JP2012140609A - Protection film for optical member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protection film for an optical member, which includes a base material layer containing components having few foreign matters (fisheyes), being transparent and having a low birefringence (low retardation) with no need for orientation control of the molecular chain, and an adhesive layer having a proper peeling strength, and which is good in the thickness precision of the base material layer, and is good in hit-markability.SOLUTION: The protection film for an optical member includes the base material layer and the adhesive layer, wherein the base material layer contains mixed components (I) of specific block copolymers (α) and (β); the number of fisheyes of ≥0.1 mm and ≤0.5 mm in the mixed components (I) is ≤100 fisheyes/1.2-m; the retardation of the base material layer is 0.1 nm to 50 nm; the total light tranmittance of the base material layer is ≥90%; the internal haze of the base material layer is ≤3.0%; and the peeling strength of the adhesive layer is 0.03 to 0.5 N/25-mm.

Description

  The present invention relates to a protective film for an optical member used for protecting a polarizing plate or the like during processing and mounting.

  In processing and mounting of an optical member such as a general polarizing plate, a protective film is used to prevent scratches and contamination of the optical member.

  For the base material layer of such a protective film, for example, a film made of polyethylene, polypropylene, polyester, polyimide, or the like is used. Among them, biaxially stretched polyethylene terephthalate is used in consideration of transparency. .

  In Patent Document 1, electronic parts are prevented from being destroyed by static electricity as much as possible, and the transparency is not impaired. In addition, the transparency is maintained when the adhesive is made antistatic, and it is indispensable for the characteristics of the surface protective film. A surface protective film capable of visual inspection without impairing the transparency is disclosed.

  Patent Document 2 relates to a member having optical anisotropy such as a flat panel display (FPD) such as a liquid crystal display (LCD) or a plasma display (PDP), and a double-sided adhesive film having an adhesive layer on both sides of a base material. The manufacturing method is disclosed.

  Patent Document 3 discloses an optical molded body using a styrene-butadiene block copolymer having good transparency, hue and impact resistance and low birefringence.

  Patent Document 4 is composed of a styrenic composition containing a block copolymer composed of a specific vinyl aromatic hydrocarbon and a conjugated diene, which has a small birefringence after molding and is excellent in transparency and impact resistance. An optical molded product is disclosed.

JP 2004-287199 A JP 2007-119562 A JP 2007-224255 A JP 2008-121022 A

  However, the conventionally disclosed base material layer as described above has problems that it is necessary to adjust the orientation of the molecular chain and that sufficient transparency cannot be obtained. Therefore, the protective film for optical members having such a base material layer does not have sufficient characteristics, and there is still room for improvement.

  Therefore, the present invention comprises a low birefringence (low retardation) base material layer that contains a component with little foreign matter (fish eye) and is transparent and does not require molecular chain orientation adjustment, and an adhesive layer with an appropriate peel strength. It is an object of the present invention to provide a protective film for an optical member that has good thickness accuracy of a base material layer and good dentability.

  As a result of intensive studies in order to solve the problems of the prior art relating to the protective film for an optical member as described above, the present inventors have found that two types of block copolymers composed of a specific vinyl aromatic hydrocarbon and a conjugated diene. It has been found that a protective film for an optical member having sufficient characteristics can be obtained by applying a base material layer containing a mixed component of a polymer and having specific physical properties and an adhesive layer having specific peel strength. The present invention has been completed.

  That is, the present invention is as follows.

[1]
A protective film for an optical member including a base material layer and an adhesive layer,
The base material layer comprises a block copolymer (α) comprising 20% by mass to 75% by mass of vinyl aromatic hydrocarbon and 25% by mass to 80% by mass of conjugated diene, and 85% by mass of vinyl aromatic hydrocarbon. A mixed component (I) with a block copolymer (β) consisting of more than 95% by mass and less than 5% by mass and less than 15% by mass,
The number of fish eyes of 0.1 mm to 0.5 mm in the mixed component (I) is 100 / 1.2 m ² or less,
The retardation of the base material layer is 0.1 nm to 50 nm,
The total light transmittance of the base material layer is 90% or more,
The internal haze of the base material layer is 3.0% or less,
The protective film for optical members whose peel strength of the adhesive layer in the protective film (based on JIS Z-0237 (adhesive tape test method)) is 0.03 to 0.5 N / 25 mm.

[2]
The optical member according to [1], wherein a layer ratio of the base material layer to the adhesive layer (the thickness of the base material layer / the thickness of the adhesive layer) in the protective film for an optical member is 50/50 to 95/5. Protective film.

[3]
The protective film for an optical member according to [1] or [2], wherein the number of fish eyes of 0.1 mm to 0.5 mm in the mixed component (I) is 50 / 1.2 m ² or less.

[4]
The protective film for optical members according to any one of [1] to [3], wherein the base material layer further contains the following component (II);
(II): (i) a vinyl aromatic hydrocarbon polymer, (ii) a copolymer comprising a vinyl aromatic hydrocarbon and an aliphatic unsaturated carboxylic acid derivative, and (iii) a rubber-modified styrene polymer. At least one polymer selected from the group consisting of:

[5]
The mass ratio of the mixed component (I) and the component (II) (block copolymer (I) / component (II)) in the base material layer is 30/70 to 99.9 / 0.1. [4] The protective film for optical members according to [4].

[6]
The protective film for optical members according to any one of [1] to [5], wherein the adhesive layer contains an acrylic adhesive.

[7]
The protective film for optical members according to any one of [1] to [6], wherein the adhesive layer contains a conductivity-imparting agent.

[8]
The protective film for optical members according to any one of [1] to [7], wherein the base material layer is formed by an inflation method.

  According to the present invention, a low birefringence (low retardation) base material layer that contains a component with little foreign matter (fish eye) and is transparent and does not require molecular chain orientation adjustment; and an adhesive layer with a specific peel strength; In this way, a protective film for an optical member having good thickness accuracy of the base material layer and good dentability can be obtained. Moreover, the said protective film for optical members is suitable for the protective film in the mounting visual inspection of an optical member.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail.

  The present invention is not limited to the following embodiment, and can be implemented with various modifications within the scope of the gist.

