JP6654371B2 - Method for producing roll-shaped acrylic resin film and method for producing polarizing plate - Google Patents

Description

  The present invention relates to a method for producing an acrylic resin film that can be used as a protective film for a polarizing plate used in a liquid crystal display device (LCD) or the like by winding the resin film into a roll shape. The present invention also relates to a method for producing a polarizing plate from a roll-shaped acrylic resin film produced by this method.

  In recent years, demand for flat panel displays (FPDs) such as liquid crystal display devices and plasma displays has been expanding, and high-performance optical films used for these have been demanded. For example, in a liquid crystal display device, it is indispensable to arrange polarizing plates on both surfaces of a glass substrate on which a liquid crystal panel is formed due to an image forming method. This polarizing plate is generally formed of a polyvinyl alcohol-based film and a polarizer made of a dichroic material such as iodine, and a polarizer protective film made of a transparent resin such as triacetyl cellulose is adhered to both surfaces using an adhesive. It has a combined structure.

  However, triacetyl cellulose does not have sufficient wet heat resistance, and a polarizing plate using a triacetyl cellulose film as a protective film may deteriorate in performance such as the degree of polarization and hue under high-temperature conditions and high-humidity heat conditions. Was. Therefore, it is known to use an acrylic resin film as a polarizer protective film having a lower moisture permeability than a triacetyl cellulose film.

  When using the solution casting film forming method when producing an acrylic resin film, a solution in which a resin is dissolved in a solvent is cast on a metal support, and the solvent is removed in a drying step to wind the film. It is manufactured by. In the case of using the melt extrusion film forming method, a resin is melted by heat, and a high temperature molten resin is melt-extruded from a T-die onto a cooling roll to form a film, and a transport process for lowering the temperature of the film is performed. After that, it is manufactured by winding a film.

  When winding the film after forming the film into a roll, if air is entrapped between the films, immediately after winding, and further over time, the air is released from the film roll and the roll is deformed, which is called a knick. There is a problem that point-like defects occur. In addition, during storage of the roll, there is a problem that a lower slack having a different diameter occurs between the upper portion of the winding core and the lower portion of the winding core due to the weight of the film, and the film is deformed and becomes defective. In particular, in the case of an acrylic resin film, the moisture permeability is lower than that of triacetyl cellulose, and it is difficult to absorb moisture. Therefore, defects caused by deformation of the film such as knicks are unlikely to be repaired in the washing and drying processes of the film at the time of manufacturing the polarizing plate, and the defects caused by the deformation of the rolls and the deformation of the film greatly reduce the yield. there were.

  As a countermeasure for solving such a problem, Japanese Patent Application Laid-Open No. 2002-220143 (Patent Document 1) discloses that a pressing roll (referred to as a “ray ion roll” in this document) is used to enter between the films at the time of winding. A method for controlling an air layer is disclosed. This document mainly describes a film produced by a solution casting method, and shows an example in which the invention is applied to a triacetyl cellulose film. Further, Japanese Patent Application Laid-Open No. 2007-91784 (Patent Document 2) discloses a method of controlling an air layer at the time of winding on a roll by performing knurling processing on an end portion in a width direction of an acrylic resin film. ing. According to this method, the film may be broken during processing depending on the height of the knurling. Further, when the film is heated and knurled by embossing, the physical properties of the film itself may be changed.

  On the other hand, it has long been known that the impact resistance is improved by blending rubber elastic particles with an acrylic resin. As an example of a document disclosing this technology, Japanese Patent Publication No. 55-27576 (Patent Document 3) can be cited. The acrylic resin in which the rubber elastic particles are blended as described above also has good film forming properties.

JP-A-2002-220143 JP 2007-91784 A JP-B-55-27576

  It is an object of the present invention to provide a method capable of suppressing defects that are likely to be caused by deformation of a roll due to aging and deformation of the film in an acrylic resin film wound in a roll shape. In particular, the present invention, as a measure to solve the above-described problem, is to control the air layer entering between the films using a press roll when winding the acrylic resin film, thereby causing deformation of the roll or deformation of the film. An object of the present invention is to provide a method for producing an acrylic resin film in which defects are less likely to occur. Another object of the present invention is to provide a method for producing a polarizing plate using a roll-shaped acrylic resin film produced by this method as a polarizer protective film.

  The method for producing a roll-shaped acrylic resin film according to the present invention comprises melting and kneading an acrylic resin, extruding a film from a T-die, and placing the film between a first cooling roll and a second cooling roll. When sandwiching into a film-shaped molded body, cutting the width direction side end of the film-shaped molded body, winding the obtained film around a winding core, winding it into a roll, and winding the film around the winding core. The take-up tension was 50 to 250 N / m, a press roll was arranged on the take-up core side, and the linear pressure of the press roll was 0.01 to 0.6 N / mm, and the above-mentioned side end was cut. This is a method of winding a film into a roll.

  The method for producing a polarizing plate according to the present invention is a method in which the roll-shaped acrylic resin film produced by the above method is unwound and bonded to a polarizer made of a polyvinyl alcohol-based resin.

  According to the method of the present invention, it is possible to manufacture an acrylic resin film in which defects due to roll deformation and film deformation due to aging are less likely to occur. Furthermore, productivity when manufacturing a polarizing plate using an acrylic resin film as a protective film can be increased.

FIG. 3 is an explanatory view schematically showing an aspect of the entire embodiment of the method according to the present invention. It is explanatory drawing which expands and shows the side surface of a winding process in this invention. It is a figure for explaining a penetration angle of a film in a winding process.

[Acrylic resin]
Examples of the acrylic resin used in the present invention include a methacrylic resin (a homopolymer of methacrylic acid ester and a copolymer containing the same as a main component). From the viewpoint of imparting impact resistance to the film, it is preferable that the acrylic resin is a mixture of rubber particles, particularly a mixture of methacrylic resin and rubber particles. The methacrylic resin is a homopolymer of methacrylic acid ester or a copolymer containing it as a main component. As the methacrylic acid ester, an alkyl ester of methacrylic acid is usually used, and the alkyl group has about 1 to 4 carbon atoms. When a copolymer is used, an acrylic acid ester known to be advantageous as a copolymer component of a methacrylic resin, or another polymerizable monomer copolymerizable with an alkyl methacrylate and / or an acrylic acid ester is used. Is used.

  The methacrylic resin is preferably 50 to 100% by weight of an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms, 0 to 50% by weight of an acrylate, and at least one of other polymerizable monomers copolymerizable therewith. It is obtained by polymerization of a monomer consisting of 0 to 49% by weight of one kind. Preferably, it is a thermoplastic polymer having a glass transition temperature of 40 ° C. or higher. Here, the acrylate is more preferably used in the range of 0.1 to 50% by weight, and the more preferable copolymerization ratio of the alkyl methacrylate is in the range of 50 to 99.9% by weight. Further, the glass transition temperature of the methacrylic resin is more preferably 60 ° C. or higher. In this specification, the term “monomer” simply includes not only a case where one kind of monomer is used, but also a state where a plurality of monomers are mixed.

