KR20130117278A - Polyvinyl alcohol-based film and polarizing film using same - Google Patents

Abstract

PURPOSE: A polyvinylalcohol-based film and a Polaroid film using the same are provided to show excellent polarization properties by minimizing optical smudge including in-plane phase difference, especially in phase difference in transverse direction (TD), permeability and haze deviation. CONSTITUTION: A polyvinylalcohol-based film contains polyvinyl alcohol and non-ionic fluorinated surfactant. The non-ionic fluorinated surfactant contains a fluoroalkyl group. The non-ionic fluorinated surfactant is selected from fluoroalkyl sulfonate, fluoroalkyl ether, and fluoroalkyl amide and a mixture thereof. The polaroid film dyes and extends the polyvinylalcohol-based film and obtains the extended film by drying the same. Moreover, a polarizing plate includes the polaroid film and protective films equipped one or more surfaces of the polaroid film.

Description

TECHNICAL FIELD [0001] The present invention relates to a polyvinyl alcohol film and a polarizing film using the same,

The present invention relates to a polyvinyl alcohol (PVA) -based film having a minimal retardation and an excellent in-plane uniformity, and a polarizing film using the same.

A polarizing plate having a function of transmitting and blocking light is generally manufactured by adhering a protective film such as a triacetylcellulose (TAC) film, an acetic acid-butyric acid cellulose (CAB) film or the like to both surfaces of a polarizing film derived from a PVA film. The polarizing film can be obtained by dyeing and uniaxially stretching a PVA-based film, fixing it with a boron compound, and then subjecting it to a drying treatment.

As described in Korean Patent No. 818135, a PVA film is generally manufactured by extruding a PVA-containing raw material solution and casting it on a support such as a heated drum or a steel belt, followed by drying . The dried PVA film is peeled off from the support and wound up. When the peeling is not uniform and easy, the PVA film containing water is partially stretched, thereby causing a variation in the refractive index in the width direction, , Optical transmittance deviation, haze deviation, and the like. In addition, when a polarizing film is produced using such a PVA film in which optical unevenness occurs, dyeing unevenness may occur and this may cause a decrease in the degree of polarization.

Therefore, in order to smoothly peel the PVA film from the support, a surfactant is generally added to the PVA-containing raw material solution as a peeling agent, and it is important to appropriately control the type and amount of the peeling agent.

Japanese Laid-Open Patent Publication No. 2005-206810 discloses that a PVA film is produced using an ether-type nonionic surfactant and two or more kinds of low-molecular-weight nonionic surfactants. However, the optical unevenness can not be completely solved.

Japanese Patent Application Laid-Open No. 2006-307059 discloses an anionic fluorosurfactant. In this case, if a small amount of impurities such as metal cations are present in the PVA raw material solution, the cation and the anion react with each other to cause aggregation , Which can create foreign objects such as fish eyes and gels, which can cause fatal defects in the display.

In particular, at the time when the display becomes thinner, a thinner PVA film is required in the market, and as the thickness becomes thinner, it is less easy to solve the problem of optical stain with conventional surfactants.

Korean Registered Patent No. 10-818135 (Mar. 31, 2008) Japanese Unexamined Patent Publication No. 2005-206810 (Aug. 4, 2005) Japan Synthetic Chemical Industry Co., Ltd. Japanese Unexamined Patent Publication No. 2006-307059 (2006.11.09) Japanese Synthetic Chemical Industry Co., Ltd.

Accordingly, an object of the present invention is to provide a polyvinyl alcohol-based film having minimized optical unevenness such as a retardation deviation and a polarizing film using the same.

According to the above object, the present invention provides a polyvinyl alcohol-based film containing polyvinyl alcohol and a nonionic fluorosurfactant.

According to another aspect of the present invention, there is provided a polarizing film obtained by dyeing, stretching and drying the polyvinyl alcohol-based film.

The present invention also provides a polarizing plate comprising the polarizing film and a protective film provided on at least one side of the polarizing film.

