JP2018159054A - Surface protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical surface protective film with low ultraviolet light transmissivity, hue change suppressed, and excellent adhesive force stability.SOLUTION: An optical surface protective film includes a base material composed of a polyester resin and an adhesive layer composed of an adhesive composition on one side of the base material. In the optical surface protective film, a b* value of the surface protective film is 2 or less, transmissivity of the surface protective film is 2% or less at a wavelength 365 nm. In the adhesive layer after adhered on glass, a rate of change of an adhesive force before heating and an adhesive force after heating at 100°C for 30 minutes is ±30% or smaller.SELECTED DRAWING: None

Description

  The present invention relates to an optical surface protective film. In particular, the surface of an optical member (for example, a polarizing plate, a wave plate, a retardation plate, an optical compensation film, a reflection sheet, a brightness enhancement film, a cover glass for a display, etc. used in a liquid crystal display) is deteriorated due to protection or ultraviolet irradiation It is useful as an optical surface protective film used to protect members that are easily damaged from ultraviolet rays.

  The protective film generally has a configuration in which an adhesive layer is provided on a film-like substrate. Such a protective film is bonded to an optical member which is an adherend through the pressure-sensitive adhesive layer, and is used for the purpose of protecting the optical member from scratches and dirt on the surface during processing, transportation, inspection, and the like. . For example, a panel of a liquid crystal display is formed by attaching an optical member such as a polarizing plate or a wave plate to a liquid crystal cell via an adhesive layer (Patent Document 1).

  As the protective film, since an appearance inspection or the like may be performed in a state of being bonded to an optical member or the like, a protective film that can prevent a hue change (discoloration such as red discoloration) of the protective film over time is required.

  In addition, since the liquid crystal sealed in the liquid crystal cell used for the panel of the liquid crystal display is deteriorated by ultraviolet rays, a protective film having an ultraviolet absorbing function is attached to a member such as a polarizing plate attached to the liquid crystal cell. And used.

  In addition, in recent years, when manufacturing cover glass for mobile terminals such as thin smartphones and tablets, bonding work is performed using a resin that is cured by active energy such as ultraviolet light and heat, but ultraviolet irradiation is not required, A member that deteriorates due to ultraviolet rays may be used, and a protective film containing an ultraviolet absorber is used to protect such a member.

  The used protective film is peeled and removed when it is no longer needed, but if you try to peel and remove the protective film attached to a cover glass used in thinned smartphones, etc., the adhesive strength will increase due to ultraviolet rays or heat. If the protective film is raised, it is difficult to peel and remove easily, which may cause damage to the cover glass.

JP 2007-304425 A

  In view of the above circumstances, the present inventors have intensively studied, and as a result, have an object of providing an optical surface protective film having a low ultraviolet transmittance, suppressed hue change, and excellent adhesive strength stability. .

  That is, the optical surface protective film of the present invention includes a base material formed from a polyester-based resin, and an optical surface protection provided with a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition on one side of the base material. The surface protective film has a b * value of 2 or less, and the surface protective film has a transmittance of 2% or less at a wavelength of 365 nm. The adhesive force and the change rate of the adhesive force after heating at 100 ° C. for 30 minutes are ± 30% or less.

  In the optical surface protective film of the present invention, the pressure-sensitive adhesive composition preferably contains an ultraviolet absorber.

  In the optical surface protective film of the present invention, the number of hydroxyl groups in the molecule of the ultraviolet absorber is preferably 3 or less.

  In the optical surface protective film of the present invention, the pressure-sensitive adhesive composition preferably contains a (meth) acrylic polymer and / or a urethane polymer as a base polymer.

  In the optical surface protective film of the present invention, the pressure-sensitive adhesive composition preferably contains 0.1 to 20 parts by weight of the ultraviolet absorber with respect to 100 parts by weight of the base polymer.

  The optical surface protective film of the present invention preferably has a thickness of the base material of 6 to 100 μm and a thickness of the pressure-sensitive adhesive layer of 1 to 30 μm.

  INDUSTRIAL APPLICABILITY By using a surface protective film having specific optical characteristics, the present invention can provide an optical surface protective film having low UV transmittance, suppressed hue change, and excellent adhesive strength stability. It is.

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

<Overall structure of surface protective film for optics>
The optical surface protective film disclosed herein (hereinafter sometimes simply referred to as “surface protective film”) generally has a pressure-sensitive adhesive layer surface in a form called an adhesive tape, an adhesive label, an adhesive film or the like as a separator. Surface protection that protects the surface of optical components especially during processing, inspection, and transportation of optical components (for example, optical components used as liquid crystal display panel components of polarizing plates, wave plates, and cover glasses) Suitable as a film. The pressure-sensitive adhesive layer in the surface protective film is typically formed continuously, but is not limited to such a form, and is formed in a regular or random pattern such as a spot or stripe. It may be an adhesive layer. In addition, the surface protective film disclosed herein may be in the form of a roll or a single sheet.

<Base material>
The optical surface protective film of the present invention is characterized by having a substrate formed of a polyester resin. The base material formed from the said polyester-type resin has a preferable characteristic as a base material of a surface protection film, such as being excellent in an optical characteristic and dimensional stability.

  As the polyester resin, a main resin component (resin component) is a polyester polymer material (polyester resin) having a main skeleton based on an ester bond such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate. Among them, those composed of a resin material having a main component (typically a component occupying 50% by weight or more) can be preferably used as the substrate. Examples of other resin materials other than the polyester resins include styrene polymers such as polystyrene and acrylonitrile-styrene copolymers; olefins such as polyethylene, polypropylene, polyolefins having a cyclic or norbornene structure, and ethylene-propylene copolymers. Examples of the resin material include: vinyl polymers; 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. The base material which consists of 2 or more types of blends of the polymer mentioned above may be sufficient.

  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 substrate as 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 improving the adhesion between the base material and the pressure-sensitive adhesive layer (the anchoring property of the pressure-sensitive adhesive layer).

  It is also possible to use a substrate that has been subjected to an antistatic treatment as the substrate. The use of the substrate is preferable because charging of the surface protective film itself when peeled can be suppressed. In addition, by subjecting the base material to an antistatic treatment, it is possible to reduce the surface protection film itself and to provide 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, a conductive substance Examples thereof include a method of applying a conductive resin, a method of depositing or plating a conductive material, a method of kneading an antistatic agent, and the like.

  The thickness of the base material is preferably 6 to 100 μm, more preferably 10 to 60 μm, and still more preferably 15 to 40 μm. When the thickness of the base material is within the above range, it is preferable because it is excellent in bonding workability to the adherend, peelability from the adherend and workability.

  The surface protective film disclosed herein can be implemented in an embodiment including other layers in addition to the base material and the pressure-sensitive adhesive layer. Examples of the other layer include an undercoat layer (anchor layer) that improves the anchoring property of the antistatic layer and the pressure-sensitive adhesive layer. Moreover, you may stick a separator in order to protect the adhesive layer surface.

<Adhesive layer>
The optical surface protective film of the present invention is characterized in that a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition is provided on one side of the substrate. The pressure-sensitive adhesive layer used in the present invention can be used without particular limitation as long as it is formed from a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive polymer. Examples of the pressure-sensitive adhesive composition include acrylic pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, synthetic rubber-based pressure-sensitive adhesives, natural rubber-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, and polyester-based pressure-sensitive adhesives. As the base polymer, it is preferable to use a pressure-sensitive adhesive composition containing a (meth) acrylic polymer and / or a urethane polymer.

