CN1635015A - Polyvinyl alcohol film roll and polarizing film prepared therefrom - Google Patents

Abstract

The invention discloses a polyvinyl alcohol film coil composed of a cylindrical core tube and a polyvinyl alcohol film coiling on the cylindrical core tube. Wherein the cylindrical core tube is made of metal material and the surface roughness is at most 100S. The film coil can be obtained by forming the film from the polyvinyl alcohol resin solution, and coiling the film onto the core tube. The film coil can provide a polyvinyl alcohol film with excellent appearance and optical evenness.

Description

Polyvinyl alcohol film roll and polarizing film prepared therefrom

technical field

The present invention relates to a polyvinyl alcohol film roll in which a very long polyvinyl alcohol film can be rolled and the rolled film has an excellent appearance. The present invention also relates to a polarizing film prepared from the above-mentioned film roll and having excellent polarizing characteristics.

Background technique

A polyvinyl alcohol film is generally produced by dissolving a polyvinyl alcohol resin in a solvent, degassing the resulting solution, forming it into a film by solution casting, and drying the film using a metal heating roll or the like. The film that has undergone the above-mentioned drying process is then dried with a drier to volatilize the moisture contained in the film, and then supplied with a predetermined amount of moisture in a humidity conditioner and wound up on a cylindrical core tube to produce a Roll-up film on the market. As a film having excellent shape stability, the above-mentioned rolled polyvinyl alcohol film has been used in many applications. One of the useful uses is in optical films, especially polarizing films.

However, when a polyvinyl alcohol film is wound onto a cylindrical core, problems arise in the appearance of the film, such as wrinkles and folds. Therefore, careful process management is required. If these problems arise, another problem will naturally arise. For example, if a polarizing film is produced from a film that has caused this problem, the polarizing characteristic is deteriorated.

Contents of the invention

An object of the present invention is to provide a roll of polyvinyl alcohol film which has excellent appearance, thus optical uniformity which is industrially advantageous, and which does not require strict process management which is usually required.

Another object of the present invention is to provide a roll of long polyvinyl alcohol film which, when unrolled, results in a polyvinyl alcohol film having excellent appearance and optical uniformity.

Another object of the present invention is to provide a polarizing film having excellent polarizing characteristics.

These and other objects of the invention will become apparent from the ensuing description.

In the process of winding the film onto the cylindrical core, in order to prevent the polyvinyl alcohol film from being wrinkled, etc., and to obtain a polyvinyl alcohol film with an excellent appearance, the winding process, the cylindrical core to be used, etc. have been carefully reviewed. Research. It was thus found that if the cylindrical core tube for winding the film is made of a metal material and the surface roughness thereof is set to be at most 100S, the phenomenon such as bending of the cylindrical core tube which may occur during the winding process can be suppressed, Also, the film can be appropriately wound onto the cylindrical core tube without wrinkling or the like, thereby producing a polyvinyl alcohol film roll having an excellent appearance.

According to the present invention, there is provided a polyvinyl alcohol film roll produced by winding a polyvinyl alcohol film onto a cylindrical core tube made of metal after forming the film from a polyvinyl alcohol resin solution. material with a surface roughness of at most 100S.

The present invention also provides a polarizing film prepared from a polyvinyl alcohol film obtained by unrolling the above-mentioned film of the present invention.

In the present invention, a polyvinyl alcohol resin is used as a film-forming material, and a film roll is prepared from a solution of the polyvinyl alcohol resin.

Polyvinyl alcohol resins are generally produced by polymerizing vinyl acetate and hydrolyzing the polyvinyl acetate. The polyvinyl alcohol resin used in the present invention is not limited to the hydrolyzate of polyvinyl acetate, can contain a small amount, for example 0～15 mol%, especially 0～5 mol% other components that can be copolymerized with vinyl acetate, for example Unsaturated carboxylic acids (including their salts, esters, amides, nitriles), olefins having 2 to 30 carbon atoms such as ethylene, propylene, n-butene or isobutene, vinyl ethers, unsaturated sulfonates and the like. The polyvinyl alcohol resin may contain a silyl group. Resins containing silyl groups can be prepared according to known methods, such as post-modification with silylating agents or hydrolysis after copolymerization with ethylenically unsaturated monomers containing silyl groups with vinyl acetate. The ethylenically unsaturated monomer containing a silyl group is, for example, vinylsilane, (meth)acrylamidoalkylsilane, and the like.

