JP6247526B2 - Manufacturing method of optical film - Google Patents

Description

  The present invention relates to a method for producing an optical film.

  Optical transparency and optical homogeneity are required for an optical film typified by a polarizer protective film for protecting a polarizer and a film substrate for a liquid crystal display device.

  As a method for producing such an optical film, a melt extrusion method is known in which a resin composition as a film raw material is melted with a melt extruder and extruded into a film form from a die. About the film obtained by this method, in order to reduce thickness unevenness and surface unevenness and improve surface smoothness, a film-like molten resin extruded from a die by a melt extrusion method is sandwiched between a pair of smoothing rolls. A method for forming a film is known (see Patent Document 1 and Patent Document 2).

JP 2000-280268 A JP 2008-55890 A

  In this sandwich molding method, the film can be uniformly smoothed with a low linear pressure by using an elastic roll having a metal film on the surface as one of the smoothing rolls.

  However, under the normal conditions of the sandwich molding method as described above, the surface smoothness necessary for an optical film may not be achieved due to the characteristics of the resin composition itself as a film raw material. Particularly when the resin composition contains fine rubber particles, it is expected that the rubber particles are pushed into the film by the sandwich molding method to improve the surface smoothness of the film. When the compatibility is low, the rubber particles are likely to aggregate in the film, and as a result, the unevenness of the film surface may increase. In such a case, the sandwich molding method under normal conditions cannot reduce fine irregularities on the surface, and there is a disadvantage that surface unevenness is observed when light is transmitted through the film and observed.

  An object of this invention is to provide the manufacturing method of an optical film which can reduce the surface nonuniformity of a film by the pinching shaping | molding after melt extrusion in view of the said present condition.

  As a result of intensive studies by the inventor in order to solve the above-mentioned problems, the occurrence of surface unevenness due to sandwich molding is caused by the resin temperature at the time of discharging from the die, the temperature of the elastic roll at the time of sandwiching, and the sandwiching time (the resin is placed on the roll It was found that it greatly depends on the contact time). Based on that knowledge, by setting the resin temperature when discharging from the die, the temperature of the elastic roll at the time of sandwiching, and the sandwiching time to specific conditions, surface unevenness that can occur due to sandwiching molding was reduced. The inventors have found that a film can be produced and have reached the present invention.

That is, the present invention includes a step of sandwiching and molding a sheet-shaped thermoplastic resin composition in a molten state discharged from a die outlet of an extruder between a pair of smoothing rolls including an elastic roll, and then forming an optical film. A method of manufacturing comprising:
The said process satisfies the following conditions, It is related with the manufacturing method of an optical film characterized by the above-mentioned.

The temperature of the thermoplastic resin composition at the time of die discharge is a glass transition temperature Tg + 90 ° C. or higher and Tg + 170 ° C. or lower of the thermoplastic resin composition,
The surface temperature of the elastic roll is Tg-70 ° C or higher and Tg-20 ° C or lower,
The temperature difference between the temperature of the thermoplastic resin composition at the time of die discharge and the surface temperature of the elastic roll is ΔT ° C. (“temperature of the thermoplastic resin composition at the time of die discharge” − “surface temperature of the elastic roll”) (ΔT−Tg) × t is equal to or greater than 1.00 ° C. × second, where t is the sandwiching time obtained by dividing the sandwiching width of the thermoplastic resin composition by the smoothing roll by the line speed. .

  Preferably, the thickness of the optical film is in the range of 30 μm or more and less than 100 μm.

  Preferably, the arithmetic average roughness Ra of the optical film surface is 0.005 μm or more and 0.033 μm or less.

  Preferably, the thermoplastic resin composition contains rubber particles.

  Preferably, the thermoplastic resin composition includes an acrylic resin and acrylic rubber particles.

  Preferably, the thermoplastic resin composition is an acrylic resin in which an N-substituted maleimide compound is copolymerized as a copolymerization component, an anhydrous glutaric acid acrylic resin, an acrylic resin having a lactone ring structure, or a glutarimide acrylic system. An aromatic vinyl-containing polymer obtained by polymerizing a resin, an acrylic resin containing a hydroxyl group and / or a carboxyl group, an aromatic vinyl monomer and another monomer copolymerizable therewith, or an aromatic ring thereof. It contains at least one selected from the group consisting of hydrogenated aromatic vinyl-containing polymers obtained by partially or fully hydrogenating, and acrylic polymers containing cyclic acid anhydride repeating units.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of an optical film which can reduce the surface nonuniformity of a film by the pinching shaping | molding after melt extrusion can be provided. By the production method of the present invention, an optical film that has little surface unevenness when observed by transmitting light through the film and can be suitably used in optical applications can be produced.

Schematic diagram of the sandwich molding process in the optical film manufacturing method of the present invention

  Hereinafter, the production method of the present invention will be described in detail.

  FIG. 1 is a diagram schematically showing sandwich molding in the method for producing an optical film of the present invention. The thermoplastic resin composition as the film raw material is charged into the extruder 10 and is heated to a temperature equal to or higher than the glass transition temperature in the extruder 10 to be in a molten state. The molten thermoplastic resin composition moves to the T die 11 attached to the outlet side of the extruder 10 and is discharged from the die outlet 12 at the tip of the die while being in a molten state. The molten thermoplastic resin composition 13 takes a sheet shape due to the shape of the die outlet at the time of discharge. In FIG. 1, an arrow shows the flow direction of a sheet-like thermoplastic resin composition. In addition, FIG. 1 is the figure which looked at the sheet-like thermoplastic resin composition from the side surface.

  The sheet surface is smoothed by sandwiching the sheet-like thermoplastic resin composition 13 in a molten state between a pair of smoothing rolls. One of the smoothing rolls is an elastic roll 14 and the other is a cast roll 15. The elastic roll 14 is a roll in which the surface of a roll made of an elastic body such as rubber is covered with a metal film. The surface metal film makes the roll surface flat and functions as a smoothing roll. The cast roll 15 is a hard roll made of metal. By sandwiching the sheet-like thermoplastic resin composition discharged from the die outlet 12 between the elastic roll 14 and the cast roll 15, the thermoplastic resin composition is cooled to a temperature not higher than its glass transition temperature, and the sheet surface The surface smoothness can be improved and surface unevenness can be reduced. In addition, the said pinching shaping | molding process is a process for smoothing the film surface, and is different from the process for extending | stretching a film.

