JP6360943B2 - Method for producing laminated film and method for producing polarizing plate - Google Patents

Description

  The present invention relates to a method for producing a laminated film and a method for producing a polarizing plate.

  2. Description of the Related Art Conventionally, polarizing plates have been widely used as polarized light supplying elements and polarized light detecting elements in display devices such as liquid crystal display devices. As the polarizing plate, one having a configuration in which a protective film is bonded to one side or both sides of a polarizing film (polarizer) using an adhesive is known.

  In recent years, with the improvement in performance and thickness of liquid crystal display devices, the polarizer is also required to be thin. For example, after a polarizer having a thickness of 10 μm or less is formed on a thermoplastic resin substrate, a resin layer using a polyvinyl alcohol resin (hereinafter, “polyvinyl alcohol” may be referred to as “PVA”) as a forming material is formed. The laminate obtained is produced by stretching and dyeing (for example, Patent Document 1).

JP 2011-002816 A

  In the production of the polarizer described above, when the stretching process and the dyeing process are not continuous processes, the film after stretching is wound into a roll, and then the roll is transported to the next process, and the film is unwound and dyed again. There are things to do. Before the film is wound, a process of bonding a protective film (also referred to as a release film or a surface protective film) to the surface of the resin layer is often performed for the purpose of protecting the resin layer in the film.

  However, when the film having the protective film bonded to the surface of the PVA-based resin layer is taken up, the position of the end in the width direction of the film (winding deviation) may occur. When a polarizing plate is produced from a film in which winding deviation has occurred, the flatness of the polarizing plate may be inferior, and scratches or wrinkles may occur. Until now, the cause of the winding deviation has not been sufficiently specified, and a method for reducing the occurrence of such winding deviation has not been established.

  This invention is made | formed in view of such a situation, Comprising: One aspect | mode of this invention aims at providing the manufacturing method of a laminated film which reduces generation | occurrence | production of winding deviation at the time of winding of a laminated film. To do. Another object is to provide a method for producing a polarizing plate using the laminated film obtained by the above-described production method.

  As a result of intensive studies to solve the above-described problems, the present inventors have found that the larger the absolute value of the charge amount of the laminated film, the more winding deviation occurs during winding. For this reason, it has been found that by defining the upper limit of the absolute value of the charge amount of the laminated film, the winding deviation at the time of winding can be reduced, and the present invention has been completed.

  One aspect of the present invention is a coating layer obtained by coating a coating liquid containing a polyvinyl alcohol-based resin on at least one surface of a base film while transporting a belt-shaped base film in the longitudinal direction. A resin layer forming step of forming a resin layer having a polyvinyl alcohol resin as a forming material on at least one surface by drying, and stretching while transporting the laminate obtained in the resin layer forming step in the longitudinal direction, A stretching process for obtaining a stretched film in which a stretched base film in which a base film is stretched and a resin film in which a resin layer is stretched are laminated, a protective film is bonded to the surface of the resin film, and a stretched base film A first laminating step for obtaining a laminated film in which a resin film and a protective film are laminated in this order; a winding step for winding the laminated film with a winding roll; Preparation of a laminated film in which the tension per unit width applied to the laminated film is 30 N / m or more at the start of the winding process, and the absolute value of the charge amount of the laminated film immediately before the winding roll is 32 kV or less Provide a method.

  In one embodiment of the present invention, the protective film preferably contains a polyolefin resin as a forming material.

  In one aspect of the present invention, in the stretching step, the laminated body is passed in the order of the first nip roll and the second nip roll, and longitudinal uniaxial stretching is performed by the difference in peripheral speed between the first nip roll and the second nip roll. Is preferred.

  In one aspect of the present invention, it is preferable that the tension per unit width applied to the laminated film is 90 N / m or less at the start of the winding process.

  One aspect of the present invention is a process for obtaining a laminated film by the above production method, a first peeling process for unwinding the laminated film, and peeling the protective film from the laminated film, and a stretched film obtained in the first peeling process. Dyeing step of obtaining a polarizing laminated film in which a resin film contained is dyed with a dichroic material, and a stretched base film and a polarizer layer formed on at least one surface of the stretched base film are laminated; The manufacturing method of a polarizing plate provided with the 2nd bonding process of bonding a protective film to the surface of at least the polarizer layer of a light-polarizing laminated film.

  In 1 aspect of this invention, it is preferable to provide the 2nd peeling process which peels an extending | stretching base film after a 2nd bonding process.

  According to one embodiment of the present invention, there is provided a method for producing a laminated film that reduces the occurrence of winding slippage at the time of winding the laminated film. Moreover, the manufacturing method of the polarizing plate using the laminated film obtained by the above-mentioned manufacturing method is provided together.

It is a flowchart which shows the manufacturing method of the laminated film which concerns on this embodiment. It is process drawing which shows 1st bonding process S3 and winding process S4. It is a flowchart which shows the manufacturing method of the polarizing plate which concerns on this embodiment.

<Method for producing laminated film>
Hereinafter, an embodiment of a method for producing a laminated film according to the present invention will be described with reference to FIG. In all the drawings below, the dimensions and ratios of the constituent elements are appropriately changed in order to make the drawings easy to see.

  FIG. 1 is a flowchart showing a method for manufacturing a laminated film according to the present embodiment. As shown in FIG. 1, the manufacturing method of the laminated | multilayer film which concerns on this embodiment is equipped with resin layer formation process S1, extending process S2, 1st bonding process S3, and winding process S4.

[Resin layer forming step S1]
In resin layer formation process S1, the resin layer which uses a polyvinyl alcohol-type resin (Hereinafter, "polyvinyl alcohol" may be called "PVA.") As a forming material is formed in the at least one surface of a base film.

  Specifically, first, a coating liquid containing a PVA-based resin is applied to at least one surface of the substrate film while conveying the belt-shaped substrate film in the longitudinal direction. After coating, a coating layer containing a PVA-based resin is formed on at least one surface of the base film. Next, this coating layer is dried to form a resin layer.

  As a base film, what is conventionally used as a protective film of a polarizing plate can be used, and as a forming material of a base film, for example, transparency, mechanical strength, thermal stability, moisture barrier property A thermoplastic resin excellent in isotropic property and stretchability is used.

  Examples of such thermoplastic resins include polyolefin resins such as chain polyolefin resins, cyclic polyolefin resins (norbornene resins), polyester resins, (meth) acrylic resins, cellulose triacetate, cellulose diacetate, and the like. Cellulose ester resins, polycarbonate resins, polyvinyl alcohol resins, polyvinyl acetate resins, polyarylate resins, polystyrene resins, polyethersulfone resins, polysulfone resins, polyamide resins, polyimide resins, or these Of the mixture. In addition, a copolymer obtained by copolymerizing the above resin monomers may be used as a material for forming a base film. Among these, polyolefin resins such as polypropylene and polyester resins such as amorphous polyethylene terephthalate are preferable.

  The base film is formed from one or more thermoplastic resins. The base film may have a single layer structure composed of one thermoplastic resin layer or a multilayer structure in which a plurality of thermoplastic resin layers are laminated. The base film is preferably composed of a resin that can be stretched at a stretching temperature suitable for stretching the resin layer in the stretching step performed after the resin layer forming step.

