KR100675201B1 - Method for manufacturing Polyvinyl alcohol film - Google Patents

Abstract

The present invention relates to a method for producing a polyvinyl alcohol film, and more particularly, in the case of solidifying by casting the unstable film melt discharged from the die to a casting drum during the production of polyvinyl alcohol film, each of the positive pressure suction device, the cleaning roll or the By installing and using both devices, width constant velocity pinning, efficient removal of generated water vapor, and uniform surface tension of the casting drum can be maintained, which greatly improves the landing stability and peeling stability of the film. The present invention relates to a method of manufacturing a polyvinyl alcohol film that can significantly improve physical properties such as polarization, transmittance, and color deviation when manufacturing a polarizing plate by minimizing film thickness and retardation deviation.

Polyvinyl alcohol film, manufacturing method, static pressure suction device, cleaning roll, polarizer

Description

Method for manufacturing polyvinyl alcohol film {Method for manufacturing Polyvinyl alcohol film}

1 is a block diagram showing a manufacturing process of a polyvinyl alcohol film according to the present invention.

<Explanation of symbols for the main parts of the drawings>

10 Hopper 20 Screw Feeder

30: extruder 40: filter

50: gear pump 60: die

70: casting drum 80: constant pressure suction device

90: cleaning roll

The present invention relates to a method of manufacturing a polyvinyl alcohol film, and more particularly, in the case of solidifying by casting the unstable film melt discharged from the die to a casting drum during the production of polyvinyl alcohol film, each of the positive pressure suction device, the cleaning roll or the By installing and using both devices, width constant velocity pinning, efficient removal of generated water vapor, and uniform surface tension of the casting drum can be maintained, which greatly improves the landing stability and peeling stability of the film. The present invention relates to a method of manufacturing a polyvinyl alcohol film that can significantly improve physical properties such as polarization, transmittance, and color deviation when manufacturing a polarizing plate by minimizing film thickness and retardation deviation.

In general, a polarizing plate has a configuration in which a protective plate such as a 3-cellulose acetate (TAC) film is attached to both surfaces of a polarizing film prepared by stretching and dyeing a polyvinyl alcohol (hereinafter, referred to as PVA) film as one axis. And is used in liquid crystal displays.

In general, for uniformity of polarization performance, there are various precautions such as the use of a PVA film having a uniform thickness, a uniform dyeing of a dichroic dye, a spotless adhesion, and the like, and in particular, the production of a uniform PVA film without variation is important. Unlike the general thermoplastic resins, the PVA resin has a very close melting point and pyrolysis temperature, thereby making it impossible to form a film by a simple heat melting method. Therefore, in order to manufacture a film using the PVA resin, a method of lowering the processing temperature and molding using a large amount of a plasticizer such as water, a polyhydric alcohol, a phthalate compound, and the like is performed.

As a method of manufacturing the PVA film, a solution casting method and an extrusion method are used. In particular, the solution casting method is prepared by stirring a PVA resin with a solvent such as water for a long time in a stirring tank to prepare a low concentration solution of about 5 to 20% by weight. Then, as a method for performing the film forming process, a large amount of moisture is contained in the order of several hundred% by weight compared to the final film, and there is a problem in that it is not economically efficient.

Due to the disadvantage that the solution casting method is not economical, the extrusion method, which is mainly used in manufacturing a polarizing PVA film, is a method of performing a film forming process using an extruder, and is processed in a limited processing time and a high concentration state compared to a conventional solution casting method. Done.

The molten melted in the extruder is transformed into a film form while passing through a die and then cast in a heated casting drum to lower the moisture content retained below a certain content, thereby changing from an unstable melt state to a stable solid state. The invention disclosed in 2001-315143 allows the outside of the drum to be dried using hot or hot air to efficiently remove water vapor generated from the film. However, the warm air or hot air blowing outside the drum is likely to act as a cause of disturbance such as shaking when the film lands on the casting drum, and water vapor generated on the surface of the film exposed to the atmosphere can be efficiently removed. Water vapor generated on the film surface in contact with the drum cannot be removed, causing uneven film deposition. If the landing is unstable in this way, it causes a nonuniformity such as thickness and refractive index variation.

The PVA film is made of a polarizing film while undergoing a continuous process such as swelling, stretching, dyeing, fixing, washing and drying. The swelling process is divided into dry and wet depending on the type, in this process, when the film is non-uniform, wrinkles occur during the stretching process or cause uneven dyeing during the dyeing process to generate color deviations.

