JP5317950B2 - Manufacturing method of optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably and continuously manufacture an optical film having insufficient mechanical strength for a long period of time without breakage even for both the ends of the film being cut after lateral stretching. <P>SOLUTION: In the method for manufacturing the optical film having tearing strength of &le;0.10 N in the widthwise direction of the film, both the ends of the film are cut with a shear cutter after the lateral stretching at a cutting velocity of &ge;99% to &lt;100% of a transfer velocity of the film during the lateral stretching. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for producing an optical film. More specifically, the present invention relates to a method for producing an optical film in which both ends of the film are cut using a shear cutter after transverse stretching.

  In recent years, the demand for visibility (brighter, easier to see, better contrast, higher viewing angle, etc.) has become stricter as the screen size and usage environment of liquid crystal display devices expand. However, the improvement of the liquid crystal cell body alone cannot sufficiently satisfy the demand for improved visibility, so it largely depends on the performance improvement of optical films such as retardation films, and various optical films have been developed and put into practical use. It is being advanced.

  In an optical film, in order to make it into a product shape or to cut off both ends where thickness and end face shape are not uniform, cutting may be performed at the time of manufacture. Known methods for cutting optical films include air cutting using a plate blade and score cutting (push cutting) using a round blade. One of the optical film cutting methods involves rubbing the upper and lower blades. It is known to use a shear cutter that performs cutting by shearing by continuous rotation (scissors cutting) (for example, Patent Documents 1 and 2). The shear cutter has a smooth cut surface and is therefore suitably used for a member that requires high cut accuracy.

  On the other hand, in order to satisfy various required characteristics of optical films, various materials such as resin films containing thermoplastic polymers have been studied. Acrylic polymers represented by polymethylmethacrylate (PMMA) have been developed as optical films because of their excellent optical properties such as high light transmittance and wavelength dependency of low refractive index (for example, patent documents). 3). Moreover, since the styrene-type polymer represented by polystyrene can express a negative phase difference, examination to apply to a negative phase difference film is made | formed (for example, patent document 4).

  However, when a resin containing an acrylic polymer or a styrene polymer is used as a film, cracks and the like are likely to occur during production, and there is room for improvement in mechanical strength. In order to improve the mechanical strength of an optical film such as an acrylic polymer or a styrene polymer, stretching is performed, the polymer chain is oriented by stretching, and the film is perpendicular to the stretching direction. It is known that the flexibility when bent at a point is improved.

JP 2006-289601 A JP 2009-154252 A JP-A-3-194503 JP 2007-72201 A

  However, optical films with insufficient mechanical strength, including acrylic polymers and styrene polymers, may have insufficient strength improvement depending on the stretching conditions and direction even when stretched. In some manufacturing processes, the film may break.

  Specifically, when the film is stretched laterally with a tenter, the film is stretched while holding the both ends of the film with clips of the tenter while the film is heated, and after the stretching, clip marks are generated at both ends of the film. Therefore, both ends of the film are usually cut before the film is wound. In transverse stretching, the film is stretched in the width direction of the polymer, and the polymer chains of the polymer are oriented in the width direction of the film. Therefore, the tear strength in the film flow direction perpendicular to the width direction of the film increases, but the width direction of the film The tear strength of is not improved. Therefore, in the step of cutting the film after transverse stretching, there has been a problem that tearing occurs in the width direction of the film and the film is broken.

  The present invention has been made in view of the above problems, and its purpose is to provide an optical film with insufficient mechanical strength for a long time without breaking even when both ends of the film are cut after transverse stretching. It is to produce stably and continuously.

  The present invention is a method for producing an optical film having a tear strength of 0.10 N or less in the width direction of the film, and is cut at 99% or more and less than 100% of the film conveyance speed during transverse stretching using a shear cutter after transverse stretching. It is a manufacturing method of the optical film which cuts the both ends of a film at speed.

  When the stretching ratio of the transverse stretching is T and the stretching ratio of the longitudinal stretching performed before the transverse stretching is M1, the ratio T / M1 of the stretching ratio is preferably 0.70 <T / M1 <2.30. .

  It is preferable to attach a protective film before winding up the optical film.

  The optical film is preferably made of a thermoplastic resin containing an acrylic polymer and / or a styrene polymer.

  The retardation Rth in the thickness direction of the optical film is preferably −30 nm or less.

According to the present invention, an optical film having insufficient mechanical strength can be produced stably and continuously.

The present invention is described in detail below. In the following description, unless otherwise specified, “part” means “part by mass”. In addition, “A to B” indicating a range indicates that the range is A or more and B or less.

<Optical film>
The tear strength in the width direction of the optical film in the present invention is 0.10 N or less. Preferably it is 0.08N or less, More preferably, it is 0.07N or less, More preferably, it is 0.06N or less, Most preferably, it is 0.05N. In an optical film having a tear strength in the width direction of the film exceeding 0.10 N, the effects of the present invention may not be sufficiently exhibited.

  The film thickness of the optical film is preferably 1 μm or more and 500 μm or less, more preferably 10 μm or more and 350 μm or less, and further preferably 10 μm or more and 100 μm or less. If the film thickness is thinner than 1 μm, the strength is poor, which is not preferable.

  The glass transition temperature of the optical film is preferably 110 ° C. or higher. More preferably, it is 115 degreeC or more, More preferably, it is 120 degreeC or more. When the glass transition temperature is 110 ° C. or higher, the flexibility of the optical film is lowered, so that breakage is likely to occur during production, and the effects of the present invention are remarkably seen. Here, the glass transition temperature is a temperature at which a polymer molecule starts micro-Brownian motion, and there are various measurement methods. In the present invention, a differential scanning calorimeter (DSC) conforms to JIS-K7121. This is defined as the temperature obtained by the starting point method.

  The optical film preferably has a total light transmittance of 90% or more, more preferably 92% or more.

  The optical film has a folding strength of 100 times in the MIT folding test conducted so that the bending direction is parallel to the film flow direction during film formation under the condition of a load of 200 g measured according to JIS P8115. The number is preferably 200 times or more, more preferably 200 times or more, still more preferably 300 times or more, and particularly preferably 400 times or more. When the folding endurance in the folding endurance test is less than 100 times, tearing in the flow direction of the film is more likely to occur than in the width direction of the film, and the transverse stretching operation itself may be difficult. Absent.

  The in-plane retardation Re and the thickness direction retardation Rth of the optical film in the present invention can be appropriately set according to the type of liquid crystal cell used in the display device and the performance of other optical compensation layers to be combined. is there.

  The absolute value of the thickness direction retardation Rth of the optical film is preferably 30 nm or more. More preferably, they are 30 nm or more and 1000 nm or less, More preferably, they are 30 nm or more and 500 nm or less, Especially preferably, they are 30 nm or more and 200 nm or less. When the optical film exhibits a negative retardation, the thickness direction retardation Rth is preferably −30 nm or less. More preferably, it is -1000 nm or more and -30 nm or less, More preferably, it is -500 nm or more and -30 nm or less, Most preferably, it is -200 nm or more and -30 nm or less. In order to set the absolute value of the phase difference to 30 nm or more, that is, to set the negative phase difference to -30 nm or less, the range of stretching conditions such as the stretching ratio and the temperature of the transverse stretching becomes narrow, and thus the effect of the present invention is remarkable. Become.

  The in-plane retardation Re of the optical film is preferably 30 nm or more. More preferably, they are 30 nm or more and 1000 nm or less, More preferably, they are 30 nm or more and 500 nm or less, Especially preferably, they are 30 nm or more and 300 nm or less.

