KR20200024714A - Substrate for surface protective film, method for manufacturing the substrate, surface protective film using the substrate, and optical film with surface protective film - Google Patents

Abstract

The present invention provides a substrate for a surface protective film which has excellent flexibility or bending resistance, and which can favorably suppress light leakage, coloring, and rainbow stains during optical inspection. The substrate for the surface protective film of the present invention is composed of a film comprising an acrylic resin and an elastomer, has in-plane retardation Re (550) of 30 nm or less, and the number of bending times to break in the MIT test of 500 or more. A method for manufacturing the substrate for the surface protective film of the present invention comprises molding of a film forming material comprising the acrylic resin and the elastomer into a film, and sequential biaxial stretching or simultaneous biaxial stretching of the molded film.

Description

Substrate for surface protection film, the manufacturing method of the base material, the surface protection film using the base material, and the optical film with surface protection film {SUBSTRATE FOR SURFACE PROTECTIVE FILM, METHOD FOR MANUFACTURING THE SUBSTRATE, SURFACE PROTECTIVE FILM USING THE SUBSTRATE, AND OPTICAL FILM WITH SURFACE PROTECTIVE FILM}

This invention relates to the base material for surface protection films, the manufacturing method of this base material, the surface protection film using this base material, and the optical film with a surface protection film.

The optical film (for example, a polarizing plate, a laminate including a polarizing plate) has a surface for protecting the optical film (finally the image display device) while the image display device to which the optical film is applied is actually used. The protective film is bonded so that peeling is possible. Practically, a laminate of an optical film / surface protective film is bonded to a display cell to produce an image display device, and an image display device is provided to an optical test (for example, a lighting test) in a state where the laminate is bonded. The surface protection film is peeled off at a suitable time later. The surface protection film typically has a resin film and an adhesive layer as a base material. According to the conventional surface protection film, light leakage, coloring, a rainbow stain, etc. generate | occur | produce at the time of optical inspection, and may cause the precision fall of an optical inspection. As a result, although there is no problem with the image display apparatus itself, it may be judged as defective by the optical inspection before shipment, and there exists a problem that the efficiency from manufacture to shipment of an image display apparatus will fall by this. In addition, the surface protection film (substantially a substrate) is required to have excellent flexibility in consideration of operability at the time of bonding and peeling.

Japanese Patent Publication No. 2017-190406

This invention is made | formed in order to solve the said conventional subject, The main objective is the surface protection film which has the outstanding flexibility or bending resistance, and can suppress light leakage, coloring, and rainbow staining at the time of optical inspection well. It is to provide the base material.

The base material for surface protection films which concerns on embodiment of this invention is comprised from the film containing acrylic resin and an elastomer, In-plane phase difference Re (550) is 30 nm or less, and the frequency | count of bending to break in MIT test is 500 or more times. 6 parts by weight or more of the elastomer with respect to 100 parts by weight of the acrylic resin.

In one embodiment, the said acrylic resin has at least 1 chosen from the group which consists of a glutarimide unit, a lactone ring unit, a maleic anhydride unit, a maleimide unit, and a glutaric anhydride unit.

In one embodiment, the elastomer is at least one selected from rubbery polymers, polyamide elastomers, polyethylene elastomers, styrene elastomers and butadiene elastomers.

In one embodiment, the said base material for surface protection films has a total light transmittance of 80% or more, and haze is 1.0% or less.

According to another situation of this invention, the manufacturing method of the said base material for surface protection films is provided. This production method includes molding a film forming material containing an acrylic resin and an elastomer into a film, and successively biaxial stretching or simultaneous biaxial stretching of the molded film.

In one embodiment, in the said manufacturing method, the extending | stretching temperature in the said sequential biaxial stretching or simultaneous biaxial stretching is Tg + 10 degreeC-Tg + 30 degreeC.

According to another situation of this invention, a surface protection film is provided. This surface protection film contains the said base material for surface protection films, and an adhesive layer.

According to still another aspect of the present invention, an optical film with a surface protective film is provided. This optical film with a surface protection film contains an optical film and the said surface protection film joined so that peeling was possible to the said optical film.

(Effects of the Invention)

According to the embodiment of the present invention, by stretching a film containing an acrylic resin and an elastomer under a predetermined stretching condition (for example, stretching temperature and stretching speed), both in-plane retardation and excellent flexibility or bending resistance are achieved. The base material for surface protection films can be implement | achieved.

EMBODIMENT OF THE INVENTION Hereinafter, although preferable embodiment of this invention is described, this invention is not limited to these embodiment.

A. Substrate for Surface Protection Film

The base material for surface protection films which concerns on embodiment of this invention is comprised from the film containing acrylic resin and an elastomer.

Arbitrary suitable acrylic resin can be employ | adopted as acrylic resin. Acrylic resin typically contains alkyl (meth) acrylate as a main component as a monomer unit. In this specification, "(meth) acryl" means an acryl and / or methacryl. As an alkyl (meth) acrylate which comprises the main skeleton of acrylic resin, the C1-C18 thing of a linear or branched alkyl group can be illustrated. These can be used individually or in combination. Moreover, you may introduce arbitrary appropriate copolymerization monomers into copolymerization by acrylic resin. The kind, number, copolymerization ratio, etc. of such a copolymerization monomer can be suitably set according to the objective. The structural component (monomer unit) of the main skeleton of acrylic resin is mentioned later, referring General formula (2).

