KR100998147B1 - Method for producing a polyvinyl alcohol film roll and polarizing film obtained therefrom - Google Patents

Abstract

The present invention is directed to a polyvinyl alcohol film roll comprising a cylindrical core tube made of a metallic material, having a surface roughness of up to 100 S, and having a polyvinyl alcohol film wound around the cylindrical core tube. The film roll is obtained by forming a film from a polyvinyl alcohol resin solution and winding the film around the core tube and the film roll can provide an optically uniform polyvinyl alcohol film having a good appearance. Can be.

Polyvinyl alcohol, film, roll, polarizing film, core tube

Description

Method of preparing a polyvinyl alcohol film roll and a polarizing film obtained therefrom {Method of preparing roll of polyvinyl alcohol film and polarizing film prepared therefrom}

The present invention relates to a roll of polyvinyl alcohol film capable of winding a very long polyvinyl alcohol film and to the wound film having a good appearance and to a polarizing film having excellent polarization properties made from the film roll.

Polyvinyl alcohol films are generally prepared by dissolving a polyvinyl alcohol resin in a solvent, removing air from the solution, forming a film through a solution casting method, and drying the film using a metal heating roll and its derivatives. It was prepared through the step of. The film undergoing the drying step described above is dried through a dryer such that the moisture contained in the film is evaporated so that a limited amount of moisture is provided again in a humidity controller, wound around a cylindrical core tube, and supplied to the market as a roll film. Thus, the rolled polyvinyl alcohol film has been used in many applications as a film having excellent form stability. One useful application is optical films, more specifically polarizing films.

However, when the polyvinyl alcohol film is wound around the cylindrical core, problems such as appearance of the film, for example, generation of wrinkles and folds, are caused. Therefore, careful process step treatment is required. If the above problem occurs, another problem occurs in the process. For example, when a polarizing film is manufactured from the film which the above-mentioned problem generate | occur | produced once, a polarization characteristic falls.

It is therefore an object of the present invention to provide a polyvinyl alcohol film roll which has an excellent appearance and therefore optical uniformity of industrial benefit and which does not normally require the demanding rigorous process treatment.

It is another object of the present invention to provide a roll of elongated polyvinyl alcohol film that can yield a polyvinyl alcohol film with excellent appearance and optical uniformity when unwound.

Still another object of the present invention is to provide a polarizing film having excellent polarization.

In order to prevent similar problems in the formation of wrinkles in the polyvinyl alcohol film and winding the film around the cylindrical core and to obtain a polyvinyl alcohol film having a good appearance, studies were carried out on the winding step, the cylindrical core used, and the like. . Therefore, if the cylindrical core tube for winding the film is made of metal material and its surface roughness is adjusted to 100S at maximum, the phenomenon such as the bending of the cylindrical core tube which may occur during winding is suppressed and the film is wrinkled or the like. It can be wound appropriately around the cylindrical core tube without production, resulting in a polyvinyl alcohol film roll with good appearance.                         

According to the present invention, there is provided a roll of polyvinyl alcohol film obtained by forming a film from a polyvinyl alcohol resin solution and then winding the polyvinyl alcohol film around a cylindrical core tube, wherein the cylindrical core tube is made of a metallic material. Surface roughness is up to 100S.

The present invention also provides a polarizing film made of a polyvinyl alcohol film released from the film roll of the present invention described above.

Hereinafter, the present invention will be described in more detail.

In the present invention, the material used for forming the film is a polyvinyl alcohol resin, and the film roll is made of a polyvinyl alcohol resin solution.

The polyvinyl alcohol resin is generally prepared through polymerizing vinyl acetate and hydrolyzing polyvinyl acetate. The polyvinyl alcohol resin used in the present invention is not limited only to the hydrolysis products of polyvinyl acetate, and other components copolymerizable with a small amount of, for example, 0-15 mol%, preferably 0-5 mol%, of vinyl acetate. Having 2 to 30 carbon atoms such as, for example, unsaturated carboxylic acids (including salts, esters, amides and nitriles thereof), ethylene, propylene, n-butene or isobutene, vinyl ethers, unsaturated sulfonic acid salts and derivatives thereof It may contain an olefin. The polyvinyl alcohol resin may contain silyl groups. The silyl group-containing resin can be prepared according to conventional methods, for example, using a silylating agent followed by modification or copolymerization of vinyl acetate and an olefinically unsaturated monomer containing silyl groups followed by hydrolysis. Silyl group-containing olefinically unsaturated monomers are, for example, vinylsilanes, (meth) acrylamide alkylsilanes and derivatives thereof.

