Dope, optical film, method for producing the same, and film roll

Abstract

To provide a containing a polymer having a structural unit derived from α - methylene lactone, which can achieve both antiblocking properties and transparency, an optical film and a method for producing the same, and a film roll using the optical film.SOLUTION: A comprising: a polymer having a structural unit derived from α - methylene lactone; and silica particles having a mean particle size of 5 to 100nm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a dope, an optical film and a manufacturing method thereof, and a film roll. [Background technology]

[0002] Polymers having structural units derived from α-methylene lactone have excellent transparency and are expected to be applied to optical components. For example, Patent Document 1 describes an optical film produced from a copolymer (resin) containing a specific structural unit derived from α-methylene lactone. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-179813 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, optical films are often required to have anti-blocking properties in addition to transparency.

[0005] The present disclosure aims to provide a dope and an optical film containing a polymer having a structural unit derived from α-methylene lactone, which can achieve both antiblocking properties and transparency, and a film roll using the optical film. The present disclosure also aims to provide a method for producing an optical film using the dope. [Means for solving the problem]

[0006] The present disclosure provides the dopes described in [1] to [4] below, the method for producing an optical film described in [5], the optical films described in [6] to

[11] , and the film roll described in

[12] . [1] A dope comprising a polymer having a structural unit derived from α-methylene lactone, silica particles having an average primary particle size of 5 to 100 nm, and a solvent. [2] The dope according to [1], wherein the silica particles have an average primary particle size of 5 to 80 nm. [3] The dope according to [1] or [2], wherein the solvent contains methylene chloride. [4] The dope according to any one of [1] to [3], further comprising an ultraviolet absorber having a molecular weight of 680 or less. [5] A method for producing an optical film, comprising a step of obtaining a film by a solution casting method using the dope according to any one of [1] to [4]. [6] An optical film comprising a polymer having structural units derived from α-methylene lactone and silica particles having an average primary particle diameter of 5 to 100 nm. [7] The optical film according to [6], wherein the silica particles have an average primary particle size of 5 to 80 nm. [8] The optical film according to [6] or [7], further comprising 10 to 10,000 ppm by mass of a solvent. [9] The optical film according to [8], wherein the solvent contains methylene chloride.

[10] The optical film according to any one of [6] to [9], further comprising an ultraviolet absorber having a molecular weight of 680 or less.

[11] The optical film according to any one of [6] to

[10] , which has a transmittance of 5% or less for light with a wavelength of 380 nm.

[12] A film roll obtained by winding the optical film according to any one of [6] to

[11] . [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide a dope and an optical film containing a polymer having a structural unit derived from α-methylene lactone, which can achieve both antiblocking property and transparency, and a film roll using the optical film. Furthermore, it is possible to provide a method for producing an optical film using the dope. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments. In the following description, "(meth)acrylic" is used as a term that encompasses both methacrylic and acrylic. Resin and polymer are used as synonymous terms. When a numerical range is indicated as X to Y, it means X or more and Y or less. For example, "5 to 100 nm" means 5 nm or more and 100 nm or less.

[0009] [Dope] The dope of the present embodiment contains a polymer having a structural unit derived from α-methylene lactone, silica particles having an average primary particle size of 5 to 100 nm, and a solvent.

[0010] (polymer) The polymer has structural units derived from α-methylene lactone.

[0011] The structural unit derived from α-methylene lactone has a structure derived from an α-methylene lactone monomer in which a methylene group is bonded to the α-carbon atom of the lactone ring. The number of ring members in the lactone ring is not particularly limited, but is preferably a 5-membered ring (γ-lactone) or a 6-membered ring (δ-lactone) from the viewpoint of the mechanical strength of the final molded product.

[0012] Representative examples of the structural unit derived from α-methylene lactone which is a five- or six-membered ring include structural units derived from α-methylene-γ-butyrolactone and α-methylene-δ-valerolactone.

[0013] The structural unit derived from α-methylene lactone preferably has a structure shown in the following formula (1).

[0014] [ka]

[0015] R in Equation (1) 1 ~R 4 are each independently a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms.

[0016] The structural unit having the structure shown in formula (1) can be formed, for example, by polymerizing a compound shown in formula (2) below.

[0017] [ka]

[0018] R in Equation (2) 1 ~R 4 is R in Equation (1). 1 ~R 4 is the same as

[0019] The hydrocarbon group is an aliphatic hydrocarbon group or an aromatic hydrocarbon group. The aliphatic hydrocarbon group is, for example, an alkyl group. The number of carbon atoms in the alkyl group is preferably 1 to 10, more preferably 1 to 8. The alkyl group may be linear or branched, or may be cyclic. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, a cyclopentyl group, and a cyclohexyl group.

[0020] Examples of the aromatic hydrocarbon group include a phenyl group, a tolyl group, and a benzyl group.

[0021] R 1 ~R 4 are preferably, each independently, a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and more preferably, all are hydrogen atoms.

[0022] The polymer may contain only one type of structural unit derived from α-methylene lactone, or may contain two or more types.

[0023] The polymer may contain structural units of any other monomer in addition to the structural units derived from α-methylene lactone. Examples of structural units derived from any other monomer include structural units derived from monomers such as alkyl (meth)acrylate, benzyl (meth)acrylate, chloromethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, styrene, vinyl toluene, α-methylstyrene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, and vinyl acetate. The polymer may contain only one type of structural unit derived from any other monomer, or may contain two or more types.

[0024] Among the structural units derived from any other monomer, from the viewpoint of further improving the heat resistance, transparency, etc. of the resulting film, it is preferable to contain a structural unit derived from alkyl (meth)acrylate, more preferably a structural unit derived from alkyl (meth)acrylate having an alkyl group with 1 to 6 carbon atoms, even more preferably a structural unit derived from alkyl (meth)acrylate having an alkyl group with 1 to 3 carbon atoms, and even more preferably a structural unit derived from methyl (meth)acrylate. The polymer may contain only one type of structural unit derived from alkyl (meth)acrylate, or may contain two or more types.

[0025] Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, a cyclopentyl group, and a cyclohexyl group.