<Acrylic adhesive>
When the pressure-sensitive adhesive layer uses an acrylic pressure-sensitive adhesive, a (meth) acrylic polymer, which is a pressure-sensitive polymer constituting the acrylic pressure-sensitive adhesive, is used as a base polymer, and as a raw material monomer constituting the same, 1 to A (meth) acrylic monomer having 14 alkyl groups can be used as the main monomer. As said (meth) acrylic-type monomer, 1 type (s) or 2 or more types can be used. By using the (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms, it becomes easy to control the peeling force (adhesive strength) to the adherend (protected body) to be low and light peeling. A surface protective film excellent in removability and removability can be 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.

  Among these, in the surface protective film of the present invention, in particular, n-butyl (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) ) A (meth) acrylic monomer having an alkyl group having 4 to 14 carbon atoms such as acrylate is preferred. In particular, by using a (meth) acrylic monomer having an alkyl group having 4 to 14 carbon atoms, it becomes easy to control the peel force (adhesive force) to the adherend to be low and has excellent removability. It becomes.

  In particular, it is preferable to contain 65% by weight or more of a (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms with respect to 100% by weight of the total amount of monomer components constituting the (meth) acrylic polymer. More preferably, it is 75% by weight or more, still more preferably 85 to 99.9% by weight, particularly preferably 90 to 99% by weight. If it is less than 65% by weight, the appropriate wettability of the pressure-sensitive adhesive composition and the cohesive strength of the pressure-sensitive adhesive layer are inferior, which is not preferable.

  In the (meth) acrylic polymer, a hydroxyl group-containing (meth) acrylic monomer can be used as a raw material monomer. 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 easy to control the crosslinking of the pressure-sensitive adhesive composition, and as a result, balance between improvement of wettability by flow and reduction of peeling force (adhesive strength) in peeling. It becomes easier 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, and the like. .

  The hydroxyl group-containing (meth) acrylic monomer is preferably contained in an amount of 25% by weight or less, more preferably 15% by weight or less, based on 100% by weight of the total amount of monomer components constituting the (meth) acrylic polymer. More preferably, it is 0.1 to 10% by weight, and particularly preferably 1 to 5% by weight. Within the above range, the balance between the wettability of the pressure-sensitive adhesive composition and the cohesive force of the resulting pressure-sensitive adhesive layer can be easily controlled, which is preferable.

  In addition, as another polymerizable monomer component, the Tg is 0 ° C. or lower (usually −100 ° C. or higher) for the reason that it is easy to balance the adhesive performance, and the glass transition temperature or peeling of the (meth) acrylic polymer. A polymerizable monomer or the like for adjusting the property can be used as long as the effects of the present invention are not impaired.

  In the (meth) acrylic polymer, a carboxyl group-containing (meth) acrylic monomer can be used as a raw material monomer. By using the carboxyl group-containing (meth) acrylic monomer, the pressure-sensitive adhesive layer (surface protective film) can be prevented from increasing in adhesive strength over time, re-peelability, adhesive strength-increasing property, and work Excellent in properties. In addition to the cohesive force of the pressure-sensitive adhesive layer, it is excellent in shearing force, which is preferable.

  Examples of the carboxyl group-containing (meth) acrylic monomer include (meth) acrylic acid, carboxylethyl (meth) acrylate, carboxylpentyl (meth) acrylate, and the like.

  The carboxyl group-containing (meth) acrylic monomer is preferably 10% by weight or less, preferably 0 to 8% by weight with respect to 100% by weight of the total amount of monomer components constituting the (meth) acrylic polymer. Is more preferable, and it is still more preferable that it is 0 to 6 weight%. Within the above range, the balance between the wettability of the pressure-sensitive adhesive composition and the cohesive force of the resulting pressure-sensitive adhesive layer can be easily controlled, which is preferable.

  Furthermore, the said (meth) acrylic-type polymer can use other polymerizable monomers other than the said raw material monomer, unless it is in the range which does not impair the characteristic of this invention. For example, as the other polymerizable monomer, a cohesive force / heat resistance improving component such as a cyano group-containing monomer, vinyl ester monomer, aromatic vinyl monomer, amide group-containing monomer, imide group-containing monomer, amino group-containing monomer, epoxy A component having a functional group that functions as an improvement in peeling force (adhesive force) and a crosslinking base point such as a group-containing monomer, N-acryloylmorpholine, and vinyl ether monomer can be used as appropriate. Among these, it is preferable to use nitrogen-containing monomers such as cyano group-containing monomers, amide group-containing monomers, imide group-containing monomers, amino group-containing monomers, and N-acryloylmorpholine. Use of a nitrogen-containing monomer is useful because it can ensure an appropriate peeling force (adhesive strength) that does not cause floating or peeling, and can provide a surface protective film having excellent shearing force. These polymerizable monomers can be used alone or in combination of two or more.

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

  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 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 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 other polymerizable monomer is preferably 0 to 30% by weight, and 0 to 10% by weight with respect to 100% by weight of the total amount of monomer components constituting the (meth) acrylic polymer. It is more preferable. The other polymerizable monomers can be appropriately adjusted in order to obtain desired characteristics.

  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, it is preferable that it is 1-40 from a compatible viewpoint with an oxyalkylene group containing compound, and it is 3-40. Is more preferable, it is more preferable that it is 4-35, and it is especially preferable that it is 5-30. 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 an oxyalkylene group containing 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. In addition, the terminal of the oxyalkylene chain may be substituted with other functional groups or the like as a hydroxyl 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. Among these, 0 to 20% by weight is preferable, and 0 to 10% by weight is more preferable. When the content of the alkylene oxide group-containing reactive monomer exceeds 20% by weight, the contamination on the adherend deteriorates, 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 reactive monomer-containing (meth) acrylic polymer having an ethylene oxide group as a base polymer, the compatibility between the base polymer and the oxyalkylene group-containing 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 (meth) acrylic polymer preferably has a weight average molecular weight (Mw) of 100,000 to 5,000,000, more preferably 200,000 to 4,000,000, still more preferably 300,000 to 3,000,000, and most preferably 300,000 to 1,200,000. It is. 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 wetness to the adherend (for example, polarizing plate) becomes insufficient, and the adherend and the pressure-sensitive adhesive layer of the surface protective film It tends to cause blisters that occur during the period. 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 does not flow easily, for example, the wettability to the polarizing plate which is an optical member becomes insufficient, and the swelling generated between the polarizing plate and the pressure-sensitive adhesive layer of the surface protective film There is a tendency to cause. In particular, by setting the glass transition temperature to −70 ° C. or lower, an adhesive layer excellent in wettability to the polarizing plate 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 polymerization method of the (meth) acrylic polymer is not particularly limited, and can be polymerized by known methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, etc. From the viewpoint of characteristics such as low contamination to the adherend (protected body), solution polymerization is a more preferable embodiment. Further, the polymer obtained may be any of a random copolymer, a block copolymer, an alternating copolymer, a graft copolymer, and the like.

<Urethane adhesive>
When using a urethane-type adhesive for the said adhesive layer, arbitrary appropriate urethane-type adhesives can be employ | adopted. As such a urethane-based pressure-sensitive adhesive, preferably, a urethane polymer that is a pressure-sensitive adhesive polymer obtained by reacting a polyol and a polyisocyanate compound is used as a base polymer. The polyurethane resin can be obtained by curing a composition containing a polyol and a polyisocyanate compound.

