TWI720114B - Adhesive composition for protective film, and protective film - Google Patents

Abstract

An adhesive composition for protective film, including: a (meth)acrylate polymer having an acid value of from 9 mgKOH/g to 70 mgKOH/g; a metallic chelate cross-linking agent; and an antistatic agent, an equivalent amount of the metallic chelate cross-linking agent being from 0.3 to 2.0 with respect to one equivalent amount of an acid group of the (meth)acrylate polymer.

Description

Adhesive composition for protective film and protective film

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

Optical components such as polarizing plates used in liquid crystal display devices are protected by a protective film in order to prevent contamination or damage on the surface during various steps such as press processing, inspection, transportation, and assembly of the liquid crystal display panel. The film is peeled and removed from the optical member at a stage where the surface protection of the optical member is not required.

When the protective film is peeled from the optical member, if static electricity is generated, there may be a problem that dust or the like adheres to the optical member, or the circuit of the liquid crystal display device is damaged. Therefore, the protective film is required to prevent static electricity (antistatic property) from being generated during peeling.

In addition, the protective film is required to have adhesive strength to the extent that it does not suddenly peel off until it is no longer needed. Furthermore, in recent years, in order to improve work efficiency, the peeling of the protective film from the adherend tends to proceed at a high speed (for example, 30 m/min), and it is required that it can be easily peeled from the adherend even during high-speed peeling. that is, For the protective film, it is required that no sudden peeling occurs, and the adhesive force of the protective film during high-speed peeling is low, and the high-speed peeling performance is excellent.

In addition, the adhesive layer used in the protective film is often formed with a highly transparent acrylic adhesive composition in order to ensure the visibility of the optical member. When manufacturing such a protective film with an acrylic adhesive layer, the adhesive composition is applied to the base film, dried and the solvent is removed, and it takes about 7 days to mature until the crosslinking reaction is completed. Therefore, it is necessary to secure a space to store the protective film until the maturation is completed. In consideration of production efficiency, it is also desired to shorten the time required until the maturation is completed (hereinafter, also referred to as "maturing completion time").

As an adhesive composition for a protective film that can form an adhesive layer with excellent antistatic properties, someone has disclosed an adhesive composition, which contains an alkyl (meth)acrylate as the main component of the acid value of (Meth)acrylic polymer of 29 or less, and fluorine-containing iminium lithium salt (for example, refer to Japanese Patent Application Laid-Open No. 2005-306937).

As an adhesive composition that can form a protective film for an adhesive layer with excellent antistatic properties and a short curing completion time, some people have disclosed an adhesive composition that contains a (methyl group) derived from a hydroxyl group. ) The (meth)acrylic polymer of the structural unit of acrylamide, and an antistatic agent (for example, refer to Japanese Patent Application Laid-Open No. 2009-126929).

As an adhesive composition for an adhesive layer with a short time to complete the maturation and low adhesive force during high-speed peeling, some people have disclosed a protective sheet including an adhesive layer containing acrylic resin, Urethane (meth)acrylate and an ionic compound are obtained by crosslinking with active energy rays (for example, refer to JP 2010-31255 A).

However, although the protective film described in JP 2005-306937 A has excellent antistatic properties, it takes a long time to complete the curing and is poor in productivity.

As a technique for ensuring antistatic properties while shortening the maturation completion time, the technique described in Japanese Patent Application Laid-Open No. 2009-126929 is disclosed as described above. The adhesive composition described in Japanese Patent Laid-Open No. 2009-126929 takes about 3 days until the maturation is completed, which is not satisfactory in terms of the maturation completion time, and further shortening is required. Moreover, the adhesion force during high-speed peeling has not been studied, and there may be cases where the adhesive force during high-speed peeling is high and the high-speed peeling performance is poor.

In addition, the protective sheet including an adhesive layer crosslinked by active energy rays described in Japanese Patent Application Laid-Open No. 2010-31255 has a short curing completion time, but the protective sheet manufacturing equipment requires active Energy ray irradiation machine.

The present invention has been made in view of the above circumstances, and its subject is to provide a protective film with a short curing completion time, excellent antistatic properties, an adhesive force that does not peel off suddenly, low adhesive force during high-speed peeling, and excellent high-speed peelability. Adhesive composition, and a protective film formed by using the adhesive composition for protective film.

The specific methods used to solve the aforementioned problems include the following aspects.

<1> An adhesive composition for a protective film, comprising: a (meth)acrylic polymer having an acid value of 9 mgKOH/g or more and 70 mgKOH/g or less, and an acidic group relative to the (meth)acrylic polymer One equivalent of a metal chelate crosslinking agent and an antistatic agent of 0.3 to 2.0 equivalents.

<2> The adhesive composition for a protective film according to the above <1>, wherein the (meth)acrylic polymer includes 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 represents a divalent linking group consisting 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 adhesive composition for protective film of the aforementioned <1> or <2>, wherein the product of the acid value of the (meth)acrylic polymer and the equivalent of the metal chelate crosslinking agent It is in the range of 3~40.

<4> The adhesive composition for a protective film as described in any one of <1> to <3>, further comprising polyether-modified polysiloxane. The content of the polyether-modified polysiloxane is relative to the 100 parts by mass of the (meth)acrylic polymer is 0.05 parts by mass or more and 1.00 parts by mass or less.

<5> The adhesive composition for a protective film as described in any one of the aforementioned <1> to <4>, further comprising a structural unit derived from a monomer having a carboxyl group, and containing a weight average molecular weight of 3,000 to 30,000 ( The meth)acrylic oligomer, and the content of the (meth)acrylic oligomer is 0.05 parts by mass or more and 2.00 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic polymer.

<6> The adhesive composition for a protective film according to the aforementioned <5>, wherein the (meth)acrylic oligomer contains 5% by mass to 30% by mass relative to all structural units A structural unit derived from a monomer containing an alkylene oxide chain.

<7> A protective film, comprising: an adhesive layer configured using the adhesive composition for a protective film as described in any one of the aforementioned <1> to <6>, and a substrate.

According to the present disclosure, it is possible to provide an adhesive composition for a protective film that has a short curing completion time, excellent antistatic properties, adhesive strength that does not peel off suddenly, low adhesive strength during high-speed peeling, and excellent high-speed peelability, and A protective film formed using this adhesive composition for protective film.

[Fig. 1] An explanatory diagram explaining the evaluation method of adhesive strength and peelability during high-speed peeling.

Hereinafter, a detailed description will be given of the adhesive composition product for the protective film of the present disclosure and the protective film. In addition, in the present disclosure, the "~" in the numerical range means to include the numerical values before and after the "~" as the lower limit and the upper limit of the numerical range, respectively.

In this specification, the amount of each component in the composition means the total amount of the plurality of substances present in the composition when there are many substances equivalent to each component in the composition, unless otherwise specified.

In this specification, (meth)acrylic polymer or (meth)acrylic oligomer means that at least the main component of the monomers constituting it is a monomer having a (meth)acrylic group The polymer or oligomer. The monomer of the main component means the monomer with the largest content (% by mass) among the monomers constituting the polymer or oligomer. The preferred embodiment of the (meth)acrylic polymer or (meth)acrylic oligomer of the present disclosure is that the content of the constituent units of the (meth)acrylate monomer derived from the main component of the system is all More than 50% by mass of the constituent unit.

In this specification, "(meth)acryl group" means both of "acryl group" and "methacryl group". "(Meth)acrylate" means both of "acrylate" and "methacrylate". "(Meth)acryloyl" means both of "acryloyl" and "methacryloyl".

<<Adhesive composition for protective film>>

The adhesive composition for protective film of the present disclosure (hereinafter, also referred to as "the adhesive composition of the present disclosure") includes: (meth)acrylic polymer with an acid value of 9 mgKOH/g or more and 70 mgKOH/g or less (Hereinafter, sometimes referred to as "specific (meth)acrylic polymer"), a metal chelate compound with an acidic group equivalent of 0.3 to 2.0 equivalents relative to the (meth)acrylic polymer Coupling agent, and antistatic agent.

The adhesive composition for protective film having the above-mentioned structure can shorten the maturation completion time when making the protective film, obtain excellent antistatic properties, have an adhesive force that does not peel off suddenly, and has low adhesive force during high-speed peeling. , A protective film with excellent high-speed peeling. The reason is considered as follows.

In order to shorten the maturation completion time, it is generally considered that the number of crosslinking points possessed by the (meth)acrylic polymer should be increased and a highly reactive crosslinking agent should be used. For example, when a (meth)acrylic polymer having a carboxyl group with an acidic group is used in combination with a metal chelate-based crosslinking agent, it is widely known that the crosslinking reaction speed is fast.

However, adhesives for protective films obtained by using (meth)acrylic polymers with acidic groups and metal chelate crosslinking agents tend to have lower elasticity and higher adhesive strength, so there is a high speed When peeling off, it is difficult to peel the protective film from the adherend. In addition, acidic groups deteriorate the antistatic properties. Therefore, the combined use of these adhesives for protective films that originally required antistatic properties was deemed unsuitable.