As described above, the film thickness and retardation variation due to non-uniform landing and peeling are acting as a major disadvantage when applied to the polarizing film of PVA film. Especially, as the liquid crystal display is gradually enlarged and high quality, its importance is important. Is more emphasized.

Accordingly, the present inventors have made efforts to solidify the film of the unstable molten state by uniformly and stably landing and peeling on the casting drum, and when the unstable film melt discharged from the die is cast and solidified on the casting drum, Composed of two channels at the landing point of the casting drum film, it is possible to install a positive pressure suction device that is capable of adjusting suction power and to apply a uniform suction force over the entire width, or to install a cleaning roll on the film peeling contact or the positive pressure suction device. And by installing a cleaning roll, it is possible to improve the film's width and retardation stability by providing constant velocity pinning of the film, efficient removal of generated water vapor, and maintaining uniform surface tension. Polarization, transmittance, By developing a method of manufacturing a suitable polyvinyl alcohol film for a polarization of the liquid crystal display in the physical properties, such as variations it can be significantly improved compared to the prior art, thereby completing the present invention.

Accordingly, the present invention provides a method for producing a polyvinyl alcohol film using a static pressure suction device consisting of two channels at a rotating casting drum film landing point, installing each of the cleaning rolls on the film peeling point, or installing both devices. The purpose is to provide.

The present invention

In manufacturing the polyvinyl alcohol film which is transformed into a film form while passing through the extruder 30, the filter 40, the gear pump 50, the die 60, and subsequently cast to the casting drum 70,

Characterized by a method of producing a polyvinyl alcohol film using a static pressure suction device (80) consisting of two channels at a rotating casting drum film landing point, a cleaning roll (90) on the film peeling point, or both. do.

The present invention will be described in more detail as follows.

According to the present invention, when casting an unstable film melt discharged from a die to solidify the polyvinyl alcohol film by casting it on a casting drum, a constant pressure suction device, a cleaning roll, or both of the above devices are installed and used. It is possible to effectively remove the generated water vapor and maintain the uniform surface tension of the casting drum, which can greatly improve the landing stability and peeling stability of the film. The present invention relates to a method for producing a polyvinyl alcohol film that can significantly improve physical properties such as rate, transmittance, color deviation, and the like.

First, the degree of substitution of the hydroxyl groups of the acetate groups in the molecular chain of the polyvinyl alcohol (PVA) resin is referred to as safing degree, and even in the case of the same molecular weight, it is divided into water solubility, poor solubility, and insolubility according to the difference in saponification degree. That is, as the relatively large functional group is substituted with the hydroxy group, the gap between the molecular chains becomes narrower, and the molecular chains form strong hydrogen bonds by the hydroxy groups.

From this, the main cause of undissolved residues remaining in the PVA film produced by the extrusion method is due to strong hydrogen bonds between molecular chains in the PVA resin previously formed before the film extrusion process. In particular, unlike water-soluble or mold release applications, polarizing PVA resin having a degree of saponification of 99.9 mol% or more has a stronger molecular chain bonding structure, and thus, it is difficult to prepare a perfect melt without undissolved products by only a short extrusion process.

Therefore, it should be suppressed to have the hydrogen bond structure between molecular chains of PVA resin as much as possible before being processed by extrusion method. For this purpose, before the saponification degree of resin in the saponification process, which is an intermediate process of manufacturing PVA resin, becomes 99.9 mol%, The anionic hydrophilic enhancer represented by the following formula (1) and the nonionic hydrophilic enhancer and the plasticizer represented by the following formula (2) are added and impregnated to complete the saponification process.

[Formula 1]

[Formula 2]

In Formula 1 or Formula 2, R ₁ is H, or COOR ₂ , R ₂ is H or an alkyl group having 1 to 20 carbon atoms, M is an alkali metal or alkaline earth metal atom, m is an integer of 1 to 20, n is an integer of 0-20, x is an integer of 0-7, x + y represents the integer of 9-11.

The injected hydrophilicity enhancer uses anionic hydrophilicity enhancer of Formula 1 and nonionic hydrophilicity enhancer of Formula 2 to improve surface tension and contact angle of PVA resin.

In Formula 2, more preferably m is an integer of 3 to 18.

