JP6973560B2 - Packaging, polyvinyl alcohol-based film storage or transportation methods, polyvinyl alcohol-based film, and polarizing film - Google Patents

Description

The present invention relates to a package, a method for storing or transporting a polyvinyl alcohol-based film, a polyvinyl alcohol-based film, and a polarizing film. More specifically, the present invention is a packaging body suitable for storage and transportation of a polyvinyl alcohol-based film which is excellent in appearance, has no optical unevenness, and is useful as a raw material for obtaining a polarizing film, and a polyvinyl alcohol-based film using the same. The present invention relates to a method for storing or transporting a film, a polyvinyl alcohol-based film thus stored and / or transported, and a polarizing film produced by using the polyvinyl alcohol-based film.

Conventionally, a polyvinyl alcohol-based film is obtained by dissolving a polyvinyl alcohol-based resin in a solvent such as water, forming a film by a solution casting method (cast method), and then forming a metal heating roll (hereinafter referred to as a metal heating roll) or the like. Manufactured by drying using. The polyvinyl alcohol-based film thus produced is used for many purposes as a film having excellent transparency and dyeability, and one of the useful uses is a polarizing film.

In order to meet such demands, it is necessary to improve the physical properties of the polyvinyl alcohol-based film itself, but it is also important to store and transport the polyvinyl alcohol-based film after production. This is because if the water content of the polyvinyl alcohol-based film fluctuates greatly during storage or transportation, or if the water content in the film surface becomes uneven, not only the film is deformed, but also the optical characteristics in the film surface change. This is because the obtained polarizing film has uneven polarization (in-plane non-uniformity of polarization) and uneven color.

As a technique for solving such a problem, for example, Patent Document 1 discloses a technique in which a roll of a polyvinyl alcohol-based film is wrapped in a water vapor barrier resin packaging film and a packaging film made of an aluminum material, and stored or transported. It has been proposed (see paragraphs 0042-0044). Further, for example, Patent Document 2 proposes a technique of fixing both ends of a packaging sheet to both ends of a core with conductive rubber bands (see paragraphs 0020 and 0025). Further, for example, Patent Document 3 proposes a package in which both ends of a packaging material are fixed to a core tube and the surplus portions of both ends are further pushed into the core (see paragraphs 0014 and FIG. 3). ..

Japanese Unexamined Patent Publication No. 2005-306483 Japanese Unexamined Patent Publication No. 2010-179922 Japanese Unexamined Patent Publication No. 2013-227073

However, even with the above-mentioned disclosure technique, it is insufficient to suppress deformation of the polyvinyl alcohol-based film and deterioration of optical performance during transportation. In the disclosed technique of Patent Document 1, moisture may enter the inside (internal space where the film roll is located) from the end portion (the end portion on the axial side of the core tube) of the water vapor barrier resin packaging film. Even with the disclosure technique of Patent Document 2, there is a possibility that moisture may enter the inside through the gap between the fixed packaging sheet and the core tube. Further, in the technique disclosed in Patent Document 3, it is difficult to prevent the moisture condensed inside the core tube from invading the inside, and as a method of preventing the invasion of moisture, a packaging material is used by using double-sided tape or an adhesive. A method of fixing the core to the outer peripheral surface of the core protrusion and a method of fusing the packaging material to the outer peripheral surface of the core protrusion to fix the core are also mentioned, but the specific procedure and structure are unknown.

Generally, polyvinyl alcohol-based films are packaged with a water content of several percent. Even if the water vapor barrier resin packaging film blocks moisture from entering from the outside, if moisture enters the inside of the package through the gap between the packaging film and the core tube, deformation or optical unevenness may occur. It ends up. Further, if the film itself is repeatedly absorbed and dehumidified by the moisture inside the package, deformation and optical unevenness also occur. This phenomenon is more likely to occur as the polyvinyl alcohol-based film becomes wider and longer, and becomes more remarkable as the film becomes thinner.
Therefore, the problem to be solved by the present invention is to provide a package of a polyvinyl alcohol-based film capable of reducing deformation of the polyvinyl alcohol-based film and occurrence of optical unevenness by suppressing the intrusion of water into the inside. It is to be.

However, as a result of diligent research by the present inventors to solve the above problems, the core tube around which the polyvinyl alcohol-based film is wound and the end portion of the core tube on the axial direction side of the water vapor barrier film which is the packaging material. The present invention has been completed by finding that the above-mentioned problems can be solved by devising the sealing form of the above.

That is, the present invention is a package obtained by wrapping a film roll in which a strip-shaped polyvinyl alcohol-based film is wound around a core tube having a shaft length longer than the film width with a steam barrier film, and the core in the steam barrier film. The package is characterized in that the end portion on the axial direction side of the tube is fixed to the outer peripheral portion of the core tube protruding from the film roll with a double-sided adhesive tape.

Further, the present invention is a package obtained by wrapping a film roll in which a strip-shaped polyvinyl alcohol-based film is wound around a core tube having a shaft length longer than the film width with a steam barrier film having a polyethylene film, wherein the steam barrier is formed. the ends of the axial direction of the core tube in the polyethylene film of the film, the film is affixed to the outer peripheral portion of the core tube projecting from the roll, and the hot adhesive tape having a vinyl acetate based hot melt adhesive layer It is a package characterized in that it is fixed to the surface of the melt adhesive layer by a heat seal.

Further, it is preferable that the package is packaged with a dry sheet together with the film roll.

Further, it is preferable that the package is packaged with a humidity indicator together with the film roll.

Further, the polyvinyl alcohol-based film preferably has a width of 4 m or more and a length of 4 km or more.

The thickness of the polyvinyl alcohol-based film is preferably 5 to 40 μm.

The present invention is also a method for storing or transporting a polyvinyl alcohol-based film, which comprises storing and / or transporting the polyvinyl alcohol-based film using the above-mentioned package.

According to the present invention, it is possible to prevent the strip-shaped polyvinyl alcohol-based film from being deformed or deteriorated in optical performance during storage and / or transportation, and to prevent the film roll from being unwound, scratched, or deteriorated due to blocking. Further, the quality in the width direction and the longitudinal direction (from the winding outer peripheral portion to the core portion) of the film roll can be kept constant. Further, not only a polarizing film having excellent in-plane uniformity can be obtained, but also unwinding at the time of manufacturing the polarizing film can be facilitated and productivity can be improved.