  The base film is an ultraviolet absorber, antioxidant, lubricant, plasticizer, mold release agent, anti-coloring agent, flame retardant, nucleating agent, antistatic agent, pigment, or coloring as long as the effects of the present invention are not impaired. You may contain additives, such as an agent.

  The thickness of the base film is preferably 1 to 500 μm, more preferably 1 to 300 μm, further preferably 5 to 200 μm, and particularly preferably 5 to 150 μm from the viewpoint of strength and handleability.

As the PVA resin, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers with other monomers copolymerizable with vinyl acetate.
Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The PVA resin is preferably a completely saponified product. The saponification degree of the PVA resin is preferably 80.0 mol% or more and 99.5 mol% or less, more preferably 90.0 mol% or more and 99.5 mol% or less, and 94.0 mol%. More preferably, it is 99.0 or less mol%. When the saponification degree of the PVA-based resin is less than 80.0 mol%, the water resistance and moist heat resistance may decrease when a polarizing plate is used. Further, if the degree of saponification of the PVA-based resin is larger than 99.5 mol%, the dyeing speed is slowed in the production process of the polarizing plate, the productivity is lowered, and a polarizing plate having sufficient polarizing performance cannot be obtained. There is.

  The degree of saponification (unit: mol%) of the PVA-based resin is the unit ratio (unit: mol) of the ratio of the acetate group contained in the polyvinyl acetate-based resin, which is the raw material of the PVA-based resin, to the hydroxyl group by the saponification step. %) And is a numerical value defined by the following formula (S1). This numerical value can be obtained by a method defined in JIS K 6726 (1994).

Degree of saponification = (number of hydroxyl groups) / (number of hydroxyl groups + number of acetate groups) × 100 (S1)
The higher the degree of saponification of the PVA-based resin, the higher the ratio of hydroxyl groups, that is, the lower the ratio of acetic acid groups that inhibit crystallization.

  The PVA-based resin described above may be a modified PVA partially modified. For example, PVA resins may be modified with olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, alkyl esters of unsaturated carboxylic acids, acrylamide, and the like. The proportion of modification is preferably less than 30 mol%, and more preferably less than 10 mol%. When modification exceeding 30 mol% is performed, it becomes difficult to adsorb the dichroic substance, and the polarization performance when used as a polarizing plate may be lowered.

  Although the average degree of polymerization of PVA-type resin is not specifically limited, 100-10000 are preferable, 1500-8000 are more preferable, 2000-5000 are more preferable. The average degree of polymerization of the PVA-based resin can be determined by the method defined by JIS K 6726 (1994), similarly to the degree of saponification.

  Examples of the PVA resin having such characteristics include PVA124 (saponification degree: 98.0 to 99.0 mol%) and PVA117 (degree of saponification: 98.0 to 99.0 mol%) manufactured by Kuraray Co., Ltd. ), PVA624 (degree of saponification: 95.0-96.0 mol%) and PVA617 (degree of saponification: 94.5-95.5 mol%); for example, AH-26 (ken) manufactured by Nippon Synthetic Chemical Industry Co., Ltd. Degree of saponification: 97.0-98.8 mol%), AH-22 (degree of saponification: 97.5-98.5 mol%), NH-18 (degree of saponification: 98.0-99.0 mol%) ), And N-300 (degree of saponification: 98.0 to 99.0 mol%); for example, JC-33 (degree of saponification: 99.0 mol% or more) of Nippon Acetate Bi-Poval Corporation, JM-33 (Degree of saponification: 93.5-95.5 mol%), JM-26 (saponification : 95.5-97.5 mol%), JP-45 (degree of saponification: 86.5-89.5 mol%), JF-17 (degree of saponification: 98.0-99.0 mol%), Examples thereof include JF-17L (degree of saponification: 98.0 to 99.0 mol%) and JF-20 (degree of saponification: 98.0 to 99.0 mol%).

  A coating liquid containing a PVA resin is obtained by swelling a PVA resin powder, a pulverized product, or a cut product with a solvent, and then heating and stirring the swollen PVA resin. As the solvent, for example, water is preferable. The concentration of the PVA resin in the coating solution is preferably 5% by mass or more and 15% by mass or less, and more preferably 5% by mass or more and 10% by mass or less.

  Application of a coating solution containing a PVA-based resin is performed using a conventionally known coating method. Conventionally known coating methods include, for example, roll coating methods such as wire bar coating method, reverse coating, and gravure coating, die coating method, comma coating method, lip coating method, screen coating method, fountain coating method, dipping method, spray method Etc. The above-mentioned coating liquid may be applied only to one side of the base film, or may be applied to both sides.

  The obtained coating layer is dried using a conventionally known apparatus. As a conventionally well-known apparatus, the apparatus provided with the some drying roll whose rotation axis is mutually parallel, for example is mentioned. The coating layer may be dried under reduced pressure as necessary. Moreover, as a method of drying a coating layer by heating, drying with a hot roll, warm air drying, etc. are mentioned, for example.

  The thickness of the resin layer obtained in the resin layer forming step S1 may be appropriately determined from the desired thickness of the laminated film and the stretching ratio in the subsequent stretching step, and is preferably 3 μm or more and 30 μm or less, for example, preferably 5 μm or more. More preferably, it is 20 μm or less.

  In order to improve the adhesion between the base film and the resin layer, at least the surface of the base film on the side where the resin layer is formed may be subjected to a surface treatment. Examples of such surface treatment include corona treatment, plasma treatment, flame (flame) treatment, and the like. For the same purpose, a coating layer may be formed on the base film via a primer layer or the like.

As a material for forming the primer layer, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropic property, stretchability, and the like is used. Examples of such thermoplastic resins include (meth) acrylic resins and polyvinyl alcohol resins.
As a material for forming the primer layer, a PVA-based resin is preferable, and a PVA resin is more preferable because both the adhesiveness between the base film and the resin layer can be exhibited.

  Examples of the method for forming the primer layer include a method in which a mixed solution of the above resin and solvent is applied to the surface of the base film and then dried. The solvent is not particularly limited as long as the resin can be dissolved, but water is preferable. The primer layer coating method is the same as the coating method of the coating liquid containing the PVA resin. 50-200 degreeC is preferable and the drying temperature when forming a primer layer has more preferable 60-150 degreeC. When water is contained as a solvent, the drying temperature is preferably 80 ° C. or higher.

  The primer layer may contain a crosslinking agent in order to improve its strength. Specific examples of the crosslinking agent include, for example, epoxy-based, isocyanate-based, dialdehyde-based, metal-based, or polymer-based crosslinking agents. Examples of the metal-based crosslinking agent include metal salts, metal oxides, metal hydroxides, and organometallic compounds. When a polyvinyl alcohol-based resin is employed as a material for forming the primer layer, a polyamide epoxy resin, a methylolated melamine resin, a dialdehyde-based crosslinking agent, a metal chelate compound-based crosslinking agent, or the like is preferably used.

