JP2016011363A - Adhesive composition, adhesive sheet and optical member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a useful adhesive sheet using an adhesive composition, which is excellent in shear force resistance and is capable of suppressing an unnecessary curl or unintended curl on an adherend when stuck onto the adherend.SOLUTION: An adhesive composition includes: (meth)acrylic polymer containing, as a monomer component, 50 to 99.9 mass% of (meth)acrylic monomer having an alkyl group with 1 to 14 carbon atoms, hydroxyl group-containing (meth)acrylic monomer and carboxyl group-containing (meth)acrylic monomer. In the (meth)acrylic polymer, weight average molecular weight is from 100,000 to 5,000,000 and the ratio of (meth)acrylic polymer whose molecular weight is 10,000 or less is 5 area% or less.

Description

  The present invention relates to an adhesive composition, an adhesive sheet, and an optical member protected by the adhesive sheet.

  The pressure-sensitive adhesive sheet of the present invention is a surface protective film used for the purpose of protecting the surface of an optical member such as a polarizing plate, a wave plate, a phase difference plate, an optical compensation film, a reflection sheet, and a brightness enhancement film used for a liquid crystal display, etc. Useful.

  In recent years, when optical components / electronic components are transported or mounted on a printed circuit board, they are transferred in a state where individual components are packaged with a predetermined sheet or in a state where an adhesive tape is attached. Among these, surface protective films are particularly widely used in the field of optical and electronic components.

  The surface protective film is generally used for the purpose of preventing scratches and dirt generated during the processing and transportation of the adherend by attaching it to the adherend (protected body) via an adhesive applied to the support film side. (Patent Document 1). For example, a panel of a liquid crystal display is formed by bonding an optical member such as a polarizing plate or a wave plate to a liquid crystal cell via an adhesive. As for these optical members, the surface protection film is bonded together through the adhesive, and the damage | wound and dirt which arise at the time of a process and conveyance of a to-be-adhered body are prevented.

  When attached to an adherend (such as a polarizing plate) on the surface protective film, unnecessary or unintentional curling (curling is curled) on the adherend (such as a polarizing plate) to which the surface protective film is attached. For example, a flat plate-like object is generally warped to one of the surfaces, and a flat-plate object is generally warped so as to be wavy.) Adjustability has been demanded. When unnecessary curling or unintentional curling occurs, the handleability is inferior. For example, when an adherend such as a polarizing plate is attached to a liquid crystal cell, problems such as entrapment of bubbles may occur.

  In addition, when curling occurs on a flat adherend, a force accompanying the curl acts in the shear direction on the adhesive layer of the surface protective film bonded to the adherend, and this force causes the adherend to adhere. Since slippage and displacement occur gradually between the body and the pressure-sensitive adhesive layer, improvement in shearing force is required.

JP-A-9-165460

  Then, the objective of this invention is providing the adhesive sheet excellent in the shear force in order to eliminate the problem in the conventional adhesive sheet.

  That is, the pressure-sensitive adhesive composition of the present invention comprises, as a monomer component, 50 to 99.9% by mass of a (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms and a hydroxyl group-containing (meth) acrylic monomer. And a pressure-sensitive adhesive composition containing a (meth) acrylic polymer containing a carboxyl group-containing (meth) acrylic monomer, wherein the (meth) acrylic polymer has a weight average molecular weight of 100,000 to 5,000,000. The ratio of the (meth) acrylic polymer having a molecular weight of 10,000 or less is 5 area% or less.

  The pressure-sensitive adhesive composition of the present invention preferably contains 0.1 to 30% by mass of the hydroxyl group-containing (meth) acrylic monomer with respect to the total amount of monomer components constituting the (meth) acrylic polymer.

  The pressure-sensitive adhesive composition of the present invention preferably contains 0.001 to 1% by mass of the carboxyl group-containing (meth) acrylic monomer with respect to the total amount of monomer components constituting the (meth) acrylic polymer.

  The pressure-sensitive adhesive composition of the present invention preferably further contains a crosslinking agent.

  The pressure-sensitive adhesive sheet of the present invention is preferably formed by forming a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition on one side or both sides of a support film.

The pressure-sensitive adhesive sheet of the present invention has a shearing force when peeled in the shearing direction at a peeling rate of 0.06 m / min after pasting at 23 ° C. for 30 minutes after sticking 1 cm ² of the pressure-sensitive adhesive layer to the TAC polarizing plate. 15 N / cm ² or more is preferable.

  The optical member of the present invention is preferably protected by the pressure-sensitive adhesive sheet.

  Since the pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition of the present invention is excellent in shearing force, it can suppress unnecessary curl and unintended curl on the adherend when bonded to the adherend. Is useful.

  Hereinafter, embodiments of the present invention will be described in detail.

<Overall structure of adhesive sheet (surface protective film)>
The pressure-sensitive adhesive sheet disclosed herein is generally in a form called a pressure-sensitive adhesive sheet, a pressure-sensitive adhesive tape, a pressure-sensitive adhesive label, a pressure-sensitive adhesive film, and the like, and in particular, an optical component (for example, a liquid crystal display panel configuration such as a polarizing plate and a wave plate It is suitable as an adhesive sheet (surface protective film) for protecting the surface of the optical component during processing or transport of the optical component used as an element. The pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet is typically formed continuously, but is not limited to such a form, for example, a pressure-sensitive adhesive formed in a regular or random pattern such as a spot or stripe. It may be an agent layer. Further, the pressure-sensitive adhesive sheet disclosed herein may be in the form of a roll or a single sheet.

<Adhesive composition>
In the pressure-sensitive adhesive composition of the present invention, as a monomer component, 50 to 99.9% by mass of a (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms, a hydroxyl group-containing (meth) acrylic monomer, and A pressure-sensitive adhesive composition containing a (meth) acrylic polymer containing a carboxyl group-containing (meth) acrylic monomer, wherein the (meth) acrylic polymer has a weight average molecular weight of 100,000 to 5,000,000. The ratio of the (meth) acrylic polymer having a molecular weight of 10,000 or less is 5 area% or less. By using the pressure-sensitive adhesive composition, the resulting pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) is excellent in shearing force, and is unnecessarily curled or unintentional in the adherend when bonded to the adherend. Curling can be suppressed and is useful.

  As a monomer component constituting the (meth) acrylic polymer, a (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms is contained. As said (meth) acrylic-type monomer, 1 type (s) or 2 or more types can be used as a main component (component with the highest compounding ratio in a monomer component). By using the (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms, it becomes easy to control the adhesive force to the adherend (protected body) to be low, and light releasability and re-peeling. A pressure-sensitive adhesive sheet having excellent properties is obtained. In the present invention, the (meth) acrylic polymer refers to an acrylic polymer and / or a methacrylic polymer, and the (meth) acrylate refers to acrylate and / or methacrylate.

  Specific examples of the (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, s-butyl (meth) ) Acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl ( (Meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate, etc. It is done.

  Especially, when using the adhesive sheet of this invention as a surface protection film, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (Meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate, etc. A (meth) acrylic monomer having an alkyl group having 6 to 14 carbon atoms is preferred. In particular, by using a (meth) acrylic monomer having an alkyl group having 6 to 14 carbon atoms, it becomes easy to control the adhesive force to the adherend to be low, and the removability is excellent.

  It contains 50 to 99.9% by mass of (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms, based on 100% by mass of the total amount of monomer components constituting the (meth) acrylic polymer, Is 60-99 mass%, More preferably, it is 70-98 mass%, More preferably, it is 80-97 mass%. If it is less than 50% by mass, the appropriate wettability of the pressure-sensitive adhesive composition and the cohesive strength of the pressure-sensitive adhesive layer will be inferior, which is not preferable.

