JP2007225745A - Protective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protective film that is superior in adhesiveness with an optical component, without inhibiting the optical performances, and is superior in strength, curling property and flexibility. <P>SOLUTION: The protective film for protecting the surface of an optical component is equipped with a base film, which has a hydrophilic resin layer containing a polymer compound having a hydrophilic group and layers, comprising a thermoplastic resin and disposed on both surfaces of the hydrophilic resin layer, wherein the protective film has a residual solvent content of 0.01 wt.% or smaller. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a protective film, and more particularly, to a protective film that has excellent adhesion to optical components without impairing optical performance, and excellent strength, curlability, and flexibility.

  Conventionally, a protective film is provided on a polarizer of an optical component, which is an optical component, or a front filter of a plasma display panel (PDP) for the purpose of protecting the surface from an external force or the like. For example, as a protective film provided on a front filter of a PDP, a film including a layer made of polyolefin may be used (see Patent Document 1). The polarizing plate includes a polarizer, a first protective film provided on one surface of the polarizer, and a second protective film provided on the other surface of the polarizer. As the film, a triacetyl cellulose film (TAC film) is widely used because it has excellent low birefringence and transparency.

JP 2005-884981 A

  However, when a film containing a layer made of polyolefin is used as a protective film for PDP, there is an advantage that impact resistance can be imparted to the protective film by the polyolefin layer. There was a problem that the adhesion of the PDP to the front filter was not always sufficient, and it was easy to peel off.

  Further, the TAC film has a high residual solvent content. For example, in a high temperature / high humidity environment, there is a problem that the protective film is easily peeled off from the polarizer due to volatilization of the residual solvent. There has been a problem that the optical performance is hindered due to changes, deterioration of the polarizer, and the like.

  The objective of this invention is providing the protective film which is excellent in adhesiveness with an optical component, and is excellent in intensity | strength, curl property, and flexibility, without inhibiting optical performance.

  Such a problem is not limited to the case where the protective film is used to protect the polarizer or the front filter of the PDP, but the display surface of a touch panel, a field emission display (FED), an electroluminescence display (ELD), or the like. The same occurs when used for protection or when protecting the display surface of a cathode ray tube display (CRT).

  In order to solve the above-mentioned problems, the present invention provides a hydrophilic film that is provided on the surface of an optical component and protects the surface from an external force or the like, and includes a polymer compound having a hydrophilic group. A substrate film having a resin layer and a thermoplastic resin layer provided on both surfaces of the hydrophilic resin layer is provided, and the residual solvent content of the protective film is 0.01% by weight or less. And

  According to the protective film of the present invention, there is an effect that the adhesiveness with the optical component is excellent and the strength, curling property and flexibility are excellent without impairing the optical performance.

  The protective film of the present invention is provided on the surface of an optical component such as glass or transparent resin, and is a protective film for protecting this surface. The protective film includes a base film having a hydrophilic resin layer containing a polymer compound having a hydrophilic group and layers made of a thermoplastic resin provided on both surfaces of the hydrophilic resin layer. .

(Hydrophilic resin layer)
The hydrophilic group of the polymer compound constituting the hydrophilic resin layer may be any functional group having hydrophilicity or water dispersibility function, such as a carboxylic acid group, a carboxylic acid group, a sulfonic acid group, or a sulfonic acid group. , Ester groups, amide groups, amino groups, hydroxyl groups, glycidyl groups, and acetyl groups. Among these, a hydroxyl group is preferable as the hydrophilic group.

  Examples of the polymer compound having a hydrophilic group include hydrophilic cellulose derivatives (methyl cellulose, carboxymethyl cellulose, hydroxy cellulose, etc.), polyvinyl alcohol derivatives (polyvinyl alcohol, vinyl acetate-vinyl alcohol copolymer, polyvinyl acetate, polyvinyl acetate). Acetal, polyvinyl homar, and polyvinyl benzal), natural polymer compounds (such as gelatin, casein, and gum arabic), hydrophilic polyester derivatives (such as partially sulfonated polyethylene terephthalate), and polyvinyl derivatives (poly) -N-vinylpyrrolidone, polyacrylamide, polyvinylimidazole, polyvinylpyrazole, etc.). These hydrophilic polymer compounds may be used alone or in combination of two or more. Among these, a cellulose derivative is preferable as the hydrophilic polymer compound.

  Examples of cellulose derivatives include cellulose esters, cellulose carbamates, and cellulose ethers. A cellulose derivative may be used independently and may combine 2 or more types.

  Examples of cellulose esters include organic acid esters, inorganic acid esters, and mixed acid esters of organic and inorganic acids. Examples of organic acid esters include aliphatic organic acid esters (cellulose C2-C6 alkyl carboxylic acid esters such as cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate, acetylalkyl). Alkyl cellulose esters such as cellulose, dichloromethyl cellulose esters, trichloromethyl cellulose esters, haloalkyl cellulose esters such as trifluoromethyl cellulose esters), and aromatic organic acid esters (cellulose phthalates, cellulose benzoates, cellulose-4-methylbenzoates, C7- C12 aromatic carboxylic acid ester). Examples of inorganic acid esters include cellulose phosphate and cellulose sulfate. In the present application, Cm-Cn means m to n carbon atoms.

  Examples of cellulose carbamates include cellulose aryl carbamates (such as cellulose phenyl carbamate) and cellulose ether carbamates (such as ethyl cellulose phenyl carbamate).

  Examples of cellulose ethers include cyanoalkyl cellulose (such as cyanoethyl cellulose), C1-C10 alkyl cellulose (such as C1-C6 alkyl cellulose such as methyl cellulose and ethyl cellulose), and aralkyl cellulose (C6-C12 aryl-C1 such as benzyl cellulose). -C4 alkyl cellulose, etc.).

  Preferred cellulose derivatives include cellulose esters having at least an acetyl group among cellulose esters such as cellulose acetate (cellulose monoacetate, cellulose diacetate, cellulose triacetate), and internally plasticized cellulose derivatives (acetyl C3-C6 acyl). And cellulose (such as cellulose acetate propionate and cellulose acetate butyrate).

