KR101811681B1 - Polyvinyl alcohol-based polymer film and method for preparing the same - Google Patents

Abstract

A polyvinyl alcohol-based polymerized film is provided. Wherein the film has a first surface and a second surface facing the first surface, the surface roughness of the first surface is A, the surface roughness of the second surface is B, and the ratio of B / 5, and the surface roughness B is less than 300 nm. When a polyvinyl alcohol-based polymerized film is used in the production of a polarizer, a very excellent polarization degree can be obtained. The present invention also provides a process for producing a polyvinyl alcohol-based polymerized film.

Description

TECHNICAL FIELD [0001] The present invention relates to a polyvinyl alcohol-based polymeric film and a method for producing the same,

The present invention relates to a polyvinyl alcohol-based polymerized film and a method for producing the same. More specifically, the present invention relates to a method for producing a polyvinyl alcohol-based polymerized film without using hot air in the process.

A polarizer is used to polarize general non-polarized natural light into polarized light. The control of light passing through a liquid crystal display (LCD) is based on the utilization of this polarization along with the molecular twist characteristics of the liquid crystal. As liquid crystal displays have increasingly broad applications, the market demand for polarizers has risen sharply. A polyvinyl alcohol (PVA) polymerized film is used as a polarization matrix of the polarizer. Therefore, the quality of the polyvinyl alcohol-based polymer film directly affects the effect of the polarizer.

Generally, in the production of a polarizer, a film is produced with polyvinyl alcohol, and then the film is processed by steps such as stretching, lamination, and coating, thereby achieving the production of a polarizer. As disclosed in JP4433462 and JP2006-342236, a polyvinyl alcohol casting solution is cast on a casting roller and a hot air-blowing method is used for heat transfer for drying.

However, when the surface of the film is uneven or defective, there is a possibility that color unevenness appears in a nonuniform region due to uneven dyeing during the stretching and dyeing process. If the difference in roughness between the two surfaces of the polyvinyl alcohol-based polymer film is very large, that is, if the ratio of both surfaces is too high, there will be color unevenness because there is a difference in the degree of adhesion of iodide ions to both surfaces during dyeing. Further, the influence of the difference in roughness between the both surfaces of the polyvinyl alcohol-based polymer film during the lamination of the triacetate cellulose film will lead to a difference in internal tension of the laminate, thereby causing a warpage of the polarizer You will see a problem. Alternatively, the defect spot will be the focal point of the stress in a subsequent stretching process, and the film may break at the defect spot during stretching. Failure to produce a film with sufficient length can result in loss of process productivity and yield. Therefore, the uniformity of the surface of the polyvinyl alcohol-based polymer film is highly related to the subsequent production of the polarizing film.

The most commonly used factor for evaluating the uniformity of a polyvinyl alcohol-based polymer film is surface roughness. As shown in Fig. 1, the polyvinyl alcohol-based polymerized film 1 has a first surface 1a and a second surface 1b opposing the first surface 1a. The surface roughness A is the surface roughness of the first surface 1a in contact with the casting roller, and the surface roughness B is the surface roughness of the second surface 1b in contact with the air. The surface roughnesses A and B each contribute to the surface of the casting roller and the air-contacted surface. In conventional air-bombardment methods, a non-uniform distribution of temperature due to air movement creates ripples or wrinkles on the surface of the film, or increased air micro-particles increase the surface roughness of the air-contacting surface. As a result, during subsequent stretching, there is a risk of film breakage, an uneven dyeing abnormity, and even the application of polarizer twists.

Therefore, there is still a need to improve the properties of the polyvinyl alcohol-based polymerized film.

The present invention relates to a polyvinyl alcohol-based polymeric film having a first surface and a second surface facing the first surface, wherein the surface roughness of the first surface is surface roughness A and the surface roughness of the second surface is surface roughness B . The ratio of B / A is 0.1 to 5, and the surface roughness B is less than 300 nm.

Further, in order to obtain a polyvinyl alcohol-based polymerized film, the present invention includes: casting a polyvinyl alcohol casting solution on a casting roller; And heating the polyvinyl alcohol casting solution on the casting roller with a wavelength frequency modulation heater to obtain a polyvinyl alcohol-based polymerized film.