FIG. 1 is a schematic cross-sectional view showing a part of the package 1 according to the embodiment of the present invention in an enlarged manner. FIG. 2 is a perspective view showing a packaging procedure of the film roll 3 in the package 1.

Hereinafter, the present invention will be specifically described.
FIG. 1 is an enlarged schematic cross-sectional view showing a part of the package 1 according to the embodiment of the present invention, and FIG. 2 is a perspective view showing a packaging procedure of the film roll 3 in the package 1.

As shown in FIG. 2, the package 1 is formed by winding a strip-shaped polyvinyl alcohol-based film around a core tube 2 having a shaft length longer than the film width to form a film roll 3, and the film roll 3 is packaged with a water vapor barrier film 4. It will be.

More specifically, first, as shown in FIG. 2A, one end of the rectangular water vapor barrier film 4 is fixed at a predetermined winding start position on the outer peripheral portion of the film roll 3. At this time, one side of the water vapor barrier film 4 is arranged and fixed so as to be parallel to the axial direction of the core tube 2.

Next, as shown in FIG. 2B, the water vapor barrier film 4 is wound around the outer periphery of the film roll 3 at least once, and then the other end of the water vapor barrier film 4 is fixed using, for example, an adhesive tape 5. At this stage, the water vapor barrier film 4 has a cylindrical shape. After that, as shown in FIG. 2C, the two ends of the core tube 2 on the axial direction side of the water vapor barrier film 4 are fixed to the outer peripheral portions of the core tube 2 protruding from the film roll 3, respectively, to form a package. 1 is completed. Details of the procedure for fixing the end portion of the water vapor barrier film 4 will be described later.

In this way, in the package 1, the film roll 3 is arranged in the internal space formed by the core tube 2 and the water vapor barrier film 4. In the present invention, by devising a sealing form between the core tube 2 and the end portion of the steam barrier film 4 on the axial direction side, the gap between the core tube 2 and the steam barrier film 4 can be changed to the internal space. It suppresses the invasion of water.

The strip-shaped polyvinyl alcohol-based film in the present invention is not particularly limited, and for example, a polyvinyl alcohol-based film produced by a method described later is used. The width of the film is preferably 4 m or more from the viewpoint of increasing the area, particularly preferably 4.5 m or more from the viewpoint of further increasing the area, and further preferably 4.5 to from the viewpoint of avoiding breakage. It is 6m.

The core tube 2 around which the strip-shaped polyvinyl alcohol-based film is wound may have a cylindrical outer shape, and a hollow cylindrical one is preferable from the viewpoint of weight reduction. Further, if the core tube 2 has a cylindrical shape, a support rod can be inserted inside and the film roll 3 can be loaded on a gantry or a processing device.
Examples of the material of the core tube 2 include metal, plastic and the like, and the material is not particularly limited. Examples of the metal include carbon steel, high-strength steel, stainless steel, aluminum, aluminum alloys such as duralumin, copper, brass, bronze and the like. A resin layer such as soft polyvinyl chloride or low-density polyethylene may be laminated on the surface or the inner surface of the metal core tube 2, and is plated with nickel, chromium, zinc, tin, or the like. You may. Examples of the plastic include rigid polyvinyl chloride, polypropylene, high-density polyethylene, ultra-high molecular weight polyethylene, polycarbonate, polyester and the like.
The outer diameter of the core tube 2 is preferably 7.5 cm or more, and particularly preferably 8.5 cm or more. If the outer diameter of the core tube 2 is too short, the film tends to wrinkle. When the core tube 2 has a cylindrical shape, the wall thickness of the core tube 2 is preferably 1.5 to 20 mm, particularly preferably 2 to 15 mm, and further preferably 3 to 10 mm. The size of the core tube 2 is generally 11 to 31 cm in outer diameter and 10 to 30 cm in inner diameter.

The axial length of the core tube 2 (that is, the length in the axial direction) needs to be longer than the film width of the above-mentioned strip-shaped polyvinyl alcohol-based film, and is 10 cm from both ends of the film roll 3 on the axial direction side. Those that protrude above are preferable. Specifically, the axial length of the core tube 2 is preferably 4.1 m or more, and from the viewpoint of further increasing the area, particularly preferably 4.6 m or more, from the viewpoint of avoiding breakage of the polyvinyl alcohol-based film. , More preferably 4.6 to 6.1 m.
Since the core tube 2 has the protrusions, brackets are provided at both ends of the protrusions, or both ends of the protrusions are placed on a pedestal or the like, so that the film roll 3 does not come into contact with the ground or other film rolls or the like. It can be floated in the air, the load of the entire package 1 can be prevented from being applied to the entire film roll 3, and blocking and deterioration of the films can be prevented. Further, a water vapor barrier film, which is a packaging film, can be fixed to both ends of the protruding portion.

The water vapor barrier film 4 used in the present invention is not particularly limited, but one having a moisture permeability of 10 g / m ² · day or less, preferably 1 g / m ² · day or less as measured according to JIS Z 0208 is used. It is possible. Specific examples include, for example, a single-layer film such as high-density polyethylene, low-density polyethylene, polypropylene, polyester, polyvinylidene chloride-coated polybropyrene, glass-deposited polyester, or a laminated film thereof, or a split cloth, paper, or non-woven fabric. A laminated film with and the like can be mentioned. Examples of the laminated film include a laminated film of glass or aluminum-deposited polyester and polyethylene, a laminated film of polyvinylidene chloride-coated polybropyrene and polyethylene, and the like.

The water vapor barrier film 4 is preferably antistatic treated from the viewpoint of preventing foreign matter from entering, and the antistatic agent may be kneaded into the film or coated on the surface. In the case of kneading, it is preferable to use an antistatic agent of about 0.01 to 5% by weight with respect to the resin, and in the case of surface coating, ^{it is preferable to use an antistatic agent of about 0.01 to 1 g / m 2.}
The antistatic agent is not particularly limited as long as it does not adversely affect the optical performance, and examples thereof include alkyldiethanolamine, polyoxyethylenealkylamine, higher fatty acid alkanolamide, and sorbitan fatty acid ester.

