JP2023025240A - Method for manufacturing polarizing film roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polarizing film roll with which it is possible to suppress generation of a winding depression at a polarizing film edge.

SOLUTION: A method for manufacturing a polarizing film roll according to the present invention is characterized by including a step for winding a polarizing film around a winding core, and in that the polarizing film is 100 μm or less in a thickness and 500 m to 4000 m in a length, and the polarizing film is wound around the winding core while applying tensile force y in said step so that the tensile force y calculated by a formula (1) becomes 30 N to 150 N inclusive, from when the tension at start of winding is over 30 N to 150 N inclusive and the winding amount is 500 m or greater to when winding is terminated. Formula (1): tensile force y=a{1-(bx/400000)}, where a represents tensile force at start of winding (a>30 N), b represents a taper ratio (%)={(tension at start of winding - tension when 4000 m is assumed to have been wound)/(tension at start of winding)×100, and x represents a winding amount (500 m≤x≤4000 m).

SELECTED DRAWING: None

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention relates to a method for manufacturing a polarizing film roll.

Polarizing films are used for image display in various image display devices. For example, in a liquid crystal display (LCD), it is essential to arrange polarizing films on both sides of a glass substrate forming a liquid crystal panel surface due to its image forming method. Further, in the organic EL display device, a circularly polarizing film obtained by laminating a polarizing film and a quarter-wave plate is arranged on the viewing side of the organic light-emitting layer in order to block specular reflection of external light on the metal electrode.

As the polarizing film, a polarizer made of a polyvinyl alcohol film and a dichroic material such as iodine is generally used, and a protective film is attached to one or both sides of the polarizer with a polyvinyl alcohol adhesive or the like. ing.

2. Description of the Related Art In recent years, image display devices such as liquid crystal display devices have become thinner, and along with this, polarizing films are also required to be thinner.

A polarizing film is usually produced by applying various processing to the raw material film while feeding the raw material film from a raw roll, and winding the obtained long polarizing film around a winding core to form a roll.・Manufactured by roll method.

As described above, the polarizing film is produced by a roll-to-roll method and stored as a polarizing film roll, but the polarizing film unwound from the polarizing film roll has defects such as streaks, dents, or curls. The problem was that it was easy.

For example, in Patent Document 1, a winding streak defect (a height difference occurring between the winding start end of the polarizing plate and the outer peripheral surface of the winding core, that is, a step portion). For the purpose of suppressing a streak-shaped recess defect extending in the width direction of the polarizing plate, a winding core provided with a first convex portion and a second convex portion extending in the circumferential direction on the outer peripheral surface, and a winding core wound around the winding core. The polarizing plate includes a polarizer and a protective film laminated on at least one surface thereof, and the polarizing plate includes one end in the width direction of the protective film A polarizing plate roll has been proposed, which is wound around the core so that one region is located on the first convex portion and the other end region is located on the second convex portion.

In addition, in Patent Document 2, for the purpose of preventing the occurrence of reverse curling and wave curling, a process of adjusting the moisture content of a raw material film that is a raw material of a transparent film, and a raw material film after adjusting the moisture content. A method for producing a polarizing plate has been proposed, which includes a step of laminating a polarizing film on one side or both sides of the polarizing film.

JP 2016-85331 A JP 2014-191155 A

However, the technique of Patent Document 1 requires a core with a special structure, and there is a problem that a general core cannot be used. In addition, the technique of Patent Document 2 requires adjustment of the moisture content of the raw material film, which poses a problem of complicating production.

An object of the present invention is to provide a method for manufacturing a polarizing film roll that can suppress the occurrence of winding dents at the edges of the polarizing film.

As a result of intensive studies, the present inventors have found that the above problems can be solved by the following method for producing a polarizing film roll, and have completed the present invention.

That is, the present invention is a method for producing a polarizing film roll, which includes a step of winding a polarizing film around a core,
The polarizing film has a thickness of 100 μm or less and a length of 500 m or more and 4000 m or less,
In the above process, the tension y calculated by the following formula (1) is 30 N or more and 150 N or less from the time when the winding amount reaches 500 m or more to the end of winding, while applying the tension y. The present invention relates to a method for manufacturing a polarizing film roll characterized by winding around a core.
Tension y = a {1-(bx/400000)} (1)
a: tension at the start of winding (a>30N)
b: Taper ratio (%) = {(Tension at the start of winding-Tension at assumed winding of 4000 m) / Tension at the start of winding} x 100
x: Winding amount (500m≤x≤4000m)

It is preferable that the polarizing film has a length of 1000 to 4000 m and a tension y of 35 N or more and 145 N or less when the winding amount reaches the length.

