JP2012159752A - Method and apparatus for manufacturing optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical film which can obtain an optical film having less appearance defects.SOLUTION: In the method for manufacturing the optical film which includes: a first extrusion step of extruding a melted resin composition with a first extruder 2; a filtration step of making the resin composition extruded by the first extruder 2 pass through a filtration filter device 3 and filtering the passed resin composition; a second extrusion step of extruding the resin composition filtered by the filtration filter device 3 with a second extruder 4 having a vent portion 4a, and film-forming the extruded resin composition into a film shape; and a cooling step of solidifying the resin composition which has been film-formed into the film shape by cooling the film-formed resin composition to obtain an optical film, when the maximum temperature of the resin composition when the resin composition is extruded by the first extruder 2 is set at T1 (°C), and the maximum temperature of the resin composition when the resin composition is extruded by the second extruder 4 having the vent portion 4a is set at T2 (°C), T2 is set to be (T1-50)°C to(T1-5)°C.

Description

  The present invention relates to an optical film manufacturing method and an optical film manufacturing apparatus used for, for example, a liquid crystal display device in order to improve a display image.

  In the liquid crystal display device, various optical films such as a retardation film and a polarizer protective film are used to improve display quality.

  In a liquid crystal display device, an optical film such as a polarizer protective film or a retardation film is laminated on one side or both sides of a liquid crystal cell for the purpose of compensating the optical characteristics of the liquid crystal, improving the viewing angle, improving the contrast, or preventing coloring. Has been.

  The optical film is generally produced by forming a resin material into a film by a casting (solution casting) method, a calendar method, a melt extrusion method, or the like.

  As a resin material for obtaining the optical film, for example, an amorphous resin such as an acrylic resin is widely known. The acrylic resin is excellent in optical transparency.

  A method for producing an optical film in which the acrylic resin is formed by melt extrusion is disclosed in Patent Document 1 below. In Patent Document 1, a raw material composition containing a thermoplastic resin composition containing 20 to 80 parts by mass of an acrylic resin and 80 to 20 parts by mass of a styrene resin and 0.05 to 0.5 parts by mass of a polymer carbon radical scavenger. An optical film is obtained by melt extrusion. Here, using a single screw extruder equipped with a T die, the temperature of the molten resin from the raw material inlet of the single screw extruder to the T die outlet is maintained below the glass transition temperature of the raw material composition + 150 ° C. The raw material composition is melt-extruded.

  Patent Document 1 describes that the single-screw extruder is preferably an extruder including a vent part and a polymer filter, and that the filtration accuracy of the polymer filter is preferably less than 20 μm. Yes.

JP 2009-279787 A

  Although the acrylic resin generally has high optical transparency, for example, when the acrylic resin is melt-extruded at a high temperature of 250 ° C. or higher, foaming may occur due to thermal decomposition.

  On the other hand, if the melt extrusion temperature is lowered to suppress foaming, the melt viscosity of the acrylic resin to be melt extruded may be increased. For this reason, melt extrusion may be difficult. Further, as described in Patent Document 1, the melt-extruded acrylic resin is often passed through a polymer filter in order to remove impurities or gelated products. When the melt viscosity is high, it becomes difficult to filter the melt-extruded acrylic resin through a polymer filter, or the polymer filter is clogged or damaged. On the other hand, if filtration with a polymer filter is not performed, appearance defects are likely to occur in the obtained optical film.

  The objective of this invention is providing the manufacturing method of an optical film and the manufacturing apparatus of an optical film which can obtain an optical film with few external appearance defects.

  According to a wide aspect of the present invention, there is provided a method for producing an optical film in which a resin composition is formed by a melt extrusion method, the first extrusion step of extruding a molten resin composition by a first extruder, and A filtration step of filtering the resin composition extruded by the first extruder through a filtration filter device, and a second extruder having a vent portion of the resin composition filtered by the filtration filter device A first extrusion step of forming a film into a film, and a cooling step of solidifying the resin composition formed into a film by cooling to obtain an optical film, wherein the first When the maximum temperature of the resin composition at the time of extrusion by the extruder is T1 (° C.) and the maximum temperature of the resin composition at the time of extrusion by the second extruder having the vent portion is T2 (° C.) , To a T2 (T1-50) ℃ ~ (T1-5) ℃, manufacturing method of an optical film is provided.

  In a specific aspect of the method for producing an optical film according to the present invention, as the resin composition, 70 to 95% by weight of an amorphous resin, and a thermoplastic elastomer resin that exhibits a phase separation form with respect to the amorphous resin A resin composition containing 5 to 30% by weight is used.

  In another specific aspect of the method for producing an optical film according to the present invention, an acrylic resin, a cyclic olefin resin, or a maleimide resin is used as the amorphous resin.

  In another specific aspect of the method for producing an optical film according to the present invention, a copolymer of a copolymer component containing a butadiene compound and a styrene compound is used as the thermoplastic elastomer resin.

  In still another specific aspect of the method for producing an optical film according to the present invention, as the thermoplastic elastomer resin, the butadiene compound is 10 to 70% by weight, the styrene compound is 3 to 30% by weight, and the acrylic compound 20 is used. A copolymer of copolymer components containing ˜80% by weight is used.

  In another specific aspect of the method for producing an optical film according to the present invention, an optical film having a glass transition temperature of 100 to 180 ° C. is obtained.

  In still another specific aspect of the method for producing an optical film according to the present invention, an optical film having a thickness of 10 to 200 μm is obtained.

  In another specific aspect of the method for producing an optical film according to the present invention, there is further provided a stretching step of stretching the optical film to obtain a stretched optical film.

  Further, according to a wide aspect of the present invention, there is provided an optical film manufacturing apparatus for forming a resin composition by a melt extrusion method, a first extruder for extruding a molten resin composition, and the first extruder. A filtration filter device for filtering the resin composition extruded by the extruder, and a second extruder for extruding the resin composition filtered by the filtration filter device to form a film into a film, The said 2nd extruder is a vent extruder which has a vent part, and the manufacturing apparatus of an optical film is provided.