  The average substitution degree of cellulose esters is, for example, about 1 to 3, preferably about 1.3 to 3, more preferably about 1.5 to 3, and further preferably about 2 to 3. In the acetyl C3-C6 acylcellulose, the ratio of the acetyl group to the C3-C6 acyl group is, for example, the former / the latter (molar ratio) = 90/10 to 5/95, preferably 70/30 to 10 / 90, more preferably about 50/50 to 15/85.

  In the cellulose derivative, the average degree of polymerization of the cellulose derivative is not particularly limited, and is, for example, about 50 to 8,000, preferably about 100 to 7,000, and more preferably about 200 to 6,000.

  As plasticization of the cellulose derivative, (a) a method in which C3-C6 acyl groups such as propionate group and butyrate group are introduced into cellulose acetate as a soft component to internally plasticize, and (b) a plasticizer into the cellulose derivative. And (c) a method of combining these methods (a) and (b).

  Examples of the plasticizer include phthalate esters, fatty acid esters, phosphate esters, and epoxy derivatives. These plasticizers may be used alone or in combination.

  Examples of the phthalic acid ester include diC1-10 alkyl phthalates such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, di (2-ethylhexyl) phthalate, dinonyl phthalate, and diisodecyl phthalate, and diC6-C8 cyclo, such as dicyclohexyl phthalate. Examples thereof include alkyl-aralkyl phthalates such as alkyl phthalate and butyl benzyl phthalate, and di (methoxyethyl) phthalate.

  Examples of fatty acid esters include adipic acid diesters (such as dioctyl adipate and di (2-ethylhexyl) adipate), azelaic acid diesters (such as dioctyl azelate and di (2-ethylhexyl) azelate), and sebacic acid diesters (dibutyl sebacate and dioctyl seba). C6-C12 aliphatic di- or tricarboxylic acid esters (C6-, such as cate, di (2-ethylhexyl) sebacate), citric acid triester (acetyl triester such as triethyl acetyl citrate, tributyl acetyl citrate, etc.) C12 aliphatic di- or tricarboxylic acid C2-C8 alkyl ester); mono- or di-C2-C4 alkyl carboxyl of glycols (ethylene glycol, triethylene glycol, polyethylene glycol, etc.) Alkyl carboxylic acid esters of polyhydric alcohols such as esters (such as triethylene glycol diacetate and triethylene glycol dipropionate), glycerol alkyl carboxylic acid esters such as triacetin and diglycerol tetracaprylate); Can be mentioned.

  Examples of phosphate esters include trialkyl phosphates (tri-C1-C10 alkyl phosphates such as triethyl phosphate, tributyl phosphate, trioctyl phosphate, and halogen-containing tri-C1-C10 alkyl phosphates such as trichloroethyl phosphate) , Triaryl phosphates (such as triphenyl phosphate, tricresyl phosphate, tris (isopropylphenyl) phosphate, tri C6-C10 aryl phosphate such as cresyl diphenyl phosphate), alkyl-diaryl phosphates (octyl diphenyl) And phosphate (such as phosphate) and tri (butoxyethyl) phosphate.

  Examples of the epoxy derivative include epoxidized fatty acid esters (alkyl epoxy stearate, diisodecyl-4,5-epoxytetrahydrophthalate, etc.) and the like. Examples of other plasticizers include oligomer type plasticizers such as polyester. Preferred plasticizers include phthalic acid esters (especially di-C1-C8 alkyl phthalates such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate), C6-C12 alkanedi or tricarboxylic acid C2-C10 alkyl esters (especially sebacic acid such as dibutyl sebacate). And diesters, citric acid triesters such as triethyl acetyl citrate), alkyl carboxylic acid esters of polyhydric alcohols (such as triacetin), and phosphoric acid esters (particularly triaryl phosphates such as triphenyl phosphate).

  The ratio between the cellulose derivative and the plasticizer can be selected according to the type of the cellulose derivative and the like. For example, the former / the latter (weight ratio) = about 100/0 to 50/50, preferably about 100/0 to 60/40. 100/0 to 70/30.

(Layer made of thermoplastic resin)
Examples of the thermoplastic resin provided on both surfaces of the hydrophilic resin layer include polycarbonate resin, polyether sulfone resin, polyethylene terephthalate resin, polyimide resin, acrylic resin, polysulfone resin, polyarylate resin, polyethylene resin, polystyrene resin, poly A vinyl chloride resin, an alicyclic olefin polymer, etc. can be mentioned. Among these, an acrylic resin is preferable as the thermoplastic resin. In addition, the layer which consists of thermoplastic resins can be made into a single layer or multiple layers. When the layer made of the thermoplastic resin is a multilayer, a layer not adjacent to the hydrophilic resin layer among the layers made of the thermoplastic resin may be used as the hydrophilic resin layer.

Examples of acrylic resins include (meth) acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate, and the hydrogen of the alkyl group depends on a functional group such as OH group, COOH group, or NH ₂ group. Homopolymers such as substituted (meth) acrylic acid alkyl esters or (meth) acrylic acid alkyl esters and styrene, vinyl acetate, α, β-monoethylenically unsaturated carboxylic acid, vinyl toluene, α-methylstyrene A copolymer with a vinyl monomer having an unsaturated bond such as can be used. As an acrylic resin, only 1 type may be used among these and 2 or more types may be used. As the acrylic resin, polymethyl methacrylate and polybutyl methacrylate are more preferable. Moreover, as an acrylic resin, the thing of the range whose glass transition temperature Tg is 0-105 degreeC is preferable.

  The resin constituting each layer of the base film includes colorants such as pigments and dyes, fluorescent brighteners, dispersants, heat stabilizers, light stabilizers, ultraviolet absorbers, infrared absorbers, antistatic agents, and antioxidants. A material in which a compounding agent such as an agent, a lubricant, or a solvent is appropriately blended can be used.

  Here, for example, as an infrared absorber, a nitroso compound, a metal complex salt thereof, a cyanine compound, a squarylium compound, a thiol nickel complex compound, a phthalocyanine compound, a naphthalocyanine compound, a triallylmethane compound, an imonium compound , Diimonium compounds, naphthoquinone compounds, anthraquinone compounds, amino compounds, aminium salt compounds, carbon black, indium tin oxide, antimony tin oxide, oxides of metals belonging to Group 4A, 5A or 6A, carbide, boron Examples thereof include near infrared absorbers such as chemical compounds. The near-infrared absorber is preferably selected so that the entire near-infrared ray (approximately 800 nm to 1100 nm) can be absorbed, and two or more kinds thereof may be used in combination. The rate is adjusted to 10% or less.

