JP2014031442A - Protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective film having an adhesive layer formed of an adhesive composition in which a (meth)acrylic acid ester-based copolymer is selected as a main agent of the adhesive composition, the protective film having such properties that when the film is stuck to various adherends, the film exhibits sufficient adhesive strength and leaves extremely little deposition of a residue derived from the adhesive layer when the film is peeled.SOLUTION: The protective film includes an adhesive layer formed of an adhesive composition containing: a (meth)acrylic acid ester-based copolymer (A) obtained by living radical polymerization and having a weight average molecular weight of 400000 to 2000000 and a molecular weight distribution of less than 2.5; an isocyanate crosslinking agent (B); and an organic tin compound (C). The protective film contains the organic tin compound (C) 2 to 20 times on a mass basis of tellurium metal included in the copolymer (A).

Description

  The present invention relates to a protective film having an adhesive layer. More specifically, the present invention relates to a protective film in which the residual monomer and the low molecular weight component in the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer are extremely small, and the adhesion of the residue to the adherend is very small.

  Conventionally, a protective film is used for various image display devices for optical purposes, such as LCD (liquid crystal display), touch panel, CRT (CRT), PDP (plasma display panel), EL (electroluminescence) display, optical recording medium, etc. It is used for purposes such as protection, antiglare and antireflection. Moreover, in LCD, it is used in order to protect a polarizer. This protective film generally has a pressure-sensitive adhesive layer on one side of the base film, and a functional coating layer such as antistatic performance and antifouling performance on the other side, or a hard coat layer if necessary. Is provided.

  And, since the optical properties are excellent and the pressure-sensitive adhesive design is relatively easy, the pressure-sensitive adhesive layer uses an acrylic pressure-sensitive adhesive based on a (meth) acrylic acid ester copolymer. . When such a protective film is applied to the adherend via an adhesive layer, it is known that a slight residue adheres at an invisible level, and this uses an acrylic adhesive. In this case, it is considered to be caused by residual monomers and low molecular weight components present in the (meth) acrylic acid ester copolymer as the main agent.

Patent Document 1 discloses an acrylic pressure-sensitive adhesive with a small amount of low molecular weight components, but it has not been sufficient as an effect of reducing the amount of adhered residue.
By the way, living polymerization is polymerization in which a growth reaction proceeds but a termination reaction and a chain transfer reaction do not occur. That is, the growth terminal of the living polymer remains active even after the monomer is consumed, and the polymerization starts again when the monomer is added. Therefore, it is known that the molecular weight of the polymer increases in proportion to the amount of monomer consumed, and a polymer having a uniform molecular weight is obtained.
On the other hand, in radical polymerization, since the lifetime of growing radicals is extremely short and there is a polymerization termination mechanism such as a bimolecular termination reaction, conventional living polymerization has been thought to be impossible, but in recent years it has been stable even in the presence of air. Since the discovery of new radicals, research on living radical polymerization has been actively conducted and various methods have been developed.
For example, a technique for producing a living radical polymer having a uniform molecular weight by polymerizing a vinyl monomer using an organic tellurium compound as a living radical polymerization initiator is disclosed (for example, see Patent Documents 2 and 3).

  Patent Document 4 discloses that the low molecular weight component having a molecular weight of 50,000 or less can be reduced to 5% by mass or less by applying the living radical polymerization. However, the organic tellurium compound used as the polymerization initiator is used for crosslinking. There was a problem that heavy peeling occurred due to delay and aging.

JP 2001-214142 A JP 2006-299278 A WO2004 / 014962 pamphlet JP 2011-74380 A

  The present invention has been made under such circumstances, a (meth) acrylate copolymer is selected as the main component in the pressure-sensitive adhesive composition, and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition is selected. When the protective film has affixed to various adherends, it provides a protective film with very little adhesion to the residue due to the adhesive layer when it is peeled while exhibiting sufficient adhesive strength for protection. It is intended to do.

As a result of intensive studies to achieve the above object, the present inventors have obtained the following knowledge.
As the main component of the pressure-sensitive adhesive composition, a (meth) acrylic acid ester copolymer having specific properties obtained by living radical polymerization is selected, and this copolymer, an isocyanate crosslinking agent, and the copolymer It was found that a protective film having a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition containing a predetermined proportion of an organotin compound with respect to the tellurium metal contained in can be adapted to the purpose. The present invention has been completed based on such findings.

That is, the present invention
[1] A (meth) acrylic acid ester copolymer (A), an isocyanate crosslinking agent (B), and an organic material having a weight average molecular weight of 400,000 to 2,000,000 and a molecular weight distribution of less than 2.5 obtained by living radical polymerization A protective film having a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition containing a tin compound (C), wherein the organotin compound (C) is 2 to 20 with respect to the tellurium metal contained in (A). A protective film characterized by containing the mass times,
[2] The protective film according to the above [1], wherein the proportion of the low molecular weight component having a weight average molecular weight of 100,000 or less in the (meth) acrylic acid ester copolymer (A) is less than 5% by mass; 3] The protective film according to [1] or [2] above, wherein the protective film has an adhesive layer on one surface of the plastic film, and a release sheet is laminated on the exposed surface side of the adhesive layer.
Is to provide.

  According to the present invention, an adhesive layer that can adhere to an adherend with a sufficient adhesive force for protection when attached to the adherend and has very little residue adhering to the adherend when peeled off. The protective film which has can be provided. By using this protective film, it is possible to suppress the loss of each function due to adhesion of residues even in application to functional optical members that require a high level of surface cleanliness among adherends. Be expected. Moreover, the crosslinking delay and heavy peeling which were problems in the conventional formulation can be improved by containing a tin compound in a predetermined ratio in the pressure-sensitive adhesive composition.