The degree of polymerization of the polyvinyl alcohol resin is not particularly limited, but is preferably 1,000 to 7,000, more preferably 1,200 to 6,000, still more preferably 1,400 to 5,000. When the degree of polymerization is less than 1,000 and the polyvinyl alcohol resin is used for the production of a polarizing film, sufficient polarization cannot be obtained, and when the degree of polymerization exceeds 7,000, since the stretching of the film is difficult, industrial production of the polarizing film is difficult. Becomes difficult.

The degree of hydrolysis of the polyvinyl alcohol resin is preferably 80 mol% or more, more preferably 85 to 100 mol%, even more preferably 98 to 100 mol%. If the degree of hydrolysis is less than 80 mol%, it is difficult to obtain sufficient polarization when the polyvinyl alcohol resin is used for producing a polarizing film.

If necessary, glycerol, diglycerol, triglycerol, ethylene glycol, triethylene glycol or polyethylene in a content of up to 30% by weight, preferably up to 25% by weight, more preferably up to 20% by weight, based on the polyvinyl alcohol resin Commonly used plasticizers such as glycols may be mixed into the polyvinyl alcohol resin. When the content of the plasticizer exceeds 30% by weight, the strength of the film tends to be lowered.

Preferably, the polyvinyl alcohol resin is based on a non-ionic, anionic or cationic surface active agent, more specifically at most 5% by weight, preferably 0.001 to 3% by weight, more preferably 0.001 to 3% based on the polyvinyl alcohol resin. In an amount of 2% by weight, it is mixed with a surfactant having a releasing activity such as polyoxy ethylene alkylamine. When the content of the surfactant exceeds 5% by weight, the appearance of the film surface tends to be lowered.

In the present invention, the polyvinyl alcohol resin film is produced using the polyvinyl alcohol resin as described above.

The manufacturing process of a polyvinyl alcohol film roll is as follows.

The polyvinyl alcohol resin is dissolved in a solvent and the final polyvinyl alcohol resin solution is formed into a film to provide a raw film web.

Examples of the solvent for preparing the polyvinyl alcohol resin solution include, for example, water, dimethyl sulfoxide (DMSO), an organic solvent of N-methylpyrrolidine, glycerol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetra Polyhydric alcohols such as ethylene glycol or trimethylolpropane, amine compounds such as ethylenediamine or diethylenetriamine and mixtures thereof.

The organic solvents described above may contain small amounts, for example 5-30% by weight of water.

The concentration of the polyvinyl alcohol resin in the polyvinyl alcohol resin solution is preferably 5 to 70% by weight in practical terms.

Film formation from polyvinyl alcohol resin solution may be carried out through conventional methods such as casting and extrusion. The film forming method is a wetting method or a roller or belt conveyor that releases the solution through air or into an inert atmosphere such as nitrogen, helium or argon through a slit and into a coagulation bath to form a non-extending film. It is a drying method in which a solution is released through a slit on a support to form a film and dried to provide a non-extended film.

Thus, the formed non-extended film can be further subjected to drying treatment, heat treatment and humidity control treatment if necessary.

The polyvinyl alcohol film is then rolled around a cylindrical core tube and provided as a film roll on the market.

The winding of the polyvinyl alcohol film around the cylindrical core tube is carried out by temporarily fixing the top of the film with a tape on the surface of the core tube and rotating it at a predetermined rotational speed.

In the present invention, the cylindrical core tube for winding the film is made of a metallic material. More specifically, aluminum is preferred in view of strength, weight preservation, ease of processing such as forming a preferred form, and preventing film mixing of foreign matter.

The cylindrical core tube requires a surface roughness of up to 100 S, preferably up to 20 S, more preferably up to 10 S. When the surface roughness exceeds 100S, weaving occurs in the winding of the film. In the present invention, the surface roughness is represented by an arithmetic mean value (Ra: centerline average height of surface roughness) as defined in JIS B 0601-1994.

