JP6738693B2 - Adhesive composition for protective film and protective film - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive composition for a protective film and a protective film.

Generally, an optical member such as a polarizing plate used in a liquid crystal display device is often protected by a protective film. The protective film prevents contamination and damage on the surface of the optical member that is likely to occur in each process such as punching, inspection, transportation, and assembly of the liquid crystal display panel, and peels off when the protection of the surface of the optical member becomes unnecessary. To be removed.

When static electricity is generated when the protective film is peeled from the optical member, dust and the like are likely to adhere to the optical member, and the circuit of the liquid crystal display device may be damaged. Therefore, the protective film is required to have a property capable of preventing static electricity generated during peeling (hereinafter, also referred to as “antistatic property”).
Further, the pressure-sensitive adhesive layer of the protective film has such an adhesiveness as not to cause displacement on the surface of the adherend or to drop off from the surface of the adherend while the protection of the adherend is required. In addition, it is required to be easily peeled from the adherend (hereinafter, also referred to as “peelability”) when the adherend has no need to be protected.
Furthermore, in recent years, for the purpose of improving work efficiency, peeling of a protective film from an adherend tends to be performed under high-speed peeling conditions (for example, 30 m/min), and even during high-speed peeling, it is easy to adhere the protective film. It is required to be peelable from the body (hereinafter, also referred to as “high-speed peelability”).

As an antistatic pressure-sensitive adhesive composition having excellent antistatic property, a pressure-sensitive adhesive composition containing a (meth)acrylic polymer having an alkyl (meth)acrylate as a main component and an acid value of 29 or less and a fluorine-containing lithium imide salt is used. It is disclosed (for example, see Patent Document 1).
Further, as a pressure-sensitive adhesive composition having excellent antistatic properties and reduced contamination to protected objects, an alkali metal salt is contained, and (meth)acrylic acid alkylene oxide adduct 15% by weight to 100% by weight is a single amount. An adhesive composition used as a body component has been disclosed (see, for example, Patent Document 2).

JP, 2005-306937, A JP, 2005-314579, A

In the antistatic pressure-sensitive adhesive composition described in Patent Document 1, since the (meth)acrylic polymer contains an acidic group, the wettability is likely to change depending on the material of the adherend due to the polar effect of the acidic group. For this reason, when the antistatic pressure-sensitive adhesive composition described in Patent Document 1 is used, it is difficult to make the peeling conditions constant during high-speed peeling regardless of the material of the adherend. Furthermore, when the antistatic pressure-sensitive adhesive composition described in Patent Document 1 is used, the antistatic property may be poor depending on the material of the adherend. Further, in the antistatic pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition described in Patent Document 2, it may be difficult to obtain sufficient antistatic property depending on the material of the adherend, and high-speed peelability may not be obtained. There is a nature.
Therefore, in order for the conventional pressure-sensitive adhesive composition for a protective film to have an adhesive force and an antistatic property that can be easily peeled from an adherend during high-speed peeling, in accordance with the material of the adherend It is necessary to change the composition of the agent. Since there are many materials for the adherend, it is actually difficult to prepare the pressure-sensitive adhesive composition according to the material for the adherend, and a pressure-sensitive adhesive composition that does not depend on the material for the adherend is required.

The present invention has been made in view of the above, and an object of the present invention is to provide a pressure-sensitive adhesive composition for a protective film and a protective film which are excellent in high-speed peelability and antistatic property regardless of the material of the adherend. ..

Specific means for solving the problems include the following aspects.
<1> The acid value is 9 mgKOH/g to 65 mgKOH/g, and the content of the constituent units derived from the monomer having a polyalkylene oxide chain exceeds 1 mass% with respect to the mass of all constituent units. Of less than 20% by mass, a (meth)acrylic polymer, a cross-linking agent, and an antistatic agent.

<2> The pressure-sensitive adhesive composition for a protective film according to <1>, wherein the (meth)acrylic polymer includes a structural unit represented by the following general formula (1).

In general formula (1), R ¹ represents a hydrogen atom or a methyl group. L represents a divalent linking group composed of at least one selected from the group consisting of an alkylene group, an arylene group, a carbonyl group and an oxygen atom.

<3> The (meth)acrylic polymer contains a structural unit derived from an alkyl(meth)acrylate, and the content ratio of the structural unit derived from the alkyl(meth)acrylate is 65 with respect to the mass of all the structural units. The pressure-sensitive adhesive composition for a protective film according to <1> or <2>, which is mass% to 99 mass %.

<4> Further, a (meth)acrylic oligomer having a weight average molecular weight of 3,000 to 20,000 is included, and the content of the (meth)acrylic oligomer is 100 parts by mass of the (meth)acrylic polymer. On the other hand, the pressure-sensitive adhesive composition for a protective film according to any one of <1> to <3>, which is 0.05 parts by mass to 5.00 parts by mass.

<5> The (meth)acrylic oligomer contains a structural unit derived from a monomer having a polyalkylene oxide chain, and the content of the structural units derived from the monomer having a polyalkylene oxide chain is The pressure-sensitive adhesive composition for a protective film according to <4>, which is 5% by mass to 30% by mass with respect to the mass of the constituent unit.

<6> The pressure-sensitive adhesive composition for a protective film according to any one of <1> to <5>, wherein the crosslinking agent is a metal chelate compound.

<7> A protective film having a pressure-sensitive adhesive layer, which is a crosslinked product of the pressure-sensitive adhesive composition for a protective film according to any one of <1> to <6>, and a substrate.

According to the present invention, it is possible to provide a pressure-sensitive adhesive composition for a protective film and a protective film which are excellent in high-speed peelability and antistatic property regardless of the material of the adherend.

It is explanatory drawing explaining the method of evaluating the adhesive force and antistatic property at the time of high-speed peeling.

Hereinafter, the pressure-sensitive adhesive composition for a protective film and the protective film of the present invention will be described in detail. In addition, in this invention, "-" in a numerical range means including the numerical value before and behind "-".
In the present specification, the amount of each component in the composition refers to the total amount of the plurality of substances present in the composition, unless a plurality of substances corresponding to each component are present in the composition. Means

In the present specification, the (meth)acrylic polymer or the (meth)acrylic oligomer is a monomer in which at least the main component of the monomers constituting the monomer has a (meth)acryloyl group. Means a polymer or oligomer. The monomer as the main component means a monomer having the highest content (mass %) among the monomers constituting the polymer or oligomer. The (meth)acrylic polymer may be, for example, a polymer in which the content of the constituent unit derived from the (meth)acrylate monomer as the main component is 50% by mass or more of all the constituent units.
In the present specification, "(meth)acrylic" is meant to include both "acrylic" and "methacrylic", and "(meth)acrylate" is intended to include both "acrylate" and "methacrylate". “(Meth)acryloyl” is meant to include both “acryloyl” and “methacryloyl”.

<<Adhesive composition for protective film>>
The pressure-sensitive adhesive composition for a protective film (hereinafter, also referred to as “pressure-sensitive adhesive composition”) of the present invention is a monomer having an acid value of 9 mgKOH/g to 65 mgKOH/g and having a polyalkylene oxide chain. It contains a (meth)acrylic polymer having a content of the constituent units derived from more than 1 mass% and less than 20 mass% with respect to the mass of all constituent units, a cross-linking agent, and an antistatic agent.

Since the pressure-sensitive adhesive composition has the above-mentioned constitution, a protective film excellent in high-speed peelability and antistatic property can be obtained regardless of the material of the adherend. The reason for this is not clear, but it can be inferred as follows.

Generally, the releasability of the protective film during high-speed peeling tends to largely depend on the material of the adherend. In particular, in the pressure-sensitive adhesive composition containing a constitutional unit derived from a monomer having an acidic group, the wettability to the adherend is changed by the polar effect of the acidic group, and therefore, depending on the material of the adherend. The adhesive strength may be different. Therefore, there is a tendency for peeling to be difficult during high-speed peeling. Further, in the pressure-sensitive adhesive composition containing a polymer having an acid value of 1 mgKOH/g or more, the antistatic performance tends to decrease.

In the pressure-sensitive adhesive composition of the present invention, the content of the constituent units derived from the monomer having a polyalkylene oxide chain is more than 1 mass% and less than 20 mass% with respect to the mass of all constituent units (meta. Since it contains an acrylic polymer, it is presumed that it suppresses the surface free energy of the pressure-sensitive adhesive layer, which tends to increase due to the polar effect of acidic groups. A large number of constituent units derived from a monomer having a polyalkylene oxide chain are likely to exist at the interface between the adherend and the pressure-sensitive adhesive composition. Therefore, even if the pressure-sensitive adhesive composition of the present invention contains a (meth)acrylic polymer having an acid value of 9 mgKOH/g to 65 mgKOH/g, the wettability of the adherend due to the polar effect of acidic groups It is possible to suppress the change of the above, and it is possible to exhibit a constant adhesive force regardless of the material or state of the adherend. In addition, the pressure-sensitive adhesive composition of the present invention has an acid value of the (meth)acrylic polymer in the above range and contains a cross-linking agent, so that it has appropriate releasability and also has a high-speed peeling property. Since it is possible to make the hardness so that the force is appropriately reduced, the high-speed peelability tends to be excellent.