  The thickness of the primer layer is preferably about 0.05 to 1 μm, more preferably 0.1 to 0.4 μm. If the thickness of the primer layer is less than 0.05 μm, sufficient adhesion between the base film and the resin layer may not be obtained.

[Stretching step S2]
In the stretching step S2, the laminate obtained in the resin layer forming step S1 is stretched while being conveyed in the longitudinal direction to obtain a stretched film. The stretched film is formed by laminating a stretched base film obtained by stretching a base film and a resin film formed on at least one surface of the stretched base film and having a resin layer stretched.

  The stretching ratio in the stretching step S2 may be appropriately selected according to the desired polarization performance when used as a polarizing plate, but is preferably more than 5 times and not more than 17 times the original length of the laminate, and more than 5 times. 8 times or less is more preferable. When the draw ratio exceeds 5 times, the orientation of the PVA-based resin is sufficient, so that sufficient polarizing performance can be obtained when a polarizing plate is used. On the other hand, when the draw ratio is 17 times or less, the stretched film is not easily broken, and processability and handleability in the subsequent process can be sufficiently secured.

  If the stretching ratio is within the above range, the stretching step S2 can be performed in multiple stages. In this case, all of the multistage stretching may be performed continuously before the subsequent dyeing process, or the second and subsequent stretching may be performed simultaneously with the dyeing process. In such an embodiment, for example, the first-stage stretching is performed by a dry method, the stretching ratio is more than 1.1 times and not more than 3.0 times, and the second-stage stretching is performed in water (for example, a dyeing bath or a crosslinking bath described later). The stretching ratio may be 2 to 5 times.

  The stretching direction in the stretching step S2 may be the longitudinal direction of the laminate (the transport direction of the laminate), the width direction, or the oblique direction. The stretching step S2 is preferably longitudinal uniaxial stretching in which uniaxial stretching is performed in the longitudinal direction of the laminate. Specifically, it is preferable to pass through the laminate in the order of the first nip roll and the second nip roll, and perform longitudinal uniaxial stretching by the difference in peripheral speed between the first nip roll and the second nip roll.

  The stretching step S2 can employ either a wet stretching method or a dry stretching method, but it is preferable to use the dry stretching method because the stretching temperature can be selected from a wide range.

  The stretching temperature may be set to be equal to or higher than the temperature at which fluidity can be achieved so that the laminate can be stretched, and is preferably from 80 ° C. to 170 ° C., more preferably from 90 ° C. to 160 ° C.

  The thickness of the resin film in the stretched film is preferably 1 μm or more and 10 μm or less, and more preferably 2 μm or more and 7 μm or less. When the thickness of the resin film is in the above range, it is easy to dye with a dichroic substance in the production of the polarizing plate, and the polarizing performance when the polarizing plate is obtained is excellent.

The length of the obtained stretched film in the longitudinal direction is preferably 1000 m or more, and may be 2000 m or more. The longer the length in the longitudinal direction of the stretched film, the easier it is to cause winding slippage in the subsequent winding step S4. However, according to this embodiment, the length of the stretched film in the longitudinal direction is more than 2000 m. In addition, the occurrence of winding deviation can be reduced. Although the upper limit of the length of the stretched film in the longitudinal direction is not particularly limited, it is, for example, 20000 m and may be 10,000 m.

[First bonding step S3]
FIG. 2 is a process diagram showing a first bonding process S3 and a winding process S4. As shown in FIG. 2, in 1st bonding process S3, the protective film 21 is bonded to the surface of the resin film in the stretched film 11 conveyed through the nip roll 101, and the laminated film 13 is obtained. The laminated film is formed by laminating a stretched base film, a resin film, and a protective film in this order.

  By laminating the protective film 21 to form the laminated film 13, the resin film can be protected in the subsequent winding step S4. Moreover, winding up and unwinding of the laminated | multilayer film 13 can be performed cleanly and smoothly because the protective film 21 is bonded.

  The protective film 21 is not particularly limited as long as it has adhesion to the stretched film 11 and can be wound in the subsequent winding step S4. The protective film 21 is configured by laminating an adhesive / peelable resin layer or an adhesive resin layer on a film made of a thermoplastic resin, as necessary.

  Examples of the thermoplastic resin include a polyolefin resin or a polyester resin, and it is preferable to include a polyolefin resin. The polyolefin resin may have a chain structure or a cyclic structure. Examples of the polyolefin resin include polyimide resin, polyethylene, polypropylene, and ethylene / propylene copolymer.

Examples of the adhesive / peelable resin layer include acrylic adhesives, natural rubber adhesives, styrene-butadiene copolymer resin adhesives, polyisobutylene adhesives, vinyl ether resin adhesives, silicone resin adhesives, and the like. Is mentioned.
Examples of the adhesive resin layer include ethylene-vinyl acetate copolymer resin.
In addition, when the film itself which uses a thermoplastic resin as a forming material has adhesiveness / peelability or adhesion, these resin layers may not be provided.

  A commercially available protect film can be used as the protect film 21, for example, Tretec 7332 (made by Toray Film Processing Co., Ltd.), protect tape # 625T (made by Sekisui Chemical Co., Ltd.), and the like.

  The adhesion force of the protective film 21 to the stretched film 11 is preferably 0.02 N / 25 mm or more and 0.08 N / 25 mm or less. If the adhesion of the protective film 21 is 0.02 N / 25 mm or more, the protective film 21 is unlikely to float (referred to as tunneling) or peel off. When the adhesion of the protective film 21 is 0.08 N / 25 mm or less, the protective film 21 can be easily peeled off.

  Here, the adhesion force of the protective film 21 to the stretched film 11 can be obtained as follows. The laminated film 13 in which the protective film 21 is bonded to the stretched film 11 is cut so that the transport direction (MD) is the long side, the width is 25 mm or a multiple thereof, and the length is about 150 mm. It produces and the stretched film 11 side is bonded and fixed to a glass plate using an adhesive. Next, using a tensile tester, the end of the protective film 21 in the length direction (one side having a width of 25 mm or a multiple thereof) is grasped, and according to JIS K 6854-2: 1999, the grip moving speed is 300 mm / Perform 180 ° peel test in minutes. Then, the average peeling force over the peeling length obtained by removing the first 25 mm gripping movement distance from the obtained force-grasping movement distance curve is obtained. This value is the adhesion force to the stretched film 11 per width of the protective film 21 in this test piece.

  With respect to the above, when a test piece having a width of 25 mm is used, this value is directly used as an adhesion force to the stretched film 11 (unit: N / 25 mm). On the other hand, when a test piece having a width that is a multiple of 25 mm is used, the obtained average peeling force may be converted per 25 mm width. For example, when a test piece having a width of 100 mm (4 times as large as 25 mm) is used, the average peeling force obtained is multiplied by ¼ to obtain the adhesion force (N / 25 mm) of the protective film 21 to the stretched film 11.