The cylindrical core tube has a cylindricality of 0.01 to 1 mm and a roundness of 1 to 1 mm, preferably of 0.01 to 0.2 mm and a roundness of 0.2 to 0.2 mm, more preferably of 0.01 to 0.1 mm and It has a roundness of 0.01 to a cylinder degree of 0.1 mm. When the roundness exceeds 1 mm, the cross section of the core tube is close to the ellipse, and the core tube tends to swing at the time the film is wound, resulting in wrinkles. In addition, when the cylindricality exceeds 1 mm, there is a tendency that the core tube is swung at the time when the core tube is wound, whereby wrinkles and weaving are generated.

In the present invention, the roundness is a value measured according to JIS H 0500 and represents the difference between the maximum value of the outer diameter and the minimum value of the outer diameter measured in a random cross section of the cylindrical core tube. The cylinder degree is a value measured according to JIS B 0182 and represents the difference between the maximum diameter and the minimum diameter of the cylindrical core tube.

The size of the cylindrical core tube varies with the size, such as the width of the polyvinyl alcohol film formed and wound. Preference is given to using cylindrical core tubes having an outer diameter of 75 to 210 mm and a cylindrical length of 0.5 to 4.0 m, more preferably an outer diameter of 85 to 170 mm and a cylindrical length of 0.5 to 3.5 m. If the outer diameter is less than 75 mm, the core tube is bent to easily wrinkle the film. When the outer diameter exceeds 210 mm, the diameter of the film roll is too large to handle the obtained film roll. In addition, when the length of the core tube is less than 0.5m, the width of the polarizing film produced from the film roll is too small, there is a tendency that the productivity of the polarizing film production step is inferior. When the said length exceeds 4.0 m, the film roll tends to be too large and inferior in workability. The thickness of the core tube is preferably 3 to 20 mm.

The polyvinyl alcohol film rolls are thus suitable for the production of polarizing films having an excellent appearance. The process for producing a polarizing film from the polyvinyl alcohol film is as follows.

The polarizing film manufacturing process can be applied to conventional processes, for example, extending the obtained polyvinyl alcohol film (orienting), dipping the film in an iodine or dichroic dye solution, and treating the boron compound; Simultaneously carrying out the extension step and the dyeing step and treating the boron compound; Dyeing and extending the film with iodine or dichroic dye and then treating the boron compound; And after the film is dyed, the dyed film is extended in the boron compound solution.

The thickness of the polyvinyl alcohol film used for producing the polarizing film is preferably 20 to 100 µm, more preferably 30 to 90 µm. If the film thickness is less than 20 mu m, the extension is difficult, and if the film thickness exceeds 100 mu m, the accuracy of the film thickness falls.

The polyvinyl alcohol film (non-extension film) can be subjected to an extension step, a dyeing step and a boron compound treatment step as described above. The extending step, the dyeing step and the boron compound treating step may be performed separately or simultaneously. In the present invention, it is preferable to perform a single axial extension step (single axial direction) during the dyeing step, the boron compound treatment step, or both steps. It is preferred to extend the film 3 to 10 times, preferably 3.5 to 6 times, on a single axis. In the single axis extension step, the film can also extend in a direction perpendicular to the single axis in a small amount (or more or more to prevent shrinkage in the cross direction). The extension temperature is preferably 40 to 170 ° C. Since it is sufficient to finally obtain the above-mentioned extension ratio, the extension operation can be performed in one step or in any of the manufacturing steps.

The dyeing step of the polyvinyl alcohol film is carried out by contacting the film with a liquid containing iodine or dichroic dye. Generally, an aqueous solution of iodide-potassium iodide is used. The concentration of iodine is 0.1-2 g / liter, the concentration of potassium iodide is 10-50 g / liter, and the mixing ratio of iodine / calcium iodide is 20-100 weight ratio. Dyeing time is effective 30 to 500 seconds, the temperature of the dyeing bath is preferably 5 to 50 ℃. Water is used as a solvent, but may contain small amounts of organic solvents that can be mixed with water. Conventional methods such as immersion coating and spraying can be applied to bring the dyeing solution into contact with the film.