Furthermore, since the pressure-sensitive adhesive composition of the present invention contains an antistatic agent, even if the acid value of the (meth)acrylic polymer is within the above range, it is possible to suppress deterioration of the antistatic property. In particular, by using a (meth)acrylic polymer containing a constitutional unit derived from a monomer having a polyalkylene oxide chain at a specific content and an antistatic agent in combination, deterioration of antistatic property is further suppressed. Therefore, the antistatic property tends to be excellent regardless of the material of the base material.
As described above, the protective film formed from the pressure-sensitive adhesive composition of the present invention is presumed to have excellent high-speed peelability and antistatic property regardless of the material of the adherend.
Hereinafter, details of each component of the pressure-sensitive adhesive composition of the present invention will be described.

<(Meth)acrylic polymer>
The pressure-sensitive adhesive composition of the present invention has an acid value of 9 mgKOH/g to 65 mgKOH/g, and the content of constituent units derived from a monomer having a polyalkylene oxide chain is relative to the mass of all constituent units. And more than 1% by mass and less than 20% by mass of (meth)acrylic polymer (hereinafter, also referred to as "specific (meth)acrylic polymer"). The pressure-sensitive adhesive composition of the present invention may further contain a (meth)acrylic polymer different from the specific (meth)acrylic polymer, if necessary.

The specific (meth)acrylic polymer includes a structural unit derived from a monomer having a polyalkylene oxide chain. Examples of polyalkylene oxide chains include polyethylene oxide chains and polypropylene oxide chains. As the polyalkylene oxide chain, a polyethylene oxide chain is preferable from the viewpoint of obtaining sufficient antistatic properties regardless of the material of the adherend.

Examples of the monomer having a polyalkylene oxide chain include 2-(ethoxyethoxy)ethyl acrylate, polyethylene glycol (meth)acrylate, methoxy polyethylene glycol (meth)acrylate, methoxy polypropylene glycol (meth)acrylate, polypropylene glycol (meth). ) Acrylate and methoxy polyethylene glycol (meth)acrylate.
Among these, as a monomer having a polyalkylene oxide chain, methoxy polyethylene glycol (meth)acrylate or methoxy polypropylene glycol (from methoxy polypropylene glycol (from the viewpoint of exhibiting antistatic property and high-speed peelability) regardless of the material of the adherend. (Meth)acrylate is preferable, and methoxypolyethylene glycol (meth)acrylate is more preferable.

The average number of moles of alkylene oxide units added to the polyalkylene oxide chain is preferably 2 to 25 moles, and more preferably 4 to 15 moles from the viewpoint of obtaining a sufficient antistatic effect regardless of the material of the adherend. preferable.
The average addition mole number of alkylene oxide units in the polyalkylene oxide chain means the average addition mole number of alkylene oxide units in the contained monomer.

The content of the constituent unit derived from the monomer having a polyalkylene oxide chain contained in the specific (meth)acrylic polymer is more than 1 mass% and less than 20 mass% with respect to the mass of all constituent units.
When the content of the constituent unit derived from the monomer having a polyalkylene oxide chain is 1% by mass or less, the antistatic property may not be sufficiently exhibited depending on the material of the adherend. When the content of the structural unit derived from the monomer having a polyalkylene oxide chain is 20% by mass or more, high-speed peelability may not be sufficiently exhibited depending on the material of the adherend. From the above viewpoint, the content of the constituent unit derived from the monomer having a polyalkylene oxide chain is preferably 2% by mass to 18% by mass, more preferably 3% by mass to 15% by mass, and 3% by mass to 10% by mass. Mass% is more preferable.

The specific (meth)acrylic polymer includes a structural unit derived from a monomer having an acidic group.
Examples of the monomer having an acidic group include (meth)acrylic acid, carboxylethyl(meth)acrylate, carboxylpentyl(meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, and 2-(meth ) Acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, ω-carboxy-polycaprolactone mono(meth)acrylate, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxy Monomers having a carboxy group such as a (meth)acrylic acid ester having a carboxy group represented by ethyl fumaric acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid and 2-(meth)acryloyloxyethyl phthalic acid And a monomer having a phosphoric acid group represented by 2-(meth)acryloyloxyethyl acid phosphate.

As the structural unit derived from the monomer having an acidic group, a structural unit derived from the monomer having a carboxy group is preferable. The constitutional unit derived from the monomer having a carboxy group may include one type alone or two or more types.

As the structural unit derived from the (meth)acrylic acid ester having a carboxy group, a structural unit represented by the following general formula (1) is preferable. When the structural unit represented by the general formula (1) is included, the carboxy group is bonded to (meth)acrylic acid via L, so that the adhesive force during high-speed peeling can be further suppressed. .. More specifically, from the viewpoint of steric hindrance, the monomer having a carboxyl group represented by the general formula (1) will be described later as compared with a monomer having a short-chain carboxyl group such as (meth)acrylic acid. This is because the reactivity with the crosslinking agent is significantly improved.

In the structural unit represented by the general formula (1), L represents a divalent linking group composed of at least one selected from the group consisting of an alkylene group, an arylene group, a carbonyl group and an oxygen atom, and R ¹ Represents a hydrogen atom or a methyl group. However, when L contains an oxygen atom, the oxygen atom forms a group bonded to at least one selected from the group consisting of an alkylene group, an arylene group and a carbonyl group, and is bonded to -COO- and -CO-. To do.

The alkylene group for L may be linear, branched or cyclic. When the alkylene group in L is linear or branched, the alkylene group preferably has 1 to 12 carbon atoms, more preferably 2 to 10 carbon atoms, and even more preferably 2 to 6 carbon atoms.
Examples of the alkylene group having 1 to 12 carbon atoms include methylene group, ethylene group, propylene group, butylene group, pentylene group, hexylene group, heptylene group, octylene group, nonylene group, decylene group and dodecylene group.

When the alkylene group in L is cyclic, examples of L include an alicyclic group (cyclo ring group). The cyclic alkylene group may be a cyclocyclic group having 3 to 5 carbon atoms, and specific preferred examples thereof include cyclohexylene.

The arylene group for L preferably has 6 to 10 carbon atoms, and more preferably a phenylene group. The bonding position in the arylene group is not particularly limited. For example, when the arylene group is a phenylene group, the bonding position may be any of 1-position and 4-position, 1-position and 2-position, and 1-position and 3-position, and 1-position and 2-position are preferable.

The alkylene group and the arylene group in L may have a substituent. Examples of the substituent include an alkyl group having 1 to 12 carbon atoms, a halogen atom, a hydroxyl group, an amino group, a nitro group, a phenyl group and the like.

The divalent linking group represented by L in the general formula (1) is a divalent linking group represented by the following general formula (2a) or general formula (2b) from the viewpoint of antistatic property and high-speed peelability. Is preferred.

In formulas (2a) and (2b), R ^{21 to} R ²⁴ each independently represent an alkylene group having 1 to 12 carbon atoms or an arylene group having 6 to 10 carbon atoms. n shows the number of 0-10, m shows the number of 1-10.
The alkylene group for R ^{21 to} R ²⁴ may be linear, branched or cyclic, preferably linear or branched, and more preferably linear.
The bonding position in the arylene group of R ^{21 to} R ²⁴ is not particularly limited. For example, when the arylene group is a phenylene group or when the cyclic alkylene group is, for example, a cyclohexylene group, the bonding position may be any of 1-position and 4-position, 1-position and 2-position, and 1-position and 3-position. Well, 1st and 2nd place are preferable.

Each of the alkylene groups for R ²¹ and R ²² independently has preferably 2 to 10 carbon atoms, and more preferably 2 to 6 carbon atoms. Examples of the alkylene group for R ²¹ and R ²² include a methylene group, an ethylene group, a propylene group, a butylene group, and a cyclohexylene group. The alkylene groups in R ²¹ and R ²² may be the same or different.
The arylene groups for R ²¹ and R ²² are each independently preferably a phenylene group or a naphthylene group, and more preferably a phenylene group.

R ²¹ and R ²² in the general formula (2a) are each independently preferably an alkylene group having 1 to 12 carbon atoms, more preferably an alkylene group having 2 to 6 carbon atoms, from the viewpoints of antistatic properties and high-speed peelability. Further, a linear or branched alkylene group having 2 to 6 carbon atoms is more preferable.

In the general formula (2a), n represents a number of 0-10. When the specific (meth)acrylic polymer includes only one type of structural unit represented by the general formula (1), n is an integer, and when two or more types are included, n is an average rational number. Becomes 0-4 are preferable and, as for n, 0-2 are more preferable.

In the general formula (2b), the alkylene group for R ²³ is preferably an alkylene group having 1 to 12 carbon atoms, more preferably an alkylene group having 2 to 6 carbon atoms, and still more preferably an alkylene group having 2 to 4 carbon atoms. Examples of the alkylene group for R ²³ include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group and a dodecylene group.

In the general formula (2b), the alkylene group for R ²⁴ is a linear or branched alkylene group having 2 to 6 carbon atoms, a cyclic alkylene group having 4 to 8 carbon atoms (divalent cyclo ring group), or An arylene group having 6 to 10 carbon atoms is preferable, a linear or branched alkylene group having 2 to 4 carbon atoms, a cyclic alkylene group having 5 to 6 carbon atoms, or a phenylene group is more preferable, and 2 to 4 carbon atoms. The linear or branched alkylene group, cyclohexylene group, or phenylene group of is more preferable.

In the general formula (2b), m represents a number of 1 to 10. When the specific (meth)acrylic polymer contains only one type of constitutional unit represented by the general formula (1), m is an integer, and when two or more types are contained, m is an average rational number. Becomes 1-4 are preferable and, as for m, 1-2 are more preferable.