The acrylic resin preferably has a structural unit selected from glutarimide units, lactone ring units, maleic anhydride units, maleimide units, and glutaric anhydride units. Acrylic resin may have only one of these structural units, and may have it in plurality. Acrylic resin which has a lactone ring unit is described, for example in Unexamined-Japanese-Patent No. 2008-181078, The description of the said publication is integrated in this specification as a reference. Glutarimide units are preferably represented by the following general formula (1):

In General formula (1), R <^1> and R <^2> represents a hydrogen or a C1-C8 alkyl group each independently, R <^3> is a C1-C18 alkyl group, a C3-C12 cycloalkyl group, or C6-C8 The aryl group of 10 is shown. In General formula (1), Preferably, R <^1> and R <^2> are respectively independently hydrogen or a methyl group, and R <^3> is hydrogen, a methyl group, a butyl group, or a cyclohexyl group. More preferably, R ¹ is a methyl group, R ² is hydrogen, and R ³ is a methyl group.

The alkyl (meth) acrylate is typically represented by the following general formula (2):

In general formula (2), R <^4> represents a hydrogen atom or a methyl group, R <^5> represents a hydrogen atom or the C1-C6 aliphatic or alicyclic hydrocarbon group which may be substituted. As a substituent, a halogen and a hydroxyl group are mentioned, for example. Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, and (meth) acrylate -Hexyl, cyclohexyl (meth) acrylate, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, (meth) acrylic acid 2,3,4,5,6-pentahydroxyhexyl and (meth) acrylic acid 2,3,4,5-tetrahydroxypentyl are mentioned. In general formula (2), R <^5> , Preferably, they are a hydrogen atom or a methyl group. Thus, particularly preferred alkyl (meth) acrylates are methyl acrylate or methyl methacrylate.

The said acryl-type resin may contain only the single glutarimide unit, and R <^1> , R <^2> and R <^{3> in the} said General formula (1) may contain the some glutarimide unit from another.

Preferably the content rate of the glutarimide unit in the said acrylic resin is 2 mol%-50 mol%, More preferably, 2 mol%-45 mol%, More preferably, 2 mol%-40 mol%, Especially Preferably it is 2 mol%-35 mol%, Most preferably, it is 3 mol%-30 mol%. When the content ratio is less than 2 mol%, there is a concern that the effects (for example, high optical properties, high mechanical strength, excellent adhesion with a polarizer, and thinning) derived from the glutarimide unit may not be sufficiently exhibited. When content rate exceeds 50 mol%, there exists a possibility that heat resistance and transparency may become inadequate, for example. Moreover, when acrylic resin has a lactone ring unit, a maleic anhydride unit, a maleimide unit, and / or a glutaric anhydride unit instead of a glutarimide unit or in addition to a glutarimide unit, the said content rate is these structural units. It may be a content ratio of the sum of.

The said acrylic resin may contain only a single alkyl (meth) acrylate unit, and R <^4> and R <^5> in the said General formula (2) may contain the several some alkyl (meth) acrylate unit.

Preferably the content rate of the alkyl (meth) acrylate unit in the said acrylic resin is 50 mol%-98 mol%, More preferably, 55 mol%-98 mol%, More preferably, 60 mol%-98 mol %, Especially preferably, it is 65 mol%-98 mol%, Most preferably, 70 mol%-97 mol%. When the content ratio is less than 50 mol%, there is a fear that the effects (for example, high heat resistance and high transparency) derived from the alkyl (meth) acrylate unit are not sufficiently exhibited. When the said content rate is more than 98 mol%, resin will fall easily, it will be easy to be broken, high mechanical strength cannot fully be exhibited, and there exists a possibility that productivity may fall.

The acrylic resin may include an alkyl (meth) acrylate unit and a unit other than a glutarimide unit, a lactone ring unit, a maleic anhydride unit, a maleimide unit, and / or a glutaric anhydride unit. For example, the acrylic resin may contain a copolymerizable vinyl monomer unit (other vinyl monomer unit) other than the above. Examples of other vinyl monomers include acrylonitrile, methacrylonitrile, ethacrylonitrile, allylglycidyl ether, maleic anhydride, itaconic anhydride, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, aminoethyl acrylate, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, cyclohexylaminoethyl methacrylate, N-vinyldiethylamine, N-acetylvinylamine , Allylamine, methalylamine, N-methylallylamine, 2-isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-acroyl-oxazoline, N-phenylmaleimide, phenylaminoethyl methacrylate , Styrene, α-methylstyrene, p-glycidyl styrene, p-amino styrene, 2-styryl-oxazoline and the like. These may be used independently and may be used together. Preferably, they are styrene monomers, such as styrene and (alpha) -methylstyrene. The content rate of another vinylic monomer unit becomes like this. Preferably it is 0 to 1 weight%, More preferably, it is 0 to 0.1 weight%. If it is such range, the expression of undesired phase difference and fall of transparency can be suppressed.