The dyed polyvinyl alcohol film is then treated with a boron compound. It is practical to use boric acid or borax as the boron compound. The boron compound is used in the form of a solution in water or in the form of a mixed solvent of water and an organic solvent and is used at a concentration of 0.5 to 2 mol / liter. From a practical point of view, it is preferable to mix a small amount of calcium iodide in the solution. The treatment of the boron compound is preferably carried out through an immersion method, but a coating method and a spray method are also applicable. The treatment is carried out for 5 to 20 minutes at a temperature of 50 to 70 ℃. The extension operation can be carried out during the boron compound treatment, if desired.

The polarizing film thus obtained is provided with an optically isotropic polymer film or sheet on one or both surfaces as a protective film through lamination. Examples of such protective films are, for example, cellulose triacetate, cellulose diacetate, polycarbonate, polymethyl methacrylate, polystyrene, polyethersulfone, polyarylate, poly-4-methylpentene, polyphenylene oxide and its Films or sheets of derivatives.

For the purpose of making the polarizing film thin, a curable polymer such as urethane resin, acrylic resin or urea resin may be coated on one or both sides of the polarizing film to form a protective layer instead of laminating a protective film.

The polarizing film (or the polarizing film provided with the protective film or the coating layer on at least one surface) may be further provided with a transparent pressure-sensitive adhesive layer on one surface through a general method. Copolymers of acrylic esters such as butyl acrylate, ethyl acrylate, methyl acrylate or 2-ethylhexyl acrylate, α-monoolefinic carboxyl such as acrylic acid, malic acid, itaconic acid, methacrylic acid or crotonic acid Pressure-sensitive adhesives comprising an acid and optionally vinyl monomers such as acrylonitrile, vinyl acetate or styrene as the main component are particularly preferred because they do not impair the polarization properties of the polarizing film. However, the pressure-sensitive adhesive is not limited thereto, and other transparent pressure-sensitive adhesives such as, for example, polyvinyl ether-based adhesives and rubber-based adhesives may also be used in the present invention.

The polarizing films thus produced are for example displays such as digital desk calculators, digital clocks, word processors, personal computers, pocket information terminals and liquid crystal display devices for automotive and mechanical gauges, sunglasses, safety goggles, stereoscopic glasses, CRTs or LCDs. It is used for anti-reflective layers, medical equipment, building materials, toys and so on.                     

The present invention will be described in more detail with reference to the following examples and comparative examples. All percentages below refer to% by weight unless otherwise indicated.

Example 1

A polyvinyl alcohol resin aqueous solution having a solid concentration of 45% (including a plasticizer and a release agent as a solid material) is a polyvinyl alcohol resin having an average degree of polymerization of 1,700 and a degree of hydrolysis of 99.7 mol%. Furnace was prepared using polyoxyethylene alkylamine. The solution was cast from a T-die on a drum roll in the form of a thin film, dried and subjected to heat-treatment and humidity-control to give a polyvinyl alcohol film having a water content of 4%.

The polyvinyl alcohol film was then wound around an aluminum cylindrical core tube having the following characteristics under the following conditions.

Aluminum Cylindrical Core Tube :

Diameter (outer diameter): 165 mm

Cylinder length: 2.7 m

Roundness: 0.07 mm

Cylindrical degree: 0.05 mm

Surface Roughness: 35 S

Winding Condition :

Contact pressure of the guide roll (tough roll) of the core tube: 150 N / m

Winding Tension: 130 N / m                     

Winding Speed: 80 m / min

The roll of polyvinyl alcohol film is then unwound at a rate of 1.23 m / min. After the film was expanded at 24 ° C. for washing in a water bath, the film was extended 1.8 times in a single axis in an iodine bath (20 ° C., 0.17 g / liter of iodine) and a boric acid bath (50 ° C., 12 ppm iodine, 47 g / borate). Liter), and a total of 4.6 times in a single axis at a winding speed of 5.6 m / min to produce a polarizing film.

Example 2

A polyvinyl alcohol film having a water content of 4% was prepared in the same manner as in Example 1.

The polyvinyl alcohol film was then wound around an aluminum cylindrical core tube having the following characteristics under the same conditions as in Example 1.

Aluminum Cylindrical Core Tube :

Diameter (outer diameter): 165 mm

Cylinder length: 2.9 m

Roundness: 0.10 mm

Cylindrical degree: 0.09 mm

Surface Roughness: 30 S

In the same manner as in Example 1, the roll of the polyvinyl alcohol film was unrolled, treated, and extended 4.6 times in a single axis to prepare a polarizing film.