  In the pressure-sensitive adhesive composition of the present invention, the (meth) acrylic polymer contains a hydroxyl group-containing (meth) acrylic monomer as a monomer component. As said hydroxyl group containing (meth) acrylic-type monomer, 1 type (s) or 2 or more types can be used. By using the hydroxyl group-containing (meth) acrylic monomer, it becomes easier to control the crosslinking of the pressure-sensitive adhesive composition, and as a result, the improvement in wettability by flow and the balance between the cohesive force and shearing force of the pressure-sensitive adhesive (layer). It becomes easy to control.

  Examples of the hydroxyl group-containing (meth) acrylic monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate. , 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl acrylate, N-methylol (meth) acrylamide, vinyl alcohol, allyl Examples thereof include alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether. In particular, it is preferable to use a hydroxyl group-containing (meth) acrylic monomer having 4 or more carbon atoms in the alkyl group, which facilitates light release at high speed release.

  The hydroxyl group-containing (meth) acrylic monomer is preferably contained in an amount of 0.1 to 30% by mass, more preferably 1%, based on 100% by mass of the total amount of monomer components constituting the (meth) acrylic polymer. -25% by mass, more preferably 2-20% by mass, most preferably 3-15% by mass. Within the above range, the balance between the wettability of the pressure-sensitive adhesive composition and the cohesive force and shear force of the pressure-sensitive adhesive (layer) can be easily controlled, which is preferable.

  In the pressure-sensitive adhesive composition of the present invention, the (meth) acrylic polymer contains a carboxyl group-containing (meth) acrylic monomer as a monomer component. As said hydroxyl group containing (meth) acrylic-type monomer, 1 type (s) or 2 or more types can be used. By using the carboxyl group-containing (meth) acrylic monomer, the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) can be prevented from increasing in adhesive strength over time. In addition, the cohesive force of the pressure-sensitive adhesive layer and the shearing force are also excellent, which is preferable.

  Examples of the carboxyl group-containing (meth) acrylic monomer include (meth) acrylic acid, carboxylethyl (meth) acrylate, carboxylpentyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, 2- ( (Meth) acryloyloxypropyl hexahydrophthalic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl maleic acid, carboxypolycaprolactone Examples thereof include mono (meth) acrylate and 2- (meth) acryloyloxyethyl tetrahydrophthalic acid.

  The carboxyl group-containing (meth) acrylic monomer is preferably contained in an amount of 0.001 to 1 mass%, more preferably 0 to 100 mass% of the total amount of monomer components constituting the (meth) acrylic polymer. 0.005 to 0.8% by mass, more preferably 0.008 to 0.6% by mass, and most preferably 0.01 to 0.5% by mass. Within the above range, the carboxyl group-containing (meth) acrylic monomer exhibits an effect as a crosslinking catalyst in the crosslinking reaction between the crosslinking agent described later and the hydroxyl group-containing (meth) acrylic monomer. Therefore, the aging time can be shortened, which is preferable. Moreover, the raise of the adhesive force with time can be suppressed and it is excellent in re-peelability, adhesive force raise prevention property, and workability | operativity. In addition to the cohesive force of the pressure-sensitive adhesive layer, it is excellent in shearing force and is a preferred embodiment. If a large number of acid functional groups such as a carboxyl group having a large polar action are present, when an antistatic agent (for example, an ionic compound) is blended, the acid functional group such as a carboxyl group and the antistatic agent interact with each other. By acting, ion conduction or the like is hindered, the conductive efficiency is lowered, and sufficient antistatic properties may not be obtained, which is not preferable.

  In addition, as another polymerizable monomer component, the lath transition temperature (Tg) is set to 0 ° C. or lower (usually −100 ° C. or higher) because the adhesive performance is easily balanced. A polymerizable monomer for adjusting the glass transition temperature and peelability can be used as long as the effects of the present invention are not impaired.

  Furthermore, the (meth) acrylic monomer having a C1-C14 alkyl group used in the (meth) acrylic polymer, a hydroxyl group-containing (meth) acrylic monomer, and a carboxyl group-containing (meth) acrylic Any other polymerizable monomer other than the monomer can be used without particular limitation as long as it does not impair the characteristics of the present invention. For example, cohesive strength / heat resistance improving components such as cyano group-containing monomers, vinyl ester monomers, aromatic vinyl monomers, amide group-containing monomers, imide group-containing monomers, amino group-containing monomers, epoxy group-containing monomers, N-acryloylmorpholine In addition, a component having a functional group functioning as an adhesive strength improvement or a crosslinking base point such as a vinyl ether monomer can be appropriately used. These polymerizable monomers may be used alone or in combination of two or more.

  Examples of the cyano group-containing monomer include acrylonitrile and methacrylonitrile.

  Examples of the vinyl ester monomer include vinyl acetate, vinyl propionate, vinyl laurate, and the like.

  Examples of the aromatic vinyl monomer include styrene, chlorostyrene, chloromethyl styrene, α-methyl styrene, and other substituted styrene.

  Examples of the amide group-containing monomer include acrylamide, methacrylamide, diethylacrylamide, N-vinylpyrrolidone, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N, N-diethylacrylamide, N, N-diethyl. Examples include methacrylamide, N, N′-methylenebisacrylamide, N, N-dimethylaminopropyl acrylamide, N, N-dimethylaminopropyl methacrylamide, diacetone acrylamide, and the like.

  Examples of the imide group-containing monomer include cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, and itaconimide.

  Examples of the amino group-containing monomer include aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, and the like.

  Examples of the epoxy group-containing monomer include glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, and allyl glycidyl ether.

  Examples of the vinyl ether monomer include methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether, and the like.

  In the present invention, the polymerizable monomer other than the (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms, the hydroxyl group-containing (meth) acrylic monomer, and the carboxyl group-containing (meth) acrylic monomer, It is preferably 0 to 10% by mass and more preferably 0 to 5% by mass with respect to 100% by mass of the total amount of monomer components constituting the (meth) acrylic polymer. By using the other polymerizable monomer within the above range, for example, cohesive force and heat resistance can be improved.

  The (meth) acrylic polymer may further contain an alkylene oxide group-containing reactive monomer as a monomer component. Moreover, as an average addition mole number of the oxyalkylene unit of the said alkylene oxide group containing reactive monomer, when mix | blending the ionic compound which is an antistatic agent, for example, it is 1 from a compatible viewpoint with the said ionic compound. It is preferably 40, more preferably 3 to 40, still more preferably 4 to 35, and particularly preferably 5 to 30. When the average added mole number is 1 or more, the effect of reducing the contamination of the adherend (protected body) tends to be obtained efficiently. Moreover, when the said average added mole number is larger than 40, since interaction with the said ionic compound is large and there exists a tendency for the viscosity of an adhesive composition to rise and for coating to become difficult, it is unpreferable. Note that the terminal of the oxyalkylene chain may be a hydroxyl group or may be substituted with another functional group.

  The alkylene oxide group-containing reactive monomer may be used alone or in combination of two or more, but the total content is the total amount of monomer components of the (meth) acrylic polymer. The content is preferably 20% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less, still more preferably 4% by mass or less, and 3% by mass or less. Particularly preferred is 1% by mass or less. If the content of the alkylene oxide group-containing reactive monomer exceeds 10% by mass, the interaction with the ionic compound is increased, ionic conduction is hindered, and the antistatic property is lowered, which is not preferable.

  Examples of the oxyalkylene unit of the alkylene oxide group-containing reactive monomer include those having an alkylene group having 1 to 6 carbon atoms, such as an oxymethylene group, an oxyethylene group, an oxypropylene group, and an oxybutylene group. It is done. The hydrocarbon group of the oxyalkylene chain may be linear or branched.

  The alkylene oxide group-containing reactive monomer is more preferably a reactive monomer having an ethylene oxide group. By using a (meth) acrylic polymer having a reactive monomer having an ethylene oxide group as a base polymer, the compatibility between the base polymer and the ionic compound is improved, and bleeding to the adherend is suitably suppressed, A low-contamination pressure-sensitive adhesive composition is obtained.