In the present disclosure, by setting the ratio of the equivalent of the acidic group to the equivalent of the metal chelate-based crosslinking agent in a predetermined range, the decrease in antistatic property due to the acidic group can be suppressed to the minimum. In addition, it is considered that by setting the acid value of the (meth)acrylic polymer to a predetermined range, appropriate hardness can be imparted to the cross-linked body, and the adhesive force during high-speed peeling can be reduced. That is, in the present disclosure, the balance of antistatic property and adhesive force is achieved based on the acid value and the amount of the metal chelate-based crosslinking agent.

Furthermore, according to the present disclosure, a (meth)acrylic polymer having a carboxyl group with an acidic group is used in combination with a metal chelate-based crosslinking agent. Therefore, compared with the conventional case where an isocyanate compound is used as a crosslinking agent , Can greatly shorten the maturation completion time, and can obtain the adhesive composition for protective film with high production efficiency.

[(Meth) acrylic polymer]

The adhesive composition for a protective film in the present disclosure includes at least one (meth)acrylic polymer having an acid value of 9 mgKOH/g or more and 70 mgKOH/g or less. The adhesive composition of the present disclosure may further include a (meth)acrylic polymer different from the aforementioned (meth)acrylic polymer if necessary.

The acid value of the (meth)acrylic polymer contained in the adhesive composition of the present disclosure takes into consideration the viewpoint of suppressing the adhesive force during high-speed peeling to be low, that is, the viewpoint of further improving the high-speed peelability. It is preferably 9 mgKOH/g or more and 70 mgKOH/g or less. Considering the same point of view, the acid value is preferably 11 mgKOH/g or more and 40 mgKOH/g or less, and the acid value is more preferably 13 mgKOH/g or more and 30 mgKOH/g or less.

If the acid value of the (meth)acrylic polymer exceeds 70 mgKOH/g, the adhesive layer prepared by including the adhesive composition of the present disclosure becomes hard, and the adhesive force of the adhesive layer becomes too low, which protects The film is easy to peel off suddenly from the adherend. In addition, the antistatic property is also reduced. In addition, if the acid value of the (meth)acrylic polymer is less than 9 mgKOH/g, when the adhesive composition of the present disclosure is used to form the adhesive layer, the formed adhesive layer is too soft and the adhesive force becomes excessive High, so it may be difficult to peel during high-speed peeling.

The acid value of the (meth)acrylic polymer or the (meth)acrylic oligomer described later is calculated according to the following calculation formula, respectively.

Acid value (mgKOH/g)={(A/100)÷B}×56.1×1000×C

A=(meth)acrylic polymer or (meth)acrylic oligomer content rate (mass%) of monomers having carboxyl group in all monomers used in (meth)acrylic oligomer

B=(meth)acrylic polymer or (meth)acrylic oligomer used in the molecular weight of the monomer with carboxyl group

C=The number of carboxyl groups contained in 1 molecule of the monomer with carboxyl groups

In addition, 56.1 is the molecular weight of KOH.

In addition, when there are multiple types of monomers having a carboxyl group, the acid value can be obtained by adding the values obtained by the above formula for each monomer.

The specific (meth)acrylic polymer in the adhesive composition of the present disclosure has an acidic group. The specific (meth)acrylic polymer preferably contains a structural unit having an acidic group. The structural unit having an acidic group is preferably a structural unit derived from a monomer having a carboxyl group. Among them, the structural unit derived from a monomer having a carboxyl group includes a structural unit derived from (meth)acrylic acid, a structural unit derived from (meth)acrylate having a carboxyl group, and the like. The structural unit derived from the (meth)acrylate having a carboxyl group includes the structural unit represented by the following general formula (1).

If it has a structural unit represented by the general formula (1), the carboxyl group is bonded via L, thereby suppressing the adhesive force during high-speed peeling to be low.

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

The alkylene group in L may be any of linear, branched and cyclic. When the alkylene group in L is linear or branched, the carbon number of the alkylene group is preferably 1-12, more preferably 2-10, and particularly preferably 2-6.

In addition, when the alkylene group in L is cyclic, for example, it may be a cyclic group having 3 to 5 carbon atoms in the alkylene group.

For the aryl group in L, the carbon number is preferably 6-10, and the phenyl group is more preferable. The bonding position in the aryl group is not particularly limited. For example, when the aryl group is a phenyl group, the bonding position can be any of the 1-position and the 4-position, the 1-position and the 2-position, and the 1-position and the 3-position, and the 1-position and the 2-position are preferred.

The alkylene and arylene groups in L may also have substituents. The substituent includes an alkyl group having 1 to 12 carbon atoms, a halogen atom, a hydroxyl group, an amino group, a nitro group, and a phenyl group.

The divalent linking group represented by L in the general formula (1) is preferably the divalent linking group represented by the following general formula (2a) or general formula (2b) in consideration of antistatic properties and high-speed peelability.

In the general 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 represents the value from 0 to 10, and m represents the value from 1 to 10.

The ^{alkylene group in R 21} to R ²⁴ may be any of linear, branched and cyclic, preferably linear or branched, and more preferably linear.

The bonding position of the aryl extension in R ²¹ to R ^{24 is not particularly limited.} For example, when the aryl group is a phenyl group or a cyclohexene group, the bonding position can be any one of the 1-position and the 4-position, the 1-position and the 2-position, and the 1-position and the 3-position, preferably the 1-position and the 2-position. Better.

Preferably, the alkylene groups in R ²¹ and R ²² each independently have a carbon number of 2-10, more preferably a carbon number of 2-6. The ^{alkylene groups in R 21} and R ²² may be the same or different.

The ^{arylene groups in R 21} and R ²² are preferably phenylene or naphthylene each independently, and phenylene is more preferred.

^{R 21} and R ²² in the general formula (2a), considering the antistatic properties and high-speed peeling properties, should each independently be an alkylene having 1 to 12 carbon atoms, preferably an alkylene having 2 to 6 carbon atoms The group is more preferable, and the alkylene group having a carbon number of 2-6 and being linear or branched is particularly preferable.

In the general formula (2a), n represents a value from 0 to 10. When the specific (meth)acrylic polymer contains 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 a rational number based on an average value. n is preferably 0~4, more preferably 0~2.

R ^{23 is} preferably an alkylene having 1 to 12 carbon atoms, more preferably an alkylene having 2 to 6 carbon atoms, and particularly preferably an alkylene having 2 to 4 carbon atoms.

R ^{24 is} preferably a straight or branched chain alkylene group with carbon number 2-6, cyclic alkylene group with carbon number 4-8 (divalent cyclic group), or carbon number 6-10. Aryl is preferred, linear or branched alkylene having 2 to 4 carbons, cyclic alkylene having 5 to 6 carbons, or phenylene is more preferred, straight chain having 2 to 4 carbons Shaped or branched alkylene, cyclohexylene, or phenylene is particularly preferred.

In the general formula (2b), m represents a value from 1 to 10. When the specific (meth)acrylic polymer contains only one type of structural unit represented by the general formula (1), m is an integer, and when two or more types are contained, m is a rational number based on an average value. m is preferably 1~4, more preferably 1~2.

The structural unit represented by the general formula (1), for example, can be introduced into the specific ( Meth)acrylic polymer.

In the general formula (1a), R ¹ and L general formula (1) in the R ¹ and L are synonymous.

The monomer represented by the general formula (1a) may be obtained by a conventional method, or may be appropriately selected from commercially available monomers. As the monomer represented by the general formula (1a), L is a monomer represented by the general formula (2a), for example, (meth)acrylic acid dimer (preferably the average value of n in the general formula (2a) Is about 0.4), ω-carboxy-polycaprolactone mono(meth)acrylate (preferably those whose average value of n in general formula (2a) is about 1.0). For these monomers, for example, "ARONIX M-5600" and "ARONIX M-5300" (above, manufactured by Toagosei Co., Ltd., trade name) commercially available products can be used.

In addition, as the monomer represented by the general formula (1a), L is a monomer represented by the general formula (2b), for example, 2-(meth)acryloxyethyl succinic acid, 2-(meth)propylene Glyoxyethyl fumaric acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid. For these monomers, for example, "LIGHT ESTER HO-MS", "LIGHT ACRYLATE HOA-MS(N)", "LIGHT ACRYLATE HOA-HH(N)", "LIGHT ACRYLATE HOA-MPL(N)" can be used "(The above, manufactured by Kyoeisha Chemical Co., Ltd., trade name) is a commercially available product.

The content of the structural unit represented by the general formula (1) in the specific (meth)acrylic polymer is preferably 3% by mass or more relative to all the structural units, preferably 6% by mass or more, and especially 8% by mass or more good.

If the content of the structural unit represented by the general formula (1) in the specific (meth)acrylic polymer is 3% by mass or more, the adhesive force during high-speed peeling can be suppressed to be lower.

In addition, the content of the structural unit represented by the general formula (1) in the specific (meth)acrylic polymer is preferably 40% by mass or less, and 20% by mass or less in consideration of high-speed peelability and antistatic properties. More preferably, 10% by mass or less is particularly preferable.

The specific (meth)acrylic polymer preferably contains at least one structural unit derived from alkyl (meth)acrylate in addition to the structural unit represented by the general formula (1).

