JP2008266591A - Surface protection film roll and its continuous manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface protection film roll wound in a roll without a separator and to provide its manufacturing method. <P>SOLUTION: A surface protection film roll has a long base film and adhesive layer which are crosslinked by electron beam irradiation, wherein the adhesive layer is prepared by irradiating an electron beam on an electron beam curing type adhesive composition comprising a reactive diuent having at least one ethylenically unsaturated double bond and a (meth)acrylic polymer. The surface protection film is wound without a separator. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is used to prevent blocking when a resin film (sheet) or a coated processed product is stacked or wound into a roll, or to wind up a surface protective film for protecting the surface of the product in a roll. It relates to a surface protective film roll. Mainly for optical films such as polarizing plates for product inspection with surface protective film attached, film resist masking for precise secondary processing, and surface protection for products where color tone and appearance are important The present invention relates to a surface protective film roll that is applied and peeled off and discarded when these products are actually used, and a continuous manufacturing method thereof.

  Liquid crystal displays, plasma displays, etc. are laminated with optical films having various functions, such as optical polarizing plates (TAC), retardation plates, EMI (electromagnetic wave) shield films, antiglare films, antireflection films, and the like. It is used. These optical films have a protective film with an adhesive layer attached to the surface in order to prevent damage to the surface during the display manufacturing process and performance inspection stage. It is peeled off at the time of film production or in the liquid crystal panel assembly process.

  The surface protective film needs to have transparency that does not interfere with the performance test, stickability that does not allow air bubbles and the like, conformability (wettability) to an uneven surface that has been antiglare treated, and the like. Furthermore, recently, since the protective film has been enlarged in size with an increase in the size of the display, the sticking process has been mechanized, and as a result, a roll-shaped surface protective film has become necessary. In the case of the mechanized sticking process, if the separator is bitten by the surface protective film roll, a separate facility for peeling the separator is required, and the laminator becomes large. Further, since the surface protective film is peeled off and discarded at the time of actual use, it is necessary to reduce the cost as much as possible, but the separator contributes to the cost increase. For these reasons, a roll in which only a surface protective film is wound without using a separator is desired.

  By the way, the pressure-sensitive adhesive layer of the optical surface protective film is compatible with the surface of the adherend quickly, does not generate air bubbles, etc., and has excellent peeling properties (peeling off at high speed and low stress). Often used adhesives. In order to smooth the surface of the pressure-sensitive adhesive layer, the solvent-based pressure-sensitive adhesive is a base material (mainly polyethylene terephthalate: PET) in a state of a coating liquid having a solid content of about 20 to 40% by mass with good coating workability. Painted on. Conventionally, since a hydroxyl group was exclusively introduced into an adhesive polymer and crosslinked with a crosslinking agent such as an isocyanate type, solvent removal and a crosslinking reaction were performed by heating during coating (for example, Patent Document 1). The isocyanate-based crosslinking agent took time to complete the reaction and required curing for 3 to 7 days. The pressure-sensitive adhesive layer until the completion of the crosslinking reaction is soft and cannot be wound into a roll without a separator. Therefore, the release-treated PET film or the like is pasted on the surface of the pressure-sensitive adhesive layer as a separator and then wound into a roll. It was common to cure in warehouses. In this case, the surface smoothness is lost due to the contact between the roll (for example, a guide roll) and the adhesive layer downstream in the coating process, or air bubbles enter between the separator and the adhesive layer during winding, The film appearance was likely to be inferior. Also, for example, the emulsion type is the same, but heat drying is an indispensable process, so to increase the line speed, the drying furnace must be lengthened, the production line is enlarged, and measures against foreign matters are taken. There was a demerit that the installation cost of the clean room would be enormous.

  On the other hand, a separator-free pressure-sensitive adhesive film has been developed (Patent Documents 2 and 3). However, Patent Document 2 is an invention that focuses on the release layer, and only general adhesives are shown. ing. In Patent Document 3, a special pressure-sensitive adhesive is used. However, curing is necessary because isocyanate crosslinking is performed in the same manner as in Patent Document 1.

On the other hand, development of a technique that does not use a separator by using a crosslinking system that does not require curing is in progress. As a crosslinking system that does not require curing, an adhesive that is cured by ultraviolet rays or an electron beam has been conventionally known. For example, Patent Document 4 discloses an ultraviolet curable pressure-sensitive adhesive, but a photopolymerization initiator that is an essential component is not preferable in that it has an odor. It is also said to cause yellowing of the pressure-sensitive adhesive and is not suitable for an optical surface protective film. On the other hand, although a pressure sensitive adhesive sheet using electron beam curing is shown in Patent Document 5, only general ones are shown as pressure sensitive adhesives, which are particularly suitable for electron beam curing and optical surface protection films. Adhesives are not shown.
JP 2006-126429 A JP 2005-255859 A Japanese Patent Laid-Open No. 2005-154782 JP 2000-109770 A JP 2004-277522 A

  Optical surface protection films are required to have high transparency, good conformability to adherends, excellent surface smoothness, excellent peeling properties, etc. It is hard to say that technology satisfies these physical properties.

  Therefore, the present invention has an object to provide a surface protective film roll excellent in such various physical properties, requiring no curing, and wound in a roll shape without using a separator, and a method for producing the same.

  The surface protective film roll of the present invention comprises a long base film and a pressure-sensitive adhesive layer crosslinked by electron beam irradiation, and this pressure-sensitive adhesive layer has at least one ethylenically unsaturated double bond in the molecule. A layer made of an electron beam curable pressure-sensitive adhesive composition containing a reactive diluent and a (meth) acrylic polymer is irradiated with an electron beam and is wound without a separator. And

  When the surface protective film cut out from the surface protective film roll is attached to an acrylic plate and allowed to stand at 23 ° C. for 25 minutes, the 180 ° adhesive force measured at a peeling speed of 30 m / min is 3 N / 25 mm width or less. In particular, it is preferable because high-speed peelability is good.

  The glass transition temperature (Tg) of the (meth) acrylic polymer is preferably 0 ° C. or less from the viewpoint of adhesive properties, and the aspect in which the reactive diluent contains (meth) acrylate having a vinyl ether group as an essential component is as follows: It is preferable at the point which improves electron beam curability. The pressure-sensitive adhesive after crosslinking preferably has a gel fraction of 50 to 100% by mass when left in ethyl acetate at 23 ° C. for 24 hours. Moreover, the surface protection film roll excellent in transparency, surface hardness, heat resistance, etc. is obtained as a base film is a film which has a lactone ring containing polymer as a main component.

  The present invention also includes a method for continuously producing the surface protective film roll, and the production method comprises a reaction having at least one ethylenically unsaturated double bond in the molecule on a long substrate film. Forming a layer of an electron beam curable pressure-sensitive adhesive composition containing a reactive diluent and a (meth) acrylic polymer, an acceleration voltage of 80 to 140 kV at a line speed of 10 to 200 m / min. In addition, the present invention is characterized in that the step of crosslinking by irradiating an electron beam with an irradiation dose of 40 to 120 kGy and the step of winding the crosslinked film into a roll without using a separator are performed.