Bonding of the protective film 21 can be performed by a conventionally known bonding method. As an example of a conventionally well-known pasting method, as shown in FIG. 2, the method of laminating | stacking the stretched film 11 and the protective film 21 and pressurizing with the nip roll 113 is mentioned. As a material of the nip roll 113, metal, rubber, or the like can be used.
In addition, when the resin layer is formed on both surfaces of the base film, the protective film 21 may be bonded to the surface of one resin layer.

  The thickness of the protective film 21 is preferably 1 μm or more and 100 μm or less, more preferably 1 μm or more and 80 μm or less, and even more preferably 1 μm or more and 50 μm or less from the viewpoint of strength, handleability, and the like.

  In 1st bonding process S3, the edge part of the protect film 21 or the stretched film 11 can be cut | disconnected as needed. Although cutting of the edge part of the protective film 21 or the stretched film 11 is not specifically limited, For example, it can perform by the slit method using a slitter. The slit method is preferable in that the end of a long film can be continuously cut and removed.

  As an example of the slit method, two circular blades called shear blades are used for slitting by applying contact pressure to the lower blade with the upper blade while rotating according to the conveyance of the film (protect film 21 or stretched film 11). A method is mentioned. As another example of the slit method, there is a method using a razor blade called a leather blade, a method of pressing a blade called a score blade against a quenching roll or the like and slitting. Even with the method using a leather blade, there is a hollow cut that slits in the air without providing a backup guide, and a groove roll method that stabilizes the meandering of the slit by inserting the blade into a roll with a groove as a backup guide . Among them, a slit method using a shear blade that can easily change the slit position of the film is preferably used.

  The portion removed by the slit is discharged from the production line. The removed portion can be discharged using a known device such as an ear winder. For example, the film may be wound and discharged by an ear winder immediately after cutting the film, or may be wound and discharged by an ear winder after the subsequent winding step S4.

[Winding process S4]
In the winding process S4, the belt-shaped laminated film 13 obtained in the first bonding process S3 is wound around the winding roll 115 while being conveyed in the longitudinal direction. In the winding step S4, the winding may be performed with the protective film 21 side inward, or may be wound with the protective film 21 side outward.

  The laminated film 13 obtained in the first bonding step S3 is easily charged. Due to the charging of the laminated film 13, the adjacent laminated films 13 in the laminated film 13 wound up in a roll shape are electrically repelled, and immediately after winding or during storage for a certain period, Deviation (winding deviation) of the position of the end may occur. As the absolute value of the charge amount of the laminated film 13 increases, the winding deviation when the laminated film 13 is wound up in a roll shape increases.

  Here, the winding deviation of the laminated film 13 refers to the maximum distance at which the end in the width direction of the laminated film 13 is displaced in a direction substantially perpendicular to the winding direction on any end surface of the roll-shaped laminated film 13. Such winding deviation can be measured using a metal ruler, a ruler, or the like.

  When the laminated film 13 in which the winding deviation has occurred is applied to the polarizing plate, the flatness of the polarizing plate may be inferior or scratches or wrinkles may be generated. Therefore, it is preferable that this winding deviation is as small as possible. The winding deviation of the laminated film 13 in the winding step S4 is preferably 5 mm or less, and more preferably 1 mm or less. When the winding deviation of the laminated film 13 is 5 mm or less, the winding deviation can be corrected when the laminated film 13 is unwound in a later step.

  As a result of intensive studies, the present inventors have found that the winding deviation of the laminated film 13 can be controlled within the above range if the absolute value of the charge amount of the laminated film 13 in the winding step S4 is 32 kV or less. Here, the measurement of the charge amount is preferably performed on the laminated film 13 immediately before the winding roll 115. Here, from the viewpoint of workability, the winding roll 115 is used when it is experimentally clear that the amount of charge of the laminated film 13 does not change immediately before the winding roll 115 and on the circumference of the winding roll 115. The charge amount may be measured for the laminated film 13 on the circumference. From the viewpoint of reducing winding deviation of the laminated film 13, the absolute value of the charge amount of the laminated film 13 is preferably 25 kV or less.

  The space where the winding step S4 is performed is preferably managed at a temperature of 13 to 33 ° C. and a relative humidity of 25 to 85%, more preferably at a temperature of 18 to 28 ° C. and a relative humidity of 40 to 70%. preferable. The higher the humidity of the space where the winding step S4 is performed, the smaller the charge amount of the laminated film 13 can be made. Moreover, it is preferable that relative humidity is 85% or less at the point of suppressing generation | occurrence | production of the rust in the apparatus used at winding-up process S4.

  In the present embodiment, the laminated film 13 is neutralized between the first bonding step S3 and the winding step S4. From the viewpoint of reducing the charge amount of the laminated film 13 at the time of winding, it is preferable that the stretched film 11 is neutralized between the stretching step S2 and the first bonding step S3 in addition to this period. The static elimination of the laminated film 13 can be performed using a conventionally known static eliminator. Conventionally known static eliminators include, for example, static eliminator bars, static eliminating yarns, or ion blow type static eliminators, and ion blow type static eliminators are preferred. Each of these static eliminators may be used alone or in combination with a plurality of devices.

  The winding of the laminated film 13 is preferably performed while applying tension to the laminated film 13. Winding deviation can be further suppressed by increasing the tension applied to the film during winding. However, it has been found that if the tension applied to the film during winding is excessively increased, a gauge band or the like is generated in the laminated film 13. Gauge bands and the like are preferably as small as possible because they may cause appearance defects in the subsequent process. On the other hand, the generation of a gauge band or the like can be suppressed by reducing the tension applied to the film during winding. However, it has also been found that if the tension applied to the film at the time of winding is too small, air mixing becomes large and winding deviation tends to occur.

  As a result of intensive investigations, the present inventors have found that when the tension per unit width applied to the laminated film 13 is 30 N / m or more at the start of winding of the laminated film 13, the mixing of air is suppressed and winding slippage is caused. It has been found that the occurrence of can be reduced. In addition, it was found that when the tension applied to the laminated film 13 is 90 N / m or less, the occurrence of winding deviation is more remarkably reduced, and a gauge band is hardly generated in the laminated film 13.

  The tension applied to the laminated film 13 when winding the laminated film 13 may be constant while the laminated film 13 is taken up, or may be different. When the tension applied to the laminated film 13 is made different, this tension is the largest immediately after the start of winding, and the tension can be gradually decreased as the diameter of the roll-shaped laminated film 13 taken up thereafter increases. preferable. At this time, according to the diameter of the laminated film 13, the ratio of the tension immediately before the end of winding to the tension immediately after the start of winding (hereinafter referred to as the taper ratio) can be determined.

  The winding speed of the laminated film 13 is preferably 5 m / min or more, more preferably 10 m / min or more, further preferably 15 m / min or more, and 20 m / min or more. Is particularly preferred. Further, the winding speed of the laminated film 13 may be 25 m / min or more. When the winding speed of the laminated film 13 is 5 m / min or more, the winding time of the laminated film 13 can be shortened, and the production efficiency is improved. On the other hand, in the conventional method, when the winding speed of the laminated film is high, winding slippage tends to occur. However, according to the method of the present invention, winding slippage hardly occurs even if the winding speed of the laminated film is increased.