  The thickness (average thickness) of the base film is preferably 20 μm to 200 μm, and more preferably 40 μm to 100 μm. In the base film, the thickness of the outermost layer is usually 5 μm to 100 μm, preferably 10 μm or more, and more preferably 10 μm to 50 μm.

  In the base film, the difference between the thickness of one outermost layer and the thickness of the other outermost layer is preferably 20 μm or less, more preferably 10 μm or less, and close to 0. The closer it is, the more preferable.

  In the base film, the thickness of the layer located in the middle (a layer other than the one outermost layer and the other outermost layer, which may be a single layer or a plurality of layers) is usually 5 μm. It is -100 micrometers, Preferably it is 10 micrometers-50 micrometers. The thickness of the intermediate layer is such that the ratio of the thickness of the one outermost layer or the other outermost layer is the thickness of the intermediate layer / the thickness of the outermost layer = It is preferably 5/1 to 1/5.

  Here, the resin constituting the one outermost layer or the other outermost layer is a hard resin, specifically, a pencil hardness (JIS K5600-5-4 test load 500 g) of 2H. More than that is preferred. As such a resin, the acrylic resin mentioned above is preferable. At this time, the base film preferably has a structure in which a relatively soft hydrophilic resin layer is sandwiched between other layers made of an acrylic resin or the like. By setting it as such a structure, the flexibility of the said protective film can be improved and handleability can be improved, fully ensuring the hardness of the surface of the said protective film. At this time, as the resin constituting the hydrophilic resin layer, the cellulose esters are preferable in that the adhesion to the optical component can be improved.

  The resin constituting the one outermost layer and the resin constituting the other outermost layer are preferably the same type of resin. By setting it as such a structure, when this polarizing plate is comprised using this protective film as a protective film of a polarizer, it can suppress that the curvature of a polarizing plate, a curve, roundness, etc. arise.

  Further, in the one outermost layer or the other outermost layer (or the surface of the protective film), linear concave portions or linear convex portions are not substantially formed, and the surface is flat. It is preferable that The fact that it is not substantially formed means that even if a linear recess or a linear protrusion is formed, a linear recess having a depth of less than 50 nm or a width of more than 500 nm, and a height of less than 50 nm or a width of 500 nm. It is a larger linear convex part. More preferably, it is a linear concave portion having a depth of less than 30 nm or a width of 700 nm, and a linear convex portion having a height of less than 30 nm or a width of greater than 700 nm. By adopting such a configuration, it is possible to prevent the occurrence of light interference and light leakage based on the light refraction at the linear concave portions or the linear convex portions, and the optical performance can be improved.

  The depth of the linear concave portion, the height of the linear convex portion, and the width thereof can be obtained by the following method. The protective film is irradiated with light, the transmitted light is projected onto the screen, and a portion with bright or dark stripes of light appearing on the screen (this portion is a portion where the depth of the concave portion and the height of the convex portion are large. ) Is cut out at 30 mm square. The surface of the cut film piece is observed using a three-dimensional surface structure analysis microscope (field region 5 mm × 7 mm), converted into a three-dimensional image, and a cross-sectional profile in the MD direction is obtained from the three-dimensional image. The cross-sectional profile is obtained at 1 mm intervals in the visual field region. An average line is drawn on the cross-sectional profile, and the length from the average line to the bottom of the concave portion is the depth of the concave portion, or the length from the average line to the top of the convex portion is the convex portion height. The distance between the intersection of the average line and the profile is the width. A maximum value is obtained from each of the measured values of the recess depth and the height of the convex portion, and the width of the concave portion or the convex portion showing the maximum value is obtained. The maximum values of the concave depth and convex height obtained from the above, the width of the concave portion and the width of the convex portion showing the maximum values, the depth of the linear concave portion of the film, the height of the linear convex portion And their width.

  In the base film, adjacent layers may be in direct contact with each other, or may be in contact with each other through an adhesive layer made of an adhesive (including a pressure-sensitive adhesive). The average thickness of the adhesive layer is usually 0.01 μm to 30 μm, preferably 0.1 μm to 15 μm. The adhesive layer is a layer having a tensile fracture strength according to JIS K7113 of 40 MPa or less. The adhesive constituting this adhesive layer includes acrylic adhesive, urethane adhesive, polyester adhesive, polyvinyl alcohol adhesive, polyolefin adhesive, modified polyolefin adhesive, polyvinyl alkyl ether adhesive, rubber adhesive, vinyl chloride, Vinyl acetate adhesive, styrene / butadiene / styrene copolymer (SBS copolymer) adhesive, hydrogenated product (SEBS copolymer) adhesive, ethylene / vinyl acetate copolymer, ethylene-styrene copolymer, etc. Ethylene adhesives and acrylic ester adhesives such as ethylene / methyl methacrylate copolymers, ethylene / methyl acrylate copolymers, ethylene / ethyl methacrylate copolymers, and ethylene / ethyl acrylate copolymers And so on.

<Functional layer>
The protective film of the present invention may further include a functional layer having the following functions on the surface of the base film. Examples of such a functional layer include a hard coat layer, an antireflection layer, an antistatic layer, an antiglare layer, an electromagnetic wave shielding layer, an infrared absorption layer, a color tone correction layer, and an antifouling layer. These functional layers may be of one type or a plurality of types.

(Hard coat layer)
The hard coat layer is a layer for reinforcing the hardness of the protective film, and preferably exhibits a hardness of “H” or higher in a pencil hardness test shown in JIS K5600-5-4 (a test plate uses a glass plate). . The protective film provided with such a hard coat layer preferably has a pencil hardness of 4H or higher. The material for forming the hard coat layer (hard coat material) is preferably a heat or photo-curable material, and organic hard coat materials such as organic silicone, melamine, epoxy, acrylic and urethane acrylate. And inorganic hard coat materials such as silicon dioxide. Among these, as the hard coat material, it is preferable to use urethane acrylate-based and polyfunctional acrylate-based hard coat materials from the viewpoint of good adhesive force and excellent productivity.

