When the value of the ratio of the maximum value of the adhesive force to the minimum value is more than 1.0 and not more than 2.0 (the occurrence of zipping is suppressed and is good).

C: When the value of the ratio to the minimum value of the maximum value of the adhesive force is more than 2.0 and not more than 5.0 (zipping occurred but within the allowable range).

D: When the value of the ratio of the maximum value of the adhesive force to the minimum value is more than 5.0 (zipping occurs remarkably).

(Examples 2 to 22, Comparative Examples 1 to 4)

The types and ratios of the acrylic copolymer A and the acrylic copolymer B are changed as shown in Table 2, and further, the amount of the isocyanate compound is the sum of the hydroxyl groups contained in the acrylic copolymer A and the hydroxyl groups contained in the acrylic copolymer B 1 A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that the isocyanate group contained in the isocyanate compound was adjusted to an amount of 1.00 equivalent relative to the equivalent weight. Using the produced adhesive composition, it carried out similarly to Example 1, and produced the adhesive film for testing. About the obtained adhesive film for tests, it carried out similarly to Example 1, and evaluated. Table 3 shows the results.

As shown in Table 3, the sum of the hydroxyl value a of the acrylic copolymer A and the hydroxyl value b of the acrylic copolymer B is in the range of 40 mgKOH/g to 90 mgKOH/g, and the hydroxyl value of a is the ratio of the hydroxyl value to b The adhesive film having a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive compositions of Examples 1 to 22 in which (hydroxyl value a/hydroxyl value b) is in the range of 0.5 to 7.0 was satisfactory or within an acceptable range in both adhesion and staining evaluation.

The pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition of Comparative Example 1 in which the total of the hydroxyl value a of the acrylic copolymer A and the hydroxyl value b of the acrylic copolymer B is less than 40 mgKOH/g had too high adhesive strength and poor adhesive strength.

The pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition of Comparative Example 2 in which the total of the hydroxyl value a of the acrylic copolymer A and the hydroxyl value b of the acrylic copolymer B exceeded 90 mgKOH/g had no adhesive strength of the pressure-sensitive adhesive layer.

The pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition of Comparative Example 3 in which the ratio of the hydroxyl value a to the hydroxyl value b (hydroxyl value a/hydroxyl value b) was less than 0.5 had high contamination.

The pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition of Comparative Example 4 in which the ratio of the hydroxyl value of a to the hydroxyl value of b (hydroxyl value a/hydroxyl value b) exceeds 7.0 has a large increase in adhesive strength by heat treatment and markedly zipping. Occurred and was outside the allowable range.

As for the disclosure of Japanese Patent Application No. 2013-112947 filed on May 29, 2013 and Japanese Patent Application No. 2014-058818 filed on March 20, 2014, the entirety of which is incorporated herein by reference.

All documents, patent applications, and technical specifications described in this specification are incorporated herein by reference to the same extent as when individual publications, patent applications, and technical specifications are specifically and individually recorded to be incorporated by reference.

Claims (10)

An acrylic copolymer A comprising a structural unit Ax derived from an (meth)acrylate alkyl ester having no hydroxyl group and a structural unit a derived from an acrylate monomer having a hydroxyl group;
Containing the structural unit Bx derived from the (meth)acrylic acid alkyl ester having no hydroxyl group and the structural unit b derived from the methacrylate monomer having a hydroxyl group, and having a weight average molecular weight smaller than the weight average molecular weight of the acrylic copolymer A Acrylic copolymer B,
Containing an isocyanate compound,
The sum of the hydroxyl value a of the acrylic copolymer A and the hydroxyl value b of the acrylic copolymer B is in the range of 40 mgKOH/g to 90 mgKOH/g,
The ratio of the hydroxyl value of a to b is in the range of 0.5 to 7.0. The method according to claim 1,
The pressure-sensitive adhesive composition in which the ratio of the weight average molecular weight of the acrylic copolymer B to the weight average molecular weight of the mixture of the acrylic copolymer A and the acrylic copolymer B is in the range of 0.1 to 0.5. The method according to claim 1 or 2,
The pressure-sensitive adhesive composition in which the hydroxyl value of a has a ratio of the hydroxyl value to b in the range of 0.5 to 2.0. The method according to claim 1 or 2,
The pressure-sensitive adhesive composition in which the content rate of the structural unit a in the acrylic copolymer A with respect to the total structural units is 30% by mass or less. The method according to claim 1 or 2,
The pressure-sensitive adhesive composition wherein the content of the structural unit b in the acrylic copolymer B is 10% by mass or more with respect to the total structural units. The method according to claim 1 or 2,
The pressure-sensitive adhesive composition in which the content of the isocyanate compound is 0.4 to 2.2 equivalents based on the amount of hydroxyl groups contained in the acrylic copolymer A and the acrylic copolymer B. The method according to claim 1 or 2,
The acrylic copolymer A and the acrylic copolymer B each have a glass transition temperature (Tg) of -40 °C or less. The method according to claim 1 or 2,
The pressure-sensitive adhesive composition in which the weight average molecular weight of the acrylic copolymer A is in the range of 400,000 to 1.5 million, and the weight average molecular weight of the acrylic copolymer B is in the range of 100,000 to 500,000. With a base material,
An adhesive film having an adhesive layer derived from the adhesive composition according to claim 1 or 2 provided on the base material. An adhesive film attaching step of attaching the adhesive film according to claim 9 to the surface of an article so that the adhesive layer and the surface are in contact,
A heat treatment step of heating the article to which the adhesive film is pasted in the affixing step,
A method for treating an article comprising a peeling step of peeling the adhesive film from the surface of the article heated in the heat treatment step.