  The present invention is a method for continuously producing an optical film stretched in the longitudinal direction by continuously performing the discharge from the extruder and the sandwich molding process.

  In the present invention, in order to sufficiently reduce the surface unevenness, the following three conditions must be satisfied.

(1) Resin composition temperature The temperature of the sheet-like thermoplastic resin composition at the time of die discharge is Tg + 90 degreeC or more and Tg + 170 degreeC or less by setting the glass transition temperature of a thermoplastic resin composition to Tg. This temperature is a resin composition temperature measured immediately after being discharged from the die and measured before being sandwiched by a pair of smoothing rolls. This resin composition temperature is to change the set temperature of the extruder, such as the extruder cylinder temperature, adapter, die temperature, etc., or to control the conditions of the extruder screw rotation speed, extruder screw type (compression ratio, etc.) Can be adjusted. When the resin composition temperature is less than Tg + 90 ° C., the elasticity of the molten film increases, and deformation of the film surface (shaping of the roll surface) hardly occurs even during the sandwiching process, making it difficult to reduce surface unevenness. When the resin composition temperature exceeds Tg + 170 ° C., the initial unevenness generated on the sheet surface becomes large, and it is difficult to sufficiently reduce the surface unevenness even if the sandwich molding process is performed. Preferably, they are Tg + 100 degreeC or more and Tg + 170 degreeC or less, More preferably, it is Tg + 110 degreeC or more and Tg + 150 degreeC or less.

(2) Elastic roll temperature The surface temperature of an elastic roll is Tg-70 degreeC or more and Tg-20 degrees C or less. By performing sandwich molding with a smoothing roll while maintaining this roll temperature, the effect of reducing surface unevenness by sandwich molding can be achieved. When the roll temperature is less than Tg−70 ° C., the molten film is solidified immediately after the roll is set, and the film surface is hardly deformed by the smoothing roll pressurization, and it is difficult to reduce surface unevenness. When the roll temperature exceeds Tg−20 ° C., the elastic roll internal pressure becomes high, the elastic roll temperature adjusting medium seal becomes weak, the temperature adjusting medium leaks, and stable production becomes difficult. In addition, since the elastic roll temperature is lower than the resin composition temperature at the time of discharging the die in this way, the sheet-like thermoplastic resin composition is rapidly cooled by sandwich molding, and by the pressurization by the smoothing roll accompanying the cooling. A smoothing effect can be realized.

  On the other hand, the surface temperature of the cast strol is not particularly limited, but is preferably Tg-50 ° C. or higher and Tg or lower. If it is less than Tg−50 ° C., the film hardly adheres on the cast roll and tends to cause wrinkles on the film surface, which is not preferable. Moreover, when it becomes higher than Tg, since a film sticks to a cast roll when a film is conveyed from a cast roll to the next cooling roll and there exists a tendency for a peeling pattern to arise in a film width direction, it is unpreferable. The temperature difference between the elastic roll and the cast roll is preferably 50 ° C. or less. If it exceeds 50 ° C., the temperature difference between both surfaces of the film becomes large immediately after sandwich molding, and there is a tendency for wrinkles or the like to occur when peeling from the cast roll, which is not preferable.

(3) Temperature difference and sandwiching time between the resin composition and the elastic roll The temperature difference between the temperature of the sheet-like thermoplastic resin composition at the time of discharging the die and the surface temperature of the elastic roll described above is expressed as ΔT ° C (“die The temperature of the thermoplastic resin composition at the time of discharge "-" the surface temperature of the elastic roll "), and the sandwiching time obtained by dividing the sandwiching width of the sheet-like thermoplastic resin composition by the smoothing roll by the line speed is t When (second), (ΔT−Tg) × t is equal to or greater than 1.00 ° C. × second.

  Here, the sandwiching width means a length in which the sheet-like thermoplastic resin composition is sandwiched between the pair of smoothing rolls in the flow direction of the sheet-like thermoplastic resin composition. In FIG. Represent. This sandwiching width can be measured by a method in which a pressure sensitive paper is placed between a cast roll and an elastic roll, and the colored width of the pressure sensitive paper is measured after sandwiching under the same conditions as in molding. The sandwiching width can be changed by adjusting the pressing force of the elastic roll against the cast roll by adjusting a pressing mechanism such as a cylinder, or by changing the internal pressure of the temperature control medium inside the elastic roll. It can be adjusted by controlling the conditions. The line speed refers to the flow speed of the sheet-like thermoplastic resin composition.

  The surface unevenness can be reduced by the viscoelastic state of the resin and the sandwiching time at the time of sandwiching in the sandwiching step. The viscoelastic state of the resin can be considered as ΔT−Tg, and ΔT which is “temperature of the thermoplastic resin composition at the time of die discharge” − “surface temperature of the elastic roll” as a resin temperature condition in the sandwiching process The difference from Tg which is the deformation start temperature corresponds to the ease of shaping in the sandwiching step. However, when the line speed is increased only by setting the viscoelastic state of the resin, the pinching effect is lowered, and the surface unevenness cannot be sufficiently reduced, and it is difficult to improve the productivity. Therefore, the sandwiching time obtained by dividing the sandwiching width of the sheet-like thermoplastic resin composition by the smoothing roll by the line speed is set to t seconds, and is controlled together with the sandwiching time. That is, when (ΔT−Tg) × t is less than 1.00 ° C. × second, even if the above-mentioned conditions (1) and (2) are satisfied, surface unevenness that can be a problem as an optical film is reduced. Cannot achieve the effect. (ΔT−Tg) × t is preferably 1.10 ° C. × second or more. The upper limit of (ΔT−Tg) × t is not particularly limited, but if the numerical value is too high, productivity (line speed) needs to be reduced, and there is an inconvenience in consideration of productivity, so preferably 5.00 ° C. It is better to set it to x seconds or less.