  Examples of the alkylene oxide group-containing reactive monomer include (meth) acrylic acid alkylene oxide adducts and reactive surfactants having reactive substituents such as acryloyl group, methacryloyl group, and allyl group in the molecule. can give.

  Specific examples of the (meth) acrylic acid alkylene oxide adduct include, for example, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, polyethylene glycol-polypropylene glycol (meth) acrylate, polyethylene glycol-polybutylene glycol (meth) ) Acrylate, polypropylene glycol-polybutylene glycol (meth) acrylate, methoxy polyethylene glycol (meth) acrylate, ethoxy polyethylene glycol (meth) acrylate, butoxy polyethylene glycol (meth) acrylate, octoxy polyethylene glycol (meth) acrylate, lauroxy polyethylene Glycol (meth) acrylate, stearoxy polyethylene glycol Le (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate, methoxy polypropylene glycol (meth) acrylate, octoxypolyethylene glycol - polypropylene glycol (meth) acrylate.

  Specific examples of the reactive surfactant include, for example, an anionic reactive surfactant having a (meth) acryloyl group or an allyl group, a nonionic reactive surfactant, and a cationic reactive surfactant. Can be given.

  The polymerization method of the (meth) acrylic polymer used in the present invention is not particularly limited and can be polymerized by known methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, etc. Solution polymerization is a more preferable embodiment from the viewpoint of characteristics such as low contamination to the adherend. Further, the polymer obtained may be any of a random copolymer, a block copolymer, an alternating copolymer, a graft copolymer, and the like.

  When synthesizing the (meth) acrylic polymer by the solution polymerization, the monomer component supply method includes a batch charging method for supplying all monomer raw materials at once, a continuous supply (dropping) method, and a divided supply (dropping) method. A method or the like can be appropriately employed. The polymerization temperature can be appropriately selected according to the type of monomer and solvent to be used, the type of polymerization initiator, and the like, for example, about 20 ° C. to 170 ° C. (typically 40 ° C. to 140 ° C.). The polymerization time can be about 60 minutes to 12 hours (typically 2 hours to 10 hours). In order to keep the content ratio of the (meth) acrylic polymer (low molecular weight component) having a molecular weight of 10,000 or less, the polymerization temperature is controlled, for example, the aging step (the polymerization temperature is increased at the end of the reaction, It is a preferred embodiment that polymerization is carried out in a stable state at a constant temperature for a certain time without providing a step of reacting the remaining monomer components at once.

  The solvent (polymerization solvent) used for the solution polymerization can be appropriately selected from known organic solvents. For example, toluene, xylene, ethyl acetate, hexane, cyclohexane, methylcyclohexane, 1,2-dichloroethane, isopropyl alcohol, 1-butanol, sec-butanol, tert-butanol, tert-butyl methyl ether, methyl ethyl ketone, acetylacetone, etc. alone Or two or more types can be used in combination. In particular, it is preferable to use ethyl acetate which is less likely to cause chain transfer and can keep the proportion of low molecular weight components low.

  In the preparation of the (meth) acrylic polymer, when the monomer component is polymerized by radiation energy (for example, irradiation with heat or ultraviolet rays), a thermal polymerization initiator or a photopolymerization initiator (photoinitiation) (Meth) acrylic polymer can be easily synthesized using a polymerization initiator such as (agent). The said polymerization initiator can be used individually or in combination of 2 or more types.

  Examples of the thermal polymerization initiator include azo polymerization initiators (for example, 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis). (2-methylpropionic acid) dimethyl, 4,4′-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [ 2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis (2-methylpropionamidine) disulfate, 2,2′-azobis (N, N′-di) Methyleneisobutylamidine) dihydrochloride, etc.); peroxide polymerization initiators (for example, dibenzoyl peroxide, t-butylpermaleate, lauro peroxide) Le etc.); redox polymerization initiators, and the like.

  The photopolymerization initiator is not particularly limited. For example, benzoin ether photopolymerization initiator, acetophenone photopolymerization initiator, α-ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, photo Active oxime photopolymerization initiator, benzoin photopolymerization initiator, benzyl photopolymerization initiator, benzophenone photopolymerization initiator, ketal photopolymerization initiator, thioxanthone photopolymerization initiator, acylphosphine oxide photopolymerization initiator An initiator or the like can be used.

  Specifically, examples of the benzoin ether photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane- 1-one [trade name: Irgacure 651, manufactured by BASF Corporation], anisole methyl ether and the like can be mentioned. Examples of the acetophenone photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone [trade name: Irgacure 184, manufactured by BASF Corp.], 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1- [4- ( 2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one [trade name: Irgacure 2959, manufactured by BASF Corp.], 2-hydroxy-2-methyl-1-phenyl-propane- 1-one [trade name: Darocur 1173, manufactured by BASF Corporation], methoxyacetophenone, and the like can be given. Examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1- [4- (2-hydroxyethyl) -phenyl] -2-hydroxy-2-methylpropane-1- ON etc. are mentioned. Examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalene sulfonyl chloride. Examples of the photoactive oxime photopolymerization initiator include 1-phenyl-1,1-propanedione-2- (o-ethoxycarbonyl) -oxime.

  The benzoin photopolymerization initiator includes, for example, benzoin. Examples of the benzyl photopolymerization initiator include benzyl and the like. Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3′-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexyl phenyl ketone, and the like. Examples of the ketal photopolymerization initiator include benzyl dimethyl ketal. Examples of the thioxanthone photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone and the like are included.

  Examples of the acylphosphine photopolymerization initiator include bis (2,6-dimethoxybenzoyl) phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) (2,4,4-trimethylpentyl) phosphine oxide, bis ( 2,6-dimethoxybenzoyl) -n-butylphosphine oxide, bis (2,6-dimethoxybenzoyl)-(2-methylpropan-1-yl) phosphine oxide, bis (2,6-dimethoxybenzoyl)-(1- Methylpropan-1-yl) phosphine oxide, bis (2,6-dimethoxybenzoyl) -t-butylphosphine oxide, bis (2,6-dimethoxybenzoyl) cyclohexylphosphine oxide, bis (2,6-dimethoxybenzoyl) octylphosphine Oxide, bis (2- Toxibenzoyl) (2-methylpropan-1-yl) phosphine oxide, bis (2-methoxybenzoyl) (1-methylpropan-1-yl) phosphine oxide, bis (2,6-diethoxybenzoyl) (2-methyl Propan-1-yl) phosphine oxide, bis (2,6-diethoxybenzoyl) (1-methylpropan-1-yl) phosphine oxide, bis (2,6-dibutoxybenzoyl) (2-methylpropane-1- Yl) phosphine oxide, bis (2,4-dimethoxybenzoyl) (2-methylpropan-1-yl) phosphine oxide, bis (2,4,6-trimethylbenzoyl) (2,4-dipentoxyphenyl) phosphine oxide Bis (2,6-dimethoxybenzoyl) benzylphosphine oxide, bis 2,6-dimethoxybenzoyl) -2-phenylpropylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2-phenylethylphosphine oxide, bis (2,6-dimethoxybenzoyl) benzylphosphine oxide, bis (2,6 -Dimethoxybenzoyl) -2-phenylpropylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2-phenylethylphosphine oxide, 2,6-dimethoxybenzoylbenzylbutylphosphine oxide, 2,6-dimethoxybenzoylbenzyloctylphosphine oxide Bis (2,4,6-trimethylbenzoyl) -2,5-diisopropylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2-methylphenylphosphine oxide, bis (2 4,6-trimethylbenzoyl) -4-methylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,5-diethylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2, 3,5,6-tetramethylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) isobutylphosphine oxide, 2,6-dimethoxybenzoyl-2,4,6-trimethyl Benzoyl-n-butylphosphine oxide, bis (2,4,4 -Trimethylbenzoyl) phenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,4-dibutoxyphenylphosphine oxide, 1,10-bis [bis (2,4,6-trimethylbenzoyl) phosphine oxide] Examples include decane and tri (2-methylbenzoyl) phosphine oxide.