The polarizing film preferably has a protective film on one or both sides of the polarizer via an adhesive layer.

Moreover, it is preferable that the thickness of the polarizer is 20 μm or less.

When the thickness of the polarizing film is 100 μm or less, the rigidity of the polarizing film is low. Therefore, if the polarizing film is wound around a winding core under tension and stored, a dent occurs at the end of the unwound polarizing film. Cheap. In particular, when a one-sided driving roll device is used, a difference in winding tension tends to occur in the width direction of the polarizing film roll. It is thought that the polarizing film roll is deformed in order to eliminate the difference in tension during storage of the polarizing film roll, and as a result, dents are generated at the ends of the polarizing film roll. A polarizing film having such edge depressions has a problem that the roll transportability is deteriorated and the yield is lowered because it cannot be used as a product. However, as in the present invention, by winding the polarizing film around the winding core while adjusting the tension y to be 30 N or more and 150 N or less from when the winding amount is 500 m or more to the end of winding, Even with a polarizing film having a thickness of 100 μm or less, it is possible to effectively suppress the occurrence of winding dents at the edges of the polarizing film. In particular, the method for producing a polarizing film roll of the present invention is effective when using a single-side drive roll device. According to the method for producing a polarizing film roll of the present invention, it is possible to reduce the difference in tension in the width direction of the polarizing film roll during winding, so that it is possible to effectively suppress the occurrence of winding dents at the ends of the polarizing film. can.

FIG. 4 is a schematic diagram showing a method for evaluating winding misalignment; It is the schematic which shows the preparation method of the sample in evaluation of a winding dent. It is the schematic which shows the measuring method of the maximum depth in evaluation of a winding dent.

A method for producing a polarizing film roll of the present invention includes a step of winding a polarizing film around a core,
The polarizing film has a thickness of 100 μm or less and a length of 500 m or more and 4000 m or less,
In the above process, the tension y calculated by the following formula (1) is 30 N or more and 150 N or less from the time when the winding amount reaches 500 m or more to the end of winding, while applying the tension y. The present invention relates to a method for manufacturing a polarizing film roll characterized by winding around a core.
Tension y = a {1-(bx/400000)} (1)
a: tension at the start of winding (a>30N)
b: Taper ratio (%) = {(Tension at the start of winding-Tension at assumed winding of 4000 m) / Tension at the start of winding} x 100
x: Winding amount (500m≤x≤4000m)

The polarizing film is not particularly limited as long as it has a thickness of 100 μm or less and a length of 500 m or more and 4000 m or less. The polarizing film preferably has a thickness of 80 μm or less, more preferably 70 μm or less. The polarizing film usually has a thickness of 10 μm or more, preferably 15 μm or more, from the viewpoint of rigidity, mechanical strength, handleability, and the like. The length of the polarizing film is preferably 700 m or longer, more preferably 800 m or longer, still more preferably 1000 m or longer, still more preferably 1500 m or longer, still more preferably 2000 m or longer, and even more preferably. is more than 2500m. The polarizing film preferably has a width of 50 to 200 cm, more preferably 100 to 150 cm.

The polarizing film preferably has a protective film on one or both sides of the polarizer via an adhesive layer. The polarizing film may further include one or more additional layers such as a functional layer, an easy-adhesion layer, a surface protective film, an adhesive layer, an optical layer, and a separator described below.

A known polarizer can be used without any particular limitation, but the thickness is preferably 20 μm or less from the viewpoint of thinning and suppressing the occurrence of cracks. The thickness of the polarizer is more preferably 18 μm or less, still more preferably 16 μm or less, and even more preferably 15 μm or less. On the other hand, the thickness of the polarizer is preferably 2 μm or more, more preferably 3 μm or more.

A polarizer using a polyvinyl alcohol-based resin is used. As a polarizer, for example, hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films are coated with dichroic dyes such as iodine and dichroic dyes. Polyene-based oriented films such as those obtained by adsorbing a substance and uniaxially stretched, polyvinyl alcohol dehydrated products, polyvinyl chloride dehydrochlorinated products, and the like can be mentioned. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic substance such as iodine is suitable.