The imidation ratio in the said acrylic resin becomes like this. Preferably it is 2.5%-20.0%. When the imidation ratio is within this range, a resin excellent in heat resistance, transparency and molding processability can be obtained, and occurrence of burning and blackening at the time of film molding and reduction of mechanical strength can be prevented. In the said acrylic resin, the imidation ratio is represented by the ratio of a glutarimide unit and an alkyl (meth) acrylate unit. This ratio can be obtained, for example, from an NMR spectrum, an IR spectrum, or the like of an acrylic resin. In this embodiment, the imidation ratio can be calculated | required by ¹ H-NMR measurement of resin using ¹ HNMR BRUKER Avance III (400 MHz). More specifically, the peak area derived from O-CH ₃ proton of alkyl (meth) acrylate near 3.5 to 3.8 ppm is set to A, and the peak derived from N-CH ₃ proton of glutarimide near 3.0 to 3.3 ppm is determined. It is calculated | required by following Formula by making area as B.

Imidation ratio Im (%) = {B / (A + B)} × 100

The acid value of the said acrylic resin becomes like this. Preferably it is 0.10 mmol / g-0.50 mmol / g. If the acid value is in this range, a resin excellent in the balance of heat resistance, mechanical properties and molding processability can be obtained. If the acid value is too small, there are cases where problems such as cost increase due to the use of a modifier for adjusting to a desired acid value and generation of gelled material due to remaining of the modifier may occur. When an acid value is too big | large, foaming at the time of film shaping | molding (for example, melt-extrusion) tends to occur, and there exists a tendency for productivity of a molded article to fall. In the said acrylic resin, an acid value is content of the carboxylic acid unit and carboxylic anhydride unit in the said acrylic resin. In this embodiment, an acid value can be computed by the titration method as described, for example in WO2005 / 054311 or Unexamined-Japanese-Patent No. 2005-23272.

The detail of acrylic resin, its manufacturing method, its characteristic, etc. is described in Unexamined-Japanese-Patent No. 2016-139027, Unexamined-Japanese-Patent No. 2007-316366, and Unexamined-Japanese-Patent No. 2008-181078, for example, The disclosure of this publication is incorporated herein by reference.

As the elastomer, any suitable elastomer may be employed. Elastomers typically have hard segments that can act as pseudo crosslinking points and soft segments that can primarily contribute to elasticity. Representative examples of the elastomers include rubbery polymers, polyamide elastomers, polyethylene elastomers, styrene elastomers and butadiene elastomers. Elastomers may be used alone or in combination. The elastomer may be appropriately selected depending on the desired properties. For example, a styrene-based elastomer may be employed in view of easy design of optical characteristics. Representative examples of styrene-based elastomers include those having a hard segment polystyrene and a soft segment polybutadiene, polyisoprene, or a copolymer of polybutadiene and polyisoprene, and hydrogenated substances thereof. In addition, the hydrogenated substance may be one in which a part of polybutadiene, polyisoprene or the like is hydrogenated, or the whole may be hydrogenated. You may use a commercial item as a styrene-type elastomer. As a commercial item of a styrene-type elastomer, For example, Taftec, a Taffren (above, Asahi Kasei Chemicals company make), Creton (Crayton Polymer Japan company make), Dynaron, JSR TR, JSR SIS (above, JSR company make) And Cefton (manufactured by Kuraresa) and Labaron (manufactured by Mitsubishi Chemical Corporation). As a polyethylene-type elastomer, what has 50 or more parts of ethylene blocks is preferable, Equerene FX (Sumitomo Chemical Co., Ltd.) etc. are mentioned as a commercial item. It is preferable that a polyamide-type elastomer has a polyether block body, As a commercial item, Pebox (made by Tokyo Corporation) is mentioned. As a rubbery polymer, core-shell particle | grains are preferable, As a commercial item, W-300 (made by Mitsubishi Chemical Corporation) etc. is mentioned.

The compounding quantity of an elastomer is 6 weight part or more with respect to 100 weight part of acrylic resin, Preferably it is 6 weight part-30 weight part, More preferably, it is 8 weight part-20 weight part. If the compounding quantity of an elastomer is such a range, the base material for surface protection films compatible with a very small in-plane retardation and excellent flexibility or bending resistance can be realized.

In embodiment of this invention, the in-plane phase difference Re (550) of the base material for surface protection films is 30 nm or less, Preferably it is 10 nm or less, More preferably, it is 5 nm or less, More preferably, it is 3 nm or less, Especially preferable Preferably 2.5 nm or less. The smaller the in-plane retardation Re 550 is, the more preferable it is. The lower limit is ideally 0 nm, for example, may be 0.1 nm. When in-plane phase difference Re (550) is such a range, when the surface protection film using the base material for surface protection films of this invention is provided to the optical inspection of an image display apparatus, light leakage, coloring, and a rainbow stain can be suppressed favorably. have. As a result, the precision of the optical inspection of an image display apparatus can be improved remarkably, and the efficiency from manufacture to shipment of an image display apparatus can be improved. Such in-plane retardation Re 550 can be realized by stretching a film containing the specific acrylic resin and the specific elastomer as described above under predetermined stretching conditions. In addition, in this specification, "Re ((lambda))" is an in-plane phase difference measured with the light of wavelength (lambda) nm in 23 degreeC. Re (λ) is obtained by the formula: Re = (nx−ny) × d when the thickness of the layer (film) is d (nm). Therefore, "Re (550)" is in-plane phase difference measured with the light of wavelength 550nm in 23 degreeC. Here, "nx" is the refractive index of the direction in which the in-plane refractive index becomes largest (that is, the slow axis direction), and "ny" is the refractive index of the direction orthogonal to the slow axis (namely, the fast axis direction) in plane.

