阅读说明：本技术 粘合剂用组合物、粘合膜和表面保护膜 (Composition for adhesive, adhesive film, and surface protective film ) 是由 冈田诗织 栗本茂 户梶翔太 龟井淳一 于 2020-03-24 设计创作，主要内容包括：一个实施方式涉及一种粘合剂用组合物,其含有(甲基)丙烯酸类聚合物(A)、碱金属盐(B)和由式(I)表示的化合物(C)。(One embodiment relates to a composition for an adhesive, which contains a (meth) acrylic polymer (a), an alkali metal salt (B), and a compound (C) represented by formula (I).)

1. A composition for an adhesive, comprising: a (meth) acrylic polymer (A), an alkali metal salt (B) and a compound (C) represented by the formula (I),

wherein X independently represents an oxygen atom or a nitrogen atom, and R independently represents a hydrogen atom, an alkyl group or a fluoroalkyl group.

2. The composition for an adhesive according to claim 1, further comprising a crosslinking agent (D).

3. The composition for an adhesive according to claim 1 or 2, wherein the (meth) acrylic polymer (a) contains: structural units derived from an alkyl (meth) acrylate monomer; and a structural unit derived from a (meth) acrylic monomer having a hydroxyl group or a carboxyl group.

4. An adhesive film obtained by using the adhesive composition according to any one of claims 1 to 3.

5. A surface protective film, having: an adhesive film obtained by using the adhesive composition according to any one of claims 1 to 3; and a substrate film.

Technical Field

Embodiments of the present invention relate to a composition for an adhesive, an adhesive film, and a surface protective film.

Background

In the display, an optical film such as a polarizing plate is used. A surface protective film may be bonded to the surface of the optical film. The surface of the optical film can be protected by the surface protective film, and scratches and adhesion of dirt can be prevented in transportation, a display manufacturing process, and the like.

In order to prevent the surface protective film from deviating from the optical film, the surface protective film generally includes a base film and an adhesive film formed on one surface of the base film. Since visual inspection of an optical film is sometimes performed in a state where a surface protective film is attached to the optical film, an acrylic adhesive having high transparency is widely used for an adhesive film. In addition, the surface protective film is peeled and removed from the optical film when it is no longer necessary. In order to make the surface protective film easily peelable when peeled off and removed, an adhesive film having a low adhesive strength is generally used.

When the surface protective film is peeled off and removed, particularly in the case of high-speed peeling, a noise phenomenon may occur. Further, there are cases where a phenomenon of dust adhering to the surface of the optical film and a phenomenon of circuit member breakage occur due to peeling electrification generated at the time of peeling removal. In order to improve productivity, the peeling speed of the surface protective film tends to increase. When the peeling speed is increased, the peeling electrification voltage is also increased, and defects due to these phenomena are likely to occur.

In recent years, demands for the appearance of optical films have been increasing due to the development of higher definition of displays. Therefore, the surface protective film is required to have the following characteristics: the adhesive is not easily left on the optical film after peeling.

The cited document 1 discloses an adhesive composition characterized by containing an ionic liquid and an acrylic polymer as an adhesive composition for forming a surface protective film. Further, cited document 2 discloses a surface protective film having a pressure-sensitive adhesive layer formed on the surface of a base film, wherein an antistatic agent and a compound containing fluorine or silicon are added to at least the outside of an acrylic pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2005-330464

Patent document 2: japanese patent laid-open publication No. 2011-63712

Disclosure of Invention

Problems to be solved by the invention

An object of one embodiment of the present invention is to provide an adhesive composition capable of producing an adhesive film excellent in antistatic properties and low staining properties. Another object of the present invention is to provide an adhesive film having excellent antistatic properties and low staining properties. Further, another object of the present invention is to provide a surface protective film having an adhesive film excellent in antistatic property and low staining property.

Means for solving the problems

The present invention includes various embodiments. The following examples of the embodiments are given. The present invention is not limited to the following embodiments.

One embodiment relates to a composition for an adhesive, comprising: a (meth) acrylic polymer (A), an alkali metal salt (B), and a compound (C) represented by formula (I).

(wherein X independently represents an oxygen atom or a nitrogen atom, and R independently represents a hydrogen atom, an alkyl group or a fluoroalkyl group.)

In one embodiment, the composition for an adhesive may further contain a crosslinking agent (D).

In one embodiment, the (meth) acrylic polymer (a) preferably contains: a structural unit derived from an alkyl (meth) acrylate monomer and a structural unit derived from a (meth) acrylic monomer having a hydroxyl group or a carboxyl group.

Another embodiment relates to an adhesive film obtained using the adhesive composition.

Still another embodiment relates to a surface protective film having: an adhesive film obtained by using the adhesive composition; and a substrate film.

Effects of the invention

According to one embodiment of the present invention, a composition for an adhesive capable of producing an adhesive film excellent in antistatic property and low contamination property can be provided. In addition, according to another embodiment of the present invention, an adhesive film excellent in antistatic property and low contamination property can be provided. Further, according to still another embodiment of the present invention, a surface protective film having an adhesive film excellent in antistatic property and low staining property can be provided.

Drawings

Fig. 1 is a schematic cross-sectional view showing an example of a surface protective film according to an embodiment.

Detailed Description

Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments.

< composition for adhesive >

The adhesive composition according to an embodiment of the present invention includes: a (meth) acrylic polymer (A), an alkali metal salt (B), and a compound (C) represented by formula (1). The adhesive composition may further contain optional components such as a crosslinking agent (D) and various additives.

As a method for imparting antistatic properties to the surface protective film, there is a method of adding an antistatic agent to an adhesive film that is in contact with an adherend. However, when the content of the antistatic agent is increased in order to improve the antistatic property, the amount of the antistatic agent attached to the adherend is also increased, and the adherend becomes easily contaminated. In general, antistatic properties and low-staining properties are in a trade-off relationship, and it tends to be difficult to achieve a balance. In the embodiment of the present invention, excellent antistatic property and low fouling property can be simultaneously realized by the composition for an adhesive containing the (meth) acrylic polymer (a), the alkali metal salt (B) and the compound (C) represented by the formula (1).

