JP6632350B2 - Pressure-sensitive adhesive for optical film, pressure-sensitive adhesive layer, optical member, and image display device - Google Patents

Description

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

  Currently, flat display panels such as a liquid crystal display panel (LCD) and a plasma display panel (PDP) are mainly used as display panels. Usually, a laminated body in which a plurality of films are laminated is bonded to the surface of the flat display panel. For example, in an LCD, an optical film such as a polarizing plate, a retardation plate, a viewing angle widening film, and a brightness improvement film is usually laminated on the surface of a liquid crystal panel. And each layer which comprises a flat display panel is normally bonded by the adhesive layer formed by various adhesives.

  On the other hand, recently, in addition to a flat display, a curved display or a flexible display has been demanded from the viewpoint of design and versatility in use. An organic electroluminescent panel (OLED) is mainly used for a curved display or a flexible display.

  The optical film and the optical film laminate laminated by the pressure-sensitive adhesive layer or the adhesive layer used for the curved display or the flexible display have an optical property and durability in addition to the optical properties and durability required for the conventional flat display panel. In addition, it is required that the optical film does not peel or float even when the optical film is deformed and held or bent for a long time.

  Patent Document 1 discloses a copolymer obtained by polymerizing a macromonomer having a (meth) acryloyl group, a glass transition temperature of 40 ° C. or more, and a number average molecular weight (Mn) of 200 to 20,000, An adhesive composition comprising a silane compound having a functional group that reacts with a group is disclosed.

  Patent Document 2 discloses a pressure-sensitive adhesive composition in which a pressure-sensitive adhesive polymer containing a macromonomer and polyisocyanate are mixed at a mass ratio of 10/90 or more and 90/10 or less.

  Patent Document 3 discloses that a (meth) acrylic monomer is from 94% by weight to 98.9% by weight, a macromonomer is from 1% by weight to 5% by weight, a carboxyl group, an amino group, an amide group, a hydroxyl group or acetoacetyl. A pressure-sensitive adhesive composition is disclosed which contains 0.1 to 1% by weight of an acrylic monomer containing any one of the groups, and has a gel fraction of 55 to 80%.

  In Patent Document 4, a macromonomer having a glass transition temperature of 0 ° C. or more and 160 ° C. or less, a (meth) acrylate having an alkyl having 4 to 12 carbons, and a monomer having a functional group are polymerized. There is disclosed a removable pressure-sensitive adhesive composition in which a graft copolymer is crosslinked with a crosslinking agent having an isocyanurate skeleton.

  Patent Document 5 discloses a weight-average molecular weight obtained by copolymerizing 0.1 to 10% by weight of a (meth) acrylic monomer having a crosslinkable functional group and 0.1 to 30% by weight of a macromonomer. Has a pressure-sensitive adhesive layer containing an acrylic polymer having a molecular weight of 50,000 or more and less than 400,000.

  Patent Document 6 discloses an adhesive composition containing a polymer having a hydroxyl group and having a macromonomer having a glass transition temperature of -100 ° C or more and less than 30 ° C.

JP-A-10-140122 JP 2010-037431 A JP 2010-150400 A JP 2011-052117 A JP 2013-018227 A WO 2014/003173

  However, the pressure-sensitive adhesive compositions described in Patent Literatures 1 to 6 have a problem that durability (bending resistance) at the time of bending in a temperature range where a curved display or a flexible display is used cannot be satisfied. I was

  As described above, in the conventional pressure-sensitive adhesive, in addition to the optical characteristics and durability required for the flat display panel, peeling or floating does not occur even if the optical film is deformed and held for a long time or repeatedly bent. It was not able to meet the demand.

  Accordingly, the present invention provides an optical film pressure-sensitive adhesive that has excellent adhesion to an optical film or the like, and hardly causes peeling or floating even when held or repeatedly bent for a long time in a state where the bonded film is deformed. It is an object to provide a pressure-sensitive adhesive layer, an optical member, and an image display device.

  The present inventors have intensively studied to solve the above-mentioned problems.

  As a result, a pressure-sensitive adhesive for an optical film containing the (meth) acrylate copolymer (A), wherein the (meth) acrylate copolymer (A) is (a1) an alkyl (meth) acrylic (A2) a structural unit derived from a macromonomer having a polymerizable functional group: from 9.9% by mass to 99.9% by mass; and (a3) a structural unit derived from a macromonomer having a polymerizable functional group; A) a structural unit derived from a functional group-containing monomer that is a (meth) acrylic acid derivative monomer having no plurality of radically polymerizable functional groups, from 0% by mass to 20% by mass; (a4) the above (a1), (a2) and A structural unit derived from a (meth) acrylate monomer other than (a3), from 0% by mass to 90% by mass; and (a1), (a2), (a3) and (a4). The total amount of the constituent units is 100% by mass, the (meth) acrylate copolymer has a glass transition temperature of −70 ° C. or more and −57 ° C. or less, and a weight average molecular weight exceeding 1,000,000. It has been found that the above object can be achieved by providing a pressure-sensitive adhesive for optical films, a pressure-sensitive adhesive layer, an optical member, and an image display device, which are 2.5 million or less, and completed the present invention.

  It has excellent adhesive strength to optical films and the like, and almost no peeling or floating occurs even if it is held or repeatedly bent for a long time in a state where the bonded film is deformed, and an optical film adhesive, and it is used. An adhesive layer, an optical member, and an image display device can be provided.

FIG. 3 is a diagram illustrating a layer configuration of an optical film having a protective layer and a conductive layer.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the present invention is not limited to only the following embodiments. In addition, the dimensional ratios in the drawings are exaggerated for convenience of description, and may be different from the actual ratios. In this specification, “weight” and “mass” and “% by weight” and “% by mass” are treated as synonyms. Unless otherwise specified, the operation and measurement of physical properties and the like are performed at room temperature (20 ° C. or more and 25 ° C. or less) / relative humidity of 40% or more and 60% or less.

  In this specification, the bending resistance can be evaluated by a bending test (for example, high temperature, high temperature and high humidity, and low temperature). The “high temperature” in the bending test is, specifically, 70 ° C. or more, 80 ° C. or more, or 85 ° C. or more. The upper limit is 110 ° C or lower or 105 ° C or lower. The term “hot and humid” in the bending test refers to a temperature of 40 ° C. or more and 85 ° C. or less or 55 ° C. or more and 85 ° C. or less and a relative humidity of 85% RH or more and 98% RH or 85% RH or more and 95% RH or less. Refers to something. Further, the “low temperature” in the bending test is 0 ° C. or lower, or −20 ° C. or lower, and the lower limit is −40 ° C. or higher.

  In this specification, 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 this time, “high temperature” and “high temperature and high humidity” are defined in the same manner as the above bending test, and the heat shock test is a durability test by repeating “high temperature” and “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 times or more and 1000 times or less.

  In addition, in this specification, "(meth) acrylate monomer" is a general term for an acrylate monomer and a methacrylate monomer. Similarly, a compound containing (meth) such as (meth) acrylic acid is a general term for a compound having “meth” in a name and a compound not having “meth” in a name. For this reason, “(meth) acryl” includes both acryl and methacryl. The “(meth) acrylate monomer” includes both an acrylate monomer and a methacrylate monomer. “(Meth) acrylic acid” includes both acrylic acid and methacrylic acid.

<Adhesive for optical film>
The pressure-sensitive adhesive for an optical film according to the present invention (hereinafter, also simply referred to as “pressure-sensitive adhesive”) contains the following (meth) acrylate copolymer (A), and is preferably a cross-linking agent (B) or a silane cup. It further contains at least one of the ring agents (C).

  Hereinafter, each of the components (A) to (C) will be described.

[(Meth) acrylate copolymer (A)]
The (meth) acrylic acid ester copolymer (A) (hereinafter, also referred to as “copolymer (A)”) is composed of (a1) a structural unit derived from an alkyl (meth) acrylic acid ester monomer of 9.9% by mass or more and 99% or more. (A2) Structural unit derived from a macromonomer having a polymerizable functional group: 0.1 to 15% by mass; (a3) not having a plurality of radically polymerizable functional groups (meth) Structural unit derived from a functional group-containing monomer that is an acrylic acid derivative monomer in an amount of 0% by mass or more and 20% by mass or less; (a4) a (meth) acrylic acid ester monomer other than (a1), (a2) and (a3) And the total amount of the structural units derived from (a1), (a2), (a3) and (a4) is 100% by mass, and the (meth) Acri The glass transition temperature of the luate ester copolymer is -70 ° C or more and -57 ° C or less, and the weight average molecular weight is more than 1,000,000 and not more than 2.5 million.

  Thus, in the present invention, the glass transition temperature of the copolymer (A) is lowered (specifically, -70 ° C or more and -57 ° C or less) and the weight average molecular weight is increased (specifically, Has a weight average molecular weight of more than 1,000,000 and not more than 2.5 million).

  In the present invention, the weight average molecular weight of the copolymer (A) is more than 1,000,000 and not more than 2.5,000,000. When the weight average molecular weight is 1,000,000 or less, the durability and bending resistance of the pressure-sensitive adhesive decrease. On the other hand, when the weight average molecular weight exceeds 2.5 million, the viscosity of the copolymer solution becomes high, and the workability (such as coating properties) of the pressure-sensitive adhesive decreases. Further, the weight average molecular weight of the copolymer (A) is preferably more than 1.2 million and not more than 2.5 million from the viewpoint of bending resistance at room temperature, and more than 1.2 million from the viewpoint of bending resistance at low temperature. It is more preferably at most 2.2 million. That is, a preferred embodiment of the present invention is a pressure-sensitive adhesive for optical films, wherein the weight average molecular weight of the copolymer (A) exceeds 1.2 million. In addition, in this specification, a weight average molecular weight is a value measured by the method shown in an Example.

  Further, the (meth) acrylate copolymer (A) according to the present invention has a glass transition temperature of −70 ° C. or more and −57 ° C. or less. When the glass transition temperature is less than -70 ° C, the elastic modulus at high temperatures is reduced, and there is a possibility that peeling or foaming may occur. On the other hand, when the glass transition temperature exceeds -57 ° C, the bending resistance (particularly under high temperature and high humidity) decreases. Further, the upper limit of the glass transition temperature of the copolymer (A) is preferably lower than -60 ° C from the viewpoint of bending resistance at a low temperature. That is, a preferred embodiment of the present invention is a pressure-sensitive adhesive for an optical film, wherein the glass transition temperature is −70 ° C. or more and less than −60 ° C. The lower limit of the glass transition temperature of the copolymer (A) is preferably -69 ° C or more, more preferably -67 ° C or more, from the viewpoint of durability at high temperatures.

  According to a preferred embodiment of the present invention, the (meth) acrylate copolymer (A) contains a hydroxyl group. When such a copolymer (A) is contained in the pressure-sensitive adhesive, the adhesiveness to a polar substrate is improved, and the crosslinking density is improved when used in combination with an isocyanate-based crosslinking agent, and the durability (particularly under high temperature and high humidity) is improved. The performance is improved. That is, it is preferable that the copolymer (A) contains a hydroxyl group that reacts with an isocyanate compound as a cross-linking agent, since the pressure-sensitive adhesive forms a cross-linked structure and can achieve both adhesion and durability.