[0026] The content of the structural unit derived from α-methylene lactone contained in the polymer is preferably 5 to 60 mass %, more preferably 7.5 to 55 mass %, and even more preferably 10 to 50 mass %, from the viewpoint of further improving heat resistance, etc. The content of each structural unit in the polymer is determined by dissolving the polymer in a heavy solvent and 1 It can be determined by measuring H-NMR and calculating the area ratio of the peaks corresponding to each structural unit.

[0027] The content of structural units derived from alkyl (meth)acrylate having an alkyl group having 1 to 6 carbon atoms contained in the polymer is preferably 40 to 95 mass %, more preferably 45 to 92.5 mass %, and even more preferably 50 to 90 mass %.

[0028] The content of structural units other than structural units derived from α-methylene lactone and structural units derived from alkyl (meth)acrylate having an alkyl group having 1 to 6 carbon atoms contained in the polymer is preferably 0 to 30 mass%, more preferably 0 to 25 mass%, and even more preferably 0 to 20 mass%.

[0029] From the viewpoint of improving the strength of the obtained film, the weight average molecular weight (Mw) of the polymer is preferably 50,000 to 1,500,000, more preferably 100,000 to 1,000,000, even more preferably 150,000 to 800,000, and still more preferably 200,000 to 600,000. The number average molecular weight (Mn) of the polymer is, for example, 30,000 to 500,000. The dispersity (Mw / Mn) is, for example, 1 or more and 5 or less.

[0030] The glass transition temperature (Tg) of the polymer is preferably 110° C. or higher, more preferably 115° C. or higher, and even more preferably 120° C. or higher, from the viewpoint of facilitating an increase in the drying temperature for the purpose of accelerating drying during film production. Furthermore, from the viewpoint of improving the strength of the film, the glass transition temperature (Tg) is preferably 200° C. or lower, more preferably 170° C. or lower, and even more preferably 140° C. or lower.

[0031] (Polymer manufacturing method) The polymer can be produced, for example, by solution polymerization or polymerization in an aqueous solvent, which comprises a polymerization step of polymerizing an α-methylene lactone monomer and any other monomers.

[0032] The aqueous solvent may contain a non-aqueous solvent (particularly a water-soluble organic solvent). Examples of the water-soluble organic solvent include alcohol solvents such as methanol, ethanol, propanol, butanol, 2-methylpropyl alcohol, and 2-methyl-2-propanol; ketone solvents such as acetone and methyl ethyl ketone; ester solvents such as ethyl acetate; and ether solvents such as dioxane, diethyl ether, and tetrahydrofuran.

[0033] The proportion of the water-soluble organic solvent in the aqueous solvent is preferably from 0 to 5 mass %, more preferably from 0 to 2 mass %, and even more preferably from 0 to 1 mass %.

[0034] In the polymerization step, it is preferable that all of the monomers are present in the system from the beginning of the polymerization step. That is, it is preferable that all of the monomers are charged into the reactor before the polymerization substantially starts. For example, it is preferable that all of the monomers are charged into the reactor before the temperature of the reactor is raised to the polymerization temperature.

[0035] When dispersing the monomer in an aqueous solvent, the dispersion may be carried out by stirring with a paddle blade or the like, or may be carried out using an emulsifying / dispersing device such as a high-speed shear turbine type disperser, a high-pressure jet homogenizer, an ultrasonic type emulsifying / dispersing machine, a medium stirring / dispersing machine, or a forced gap passing type disperser.

[0036] When polymerizing the monomers, additives such as a polymerization initiator, a chain transfer agent, and a dispersant may be added as needed.

[0037] Examples of the polymerization initiator include organic peroxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropyl carbonate, t-amylperoxy-2-ethylhexanoate, and t-butylperoxy-2-ethylhexanoate; and azo compounds such as 2,2'-azobis(isobutyronitrile), 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl-2,2'-azobis(2-methylpropionate). The amount of the polymerization initiator added can be adjusted as needed, but is preferably 0.01 to 5 parts by mass, more preferably 0.05 to 3 parts by mass, and even more preferably 0.1 to 2 parts by mass, per 100 parts by mass of the monomer.

[0038] Examples of the chain transfer agent include monofunctional thiol compounds such as n-dodecyl mercaptan and β-mercaptopropionic acid, bifunctional thiol compounds such as polysiloxanes modified at both ends with mercapto groups, and side-chain polyfunctional mercapto-modified polysiloxanes in which the side chains are modified with mercapto groups. The amount of the chain transfer agent added may be adjusted appropriately as needed, but is preferably 0.001 to 1 part by mass, and more preferably 0.01 to 0.3 parts by mass, per 100 parts by mass of the monomer.

[0039] Examples of dispersants include water-soluble polymer dispersion stabilizers such as polyvinyl alcohol (PVA), polyvinylpyrrolidone, cellulose, gelatin, sodium polyacrylate, and sodium polymethacrylate; anionic surfactants such as sodium lauryl sulfate and polyoxyethylene alkylphenyl ether sulfate salts (e.g., polyoxyethylene distyrylphenyl ether ammonium sulfate); cationic surfactants such as alkylamine salts and quaternary ammonium salts; zwitterionic surfactants such as lauryl dimethylamine oxide; nonionic surfactants such as polyoxyethylene alkyl ethers; and inorganic dispersants such as alginates, zein, and casein; barium sulfate, calcium sulfate, barium carbonate, magnesium carbonate, calcium phosphate, talc, clay, diatomaceous earth, bentonite, titanium hydroxide, thorium hydroxide, and metal oxide powders. The amount of dispersant added can be adjusted as needed, but is preferably 0.1 to 3 parts by weight, and more preferably 0.2 to 2 parts by weight, per 100 parts by weight of the monomer.

