JP2022033203A - Surface protection film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface protection film that has excellent antistatic performance, has well-balanced adhesion both at low and high peeling rates, and has excellent durability and reworkability.

SOLUTION: In a surface protection film, an acrylic polymer comprises a copolymer of (A) a methacrylate monomer with a C4-C18 alkyl group, (B) a monomer containing a hydroxy group, (D) a polyalkylene glycol monomethacrylate monomer and/or (E) a nitrogen-containing vinyl monomer or alkoxy group-containing alkyl methacrylate monomer, and a crosslinker comprises (F) an isocyanate compound having three or more functional groups and (G) a bifunctional acyclic aliphatic isocyanate compound. The surface protection film has a surface resistivity of 5.0×10⁺¹⁰ Ω/sq or less and a peeling charge voltage of ±0-1kV.

SELECTED DRAWING: None

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a surface protective film used in a manufacturing process of a liquid crystal display. More specifically, surface protection used to protect the surface of an optical member such as a polarizing plate or a retardation plate by attaching it to the surface of an optical member such as a polarizing plate or a retardation plate constituting a liquid crystal display. It's about film.

Conventionally, in the manufacturing process of an optical member such as a polarizing plate and a retardation plate, which are members constituting a liquid crystal display, a surface protective film for temporarily protecting the surface of the optical member is attached. Such a surface protective film is used only in the process of manufacturing the optical member, and is peeled off from the optical member and removed when the optical member is incorporated into the liquid crystal display. Since such a surface protective film for protecting the surface of the optical member is used only in the manufacturing process, it is also generally called a process film.

The surface protective film used in the process of manufacturing the optical member as described above has an adhesive layer formed on one side of an optically transparent polyethylene terephthalate (PET) resin film, and is bonded to the optical member. Until then, a peeling-treated release film for protecting the pressure-sensitive adhesive layer is bonded onto the pressure-sensitive adhesive layer.
In addition, optical members such as polarizing plates and retardation plates are inspected with optical evaluations such as display capability, hue, contrast, and foreign matter contamination of the liquid crystal display plate with the surface protective film bonded. As the required performance for the surface protective film, it is required that no air bubbles or foreign substances adhere to the pressure-sensitive adhesive layer.
Further, in recent years, when the surface protective film is peeled off from an optical member such as a polarizing plate or a retardation plate, the peeling charge generated by the static electricity generated when the adherend peels off the adhesive layer is electrically controlled by the liquid crystal display. There is a concern that it may affect circuit failure, and excellent antistatic performance is required for the pressure-sensitive adhesive layer.
Further, when the surface protective film is attached to an optical member such as a polarizing plate or a retardation plate, the surface protective film may be peeled off and then reattached for various reasons. In addition, it is required that it can be easily peeled off from the optical member of the adherend (reworkability).
Further, when the surface protective film is finally peeled off from an optical member such as a polarizing plate or a retardation plate, it is required to be able to peel off quickly. It is required that the adhesive strength does not change much depending on the peeling speed so that the peeling can be performed quickly even by so-called high-speed peeling.

As described above, in recent years, as the required performance for the pressure-sensitive adhesive layer constituting the surface protective film, (1) balancing the adhesive strength at a low peeling speed and a high-speed peeling speed, and (2) adhesive residue. (3) Excellent antistatic performance, (4) rework performance, etc. are required from the viewpoint of ease of use when using the surface protective film.
However, although each of these (1) to (4), which is the required performance for the pressure-sensitive adhesive layer constituting the surface protective film, can be satisfied, the pressure-sensitive adhesive layer of the surface protective film is required. It was a very difficult task to satisfy all the required performances (1) to (4) at the same time.

For example, the following proposals are known for (1) balancing the adhesive force at a low peeling speed and a high peeling speed, and (2) preventing the generation of adhesive residue. ..

Acrylic adhesive with a main component of a copolymer of a (meth) acrylic acid alkyl ester having an alkyl group having 7 or less carbon atoms and a carboxyl group-containing copolymer compound, which is crosslinked with a crosslinking agent. In the agent layer, there is a problem that the adhesive is transferred to the adherend side when it is adhered for a long period of time, and the adhesive force to the adherend has a large increase with time. In order to avoid this, a copolymer of a (meth) acrylic acid alkyl ester having an alkyl group having 8 to 10 carbon atoms and a copolymerizable compound having an alcoholic hydroxyl group is used, and this is used as a cross-linking agent. Those provided with a crosslinked pressure-sensitive adhesive layer are known (Patent Document 1).
Further, a pressure-sensitive adhesive layer is provided in which a small amount of a copolymer of a (meth) acrylic acid alkyl ester and a carboxyl group-containing copolymer compound is blended with the same copolymer as described above, and the copolymer is crosslinked with a crosslinking agent. Something like that has been proposed. However, when they are used to protect the surface of plastic plates with low surface tension and a smooth surface, they cause peeling phenomena such as floating due to heating during processing and storage, and at high speeds, which is a manual work area. There was also a problem that the re-peelability at the time of peeling was inferior.

In order to solve these problems, a) 100 parts by weight of the (meth) acrylic acid alkyl ester containing a (meth) acrylic acid alkyl ester having an alkyl group having 8 to 10 carbon atoms as a main component, and b) a carboxyl group. The above-mentioned copolymer is added to a copolymer of a monomer mixture consisting of 1 to 15 parts by weight of a copolymerizable compound contained and c) 3 to 100 parts by weight of a vinyl ester of an aliphatic carboxylic acid having 1 to 5 carbon atoms. b) A pressure-sensitive adhesive composition containing an equivalent or more of a cross-linking agent with respect to the carboxyl group of the component has been proposed (Patent Document 2).
The pressure-sensitive adhesive composition described in Patent Document 2 does not cause a peeling phenomenon such as floating during processing or storage, and moreover, it has a small adhesive strength with time and is excellent in re-peelability. Even if it is stored for a long period of time, especially in a high temperature atmosphere, it can be peeled off again with a small force, and at that time, no adhesive residue is generated on the adherend, and even when high-speed peeling is performed, it can be peeled off again with a small force.

Further, regarding (3) excellent antistatic performance, a method of kneading an antistatic agent into a base film is shown as a method for imparting antistatic properties to the surface protective film. Examples of the antistatic agent include (a) various cationic antistatic agents having a cationic group such as a quaternary ammonium salt, a pyridinium salt, and a primary to tertiary amino group, and (b) a sulfonic acid base and a sulfuric acid. Anionic antistatic agents having anionic groups such as ester bases, phosphate ester bases and phosphonic acid bases, (c) amphoteric antistatic agents such as amino acid-based and aminosulfate ester-based, (d) amino alcohol-based and glycerin-based , Nonionic antistatic agents such as polyethylene glycol type, (e) high molecular weight antistatic agents obtained by increasing the molecular weight of the antistatic agents as described above, and the like are disclosed (Patent Document 3).
Further, in recent years, it has been proposed to contain such an antistatic agent in the base film, or to directly contain the antistatic agent in the pressure-sensitive adhesive layer instead of applying it to the surface of the base film.

