TW202219560A - Method for manufacturing polarizing film and apparatus for manufacturing polarizing film - Google Patents

Abstract

This invention provides a method for manufacturing polarizing film in which uneven dyeing is suppressed from forming.

A method for manufacturing a polarizing film of this invention produces a polarizing film from a polyvinyl alcohol-based resin film, and includes a first treatment step of bringing the polyvinyl alcohol-based resin film into contact with a first treatment liquid, and a transport step of brining the polyvinyl alcohol-based resin film into contact with a roller in a state where the first treatment liquid is interposed and conveying the polyvinyl alcohol-based resin film in this order, wherein the first treatment liquid contains iodine, and the roller has at least one of a recess with a depth of 0.03mm or more and 0.9mm or less or a protrusions with a height of 0.03mm or more and 9mm or less, on the surface in contact with the polyvinyl alcohol-based resin film.

Description

Manufacturing method of polarizing film and manufacturing apparatus of polarizing film

The present invention relates to a method for producing a polarizing film and an apparatus for producing a polarizing film for producing a polarizing film from a polyvinyl alcohol-based resin film.

Conventionally, a polarizing film system in which a dichroic dye such as iodine is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol-based resin film is known. For example, Japanese Patent Laid-Open No. 2001-141926 (Patent Document 1) discloses that a dyeing treatment for dyeing a polyvinyl alcohol-based resin film with a dichroic dye and a crosslinking treatment for a crosslinking agent are sequentially performed Treatment, film drying treatment, and stretching treatment are applied to the polyvinyl alcohol-based resin film between production steps to produce a polarizing film.

In Japanese Patent Laid-Open No. 2012-173477 (Patent Document 2), it is described that a metal guide roller with grooves is used in conveying a resin film, thereby reducing scratches generated on the polarizer. In Japanese Patent Laid-Open No. 2000-147252 (Patent Document 3), it has been disclosed that a spiral rubber roller is used in conveying the polarizing film, thereby suppressing cracking.

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2001-141926

[Patent Document 2] Japanese Patent Laid-Open No. 2012-173477

[Patent Document 3] Japanese Patent Laid-Open No. 2000-147252

The polarizing film is industrially produced by applying the following manufacturing method: the long polyvinyl alcohol-based resin film is continuously conveyed along the conveying route of the film possessed by the manufacturing apparatus of the polarizing film, and the film is sequentially dipped at the same time. In each tank in which the above-mentioned dyeing treatment, cross-linking treatment and the like are performed on the conveying route. In conveying the film, from the viewpoint of the surface of the protective film, the conveying speed of the film is preferably the same as the rotation speed of the guide roller. In particular, the film in the wet state is easily damaged by the contact with the roll. For example, as described in Patent Documents 2 and 3, it has been found that even if the grip property of the film can be improved by subjecting the surface of the guide roller to concavo-convex processing, when a polarizing film with high transmittance is produced by such a method, the Scattered with uneven staining.

In view of the above-mentioned circumstances, an object of the present invention is to provide a manufacturing method and a manufacturing apparatus of a polarizing film for suppressing the formation of a polarizing film in which uneven dyeing is formed on a polarizing film.

The present invention provides a manufacturing method and a manufacturing apparatus of the polarizing film shown below.

[1] A method for producing a polarizing film, comprising producing a polarizing film from a polyvinyl alcohol-based resin film, and the method for producing a polarizing film sequentially includes:

The first treatment step is to bring the polyvinyl alcohol-based resin film into contact with the first treatment liquid;

The conveying step is to make the polyvinyl alcohol-based resin film contact a roller with the first treatment liquid interposed therebetween, and convey the polyvinyl-alcohol-based resin film;

wherein, the first treatment liquid system contains iodine,

The said roller has at least one of a recessed part with a depth of 0.03 mm or more and 0.9 mm or less and a convex part with a height of 0.03 mm or more and 0.9 mm or less on the surface in contact with the polyvinyl alcohol-based resin film.

[2] The method for producing a polarizing film according to [1], wherein the first treatment liquid system contains boric acid.

[3] The method for producing a polarizing film according to [1] or [2], further comprising a second treatment step in which the polyvinyl alcohol-based resin film is brought into contact with a liquid different from the first treatment liquid 2nd treatment liquid.

[4] The method for producing a polarizing film according to any one of [1] to [3], wherein the roll is a sponge roll.

[5] The method for producing a polarizing film according to any one of [1] to [4], wherein the polarizing film has a sensitivity-correcting single transmittance of 43% or more.

[6] An apparatus for producing a polarizing film from a polyvinyl alcohol-based resin film, the apparatus having:

a first treatment bath containing the first treatment solution;

a roller disposed in the aforementioned first treatment bath; and,

The conveying route through the aforementioned rollers;

wherein, the first treatment liquid system contains iodine,

The polyvinyl alcohol-based resin film is transported along the transport path, and is immersed in the first treatment bath,

The said roller has at least one of a recessed part with a depth of 0.03 mm or more and 0.9 mm or less and a convex part with a height of 0.03 mm or more and 0.9 mm or less on the surface in contact with the polyvinyl alcohol-based resin film.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the polarizing film which suppresses the formation of uneven dyeing can be provided.

10: Embryo film, resin film, film composed of polyvinyl alcohol-based resin

11: Embryo film roll, roll

13: Swelling bath

14: Dye Bath

15: Crosslinking bath

16: Complementary Color Bath

17: Clean the bath

21: Drying oven

23: polarizing film

30 to 32, 34 to 36, 38 to 40, 42 to 46: Guide rollers

50 to 52, 53a, 53b, 54 to 55: nip rolls

60: Roller

61: Recess

Fig. 1 is a schematic view of (a) a plan view and (b) a cross-sectional view of a roller having a concavo-convex portion.

FIG. 2 is a cross-sectional view schematically showing an example of a polarizing film manufacturing apparatus used in the manufacturing method according to the present embodiment.

FIG. 3 is a schematic cross-sectional view of the guide roller B-4.