[0040] Examples of additives other than the polymerization initiator, chain transfer agent, and dispersant include phenolic, phosphorus, and sulfur-based antioxidants; polymerization inhibitors such as 4-tertiarybutylcatechol (TBC), hydroquinone, and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4H-TEMPO); stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fiber and carbon fiber; near-infrared absorbers; flame retardants such as tris(dibromopropyl)phosphate, triallyl phosphate, and antimony oxide; retardation adjusters such as retardation increasers, retardation decreasers, and retardation stabilizers; antistatic agents including anionic, cationic, and nonionic surfactants; colorants such as inorganic pigments, organic pigments, and dyes; organic and inorganic fillers; resin modifiers; and organic and inorganic fillers. The content of these additives may be 0 to 5 parts by mass or 0 to 3 parts by mass per 100 parts by mass of the monomer.

[0041] The polymerization reaction may be carried out in the form of, for example, suspension polymerization, emulsion polymerization, etc. From the viewpoint of further improving the transparency of the resulting polymer, suspension polymerization is preferred, in which the reaction is carried out by suspending monomers in an aqueous solvent in the presence of a dispersant.

[0042] After the polymerization step, the polymer particles can be recovered by solid-liquid separation. The solid-liquid separation method can be, for example, filtration, centrifugation, or a combination thereof. The resulting polymer can then be dried. The drying temperature is, for example, 60°C or higher and 120°C or lower.

[0043] Alternatively, water may be removed directly by drying without solid-liquid separation. The polymer can be obtained as a powder by drying using various dryers.

[0044] (silica particles) The average primary particle diameter of the silica particles is 5 to 100 nm, preferably 5 to 80 nm, more preferably 10 to 80 nm, and even more preferably 15 to 70 nm, from the viewpoint of suppressing a decrease in transparency while exhibiting sufficient antiblocking properties. The shape of the silica particles is, for example, spherical, crushed, etc. Note that when the silica particles have a shape other than spherical, the average length in the major axis direction is taken as the average primary particle diameter. The average primary particle diameter of the silica particles in this embodiment can be measured, for example, by the method described in the Examples.

[0045] The silica particles are not particularly limited as long as the average primary particle diameter is within the above range, and examples thereof include crystalline silica and amorphous silica. From the viewpoint of improving dispersibility when formed into a film, silica particles that have been treated to be hydrophilic or hydrophobic are preferred, and hydrophobic silica particles are more preferred. The hydrophobic silica particles may have any substituent on their surface. Examples of the substituent include a hydrocarbon group, an ethylenic double bond-containing group such as a methacrylic group, etc. Examples of the hydrocarbon group include an aliphatic saturated hydrocarbon group having approximately 1 to 20 carbon atoms, and an aromatic hydrocarbon group having approximately 6 to 20 carbon atoms. Examples of the aliphatic saturated hydrocarbon group include an alkyl group having 1 to 20 carbon atoms, such as a methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, cyclohexylethyl group, heptyl group, octyl group, nonyl group, and decyl group. However, an alkyl group having 1 to 10 carbon atoms is preferred, an alkyl group having 1 to 6 carbon atoms is more preferred, and an alkyl group having 1 to 3 carbon atoms is even more preferred. The aromatic hydrocarbon group is preferably an aryl group having about 6 to 10 carbon atoms, such as a phenyl group or a toluyl group.

[0046] The hydrocarbon group may be bonded to a polar group such as an oxirane-containing group such as an epoxy group or a glycidyl group; a halogeno group such as a fluoro group or a chloro group; an amino group; a modified amino group such as a methylamino group, a dimethylamino group, a phenylamino group, an aminoethylamino group or a hexylidenylamino group; a mercapto group; an isocyanato group; an ester group, an amide group, a thioester group, a carbonate group, a urethane group or a urea group. The polar group is a group other than a hydrocarbon group, and specifically refers to a group containing a heteroatom such as a nitrogen atom, an oxygen atom, a sulfur atom or a halogen atom.

[0047] (solvent) The solvent is preferably an organic solvent. Examples of the organic solvent include chain ketone solvents such as acetone and methyl ethyl ketone; cyclic ketone solvents such as cyclohexanone (anone) and cyclopentanone; alkyl chloride solvents such as methylene chloride, chloroform, 1,2-dichloroethane, and 1,1-dichloroethane; cyclic ester solvents such as γ-butyrolactone (GBL), γ-valerolactone, and δ-valerolactone; amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone (NMP), and N,N'-dimethylimidazolidinone (DMI); sulfoxide solvents such as dimethyl sulfoxide; aromatic solvents such as toluene, xylene, and benzene; and alcohol solvents such as methanol, ethanol, isopropanol, n-butanol, 2-butanol, methyl cellosolve, ethyl cellosolve, and butyl cellosolve. From the viewpoint of easy removal of the solvent from the dope, the solvent preferably contains methylene chloride. The solvent may consist of one kind or two or more kinds.

[0048] The solvent preferably contains 50% by mass or more of methylene chloride, more preferably 60% by mass or more, and even more preferably 70% by mass or more. The solvent may contain only methylene chloride, or may contain methylene chloride and an alcohol solvent. The alcohol solvent is preferably ethanol. When the solvent is a mixed solvent of methylene chloride and an alcohol solvent, the mass ratio of the methylene chloride to the alcohol solvent is preferably 99:1 to 60:40, more preferably 95:5 to 70:30, and even more preferably 90:10 to 75:25.

[0049] (ultraviolet absorber) The dope of this embodiment may further contain an ultraviolet absorber.

[0050] The molecular weight of the ultraviolet absorber is preferably 680 or less, more preferably 600 or less, and even more preferably 500 or less. The molecular weight of the ultraviolet absorber is preferably 100 or more, more preferably 150 or more, and even more preferably 200 or more. The amount of the ultraviolet absorber added is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, based on the total solid content of the dope, from the viewpoint of imparting the necessary ultraviolet absorbing performance. The amount is preferably 10% by mass or less, more preferably 5% by mass or less, from the viewpoint of effectively exhibiting the properties attributable to other components contained in the dope.