  The protective film of the present invention is a pressure-sensitive adhesive composition containing a (meth) acrylic ester copolymer (A), an isocyanate crosslinking agent (B), and an organotin compound (C) obtained by living radical polymerization. A protective film having a formed pressure-sensitive adhesive layer, wherein the organotin compound (C) is contained 2 to 20 times by mass with respect to tellurium metal contained in the copolymer (A). And

[(Meth) acrylic ester copolymer (A)]
The (meth) acrylic acid ester copolymer (A) is a component contained as a main component in the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer in the protective film of the present invention, and has the following properties. The “(meth) acrylic acid ester” refers to both an acrylic acid ester and a methacrylic acid ester. The same applies to other similar terms.
(Properties)
The (meth) acrylic acid ester copolymer (A) has a weight average molecular weight Mw in the range of 400,000 to 2,000,000 and a molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn ratio) of 2.5. It is necessary to be less than. If the weight average molecular weight is less than 400,000, the amount of components having a weight average molecular weight of 100,000 or less inevitably increases, and adhesion of residues to the adherend cannot be prevented. On the other hand, when it exceeds 2 million, the smoothness of the coated surface deteriorates due to an increase in viscosity. In addition, a large amount of solvent is required to suppress such increase in viscosity, which is not preferable from the viewpoint of cost or environmental measures. If the weight average molecular weight is too high, the control may be insufficient when the polymerization proceeds, and the molecular weight distribution may be widened.
In consideration of a small amount of residue, adhesion durability, and coating suitability, the weight average molecular weight is preferably 500,000 to 1,500,000, more preferably 850,000 to 1,200,000.

Further, when the molecular weight distribution (Mw / Mn ratio) is 2.5 or more, it becomes difficult to reduce low molecular weight components in the (meth) acrylic acid ester copolymer (A) described later, The object of the present invention may not be achieved. A preferred molecular weight distribution (Mw / Mn ratio) is less than 2.5. Particularly preferred is 1.0 to 2.2.
Furthermore, in the (meth) acrylic acid ester copolymer (A), the proportion of the low molecular weight component having a weight average molecular weight Mw of 100,000 or less contained therein is preferably less than 5% by mass. When the proportion of the low molecular weight component is 5% by mass or more, a protective film having a pressure-sensitive adhesive layer formed using a pressure-sensitive adhesive composition containing such a copolymer is applied to the adherend. When pasted through a layer, the adhesion of the residue to the adherend may not be suppressed to a sufficiently low level.
Therefore, the ratio of the low molecular weight component having a weight average molecular weight of 100,000 or less is more preferably 3% by mass or less, further preferably 2% by mass or less, and particularly preferably 1% by mass or less.
In addition, the ratio of the said low molecular weight component, the weight average molecular weight Mw, and the number average molecular weight Mn are the values of standard polystyrene conversion measured by the gel permeation chromatography (GPC) method.

(composition)
The (meth) acrylic acid ester copolymer (A) is a (meth) acrylic acid ester monomer unit (a) having an alkyl group having 1 to 20 carbon atoms (hereinafter referred to as a non-functional monomer unit ( a) and a (meth) acrylic acid ester monomer unit (b) having a reactive functional group (hereinafter sometimes referred to as a functional monomer unit (b)). Are preferably contained at a mass ratio of 80:20 to 99.9: 0.1. The reactive functional group in the functional monomer unit (b) is a functional group that becomes a cross-linking point cross-linked by a cross-linking agent described later, and the content of the functional monomer unit (b) is Based on the total amount with the non-functional monomer unit (a), if it is less than 0.1% by mass, the (meth) acrylic acid ester copolymer (A) is insufficiently crosslinked, and the pressure-sensitive adhesive composition May be inferior in adhesive strength and durability. From such a viewpoint, the content of (b) is more preferably 0.5% by mass or more, and particularly preferably 1% by mass or more.
On the other hand, if the content of (b) exceeds 20% by mass, gelation tends to occur during the production of the pressure-sensitive adhesive, and the pot life after addition of the crosslinking agent becomes too short, which may cause workability problems. There is. In addition, the cohesive force becomes too high, and the adhesive force may be lowered to deteriorate the adhesion to the adherend. From such a viewpoint, the content of (b) is more preferably 10% by mass or less.
Further, from the viewpoint of excluding the possibility that the functional group of the functional monomer unit (b) may coordinate to the initiator (organic tellurium compound) and the control of the polymerization becomes insufficient, the functional monomer unit. The content of (b) is particularly preferably 8% by mass or less.

  The (meth) acrylic acid ester copolymer (A) is a (meth) acrylic acid ester having a C1-C20 alkyl group that forms the non-functional monomer unit (a), The (meth) acrylic acid ester having a reactive functional group forming the functional monomer unit (b) can be copolymerized with another monomer used as desired.

  Examples of the (meth) acrylic acid ester having an alkyl group having 1 to 20 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and pentyl (meth) acrylate. , Hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate And stearyl (meth) acrylate. These may be used alone or in combination of two or more.

  On the other hand, examples of (meth) acrylic acid ester having a reactive functional group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl. Hydroxyalkyl (meth) acrylate such as (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, monomethylaminoethyl (meth) acrylate, monoethylaminoethyl (meth) acrylate, monomethylamino And monoalkylaminoalkyl (meth) acrylates such as propyl (meth) acrylate and monoethylaminopropyl (meth) acrylate. These may be used singly or in combination of two or more. In the present invention, hydroxyalkyl (meth) acrylate is preferably used from the viewpoint of crosslinkability and the like.

  Examples of other monomers used as desired include vinyl esters such as vinyl acetate and vinyl propionate; olefins such as ethylene, propylene and isobutylene; halogenated olefins such as vinyl chloride and vinylidene chloride; styrene Styrene monomers such as α-methylstyrene; diene monomers such as butadiene, isoprene and chloroprene; nitrile monomers such as acrylonitrile and methacrylonitrile; acrylamide, N-methylacrylamide, N, N- Examples include acrylamides such as dimethylacrylamide. These may be used alone or in combination of two or more.

From the viewpoint of performance as an adhesive, the (meth) acrylic acid ester copolymer (A) is a copolymer of butyl acrylate and 4-hydroxybutyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate. Copolymer of 4-hydroxybutyl acrylate, copolymer of butyl acrylate and 2-hydroxyethyl acrylate, copolymer of butyl acrylate, cyclohexyl acrylate and 4-hydroxybutyl acrylate, or butyl acrylate A copolymer of methyl acrylate and 4-hydroxybutyl acrylate is preferred.
In this case, the content of the 4-hydroxybutyl acrylate unit or 2-hydroxyethyl acrylate unit serving as a crosslinking point in the copolymer is preferably about 0.5 to 10% by mass, and preferably 1 to 8% by mass. Particularly preferred.

