JP6046925B2 - Method for producing thermoplastic resin film - Google Patents

Description

The present invention relates to the production how the thermoplastic resin film.

In a flat panel display such as a liquid crystal display device or a plasma display, a film made of a thermoplastic resin is used as an optical film.
For example, a polarizing plate used in a liquid crystal panel incorporated in a liquid crystal display device is usually excellent in transparency and low in optical anisotropy as a protective film on at least one surface of a polyvinyl alcohol polarizing film. An optical film made of triacetyl cellulose is used in a laminated state.

  A triacetyl cellulose film is usually produced by a cast casting method, has excellent thickness accuracy, and is suitable for use as an optical film. However, an organic solvent such as methylene chloride or methanol is used for the production of the film. It is necessary and the environmental load is large. Therefore, there is a demand for an optical film that is excellent in thickness accuracy and has a small environmental load.

As a method for producing a thermoplastic resin film, there are an inflation method, a calendar method, a T-die method, and the like.
In the T-die method, a molten thermoplastic resin is extruded from a die having a slit-like lip into a sheet or film, and the extruded molten thermoplastic resin is sandwiched between two metal rolls and cooled and solidified simultaneously. This is a method for producing a resin film by taking it out (see Patent Document 1, etc.). Such a T-die method can produce a resin film with good thickness accuracy as compared with other resin film production methods, and further eliminates the need for using an organic solvent and has a low environmental impact. Widely adopted as a method for producing resin films.

JP 2011-089027 A

  However, in the T-die method, the molten thermoplastic resin is extruded from a very narrow slit, so that the molten thermoplastic resin wraps around the end of the die at the manifold and delta portions becomes unstable due to the resin pressure inside the die. For this reason, there is a difference in the resin flow rate between the vicinity of the center of the die and the vicinity of the end of the die, and the extruded sheet-like or film-like molten thermoplastic resin is more on the center side than on the end side. It tends to be thick, and edge oscillation, generally called a draw resonance phenomenon, occurs, which is a major factor for greatly reducing the thickness accuracy of the resulting resin film.

  Furthermore, since the distance (air gap) from when the molten thermoplastic resin is extruded through the lip (slit) of the die to being sandwiched between the metal rolls is relatively long and the amount of take-up is large, there is a problem with the molten thermoplastic resin. A phenomenon called a neck-in phenomenon occurs. The neck-in phenomenon is a direction (width) perpendicular to the flow direction when the molten thermoplastic resin is drawn (stretched) in the transport direction (flow direction) of the extruded molten thermoplastic resin and molded to a predetermined thickness. Direction). This neck-in phenomenon reduces the production efficiency of the resin film and narrows the shrinkage rate between the edge and the center of the resin film in order to narrow the width that can be adopted as a product (or collected by cutting off both ends). This causes a difference in the thickness of the center portion and becomes thicker than the end side.

  Due to these phenomena, although the resin film obtained by the T-die extrusion method has better thickness accuracy than the resin film obtained by other molding methods, the thickness accuracy is used as an optical film. Is not enough.

  Therefore, the objective of this invention is providing the manufacturing method and thermoplastic resin film of a thermoplastic resin film which have high thickness precision.

As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.
That is, the present invention includes the following configurations.
(1) A method for producing a thermoplastic resin film in which a sheet-like molten thermoplastic resin material extruded from a die is sandwiched between two cooling rolls and molded, wherein the thermoplastic resin material is an acrylic resin Including at least one thermoplastic resin selected from the group consisting of a resin, a polycarbonate resin, a styrene resin, and a methyl methacrylate-styrene resin, and at least one of the two cooling rolls has an outer peripheral surface an elastic roll having a metal thin film, and, of the two cooling rolls, the outer peripheral surface of the both end portions of at least one of the cooling roll has a smaller outer diameter than the outer diameter of the roll central portion The step portions are each formed in a circumferential shape, the step portion has a step of 0.01 to 0.2 mm, and the molten thermoplastic resin material has two cooling rollers. The molten thermoplastic resin is also sandwiched between the stepped portion and the other cooling roll, and the molten thermoplastic resin does not contact or contact the stepped portion. Thermoplastic to be produced is such that the linear pressure that the molten thermoplastic resin material receives between the step portion and the other cooling roll is 0 kgf / cm so that the surface shape of the step portion is not transferred to the surface of the material. A method for producing a thermoplastic resin film, wherein the resin film has a thickness of 0.5 to 0.02 mm.
(2) The method for producing a thermoplastic resin film according to (1), wherein the stepped portion (S) is 0.1T <S <2.0T with respect to an average thickness (T) of the thermoplastic resin film. .
( 3 ) The method for producing a thermoplastic resin film according to (1) or ( 2), wherein the thermoplastic resin material contains rubber particles.

  According to the present invention, of the two cooling rolls, at least one of the cooling rolls has a stepped portion, and the linear pressure that the molten thermoplastic resin material receives between the stepped portion and the other cooling roll is Since it is substantially 0 kgf / cm, the thickness difference between an edge part and a center part becomes small, and the thermoplastic resin film which has high thickness accuracy can be obtained. Furthermore, since no organic solvent such as methylene chloride or methanol is used, the burden on the environment is small.

It is a schematic explanatory drawing which shows one Embodiment of the manufacturing method of this invention. It is a schematic sectional explanatory drawing which shows the roll structure concerning one Embodiment of this invention. It is a schematic front view which shows the cooling roll in which the level | step-difference part which can be used by one Embodiment of this invention was formed.

  The method for producing a thermoplastic resin film of the present invention comprises a sheet-like molten thermoplastic resin material extruded from a die (that is, a molten thermoplastic resin material or composition) between two predetermined cooling rolls. And a thermoplastic resin film having a high thickness accuracy. In the present invention, the thermoplastic resin material only needs to contain a thermoplastic resin as a main component. The main component means a component whose content in the material exceeds 50%.

(Thermoplastic resin material)
The thermoplastic resin contained as a main component in the thermoplastic resin material, melted if processable resin is not particularly limited, A acrylic resin, polycarbonate resin, styrene resin and methyl methacrylate - styrene resin It is preferably at least one selected from the group consisting of

<Acrylic resin>
As the acrylic resin, for example, a methacrylic resin is used. The methacrylic resin is a polymer mainly composed of a methacrylic acid ester, and may be a homopolymer of a methacrylic acid ester, or a methacrylic acid ester of 50% by weight or more and other monomers of 50% by weight or less. A copolymer may also be used. Here, as the methacrylic acid ester, an alkyl ester of methacrylic acid is usually used.

