JP6770799B2 - Adhesive for optical film, adhesive layer for optical film, optical member and image display device - Google Patents

Description

The present invention relates to an adhesive for an optical film, an adhesive layer for an optical film, an optical member, and an image display device.

Currently, as a display panel, a flat display panel such as a liquid crystal display panel (LCD) and a plasma display panel (PDP) is mainly used. A laminate in which a plurality of films are laminated is usually attached to the surface of a flat display panel. For example, in an LCD, an optical film such as a polarizing plate, a retardation plate, a viewing angle expanding film, and a brightness improving film is usually laminated on the surface of a liquid crystal panel. Each layer constituting the flat display panel is usually bonded by an adhesive layer formed of various adhesives.

On the other hand, recently, in addition to flat displays, curved displays or flexible displays have been required due to their design and versatility of usage. Organic electroluminescence panels (OLEDs) are mainly used for curved displays or flexible displays.

The optical film used for this curved display or flexible display, and the optical film laminate laminated by the adhesive layer or the adhesive layer, have the optical properties and durability required for a conventional flat display panel. Therefore, it is required that the optical film does not peel off or float even if it is held for a long time or subjected to a bending test in a deformed state.

The pressure-sensitive adhesive layer used in the conventional optical film laminate (optical member) for a flat display panel is an alkyl (meth) acrylate monomer and an alkoxy as a pressure-sensitive adhesive for bonding a touch panel member, which is one of the optical films. Adhesives for attaching touch panel members, which are copolymers containing alkyl (meth) acrylate monomers, have been proposed (Patent Documents 1 and 2).

Further, a pressure-sensitive adhesive sheet obtained by cross-linking a pressure-sensitive adhesive composition containing an acrylic acid ester-based polymer, an acrylic-based cross-linking monomer, and a cross-linking initiator has been proposed (Patent Document 3).

Further, a pressure-sensitive adhesive composition containing an acrylic copolymer containing a hydroxyl group and an alkylene oxide group and a polyfunctional isocyanate-based curing agent and which realizes an interpenetrating network structure in a cured state having a gel content of 80% or more and 99% or less. It has been proposed (Patent Document 4).

Further, it has been proposed as an adhesive for an optical adhesive sheet capable of suppressing a change in capacitance that causes a malfunction when an adhesive containing an alkoxyalkyl (meth) acrylic acid ester monomer is applied to an optical member. (Patent Document 5).

Further, a photopolymerizable pressure-sensitive adhesive composition containing an acrylic syrup containing an alkoxyalkyl (meth) acrylic acid ester monomer, a monomer having two or more polymerizable unsaturated groups, a cross-linking agent, and a photopolymerization initiator has been proposed. (Patent Document 6).

Japanese Patent No. 2013-186808 Japanese Patent No. 2013-185125 Japanese Patent No. 2014-025073 Japanese Patent No. 2014-055299 Japanese Patent No. 2013-129704 Japanese Patent No. 2007-161909

However, in Patent Documents 1, 2 and 4, the durability at the time of bending cannot be satisfied in the Tg region proposed in these documents. Further, in Patent Document 3, a bifunctional or higher functional acrylic crosslinked monomer is used in order to introduce a crosslinked structure of the pressure-sensitive adhesive layer. When such a polyfunctional acrylic crosslinked monomer is used, the degree of crosslinking of the pressure-sensitive adhesive layer becomes too high, the stress relaxation property deteriorates, and peeling occurs during the bending test. Further, in Patent Documents 5 and 6, the durability test cannot be satisfied with the molecular weight in the disclosed example, and peeling and floating occur.

As described above, in the conventional adhesive, in addition to the optical characteristics and durability required for the flat display panel, peeling and floating occur even if the optical film is held for a long time or subjected to a bending test in a deformed state. It could not meet the demand that there was nothing to do.

Therefore, in the present invention, the adhesive strength to an optical film or the like is excellent, and under various durability test conditions, peeling or floating occurs even if the bonded film is held for a long time or bent in a deformed state. It is an object of the present invention to provide an adhesive for an optical film, an adhesive layer using the same, an optical member, and an image display device.

The present inventors have conducted diligent research to solve the above problems.

As a result, the pressure-sensitive adhesive for an optical film containing the (meth) acrylic acid ester copolymer (A), wherein the (meth) acrylic acid ester copolymer (A) is (a1) alkyl (meth) acrylic. Constituent unit derived from acid ester monomer 10% by mass or more and 95% by mass or less; (a2) Constituent unit derived from (meth) acrylic acid ester monomer having an alkoxyalkyl group or alkylene oxide group 5% by mass or more and 90% by mass or less (A3) A structural unit derived from a functional group-containing monomer which is a (meth) acrylic acid ester monomer having no plurality of radically polymerizable functional groups: 0% by mass or more and 20% by mass or less; the above (a1), (a2) and The total amount of the constituent units derived from the component (a3) is 100% by mass, and the glass transition temperature of the (meth) acrylic acid ester copolymer (A) is −70 ° C. or higher and −55 ° C. or lower, and It has been found that the above object can be achieved by providing a pressure-sensitive adhesive for an optical film having a weight average molecular weight of more than 1 million and 2.5 million or less, and a pressure-sensitive adhesive layer, an optical member, and an image display device using the same. , The present invention has been completed.

For optical films that have excellent adhesive strength to optical films, etc., and do not peel off or float even if the bonded film is held for a long time or bent under various durability test conditions. A pressure-sensitive adhesive and a pressure-sensitive adhesive layer, an optical member, and an image display device using the pressure-sensitive adhesive can be provided.

It is a figure which shows the layer structure of the optical film which has a protective layer and a conductive layer.

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

<Adhesive for optical film>
The pressure-sensitive adhesive for an optical film of the present invention is a pressure-sensitive adhesive for an optical film containing a (meth) acrylic acid ester copolymer (A), and the (meth) acrylic acid ester copolymer (A) is (1). a1) Constituent unit derived from alkyl (meth) acrylic acid ester monomer 10% by mass or more and 95% by mass or less; (a2) Structural unit derived from (meth) acrylic acid ester monomer having an alkoxyalkyl group or an alkylene oxide group 5 mass % Or more and 90% by mass or less; (a3) Structural unit derived from a functional group-containing monomer which is a (meth) acrylic acid ester monomer having a plurality of radically polymerizable functional groups 0% by mass or more and 20% by mass or less; The total amount of the constituent units derived from the components a1), (a2) and (a3) is 100% by mass, and the glass transition temperature of the (meth) acrylic acid ester copolymer (A) is −70 ° C. or higher. The temperature is 55 ° C. or lower, and the weight average molecular weight is more than 1 million and 2.5 million or less.

Hereinafter, each component of the pressure-sensitive adhesive of the present invention will be described in detail.

In the present specification, the "(meth) acrylic acid ester monomer" is a general term for an acrylic acid ester monomer and a methacrylic acid ester monomer. Similarly, compounds containing (meta) such as (meth) acrylic acid are a general term for compounds having "meta" in their names and compounds having no "meta". For this reason, "(meth) acrylic" includes both acrylic and methacrylic. The "(meth) acrylic acid ester monomer" includes both an acrylic acid ester monomer and a methacrylic acid ester monomer. "(Meta) acrylic acid" includes both acrylic acid and methacrylic acid. Further, the "adhesive for optical film" may be simply referred to as "adhesive". Further, the "(meth) acrylic acid ester copolymer (A)" is also referred to as a "copolymer (A)".

As described above, in the present invention, the glass transition temperature is lowered (specifically, −70 ° C. or higher and −55 ° C. or lower) and the weight average molecular weight is increased (specifically, the weight average molecular weight is high). It is characterized by exceeding 1 million and 2.5 million or less).

In the present invention, the weight average molecular weight of the copolymer (A) is more than 1 million and 2.5 million or less. If the weight average molecular weight is 1 million or less, the durability is inferior, and peeling or floating occurs. In addition, there is a risk of deterioration of adhesiveness. In addition, the bending resistance at high temperature and high temperature and humidity is lowered, and the adhesive strength is lowered. If it exceeds 2.5 million, the viscosity of the copolymer solution becomes very high and workability such as coatability deteriorates.

Here, the bending resistance can be evaluated by a bending test (for example, high temperature, low temperature, high temperature and high humidity).

Specifically, the high temperature in the bending test is 70 ° C. or higher, 80 ° C. or higher, or 85 ° C. or higher. The upper limit is 110 ° C. or lower, or 105 ° C. or lower.

Further, in the bending test, the low temperature is specifically 0 ° C. or lower or −20 ° C. or lower, and the lower limit is −40 ° C. or higher.

In the bending test, the high temperature and humidity specifically means 40 ° C or higher and 85 ° C or lower, or 55 ° C or higher and 85 ° C or lower, and a relative humidity of 85% RH or higher and 98% RH or lower, or 85% RH or higher. Say 95% RH or less.

Further, the durability can be evaluated by a durability test (for example, a high temperature test, a high temperature and high humidity test, a heat shock test). At that time, "high temperature" and "high temperature and humidity" are defined in the same manner as the above-mentioned bending test, and the heat shock test is a durability test by repeating "high temperature" and "low temperature", and is referred to as "low temperature". Is 0 ° C. or lower, −20 ° C. or lower, or −40 ° C. or lower, and the lower limit is −50 ° C. or higher or −45 ° C. or higher. The number of repetitions is not particularly limited, but is about 100 or more and 1000 or less.

According to the preferred embodiment of the present invention, the weight average molecular weight exceeds 1.2 million. If it exceeds 1.2 million, the elastic modulus will increase, and the durability, bending resistance, and adhesive strength will be excellent. That is, the elastic modulus at high temperature can be secured, and as a result, the crosslink density can be designed to be low, so that the adhesive strength is excellent, and as a result, durability and bending resistance can be secured.

The weight average molecular weight is more preferably 1.1 million or more and 2.48 million or less, and further preferably 1.2 million or more and 2.45 million or less, from the viewpoints of durability, bendability, adhesiveness, and workability. In this specification, the weight average molecular weight refers to a value measured by the method shown in Examples.

Further, as described above, in the present invention, the glass transition temperature is −70 ° C. or higher and −55 ° C. or lower. If the temperature is lower than −70 ° C., durability cannot be maintained. In addition, there is a risk that peeling or foaming may occur due to a decrease in elastic modulus at high temperatures. On the other hand, if the temperature exceeds −55 ° C., durability during bending, especially at low temperature, cannot be maintained.

According to the preferred embodiment of the present invention, the glass transition temperature is preferably −69 ° C. or higher, more preferably −68 ° C. or higher, still more preferably −67 ° C. or higher, from the viewpoint of achieving both durability and bending durability. is there. The glass transition temperature is preferably −56 ° C. or lower.

According to the preferred embodiment of the present invention, the (meth) acrylic acid ester copolymer (A) contains a hydroxyl group. With such a configuration, there are technical effects such as improvement of adhesion and improvement of characteristics when an isocyanate cross-linking agent is used. That is, it is preferable that the pressure-sensitive adhesive layer contains a hydroxyl group that reacts with isocyanate, which is a cross-linking agent, because it forms a cross-linked structure and can achieve both adhesiveness and durability.