  According to the present invention, since the pressure-sensitive adhesive layer is crosslinked by electron beam irradiation, the curing of the surface protective film is unnecessary, and a pressure-sensitive adhesive layer having a hardness that can be rolled up as it is without using a separator is formed. I was able to. Therefore, it was useful for a mechanized sticking process, and an efficient industrial production was possible, and an inexpensive surface protective film roll could be provided.

  First, the electron beam curable pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer of the present invention will be described. However, the scope of the present invention is not limited to these descriptions, and the present invention is not limited to the following examples. Modifications can be made as appropriate without departing from the spirit of the invention. The “polymer” in the present invention includes not only a homopolymer but also a copolymer or a ternary or higher copolymer. The “monomer” of the present invention is an addition polymerization type monomer.

  The electron beam curable pressure-sensitive adhesive composition of the present invention comprises a (meth) acrylic polymer and a reactive diluent having at least one ethylenically unsaturated double bond in the molecule.

  The (meth) acrylic polymer refers to a polymer in which 60% by mass or more is alkyl (meth) acrylate in 100% by mass of monomer components used for polymer synthesis. The alkyl (meth) acrylate is preferably 70% by mass or more, more preferably 80% by mass or more, and most preferably 90% by mass or more in 100% by mass of the monomer component.

  The number of carbon atoms in the alkyl group of the alkyl (meth) acrylate is preferably 4 to 12 from the viewpoint of adhesive properties. The upper limit of this carbon number is preferably 10, more preferably 8. If the carbon number is less than 4 (3 or less) or more than 12 (13 or more), the adhesive strength may be reduced. Specifically, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) ) Acrylate, cyclohexyl (meth) acrylate, cyclohexylmethyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl ( Examples include meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate and the like, among which butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate And isooctyl acrylate are more preferred. These may be used alone or in combination of two or more, and is not limited. Moreover, (meth) acrylates having a ring structure such as isobornyl (meth) acrylate can also be used as (meth) acrylates other than those described above.

  Furthermore, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, caprolactone-modified hydroxy (meth) acrylate, monoester of (meth) acrylic acid and polyalkylene glycol Hydroxyl group-containing (meth) acrylates such as; (meth) acrylic acid, cinnamic acid and crotonic acid and other unsaturated monocarboxylic acids; maleic acid, fumaric acid, itaconic acid and citraconic acid and other unsaturated dicarboxylic acids, etc. Salts of these or anhydrides thereof; carboxyl group-containing monomers such as monoesters of these unsaturated dicarboxylic acids; glycidyl group-containing (meth) such as glycidyl methacrylate (for example, “Blemmer (registered trademark) G” manufactured by NOF Corporation) Acrylates; for example Isocyanate group-containing (meth) acrylates such as “Karenz (registered trademark)” series (manufactured by Showa Denko KK); methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, methoxyethoxyethyl (meth) acrylate, ethoxyethoxyethyl Alkoxy (meth) acrylates such as (meth) acrylate and methoxypolyethylene glycol (meth) acrylate; Allyl (meth) acrylates; Vinyl monomers such as vinyl acetate; Aromatic monomers such as styrene; Non-acrylic monomers such as acrylonitrile Saturated cyanide compounds and the like can also be used for the synthesis of (meth) acrylic polymers.

  The (meth) acrylic polymer may have an ethylenically unsaturated double bond in the side chain. This is because electron beam curability is enhanced. In order to introduce an ethylenically unsaturated double bond into the side chain of a (meth) acrylic polymer, (1) using a carboxyl group-containing monomer as a part of the monomer component, the resulting carboxyl group-containing (meth) acrylic A method of adding a glycidyl group-containing monomer to a polymer, (2) using a glycidyl group-containing monomer as part of the monomer component, and adding a carboxyl group-containing monomer to the resulting glycidyl group-containing (meth) acrylic polymer Examples thereof include (3) a method in which a hydroxyl group-containing monomer is used as a part of the monomer component, and an isocyanate group-containing (meth) acrylate is added to the obtained hydroxyl group-containing (meth) acrylic polymer. Details are described in, for example, JP-A-11-263893 and JP-A-2005-320522.

  The (meth) acrylic polymer preferably has a Tg of 0 ° C. or lower. This is because sufficient adhesive strength can be secured at room temperature.

Here, the Tg of the polymer can be determined by DSC (differential scanning calorimeter), DTA (differential thermal analyzer), and TMA (thermomechanical analyzer). In addition, since Tg (K) of homopolymer is described in various documents (for example, polymer handbook), Tg (K) of copolymer is different from Tg _n (K) of various homopolymers and mass fraction of monomer ( W _n ) and the following equation.

Where W _n ; mass fraction of each monomer
Tg _n : Tg (K) of homopolymer of each monomer

  The Tg of the main homopolymer is 106 ° C. for polyacrylic acid, 8 ° C. for polymethyl acrylate, −22 ° C. for polyethyl acrylate, −54 ° C. for poly n-butyl acrylate, and −70 ° C. for poly 2-ethylhexyl acrylate. Poly-2-hydroxyethyl acrylate is −32 ° C., poly 2-hydroxyethyl methacrylate is 71 ° C., polymethyl methacrylate is 105 ° C., polyvinyl acetate is 32 ° C., polyacrylonitrile is 125 ° C., and polystyrene is 100 ° C.

  The weight average molecular weight (Mw) of the (meth) acrylic polymer is preferably about 10,000 to 700,000. Adhesive properties are improved. 20,000 to 600,000 are more preferable, and 3 to 500,000 are more preferable. In order to adjust the molecular weight, it is preferable to add a known chain transfer agent such as a thiol compound. Specific examples of the thiol compound include alkyl mercaptans such as t-butyl mercaptan, n-octyl mercaptan and n-dodecyl mercaptan; aromatic mercaptans such as thiophenol and thionaphthol; thioglycolic acid; octyl thioglycolate, ethylene Thioglycolic acid alkyl esters such as glycol dithioglycolate, trimethylolpropane tris- (thioglycolate), pentaerythritol tetrakis- (thioglycolate); β-mercaptopropionic acid; octyl β-mercaptopropionic acid, 1,4 Β-mercaptopro such as butanediol di (β-thiopropionate), trimethylolpropane tris- (β-thiopropionate), pentaerythritol tetrakis- (β-thiopropionate) It includes propionic acid alkyl esters may be used alone, or two or more. As the chain transfer agent, α-methylstyrene dimer, carbon tetrachloride and the like can also be used. The amount of chain transfer agent used may be set according to the type, monomer type, and the like, and is not particularly limited, but is preferably about 0.1 to 15% by mass with respect to the monomer component.

  In the polymerization of (meth) acrylic polymer, it can be produced by various methods such as solution polymerization, bulk polymerization, suspension polymerization, emulsion polymerization, etc., but solution polymerization with easy heat removal or bulk polymerization that does not require removal of the solvent is possible. Is preferred. Specific examples of the solvent used in the solution polymerization include aromatic hydrocarbons such as toluene and xylene; aliphatic esters such as ethyl acetate and butyl acetate; alicyclic hydrocarbons such as cyclohexane; hexane And aliphatic hydrocarbons such as pentane and the like, but are not particularly limited as long as the polymerization reaction is not inhibited. These solvents may be used alone or in combination of two or more. What is necessary is just to determine the usage-amount of a solvent suitably.