Since the polyvinyl alcohol film according to the present invention minimizes optical unevenness such as in-plane retardation, in particular, transverse (TD) retardation, and other transmittance and haze deviation, the polarizing film produced using the film has little dyeing unevenness Exhibits excellent polarization performance.

Fig. 1 shows an example of a process for producing the PVA-based film of the present invention.

One of the typical causes of optical unevenness on the PVA film is that when the PVA film is produced, the film is not uniformly and easily peeled off from the support after the casting process on the support such as the drum and the steel belt.

However, since the PVA film of the present invention contains a nonionic fluorosurfactant as a surfactant, it is possible to adjust the surface tension between a PVA film and a support such as a drum and a steel belt to produce a PVA film having a small thickness, It is possible to easily peel off when producing a thin film having a thickness of 40 m or less, or even 30 m or less. In addition, the PVA film of the present invention is easy to peel off and optically free from defects when a plastic support film other than the drum and the steel belt is used as a support. In addition to the case where the plastic support film is a general polyester film, Olefin, and olefin.

Conventionally, in order to improve the peelability in the production of a film, there have been many cases in which two or more surfactants have been mixed and used. In the case of the film of the present invention, however, even when a nonionic fluorosurfactant is used singly, .

The nonionic fluorosurfactant which may be contained in the PVA film of the present invention contains a fluoro functional group, preferably contains a fluoroalkyl group, and examples thereof include a fluoroalkylsulfonate, a fluoroalkyl ether, a fluoro Alkyl amides, or mixtures thereof.

Specific examples of the fluoroalkylsulfonate include perfluorobutanesulfonate, perfluorooctanesulfonate, perfluoromethane sulfonate, perfluoroethanesulfonate, and mixtures thereof. Specific examples of the fluoroalkyl ether include perfluorobutyl ether, perfluorooctyl ether, perfluoromethyl ether, perfluoroethyl ether, and mixtures thereof. Specific examples of the fluoroalkyl amides also include perfluorobutanamide, perfluorooctanamide, perfluoromethane amide, perfluoroethanamide, and mixtures thereof.

These nonionic fluorine-containing surfactants may be used alone or in combination of two or more.

The PVA film of the present invention may contain such a nonionic fluorosurfactant in an amount of 0.01 to 1 part by weight, more preferably 0.01 to 0.02 parts by weight, based on 100 parts by weight of PVA.

The PVA as the main component of the film of the present invention preferably has a degree of saponification of 99 mol% or more, more preferably 99.5 mol% or more, preferably 1700 or more, and more preferably 1700 to 5000. When the PVA has a degree of saponification of less than 99 mol%, the durability of the polarizing plate obtained by dyeing and stretching the PVA may be deteriorated. When the degree of saponification is less than 1700, sufficient elongation The optical characteristics may be deteriorated.

The PVA film of the present invention may further include a plasticizer in addition to PVA and a surfactant. The plasticizer serves to improve the processability by weakening the hydrogen bonding at the time of film formation, and may be a mixture of glycerin, ethylene glycol, polyethylene glycol, May be used as the plasticizer. Particularly, it is preferable to use glycerin which has good affinity for PVA 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 PVA.

The PVA film of the present invention comprises a step of extruding a raw material solution containing PVA and a nonionic fluorosurfactant through an extruder, coating on a support and then primary drying; Peeling the PVA-containing coating film formed on the support with the support; And secondly drying the peeled PVA-containing coating film.

In the above production method, the PVA-containing raw material solution can be prepared by dissolving PVA in a solvent as described above, adding a nonionic fluorosurfactant and a plasticizer, and mixing the mixture. And can further knead them in an extruder. It is preferable that the plasticizer and the surfactant are added at the same temperature as the solution in consideration of the uniform dissolution and saponification degree of the PVA required in the present invention. For example, 50 to 150 ° C is suitable.

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

As the solvent, dimethylsulfoxide, dimethylformamide, water, tetraethylene glycol, diethyltriamine or a mixed solvent thereof can be used and can be used in an amount suitable for achieving uniform dissolution of PVA.