  In this thermoplastic polymer, as the alkyl methacrylate, for example, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, Examples thereof include alkyl methacrylates having an alkyl group having 1 to 8 carbon atoms, such as 2-ethylhexyl methacrylate, cyclohexyl methacrylate, and 2-hydroxyethyl methacrylate. The alkyl group preferably has 1 to 4 carbon atoms. Among these, methyl methacrylate is particularly preferably used from the viewpoint of durability. As the alkyl methacrylate, one type may be used alone, or two or more types may be used in combination.

  As the acrylate, an alkyl acrylate is generally used. Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, and acryl. Examples include alkyl acrylates having 1 to 8 carbon atoms in the alkyl group, such as cyclohexyl acid and 2-hydroxyethyl acrylate. The alkyl group preferably has 1 to 4 carbon atoms. Acrylic esters may be used alone or in combination of two or more.

  Examples of other polymerizable monomers copolymerizable with the alkyl methacrylate and / or the acrylate include various monomers conventionally known in this field. Examples of such a monomer include a monofunctional monomer having one polymerizable carbon-carbon double bond in the molecule and a polyfunctional monomer having at least two polymerizable carbon-carbon double bonds in the molecule. Monomers are preferred, and monofunctional monomers are preferably used. Specific examples of the monofunctional monomer include styrene monomers such as styrene, α-methylstyrene, vinyltoluene, halogenated styrene, and hydroxystyrene; vinyl cyanide such as acrylonitrile and methacrylonitrile; acrylic acid And unsaturated acids such as methacrylic acid, maleic anhydride and itaconic anhydride; maleimides such as N-methylmaleimide, N-cyclohexylmaleimide and N-phenylmaleimide; unsaturated alcohols such as methallyl alcohol and allyl alcohol. Other monomers such as vinyl acetate, vinyl chloride, ethylene, propylene, 4-methyl-1-pentene, 2-hydroxymethyl-1-butene, methyl vinyl ketone, N-vinyl pyrrolidone, and N-vinyl carbazole. Can be

  Specific examples of the polyfunctional monomer include polyunsaturated carboxylic acid esters of polyhydric alcohols such as ethylene glycol dimethacrylate, butanediol dimethacrylate, and trimethylolpropane triacrylate; allyl acrylate, allyl methacrylate, 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 polyalkenyls such as divinylbenzene And the like.

  Such other polymerizable monomers copolymerizable with the alkyl methacrylate and / or the acrylate may be used alone or in combination of two or more.

  As described above, the methacrylic resin is preferably, as described above, 50 to 100% by weight, more preferably 50 to 99.9% by weight, of an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms, and 0 to 50% by weight of an acrylate. %, More preferably 0.1 to 50% by weight, and a thermoplastic polymer obtained by polymerizing a monomer composed of at least one of 0 to 49% by weight of another polymerizable monomer copolymerizable therewith. Is preferred, and polymers falling within this range can be used alone or as a mixture of two or more polymers. The thermoplastic polymer may have a glass transition temperature of 40 ° C. or higher, preferably 60 ° C. or higher. When the glass transition temperature of the thermoplastic polymer is 40 ° C. or higher, the heat resistance of the obtained film is further improved. The glass transition temperature can be appropriately set by changing the type and amount of another monomer copolymerized with the alkyl methacrylate.

  The methacrylic resin may have a ring structure in the polymer main chain since it can increase the durability of the film. The ring structure is preferably a heterocyclic structure such as a cyclic acid anhydride structure, a cyclic imide structure and a lactone ring structure. Specific examples include a cyclic acid anhydride structure such as a glutaric anhydride structure and a succinic anhydride structure; a cyclic imide structure such as a glutarimide structure and a succinimide structure; and a lactone ring structure such as butyrolactone and valerolactone. . As the content of the ring structure in the main chain is increased, the glass transition temperature of the methacrylic resin can be increased. A cyclic acid anhydride structure or a cyclic imide structure is introduced by copolymerizing a monomer having a cyclic structure such as maleic anhydride or maleimide, and a cyclic acid anhydride structure is introduced by a dehydration / demethanol condensation reaction after polymerization. It can be introduced into the main chain by a method, a method of reacting an amino compound to introduce a cyclic imide structure, or the like.

  A resin (polymer) having a lactone ring structure is obtained as follows. First, a polymer having a hydroxyl group and an ester group in a polymer chain is prepared. Thereafter, the hydroxyl group and the ester group in the obtained polymer are cyclized and condensed by heating in the presence of a catalyst such as an organic phosphoric acid compound, if necessary, to form a lactone ring structure. Polymers having a hydroxyl group and an ester group in the polymer chain include, for example, methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, An acrylate or a methacrylate having a hydroxyl group and an ester group such as n-butyl (hydroxymethyl) acrylate and t-butyl 2- (hydroxymethyl) acrylate is obtained by using as a part of the monomer. be able to. A more specific method for preparing a polymer having a lactone ring structure is described in, for example, JP-A-2007-254726.

  The method for polymerizing the above thermoplastic polymer is not particularly limited, but can be carried out by usual methods such as suspension polymerization, emulsion polymerization and bulk polymerization. It is preferable to use a chain transfer agent during polymerization in order to obtain a suitable glass transition temperature or a viscosity that indicates suitable moldability into a film. The amount of the chain transfer agent may be appropriately determined depending on the type and composition of the monomer.

  As described above, rubber particles may be added to such a methacrylic resin from the viewpoint of imparting impact resistance to the film. The rubber particles used preferably have an average particle diameter in the range of 0.05 to 0.4 μm, more preferably 0.06 to 0.3 μm, especially 0.1 to 0.25 μm. When the average particle diameter of the rubber particles is in such a range, the transparency of the film is hardly impaired, and more favorable impact resistance can be imparted. The rubber particles are preferably 3 to 60 parts by weight, more preferably 5 to 50 parts by weight, and still more preferably 10 to 40 parts by weight, in a total of 100 parts by weight of the acrylic resin (for example, methacrylic resin) and the rubber particles. Included in percentage.

  The rubber particles preferably contain 50 to 99.9% by weight of an alkyl acrylate and 0 to 49.9% by weight of at least one other vinyl monomer copolymerizable therewith, and have a copolymerizable crosslinkable property. In the presence of 100 parts by weight of an elastic copolymer having a layer obtained by polymerizing a monomer composed of 0.1 to 10% by weight of a monomer, 50 to 100% by weight of a methacrylate ester and an acrylate ester The latter monomer is polymerized by polymerizing 10 to 400 parts by weight of 0 to 50% by weight and 0 to 49% by weight of at least one other vinyl monomer copolymerizable therewith. Is a rubber-containing polymer obtained by bonding at least one polymerized layer to the surface of the elastic copolymer. Rubber particles having different average particle diameters can be produced by changing polymerization conditions.

  This rubber-containing polymer is obtained, for example, by the following method. The above components for the elastic copolymer are polymerized in at least one-step reaction by an emulsion polymerization method or the like to obtain an elastic copolymer. In the presence of the obtained elastic copolymer, the above-mentioned monomer containing methacrylic acid ester is polymerized by at least one-step reaction by an emulsion polymerization method or the like. By such a multi-stage polymerization, the monomer containing a methacrylic ester used in the subsequent stage is graft-copolymerized to the elastic copolymer, and a crosslinked elastic copolymer having a graft chain is produced. That is, the rubber-containing polymer becomes a graft copolymer having a multilayer structure containing an alkyl acrylate as a main component of the rubber. In the case where the polymerization of the elastic copolymer is performed in two or more steps, or in the case where the subsequent polymerization of the monomer having a methacrylic acid ester as a main component is performed in two or more steps, the amount of each step is a single amount. It suffices that the overall monomer composition, not the body composition, falls within the above range.