  That is, a preferred embodiment of the present invention is a pressure-sensitive adhesive for optical films, wherein the (meth) acrylate copolymer (A) contains a hydroxyl group.

((A1) alkyl (meth) acrylate monomer)
The (meth) acrylate copolymer (A) of the present invention contains a structural unit derived from an alkyl (meth) acrylate monomer (hereinafter, also referred to as component (a1) or simply (a1)). It is considered that the inclusion of such a component in the pressure-sensitive adhesive of the present invention has the significance of securing the adhesiveness and securing the basic characteristics.

  The component (a1) is not particularly limited as long as the alkyl group is introduced into the ester portion of the (meth) acrylate.

  The number of carbon atoms of the alkyl group is not particularly limited, but is preferably 1 or more and 20 or less. From the viewpoint of the glass transition temperature of the copolymer (A) and the compatibility when used in combination with a crosslinking agent, the number of carbon atoms is 2 or more. It is more preferably 18 or less, more preferably 3 to 16 carbon atoms, and particularly preferably 4 to 12 carbon atoms. The alkyl group may be linear, branched or cyclic, but is preferably linear or branched from the viewpoint of lowering the glass transition temperature of the copolymer (A). . In the case of a ring, the carbon number is 3 or more. That is, in a preferred embodiment of the present invention, the (a1) alkyl (meth) acrylate monomer is an adhesive for an optical film, wherein the alkyl group has 1 to 18 carbon atoms.

  The component (a1) is typically represented by the following chemical formula 1.

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

  The alkyl group is not particularly limited, but may be 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 amyl group, an isoamyl group, a tert-amyl group, 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, decyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, or octadecyl group. . In particular, from the viewpoint of adhesiveness, a methyl group, a butyl group, a 2-ethylhexyl group, an n-hexyl group, a nonyl group, and an isononyl group are preferable.

  As the component (a1), those having a homopolymer having a glass transition temperature of −70 ° C. or more and −30 ° C. or less from the viewpoint of easily controlling the glass transition temperature of the copolymer (A) to a desired range. Preferably, those in the range of -70 ° C or higher and -50 ° C or lower are preferable.

  Therefore, as the alkyl (meth) acrylate monomer, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate , N-pentyl (meth) acrylate, isopentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) A) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate, and the like. Among them, 2-ethylhexyl (meth) acrylate is particularly preferred from the viewpoint that the glass transition temperature of the copolymer (A) can be easily controlled to a desired range. These can be used alone or in combination of two or more.

  As commercial products, 2EHA and BA (all manufactured by Nippon Shokubai Co., Ltd.) are suitable.

  The content of the structural unit derived from the component (a1) in the copolymer (A) is defined assuming that the total amount of the structural units derived from the components (a1), (a2), (a3), and (a4) is 100% by mass. , 9.9 mass% or more and 99.9 mass% or less. When the content is less than 9.9% by mass, the proportion of components other than (a1) in the copolymer (A) increases, so that it is difficult to balance adhesion, durability and bending resistance. On the other hand, when the content exceeds 99.9% by mass, it becomes difficult to impart cohesive force to the pressure-sensitive adhesive, and the adhesiveness is reduced. Further, the lower limit of the content is preferably 50% by mass or more from the viewpoint of durability and adhesiveness, and more preferably 60% by mass or more, and further more preferably, from the viewpoint of bending resistance at low temperatures. Is 70% by mass or more.

  In addition, the upper limit of the content is preferably 95% by mass or less, more preferably 90% by mass or less, from the viewpoint of bending resistance at high temperatures. That is, a preferred embodiment of the present invention is a pressure-sensitive adhesive for an optical film, wherein the constituent unit derived from the (a1) alkyl (meth) acrylate monomer is 60% by mass or more and 90% by mass or less.

((A2) Macromonomer having polymerizable functional group)
The (meth) acrylate copolymer (A) of the present invention contains a structural unit derived from a macromonomer having a polymerizable functional group (hereinafter, also referred to as component (a2) or simply as component (a2)). The component (a2) is a high molecular weight monomer having a polymerizable functional group (ethylenically unsaturated group), and has a polymer chain portion and a polymerizable functional group.

  By including the copolymer (A) polymerized using such a monomer in the adhesive, the bending resistance is improved. The mechanism is considered to differ depending on the glass transition temperature of the polymer chain portion of the macromonomer. Specifically, when the glass transition temperature of the polymer chain portion is high, the polymer chain portion forms a hard segment in the pressure-sensitive adhesive, thereby generating a cohesive force in the pressure-sensitive adhesive. Thereby, it is considered that the bending strength is improved by increasing the adhesive strength to the base material. On the other hand, when the glass transition temperature of the polymer chain portion of the macromonomer is low, it is considered that the pressure-sensitive adhesive becomes flexible and the followability to the base material is increased, so that the bending resistance is improved. Note that the above mechanism is presumed, and the present invention is not limited to the above mechanism at all.

  As the polymerizable functional group of the component (a2), a group having an ethylenically unsaturated double bond (ethylenically unsaturated group) is preferable. Specifically, it is preferably at least one selected from the group consisting of a vinyl group, an allyl group, a (meth) acryloyl group, and a propenyl group. The polymerizable functional group is preferably present at the terminal of the macromonomer, and more preferably present at only one terminal of the macromonomer, from the viewpoint of stability during polymerization. However, the polymerizable functional group may be present as a side chain of the macromonomer, or may be present at both ends of the macromonomer chain.

  The polymer chain portion of the component (a2) includes methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, alkyl (meth) acrylate, stearyl (meth) acrylate, n-butyl (meth) acrylate, (Co) polymer having a repeating unit derived from isobutyl (meth) acrylate, t-butyl (meth) acrylate, styrene, acrylonitrile, hydroxy (meth) acrylate, ethylhexyl acrylate, dimethylsiloxane or the like as a main constituent unit Is preferred. These polymer chain portions may be composed of a single repeating unit, or may be composed of a plurality of repeating units. Further, when the polymer chain is a copolymer composed of a plurality of repeating units, the repeating form is not limited, and may be any of an alternating copolymer, a random copolymer, and a block copolymer.

  The component (a2) is typically represented by the following chemical formula 2.

Here, in Formula 2, R ₃ represents a hydrogen atom or a methyl group, and X represents a single bond or a divalent bonding group.

  Examples of the divalent linking group include a linear, branched, or cyclic alkylene group, an aralkylene group, and an arylene group. These may further have a substituent such as a hydroxy group and a cyano group. The carbon number of the alkylene group is preferably 1 or more and 10 or less, more preferably 1 or more and 4 or less. Examples of the alkylene group include a methylene group, an ethylene group, a trimethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, an octylene group, a decylene group, and a cyclohexylene-1,4-dimethylene group. Among these, a methylene group, an ethylene group, a propylene group and the like are preferable. The aralkylene group preferably has 7 to 13 carbon atoms. Examples of the aralkylene group include a benzylidene group and a cinnamylidene group. The arylene group preferably has 6 to 12 carbon atoms. Examples of the arylene group include a phenylene group, a cumenylene group, a mesitylene group, a tolylene group, and a xylylene group. Among these, a phenylene group is preferred.

During divalent linking group, _{further, -NR 2 -, - COO -} , - OCO -, - O -, - S -, - SO 2 NH -, - NHSO 2 -, - NHCOO -, - OCONH- Alternatively, a group derived from a heterocycle may be interposed as a bonding group. R ₂ is hydrogen or an alkyl group such as a methyl group, an ethyl group, and a propyl group.

  In the above Chemical Formula 2, Y represents methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, alkyl (meth) acrylate, stearyl (meth) acrylate, n-butyl (meth) acrylate, A polymer obtained by homopolymerizing or copolymerizing one or more monomers selected from isobutyl (meth) acrylate, t-butyl (meth) acrylate, styrene, acrylonitrile, hydroxy (meth) acrylate, and ethylhexyl acrylate; Represents a polysiloxane (polyorganosiloxane) having a group bonded to a silicon atom. Among them, Y is a polymer obtained by homopolymerizing methyl (meth) acrylate, styrene, n-butyl (meth) acrylate or isobutyl (meth) acrylate, a polymer obtained by copolymerizing acrylonitrile and styrene, or a polyorganosiloxane. Is preferred.

  Further, from the viewpoint of durability at high temperatures, Y is particularly preferably a polymer obtained by homopolymerizing methyl (meth) acrylate, styrene or isobutyl (meth) acrylate, or a polymer obtained by copolymerizing acrylonitrile and styrene. Alternatively, from the viewpoint of bending resistance at a low temperature, Y is preferably a polyorganosiloxane, and particularly preferably a polydimethylsiloxane. As long as the performance of the pressure-sensitive adhesive is not affected, some of the methyl groups of the polydimethylsiloxane may be substituted with a hydrogen atom or an organic group other than the methyl group (such as an ethyl group or a phenyl group).

  The polydimethylsiloxane can be obtained by hydrolyzing and condensing dimethyldialkoxysilane such as dimethyldimethoxysilane and dimethyldiethoxysilane. At this time, an organic group other than a methyl group can be introduced into polydimethylsiloxane by using an alkoxysilane having an organic group other than a methyl group (for example, diethyldiethoxysilane or the like) in combination. Further, in addition to the dialkoxy-type silane compound, a small amount of a trialkoxy-type silane compound may be added.

  The number average molecular weight (Mn) of the component (a2) is preferably in the range of 2,000 or more and 20,000 or less, more preferably in the range of 2,000 or more and 10,000 or less. More preferably, it is in the range of 000 to 8,000. When the number average molecular weight (Mn) is 2,000 or more, the performance of the pressure-sensitive adhesive can be improved even when the addition amount of the component (a2) in synthesizing the copolymer (A) is small. . On the other hand, if it is 20,000 or less, the viscosity of the pressure-sensitive adhesive is low and the workability is good. The value of the number average molecular weight (Mn) can be controlled by appropriately selecting the amounts of a chain transfer agent, a polymerization initiator, and the like to be added to the polymerization system. In the present invention, as the number average molecular weight (Mn) of the macromonomer, a value in terms of polystyrene measured by a GPC (gel permeation chromatography) method is adopted.

  The glass transition temperature of the polymer chain portion of the component (a2) is preferably from 50 ° C to 110 ° C. In such a range, the polymer chain portion forms a hard segment in the pressure-sensitive adhesive, so that the pressure-sensitive adhesive has cohesive force. As a result, the adhesiveness of the pressure-sensitive adhesive to the base material is improved, and excellent bending resistance can be exhibited. Alternatively, the glass transition temperature of the polymer chain portion of the component (a2) is preferably from −40 ° C. to −125 ° C. In such a range, since the component (a2) is a macromonomer having a polyorganosiloxane structure, compatibility with the acrylic resin can be ensured and low-temperature characteristics can be satisfied. Further, in such a range, the pressure-sensitive adhesive exhibits flexibility in a wide temperature range, so that the pressure-sensitive adhesive has good followability to the base material, and can exhibit excellent bending resistance (particularly at a low temperature). .