  Reaction conditions such as polymerization reaction temperature and reaction time may be appropriately set according to, for example, the composition and amount of the monomer, and are not particularly limited. Further, the reaction pressure is not particularly limited, and may be any of normal pressure (atmospheric pressure), reduced pressure, and increased pressure. The polymerization reaction is desirably performed in an atmosphere of an inert gas such as nitrogen gas.

  Although it does not limit as a polymerization catalyst (polymerization initiator), For example, methyl ethyl ketone peroxide, benzoyl peroxide, dicumyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, t-butyl peroxide-2- Ethyl hexanoate, t-butyl peroxy octoate, t-butyl peroxybenzoate, lauroyl peroxide, cyclohexanone peroxide, axial viewing peroxide, bis (4-t-butylcyclohexyl) peroxydicarbonate, trade name “ Organic peroxides such as “NIPER BMT-K40” (manufactured by NOF Corporation; mixture of m-toluoyl peroxide and benzoyl peroxide), 2,2′-azobisisobutyronitrile, 2-phenylazo-2, 4-dimethyl Known compounds such as azo compounds such as -4-methoxyvaleronitrile and trade name “ABN-E” [Nippon Hydrazine Kogyo; 2,2′-azobis (2-methylbutyronitrile)] can be used. . These may use only one type and may use two or more types together. The amount used can be adjusted as appropriate.

  The electron beam curable pressure-sensitive adhesive composition used in the present invention essentially contains a reactive diluent. This is to improve viscosity adjustment and electron beam curability. “Reactive” means that a radical polymerization reaction is possible and thus the reactive diluent is a compound having at least one ethylenically unsaturated double bond in the molecule.

  Specifically, all the monomers that can be used when synthesizing the aforementioned (meth) acrylic polymer can be used.

  Other N-vinyl compounds such as N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethyl (meth) acrylamide, N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylformamide, N-vinylacetamide, etc. Class: methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, cyclohexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether, methoxypolyethylene Glycol vinyl ether, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl Ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, monofunctional monomers such as ether and chloroethyl vinyl ether is available.

  Also, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate , Tetrapropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, ethylene oxide modified bisphenol A type di (meth) acrylate, propylene oxide modified Bisphenol A type di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, glycerin di (meth) acrylate , Pentaerythritol di (meth) acrylate, trimethylolpropane di (meth) acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, diethylene glycol diglycidyl ether di (meth) acrylate, diglycidyl phthalate di (meth) Bifunctional monomers such as acrylate and hydroxypivalic acid-modified neopentyl glycol di (meth) acrylate can also be suitably used.

  Trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tri (meth) acryloyloxyethoxy Trifunctional or higher polyfunctional monomers such as trimethylolpropane and glycerin polyglycidyl ether poly (meth) acrylate can also be suitably used.

  In particular, when (meth) acrylate (1) having a vinyl ether group represented by the following structural formula is used for a part or all of the reactive diluent, curing with an electron beam is accelerated and the line speed is increased, that is, the cost is reduced. It is preferable because it leads.

[In Formula 1, R ¹ represents a hydrogen atom or a methyl group, R ² represents a divalent organic residue having 2 to 20 carbon atoms, and R ³ represents a hydrogen atom or an organic residue having 1 to 11 carbon atoms. ]

  Here, the “divalent organic residue having 2 to 20 carbon atoms” means a linear, branched or cyclic alkylene group having 2 to 20 carbon atoms, and an ether bond and / or an ester bond in the structure. An alkylene group having 2 to 20 carbon atoms having an oxygen atom and an optionally substituted divalent aromatic group having 6 to 11 carbon atoms are preferred. Among these, a C2-C6 alkylene group and a C2-C9 alkylene group which has an oxygen atom by an ether bond in a structure are preferable.

  Examples of the “organic residue having 1 to 11 carbon atoms” include alkyl having 1 to 11 carbon atoms such as methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, and cyclohexyl group. A group and an optionally substituted aromatic group having 6 to 11 carbon atoms are preferable. Among these, an alkyl group having 1 to 2 carbon atoms and an aromatic group having 6 to 8 carbon atoms are preferable.

  Specific examples are as follows. 2-vinyloxyethyl (meth) acrylate, 3-vinyloxypropyl (meth) acrylate, 1-methyl-2-vinyloxyethyl (meth) acrylate, 2-vinyloxypropyl (meth) acrylate, 4-vinyloxybutyl (meth) acrylate, 1- Methyl-3-vinyloxypropyl (meth) acrylate, 1-vinyloxymethylpropyl (meth) acrylate, 2-methyl-3-vinyloxypropyl (meth) acrylate, 3-methyl-3-vinyloxypropyl (meth) acrylate 1,1-dimethyl-2-vinyloxyethyl (meth) acrylate, 3-vinyloxybutyl (meth) acrylate, 1-methyl-2-vinyloxypropyl (meth) acrylate, 2-vinyloxybutyl (meth) acrylate, 4-vinyloxycyclo F Sil (meth) acrylate, 5-vinyloxypentyl (meth) acrylate, 6-vinyloxyhexyl (meth) acrylate, 4-vinyloxymethylcyclohexylmethyl (meth) acrylate, 3-vinyloxymethylcyclohexylmethyl (meth) acrylate, 2-vinyloxymethylcyclohexylmethyl (meth) acrylate, p-vinyloxymethylphenylmethyl (meth) acrylate, m-vinyloxymethylphenylmethyl (meth) acrylate, o-vinyloxymethylphenylmethyl (meth) acrylate, 2- (Vinyloxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyisopropoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxy) propyl (meth) acrylate, 2- (vinyloxyethoxy) Sopropyl (meth) acrylate, 2- (vinyloxyisopropoxy) propyl (meth) acrylate, 2- (vinyloxyisopropoxy) isopropyl (meth) acrylate, 2- (vinyloxyethoxyethoxy) ethyl (meth) acrylate, 2- (Vinyloxyethoxyisopropoxy) ethyl (meth) acrylate, 2- (vinyloxyisopropoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyisopropoxyisopropoxy) ethyl (meth) acrylate.

  2- (vinyloxyethoxyethoxy) propyl (meth) acrylate, 2- (vinyloxyethoxyisopropoxy) propyl (meth) acrylate, 2- (vinyloxyisopropoxyethoxy) propyl (meth) acrylate, 2- (vinyloxyiso Propoxyisopropoxy) propyl (meth) acrylate, 2- (vinyloxyethoxyethoxy) isopropyl (meth) acrylate, 2- (vinyloxyethoxyisopropoxy) isopropyl (meth) acrylate, 2- (vinyloxyisopropoxyethoxy) isopropyl ( (Meth) acrylate, 2- (vinyloxyisopropoxyisopropoxy) isopropyl (meth) acrylate, 2- (vinyloxyethoxyethoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyate) Ciethoxyethoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyisopropoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyisopropoxyethoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyisopropoxyethoxy) Ethoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyisopropoxyethoxyethoxyethoxyethoxy) ethyl (meth) acrylate, polyethylene glycol monovinyl ether (meth) acrylate, polypropylene glycol monovinyl ether (meth) acrylate.