  In the method for producing an optical film according to the present invention, the resin composition melted by the first extruder is extruded, and then the resin composition extruded by the first extruder is passed through a filter device for filtration. After that, the resin composition filtered by the filtration filter device is extruded and formed into a film by a second extruder having a vent portion, so that an optical film with few appearance defects can be obtained.

  An apparatus for producing an optical film according to the present invention includes a first extruder for extruding a molten resin composition, a filtration filter device for filtering the resin composition extruded by the first extruder, and the filtration A second extruder for extruding the resin composition filtered by the filter device to form a film, and the second extruder is a vent extruder having a vent portion. By using the optical film manufacturing apparatus according to the present invention, an optical film with few appearance defects can be obtained.

FIG. 1 is a schematic configuration diagram illustrating an example of an optical film manufacturing apparatus used in an optical film manufacturing method according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing an enlarged internal structure of the second extruder in the apparatus shown in FIG.

  Details of the present invention will be described below.

  Conventionally, an optical film is generally produced by forming a resin composition into a film by a casting (solution casting) method, a calendar method, a melt extrusion method, or the like. Among them, the melt extrusion method is widely used because an optical film can be obtained with high production efficiency.

  Also in the method for producing an optical film according to the present invention, a resin composition is formed by a melt extrusion method to obtain an optical film.

  The method for producing an optical film according to the present invention includes a first extrusion step of extruding a resin composition melted by a first extruder, and a filtration filter device for extruding the resin composition extruded by the first extruder. A filtration step of passing and filtering, a second extrusion step of extruding the resin composition filtered by the filtration filter device with a second extruder having a vent portion, and forming a film into a film, and a film A cooling step of solidifying the resin composition formed into a film by cooling to obtain an optical film.

  In the optical film manufacturing method according to the present invention, there is provided an optical film manufacturing apparatus in which a first extruder, a filtration filter device, and a second extruder having a vent portion are arranged in this order from the upstream side to the downstream side. Used. The second extruder is a vent extruder having a vent part. The apparatus for producing the optical film is a melt extrusion apparatus.

  Furthermore, in the method for producing an optical film according to the present invention, the maximum temperature of the resin composition at the time of extrusion by the first extruder is T1 (° C.), and at the time of extrusion by the second extruder having the vent portion. When the maximum temperature of the resin composition is T2 (° C.), T2 is set to (T1-50) ° C. to (T1-5) ° C.

  An optical film manufacturing apparatus according to the present invention is an optical film manufacturing apparatus for forming a resin composition by a melt extrusion method, the first extruder for extruding a molten resin composition, A filtration filter device for filtering the resin composition extruded by the first extruder, and a second extruder for extruding the resin composition filtered by the filtration filter device to form a film into a film Prepare. The second extruder is a vent extruder having a vent portion.

  Conventionally, when a resin composition is heated and melted and extruded, the resin may be thermally decomposed to cause foaming. For example, acrylic resins are thermally decomposed when heated to 250 ° C. or higher, and foaming is likely to occur. When foaming occurs, appearance defects occur in the optical film. Furthermore, when the acrylic resin is exposed to a high temperature, on the other hand, a polymer filter is provided at the tip of the extruder in order to remove foreign substances in the resin composition or to remove the gelled product generated during melt extrusion molding. Often installed. If the melt extrusion temperature is lowered to suppress the thermal decomposition of the resin, the viscosity of the resin composition increases. For this reason, clogging of the polymer filter may occur, and it may be difficult to filter the resin composition, or the polymer filter may be damaged by being loaded.

  Therefore, in the conventional optical film manufacturing apparatus, foreign matters or gelled substances are removed by the polymer filter, clogging and breakage of the polymer filter are suppressed, and foaming due to thermal decomposition of the resin is further suppressed. It was difficult to obtain a small optical film.

  On the other hand, from the upstream side to the downstream side, the first extruder, the filtration filter device, and the second extruder having the vent part are used in this order, thereby using the optical film manufacturing apparatus described above. Extruding the resin composition at a relatively high temperature with one extruder and passing it through a filtration filter device, and then extruding the resin composition at a relatively low temperature with a second extruder having the vent portion, By removing the volatile matter by the vent portion in the extruder of No. 2, an optical film with suppressed appearance defects can be obtained.

  Hereinafter, the present invention will be further clarified while describing specific embodiments and examples of the present invention.

  In FIG. 1, the manufacturing apparatus of the optical film used for the manufacturing method of the optical film which concerns on one Embodiment of this invention is shown.

  An apparatus 1 shown in FIG. 1 is an optical film manufacturing apparatus and a melt extrusion apparatus. The apparatus 1 includes a first extruder 2, a filtration filter device 3, and a second extruder 4 from the upstream side to the downstream side.

  The first extruder 2 is provided with a hopper 2a for introducing the resin composition on the upstream side. The apparatus 1 further includes a dryer 11. The dryer 11 is provided in order to dry the pellet-shaped resin composition before extrusion. The pellet-shaped resin composition dried by the dryer 11 is put into the first extruder 2 from the hopper 2a.

  The first extruder 2 is used for extruding a molten resin composition. The first extruder 2 is connected to the filtration filter device 3. In the first extruder 2, the resin composition is heated and melted, kneaded, and extruded. The resin composition extruded by the first extruder 2 is guided to the filtration filter device 3. A polymer filter is preferably used as the filtration filter device 3.

  From the viewpoint of further suppressing clogging and breakage of the filtration filter device 3, when the glass transition temperature of a resin such as an amorphous resin contained in the resin composition is Tg (° C.), the first The maximum temperature T1 of the resin composition during extrusion by the extruder 2 is preferably (Tg + 80) ° C. or higher, more preferably (Tg + 100) ° C. or higher, preferably (Tg + 180) ° C. or lower, more preferably (Tg + 160) ° C. It is as follows. The maximum temperature T1 indicates the maximum temperature at which the resin reaches from when the resin is introduced into the first extruder 2 until the resin is extruded from the first extruder 2.

  The filtration filter device 3 is used for filtering the resin composition extruded by the first extruder 2. By allowing the resin composition extruded by the first extruder 2 to pass through the filtration filter device 3 and filtering, the foreign matters and gelled product contained in the resin composition can be removed. The resin composition filtered by the filtration filter device 3 is guided to the second extruder 4.

