KR101332381B1 - Polyvinyl alcohol-based polymeric film and method for preparing same - Google Patents

Abstract

The present invention relates to a polyvinyl alcohol-based polymer film, characterized in that it comprises a phase difference reducing agent represented by the formula (1), the polyvinyl alcohol-based polymer film according to the present invention is minimized in-plane retardation and the phase difference in the thickness direction It is optically close to isotropic and is excellent in yield and cost since it does not require the removal of both ends of the film due to retardation.

Description

TECHNICAL FIELD [0001] The present invention relates to a polyvinyl alcohol-based polymer film and a method for producing the same. BACKGROUND ART [0002]

The present invention relates to a polyvinyl alcohol-based polymer film having a very low retardation, a manufacturing method thereof, and a polarizing film using the same.

A polarizing plate having a function of transmitting and blocking light generally has a structure in which a protective film such as a triacetylcellulose (TAC) film, acetic acid-butyric acid cellulose (CAB) film or the like is adhered to both surfaces of a polarizing film derived from a polyvinyl alcohol- . At this time, the polarizing film may be monoaxially stretched after dyeing a polyvinyl alcohol (PVA) polymer film, or uniaxially stretched or uniaxially stretched while being dyed, and then dyed. A fixing treatment with a compound and then a drying treatment.

As disclosed in Korean Patent No. 818135, a PVA film is produced by extruding a PVA-containing raw material solution, casting it on a heated drum or a steel belt, and then drying it on a drum or a steel belt, Has come. However, when using a steel belt, the belts should be connected to each other in the MD direction (longitudinal direction) of the belt. When the raw material solution is discharged on the belt and dried on it, optical defects (phase difference, and Refractive index and transmittance nonuniformity).

Due to the problems of the steel belt, the method of using a drum is the most widely used, but in this case, the drum is very large (diameter) because the film must be dried on the drum until the PVA film can be peeled off. Since fine stretching occurs at the time of peeling from the drum, optical defects (phase difference) also occur.

When the optical defect occurs as described above, due to the phase difference scattering in the TD direction (lateral direction or width direction), a process of slitting and removing up to 30% of both ends of the film should be performed. Is not recyclable for optics, resulting in relatively large losses in yield and cost.

In addition, in order to be applied to a polarizing plate for a product such as a liquid crystal monitor or a liquid crystal television that requires high contrast and a clear image, the optical isotropic property of the PVA film is further required, but the conventional PVA film has a degree of about 30 to 80 nm. Since a relatively large thickness direction retardation (Rth) may cause problems such as color distortion in the side, a thickness direction retardation is also urgently required to reduce the PVA film.

KR 10-0818135 B1 Mar 31, 2008

Accordingly, it is an object of the present invention to provide a polyvinyl alcohol polymer film having a very low phase difference, including a phase difference reducing agent, a polarizing film using the same, and a method of easily preparing the film.

In order to achieve the above object,

It provides a polyvinyl alcohol-based polymer film and a polarizing film obtained by dyeing and stretching the polyvinyl alcohol-based polymer film, characterized in that it comprises a phase difference reducing agent represented by the following formula (1):

[Formula 1]

In Formula _1, R 1 is hydrogen or C _{12 -18} alkyl group, R ₂ to R ₄ are each independently C _{1 -3} alkyl.

The present invention also provides a method for producing the polyvinyl alcohol polymer film.

As described above, according to the present invention including the phase difference reducing agent in the polyvinyl alcohol-based polymer film, the in-plane retardation and the phase difference in the thickness direction of the polyvinyl alcohol-based polymer film can be minimized to obtain a more optically isotropic film. It does not require removal of both ends of the film, which is excellent in yield and cost.

1 is a process schematic showing one embodiment of a method for producing a polyvinyl alcohol-based polymer film according to the present invention.
Figure 2 is a process schematic showing one embodiment of a method for producing another polyvinyl alcohol-based polymer film according to the present invention.

Polyvinyl alcohol-based polymer film according to the invention is characterized in that it comprises a phase difference reducing agent represented by the following formula (1):

[Formula 1]

In Formula 1,

R ₁ is hydrogen or C _{12 -18} alkyl group, preferably an alkyl C _{12 -16} alkyl group, more preferably a C _{14 -16,}

R ₂ to R ₄ each independently is C _{1 -3} alkyl, more preferably methyl or ethyl.