The method of the present invention can obtain a polarizer having better quality and better polarization degree while effectively and uniformly distributing temperature, reducing energy consumption, increasing productivity and yield, and avoiding the generation of color unevenness and warping .

1 shows a polyvinyl alcohol-based polymerized film according to the present invention;
2 is a schematic view of a wavelength-frequency modulation heater and a casting roller for a polyvinyl alcohol-based polymerized film according to the present invention;
3 is a schematic diagram of a wavelength frequency modulation heater having a preheating zone, a warming zone, and a buffer zone in accordance with the present invention.

In the following, an embodiment for explaining the present invention in detail is provided. Those of ordinary skill in the art can easily implement the advantages and effects of the present invention based on the teachings of the present specification. Further, the present invention can be performed or applied based on another embodiment. Various embodiments of the disclosure may be modified or changed in accordance with other implementations and applications without departing from the essence of the invention.

The structure, ratio, and size of the drawings attached hereto are not intended to limit the limitations that may be performed in the present invention, but to provide a description of the disclosure of the present specification do. Accordingly, these figures have no substantial technical significance. Modifications of any structure, change of ratio or adjustment of size are all included within the scope of the technical disclosure disclosed in the present invention without affecting the object of the present invention and the effect produced. At the same time, terms such as "top,"" bottom, ""front,"" rear ", and "one ", as used herein, are for the sake of clarity and do not limit the scope of the invention. Without intending to intentionally alter the technical content, it is believed that changes or adjustments of relative relationships are also included within the scope of the invention to be practiced.

The production of the polyvinyl alcohol-based polymerized film used in the present invention is obtained by formulating a polyvinyl alcohol casting solution, casting a polyvinyl alcohol casting solution on a casting roller, and drying.

Specifically, in the method for producing a polyvinyl alcohol-based polymerized film of the present invention, the polyvinyl alcohol casting solution mainly comprises polyvinyl alcohol, a plasticizer and water. The polyvinyl alcohol can be obtained by polymerizing a vinyl ester-based resin monomer to obtain a polyvinyl ester-based resin, and then saponifying. Examples of such polyvinyl ester monomers include, but are not limited to, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl caprylate, and preferably vinyl acetate. Further, it is also possible to use an olefin compound (e.g., ethylene, propene and butene), or an acrylate ester derivative (e.g., acrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, And copolymers formed by copolymerization of the above-mentioned vinyl ester-based monomers can also be used. In general, in order to obtain the desired optical properties, the degree of saponification of the polyvinyl alcohol-based resin is 90% or more, and more preferably 99% or more. The degree of polymerization of the polyvinyl alcohol-based resin is 800 to 10,000. When the degree of polymerization is 2200 or more, it has better processability. If the degree of polymerization is more than 10,000, it is disadvantageous in dissolution. If the degree of polymerization is less than 800, it is disadvantageous in stretching due to low strength.

Generally, when the content of the polyvinyl alcohol-based resin in the polyvinyl alcohol casting solution used is insufficient, the viscosity of the casting solution is too low and the dry loading is too large. This leads to a reduction in efficiency of film formation. On the other hand, if the content of the polyvinyl alcohol-based resin is too high, the polyvinyl alcohol-based resin can hardly be decomposed, and the viscosity of the casting solution is too high. The resulting insoluble material will be in a gel state, which will affect the formation of a uniform film. Therefore, in the polyvinyl alcohol casting solution used in the method of the present invention, the content of the polyvinyl alcohol-based resin is usually 10 parts by weight to 50 parts by weight, preferably 15 parts by weight to 40 parts by weight, 20 to 30 parts by weight.

In the above-mentioned polyvinyl alcohol casting solution, it may also contain a plasticizer besides a polyvinyl alcohol-based resin in order to improve the processability of film formation. Examples of commonly used plasticizers include polyalcohols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, and glycerol, preferably ethylene glycol and glycerol. If the content of the plasticizer is insufficient, the formed polyvinyl alcohol-based polymerized film can easily form crystals, which may affect the dyeing effect in subsequent processing. On the other hand, if the content of the plasticizer is too high, the mechanical properties of the polyvinyl alcohol-based polymer film may be damaged. Therefore, the amount of the polyalcohol plasticizer to be added to the polyvinyl alcohol resin is usually 3 parts by weight to 30 parts by weight, preferably 7 parts by weight to 20 parts by weight, more preferably 9 parts by weight to 15 parts by weight .