[ (meth) acrylic Polymer (A) ]

The (meth) acrylic polymer (a) is a polymer containing a structural unit derived from a (meth) acrylic monomer. The (meth) acrylic monomer has at least one (meth) acryloyl group in the molecule. In the present specification, "(meth) acrylic monomer" is a total of acrylic monomer and methacrylic monomer, and "(meth) acryloyl group" is a total of acryloyl group and methacryloyl group.

The structural unit derived from a (meth) acrylic monomer preferably contains at least 1 structural unit derived from an alkyl (meth) acrylate monomer (M1). The structural unit derived from the (meth) acrylic monomer may contain 2 or more structural units derived from the alkyl (meth) acrylate monomer (M1).

The alkyl (meth) acrylate monomer (M1) is preferably a monomer represented by the following formula (M1) (hereinafter sometimes referred to as monomer "(M1)").

In the formula, R^1aRepresents a hydrogen atom or a methyl group, R^1bRepresents an alkyl group.

The alkyl group may be linear, branched or cyclic. The alkyl group is preferably a linear alkyl group. The number of carbon atoms of the alkyl group is preferably 1 to 22, more preferably 1 to 16, and still more preferably 1 to 12.

The alkyl (meth) acrylate monomer (M1) preferably contains at least one monomer selected from, for example, the following monomers: methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 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, myristyl (meth) acrylate, isomyristyl (meth) acrylate, pentadecyl (meth) acrylate, isopropyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, dodecyl (meth) acrylate, butyl acrylate, isobutyl (meth) acrylate, butyl acrylate, Cetyl (meth) acrylate (cetyl (meth) acrylate), isocetyl (meth) acrylate, heptadecyl (meth) acrylate, stearyl (meth) acrylate (stearyl (meth) acrylate), and isostearyl (meth) acrylate.

When the monomer forming the structural unit of the (meth) acrylic polymer (a) contains the alkyl (meth) acrylate monomer (M1), the content thereof is preferably 50 parts by mass or more, more preferably 55 parts by mass or more, and still more preferably 60 parts by mass, based on 100 parts by mass of the total of all the monomers. When the content is 50 parts by mass or more, good adhesion between the adhesive film and the adherend tends to be easily obtained. In consideration of the use of other monomers, the content of the alkyl (meth) acrylate monomer (M1) is preferably 99 parts by mass or less, more preferably 95 parts by mass or less, and still more preferably 90 parts by mass or less, based on 100 parts by mass of the total of all the monomers.

The structural unit derived from a (meth) acrylic monomer preferably contains at least 1 structural unit derived from a (meth) acrylic monomer (M2) having a hydroxyl group or a carboxyl group. The (meth) acrylic monomer (M2) has at least a hydroxyl group, a carboxyl group, or both a hydroxyl group and a carboxyl group. The structural unit derived from the (meth) acrylic monomer may contain two or more structural units derived from the (meth) acrylate monomer (M2).

The (meth) acrylic monomer (M2) preferably contains at least one selected from the group consisting of a monomer represented by the following formula (M2-1) (hereinafter sometimes referred to as "monomer (M2-1)"), a monomer represented by the following formula (M2-2) (hereinafter sometimes referred to as "monomer (M2-2)") and (meth) acrylic acid. The (meth) acrylic monomer (M2) more preferably contains the monomer (M2-1).

In the formula, R^2aRepresents a hydrogen atom or a methyl group, R^2bRepresents a 2-valent linking group.

In the formula, R^3aRepresents a hydrogen atom or a methyl group, R^3bRepresents a 2-valent linking group.

In each of the monomer (m2-1) and the monomer (m2-2), the 2-valent linking group preferably contains 1 or more groups selected from, for example, an alkylene group, an oxy group and a carbonyl group. The alkylene group may be linear, branched or cyclic. The alkylene group is preferably a linear alkylene group. The number of carbon atoms of the alkylene group is preferably 1 to 22, more preferably 1 to 16, and still more preferably 1 to 12. The 2-valent linking group is more preferably an alkylene group, and still more preferably a linear alkylene group.

The (meth) acrylic monomer (M2) preferably contains at least one monomer selected from, for example, the following: hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 8-hydroxyoctyl (meth) acrylate; hydroxyl group-containing (meth) acrylamides such as N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, and N-hydroxyethyl (meth) acrylamide; 2-carboxyethyl (meth) acrylate, 5-carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethylhexahydrophthalic acid, 2- (meth) acryloyloxypropylhexahydrophthalic acid, 2- (meth) acryloyloxyethylphthalic acid, 2- (meth) acryloyloxyethyltetrahydrophthalic acid, 2- (meth) acryloyloxypropyltetrahydrophthalic acid, (meth) acrylates having a carboxyl group such as 2- (meth) acryloyloxypropylphthalic acid, 2- (meth) acryloyloxyethylsuccinic acid, 2- (meth) acryloyloxypropylsuccinic acid, 2- (meth) acryloyloxyethylsuccinic acid, 2- (meth) acryloyloxypropylmaleic acid, and carboxypolycaprolactone mono (meth) acrylate; and (meth) acrylic acid. The (meth) acrylic monomer (M2) more preferably contains at least one selected from, for example, hydroxyalkyl (meth) acrylates and (meth) acrylic acids, and still more preferably contains hydroxyalkyl (meth) acrylates.

When the monomer forming the structural unit of the (meth) acrylic polymer (a) contains the (meth) acrylic monomer (M2), the content thereof is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, further preferably 2 parts by mass or more, and particularly preferably 2.5 parts by mass or more, based on 100 parts by mass of the total of all the monomers. When the content is 0.1 parts by mass or more, sufficient adhesiveness tends to be easily obtained. The content of the (meth) acrylic monomer (M2) is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, still more preferably 14 parts by mass or less, and particularly preferably 12 parts by mass or less, based on 100 parts by mass of the total of all the monomers. When the content is 20 parts by mass or less, the effect of preventing the adherend from being contaminated tends to be easily obtained.

The structural unit derived from a (meth) acrylic monomer may contain at least one structural unit derived from another (meth) acrylic monomer (M3) different from the structural unit derived from the alkyl (meth) acrylate monomer (M1) and the structural unit derived from the (meth) acrylate monomer (M2). The structural unit derived from a (meth) acrylic monomer may contain 2 or more structural units derived from a (meth) acrylic monomer (M3).