[(Meta) acrylic acid ester copolymer (A)]
((A1) Alkyl (meth) acrylic acid ester monomer)
The (meth) acrylic acid ester copolymer (A) of the present invention contains a structural unit derived from an alkyl (meth) acrylic acid ester monomer as a component (a1).

It is considered that the inclusion of such a component in the pressure-sensitive adhesive of the present invention has the significance of ensuring the adhesiveness and the basic characteristics.

The alkyl (meth) acrylic acid ester monomer is not particularly limited as long as the alkyl group is introduced into the ester moiety of the (meth) acrylic acid ester.

The number of carbon atoms of the alkyl group is not particularly limited, but the number of carbon atoms is preferably 1 or more and 20 or less, and particularly preferably 2 or more and 18 or less carbon atoms from the viewpoint of compatibility and keeping the glass transition temperature low. It is more preferably 4 or more and 12 or less. According to a preferred embodiment of the present invention, the number of carbon atoms of the alkyl in the component (a1) is 1 or more and 18 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. In the case of a ring, the number of carbon atoms is 3 or more.

The alkyl (meth) acrylic acid ester monomer typically has the following formula 1:

Indicated by.

Here, in the above formula 1, R ₁ is a hydrogen atom or a methyl group, and R ₂ is the above alkyl group.

The alkyl group is not particularly limited, but is a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, an isobutyl group, an n-hexyl group, a 2-hexyl group, 3 -Hexyl group, cyclohexyl group, 1-methylcyclohexyl group, n-heptyl group, 2-heptyl group, 3-heptyl group, isoheptyl group, tert-heptyl group, n-octyl group, isooctyl group, tert-octyl group, 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 can be mentioned. In particular, a butyl group, a 2-ethylhexyl group, a methyl group, an n-hexyl group, a nonyl group, and an isononyl group are preferable from the viewpoint of ensuring adhesiveness and basic properties.

Therefore, the alkyl (meth) acrylic acid ester monomer includes methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth) acrylate. , Tert-butyl (meth) acrylate, n-pentyl (meth) acrylate, isopentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, nonyl There are (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate and the like. These can be used alone or in combination of two or more.

As commercially available products, 2EHA, BA (all manufactured by Nippon Shokubai Co., Ltd.) and the like are suitable.

The total amount of the constituent components derived from (a1), (a2) and (a3) is 100% by mass, but the component (a1) is 10% by mass or more and 95% by mass or less. If it is less than 10% by mass, various durability is inferior, and bending resistance at high temperature and low temperature is inferior. On the other hand, if it exceeds 95% by mass, various durability is inferior, bending resistance at high temperature is inferior, and adhesive strength at high temperature is lowered.

The component (a1) is preferably more than 10% by mass and less than 90% by mass, more preferably 12% by mass or more and 85% by mass or less, and further, from the viewpoint of more exerting the desired effect of the present invention. It is preferably 15% by mass or more and 80% by mass or less.

((A2) (meth) acrylic acid ester monomer having an alkoxyalkyl group or an alkylene oxide group)
The (meth) acrylic acid ester copolymer (A) of the present invention contains a (meth) acrylic acid ester monomer having an alkoxyalkyl group or an alkylene oxide group.

The (meth) acrylic acid ester monomer having an alkoxyalkyl group or an alkylene oxide group is not particularly limited as long as it has an alkoxyalkyl group or an alkylene oxide structure in the (meth) acrylic acid ester molecule. It is considered that such a component has an effect of improving adhesiveness and durability by being contained in the pressure-sensitive adhesive of the present invention. If the content of the (meth) acrylic acid ester monomer having an alkoxyalkyl group structure is relatively small (for example, 20% by mass or less, or 18% by mass or less), the adhesiveness may be improved.

The number of carbon atoms in the alkoxy moiety of the alkoxyalkyl group is not particularly limited, but is preferably 1 or more and 8 or less from the viewpoint of improving adhesiveness and durability and efficiently exerting the desired effect of the present invention. .. The specific examples listed below are suitable for the alkoxy moiety having 1 or more and 8 or less carbon atoms.

The number of carbon atoms in the alkyl moiety of the alkoxyalkyl group is not particularly limited, but the number of carbon atoms is 1 or more from the viewpoint of balancing the improvement of adhesiveness and the improvement of durability and the efficient exertion of the desired effect of the present invention. It is preferably 20 or less, more preferably 1 or more and 6 or less carbon atoms, and further preferably 1 or more and 4 or less carbon atoms. Specific examples of the alkyl moiety having 1 to 20 carbon atoms can be appropriately selected from the specific examples listed above.

The number of carbon atoms in the alkylene portion of the alkylene oxide group is not particularly limited, but the number of carbon atoms is 1 or more and 4 or less from the viewpoint of improving adhesiveness and durability and efficiently exerting the desired effect of the present invention. Is preferable, and the number of carbon atoms is more preferably 1 or more and 3 or less.

A (meth) acrylic acid ester monomer having an alkoxyalkyl group or an alkylene oxide group typically has the following formula 2:

Indicated by.

Here, in the above formula 2,
R ₃ is a hydrogen atom or a methyl group and
R ₄ is an alkoxyalkyl group or - _(A-O) n -X.

The alkoxy moiety of the alkoxyalkyl group is preferably alkoxy having 1 or more and 8 or less carbon atoms, and the above-mentioned specific examples are similarly valid. Further, the alkyl preferably has 1 or more and 20 or less carbon atoms, and the above-mentioned specific examples are similarly valid.

Here, as the alkoxyalkyl group, a methoxyethyl group, an ethoxymethyl group, an ethoxyethyl group, a propoxyethyl group, a butoxyethyl group, a methoxypropyl group, a methoxybutyl group, and a 2-ethylhexyloxy group are preferable.

Further, A is a methylene group, an ethylene group, a propylene group or a butylene group, and n is preferably 1 or more and 10 or less, and more preferably 1 or more and 4 or less.

Further, X is an alkyl group. Such an alkyl group may be linear or branched, and the carbon number is preferably 1 or more and 20 or less, more preferably 1 or more and 10 or less, and further preferably 1 or more and 9 or less. Is more preferable. Specific examples of such an alkyl group are preferably those listed above, and in particular, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, an isobutyl group, and an n-hexyl group. , 2-Hexyl group, 3-Hexyl group, Cyclohexyl group, 1-Methylcyclohexyl group, n-Heptyl group, 2-Heptyl group, 3-Heptyl group, Isoheptyl group, tert-Heptyl group, n-octyl group, Isooctyl group , Tert-octyl group, 2-ethylhexyl group, nonyl group, isononyl group are suitable.

From the above, 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), methoxydipropylene glycol (meth) acrylate, 2-ethylhexyl-diglycol acrylate Is preferable. These can be used alone or in combination of two or more.

Among these, from the viewpoint of improving adhesiveness and durability and efficiently exerting the desired effects of the present invention, in particular, 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, methoxy-triethylene glycol (meth) acrylate, 2-ethylhexyloxy -Diethylene glycol (meth) acrylate and 2-ethylhexyl-diglycol acrylate are more preferable. These can be used alone or in combination of two or more.

The total amount of the structural units derived from the above (a1), (a2) and (a3) is 100% by mass, but the component (a2) is 5% by mass or more and 90% by mass or less. If it is less than 5% by mass, the effects of improving the adhesiveness and the durability may not be exhibited. On the other hand, if it exceeds 90% by mass, the amount of polyfunctional (meth) acrylate such as the di (meth) acrylate component, which is an impurity contained in the component (a2), increases as a result, resulting in gelation, resulting in a pressure-sensitive adhesive. There is a risk that it will not function as.

The component (a2) is preferably 5% by mass or more and 80% by mass or less, more preferably 5% by mass or more and 70% by mass or less, and 10% by mass from the viewpoint of more exerting the desired effect of the present invention. It may be% or more and 40% by mass or less.

Commercially available products include AME (manufactured by Nippon Catalyst Co., Ltd.), Light Acrylate EC-A, Light Acrylate EC-2A, Light Acrylate MTG-A, Light Acrylate EHDG-AT, Light Acrylate 130A, Light Acrylate DPM-A, ( Above, Kyoeisha Chemical Co., Ltd.), Viscort # 190, 2-MTA2-MTA, MPE400A, MPE400A, MPE550A, MPE550A, (above, manufactured by Osaka Organic Chemical Industry Co., Ltd.) are suitable.

((A3) Functional group-containing monomer which is a (meth) acrylic acid ester monomer having a plurality of radically polymerizable functional groups)
In a preferred embodiment of the present invention, the (meth) acrylic acid ester copolymer (A) of the present invention is a functional (meth) acrylic acid ester monomer having no plurality of radically polymerizable functional groups as the component (a3). It may contain a structural unit derived from a group-containing monomer.

Such a functional group-containing monomer is not particularly limited as long as it is a (meth) acrylic acid ester monomer having no plurality of radically polymerizable functional groups, but according to a preferred embodiment of the present invention, such a monomer is hydroxyl. A (meth) acrylic acid ester monomer having a group, an acyl group or an epoxy group, or a (meth) acrylic monomer having an amide group. It is considered that such a component has an effect of improving adhesiveness by being contained in the pressure-sensitive adhesive of the present invention.

Although the component (a3) is an optional component, it has the effect of improving the adhesiveness when it is contained in the pressure-sensitive adhesive of the present invention in combination with the above-mentioned components (a1) and (a2). The effect of can be played more efficiently.

<(Meta) acrylic acid ester monomer having a hydroxyl group, an acyl group or an epoxy group>
A (meth) acrylic acid ester monomer having a hydroxyl group, an acyl group or an epoxy group typically has the following formula 3:

Indicated by.

Here, in the above formula 3,
R ₅ is a hydrogen atom or a methyl group and
R ₆ is a divalent organic group or single bond
R ₇ is a hydroxyl group, an acyl group or an epoxy group.

The number of carbon atoms of the acyl group is also not particularly limited, but is preferably 1 or more and 18 or less, and more preferably 1 or more and 6 or less. The acyl group shall contain an acetoxy group.

Here, the divalent organic group is not particularly limited, but an alkylene group having 1 or more and 10 or less carbon atoms is preferable. Among them, an alkylene group having 1 or more and 3 or less carbon atoms is preferable in consideration of the storage elastic modulus at a high temperature.

The alkylene group having 1 or more and 10 or less carbon atoms is a divalent substituent obtained by removing one hydrogen atom of the above-mentioned alkyl group having 1 or more and 10 or less carbon atoms. Further, the alkylene group or the acyl group replaces at least one alkyl group having 1 or more and 8 or less carbon atoms, a phenoxyalkyl group (the number of carbon atoms of the alkyl group: 1 to 8 carbon atoms), a phenyl group or a cyclohexyl group. It may have as a group. An alkyl group having 1 to 8 carbon atoms can be appropriately selected from the above.

