JP6998134B2 - Adhesive composition for optical film, adhesive layer and manufacturing method thereof, optical member, and image display device - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive composition for an optical film. The present invention also relates to a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for an optical film. Further, the present invention also relates to an optical member using the pressure-sensitive adhesive layer and an image display device using the optical member. Furthermore, the present invention also relates to a method for producing the pressure-sensitive adhesive layer.

A polarizing film (polarizing plate) is indispensable for a liquid crystal panel such as a liquid crystal display device which is a kind of image display device. In addition, various optical members such as optical films are attached in order to improve the display quality of the display. When these optical members are attached to a liquid crystal panel, an adhesive is usually used. In addition, an adhesive is usually used when two or more optical films of the same type or different types are attached to each other.

As a necessary property of the pressure-sensitive adhesive, durability in the bonded state of the pressure-sensitive adhesive is required. The said durability means a property that a defect such as peeling or floating due to an adhesive does not occur in a durability test by heating, humidification, etc., which is usually performed as an environmental promotion test. On the other hand, in recent years, optical films used for in-vehicle panels are required to have higher durability than conventional ones. That is, it is required that problems such as peeling and floating caused by the adhesive do not occur in the durability test in a higher temperature and higher humidity environment than in the past.

Further, when the optical film is bonded to the liquid crystal panel by using the adhesive, the bonded position may be incorrect or a foreign substance may be caught in the bonded surface. In such a case, it is necessary to peel off the optical film from the liquid crystal panel and reattach it. In particular, in recent years, in addition to the conventional manufacturing process of a liquid crystal display device, the use of a liquid crystal display device such as a thin liquid crystal panel using chemically etched glass has increased, and the optical film has become thin and brittle. .. Therefore, when a conventional adhesive that aims only at durability is used for such a thin liquid crystal display device or a thin optical film, the following problems have arisen. That is, there is a problem that the thin liquid crystal display device and the thin optical film are broken or broken. Therefore, in the peeling step, the property of the pressure-sensitive adhesive, which is reworkability, is required. The reworkability refers to a removability that allows the optical film to be easily peeled off without adhesive residue from the liquid crystal display device or the like.

Further, in order to improve productivity, it is more desirable to have excellent handleability in terms of the manufacturing process.

Acrylic adhesives are widely used as such adhesives. Generally, bonding using an acrylic pressure-sensitive adhesive containing a solvent is performed as follows. That is, first, a pressure-sensitive adhesive composition containing a (meth) acrylate-based resin and a cross-linking agent is prepared, and this is applied to the peeling surface side of the film for the process. Then, the layer made of the pressure-sensitive adhesive composition after coating is dried and then cured to form a crosslinked structure between the (meth) acrylate-based resins. By transferring the pressure-sensitive adhesive layer formed on the process film side to one surface of the optical film as an adherend, an optical member (adhesive type optical film) containing the process film can be obtained. After that, the optical film having the pressure-sensitive adhesive layer from which the process film has been peeled off is bonded to another optical film or liquid crystal panel which is the other adherend. As a result, the pressure-sensitive adhesive layer is brought into close contact between the two adherends. As described above, if the pressure-sensitive adhesive layer that has been subjected to the cross-linking treatment on one surface of the optical film is formed in advance, there is an advantage that the drying step for fixing is not required after the bonding.

Many proposals have been made so far for the above-mentioned pressure-sensitive adhesive compositions for optical films.

For example, Patent Document 1 discloses a pressure-sensitive adhesive composition for an optical film containing the following components (A), component (B), component (C) and component (D). The component (A) is an acrylic polymer obtained by copolymerizing at least the following components (a1), (a2) and (a3). The weight average molecular weight of the component (A) is 800,000 to 1.6 million, and Mw / Mn is 10 to 50. The (a1) is a (meth) acrylic acid alkyl ester and / or a (meth) acrylic acid alkoxyalkyl ester, and the content is 5 to 89.5% by weight. The (a2) is an aromatic ring-containing monomer, and the content is 10 to 85% by weight. The (a3) is a hydroxyl group-containing monomer, and the content is 0.5 to 10% by weight. The component (B) is an isocyanate-based cross-linking agent and contains 0.005 to 5 parts by weight with respect to 100 parts by weight of the component (A). The component (C) is a silane coupling agent and contains 0.05 to 1.0 part by weight with respect to 100 parts by weight of the component (A). The component (D) is a crosslinking accelerator and contains 0.001 to 0.5 parts by weight with respect to 100 parts by weight of the component (A). With such a configuration, a pressure-sensitive adhesive composition for an optical film can be obtained, which can suppress contamination during re-peeling and peeling under harsh conditions while maintaining good durability and light leakage prevention.

Further, Patent Document 2 discloses a pressure-sensitive adhesive containing a (meth) acrylic polymer and a cross-linking agent. The (meth) acrylic polymer has 3 to 10% by weight of a heterocycle-containing acrylic monomer, 0.5 to 5% by weight of a carboxyl group-containing monomer, 0.05 to 2% by weight of a hydroxy group-containing monomer, and an alkyl as monomer components. (Meta) acrylate contains 83 to 96.45% by weight. The (meth) acrylic polymer has a weight average molecular weight of 1.5 million to 2.8 million. With such a configuration, durability can be satisfied even when the pressure-sensitive adhesive layer is thinned.

Further, Patent Document 3 discloses a pressure-sensitive adhesive composition for an optical film containing a (meth) acrylic polymer (A). The (meth) acrylic polymer (A) contains, as a monomer unit, an alkyl (meth) acrylate (a1) 67 to 96.99% by weight, an aromatic ring-containing (meth) acrylic monomer (a2) 1 to 20% by weight, and the like. It contains 2 to 10% by weight of the carboxyl group-containing monomer (a3) and 0.01 to 3% by weight of the hydroxy group-containing monomer (a4). The (meth) acrylic polymer (A) has a Mw of 1.6 million or more and a Mw / Mn of 1.8 or more and 10 or less. With such a configuration, it is possible to form an adhesive layer that can satisfy reworkability and durability and can improve display unevenness due to white spots in the peripheral portion.

Further, in Patent Documents 4 and 5, a pressure-sensitive adhesive composition for an optical film containing a (meth) acrylic polymer, having a solid content of 20% by weight or more and a solvent content of 80% by weight or less. Is disclosed. The (meth) acrylic polymer has an alkyl (meth) acrylate 30 to 98.9% by weight, a polymerizable aromatic ring-containing monomer 1 to 50% by weight, and a hydroxy group-containing monomer 0.1 to 20% by weight as a monomer unit. And 0 to 4% by weight of the carboxyl group-containing monomer are copolymerized. The (meth) acrylic polymer has a weight average molecular weight of 300,000 to 1.2 million by gel permeation chromatography. The (meth) acrylic polymer does not contain a carboxyl group-containing monomer as a monomer unit. With such a configuration, it is possible to achieve excellent removability, durability, smoothness of the coated surface, and reduction of the amount of solvent used in a well-balanced manner, and it is possible to reduce the generation of microgels in the pressure-sensitive adhesive layer.

Further, Patent Document 6 discloses an adhesive composition containing a (meth) acrylic acid ester polymer (A) and an isocyanate-based cross-linking agent (B). The (meth) acrylic acid ester polymer (A) has a weight average molecular weight of 1.5 million to 2.5 million, and contains a monomer unit having a hydroxyl group and a monomer unit having an aromatic ring. The (meth) acrylic acid ester polymer (A) does not contain a monomer unit having a carboxyl group. The (meth) acrylic acid ester polymer (A) contains 1 to 10% by mass of the monomer unit having a hydroxyl group and 1 to 10% by mass of the monomer unit having the aromatic ring. With such a configuration, it is possible to obtain a pressure-sensitive adhesive composition that does not adversely affect the adherend such as a transparent conductive film due to the acid component and has excellent durability.

Further, Patent Document 7 discloses a pressure-sensitive adhesive containing an acrylic polymer, a cross-linking agent and a silane coupling agent. The acrylic polymer contains an alkyl (meth) acrylate (a1), a (meth) acrylate having an aromatic ring structure (a2), and a monomer (a3) as a monomer unit. The content ratio of the component (a1) is 49.9 to 84.9% by weight. The content ratio of the component (a2) is 15 to 50% by weight. The component (a3) is a monomer excluding the component (a1) and the component (a2), and the content ratio thereof is 0.1 to 5% by weight. The acrylic polymer has Mw of 1.4 million to 2.5 million and Mw / Mn of 3 to 10. With such a configuration, it is possible to provide an adhesive optical film having good durability and display uniformity and good handleability.

Japanese Unexamined Patent Publication No. 2007-138557 Japanese Unexamined Patent Publication No. 2007-277510 Japanese Unexamined Patent Publication No. 2011-105918 Japanese Unexamined Patent Publication No. 2012-140578 Japanese Unexamined Patent Publication No. 2012-140579 Japanese Unexamined Patent Publication No. 2014-152317 Japanese Unexamined Patent Publication No. 2009-276451

However, according to the studies by the present inventors, it has been found that the following problems 1 to 3 cannot be solved at the same time even with the pressure-sensitive adhesive layers described in Patent Documents 1 to 7. Problem 1 is that the compatibility between durability and reworkability was insufficient. Problem 2 is that the handleability of not requiring the aging process was not sufficient. Problem 3 is that oligomer contamination occurs and contaminates coating lines, liquid crystal panels, and the like.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a means for simultaneously solving the above-mentioned problems 1 to 3 in the pressure-sensitive adhesive composition for an optical film.

Another object of the present invention is to provide a pressure-sensitive adhesive layer formed from such a pressure-sensitive adhesive composition, an optical member using the pressure-sensitive adhesive layer, and an image display device using the optical member. be.

Yet another object of the present invention is to provide a method for producing an adhesive layer.

As a result of diligent research to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by a pressure-sensitive adhesive composition having a specific constituent component, and have completed the present invention.

That is, the present invention is a pressure-sensitive adhesive composition for an optical film containing a (meth) acrylate copolymer (A), a peroxide (B), and a cross-linking agent (C) other than the peroxide. The oxide (B) is a pressure-sensitive adhesive composition for an optical film having a one-minute half-life temperature of 80 ° C. or higher and 125 ° C. or lower, and the cross-linking agent (C) other than the peroxide does not contain a blocked isocyanate compound. be.

According to the present invention, in a pressure-sensitive adhesive composition for an optical film, a means capable of achieving both durability and reworkability, further improving handleability that does not require an aging treatment, and sufficiently suppressing oligomer contamination. Is provided.

Hereinafter, embodiments for carrying out the present invention will be described.

{Adhesive composition for optical film}
The pressure-sensitive adhesive composition for an optical film according to the present invention contains a (meth) acrylate copolymer (A), a peroxide (B), and a cross-linking agent (C) other than the peroxide, and the peroxide ( B) has a 1-minute half-life temperature of 80 ° C. or higher and 125 ° C. or lower, and the cross-linking agent (C) other than the peroxide does not contain a blocked isocyanate compound.

Hereinafter, each component constituting the pressure-sensitive adhesive composition for an optical film according to the present invention will be described in order.

In the present specification, "(meth) acrylate" is a general term for acrylate and methacrylate. Similarly, compounds containing (meta) such as (meth) acrylic acid are a general term for compounds having "meta" in the name and compounds having no "meta". Further, the "(meth) acrylate copolymer (A)" is also referred to as a "copolymer (A)".