  The content of the thermal polymerization initiator and the photopolymerization initiator is not particularly limited, but for example, 0.01 to 1 part by mass with respect to 100 parts by mass of the total amount of monomer components for preparing the (meth) acrylic polymer. Preferably, it is 0.05 to 0.5 parts by mass. When the content is less than 0.01 parts by mass, the polymerization reaction may become insufficient. Moreover, when the said content exceeds 1 mass part, the molecular weight of a (meth) acrylic-type polymer will become small too much, and there exists a possibility that the content rate of the (meth) acrylic-type polymer (low molecular weight component) of molecular weight 10,000 or less may become large. This is not preferable. Further, an increase in the content ratio of the (meth) acrylic polymer having a molecular weight of 10,000 or less may cause the low molecular weight component to bleed out and reduce the shearing force.

  Examples of the radiation include ultraviolet (UV), laser beam, α-ray, β-ray, γ-ray, X-ray, and electron beam. Ultraviolet rays are preferable from the viewpoints of controllability, ease of handling, and cost. Used for. More preferably, ultraviolet rays having a wavelength of 200 to 400 nm are used. Ultraviolet rays can be irradiated using an appropriate light source such as a high-pressure mercury lamp, a microwave excitation lamp, or a chemical lamp.

  Furthermore, it is also possible to use a photopolymerization initiation assistant such as amines together with the photopolymerization initiator. Examples of the photopolymerization initiation assistant include 2-dimethylaminoethylbenzoate, dimethylaminoacetophenone, p-dimethylaminobenzoic acid ethyl ester, p-dimethylaminobenzoic acid isoamyl ester, and the like. These compounds may be used alone or in combination of two or more. The photopolymerization initiation assistant is preferably added in an amount of 0.05 to 10 parts by weight, more preferably 0.1 to 7 parts by weight, based on 100 parts by weight of the (meth) acrylic polymer. . Within the above range, it is preferable from the viewpoint of easily controlling the polymerization reaction and obtaining an appropriate molecular weight.

In addition, when the photopolymerization initiator is blended, the pressure-sensitive adhesive composition is directly applied on an adherend (protected body) or after being applied to a predetermined coated body such as a separator. Alternatively, the pressure-sensitive adhesive layer can be obtained by light irradiation after coating on one side of the support (base material). Usually, the pressure-sensitive adhesive layer is obtained by irradiating ultraviolet rays having an illuminance of 1 to 200 mW / cm ² at a wavelength of 300 to 400 nm and photopolymerizing them with a light amount of about 200 to 4000 mJ / cm ² .

  The (meth) acrylic polymer has a weight average molecular weight (Mw) of 100,000 to 5,000,000, preferably 200,000 to 4,000,000, more preferably 300,000 to 3,000,000. When the weight average molecular weight is smaller than 100,000, the adhesive force tends to be generated due to the reduced cohesive force of the pressure-sensitive adhesive layer. On the other hand, when the weight average molecular weight exceeds 5,000,000, the fluidity of the polymer is lowered, the wettability to the adherend (for example, an optical member such as a polarizing plate) is insufficient, and the adherence between the adherend and the adhesive sheet There is a tendency to cause blisters occurring between the agent layer and the agent layer. In addition, a weight average molecular weight means what was obtained by measuring by GPC (gel permeation chromatography).

  The glass transition temperature (Tg) of the (meth) acrylic polymer is preferably 0 ° C. or lower, more preferably −10 ° C. or lower (usually −100 ° C. or higher). When the glass transition temperature is higher than 0 ° C., the polymer is difficult to flow, for example, the wettment to the adherend becomes insufficient, which causes blisters generated between the adherend and the adhesive layer of the adhesive sheet. Tend. In particular, by setting the glass transition temperature to −61 ° C. or less, an adhesive layer excellent in wettability to the adherend and light peelability can be easily obtained. In addition, the glass transition temperature of a (meth) acrylic-type polymer can be adjusted in the said range by changing the monomer component and composition ratio to be used suitably.

  The said (meth) acrylic-type polymer is characterized by the ratio of the (meth) acrylic-type polymer of molecular weight 10,000 or less being 5 area% or less. By controlling the content of the (meth) acrylic polymer having a molecular weight of 10,000 or less, the pressure-sensitive adhesive composition can suppress bleed-out of low molecular weight components, and the resulting pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) has a shearing force. Therefore, unnecessary curling and unintended curling in the adherend can be suppressed when it is bonded to the adherend, which is useful. The content ratio of the (meth) acrylic polymer having a molecular weight of 10,000 or less (ratio in the total amount of (meth) acrylic polymer generated during polymerization) is preferably 4.9 area% or less, more preferably 4. It is 8 area% or less.

  In the polymerization of the (meth) acrylic polymer in the present invention, it is preferable to synthesize without using a chain transfer agent. When the chain transfer agent is used, not only the (meth) acrylic polymer having a desired weight average molecular weight of 100,000 to 5,000,000 but also the (meth) acrylic polymer having a molecular weight of 10,000 or less exceeds the desired content ratio. Since this may cause a decrease in shearing force, it is not preferable.

  In the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive composition can contain an antistatic agent, and the antistatic agent can contain an ionic compound. Examples of the ionic compound include an alkali metal salt and / or an ionic compound (such as an ionic liquid) having a low melting point (melting point of 150 ° C. or lower). By containing these antistatic agents, excellent antistatic properties can be imparted.

  Moreover, 1 mass part or less is preferable with respect to 100 mass parts of said (meth) acrylic-type polymers, 0.001-0.9 mass part is more preferable, More preferably, it is 0.00. 005 to 0.8 parts by mass. It is preferable for it to be in the above-mentioned range since it is easy to achieve both antistatic properties and low contamination.

  In the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive composition may contain an organopolysiloxane having a polyoxyalkylene chain (as a main chain and / or a side chain). By using the organopolysiloxane, it is presumed that the surface free energy on the surface of the pressure-sensitive adhesive is reduced, and light release at high speed peeling is realized.

  The organopolysiloxane used in the present invention preferably has an HLB (Hydrophile-Lipophile Balance) value of 1 to 16, more preferably 3 to 14. When the HLB value is out of the above range, the contamination of the adherend is deteriorated, which is not preferable.

  Moreover, 0.01-5 mass parts is preferable with respect to 100 mass parts of said (meth) acrylic-type polymers, More preferably, it is 0.03-3 mass parts, More preferably. Is 0.05 to 1 part by mass. It is preferable for it to be in the above-mentioned range since it is easy to achieve both antistatic properties and light releasability (removability).

<Crosslinking agent>
In the pressure-sensitive adhesive sheet (surface protective film) of the present invention, the pressure-sensitive adhesive composition preferably contains a crosslinking agent. Moreover, in this invention, it is set as an adhesive layer using the said adhesive composition. For example, when the pressure-sensitive adhesive contains the (meth) acrylic polymer, the structural unit of the (meth) acrylic polymer, the structural ratio, the selection and addition ratio of the crosslinking agent, etc. are appropriately adjusted for crosslinking. A pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) having better heat resistance can be obtained.

  As the crosslinking agent used in the present invention, an isocyanate compound, an epoxy compound, a melamine resin, an aziridine derivative, a metal chelate compound, or the like may be used. In particular, the use of an isocyanate compound is a preferred embodiment. Moreover, these compounds may be used independently and may be used in mixture of 2 or more types.