The (meth) acrylic monomer (M3) preferably contains a (meth) acrylic monomer having a (poly) oxyalkylene group such as a (poly) alkylene glycol monoalkyl ether mono (meth) acrylate. In the present specification, "(poly) alkylene glycol" is a general term for "alkylene glycol" and "polyalkylene glycol", and "(poly) alkylene oxide" is a general term for "alkylene oxide" and "polyoxyalkylene".

When the monomer forming the structural unit of the (meth) acrylic polymer (a) contains the (meth) acrylate monomer (M3), the content thereof is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and further preferably 3 parts by mass or more, based on 100 parts by mass of the total of all the monomers. The content of the (meth) acrylic monomer (M3) is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 10 parts by mass or less, based on 100 parts by mass of the total of all the monomers.

The (meth) acrylic polymer (a) may contain another structural unit different from the structural unit derived from the (meth) acrylic monomer. Examples of the other structural units include structural units derived from the following monomers: vinyl ester monomers such as vinyl acetate; styrene monomers such as styrene and sodium styrene sulfonate; olefin monomers such as butadiene; vinyl group-containing monomers such as halogen-containing monomers including vinyl chloride and tetrafluoroethylene.

The (meth) acrylic polymer (a) preferably contains a structural unit derived from a (meth) acrylic monomer (M2), more preferably contains a structural unit derived from an alkyl (meth) acrylate monomer (M1) and a structural unit derived from a (meth) acrylic monomer (M2).

The method for polymerizing the (meth) acrylic polymer (a) is not particularly limited. As the polymerization method of the (meth) acrylic polymer (a), a known polymerization method such as solution polymerization, emulsion polymerization, suspension polymerization, bulk polymerization, or the like can be used.

As the polymerization initiator in polymerizing the (meth) acrylic polymer (a), a compound which generates a radical by heat can be used. Specific examples thereof include organic peroxides such as benzoyl peroxide and lauroyl peroxide; azo compounds such as 2, 2 '-azobisisobutyronitrile and 2, 2' -azobis (2-methylbutyronitrile).

The glass transition temperature (Tg) of the (meth) acrylic polymer (A) is preferably 0 ℃ or lower, more preferably-5 ℃ or lower, and still more preferably-10 ℃ or lower. The glass transition temperature of the (meth) acrylic polymer (A) is preferably-50 ℃ or higher, more preferably-40 ℃ or higher, and still more preferably-25 ℃ or higher.

In the present specification, the glass transition temperature (Tg) of the (meth) acrylic polymer (a) is a theoretical calculation value determined by the following FOX formula.

1/Tg＝W1/Tg1+W2/Tg2+......+Wn/Tgn

(wherein Tg is the glass transition temperature (. degree. C.) of the (meth) acrylic polymer (A), W1, W2, and W.9.. and Wn are the mass fractions of the monomers based on the mass of all the monomers, respectively, and Tg1, Tg2, and T... and Tgn are the glass transition temperatures of homopolymers of the monomers, respectively.) As the glass transition temperatures of the homopolymers used in the calculation, literature values can be used.

Examples of the method for adjusting the glass transition temperature of the (meth) acrylic polymer (a) include the following methods. For example, by using an alkyl (meth) acrylate having a large carbon number, the glass transition temperature can be lowered. On the other hand, the glass transition temperature can be increased by using an alkyl (meth) acrylate having a small carbon number. Even when a methacrylate ester is used, the glass transition temperature tends to be high.

The weight average molecular weight of the (meth) acrylic polymer (a) is preferably 50000 or more, more preferably 80000 or more, and further preferably 100000 or more. The weight average molecular weight of the (meth) acrylic polymer (a) is preferably 800000 or less, more preferably 700000 or less, and further preferably 600000 or less. In the present specification, the weight average molecular weight is a value obtained by Gel Permeation Chromatography (GPC) using a calibration curve of standard polystyrene. Specifically, the measurement method described in the examples may be used. When the weight average molecular weight is 50000 or more, an adhesive film having good adhesive force tends to be obtained. When the weight average molecular weight is 800000 or less, the adhesive composition is easily prevented from becoming high in viscosity.

The adhesive composition may contain only 1 (meth) acrylic polymer (a), or may contain 2 or more (meth) acrylic polymers (a).

[ alkali Metal salt (B) ]

The alkali metal salt (B) contains an alkali metal ion and a counter anion. It is considered that the adhesive film is provided with conductivity by containing the alkali metal salt (B) in the adhesive composition, and the adhesive film exhibits good antistatic property. The alkali metal salt (B) preferably contains at least 1 selected from lithium ions, sodium ions and potassium ions, more preferably contains at least 1 selected from lithium ions and sodium ions, and still more preferably contains lithium ions. When lithium ions are contained, more excellent antistatic properties can be obtained.

The counter anion preferably contains at least 1 selected from, for example, chloride, perchlorate, hexafluorophosphate, hexafluoroarsenate, tetrafluoroborate, tetraphenylborate, trifluoromethanesulfonate, bis (trifluoromethanesulfonyl) imide and bis (pentafluoroethanesulfonyl) imide.

Examples of the alkali metal salt (B) include a salt represented by the following formula (hereinafter, a salt represented by the formula (B1) may be referred to as "salt (B1)"). The same applies to the salts represented by any one of formulae (b2) to (b 6). ).

In each formula, M represents an alkali metal ion, R represents a fluorine atom, an alkyl group, a fluoroalkyl group, an aryl group or a fluoroaryl group, and R represents a fluorine atom, an alkyl group, a fluoroalkyl group, an aryl group or a fluoroaryl group¹And R²Each independently represents a fluorine atom, an alkyl group, a fluoroalkyl group, an aryl group or a fluoroaryl group.

The carbon number of the alkyl group and the fluoroalkyl group is preferably 1 to 6, more preferably 1 to 4. The fluoroalkyl group may be one in which a part of hydrogen atoms contained in the alkyl group is substituted with fluorine atoms, or may be one in which all hydrogen atoms are substituted with fluorine atoms (i.e., a perfluoroalkyl group), and is preferably a perfluoroalkyl group. The carbon number of the aryl group and the fluoroaryl group is preferably 6 to 20, more preferably 6 to 10. The fluoroaryl group may be a fluoroaryl group in which a part of hydrogen atoms contained in an aryl group is replaced with fluorine atoms, or a fluoroaryl group (that is, a perfluoroaryl group) in which all hydrogen atoms are replaced with fluorine atoms, and is preferably a perfluoroaryl group.