The constitutional unit represented by the general formula (1) is obtained by, for example, copolymerizing a monomer represented by the following general formula (1a) with another monomer constituting the specific (meth)acrylic polymer. Thus, it becomes possible to introduce it into a specific (meth)acrylic polymer.

In the general formula (1a), ^{R 1} and L are respectively the same as ^{R 1} and L in the general formula (1).

The monomer represented by the general formula (1a) may be one produced by a conventional method or one appropriately selected from commercially available monomers. Among the monomers represented by the general formula (1a), examples of the monomer in which L is represented by the general formula (2a) include, for example, (meth)acrylic acid dimer (preferably n in the general formula (2a)). Of about 0.4) and ω-carboxy-polycaprolactone mono(meth)acrylate (preferably, the average value of n in the general formula (2a) is about 1.0).
As these monomers, for example, those commercially available as "Aronix M-5600" and "Aronix M-5300" (all manufactured by Toagosei Co., Ltd., trade name) can be used.

Further, as the monomer in which L is represented by the general formula (2b) among the monomers represented by the general formula (1a), for example, 2-(meth)acryloyloxyethylsuccinic acid, 2-(meth) ) Acryloyloxyethyl fumaric acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid and 2-(meth)acryloyloxyethyl phthalic acid. Examples of these monomers include “light ester HO-MS”, “light acrylate HOA-MS(N)”, “light acrylate HOA-HH(N)” and “light acrylate HOA-MPL(N)”. (These are products of Kyoeisha Kagaku Co., Ltd., trade names).

The content of the structural unit represented by the general formula (1) is preferably 4% by mass to 30% by mass, and 5% by mass to 20% by mass, based on the mass of all structural units of the specific (meth)acrylic polymer. Is more preferable, and 8% by mass to 15% by mass is further preferable.
When the content of the structural unit represented by the general formula (1) is 4% by mass or more, the adhesive force during high-speed peeling tends to be suppressed to a lower level. When the content of the structural unit represented by the general formula (1) is 30% by mass or less, it tends to be excellent in suppression of decrease in adhesive strength due to the material of the adherend and antistatic property.

The specific (meth)acrylic polymer contains at least one structural unit derived from an alkyl (meth)acrylate, in addition to a structural unit derived from a monomer having a polyalkylene oxide chain and a structural unit having an acidic group. It is preferable.

Examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-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( Examples thereof include (meth)acrylate, isomyristyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate and isobornyl (meth)acrylate. The alkyl group of the alkyl (meth)acrylate may be linear, branched or cyclic.
The constitutional unit derived from the alkyl (meth)acrylate may include one type alone or two or more types.

From the viewpoint of easily adjusting the adhesive strength suitable for the protective film, the alkyl(meth)acrylate is preferably an alkyl(meth)acrylate having a glass transition temperature of −30° C. or lower when formed into a homopolymer.

The glass transition temperature of the homopolymer was measured using a differential scanning calorimeter (DSC) (manufactured by Seiko Instruments, Inc., EXSTAR6000) as the homopolymer in a nitrogen stream in a measurement sample of 10 mg and a heating rate of 10° C./min. The measurement was performed under the conditions, and the inflection point of the obtained DSC curve was taken as the glass transition temperature of the homopolymer.

Examples of the alkyl(meth)acrylate having a glass transition temperature of −30° C. or lower when formed into a homopolymer include, for example, n-butyl acrylate (−57° C.), 2-ethylhexyl acrylate (−76° C.), and n-dodecyl. Methacrylate (-65°C), n-octyl acrylate (-65°C), isooctyl acrylate (-58°C), isononyl acrylate (-58°C), isomyristyl acrylate (-56°C) and 2-acryloyloxyethyl-. Examples include succinic acid (-40°C).

Among these, from the viewpoint of easily adjusting the adhesive strength suitable for a protective film, n-butyl acrylate and 2- At least one selected from ethylhexyl acrylate is preferable.

The specific (meth)acrylic polymer is a structural unit derived from an alkyl (meth)acrylate (preferably a structural unit derived from an alkyl (meth)acrylate having a glass transition temperature of -30°C or lower when made into a homopolymer). When containing, the total content of the structural unit derived from the alkyl (meth)acrylate (preferably the structural unit derived from the alkyl (meth)acrylate having a glass transition temperature of -30° C. or less when formed into a homopolymer) is 65 mass%-99 mass% are preferable with respect to the mass of all the structural units, 75 mass%-97 mass% are more preferable, 80 mass%-95 mass% are still more preferable. When the total content of the constituent units derived from alkyl (meth)acrylate is 65% by mass or more, the conformability (wettability) tends to be more excellent. When the total content of the structural units derived from alkyl (meth)acrylate is 99% by mass or less, the adhesive force at the time of high speed peeling does not become too high, and the high speed peelability tends to be more excellent.

The specific (meth)acrylic polymer further includes other structural units other than the structural unit derived from the monomer having a polyalkylene oxide chain, the structural unit having an acidic group, and the structural unit derived from the alkyl (meth)acrylate. May be included. As the monomer capable of forming another structural unit, a monomer having a polyalkylene oxide chain, a structural unit having an acidic group and a monomer represented by a structural unit derived from an alkyl (meth)acrylate is used. It is not particularly limited as long as it can be polymerized, and can be appropriately selected depending on the purpose.

Examples of the monomer capable of forming other structural units include (meth)acrylic monomers having a hydroxyl group represented by 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, and phenoxy. Aromatic ring-containing (meth)acrylic monomers represented by ethyl (meth)acrylate and benzyl (meth)acrylate, aminoethyl (meth)acrylate, and nitrogen atoms represented by dimethylaminoethyl (meth)acrylate Having (meth)acrylic monomers, styrene, aromatic monovinyl monomers represented by α-methylstyrene, acrylonitrile, vinyl cyanide monomers represented by methacrylonitrile, vinyl formate, vinyl acetate, Examples thereof include vinyl carboxylate monomers typified by vinyl propionate.

The acid value of the specific (meth)acrylic polymer is 9 mgKOH/g to 65 mgKOH/g. When the acid value of the specific (meth)acrylic polymer exceeds 65 mgKOH/g, the formed pressure-sensitive adhesive layer becomes too hard when the pressure-sensitive adhesive composition is crosslinked to form a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is formed. The adhesive strength of the adherend becomes low, and the protective film may fall off from the surface of the adherend during the period when the adherend needs to be protected. Further, the antistatic property tends to be lowered. When the acid value of the specific (meth)acrylic polymer is less than 9 mgKOH/g, the pressure-sensitive adhesive layer is too soft and the adhesive force is apt to be high, and peeling tends to be difficult at the time of high-speed peeling. From the viewpoint of further improving the high-speed peelability, the acid value of the specific (meth)acrylic polymer is preferably 9 mgKOH/g to 50 mgKOH/g, more preferably 9 mgKOH/g to 35 mgKOH/g, and 16 mgKOH/g to 25 mgKOH/g. g is more preferred.

The acid value of the specific (meth)acrylic polymer or the (meth)acrylic oligomer described below is determined by the following calculation formulas.

Acid value (mgKOH/g)={(A/100)÷B}×56.1×1000×C
A = Content (% by mass) of monomers having an acidic group in all monomers used for the specific (meth)acrylic polymer or (meth)acrylic oligomer
B=molecular weight of monomer having acidic group used in specific (meth)acrylic polymer or (meth)acrylic oligomer C=number of acidic groups contained in one molecule of monomer having acidic group 56.1 is the molecular weight of KOH.
Further, when there are plural kinds of monomers having an acidic group, the acid value can be calculated by summing the values calculated by the above formula for each monomer.

The weight average molecular weight (Mw) of the specific (meth)acrylic polymer is not particularly limited. The weight average molecular weight (Mw) of the specific (meth)acrylic polymer is preferably 100,000 to 1,000,000, more preferably 100,000 to 600,000, and even more preferably 100,000 to 400,000. When the weight average molecular weight (Mw) of the specific (meth)acrylic polymer is 100,000 or more, it is possible to more effectively suppress the specific (meth)acrylic polymer from remaining on the adherend during high-speed peeling, and to adhere It tends to cause less pollution to the body. When the weight average molecular weight (Mw) of the specific (meth)acrylic polymer is 1,000,000 or less, the conformability (wettability) tends to be more excellent.

The weight average molecular weight (Mw) of the specific (meth)acrylic polymer or the later-described (meth)acrylic oligomer is a value measured according to the following (1) to (3).

(1) A specific (meth)acrylic polymer or (meth)acrylic oligomer solution is applied to release paper and dried at 100° C. for 2 minutes to obtain a film-shaped specific (meth)acrylic polymer or (meth)acrylic An oligomer is obtained.
(2) Using the film-shaped specific (meth)acrylic polymer or (meth)acrylic oligomer obtained in (1) above and tetrahydrofuran, a sample solution having a solid content concentration of 0.2% by mass is obtained. ..
(3) Under the following conditions, the weight average molecular weight (Mw) of the specific (meth)acrylic polymer or (meth)acrylic oligomer is measured as a standard polystyrene conversion value using gel permeation chromatography (GPC). ..

(conditions)
GPC: HLC-8220 GPC [manufactured by Tosoh Corporation]
Column: TSK-GEL GMHXL 4 used Mobile phase solvent: Tetrahydrofuran Flow rate: 0.6 mL/min Column temperature: 40°C

The content of the specific (meth)acrylic polymer in the pressure-sensitive adhesive composition can be appropriately selected according to the purpose. The content of the specific (meth)acrylic polymer is preferably 80% by mass to 99% by mass, more preferably 85% by mass to 99% by mass, and 90% by mass to 98% by mass based on the total mass of the solid content of the pressure-sensitive adhesive composition. Mass% is more preferable. The total solid content means the total mass of the residue obtained by removing volatile components such as a solvent from the pressure-sensitive adhesive composition.