The protective film for an optical member of the present embodiment is a protective film for an optical member including a base material layer and an adhesive layer, and the base material layer is conjugated with 20% by mass to 75% by mass of a vinyl aromatic hydrocarbon. A block copolymer (α) comprising 25% by weight to 80% by weight of a diene, and a block comprising 85% by weight to 95% by weight of a vinyl aromatic hydrocarbon and 5% by weight to less than 15% by weight of a conjugated diene. A mixture component (I) with a copolymer (β), wherein the number of fish eyes of 0.1 mm to 0.5 mm in the mixture component (I) is 100 / 1.2 m ² or less; The retardation of the layer is 0.1 nm to 50 nm, the total light transmittance of the base material layer is 90% or more, the internal haze of the base material layer is 3.0% or less, and the adhesive layer in the protective film Peel strength ( Conform to IS Z-0237 (adhesive tape test method)) is 0.03~0.5N / 25mm.

  The protective film for an optical member of the present embodiment has, for example, a release film attached to one side surface of the base material layer via an adhesive layer, and after mounting the release film is peeled off for mounting, a deflection plate, a display, etc. Adhere to and use. When the protective film affixed to the article such as the polarizing plate and the display ends the role of preventing scratches and dirt attached during the manufacturing process of the article such as the polarizing plate and the display, the polarizing plate and the display, etc. It peels from the surface (peeling surface).

[Base material layer]
<Mixed component (I)>
The base material layer used in this embodiment is composed of a block copolymer (α) composed of 20% by mass to 75% by mass of vinyl aromatic hydrocarbon and 25% by mass to 80% by mass of conjugated diene, and vinyl aromatic. It contains a mixed component (I) of a block copolymer (β) composed of more than 85% by mass of hydrocarbon and 95% by mass or less and conjugated diene of 5% by mass to less than 15% by mass. In the block copolymer (α), the content of the vinyl aromatic hydrocarbon is preferably 20% by mass or more and less than 70% by mass. In the block copolymer (β), the vinyl aromatic hydrocarbon content is more preferably more than 87 mass% and not more than 93 mass%. By including such a mixed component (I), it is possible to obtain a base layer having low birefringence (low retardation) that is transparent and does not require molecular chain orientation adjustment. In particular, the thickness accuracy of the base material layer is improved by using the mixed component (I) of two types of block copolymers (α) and (β) having different vinyl aromatic hydrocarbon contents.

  The vinyl aromatic hydrocarbon content and the conjugated diene content in the block copolymers (α) and (β) are measured using an ultraviolet spectrophotometer to measure the absorption light intensity with respect to light of a predetermined wavelength. Is obtained.

  The block copolymers (α) and (β) include at least a segment composed of “a vinyl aromatic hydrocarbon homopolymer” and / or “a copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene”. And at least one segment composed of “a conjugated diene homopolymer” and / or “a copolymer of a vinyl aromatic hydrocarbon and a conjugated diene”.

  The polymer structure of the block copolymers (α) and (β) is not particularly limited, and examples thereof include polymer structures such as linear block copolymers and radial block copolymers represented by the following general formula. A polymer structure obtained by arbitrarily mixing these polymer structures may be used.

  Further, in the radial block copolymer represented by the following general formula, at least one A and / or B may be bonded to X.

(AB) _n , A- (BA) _n , B- (AB) _{n + 1}
[(A−B) k] _{m + 1} −X, [(A−B) k−A] _{m + 1} −X
[(B−A) k] _{m + 1} −X, [(B−A) k−B] _{m + 1} −X
In each of the above general formulas, the segment A is composed of “vinyl aromatic hydrocarbon homopolymer” and / or “copolymer composed of vinyl aromatic hydrocarbon and conjugated diene”, and segment B is composed of “conjugated diene homopolymer”. The polymer "and / or" the copolymer comprising a vinyl aromatic hydrocarbon and a conjugated diene ".

  The preferred vinyl aromatic hydrocarbon content in segment A is 50% by mass or more, and the preferred vinyl aromatic hydrocarbon content in segment B is less than 50% by mass.

  In the above general formula, X is a residue of a coupling agent such as silicon tetrachloride, tin tetrachloride, 1,3 bis (N, N-glycidylaminomethyl) cyclohexane, epoxidized soybean oil, or polyfunctional organolithium Indicates the residue of an initiator such as a compound.

  n, k and m are each independently an integer of 1 or more, generally an integer of 1 to 5.

  Moreover, the structure of the polymer chain bonded to X may be the same or different.

  Even if the vinyl aromatic hydrocarbons in the copolymer of vinyl aromatic hydrocarbon and conjugated diene in the segments A and B constituting the block copolymers (α) and (β) are uniformly distributed, they are tapered. It may be distributed in the form of (gradual decrease).

  Further, in the block copolymers (α) and (β), a plurality of portions where vinyl aromatic hydrocarbons are uniformly distributed and / or a portion where they are distributed in a tapered shape coexist in the segment. May be.

  Vinyl aromatic hydrocarbon content in segment A ({vinyl aromatic hydrocarbon in segment A / (vinyl aromatic hydrocarbon in segment A + conjugated diene)} × 100) and vinyl aromatic in segment B The relationship between the hydrocarbon content ({vinyl aromatic hydrocarbon in segment B / (vinyl aromatic hydrocarbon in segment B + conjugated diene)} × 100) Is greater than the vinyl aromatic hydrocarbon content in segment B.

  The difference in vinyl aromatic hydrocarbon content between segment A and segment B is preferably 5% by mass or more.

  The mass ratio ((α) / (β)) of the block copolymers (α) and (β) in the mixed component (I) is preferably 90/10 to 10/90, and 80/20 to 20 / 80 is more preferable, and 70/30 to 30/70 is even more preferable.

  The block copolymers (α) and (β) can be obtained by polymerizing a vinyl aromatic hydrocarbon and a conjugated diene in a hydrocarbon solvent in the presence of a polymerization initiator.

  Examples of the vinyl aromatic hydrocarbon include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, 1,1. -Diphenylethylene, N, N-dimethyl-p-aminoethylstyrene, N, N-diethyl-p-aminoethylstyrene and the like can be mentioned, and styrene is particularly common. These may be used alone or in combination of two or more.

  The conjugated diene is a diolefin having a pair of conjugated double bonds. For example, 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3- Butadiene, 1,3-pentadiene, 1,3-hexadiene and the like can be mentioned, and particularly common ones include 1,3-butadiene, isoprene and the like. These may be used alone or in combination of two or more.