The in-plane retardation Re here is
Re = (nx−ny) × d
The thickness direction retardation Rth is
Rth = [(nx + ny) / 2−nz] × d
Defined. Nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the direction perpendicular to nx in the film plane, nz is the refractive index in the film thickness direction, and d is the film thickness (nm). . The slow axis direction is a direction in which the refractive index in the film plane is maximum.

  The optical film in the present invention is preferably made of a thermoplastic resin. A known thermoplastic resin can be used as the thermoplastic resin. The thermoplastic resin is not particularly limited as long as it is softened by heating and exhibits plasticity and solidifies when cooled. For example, polyethylene, polypropylene, ethylene-propylene copolymer, olefin polymer such as poly (4-methyl-1-pentene), norbornene polymer; halogen-containing polymer such as vinyl chloride and chlorinated vinyl resin; polystyrene, styrene-methacrylic acid Styrenic resin such as methyl copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer; acrylic resin such as polymethyl methacrylate; polyester such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate Polyamides such as nylon 6, nylon 66 and nylon 610; celluloses such as triacetyl cellulose; polyacetals; polycarbonates; polyphenyleneoxy ; Polyphenylene sulfide; polyether ether ketone; polyether nitrile; polysulfone; polyether sulfone; polyoxyethylene Penji alkylene; polyamideimide, and the like, may be contained two or more of these. Amorphous thermoplastic resins are preferred for optical applications, and examples include acrylic resins, styrene resins, and cycloolefin polymers (olefin resins).

  The optical film in the present invention is preferably made of a thermoplastic resin containing an acrylic polymer and / or a styrene polymer. Since an optical film made of a thermoplastic resin containing an acrylic polymer and / or a styrene polymer is brittle, it is easily broken during production, and the effects of the present invention become remarkable.

  The glass transition temperature of the thermoplastic resin is preferably 110 ° C. or higher. More preferably, it is 110 degreeC or more and 300 degrees C or less, More preferably, they are 115 degreeC or more and 250 degrees C or less, Most preferably, they are 120 degreeC or more and 200 degrees C or less. When the glass transition temperature is 110 ° C. or higher, the flexibility of the optical film is lowered, so that breakage is likely to occur during production, and the effects of the present invention are remarkably seen.

  When the optical film contains an acrylic polymer, the content of the acrylic polymer in the optical film is preferably 30% by mass or more, more preferably 50% by mass or more, still more preferably 70% by mass or more, and particularly preferably. 90% by mass or more, and most preferably 95% by mass or more. The acrylic polymer is suitable as an optical film because it has excellent optical properties such as high light transmittance and wavelength dependency of low refractive index.

  When the optical film contains a styrene polymer, the content of the styrene polymer in the optical film is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more. Preferably it is 90 mass% or more, Most preferably, it is 95 mass% or more. Since the styrenic polymer has negative intrinsic birefringence, it becomes possible to give a negative retardation to the optical film, and the retardation of the obtained optical film can be made negative.

  In addition, the positive / negative of the intrinsic birefringence of the polymer is the molecular chain in the layer out of light incident perpendicularly to the principal surface of the layer in a layer (for example, a sheet or film) in which the molecular chain of the polymer is uniaxially oriented. Can be determined based on a value “n1−n2” obtained by subtracting the refractive index n2 of the layer with respect to the vibration component perpendicular to the alignment axis from the refractive index n1 of the layer with respect to the vibration component parallel to the direction (orientation axis) of the film. The intrinsic birefringence value can be determined by calculation based on the molecular structure of each polymer. In addition, the intrinsic birefringence of the resin is determined by the balance of intrinsic birefringence of each polymer and additive contained in the resin.

  Furthermore, when the optical film is made of a thermoplastic resin containing an acrylic polymer and a styrene polymer, the total content of the acrylic polymer and the styrene polymer in the optical film is preferably 30% by mass or more. More preferably, it is 50 mass% or more, More preferably, it is 70 mass% or more, Especially preferably, it is 90 mass% or more, Most preferably, it is 95 mass% or more. When the film contains an acrylic polymer and a styrene polymer, the excellent optical properties of the acrylic polymer and the styrene polymer become a thermoplastic resin having both negative intrinsic birefringence and a negative retardation. It can be suitably used for an optical film having a retardation, particularly a retardation film.

  As the acrylic polymer, a known acrylic polymer containing a structural unit derived from (meth) acrylic acid ester can be used. The total content of the structural units derived from the (meth) acrylic acid ester of the acrylic polymer is preferably 10% by mass or more, more preferably 30% by mass or more, still more preferably 50% by mass or more, and even more particularly preferably. Is 70% by mass or more. The acrylic polymer may introduce a ring structure into the main chain by copolymerization with a monomer having a ring structure, a cyclization reaction after polymerization, or the like. In this case, if the total of the structural units derived from the (meth) acrylic acid ester and the ring structure is 50% by mass or more of the total structural units, an acrylic polymer is obtained.

  Examples of (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and t-butyl (meth) acrylate. , N-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate , (Meth) acrylic acid 3-hydroxypropyl, (meth) acrylic acid 2,3,4,5,6-pentahydroxyhexyl, (meth) acrylic acid 2,3,4,5-tetrahydroxypentyl, 2- ( Α-hydroxyacrylic acids such as hydroxymethyl) methyl acrylate and 2- (hydroxyethyl) methyl acrylate Chill is a structural unit derived from the monomers such. The acrylic polymer particularly preferably has a methyl (meth) acrylate unit, and in this case, the optical properties and thermal stability of the molded product are improved. The acrylic polymer may have two or more of these structural units as (meth) acrylic acid ester units.

  The acrylic polymer may have a structural unit other than the (meth) acrylic acid ester unit. When a cyclic structure is introduced into the main chain by a cyclization reaction, the acrylic polymer is preferably copolymerized with a monomer having a hydroxyl group or a carboxylic acid group at the time of polymerization. Specifically, as a monomer having a hydroxyl group, methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, 2- (hydroxymethyl) acrylic Acid butyl, 2- (hydroxyethyl) methyl acrylate, and (meth) acrylic acid units as monomers having a carboxylic acid group include, for example, acrylic acid, methacrylic acid, crotonic acid, 2- (hydroxymethyl) acrylic Examples thereof include structural units derived from monomers such as acid and 2- (hydroxyethyl) acrylic acid. Two or more kinds of these monomers may be copolymerized. A monomer having a hydroxyl group or a carboxylic acid group changes to a ring structure by a cyclization reaction, but is derived from a monomer having an unreacted hydroxyl group or carboxylic acid group in an acrylic polymer having a ring structure in the main chain. A structural unit may be included.

  The weight average molecular weight of the acrylic polymer is preferably 10,000 to 500,000, more preferably 50,000 to 300,000.

  The styrenic polymer is not particularly limited, and a known styrenic polymer containing a structural unit derived from a styrenic monomer can be used. The styrenic monomer is not particularly limited, and examples thereof include styrene, vinyl toluene, α-methyl styrene, α-hydroxymethyl styrene, α-hydroxyethyl styrene, and chlorostyrene. The content of the structural unit derived from the styrenic monomer of the styrenic polymer is preferably 10% by mass or more, more preferably 30% by mass or more, still more preferably 50% by mass or more, and even more preferably 70% by mass. That's it. The styrenic polymer may introduce a ring structure into the main chain by copolymerization with a monomer having a ring structure, a cyclization reaction after polymerization, or the like. In this case, if the total of the structural units derived from the styrenic monomer and the ring structure is 50% by mass or more of the total structural units, the styrenic polymer is obtained.