The PVA-based film of the present invention is obtained by coating a PVA-containing raw material solution on a support and drying the same. The support may be a drum, a steel belt, a plastic supporting film, A process for producing a PVA-based film using a plastic support film as a support is shown. Hereinafter, an example of a production process of the PVA film of the present invention will be described in more detail with reference to FIG.

First, the PVA-containing raw material solution 10 having the above composition is extruded through an extruder 20, particularly a twin extruder, to completely remove bubbles generated during the dissolving process, Prior to proceeding, the extrudate of the PVA-containing feed solution may preferably be passed through a filter (not shown in FIG. 1) for the purpose of removing foreign matter. The temperature of the extruder may be between 95 and 100 < 0 > C.

The extrudate of the PVA-containing raw material solution is then coated on the support film 30. The support film 30 may be a polyethylene terephthalate (PET) film, a polyethylene naphthalate (PEN) film, a polycarbonate (PC) , Cellulose triacetate (TAC) film, acrylic film, cycloolefin film, and olefin film can all be used. In addition, various coating methods such as die coating, gravure coating, gap coating, and layer bar coating are all available.

The PVA-containing coating film 50 formed on the support film 30 is then primarily dried by passing it through an air chamber 40 so that the PVA-containing coating film 50 has a water content of about 5 to 20 %, The coating film is peeled from the supporting film (30). Thereafter, the peeled PVA-containing coating film 50 is subjected to second-stage multi-stage drying (not shown in FIG. 1) while passing through about 5 to 15 heat treatment rolls and a floating dryer, Can be obtained. The temperature of the air chamber (primary drying) and the floating dryer (secondary drying) may be 80 to 150 ° C, respectively, and the temperature of the floating dryer may be higher than the temperature of the air chamber.

The thus-prepared PVA film of the present invention can have a thickness of 10 to 200 탆, can have a thickness of 10 to 60 탆, exhibits excellent optical properties with a thickness of 10 to 40 탆 Lt; / RTI >

In addition, the film of the present invention can be manufactured to have a width of 1M or more, further 6M or more, for example, 1M to 10M, 1M to 6M, or 6M to 10M, ) Can be minimized and thus optically uniform properties can be obtained.

Since the PVA film of the present invention contains a nonionic fluorosurfactant, the PVA film according to the present invention has an in-plane retardation, particularly a retardation in the transverse direction (TD), as compared with a PVA film containing an ionic surfactant or a nonionic fluorine- And has little optical stain such as other transmittance and haze deviations.

Further, the present invention provides a polarizing film produced from the PVA-based film by a conventional method such as dyeing and stretching the PVA-based 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 almost no uniformity of dyeing, is very uniform, and has excellent polarization performance.

Further, the polarizing plate can be produced by a conventional method using the polarizing film, and specifically, a polarizing plate can be manufactured by forming a protective film on at least one surface of the polarizing film.

Hereinafter, the present invention will be described in more detail by way of examples. The following examples are illustrative of the present invention, but the present invention is not limited to the following examples.

Production of PVA film

Examples 1 to 3: Preparation of PVA Films (Nonionic Fluorine Surfactant)

Step (1): Preparation of raw material solution

PVA having a degree of saponification of 99.99 mol% and a degree of polymerization of 2400 to 3300 was dissolved in water, a glycerin plasticizer was added, and perfluorobutane sulfonate, which is a nonionic fluorine surfactant, was added as a releasing agent and mixed to prepare a PVA- Prepared. At this time, PVA was used in an amount of 20% by weight in the solution, and the plasticizer and the release agent were used in an amount of 12 parts by weight and 0.10 to 0.12 parts by weight based on 100 parts by weight of PVA, respectively.

Step (2): Formation of PVA-based film

The raw material solution obtained in the previous step was extruded through a twin-screw extruder at 95 ° C, and the extrudate was passed through a filter (material: aluminum, mesh size: 5 μm, temperature: 90 ° C.) The coating film, which was primarily dried on the drum, was then peeled from the drum by a stripper roll.