  Examples of the hydrocarbon solvent include aliphatic hydrocarbons such as n-butane, isobutane, n-pentane, n-hexane, n-heptane, and n-octane; cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, cyclohexane Alicyclic hydrocarbons such as heptane and methylcycloheptane; and aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene can be used. These may be used alone or in combination of two or more.

  As a polymerization initiator for the polymerization of the block copolymers (α) and (β), it is generally known that the conjugated diene and the vinyl aromatic compound have anionic polymerization activity. An aromatic hydrocarbon alkali metal compound, an aromatic hydrocarbon alkali metal compound, an organic aminoalkali metal compound, or the like can be used.

  Examples of the alkali metal constituting these include lithium, sodium, potassium, and the like, and preferable organic alkali metal compounds are aliphatic and aromatic hydrocarbon lithium compounds having 1 to 20 carbon atoms, in one molecule. Examples thereof include a compound containing one lithium, a dilithium compound containing a plurality of lithium in one molecule, a trilithium compound, and a tetralithium compound.

  Specifically, n-propyl lithium, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, hexamethylene dilithium, butadienyl dilithium, isoprenyl dilithium, diisopropenylbenzene and sec-butyl lithium In addition, a reaction product of divinylbenzene, sec-butyllithium and a small amount of 1,3-butadiene can be used.

  Furthermore, organic alkali metal compounds disclosed in US Pat. No. 5,708,092, British Patent 2,241,239, US Pat. No. 5,527,753, etc. are also used. can do.

  These polymerization initiators may be used alone or in combination of two or more.

  The polymerization temperature for producing the block copolymers (α) and (β) is generally −10 ° C. to 150 ° C., preferably 40 ° C. to 120 ° C.

  The time required for the polymerization varies depending on conditions, but is usually within 10 hours, particularly preferably 0.5 to 5 hours.

  The polymerization atmosphere is preferably replaced with an inert gas such as nitrogen gas.

  The polymerization pressure is not particularly limited as long as it is in a range sufficient to maintain the monomer and solvent in the liquid layer within the above polymerization temperature range.

  Furthermore, it is preferable to take care not to mix impurities, such as water, oxygen, carbon dioxide gas, etc., which inactivate the catalyst and living polymer into the polymerization system.

The number of fish eyes of 0.1 mm to 0.5 mm in the mixed component (I) is 100 / 1.2 m ² or less, preferably 50 / 1.2 m ² or less, more preferably 30 / 1.2 m ² or less. When the number of fish eyes of 0.1 mm or more and 0.5 mm or less is within the above range, when the protective film is attached to an optical sheet such as a polarizing plate, unevenness of the surface of the optical sheet due to the fish eye is prevented. it can. And the fish eye which causes the malfunction of an optical test | inspection reduces, It contributes to the precision improvement of an optical test | inspection. In order to make the number of fish eyes of 0.1 mm or more and 0.5 mm or less within the above range, a conventionally known method may be used, for example, as described in JP-A Nos. 2000-351808 and 2009-126945. The manufacturing method of the made block copolymer is mentioned. In these manufacturing methods, the aperture size of the filter used is preferably 40 μm or less.

  In addition, the number of fish eyes of 0.1 mm or more and 0.5 mm or less in the mixed component (I) can be measured by the method described in Examples described later.

  The above-mentioned mixed component (I) may be used alone or in combination of two or more.

<Ingredient (II)>
The base material layer used in the present embodiment may further contain the following component (II).
(II): (i) a vinyl aromatic hydrocarbon polymer, (ii) a copolymer comprising a vinyl aromatic hydrocarbon and an aliphatic unsaturated carboxylic acid derivative, and (iii) a rubber-modified styrene polymer. At least one polymer selected from the group consisting of:

[Component (i)]
Of the component (II) used in the present embodiment, (i) vinyl aromatic hydrocarbon polymer (hereinafter sometimes referred to as component (i)) is a vinyl aromatic hydrocarbon homopolymer, or A copolymer of a vinyl aromatic hydrocarbon and a monomer copolymerizable with the vinyl aromatic hydrocarbon (excluding the component (ii) described later). Vinyl aromatic hydrocarbons mainly refer to styrene monomers, specifically styrene, α-alkyl-substituted styrenes such as α-methylstyrenes, alkyl-substituted styrenes, halogen-substituted styrenes. What is necessary is just to select at least 1 type suitable for the purpose. Examples of the monomer copolymerizable with the vinyl aromatic hydrocarbon include acrylonitrile and maleic anhydride.

  Examples of the component (i) include polystyrene, styrene-α-methylstyrene copolymer, acrylonitrile-styrene copolymer, and styrene-maleic anhydride copolymer. Particularly preferable component (i) is polystyrene. Can be mentioned.

  The weight average molecular weight of component (i) is preferably 50,000 to 500,000. In the present embodiment, the weight average molecular weight is a weight average molecular weight (polystyrene equivalent molecular weight) measured by gel permeation chromatography (GPC).

  As the component (i) described above, one type may be used alone, or two or more types may be used in combination.

[Component (ii)]
Of the component (II) used in the present embodiment, (ii) a copolymer comprising a vinyl aromatic hydrocarbon and an aliphatic unsaturated carboxylic acid derivative (hereinafter sometimes referred to as component (ii)). ), The vinyl aromatic hydrocarbon means the styrene monomer described in the section of component (i).

In addition, in the component (ii), examples of the aliphatic unsaturated carboxylic acid derivatives include ester derivatives (methyl acrylate, ethyl acrylate, acrylic) of an alcohol and acrylic acid having C1 to C12, preferably C2 to C12, for example. Propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, etc.); or ester derivatives of C1-C12, preferably C2-C12, more preferably C3-C12 alcohols and methacrylic acid; Saturated dicarboxylic acids such as fumaric acid, itaconic acid, maleic acid and the like, or mono- or diester derivatives of these dicarboxylic acids with C2 to C12 alcohols, and the like can be mentioned. These may be used alone or in combination of two or more.

  In general, these are mainly composed of the above ester derivatives, and the amount of the ester derivatives is preferably 50 mol% or more, more preferably 70 mol% or more.

  In addition, the type of the ester derivative is preferably ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, or the like.

  As a method for producing component (ii), a known method for producing a styrene resin, for example, a bulk polymerization method, a solution polymerization method, a suspension polymerization method, an emulsion polymerization method or the like can be used. The weight average molecular weight of component (ii) is preferably 50,000 to 500,000.