Regarding (4) rework performance, for example, a pressure-sensitive adhesive in which an isocyanate-based compound curing agent and a specific silicate oligomer are blended in an acrylic resin in an amount of 0.0001 to 10 parts by weight with respect to 100 parts by weight of the acrylic resin. An agent composition has been proposed (Patent Document 4).
In Patent Document 4, an acrylic acid alkyl ester having an alkyl group having about 2 to 12 carbon atoms, a methacrylate alkyl ester having an alkyl group having about 4 to 12 carbon atoms, or the like is used as a main monomer component, and for example, a carboxyl group-containing monomer or the like. It is said that it can contain other functional group-containing monomer components. Generally, it is preferable to contain the above main monomer in an amount of 50% by weight or more, and the content of the functional group-containing monomer component is 0.001 to 50% by weight, preferably 0.001 to 25% by weight, and more preferably. It is said that it is desired to be 0.01 to 25% by weight. Such a pressure-sensitive adhesive composition described in Patent Document 4 has a small change in cohesive force and adhesive force with time even under high temperature or high temperature and high humidity, and exhibits an excellent effect on the adhesive force to a curved surface. It is said to have reworkability.
In general, when the pressure-sensitive adhesive layer has a soft property, adhesive residue is likely to occur, and the reworkability is likely to decrease. That is, it is difficult to re-peel the material when it is mistakenly attached, and it is easy to re-attach it. From this, it is considered necessary to crosslink a monomer having a functional group such as a carboxyl group with the main agent to make the pressure-sensitive adhesive layer have a certain hardness in order to have reworkability.

Japanese Unexamined Patent Publication No. 63-225677 Japanese Unexamined Patent Publication No. 11-256111 Japanese Unexamined Patent Publication No. 11-070629 Japanese Unexamined Patent Publication No. 8-199130

In the prior art, the required performances for the adhesive layer constituting the surface protective film include balancing the adhesive force at a low peeling speed and a high peeling speed, excellent antistatic performance, and reworking performance. I have been asked. However, although each of them could meet the individual required performance, it could not satisfy all the required performance of the pressure-sensitive adhesive layer of the surface protective film.

The present invention has been made in view of the above circumstances, has excellent antistatic performance, has an excellent balance of adhesive force at a low peeling speed and a high peeling speed, and has excellent durability and rework. An object of the present invention is to provide a surface protective film having excellent performance.

In order to solve the above problems, the present invention forms a pressure-sensitive adhesive layer in which a pressure-sensitive adhesive composition containing an acrylic polymer, an (H) antistatic agent, and a cross-linking agent is cross-linked on one side of a resin film. A (meth) acrylic acid ester monomer having (A) alkyl groups having C4 to C18 carbon atoms when the total amount of the acrylic polymers is 100 parts by weight. Contains 50 to 91 parts by weight of at least one of the above, 0.1 to 10 parts by weight of the total of at least one copolymerizable monomer containing (B) hydroxyl group, and (C) carboxyl group. The total amount of the copolymerizable monomers is 0 to 1.0 part by weight (however, the case where the copolymerizable monomer containing (C) carboxyl group is not contained) and the copolymerizable monomer group (D). ) The total of at least one of the polyalkylene glycol mono (meth) acrylic acid ester monomer or the alkoxypolyalkylene glycol mono (meth) acrylic acid ester monomer is more than 0 parts by weight and 49.9 parts by weight or less, and / or (E). A copolymer obtained by copolymerizing at least one of a nitrogen-containing vinyl monomer containing no hydroxyl group and an isocyanate group or an alkoxy group-containing alkyl (meth) acrylate monomer containing no hydroxyl group with a total of more than 0 parts by weight and 20 parts by weight or less. 8-Hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2 -At least one selected from the compound group consisting of hydroxyethyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, and N-hydroxyethyl (meth) acrylamide. , The (H) antistatic agent is contained in an amount of 0.01 to 5.0 parts by weight with respect to 100 parts by weight of the copolymer, and is a solid ion having a melting point of 30 ° C. or higher and 50 ° C. or lower at a temperature of 30 ° C. A sex compound or an acryloyl group-containing ionic compound copolymerized in the copolymer at a ratio of 0.1 to 5.0% by weight, and the cross-linking agent is (F) a trifunctional or higher functional isocyanate compound. And (G) a bifunctional acyclic aliphatic isocyanate compound, and the pressure-sensitive adhesive composition is an isociane having (F) trifunctionality or higher with respect to 100 parts by weight of the acrylic polymer. The total of the compound and the (G) bifunctional acyclic aliphatic isocyanate compound is contained in a proportion of 0.1 to 5.0 parts by weight, and the (F) trifunctional or higher functional isocyanate compound is contained. The weight ratio (F / G) with the (G) bifunctional acyclic aliphatic isocyanate compound is 1 to 90, and the (G) bifunctional acyclic aliphatic isocyanate compound is the aliphatic diisocyanate compound. Provided is a surface protective film characterized by being a bifunctional acyclic aliphatic isocyanate compound produced by reacting with a diol compound.

Further, when the total amount of the acrylic polymers of the copolymer is 100 parts by weight,
(A) 50 to 91 parts by weight of a (meth) acrylic acid ester monomer having an alkyl group having C4 to C18 carbon atoms.
(B) 0.1 to 10 parts by weight of a copolymerizable monomer containing a hydroxyl group,
(C) 0 to 1.0 part by weight of a copolymerizable monomer containing a carboxyl group.
(D) Polyalkylene glycol mono (meth) acrylic acid ester monomer or alkoxypolyalkylene glycol mono (meth) acrylic acid ester monomer from 0 to 49.9 parts by weight,
(E) It is preferable that a nitrogen-containing vinyl monomer containing no hydroxyl group and an isocyanate group or an alkoxy group-containing alkyl (meth) acrylate monomer containing no hydroxyl group is contained in an amount of 0 to 20 parts by weight.

Further, the weight ratio (F / G) of the (F) trifunctional or higher functional isocyanate compound to the (G) bifunctional acyclic aliphatic isocyanate compound is 1 to 90, and 100 parts by weight of the acrylic polymer is used. On the other hand, the total amount of the (F) trifunctional or higher functional isocyanate compound and the (G) bifunctional acyclic aliphatic isocyanate compound is preferably 0.1 to 5.0 parts by weight.

Further, the (G) bifunctional acyclic aliphatic isocyanate compound is a compound produced by reacting a diisocyanate compound with a diol compound. The diisocyanate compound is an aliphatic diisocyanate, and preferably consists of one selected from the compound group consisting of tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate. Examples of the diol compound include 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, and 2-ethyl. A group of compounds consisting of -2-butyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol monohydroxybivalate, polyethylene glycol, and polypropylene glycol. It is preferably composed of one selected from the above.

Further, the copolymerizable monomer containing the (B) hydroxyl group is 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxyethyl (meth). ) At least one selected from the compound group consisting of acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, and N-hydroxyethyl (meth) acrylamide is preferable.

Further, the copolymerizable monomer containing the (C) carboxyl group is (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthal. Acid, 2- (meth) acryloyloxypropyl hexahydrophthalic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl maleine It is preferably at least one selected from the compound group consisting of an acid, a carboxypolycaprolactone mono (meth) acrylate, and 2- (meth) acryloyloxyethyl tetrahydrophthalic acid.

Further, the (D) polyalkylene glycol mono (meth) acrylic acid ester monomer is selected from polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate, and ethoxypolyalkylene glycol (meth) acrylate. Moreover, it is preferable that it is at least one kind.

The trifunctional or higher functional isocyanate compound is an isocyanurate form of a hexamethylene diisocyanate compound, an isocyanurate form of an isophorone diisocyanate compound, an adduct form of a hexamethylene diisocyanate compound, an adduct form of an isophorone diisocyanate compound, or a burette of a hexamethylene diisocyanate compound. Body, bullet form of isophorone diisocyanate compound, isocyanurate form of tolylene diisocyanate compound, isocyanurate form of xylylene diisocyanate compound, isocyanurate form of hydrogenated xylylene diisocyanate compound, adduct form of tolylene diisocyanate compound, xylylene diisocyanate compound It is preferable that at least one selected from the compound group consisting of the adduct body of the above and the adduct body of the hydrogenated xylylene diisocyanate compound.