Thickness direction retardation Rth (550) of the base material for surface protection films becomes like this. Preferably it is 50 nm or less, More preferably, it is 25 nm or less, More preferably, it is 15 nm or less, Especially preferably, it is 10 nm or less. The smaller the thickness direction retardation Rth 550 is, the more preferable it is. The lower limit is ideally 0 nm, for example, may be 0.5 nm. When the thickness direction retardation Rth 550 is within this range, light leakage, coloring, and rainbow unevenness in the oblique direction can be satisfactorily suppressed in the optical inspection. As a result, the precision can be remarkably improved also in the optical inspection of a large image display apparatus. Nz coefficient of the base material for surface protection films, Preferably it is 1.1-20, More preferably, it is 1.5-5.4. Therefore, the refractive index characteristic of the base material for surface protection films can show the relationship of nx> ny> nz, for example. If the Nz coefficient is within this range, light leakage, coloring and rainbow unevenness in the oblique direction can be suppressed more favorably in optical inspection. "Rth ((lambda))" is a phase difference of the thickness direction measured with the light of wavelength (lambda) nm in 23 degreeC. Rth (λ) is obtained by the formula: Rth = (nx−nz) × d when the thickness of the layer (film) is d (nm). Therefore, "Rth (550)" is a phase difference of the thickness direction measured with the light of wavelength 550nm in 23 degreeC. Here, "nz" is the refractive index of the thickness direction. In addition, "Nz coefficient" is calculated | required as Nz = Rth ((lambda)) / Re ((lambda)).

The base material for surface protection films may show the reverse dispersion wavelength characteristic in which an in-plane phase difference becomes large with the wavelength of a measurement light, may show the positive wavelength dispersion characteristic that an in-plane phase difference becomes small with the wavelength of a measurement light, and an in-plane phase difference The flat wavelength dispersion characteristic which hardly changes with the wavelength of the measurement light may be exhibited.

The total light transmittance of the base material for surface protection films becomes like this. Preferably it is 80% or more, More preferably, it is 85% or more, More preferably, it is 90% or more, Especially preferably, it is 95% or more. Moreover, haze of the base material for surface protection films becomes like this. Preferably it is 1.0% or less, More preferably, it is 0.7% or less, More preferably, it is 0.5% or less, Especially preferably, it is 0.3% or less. According to embodiment of this invention, the base material for surface protection films which have such a very small in-plane phase difference Re (550) and has such very excellent transparency can be implement | achieved.

In embodiment of this invention, the base material for surface protection films has the frequency | count of bending to break in MIT test 500 or more, Preferably it is 1000 or more, More preferably, it is 1500 or more, More preferably Is more than 2000 times. That is, the base material for surface protection films can have very excellent flexibility or bending resistance. Due to such excellent flexibility or bending resistance of the base material for surface protection films, it is possible to obtain a surface protection film which is excellent in operability at the time of bonding and peeling and in which cracking is suppressed. According to the embodiment of the present invention, such excellent flexibility or bending resistance and very small in-plane retardation Re 550 as described above can be compatible. It is one of the results of the present invention to realize such compatibility. In addition, the MIT test can be performed in accordance with JIS P 8115.

The modulus of elasticity of the substrate for the surface protective film is preferably 50 MPa to 350 MPa at a tensile rate of 100 mm / min. If elastic modulus is such a range, the surface protection film excellent in conveyance and operability can be obtained. According to the embodiment of the present invention, excellent elastic modulus (strength) and excellent flexibility or bending resistance (flexibility) as described above can be achieved. In addition, an elasticity modulus is measured based on JISK71127: 1999.

The tensile elongation of the base material for surface protection films becomes like this. Preferably it is 70%-200%. If the tensile elongation is in this range, there is an advantage that it is difficult to break during conveyance. In addition, tensile elongation is measured based on JISK6778.

The thickness of the base material for surface protection films is 10 micrometers-100 micrometers typically, Preferably they are 20 micrometers-70 micrometers.

B. Manufacturing Method of Substrate for Surface Protection Film

The manufacturing method of the base material for surface protection films which concerns on embodiment of this invention shape | molds the film formation material (resin composition) containing the acrylic resin and elastomer of Claim A to the film form, and the said shape | molded film It includes stretching.

In addition to the said acrylic resin and the said elastomer, a film forming material may contain other resin, may contain the additive, and may contain the solvent. Arbitrary suitable additives may be employ | adopted according to the objective as an additive. Specific examples of the additive include reactive diluents, plasticizers, surfactants, fillers, antioxidants, anti-aging agents, ultraviolet absorbers, leveling agents, thixotropic agents, antistatic agents, conductive materials, and flame retardants. The number, type, combination, addition amount, etc. of the additives can be appropriately set according to the purpose.