  After performing the sandwiching process as described above, if necessary, further improve the film winding form such as knurling or bonding a protective film to the film end, or slit the both ends of the film to obtain the desired product. An optical film can be manufactured by performing the process of cut | judging to a width | variety, the process of inspecting the foreign material in a film, and the process of extending | stretching.

  The thickness of the optical film produced by the present invention is not particularly limited. However, the thinner the optical film is, the more difficult it is to reduce surface unevenness by sandwich molding. In particular, for an extremely thin film having a thickness of 30 μm or more and less than 100 μm, an excellent surface unevenness reduction effect is realized. Is extremely difficult. However, according to the present invention, an excellent effect of reducing surface unevenness can be realized even in a thin film having a thickness of 30 μm or more and less than 100 μm. Therefore, the significance of applying the present invention to such a thin film is extremely large.

  According to the present invention, an optical film having an extremely low surface roughness can be produced. Specifically, the optical film produced according to the present invention can achieve an arithmetic average roughness Ra of 0.005 μm or more and 0.033 μm or less, preferably 0.030 μm or less, and further 0.025 μm or less. . Thus, a film having a very low surface roughness can be preferably used because it can suppress scattering of light transmitted through the film and does not deteriorate display characteristics when used in an optical film.

  The thermoplastic resin composition that can be used in the present invention is not particularly limited as long as it is a thermoplastic resin composition that can be used as an optical film and can be molded by melt extrusion. For example, polycarbonate resin, aromatic vinyl resin and hydrogenated product thereof, polyolefin resin, acrylic resin, polyester resin, polyarylate resin, polyimide resin, polyethersulfone resin, polyamide resin, cellulose resin, A thermoplastic resin composition such as polyphenylene oxide resin may be used.

  A thermoplastic resin composition containing rubber particles can be used as the material of the optical film, but the rubber particles may be present on the film surface, which may impair the surface smoothness of the film. In such a case, it is expected that the rubber particles are pushed into the film and the surface smoothness of the film is improved by performing sandwich molding after melt extrusion. However, when the compatibility between the rubber particles and the matrix resin is low, the rubber particles are likely to aggregate in the film, and as a result, the unevenness of the film surface may increase. In such a case, there is a disadvantage that surface unevenness cannot be reduced by sandwich molding under normal conditions, and as a result, surface unevenness that is undesirable for an optical film is observed.

  However, according to the present invention, even if the thermoplastic resin composition contains rubber particles, and the rubber particles have low compatibility with the matrix resin, the fine irregularities on the surface are reduced, and the surface unevenness is reduced. The effect of reducing can be achieved.

  Hereinafter, a rubber-like polymer-containing acrylic resin composition which is an example of a rubber particle-containing thermoplastic resin composition to which the present invention can be suitably applied will be specifically described.

  The rubbery polymer may be a polymer having a glass transition temperature of less than 20 ° C., and examples thereof include a butadiene-based cross-linked polymer, a (meth) acrylic cross-linked polymer, and an organosiloxane cross-linked polymer. . Among these, a (meth) acrylic crosslinked polymer (acrylic rubbery polymer) is particularly preferable in terms of weather resistance (light resistance) and transparency of the film.

  Examples of the acrylic rubber-like polymer include ABS resin rubber and ASA resin rubber. From the viewpoint of transparency and the like, an acrylic graft copolymer (hereinafter referred to as an acrylic ester rubber-like polymer) shown below is included. And simply referred to as “acrylic graft copolymer”).

  The acrylic graft copolymer can be obtained by polymerizing a monomer mixture containing methacrylic acid ester as a main component in the presence of an acrylic ester rubbery polymer.

  The acrylic ester rubber-like polymer is a rubber-like polymer mainly composed of an acrylic ester. Specifically, 50 to 100% by weight of an acrylic ester and other vinyl monomers that can be copolymerized are used. A monomer mixture consisting of 50 to 0% by weight (100% by weight) and 0.05 to 10 parts by weight of a polyfunctional monomer having two or more non-conjugated reactive double bonds per molecule (single A polymer obtained by polymerizing a monomer mixture (100 parts by weight) is preferable. All the monomers may be mixed and used, or may be used in two or more stages by changing the monomer composition.

  As the acrylic ester, an alkyl group having 1 to 12 carbon atoms is preferably used from the viewpoint of polymerizability and cost. For example, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-butyl acrylate, isobutyl acrylate, benzyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, Examples thereof include phenyl acrylate and phenoxyethyl acrylate. These monomers may be used in combination of two or more. The amount of the acrylate ester is preferably 50% by weight or more and 100% by weight or less, more preferably 60% by weight or more and 99% by weight or less, and further preferably 70% by weight or more and 99% by weight or less, in 100% by weight of the monomer mixture. Most preferably, it is at least 99% by weight. If it is less than 50% by weight, the impact resistance is lowered, the elongation at the time of tensile rupture is lowered, and cracks tend to be generated when the film is cut.

  As other vinyl monomers that can be copolymerized, methacrylic acid esters are particularly preferred from the viewpoint of weather resistance and transparency, such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, Examples thereof include 2-butyl methacrylate, isobutyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, phenoxyethyl methacrylate, 2-ethylhexyl methacrylate, phenyl methacrylate, n-octyl methacrylate and the like. Aromatic vinyls and derivatives thereof, and vinyl cyanides are also preferable, and examples thereof include styrene, methylstyrene, acrylonitrile, methacrylonitrile and the like. Other examples include unsubstituted and / or substituted maleic anhydrides, (meth) acrylamides, vinyl esters, vinylidene halides, (meth) acrylic acid and salts thereof, and (hydroxyalkyl) acrylate esters.

  The polyfunctional monomer may be a commonly used one such as allyl methacrylate, allyl acrylate, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl malate, divinyl adipate, divinyl benzene, ethylene glycol dimethacrylate, Diethylene glycol methacrylate, triethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, tetromethylol methane tetramethacrylate, dipropylene glycol dimethacrylate and acrylates thereof can be used. Two or more of these polyfunctional monomers may be used.

  The amount of the polyfunctional monomer is preferably 0.05 to 10 parts by weight, and more preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the total amount of the monomer mixture. If the addition amount of the polyfunctional monomer is less than 0.05 parts by weight, there is a tendency that a crosslinked product cannot be formed, and even if it exceeds 10 parts by weight, the crack resistance of the film tends to be lowered.