A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine and uniaxially stretching it can be produced, for example, by dyeing polyvinyl alcohol by immersing it in an aqueous solution of iodine and stretching it to 3 to 7 times its original length. If necessary, it may contain boric acid, zinc sulfate, zinc chloride, or the like, or it may be immersed in an aqueous solution of potassium iodide or the like. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed with water before dyeing. By washing the polyvinyl alcohol film with water, dirt and anti-blocking agents on the surface of the polyvinyl alcohol film can be washed away, and by swelling the polyvinyl alcohol film, uneven dyeing can be prevented. be. Stretching may be performed after dyeing with iodine, stretching may be performed while dyeing, or dyeing with iodine may be performed after stretching. It can also be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

The polarizer preferably contains boric acid from the viewpoint of stretching stability and humidification reliability. In addition, the content of boric acid contained in the polarizer is preferably 22% by weight or less, more preferably 20% by weight or less, relative to the total amount of the polarizer, from the viewpoint of suppressing the generation of cracks. From the viewpoint of stretching stability and humidification reliability, the boric acid content relative to the total amount of the polarizer is preferably 10% by weight or more, more preferably 12% by weight or more.

As a thin polarizer, typically,
Patent No. 4751486,
Patent No. 4751481 specification,
Patent No. 4815544 specification,
Patent No. 5048120,
WO 2014/077599 pamphlet,
International Publication No. 2014/077636,
and the like, or thin polarizers obtained from the production methods described therein.

As for the thin polarizer, among the production methods including the step of stretching and the step of dyeing in the state of a laminate, it is possible to stretch at a high magnification and improve the polarization performance. Those obtained by a production method including a step of stretching in an aqueous boric acid solution as described in Japanese Patent No. 4751481 and Japanese Patent No. 4815544 are preferred, particularly Japanese Patent No. 4751481 and Japanese Patent No. 4815544. It is preferably obtained by a manufacturing method including a step of auxiliary stretching in the air before stretching in a boric acid aqueous solution. These thin polarizers can be obtained by a manufacturing method including a step of stretching a polyvinyl alcohol-based resin (hereinafter also referred to as a PVA-based resin) layer and a stretching resin substrate in a laminate state, and a step of dyeing. According to this manufacturing method, even if the PVA-based resin layer is thin, it can be stretched without problems such as breakage due to stretching because it is supported by the stretching resin substrate.

As a material for the protective film, a material excellent in transparency, mechanical strength, thermal stability, water barrier property, isotropy, etc. is preferable. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, and styrenes such as polystyrene and acrylonitrile-styrene copolymer (AS resin). type polymer, polycarbonate type polymer, and the like. In addition, polyethylene, polypropylene, polyolefins having a cyclo- or norbornene structure, polyolefin-based polymers such as ethylene/propylene copolymers, vinyl chloride-based polymers, amide-based polymers such as nylon and aromatic polyamides, imide-based polymers, and sulfone-based polymers , polyethersulfone-based polymer, polyetheretherketone-based polymer, polyphenylene sulfide-based polymer, vinyl alcohol-based polymer, vinylidene chloride-based polymer, vinyl butyral-based polymer, arylate-based polymer, polyoxymethylene-based polymer, epoxy-based polymer, or the above Blends of polymers are also examples of polymers that form the protective film.

One or more of any suitable additives may be included in the protective film. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, and colorants.

The content of the polymer in the protective film is preferably 50-100% by weight, more preferably 50-99% by weight, still more preferably 60-98% by weight, still more preferably 70-97% by weight. If the content of the polymer in the protective film is less than 50% by weight, there is a possibility that the high transparency inherent in the polymer cannot be sufficiently exhibited.

As the protective film, a retardation film, a brightness enhancement film, a diffusion film, or the like can be used. Examples of the retardation film include those having a front retardation of 40 nm or more and/or a thickness direction retardation of 80 nm or more. The front retardation is usually controlled in the range of 40-200 nm, and the thickness direction retardation is usually controlled in the range of 80-300 nm. When a retardation film is used as the protective film, the retardation film also functions as a protective film for the polarizer, so that thickness reduction can be achieved.