  The content of the polyurethane-based resin in the urethane-based pressure-sensitive adhesive is preferably 40% by weight or more, more preferably 50% by weight or more, still more preferably 55% by weight or more, and more preferably as a lower limit. Is 60% by weight, particularly preferably 65% by weight, most preferably 70% by weight, and the upper limit is preferably 99.999% by weight or less, more preferably 99.99% by weight or less. More preferably 99.9% by weight or less, still more preferably 99% by weight or less, particularly preferably 95% by weight or less, and most preferably 90% by weight or less. The polyurethane resin may be only one type or two or more types.

  Moreover, as said polyol, only 1 type may be sufficient and 2 or more types may be sufficient.

  Any appropriate polyol can be adopted as the polyol as long as the polyol has two or more OH groups. Examples of such a polyol include a polyol having 2 OH groups (diol), a polyol having 3 OH groups (triol), a polyol having 4 OH groups (tetraol), and a polyol having 5 OH groups. (Pentaol), polyol having 6 OH groups (hexaol) and the like.

  Moreover, as the polyol, a polyol (triol) having three OH groups can be preferably used. Thus, by adopting a polyol (triol) having three OH groups as a polyol, for example, it can be a pressure-sensitive adhesive layer having a high wetting rate, and by combining with a specific substrate employed in the present invention, It is possible to provide a surface protective film having a higher detection rate of scratches and foreign matter contamination. The content ratio of the polyol (triol) having 3 OH groups in the polyol is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, and further preferably 80 to 100% by weight. More preferably, it is 90 to 100% by weight, particularly preferably 95 to 100% by weight, and most preferably substantially 100% by weight.

  As the polyol, a polyol having a number average molecular weight (Mn) of 400 to 20000 can be preferably contained. The content ratio of the polyol having a number average molecular weight (Mn) of 400 to 20000 in the polyol is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, and further preferably 90 to 100% by weight. Particularly preferred is 95 to 100% by weight, and most preferred is substantially 100% by weight.

  Moreover, in this invention, as a polyol (triol) which has three OH groups as a polyol, Preferably, a number average molecular weight (Mn) is 7000-20000 triol, and a number average molecular weight (Mn) is 2000-6000. A triol is used in combination with a triol having a number average molecular weight (Mn) of 400 to 1900, more preferably a triol having a number average molecular weight (Mn) of 8000 to 15000 and a triol having a number average molecular weight (Mn) of 2000 to 5000. And a triol having a number average molecular weight (Mn) of 500 to 1800, more preferably a triol having a number average molecular weight (Mn) of 8000 to 12000, and a triol having a number average molecular weight (Mn) of 2000 to 4000 In combination with a triol having a number average molecular weight (Mn) of 500 to 1500 It is when.

  Examples of the polyol include polyester polyol, polyether polyol, polycaprolactone polyol, polycarbonate polyol, and castor oil-based polyol.

  As said polyester polyol, it can obtain by esterification reaction of a polyol component and an acid component, for example.

  Examples of the polyol component include ethylene glycol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl- 1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 2- Examples include methyl-1,8-octanediol, 1,8-decanediol, octadecanediol, glycerin, trimethylolpropane, pentaerythritol, hexanetriol, and polypropylene glycol.

  Examples of the acid component include succinic acid, methyl succinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, 1,12-dodecanedioic acid, 1,14-tetradecanedioic acid, dimer acid, 2-methyl-1 , 4-cyclohexanedicarboxylic acid, 2-ethyl-1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 4,4′-biphenyl dicarboxylic acid Examples thereof include acids and acid anhydrides thereof.

  Examples of the polyether polyol include water, low-molecular polyol (propylene glycol, ethylene glycol, glycerin, trimethylolpropane, pentaerythritol, etc.), bisphenols (bisphenol A, etc.), dihydroxybenzene (catechol, resorcin, hydroquinone, etc.). The polyether polyol obtained by carrying out addition polymerization of alkylene oxides, such as ethylene oxide, a propylene oxide, a butylene oxide, etc. is mentioned by using these as initiators. Specific examples include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like.

  Examples of the polycaprolactone polyol include caprolactone-based polyester diols obtained by ring-opening polymerization of cyclic ester monomers such as ε-caprolactone and σ-valerolactone.

  Examples of the polycarbonate polyol include a polycarbonate polyol obtained by polycondensation reaction of the polyol component and phosgene; the polyol component, dimethyl carbonate, diethyl carbonate, diprovir carbonate, diisopropyl carbonate, dibutyl carbonate, ethyl butyl carbonate, ethylene carbonate. Polycarbonate polyol obtained by ester exchange condensation with carbonic acid diesters such as propylene carbonate, diphenyl carbonate and dibenzyl carbonate; copolymer polycarbonate polyol obtained by using two or more of the above polyol components in combination; the above various polycarbonate polyols and carboxyl groups Polycarbonate polyol obtained by esterification reaction with a containing compound; the above-mentioned various polycarbonate polyols and a hydroxyl group-containing compound Polycarbonate polyol obtained by etherification reaction of polycarbonate; polycarbonate polyol obtained by transesterification of the above-mentioned various polycarbonate polyols and ester compounds; polycarbonate polyol obtained by transesterification of the above-mentioned various polycarbonate polyols with hydroxyl group-containing compounds Polyester polyester polyols obtained by polycondensation reaction of the above polycarbonate polyols and dicarboxylic acid compounds; copolymer polyether polycarbonate polyols obtained by copolymerization of the various polycarbonate polyols and alkylene oxides; .

  Examples of the castor oil-based polyol include castor oil-based polyol obtained by reacting a castor oil fatty acid with the polyol component. Specific examples include castor oil-based polyols obtained by reacting castor oil fatty acid with polypropylene glycol.

  1 type may be sufficient as the said polyisocyanate compound (polyfunctional isocyanate compound), and 2 or more types may be sufficient as it.

  Any appropriate polyisocyanate compound that can be used for the urethanization reaction can be adopted as the polyisocyanate compound (polyfunctional isocyanate compound). Examples of such polyisocyanate compounds include polyfunctional aliphatic isocyanate compounds, polyfunctional alicyclic isocyanate compounds, and polyfunctional aromatic isocyanate compounds.

  Examples of the polyfunctional aliphatic isocyanate compound include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4. , 4-trimethylhexamethylene diisocyanate and the like.

  Examples of the polyfunctional alicyclic isocyanate compound include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated xylylene diisocyanate. , Hydrogenated tolylene diisocyanate, hydrogenated tetramethylxylylene diisocyanate, and the like.

  Examples of the polyfunctional aromatic diisocyanate compound include phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2 ′ monodiphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-Toluidine diisocyanate, 4,4′-diphenyl ether diisocyanate, 4,4′-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, xylylene diisocyanate, and the like.

  Examples of the polyisocyanate compound include trimethylolpropane adducts of various polyfunctional isocyanate compounds as described above, burettes reacted with water, and trimers having an isocyanurate ring. These may be used in combination.

  The content of the polyisocyanate compound is preferably 5 to 60 parts by weight, more preferably 10 to 50 parts by weight, and still more preferably 15 to 40 parts by weight with respect to 100 parts by weight of the polyol.

  The equivalent ratio of NCO group to OH group in the polyol and the polyisocyanate compound is preferably more than 1.0 and not more than 5.0, more preferably 1.1 to 5 as NCO group / OH group. 0.0, more preferably 1.2 to 4.0, particularly preferably 1.5 to 3.5, and most preferably 1.8 to 3.0.