[0051] Examples of ultraviolet absorbers include benzophenone compounds, salicylate compounds, benzoate compounds, triazole compounds, and triazine compounds. Examples of benzophenone compounds include 2,4-dihydroxybenzophenone, 4-n-octyloxy-2-hydroxybenzophenone, and 2,2'-dihydroxy-4,4'-dimethoxybenzophenone. Examples of salicylate compounds include pt-butylphenyl salicylate. Examples of benzoate compounds include 2,4-di-t-butylphenyl-3',5'-di-t-butyl-4'-hydroxybenzoate. Examples of triazole compounds include 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol], 2-(3,5-di-tert-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(2H-benzotriazol-2-yl)-p-cresol, 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-benzotriazol-2-yl-4,6-di-tert-butylphenol, 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-t-butylphenol, 2-(2H-benzotriazol-2-yl)-4,6-di-t-butylphenol, and 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol. Examples of triazine compounds include 2-mono(hydroxyphenyl)-1,3,5-triazine compounds, 2,4-bis(hydroxyphenyl)-1,3,5-triazine compounds, and 2,4,6-tris(hydroxyphenyl)-1,3,5-triazine compounds. Commercially available ultraviolet absorbers include "Tinuvin (registered trademark) 928" (molecular weight 442) (manufactured by BASF Japan Ltd.), "ADK STAB (registered trademark) LA-32" (molecular weight 225), "ADK STAB (registered trademark) LA-31" (molecular weight 659), "ADK STAB (registered trademark) LA-29" (molecular weight 323), and "ADK STAB (registered trademark) LA-24" (molecular weight 447) (each manufactured by ADEKA Corporation), and "Eversorb (registered trademark) BL4" (manufactured by Everlight Chemical Co., Ltd.).The dope may contain only one type of ultraviolet absorber or may contain two or more types of ultraviolet absorbers. In addition, as the ultraviolet absorber, an ultraviolet absorber that easily absorbs light of longer wavelengths may be used to cut blue light.

[0052] From the viewpoint of efficient film production, the viscosity of the dope is preferably from 1 to 500,000 cP, more preferably from 100 to 100,000 cP, and even more preferably from 1,000 to 50,000 cP.

[0053] From the viewpoint of efficient film production, the solid content of the dope is preferably 5 to 40% by mass, more preferably 8 to 35% by mass, and even more preferably 10 to 30% by mass. The contents of the polymer and silica particles in the dope can be appropriately adjusted so that the solid content of the dope is within the above range. The polymer content of the total solid content of the dope is preferably 80 to 99.99% by mass, more preferably 80 to 99.95% by mass, and even more preferably 90 to 99% by mass. Furthermore, the silica particle content of the total solid content of the dope is preferably 0.01 to 10% by mass, more preferably 0.05 to 8% by mass, and even more preferably 0.01 to 5% by mass.

[0054] The dope may contain, in addition to the polymer having the structural unit derived from α-methylene lactone, other polymers, other additives, etc., depending on the desired film properties.

[0055] Examples of other polymers include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, and poly(4-methyl-1-pentene); halogen-containing polymers such as vinyl chloride and chlorinated vinyl resin; acrylic polymers such as polymethyl methacrylate; styrene polymers such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, and acrylonitrile-butadiene-styrene block copolymer; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyamides such as nylon 6, nylon 66, and nylon 610; polyacetal; polycarbonate; polyphenylene oxide; polyphenylene sulfide; polyether ether ketone; polysulfone; polyethersulfone; polyoxybenzylene; polyamide imide; cellulose derivatives such as triacetyl cellulose, diacetyl cellulose, and cellulose propionate; elastic organic fine particles such as polybutadiene rubber and acrylic rubber; and rubbery polymers such as ABS resin and ASA resin blended with polybutadiene rubber or acrylic rubber. The content of the other polymers is preferably 0 to 50% by mass, more preferably 0 to 40% by mass, even more preferably 0 to 30% by mass, even more preferably 0 to 20% by mass, and most preferably 0 to 10% by mass, based on the total solid content of the dope.

[0056] Examples of other additives include hindered phenol-based, phosphorus-based, and sulfur-based antioxidants; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fiber and carbon fiber; flame retardants such as tris(dibromopropyl)phosphate, triallyl phosphate, and antimony oxide; antistatic agents such as anionic, cationic, and nonionic surfactants; colorants such as inorganic pigments, organic pigments, and dyes; organic fillers; inorganic fillers such as silicon oxide, zirconium oxide, and titanium oxide; resin modifiers; organic or inorganic fillers; plasticizers; lubricants; antistatic agents; flame retardants; fluidizing agents; and compatibilizers. The dope may contain only one or more of the other additives. The content of the other additives is preferably 0 to 5% by mass, more preferably 0 to 4% by mass, and even more preferably 0 to 3% by mass, based on the total solid content of the dope.

[0057] [Dope manufacturing method] The dope can be prepared by dissolving or dispersing a polymer having structural units derived from α-methylene lactone, silica particles having an average primary particle size of 5 to 100 nm, an ultraviolet absorber, and other optional polymers and additives in a solvent. The method for dissolving or dispersing the polymer, silica particles, ultraviolet absorber, and other optional polymers and additives in a solvent may be, for example, a method in which the polymer, silica particles, ultraviolet absorber, and other optional polymers and additives are introduced into a solvent and mixed by appropriate shearing and / or stirring. The order in which the polymer, silica particles, ultraviolet absorber, and other optional polymers and additives are introduced into the solvent is not particularly limited. The polymer, silica particles, ultraviolet absorber, and other optional polymers and additives may be introduced all at the same time or sequentially. The polymer, silica particles, ultraviolet absorber, and other optional polymers and additives may be premixed, preferably by heating and melting, and then melt-kneaded by appropriate application of shear force to prepare a resin composition (e.g., a pellet-shaped or powder-shaped resin composition), which is then mixed with a solvent to prepare the dope. In these mixing steps, the temperature and pressure can be appropriately adjusted. In addition, if the raw materials used for preparing the dope are liquid (including the case where the raw materials are dissolved in a solvent and then added), they may be filtered before use, and after the above-mentioned mixing step, the obtained dope may be filtered and / or degassed. As a filtration method, known filters such as disc filters and pleated filters can be used, and the filtrate may be roughly filtered using a wire mesh or the like before filtration, or may be passed through pores in order from larger to smaller diameters. The filtration accuracy is preferably 0.1 to 20 μm, more preferably 1 to 15 μm, and even more preferably 2 to 10 μm. As a defoaming method, known methods such as vacuum defoaming and ultrasonic defoaming can be used. When vacuum defoaming is performed, it is preferable to appropriately adjust the vacuum level so that the dope placed in the dissolution tank does not develop skin on the surface. It is also preferable to keep the dissolution tank filled with the vapor of the solvent used.