  The winding speed of the laminated film 13 is preferably 70 m / min or less, more preferably 50 m / min or less, and further preferably 30 m / min or less. When the winding speed of the laminated film 13 is 70 m / min or less, the mixing of air is suppressed and winding deviation hardly occurs.

<Production method of polarizing plate>
Hereinafter, an embodiment of a method for producing a polarizing plate according to the present invention will be described with reference to FIG. The manufacture of the polarizing plate according to the present embodiment is performed using the laminated film obtained by the above-described manufacturing method.

  FIG. 3 is a flowchart showing a method for manufacturing a polarizing plate according to this embodiment. As shown in FIG. 3, the manufacturing method of the polarizing plate which concerns on this embodiment is provided with 1st peeling process S5, dyeing | staining process S6, 2nd bonding process S7, and 2nd peeling process S8.

[First peeling step S5]
In 1st peeling process S5, the laminated | multilayer film obtained are unwound, a protective film is peeled from a laminated | multilayer film, and a stretched film is obtained again. The protective film peeling method is not particularly limited. The protective film peeled off from the laminated film is preferably wound on a winding shaft. At this time, the protective film may be peeled off by hand and wound around the take-up shaft, or may be adsorbed by a suction roll and conveyed to the take-up shaft and taken up. Moreover, it is preferable that peeling of a protective film is performed, removing electricity centering on a peeling location as needed.

[Dyeing step S6]
In the dyeing step S6, the resin film contained in the stretched film obtained in the first peeling step S5 is dyed with a dichroic substance, and the stretched substrate film and the polarized light formed on at least one surface of the stretched substrate film A polarizing laminated film in which a child layer is laminated is obtained.

  The dyeing step S6 includes a dyeing process, a crosslinking process, a washing process, and a drying process. First, in the dyeing process, while transporting the belt-like stretched film in the longitudinal direction, the resin film contained in the stretched film is dyed with a dichroic substance to adsorb and orient the dichroic substance. Next, in the crosslinking treatment, the resin film dyed with the dichroic substance is crosslinked with a crosslinking agent. Furthermore, in the washing treatment, the crosslinked resin film is washed with a crosslinking agent. Further, the washed resin film is dried to obtain a polarizing laminated film.

  The dyeing process is performed by immersing the stretched film in a liquid containing a dichroic substance (hereinafter, dye bath). As this dyeing bath, a solution in which a dichroic substance is dissolved in a solvent can be used. As a solvent for the dyeing bath, for example, water is preferable. An organic solvent compatible with water may be further added to the dyeing bath. Specific examples of the organic solvent include methanol, ethanol, propanol, or glycerin.

  Examples of the dichroic substance used in the present embodiment include iodine or a dichroic organic dye known as a coloring material for a polarizing film. Examples of dichroic organic dyes include red BR, red LR, red R, pink LB, Rubin BL, Bordeaux GS, sky blue LG, lemon yellow, blue BR, blue 2R, navy RY, green LG, violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Spura Blue G, Spura Blue GL, Spura Orange GL, Direct Includes Sky Blue, Direct First Orange S and First Black. A dichroic substance may be used individually by 1 type, and may use 2 or more types together.

  The concentration of the dichroic substance in the dyeing bath is preferably 0.01% by mass or more and 10% by mass or less, and more preferably 0.02% by mass or more and 7% by mass or less.

  When iodine is used as the dichroic substance, it is preferable to further add iodide to a dyeing bath containing iodine for the purpose of improving dyeing efficiency. Examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. It is preferable to add potassium iodide. Moreover, the dyeing bath may contain a crosslinking agent.

The iodide concentration in the dyeing bath is preferably 0.01% by mass or more and 20% by mass or less. When potassium iodide is added to a dyeing bath containing iodine, the ratio of iodine to potassium iodide is preferably 1: 5 to 1: 100, and 1: 6 to 1:80 in terms of mass ratio. Is more preferable.
The temperature of the dyeing bath is preferably 10 ° C. or more and 60 ° C. or less, and more preferably 20 ° C. or more and 40 ° C. or less.

  In the dyeing step S6, subsequent to the dyeing process, a crosslinking process is performed in which a stretched film including a resin film dyed in a liquid containing a crosslinking agent (hereinafter, a crosslinking bath) is immersed.

  As a crosslinking agent used in this embodiment, a boron compound, glyoxal, or glutaraldehyde is preferable, and a boron compound is more preferable. Examples of the boron compound include boric acid and borax. Only 1 type may be used for a crosslinking agent and it may use 2 or more types together.

  As the crosslinking bath of this embodiment, a solution in which a crosslinking agent is dissolved in a solvent can be used. As the solvent, for example, water is preferable. The crosslinking bath may further contain an organic solvent compatible with water. Specific examples of the organic solvent are the same as described above. The concentration of the crosslinking agent in the crosslinking bath is preferably 1% by mass or more and 20% by mass or less, and more preferably 6% by mass or more and 15% by mass or less.

The crosslinking bath of the present embodiment can further contain an iodide. By adding iodide to the cross-linking bath, the polarization performance in the plane of the obtained polarizing plate can be made uniform.
Specific examples of iodide are the same as described above.

The concentration of iodide in the crosslinking bath is preferably 0.05% by mass or more and 15% by mass or less, and more preferably 0.5% by mass or more and 8% by mass or less.
The temperature of the crosslinking bath is preferably 10 ° C. or higher and 90 ° C. or lower.

In the dyeing step S6, subsequent to the crosslinking treatment, a washing treatment is performed in which a stretched film including a resin film crosslinked in pure water (hereinafter referred to as a washing bath) such as ion exchange water or distilled water is immersed. Thereby, the chemical | medical agent left on the crosslinked resin film, for example, an excess dichroic substance and an unreacted crosslinking agent can be reduced. The washing bath may further contain an organic solvent compatible with water. Specific examples of the organic solvent are the same as described above.
The washing temperature is preferably 3 ° C. or higher and 50 ° C. or lower, and more preferably 4 ° C. or higher and 20 ° C. or lower.

  The cleaning process according to the present embodiment may be a cleaning process using an aqueous solution containing iodide, or a combination of a cleaning process using an aqueous solution containing iodide and a cleaning process using pure water. Specific examples of iodide are the same as described above. By including iodide in the washing bath, the hue of the obtained polarizing plate can be prepared. Moreover, the washing bath may contain a crosslinking agent, and in order to prevent defects due to precipitation of the crosslinking agent on the film surface, an addition amount of 1 part by mass or less is more preferable with respect to 100 parts by mass of water.

  The concentration of iodide in the cleaning bath is preferably 1% by mass or more and 15% by mass or less.

  In the dyeing step S6, subsequent to the cleaning process, a drying process for drying the stretched film including the cleaned resin film is performed. A conventionally well-known method can be employ | adopted for a drying process, for example, natural drying, ventilation drying, heat drying, etc. are mentioned. For example, in the case of heat drying, the drying temperature is preferably 20 ° C. or higher and 95 ° C. or lower. If the drying temperature is too low, the drying time becomes longer and the production efficiency decreases. On the other hand, when the drying temperature is too high, the obtained polarizing plate deteriorates, and the polarizing performance and the hue deteriorate. The drying time is preferably 2 minutes or more and 20 minutes or less.