  The hard coat layer contains various fillers for the purpose of adjusting the refractive index, improving the flexural modulus, stabilizing the volume shrinkage, and improving heat resistance, antistatic properties, and antiglare properties, as desired. it can. Further, the hard coat layer can contain additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, a leveling agent, and an antifoaming agent.

  Fillers for adjusting the refractive index and antistatic properties of the hard coat layer include titanium oxide, zirconium oxide, zinc oxide, tin oxide, cerium oxide, antimony pentoxide, tin-doped indium oxide (ITO), and antimony. Examples thereof include doped tin oxide (IZO), aluminum-doped zinc oxide (AZO), and fluorine-doped tin oxide (FTO). As the filler, antimony pentoxide, ITO, IZO, ATO, and FTO are preferable in that transparency can be maintained. The primary particle diameter of these fillers is usually 1 nm to 100 nm, preferably 1 nm to 30 nm.

  The filler for imparting antiglare properties preferably has an average particle size of 0.5 μm to 10 μm, more preferably 1.0 μm to 7.0 μm, and even more preferably 1.0 μm to 4.0 μm. Specific examples of fillers that impart antiglare properties include polymethyl methacrylate resins, vinylidene fluoride resins and other fluororesins, silicone resins, epoxy resins, nylon resins, polystyrene resins, phenol resins, polyurethane resins, crosslinked acrylic resins, Filler made of organic resin such as crosslinked polystyrene resin, melamine resin, benzoguanamine resin; or inorganic such as titanium oxide, aluminum oxide, indium oxide, zinc oxide, antimony oxide, tin oxide, zirconium oxide, ITO, magnesium fluoride, silicon oxide The filler which consists of a compound can be mentioned.

The hard coat layer has a refractive index n _H between the refractive index n _L of an antireflection layer to be described later and n _H ≧ 1.53 and n _H ^1/2 −0.2. It is preferable to have a relationship of <n _L <n _H ^1/2 +0.2 in order to develop the antireflection function.

(Antireflection layer)
The antireflection layer is a layer for preventing the transfer of external light, and is a layer laminated on the surface (surface exposed to the outside) of the base film directly or via another layer such as a hard coat layer. is there. The protective film having an antireflection layer preferably has a reflectance of 2.0% or less at an incident angle of 5 ° and a wavelength of 430 nm to 700 nm, and preferably has a reflectance of 1.0% or less at a wavelength of 550 nm.

  The thickness of the antireflection layer is preferably 0.01 μm to 1 μm, and more preferably 0.02 μm to 0.5 μm. The antireflective layer is smaller than the refractive index of the layer (base film, hard coat layer, etc.) serving as a substrate on which the antireflective layer is laminated, and preferably has a refractive index of 1.30 to 1.45. Examples include those obtained by laminating a low refractive index layer, and those obtained by repeatedly laminating a low refractive index layer made of an inorganic compound and a high refractive index layer made of an inorganic compound.

  The material for forming the low refractive index layer (low refractive index forming material) is not particularly limited as long as the layered body has a low refractive index. The method for forming the low refractive index layer is not particularly limited, but the wet coating method is preferable because it is a simpler method than the vacuum deposition method or the like. Examples of the low refractive index forming material include a resin material such as an ultraviolet curable acrylic resin, a hybrid material in which inorganic fine particles such as colloidal silica are dispersed in the resin, and a sol-gel using a metal alkoxide such as tetraethoxysilane. Materials etc. can be mentioned. The material for forming these low refractive index layers may be a polymerized polymer, or may be a monomer or oligomer serving as a precursor. Moreover, it is preferable that each material contains the compound containing a fluorine group, in order to provide the surface antifouling property.

As the sol-gel material, a sol-gel material containing a fluorine group can be used. Examples of the sol-gel material containing a fluorine group include perfluoroalkylalkoxysilane. As perfluoroalkyl alkoxysilane, for example, general formula (1): CF ₃ (CF ₂ ) nCH ₂ CH ₂ Si (OR) ₃ (wherein R represents an alkyl group having 1 to 5 carbon atoms, n represents an integer of 0 to 12). Specifically, as perfluoroalkylalkoxysilane, trifluoropropyltrimethoxysilane, trifluoropropyltriethoxysilane, tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, heptadecafluorodecyltrimethoxysilane , And heptadecafluorodecyltriethoxysilane. Among these, as a perfluoroalkyl alkoxysilane, the said n is a compound with 2-6.

  The low refractive index layer can be made of a cured product of a thermosetting fluorine-containing compound or a fluorine compound containing an ionizing radiation curable type. The cured product preferably has a dynamic friction coefficient of 0.03 to 0.15, and a contact angle with water of 90 to 120 degrees. Examples of the curable fluorine-containing compound include a perfluoroalkyl group-containing silane compound (for example, (heptadecafluoro-1,1,2,2-tetradecyl) triethoxysilane), etc. And a fluorine-containing copolymer having the above monomer as a structural unit.

  Specific examples of the fluorine-containing monomer unit include, for example, fluoroolefins (for example, fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoro-2,2-dimethyl-1,3-dioxole, etc. ), (Meth) acrylic acid moieties or fully fluorinated alkyl ester derivatives (for example, Biscoat 6FM (manufactured by Osaka Organic Chemicals) and M-2020 (manufactured by Daikin)), fully or partially fluorinated vinyl ethers, and the like. As a monomer for imparting a crosslinkable group, in addition to a (meth) acrylate monomer having a crosslinkable functional group in the molecule like glycidyl methacrylate, it has a carboxyl group, a hydroxyl group, an amino group, a sulfonic acid group, etc. ) Acrylate monomers (for example, (meth) acrylic acid, methylol (meth) acrylate, hydroxyalkyl (meth) acrylate, allyl acrylate, etc.). The latter is disclosed in JP-A-10-25388 and JP-A-10-147739 that a crosslinked structure can be introduced after copolymerization.