The retardation film includes a birefringent film obtained by uniaxially or biaxially stretching a thermoplastic resin film. The stretching temperature, stretching ratio, and the like are appropriately set according to the retardation value, film material, and thickness.

Although the thickness of the protective film can be determined as appropriate, it is about 1 to 50 μm from the viewpoints of strength, workability such as handleability, and thinness. The thickness of the protective film is preferably 5-50 μm, more preferably 10-50 μm, still more preferably 10-40 μm.

A functional layer such as a hard coat layer, an antireflection layer, an antisticking layer, a diffusion layer or an antiglare layer can be provided on the surface of the protective film to which the polarizer is not adhered. The functional layers such as the hard coat layer, antireflection layer, anti-sticking layer, diffusion layer, and antiglare layer can be provided on the protective film itself, or can be provided separately from the protective film. can.

The adhesive layer is formed of an adhesive. The type of adhesive is not particularly limited, and various types can be used. The adhesive layer is not particularly limited as long as it is optically transparent. As the adhesive, various forms such as water-based, solvent-based, hot-melt, and active energy ray-curable types are used. Alternatively, an active energy ray-curable adhesive is suitable.

Examples of water-based adhesives include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl-based latex-based adhesives, and water-based polyesters. A water-based adhesive is usually used as an adhesive consisting of an aqueous solution and usually contains 0.5 to 60% by weight of solids.

Active energy ray-curable adhesives are adhesives that are cured by active energy rays such as electron beams and ultraviolet rays (radical curing type, cationic curing type). can be used. For the active energy ray-curable adhesive, for example, a photoradical-curable adhesive can be used. When a photoradical-curable active energy ray-curable adhesive is used as an ultraviolet-curable adhesive, the adhesive contains a radically polymerizable compound and a photopolymerization initiator.

The method of applying the adhesive is appropriately selected depending on the viscosity of the adhesive and the desired thickness. Examples of coating methods include reverse coaters, gravure coaters (direct, reverse and offset), bar reverse coaters, roll coaters, die coaters, bar coaters and rod coaters. In addition, a method such as a dipping method can be appropriately used for coating.

The thickness of the adhesive layer can be determined as appropriate, but is preferably 0.01 to 5 μm, more preferably 0.05 to 3 μm, still more preferably 0.05 to 2 μm.

In laminating the polarizer and the protective film, an easy-adhesion layer can be provided between the protective film and the adhesive layer. The easy-adhesion layer can be formed of various resins having, for example, a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone system, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, or the like. These polymer resins can be used singly or in combination of two or more. Other additives may be added to form the easy-adhesion layer. More specifically, stabilizers such as tackifiers, ultraviolet absorbers, antioxidants, and heat stabilizers may be used.

The easy-adhesion layer is usually provided in advance on the protective film, and the easy-adhesion layer side of the protective film and the polarizer are laminated by an adhesive layer. Formation of the easy-adhesion layer is carried out by applying a material for forming the easy-adhesion layer onto the protective film by a known technique, followed by drying. The easily adhesive layer-forming material is usually prepared as a solution diluted to an appropriate concentration in consideration of the thickness after drying, the smoothness of coating, and the like. The thickness of the easy-adhesion layer after drying is preferably 0.01 to 5 μm, more preferably 0.02 to 2 μm, still more preferably 0.05 to 1 μm. A plurality of easy-adhesion layers can be provided, and in this case also, the total thickness of the easy-adhesion layers is preferably within the above range.

The polarizing film may have an adhesive layer.

In the case of a polarizing film in which protective films are provided on both sides of a polarizer, a pressure-sensitive adhesive layer is provided directly or via another layer on the surface of one of the protective films. A surface protective film may be provided directly on the surface of the other protective film or via another layer.

In the case of a polarizing film in which a protective film is provided only on one side of a polarizer, an adhesive layer is provided on the polarizer side directly or via another layer. A surface protective film may be provided directly on the protective film side or via another layer.

The other layers are not particularly limited, and include known functional layers and optical layers provided on the polarizing film. Examples of optical layers include reflectors, transflective plates, retardation plates (including 1/2 and 1/4 wavelength plates), viewing angle compensation films, and brightness enhancement films. One layer may be provided as the other layer, or two or more layers may be provided.