  The preferred monomer composition of the methacrylic resin is 50 to 100% by weight of alkyl methacrylate, 0 to 50% by weight of alkyl acrylate, and 0 to 49% by weight of other monomers based on all monomers. More preferably, the alkyl methacrylate is 50 to 99.9% by weight, the alkyl acrylate is 0.1 to 50% by weight, and other monomers are 0 to 49% by weight. However, the total amount of monomers does not exceed 100% by weight.

  Examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate and the like, and the alkyl group usually has 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms. Of these, methyl methacrylate is preferably used.

  Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and the like. The alkyl group usually has 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms.

The monomer other than alkyl methacrylate and alkyl acrylate may be, for example, a monofunctional monomer, that is, a compound having one polymerizable carbon-carbon double bond in the molecule, or polyfunctional. Monomers, that is, compounds having at least two polymerizable carbon-carbon double bonds in the molecule may be used, and monofunctional monomers are preferably used.
Examples of the monofunctional monomer include styrene monomers such as styrene, α-methylstyrene, and vinyl toluene; alkenyl cyanides such as acrylonitrile and methacrylonitrile; acrylic acid, methacrylic acid, maleic anhydride, N -Substituted maleimide and the like.
Examples of the polyfunctional monomer include polyunsaturated carboxylic acid esters of polyhydric alcohols such as ethylene glycol dimethacrylate, butanediol dimethacrylate, trimethylolpropane triacrylate; allyl acrylate, allyl methacrylate, cinnamon Alkenyl esters of unsaturated carboxylic acids such as allyl acid; polyalkenyl esters of polybasic acids such as diallyl phthalate, diallyl maleate, triallyl cyanurate, triallyl isocyanurate; aromatic polyalkenyl compounds such as divinylbenzene Can be mentioned.

  In addition, as for alkyl methacrylate, alkyl acrylate, and monomers other than these, you may use those 2 or more types as needed, respectively.

  From the viewpoint of heat resistance, the methacrylic resin preferably has a heat distortion temperature (glass transition temperature) of 70 ° C. or higher, more preferably 80 ° C. or higher, and further preferably 90 ° C. or higher. This glass transition temperature can be appropriately set by adjusting the type of monomer and the ratio thereof.

  The methacrylic resin can be prepared by polymerizing the monomer component by a method such as suspension polymerization, emulsion polymerization or bulk polymerization. At that time, it is preferable to use an appropriate chain transfer agent at the time of polymerization in order to obtain a suitable glass transition temperature or to obtain a melt viscosity exhibiting a moldability to a suitable laminate. What is necessary is just to determine the addition amount of a chain transfer agent suitably according to the kind of monomer, its ratio, etc.

<Polycarbonate resin>
As the polycarbonate resin, for example, an aromatic polycarbonate resin excellent in heat resistance, mechanical strength, transparency and the like is preferably used.
As an aromatic polycarbonate resin, for example, a resin obtained by reacting a dihydric phenol and a carbonate precursor by an interfacial polycondensation method or a melt transesterification method; obtained by polymerizing a carbonate prepolymer by a solid phase transesterification method Examples thereof include resins obtained by polymerizing cyclic carbonate compounds by a ring-opening polymerization method.

  Examples of the dihydric phenol include hydroquinone, resorcinol, 4,4′-dihydroxydiphenyl, bis (4-hydroxyphenyl) methane, bis {(4-hydroxy-3,5-dimethyl) phenyl} methane, 1,1- Bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 2,2-bis (4-hydroxyphenyl) propane (commonly called bisphenol A), 2,2-bis { (4-hydroxy-3-methyl) phenyl} propane, 2,2-bis {(4-hydroxy-3,5-dimethyl) phenyl} propane, 2,2-bis {(4-hydroxy-3,5-dibromo) ) Phenyl} propane, 2,2-bis {(3-isopropyl-4-hydroxy) phenyl} propane, 2,2-bis {(4 Hydroxy-3-phenyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) -3-methylbutane, 2,2-bis (4-hydroxyphenyl) -3,3-dimethylbutane, 2,4-bis (4-hydroxyphenyl) -2-methylbutane, 2,2-bis (4-hydroxyphenyl) pentane, 2,2-bis (4-hydroxyphenyl) -4 -Methylpentane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -4-isopropylcyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3 5-trimethylcyclohexane, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis {(4-hydroxy 3-methyl) phenyl} fluorene, α, α′-bis (4-hydroxyphenyl) -o-diisopropylbenzene, α, α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene, α, α′-bis (4-hydroxyphenyl) -p-diisopropylbenzene, 1,3-bis (4-hydroxyphenyl) -5,7-dimethyladamantane, 4,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxydiphenylsulfoxide, 4 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl ketone, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl ester, etc., and these may be used alone or in combination of two or more. can do.

  Among them, bisphenol A, 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl)- 3-methylbutane, 2,2-bis (4-hydroxyphenyl) -3,3-dimethylbutane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 1,1-bis (4-hydroxyphenyl) ) -3,3,5-trimethylcyclohexane and α, α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene are preferably used alone or in combination of two or more. Bisphenol A alone, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, At least one selected from the group consisting of enol A, 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, and α, α'-bis (4-hydroxyphenyl) -m-diisopropylbenzene. The combined use with a monohydric phenol is preferred.

  As the carbonate precursor, for example, carbonyl halide, carbonate ester, haloformate or the like is used, and specific examples include phosgene, diphenyl carbonate, dihaloformate of dihydric phenol, and the like.

<Styrene resin>
The styrene resin is a polymer containing 50% by mass or more, preferably 70% by mass or more of styrene units as a constituent unit, and a part of the polymer can be copolymerized with styrene as long as it contains 50% by mass or more of styrene units Such a copolymer may be substituted with a monofunctional unsaturated monomer unit.

  As the styrene unit, for example, in addition to styrene, halogenated styrenes such as chlorostyrene and bromostyrene; substituted styrenes such as alkylstyrenes such as vinyltoluene and α-methylstyrene, and the like, and radical polymerization A compound having one possible double bond in the molecule.

  Examples of monofunctional unsaturated monomers copolymerizable with styrene include, for example, methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid. Methacrylic acid esters such as 2-hydroxyethyl acid; methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, etc. Acrylic acid esters; unsaturated acids such as methacrylic acid and acrylic acid; α-methylstyrene, methacrylonitrile, maleic anhydride, phenylmaleimide, cyclohexylmaleimide and the like. Moreover, this copolymer may further contain a glutaric anhydride unit and a glutarimide unit.