The PVA-containing coated film thus peeled was subjected to multi-stage drying and winding at a temperature of 80 DEG C while passing through several drying rolls and a floating dryer to obtain a PVA-based film.

Examples 4 and 5: Preparation of PVA film (nonionic fluorine-based surfactant)

Step (1): Preparation of raw material solution

(1) of Example 1 to prepare a raw material solution.

Step (2): Formation of PVA-based film

The raw material solution obtained in the previous step was extruded through a twin screw extruder at 95 ° C, and the extrudate was passed through a filter and then die-coated on a polyethylene terephthalate (PET) support film. Then, the PVA-containing coating film formed on the supporting film was primarily dried at 90 캜 while passing through the air chamber to peel off the coating film from the supporting film when the water content of the PVA-containing coating film was approximately 5 to 20%.

The PVA-containing coated film thus peeled was subjected to multi-stage drying and winding at a temperature of 80 DEG C while passing through several drying rolls and a floating dryer to obtain a PVA-based film.

Comparative Examples 1 and 2: Preparation of PVA film (ionic fluorine-based surfactant)

A PVA film was obtained in the same manner as in Example 1 except that trifluoromethyl polyoxy tetrafluoroethylene carbonate sodium, which is an ionic fluorine surfactant, was used as a releasing agent.

Comparative Examples 3 and 4: Preparation of PVA Films (Nonionic Nonfluorinated Surfactant)

In Comparative Example 3, except for using a mixture of polyoxyethylene dodecylether, polyoxyethylene dodecylamine and lauryldiethylamide as nonionic nonfluorinated surfactants as the release agent, 4, the same procedure as in Comparative Example 2 was carried out to obtain a PVA-based film.

Test Example 1: Evaluation of peelability

The peel strength of the PVA film coated on the drum or the support film during the manufacturing process was measured by using an adhesive strength meter (Heidon) to measure the peel strength of 20 g / inch or less, 20 to 50 g / inch "and "X" in the range exceeding 50 g / inch.

Test Example 2: Evaluation of optical stain and foreign matter

The PVA films prepared in the above Examples and Comparative Examples were passed through a beam project to observe optical dyes and presence of foreign substances.

Test Example 3: In-plane retardation measurement (transverse direction)

The PVA films prepared in the above Examples and Comparative Examples were irradiated with light having a wavelength of 40 nm in a film normal direction from a birefringence meter (KOBRA-WPR, Oji Scientific Instrument), and in-plane retardation measurement (transverse direction) was measured.

Production of polarizing film

Each of the PVA films produced in the above-mentioned Examples and Comparative Examples was continuously treated in the order of preliminary swelling, dyeing, uniaxial stretching, fixing treatment, drying treatment and heat treatment to prepare a polarizing film.

Specifically, the PVA film was immersed in water at 30 DEG C for 60 seconds, preliminarily swollen, and then immersed in an aqueous solution of 40 g / L of boric acid, 0.4 g / L of iodine and 60 g / L of potassium iodide dissolved at 35 DEG C for 2 minutes, . After the dyeing, the PVA film was uniaxially stretched to 6 times in a 4% boric acid aqueous solution at 55 ° C, and then immersed in an aqueous solution of 30 ° C in which 60 g / L of potassium iodide, 40 g / L of boric acid and 10 g / Lt; / RTI > Thereafter, the PVA-based film was taken out, hot-air dried at 40 ° C, and further heat-treated at 100 ° C for 5 minutes to obtain a final polarizing film.

Test Example 4: Evaluation of stain occurrence of polarizing film

Each polarizing film thus prepared was placed on an LCD backlight to observe the presence of staining unevenness.

Test Example 5: Measurement of polarization degree

The polarizability (%) of each of the prepared polarizing films was measured using a polarization degree meter (UV-2450, manufactured by Simazu Instrument) according to JIS Z8701 method.