As used herein, the term "alkyl" refers to a linear or branched saturated hydrocarbon radical chain. Specific examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-pentyl, isopentyl, hexyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, hepta Decyl and octadecyl, and the like, but are not limited thereto.

The retardation reducing agent is a material used to reduce the optical anisotropy of the film, it is preferable that the material itself does not have a structure such as a disk-like or rod-shaped containing an aromatic group in the structure of the compound, in particular represented by the formula (2) Compounds are preferred. When an aromatic group rich in electrons is included in the structure of a compound which is a phase difference reducing agent included in the film, a phase difference due to a speed difference of light propagating in the film may occur, which may cause optical anisotropy.

(2)

The retardation reducing agent may be used in an amount of 0.1 to 5 parts by weight, preferably 0.1 to 3 parts by weight, more preferably 0.1 to 1.0 parts by weight based on 100 parts by weight of the polyvinyl alcohol polymer film. If the content of the phase difference reducing agent is less than 0.1 parts by weight, the desired phase difference reduction effect cannot be obtained. If the content of the phase difference reducing agent is greater than 5 parts by weight, the optical properties are deteriorated due to a decrease in transmittance due to an increase in haze.

The polyvinyl alcohol polymer film of the present invention containing the retardation reducing agent has an in-plane retardation (Ro) value of 0 to 50 nm, -10 to 25 nm, preferably -5 to 10 nm, more preferably 0 to 10 nm, and the phase difference (Rth) value in the thickness direction is -10 to 80 nm, -10 to 40 nm, preferably -10 to 25 nm, and more preferably -10 to 10 nm.

When the polyvinyl alcohol-based polymer film has an in-plane retardation value in the above range and a retardation value in the thickness direction, the polyvinyl alcohol-based polymer film may be more optically isotropic, and may not require a step of removing both ends of the film due to the retardation. It is also advantageous in terms of cost.

One embodiment of a method for producing a polyvinyl alcohol-based polymer film according to the present invention is shown in Figure 1 as a process schematic.

Also, Another embodiment of a method for producing a polyvinyl alcohol polymer film according to the present invention is shown in Figure 2 as a process schematic.

Referring to Figure 1, the production method of the polyvinyl alcohol-based polymer film of the present invention is a raw material solution consisting of polyvinyl alcohol having a saponification degree of 99 mol% or more, a polymerization degree of 1700 or more, a phase difference reducing agent, a plasticizer, a releasing agent, and a solvent of Chemical Formula 1 ( 10) after extruding through the extruder 110, characterized in that it comprises the supply and drying on the casting drum 120.

In addition, referring to Figure 2, another method for producing a polyvinyl alcohol-based polymer film according to the present invention is prepared by extruding the raw material solution 10 through an extruder 210 and then coated and dried on a support film 220 can do.

The polyvinyl alcohol used in the present invention may have a saponification degree of 99 mol% or more, preferably 99.5 mol% or more, and a degree of polymerization of 1,700 or more, preferably 1,700 to 5,000. If the polyvinyl alcohol has a saponification degree of less than 99 mol%, the durability of the polarizing plate obtained by dyeing and stretching polyvinyl alcohol is lowered. If the polyvinyl alcohol has a degree of polymerization of less than 1,700, the stretching process for manufacturing the polarizing plate is performed. Sufficient stretching is impossible and the optical characteristic falls.

The polyvinyl alcohol-containing raw material solution used in the present invention includes polyvinyl alcohol, a phase difference reducing agent, a plasticizer, a releasing agent, and a solvent of Formula 1, specifically, after dissolving polyvinyl alcohol in a solvent, Formula 1 It is obtained by adding and mixing a phase difference reducing agent, a plasticizer, and a release agent, and further kneading them in an extruder.

The polyvinyl alcohol may be used in an amount of 10 to 60% by weight, preferably 20 to 50% by weight, in consideration of uniform solubility in the solution.