Arbitrary suitable shaping | molding methods can be employ | adopted as a method of forming a film from a film forming material. As a specific example, the compression molding method, the transfer molding method, the injection molding method, the extrusion molding method, the blow molding method, the powder molding method, the FRP molding method, the cast coating method (for example, the casting method), the calender molding method, the hot press method and the like can be mentioned. Extrusion molding or cast coating is preferred. It is because the smoothness of the film obtained can be raised and favorable optical uniformity can be obtained. Molding conditions can be suitably set according to the composition and kind of resin used, the characteristic desired for the base material for surface protection films, etc.

The stretching method of a film is typically biaxial stretching, More specifically, it is sequential biaxial stretching or simultaneous biaxial stretching. It is because the base material for surface protection films with small in-plane phase difference Re (550) and excellent in flexibility or bending resistance is obtained. Sequential biaxial stretching or simultaneous biaxial stretching is typically performed using a tenter stretching machine. Therefore, the extending direction of a film is typically the longitudinal direction and the width direction of a film.

The stretching temperature may vary depending on the in-plane retardation and thickness desired for the substrate for the surface protection film, the kind of resin used, the thickness of the film used, the stretching ratio, and the like. Specifically, the stretching temperature is preferably Tg + 5 ° C to Tg + 50 ° C with respect to the glass transition temperature (Tg) of the film, and more preferably Tg + 10 ° C to Tg + 30 ° C. By extending | stretching at such temperature, the base material for surface protection films which have a suitable characteristic in embodiment of this invention can be obtained.

The draw ratio may vary depending on the in-plane retardation and thickness desired for the substrate for the surface protection film, the kind of resin used, the thickness of the film used, the stretching temperature and the like. When adopting biaxial stretching (e.g., sequential biaxial stretching or simultaneous biaxial stretching), the stretching ratio in the first direction (e.g., longitudinal direction) and the second direction (e.g., width direction) The draw ratio is preferably as small as possible, and more preferably substantially the same. With such a configuration, a substrate for a surface protection film having a small in-plane retardation Re 550 and excellent in flexibility or bending resistance can be obtained. In the case of adopting biaxial stretching (e.g., sequential biaxial stretching or simultaneous biaxial stretching), the stretching ratio is in the first direction (e.g., longitudinal direction) and the second direction (e.g., width direction). For each, for example, it may be 1.1 times to 3.0 times.

In the embodiment of the present invention, the stretching rate is preferably 10% / second or less, more preferably 7% / second or less, still more preferably 5% / second or less, particularly preferably 2.5% /. Seconds or less. By stretching the film containing the specific acrylic resin and the specific elastomer as described above at such a small drawing speed, a substrate for a surface protection film having a small in-plane retardation Re 550 and excellent in flexibility or bending resistance can be obtained. . The lower limit of the stretching speed may be 1.2% / second, for example. If the stretching speed is too small, the productivity may not be practical. In addition, when adopting biaxial stretching (e.g., successive biaxial stretching or simultaneous biaxial stretching), the stretching speed in the first direction (e.g., longitudinal direction) and the second direction (e.g., width direction) The stretching speed of) is preferably as small as possible, and more preferably substantially the same. With such a configuration, the in-plane retardation Re 550 can be made smaller, and more excellent in flexibility or bending resistance.

C. Surface Protective Film

The base material for surface protection films of said A and B can be used suitably for a surface protection film. Therefore, embodiment of this invention also includes a surface protection film. The surface protection film which concerns on embodiment of this invention contains the base material for surface protection films and adhesive layer of any one of said A and B.

Arbitrary appropriate adhesives can be employ | adopted as an adhesive which forms an adhesive layer. As a base resin of an adhesive, acrylic resin, styrene resin, silicone resin, urethane resin, rubber type resin is mentioned, for example. Such a base resin is described, for example in Unexamined-Japanese-Patent No. 2015-120337 or Unexamined-Japanese-Patent No. 2011-201983. The description of these publications is incorporated herein by reference. Acrylic resin is preferable from a viewpoint of chemical resistance, adhesiveness for preventing the penetration of the processing liquid during immersion, degree of freedom to the adherend, and the like. As a crosslinking agent which can be contained in an adhesive, an isocyanate compound, an epoxy compound, an aziridine compound is mentioned, for example. The adhesive may contain a silane coupling agent, for example. The formulation of the pressure-sensitive adhesive may be appropriately set according to the purpose and desired characteristics.

The storage modulus of the pressure-sensitive adhesive layer is preferably 1.0 × 10 ⁴ Pa to 1.0 × 10 ⁷ Pa, more preferably 2.0 × 10 ⁴ Pa to 5.0 × 10 ⁶ Pa. Blocking at the time of roll formation can be suppressed as the storage elastic modulus of an adhesive layer is such a range. The storage modulus can be determined, for example, from dynamic viscoelasticity measurements at a temperature of 23 ° C. and an angular velocity of 0.1 rad / s.