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, and still more preferably 1,400 to 5,000. If the degree of polymerization is less than 1,000, sufficient polarization characteristics cannot be obtained when the polyvinyl alcohol resin film is used to produce a polarizing film. If the degree of polymerization is higher than 7,000, since it is difficult to stretch the film, industrial production of a polarizing film tends to become difficult.

The degree of hydrolysis of the polyvinyl alcohol resin is preferably not less than 80 mol%, more preferably 85 to 100 mol%, further preferably 98 to 100 mol%. If the degree of hydrolysis is lower than 80 mol%, it is difficult to obtain sufficient polarization characteristics when the polyvinyl alcohol resin film is used to produce a polarizing film.

If necessary, commonly used plasticizers such as glycerin, diglycerin, triglycerin, ethylene glycol, triethylene glycol or polyethylene glycol can be added to the polyvinyl alcohol resin. Based on the polyvinyl alcohol resin, the amount Up to 30% by weight, preferably up to 25% by weight, more preferably up to 20% by weight. If the plasticizer amount exceeds 30% by weight, film strength is liable to deteriorate.

Preferably, nonionic, anionic or cationic surfactants are added to the polyvinyl alcohol resin, especially surfactants with a mold release effect, such as polyoxyethylene alkylamine, based on the polyvinyl alcohol resin, the amount used is the most It is 5% by weight, preferably 0.001 to 3% by weight, more preferably 0.001 to 2% by weight. If the amount of the surfactant exceeds 5% by weight, the appearance of the film surface is liable to deteriorate.

In the present invention, the above polyvinyl alcohol resin is used to prepare a polyvinyl alcohol resin film.

The process for preparing polyvinyl alcohol film rolls is as follows:

The polyvinyl alcohol resin is dissolved in a solvent, and the obtained polyvinyl alcohol resin solution is formed into a film to obtain a raw film web.

Examples of solvents for preparing the polyvinyl alcohol resin solution include, for example, water; organic solvents such as dimethyl sulfoxide (DMSO), N-methylpyrrolidone, polyhydric alcohols such as glycerin, ethylene glycol, propylene glycol, diethylene glycol, Triethylene glycol, tetraethylene glycol or trimethylolpropane, amine compounds such as ethylenediamine or diethylenetriamine; and mixtures thereof.

The above-mentioned organic solvent may contain a small amount, for example, 5 to 30% by weight of water.

From a practical point of view, the concentration of the polyvinyl alcohol resin in the polyvinyl alcohol resin solution is preferably 5-70% by weight.

The polyvinyl alcohol resin solution can be formed into a film by known methods such as casting and extrusion. The film forming method can be wet or dry. In the wet process, the solution is passed through a slit to be expelled into an atmosphere of air or an inert gas, such as nitrogen, helium, or argon, and then introduced into a coagulation bath to form an unstretched film; in the dry process, the solution is passed through a slit It is discharged onto a support device such as a roller or belt conveyor to form a film, which dries as an unstretched film.

The unstretched film formed above may be further subjected to drying treatment, heat treatment and humidity conditioning treatment if necessary.

The polyvinyl alcohol film is then wound onto a cylindrical core tube to form a film roll for the market. The polyvinyl alcohol film was wound onto the cylindrical core tube by temporarily fastening the top of the film to the core tube surface with tape, and then rotating the core tube at a predetermined winding speed.

In the present invention, the cylindrical core tube for winding the film is made of metal material. Aluminum is particularly preferred from the viewpoints of strength, light weight, ease of processing such as forming into a desired shape, and prevention of foreign matter from entering the film.