<(Meta) acrylate copolymer (A)>
The pressure-sensitive adhesive composition for an optical film according to the present invention indispensably contains a (meth) acrylate copolymer (A). Adhesiveness (adhesiveness) is exhibited by the copolymer (A) reacting with the peroxide (B) described later and / or the cross-linking agent (C) other than the peroxide to form a cross-linked structure. ..

The weight average molecular weight (Mw) of the copolymer (A) according to the present invention is not particularly limited, but is preferably 800,000 or more and 2.5 million or less from the viewpoint of durability and productivity at the time of coating, 130. It is more preferably 10,000 or more and 2.2 million or less, and further preferably 1.5 million or more and 2 million or less. The weight average molecular weight (Mw) of the copolymer (A) according to the present invention can be determined by a person skilled in the art by appropriately adjusting the polymerization initiator used in the polymerization reaction described later, reaction conditions such as reaction temperature and reaction time, and the like. If there is, it can be easily controlled. In this specification, the weight average molecular weight can be measured by the method shown in Examples.

In the present invention, the structural unit constituting the copolymer (A) is not particularly limited, but includes (a1) a structural unit derived from an alkyl (meth) acrylate monomer (hereinafter, also simply referred to as “component (a1)”). Is preferable. Further, a structural unit derived from the component (a1), (a2) a (meth) acrylate monomer having a hydroxyl group (hereinafter, also simply referred to as “component (a2)”) and (a4) a structural unit derived from a monomer having a carboxyl group. It is also preferable to include at least one of (hereinafter, also simply referred to as “component (a4)”). That is, the copolymer (A) according to the present invention preferably contains the component (a1) and the component (a2); it is also preferable to contain the component (a1) and the component (a4); Further, it is also preferable to include the component (a1), the component (a2), and the component (a4). Further, the copolymer (A) according to the present invention is a structural unit derived from a (meth) acrylate monomer having (a3) an aromatic ring (hereinafter referred to as “)”.
It is also preferable to simply include (also referred to as "component (a3)"). Further, it is more preferable that the copolymer (A) according to the present invention further contains the above-mentioned component (a3) together with the above-mentioned component (a1) and at least one of the above-mentioned component (a2) and the above-mentioned component (a4).

In the present specification, "the copolymer X contains a structural unit derived from the monomer Y ₁ and a structural unit derived from the monomer Y ₂ " means that the copolymer X is obtained by copolymerization. The raw material monomer used is meant to include the monomer Y ₁ and the monomer Y ₂ . Therefore, for example, the above-mentioned structural unit derived from the (a1) alkyl (meth) acrylate monomer, (a2) the structural unit derived from the (meth) acrylate monomer having a hydroxyl group, and (a3) the (meth) acrylate having an aromatic ring. In the case where the copolymer (A) according to the present invention contains a structural unit derived from a monomer, in other words, (a1) an alkyl (meth) acrylate monomer and (a2) a (meth) acrylate monomer having a hydroxyl group. And (a3) a (meth) acrylate monomer having an aromatic ring are copolymerized with each other.

Hereinafter, the structural units derived from each monomer that can form the copolymer (A) according to the present invention will be described in order.

[Constituent unit derived from (a1) alkyl (meth) acrylate monomer]
The copolymer (A) according to the present invention preferably contains the component (a1). It is considered that the inclusion of such a component (a1) as a constituent unit of the copolymer (A) according to the present invention has significance in ensuring adhesiveness and basic properties.

In the present invention, the structure of the alkyl (meth) acrylate monomer is not particularly limited, and is not particularly limited as long as the alkyl group is introduced into the ester moiety of the (meth) acrylate.

The number of carbon atoms of the alkyl group is not particularly limited, but is preferably 1 or more and 20 or less, more preferably 1 or more and 12 or less, still more preferably 1 or more and 10 or less, from the viewpoint of versatility, price, handling and the like. It is more preferably 1 or more and 8 or less, and particularly preferably 1 or more and 6 or less. The alkyl group may be linear, branched, or cyclic, but is preferably linear or branched from the viewpoint of lowering the glass transition temperature. When the alkyl group is cyclic, the number of carbon atoms is 3 or more.

The alkyl group is not particularly limited, but is a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a t-butyl group, an isobutyl group, an n-hexyl group, a 2-hexyl group, and the like. 3-Hexyl group, Cyclohexyl group, 1-Methylcyclohexyl group, n-Heptyl group, 2-Heptyl group, 3-Heptyl group, Isoheptyl group, t-Heptyl group, n-octyl group, Isooctyl group, t-octyl group, Examples thereof include 2-ethylhexyl group, nonyl group, isononyl group, decyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group and the like. In particular, from the viewpoint of ensuring adhesiveness and ensuring basic properties, a methyl group, an n-butyl group, an n-hexyl group, a 2-ethylhexyl group, a nonyl group and an isononyl group are preferable.

Therefore, specific examples of the alkyl (meth) acrylate monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth). Acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, isopentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, Examples thereof include nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, and lauryl (meth) acrylate. Of these, methyl (meth) acrylate and n-butyl (meth) acrylate are preferable from the viewpoint of heat durability and adhesive strength. These can be used alone or in combination of two or more.

The content of the component (a1) in the copolymer (A) according to the present invention (the amount of the alkyl (meth) acrylate monomer as the raw material monomer) is not particularly limited, but is the same as the content of other raw material monomers described later. From the viewpoint of good balance, improvement of durability, suppression of light leakage, etc., 50% by mass or more and 95% by mass or less with respect to 100% by mass of the total amount of the constituent units constituting the copolymer (A). It is preferably 60% by mass or more and 93% by mass or less, and particularly preferably 70% by mass or more and 90% by mass or less. In the present specification, "100% by mass of the total amount of the constituent units constituting the copolymer (A)" means all the raw material monomers used when the copolymer (A) is obtained by copolymerization. It means that the total amount is 100% by mass.

[(A2) Structural unit derived from (meth) acrylate monomer having a hydroxyl group]
The copolymer (A) according to the present invention preferably contains (a2) a structural unit derived from a (meth) acrylate monomer having a hydroxyl group. By including such a component (a2) as a constituent unit of the copolymer (A) according to the present invention, the reworkability is improved, and the component (a2) is reactive with the intermolecular cross-linking agent. Therefore, it is considered to have a significance of improving the cohesiveness and heat resistance of the pressure-sensitive adhesive layer described later.

In the present invention, the structure of the (meth) acrylate monomer having a hydroxyl group is not particularly limited, and is not particularly limited as long as the hydroxyl group is introduced into a part of the (meth) acrylate monomer.

Specific examples of the (meth) acrylate monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 1,6-hexanediol mono (meth) acrylate, and pentaerythritol tri (meth). ) Acrylate, Dipentaerythritol Penta (meth) acrylate, Neopentyl glycol mono (meth) acrylate, Trimethylol propandi (meth) acrylate, Trimethylol ethanedi (meth) acrylate, 2-Hydroxypropyl (meth) acrylate, 2- Hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenyloxypropyl (meth) acrylate, 4-hydroxycyclohexyl (meth) acrylate, hydroxymethyl (meth) acrylamide, hydroxyethyl (meth) acrylamide, cyclohexanedimethanol monoacrylate, etc. Further, examples thereof include compounds obtained by an addition reaction between a glycidyl group-containing compound such as an alkyl glycidyl ether, an allyl glycidyl ether, and a glycidyl (meth) acrylate and a (meth) acrylic acid. Among them, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxyethyl (meth) are used from the viewpoint of efficiently functioning as a cross-linking point when an isocyanate-based cross-linking agent described later is used. Acrylamide and cyclohexanedimethanol monoacrylate are preferable, and 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are more preferable. These can be used alone or in combination of two or more.

The content of the component (a2) in the copolymer (A) according to the present invention (the amount of the (meth) acrylate monomer having a hydroxyl group as a raw material monomer) is not particularly limited, but the isocyanate-based cross-linking agent described later may be used. From the viewpoint of improving durability by ensuring a good balance of cross-linking points during use, 0.01% by mass or more with respect to 100% by mass of the total amount of the constituent units constituting the copolymer (A). It is preferably 10% by mass or less, preferably 0.1.
It is more preferably mass% or more and 5% by mass or less, and particularly preferably 0.3% by mass or more and 5% by mass or less.

[(A3) Structural unit derived from (meth) acrylate monomer having an aromatic ring]
It is more preferable that the copolymer (A) according to the present invention further contains a structural unit derived from a (meth) acrylate monomer having an aromatic ring (a3). Such a component (a3) can mainly contribute to the suppression of light leakage in the pressure-sensitive adhesive composition for an optical film.

In the present invention, the structure of the (meth) acrylate monomer having an aromatic ring is not particularly limited, and has any structure as long as the structure contains an aromatic ring (aromatic ring) and a (meth) acryloyl group. It may be a thing. Here, the aromatic ring is not particularly limited, and examples thereof include a benzene ring, a naphthalene ring, and a biphenyl ring.

Specific examples of the (meth) acrylate monomer having an aromatic ring include benzyl (meth) acrylate, phenyl (meth) acrylate, o-phenylphenol (meth) acrylate, phenoxymethyl (meth) acrylate, and phenoxyethyl (meth) acrylate. Phenoxypropyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, ethylene oxide-modified nonylphenol (meth) acrylate, ethylene oxide-modified cresol (meth) acrylate, phenolethylene oxide-modified (meth) acrylate, 2-hydroxy-3-phenoxypropyl ( Those having a benzene ring such as meth) acrylate, methoxybenzyl (meth) acrylate, chlorobenzyl (meth) acrylate, cresyl (meth) acrylate, and polystyryl (meth) acrylate; hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth). ) Acrylate, 2-naphthoxyethyl acrylate, 2- (4-methoxy-1-naphthoxy) ethyl (meth) acrylate or the like having a naphthalene ring; examples thereof include those having a biphenyl ring such as biphenyl (meth) acrylate. Of these, benzyl (meth) acrylate and phenoxyethyl (meth) acrylate are preferable from the viewpoint of suppressing light leakage and facilitating ensuring durability. It should be noted that these may contain only one kind, or may contain two or more kinds in combination.

The content of the component (a3) in the copolymer (A) according to the present invention (the amount of the (meth) acrylate monomer having an aromatic ring as a raw material monomer) is not particularly limited, but light leakage can be sufficiently suppressed. From the viewpoint of ensuring durability, the content is preferably 10% by mass or more and 30% by mass or less, preferably 10.5% by mass or more and 25% by mass or less, based on 100% by mass of the total amount of the constituent units constituting the copolymer (A). It is more preferably 1% by mass or less, and particularly preferably 11% by mass or more and 20% by mass or less.

[(A4) Structural unit derived from a monomer having a carboxyl group]
In the present invention, the copolymer (A) can optionally further contain (a4) a structural unit derived from a monomer having a carboxyl group. Such a component (a4) can mainly contribute to ensuring durability and adhesion to a liquid crystal panel in the pressure-sensitive adhesive composition for an optical film.

In the present invention, the structure of the monomer having a carboxyl group is not particularly limited, and any structure may be used as long as the structure contains a carboxyl group and a polymerizable unsaturated bond.