  Examples of the isocyanate compound (isocyanate-based crosslinking agent) include aliphatic polyisocyanates such as trimethylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate (HDI), dimer diisocyanate, cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate. Aliphatic isocyanates such as (IPDI), aromatic isocyanates such as 2,4-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, xylylene diisocyanate (XDI), allophanate bonds, biuret bonds, isocyanates Nurate bond, uretdione bond, urea bond, carbodiimide bond, uretonimine bond, oxy Polyisocynate modified product obtained by modifying the like trione bond. For example, as commercial products, the product names Takenate 300S, Takenate 500, Takenate D165N, Takenate D178N (above, Takeda Pharmaceutical Co., Ltd.), Sumijoule T80, Sumijoule L, Death Module N3400 (above, Sumika Bayer Urethane Co., Ltd.) Millionate MR, Millionate MT, Coronate L, Coronate HL, Coronate HX (above, manufactured by Nippon Polyurethane Industry Co., Ltd.) and the like. These isocyanate compounds may be used alone, or may be used in combination of two or more, and a bifunctional isocyanate compound and a trifunctional or higher isocyanate compound may be used in combination. By using a cross-linking agent in combination, it becomes possible to achieve both tackiness and resilience resistance (adhesiveness to a curved surface), and a pressure-sensitive adhesive sheet (surface protective film) with better adhesion reliability can be obtained.

  Examples of the epoxy compound include N, N, N ′, N′-tetraglycidyl-m-xylenediamine (trade name: TETRAD-X, manufactured by Mitsubishi Gas Chemical Company) and 1,3-bis (N, N-dioxy). Glycidylaminomethyl) cyclohexane (trade name: TETRAD-C, manufactured by Mitsubishi Gas Chemical Company, Inc.).

  Examples of the melamine resin include hexamethylol melamine. Examples of the aziridine derivative include commercially available product names HDU, TAZM, TAZO (manufactured by Mutual Yakugyo Co., Ltd.) and the like.

  Examples of the metal chelate compound include aluminum, iron, tin, titanium, and nickel as metal components, and acetylene, methyl acetoacetate, and ethyl lactate as chelate components.

  The content of the crosslinking agent used in the present invention is, for example, preferably 0.01 to 20 parts by mass, and 0.1 to 18 parts by mass with respect to 100 parts by mass of the (meth) acrylic polymer. It is more preferably contained, more preferably 0.5 to 16 parts by mass, and most preferably 1 to 14 parts by mass. When the content is less than 0.01 parts by mass, the crosslinking formation by the crosslinking agent becomes insufficient, the cohesive force of the resulting pressure-sensitive adhesive layer becomes small, and sufficient heat resistance may not be obtained, It tends to cause glue residue. On the other hand, when the content exceeds 20 parts by mass, the cohesive force of the polymer is large, the fluidity is lowered, the wettability to the adherend (for example, a polarizing plate which is an optical member) is insufficient, and the covering is performed. There is a tendency to cause blisters generated between the adherend and the pressure-sensitive adhesive layer (pressure-sensitive adhesive composition layer). Furthermore, when the amount of the crosslinking agent is large, the peeling charging property tends to be lowered. These crosslinking agents may be used alone or in combination of two or more.

  The pressure-sensitive adhesive composition may further contain a crosslinking catalyst in order to more effectively advance any of the crosslinking reactions described above. Examples of such crosslinking catalysts include tin catalysts such as dibutyltin dilaurate and dioctyltin dilaurate, tris (acetylacetonato) iron, tris (hexane-2,4-dionato) iron, tris (heptane-2,4-dionato). ) Iron, tris (heptane-3,5-dionato) iron, tris (5-methylhexane-2,4-dionato) iron, tris (octane-2,4-dionato) iron, tris (6-methylheptane-2) , 4-Dionato) iron, tris (2,6-dimethylheptane-3,5-dionato) iron, tris (nonane-2,4-dionato) iron, tris (nonane-4,6-dionato) iron, tris ( 2,2,6,6-tetramethylheptane-3,5-dionato) iron, tris (tridecan-6,8-dionato) iron, tris (1-phenylbutane-1, -Dionato), tris (hexafluoroacetylacetonato) iron, tris (ethyl acetoacetate) iron, tris (acetoacetate-n-propyl) iron, tris (isopropyl acetoacetate) iron, tris (acetoacetate-n-butyl) Iron, tris (acetoacetate-sec-butyl) iron, tris (acetoacetate-tert-butyl) iron, tris (methyl propionylacetate) iron, tris (ethyl propionylacetate) iron, tris (propionylacetate-n-propyl) iron , Tris (propionyl acetate-isopropyl) iron, tris (propionyl acetate-n-butyl) iron, tris (propionyl acetate-sec-butyl) iron, tris (propionyl acetate-tert-butyl) iron, tris (benzyl acetoacetate) iron, Tris (dimethyl malonate) iron, tris (diethyl malonate) iron, trimethoxy iron, Iron-based catalysts such as triethoxy iron, triisopropoxy iron, and ferric chloride can be used. These crosslinking catalysts may be used alone or in combination of two or more.

  Although the content of the crosslinking catalyst is not particularly limited, for example, about 0.0001 to 1 part by mass is preferable with respect to 100 parts by mass of the (meth) acrylic polymer, and 0.001 to 0.5 part by mass is preferable. More preferred. Within the above range, when the pressure-sensitive adhesive layer is formed, the speed of the cross-linking reaction is high, and the pot life of the pressure-sensitive adhesive composition is lengthened.

  The pressure-sensitive adhesive composition of the present invention may contain a polyoxyalkylene chain-containing compound that does not contain organopolysiloxane. By containing the said compound in an adhesive composition, the adhesive composition which was further excellent in the wettability to a to-be-adhered body can be obtained.

  Specific examples of the polyoxyalkylene chain-containing compound not containing the organopolysiloxane include, for example, polyoxyalkylene alkylamine, polyoxyalkylene diamine, polyoxyalkylene fatty acid ester, polyoxyalkylene sorbitan fatty acid ester, polyoxyalkylene alkylphenyl. Nonionic surfactants such as ether, polyoxyalkylene alkyl ether, polyoxyalkylene alkyl allyl ether, polyoxyalkylene alkyl phenyl allyl ether; polyoxyalkylene alkyl ether sulfate ester salt, polyoxyalkylene alkyl ether phosphate ester salt, Polyoxyalkylene alkyl phenyl ether sulfate ester salt, polyoxyalkylene alkyl phenyl ether phosphate ester Anionic surfactants such as tellurium salts; other cationic surfactants having polyoxyalkylene chains (polyalkylene oxide chains), amphoteric surfactants, polyether compounds having polyoxyalkylene chains (and derivatives thereof) ), Polyester compounds having a polyoxyalkylene chain (and derivatives thereof), acrylic compounds having a polyoxyalkylene chain (and derivatives thereof), and the like. Moreover, you may mix | blend a polyoxyalkylene chain containing monomer with an acrylic polymer as a polyoxyalkylene chain containing compound. Such polyoxyalkylene chain-containing compounds may be used alone or in combination of two or more.

  Specific examples of the polyether compound having a polyoxyalkylene chain include polypropylene glycol (PPG) -polyethylene glycol (PEG) block copolymer, PPG-PEG-PPG block copolymer, and PEG-PPG-PEG. Examples thereof include block copolymers. Examples of the derivative of the polyether compound having a polyoxyalkylene chain include an oxypropylene group-containing compound whose end is etherified (PPG monoalkyl ether, PEG-PPG monoalkyl ether, etc.), an oxypropylene group whose end is acetylated Examples of such compounds include terminal acetylated PPG and the like.

  Specific examples of the acrylic compound having a polyoxyalkylene chain include a (meth) acrylate polymer having an oxyalkylene group. The oxyalkylene group has an added mole number of oxyalkylene units, for example, when an ionic compound is used as an antistatic agent, 1 to 50 is preferable from the viewpoint of coordination of the ionic compound, and 2 to 30 Is more preferable, and 2 to 20 is more preferable. Moreover, the terminal of the oxyalkylene group may be a hydroxyl group, or may be substituted with an alkyl group, a phenyl group or the like.