The cylindrical core tube is required to have a surface roughness of at most 100S, preferably at most 20S, more preferably at most 10S. If the surface roughness exceeds 100S, knitting occurs during film winding. In the present invention, the surface roughness is the arithmetic mean (Ra: average height of the center line of the surface roughness) defined in JIS B 0601-1994.

Preferably, the roundness of the cylindrical core tube is 0.01-1 mm, the cylindricity is 0.01-1 mm, preferably the roundness is 0.01-0.2 mm, the cylindricity is 0.01-0.2 mm, and the roundness is more preferably 0.01-0.1 mm. The degree is 0.01 ~ 0.1mm. If the roundness is greater than 1mm, the cross-section of the core tube is close to an ellipse, and the core tube will fluctuate and wrinkle easily when the film is wound. Also, if the cylindricity is greater than 1 mm, the core tube will fluctuate when the film is wound, and wrinkles and knitting are likely to occur.

In the present invention, the roundness is a value measured in accordance with JIS H 0500, which is the difference between the largest outer diameter and the smallest outer diameter measured on an arbitrary section of a cylindrical core tube. Cylindricity is a value measured in accordance with JIS B0182, which is the difference between the maximum diameter and the minimum diameter of a cylindrical core tube.

The size of the cylindrical core pipe varies according to the size, such as width, etc. of the polyvinyl alcohol film to be formed and wound. Preferably, a cylindrical core tube with an outer diameter of 75-210 mm and a cylindrical length of 0.5-4.0 m is used; more preferably, the outer diameter is 85-170 mm, and the cylindrical length is 0.5-3.5 m. If the outer diameter is less than 75mm, the core tube is bent and the film is prone to wrinkle. If the outer diameter is larger than 210 mm, the resulting film roll is difficult to convey because the diameter of the film roll is too large. Also, if the length of the core tube is less than 0.5 m, the width of the polarizing film to be produced from a film roll is very small, and the productivity in the process of producing the polarizing film tends to decrease. If the length is greater than 4.0 m, workability tends to decrease due to excessive weight of the film roll. Preferably, the thickness of the core tube is about 3-20 mm.

The polyvinyl alcohol film roll prepared above has excellent appearance and is suitable for preparing polarizing films. A method of preparing a polarizing film from the polyvinyl alcohol film prepared above will be described below.

The method used to prepare the polarizing film is a suitable known method, such as stretching (orienting) the obtained polyvinyl alcohol film, and then dipping the film in a solution of iodine or a dichroic dye for dyeing, followed by boron compound. A method of treatment; a method of simultaneously stretching and dyeing, and then treating with a boron compound; a method of dyeing a film with iodine or a dichroic dye, stretching, and then treating with a boron compound; after dyeing the film, A method of stretching a dyed film in a solution of a boron compound. The method for producing a polarizing film from the polyvinyl alcohol film of the present invention can be appropriately selected from these methods.

The thickness of the polyvinyl alcohol film used in preparing the polarizing film is preferably 20 to 100 μm, more preferably 30 to 90 μm. If the film thickness is less than 20 μm, it is difficult to stretch; if the film thickness is more than 100 μm, the film thickness accuracy decreases.

As described above, the polyvinyl alcohol film (unstretched film) was stretched, dyed and treated with a boron compound. Stretching, dyeing and boron compound treatment can be performed step by step or simultaneously. In the present invention, it is preferable to perform uniaxial stretching (uniaxial orientation) in performing one or both of the dyeing process and the boron compound treatment process.

Preferably, the film is uniaxially stretched 3 to 10 times, particularly preferably 3.5 to 6 times. In the case of uniaxial stretching, the film may also be stretched in a direction perpendicular to the uniaxial stretching by a small amount (up to or better than a degree to prevent shrinkage in the perpendicular direction). The stretching temperature is preferably 40 to 170°C. It is sufficient to finally obtain the above stretching ratio, and thus the stretching operation may be performed at a single stage or at any stage of the production process.