As the water vapor barrier film 4, it is also preferable to use a laminate in which a moisture absorbing film is laminated on the water vapor barrier film in terms of adjusting the humidity of the internal space of the package 1. As such a hygroscopic film, for example, an inorganic or organic desiccant such as calcium chloride, silica gel, zeolite, saccharide, or water-absorbent resin can be molded into synthetic resin, natural cellulose, synthetic cellulose, glass cloth, non-woven fabric, or the like. A thermoplastic resin film such as a polyester film, a polyethylene film, a polypropylene film, a Teflon (registered trademark) film, etc. The one sandwiched between them can be mentioned. When such a laminate is used, it is packaged so that the moisture absorbing film side is inside the package 1.

The feature of the present invention is that the end of the core tube 2 on the axial direction side of the water vapor barrier film 4 is fixed to the outer peripheral portion of the core tube 2 protruding from the film roll 3 with double-sided adhesive tape 6 or wound around the outer peripheral portion. It is fixed to the outer surface of the adhesive tape 7 with a heat seal.

First, a method of fixing with the double-sided adhesive tape 6 will be described (see FIG. 1).
In addition, in FIG. 1, in order to make it easy to understand, the water vapor barrier film 4 is drawn with a space between the film roll 3 and the core tube 2, but in reality, the water vapor barrier film 4 is drawn with the film roll 3 and the film roll 3. The film roll 3 is sealed by the water vapor barrier film 4 by being wound around the outer peripheral portion of the core tube 2 so as to be in close contact with the core tube 2 and fixed.

The double-sided adhesive tape 6 used in the present invention is not particularly limited, and known materials can be used. For example, a resin film such as polyethylene, PET, urethane, or polyester or a non-woven fabric coated on both sides with an adhesive such as acrylic, rubber, silicon, or urethane may be used. The material and thickness of the pressure-sensitive adhesive may be the same on both sides or may be different. It is also possible to use a double-sided adhesive tape that does not use a core material.

The thickness of the double-sided adhesive tape 6 is preferably 0.01 to 2 mm from the viewpoint of low cost, particularly preferably 0.02 to 1.5 mm from the viewpoint of reducing the water transmittance, and 0.03 to 1. from the viewpoint of handleability. 0 mm is more preferable. The width of the double-sided adhesive tape 6 is preferably 1 to 20 cm from the viewpoint of low cost, particularly preferably 3 to 15 cm from the viewpoint of reducing the water transmittance, and further preferably 5 to 10 cm from the viewpoint of handleability.

The adhesive strength of the double-sided adhesive tape 6 is preferably 0.5 to 35 N / 25 mm in that it does not peel off during transportation, and particularly preferably 1 to 30 N / 25 mm in that it can be removed after transportation. In this respect, it is more preferably 2 to 25 N / 25 mm. The adhesive strength of the double-sided adhesive tape 6 may be the same or different on both sides.

The position of the double-sided adhesive tape 6 on the core tube 2 is not particularly limited as long as it is the outer peripheral portion of the core tube 2 protruding from the film roll 3, but it is preferable that the position is closer to the end portion of the core tube 2.

Next, regarding a method of fixing the end portion of the water vapor barrier film 4 on the axial direction side to the outer surface of the adhesive tape 7 wound around the outer peripheral portion of the core tube 2 protruding from the film roll 3 with a heat seal. This will be described (see FIG. 1).

The adhesive tape 7 used in the present invention is not particularly limited, and known adhesive tapes can be used. For example, an adhesive such as acrylic, rubber, silicon, or urethane is applied to one surface (surface A) of a resin film such as polyethylene, PET, urethane, or polyester, and the other surface (surface B) is coated with an adhesive. Examples thereof include those coated with a hot melt type adhesive such as polyester type, ethylene vinyl acetate type, and polypropylene type. When a thermoplastic film such as polyethylene or polyester is laminated on the inner surface of the water vapor barrier film 4, an adhesive is not necessarily required on the surface B, and the thermoplastic film is heated from the outer surface of the water vapor barrier film 4. It can be fused to the outer surface of the adhesive tape 7.

The thickness of the adhesive tape 7 is preferably 0.01 to 3 mm from the viewpoint of low cost, particularly preferably 0.1 to 2.5 mm from the viewpoint of reducing the water transmittance, and 0.3 to 2.0 mm from the viewpoint of handleability. Is more preferable. The width of the adhesive tape 7 is preferably 1 to 20 cm from the viewpoint of low cost, particularly preferably 3 to 15 cm from the viewpoint of reducing the water transmittance, and further preferably 5 to 10 cm from the viewpoint of handleability.

The adhesive strength of the adhesive tape 7 on the surface to be adhered to the core tube 2 is preferably 0.5 to 35 N / 25 mm in terms of not causing peeling during transportation, and 1 to 30 N in terms of ease of removal after transportation. It is particularly preferably / 25 mm, and further preferably 2 to 25 N / 25 mm in terms of handleability. Further, the adhesive strength of the adhesive tape 7 on the surface to be adhered to the water vapor barrier film 4 is preferably 5N / 25mm or more, particularly preferably 10N / 25mm or more, and further preferably 15N in terms of not causing peeling during transportation. / 25 mm or more. The adhesive strength of the adhesive tape 7 may be the same on both sides or may be different.

The position of the adhesive tape 7 on the core tube 2 is not particularly limited as long as it is the outer peripheral portion of the core tube 2 protruding from the film roll 3, but it is preferable that the position is closer to the end portion of the core tube 2.

Further, the film roll 3 may be wrapped with the water vapor barrier film 4 and then further wrapped with a packaging film made of an aluminum material. Such packaging films include an aluminum foil, a laminated film of an aluminum foil and a moisture resistant plastic film (for example, a laminated film of an aluminum foil and a polyolefin film), and a laminated film of an aluminum vapor-deposited film and a moisture-resistant plastic film (for example, an aluminum vapor-deposited film). Polyethylene film laminated film), laminated film of aluminum vapor-deposited film and moisture-resistant plastic film (for example, laminated film of aluminum vapor-deposited polyester film and polyethylene film) and the like.
In particular, a laminated film of an aluminum foil and a polyolefin film (for example, a laminated film of an aluminum foil and a polyethylene film) and an aluminum vapor-deposited film and a polyolefin film laminated film (for example, a laminated film of an aluminum vapor-deposited polyester film and a polyethylene film) are particularly useful in the present invention. In particular, a laminated film having a structure of stretched polypropylene film / polyethylene film / aluminum foil / polyethylene film, a laminated film having a structure of stretched polypropylene film / low density polyethylene film / aluminum foil, and the like are useful.