  In the above rubber-containing polymer, examples of the alkyl acrylate used to constitute the elastic copolymer include those having an alkyl group having 1 to 8 carbon atoms. Among these, an alkyl group having 4 to 8 carbon atoms, such as butyl acrylate or 2-ethylhexyl acrylate, is preferred.

  In the rubber-containing polymer, other vinyl monomers which are optionally used for constituting an elastic copolymer and can be copolymerized with an alkyl acrylate include, for example, methyl methacrylate, butyl methacrylate, and methacrylic acid. Preferred are alkyl methacrylates such as cyclohexyl, styrene, acrylonitrile and the like.

  In the rubber-containing polymer, the copolymerizable crosslinkable monomer used to form the elastic copolymer may be one having at least two polymerizable carbon-carbon double bonds in one molecule. . Examples of such a crosslinkable monomer include unsaturated carboxylic acid diesters of glycols such as ethylene glycol dimethacrylate and butanediol dimethacrylate; and unsaturated monomers such as allyl acrylate, allyl methacrylate and allyl cinnamate. Alkenyl esters of saturated carboxylic acids; polyalkenyl esters of polycarboxylic acids such as diallyl phthalate, diallyl maleate, triallyl cyanurate and triallyl isocyanurate; unsaturated polyhydric alcohols such as trimethylolpropane triacrylate Carboxylate; divinylbenzene and the like. Of these, alkenyl esters of unsaturated carboxylic acids and polyalkenyl esters of polycarboxylic acids are preferred. These crosslinkable monomers can be used alone or in combination of two or more, if necessary.

  As described above, the elastic copolymer obtained by the polymerization of the monomer mainly composed of the alkyl acrylate includes 50 to 100% by weight of methacrylate, 0 to 50% by weight of acrylate, A monomer comprising at least one of 0 to 49% by weight of another copolymerizable vinyl monomer is grafted. The methacrylate ester to be grafted onto the elastic copolymer is preferably an alkyl methacrylate ester, and examples thereof include methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and cyclohexyl methacrylate. Examples of the acrylate which is copolymerized with these methacrylates as desired include alkyl acrylates such as methyl acrylate, butyl acrylate and cyclohexyl acrylate. Examples of other vinyl monomers copolymerizable with methacrylic acid esters and / or acrylic acid esters include styrene and acrylonitrile.

  The grafted monomer is preferably used in an amount of 10 to 400 parts by weight, more preferably 20 to 200 parts by weight, based on 100 parts by weight of the elastic copolymer, and can be polymerized by at least one or more steps of reaction. If the amount of the monomer to be grafted is 10 parts by weight or more, aggregation of the elastic copolymer hardly occurs and transparency is improved.

  In addition, a hard layer mainly composed of methacrylic acid ester can be provided inside the above-mentioned elastic copolymer layer. In this case, the monomer of the hard layer constituting the innermost layer may be first polymerized. Next, in the presence of the obtained hard polymer, the monomers constituting the above elastic copolymer are polymerized. Further, in the presence of the obtained elastic copolymer, the above-mentioned methacrylic acid ester is mainly used, and the monomer to be grafted may be polymerized. Here, the hard layer serving as the innermost layer is obtained by polymerizing a monomer composed of 70 to 100% by weight of a methacrylate ester and 0 to 30% by weight of another vinyl monomer copolymerizable therewith. Is preferred. At this time, it is also effective to use a copolymerizable crosslinkable monomer as one of the other vinyl monomers. As the methacrylate, alkyl methacrylate, particularly methyl methacrylate, is effective. Such a rubber-containing polymer having a three-layer structure is disclosed, for example, in Japanese Patent Publication No. 55-27576 (Patent Document 3). In particular, one described in Example 3 of Patent Document 3 is one of preferred compositions.

  The average particle size of the rubber particles can be determined by observing with an electron microscope. For example, each rubber particle is independently mixed with a methacrylic resin to form a film, and the rubber component is dyed on the cross section thereof using ruthenium oxide. After staining, it can be determined from the diameter of the outer layer of the stained particle by observing with an electron microscope. Therefore, the particle diameter here is the number average particle diameter.

  The acrylic resin may contain ordinary additives such as an ultraviolet absorber, an organic dye, an inorganic dye, a pigment, an antioxidant, an antistatic agent, and a surfactant. Among these, an ultraviolet absorber is preferably used because it gives a film having better weather resistance for a longer time. Examples of the ultraviolet absorber include benzotriazole-based ultraviolet absorbers, 2-hydroxybenzophenone-based ultraviolet absorbers, and phenyl salicylate-based ultraviolet absorbers that are generally used. Specific examples of the benzotriazole-based ultraviolet absorber include 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3,5- Di-tert-butyl-2-hydroxyphenyl) benzotriazole, 2- (3-tert-butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3,5-di-tert- Butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3,5-di-tert-amyl-2-hydroxyphenyl) benzotriazole, 2- Such as 2'-hydroxy-5'-tert-octylphenyl) benzotriazole are exemplified.

  Specific examples of the 2-hydroxybenzophenone-based ultraviolet absorber include 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2,4-dihydroxybenzophenone, and 2-hydroxy-4-methoxy-4 ′. -Chlorobenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone and the like.

  Specific examples of the phenyl salicylate-based ultraviolet absorber include p-tert-butylphenyl salicylate, p-octylphenyl salicylate, and the like.

  These ultraviolet absorbers can be used alone or in combination of two or more. The content of the ultraviolet absorbent is appropriately set depending on the thickness of the desired acrylic resin extruded film, but is usually 0.1 part by weight or more, preferably 0.3 part by weight or more based on 100 parts by weight of the acrylic resin. And usually not more than 5 parts by weight. The transmittance of the extruded acrylic resin film having a desired thickness at a wavelength of 380 nm is preferably 25% or less, more preferably 15% or less, and still more preferably 5% or less. For example, in the case of a film having a thickness of 80 μm, in order to exhibit the same ultraviolet absorbing ability as a triacetyl cellulose film used as an optical film, based on a total of 100 parts by weight of methacrylic resin and rubber particles, the ultraviolet absorber The amount is preferably about 2.0 parts by weight. Additives such as these ultraviolet absorbers preferably have a melting point of 180 ° C. or higher in order to prevent the acrylic resin from evaporating as volatiles when discharged from the die and contaminating rolls and the like.