The pressure-sensitive adhesive layer is provided on one side of the polarizing film in order to bond the polarizing film to a cell substrate such as a liquid crystal cell.

The thickness of the adhesive layer is, for example, about 1 to 40 μm, preferably 2 to 40 μm, more preferably 2 to 35 μm, still more preferably 2 to 30 μm.

An appropriate adhesive can be used for forming the adhesive layer, and the type thereof is not particularly limited. Examples of adhesives include rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, urethane-based adhesives, vinyl alkyl ether-based adhesives, polyvinyl alcohol-based adhesives, polyvinylpyrrolidone-based adhesives, polyacrylamide-based adhesives, Cellulose-based pressure-sensitive adhesives and the like can be mentioned.

Among these pressure-sensitive adhesives, those having excellent optical transparency, appropriate wettability, cohesiveness, and adhesion properties, and excellent weather resistance and heat resistance are preferably used. Acrylic pressure-sensitive adhesives are preferably used as those exhibiting such characteristics.

As a method for forming an adhesive layer, for example, the adhesive is applied to a release-treated separator or the like, and the polymerization solvent or the like is dried and removed to form an adhesive layer, and then transferred to a polarizing film, or the above method. Examples include a method of applying an adhesive and removing the polymerization solvent by drying to form an adhesive layer on the polarizing film. In applying the pressure-sensitive adhesive, one or more solvents other than the polymerization solvent may be newly added as appropriate.

A silicone release liner is preferably used as the release-treated separator. In the step of applying the adhesive on such a liner and drying it to form an adhesive layer, as a method for drying the adhesive, an appropriate method can be appropriately adopted depending on the purpose. Preferably, a method of drying the coating film by heating is used. The drying temperature is preferably 40°C to 200°C, more preferably 50°C to 180°C, and particularly preferably 70°C to 170°C. A pressure-sensitive adhesive having excellent adhesive properties can be obtained by setting the heating temperature within the above range.

An appropriate drying time can be adopted as appropriate. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, particularly preferably 10 seconds to 5 minutes.

Various methods are used as a method for forming the pressure-sensitive adhesive layer. Specifically, for example, roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, die coating, etc. A method such as an extrusion coating method can be mentioned.

When the pressure-sensitive adhesive layer is exposed, the pressure-sensitive adhesive layer may be protected with a release-treated sheet (separator) until practical use.

Examples of the constituent material of the separator include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, porous materials such as paper, cloth, and nonwoven fabric, nets, foam sheets, metal foils, and laminates thereof. Although thin sheets can be used, plastic films are preferably used because of their excellent surface smoothness.

The plastic film is not particularly limited as long as it can protect the pressure-sensitive adhesive layer. Examples include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride Examples include polymer films, polyethylene terephthalate films, polybutylene terephthalate films, polyurethane films, ethylene-vinyl acetate copolymer films, and the like.

If necessary, the separator may be subjected to release and antifouling treatment using a silicone, fluorine, long-chain alkyl or fatty acid amide release agent, silica powder, etc.; It is also possible to perform antistatic treatment such as. In particular, by appropriately subjecting the surface of the separator to release treatment such as silicone treatment, long-chain alkyl treatment, fluorine treatment, etc., the releasability from the pressure-sensitive adhesive layer can be further enhanced.

The surface protection film usually has a base film and an adhesive layer, and protects the polarizing film via the adhesive layer.

As the base film of the surface protection film, a film material having or near isotropy is selected from the viewpoint of inspection property and management property. Examples of film materials include polyester resins such as polyethylene terephthalate film, cellulose resins, acetate resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, acrylic resins, and the like. Examples include transparent polymers such as resins. Among these, polyester-based resins are preferred. The base film may be used as a laminate of one or more film materials, or may be a stretched product of the film. The thickness of the base film is preferably 10-150 μm, more preferably 20-150 μm.

The pressure-sensitive adhesive that forms the pressure-sensitive adhesive layer of the surface protection film includes (meth)acrylic polymers, silicone-based polymers, polyesters, polyurethanes, polyamides, polyethers, and pressure-sensitive adhesives based on polymers such as fluorine-based and rubber-based polymers. An agent can be appropriately selected and used. From the viewpoint of transparency, weather resistance, heat resistance, etc., an acrylic pressure-sensitive adhesive having an acrylic polymer as a base polymer is preferable. The thickness (dry film thickness) of the adhesive layer is preferably 1 to 40 μm, more preferably 1 to 30 μm.