Specific examples of monomers having a carboxyl group include (meth) acrylic acid, maleic acid, maleic anhydride, fumaric acid, fumaric anhydride, crotonic acid, itaconic acid, itaconic anhydride, myristoleic acid, palmitoleic acid, and olein. Acids and the like can be mentioned. Among them, from the viewpoint of excellent copolymerizability with other (meth) acrylic monomers, (meth) acrylic acid, maleic acid, maleic anhydride, fumaric acid, fumaric anhydride, crotonic acid, itaconic acid, and anhydrous. Itaconic acid is preferred, and (meth) acrylic acid is more preferred. It should be noted that these may contain only one kind, or may contain two or more kinds in combination.

The content of the component (a4) when the component (a4) is further contained (the amount of the monomer having a carboxyl group as a raw material monomer) is not particularly limited, but from the viewpoint of ensuring durability and not deteriorating reworkability, the content is not particularly limited. It is preferably more than 0% by mass and 10% by mass or less, and more preferably more than 0% by mass and 8% by mass or less, based on 100% by mass of the total amount of the constituent units constituting the copolymer (A). It is preferably more than 0% by mass and 5% by mass or less.

[(A5): Monomer-derived structural unit other than the component (a1), the component (a2), the component (a3), and the component (a4)]
The copolymer (A) according to the present invention is optionally a structural unit derived from a monomer other than the above-mentioned component (a1), component (a2), component (a3), and component (a4) (hereinafter, simply "component (hereinafter, simply" component (a4)). a5) ”) can also be included. In the present invention, the total amount of the component (a1), the component (a2), the component (a3), the component (a4) and the component (a5) is 100% by mass. That is, for example, when the copolymer (A) contains all the structural units derived from the component (a1), the component (a2), the component (a3), the component (a4) and the component (a5), the component (a1) , The total amount of the component (a2), the component (a3), the component (a4) and the component (a5) is 100% by mass, and when any one or more of the constituent units derived from the components is not contained, The total amount of the remaining components is 100% by mass.

The raw material monomer constituting the component (a5) is not particularly limited, and for example, a (meth) acrylate monomer having an alkoxyalkyl group or an alkylene oxide group is preferably used.

Examples of (meth) acrylate monomers having an alkoxyalkyl group or an alkylene oxide group are methoxyethyl (meth) acrylate, ethoxymethyl (meth) acrylate, ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, butoxyethyl (meth). ) Acrylate, methoxypropyl (meth) acrylate, methoxybutyl (meth) acrylate; ethoxy-diethylene glycol (meth) acrylate, ethoxy-triethylene glycol (meth) acrylate, methoxy-triethylene glycol (meth) acrylate, methoxy-diethylene glycol (meth) ) Acrylate, propoxy-diethylene glycol (meth) acrylate, methoxy-triethylene glycol (meth) acrylate, 2-ethylhexyloxy-didiethylene glycol (meth) acrylate, methoxy-polyethylene glycol (meth) acrylate (n = 4-10), methoxy Examples thereof include, but are not limited to, dipropylene glycol (meth) acrylate and 2-ethylhexyl-diglycol acrylate.

Acrylic monomers having an epoxy group such as glycidyl (meth) acrylate and methyl glycidyl (meth) acrylate; dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, Nt-butylaminoethyl (meth) acrylate, Acrylate having an amino group such as (meth) acryloylyloxyethyltrimethylammonium chloride; acrylic having an amide group such as (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N, N-methylenebis (meth) acrylamide and the like. Monomer; Acrylic monomer having a phosphate group such as 2-methacryloyloxyethyl diphenyl phosphate (meth) acrylate, trimethacryloyl oxyethyl phosphate (meth) acrylate, triacrylloyl oxyethyl phosphate (meth) acrylate; sulfopropyl (meth). ) Acrylate monomer having a sulfonic acid group such as sodium acrylate, sodium 2-sulfoethyl (meth) acrylate, sodium 2-acrylamide-2-methylpropanesulfonate; acrylic monomer having a urethane group such as urethane (meth) acrylate, etc. Be done. Acrylic vinyl monomers having a phenyl group such as p-tert-butylphenyl (meth) acrylate and o-biphenyl (meth) acrylate; 2-acetoacetoxyethyl (meth) acrylate, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris. Vinyl monimer having a silane group such as (β-methoxyethyl) silane, vinyl triacetyl silane, methacryloyloxypropyl trimethoxysilane; styrene, chlorostyrene, α-methylstyrene, vinyltoluene, vinyl chloride, vinyl acetate, vinyl propionate, Acrylonitrile, vinyl pyridine and the like are also mentioned as raw material monomers constituting the component (a5).

The above-mentioned substances can be used alone or in combination of two or more as the component (a5). Further, from the viewpoint that the reaction with the cross-linking agent described later can be easily controlled when the copolymer (A) according to the present invention is produced, the molecular weight of the component (a5) becomes high due to the problem of copolymerizability. It is preferable not to contain an olefin-based monomer because of problems such as difficulty.

The content of the component (a5) when the component (a5) is further contained (the amount of the raw material monomers other than the above (a1), (a2), (a3) and (a4)) is not particularly limited, but is crosslinkable. From the viewpoint of ensuring and ensuring durability, it is preferably more than 0% by mass and 20% by mass or less, more than 0% by mass, based on 100% by mass of the total amount of the constituent units constituting the copolymer (A). It is more preferably 10% by mass or less, and particularly preferably more than 0% by mass and 5% by mass or less.

[Method for producing (meth) acrylate copolymer (A)]
Next, a method for producing the copolymer (A) will be described. In the present invention, the method for producing the copolymer (A) is not particularly limited, and is a solution polymerization method using a polymerization initiator, a bulk polymerization method, an emulsion polymerization method, a suspension polymerization method, a reverse phase suspension polymerization method, and a thin film. Conventionally known methods such as a polymerization method and a spray polymerization method can be used. Examples of the polymerization control method include an adiabatic polymerization method, a temperature control polymerization method, and an isothermal polymerization method. As the polymerization initiator, either a thermal polymerization initiator or a photopolymerization initiator may be used. Further, in addition to or in addition to the method of initiating the polymerization with a polymerization initiator, a method of initiating the polymerization by irradiating an active energy ray such as radiation, an electron beam, or an ultraviolet ray can also be adopted. Of these, a solution polymerization method using a thermal polymerization initiator or a massive polymerization method using a photopolymerization initiator is more preferable because the molecular weight can be easily adjusted and impurities can be reduced.

In the solution polymerization method using a thermal polymerization initiator, it has a monomer solution as a raw material of the copolymer (A), for example, an alkyl (meth) acrylate monomer, a (meth) acrylate monomer having a hydroxyl group, and an aromatic ring (meth). ) A thermal polymerization initiator is added to a raw material monomer solution consisting of an acrylate monomer, a monomer having a carboxyl group arbitrarily contained, and a monomer other than the above, which is optionally contained, and a polymerization reaction is carried out. More specifically, ethyl acetate, toluene, methyl ethyl ketone, acetone or the like is used as a solvent, and preferably 0.01 part by mass or more and 1 part by mass or less of the thermal polymerization initiator is added to 100 parts by mass of the total amount of the raw material monomers. Then, in a nitrogen atmosphere, for example, a method of reacting at a reaction temperature of 40 ° C. or higher and 90 ° C. or lower (or 60 ° C. or higher and 90 ° C. or lower) for 3 hours or more and 10 hours or less can be mentioned.

Examples of the thermal polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis (2-methylbutyronitrile), azobiscyanovaleric acid, and 2,2'-azobis (). 4-methoxy-2.4-dimethylvaleronitrile), 2,2'-azobis (2.4-dimethylvaleronitrile), dimethyl 2,2'-azobis (2-methylpropionate), 2,2'- Azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis [N- (2-propenyl)-
2-Methylpropionamide], 2,2'-azobis (N-butyl-2-methylpropionamide), 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2, 2'-Azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate, 2,2'-azobis (2-methylpropionamidine) dihydrochloride, 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] Hydrate, 2,2'-azobis [2- (2-imidazolin-2-yl) propane], 2,2'-azobis (1-imino-1-) Pyrrolidino-2-methylpropane) dihydrochloride, azo compounds such as 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamide]; t-butylperoxypivalate, t-butylperoxy Organic peroxides such as benzoate, t-butylperoxy-2-ethylhexanoate, di-t-butyl peroxide, cumene hydroperoxide, benzoyl peroxide, t-butyl hydroperoxide; hydrogen peroxide, peroxide. Examples thereof include inorganic peroxides such as ammonium sulfate, potassium persulfate, and sodium persulfate. Only one kind of these thermal polymerization initiators may be used alone, or two or more kinds thereof may be used in combination.

In the bulk polymerization method using a photopolymerization initiator, for example, a raw material monomer and a photopolymerization initiator are added, and the reaction initiation temperature is set to 20 ° C. or higher and 35 ° C. or lower under a nitrogen atmosphere, and irradiation with active energy rays is performed. When the temperature in the reaction system rises from the reaction start temperature to 5 ° C. or higher and 15 ° C. or lower, a method of stopping the reaction by introducing air into the reaction system to obtain the copolymer (A) can be mentioned. ..

Examples of active energy rays used in the massive polymerization method include ultraviolet rays, laser rays, α rays, β rays, γ rays, X-rays, electron beams, etc., but they have good controllability, handleability, and cost. From this point of view, ultraviolet rays are preferably used. More preferably, ultraviolet rays having a wavelength of 200 nm or more and 400 nm or less are used. Ultraviolet rays can be irradiated using a light source such as a high-pressure mercury lamp, a microwave-excited lamp, a chemical lamp, or a black light. The illuminance is preferably 3.2 mW / cm ² or more and 5.6 mW / cm ² or less.

Examples of the photopolymerization initiator include acetophenone, 3-methylacetophenone, benzyldimethylketal, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1- (4-isopropylphenyl) -2-hydroxy-. 2-Methylpropane-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1-one, 2-hydroxy-2-methyl-1-phenylpropane-1-one, etc. Acetphenones; Benzophenones such as benzophenone, 4-chlorobenzophenone, 4,4'-diaminobenzophenone; Benzophenones such as benzoinpropyl ether and benzoinethyl ether; Thioxanthones such as 4-isopropylthioxanthone; 1-hydroxy Examples thereof include cyclohexylphenyl ketone, xanthone, fluorenone, camphorquinone, benzaldehyde, anthraquinone and the like. Only one kind of these photopolymerization initiators may be used alone, or two or more kinds thereof may be used in combination.

Commercially available products may be used as the photopolymerization initiator, and examples of the commercially available products include, for example, Irgacure (registered trademark) 184, 819, 907, 651, 1700, 1800, 819, 369, 261 and DaroCure (registered trademark) TPO. , DaroCure (registered trademark) 1173 (above, BASF Japan Co., Ltd.), EzaCure (registered trademark) KIP150, TZT (above, DKSH Japan Co., Ltd.), Kayacure (registered trademark) BMS, DMBI (above, Nippon Kayaku Co., Ltd.) (Made by company), etc.

The amount of the photopolymerization initiator used is preferably 0.0005 parts by mass or more and 1 part by mass or less, more preferably 0.002 parts by mass or more and 0.5 parts by mass or less, based on 100 parts by mass of the total amount of the raw material monomers. be.