<Methyl methacrylate-styrene resin>
Examples of the methyl methacrylate-styrene resin include a copolymer having a styrene unit content of 20 to 95% by mass and a methyl methacrylate unit content of 80 to 5% by mass, preferably a styrene unit content of 70% by mass or more and methyl methacrylate. Examples thereof include a copolymer having a unit content of 30% by mass or less. As a styrene unit, the styrene unit described in the said styrene resin can be used.

  For thermoplastic resin materials, depending on the purpose, for example, rubber particles, light diffusing agents, matting agents, ultraviolet absorbers, surfactants, impact agents, polymeric antistatic agents, antioxidants, flame retardants In addition, additives such as lubricants, dyes, and pigments may be included alone or in combination of two or more.

<Rubber particles>
The thermoplastic resin material preferably contains rubber particles (or particles comprising at least an elastic polymer). Thereby, impact resistance can be provided to the thermoplastic resin film obtained.
Here, as the rubber particles, for example, acrylic rubber particles, butadiene rubber particles, styrene-butadiene rubber particles, and the like can be used. Among them, acrylic rubber particles are preferable in terms of weather resistance and durability. preferable.

  The acrylic rubber particles have a layer (elastic polymer layer) made of an elastic polymer mainly composed of an acrylate ester, and may be single-layer particles made only of an elastic polymer, or an elastic weight. Particles having a multilayer structure composed of a combined layer and a layer made of a hard polymer (hard polymer layer) may be used, or one or more kinds of acrylic rubber particles may be mixed and used.

  When the acrylic rubber particles have a multilayer structure, examples of the layer structure include a two-layer structure comprising an inner layer (elastic polymer layer) / outer layer (hard polymer layer), an inner layer (hard polymer layer) / Two-layer structure consisting of outer layer (elastic polymer layer), three-layer structure consisting of innermost layer (hard polymer layer) / intermediate layer (elastic polymer layer) / outermost layer (hard polymer layer), innermost layer (elastic weight) Combined layer) / intermediate layer (hard polymer layer) / outermost layer (elastic polymer layer) 3 layer structure, innermost layer (elastic polymer layer) / inner layer side intermediate layer (hard polymer layer) / outer layer side intermediate Examples thereof include a four-layer structure comprising a layer (elastic polymer layer) / outermost layer (hard polymer layer). Of these layer structures, the outermost layer is a hard polymer layer, and the outer side is covered with a hard polymer layer having a different composition, specifically, the innermost layer (elastic polymer layer) / Three-layer structure consisting of intermediate layer (hard polymer layer) / outermost layer (hard polymer layer), innermost layer (hard polymer layer) / inner layer side intermediate layer (elastic polymer layer) / outer layer side intermediate layer (hard weight) It may be a four-layer structure composed of a combined layer) / outermost layer (hard polymer layer).

  The elastic polymer part in the acrylic rubber particle is a part including at least an elastic polymer. When the acrylic rubber particle has a single-layer structure of an elastic polymer, it means all of the acrylic rubber particle, When the system rubber particles have a multilayer structure, it means the outermost elastic polymer layer among the layers constituting the acrylic rubber particles and the inner elastic polymer layer covered with the elastic polymer layer.

  The elastic polymer layer constituting the acrylic rubber particles contains an alkyl acrylate and a polyfunctional monomer, and polymerizes monomer components including an alkyl methacrylate and other monofunctional monomers as necessary. It is preferable that the elastic polymer is formed.

  As the alkyl acrylate used for forming the elastic polymer layer, the alkyl group usually has 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms, such as methyl acrylate, ethyl acrylate, butyl acrylate. , 2-ethylhexyl acrylate, and the like, and these may be used alone or in combination of two or more.

  The polyfunctional monomer used in forming the elastic polymer layer is a compound having two or more double bonds capable of radical polymerization in the molecule, and specifically includes ethylene glycol dimethacrylate, triethylene glycol. Polyunsaturated carboxylic acid esters of polyhydric alcohols such as dimethacrylate, butanediol dimethacrylate, ethylene glycol diacrylate, 1,2-propylene glycol diacrylate, 1,3-propylene glycol diacrylate, trimethylolpropane triacrylate; acrylic Alkenyl esters of unsaturated carboxylic acids such as allyl acrylate, allyl methacrylate and allyl cinnamate; polyalkenyl esters of polybasic acids such as diallyl phthalate, diallyl maleate, triallyl cyanurate, triallyl isocyanurate Le; and aromatic polyalkenyl compounds such as divinylbenzene and the like, which may be used alone or in combination.

  As the alkyl methacrylate optionally used for forming the elastic polymer layer, the alkyl group usually has 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms, such as methyl methacrylate, ethyl methacrylate, methacrylic acid. Examples thereof include butyl acid and 2-ethylhexyl methacrylate, and these may be used alone or in combination of two or more.

  Examples of other monofunctional monomers that are optionally used in forming the elastic polymer layer include aromatic alkenyl compounds such as styrene, α-methylstyrene, and vinyl toluene; alkenyl cyanides such as acrylonitrile and methacrylonitrile. Compound; acrylic acid, methacrylic acid, maleic anhydride, N-substituted maleimide and the like may be mentioned, and these may be used alone or in combination of two or more.

  The preferred composition of the monomer component forming the elastic polymer layer in the acrylic rubber particles is, for example, based on the total amount of alkyl acrylate, polyfunctional monomer, alkyl methacrylate, and other monofunctional monomers. The alkyl acrylate is 50 to 99.9% by weight, the polyfunctional monomer is 0.1 to 10% by weight, the alkyl methacrylate is 0 to 49.9% by weight, and the other monofunctional monomer is 0 to 49%. .9% by weight. However, the total of the monomer components does not exceed 100% by weight.

  The hard polymer layer constituting the acrylic rubber particles usually contains an alkyl methacrylate, and if necessary, a monomer component containing an alkyl acrylate, another monofunctional monomer or a polyfunctional monomer. It is preferably formed of a hard polymer obtained by polymerization.

  Alkyl methacrylate, alkyl acrylate, other monofunctional monomers and polyfunctional monomers used when forming the hard polymer layer include alkyl methacrylate, alkyl acrylate, The thing similar to what was mentioned above as another monofunctional monomer and a polyfunctional monomer is mentioned.