(Polymerization method)
The (meth) acrylic acid ester copolymer (A) is polymerized by living radical polymerization. Living radical polymerization has a feature that the reaction at the active site is very gradual compared to free radical polymerization. That is, in free radical polymerization, since the reaction at the active site is very fast, it is considered that polymerization is performed from a monomer having high reactivity, and then a monomer having low reactivity is polymerized. On the other hand, in living radical polymerization, since the reaction at the active site is slow, the polymerization proceeds evenly without being affected by the reactivity of the monomer, and any copolymer obtained has a more uniform composition. It is considered to be. Therefore, the (meth) acrylic acid ester copolymer (A) obtained by living radical polymerization is a (meth) acrylic acid ester system consisting only of the non-functional monomer unit (a) as compared with that obtained by free radical polymerization. It is considered that the generation rate of the homopolymer is overwhelmingly small. For this reason, even if the (meth) acrylic acid ester copolymer (A) obtained by living radical polymerization has a low molecular weight, the possibility of being crosslinked by the crosslinking agent (B) described later becomes very high. . As a result, the pressure-sensitive adhesive layer based on the (meth) acrylic acid ester copolymer (A) obtained by living radical polymerization can suppress the adhesion of the residue to the adherend to a very low level. It is considered possible.
As the living radical polymerization method, a conventionally known method, for example, an atom transfer radical polymerization method using an atom transfer radical polymerization agent (ATRP polymerization method) as a polymerization control agent, a reversible addition-cleavage chain using a reversible addition-cleavage chain transfer agent. A polymerization method by transfer (RAFT polymerization method), a polymerization method using an organic tellurium compound as a polymerization initiator, and the like can be employed. Among these living radical polymerization methods, a method using an organic tellurium compound as a polymerization initiator is preferable because of controllability of molecular weight and polymerization in an aqueous system. Below, the method of using an organic tellurium compound as a polymerization initiator is shown.

［式中、Ｒ¹は、炭素数１〜８のアルキル基、アリール基、置換アリール基又は芳香族ヘテロ環基を示す。Ｒ²及びＲ³は、水素原子又は炭素数１〜８のアルキル基を示す。Ｒ⁴は、アリール基、置換アリール基、芳香族ヘテロ環基、アシル基、オキシカルボニル基又はシアノ基を示す。］ <Living radical polymerization using organic tellurium compounds>
The (meth) acrylic acid ester copolymer (A) is obtained by using, for example, a living radical polymerization initiator represented by the following general formula (1) (hereinafter sometimes referred to as organic tellurium compound I). It can be produced by polymerizing a mixture of monomers.

[Wherein, R ¹ represents an alkyl group having 1 to 8 carbon atoms, an aryl group, a substituted aryl group or an aromatic heterocyclic group. R ² and R ³ represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. R ⁴ represents an aryl group, a substituted aryl group, an aromatic heterocyclic group, an acyl group, an oxycarbonyl group or a cyano group. ]

Specific examples of the group represented by R ¹ are as follows.
Examples of the alkyl group having 1 to 8 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, cyclopropyl group, n-butyl group, sec-butyl group, tert-butyl group, cyclobutyl group, and n-pentyl. Examples thereof include linear, branched or cyclic alkyl groups having 1 to 8 carbon atoms such as a group, n-hexyl group, n-heptyl group and n-octyl group. As a preferable alkyl group, it is a C1-C4 linear or branched alkyl group, More preferably, it is a methyl group or an ethyl group.
As the aryl group, a phenyl group, a naphthyl group, etc., as a substituted aryl group, a phenyl group having a substituent, a naphthyl group having a substituent, etc., as an aromatic heterocyclic group, a pyridyl group, furyl Group, thienyl group and the like. Examples of the substituent of the aryl group having the above substituent include a halogen atom, a hydroxyl group, an alkoxy group, an amino group, a nitro group, a cyano group, and a carbonyl-containing group represented by —COR ⁵ (R ⁵ = carbon number). 1-8 alkyl groups, aryl groups, C1-C8 alkoxy groups, aryloxy groups), sulfonyl groups, trifluoromethyl groups, and the like. Preferred aryl groups include a phenyl group and a trifluoromethyl substituted phenyl group. These substituents may be substituted one or two, and the para-position or ortho-position is preferred.

Each group represented by R ² and R ³ is specifically as follows.
Examples of the alkyl group having 1 to 8 carbon atoms include the same alkyl groups as those described above for R ¹ .
Each group represented by R ⁴ is specifically as follows.
Examples of the aryl group, substituted aryl group, and aromatic heterocyclic group include the same groups as those described above for R ¹ .
Examples of the acyl group include a formyl group, an acetyl group, and a benzoyl group.
As the oxycarbonyl group, a group represented by —COOR ⁶ (R ⁶ ═H, alkyl group having 1 to 8 carbon atoms, aryl group) is preferable, and examples thereof include a carboxyl group, a methoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, Examples thereof include an n-butoxycarbonyl group, a sec-butoxycarbonyl group, a tert-butoxycarbonyl group, an n-pentoxycarbonyl group, and a phenoxycarbonyl group. Preferred oxycarbonyl groups include methoxycarbonyl group and ethoxycarbonyl group.

Preferred examples of each group represented by R ⁴ include an aryl group, a substituted aryl group, and an oxycarbonyl group. A preferable aryl group includes a phenyl group. Preferable substituted aryl groups include halogen atom substituted phenyl groups and trifluoromethyl substituted phenyl groups. In addition, in the case of a halogen atom, these substituents include those having 1 to 5 substituents. In the case of an alkoxy group or a trifluoromethyl group, one or two substituted groups may be mentioned, and in the case of one substitution, the para position or the ortho position is preferable, and in the case of two substitutions, the meta position is preferable. Preferred oxycarbonyl groups include methoxycarbonyl group and ethoxycarbonyl group.