The alkali metal salt (B) preferably contains at least one selected from the group consisting of the salts (B1) to (B6), more preferably contains at least one selected from the group consisting of the salt (B1), the salt (B5) and the salt (B6), and still more preferably contains at least one selected from the group consisting of the salt (B1) and the salt (B5). In particular, the alkali metal salt (B) preferably contains the salt (B5) from the viewpoints of good compatibility with the (meth) acrylic polymer (a), no chlorine, easy release of alkali metal ions, and the like.

Specifically, the alkali metal salt (B) preferably contains at least 1 kind of alkali metal salt selected from the group consisting of: lithium chloride (LiCl) and lithium perchlorate (LiClO)₄) Lithium hexafluorophosphate (LiPF)₆) Lithium hexafluoroarsenate (LiAsF)₆) Lithium tetrafluoroborate (LiBF)₄) Lithium tetraphenylborate (LiB (C)₆ H₅)₄) Lithium trifluoromethanesulfonate (LiCF)₃SO₃) Lithium bis (trifluoromethanesulfonyl) imide (LiN (CF)₃SO₂)₂) Lithium bis (pentafluoroethanesulfonyl) imide (LiN (C)₂F₅SO₂)₂) Lithium salts, etc.; sodium chloride (NaCl), sodium perchlorate (NaClO)₄) Sodium hexafluorophosphate (NaPF)₆) Sodium hexafluoroarsenate (NaAsF)₆) Sodium tetrafluoroborate (NaBF)₄) Sodium tetraphenylborate (NaB (C)₆H₅)₄) Sodium trifluoromethanesulfonate (NaCF)₃SO₃) Bis (trifluoromethanesulfonyl) imide sodium (NaN (CF)₃SO₂)₂) Bis (pentafluoroethanesulfonyl) imide sodium salt (NaN (C)₂F₅SO₂)₂) And the like sodium salts; and potassium chloride (KCl) and potassium perchlorate (KClO)₄) Potassium hexafluorophosphate (KPF)₆) Potassium hexafluoroarsenate (KAsF)₆) Potassium tetrafluoroborate (KBF)₄) Potassium tetraphenylborate (KB (C)₆H₅)₄) Potassium trifluoromethanesulfonate (KCF)₃SO₃) Potassium bis (trifluoromethanesulfonyl) imide (KN (CF)₃SO₂)₂) Bis (pentafluoroethanesulfonyl) imide potassium (KN (C)₂F₅SO₂)₂) And the like.

The alkali metal salt (B) is preferably a salt having a melting point of more than 25 ℃ and being solid at room temperature (e.g., 25 ℃). Since a salt which is solid at room temperature is less likely to flow out of the adhesive film, it is preferable from the viewpoint of preventing contamination of the adherend with the adhesive film.

The binder composition may contain only 1 kind of the alkali metal salt (B), or may contain 2 or more kinds of the alkali metal salts (B). The content of the alkali metal salt (B) is preferably 0.1 part by mass or more, more preferably 0.2 part by mass or more, and further preferably 0.5 part by mass or more, based on 100 parts by mass of the (meth) acrylic polymer (a). When the amount is 0.1 part by mass or more, more excellent antistatic property can be obtained. The content of the alkali metal salt (B) is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and further preferably 5 parts by mass or less, based on 100 parts by mass of the (meth) acrylic polymer (a). When the amount is 10 parts by mass or less, more favorable low-staining properties can be obtained.

[ Compound (C) represented by formula (I) ]

The adhesive composition contains a compound (C) represented by the following formula (I). In the adhesive film, it is considered that the compound (C) promotes the movement of alkali metal ions contained in the alkali metal salt (B), and improves the antistatic property.

In the formula (I), X independently represents an oxygen atom or a nitrogen atom, and R independently represents a hydrogen atom, an alkyl group or a fluoroalkyl group.

In the case where X is an oxygen atom, -X-contained in the formula (I) represents-O-. In the case where X is a nitrogen atom, a hydrogen atom may be bonded to the nitrogen atom, and-X-contained in the formula (I) may be represented by-NH-.

The alkyl group may be linear, branched or cyclic. The alkyl radical is preferably represented by the formula-C_nH_2n+1(n is an integer of 1 or more). N is preferably 1 to 12, more preferably 1 to 8, and further preferably 1 to 121 to 4.

The fluoroalkyl group may be linear, branched or cyclic. Examples of the fluoroalkyl group include: a fluoroalkyl group in which a part of hydrogen atoms contained in an alkyl group is substituted with a fluorine atom; and fluoroalkyl groups in which all hydrogen atoms contained in an alkyl group are replaced with fluorine atoms (i.e., perfluoroalkyl groups). The fluoroalkyl radical is preferably composed of-C_nH_mF_2n+1-m(n is an integer of 1 or more, and m is an integer of 0 or more, however, m is an integer of 2n or less). N is preferably 1 to 12, more preferably 1 to 8, and further preferably 1 to 4. m is preferably 0 to 2n, more preferably 0 to n, and further preferably 0.

In the formula (I), the compound in which R is independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms or a fluoroalkyl group having 1 to 12 carbon atoms is a preferable compound from the viewpoint of improving the low-staining property of the adhesive film.

Examples of the compound (C) include a cyclic carbonate compound and a cyclic urea compound. Specifically, the compound (C) preferably contains at least 1 selected from the following compounds: cyclic carbonate compounds such as ethylene carbonate, propylene carbonate, 1, 2-butylene carbonate, trans-2, 3-butylene carbonate, cis-2, 3-butylene carbonate, 1, 2-pentylene carbonate, trans-2, 3-pentylene carbonate, cis-2, 3-pentylene carbonate, fluoroethylene carbonate, trifluoromethylethylene carbonate, and 4, 5-difluoroethylene carbonate; and cyclic urea compounds such as 2-imidazolidinone. The cyclic carbonate compound is represented by formula (I), and two X are oxygen atoms. The cyclic urea compound is a compound represented by formula (I) wherein two X are nitrogen atoms. The compound (C) preferably contains a cyclic carbonate compound, and more preferably contains at least one selected from ethylene carbonate and propylene carbonate. From the viewpoint of conductivity, the compound (C) preferably contains at least ethylene carbonate.