  As a material for forming the low refractive index layer, a material containing a sol in which fine particles such as silica, alumina, titania, zirconia, magnesium fluoride and the like are dispersed in an alcohol solvent is used because it can improve scratch resistance. Can do. In this case, the fine particles are preferably as low as possible from the viewpoint of antireflection properties. Such fine particles may have voids, and silica hollow fine particles are particularly preferable. The average particle size of the hollow fine particles is preferably 5 nm to 2,000 nm, and more preferably 20 nm to 100 nm. Here, the average particle diameter is a number average particle diameter by observation with a transmission electron microscope.

  In the case of a low refractive index layer made of a cured product of a fluorine-containing compound, the scratch resistance of the low refractive index layer tends to decrease when the refractive index of the cured product is lowered. By optimizing the amount of addition, it is possible to achieve both scratch resistance and a low refractive index.

  Here, examples of the method for forming the low refractive index layer include coating methods such as dip coating, air knife coating, curtain coating, roller coating, wire bar coating, and gravure coating. The thickness of the low refractive index layer is preferably about 0.05 μm to 0.3 μm, particularly preferably 0.1 μm to 0.3 μm.

(Anti-fouling layer)
The antifouling layer is a layer that can impart water repellency, oil repellency, sweat resistance, antifouling properties, and the like to the surface of the laminate. As a material used for forming the antifouling layer, a fluorine-containing organic compound is suitable. Examples of the fluorine-containing organic compound include fluorocarbon, perfluorosilane, and polymer compounds thereof. As a method for forming the antifouling layer, a physical vapor deposition method such as vapor deposition or sputtering, a chemical vapor deposition method such as CVD, a wet coating method, or the like can be used depending on the material to be formed. The average thickness of the antifouling layer is preferably 1 nm to 50 nm, more preferably 3 nm to 35 nm.

  When the functional layer as described above is formed, the surface of the laminated body can be subjected to a hydrophilic treatment. As means for hydrophilic treatment, for example, surface treatment methods such as corona discharge treatment, sputtering treatment, low-pressure UV irradiation, and plasma treatment can be employed.

  The residual solvent content of the protective film is 0.01% by weight or less. When the amount of the residual solvent is within the above range, for example, the protective film can be prevented from being peeled off from the optical component to be applied by the solvent volatilized from the protective film in a high temperature / high humidity environment. By preventing the film from being deformed, the influence on the optical performance of the optical component (for example, a polarizer) can be suppressed. The protective film in which the residual solvent amount falls within the above range may be obtained, for example, by co-extrusion molding of a plurality of resins, or a single thermoplastic resin layer may be bonded by dry lamination or thermal lamination. However, those obtained by coextrusion molding are preferred in terms of productivity. In the case of coextrusion molding, it is not necessary to go through a complicated process (for example, a drying process or a coating process). Therefore, there is little mixing of external foreign matters such as dust, and excellent optical performance can be exhibited.

Preferably the moisture permeability of the protective film is 10g ^/ m 2 · 24h or ^more, more preferably ^{10g / m 2 · 24h~200g / m} 2 · 24h. By setting the moisture permeability of the protective film to the above-mentioned preferable range, the adhesion between the layers constituting the protective film can be improved. The moisture permeability can be measured by the cup method described in JIS Z 0208 under the test conditions of leaving for 24 hours in an environment of 40 ° C. and 92% RH.

  The protective film preferably has a total light transmittance of 85% or more, and more preferably 90% or more. The protective film preferably has a haze of 2% or less, and more preferably 1% or less.

The absolute value of the photoelastic coefficient of the protective film is preferably 30 × 10 ⁻¹³ cm ² / dyn or less, more preferably 10 × 10 ⁻¹³ cm ² / dyn or less, and more preferably 5 × 10 ⁻¹³ cm ^2. More preferably, it is not more than / dyn. When the photoelastic coefficient is larger than the above numerical value, for example, when the protective film is attached to the polarizer, the protective film tends to develop a phase difference due to the shrinkage stress of the attached polarizer, There is a risk of deteriorating optical performance.

Protective film is a value defined by the in-plane retardation _{Re (Re = d × (n} x -n y), n x, n y are in-plane principal refractive index of the protective film; d is of the protective film Those having a small (average thickness) are preferred. Specifically, the in-plane retardation Re of the protective film is preferably 50 nm or less, more preferably 10 nm or less at a wavelength of 550 nm.

The protective film has a refractive index na (λ) at a wavelength λ in the range of 380 nm to 780 nm in the hydrophilic resin layer, and a refractive index at a wavelength λ in the range of 380 nm to 780 nm in a layer adjacent to the hydrophilic resin layer. As λ), it is preferable to satisfy the relationship of the formula (1).
| Na (λ) −nb (λ) | ≦ 0.05 (1)
In particular, it is more preferable that | na (λ) −nb (λ) | ≦ 0.045. Note that na (λ) and nb (λ) are average values of the main refractive indexes at the wavelength λ. When the value of | na (λ) −nb (λ) | exceeds the above value, interference fringes may occur on the surface of the protective film due to interface reflection caused by a difference in refractive index at the interface.

<Uses of protective film>
A protective film is used as a protective film of the following optical component used for an optical use, for example. That is, as an optical component, it can be set as the member arrange | positioned at the display surface side of a flat panel display (FPD), for example. Examples of such optical components include polarizing plates (or polarizers) used in liquid crystal display devices (LCDs), front filters for plasma display panels (PDPs), touch panels, field emission displays (FEDs), and electroluminescence displays. (ELD) display surface and the like. Moreover, the protective film of this invention can also be affixed on the display surface of a cathode ray tube display (CRT). Further, the protective film can be used by being attached to a window glass provided in a building such as an automobile or a train.

The present invention will be described in more detail with reference to examples and comparative examples.
The polarizing plates and display devices shown in Examples and Comparative Examples were evaluated by the following methods.

<Refractive index of hard coat layer and low refractive index layer>
Using high-speed spectroscopic ellipsometry (manufactured by JA Woollam, M-2000U) under the conditions of a temperature of 20 ° C. ± 2 ° C. and a humidity of 60 ± 5%, the incident angles are 55 °, 60 °, and 65 °, A spectrum in the wavelength region of 400 to 1000 nm was measured and calculated from these measurement results.

<Refractive index of each resin layer>
A thermoplastic resin is molded into a single layer, and a refractive index at wavelengths of 633 nm, 407 nm, and 532 nm under the conditions of a temperature of 20 ° C. ± 2 ° C. and a humidity of 60 ± 5% using a prism coupler (manufactured by Metricon, model 2010). From the value, the refractive index of 380 nm to 780 nm was calculated by the Caucy's dispersion formula.