  The volume average particle diameter of the rubber-like polymer is preferably 20 to 450 nm, more preferably 20 to 300 nm, still more preferably 20 to 150 nm, and most preferably 30 to 80 nm. If it is less than 20 nm, crack resistance may deteriorate. On the other hand, if it exceeds 450 nm, the transparency may decrease. The volume average particle diameter can be measured by a dynamic scattering method, for example, by using MICROTRAC UPA150 (manufactured by Nikkiso Co., Ltd.).

  The acrylic graft copolymer is a monomer mixture 95 containing a methacrylic ester as a main component in the presence of 5 to 90 parts by weight (more preferably, 5 to 75 parts by weight) of an acrylate ester rubbery polymer. Those obtained by polymerizing ˜25 parts by weight in at least one stage are preferred. The methacrylic acid ester in the graft copolymer composition (monomer mixture) is preferably 50% by weight or more. If it is 50% by weight or less, the hardness and rigidity of the resulting film tend to decrease. As monomers used for graft copolymerization, the above-mentioned methacrylic acid esters, acrylic acid esters, and vinyl monomers copolymerizable with these can be used in the same manner, and methacrylic acid esters and acrylic acid esters are preferably used. Is done. Methyl methacrylate, methyl acrylate, ethyl acrylate, and n-butyl acrylate are preferred from the viewpoint of suppressing compatibility with acrylic resins from the viewpoint of suppressing methylation of zipper depolymerization.

  From the viewpoint of optical isotropy, a (meth) acrylic monomer having an alicyclic structure, a heterocyclic structure or an aromatic group (referred to as a “ring structure-containing (meth) acrylic monomer”). ) Are preferred, and specific examples include benzyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and phenoxyethyl (meth) acrylate. The amount used is 1 to 100% by weight in 100% by weight of the total amount of the monomer mixture (the total amount of the ring structure-containing (meth) acrylic monomer and other monofunctional monomers copolymerizable therewith). 5 to 70% by weight is more preferable, and 5 to 50% by weight is most preferable. As the other monofunctional monomer copolymerizable therewith, the above-mentioned methacrylic acid ester, acrylic acid ester, and other copolymerizable vinyl monomers can be used in the same manner.

  The graft ratio with respect to the acrylic ester rubbery polymer is preferably 10 to 250%, more preferably 40 to 230%, and most preferably 60 to 220%. If the graft ratio is less than 10%, the acrylic graft copolymer tends to aggregate in the molded article, which may reduce transparency and cause foreign matter. Moreover, there exists a tendency for the elongation at the time of a tensile fracture to fall and to become easy to generate | occur | produce a crack at the time of film cutting. If it is 250% or more, the melt viscosity at the time of molding, for example, at the time of film molding tends to be high, and the moldability of the film tends to decrease. The calculation formula will be described in the section of the embodiment.

  The graft ratio is a weight ratio of the graft component in the acrylic graft copolymer, and is measured by the following method.

  2 g of the obtained acrylic graft copolymer was dissolved in 50 ml of methyl ethyl ketone, and centrifuged for 1 hour at a rotational speed of 30000 rpm and a temperature of 12 ° C. using a centrifuge (manufactured by Hitachi Koki Co., Ltd., CP60E). And soluble components (set a total of three centrifuge operations). The obtained insoluble matter is calculated by the following formula as an acrylic ester graft polymer.

Graft ratio (%) = [{(weight of methyl ethyl ketone insoluble matter) − (weight of acrylic ester rubber-like polymer)} / (weight of acrylic ester rubber-like polymer)] × 100
The acrylic graft copolymer can be produced by a general emulsion polymerization method. Specifically, a method of continuously polymerizing an acrylate monomer using an emulsifier in the presence of a water-soluble polymerization initiator can be exemplified.

  In the emulsion polymerization method, it is preferable to carry out continuous polymerization in a single reaction tank, and using two or more reaction tanks is not preferable because the mechanical stability of the latex decreases.

  The polymerization temperature is preferably 30 ° C. or higher and 100 ° C. or lower, more preferably 50 ° C. or higher and 80 ° C. or lower. If the temperature is lower than 30 ° C., the productivity tends to decrease, and if the temperature exceeds 100 ° C., the quality tends to decrease due to the excessive increase in the target molecular weight. Raw materials such as acrylate monomers, initiators, emulsifiers and deionized water that are continuously added to the polymerization reactor are added accurately under the control of the metering pump, but the polymerization heat generated in the reactor In order to ensure the amount of heat removal, there is no problem even if it is cooled in advance if necessary. The latex discharged from the reaction vessel may be added with a polymerization inhibitor, a coagulant, a flame retardant, an antioxidant, and a pH adjuster as necessary. You can go. Thereafter, the copolymer can be obtained through known methods such as coagulation, heat treatment, dehydration, washing with water, and drying.

  In emulsion polymerization, a usual polymerization initiator can be used. For example, inorganic peroxides such as potassium persulfate and sodium persulfate, organic peroxides such as cumene hydroperoxide and benzoyl peroxide, and oil-soluble initiators such as azobisisobutyronitrile are also used. These may be used alone or in combination of two or more. These initiators are used as normal redox polymerization initiators in combination with reducing agents such as sodium sulfite, sodium thiosulfate, sodium formaldehyde, sulfoxylate, ascorbic acid, ferrous sulfate and disodium ethylenediaminetetraacetate complex. May be used.

  A chain transfer agent may be used in combination with the polymerization initiator. Examples of the chain transfer agent include alkyl mercaptans having 2 to 20 carbon atoms, mercapto acids, thiophenol, carbon tetrachloride and the like, and these may be used alone or in combination of two or more.