Further, it is preferable that the acrylic polymer contains at least one or more of the (E) hydroxyl group-free nitrogen-containing vinyl monomer or the alkoxy group-containing alkyl (meth) acrylate monomer as the copolymerizable monomer group.

Further, the (H) antistatic agent is an ionic compound having a melting point of 30 to 50 ° C., which is contained in an amount of 0.01 to 5.0 parts by weight with respect to 100 parts by weight of the copolymer. , 0.1 to 5.0% by weight of the copolymer is preferably an acryloyl group-containing ionic compound.

Further, the pressure-sensitive adhesive force of the pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition at a low-speed peeling speed of 0.3 m / min is 0.05 to 0.1 N / 25 mm, and the high-speed peeling speed is 30 m / min. The adhesive strength is preferably 1.0 N / 25 mm or less.

Further, it is preferable that the surface resistivity of the pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition is 5.0 × 10 ⁺¹⁰ Ω / □ or less, and the peeling band voltage is ± 0 to 1 kV.

The present invention also provides a surface protective film characterized in that a pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition is formed on one side or both sides of a resin film.

Further, the surface protective film of the present invention can be used as a surface protective film for a polarizing plate.

Further, it is preferable that the surface protective film of the present invention is antistatic and antifouling treated on the surface of the resin film opposite to the side on which the pressure-sensitive adhesive layer is formed.

According to the present invention, all the performances required for the pressure-sensitive adhesive layer of the surface protective film, which cannot be solved by the prior art, can be satisfied, and excellent antistatic performance can be obtained, and the glue can be obtained. It became possible to prevent the remaining occurrence. Specifically, while maintaining excellent antistatic performance, the amount of antistatic agent added can be reduced, and the performance of preventing the generation of adhesive residue can be further improved.
Further, by using (F) a trifunctional or higher functional isocyanate compound in combination with (G) a bifunctional acyclic aliphatic isocyanate compound, the crosslinkability is excellent, the stain resistance is good, and the peeling speed is low. The balance of adhesive strength is excellent at high peeling speeds and high speeds.

Hereinafter, the present invention will be described based on a preferred embodiment.
The pressure-sensitive adhesive composition of the present invention has (A) a hydroxyl group as a group of monomers copolymerizable with at least one of (meth) acrylic acid ester monomers having an alkyl group having C4 to C18 carbon atoms. Containing copolymerizable monomer, (C) carboxyl group-containing copolymerizable monomer, (D) polyalkylene glycol mono (meth) acrylic acid ester monomer, and (E) hydroxyl group-free nitrogen-containing vinyl It is composed of an acrylic polymer of a copolymer containing a monomer or an alkoxy group-containing alkyl (meth) acrylate monomer and at least one selected from a group of copolymerizable monomers, and further (F) trifunctional. It is characterized by containing the above isocyanate compound, (G) a bifunctional acyclic aliphatic isocyanate compound, and (H) an antistatic agent.
Further, when the total amount of the acrylic polymers of the copolymer is 100 parts by weight, 50 to 91 parts by weight of the (meth) acrylic acid ester monomer having the number of carbon atoms of the (A) alkyl group of C4 to C18 is 50 to 91 parts by weight. B) 0.1 to 10 parts by weight of the copolymerizable monomer containing a hydroxyl group, 0 to 1.0 part by weight of the copolymerizable monomer containing the (C) carboxyl group, and the (D) polyalkylene glycol. It contains 0 to 50 parts by weight of a mono (meth) acrylic acid ester monomer, and 0 to 20 parts by weight of the (E) hydroxyl group-free nitrogen-containing vinyl monomer or alkoxy group-containing alkyl (meth) acrylate monomer. Is preferable.

(A) Examples of the (meth) acrylic acid ester monomer having an alkyl group having C4 to C18 carbon atoms include butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, and heptyl (meth). ) Acrylate, Octyl (meth) acrylate, Isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, Nonyl (meth) acrylate, Isononyl (meth) acrylate, Decyl (meth) acrylate, Isodecyl (meth) acrylate, Undecyl (meth) ) Acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, myristyl (meth) acrylate. , Isomyristyl (meth) acrylate, cetyl (meth) acrylate, isosetyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, and the like.
When the total amount of the acrylic polymers of the copolymer is 100 parts by weight, the (A) alkyl group contains 50 to 91 parts by weight of the (meth) acrylic acid ester monomer having C4 to C18 carbon atoms. Is preferable.

(B) Examples of the copolymerizable monomer containing a hydroxyl group include 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxyethyl (meth) acrylate. Examples thereof include hydroxyalkyl (meth) acrylates such as N-hydroxy (meth) acrylamide, hydroxyl group-containing (meth) acrylamides such as N-hydroxymethyl (meth) acrylamide and N-hydroxyethyl (meth) acrylamide.
8-Hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) ) At least one selected from the compound group consisting of acrylamide and N-hydroxyethyl (meth) acrylamide is preferable.
When the total amount of the acrylic polymers of the copolymer is 100 parts by weight, it is preferable that the copolymerizable monomer containing the (B) hydroxyl group is contained in a ratio of 0.1 to 10 parts by weight.

(C) Copolymerizable monomers containing a carboxyl group include (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, 2 -(Meta) acryloyloxypropyl hexahydrophthalic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl maleic acid, carboxy It is preferably at least one selected from the compound group consisting of polycaprolactone mono (meth) acrylate and 2- (meth) acryloyloxyethyl tetrahydrophthalic acid.
When the total amount of the acrylic polymers of the copolymer is 100 parts by weight, it is preferable that the copolymerizable monomer containing the (C) carboxyl group is contained in a ratio of 0 to 1.0 part by weight. In the pressure-sensitive adhesive layer according to the present invention, the pressure-sensitive adhesive composition may not contain (C) a copolymerizable monomer containing a carboxyl group.

The (D) polyalkylene glycol mono (meth) acrylic acid ester monomer may be a compound in which one hydroxyl group is esterified as a (meth) acrylic acid ester among a plurality of hydroxyl groups of the polyalkylene glycol. Since the (meth) acrylic acid ester group becomes a polymerizable group, it can be copolymerized with the main polymer. The other hydroxyl group may be OH as it is, or may be an alkyl ether such as methyl ether or ethyl ether, a saturated carboxylic acid ester such as an acetate ester, or the like.
Examples of the alkylene group contained in the polyalkylene glycol include, but are not limited to, an ethylene group, a propylene group, and a butylene group. The polyalkylene glycol may be a copolymer of two or more kinds of polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polybutylene glycol. Examples of the polyalkylene glycol copolymer include polyethylene glycol-polypropylene glycol, polyethylene glycol-polybutylene glycol, polypropylene glycol-polybutylene glycol, polyethylene glycol-polypropylene glycol-polybutylene glycol, and the like. It may be a block copolymer or a random copolymer.
It is preferable that the polyalkylene glycol mono (meth) acrylic acid ester monomer (D) has an average number of repetitions of alkylene oxide constituting the polyalkylene glycol chain of 3 to 14. The "average number of repetitions of alkylene oxide" is the average number of repetitions of the alkylene oxide unit in the portion of the "polyalkylene glycol chain" contained in the molecular structure of the (D) polyalkylene glycol mono (meth) acrylic acid ester monomer. be.