The hydrophilicity enhancer is used in an amount of 0.001 to 0.3 parts by weight, preferably 0.002 to 0.1 parts by weight of the anionic hydrophilic enhancer and the nonionic hydrophilic enhancer, respectively, based on 100 parts by weight of the PVA resin.

When the amount of each hydrophilic enhancer is less than 0.001 part by weight, the effects of surface tension and contact angle are insignificant, and when the amount is more than 0.3 part by weight, transfer to the film surface is likely to cause wrinkles due to adhesion between films during long-term storage. It is preferable to maintain the above range, and in such a case, uniform swelling, dyeing and drying are possible, and thus the polarizer can be manufactured without color deviation.

In addition to using the plasticizer commonly used in the art in order to lower the temperature during processing in addition to the hydrophilic enhancer, in addition to the above role plays a key role in inhibiting hydrogen bonds between the molecular chains of the resin and maintaining the molecular chain spacing. The plasticizer may be used two or more selected from polyhydric alcohols, water and phthalate compounds, specifically, for example, the polyhydric alcohols may be used, such as glycerin, ethylene glycol, propylene glycol, diethylene glycol and triethylene glycol, As the phthalate compound, dibutyl phthalate, diisobutyl phthalate, dioctyl phthalate, diisooctyl phthalate, dinonyl phthalate, diisononyl phthalate and diisodecyl phthalate can be used.

Such plasticizers are used in an amount of 1 to 35 parts by weight, preferably 5 to 25 parts by weight, and water of 30 to 350 parts by weight, preferably 80 to 250 parts by weight, and a phthalate compound, based on 100 parts by weight of the PVA resin. Silver is used in a mixture of 1 to 100 ppm, preferably 3 to 50 ppm.

If the amount of polyhydric alcohols used in the plasticizer is less than 1 part by weight, the effect is insignificant, and if it exceeds 35 parts by weight, the polarizing plate is not completely removed and remains, resulting in deterioration of optical properties and too flexible to handle. Therefore, it is preferable to maintain the above range. In addition, when the amount of water used in the plasticizer is less than 30 parts by weight, thermal decomposition of the polyvinyl alcohol occurs easily, and when it exceeds 350 parts by weight, it is difficult to handle such as transfer in the extruder 30, and the amount of moisture to be removed is too high. Since this inefficient problem occurs, it is desirable to maintain the above range. Moreover, when the usage-amount of a phthalate compound is less than 1 ppm in the said plasticizer, the effect is insignificant, and when it exceeds 100 ppm, since the problem of reducing the permeability of a film arises, it is preferable to maintain the said range.

In particular, polyhydric alcohols such as glycerin and phthalate compounds have lower volatility than water alone, which is more effective in preventing hydrogen bonds in raw materials and increases stability and long-term integrity, and also reduces the adhesion between water-containing raw materials. It will play a role of improving flow.

This role enables a uniform feed of the raw material in the screw feeder 20 during the extrusion process, resulting in a film of uniform thickness.

Meanwhile, the polyvinyl alcohol composite resin composition prepared by impregnating the hydrophilicity enhancer and the plasticizer during the saponification process is extruded using a conventional method used in the art. At this time, when the hydrophilicity enhancer and the plasticizer are added to the multi-screw extruder 30 adjusted to an extrusion temperature of 50 to 150 ° C, preferably 80 to 120 ° C, and melted, the mixture is melted and melted with little generation of undissolved seafood. If the temperature is less than 50 ℃ does not melt and extrusion processing is impossible, if it exceeds 150 ℃ it is good to maintain the above range because the PVA resin is partially thermally decomposed and discolored.

The molten melt is transformed into a film form while passing through the filter 40, the gear pump 50, and the die 60 to remove foreign substances, and then cast to a continuously rotating casting drum 70. At this time, in order to uniformly land the PVA film, a static pressure suction device 80 is installed at the film landing point of the casting drum 70 or a cleaning roll 90 is installed on the film peeling point. Alternatively, install both the static suction unit and the cleaning roll.

Here, the positive pressure suction device 80 is composed of two channels, and is capable of adjusting the suction force, and is designed to apply a uniform suction force to the full width.

Thus, by applying the same suction force adjusted for the film full width, the widthwise constant velocity pinning of the film becomes possible, and in particular, the water vapor generated from the film can be efficiently sucked or condensed between the film surface and the casting drum 70. It can be removed as it will be able to further increase the landing stability.