  As the component (a2), either a synthetic product or a commercially available product may be used. When the component (a2) is synthesized, there is no particular limitation on the synthesis method. For example, (1) a polymer chain (living polymer anion) constituting a macromonomer is produced by living anion polymerization, and methacrylic acid chloride or the like is acted on the polymer chain. (2) In the presence of a chain transfer agent such as mercaptoacetic acid, a radical polymerizable monomer such as methyl methacrylate is polymerized to obtain an oligomer having a carboxyl group at a terminal, which is then combined with glycidyl methacrylate or the like. (3) A radically polymerizable monomer such as methyl methacrylate is polymerized in the presence of an azo-based polymerization initiator containing a carboxyl group to obtain an oligomer having a carboxyl group at a terminal, and then the macromolecule is reacted with glycidyl methacrylate. Any method such as a method of monomerization can be used.

  By producing a macromonomer using the above-described method, for example, the following groups are introduced as the divalent bonding group represented by X in the above Chemical Formula 2.

  Commercially available products of the component (a2) include, for example, macromonomers (product name: 45% AA-6 (AA-6S), AA-6S whose terminal is a methacryl group and whose polymer chain is polymethyl methacrylate (PMMA)) -6; manufactured by Toagosei Co., Ltd.), a macromonomer having a polymer chain portion of polystyrene (product name: AS-6S, AS-6; manufactured by Toagosei Co., Ltd.), and a copolymer having a polymer chain portion of styrene / acrylonitrile (Product name: AN-6S; manufactured by Toagosei Co., Ltd.), a macromonomer having a polymer chain portion of polybutyl acrylate (product name: AB-6; manufactured by Toagosei Co., Ltd.), and a polymer chain portion of polyisobutyl Methacrylate macromonomer (product name: AW-6S; manufactured by Toagosei Co., Ltd.), polymer chain part of which is polydimethylsiloxy Down in a macro monomer (product name: AK-5; manufactured by Toagosei Co., Ltd.) and the like can be used. These macromonomers may be used alone or in combination of two or more.

  The content of the structural unit derived from the component (a2) in the copolymer (A) is defined assuming that the total amount of the structural units derived from the components (a1), (a2), (a3), and (a4) is 100% by mass. , 0.1 mass% or more and 15 mass% or less. When the content is less than 0.1% by mass, the effect of the addition of the component (a2) on the adhesive performance is not observed. On the other hand, if the content exceeds 15%, it becomes difficult to balance adhesion, durability, and bending resistance, and the transparency also decreases.

  In addition, as an embodiment of the present invention, the upper limit of the content is preferably 8% by mass or less from the viewpoint of bending resistance at high temperatures, and less than 5% by mass from the viewpoint of bending resistance at low temperatures. In addition, the lower limit of the content is preferably 0.5% by mass or more, and more preferably 1% by mass or more, from the viewpoint of obtaining the effect of the addition of the component (a2).

((A3) Functional group-containing monomer which is a (meth) acrylic acid derivative monomer not having a plurality of radically polymerizable functional groups)
In a preferred embodiment of the present invention, the (meth) acrylate copolymer (A) is a functional group-containing monomer (hereinafter referred to as (a3)) which is a (meth) acrylic acid derivative monomer having no plurality of radically polymerizable functional groups. (A3).

  The term “(meth) acrylic acid derivative” refers to a compound obtained using (meth) acrylic acid as a starting material, and is preferably (meth) acrylic acid ester or (meth) acrylamide.

  That is, the component (a3) has one of a methacryl group or an acrylic group and one or more functional groups other than the (meth) acryl group. It is preferably a (meth) acrylamide monomer.

  The component (a3) is an optional component, but has an effect of improving adhesiveness by being included in the pressure-sensitive adhesive of the present invention in combination with the component (a2) described above, whereby the intended effect of the present invention can be further improved. It can be played efficiently.

  When the monomer constituting the (meth) acrylate copolymer (A) corresponds to both the component (a1) and the component (a3), the monomer is classified as the component (a3).

  As the functional group contained in the component (a3), a functional group that reacts with the crosslinking agent when the crosslinking agent (B) is used is preferable, and a hydroxyl group, an acyl group, or an epoxy group is more preferable. By containing the copolymer (A) obtained by using such a monomer having a functional group in the adhesive, the copolymer (A) is crosslinked with the crosslinking agent (B), and the durability under high temperature is achieved. Is thought to improve. That is, in a preferred embodiment of the present invention, (a3) the functional group-containing monomer that is a (meth) acrylic acid derivative monomer having no plurality of radically polymerizable functional groups has a hydroxyl group, an acyl group, or an epoxy group (meth) It is an acrylic acid derivative monomer and is a pressure-sensitive adhesive for optical films.

{(A3-1) (meth) acrylate monomer having hydroxyl group, acyl group or epoxy group}
The (meth) acrylate monomer having a hydroxyl group, an acyl group or an epoxy group (hereinafter, also referred to as a component (a3-1)) is typically represented by the following chemical formula 3.

Here, in the above chemical formula 3,
R ₄ is a hydrogen atom or a methyl group,
R ₅ is a single bond or a divalent organic group,
R ₆ is a hydroxyl group, an acyl group or an epoxy group.

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

  Here, the divalent organic group is not particularly limited, but an alkylene group having 1 to 10 carbon atoms is preferable. Examples of the alkylene group having 1 to 10 carbon atoms include the same as described above. Further, the alkylene group or the acyl group substitutes at least one alkyl group having 1 to 8 carbon atoms, a phenoxyalkyl group (carbon number of the alkyl group: 1 to 8 carbon atoms), a phenyl group or a cyclohexyl group. It may have as a group. The alkyl group having 1 to 8 carbon atoms can be appropriately selected from the above.

  From 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 preferable, and among them, from the viewpoint of adhesiveness, 4-hydroxybutyl (meth) acrylate , 2-hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, acetoacetoxyethyl (meth) acrylate and the like are preferred. These can be used alone or in combination of two or more.

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

{(A3-2) (meth) acrylamide monomer having a hydroxyl group, an acyl group or an epoxy group}
A (meth) acrylamide monomer having a hydroxyl group, an acyl group or an epoxy group (hereinafter, also referred to as a component (a3-2)) is typically represented by the following chemical formula 4.

Here, in the above Chemical Formula 4, R ₇ is a hydrogen atom or a methyl group, R ₈ is a single bond or a divalent organic group, R ₉ is a hydroxyl group, an acyl group or an epoxy group, R ₁₀ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.

  The divalent organic group is not particularly limited, but is preferably an alkylene group having 1 to 10 carbon atoms. Further, the alkylene group or the acyl group may have at least one alkyl group having 1 to 8 carbon atoms, a phenyl group or a cyclohexyl group as a substituent.

  Examples of the alkyl group having 1 to 10 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, 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, Preferred are 2-ethylhexyl, nonyl, isononyl, decyl and the like.

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

  The alkylene group having 1 to 10 carbon atoms is a divalent substituent obtained by removing one hydrogen atom from the alkyl group having 1 to 10 carbon atoms.

  From the above, N- (2-hydroxyethyl) (meth) acrylamide, N- (2-hydroxypropyl) (meth) acrylamide, N- (2,2-dimethyl-β-hydroxyethyl) (meth) acrylamide, diacetone (Meth) acrylamide is preferred. Among them, N- (2-hydroxyethyl) (meth) acrylamide is particularly preferred from the viewpoint of improving the adhesiveness. These may be used alone or in combination of two or more.

  HEAA (registered trademark) (manufactured by KJ Chemicals Co., Ltd.) and DAAM (manufactured by Nippon Kasei Co., Ltd.) are suitable as commercially available products.

  The components (a3-1) and (a3-2) may be used alone or as a mixture. When the component (a3-1) and the component (a3-2) are used in combination, the glass transition temperature can be kept low while maintaining good adhesion to the polar substrate by ensuring hydrophilicity. .

  The content of the constituent units derived from the component (a3) in the copolymer (A) is defined assuming that the total amount of the constituent units derived from the components (a1), (a2), (a3) and (a4) is 100% by mass. , 0 mass% or more and 20 mass% or less. If the content exceeds 20% by mass, the balance of adhesion, durability and bending resistance is deteriorated due to the effects of the increase in the glass transition temperature and the degree of crosslinking. The lower limit of the content is preferably 0.1% by mass or more, and more preferably 2% by mass or more, from the viewpoint of bending resistance at high temperatures. The upper limit of the content is preferably less than 15 parts by mass from the viewpoint of bending resistance at a low temperature.

((A4) (meth) acrylate monomers other than (a1), (a2) and (a3))
The (meth) acrylic acid ester copolymer (A) of the present invention comprises a (meth) acrylic acid ester monomer other than the above (a1), (a2) and (a3) (hereinafter, component (a4), or simply (a4) ) May also be included.

  The component (a4) is not particularly limited as long as it is a (meth) acrylate monomer other than (a1), (a2) and (a3). From the viewpoint of lowering the glass transition temperature of the polymer (A), a (meth) acrylate monomer having an alkoxyalkyl group or an alkylene oxide group is preferred.

  The (meth) acrylate 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) acrylate ester molecule. It is considered that such components are contained in the pressure-sensitive adhesive of the present invention, and have an effect of improving adhesion and improving durability. In addition, by containing the component (a4), bending resistance at low temperatures can be imparted, and low-temperature characteristics can be secured without lowering adhesiveness. However, since the pressure-sensitive adhesive of the present invention contains the component (a2), the desired effect of the present invention can be exhibited even if the component (a4) is an optional component.

  The number of carbon atoms of the alkoxy moiety in the alkoxyalkyl group is not particularly limited, but is preferably 1 or more and 20 or less from the viewpoint of improving adhesion and durability, and efficiently exhibiting the intended effect of the present invention. Preferably, it has 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbon atoms, and particularly preferably 1 to 4 carbon atoms. As the alkoxy moiety having 1 to 20 carbon atoms, the specific examples listed above are preferable.

  The number of carbon atoms in the alkyl portion of the alkoxyalkyl group is not particularly limited, but is preferably 1 or more and 6 carbon atoms in view of the balance between the improvement in adhesion and the improvement in durability and the efficient effect of the present invention. The carbon number is preferably 1 or less, and more preferably 1 or more and 4 or less.

  The number of carbon atoms of the alkylene moiety in the alkylene oxide group is not particularly limited, but is preferably 1 or more and 4 carbon atoms from the viewpoint of improving adhesion and durability, and efficiently exhibiting the intended effects of the present invention. The number of carbon atoms is preferably 1 or more and 3 or less.

  The (meth) acrylate monomer having an alkoxyalkyl group or an alkylene oxide group is typically represented by the following chemical formula 5.