In the above-described method, a polyvinyl alcohol-based resin solution (together with an optionally added plasticizer and a release agent) After forming a polyvinyl alcohol casting solution, a filter was used for filtration. A gear pump and a T-type die coater are then used to cast the polyvinyl alcohol casting solution onto a casting roller having a width of 2 meters (meters) to 10 meters, preferably 4 meters to 6 meters. Thereafter, the film is dried at a high temperature to form a polyvinyl alcohol-based polymer film having a thickness of 10 m to 100 m, and the polyvinyl alcohol-based polymer film is peeled from the casting roller. Then, a polarizer is produced by using the following conventional technique. The polyvinyl alcohol-based polymer film is stretched at a speed of 5 meters / minute, and is wetted with water at 25 to 40 DEG C, and at 25 to 35 DEG C (having 0.05 g / L of iodine and 6 g / L of potassium iodide ) Aqueous iodine compound solution and uniaxially stretched in a water tank (with an aqueous solution of 5 g / L potassium iodide and 8 g / L boric acid) at 30 ° C to 60 ° C (5 g / L potassium iodide And an aqueous solution of 10 g / L boric acid), dried, laminated with a triacetate cellulose (TAC) film, and dried in an oven at 55 ° C to 70 ° C. Total elongation in the entire process may be at least six times.

There is no particular limitation on the speed of the casting roller. However, in general, the lower limit of the speed is 1 m / min or more, preferably 3 m / min or more, and more preferably 4 m / min or more. In general, the upper limit of the speed is 20 m / min or less, preferably 15 m / min or less. If the speed of the roller is too low, the productivity may be lowered. If the speed of the roller is too high and the heating is insufficient or uneven, the quality of the resultant polyvinyl alcohol-based polymer film may be deteriorated.

The method for drying the polyvinyl alcohol-based polymerized film of the present invention includes directly using a wavelength frequency-modulated heater for drying by heating. In a wavelength-frequency modulation heater, an infrared ray is generated by an emitter and thermal energy is transmitted through a light wave. The irradiated object absorbs thermal energy according to "molecular resonance theory ". The advantage of wavelength frequency modulation heaters is that heat is not limited to the heat transfer medium by heating by quartz and utilizing wavelength-based heating characteristics. In addition, the mirror reflector of the wavelength frequency modulation heater allows to achieve higher utilization efficiency of the thermal energy (which can be up to 95%), while the non-transparent quartz tube or ceramic electric heating plate has a heating efficiency of only 50% to 75% Respectively. In addition, the wavelength frequency modulation heater does not affect the ambient temperature, thereby saving electrical energy consumption.

In one embodiment of the invention, the wavelength frequency modulation heater usually has a plurality of wavelength frequency modulated heating tubes, each heating tube having a body and a quartz tube. The temperature of the main body can be raised to 700 to 800 占 폚. The periphery of the body is covered with a quartz tube and sealed. Cryogenic air is introduced between the body and the quartz tube to reduce the surface temperature of the quartz tube from 110 캜 to 130 캜. When the temperature of the body is raised to 700 to 800 占 폚, the wavelength range for heating by the wavelength frequency modulation heater is 2 占 퐉 to 5 占 퐉, and the generated wavelength of 3 占 퐉 is most suitable for adsorption of water molecules.

By heating the polyvinyl alcohol casting solution on the casting roller at an infrared wavelength to obtain a polyvinyl alcohol-based polymerized thin film, the polyvinyl alcohol casting solution Moisture begins to drift internally, but the polyvinyl alcohol casting solution is not the first to dry to form a crust. Wherein the polyvinyl alcohol based polymeric film comprises a first surface and a second surface facing the first surface, the first surface contacting the casting roller and having a surface roughness of surface roughness A, the surface of the second surface The roughness is referred to as surface roughness B, the ratio of surface roughness B / surface roughness A is 0.1 to 5, and B is less than 300 nm. Then, the polyvinyl alcohol-based polymerized film is peeled from the casting roller.