  The polyurethane resin may contain a fatty acid ester that can be used as a wettability additive. When the polyurethane resin contains a fatty acid ester, the wetting speed can be improved. 1 type of fatty acid ester may be sufficient and 2 or more types may be sufficient as it.

  The content ratio of the fatty acid ester is preferably 5 to 50 parts by weight, more preferably 10 to 45 parts by weight, still more preferably 15 to 40 parts by weight, with respect to 100 parts by weight of the polyol. Preferably it is 20-35 weight part, Most preferably, it is 25-30 weight part. By adjusting the content ratio of the fatty acid ester within the above range, the wetting rate can be further improved. If the content of the fatty acid ester is too small, the wetting rate may not be sufficiently improved. When the content ratio of the fatty acid ester is too large, there may be a problem that the cost becomes disadvantageous, a problem that the adhesive property cannot be maintained, or a problem that the adherend is contaminated.

  The number average molecular weight (Mn) of the fatty acid ester is preferably 200 to 400, more preferably 210 to 395, still more preferably 230 to 380, particularly preferably 240 to 360, most preferably. 270-340. By adjusting the number average molecular weight (Mn) of the fatty acid ester within the above range, the wetting rate can be further improved. If the number average molecular weight (Mn) of the fatty acid ester is too small, the wetting rate may not be improved even if the blending amount is large. If the number average molecular weight (Mn) of the fatty acid ester is too large, the curability of the pressure-sensitive adhesive at the time of drying deteriorates, and there is a possibility that it will not only affect the wettability but also adversely affect other pressure-sensitive adhesive properties.

  Any appropriate fatty acid ester can be adopted as the fatty acid ester as long as the effects of the present invention are not impaired. Examples of such fatty acid esters include polyoxyethylene bisphenol A lauric acid ester, butyl stearate, 2-ethylhexyl palmitate, 2-ethylhexyl stearate, behenic acid monoglyceride, cetyl 2-ethylhexanoate, myristic acid Isopropyl, isopropyl palmitate, cholesteryl isostearate, lauryl methacrylate, coconut fatty acid methyl, methyl laurate, methyl oleate, methyl stearate, myristyl myristate, octyldodecyl myristate, pentaerythritol monooleate, pentaerythritol monostearate , Pentaerythritol tetrapalmitate, stearyl stearate, isotridecyl stearate, triglyceride 2-ethylhexanoate , Butyl laurate, and the like octyl oleate.

  The polyurethane resin may include a leveling agent. By including a leveling agent in the polyurethane resin, it is possible to prevent uneven appearance due to the skin. The leveling agent may be only one kind or two or more kinds.

  As a method of obtaining a polyurethane resin by curing the composition containing the polyol and the polyisocyanate compound, any method may be used as long as the effects of the present invention are not impaired, such as a urethanization reaction method using bulk polymerization or solution polymerization. Appropriate methods can be employed. However, in the conventional polyurethane-based resin obtained via a so-called urethane prepolymer, the effect of the present invention may not be exhibited. Therefore, the composition containing the polyol and the polyisocyanate compound is cured to form a polyurethane. The method for obtaining the resin is preferably a method other than the method for obtaining the polyurethane resin through the urethane prepolymer.

<Ultraviolet absorber>
In the optical surface protective film of the present invention, the pressure-sensitive adhesive composition preferably contains an ultraviolet absorber, and the number of hydroxyl groups in the molecule of the ultraviolet absorber is preferably 3 or less. By using an ultraviolet absorber, it becomes possible to protect a member that is easily deteriorated by ultraviolet rays. Furthermore, by using an ultraviolet absorber having 3 or less hydroxyl groups, the adhesive layer has excellent adhesive force stability, preferable. In addition, when there are many hydroxyl groups in the molecule | numerator of the said ultraviolet absorber, it will be estimated that a ultraviolet absorber reacts with a crosslinking agent and inhibits hardening of an adhesive composition.

  The ultraviolet absorber is not particularly limited, and for example, a triazine ultraviolet absorber, a benzotriazole ultraviolet absorber, a benzophenone ultraviolet absorber, an oxybenzophenone ultraviolet absorber, a salicylic acid ester ultraviolet absorber, a cyanoacrylate An ultraviolet absorber etc. can be mentioned, These can be used individually by 1 type or in combination of 2 or more types. Among these, the number of hydroxyl groups in the molecule of the ultraviolet absorber is more preferably 3 or less.

Specific examples of the triazine ultraviolet absorber having 3 or less hydroxyl groups in one molecule include 2,4-bis-[{4- (4-ethylhexyloxy) -4-hydroxy} -phenyl] -6. -(4-Methoxyphenyl) -1,3,5-triazine (Tinosorb S, manufactured by BASF), 2,4-bis [2-hydroxy-4-butoxyphenyl] -6- (2,4-dibutoxyphenyl) -1,3,5-triazine (TINUVIN 460, manufactured by BASF), 2- (4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl) -5-hydroxyphenyl and _[(C 10 _{-C 16} (predominantly _C 12 _{-C 13)} alkyloxy) methyl] reaction product of oxirane (TINUVIN 400, manufactured by BASF), 2- [4,6- bis ( , 4-Dimethylphenyl) -1,3,5-triazin-2-yl] -5- [3- (dodecyloxy) -2-hydroxypropoxy] phenol), 2- (2,4-dihydroxyphenyl) -4 , 6-Bis- (2,4-dimethylphenyl) -1,3,5-triazine and (2-ethylhexyl) -glycidic acid ester reaction product (TINUVIN405, manufactured by BASF), 2- (4,6-diphenyl) -1,3,5-triazin-2-yl) -5-[(hexyl) oxy] -phenol (TINUVIN 1577, manufactured by BASF), 2- (4,6-diphenyl-1,3,5-triazine-2- Yl) -5- [2- (2-ethylhexanoyloxy) ethoxy] -phenol (ADK STAB LA46, manufactured by ADEKA), 2- (2-hydroxy-4- 1-octyloxycarbonylethoxy] phenyl) -4,6-bis (4-phenylphenyl) -1,3,5-triazine (TINUVIN 479, the BASF Corporation) and the like can be used.

Examples of the benzotriazole ultraviolet absorber include 2- (2H-benzotriazol-2-yl) -6- (1-methyl-1-phenylethyl) -4- (1,1,3,3-tetramethylbutyl). ) Phenol (TINUVIN 928, manufactured by BASF), 2- (2-hydroxy-5-tert-butylphenyl) -2H-benzotriazole (TINUVIN PS, manufactured by BASF), benzenepropanoic acid and 3- (2H-benzotriazole-2) - yl) -5- (1,1-dimethylethyl) -4-hydroxy _{(C 7} - ₉ side chain and ester compounds of linear alkyl) (TINUVIN384-2, manufactured by BASF), 2-(2H-benzotriazole - 2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol (TINUVIN900) BASF), 2- (2H-benzotriazol-2-yl) -6- (1-methyl-1-phenylethyl) -4- (1,1,3,3-tetramethylbutyl) phenol (TINUVIN 928, BASF) Product), methyl-3- (3- (2H-benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl) propionate / polyethylene glycol 300 reaction product (TINUVIN 1130, manufactured by BASF), 2- (2H-benzotriazol-2-yl) -p-cresol (TINUVIN P, manufactured by BASF), 2 (2H-benzotriazol-2-yl) -4-6-bis (1-methyl-1-phenylethyl) phenol (TINUVIN234, manufactured by BASF), 2- [5-chloro (2H) -benzotriazol-2-yl -4-methyl-6- (tert-butyl) phenol (TINUVIN 326, manufactured by BASF), (TINUVIN 326 FL, manufactured by BASF), 2- (2H-benzotriazol-2-yl) -4,6-di-tert-pentyl Phenol (TINUVIN 328, manufactured by BASF), 2- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol (TINUVIN 329, manufactured by BASF), methyl 3- (3- Reaction product of (2H-benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl) propionate and polyethylene glycol 300 (TINUVIN213, manufactured by BASF), 2- (2H-benzotriazol-2-yl ) -6-dodecyl-4-methylphenol (T NUVIN571, manufactured by BASF), 2- [2-hydroxy-3- (3,4,5,6-tetrahydrophthalimido-methyl) -5-methylphenyl] benzotriazole (Sumisorb 250, manufactured by Sumitomo Chemical Co., Ltd.), etc. Can do.