Based on the above, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, acetoacetoxyethyl (meth) acrylate, 2-hydroxymethyl (meth) acrylate, 2-hydroxypropyl (meth) ) Acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 1,4-cyclohexanedimethanol (meth) monoacrylate and the like are suitable, and among them, 4-hydroxybutyl (meth) acrylate is preferable from the viewpoint of adhesiveness. , 2-Hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, acetoacetoxyethyl (meth) acrylate and the like are preferable. These can be used alone or in combination of two or more.

Commercially available products include 2HEA (above, manufactured by Nihon Kasei Co., Ltd.), 4HBA (above, manufactured by Nihon Kasei Co., Ltd.), light ester HOA (N), light ester HOP-A (N), light acrylate HOB-A, and epoxy. Ester M-600A (above, manufactured by Kyoeisha Chemical Co., Ltd.), CHDMMA (above, manufactured by Nihon Kasei Co., Ltd.), GMA (manufactured by Mitsubishi Gas Chemical Co., Ltd.), AAEM (above, manufactured by Nihon Kasei Chemical Co., Ltd.) are suitable.

<(Meta) acrylic monomer having an amide group>
The (meth) acrylic monomer having an amide group has a hydroxyl group, an acyl group or an epoxy group according to one embodiment.

In addition, the (meth) acrylic monomer having an amide group typically has the following formula 4:

Indicated by.

Here, in the above formula 4,
R ₈ is a hydrogen atom or a methyl group and
R ₉ is a single bond or divalent organic group
R ₁₀ is a hydrogen atom, an alkyl group having 1 or more and 10 or less carbon atoms, a hydroxyl group, an acyl group, an epoxy group, an alkoxy group having 1 or more and 8 or less carbon atoms, or a dimethylamino group.
R ₁₁ is a hydrogen atom or an alkyl group having 1 or more and 10 or less carbon atoms.

The divalent organic group is not particularly limited, but an alkylene group having 1 or more and 10 or less carbon atoms is preferable. Examples of the alkylene group having 1 or more and 10 or less carbon atoms include those described above. Further, the alkylene group or the acyl group may have at least one alkyl group having 1 or more and 8 or less carbon atoms, a phenyl group or a cyclohexyl group as a substituent.

Examples of the alkyl group having 1 or more and 10 or less carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, an isobutyl group, an n-hexyl group, and a 2-hexyl group. 3-Hexyl group, cyclohexyl group, 1-methylcyclohexyl group, n-heptyl group, 2-heptyl group, 3-heptyl group, isoheptyl group, tert-heptyl group, n-octyl group, isooctyl group, tert-octyl group, 2-Ethylhexyl group, nonyl group, isononyl group, decyl group and the like are suitable. This example of an alkyl group having 1 or more and 10 or less carbon atoms is applicable throughout the present specification.

The number of carbon atoms of the acyl group is also not particularly limited, but is preferably 1 or more and 18 or less, and more preferably 1 or more and 6 or less. The acyl group shall contain an acetoxy group.

Alkoxy groups having 1 or more and 8 or less carbon atoms include methoxy group, ethoxy group, propyloxy group, isopropyloxy group, butoxy group, sec-butoxy group, tert-butoxy group, isobutoxy group, n-hexyloxy group and 2-. A hexyloxy group, a 3-hexyloxy group, a cyclohexyloxy group, a heptyloxy group, an octyloxy group and the like are suitable.

Further, R ₁₀ and R ₁₁ may form a ring with each other, and may have an oxygen atom in the ring.

From the above, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, (meth) acryloylmorpholin, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, diacetone ( Meta) acrylamide, (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N-isopropyl (meth) acrylamide, Nn-butoxymethylacrylamide, N-isobutoxymethylacrylamide, N-methoxymethylacrylamide, N-t-butylacrylamide, N, N'-methylenebisacrylamide and the like are preferable, and among them, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, and (meth) are preferable from the viewpoint of improving adhesiveness. ) Acryloylmorpholin, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, diacetone (meth) acrylamide, (meth) acrylamide and the like are preferable. These can be used alone or in combination of two or more.

Commercially available products include HEAA, ACMO, DMAPAA, DMAA, NIPAM, DEAA (above, manufactured by KJ Chemicals), DAAm (above, manufactured by Nihon Kasei), NBMA, IBMA, NMMA, TBAA, MBAA (above, MRC Unitech). NMAM (manufactured by Miki Riken Kogyo Co., Ltd.) is suitable.

The total amount of the constituent components derived from (a1), (a2) and (a3) is 100% by mass, but the component (a3) is 0% by mass or more and 20% by mass or less. If it exceeds 20% by mass, the desired effect of the present invention may not be achieved.

The component (a3) is preferably more than 0% by mass and 19% by mass or less, more preferably 1% by mass or more and 18% by mass or less, and 5% by mass from the viewpoint of more exerting the desired effect of the present invention. It may be% or more and 15% by mass or less.

[Production of (meth) acrylic acid ester copolymer (A)]
The method for producing the (meth) acrylic acid ester copolymer (A) is not particularly limited, and is a solution polymerization method using a polymerization initiator, an emulsion polymerization method, a massive polymerization method, a suspension polymerization method, and a reverse phase suspension. Conventionally known methods such as a polymerization method, a thin film 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 the method of initiating the polymerization with a polymerization initiator, a method of initiating the polymerization by irradiating with radiation, an electron beam, ultraviolet rays or the like 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 preferable, and among them, a solution polymerization method using a polymerization initiator is easy to adjust the molecular weight and has few impurities. It is even more preferable because it can be done.

For example, ethyl acetate, toluene, methyl ethyl ketone or the like is used as a solvent, and the polymerization initiator is preferably 0.001 or more by mass with respect to 100 parts by mass of the total amount of the raw material monomers of the (meth) acrylic acid ester copolymer (A). Parts are added, more preferably 0.01 parts by mass or more and 0.5 parts by mass or less, and in a nitrogen atmosphere, for example, at a reaction temperature of 40 ° C. or higher and 90 ° C. or lower (or 60 ° C. or higher and 90 ° C. or lower). It is obtained by reacting for 3 hours or more and 10 hours or less.

Examples of the polymerization initiator include 2,2-azobisisobutyronitrile (AIBN), 2,2-dimethoxy-1,2-diphenylethane-1-one, and 2,2'-azobis (2-methyl). Butyronitrile), azobis cyanovaleric acid, 2,2'-azobis (4-methoxy-24-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-methylpropion amidine] 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]; tert-butylperoxypivalate, tert-butyl Organic peroxides such as peroxybenzoate, tert-butylperoxy-2-ethylhexanoate, di-tert-butyl peroxide, cumene hydroperoxide, benzoyl peroxide, tert-butyl hydroperoxide; hydrogen peroxide , Inorganic peroxides such as ammonium persulfate, potassium persulfate, sodium persulfate and the like. These may be used alone or in combination of two or more.

Examples of photopolymerization initiators include acetophenone, 3-methylacetophenone, benzyldimethylketal, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-methyl-1- [4. -(Methylthio) phenyl] -2-morpholinopropane-1-one, 2-hydroxy-2-methyl-1-phenylpropane-1-one and other acetophenones; benzophenone, 4-chlorobenzophenone, 4,4'-diamino Benzophenones such as benzophenone; benzoin ethers such as benzoinpropyl ether and benzoin ethyl ether; thioxanthones such as 4-isopropylthioxanthone; xanthone, fluorenone, phenylquinone, benzaldehyde, anthraquinone and the like. These may be used alone or in combination of two or more.

Commercially available products may be used as the photopolymerization initiator, for example, IRGACURE (registered trademark) -184, 819, 907, 651, 1700, 1800, 819, 369, 261 and DAROCUR-TPO (all manufactured by BASF Japan Co., Ltd.). , DaroCure (registered trademark) -1173 (Merck Co., Ltd.), EzaCure KIP150, TZT (above, DKSH Japan Co., Ltd.), KayaCure (registered trademark) BMS, DMBI (above, Nippon Kayaku Co., Ltd.) Be done.

In addition, a chain transfer agent can also be used to adjust the molecular weight in the synthesis of the (meth) acrylic acid ester copolymer (A). For example, methyl mercaptan, t-butyl mercaptan, decyl mercaptan, benzyl mercaptan, lauryl mercaptan, stearyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, mercaptoacetic acid, mercaptopropionic acid and its esters, 2-ethylhexylthioglycol, thioglycol. Mercaptans such as octyl acid; alcohols such as methanol, ethanol, propanol, n-butanol, isopropanol, t-butanol, hexanol, benzyl alcohol, allyl alcohol; halogenated hydrocarbons such as chloroethane, fluoroethane, trichloroethylene; acetone , Methylethylketone, cyclohexanone, acetophenone, acetaldehyde, propionaldehyde, n-butylaldehyde, furfural, benzaldehyde and other carbonyls; methyl-4-cyclohexene-1,2-dicarboxylic acid anhydride, α-methylstyrene and the like. These may be used alone or in combination of two or more.

Further, in the production of the (meth) acrylic acid ester copolymer (A), the amount of each raw material monomer used is 10% by mass or more and 95% by mass or less for the component (a1) and 5% by mass for the component (a2). % Or more and 90% by mass or less, and the component (a2) is 0% by mass or more and 20% by mass or less. The preferred range of these amounts used is as described above.

As described above, the pressure-sensitive adhesive for optical films of the present invention is a pressure-sensitive adhesive for optical films containing the (meth) acrylic acid ester copolymer (A), and the (meth) acrylic acid ester copolymer (meth) acrylic acid ester copolymer (as described above). A) is (a1) a structural unit derived from an alkyl (meth) acrylic acid ester monomer and 10% by mass or more and 95% by mass or less; (a2) derived from a (meth) acrylic acid ester monomer having an alkoxyalkyl group or an alkylene oxide group. Constituent unit of 5% by mass or more and 90% by mass or less; (a3) Structural unit derived from a functional group-containing monomer which is a (meth) acrylic acid ester monomer having a plurality of radically polymerizable functional groups 0% by mass or more and 20% by mass. The total amount of the structural units derived from the components (a1), (a2) and (a3) is 100% by mass, and the glass transition temperature of the (meth) acrylic acid ester copolymer (A) is It is −70 ° C. or higher and −55 ° C. or lower, and the weight average molecular weight is more than 1 million and 2.5 million or less.

An optical member (adhesive type optical film) having an adhesive layer obtained from an optical film adhesive having such a structure can have the desired effect of the present invention.

[Crosslinking agent (B)]
The pressure-sensitive adhesive of the present invention preferably further contains a cross-linking agent (B) in order to efficiently exert the desired effect of the present invention. By containing the cross-linking agent, the degree of cross-linking of the copolymer (A) is increased, and the desired properties are improved. When the cross-linking agent (B) is contained, the amount added is preferably 0.001 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the (meth) acrylic acid ester copolymer (A). It is preferably 0.01 part by mass or more and 5 parts by mass or less, more preferably 0.01 part by mass or more and 1 part by mass or less, and even more preferably 0.08 part by mass or more. Within such a range, there is a technical effect of bending durability (particularly high temperature). If the degree of cross-linking is too high, the bending resistance in a high temperature and high temperature and high humidity environment may decrease.