  Particularly preferred component (ii) is a copolymer mainly composed of styrene and n-butyl acrylate, and the total amount of n-butyl acrylate and styrene is 50% by mass or more, more preferably n-acrylate. It is an aliphatic unsaturated carboxylic acid ester-styrene copolymer in which the total amount of butyl and styrene is 60% by mass or more. That is, it is an aliphatic unsaturated carboxylic acid ester-styrene copolymer mainly composed of n-butyl acrylate and styrene.

  Component (ii) described above may be used alone or in combination of two or more.

[Component (iii)]
Of the component (II) used in the present embodiment, (iii) rubber-modified styrenic polymer (hereinafter sometimes referred to as component (iii)) includes, for example, vinyl aromatic hydrocarbons and vinyl Examples thereof include those obtained by polymerizing a mixture of a monomer copolymerizable with an aromatic hydrocarbon and an elastomer. Examples of the polymerization method include suspension polymerization, emulsion polymerization, bulk polymerization, and bulk-suspension polymerization. The vinyl aromatic hydrocarbon refers to the styrene monomer described in the section of component (i). Examples of the monomer copolymerizable with the vinyl aromatic hydrocarbon include α-methylstyrene, acrylonitrile, acrylic ester, methacrylic ester, maleic anhydride and the like. As the copolymerizable elastomer, natural rubber, synthetic isoprene rubber, butadiene rubber, styrene-butadiene rubber, high styrene rubber or the like is used.

  The blending ratio of these elastomers is “100 parts by mass of vinyl aromatic hydrocarbon” or “total 100 parts by mass of vinyl aromatic hydrocarbon and monomers copolymerizable with vinyl aromatic hydrocarbon”. On the other hand, it is preferable that it is 3-50 mass parts.

  The above-mentioned elastomer is dissolved in the above-mentioned monomer or in a latex form, and is used for emulsion polymerization, bulk polymerization, bulk-suspension polymerization, and the like.

  Particularly preferred component (iii) includes impact-resistant rubber-modified styrene polymer (HIPS). Component (iii) can be used as an agent for improving rigidity, impact resistance and slipperiness. The weight average molecular weight of component (iii) is preferably 50,000 to 500,000. The content of component (iii) is preferably 20 parts by mass or less with respect to a total of 100 parts by mass of the mixed component (I) and component (II) in consideration of maintaining transparency. It is particularly preferably 10 to 10 parts by mass.

  As the component (iii) described above, one type may be used alone, or two or more types may be used in combination.

  The MFR (temperature 200 ° C., load 5 kg under G condition) of the components (i) to (iii) in the component (II) used in the present embodiment is 0.1 to 100 g / 10 min from the point of molding. Is preferably 0.5 to 50 g / 10 min, and more preferably 1 to 30 g / 10 min.

  In the block copolymer composition of the base material layer used in the present embodiment, the mass ratio of the mixed component (I) and the component (II) (mixed component (I) / component (II)) is: The ratio is preferably 30/70 to 99.9 / 0.1, more preferably 35/65 to 99.5 / 0.5, and still more preferably 40/60 to 99/1. By combining the mixed component (I) and the component (II) at such a mass ratio, a protective film for an optical member having improved rigidity can be obtained.

<Characteristics of base material layer>
The retardation of the base material layer used in the present embodiment is 0.1 nm to 50 nm, preferably 0.1 nm to 40 nm, and more preferably 0.1 nm to 30 nm.

  When the base material layer contains the mixed component (I) and the retardation is within the above range, the optical anisotropy becomes small. Therefore, the protective film having the base material layer is attached to an article such as a polarizing plate and a display. Appearance inspection in the attached state becomes possible.

  The retardation of the base material layer can be measured by, for example, a parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments. In detail, it can measure by the method as described in the below-mentioned Example.

  The absolute value (| Δn |) of birefringence and retardation (Re) have the following relationship.

Re = | Δn | × d
(| Δn |: absolute value of birefringence, Re: retardation, d: thickness of sample (nm))
The absolute value (| Δn |) of birefringence is a value shown below.

| Δn | = | nx−ny |
(Nx: refractive index in the stretching direction, ny: refractive index perpendicular to the stretching direction in the plane)
In the retardation, the vinyl aromatic hydrocarbon content of the block copolymers (α) and (β) constituting the base layer is adjusted within the range specified in the present embodiment, or the stretch ratio of the base layer It is possible to measure and adjust the relationship between retardation and retardation. About the relationship between a draw ratio and retardation, a retardation can be made small by making a draw ratio small.

  The total light transmittance of the base material layer used in the present embodiment is 90% or more, and preferably 92% or more. Although the upper limit of the total light transmittance of a base material layer is not specifically limited, For example, it is 100%. The internal haze (hereinafter also simply referred to as “haze”) of the base material layer used in the present embodiment is 3.0% or less, preferably 2.0% or less. Although the minimum of the internal haze of a base material layer is not specifically limited, For example, it is 0%. When the total light transmittance and internal haze are within the above ranges, appearance inspection is possible without impairing transparency in a state where the protective film having the base material layer is attached to an article such as a polarizing plate and a display. Become. In the present embodiment, the total light transmittance and the internal haze can be measured in accordance with ASTM D1003 (liquid paraffin is applied to a film having a test piece thickness of 100 μm).

<Method for forming base material layer>
Examples of the method for forming the base material layer used in this embodiment include an extrusion method, an inflation method, and a solution casting method. In order to prevent optical anisotropy, a solution casting method is generally used, but the base material layer used in the present embodiment includes the above-mentioned mixed component (I) and does not require alignment adjustment of molecular chains. Since it has a characteristic of low birefringence (low retardation), it is preferably formed by an inexpensive inflation method.

[Adhesive layer]
The protective film for optical members according to the present embodiment includes an adhesive layer. In the protective film for an optical member according to the present embodiment, the pressure-sensitive adhesive layer is laminated on the base material layer described above, but another layer may be included between the pressure-sensitive adhesive layer and the base material layer. Examples of such other layers include a layer containing an antistatic agent.

  As the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer used in the present embodiment, for example, an acrylic-based, urethane-based, rubber-based, or silicone-based pressure-sensitive adhesive can be used. The pressure-sensitive adhesive is preferably highly transparent, and an acrylic pressure-sensitive adhesive is preferable because of easy adjustment of the adhesive properties. The pressure-sensitive adhesive may contain a tackifier or the like in order to impart moderate tackiness. Examples of the tackifier include rosin, terpene, coumarone, phenol, styrene, and petroleum resins.