A chain transfer agent can also be used to regulate the molecular weight of the copolymer (A). For example, methyl mercaptan, t-butyl mercaptan, decyl mercaptan, benzyl mercaptan, stearyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, mercaptoacetic acid, mercaptopropionic acid and its esters, 2-ethylhexylthioglycol, octyl thioglycolate, etc. Mercaptans; alcohols such as methanol, ethanol, propanol, n-butanol, isopropanol, t-butanol, hexanol, benzyl alcohol, allyl alcohol; halogenated hydrocarbons such as chlorethane, fluoroethane, trichloroethylene; acetone, methyl ethyl ketone, Carbonyls such as cyclohexanone, acetophenone, acetaldehyde, propionaldehyde, n-butylaldehyde, furfural, benzaldehyde; methyl-4-cyclohexene-1,2-dicarboxylic acid anhydride, α-methylstyrene and the like can be mentioned. These may be used alone or in combination of two or more.

<Peroxide (B)>
The pressure-sensitive adhesive composition for an optical film of the present invention contains a peroxide (B) as an essential component. In addition, in this specification, "peroxide" means a compound which has a peroxide structure "-O-O-" in a molecular structure.

In the present invention, the peroxide (B) has a one-minute half-life temperature of 80 ° C. or higher and 125 ° C. or lower. If a peroxide having a 1-minute half-life temperature of less than 80 ° C. is used, the storage stability after blending the pressure-sensitive adhesive solution may deteriorate, while a peroxide having a 1-minute half-life temperature exceeding 125 ° C. is used. Therefore, the effect of peroxide under low temperature drying conditions cannot be expected. On the other hand, when the one-minute half-life temperature is 80 ° C. or higher and 125 ° C. or lower, the peroxide (B) can be decomposed at a low temperature and in a short time, and such a peroxide (B) is used. Therefore, when the pressure-sensitive adhesive layer for an optical film is formed from the pressure-sensitive adhesive composition for an optical film of the present invention, it can be heat-treated at a low temperature and in a short time. However, it is preferable from the viewpoint of avoiding the possibility of deterioration or deformation.

The "half-life of peroxide" is an index showing the decomposition rate of peroxide, and means the time until the residual amount of peroxide is halved. The decomposition temperature for obtaining a half-life at a certain time and the half-life time at a certain temperature are described in the manufacturer's catalog, etc. For example, the 9th edition of the organic peroxide catalog published by Nichiyu Co., Ltd. (2003). May of the year).

In the present invention, the peroxide (B) may act as a cross-linking agent, may act as a polymerization initiator, or may have both roles.

Specific examples of the peroxide (B) according to the present invention include diisopropylperoxydicarbonate (1 minute half-life temperature 88.3 ° C.) and di (2-ethylhexyl) peroxydicarbonate (90.6 ° C.). ), Di (4-t-butylcyclohexyl) peroxydicarbonate (92.1 ° C), di-sec-butylperoxydicarbonate (92.4 ° C), t-butylperoxyneodecanoate (92.1 ° C) 103.5 ° C), t-hexyl peroxypivalate, (109.1 ° C), t-butyl peroxypivalate (110.3 ° C), dilauroyl peroxide (116.4 ° C), Examples thereof include bis-n-octanoyl peroxide (117.4 ° C.) and 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (124.3 ° C.). Of these, diisopropyl peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate, and t-butylperoxyneodecanoate are preferably used. These may be used alone, but it is also preferable to use two or more of them in combination from the viewpoint of adjusting the reactivity. As an example of using two or more kinds in combination, a combination of di (4-t-butylcyclohexyl) peroxydicarbonate and dilauroyl peroxide is suitable.

Further, the peroxide (B) may be synthesized or a commercially available product may be used.

As commercial products, for example, trade names manufactured by Nichiyu Co., Ltd .: "Parloyl (registered trademark) IB" (1 minute half-life temperature 85.1 ° C), "Park Mill (registered trademark) ND" (94.0 ° C). ), "Parloyl® NPP" (94.0 ° C.), "Parloyl® IPP" (88.3 ° C.), "Parloyl® SBP" (92.4 ° C.), "Perocta (registered trademark) ND" (92.4 ° C), "Parloyl (registered trademark) TCP" (92.1 ° C), "Parloyl (registered trademark) OPP" (90.6 ° C), "Perhexyl" (Registered Trademark) ND "(100.9 ° C)," Perbutyl (Registered Trademark) ND "(103.5 ° C)," Perbutyl (Registered Trademark) NHP "(104.6 ° C)," Perhexyl (Registered) "PV" (109.1 ° C), "Perbutyl (registered trademark) PV" (110.3 ° C), "Parloyl (registered trademark) 355" (112.6 ° C), "Parloyl (registered trademark)" Examples include "L" (116.4 ° C.), "Perocta (registered trademark) O" (124.3 ° C.), and "Perhexa (registered trademark) 25O" (118.8 ° C.).

In the present invention, the content of the peroxide (B) is not particularly limited, but is preferably 0.02 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the copolymer (A). When the content of the peroxide (B) is 0.02 parts by mass or more, the effect of the peroxide can be expected. On the other hand, when it is 10 parts by mass or less, the crosslink density does not increase too much and the durability is not deteriorated, and it is possible to avoid deteriorating the stability of the pressure-sensitive adhesive liquid.

Further, from the viewpoint of further satisfying the heating durability at high temperature, the content of the peroxide (B) is 0.05 parts by mass or more and 9 parts by mass with respect to 100 parts by mass of the copolymer (A). It is more preferably 0.1 parts by mass or more, and particularly preferably 5 parts by mass or less.

<Crosslinking agent (C) other than peroxide>
The pressure-sensitive adhesive composition for an optical film of the present invention contains a cross-linking agent (C) other than a peroxide as an essential component. Since the cross-linking agent (C) other than the peroxide reacts with the copolymer (A) to form a cross-linked structure, it is mainly used for adhesiveness (adhesiveness) and durability in the pressure-sensitive adhesive composition for optical films. Can contribute. Further, the reason why "other than peroxide" is defined here is to distinguish it from the above-mentioned "peroxide (B)".

In the present invention, the cross-linking agent (C) other than the peroxide does not contain a blocked isocyanate compound. The "blocked isocyanate compound" is an isocyanate compound in which an isocyanate group is protected by using a blocking agent (also referred to as a "protecting group").

Conventionally, a blocked isocyanate compound is generally used as a curing agent for paints and the like, but heat treatment at a high temperature for a long time is required. On the other hand, for example, Japanese Patent Application Laid-Open No. 2011-132297 discloses an invention capable of curing a pressure-sensitive adhesive at a low temperature and / or in a short time by using a peroxide and a blocked isocyanate compound in combination. ing.

However, according to the research by the present inventors, it has been found that the durability of the obtained pressure-sensitive adhesive composition may be lowered when the peroxide and the blocked isocyanate compound are used in combination. Therefore, according to the research by the present inventors, the cross-linking agent (C) containing no blocked isocyanate compound is used in combination with the above-mentioned specific peroxide (B), and the present invention is described in JP-A-2011-132297. It has been found that the pressure-sensitive adhesive can be cured at a lower temperature and in a shorter time than the above-mentioned technique, and the durability of the obtained pressure-sensitive adhesive composition can be improved, which has led to the completion of the present invention.

In the present invention, the cross-linking agent (C) other than the peroxide is at least one selected from the group consisting of an isocyanate-based cross-linking agent, a carbodiimide-based cross-linking agent, an oxazoline-based cross-linking agent, an epoxy-based cross-linking agent, and an aziridine-based cross-linking agent. It is preferable to include it. Hereinafter, various cross-linking agents will be described.

[Isocyanate-based cross-linking agent]
In the present invention, an isocyanate-based cross-linking agent is preferably used as the cross-linking agent (C) other than the peroxide. In this case, as described above, it is used as an isocyanate-based cross-linking agent in the form of an unblocked isocyanate compound.

As the isocyanate-based cross-linking agent preferably used in the present invention, triallyl isocyanurate, diimmerate diisocyanate, 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6). -TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylenediocyanate, xylylene diisocyanate (XDI), Aromatic diisocyanates such as tetramethylxylidene diisocyanate (TMXDI), trizine diisocyanate (TODI), 1,5-naphthalenediisocyanate (NDI); hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, norbornan. Alibo diisocyanates such as diisocyanatomethyl (NBDI); alicyclic such as transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), H6-XDI (hydrogenated XDI), H12-MDI (hydrogenated MDI) Formula diisocyanates; carbodiimide-modified diisocyanates of the above-mentioned diisocyanates; or these isocyanurate-modified diisocyanates and the like can be mentioned. Adducts of the isocyanate compound and a polyol compound such as trimethylolpropane, and biuret or isocyanurate of these isocyanate compounds can also be preferably used.

Further, as these isocyanate-based cross-linking agents, synthetic ones may be used, or commercially available products may be used.

Examples of commercially available products include Coronate (registered trademark) L, Coronate (registered trademark) HL, Coronate (registered trademark) HX, Coronate (registered trademark) 2030, Coronate (registered trademark) 2031 (all manufactured by Toso Co., Ltd.). Takenate (registered trademark) D-102, Takenate (registered trademark) D-110N, Takenate (registered trademark) D-131N, Takenate (registered trademark) D-200, Takenate (registered trademark) D-202 (above, Mitsui Chemicals, Inc.) Duranate (registered trademark) 24A-100, Duranate (registered trademark) TPA-100, Duranate (registered trademark) TKA-100, Duranate (registered trademark) P301-75E, Duranate (registered trademark) E402-90T, Duranate (Registered Trademark) E405-80T, Duranate (Registered Trademark) TSE-100, Duranate (Registered Trademark) D-101, Duranate (Registered Trademark) D-201 (all manufactured by Asahi Kasei Chemicals Co., Ltd.), Sumijuru (Registered Trademark) N-75, N-3200, N-3300 (above, Sumika Bayer Urethane Co., Ltd.) and the like can be mentioned. Among these, Coronate (registered trademark) L, Coronate (registered trademark) HL, Coronate (registered trademark) HX, Takenate (registered trademark) D-110N, Duranate (registered trademark) 24A-100, Duranate (registered trademark) TPA -100 is mentioned. Of these, Takenate (registered trademark) D-110N, Takenate (registered trademark) D-131N, Coronate (registered trademark) L, Coronate (registered trademark) HX, and Duranate (registered trademark) 24A-100 are preferable.

[Carbodiimide-based cross-linking agent]
In the present invention, the carbodiimide-based cross-linking agent is not particularly limited, but for example, a high molecular weight polycarbodiimide produced by decarboxylating a diisocyanate in the presence of a carbodiimidization catalyst is used.

Examples of the diisocyanate used in the decarbonation condensation reaction include 4,4'-diphenylmethane diisocyanate, 3,3'-dimethoxy-4,4'-diphenylmethane diisocyanate, and 3,3'-dimethyl-4,4'-. Diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 3,3'-dimethyl-4,4'-diphenyl ether diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1-methoxyphenyl-2,4 -Diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate and the like can be mentioned.

Examples of the carbodiimidization catalyst used in the decarboxylation condensation reaction include 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, and 1-ethyl-3-methyl-. Examples thereof include 2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide, and phosphorene oxides such as these 3-phosphoren isomers.

As the high molecular weight polycarbodiimide, a synthesized one may be used, or a commercially available product may be used.