In addition, the surface protective film can be provided with a release treatment layer on the opposite surface of the base film provided with the pressure-sensitive adhesive layer by using a low-adhesion material such as silicone treatment, long-chain alkyl treatment, or fluorine treatment. .

A polarizing film roll is manufactured by winding the long polarizing film around a core. As the take-up device, a single-side drive roll device or a double-side drive roll device may be used, but it is preferable to use a single-side drive roll device.

Although the outer diameter of the winding core is not particularly limited, it is preferably 100 to 500 mm, more preferably 150 to 400 mm. The width of the winding core may be appropriately adjusted according to the width of the polarizing film.

In the winding process, the tension y calculated by the following formula (1) is 30 N or more and 150 N or less from the time when the winding amount becomes 500 m or more to the end of winding, while applying the tension y. Wind the film around the core.
Tension y = a {1-(bx/400000)} (1)
a: tension at the start of winding (a>30N)
b: Taper ratio (%) = {(Tension at the start of winding-Tension at assumed winding of 4000 m) / Tension at the start of winding} x 100
x: Winding amount (500m≤x≤4000m)

If the tension y is less than 30 N, a winding deviation occurs and causes a transport failure at the next payout. On the other hand, when the tension y exceeds 150 N, a winding dent occurs at the edge of the polarizing film.

The tension y when the winding amount is 500 m is preferably 40 N or more, more preferably 50 N or more, still more preferably 90 N or more, and preferably 130 N or less, more preferably 120 N or less, and still more preferably 110N or less.

When the length of the polarizing film is 1000 to 4000 m, the tension y when the winding amount reaches the above length (that is, when the polarizing film is completely wound) is preferably 35 N or more. , more preferably 40 N or more, more preferably 45 N or more, and preferably 145 N or less, more preferably 140 N or less, and still more preferably 135 N or less.

Further, when the length of the polarizing film is 2000 to 3000 m, the tension y when the winding amount reaches the above length (that is, when the polarizing film is completely wound) is 40 N or more. is preferably 50 N or more, still more preferably 60 N or more, and preferably 135 N or less, more preferably 120 N or less, and still more preferably 110 N or less.

The tension at the start of winding is more than 30 N, preferably 35 N or more, preferably 300 N or less, more preferably 280 N or less, still more preferably 270 N or less, and still more preferably 200 N or less. and more preferably 150 N or less.

As shown in the above formula, the taper rate is a value calculated from the tension at the start of winding and the tension at the time of 4000 m winding. Even if the length of the polarizing film to be actually wound is less than 4000 m, the taper rate is determined by setting the tension when it is assumed that the film is wound up to 4000 m.

The taper rate is not particularly limited, but is preferably 1% or more, more preferably 5% or more, still more preferably 10% or more, still more preferably 20% or more, and preferably 99%. or less, more preferably 90% or less, still more preferably 85% or less, still more preferably 80% or less, still more preferably 75% or less, still more preferably 60% or less, and further It is preferably 50% or less, more preferably 40% or less.

The maximum depth of the concavity at the edge of the polarizing film is preferably 2.5 mm or less, more preferably less than 2.0 mm.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples. All parts and percentages in each example are based on weight.

(Production of polarizer)
A polyvinyl alcohol film (PVA-based resin film) having an average degree of polymerization of 2400, a degree of saponification of 99.9 mol%, and a thickness of 30 μm is immersed in hot water at 30° C., and the length of the PVA-based resin film is adjusted while swelling. The film was uniaxially stretched to 2.0 times the length. Then, it is immersed in an iodine solution of 0.3% by weight (weight ratio: iodine/potassium iodide = 0.5/8) at 30°C, and the length of the PVA-based resin film becomes 3.0 times the original length. It was dyed while being uniaxially stretched. Thereafter, the PVA-based resin film was stretched in an aqueous solution containing 4% by weight of hexaboric acid and 5% by weight of potassium iodide so that the length of the PVA-based resin film was 6 times its original length. Furthermore, after performing an iodine ion impregnation treatment with an aqueous solution of 3% by weight of potassium iodide (iodine impregnation bath), it was dried in an oven at 60° C. for 4 minutes to obtain a polarizer with a thickness of 12 μm.