  There is no particular limitation on the emulsifier used in the emulsion polymerization method, and any emulsifier for ordinary emulsion polymerization can be used. For example, sulfate ester surfactants such as sodium alkyl sulfate, sulfonate surfactants such as sodium alkylbenzene sulfonate, sodium alkyl sulfonate, sodium dioctyl sulfosuccinate, sodium alkyl phosphate, polyoxyethylene alkyl ether Anionic surfactants such as phosphate surfactants such as sodium phosphate ester are listed. The sodium salt may be other alkali metal salt such as potassium salt or ammonium salt. These emulsifiers may be used alone or in combination of two or more. Furthermore, nonionic surfactants represented by polyoxyalkylenes or alkyl-substituted or aryl-substituted terminal hydroxyl groups may be used or partially used together. Among these, from the viewpoint of polymerization reaction stability and particle system controllability, sulfonate surfactants or phosphate surfactants are preferable. Among them, dioctylsulfosuccinate or polyoxyethylene alkyl ether phosphate is preferable. Ester salts can be used more preferably.

  The use amount of the emulsifier is preferably 0.05 part by weight or more and 10 parts by weight or more preferably 0.1 part by weight or more and 1.0 part by weight or less with respect to 100 parts by weight of the whole monomer component. If the amount is less than 0.05 parts by weight, the copolymer particle system tends to be too large. If the amount is more than 10 parts by weight, the copolymer particle system tends to be too small, and the particle size distribution tends to deteriorate. .

  Although it does not specifically limit as a rubber-like polymer containing acrylic resin composition in this invention, It is preferable that it is a mixed composition of one or more types of acrylic rubber-like polymers and one or more types of acrylic resins.

  The acrylic rubbery polymer is preferably blended so that the rubbery polymer contained in the acrylic rubbery polymer is contained in an amount of 1 to 60 parts by weight in 100 parts by weight of the thermoplastic resin composition. -30 parts by weight is more preferable, and 1-25 parts by weight is more preferable. If it is less than 1 part by weight, the crack resistance and vacuum formability of the film may deteriorate, the photoelastic constant may increase, and optical isotropy may deteriorate. On the other hand, when it exceeds 60 parts by weight, the heat resistance, surface hardness, transparency, and bending whitening resistance of the film tend to deteriorate.

  The acrylic rubber-like polymer and acrylic resin may be mixed directly during film production. Once the acrylic rubber-like polymer and methacrylic resin are mixed into pellets, the film is produced again. May be implemented.

  Although there is no restriction | limiting in particular as acrylic resin, The methacryl resin which used methyl methacrylate as a monomer component can be used, and what contained 30-100 weight% of methyl methacrylate is preferable. Further, a heat-resistant acrylic resin can be used, for example, an acrylic resin in which an N-substituted maleimide compound is copolymerized as a copolymerization component, an acrylic resin having a glutaric anhydride, an acrylic resin having a lactone ring structure, glutar Imido acrylic resins, acrylic resins containing hydroxyl groups and / or carboxyl groups, aromatic vinyl monomers and aromatic vinyl-containing polymers obtained by polymerizing other monomers copolymerizable therewith, or aromatics thereof Hydrogenated aromatic vinyl-containing polymers obtained by partially or fully hydrogenating aromatic rings (for example, styrene polymers obtained by polymerizing styrene monomers and other monomers copolymerizable therewith) Partially hydrogenated styrene polymers obtained by partial hydrogenation of aromatic rings), acrylic polymers containing cyclic acid anhydride repeating units, etc. It can be mentioned. From the viewpoints of heat resistance and optical properties, a glutarimide acrylic resin can be more preferably used. The glutarimide acrylic resin will be described in detail below. Specific examples of the glutarimide acrylic resin include the following general formula (1).

(Wherein R ¹ and R ² are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ³ is an alkyl group having 1 to 18 carbon atoms or a cycloalkyl having 3 to 12 carbon atoms. Or a substituent containing an aromatic ring having 5 to 15 carbon atoms.)
(Hereinafter also referred to as “glutarimide unit”),
The following general formula (2)

(In the formula, R ⁴ and R ⁵ are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ⁶ is an alkyl group having 1 to 18 carbon atoms or a cycloalkyl having 3 to 12 carbon atoms. Or a substituent containing an aromatic ring having 5 to 15 carbon atoms.)
A glutarimide acrylic resin containing a unit represented by (hereinafter also referred to as “(meth) acrylic acid ester unit”) can be suitably used.

  Moreover, the said glutarimide acrylic resin is the following general formula (3) as needed.

(Wherein R ⁷ is hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ⁸ is an aryl group having 6 to 10 carbon atoms.)
(Hereinafter also referred to as “aromatic vinyl unit”).

In the general formula (1), R ¹ and R ² are each independently hydrogen or a methyl group, R ³ is preferably hydrogen, a methyl group, a butyl group, or a cyclohexyl group, and R ¹ is More preferably, it is a methyl group, R ² is hydrogen, and R ³ is a methyl group.

The glutarimide acrylic resin may include only a single type as a glutarimide unit, or may include a plurality of types in which R ¹ , R ² , and R ³ in the general formula (1) are different. May be.

  The glutarimide unit can be formed by imidizing the (meth) acrylic acid ester unit represented by the general formula (2).

  In addition, acid anhydrides such as maleic anhydride, or half esters of such acid anhydrides and linear or branched alcohols having 1 to 20 carbon atoms; acrylic acid, methacrylic acid, maleic acid, maleic anhydride, The glutarimide unit can also be formed by imidizing an α, β-ethylenically unsaturated carboxylic acid such as itaconic acid, itaconic anhydride, crotonic acid, fumaric acid or citraconic acid.

In the above general formula (2), R ⁴ and R ⁵ are each independently hydrogen or a methyl group, R ⁶ is preferably hydrogen or a methyl group, R ⁴ is hydrogen, and R ⁵ is More preferably, it is a methyl group, and R ⁶ is more preferably a methyl group.

The glutarimide acrylic resin may contain only a single type as a (meth) acrylic acid ester unit, or a plurality of different R ^{4 s} , R ^{5 s} , and R ^{6 s} in the general formula (2). The type may be included.

  The glutarimide resin preferably contains styrene, α-methylstyrene or the like, more preferably styrene, as the aromatic vinyl structural unit represented by the general formula (3).

Moreover, the said glutarimide acrylic resin may contain only a single kind as an aromatic vinyl structural unit, and may contain the some kind from which R < ⁷ > and R < ⁸ > differ.

In the glutarimide acrylic resin, the content of the glutarimide unit represented by the general formula (1) is not particularly limited, and is preferably changed depending on, for example, the structure of R ³ .