Examples of commercially available products include the Carbodilite (registered trademark) series manufactured by Nisshinbo Chemical Co., Ltd. Among them, Carbodilite (registered trademark) V-01, V-03, V-05, V-07, and V-09 are preferable because they have excellent compatibility with organic solvents.

[Oxazoline-based cross-linking agent]
In the present invention, the oxazoline-based cross-linking agent is not particularly limited, but may include an oxazoline group-containing acrylic / styrene polymer having a main chain consisting of an acrylic skeleton or a styrene skeleton and having an oxazoline group in the side chain of the main chain. , An oxazoline group-containing polymer such as an oxazoline group-containing acrylic polymer having a main chain composed of an acrylic skeleton and having an oxazoline group in the side chain of the main chain is preferably used.

Examples of the oxazoline group include a 2-oxazoline group, a 3-oxazoline group, a 4-oxazoline group and the like, and a 2-oxazoline group is preferable.

Further, the oxazoline group-containing polymer may have a polyoxyalkylene group in addition to the oxazoline group.

Specific examples of the oxazoline group-containing polymer include oxazoline groups such as Epocross (registered trademark) WS-300, Epocross (registered trademark) WS-500, and Epocross (registered trademark) WS-700 manufactured by Nippon Catalyst Co., Ltd. Examples of acrylic polymers include oxazoline group-containing acrylic / styrene polymers such as Epocross (registered trademark) K-1000 series and Epocross (registered trademark) K-2000 series manufactured by Nippon Catalyst Co., Ltd.

[Epoxy cross-linking agent]
In the present invention, the epoxy-based cross-linking agent is not particularly limited, and a known epoxy-based cross-linking agent can be appropriately adopted. As a commercial product, for example, "TETR" manufactured by Mitsubishi Gas Chemical Company, Inc.
Examples include "AD-C", "TETRAD-X", "ADEKA RESIN EPU series" and "ADEKA RESIN EPR series" manufactured by ADEKA Corporation, and "Selokiside" manufactured by Daicel Corporation. In particular, liquid epoxy resins such as these are preferable because they facilitate a mixing operation when producing a pressure-sensitive adhesive composition for an optical film.

[Aziridine-based cross-linking agent]
In the present invention, the aziridine-based cross-linking agent is not particularly limited, but a polyfunctional aziridine compound having a plurality of aziridine rings can be preferably used. Examples of the polyfunctional aziridine compound include US Pat. No. 3,225,013, US Pat. No. 4,490,505, US Pat. No. 5,534,391, and JP-A-2003. Examples thereof include the compounds disclosed in the specification of No. 104970.

Examples of commercially available aziridine-based cross-linking agents include Chemitite (registered trademark) PZ-33 and Chemitite (registered trademark) DZ-22E manufactured by Nippon Shokubai Co., Ltd.

In the present invention, the cross-linking agent (C) other than the peroxide is at least one selected from the group consisting of an isocyanate-based cross-linking agent, a carbodiimide-based cross-linking agent, an oxazoline-based cross-linking agent, an epoxy-based cross-linking agent, and an azilysin-based cross-linking agent. As long as the seeds are included, only one kind may be used alone, or two or more kinds may be used in combination. When two or more kinds of cross-linking agents are used in combination, two or more kinds of cross-linking agents of the same system (for example, two kinds of isocyanate-based cross-linking agents) may be combined, or one or more kinds of cross-linking agents of different systems (for example, isocyanate-based) are used in combination. One type of cross-linking agent and one type of carbodiimide-based cross-linking agent may be combined).

The content of the cross-linking agent (C) other than the peroxide in the pressure-sensitive adhesive composition for an optical film according to the present invention is not particularly limited, but is 0.001 mass by mass with respect to 100 parts by mass of the copolymer (A). It is preferably 2 parts or more and 2 parts by mass or less. When the content of the cross-linking agent (C) other than the peroxide is 0.001 part by mass or more, the cross-linking effect can be sufficiently obtained, the durability can be ensured, and the adhesive chipping property is also good. On the other hand, when the content is 2% by mass or less, the pressure-sensitive adhesive layer does not become too hard, and durability can be ensured. In addition, in this specification, "glue chipping property" means an edge of an optical member (for example, a polarizing plate) having an adhesive layer using the adhesive composition of the present invention. The property that the adhesive layer is chipped from the portion (cut surface). The degree of "glue chipping property" is evaluated according to the criteria described in the examples.

Further, from the viewpoint of further ensuring durability by exhibiting the cross-linking effect, the content of the cross-linking agent (C) other than the peroxide is 0.01 part by mass with respect to 100 parts by mass of the copolymer (A). It is more preferably 1.5 parts by mass or less, and particularly preferably 0.05 parts by mass or more and 1.0 part by mass or less.

<Silane coupling agent (D)>
The pressure-sensitive adhesive composition for an optical film of the present invention preferably further contains a silane coupling agent (D). The silane coupling agent (D) can contribute mainly to the improvement of durability and the improvement of adhesion to glass when the adherend is glass in the pressure-sensitive adhesive composition for an optical film. In addition, in this specification, a "silane coupling agent" means a compound which does not have a siloxane bond (Si—O—Si bond) and has two or more reactive groups in the molecule.

In the present invention, the silane coupling agent (D) is not particularly limited, but specifically, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, methyltrimethoxysilane, and dimethyldimethoxy. Silane, trimethylmethoxysilane, n-propyltrimethoxysilane, ethyltrimethoxysilane, diethyldiethoxysilane, n-butyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltrimethoxysilane, phenyltrimethoxysilane, diphenyl Dimethoxysilane, cyclohexylmethyldimethoxysilane, vinyltricrolsilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, β- (3,4-epylcyclohexyl) ethyltrimethoxysilane, 3-glycid Xipropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyl Methyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropylmethyldimethoxysilane, N-β- (aminoethyl) -γ -Aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxy Silane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, bis- (3- [triethoxysilyl] propyl) tetrasulfide, γ-isoxapropyltriethoxysilane, etc. Can be mentioned. Further, a silane coupling agent having a functional group such as an epoxy group (glycidoxy group), an amino group, a mercapto group, and a (meth) acryloyl group, and a silane cup containing a functional group reactive with these functional groups. A compound having a hydrolyzable silyl group obtained by reacting a ring agent, another coupling agent, polyisocyanate or the like at an arbitrary ratio with respect to each functional group can also be used.

The silane coupling agent (D) may be synthesized or a commercially available product may be used. Commercially available products of the silane coupling agent include, for example, KBM-303, KBM-403, KBE-402, KBE-403, KBE-502, KBE-503, KBM-5103, KBM-573, KBM-802, KBM-. 803, KBE-846, KBE-9007 (all manufactured by Shin-Etsu Chemical Co., Ltd.) and the like can be mentioned.

As the silane coupling agent (D), only one type may be used alone, or two or more types may be used in combination.

When the pressure-sensitive adhesive composition for an optical film of the present invention contains the silane coupling agent (D), the content of the silane coupling agent (D) is not particularly limited, but is 100 parts by mass of the copolymer (A). On the other hand, it is preferably 0.001 part by mass or more and 10 parts by mass or less, more preferably 0.005 part by mass or more and 5 parts by mass or less, and further preferably 0.01 part by mass or more and 3 parts by mass or less. Particularly preferably, it is 0.01 part by mass or more and 1 part by mass or less. When the content is 0.001 part by mass or more, it is preferable from the viewpoint that the effect on durability is exhibited. On the other hand, when the content is 10 parts by mass or less, it is preferable from the viewpoint that the deterioration of heat foaming derived from the low molecular weight compound is eliminated.

<Sylicate oligomer (E)>
The pressure-sensitive adhesive composition for an optical film of the present invention preferably further contains a silicate oligomer (E). The silicate oligomer (E) can mainly contribute to the improvement of reworkability in the pressure-sensitive adhesive composition for an optical film.

The silicate oligomer (E) according to the present invention preferably has a structure represented by the following chemical formula 1.

In the above chemical formula 1, R ¹ and R ² are independent hydrogen atoms, an alkyl group having 1 or more and 6 or less carbon atoms, or a phenyl group; and X ¹ and X ² are independent hydrogen atoms, respectively. , An alkyl group having 1 or more and 20 or less carbon atoms, or a phenyl group; n is an integer of 1 or more and 100 or less. n is preferably an integer of 2 or more and 100 or less. Such alkyl and phenyl groups may or may not be substituted. Further, the alkyl group may have a linear structure or a branched chain structure.

In the present invention, from the viewpoint of easily achieving both durability and reworkability, among the compounds represented by Chemical Formula 1, a methyl silicate oligomer in which all of R ¹ and R ² and X ¹ and X ² are methyl groups. It is preferable to have. As the silicate oligomer (E), only one of the compounds shown above may be used alone, or two or more thereof may be used in combination.

In the present invention, the weight average molecular weight of the silicate oligomer (E) is not particularly limited, but is preferably 300 or more and 30,000 or less, more preferably 500 or more and 25,000 or less, still more preferably 600 or more and 5,000 or less, and particularly. It is preferably 600 or more and 5000 or less. When the weight average molecular weight is 300 or more, it is preferable from the viewpoint that reworkability can be easily ensured. On the other hand, when it is 30,000 or less, it is preferable from the viewpoint that durability can be easily ensured.

When the pressure-sensitive adhesive composition for an optical film of the present invention contains the silicate oligomer (E), the content of the silicate oligomer (E) is not particularly limited, but is preferable with respect to 100 parts by mass of the copolymer (A). Is 0.01 parts by mass or more and 50 parts by mass or less, more preferably 0.3 parts by mass or more and 10 parts by mass or less, and further preferably 0.5 parts by mass or more and 5 parts by mass or less. When the content is 0.01 part by mass or more, the effect on durability is exhibited, which is preferable. On the other hand, when the content is 50 parts by mass or less, reworkability and durability are easily compatible with each other, which is preferable.

<Solvent>
The pressure-sensitive adhesive composition for an optical film of the present invention may contain a solvent, if necessary. The solvent is not particularly limited, but esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; cyclohexane and methyl. Alicyclic hydrocarbons such as cyclohexane; organic solvents such as ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone can be mentioned. Only one kind of these solvents may be used alone, or two or more kinds thereof may be used in combination.

The solid content in the pressure-sensitive adhesive composition for optical film is not particularly limited, but is preferably 10% by mass or more and 50% by mass with respect to 100% by mass of the total amount of the pressure-sensitive adhesive composition for optical film from the viewpoint of coatability and productivity. It is 1% by mass or less, more preferably 12% by mass or more and 30% by mass or less.

<Other additive ingredients>
The pressure-sensitive adhesive composition for an optical film of the present invention can be used as a cross-linking accelerator, an antistatic agent, a filler, a colorant (pigment, dye, etc.), an ultraviolet absorber, an antioxidant, a chain transfer agent, and a plasticizer, if necessary. Known additive components (other additive components) such as agents, softeners, surfactants, and antistatic agents may be contained within a range that does not impair the effects of the present invention.

<Manufacturing (preparation) method of adhesive composition>
In the present invention, the pressure-sensitive adhesive composition for an optical film is not particularly limited, and is optionally contained, for example, a copolymer (A), a peroxide (B), and a cross-linking agent (C) other than the peroxide. It can be prepared by mixing a possible silane coupling agent (D), silicate oligomer (E), solvent, and other additives. The mixing order and mixing temperature of each of the above components are not particularly limited and may be appropriately adjusted by those skilled in the art.