At this time, the first channel suction force of the positive pressure suction device 80 is maintained at 0.01 ~ 0.5 Kgf / cm ² , preferably 0.05 ~ 0.2 Kgf / cm ² , the second channel suction force is 0.1 ~ 5.0 Kgf / cm ² In this case, the film is preferably landed by maintaining 0.3 to 2.0 Kgf / cm ² .

As described above, when the first channel suction force is lower than 0.01 Kgf / cm ² , the effect as the static pressure suction device 80 is insignificant, and when the first channel suction force is higher than 0.5 Kgf / cm ² , the film is refracted and landed, causing curl. . If the second channel suction force is lower than 0.1 Kgf / cm ² , the effect as a static pressure suction device 80 is insignificant, and if the second channel suction force is higher than 5.0 Kgf / cm ² , the suction force of the first channel is affected and the film is shaken when landing.

The cleaning roll 90 essentially maintains the surface tension with respect to the entire width of the casting drum 70, thereby essentially eliminating the landing nonuniformity due to the difference in surface tension, and in particular, the casting drum 70 with respect to the full width of the PVA film. By allowing the same adhesive force to be applied to enable uniform peeling during peeling, it is possible to fundamentally prevent retardation differences due to partial stretching.

At this time, the cleaning roll 90 has a porosity of 30 to 150%, preferably 50 to 120%, and a pore size of 1 to 500 μm, preferably of 10 to 120 μm, Made from expanded PVA, since water is most suitable as a solvent for surface tension modification without affecting the PVA film. Here, when the porosity of the foamed PVA is lower than 30%, the absorption is low and the effect is insignificant. If the porosity is higher than 150%, the durability of the roll is poor and easily damaged. In addition, when the pore size is lower than 1 μm, it is difficult to form an open cell structure. When the pore size is 500 μm or more, the elastic modulus is low, so that it is difficult to maintain the shape as a roll.

In addition, the cleaning roll has high hydrophilicity and water, alcohol or the like as a solvent having a boiling point of 100 ° C. or less. As the above-mentioned alcohol, methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol and the like are preferable.

In this case, water and alcohols that are solvents may be used alone or in combination.

The cast PVA film is first dried in the casting drum 70, and the moisture contained therein is lowered to 5 to 70 parts by weight based on 100 parts by weight of the PVA resin to be peeled off. In this case, when a large amount of water is removed rapidly for a short time, it is a main cause of film warping due to the moisture content gradient between the casting surface and the atmospheric surface of the PVA film due to the casting characteristics. The force applied to the film during peeling causes film deformation.

The peeled PVA film has a non-uniform moisture content in and out of the process characteristics, which may cause distortion as described above in the next drying process. Therefore, it is possible to stabilize the non-uniform moisture by arranging several drying rolls of small diameter after the casting drum 70.

The PVA film stabilized by passing through the drying roll as a result is a film having a desired moisture content by going through a floating dryer composed of a plurality of air nozzles and maintained at 30 to 180 ℃.

Films dried up to a certain moisture content have edge portions having non-uniform thicknesses cut by a cutter and wound by a roll of a winder. At this time, in order to minimize the deformation of the PVA film and adhesion between the PVA film is wound in a tensionless state.

PVA film prepared according to the present invention as described above is to produce a polarizing PVA film through the swelling, stretching, dyeing, fixing, washing and drying process, looking at each process as follows.

The swelling process can be both dry and wet, but it is important that the PVA film has uniform swelling properties in a short time. If the time is longer, wrinkles are generated on the surface of the PVA film in the stretching process, which is a major cause of color unevenness. Such swelling can be improved by lowering the surface tension of the film. In addition, the stretching process is carried out uniaxial stretching, it is possible to draw in the swelling bath and dye bath, and the dyeing process is carried out using iodine or dichroic dye to uniform dyeing so that color deviation of the final polarizer does not occur It is important to follow.

The fixing process for stabilizing the adsorbed dye is carried out in the presence of boron or boron compounds, washing with water to remove dyes and fixatives remaining on the surface, and water remaining on the surface after washing with water is removed by drying. At this time, when the contact angle of the PVA film is sufficiently low, the moisture does not exist in the form of water during drying, and thus does not cause color deviation.

The polyvinyl alcohol film thus prepared is expected to be useful in the production of polarizing plates by significantly improving the landing stability and peeling stability of the film compared to the prior art, thereby significantly improving physical properties such as polarization, transmittance, and color deviation.