Hereinafter, the manufacturing method of the polarizing film concerning one aspect of this invention (henceforth, it is also called "the manufacturing method concerning this embodiment") is demonstrated with reference to drawings. However, the present invention is not limited to this aspect.

[Manufacturing method of polarizing film]

The manufacturing method concerning this embodiment is the manufacturing method of the polarizing film which manufactures a polarizing film from a polyvinyl alcohol-type resin film. Specifically, it has a first treatment step in which the polyvinyl alcohol-based resin film is brought into contact with the first treatment liquid, and a conveying step in which the polyvinyl alcohol-based resin film is interposed with the first treatment liquid. The state touches the roller and conveys the aforementioned polyvinyl alcohol-based resin film. The above-mentioned treatment liquid system contains iodine. Moreover, the said roller has at least one of a recessed part with a depth of 0.03 mm or more and 0.9 mm or less and a convex part with a height of 0.03 mm or more and 0.9 mm or less on the surface in contact with the polyvinyl alcohol-based resin film. By having such a recessed part or a convex part, the grip property (grip property) of a film can be improved. Moreover, such a concave portion or a convex portion is unlikely to cause uneven dyeing of the film.

In this specification, a recessed part means the area|region which is more recessed than the periphery, Preferably it is the area|region which a polyvinyl-alcohol-type resin film does not contact. The outer shape of the concave portion is not limited, and among the straight lines connecting the outer shape of the concave portion, the length of the straight line that becomes the maximum length (the longest length) and the length of the straight line that becomes the shortest length (the shortest length) are the same degree as a circle or rectangle. Recesses, etc.; groove-shaped recesses, etc., whose longest and shortest lengths are different. The groove-shaped concave portion can be formed so as to cover the entire circumference of the roller. The width of the recessed portion is, for example, 0.3 mm or more and 50 mm or less. The depth of the recessed part in the roll used for the manufacturing method of this embodiment is 0.03 mm or more and 0.9 mm or less.

In this specification, a convex part means the area|region which is more convex than the periphery, Preferably it is the area|region contacted by the pressure stronger than the other area|regions of a polyvinyl-alcohol-type resin film. The outer shape of the convex portion is not limited, and among the straight lines connecting the outer shapes of the convex portions, the length of the straight line that becomes the largest length (the longest length) and the length of the straight line that becomes the shortest length (the shortest length) are approximately the same as the circle. , convex parts such as rectangles, convex parts with different longest and shortest lengths, etc. The convex portion may be formed to cover the entire circumference of the roller. The width of the convex portion is, for example, 0.3 mm or more and 50 mm or less. The height of the convex part in the roll used for the manufacturing method of this embodiment is 0.03 mm or more and 0.9 mm or less.

The concave portion or the convex portion may be one or plural. The area of the outer shape of the concave portion or the convex portion is not limited, but is, for example, 0.03 mm ² or more, 0.07 mm ² or more, or 1 mm ² or more. When the area of the outer shape of one concave portion or one convex portion is less than 1 mm ² , it is preferable to have plural concave portions or convex portions. From the viewpoint of maintaining the grip property of the film, the total area of the outer shape of the concave portion with a depth of 0.03 mm or more and 0.9 mm or less and a convex portion with a height of 0.03 mm or more and 0.9 mm or less is 0.1% or more of the surface area of the roll, and 1% or more is preferably, for example, 30% or less, preferably 20% or less.

On the other hand, the roller preferably has a concave portion having a depth of 0.3 mm or more and 0.9 mm or less, or a convex portion having a height of 0.3 mm or more and 0.9 mm or less on the surface in contact with the polyvinyl alcohol-based resin film. It does not have a concave portion with a depth exceeding 0.9 mm or a convex portion with a height exceeding 0.9 mm. By using such a roller, the grip property of the film can be improved, and at the same time, uneven dyeing of the film can be suppressed.

The reason why the uneven dyeing is formed in the polarizing film is not clear in detail, but it is presumed that the treatment liquid tends to accumulate in or near the concave or convex portion, and the treatment liquid may cause uneven dyeability.

In this embodiment, after the polyvinyl alcohol-based resin film is brought into contact with the first treatment liquid containing iodine in the first treatment step, the obtained polyvinyl alcohol-based resin film is caused to interpose the above-mentioned first treatment liquid. In the state, uneven dyeing can be suppressed by conveying using a roller having a concave portion having a depth of 0.3 mm or more and 0.9 mm or less, or a convex portion having a height of 0.3 mm or more and 0.9 mm or less.

In this specification, the depth of the concave portion refers to the maximum value of the difference in height between the surface of the concave portion and the peripheral surface of the concave portion, wherein the peripheral surface of the concave portion is the surface other than the concave portion and the convex portion. In this specification, the height of the convex portion refers to the maximum value of the difference in height between the surface of the convex portion and the peripheral surface of the convex portion, wherein the peripheral surface of the convex portion is the surface other than the convex portion and the concave portion. Fig. 1(a) is a plan view schematically showing a roller used in the method of the present embodiment, and a roller having a concave portion in a region in contact with the polyvinyl alcohol-based resin film, and Fig. 1(b) Section b-b in Figure 1(a). The roller 60 shown to FIG.1(a) and FIG.1(b) has the recessed part 61 in the area|region contacting the polyvinyl alcohol-type resin film. About the recessed part 61, the depth D is 0.03 mm or more and 0.9 mm or less.

The type of the roller used in the above-mentioned conveying step is not particularly limited, and may be, for example, a guide roller that is a free roller that supports one side of the film, or a roller (nip roller, etc.) that sandwiches a pair of films. The shape of this roll is not limited, and a spiral roll, a crown roll, etc. are mentioned.

In addition, the material is not limited, and sponge rolls, rubber rolls, wooden rolls, or metal rolls can be used, but from the viewpoint of grip, it is preferable to use a sponge roll or roll whose surface is foamed. Surface by cutting groove Works of micro-groove rollers and so on. By using a roller with excellent grip, the PVA-based resin film can be prevented from sliding on the surface of the roller, and the formation of flaws on the surface of the PVA-based resin film can be suppressed.