The humidity of the internal space (internal space in which the film roll 3 is located) of the package 1 of the present invention thus obtained is preferably 20 to 80% RH. It is particularly preferably 30 to 70% RH, and particularly preferably 35 to 65% RH. If the humidity is too low or too high, the polyvinyl alcohol-based film on the surface of the film roll 3 tends to dry / absorb moisture and deform, and if the humidity is too low or too high and fluctuates multiple times, the polyvinyl alcohol The appearance and optical performance of the system film tend to deteriorate. Specifically, white haze occurs and optical unevenness increases.

As a method for adjusting the humidity of the internal space of the package 1 to the above range, a method of packaging a dry sheet in which a desiccant such as silica gel, calcium chloride, and zeolite is sandwiched between a thermoplastic film or paper together with a film roll 3 is used. Can be mentioned. The hygroscopicity of the dried sheet is preferably 30% by weight or more, particularly preferably 50% by weight or more, still more preferably 70% by weight, based on its own weight (weight in a dry state) at 30 ° C. and 90% RH. % Or more.

The humidity of the internal space of the package 1 can be measured by providing an opening in the water vapor barrier film 4 with a hygrometer, but in the present invention, the humidity history during transportation can be easily confirmed. It is preferable to use an electronically recordable card type or seal type humidity indicator.

Examples of such an electronically recordable card type humidity indicator include "Ondotori" manufactured by T & D Corporation, "WATCH LOGGER" manufactured by Fujita Electric Works, and "midi LOGGER" manufactured by Graphtec.

In addition, examples of the seal-type humidity indicator include those using a compound such as cobalt bromide, which develops an irreversible color when exposed to high humidity or low humidity for a predetermined time.
For example, a plurality of labels having a diameter of about 5 mm are lined up on the film surface, and these labels are 50% RH detection label, 60% RH detection label, 70% RH detection label, 80% RH detection label, and 90% RH detection label. The label corresponding to the reached humidity confirms the maximum reached humidity by changing the color from blue to pink, changing from white to blue, or bleeding blue. Humidity indicators from 5% RH on the low humidity side to 90% RH on the high humidity side are commercially available. The measurement accuracy is about ± 5% RH.

In the present invention, the humidity indicator can be packaged together with the film roll 3, and specifically, the humidity indicator can be attached and packaged inside the outermost layer of the film roll 3 or the water vapor barrier film 4.

Further, the package 1 of the present invention can be entirely packed with a heat insulating material and stored and / or transported. As a matter of course, the humidity of the internal space of the package 1 depends on the temperature. In recent years, the temperature during storage and / or transportation has been controlled from the viewpoint of quality assurance, but the actual condition often fluctuates in the range of 0 to 80 ° C. In order to adjust the humidity of the internal space of the package 1 to the above range, it is also important to control the temperature of the package 1. The heat insulating material used in the present invention is not particularly limited, but an aluminum-deposited sheet is preferable in terms of heat insulating properties, and aluminum-deposited felt is particularly preferable in terms of impact resistance. It is preferable to recycle the heat insulating material.

Hereinafter, the polyvinyl alcohol-based film used in the present invention will be described.
The polyvinyl alcohol-based film of the present invention is obtained by pouring an aqueous solution of a polyvinyl alcohol-based resin into a cast mold to form a film, and continuously drying the film using a metal heating roll.

As the polyvinyl alcohol-based resin, an unmodified polyvinyl alcohol-based resin, that is, a resin produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate is usually used. If necessary, use a resin obtained by saponifying a copolymer of vinyl acetate and a small amount (usually 10 mol% or less, preferably 5 mol% or less) of a component copolymerizable with the vinyl acetate. You can also. Examples of the component copolymerizable with vinyl acetate include unsaturated carboxylic acids (including, for example, salts, esters, amides, nitriles, etc.) and olefins having 2 to 30 carbon atoms (for example, ethylene, propylene, n-butene). , Isobutene, etc.), vinyl ethers, unsaturated sulfonates, etc. Further, a modified polyvinyl alcohol-based resin obtained by chemically modifying the hydroxyl group after saponification can also be used.

Further, as the polyvinyl alcohol-based resin, a polyvinyl alcohol-based resin having a 1,2-diol structure in the side chain can also be used. The polyvinyl alcohol-based resin having a 1,2-diol structure in such a side chain is, for example, (i) a method for saponifying a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene, (ii) acetic acid. Methods for saponifying and decarbonizing a copolymer of vinyl and vinyl ethylene carbonate, (iii) saponifying and decarbonating a copolymer of vinyl acetate and 2,2-dialkyl-4-vinyl-1,3-dioxolane. It can be obtained by a method of ketalization, (iv) a method of saponifying a copolymer of vinyl acetate and glycerin monoallyl ether, and the like.

The weight average molecular weight of the polyvinyl alcohol-based resin is preferably 100,000 to 300,000, particularly preferably 110,000 to 280,000, and even more preferably 120,000 to 260,000.
If the weight average molecular weight is too small, it tends to be difficult to obtain sufficient optical performance when producing an optical film from a polyvinyl alcohol-based resin, and if it is too large, the polyvinyl alcohol-based film is stretched to form a polarizing film. In some cases, stretching becomes difficult and industrial production tends to be difficult.
The weight average molecular weight of the polyvinyl alcohol-based resin is the weight average molecular weight measured by the GPC-MALS method.

The average degree of saponification of the polyvinyl alcohol-based resin used in the present invention is preferably 98 mol% or more, particularly preferably 99 mol% or more, still more preferably 99.5 mol% or more, and particularly preferably 99.8. More than mol%. If the average saponification degree is too small, sufficient optical performance tends not to be obtained when forming a polarizing film from a polyvinyl alcohol-based film.
Here, the average saponification degree in the present invention is measured according to JIS K 6726.