  The preferred composition of the monomer component forming the hard polymer layer in the acrylic rubber particles is, for example, when the hard polymer layer is present outside the elastic polymer portion, alkyl methacrylate, alkyl acrylate, etc. Based on the total amount of the monofunctional monomer and polyfunctional monomer, the alkyl methacrylate is 50 to 100% by weight, the alkyl acrylate is 0 to 50% by weight, and the other monofunctional monomer is 0 to 50%. % When the polyfunctional monomer is 0 to 10% by weight and the hard polymer layer is present inside the elastic polymer part (that is, when the elastic polymer part contains the hard polymer layer) Is 70-100% by weight of alkyl methacrylate, 0-30% by weight of alkyl acrylate, based on the total amount of alkyl methacrylate, alkyl acrylate, other monofunctional monomer, and polyfunctional monomer, Other monofunctional Mer 0-30 wt%, a polyfunctional monomer is the proportion of 0-10 wt%. However, the total of the monomer components does not exceed 100% by weight.

  The weight ratio between the elastic polymer layer and the hard polymer layer in the case where the acrylic rubber particles have a multilayer structure is not particularly limited. For example, the ratio between the elastic polymer layer and the hard polymer layer that are adjacent to each other is not limited. Is usually 10 to 400 parts by weight, preferably 20 to 200 parts by weight, based on 100 parts by weight of the elastic polymer.

Acrylic rubber particles can be prepared by polymerizing monomer components forming an elastic polymer by an emulsion polymerization method or the like in at least one stage of reaction.
For example, when preparing acrylic rubber particles having a three-layer structure consisting of the innermost layer (hard polymer layer) / intermediate layer (elastic polymer layer) / outermost layer (hard polymer layer), first, the innermost layer and A monomer component for forming the hard polymer layer is polymerized by at least one stage reaction by emulsion polymerization or the like to obtain a hard polymer, and an elastic polymer is formed in the presence of the hard polymer. The monomer component is polymerized by an at least one-stage reaction by an emulsion polymerization method or the like, and is grafted to a hard polymer. Then, in the presence of the obtained elastic polymer layer, the monomer component forming the hard polymer may be grafted to the elastic polymer by polymerizing it by an emulsion polymerization method or the like in at least one stage reaction. . When the polymerization of each layer is performed in two or more stages, it is sufficient that the monomer composition as a whole is within a predetermined range, not the monomer composition of each stage.

  Regarding the particle diameter of the acrylic rubber particles, the average particle diameter of the elastic polymer layer mainly composed of acrylic acid ester in the rubber particles is preferably from 0.01 to 0.4 μm, more preferably from 0. It is 05-0.3 micrometer, More preferably, it is 0.07-0.25 micrometer.

The average particle diameter is the diameter of the dyed portion by mixing acrylic rubber particles with methacrylic resin to form a film, dyeing the elastic polymer layer with ruthenium oxide in the cross section, and observing with an electron microscope. Can be obtained from
That is, when acrylic rubber particles are mixed with methacrylic resin and the cross section is dyed with ruthenium oxide, the methacrylic resin of the parent phase is not dyed and there is a hard polymer layer outside the elastic polymer layer. Since the hard polymer layer is not dyed and only the elastic polymer layer is dyed, the particle diameter is obtained from the diameter of the portion of the elastic polymer layer thus dyed that is observed in an almost circular shape by an electron microscope. Can do. When a hard polymer layer is present inside the elastic polymer layer, this hard polymer is not dyed, and the outer elastic polymer layer is observed in a dyed two-layer structure. In this case, the outer side of the two-layer structure, that is, the outer diameter of the elastic polymer layer may be considered.

  The content ratio of the rubber particles in the thermoplastic resin material may be adjusted as appropriate so that the impact resistance of the thermoplastic resin film becomes a desired one. When the rubber particles have a multilayer structure, the thermoplastic resin is usually used. It is 40% by weight or less, preferably 30% by weight or less, preferably 5% by weight or more, more preferably 10% by weight or more based on the total amount of the material. In this case, it is usually 80% by weight or less, preferably 70% by weight or less, preferably 30% by weight or more, more preferably 50% by weight or more based on the total amount of the thermoplastic resin material.

(Method for producing thermoplastic resin film)
Hereinafter, an embodiment of a method for producing a thermoplastic resin film of the present invention will be described with reference to the drawings. FIG. 1 is a schematic explanatory view showing one embodiment of the production method of the present invention. FIG. 2 is a schematic cross-sectional explanatory view showing a roll configuration according to an embodiment of the present invention. FIG. 3 is a schematic front view showing a cooling roll formed with a step portion that can be used in an embodiment of the present invention.

  In the present invention, first, the thermoplastic resin material described above is put into an extruder 1 and melt-kneaded, and as shown in FIG. 1, a sheet-like molten thermoplastic resin material is formed from the tip (lip) of the T-shaped die 2. Extrude 3

  Examples of the extruder 1 include a single screw extruder and a twin screw extruder. Moreover, when manufacturing the multilayer thermoplastic resin film which consists of two or more layers, you may use a some extruder. For example, in the case of producing a three-layer thermoplastic resin film, three or two extruders are used to melt and knead the respective thermoplastic resin materials, and three types of molten thermoplastic resin materials 3 It may be distributed by a layer distribution type or a two-type three-layer distribution type feed block (not shown), and may be co-extruded by flowing into a single-layer T-type die, or each molten thermoplastic resin material may be applied to a multi-manifold die. You may make it flow separately and distribute | distribute to a 3 layer structure before a lip, and may coextrude.

  The extruder 1 appropriately has a screen mesh for filtering and removing relatively large foreign matters in the thermoplastic resin material; a polymer for filtering and removing relatively small foreign matters and gels in the thermoplastic resin material. A filter; a gear pump for stably quantifying the amount of resin to be extruded may be provided.

The T-type die 2 is a die having a slit-like lip, and examples thereof include a feed block die, a manifold die, a fish tail die, a coat hanger die, and a screw die. In the case of producing a multilayer thermoplastic resin film, a multi-manifold die or the like may be used.
The length in the width direction of the lip of the T-type die 2 is not particularly limited, but is preferably 1.2 to 1.5 times the product width. The opening degree of the lip may be appropriately adjusted depending on the desired product thickness, but is usually 1.01 to 10 times, preferably 1.1 to 5 times the desired product thickness. The opening degree of the lip is preferably adjusted with bolts arranged in the width direction of the T-type die 2. The lip opening does not have to be constant in the width direction. For example, the draw resonance phenomenon can be suppressed by adjusting the lip opening at the end narrower than the lip opening at the center.

  Next, the extruded sheet-like molten thermoplastic resin material 3 is sandwiched between two cooling rolls 4 and 5 and molded.