As the solvent, dimethyl sulfoxide, dimethylformamide, water, tetraethylene glycol, diethyltriamine or a mixture thereof may be used, preferably water may be used, and uniform dissolution of polyvinyl alcohol It may be used in an amount suitable to achieve

Plasticizers serve to weaken the hydrogen bonding during film formation to improve processability, and polyhydric alcohol compounds such as glycerin, ethylene glycol, polyethylene glycol, and mixtures thereof can be used as plasticizers. In particular, it is preferable to use glycerin which has good affinity for polyvinyl alcohol and can minimize the occurrence of optical deviation. The plasticizer may be used in an amount of 5 to 20 parts by weight based on 100 parts by weight of the polyvinyl alcohol.

The release agent serves to improve the peelability when peeling the film from the drum, or to improve the peelability when peeling off the supporting film while winding the final dried film, and may be an amphoteric surfactant, a cationic surfactant, or a binder. Mild surfactants or mixtures thereof can be used as the release agent. Specific examples of the amphoteric surfactant include laurylbetaine, stearylbetaine, lauryldimethylamine oxide and mixtures thereof. Specific examples of cationic surfactants include lauryltrimethylene ammonium, stearyltrimethylene ammonium, Coconut amine acetate, stearylamine acetate, and mixtures thereof,

Specific examples of the nonionic surfactant include alkyl ether types such as polyoxyethylene lauryl ether and polyoxyethylene oleyl ether; Alkyl phenyl ether type such as polyoxyethylene octyl phenyl ether; Alkyl ester types such as polyoxyethylene laurate; Alkylamine type such as polyoxyethylene lauryl amino ether; Alkyl amide types such as polyoxyethylene lauric acid amide; Polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether; Alkanoyl amide types such as lauric acid diethanolamide and oleic acid diethanolamide; Allylphenyl ether type such as polyoxyethylene allyl phenyl ether; And mixtures thereof. The release agent may be used in an amount of 0.01 to 1 part by weight based on 100 parts by weight of the polyvinyl alcohol.

The plasticizer and the release agent which may be added to the solution are preferably added at the same temperature as the solution in consideration of the uniform dissolution and saponification degree of the polyvinyl alcohol required in the present invention, wherein the temperature is from room temperature to 150 ° C. desirable.

Referring to FIG. 1, by one method of the present invention, the polyvinyl alcohol-containing raw material solution 10 of the above-described composition is extruded through an extruder 110, in particular a twin extruder. Bubbles generated during the dissolution process can be completely removed, and prior to feeding onto the casting drum 120, the extrudate of the polyvinyl alcohol-containing raw material solution can be passed through a filter, preferably for removing foreign matter (FIG. 1). Not shown). The temperature of the extruder 120 may be 95 to 150 ℃.

The extrudate of the polyvinyl alcohol-containing stock solution is then fed onto the casting drum 120 for coating or sheeting, wherein the stock solution extrudate is conventionally passed through a die on a casting drum heated to about 80 to 100 ° C. It can be supplied by the method and coated or sheeted. Casting drum 120 used in the present invention may have a diameter of 1 to 5M, it may be made of a metal material selected from nickel, chromium, copper, stainless steel and alloys thereof.

Casting drum (120) The polyvinyl alcohol-containing raw material solution coating layer 11 formed thereon is pre-dried on the casting drum 120, and the pre-dried polyvinyl alcohol-based polymer film 12 is cast using a stripper roll 130. After gently peeling from the drum 120, the desired final polyvinyl alcohol polymer film can be obtained by drying and winding in multiple stages at a temperature of 150 DEG C or lower while passing through several drying rolls and a floating dryer (FIG. 1 not shown).

In addition, referring to Figure 2, according to another method of the present invention, the extrudate of the polyvinyl alcohol-containing raw material solution can be supplied on the support film 220 instead of the casting drum to be coated or sheeted In this case, like the method of using a casting drum, the polyvinyl alcohol-containing raw material solution 10 can be completely extruded through the extruder 210, in particular a twin extruder to remove the bubbles generated during the dissolution process, Prior to feeding the extrudate of the polyvinyl alcohol-containing raw material solution onto the support film 220, the extrudate of the polyvinyl alcohol-containing raw material solution may be passed through a filter, preferably for removing foreign matter (FIG. 2). Not shown).