As the polyvinyl alcohol-based resin used in the present invention, two or more kinds having different modified species, modified amounts, weight average molecular weight, average saponification degree and the like may be used in combination.

Using such a polyvinyl alcohol-based resin, an aqueous solution of a polyvinyl alcohol-based resin is produced. It is preferable that the polyvinyl alcohol-based resin is washed with water and dehydrated using a centrifuge or the like to obtain a polyvinyl alcohol-based resin wet cake having a water content of 50% by weight or less. If the water content of the wet cake is too large, it tends to be difficult to adjust the concentration to the desired aqueous solution.
The polyvinyl alcohol-based resin wet cake is dissolved in warm water or hot water to prepare a polyvinyl alcohol-based resin aqueous solution.

The method for preparing the polyvinyl alcohol-based resin aqueous solution is not particularly limited, and for example, it may be prepared using a heated multi-screw extruder, and the melting can provided with the vertical circulation flow generation type stirring blade is described above. It is also possible to add the polyvinyl alcohol-based resin wet cake and dissolve it by blowing steam into the can to prepare an aqueous solution having a desired concentration.

In addition to polyvinyl alcohol-based resins, polyvinyl alcohol-based resin aqueous solutions include commonly used plasticizers such as glycerin, diglycerin, triglycerin, ethylene glycol, triethylene glycol, polyethylene glycol, and trimethylolpropane, and nonionic properties. It is preferable to contain at least one of the anionic and cationic surfactants in terms of film-forming property of the polyvinyl alcohol-based film.

The resin concentration of the polyvinyl alcohol-based resin aqueous solution thus obtained is preferably 15 to 60% by weight, particularly preferably 17 to 55% by weight, and even more preferably 20 to 50% by weight.
If the resin concentration of the aqueous solution is too low, the drying load becomes large and the production capacity tends to be inferior. If the resin concentration is too high, the viscosity becomes too high and uniform dissolution tends to be difficult.

For the polyvinyl alcohol-based film of the present invention, a polyvinyl alcohol-based resin aqueous solution is prepared using the polyvinyl alcohol-based resin, and the aqueous solution is discharged and cast into a casting mold to form a film by a casting method. It can be continuously produced by drying, and can be produced, for example, by the following steps (A) to (D).
(A) A step of forming a film by a casting method (B) A step of heating and drying the formed film (C) A step of slitting the dried film and then winding it into a roll to obtain a film roll (A) D) The process of packaging the film roll with a steam barrier film (and further packaging film if necessary) to form a package.

Here, examples of the cast type include cast drums (drum type rolls), endless belts, and the like, but cast drums are preferable because they are excellent in width, length, and film thickness uniformity. Hereinafter, the case where the cast type is a cast drum will be described.
Hereinafter, the above steps (A) to (D) will be sequentially described.

[Step (A)]
In the step (A), first, the polyvinyl alcohol-based resin aqueous solution is usually defoamed.
Examples of the defoaming method include static defoaming and defoaming with a multi-screw extruder having a vent. As the multi-screw extruder having a vent, a twin-screw extruder having a vent is usually used.

After the defoaming treatment, the polyvinyl alcohol-based resin aqueous solution is introduced into the T-shaped slit die in a fixed amount and cast into a cast mold to form a film.

The temperature of the polyvinyl alcohol-based resin aqueous solution at the outlet of the T-shaped slit die is preferably 80 to 100 ° C, particularly preferably 85 to 98 ° C.
If the temperature of the polyvinyl alcohol-based resin aqueous solution is too low, it tends to cause poor flow, and if it is too high, it tends to foam.

The viscosity of the polyvinyl alcohol-based resin aqueous solution is preferably 50 to 200 Pa · s at the time of ejection, and particularly preferably 70 to 150 Pa · s.
If the viscosity of the aqueous solution is too low, it tends to cause poor flow, and if it is too high, it tends to be difficult to spill.

The discharge rate of the polyvinyl alcohol-based resin aqueous solution discharged from the T-type slit die to the cast drum is preferably 0.1 to 5 m / min, particularly preferably 0.2 to 4 m / min, and even more preferably 0. It is 3 to 3 m / min.
If the discharge rate is too low, the productivity tends to decrease, and if it is too high, the salivation tends to be difficult.

The diameter of such a cast drum is preferably 2 to 5 m, particularly preferably 2.4 to 4.5 m, and even more preferably 2.8 to 4 mm.
If the diameter is too small, the drying length is insufficient and the feed rate of the film formed on the drum tends to be low, and if it is too large, the transportability tends to decrease.

The width of the cast drum is preferably 4 m or more, particularly preferably 4.5 m or more, still more preferably 5 m or more, and particularly preferably 5 to 7 m.
If the width of the cast drum is too small, productivity tends to decrease.

The rotation speed of the cast drum is preferably 3 to 50 m / min, particularly preferably 4 to 40 m / min, and even more preferably 5 to 35 m / min.

The surface temperature of the cast drum is preferably 40 to 99 ° C, particularly preferably 60 to 95 ° C.
If the surface temperature is too low, it tends to be poorly dried, and if it is too high, it tends to foam.

[Step (B)]
Next, the step (B) will be described.
The step (B) is a step of heating and drying the produced polyvinyl alcohol-based film.

Drying of the film formed by the cast drum is usually performed by alternately contacting the front surface and the back surface of the film with a plurality of metal heating rolls. The surface temperature of the metal heating roll is usually 40 to 150 ° C, preferably 50 to 140 ° C. If the surface temperature is too low, it tends to be poorly dried, and if it is too high, it will be too dry, which tends to cause poor appearance such as swelling.
The metal heating roll is, for example, a roll having a surface surface of which is hard chrome plated or mirror-treated and has a diameter of 0.2 to 2 m, and is usually dried using 2 to 30 rolls, preferably 10 to 25 rolls. Can be done.