<Cooling roll>
The two cooling rolls 4 and 5 may be metal rolls or may be elastic rolls, or one may be a metal roll and the other may be an elastic roll. Since a high thickness accuracy can be imparted to the resulting resin film, it is preferable that one is a metal roll and the other is an elastic roll.

  The metal roll is not particularly limited as long as it has high rigidity, and examples thereof include a drilled roll and a spiral roll. The surface state of the metal roll is not particularly limited, and may be, for example, a mirror surface, or may have a pattern or unevenness.

  Examples of the elastic roll include a rubber roll and an elastic roll provided with a metal thin film on the outer peripheral portion (hereinafter sometimes referred to as a metal elastic roll), among which a metal elastic roll is preferable.

As shown in FIG. 2, the metal elastic roll is disposed so as to cover a substantially cylindrical shaft roll 7 that is rotatably provided and the outer peripheral surface of the shaft roll 7, and contacts the molten thermoplastic resin material 3. It consists of a cylindrical metal thin film 8 and a fluid 9 enclosed between the shaft roll 7 and the metal thin film 8, and the metal elastic roll exhibits elasticity by the fluid 9.
The shaft roll 7 is not specifically limited, For example, it consists of stainless steel etc.
The metal thin film 8 is made of, for example, stainless steel, and preferably has a thickness of about 2 to 5 mm. The metal thin film 8 preferably has flexibility, flexibility, etc., and preferably has a seamless structure without a welded joint. The metal elastic roll provided with such a metal thin film 8 is excellent in durability, and if the metal thin film 8 is mirror-finished, it can be handled in the same manner as a normal mirror roll. If given, it becomes a roll that can transfer the shape, so it is easy to use.

  The fluid 9 is not particularly limited as long as it is a fluid, and examples thereof include water and oil. In the case of water, it is suitably used when setting a roll temperature of 100 ° C. or lower, and can be adapted to a roll temperature of 100 ° C. or higher by applying pressure to obtain pressurized water. Further, when setting to a higher roll temperature, oil is preferably used.

  In general, since the width of the cooling roll is longer than the width of the sheet-like molten thermoplastic resin material 3, the sheet-like molten thermoplastic resin material 3 receives a force over the entire width in the width direction. Of the rolls 4 and 5, stepped portions are respectively formed circumferentially on the outer peripheral surfaces of both end portions of at least one cooling roll. In the present invention, when the sheet-like molten thermoplastic resin material 3 is sandwiched between the two cooling rolls 4, 5, it can be sandwiched between the stepped portion and the other cooling roll. That is, each of the cooling rolls 4 and 5 may have stepped portions on the outer peripheral surfaces of both ends, or may have stepped portions on the outer peripheral surfaces of both ends of only one cooling roll. Especially, it is preferable that it is the latter, and it is especially preferable that the cooling roll in which a level difference part is not formed is a metal elastic roll, and the cooling roll which has a level difference part is a metal roll. As described above, since the metal elastic roll is made of a metal thin film having a circular outer periphery, it is difficult to form a stepped portion, and when the stepped portion is formed, the strength of the metal thin film becomes uneven. The part is preferably applied to the metal roll instead of the metal elastic roll.

  In the present invention, the “outer diameter” of the step portion provided on the outer peripheral surface of both end portions of the cooling roll 4 or 5 is smaller than the outer diameter of the roll center portion, and as shown in FIG. When the depth (S) is provided, the outer diameter Q of the stepped portion is represented by (outer diameter R-2S of the central portion of the roll). The level | step difference S is suitably set according to the thickness of the thermoplastic resin film to manufacture, and it is preferable that it is 0.01-0.2 mm. The step S is more preferably 0.02 to 0.18 mm. If the level difference S is larger than 0.2 mm, the film end tends to be wavy and the influence on the film surface is increased, and the film is likely to break. Furthermore, the step S is more preferable if it is in a range where a relationship of 0.1T <S <2.0T is established with respect to the average thickness (T) of the thermoplastic resin film. Further, when the step S is 0.1T or less with respect to the thickness (T) of the thermoplastic resin film, it cannot absorb the film thickness variation at the end, and linear pressure is applied. It tends to result in a decrease in the overall thickness accuracy. Further, when the step S is 2.0T or more with respect to the thickness (T) of the thermoplastic resin film, the end of the film is easily wavy and the influence on the film surface is increased. It becomes easy to cause breakage. In addition, the mirror surface process may be given also to the outer peripheral surface of the level | step-difference part.

  As shown in FIG. 3, the cooling roll having a stepped portion has a width a1 (that is, a portion overlapping the sheet-like molten thermoplastic resin material 3) in the stepped portion 10 of the cooling roll of 10 to 200 mm, preferably 20 to 20 mm. The outer diameter R of the central portion 11 excluding the stepped portion 10 of the cooling roll is preferably 200 to 500 mm. The width a2 in the central portion 11 excluding the step portion 10 of the cooling roll may be appropriately adjusted from the width of the sheet-like molten thermoplastic resin material 3 and the width a1 in the step portion 10 of the cooling roll. The width a1 is preferably within the above range.

  The shape of the stepped portion 10 is not particularly limited. For example, as shown in FIG. 3, the stepped portion 10 of the cooling roll has a constant outer diameter Q, and is inclined from the central portion 11 side to the end portion. In particular, from the viewpoint of ease of processing of the roll, a shape in which the outer diameter Q of the stepped portion 10 of the cooling roll is constant is preferable.

  The step (or depth) S in the step portion 10 is such that when the sheet-like molten thermoplastic resin material 3 is sandwiched between the two cooling rolls 4, 5, the molten thermoplastic resin material 3 is separated from the step portion 10. There is no particular limitation as long as the linear pressure described below received between the cooling rolls is substantially 0 kgf / cm, and the step S is 0.005 to 0.5 mm, although it depends on the thickness of the desired thermoplastic resin film. Preferably, it is 0.01 to 0.2 mm, more preferably 0.02 to 0.1 mm. When the level difference S exceeds 0.5 mm, there is a possibility that further improvement of the effect commensurate with the processing time and cost may not be seen only by processing time and cost for cutting the cooling roll. On the other hand, when it is less than 0.005 mm, when the sheet-like molten thermoplastic resin material 3 is sandwiched between two cooling rolls, linear pressure is also applied to the stepped portion provided at the end of the resin material 3. Therefore, it may be difficult to improve the thickness accuracy. When the step portion has a step (depth) S of 0.01 to 0.2 mm, it is possible to prevent undulation at the end of the film, to improve the film surface, and to break the film. In addition, it is possible to obtain an effect that the thickness accuracy of the entire film can be increased.