  Examples of the benzophenone ultraviolet absorber (benzophenone compound) and oxybenzophenone ultraviolet absorber (oxybenzophenone compound) include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, and 2-hydroxy-4. -Methoxybenzophenone-5-sulfonic acid (anhydrous and trihydrate), 2-hydroxy-4-octyloxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 4-benzyloxy-2-hydroxybenzophenone, 2,2 ' , 4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4,4-dimethoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone (KEMISORB 111, manufactured by Chemipro Kasei), etc. Can do.

  Examples of the salicylic acid ester ultraviolet absorber (salicylic acid ester compound) include, for example, phenyl-2-acryloyloxybenzoate, phenyl-2-acryloyloxy-3-methylbenzoate, phenyl-2-acryloyloxy- 4-methylbenzoate, phenyl-2-acryloyloxy-5-methylbenzoate, phenyl-2-acryloyloxy-3-methoxybenzoate, phenyl-2-hydroxybenzoate, phenyl-2-hydroxy- 3-methylbenzoate, phenyl-2-hydroxy-4methylbenzoate, phenyl-2-hydroxy-5-methylbenzoate, phenyl 2-hydroxy-3-methoxybenzoate, 2,4-di-tert- Butylphenyl-3,5-di-tert-butyl 4-hydroxybenzoate (TINUVIN120, manufactured by BASF), and the like.

  Examples of the cyanoacrylate ultraviolet absorber (cyanoacrylate compound) include alkyl-2-cyanoacrylate, cycloalkyl-2-cyanoacrylate, alkoxyalkyl-2-cyanoacrylate, alkenyl-2-cyanoacrylate, alkynyl- Examples include 2-cyanoacrylate.

  The ultraviolet absorber may be used alone or in combination of two or more, but the total content of the ultraviolet absorber is based on 100 parts by weight of the base polymer. 0.1 to 20 parts by weight, more preferably 0.5 to 15 parts by weight, and still more preferably 1 to 10 parts by weight. It is preferable to set the content of the ultraviolet absorber in the above range since the ultraviolet absorbing function of the pressure-sensitive adhesive layer can be sufficiently exhibited and does not hinder ultraviolet polymerization.

<Antioxidant>
In the optical surface protective film of the present invention, the pressure-sensitive adhesive composition can contain an antioxidant agent, and examples thereof include a radical chain inhibitor and a peroxide decomposer.

  Examples of the radical chain inhibitor include phenolic antioxidants and amine antioxidants.

  Examples of the peroxide decomposing agent include a sulfur-based antioxidant and a phosphorus-based antioxidant.

  Examples of the phenolic antioxidant include monophenolic antioxidants, bisphenolic antioxidants, and high-molecular phenolic antioxidants.

  Examples of the monophenol antioxidant include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, and stearin-β-. (3,5-di-t-butyl-4-hydroxyphenyl) propionate.

  Examples of the bisphenol antioxidant include 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 4,4. '-Thiobis (3-methyl-6-tert-butylphenol), 4,4'-butylidenebis (3-methyl-6-tert-butylphenol), 3,9-bis [1,1-dimethyl-2- [β- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] 2,4,8,10-tetraoxaspiro [5,5] undecane.

  Examples of the polymeric phenolic antioxidant include 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4. , 6-Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] Methane, bis [3,3′-bis- (4′-hydroxy-3′-t-butylphenyl) butyric acid] glycol ester, 1,3,5-tris (3 ′, 5′-di-t- Butyl-4'-hydroxybenzyl) -S-triazine-2,4,6- (1H, 3H, 5H) trione, tocophenol, pentaerythritol tetrakis [3- (3 ', 5'-di-tert-butyl -4'-hydr Loxyphenyl) propionate] and the like.

  Examples of the sulfur-based antioxidant include dilauryl 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate.

  Examples of the phosphorus antioxidant include triphenyl phosphite, diphenylisodecyl phosphite, and phenyl diisodecyl phosphite.

  The antioxidant may be used alone or in combination of two or more, but the total content of the antioxidant is 100 parts by weight of the base polymer. 0.01 to 1 part by weight, more preferably 0.1 to 0.8 part by weight, and still more preferably 0.2 to 0.7 part by weight. By making content of the said antioxidant into the said range, since deterioration by the oxidation of an adhesive layer can fully be suppressed and an adhesive characteristic is stabilized, it is preferable.

<Oxyalkylene group-containing compound>
The pressure-sensitive adhesive composition used in the present invention can also contain an oxyalkylene group-containing compound. By containing the oxyalkylene group-containing compound, it is possible to further develop light peelability. Examples of the oxyalkylene group-containing compound include an organopolysiloxane having an oxyalkylene chain and an oxyalkylene group-containing compound not containing an organopolysiloxane.

<Crosslinking agent>
In the surface protective film of the present invention, the pressure-sensitive adhesive composition preferably contains a crosslinking agent. Moreover, in this invention, it can be set as an adhesive layer using the said adhesive composition. For example, in the case where the pressure-sensitive adhesive composition is an acrylic pressure-sensitive adhesive containing the (meth) acrylic polymer, the constitutional unit, the structural ratio, the selection and addition ratio of the cross-linking agent, etc. are appropriately determined. By adjusting and crosslinking, a pressure-sensitive adhesive layer (surface protective film) having more excellent heat resistance can be obtained. Moreover, in the case of a urethane-based pressure-sensitive adhesive containing the urethane-based polymer, it is excellent in initial reworkability by appropriately adjusting the constitutional unit of the polyol, the composition ratio, the selection of the crosslinking agent and the additive ratio, and the like, A pressure-sensitive adhesive layer (surface protective film) having excellent adhesion reliability after aging 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 or an epoxy 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 compounds include aliphatic polyisocyanates such as trimethylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate (HDI), dimer acid diisocyanate, cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate (IPDI), 1, Alicyclic isocyanates such as 3-bis (isocyanatomethyl) cyclohexane, aromatic isocyanates such as 2,4-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, xylylene diisocyanate (XDI), and the isocyanate compound Allophanate bond, biuret bond, isocyanurate bond, uretdione bond, urea bond, carbodiimide bond, Reton'imin bond, polyisocynate modified products thereof obtained by modifying the like oxadiazinetrione bond. For example, as commercial products, the product names Takenate 300S, Takenate 500, Takenate 600, Takenate D165N, Takenate D178N (above, manufactured by Mitsui Chemicals), 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 Tosoh Corporation), 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 is possible to achieve both adhesiveness and repulsion resistance (adhesion to curved surfaces), and an adhesive layer (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 weight, and 0.1 to 15 parts by weight with respect to 100 parts by weight of the (meth) acrylic polymer. More preferred is 0.5 to 10 parts by weight, and most preferred is 1 to 8 parts by weight. When the content is less than 0.01 parts by weight, 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 weight, the cohesive force of the polymer is large, the fluidity is lowered, the wettability to the adherend (for example, polarizing plate) becomes insufficient, and the adherend and the pressure-sensitive adhesive. There is a tendency to cause blisters generated between the layer (adhesive composition layer). These crosslinking agents may be used alone or in combination of two or more. In the case of the urethane-based pressure-sensitive adhesive containing the urethane-based polymer, the content of the crosslinking agent is preferably 5 to 30 parts by weight, more preferably 5 to 28, with respect to 100 parts by weight of the polyol. Parts by weight, more preferably 5 to 25 parts by weight, and particularly preferably 5 to 23 parts by weight. By adjusting the content of the cross-linking agent within the above range, the obtained pressure-sensitive adhesive layer is excellent in initial adhesiveness when adhered to an adherend and in adhesive reliability after aging.