In the present invention, it is preferable to heat-treat the film after drying with a metal heating roll. The heat treatment temperature is preferably 60 to 150 ° C, particularly preferably 70 to 140 ° C. If the heat treatment temperature is too low, the water resistance of the polyvinyl alcohol-based film tends to be insufficient or a phase difference shake tends to occur, and if it is too high, the stretchability during the production of the polarizing film tends to decrease. Examples of such a heat treatment method include a method of using a floating dryer, a method of cooling to about room temperature after drying and then contacting the film with a high-temperature metal heating roll again, and a method of irradiating both sides of the film with near infrared rays using an infrared lamp. Techniques and the like can be mentioned.

In the above description, a method of preparing a polyvinyl alcohol-based resin aqueous solution, casting the aqueous solution in a cast mold, forming a film by a casting method, and drying the film to produce a polyvinyl alcohol-based film has been described. It is also possible to cast the solution on a resin film or a metal belt, form a film, and dry it to produce a polyvinyl alcohol-based film.

[Step (C)]
The film that has been dried in the step (B) and further heat-treated as necessary becomes a product (polyvinyl alcohol-based film of the present invention) through the step (C). The step (C) is dried. This is a process in which both ends of the film are cut off with slits, and then the film is wound around a core tube (hereinafter, also referred to as a roll) having a shaft length longer than the film width, and the strip-shaped polyvinyl alcohol-based film is wound into a roll.

By the method described above, a film roll in which a polyvinyl alcohol-based film is wound around a roll is manufactured.
The length of the polyvinyl alcohol-based film is preferably 4 km or more from the viewpoint of increasing the area, particularly preferably 4.5 km or more from the viewpoint of further increasing the area, and further preferably 5 to 50 km from the viewpoint of transport weight. Is.

The thickness of the polyvinyl alcohol-based film of the present invention is preferably 60 μm or less from the viewpoint of thinning the polarizing film, and particularly preferably 50 μm or less from the viewpoint of further thinning, from the viewpoint of avoiding breakage. More preferably, it is 5 to 40 μm.

Such a polyvinyl alcohol-based film is preferably used as a polyvinyl alcohol-based film for optics, and further preferably used as a raw fabric for a polarizing film.

[Step (D)]
The obtained film roll becomes a package through the step (D).
As described above, the step (D) is a step of packaging the film roll with a water vapor barrier film and, if necessary, further packaging it with a packaging film to form a package. After storage, the obtained package is transported to the shipping destination and used, for example, for manufacturing a polarizing film.

[Storage and / or transportation]
The package in which the film roll is packaged is supported by providing brackets (support plates) on the protrusions at both ends of the core tube or placing the protrusions at both ends on a pedestal, so-called air without touching the ground. It is stored and transported while floating on the surface. Brackets are usually used when the width of the film is relatively small, and mounts are usually used when the width of the film is relatively large.

In the case of wide film rolls, a gantry is usually used. The gantry is formed by connecting a pair of support pedestals on both sides with a connecting plate. The support base is formed by horizontally hanging a frame portion between the columns at both ends of the base base, and the protruding portion of the core tube is placed on the frame portion of the support base.

When storing and / or transporting the packaged film roll, it is desirable to avoid extremely high and low temperature, low humidity and high humidity conditions, specifically, the temperature is 10 to 30 ° C. and the humidity is 40 to 75% RH. Is good.
However, the package of the present invention is characterized in that even if it is exposed to a harsh atmosphere deviating from such conditions for a long time, there is no concern about unwinding of the film roll and a remarkable effect is exhibited.

Hereinafter, a method for producing a polarizing film obtained by using the polyvinyl alcohol-based film of the present invention will be described.

The polarizing film of the present invention is produced by unwinding the polyvinyl alcohol-based film from a roll, transferring it in the horizontal direction, and performing steps such as swelling, dyeing, boric acid crosslinking, stretching, washing, and drying.

The swelling step is performed before the dyeing step. In addition to being able to clean the dirt on the surface of the polyvinyl alcohol-based film by the swelling step, there is also an effect of preventing uneven dyeing by swelling the polyvinyl alcohol-based film. In the swelling step, water is usually used as the treatment liquid. If the main component of the treatment liquid is water, the treatment liquid may contain a small amount of an iodide compound, additives such as a surfactant, alcohol and the like. The temperature of the swelling bath is usually about 10 to 45 ° C., and the immersion time in the swelling bath is usually about 0.1 to 10 minutes.

The dyeing step is performed by contacting the film with a liquid containing iodine or a dichroic dye. Usually, an aqueous solution of iodine-potassium iodide is used, and an iodine concentration of 0.1 to 2 g / L and a potassium iodide concentration of 1 to 100 g / L are suitable. It is practical that the dyeing time is about 30 to 500 seconds. The temperature of the treatment bath is preferably 5 to 50 ° C. The aqueous solution may contain a small amount of an organic solvent compatible with water in addition to the water solvent.

The boric acid cross-linking step is carried out using a boron compound such as boric acid or borax. The boron compound is used in the form of an aqueous solution or a water-organic solvent mixture at a concentration of about 10 to 100 g / L, and it is preferable that potassium iodide coexists in the solution from the viewpoint of stabilizing the polarization performance. The temperature at the time of treatment is preferably about 30 to 70 ° C., the treatment time is preferably about 0.1 to 20 minutes, and if necessary, a stretching operation may be performed during the treatment.

In the stretching step, stretching is performed 3 to 10 times, preferably 3.5 to 6 times in the uniaxial direction. At this time, some stretching (stretching to the extent of preventing shrinkage in the width direction or more) may be performed in the direction perpendicular to the stretching direction. The temperature at the time of stretching is preferably 30 to 170 ° C. Further, the stretching ratio may be finally set in the above range, and the stretching operation can be performed not only in one step but also in any range of the manufacturing process.

The washing step is performed by immersing the polyvinyl alcohol-based film in, for example, an aqueous solution of iodide such as water or potassium iodide, and this step can remove precipitates generated on the surface of the film. When an aqueous potassium iodide solution is used, the potassium iodide concentration is preferably about 1 to 80 g / L. The temperature during the cleaning treatment is usually 5 to 50 ° C, preferably 10 to 45 ° C. The processing time is usually 1 to 300 seconds, preferably 10 to 240 seconds. In addition, washing with water and washing with an aqueous solution of potassium iodide may be performed in an appropriate combination.