The surface temperature (Tr) of the cooling rolls 4 and 5 is, for example, (Th−55 ° C.) ≦ Tr ≦ (Th + 55 ° C.) with respect to the thermal deformation temperature (Th) of the thermoplastic resin described above and below, preferably ( (Th−20 ° C.) ≦ Tr ≦ (Th + 20 ° C.), more preferably (Th−15 ° C.) ≦ Tr ≦ (Th + 10 ° C.), and even more preferably (Th−10 ° C.) ≦ Tr ≦ (Th + 5 ° C.) It is desirable to do. If the surface temperature (Tr) is lower than (Th−55 ° C.), the heat shrinkability of the thermoplastic resin is increased, and a resin film with high thickness accuracy may not be obtained, and the surface temperature (Tr) is (Th + 55). If it is higher than (° C.), the peel mark from the cooling roll may be noticeable.
The heat distortion temperature (Th) of the thermoplastic resin is determined by the composition of the thermoplastic resin and is usually about 60 to 200 ° C. The heat distortion temperature (Th) of the thermoplastic resin is a temperature measured according to ASTM D-648.
In the case of producing a multilayer thermoplastic resin film, the surface temperature (Tr) is based on the resin having the highest thermal deformation temperature (Th).

  The gap (roll gap) between the two cooling rolls is appropriately adjusted according to the desired product thickness, and both surfaces of the sheet-like molten thermoplastic resin material 3 are in contact with the surface of the central portion 11 of the cooling rolls 4 and 5, respectively. The roll gap is set in the same way. Therefore, when the sheet-like molten thermoplastic resin material 3 is sandwiched between two cooling rolls, the sheet-like molten thermoplastic resin material 3 receives a constant pressure from the central portion 11 of the cooling rolls 4 and 5 and is formed into a thermoplastic resin film.

When the cooling rolls 4 and 5 are metal rolls, the pressure is applied to the cooling roll because the central portion 11 of the cooling roll and the sheet-like molten thermoplastic resin material 3 are in line contact (in the width direction). Is divided by the width of the portion of the sheet-like molten thermoplastic resin material that is actually under pressure (for example, the width a2 in FIG. 3), and is expressed by the linear pressure (kgf / cm). The force applied to the cooling roll is normally applied by air cylinders (not shown) connected to both end faces of at least one of the first cooling roll 4 and the second cooling roll 5. The force applied to the cooling roll is not limited to the air cylinder, but may be a hydraulic cylinder or the like. In addition, the width | variety of the part which has actually received the pressure of the sheet-like molten thermoplastic resin material is the width a2 ( 3) refers to the width of the central portion 11 of the shorter cooling roll, and when there are step portions at both ends of only one cooling roll, the central portion of the cooling roll having step portions at both ends. 11 width a2. Moreover, when it has a level | step-difference part in the both ends of both cooling rolls, and the width | variety a2 (refer FIG. 3) of the center part 11 of a cooling roll is the same length, the center part of a cooling roll 11 is the width of the portion of the sheet-like molten thermoplastic resin material that is actually receiving pressure.
On the other hand, for example, as shown in FIG. 2, when one cooling roll is an elastic roll, or when both cooling rolls are elastic rolls, the surface of the elastic roll (in the case of the metal elastic roll shown in FIG. 2) The metal thin film 8) is depressed by pressure, and the elastic roll and the sheet-like molten thermoplastic resin material 3 are in contact with each other. Even in this case, the force applied to the cooling roll is reduced by the sheet-like molten thermoplastic resin. Let us consider the definition of linear pressure divided by the width of the formally contacting part of the material.
In addition, the width | variety of the part which a sheet-like molten thermoplastic resin material contacts formally is the same as the width | variety a1 of the part which has received the actual pressure of the sheet-like molten thermoplastic resin material mentioned above.

  The linear pressure that the sheet-like molten thermoplastic resin material 3 receives from the central portion 11 of the two cooling rolls is usually 1 to 25 kgf / cm, preferably 2 to 22 kgf / cm, and preferably 5 to 20 kgf / cm. More preferably, it is cm. If the linear pressure is less than 1 kgf / cm, the pressure on the surface of the molten thermoplastic resin material 3 is insufficient to form a good surface, and a beautiful surface thermoplastic resin film with high thickness accuracy can be obtained. There is a risk of not. On the other hand, if the linear pressure is greater than 25 kgf / cm, the shearing force applied to the molten thermoplastic resin material 3 increases, so that the orientation of the molten thermoplastic resin material 3 increases, and the birefringence of the resulting thermoplastic resin film May increase.

In the present invention, the linear pressure received by both ends of the molten thermoplastic resin material 3, that is, the linear pressure received by the molten thermoplastic resin material 3 between the stepped portion 10 and the other cooling roll is substantially 0 (zero). ). In addition, even when there are stepped portions 10 at both ends of one cooling roll and stepped portions 10 are also provided at both ends of the other cooling roll, both ends of the molten thermoplastic resin material 3 are at the stepped portions 10. The received linear pressure is substantially 0 (zero).
Here, when the linear pressure is substantially 0 (zero), when the molten thermoplastic resin material 3 is sandwiched between the cooling rolls 4, 5, the molten thermoplastic resin material 3 enters the stepped portion 10. Although it contacts, the surface shape of the level | step-difference part 10 is not transcribe | transferred on the surface of the molten thermoplastic resin material 3 which contacts the level | step-difference part 10. FIG.

  Further, as shown in FIG. 2, when one cooling roll 4 is a metal elastic roll and the other cooling roll 5 is a metal roll, the molten thermoplastic resin material 3 is placed between the metal elastic roll and the metal roll. When sandwiched, the molten thermoplastic resin material 3 can be uniformly pressurized in the width direction. That is, the metal elastic roll elastically deforms in a concave shape along the outer peripheral surface of the metal roll through the molten thermoplastic resin material 3, and the metal elastic roll and the metal roll have a predetermined contact length through the molten thermoplastic resin material 3. The length L is actually the length of the curve along the curvature of the roll. However, for convenience, the molten thermoplastic resin material 3 is placed between the rolls as shown in FIG. Expressed as the linear distance between the point sandwiched between and the point that leaves the roll). Thereby, the metal elastic roll and the metal roll come to be pressure-bonded to the molten thermoplastic resin material 3 by surface contact, and the molten thermoplastic resin material sandwiched between these rolls is uniformly pressed into a planar shape. Filmed. When it is formed into a film in this way, high thickness accuracy can be imparted to the obtained resin film, and further, distortion can be suppressed from remaining in the resin film.