As for the alkyl (meth)acrylate, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, ( Second butyl meth)acrylate, third butyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ( N-nonyl meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, isotetradecyl (meth)acrylate, (meth) Stearyl acrylate, (meth) Cyclohexyl acrylate, isobornyl (meth)acrylate. The alkyl group of the alkyl (meth)acrylate may be any one of linear, branched, or cyclic.

Among them, alkyl (meth)acrylates having a glass transition temperature of -30°C or less when forming a homopolymer are preferred.

The specific (meth)acrylic polymer may contain one type of structural unit derived from alkyl (meth)acrylate alone, or two or more types, preferably two or more types.

Among them, the structural unit derived from alkyl (meth)acrylate preferably contains at least one of n-butyl acrylate and 2-ethylhexyl acrylate, and more preferably contains both.

The specific (meth)acrylic polymer contains structural units derived from alkyl (meth)acrylate (preferably from the structure of alkyl (meth)acrylate whose glass transition temperature when forming a homopolymer is below -30°C) Unit), the total content of structural units derived from alkyl (meth)acrylate (preferably derived from structural units derived from alkyl (meth)acrylate whose glass transition temperature when forming a homopolymer is -30°C or less) , Relative to all constituent units, it is preferably 65% by mass or more and 99% by mass or less, more preferably 75% by mass or more and 97% by mass or less, and more preferably 80% by mass or more and 95% by mass or less. When the total content of the structural units derived from the alkyl (meth)acrylate is 65% by mass or more, the compliance (wettability) tends to be more excellent. In addition, when the total content of the structural units derived from the alkyl (meth)acrylate is 99% by mass or less, the adhesive force during high-speed peeling does not become too high, and there is a tendency that the high-speed peelability is excellent.

The specific (meth)acrylic polymer may further contain other structural units other than the structural unit represented by the general formula (1) and the structural unit derived from alkyl (meth)acrylate. As long as other components can communicate with The structural units represented by the formula (1) only need to constitute a polymer together, and are not particularly limited, and can be appropriately selected according to the purpose.

Examples of monomers capable of forming other structural units include monomers having hydroxyl groups, monomers having alkylene oxide chains, and monomers having cyclic groups.

Monomers having a hydroxyl group, for example, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate Hydroxypropyl ester, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, 3-methyl-3-hydroxy (meth)acrylate Butyl ester.

Monomers having alkylene oxide chains, for example, methoxyethyl (meth)acrylate, 2-(ethoxyethoxy)ethyl acrylate, polyethylene glycol (meth)acrylate, methyl acrylate Oxypolyethylene glycol (meth)acrylate, methoxy polypropylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate.

The monomer having a cyclic group includes, for example, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

The glass transition temperature of the specific (meth)acrylic polymer is preferably -40°C or less from the viewpoint of high-speed peelability, and more preferably -50°C or less.

The glass transition temperature (Tg) of the specific (meth)acrylic polymer is the molar average glass transition temperature obtained by converting the absolute temperature (K) calculated according to the following formula to the Celsius temperature (°C).

1/Tg=m1/Tg1+m2/Tg2+‧‧‧+m(k-1)/Tg(k-1)+mk/Tgk

In the formula, Tg1, Tg2, ‧‧‧, Tg(k-1), Tgk respectively represent the glass transition expressed in absolute temperature (K) when the monomers constituting the (meth)acrylic polymer form a homopolymer temperature. m1, m2, ‧‧‧, m(k-1), mk respectively represent the molar fraction of each monomer constituting the (meth)acrylic polymer, m1+m2+‧‧‧+m(k-1) +mk=1.

In addition, "the glass transition temperature expressed in absolute temperature (K) when forming a homopolymer" refers to the glass transition temperature expressed in absolute temperature (K) of a homopolymer prepared by polymerizing the monomer alone.

Regarding the glass transition temperature of the homopolymer, a differential scanning calorimetry device (DSC) (manufactured by SEIKO INSTRUMENTS, EXSTAR6000) was used to measure the sample under the conditions of 10 mg and a temperature increase rate of 10°C/min in a nitrogen stream. The homopolymer was measured, and the inflection point of the obtained DSC curve was taken as the glass transition temperature of the homopolymer.

Regarding the "Glass Transition Temperature in Celsius (°C) of Homopolymers" of representative monomers, methyl acrylate is 5°C, ethyl acrylate is -27°C, methyl methacrylate is 103°C, and acrylic acid N-butyl ester is -57°C, 2-ethylhexyl acrylate is -76°C, n-lauryl methacrylate is -65°C, n-octyl acrylate is -65°C, isooctyl acrylate is -58°C, Isononyl acrylate is -58°C, isotetradecyl acrylate is -56°C, acrylic acid is 163°C, ω-carboxy-polycaprolactone (n≒2) monoacrylate is -30°C, 2-propenyloxy Ethyl-succinic acid is -40°C.

By using, for example, these representative monomers, the aforementioned glass transition temperature can be adjusted appropriately.

The weight average molecular weight of the specific (meth)acrylic polymer is not particularly limited. The weight average molecular weight (Mw) of the specific (meth)acrylic polymer is preferably 200,000 or more and 1 million or less, and 300,000 or more and 800,000. The following is better. If the weight average molecular weight (Mw) of the specific (meth)acrylic polymer is 200,000 or more, it can more effectively prevent the specific (meth)acrylic polymer from remaining on the adhesive during high-speed peeling. The body and pollution tend to decrease. In addition, if it is 1 million or less, the compliance (wettability) tends to be more excellent.

In addition, the dispersion degree (Mw/Mn) of the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the specific (meth)acrylic polymer is preferably 20 or less, and more preferably in the range of 3-15 good. If the value of the degree of dispersion (Mw/Mn) is 20 or less, there is a tendency that the specific (meth)acrylic polymer remains on the adherend during high-speed peeling and the staining properties tend to be further reduced.

In addition, the weight average molecular weight (Mw) and number average molecular weight (Mn) of the (meth)acrylic polymer are values measured in accordance with the following (1) to (3).

(1) A solution of (meth)acrylic polymer was applied to release paper, and dried at 100°C for 2 minutes to obtain a film-like (meth)acrylic polymer.

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

(3) Measure the weight average molecular weight (Mw) and number average molecular weight (Mn) of (meth)acrylic polymers using gel permeation chromatography (GPC) under the following conditions with standard polystyrene conversion values .

(condition)

GPC: HLC-8220 GPC [Tosoh Corporation System]

Column: 4 for TSK-GEL GMHXL

Mobile phase solvent: tetrahydrofuran

Flow rate: 0.6mL/min

Column temperature: 40℃

The content of the specific (meth)acrylic polymer in the adhesive composition can be appropriately selected according to the purpose and the like. The content of the specific (meth)acrylic polymer is preferably 80% by mass or more and 99% by mass or less of the total solid content of the adhesive composition, more preferably 85% by mass or more and 99% by mass or less, 90 The mass% or more and 98 mass% or less is particularly preferred. In addition, the total mass of solid content means the total mass of the residue after removing the solvent and other volatile components from the adhesive composition.

[(Meth) acrylic oligomer]

The adhesive composition of the present disclosure may have structural units derived from a monomer having a carboxyl group, and may include (meth)acrylic oligomers with a weight average molecular weight of 3,000 or more and 30,000 or less.

When the adhesive composition of the present disclosure further includes the above-mentioned (meth)acrylic oligomer, the amount of the antistatic agent can be suppressed, and the content of the polyether-modified polysiloxane when the polyether-modified polysiloxane described later is contained the amount. Thereby, when the protective film is peeled from the adherend, a part of the adhesive layer becomes less likely to remain on the adherend, so the occurrence of contamination (stain) on the adherend is suppressed, and the contamination tends to decrease. In addition, since the compatibility of the (meth)acrylic polymer is reduced, the occurrence of white turbidity can be suppressed.

When the adhesive composition of the present disclosure contains (meth)acrylic oligomer, it may be only one (meth)acrylic oligomer, or may be different in monomer composition, weight average molecular weight, etc. More than species.

The structural unit derived from the monomer having a carboxyl group contained in the (meth)acrylic oligomer contributes to the improvement of high-speed peelability. The type of the monomer having a carboxyl group is not particularly limited.

The monomer having a carboxyl group includes the monomer having a carboxyl group in the aforementioned (meth)acrylic polymer, and among these, (meth)acrylic acid is preferred.

The content of the structural unit derived from the monomer having a carboxyl group in the (meth)acrylic oligomer is preferably 0.1% by mass or more and 10% by mass or less relative to all the structural units from the viewpoint of reducing pollution, 0.5 It is more preferable that the mass% is more than 7.0 mass%, and more preferably 1.0 mass% or more and 5.0 mass% or less.

The (meth)acrylic oligomer preferably contains a structural unit derived from alkyl (meth)acrylate. The structural unit derived from the alkyl (meth)acrylate contributes to the adjustment of the adhesive force.

As for the alkyl (meth)acrylate, the alkyl (meth)acrylate among the above-mentioned (meth)acrylic polymers can be cited.

Among them, considering that the adhesive layer can still exhibit high durability even when exposed to a high temperature and high humidity environment, it is preferably alkyl (meth)acrylate with 4 to 12 carbon atoms, which has a branched chain carbon number 4~12 alkyl (meth)acrylate is more preferred, and 2-ethylhexyl methacrylate is particularly preferred.