  The (meth) acrylate polymer having an oxyalkylene group is preferably a polymer containing (meth) acrylic acid alkylene oxide as a monomer component (unit). As a specific example of the (meth) acrylic acid alkylene oxide, Examples thereof include ethylene glycol group-containing (meth) acrylates. For example, methoxy-polyethylene glycol (meth) acrylate types such as methoxy-diethylene glycol (meth) acrylate and methoxy-triethylene glycol (meth) acrylate, ethoxy-diethylene glycol (meta ) Acrylate, ethoxy-polyethylene glycol (meth) acrylate type such as ethoxy-triethylene glycol (meth) acrylate, butoxy-diethylene glycol (meth) acrylate , Butoxy-polyethylene glycol (meth) acrylate type such as butoxy-triethylene glycol (meth) acrylate, phenoxy-polyethylene glycol (meth) acrylate type such as phenoxy-diethylene glycol (meth) acrylate, phenoxy-triethylene glycol (meth) acrylate Methoxy-polypropylene glycol (meth) acrylate type such as 2-ethylhexyl-polyethylene glycol (meth) acrylate, nonylphenol-polyethylene glycol (meth) acrylate type, methoxy-dipropylene glycol (meth) acrylate, and the like.

  Moreover, other monomer components other than the (meth) acrylic acid alkylene oxide can be used as the monomer component. Specific examples of other monomer components include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, and isobutyl (meth) acrylate. , Hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate , Acrylate and / or methacrylate having an alkyl group having 1 to 14 carbon atoms such as isodecyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, and n-tetradecyl (meth) acrylate Door and the like.

  Further, as other monomer components other than the (meth) acrylic acid alkylene oxide, carboxyl group-containing (meth) acrylate, phosphoric acid group-containing (meth) acrylate, cyano group-containing (meth) acrylate, vinyl esters, aromatic vinyl Compound, acid anhydride group-containing (meth) acrylate, hydroxyl group-containing (meth) acrylate, amide group-containing (meth) acrylate, amino group-containing (meth) acrylate, epoxy group-containing (meth) acrylate, N-acryloylmorpholine, vinyl ether It is also possible to use a kind etc. suitably.

  In a preferred embodiment, the polyoxyalkylene chain-containing compound not containing the organopolysiloxane is a compound having a (poly) ethylene oxide chain at least partially. By blending the compound having the (poly) ethylene oxide chain, the compatibility between the base polymer and the antistatic agent is improved, bleeding to the adherend is suitably suppressed, and a low-staining adhesive composition is obtained. can get. In particular, when a PPG-PEG-PPG block copolymer is used, a pressure-sensitive adhesive composition excellent in low contamination can be obtained. As said polyethylene oxide chain containing compound, it is preferable that the mass ratio of the (poly) ethylene oxide chain to the said whole compound is 5-90 mass%, More preferably, it is 5-85 mass%, More preferably, it is 5-80 mass. %, Most preferably 5 to 75% by mass.

  The number average molecular weight (Mn) of the polyoxyalkylene chain-containing compound not containing the organopolysiloxane is preferably 50000 or less, more preferably 200 to 30000, still more preferably 200 to 10000, and more preferably 200 to 5000. Particularly preferably used. When Mn is larger than 50000, compatibility with the (meth) acrylic polymer is lowered, and the pressure-sensitive adhesive layer tends to be whitened. If Mn is less than 200, contamination with the polyoxyalkylene compound may easily occur. In addition, Mn means the value of polystyrene conversion obtained by GPC (gel permeation chromatography) here.

  Specific examples of commercially available polyoxyalkylene chain-containing compounds that do not contain the organopolysiloxane include, for example, Adekapluronic 17R-4, Adekapluronic 25R-2 (all of which are manufactured by ADEKA), Emulgen 120 ( And Kao).

  As a compounding quantity of the polyoxyalkylene chain containing compound which does not contain the said organopolysiloxane, it can be set as 0.005-20 mass parts with respect to 100 mass parts of said (meth) acrylic-type polymers, Preferably it is 0. 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, and most preferably 0.1 to 1 part by mass. When the blending amount is too small, when the antistatic agent is blended, the effect of preventing bleeding of the antistatic agent is reduced. When the blending amount is too large, contamination with the polyoxyalkylene compound may easily occur.

  Furthermore, the pressure-sensitive adhesive composition may contain an acrylic oligomer. The acrylic oligomer preferably has a weight average molecular weight (Mw) of 1000 or more and less than 30000, more preferably 1500 or more and less than 20000, and still more preferably 2000 or more and less than 10,000. When the weight average molecular weight is 30000 or more, the adhesion (adhesion) property is lowered. On the other hand, when the weight average molecular weight is less than 1000, the molecular weight becomes low, which causes a decrease in the adhesive strength of the adhesive sheet.

For the acrylic oligomer, a (meth) acrylic acid ester monomer can be used. For example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, (meth) Butyl acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, (Meth) acrylic acid-2-ethylhexyl, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, (meth) acrylic acid Decyl, isodecyl (meth) acrylate, undecyl (meth) acrylate , (Meth) such as acrylic acid dodecyl (meth) acrylic acid alkyl ester;
(Meth) acrylic acid aryl esters such as phenyl (meth) acrylate and benzyl (meth) acrylate;
Examples thereof include (meth) acrylic acid esters obtained from terpene compound derivative alcohols.
The acrylic oligomer may be a (meth) acrylic monomer having an alicyclic structure, such as dicyclopentanyl methacrylate, dicyclopentanyl acrylate, dicyclopentanyloxyethyl methacrylate, dicyclopentanyl. Oxyethyl acrylate, tricyclopentanyl methacrylate, tricyclopentanyl acrylate, 1-adamantyl methacrylate, 1-adamantyl acrylate, 2-methyl-2-adamantyl methacrylate, 2-methyl-2-adamantyl acrylate, 2-ethyl-2- Examples include (meth) acrylic acid esters such as adamantyl methacrylate and 2-ethyl-2-adamantyl acrylate. Such (meth) acrylic monomers can be used alone or in combination of two or more.

  In addition to the (meth) acrylic monomer component unit, the acrylic oligomer may be obtained by copolymerizing another monomer component (copolymerizable monomer) copolymerizable with the (meth) acrylic monomer. Is possible.

  Further, the pressure-sensitive adhesive composition can contain a compound that causes keto-enol tautomerism as a crosslinking retarder. For example, in a pressure-sensitive adhesive composition containing a cross-linking agent or a pressure-sensitive adhesive composition that can be used by blending a cross-linking agent, an embodiment including a compound that produces the keto-enol tautomerism can be preferably employed. Thereby, the excessive viscosity raise and gelation of an adhesive composition after a crosslinking agent mixing | blending can be suppressed, and the effect of extending the pot life of an adhesive composition may be implement | achieved. When at least an isocyanate compound is used as the crosslinking agent, it is particularly meaningful to contain a compound that causes keto-enol tautomerism. This technique can be preferably applied when, for example, the pressure-sensitive adhesive composition is in an organic solvent solution or a solvent-free form.

  Various β-dicarbonyl compounds can be used as the compound that causes keto-enol tautomerism. Specific examples include acetylacetone, 2,4-hexanedione, 3,5-heptanedione, 2-methylhexane-3,5-dione, 6-methylheptane-2,4-dione, 2,6-dimethylheptane- Β-diketones such as 3,5-dione; acetoacetates such as methyl acetoacetate, ethyl acetoacetate, isopropyl acetoacetate, tert-butyl acetoacetate; ethyl propionyl acetate, ethyl propionyl acetate, isopropyl propionyl acetate, propionyl acetate propionyl acetates such as tert-butyl; isobutyryl acetates such as ethyl isobutyryl acetate, ethyl isobutyryl acetate, isopropyl isobutyryl acetate, tert-butyl isobutylyl acetate; malonates such as methyl malonate and ethyl malonate; etc. And the like. Among these, acetylacetone and acetoacetic acid esters are preferable compounds. Such compounds that produce keto-enol tautomerism may be used alone or in combinations of two or more.