Table 1 below summarizes the structures of the examples and comparative examples, and Table 2 shows the results of the above test examples.

division PVA
Degree of polymerization Surfactants dry
materials thickness
(탆) width
(M) Kinds input
(Parts by weight) Example 1 2400 Perfluorobutanesulfonate 0.12 drum 75 1.0 Example 2 2400 Perfluorobutanesulfonate 0.10 drum 25 1.5 Example 3 3300 Perfluorobutanesulfonate 0.10 drum 25 2.8 Example 4 3300 Perfluorobutanesulfonate 0.10 film 25 2.8 Example 5 3300 Perfluorobutanesulfonate 0.10 film 75 2.8 Comparative Example 1 2400 Trifluoromethylpolyoxy
Sodium tetrafluoroethylene carbonate 0.12 drum 75 2.8 Comparative Example 2 2400 Trifluoromethylpolyoxy
Sodium tetrafluoroethylene carbonate 0.12 drum 25 2.8
Comparative Example 3 3300 Polyoxyethylene dodecyl ether 0.02
drum
25
2.8 Polyoxyethylene dodecylamine 0.06 Lauryldiethylamide 0.02
Comparative Example 4 3300 Polyoxyethylene dodecyl ether 0.02
film
25
2.8 Polyoxyethylene dodecylamine 0.06 Lauryldiethylamide 0.02

division PVA film Polarizing film Peelability optics
stain Foreign substance In-plane phase difference
(nm) dyeing
stain Polarization degree
(%) Example 1 ○ radish radish 3 radish 99.99 Example 2 ○ radish radish 5 radish 99.99 Example 3 ○ radish radish 4 radish 99.99 Example 4 ○ radish radish 3 radish 99.99 Example 5 ○ radish radish 4 radish 99.99 Comparative Example 1 ○ radish U 25 radish 99.97 Comparative Example 2 △ U U 35 U 99.98 Comparative Example 3 △ U radish 33 U 99.97 Comparative Example 4 △ U radish 20 U 99.98

As shown in Tables 1 and 2, the PVA film containing the nonionic fluorosurfactant as in Examples 1 to 5 exhibited excellent physical properties such as optical unevenness, foreign matter in the film, peelability, phase difference deviation, and stain after dyeing the polarizing plate , But the films containing two or more kinds of surfactants containing ionic surfactants or non-fluoric surfactants as in Comparative Examples 1 to 4 exhibited poor properties in terms of their physical properties.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, It is to be understood that the invention may be practiced within the scope of the appended claims.

10: Raw material solution containing PVA
20: extruder 30: support film
40: air chamber 50: PVA-containing coating film

Claims (10)

A polyvinyl alcohol film containing polyvinyl alcohol and a nonionic fluorine surfactant.
The method of claim 1,
A polyvinyl alcohol-based film, wherein the nonionic fluorine-based surfactant contains a fluoroalkyl group.
The method of claim 1,
The polyvinyl alcohol-based film, characterized in that the nonionic fluorine-based surfactant is selected from the group consisting of fluoroalkyl sulfonates, fluoroalkyl ethers, fluoroalkyl amides, and mixtures thereof.
The method of claim 3, wherein
Wherein said fluoroalkyl sulfonate is selected from the group consisting of perfluorobutanesulfonate, perfluorooctanesulfonate, perfluoromethane sulfonate, perfluoroethanesulfonate, and mixtures thereof. Polyvinyl alcohol film.
The method of claim 1,
Wherein the polyvinyl alcohol-based film further comprises glycerin in an amount of 5 to 20 parts by weight based on 100 parts by weight of the polyvinyl alcohol.
The method of claim 1,
Wherein the polyvinyl alcohol has a degree of saponification of 99 mol% or more and a degree of polymerization of 1700 to 5000. The polyvinyl alcohol-
The method of claim 1,
Wherein the polyvinyl alcohol-based film has a thickness of 10 占 퐉 to 60 占 퐉.
The method of claim 1,
Wherein the polyvinyl alcohol-based film has a width of 1M to 6M.
The polarizing film obtained by dyeing, extending | stretching, and drying the polyvinyl alcohol-type film of any one of Claims 1-8.
A polarizing plate comprising the polarizing film of claim 9 and a protective film provided on at least one side of the polarizing film.

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