  Specific types of the styrenic polymer are not particularly limited. For example, polystyrene, styrene-methyl (meth) acrylate copolymer, acrylonitrile-styrene copolymer, acrylonitrile-styrene-maleimide copolymer, styrene-butadiene. It may be a block copolymer. A styrene polymer containing a structural unit derived from a vinyl cyanide monomer such as acrylonitrile or methacrylonitrile is preferable because it has excellent compatibility with an acrylic polymer, and includes a structural unit derived from acrylonitrile. Styrenic polymers are more preferred, and acrylonitrile-styrene copolymers and acrylonitrile-styrene-maleimide copolymers are particularly preferred.

  Whether or not the styrene polymer has compatibility with the acrylic polymer can be confirmed by measuring the Tg of the resin obtained by mixing the two by the method described later. In general, if only one Tg of the resin is confirmed, it can be said that the styrene polymer is compatible with the acrylic polymer.

  When the styrenic polymer is an acrylonitrile-styrene copolymer, the ratio of the styrene units in all the structural units of the copolymer is not particularly limited, but it is usually in the range of about 60 to 80% by mass. .

  When the styrenic polymer is an acrylonitrile-styrene-maleimide copolymer, the proportion of styrene units in all the structural units of the copolymer is not particularly limited, but is usually in the range of about 55 to 80% by mass. Good.

  The styrenic polymer may contain a rubbery polymer having a styrenic polymer in the graft chain. The rubbery polymer having a styrene polymer in the graft chain is not particularly limited. For example, it is produced by polymerizing a monomer containing a styrene monomer in the presence of fine particle acrylic rubber, butadiene rubber or the like. Is possible.

  The rubbery polymer having a styrene polymer in the graft chain is preferably a rubber polymer having a styrene polymer containing a structural unit derived from acrylonitrile in the graft chain. When the graft chain contains a structural unit derived from acrylonitrile, the compatibility with the acrylic polymer is improved, so that the rubbery polymer is uniformly dispersed in the resin, and the total light transmittance of the obtained retardation film is increased. improves. Specific examples include ASA resin, ABS resin, and AES resin obtained by grafting acrylonitrile-styrene copolymer to acrylic rubber, butadiene rubber, or ethylene-propylene rubber, and does not reduce the negative intrinsic birefringence of the styrene polymer. Therefore, ASA resin is particularly preferable.

  The weight average molecular weight of the styrenic polymer is preferably 10,000 to 500,000, more preferably 50,000 to 300,000.

  When the optical film includes a polymer having a structural unit derived from a (meth) acrylic acid ester and a structural unit derived from a styrene monomer, the structural unit derived from a (meth) acrylic acid ester and the styrene monomer 10 mass% or more is preferable, as for the sum total of the content rate of the derived structural unit, More preferably, it is 30 mass% or more, More preferably, it is 50 mass% or more, More preferably, it is 70 mass% or more. In this case, when the structural unit derived from the (meth) acrylic ester is the same amount as the structural unit derived from the styrene monomer or more than the structural unit derived from the styrene monomer, the polymer is acrylic. This is a polymer. Moreover, when there are few structural units derived from a (meth) acrylic acid ester than the structural unit derived from a styrene-type monomer, this polymer shall be a styrene-type polymer.

  Moreover, this acrylic polymer is not specifically limited, You may have another structural unit. Moreover, this styrene-type polymer is not specifically limited, You may have another structural unit. Such structural units include, for example, acrylonitrile, methacrylonitrile, methallyl alcohol, allyl alcohol, ethylene, propylene, 4-methyl-1-pentene, vinyl acetate, 2-hydroxymethyl-1-butene, methyl vinyl ketone, It is a structural unit derived from a monomer such as N-vinylpyrrolidone or N-vinylcarbazole. The acrylic polymer and the styrene polymer may have two or more of these structural units.

  The acrylic polymer is not particularly limited, but preferably has a ring structure in the main chain. The styrenic polymer is not particularly limited, but preferably has a ring structure in the main chain. When the main chain has a ring structure, the heat resistance of the obtained optical film is improved. As the ring structure of the main chain, N-substituted maleimides such as cyclohexylmaleimide, methylmaleimide, phenylmaleimide, benzylmaleimide, or a ring structure derived from N-substituted maleimide by copolymerization with maleic anhydride or anhydride-derived Or a lactone ring structure, a glutaric anhydride structure, a glutarimide structure, a ring structure derived from an N-substituted maleimide, or the like may be introduced into the main chain by a cyclization reaction after polymerization. Good. From heat resistance, lactone ring structure, cyclic imide structure (ring structure derived from N-alkyl-substituted maleimide, glutarimide ring, etc.) and cyclic acid anhydride structure (ring structure derived from maleic anhydride, glutaric anhydride, etc.) What has is preferable. A lactone ring structure, a glutarimide ring structure, and a glutaric anhydride structure are preferred because they can impart positive intrinsic birefringence to the resin and, as a result, can impart a positive retardation to the resulting optical film. Among these, those having a lactone ring structure in the main chain are particularly preferred from the viewpoint of optical properties such as wavelength dependency.

  The lactone ring structure of the main chain may be a 4- to 8-membered ring, but a 5- to 6-membered ring is more preferable, and a 6-membered ring is still more preferable in terms of structural stability. In addition, when the main chain lactone ring structure is a 6-membered ring, the synthesis yield is high in synthesizing the polymer before introducing the lactone ring structure into the main chain, and the content ratio of the lactone ring structure is high. The structure represented by the following general formula (1) is preferable from the viewpoint that a polymer is easily obtained and that the copolymerizability with a (meth) acrylic acid ester such as methyl methacrylate is good.

(In the formula, R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom. Examples of the group include an alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, and a propyl group; an unsaturated aliphatic hydrocarbon group having 1 to 20 carbon atoms such as an ethenyl group and a propenyl group. An aromatic hydrocarbon group having 1 to 20 carbon atoms, such as a phenyl group or a naphthyl group; one or more hydrogen atoms in the alkyl group, the unsaturated aliphatic hydrocarbon group and the aromatic hydrocarbon group; Is a group substituted with at least one group selected from a hydroxyl group, a carboxyl group, an ether group and an ester group.)
When the acrylic polymer or the styrene polymer has a ring structure in the main chain, the content of the ring structure is not particularly limited, but is usually 5 to 90% by mass, preferably 10 to 70% by mass, 60 mass% is more preferable, and 10-50 mass% is further more preferable. When the said content rate becomes small too much, the heat resistance of the resin molded product obtained by shape | molding resin may fall, or solvent resistance and surface hardness may become inadequate. On the other hand, when the said content rate becomes large too much, the moldability and handling property of resin will fall.

  The optical film in the present invention is not particularly limited, but is preferably made of a thermoplastic resin including an acrylic polymer having a positive intrinsic birefringence and a styrene polymer having a negative intrinsic birefringence. In this case, the ratio of the content of the acrylic polymer having positive intrinsic birefringence and the content of the styrene polymer having negative intrinsic birefringence is preferably 5/95 to 95/5, more preferably, 10/90 to 90/10, more preferably 20/80 to 80/20, and particularly preferably 50/50 to 80/20. By changing the contents of the acrylic polymer having positive intrinsic birefringence and the styrene polymer having negative intrinsic birefringence, the retardation of the optical film can be controlled in a wide range from positive to negative.