<Tensile elastic modulus of each resin layer>
A thermoplastic resin is molded as a single layer, a 1 cm × 25 cm test piece is cut out, and a tensile tester (Tensilon UTM-10T-PL, manufactured by Toyo Baldwin Co., Ltd.) is used at a tensile speed of 25 mm / min based on ASTM882. Measured under conditions. The same measurement was performed 5 times, and the arithmetic average value was taken as the representative value of the tensile modulus.

<Thickness of each resin layer>
After embedding the protective film in an epoxy resin, it was sliced using a microtome (manufactured by Yamato Kogyo Co., Ltd., RUB-2100), and the cross section was observed and measured using a scanning electron microscope.

<Water permeability of protective film>
The measurement was performed by a method according to the cup method described in JIS Z 0208 under the test conditions of leaving for 24 hours in an environment of 40 ° C. and 92% RH. The unit of moisture permeability is g / m ² · 24h.

<Residual solvent content of protective film>
The residual solvent content of the protective film was determined by adding 50 mg of protective film to a glass tube sample container with an inner diameter of 4 mm from which moisture and organic substances adsorbed on the surface were completely removed, and then heating the container at a temperature of 200 ° C. for 30 minutes. And the gas which came out of the container was collected continuously. The collected gas was analyzed by a thermal desorption gas chromatography mass spectrometer (TDS-GC-MS).

<Measuring method of depth of linear concave part, height of linear convex part and their width>
By the method described above, the depth of the linear concave portion, the height of the linear convex portion, and the width thereof were measured. The maximum value of the obtained concave depth and convex height, the width of the concave portion and the width of the convex portion showing the maximum value, the depth of the linear concave portion of the film, the height of the linear convex portion and those And evaluated according to the following criteria.
A: Depth of linear recess or height of projection is 20 nm or less and width is 800 nm or more. O: Depth of linear recess or height of projection is 30 nm or less and width is 700 nm or more. X: Depth of linear concave part or height of convex part is 50 nm or less and width is 500 nm or more

<Adhesion>
The protective film was allowed to stand at a temperature of 60 ° C. and a humidity of 90% for 300 hours, and the interface peeling of the protective film end face after the standing was visually observed.
○: No peeling ×: Peeling is observed on the end face

<Pencil hardness>
With reference to JIS K5600-5-4, while applying a load of 500 g from above, scratch the surface of the protective film (surface opposite to the polarizer side) by about 5 mm with a pencil inclined at an angle of 45 degrees. The degree of damage was confirmed.

<Observation of interference fringes>
A protective film is placed on a black cloth that does not transmit light, such as a dark curtain, and the surface of the protective film is visually observed with a three-wavelength fluorescent lamp (manufactured by Matsushita Electric Industrial Co., Ltd., National Fluorescent Lamp: FL20SS / ENW / 18). The evaluation was based on the following criteria.
○: Interference fringes are not visible △: Interference fringes are slightly visible ×: Interference fringes are conspicuous

<Flexibility test>
A protective film was punched into 1 cm × 5 cm to obtain a test film. The obtained test film was wound around a steel rod having a diameter of 3 mmφ, and whether or not the wound film was broken at the rod was tested. The test was conducted a total of 10 times, and the flexibility was expressed by the following index according to the number of times the test was not broken.
○: One or less pieces of broken film ×: Two or more pieces of broken film

<Evaluation of curling properties>
The protective film was cut into a size of 10 cm × 10 cm, placed on a horizontal plate, the curl state of the test piece was observed, and the curl property was evaluated according to the following criteria.
A: No curling is observed and good. B: Almost inconspicuous but slightly curled.
X: Curl is clearly recognized and there is a problem in practical use.

<Durability test>
The liquid crystal display or plasma display including this protective film was taken out after being left in a thermostatic bath having a temperature of 60 ° C. and a humidity of 90% for 500 hours, and the following items were evaluated.
(With or without air bubbles)
The number of bubbles generated on the surface was visually measured.
○: No bubbles are observed ×: Bubbles are observed (existence of peeling)
The peeling at the end face of the protective film was visually judged.
○: Peeling is not seen ×: Peeling is seen

<Production Example 1: Production of cellulose acetate butyrate>
Cellulose acetate butyrate as acetylacylcellulose which is a polymer compound having a hydrophilic group (acetyl group substitution degree: 1.0, butyryl group substitution degree: 1.7, weight average molecular weight: 155,000; yeast Cellulose acetate butyrate by kneading 91% by weight of CAB-381-20) manufactured by Man Chemical Co., Ltd. and 9% by weight of diglycerin tetracaprylate, a plasticizer, at 190 ° C. using a biaxial extruder and cutting to about 5 mm. Got the rate.

<Production Example 2: Production of maleimide / olefin copolymer>
In a reaction kettle equipped with a stirrer, a nitrogen introducing tube, a thermometer, and a deaeration tube, 100 parts by weight of N-methylmaleimide, 0.67 parts by weight of t-butylperoxyneodecanoate and a mixed solvent of toluene and methanol (1 : 1 part by weight) 1050 parts by weight were charged and purged several times with nitrogen, and then 400 parts by weight of isobutene was added and reacted at 60 ° C. for 6 hours. The obtained N-methylmaleimide / isobutene copolymer particles were centrifuged and dried. From the results of elemental analysis of the obtained N-methylmaleimide / isobutene copolymer (C; 64.7% by weight, H; 7.8% by weight, N; 8.4% by weight), the produced N-methylmaleimide / isobutene The N-methylmaleimide unit and isobutene unit in the copolymer were each 50 mol%. After dry blending 80% by weight of the N-methylmaleimide / isobutene copolymer and 20% by weight of an acrylonitrile / styrene copolymer having an acrylonitrile content of 30% by weight, a 30 mmφ twin screw extruder (trade name: TEX30, manufactured by Nippon Steel Works, Ltd.) And pelletized after melt-kneading. The glass transition temperature of the obtained resin composition pellet was 140 ° C.