Polyvinyl alcohol films are dyed by contacting a liquid containing iodine or a dichroic dye with the film. Usually an aqueous solution of iodine-potassium iodide is used. Preferably, the concentration of iodine is 0.1-2 g/l, the concentration of potassium iodide is 10-50 g/l, and the mixing weight ratio of iodine/potassium iodide is 20-100. In practice, the dyeing time is about 30-500 seconds, and preferably, the temperature of the dyeing bath is 5-50°C. Water is used as the solvent, but the solvent may contain a small amount of water-miscible organic solvent. Any known method, such as dipping, coating and spraying, is suitable for bringing the dyeing solution into contact with the film.

The dyed polyvinyl alcohol film can then be treated with a boron compound. From a practical point of view, boric acid or borax is used as the boron compound. The boron compound used is a solution dissolved in water or a mixed solvent of water and an organic solvent, and its concentration is about 0.5-2 mol/liter. From a practical point of view, it is preferable to add a small amount of potassium iodide to the solution. The boron compound treatment is preferably carried out by dipping, but coating and spraying methods are of course also suitable. The treatment is carried out at a temperature of about 50-70° C. for about 5-20 minutes. The stretching operation can be performed during the boron compound treatment if desired.

An optically isotropic polymer film or sheet may be laminated on either side or both sides of the polarizing film thus obtained as a protective film. Examples of protective films include, for example, cellulose triacetate, cellulose diacetate, polycarbonate, polymethyl methacrylate, polystyrene, polyethersulfone, polyarylate, poly-4-formaldehyde Films or sheets of pentene, polyphenylene ether, etc.

In order to make the polarizing film thin, a curable polymer such as urethane resin, acrylic resin or urea resin may be coated on either side or both sides of the polarizing film to form a protective layer without laminating the protective film.

A transparent pressure-sensitive adhesive layer can be provided on one side of the polarizing film (or a polarizing film provided with a protective film or coating on at least one side thereof) by a usual method. Since the polarizing properties of the polarizing film are not impaired, it is particularly preferred that the pressure-sensitive adhesive contains an acrylate such as butyl acrylate, ethyl acrylate, methyl acrylate or 2-ethylhexyl acrylate, α-monoene Copolymers of carboxylic acids such as acrylic acid, maleic acid, itaconic acid, methacrylic acid or crotonic acid, and optionally vinyl monomers such as acrylonitrile, vinyl acetate or styrene. However, the pressure-sensitive adhesive is not limited to these substances, and any known transparent pressure-sensitive adhesive can be used in the present invention, such as polyvinyl ether-based adhesives and rubber-based adhesives. agent.

The polarizing film prepared above is used, for example, in digital desktop calculators, digital watches, word processors, personal computers, pocket information terminals, liquid crystal display devices for automobiles and machine meters, sunglasses, safety goggles, stereoscopic glasses, display devices ( Such as anti-reflection layer of CRT or LCD), medical equipment, building materials, toys, etc.

Detailed ways

The present invention will be described in more detail through the following examples and comparative examples, wherein unless otherwise specified, all "%" are weight %".

Example 1

The polyvinyl alcohol resin with an average degree of polymerization of 1,700 and a degree of hydrolysis of 99.7 mol%, glycerol as a plasticizer, and polyoxyethylene alkylamine as a surfactant (release agent) to prepare a solid concentration of 45% (including Aqueous solution of polyvinyl alcohol resin with plasticizer and release agent as solid matter). The solution was cast from a T-die onto a drum roll to form a film and dried, followed by heat treatment and humidity adjustment to obtain a polyvinyl alcohol film with a water content of 4%.

The polyvinyl alcohol film was then wound onto an aluminum cylindrical core tube having the properties described below under the conditions described below.