From the viewpoint of achieving both antistatic properties and low fouling properties, the compound (C) is preferably a compound having a melting point of more than 25 ℃. A compound having a melting point of more than 25 ℃ is not likely to flow out of the adhesive film, and is therefore preferable from the viewpoint of preventing contamination of the adhesive film to an adherend.

The adhesive composition may contain only 1 kind of compound (C), or may contain 2 or more kinds of compounds (C). The content of the compound (C) is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, and further preferably 1 part by mass or more, based on 100 parts by mass of the (meth) acrylic polymer (a). When the amount is 0.2 parts by mass or more, more excellent antistatic property can be obtained. The content of the compound (C) is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and further preferably 8 parts by mass or less, based on 100 parts by mass of the (meth) acrylic polymer (a). When the amount is 15 parts by mass or less, more favorable low-staining properties can be obtained.

[ crosslinking agent (D) ]

The adhesive composition may contain a crosslinking agent (D). The crosslinking agent (D) preferably contains at least 1 selected from, for example, an isocyanate compound, an epoxy compound, a (meth) acrylate compound and a metal chelate compound. From the viewpoint of being able to promote the crosslinking reaction by heating, the crosslinking agent (D) more preferably contains at least 1 selected from, for example, an isocyanate compound and an epoxy compound, and further preferably contains an isocyanate compound.

The isocyanate compound may be an isocyanate compound having 2 or more functions. The isocyanate compound preferably contains at least 1 selected from the group consisting of a 2-functional isocyanate compound and an isocyanate compound having 3 or more functions. The isocyanate compound may contain only a 2-functional isocyanate compound, or may contain only an isocyanate compound having 3 or more functions. The isocyanate compound may contain a 2-functional isocyanate compound and an isocyanate compound having 3 or more functions.

The 2-functional isocyanate compound may be 1 or 2 or more selected from compounds having 2 isocyanate groups (-NCO) in 1 molecule. Examples of the 2-functional isocyanate compound include aliphatic diisocyanates; an aromatic diisocyanate; an addition product of at least one member selected from the group consisting of aliphatic diisocyanates and aromatic diisocyanates; and allophanate products of at least one member selected from aliphatic diisocyanates and aromatic diisocyanates. The "addition product of at least one member selected from the group consisting of aliphatic diisocyanates and aromatic diisocyanates" is, for example, an addition product of at least one member selected from the group consisting of aliphatic diisocyanates and aromatic diisocyanates and a 2-functional polyol. A 2-functional polyol is a compound having 2 hydroxyl groups (-OH) in 1 molecule. Examples of the 2-functional polyol include ethylene glycol and propylene glycol.

Specific examples of the aliphatic diisocyanate include Hexamethylene Diisocyanate (HDI), isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate (TMDI), hydrogenated xylylene diisocyanate (H6XDI), and the like. Specific examples of the aromatic diisocyanate include diphenylmethane diisocyanate (MDI), Xylylene Diisocyanate (XDI), dimethylbiphenyl diisocyanate (TOID), and Toluene Diisocyanate (TDI).

The 3-or more-functional isocyanate compound may be 1 or 2 or more selected from compounds having 3 or more isocyanate groups in 1 molecule, and preferably 1 or 2 or more selected from compounds having 3 isocyanate groups in 1 molecule. Examples of the 3-or more-functional isocyanate compound include addition products of 2-functional isocyanate compounds; 2 isocyanurate product of a functional isocyanate compound; biuret products of 2-functional isocyanate compounds, and the like. The "addition product of a 2-functional isocyanate compound" is, for example, an addition product of a 2-functional isocyanate compound and a polyol having 3 or more functions. The polyol having 3 or more functions is a compound having 3 or more hydroxyl groups (-OH) in 1 molecule. Examples of the 3-or more-functional polyol include Trimethylolpropane (TMP) and glycerin.

Examples of the isocyanate compound include isocyanate compounds represented by the following formula (hereinafter, the isocyanate compound represented by the formula (d1) may be referred to as "isocyanate compound (d 1)", and the same applies to the isocyanate compounds represented by any of the formulae (d2) to (d 6)).

OCN-R-NCO (d1)

In the formulae, R independently represents an organic group having a valence of 2, and R¹Represents a substituent having a valence of 1, R²Represents an organic group having a valence of 2, R³Represents a 3-valent organic group.

R is preferably a substituted or unsubstituted hydrocarbon group, more preferably a linear or branched aliphatic hydrocarbon group; an alicyclic hydrocarbon group; or an aromatic hydrocarbon group. The aliphatic hydrocarbon group, alicyclic hydrocarbon group and aromatic hydrocarbon group may be substituted or unsubstituted. The aliphatic hydrocarbon group is preferably an alkylene group. The aliphatic hydrocarbon group preferably has 1 to 22 carbon atoms, more preferably 1 to 12 carbon atoms, and further preferably 1 to 8 carbon atoms. The alicyclic hydrocarbon group is preferably a cycloalkylene group. The alicyclic hydrocarbon group preferably has 3 to 12 carbon atoms, more preferably 5 to 8 carbon atoms, and further preferably 6 carbon atoms. The number of carbon atoms of the aromatic hydrocarbon group is preferably 6 to 20, more preferably 6 to 10, and further preferably 6. The aromatic hydrocarbon group may have at least 1 substituent selected from the group consisting of a linear or branched aliphatic hydrocarbon group and an alicyclic hydrocarbon group.

Examples of the hydrocarbon group include linear or branched aliphatic hydrocarbon groups such as methylene, ethylene, propylene, trimethylene, methylethylene, tetramethylene, 1-methyltrimethylene, 2-methyltrimethylene, pentamethylene, 1-methyltetramethylene, 2-methyltetramethylene, hexamethylene, 1-methylpentylene, 2-methylpentylene, 3-methylpentylene, 1-ethyltetramethylene, 2-ethyltetramethylene, heptamethylene, and octamethylene; alicyclic hydrocarbon groups such as cyclopentylene, cyclohexylene and cycloheptylene; and aromatic hydrocarbon groups such as phenylene, tolylene, xylylene, and naphthylene.

R¹May be a substituent containing a hydroxyl group. R²Preferably a substituted or unsubstituted hydrocarbon group, more preferably a substituted or unsubstituted alkylene group。R³Preferably a substituted or unsubstituted hydrocarbyl group, more preferably a substituted or unsubstituted alkanetriyl group. When the hydrocarbon group has a substituent, a hydroxyl group may be mentioned as the substituent.