[0058] [Method of manufacturing optical film] The method for producing an optical film of the present embodiment includes a step of forming a film from a dope containing the polymer having the structural unit derived from α-methylene lactone, silica particles having an average primary particle size of 5 to 100 nm, and a solvent by a solution casting method to obtain a film.

[0059] The solution casting method may be a conventionally known method, for example, a solution casting method including the steps of preparing the above-mentioned dope, coating the dope on a support, and removing the solvent from the coated dope to obtain a film.

[0060] The support may be any of the conventional supports used in solution casting. Examples of such supports include metal supports such as stainless steel endless belts and rotating metal drums, films (e.g., plastic films such as polyimide films and polyester films (biaxially oriented polyethylene terephthalate films)), and glass. The dope may be applied by any of the conventional methods used in solution casting. Examples of such methods include coating using a die coater, doctor blade coater, roll coater, comma coater, lip coater, etc.

[0061] The method for removing the solvent from the dope to obtain a film may be a conventional method used in a solution casting method. For example, a method in which the dope is heated to volatilize the solvent may be mentioned. The drying temperature may be appropriately set depending on the solvent used. For example, in the drying process of the optical film of this embodiment, the temperature may be gradually increased within a range of 40 to 180°C in order to prevent bumping of the solvent.

[0062] Furthermore, from the viewpoint of suppressing condensation on the film surface, drying may be performed in dry air. Furthermore, drying may be performed from the support side using radiant heat from a heater or the like. The film may be peeled off from the support after drying. Alternatively, the film may be dried to a degree that allows it to become self-supporting, and then peeled off from the support, followed by additional drying. Additional drying may involve drying while holding both ends in the width direction with a tenter, optionally adjusting the expansion or contraction of the film according to sagging or shrinkage due to drying, or drying by passing the film alternately through multiple rolls arranged above and below in an oven (vertical pass method). Whether the tenter method or the vertical pass method is used can be selected appropriately depending on the amount of solvent remaining in the film, and both methods may be performed, or multiple times.

[0063] The thickness of the unstretched film is preferably 60 to 200 μm, more preferably 70 to 180 μm, and even more preferably 80 to 160 μm, from the viewpoint of stretching at a sufficient areal ratio in the subsequent stretching step.

[0064] The unstretched film contains the solvent (residual solvent) used in preparing the dope. The amount of the residual solvent in the unstretched film is preferably 0 to 2% by mass, more preferably 0.01 to 1% by mass, and even more preferably 0.02 to 0.8% by mass, from the viewpoints of exhibiting the strength and hardness properties of the film and suppressing expansion and contraction of the film after stretching.

[0065] If necessary, the unstretched film obtained by the solution casting method may be stretched to form a stretched film.

[0066] The film may be stretched by any conventionally known stretching method, including, for example, uniaxial stretching such as free-width uniaxial stretching and fixed-width uniaxial stretching, and biaxial stretching such as sequential biaxial stretching and simultaneous biaxial stretching.

[0067] The stretching temperature when stretching the film is preferably around the glass transition temperature of the polymer. More specifically, it is preferably (glass transition temperature - 30)°C to (glass transition temperature + 100)°C, more preferably (glass transition temperature - 20)°C to (glass transition temperature + 50)°C, and even more preferably (glass transition temperature - 10)°C to (glass transition temperature + 30)°C.

[0068] The areal magnification when stretching the film of this embodiment is, for example, 1.8 to 10 times, and from the viewpoint of improving the strength and hardness of the film after stretching, it is preferably 2 to 7 times, more preferably 2.2 to 6 times, even more preferably 2.5 to 5 times, and even more preferably 2.6 to 4.5 times.

[0069] The thickness of the stretched film obtained by the above-mentioned film production method is preferably 10 to 60 μm, more preferably 15 to 55 μm, and even more preferably 20 to 50 μm.

[0070] By using the dope of this embodiment to obtain a film by a solution casting method, the film has sufficient anti-blocking properties even if it contains silica particles with a small particle size, such as an average primary particle size of 5 to 100 nm. This is presumably because the silica particles contained in the dope are pushed up to the surface of the film as the solvent evaporates, and are unevenly distributed on the surface of the film. Furthermore, since the average primary particle size of the silica particles is sufficiently small, the film also has excellent transparency.

[0071] In the solution casting method, it is not necessary to heat the dope to a high temperature (about 250 to 300°C) during film formation, and a film can be obtained under relatively low temperature conditions (for example, about 40 to 180°C as mentioned above). Therefore, as the UV absorber that can be contained in the dope, a UV absorber with a lower molecular weight and lower heat resistance can be used compared to the UV absorber used when obtaining a film by the melt extrusion method, and further, the content thereof can be reduced. Therefore, when obtaining a film by the solution casting method, by appropriately selecting the UV absorber when preparing the dope to be used in the solution casting method, desired properties not available in films obtained by the melt extrusion method can be imparted.

[0072] [Optical film] The optical film (stretched film) of this embodiment contains a polymer having a structural unit derived from α-methylene lactone and silica particles having an average primary particle size of 5 to 100 nm.

[0073] The content of the polymer having a structural unit derived from α-methylene lactone in the optical film is preferably 80 to 99.99 mass%, more preferably 85 to 99.95 mass%, and even more preferably 90 to 99.9 mass%, and the content of silica particles in the optical film is preferably 0.01 to 10 mass%, more preferably 0.05 to 8 mass%, and even more preferably 0.01 to 5 mass%.

[0074] The polymer having a structural unit derived from α-methylene lactone and the silica particles having an average primary particle diameter of 5 to 100 nm may be the same as those contained in the dope. The optical film of this embodiment can be obtained by the method using the dope.