  Generally, the content of the glutarimide unit is preferably 1% by weight or more of the glutarimide resin, more preferably 1% to 95% by weight, and 2% to 90% by weight. More preferably, it is more preferably 3 to 80% by weight.

  If the content of the glutarimide unit is within the above range, the heat resistance and transparency of the resulting glutarimide resin may decrease, or the moldability and mechanical strength when processed into a film may decrease. There is no.

  On the other hand, when the content of the glutarimide unit is less than the above range, the resulting glutarimide resin tends to be insufficient in heat resistance or impaired in transparency. On the other hand, if the amount is larger than the above range, the heat resistance and melt viscosity are unnecessarily increased, the molding processability is deteriorated, the mechanical strength during film processing becomes extremely brittle, or the transparency is impaired. Tend.

  In the glutarimide acrylic resin, the content of the aromatic vinyl unit represented by the general formula (3) is not particularly limited, and can be appropriately set according to required physical properties. Depending on the application used, the content of the aromatic vinyl unit represented by the general formula (3) may be zero. When the aromatic vinyl unit represented by the general formula (3) is included, it is preferably 10% by weight or more, preferably 10% by weight to 40% by weight, based on the total repeating unit of the glutarimide acrylic resin. More preferably, it is more preferable to set it as 15 to 30 weight%, and it is especially preferable to set it as 15 to 25 weight%.

  If the content of the aromatic vinyl unit is within the above range, the resulting glutarimide acrylic resin will not have insufficient heat resistance, and the mechanical strength during film processing will not decrease.

  On the other hand, when there is more content of an aromatic vinyl unit than the said range, there exists a tendency for the heat resistance of the glutarimide resin obtained to be insufficient.

  The glutarimide acrylic resin may be further copolymerized with other units other than the glutarimide unit, the (meth) acrylic acid ester unit, and the aromatic vinyl unit, if necessary.

  As other units, for example, nitrile monomers such as acrylonitrile and methacrylonitrile, and maleimide monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide are copolymerized. A structural unit can be mentioned.

  These other units may be directly copolymerized or graft copolymerized in the glutarimide acrylic resin.

The weight average molecular weight of the glutarimide acrylic resin is not particularly limited, but is preferably 1 × 10 ^{4 to} 5 × 10 ⁵ . If it is in the said range, moldability will not fall or the mechanical strength at the time of film processing will not be insufficient.

  On the other hand, when the weight average molecular weight is smaller than the above range, the mechanical strength when formed into a film tends to be insufficient. Moreover, when larger than the said range, the viscosity at the time of melt-extrusion is high, there exists a tendency for the moldability to fall and for the productivity of a molded article to fall.

  The glass transition temperature of the glutarimide acrylic resin is not particularly limited, but is preferably 110 ° C. or higher, and more preferably 120 ° C. or higher. When the glass transition temperature is within the above range, the applicable range of the obtained thermoplastic resin composition can be expanded.

  Although the manufacturing method of the said glutarimide acrylic resin is not restrict | limited in particular, For example, the method etc. which are described in Unexamined-Japanese-Patent No. 2008-273140 are mentioned.

  In the thermoplastic resin composition used in the present invention, an antioxidant, an ultraviolet absorber, an ultraviolet stabilizer, etc. for improving stability to heat and light may be added alone or in combination of two or more.

  The optical film produced in the present invention is used for a member used in a display device such as a liquid crystal display device, for example, a polarizing plate protective film, a retardation film, a brightness enhancement film, a liquid crystal substrate, a light diffusion sheet, a prism sheet and the like. Can do. Especially, it is suitable for a polarizing plate protective film and retardation film.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples. In addition, the measuring method of each physical property measured in the following examples and comparative examples is as follows.

(Glass-transition temperature)
Using a differential scanning calorimeter (DSC) SSC-5200 manufactured by Seiko Instruments Inc., the sample was once heated to 200 ° C. at a rate of 25 ° C./minute, held for 10 minutes, and then at a rate of 25 ° C./minute to 50 ° C. Measurement is performed while the temperature is raised to 200 ° C. at a rate of temperature increase of 10 ° C./min through preliminary adjustment to lower the temperature, and an integral value is obtained from the obtained DSC curve (DDSC), and the glass transition temperature is determined from the maximum point. Asked.

(Evaluation of unevenness)
A film was placed between the point light source and the screen, and the shadow projected on the screen was visually judged according to the following criteria.
○: There is no shadow Δ: Thin shadow is confirmed ×: Shading is strongly confirmed (film surface roughness)
The shape of both surfaces of the obtained film was measured using a three-dimensional surface structure analysis microscope (Zygo NewView 5030) to obtain the arithmetic average surface roughness Ra on both surfaces of the film, and the value of the rough surface, that is, the surface having a large Ra was determined as the film surface roughness. Say it.

(Production Example 1)
<Manufacture of glutarimide acrylic resin (A1)>
A glutarimide acrylic resin (A1) was produced using polymethyl methacrylate as the raw material resin and monomethylamine as the imidizing agent.

  In this production, a tandem reaction extruder in which two extrusion reactors were arranged in series was used.

  As for the tandem type reactive extruder, the meshing type co-directional twin-screw extruder having a diameter of 75 mm for both the first and second extruders and L / D (ratio of the length L to the diameter D of the extruder) of 74. The raw material resin was supplied to the raw material supply port of the first extruder using a constant weight feeder (manufactured by Kubota Corporation).

  The degree of vacuum of each vent in the first extruder and the second extruder was set to -0.095 MPa. Furthermore, the pressure control mechanism in the part connects the first extruder and the second extruder with a pipe having a diameter of 38 mm and a length of 2 m, and connects the resin discharge port of the first extruder and the raw material supply port of the second extruder. Used a constant flow pressure valve.

  The resin (strand) discharged from the second extruder was cooled by a cooling conveyor and then cut by a pelletizer to form pellets. Here, in order to determine the pressure in the component connecting the resin discharge port of the first extruder and the raw material supply port of the second extruder, or to determine the extrusion fluctuation, the discharge port of the first extruder, the first extruder and the first extruder Resin pressure gauges were provided at the center of the connecting parts between the two extruders and at the discharge port of the second extruder.