  Content of the compound which produces the keto-enol tautomerism can be 0.1-20 mass parts with respect to 100 mass parts of said (meth) acrylic-type polymers, and usually 0.5-15. It is appropriate to set it as a mass part (for example, 1-10 mass parts). If the amount of the compound is too small, it may be difficult to achieve a sufficient use effect. On the other hand, if the compound is used more than necessary, it may remain in the pressure-sensitive adhesive layer and reduce the cohesive force.

  Furthermore, the pressure-sensitive adhesive composition used in the pressure-sensitive adhesive sheet of the present invention may contain other known additives as long as the properties are not impaired. For example, powders such as colorants and pigments , Surfactant, plasticizer, tackifier, surface lubricant, leveling agent, antioxidant, corrosion inhibitor, light stabilizer, UV absorber, polymerization inhibitor, silane coupling agent, inorganic or organic filling An agent, a metal powder, a particle, a foil, and the like can be appropriately added depending on the use.

  The pressure-sensitive adhesive sheet of the present invention preferably has a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition (formed by crosslinking the pressure-sensitive adhesive composition) on one side or both sides of the support film. The crosslinking of the pressure-sensitive adhesive composition is generally performed after application of the pressure-sensitive adhesive composition, but it is also possible to transfer a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition after crosslinking to a support film or the like. is there. The method for forming the pressure-sensitive adhesive layer on the support film is not particularly limited. For example, the pressure-sensitive adhesive composition is applied to the support film, and the polymerization solvent is removed by drying, so that the pressure-sensitive adhesive layer is formed on the support film. It is produced by forming. Thereafter, curing may be performed for the purpose of adjusting the component transfer of the pressure-sensitive adhesive layer or adjusting the crosslinking reaction. In addition, when a pressure-sensitive adhesive composition is applied on a support film to prepare a pressure-sensitive adhesive sheet, one or more solvents other than the polymerization solvent are newly added to the pressure-sensitive adhesive composition so that the pressure-sensitive adhesive composition can be uniformly applied on the support film. You may add to.

<Support film>
The pressure-sensitive adhesive sheet of the present invention is preferably formed by forming a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition on one side or both sides of a support film. In the technology disclosed herein, the resin material constituting the support film can be used without any particular limitation. For example, transparency, mechanical strength, thermal stability, moisture shielding property, isotropic property, flexibility It is preferable to use a material excellent in properties such as property and dimensional stability. In particular, since the support film has flexibility, the pressure-sensitive adhesive composition can be applied by a roll coater or the like, and can be wound into a roll, which is useful.

  Examples of the support film (support, substrate) include polyester polymers such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate; cellulose polymers such as diacetyl cellulose and triacetyl cellulose; polycarbonates A plastic film composed of a resin material comprising a polymer; an acrylic polymer such as polymethyl methacrylate; etc. as a main resin component (a main component of the resin component, typically a component occupying 50% by mass or more), It can be preferably used as a support film. Other examples of the resin material include styrene polymers such as polystyrene and acrylonitrile-styrene copolymers; olefin polymers such as polyethylene, polypropylene, polyolefins having a cyclic or norbornene structure, and ethylene-propylene copolymers; Examples of the resin material include vinyl chloride polymers; amide polymers such as nylon 6, nylon 6,6, and aromatic polyamide. Still other examples of the resin material include imide polymers, sulfone polymers, polyether sulfone polymers, polyether ether ketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers. , Arylate polymers, polyoxymethylene polymers, epoxy polymers and the like. A support film made of a blend of two or more of the above-described polymers may be used.

  As the support film, a plastic film made of a transparent thermoplastic resin material can be preferably used. Among the plastic films, it is more preferable to use a polyester film. Here, the polyester film is one having a polymer material (polyester resin) having a main skeleton based on an ester bond such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or polybutylene terephthalate as a main resin component. Say. Such a polyester film has preferable characteristics as a support film for the pressure-sensitive adhesive sheet (surface protective film), such as excellent optical characteristics and dimensional stability, and has the property of being easily charged as it is.

  Various additives such as an antioxidant, an ultraviolet absorber, a plasticizer, and a colorant (pigment, dye, etc.) may be blended in the resin material constituting the support film, if necessary. For example, a known or conventional surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and application of a primer may be performed. Such a surface treatment can be, for example, a treatment for enhancing adhesion and anchoring properties between the support film and the pressure-sensitive adhesive layer and other layers (for example, an antistatic layer). Surface treatment in which polar groups such as hydroxyl groups are introduced on the surface of the support film can be preferably employed.

  Moreover, it is also possible to use the plastic film by which antistatic treatment was made | formed as said support film. By using the support film, it is possible to suppress the charge of the pressure-sensitive adhesive sheet (surface protective film) itself when peeled and to have an excellent antistatic ability to the adherend. In addition, there is no restriction | limiting in particular as a method to provide an antistatic function, A conventionally well-known method can be used, for example, antistatic resin which consists of an antistatic agent and a resin component, a conductive polymer, and a conductive substance. Examples thereof include a method of applying a conductive resin, a method of forming an antistatic layer, a method of depositing or plating a conductive substance, and a method of kneading an antistatic agent directly on a support film.

  The thickness of the support film is usually 5 to 200 μm, preferably about 10 to 150 μm. When the thickness of the support film is within the above range, it is preferable because the workability for bonding to the adherend and the workability for peeling from the adherend are excellent.

  Moreover, as a formation method of the adhesive layer at the time of manufacturing the adhesive sheet of this invention, the well-known method used for manufacture of adhesive sheets is used. Specific examples include roll coating, gravure coating, reverse coating, roll brushing, spray coating, air knife coating, extrusion coating using a die coater, and the like.

  The pressure-sensitive adhesive sheet of the present invention is usually prepared so that the thickness of the pressure-sensitive adhesive layer is preferably 3 to 100 μm, more preferably about 5 to 50 μm. It is preferable for the thickness of the pressure-sensitive adhesive layer to be within the above-mentioned range, since it is easy to obtain a suitable balance between removability and adhesion (adhesion).

<Separator>
In the pressure-sensitive adhesive sheet (surface protective film) of the present invention, a separator can be bonded to the surface of the pressure-sensitive adhesive layer for the purpose of protecting the pressure-sensitive adhesive surface as necessary.

  Examples of the material constituting the separator include paper and plastic film, and a plastic film is preferably used from the viewpoint of excellent surface smoothness. The film is not particularly limited as long as it can protect the pressure-sensitive adhesive layer. For example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer Examples thereof include a coalesced film, a polyethylene terephthalate film, a polybutylene terephthalate film, a polyurethane film, and an ethylene-vinyl acetate copolymer film.

  The thickness of the separator is usually about 5 to 200 μm, preferably about 10 to 100 μm. It is preferable for it to be in the above-mentioned range since it is excellent in workability for bonding to the pressure-sensitive adhesive layer and workability for peeling from the pressure-sensitive adhesive layer. For the separator, if necessary, mold release and antifouling treatment with a silicone type, fluorine type, long chain alkyl type or fatty acid amide type release agent, silica powder, etc., coating type, kneading type, vapor deposition type It is also possible to carry out antistatic treatment such as.

  The optical member of the present invention is preferably protected by the pressure-sensitive adhesive sheet. Since the pressure-sensitive adhesive sheet is excellent in shearing force, curling of the adherend (optical member) to which the pressure-sensitive adhesive sheet is bonded can be suppressed, and since the handleability is excellent, the pressure-sensitive adhesive sheet is useful.

  Hereinafter, several examples related to the present invention will be described, but the present invention is not intended to be limited to those shown in the specific examples. In the following description, “part” and “%” are based on mass unless otherwise specified. In addition, the compounding amount in Table 1 indicates a solid content.