  These may be used alone or in admixture of two or more. Among these, 2-vinyloxyethyl (meth) acrylate, 3-vinyloxypropyl (meth) acrylate, 1-methyl-2-vinyloxyethyl (meth) acrylate, 4-vinyloxybutyl (meth) acrylate, 4-vinyloxycyclohexyl (meth) Acrylate, 5-vinyloxypentyl (meth) acrylate, 6-vinyloxyhexyl (meth) acrylate, 4-vinyloxymethylcyclohexylmethyl (meth) acrylate, p-vinyloxymethylphenylmethyl (meth) acrylate, 2- (vinyl Roxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxyethoxy) ethyl (meth) acrylate, and 2- (vinyloxyethoxyethoxyethoxy) ethyl (meth) acrylate are preferred. Most preferred are 2-vinyloxyethyl acrylate (sometimes referred to as VEEA) and 2-vinyloxyethyl methacrylate (sometimes referred to as VEEM).

  An electron beam curable pressure-sensitive adhesive composition containing a vinyl ether group-containing (meth) acrylate, particularly a reactive diluent containing VEEA and / or VEEM, is a general reactive diluent (the above monofunctional monomer or polyfunctional monomer). Faster curability than the case of using only. In addition, the surface protective film obtained after crosslinking / curing with an electron beam exhibits initial tack, adhesive strength, cohesive strength and the like in a well-balanced manner. In particular, a vinyl ether group-containing (meth) acrylate can increase the crosslink density and suppress the movement of the polymer molecular chain, and can adapt the wettability and adhesive force to the substrate to the required characteristics as a surface protective film.

  The vinyl ether group-containing (meth) acrylate preferably has a viscosity at 25 ° C. in the range of 0.1 to 1500 mPa · s. When the viscosity is less than 0.1 mPa · s, not only is it difficult to adjust the thickness of the pressure-sensitive adhesive layer, but generally the volatility is increased and the working environment may be deteriorated. 1500 mPa · s If it exceeds 1, the viscosity of the pressure-sensitive adhesive composition may be too high to be applied.

  The molecular weight of the vinyl ether group-containing (meth) acrylate is preferably 140 to 2000. When it exceeds 2000, the viscosity of the pressure-sensitive adhesive composition may be too high to be applied. The molecular weight is more preferably 1000 or less, further preferably 800 or less, and particularly preferably 500 or less.

  The proportion of the vinyl ether group-containing (meth) acrylate in the reactive diluent may be appropriately set according to the type of the vinyl ether group-containing (meth) acrylate, etc., but 1 to 100% by mass of the reactive diluent. 50 mass% is preferable. More preferably, it is 3-40 mass%, More preferably, it exists in the range of 5-30 mass%. The reactive diluent other than the vinyl ether group-containing (meth) acrylate is not particularly limited as long as it is compatible with the vinyl ether group-containing (meth) acrylate, and is appropriately selected from the monofunctional monomers and polyfunctional monomers exemplified above. That's fine.

  In the electron beam curable pressure-sensitive adhesive composition used in the present invention, a (meth) acrylic polymer and a reactive diluent are essential components. The ratio of the two may be appropriately adjusted so that the composition has a viscosity suitable for coating, but when the total of both is 100% by mass, the (meth) acrylic polymer is contained in an amount of 20 to 80% by mass. It is preferable to make it. If it is less than 20% by mass, the amount of the reactive diluent is large, so that volume shrinkage during electron beam curing becomes large, which is not preferable. When it exceeds 80% by mass, the amount of the reactive diluent is too small, the viscosity of the composition becomes high, and uniform coating becomes difficult. In addition, it is preferable to adjust the viscosity of a composition in the range of 50-2000 mPa * s in 25 degreeC. A more preferable viscosity range is 70 to 1500 mPa · s.

  The electron beam curable pressure-sensitive adhesive composition used in the present invention includes an ethylenically unsaturated double bond-containing oligomer such as unsaturated polyester, epoxy (meth) acrylate, urethane (meth) acrylate, and polyester (meth) acrylate; -Other polymers such as vinyl acetate copolymer, ethylene-acrylic copolymer, polybutadiene, polyisoprene may be added. Double bond-containing oligomers undergo polymerization / crosslinking reactions when irradiated with electron beams, and other polymers are also involved in polymerization / crosslinking reactions due to hydrogen abstraction reactions caused by electron beam irradiation. To do. When these compounds are included in the electron beam curable pressure-sensitive adhesive composition, the amount of the (meth) acrylic polymer may be reduced by that amount to determine the ratio with the reactive diluent. The ratio of the (meth) acrylic polymer to the above-mentioned oligomer and other polymer is such that the (meth) acrylic polymer is 60 to 100% by mass when the total of both is 100% by mass. It is preferable to do. This is because a pressure-sensitive adhesive layer having excellent transparency can be formed.

  The electron beam curable pressure-sensitive adhesive composition may contain a solvent. The viscosity can be adjusted without increasing the amount of reactive diluent. Solvents that can be used are those that can be used as the solvent for the solution polymerization described above. When the total amount of (meth) acrylic polymer, reactive diluent and solvent is 100% by mass, the solvent is preferably 0 to 50% by mass. Usable solvents are the same as those usable for solution polymerization.

  The electron beam curable pressure-sensitive adhesive composition may be blended with known tackifiers and plasticizers as long as transparency is not impaired. Examples of the tackifier include terpene resins, terpene phenol resins, phenol resins, aromatic hydrocarbon modified terpene resins, rosin resins, modified rosin resins, synthetic petroleum resins (aliphatic, aromatic and alicyclic synthetic petroleum resins, etc. ), Coumarone-indene resin, xylene resin, styrene resin, dicyclopentadiene resin, and those having unsaturated double bonds that can be hydrogenated include hydrogenated products thereof. One type of tackifier may be used, or two or more types may be used in combination. The amount of the tackifier used is usually 50% or less based on the mass of the polymer constituting the adhesive, and preferably 1 to 25% from the viewpoint of the adhesive strength and tack of the adhesive.

  Examples of the plasticizer include various known plasticizers such as hydrocarbons such as liquid paraffin, polybutene, and liquid polybutadiene, phthalic acid esters, aliphatic dibasic acid esters, glycol esters, phosphoric acid esters, and epoxy plasticizers. Can be mentioned. The amount of the plasticizer used is usually 20% or less based on the mass of the polymer constituting the adhesive, and preferably 1 to 15% from the viewpoint of the adhesive strength and tack of the adhesive.