  The second extruder 4 is used for extruding the resin composition filtered by the filtration filter device 3. The second extruder 4 has a vent portion 4a. The 2nd extruder 4 has a vent hole in the vent part 4a. The second extruder 4 is a vent extruder. The filtration filter device 3 is connected to the second extruder 4. When the resin composition filtered by the filtration filter device 3 is extruded by the second extruder 4, volatile components are discharged from the vent portion 4 a and removed. For example, volatile matter such as monomers, decomposition resin gas, residual moisture, nitrogen existing in voids, and the like are discharged by the vent portion 4a.

  A die 4 b is attached to the tip of the second extruder 4. A melt of the resin composition is guided to the mold 4b. The resin composition in the second extruder 4 is extruded into a film from the opening of the mold 4b, discharged, and formed into a film. From the viewpoint of further improving the moldability, the mold 4b is preferably a T die. An exhaust duct 12 is preferably provided in the vicinity of the mold 4b.

  In FIG. 2, the internal structure of the 2nd extruder 4 which has the vent part 4a is shown typically.

  As shown in FIG. 2, the 2nd extruder 4 has the screw 31 inside. The screw 31 has a heating and compression unit 31a in which the valley diameter of the screw 31 gradually increases. In the heating and compression unit 31a, the internal space through which the resin composition flows becomes narrow, and the resin composition is compressed. A vent part 4a is provided downstream of the heating and compression part 31a. An optical film with few appearance defects can be obtained by discharging the volatile component in the resin composition compressed in advance by the heating and compression unit 31a by lowering the pressure by the vent unit 4a.

  From the viewpoint of suppressing foaming due to thermal decomposition of the resin contained in the resin composition and obtaining an optical film more excellent due to appearance defects, the maximum temperature of the resin composition at the time of extrusion by the first extruder 2 is T1. T2 is preferably (T1-50) ° C. or higher, when T2 (° C.) is the maximum temperature of the resin composition at the time of extrusion by the second extruder 4 having the vent portion 4a. More preferably, it is (T1-30) ° C. or higher, preferably (T1-5) ° C. or lower, more preferably (T1-10) ° C. or lower. In particular, T2 (° C.) is particularly preferably (T1-50) ° C. to (T1-5) ° C. The maximum temperature T2 indicates the maximum temperature at which the resin reaches after the resin is introduced into the second extruder 4 until the resin is extruded from the second extruder 4.

  A resin film 21 that is a resin composition formed into a film is guided onto the surface of the roll 13. The roll 13 is a cooling roll. It is preferable that the resin film 21 is supplied onto the surface of the roll 13 and pinched. You may provide a touch roll so that the resin film 21 may be pressed with respect to the roll 13 using a touch roll in order to clamp. An air knife or electrostatic pinning may be used instead of the touch roll.

  The resin film 21 cooled by the roll 13 which is a cooling roll is further cooled by the cooling rolls 15 and 16 and solidified. Thereafter, the resin film 21 is taken up and wound up by the pair of take-up rolls 17 and 18. In this way, an optical film can be obtained.

  By using the apparatus 1 described above, an optical film with reduced appearance defects can be obtained. In particular, by setting T2 (° C.) to (T1-50) ° C. to (T1-5) ° C., it is possible to obtain an optical film in which appearance defects are considerably suppressed.

  The obtained optical film is preferably stretched. That is, it is preferable that the film is further provided with a stretching step of stretching the optical film formed into a film after the cooling step to obtain a stretched optical film. By stretching, it can be processed into a retardation film, and an optical film that is a retardation film is obtained. A retardation film that compensates for light distortion when passing through each member such as a liquid crystal or a polarizing plate used in a liquid crystal display device can be obtained by uniaxially or biaxially stretching to impart orientation to the optical film. it can.

  The stretching method is not particularly limited. As the stretching method, a conventionally known stretching method can be used. As the stretching method, a method of uniaxial stretching (longitudinal uniaxial stretching) in the longitudinal direction (length direction), a method of uniaxial stretching (lateral uniaxial stretching) in the transverse direction (width direction), and sequential stretching in both directions (two A method of performing axial stretching) and the like. The ends on both sides in the width direction of the stretched film are preferably removed by cutting.

  Next, the material for obtaining the optical film and the details of the obtained optical film will be described.

(Material for obtaining optical film)
The resin for obtaining the optical film is not particularly limited. The resin for obtaining the optical film is preferably an amorphous resin, and more preferably an acrylic resin, a cyclic olefin resin, or a maleimide resin. Such a resin is thermally decomposed at a high temperature of 250 ° C. or more, and foaming is likely to occur or gelation is likely to occur. On the other hand, such a resin has a high viscosity when the melting temperature is relatively low. Even if it is resin which has such a property, the optical film by which the external appearance defect was suppressed can be obtained by using the apparatus 1. FIG.

  As the resin composition, it is preferable to use a resin composition containing 70 to 95% by weight of an amorphous resin and 5 to 30% by weight of a thermoplastic elastomer-based resin that exhibits a phase separation form with respect to the amorphous resin. . With such a resin composition, it has been extremely difficult to obtain an optical film with few appearance defects in a conventional optical film manufacturing apparatus.

  On the other hand, by using an optical film manufacturing apparatus including the first extruder, the filtration filter device, and the second extruder having the vent portion, an amorphous resin of 70 to 95% by weight is obtained. Even if a resin composition containing 5 to 30% by weight of a thermoplastic elastomer-based resin exhibiting a phase separation form with respect to the amorphous resin is used, an optical film with suppressed appearance defects can be obtained.

[Amorphous resin]
The amorphous resin is not particularly limited. As the amorphous resin, a resin having high transparency, heat resistance and matching with liquid crystal, a small photoelastic coefficient, suitable properties as an optical member, and substantially no crystallinity is preferably used. It is done. In view of such properties, the amorphous resin is preferably an acrylic resin, a cyclic olefin resin, or a maleimide resin. Specific examples of the amorphous resin include an acrylic resin having a (meth) acryloyl group or a (meth) acryloyl group-derived group in the molecular side chain, and an alicyclic hydrocarbon structure in the molecular main chain or side chain. And a maleimide resin having a maleimide structure. As for the said amorphous resin, only 1 type may be used and 2 or more types may be used together.