[Production method of acrylic resin film]
Next, an embodiment of a method for producing an acrylic resin film of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view schematically showing an entire embodiment of a manufacturing method according to the present invention. In this figure, a film-like material 1 extruded in a molten state, and a film-like molded body 2 and an acrylic resin film 3 which are obtained by cooling and solidifying the film-like material 1 are shown by broken lines. Then, the film-shaped material 1 extruded from the T-die 10 is sandwiched between the first cooling roll 11 and the second cooling roll 12 to form the film-shaped molded body 2, passing through the third cooling roll 13 which is arranged as necessary. Then, the sheet is transported by the transport rolls 20 and 20. During the conveyance, the width direction side end of the film-shaped molded body 2 is cut by the cutter 14 to form the acrylic resin film 3 having a target width. Thereafter, the sheet passes through the accumulator 15, the nip roll 16, and the dancer roll 17, and is guided to the winding core 19 by the transport roll 20. A press roll 18 is disposed on the take-up core 19 side. The press roll 18 presses the film 3 against the take-up core 19 and winds the film 3 to obtain a roll-shaped acrylic resin film 5 (an acrylic resin film wound in a roll shape). Until the film is wound, a processing process such as stretching or surface treatment including coating may be included.

  The method for producing an acrylic resin film includes an extrusion step of extruding an acrylic resin from the T-die 10 as a film-like material 1. The extruder melts and kneads the acrylic resin by using one having one or two screws depending on the form of the resin charged therein. Until the film-like material 1 is extruded from the T-die 10, a screen mesh for filtering and removing relatively large foreign matters and the like in the resin, and a relatively small foreign matter and gel in the resin are appropriately filtered. A polymer filter for removing, a gear pump for stably quantifying the amount of resin to be extruded, and the like may be provided.

  The T die 10 is a die having a slit-shaped lip, and a manifold die, a fish tail die, a coat hanger die, a screw die and the like can be appropriately selected and used. When manufacturing a multilayer resin film, a multi-manifold die or the like may be used. The lip width of the T-die 10 is appropriately set according to the film width of the film-shaped molded article 2 manufactured by extrusion, within a range that does not lower the production efficiency. Usually, those having a lip width of about 1.2 to 1.5 times the width of the film-shaped molded body 2 to be manufactured are preferably used.

  A flexible lip that can adjust the opening of the slit-shaped lip with bolts arranged in the width direction of the T-die 10 is preferably used, but is not particularly limited. The lip opening is appropriately adjusted according to the desired film thickness. Generally, the thickness is adjusted to be about 1.01 to 10 times, preferably about 1.1 to 5 times the thickness of the target film. The lip opening is generally not uniform in the width direction but has a distribution in the width direction in order to make the thickness of the obtained film uniform.

  The method for producing an acrylic resin film further includes a forming step of contacting at least one roll of the film-like material 1 extruded in the above-described extrusion step to form a film-like molded body 2. If the number of rolls is at least one, the film-shaped molded body 2 can be obtained. In the present invention, the film-shaped material 1 extruded in a molten state is sandwiched between the first cooling roll 11 and the second cooling roll 12 to be formed into a film-shaped molded body 2. At this time, a gap (roll gap) between the first cooling roll 11 and the second cooling roll 12 is appropriately adjusted according to a desired film thickness. It is preferable to set a roll gap so that both surfaces of the film-shaped material 1 are surely in contact with the surfaces of the two cooling rolls 11 and 12 at the same time.

  The cooling rolls 11 and 12 can be made of metal or rubber. For example, both the first cooling roll 11 and the second cooling roll 12 may be metal rolls, or one may be a rubber roll and the other may be a metal roll. Further, both may be rubber rolls. However, it is preferable to use a metal roll in order to finish the surface of the obtained film-shaped molded body 2 to a glossy surface. In particular, it is preferable that the surface of the metal roll is polished and plated to obtain a higher glossy surface. In this case, the metal roll is preferably a so-called metal elastic roll in which a heat medium is arranged inside a cylindrical metal and the cylindrical metal can be deformed by the pressure of the internal heat medium. In particular, it is preferable that the first cooling roll 11 is formed of such a metal elastic roll.

  For the other second cooling roll 12, a metal rigid body is preferably used. A roll made of a rigid metal body, that is, a rigid metal roll is preferably a highly rigid and temperature-adjustable roll, and examples thereof include a drilled roll and a spiral roll.

  The shape of the surface of the second cooling roll 12, which is preferably made of a rigid metal body, is transferred to the surface of the acrylic resin film. Therefore, in order to suppress the external haze of the film and obtain a transparent film, the average surface roughness Ra is preferably 0.04 or less. The average surface roughness Ra is a value measured according to “Definition and display of surface roughness” of JIS B0601-1982.

  The surface temperature of the second cooling roll 12 is preferably adjusted to a range of preferably 60 to 130C, more preferably 80 to 115C. By adjusting to such a temperature range, the film-shaped molded body 2 is more easily peeled off from the second cooling roll 12. Further, it is difficult to shrink during cooling and solidification, and a uniform film can be obtained. Further, in order to facilitate the peeling of the film-like material 1 from the first cooling roll 11, the surface temperature of the second cooling roll 12 may be adjusted to be higher than the surface temperature of the first cooling roll 11 by 1 ° C. or more. preferable.

  The film-shaped molded body 2 made of the acrylic resin obtained through the above-described extrusion step and molding step is then gradually cooled while being in contact with one or more rolls. In the example shown in FIG. 1, the film-shaped material 1 cooled by being sandwiched between the first cooling roll 11 and the second cooling roll 12 is then placed on the opposite side of the second cooling roll 12 from the first cooling roll 11. The third cooling roll 13 provided is contacted and cooled. The film-shaped molded body 2 thus cooled and solidified is continuously sent to the next step while being supported by the transport rolls 20 and 20.

  In the present invention, a slit step is provided in which the width-direction side end of the film-shaped molded body 2 is cut by the cutter 14 to obtain the acrylic resin film 3 having a target width. The film-shaped molded body 2 extruded from the T-die 10 and cooled by the cooling rolls 11, 12, 13 has a large thickness variation at both ends in the width direction. Therefore, if the film is wound as it is, the appearance of the roll-shaped resin film deteriorates. In addition, the acrylic resin film is generally easily broken, and the film-shaped molded body 2 obtained by the extrusion as described above is thicker at both ends in the width direction than at the center. For this reason, if the film is wound as it is, it may cause breakage during the conveyance, so the slitting step is provided.

  The film-shaped molded body 2 obtained in the previous molding step is cut at both end portions in the width direction according to a desired product width in the slitting step, and becomes a product (acrylic resin film 3). The cutter 14 used for this purpose may be any cutter that can cut the film-shaped molded body 2 along the traveling direction, that is, in parallel with the traveling direction. For example, a rotary shear cutter for pressing a round blade cutter from the upper or lower surface of the film-shaped molded body 2 is preferably used from the viewpoint of preventing the film from breaking. Further, a laser cutter that cuts both end portions of the film-shaped molded body 2 with a laser can also be used.

  The thickness of the film-shaped molded body 2 and the acrylic resin film 3 obtained by cutting and removing both ends in the width direction may be selected according to the intended use. For example, it is preferably in the range of 10 to 500 μm, more preferably in the range of 20 to 100 μm. In particular, when the thickness of the acrylic resin film 3 is 100 μm or less, the rigidity of the film is weak, and a polygon is easily generated in a wound state due to its own weight, so that the effect of the present invention is more expected. Here, the polygon means a phenomenon in which the cross section of the roll-shaped acrylic resin film 5 wound up in a roll shape becomes a polygonal shape where a cross section should be originally circular (a cylindrical cross section).