As the organic tellurium compound I represented by the general formula (1), R ¹ represents an alkyl group having 1 to 4 carbon atoms, and R ² and R ³ represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. And R ⁴ is an aryl group, a substituted aryl group, or an oxycarbonyl group. Particularly preferably, R ¹ represents an alkyl group having 1 to 4 carbon atoms, R ² and R ³ represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ⁴ represents a phenyl group or a substituted phenyl group. , A methoxycarbonyl group, and an ethoxycarbonyl group.

The organic tellurium compound represented by the general formula (1) is specifically as follows.
Examples of the organic tellurium compound include (methylterranyl-methyl) benzene, (1-methylterranyl-ethyl) benzene, (2-methylterranyl-propyl) benzene, 1-chloro-4- (methylterranyl-methyl) benzene, 1-hydroxy-4- (Methylterranyl-methyl) benzene, 1-methoxy-4- (methylterranyl-methyl) benzene, 1-amino-4- (methylterranyl-methyl) benzene, 1-nitro-4- (methylterranyl-methyl) benzene, 1-cyano- 4- (methylterranyl-methyl) benzene, 1-methylcarbonyl-4- (methylterranyl-methyl) benzene, 1-phenylcarbonyl-4- (methylterranyl-methyl) benzene, 1-methoxycarbonyl-4- (methylterranyl-methyl) benzene 1-phenoxycarbonyl-4- (methylterranyl- Methyl) benzene, 1-sulfonyl-4- (methylterranyl-methyl) benzene, 1-trifluoromethyl-4- (methylterranyl-methyl) benzene, 1-chloro-4- (1-methylterranyl-ethyl) benzene, 1-hydroxy -4- (1-methylteranyl-ethyl) benzene, 1-methoxy-4- (1-methylterranyl-ethyl) benzene, 1-amino-4- (1-methylterranyl-ethyl) benzene, 1-nitro-4- (1 -Methyl terranyl-ethyl) benzene, 1-cyano-4- (1-methyl teranyl-ethyl) benzene, 1-methylcarbonyl-4- (1-methyl teranyl-ethyl) benzene, 1-phenylcarbonyl-4- (1-methyl terranyl- Ethyl) benzene, 1-methoxycarbonyl-4- (1-methylterranyl-ethyl) benzene, 1-phenoxy Rubonyl-4- (1-methylterranyl-ethyl) benzene, 1-sulfonyl-4- (1-methylterranyl-ethyl) benzene, 1-trifluoromethyl-4- (1-methylterranyl-ethyl) benzene [or 1- ( 1-methylterranyl-ethyl) -4-trifluoromethylbenzene. 1- (1-methylteranyl-ethyl) -3,5-bis-trifluoromethylbenzene, 1,2,3,4,5-pentafluoro-6- (1-methylterranyl-ethyl) benzene, 1-chloro -4- (2-methylteranyl-propyl) benzene, 1-hydroxy-4- (2-methylteranyl-propyl) benzene, 1-methoxy-4- (2-methylterranyl-propyl) benzene, 1-amino-4- (2 -Methyl teranyl-propyl) benzene, 1-nitro-4- (2-methyl teranyl-propyl) benzene, 1-cyano-4- (2-methyl teranyl-propyl) benzene, 1-methylcarbonyl-4- (2-methyl teranyl-propyl) ) Benzene, 1-phenylcarbonyl-4- (2-methylterranyl-propyl) benzene, 1-methoxycarbonyl-4- (2-methylterranyl) Propyl) benzene, 1-phenoxycarbonyl-4- (2-methylterranyl-propyl) benzene, 1-sulfonyl-4- (2-methylterranyl-propyl) benzene, 1-trifluoromethyl-4- (2-methylterranyl-propyl) Benzene, 2- (methylterranyl-methyl) pyridine, 2- (1-methylterranyl-ethyl) pyridine, 2- (2-methylterranyl-propyl) pyridine, 2-methyl-2-methylterranyl-propanal, 3-methyl-3- Methyl terranyl-2-butanone, 2-methyl terranyl-methyl ethanoate, 2-methyl terranyl-methyl propionate, 2-methyl terranyl-2-methyl propionate, 2-methyl terranyl-ethyl ethanoate, 2-methyl terranyl-ethyl propionate, 2 -Methylteranyl-2-methylpro Ethyl propionic acid [or ethyl-2-methyl-2-Mechiruteraniru - called propionate. ], 2- (n-butyl terranyl) -2-methylpropionate ethyl [or ethyl-2-methyl-2-n-butyl terranyl-propionate. ], 2-methyl terranyl acetonitrile, 2-methyl terranyl propionitrile, 2-methyl-2-methyl terranyl propionitrile, (phenyl terranyl-methyl) benzene, (1-phenyl terranyl-ethyl) benzene , (2-phenylterranyl-propyl) benzene and the like.

Further, in the above, all compounds in which methyl teranyl, 1-methyl terranyl and 2-methyl terranyl are changed to ethyl teranyl, 1-ethyl teranyl, 2-ethyl terranyl, butyl terranyl, 1-butyl terranyl and 2-butyl terranyl, respectively, are included. Preferably, (methylterranyl-methyl) benzene, (1-methylterranyl-ethyl) benzene, (2-methylterranyl-propyl) benzene, 1-chloro-4- (1-methylterranyl-ethyl) benzene, 1-trifluoromethyl-4 -(1-methylteranyl-ethyl) benzene [1- (1-methylterranyl-ethyl) -4-trifluoromethylbenzene], methyl 2-methylterranyl-2-methylpropionate, ethyl 2-methylterranyl-2-methylpropionate [ Ethyl-2-methyl-2-methylterranyl-propionate], 2- (n-butylterranyl) -2-methylpropionate [ethyl-2-methyl-2-n-butylterranyl-propionate], 1- (1-methylterranyl- Ethyl) -3,5-bis-trifluoromethylbenzene, 1,2,3,4,5-pe Tafluoro-6- (1-methylterranyl-ethyl) benzene, 2-methylterranylpropionitrile, 2-methyl-2-methylterranylpropionitrile, (ethylterranyl-methyl) benzene, (1-ethylterranyl-ethyl) benzene , (2-ethylteranyl-propyl) benzene, methyl 2-ethylteranyl-2-methylpropionate, ethyl 2-ethylteranyl-2-methylpropionate, 2-ethylterranylpropionitrile, 2-methyl-2-ethylterranyl Propionitrile, (n-butylteranyl-methyl) benzene, (1-n-butylteranyl-ethyl) benzene, (2-n-butylteranyl-propyl) benzene, 2-n-butylteranyl-2-methylpropionate methyl, 2- n-butyl terranyl-2-methylpropionate ethyl, 2- Examples thereof include n-butyl terranyl propionitrile and 2-methyl-2-n-butyl terranyl propionitrile.
These organic tellurium compounds represented by the general formula (1) may be used singly or in combination of two or more.