  The acrylic resin is used for films for optical applications. The acrylic resin can be obtained by homopolymerizing or copolymerizing an acrylate monomer. The acrylate monomer is preferably a resin represented by the following formula (21).

CH ₂ = C (R1) COOR2 (Formula (21))
In the above formula (21), R1 represents a hydrogen atom or a methyl group, and R2 represents an aliphatic hydrocarbon group, an aromatic hydrocarbon group, a hydrocarbon group containing a halogen atom, a hydrocarbon group containing an amine structure, and an ether. A monovalent group selected from the group consisting of a hydrocarbon group containing a structure is shown.

  The acrylic ester monomer is not particularly limited. Examples of the acrylic ester monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, Isobutyl methacrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth ) 2-ethylhexyl acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, n-tridecyl (meth) acrylate, myristyl (meth) acrylate, cetyl (meth) acrylate, (meth) acrylic Stearyl acid, allyl (meth) acrylate, vinyl (meth) acrylate, benzyl (meth) acrylate (Meth) acrylic acid phenyl, (meth) acrylic acid 2-naphthyl, (meth) acrylic acid 2,4,6-trichlorophenyl, (meth) acrylic acid 2,4,6-tribromophenyl, (meth) acrylic acid Isobornyl, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, diethylene glycol monomethyl ether (meth) acrylate, polyethylene glycol monomethyl ether (meth) acrylate, polypropylene glycol monomethyl ether (meth) acrylate , Tetrahydrofluoryl (meth) acrylate, 2,3-dibromopropyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2,2,2-trifluoroethyl (meth) acrylate, (meth) acryl Acid hexafluoroisopropyl Glycidyl (meth) acrylate, 3-trimethoxysilylpropyl (meth) acrylate, 2-diethylaminoethyl (meth) acrylate, 2-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate , 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, (meth) acrylic acid, itaconic acid, crotonic acid, (anhydrous) maleic acid, fumaric acid, 2 -(Meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, neopentyl di (meth) acrylate, dimethylol tricyclodecane di (meth) acrylate, bifunctional epoxy (meth) acrylate, caprolactone modified (Meta) Acrylate, dipentaerythritol hexa (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, trimethylolpropane triacrylate, trimethylolpropane tetraacrylate, (meth) acrylonitrile, N-vinylpyrrolidone, N -Vinyl caprolactam, N-vinyllaurylactam, (meth) acrylamide, dimethyl (meth) acrylamide, diethylaminoethyl (meth) acrylate, PEG # 200 di (meth) acrylate, PEG # 400 di (meth) acrylate, PEG # 600 di (meth) acrylate, polyfunctional urethane acrylate, etc. are mentioned. When obtaining the said acrylic resin, only 1 type may be used for the said acrylic ester-type monomer, and 2 or more types may be used together. The (meth) acryl means acryl or methacryl.

  When obtaining the acrylic resin, a radical polymerizable monomer copolymerizable with the acrylic ester monomer may be used together with the acrylic ester monomer. For example, a vinyl monomer having a polar group may be used. Examples of the radical polymerizable monomer include maleic anhydride and styrene. As for the said radically polymerizable monomer, only 1 type may be used and 2 or more types may be used together.

  Abrasion resistance and heat resistance of the acrylic resin can be enhanced by crosslinking and modifying by various methods. The crosslinking method is not particularly limited. Examples of the crosslinking method include a method in which a crosslinking assistant is added to a (meth) acrylic acid ester monomer and polymerized.

  The said crosslinking adjuvant is not specifically limited. Examples of the crosslinking aid include radical generators such as benzoyl peroxide, divinylbenzene, trimethylolpropane tri (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and 1,9-nonanediol di (meta). And polyfunctional monomers such as acrylate and 1,2,4-benzenetricarboxylic acid triallyl ester. As for the said crosslinking adjuvant, only 1 type may be used and 2 or more types may be used together.

  The content of the acrylate ester monomer is preferably in the range of 5 to 99 mol% of the whole polymer, and more preferably in the range of 30 to 90 mol%.

  As a method for polymerizing the acrylic resin, any of known radical polymerization methods such as bulk polymerization method, solution polymerization method, suspension polymerization method and emulsion polymerization method can be selected. From the viewpoint of the polymerization process, and from the viewpoint of improving the quality of the film, the solution polymerization method and the bulk polymerization method are preferable.

  Conventionally, use of a norbornene resin, which is a kind of the cyclic olefin resin, as an optical material has been studied. Examples of the cyclic olefin resins include ring-opening (co) polymers of norbornene monomers, addition copolymers of norbornene monomers and olefin monomers, addition copolymers of norbornene monomers, and derivatives thereof. It is done. As for the said norbornene-type resin, only 1 type may be used and 2 or more types may be used together. In order to reduce the amount of carbon-carbon unsaturated double bonds and improve the weather resistance, the norbornene-based resin may be saturated by hydrogenation.

  The norbornene monomer constituting the norbornene resin is not particularly limited as long as it is a monomer having a norbornene ring. Examples of the norbornene-based monomer include bicyclic compounds such as norbornene and norbornadiene, tricyclic compounds such as dicyclopentadiene and dihydroxypentadiene, tetracyclic compounds such as tetracyclododecene, pentacyclic compounds such as cyclopentadiene trimer, tetra 7-rings such as cyclopentadiene, alkyl substitutions such as methyl, ethyl, propyl and butyl, alkenyl substitutions such as vinyl, alkylidene substitutions such as ethylidene, phenyls, tolyl and naphthyl Aryl substituents, and ester groups, ether groups, cyano groups, halogen groups, alkoxycarbonyl groups, pyridyl groups, hydroxyl groups, carboxylic acid groups, amino groups, hydroxyl-free groups, silyl groups, epoxy groups, and (meth) acryloyl, etc. Polar groups containing elements other than carbon and hydrogen Substitution products having like. As for the said norbornene-type monomer, only 1 type may be used and 2 or more types may be used together.

  A tricyclic or higher polycyclic norbornene monomer is preferable because it is easily available, has excellent reactivity, and can improve the heat resistance of the optical film. Tricyclic, tetracyclic and pentacyclic norbornene-based monomers are preferable. Monomers are more preferred.