The type of the cross-linking agent (B) that can be used in the pressure-sensitive adhesive of the present invention is not particularly limited, and is an isocyanate compound, a carbodiimide compound, an oxazoline compound, an epoxy compound, a polyfunctional acrylic acid ester monomer, a peroxide, and a titanium coupling agent. , A zirconium compound, a metal aluminum chelate, a hydrazide compound and a thermoacid generator, preferably at least one selected from the group. In particular, the cross-linking agent (B) is an isocyanate compound, a carbodiimide compound, an oxazoline compound, an epoxy compound (excluding cases corresponding to (a1), (a2) and (a3)), and a polyfunctional acrylic acid ester monomer (((a1), (a2) and (a3)). It is preferable that it is at least one selected from the group consisting of a1), (a2) and (a3)) and peroxide, and from the viewpoint of ensuring adhesiveness and durability, an isocyanate compound is preferable. And at least one of the peroxides is preferred.

The cross-linking agent (B) of the present invention includes a cross-linking agent (B) that forms a cross-linking structure by itself (curing agent type), and a cross-linking agent (B) that does not form a cross-linking structure by itself but promotes a cross-linking reaction (curing catalyst). Type) is included, and in particular, the latter is a peroxide, a thermoacid generator, and the like.

(Isocyanate compound)
The isocyanate compound preferably used as the cross-linking agent (B) is not particularly limited, and is, for example, triaryl isocyanate, diisocyanate dimerate, 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate. Diisocyanis (2,6-TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylenediocyanide, xylylene Aromatic diisocyanates such as isocyanate (XDI), tetramethylxylene diisocyanate (TMXDI), trizine diisocyanis (TODI), 1,5-naphthalenediis isocyanate (NDI); hexamethylene diisocyanis (HDI), trimethylhexamethylene diisocyanis (TMHDI) , Lysine diisocyanates, aliphatic diisocyanates such as norbornan diisocyanatomethyl (NBDI); transcyclohexane-1,4-diisocyanates, isophorone diisocyanates (IPDI), H6-XDI (hydrogenated XDI), H12-MDI (hydrousated MDI) ) And the like; carbodiimide-modified diisocyanates of the above diisocyanates; or these isocyanurate-modified diisocyanates and the like, and one or more of these can be used. In addition, it may be used in combination with a peroxide described later. Adducts of the above isocyanate compounds and polyol compounds such as trimethylolpropane, and biuret and isocyanurates of these isocyanate compounds can also be preferably used.

Further, the isocyanate compound may be synthesized or a commercially available product 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 Nippon Polyurethane Industry Co., Ltd.). ), Takenate (registered trademark) D-102, Takenate (registered trademark) D-110N, Takenate (registered trademark) D-200, Takenate (registered trademark) D-202 (all manufactured by Mitsui Chemicals, Inc.), Duranate (registered) Trademarks) 24A-100, Duranate® TPA-100, Duranate® TKA-100, Duranate® P301-75E, Duranate® E402-90T, Duranate® 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.), Sumijour (registered trademark) N-75, N-3200 , N-3300 (above, Sumika Bayer Urethane Co., Ltd.) and the like. 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 preferable, and Coronate (registered trademark) L, Coronate (registered trademark) HX, and Duranate (registered trademark) 24A-100 are more preferable.

(Carbodiimide compound)
The carbodiimide compound preferably used as the cross-linking agent (B) is not particularly limited, and examples thereof include those described in paragraphs "0039" to "0046" of JP2012-246444 and those appropriately modified. Be done.

(Oxazoline compound)
The oxazoline compound preferably used as the cross-linking agent (B) is not particularly limited, and examples thereof include those described in paragraph “0037” of Japanese Patent Application Laid-Open No. 2015-087539 or those obtained by appropriately modifying them.

(Epoxy compound)
As the epoxy-based cross-linking agent (epoxy compound), any suitable epoxy-based cross-linking agent can be adopted. Commercially available products include, for example, "Tetrad C" and "Tetrad X" manufactured by Mitsubishi Gas Chemical Company, Inc., "Adeka Resin EPU Series" and "Adeka Resin EPR Series" manufactured by ADEKA Corporation, and "Adeka Resin EPR Series" manufactured by Daicel Corporation. "Selokiside" and the like. In particular, liquid epoxy resins such as these are preferable because they facilitate the pressure-sensitive adhesive mixing operation when producing the pressure-sensitive adhesive layer.

(Polyfunctional acrylic acid ester monomer)
Examples of the polyfunctional acrylic acid ester monomer include hydrocarbon-based or hydrocarbon ether-based polyfunctional monomers. A hydrocarbon-based or hydrocarbon ether-based polyfunctional monomer is a compound in which a hydroxyl group of a polyhydric alcohol having a hydrocarbon group having 10 or more and 100 or less carbon atoms or a hydrocarbon ether group as a main skeleton is (meth) acrylated. Yes, it is preferable in terms of adhesiveness due to crosslinking. Examples of the hydrocarbon group of the polyhydric alcohol include a linear or branched aliphatic hydrocarbon group, an aromatic hydrocarbon group, an alicyclic hydrocarbon group, and a hydrocarbon group combining these hydrocarbon groups. Examples of the hydrocarbon ether group include those obtained by etherifying the hydrocarbon group. Examples of the polyhydric alcohol having a hydrocarbon ether group as a main skeleton include a compound obtained by adding an alkylene oxide having 2 or more and 4 or less carbon atoms to the polyhydric alcohol (additional number of 1 to 30 or less) and 2 or more carbon atoms. Examples thereof include polyalkylene glycols (addition number 1 or more and 30 or less) obtained from alkylene oxides of 4 or less.

Specific examples of the above-mentioned hydrocarbon-based bifunctional monomer include 1,3-butylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, and 1,6-hexanezirdi (meth) acrylate. ) Di (meth) acrylate of alkylene glycol such as acrylate and neopentyl glycol di (meth) acrylate; alicyclic hydrocarbon such as cyclohexanedimethanol di (meth) acrylate and tricyclodecanedimethanol di (meth) acrylate Di (meth) acrylate of a diol compound having a group; di (meth) acrylate of a diol compound having an aromatic hydrocarbon group such as bisphenol A di (meth) acrylate can be mentioned.

Specific examples of the hydrocarbon ether-based bifunctional monomer include alkoxylated hexanediol di (meth) acrylate, alkoxylated cyclohexanedimethanol di (meth) acrylate, and alkoxylated di (meth) acrylate. , Alkylated neopentyl glycol di (meth) acrylate, alkoxylated bisphenol A di (meth) acrylate, etc. Di of the compound in which alkylene oxide is added to the alkylene glycol or diol compound described in the above hydrocarbon-based bifunctional monomer. Examples include (meth) acrylate. Specific examples of the hydrocarbon ether-based bifunctional monomer include diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and polyethylene glycol di (meth) acrylate. Examples thereof include di (meth) acrylate of polyalkylene glycol such as tripropylene glycol di (meth) acrylate and dipropylene glycol di (meth) acrylate, and dioxane glycol di (meth) acrylate.

Examples of the hydrocarbon-based or hydrocarbon ether-based trifunctional monomer or tetrafunctional monomer include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, and glyceryl tri (meth) acrylate. Tri (meth) acrylate or tetra (meth) acrylate of a tri or tetraol compound such as pentaerythritol tetra (meth) acrylate or trimethylolpropane tetra (meth) acrylate, or alkylene oxide is added to the above tri or tetraol compound. Examples thereof include tri (meth) acrylate and tetra (meth) acrylate of the compound.

Further, as the non-urethane-based polyfunctional monomer (b) other than the above-mentioned hydrocarbon-based or hydrocarbon ether-based monomer, polyester poly (meth) acrylate and epoxy (meth) acrylate having two or more (meth) acrylate groups at the ends are used. And so on.

(Peroxide)
As a peroxide preferably used as a cross-linking agent (B), any peroxide that can generate radicals by heating to achieve cross-linking of the pressure-sensitive adhesive can be used, but in consideration of workability and stability, 1 It is preferable to use a peroxide having a half-life temperature of 80 ° C. or higher and 160 ° C. or lower, more preferably 90 ° C. or higher and 140 ° C. or lower. The half-life of peroxide is an index showing the decomposition rate of peroxide, which is the time when the amount of decomposition of peroxide is halved, and the decomposition temperature for obtaining the half-life at an arbitrary time. The half-life at any temperature is described in the manufacturer's catalog, etc., for example, in the 9th edition (May 2003) of the organic peroxide catalog published by Nippon Oil (Nippon Oil) Co., Ltd. ing.

Examples of such peroxides include bis (2-ethylhexyl) peroxydicarbonate (1 minute half-life temperature 90.6 ° C.) and bis (4-t-butylcyclohexyl) peroxydicarbonate (92.1 ° C.). ), Bis-sec-butylperoxydicarbonate (92.4 ° C.), t-butylperoxyneodecanoate (103.5 ° C.), t-hexylperoxypivalate, (109.1 ° C.). ), T-Butylperoxypivalate (110.3 ° C), dilauroyl peroxide (116.4 ° C), bis-n-octanoyl peroxide (117.4 ° C), 1,1,3 , 3-Tetramethylbutylperoxy-2-ethylhexanoate (124.3 ° C), bis (4-methylbenzoyl) peroxide (128.2 ° C), dibenzoyl peroxide (130.0 ° C) , T-Butyl peroxybutyrate (136.1 ° C.), and bis (4-t-butylcyclohexyl) peroxydicarbonate, dilauroyl peroxide, and dibenzoyl peroxide having excellent cross-linking reaction efficiency are preferable. Used. In particular, bis (4-t-butylcyclohexyl) peroxydicarbonate is preferable from the viewpoint of decomposition temperature. One kind or two or more kinds of these can be used. Further, it may be used in combination with the above-mentioned isocyanate compound.

(Titanium coupling agent)
The titanium coupling agent preferably used as the cross-linking agent (B) is not particularly limited, and is not particularly limited, for example, those described in paragraph "0072" of JP-A-2014-085616 or any of them as appropriate. Modified ones can be mentioned.

(Zirconium compound)
The zirconium compound preferably used as the cross-linking agent (B) is not particularly limited, and examples thereof include those described in paragraph "0073" of JP-A-2014-085616 or those appropriately modified.

(Metallic aluminum chelate)
The metal aluminum chelate preferably used as the cross-linking agent (B) is not particularly limited, and is, for example, the one described in paragraph "0058" of JP2012-229373A or the paragraph "0058" of JP2008-251089A. Examples thereof include those described in "0037" and those obtained by appropriately modifying them.