  The acrylic polymer and the styrene polymer are not particularly limited and can be produced by a known production method. For example, the acrylic polymer can be formed by polymerizing a monomer group containing the above-mentioned acrylic acid ester, and the styrene polymer can be formed by polymerizing the monomer group containing the above-mentioned styrene monomer.

  The polymerization method is not particularly limited, and polymerization using a radical or ionic initiator is possible. The polymerization form is not particularly limited, and bulk polymerization, solution polymerization, emulsion polymerization and suspension polymerization can be performed. Moreover, after polymerization, if necessary, treatment such as drying or devolatilization can be performed to obtain powder or pellets.

  An acrylic polymer or a styrene polymer having a ring structure in the main chain can be produced by a known method. An acrylic polymer whose ring structure is a glutaric anhydride structure or a glutarimide structure can be produced, for example, by the method described in WO2007 / 26659 or WO2005 / 108438. An acrylic polymer whose ring structure is a maleic anhydride structure or a structure derived from N-substituted maleimide can be produced, for example, by the method described in JP-A-57-153008 and JP-A-2007-31537. An acrylic polymer whose ring structure is a lactone ring structure can be produced, for example, by the method described in JP-A-2006-96960, JP-A-2006-171464, or JP-A-2007-63541.

  The thermoplastic resin in the present invention may contain other thermoplastic resins other than the acrylic polymer and styrene polymer described above. These other thermoplastic resins are not particularly limited in type, but are, for example, olefin polymers such as polyethylene, polypropylene, ethylene-propylene polymer, poly (4-methyl-1-pentene); vinyl chloride, chlorinated vinyl. Halogen-containing polymers such as resins; 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: polyoxypentylene; polyamideimide; rubber polymer containing polybutadiene rubber, acrylic rubber, butadiene rubber, etc. . The amount of the other thermoplastic resin added is preferably less than 50% by mass, more preferably less than 20% by mass, further preferably less than 10% by mass, and particularly preferably less than 3% by mass.

  When other thermoplastic resins contain a rubbery polymer, an improvement in the bending resistance of the film including the optical film can be expected. When the rubber mass is included, the content of the rubbery polymer in the optical film is preferably less than 30% by mass, more preferably 20% by mass or less, and further preferably 10% by mass or less. Since the rubbery polymer has a graft portion having a composition compatible with an acrylic polymer or a styrene polymer, the rubber mass can be uniformly dispersed in the optical film. Further, the average particle diameter of the rubbery polymer is preferably 300 nm or less, and more preferably 150 nm or less, from the viewpoint of improving transparency when formed into a film.

  The thermoplastic resin in the present invention may contain other additives. Other additives include, for example, retardation adjusting agents such as retardation increasing agents and retardation reducing agents; stabilizers such as retardation stabilizing agents, light-resistant stabilizers, weathering stabilizers, thermal stabilizers; glass fibers and carbon fibers. Reinforcing materials such as: UV absorbers; near infrared absorbers; antioxidants; flame retardants such as tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide; representatives of anionic, cationic, and nonionic surfactants Antistatic agents; Colorants such as inorganic pigments, organic pigments, dyes; Organic fillers, inorganic fillers; Resin modifiers; Plasticizers; Lubricants; Flame retardants; Rubber masses such as ASA and ABS. The addition amount of other additives is, for example, 0 to 5% by mass, preferably 0 to 2% by mass, and more preferably 0 to 0.5% by mass.

  The method for producing the thermoplastic resin in the present invention is not particularly limited, and can be produced by mixing the above-described polymer or resin and a known additive by a known method, if necessary. For example, a film-like thermoplastic resin can be produced by mixing a polymer, a resin, and an additive after dissolving them in a solvent and then forming a film by a solution casting method and drying. Further, the polymer, resin and additive may be melted and mixed with an extruder or the like, and may be pelletized with a pelletizer or the like as necessary.

  The optical film in the present invention includes an antistatic layer, an adhesive layer, an adhesive layer, an easy-adhesion layer, an antiglare layer (non-glare layer), a photocatalyst layer, an antifouling layer, an antireflection layer, and a hard film. Various functional coating layers such as a coating layer, an ultraviolet shielding layer, a heat ray shielding layer, an electromagnetic wave shielding layer, a light diffusing layer, a gas barrier layer, etc. can be laminated or coated on the optical film. The laminated body which laminated | stacked the coated member via the adhesive or the adhesive agent may be sufficient. In addition, the stacking order of each layer is not particularly limited, and the stacking method is not particularly limited.

Although the optical film in this invention is not specifically limited, It is suitable to use for an optical use. Preferably, a polarizer protective film, a retardation film, a viewing angle compensation film, a light diffusion film, a reflection film, an antireflection film, an antiglare film, a brightness enhancement film, a conductive film for a touch panel, used for a polarizing plate for a liquid crystal display device, Examples include protective films for various optical disks (VD, CD, DVD, MD, LD, etc.) substrates, diffusion plates, light guides, retardation plates, prism sheets, etc. Among these, retardation films are particularly preferable. For example, retardation films of various LCDs such as STN type LCD, TFT-TN type LCD, OCB type LCD, VA type LCD, IPS type LCD, retardation film having the function of polarizer protective film, laminated film with polarizing plate It can be suitably used for an optical compensation film and a polarizing plate optical compensation film. In particular, in a retardation film, in order to satisfy the required performance of retardation required in the market, there are many restrictions on stretching conditions such as temperature and magnification, and the effects of the present invention are particularly remarkably exhibited.

<< Optical film manufacturing method >>
Next, the manufacturing method of the optical film of this invention is demonstrated. The manufacturing method of the optical film of this invention is not specifically limited, A well-known manufacturing method is possible.

  Examples of the film forming method before stretching include known film forming methods such as a solution casting method (solution casting method), a melt extrusion method, a calendar method, and a compression molding method. Among these, the solution casting method (solution casting method) and the melt extrusion method are preferable.

  As a specific example of the melt extrusion method, the kneader used for extrusion kneading is not particularly limited. For example, a known kneader such as a single screw extruder, a twin screw extruder, or a pressure kneader is used. Can be used. Moreover, after adding a thermoplastic resin and an additive as needed, and pre-blending with mixers, such as an omni mixer, the obtained mixture may be extrusion-kneaded from a kneader.

  Examples of the melt extrusion method include a T-die method and an inflation method, and the molding temperature at that time is preferably 200 to 350 ° C., more preferably 250 to 300 ° C., still more preferably 255 to 300 ° C., and particularly preferably. Is 260-300 ° C.

  When the T-die method is used, a resin film wound into a roll can be obtained by attaching a T-die to the tip of the extruder and winding the film extruded from the T-die. At this time, it is also possible to control the temperature and speed of winding and to stretch (uniaxial stretching) in the extrusion direction of the film. Further, the film may be stretched in a direction perpendicular to the extrusion direction, and sequential biaxial stretching or simultaneous biaxial stretching may be performed.

  When an extruder is used for extrusion molding, the type is not particularly limited and may be uniaxial, biaxial, or multiaxial, but its L / D value is (L is the value of the extruder) In order to sufficiently plasticize the thermoplastic resin to obtain a good kneaded state, the length of the cylinder, D is the cylinder inner diameter) is preferably 10 or more and 100 or less, more preferably 15 or more and 80 or less, and still more preferably Is 20 or more and 60 or less. When the L / D value is less than 10, the thermoplastic resin cannot be sufficiently plasticized and a good kneaded state may not be obtained. On the other hand, when the L / D value exceeds 100, the resin in the resin may be thermally decomposed due to excessive shearing heat generation on the thermoplastic resin.