  Examples of the olefin monomer constituting the norbornene resin include, for example, ethylene, propylene, 1-butene, 3-methyl-1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1- Examples include pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene and 1-hexadecene. Since the copolymerizability is high, α-olefin monomers having 2 to 10 carbon atoms are preferable, and ethylene is more preferable.

  As a polymerization method of the cyclic olefin resin, a conventionally known method such as ring-opening metathesis polymerization or addition polymerization can be used.

  Conventionally, use of the maleimide resin as an optical application material has been studied. As said maleimide-type resin, the maleimide-olefin copolymer which uses the following structural component (X1) and the following structural component (X2) as a structural component is mentioned. The maleimide resin can be obtained, for example, by radical copolymerization reaction of maleimides and olefins.

  In said formula (X1), R1 shows a hydrogen atom or a C1-C6 alkyl group.

  R2 and R3 in the above formula (X2) each represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. R2 and R3 may be the same or different.

  Examples of the compound that gives the component (X1) include N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, Ni-propylmaleimide, Nn-butylmaleimide, Ni-butylmaleimide, Ns-butylmaleimide, Nt-butylmaleimide, Nn-pentylmaleimide, Nn-hexylmaleimide, Nn-heptylmaleimide, Nn-octylmaleimide, N-laurylmaleimide, N-stearyl Maleimide, N-cyclopropylmaleimide, N-cyclobutylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N- (2-methylphenyl) maleimide, N- (2-ethylphenyl) maleimide, N- (2-isopropyl) Phenyl) maleimide, N- (3-methylphenyl) Maleimide, N- (3-ethylphenyl) maleimide, N- (4-methylphenyl) maleimide, N- (4-ethylphenyl) maleimide, N- (2,6-dimethylphenyl) maleimide, N- (2,6 -Diethylphenyl) maleimide, N- (2,6-diisopropylphenyl) maleimide, N- (2,4,6-trimethylphenyl) maleimide, N-carboxyphenylmaleimide, N- (2-chlorophenyl) maleimide, N- ( N-substituted maleimides such as 2,6-dichlorophenyl) maleimide, N- (2-bromophenyl) maleimide, N- (perbromophenyl) maleimide, N- (2,4-dimethylphenyl) maleimide and p-tolylmaleimide Can be mentioned. Among these, N-methylmaleimide, N-ethylmaleimide, N-isopropylmaleimide or N-cyclohexylmaleimide is preferable. As for the compound which gives the said structural component (1), only 1 type may be used and 2 or more types may be used together.

  Examples of the compound that gives the component (X2) include isobutene, 2-methyl-1-butene, 2-methyl-1-pentene, 2-methyl-1-hexene, 1-methyl-1-heptene, 1-isooctene, Examples include olefins such as 2-methyl-1-octene, 2-ethyl-1-pentene, 2-methyl-2-butene, 2-methyl-2-pentene, and 2-methyl-2-hexene. Isobutene is preferable from the viewpoint of enhancing the heat resistance, mechanical properties and transparency of the optical film. As for the compound which gives the said structural component (X2), only 1 type may be used and 2 or more types may be used together.

  The content of the constituent component (X1) is preferably in the range of 30 to 70 mol%, more preferably in the range of 40 to 60 mol% of the entire copolymer. If the content of the component (X1) is too small, sufficient heat resistance or transparency may not be obtained. When there is too much content of the said structural component (X1), moldability may fall.

  As the polymerization method of the maleimide resin, any of known polymerization methods such as bulk polymerization method, solution polymerization method, suspension polymerization method and emulsion polymerization method can be selected. From the viewpoint of further enhancing the transparency and color tone of the optical film, the precipitation polymerization method is more preferable.

  The maleimide-olefin copolymer can also be obtained by post-amidating a resin obtained by copolymerization of maleic anhydride and olefins with ammonia or alkylamine.

The photoelastic coefficient of the amorphous resin is preferably 2.0 × 10 ⁻¹¹ Pa ⁻¹ or less. When an optical film is used as a polarizer protective film, various external forces such as a contraction stress of the polarizing plate, a distortion at the time of bonding to the polarizing plate, and a stress due to distortion at the time of incorporation into the display are applied. Stress is generated. In a high temperature and high humidity environment, the contraction stress of the polarizing plate is large. The photoelastic coefficient is defined by the following formula (31), and is a value representing a change in birefringence with respect to a stress generated in the film.

C = Δn / σ Expression (31)
C: Photoelastic coefficient (Pa ⁻¹ )
Δn: expressed birefringence σ: film internal stress (Pa)

The smaller the photoelastic coefficient, the smaller the amount of change in birefringence due to external force. When the photoelastic coefficient is 2.0 × 10 ⁻¹¹ Pa ⁻¹ or less, the optical performance hardly changes greatly due to deformation by an external force, and a more suitable film can be obtained depending on the use of the optical film. The photoelastic coefficient of the amorphous resin is more preferably 1.0 × 10 ⁻¹¹ Pa ⁻¹ or less.

  The glass transition temperature of the amorphous resin is an important factor that affects optical properties or durability. Considering the thermal environment to which the optical film used in the liquid crystal display device is exposed, the glass transition temperature of the amorphous resin is preferably 100 ° C. or higher, and more preferably 110 ° C. or higher.

[Thermoplastic elastomer resin]
As the thermoplastic elastomer resin, a copolymer of a copolymer component containing a butadiene compound and a styrene compound (hereinafter also referred to as copolymer A) is used. By using this copolymer, flexibility and toughness can be enhanced without reducing the heat resistance of the optical film. The copolymer component constituting the copolymer A may contain a copolymer component other than the butadiene compound and the styrene compound. As for the said thermoplastic elastomer resin, only 1 type may be used and 2 or more types may be used together.

  Examples of the copolymer A include, for example, methyl (meth) acrylate-styrene-butadiene copolymer (MBS), styrene-butadiene block copolymer (SB), styrene-ethylene-butylene copolymer (SEBS), Examples include hydrogenated styrene-butadiene block copolymers.