The content of the structural unit derived from alkyl (meth)acrylate in the (meth)acrylic oligomer, considering durability, is preferably 65% by mass or more, preferably 75% by mass or more, relative to all the structural units More preferably, more than 80% by mass is particularly preferred.

In addition, the content of the structural unit derived from the alkyl (meth)acrylate in the (meth)acrylic oligomer is preferably 99% by mass or less from the viewpoint of durability, and more preferably 95% by mass or less. 90% by mass or less is particularly preferred.

The (meth)acrylic oligomer preferably contains a structural unit derived from a monomer having an alkylene oxide chain.

The content of the structural unit derived from the monomer having an alkylene oxide chain in the (meth)acrylic oligomer is preferably 5 mass% or more and 30 mass% or less, preferably 5 mass% or more, relative to all the structural units. The mass% or less is more preferable, and 5 mass% or more and 15 mass% or less are particularly preferable.

When the content of the structural unit derived from the monomer having an alkylene oxide chain is 5 mass% or more, there is a tendency that the antistatic property is more excellent. In addition, when the content rate of the structural unit derived from the monomer having an alkylene oxide chain is 30% by mass or less, there is a tendency that there is less unpolymerized but remaining monomer after the polymerization reaction, and the pollution is further reduced.

For (meth)acrylic oligomers, within the scope of exerting the effects of the present disclosure, they may also include constituent units derived from monomers having a carboxyl group, constituent units derived from alkyl (meth)acrylate, and constituent units derived from The structural unit (other structural unit) other than the structural unit of the monomer having an alkylene oxide chain.

At this time, the structural units derived from the monomer having a carboxyl group of the (meth)acrylic oligomer, the structural unit derived from the alkyl (meth)acrylate, and the structural unit derived from the monomer having an alkylene oxide chain are in all The total content of the constituent units is preferably 80% by mass or more relative to all the constituent units, more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

Examples of the monomers constituting other structural units include the monomers having a hydroxyl group and the monomers having a cyclic group as described above.

The content of the (meth)acrylic oligomer is preferably 0.05 parts by mass to 2.00 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer, more preferably 0.10 parts by mass to 1.50 parts by mass, and 0.10 Part by mass or more and 1.20 parts by mass or less is particularly preferred. When the content of the (meth)acrylic oligomer is 0.05 parts by mass or more, the adhesive force during high-speed peeling does not become too high, and the high-speed peelability tends to be more excellent. When the content of the (meth)acrylic oligomer is 2.00 parts by mass or less, it is easy to provide the adhesive layer with the necessary adhesive force to the extent that the protective film does not suddenly peel off from the adherend, and the high-speed peelability tends to be better .

The acid value of the (meth)acrylic oligomer, considering that it is fully crosslinked with the (meth)acrylic polymer to further improve the high-speed peelability, is preferably 10mgKOH/g or more, preferably 15mgKOH/g or more Better.

In addition, the acid value of the (meth)acrylic oligomer is preferably 200 mgKOH/g or less, more preferably 100 mgKOH/g or less, and particularly preferably 50 mgKOH/g or less from the viewpoint of maintaining good antistatic properties.

In addition, the calculation method of the acid value of the (meth)acrylic oligomer is as already mentioned.

The weight average molecular weight of the (meth)acrylic oligomer, considering the viewpoint of preventing the (meth)acrylic oligomer from remaining on the adherend during high-speed peeling, is preferably 1,000 or more, more preferably 4,000 or more, and 7,000 or more Especially good. The weight average molecular weight of the (meth)acrylic oligomer is preferably 30,000 or less from the viewpoint of reducing the haze of the adhesive layer, preferably 25,000 or less, and particularly preferably 20,000 or less.

The degree of dispersion (Mw/Mn) represented by the ratio of the weight average molecular weight (Mw) of the (meth)acrylic oligomer to the number average molecular weight (Mn) is not particularly limited. For example, from the viewpoint of further reducing pollution, the dispersion degree (Mw/Mn) of the (meth)acrylic oligomer is preferably in the range of 1-30.

The weight average molecular weight (Mw) and number average molecular weight (Mn) of the (meth)acrylic oligomer, and the weight average molecular weight (Mw) and number average molecular weight (Mn) of the (meth)acrylic polymer described above The measurement method is the same for measurement.

The glass transition temperature (Tg) of the (meth)acrylic oligomer is preferably 50°C or less. When the Tg of the (meth)acrylic oligomer is 50°C or less, the increase in adhesive force due to heat treatment can be suppressed, and the high-speed peelability is more excellent.

The glass transition temperature of the (meth)acrylic oligomer is calculated in the same way as the calculation method of the glass transition temperature of the (meth)acrylic polymer described above.

[Metal Chelate Crosslinking Agent]

The adhesive composition of the present disclosure includes a specific (meth)acrylic polymer, and also includes at least one metal chelate with an acidic group of 0.3 to 2.0 equivalents relative to the (meth)acrylic polymer. The cross-linking agent.

The metal chelate crosslinking agent reacts with the carboxyl group contained in the (meth)acrylic polymer to form a crosslinked structure. By using a metal chelate-based crosslinking agent, the crosslinking reaction is quicker than when an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, etc. are used, and the curing completion time can be shortened.

The metal chelate-based crosslinking agent includes one formed by coordinately bonding a polyvalent metal and an organic compound. For multivalent metal atoms, for example, Al, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, Ti. Among them, considering the viewpoints of low cost and easy acquisition, Al, Zr, and Ti are preferable, and Al is more preferable.

Examples of the atoms in the coordinately bonded organic compounds include oxygen atoms, and examples of the organic compounds include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, and ketone compounds.

In this disclosure, in particular, aluminum acetone acetone, which is stable and easy to handle, can be suitably used. In addition, two or more types of metal chelate-based crosslinking agents may be used in combination.

The equivalent weight of the metal chelate crosslinking agent is 0.3 equivalent or more and 2.0 equivalent or less, preferably 0.4 equivalent or more and 1.5 equivalent or less, more preferably 0.6 equivalent relative to 1 equivalent of the acidic group of the specific (meth)acrylic polymer Above 1.2 equivalent. If the content of the metal chelate crosslinking agent is less than 0.3 equivalent, it will peel off at high speed The adhesive force becomes higher. If the content of the metal chelate-based crosslinking agent exceeds 2.0 equivalents, the adhesive force of the adhesive layer becomes too low, the protective film is easily peeled from the adherend, and the antistatic property is also reduced.

The above equivalent is a value calculated according to the following formula.

Equivalent=(A×B/C)/(D ₁ ×E ₁ /F ₁ +D ₂ ×E ₂ /F ₂ +‧‧‧‧+D _n ×E _n /F _n )

A=The valence of the metal of the metal chelate crosslinking agent

B = The mass parts of the metal chelate crosslinking agent (the amount of solid content)

C=Molecular weight of metal chelate crosslinking agent

D ₁ , D ₂ , ‧‧‧D _n = the content of each monomer having acidic groups in all monomers used in the (meth)acrylic polymer (mass%)

E ₁ , E ₂ , ‧‧‧E _n = the number of acidic groups contained in one molecule of each monomer with acidic groups

F ₁ , F ₂ , ‧‧‧F _n = the molecular weight of the monomers with acidic groups used in (meth)acrylic polymers

In addition, n represents the number of types of monomers used. For example, when the (meth)acrylic monomer used is one type, only D _{1 is} used for calculation, and D ₂ ‧‧‧D _{n is} not used for calculation.

Regarding the metal chelate crosslinking agent, it is preferable to use the product of the acid value of the specific (meth)acrylic polymer and the equivalent of the metal chelate crosslinking agent in the range of 3 or more and 40 or less. It is more preferable to use it in the range of 5 to 35, and it is particularly preferable to use it in the range of 8 to 35. If the product of the acid value of the specific (meth)acrylic polymer and the equivalent of the metal chelate crosslinking agent is 3 or more, the high-speed peelability tends to be more excellent. In addition, if the product of the equivalent with the metal chelate crosslinking agent is 40 or less, it is easy to give the adhesive layer protective film the necessary adhesive strength, high-speed peelability, and resistance to the extent that the protective film does not suddenly peel off from the adherend. Tendency to be more excellent in electrostatic properties.

[Antistatic Agent]

The adhesive composition of the present disclosure contains at least one antistatic agent.

Examples of antistatic agents include ionic compounds. Examples of the aforementioned ionic compound include alkali metal salts and organic salts. The aforementioned antistatic agent has a high ion dissociation property and easily exhibits excellent antistatic properties even in a small amount, and an alkali metal salt and an organic salt are preferable. Considering that if the content of the antistatic agent can be reduced, the pollution can be further suppressed, and there is a better tendency.

Regarding the aforementioned alkali metal salt, any metal salt with lithium ion (Li ⁺ ), sodium ion (Na ⁺ ), potassium ion (K ⁺ ), rubidium (Rb ⁺ ), etc. as cations is sufficient, and there is no particular limitation. .