Example 3                     

A polyvinyl alcohol film having a water content of 4% was prepared in the same manner as in Example 1.

The polyvinyl alcohol film was then wound around an aluminum cylindrical core tube having the following characteristics under the same conditions as in Example 1.

Aluminum Cylindrical Core Tube:

Diameter (outer diameter): 114 mm

Cylinder length: 2.2 m

Roundness: 0.05 mm

Cylindrical degree: 0.08 mm

Surface Roughness: 35 S

In the same manner as in Example 1, the roll of the polyvinyl alcohol film was unrolled, treated, and extended 4.6 times in a single axis to prepare a polarizing film.

Example 4

A polyvinyl alcohol film having a water content of 4% was prepared in the same manner as in Example 1.

The polyvinyl alcohol film was then wound around an aluminum cylindrical core tube having the following characteristics under the same conditions as in Example 1.

Aluminum Cylindrical Core Tube:

Diameter (outer diameter): 165 mm

Cylinder length: 3.3 m                     

Roundness: 0.1 mm

Cylindrical degree: 0.09 mm

Surface Roughness: 35 S

In the same manner as in Example 1, the roll of the polyvinyl alcohol film was unrolled, treated, and extended 4.6 times in a single axis to prepare a polarizing film.

Comparative Example 1

A polyvinyl alcohol film having a water content of 4% was prepared in the same manner as in Example 1.

The polyvinyl alcohol film was then wound around a cylindrical core tube made of plastic (polyvinyl chloride) having the following properties under the following conditions.

Plastic cylindrical core tube:

Diameter (outer diameter): 165 mm

Cylinder length: 2.7 m

Roundness: 0.8 mm

Cylindrical degree: 1.2 mm

Surface Roughness: 40 S

Winding Condition:

Contact pressure of guide roll (reinforcement roll) of core tube: 150 N / m

Winding Tension: 130 N / m

Winding Speed: 80 m / min                     

In the same manner as in Example 1, the roll of the polyvinyl alcohol film was unrolled, treated, and extended 4.6 times in a single axis to prepare a polarizing film.

The film roll did not loosen stably due to the wrinkles formed when winding the film, and thus a uniform elongated film could not be obtained.

Comparative Example 2

A polyvinyl alcohol film having a water content of 4% was prepared in the same manner as in Example 1.

The polyvinyl alcohol film was then wound around a cylindrical core tube made of paper having the following characteristics under the following conditions.

Paper cylindrical core tube:

Diameter (outer diameter): 153 mm

Cylinder length: 1.6 m

Roundness: 1.2 mm

Cylindrical degree: 1.5 mm

Surface Roughness: 40 S

Winding Condition:

Contact pressure of guide roll (reinforcement roll) of core tube: 150 N / m

Winding Tension: 130 N / m

Winding Speed: 80 m / min

In the same manner as in Example 1, the roll of the polyvinyl alcohol film was unrolled, treated, and extended 4.6 times in a single axis to prepare a polarizing film.

The film roll did not loosen stably due to the wrinkles formed when winding the film, and thus a uniform elongated film could not be obtained.

Comparative Example 3

A polyvinyl alcohol film having a water content of 4% was prepared in the same manner as in Example 1.

The polyvinyl alcohol film was then burned around an aluminium cylindrical core tube having the following characteristics under the following conditions.

Paper cylindrical core tube:

Diameter (outer diameter): 165 mm

Cylinder length: 2.7 m

Roundness: 1.1 mm

Cylindrical degree: 1.3 mm

Surface Roughness: 120 S

Winding Condition:

Contact pressure of guide roll (reinforcement roll) of core tube: 150 N / m

Winding Tension: 130 N / m

Winding Speed: 80 m / min

In the same manner as in Example 1, the roll of the polyvinyl alcohol film was unrolled, treated, and extended 4.6 times in a single axis to prepare a polarizing film. However, since the edge portion of the film is folded to cause blocking, breakage of the film often occurs during the extension step of the film, and thus a polarizing film could not be obtained.

The polyvinyl alcohol and polarizing films obtained in the examples and the comparative examples were evaluated according to the following methods, and the results are shown in Table 1.