The thickness of the pressure-sensitive adhesive layer is preferably 1 µm to 60 µm, more preferably 3 µm to 30 µm. When thickness is too thin, adhesiveness will become inadequate and air bubbles etc. may enter in an adhesive interface. If the thickness is too thick, a problem such as an adhesive sticking out tends to occur.

In practice, the separator is temporarily detachably attached to the pressure-sensitive adhesive layer surface until the surface protective film is actually used (that is, bonded to an optical film or an image display device). By forming a separator, while protecting an adhesive layer, it becomes possible to wind up a surface protection film in roll shape. As the separator, for example, a plastic (eg, polyethylene terephthalate (PET), polyethylene, polypropylene) film coated with a release agent such as a silicone release agent, a fluorine release agent, or a long chain alkyl acrylate release agent, a nonwoven fabric or paper Etc. can be mentioned. The thickness of a separator can employ | adopt arbitrary appropriate thickness according to the objective. The thickness of a separator is 10 micrometers-100 micrometers, for example.

D. Optical film with surface protection film

The surface protection film described in the above C is used to protect the optical film while the optical film (finally an image display device) is actually used. Therefore, embodiment of this invention also includes the optical film with a surface protection film. The optical film with a surface protection film which concerns on embodiment of this invention contains an optical film and the surface protection film of the said C term | claim which joined so that peeling was possible to the said optical film.

The optical film may be a single film or a laminate. As a specific example of an optical film, a polarizer, retardation film, a polarizing plate (typically the laminated body of a polarizer and a protective film), the conductive film for touch panels, a surface treatment film, and the laminated body which laminated these suitably according to the objective (for example, And an anti-reflective circular polarizing plate, a polarizing plate with a conductive layer for a touch panel, a polarizing plate with a retardation layer, and a prism sheet integrated polarizing plate).

(Example)

Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. The measuring method of each characteristic in an Example is as follows. In addition, "part" and "%" in an Example are a basis of weight unless there is particular notice.

(1) In-plane phase difference Re (550) and thickness direction phase difference Rth (550)

The base material (biaxially stretched film) for surface protection films obtained by the Example and the comparative example was cut out in length 4cm and width 4cm, and it was set as the measurement sample. About the said measurement sample, in-plane phase difference and thickness direction phase difference were measured using the product name "Axoscan" by Axometrics. The measurement wavelength was 550 nm and the measurement temperature was 23 degreeC.

(2) haze

About the measurement sample like said (1), haze was measured using the haze meter (made by Murakami Shikisai Kijutsu Kenkyujo, HM-150 type). The measurement temperature was 23 ° C.

(3) MIT test

The MIT test was conducted in accordance with JIS P 8115. Specifically, the base material (biaxially stretched film) for surface protection films obtained by the Example and the comparative example was cut out to 15 cm in length and 1.5 cm in width, and it was set as the measurement sample. The measurement sample is attached to MIT TYPE FOLDING ENDURANCE TESTER type BE-202 (manufactured by Tester Sangyo Co., Ltd.) (load 1.0kgf, clamp R: 0.38mm), test speed 90cpm and bending angle 90 ° The bending was performed repeatedly at an upper limit of 2000 times, and the number of times of bending when the measurement sample was broken was used as the test value.

(4) rainbow stain

The base material (biaxially stretched film) for surface protection films obtained by the Example and the comparative example was arrange | positioned between two polarizing plates of a cross nicol state. At that time, the base material for surface protection films was arrange | positioned so that the longitudinal direction of the base material for surface protection films and the transmission axis direction of one polarizing plate may become parallel. In that state, the light of fluorescent lamp was irradiated from the lower side of a lower polarizing plate, and the presence or absence of the rainbow spot was observed visually. The following criteria evaluated.

○: Rainbow stains were not confirmed

(Triangle | delta): Rainbow stain was confirmed a little

X: Rainbow stain was confirmed remarkably

(5) flexibility or bending resistance

The 180 degree bending test was repeated 100 times about the base material (biaxially stretched film) for surface protection films, and the presence or absence of fracture was confirmed. The following criteria evaluated.

(Circle): The break was not confirmed

×: Break was confirmed

<Example 1>

1-1.Polymerization of Acrylic Resin and Blending Elastomer

229.6 parts of methyl methacrylate (MMA), 33 parts of methyl 2- (hydroxymethyl) acrylate (MHMA), 248.6 parts of toluene, and n- in a reaction vessel equipped with a stirring device, a temperature sensor, a cooling tube and a nitrogen introduction tube. 0.19 part of dodecyl mercaptan was thrown in, and it heated up to 105 degreeC, passing nitrogen through this. At the start of reflux at elevated temperature, 0.28 parts of t-amyl peroxy isonanoate (Luprox® 570, manufactured by Alkema Yoshitomi Corporation) was added as a polymerization initiator, and t-amyl peroxy isonanoate was further added. 0.56 parts and 12.4 parts of styrene were dripped over 2 hours, solution polymerization advanced under reflux of about 105 degreeC-110 degreeC, and after completion | finish of dripping, further aged for 4 hours at the same temperature. Next, 0.21 part of stearyl phosphate ("Phoslex A-18" by Sakai Chemical Industries, Ltd.) was added to the obtained polymerization solution as a catalyst (cyclization catalyst) of a cyclization condensation reaction, and it was locked for 2 hours under reflux of about 90-110 degreeC. Cyclization condensation reaction was performed to form a tonal ring structure. Next, the obtained polymerization solution was passed through a multi-tube heat exchanger heated to 240 ° C to complete the cyclization condensation reaction. Thus, acrylic resin which has a lactone ring unit was obtained.