  The width of the acrylic resin film 3 obtained after cutting the side end may also be selected according to the application. For example, it is preferably in the range of 250 to 3000 mm, more preferably in the range of 500 to 2000 mm. In particular, when the width of the film is 500 mm or more, the effect of the present invention is more expected because a polygon is easily generated in a wound state due to its own weight.

[Method of winding acrylic resin film]
The acrylic resin film 3 from which both ends in the width direction have been cut and removed in the slitting process is sequentially wound up on a winding core 19 via an accumulator 15, a nip roll 16, and a dancer roll 17, and is roll-shaped acrylic. The resin film 5 is obtained. A press roll 18 is disposed on the take-up core 19 side, and the press roll 18 takes up the acrylic resin film 3 so as to press it against the take-up core 19 side. The accumulator 15 and the nip roll 16 may be arranged before the slitting step, that is, before the cutter 14.

  When the winding of the roll-shaped resin film 5 advances to a predetermined length or a predetermined diameter and ends, the rotation of the winding core 19 is stopped and replaced with another winding core 19. As a result of this exchange work, even when the transport of the film is temporarily stopped, the production of the film by the T-die 10 and the cooling rolls 11, 12, and 13 is not stopped, that is, the winding core 19 is not required. An accumulator 15 is provided for the purpose of storing a film at the time of replacement. The nip roll 16 applies the same transport tension to the entire line as in the steady state when the transport of the film is temporarily stopped due to the exchange of the take-up core 19, in other words, the nip roll 19 applies When the winding tension is lost, it plays a role such as applying a substitute tension. The dancer roll 17 is provided for adjusting the tension (winding tension) of the acrylic resin film 3 wound around the winding core 19. In FIG. 1, the tension of the film 3 to be wound is controlled by moving the roll located at the center of the three rolls up and down. Therefore, the winding tension of the acrylic resin film 3 is measured via the dancer roll 17.

  The press roll 18 may be arranged at a position where it comes into contact with the acrylic resin film 3 to be wound. Preferably, the acrylic resin film 3 is wound up and arranged at a position or slightly before the rolled acrylic resin film 5. As shown in FIG. 1, it is general that the pressing roller 18 comes into contact with the outermost surface of the roll-shaped acrylic resin film 5. However, for example, if the outermost surface of the roll-shaped acrylic resin film 5 is about 10 mm from the outermost surface, the pressing roll 18 does not contact the outermost surface of the roll-shaped acrylic resin film 5, that is, the roll-shaped acrylic resin film. It may be located slightly before the portion that becomes 5.

  When the winding diameter of the roll-shaped acrylic resin film 5 reaches a predetermined length, the winding operation is temporarily interrupted, and the acrylic resin film 3 is cut. Next, the roll-shaped acrylic resin film 5 is removed together with the take-up core 19, and another take-up core 19 is placed on the gantry, and the cut acrylic resin film 3 is fixed to the new take-up core 19. Then, the winding operation is restarted.

  The winding tension when winding the acrylic resin film 3 into a roll shape is in the range of 50 to 250 N / m. This winding tension is preferably in the range of 60 to 200 N / m, and more preferably in the range of 70 to 170 N / m. If the winding tension is less than 50 N / m, there is a greater possibility that the roll-shaped acrylic resin film 5 will be misaligned. On the other hand, when the winding tension exceeds 250 N / m, the gauge band is significantly generated in the roll-shaped acrylic resin film 5. The gauge band referred to here is a bump or a winding bump which is observed in a protruding shape along the circumferential direction of the surface of the acrylic resin film 5 wound up in a roll shape.

The winding tension may be constant irrespective of the winding diameter of the roll-shaped acrylic resin film 5, but is preferably changed according to the winding diameter. In the latter case, the winding tension may change linearly according to the winding diameter, or the winding tension may change according to a curve or a certain function according to the winding diameter. The change rate at this time is called a taper rate. The taper ratio is defined by the ratio of the initial winding tension F1 and the changed winding tension F2, that is, the following expression (1).
[1- (F2 / F1)] × 100 [%] (1)

  The winding tension may be greater than the initial value or smaller than the initial value as the winding diameter increases. If the winding is started with the initial winding tension, and is then increased from the initial value for a while immediately afterward, and then gradually lowered to become smaller than the initial value, the roll-shaped acrylic resin film 5 by the winding core 19 can be formed. And the roll appearance is good. In the present invention, even when the winding tension is changed according to the winding diameter, the winding tension is set in the range of 50 to 250 N / m from the initial winding to the end of winding.

  The holding roll 18 is, for example, a metal roll, a rubber roll, a carbon roll, or the like. A crown roll having different roll diameters at the center and the end in the width direction of the pressing roll 18 may be used. When a crown roll is used, the crown amount, that is, the portion between the portion having the largest roll diameter (usually appearing at the center in the width direction) and the portion having the smallest roll diameter (usually appearing at the end portion in the width direction) is used. The difference in diameter is preferably in the range of 1 to 100 μm.

  When a rubber roll is used, its hardness is a type A according to JIS K6233-3: 2012 "Vulcanized rubber and thermoplastic rubber-Determination of hardness-Part 3: Durometer hardness", and is in the range of A10 to A90. Is preferred. The durometer hardness type A is generally called “Shore hardness A”. If a rubber roll having such a hardness is used, the film can come into contact with the surface of the film, so that the roll appearance is improved. In addition, even when a metal roll is used, a roll-shaped acrylic resin film 5 having a better roll appearance can be obtained by winding a cushioning material around the surface.

  When the acrylic resin film 3 is wound around the winding core 19 to form the roll-shaped acrylic resin film 5, the winding tension is controlled, and the pressing is performed toward the winding core 19 using the holding roll 18. The linear pressure of the pressing roll 18 is controlled according to the diameter of the rolled acrylic resin film 5 taken. The linear pressure of the pressing roll 18 is in the range of 0.01 to 0.6 N / mm. This linear pressure is preferably in the range of 0.05 to 0.5 N / mm, and more preferably in the range of 0.1 to 0.4 N / mm. If the linear pressure exceeds 0.6 N / mm, a gauge band is often remarkably observed on the surface of the roll-shaped acrylic resin film 5, which is not preferable. Further, in order to press down the acrylic resin film 3, a linear pressure of at least about 0.01 N / mm is required.

  The linear pressure of the holding roll 18 may be constant or may be changed according to the winding diameter of the roll-shaped acrylic resin film 5. The change in linear pressure may be linear according to the winding diameter, or may follow a curve or a certain function. It is preferable that the linear pressure is weakened (reduced) as the winding diameter increases. Further, the linear pressures on both ends of the film may be controlled independently.

  FIG. 2 is an explanatory diagram showing, in an enlarged manner, a winding process starting from the transport roll 20, winding the acrylic resin film 3 around the winding core 19, and obtaining the roll-shaped acrylic resin film 5. In FIG. 2, when the number of the transport rolls 20 disposed immediately before the press roll 18 and the acrylic resin film after the both ends are cut enter the take-up core 19 side while being pressed by the press roll 18. Are shown in a form different from that in FIG. In FIG. 2, the acrylic resin film 3 having passed through the dancer rolls 17 shown in FIG. 1 is transported along three transport rolls 20. After that, the roll-shaped acrylic resin film 5 is obtained by being wound around the winding core 19 while being held down by the holding roll 18.