The (D) polyalkylene glycol mono (meth) acrylic acid ester monomer was selected from polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate, and ethoxypolyalkylene glycol (meth) acrylate. It is preferably at least one kind.
More specifically, polyethylene glycol-mono (meth) acrylate, polypropylene glycol-mono (meth) acrylate, polybutylene glycol-mono (meth) acrylate, polyethylene glycol-polypropylene glycol-mono (meth) acrylate, polyethylene glycol-poly. Butylene glycol-mono (meth) acrylate, polypropylene glycol-polybutylene glycol-mono (meth) acrylate, polyethylene glycol-polyethylene glycol-polybutylene glycol-mono (meth) acrylate; methoxypolyethylene glycol- (meth) acrylate, methoxypolyethylene glycol -(Meta) acrylate, methoxypolybutylene glycol- (meth) acrylate, methoxy-polyethylene glycol-polypropylene glycol- (meth) acrylate, methoxy-polyethylene glycol-polybutylene glycol- (meth) acrylate, methoxy-polyethylene glycol-polybutylene Glycol- (meth) acrylate, methoxy-polyethylene glycol-polypropylene glycol-polybutylene glycol- (meth) acrylate; ethoxypolyethylene glycol- (meth) acrylate, ethoxypolyethylene glycol- (meth) acrylate, ethoxypolybutylene glycol- (meth) Acrylate, ethoxy-polyethylene glycol-polyethylene glycol- (meth) acrylate, ethoxy-polyethylene glycol-polybutylene glycol- (meth) acrylate, ethoxy-polyethylene glycol-polybutylene glycol- (meth) acrylate, ethoxy-polyethylene glycol-polypropylene glycol -Polybutylene glycol- (meth) acrylate and the like.
When the total amount of the acrylic polymers of the copolymer is 100 parts by weight, it is preferable that the (D) polyalkylene glycol mono (meth) acrylic acid ester monomer is contained in a ratio of 0 to 50 parts by weight. In the pressure-sensitive adhesive layer according to the present invention, the pressure-sensitive adhesive composition may not contain (D) a polyalkylene glycol mono (meth) acrylic acid ester monomer.

Among (E), examples of the (E-1) nitrogen-containing vinyl monomer include a vinyl monomer containing an amide bond, a vinyl monomer containing an amino group, and a vinyl monomer having a nitrogen-containing heterocyclic structure. More specifically, N-vinyl-2-pyrrolidone, N-vinylpyrrolidone, methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinyl. Cyclic nitrogen vinyl compounds having an N-vinyl-substituted heterocyclic structure, such as pyrrol, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholin, N-vinylcaprolacttam, N-vinyllauryllolactum; N-( Meta) acryloyl morpholine, N- (meth) acryloyl piperazine, N- (meth) acryloyl azylidine, N- (meth) acryloyl azetidin, N- (meth) acryloyl pyrrylidine, N- (meth) acryloyl piperidin, N- (meta). ) Cyclic nitrogen vinyl compounds having a heterocyclic structure of N- (meth) acryloyl substitution such as acryloyl azepan, N- (meth) acryloyl azocan; nitrogen atoms such as N-cyclohexylmaleimide and N-phenylmaleimide and Cyclic nitrogen vinyl compound having a heterocyclic structure having an ethylene-based unsaturated bond in the ring; (meth) acrylamide, N-methyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-t-butyl (meth) Unsubstituted or monoalkyl-substituted (meth) acrylamide such as acrylamide; N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropylacrylamide, N, N-diisopropyl (meth). ) Acrylamide, N, N-dibutyl (meth) acrylamide, N-ethyl-N-methyl (meth) acrylamide, N-methyl-N-propyl (meth) acrylamide, N-methyl-N-isopropyl (meth) acrylamide, etc. Dialkyl-substituted (meth) acrylamide; N, N-dimethylaminomethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminoisopropyl (Meta) acrylate, N, N-dimethylaminobutyl (meth) acrylate, N, N-diethylaminomethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N-ethyl-N-methylaminoethyl (meth) ) Acrylic, N-methyl-N-propylaminoethyl (meth) acrylate, N-methyl-N-isopropylaminoethyl (me D) Dialkylamino (meth) acrylates such as acrylate, N, N-dibutylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate; N, N-dimethylaminopropyl (meth) acrylamide, N, N- Diethylaminopropyl (meth) acrylamide, N, N-dipropylaminopropyl (meth) acrylamide, N, N-diisopropylaminopropyl (meth) acrylamide, N-ethyl-N-methylaminopropyl (meth) acrylamide, N-methyl- N, N-dialkyl-substituted aminopropyl (meth) acrylamides such as N-propylaminopropyl (meth) acrylamide, N-methyl-N-isopropylaminopropyl (meth) acrylamide; N-vinylformamide, N-vinylacetamide, N- N-vinylcarboxylic acid amides such as vinyl-N-methylacetamide; N-methoxymethyl (meth) acrylamide, N-ethoxyethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, diacetone acrylamide, N, N -(Meta) acrylamides such as methylenebis (meth) acrylamide; unsaturated carboxylic acid nitriles such as (meth) acrylonitrile; and the like.

(E-1) As the nitrogen-containing vinyl monomer, those containing no hydroxyl group are preferable, and those containing no hydroxyl group and a carboxyl group are more preferable. Examples of such a monomer include the monomers exemplified above, for example, an acrylic monomer containing an N, N-dialkyl substituted amino group or an N, N-dialkyl substituted amide group; N-vinyl-2-pyrrolidone, N-vinyl. N-vinyl-substituted lactams such as caprolactam and N-vinyl-2-piperidone; N- (meth) acryloyl-substituted cyclic amines such as N- (meth) acryloylmorpholine and N- (meth) acryloylpyrrolidine are preferred.

Among (E), examples of the (E-2) alkoxy group-containing alkyl (meth) acrylate monomer include 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, and 2-propoxyethyl (meth) acrylate. 2-Isopropoxyethyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, 2-methoxypropyl (meth) acrylate, 2-ethoxypropyl (meth) acrylate, 2-propoxypropyl (meth) acrylate, 2-isopropoxy Propyl (meth) acrylate, 2-butoxypropyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, 3-ethoxypropyl (meth) acrylate, 3-propoxypropyl (meth) acrylate, 3-isopropoxypropyl (meth) Acrylate, 3-butoxypropyl (meth) acrylate, 4-methoxybutyl (meth) acrylate, 4-ethoxybutyl (meth) acrylate, 4-propoxybutyl (meth) acrylate, 4-isopropoxybutyl (meth) acrylate, 4- Butoxybutyl (meth) acrylate and the like can be mentioned.
These alkoxy group-containing alkyl (meth) acrylate monomers have a structure in which the atom of the alkyl group in the alkyl (meth) acrylate is substituted with an alkoxy group.

When the total amount of the acrylic polymers of the copolymer is 100 parts by weight, the weight of the (E-1) hydroxyl group-free nitrogen-containing vinyl monomer or the (E-2) alkoxy group-containing alkyl (meth) acrylate monomer is 0 to 20 parts by weight. It is preferable that it is contained in a proportion of a portion. (E-1) A nitrogen-containing vinyl monomer containing no hydroxyl group and (E-2) an alkyl (meth) acrylate monomer containing an alkoxy group may be used alone or in combination of two or more. In the pressure-sensitive adhesive layer according to the present invention, the pressure-sensitive adhesive composition may not contain (E) a nitrogen-containing vinyl monomer containing no hydroxyl group or an alkoxy group-containing alkyl (meth) acrylate monomer.