  As the copolymer A, a copolymer of copolymer components containing 10 to 70% by weight of a butadiene compound, 3 to 30% by weight of a styrene compound, and 20 to 80% by weight of an acrylic compound (hereinafter referred to as copolymer). (Also referred to as coalescence A1) is preferably used. The copolymer component constituting the copolymer A1 only needs to contain the butadiene-based compound, styrene-based compound, and acrylic compound in the content described above, and may include other copolymer components. When the butadiene compound constituting the copolymer A1 is 10% by weight or more, the optical film can be further prevented from becoming brittle, and when it is 70% by weight or less, the heat resistance of the optical film is further increased. . When the styrene compound constituting the copolymer A1 is 3% by weight or more, the workability is further improved, and when it is 30% by weight or less, the optical film can be further prevented from becoming brittle. When the acrylic compound constituting the copolymer A1 is 20% by weight or more, the transparency of the optical film can be further increased, and when it is 80% by weight or less, the optical film becomes more brittle. It can be further suppressed.

  The thermoplastic elastomer resin exhibits a phase separation form with respect to the amorphous resin. The thermoplastic elastomer-based resin is preferably insoluble in the amorphous resin and dispersed in the amorphous resin as the matrix phase while maintaining a certain domain structure. After melt-kneading the amorphous resin and the thermoplastic elastomer resin, the amorphous resin constitutes a matrix as a continuous phase, and the thermoplastic elastomer resin forms an island structure in the continuous phase. It is preferable that the thermoplastic elastomeric resin constituting the domain is dispersed in the matrix as a discontinuous phase.

  As the domain size of the thermoplastic elastomer resin dispersed in the matrix phase of the amorphous resin, the aspect ratio obtained by dividing the domain major axis size by the domain minor axis size is preferably 1-50, The domain major axis size is preferably 0.1 to 5 μm. When the aspect ratio is 50 or less, the tear propagation resistance in the principal axis direction of the molecular orientation is further increased, and it is difficult for the film to be cut during the conveyance of the film, and the film is less likely to buckle along the molecular orientation principal axis. When the domain major axis size is 0.1 μm or more, the front retardation R0 and the thickness retardation Rth tend to be in the desired ranges, and the durability under heating is further enhanced. When the domain major axis size exceeds 5 μm, transparency tends to decrease.

  When evaluating the domain dispersion state of the thermoplastic elastomer resin dispersed in the matrix phase of the amorphous resin, the optical film is dyed with ruthenium tetroxide or the like. Next, using an microtome, the optical film is cut to a thickness of about 0.05 μm in the longitudinal and width directions during extrusion molding. The section of the cut optical film is observed using a transmission electron microscope (JEM-1200EXII, manufactured by JEOL Ltd.). In the cross-sectional area of 80 μm × 100 μm, the average dispersion diameter and aspect ratio of the domains of the thermoplastic elastomer resin are measured.

  The difference in refractive index between the amorphous resin and the thermoplastic elastomer resin is preferably 0.2 or less. When the difference in refractive index is 0.2 or less, the transparency or residual retardation of the optical film can be further improved, and optical distortion or the like is further less likely to occur. A more preferable upper limit of the difference in refractive index is 0.1, a more preferable upper limit is 0.05, and a more preferable upper limit is 0.03.

[Other ingredients]
In the above resin composition, an antioxidant such as phenol and phosphorus, an antistatic agent such as amine, an ester of an aliphatic alcohol, a polyhydric alcohol, and the like, as long as the object of the present invention is not impaired. Lubricants such as partial esters, higher fatty acids and their amides, and ultraviolet absorbers such as benzophenone and benzotriazole may be added.

  Specific examples of the antioxidant include 2,6-di-t-butyl-4-methylphenol, 2- (1-methylcyclohexyl) -4,6-dimethylphenol, 2,2-methylene-bis- ( 4-ethyl-6-t-butylphenol) and tris (di-nonylphenyl phosphite). Specific examples of the ultraviolet absorber include pt-butylphenyl salicylate, 2,2′-dihydroxy-4-methoxy-benzophenone and 2- (2′-dihydroxy-4′-m-octoxyphenyl) benzotriazole. Etc. Specific examples of the lubricant include paraffin phenos and hydrogenated oil. Specific examples of the antistatic agent include stearoazitopropyldimethyl-β-hydroxyethylammonium trate.

(Optical film)
In the method for producing an optical film according to the present invention, it is preferable to obtain an optical film having a glass transition temperature of 100 to 180 ° C. In the manufacturing method of the optical film which concerns on this invention, the optical film whose glass transition temperature is 100-180 degreeC can be obtained easily. In particular, the amorphous resin is at least one selected from the group consisting of acrylic resins, cyclic olefin resins, and maleimide resins, and the copolymer A1 is used as the thermoplastic elastomer resin. In such a case, an optical film having a glass transition temperature of 100 to 180 ° C. can be obtained more easily. When the glass transition temperature of the obtained optical film is 100 to 180 ° C., the durability and heat resistance stability of the optical film under high temperature conditions can be further enhanced.

  In the method for producing an optical film according to the present invention, the front retardation R0 (nm) defined by the following formula (11) is 5 or less, and the thickness direction retardation Rth (nm) defined by the following formula (12) ) Is preferably −5 or more and 5 or less. In the method for producing an optical film according to the present invention, an optical film in which the R0 (nm) is 5 or less and the Rth (nm) is −5 or more and 5 or less can be easily obtained.

R0 (nm) = (nx−ny) × d (11)
Rth (nm) = ((nx + ny) / 2−nz) × d (12)
nx: maximum refractive index in the film plane ny: refractive index in the direction perpendicular to the nx direction in the film plane nz: refractive index in the film thickness direction perpendicular to the refractive index directions of nx and ny d: average thickness of the optical film ( nm)

  When R0 (nm) is 5 or less and Rth (nm) is −5 or more and 5 or less, the optical film has sufficient optical properties and contributes to improving the display quality of a liquid crystal display (LCD). To do. Therefore, the optical film can be suitably used as a polarizer protective film. The R0 (nm) is more preferably 2 nm or less. The Rth (nm) is more preferably -3 or more and 3 or less.