{Use}
The above-mentioned pressure-sensitive adhesive composition for an optical film of the present invention is suitable for various uses. For example, it is preferably used for an optical member such as an optical film. In particular, in recent years, it is preferably used for a thin adhesive optical film used for a large liquid crystal panel. Examples of such an optical film include a polarizing plate, a retardation plate for preventing coloration, an optical compensation film such as a viewing angle expanding film for improving the viewing angle of a liquid crystal display, and a brightness improving film for increasing the contrast of the display. Further, there is a case where these are laminated.

In the present invention, the form of the pressure-sensitive adhesive layer formed from the above-mentioned pressure-sensitive adhesive composition for an optical film, the form of an optical member formed by forming the pressure-sensitive adhesive layer on an optical film or the like, and the optical film being a polarizing plate. A form or a form in which the optical member is applied to an image display device such as a liquid crystal display device, an organic EL display device, a plasma display (PDP), a curved display or a flexible display can also be provided. Each will be described below.

<Adhesive layer>
According to one embodiment of the present invention, there is provided an optical film pressure-sensitive adhesive layer formed from the above-mentioned optical film pressure-sensitive adhesive composition of the present invention.

The thickness (thickness after drying) of the pressure-sensitive adhesive layer of the present invention can be appropriately set by those skilled in the art depending on the intended use, but is preferably 1 μm or more and 200 μm or less, and more preferably 3 μm or more and 75 μm or less. It is more preferably 5 μm or more and 40 μm or less, particularly preferably 7 μm or more and 35 μm or less, and most preferably 10 μm or more and 30 μm or less. When the thickness is within the above range, it is preferable from the viewpoint that durability and adhesive properties can be well balanced.

The gel fraction immediately after drying of the pressure-sensitive adhesive layer of the present invention is not particularly limited, but is preferably 95% or less from the viewpoint of punching and slitting. Further, it is preferably 40% or more, and more preferably 65% or more, from the viewpoint that there is no concern about dents on the pressure-sensitive adhesive layer immediately after drying and durability, and aging treatment is not required. The gel fraction can be controlled by adjusting the amount of cross-linking agent and the amount of peroxide. As the gel fraction immediately after drying of the pressure-sensitive adhesive layer, the value measured by the method described in the examples is adopted.

[Manufacturing method of adhesive layer]
According to another embodiment of the present invention, the above-mentioned pressure-sensitive adhesive composition for an optical film of the present invention is applied onto a release-treated release sheet, and then heat-treated to cause a cross-linking reaction. A method for producing the agent layer is also provided.

When the pressure-sensitive adhesive composition is used for an optical film, the pressure-sensitive adhesive composition may be applied directly onto the optical film to form a pressure-sensitive adhesive layer, but the pressure-sensitive adhesive composition may be formed on a film having releasability. It is desirable to apply an object to form an adhesive layer and then transfer it to various optical films for use. In addition, the releasable film with an adhesive layer produced in this way can also be wound together in the manufacturing process into a roll shape, and variously cut and processed as necessary. When the film is attached to an optical film, a liquid crystal panel, or the like, the film having the releasability can be removed and used. Further, the releasable film can also serve to protect the pressure-sensitive adhesive layer until the pressure-sensitive adhesive layer is put into practical use. In the present specification, a film having such releasability is also referred to as a releasable sheet (separator).

Examples of the constituent materials of the release sheet include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester film, porous materials such as paper, cloth, and non-woven fabric, nets, foam sheets, metal foils, and laminates thereof. However, a plastic film is preferably used because of its excellent surface smoothness.

The thickness of the release sheet is usually 5 μm or more and 200 μm or less, preferably 5 μm or more and 100 μm or less.

For the release sheet, if necessary, a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based mold release agent, a mold release treatment and an antifouling treatment with silica powder, etc., a coating type, a kneading type, and a vapor deposition. Further antistatic treatment such as mold can be performed. In particular, from the viewpoint of further enhancing the peelability from the pressure-sensitive adhesive layer, it is preferable to perform a peeling treatment such as a silicone treatment, a long-chain alkyl treatment, or a fluorine treatment on the surface of the release sheet.

The coating method for applying the pressure-sensitive adhesive composition for an optical film of the present invention onto a release-treated release sheet is not particularly limited, and various known methods are used. For example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, extrusion coat method by die coater, etc. The method can be mentioned.

In the method for producing an adhesive layer of the present invention, a step of applying the above-mentioned adhesive composition for an optical film on a release sheet and then heat-treating it is performed. The heat treatment step not only dries and removes the solvent in the coating film obtained by coating, but also fulfills the purpose of cross-linking the above-mentioned pressure-sensitive adhesive composition for an optical film. The temperature of the heat treatment is not particularly limited, but is preferably 40 ° C. or higher and 150 ° C. or lower, more preferably 50 ° C. or higher and 130 ° C. or lower, from the viewpoint that a pressure-sensitive adhesive layer having excellent adhesive properties can be obtained. Yes, more preferably 80 ° C. or higher and 120 ° C. or lower, and particularly preferably 110 ° C. or higher and 120 ° C. or lower.

The time of the heat treatment can be appropriately set, but is preferably 5 seconds or more and 20 minutes or less, more preferably 5 seconds or more and 10 minutes or less, and further preferably 10 seconds or more and 5 minutes or less, particularly. It is preferably 10 seconds or more and 2 minutes or less.

The heat treatment means is not particularly limited, and various known methods are used. For example, a parallel drying method that blows hot air in the same direction up and down in the film transport direction, a counter drying method that blows hot air in different directions up and down in the film transport direction, and a float drying method that blows hot air directly from the top and bottom of the film. The method can be mentioned.

{Optical member}
According to one embodiment of the present invention, there is provided an optical member having the above-mentioned pressure-sensitive adhesive layer for an optical film and a first optical film provided on one surface of the pressure-sensitive adhesive layer.

Further, the optical member of the present invention may further have glass or a second optical film on the surface of the pressure-sensitive adhesive layer of the present invention opposite to the surface on which the first optical film is provided. Here, the "first optical film" and the "second optical film" may be films having the same configuration (material, function, etc.), and may have different configurations (material, function, etc.). It may be a film to have. Further, in the present invention, a form in which the first optical film (or the second optical film) is a polarizing plate is also provided.

In the present invention, the above-mentioned pressure-sensitive adhesive composition may be used by directly applying it to one or both sides of an optical film to form a pressure-sensitive adhesive layer, but for the above-mentioned reason, the pressure-sensitive adhesive layer may be previously applied to a separator or the like. It is desirable to form and use it by transferring it to one or both sides of the optical film. Further, before the transfer, the surface of the optical film may be subjected to a base treatment such as formation of an easy-adhesion treatment layer or an antistatic layer depending on the material thereof. Further, the easy-adhesion treatment may be performed on the surface of the pressure-sensitive adhesive layer. From the viewpoint of firmly adhering the optical film and the pressure-sensitive adhesive layer, it is preferable to have an easy-adhesion-treated layer between the optical film and the pressure-sensitive adhesive layer for the optical film of the present invention.

<Easy-adhesive treatment layer (easy-adhesive layer)>
The optical member of the present invention preferably further has at least one easy-adhesion-treated layer between the first optical film and the pressure-sensitive adhesive layer for the optical film.

Further, as a more preferable form, the optical member of the present invention has the first easy-adhesion-treated layer on the surface of the first optical film on the side facing the pressure-sensitive adhesive layer for the optical film, and the optical film. A second easy-adhesion-treated layer is provided on the surface of the pressure-sensitive adhesive layer on the side facing the first optical film. As described above, in the optical member, the configuration having both the first and second easy-adhesion-treated layers is preferable from the viewpoint that the optical film and the pressure-sensitive adhesive layer can be more firmly bonded.

The easy-adhesion-treated layer may be a member that treats the surface of a member that comes into contact with the pressure-sensitive adhesive layer, such as corona treatment or plasma treatment, or a member that contacts a separate member such as a primer layer with the pressure-sensitive adhesive layer. It may be provided on the surface of.

The material constituting the primer layer is preferably a material that has good adhesion to a member that comes into contact with the primer layer and forms a film having excellent cohesive force. For example, various polymers, metal oxide sol, silica sol and the like are used, and among them, polymers are preferably used. The primer layer may have an antistatic function.

Examples of the polymers constituting the primer layer include oxazoline group-containing polymers, polyurethane resins, polyester resins, and polymers containing an amino group in the molecule. Of these, polyurethane resins and oxazoline group-containing polymers are more preferably used.

Commercially available products can be used as the oxazoline group-containing polymer. For example, Epocross (registered trademark) series manufactured by Nippon Shokubai Co., Ltd. (for example, Epocross (registered trademark) WS700) and the like can be mentioned, but the present invention is not limited thereto. Further, as the polyurethane resin, the polyester resin, the polymers containing an amino group in the molecule, and the like, those disclosed in paragraphs "0107" to "0113" of JP-A-2011-105918 can be appropriately adopted.

The thickness of the primer layer is about 10 nm or more and 5000 nm or less, preferably 50 nm or more and 500 nm or less. Within the above range, the optical characteristics can be maintained while exhibiting sufficient strength and adhesion.

The method for forming the primer layer is not particularly limited, and the primer layer can be formed by applying the raw material (primer) of the primer layer by a coating method such as a coating method, a dipping method, or a spray method and drying the primer layer. ..

<Optical film>
In the present invention, the optical film (first optical film or second optical film) includes optics such as a polarizing plate, a retardation plate for preventing coloration, and a viewing angle expanding film for improving the viewing angle of a liquid crystal display. Examples thereof include, but are not limited to, a compensation film, a brightness improving film for enhancing the contrast of the display, and a film in which these are laminated.

<Polarizer>
In the present invention, a polarizing plate suitable as an optical film is produced by bonding a protective film and a polarizing element to each other using a conventionally known method, and heat-drying or curing with ultraviolet rays, electron beams, or the like. obtain. The applied adhesive exhibits adhesiveness by drying or curing with ultraviolet rays, electron beams, or the like to form an adhesive layer.

The polarizing element is not particularly limited, and conventionally known ones can be used. For example, a dichroic material such as iodine or a bicolor dye is adsorbed on a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, or an ethylene / vinyl acetate copolymer partially saponified film. Examples thereof include uniaxially stretched films, polyvinyl alcohol dehydrated products, polyvinyl chloride dehydrogenated products, and other polyene-based oriented films.

Of these, a substituent produced by dyeing a polyvinyl alcohol film having an average degree of polymerization of 2000 or more and 2800 or less and a saponification degree of 90 mol% or more and 100 mol% or less with iodine and uniaxially stretching the film to 3 times or more and 8 times or less is particularly preferable. .. More specifically, such a polarizing element can be obtained by immersing, for example, a polyvinyl alcohol film in an aqueous solution of iodine, dyeing the film, and stretching the film.

As a method of immersing in an aqueous solution of iodine, for example, a method of immersing in an aqueous solution containing 0.1% by mass or more and 10% by mass or less of iodine and / or potassium iodide is preferable. Further, if necessary, it may be immersed in an aqueous solution of boric acid or potassium iodide at 50 ° C. or higher and 70 ° C. or lower, or immersed in water at 25 ° C. or higher and 35 ° C. or lower to prevent washing and uneven dyeing. May be good. Stretching may be performed after staining with iodine, stretching while staining, or stretching and then staining with iodine. After dyeing and stretching, it may be washed with water and dried at 35 ° C. or higher and 55 ° C. or lower for 1 minute or longer and 10 minutes or shorter. A wide variety of such modulators are commercially available.