(F) The trifunctional or higher functional isocyanate compound may be at least one or two or more selected from polyisocyanate compounds having at least three or more isocyanate (NCO) groups in one molecule. The polyisocyanate compound is classified into an aliphatic isocyanate, an aromatic isocyanate, an acyclic isocyanate, an alicyclic isocyanate and the like, but any of them may be used. Specific examples of the polyisocyanate compound include aliphatic isocyanate compounds such as hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and trimethylhexamethylene diisocyanate (TMDI), diphenylmethane diisocyanate (MDI), and xylylene diisocyanate (XDI). , Aromatic isocyanate compounds such as hydrogenated xylylene diisocyanate (H6XDI), dimethyldiphenylenedi isocyanate (TOID), and tolylene diisocyanate (TDI).
Examples of trifunctional or higher functional isocyanate compounds include bullet-modified compounds of diisocyanates (compounds having two NCO groups in one molecule), isocyanurate-modified compounds, and trivalent or higher-valent polyols such as trimethylolpropane (TMP) and glycerin. Examples thereof include an adduct form (polyol modified form) with (a compound having at least 3 or more OH groups in one molecule). It is preferable that the (F) trifunctional or higher functional isocyanate compound is contained in an amount of 0.5 to 5.0 parts by weight with respect to 100 parts by weight of the copolymer.

Further, examples of the (F) trifunctional or higher functional isocyanate compound used in the present invention include an isocyanurate compound of a hexamethylene diisocyanate compound, an isocyanurate form of an isophorone diisocyanate compound, an adduct form of a hexamethylene diisocyanate compound, and an adduct form of an isophorone diisocyanate compound. At least one selected from the (F-1) first aliphatic isocyanate compound group consisting of a burette of a hexamethylene diisocyanate compound and a buretto of an isophorone diisocyanate compound, and isocia of a tolylene diisocyanate compound. It consists of a nurate form, an isocyanurate form of a xylylene diisocyanate compound, an isocyanurate form of a hydrogenated xylylene diisocyanate compound, an adduct form of a tolylene diisocyanate compound, an adduct form of a xylylene diisocyanate compound, and an adduct form of a hydrogenated xylylene diisocyanate compound. , (F-2) It is preferable to contain at least one selected from the group of second aromatic isocyanate compounds. It is preferable to use (F-1) the first aliphatic isocyanate compound group and (F-2) the second aromatic isocyanate compound group in combination. In the present invention, as the (F) trifunctional or higher functional isocyanate compound, at least one selected from the (F-1) first aliphatic isocyanate compound group and (F-2) second. By using at least one selected from the aromatic isocyanate compound group in combination, the balance of adhesive force between the low-speed peeling region and the high-speed peeling region can be further improved.
Further, the (F) trifunctional or higher functional isocyanate compound is at least one selected from the (F-1) first aliphatic isocyanate compound group, and the (F-2) second. It contains at least one selected from the aromatic isocyanate compound group, and is preferably contained in a total of 0.5 to 5.0 parts by weight with respect to 100 parts by weight of the copolymer. .. Further, at least one selected from the (F-1) first aliphatic isocyanate compound group and (F-2) selected from the second aromatic isocyanate compound group. The mixing ratio of (F-1): (F-2) with at least one or more is preferably in the range of 10%: 90% to 90%: 10% by weight.

Further, the (G) bifunctional acyclic aliphatic isocyanate compound used in the present invention is an acyclic and aliphatic one among the bifunctional isocyanate compounds. The bifunctional acyclic aliphatic isocyanate compound (G) is preferably a compound produced by reacting a diisocyanate compound with a diol compound.
For example, a diisocyanate compound has a general formula "O = C = N-X-N = C = O" (where X is a divalent group), and a general formula "HO-Y-OH" (where Y is a divalent group). ), Examples of the compound produced by reacting the diisocyanate compound with the diol compound include the compound represented by the following general formula Z.

[General formula Z]
O = C = N-X- (NH-CO-O-YO-CO-NH-X) _n -N = C = O

Here, n is an integer of 0 or more. When n is 0, the general formula Z represents “O = C = N—X—N = C = O”. (G) As the bifunctional acyclic aliphatic isocyanate compound, a compound having n of 0 in the general formula Z (a diisocyanate compound unreacted with a diol compound) may be contained, but a compound in which n is an integer of 1 or more. Is preferably contained as an essential component. (G) The bifunctional acyclic aliphatic isocyanate compound may be a mixture composed of a plurality of compounds having different n in the general formula Z.

The diisocyanate compound represented by the general formula “O = C = N—X—N = C = O” is an aliphatic diisocyanate. X is preferably an acyclic and aliphatic divalent group. The aliphatic diisocyanate is preferably one or more selected from the compound group consisting of tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate.

The diol compound represented by the general formula "HO-Y-OH" is an aliphatic diol. Y is preferably an acyclic and aliphatic divalent group. Examples of the diol compound include 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, and 2-ethyl-2. -From the compound group consisting of butyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol monohydroxybivalate, polyethylene glycol, and polypropylene glycol. It is preferably composed of one or more selected species.

The weight ratio (F / G) of the (F) trifunctional or higher functional isocyanate compound to the (G) bifunctional acyclic aliphatic isocyanate compound is preferably 1 to 90.
The total amount of the (F) trifunctional or higher functional isocyanate compound and the (G) bifunctional acyclic aliphatic isocyanate compound is 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the acrylic polymer. It is preferable to have.

The (H) antistatic agent is preferably (H-1) an ionic compound having a melting point of 30 to 50 ° C. or (H-2) an acryloyl group-containing ionic compound.
In the present invention, as the (H) antistatic agent, (H-1) an ionic compound having a melting point of 30 to 50 ° C. is added to the copolymer, or (H-2) an acryloyl group-containing ionic compound is co-used. Copolymerize in the polymer. Since these (H) antistatic agents have a low melting point and have a long-chain alkyl group, it is presumed that they have a high affinity with the acrylic copolymer.

(H-1) The ionic compound having a melting point of 30 to 50 ° C. is an ionic compound having a cation and an anion, and the cation is a pyridinium cation, an imidazolium cation, a pyrimidinium cation, or a pyrazonium cation. , Pyrrolidinium cations, ammonium cations and other nitrogen-containing onium cations, phosphonium cations, sulfonium cations and the like, and the anions are hexafluorinated phosphate (PF _6- ⁾ , thiocyanate (SCN- ⁾ , alkylbenzene sulfonates. Examples thereof include compounds that are inorganic or organic anions such as acid salts (RC ₆ H ₄ SO _3- ⁾ , perchlorates (ClO _4- ⁾ , ^and borate tetrafluoride (BF _4- ). It is preferably solid at room temperature (for example, 30 ° C.), and a melting point of 30 to 50 ° C. can be obtained by selecting the chain length of the alkyl group, the position of the substituent, the number of substituents, and the like. The cation is preferably a quaternary nitrogen-containing onium cation, and is a quaternary pyridinium cation such as 1-alkylpyridinium (the carbon atom at the 2nd to 6th positions may have a substituent or may be unsubstituted), or 1, Examples thereof include a quaternary imidazolium cation such as 3-dialkyl imidazolium (the carbon atom at the 2, 4 and 5 positions may have a substituent or not substituted), a quaternary ammonium cation such as tetraalkylammonium and the like. ..
(H-1) The ionic compound having a melting point of 30 to 50 ° C. is preferably contained in an amount of 0.01 to 5.0 parts by weight with respect to 100 parts by weight of the copolymer.