  In addition, the electron beam curable pressure-sensitive adhesive composition includes an antioxidant, a surfactant, a silane coupling agent, an antistatic agent (containing an ethylenically unsaturated double bond capable of electron beam crosslinking) depending on the application. Inorganic fillers, fluorescent brighteners, color tone modifiers, and the like may be added as appropriate.

  The electron beam curable pressure-sensitive adhesive composition is obtained by obtaining a (meth) acrylic polymer, then removing the solvent as necessary, and adding a reactive diluent (the above-mentioned various additive components if necessary). What is necessary is just to mix by the method of. In addition, in this invention, well-known crosslinking agents, such as a polyisocyanate compound and a melamine resin, are not added to a composition. This is because it is not suitable for the purpose of the present invention in which the pressure-sensitive adhesive layer is crosslinked by electron beam irradiation in order to eliminate the curing period.

  Next, the base film of the surface protective film roll of the present invention will be described. When applied to optical applications, the base film is desired to have good transparency and scratch resistance. For example, the visible light transmittance measured in accordance with ASTM-D-1003 is 85% or more, pencil A plastic film having a hardness (JIS K-5600-5-4) of F or more is suitable. Specifically, polyester films such as PET and polyethylene naphthalate (PEN), cellulose films such as triacetyl cellulose (TAC), acrylic films such as polymethyl methacrylate, polyolefin films having a cyclic structure, polystyrene, etc. Polystyrene-based film can be used.

  In addition, a lactone film mainly composed of a polymer containing 10 to 90% by mass (more preferably 10 to 50% by mass) of a lactone ring-containing unit represented by the following general formula (2) has transparency and scratch resistance. The base film is excellent in heat resistance and particularly suitable for optical applications.

[Wherein, R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. ]

  Examples of the “organic residue having 1 to 20 carbon atoms” include those having 1 to 20 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, and a cyclohexyl group. Examples include alkyl groups, aryl groups such as phenyl groups, and aralkyl groups such as benzyl groups. In addition, these organic residues may contain nitrogen, oxygen, and sulfur atoms.

  The polymer containing the lactone ring-containing unit includes 2- (hydroxymethyl) methyl acrylate, 2- (hydroxymethyl) ethyl acrylate, 2- (hydroxymethyl) isopropyl acrylate, 2- (hydroxymethyl) -n-butyl acrylate, 2 A polymer is synthesized using a raw material component containing 10 to 90% by mass of a monomer having an ester group and a hydroxyl group in one molecule such as-(hydroxymethyl) -t-butyl acrylate, and then under reduced pressure as necessary. It can be obtained by carrying out an intramolecular cyclocondensation reaction at about 150 to 350 ° C. As the comonomer, any of the monomers that can be used as the raw material for the (meth) acrylic polymer described above can be used, and methyl methacrylate is particularly preferable from the viewpoint of excellent transparency and scratch resistance.

  The base film of the present invention is a film containing the lactone ring-containing polymer as a main component, and the lactone ring-containing polymer is preferably contained in an amount of 50% by mass or more in the film. More preferably, it is 60-100 mass%, More preferably, it is 70-100 mass%, Most preferably, it is 80-100 mass%. The base film is particularly suitable for optical applications because it has few fish eyes. Further, since the surface smoothness is also excellent, it is possible to reduce the thickness. In addition, as resin which can be used together with a lactone ring containing polymer, it is raw material resin of the film which can be used as an above-described base film.

  The base film may contain other additives. Examples of other additives include hindered phenol-based, phosphorus-based and sulfur-based antioxidants; light-resistant stabilizers, weather-resistant stabilizers, heat-stabilizers, and other stabilizers; reinforcing materials such as glass fibers and carbon fibers. UV absorbers such as phenyl salicylate, (2,2′-hydroxy-5-methylphenyl) benzotriazole, 2-hydroxybenzophenone; near infrared absorbers; tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide Flame retardants such as: antistatic agents such as anionic, cationic and nonionic surfactants; colorants such as inorganic pigments, organic pigments and dyes; organic fillers and inorganic fillers; resin modifiers; Inorganic fillers; plasticizers; lubricants; antistatic agents and the like. These additives can contain a particle size that does not impair the smoothness of the base film, if necessary.

  The base film raw material polymer can be formed into a film by a known method such as a solution casting method (solution casting method), a melt extrusion method or an inflation method. After film formation, the film may be uniaxially or biaxially stretched by a known method. As thickness of a base film, about 5-200 micrometers is preferable and about 10-100 micrometers is more preferable.

  Next, the manufacturing method of the surface protection film roll of this invention is demonstrated. The method for producing the surface protective film roll of the present invention includes a step of forming a layer of an electron beam curable pressure-sensitive adhesive composition on a long base film, and irradiating the pressure-sensitive adhesive composition layer with an electron beam. It is characterized in that the step of cross-linking and the step of winding the surface protective film after cross-linking into a roll without using a separator are carried out continuously.

  The method for applying the electron beam curable pressure-sensitive adhesive composition on the base film is not particularly limited. As the coating head, a lip coater, a slot die, and a micro gravure (registered trademark of Yasui Seiki) are preferable. In this case, any of a method of directly applying the pressure-sensitive adhesive composition to the base material, a method of applying the pressure-sensitive adhesive composition to a release film, and then transferring the coated material onto the base material film can be employed. . After apply | coating an adhesive composition, an uncrosslinked adhesive layer is formed on a base film by making it dry as needed. As thickness of an adhesive layer, about 1-100 micrometers is preferable and about 5-50 micrometers is more preferable. More preferably, it is 15-25 micrometers. In addition, when the solvent is not contained in an adhesive composition, the thickness of an adhesive layer hardly changes before and after bridge | crosslinking.

  The base film may be subjected to a peeling treatment. For the release treatment, a known method can be employed. For example, a release agent such as a silicone resin, a fluororesin, or a long-chain alkyl compound may be applied to one side of the base film to form a release layer. . An electron beam curable mold release agent may be used. As the silicone resin, a silicone resin generally used as a release agent can be used. For example, it is used in the technical field described in “Silicon Material Handbook” (Toray Dow Corning, 19933.8). It can be used by selecting from silicone resins. Thermosetting or electron beam curable silicone resins are preferred. When the release treatment is performed, the pressure-sensitive adhesive layer may be provided on the side of the substrate film opposite to the release treatment surface or on the release treatment surface side of the substrate film. This is because, when the roll is rewound after being wound into a roll, it peels off at the interface between the release treatment surface and the pressure-sensitive adhesive layer. In addition, when the base film is difficult to adhere, a mold release process is unnecessary, and conversely, it may be preferable to perform an adhesion improving process such as a corona process, a plasma process, or an electron beam irradiation process.

  In addition, the peelability is adjusted so that the unwinding force (peeling force) of the surface protective film roll does not become excessive on the outermost layer (outermost surface layer) after the surface protective film is applied to the adherend. In this case, one or more layers having various functions such as hard coat properties, antistatic properties, antifouling properties, and printability may be laminated.