In the polymerization step in the present invention, an azo polymerization initiator may be added as a polymerization accelerator in addition to the organic tellurium compound. The azo polymerization initiator is not particularly limited as long as it is an initiator used for ordinary radical polymerization. However, for example, 2,2′-azobis (isobutyronitrile) (AIBN), 2,2′-azobis ( 2-methylbutyronitrile) (AMBN), 2,2′-azobis (2,4-dimethylvaleronitrile) (ADVN), 1,1′-azobis (1-cyclohexanecarbonitrile) (ACHN), dimethyl-2 2,2′-azobisisobutyrate (MAIB), 4,4′-azobis (4-cyanovaleric acid) (ACVA), 1,1′-azobis (1-acetoxy-1-phenylethane), 2,2 '-Azobis (2-methylbutyramide), 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylamidinopropane) dihydrochloride, 2, 2'-azobis [2- (2-imi Zolin-2-yl) propane], 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis (2,4,4-trimethylpentane), 2 -Cyano-2-propylazoformamide, 2,2'-azobis (N-butyl-2-methylpropionamide), 2,2'-azobis (N-cyclohexyl-2-methylpropionamide) and the like.
When the azo polymerization initiator is used, it is preferably 0.01 to 100 mol, more preferably 0.1 to 100 mol, still more preferably 0 with respect to 1 mol of the organic tellurium compound of the formula (1) used as the polymerization initiator. It is desirable to be used at a ratio of 0.1 to 5 mol.

The method for forming the (meth) acrylic acid ester copolymer (A) by living radical polymerization is specifically as follows.
In a container substituted with an inert gas, the mixture of monomers described above, the living radical polymerization initiator represented by the general formula (1) and, if desired, an azo polymerization initiator are mixed. At this time, examples of the inert gas include nitrogen, argon, helium and the like. Preferably, argon and nitrogen are used. Particularly preferred is nitrogen.
The use amount of the monomer and the living radical polymerization initiator (organic tellurium compound) represented by the general formula (1) is the (meth) acrylic acid ester copolymer (A) (hereinafter referred to as living radical copolymer). The molecular weight or molecular weight distribution of the combination (A) may be appropriately adjusted. The preferred amount used is a value (unit of amount used) divided by the weight average molecular weight (Mw) of the target copolymer (A), which is approximately the sum of the values obtained by multiplying the molecular weight of each monomer by the charge ratio. Is the number of moles). In some cases, the amount is about 0.3 to 3 times the value.

  The polymerization is usually performed without a solvent, but an organic solvent generally used in radical polymerization may be used. Examples of the solvent that can be used include benzene, toluene, N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, chloroform, carbon tetrachloride, tetrahydrofuran (THF), ethyl acetate, trifluoromethylbenzene, and the like. Can be mentioned. Moreover, an aqueous solvent can also be used, for example, water, methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, 1-methoxy-2-propanol, etc. are mentioned. The amount of the solvent used may be appropriately adjusted. For example, the solvent is 0.01 to 100 ml, preferably 0.05 to 10 ml, particularly preferably 0.05 to 0.5 ml per 1 g of the monomer. It is.

Next, the mixture is stirred. The reaction temperature and reaction time may be appropriately adjusted depending on the molecular weight or molecular weight distribution of the resulting living radical copolymer (A), but are usually stirred at 60 to 150 ° C. for 5 to 100 hours. Preferably, it is good to stir at 80-120 degreeC for 10 to 30 hours. At this time, the pressure is usually normal pressure, but it may be increased or decreased.
After completion of the reaction, purify the desired living radical copolymer (A) as necessary by removing the solvent and residual monomer under reduced pressure, precipitation filtration, reprecipitation, column separation, etc. To do. The reaction treatment can be performed by any treatment method as long as there is no problem with the object.
For example, in the (meth) acrylic acid ester copolymer (A), in order to make the proportion of the low molecular weight component having a weight average molecular weight Mw of 100,000 or less contained therein less than 5% by mass, the following fractionation method is used. Can be adopted.
(Separation method of component (A))
Specific examples of the method for fractionating component (A) include first lower alcohols such as methanol, ethanol, n-propanol and isopropanol, or aliphatic hydrocarbons having 5 to 10 carbon atoms such as pentane, hexane and heptane, preferably Add 100 parts by mass of methanol or hexane and add component (A) as a solid in a proportion of about 1 to 30 parts by mass and stir at room temperature to form a precipitate. Next, the precipitate is subjected to solid-liquid separation by a method such as decantation, and then washed with the lower alcohol or an aliphatic hydrocarbon having 5 to 10 carbon atoms, and then contained in the adhesive composition as a main agent. By this fractionation method, the proportion of the low molecular weight component having a weight average molecular weight Mw of 100,000 or less in the component (A) can be made less than 5% by mass.