The drying step may be carried out in the air at 40 to 80 ° C. for 1 to 10 minutes.

The degree of polarization of the polarizing film is preferably 99.8% or more, and particularly preferably 99.9% or more. If the degree of polarization is too low, it tends to be impossible to secure the contrast in the liquid crystal display.
_{The degree of polarization is generally the light transmittance (H 11} ) measured at the wavelength λ and the two polarizations in a state where two polarizing films are superposed so that their orientation directions are in the same direction. It is calculated according to the following equation from _{the light transmittance (H 1} ) measured at the wavelength λ in a state where the films are superposed so that the orientation directions are orthogonal to each other.
[(H ₁₁ −H ₁ ) / (H ₁₁ + H ₁ )] ^1/2

Further, the simple substance transmittance of the polarizing film of the present invention is preferably 42% or more, particularly preferably 43% or more. If the single transmittance is too low, it tends to be impossible to achieve high brightness of the liquid crystal display.
The simple substance transmittance is a value obtained by measuring the light transmittance of a single polarizing film using a spectrophotometer.

The polarizing film thus obtained is formed into a polarizing plate by adhering an optically isotropic resin film as a protective film on one or both sides thereof via an adhesive. Examples of the protective film include films such as cellulose triacetate, cellulose diacetate, polycarbonate, polymethylmethacrylate, cycloolefin polymer, cycloolefin copolymer, polystyrene, polyether sulfone, polyarylene ester, poly-4-methylpentene, and polyphenylene oxide. Or a sheet.

The bonding is performed by a known method. For example, a liquid adhesive composition is uniformly applied to a polarizing film, a protective film, or both, and then the two are bonded and pressure-bonded to heat or activate energy. It is done by irradiating a line.

Further, for the purpose of thinning the polarizing film, a curable resin such as a urethane resin, an acrylic resin, or a urea resin is applied to one or both sides of the protective film instead of the protective film, and the film is cured to form a polarizing plate. You can also do it.

The polarizing film obtained by the present invention has no defects and is excellent in in-plane uniformity of polarization performance, and has excellent in-plane uniformity of polarization performance, such as personal digital assistants, personal computers, televisions, projectors, signage, electronic desk computers, electronic clocks, word processors, automobiles and machines. Liquid crystal displays such as instruments, sunglasses, anti-glare glasses, three-dimensional glasses, wearable displays, antireflection layers for display elements (CRT, LCD, organic EL, electronic paper, etc.), optical communication equipment, medical equipment, building materials , Preferred for toys and the like.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

<Measurement conditions>
(1) Optical unevenness of polyvinyl alcohol film A test piece of a polyvinyl alcohol film having a length of 30 cm and a width of 30 cm was cut out, and two polarizing plates in a cross Nicol state (single transmittance 43.5%, degree of polarization 99. Optical unevenness was observed in the transmission mode using a light box having a surface illuminance of 14,000 lpx in a dark room and sandwiched between 9%) at an angle of 45 °, and evaluated according to the following criteria.
○ ・ ・ ・ No shading can be seen in the plane.
× ・ ・ ・ The shade can be confirmed on the entire surface.

(2) Polarization degree (%) of polarizing film, simple substance transmittance (%)
An automatic polarizing film measuring device that cuts out a total of 9 points, 3 points in the length direction and 3 points each in the width direction, centering on the central part of the obtained polarizing film in the length direction. (Nippon Kogaku Co., Ltd .: VAP-7070) was used to measure the degree of polarization and the single transmittance, and the average values of the respective values were taken as the degree of polarization and the single transmittance of the polarizing film.

(3) Color unevenness of polarizing film A test piece having a length of 30 cm and a width of 13 cm was cut out from the obtained polarizing film, and two polarizing plates in a cross Nicol state (single transmittance 43.5%, degree of polarization 99.9) were cut out. %), And the color unevenness was observed in the transmission mode using a light box with a surface illuminance of 14,000 lpx in a dark room, and evaluated according to the following criteria.
○ ・ ・ ・ No color unevenness △ ・ ・ ・ Slight color unevenness × ・ ・ ・ Color unevenness

<Example 1>
(Manufacturing of film rolls)
Add 1,000 kg of polyvinyl alcohol-based resin having a weight average molecular weight of 142,000 and a saponification degree of 99.8 mol%, 2,500 kg of water, and 100 kg of glycerin as a plasticizer, and raise the temperature to 140 ° C. with stirring to concentrate the resin. The concentration was adjusted to 25% by weight to obtain a uniformly dissolved polyvinyl alcohol-based resin aqueous solution.
Next, the polyvinyl alcohol-based resin aqueous solution is supplied to a twin-screw extruder to defoam, then the aqueous solution temperature is set to 95 ° C., and the aqueous solution is discharged and flowed from a T-shaped slit die discharge port to a cast drum having a surface temperature of 90 ° C. The film was stretched and formed.
Next, the obtained film was dried with a plurality of metal heating rolls, heat-treated at 120 ° C. for 3 minutes using a floating dryer, and cut off with a slit to a width of 4 m. Finally, a strip-shaped polyvinyl alcohol-based film having a water content of 4% by weight (width 4 m, length 5 km, thickness 40 μm) is wound around an aluminum core tube having an outer diameter of 17 cm, an inner diameter of 16 cm, and a length of 4.4 m. Obtained a film roll (A) wound around a core tube. A test piece of a polyvinyl alcohol-based film was cut out from the tip of the obtained film roll (A), and optical unevenness was observed. The results are shown in Table 1.