  In FIGS. 1 and 2, the pressing roll 18 is configured to move the acrylic resin film 3 cut to a predetermined width in the winding direction of the roll-shaped acrylic resin film 5 wound on the winding core 19. Enter at an arbitrary angle and take up the presser. FIG. 3 is a view for explaining an angle (also referred to as “entrance angle” in this specification) when the acrylic resin film 3 enters the roll-shaped acrylic resin film 5 on the winding core 19. FIG. 4 corresponds to a state in which the approach angle θ is added to FIG. That is, the tangential direction A (that is, the winding direction) of the roll-shaped acrylic resin film 5 at the point where the acrylic resin film 3 comes into contact with the roll-shaped acrylic resin film 5 (a substantially linear portion in three dimensions), and The angle formed between the resin film 3 and the traveling direction B until the resin film 3 comes into contact with the pressing roll 18 is defined as an approach angle θ. When the pressing roll 18 is arranged so as to press the acrylic resin film 3 against the roll-shaped acrylic resin film 5, the tangential direction (winding direction) A is between the center axis of the pressing roll 18 and the winding core 19. The direction is orthogonal to a line segment (a plane in three dimensions) connecting the central axis. When the acrylic resin film 3 enters from the direction in which the acrylic resin film 3 is wound without the holding roll 18, that is, when the acrylic resin film 3 enters from the direction A in FIG. And The approach angle θ thus defined can take an appropriate value in a range from 0 degrees to about 120 degrees.

  The winding amount of the acrylic resin film 3 is preferably in a range from 1 m to 9000 m, and more preferably in a range from 10 m to 6000 m. When the winding amount is less than 1 m, the effect of the present invention is not particularly necessary because the winding amount is small. On the other hand, when the winding amount exceeds 9000 m, the weight of the roll-shaped acrylic resin film 5 increases, and transport becomes difficult.

  Examples of the material of the winding core 19 used for winding the acrylic resin film 3 include polyolefin resins such as polyethylene and polypropylene, vinyl chloride resins, polystyrene resins, and ABS (acrylonitrile / butadiene / styrene copolymer). A) Plastics, such as resin, polyamide-based resin, polyester-based resin, and fiber-reinforced plastics (Fiber Reinforced Plastics), or paper. When the acrylic resin film 3 is used as an optical film, a plastic core is preferably used as the winding core 19 in order to prevent dust from being introduced.

[Polarizing plate and manufacturing method thereof]
The acrylic resin film manufactured in a roll shape as described above can be suitably used as a protective film (polarizer protective film) for a polarizing plate. Therefore, next, a polarizing plate using this acrylic resin film and a method for manufacturing the same will be described.

  When the roll-shaped acrylic resin film is applied to the production of a polarizing plate, industrially, for example, the roll-shaped acrylic resin film is unwound and the polyvinyl alcohol-based resin is separately transported in a long shape. To a polarizer consisting of In this case, the acrylic resin film can be bonded to only one side of the polarizer as a protective film, or can be bonded to both sides of the polarizer. When an acrylic resin film is pasted on one side of the polarizer, another resin film can be pasted on the other side of the polarizer, or the polarizing plate can be applied to a liquid crystal cell or the like. An adhesive layer can be provided directly. When laminating an acrylic resin film on one side of the polarizer and laminating another resin film on the other side of the polarizer, the other resin film is also usually continuously transported in a long shape, Affixed to polarizer. For bonding the polarizer to the acrylic resin film and bonding the polarizer to another resin film, an adhesive is usually used.

<Polarizer>
As the polarizer, a polarizer obtained by adsorbing and orienting a dichroic dye on a polyvinyl alcohol-based resin film and imparting predetermined polarization characteristics can be used. As the dichroic dye, iodine or a dichroic organic dye is used. That is, specifically, as a polarizer, an iodine-based polarizer film in which iodine is adsorbed and oriented on a polyvinyl alcohol-based resin film, and a dye-based polarizer film in which a dichroic organic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film Etc. can be used.

  The polyvinyl alcohol resin constituting the polarizer can be produced by saponifying a polyvinyl acetate resin. As the polyvinyl acetate-based resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, a copolymer of vinyl acetate with another monomer copolymerizable therewith is used. Other monomers copolymerizable with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and the like. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc. modified with aldehydes may also be used.

The polarizer is usually manufactured through the following steps (i) to (v).
(I) A humidity control step of adjusting the water content of the polyvinyl alcohol-based resin film.
(Ii) a step of uniaxially stretching the polyvinyl alcohol-based resin film.
(Iii) a step of dyeing the polyvinyl alcohol-based resin film with a dichroic dye to adsorb and orient the dichroic dye.
(Iv) a step of treating the polyvinyl alcohol-based resin film on which the dichroic dye is adsorbed and oriented with an aqueous boric acid solution;
(V) a washing step of washing off the boric acid aqueous solution;
The uniaxial stretching can be performed before dyeing, can be performed during dyeing, or can be performed during boric acid treatment after dyeing. Further, uniaxial stretching may be performed in these plural stages. The method of uniaxial stretching may be a method of uniaxially stretching between rolls having different peripheral speeds, or a method of uniaxially stretching using a hot roll. The stretching may be dry stretching in the air or wet stretching in which the film is swollen with a solvent. The stretching ratio is usually about 4 to 8 times. The thickness of the finally obtained polarizer film can be, for example, about 1 to 50 μm.

<Another resin film>
When an acrylic resin film is bonded to one surface of the polarizer and another resin film is bonded to the other surface of the polarizer, the other resin film may be a chain-like polyolefin resin such as a polypropylene resin, Cyclic polyolefin resin, cellulose resin (for example, cellulose acetate resin represented by triacetyl cellulose or diacetyl cellulose), polycarbonate resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polystyrene resin, acrylonitrile. Butadiene / styrene copolymer resin, acrylonitrile / styrene copolymer resin, polyvinyl acetate resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyamide resin, polyacetal resin, modified polyphenylene ether resin, polysul Down resins, polyethersulfone resins, polyarylate resins, polyamideimide resins, it is possible to use a film made of polyimide resin. The thickness of these other resin films is usually 5-200 μm, preferably 10-170 μm. Form in which the acrylic resin film produced by the method of the present invention is bonded to one surface of a polarizer, and the acrylic resin film produced by a method different from the method of the present invention is bonded to the other surface of the polarizer. Are of course included in the present invention.

  Further, as a resin film to be bonded to the surface of the polarizer on the side opposite to the acrylic resin film, a wavelength plate such as a 波長 wavelength plate or a 波長 wavelength plate, a viewing angle compensation film, or the like is included. A phase difference film may be used. With such a structure in which the retardation films are laminated, the number of laminated films can be reduced. Therefore, it is possible to reduce the weight and thickness of the liquid crystal display device to which this is applied. As the retardation film including the wave plate and the viewing angle compensation film, conventionally known films can be used. For example, it is composed of polycarbonate resin, polyvinyl alcohol resin, polystyrene resin, (meth) acrylate resin, polyolefin resin such as polypropylene, cyclic polyolefin resin, polyarylate resin, polyimide resin, polyamide resin, and the like. A retardation film can be obtained by stretching the film by an appropriate method such as uniaxial or biaxial. The retardation film may be a birefringent film in which the refractive index in the thickness direction of the film is controlled by applying a shrinking force and / or a stretching force while adhering to the heat shrinkable film.