In this living radical polymerization method, by using a mixture of monomers constituting the (meth) acrylate copolymer (A), a random copolymer (meth) acrylate copolymer is used. A coalescence (A) can be obtained. Regardless of the type of monomer, the random copolymer can provide a copolymer having a ratio (molar ratio) of monomers to be reacted.
The living radical polymerization initiator represented by the general formula (1) used in the present invention can perform excellent molecular weight control and molecular weight distribution control under very mild conditions.
The molecular weight of the (meth) acrylic ester copolymer (A) comprising the living radical copolymer obtained in the present invention is the reaction time, the living radical polymerization initiator (organic tellurium compound) represented by the general formula (1) ). Specifically, in order to increase the molecular weight, the blending ratio of the organic tellurium compound to the monomer may be reduced and the polymerization time may be increased. However, this requires a long time to obtain a copolymer (A) having a large molecular weight. Thus, reduction of the polymerization time can be achieved by increasing the polymerization temperature or adding the azo polymerization initiator. However, if the polymerization temperature is too high, or if the amount of the azo polymerization initiator added is too large, the molecular weight distribution of the copolymer (A) will be increased, so adjustment with it is necessary.
Thus, the weight average molecular weight is 400,000 to 2 million, the molecular weight distribution (Mw / Mn ratio) is less than 2.5, and the proportion of low molecular weight components having a weight average molecular weight of 100,000 or less is 5 mass. % (Meth) acrylic acid ester copolymer (A) can be easily obtained.

[Isocyanate-based crosslinking agent (B)]
In the said adhesive composition, an isocyanate type crosslinking agent (B) is contained as an essential component.
Examples of the isocyanate-based crosslinking agent (B) include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, and the like. And their biuret, isocyanurate, and reaction products with low molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Examples thereof include adducts (for example, trimethylolpropane-modified tolylene diisocyanate).
In this invention, this crosslinking agent may be used individually by 1 type, and may be used in combination of 2 or more type. Moreover, although the usage-amount is based also on the kind of crosslinking agent, it is 0.01-20 mass parts normally with respect to 100 mass parts of said (meth) acrylic acid ester-type copolymers (A), Preferably, it is 0.0. It is selected in the range of 1 to 10 parts by mass, particularly preferably 0.5 to 5 parts by mass.

[Organic tin compound (C)]
In the said adhesive composition, an organotin compound (C) is contained as an essential component.
In the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition, the inclusion of a tellurium compound derived from a polymerization initiator has been a problem of crosslinking delay and heavy peeling. By containing, the effect which can solve the said problem is produced.
As this organotin compound, for example, dibutyltin dilaurate (DBTDL) or dibutyltin dioctylate (DBTDO), which has been conventionally used as a crosslinking accelerator, is preferable from the viewpoint of the above effects. The usage-amount is the range of 2-20 mass times with respect to the tellurium metal contained in a (meth) acrylic acid ester type copolymer (A). When this amount is less than 2 times by mass, the above-mentioned effect is not sufficiently exhibited and the object of the present invention cannot be achieved. On the other hand, when the amount exceeds 20 times by mass, the improvement of the effect is not recognized so much for the amount. The preferred amount used is 2 to 15 times the mass of tellurium metal.

[Preparation of pressure-sensitive adhesive composition]
There is no restriction | limiting in particular in the preparation method of the adhesive composition used by this invention, For example, the (meth) acrylic acid ester type copolymer (A) mentioned above, an isocyanate type crosslinking agent (B), organotin compound ( C) and various additives used as necessary, for example, antioxidants, ultraviolet absorbers, antistatic agents, light diffusing agents, light stabilizers, silane coupling agents, leveling agents, antifoaming agents, etc., and stirring The pressure-sensitive adhesive composition can be prepared by mixing.
Examples of the solvent include aliphatic hydrocarbons such as hexane and heptane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methylene chloride and ethylene chloride, alcohols such as methanol, ethanol, propanol, and butanol, acetone. , Ketones such as methyl ethyl ketone, 2-pentanone, isophorone and cyclohexanone, esters such as ethyl acetate and butyl acetate, cellosolv solvents such as ethyl cellosolve, glycol ether solvents such as propylene glycol monomethyl ether, and the like. These solvents may be used alone or in a combination of two or more.
The solid content concentration of the pressure-sensitive adhesive composition is not particularly limited as long as the composition has a viscosity suitable for coating.

Next, the protective film of the present invention will be described.
The protective film of the present invention has a pressure-sensitive adhesive layer formed of the above-mentioned pressure-sensitive adhesive composition, and has, for example, the pressure-sensitive adhesive layer on one surface of a plastic film, and the pressure-sensitive adhesive layer. A laminated film having a structure in which a release sheet is laminated on the exposed surface side is preferable.

[Plastic film]
In the protective film of the present invention, the plastic film used as a substrate is not particularly limited, for example, a polyester film such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene film, polypropylene film, cellophane, diacetyl cellulose film, Triacetyl cellulose film, acetyl cellulose butyrate film, polyvinyl chloride film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, polymethylpentene film, polysulfone film, polyether Ether ketone film, polyether sulfone film, polyether De films, polyimide films, fluororesin films, polyamide films, acrylic resin films, norbornene resin films, cycloolefin resin films or the like. In addition, when using a protective film for optical purposes, the inspection work should be performed with the protective film attached to the adherend, or the protective film may be visually recognized from above while the protective film is attached to the consumer's preference. Therefore, the plastic film is preferably a transparent plastic film.
The thickness of these plastic films is not particularly limited and is appropriately selected, but is usually in the range of 10 to 250 μm, preferably 30 to 200 μm. Moreover, this plastic film can be surface-treated by an oxidation method, an uneven | corrugated method, etc. on one side or both surfaces as needed for the purpose of improving the adhesiveness with the layer provided in the surface. Examples of the oxidation method include corona discharge treatment, plasma treatment, chromic acid treatment (wet), flame treatment, hot air treatment, ozone / ultraviolet irradiation treatment, and examples of the unevenness method include a sand blast method, a solvent, and the like. Treatment methods and the like. These surface treatment methods are appropriately selected according to the type of the base film, but generally, the corona discharge treatment method is preferably used from the viewpoints of effects and operability. Moreover, what gave the primer process to the single side | surface or both surfaces can also be used.