Here, in Chemical Formula 5, R ₁₁ is a hydrogen atom or a methyl group, and R ₁₂ is an alkoxyalkyl group or — (A—O) _n —X.

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

  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, more preferably 1 or more and 4 or less.

  X is an alkyl group. Such an alkyl group may be linear or branched, and preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, still more preferably 1 to 5 carbon atoms. And it is particularly preferable that the number is 1 or more and 3 or less. As specific examples of such an alkyl group, those listed above are preferable, and a methyl group, an ethyl group or a propyl group is particularly preferable.

  From the above, methoxyethyl (meth) acrylate, ethoxymethyl (meth) acrylate, ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, methoxypropyl (meth) acrylate, methoxybutyl (meth) Acrylates: 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- Triethylene glycol (meth) acrylate (n = 4 to 10), methoxy dipropylene glycol (meth) acrylate. These can be used alone or in combination of two or more.

  Among these, from the viewpoint of improving the adhesiveness and durability and efficiently exhibiting the intended 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 is more preferred. These can be used alone or in combination of two or more.

  Commercial products include AME (manufactured by Nippon Shokubai Co., Ltd.), Light Acrylate EC-A, Light Acrylate MTG-A, Light Acrylate EHDG-AT, Light Acrylate 130A, Light Acrylate DPM-A, (all manufactured by Kyoeisha Chemical Co., Ltd.) ), Biscoat # 190, 2-MTA, MPE400A, MPE550A (all manufactured by Osaka Organic Chemical Co., Ltd.).

  The content of the structural unit derived from the component (a4) in the copolymer (A) is defined assuming that the total amount of the structural units derived from the components (a1), (a2), (a3), and (a4) is 100% by mass. , 0 mass% or more and 90 mass% or less. When the content exceeds 90% by mass, the adhesiveness is lowered and the glass transition temperature is increased, and the balance among the adhesiveness, durability and bending resistance is deteriorated.

  Further, the upper limit of the content is preferably 49.9% by mass or less, more preferably 35% by mass or less from the viewpoint of durability and adhesiveness, and further more preferably from the viewpoint of bending resistance at low temperatures. Preferably it is less than 30% by mass.

  Even if the amount of the structural unit derived from the component (a4) is sufficiently small, for example, less than 5% by mass, the intended effect of the present invention is sufficiently exhibited because the component (a2) is essentially contained. Can be done.

(Production of (meth) acrylate copolymer (A))
The method for producing the (meth) acrylate copolymer (A) is not particularly limited, and may be a solution polymerization method, a bulk polymerization method, an emulsion polymerization method, a suspension polymerization method, a reverse phase suspension polymerization method, a thin film polymerization method. A conventionally known method such as a spray polymerization method can be used. Examples of the polymerization control method include an adiabatic polymerization method, a temperature-controlled polymerization method, and an isothermal polymerization method. In the above polymerization method, it is preferable to use a polymerization initiator. As the polymerization initiator, any of a thermal polymerization initiator and a photopolymerization initiator may be used. Alternatively, in addition to the method of initiating polymerization with a polymerization initiator, a method of initiating polymerization by irradiating radiation, an electron beam, ultraviolet light, or the like may be employed. Among them, (i) a solution polymerization method using a thermal polymerization initiator or (ii) a bulk polymerization method using a photopolymerization initiator is preferable. Further, the polymerization method (i) is particularly preferable because the molecular weight can be easily adjusted and the amount of impurities is small. For example, using a solvent such as ethyl acetate, toluene, or methyl ethyl ketone, the polymerization initiator is preferably 0.001 part by mass with respect to 100 parts by mass of the total amount of the raw material monomers of the (meth) acrylate copolymer (A). As described above, more preferably, 0.01 to 0.50 parts by mass is added, and the reaction is carried out under a nitrogen atmosphere, for example, at a reaction temperature of 60 to 90 ° C. for 3 to 10 hours.

  Examples of the thermal polymerization initiator include 2,2-azobisisobutyronitrile (AIBN), 2,2′-azobis (2-methylbutyronitrile), azobiscyanovaleric acid, and 2,2′-azobis (4 -Methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis (2.4-dimethylvaleronitrile), dimethyl 2,2'-azobis (2-methylpropionate), 2,2'-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis [N- (2-propenyl) -2-methylpropionamide], 2,2 ′ -Azobis (N-butyl-2-methylpropionamide), 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis 2- (2-imidazolin-2-yl) propane] disulfate dihydrate, 2,2′-azobis (2-methylpropionamidine) dihydrochloride, 2,2′-azobis [N- (2-carboxyethyl ) -2-Methylpropionamidine] hydrate, 2,2′-azobis [2- (2-imidazolin-2-yl) propane], 2,2′-azobis (1-imino-1-pyrrolidino-2-methyl) Azo compounds such as propane) dihydrochloride and 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide]; tert-butylperoxypivalate, tert-butylperoxybenzoate, tert-butyl Peroxy-2-ethylhexanoate, di-tert-butyl peroxide, cumene high B peroxide, benzoyl peroxide, organic peroxides such as tert- butyl hydroperoxide; hydrogen peroxide, ammonium persulfate, potassium persulfate, inorganic peroxides such as sodium persulfate. These may be used alone or in combination of two or more.

  Examples of the photopolymerization initiator include acetophenone, 3-methylacetophenone, benzyldimethylketal, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-methyl-1- [4 Acetophenones such as-(methylthio) phenyl] -2-morpholinopropan-1-one and 2-hydroxy-2-methyl-1-phenylpropan-1-one; benzophenone, 4-chlorobenzophenone, 4,4'-diamino Benzophenones such as benzophenone; benzoin ethers such as benzoin propyl ether and benzoin ethyl ether; thioxanthones such as 4-isopropylthioxanthone; xanthone, fluorenone, camphorquinone, benzaldehyde, and anthraquinone. These may be used alone or in combination of two or more.

  As the photopolymerization initiator, commercially available products may be used. For example, Irgacure (registered trademark) -184, 819, 907, 651, 1700, 1800, 819, 369, 261, Darocure (registered trademark) -TPO, Darocure (registered trademark) ) -1173 (above, manufactured by BASF Japan Co., Ltd.), EZACURE (registered trademark) KIP150, TZT (above, manufactured by DKSH Japan Co., Ltd.), Kayacure (registered trademark) BMS, DMBI (above, manufactured by Nippon Kayaku Co., Ltd.) Is mentioned.

  In addition, in synthesizing the (meth) acrylate copolymer (A), a chain transfer agent may be used in order to adjust the molecular weight. 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 esters thereof, 2-ethylhexylthioglycol, thioglycol Mercaptans such as octyl acid; alcohols such as methanol, ethanol, propanol, n-butanol, isopropanol, t-butanol, hexanol, benzyl alcohol and allyl alcohol; halogenated hydrocarbons such as chloroethane, fluoroethane and trichloroethylene; acetone , Methyl ethyl ketone, cyclohexanone, acetophenone, acetaldehyde, propionaldehyde n- butyraldehyde, furfural, carbonyls, such as benzaldehyde; methyl-4-cyclohexene-1,2-dicarboxylic acid anhydride, such as α- methyl styrene. These may be used alone or in combination of two or more.

  The amount of each raw material monomer used in producing the (meth) acrylic acid ester copolymer (A) is such that the component (a1) is at least 9.9% by mass and at most 99.9% by mass, and (a2) The component is made 0.1% by mass or more and 15% by mass or less, the component (a3) is made 0% by mass or more and 20% by mass or less, and the component (a4) is made 0% by mass or more and 90% by mass or less. The preferred ranges of these amounts are as described above.

  As described above, the pressure-sensitive adhesive for an optical film of the present invention is a pressure-sensitive adhesive for an optical film, including the (meth) acrylate copolymer (A), wherein the (meth) acrylate copolymer ( A) is (a1) a structural unit derived from an alkyl (meth) acrylate monomer in the range of 9.9% by mass to 99.9% by mass; and (a2) a structural unit derived from a macromonomer having a polymerizable functional group. (A3) a structural unit derived from a functional group-containing monomer that is a (meth) acrylic acid derivative monomer having no plurality of radically polymerizable functional groups, and 0% to 20% by mass; (A4) a structural unit derived from a (meth) acrylate monomer other than (a1), (a2) and (a3), from 0% by mass to 90% by mass; 2) The total amount of the structural units derived from (a3) and (a4) is 100% by mass, and the (meth) acrylate copolymer has a glass transition temperature of -70 ° C or more and -57 ° C or less. And the weight average molecular weight is more than 1,000,000 and not more than 2.5,000,000.

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

[Crosslinking agent (B)]
It is preferable that the pressure-sensitive adhesive of the present invention further contains a crosslinking agent (B) in order to exhibit the intended effects of the present invention efficiently.

  The type of the crosslinking agent (B) that can be used for the pressure-sensitive adhesive of the present invention is not particularly limited, and isocyanate compounds, carbodiimide compounds, oxazoline compounds, epoxy compounds, polyfunctional acrylate monomers, peroxides, and titanium coupling agents. , A zirconium compound, a metal aluminum chelate, a hydrazide compound, and a thermal acid generator. In particular, when the crosslinking agent (B) is an isocyanate compound, a carbodiimide compound, an oxazoline compound, an epoxy compound (except when it corresponds to the components (a1), (a2), (a3) and (a4)), a polyfunctional acrylic It is preferably at least one selected from the group consisting of an acid ester monomer (excluding cases corresponding to the components (a1), (a2), (a3) and (a4)) and a peroxide. From the viewpoint of ensuring durability and at least one of an isocyanate compound and a peroxide, it is preferable.

  The crosslinking agent (B) of the present invention includes those which form a crosslinked structure by themselves (curing agent type), and those which do not form a crosslinked structure by themselves but which promote a crosslinking reaction (curing catalyst) Type), and particularly the latter are peroxides, thermal acid generators and the like.

  The amount of the crosslinking agent (B) to be added is preferably 0.001 to 20 parts by mass, more preferably 0.1 to 100 parts by mass, based on 100 parts by mass of the (meth) acrylate copolymer (A). It is from 0.01 to 5 parts by mass, and more preferably from 0.01 to 1 part by mass from the viewpoint of adhesiveness and durability. Further, the upper limit of the addition amount of the crosslinking agent (B) is particularly preferably less than 1% by mass from the viewpoints of adhesiveness and bending resistance under high temperature and high humidity.

  That is, a preferred embodiment of the present invention is a pressure-sensitive adhesive for an optical film, which further contains a crosslinking agent (B). In another preferred embodiment of the present invention, the crosslinking agent (B) is contained in an amount of 0.001 to 20 parts by mass based on 100 parts by mass of the (meth) acrylate copolymer (A). Is an adhesive for optical films.