(H-2) The acryloyl group-containing ionic compound is an ionic compound having a cation and an anion, and the cation is (meth) acryloyloxyalkyltrialkylammonium [R 3N ⁺ -C _n H _{2n -} OCOCQ. = CH ₂ , where Q = H or CH ₃ , R = alkyl] and other (meth) acryloyl group-containing cations, where the anions are hexafluorinated phosphate (PF _6- ⁾ , thiocyanate (SCN- ⁾ . ), Organic sulfonate (RSO _3- ⁾ , perchlorate (ClO _4- ⁾ , thiocyanate (BF _4- ), ^{F -} containing imide salt (RF ₂ ^- N-), etc. Examples include compounds that are anions. ^Examples of the RF of the ^F _- containing imide salt (RF ^2N- ) include a perfluoroalkanesulfonyl group such as a trifluoromethanesulfonyl group and a pentafluoroethanesulfonyl group, and a fluorosulfonyl group. Examples of the F-containing imide salt include bis (fluorosulfonyl) imide salt [(FSO ₂ ) ₂ N- ^] , bis (trifluoromethanesulfonyl) imide salt [(CF ₃ SO ₂ ) ₂ N- ^] , and bis (pentafluoroethanesulfonyl). ) Bissulfonylimide salts such as imide salt [(C ₂ F ₅ SO ₂ ) ₂ N- ^] can be mentioned.
(H-2) The acryloyl group-containing ionic compound is preferably copolymerized in an amount of 0.1 to 5.0% by weight in the copolymer.

Specific examples of the (H) antistatic agent are not particularly limited, but specific examples of the (H-1) ionic compound having a melting point of 30 to 50 ° C. are 1-octylpyridinium hexafluoride. Acid, 1-nonylpyridinium hexafluorophosphate, 2-methyl-1-dodecylpyridinium hexafluorophosphate, 1-octylpyridinium dodecylbenzenesulfonate, 1-dodecylpyridinium thiocyanate, 1-dodecyl Examples thereof include pyridinium dodecylbenzene sulfonate, 4-methyl-1-octylpyridinium hexafluorophosphate and the like. Further, as a specific example of the (H-2) acryloyl group-containing ionic compound, dimethylaminomethyl (meth) acrylate methyl hexafluorophosphate [(CH ₃ ) ₃ N ⁺ CH ₂ OCOCQ = CH ₂ · PF ₆ ^-However , Q = H or CH ₃ ], dimethylaminoethyl (meth) acrylate bis (trifluoromethanesulfonyl) imidemethyl salt [(CH ₃ ) ₃ N ⁺ (CH ₂ ) ₂ OCOCQ = CH ₂ · (CF ₃ SO ₂ ) ) ₂ N- ^, but Q = H or CH ₃ ], dimethylaminomethylmethacrylate bis (fluorosulfonyl) imidemethyl salt [(CH ₃ ) ₃ N ⁺ CH ₂ OCOCQ = CH ₂ · (FSO ₂ ) ₂ N- ^, but , Q = H or CH ₃ ] and the like.

The pressure-sensitive adhesive composition may optionally contain a polyether-modified siloxane compound. The polyether-modified siloxane compound is a siloxane compound having a polyether group, and in addition to the usual siloxane unit [-SiR ¹ ₂ -O-], the siloxane unit having a polyether group [-SiR ¹ (R ² O (R 2 O)). It has R ³ O) _n R ⁴ ) -O-]. Here, R ¹ is one or more kinds of alkyl groups or aryl groups, R ² and R ³ are one or more kinds of alkylene groups, and R ⁴ is one or more kinds of alkyl groups or acyl groups. Etc. (terminal group). Examples of the polyether group include a polyoxyalkylene group such as a polyoxyethylene group [(C ₂ H ₄ O) _n ] and a polyoxypropylene group [(C ₃ H ₆ O) _n ].
The polyether-modified siloxane compound is preferably a polyether-modified siloxane compound having an HLB value of 7 to 12. Further, it is preferable that 0.01 to 0.5 parts by weight of the polyether-modified siloxane compound is contained with respect to 100 parts by weight of the copolymer. More preferably, it is 0.1 to 0.5 parts by weight.
The HLB is, for example, a hydrophilic lipophilic balance (hydrophilic lipophilic ratio) defined in JIS K3211 (surfactant term) and the like.
The polyether-modified siloxane compound can be obtained, for example, by grafting an organic compound having an unsaturated bond and a polyoxyalkylene group on a polyorganosiloxane backbone having a silicon hydride group by a hydrosilylation reaction. Specifically, dimethylsiloxane / methyl (polyoxyethylene) siloxane copolymer, dimethylsiloxane / methyl (polyoxyethylene) siloxane / methyl (polyoxypropylene) siloxane copolymer, dimethylsiloxane / methyl (polyoxypropylene) Examples thereof include siloxane polymers.
By blending the polyether-modified siloxane compound into the pressure-sensitive adhesive composition, the pressure-sensitive adhesive strength and rework performance of the pressure-sensitive adhesive can be improved. If the pressure-sensitive adhesive composition does not contain a polyether-modified siloxane compound, the cost will be lower.

Further, as other components, copolymerizable (meth) acrylic monomers containing alkylene oxides, (meth) acrylamide monomers, dialkyl-substituted acrylamide monomers, surfactants, curing accelerators, thermoplastics, fillers, curing retarders, etc. Known additives such as processing aids, antioxidants, and antioxidants can be appropriately added. These may be used alone or in combination of two or more.

The main agent copolymer used in the pressure-sensitive adhesive composition of the present invention is (A) as a group of monomers copolymerizable with at least one kind of (meth) acrylic acid ester monomer having an alkyl group having C4 to C18 carbon atoms (A). B) Containing a copolymerizable monomer containing a hydroxyl group, (C) a copolymerizable monomer containing a carboxyl group, (D) a polyalkylene glycol mono (meth) acrylic acid ester monomer, and (E) a hydroxyl group. It can be synthesized by copolymerizing with at least one selected from the copolymerizable monomer group consisting of a non-nitrogen-containing vinyl monomer or an alkoxy group-containing alkyl (meth) acrylate monomer. The polymerization method of the copolymer is not particularly limited, and an appropriate polymerization method such as solution polymerization or emulsion polymerization can be used.
When (H-2) an acryloyl group-containing ionic compound is used as the (H) antistatic agent, the copolymer of the main agent used in the pressure-sensitive adhesive composition of the present invention has (A) an alkyl group having C4 carbon atoms. ~ C18 (meth) acrylic acid ester monomer, at least one copolymerizable monomer group, (B) a copolymerizable monomer containing a hydroxyl group, and (C) a copolymerizable monomer containing a carboxyl group. , (D) Polyalkylene glycol mono (meth) acrylic acid ester monomer and (E) a copolymerizable monomer group consisting of a nitrogen-containing vinyl monomer containing no hydroxyl group or an alkoxy group-containing alkyl (meth) acrylate monomer. It can be synthesized by copolymerizing at least one of them with (H-2) an acryloyl group-containing ionic compound.
The pressure-sensitive adhesive composition of the present invention comprises, in addition to the above-mentioned copolymer, (F) a trifunctional or higher functional isocyanate compound, (G) a bifunctional acyclic aliphatic isocyanate compound, (H) an antistatic agent, and optionally any It can be prepared by blending an additive. When the (H-2) acryloyl group-containing ionic compound is polymerized in the copolymer of the main agent, the (H) antistatic agent may be further added to the copolymer, or may be added. It doesn't have to be.