<Adhesion between polarizer and resin film (protective film)>
As described above, an adhesive is usually used for bonding the acrylic resin film to the polarizer and bonding another resin film. Prior to bonding, at least one of the bonding surfaces of each of the films is preferably subjected to a corona discharge treatment, a plasma irradiation treatment, an electron beam irradiation treatment, or another surface activation treatment. The adhesive can be arbitrarily selected and used from those exhibiting an adhesive force to each member. Typically, an active energy ray-curable adhesive containing a component which is cured by irradiation with an active energy ray can be used.

  When an active energy ray-curable adhesive is used, components that cure the composition by irradiation with active energy rays (hereinafter sometimes simply referred to as “curable components”) include epoxy compounds, okitacene compounds, and acrylic compounds. And so on. When a cationically polymerizable compound such as an epoxy compound or an okitacene compound is used, a cationic polymerization initiator is blended. When a radical polymerizable compound such as an acrylic compound is used, a radical polymerization initiator is blended. Among these, an adhesive using an epoxy compound as one of the curable components is preferable, and an adhesive using an alicyclic epoxy compound in which an epoxy group is directly bonded to a saturated hydrocarbon ring as one of the curable components is particularly preferable. preferable. It is also effective to use an oxetane compound in combination therewith.

  As the epoxy compound, a commercially available product can be easily obtained. For example, "Epicoat" series sold by Japan Epoxy Resin Co., "Epiclon" series sold by DIC Corporation, "Epototo" series sold by Toto Kasei Co., Ltd. "Adeka Resin" series sold by Adeka Company, "Denacol" series sold by Nagase ChemteX Corporation, "Dow Epoxy" series sold by Dow Chemical Company, sold by Nissan Chemical Industries, Ltd. "Tepic" and so on.

  An alicyclic epoxy compound having an epoxy group directly bonded to a saturated hydrocarbon ring can also be easily obtained as a commercial product. For example, there are the "Celoxide" series and "Cyclomer" series sold by Daicel Chemical Industries, Ltd., and the "Syracure" series sold by Dow Chemical Company, respectively, under the trade names.

  Oxetane compounds can also be easily obtained as commercial products. For example, there are the "Aron Oxetane" series sold by Toagosei Co., Ltd. and the "ETERNACOLL" series sold by Ube Industries, Ltd., respectively, under trade names.

  As for the cationic polymerization initiator, a commercially available product can be easily obtained. For example, "Kayarad" series sold by Nippon Kayaku Co., Ltd., "Cyracure" series sold by Union Carbide, and "CPI" photoacid generator sold by San Apro Co., Ltd. Series, photoacid generators "TAZ", "BBI" and "DTS" sold by Midori Chemical Co., Ltd., "ADEKA OPTOMER" series sold by ADEKA Corporation, sold by Rhodia RHODORSIL ”series.

  The active energy ray-curable adhesive can contain a photosensitizer as needed. By using the photosensitizer, the reactivity is improved, and the mechanical strength and the adhesive strength of the cured product layer can be further improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, anthracene compounds, halogen compounds, and photoreducible dyes.

  Various additives can be added to the active energy ray-curable adhesive within a range that does not impair the adhesiveness. Examples of the additive include an ion trapping agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow regulator, a plasticizer, and an antifoaming agent. Furthermore, a curable component that cures by a different reaction mechanism from cationic polymerization can be added as long as the adhesiveness is not impaired.

  The active energy ray-curable adhesive described above is applied to a bonding surface of a protective film or a resin film or a bonding surface of a polarizer. After laminating both films via the coating layer, the film is cured by irradiating it with an active energy ray to form an adhesive layer for bonding the polarizer to the protective film and / or the resin film. When bonding a protective film or a resin film to both surfaces of the polarizer, the bonding of the polarizer to one surface and the other surface may be performed sequentially or simultaneously. Performing them simultaneously is advantageous in terms of productivity. The adhesive applied to both surfaces of the polarizer may have the same composition or different compositions. Irradiation with active energy rays for curing both of them is preferably performed simultaneously from the viewpoint of productivity.

  The active energy rays used for curing the active energy ray-curable adhesive may be, for example, X-rays having a wavelength of 1 to 10 nm, ultraviolet rays having a wavelength of 10 to 400 nm, and visible rays having a wavelength of 400 to 800 nm. Among these, ultraviolet rays are preferably used in terms of ease of use, ease of preparation of the active energy ray-curable adhesive, stability and curing performance. As the ultraviolet light source, for example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, a metal halide lamp, or the like having a light emission distribution at a wavelength of 400 nm or less can be used. it can.

  The thickness of the adhesive layer obtained by using the active energy ray-curable adhesive can usually range from about 0.1 to 50 μm. It is more preferable that the thickness be 10 μm or less, and more preferably 5 μm or less, in a range where a sufficient adhesive force can be obtained.

<Adhesive layer>
The polarizing plate is usually provided with an adhesive layer for bonding to a liquid crystal cell or the like. An acrylic resin film produced according to the method of the present invention is bonded to one surface of a polarizer as a protective film. In a polarizing plate having a structure in which another resin film or a retardation film is bonded to the other surface of the polarizer, usually, an adhesive layer is provided on a surface opposite to the acrylic resin film as a protective film. An acrylic resin film produced according to the method of the present invention may be bonded to one surface of a polarizer as a protective film, and a pressure-sensitive adhesive layer may be directly provided on the other surface of the polarizer. For forming the pressure-sensitive adhesive layer, a resin containing an acrylate ester as a main constituent monomer is used. Specifically, an acrylic pressure-sensitive adhesive in which a crosslinking agent and the like are blended with an adhesive resin composed of an acrylic resin in which a small amount of a polar functional group-containing monomer such as acrylic acid or 2-hydroxyethyl acrylate is copolymerized is used. It is preferably used from the viewpoints of transparency, appropriate adhesive strength, and the like.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In the examples, percentages and parts representing contents and amounts used are by weight unless otherwise specified.

[Example 1]
(1) Preparation of Raw Material Resin As a methacrylic resin, a pellet of a thermoplastic polymer (glass transition temperature: 104 ° C.) which is a copolymer of 97% by weight of methyl methacrylate and 3% by weight of methyl acrylate was used. Acrylic rubber particles are produced in the same manner as in Example 3 of JP-B-55-27576 (Patent Document 3), and the innermost layer is a hard material in which a small amount of allyl methacrylate is copolymerized with methyl methacrylate. An elastic polymer composed of butyl acrylate as the main component of the coalesced and intermediate layers, and further copolymerized with styrene and a small amount of allyl methacrylate. A spherical three-layer structure made of a polymer having an average particle diameter of 0.22 μm was used.

  70 parts of methacrylic resin pellets and 30 parts of acrylic rubber particles were mixed by a super mixer. Next, the mixture was melt-kneaded with a twin-screw extruder to form a resin composition pellet, which was used as an acrylic resin.