(Protective film)
<Protective film 1>
25 μm TAC film with HC: TJ25UL (manufactured by Fujifilm, raw material: triacetylcellulose-based polymer) coated with acrylic resin hard coat 40 μm TAC film: KC4UYW (manufactured by Konica Minolta, raw material: triacetylcellulose-based polymer)
37 μm λ/4 TAC with HC: KC2UGR-HC (manufactured by Konica Minolta, raw material: triacetyl cellulose-based polymer) coated with acrylic resin hard coat <Protective film 2>
25 μm TAC film: KC2UA (manufactured by Konica Minolta, raw material: triacetyl cellulose polymer)
13 μm COP film: ZF-014 (manufactured by Nippon Zeon, raw material: cycloolefin polymer)
Manufacture of 30 μm acrylic film 8,000 g of methyl methacrylate (MMA) and 2,000 g of 2-(hydroxymethyl) were placed in a 30 L kettle-type reactor equipped with a stirrer, temperature sensor, cooling tube, and nitrogen inlet tube.
Methyl acrylate (MHMA), 10,000 g of 4-methyl-2-pentanone (methyl isobutyl ketone, MIBK), and 5 g of n-dodecyl mercaptan were charged, heated to 105° C. and refluxed while passing nitrogen. By the way, 5.0 g of t-butylperoxyisopropyl carbonate (Kayacarbon BIC-7, manufactured by Kayaku Akzo Co., Ltd.) was added as a polymerization initiator, and at the same time, 10.0 g of t-butylperoxyisopropyl carbonate and 230 g of Solution polymerization was carried out at about 105 to 120° C. under reflux while dropping a solution of MIBK over 4 hours, and aging was further carried out over 4 hours.
To the resulting polymer solution, 30 g of a stearyl phosphate/distearyl phosphate mixture (Phoslex A-18, manufactured by Sakai Chemical Industry Co., Ltd.) was added, and cyclization was performed under reflux at about 90 to 120°C for 5 hours. A condensation reaction was carried out. Next, the obtained polymer solution was fed to a vent type screw twin screw extruder with a barrel temperature of 260° C., a number of rotations of 100 rpm, a degree of pressure reduction of 13.3 to 400 hPa (10 to 300 mmHg), one rear vent, and four fore vents. (φ = 29.75 mm, L / D = 30) is introduced at a processing rate of 2.0 kg / h in terms of resin amount, further cyclic condensation reaction and devolatilization are performed in this extruder, and extruded. to obtain transparent pellets of the lactone ring-containing polymer.
When the dynamic TG measurement was performed on the obtained lactone ring-containing polymer, a mass decrease of 0.17% by mass was detected. This lactone ring-containing polymer had a weight average molecular weight of 133,000, a melt flow rate of 6.5 g/10 min, and a glass transition temperature of 131°C.
The obtained pellets and acrylonitrile-styrene (AS) resin (Toyo AS AS20, manufactured by Toyo Styrene Co., Ltd.) are kneaded and extruded at a mass ratio of 90/10 using a single screw extruder (screw 30 mmφ). A clear pellet was obtained. The glass transition temperature of the obtained pellets was 127°C.
The pellets were melt-extruded from a coat hanger type T die with a width of 400 mm using a 50 mm diameter single screw extruder to produce a film with a thickness of 120 μm, which was subjected to a temperature condition of 150 ° C. using a biaxial stretching device. , and 2.0 times to obtain an acrylic film having a thickness of 30 μm. When the optical properties of this stretched film were measured, the total light transmittance was 93%, the in-plane retardation Δnd was 0.8 nm, and the thickness direction retardation Rth was 1.5 nm.

(Preparation of water-based adhesive)
A polyvinyl alcohol resin containing an acetoacetyl group (average degree of polymerization: 1200, degree of saponification: 98.5 mol%, degree of acetoacetylation: 5 mol%) was dissolved in pure water at a temperature of 30°C, A water-based adhesive was obtained by adjusting the solid content concentration to 4%.

Example 1
On one side of each of protective film 1 (25 μm TAC film with HC) and protective film 2 (25 μm TAC film), the water-based adhesive was applied so that the thickness of the adhesive layer after drying was 80 nm. Films 1 and 2 were obtained. Then, under a temperature condition of 23°C, the adhesive-attached protective film 1 is attached to one surface of the polarizer, and the adhesive-attached protective film 2 is attached to the other surface of the polarizer using a roll machine. and dried for 6 minutes to prepare a polarizing film (thickness: 69 µm). Then, the produced polarizing film was wound around a core using a one-sided drive roll device to produce a polarizing film roll. Table 1 shows the conditions for winding.