The material system of the sponge of the sponge roller includes, for example, a polyurethane resin, a polysiloxane-based resin, a polyvinyl chloride-based resin, and the like, and among them, a polyurethane resin is preferably used.

By the said 1st process step, the 1st process liquid exists on the surface of the said film. Therefore, in the transporting step, the membrane contacting the first treatment liquid is transported in a state in which the first treatment liquid exists on the surface thereof, that is, in a state in which the first treatment liquid is interposed therebetween. Examples of the rollers used in the conveying step include those in the first treatment bath, those disposed in the first treatment bath in a state where at least a part of the film is immersed in the first treatment liquid, or the film is first contacted after the film is taken out from the first treatment bath. to the roll and so on.

The first treatment bath here is a treatment bath containing a treatment liquid containing iodine, and corresponds to, for example, a dyeing bath described later. In addition, when the cross-linking liquid and the color-compensating liquid contain iodine, they may correspond to a cross-linking bath and a color-compensating bath. The number of treatment baths corresponding to the first treatment bath may be one or two or more. Hereinafter, the manufacturing method concerning this embodiment is demonstrated concretely.

[Polyvinyl alcohol-based resin film]

The polarizing film can be obtained, for example, by adsorbing and orienting a dichroic dye (iodine, a dichroic dye, etc.) on a uniaxially stretched polyvinyl alcohol-based resin film. The polyvinyl alcohol-based resin film means a film composed of a polyvinyl alcohol-based resin, and, for example, saponified polyvinyl acetate-based resin and the like can be exemplified. Polyvinyl acetate-based resins are copolymers of vinyl acetate and other monomers that can be copolymerized with vinyl acetate (for example, ethylene-vinyl acetate) in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate. copolymers) etc. Examples of other copolymerizable monomer systems include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and the like. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000. The degree of saponification is usually 85 mol% or more, preferably 90 mol% or more, more preferably 99 to 100 mol% Ear%. These polyvinyl alcohol-based resins can be modified, for example, polyvinyl formaldehyde modified with aldehydes, polyvinyl acetal, polyvinyl butyral, and the like can be used.

The polyvinyl alcohol-based resin film used as the starting material in the production method of the present embodiment can be used with a thickness of 80 μm or less, preferably 60 μm or less, more preferably 45 μm or less, and still more preferably An unstretched polyvinyl alcohol-based resin film (embryo film) of 30 μm or less. Thereby, the polarizing film of the thin film which the market demand is gradually increasing can be obtained. The width of the embryo membrane is not particularly limited, for example, it is 400 mm or more and 8000 mm or less, preferably 2000 mm or more and 5500 mm or less. The thickness of the unstretched polyvinyl alcohol-based resin film may be 10 μm or more, or 20 μm or more. The embryo film system, for example, is prepared as a roll (an embryo film roll) of a long unstretched polyvinyl alcohol-based resin film. In addition, the unstretched polyvinyl alcohol-based resin film (green film) can usually be supplied as a roll-shaped film.

The above-mentioned polyvinyl alcohol-based resin film can be laminated on a base film to be supported. That is, the polyvinyl alcohol-based resin film system can be prepared as a laminate film of a base film and a polyvinyl alcohol-based resin film laminated thereon. In this case, the polyvinyl alcohol-based resin film can be produced, for example, by applying a coating liquid containing a polyvinyl alcohol-based resin on at least one surface of a base film, and then drying it.

As the base film system, for example, a film made of a thermoplastic resin can be used. A specific example may be a film made of a light-transmitting thermoplastic resin, preferably an optically transparent thermoplastic resin, for example, a chain polyolefin-based resin (polypropylene-based resin, etc.), a cyclic polyolefin-based resin Polyolefin-based resins (norbornene-based resins, etc.); cellulose-based resins such as triacetyl cellulose and diacetyl cellulose; such as polyethylene terephthalate, polybutylene terephthalate Diester polyester resin; polycarbonate resin; (meth)acrylic resin such as methyl methacrylate resin; polystyrene resin; polyvinyl chloride resin; acrylonitrile/butadiene/ Styrene resin; Acrylonitrile/styrene resin; Polyvinyl acetate resin; Polyvinylidene chloride Vinyl resins; Polyamide resins; Polyacetal resins; Modified polyphenylene ether resins; Resins; polyimide resins, etc.

[Processing steps]

The manufacturing method concerning this embodiment is the manufacturing method of the polarizing film which manufactures a polarizing film from a polyvinyl alcohol-type resin film. Hereinafter, in the present specification, a series of production steps until a polarizing film is produced from a polyvinyl alcohol-based resin film will be described using the term "processing step". That is, regarding the manufacturing method of this embodiment, a polarizing film can be produced from a polyvinyl alcohol-type resin film by performing one or a plurality of processing steps. The above-mentioned one or a plurality of treatment steps include, for example, a swelling step, a dyeing step, a cross-linking step (boric acid step) for performing various treatments such as swelling, dyeing, cross-linking, color correction, and washing on the polyvinyl alcohol-based resin film. ), complementary color steps and cleaning steps, etc.

Specifically, the swelling step is a step of bringing the swelling liquid into contact with the embryo membrane to perform swelling treatment. The dyeing step is a step in which the dyeing liquid is brought into contact with the polyvinyl alcohol-based resin film (hereinafter, also referred to as a "swelled film") after the swelling treatment to perform the dyeing treatment. The cross-linking step (boric acid step) is a step in which the cross-linking liquid is brought into contact with the polyvinyl alcohol-based resin film (hereinafter, also referred to as "dyeing film") after the dyeing treatment, and the cross-linking treatment is performed. The color correction step is a step in which the color correction liquid is brought into contact with the polyvinyl alcohol-based resin film (hereinafter, also referred to as a "crosslinked film") after the crosslinking treatment to perform color adjustment treatment. In addition, in the cleaning step, the polyvinyl alcohol-based resin film (hereinafter, also referred to as "color correction film") after the color adjustment treatment is removed by adhering the cleaning solution in the above-mentioned cross-linking step and color correction step. Wait for the steps of cleaning treatment of the remaining adhered boric acid, iodine and other chemicals. The above-mentioned one or a plurality of processing steps are not limited to the above-mentioned steps as long as the effects of the present invention are exhibited, and other steps may be included. The above-mentioned one or a plurality of processing steps may be appropriately combined with the above-mentioned steps and other steps.