  In this case, the set temperature of the cylinder is preferably 200 to 350 ° C or less, more preferably 250 to 300 ° C or less. If setting temperature is less than 200 degreeC, the melt viscosity of a thermoplastic resin will become high too much, and the productivity of a resin film will fall. On the other hand, when the set temperature exceeds 350 ° C., the resin in the thermoplastic resin may be thermally decomposed.

  When an extruder is used for extrusion molding, the shape is not particularly limited, but the extruder preferably has one or more open vent portions. By using such an extruder, the decomposition gas can be sucked from the open vent portion, and the amount of volatile components remaining in the obtained resin film can be reduced. In order to suck the decomposition gas from the open vent portion, for example, the open vent portion may be in a reduced pressure state, and the degree of pressure reduction is preferably in the range of 931 to 1.3 hPa as the pressure of the open vent portion, 798 A range of ˜13.3 hPa is more preferable. When the pressure in the open vent is higher than 931 hPa, volatile components or monomer components generated by the decomposition of the resin are likely to remain in the thermoplastic resin. On the other hand, it is industrially difficult to keep the pressure of the open vent part lower than 1.3 hPa.

  When producing a film before stretching, it is preferable to incorporate a filtration step such as filtration with a polymer filter. By incorporating the filtration step, foreign substances present in the thermoplastic resin can be removed, so that defects in the appearance of the obtained film can be reduced. In addition, at the time of filtration by a polymer filter, a thermoplastic resin will be in a high temperature molten state. For this reason, the thermoplastic resin deteriorates when it passes through the polymer filter, and gas components and colored degradation products formed by the deterioration flow into the resin, and the resulting film has perforations, flow patterns, flow streaks. Such defects may be observed. This defect is particularly apt to be observed during the continuous forming of a film. For this reason, when molding a thermoplastic resin filtered through a polymer filter, the molding temperature decreases the melt viscosity of the thermoplastic resin and shortens the residence time of the thermoplastic resin in the polymer filter, for example 255. It is -350 degreeC and 260-320 degreeC is preferable.

  The configuration of the polymer filter is not particularly limited, but a polymer filter in which a large number of leaf disk filters are arranged in a housing can be suitably used. The filter material of the leaf disk type filter may be any of a type in which a metal fiber nonwoven fabric is sintered, a type in which metal powder is sintered, a type in which several metal meshes are laminated, or a hybrid type in which they are combined. The sintered type is most preferred.

  The filtration accuracy by the polymer filter is not particularly limited, but is usually 15 μm or less, preferably 10 μm or less, more preferably 5 μm or less. When the filtration accuracy is 1 μm or less, the residence time of the thermoplastic resin becomes longer, so that the thermal deterioration of the resin increases, and the productivity of the resin film decreases. On the other hand, if the filtration accuracy exceeds 15 μm, it is difficult to remove foreign substances in the thermoplastic resin.

The filtration area with respect to the resin processing amount per hour in the polymer filter is not particularly limited, and can be appropriately set according to the processing amount of the thermoplastic resin. The filtration area is, for example, 0.001 to 0.15 m ² / (kg / hour).

  The shape of the polymer filter is not particularly limited. For example, an inner flow type having a plurality of resin flow ports and a resin flow path in the center pole; the inner peripheral surface of the leaf disk filter at a plurality of vertices or faces And an external flow type having a resin flow path on the outer surface of the center pole. In particular, it is preferable to use an external flow type in which the resin stays are small.

  Although there is no restriction | limiting in particular in the residence time of the thermoplastic resin in a polymer filter, Preferably it is 20 minutes or less, More preferably, it is 10 minutes or less, More preferably, it is 5 minutes or less. Further, the filter inlet pressure and the filter outlet pressure during filtration are, for example, 3 to 15 MPa and 0.3 to 10 MPa, respectively, and the pressure loss (the pressure difference between the filter inlet pressure and the outlet pressure) is 1 MPa to 15 MPa. A range is preferred. When the pressure loss is 1 MPa or less, the flow path through which the thermoplastic resin passes through the filter tends to be biased, and the quality of the obtained resin film tends to deteriorate. On the other hand, when the pressure loss exceeds 15 MPa, the polymer filter is easily damaged.

  What is necessary is just to set suitably the temperature of the thermoplastic resin introduce | transduced into a polymer filter according to the melt viscosity, for example, it is 250-300 degreeC, Preferably it is 255-300 degreeC, More preferably, it is 260-300 degreeC. is there.

  The specific process of obtaining a resin film with few foreign substances and colored substances by filtration using a polymer filter is not particularly limited. For example, (1) a process of forming and filtering a thermoplastic resin in a clean environment, and subsequently molding the thermoplastic resin in a clean environment; (2) clean the thermoplastic resin having foreign matter or colored matter A process of molding a thermoplastic resin in a clean environment after filtration in an environment; (3) a process of molding a thermoplastic resin having foreign matters or colored substances at the same time as a filtration treatment in a clean environment; Etc. You may perform the filtration process of the thermoplastic resin by a polymer filter in multiple times for each process.

  When filtering the thermoplastic resin with the polymer filter, it is preferable to stabilize the pressure of the thermoplastic resin in the filter by installing a gear pump between the extruder and the polymer filter.

  It is preferable to extrude the thermoplastic resin as it is after the production to obtain a resin film. Compared with the case where the thermoplastic resin is pelletized and then the obtained pellet is remelted to form an optical film, the thermal history can be reduced, so that the thermal deterioration of the thermoplastic resin can be suppressed. Moreover, in this method, since mixing of the foreign material from an environment can be suppressed, it can suppress that a foreign material exists in the obtained optical film or coloring of the obtained optical resin film. A gear pump and a polymer filter are preferably arranged between the extruder and the T die.

  Next, the stretching method used in the method for producing the optical film of the present invention will be described. As the stretching method, a conventionally known stretching method can be applied as long as it includes a step of transverse stretching. From the viewpoint of developing a large in-plane retardation Re and a thickness direction retardation Rth, lateral uniaxial stretching is preferred. Sequential biaxial stretching is also one of the preferred forms in that the necessary in-plane retardation Re and thickness direction retardation Rth are expressed. Furthermore, in order to improve the tear strength in the width direction of the film after transverse stretching, longitudinal and transverse longitudinal stretching, in which longitudinal stretching is further performed in addition to longitudinal and transverse sequential biaxial stretching, is also one of the preferred embodiments. Each stretching process may be performed continuously from the extrusion film forming process or may be performed individually. In addition, what is necessary is just to set extending | stretching conditions, such as a draw ratio, extending | stretching temperature, an extending | stretching speed, suitably according to a desired phase difference and desired bending resistance, and there is no limitation in particular.

  The stretching temperature is preferably around the glass transition temperature of the film raw material polymer or the film before stretching. Specifically, it is preferably performed at (glass transition temperature−30) ° C. to (glass transition temperature + 50) ° C., more preferably (glass transition temperature−20) ° C. to (glass transition temperature + 20) ° C., more preferably. It is (glass transition temperature−10) ° C. to (glass transition temperature + 10) ° C. When it is lower than (glass transition temperature-30) ° C., a sufficient draw ratio cannot be obtained, which is not preferable. When the temperature is higher than (glass transition temperature + 50) ° C., resin flow occurs and stable stretching cannot be performed.