[Second bonding step S7]
In 2nd bonding process S7, the bonding film which bonded the protective film using the adhesive agent at least to the surface of the polarizer layer of the light-polarizing laminated film is obtained.

  As a material for the protective film, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is preferable. Examples of the thermoplastic resin include acetyl cellulose resins such as triacetyl cellulose, cycloolefin resins, cycloolefin copolymer resins, polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, polycarbonate resins, and polyresins. Examples thereof include acrylic resins such as methyl methacrylate, acyclic olefin resins such as polypropylene and polyethylene, and mixtures thereof.

  The thickness of the protective film is preferably 1 μm or more and 200 μm or less, more preferably 5 μm or more and 100 μm or less, and further preferably 10 μm or more and 50 μm or less.

  In addition, when providing a protective film on both surfaces of a light-polarizing laminated film in this embodiment, the protective film which consists of the same resin material may be used on both surfaces, and the protective film which consists of a different resin material may be used.

  Examples of the adhesive include a water-based adhesive and an active energy ray-curable adhesive. Examples of the water-based adhesive include an adhesive in which a polyvinyl alcohol-based resin is dissolved or dispersed in water. Examples of the active energy ray-curable adhesive include an adhesive containing a curable compound that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays.

  As active energy ray-curable adhesive, since it exhibits good adhesion, active energy ray-curable adhesive containing either or both of a cationic polymerizable curable compound and a radical polymerizable curable compound It is preferable to use an agent composition. The active energy ray-curable adhesive can further include a cationic polymerization initiator or a radical polymerization initiator for initiating the curing reaction of the curable compound.

  Examples of cationically polymerizable curable compounds include epoxy compounds (compounds having one or more epoxy groups in the molecule) and oxetane compounds (one or two or more oxetane rings in the molecule). Compound), or a combination thereof.

  Examples of the radical polymerizable curable compound include (meth) acrylic compounds (compounds having one or more (meth) acryloyloxy groups in the molecule) and radical polymerizable double bonds. Other vinyl compounds or combinations thereof can be mentioned.

  The active energy ray curable adhesive may be a cationic polymerization accelerator, an ion trap agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow modifier, a plasticizer, Additives such as foaming agents, antistatic agents, leveling agents and solvents can be contained.

  Hereinafter, the formation method of a bonding film is demonstrated. When bonding a protective film using an active energy ray curable adhesive, a protective film is laminated | stacked on a polarizing laminated film through an active energy ray curable adhesive. Next, an active energy ray such as ultraviolet ray, visible light, electron beam, or X-ray is irradiated to cure the adhesive layer made of the active energy ray-curable adhesive. As the active energy ray, ultraviolet rays are preferable, and as a light source in this case, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, a metal halide lamp, or the like is used. it can.

  On the other hand, when bonding a protective film using a water-based adhesive, the protective film may be laminated on the polarizing laminated film via the water-based adhesive and then dried by heating.

  Furthermore, for the purpose of improving the adhesion with the adhesive, the polarizing laminate film and / or the protective film can be subjected to a surface treatment. Examples of the surface treatment include corona treatment, plasma treatment, flame treatment, ultraviolet treatment, primer treatment, saponification treatment, solvent treatment by solvent application and drying.

  In addition, a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer is formed on the surface of the protective film opposite to the polarizing laminated film. Also good.

[Second peeling step S8]
In 2nd peeling process S8, a stretched base film is peeled from a bonding film, and a polarizing plate is obtained.
It is preferable that the stretched base film peeled off from the bonding film is wound around the winding shaft as in the first peeling step S5. The peeling method of a extending | stretching base film is not specifically limited, For example, the method similar to 1st peeling process S5 is employable. Moreover, it is preferable that peeling of a extending | stretching base film is performed, removing electricity centering on a peeling location as needed.

  According to the manufacturing method of the laminated film of the above method, the laminated film which reduces generation | occurrence | production of winding deviation at the time of winding of a laminated film is obtained.

  According to the method for producing a polarizing plate as described above, since the above-described laminated film is used, a polarizing plate with less occurrence of winding deviation at the time of winding the laminated film is obtained.

<Modification>
The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the effects of the present invention.

  For example, insolubilization treatment is performed between the stretching step S2 and the first bonding step S3 or between the first peeling step S5 and the dyeing step S6 in order to insolubilize the resin film on the stretched substrate film. Also good. The insolubilization treatment can be performed by immersing the stretched film in a solution containing a crosslinking agent (hereinafter, insolubilization bath). The crosslinking agent contained in the insolubilizing bath is the same as the crosslinking agent used for the crosslinking treatment in the dyeing step S6. As a solvent for the insolubilizing bath, for example, water is preferable. The insolubilizing bath may further contain an organic solvent compatible with water. Specific examples of the organic solvent are the same as described above.

  The concentration of the crosslinking agent in the insolubilizing bath is preferably 1% by mass or more and 4% by mass or less. Further, the temperature of the insolubilizing bath is preferably 25 ° C. or higher, more preferably 30 ° C. or higher and 85 ° C. or lower, and further preferably 30 ° C. or higher and 60 ° C. or lower. The time for immersing the laminated film in the insolubilizing bath is preferably 5 seconds or more and 800 seconds or less, and more preferably 8 seconds or more and 500 seconds or less.

  Moreover, although the dyeing | staining process is performed after extending process S2, it can also perform before extending process S2 and these processes simultaneously.

  Furthermore, in the dyeing process, the crosslinking process is performed after the dyeing process, but can be performed simultaneously with the dyeing process by blending a crosslinking agent in the dyeing bath. Moreover, you may perform a crosslinking process separately twice or more using 2 or more types of crosslinking baths from which a composition differs.

  Although the example which peels a stretched base film finally was shown in the said embodiment, you may use as a protective film of a polarizing plate as it is, without peeling a stretched base film.

  You may laminate | stack the adhesive layer for bonding a polarizing plate to another member (For example, liquid crystal cell in the case of applying to a liquid crystal display device) on the surface of the polarizer layer in the obtained polarizing plate at least. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition obtained by adding a crosslinking agent to a base polymer. Examples of the base polymer include (meth) acrylic resins, styrene resins, silicone resins, and the like. As a crosslinking agent, an isocyanate compound, an epoxy compound, an aziridine compound etc. are mentioned, for example. The pressure-sensitive adhesive composition may further contain fine particles to form a pressure-sensitive adhesive layer exhibiting light scattering properties. The thickness of the pressure-sensitive adhesive layer is preferably 1 μm or more and 40 μm or less, and more preferably 3 μm or more and 25 μm or less.