It is preferable that the above-mentioned processing step includes the operation of uniaxially extending the polyvinyl alcohol-based resin film before any one of the steps such as the above-mentioned swelling step or in any one of the steps. For example, after the unstretched embryo membrane is uniaxially stretched in air or inert gas (dry stretching), a swelling step, a dyeing step, a cross-linking step, a color correction step, and a washing step are sequentially performed. In addition, the swelling step, the dyeing step, the cross-linking step, the color-repairing step, and the washing step are sequentially performed using an unstretched embryo membrane, and the polyvinyl alcohol-based system is wet-processed before or during the above-mentioned cross-linking step. The resin film is uniaxially stretched.

Hereinafter, it demonstrates concretely by exemplifying the manufacturing method concerning this embodiment, referring FIG. 2. FIG. FIG. 2 is a cross-sectional view schematically showing an example of a polarizing film manufacturing apparatus used in the manufacturing method according to the present embodiment.

In the polarizing film manufacturing apparatus shown in FIG. 2, the green (unstretched) film 10 made of polyvinyl alcohol-based resin is continuously rolled out from the green film roll 11 and conveyed along the film conveying route, according to the The sequence passes through the swelling bath (swelling liquid contained in the swelling tank) 13, the dyeing bath (the dyeing liquid contained in the dyeing tank) 14, the cross-linking bath (the cross-linking liquid contained in the cross-linking tank) set on the film conveying route solution) 15, a color-compensating bath (the color-compensating solution contained in the color-compensating tank) 16, and the cleaning bath (the cleaning solution contained in the cleaning tank) 17, whereby the swelling step, the dyeing step, and the post-processing can be performed in sequence. step, color complementing step and washing step. In addition, the polarizing film 23 is obtained by passing the green (unstretched) film 10 which has passed through the above-mentioned treatment bath in sequence, and finally passes it through the drying furnace 21 . Then, the polarizing film manufacturing apparatus can directly transport the polarizing film 23 to, for example, the following polarizing plate manufacturing step (step of attaching a protective film to one side or both sides of the polarizing film 23 ). The arrows in Fig. 2 indicate the conveying direction of the film.

In the description of Fig. 2, "treatment tank" is a general term that includes swelling tank, dyeing tank, cross-linking tank, color correction tank and cleaning tank, and "treatment liquid" includes swelling liquid, dyeing liquid, cross-linking liquid, and color-repairing liquid. And the general term for cleaning liquid, "treatment bath" includes swelling bath, dyeing bath, cross-linking bath, color complementary bath and cleaning bath. general term. The swelling bath, the dyeing bath, the crosslinking bath, the color correction bath and the cleaning bath respectively constitute the swelling part, the dyeing part, the crosslinking part, the color correction part and the washing part in the above-mentioned polarizing film manufacturing apparatus.

The film conveying route of the polarizing film manufacturing apparatus is in addition to the above-mentioned treatment bath. Arranged in the appropriate position and constituted. The guide rollers 30 to 32, 34 to 36, 38 to 40, and 42 to 46 can support the conveyed film and change the film conveying direction. The nip rollers 50 to 52, 53a, 53b, 54 to 55 press and clamp the film conveyed along the above-mentioned film conveying route, so that the driving force generated by the rotation can be applied to the film, and the film conveying can be changed. direction. Guide rolls and nip rolls can be arranged before and after each treatment bath and in the treatment bath, whereby introduction of the film into the treatment bath, dipping, and extraction from the treatment bath are performed. For example, one or more guide rolls may be provided in each treatment bath, and the film may be immersed in each treatment bath by conveying the film along these guide rolls.

The polarizing film manufacturing apparatus arranges nip rolls 50 to 52, 53a, 53b, and 54 before and after each treatment bath. Thereby, in any one or more processing baths, the longitudinal uniaxial stretching can be performed by applying a peripheral speed difference between the nip rolls arranged before and after the rolls. Hereinafter, each step will be described.

<swelling step>

The swelling step is performed for the purpose of removing foreign matter on the surface of the embryonic membrane 10 , removing the plasticizer in the embryonic membrane 10 , imparting easy dyeability, and plasticizing the embryonic membrane 10 . The treatment conditions are determined within a range that can achieve the above-mentioned purpose without causing extreme dissolution and devitrification of the embryonic membrane 10 .

The above swelling step can make the embryo membrane 10 continuously roll out from the embryo membrane reel 11, and transport along the film conveying route at the same time, so that the embryo membrane 10 is immersed in the swelling bath 13 for a predetermined time, and then pulled out as a swelling membrane, Thereby, swelling treatment is performed. In addition to pure water, the swelling liquid used in the swelling bath can be added with boric acid (Japanese Patent Application Laid-Open No. 10-153709), chlorinated water in the range of about 0.01 to 10% by mass. (Japanese Patent Laid-Open No. 06-281816), aqueous solutions of inorganic acids, inorganic salts, water-soluble organic solvents, alcohols, and the like.

The temperature of the swelling bath 13 is, for example, about 10 to 70°C, preferably about 15 to 50°C, and more preferably about 15 to 35°C. The immersion time of the embryo membrane 10 is preferably about 10 to 600 seconds, more preferably about 15 to 300 seconds.

In the swelling treatment described above, since the embryo membrane 10 is swelled in the thickness direction, it is easy to cause wrinkles in the swelled membrane. As a means for removing the wrinkles while conveying the swelled film, a known roll having a width expanding function or a known width expanding device can be used. Yet another means for suppressing the occurrence of wrinkles is to apply a stretching treatment. For example, the uniaxial stretching treatment can be performed in the swelling bath 13 by utilizing the difference in peripheral speed between the nip roll 50 and the nip roll 51 .