The method for producing the specific (meth)acrylic polymer is not particularly limited. For example, it can be produced by polymerizing a monomer by a known polymerization method represented by solution polymerization, emulsion polymerization, suspension polymerization and bulk polymerization. Among these polymerization methods, solution polymerization is preferable because the treatment method is relatively simple and can be performed in a short time.

In solution polymerization, generally, a predetermined organic solvent, a monomer, a polymerization initiator, a catalyst and, if necessary, a chain transfer agent are charged in a polymerization tank, and the mixture is stirred in a nitrogen stream or under reflux of the organic solvent for several hours with stirring. The reaction is carried out by heating for a time. The polymerization initiator is not particularly limited and, for example, an azo compound can be used.
The weight average molecular weight (Mw) and number average molecular weight (Mn) of the (meth)acrylic polymer are adjusted to desired molecular weights by adjusting the reaction temperature, the reaction time, the amount of organic solvent, and the type and amount of the catalyst. it can.

[(Meth)acrylic oligomer]
The pressure-sensitive adhesive composition of the present invention preferably contains a (meth)acrylic oligomer having a weight average molecular weight of 3,000 to 20,000.
When the pressure-sensitive adhesive composition further contains a (meth)acrylic oligomer, the content of the antistatic agent can be suppressed. Further, when the pressure-sensitive adhesive composition contains the polyether-modified silicone described below, the content of the polyether-modified silicone tends to be suppressed by further containing the (meth)acrylic oligomer. As a result, when the protective film is peeled off from the adherend, a part of the pressure-sensitive adhesive layer is less likely to remain on the adherend, which tends to suppress the occurrence of contamination on the adherend. Furthermore, there is a tendency to suppress white turbidity caused by a decrease in the compatibility of the specific (meth)acrylic polymer.

The (meth)acrylic oligomer preferably contains a structural unit derived from a monomer having a carboxy group from the viewpoint of suppressing the occurrence of contamination of the adherend. The kind of the monomer having a carboxy group is not particularly limited.
Examples of the constitutional unit derived from the monomer having a carboxy group include the constitutional unit derived from the monomer having a carboxy group in the above-mentioned specific (meth)acrylic polymer. The constituent unit derived from the monomer having a carboxy group is preferably a constituent unit derived from (meth)acrylic acid.

The content of the structural unit derived from the monomer having a carboxy group in the (meth)acrylic oligomer is 0.1% by mass based on the mass of all the structural units from the viewpoint of lowering the contamination of the adherend. -10 mass% is preferred, 0.5 mass%-7.0 mass% is more preferred, and 1.0 mass%-5.0 mass% is still more preferred.

The (meth)acrylic oligomer preferably contains a structural unit derived from an alkyl(meth)acrylate. When the (meth)acrylic oligomer contains a structural unit derived from an alkyl(meth)acrylate, the adhesive strength can be easily adjusted.
Examples of the alkyl (meth)acrylate include the alkyl (meth)acrylate in the specific (meth)acrylic polymer described above.
The alkyl (meth)acrylate contained in the (meth)acrylic oligomer has a carbon number of 4 to 12 from the viewpoint of exhibiting high durability even when the pressure-sensitive adhesive layer is exposed to a high temperature and high humidity environment. Are preferred, alkyl(meth)acrylates having a branched chain and having 4 to 12 carbon atoms are more preferred, and 2-ethylhexyl methacrylate is even more preferred.

From the viewpoint of durability, the content of the structural unit derived from alkyl(meth)acrylate contained in the (meth)acrylic oligomer is preferably 65% by mass to 99% by mass, and 75% by mass with respect to the mass of all the structural units. % To 95 mass% is more preferable, and 80 mass% to 90 mass% is still more preferable.

The (meth)acrylic oligomer preferably contains a structural unit derived from a monomer having a polyalkylene oxide chain. Examples of the monomer having a polyalkylene oxide chain include the monomers having a polyalkylene oxide chain in the above-mentioned specific (meth)acrylic polymer.

When the (meth)acrylic oligomer contains a constitutional unit derived from a monomer having a polyalkylene oxide chain, the average number of moles of alkylene oxide units added to the polyalkylene oxide chain is preferably 2 to 25 moles, Regardless of the material of the adherend, 9 mol to 23 mol is more preferable from the viewpoint of obtaining a sufficient antistatic effect. The average number of added moles has the same meaning as the average number of added moles of the polyalkylene oxide chain in the above-mentioned specific (meth)acrylic polymer.

The content of the structural unit derived from the monomer having a polyalkylene oxide chain in the (meth)acrylic oligomer is preferably 5% by mass to 30% by mass, and 5% by mass to 20% by mass based on the mass of all structural units. % Is more preferable, and 5% by mass to 15% by mass is particularly preferable.
When the content of the constituent unit derived from the monomer having a polyalkylene oxide chain is 5% by mass or more, the antistatic property tends to be more excellent. When the content of the constituent unit derived from the monomer having a polyalkylene oxide chain is 30% by mass or less, the content of the monomer remaining without being polymerized after the polymerization reaction is suppressed, and the deposition It is possible to lower pollution to the body.

The (meth)acrylic oligomer has a constitutional unit derived from a monomer having a carboxy group, a constitutional unit derived from an alkyl(meth)acrylate, and a polyalkylene oxide chain within a range in which the effect of the present invention is exhibited. Other constituent units other than the constituent units derived from the monomer may be contained.
In this case, a constitutional unit derived from a monomer having a carboxy group, a constitutional unit derived from an alkyl(meth)acrylate, and a unit amount having a polyalkylene oxide chain, which occupy all the constitutional units of the (meth)acrylic oligomer The total content of the structural units derived from the body is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, based on the mass of all structural units.

Examples of the monomer capable of forming other structural units include (meth)acrylic monomers having a hydroxyl group represented by 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, and phenoxy. Aromatic ring-containing (meth)acrylic monomers represented by ethyl (meth)acrylate and benzyl (meth)acrylate, aminoethyl (meth)acrylate, and nitrogen atoms represented by dimethylaminoethyl (meth)acrylate Having (meth)acrylic monomers, styrene, aromatic monovinyl monomers represented by α-methylstyrene, acrylonitrile, vinyl cyanide monomers represented by methacrylonitrile, vinyl formate, vinyl acetate, Examples thereof include vinyl carboxylate monomers typified by vinyl propionate.

When the pressure-sensitive adhesive composition of the present invention contains a (meth)acrylic oligomer, the (meth)acrylic oligomer may be a single type, or two or more types having different monomer compositions, weight average molecular weights and the like. May be

The content of the (meth)acrylic oligomer is preferably 0.05 parts by mass to 5.00 parts by mass with respect to 100 parts by mass of the specific (meth)acrylic polymer. When the content of the (meth)acrylic oligomer is 0.05 parts by mass or more, the adhesive force at the time of high-speed peeling does not become too high, and the high-speed peelability tends to be excellent. When the content of the (meth)acrylic oligomer is 5.00 parts by mass or less, the protective film is prevented from falling off from the surface of the adherend during the period when the protection of the adherend is required, In addition, the high speed peelability tends to be more excellent. From the above viewpoint, the content of the (meth)acrylic oligomer is more preferably 0.10 parts by mass to 3.00 parts by mass, further preferably 0.10 parts by mass to 2.50 parts by mass.

The acid value of the (meth)acrylic oligomer is preferably 10 mgKOH/g to 200 mgKOH/g, more preferably 15 mgKOH/g to 100 mgKOH/g, and even more preferably 15 mgKOH/g to 50 mgKOH/g.
When the acid value of the (meth)acrylic oligomer is 10 mgKOH/g or more, it becomes possible to sufficiently crosslink the specific (meth)acrylic polymer and the crosslinking agent described later, and moreover the high-speed peelability is further improved. Tends to improve. When the acid value of the (meth)acrylic oligomer is 200 mgKOH/g or less, the antistatic property tends to be better maintained.
The method for calculating the acid value of the (meth)acrylic oligomer is as described above.

The weight average molecular weight of the (meth)acrylic oligomer is preferably 3,000 to 20,000. When the weight average molecular weight of the (meth)acrylic oligomer is 3,000 or more, it tends to be possible to prevent the (meth)acrylic oligomer from remaining on the adherend. Further, when the weight average molecular weight of the (meth)acrylic oligomer is 20,000 or less, the haze of the pressure-sensitive adhesive layer tends to be lowered. From the above viewpoint, the weight average molecular weight of the (meth)acrylic oligomer is preferably 4,000 to 15,000, more preferably 5,000 to 10,000.

The weight average molecular weight (Mw) of the (meth)acrylic oligomer is measured in the same manner as the method for measuring the weight average molecular weight (Mw) of the specific (meth)acrylic polymer described above.

<Crosslinking agent>
The pressure-sensitive adhesive composition of the present invention contains at least one crosslinking agent. By including a crosslinking agent, it becomes possible to form a crosslinked structure by reacting with an acidic group represented by a carboxy group in a specific (meth)acrylic polymer. The crosslinking agent is not particularly limited as long as it can form a crosslinked structure by reacting with the acidic group in the specific (meth)acrylic polymer contained in the pressure-sensitive adhesive composition of the present invention, and examples thereof include an epoxy compound and an isocyanate. Examples thereof include compounds, aziridine compounds, and metal chelate compounds. Compared with the case of using an isocyanate compound, an epoxy compound, or the like, a metal chelate compound is preferable as the cross-linking agent from the viewpoint that the cross-linking reaction is faster and the curing completion time can be shortened.