  In the 1st extruder, the polymethyl methacrylate resin (Mw: 105,000) was used as raw material resin, and the imide resin intermediate body 1 was manufactured using monomethylamine as an imidation agent. At this time, the temperature of the highest temperature part of the extruder was 280 ° C., the screw rotation speed was 55 rpm, the raw material resin supply amount was 150 kg / hour, and the addition amount of monomethylamine was 2.0 parts with respect to 100 parts of the raw material resin. The constant flow pressure valve was installed immediately before the raw material supply port of the second extruder, and the monomethylamine press-fitting portion pressure of the first extruder was adjusted to 8 MPa.

  In the second extruder, the imidizing agent and by-products remaining in the rear vent and the vacuum vent were devolatilized, and then dimethyl carbonate was added as an esterifying agent to produce an imide resin intermediate 2. At this time, each barrel temperature of the extruder was 260 ° C., the screw rotation speed was 55 rpm, and the addition amount of dimethyl carbonate was 3.2 parts with respect to 100 parts of the raw resin. Furthermore, after removing the esterifying agent with a vent, it was extruded from a strand die, cooled in a water tank, and then pelletized with a pelletizer to obtain a glutarimide acrylic resin (A1).

  The obtained glutarimide acrylic resin (A1) is an acrylic resin obtained by copolymerizing a glutamylimide unit and a meth) acrylic acid ester unit.

(Production Example 2)
<Production of graft copolymer (B2)>
The following substances were charged into an 8 L polymerization apparatus equipped with a stirrer.
Deionized water 200 parts Polyoxyethylene lauryl ether sodium phosphate 0.05 parts sodium formaldehyde sulfoxylate 0.11 parts ethylenediaminetetraacetic acid-2-sodium 0.004 parts ferrous sulfate 0.001 parts Was sufficiently substituted with nitrogen gas to make it substantially free of oxygen, the internal temperature was set to 40 ° C., and the raw material mixture of acrylic rubber particles (B-1) (90% butyl acrylate, 10% methyl methacrylate) 45.491 parts of allyl methacrylate and 0.041 parts cumene hydroperoxide) were continuously added to 45 parts by weight of the monofunctional monomer consisting of 225 minutes. (B-1) 20 minutes, 40 minutes, and 60 minutes after the start of addition, sodium polyoxyethylene lauryl ether phosphate (polyoxyethylene lauryl ether phosphate (trade name: Phosphanol RD, manufactured by Toho Chemical Industry Co., Ltd.) -510Y sodium salt) was added in an amount of 0.2 parts to the polymerization machine, and after completion of the addition, the polymerization was further continued for 0.5 hours to obtain acrylic rubber particles (polymer of (B-1)). The conversion rate was 98.6%.

  Thereafter, the internal temperature was set to 60 ° C. and 0.2 part of sodium formaldehyde sulfoxide was charged, and then the raw material mixture of the hard polymer layer (B-2) (methyl methacrylate 57.8, butyl acrylate 4 %, 55 parts by weight of monofunctional monomer consisting of benzyl methacrylate 35.2%, 55.554 parts of t-dodecyl mercaptan 0.3 parts cumene hydroperoxide 0.254 parts) over 210 minutes The polymerization was continuously added, and the polymerization was further continued for 1 hour to obtain a graft copolymer latex. The polymerization conversion rate was 100.0%. The obtained latex was salted out and coagulated with magnesium sulfate, washed with water and dried to obtain a white powdered graft copolymer (B2).

  The average particle diameter of the rubber particles (polymer of B-1) of the graft copolymer (B2) was 121 nm. The graft ratio of the graft copolymer (B2) was 56%.

(Production Example 3)
<Manufacture of resin pellets>
A single-screw extruder using a full flight screw with a diameter of 40 mm was used, the temperature setting zone of the extruder was set to 255 ° C., the screw rotation speed was 52 rpm, 53 parts by weight of glutarimide acrylic resin (A1), and white A mixture of 47 parts by weight of the powdered graft copolymer (B2) was supplied at a rate of 10 kg / hr. The resin that came out as a strand from a die provided at the exit of the extruder was cooled in a water tank and pelletized with a pelletizer.

Example 1
As the thermoplastic resin composition, the resin pellets obtained in Production Example 3 (glass transition temperature Tg 120 ° C.) were used, dried for 4 hours at 80 ° C. with a dryer, and then supplied to a φ90 mm single screw extruder. At the exit of the extruder, screen meshes were stacked in the order of # 40, # 100, # 400, # 400, # 100, # 40 from the extruder side. The resin was heated and melted so that the resin temperature became 245 ° C. at the outlet of the extruder, and the molten resin was extruded to a T die through a gear pump. At this time, the resin temperature immediately after discharge at the T-die outlet was 245 ° C. Preliminarily adjust the sandwiched width of the discharged molten film to 5 mm with a cast roll adjusted to 100 ° C. and a touch roll adjusted to 60 ° C. (flex roll as an elastic roll) at a line speed of 17 m / min. After being sandwiched and cooled and solidified under the adjusted touch roll pressing conditions, the film was taken up by a take-up roll to obtain a film original film having a thickness of 60 μm on the take-up core. At this time, (ΔT−Tg) × t was 1.15 ° C. × second. The raw fabric was slit at both ends to have a width of 1450 mm.

  The obtained rubber particle-containing acrylic resin film was smooth without any unevenness. Further, Ra on the film surface was 0.025 μm.

(Example 2)
The rubber particle-containing acrylic resin film was obtained in the same manner as in Example 1 except that the resin temperature at the T-die outlet was 235 ° C. and the line speed was 15 m / min. In this case, (ΔT−Tg) × t was 1.10 ° C. × second.

  The obtained rubber particle-blended acrylic resin film was smooth and smooth. Further, Ra on the film surface was 0.032 μm.

(Example 3)
The rubber particle-containing acrylic resin film was obtained in the same manner as in Example 1 except that the resin temperature at the T-die outlet was 235 ° C., the line speed was 12 m / min, and the thickness was 100 μm. In this case, (ΔT−Tg) × t was 1.38 ° C. × second.

  The obtained rubber particle-blended acrylic resin film was smooth and smooth. Further, Ra on the film surface was 0.024 μm.