Aluminum Cylindrical Core Tube

Diameter (outer diameter): 165mm

Column length: 2.7m

Roundness: 0.07mm

Cylindricity: 0.05mm

Surface roughness: 35S

Winding conditions

Contact pressure between guide roller (contact roller) and core tube: 150N/m

Winding tension: 130N/m

Winding speed: 80m/min

The roll of polyvinyl alcohol film was then unrolled at a speed of 1.23 m/min. After swelling the film in a water bath for cleaning at 24°C, the film was uniaxially stretched 1.8 times in an iodine bath (20°C, iodine 0.17g/l) and then stretched 1.8 times in a boric acid bath (50°C, iodine 12ppm, boric acid 47g/l). In l), the film was uniaxially stretched 1.7 times, and then the film was further uniaxially stretched 4.6 times at a winding speed of 5.6 m/min to obtain a polarizing film.

Example 2

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

Subsequently, a polyvinyl alcohol film was wound on an aluminum cylindrical core tube having the following properties under the same conditions as in Example 1.

Aluminum Cylindrical Core Tube

Diameter (outer diameter): 165mm

Column length: 2.9m

Roundness: 0.10mm

Cylindricity: 0.09mm

Surface roughness: 30S

The polyvinyl alcohol film roll was unrolled, treated, and uniaxially stretched 4.6 times in the same manner as in Example 1 to obtain a polarizing film.

Example 3

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

Subsequently, a polyvinyl alcohol film was wound on an aluminum cylindrical core tube having the following properties under the same conditions as in Example 1.

Aluminum Cylindrical Core Tube

Diameter (outer diameter): 114mm

Column length: 2.2m

Roundness: 0.05mm

Cylindricity: 0.08mm

Surface roughness: 35S

The polyvinyl alcohol film roll was unrolled, treated, and uniaxially stretched 4.6 times in the same manner as in Example 1 to obtain a polarizing film.

Example 4

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

Subsequently, a polyvinyl alcohol film was wound on an aluminum cylindrical core tube having the following properties under the same conditions as in Example 1.

Aluminum Cylindrical Core Tube

Diameter (outer diameter): 165mm

Column length: 3.3m

Roundness: 0.1mm

Cylindricity: 0.09mm

Surface roughness: 35S

The polyvinyl alcohol film roll was unrolled, treated, and uniaxially stretched 4.6 times in the same manner as in Example 1 to obtain a polarizing film.

Comparative example 1

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

Subsequently, the polyvinyl alcohol film was wound on a cylindrical core tube made of plastic (polyvinyl chloride) having the following properties under the conditions described below.

Plastic cylindrical core tube

Diameter (outer diameter): 165mm

Column length: 2.7m

Roundness: 0.8mm

Cylindricity: 1.2mm

Surface Roughness: 40S

Winding conditions

Contact pressure between guide roller (contact roller) and core tube: 150N/m

Winding tension: 130N/m

Winding speed: 80m/min

The polyvinyl alcohol film roll was unrolled, treated, and uniaxially stretched 4.6 times in the same manner as in Example 1 to obtain a polarizing film. Since wrinkles are generated when the film is wound, the film roll cannot be unwound stably, so uniform stretching cannot be achieved.

Comparative example 2

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

The polyvinyl alcohol film was then wound onto a cylindrical core tube made of paper having the properties described below under the conditions described below.

Paper cylindrical core tube

Diameter (outer diameter): 153mm

Column length: 1.6m

Roundness: 1.2mm

Cylindricity: 1.5mm

Surface Roughness: 40S

Winding conditions

Contact pressure between guide roller (contact roller) and core tube: 150N/m

Winding tension: 130N/m

Winding speed: 80m/min

The polyvinyl alcohol film roll was unrolled, treated, and uniaxially stretched 4.6 times in the same manner as in Example 1 to obtain a polarizing film. Since wrinkles are generated when the film is wound, the film roll cannot be unwound stably, so uniform stretching cannot be achieved.

Comparative example 3

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

The polyvinyl alcohol film was then wound onto an aluminum cylindrical core tube having the properties described below under the conditions described below.