(Hydrazide compound)
The hydrazide compound is not particularly limited, and a hydrazine-based cross-linking agent having at least two hydrazino groups and semicarbazide groups is suitable. Examples of the compound having at least two hydrazino groups include polyhydrazides of aliphatic polybasic acids such as dihydrazide oxalate, dihydrazide malonic acid, dihydrazide succinate, dihydrazide glutarate, dihydrazide adipic acid, and dihydrazide sebacic acid; aromatic acids. Examples include polyhydrazide of polybasic acid; polyhydrazide of polyacrylic acid; polyhydrazide of aromatic hydrocarbons; hydrazine-pyridine derivative; polyhydrazide of unsaturated polybasic acid such as dihydrazide maleate; polyhydrazide carbonate and the like. Further, as the compound having at least two semicarbazide groups, for example, semicarbazide compounds such as polysemicarbazide such as aliphatic, alicyclic and aromatic compounds can be used.

(Thermal acid generator)
Examples of the thermoacid generator include hexafluoroantimonate-based sulfonium salts exemplified as energy acid generators, and commercially available products manufactured by Sanshin Chemical Co., Ltd., SI-60, SI-60L, SI-80, SI- Examples thereof include 80L, SI-100, SI-100L, and CI-2624 manufactured by Nippon Soda Co., Ltd. The thermoacid generator may be used alone or in combination of two or more. The amount of the thermoacid generator used is preferably 0.001 part by mass or more and 20 parts by mass or less, preferably 0.05 part by mass, with respect to 100 parts by mass of the (meth) acrylic acid ester copolymer (A). It is 10 parts by mass or less, more preferably 0.1 parts by mass or more and 3 parts by mass or less.

[Silane Coupling Agent (C)]
The pressure-sensitive adhesive of the present invention can further contain a silane coupling agent from the viewpoint of improving at least one property such as durability and adhesiveness.

A silane coupling agent refers to an agent that does not have a siloxane bond and has two or more different reactive groups in the molecule.

The silane coupling agent used in the pressure-sensitive adhesive of the present invention is not particularly limited, and for example, 3-glycidoxypropyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, n-propyltrimethoxysilane. , Ethyltrimethoxysilane, diethyldiethoxysilane, n-butyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, cyclohexylmethyldimethoxysilane, vinyltricrolsilane, Vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, γ-glycidoxy Propyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxy Silane, γ-acryloxypropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropylmethyldimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- ( Aminoethyl) -γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ- Examples thereof include mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, bis- (3- [triethoxysilyl] propyl) tetrasulfide, and γ-isocyanuppropyltriethoxysilane. Furthermore, a silane cup containing 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 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 may be synthesized or a commercially available product may be used. Commercially available silane coupling agents 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.

The silane coupling agent may be used alone or in combination of two or more.

In the present invention, the amount added when the silane coupling agent is contained is more preferably 0.0001 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the pressure-sensitive adhesive (A), and 0.001 parts by mass. It is more preferably parts or more and 5 parts by mass or less, and particularly preferably 0.01 parts by mass or more and 3 parts by mass or less. Within such a range, durability can be improved.

Therefore, according to a preferred embodiment of the present invention, the silane coupling agent (C) further contains 0.001 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the (meth) acrylic acid ester copolymer (A). , Adhesives for optical films are provided.

[Use]
The pressure-sensitive adhesive of the present invention described above is suitable for various uses. For example, it is preferably used for optical films. Such an optical film is not particularly limited, and examples thereof include those used for forming an image display device such as a liquid crystal display device. For example, the optical film includes at least a polarizing plate or a retardation plate, and further includes a conductive layer and a protective layer. An optical compensation film such as a cover film, a transparent conductive film, a wind film, a viewing angle expanding film for improving the viewing angle of a liquid crystal display, a brightness improving film for increasing the contrast of the display, and further. Examples include those in which these are laminated.

In the present invention, the form of the pressure-sensitive adhesive layer formed of the above-mentioned pressure-sensitive adhesive, the form of an optical member formed of the pressure-sensitive adhesive layer formed on an optical film or the like, and the shape of the optical member are such that the pressure-sensitive optical film (for example, , Adhesive polarizing plate), 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. sell.

<Adhesive layer>
The present invention also provides a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive of the present invention.

In the present invention, the pressure-sensitive adhesive layer can be formed by applying the pressure-sensitive adhesive of the present invention to a base material or the like and drying and removing the solvent or the like. Further, when applying the pressure-sensitive adhesive, one or more kinds of solvents may be newly added as appropriate.

As the base material of the pressure-sensitive adhesive layer, a separator described later can be used.

The coating method 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.

As a method for drying the solvent existing in the pressure-sensitive adhesive, an appropriate method can be adopted depending on the purpose. Preferably, a method of heating and drying the coating film is used. The heating and drying temperature is preferably 40 ° C. or higher and 200 ° C. or lower, more preferably 50 ° C. or higher and 180 ° C. or lower, and particularly preferably 70 ° C. or higher and 170 ° C. or lower. By setting the heating temperature in the above range, an adhesive layer having excellent adhesive properties can be obtained.

In addition, the drying time can be set as appropriate. It is preferably 5 seconds or more and 30 minutes or less, more preferably 5 seconds or more and 20 minutes or less, and particularly preferably 10 seconds or more and 15 minutes or less. The heat drying can be performed twice or more under different conditions.

The thickness (dry film thickness) of the pressure-sensitive adhesive layer of the present invention is not particularly limited and can be appropriately set depending on the intended use. For example, when used in an optical film, it is preferably 1 μm or more and 200 μm or less, more preferably 5 μm or more and 150 μm or less, and 10 μm or more and 120 μm or less from the viewpoint of adhesiveness, durability and bending durability. Is particularly preferred.

According to a preferred embodiment of the present invention, the storage elastic modulus at −20 ° C. (G'(-20)) is 1 × 10 ⁵ Pa or less, and the storage elastic modulus at 85 ° C. (G'(85)). )) Is 1 × 10 ⁴ Pa or more.

When the storage elastic modulus (G'(-20)) of the pressure-sensitive adhesive layer at −20 ° C. is 1 × 10 ⁵ Pa or less, it has the property of a pressure-sensitive adhesive that can follow when bent. Further, the storage elastic modulus (G'(85)) at 85 ° C. is 1 × 10 ⁴ Pa or more, which means that the product has sufficient heat resistance.

The storage elastic modulus (G'(-20)) of the pressure-sensitive adhesive layer at −20 ° C. is more preferably 5 × 10 ⁴ Pa or less, and further preferably 3 × 10 ⁴ Pa or less. The lower limit of the storage elastic modulus (G'(-20)) at −20 ° C. is preferably 1 × 10 ⁴ Pa or more, more preferably 2 × 10 ⁴ Pa or more. ..

On the other hand, the storage elastic modulus (G'(85)) at 85 ° C. is preferably 1 × 10 ⁴ Pa or more, more preferably 2 × 10 ⁴ Pa or more, and 3 × 10 ⁴ Pa or more. is there. Further, the upper limit of the storage elastic modulus (G'(85)) at 85 ° C. is more preferably 2 × 10 ⁵ Pa or less, and further preferably 1 × 10 ⁵ Pa or less.

Further, the ratio of G'(-20) to G'(85), that is, the value of G'(-20) / G'(85) is not limited, but the adhesiveness, durability and bending durability are not limited. From the above viewpoint, it is preferably 1.0 or more and 5.0 or less, and more preferably 1.1 or more and 4.0 or less. The storage elastic modulus shall be measured by the method described in Examples.

Further, when the pressure-sensitive adhesive layer according to the present invention is exposed, the pressure-sensitive adhesive layer can be protected by a peel-treated sheet (separator) or the like until it is put into practical use. Further, when the pressure-sensitive adhesive layer is usually provided by coating with an adhesive and then heating and drying, a method is often adopted in which the pressure-sensitive adhesive is applied on a separator, heat-dried, and then bonded to an optical film.

Examples of the constituent material of the separator 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. A thin leaf body can be mentioned, but a plastic film is preferably used because of its excellent surface smoothness.

The thickness of the base material (for example, separator) is usually 5 μm or more and 200 μm or less, preferably 5 μm or more and 100 μm or less.

Further, the separator may be subjected to a mold release treatment and an antifouling treatment with a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based mold release agent, silica powder, etc., as needed, a coating type, a kneading type, and a vapor deposition. Antistatic treatment such as mold can be performed. In particular, the peelability from the pressure-sensitive adhesive layer can be further enhanced by appropriately performing a peeling treatment such as a silicone treatment, a long-chain alkyl treatment, or a fluorine treatment on the surface of the separator.

The present invention also provides a form of an adhesive layer having a corona-treated layer or a plasma-treated layer on at least one side.

<Optical member>
The present invention also provides an optical member in which the pressure-sensitive adhesive layer of the present invention is formed on at least one side of an optical film. In other words, the "optical member" can be said to be an "adhesive optical film".

The optical member of the present invention may have a structure in which an adhesive layer is formed by directly applying the adhesive of the present invention on one side or both sides of an optical film, or may be applied on a separator to adhere. The agent layer may be formed and then transferred to the optical film, or the pressure-sensitive adhesive layer may be indirectly formed via the easy-adhesive layer. Therefore, in a preferred embodiment of the present invention, an optical member having an easy-adhesion layer between the optical film and the pressure-sensitive adhesive layer is also provided.

The easy-adhesive layer may be one 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 another member such as a primer layer with the pressure-sensitive adhesive layer. It may be provided on the surface of. That is, in a preferred embodiment of the present invention, the easy-adhesion layer is a corona-treated layer, a plasma-treated layer, or a primer layer from the viewpoint of firmly adhering the optical film and the pressure-sensitive adhesive layer.

[Primer layer]
In the present invention, the material forming the primer layer can be any of an adhesive layer, an optical film (for example, a transparent protective film in a polarizing plate) (or a member in contact with the adhesive layer), or an ordinary optical film. It is preferable to form a film that exhibits good adhesion and has excellent cohesive force. For example, various polymers, metal oxide sol, silica sol and the like are used, and among them, polymers are particularly preferably used. The primer layer may have an antistatic function as described above.

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

As such an oxazoline group-containing polymer, a general commercial product is used, and examples thereof include, but are not limited to, the Epocross (registered trademark) series manufactured by Nippon Shokubai Co., Ltd. (for example, Epocross (registered trademark) WS700). As the polyurethane resin, polyester resin, polymers containing an amino group in the molecule, and the like, those disclosed in paragraphs "0107" to "0113" of JP2011-105918A can be appropriately adopted.

In the present invention, a primer layer for forming a primer layer can be applied and dried on an optical film by using a coating method such as a coating method, a dipping method, or a spray method to form a primer layer.

The thickness (dry film 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 such a range, it has bulk properties, and can maintain optical properties while exhibiting sufficient strength and sufficient adhesion.

As described above, according to the preferred embodiment of the present invention, the optical film has a conductive layer. At this time, the material for forming the conductive layer is not particularly limited, but the material for forming the conductive layer is indium tin oxide (ITO: Indium Tin Oxide), silver nanowire, indium zinc oxide, indium oxide. Selected from the group consisting of zinc oxide composite oxide, polythiophene, carbon nanotubes, aluminum zinc oxide, gallium zinc oxide, fluorine zinc oxide, fluorine indium oxide, antimonthine oxide, fluorine tin oxide and phosphorus oxide oxide. It is preferable that the amount is at least one.