The thickness of the polarizing element is not particularly limited, but is generally 3 μm or more and 80 μm or less.

In the present invention, a polarizing plate having one or both sides protected is preferable as the optical film from the viewpoint that higher durability is required as the optical film. The method of protection is not particularly limited, and a known method such as laminating a protective film can be appropriately adopted.

As the protective film, a material having excellent transparency, mechanical strength, thermal stability, moisture barrier property, isotropic property and the like is preferable. For example, acrylic resin, cellulose resin such as triacetyl cellulose, polyester resin such as polyethylene terephthalate and polyethylene naphthalate, polyether sulfone resin, polysulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin. Examples thereof include based resins, (meth) acrylic resins such as polymethylmethacrylate, cyclic polyolefin-based resins (norbornen-based resins), polyarylate-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, epoxy-based resins, and mixtures thereof.

A transparent protective film is attached to one side of the polarizing element with an adhesive, but the other side is a transparent protective film or a (meth) acrylic, urethane, acrylic urethane, or epoxy type as a protective layer. , A thermosetting resin such as silicone or an ultraviolet curable resin can be used.

The thickness of the polarizing plate is not particularly limited, but is generally 20 μm or more and 200 μm or less. Further, in the present invention, from the viewpoint of thinning, it is preferably 100 μm or less, more preferably 75 μm or less, and particularly preferably 50 μm or less. Such a thin polarizing plate is preferable from the viewpoint of more remarkably exhibiting the effect of the pressure-sensitive adhesive composition of the present invention.

The method for manufacturing the polarizing plate is not particularly limited, and for example, after applying the adhesive, the polarizing element and the protective film can be bonded to each other with a roll laminator or the like. After the bonding, it may be dried or cured with ultraviolet rays, an electron beam or the like as appropriate. Further, when the adhesive is applied, it may be applied to either the protective film or the polarizing element, or may be applied to both of them. The adhesive is preferably applied so that the thickness of the adhesive layer after drying is 10 nm or more and 10 μm or less. Further, the adhesive is not particularly limited and may be appropriately adopted from known adhesives according to the material of the polarizing element. For example, when a polyvinyl alcohol-based film is used as the polarizing element, an acrylic-based, epoxy-based, or acrylic-epoxy-based adhesive can be used as the polyvinyl alcohol-based adhesive or the ultraviolet curable adhesive. The thickness of the adhesive layer is preferably 10 nm or more and 200 nm or less for the polyvinyl alcohol-based adhesive and 0 for the ultraviolet curable adhesive because a uniform in-plane thickness can be obtained and sufficient adhesive strength can be obtained. It is preferably 2 μm or more and 10 μm or less.

In the present invention, a pressure-sensitive polarizing plate having a pressure-sensitive adhesive layer formed therein can also be provided. Since the configuration and manufacture of the adhesive polarizing plate are the same as those of the optical film having the adhesive layer described above, the description thereof will be omitted here.

{Image display device}
The present invention also provides an image display device using at least one of the above-mentioned optical members.

The image display device is not particularly limited, and examples thereof include a liquid crystal display device, an organic EL display device, and a plasma display (PDP). Further, from the viewpoint of more remarkably exhibiting the effect of the pressure-sensitive adhesive composition of the present invention, a particularly thin image display device is preferably applied.

The present invention will be described in more detail with reference to the following examples and comparative examples, but the technical scope of the present invention is not limited to the following examples.

Further, in the following operations, unless otherwise specified, the operations and measurements of physical properties are performed under the condition of 23 ° C. and 55% RH relative humidity.

[Production Example 1 (Preparation of (meth) acrylate copolymer (A1)]
N-butyl acrylate (manufactured by Nippon Catalyst Co., Ltd.) 70% by mass, methyl acrylate (manufactured by Nippon Catalyst Co., Ltd.) 18% by mass, in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a cooler. 4-Hydroxybutyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) 1% by mass, benzyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) 11% by mass and 2,2'-azobisisobutyronitrile as a polymerization initiator (manufactured by Osaka Organic Chemical Industry Co., Ltd.) Wako Pure Chemical Industries, Ltd.) 0.1% by mass was charged together with 100% by mass of ethyl acetate, and nitrogen gas was introduced while gently stirring. After substituting with nitrogen gas, the liquid temperature in the flask was controlled to around 55 ° C., and a polymerization reaction was carried out for 5 hours to prepare a solution of a (meth) acrylate copolymer (A1) having a weight average molecular weight (Mw) of 1.9 million. ..

[Preparation of Production Examples 2 to 15 (meth) acrylate copolymers (A2) to (A15)]
The same operation as in Production Example 1 except that the type and composition ratio of each monomer forming the (meth) acrylate copolymer, the amount of the polymerization initiator and the reaction time were changed as shown in Table 1 below. Was carried out to prepare a solution of the (meth) acrylate copolymer (A2) to (A15). The weight average molecular weight (Mw) of each is also shown in Table 1.

The weight average molecular weight (Mw) in each of the above-mentioned production examples was measured according to the following method.

(Measurement of weight average molecular weight (Mw))
The weight average molecular weight of each (meth) acrylate copolymer prepared in each of the above-mentioned production examples was measured by GPC (gel permeation chromatography) under the following measurement conditions.
-Analyzer: HLC-8120GPC manufactured by Tosoh Corporation
-Column: Tosoh, G7000H _XL + GMH _XL + GMH _XL
-Column size: 7.8 mm φ x 30 cm each 90 cm in total
-Column temperature: 40 ° C
・ Flow rate: 0.8 ml / min
・ Injection amount: 100 μl
・ Eluent: Tetrahydrofuran ・ Detector: Differential refractometer (RI)
-Standard sample: Polystyrene.

<Example 1>
[Preparation of Adhesive Composition for Optical Film]
The solid content of the (meth) acrylate copolymer (A11) solution obtained in Production Example 11 is 100% (w / w) (that is, 100 parts by mass of the (meth) acrylate copolymer (A11)). Parloyl (registered trademark) TCP (manufactured by Nichiyu Co., Ltd.) as an oxide (B) 0.3 parts by mass, Takenate (registered trademark) D110-N (trillinated isocyanate tri) as a cross-linking agent (C) other than peroxide A 75 wt% ethyl acetate solution of a polymer propane adduct, the number of isocyanate groups in one molecule: 3, 0.1 parts by mass (in terms of active ingredient), and KBM- as a silane coupling agent (D). 403 (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Industry Co., Ltd.) A solution of the pressure-sensitive adhesive composition for an optical film of Example 1 containing 0.1 parts by mass (solid content 15% (w / /) w)) was prepared.

[Formation of adhesive layer]
The solution of the pressure-sensitive adhesive composition for an optical film obtained above is treated with a silicone-treated polyethylene terephthalate (PET) film having a thickness of 38 μm (manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., MRF38, without an oligomer-preventing layer). The pressure-sensitive adhesive layer after drying was applied to one side so that the thickness of the pressure-sensitive adhesive layer was 20 μm, and heat-treated at 110 ° C. for 2 minutes to form the pressure-sensitive adhesive layer of Example 1. The heat treatment was carried out by a float drying method in which hot air was directly blown from above and below the film.

[Manufacturing of optical members]
(Manufacturing of polarizing plate)
A single-sided protective polarizing plate was produced as an optical film by the following steps.

A 20 μm-thick polyvinyl alcohol film was stretched up to 3 times while being dyed in an iodine solution at 30 ° C. and a concentration of 0.3% by mass for 1 minute between rolls having different speed ratios. Then, it was stretched at 60 ° C. in an aqueous solution containing boric acid having a concentration of 4% by mass and potassium iodide having a concentration of 10% by mass for 0.5 minutes until the total stretching ratio became 6 times. Then, it was washed by immersing it in an aqueous solution containing potassium iodide having a concentration of 1.5% by mass at 30 ° C. for 10 seconds, and then dried at 50 ° C. for 4 minutes to obtain a substituent. A 20 μm-thick acrylic film (lactone-modified acrylic resin film) was bonded to one side of the polarizing element with a polyvinyl alcohol-based adhesive to prepare a single-sided protective thin polarizing plate having a total thickness of 27 μm.

(Preparation of polarizing plate with adhesive layer)
A corona discharge treatment was performed with a corona discharge amount of 80 [W · min / m ² ] on the polarizing element side forming the pressure-sensitive adhesive layer of the polarizing plate obtained above to form an easy-adhesion-treated layer. Next, the PET film (which was subjected to the silicone treatment) on which the pressure-sensitive adhesive layer was formed was transferred so that the easy-adhesion-treated layers were in contact with each other, and the optical member of Example 1, that is, the polarizing plate with the pressure-sensitive adhesive layer was produced. ..

<Examples 2 to 39 and Comparative Examples 1 to 7>
As shown in Table 2 below, the (meth) acrylate copolymer (A), the peroxide (B), and the cross-linking agent (C) other than the peroxide constituting the pressure-sensitive adhesive composition for an optical film, and necessary. Examples except that the types and addition amounts (blending amounts) of the silane coupling agent (D) and the silicate oligomer (E), and the temperature and time of the heat treatment for forming the pressure-sensitive adhesive layer were changed according to the above. In the same manner as in the operation of No. 1, a polarizing plate with an adhesive layer corresponding to each Example and Comparative Example was produced.

{evaluation}
The following evaluations were performed on the polarizing plates (optical members) with each pressure-sensitive adhesive layer produced in the above Examples and Comparative Examples. The results of each evaluation are shown in Table 3 below.

<Durability>
The optical members produced in the above Examples and Comparative Examples were cut into 37-inch sizes and used as samples, and attached to 0.7 mm-thick non-alkali glass (Eagle XG, manufactured by Corning Inc.) using a laminator. Then, it was autoclaved at 50 ° C. and 0.5 MPa for 15 minutes to completely adhere the sample to the non-acrylic glass. The treated samples were subjected to the durability tests (1) to (3) below, and the appearance between the polarizing plate and the glass was visually evaluated according to the following criteria after each test.

(1) Treatment at 105 ° C. for 500 hours (heating test)
(2) Treatment was performed for 500 hours in an atmosphere of 60 ° C./95% relative humidity RH (humidification test).
(3) After leaving it in an environment of 85 ° C for 30 minutes, leaving it in an environment of -40 ° C for 30 minutes was regarded as one cycle, and a total of 300 cycles (300 hours) were processed in one cycle of 1 hour (heat shock (heat shock (heat shock)). HS) Test).

Visual evaluation ◎: No change in appearance such as foaming, peeling, and no floating.
◯: There is slight peeling or foaming at the edges, but there is no problem in practical use.
Δ: There is peeling or foaming at the end, but there is no problem in practical use unless it is for special purposes.
×: There is a remarkable peeling at the end, and there is a problem in practical use.