Examples of the metal chelate compound include compounds in which a polyvalent metal atom is coordinately bonded to an organic compound. Examples of polyvalent metal atoms include Al, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, and Ti. Can be mentioned. Among these, Al, Zr, and Ti are preferable, and Al is more preferable, from the viewpoint of low cost and availability.
An oxygen atom etc. are mentioned as an atom in the organic compound to which a polyvalent metal atom coordinate-bonds. Examples of the organic compound include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, ketone compounds and the like.
As the metal chelate compound, aluminum trisacetylacetonate, which is particularly stable and easy to handle, can be preferably used. The metal chelate compounds may be used alone or in combination of two or more.

The equivalent of the cross-linking agent is preferably 0.3 equivalent to 2.0 equivalents, more preferably 0.4 equivalent to 1.5 equivalents, more preferably 0.1 equivalent to 1 equivalent of the acidic group of the specific (meth)acrylic polymer. 6 equivalents to 1.2 equivalents are more preferred.
When the content of the cross-linking agent is 0.3 equivalent or more, the adhesive force at the time of high-speed peeling tends to be suppressed to be low, and when the content of the cross-linking agent is 2.0 equivalent or less, the adherend and the protective film are removed. There is a tendency that it becomes possible to impart an adhesive strength to the adhesive layer to such an extent that it will not be abruptly peeled.

The equivalent of the cross-linking agent is a value calculated by the following formula.
Equivalent weight=(A×B/C)/(D ₁ ×E ₁ /F ₁ +D ₂ ×E ₂ /F ₂ +... +D _n ×E _n ×F _n ).
A = Metal valence of the cross-linking agent B = Number of parts by mass of the cross-linking agent (amount as solid content)
C = molecular weight of cross-linking agent
D ₁ , D ₂ ,... D _n =content rate (% by mass) of each monomer having an acidic group in all monomers used for the specific (meth)acrylic polymer
E ₁ , E ₂ ,... E _n =Number of acidic groups contained in one molecule of each monomer having an acidic group F ₁ , F ₂ ,... F _n =Specific (meth)acrylic polymer , The molecular weight of each monomer having an acidic group, n represents the number of types of monomers used, for example, the (meth) acrylic monomer used is one In some cases, only D ₁ is used in the calculation and D ₂ ... D _n are not used in the calculation.

<Antistatic agent>
The pressure-sensitive adhesive composition of the present invention contains at least one antistatic agent.
Examples of the antistatic agent include ionic compounds such as alkali metal salts and organic salts. As the antistatic agent, an alkali metal salt and an organic salt are preferable because they have a high ionic dissociation property and easily exhibit an excellent antistatic property even when a small amount is used.

The alkali metal salt is not particularly limited as long as it is a metal salt having lithium ion (Li ⁺ ), sodium ion (Na ⁺ ), potassium ion (K ⁺ ), rubidium (Rb ⁺ ) and the like as cations.
Examples of the combination of alkali metal salts include, for example, at least one cation selected from the group consisting of Li ⁺ , Na ⁺ and K ⁺ , and 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 selected from the group consisting of and is preferably used.

Among them, as the alkali metal salt, LiBr, LiI, LiBF ₄ , LiPF ₆ , LiSCN, LiClO ₄ , LiCF ₃ SO ₃ , Li(FSO ₂ ) ₂ N, Li(CF ₃ SO ₂ ) are used as the alkali metal salt from the viewpoint of antistatic properties. _At least one lithium salt selected from the group consisting of ₂ N, Li(C ₂ F ₅ SO ₂ ) ₂ N and Li(CF ₃ SO ₂ ) ₃ C is preferable, and LiClO ₄ , LiCF ₃ SO ₃ , Li(CF). More preferred is at least one lithium salt selected from the group consisting of ₃ SO ₂ ) ₂ N, Li(C ₂ F ₅ SO ₂ ) ₂ N and Li(CF ₃ SO ₂ ) ₃ C. These alkali metal salts may be used alone or in combination of two or more.

The organic salt preferably contains an organic cation and its counter ion.
The melting point of the organic salt is preferably 30° C. or higher. When the melting point of the organic salt is 30° C. or higher, migration to the adherend is small and contamination tends to be suppressed, which is preferable.
Examples of the organic cation include an imidazolium cation, a pyridinium cation, an alkylpyrrolidinium cation, an ammonium cation having an organic group as a substituent, a sulfonium cation having an organic group as a substituent, and a phosphonium cation having an organic group as a substituent. Can be mentioned. Among these, at least one selected from the group consisting of pyridinium cations and imidazolium cations is preferable as the organic cation from the viewpoint of antistatic properties.

The anion serving as the counter ion of the organic cation is not particularly limited and may be either an inorganic anion or an organic anion. Among them, as the anion portion serving as a counter ion of the organic cation, a fluorine-containing anion containing a fluorine atom is preferable, and a hexafluorophosphate anion (PF ₆ ⁻ ) is more preferable, because it is more excellent in antistatic properties.

Preferable examples of the organic salt include pyridinium salt, imidazolium salt, alkylammonium salt, alkylpyrrolidinium salt and alkylphosphonium salt. Among them, the organic salt is preferably at least one selected from the group consisting of a pyridinium salt and an imidazolium salt, and more preferably a salt of a pyridinium cation or an imidazolium cation and a fluorine-containing anion.

The content of the antistatic agent is preferably 0.05 parts by mass to 1.50 parts by mass, and more preferably 0.10 parts by mass to 1.00 parts by mass, relative to 100 parts by mass of the specific (meth)acrylic polymer. .. When the content of the antistatic agent is 0.05 parts by mass or more based on 100 parts by mass of the specific (meth)acrylic polymer, the antistatic property tends to be more excellent. When the content of the antistatic agent is 1.50 parts by mass or less, the efficiency of the antistatic effect with respect to the content of the antistatic agent tends to be higher.

[Polyether-modified silicone]
The pressure-sensitive adhesive composition of the present invention preferably contains at least one kind of polyether-modified silicone. Further, since the polyether-modified silicone has a reactive group, the pressure-sensitive adhesive film can be more easily peeled from the adherend, and the pressure-sensitive adhesive film having less contamination on the adherend tends to be obtained.

The polyether-modified silicone more effectively exhibits antistatic properties when used together with a specific (meth)acrylic polymer having a constitutional unit represented by the general formula (1), an antistatic agent, and a crosslinking agent. It is possible.

When the polyether-modified silicone has a polyether group and a hydroxy group at the end of the polyether group, it exhibits more excellent antistatic properties and tends to effectively suppress contamination of the adherend. In particular, since the polyether-modified silicone has a polyalkylene oxide chain having a hydroxy group at the terminal in the molecule, the antistatic property tends to be effectively exhibited. Since the polyether-modified silicone is unevenly distributed near the surface of the pressure-sensitive adhesive layer derived from the pressure-sensitive adhesive composition, the polyalkylene oxide chain interacting with the alkali metal salt tends to be localized near the surface of the pressure-sensitive adhesive layer. .. As a result, it is presumed that the surface resistance value on the surface of the pressure-sensitive adhesive layer is reduced. By using the polyether-modified silicone together, the amount of the antistatic agent in the pressure-sensitive adhesive composition tends to be suppressed.

The polyether-modified silicone contains a constitutional unit derived from a dialkylsiloxane and a constitutional unit derived from an alkyl(hydroxypolyalkyleneoxyalkyl)siloxane, from the viewpoint of lowering the antistatic property and the stain on the adherend. Polysiloxane compounds are preferred.
The alkyl group in the dialkylsiloxane preferably has 1 to 4 carbon atoms, and more preferably 1 carbon atom.
The polyalkylene oxide chain in the alkyl(hydroxypolyalkyleneoxyalkyl)siloxane preferably has 2 to 4 carbon atoms, and more preferably 2 to 3 carbon atoms. The number of carbon atoms in the polyalkylene oxide chain in the alkyl(hydroxypolyalkyleneoxyalkyl)siloxane is preferably 1 to 100, more preferably 10 to 100. The alkyl group in the alkyl(hydroxypolyalkyleneoxyalkyl)siloxane preferably has 1 to 4 carbon atoms.

When the polyether-modified silicone contains a structural unit derived from a dialkylsiloxane and a structural unit derived from an alkyl(hydroxypolyalkyleneoxyalkyl)siloxane, the content of the structural unit derived from the dialkylsiloxane is preferably 100 or less, 1 -80 is more preferable. In addition, the number of constituent units derived from an alkyl(hydroxypolyalkyleneoxyalkyl)siloxane is preferably 2 to 100, more preferably 2 to 80.

The polyether-modified silicone is preferably a polysiloxane compound represented by the following general formula (3), from the viewpoints of tackiness, antistatic property, and lowering of contamination on an adherend.

In general formula (3), p is the number of repeating dimethylsiloxane constitutional units and represents a number of 0 to 100. q is the repeating number of the methyl propylene siloxane structural unit which has a polyethylene oxide chain, and represents the number of 2-100. In addition, a is the number of repeating ethylene oxide constitutional units and represents a number of 1 to 100. Here, when the compound represented by general formula (3) is an aggregate of a plurality of compounds, p, q, and a are average values as an aggregate of compounds and are rational numbers.