Examples of the acrylic pressure-sensitive adhesive include an acrylic pressure-sensitive adhesive composed of an acrylic polymer obtained by copolymerizing an alkyl acrylate ester as a main component and a polar monomer component thereto.
The acrylic acid alkyl ester is an alkyl ester of acrylic acid or methacrylic acid, and is not particularly limited. For example, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, ( Examples thereof include pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, and lauryl (meth) acrylate.

  Examples of the polar monomer component include monomers having a carboxyl group or a hydroxyl group, such as acrylic acid, maleic anhydride, and 2-hydroxyethyl (meth) acrylate. These polar monomers become functional groups in the acrylic polymer.

  The acrylic pressure-sensitive adhesive may be an acrylic pressure-sensitive adhesive composition by blending a crosslinking agent capable of crosslinking the acrylic polymer. As the crosslinking agent, for example, a polyisocyanate compound such as aliphatic diisocyanate, aromatic diisocyanate, or aromatic triisocyanate is used. Furthermore, a crosslinking accelerator composed of an organometallic compound or the like can be added to those having a slow crosslinking reaction.

  A plasticizer can be added to the pressure-sensitive adhesive used in this embodiment. Examples of the plasticizer include adipic acid ester type, glycol ester type, sebacic acid ester type, trimellitic acid ester type, pyromellitic acid ester type, phthalic acid ester type and phosphoric acid ester type plasticizer. When used for the acrylic pressure-sensitive adhesive, a phthalate ester plasticizer is preferred, but it is not limited thereto.

  Moreover, the adhesion layer used for this Embodiment may contain an electroconductivity imparting agent. The content of the conductivity imparting agent in the adhesive layer is preferably a mixing ratio of 2% by mass to 30% by mass with respect to the adhesive.

  A preferable conductivity imparting agent to be included in the adhesive layer is a conductivity imparting agent that dissolves in an organic solvent such as an aromatic hydrocarbon, ester, or ketone, and has an ion conductivity having a hydroxyl group (—OH) as a functional group. Polymers.

  By containing a conductivity-imparting agent in the adhesive layer, static electricity on the surface of the optical member generated at the time of peeling can be reduced.

  The peel strength (adhesive strength) of the adhesive layer in the protective film for optical members according to the present embodiment is 0.03 to 0.5 N / 25 mm, and preferably 0.05 to 0.45 N / 25 mm. When the peel strength is within the above range, the pressure-sensitive adhesive layer in the protective film can be sufficiently adhered to the surface of the adherend, and the protective film can be easily removed after the protection function is completed. The peel strength can be adjusted by the type of adhesive and the coating amount of the adhesive. In the present embodiment, the peel strength is defined as a peel resistance value with respect to the stainless steel adherend obtained by a measurement method defined in JIS Z-0237 (adhesive tape test method).

[Peeling film]
The protective film for optical members according to the present embodiment may include a release film. In the protective film for an optical member according to the present embodiment, the release film is preferably laminated on the above-described adhesive layer. Another layer may be included between the adhesive layer and the release film. Examples of such other layers include a release layer typified by silicone.

  As a base film which comprises the peeling film used for this Embodiment, the film which consists of thermoplastic resins, such as a polyester film, an ethylene vinyl acetate copolymer film, a polyethylene film, can be mentioned. Among them, a polyethylene terephthalate film is preferable.

  Although there is no restriction | limiting in particular in the thickness of a peeling film, Preferably it is 100 micrometers or less, More preferably, it is 50 micrometers or less.

[Production method and characteristics of protective film for optical member]
The protective film for optical members of this Embodiment can be manufactured using the manufacturing method of the film with an adhesive normally used. For example, a pressure-sensitive adhesive diluted with a solvent is applied onto the base material layer or the release film, dried to remove the solvent, and then the pressure-sensitive adhesive layer is formed on the pressure-sensitive adhesive layer. -The method of laminating | stacking a peeling film or a base material layer using a glue bonding apparatus is mentioned. Here, examples of the solvent include a mixed solvent of toluene and methyl ethyl ketone.

  The thickness of the protective film for an optical member of the present embodiment is preferably 200 μm or less, more preferably 150 μm or less when including the base material layer, the adhesive layer, and the release film.

  In the protective film for an optical member, the preferable thickness of the base material layer is 5 to 100 μm, and the preferable thickness of the adhesive layer is 5 to 50 μm. In the protective film for an optical member, the layer ratio of the base material layer to the adhesive layer (the thickness of the base material layer / the thickness of the adhesive layer) is preferably 50/50 to 95/5. It is preferable for maintaining the transparency of the protective film for an optical member that the layer ratio between the base material layer and the adhesive layer is within the above range.

  In the protective film for optical members according to the present embodiment, when a release film is included, a preferable thickness of the base film used for the release film is 5 to 50 μm.

  When the protective film for an optical member according to the present embodiment includes another layer between the base material layer and the adhesive layer or between the adhesive layer and the release film, the thickness of the other layer is 0.1. It is preferably ˜20 μm, more preferably 0.1 to 15 μm, and further preferably 0.1 to 10 μm.

  The protective film for an optical member according to the present embodiment has excellent dent characteristics on the surface of an object to be pasted after being pasted, and is optical such as a flat panel display (FPD) such as a liquid crystal display (LCD) or a plasma display (PDP). It can be suitably used as a protective film for members. In addition, the protective film for optical members according to the present embodiment has a base layer having small retardation, excellent transparency, and good thickness accuracy, and thus is suitably used as a surface protective film particularly in optical member visual inspection. it can.

  Hereinafter, the present invention will be specifically described by way of examples. This invention is not restrict | limited by the Example mentioned later.

<Example of production of block copolymer (hereinafter also referred to as “component (a)”)>
(Block copolymer A-1)
Using an autoclave equipped with a stirrer, in a nitrogen gas atmosphere, in a cyclohexane solution containing 15 parts by mass of styrene, 0.105 parts by mass of n-butyllithium and 0.1 times that of tetramethylethylenediamine with respect to n-butyllithium Mole was added and polymerization was carried out by continuously feeding at 70 ° C. for 20 minutes.