Subsequently, from the completion of the cyclization condensation reaction, the resin solution has a barrel temperature of 250 ° C. and one rear vent and four pore vents (hereinafter referred to as first, second, third and fourth vents). And 31.2 parts / time in a vent type screw twin screw extruder (L / D = 52) having a side feeder between the third and fourth vents and having a leaf disc type polymer filter (filtration accuracy of 5 µm) disposed at the front end thereof. We introduced at processing speed of city (resin amount conversion). At that time, ion-exchanged water was charged from behind the second vent at a feed rate of 0.47 parts / hr, and 0.66 parts of an ultraviolet absorber (ADEKASTAB LA-F70 manufactured by ADEKA) was dissolved in 1.23 parts of toluene. The solution was introduced from behind the third vent at an input rate of 0.59 parts / hour, and ion-exchanged water was introduced from behind the fourth vent at an input rate of 0.47 parts / hour. In addition, pellets of a polyethylene elastomer (manufactured by Sumitomo Chemical Co., Ltd., product name "Equerene FX") were introduced at a feed rate of 0.63 parts / hour from the side feeder. In this way, pellets containing an acrylic resin having a lactone ring unit and a polyethylene elastomer were produced. The obtained pellet contained 10 weight part of elastomers with respect to 100 weight part of acrylic resins.

1-2.Preparation of film containing acrylic resin and elastomer

After vacuum-drying the obtained pellet at 80 degreeC for 5 hours, a single screw extruder (made by Isuzu Kakoki company, screw diameter 25mm, cylinder set temperature: 250 degreeC), T die (width 200mm, set temperature: 250 degreeC), chill roll ( Setting film: 120-130 degreeC) Using the film forming apparatus provided with the winding machine, the film containing the acrylic resin of 160 micrometers in thickness, and an elastomer was produced. The glass transition temperature (Tg) of the film containing acrylic resin and elastomer was 121 degreeC.

1-3.Production of base material for surface protection film

The film containing acrylic resin and elastomer obtained above were simultaneously biaxially stretched twice in the longitudinal direction and the width direction, respectively. The stretching temperature was [Tg + 10 ° C.] (ie, 131 ° C.), and the stretching speed was 1.4% / second in both the longitudinal direction and the width direction. Thus, the base material (40 micrometers in thickness) for surface protection films was obtained. Re (550) of the obtained base material for surface protection films was 0.3 nm, Rth (550) was 1.6 nm, haze was 0.6%, and the MIT test value exceeded 2000 times of an upper limit. The obtained base material for surface protection films was used for evaluation of said (4) and (5). The results are shown in Table 1.

<Example 2>

The base material for surface protection films was obtained like Example 1 except having set the compounding quantity of the elastomer to 15 weight part, and extending | stretching temperature to [Tg + 20 degreeC]. Re (550) of the obtained base material for surface protection films was 0.5 nm, Rth (550) was 9 nm, haze was 0.2%, and MIT test value exceeded 2000 times of an upper limit. The obtained base material for surface protection films was used for evaluation of said (4) and (5). The results are shown in Table 1.

<Example 3>

The base material for surface protection films was obtained like Example 1 except having set the compounding quantity of the elastomer to 8 weight part, and extending | stretching temperature to [Tg + 30 degreeC]. Re (550) of the obtained base material for surface protection films was 2 nm, Rth (550) was 20 nm, haze was 0.3%, and MIT test value was 1032 times. The obtained base material for surface protection films was used for evaluation of said (4) and (5). The results are shown in Table 1.

<Example 4>

Example 1 except having used 10 weight part of styrene-type elastomers (made by Asahi Kasei Co., Ltd., product name "Taftec") instead of 10 weight part of polyethylene-type elastomers, and making extending | stretching temperature [Tg + 20 degreeC] In the same manner as in the above, a substrate for a surface protective film was obtained. Re (550) of the obtained base material for surface protection films was 0.8 nm, Rth (550) was 3 nm, haze was 0.3%, and MIT test value exceeded 2000 times of an upper limit. The obtained base material for surface protection films was used for evaluation of said (4) and (5). The results are shown in Table 1.

Example 5

The base material for surface protection films was obtained like Example 4 except having set the compounding quantity of the elastomer to 15 weight part, and extending | stretching temperature to [Tg + 30 degreeC]. Re (550) of the obtained base material for surface protection films was 1.2 nm, Rth (550) was 5.1 nm, haze was 0.4%, and MIT test value exceeded 2000 times of upper limits. The obtained base material for surface protection films was used for evaluation of said (4) and (5). The results are shown in Table 1.