[0075] The optical film may contain a solvent. The solvent is derived from the solvent used in preparing the dope. The content of the solvent in the optical film may be 10 to 10,000 ppm by mass. The content of the solvent in the optical film is preferably 5,000 ppm by mass or less, more preferably 3,000 ppm by mass or less, and even more preferably 1,000 ppm by mass or less. The content of the solvent in the optical film is preferably 15 ppm by mass or more. The content of the solvent in the optical film can be determined using gas chromatography (manufactured by Shimadzu Corporation, device name: GC-2014). Specifically, the mass of the film is measured, and the solvent content in the optical film can be calculated by dissolving the film in N,N-dimethylacetamide and then quantifying the amount of solvent by gas chromatography.

[0076] The transmittance of the optical film of this embodiment to light with a wavelength of 380 nm is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less. The transmittance of the optical film of this embodiment to light with a wavelength of 380 nm can be measured, for example, by the method described in the Examples.

[0077] The total light transmittance of the optical film of this embodiment is preferably 91% or more, more preferably 92% or more. The total light transmittance of the optical film of this embodiment can be measured, for example, by the method described in the Examples.

[0078] The internal haze of the optical film of this embodiment is preferably 1.0 or less, more preferably 0.6 or less, and even more preferably 0.3 or less. The internal haze is the degree of light scattering throughout the film (total haze) minus the influence of reflection on the film surface. The internal haze of the optical film of this embodiment can be measured, for example, by the method described in the Examples.

[0079] The optical film of this embodiment can be applied to, for example, optical components. Specific examples of applications include light guide members, film applications, lenses (optical lenses, etc.), covers, and foam applications (for example, cushioning materials, heat-insulating materials, vibration-damping materials, soundproofing materials, sealing materials, packing materials, etc.). Furthermore, since the optical film of this embodiment has excellent strength and hardness, it is suitable for flexible display applications, and is particularly suitable as an outermost cover window. It is also suitable as a protective film for each layer of a flexible display. Specifically, it can be used by laminating it with another film such as thin-film glass or transparent polyimide. Furthermore, it can also be used as a protective film for an anti-reflection layer, a touch panel, a base portion, etc.

[0080] The film roll of this embodiment is formed by winding the optical film. [Example]

[0081] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Various physical properties were measured and evaluated as follows.

[0082] [Weight average molecular weight (Mw) and number average molecular weight (Mn) of polymer] The weight-average molecular weight and number-average molecular weight of the polymer were determined in terms of polystyrene using gel permeation chromatography (GPC) using the following apparatus and conditions: System: Tosoh GPC system HLC-8220 Measurement column configuration: Guard column (Tosoh Corporation, TSKguardcolumn SuperHZ-L) Two separation columns (Tosoh Corporation, TSKgel SuperHZM-M) connected in series Reference column configuration: Reference column (Tosoh Corporation, TSKgel SuperH-RC) Developing solvent: chloroform (Fujifilm Wako Pure Chemical Industries, Ltd., special grade) Developing solvent flow rate: 0.6 mL / min Standard sample: TSK standard polystyrene (Tosoh, PS-oligomer kit) Column temperature: 40℃

[0083] [Polymer glass transition temperature (Tg)] The glass transition temperature of the polymer was determined in accordance with the provisions of JIS K 7121. Specifically, using a differential scanning calorimeter (Rigaku Thermo plus EVO DSC-8230) in a nitrogen gas atmosphere, approximately 10 mg of a sample was heated from room temperature to 200°C (heating rate 20°C / min), and the temperature was evaluated by the starting point method from the DSC curve obtained. α-Alumina was used as a reference.

[0084] [Dope viscosity] The viscosity of the dope was measured at 25°C using a BHII type viscometer (manufactured by Toki Sangyo Co., Ltd.).

[0085] [Internal haze of stretched film] The internal haze of the stretched film was determined in accordance with the provisions of JIS K 7136. Specifically, a haze meter (NDH-1001DP, manufactured by Nippon Denshoku Industries Co., Ltd.) was used to measure the internal haze by filling a quartz cell with an optical path length of 10 mm with 1,2,3,4-tetrahydronaphthalene (tetralin), immersing the stretched film in the cell, and calculating the internal haze value per 100 μm.

[0086] [Slipperiness of stretched film] The slipperiness of the stretched film was determined in accordance with the provisions of JIS K 7125. First, a stretched film cut to a size of 80 mm x 100 mm was fixed on a stainless steel plate with the surface held horizontal. Next, a stretched film cut to a size of 70 mm x 100 mm with an auxiliary plate attached to its short edge was placed on top of the fixed stretched film, and a cylindrical weight (540 g, diameter 62 mm) with a 2 mm thick cushioning material attached was placed on top of that. In this state, a spring balance was attached to the auxiliary plate, and the attached spring balance was pulled horizontally at a rate of 300 mm / min. The maximum load indicated by the spring balance before the weight began to move, i.e., the stretched film began to slide against itself, was measured and used as the slipperiness of the stretched film surface. The higher the slipperiness of the stretched film surface, the smaller the measured maximum load value.

[0087] [Total light transmittance of stretched film] The total light transmittance of the stretched film was determined in accordance with the provisions of JIS K 7361. Specifically, it was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., NDH-1001DP).

[0088] [Light transmittance of stretched film] The light transmittance of the stretched film was measured for light with a wavelength of 380 nm using a spectrophotometer (Shimadzu Corporation, UV-3600).

[0089] [Average primary particle diameter of silica particles (TEM diameter)] The average primary particle diameter (TEM diameter) of silica particles was measured by observation with a transmission electron microscope (H-7650, manufactured by Hitachi High-Technologies Corporation). The particles were observed at a magnification of 200,000 times, and the length of each of 100 randomly selected particles in the long axis direction was measured, and the average value was taken as the average primary particle diameter.