<Crosslinking catalyst>
The pressure-sensitive adhesive composition may further contain a cross-linking catalyst for causing any of the above-described cross-linking reactions to proceed more effectively. Examples of such a crosslinking catalyst include tin-based catalysts such as dibutyltin dilaurate and dioctyltin dilaurate (dioctyltin dilaurate), tris (acetylacetonato) iron, tris (hexane-2,4-dionato) iron, and 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, tri (1-phenylbutane-1,3-dionato) iron, 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 (propionyl acetate-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 (malonic acid) Diethyl) iron, trimethoxy iron, triethoxy iron, triisopropoxy iron, ferric chloride and other iron-based catalysts 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, it is preferably about 0.0001 to 1 part by weight with respect to 100 parts by weight of the (meth) acrylic polymer, 0.001 to 0.5 Part by weight is 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. Moreover, only 1 type may be sufficient and 2 or more types may be sufficient. In the case of the urethane-based pressure-sensitive adhesive containing the urethane-based polymer, the content of the crosslinking catalyst is preferably 0.01 to 1 part by weight, more preferably 100 parts by weight of the polyol. 0.08 to 0.5 parts by weight.

<Other additives>
Furthermore, the pressure-sensitive adhesive composition may contain other known additives as long as the effects of the present invention are not impaired. For example, powders such as lubricants, colorants, pigments, solvents, plastics, etc. Agent, softener, tackifier, low molecular weight polymer, surface lubricant, leveling agent, wettability additive, antioxidant, corrosion inhibitor, light stabilizer, heat stabilizer, UV absorber, polymerization inhibitor, silane Coupling agents, antistatic agents, inorganic or organic fillers, metal powders, particles, foils, and the like can be added as appropriate according to the intended use.

<Optical surface protective film>
The optical surface protective film (surface protective film) of the present invention comprises a base material made of a polyester-based resin, and a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition on one side of the base material. However, in this case, the crosslinking of the pressure-sensitive adhesive composition is generally performed after the application of the pressure-sensitive adhesive composition, but the pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition after crosslinking may be transferred to a substrate or the like. Is possible.

  The method for forming the pressure-sensitive adhesive layer on the base material is not particularly limited. For example, the pressure-sensitive adhesive layer is applied to the base material by applying the pressure-sensitive adhesive composition (solution) to the base material and drying and removing the polymerization solvent. It is produced by forming on top. Thereafter, curing may be performed for the purpose of adjusting the component transfer of the pressure-sensitive adhesive layer or adjusting the crosslinking reaction. Moreover, when producing a surface protective film by applying the pressure-sensitive adhesive composition on the substrate, one or more solvents other than the polymerization solvent are added to the pressure-sensitive adhesive composition so that the surface-protective film can be uniformly applied on the substrate. You may add a new one.

  Moreover, as a formation method of the adhesive layer at the time of manufacturing the surface protection film of this invention, the well-known method used for manufacture of adhesive tapes 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 thickness of the pressure-sensitive adhesive layer is preferably 1 to 30 μm, more preferably 2 to 28 μm, and still more preferably 3 to 25 μm. It is preferable for the thickness of the pressure-sensitive adhesive layer to be in the above-mentioned range since it is easy to obtain an appropriate balance between removability and pressure-sensitive adhesiveness.

  The surface protective film of the present invention preferably has a total thickness of 7 to 130 μm, more preferably 10 to 100 μm, and still more preferably 20 to 50 μm. Within the above range, the adhesive properties (removability, adhesiveness, adhesive force stability, etc.), workability, and appearance properties are excellent, and a preferred embodiment is obtained. In addition, the said total thickness means the sum total of the thickness containing all layers, such as a base material, an adhesive layer, a separator, and another layer.

<Separator>
The surface protective film of the present invention can be attached with a separator for the purpose of protecting the pressure-sensitive adhesive layer surface, if necessary.

  Examples of the material constituting the separator include paper and plastic film, and a plastic film is preferably used because of its 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 5 to 200 μm, preferably 8 to 100 μm, more preferably about 10 to 50 μm. For the separator, silicone type, fluorine type, long chain alkyl type or fatty acid amide type release agent, mold release and antifouling treatment with silica powder, coating type, kneading type, vapor deposition type, if necessary It is also possible to carry out antistatic treatment such as.

  The surface protective film disclosed herein can be implemented in an embodiment including another layer in addition to the support and the pressure-sensitive adhesive layer. Examples of the other layer include an undercoat layer (anchor layer) that improves the anchoring property of the antistatic layer and the pressure-sensitive adhesive layer.

<Usage method of optical surface protective film>
As a method for using the optical surface protective film of the present invention, for example, the surface of the pressure-sensitive adhesive layer constituting the optical surface protective film of the present invention is bonded to the surface of a part of the printed portion of printed glass and cured with ultraviolet light. In the process, an optical surface protective film is not bonded, and an ultraviolet curable resin is applied to an exposed portion, and a portion of the optical surface protective film to which an optical curable resin is not applied is prevented from being deteriorated by ultraviolet light. It is. According to this method of use, the curing reaction proceeds by irradiation with ultraviolet rays, and a member such as a printed portion to be prevented from being deteriorated by irradiation with ultraviolet rays can be protected, which is useful.

<Optical member>
In the present invention, the optical member can be protected by sticking the surface of the pressure-sensitive adhesive layer of the optical surface protective film to the optical member. The surface protective film is capable of preventing an increase in adhesive force even when heated after being applied and stored on an optical member that is an adherend of an adhesive layer, and has excellent adhesive strength stability and removability. Since it is excellent, it can be used for surface protection applications (surface protective film) at the time of processing, conveyance, shipping, etc., and thus is useful for protecting the surface of the optical member (polarizing plate, etc.). In addition, since the change in hue of the pressure-sensitive adhesive layer constituting the surface protective film is suppressed and the transmittance of ultraviolet rays is suppressed low throughout the surface protective film, inspection is performed with the surface protective film bonded to the optical member. This is a preferred embodiment because it can be used for applications where it is desired to suppress curing and deterioration associated with ultraviolet irradiation.