<Production Example 3: Preparation of hard coat material H>
30 parts of a hexafunctional urethane acrylate oligomer, 40 parts of butyl acrylate, 30 parts of isobornyl methacrylate, and 10 parts of 2,2-diphenylethane-1-one were mixed with a homogenizer, and antimony pentoxide fine particles (average particle diameter of 20 nm, A 40% methyl isobutyl ketone solution in which the hydroxyl group is bonded to the antimony atoms appearing on the surface of the pyrochlore structure at a ratio of 50%, and the weight of the antimony pentoxide fine particles is 50% of the total solid content of the hard coat layer forming composition. The hard coat material H was prepared by mixing at a ratio of weight%.

<Production Example 4: Preparation of low refractive index forming material L)
70 parts by weight of vinylidene fluoride and 30 parts by weight of tetrafluoroethylene, which are fluorine-containing monomers, were dissolved in methyl isobutyl ketone. Next, hollow silica isopropanol dispersion sol (manufactured by Catalytic Chemical Industry Co., Ltd., solid content: 20% by weight, average primary particle diameter: about 35 nm, outer shell thickness: about 8 nm) is hollowed into this dissolved matter with respect to the fluorine-containing monomer solid content. 30% by weight of silica solid content, 3% by weight of dipentaerythritol hexaacrylate (manufactured by Shin-Etsu Chemical Co., Ltd.) with respect to the solid content, and Irgacure 184 (produced by Ciba Specialty Chemicals) with respect to the solid content 5% by weight was added to prepare a low refractive index forming material L.

<Production Example 5: Production of triacetyl cellulose film>
100 parts by mass of triacetyl cellulose (TAC) having an acetylation degree of 61.0% and 15 parts by mass of triphenyl phosphate are dissolved in a mixed solvent of 450 parts by mass of methylene chloride and 50 parts by mass of methanol and placed on a 35 ° C. stainless steel belt. The film was cast and peeled off from the stainless steel belt and gradually raised in temperature while being conveyed using a roll conveying device, and finally dried at 120 ° C. to produce a triacetyl cellulose film.

<Example 1>
(Creation of protective film)
Polymethylmethacrylate resin (indicated as PMMA in the table, water absorption 0.3%) was charged into the first double-flight type single screw extruder equipped with a leaf disk-shaped polymer filter with an opening of 10 μm, and the exit temperature of the extruder The molten resin was supplied at 260 ° C. to the first manifold die constituting the multi-manifold die and having a die slip surface roughness Ra of 0.1 μm.

  In addition, the cellulose acetate butyrate obtained in Production Example 1 (indicated as CAB in the table, water absorption 1.6%) is a second double-flight type uniaxial shaft provided with a leaf disk-shaped polymer filter having an opening of 10 μm. The molten resin was introduced into the extruder at an extruder outlet temperature of 260 ° C., and supplied to a second manifold die constituting the multi-manifold die with a die slip surface roughness Ra of 0.1 μm. Then, molten polymethyl methacrylate resin, cellulose acetate butyrate, and ethylene-vinyl acetate copolymer as an adhesive are each discharged from a multi-manifold die at 260 ° C. and cast onto a cooling roll adjusted to 130 ° C. Then, it is passed through a cooling roll whose temperature is adjusted to 50 ° C., and a polymethyl methacrylate resin layer (20 μm: resin layer A) —adhesive layer (4 μm) —cellulose acetate butyrate layer (32 μm: resin layer B) —adhesive layer A base film 1 having a width of 600 mm and a thickness of 80 μm composed of a three-layer structure of (4 μm) -polymethyl methacrylate resin layer (20 μm: resin layer C) was obtained by coextrusion molding.

(Formation of antireflection layer)
Corona discharge treatment was performed on both surfaces of the base film 1 using a high frequency transmitter (output 0.8 kW) to obtain a base film 1A having a surface tension of 0.055 N / m. Next, the hard coat material H is applied to one side of the base film 1A using a die coater in an environment of a temperature of 25 ° C. and a humidity of 60% RH, and dried in a drying furnace at 80 ° C. for 5 minutes. A film was obtained. Further, this film was irradiated with ultraviolet rays (integrated irradiation amount 300 mJ / cm ² ) to form a hard coat layer having a thickness of 5 μm to obtain a base film 1B with a hard coat layer. The refractive index of the hard coat layer was 1.62, and the pencil hardness on the hard coat layer side exceeded 4H.

On the hard coat layer side of the base film 1B with the hard coat layer, a low refractive index layer forming material L is applied using a wire bar coater in an environment of a temperature of 25 ° C. and a humidity of 60% RH, and left for 1 hour. The coating obtained was heat-treated at 120 ° C. for 10 minutes in an oxygen atmosphere, and then irradiated with ultraviolet light from a low-pressure mercury lamp under the conditions of an output of 160 W / cm and an irradiation distance of 60 mm, and a low refractive index of 100 nm in thickness. A layer (refractive index 1.37) was formed to obtain the protective film 1. The protective film 1 had a residual solvent content of 0.01% by weight or less and a photoelastic coefficient of 2 × 10 ⁻¹³ cm ² / dyn. Moreover, the depth of the linear recessed part or the height of the convex part of the surface of the protective film was 20 nm or less, and the width | variety was the range of 800 nm or more.

<Example 2>
A base film was obtained in the same manner as in Example 1 except that the maleimide / olefin copolymer obtained in Production Example 2 (indicated in the table as MIO) was used instead of the polymethyl methacrylate resin in Example 1. A protective film 2 was produced by laminating the hard coat layer and the low refractive index layer on the base film. The protective film 2 had a residual solvent content of 0.01% by weight or less and a photoelastic coefficient of 9.5 × 10 ⁻¹³ cm ² / dyn. Moreover, the depth or convex part of the linear recessed part of the surface of the protective film 2 was the range whose height is 20 nm or less and whose width is 800 nm or more. The pencil hardness on the hard coat layer side exceeded 4H.

<Comparative Example 1: No hydrophilic resin layer>
A 20 μm-thick single-layer extrusion film made of polystyrene resin (shown as PS in the table) is pressure-bonded to both sides of a 32 μm-thick alicyclic olefin resin film (manufactured by Zeon Corporation, ZEONOR film, indicated as COP in the table) The base film bonded from the laminate was obtained, and the protective film 3 was produced by laminating the hard coat layer and the low refractive index layer on the base film. The protective film 3 had a residual solvent content of 0.01% by weight or less and a photoelastic coefficient of 6.0 × 10 ⁻¹³ cm ² / dyn. Moreover, the depth or convex part of the linear recessed part of the surface of a protective film was the range whose height is 20 nm or less and whose width is 800 nm or more.