The isocyanate compound preferably contains at least one selected from the isocyanate compounds (d1) to (d6), and more preferably contains at least one selected from the isocyanate compounds (d2) to (d 6). In particular, from the viewpoint of obtaining good antistatic properties and adhesion, the isocyanate compound preferably contains at least one selected from the group consisting of the isocyanate compounds (d3) and (d4), and more preferably contains the isocyanate compound (d 3).

When the pressure-sensitive adhesive composition contains the crosslinking agent (D), the content of the crosslinking agent (D) is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and further preferably 1 part by mass or more, based on 100 parts by mass of the (meth) acrylic polymer (a). The content of the crosslinking agent (D) is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 10 parts by mass or less, based on 100 parts by mass of the (meth) acrylic polymer (a). The adhesive composition may contain 1 kind of the crosslinking agent (D) alone, or may contain 2 or more kinds of the crosslinking agents (D) in combination.

The adhesive composition may also contain a curing accelerator. The curing accelerator is preferably one which can accelerate the reaction rate of the functional group contained in the (meth) acrylic polymer with the functional group contained in the curing agent (D). Here, the functional group means a (meth) acryloyl group, a hydroxyl group, a carboxyl group, an epoxy group, an isocyanate group, or the like.

As the curing accelerator, for example, an organic metal compound, a tertiary amine compound, or the like can be used. Specific examples of the organic metal compound include tin-based catalysts such as dibutyltin dilaurate, dibutyltin dichloride and dibutyltin oxide.

The adhesive composition may contain a solvent. The solvent is preferably an organic solvent. Examples of the organic solvent include formic acid, acetic acid, methanol, ethanol, propanol, methyl cellosolve, acetone, acetylacetone, acetonitrile, hexane, benzene, toluene, dichloromethane, ethyl acetate, butyl acetate, chlorobenzene, and dichlorobenzene.

[ other optional ingredients ]

The adhesive composition may contain other optional components. Examples of the other optional components include surfactants, plasticizers, fillers, curing retarders, processing aids, antioxidants, and the like. The adhesive composition may contain 1 kind of any other component alone, or may contain 2 or more kinds in combination.

< adhesive film >

The adhesive film according to the embodiment of the present invention is a film obtained by using the adhesive composition. In the adhesive film, the (meth) acrylic polymer (a) may be crosslinked. The method for producing the adhesive film is not particularly limited, and a known production method may be used. The adhesive film can be obtained, for example, by forming a layer of the adhesive composition on the surface of the support film and drying and/or curing the layer of the adhesive composition. Alternatively, the adhesive film may be formed by, for example, an extrusion method. The adhesive film formed on the support film may be used after being peeled from the support film, or may be used in a state of a laminate having the adhesive film and the support film without being peeled from the support film.

A known coating method, a known printing method, or the like can be applied to the method of forming the layer of the adhesive composition. Examples of the coating method include coating methods such as casting, spray coating, spin coating, dip coating, bar coating, comma blade coating, and die coating; gravure printing such as gravure printing, stencil printing such as screen printing, and the like.

The drying and curing of the layer of the adhesive composition may be performed by heating. The heating temperature may be set to 50 to 150 ℃, for example. The heating time may be set to, for example, 1 minute to 10 hours.

The thickness of the adhesive film is not particularly limited. The thickness of the adhesive film is, for example, preferably 1 μm or more, more preferably 3 μm or more, and still more preferably 5 μm or more. When the thickness of the adhesive film is 1 μm or more, sufficient strength can be maintained, and good adhesiveness tends to be easily obtained. The thickness of the adhesive film is, for example, preferably 20 μm or less, more preferably 18 μm or less, and still more preferably 15 μm or less. When the particle diameter is 20 μm or less, the following tendency is exhibited: the adhesive film can maintain sufficient flexibility, easily follow the shape of an adherend, and easily prevent the adhesive film from peeling off from the adherend.

The surface resistivity of the adhesive film is preferably 1.0X 10¹²Omega/□ or less, more preferably 5.0X 10¹¹Omega/□ or less, more preferably 2.5X 10¹¹Omega/□ or less. At 1.0X 10¹²When the ratio Ω/□ is less, generation of static electricity due to charging can be effectively suppressed when the adhesive film is peeled from an adherend. As a result, the peeling electrification voltage due to static electricity generated when the adhesive film is peeled from the adherend is reduced, and the influence on the adherend can be suppressed. If the peeling electrification voltage is high, there may be a case where a trouble occurs due to a phenomenon in which dust adheres to an adherend, a phenomenon in which a circuit member arranged in the vicinity of the adherend is broken, or the like.

The adhesive film is preferably free from adhesive attachment to an adherend in the following evaluation. If the pressure-sensitive adhesive is adhered, the appearance of the adherend may be poor.

The adhesive film was adhered to an adherend and allowed to stand for a predetermined time under high-temperature and high-humidity conditions of 85 ℃ and 85% RH (RH: relative humidity). Then, the adhesive film was peeled off from the adherend, and the presence or absence of adhesion of the adhesive to the adherend was visually confirmed. The "prescribed time" may be set to 3 days, 20 days, or 40 days.

< surface protective film >

The surface protective film according to an embodiment of the present invention includes an adhesive film and a substrate film obtained using the adhesive composition. The surface protective film may have any other film such as a cover film. Examples of the surface protective film include: a surface protective film having a substrate film and an adhesive film provided on one surface of the substrate film; a surface protective film including a base film, an adhesive film provided on one surface of the base film, and a cover film provided on the surface of the adhesive film opposite to the base film.

Fig. 1 is a schematic cross-sectional view showing an example of a surface protective film. In fig. 1, the surface protection film 1 has: a substrate film 4, an adhesive film 3 provided on one surface of the substrate film 4, and a cover film 2 provided on the surface of the adhesive film 3 opposite to the substrate film 4.

The substrate film preferably has a plastic film. The base material film may have a plastic film and any layer such as an antistatic layer, an antifouling layer, and an adhesion-imparting layer provided on at least one surface of the plastic film. In the case where the base material film has an antistatic layer and/or an antifouling layer, the antistatic layer and/or the antifouling layer is preferably provided on the side of the base material film opposite to the adhesive film. The substrate film may have only 1 arbitrary layer, or may have 2 or more arbitrary layers in combination.