(Manufacturing of packaging)
As a water vapor barrier film, a laminated film of an aluminum-deposited polyester film (polyethylene terephthalate film in which 50 nm of aluminum was vapor-deposited, 12 μm thickness) and a polyethylene film (25 μm thickness) was prepared, and a humidity indicator was attached to the polyethylene side which is the inner surface. The detection labels for the humidity indicator are 5% RH, 10% RH, 20% RH, 30% RH, 40% RH, 50% RH, 60% RH, 70% RH, 80% RH, 90% RH.
Then, in an environment of 23 ° C. and 50% RH, the water vapor barrier film was double-wound on the obtained film roll (A) with the polyethylene film inside. A core tube protruding portion (both ends) protruding from the film roll (A) using double-sided adhesive tape (strong double-sided tape for clean room MK-CDT manufactured by Tanimura Co., Ltd.) on the axial side end of the core tube in the steam barrier film. A package (B) was obtained by fixing to the outer peripheral portion near the end of each 20 cm). The specifications of the double-sided adhesive tape are as follows.
Thickness 0.12 mm, width 30 mm, adhesive strength 19 N / 25 mm (against aluminum plate)

(storage)
The protrusion of the core tube from the film roll was placed on a pedestal, and the obtained package (B) was floated in the air without being grounded. It was stored at 10% RH for 7 days, followed by storage at 25 ° C. and 50% RH for 7 days. When the package (B) after storage was unpacked and the humidity history of the internal space of the package (B) was confirmed by the humidity indicator, the minimum humidity was 30% RH and the maximum humidity was 70% RH. No unwinding occurred in the film roll (A) after storage. Further, when the optical unevenness of the film at the tip of the film roll (A) (the portion 20 m from the end of the film) was measured, no difference from that before storage could be confirmed.

(Manufacturing of polarizing film)
A test piece of a polyvinyl alcohol-based film having a width (TD direction) of 30 cm and a length (MD direction) of 30 cm was cut out from the tip of the film roll (A) after storage (a portion 20 m from the film end), and the water temperature was 25 ° C. It was immersed in a water tank and stretched 1.7 times. Next, it was immersed in an aqueous solution at 28 ° C. consisting of 0.5 g / L of iodine and 30 g / L of potassium iodide, stretched 1.6 times while dyeing, and continuously boric acid 40 g / L and iodide. It was immersed in an aqueous solution (55 ° C.) having a composition of potassium 30 g / L and uniaxially stretched 2.1 times for boric acid treatment. Then, it was washed with an aqueous solution of potassium iodide and dried to obtain a polarizing film having a total draw ratio of 5.8 times. Table 2 shows the polarization characteristics of the obtained polarizing film.

<Example 2>
(Manufacturing of packaging)
A package was manufactured using the film roll (A) obtained in the same manner as in Example 1.
As a water vapor barrier film, a laminated film of an aluminum-deposited polyester film (polyethylene terephthalate film in which 50 nm of aluminum was vapor-deposited, 12 μm thickness) and a polyethylene film (25 μm thickness) was prepared, and a humidity indicator was attached to the polyethylene side which is the inner surface. The detection labels for the humidity indicator are 5% RH, 10% RH, 20% RH, 30% RH, 40% RH, 50% RH, 60% RH, 70% RH, 80% RH, 90% RH.
Next, an adhesive tape having an acrylic pressure-sensitive adhesive laminated on one surface (surface A) of the PET substrate and a vinyl acetate-based hot melt adhesive laminated on the other surface (surface B) is applied to the surface A side as a film. It was attached to the outer peripheral portion near the end of the core tube protruding portion (20 cm at both ends) protruding from the roll (A).
Finally, the water vapor barrier film was double-wound on the obtained film roll (A) in an environment of 23 ° C. and 50% RH with the polyethylene film inside. The axial side end of the core tube of the water vapor barrier film (polyethylene film surface) was heat-sealed on the outer surface of the adhesive tape at 110 ° C. to obtain a package (B).

(Storage and manufacture of polarizing film)
Storage and production of the polarizing film were carried out in the same manner as in Example 1. The results are shown in Tables 1 and 2.

<Comparative Example 1>
The same as in Example 1 except that the axial side end of the core tube of the steam barrier film was fixed to the outer peripheral portion of the core tube projecting portion near the end without using the adhesive tape. , The packaging was manufactured, stored, and the polarizing film was manufactured. The results are shown in Tables 1 and 2.

As is clear from the comparison between Examples 1 and 2 and Comparative Example 1, the polyvinyl alcohol-based film stored in the package of the present invention has a low maximum humidity during storage, and has a maximum humidity and a minimum humidity during storage. Since the difference between the two is small, deformation during storage is unlikely to occur, and even after storage, the optical unevenness is small as in the initial stage.
Further, since the polarizing film manufactured from the package of the present invention is prevented from deforming or deteriorating the optical performance of the polyvinyl alcohol-based film used for manufacturing, the degree of polarization and the single transmittance are high, and color unevenness occurs. Hateful.

The polarizing film manufactured from the package of the present invention has excellent polarization performance, and is used for portable information terminals, personal computers, televisions, projectors, signage, electronic desk calculators, electronic clocks, word processors, electronic paper, game machines, videos, and so on. For cameras, photo albums, thermometers, audio, liquid crystal displays such as automobile and mechanical instruments, sunglasses, anti-glare glasses, stereoscopic glasses, wearable displays, display elements (CRT, LCD, organic EL, electronic paper, etc.) It is preferably used for antireflection layers, optical communication devices, medical devices, building materials, toys and the like.

1: Package 2: Core tube 3: Film roll 4: Steam barrier film 5: Adhesive tape 6: Double-sided adhesive tape 7: Adhesive tape

Claims (6)

A package obtained by wrapping a film roll in which a strip-shaped polyvinyl alcohol-based film is wound around a core tube having a shaft length longer than the film width with a steam barrier film having a polyethylene film.
An adhesive tape having an axial end of the core tube of the polyethylene film of the water vapor barrier film attached to the outer peripheral portion of the core tube protruding from the film roll and having a vinyl acetate-based hot melt adhesive layer. A package characterized by being fixed to the surface of the vinyl acetate-based hot melt adhesive layer by a heat seal. The package according to claim 1, wherein a dry sheet is packaged together with the film roll. The package according to claim 1 or 2, wherein a humidity indicator is packaged together with the film roll. The package according to any one of claims 1 to 3, wherein the polyvinyl alcohol-based film has a width of 4 m or more and a length of 4 km or more. The package according to any one of claims 1 to 4, wherein the polyvinyl alcohol-based film has a thickness of 5 to 40 μm. A method for storing or transporting a polyvinyl alcohol-based film, which comprises storing and / or transporting the polyvinyl alcohol-based film using the package according to any one of claims 1 to 5.

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