For example, use may be suitably selected from consisting of Li ^+, Na ^+, K ⁺ in the group consisting of at least one kind of cation selected from the group consisting of ^{Cl -, Br -, I -} , BF 4 -, PF 6 _{^{-, SCN -, ClO 4 -}} , CF 3 SO 3 -, (FSO 2) 2 N -, (CF 3 SO 2) 2 N -, (C 2 F 5 SO 2) 2 N -, (CF 3 SO 2 ) ₃ C ^- A metal salt composed of at least one anion in the group consisting of 3 C -.

Among them, as for the alkali metal salt, considering the antistatic property, LiBr, LiI, LiBF ₄ , LiPF ₆ , LiSCN, LiClO ₄ , LiCF ₃ SO ₃ , Li(FSO ₂ ) ₂ N, Li(CF ₃ SO ₂ ) ₂ N, Li(C ₂ F ₅ SO ₂ ) ₂ N, Li(CF ₃ SO ₂ ) ₃ C and other lithium salts are preferred, LiClO ₄ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N , Li(C ₂ F ₅ SO ₂ ) ₂ N, Li(CF ₃ SO ₂ ) ₃ C is more preferable. These alkali metal salts may be used alone, or two or more of them may be mixed and used.

The aforementioned organic salt contains an organic cation and its counter ion.

For organic salts, the melting point is preferably 30°C or higher. If the melting point of the organic salt is 30°C or higher, the transfer to the adherend is small and the pollution is low, which is preferable.

As for organic cations, for example, imidazolium cations, pyridinium cations, alkylpyrrolidinium cations, ammonium cations having organic groups as substituents, sulfonium cations having organic groups as substituents, and organic groups as substituents The phosphonium cation of the base. Among these, from the viewpoint of antistatic properties, pyridinium cations and imidazolium cations are more preferable.

The anion part that becomes the counter ion of the organic cation is not particularly limited, and may be either an inorganic anion or an organic anion. Wherein, due to the excellent antistatic properties, containing a fluorine atom is particularly preferred fluorine-containing anion, a hexafluorophosphate anion (PF ₆ ^-) better.

As an example of an organic salt, a pyridinium salt, an imidazolium salt, an alkylammonium salt, an alkylpyrrolidinium salt, an alkylphosphonium salt, etc. are mentioned suitably. Among them, pyridinium salts and imidazolium salts are preferred, and salts of pyridinium cations, imidazolium cations, and fluorine-containing anions are particularly preferred.

The content of the antistatic agent in the adhesive composition of the present disclosure is preferably 0.05 parts by mass to 0.50 parts by mass relative to 100 parts by mass of the specific (meth)acrylic polymer, preferably 0.10 parts by mass to 0.30 parts by mass The following is better. When the content of the antistatic agent is 0.05 parts by mass or more with respect to 100 parts by mass of the (meth)acrylic polymer, the antistatic properties tend to be excellent. On the other hand, when the content of the antistatic agent is 0.50 parts by mass or less, the antistatic effect tends to be higher than the efficiency of the content of the antistatic agent.

[Polyether modified polysiloxane]

The adhesive composition of the present disclosure may contain at least one polyether modified polysiloxane. With the polyether modified polysiloxane having reactive groups, the adhesive film can be easily peeled from the adherend, and an adhesive film with less pollution to the adherend can be obtained.

When polyether-modified polysiloxane is used together with a specific (meth)acrylic polymer having a structural unit represented by the general formula (1), and a metal chelate-based crosslinking agent, it can effectively exhibit antistatic properties.

The polyether modified polysiloxane has a polyether group and a hydroxyl group at the end of the polyether group, which can show more excellent antistatic properties and can effectively inhibit the contamination of the adherend. In particular, by having a polyalkylene oxide chain with a hydroxyl terminal in the molecule of the polyether modified polysiloxane, the antistatic performance can be effectively exerted. It is believed that the reason is that the polyether-modified polysiloxane is biased near the surface of the adhesive layer obtained from the adhesive composition for the protective film, whereby the polyalkylene oxide chain interacts with the alkali metal salt Concentrated near the surface of the adhesive layer, as a result, the surface resistance value of the surface of the adhesive layer can be reduced. In this way, the combined use of polyether-modified polysiloxane can suppress the amount of antistatic agent in the adhesive composition of the present disclosure.

For polyether-modified polysiloxanes, considering the antistatic properties and reducing the pollution to the adherend, it is preferable to include constituent units derived from dialkylsiloxanes and those derived from alkyl (hydroxypolyalkylene oxide). The polysiloxane compound which is a constituent unit of oxyalkyl)siloxane is preferred.

For the alkyl group in the dialkylsiloxane, the carbon number is preferably 1 to 4, and 1 is more preferable.

In addition, the number of carbon atoms in the alkylene oxide chain in the alkyl (hydroxypolyalkyleneoxyalkyl) siloxane is preferably 2 to 4, and more preferably 2 to 3. The content of the alkylene oxide chain in the alkyl (hydroxypolyalkyleneoxyalkyl) siloxane is preferably 1-100, more preferably 10-100. The alkyl group in the alkyl (hydroxypolyalkyleneoxyalkyl) siloxane preferably has a carbon number of 1 to 4.

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

For polyether-modified polysiloxane, considering the adhesion, antistatic properties, and reducing the pollution to the adherend, the polysiloxane compound represented by the following general formula (3) is preferred.

In the general formula (3), p is the repeating number of the dimethylsiloxane structural unit, and represents a value of 0-100. q is the repeating number of the methacrylic acid constitutive unit having a polyethylene oxide chain, and represents a value of 2-100. In addition, a is the repeating number of the ethylene oxide structural unit, and represents a value of 1-100. Here, when the compound represented by the general formula (3) is an aggregate of a plurality of compounds, p, q, and a are rational numbers of the average value of the aggregate of compounds.

The repeating number a of the polyethylene oxide constituent unit is a value of 1 to 100, preferably a value of 10 to 100. When a is 1 or more, sufficient conductivity may be obtained and the antistatic effect tends to be improved. In addition, when a is 100 or less, the compatibility with other components constituting the adhesive composition tends to be improved, and the transparency of the adhesive layer tends to be improved.

In addition, the repeating number p of the dimethylsiloxane structural unit is a value of 0 to 100, preferably a value of 1 to 80. When p is 0 or more, the antistatic effect tends to be improved. In addition, when p is 100 or less, the compatibility with other components constituting the adhesive composition is improved, and the transparency of the adhesive layer tends to be improved.

Furthermore, the repeating number q of the methacrylic siloxane structural unit is a value of 2 to 100, and a value of 2 to 80 is more preferable. If q is 2 or more, there is a tendency that sufficient conductivity can be obtained and the antistatic effect will be improved. In addition, when q is 100 or less, compatibility with other components constituting the adhesive composition is improved, and the transparency of the adhesive layer tends to be improved.

The weight average molecular weight of the polyether-modified silicone is not particularly limited. For example, it may be 5,000 or more and 20,000 or less, preferably 6,000 or more and 15,000 or less.

In addition, there is no particular limitation on the HLB value of the polyether-modified polysiloxane. Considering the compatibility with the resin, the surface offset, and the adhesion, it is preferably 5 or more, but not 16 or more. 7 Above 15 is more preferable.

The aforementioned HLB value is a measure of the balance between the hydrophilicity and hydrophobicity of the polyether-modified silicone. In this disclosure, the Griffin method is calculated according to the following formula, but when the polyether-modified polysiloxane is a commercially available product, the product catalog data is preferentially used.

HLB={(Sum of formula weight of hydrophilic group part)/(Molecular weight of polyether modified polysiloxane)}×20

The polyether-modified polysiloxane has in the molecule: dimethylsiloxane structural unit and methylpropylene siloxane structural unit with polyethylene oxide chain. These structural units may each constitute a block copolymer, or may constitute a random copolymer.

Specific examples of the polyether-modified silicone represented by the aforementioned general formula (3), for example, include "SF-8428", "FZ-2162", "SH-3773M" [above, Toray Dow Corning Co., Ltd. system].

The polyether-modified polysiloxane may be selected from the above-mentioned commercial products. In addition, for polyether-modified polysiloxane, organic compounds with unsaturated bonds and polyethylene oxide chains can be grafted to the main chain of dimethyl polysiloxane with hydrogenated silicon by hydrosilation reaction. And get.

The content of the polyether-modified polysiloxane in the adhesive composition of the present disclosure is preferably 0.05 parts by mass to 1.00 parts by mass relative to 100 parts by mass of the specific (meth)acrylic polymer, preferably 0.05 parts by mass The above is more preferably 0.70 parts by mass or less, and more preferably 0.05 parts by mass or more and 0.30 parts by mass or less.

When the content of the polyether-modified silicone is 0.05 parts by mass or more, there is a tendency that the antistatic property is more excellent. In addition, when the content of polyether-modified silicone is 1.00 parts by mass or less, the occurrence of contamination (stain) on the adherend can be suppressed, and the compatibility with the specific (meth)acrylic polymer can be suppressed White turbidity occurs due to decreased sex.

The adhesive composition of the present disclosure may include: a polysiloxane compound represented by the aforementioned general formula (3), and a dimethyl polysiloxane having a structure different from that of the general formula (3) and containing a polyethylene oxide group Oxyane compounds.