At least one surface of the plastic film may be subjected to a surface treatment such as an antistatic treatment, an antifouling treatment, an adhesion imparting treatment, a corona treatment, or a plasma treatment. Examples of the antistatic treatment include coating and mixing of an antistatic agent. In the case where the base material film is subjected to the antistatic treatment and/or the antifouling treatment, the antistatic treatment and/or the antifouling treatment is preferably performed on the side of the base material film opposite to the adhesive film. The substrate film may be subjected to only 1 kind of surface treatment, or may be subjected to 2 or more kinds of surface treatments in combination.

In the antistatic layer and antistatic treatment, a known antistatic agent can be used. In the antifouling layer and the antifouling treatment, known release agents such as silicone release agents and fluorine release agents; silica fine particles and the like.

The plastic film is preferably a polyester film. The plastic film is preferably a film containing at least 1 selected from, for example, the following: polyethylene terephthalate (PET), triacetyl cellulose (TAC), polyethylene naphthalate (PEN), polymethyl methacrylate (PMMA), Polycarbonate (PC), Polyimide (PI), Polyethylene (PE), polypropylene (PP), polyvinyl alcohol (PVA), polyvinyl chloride (PVC), cycloolefin copolymer (COC), cycloolefin polymer (COP), norbornene-containing resin, polyethersulfone, cellophane, and aromatic polyamide.

The thickness of the substrate film is not particularly limited. The thickness of the base film is, for example, preferably 10 μm or more, more preferably 30 μm or more, and further preferably 50 μm or more. When the thickness of the base film is 10 μm or more, the following tendency is exhibited: the strength can be sufficiently maintained, and good film winding property and processability can be easily obtained. The thickness of the base film is, for example, preferably 200 μm or less, more preferably 150 μm or less, and still more preferably 100 μm or less. When the particle diameter is 200 μm or less, the following tendency is observed: the surface protective film can maintain sufficient flexibility, easily follow the shape of an adherend, and easily prevent the surface protective film from peeling off from the adherend.

The cover film preferably has a plastic film. The cover film preferably has a plastic film and a release layer provided on the adhesive film side of the plastic film. Alternatively, the surface of the plastic film on the adhesive film side is preferably subjected to a release treatment. For the release layer and the release treatment, known release agents such as silicone release agents and fluorine release agents can be used.

The plastic film is preferably a film containing at least 1 kind selected from the polymers and resins listed as examples of the plastic film in the above description of the base film, and more preferably a polyester film.

The thickness of the cover film is not particularly limited. The thickness of the coating film is, for example, preferably 10 μm or more, more preferably 30 μm or more, and further preferably 50 μm or more. The thickness of the coating film is, for example, preferably 200 μm or less, more preferably 150 μm or less, and further preferably 100 μm or less.

The method for producing the surface protective film is not particularly limited, and a known method may be used. The surface protective film can be obtained by forming an adhesive film on one surface of a base film, for example. Specifically, the surface protective film can be obtained by forming a layer of the adhesive composition on one surface of the base film and drying and/or curing the layer of the adhesive composition. The surface protective film can be formed by, for example, coextrusion.

As a method for forming the adhesive film, the method for producing the adhesive film described in the description of the adhesive film can be used. In the method for producing the adhesive film, a base film may be used instead of the support film.

The object to be protected by the surface protective film is not particularly limited. The surface protective film may be used by being stuck so that the surface on the adhesive film side is in contact with the object to be protected. In the case where the surface protective film has a cover film, the cover film may be peeled off and then the surface protective film may be attached to a protection target. Examples of objects to be protected include optical components such as polarizing plates, display devices such as Liquid Crystal Displays (LCDs), Plasma Displays (PDPs), Cathode Ray Tubes (CRTs), Field Emission Displays (FEDs), organic EL displays, 3D displays, and electronic papers, automobile components, home appliance components, portable terminals, electronic components, and building materials.

Examples

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

< production of adhesive composition >

Example A1

In a reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen gas inlet tube, 90 parts by mass of 2-ethylhexyl acrylate, 10 parts by mass of 4-hydroxybutyl acrylate, 50 parts by mass of ethyl acetate as a solvent and 0.1 part by mass of azobisisobutyronitrile as a polymerization initiator were added. Then, nitrogen gas was introduced, and the air in the reaction system was replaced with nitrogen gas for 1 hour. Then, the reaction was carried out at 75 ℃ for 7 hours to obtain a solution of (meth) acrylic polymer (A-1) having a weight average molecular weight of 50 ten thousand.

To the obtained solution of the (meth) acrylic polymer (a-1) (containing 100 parts by mass of the (meth) acrylic polymer (a-1)), 1 part by mass of lithium trifluoromethanesulfonate and 3 parts by mass of ethylene carbonate were added and stirred. Subsequently, Duranate AE700-100 (an allophanate product of a hexamethylene diisocyanate compound) 6.0 parts by mass, acetylacetone 5.0 parts by mass, and dibutyltin dilaurate 0.005 parts by mass were added thereto, and mixed with stirring, and then ethyl acetate and butyl acetate (in a mass ratio of 1: 1) were added thereto to adjust the concentration, thereby obtaining an adhesive composition of example a1 (the nonvolatile content concentration was 20% by mass).

The weight average molecular weight of the (meth) acrylic polymer is a value measured by Gel Permeation Chromatography (GPC) and converted by a standard polystyrene standard curve. The measurement conditions of the GPC method are as follows.

The device comprises the following steps: HLC-8320GPC (RI detector built-in), manufactured by Tosoh corporation

A detector: RI (differential refractometer)

Solvent: pure grade 1 THF (tetrahydrofuran)

Protection of the column: TSK-guard column Super MP (HZ) -H (1 root)

The size of the protective column is as follows: 4.6mm (ID) x 20mm

A chromatographic column: TSK-GEL Super Multi-pore HZ-H manufactured by Tosoh corporation (3 pieces connected)

Size of chromatographic column: 4.6mm (ID) x 150mm

Temperature: 40 deg.C

Sample concentration: 0.01g/5mL

Injection amount: 10 μ L

Flow rate: 0.35 mL/min

The glass transition temperature (Tg) of the (meth) acrylic polymer is determined by the above formula FOX. The glass transition temperature of the homopolymer used was the value described in "synthetic resin for coating material entry".