Hereinafter, the present invention will be described in more detail based on the following examples, but the present invention is not limited thereto.

Example 1

In preparing a polyvinyl alcohol film having a saponification degree of 99.98 mol% and a polymerization degree of 2,400, with respect to 100 parts by weight of PVA resin during the saponification process, 11 parts by weight of glycerin as a plasticizer, 150 parts by weight of water, 30 ppm of dioctylphthalate and a hydrophilicity enhancer were used. 0.050 part by weight of dibutylsodium sulfa sulfate and polyoxyethylene were also impregnated with 0.050 part by weight of decyl ether.

The impregnated raw material was introduced into a multi-screw extruder having a temperature of 100 ° C.

In the extruder, the homogeneous mixed molten composite resin composition was transformed into a film while passing through a die, and then discharged into a casting drum at 85 ° C. to perform a first drying process.

At this time, it consists of two channels on the casting drum, the suction force can be adjusted at the same time, the constant pressure suction device is installed so that the uniform suction force is applied to the full width, the first channel is 0.1 Kgf / cm ² , the second channel is The film was landed by adjusting the suction force to 1.3 Kgf / cm ² , and the water vapor generated was removed by suction.

The dried PVA film was prepared by secondary drying in a floating drier, in which a plurality of air nozzles were mounted on the upper and lower sides thereof, and then, after uneven portions of the edge were cut, the wound PVA film was wound on a roll in a winding machine.

Example 2

In the same manner as in Example 1, 100 parts by weight of a PVA resin having a degree of saponification of 99.95 mol and a polymerization degree of 1,700, 9 parts by weight of glycerin as a plasticizer, 100 parts by weight of water, 30 ppm of dioctylphthalate, and a dibutylsodium sulfadier as a hydrophilicity enhancer. PVA film was manufactured by setting the temperature of a multi-screw extruder to 90 degreeC using 0.050 weight part of pates and 0.050 weight part of polyoxyethylene also decyl ether.

Example 3

In the same manner as in Example 1, the PVA film was manufactured by removing the static pressure suction device and installing only a cleaning roll to maintain a uniform surface tension with respect to the casting drum full width on the peeling point of the film.

At this time, the cleaning roll was made of foamed PVA having an open cell structure having a porosity of 90% and a pore size of 90 μm, and water was used as a solvent.

Example 4

In the same manner as in Example 2, the PVA film was prepared by removing the static pressure suction device and installing a cleaning roll to maintain a uniform surface tension with respect to the casting drum full width on the peeling point of the film.

At this time, the cleaning roll was made of foamed PVA having an open cell structure having a porosity of 90% and a pore size of 90 μm, and water was used as a solvent.

Example 5

The PVA film was prepared in the same manner as in Example 1 except that a cleaning roll was installed to maintain a uniform surface tension with respect to the casting drum full width on the peeling point of the film.

At this time, the cleaning roll was made of foamed PVA having an open cell structure having a porosity of 90% and a pore size of 90 μm, and water was used as a solvent.

Example 6

In the same manner as in Example 2, a PVA film was prepared by installing a cleaning roll to maintain a uniform surface tension with respect to the casting drum full width on the peeling point of the film.

At this time, the cleaning roll was made of foamed PVA having an open cell structure having a porosity of 90% and a pore size of 90 μm, and water was used as a solvent.

Comparative Example 1

In the same manner as in Example 1, a PVA film was prepared without installing a static pressure suction device.

At this time, a long striped color deviation of 5 to 10 mm in width and 50 to 100 mm in length due to dyeing unevenness occurred.

Comparative Example 2

A PVA film was prepared in the same manner as in Example 2, without installing a static pressure suction device.

At this time, a long striped color deviation of 3 to 6 mm in width and 30 to 60 mm in length due to dyeing unevenness occurred.