  Next, polymerization was performed by continuously supplying a cyclohexane solution containing 2 parts by mass of styrene and 70 parts by mass of 1,3-butadiene at 70 ° C. for 80 minutes.

  Next, a cyclohexane solution containing 13 parts by mass of styrene was continuously supplied at 70 ° C. for 20 minutes for polymerization.

  Thereafter, methanol is added in an equimolar amount to n-butyllithium, and 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6- 0.4 parts by mass of di-t-pentylphenyl acrylate was added to 100 parts by mass of the block copolymer. Thereafter, the solvent was removed to obtain a block copolymer A-1.

(Block copolymer A-2)
Using an autoclave equipped with a stirrer, in a nitrogen gas atmosphere, in a cyclohexane solution containing 20 parts by mass of styrene, 0.100 parts by mass of n-butyllithium and 0.1 times that of tetramethylethylenediamine with respect to n-butyllithium Mole was added and polymerization was carried out by continuously feeding at 70 ° C. for 25 minutes.

  Next, polymerization was carried out by continuously supplying a cyclohexane solution containing 4 parts by mass of styrene and 58 parts by mass of 1,3-butadiene at 70 ° C. for 65 minutes.

  Next, polymerization was carried out by continuously supplying a cyclohexane solution containing 18 parts by mass of styrene at 70 ° C. for 25 minutes.

  Thereafter, methanol is added in an equimolar amount to n-butyllithium, and 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6- is used as a stabilizer. 0.3 parts by mass of di-t-pentylphenyl acrylate was added to 100 parts by mass of the block copolymer. Thereafter, the solvent was removed to obtain a block copolymer A-2.

(Block copolymer A-3)
Using an autoclave equipped with a stirrer, in a nitrogen gas atmosphere, in a cyclohexane solution containing 25 parts by mass of styrene, 0.092 parts by mass of n-butyllithium and 0.1 times that of tetramethylethylenediamine with respect to n-butyllithium Mole was added and polymerization was carried out by continuously feeding at 70 ° C. for 30 minutes.

  Next, polymerization was performed by continuously supplying a cyclohexane solution containing 2 parts by mass of styrene and 20 parts by mass of 1,3-butadiene at 70 ° C. for 25 minutes.

  Next, polymerization was performed by continuously supplying a cyclohexane solution containing 4 parts by mass of styrene and 24 parts by mass of 1,3-butadiene at 70 ° C. for 35 minutes.

  Next, polymerization was carried out by continuously supplying a cyclohexane solution containing 25 parts by mass of styrene at 70 ° C. for 30 minutes.

  Thereafter, methanol is added in an equimolar amount to n-butyllithium, and 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6- is used as a stabilizer. 0.3 parts by mass of di-t-pentylphenyl acrylate was added to 100 parts by mass of the block copolymer. Thereafter, the solvent was removed to obtain a block copolymer A-3.

(Block copolymer A-4)
Using an autoclave equipped with a stirrer, in a nitrogen gas atmosphere, in a cyclohexane solution containing 30 parts by mass of styrene, 0.088 parts by mass of n-butyllithium and 0.1 times that of tetramethylethylenediamine with respect to n-butyllithium Mole was added and polymerization was carried out by continuously feeding at 70 ° C. for 35 minutes.

  Next, polymerization was carried out by continuously supplying a cyclohexane solution containing 3 parts by mass of styrene and 15 parts by mass of 1,3-butadiene at 70 ° C. for 25 minutes.

  Next, polymerization was performed by continuously supplying a cyclohexane solution containing 4 parts by mass of styrene and 19 parts by mass of 1,3-butadiene at 70 ° C. for 30 minutes.

  Next, a cyclohexane solution containing 29 parts by mass of styrene was continuously supplied at 70 ° C. for 35 minutes for polymerization.

  Thereafter, methanol is added in an equimolar amount to n-butyllithium, and 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6- is used as a stabilizer. 0.3 parts by mass of di-t-pentylphenyl acrylate was added to 100 parts by mass of the block copolymer. Thereafter, the solvent was removed to obtain a block copolymer A-4.

(Block copolymer A-5)
Using an autoclave equipped with a stirrer, in a nitrogen gas atmosphere, in a cyclohexane solution containing 26 parts by mass of styrene, 0.052 parts by mass of n-butyllithium and tetramethylethylenediamine 0.3 times that of n-butyllithium Mole was added and polymerization was carried out by continuously feeding at 70 ° C. for 35 minutes.

  Next, polymerization was carried out by continuously supplying a cyclohexane solution containing 30 parts by mass of styrene and 6.5 parts by mass of 1,3-butadiene at 70 ° C. for 45 minutes.

  Next, polymerization was performed by continuously supplying a cyclohexane solution containing 10 parts by mass of styrene and 1.5 parts by mass of 1,3-butadiene at 70 ° C. for 15 minutes.

  Next, a cyclohexane solution containing 26 parts by mass of styrene was continuously supplied at 70 ° C. for 30 minutes for polymerization.

  Thereafter, methanol is added in an equimolar amount to n-butyllithium, and 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6- is used as a stabilizer. 0.3 parts by mass of di-t-pentylphenyl acrylate was added to 100 parts by mass of the block copolymer. Thereafter, the solvent was removed to obtain a block copolymer A-5.

(Block copolymer A-6)
Using an autoclave equipped with a stirrer, in a nitrogen gas atmosphere, in a cyclohexane solution containing 36 parts by mass of styrene, 0.054 parts by mass of n-butyllithium and tetramethylethylenediamine 0.3 times that of n-butyllithium Mole was added and polymerization was carried out by continuously feeding at 70 ° C. for 45 minutes.

  Next, polymerization was performed by continuously supplying a cyclohexane solution containing 15 parts by mass of styrene and 12 parts by mass of 1,3-butadiene at 70 ° C. for 35 minutes.

  Next, polymerization was carried out by continuously supplying a cyclohexane solution containing 37 parts by mass of styrene at 70 ° C. for 45 minutes.

  Thereafter, methanol is added in an equimolar amount to n-butyllithium, and 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6- is used as a stabilizer. 0.3 parts by mass of di-t-pentylphenyl acrylate was added to 100 parts by mass of the block copolymer. Thereafter, the solvent was removed to obtain a block copolymer A-6.