Examples A2 to 10 and comparative examples A1 to 7

Solutions of (meth) acrylic polymers (A-2) to (A-4) were obtained in the same manner as in example A1, except that the monomers shown in Table 1 were used. Adhesive compositions of examples a2 to a10 and comparative examples a1 to a7 were obtained in the same manner as in example a1, except that the components shown in tables 2 and 3 were used. The (meth) acrylic polymer (A-5) was "SK Dyne (registered trademark) 1499M" available from Soken chemical Co., Ltd. The amounts (parts by mass) of the solid components of the respective components are shown in tables 1 to 3.

TABLE 1

TABLE 2

Unit is mass portion

TABLE 3

Unit: mass portion of

The abbreviations used in tables 1 to 3 are shown in Table 4.

TABLE 4

(B-1) and (B-2) are alkali metal salts having a melting point of more than 25 ℃ and being solid at a temperature of 25 ℃. (b-1) is an alkaline earth metal salt having a melting point of more than 25 ℃ and being solid at a temperature of 25 ℃.

(C-1) is the compound (C) represented by the formula (I), and is a compound having a melting point of 36 ℃ and being solid at a temperature of 25 ℃. (C-2) is the compound (C) represented by the formula (I), and is a compound which has a melting point of-55 ℃ and is liquid at a temperature of 25 ℃.

(c-1) to (c-3) are polyalkylene glycols, and (c-1) and (c-2) are both liquid compounds at a temperature of 25 ℃. (c-3) is a polyalkylene glycol, and is a compound which is solid at a temperature of 25 ℃.

< preparation of surface protective film >

Example B1

The adhesive composition of example a1 was coated on a polyethylene terephthalate (PET) film, and heated at 110 ℃ for 2 minutes to be dried and cured, thereby forming an adhesive film having a thickness of 10 μm. Then, a polyethylene terephthalate (PET) film coated with a silicone resin was laminated on the adhesive film to obtain a laminated film. The laminated film was aged at 40 ℃ for 3 days to obtain the surface protective film of example B1 having "PET film (base film)/adhesive film/PET film coated with silicone resin (cover film)". Examples B2 to B10 and comparative examples B1 to B7

Surface protective films of examples B2 to B10 and comparative examples B1 to B7 were obtained in the same manner as in example B1 using the adhesive compositions of examples a2 to a10 and comparative examples a1 to a 7.

< test methods and evaluations >

The surface resistivity, adhesive force and low staining property of the adhesive films were evaluated for the surface protective films of examples B1 to B10 and comparative examples B1 to B7. The evaluation results are shown in tables 5 and 6.

< surface resistivity >

The evaluation was carried out at a temperature of 23 ℃ and a humidity of 50% RH. The cover film was peeled off from the surface protective film, and the surface resistivity (Ω/□) of the adhesive film was measured using a resistivity meter ("Hiresta-UX MCP-HT800 high resistivity meter", manufactured by Mitsubishi Motor corporation). In tables 5 and 6, "aE + b" means "a.times.10^b”。

< adhesion >

The surface protective film was cut to obtain a film for evaluation having a width of 25mm and a length of 150 mm. The cover film was peeled off from the evaluation film, and the evaluation film was bonded to a glass plate so that the surface of the adhesive film side was in contact with the surface of the degreased glass plate, thereby preparing a measurement sample. The film for evaluation was peeled from the measurement sample at room temperature (25 ℃ C.) and 180 ℃ direction at a peeling speed of 300 mm/min by using a tensile tester (Autograph AG-X/R manufactured by Shimadzu corporation) to measure the peel strength. The peel strength obtained was used as the adhesive strength (N/25 mm).

< Low fouling >

A polarizing plate having an adhesive layer on one surface thereof (Sumikaran (registered trademark) manufactured by sumitomo chemical corporation) was bonded to a glass plate with a roller so that the surface of the polarizing plate on the adhesive layer side was in contact with the surface of the glass plate. Then, a surface protective film was bonded to the polarizing plate by using a roller so that the adhesive film was in contact with the surface of the polarizing plate, thereby obtaining a laminate. The laminate was stored at 85 ℃ and 85% RH for 1 day, 3 days, 20 days, or 40 days, and then the surface protective film was peeled off. The surface of the peeled polarizing plate was visually observed for contamination.

The evaluation criteria are as follows. The term "contaminated" means a state where the surface of the polarizing plate is white and is known to be contaminated at first glance, and "contaminated a little" means a state where the vicinity of the end of the polarizing plate or the vicinity of the air bubbles is white at first glance.

No pollution in both 20-day storage and 40-day storage 5 points

"No pollution" in 20 days storage, but "little pollution" in 40 days storage in 4 points

"No pollution" in 3 days storage, but little pollution "in 20 days storage in 3 minutes

In case of "contaminated" in 20 days of storage, 2 points

In case of "contaminated" in 3 days of storage, 1 point

TABLE 5

TABLE 6

The surface resistivity of all the surface protective films of examples B1 to B10 was 1.0X 10¹²Omega/□ or less, and has excellent antistatic property. In particular, the surface protective films of examples B1 and B2 exhibited excellent adhesion to an adherend and both high antistatic properties and high low staining properties.

The surface protective films of comparative examples B1 to B3 did not exhibit excellent antistatic properties because they did not contain the alkali metal salt (B) or the compound (C) represented by formula (I) in the adhesive film. In addition, the surface protective films of comparative examples B4, B6, and B7 were poor in low staining property. Presumably: one of the reasons is that the alkylene glycol used in place of the alkali metal salt (B) and the compound (C) represented by the formula (I) causes fine cohesive failure of the adhesive film. In comparative example B5, since calcium carbonate was not dissolved in the adhesive composition, an adhesive film could not be produced.

An adhesive film formed using the adhesive composition of the embodiment of the present invention exhibits excellent adhesiveness, antistatic property and low staining property, and a surface protective film provided with the adhesive film is suitable for protection of optical parts and the like.

The disclosure of the present application is related to the subject matter described in japanese patent application 2019-086702 filed on 26.4.2019, the entire disclosure of which is hereby incorporated by reference.

Description of the symbols

1 surface protective film

2 covering film

3 adhesive film

4 base material film