(Isocyanate compound)
The isocyanate compound suitably used as the crosslinking agent (B) is not particularly limited, and examples thereof include triallyl isocyanate, dimer acid diisocyanate, 2,4-tolylene diisocyanate (2,4-TDI), and 2,6-triisocyanate. Diisocyanate (2,6-TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylene diisocyanate, xylylene Aromatic diisocyanates such as diisocyanate (XDI), tetramethylxylidene diisocyanate (TMXDI), tolidine diisocyanate (TODI) and 1,5-naphthalenediisocyanate (NDI); hexamethylene diisocyanate (HDI), trimethylhexyl Aliphatic diisocyanates such as samethylene diisocyanate (TMHDI), lysine diisocyanate, norbornane diisocyanatomethyl (NBDI); transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), H6-XDI (hydrogenated XDI), H12 -Alicyclic diisocyanates such as -MDI (hydrogenated MDI); carbodiimide-modified diisocyanates of the above diisocyanates; or isocyanurate-modified diisocyanates thereof; one or more of these can be used. Moreover, you may use together with the peroxide mentioned later. Adducts of the above isocyanate compounds and polyol compounds such as trimethylolpropane, and biuret and isocyanurate forms of these isocyanate compounds can also be suitably used.

  The isocyanate compound may be synthesized or a commercially available product may be used.

  Commercially available products include, for example, 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) Trademark) 24A-100, Duranate (R) TPA-100, Duranate (R) TKA-100, Duranate (R) P301-75E, Duranate (R) E402-90T, Duranate (R) E405-80T. , Duranate (registered trademark) TSE-100, Duranate Nate (registered trademark) D-101, Duranate (registered trademark) D-201 (all manufactured by Asahi Kasei Chemicals Corporation), Sumijur (registered trademark) N-75, N-3200, N-3300 (all manufactured by Sumika Bayer) Urethane Co., Ltd.). Among these, Coronate (registered trademark) L, Coronate (registered trademark) HL, Coronate (registered trademark) HX, Takenate (registered trademark) D-110N, Duranate (registered trademark) 24A-100, and 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 suitably used as the crosslinking agent (B) is not particularly limited, and examples thereof include those described in paragraphs “0039” to “0046” of JP-A-2012-246444 or those obtained by appropriately modifying them. Can be

(Oxazoline compound)
The oxazoline compound suitably used as the cross-linking agent (B) is not particularly limited, and examples thereof include those described in paragraphs “0031” to “0037” of JP-A-2015-087539 or those appropriately modified. No.

(Epoxy compound)
As the epoxy crosslinking agent (epoxy compound), any appropriate epoxy crosslinking agent can be adopted. Commercially available products include, for example, "Tetrad C" and "Tetrad X" manufactured by Mitsubishi Gas Chemical Co., Ltd., "ADEKARESIN EPU series" and "ADEKARESIN EPR series" manufactured by ADEKA Corporation, and "CELLOXIDE" manufactured by Daicel Corporation. And the like. In particular, liquid epoxy resins such as these are preferred because the operation of mixing the adhesive when producing the adhesive layer is facilitated.

(Polyfunctional acrylate monomer)
Examples of the polyfunctional acrylate monomer include a hydrocarbon-based or hydrocarbon ether-based polyfunctional monomer. The hydrocarbon-based or hydrocarbon-ether-based polyfunctional monomer is a compound obtained by (meth) acrylate-forming a hydroxyl group of a polyhydric alcohol having a main skeleton of a hydrocarbon group having 10 to 100 carbon atoms or a hydrocarbon ether group. 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 obtained by 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 to 4 carbon atoms to the polyhydric alcohol (addition number: 1 to 30), or a compound having 2 or more carbon atoms. And polyalkylene glycols (addition numbers of 1 to 30) obtained from alkylene oxides of 4 or less.

  Specific examples of the hydrocarbon-based bifunctional monomer include, for example, 1,3-butylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) A) acrylates, di (meth) acrylates of alkylene glycols such as neopentyl glycol di (meth) acrylate; alicyclic carbonizations such as cyclohexane dimethanol di (meth) acrylate and tricyclodecane dimethanol di (meth) acrylate Di (meth) acrylate of a diol compound having a hydrogen group; di (meth) acrylate of a diol compound having an aromatic hydrocarbon group such as bisphenol A di (meth) acrylate;

  Specific examples of the hydrocarbon ether-based bifunctional monomer include, for example, alkoxylated hexanediol di (meth) acrylate, alkoxylated cyclohexane dimethanol di (meth) acrylate, and alkoxylated di (meth) acrylate. Dialkyl (meth) acrylates such as alkoxylated neopentyl glycol di (meth) acrylate and alkoxylated bisphenol A di (meth) acrylate, and di (alkylene glycol or diol compounds described above) to which dialkylene compound is added with alkylene oxide. (Meth) acrylate and the like. 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, polyethylene glycol di (meth) acrylate, Examples thereof include poly (alkylene glycol) di (meth) acrylates 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, for example, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, glyceryl tri (meth) acrylate, Tri (meth) acrylate or tetra (meth) acrylate of tri or tetraol compounds such as pentaerythritol tetra (meth) acrylate and trimethylolpropane tetra (meth) acrylate, and compounds obtained by adding an alkylene oxide to the above tri or tetraol compound Tri (meth) acrylate or tetra (meth) acrylate.

  Examples of the non-urethane-based multifunctional monomer (b) other than the hydrocarbon-based or hydrocarbon-ether-based polyester include polyester (poly) (meth) acrylate and epoxy (meth) acrylate having two or more (meth) acrylate groups at terminals. And the like.

(Peroxide)
As the peroxide suitably used as the crosslinking agent (B), any peroxide can be used as long as it can generate a radical by heating to achieve crosslinking of the pressure-sensitive adhesive. It is preferable to use a peroxide having a half-life time of preferably from 80 ° C to 160 ° C, more preferably from 90 ° C to 140 ° C. The half-life of peroxide is an index indicating the rate of decomposition of peroxide, and is the time during which the amount of decomposition of peroxide is halved, and the decomposition temperature for obtaining a half-life at any time. The half-life at an arbitrary temperature is described in a manufacturer's catalog and the like. For example, it is described in the 9th edition of the organic peroxide catalog issued by NOF Corporation (May 2003). 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-butyl peroxydicarbonate (92.4 ° C.), t-butyl peroxy neodecanoate (103.5 ° C.), t-hexyl peroxypivalate, (109.1 ° C.) ), T-butyl peroxypivalate (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), dibenzoy Bis (4-t-butylcyclohexyl) peroxydicarbonate and dilauroylperoxide which are excellent in crosslinking reaction efficiency, such as peroxide (130.0 ° C) and t-butylperoxybutyrate (136.1 ° C). Oxides and dibenzoyl peroxide are preferably used. In particular, bis (4-t-butylcyclohexyl) peroxydicarbonate is preferred from the viewpoint of decomposition temperature. One or more of these can be used. Moreover, you may use together with the above-mentioned isocyanate compound.

(Titanium coupling agent)
The titanium coupling agent suitably used as the crosslinking agent (B) is not particularly limited, and includes, for example, those described in paragraph “0072” of JP-A-2014-085616 or those appropriately modified.

(Zirconium compound)
The zirconium compound suitably used as the cross-linking agent (B) is not particularly limited, and includes, for example, those described in paragraph “0073” of JP-A-2014-085616 or those appropriately modified.

(Metal aluminum chelate)
The metal aluminum chelate suitably used as the cross-linking agent (B) is not particularly limited, and examples thereof include those described in paragraph “0058” of JP-A-2012-229373 and paragraph “0058” of JP-A-2008-251089. 0037 ”or those appropriately modified.

(Hydrazide compound)
The hydrazide compound is not particularly limited, and a hydrazine-based crosslinking agent having at least two hydrazino groups and semicarbazide groups is suitable. Examples of the compound having at least two hydrazino groups include polyhydrazide of an aliphatic polybasic acid such as oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide and the like; Polyhydrazide of polybasic acid; polyhydrazide of polyacrylic acid; polyhydrazide of aromatic hydrocarbon; hydrazine-pyridine derivative; polyhydrazide of unsaturated polybasic acid such as maleic dihydrazide; and polyhydrazide carbonate. Further, as the compound having at least two semicarbazide groups, for example, semicarbazide compounds such as polysemicarbazide such as aliphatic, alicyclic, and aromatic can be used.

(Thermal acid generator)
Examples of the thermal acid generator include hexafluoroantimonate-based sulfonium salts exemplified as the energy acid generator, and commercially available products include SI-60, SI-60L, SI-80, SI-80L, and SI-80. 100, SI-100L (manufactured by Sanshin Chemical Co., Ltd.) and CI-2624 (manufactured by Nippon Soda Co., Ltd.). The thermal acid generator may be used alone or in combination of two or more.

  That is, in a preferred embodiment of the present invention, the crosslinking agent (B) is at least one of an isocyanate compound, a carbodiimide compound, an oxazoline compound, an epoxy compound, a polyfunctional acrylate monomer, a peroxide, a hydrazide compound, and a thermal acid generator. It is a kind of adhesive for optical films.

[Silane coupling agent (C)]
The pressure-sensitive adhesive of the present invention can further contain a silane coupling agent (C) from the viewpoint of improving adhesiveness. Either component (C) or component (B) may be used, or both may be used in combination.

  The silane coupling agent refers to a compound having no siloxane bond and having two or more different reactive groups in a molecule.

  The silane coupling agent (C) used in the pressure-sensitive adhesive of the present invention is not particularly limited. For example, 3-glycidoxypropyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, n-propyl Trimethoxysilane, ethyltrimethoxysilane, diethyldiethoxysilane, n-butyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, cyclohexylmethyldimethoxysilane, vinyl Trichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glyciyl Doxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxy Propylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropylmethyldimethoxysilane, N-β- (aminoethyl)- γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltri Methoki Silane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, bis- (3- [triethoxysilyl] propyl) tetrasulfide, γ-isocyanatopropyltriethoxysilane, etc. No. Furthermore, a silane coupling agent having a functional group such as an epoxy group (glycidoxy group), an amino group, a mercapto group, and a (meth) acryloyl group; and a silane coupling agent containing a functional group having reactivity with these functional groups. A compound having a hydrolyzable silyl group obtained by reacting a ring agent, another coupling agent, a polyisocyanate, or the like at an arbitrary ratio for 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-403. 803, KBE-846 and KBE-9007 (all manufactured by Shin-Etsu Chemical Co., Ltd.).

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

  In the present invention, the addition amount when the silane coupling agent (C) is contained is more preferably 0.0001 to 10 parts by mass, based on 100 parts by mass of the copolymer (A), It is more preferably from 0.001 to 5 parts by mass, particularly preferably from 0.01 to 3 parts by mass. Within such a range, the durability can be improved. That is, in a preferred embodiment of the present invention, the silane coupling agent (C) is contained in an amount of from 0.001 to 5 parts by mass based on 100 parts by mass of the (meth) acrylate copolymer (A). , An optical film adhesive.