In order to eliminate film slack in the conveying direction when the above-mentioned swelling treatment-based film swells and expands in the conveying direction of the film, when the embryo film is not actively stretched, it is preferable to, for example, control the arrangement of the film before and after the swelling bath 13. The means of the speed of the nip rolls 50, 51, etc. In addition, for the purpose of stabilizing the conveyance of the film in the swelling bath 13, a water jet can be used to control the water flow in the swelling bath 13, or an EPC device (Edge Position Control device: detecting the edge of the film and preventing the Snaking device) etc.

In the example shown in FIG. 2 , the swellable film drawn from the swellable bath 13 is introduced into the dyeing bath 14 through the guide roll 32 and the nip roll 51 in this order.

<Dyeing step>

The dyeing step is performed for the purpose of adsorbing dichroic dyes such as iodine, and reorienting the polyvinyl alcohol-based resin film after the swelling treatment. The treatment conditions are determined within a range in which the above-mentioned purpose can be achieved and in such a range that extreme dissolution and devitrification of the film do not occur. In the dyeing step, the swollen film after the swell treatment can be conveyed through the film conveying route constructed by the nip roll 51, the guide rolls 34 to 35 and the nip roll 52, and then dipped. After a predetermined time in the dyeing bath 14, the dyeing process is performed by pulling out as a dyed film. In order to improve the dyeability of the dichroic dye, the swelled film supplied to the dyeing step is preferably a film that is subjected to at least a certain degree of uniaxial stretching treatment, and it is preferred to perform uniaxial stretching treatment during dyeing treatment instead of before dyeing treatment. uniaxial stretching treatment, or, in addition to uniaxial stretching treatment before dyeing treatment, uniaxial stretching treatment is also carried out during dyeing treatment.

Preferably, iodine is used as a dichroic dye, and the dyeing liquid used in the dyeing bath 14 can be, for example, an aqueous solution whose concentration is iodine/potassium iodide/water=about 0.003 to 1/about 0.1 to 20/100 in mass ratio. In place of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide and other iodides may be used in combination. Moreover, compounds other than iodide, for example, boric acid, zinc chloride, cobalt chloride, etc. may coexist. When boric acid is added, it is distinguished from the crosslinking liquid described later in that it contains a dichroic dye. In this specification, when an aqueous solution contains about 0.003 mass part or more of a dichroic dye with respect to 100 mass parts of water, the said aqueous solution can be regarded as a dyeing liquid. The temperature of the dyeing bath 14 when dipping the swellable film is usually about 10 to 45°C, preferably 10 to 40°C, more preferably 20 to 35°C, and the immersion time of the swellable film is usually about 20 to 600 seconds, preferably 30 to 300 seconds.

As described above, in the dyeing step, the uniaxial extension of the swelled film may be performed in the dyeing bath 14 . The uniaxial stretching of the swollen film can be performed by giving a peripheral speed difference between the nip rolls 51 and 52 arranged before and after the dyeing bath 14 .

In the above-mentioned dyeing treatment, in order to remove wrinkles while conveying the polyvinyl alcohol-based resin film in the same manner as in the above-mentioned swelling treatment, the above-mentioned guide rolls 34, 35, and 36 can be used. Equipped with a well-known widening device. Another means for suppressing the occurrence of wrinkles is to apply a stretching treatment in the same manner as the swelling treatment.

In the example shown in FIG. 2 , the dyed film drawn from the dyeing bath 14 is introduced into the crosslinking bath 15 through the guide roll 36 and the nip roll 52 in this order.

<An aspect of the dyeing step>

In one aspect of the dyeing step, the dyeing step is the first treatment step, and the dyeing liquid is the first treatment liquid. In this aspect, among the guide rollers 34, 35, and 36 shown in FIG. 2, at least one guide roller has a concave portion having a depth of 0.03 mm or more and 0.9 mm or less on the surface in contact with the polyvinyl alcohol-based resin film. and at least one of the rolls (hereinafter, also referred to as "first rolls") of convex portions having a height of 0.03 mm or more and 0.9 mm or less. In FIG. 2 , the first roller is transported by contacting the polyvinyl alcohol-based resin film with the dyeing liquid interposed therebetween, and does not have a concave portion with a depth exceeding 0.9 mm on the surface in contact with the polyvinyl-alcohol-based resin film. , or protrusions with a height exceeding 0.9mm. According to the manufacturing method of this aspect, the formation of uneven dyeing in the polarizing film can be suppressed.

In the production method of the present embodiment, the dyeing step is not limited to the above-exemplified method as long as the effect of the present invention can be obtained, and all modifications can be made within the meaning equivalent to the scope of the patent application. Furthermore, in the production method according to the present embodiment, the processing step belonging to the first processing step is not limited to the case of the dyeing step, and the processing liquid contained in the processing bath only needs to be a processing step that does not contain iodine. Can. For example, it may correspond to a cross-linking step or a complementary coloring step. In these cases, a polarizing film without poor recognition due to uneven dyeing can be provided. In the production method having a plurality of treatment steps using treatment liquids with different compositions in each treatment step, at least one treatment step may be the first treatment step, and the other treatment steps may be different from the first treatment step. The second processing step. A treatment liquid having a composition different from that of the first treatment liquid used in the second treatment step was used as the second treatment liquid.

When the crosslinking step and the color correction step are the first processing steps, the description of the conveying step in one aspect of the above-mentioned dyeing step may be the description of the conveying step in these processing steps.

<Crosslinking step>

For the above dyed film, the crosslinking step is performed for the purpose of imparting water resistance. The above-mentioned cross-linking step may be performed once or several times. In the cross-linking step, the dyed film conveyed along the film conveying route constructed by the nip rolls 52, the guide rolls 38 to 40 and the nip roll 53a is immersed in the cross-linking bath 15 for a predetermined time, and then pulled out. A crosslinking treatment is performed as a crosslinked film.

As a cross-linking liquid, a solution obtained by dissolving a cross-linking agent in a solvent can be used. As a crosslinking agent, boron compounds, such as boric acid and borax, glyoxal, glutaraldehyde, etc. are mentioned, for example. One type of these types may be used alone, or two or more types may be used in combination. As the solvent system, for example, water can be used, but further, an organic solvent having compatibility with water can be included. The concentration of the crosslinking agent in the crosslinking liquid is not limited to this, but is preferably in the range of 0.1 to 15% by mass, more preferably 1 to 12% by mass.