[Adhesive layer]
In the protective film of the present invention, the pressure-sensitive adhesive layer provided on one surface of the plastic film is provided by directly applying and drying the above-mentioned pressure-sensitive adhesive composition of the present invention on the plastic film, and further releasing the mold thereon. Sheets may be laminated, or applied and dried on the release treatment surface of the release sheet to form an adhesive layer, and this adhesive layer with release sheet is adhered to one side of the plastic film. Also good.
As a method for applying the pressure-sensitive adhesive composition, a known method such as knife coating, roll coating, bar coating, blade coating, die coating, gravure coating or the like can be applied to a predetermined thickness. A drying method can be used.
The thickness of the pressure-sensitive adhesive layer is usually about 2 to 30 μm, preferably 5 to 25 μm.
Examples of the release sheet include papers such as glassine paper, coated paper, and laminate paper, and various plastic films coated with a release agent such as silicone resin. As a plastic film, what was mentioned by the said plastic film can be used suitably. Although there is no restriction | limiting in particular about the thickness of this release sheet, Usually, it is about 10-100 micrometers.
The protective film of the present invention may be one in which a release sheet is usually laminated on the exposed surface side of the pressure-sensitive adhesive layer, or without using a separate release sheet, the pressure-sensitive adhesive layer of the plastic film A release layer is provided on the surface opposite to the lamination surface, and is wound in a roll shape so that the exposed surface side of the pressure-sensitive adhesive layer is in contact with the surface of the release layer, or stacked in a stacked manner. Also good.

[Coating layer]
In the protective film of this invention, the coating layer which has antistatic performance and / or antifouling performance can be provided in the surface on the opposite side to the adhesive layer of a plastic film.
The coating layer having antistatic performance can be formed, for example, by applying and drying a coating liquid in which a conductive material is dispersed in a thermoplastic resin matrix.
On the other hand, a coating layer having antifouling performance can be formed by applying and drying a coating liquid generally containing a fluororesin.
As a coating method of the various coating liquids, for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like can be used.
The thickness of the coating layer having the conductive performance thus formed is usually about 0.05 to 1 μm, preferably 0.3 to 0.7 μm. The thickness of the coating layer having antifouling performance is Usually, it is about 1 to 10 nm, preferably 3 to 8 nm.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
In addition, about the acrylate copolymer obtained in each example, the low molecular weight component of the weight average molecular weight Mw of the standard polystyrene conversion, the number average molecular weight Mn, and the weight average molecular weight 100,000 or less by gel permeation chromatography (GPC) method The content of was determined by the following method.
<GPC method>
Measuring apparatus: Tosoh Corporation's high-speed GPC device "HLC-8120GPC", high-speed columns "TSK gold column H _XL- H", "TSK Gel GMH _XL ", "TSK Gel G2000 H _XL " ) In this order and measured.
Column temperature: 40 ° C., liquid feed rate: 1.0 mL / min, detector: differential refractometer

Moreover, about the protective film obtained in each case, the adhesive force with respect to polymethylmethacrylate (PMMA), the peeling force of a release sheet (SP), and the amount of residual particles (residual particle number test) were calculated | required with the following method.
(1) Adhesive strength to PMMA From a protective film obtained in the following example, a 25 mm width and a 100 mm length were cut out, and a release sheet was peeled off to obtain a test piece. Was used as a test plate.
In addition, after attaching the test piece and the test plate, the sample was allowed to stand for 24 hours in an environment of 23 ° C. and 50% relative humidity, and then 1) left at 23 ° C. for 1 week while maintaining the relative humidity of 50%. 2) Leave at 23 ° C. for 1 month, or 3) leave at 40 ° C. for 2 weeks, and then use each test piece and test plate after steps 1) to 3) at 25 millimeters per Newton Was measured. Except for the above conditions, the adhesive strength was measured under the conditions of a peeling speed of 300 mm / min and a peeling angle of 180 ° using a tensile tester [Orientec, “Tensilon”] according to JIS Z 0237: 2009. .

(2) Peeling force of release sheet (SP) For the protective films of the following examples, a 50 mm wide and 150 mm long sample was cut out and left at 23 ° C. for 1 week at 50% relative humidity or at 40 ° C. for 2 weeks. After leaving, the peel strength of SP was measured for each sample under the conditions of a peel rate of 300 mm / min and a peel angle of 180 ° using a tensile tester [Orientec, “Tensilon”].
(3) Residual particle number test The protective film obtained in the example or the comparative example was attached in a clean room by reciprocating a 5 kg (49N) rubber roller on a mirror surface of a 4-inch silicon wafer at room temperature, After leaving for 60 minutes, peeling was performed. At this time, the number of residual foreign matters having a particle size of 0.27 μm or more on the wafer was measured by a laser surface inspection apparatus (manufactured by Hitachi Electronics Engineering).

Synthesis Example 1 (Ethyl-2-methyl-2-n-butylteranyl-propionate)
6.38 g (50 mmol) of metal tellurium [manufactured by Aldrich, product name “Tellurium (−40 mesh)”] was suspended in 50 ml of tetrahydrofuran (THF), and n-butyllithium [manufactured by Aldrich, 1.6 mol]. / L hexane solution] 34.4 ml (55 mmol) was slowly added dropwise at room temperature. The reaction solution was stirred until the metal tellurium disappeared completely. To this reaction solution, 10.7 g (55 mmol) of ethyl-2-bromo-isobutyrate was added at room temperature and stirred for 2 hours. After completion of the reaction, the solvent was concentrated under reduced pressure, followed by distillation under reduced pressure to obtain 8.98 g (yield 59.5%) of ethyl-2-methyl-2-n-butylteranyl-propionate as a yellow oil. .

Example 1
(1) Production of Acrylate Ester Copolymer (A) Consisting of Random Copolymer by Living Radical Polymerization As monomers, butyl acrylate [BA, manufactured by Tokyo Chemical Industry Co., Ltd.] and 4-hydroxybutyl acrylate [4HBA, Tokyo Chemical Industry] Acrylic ester copolymer (A) comprising a random copolymer of BA / 4HBA was produced by living radical polymerization shown below using a mass ratio of 97: 3. The properties of this copolymer are shown in Table 1.
<Living radical polymerization>
In a glove box substituted with argon, 68.5 μL of ethyl-2-methyl-2-n-butylterranyl-propionate prepared in Synthesis Example 1, 107 g of butyl acrylate (same as above), 3.3 g of 4-hydroxybutyl acrylate (same as above) and 4.6 mg of 2,2′-azobis (isobutyronitrile) [AIBN; manufactured by Aldrich] was reacted at 60 ° C. for 20 hours.
After completion of the reaction, the reactor was taken out of the glove box and dissolved in 500 ml of ethyl acetate, and then the polymer solution was passed through a column made of activated alumina [manufactured by Wako Pure Chemical Industries, Ltd.]. Toluene was added so that the viscosity of the polymer solution was 5000 mPa · s (25 ° C.). The obtained polymer had a solid content of 15% by mass.
Further, according to GPC, the proportion of low molecular weight components having a molecular weight of 100,000 or less was 1.95% by mass, the weight average molecular weight was 1,30,000 and the molecular weight distribution was 2.06.
Further, the polymer solution was dried and then incinerated, and it was confirmed by ICP / MS that the amount of residual tellurium relative to the solid content of the polymer solution was 100 ppm.