Aluminum Cylindrical Core Tube

Diameter (outer diameter): 165mm

Column length: 2.7m

Roundness: 1.1mm

Cylindricity: 1.3mm

Surface roughness: 120S

Winding conditions

Contact pressure between guide roller (contact roller) and core tube: 150N/m

Winding tension: 130N/m

Winding speed: 80m/min

The polyvinyl alcohol film roll was unrolled, treated, and uniaxially stretched 4.6 times in the same manner as in Example 1 to obtain a polarizing film. However, since the edge portion of the film is folded and jammed, film breakage frequently occurs when the film is stretched, and a polarizing film cannot be produced.

The polyvinyl alcohol films and polarizing films produced in Examples and Comparative Examples were evaluated according to the following methods. The results are shown in Table 1.

folds appear

For the appearance of wrinkles, the polyvinyl alcohol film wound up to 1,000 m was visually observed and evaluated according to the following criteria.

○: Crease formation was not found.

X: Wrinkle formation was found.

uneven dyeing

For uneven dyeing, the polarizing film was visually observed and evaluated according to the following criteria.

○: No uneven dyeing was found.

X: Uneven dyeing was found.

Polarization characteristics

The single-percent transmittance and polarization degree of the polarizing film were measured at five positions in the transverse direction with a spectrocolorimeter (Nippon Denshoku Kogyo Kabushiki Kaisha Σ90 type), and the average values were obtained respectively.

Table 1

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3

Cylindrical core tube

Material Aluminum (Al) Aluminum (Al) Aluminum (Al) Aluminum (Al) Plastic Paper Aluminum (Al)

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

Cylindricity(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

Wrinkles ○ ○ ○ ○ ○ ○ × × ×

Uneven dyeing ○ ○ ○ ○ ○ ○ ○ × × ×

Polarization characteristics

Transmittance (%) 42.7 42.8 42.7 42.9 42.6 42.4 -*

Degree of Polarization (%) 99 99.2 99.1 99.1 97.6 96.8 -*

*: No polarizing film was produced due to film breakage.

As shown in Table 1, the polyvinyl alcohol film rolls prepared in Examples were good in the rolled state without wrinkles, so the polarizing film prepared therefrom had no uneven dyeing and had excellent optical properties.

In contrast, the roll of polyvinyl alcohol film prepared in Comparative Example had wrinkles, so the unwinding was unstable and uniform stretching could not be achieved. Therefore, uneven dyeing occurs and the prepared polarizing film has poor optical characteristics. In particular, in Comparative Example 3, film breakage frequently occurred when the film was stretched, and thus no polarizing film was produced.

As described above, in the present invention, a polyvinyl alcohol film formed from a polyvinyl alcohol resin solution is wound around a cylindrical core tube made of a metal material with a surface roughness of at most 100S. As a result, no wrinkles were formed on the wound film, so the appearance was good and the produced polyvinyl alcohol film had uniformity as a whole.

Therefore, since no uneven stretching and uneven dyeing occur in the dyeing and stretching process in the production of the polarizing film, the polarizing film prepared from the roll of the polyvinyl alcohol film has excellent polarizing characteristics.

If the roundness of the cylindrical core tube is further 0.01-1 mm, and the cylindricity is 0.01-1 mm, the fluctuation of the core tube during winding is reduced, thereby obtaining a better winding state.

The cylindrical core tube preferably has an outer diameter of 75 to 210 mm and a length of 0.5 to 4.0 m because of ease of transportation and thus good processability and productivity.

Claims (4)

1. A polyvinyl alcohol film roll, which is obtained by winding the polyvinyl alcohol film on a cylindrical core tube after forming a film from a polyvinyl alcohol resin solution, wherein the cylindrical core tube is made of a metal material into, the surface roughness is at most 100S. 2. The film roll according to claim 1, wherein the circularity of the cylindrical core tube is 0.01-1mm, and the cylindricity is 0.01-1mm. 3. The film roll according to claim 1, wherein the cylindrical core tube has an outer diameter of 75-210 mm and a length of 0.5-4.0 m. 4. A polarizing film produced from a polyvinyl alcohol film, wherein the polyvinyl alcohol film is unrolled from the roll of claim 1.