Examples 2-11, Comparative Examples 1-5
A polarizing film roll was produced in the same manner as in Example 1 except that the types of protective films 1 and 2, the thickness and length of the polarizing film, and the conditions during winding were changed as shown in Table 1.

The polarizing film rolls produced in Examples and Comparative Examples were evaluated as follows. Table 1 shows the results.

<Evaluation of winding misalignment>
The polarizing film rolls produced in Examples and Comparative Examples were stored in an environment of 25° C. and 55% for 7 days. After that, with the inner peripheral edge of the polarizing film roll as a reference, as shown in FIG. Quantity. When the amount of winding deviation was 200 mm or less, it was evaluated as ◯, and when the amount of winding deviation exceeded 200 mm, it was evaluated as x.

<Evaluation of winding dent>
The polarizing film rolls produced in Examples and Comparative Examples were stored for 7 days in an environment of 25° C. and 55% on a bearing carriage. Thereafter, as shown in FIG. 2, the polarizing film was unwound from the polarizing film roll 3, and the polarizing film 4 (3 m in length) was cut off from the 3 to 6 m portion from the start of unwinding. Then, two samples 5 having a width of 200 mm were cut from both ends of the polarizing film 4 . As shown in FIG. 3, all of the winding indentations 6 were cut out from two samples 5, and the winding indentations 6 were cut in half across the width of the polarizing film so as to pass through the central portion 7. As shown in FIG. Then, the winding recessed portion 6 cut in half was placed on a flat plate, and the maximum depth D from the plane was measured and evaluated according to the following criteria. In addition, when there are a plurality of winding recesses 6, the average value of the maximum depth D was used.
◎: Less than 2.0 mm ○: 2.0 to 2.5 mm
×: more than 2.5 mm

From Table 1, it can be seen that in Examples 1 to 11 according to the method for producing a polarizing film roll of the present invention, the amount of winding misalignment is small, and the depth of the winding dents of the polarizing film is also small. On the other hand, in Comparative Examples 1 to 3, since the tension y at the end of winding exceeded 150 N, it can be seen that the depth of the winding dent portion of the polarizing film is large. In Comparative Example 4, the taper ratio was 0%, and the tension y at the end of winding exceeded 150 N, so it can be seen that the depth of the winding recesses of the polarizing film was large. In Comparative Example 5, the taper ratio is 0% and the tension at the start of winding is 30 N, so it can be seen that the amount of winding misalignment is large.

The polarizing film of the present invention is used alone or as an optical film in which it is laminated for use in image display devices such as liquid crystal display devices (LCD) and organic EL display devices.

1: inner peripheral edge 2: outermost peripheral edge 3: polarizing film roll 4: polarizing film 5: sample 6: winding recess 7: center D: maximum depth

Claims (4)

A method for manufacturing a polarizing film roll, comprising winding a polarizing film around a core,
The polarizing film has a thickness of 100 μm or less and a length of 500 m or more and 4000 m or less,
In the step,
The tension at the start of winding is more than 30N and 150N or less,
The polarizing film is wound around the winding core while applying the tension y so that the tension y calculated by the following formula (1) is 30 N or more and 150 N or less from when the winding amount reaches 500 m or more to the end of winding. A method for producing a polarizing film roll, comprising:
Tension y = a {1-(bx/400000)} (1)
a: tension at the start of winding (a>30N)
b: Taper ratio (%) = {(Tension at the start of winding-Tension at assumed winding of 4000 m) / Tension at the start of winding} x 100
x: Winding amount (500m≤x≤4000m) The method for producing a polarizing film roll according to claim 1, wherein the polarizing film has a length of 1000 to 4000 m, and the tension y is 35 N or more and 145 N or less when the winding amount reaches the length. The method for producing a polarizing film roll according to claim 1 or 2, wherein the polarizing film has a protective film on one or both sides of a polarizer via an adhesive layer. The method for producing a polarizing film roll according to claim 3, wherein the thickness of the polarizer is 20 µm or less.

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