(Block copolymer A-7)
Using an autoclave equipped with a stirrer, in a nitrogen gas atmosphere, in a cyclohexane solution containing 37 parts by mass of styrene, 0.061 parts by mass of n-butyllithium and 0.3 times that of tetramethylethylenediamine with respect to n-butyllithium Mole was added and polymerization was carried out by continuously feeding at 70 ° C. for 45 minutes.

  Next, polymerization was performed by continuously supplying a cyclohexane solution containing 7 parts by mass of styrene and 19 parts by mass of 1,3-butadiene at 70 ° C. for 30 minutes.

  Next, polymerization was carried out by continuously supplying a cyclohexane solution containing 37 parts by mass of styrene at 70 ° C. for 45 minutes.

  Thereafter, methanol is added in an equimolar amount to n-butyllithium, and 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6- is used as a stabilizer. 0.3 parts by mass of di-t-pentylphenyl acrylate was added to 100 parts by mass of the block copolymer. Thereafter, the solvent was removed to obtain a block copolymer A-7.

(Block copolymer A-8)
Using an autoclave equipped with a stirrer, in a nitrogen gas atmosphere, in a cyclohexane solution containing 25 parts by mass of styrene, 0.087 parts by mass of n-butyllithium and 0.1 times that of tetramethylethylenediamine with respect to n-butyllithium Mole was added and polymerization was carried out by continuously feeding at 70 ° C. for 30 minutes.

  Next, polymerization was performed by continuously supplying a cyclohexane solution containing 22 parts by mass of styrene and 24 parts by mass of 1,3-butadiene at 70 ° C. for 60 minutes.

  Next, a cyclohexane solution containing 29 parts by mass of styrene was continuously supplied at 70 ° C. for 35 minutes for polymerization.

  Thereafter, methanol is added in an equimolar amount to n-butyllithium, and 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6- is used as a stabilizer. 0.3 parts by mass of di-t-pentylphenyl acrylate was added to 100 parts by mass of the block copolymer. Thereafter, the solvent was removed to obtain a block copolymer A-8.

(Block copolymer A-9)
Using an autoclave equipped with a stirrer, in a nitrogen gas atmosphere, in a cyclohexane solution containing 32 parts by mass of styrene, 0.086 parts by mass of n-butyllithium and 0.1 times that of tetramethylethylenediamine with respect to n-butyllithium Mole was added and polymerization was carried out by continuously feeding at 70 ° C. for 35 minutes.

  Next, polymerization was performed by continuously supplying a cyclohexane solution containing 5 parts by mass of styrene and 13 parts by mass of 1,3-butadiene at 70 ° C. for 25 minutes.

  Next, polymerization was performed by continuously supplying a cyclohexane solution containing 6 parts by mass of styrene and 15 parts by mass of 1,3-butadiene at 70 ° C. for 30 minutes.

  Next, a cyclohexane solution containing 29 parts by mass of styrene was continuously supplied at 70 ° C. for 35 minutes for polymerization.

  Thereafter, methanol is added in an equimolar amount to n-butyllithium, and 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6- is used as a stabilizer. 0.3 parts by mass of di-t-pentylphenyl acrylate was added to 100 parts by mass of the block copolymer. Thereafter, the solvent was removed to obtain a block copolymer A-4.

  Table 1 shows the structures and styrene contents (% by mass) of the block copolymers A-1 to A-9.

<Ingredient (II)>
(Polymer B-1)
A styrene-n-butyl acrylate copolymer was used as component (ii) in component (II).

(Polymer B-2)
A styrene-n-butyl acrylate copolymer was used as component (ii) in component (II).

(Polymer B-3)
As component (i) in component (II), general purpose polystyrene (GPPS) (manufactured by PS Japan Co., Ltd., PSJ polystyrene 685) was used.

(Polymer B-4)
As the component (iii) in the component (II), an impact-resistant rubber-modified styrene polymer (HIPS) (manufactured by PS Japan Co., Ltd., PSJ polystyrene 475D) was used.

  The polymers B-1 to B-4 are shown in Table 2.

Next, the method for measuring and evaluating the properties applied in the block copolymer and the examples and comparative examples will be described.

(1) Styrene content It calculated from the absorption intensity of 262 nm using the ultraviolet spectrophotometer (Hitachi UV200).

(2) Number of fish eyes A block copolymer or a mixed component of the block copolymer is formed into a sheet having a thickness of 100 μm using a 20 mm sheet extruder, and 0.1 mm or more in a sheet area of 1.2 m ^2. The number of fish eyes of 0.5 mm or less was measured with a CCD camera.

(3) Retardation Each component was blended as shown in Table 3, and the film of the substrate layer having a thickness of 100 μm formed by the inflation method was rotated in parallel Nicols using KOBRA-WR manufactured by Oji Scientific Instruments Co., Ltd. The retardation value was measured by the method at an incident angle of 0 degree and a wavelength of 587 nm.

(4) Total light transmittance and haze Each component was blended as shown in Table 3, and a test piece was prepared by applying liquid paraffin to a film of a substrate layer having a thickness of 100 μm formed by an inflation method. The total light transmittance and haze of the test piece were measured according to ASTM D1003.

(5) Peel strength The peel strength of the adhesive layer in the protective film for optical members obtained in Examples and Comparative Examples was obtained by the measurement method defined in JIS Z-0237 (adhesive tape test method). It was set as the peeling resistance value with respect to the stainless steel adherend plate.

(6) Thickness accuracy As shown in Table 3, for the film of the base layer having a thickness of 100 μm blended with the respective components and formed by the inflation method, the minimum at equal intervals in the full width (horizontal) direction of the film using a dial gauge A total of 30 or more thicknesses of 15 points and a minimum of 15 points in the machine (vertical) direction were measured, and the average value was calculated. Next, the value of ½ of the difference between the maximum value and the minimum value in the measured thickness value is expressed as a percentage of the previously calculated average value, and a sign of ± is added to the thickness of the base material layer. Displayed as accuracy. The evaluation criteria for the thickness accuracy were as follows.

(Evaluation criteria)
○: The thickness accuracy of the base material layer was within ± 10%.
X: The thickness accuracy of the base material layer exceeded ± 10%.

(7) Scratch property The release film is peeled off from the protective film for optical members obtained in Examples and Comparative Examples, and the protective film (adhesive layer side) is biaxially stretched polyethylene terephthalate film (area is 0.1 m ² ). The surface state of the biaxially stretched polyethylene terephthalate film when the protective film was peeled off after 1 week was visually observed. The dentability was evaluated according to the following criteria.