  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, “parts” and “%” are based on weight unless otherwise specified. Further, the blending amount (addition amount) in the table is shown.

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

<Measurement of glass transition temperature (Tg) of acrylic polymer>
The glass transition temperature (Tg) (° C.) was determined by the following formula using the following literature values as the glass transition temperature Tgn (° C.) of the homopolymer of each monomer.
Formula: 1 / (Tg + 273) = Σ [Wn / (Tgn + 273)]
(Wherein, Tg (° C.) is the glass transition temperature of the copolymer, Wn (−) is the weight 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
2-hydroxyethyl acrylate (HEA): -15 ° C
In addition, as a reference value, “Synthesis / design of acrylic resin and development of new application” (published by Central Management Development Center Publishing Department) was referred.

<Measurement of weight average molecular weight (Mw) of acrylic polymer>
The weight average molecular weight (Mw) of the (meth) acrylic polymer to be used was measured using a GPC device (HLC-8220GPC) manufactured by Tosoh Corporation. The measurement conditions are as follows.
Sample concentration: 0.2% by weight (THF solution)
Sample injection volume: 10 μl
Eluent: THF
Flow rate: 0.6 ml / min
Measurement temperature: 40 ° C
column:
Sample column; TSKguardcolumn SuperHZ-H (1) + TSKgel SuperHZM-H (2)
Reference column; TSKgel SuperH-RC (1)
Detector: Differential refractometer (RI)
The weight average molecular weight was determined in terms of polystyrene. Moreover, when measuring not only an acrylic polymer but a number average molecular weight (Mn), it measured similarly to a weight average molecular weight (Mw).

<Measurement of b * value>
After aging the surface protection film for optics (surface protection film) according to each example for 7 days at room temperature, after cutting into a size of 50 mm in width and 50 mm in length, and peeling the separator from the adhesive layer surface of the surface protection film, The “b * value” was measured with a high-speed integrating sphere-type transmittance measuring device (Murakami Color Research Laboratory, model “DOT-3C”). The b * value indicates the CIELab value.

  The b * value of the surface protective film is 2 or less, preferably 1.6 or less, and more preferably 1.2 or less. If the b * value is within the above range, the change in the hue of the pressure-sensitive adhesive layer can be suppressed, and it is possible to inspect even when it is attached to an optical member, which is a practically problematic level, which is preferable.

<Measurement of transmittance>
Transmittance was measured using a spectrophotometer U-4100 manufactured by Hitachi, Ltd., with light having a wavelength of 300 to 400 nm, from the substrate side of the surface protective film for optics obtained by Examples and Comparative Examples. Then, the transmittance (%) was obtained. The transmittance (ultraviolet ray transmittance) represents the transmittance (%) at a wavelength of 365 nm among the transmittances for light having a wavelength within the above range.

  The transmittance is 2% or less, preferably 1.8% or less, and more preferably 1.6% or less. If the transmittance exceeds 2%, the transmittance of ultraviolet rays is high, and curing and deterioration due to ultraviolet irradiation cannot be prevented. For example, problems such as a decrease in strength of the printed portion occur, which is not preferable.

<Initial adhesive strength (adhesive strength before heating)>
The surface protective film according to each example was cut to a width of 25 mm, and the adhesive layer side of the optical surface protective film from which the separator was peeled off was placed on the surface of a glass plate (manufactured by Matsunami Glass Industrial Co., Ltd., trade name: Micro Slide Glass S). After pasting together using a 2 kg roller, it was allowed to stand at room temperature (23 ° C., 50% RH) for 20 minutes, and then peeled off with a tensile / compression tester (device name “TG-1kN”, manufactured by Minebea Co., Ltd.). The film was peeled at a peeling speed of 0.3 m / min, and the peel strength (adhesive strength to glass) of the surface protective film was measured as “initial adhesive strength (adhesive strength before heating)” (N / 25 mm).
Measurement conditions: Temperature: 23 ± 2 ° C., Humidity: 50 ± 5% RH

<Adhesive strength after heating>
Similar to the initial adhesive strength, after preparing a test piece, after heating at 100 ° C. for 30 minutes, left at room temperature (23 ° C., 50% RH) for 1 hour, under the same conditions as the initial adhesive strength, “Adhesive strength after heating” (N / 25 mm) was measured.

  The adhesion to glass is preferably 0.2 N / 25 mm or less, more preferably 0.15 N / 25 mm or less, and even more preferably in both the initial (before heating) and the adhesion after heating. Is 0.1 N / 25 mm or less. When the adhesive strength exceeds 0.2 N / 25 mm, the adhesive strength becomes too high, and light peelability (removability) becomes difficult. For example, when used as a surface protective film, This is not preferable because adhesive residue may be generated on the body and the base material may be damaged.

<Change rate of adhesive strength before and after heating>
The rate of change in adhesive strength before and after heating was calculated by the following formula.
(Change rate of adhesive strength before and after heating (%)) = 100 × (adhesive strength after heating−adhesive strength before heating) / (adhesive strength before heating)

  The rate of change in adhesive strength before and after the heating is ± 30% or less, preferably ± 25% or less, and more preferably ± 20% or less. When the change rate exceeds ± 30%, it causes a problem of heavy peeling and peeling, which is not preferable.

[Example 1]
[Preparation of acrylic polymer]
In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser, 200 parts by weight of 2-ethylhexyl acrylate (2EHA), 8 parts by weight of 2-hydroxyethyl acrylate (HEA), 2 as a polymerization initiator , 2'-azobisisobutyronitrile (0.4 parts by weight) and ethyl acetate (312 parts by weight) as a solvent, nitrogen gas was introduced with gentle stirring, and the liquid temperature in the flask was kept at around 65 ° C. A time polymerization reaction was performed to prepare an acrylic polymer solution (40% by weight). The acrylic polymer had a weight average molecular weight (Mw) of 540,000 and a glass transition temperature (Tg) of −68 ° C.

[Preparation of acrylic adhesive solution]
The acrylic polymer solution (40% by weight) is diluted to 29% by weight with ethyl acetate, and isocyanurate of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd.) as a crosslinking agent with respect to 100 parts by weight of the solid content in the solution. , Trade name: Coronate HX, “C / HX” in Table 1): 4 parts by weight, dibutyltin dilaurate as a crosslinking catalyst (manufactured by Tokyo Fine Chemical Co., Ltd., trade name: ENVILIZER OL-1, “OL-” in Table 1) 1 ", 0.5 wt% ethyl acetate solution): 0.015 parts by weight, 2,4-bis-[{4- (4-ethylhexyloxy) -4-hydroxy} -phenyl] -6--6 as an ultraviolet absorber (4-Methoxyphenyl) -1,3,5-triazine (trade name: Tinosorb S, manufactured by BASF): 2 parts by weight, acetylacetone as a crosslinking retarder And mixed and stirred with 3 parts by weight relative to the total amount of solvent, to obtain an acrylic pressure-sensitive adhesive solution (adhesive composition).

[Production of optical surface protective film]
The acrylic pressure-sensitive adhesive solution is applied to the surface opposite to the antistatic treatment surface of the polyethylene terephthalate film with an antistatic treatment layer (trade name: Diafoil T100G38, manufactured by Mitsubishi Plastics, Inc., thickness 38 μm) as a base material. And heated at 130 ° C. for 1 minute to form an adhesive layer having a thickness of 21 μm. Next, the surface of the pressure-sensitive adhesive layer was bonded with a silicone-treated surface of a separator (21 μm thick polyethylene terephthalate film with a silicone treatment on one side) to prepare an optical surface protective film.