In the cross-linking treatment, if necessary, other cross-linking agents may be used instead of boric acid, or boric acid and other cross-linking agents may be used in combination. The temperature of the crosslinking bath when dipping the dyed film is usually about 20 to 85°C, preferably 30 to 70°C, and the immersion time of the dyed film is usually about 10 to 600 seconds, preferably 20 to 300 seconds. Furthermore, when the pre-stretched polyvinyl alcohol-based resin film is sequentially subjected to dyeing treatment and cross-linking treatment before the swelling treatment, the temperature of the cross-linking bath is usually 50°C or higher, preferably 50 to 85°C.

The cross-linking treatment may be performed once or a plurality of times. In this case, the composition and temperature of the crosslinking bath used may be the same or different as long as they are within the above-mentioned ranges. Moreover, the uniaxial stretching process may be performed in a crosslinking bath by utilizing the peripheral speed difference of each nip roll.

In the cross-linking treatment, similarly to the swelling treatment, in order to remove wrinkles and transport the polyvinyl alcohol-based resin film, a known roll having a function of widening the width of the guide rolls 38, 39, and 40 can be used, or a known roll can be used. The extended width device. Another means for suppressing the occurrence of wrinkles is to apply a stretching treatment in the same manner as the swelling treatment.

In the example shown in FIG. 2 , the cross-linked film drawn from the cross-linking bath 15 passes through the guide roll 40 and the nip roll 53 a in this order and is introduced into the complementary color bath 16 .

<Complementary color step>

For the above-mentioned cross-linked film, a complementary color step is performed for the purpose of adjusting the hue. In the above-mentioned color correction step, the cross-linked film conveyed along the film conveying route constructed by the nip roller 53a, the guide rollers 42 to 44 and the nip roller 53b can be immersed in the color correction bath 16 for a predetermined time, and then pulled out. Complementary color treatment is performed as a color correction film. The temperature of the color-compensating bath during immersion of the cross-linked film is usually about 20 to 65°C, and the immersion time of the cross-linked film is usually about 1 to 300 seconds, preferably 2 to 100 seconds.

The uniaxial stretching process can also be performed in the complementary color bath 16 by utilizing the difference in the peripheral speed of the respective nip rolls 53 a and 53 b arranged before and after the complementary color bath 16 . In the example shown in FIG. 2 , the color correction film pulled out from the complementary color bath 16 is introduced into the cleaning bath 17 used in the cleaning step described next along the film conveying route.

<Extended step>

Here, as described above, the polyvinyl alcohol-based resin film is preferably between a series of treatment steps (that is, in one or a plurality of treatment steps, before and after any one step and/or during any one or more treatment steps) ), uniaxially stretched wet or dry. A specific method of the uniaxial stretching treatment can be, for example, a roll that performs vertical uniaxial stretching by providing a peripheral speed difference between two nip rolls (for example, two nip rolls arranged before and after the treatment bath) constituting the film conveying path. Inter-roll stretching, such as hot-roll stretching and stretching device stretching described in Japanese Patent No. 2731813, is preferably inter-roll stretching. The uniaxial extension step can be subordinate to the polyvinyl alcohol system of the starting material The embryo film of the resin film is carried out several times until the polarizing film is obtained. The stretching treatment is also effective for suppressing the occurrence of wrinkles in the film.

The final cumulative extension magnification of the polarizing film based on the above-mentioned embryonic membrane is usually about 3.5 to 7 times, preferably 4 to 6.5 times. The extension step may be any one of the treatment steps, and when the extension treatment is performed in two or more treatment steps, the extension treatment may be performed in any one of the treatment steps.

<Cleaning step>

The washing step is intended to remove chemicals such as excess boric acid, iodine and the like adhering to the film in the cross-linking step, the color-repairing step, and the like. For example, in the cleaning bath 17 of the polarizing film manufacturing apparatus shown in FIG. The film is conveyed along the film conveyance route constructed by the two nip rolls 53b and 54 before and after the washing bath 17, and at the same time, washing treatment is performed. The first nip roll 53b and the second nip roll 54 function as dewatering rolls, respectively, to wash and remove excess boric acid, iodine and other chemicals adhering to the color correction film.

In the above-mentioned washing step, similarly to the swelling step, etc., for the purpose of removing wrinkles and conveying the polyvinyl alcohol-based resin film, a known roller having a widening function on the guide rollers 45 and 46 can be used, or a known roller having a widening function can be used. widening device. In addition, in the washing step, a stretching treatment may be given in order to suppress the occurrence of wrinkles.

As the cleaning solution used in the cleaning step, water and any of conventionally known cleaning solutions used for cleaning of such polyvinyl alcohol-based resin films can be used. The temperature range of the cleaning solution used in the cleaning step can also be set to the same temperature range as the conventional one (for example, 2 to 60° C.). When the cleaning liquid is removed from the film after the cleaning step, the cleaning liquid removal means is, for example, a nip roll 54. In addition to this nip roll, a means for removing the liquid by blowing air to the film, contact A doctor blade, a suction roll, a water removal roll, etc., for removing the liquid from the above-mentioned film.

<Other steps: such as drying step>

The manufacturing method related to this embodiment may include steps other than the above-mentioned processing steps. As for other steps, for example, a drying step can be cited. The drying step is a step of drying the polyvinyl alcohol-based resin film after the washing step. The drying method in the above drying step is not particularly limited, but for example, hot air drying can be performed using the drying furnace 21 shown in FIG. 2 . At this time, the drying temperature is, for example, about 30 to 100° C., and the drying time is, for example, about 30 to 600 seconds. The process of drying a polyvinyl alcohol-type resin film can also be performed using a far-infrared heater. In the above manner, a polarizing film can be produced. The thickness of the polarizing film is, for example, about 5 to 50 μm .