  The draw ratio defined by the area ratio is preferably in the range of 1.1 to 25 times, more preferably in the range of 1.2 to 10 times, and still more preferably in the range of 1.3 to 5 times. If it is smaller than 1.1 times, it is not preferable because it does not lead to the development of retardation performance accompanying to stretching and the improvement of toughness. If it is larger than 25 times, the effect of increasing the draw ratio is not recognized.

  The stretching speed (one direction) is preferably in the range of 10 to 20000% / min, more preferably in the range of 100 to 10000% / min. If it is slower than 10% / min, it takes time to obtain a sufficient draw ratio, and the production cost is increased, which is not preferable. If it is faster than 20000% / min, the stretched film may be broken, which is not preferable.

  Examples of the stretching apparatus include a roll stretching machine, a tenter-type stretching machine, an oven stretching machine, and a small experimental stretching apparatus such as a tensile tester, a uniaxial stretching machine, and a sequential biaxial stretching machine. The retardation film of the present invention can also be obtained using this apparatus. The longitudinal stretching step is usually performed by a roll stretching machine or an oven stretching machine, and the transverse stretching process is often a tenter type stretching machine.

  In the longitudinal stretching, stretching is performed between nip rolls having a difference in peripheral speed, and the mechanical properties in the longitudinal direction are improved by molecular orientation. For longitudinal stretching, using a roll stretching machine, preheating to a temperature for stretching while continuously contacting a large number of rolls, and stretching between nip rolls in a short section (in some cases using an auxiliary heater, etc.) There is a method in which nip rolls are arranged at the inlet and outlet of an oven using an oven stretching machine, and the process from preheating to stretching and cooling is performed in the oven. The ratio of longitudinal stretching is preferably 1.2 to 4.0 times, and more preferably 1.5 to 3.0 times.

  The tenter-type transverse stretching machine includes, for example, an oven including preheating, stretching, and heat treatment zones, and a laterally extending clip travel device. In the transverse stretching process, the lateral edge of the traveling film is gripped with a clip, heated to the stretching temperature in the preheating zone in the oven, stretched in the transverse direction in the stretching zone, and then heat treated in the heat treatment zone if necessary. After cooling. The lateral pulling is performed by opening the guide rail of the clip traveling device and widening the distance between the left and right two rows of clips. The temperature of each zone of preheating and stretching is preferably Tg-10 ° C to Tg + 50 ° C, more preferably Tg-5 ° C to Tg + 30 ° C, where Tg is the glass transition temperature of the optical film. The temperature of the heat treatment zone is preferably −40 ° C. to −2 ° C. and more preferably −35 ° C. to −5 ° C. than the temperature of the stretching zone. Cooling may be performed forcibly by providing a cooling zone, but the temperature can be lowered as the film travels. After cooling, the film is released from the gripped clip and pulled by the downstream take-up roll. The magnification of the transverse stretching is preferably 1.2 to 4.0 times, more preferably 1.5 to 3.5 times.

  In the method for producing an optical film of the present invention, when the stretching ratio of the transverse stretching is T and the stretching ratio of the longitudinal stretching performed before the transverse stretching is M1, the ratio T / M1 of the stretching ratio is 0.70 <T. It is preferable that /M1<2.30. If T / M1 is less than 0.70, the strength balance between the flow direction and the width direction of the film may be lost, and tearing in the flow direction may occur frequently. If T / M1 exceeds 2.30, Control of optical properties may be difficult due to restrictions such as exit width.

  Although not particularly limited, FIG. 1 is a schematic view of an example of an embodiment of the present invention as viewed from the top of a film after transverse stretching, and FIG. 2 is an example of an embodiment of the present invention from an extruder to a winding device. It is the schematic which looked at from the side. After the film after transverse stretching is released from the tenter clip W of the transverse stretching machine, the film is cut at both ends by the shear cutter S through the guide roll G. Further, the film passes through a nip roll N for stabilizing the running of the film, and after being separated from the cut portion (ear) D, the protective film P is pasted and wound up by a winding device R, and a roll-shaped optical film is obtained. Become.

  Before the guide roll G is cut, a plurality of rolls, preferably 2 to 5 rolls, more preferably 2 to 3 rolls, are suitable for the purpose of suppressing vibrations in the transverse stretching step. In addition, the first guide roll that comes into contact with the first after the transverse stretching among the plurality of guide rolls corresponds to the change of the width of the original film before transverse stretching and the transverse stretching ratio. It may be.

  In the method for producing an optical film of the present invention, both ends of the film are cut after transverse stretching. In the transverse stretching process, the clip trace portion of the clip is not stretched and is very fragile. Therefore, stable film running can be obtained by cutting both ends (hereinafter sometimes referred to as trimming). The step of cutting can be performed after the film is released from the clip after transverse stretching and before the downstream winding step.

  In the method for producing an optical film of the present invention, a shear cutter is used for cutting both ends of the film. A shear cutter is a device that cuts by shearing by rubbing the upper and lower blades and continuously rotating (scissors), and is suitable for members that require high cutting accuracy because the cutting surface is smooth. ing. In the case of FIG. 2, it is common to cut the film by rotating the upper blade of the shear cutter S counterclockwise and the lower blade clockwise. Both the upper blade and the lower blade may be rotationally driven by a drive roll, or only one of the blades may be rotationally driven, and the other blade may be passively rotated according to the film conveyance.

  In the method for producing an optical film of the present invention, the cutting speed of the shear cutter is 99% or more and less than 100% of the film conveyance speed during transverse stretching. Preferably they are 99.0% or more and 99.8% or less, More preferably, they are 99.0% or more and 99.5% or less. Note that the cutting speed of the shear cutter matches the rotational speed of the blade of the shear cutter, and can be adjusted by the rotational speed of the drive roll of the shear cutter. If the cutting speed of the shear cutter is less than 99% or 100% or more of the film conveyance speed during transverse stretching, the film breaks during production and a roll cannot be obtained stably. When the rotation speeds of the upper blade and the lower blade are different, in the present invention, the rotation speed of the slower blade is the cutting speed of the shear cutter.

  Although it does not specifically limit, FIG. 3 is the schematic which looked at an example of the shear cutter cutting part which is embodiment of this invention from the front in the flow direction (film running direction of FIG. 1). The shear cutter cuts by shearing by rubbing the upper blade S1 and the lower blade S2, but, for example, a structure in which an upper blade having an inclined side surface of the lower blade S2 is rubbed is common. Therefore, when viewed from the side, there is a portion where the upper blade S1 and the lower blade S2 overlap, that is, biting. The biting depth d1 between the upper blade and the lower blade is preferably 0.5 to 3 mm, more preferably 1 to 2 mm. If the biting depth d1 is less than 0.5 mm, cutting failure is likely to occur, so the cut end may not be smooth. If it exceeds 3 mm, the blade edge will be worn significantly, causing malfunction of the device and hindering stable production. There is a fear. Further, the upper blade S1 and the lower blade S2 are not parallel, and for example, it is common to set the upper blade S1 to have a slight inclination with respect to the lower blade S2 when viewed from the front in the film flow direction. The angle θ formed by the upper blade and the lower blade is preferably 0.1 to 1.5 °, more preferably 0.1 to 0.3 °. If the angle θ formed by the upper blade and the lower blade is less than 0.1 °, the cut end may not be finished smoothly. If the angle θ exceeds 1.5 °, the blade edge may be extremely worn, resulting in a cutting failure.