A dimethylpolysiloxane compound having a structure different from the general formula (3) and containing a polyethylene oxide chain, for example, a compound in which the end of the polyethylene oxide chain is an alkoxy group or an oxy group , Compounds containing polyethylene oxide chains in the main chain or at the end rather than in the side chain.

Specifically, 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", "SH-8400" (above, manufactured by Toray Dow Corning Co., Ltd.).

When the aforementioned adhesive composition contains a dimethylpolysiloxane compound having a structure different from the aforementioned general formula (3) and containing a polyethylene oxide chain, its content is preferably the total mass of the polysiloxane compound Among them, 0.05% by mass or less is preferable, and 0.03% by mass or less is more preferable.

[Other ingredients]

The adhesive composition for protective film of the present disclosure may contain weather resistance stabilizers and viscosity-increasing agents as needed, in addition to specific (meth)acrylic polymers, metal chelate crosslinking agents, and antistatic agents. Agents, plasticizers, softeners, peeling aids, dyes, pigments, inorganic fillers, surfactants, etc.

<Protective Film>

The protective film of the present disclosure includes an adhesive layer obtained from the adhesive composition for the protective film, and a base material.

When the aforementioned adhesive layer is obtained from the adhesive composition for a protective film, an adhesive layer with excellent adhesiveness, suppression of the generation of static electricity due to peeling and charging, and high-speed peelability can be formed.

The substrate used in the protective film of the present disclosure is not particularly limited as long as the adhesive layer can be formed on the substrate.

As for the base material, considering the viewpoint of inspection and management of optical components by fluoroscopy, the use of selected from polyester resins, acetate resins, polyether resins, polycarbonate resins, and polycarbonate resins can be cited. A film made of resins such as amide resins, polyimide resins, polyolefin resins, and acrylic resins. Among them, in terms of the substrate, a film obtained using a polyester resin is preferable from the viewpoint of surface protection performance, and a film obtained using a polyethylene terephthalate resin is particularly preferable in consideration of practicality.

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

An antistatic layer can also be provided on one or both sides of the substrate. In addition, in order to improve the adhesion with the adhesive layer, corona discharge treatment or the like may be applied to the surface of the substrate on the side where the adhesive layer is provided.

The protective film of the present disclosure is formed by disposing an adhesive layer obtained from the adhesive composition of the present disclosure on a substrate.

The method of forming the adhesive layer can be, for example, a method of directly or as necessary diluting the adhesive composition with a suitable solvent and coating it on the substrate, and then drying to remove the solvent.

In addition, the following method can also be used: first, the adhesive composition is coated on a release sheet composed of a suitable film such as paper or polyester film that has been subjected to mold release treatment with silicone resin, etc., and then heated and dried to form an adhesive bond. Then, the adhesive layer side of the release sheet is crimped to the substrate, and the adhesive layer is transferred to the substrate.

In the adhesive layer of the protective film of the present disclosure, the specific (meth)acrylic polymer is crosslinked by a metal chelate crosslinking agent. Thereby, the adhesive force during high-speed peeling of the adhesive layer can be suppressed to be low, and further, the curing completion time can be shortened.

The conditions for crosslinking the specific (meth)acrylic polymer with the metal chelate-based crosslinking agent are not particularly limited.

The thickness of the adhesive layer formed on the substrate can be appropriately set according to the adhesive force required for the protective film, the surface roughness of the optical member, etc. Generally, 1 μm or more and 100 μm or less can be exemplified, preferably 5 μm or more and 50 μm or less , Particularly preferably a thickness of about 15 μm or more and 30 μm or less.

If the adhesive strength of the adhesive layer becomes higher, the workability during high-speed peeling of a large area will decrease. Therefore, the adhesive force (peeling force) at a peeling speed of 30m/min (high-speed peeling) should be less than 2.00N/25mm. , Less than 1.20N/25mm is better, less than 0.70N/25mm is especially better.

In addition, considering the viewpoint of preventing sudden peeling of the protective film, the adhesive force (peeling force) at a peeling speed of 30m/min (high-speed peeling) is preferably 0.05N/25mm or more, more preferably 0.20N/25mm or more.

As far as the protective film is concerned, it is laminated on the surface of the optical component and protects the surface of the optical component from contamination or damage. When the optical component is processed into a liquid crystal display panel, the protective film can be directly laminated on the surface of the optical component. The state is provided for the various steps of press processing, inspection, transportation, LCD panel assembly, etc., if necessary, it can be subjected to heating and pressure treatment such as autoclave treatment, high temperature curing treatment, etc., and then peeling and removing from the optical member at the stage where surface protection is not required .

Examples of optical members include members that constitute devices (optical devices) such as image display devices and input devices, or members used in such devices, for example, polarizing plates, wavelength plates, retardation plates, optical compensation films, and brightness Reinforcement film, light guide plate, reflective film, anti-reflection film, transparent conductive film (ITO film, etc.).

As for the optical member using the protective film of this disclosure, a polarizing plate is preferable.

[Example]

Hereinafter, the present disclosure will be explained in more detail through examples, but the present disclosure is not limited to these examples.

(Manufacturing example A-1)

-Production of (meth)acrylic polymer (A-1)-

In a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a reflux cooler, 70.0 parts by mass of ethyl acetate was added. In a separate container, 60.0 parts by mass of n-butyl acrylate (BA) and 2-ethyl acrylate were added. 31.0 parts by mass of hexyl ester (2EHA) and 9.0 parts by mass of the monomer represented by the general formula (1a) (product name: ARONIX M-5300, manufactured by Toagosei Co., Ltd.) are used as monomers and mixed to prepare a monomer mixture . 20.0% by mass of the monomer mixture was added to the reactor, and after replacing the air in the aforementioned reaction vessel with nitrogen, 0.01 parts by mass of azobisbutyronitrile (hereinafter also referred to as "AIBN") was added as a polymerization initiator, The temperature of the mixture in the aforementioned reaction vessel was increased to 85°C under stirring in a nitrogen atmosphere, and the initial reaction was started. After the initial reaction was almost completed, the remaining monomer mixture 80.0% by mass, 15.0 mass parts of ethyl acetate and 0.10 mass parts of AIBN were added successively, and reacted for about 2 hours, and then further React for 2 hours. After that, a solution obtained by dissolving 0.10 parts by mass of tert-butyl peroxypivalate in 25.0 parts by mass of ethyl acetate was added dropwise to the above mixture over 1 hour, and the reaction was further carried out 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. The acid value, glass transition temperature (Tg), weight average molecular weight (Mw), weight average molecular weight (Mw) of the obtained (meth)acrylic polymer (A-1) solution relative to the number average molecular weight (Mn) The ratio of dispersion (Mw/Mn) is shown in Table 1.

In addition, the "solid content" is the residue after removing the solvent from the solution of the (meth)acrylic polymer. The acid value, the glass transition temperature (Tg), the weight average molecular weight (Mw), and the degree of dispersion (Mw/Mn) are calculated by the method described above.

The acid value is calculated as follows.

Acid value (mgKOH/g)={(A/100)÷B}×56.1×1000×C

A=(Meth)acrylic polymer or (meth)acrylic oligomer content rate (mass%) of monomers having carboxyl group in all monomers used in (meth)acrylic oligomer: 9.0

B=The molecular weight of ARONIXM-5300: 300.4

C=Number of carboxyl groups contained in 1 molecule of monomer with carboxyl group: 1

Acid value={(9.0/100)÷300.4}×56.1×1000×1=about 16.8

(Manufacturing examples A-2~A-10)

-Manufacturing of (meth)acrylic polymers (A-2)~(A-10)-

The monomer composition in Production Example 1 was changed to the monomer composition shown in Table 1, and the initiator amount and the like were appropriately adjusted, except that the same procedure as in Production Example 1 was carried out to produce a (meth)acrylic polymer (A- 2)~(A-10) solution. The acid value, glass transition temperature (Tg), weight average molecular weight (Mw) and degree of dispersion (Mw/Mn) of the obtained acrylic polymer are shown in Table 1.

In addition, the acid value, the glass transition temperature (Tg), the weight average molecular weight (Mw), and the degree of dispersion (Mw/Mn) are calculated by the method already described.

(Manufacturing Example B)

-Production of (meth)acrylic oligomer (B)-

In a reaction vessel equipped with a stirring blade, a thermometer, a nitrogen introduction tube, a cooler, and a dropping funnel, 100.0 parts by mass of methyl ethyl ketone, methoxy polyethylene glycol methacrylate (the average addition value of the alkylene oxide unit Ears 23) (MePEGMA) 10.0 parts by mass, heated to reflux temperature while stirring in a nitrogen atmosphere. In the dropping funnel was added a pre-mixed solution of 87.0 parts by mass of 2-ethylhexyl methacrylate (2EHMA), 3.0 parts by mass of acrylic acid (AA), 100.0 parts by mass of methyl ethyl ketone, and 5.0 parts by mass of azobisisobutyronitrile. , Added to the reaction vessel at reflux temperature one by one over 120 minutes. After that, the reaction was performed while maintaining the reflux temperature for 240 minutes, and the reaction was terminated.

The solid content of the solution of the obtained (meth)acrylic oligomer (B) was 33.0% by mass. Table 1 shows the acid value, weight average molecular weight (Mw), and degree of dispersion (Mw/Mn) of the solution of the (meth)acrylic oligomer (B).