The repeating number a of the ethylene oxide constitutional unit is a number of 1 to 100, preferably a number of 10 to 100. When a is 1 or more, sufficient conductivity is obtained, and the antistatic property tends to be further improved. Moreover, when a is 100 or less, the compatibility with other components constituting the pressure-sensitive adhesive composition is improved, and the transparency of the pressure-sensitive adhesive layer tends to be further improved.

Moreover, the repeating number p of the dimethylsiloxane structural unit is a number of 0 to 100, and preferably a number of 1 to 80. Furthermore, the repeating number q of the methyl propylene siloxane constitutional unit is a number of 2 to 100, preferably a number of 2 to 80. When q is 2 or more, sufficient conductivity is obtained, and the antistatic property tends to be further improved. Further, when q is 100 or less, the compatibility with other components constituting the pressure-sensitive adhesive composition is improved, and the transparency of the pressure-sensitive adhesive layer tends to be improved.

The weight average molecular weight of the polyether-modified silicone is not particularly limited and may be, for example, 5,000 to 20,000, preferably 6,000 to 15,000.

Further, the HLB value of the polyether-modified silicone is not particularly limited. The HLB value is preferably 5 to 16 and more preferably 7 to 15 from the viewpoint of compatibility with the resin, surface uneven distribution, and tackiness.
The HLB value represents a scale showing the balance between hydrophilicity and hydrophobicity of the polyether-modified silicone. In the present specification, the HLB value follows the definition of the Griffin method calculated by the following formula, but when the polyether-modified silicone is a commercial product, its catalog data is preferentially adopted.
HLB={(sum of formula weight of hydrophilic group portion)/(molecular weight of polyether modified silicone)}×20

The polyether-modified silicone may have a dimethylsiloxane constitutional unit and a methylpropylenesiloxane constitutional unit having a polyethylene oxide chain in the molecule. Each of these structural units may form a block copolymer or a random copolymer.

Specific examples of the polyether-modified silicone represented by the general formula (3) include "SF-8428", "FZ-2162" and "SH-3773M" [above, manufactured by Toray Dow Corning Co., Ltd.]. Can be mentioned.

The polyether modified silicone may be selected from the above commercial products. The polyether-modified silicone can also be obtained by grafting an organic compound having an unsaturated bond and a polyethylene oxide chain to a dimethylpolysiloxane main chain having silicon hydride by a hydrosilylation reaction.

The content of the polyether-modified silicone is preferably 0.05 parts by mass to 1.00 parts by mass, more preferably 0.05 parts by mass to 0.70 parts by mass with respect to 100 parts by mass of the specific (meth)acrylic polymer. It is preferably 0.05 part by mass to 0.30 part by mass.
When the content of the polyether-modified silicone is 0.05 parts by mass or more, the antistatic property tends to be more excellent. When the content of the polyether-modified silicone is 1.00 parts by mass or less, the generation of contamination (cumin) on the adherend is suppressed, and the compatibility with the specific (meth)acrylic polymer decreases. It tends to be possible to suppress the occurrence of white turbidity.

The pressure-sensitive adhesive composition may include a polysiloxane compound represented by the general formula (3) and a dimethylpolysiloxane compound having a structure different from that of the general formula (3) and containing a polyethyleneoxy group.
Examples of the dimethylpolysiloxane compound having a structure different from that of the general formula (3) and containing a polyethylene oxide chain include, for example, a compound in which the terminal of the polyethylene oxide chain is an alkoxy group or an acyloxy group, and the polyethylene oxide chain has a side chain. However, compounds included in the main chain or at the end are included.

Specific examples of the dimethylpolysiloxane compound having a structure different from that of the general formula (3) and containing a polyethylene oxide chain include, for example, “BY-16-201”, “FZ-77”, “FZ-2104”, "FZ-2110", "FZ-2203", "FZ-2207", "FZ-2208", "L-7001", "L-7002", "SF-8427", "SH-3749" and "SH". -8400" (above, manufactured by Toray Dow Corning Co., Ltd.).

When the pressure-sensitive adhesive composition has a structure different from that of the general formula (3) and contains a dimethylpolysiloxane compound containing a polyethylene oxide chain, its content is 0. The amount is preferably 05% by mass or less, more preferably 0.03% by mass or less.

[Other ingredients]
The pressure-sensitive adhesive composition contains, in addition to a specific (meth)acrylic polymer, a cross-linking agent, an antistatic agent, and (meth)acrylic oligomer and polyether modified silicone which are optional components, a weather resistance stabilizer, if necessary. , Tackifiers, plasticizers, softening agents, release aids, dyes, pigments, inorganic fillers, surfactants and the like can be contained as appropriate.

≪Protective film≫
The protective film of the present invention has a pressure-sensitive adhesive layer, which is a cross-linked product of the pressure-sensitive adhesive composition of the present invention, and a substrate. The protective film of the present invention, which has the pressure-sensitive adhesive layer derived from the pressure-sensitive adhesive composition of the present invention, tends to have excellent high-speed peelability and antistatic property regardless of the material of the adherend.

The base material used for the protective film of the present invention is not particularly limited as long as the pressure-sensitive adhesive layer can be formed on the base material.
The base material is a polyester resin, an acetate resin, a polyether sulfone resin, a polycarbonate resin, a polyamide resin, a polyimide resin, a polyolefin resin, or an acrylic resin from the viewpoint of inspection and management of optical members by fluoroscopy. A film using a resin such as Among them, as the substrate, a film using a polyester resin is preferable from the viewpoint of surface protection performance, and in consideration of practicality, a film using a polyethylene terephthalate (PET) resin is more preferable.

The thickness of the substrate can be generally 500 μm or less, preferably 5 μm to 300 μm, and more preferably 10 μm to 200 μm.

An antistatic layer may be provided on one side or both sides of the substrate. Further, the surface of the base material on the side where the pressure-sensitive adhesive layer is provided may be subjected to corona discharge treatment or the like in order to improve the adhesion to the pressure-sensitive adhesive layer.

A pressure-sensitive adhesive layer derived from the pressure-sensitive adhesive composition of the present invention is provided on the substrate.
As a method for forming the pressure-sensitive adhesive layer, for example, a method of diluting the pressure-sensitive adhesive composition as it is or with an appropriate solvent as necessary, applying this to a substrate, and then drying to remove the solvent is adopted. can do.
In addition, first, a pressure-sensitive adhesive composition is applied onto a release sheet made of an appropriate film such as paper or polyester film that has been subjected to a release treatment with a silicone resin, and dried by heating to form a pressure-sensitive adhesive layer, Next, a method of pressing the pressure-sensitive adhesive layer side of the release sheet to the base material and transferring the pressure-sensitive adhesive layer to the base material can also be adopted.

The pressure-sensitive adhesive layer in the present invention is a pressure-sensitive adhesive layer obtained by crosslinking a specific (meth)acrylic polymer with a crosslinking agent. This makes it possible to suppress the adhesive force of the adhesive layer during high-speed peeling to a low level.
The conditions for crosslinking the specific (meth)acrylic polymer with the crosslinking agent are not particularly limited. For example, curing at a temperature of 23° C. and 50% RH for several tens of minutes to several days completes the crosslinking reaction of the pressure-sensitive adhesive composition.

The thickness of the pressure-sensitive adhesive layer formed on the substrate can be appropriately set depending on the pressure-sensitive adhesive strength required for the protective film, the surface roughness of the optical member, and the like. The thickness of the pressure-sensitive adhesive layer is generally 1 μm to 100 μm, preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm.

When the adhesive force of the adhesive layer is high, it tends to be difficult to peel from the adherend during high-speed peeling over a large area. Therefore, the adhesive force (peeling force) at a peeling speed of 30 m/min (high-speed peeling) is 2. It is preferably less than 00 N/25 mm, more preferably 1.00 N/25 mm or less.
From the viewpoint of preventing the protective film from falling off from the surface of the adherend during the period when protection of the adherend is required, the adhesive force (peeling force) at a peeling speed of 30 m/min (high-speed peeling) is , 0.15 N/25 mm is preferable, and 0.20 N/25 mm or more is more preferable.

The use of the protective film of the present invention is not particularly limited, and for example, the protective film of the present invention may be laminated on the surface of the optical member to protect the surface of the optical member from being contaminated or damaged. The protective film of the present invention may be adhered to a metal plate such as iron or stainless steel (SUS) to protect the surface of the metal plate from being contaminated or damaged.

When the protective film is used for the optical member, the optical member is subjected to each process such as punching, inspection, transportation, and assembly of the liquid crystal display panel with the protective film laminated on the optical member, and if necessary. Then, a heating and pressurizing treatment such as an autoclave treatment and a high temperature aging treatment is performed, and when the surface protection becomes unnecessary, the optical member is peeled and removed.