As shown in Fig. 2, the general arrangement in which the wavelength frequency modulation heater 3 is installed has a heating space. The heating space may accommodate the casting roller 4. The wavelength frequency modulation heater 3 includes a plurality of wavelength frequency modulation heating tubes 31 which are disposed on the inner surface of the heating space and surround the casting roller 4. A radiation zone (5) is located between the wavelength frequency modulation heater (3) and the casting roller (4). A polyvinyl alcohol casting solution 2 is provided by a casting device such as a T-type mold coater 6 and is cast on a casting roller 4 to form a polyvinyl alcohol based polymeric film 1.

The method for drying the polyvinyl alcohol-based polymerized film of the present invention does not use the high temperature air used in the ordinary drying method. Specifically, the wind speed of the radiation zone 5 is less than 0.5 m / s, preferably less than 0.01 m / s. That is, a wind speed in the range of 0.01 m / s to 0.5 m / s can be performed, and particularly when the speed is close to 0 m / s or only the wind speed generated by the rotation of the roller comes out, ≪ / RTI > In addition, the amount of suspended particles having a diameter of 0.5 탆 or more in the radiation zone 5 is less than 1000 particles / cubic meter, more preferably less than 500 particles / cubic meter, Preferably less than 200 particles / cubic meter. Therefore, when the surface of the polyvinyl alcohol-based polymer film is dried on the casting roller, the surface of the polyvinyl alcohol-based polymer film which is in contact with the air is not affected by irregular wind pressure as compared with a conventional drying method using hot air. The surface roughness is less than 300 nm.

In order to further increase the drying efficiency of the wavelength frequency modulation heater, the distribution of the heating temperature can be performed. As shown in Figure 3, the temperature control zone of the wavelength frequency modulation heater can be divided into three thermostatic-controlling zones. The region of the heating space from where the polyvinyl alcohol casting solution is cast to the point where the polyvinyl alcohol based polymer film is peeled includes a pre-heating zone 3a, a warming zone 3b, And a buffer zone 3c. The temperature of the preheating zone 3a is regulated within the range of 85 ° C to 130 ° C. The temperature of the warming zone 3b is regulated within the range of 95 캜 to 150 캜. The temperature of the buffer zone 3c is controlled within the range of 55 캜 to 100 캜. The preferred temperature range of the preheating zone 3a is 95 캜 to 110 캜. The preferred temperature range of the warming zone 3b is 95 캜 to 120 캜. The preferred temperature range of the buffer zone 3c is 60 占 폚 to 75 占 폚. In addition, for example, a region of the casting roller 4 at a periphery of the casting roller 4 in the range of 0 to 270 degrees (where the polyvinyl alcohol casting solution is cast at 0 degrees) 5), the preheating zone 3a may be an area between 0 and 90 degrees, the warming zone 3b may be an area between 90 and 180 degrees, and the buffer zone 3c may be an area 180 degrees But it is not limited thereto. The range of each temperature-sensitive control zone may be distributed as needed. By this type of drying method, drying by heating and even temperature distribution can be made to improve productivity. This can also reduce the surface roughness of the surface of the polyvinyl alcohol-based polymer film in contact with air.

Accordingly, the ratio of the surface roughness B / the surface roughness A of the obtained polyvinyl alcohol-based polymer film to the surface roughness B / the surface roughness A is 0.1 to 5, and the surface roughness B of the surface of the polyvinyl alcohol-based polymer film in contact with air is less than 300 nm . Furthermore, the ratio of surface roughness B / surface roughness A is 0.3 to 3.

Example

The following examples are used to further illustrate the features and effects of the present invention.

a) Measurement of illuminance

The surface roughness of the surface of the polyvinyl alcohol-based polymer film in contact with the casting roller was varied depending on the roughness of the casting roller (i.e., less than 100 nm). Based on the standard image quality of JIS B 0601-2001, the surface roughness of the air-contact surface was measured using an optical 3D surface profile scanner, which was a non-contact confocal plus the interferometric technique. The model number of the scanner was SENSOFAR PLu.

b) the degree of polarization, transmittance, and color stain,

I. Polarizability and transmittance of the polarizer were measured using a spectrophotometer (U-4100, manufactured by Hitachi). The polarization degree Py was calculated from the parallel transmission rate T ₀ and the vertical transmission rate T ₉₀ of the following equation:

Py = [(T ₀ -T ₉₀ ) / (T ₀ + T ₉₀ )] ^1/2 100

II. Visual detection at the right-angle intersection is used to determine the amount of 1 m ² of color blot in the polarizer sample.

c) Measurement of distortion

A 20 cm x 20 cm polarizer sample was obtained, placed flat on a desk, and the height of the warp at four edges was measured. The highest value was recorded.