Further, according to a preferred embodiment of the present invention, the optical film has a protective layer. By forming the protective layer, corrosion of the metal of the conductive layer can be suppressed.

According to a preferred embodiment of the present invention, the optical film comprises a polarizing plate. Therefore, in the following, as an example, a case where a polarizing plate is included in the optical film according to the present invention will be described.

[Polarizer]
In the present invention, a polarizing plate suitable as an optical film is produced by bonding a protective film and a polarizing element with an adhesive and curing by heat drying or ultraviolet rays, an electron beam or the like by a conventionally known method. obtain. The applied adhesive exhibits adhesiveness by drying or curing with ultraviolet rays, electron beams, etc. to form an adhesive layer. Further, in the present invention, even if a film such as a retardation film is bonded to a polarizer, the retardation film is considered as a part of the polarizing plate. The retardation film may be used as a protective film for protecting the polarizer.

The polarizer is not particularly limited, and conventionally known polarizers can be used. For example, a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or an ethylene / vinyl acetate copolymer partially saponified film is adsorbed with a bicolor material such as iodine or a bicolor dye to be uniaxial. Examples thereof include a stretched film, a polyene-oriented film such as a dehydrated product of polyvinyl alcohol and a dehydrogenated product of polyvinyl chloride.

Of these, a polarizer 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 polarizer is obtained by immersing, for example, a polyvinyl alcohol film in an aqueous solution of iodine, dyeing, and stretching. As the aqueous solution of iodine, for example, it is preferable to immerse it in an aqueous solution containing 0.1% by mass or more and 1.0% by mass or less of iodine and / or potassium iodide. 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, and may be stretched. Further, in order to wash and prevent uneven dyeing, it may be immersed in water at 25 ° C. or higher and 35 ° C. or lower.

Stretching may be performed after dyeing with iodine, stretching while dyeing, or stretching and then dyeing with iodine.

After dyeing and stretching, it may be washed with water or an aqueous solution containing iodine and / or potassium iodide, and dried at 35 ° C. or higher and 55 ° C. or lower for 1 minute or longer and 10 minutes or shorter. There are a wide variety of such polarizers.

The thickness of the polarizer is not particularly limited, but is more preferably about 1 μm or more and 50 μm or less.

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

A transparent protective film may be attached to one side of the polarizer with an adhesive, but in that case, a transparent protective film or a (meth) acrylic, urethane, or acrylic as a protective layer is used on the other side. A thermosetting resin such as urethane-based, epoxy-based, or silicone-based resin 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 and bending, it is preferably 100 μm or less, more preferably 90 μm or less, and particularly preferably 80 μm or less. Such a thin polarizing plate is preferable from the viewpoint of more remarkably exhibiting the effect of the pressure-sensitive adhesive of the present invention. Therefore, according to the preferred embodiment of the present invention, the optical film is a polarizing plate, and the thickness of the polarizing plate is 100 μm or less.

The method for producing the polarizing plate is not particularly limited, and for example, after applying the adhesive, the polarizing element and the protective film can be bonded together 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 polarizer, or may be applied to both. The adhesive is preferably applied so that the thickness of the adhesive layer after drying is 10 nm or more and 10000 nm or less. Further, the adhesive is not particularly limited, and a known adhesive may be appropriately adopted according to the material of the polarizer. For example, when a polyvinyl alcohol-based film is used as the polarizer, an acrylic-based, epoxy-based, or acrylic-epoxy-based adhesive can be used as the polyvinyl alcohol adhesive or the ultraviolet curable adhesive.

The thickness of the adhesive layer is 10 nm or more and 200 nm or less for the polyvinyl alcohol adhesive and 0.2 μm or more and 10 μm or less for the ultraviolet curable adhesive because a uniform in-plane thickness is obtained and sufficient adhesive strength is obtained. It is preferable to have.

<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 of the present invention, it is particularly preferably applied to a thin image display device, a curved display, a flexible display and the like.

As described above, the present invention relates to an adhesive for an optical film, an adhesive layer for an optical film, an adhesive optical film, and an image display device, and the obtained laminates are laminated under each durability test condition. It is possible to provide an adhesive that does not peel off or float even when the film is held for a long time or subjected to a bending test in a deformed state. Further, the pressure-sensitive adhesive of the present invention is suitably used for laminating thin-layer adherends including an optical film or sheet, and various films or sheets used for liquid crystal display elements such as flexible displays, electroluminescence elements and the like. It is suitably used for the production of, and can be commercialized in these technical fields.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. In addition, each part and% in each example is based on mass. All the conditions for leaving at room temperature, which are not specified below, are 23 ° C. and 55% RH.

<Measurement of weight average molecular weight of (meth) acrylic acid ester copolymer (A)>
The weight average molecular weight of the (meth) acrylic acid ester copolymer (A) was measured by GPC (gel permeation chromatography).

-Analyzer: HLC-8120GPC manufactured by Tosoh Corporation
-Column: Made by Tosoh, G7000HXL + GMHXL + GMHXL
-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.

(Creation of thin polarizing plate)
The production of a thin polarizing plate will be described with reference to FIG.

A 20 μm-thick polyvinyl alcohol film was stretched up to 3 times between rolls having different speed ratios while dyeing in an iodine solution at 30 ° C. and a 0.3% concentration for 1 minute. Then, it was stretched at 60 ° C. in an aqueous solution containing 4% boric acid and 10% potassium iodide 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% at 30 ° C. for 10 seconds, and then dried at 50 ° C. for 4 minutes to obtain a polarizer 4 having a thickness of 7 μm.

A polycarbonate film 2 having a thickness of 20 μm on one side of the polarizing element 4, and a retardation film 6 (1/4 wave plate, manufactured by Teijin Co., Ltd.) having a thickness of 50 μm on the surface of the polarizer 4 on the opposite side. ) Are laminated with polyvinyl alcohol-based adhesives 3 and 5, respectively, to prepare a thin polarizing plate 1 having a total thickness of 77 μm.

<Creation of conductive layer>
As shown in FIG. 1, the following coating material for forming a conductive layer is applied to the six surfaces of the retardation film of the thin polarizing plate by a die coating method so that the solid content coating amount is 1 g / m ^2, and at 80 ° C. After drying, the conductive layer 7 (thickness: 0.05 μm) was laminated on the retardation film 6.

(Paint for forming conductive layer)
70 parts by mass of ultrapure water (ultrapure water Ultrapure Water, manufactured by Wako Pure Chemical Industries, Ltd.) and rust preventive (Cambrios, USA) per 30 parts by mass of silver nanowire dispersion solution (CleraOhm Ink-AAQ, manufactured by Cambrios, USA). , ClearOhm SFT-D) was added in 0.12 parts to prepare a coating material for forming a conductive layer.

<Creation of protective layer>
On the conductive layer 7 laminated on the retardation film 6 above, the following protective layer forming paint is applied by a die coating method so that the thickness of the protective layer (thickness after curing) is 210 nm, and at 80 ° C. The protective layer 8 was formed by drying and irradiating with UV (LH10-70UV lamp manufactured by Heraeus) and curing (integrated light amount: 200 mJ / cm ² ).

(Paint for forming protective layer)
A coating material for forming a protective layer was prepared by adding 95 parts by mass of ethyl acetate per 5 parts by mass of an acrylic resin-based paint (Chugoku Marine Paint Co., Ltd., Forseed No. 420C resin concentration 50% by mass).

(Manufacturing Example 1)
<Preparation of (meth) acrylic acid ester copolymer (A1)>
60 parts of 2-ethylhexyl acrylate, 35 parts of methoxyethyl acrylate, 5 parts of 2-hydroxyethyl acrylate, 2,2 as a polymerization initiator in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a cooler. '-0.1 part of azobisisobutyronitrile (AIBN) was charged together with 100 parts of ethyl acetate, nitrogen gas was introduced with gentle stirring to replace nitrogen, and then the liquid temperature in the flask was maintained at around 55 ° C. The polymerization reaction was carried out for 5 hours to prepare a solution of a (meth) acrylic acid ester copolymer (A1) having an Mw (weight average molecular weight) of 1.7 million.

(Manufacturing Examples 2 to 17, 20 to 25)
In Production Example 1, the type or proportion of the monomer forming the (meth) acrylic acid ester copolymer (A) and the polymerization initiator were changed as shown in Table 1, except that the same as in Production Example 1. A solution of the copolymers (A2 to 17) to (A20 to 25) was prepared. The Tg (glass transition temperature) and Mw (weight average molecular weight) of the (meth) acrylic acid ester copolymers (A1 to 17) to (A20 to 25) are as shown in Table 1.

(Manufacturing Examples 18 and 19)
Acrylic syrup (A18, 19) was prepared as shown below.

The reaction was carried out in a reaction box in which four black lights (FL20SBL manufactured by Sankyo Electric Co., Ltd.), which are UV lamps, were installed on four sides of the flask in an environment where external ultraviolet rays were cut off.

The monomer composition shown in Table 1 was put into a two-liter four-necked flask equipped with a stirrer, a thermometer, a nitrogen gas introduction tube and a cooling tube in the above box, and the air in the flask was replaced with nitrogen. While heating to 30 ° C.

Next, 0.005 part of 2,2-dimethoxy-1,2-diphenylethane-1-one (IRGACURE (registered trademark) 651; manufactured by BASF Japan Ltd.) was added as a polymerization initiator under stirring and mixed uniformly. did.

Here, in order to start the polymerization, an integrated light amount of 200 mJ / cm ² was irradiated with a black light. After the reaction started, the temperature of the reaction system rose, but when the temperature rise from the start reached 10 ° C, air was introduced into the flask with an air pump to forcibly stop the reaction and acrylic. A syrup (A18, 19) was obtained. The Tg (glass transition temperature) and Mw (weight average molecular weight) of the (meth) acrylic acid ester copolymer (A18, 19) in the acrylic syrup (A18, 19) are as shown in Table 1.

(Manufacturing Example 26)
Acrylic syrup (A26) was prepared as shown below.

The reaction was carried out in a reaction box in which four black lights (FL20SBL manufactured by Sankyo Electric Co., Ltd.), which are UV lamps, were installed on four sides of the flask in an environment where external ultraviolet rays were cut off.

60 parts of 2-ethylhexyl acrylate, 35 parts of methoxyethyl acrylate, 5 parts of 2-hydroxyethyl acrylate and a 2-liter four-necked flask equipped with a stirrer, a thermometer, a nitrogen gas introduction tube and a cooling tube in the above box. 0.1 part of n-dodecyl mercaptan was added as a chain transfer agent, and the flask was heated to 50 ° C. while replacing the air in the flask with nitrogen. Then, as a polymerization initiator, 0.0025 parts of 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) (V-70; manufactured by Wako Pure Chemical Industries, Ltd.) was added under stirring and mixed uniformly. did. After the polymerization initiator was added, the temperature of the reaction system rose, but when the polymerization reaction was continued without cooling, the temperature of the reaction system reached 120 ° C. and then gradually began to fall.