In addition, the acid value, the glass transition temperature (Tg), the weight average molecular weight (Mw), and the degree of dispersion (Mw/Mn) are calculated by the method already described.

The abbreviations in Table 1 are as follows.

‧BA: n-Butyl Acrylate

‧2EHA: 2-ethylhexyl acrylate

‧M-5300: ω-carboxy-polycaprolactone (n≒2) monoacrylate (trade name: ARONIX M-5300, manufactured by Toagosei Co., Ltd.) (monomer represented by general formula (1a))

‧2EHMA: 2-ethylhexyl methacrylate

‧AA: Acrylic

‧HOA-MS: 2-propylene oxyethyl-succinic acid (monomer represented by general formula (1a), manufactured by Kyoeisha Chemical Co., Ltd., trade name: LIGHT ACRYLATE HOA-MS(N))

‧MePEGMA: Methoxy polyethylene glycol methacrylate (the average addition mole number of the alkylene oxide unit is 23)

<Example 1>

Into a four-necked flask equipped with a stirring blade, a thermometer, a cooler, and a dropping funnel, the solution (solid content 48.0% by mass) of the (meth)acrylic polymer (A-1) prepared in Production Example 1 was added by 208.3 mass Parts (100 parts by mass of solid content), a solution (33.0% by mass of solid content) of the (meth)acrylic oligomer (B) prepared in Production Example 3, 1.5 parts by mass (0.50 parts by mass of solid content), as a resistance The electrostatic agent Li(CF ₃ SO ₂ ) ₂ N (LiTFSI manufactured by Morita Chemical Industry Co., Ltd.) was 0.20 parts by mass, and the liquid temperature in the flask was maintained at around 25° C., and mixing and stirring were performed for 4.0 hours. 0.10 parts by mass of SH-3773M (trade name, manufactured by Toray Dow Corning, solid content 100.0% by mass) as polyether-modified polysiloxane, and aluminum acetone as a metal chelate crosslinking agent (Trade name: Aluminum chelate A, manufactured by Kawaken Fine Chemicals Co., Ltd.) 32.9 parts by mass (solid) of aluminum chelate A diluted product (solid content 9.72% by mass) obtained by diluting acetone and toluene The composition is 3.2 parts by mass, 1.0 equivalent), and fully stirred to obtain an adhesive composition solution for a protective film. Using this adhesive composition solution, a protective film for testing was made according to the following manufacturing method of the adhesive sheet for testing, and various physical property tests were performed. The results obtained are shown in Table 2.

In addition, the equivalent of aluminum ginsenoside (aluminum chelate) contained in the above-mentioned aluminum chelate A dilution is shown to be 1 equivalent with respect to the carboxyl group contained in the (meth)acrylic polymer.

The calculation of the equivalent weight of the aluminum chelate is performed using the method already described, and specifically it is calculated as follows.

Equivalent=(A×B/C)/(D ₁ ×E ₁ /F ₁ +D ₂ ×E ₂ /F ₂ +‧‧‧‧+D _n ×E _n /F _n )

A=The valence of the metal of aluminum chelate: 3.0

B= parts by mass of aluminum chelate (amount of solid content): 3.2 parts by mass

C=The molecular weight of aluminum chelate: 324.3

D ₁ = The content rate (mass%) of each monomer having an acidic group in all monomers used in the (meth)acrylic polymer: 9.0% by mass

E ₁ = the number of acidic groups contained in one molecule of each monomer having an acidic group: 1

F ₁ = Molecular weight of ARONIX M-5300: 300.4

n=Type of (meth)acrylic monomer used: 1

Equivalent=(A×B/C)/(D ₁ ×E ₁ /F ₁ )=(3×3.2/324.3)/(9×1/300.4)=about 1.0

(1) Production of protective film for testing

In such a way that the coating amount after drying becomes 20g/m ² , the polyethylene terephthalate (PET) film (trade name: Teijin Tetoron Film Type G2, thickness 38μm, Teijin-DuPont Film Co., Ltd.) (Preparation) Coat the adhesive composition solution on it, and dry it with a hot air circulating dryer at 100°C for 60 seconds to form an adhesive layer, and make a PET film with the adhesive layer. After that, on a release film (trade name: FILMBYNA 100E-0010NO23, thickness 100 μm, manufactured by Fujimori Kogyo Co., Ltd.) that has been surface-treated with a silicone-based release agent, the adhesive layer is brought into contact with each other. Place the PET film with the adhesive layer to form a laminate. After pressing and bonding the laminate with a pressure nip roller, the laminate is cured under the conditions of 23°C and 50%RH for 1 hour. Obtain a protective film for testing.

(2) Adhesion and peelability during high-speed peeling

The protective film for the test obtained in (1) above was cut into 25mm×150mm to make a protective film. The release film was removed from the protective film, and the exposed adhesive layer was attached to the TAC film (trade name: Lonza TAC100, manufactured by PANAC Co., Ltd.), a 2 kg rubber roller was crimped back and forth twice to prepare a test sample. After placing the test sample at 23°C and 50%RH for 24 hours, the adhesive force at 180° peeling as shown in Figure 1 was measured at a high-speed peeling speed of 30m/min, and the following evaluation criteria were followed. The balance of peelability and adhesive force during high-speed peeling was evaluated, and the results are shown in Table 2.

In terms of evaluation, the test sample is placed on a glass plate with the surface of the TAC film in contact as shown in Figure 1, holding one end of the test sample, and pulling it along the surface of the glass plate in a direction of 180° to remove the PET film from the adhesive. The adhesive layer is peeled off.

[Evaluation criteria]

AA: 0.20N/25mm or more and less than 0.70N/25mm (excellent peelability, and is not prone to sudden peeling, excellent adhesion)

A: 0.05N/25mm or more and less than 0.20N/25mm, or 0.70N/25mm or more and less than 1.20N/25mm (excellent peelability, and less prone to sudden peeling, slightly superior adhesion)

B: 1.20N/25mm or more and less than 2.0N/25mm (peelability is slightly worse, but within the allowable range)

C: 2.0N/25mm or more (the peelability is poor, and it is an unacceptable range)

D: Less than 0.05N/25mm (there is a possibility of sudden peeling, this is an unacceptable range)

(3) Antistatic

The test protective film obtained in (1) above was cut into 25 mm×150 mm to prepare a test protective film. The peeling film was removed from the protective film for the test, the exposed adhesive layer was attached to the TAC film (trade name: Lonza TAC100, manufactured by PANAC Co., Ltd.), and a 2 kg rubber roller was pressed back and forth twice. Make test samples. After placing the test sample at 23°C and 50%RH for 24 hours, it is the same as the above (2) In such a method, peeling is performed in the 180° direction at a peeling speed of 30 m/min (high speed) as shown in FIG. 1. The potential of the TAC film surface generated at this time was measured with a potential measuring device (trade name: KSD-0303, manufactured by Kasuga Electric Co., Ltd.) fixedly arranged at a predetermined position (a position 10 mm from the surface of the TAC film). The absolute value of the measured value was used as the peeling static voltage, and the antistatic property was evaluated according to the following evaluation criteria. The results are shown in Table 2.

[Evaluation criteria]

AA: less than 0.4kv (excellent antistatic property)

A: 0.4kv or more and less than 0.6kv (excellent antistatic property)

B: 0.6kv or more and less than 1.0kv (the antistatic property is slightly worse, but it is an allowable range)

C: 1.0kv or more (poor antistatic)

(4) Time of maturation completion

In such a way that the coating amount after drying becomes 20g/m ² , the polyethylene terephthalate (PET) film (trade name: Teijin Tetoron Film Type G2, thickness 38μm, Teijin-DuPont Film Co., Ltd.) (Preparation) Coat the adhesive composition solution for the protective film and dry it at 100°C with a hot-air circulating dryer for 60 seconds to form an adhesive layer to produce a PET film with an adhesive layer. After that, the mold release film (trade name: FILMBYNA 100E-0010NO23, thickness 100μm, manufactured by Fujimori Kogyo Co., Ltd.) is surface-treated with a silicone-based mold release agent, and placed in contact with the adhesive layer. The PET film with the adhesive layer is placed to form a laminate, and the laminate is press-bonded and bonded by a pressure nip roller pair. Maturation was performed in an environment of 23°C and 50% RH to obtain a protective film for testing. At this time, the curing time is set to 1 hour, 24 hours, and 96 hours. Immediately after each curing time, the protective film for the test is cut into 25mm in such a way that the adhesive layer exposed after the release film is peeled off is in contact with each other. Each test protective film obtained by ×150 mm was attached to a TAC film (trade name: Lonza TAC100, manufactured by PANAC Co., Ltd.), and a 2 kg rubber roller was pressed back and forth twice to prepare a test sample.

After leaving the test sample at 23°C and 50%RH for 24 hours, it was peeled off in the 180° direction at a peeling speed of 30m/min (high speed) in the same way as in (2) above as shown in Figure 1. , And evaluate the maturation completion time according to the following evaluation criteria. The results obtained are shown in Table 2.