Example  One

Polyvinyl alcohol polymerization resin (100 parts by weight) and glycerin (11 parts by weight) having a degree of polymerization of 2400 and an alkalinity of 99.9% were added to water and the temperature was raised to 100 占 폚. The solution was stirred for dissolution and adjusted to a polyvinyl alcohol polymerization aqueous solution (i.e., a polyvinyl alcohol casting solution) having a concentration of 25 parts by weight. The aqueous solution was filtered using a filter. Thereafter, using a gear pump and a T-type mold coating machine, in a heating space (having a width of 4 meters) Polyvinyl alcohol casting solution was cast on a casting roller, wherein the casting roller speed was 4 m / min at a temperature of 95 캜. The area of the heating space from where the polyvinyl alcohol casting solution was cast to where the polyvinyl alcohol based polymer film was peeled was divided into a preheating zone, a warming zone and a buffer zone. Each zone occupied an area of 90 degrees of the casting roller. The casting solution was dried to form a polyvinyl alcohol-based polymer film. The preheating zone, the warming zone, and the buffer zone were heated to a temperature of 3 [micro] m using a wavelength frequency modulation heater (NGK INSULATORS, LTD. Lt; 0 > C, 110 [deg.] C and 90 [deg.] C. Drying process No hot air or blown air was used. The actual wind speed was 0.5 m / s. The amount of suspended particles having a diameter of 0.5 mu m or more was 120 particles / cubic meter. Then, the polyvinyl alcohol-based polymer film was peeled from the casting roller and dried using a heating roller (at 85 캜) and an oven (at 120 캜) to obtain a polyvinyl alcohol-based polymer film having a thickness of 60 탆 Respectively. Ten samples each having a size of 20 cm x 20 cm were obtained at arbitrary positions of the polyvinyl alcohol-based polymer film. Surface roughness B in contact with air was measured at 43 ㎚ and surface roughness A in contact with materials was measured at 30.5 ㎚.

The polyvinyl alcohol-based polymer film was stretched at a speed of 1 m / min and wetted with water at 30 캜. At 30 캜, an iodine compound solution (containing 0.05 g / L of iodine and 6 g / L of potassium iodide) And uniaxially stretched in a water tank (containing an aqueous solution of 5 g / L of potassium iodide and 8 g / L of boric acid) at 60 DEG C (5 g / L potassium iodide and 10 g / L boric acid ), Laminated with a triacetate cellulose (TAC) film, dried in an oven at 60 ° C and cross-linked to produce a polarizer. Total elongation was more than 5 times in the whole process.

Example  2

A polyvinyl alcohol-based polymer film for evaluation was produced using the same process as in Example 1, except that the casting roller speed was set at 6 m / min. Other analytical data are shown in Table 1 below.

Example  3

A polyvinyl alcohol-based polymer film for evaluation was produced using the same process as in Example 1, except that the casting roller speed was 8 m / min. Other analytical data are shown in Table 1 below.

Example  4

A polyvinyl alcohol-based polymer film for evaluation was produced using the same process as in Example 1, except that the degree of polymerization of the polyvinyl alcohol-polymerized resin was 1700 and the casting roller speed was 8 m / min. Other analytical data are shown in Table 1 below.

Example  5

A polyvinyl alcohol-based polymer film for evaluation was produced using the same process as in Example 1, except that the degree of polymerization of the polyvinyl alcohol-polymerized resin was 3500 and the casting roller speed was 8 m / min. Other analytical data are shown in Table 1 below.

Comparative Example  One

A polyvinyl alcohol-based polymer film for evaluation was produced using the same process as in Example 1, except that the casting roller speed was 8 m / min and the hot air speed was 10 m / s. Other analytical data are shown in Table 1 below.

Comparative Example  2

Evaluation was carried out using the same process as in Example 1, except that the casting roller speed was 8 m / min, the wavelength frequency modulation heater (shortened by IR) was not used, and hot air was additionally used at a rate of 10 m / s A polyvinyl alcohol-based polymeric film was prepared. Other analytical data are shown in Table 1 below.