[Application]
The pressure-sensitive adhesive of the present invention described above is suitable for various uses. For example, it is preferably used for an optical film. Such an optical film is not particularly limited and includes those used for forming an image display device such as a liquid crystal display device. Examples thereof include at least a polarizing plate or a retardation plate, and further include a conductive layer and a protective layer. And at least one of the above, a cover film, a transparent conductive film, a window film, an optical compensation film such as a viewing angle widening film for improving the viewing angle of a liquid crystal display, a brightness enhancement film for increasing the contrast of the display, and more. The thing which these were laminated | stacked is mentioned.

  In the present invention, there is provided a form of a pressure-sensitive adhesive layer formed by the above-mentioned pressure-sensitive adhesive, and a form of an optical member having the pressure-sensitive adhesive layer formed on an optical film or the like. Further, the optical member is an adhesive optical film (for example, an adhesive polarizing plate), or the optical member is a liquid crystal display, an organic EL display, a plasma display (PDP), a curved display, a flexible display, or the like. And the like which are applied to the image display device or the like.

<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 substrate or the like, and drying and removing a solvent and the like. In applying the adhesive, one or more solvents may be newly added as appropriate.

  In addition, as a 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 coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, extrusion coating with a die coater, etc. Method.

  As a method for drying the solvent present 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 from 40 ° C to 200 ° C, more preferably from 50 ° C to 180 ° C, and particularly preferably from 70 ° C to 170 ° C. By setting the heating temperature within the above range, a pressure-sensitive adhesive layer having excellent pressure-sensitive adhesive properties can be obtained.

  The drying time can be appropriately set, but is preferably 5 seconds to 30 minutes, more preferably 5 seconds to 20 minutes, and particularly preferably 10 seconds to 15 minutes. The heating and drying can be performed two or more times 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 for 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 still more preferably 10 μm or more and 120 μm or less from the viewpoints of adhesiveness, durability and bending durability. Is particularly preferred.

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

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

Storage modulus at -20 ° C. for the adhesive layer (G '(- 20)) is 5 preferably × at ¹⁰ 4 Pa or less, more preferably 4 × ¹⁰ 4 Pa or less, 3 × 10 ⁴ Even more preferably, it is Pa or less.
Further, 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 1.0 × 10 ⁴ Pa or more, and from the viewpoint of durability, it is 1.2 × 10 ⁴ Pa or more. More preferred. Further, the upper limit of the storage elastic modulus (G ′ (85)) at 85 ° C. is more preferably 2 × 10 ⁵ Pa or less, further preferably 1 × 10 ⁵ Pa or less.

  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. In light of the above, it is preferably 1.0 or more and 5.0 or less, and more preferably 1.1 or more and 4.0 or less. Still more preferably, G '(-20) / G' (85) is 1.1 or more and less than 3.0 from the viewpoint of durability at high temperatures. The storage modulus is measured by the method described in the 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 sheet (separator) or the like that has been subjected to a release treatment until practical use.

  As a constituent material of the separator, for example, polyethylene, polypropylene, polyethene terephthalate, plastic films such as polyester films, paper, cloth, porous materials such as nonwoven fabrics, nets, foam sheets, metal foils, and laminates thereof An appropriate thin leaf body may be used, but a plastic film is preferably used because of its excellent surface smoothness.

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

  If necessary, the separator may be a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based release agent, release treatment and antifouling treatment with silica powder, coating type, kneading type, vapor deposition. Antistatic treatment of a mold or the like can be performed. In particular, by appropriately performing a release treatment such as a silicone treatment, a long-chain alkyl treatment, or a fluorine treatment on the surface of the separator, the releasability from the pressure-sensitive adhesive layer can be further improved.

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

<Optical members>
The present invention also provides an optical member having the pressure-sensitive adhesive layer of the present invention 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 configuration in which a pressure-sensitive adhesive layer is formed by directly applying the pressure-sensitive adhesive of the present invention to one or both surfaces of an optical film, or indirectly via an easy-adhesion layer. Alternatively, a configuration in which an adhesive layer is formed may be used. Therefore, in a preferred embodiment of the present invention, there is also provided an optical member having an easy-adhesion layer between the optical film and the pressure-sensitive adhesive layer.

  As the easy-adhesion layer, a material for treating the surface of a member that comes into contact with the pressure-sensitive adhesive layer, such as corona treatment or plasma treatment, or a separate member such as a primer layer, a member that comes into contact with the pressure-sensitive adhesive layer, May be provided on the surface. That is, a preferred embodiment of the present invention is an optical member in which 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.

[Primer layer]
In the present invention, the material for forming the primer layer is suitable for both the pressure-sensitive adhesive layer and the optical film (for example, a transparent protective film in the case of a polarizing plate) (or a member that comes into contact with the pressure-sensitive adhesive layer), or a normal optical film. Those which show adhesion and form a film having excellent cohesion are preferred. For example, various polymers, metal oxide sols, silica sols and the like are used, and among them, polymers are particularly preferably used. The primer layer may have an antistatic function as described above.

  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 the oxazoline group-containing polymer, a general commercial product is used, and examples thereof include, but are not limited to, Epocross (registered trademark) series manufactured by Nippon Shokubai Co., Ltd. (for example, Epocross (registered trademark) WS700). As for polyurethane resins, polyester resins, polymers containing an amino group in the molecule, and the like, those disclosed in paragraphs “0107” to “0113” of JP-A-2011-105918 can be appropriately employed.

  In the present invention, a primer layer for forming a primer layer can be applied and dried on the optical film by using a coating method such as a coating method, a dipping method and 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 properties as a bulk and can maintain optical characteristics while exhibiting sufficient strength and sufficient adhesion.

  As described above, according to a 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 may be indium tin oxide (ITO), silver nanowire, indium zinc oxide, or indium oxide. Selected from the group consisting of zinc oxide composite oxides, polythiophenes, carbon nanotubes, aluminum zinc oxide, gallium zinc oxide, zinc fluoride oxide, indium fluoride oxide, antimony tin oxide, tin fluoride oxide and phosphorus tin oxide Preferably, at least one kind is used.

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

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

Hereinafter, a case where the optical film according to the present invention is a polarizing plate will be described as an example.

[Polarizer]
In the present invention, a polarizing plate suitable as an optical film is manufactured by bonding a protective film and a polarizer using an adhesive, heating and drying or curing with an electron beam or the like by a conventionally known method. obtain. The applied adhesive expresses adhesiveness by drying or curing by ultraviolet rays, electron beams, or the like, and forms an adhesive layer. Further, in the present invention, even when a film such as a retardation film is bonded to a polarizer, the retardation film is considered as a part of the polarizing plate. In some cases, the retardation film is used as a protective film for protecting the polarizer.

  The polarizer is not particularly limited, and a conventionally known polarizer can be used. For example, a dichroic material such as iodine or a dichroic dye is adsorbed on a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, an ethylene-vinyl acetate copolymer partially saponified film, and thus uniaxially. Stretched materials, polyene oriented films such as polyvinyl alcohol dehydration products and polyvinyl chloride dehydrochlorination products, etc., are exemplified.

  Among them, a polarizer produced by dyeing a polyvinyl alcohol film having an average degree of polymerization of 2,000 to 2,800 and a degree of saponification of 90 to 100% by mol with iodine and uniaxially stretching the film to 3 to 8 times, is particularly preferable. . More specifically, such a polarizer is obtained by, for example, immersing a polyvinyl alcohol film in an aqueous solution of iodine, dyeing the film, and stretching the film. The aqueous solution of iodine is preferably immersed in an aqueous solution containing, for example, 0.1% by mass or more and 1.0% by mass or less of iodine and / or potassium iodide. If necessary, the film may be immersed in an aqueous solution of boric acid or potassium iodide at 50 ° C. or higher and 70 ° C. or lower, or stretched. In addition, in order to wash and prevent uneven dyeing, it may be immersed in water at 25 ° C. or more and 35 ° C. or less.

  The stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be stretched and then dyed 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 more and 55 ° C. or less for about 1 minute or more and 10 minutes or less. There are a wide variety of such polarizers.

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

  As the protective film, a material having excellent transparency, mechanical strength, heat stability, moisture barrier properties, isotropy, and the like is preferable. For example, a cellulose resin such as triacetyl cellulose, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate, a polyether sulfone resin, a polysulfone resin, a polycarbonate resin, a polyamide resin, a polyimide resin, a polyolefin resin, and a (meth) acryl such as polymethyl methacrylate. 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. In this case, a transparent protective film or a (meth) acrylic, urethane, acrylic, A thermosetting resin such as a 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. In the present invention, the thickness is preferably 100 μm or less from the viewpoint of thinning and bending. Therefore, according to a 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. Further, the thickness is 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 effects of the pressure-sensitive adhesive of the present invention.

  The method for manufacturing the polarizing plate is not particularly limited, and for example, after applying an adhesive, the polarizing plate and the protective film can be bonded by a roll laminator or the like.

  After lamination, a drying step or a curing step with ultraviolet rays, an electron beam or the like may be appropriately performed.

  When applying the adhesive, the adhesive 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. In addition, the adhesive is not particularly limited, and may be appropriately selected from known adhesives 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 acryl-epoxy-based adhesive can be used as the polyvinyl alcohol-based adhesive or the ultraviolet-curable adhesive.

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

<Image display device>
The present invention also provides an image display device using at least one of the optical members described above.

  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). From the viewpoint of more remarkably exhibiting the effects 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, or the like. That is, a preferred embodiment of the present invention is an image display device that is a curved display or a flexible display.

  As described above, the present invention relates to an optical film pressure-sensitive adhesive, an optical film pressure-sensitive adhesive layer, a pressure-sensitive adhesive optical film, and an image display device. It is possible to provide a pressure-sensitive adhesive that hardly peels or floats even when the film is deformed and subjected to a long-term holding or bending test. Further, the pressure-sensitive adhesive of the present invention is suitably used for lamination of a thin-layer adherend including an optical film or sheet, and further various films or sheets used for a liquid crystal display element such as a flexible display and an electroluminescence element. It can be suitably used for the production of and is commercially available in these technical fields.

  Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. All parts and percentages in each example are based on mass. Hereinafter, all room temperature storage conditions not particularly specified are 23 ° C./55% RH.

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

・ Analyzer: Tosoh Corporation, HLC-8120GPC
・ Column: G7000HXL + GMHXL + GMHXL, manufactured by Tosoh Corporation
・ Column size: 7.8mmφ × 30cm each 90cm in total
-Column temperature: 40 ° C
・ Flow rate: 0.8 ml / min
・ Injection volume: 100 μl
・ Eluent: tetrahydrofuran ・ Detector: differential refractometer (RI)
-Standard sample: polystyrene.

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

  A polyvinyl alcohol film having a thickness of 20 μm was stretched up to 3 times while being dyed in a 0.3% iodine solution at 30 ° C. for 1 minute between rolls having different speed ratios. Thereafter, the film was stretched while immersing it in an aqueous solution containing boric acid of 4% concentration and 10% of potassium iodide at 60 ° C. for 0.5 minute until the total stretching ratio became 6 times. Next, after washing by immersion in an aqueous solution containing 1.5% concentration of potassium iodide at 30 ° C. for 10 seconds, drying was performed at 50 ° C. for 4 minutes to obtain a polarizer 4 having a thickness of 7 μm.