<Polarizing film>

According to the manufacturing method concerning this embodiment, the polarizing film which suppresses the formation of stripe-shaped uneven dyeing on the surface can be obtained. The optical sensitivity correction monomer transmittance Ty of the above polarizing film is based on the balance between the optical sensitivity correction polarization degree Py, preferably 43 to 50%, more preferably 43 to 49%, and 44 to 48%. Better yet. In any position in the width direction, the viewing sensitivity correction polarization degree Py is preferably 90.0% or more, and more preferably 98.0% or more.

The sensitivity-corrected single transmittance (Ty) and the sensitivity-corrected polarization (Py) can be obtained by the following measurement methods. First, for the above polarizing film, the MD transmittance and TD transmittance in the wavelength range of 380 to 780 nm were measured using a spectrophotometer with an integrating sphere (“V7100” manufactured by JASCO Corporation), according to the following Statement:

Monomer penetration rate (%)=(MD+TD)/2

The degree of polarization (%)={(MD-TD)/(MD+TD)}×100, and the transmittance and the degree of polarization at each wavelength were calculated.

Here, the "MD transmittance" refers to the transmittance when the direction of the polarized light emitted from the Glan-Thompson prism is parallel to the transmission axis of the polarizing film sample, and is expressed in the above formula Indicated as "MD". In addition, the so-called "TD transmittance" refers to the transmittance when the direction of the polarized light emitted from the Glan-Thompson prism is orthogonal to the transmission axis of the polarizing film sample. , denoted as "TD". Next, for the above-mentioned single transmittance and polarization degree, the two-dimensional field of view (C light source) according to JIS Z 8701:1999 "Display method of color - XYZ color system and X ₁₀ Y ₁₀ Z ₁₀ color system" is used. Sensitivity correction is performed to obtain the sensitivity-corrected single transmittance (Ty) and the sensitivity-corrected polarization (Py).

The width of the polarizing film is, for example, 50 mm or more and 5000 mm or less, preferably 500 mm or more and 4000 mm or less. The above-mentioned polarizing film can be sequentially wound up to a winding roll to form a roll, or it can be directly supplied to the step of producing a polarizing plate without being wound up (the step of layering a protective film on one side or two sides of the polarizing film, etc.).

<Polarizer>

The polarizing plate system can be obtained by bonding a protective film to at least one side of the polarizing film produced as described above via an adhesive. The protective film includes, for example, a film composed of an acetyl cellulose-based resin such as triacetin and diacetyl cellulose; such as polyethylene terephthalate, polyethylene naphthalate Films composed of polyester-based resins of diester and polybutylene terephthalate; polycarbonate-based resin films, cyclic olefin-based resin films; acrylic resin films; chain-shaped olefin-based resins composed of polypropylene-based resins formed film.

In order to improve the adhesion between the polarizing film and the protective film, corona treatment, flame treatment, plasma treatment, ultraviolet irradiation, primer coating treatment, saponification treatment, etc. can be applied to the bonding surface of the polarizing film and/or the protective film. Surface treatment. The adhesive used for bonding the polarizing film and the protective film includes an active energy ray-curable adhesive such as an ultraviolet-curable adhesive, an aqueous solution of a polyvinyl alcohol-based resin, an aqueous solution prepared with a crosslinking agent, an amine Water-based adhesives of carboxylate-based emulsion adhesives, etc.

[Example]

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples.

(Preparation of Guide Roller A-1)

A guide roller having no concave portion and convex portion on a surface of 70 mm in diameter and 600 mm in width was prepared as a guide roller A-1.

(Preparation of Guide Roller A-2)

A sponge roll having the same size as the guide roll A-1 prepared above, and having countless substantially circular recesses on the surface was prepared as the guide roll A-2. For 10 concave portions contained in an arbitrary region of the surface of the guide roller A-2, the depth is 0.2 to 0.5 mm and the average value thereof is 0.3 mm, and the area is 0.03 to 0.20 mm ² and the average value thereof is 0.07 mm ² . The occupied area of the concave portion is 15% of the roll surface.

(Preparation of guide rollers B-1, B-2, B-3, B-4, B-5)

Using the guide roller A-2, a plurality of groove-shaped recesses with depths d [mm] and widths w [mm] are formed on the surface at intervals of g [mm] in the width direction, and set as Guide rollers B-1, B-2, B-3, B-4, B-5. The respective depth d, width w, and interval g are shown in Table 1. FIG. 3 is a schematic view showing a cross section of the guide roller B-4.

[Table 1]

(Example 1)

Using the same polarizing film manufacturing apparatus as the apparatus shown in FIG. 2, the polarizing film 23 was continuously manufactured from the long polyvinyl alcohol film (PVA-based resin film 10). The polyvinyl alcohol film used is a polyvinyl alcohol film with a thickness of 60 μm, and the polyvinyl alcohol constituting the film has a degree of saponification of 99.9 mol% or more, and an average degree of polymerization of 2400. In the dyeing bath 14, two guide rollers A-2 are arranged.

[a] Swelling treatment step

The PVA-based resin film 10 is conveyed while continuously being unwound from the unwinding reel 11, and is immersed in a swelling bath 13 containing pure water at 30°C, and a peripheral speed difference is provided between the nip rolls 50 and 51 to prevent slack. On the other hand, 1.5-fold stretching between rolls (longitudinal uniaxial stretching) and swelling treatment were performed.

[b] Dyeing treatment step

Then, in order to apply a 1st dyeing process, the PVA-type resin film 10 which passed the nip roll 51 was immersed in the dyeing bath 14 of 30 degreeC of iodine/potassium iodide/water (mass ratio) 0.03/1.0/100 for 120 seconds. In this dyeing treatment, a peripheral speed difference is provided between the nip rolls arranged before and after the dyeing bath 14, and the inter-roll stretching (longitudinal uniaxial stretching) is performed 1.5 times.