When the temperature of the reaction system dropped to 115 ° C., 7.5 parts of 2-ethylhexyl acrylate, 19.5 parts of methoxyethyl acrylate, 3 parts of 2-hydroxyethyl acrylate and 0.08 part of n-dodecyl mercaptan were added and forced. It was cooled and cooled to 50 ° C. Further, 0.005 part of V-70 as a polymerization initiator was added under stirring and mixed uniformly. After the polymerization initiator was added, the temperature of the reaction system rose, but when the polymerization reaction was continued without cooling, the temperature of the reaction system reached 125 ° C. and then gradually began to fall.

When the temperature of the reaction system dropped to 120 ° C., 5.7 parts of 2-ethylhexyl acrylate, 15 parts of methoxyethyl acrylate, and 2.3 parts of 2-hydroxyethyl acrylate were added to perform forced cooling, and acrylic syrup (A26) was added. Got

The glass transition temperature of the (meth) acrylic acid ester copolymer (A) is a theoretical value calculated by the FOX formula: from the monomer units constituting each polymer and their ratios.

FOX formula: 1 / Tg = w1 / Tg1 + w2 / Tg2 + ... + wn / Tgn
(Tg: glass transition temperature (K) of polymer, Tg1, Tg2, ... Tgn: glass transition temperature (K) of homopolymer of each monomer, w1, w2, ... wn: weight fraction of each monomer )
The theoretical glass transition temperature obtained from the above FOX equation is in good agreement with the measured glass transition temperature obtained by differential scanning calorimetry (DSC) or dynamic viscoelasticity.

<Example 1>
(Preparation of adhesive)
With respect to 100 parts of the solid content of the (meth) acrylic acid ester copolymer (A1) solution obtained in Production Example 1, an isocyanate cross-linking agent Takenate (registered trademark) D110N (methylolylene isocyanate tri) is used as a cross-linking agent (B). A solution of an acrylic pressure-sensitive adhesive (solid content: 15%) was prepared by blending 0.1 part of a 75% ethyl acetate solution of a methylolpropane adduct (number of isocyanate groups in one molecule: 3, manufactured by Mitsui Kagaku Co., Ltd.). ..

(Formation of adhesive layer)
Next, the above acrylic pressure-sensitive adhesive solution was applied to one side of a 50 μm-thick polyethylene terephthalate (PET) film (MRF50, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) that had been subjected to a silicone treatment (peeling treatment). The film was applied with a die coater so that the thickness of the layer was 100 μm, dried at 80 ° C. for 3 minutes, and then dried at 120 ° C. for 10 minutes to form an adhesive layer (100 μm).

(Preparation of polarizing plate with adhesive layer)
Corona treatment was performed on the protective layer 8 side with a corona discharge amount of 80 [W · min / m2] to form an easy-adhesion layer (not shown) on the protective layer.

Next, the silicone-treated PET film on which the pressure-sensitive adhesive layer was formed was transferred so that the pressure-sensitive adhesive layer and the protective layer 8 were in contact with each other via the easy-adhesive layer, and a polarizing plate with a pressure-sensitive adhesive layer (optical member) was transferred. ) Was prepared.

<Examples 2-31 and Comparative Examples 1-6>
As shown in Table 2, the type of (meth) acrylic acid ester copolymer (A) (polymer type), the type of the cross-linking agent or the amount used thereof was changed, and in some cases, at the ratio shown in Table 2. A polarizing plate (optical member) with an adhesive layer was prepared in the same manner as in Example 1 except that a silane coupling agent was used and, in some cases, a polymerization initiator was used in the proportion shown in Table 2. did.

<Examples 32 and 33>
Trimethylolpropane triacrylate (light acrylate TMP-A; manufactured by Kyoei Kagaku Co., Ltd., hereinafter "TMP-A" in the amount shown in Table 2 with respect to 100 g of the active ingredient in the acrylic syrup obtained in Production Examples 18 and 19. , Biuret-type hexamethylene diisocyanate (Duranate (registered trademark) 24A-100; manufactured by Asahi Kasei Chemicals Co., Ltd., hereinafter referred to as “24A-100”), 2-hydroxy-2-methyl-I-phenyl-propane-1 -On (Irgacure (registered trademark) 1173; manufactured by BASF Japan, hereinafter referred to as "I-1173") and 3-glycidoxypropyltriethoxysilane (KBE-403; Shinetsu Chemical Industry Co., Ltd.), which is a silane coupling agent. (Hereinafter referred to as "KBE-403") was added, and the mixture was mixed and defoamed to obtain a photopolymerizable pressure-sensitive adhesive composition (a solution of an acrylic pressure-sensitive adhesive).

Here, 32.5 g of each of the (meth) acrylic acid ester copolymers (A18) and (A19) is contained in 100 g of the active ingredient in the acrylic syrup, and 67.5 g of the remaining unreacted monomer is contained. It has been.

This photopolymerizable pressure-sensitive adhesive composition is applied onto the peel-treated surface of a polyethylene terephthalate (PET) film having a thickness of 50 μm that has been peeled on one side (that is, treated with silicone) so as to have a coating thickness of 100 μm. Then, by attaching a peeled PET separator having a thickness of 50 μm on the coated surface, the PET separators are arranged above and below the pressure-sensitive adhesive composition and sealed in a sandwich shape, and then 5.0 mW with black light. A colorless and transparent acrylic sheet (adhesive layer) was obtained by irradiating with the same light for 10 minutes.

Next, one PET separator is peeled off to expose a colorless and transparent acrylic sheet (adhesive layer), and the pressure-sensitive adhesive layer and the protective layer 8 are transferred so as to be in contact with each other via the easy-adhesive layer, and the pressure-sensitive adhesive layer is transferred. A polarizing plate with a plate was prepared.

<Comparative Example 7>
Trimethylolpropane triacrylate (light acrylate TMP-A; manufactured by Kyoei Kagaku Co., Ltd., hereinafter referred to as "TMP-A") in the amount shown in Table 2 with respect to 100 g of the active ingredient in the acrylic syrup obtained in Production Example 26. , Biuret type hexamethylene diisocyanate (Duranate (registered trademark) 24A-100; manufactured by Asahi Kasei Chemicals Co., Ltd., hereinafter referred to as "24A-100"), 2-hydroxy-2-methyl-I-phenyl-propane-1-one (Irgacure (registered trademark) 1173; manufactured by BASF Japan, hereinafter referred to as "I-1173") and 3-glycidoxypropyltriethoxysilane (KBE-403; manufactured by Shin-Etsu Chemical Industry Co., Ltd.), which is a silane coupling agent. Hereinafter referred to as "KBE-403") was added and mixed and defoamed to obtain a photopolymerizable pressure-sensitive adhesive composition (a solution of an acrylic pressure-sensitive adhesive).

Here, 32.5 g of the (meth) acrylic acid ester copolymer (A26) is contained in 100 g of the active ingredient in the acrylic syrup, and 67.5 g of the remaining unreacted monomer is contained.

This photopolymerizable pressure-sensitive adhesive composition is applied onto the peel-treated surface of a polyethylene terephthalate (PET) film having a thickness of 50 μm that has been peeled on one side (that is, treated with silicone) so as to have a coating thickness of 100 μm. Then, by attaching a peeled PET separator having a thickness of 50 μm on the coated surface, the PET separators are arranged above and below the pressure-sensitive adhesive composition and sealed in a sandwich shape, and then 5.0 mW with black light. A colorless and transparent acrylic sheet (adhesive layer) was obtained by irradiating with the same light for 10 minutes.

Next, one PET separator is peeled off to expose a colorless and transparent acrylic sheet (adhesive layer), and the pressure-sensitive adhesive layer and the protective layer 8 are transferred so as to be in contact with each other via the easy-adhesive layer, and the pressure-sensitive adhesive layer is transferred. A polarizing plate with a plate was prepared.

The following evaluations were performed on the polarizing plate (optical member) (sample) with an adhesive layer obtained in the above Examples and Comparative Examples. The evaluation results are shown in Table 3.

<Durability>
A film having a thickness of 0.7 mm and a silicon nitride (SiNx) film having a thickness of 50 nm on the outermost surface was used as a substitute for the flexible panel.

The polarizing plate sample with the pressure-sensitive adhesive layer was made into a 5-inch size, the polyethylene terephthalate (PET) film was peeled off, and the sample was attached to the polyimide film using a laminator. Then, it was autoclaved at 50 ° C. and 0.5 MPa for 15 minutes to completely adhere the sample to the polyimide film. Then, the sample was sandwiched and fixed with a glass plate so that the inner diameter (diameter) could be held at 6 mm.

(1) The treated sample was treated at 85 ° C. (10% RH or less) for 500 hours (heating test).

(2) Further, the treatment was carried out for 500 hours in an atmosphere of 60 ° C./95% RH (humidification test).

(3) In addition, an environment of 85 ° C. and −40 ° C. was applied for 300 cycles in 1 hour per cycle (heat shock test).

For each test, the appearance of the polarizing plate and the polyimide film was visually evaluated according to the following criteria.

◎: No change in appearance such as foaming, peeling, floating, and no cracks.

◯: There is slight peeling, foaming, or cracks at the edges, but there is no problem in practical use.

Δ: There is peeling, foaming, or cracks at the edges, 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.

For the tests (1), (2) and (3), samples are prepared and the tests are performed independently.

<Folding resistance (folding test 100,000 times)>
The same sample used in the above durability test (autoclaved at 50 ° C. and 0.5 MPa for 15 minutes) was newly prepared and bent with a bending tester (manufactured by Yuasa System Co., Ltd.). Conditions were set so that the (diameter) was 6 mm, and 100,000 cycles were repeated with bending and 180 ° opening as one cycle.

As a test environment,
(1) Under an atmosphere of 23 ° C / 55% RH
(2) 85 ° C (10% RH or less),
(3) Under an atmosphere of 60 ° C / 95% RH
(4) The temperature was −20 ° C.

The appearance of the polarizing plate and the polyimide film after the test was visually evaluated according to the following criteria. The same result can be obtained by conducting the test with a bending tester manufactured by Tester Sangyo Co., Ltd.

For the tests (1), (2), (3) and (4), samples are prepared and the tests are performed independently.

◎: No change in appearance such as foaming, peeling, floating, and no cracks.

◯: There is slight peeling, foaming, or cracks at the edges, but there is no problem in practical use.

Δ: There is peeling, foaming, or cracks at the edges, 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.

<Adhesive strength>
The same samples used in the above durability test were newly prepared, cut into 25 mm width × 100 mm length, respectively, and then autoclaved at 50 ° C. and 0.5 Mpa for 15 minutes to completely adhere to each other. Then, after allowing to stand for 1 hour in an atmosphere of 23 ° C./55% RH, the adhesive strength of the sample was measured.