(Standard)
○: The number of dents was 2 or less.
X: The number of dents exceeded two.

[Examples 1-7 and Comparative Examples 1-6]
<Base material layer>
Each component was blended as shown in Table 3, and melt kneaded and pelletized with a 40 mm twin screw extruder equipped with a 10 μm size (opening size) sintered filter. Then, the obtained pellet was used for inflation film formation (40 mm extruder, die diameter 200 mm, die temperature 200 ° C., blow ratio 1.5) to prepare a film of a substrate layer having a thickness of 30 μm.

<Release film>
As the release film, a biaxially stretched polyethylene terephthalate film having a thickness of 20 μm and treated with silicone on one side was used.

<Adhesive layer>
The adhesive layer was formed as follows. A pressure-sensitive adhesive solution obtained by diluting an acrylic pressure-sensitive adhesive (Byron 200 manufactured by Soken Chemical Co., Ltd.) with a solution of toluene / methyl ethyl ketone = 1/1 until the solid content becomes 25% is solidified on the release film on the silicone-treated surface. A uniform concentration was applied in an amount of 10 g / m ² and dried at 100 ° C. for 2 minutes to form an adhesive layer.

  The adhesive layer side of the release film on which the adhesive layer was formed was adhered to the base material layer to obtain a protective film for an optical member. The layer ratio of the base material layer to the adhesive layer (the thickness of the base material layer / the thickness of the adhesive layer) was 70/30. Moreover, the total thickness of the base material layer and the adhesive layer in the protective film for an optical member was 43 μm.

  Number of fish eyes of component (I), retardation of substrate layer, total light transmittance of substrate layer, haze of substrate layer, thickness accuracy of substrate layer, peel strength of adhesive layer, and protective film for optical member Scratchability was measured as described above. Table 3 shows the measurement results.

[Comparative Example 7]
A protective film for an optical member was obtained in the same manner as in Example 1, except that the pressure-sensitive adhesive solution was applied to the release film on the silicone-treated surface in a solid content concentration of 1 g / m ² . The layer ratio of the base material layer to the adhesive layer (the thickness of the base material layer / the thickness of the adhesive layer) of the protective film for optical members was 97/3. Moreover, the total thickness of the base material layer and the adhesive layer in the protective film for optical members was 31 μm.

  Number of fish eyes of component (I), retardation of substrate layer, total light transmittance of substrate layer, haze of substrate layer, thickness accuracy of substrate layer, peel strength of adhesive layer, and protective film for optical member Scratchability was measured as described above. Table 3 shows the measurement results.

[Comparative Example 8]
When each component was blended and pelletized as shown in Table 3, a protective film for an optical member was obtained in the same manner as in Example 1 except that a 100 mesh size (aperture size: 149 μm) filter was used. . The layer ratio of the base material layer to the adhesive layer (the thickness of the base material layer / the thickness of the adhesive layer) was 70/30. Moreover, the total thickness of the base material layer and the adhesive layer in the protective film for an optical member was 43 μm.

  Number of fish eyes of component (I), retardation of substrate layer, total light transmittance of substrate layer, haze of substrate layer, thickness accuracy of substrate layer, peel strength of adhesive layer, and protective film for optical member Scratchability was measured as described above. Table 3 shows the measurement results.

  When the base material layer which consists of mixed component (I) which contains many fish eyes like the comparative example 8, it was a result inferior to dent property.

As shown in Table 3, the protective film for optical members of the present embodiment (Examples 1 to 7) has a base layer having good thickness accuracy, small retardation and excellent transparency, and has an appropriate peel strength. It has been found that it has an adhesive layer and is excellent in dentability on the surface of an object to be applied after application, and has no adhesion of an adhesive, and is suitable as a protective film for optical members.

  The protective film for an optical member of the present invention contains a mixed component (I) with little foreign matter (fish eye), and has a low thickness birefringence (low retardation) that has a good thickness accuracy and is transparent and does not require molecular chain orientation adjustment. As a protective film for members having optical anisotropy such as flat panel displays (FPD) such as liquid crystal displays (LCDs) and plasma displays (PDPs) It can be suitably used. The protective film for optical members of the present invention can be suitably used as a protective film particularly for visual inspection of optical members.

Claims (8)

A protective film for an optical member including a base material layer and an adhesive layer,
The base material layer comprises a block copolymer (α) comprising 20% by mass to 75% by mass of vinyl aromatic hydrocarbon and 25% by mass to 80% by mass of conjugated diene, and 85% by mass of vinyl aromatic hydrocarbon. A mixed component (I) with a block copolymer (β) consisting of more than 95% by mass and less than 5% by mass and less than 15% by mass,
The number of fish eyes of 0.1 mm to 0.5 mm in the mixed component (I) is 100 / 1.2 m ² or less,
The retardation of the base material layer is 0.1 nm to 50 nm,
The total light transmittance of the base material layer is 90% or more,
The internal haze of the base material layer is 3.0% or less,
The protective film for optical members whose peel strength of the adhesive layer in the protective film (based on JIS Z-0237 (adhesive tape test method)) is 0.03 to 0.5 N / 25 mm.   2. The optical member according to claim 1, wherein the ratio of the base material layer to the adhesive layer (the thickness of the base material layer / the thickness of the adhesive layer) in the protective film for an optical member is 50/50 to 95/5. Protective film. The protective film for optical members according to claim 1 or 2, wherein the number of fish eyes of 0.1 mm to 0.5 mm in the mixed component (I) is 50 / 1.2 m ² or less. The protective film for optical members according to any one of claims 1 to 3, wherein the base material layer further contains the following component (II):
(II): (i) a vinyl aromatic hydrocarbon polymer, (ii) a copolymer comprising a vinyl aromatic hydrocarbon and an aliphatic unsaturated carboxylic acid derivative, and (iii) a rubber-modified styrene polymer. At least one polymer selected from the group consisting of:   The mass ratio of the mixed component (I) and the component (II) (block copolymer (I) / component (II)) in the base material layer is 30/70 to 99.9 / 0.1. The protective film for optical members according to claim 4.   The protective film for optical members according to claim 1, wherein the adhesive layer contains an acrylic adhesive.   The protective film for optical members according to any one of claims 1 to 6, wherein the adhesive layer contains a conductivity-imparting agent.   The protective film for optical members according to claim 1, wherein the base material layer is formed by an inflation method.