The copolymer is preferably an acrylic polymer, and preferably contains 50 to 100% by weight of an acrylic monomer such as (meth) acrylic acid ester monomer, (meth) acrylic acid, and (meth) acrylamides.
The acid value of the acrylic polymer is preferably 0.01 to 8.0. As a result, the contamination property can be improved and the performance of preventing the generation of adhesive residue can be improved.
Here, the "acid value" is one of the indexes representing the acid content, and is represented by the number of mg of potassium hydroxide required to neutralize 1 g of the polymer containing a carboxyl group.

The pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition has an adhesive force of 0.05 to 0.1 N / 25 mm at a low-speed peeling speed of 0.3 m / min and a high-speed peeling speed of 30 m / min. The adhesive strength is preferably 1.0 N / 25 mm or less. As a result, it is possible to obtain a performance in which the adhesive force does not change much depending on the peeling speed, and it is possible to quickly peel even by high-speed peeling. Further, since it is reattached, even when the surface protective film is once peeled off, it does not require an excessive force and can be easily peeled off from the adherend.

It is preferable that the surface resistivity of the pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition is 5.0 × 10 ⁺¹⁰ Ω / □ or less, and the peeling band voltage is ± 0 to 1 kV. In the present invention, "± 0 to 1 kV" means 0 to -1 kV and 0 to + 1 kV, that is, -1 to + 1 kV. If the surface resistivity is large, the ability to release the static electricity generated by charging during peeling is inferior. Therefore, by making the surface resistivity sufficiently small, the peeling that occurs due to the static electricity generated when the adherend peels off the adhesive layer. The band resistivity is reduced, and it is possible to suppress the influence on the electric control circuit of the adherend and the like.

The gel fraction of the pressure-sensitive adhesive layer (the pressure-sensitive adhesive after cross-linking) obtained by cross-linking the pressure-sensitive adhesive composition of the present invention is preferably 95 to 100%. Due to such a high gel content, the adhesive strength does not become excessive at a low peeling speed, the elution of unpolymerized monomers or oligomers from the copolymer is reduced, and the reworkability and high temperature / high humidity are achieved. Durability is improved and contamination of the adherend can be suppressed.

The pressure-sensitive adhesive film of the present invention is formed by forming a pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition of the present invention on one or both sides of a resin film. Further, the surface protective film of the present invention is a surface protective film formed by forming a pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition of the present invention on one or both sides of a resin film. Since the pressure-sensitive adhesive composition of the present invention contains the above-mentioned components (A) to (H) in a well-balanced manner, it has excellent antistatic performance, and has a low peeling speed and a high peeling speed. It has an excellent balance of adhesive strength, and also has excellent durability and rework performance (no contamination transfer to the adherend after tracing the surface protective film with a ballpoint pen through the adhesive layer). .. Therefore, it can be suitably used as a surface protective film for a polarizing plate.

As the base film of the pressure-sensitive adhesive layer and the release film (separator) for protecting the pressure-sensitive adhesive surface, a resin film such as a polyester film can be used.
On the base film, on the side opposite to the side where the adhesive layer of the resin film is formed, antifouling treatment with silicone-based or fluorine-based mold release agent or coating agent, silica fine particles, etc., application of antistatic agent, etc. Antistatic treatment such as kneading can be applied.
The release film is subjected to a mold release treatment with a silicone-based or fluorine-based mold release agent or the like on the surface of the pressure-sensitive adhesive layer that is combined with the adhesive surface.

Hereinafter, the present invention will be specifically described with reference to Examples.

<Manufacturing of acrylic copolymer>
[Example 1]
Nitrogen gas was introduced into a reactor equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen introduction tube, and the air in the reactor was replaced with nitrogen gas. Then, 100 parts by weight of 2-ethylhexyl acrylate, 3.0 parts by weight of 8-hydroxyoctyl acrylate, and 10 parts by weight of polypropylene glycol monoacrylate (average number of repetitions of alkylene oxides constituting the polyalkylene glycol chain n = 12) were added to the reaction apparatus. 60 parts by weight of the solvent (ethyl acetate) was added. Then, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours and reacted at 65 ° C. for 6 hours to obtain an acrylic copolymer solution having a weight average molecular weight of 500,000 and used in Example 1. I got 1. A part of the acrylic copolymer was collected and used as a sample for measuring the acid value described later.
[Examples 2 to 9 and Comparative Examples 1 to 4]
The composition of the monomers is the same as that of the acrylic copolymer solution 1 used in Example 1 above, except that the compositions of the monomers are as described in (A) to (E) and (H-2) of Table 1. , Acrylic copolymer solutions used in Examples 2 to 9 and Comparative Examples 1 to 4 were obtained.

<Manufacturing of adhesive composition and surface protective film>
[Example 1]
To the acrylic copolymer solution 1 of Example 1 produced as described above, 1.5 parts by weight of 1-octylpyridinium hexafluorophosphate was added and stirred, and then Coronate HX (hexamethylene diisocyanate compound isocyanate) was added. 2.0 parts by weight of (nurate) and 0.5 parts by weight of the bifunctional acyclic aliphatic isocyanate compound G-1 of Synthesis Example 1 were added and mixed by stirring to obtain the pressure-sensitive adhesive composition of Example 1. .. This pressure-sensitive adhesive composition is applied onto a release film made of a polyethylene terephthalate (PET) film coated with a silicone resin, and then dried at 90 ° C. to remove the solvent, and the pressure-sensitive adhesive layer has a thickness of 25 μm. I got a sheet.
After that, the adhesive sheet is transferred to the surface opposite to the antistatic and antifouling treated polyethylene terephthalate (PET) film on one surface, and "antistatic and antifouling treated". A surface protective film of Example 1 having a laminated structure of "PET film / adhesive layer / release film (PET film coated with silicone resin)" was obtained.
[Examples 2 to 9 and Comparative Examples 1 to 4]
Examples 2 to 9 and Comparative Examples 1 to 1 are the same as the surface protective film of Example 1 above, except that the compositions of the additives are as described in Table 2 (F) to (H), respectively. The surface protection film of No. 4 was obtained.

Tables 1 and 2 divide the integrated table showing the compounding ratio of each component into two, and in each case, the numerical value of the weight part obtained by assuming that the total of the group (A) is 100 parts by weight is enclosed in parentheses. Indicated by. The compound names of the abbreviations of the respective components used in Tables 1 and 2 are shown in Tables 3 and 4. Coronate (registered trademark) HX, HL and L are trade names of Nippon Polyurethane Industry Co., Ltd., and Takenate (registered trademark) D-140N, D-127N, D-110N and D-120N are Mitsui Chemicals shares. The product name of the company.
In Table 1, among the (H) antistatic agents, the (H-2) quaternary ammonium salt-type ionic compound copolymerized in the copolymer is added after the polymerization (H). It is described in a column separate from the antistatic agent.

<Synthesis of bifunctional acyclic aliphatic isocyanate compound>
The bifunctional acyclic aliphatic isocyanate compounds of Synthesis Examples 1 to 3 were synthesized by the following methods. As shown in Tables 5 and 6, the diisocyanate and the diol compound were mixed at a molar ratio of NCO / OH = 16 and reacted at 120 ° C. for 3 hours, and then under reduced pressure using a thin film evaporator. The unreacted diisocyanate was removed to obtain the desired bifunctional acyclic aliphatic isocyanate compound.