Another optical layer may be laminated on at least the surface of the polarizer layer in the obtained polarizing plate.
Examples of the other optical layer include a reflective polarizing film, a film with a surface antireflection function, a reflection film having a reflection function on the surface, a transflective film having both a reflection function and a transmission function, and a viewing angle compensation film. The polarizing plate of this embodiment can be suitably applied to the viewing side and the back side of the display device.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[Example 1]
[Preparation of base film]
A long film having a three-layer structure in which a resin layer made of homopolypropylene that is a homopolymer of propylene is arranged on both sides of a resin layer made of a random copolymer of propylene / ethylene containing about 5% by mass of ethylene units is prepared. A base film was obtained. The base film was produced by co-extrusion using a multilayer extruder.
The following materials were used as a random copolymer of propylene / ethylene and homopolypropylene.
Propylene / ethylene random copolymer: Sumitomo (registered trademark) Nobrene (registered trademark) W151, manufactured by Sumitomo Chemical Co., Ltd., melting point = 138 ° C.
Homopolypropylene: Sumitomo (registered trademark) Nobrene (registered trademark) FLX80E4, manufactured by Sumitomo Chemical Co., Ltd., melting point = 163 ° C.
The total thickness of the obtained base film was 100 μm, and the thickness ratio (FLX80E4 / W151 / FLX80E4) of each layer was 3/4/3.

[Formation of primer layer]
PVA powder (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., “Z-200”, average polymerization degree 1100, saponification degree 99.5 mol%) was dissolved in 95 ° C. hot water to prepare a 3 mass% PVA aqueous solution.
The resulting PVA aqueous solution is mixed with 1 part by mass of a cross-linking agent (manufactured by Taoka Chemical Co., Ltd., “Smileze Resin (registered trademark) 650”) with respect to 2 parts by mass of the PVA powder, and applied for primer layer formation. Liquid.

  While the produced substrate film was continuously conveyed, one side thereof was subjected to corona treatment. Next, the obtained primer layer forming coating solution was applied to the surface of the substrate film subjected to the corona treatment using a micro gravure coater. The substrate film after coating was dried at 80 ° C. for 3 minutes to form a primer layer having a thickness of 0.2 μm.

[Production of laminate (resin layer forming step)]
PVA powder (manufactured by Kuraray Co., Ltd., “PVA124”, average polymerization degree 2400, saponification degree 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C. to prepare an 8 mass% PVA aqueous solution. The obtained PVA aqueous solution was coated on the primer layer using a die coater while transporting the base film on which the primer layer was formed. The substrate film after coating was dried stepwise at 90 ° C. for 1 minute, 70 ° C. for 3 minutes, and 60 ° C. for 4 minutes to form a resin layer having a thickness of 10 μm.

  Further, the surface of the base film opposite to the surface on which the resin layer was formed was subjected to the same treatment as above to sequentially form a primer layer having a thickness of 0.2 μm and a resin layer having a thickness of 10.0 μm. Thus, the laminated body provided with the primer layer and the resin layer on both surfaces of the base film, that is, a laminated body having a layer structure of resin layer / primer layer / base film / primer layer / resin layer was obtained.

[Production of stretched film (stretching step)]
While transporting the laminate continuously, free end uniaxial stretching in the transport direction of the laminate, that is, longitudinal uniaxial stretching, was performed using a nip roll to obtain a stretched film. The stretching temperature for longitudinal uniaxial stretching was 160 ° C., and the stretching speed was 2.5 m / min for the inlet speed and 14.5 m / min for the outlet speed. As a result, the draw ratio of the laminate was 5.80 times. Moreover, the length of the longitudinal direction of the stretched film was 2000 m.

[Production of laminated film (first bonding step)]
A protective film using polyethylene as a forming material was bonded to the surface of the resin film formed on one surface of the obtained stretched film to obtain a laminated film.

<Evaluation 1 (Evaluation of winding deviation)>
[Winding of laminated film (winding process)]
The obtained laminated film was wound at a winding speed of 14.5 m / min with the surface on which the protective film was bonded facing outward.
At this time, the tension at the start of winding was 60 N / m. Further, the taper ratio was 20%. The amount of charge of the laminated film immediately before winding was measured by using a static electricity measuring device (SIMX, FMX-003) about 25 mm away from the surface of the laminated film. As a result, the absolute value of the charge amount of the laminated film was 0.4 kV. The laminated film that was allowed to stand for 1 week after winding was measured for winding deviation and was within 1 mm, and the appearance was good.
In addition, the charge amount of the stretched film or the laminated film was adjusted between the stretching process and the winding process by using a plurality of ion ventilation type electrostatic removal devices. In addition, the space for performing the winding process was set to a temperature of 23 ° C. and a relative humidity of 55%.

[Example 2]
The laminated film of Example 2 was produced in the same manner as in Example 1 except that the removal amount of the ion blow type electrostatic removing device was adjusted and the absolute value of the charge amount of the laminated film immediately before winding was 21 kV. . Moreover, the length of the longitudinal direction of the stretched film was 3500 m. The laminated film that was allowed to stand for 1 week after winding was measured for winding deviation and was within 1 mm, and the appearance was good.

[Example 3]
The laminated film of Example 3 was prepared in the same manner as in Example 1 except that the removal amount of the ion blow type electrostatic removing device was adjusted and the absolute value of the charge amount of the laminated film immediately before winding was 28 kV. . Moreover, the length of the longitudinal direction of the stretched film was 4400 m. The laminated film, which was allowed to stand for 1 week after winding, was measured for winding deviation and found to be 5 mm, and the appearance was good.

[Example 4]
The tension applied to the laminated film at the start of winding was 100 N / m. At the same time, the removal amount of the ion blow type electrostatic removal device was adjusted, and the same procedure as in Example 1 was conducted except that the absolute value of the charge amount of the laminated film immediately before winding was 31 kV. Produced. Moreover, the length of the longitudinal direction of the stretched film was 2000 m. When the winding deviation was measured for the laminated film left for 1 week after winding, it was within 1 mm, but a gauge band was generated at the center of the roll-shaped laminated film.

[Comparative Example 1]
The tension applied to the laminated film at the start of winding was 80 N / m. At the same time, the removal amount of the ion blow type electrostatic removal device was adjusted, and the same procedure as in Example 1 was performed except that the absolute value of the charge amount of the laminated film immediately before winding was set to 33 kV. Produced. Moreover, the length of the longitudinal direction of the stretched film was 4000 m. The laminated film, which was allowed to stand for 1 week after winding, was measured for winding deviation and found to be 20 mm, and the appearance was good. However, when the obtained laminated film was unwound, the laminated film meandered and wrinkles were generated.

[Comparative Example 2]
The obtained laminated film was wound at a winding speed of 14.5 m / min with the surface on which the protective film was bonded facing outward.
At this time, the tension at the start of winding was 25 N / m. Further, the taper ratio was 20%. Moreover, the length of the longitudinal direction of the stretched film was 2500 m. The laminated film that was allowed to stand for 1 week after winding was measured for winding deviation and was larger than 5 mm, and the appearance was good.

  Regarding Examples 1 to 4 and Comparative Examples 1 and 2, the tension at the start of winding (N / m), the absolute value of the charge amount of the laminated film (kV), the winding deviation and the appearance defect of the roll-like laminated film are shown. Summarized in 1. Regarding the winding deviations in Examples 1 to 4 and Comparative Examples 1 and 2, the case where the winding deviation was within 5 mm was determined as “possible”, and the case where the winding deviation exceeded 5 mm was determined as “impossible”.