Adhesive strength is as follows: The sample is subjected to a tensile tester with a constant temperature bath (TENSILON universal material tester STA-1150 manufactured by Orientec) under the conditions of 23 ° C. and 55% RH relative humidity, peeling angle 180 °, peeling speed 300 mm. It was determined by measuring the adhesive force (N / 25 mm) at the time of peeling according to the method of the adhesive tape and adhesive sheet test of JIS Z0237 (2009) at / min. The measurement at 85 ° C. was performed in the same manner as above except that the temperature was 85 ° C. (10% RH or less) using the above equipment.

Here, the test at room temperature and the test at 85 ° C. are also independently performed.

(Measurement of storage elastic modulus)
For the pressure-sensitive adhesive layers produced in each Example and Comparative Example, the storage elastic modulus in the measurement range of −30 ° C. or higher and 150 ° C. or lower was measured using a viscoelasticity measuring device (manufactured by Anton Pearl Co., Ltd .: model: MCR300). More specifically, after laminating the prepared adhesive layer to a thickness of 400 μm, the sample size is cut to a diameter of 8 mm, the measurement sample is set on a parallel plate jig, and the angular frequency is in the temperature range of -30 ° C or higher and 150 ° C or lower. The measurement was performed under the conditions of 1 rad / s, normal force 3N, and heating rate 5 ° C./min. The storage elastic modulus in the measurement range of −30 ° C. or higher and 150 ° C. or lower was measured, and the table shows the value of the storage elastic modulus at “-20 ° C.” and “85 ° C.”.

<Discussion>
As shown in Table 3, it can be seen that the adhesives for optical films of the examples are all excellent in durability, bending test, and adhesive strength. The following will be considered in more detail.

First, Example 1 is considered as a standard formulation.

In Example 2, the amount of the cross-linking agent is increased. Therefore, it can be seen that the heat resistance (particularly, the bendability at high temperature) is improved.

In Example 3, the degree of cross-linking is improved by peroxide cross-linking. Therefore, it can be seen that the heat resistance (particularly, the bendability at high temperature) is improved.

In Example 4, it can be seen that the adhesiveness is improved by the effect of the Si coupling agent.

In Example 5, the heat resistance (particularly, the bendability at high temperature and high humidity) is improved by changing the type of the cross-linking agent.

In Example 6, by increasing the amount of the cross-linking agent in Example 5, the characteristics are changed and the heat resistance (particularly, the bendability at high temperature) is further improved.

In Example 7, the degree of cross-linking is improved by the peroxide cross-linking, and the heat resistance (particularly, the bendability at a high temperature) is improved.

In Example 8, it can be seen that the adhesiveness is improved by the effect of the Si coupling agent.

In Examples 9-16, the amount of AME is reduced from the standard formulation. As a result, in Example 9, Tg is lowered and the adhesiveness at room temperature is slightly improved.

In Example 10, by increasing the amount of the cross-linking agent, the characteristics are changed, and the heat resistance (particularly, the bendability at a high temperature) is improved as compared with Example 9.

In Example 11, the degree of cross-linking is improved by the peroxide cross-linking, and the heat resistance (particularly, the bendability at a high temperature) is improved as compared with Example 9.

It can be seen that in Example 12, the adhesiveness is improved as compared with Example 9 due to the effect of the Si coupling agent.

In Example 13, by changing the type of the cross-linking agent, the characteristics are generally improved except for the adhesiveness at high temperature.

In Example 14, due to the change in characteristics due to the increase in the amount of the cross-linking agent, the resistance to high temperature and high humidity (that is, the bendability at high temperature and high humidity) and the adhesiveness are slightly lowered as compared with Example 13.

In Example 15, the degree of cross-linking is improved by the peroxide cross-linking, and the high temperature and high humidity resistance (that is, the bending property at high temperature and high humidity) and the adhesiveness are slightly lowered as compared with Example 13. Since the copolymer (A2) of Production Example 2 has a lower Tg than the copolymer (A1) of Production Example 1 and the cohesive force of the pressure-sensitive adhesive layer is lower (even if the degree of cross-linking is high). ) It is probable that the adhesive strength was slightly reduced.

In Example 16, it can be seen that the adhesiveness is improved as compared with Example 13 due to the effect of the Si coupling agent.

Example 17 reduces the amount of AME from the standard formulation. As a result, Tg is lowered and the adhesiveness at room temperature is slightly improved.

In Example 18, the standard formulation is changed to an EC-A-based type. As a result, the adhesiveness at room temperature is slightly improved as compared with Example 1.

Example 19 is an AME, EC-A composite type. As a result, the overall characteristics are improved, the heat resistance is improved, the bending resistance at low temperature is improved, and the adhesiveness is improved.

Examples 20 to 22 are introduction types of EHDG-AT. Example 20 has a relatively small amount, Example 21 has a slightly large amount, and Example 22 has a large amount. As a result, in Example 20, Tg was lowered and the adhesiveness was slightly lowered as compared with Example 1. In Examples 21 to 22, Tg is lowered, and heat resistance, high temperature and high humidity resistance, and adhesiveness are slightly lowered as compared with Example 20.

In Example 23, BA is introduced and the Tg type is high, but G'is improved and heat resistance (particularly, bendability at high temperature) is improved.

In Example 24, the hydroxyl group monomer is changed from the standard, which reduces the high temperature storage elastic modulus.

Examples 25 to 26 are types in which an amide monomer is introduced, whereby the storage elastic modulus, heat resistance (particularly, bendability at high temperature) and adhesiveness are improved.

In Example 27, the amount of the hydroxyl group monomer was reduced, but the storage elastic modulus and the adhesiveness were slightly lowered.

In Example 28, the amount of the hydroxyl group monomer was increased, and the bending resistance was slightly reduced, but the adhesiveness was improved.

In Example 29, the molecular weight was increased, but the high-temperature storage elastic modulus, heat resistance, and adhesiveness were improved.

In Example 30, the molecular weight is slightly lowered, but the durability and bending resistance (particularly, high temperature and high humidity) are lowered.

Example 31 is the lower limit region of the molecular weight, but the durability and the bending resistance are lowered.

Examples 32 to 33 are ultraviolet curable types, but the result is that Example 32 is the same as Example 1, and Example 33 has a lower Tg and heat resistance (particularly) as compared with Example 20. , Durability at high temperature), adhesiveness is slightly reduced.

1 Thin polarizing plate,
2 Polycarbonate film,
3 Polyvinyl alcohol adhesive,
4 Polarizer,
5 Polyvinyl alcohol adhesive,
6 Phase difference film,
7 Conductive layer,
8 Protective layer.

Claims (19)

An adhesive for optical films containing the (meth) acrylic acid ester copolymer (A).
The (meth) acrylic acid ester copolymer (A)
(A1) Constituent unit derived from alkyl (meth) acrylic acid ester monomer: 10% by mass or more and 95% by mass or less;
(A2) A structural unit derived from a (meth) acrylic acid ester monomer having an alkoxyalkyl group or an alkylene oxide group: 5% by mass or more and 90% by mass or less;
(A3) a plurality having no radical polymerizable functional group (meth) Configuration Unit from functional group-containing monomer is an acrylic acid ester monomer 5% by weight to 20% by weight and;
The total amount of the structural units derived from the components (a1), (a2) and (a3) is 100% by mass.
Wherein the (meth) acrylic acid ester copolymer (A), the glass transition temperature is at -55 ° C. or less -70 ° C. or higher, and state, and are 2.5 million or less than the weight average molecular weight 1,000,000,
Crosslinking agent (B), the (meth) acrylic acid ester copolymer (A) with respect to 100 parts by weight of Ru contained in 20 parts by mass or less 0.001 parts by mass, the adhesive for an optical film. The pressure-sensitive adhesive for an optical film according to claim 1, wherein the weight average molecular weight exceeds 1.2 million. The functional group-containing monomer (a3) which is a (meth) acrylic acid ester monomer having a plurality of radically polymerizable functional groups is a (meth) acrylic acid ester monomer having a hydroxyl group, an acyl group or an epoxy group, or an amide. The pressure-sensitive adhesive for an optical film according to claim 1 or 2, which is a (meth) acrylic monomer having a group. The pressure-sensitive adhesive for an optical film according to any one of claims 1 to 3, wherein the alkyl having 1 or more and 18 or less carbon atoms in the component (a1). The pressure-sensitive adhesive for an optical film according to any one of claims 1 to 4, wherein the component (a1) is 15% by mass or more and 80% by mass or less. The pressure-sensitive adhesive for an optical film according to any one of claims 1 to 5, wherein the (meth) acrylic acid ester copolymer (A) contains a hydroxyl group. The cross-linking agent (B) is an isocyanate compound, a carbodiimide compound, an oxazoline compound, an epoxy compound, a polyfunctional acrylic acid ester monomer, a peroxide, a titanium coupling agent, a zirconium compound, a metal aluminum chelate, a hydrazide compound and a thermoacid generator. The pressure-sensitive adhesive for an optical film according to any one of claims 1 to 6 , which is at least one selected from the group consisting of. Any of claims 1 to 7 , wherein the silane coupling agent (C) is contained in an amount of 0.001 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the (meth) acrylic acid ester copolymer (A). The pressure-sensitive adhesive for an optical film according to item 1. A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive for an optical film according to any one of claims 1 to 8 . The pressure-sensitive adhesive layer according to claim 9 , which has a corona-treated layer or a plasma-treated layer on at least one side. The storage elastic modulus (G'(-20)) at −20 ° C. is 1 × 10 ⁵ Pa or less, and
The pressure-sensitive adhesive layer according to claim 9 or 10 , wherein the storage elastic modulus (G'(85)) at 85 ° C. is 1 × 10 ⁴ Pa or more. The pressure-sensitive adhesive layer according to any one of claims 9 to 11 , wherein G'(-20) / G'(85) is 1.0 or more and 5.0 or less. An optical member in which the pressure-sensitive adhesive layer according to any one of claims 9 to 12 is formed on at least one side of the optical film. The optical member according to claim 13 , further comprising an easy-adhesion layer between the optical film and the pressure-sensitive adhesive layer. The optical member according to claim 14 , wherein the easy-adhesion layer is a corona-treated layer, a plasma-treated layer, or a primer layer. The optical film is a polarizing plate,
The optical member according to any one of claims 13 to 15 , wherein the thickness of the polarizing plate is 100 μm or less. The optical film has a conductive layer, and the material forming the conductive layer is indium tin oxide, silver nanowire, indium zinc oxide, indium oxide-zinc oxide composite oxide, polythiophene, carbon nanotube, aluminum zinc oxide. , At least one selected from the group consisting of gallium zinc oxide, fluorine zinc oxide, fluorine indium oxide, antimonthine oxide, fluorine tin oxide and phosphorus tin oxide, any of claims 13 to 16 . The optical member according to item 1. An image display device using at least one optical member according to any one of claims 13 to 17 . The image display device according to claim 18 , which is a curved display or a flexible display.