The contact length L may be a length that can uniformly press the resulting molten thermoplastic resin material 3 in the width direction. Therefore, the metal elastic roll only needs to have elasticity to such an extent that the contact length L can be formed when the metal elastic roll is elastically deformed.
The contact length L is 1 to 20 mm, preferably 1 to 10 mm, and more preferably 1 to 7 mm. The contact length L can be arbitrarily set, for example, by adjusting the thickness of the metal thin film 8 and the amount of fluid 9 enclosed.

The thermoplastic resin film thus obtained may be cut at both ends 12 and 12 of the thermoplastic resin film because the thickness accuracy at both ends of the film is lower than the thickness accuracy at the center of the film.
The cutting method is not particularly limited, but for example, a method using a rotary shear cutter that presses a cutter with a round blade from the upper and lower surfaces of the thermoplastic resin film from the viewpoint of preventing the thermoplastic resin film from being broken. preferable.

  The structure of the thermoplastic resin film is not particularly limited, and may be a single layer structure or a plurality of layer structures. In the case of a plurality of layer structures, for example, it may be a structure of two layers, three layers, or four layers or more of the same or different thermoplastic resin materials such as polycarbonate resin and acrylic resin.

  The thickness of the resin film can be adjusted by the thickness of the molten thermoplastic resin material 3 extruded from the die 2, the roll gap of the two cooling rolls 4, 5, and the like. The thickness of the resin film that can be produced according to the present invention is, for example, 0.5 to 0.02 mm, preferably 0.25 to 0.03 mm, and more preferably 0.1 to 0.04 mm.

  The thermoplastic resin film can be suitably used for an optical film in a flat panel display such as a liquid crystal display device or a plasma display. In particular, the surface of the substrate film is subjected to a surface treatment such as a hard coat treatment or an antiglare treatment. It can be more suitably used as the substrate film in an optical film.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. In the examples, “%” and “part” representing the content or amount used are based on weight unless otherwise specified.

The measuring method of the linear pressure at the end in each example is as follows.
Pressures of air cylinders respectively connected to both end faces of the second cooling roll when the sheet-like molten thermoplastic resin composition extruded from the die is sandwiched between the first cooling roll and the second cooling roll The total value of the value multiplied by the cross-sectional area of the cylinder is the force applied to the second cooling roll, and this force is the width of the sheet-like molten thermoplastic resin composition in contact with the second cooling roll. The value divided by was calculated as the linear pressure (kgf / cm) at the end. Note that there are stepped portions at both ends of the second cooling roll, and when the sheet-like molten thermoplastic resin composition does not contact the stepped portion (more specifically, the bottom of the stepped portion), or the composition is in the stepped portion. When the surface shape of the stepped portion is not transferred to the surface of the composition that is in contact with the stepped portion, the linear pressure at the end is set to 0 kgf / cm.

Evaluation of the thickness accuracy of the thermoplastic resin film was performed under the following conditions.
<Thickness accuracy in the flow direction (MD) of the resin film>
The obtained resin film (length in the flow direction × length in the width direction = 1500 mm × 900 mm) is divided into nine equal parts in the width direction, and the third row has a measurement sample (length in the flow direction × length in the width direction). S = 1500 mm × 100 mm). Using a micrometer, measure the thickness of the sample at 50 points at intervals of 30 mm in the flow direction. From the maximum and minimum values of the measured thickness and the average thickness of the measured 50 points, determine the thickness deflection and thickness accuracy. It calculated from the following formula.
Thickness deflection (μm) = maximum thickness−minimum thickness Thickness accuracy (%) = (thickness deflection / average thickness) × 100
<Thickness accuracy in direction (TD) perpendicular to flow direction of resin film>
The obtained resin film (length in the flow direction × length in the width direction = 1500 mm × 900 mm) is strip-shaped sample with a width of 50 mm in the flow direction (length in the flow direction × length in the width direction = 50 mm × 900 mm). Was cut out in the width direction. Using a micrometer, a strip sample was measured at 30 points in the width direction at intervals of 30 mm. From the maximum and minimum values of the measured value and the average thickness of 15 points measured, the amount of thickness fluctuation and thickness The accuracy was calculated from the following formula.
Thickness deflection (μm) = maximum thickness−minimum thickness Thickness accuracy (%) = (thickness deflection / average thickness) × 100

The cooling rolls used in the following examples and comparative examples are as follows.
Cooling roll A: A stainless steel thin film with a thickness of 2 mm with one side mirrored so as to cover the outer periphery of the shaft roll made of stainless steel is arranged so that the mirror-finished surface becomes the roll outer surface, and the shaft roll and metal A metal elastic roll (surface temperature: 87 ° C.) having an outer diameter of 350 mm and a width of 1600 mm, in which a fluid made of a heat transfer oil is enclosed between the conductive thin film.
Cooling roll B: A spiral metal roll (having a spiral fluid passage inside) (surface temperature: 87 ° C.) made of stainless steel having a mirror-finished surface and having an outer diameter of 350 mm and a width of 1600 mm.
Cooling roll C: as shown in FIG. 3, the outer diameter R of the central portion 11 is 350 mm, the width a2 of the central portion 11 is 1400 mm, and the step S is 50 μm on the outer peripheral surface of both ends. A spiral metal roll made of steel (with a spiral fluid passage inside) (surface temperature: 87 ° C.). The width a1 was about 100 mm.

In the following examples and comparative examples, the following polycarbonate resins, acrylic resins and rubber particles were used.
<Polycarbonate resin>
“Caliber 300-15” (thermal deformation temperature: 140 ° C.) manufactured by Sumitomo Dow Co., Ltd. was used as the polycarbonate resin.
<Acrylic resin>
As the acrylic resin, pellets of a thermoplastic polymer (thermal deformation temperature 104 ° C.) obtained by bulk polymerization of a monomer composed of 97.8% methyl methacrylate and 2.2% methyl acrylate were used. The heat distortion temperature is an extrapolated glass transition start temperature obtained at a heating rate of 10 ° C./min by differential scanning calorimetry according to JIS K7121: 1987 as the glass transition temperature.
<Rubber particles>
As rubber particles, the innermost layer is a hard polymer obtained by polymerization of a monomer consisting of 93.8% methyl methacrylate, 6.0% methyl acrylate, and 0.2% allyl methacrylate, and the intermediate layer Is an elastic polymer obtained by polymerization of a monomer composed of 81% butyl acrylate, 17% styrene and 2% allyl methacrylate, and the outermost layer is composed of 94% methyl methacrylate and 6% methyl acrylate. The weight ratio of innermost layer / intermediate layer / outermost layer is 35/45/20, and the average particle size of the elastic polymer layer of the intermediate layer is 0. The rubber particles having a spherical three-layer structure by an emulsion polymerization method having a diameter of.
The average particle diameter of the rubber particles is determined by mixing the rubber particles with a methacrylic resin to form a film, dyeing the elastic polymer (intermediate layer) with ruthenium oxide in the cross section, and observing with an electron microscope. It was obtained from the diameter.