In this case, as the support film 220, various general films such as polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, polycarbonate (PC) film, triacetate cellulose (TAC) film, or acryl film All can be used, and it is preferable that it is a film whose roughness is 5 micrometers or less. It is not preferable to use a support film having a roughness of more than 5 μm because the roughness of the support film is transferred to the polyvinyl alcohol film to cause optical problems such as haze rise and transmittance decrease.

In this case, the coating may be performed by die coating, gravure coating, gap coating, or layer bar coating.

The polyvinyl alcohol-containing raw material solution coating layer 11 formed on the support film is dried while passing through the floating dryer 230, and the desired final poly is obtained by peeling and winding the dried coating film with the support film 220. The vinyl alcohol polymer film 12 can be obtained. The temperature of the floating dryer 230 may be 40 to 150 ° C. The temperature of the floating dryer 230 may be appropriately adjusted according to the thickness of the support film 220.

The polyvinyl alcohol polymer film of the present invention prepared by the above methods may have a thickness of 20 to 200 ㎛ and a water content of 3 to 10%, in-plane retardation of 0 to 50 nm and a thickness of -10 to 80 nm It has a very low phase difference such as a direction phase difference.

Further, the present invention can produce a polarizing film from the above polyvinyl alcohol polymer film by a conventional method such as dyeing and stretching the above polyvinyl alcohol polymer film and then drying. At this time, the dyeing and stretching may be performed in any order or simultaneously.

The thus obtained polarizing film of the present invention has a very uniform and excellent polarization performance.

As described above, according to the present invention including the phase difference reducing agent in the polyvinyl alcohol-based polymer film, the in-plane retardation and the phase difference in the thickness direction of the polyvinyl alcohol-based polymer film can be minimized to obtain a more optically isotropic film. It does not require removal of both ends of the film, which is excellent in yield and cost.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments for better understanding of the present invention. However, the following examples are intended to illustrate the present invention, but the scope of the present invention is not limited to or by the following examples.

Example  One

After dissolving polyvinyl alcohol having a saponification degree of 99.99 mol% and a polymerization degree of 3,000 in water, a polyvinyl alcohol-containing raw material solution was prepared by adding and mixing a phase difference reducing agent, a glycerin plasticizer and a surfactant represented by the following Chemical Formula 2. In this case, polyvinyl alcohol was used in an amount of 30% by weight in the solution, and a phase difference reducing agent, a plasticizer, and a release agent were used in amounts of 0.1 part by weight, 12 parts by weight, and 0.2 parts by weight with respect to 100 parts by weight of polyvinyl alcohol, respectively.

(2)

The raw material solution was extruded at 120 ° C. through a twin screw extruder and then the extrudate was passed through a filter and then fed through a die onto a casting drum heated to 95 ° C. for coating.

The polyvinyl alcohol polymer film pre-dried on the casting drum was gently peeled from the casting drum using a stripper roll, and then polyvinyl was dried and wound at a temperature of 40 to 150 DEG C while passing through several drying rolls and a floating dryer. An alcoholic polymer film was obtained. The average thickness of the prepared polyvinyl alcohol polymer film was 75 μm.

Example  2 and 3

As shown in Table 1 below, except that the amount of the phase difference reducing agent was changed, the same method as in Example 1 was carried out to obtain a polyvinyl alcohol polymer film.

Example  4

An extrudate of the polyvinyl alcohol-containing raw material solution is coated by a die on a polyethylene terephthalate (PET) support film having a roughness of 0.02 μm instead of a casting drum and coated, and a pre-dried polyvinyl alcohol polymer film is floated on the support film. A polyvinyl alcohol-based polymer film was obtained in the same manner as in Example 1 except that the multi-stage dried and dried coating film was peeled off from the support film while winding through a dryer.

Comparative Example  One

As shown in Table 1, except that the phase difference reducing agent was not added, the same method as in Example 1 was carried out to obtain a polyvinyl alcohol-based polymer film.