  As the upper blade and the lower blade, any of so-called dish-shaped blades, saddle-shaped blades, and other shapes of circular blades may be used. The material of the upper blade and the lower blade may be made of metal or ceramic, but it is preferable to use cemented carbide or high-speed steel. From the viewpoint of the amount of chips generated and the smoothness of the cut surface, it is preferable to use a cemented carbide blade made of a cemented carbide. The upper blade has a diameter of about 90 mm to 150 mm and a thickness of about 1 mm to 5 mm. The diameter of the lower blade is about 90 mm to 150 mm, and the thickness is about 1 mm to 10 mm.

  In the method for producing an optical film of the present invention, it is not particularly limited, and it is possible to wind the cut film as it is on a roll or after performing a treatment such as knurling, but before winding the optical film. It is preferable to attach a protective film to the optical film. By sticking a protective film, the film after sticking can be transported while suppressing breakage and cracking.

  As a protective film which can be used for this invention, the film by which the adhesion layer was coated or coextruded on the base material is mentioned. Examples of the substrate include polyolefin resins such as polyethylene. The adhesive layer is preferably EVA (ethylene-vinyl acetate copolymer), metallocene L-LDPE (linear low-density polyethylene polymerized using a metallocene catalyst), or the like. The thickness of the protective film is preferably in the range of 10 to 100 μm, and more preferably in the range of 20 to 90 μm.

  The initial adhesive strength of the adhesive layer is preferably in the range of 0.02 N / 50 mm width or more and less than 0.15 N / 50 mm width. In addition, initial adhesive force means the value measured by the 180 degree peeling test based on JISZ-0237. Specifically, PMMA (polymethyl methacrylate) is placed on a stainless steel plate, a test piece (protective film) is attached on PMMA, and the test piece is peeled off at a speed of 300 mm / min in the 180 ° direction. Four loads are measured at intervals of 20 mm, and the average value is defined as the initial adhesive strength. When a protective film having a high adhesive strength such that the initial adhesive strength greatly exceeds 0.15 N / 50 mm width is used, there is a possibility that lateral tearing may occur when the protective film is peeled off in the next step after transverse stretching. Absent.

  The pressure-sensitive adhesive layer in the protective film may be provided over the entire surface in contact with the optical film or provided only in part as long as the protective film can be stably attached to the optical stretched film of the present invention. Also good. Further, one side or both sides of the optical film may be used.

  In the protective film attaching step, the above-described protective film is attached to the optical film obtained after the transverse stretching. The method of sticking the protective film is, for example, by setting a protective film roll on a drive shaft having a motor such as a feeding machine (or unwinding machine) installed below or above the running film line and running. Examples of the method include bonding the optical film and the protective film by pressing them with two rubber rolls.

  In the winding process performed by the next winding apparatus, the optical film (film laminate) is wound into a roll. More specifically, a winding core is set in a winding machine, the said film laminated body is wound around the said winding core, and winding speed is adjusted so that it may become substantially the same speed as the line speed of a film. Here, it is preferable that the optical film is wound into a roll shape by setting the tension taper to a ratio in the range of 5% to 30% and decreasing the tension as the roll diameter increases.

  The initial tension at the time of winding is appropriately set depending on the film thickness of the film to be wound, etc., and can be set, for example, in the range of more than 2N and less than 100N. Furthermore, the said winding speed can be set in the range of 1-100 m / min, for example.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the examples shown below. In the following description, for convenience, “part by mass” may be simply referred to as “part”, and “liter” may be simply referred to as “L”.

<Glass transition temperature>
The glass transition temperature (Tg) of each sample was determined in accordance with JIS K7121 regulations. Specifically, using a differential scanning calorimeter (manufactured by Rigaku, DSC-8230), a sample of about 10 mg was heated from a normal temperature to 200 ° C. at a heating rate of 20 ° C./min in a nitrogen gas atmosphere. It calculated by the starting point method from the DSC curve. Α-alumina was used as a reference.

<Weight average molecular weight>
The weight average molecular weight of the acrylic resin was determined by gel permeation chromatography (GPC) under the following conditions.
System: GPC system HLC-8220 manufactured by Tosoh Corporation
Developing solvent: Chloroform (made by Wako Pure Chemical Industries, special grade), flow rate: 0.6 ml / min Standard sample: TSK standard polystyrene (manufactured by Tosoh Corporation, PS-oligomer kit)
Measurement side column configuration: guard column (manufactured by Tosoh Corp., TSKguardcolumn SuperHZ-L), separation column (manufactured by Tosoh Corp., TSKgel SuperHZM-M) 2 series connection reference side column configuration: reference column (manufactured by Tosoh Corp., TSKgel SuperH-RC) )
<Tear strength>
For the tear strength in the width direction of the film, a test film having a length of 150 mm and a width of 50 mm in which the longitudinal direction is the width direction of the film is prepared in accordance with JIS K7128-1, and a tear tester (Instron Japan Limited) : The model 1185) was used to test the tear line parallel to the width direction of the film at the time of film formation at 23 ° C. under the condition of 200 mm / min. did.

<Folding strength>
In accordance with JIS P8115, the folding strength of the film is determined by allowing a test film having a length of 90 mm and a width of 15 mm to be the width direction of the film to stand at 23 ° C. and 50% RH for 1 hour or longer. And using a MIT folding resistance tester (manufactured by Tester Sangyo Co., Ltd., BE-201 type) under the condition of a load of 200 g so that the fold line is parallel to the film flow direction during film formation. The average value of the number of times until the film of one sample broke was taken as the measurement result.

<Phase difference>
The in-plane retardation Re and the thickness direction retardation Rth of the optical film were measured at a measurement wavelength of 589 nm using a phase difference measuring device (manufactured by Oji Scientific Instruments, KOBRA-WR). The thickness direction retardation Rth was calculated based on a value measured by tilting 40 ° with the slow axis as the tilt axis.
(Production Example 1)
MMA 40 parts, MHMA 10 parts, toluene 50 parts, ADK STAB 2112 (manufactured by ADEKA) 0.025 part was charged into a reaction kettle equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introduction pipe, and nitrogen was passed through this at 105 ° C. When the mixture was heated to reflux and refluxed, 0.05 part of tertiary amyl peroxy isononanoate (manufactured by Arkema Yoshitomi, trade name: Luperox 570) was added as an initiator, and at the same time, tertiary amyl peroxy isononanoate 0. While dropping 1 part over 3 hours, solution polymerization was performed under reflux at about 105 to 110 ° C., and further aging was performed for 4 hours.

  To the obtained polymer solution, 0.05 part of 2-ethylhexyl phosphate (manufactured by Sakai Chemicals, trade name: Phoslex A-8) was added, and a cyclization condensation reaction was performed at 90 to 105 ° C. under reflux for 2 hours. It was. Next, the obtained polymer solution was heated to 240 ° C. through a heat exchanger, barrel temperature 240 ° C., degree of vacuum 13.3 to 400 hPa (10 to 300 mmHg), rear vent number 1 and fore vent number 4 A side feeder is provided between the third vent and the fourth vent (referred to as the first, second, third, and fourth vents from the upstream side), and a leaf disk type polymer filter (filtered at the tip) It was introduced into a vent type screw twin screw extruder (L / D = 52) with a precision of 5 μm) at a processing rate of 65 parts / hour in terms of resin amount, and devolatilized.