(2) Preparation of pressure-sensitive adhesive composition 100 parts by mass (solid content) of (meth) acrylic acid ester copolymer (A) comprising the random copolymer produced in (1) above, and isocyanurate type HDI as a crosslinking agent [Nippon Polyurethane Industry Co., Ltd., trade name “Coronate HX”, NCO content: 21.3 mass%, solid content 100%] 2.00 parts by mass and DBTDL 245 ppm were dissolved in methyl ethyl ketone as a solvent to obtain a solid content concentration A 13% by weight pressure-sensitive adhesive composition was prepared.

(3) Preparation of protective film As a plastic film, the antistatic / antifouling non-treated surface of a 38 μm thick antistatic antifouling polyethylene terephthalate film [trade name “PET38SLD52” manufactured by Toray Industries, Inc.] The obtained pressure-sensitive adhesive composition was applied with a knife type coater so that the dry thickness was 5 μm, and then heated and dried at 90 ° C. for 1 minute to form a pressure-sensitive adhesive layer.
Next, the exposed surface side of the pressure-sensitive adhesive layer obtained above was bonded to the release treatment surface of a release sheet [trade name “SP-PET 381031” manufactured by LINTEC Co., Ltd.] having a thickness of 38 μm. A protective film composed of a pressure-sensitive adhesive layer / release sheet was prepared, and various properties of this protective film were determined. The results are shown in Table 2.

Example 2
In Example 1, except having changed the quantity of DBTDL into 490 ppm, it carried out similarly to Example 1, and prepared the adhesive composition, and also produced the protective film. Various characteristics were determined for this protective film. The results are shown in Table 2.

Example 3
In Example 1, except that the amount of DBTDL was changed to 979 ppm, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, and a protective film was further produced. Various characteristics were determined for this protective film. The results are shown in Table 2.

Comparative Examples 1-4
In Example 1, each adhesive composition was prepared in the same manner as in Example 1 except that the amount of DBTDL was changed as shown in Table 1, and each protective film was further produced. Various characteristics were determined for each protective film. The results are shown in Table 2.

Comparative Example 5
(1) Manufacture of acrylic acid ester copolymer by free radical polymerization As a monomer, butyl acrylate (same as above) and 4-hydroxybutyl acrylate (same as above) were used in a mass ratio of 97: 3. An acrylic acid ester copolymer of BA / 4HBA was produced by radical polymerization. The properties of this copolymer are shown in Table 1.
<Free radical polymerization>
Nitrogen gas is sealed in a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen introduction tube, and then 90 parts by mass of ethyl acetate, 75 parts by mass of butyl acrylate, 2.3 parts by mass of 4-hydroxybutyl acrylate, polymerization Initiator 2,2′-azobis (isobutylnitrile) (AIBN) (0.2 part by mass) was charged and allowed to react for 7 hours at the reflux temperature of ethyl acetate with stirring. After completion of the reaction, 95 parts by mass of toluene was added and cooled to room temperature. An acrylate copolymer having a solid content of 13% by mass was obtained.
Thereafter, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, and a protective film was further produced. The various properties of this protective film are shown in Table 2.

[note]
(1) The Te content in the acrylic ester copolymer was measured by the following method.
Measuring instrument: ICP / MS
The polymer solution was dried, incinerated, and analyzed by ICP / MS.
(2) phr: parts by mass with respect to 100 parts by mass of the main agent (3) DBTDL: dibutyltin dilaurate (4) BA: butyl acrylate (5) 4HBA: 4-hydroxybutyl acrylate (6) coronate HX: manufactured by Nippon Polyurethane Industry Co., Ltd. , Isocyanurate type HDI, NCO content: 23.1% by mass, solid content: 100%
(7) LRP: Living radical polymerization (8) FRP: Free radical polymerization

As can be seen from Table 2, the adhesive strength of the protective film of the example is less reduced with time than the adhesive strength of the protective film of the comparative example. Moreover, about the peeling force with respect to a release sheet, the direction of the protective film of a comparative example is large with time compared with the protective film of an Example, and heavy peeling-ization is progressing.
In the residual particle number test, a large difference is not recognized between the protective films of Examples 1 to 3 by the living radical polymerization and the protective films of Comparative Examples 1 to 4, but in the protective film of Comparative Example 5 by free radical polymerization. The number of particles by the residual particle number test is as high as 7800.

  The protective film of the present invention has a pressure-sensitive adhesive layer, and there are very few residual monomers and low molecular weight components in the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer, and very little residue adheres to the adherend. It is a film and is used for the purpose of anti-glare properties and antireflection, as well as surface protection of various image display devices.

Claims (3)

  (Meth) acrylic acid ester copolymer (A), isocyanate crosslinking agent (B), and organotin compound (A) having a weight average molecular weight of 400,000 to 2,000,000 and a molecular weight distribution of less than 2.5 obtained by living radical polymerization A protective film having a pressure-sensitive adhesive layer formed by a pressure-sensitive adhesive composition containing C), and containing the organotin compound (C) in an amount of 2 to 20 times the tellurium metal contained in (A). The protective film characterized by performing.   The protective film according to claim 1, wherein the proportion of the low molecular weight component having a weight average molecular weight of 100,000 or less in the (meth) acrylic acid ester copolymer (A) is less than 5% by mass.   The protective film of Claim 1 or 2 which has an adhesive layer in one side of a plastic film, and a release sheet is laminated | stacked on the exposed surface side of this adhesive layer.