(2) Preparation of Acrylic Resin Film The obtained pellet is melted by a 130 mmφ single screw extruder, extruded from a T-die, and is a metal elastic roll (elastic roll whose surface is made of stainless steel) described with reference to FIG. Cooling was performed by sandwiching the first cooling roll 11 and a second cooling roll 12 (surface temperature: 102 ° C.), which is a rigid roll of stainless steel. Further, the mixture was passed through the third cooling roll 13 and the discharge amount and the line speed were appropriately adjusted so that the thickness became 80 μm, thereby obtaining an acrylic resin film. After slitting the obtained film to a width of 1330 mm, the film was wound around a winding core having a diameter of 6 inches (15.2 mm) to a length of 2000 m.

  The winding conditions at this time were a winding tension of 135 N / m, and winding was performed using a holding roll to obtain a roll-shaped acrylic resin film. A rubber roll was used as the holding roll. A linear pressure of 0.36 N / mm was applied to the roll-shaped acrylic resin film by the holding roll. The appearance of the obtained roll-shaped acrylic resin film was evaluated as in the following (A) to (D).

(A) Evaluation of Presence or Absence of Polygon “Polygon” is a phenomenon in which the cross-section of an acrylic resin film wound up in a roll shape becomes a polygonal shape where it should be a circular shape (columnar cross-section). Here, the surface of the acrylic resin film wound up in a roll shape (the outermost surface of the film corresponding to the cylindrical side surface) was palpated to evaluate whether or not the film was deformed. Evaluation was performed twice immediately after winding and 10 days later. The results are shown in Table 1, where the level at which no unevenness is felt and the cross section is confirmed to be a circle is “○”, and the level at which unevenness is felt and the cross section is not a circle is “X” is shown in Table 1. .

(B) Evaluation of Film Slack "Film slack" is a phenomenon in which an acrylic resin film wound up in a roll shape hangs downward due to its weight. Here, when the acrylic resin film is wound into a roll, a pressure sensor is placed near the winding core, and when the roll is rotated in the wound state, there is a change in the value detected by the pressure sensor. Was evaluated. When the roll is rotated, there is no change in pressure, and when it is determined that there is no lower slack, the change in pressure is detected when the roll is rotated, and it is determined that there is lower slack. The results are shown in Table 1 with “x” as the case.

(C) Evaluation of High Edge The “high edge” is a phenomenon in which the width direction end of the acrylic resin film wound in a roll shape is higher than the width direction center. Here, the acrylic resin film wound into a roll was visually observed and evaluated. The results are shown in Table 1, where "○" indicates that no high edge was observed and "x" indicates that a high edge was observed.

(D) Evaluation of Gauge Band The “gauge band” is a bump or a winding bump observed along the circumferential direction of the surface of the acrylic resin film wound into a roll. Here, the end of one side (the surface corresponding to the bottom of the cylinder) of the acrylic resin film wound up in a roll shape is illuminated with a HID lamp (High Intensity Discharged Lump), and the film surface (corresponding to the side of the cylinder) is illuminated. From the surface to be measured), and the presence or absence of a gauge band was evaluated. The results are shown in Table 1, where "O" indicates that the gauge band was not observed and "X" indicates that the gauge band was observed.

[Example 2]
The roll-shaped acrylic resin film was wound up under the same conditions as in Example 1 except that a linear pressure of 0.18 N / mm was applied to the roll-shaped acrylic resin film.

[Example 3]
In Example 2, winding was performed under the same conditions except that the thickness of the obtained acrylic resin film was changed to 60 μm.

[Example 4]
In Example 2, winding was performed under the same conditions except that the thickness of the obtained acrylic resin film was changed to 40 μm.

[Comparative Example 1]
The winding was performed under the same conditions as in Example 1 except that the winding tension was set to 75 N / m and the holding roll was not used.

[Comparative Example 2]
The winding was performed under the same conditions as in Example 1 except that the winding tension was 190 N / m, and the holding roll was not used.

[Comparative Example 3]
The winding was performed under the same conditions as in Example 1 except that the winding tension was set to 260 N / m and the holding roll was not used.

[Comparative Example 4]
The roll-shaped acrylic resin film was wound under the same conditions as in Example 1 except that a linear pressure of 0.72 N / mm was applied to the roll-shaped acrylic resin film.

  As shown in Table 1, although the winding tension is within the range specified in the present invention, Comparative Examples 1 and 2, in which the holding roll was not wound, showed good appearance immediately after production, but were stored as they were. Produces a polygon. In addition, the film is also sagged. In Comparative Example 3 in which the winding tension was increased, although the appearance of the obtained roll-shaped resin film was not changed when the obtained resin film was stored as it was, the film was loosened, a high edge, and a gauge band were generated. When the pressing roll is operated in this state, although it is possible that the lower slack of the film may be eliminated, it is considered that it is difficult to eliminate the high edge and the gauge band. Although the pressing roll is arranged, the comparative example 4 in which the linear pressure is increased has a high edge and a gauge band.

  On the other hand, Examples 1 to 4 in which the winding tension was in the range defined by the present invention and the pressing roller was arranged and the linear pressure was in the range defined in the present invention had no defects as described above. It has been wound up in good condition, and its condition has not changed after storage for 10 days.

REFERENCE SIGNS LIST 1 film-like material extruded in a molten state 2 film-like molded body 3 acrylic resin film whose side end is cut 5 roll-like acrylic resin film 10 T die 11 first cooling roll (metal elastic roll)
12 Second cooling roll (metal rigid roll)
13 Third cooling roll 14 Cutter 15 Accumulator 16 Nip roll 17 Dancer roll 18 Pressing roll 19 Winding core 20 Transport roll θ Entry angle

Claims (8)

An acrylic resin is melt-kneaded and a film is extruded from a T-die, and the film is sandwiched between a first cooling roll and a second cooling roll to form a film-shaped product. A method for producing an acrylic resin film having a thickness of 80 μm or less, by cutting the width direction side end, winding the obtained film around a winding core and winding it into a roll,
The winding tension when winding the film around the winding core is 50 to 250 N / m,
A roll, wherein a press roll is disposed on the take-up core side, and a linear pressure of the press roll is set to 0.18 to 0.6 N / mm, and the film whose side end is cut is wound into a roll. Of producing acrylic acrylic resin film. The method for producing a roll-shaped acrylic resin film according to claim 1, wherein the acrylic resin film has a thickness of 20 µm or more and 80 µm or less. The method for manufacturing a roll-shaped acrylic resin film according to claim 1 or 2, wherein the pressing roll is disposed at or before a position where the acrylic resin film is wound up and becomes the roll-shaped acrylic resin film. . The method for producing a roll-shaped acrylic resin film according to any one of claims 1 to 3, wherein the acrylic resin film has a width of 500 mm or more and 2000 mm or less. The method for producing a roll-shaped acrylic resin film according to any one of claims 1 to 4 , wherein the second cooling roll has a surface temperature of 60C or more and 130C or less. The method for producing a roll-shaped acrylic resin film according to any one of claims 1 to 5 , wherein a winding amount of the acrylic resin film is 1 m or more and 9000 m or less. The method for producing a roll-shaped acrylic resin film according to any one of claims 1 to 6 , wherein the acrylic resin contains rubber particles. A method for producing a polarizing plate, comprising: unwinding a roll-shaped acrylic resin film produced by the method according to any one of claims 1 to 7 and bonding it to a polarizer made of a polyvinyl alcohol-based resin.

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