  Subsequently, electron beam irradiation is performed to crosslink and cure the pressure-sensitive adhesive layer. The electron beam may be irradiated from either the pressure-sensitive adhesive layer side or the base film layer side. In order to achieve a degree of crosslinking that can be wound into a roll without a separator immediately after irradiation with an electron beam, the electron beam acceleration voltage should be 80 to 140 kV. preferable. When the pressure is less than 80 kV, the pressure-sensitive adhesive layer is uncured and cannot be wound up without a separator, and the problem of odor of unreacted substances occurs. If it exceeds 140 kV, the film base material is deteriorated or colored, and the reactive diluent contained in the pressure-sensitive adhesive layer volatilizes in the air, and the target pressure-sensitive adhesive properties may not be obtained. A more preferable acceleration voltage range is 90 to 135 kV, and a further preferable range is 90 to 110 kV.

  The irradiation dose is preferably 40 to 120 kGy. If it is less than 40 kGy, the effect of the pressure-sensitive adhesive layer becomes insufficient, and it is impossible to wind up without a separator, or the problem of odor of unreacted substances occurs. Moreover, when it exceeds 120 kGy, since bridge | crosslinking of an adhesive layer advances too much and adhesive force falls, it is unpreferable. A more preferable upper limit of the irradiation dose is 110 kGy, and a more preferable upper limit is 100 kGy.

  The electron beam irradiation apparatus is not particularly limited as long as it can irradiate the electron beam with the acceleration voltage. Also, the electron beam source is not particularly limited. For example, various electrons such as Cockloft-Walton type, Van de Graf type, resonant transformer type, insulated core transformer type, linear type, dynamitron type, high frequency type, etc. A line accelerator can be used. In addition, in the electron beam irradiation, if a large amount of oxygen (air) is present, the polymerization curing reaction is inhibited. Therefore, it is desirable to irradiate in an inert gas atmosphere.

  After the electron beam irradiation, the obtained surface protective film is wound up in a roll shape with the pressure-sensitive adhesive layer inside without using a separator. When the pressure-sensitive adhesive layer is provided on the surface of the release agent layer, the pressure-sensitive adhesive layer may be wound outside in a roll shape. As the winding core, usually, plastic cores such as 3 inches, 6 inches, and 8 inches, metal cores, paper tubes, and the like can be used, and any of them can be used.

  Each process of forming an above-mentioned adhesive composition layer, an electron beam irradiation process, and a winding-up process is continuously performed with respect to the running long film. The length of the long film is not particularly limited, but is preferably 80 m or more. The higher the line speed, the better from the viewpoint of productivity, but the range of the acceleration voltage is preferably 10 to 200 m / min, more preferably 20 m / min or more. If it is less than 10 m / min, it cannot be said that it is suitable from the point of productivity. If it exceeds 200 m / min, air (bubbles) are likely to be caught (bite) during winding of the roll, and the surface smoothness of the adhesive surface is lowered, which is not preferable. In each process, in order to improve the smoothness of the pressure-sensitive adhesive layer surface, a roll surface-treated with a fluororesin such as polytetrafluoroethylene is used as a roll that comes into contact with the pressure-sensitive adhesive surface, or an air support roller is used. A non-contact type roll may be used.

  Thus, by setting the acceleration voltage, irradiation dose, and line speed of the electron beam when crosslinking the pressure-sensitive adhesive layer of the surface protective film roll of the present invention within the above ranges, it has suitable pressure-sensitive adhesive properties that will be described later. In addition, a long surface protective film that can be continuously wound without any inconvenience without a separator can be continuously produced.

  In FIG. 1, an example of the continuous manufacturing apparatus of the surface protection film roll was shown. The pressure-sensitive adhesive composition introduced from the pressure-sensitive adhesive composition tank 2 is applied from the base film roll 1 to the continuously drawn film surface by the coating machine 3. This corresponds to the step of forming the pressure-sensitive adhesive composition layer. The film on which the pressure-sensitive adhesive composition layer is formed is subsequently introduced into the electron beam irradiation unit 5 in which the electron beam irradiation device 4 is stored, and is irradiated with an electron beam (electron beam irradiation step). In the figure, 6 is a support roll, 7 is a tension control roll, 8 is a guide roll, and 9 is a touch roll. By the movement of these rolls, the surface protective film is wound up to become the surface protective film roll 10. Further, the position of each part, the arrangement / number of rolls, etc. are not limited to this example, and can be changed as appropriate.

The pressure-sensitive adhesive layer after electron beam irradiation, that is, after crosslinking, is a polymer having a three-dimensional network structure. As a standard of the degree of crosslinking, it is 50 to 100% by mass when expressed in terms of gel fraction. This gel fraction (mass%) is determined from the mass obtained by leaving a predetermined amount of the pressure-sensitive adhesive after crosslinking in ethyl acetate at 23 ° C. for 24 hours and then drying the remaining gel at 80 ° C. for 120 minutes. The value obtained based on the formula is adopted.
Gel fraction X (mass%) = 100 × [mass after drying gel / mass of pressure-sensitive adhesive before dissolution]

  When the pressure-sensitive adhesive layer exhibits a gel fraction in the above range, it can be said that crosslinking of the (meth) acrylic polymer and polymerization / curing reaction of the reactive diluent are necessary and sufficient. The surface protective film can be wound into a roll shape immediately after irradiation with an electron beam without performing curing and without using a separator. Further, there is no appearance defect due to entrainment of bubbles or contact with a roll downstream of the coating process. In addition, there is a surface protection film that is excessively cross-linked by irradiation with an electron beam after being attached to an adherend to reduce the force required for peeling, but in the surface protection film roll of the present invention, Since the pressure-sensitive adhesive layer is already irradiated with an electron beam at the stage of use, it is clearly distinguished.

  The surface protective film wound around the surface protective film roll of the present invention is considered to be used after being unrolled from the roll and appropriately cut and then laminated on the optical film. After being laminated on the optical film and finishing the role of “protection”, the surface protection film is peeled off, but recently, a high-speed peeling process by a machine has been performed. As the peel speed increases, the peel force (adhesive strength) tends to increase. Therefore, if the peel speed is inferior, a part that peels off smoothly and a part that does not peel off easily are generated, and the sound is peeled off with a noise. The phenomenon (zipping peeling) occurs, and the optical film surface is damaged or broken. For this reason, the surface protective film is required to have an adhesive strength that does not damage the optical film as an adherend even during high-speed peeling. Therefore, it was specified that the surface protective film of the present invention preferably has a 180 ° peel strength (adhesive strength) of 3 N / 25 mm or less with respect to the acrylic plate when peeled at a high speed, that is, 30 m / min. If the high-speed peel adhesive strength is 3 N / 25 mm or less, it can be smoothly peeled off from the adherend without causing inconvenience such as zipping. The lower limit is preferably 0.5 N / 25 mm. In addition, the fact that the high-speed peeling force is small means that the peeling force is further reduced at low-speed peeling, but if the adhesive force is too small, it may be assumed that the adhesive peels off during use after being attached to the adherend. Therefore, for example, it is preferable to show a peeling force of about 0.05 to 0.3 N / 25 mm at a low speed peeling of 0.3 m / min. Moreover, it is preferable for the value obtained by dividing the high-speed peel adhesive force by the low-speed peel adhesive force to be 15.0 or less because an increase in the adhesive force during high-speed peel can be suppressed.