  In the method for producing an optical film according to the present invention, it is preferable to obtain an optical film having a haze value of 10% or less. In the method for producing an optical film according to the present invention, an optical film having a haze value of 10% or less can be easily obtained. A preferable upper limit of the haze value is 8%, a more preferable upper limit is 7%, and a more preferable upper limit is 6%. The lower the haze value, the better the transparency of the optical film. If the haze value is too high, light leakage or the like tends to occur when the optical film is used as a polarizer protective film or the like.

  The average thickness of the obtained optical film is not particularly limited. The average thickness of the optical film is preferably in the range of 10 to 100 μm. The more preferable lower limit of the average thickness of the optical film is 20 μm, and the more preferable upper limit is 80 μm. When the average thickness of the optical film is within the above preferable range, the predetermined birefringence developability is not impaired, the material has a certain mechanical strength, and is a member regarded as important when laminated on a liquid crystal display device. Weight reduction can be promoted.

  The surface of the optical film may be subjected to surface activation treatment such as corona treatment, plasma treatment, ultraviolet irradiation and various chemical treatments. Furthermore, various performances can be added to the surface of the optical film by performing various functional coatings, laminating, and the like by coating or vapor deposition, thereby further enhancing the utility value. For example, the optical film is subjected to corona discharge treatment so that the contact degree of water on the surface is about 40 to 50 degrees for the purpose of improving the bonding property with the polarizing plate or the polarizer within a range not impairing the optical characteristics. May be.

  The said optical film is used suitably as a polarizer protective film, and is used more suitably in order to obtain a polarizing plate. The polarizing plate includes a polarizer and the optical film. The polarizer is preferably bonded to the optical film through an adhesive layer. The polarizer is preferably made of a polyvinyl alcohol resin. The adhesive layer is preferably formed of a polyvinyl alcohol resin. The polarizing plate preferably further includes an adhesive layer as the outermost layer.

  Hereinafter, the present invention will be described in more detail with reference to examples of the present invention. The present invention is not limited to the following examples.

Example 1
(1) Preparation of pellets Methyl methacrylate-styrene-maleic acid copolymer (methyl methacrylate component content 55 mol%, styrene component content 30 mol%, maleic acid component content 15 mol%, glass transition temperature Tg : 120 ° C.) 85% by weight, butadiene-styrene-methyl methacrylate-acrylonitrile copolymer (35% by weight of butadiene component as butadiene compound, 10% by weight of styrene component as styrene compound, acrylic A methyl methacrylate component content of 50% by weight and an acrylonitrile component content of 5% by weight (15% by weight) were mixed using a twin-screw extruder to produce pellets as a resin composition.

(2) Production of Polarizer Protective Film by Melt Extrusion Molding Using the apparatus 1 shown in FIG. 1, a polarizer protective film was produced as follows.

  The pellets were put into the first extruder 2 (single screw extruder having a diameter of 50 mm), the pellets were melted in the first extruder 2, and the molten resin composition was extruded from the first extruder 2. The resin composition extruded by the first extruder 2 was filtered through a filtration filter device 3 (disk-type metal sintered filter having a filtration accuracy of 5 μm). The resin composition filtered by the filtration filter device 3 was extruded by a second extruder 4 (single screw extruder having a diameter of φ50 mm) having a vent portion 4a and formed into a film. At this time, volatile components were removed from the vent portion 4a. Furthermore, the resin composition formed into a film was taken up by the cooling roll 13 and solidified by cooling to obtain a polarizer protective film.

  In the manufacturing process of the optical film, the maximum temperature T1 of the resin composition at the time of extrusion by the first extruder 2 was 250 ° C. The maximum temperature T2 (° C.) of the resin composition at the time of extrusion by the second extruder 4 having the vent portion 4a was 230 ° C. The surface temperature of the cooling roll 13 was 120 ° C. The effective width of the polarizer protective film was 600 mm.

  The cooling roll 13 has an outer diameter of 200 mm, an effective width of 900 mm, a material of S45C, a surface that is HCr plated, and a heat medium circulation heating type temperature adjustment mechanism (oil is used as a heat medium). A cooling roll was used.

(3) Production of Polarizing Plate An unstretched PVA film having a thickness of 75 μm formed of polyvinyl alcohol (PVA) having a polymerization degree of 2400 and a saponification degree of 99% was prepared. This unstretched PVA film was washed with water at room temperature and then stretched uniaxially at a stretch ratio of 5 to obtain a stretched PVA film.

  While maintaining the tension of the obtained stretched PVA film, it is immersed in a dyeing bath (an aqueous solution containing 0.5% by weight iodine and 5% by weight potassium iodide) to adsorb the dichroic dye to the stretched PVA film. It was. Thereafter, crosslinking is performed in a crosslinking bath (an aqueous solution containing 10% by weight boric acid and 10% by weight potassium iodide) at 50 ° C. for 5 minutes, dried at 70 ° C. for 5 minutes, and a moisture content is 8% by weight. A film-like polarizer was produced.

  One side of the obtained polarizer protective film was subjected to corona discharge treatment. A / B agent of a two-component mixed aqueous urethane adhesive (Toyo Morton Co., Ltd .: EL-436A / B) is mixed at 10/3 (weight ratio) with water so that the solid content is 10% by weight. Diluted to prepare an adhesive solution. Using the Mayer bar # 8, the obtained adhesive solution was applied to the corona discharge treated surface of the polarizer protective film to form an adhesive layer on one surface of the polarizer protective film. A polarizer protective film having an adhesive layer formed on one side was attached to both sides of the polarizer from the adhesive layer side to obtain a sandwich-like laminate. This laminate was stored in a 45 ° C. constant temperature bath for 72 hours, dried and cured to prepare a polarizing plate.

(Example 2)
75% by weight of methyl methacrylate-styrene-maleic acid copolymer (methyl methacrylate component content 55 mol%, styrene component content 30 mol%, maleic acid component content 15 mol%, Tg: 120 ° C.), Butadiene-styrene-methyl methacrylate-acrylonitrile copolymer (butadiene content 20% by weight, styrene component content 10% by weight, methyl methacrylate component content 65% by weight, acrylonitrile component content 5% by weight) 25 % By weight was mixed using a twin screw extruder to produce pellets as a resin composition.