  On one side of the polarizer 4, a polycarbonate-based film 2 having a thickness of 20 μm, and on the opposite side of the polarizer 4, a retardation film 6 having a thickness of 50 μm (１ ／ wavelength plate, “WRS” manufactured by Teijin Limited) ) Were bonded with polyvinyl alcohol-based adhesives 3 and 5, respectively, to produce a thin polarizing plate 1 having a total thickness of 77 μm.

<Creation of conductive layer>
As shown in FIG. 1, the following conductive layer forming paint is applied to the surface of the retardation film 6 of the thin polarizing plate by a die coating method so that the solid content is 1 g / m ^2. After drying, the conductive layer 7 was laminated on the retardation film 6.

(Coating for forming conductive layer)
70 parts by mass of ultrapure water (Wako Pure Chemical Industries, Ltd., Ultrapure Water Ultrapure Water) per 30 parts by mass of a silver nanowire dispersion solution (Claraohm Ink-A AQ, manufactured by Cambrios, USA), and a rust inhibitor (Cambridge, US) Co., Ltd., ClearOhm SFT-D) was added in an amount of 0.12 parts to prepare a conductive layer forming paint.

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

(Paint for forming protective layer)
95 parts by mass of ethyl acetate was added to 5 parts by mass of an acrylic resin-based paint (manufactured by China Paint Co., Ltd., FOLDEID No. 420C resin concentration: 50% by mass) to prepare a paint for forming a protective layer.

(Production Example 1)
<Preparation of (meth) acrylate copolymer (A1)>
90 parts of 2-ethylhexyl acrylate, 2 parts of methyl methacrylate macromonomer AA-6 (manufactured by Toagosei Co., Ltd.) and 4 parts of 4-hydroxybutyl were placed in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. After charging 8 parts of acrylate and 0.1 part of 2,2′-azobisisobutyronitrile (AIBN) as a polymerization initiator together with 100 parts of ethyl acetate, introducing nitrogen gas while gently stirring to replace with nitrogen, The polymerization reaction was carried out for 5 hours while maintaining the temperature of the liquid in the flask at around 55 ° C. to prepare a solution of the (meth) acrylate copolymer (A1) having a Mw (weight average molecular weight) of 1.7 million.

(Production Examples 2-19, 21-25, 27-28)
In Production Example 1, except that the kind of the monomer forming the (meth) acrylic acid ester copolymer (A) or the ratio thereof and the polymerization initiator were changed as shown in Table 1, the same as in Production Example 1, Solutions of (meth) acrylate copolymers (A2) to (A19), (A21) to (A25), and (A27) to (A28) were prepared. Table 1 shows the Tg (glass transition temperature) and Mw (weight average molecular weight) of the (meth) acrylate copolymers (A2) to (A19), (A21) to (A25), and (A27) to (A28). As shown in FIG.

(Production Example 20)
Acrylic syrup (A20) was prepared as shown below.

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

  90 parts of 2-ethylhexyl acrylate and methyl methacrylate macromonomer AA-6 (manufactured by Toagosei Co., Ltd.) were placed in a 2-liter four-necked flask equipped with a stirrer, a thermometer, a nitrogen gas inlet tube and a cooling tube in the above box. Two parts and 8 parts of 4-hydroxybutyl acrylate were charged, and the flask was heated to 30 ° C. while replacing the air in the flask with nitrogen.

  Next, 0.005 part of 2,2-dimethoxy-1,2-diphenylethan-1-one (Irgacure (registered trademark) 651, manufactured by BASF Japan Co., Ltd.) was charged as a polymerization initiator under stirring and uniformly. Mixed.

Here, black light (integrated light amount: 200 mJ / cm ² ) was applied to start polymerization. After the start of the reaction, the temperature of the reaction system rose, but when the rise in the reaction temperature from the start reached 10 ° C., the reaction was forcibly stopped by introducing air into the flask with an air pump, and the acrylic A syrup (A20) was obtained. The Tg (glass transition temperature) and Mw (weight average molecular weight) of the (meth) acrylate copolymer in the acrylic syrup (A20) are as shown in Table 1.

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

  90 parts of 2-ethylhexyl acrylate, 2 parts of methyl methacrylate macromonomer AA-6 (manufactured by Toagosei Co., Ltd.) were placed in a two-liter four-necked flask equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, and a cooling tube. -Hydroxybutyl acrylate (8 parts) and n-dodecyl mercaptan (0.1 parts) as a chain transfer agent were charged, and the flask was heated to 50 ° C while replacing the air in the flask with nitrogen. Next, 0.0025 parts of 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) (V-70; manufactured by Wako Pure Chemical Industries, Ltd.) was added as a polymerization initiator under stirring. Mix evenly.

  After the addition of the polymerization initiator, the temperature of the reaction system increased, but when the polymerization reaction was continued without cooling, the temperature of the reaction system reached 120 ° C., and then gradually started to decrease. When the temperature of the reaction system dropped to 115 ° C., 27 parts of 2-ethylhexyl acrylate, 0.6 part of methyl methacrylate macromonomer AA-6 (manufactured by Toagosei Co., Ltd.), 2.4 parts of 4-hydroxybutyl acrylate, and n- 0.08 part of dodecyl mercaptan was charged and forced cooling was performed to cool to 50 ° C. Further, 0.005 part of V-70 as a polymerization initiator was charged with stirring and uniformly mixed.

  After the addition of the polymerization initiator, 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 began to gradually decrease. When the temperature of the reaction system dropped to 120 ° C., 20.7 parts of 2-ethylhexyl acrylate, 0.46 parts of methyl methacrylate macromonomer AA-6 (manufactured by Toagosei Co., Ltd.), and 1.84 parts of 4-hydroxybutyl acrylate were added. The mixture was charged and forcedly cooled to obtain an acrylic syrup (A26). The Tg (glass transition temperature) and Mw (weight average molecular weight) of the (meth) acrylate copolymer in the acrylic syrup (A26) are as shown in Table 1.

  The glass transition temperature of the (meth) acrylate copolymer (A) is a theoretical value calculated from the FOX equation based on the monomer units constituting each polymer and the ratio thereof.

Formula of FOX: 1 / Tg = w1 / Tg1 + w2 / Tg2 +... + Wn / Tgn
(Tg: glass transition temperature of polymer (K), Tg1, Tg2,... Tgn: glass transition temperature of homopolymer of each monomer (K), w1, w2,... Wn: weight fraction of each monomer )
Note that the theoretical glass transition temperature obtained from the above-mentioned FOX equation agrees well with the measured glass transition temperature obtained by differential scanning calorimetry (DSC), dynamic viscoelasticity, or the like.

In Table 1, the abbreviations are as follows:
(A1) Component 2EHA: 2-ethylhexyl acrylate (homopolymer Tg -68 ° C)
BA: butyl acrylate (homopolymer Tg -45 ° C)
(A2) Component AA-6: macromonomer AA-6 (homopolymer Tg 105 ° C)
AS-6: Macromonomer AS-6 (Homopolymer Tg 100 ° C)
AN-6S: Macromonomer AN-6S (Homopolymer Tg 99 ° C)
AB-6: Macromonomer AB-6 (Homopolymer Tg -45 ° C)
AW-6S: Macromonomer AW-6S (Homopolymer Tg 67 ° C)
AK-5: Macromonomer AK-5 (Homopolymer Tg -123 ° C)
(All (a2) components are manufactured by Toagosei Co., Ltd.)
(A3) Component HEAA: N- (2-hydroxyethyl) acrylamide (homopolymer Tg 98 ° C.)
4HBA: 4-hydroxybutyl acrylate (homopolymer Tg-40 ° C)
GMA: glycidyl methacrylate (homopolymer Tg 41 ° C.)
AAEM: acetoacetoxyethyl methacrylate (homopolymer Tg 9 ° C)
(A4) Component MEA: methoxyethyl acrylate (Homopolymer Tg-50 ° C)
EC-2: A: Ethoxy-diethylene glycol acrylate (homopolymer Tg -70 ° C).

<Example 1>
(Preparation of adhesive)
As a crosslinking agent (B), an isocyanate crosslinking agent Takenate (registered trademark) D-110N (xylylene diisocyanate) was used as the crosslinking agent (B) with respect to 100 parts of the solid content of the (meth) acrylate copolymer (A1) solution obtained in Production Example 1. 0.1 part of a 75% ethyl acetate solution of a trimethylolpropane adduct of Example 1 (the number of isocyanate groups in one molecule: 3; manufactured by Mitsui Chemicals, Inc.) and a solution of an acrylic pressure-sensitive adhesive (solid content: 15%) Was prepared.

(Formation of adhesive layer)
Then, the solution of the acrylic pressure-sensitive adhesive was applied to one side of a 50 μm-thick polyethylene terephthalate (PET) film (MRF50, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) which had been subjected to a silicone treatment (peeling treatment) and dried. The composition was applied with a die coater so that the thickness of the agent layer became 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)
On the protective layer 8 side, a corona treatment was performed with a corona discharge amount of 80 W · min / m ² 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 is formed is transferred so that the pressure-sensitive adhesive layer and the protective layer 8 are in contact with each other via an easy-adhesion layer. ) Was prepared.

<Examples 2 to 26, 28 to 29 and Comparative Examples 1 to 5>
As shown in Table 2, the type of the (meth) acrylate copolymer (A) (polymer type), the type of the cross-linking agent, or the amount of use thereof was changed. 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 a ratio shown in Table 2. did.

<Example 27>
Trimethylolpropane triacrylate (light acrylate TMP-A; manufactured by Kyoeisha Chemical Co., Ltd .; hereinafter referred to as "TMP-") in the amount shown in Table 2 with respect to 100 g of the active ingredient in the acrylic syrup obtained in Production Example 20 A "), biuret-type hexamethylene diisocyanate (Duranate (registered trademark) 24A-100; manufactured by Asahi Kasei Chemicals Corporation, hereinafter referred to as" 24A-100 "), 2-hydroxy-2-methyl-1-phenyl-propane- 1-one (Irgacure (registered trademark) 1173; manufactured by BASF Japan Ltd .; hereinafter, referred to as “I-1173”) and 3-glycidoxypropyltriethoxysilane (KBE-403; Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent Ltd., hereinafter referred to as “KBE-403”) Process to obtain photopolymerizable pressure-sensitive adhesive composition (solution of acrylic adhesive).

  Here, 100 g of the active ingredient in the acrylic syrup contains 32.5 g of the (meth) acrylate copolymer (A20) and 67.5 g of the remaining unreacted monomer.

  This photopolymerizable pressure-sensitive adhesive composition is applied to a release-treated surface of a 50 μm-thick polyethylene terephthalate (PET) film that has been subjected to a single-sided release treatment (that is, a silicone treatment) so as to have a coating thickness of 100 μm. Then, a PET separator having a thickness of 50 μm, which has been subjected to a peeling treatment, is attached to the coated surface, and the PET separator is disposed above and below the pressure-sensitive adhesive composition, sealed in a sandwich form, and then 5.0 mW with black light. Was irradiated for 10 minutes to obtain a colorless and transparent acrylic sheet (adhesive layer).