  Each characteristic in the following description was measured or evaluated as follows.

<Measurement of weight average molecular weight (Mw) of (meth) acrylic polymer>
The weight average molecular weight (Mw) was measured using a GPC apparatus (HLC-8320GPC) manufactured by Tosoh Corporation. The measurement conditions are as follows.

Sample concentration: 0.2% by mass (THF solution)
Sample injection volume: 100 μl
Eluent: THF
Flow rate: 0.5 ml / min
Measurement temperature: 40 ° C
column:
Sample column; TSKgel GMH-H (S) (2)
Reference column; TSKgel GMH-H (S) (2)
Detector: Differential refractometer (RI)
The weight average molecular weight was determined in terms of polystyrene. The content ratio of (meth) acrylic polymer having a molecular weight of 10,000 or less (ratio in the total amount of (meth) acrylic polymer generated during polymerization: area%) is obtained from the area of the integrated molecular weight distribution curve obtained from the GPC measurement result. It was.

<Glass transition temperature (Tg) of (meth) acrylic polymer>
The glass transition temperature Tg (° C.) was determined by the following formula (18) using the following literature value as the glass transition temperature Tgn (° C.) of the homopolymer of each monomer.

Formula (18): 1 / (Tg + 273) = Σ [Wn / (Tgn + 273)]
[Wherein, Tg (° C.) is the glass transition temperature of the copolymer, Wn (−) is the mass fraction of each monomer, Tgn (° C.) is the glass transition temperature of the homopolymer of each monomer, and n is the type of each monomer Represents. ] Literature values:
2-ethylhexyl acrylate (2EHA): -70 ° C
4-hydroxybutyl acrylate (4HBA): -32 ° C
Acrylic acid (AA): 106 ° C

  As reference values, “Synthesis / design of acrylic resin and development of new applications” (published by Central Management Development Center Publishing Department) and “Polymer Handbook” (John Wiley & Sons) were referred to.

<Measurement of shear force>
After the pressure-sensitive adhesive sheet is cut to a size of 10 mm in width and 100 mm in length and the separator is peeled off, a TAC polarizing plate (Nitto Denko Corporation) is used so that the pressure-sensitive adhesive (adhesion) area of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is 1 cm ^2. Manufactured by SEG1423DU polarizing plate, width: 25 mm, length: 100 mm), and pulled in the shear direction at a pulling speed of 0.06 m / min at 23 ° C., and the maximum load (N / cm ² ) at that time is the shear force did.

Incidentally, the shear force, 15N / cm ² or more, more preferably, 15~50N / cm ^2, and more preferably from 16~40N / cm ^2. If the shearing force is within the above range, it can withstand the force in the shearing direction that occurs when the adherend tries to curl, and the adhesive sheet does not slip or slip, and the adherend is curled. Since it can suppress, it is preferable.

<Example 1>
<Preparation of (meth) acrylic polymer>
In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser, 100 parts by mass of 2-ethylhexyl acrylate (2EHA), 10 parts by mass of 4-hydroxybutyl acrylate (4HBA), acrylic acid (AA) 0.02 part by mass, 2,2′-azobisisobutyronitrile (AIBN) 0.2 part by mass and 157 parts by mass of ethyl acetate as a polymerization initiator were charged, nitrogen gas was introduced while gently stirring, The liquid temperature inside was kept at around 60 ° C., and a polymerization reaction (no aging step) was carried out for 8 hours to prepare a (meth) acrylic polymer solution (40 mass%).
The (meth) acrylic polymer had a weight average molecular weight of 660,000 and a glass transition temperature (Tg) of −67 ° C.
The content ratio of the (meth) acrylic polymer having a molecular weight of 10,000 or less was 2.8 area%.

<Preparation of acrylic adhesive solution>
The acrylic polymer solution (40% by mass) is diluted to 20% by mass with ethyl acetate, and isocyanurate of hexamethylene diisocyanate (Nippon Polyurethane Industry Co., Ltd.) as a crosslinking agent to 500 parts by mass (100 parts by mass of solid content) of this solution. Co., Ltd., Coronate HX: C / HX) 1.5 parts by mass (solid content 1.5 parts by mass), 3 parts by mass of dibutyltin dilaurate (1% by mass ethyl acetate solution) as a crosslinking catalyst (solid content 0.03 parts by mass) ) Was added and mixed and stirred to prepare an acrylic pressure-sensitive adhesive solution.

<Support film>
A transparent polyethylene terephthalate (PET) film (polyester film) having a thickness of 38 μm, a width of 30 cm, and a length of 40 cm was used as a support film.

<Preparation of pressure-sensitive adhesive sheet (surface protective film)>
The acrylic pressure-sensitive adhesive solution was applied to the support film and heated at 130 ° C. for 1 minute to form a pressure-sensitive adhesive layer having a thickness of 15 μm. Next, a silicone-treated surface of a polyethylene terephthalate film (thickness 25 μm), which is a separator having a silicone treatment on one side, was bonded to the surface of the pressure-sensitive adhesive layer to produce a pressure-sensitive adhesive sheet.

<Examples 2 to 4>
Based on the content of Table 1, a pressure-sensitive adhesive sheet was produced in the same manner as in Example 1.

<Example 5>
In Example 5, a pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that 0.4 part by mass of AIBN was blended, based on the blending contents of Table 1.

<Comparative Example 1>
In Comparative Example 1, the temperature of the liquid in the flask was kept at around 60 ° C. for 4 hours, and further the temperature was raised to 70 ° C. and the polymerization reaction was carried out for 4 hours to obtain a (meth) acrylic polymer solution (40 A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 based on the contents of Table 1, except that (mass%) was prepared.

  Table 1 shows the results of various measurements and evaluations described above for the pressure-sensitive adhesive sheets according to Examples and Comparative Examples.

  From the results of Table 1 above, it was confirmed that in all Examples, the shearing force was excellent. In Example 5, the content of the (meth) acrylic polymer (low molecular weight component) having a molecular weight of 10,000 or less is desired by blending a larger amount of AIBN than in the other examples. Although it was within the range, a high value was shown.

  On the other hand, in Comparative Example 1, the content ratio of the (meth) acrylic polymer (low molecular weight component) having a molecular weight of 10,000 or less exceeded the desired range. It was confirmed that the shear force was inferior.

Claims (7)

As a monomer component, 50 to 99.9% by mass of a (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms, a hydroxyl group-containing (meth) acrylic monomer, and a carboxyl group-containing (meth) acrylic monomer A pressure-sensitive adhesive composition containing a (meth) acrylic polymer containing a monomer,
The (meth) acrylic polymer has a weight average molecular weight of 100,000 to 5,000,000, and a proportion of a (meth) acrylic polymer having a molecular weight of 10,000 or less is 5 area% or less. object. The pressure-sensitive adhesive according to claim 1, comprising 0.1 to 30% by mass of the hydroxyl group-containing (meth) acrylic monomer with respect to the total amount of the monomer components constituting the (meth) acrylic polymer. Composition. The carboxyl group-containing (meth) acrylic monomer is contained in an amount of 0.001 to 1% by mass with respect to the total amount of monomer components constituting the (meth) acrylic polymer. Adhesive composition. The said adhesive composition contains a crosslinking agent further, The adhesive composition in any one of Claims 1-3 characterized by the above-mentioned. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to claim 1 on one or both sides of a support film. When the adhesive area of 1 cm ² of the pressure-sensitive adhesive layer is bonded to a TAC polarizing plate and peeled in the shearing direction at a peeling speed of 0.06 m / min after pasting at 23 ° C. for 30 minutes, the shear force is 15 N / cm ² or more. The pressure-sensitive adhesive sheet according to claim 5, wherein the pressure-sensitive adhesive sheet is provided. An optical member protected by the adhesive sheet according to claim 5.