  A polarizer protective film and a polarizing plate were produced in the same manner as in Example 1 except that the obtained pellet was used.

(Example 3)
A polarizer protective film was obtained in the same manner as in Example 1 except that the maximum temperature T1 of the resin composition at the time of extrusion by the first extruder 2 was changed to 240 ° C.

(Example 4)
A polarizer protective film was obtained in the same manner as in Example 1 except that the maximum temperature T1 of the resin composition during extrusion by the first extruder 2 was changed to 260 ° C.

(Example 5)
A polarizer protective film was obtained in the same manner as in Example 1 except that the maximum temperature T2 (° C.) of the resin composition at the time of extrusion by the second extruder 4 having the vent portion 4a was changed to 220 ° C. It was.

(Example 6)
A polarizer protective film is obtained in the same manner as in Example 1 except that the maximum temperature T2 (° C.) of the resin composition at the time of extrusion by the second extruder 4 having the vent portion 4a is changed to 240 ° C. It was.

(Comparative Example 1)
A polarizer protective film was obtained in the same manner as in Example 1 except that the resin composition filtered by the filtration filter device 3 was directly guided to the mold and extruded without using the second extruder 4. In Comparative Example 1, the volatile matter was not removed by the vent part.

(Comparative Example 2)
Without using the second extruder 4, the resin composition filtered by the filtration filter device 3 was directly guided to the mold and extruded, and the highest resin composition at the time of extrusion by the first extruder 2. It tried to obtain a polarizer protective film like Example 1 except having changed temperature T1 into 220 degreeC.

  As a result, the temperature of the resin composition when passing through the filtration filter device 3 was too low, the filtration filter device 3 was clogged during extrusion, and the filtration filter device 3 was damaged when the extrusion was continued for a long time. Therefore, the comparative example 2 was not evaluated as described later.

(Comparative Example 3)
A polarizer protective film was obtained in the same manner as in Example 1 except that the resin composition extruded by the first extruder 2 was directly guided to the second extruder 4 without using the filter device 3. .

(Evaluation)
(1) Glass transition temperature Tg
Using a differential scanning calorimeter (“DSC2920 Modulated DSC” manufactured by TA Instruments), the glass transition temperature at the final temperature rise of the obtained polarizer protective film was measured under the following temperature program conditions.

Temperature program conditions:
The temperature is raised from room temperature to 50 ° C. at a rate of 10 ° C./min, and held at 50 ° C. for 5 minutes. Next, the temperature is raised from 50 ° C. to 200 ° C. at a rate of 10 ° C./min and held at 200 ° C. for 5 minutes. Next, the temperature is lowered from 200 ° C. to −50 ° C. at a rate of 10 ° C./min, and held at −50 ° C. for 5 minutes. Next, the temperature is raised from −50 ° C. to 200 ° C. at a rate of 10 ° C./min, and held at 200 ° C. for 5 minutes.

(2) Appearance defects The polarizer protective films (raw film) obtained in Examples and Comparative Examples were continuously unwound and uniaxially stretched in the width direction at a draw ratio of 2.0 using a tenter stretching machine. Thus, a stretched optical film was obtained.

The stretched optical film was cut into an area of 0.1 m ² and sandwiched between polarizing plates in a crossed Nicol state to obtain a sample. The obtained sample was placed on a work table having a desktop illuminance of 1000 lux, and the number of point defects having a size of 100 μm or more was visually counted using reflected light and transmitted light.

  The results are shown in Table 1 below.

DESCRIPTION OF SYMBOLS 1 ... Apparatus 2 ... 1st extruder 2a ... Hopper 3 ... Filtration filter apparatus 4 ... 2nd extruder 4a ... Vent part 4b ... Mold 11 ... Dryer 12 ... Exhaust duct 13 ... Roll 15,16 ... Cooling roll 21 ... Resin film 31 ... Screw 31a ... Heating and compression part

Claims (9)

A method for producing an optical film for forming a resin composition by a melt extrusion method,
A first extrusion step of extruding a molten resin composition by a first extruder;
A filtration step of filtering the resin composition extruded by the first extruder through a filtration filter device;
A second extrusion step of extruding the resin composition filtered by the filtration filter device with a second extruder having a vent portion and forming a film into a film;
A cooling step of solidifying the resin composition formed into a film by cooling to obtain an optical film,
The maximum temperature of the resin composition at the time of extrusion by the first extruder is T1 (° C.), and the maximum temperature of the resin composition at the time of extrusion by the second extruder having the vent portion is T2 (° C.). In this case, T2 is set to (T1-50) ° C. to (T1-5) ° C.   The resin composition comprising 70 to 95% by weight of an amorphous resin and 5 to 30% by weight of a thermoplastic elastomer-based resin that exhibits a phase separation form with respect to the amorphous resin is used as the resin composition. 2. A method for producing an optical film according to 1.   The method for producing an optical film according to claim 2, wherein an acrylic resin, a cyclic olefin resin, or a maleimide resin is used as the amorphous resin.   The method for producing an optical film according to claim 2 or 3, wherein a copolymer of a copolymer component containing a butadiene compound and a styrene compound is used as the thermoplastic elastomer resin.   As the thermoplastic elastomer resin, a copolymer of a copolymer component containing 10 to 70% by weight of a butadiene compound, 3 to 30% by weight of a styrene compound, and 20 to 80% by weight of an acrylic compound is used. Item 5. A method for producing an optical film according to Item 4.   The manufacturing method of the optical film of any one of Claims 1-5 which obtains the optical film whose glass transition temperature is 100-180 degreeC.   The manufacturing method of the optical film of any one of Claims 1-6 which obtains the optical film whose thickness is 10-200 micrometers.   The method for producing an optical film according to claim 1, further comprising a stretching step of stretching the optical film to obtain a stretched optical film. An apparatus for producing an optical film for forming a resin composition by a melt extrusion method,
A first extruder for extruding the molten resin composition;
A filtration filter device for filtering the resin composition extruded by the first extruder;
A second extruder for extruding the resin composition filtered by the filtration filter device and forming a film into a film,
The apparatus for producing an optical film, wherein the second extruder is a vent extruder having a vent portion.

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