[0090] The materials used in the examples are described below. Methyl methacrylate (MMA) and α-methylene-γ-butyrolactone (ML) are commercially available products manufactured by Tokyo Chemical Industry Co., Ltd. Perloyl L (dilauroyl peroxide, LPO) is a commercially available product manufactured by NOF Corporation. Polyoxyethylene distyrylphenyl ether sulfate ester ammonium salt (trade name "Hitenol (registered trademark) NF-08") is a commercially available product manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

[0091] <Production of Polymer 1> A reactor equipped with a stirrer, temperature sensor, cooling tube, and nitrogen inlet tube was prepared. 75 parts by mass of deionized water containing 1 part by mass of Hitenol (registered trademark) NF-08 dissolved as a dispersant was charged into the vessel. A previously prepared mixture of 37.5 parts by mass of MMA, 12.5 parts by mass of ML, and 0.25 parts by mass of LPO (polymerization initiator) was then charged. The mixture in the reactor was then stirred at 3,000 rpm for 15 minutes using a TK homomixer MARK II model 2.5 (manufactured by Primix Corporation) to form a uniform suspension.

[0092] 125 parts by mass of deionized water was added to the suspension and then transferred to a reactor. After transfer, nitrogen gas was blown in while stirring, and the reaction solution (suspension) was heated to 65°C. The reaction started when the internal temperature reached 65°C. The reactor was maintained at 65°C until the liquid temperature reached a peak temperature due to self-heating, after which it was maintained at 75°C. Two hours after the start of the reaction, the reaction solution (suspension) was heated to 90°C and stirred for 4 hours to complete the polymerization reaction. The reaction solution (suspension) was then cooled, and the polymer was collected by filtration. It was then dried using a hot air dryer to obtain Polymer 1 (powder). Polymer 1 had a molecular weight Mw of 283,000, Mn of 129,000, and Tg of 127°C.

[0093] <Production of Polymer 2> Except for using 30 parts by mass of MMA and 20 parts by mass of ML, polymer 2 (powder) was obtained in the same manner as in the production of polymer 1. Polymer 2 had a molecular weight Mw of 263,000, Mn of 117,000, and Tg of 136°C.

[0094] <Preparation of Methanol Dispersion T1 of Silica Particles> A uniform solution was obtained by adding 820 parts by mass of methanol, 161 parts by mass of water, 67.5 parts by mass of 25% aqueous ammonia, and 9 parts by mass of pyridine to a stainless steel vessel equipped with a stirrer, a dropping port, and a thermometer, and stirring for 30 minutes. The solution was adjusted to 49-51°C and stirred, while a premixed solution of 284 parts by mass of tetramethyl orthosilicate (TMOS) and 124 parts by mass of methanol was added dropwise from the dropping port over 1 hour. After the dropwise addition, hydrolysis was continued for 1 hour, yielding an alcoholic solution dispersion 1 of silica particles. The TEM diameter of the obtained silica particles (i.e., silica particles before surface treatment) was 22 nm. The obtained dispersion 1 was again heated to 50°C, and 13.1 parts by mass of phenyltrimethoxysilane (KBM-103, manufactured by Shin-Etsu Chemical Co., Ltd.) and 21.1 parts by mass of hexamethyldisilazane (SZ-31, manufactured by Shin-Etsu Chemical Co., Ltd.) were added dropwise from the dropping port over 6 hours. After the completion of the addition, the mixture was allowed to age for 1 hour, thereby obtaining an alcoholic solution dispersion 2 of silica particles having methacrylic groups. Next, using a commercially available ultrafiltration membrane equipped with a ceramic tubular ultrafiltration membrane with a molecular weight cutoff of approximately 10,000, dispersion 2 was subjected to solvent substitution at room temperature while adding methanol appropriately, and concentrated until the SiO2 concentration reached approximately 11%, thereby obtaining methanol dispersion T1 of silica particles with methacrylic groups on the particle surface.

[0095] <Preparation of Silica Particle Methanol Dispersion T2> A stainless steel vessel equipped with a stirrer, a dropping port, and a thermometer was charged with 161 parts by mass of methanol, 22 parts by mass of water, 27 parts by mass of 25% aqueous ammonia, and 1.1 parts by mass of acetone, and the mixture was stirred for 30 minutes to obtain a homogeneous solution. The temperature of the solution was adjusted to 49-51°C, and 57 parts of TMOS was added dropwise through the dropping port over 90 minutes while stirring. After the dropwise addition, hydrolysis was continued for 30 minutes, yielding an alcoholic solution dispersion 3 of silica particles. The TEM diameter of the obtained silica particles (i.e., silica particles before surface treatment) was 70 nm. The obtained dispersion 3 was again heated to 50°C, and 1.9 parts by mass of KBM-103 and 0.8 parts by mass of SZ-31 were added dropwise from the dropping port over 1 hour. After the completion of the dropping, aging was continued for 15 hours to obtain alcoholic solution dispersion 4 of silica particles having phenyl groups and methyl groups on the particle surface. Next, using a commercially available ultrafiltration membrane equipped with a ceramic tubular ultrafiltration membrane with a molecular weight cutoff of approximately 10,000, dispersion 4 was subjected to solvent replacement by adding methanol appropriately at room temperature, and concentrated until the SiO2 concentration reached approximately 11%, thereby obtaining methanol dispersion T2 of silica particles having phenyl groups and methyl groups on the particle surface.

[0096] Example 1 <Production of Dope 1> 96.4 parts by mass of Polymer 1, 0.9 parts by mass of Methanol Dispersion T1 of Silica Particles with an Average Primary Particle Diameter of 22 nm, and 3.5 parts by mass of UV absorber LA-32 (manufactured by ADEKA Corporation) were dissolved in a 9:1 mixed solvent of methylene chloride and ethanol to a solid content of 25% by mass to prepare Dope 1. The viscosity of Dope 1 was 10,000 cP.

[0097] <Production of Stretched Film 1> The dope 1 was cast onto a support (PET film) using a coater to a thickness of 100 μm after drying. The film was heated to 20 to 60°C to evaporate the solvent, and the resulting film was peeled off from the support. The film was dried at 80 to 150°C while applying a tension of 3 kg per 100 cm of width to obtain unstretched film 1. The resulting unstretched film 1 was cut into a size of 96 mm x 96 mm and sequentially biaxially stretched in the machine direction (MD) and transverse direction (TD) at a stretching rate of 300% / min at a temperature of Tg + 18°C. The stretched film was then cooled to obtain a 25 μm stretched film 1. The resulting stretched film 1 had a slipperiness of 1.9 N and a transmittance of 3.9% for light with a wavelength of 380 nm.