<Reworkability>
The optical members produced in the above Examples and Comparative Examples were cut into a width of 25 mm and a length of 100 mm as Sample 1, and a piece cut into a length of 420 mm and a width of 320 mm as Sample 2 (3 sheets were prepared). The samples 1 and 2 were attached to a 0.7 mm-thick non-alkali glass plate (Eagle XG manufactured by Corning Inc.) using a laminator, and then autoclaved at 50 ° C. and 5 atm for 15 minutes to complete the process. It was brought into close contact (initial). Then, it was heat-treated for 48 hours under the drying condition of 50 degreeC (after heating).

The adhesive strength of the sample 1 was measured. Adhesive strength is JIS Z0237 (Peeling angle 180 °, peeling speed 300 mm / min) under the conditions of a tensile tester (Tencilon universal material tester STA-1150 manufactured by Orientech) at 23 ° C and 50% relative humidity RH. It was determined by measuring the adhesive force (N / 25 mm) when the sample 1 was peeled off according to the method of the adhesive tape and the adhesive sheet test of 2009).

Further, with respect to the above sample 2 (3 sheets), the sample was peeled off from the non-alkali glass plate by human hands, and the reworkability was evaluated according to the following criteria (actual reworkability).

Evaluation ◎: All three sheets can be peeled off well without adhesive residue or film breakage.
◯: The film was broken in a part of the three sheets, but it was peeled off by peeling again.
Δ: All three films were broken, but could be peeled off by peeling again.
X: All three sheets had adhesive residue, or the film was broken and could not be peeled off no matter how many times it was peeled off.

As described above, the reworkability of the samples of each Example and the comparative example was judged by comprehensively combining the results of the adhesive strength and the actual reworkability.

<Light leakage>
The optical members produced in the above Examples and Comparative Examples were cut out into samples having a size of 420 mm in length × 320 mm in width so that the upper and lower polarizing plates were orthogonal to each other. This sample was attached to both sides of a 0.7 mm-thick non-alkali glass plate (Eagle XG manufactured by Corning Inc.) with a laminator so as to form a cross Nicol. Then, it was autoclaved at 50 ° C. and 5 atm for 15 minutes to prepare a secondary sample (initial). Then, the secondary sample was treated under the condition of 105 ° C. for 48 hours (after heating). The heated secondary sample was placed on a 10,000 candela backlight and light leakage was visually evaluated according to the following criteria.

Visual evaluation ◎: There is no corner unevenness and there is no problem in practical use.
◯: There is a slight corner unevenness, but it does not appear in the display area, so there is no problem in practical use.
Δ: Corner unevenness occurs and appears slightly in the display area, but there is no problem in practical use.
X: Corner unevenness occurs and appears tightly in the display area, which is a problem in practical use.

<Gel fraction>
Based on the heat treatment temperature and time (see Table 2) described in each of the above-mentioned Examples and Comparative Examples, the separately formed pressure-sensitive adhesive layer was sandwiched between the release-treated polyethylene terephthalate (PET) films from both sides. A sample having the same composition was prepared and used as a sample for measuring the gel fraction.

Each sample was weighed immediately after the heat treatment to give an initial weight of W1. Each sample was then immersed in an ethyl acetate solution and left in an environment of 23 ° C. 55% RH for 1 week. Then, the insoluble matter was taken out, ethyl acetate was removed, and the sample was weighed after being dried, and the weight (W2) was measured. Then, the gel fraction of each sample was obtained by the following formula 1.

<Agingless>
When the gel fraction of the adhesive layer immediately after drying is equal to or higher than a certain value, there is no concern about dents and durability, and there is no need for aging treatment (referred to as "aging-less").

Therefore, based on the gel fraction of each sample measured by the above-mentioned method, the judgment was made according to the following criteria, and the necessity of aging treatment of each sample was evaluated.
◯: Gel fraction 65% or more There is no effect on dents, workability, and durability; no aging treatment is required. Δ: Gel fraction 40% or more and less than 65% No effect on dents; no aging treatment required.
×: Gel fraction less than 40% There is a concern about dents, deterioration of workability, and deterioration of durability; aging treatment is required.

<Oligomer contamination>
Polyethylene terephthalate (PET) film without oligomer-preventing layer (thickness 38 μm, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., MRF38) in which a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive compositions formed in the above-mentioned Examples and Comparative Examples is laminated. ) Was applied to the coating line for 2 hours under the heat treatment temperature of each Example and Comparative Example shown in Table 2 above. Whether or not PET oligomers were deposited on the guide rolls on the line when heat-treated while transporting each film sample was visually confirmed according to the following criteria.
〇: No PET oligomer precipitation on the guide roll.
Δ: There is a slight amount of PET oligomer precipitation in the form of a guide roll.
X: A large amount of PET oligomer is deposited on the guide roll.

<Glue chipping property>
The end of a square (1 sheet) made by punching a polarizing plate with an adhesive layer produced in each of the above-mentioned Examples and Comparative Examples into a square having a side length of 100 mm with an automatic cutting machine NZ-600 manufactured by Ogino Seiki Seisakusho. The adhesive chipping property from New Zealand was evaluated according to the following criteria.
〇: The depth of glue chipping from the end is less than 100 μm.
Δ: The depth of glue chipping from the end is 100 μm or more and less than 300 μm.
X: The depth of glue chipping from the end is 300 μm or more.

As is clear from Table 3 above, the polarizing plates with an adhesive layer (Examples 1 to 39) using the adhesive composition for an optical film of the present invention have both durability and reworkability, and are aging. It was found that the handling property, which does not require treatment, was excellent, and the oligomer contamination could be sufficiently suppressed. Further, the polarizing plates with a pressure-sensitive adhesive layer (Examples 1 to 39) using the pressure-sensitive adhesive composition for an optical film of the present invention also gave good results in the evaluation of light leakage. Further, when the polarizing plate with the pressure-sensitive adhesive layer (Examples 1 to 39) using the pressure-sensitive adhesive composition for an optical film of the present invention is punched out, the phenomenon that the glue is chipped from the end portion is also significantly suppressed. ..

Claims (20)

A pressure-sensitive adhesive composition for an optical film containing a (meth) acrylate copolymer (A), a peroxide (B), and a cross-linking agent (C) other than the peroxide.
The (meth) acrylate copolymer (A) is a structural unit derived from (a1) an alkyl (meth) acrylate monomer and
At least one of (a2) a structural unit derived from a (meth) acrylate monomer having a hydroxyl group and (a4) a structural unit derived from a monomer having a carboxyl group.
(A3) A structural unit derived from a (meth) acrylate monomer having an aromatic ring, and
Including
The (meth) acrylate copolymer (A) has the (meth) acrylate having the (a3) aromatic ring with respect to 100% by mass of the total amount of the structural units constituting the (meth) acrylate copolymer (A). Containing a constituent unit derived from a monomer in an amount of 10% by mass or more and 30% by mass or less,
The peroxide (B) has a one-minute half-life temperature of 80 ° C. or higher and 125 ° C. or lower.
A pressure-sensitive adhesive composition for an optical film, wherein the cross-linking agent (C) other than the peroxide does not contain a blocked isocyanate compound. The optics according to claim 1, wherein the content of the peroxide (B) is 0.02 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the (meth) acrylate copolymer (A). Adhesive composition for film. Claim 1 that the content of the cross-linking agent (C) other than the peroxide is 0.001 part by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the (meth) acrylate copolymer (A). Alternatively , the pressure-sensitive adhesive composition for an optical film according to 2. The (meth) acrylate copolymer (A) has the (meth) acrylate having the (a2) hydroxyl group with respect to 100% by mass of the total amount of the structural units constituting the (meth) acrylate copolymer (A). The pressure-sensitive adhesive composition for an optical film according to any one of claims 1 to 3 , which contains 0.01% by mass or more and 10% by mass or less of a constituent unit derived from a monomer. The (meth) acrylate copolymer (A) is a composition derived from the monomer having a carboxyl group (a4) with respect to 100% by mass of the total amount of the structural units constituting the (meth) acrylate copolymer (A). The pressure-sensitive adhesive composition for an optical film according to any one of claims 1 to 4 , wherein the unit is more than 0% by mass and 10% by mass or less. The (meth) acrylate copolymer (A) contains the component (a5) in an amount of more than 0% by mass and 20% by mass based on 100% by mass of the total amount of the constituent units constituting the (meth) acrylate copolymer (A). Including mass% or less
The component (a5) is a structural unit derived from a monomer other than an alkyl (meth) acrylate monomer, a (meth) acrylate monomer having a hydroxyl group, a (meth) acrylate monomer having an aromatic ring, and a monomer having a carboxyl group. The pressure-sensitive adhesive composition for an optical film according to any one of claims 1 to 5 . Any one of claims 1 to 6 , further comprising 0.01 parts by mass or more and 1 part by mass or less of the silane coupling agent (D) with respect to 100 parts by mass of the (meth) acrylate copolymer (A). The pressure-sensitive adhesive composition for an optical film according to. The pressure-sensitive adhesive composition for an optical film according to any one of claims 1 to 7 , further comprising a silicate oligomer (E) having a structure represented by the following chemical formula 1.

In the chemical formula 1,
R ¹ and R ² are independently hydrogen atoms, alkyl groups having 1 to 6 carbon atoms, or phenyl groups;
X ¹ and X ² are independently hydrogen atoms, alkyl groups having 1 to 20 carbon atoms, or phenyl groups;
n is an integer of 1 or more and 100 or less. The pressure-sensitive adhesive composition for an optical film according to claim 8 , wherein the silicate oligomer (E) contains a methyl silicate oligomer. The pressure-sensitive adhesive composition for an optical film according to claim 8 or 9 , wherein the silicate oligomer (E) has a weight average molecular weight of 300 or more and 30,000 or less. The cross-linking agent (C) other than the peroxide includes at least one selected from the group consisting of an isocyanate-based cross-linking agent, a carbodiimide-based cross-linking agent, an oxazoline-based cross-linking agent, an epoxy-based cross-linking agent, and an aziridine-based cross-linking agent. Item 2. The pressure-sensitive adhesive composition for an optical film according to any one of Items 1 to 10 . An optical film pressure-sensitive adhesive layer formed from the optical film pressure-sensitive adhesive composition according to any one of claims 1 to 11 . The pressure-sensitive adhesive layer for an optical film according to claim 12 ,
A first optical film provided on one surface of the pressure-sensitive adhesive layer and
The optical member. 13. The optical member according to claim 13 , further comprising glass or a second optical film on a surface of the pressure-sensitive adhesive layer opposite to the surface on which the first optical film is provided. The optical member according to claim 13 or 14 , further comprising at least one easy-adhesion-treated layer between the first optical film and the pressure-sensitive adhesive layer for the optical film. A first easy-adhesion-treated layer is provided on the surface of the first optical film on the side facing the pressure-sensitive adhesive layer for the optical film.
The optical member according to claim 15 , further comprising a second easy-adhesion-treated layer on the surface of the pressure-sensitive adhesive layer for an optical film on the side facing the first optical film. The optical member according to any one of claims 13 to 16 , wherein the first optical film is a polarizing plate. An image display device using at least one optical member according to any one of claims 13 to 17 . A pressure-sensitive adhesive for an optical film, which comprises applying the pressure-sensitive adhesive composition for an optical film according to any one of claims 1 to 11 onto a release-treated release sheet, and then heat-treating the pressure-sensitive adhesive composition to cause a crosslinking reaction. How to make the layer. The method for producing an adhesive layer for an optical film according to claim 19 , wherein the temperature of the heat treatment is 80 ° C. or higher and 120 ° C. or lower.