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

<Comparative Example 6>
Trimethylolpropane triacrylate (light acrylate TMP-A; manufactured by Kyoeisha Chemical Co., Ltd .; hereinafter, referred to as "TMP-A") in an amount shown in Table 2 with respect to the active ingredient of 100 g of the acrylic syrup obtained in Production Example 26 ), Biuret-type hexamethylene diisocyanate (Duranate (registered trademark) 24A-100; manufactured by Asahi Kasei Chemicals Corporation, hereinafter referred to as "24A-100"), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Irgacure (registered trademark) 1173; manufactured by BASF Japan Ltd .; hereinafter, referred to as "I-1173") and 3-glycidoxypropylmethyldiethoxysilane (KBE-403; Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent , Hereinafter referred to as “KBE-403”). It was obtained photopolymerizable pressure-sensitive adhesive composition (solution of acrylic adhesive) and foam processing. Then, a polarizing plate with an adhesive layer was produced in the same manner as in Example 27.

  The following evaluation was performed on the polarizing plate (optical member) with the pressure-sensitive adhesive layer obtained in the above Examples and Comparative Examples. Table 3 shows the evaluation results.

<Durability>
A film having a 50-nm-thick silicon nitride (SiN _x ) film on the outermost surface of a 0.7-mm-thick polyimide film was used as a substitute for a flexible panel.

  The sample of the polarizing plate with the pressure-sensitive adhesive layer was 5 inches in size, the polyethylene terephthalate (PET) film was peeled off, and the sample was adhered to a polyimide film using a laminator.

  Subsequently, the sample was autoclaved at 50 ° C. and 0.5 MPa for 15 minutes to completely adhere the sample to the polyimide film. Thereafter, the sample was sandwiched and fixed between glass plates so that the inner diameter (diameter) could be maintained at 6 mm.

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

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

  (3) Further, the environment of 85 ° C. and −40 ° C. was subjected to 300 cycles for 1 hour and 1 hour (heat shock test, “HS 300 cycles” in Table 3).

  In each test, the appearance of the polarizing plate and the polyimide film was visually evaluated based on the following criteria.

◎: No change in appearance such as foaming, peeling, floating, cracks, etc. ○: Peeling, foaming, or cracking at the edge slightly, but no practical problem △: Peeling, foaming, or at the edge There is a crack, but there is no practical problem unless it is a special use. ×: There is significant peeling at the end, and there is a practical problem.

  In the tests (1), (2) and (3), samples were prepared and tested independently.

<Bending resistance (bending test 100,000 times)>
The same sample as that used in the durability test (autoclaved at 50 ° C. and 0.5 MPa for 15 minutes) was newly prepared, and was newly bent at a bending tester (manufactured by Yuasa System Equipment Co., Ltd.). Conditions were set such that the inner diameter (diameter) was 6 mm, and 100,000 cycles were repeated with bending and opening at 180 ° as one cycle. As test environments, (1) under an atmosphere of 23 ° C./55% RH, (2) under an atmosphere of 85 ° C. (10% RH or less), (3) under an atmosphere of 60 ° C./95% RH, (4) -20 C. was performed. The appearances of the polarizing plate and the polyimide film after the test were visually evaluated according to the following criteria.

  In the tests (1), (2), (3) and (4), samples were prepared and tested independently.

  ：: No change in appearance such as foaming, peeling, floating, cracks, etc.

  ：: Slight peeling, foaming or cracking at the end, but no practical problem

  Δ: Peeling, foaming, or cracks at the end, but practically no problem unless special use

  X: There is significant peeling at the end, and there is a problem in practical use.

<Adhesive strength>
The same samples as those used in the above durability test were newly prepared, cut into 25 mm in width and 100 mm in length, and then autoclaved at 50 ° C. and 0.5 MPa for 15 minutes to be completely adhered. Thereafter, the sample was allowed to stand for 1 hour in an atmosphere of 23 ° C./55% RH, and then the adhesive strength of the sample was measured.

  The adhesive force was measured using a tensile tester equipped with a thermostat (Tensilon Universal Material Tester STA-1150, manufactured by Orientec Co., Ltd., STA-1150) at a peeling angle of 180 ° and a peeling rate of 23 ° C. and a relative humidity of 55% RH. It was determined by measuring the adhesive force (N / 25 mm) at the time of peeling at 300 mm / min according to the method of testing adhesive tapes and adhesive sheets according to JIS Z0237 (2009). The measurement at 85 ° C. was performed in the same manner as described above, except that the environment was set to 85 ° C. (10% RH or less) using the above-mentioned equipment.

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

  The adhesive strength at room temperature (23 ° C./55% RH) is preferably 8 N / 25 mm or more, more preferably 10 N / 25 mm or more, and even more preferably more than 11 N / 25 mm.

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

  As shown in Table 3, it can be seen that all of the pressure-sensitive adhesives for optical films of Examples 1 to 29 have excellent durability, bending resistance, and adhesive strength.

  On the other hand, when the molecular weight of the (meth) acrylate copolymer is lower than the lower limit of the range of the present invention (Comparative Examples 1 and 6), the structural units derived from each of the components (a1) to (a4) correspond to the present invention. When it is out of the range (Comparative Examples 2, 3, and 5), and when the glass transition temperature is higher than the upper limit of the range of the present invention (Comparative Example 4), each performance of the pressure-sensitive adhesive may be inferior to Examples. Understand.

DESCRIPTION OF SYMBOLS 1 Thin polarizing plate 2 Polycarbonate film 3 Polyvinyl alcohol adhesive 4 Polarizer 5 Polyvinyl alcohol adhesive 6 Retardation film 7 Conductive layer 8 Protective layer.

Claims (22)

A pressure-sensitive adhesive for an optical film, comprising a (meth) acrylate copolymer (A),
The (meth) acrylate copolymer (A)
(A1) from 9.9% by mass to 99.9% by mass of structural units derived from an alkyl (meth) acrylate monomer;
(A2) a structural unit derived from a macromonomer having a polymerizable functional group in an amount of 0.1% by mass to 15% by mass;
(A3) a structural unit derived from a functional group-containing monomer that is a (meth) acrylic acid derivative monomer having no plurality of radically polymerizable functional groups, from 0% by mass to 20% by mass;
(A4) Structural units derived from (meth) acrylate monomers other than (a1), (a2) and (a3), from 0% by mass to 90% by mass;
Including
The total amount of the structural units derived from (a1), (a2), (a3) and (a4) is 100% by mass;
An adhesive for an optical film, wherein the (meth) acrylate copolymer has a glass transition temperature of -70 ° C or more and -57 ° C or less and a weight average molecular weight of more than 1,000,000 and not more than 2.5 million.   The pressure-sensitive adhesive for an optical film according to claim 1, wherein the glass transition temperature is −70 ° C. or higher and lower than −60 ° C. 3.   The pressure-sensitive adhesive for an optical film according to claim 1, wherein the weight average molecular weight exceeds 1.2 million.   (A3) The functional group-containing monomer which is a (meth) acrylic acid derivative monomer having no plurality of radically polymerizable functional groups is a (meth) acrylic acid derivative monomer having a hydroxyl group, an acyl group or an epoxy group. Item 4. The pressure-sensitive adhesive for an optical film according to any one of Items 1 to 3.   The pressure-sensitive adhesive for optical films according to any one of claims 1 to 4, wherein the alkyl (meth) acrylate monomer (a1) has an alkyl group having 1 to 18 carbon atoms.   The pressure-sensitive adhesive for an optical film according to any one of claims 1 to 5, wherein the constituent unit derived from the (a1) alkyl (meth) acrylate monomer is from 60% by mass to 90% by mass.   The pressure-sensitive adhesive for optical films according to any one of claims 1 to 6, wherein the (meth) acrylate copolymer (A) contains a hydroxyl group.   The pressure-sensitive adhesive for an optical film according to claim 1, further comprising a crosslinking agent (B).   The optical film according to claim 8, wherein the crosslinking agent (B) is contained in an amount of 0.001 to 20 parts by mass based on 100 parts by mass of the (meth) acrylate copolymer (A). Adhesive.   The crosslinking agent (B) is an isocyanate compound, a carbodiimide compound, an oxazoline compound, an epoxy compound, a polyfunctional acrylate monomer, a peroxide, a titanium coupling agent, a zirconium compound, a metal aluminum chelate, a hydrazide compound, and a thermal acid generator The pressure-sensitive adhesive for an optical film according to claim 8, wherein the pressure-sensitive adhesive is at least one selected from the group consisting of:   The silane coupling agent (C) is contained in an amount of 0.001 to 5 parts by mass based on 100 parts by mass of the (meth) acrylate copolymer (A). Item 2. The pressure-sensitive adhesive for optical films according to item 1. The (a2) macromonomer having a polymerizable functional group is methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, alkyl (meth) acrylate, stearyl (meth) acrylate, n-butyl ( At least one homopolymer or copolymer selected from the group consisting of (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, styrene, acrylonitrile, hydroxy (meth) acrylate and ethylhexyl acrylate; or The optical film pressure-sensitive adhesive according to any one of claims 1 to 11, comprising a polyorganosiloxane. Formed by forming an optical film pressure-sensitive adhesive according to any one of claims 1 to 12 pressure-sensitive adhesive layer. Storage elastic modulus (G ′ (− 20)) at −20 ° C. is 1 × 10 ⁵ Pa or less, and
The pressure-sensitive adhesive layer according to claim 13 , wherein the storage elastic modulus (G '(85)) at 85 ° C is 1 × 10 ⁴ Pa or more. The pressure-sensitive adhesive layer according to claim 13 , wherein G ′ (− 20) / G ′ (85) is 1.0 or more and 5.0 or less. An optical member comprising the pressure-sensitive adhesive layer according to claim 13 formed on at least one side of an optical film.   The optical member according to claim 16, further comprising an easy-adhesion layer between the optical film and the pressure-sensitive adhesive layer.   The optical member according to claim 17, wherein the easy-adhesion layer is a corona treatment layer, a plasma treatment layer, or a primer layer. The optical film includes a polarizing plate,
The optical member according to any one of claims 16 to 18, wherein the thickness of the polarizing plate is 100 µm or less.   The optical film has a conductive layer, the material forming the conductive layer is indium tin oxide, silver nanowire, indium zinc oxide, indium oxide-zinc oxide composite, polythiophene, carbon nanotube, aluminum zinc oxide, 20. At least one selected from the group consisting of gallium zinc oxide, fluorine zinc oxide, fluorine indium oxide, antimony tin oxide, fluorine tin oxide and phosphorus tin oxide. Item 6. The optical member according to item 1.   An image display device using at least one optical member according to any one of claims 16 to 20.   22. The image display device according to claim 21, which is a curved display or a flexible display.