[0098] Example 2 <Production of Dope 2> Dope 2 with a solid content of 25% by mass was produced in the same manner as in Example 1, except that 97.4 parts by mass of polymer 1 was used, 0.1 parts by mass of silica particles (R972: Aerosil (Si nanoparticles) manufactured by Evonik) with an average primary particle size of 16 nm was used instead of methanol dispersion T1 of silica particles, and 2.5 parts by mass of LA-24 (manufactured by ADEKA) was used instead of LA-32. The viscosity of dope 2 was 10,000 cP.

[0099] <Production of Stretched Film 2> The dope 2 was cast onto a support (PET film) using a coater to a dry thickness of 150 μm, heated to 20 to 60°C to evaporate the solvent, and the resulting film was peeled off from the support. The film was dried at 80 to 150°C while applying a tension of 3 kg per 100 cm width to obtain unstretched film 2. The resulting unstretched film 2 was cut into a size of 96 mm x 96 mm and sequentially biaxially stretched in the machine direction (MD) and transverse direction (TD) at a stretching rate of 300% / min at a temperature of Tg + 18°C, followed by cooling to obtain stretched film 2 of 50 μm. The resulting stretched film 2 had a slipperiness of 1.8 N and a transmittance of 1.8% for light with a wavelength of 380 nm.

[0100] Example 3 <Production of Dope 3> Dope 3 with a solid content of 25% by mass was produced in the same manner as in Dope 1 in Example 1, except that 98.9 parts by mass of Polymer 2 was used instead of Polymer 1, 0.1 parts by mass of silica particles (R812: Aerosil (Si nanoparticles) manufactured by Evonik) with an average primary particle size of 50 nm was used instead of Silica Particle Methanol Dispersion T1, and 1.0 part of Eversorb BL4 (manufactured by Everlite Chemical Co.) was used instead of LA-32. The viscosity of Dope 3 was 15,000 cP.

[0101] <Production of Stretched Film 3> A stretched film 3 having a thickness of 25 μm was obtained in the same manner as in the production of stretched film 1 in Example 1, except that dope 3 was used instead of dope 1. The obtained stretched film 3 had a slipperiness of 2.2 N and a transmittance of 0.1% for light with a wavelength of 380 nm.

[0102] Example 4 <Production of Dope 4> Dope 4 having a solid content of 25% by mass was produced in the same manner as in Example 1, except that methanol dispersion T2 of silica particles having an average primary particle size of 70 nm was used instead of methanol dispersion T1 of silica particles. The viscosity of dope 4 was 10,000 cP.

[0103] <Production of Stretched Film 4> A 40 μm stretched film 4 was obtained in the same manner as in the production of stretched film 1 in Example 1, except that dope 4 was used instead of dope 1 and sequential biaxial stretching was performed to an areal stretching ratio of 2.5. The obtained stretched film 4 had a slipperiness of 1.1 N and a transmittance of 2.6% for light with a wavelength of 380 nm.

[0104] (Comparative Example 1) <Production of Dope 5> Dope 5 having a solid content of 25% by mass was prepared in the same manner as in Example 1, except that the methanol dispersion T1 of silica particles and the ultraviolet absorber LA-32 were not used. The viscosity of Dope 5 was 10,000 cP.

[0105] <Production of Stretched Film 5> A stretched film 5 having a thickness of 25 μm was obtained in the same manner as in the production of stretched film 1 in Example 1, except that dope 5 was used instead of dope 1. The obtained stretched film 5 had a slipperiness of 4.0 N or more and a transmittance of 90% or more for light with a wavelength of 380 nm.

[0106] (Comparative Example 2) <Production of Dope 6> Dope 6 having a solid content of 25% by mass was prepared in the same manner as in Example 1, except that 0.1 parts by mass of silica particles (KE-P30, manufactured by Nippon Shokubai Co., Ltd.) having an average primary particle size of 300 nm was used instead of the methanol dispersion T1 of silica particles, and LA-32, an ultraviolet absorber, was not used. The viscosity of Dope 6 was 10,000 cP.

[0107] <Production of Stretched Film 6> A stretched film 6 having a thickness of 25 μm was obtained in the same manner as in the production of the stretched film 1 in Example 1, except that dope 6 was used instead of dope 1. The obtained stretched film 6 had a slipperiness of 1.0 N and a transmittance of 90% or more for light with a wavelength of 380 nm.

[0108] Table 1 shows the results of measuring the content and average primary particle diameter of silica particles contained in the film, total light transmittance, internal haze, lubricity, and transmittance of light with a wavelength of 380 nm for the above stretched films 1 to 6.

[0109] [Table 1]

Claims

1. a polymer having a structural unit derived from α-methylene lactone; Silica particles having an average primary particle size of 5 to 100 nm; A solvent; Including, dope.

2. 2. The dope according to claim 1, wherein the average primary particle size of the silica particles is 5 to 80 nm.

3. The dope according to claim 1 , wherein the solvent comprises methylene chloride.

4. The dope according to claim 1, further comprising an ultraviolet absorber having a molecular weight of 680 or less.

5. A method for producing an optical film, comprising a step of obtaining a film by a solution casting method using the dope according to any one of claims 1 to 4.

6. a polymer having a structural unit derived from α-methylene lactone; Silica particles having an average primary particle size of 5 to 100 nm; An optical film comprising:

7. 7. The optical film according to claim 6, wherein the average primary particle diameter of the silica particles is 5 to 80 nm.

8. The optical film according to claim 6, further comprising a solvent in an amount of 10 to 10,000 ppm by mass.

9. The optical film of claim 8 , wherein the solvent comprises methylene chloride.

10. The optical film according to claim 6 , further comprising an ultraviolet absorber having a molecular weight of 680 or less.

11. The optical film according to claim 6 , which has a transmittance of 5% or less for light with a wavelength of 380 nm.

12. A film roll comprising the optical film according to any one of claims 6 to 11 wound thereon.

Images