Examples of the optical member include a member that constitutes a device (optical device) such as an image display device and an input device, or a member used for these devices. Specific examples of the optical member include a polarizing plate, a wavelength plate, a retardation plate, an optical compensation film, a brightness enhancement film, a light guide plate, a reflection film, an antireflection film, a transparent conductive film (ITO film) and the like.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

(Production Example A-1)
-Production of (meth)acrylic polymer (A-1)-
70.0 parts by mass of ethyl acetate was placed in a reaction vessel equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a reflux condenser, and n-butyl acrylate (BA) 60.0 as a monomer was placed in another vessel. Parts by mass, 2-ethylhexyl acrylate (2EHA) 24.9 parts by mass, Aronix M-5300 (monomer represented by general formula (1a), manufactured by Toagosei Co., Ltd.) 10.0 parts by mass, methoxypolyethylene glycol acrylate (Average number of moles of alkylene oxide units added: 9) 5.1 parts by mass of (MePEGA) were added and mixed to obtain a monomer mixture. Of this monomer mixture, 20.0% by mass was added to the reaction vessel, and then the air in the reaction vessel was replaced with nitrogen gas, and then azobisisobutyronitrile (hereinafter referred to as "AIBN") was used as a polymerization initiator. Also referred to as 0.01 parts by mass, and the temperature of the mixture in the reaction vessel was raised to 85° C. in a nitrogen atmosphere with stirring to start the initial reaction. After the initial reaction was almost completed, the remaining monomer mixture (80.0% by mass), ethyl acetate (15.0 parts by mass), and AIBN (0.10 parts by mass) were successively added to the mixture for about 2 hours, followed by reaction. And further reacted for 2 hours. Then, a solution prepared by dissolving 0.10 parts by mass of AIBN in 25.0 parts by mass of ethyl acetate was added dropwise to the above mixture over 1 hour, and the mixture was further reacted for 1.5 hours. After the reaction was completed, a solution of (meth)acrylic polymer (A-1) was obtained.
The solid content of the solution of the (meth)acrylic polymer (A-1) was 48.0% by mass. Table 1 shows the acid value and weight average molecular weight (Mw) of the obtained (meth)acrylic polymer (A-1).
The "solid content" is the residue obtained by removing the solvent from the solution of the (meth)acrylic polymer. The acid value and the weight average molecular weight (Mw) are obtained by the method described above.

The acid value was calculated as follows.
Acid value (mgKOH/g)={(A/100)÷B}×56.1×1000×C
A=Content (% by mass) of monomers having an acidic group in all monomers used for the (meth)acrylic polymer or the (meth)acrylic oligomer: 10.0
B=molecular weight of Aronix M-5300 which is a monomer having an acidic group which is a constituent unit of the (meth)acrylic polymer (A-1): 300.4
C=Number of acidic groups contained in one molecule of monomer having acidic group: 1
Acid value={(10.0/100)÷300.4}×56.1×1000×1=18.7

(Production Examples A-2 to A-21)
-Production of (meth)acrylic polymers (A-2) to (A-21)-
In Production Example A-1, except that the monomer composition shown in Table 1 was changed and the amount of the polymerization initiator was appropriately adjusted, the same procedure as in Production Example A-1 was performed ((meth)acrylic polymer (A -2) to (A-21) solutions were produced. The acid value and weight average molecular weight (Mw) of the obtained (meth)acrylic polymer are shown in Table 1.
The acid value and the weight average molecular weight (Mw) are obtained by the method described above.

(Production Example B)
-Production of (meth)acrylic oligomer (B)-
In a reaction vessel equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, a condenser, and a dropping funnel, 100.0 parts by mass of methyl ethyl ketone, methoxypolyethylene glycol methacrylate (average added mole number of alkylene oxide units: 23) (MePEGMA) 10 0.0 mass part was added, and the mixture was heated to the reflux temperature while stirring under a nitrogen atmosphere. Preliminarily mixed in the dropping funnel with 85.0 parts by mass of 2-ethylhexyl methacrylate (2EHMA), 5.0 parts by mass of acrylic acid (AA), 100.0 parts by mass of methyl ethyl ketone, and azobisisobutyronitrile. 0 parts by mass of the mixed solution was added, and the mixture was sequentially added to the reaction vessel at the reflux temperature over 120 minutes. After that, the reaction was continued for 240 minutes while maintaining the reflux temperature to complete the reaction.
The solid content of the obtained solution of the (meth)acrylic oligomer (B) was 33.0% by mass. Table 1 shows the acid value and weight average molecular weight (Mw) of the (meth)acrylic oligomer (B).
The acid value and the weight average molecular weight (Mw) are obtained by the method described above.

The abbreviations in Table 1 are as follows. In addition, "-" in Table 1 indicates that the corresponding component is not included.
BA: n-butyl acrylate 2EHA: 2-ethylhexyl acrylate 2HEA: 2-hydroxyethyl acrylate 2EHMA: 2-ethylhexyl methacrylate 2MTA: 2-methoxyethyl acrylate M-5300: ω-carboxy-polycaprolactone (n ≈2) Monoacrylate (monomer represented by general formula (1a)) (Brand name: Aronix M-5300, manufactured by Toagosei Co., Ltd.)
-AA: acrylic acid-HOA-MS: 2-acryloyloxyethyl-succinic acid (monomer represented by general formula (1a)) (trade name: Light acrylate HOA-MS(N), manufactured by Kyoeisha Chemical Co., Ltd.) )
MePEGA: methoxy polyethylene glycol acrylate (average number of moles of alkylene oxide units added is 4 or 9 respectively)
MePEGMA: methoxy polyethylene glycol methacrylate (average number of moles of alkylene oxide units added is 23)
MePPGA: methoxy polypropylene glycol acrylate (average number of moles of alkylene oxide units added is 2)

<Example 1>
A solution (solid content 48.0% by mass) of the (meth)acrylic polymer (A-1) prepared in Production Example A-1 was placed in a four-necked flask equipped with a stirring blade, a thermometer, a condenser, and a dropping funnel. 208.3 parts by mass (100 parts by mass as the solid content), 1.2 parts by mass (solid content of 33.0% by mass) of the solution of the (meth)acrylic oligomer (B) prepared in Production Example B (0 as the solid content). .40 parts by mass) and 0.150 parts by mass of Li(CF ₃ SO ₂ ) ₂ N (LiTFSI manufactured by Morita Chemical Industry Co., Ltd.) as an antistatic agent, and the liquid temperature in the flask was kept at around 25° C. Mixing and stirring were performed for an hour. To this, 0.100 parts by mass of SH-3773M (manufactured by Toray Dow Corning Co., Ltd., solid content: 10.0% by mass) as a polyether-modified silicone, and aluminum trisacetylacetonate (trade name: aluminum chelate A as a crosslinking agent , Kawaken Fine Chemical Co., Ltd.) with 25.7 parts by mass of aluminum chelate diluted with acetylacetone and toluene (solid content of 9.72% by mass) (2.5 parts by mass as solid content, 0.69 equivalent). The mixture was added and sufficiently stirred to obtain a pressure-sensitive adhesive composition solution.
Using this pressure-sensitive adhesive composition solution, a test protective film was prepared according to the following method for preparing a test protective film, and various physical properties tests were conducted. The obtained results are shown in Table 2.
The equivalent weight of aluminum trisacetylacetonate (aluminum chelate) contained in the above-mentioned diluted aluminum chelate is based on the acidic groups contained in the (meth)acrylic polymer.
The calculation of the equivalent weight of the aluminum chelate was performed by the method described above, and specifically, it was calculated as follows.
Equivalent weight=(A×B/C)/(D ₁ ×E ₁ /F ₁ +D ₂ ×E ₂ /F ₂ +... +D _n ×E _n ×F _n ).
A = Metal valence of aluminum chelate: 3.0
B=part by mass of aluminum chelate (amount as solid content): 2.5 parts by mass C=molecular weight of aluminum chelate: 324.3
D ₁ =content (mass %) of each monomer having an acidic group in all monomers used for the (meth)acrylic polymer: 10.0 mass %.
E ₁ =Number of acidic groups contained in one molecule of the monomer having each acidic group: 1
F ₁ =Aronix M-5300 molecular weight: 300.4
n=Type of (meth)acrylic monomer used: 1
Equivalent=(A×B/C)/(D ₁ ×E ₁ /F ₁ )=(3×2.5/324.3)/(10.0×1/300.4)=0.69

[Evaluation]
(1) Preparation of Test Protective Film As a base material, a polyethylene terephthalate (PET) film (trade name: Teijin Tetron Film Type G2, thickness 38 μm, manufactured by Teijin DuPont Films Co., Ltd.) having a coating amount after drying of 20 g The adhesive composition solution was applied at a temperature of 100 m/m ² and dried at 100° C. for 60 seconds with a hot air circulation dryer. After that, a PET film coated with the adhesive composition solution and a release film surface-treated with a silicone-based release agent (trade name: Film Vina 100E-0010NO23, thickness 100 μm, manufactured by Fujimori Industry Co., Ltd.) are adhered. The coated surface of the release agent composition solution was laminated so as to contact the surface-treated surface of the release film to form a laminate. The laminated body was passed through a pair of pressure nip rolls and bonded by pressure bonding, and then aged for 1 hour under the condition of 23° C. and 50% RH to prepare a test protective film.

<Preparation of test samples 1 to 4>
<Test sample 1>
The release film of the test protective film prepared in the above (1) was peeled off, and a triacetyl cellulose (TAC) film (trade name: Lonza TAC100, manufactured by Panac Co., Ltd.) was superposed as an adherend and pressed. It was passed through a nip roll, pressure-bonded, and stuck together, and cut into a size of 25 mm×150 mm to obtain a test sample 1 (to TAC).

<Test sample 2>
The release film of the test protective film prepared in the above (1) is peeled off, and the PET film (trade name: Cosmoshine A-4300, manufactured by Toyobo Co., Ltd.) as an adherend is overlaid and passed through a pressure nip roll. The test sample 2 (compared to PET) was obtained by pressing and pasting together and cutting into a size of 25 mm×150 mm.