Comparative Example  3

Except that the casting roller speed was set to 8 m / min and the wavelength frequency modulation heater (shortened by IR) and the high-temperature air were not used, the polyvinyl alcohol polymerized film for evaluation was produced using the same process as in Example 1 Respectively. Since heat was not transferred to the film, the film could not be dried and peeled off. The illuminance, the degree of polarization and the color unevenness of the peeled film were measured, but actual data could not be obtained due to the undried film.

Table 1 lists the evaluation results of Example 1-5 and Comparative Example 1-3.

Degree of polymerization Roller speed
(m / min) IR
(℃ ¹ ) Hot air Illumination B (nm) Illuminance ratio
(B / A ² ) Polarization degree
(%) Permeability
(%) Warp
(Mm) Color blur (block)
) Example 1 2400 4 110 NA 43 1.410 99.8 42.8 One 0 Example 2 2400 6 110 NA 52 1.705 99.8 42.6 2 0 Example 3 2400 8 110 NA 66 2.164 99.6 42.6 2 0 Example 4 1700 8 110 NA 62 2.033 99.2 42.7 2 0 Example 5 3500 8 110 NA 68 2.230 99.5 42.6 2 0 Comparative Example 1 2400 8 110 10 m / s 143 4.689 99.4 42.4 5 8 Comparative Example 2 2400 8 NA 10 m / s 162 5.311 98.9 42.3 7 12 Comparative Example 3 2400 8 NA NA NA NA NA NA NA NA

footnote 1. The temperature of the wavelength frequency modulation heater (abbreviated as IR) is the temperature of the warming zone 3b of FIG.

Footnote 2. Surface roughness A is the surface roughness of the polyvinyl alcohol-based polymer film in contact with the casting roller. The surface roughness B is the surface roughness of the polyvinyl alcohol-based polymer film in contact with air.

Based on this, the surface area A is the surface roughness of the surface of the polyvinyl alcohol-based polymer film in contact with the casting roller. The surface region B is the surface roughness of the surface of the polyvinyl alcohol-based polymer film in contact with air. The ratio of surface roughness B / surface roughness A is 0.1 to 5. The surface roughness B of the obtained polyvinyl alcohol-based polymer film (in contact with air) is less than 300 nm.

The above embodiments are used to illustrate the principles and effects of the present invention and are not intended to limit the present invention. The embodiments can be modified by those skilled in the art without departing from the spirit and scope of the present invention. Accordingly, the scope of the present invention is the same as the appended claims.

Claims (8)

Casting a polyvinyl alcohol casting solution onto a casting roller; And
After the casting of the polyvinyl alcohol casting solution, without using hot air And heating the polyvinyl alcohol casting solution on the casting roller with a wavelength frequency modulation heater to obtain a polyvinyl alcohol-based polymerized film,
Wherein the wavelength frequency modulation heater generates infrared light by an emitter for heating and the wavelength frequency modulation heater has a heating space for receiving the casting roller and a radiation zone is disposed between the inner surface of the heating space and the casting roller , And the radiation zone Wherein the heating space of the wavelength frequency modulation heater has a pre-heating zone having a temperature of 85 ° C to 130 ° C, a temperature of 95 ° C to 150 ° C Wherein the buffer zone is divided into a warming zone and a buffer zone having a temperature of 55 ° C to 100 ° C.
The method according to claim 1,
Wherein the casting roller has a rotation speed of 4 m / min to 20 m / min.
The method according to claim 1,
Wherein the air velocity in the radiation zone is not more than 0.01 m / s.
The method according to claim 1,
Wherein the radiation zone has suspended particles having a diameter of at least 0.5 mu m thereon at less than 200 particles / cubic meter.
The method according to claim 1,
Wherein the wavelength frequency modulation heater has a wavelength in the range of 2 탆 to 5 탆 for heating.
The method according to claim 1,
Wherein the polyvinyl alcohol based polymeric film comprises a first surface and a second surface facing the first surface, the first surface having surface roughness A, the second surface having surface roughness B, the surface roughness B / Surface roughness A is 0.1 to 5, and the surface roughness B is less than 300 nm.
The method according to claim 6,
Wherein the ratio of the surface roughness B / the surface roughness A is 0.3 to 3.
The method according to claim 1,
Wherein the polyvinyl alcohol-based polymeric film has a thickness of 10 m to 100 m.

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