Comparative Example  2

As shown in Table 1, a polyvinyl alcohol polymer film was obtained in the same manner as in Example 1, except that 0.1 part by weight of a material having a rod-like structure of Formula 3 was added as a phase difference reducing agent. .

(3)

Comparative Example  3

As shown in Table 1 below, except that 5 parts by weight of sodium dodecylbenzenesulfonate was added as a phase difference reducing agent, the same method as in Example 1 was carried out to obtain a polyvinyl alcohol polymer film.

Experimental Example : Phase difference  Measure

The polymer films prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to a phase difference measuring instrument (product name: Rets, manufactured by Otsuka Electronics Co., Ltd.) in a Rets R & D mode in a wavelength range of 380 nm to 780 nm in front and at a 45 degree side surface. The phase difference in was measured. In-plane retardation value Ro and thickness direction retardation value Rth were measured and described in Table 1 below.

In addition, the width direction dispersion of the phase difference was measured, and the area | region which removed +/- 5 on the basis of the center value was removed, and the removal amount of both ends was shown in% based on the quantity of the polymer film.

Phase difference reducing agent
Input amount (part by weight) Phase difference Removal amount at both ends
(%) Ro [nm] Rth [nm] Example 1 0.10 3 ± 3 5 ± 3 0 Example 2 0.50 5 ± 5 10 ± 5 0 Example 3 0.10 10 ± 5 20 ± 5 0 Example 4 0.10 1 ± 3 3 ± 3 0 Comparative Example 1 0 30 to 50 40-90 15 Comparative Example 2 0.10 50-320 150-290 45 Comparative Example 3 5 90-110 250-330 30

From the results of Table 1, the polyvinyl alcohol-based polymer film of Examples 1 to 4 prepared according to the method of the present invention not only has much lower in-plane retardation and thickness direction retardation than the films prepared in Comparative Examples 1 to 3 Therefore, it turns out that it is not necessary to remove both ends of a film.

10: raw material solution 11: coating layer
12: polyvinyl alcohol polymer film 110: extruder
120: casting drum 130: stripper roll
210: extruder 220: support film
230: floating dryer

Claims (11)

To include a phase difference reducing agent represented by the formula (2), the phase difference reducing agent is used in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the polyvinyl alcohol-based polymer film,
A polyvinyl alcohol polymer film having an in-plane retardation of 0 to 50 nm and a retardation in a thickness direction of -10 to 80 nm:
(2)

.
delete delete delete delete The method of claim 1,
The polyvinyl alcohol polymer film, characterized in that the film has a thickness of 20 to 200㎛.
A polarizing film obtained by dyeing and stretching the polyvinyl alcohol polymer film of claim 1 and then drying.
A raw material solution composed of polyvinyl alcohol having a degree of saponification of 99 mol% or more and a polymerization degree of 1,700 or more, a phase difference reducing agent, a plasticizer, a releasing agent, and a solvent represented by the following Chemical Formula 2 is extruded through an extruder, and then supplied onto a casting drum at 80 to 100 ° C. Peeling from the casting drum, followed by drying at a temperature of 40 to 150 ° C.,
The phase difference reducing agent is used in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the polyvinyl alcohol polymer film.
Method for producing a polyvinyl alcohol polymer film according to claim 1
(2)

.
A raw material solution composed of polyvinyl alcohol having a degree of saponification of 99 mol% or more and a polymerization degree of 1,700 or more, a phase difference reducing agent, a plasticizer, a releasing agent, and a solvent represented by the following Chemical Formula 2 was extruded through an extruder, and then supplied onto a support film having a roughness of 5 μm or less. Coating to dry in multiple stages at a temperature of 40 to 150 ℃,
The phase difference reducing agent is used in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the polyvinyl alcohol polymer film.
Method for producing a polyvinyl alcohol polymer film according to claim 1
(2)

.
The method of claim 9,
The support film may be a polyethylene terephthalate (PET) film, a polyethylene naphthalate (PEN) film, a polycarbonate (PC) film, a triacetic cellulose (TAC) film, or an acryl film. Method for producing a film.
10. The method according to claim 8 or 9,
Wherein the polyvinyl alcohol has a degree of polymerization of 1,700 to 5,000.

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