<Test method and evaluation>
The surface protective films of Examples 1 to 9 and Comparative Examples 1 to 4 were aged at 23 ° C. and 50% RH for 7 days, and then the release film (silicone resin coated PET film) was peeled off to obtain an adhesive. The exposed layer was used as a sample for measuring the surface resistance.
Further, the surface protective film on which the pressure-sensitive adhesive layer is exposed is attached to the surface of the polarizing plate attached to the liquid crystal cell via the pressure-sensitive adhesive layer, left for 1 day, and then left at 50 ° C., 5 atm for 20 minutes. A sample that had been autoclaved and left at room temperature for another 12 hours was used as a measurement sample for adhesive strength, peeling band voltage, reworkability, and durability.

<Adhesive strength>
The measurement sample obtained above (a 25 mm wide surface protective film bonded to the surface of the polarizing plate) was subjected to a low speed peeling speed (0.3 m / min) and a high speed in the 180 ° direction using a tensile tester. The peeling strength was taken as the adhesive strength after peeling at the peeling speed (30 m / min).

<Surface resistivity>
After aging, before bonding to the polarizing plate, the release film (PET film coated with silicone resin) is peeled off to expose the adhesive layer, and the resistance meter Hiresta UP-HT450 (manufactured by Mitsubishi Chemical Analytec) is used. The surface resistance of the pressure-sensitive adhesive layer was measured.

<Peeling band voltage>
High-precision electrostatic sensors SK-035 and SK-200 (stocks) can be used to measure the voltage (band voltage) generated by charging the polarizing plate when the measurement sample obtained above is peeled 180 ° at a tensile speed of 30 m / min. It was measured using (manufactured by the company Keyence), and the maximum value of the measured value was taken as the peeling band voltage.

<Reworkability>
After tracing the surface protective film of the measurement sample obtained above with a ball pen (load 500 g, 3 reciprocations), the surface protective film is peeled off from the polarizing plate, the surface of the polarizing plate is observed, and the polarizing plate is contaminated. Confirmed that there was no migration. The evaluation target criteria are "○" when there is no contamination transfer on the polarizing plate, "△" when contamination transfer is confirmed at least in part along the trajectory traced with the ballpoint pen, and along the trajectory traced with the ballpoint pen. When the transfer of contamination was confirmed and the detachment of the adhesive was confirmed from the surface of the adhesive, it was evaluated as "x".

<Durability>
The measurement sample obtained above was left in an atmosphere of 60 ° C. and 90% RH for 250 hours, then taken out to room temperature, left for another 12 hours, and then the adhesive strength was measured and clearly compared with the initial adhesive strength. It was confirmed that there was no significant increase. The evaluation target criteria were evaluated as "◯" when the adhesive strength after the test was 1.5 times or less of the initial adhesive strength, and "x" when the adhesive strength exceeded 1.5 times.

Table 7 shows the evaluation results. The surface resistivity is expressed by a method in which "m × 10 ^{+ n} " is set to "mE + n" (where m is an arbitrary real number and n is a positive integer).

The surface protective films of Examples 1 to 9 have an adhesive strength of 0.05 to 0.1 N / 25 mm at a low peeling speed of 0.3 m / min and an adhesive strength of 1 at a high peeling speed of 30 m / min. It is 0.0 N / 25 mm or less, the surface resistance is 5.0 × 10 ⁺¹⁰ Ω / □ or less, the peeling band voltage is ± 0 to 1 kV, and a ball pen is used on the surface protective film via the adhesive layer. After tracing, there was no transfer of contamination to the adherend, and the durability was excellent when left in an atmosphere of 60 ° C. and 90% RH for 250 hours.
That is, (1) balancing the adhesive force at a low peeling speed and a high peeling speed, (2) preventing the generation of adhesive residue, (3) excellent antistatic performance, and (4). It meets all the required performance of rework performance at the same time.

The surface protective film of Comparative Example 1 does not contain (F) a trifunctional or higher functional isocyanate compound and (G) a bifunctional acyclic aliphatic isocyanate compound, which serve as a cross-linking agent, and has a low peeling rate of 0. The adhesive strength at a high peeling speed of 30 m / min at a high speed of .3 m / min was too large, the surface resistance and the peeling band voltage were high, and the reworkability and durability were inferior.
The surface protective film of Comparative Example 2 contains a uretdione ring-containing diisocyanate compound, which is a bifunctional cyclic isocyanate compound, instead of containing (G) a bifunctional acyclic aliphatic isocyanate compound, and has a high peeling speed of 30 m. The adhesive strength at / min was too large, and the durability was inferior.
The surface protective film of Comparative Example 3 contains an excess of (F) trifunctional or higher functional isocyanate compounds.
(G) The pot life was too short, probably because the bifunctional acyclic aliphatic isocyanate compound was not contained, and the cross-linking proceeded before the coating, so that the coating could not be performed.
The surface protective film of Comparative Example 4 has a larger amount of (G) bifunctional acyclic aliphatic isocyanate compound than (F) trifunctional or higher functional isocyanate compound, and has a high peeling speed of 30 m / min. The adhesive strength was too high and the durability was inferior.
As described above, in the surface protective films of Comparative Examples 1 to 4, (1) balancing the adhesive force at the low peeling speed and the high peeling speed, and (2) preventing the generation of adhesive residue. It was not possible to satisfy all the required performances of (3) excellent antistatic performance and (4) rework performance at the same time.

Claims (1)

A surface protective film formed by forming a pressure-sensitive adhesive layer obtained by cross-linking a pressure-sensitive adhesive composition containing an acrylic polymer, an (H) antistatic agent, and a cross-linking agent on one or both sides of a resin film.
When the acrylic polymer has a total of 100 parts by weight of the acrylic polymer,
(A) The total of at least one of the (meth) acrylic acid ester monomers having an alkyl group having C4 to C18 carbon atoms is 50 to 91 parts by weight.
(B) The total of at least one copolymerizable monomer containing a hydroxyl group is 0.1 to 10 parts by weight.
As a copolymerizable monomer group, the total of at least one of (D) polyalkylene glycol mono (meth) acrylic acid ester monomer or alkoxypolyalkylene glycol mono (meth) acrylic acid ester monomer exceeds 0 part by weight and 49.9 parts by weight. Hereinafter, the total of at least one of (E) a nitrogen-containing vinyl monomer containing no hydroxyl group and an isocyanate group or an alkoxy group-containing alkyl (meth) acrylate monomer containing no hydroxyl group shall be in excess of 0 parts by weight and 20 parts by weight or less. , Is a copolymer acrylic polymer obtained by copolymerizing.
The copolymerizable monomer containing the (B) hydroxyl group is 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, or 2-hydroxyethyl (meth) acrylate. , N-Hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, and N-hydroxyethyl (meth) acrylamide, which are at least one selected from the compound group.
The cross-linking agent comprises (F) a trifunctional or higher functional isocyanate compound and (G) a bifunctional acyclic aliphatic isocyanate compound.
In the pressure-sensitive adhesive composition, the total of the (F) trifunctional or higher functional isocyanate compound and the (G) bifunctional acyclic aliphatic isocyanate compound is 0.1 with respect to 100 parts by weight of the acrylic polymer. It is contained in a proportion of ~ 5.0 parts by weight.
The weight ratio (F / G) of the (F) trifunctional or higher functional isocyanate compound to the (G) bifunctional acyclic aliphatic isocyanate compound is 1 to 90.
The (G) bifunctional acyclic aliphatic isocyanate compound is a bifunctional acyclic aliphatic isocyanate compound produced by reacting an aliphatic diisocyanate compound with a diol compound.
The surface protective film is a surface protective film having a surface resistivity of 5.0 × 10 ⁺¹⁰ Ω / □ or less and a peeling band voltage of ± 0 to 1 kV.