[Evaluation criteria]

A: The absolute value of the difference between the adhesive force after curing for 1 hour and the adhesive force after curing for 24 hours is less than 0.05N/25mm (the curing is completed within 1 hour, and the curing completion time is short, which is good)

B: Does not meet the evaluation A, and the absolute value of the difference between the adhesive force after aging for 24 hours and the adhesive force after aging for 96 hours is 0.05N/25mm or less (the aging is completed within 1 hour or more within 24 hours, and the aging completion time is slightly shorter , Slightly good)

C: Does not meet either of the evaluations A and B (the maturation is not completed within 24 hours, and the maturation completion time is long, which is bad)

<Example 2~Example 18, Comparative Examples 1~7>

Except having changed the composition of Example 1 to the composition shown in Table 2, the same procedure as in Example 1 was carried out, and the adhesive composition for protective film shown in Table 2 was produced. Using the prepared adhesive composition, a protective film for testing was made according to the following manufacturing method of protective film for testing, and various physical properties were tested. The results obtained are shown in Table 2.

In addition, when the aging was not completed within 1 hour, that is, when the evaluation of the aging completion time was B or C, the aging was performed for 240 hours to obtain a protective film for a test. Specifically, Comparative Examples 5, 6, and 7 were cured for 240 hours to obtain a protective film for a test.

In addition, the addition part of the crosslinking agent in Comparative Examples 5 and 6 was set so that the total amount of the isocyanate groups contained in the isocyanate compound and the carboxyl groups contained in the (meth)acrylic polymer became 1 equivalent. In addition, the addition part of the crosslinking agent in Comparative Example 7 was set so that the epoxy group contained in the epoxy compound was 1 equivalent to the total of the carboxyl group contained in the (meth)acrylic polymer.

【Table 2】

The abbreviations in Table 2 are as follows.

‧LiTFSI: Li(CF ₃ SO ₂ ) ₂ N (manufactured by Morita Chemical Industry Co., Ltd.)

‧LiTFS: LiCF ₃ SO ₃ (manufactured by Morita Chemical Industry Co., Ltd.)

‧ Organic Salt A: N- hexylpyridinium ‧PF ₆ ^- (pyridinium ion having a hexyl group as an organic salt of an organic cation, a melting point of 45 ℃)

‧SH-3773M: Dimethylsiloxane compound with polyalkoxyl group introduced into the side chain (manufactured by Toray Dow Corning Co., Ltd., the end of the polyalkoxyl group is a hydroxyl group, HLB value = 8)

‧Al chelate: obtained by diluting ginseng aluminum acetone aluminum (trade name: aluminum chelate A, manufactured by Kaiken Fine Chemical Co., Ltd.) with toluene and acetone to a solid content of 9.7% by mass

‧Isocyanate crosslinking agent A: adduct of toluene diisocyanate and trimethylolpropane (trade name: CORONATE L, manufactured by Tosoh Corporation, solid content 100% by mass)

‧Isocyanate crosslinking agent B: adduct of hexamethylene diisocyanate and trimethylolpropane (trade name: DESMODUR N3300, manufactured by Sumika Covestro Urethane Co., Ltd., solid content 100% by mass)

‧Epoxy crosslinking agent A: 1,3-phenylene bis(N,N-diepoxypropyl methylamine) (trade name: TETRAD-X, manufactured by Mitsubishi Gas Chemical Co., Ltd., solid content 100 mass %)

It can be seen that in Examples 1 to 5, since a (meth)acrylic polymer with an acid value of 9 mgKOH/g or more and 70 mgKOH/g or less is used, the acidic group 1 equivalent of the above-mentioned (meth)acrylic polymer is 0.3 The metal chelate crosslinking agent and antistatic agent with the equivalent of more than 2.0 equivalents have a short curing completion time, excellent antistatic properties, adhesive strength to the extent that they will not peel off suddenly, and excellent high-speed peeling. It can be seen that especially in Examples 2 to 5, even if the acid value of the (meth)acrylic polymer is above 9mgKOH/g In the case of an increase or decrease in the range of 70 mgKOH/g or less, the curing completion time is also short, and the antistatic property is excellent, and the adhesive force is not suddenly peeled off, and the high-speed peeling property is excellent.

It can be seen that in Examples 6 to 8, the equivalent weight of the metal chelate crosslinking agent is increased within the range of 0.3 to 2.0 equivalents relative to 1 equivalent of the acidic group of the (meth)acrylic polymer. In the case of reduction, the curing completion time is also short, and the antistatic property is excellent, and it has an adhesive force to the extent that it does not peel off suddenly, and it has excellent peelability during high-speed peeling.

It can be seen that in Examples 9 and 10, even when LiTFS of an alkali metal salt other than LiTFSI and an organic salt A of an ionic compound other than an alkali metal salt are used as the antistatic agent, the maturation completion time is short and the antistatic property is excellent. It has adhesive strength to the extent that it does not suddenly peel off, and it has excellent high-speed peeling properties.

It can be seen that in Examples 11 to 13, even when a (meth)acrylic polymer made from a monomer whose main component in the monomer composition or the type of acidic group is changed is used, the obtained protective film adhesive The adhesive composition has a short curing completion time, is excellent in antistatic properties, has an adhesive force that does not suddenly peel off, and has excellent high-speed peeling properties.

It can be seen that in Examples 14 and 15, even when the content of polyether-modified silicone is increased or decreased within the range of 0.05 parts by mass to 1.0 part by mass, the maturation completion time is short and the antistatic property is excellent. , It has the adhesive force to the extent that it will not peel off suddenly, and it has excellent high-speed peeling performance.

It can be seen that in Examples 16 to 18, even if the content of (meth)acrylic oligomer is increased or decreased, or even if it does not contain (meth)acrylic oligomer and polyether modified silicone Bottom, the curing completion time is short, and the antistatic property is excellent, it has the adhesive force to the extent that it will not peel off suddenly, and the high-speed peeling property is excellent.

It can be seen that in Comparative Example 1, a (meth)acrylic polymer having an acid value of less than 9 mgKOH/g was used, so the high-speed peelability was poor. It can be seen that in Comparative Example 2, a (meth)acrylic polymer with an acid value of more than 70 mgKOH/g was used, Therefore, the adhesive force is low, and there is a possibility of sudden peeling from the adherend. In addition, the antistatic performance is poor. It can be seen that in Comparative Example 3, the equivalent weight of the metal chelate-based crosslinking agent was less than 0.3 equivalent, so the high-speed peelability was poor. It can be seen that in Comparative Example 4, the equivalent weight of the metal chelate-based crosslinking agent exceeds 2.0 equivalents, so the adhesive force is low, and there is a possibility of sudden peeling from the adherend. In addition, the antistatic performance is poor. It can be seen that in Comparative Example 5, a toluene diisocyanate-based crosslinking agent was used instead of a metal chelate-based crosslinking agent, so the antistatic property was poor, and the maturation completion time was also long. It can be seen that in Comparative Example 6, a hexamethylene diisocyanate-based crosslinking agent was used instead of a metal chelate-based crosslinking agent, so the maturation completion time was long. It can be seen that in Comparative Example 7, an epoxy-based crosslinking agent was used, so the maturation completion time was long.

In contrast, it can be seen that the protective film formed from the adhesive composition of the present disclosure has a short curing completion time, is excellent in antistatic properties, has an adhesive force that does not suddenly peel off, and the adhesive force during high-speed peeling can be suppressed to be low.

Claims (7)

An adhesive composition for a protective film, comprising: a (meth)acrylic polymer having an acid value of 9 mgKOH/g or more and 70 mgKOH/g or less, with respect to 1 equivalent of acidic groups of the (meth)acrylic polymer 0.3 to 2.0 equivalents of metal chelate crosslinking agent and antistatic agent. For example, the adhesive composition for protective film of the first item of the scope of patent application, wherein the (meth)acrylic polymer contains the structural unit represented by the following general formula (1); [化1]

In the general formula (1), R ¹ represents a hydrogen atom or a methyl group; L represents a divalent linking group consisting of at least one selected from the group consisting of an alkylene group, an arylene group, a carbonyl group, and an oxygen atom. For example, the adhesive composition for protective film of the first item of the scope of patent application, wherein the product of the acid value of the (meth)acrylic polymer and the equivalent of the metal chelate crosslinking agent is 3 or more and 40 or less Within the range. For example, the adhesive composition for protective film in the first item of the scope of patent application further includes polyether-modified polysiloxane. The content of the polyether-modified polysiloxane is relative to 100% of the (meth)acrylic polymer. Parts by mass are 0.05 parts by mass or more and 1.00 parts by mass or less. For example, the adhesive composition for protective film in the first item of the scope of the patent application further includes a structural unit derived from a monomer having a carboxyl group, and includes a (meth)acrylic oligomer with a weight average molecular weight of 3,000 or more and 30,000 or less, The content of the (meth)acrylic oligomer is 0.05 parts by mass or more and 2.00 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic polymer. For example, the adhesive composition for a protective film of the 5th item of the scope of patent application, wherein the (meth)acrylic oligomer contains 5% by mass or more and 30% by mass or less relative to all structural units. The constituent unit of monomers containing alkylene oxide chains. A protective film comprising: an adhesive layer configured by using the adhesive composition for a protective film as in any one of items 1 to 6 of the scope of patent application, and a substrate.

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