<Examples 2-5, Comparative Examples 1-3>
Based on the contents shown in Table 1, an optical surface protective film was prepared in the same manner as in Example 1.

<Examples 6 and 7>
Instead of the base material used in Example 1, a polyester film having a thickness of 12 μm (trade name: Diafoil T100G12, manufactured by Mitsubishi Plastics, Inc.) was used, and the same method as in Example 1 was performed based on the blending contents shown in Table 1. An optical surface protective film was prepared.

<Examples 8 and 9>
In place of the base material used in Example 1, a polyester film having a thickness of 80 μm (trade name: SRF, manufactured by Toyobo Co., Ltd.) was used. A surface protective film was produced.

<Example 10>
[Preparation of urethane adhesive solution]
As the polyol, Preminol S3011 (Asahi Glass Co., Ltd., Mn = 10000): 85 parts by weight, Sannix GP3000 (Sanyo Chemical Industries, Mn = 3000): 13 parts by weight, Sannix GP1000 (Sanyo Chemical Industries, Mn = 1000) ) 2 parts by weight, Tinuvin 384-2 (manufactured by BSF) as an ultraviolet absorber: 10 parts by weight, polyfunctional alicyclic isocyanate compound (manufactured by Tosoh, trade name: Coronate HX) as a crosslinking agent: 18 parts by weight, Cross-linking catalyst (manufactured by Nippon Kagaku Sangyo Co., Ltd., trade name: Nursem Ferric): 0.08 parts by weight, as an antioxidant, Irganox 1010 (manufactured by BASF): 0.5 parts by weight, fatty acid ester as a wettability additive Isopropyl myristate (trade name: EXCEPARL IPM): 30 parts by weight, rare As a solvent, ethyl acetate: 210 parts by weight was blended and stirred with a disper to obtain a urethane-based adhesive solution (adhesive composition).

[Production of optical surface protective film]
The urethane-based pressure-sensitive adhesive composition is applied to the surface opposite to the antistatic treatment surface of a polyethylene terephthalate film with an antistatic treatment layer (trade name: Diafoil T100G38, manufactured by Mitsubishi Plastics, Inc., thickness 38 μm) as a base material. And it heated at 130 degreeC for 1 minute, and formed the 20-micrometer-thick adhesive layer. Next, the surface of the pressure-sensitive adhesive layer was bonded with a silicone-treated surface of a separator (a polyethylene terephthalate film with a thickness of 25 μm, which was silicone-treated on one side) to produce an optical surface protective film.

  Tables 1 and 2 show the results of the above-described blending contents, various measurements, and evaluations on the optical surface protective films with separators according to Examples and Comparative Examples. In addition, the compounding quantity in Table 1 shows an active ingredient.

Details of the abbreviations in Table 1 are shown below.
<Base material>
Diafoil T100G38: thickness 38 μm, manufactured by Mitsubishi Plastics, Inc., trade name: Diafoil T100G38
Diafoil T100G12: thickness 12 μm, manufactured by Mitsubishi Plastics, Inc., trade name: Diafoil T100G12
SRF: 80 μm thickness, manufactured by Toyobo Co., Ltd., trade name: SRF

<Ultraviolet absorber>
Tinosorb S: 2,4-bis-[{4- (4-ethylhexyloxy) -4-hydroxy} -phenyl] -6- (4-methoxyphenyl) -1,3,5-triazine, trade name: Tinosorb S Manufactured by BASF, number of hydroxyl groups: 2)
Tinuvin 571: 2- (2H-benzotriazol-2-yl) -6-dodecyl-4-methylphenol, manufactured by BASF, trade name: Tinuvin 571, number of hydroxyl groups: 1)
Esters of - ₍₉ side chain and straight alkyl _{C 7)} benzenepropanoic acid and 3- (2H-benzotriazol-2-yl) -5- (1,1-dimethylethyl) -4-hydroxy: Tinuvin 384-2 Compound, manufactured by BASF, trade name: Tinuvin 384-2, number of hydroxyl groups: 1)
Tinuvin 326: 2- [5-chloro (2H) -benzotriazol-2-yl] -4-methyl-6- (tert-butyl) phenol, manufactured by BASF, trade name: TINUVIN 326, number of hydroxyl groups: 1)
KEMISORB 111: 2,2′-dihydroxy-4-methoxybenzophenone, manufactured by Chemipro Kasei Co., Ltd., trade name: KEMISORB 111, number of hydroxyl groups: 2)
SEESORB 106: 2-hydroxy-4-methoxybenzophenone, manufactured by Cypro Kasei Co., Ltd., trade name: SEESORB 106, number of hydroxyl groups: 4)
<Antioxidant>
Irganox 1010: Pentaerythritol = tetrakis [3- (3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) propionate], manufactured by BASF, trade name: Irganox 1010
<Wetting additive>
Isopropyl myristate, manufactured by Kao, trade name: EXCEPARL IPM

  From Table 2 above, it was confirmed that in all Examples, the change in hue was suppressed, ultraviolet curing could be prevented, and an increase in adhesive strength after heating could be prevented. On the other hand, in Comparative Example 1, the ultraviolet transmittance was slightly high, and the deterioration prevention during ultraviolet irradiation was insufficient. In Comparative Example 2, the ultraviolet absorber used has many hydroxyl groups, and the rate of change in adhesive strength before and after heating is large, resulting in heavy peeling and unsuitable for light peeling applications. Since no agent was used, it was confirmed that the ultraviolet ray transmittance was very high and the use was not suitable for a material (member) for which ultraviolet curing (absorption) is to be prevented.

The optical surface protective film disclosed herein is an optical member used in the production or transportation of an optical member used as a component of a liquid crystal display panel, a plasma display panel (PDP), an organic electroluminescence (EL) display, or the like. It is suitable as a surface protective film for protecting the film. In particular, optical materials applied to optical members such as polarizing plates, wave plates, retardation plates, optical compensation films, brightness enhancement films, light diffusion sheets, and reflective sheets for liquid crystal display panels, and glass members for displays. It is useful as a surface protective film.

Claims (6)

A surface protective film for optics comprising a base material formed from a polyester-based resin, and an adhesive layer formed from an adhesive composition on one side of the base material,
The b * value of the surface protective film is 2 or less, the transmittance of the surface protective film at a wavelength of 365 nm is 2% or less, the adhesive strength before heating after pasting the adhesive layer on glass, and 100 An optical surface protective film characterized in that the rate of change in adhesive strength after heating at 30 ° C. for 30 minutes is ± 30% or less.   The optical surface protective film according to claim 1, wherein the pressure-sensitive adhesive composition contains an ultraviolet absorber.   The optical surface protective film according to claim 2, wherein the number of hydroxyl groups in the molecule of the ultraviolet absorber is 3 or less.   The optical surface protective film according to claim 1, wherein the pressure-sensitive adhesive composition contains a (meth) acrylic polymer and / or a urethane polymer as a base polymer.   The optical surface protective film according to claim 4, wherein the pressure-sensitive adhesive composition contains 0.1 to 20 parts by weight of the ultraviolet absorber with respect to 100 parts by weight of the base polymer. The thickness of the said base material is 6-100 micrometers, and the thickness of the said adhesive layer is 1-30 micrometers, The surface protection film for optics in any one of Claims 1-5 characterized by the above-mentioned.