[c] Cross-linking treatment step and complementary color treatment step

Next, in order to perform cross-linking treatment for the purpose of water resistance, the PVA-based resin film 10 passing through the nip rolls 52 is immersed in a cross-linking bath 15 having a potassium iodide/boric acid/water (mass ratio) of 10/5/100 at 55° C. 30 seconds in. Also in this crosslinking treatment, a peripheral speed difference was provided between the nip rolls, and the stretching between the rolls was performed 2.0 times (longitudinal uniaxial stretching). Then, the PVA-based resin film 10 after the crosslinking treatment was immersed in a color-correcting bath 16 having a potassium iodide/boric acid/water (mass ratio) of 10/5/100 at 40° C. for 15 seconds (color-correcting treatment). Also in this color correction treatment, a peripheral speed difference was provided between the nip rolls, and the stretching between the rolls was performed 1.2 times (longitudinal uniaxial stretching).

After that, the PVA-based resin film 10 after the color correction treatment was immersed in a cleaning bath 17 containing pure water at 15° C., and then passed through a drying oven 21 and dried at 70° C. for 3 minutes to prepare a polarizing film. twenty three.

(Example 2)

The polarizing film manufacturing apparatus was carried out in the same manner as in Example 1, except that the guide roller B-1 was used instead of the guide roller A-2 for the two guide rollers arranged in the dyeing bath 14. Then, the polarizing film 23 is produced.

(Example 3)

The polarizing film manufacturing apparatus was carried out in the same manner as in Example 1, except that the guide roller B-2 was used instead of the guide roller A-2 for the two guide rollers arranged in the dyeing bath 14. Then, the polarizing film 23 is produced.

(Example 4)

The polarizing film manufacturing apparatus was carried out in the same manner as in Example 1, except that the guide roller B-3 was used instead of the guide roller A-2 for the two guide rollers arranged in the dyeing bath 14. Then, the polarizing film 23 is produced.

(Example 5)

The polarizing film manufacturing apparatus was carried out in the same manner as in Example 1, except that the guide roller B-4 was used instead of the guide roller A-2 for the two guide rollers arranged in the dyeing bath 14. Then, the polarizing film 23 is produced.

(Comparative Example 1)

The polarizing film manufacturing apparatus was carried out in the same manner as in Example 1, except that the guide roller A-1 was used instead of the guide roller A-2 for the two guide rollers arranged in the dyeing bath 14. Then, the polarizing film 23 is produced.

(Comparative Example 2)

In the polarizing film manufacturing apparatus, the same procedure as in Example 1 was carried out, except that the guide roller B-5 was used instead of the guide roller A-2 for the two guide rollers arranged in the dyeing bath 14. Then, the polarizing film 23 is produced.

(Evaluate)

For the polarizing films produced in Examples 1 to 5 and Comparative Examples 1 and 2, the visual sensitivity correction monomer transmittance Ty was measured, and the rotatability and dyeing unevenness of the guide roller were visually observed according to the following criteria The rotation of the guide roller and uneven dyeing were evaluated. In each of Examples 1 to 5 and the polarizing films produced in Comparative Examples 1 and 2, the visual sensitivity correction monomer transmittance Ty was 44.0%. The evaluation results are shown in Table 2.

<Rotation of Guide Roller>

A: The roll rotates at the same speed as the film.

B: Although it is slower than the movement of a film, the roller does not stop rotating.

C: Although the film moved, the roller occasionally stopped.

D: Although the film moves, the roller stops.

<Uneven dyeing>

A: Uneven dyeing cannot be recognized.

B: Although uneven dyeing is faintly recognized, it is not to such an extent that it becomes a problem.

C: Uneven dyeing is clearly recognized.

[Table 2]

From the results shown in Table 2, it can be seen that in the dyeing bath, in Examples 1 to 5 using guide rolls having recesses with a depth of 0.9 mm or less, dyeing unevenness to a degree that would be a problem was not recognized. In addition, in Examples 1 to 5, as in Comparative Example 1, the rotation of the guide roller was suppressed from being completely stopped.

10: Embryo film, resin film, film composed of polyvinyl alcohol-based resin

11: Embryo film roll, roll

13: Swelling bath

14: Dye Bath

15: Crosslinking bath

16: Complementary Color Bath

17: Clean the bath

21: Drying oven

23: polarizing film

30 to 32, 34 to 36, 38 to 40, 42 to 46: Guide rollers

50 to 52, 53a, 53b, 54 to 55: nip rolls

Claims (6)

A manufacturing method of a polarizing film, which is to manufacture a polarizing film from a polyvinyl alcohol-based resin film, and the manufacturing method of the polarizing film sequentially includes: The first treatment step is to bring the polyvinyl alcohol-based resin film into contact with the first treatment liquid; The conveying step is to make the polyvinyl alcohol-based resin film contact a roller with the first treatment liquid interposed therebetween, and convey the polyvinyl-alcohol-based resin film; wherein, the first treatment liquid system contains iodine, The said roller has at least one of a recessed part with a depth of 0.03 mm or more and 0.9 mm or less and a convex part with a height of 0.03 mm or more and 0.9 mm or less on the surface in contact with the polyvinyl alcohol-based resin film. The manufacturing method of the polarizing film of Claim 1 whose said 1st process liquid system contains boric acid. The method for producing a polarizing film according to claim 1 or 2, further comprising a second treatment step in which the polyvinyl alcohol-based resin film is brought into contact with a second treatment liquid different from the first treatment liquid. The manufacturing method of the polarizing film of any one of Claims 1-3 whose said roller is a sponge roller. The method for producing a polarizing film according to any one of claims 1 to 4, wherein the optical sensitivity correction single transmittance of the polarizing film is 43% or more. A device for manufacturing a polarizing film is used to manufacture a polarizing film from a polyvinyl alcohol-based resin film, the device having: a first treatment bath containing the first treatment solution; a roller disposed in the aforementioned first treatment bath; and, The conveying route through the aforementioned rollers; wherein, the first treatment liquid system contains iodine, The said polyvinyl alcohol-type resin film is conveyed along the said conveyance route, and is immersed in the said 1st processing bath, The said roller has at least one of a recessed part with a depth of 0.03 mm or more and 0.9 mm or less and a convex part with a height of 0.03 mm or more and 0.9 mm or less on the surface in contact with the polyvinyl alcohol-based resin film.

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