Moreover, regarding Examples 1 to 4 and Comparative Examples 1 and 2, if the winding deviation was “OK”, it was determined to be acceptable. In particular, when the appearance of the laminated film was good, the overall evaluation was indicated as “◎”, and when a gauge band or the like was confirmed on the laminated film, the overall evaluation was indicated as “◯”.
On the other hand, the case where the winding deviation was “impossible” was rejected, and the comprehensive evaluation was shown as “x”.

  As shown in Table 1, in Examples 1 to 4, since the tension at the start of winding was 30 N / m or more and the absolute value of the charge amount of the laminated film was 32 kV or less, the winding deviation of the laminated film was 5 mm. It can be controlled within. On the other hand, in Comparative Example 1, the tension at the start of winding was 30 N / m or more. However, since the absolute value of the charge amount of the laminated film was larger than 32 kV, it was found that the winding deviation of the laminated film was larger than 5 mm. It was. Moreover, in the comparative example 2, since the tension | tensile_strength at the time of winding start was smaller than 30 N / m, it turned out that the winding shift | offset | difference of a laminated film becomes larger than 5 mm.

  Moreover, in Example 4, although winding deviation did not arise, since the tension | tensile_strength at the time of winding start was larger than 90 N / m, it turned out that a gauge band generate | occur | produces on the surface of a roll-shaped laminated film.

<Evaluation 2 (Appearance Evaluation of Polarizing Plate)>
[Preparation of polarizing laminated film (first peeling step and dyeing step)]
The protective film was peeled off while unwinding the laminated films obtained in Examples 1 to 4 and Comparative Examples 1 and 2. Next, while continuously transporting the obtained stretched film, it was immersed in a 60 ° C. warm water bath for 60 seconds, and then immersed in a 30 ° C. dyeing bath containing iodine and potassium iodide for about 150 seconds. The film was stained. Next, the dyed resin film was washed with pure water at 10 ° C. to reduce excess iodine and potassium iodide. Furthermore, the dyed resin film was crosslinked by being immersed in a 76 ° C. crosslinking bath containing boric acid and potassium iodide for 600 seconds. Furthermore, the crosslinked resin film was washed with pure water at 10 ° C. for 4 seconds, and then dried at 80 ° C. for 300 seconds to produce a polarizing laminated film.

[Preparation of polarizing plate (second bonding step and second peeling step)]
PVA powder (manufactured by Kuraray Co., Ltd., “KL-318”, average polymerization degree 1800) was dissolved in 95 ° C. hot water to prepare a 3 mass% PVA aqueous solution. The obtained PVA aqueous solution was mixed with a cross-linking agent (manufactured by Taoka Chemical Co., Ltd., “SUMIREZ RESIN (registered trademark) 650”) at a ratio of 1 part by mass with respect to 2 parts by mass of PVA to obtain an adhesive.

  The obtained adhesive was coated on the polarizer layers on both sides of the polarizing laminated film while continuously transporting the polarizing laminated film. Next, as a protective film, a 40 μm thick triacetyl cellulose (TAC) (“KC4UY” manufactured by Konica Minolta Co., Ltd.) whose adhesive surface was saponified was pasted on the polarizer coated with the adhesive. And crimped by passing between a pair of laminating rolls. Thus, the bonding film which consists of a layer structure of TAC / polarizer layer / primer layer / stretched base film / primer layer / polarizer layer / TAC was obtained.

  The obtained laminated film was peeled and divided at the interface between the stretched substrate film and the primer layer, and a film composed of TAC / polarizer layer / primer layer / stretched substrate film and primer layer / polarizer layer / TAC. A polarizing plate was obtained. The stretched substrate film was peeled from the film composed of TAC / polarizer layer / primer layer / stretched substrate film to obtain one more polarizing plate.

In Examples 1 to 4 and Comparative Examples 1 and 2, problems such as film breakage did not occur when the stretched substrate film was peeled off.
In Comparative Examples 1 and 2, wrinkles occurred when the laminated film was unwound. It was found that such wrinkled portions became uneven dyeing, resulting in poor appearance.

  From the above results, it was confirmed that the present invention is useful.

  DESCRIPTION OF SYMBOLS 11 ... Stretched film, 13 ... Laminated film, 21 ... Protect film, 101, 113 ... Nip roll, 115 ... Winding roll

Claims (7)

A method for producing a laminated film that reduces the winding deviation of the laminated film to 5 mm or less,
While transporting the belt-shaped base film in the longitudinal direction, at least one surface of the base film is coated with a coating liquid containing a polyvinyl alcohol-based resin, and at least by drying the obtained coating layer A resin layer forming step of forming a resin layer using the polyvinyl alcohol-based resin as a forming material on the one surface;
The laminate obtained in the resin layer forming step was stretched while being conveyed in the longitudinal direction, and a stretched base film in which the base film was stretched and a resin film in which the resin layer was stretched were laminated. A stretching process for obtaining a stretched film;
A first bonding step of bonding a protective film on the surface of the resin film, and obtaining a laminated film in which the stretched base film, the resin film, and the protective film are laminated in this order;
A winding step of winding the laminated film with a winding roll;
The length in the longitudinal direction of the stretched film is 1000 m or more,
At the start of the winding process, the tension per unit width of the laminated film is 30 N / m or more,
The manufacturing method of a laminated | multilayer film whose absolute value of the charge amount of the said laminated | multilayer film just before the said winding roll is 0.4 kV or more and 32 kV or less.   The said protective film is a manufacturing method of the laminated | multilayer film of Claim 1 containing polyolefin resin as a forming material.   In the stretching step, the first nip roll and the second nip roll are sequentially passed through the laminate, and longitudinal uniaxial stretching is performed by a difference in peripheral speed between the first nip roll and the second nip roll. The manufacturing method of the laminated | multilayer film of 2.   The manufacturing method of the laminated | multilayer film of any one of Claims 1-3 whose tension | tensile_strength per unit width concerning the said laminated | multilayer film is 90 N / m or less at the time of the start of the said winding-up process. The manufacturing method of the laminated | multilayer film of any one of Claims 1-4 which manages the space which performs the said winding-up process at the temperature of 13-33 degreeC, and relative humidity 25-85%. The process of obtaining a laminated film with the manufacturing method of any one of Claims 1-5 ,
Unwinding the laminated film, and removing the protective film from the laminated film;
A polarizer formed by dyeing the resin film contained in the stretched film obtained in the first peeling step with a dichroic material and on at least one surface of the stretched substrate film and the stretched substrate film A dyeing step of obtaining a polarizing laminated film in which the layers are laminated;
The manufacturing method of a polarizing plate provided with the 2nd bonding process of bonding a protective film on the surface of the said polarizer layer of the said polarizing laminated film at least. The manufacturing method of the polarizing plate of Claim 6 provided with the 2nd peeling process which peels the said extending | stretching base film after the said 2nd bonding process.

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