  The 180 ° peel strength (adhesive strength) is obtained when a 25 mm wide surface protective film is applied to an acrylic plate, left at 23 ° C. for 25 minutes, and then peeled off at 180 ° at a peel rate of 30 m / min. Use the maximum measured value. More detailed measurement methods are described in the examples. In the unit “N / 25 mm”, the “/ 25 mm” portion means the width of the surface protective film that is pressure-bonded to the adherend.

  EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the scope of the present invention is not limited only to these examples. Unless otherwise specified, “%” indicates “mass%” and “part” indicates “part by mass”.

Example 1
1. Synthesis of acrylic polymer 70 parts of 2-ethylhexyl acrylate (2EHA), 30 parts of n-butyl acrylate and 0.1 part of n-dodecyl mercaptan were mixed well, 40% of which was mixed with 48.35 parts of ethyl acetate, , Added to a flask equipped with a stirrer, inert gas inlet tube, reflux condenser and dropping funnel. The initial monomer concentration is 45.30%. While flowing nitrogen gas, the internal temperature of the flask was raised to 75 ° C., and “ABN-E” (manufactured by Nippon Hydrazine Kogyo Co., Ltd .; 2,2′-azobis (2-methylbutyronitrile)) as a polymerization initiator Was added in an amount of 0.025 parts. After confirming the start of polymerization by exotherm, 10 minutes after the start of polymerization, the remainder of the mixture was dropped from the dropping funnel over about 80 minutes. At this time, a solution prepared by dissolving 0.025 part of “ABN-E” in 19.17 parts of ethyl acetate was added dropwise from another dropping funnel. After the completion of the dropwise addition, the mixture was further stirred at 76 ° C. for 4.5 hours. 1 was obtained. The solid content concentration of this solution was 59.1%, and the viscosity (B-type viscometer; 23 ° C.) was 4000 mPa · s. Moreover, Tg calculated by the said calculation formula of the obtained polymer was -66 degreeC, and Mw of the polymer measured by the following method was 200,000.

[Mass average molecular weight (Mw)]
GPC measuring apparatus: Liquid Chromatography Model 510 (manufactured by Waters) was used under the following conditions.
Detector: M410 differential refractometer Column: Ultra Styragel Linear (7.8 mm × 30 cm)
Ultra Styragel 100Å (7.8mm × 30cm)
Ultra Styragel 500Å (7.8mm × 30cm)
Solvent: ethyl acetate

  The sample concentration was 0.2%, the injection amount was 200 microliters / time, and the polystyrene standard sample conversion value was Mw.

2. Production of electron beam curable pressure-sensitive adhesive composition 67.7 parts of No. 1 was placed in a reaction vessel, and 52 parts of 2EHA was added while removing ethyl acetate at 80 ° C. and a reduced pressure of 266 hPa. To this mixture, 8 parts of 2-vinyloxyethyl acrylate (VEEA) was further added, and the electron beam curable pressure-sensitive adhesive composition No. 1 of the present invention was added. 1 was produced. This composition No. The viscosity of No. 1 was 1000 mPa · s. In addition, this composition No. No. 1 is composed of 40% acrylic polymer and 60% reactive diluent (when the total amount of reactive diluent is 100%, VEEA is 13.3%, 2EHA is 86.7%).

3. Production of Surface Protective Film Roll One side of a film made of 2- (hydroxymethyl) methyl acrylate copolymer (hereinafter referred to as PHMA) having a width of 0.5 m and a thickness of 25 μm was subjected to a release treatment. The mold release treatment was performed by applying a thermosetting silicone release agent (“LTC750A”; manufactured by Toray Dow Corning) so that the coating amount after drying was 0.3 g / m ² , at 90 ° C. It was performed by drying and curing for 30 seconds.

  In the coating machine having a slot die, the electron beam curable pressure-sensitive adhesive composition No. No. 1 was introduced and the release-treated PHMA base film was run at a line speed of 10 m / min while the pressure-sensitive adhesive composition No. 1 was applied to a thickness (after cross-linking) of 20 μm, introduced into an electron beam irradiation section, and irradiated with an electron beam having an acceleration voltage of 135 kV from the pressure-sensitive adhesive layer side so that an irradiation dose was 80 kGy. A surface protective film of about 100 m was continuously produced and wound around a plastic core having an inner diameter of 3 inches without using a separator. 1 was obtained.

  A tension control roll that touches the pressure-sensitive adhesive layer was installed immediately upstream of the winding part, but troubles such as adhesion of the pressure-sensitive adhesive to the roll did not occur. Further, the obtained surface protective film roll No. No. 1 was excellent in surface smoothness of the protective film itself, with no bubble entrapment or poor film appearance due to contact with a roll downstream of the coating process. After the production, the product was stored at 23 ° C. for 1 day, and then the characteristics were evaluated by the method described later. The results are shown in Table 1.

Example 2
Instead of the base film used in Example 1, a PET film (“K1504” manufactured by Toyobo Co., Ltd .: thickness 38 μm) subjected to one-side silicone release treatment was used, and an adhesive was provided on the opposite side of the release treatment surface. The present invention was carried out in the same manner as in Example 1 except that the composition layer was formed so that the thickness after drying was 18 μm, the electron beam irradiation voltage was 110 kV, the irradiation dose was 100 kGy, and the line speed was 20 m / min. Surface protective film roll no. 2 was produced.

  The obtained surface protective film roll No. No. 2 had no film appearance defect due to entrainment of bubbles and was excellent in surface smoothness of the protective film itself. There are no problems in use, but several convex parts with a diameter of about 0.3 mm were found on the release treatment surface of the surface protective film, such as dirt on the support roll located immediately downstream of the coating process. . Since the release treatment layer is in contact with the support roll, it is peeled off very little by little, and when it is deposited and deposited on the support roll and becomes a size of about φ0.3 mm, it drops off from the support roll and resurfaces again. It is inferred that it adhered to the protective film. After the production, after storing at 23 ° C. for 1 day, the characteristics were evaluated, and the results are shown in Table 1.

Example 3
In Example 2, except that the electron beam irradiation voltage was changed from 110 kV to 100 kV, and the irradiation dose was changed from 100 kGy to 40 kGy, the surface protective film roll No. 3 was produced. The obtained surface protective film roll No. No. 3 had no film appearance defect due to entrainment of bubbles and was excellent in surface smoothness of the protective film itself. After the production, after storing at 23 ° C. for 1 day, the characteristics were evaluated, and the results are shown in Table 1.

Comparative Example Re-peeling slightly adhesive type solvent-type acrylic adhesive (“Acryset (registered trademark) AST-8220R”; manufactured by Nippon Shokubai Co., Ltd .; solid content 40%; viscosity 1000 mPa · s) 20 parts of ethyl and 2 parts of a polyisocyanate crosslinking agent (“Coronate (registered trademark) L-55E”; manufactured by Nippon Polyurethane Industry Co., Ltd.) were added and mixed. 2.