The presence of wrinkles

A 1,000 m wound polyvinyl alcohol film was visually observed in relation to the presence of wrinkles and evaluated according to the following criteria.

(Circle): A wrinkle formation is not observed.

X: Wrinkle formation was observed.

Uneven dyeing

Polarizing films were visually observed with respect to nonuniform staining and evaluated according to the following criteria.

(Circle): Uneven dyeing is not observed.

X: Uneven dyeing is observed.

Polarization characteristics

Simplex percent transmission and polarization degree of the polarizing film were measured using a spectrocolorimeter (Model Σ90 manufactured by Nippon Denshoku Industries Co., Ltd.) at five points in the transverse direction and their respective average values. Obtained.

Example Comparative Example One 2 3 4 One 2 3 Cylindrical core tube matter aluminum aluminum aluminum aluminum plastic paper aluminum Diameter (mm) 165 165 114 165 165 153 165 Length (m) 2.7 2.9 2.2 3.3 2.7 1.6 2.7 Roundness (mm) 0.07 0.1 0.05 0.1 0.8 1.2 1.1 Cylindrical degree (mm) 0.05 0.09 0.08 0.09 1.2 1.5 1.3 Surface roughness 35S 30S 35S 35S 40S 40S 120S Polyvinyl alcohol film The presence of wrinkles ○ ○ ○ ○ × × × Non-uniform dyeing ○ ○ ○ ○ × × × Polarization send(%) 42.7 42.8 42.7 42.9 42.6 42.4 -* % Polarization 99 99.2 99.1 99.1 97.6 96.8 -*

* No film was obtained due to breakage of the film.

As shown in Table 1, the polyvinyl alcohol film rolls obtained in the examples had a good wound state and no wrinkles, so that the polarizing film obtained therefrom had non-uniform dyeing and had excellent optical properties.

In contrast, the polyvinyl alcohol film rolls obtained in the comparative example were wrinkled, and thus unstable unstable to obtain a uniform extended film. Thus, uneven dyeing occurred and the resulting polarizing film had low optical properties. More specifically, in Comparative Example 3, breakage of the film frequently occurred when the film was extended, thereby failing to obtain a polarizing film.

As described above, in the present invention, a polyvinyl alcohol film formed from a polyvinyl alcohol resin solution was wound around a cylindrical core tube made of a metallic material and having a surface roughness of up to 100S. As a result, no wrinkles were formed in the wound film, and thus a polyvinyl alcohol film with a good appearance and an overall homogeneity could be obtained.                     

Therefore, since non-uniform extension and non-uniform dyeing do not occur in the dyeing and extending step in the production of the polarizing film, the polarizing film produced from the above-mentioned polyvinyl alcohol film roll has excellent flatness.

If the cylindrical core tube further has a roundness of 0.01 to 1 mm and a cylinder degree of 0.01 to 1 mm, the fluctuation of the wound core tube is reduced, and thus a better winding state can be obtained.

It is preferable that the cylindrical core tube has an outer diameter of 75 to 210 mm and a length of 0.5 to 4.0 m because of easy handling and thus good workability and productivity.

The film roll according to the present invention has the advantage of providing an optically uniform polyvinyl alcohol film having an excellent appearance, such as a digital desk calculator, a digital clock, a word processor, a personal computer, a pocket information terminal, and a liquid for automotive and mechanical gauges. It is applicable to various fields such as crystal display devices, sunglasses, safety goggles, stereoscopic glasses, reflection-reduction layers for displays such as CRT or LCD, medical equipment, building materials, toys.

Claims (4)

A method of producing a polyvinyl alcohol film roll for use as a polarizing film, the method comprising forming a film from a polyvinyl alcohol resin solution and winding the polyvinyl alcohol film around a cylindrical core tube, wherein the cylinder The core tube is made of aluminum and has a surface roughness of up to 100 S, a roundness of 0.01 to 1 mm, and a cylinder degree of 0.01 to 1 mm, wherein the polyvinyl alcohol film has a thickness of 30 to 90 µm. Method for producing a film roll. delete The method of claim 1, wherein the cylindrical core tube has an outer diameter of 75 to 210 mm and a length of 0.5 to 4.0 m. delete