<Examples 1-3, Comparative Examples 1-3>
(Production of single layer resin film)
First, a thermoplastic resin composition was prepared as follows. That is, 70 parts of acrylic resin and 30 parts of rubber particles are mixed with a super mixer and melt kneaded with a twin screw extruder to obtain a thermoplastic resin composition made of acrylic resin and rubber particles as pellets. It was.
Next, the configuration of the first cooling roll and the second cooling roll was the roll configuration shown in Table 1. Then, the thermoplastic resin composition obtained above is melted by a 120 mmφ single screw extruder (manufactured by Hitz Industrial Machine Techno Co., Ltd.), and a T-die having a lip width of 1650 mm and a lip opening of 0.6 mm (Hitz Industrial Machine Techno ( The sheet-like melted thermoplastic resin composition was extruded through a product manufactured by KK
The extruded sheet-like molten thermoplastic resin composition was sandwiched between a first cooling roll and a second cooling roll, and molded and cooled to obtain a resin film having a thickness shown in Table 1. Table 1 shows the linear pressure received at both ends of the cooling roll when the sheet-like molten thermoplastic resin composition is sandwiched between the first cooling roll and the second cooling roll. Further, the thickness accuracy of the obtained resin film was measured, and the results are shown in Table 1.

<Example 4, comparative example 4>
(Production of three-layer resin film)
First, in the same manner as in Examples 1 to 3 and Comparative Examples 1 to 3, 70 parts of an acrylic resin and 30 parts of rubber particles are mixed with a super mixer and melt kneaded with a twin screw extruder. A thermoplastic resin composition composed of an acrylic resin and rubber particles was obtained as pellets.
Next, the configuration of the first cooling roll and the second cooling roll was the roll configuration shown in Table 1. The polycarbonate resin was melted with a 120 mmφ single screw extruder (manufactured by Hitz Industrial Machine Techno Co., Ltd.), and the thermoplastic resin composition obtained above was melted with a 50 mmφ single screw extruder (manufactured by Hitz Industrial Machine Techno Co., Ltd.). Is laminated with a thermoplastic resin composition on both sides of a polycarbonate resin through a two-type, three-layer distribution type feed block (manufactured by Hitz Industrial Machine Techno Co., Ltd.), and the lip width is 1650 mm and the lip opening is 0.6 mm. A sheet-shaped molten thermoplastic resin composition composed of three layers was extruded through a mold die (manufactured by Hitz Industrial Machine Techno Co., Ltd.).
The extruded sheet-like molten thermoplastic resin composition was sandwiched between a first cooling roll and a second cooling roll, and molded and cooled to obtain a resin film having a thickness shown in Table 1. Table 1 shows the linear pressure received at both ends of the cooling roll when the sheet-like molten thermoplastic resin composition is sandwiched between the first cooling roll and the second cooling roll. Further, the thickness accuracy of the obtained resin film was measured, and the results are shown in Table 1.

In the examples, step portions were formed at both ends of one of the two cooling rolls, and the sheet-like molten thermoplastic resin composition was sandwiched between the two cooling rolls. In some cases, the thermoplastic resin composition was not in contact with the stepped portion (bottom portion), and the linear pressure at the end received by the thermoplastic resin composition was 0 kgf / cm. In Examples, step portions are formed at both ends of one of the two cooling rolls, and the linear pressure at the end received by the sheet-like thermoplastic resin composition is 0 kgf / cm. Therefore, the thickness accuracy of MD of the thermoplastic resin film obtained in each example is 1.1 to 2.6%, and the thickness accuracy of TD is 0.4 to 1.6%, which is high. It was thickness accuracy.
On the other hand, in the comparative example, no stepped portion was formed at both ends of both cooling rolls, and the linear pressure at the end received by the sheet-like thermoplastic resin composition was not substantially 0 kgf / cm. The thickness accuracy of MD of the thermoplastic resin film obtained in each comparative example was 3.0 to 9.9%, the thickness accuracy of TD was 1.6 to 6.6%, and the thickness accuracy was low.

DESCRIPTION OF SYMBOLS 1 Extruder 2 Dies 3 Molten thermoplastic resin material (or composition)
4, 5 Cooling roll 7 Axis roll 8 Metal thin film 9 Fluid 10 Step part 11 Center part

Claims (3)

A method for producing a thermoplastic resin film in which a sheet-like molten thermoplastic resin material extruded from a die is sandwiched and molded between two cooling rolls,
The thermoplastic resin material includes at least one thermoplastic resin selected from the group consisting of acrylic resins, polycarbonate resins, styrene resins, and methyl methacrylate-styrene resins,
Of the two cooling rolls, at least one of the cooling rolls is an elastic roll having a metal thin film on its outer peripheral surface, and of the two cooling rolls, at both ends of at least one of the cooling rolls. On the outer peripheral surface, step portions each having an outer diameter smaller than the outer diameter of the roll center portion are formed in a circumferential shape,
The step portion has a step of 0.01 to 0.2 mm,
When the molten thermoplastic resin material is sandwiched between two cooling rolls, it is also sandwiched between the stepped portion and the other cooling roll, and the molten thermoplastic resin does not contact the stepped portion, Alternatively, the linear pressure that the molten thermoplastic resin material receives between the stepped portion and the other cooling roll is such that the surface shape of the stepped portion is not transferred to the surface of the molten thermoplastic resin material even if contacted. 0 kgf / cm,
A method for producing a thermoplastic resin film, wherein the thickness of the produced thermoplastic resin film is 0.5 to 0.02 mm.   2. The method for producing a thermoplastic resin film according to claim 1, wherein the stepped portion (S) satisfies 0.1T <S <2.0T with respect to an average thickness (T) of the thermoplastic resin film. The thermoplastic resin material, method for producing a thermoplastic resin film according to claim 1 or 2 are those containing rubber particles.

Images