Example 4
The rubber particle-containing acrylic resin film was obtained in the same manner as in Example 1 except that the resin temperature at the T-die outlet was 230 ° C., the line speed was 10 m / min, and the thickness was 125 μm. In this case, (ΔT−Tg) was 1.50 ° C. × second.

  The obtained rubber particle-blended acrylic resin film was smooth and smooth. Further, Ra on the film surface was 0.024 μm.

(Example 5)
The rubber particle-containing acrylic resin film was obtained in the same manner as in Example 1 except that the thickness was 190 μm, the resin temperature at the T-die outlet was 230 ° C., and the line speed was 6 m / min. At this time, (ΔT−Tg) was 2.50 ° C. × second.

  The obtained rubber particle-blended acrylic resin film was smooth and smooth. Further, Ra on the film surface was 0.023 μm.

(Comparative Example 1)
Except that the resin temperature at the T-die outlet is 235 ° C., the line speed is 20 m / min, the extrusion discharge amount is changed so that the film thickness is 60 μm, and the line speed is 20 m / min. A rubber particle-containing acrylic resin film was obtained. At this time, (ΔT−Tg) was 0.83 ° C. × second.

  The obtained rubber particle-containing acrylic resin film had a feeling of unevenness. The Ra on the film surface was 0.034 μm.

(Comparative Example 2)
Except for changing the extrusion discharge amount so that the film thickness becomes 60 μm at a line speed of 20 m / min and by changing the line speed to 20 m / min, the same procedure as in Example 1 was performed to obtain a rubber particle-containing acrylic resin film. At this time, (ΔT−Tg) was 0.98 ° C. × second.

  The rubber particle-containing acrylic resin film thus obtained was confirmed to have a thin unevenness. Further, Ra on the film surface was 0.035 μm.

(Comparative Example 3)
A rubber particle-containing acrylic resin film was obtained in the same manner as in Example 1 except that the resin temperature at the T-die outlet was 235 ° C. and the sandwich width was 5 mm to 3 mm. At this time, (ΔT−Tg) was 0.58 ° C. × second.

  The resulting rubber particle-containing acrylic resin film was strongly confirmed to be uneven. The film surface Ra was 0.038 μm.

(Comparative Example 4)
Except for setting the resin temperature at the T-die outlet to 300 ° C., the same procedure as in Example 1 was performed to obtain a rubber particle-containing acrylic resin film. At this time, (ΔT−Tg) ° C. × second was 2.12.

The resulting rubber particle-containing acrylic resin film was strongly confirmed to be uneven. The Ra on the film surface was 0.049 μm.
(Comparative Example 5)
Except for forming without sandwiching after extrusion, the same procedure as in Example 1 was performed to obtain a rubber particle-containing acrylic resin film.

The resulting rubber particle-containing acrylic resin film was strongly confirmed to be uneven. The Ra on the film surface was 0.043 μm.
(Comparative Example 6)
Except that the touch roll temperature was 40 ° C., the same method as in Example 1 was performed to obtain a rubber particle-containing acrylic resin film. At this time, (ΔT−Tg) ° C. × second was 1.50.

  The resulting rubber particle-containing acrylic resin film was strongly confirmed to be uneven. Moreover, Ra of the film surface was 0.040 micrometer.

DESCRIPTION OF SYMBOLS 10 Extruder 11 Die 12 Die exit 13 Sheet-like thermoplastic resin composition 14 Elastic roll 15 Cast roll 16 Nipping width

Claims (4)

A method for producing an optical film through a step of sandwiching and molding a sheet-like thermoplastic resin composition in a molten state discharged from a die outlet of an extruder, between a pair of smoothing rolls including an elastic roll. ,
The thermoplastic resin composition includes an acrylic resin and acrylic rubber particles,
The acrylic resin is a methacrylic resin having 30 to 100% by weight of methyl methacrylate as a monomer component,
The acrylic rubber particles comprise a monomer mixture comprising 50 to 100% by weight of an acrylic ester and 50 to 0% by weight of another copolymerizable vinyl monomer, and two or more non-conjugated molecules per molecule. Acrylic graft containing an acrylic ester rubbery polymer which is a polymer of 0.05 to 10 parts by weight of a polyfunctional monomer having a reactive double bond (based on 100 parts by weight of the monomer mixture) A copolymer,
The said process satisfies the following conditions, The manufacturing method of the optical film characterized by the above-mentioned.
The temperature of the thermoplastic resin composition at the time of die discharge is a glass transition temperature Tg + 90 ° C. or higher and Tg + 170 ° C. or lower of the thermoplastic resin composition,
The surface temperature of the elastic roll is Tg-70 ° C or higher and Tg-20 ° C or lower,
The temperature difference between the temperature of the thermoplastic resin composition at the time of die discharge and the surface temperature of the elastic roll is ΔT ° C. (“temperature of the thermoplastic resin composition at the time of die discharge” − “surface temperature of the elastic roll”) (ΔT−Tg) × t is equal to or greater than 1.00 ° C. × second, where t is the sandwiching time obtained by dividing the sandwiching width of the thermoplastic resin composition by the smoothing roll by the line speed. .   The manufacturing method of the optical film of Claim 1 which is the range whose thickness of the said optical film is 30 micrometers or more and less than 100 micrometers.   The method for producing an optical film according to claim 1 or 2, wherein an arithmetic average roughness Ra of the optical film surface is 0.005 µm or more and 0.033 µm or less. The thermoplastic resin composition is an acrylic resin copolymerized with an N-substituted maleimide compound as a copolymer component, an anhydrous glutaric acid acrylic resin, an acrylic resin having a lactone ring structure, a glutarimide acrylic resin, a hydroxyl group And / or an aromatic vinyl-containing polymer obtained by polymerizing an acrylic resin containing a carboxyl group, an aromatic vinyl monomer and another monomer copolymerizable therewith, or an aromatic ring thereof. or all hydrogenated hydrogenated aromatic vinyl-containing polymers obtained by, and at least one selected from the group consisting of acrylic polymer having a cyclic acid anhydride repeating unit, claims 1 to 3 The manufacturing method of the optical film in any one of.

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