<Example 6>

20 parts by weight of a polyamide-based elastomer (product name: "Pebox" manufactured by Tokyo Zeolite Co., Ltd.) was used instead of 10 parts by weight of polyethylene-based elastomer, and the stretching temperature was set to [Tg + 20 ° C]. In the same manner as in Example 1, a substrate for a surface protective film was obtained. Re (550) of the obtained base material for surface protection films was 2.3 nm, Rth (550) was 3.1 nm, haze was 0.8%, and MIT test value exceeded 2000 times of upper limits. The obtained base material for surface protection films was used for evaluation of said (4) and (5). The results are shown in Table 1.

<Example 7>

10 parts by weight of core-shell rubber-like particles (manufactured by Mitsubishi Chemical Corporation, product name "W-300") were used instead of 10 parts by weight of polyethylene-based elastomer, and the stretching temperature was set to [Tg + 20 ° C]. Was carried out similarly to Example 1, and obtained the base material for surface protection films. Re (550) of the obtained base material for surface protection films was 0.3 nm, Rth (550) was 1 nm, haze was 0.3%, and MIT test value was 592 times. The obtained base material for surface protection films was used for evaluation of said (4) and (5). The results are shown in Table 1.

Comparative Example 1

A commercially available norbornene-based resin film (made by Nippon Xeon, trade name "Zenoa", Tg: 150 ° C) was used in place of the film containing acrylic resin and elastomer, and the stretching temperature was set to [Tg + 20 ° C]. Except having been carried out similarly to Example 1, the base material for surface protection films was obtained. Re (550) of the obtained base material for surface protection films was 2 nm, Rth (550) was 8 nm, haze was 0.1%, and MIT test value was 150 times. The obtained base material for surface protection films was used for evaluation of said (4) and (5). The results are shown in Table 1.

Comparative Example 2

An ultra high phase difference polyethylene terephthalate film (made by Mitsubishi Chemical Corporation, brand name "Diafoyl", Tg: 81 degreeC) instead of the film containing acrylic resin and an elastomer, and extending | stretching temperature as [Tg + 20 degreeC] A substrate for a surface protective film was obtained in the same manner as in Example 1 except for the above. Re (550) of the obtained base material for surface protection films was 4500 nm, Rth (550) was 6000 nm, haze was 1.3%, and MIT test value exceeded 2000 times of an upper limit. The obtained base material for surface protection films was used for evaluation of said (4) and (5). The results are shown in Table 1.

Comparative Example 3

The base material for surface protection films was obtained like Example 1 except having set the compounding quantity of the elastomer to 5 weight part, and extending | stretching temperature to [Tg + 20 degreeC]. Re (550) of the obtained base material for surface protection films was 0.6 nm, Rth (550) was 1.3 nm, haze was 0.2%, and MIT test value was 412 times. The obtained base material for surface protection films was used for evaluation of said (4) and (5). The results are shown in Table 1.

<Evaluation>

As is apparent from Table 1, it can be seen that the substrate for the surface protection film of the example of the present invention is prevented from rainbow staining and has excellent bending resistance (or flexibility). It is inferred that this can be realized by stretching a film containing a specific acrylic resin and a specific elastomer under a predetermined stretching condition. In addition, from the results of Comparative Example 3, it can be seen that there may exist a critical value at which bending resistance (or flexibility) falls below an allowable range in the near side where the compounding amount of the elastomer exceeds 5 parts by weight. Moreover, also about light leakage and coloring, it confirmed that the same result as a rainbow stain was obtained.

The base material for surface protection films of this invention is used suitably for a surface protection film. The surface protective film of the present invention is used to protect the optical film while the optical film (finally the image display device) is actually used. By using the base material for surface protection films and surface protection film of this invention, the precision of the optical inspection of an image display apparatus can be improved significantly.

Claims (8)

It consists of a film containing an acrylic resin and an elastomer, the in-plane retardation Re (550) is 30 nm or less, the number of bendings to break in an MIT test is 500 or more times, and the elastomer with respect to 100 parts by weight of the acrylic resin The base material for surface protection films containing 6 weight part or more. The method of claim 1,
The base material for surface protection films which have at least 1 said acrylic resin chosen from the group which consists of a glutarimide unit, a lactone ring unit, a maleic anhydride unit, a maleimide unit, and a glutaric anhydride unit. The method of claim 1,
The base material for surface protection films whose said elastomer is at least 1 chosen from a rubbery polymer, a polyamide-type elastomer, a polyethylene-type elastomer, a styrene-type elastomer, and a butadiene-type elastomer. The method of claim 1,
The base material for surface protection films whose total light transmittance is 80% or more, and haze is 1.0% or less. As a manufacturing method of the base material for surface protection films of Claim 1,
A method for producing a substrate for a surface protection film, comprising molding a film-forming material containing an acrylic resin and an elastomer into a film, and successively biaxially stretching or simultaneously biaxially stretching the molded film. The method of claim 5, wherein
The manufacturing method of the base material for surface protection films whose extending | stretching temperature in the said sequential biaxial stretching or simultaneous biaxial stretching is Tg + 10 degreeC-Tg + 30 degreeC. The surface protection film containing the base material for surface protection films and an adhesive layer in any one of Claims 1-4. The optical film with a surface protection film containing an optical film and the surface protection film of Claim 7 bonded so that peeling was possible to the said optical film.