Table 1 summarizes the ingredients used, such as PVA resin, plasticizer and hydrophilicity enhancer used in Examples 1 to 6 and Comparative Examples 1 to 2, the amount used, and whether the components are injected during saponification.

division Resin polymerization degree Resin saponification degree (mol%) Plasticizer (parts by weight) Landing stability improvement device Alcohol water Phthalates (ppm) Static pressure suction device Cleaning roll Example 1 2400 99.98 11 150 30 install Not installed Example 2 1700 99.95 9 100 30 install Not installed Example 3 2400 99.98 11 150 30 Not installed install Example 4 1700 99.95 9 100 30 Not installed install Example 5 2400 99.98 11 150 30 install install Example 6 1700 99.95 9 100 30 install install Comparative Example 1 2400 99.98 11 150 30 Not installed Not installed Comparative Example 2 1700 99.98 9 100 30 Not installed Not installed

Test Example

[Measurement of physical properties]

(1) thickness deviation:

Width in Width-5 cm to Film Full Width (TD)

Extrusion direction thickness-It measured using the film thickness meter (Anlith Thickness Tester Model KG6001A) at 20 degreeC by 20 cm space | interval at the same measurement number as the width direction.

(2) Retardation (R):

R = t × Δn (where t = film thickness (nm), Δn = birefringence)

Retardation (R) was measured using an automatic birefringence measuring device KOBRA WR (Crown Measuring Equipment Co., Ltd.).

Retardation difference (ΔR): The difference between the maximum value and the minimum value of the retardation value is shown at any point of the film full width TD.

(3) transmittance (%) and polarization (%):

Transmittance (%) and polarization rate (%) were measured using UV-Vis spectrophotometer (Shimachusa Model UV 2450) having one 100% polarizer.

(4) color deviation:

A 1 square square meter polarizing plate was measured for color deviation using a Polaris scope (Model 243 from PITIZ INSTRUMENTS).

The extrusion direction, width direction thickness and deviation, retardation deviation, polarization ratio, transmittance and color deviation of the PVA films prepared in Examples 1 to 6 and Comparative Examples 1 to 2 were measured, and the results are shown in Table 2 below. It was.

division Extrusion direction film thickness deviation (㎛) Width direction film thickness deviation (㎛) Retardation deviation △ Re (nm) Polarization rate (%) Transmittance (%) Color deviation Example 1 75 ± 0.4 75 ± 2.7 44 99.7 43.6 none Example 2 75 ± 0.5 75 ± 2.5 42 99.2 42.9 none Example 3 75 ± 3.0 75 ± 0.6 25 99.1 44.1 none Example 4 75 ± 3.6 75 ± 0.5 22 98.8 43.7 none Example 5 75 ± 0.3 75 ± 0.3 13 99.9 44.3 none Example 6 75 ± 0.2 75 ± 0.3 12 99.7 43.8 none Comparative Example 1 75 ± 5.2 75 ± 4.7 103 95.3 42.1 has exist Comparative Example 2 75 ± 6.7 75 ± 5.6 110 93.7 41.7 has exist

As shown in Table 2, the PVA films of Examples 1 to 6 prepared by using the specific apparatus according to the present invention, thickness deviation, retardation difference, polarization rate, transmittance and color compared to Comparative Examples 1 to 2 It was confirmed that the excellence was equal to or higher than the deviation.

In particular, the conventional polarizing film using polyvinyl alcohol acted as a barrier to widening due to the retardation deviation and color deviation, but the PVA film according to the present invention has a considerably reduced thickness deviation and retardation deviation. The effect was confirmed.

As described above, the present invention provides a static pressure suction device at the film landing point of the casting drum, a cleaning roll is installed on the film peeling point, or both the devices are installed in the width direction constant velocity pinning of the film. By enabling efficient removal of water vapor and maintaining a uniform surface tension, the landing and peeling stability of the PVA film can be greatly improved, thereby minimizing variations in thickness and retardation of the film, thereby minimizing polarization and transmittance in manufacturing a polarizing plate. The polyvinyl alcohol film which can improve physical properties, such as a color deviation, compared with the past, can be manufactured. In particular, such polyvinyl alcohol films can be applied as polarizers in various LCD applications.

Claims (4)

In manufacturing the polyvinyl alcohol film which is transformed into a film form while passing through the extruder 30, the filter 40, the gear pump 50, the die 60, and subsequently cast to the casting drum 70, A method of producing a polyvinyl alcohol film, characterized in that a polyvinyl alcohol film is produced by installing a cleaning roll 90 on a rotating casting drum film peeling point. delete The method according to claim 1, The cleaning roll is a method for producing a polyvinyl alcohol film, characterized in that the open cell structure made of high-hydrophilic foamed PVA having a porosity of 30 to 150%, a pore size of 1 to 500 ㎛. The method according to claim 3, The cleaning roll has a high hydrophilicity, and a boiling point contains a solvent having a boiling point of 100 ℃ or less polyvinyl alcohol film production method.

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