<Test sample 3>
A PET (hereinafter, also referred to as "HCPET") film (trade name: KB film G01S, whose surface is hard-coated as an adherend, after the release film of the test protective film produced in (1) above is peeled off. (Made by Kimoto Co., Ltd.) so that the surface coated with the hard coat and the pressure-sensitive adhesive layer are in contact with each other, passed through a pressure nip roll and pressure-bonded to each other, and cut into a size of 25 mm×150 mm, and a test sample 3 (Vs. HCPET).

<Test sample 4>
The release film of the test protective film prepared in (1) above was peeled off, cold-rolled as an adherend, and brightly annealed (non-oxidation annealed) stainless steel plate (BASUS) (trade name: SUS304 (BA ), manufactured by Paltec Co., Ltd., and passed through a pressure nip roll to be bonded by pressure bonding and cut into a size of 25 mm×150 mm to obtain a test sample 4 (versus BASUS).

(2) High-speed peelability Each of the test samples 1 to 4 prepared above was left for 24 hours under the conditions of 23° C. and 50% RH. Then, using a device as shown in FIG. 1, the adhesive force at 180° peeling was measured under a high peeling speed of 30 m/min. Specifically, as shown in FIG. 1, the test sample is placed on the glass plate so that the glass plate and the surface of the adherend are in contact with each other, and one end of the test sample is gripped so that the surface of the glass plate is The substrate (PET film) was peeled from the pressure-sensitive adhesive layer by pulling it along the direction of 180°.
High-speed peelability was evaluated according to the following evaluation criteria, and the results are shown in Table 2.

[Evaluation criteria]
AA: The adhesive strength to all adherends is 0.20 N/25 mm to 1.00 N/25 mm, the releasability is very excellent, and the adhesive strength is excellent.
A: The adhesive force to all adherends is more than 0.15 N/25 mm and less than 2.00 N/25 mm, and the adhesive force to at least one adherend is more than 0.15 N/25 mm to 0. It is less than 20 N/25 mm, or more than 1.00 N/25 mm and less than 2.00 N/25 mm, and has excellent releasability and slightly excellent adhesive strength.
B: The adhesive force to at least one adherend is 2.00 N/25 mm or more, and the peelability is slightly inferior and is in an unacceptable range.
C: The adhesive force to at least two adherends is 2.00 N/25 mm or more, the peelability is poor, and it is in an unacceptable range.
D: Adhesive strength to at least one adherend is 0.15 N/25 mm or less, which is extremely inferior so that unintended detachment from the surface of the adherend may occur, and is in a range unacceptable as a protective film.

(3) Antistatic property Each of the test samples 1 to 4 prepared above was allowed to stand for 24 hours under the conditions of 23° C. and 50% RH, and then subjected to 180 as shown in FIG. 1 in the same manner as in the above (2). Peeling was performed in the direction of ° at a peeling speed of 30 m/min (high speed).
The potential of the surface of the adherend generated when peeled off is fixedly arranged at a predetermined position (a position 10 mm away from the surface of the adherend) (trade name: KSD-0303, Kasuga Electric Co., Ltd.) (Made by the company). Using the absolute value of this measured value as the peeling electrification voltage, antistatic properties were evaluated according to the following evaluation criteria, and the results are shown in Table 2.

[Evaluation criteria]
AA: The absolute value of the peeling electrification voltage of all adherends is 0.5 kv or less, and the antistatic property is very excellent.
A: The absolute value of the peeling electrification voltage of all adherends exceeds 0.5 kv and 1.0 kv or less, and the antistatic property is excellent.
B: The absolute value of the peeling electrification voltage of at least one adherend exceeds 1.0 kv and is 1.5 kv or less, and the antistatic property is slightly inferior and is in an unacceptable range.
C: The absolute value of the peeling electrification voltage of at least one adherend exceeds 1.5 kv, the antistatic property is poor, and it is in an unacceptable range.

<Examples 2 to 23 and Comparative Examples 1 to 8>
The pressure-sensitive adhesive composition shown in Table 2 was prepared in the same manner as in Example 1 except that the composition in Example 1 was changed to the composition shown in Table 2. A test protective film was produced using the obtained pressure-sensitive adhesive composition, and test samples 1 to 4 were produced using this test protective film. Each evaluation was performed using these samples 1 to 4, and the obtained results are shown in Table 2.

The abbreviations in Table 2 are as follows. In addition, "-" in Table 2 indicates that the corresponding component is not included.
· LiTFSI: lithium bis (trifluoromethane _{sulfonimide), Li (CF 3 SO 2} ) 2 N ( manufactured by Morita Chemical Industries Co., Ltd.)
· LiTFS: lithium trifluoromethanesulfonate, LiCF ₃ SO ₃ (manufactured by Morita Chemical Industries Co., Ltd.)
Ionic Solid A: N-hexyl pyridinium-PF 6 _- ^(Organic salts having hexyl pyridinium ion as an organic cation, the melting point 45 ° C.)
SH-3773M: a dimethylsiloxane compound in which a polyoxyalkylene chain is introduced into the side chain (manufactured by Toray Dow Corning Co., Ltd., the end of the polyoxyalkylene chain is a hydroxyl group, HLB value=8)
Aluminum chelate: Aluminum trisacetylacetonate (trade name: Aluminum chelate A, manufactured by Kawaken Fine Chemical Co., Ltd.) diluted with toluene and acetylacetone to a solid content of 9.7% by mass.

The acid value is in the range of 9 mgKOH/g to 65 mgKOH/g, and the content of the constituent units derived from the monomer having a polyalkylene oxide chain exceeds 1 mass% with respect to the mass of all constituent units. Is less than 20% by mass, a protective film having a crosslinked product of the pressure-sensitive adhesive composition of Examples 1 to 23 containing a (meth)acrylic polymer, a crosslinking agent, and an antistatic agent is Even when it was used for wearing, it was excellent in high-speed peelability and antistatic property.
Particularly, the protective films having the crosslinked products of the pressure-sensitive adhesive compositions of Examples 6, 8, 11 and 17 were excellent in high speed peelability and antistatic property.
On the other hand, Comparative Examples 1, 2, 7 and 8 containing a (meth)acrylic polymer that does not include a constitutional unit derived from a monomer having a polyalkylene oxide chain, and a single amount having a polyalkylene oxide chain All of Comparative Example 3 containing the (meth)acrylic polymer in which the content ratio of the constitutional units derived from the body is 1.0% by mass based on the mass of all the constitutional units have a high value of the peeling electrification voltage with respect to PET. , Was inferior in antistatic property. Comparative Example 4 containing the (meth)acrylic polymer in which the content of the constituent units derived from the monomer having a polyalkylene oxide chain is 20 mass% with respect to the mass of all constituent units is high-speed peelability with respect to PET. Was inferior to
Further, Comparative Examples 5 and 6 each containing a (meth)acrylic polymer having an acid value outside the range of 9 mgKOH/g to 65 mgKOH/g were inferior in high-speed peelability. Comparative Example 6 having an acid value of 65 mgKOH/g or more was inferior in antistatic property in addition to high-speed peelability.

From the above, the protective film having a crosslinked product of the pressure-sensitive adhesive composition of the present invention, regardless of the material of the adherend, during the period when protection of the adherend is required, from the surface of the adherend to the protective film It has an adhesive strength such that it does not fall off, the adhesive strength at the time of high-speed peeling is kept low, and it is excellent in antistatic properties. From this, the protective film having the crosslinked product of the pressure-sensitive adhesive composition of the present invention is excellent in high-speed peelability and antistatic property regardless of the material of the adherend.

Claims (6)

The acid value is 9 mgKOH/g to 65 mgKOH/g, the weight average molecular weight is 91,000 to 1,000,000, and the content of the constituent units derived from the monomer having a polyalkylene oxide chain is A (meth)acrylic polymer that is 3% by mass or more and 15% by mass or less based on the mass of the unit;
A cross-linking agent,
At least one of a (meth)acrylic oligomer and a polyether-modified silicone,
And an antistatic agent, only including,
The cross-linking agent is a metal chelate compound,
The (meth)acrylic oligomer is a pressure-sensitive adhesive composition for a protective film , which contains a structural unit derived from a monomer having a polyalkylene oxide chain and has a weight average molecular weight of 3,000 to 20,000 . The pressure-sensitive adhesive composition for a protective film according to claim 1, wherein the (meth)acrylic polymer contains a structural unit represented by the following general formula (1).


(In the general formula (1), R ¹ represents a hydrogen atom or a methyl group. L is a divalent group composed of at least one selected from the group consisting of an alkylene group, an arylene group, a carbonyl group and an oxygen atom. Indicates a linking group.) The (meth)acrylic polymer contains a constituent unit derived from an alkyl(meth)acrylate, and the content of the constituent unit derived from the alkyl(meth)acrylate is 65% by mass to the mass of all constituent units. It is 97 mass %, The adhesive composition for protective films of Claim 1 or Claim 2. The (meth)acrylic oligomer is included, and the content of the (meth)acrylic oligomer is 0.05 parts by mass to 5.00 parts by mass with respect to 100 parts by mass of the (meth)acrylic polymer. Item 4. The pressure-sensitive adhesive composition for a protective film according to any one of items 1 to 3. The (meth) acrylic oligomer, pre SL content of the constituent unit derived from a monomer having a polyalkylene oxide chain, according to claim 1 which is 5% to 30% by weight, based on the weight of all the structural units protective film pressure-sensitive adhesive composition according to any one of-claims 4. A protective film comprising: a pressure-sensitive adhesive layer, which is a cross-linked product of the pressure-sensitive adhesive composition for a protective film according to any one of claims 1 to 5 , and a substrate.