  A surface protective film was continuously produced in the same manner as in Example 1 except that the line speed was reduced to 2 m / min, the electron beam irradiation step was not performed, and a 105 ° C. hot air drying furnace (length 2 m) was passed. However, adhesion of the pressure-sensitive adhesive to the tension control roll occurred, and when it was produced about 20 m, continuous production was no longer possible. Further, the obtained surface protective film roll No. In No. 3, bubbles were generated between the films, and the appearance was poor. Even if the tension is adjusted with a touch roll (rolling roll winding roll) or a tension control roll, the pressure-sensitive adhesive layer may protrude beyond the coating width or the appearance of the pressure-sensitive adhesive layer may be poor. Did not heal.

  One day later, when the adhesive strength (with respect to the acrylic plate) at a low speed (0.3 m / min) was measured by the method described later, it was 0.2 N / 25 mm, which was larger than the expected value. It was. Thus, when the low-speed adhesive force was measured once daily after production, the adhesive force became constant on the fourth day, and it was found that the crosslinking was completed. About the film characteristic of the comparative example, it measured with the product of the 4th day. The results are shown in Table 1.

  The film property evaluation method in the surface protective film roll obtained in each example is as follows.

[Haze]
Using a turbidimeter (manufactured by JEOL Ltd .; “NDH-1001DP”), the haze of the surface protective film cut out from the roll was measured based on JIS K7105.

[Gel fraction]
1. A surface protective film sample is accurately cut out from the roll to 40 mm × 40 mm and weighed (w1). (N = 2)
2. The sample is immersed in 100 g of ethyl acetate in a 140 cc glass bottle, covered and left at 23 ° C. for 24 hours.
3. Remove film from glass bottle and weigh after drying (w2)
4). The content containing the gel peeled off from the film was filtered through a 200-mesh wire mesh that had been weighed (w3) in advance, and dried with the wire mesh at 80 ° C. for 120 minutes. The mass is measured (w4).
5. The gel fraction is determined by the following formula.
Gel fraction X (mass%) = 100 × [mass after drying gel / mass of pressure-sensitive adhesive before dissolution]
= 100 * [(w4-w3) / (w1-w2)]

  In addition, when the gel and the film are not separated in ethyl acetate, filtration and drying are performed with the gel-attached film, and the total mass of the gel, the film and the wire mesh is measured (w5). Was measured (w6), and the mass of the gel after drying (w5-w3-w6) and the mass of the adhesive before dissolution (w1-w6) were determined.

[Familiarity]
A test piece of 40 mm × 40 mm is cut out from the surface protective film roll, and placed gently on the antiglare-treated film (“BOF-H141S”; BUFFALO liquid crystal protective film) with the pressure-sensitive adhesive layer down. Then, the time and state until the entire surface of the sample became familiar (wet) with the antiglare treatment film was visually observed. The test was performed three times, and the following evaluation points were averaged.
1 point: at 6 minutes, the familiar part is 50% or less of the sample area.
2 points: at 6 minutes, the familiar part is 70% or less of the sample area.
3 points: Almost the entire surface of the sample fits in 31 seconds to 3 minutes.
4 points: Almost the entire surface of the sample is adapted in 21 seconds to 30 seconds.
5 points: The entire surface of the sample fits within 20 seconds.

[Adhesive properties]
A 25 mm wide test piece was cut out from the surface protective film roll obtained in each of the above examples.
An acrylic plate (standard test plate made by Nippon Test Panel Co., Ltd.) having a thickness of 3 mm is used as an adherend, and the test piece is bonded to an acrylic plate in an atmosphere of 23 ° C. and a relative humidity of 65%. In such a manner, the pressure is reciprocated once by a 2 kg rubber roller. After leaving for 25 minutes after pressure bonding, the peeling speed was 0.3 m / min for low speed peeling and 30 m / min for high speed peeling, and 180 ° peeling adhesive strength was measured in an atmosphere of 23 ° C. according to JIS K 6854. . Table 1 also shows the values obtained by dividing the low-speed peel adhesive strength, the high-speed peel adhesive strength, and the high-speed peel adhesive strength by the low-speed peel adhesive strength (shown as “high speed / low speed”).

  Since the surface protective film roll of the present invention crosslinks and cures the pressure-sensitive adhesive layer by electron beam irradiation, it is possible to form a pressure-sensitive adhesive layer that can be rolled up without using a separator without curing. did it. Therefore, the line speed can be increased, and the cost of the surface protective film roll can be reduced. In addition, since no separator is used, a step of peeling the separator is not necessary and the cost of the separator is not required when mechanically attaching to the adherend using a laminator.

  The surface protective film roll of the present invention is a film roll for protecting the surface of an optical member such as an optical polarizing plate (TAC), a retardation plate, an EMI (electromagnetic wave) shield film, an antiglare film, an antireflection film and the like. Is available. It can also be used as a film roll for protecting the surface of other plastics and metal plates.

It is an example of the continuous manufacturing apparatus of the surface protection film roll of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base film roll 2 Adhesive composition tank 3 Coating machine 4 Electron beam irradiation apparatus 5 Electron beam irradiation part 6 Support roll 7 Tension control roll 8 Guide roll 9 Touch roll 10 Surface protection film roll

Claims (7)

  A long base film and a pressure-sensitive adhesive layer cross-linked by electron beam irradiation, the pressure-sensitive adhesive layer comprising a reactive diluent (meth) having at least one ethylenically unsaturated double bond in the molecule; A surface protective film roll, wherein a layer made of an electron beam curable pressure-sensitive adhesive composition containing an acrylic polymer is irradiated with an electron beam and is wound without a separator.   The surface protective film cut out from the surface protective film roll is attached to an acrylic plate and allowed to stand at 23 ° C. for 25 minutes, and then the 180 ° adhesive force measured at a peeling speed of 30 m / min is 3 N / 25 mm or less. The surface protective film roll described in 1.   The surface protective film roll according to claim 1 or 2, wherein the glass transition temperature (Tg) of the (meth) acrylic polymer is 0 ° C or lower.   The surface protective film roll in any one of Claims 1-3 in which the said reactive diluent contains the (meth) acrylate which has a vinyl ether group as an essential component.   The surface protection film roll according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive after crosslinking has a gel fraction of 50 to 100 mass% when left in ethyl acetate at 23 ° C for 24 hours.   The surface protective film roll according to any one of claims 1 to 5, wherein the base film is a film containing a lactone ring-containing polymer as a main component.   A method for continuously producing the surface protective film roll according to any one of claims 1 to 6, comprising at least one ethylenically unsaturated double bond in a molecule on a long base film. A step of forming a layer of an electron beam curable pressure-sensitive adhesive composition containing a reactive diluent and a (meth) acrylic polymer, and an acceleration voltage of 80 to 140 kV at a line speed of 10 to 200 m / min. And the surface which performs the process of irradiating an electron beam with an irradiation dose of 40-120 kGy and crosslinking, and the process of winding up the surface protection film after crosslinking in a roll shape without using a separator. Continuous production method of protective film roll.