<Comparative Example 2: Use of triacetyl cellulose film as hydrophilic resin layer>
A single-layer extruded film of 20 μm thickness made of polymethylmethacrylate resin is attached to both sides of the 32 μm-thick triacetyl cellulose film obtained in Production Example 5 (indicated as TAC in the table, water absorption 4%) with an acrylic adhesive. In addition, a base film was obtained, and the hard coat layer and the low refractive index layer were laminated on the base film to prepare a protective film 4. The protective film 4 had a residual solvent content of 0.2% by weight and a photoelastic coefficient of 2 × 10 ⁻¹³ cm ² / dyn. Moreover, the depth or convex part of the linear recessed part of the surface of the protective film 4 was the range whose height is 30 nm or less and whose width is 700 nm or more.

<Comparative Example 3: Single layer (PMMA)>
A protective film 5 was prepared by stacking the hard coat layer and the low-refractive index layer on a base film made of a single-layer extruded film having a thickness of 80 μm made of polymethyl methacrylate resin. In Example 1, the protective film 5 was used in place of the protective film 1. The protective film 5 had a residual solvent content of 0.01% by weight or less and a photoelastic coefficient of −6 × 10 ⁻¹³ cm ² / dyn. Moreover, the depth or convex part of the linear recessed part of the surface of a protective film was the range whose height is 20 nm or less and whose width is 800 nm or more.

<Comparative Example 4: Single layer (TAC)>
Instead of the protective film 1, a single-layer cast molded film made of triacetyl cellulose having a thickness of 80 μm is used as a base film, and the hard coat layer and the low refractive index layer are laminated on the base film to produce a protective film 6. did. The protective film 6 had a residual solvent content of 0.2% by weight or less and a photoelastic coefficient of 12 × 10 ⁻¹³ cm ² / dyn. Moreover, the depth or convex part of the linear recessed part of the surface of a protective film was the range whose height is 20 nm or less and whose width is 800 nm or more.

  The evaluation results of the obtained protective films 1 to 6 are shown in Table 1.

  As shown in Table 1, in Examples 1 and 2, it was found that there was no interference fringe and excellent adhesion, surface hardness, curling property, and flexibility. In contrast, Comparative Example 1 was inferior in terms of adhesion and generation of interference fringes. In Comparative Example 2, the curling property was insufficient. In Comparative Example 3, the flexibility was insufficient. In Comparative Example 4, interference fringes were generated, and curling properties and flexibility were insufficient.

<Example 3>
An acrylic adhesive is applied to the surface of the protective film 1 obtained in Example 1 where the hard coat layer is not formed, and the protective film 1 is bonded to the display surface of a commercially available 40-inch liquid crystal display. Display device D1 was obtained.

<Example 4>
An acrylic pressure-sensitive adhesive is applied to the surface of the protective film 2 of Example 2 on which the hard coat layer is not formed, and the protective film 2 is bonded to the display surface of a commercially available 40-inch liquid crystal display. D2 was obtained.

<Example 5>
An acrylic pressure-sensitive adhesive is applied to the surface of the protective film 1 obtained in Example 1 where the hard coat layer is not formed, and the protective film 1 is bonded to a front filter of a commercially available 50-inch plasma display, A display device D3 was obtained.

<Example 6>
An acrylic pressure-sensitive adhesive is applied to the surface of the protective film 2 obtained in Example 2 where the hard coat layer is not formed, and the protective film 2 is bonded to a front filter of a commercially available 50-inch plasma display, A display device D4 was obtained.

<Comparative Example 5>
An acrylic pressure-sensitive adhesive is applied to the surface of the protective film 4 obtained in Comparative Example 2 where the hard coat layer is not formed, and the protective film 4 is bonded to the display surface of a commercially available 40-inch liquid crystal display. Display device D5 was obtained.

<Comparative Example 6>
An acrylic pressure-sensitive adhesive is applied to the surface of the protective film 4 obtained in Comparative Example 2 where the hard coat layer is not formed, and the protective film 4 is bonded to a front filter of a commercially available 50-inch plasma display, A display device D6 was obtained.

  Table 2 shows the evaluation results of these display devices D1 to D6.

As shown in Table 2, in the display devices of Examples 3 to 6, no bubbles or peeling were observed in the protective film. On the other hand, in the display devices of Comparative Examples 5 and 6, bubbles and peeling were observed in the protective film.

Claims (10)

A protective film provided on the surface of the optical component for protecting the surface,
A base film having a hydrophilic resin layer containing a polymer compound having a hydrophilic group and layers made of a thermoplastic resin provided on both surfaces of the hydrophilic resin layer,
A protective film having a residual solvent content of 0.01% by weight or less. The protective film according to claim 1,
The protective film, wherein the polymer compound having a hydrophilic group is a cellulose ester. In the protective film of Claim 2,
The cellulose ester is an acetylacylcellulose having an acyl group having 3 to 6 carbon atoms. In the protective film in any one of Claims 1-3,
The protective film according to claim 1, wherein the base film is obtained by a coextrusion molding method. In the protective film in any one of Claims 1-4,
The surface of the said base film is a flat surface in which the linear recessed part or the linear convex part is not substantially formed, The protective film characterized by the above-mentioned. In the protective film in any one of Claims 1-5,
A protective film further comprising an antireflection layer provided on the surface of the base film. The protective film according to claim 6,
A protective film having an incident angle of 5 °, a reflectance at a wavelength of 430 nm to 700 nm of 2.0% or less, and a reflectance at a wavelength of 550 nm of 1.0% or less. The protective film according to claim 7,
A protective film, further comprising a hard coat layer provided between the base film and the antireflection layer. In the protective film in any one of Claims 1-8,
The protective film, wherein the optical component is a polarizer constituting a polarizing plate. In the protective film in any one of Claims 1-8,
The protective film according to claim 1, wherein the optical component is a front filter of a plasma display panel.