  At that time, a separately prepared mixed solution of antioxidant / cyclization catalyst deactivator was added at a rate of 1.05 parts / hour from the back of the first vent, and 1.05 parts / hour of ion-exchanged water. Were charged from the back of the second and third vents, respectively. In the mixed solution of the antioxidant / cyclization catalyst deactivator, 5 parts of antioxidant (manufactured by Ciba Specialty Chemicals, Irganox 1010) and 46 parts of zinc octylate (manufactured by Nippon Chemical Industry Co., Ltd.) as the deactivator , Nikka octix zinc (3.6% by mass) was dissolved in 54 parts of toluene. Moreover, pellets of a styrene-acrylonitrile copolymer (styrene / acrylonitrile ratio was 73 mass% / 27 mass%, weight average molecular weight 220,000) were charged from the side feeder at a charging speed of 35 parts / hour.

By the devolatilization operation, a thermoplastic resin (A) pellet having a negative intrinsic birefringence in which the content of the styrene polymer was 35% by mass was obtained. The glass transition temperature of the thermoplastic resin (A) was 120 ° C., and the weight average molecular weight was 163,000.
Example 1
The resin pellet (A) obtained in Production Example 1 was melt extruded at a temperature of 270 ° C. to form an unstretched film having a thickness of 180 μm, and then heated to a temperature of 150 ° C. and stretched 2.5 times in the longitudinal direction. Went. Next, a position 20 mm from both ends of the film was gripped by a 2 inch clip, supplied to a tenter, and stretched 2.4 times in the transverse direction at a temperature of 133 ° C. The film released from the clip was introduced into the trimming apparatus, and the rotational speed of the drive roll was adjusted so that the cutting speed was 99.4% of the film conveyance speed in the tenter. Here, the upper blade and the lower blade mesh with each other at a depth of 1.5 mm, and both end portions of the film are cut with a shear cutter in which the angle of the upper blade with respect to the lower blade is adjusted to 0.3 °, and the phase difference Rth in the thickness direction An optical film having a film width of 500 mm and a thickness of −90 nm was obtained. The tear strength in the width direction of the optical film was 0.05 N, the glass transition temperature was 120 ° C., and the bending strength by the MIT test was 450 times. Thereafter, a 30 μm-thick polyethylene protective film (trade name: Tretec 7332, manufactured by Toray Film Processing Co., Ltd., initial adhesive strength at 23 ° C .: 0.07 N / 50 mm width) was attached to the optical film. Then, using a winding device (maximum winding width: Φ600 mm), a film roll of 500 m was continuously obtained by winding with an initial tension set to 80 N and a tension taper set to 15%. During that time, no problems such as film breakage occurred.
(Example 2)
The resin pellet (A) obtained in Production Example 1 is melt-extruded at a temperature of 270 ° C. to form an unstretched film having a thickness of 200 μm, and then heated to a temperature of 125 ° C. and stretched 1.8 times in the longitudinal direction. Went. Next, a position 20 mm from both ends of the film was gripped by a 2-inch clip, supplied to a tenter, and stretched 2.8 times in the transverse direction at a temperature of 130 ° C. The film released from the clip was introduced into the trimming apparatus, and the rotation speed of the drive roll was adjusted so that the cutting speed was 99.2% of the film conveyance speed in the tenter. Here, the upper blade and the lower blade mesh with each other at a depth of 1.5 mm, and both end portions of the film are cut with a shear cutter in which the angle of the upper blade with respect to the lower blade is adjusted to 0.3 °. An optical film having a film width of 500 mm and an Rth of −125 nm was obtained. The tear strength in the width direction of the optical film was 0.04 N, the glass transition temperature was 120 ° C., and the bending strength by the MIT test was 820 times. Thereafter, a protective film made of polyethylene having a film thickness of 30 μm (trade name: Toraytec 7332, manufactured by Toray Film Processing Co., Ltd., initial adhesive strength at 23 ° C .: 0.07 N / 50 mm width) was attached. Then, using a winding device (maximum winding width: Φ600 mm), a film roll of 500 m was continuously obtained by winding with an initial tension set to 80 N and a tension taper set to 15%. During that time, no problems such as film breakage occurred.
(Example 3)
The resin pellet (A) obtained in Production Example 1 is melt-extruded at a temperature of 270 ° C. to form an unstretched film having a thickness of 180 μm, and then heated to a temperature of 160 ° C. and stretched 1.8 times in the longitudinal direction. Went. Next, a position 20 mm from both ends of the film was gripped by a 2-inch clip, supplied to a tenter, and stretched 2.2 times in the transverse direction at a temperature of 155 ° C. The film released from the clip is introduced into a trimming device in which the roll rotation speed is adjusted to 99.4% of the film conveyance speed in the tenter, and both ends of the film are cut with a shear cutter, and further in the longitudinal direction at a temperature of 125 ° C. By stretching the film by 1.8 times, an optical film with a film width of 400 mm having a thickness direction retardation Rth of −50 nm was obtained. The tear strength in the width direction of the optical film was 0.05 N, and the bending strength according to the MIT test was 260 times. A 500 m film roll was continuously obtained by pasting and winding a polyethylene protective film on the optical film. During that time, no problems such as film breakage occurred.
(Comparative Example 1)
The same operation as in Example 1 was performed except that the rotation speed of the drive roll was adjusted so that the cutting speed was the same as the film conveyance speed in the tenter, but the film was not able to withstand the tension and was broken and stabilized. Film roll could not be obtained.
(Comparative Example 2)
The same operation as in Example 1 was performed except that the rotational speed of the drive roll was adjusted so that the cutting speed was 98.0% of the film conveying speed in the tenter. A wrinkle occurred and a trimming failure occurred. Further, the film roll was not able to be stably obtained due to breakage from the trimming failure end.

As described above, by using the method for producing an optical film of the present invention, an optical film having excellent optical properties can be produced stably. Therefore, this invention can be used suitably for manufacture of various optical films, such as a protective film, an antireflection film, retardation film, and a polarizing film, used for flat panel display apparatuses, such as a liquid crystal display device.

It is the schematic which looked at the example of embodiment of this invention from the film upper part after transverse stretching. The lower part of the figure is the film traveling direction. It is the schematic which looked at an example of embodiment of this invention from the side after horizontal extending | stretching to a winding apparatus. The right side of the figure is the film traveling direction. It is the schematic which looked at an example of the shear cutter cutting part vicinity which is embodiment of this invention from the flow direction (film running direction of FIG. 1) directly in front.

G: Guide roll S: Shear cutter F: Optical film N: Nip roll D: Cut part (ear)
W: Tenter clip of transverse stretching machine R: Winding device P: Protective film S1: Shear cutter upper blade S2: Shear cutter lower blade θ: Angle formed by upper blade and lower blade d1: Depth of engagement between upper blade and lower blade The

Claims (5)

  A method for producing an optical film having a tear strength of 0.10 N or less in the width direction of the film, wherein both ends of the film are cut at a cutting speed of 99% or more and less than 100% of the film transport speed during transverse stretching using a shear cutter after transverse stretching The manufacturing method of the optical film which cut | disconnects a part.   2. The stretching ratio T / M1 is 0.70 <T / M1 <2.30, where T is the stretching ratio of the transverse stretching and M1 is the stretching ratio of the longitudinal stretching performed before the transverse stretching. The manufacturing method of the optical stretched film as described in any one of.   The manufacturing method of the optical film of Claim 1 or 2 which affixes a protective film before winding up this optical film.   The method for producing an optical film according to any one of claims 1 to 3, wherein the optical film is made of a thermoplastic resin containing an acrylic polymer and / or a styrene polymer. The method for producing an optical film according to claim 1, wherein a retardation Rth in the thickness direction of the optical film is −30 nm or less.

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